Orthopedic With Answer Sp Review | Dr Hutaif General Or -...

Question 1

A 35-year-old male presents to the trauma bay following a motorcycle collision. Pelvic radiographs demonstrate a 3.5 cm symphyseal diastasis. A CT scan confirms an anteroposterior compression type II (APC-II) pelvic ring injury with disruption of the anterior sacroiliac ligaments but intact posterior sacroiliac ligaments. He is hemodynamically stable. What is the most appropriate definitive management for this patient's pelvic injury?

Explanation

An APC-II pelvic ring injury represents a rotationally unstable but vertically stable injury characterized by disruption of the symphysis pubis and the anterior sacroiliac ligaments, while the strong posterior sacroiliac ligaments remain intact. Because vertical stability is maintained, anterior ring stabilization alone (most commonly via open reduction and internal fixation of the pubic symphysis with a plate) is sufficient definitive treatment to restore rotational stability. Adding posterior fixation (iliosacral screws) is indicated for APC-III injuries, which involve disruption of both anterior and posterior SI ligaments, rendering the pelvis both rotationally and vertically unstable.

Question 2

A 64-year-old female presents with insidious onset of right thigh pain. She has been on oral alendronate for the past 9 years for osteoporosis. Radiographs of the right femur reveal a fracture. Which of the following radiographic characteristics is most highly associated with a bisphosphonate-related atypical femur fracture?

Explanation

Atypical femur fractures (AFFs) are associated with prolonged bisphosphonate use (typically >5 years), which heavily suppresses bone turnover and allows microdamage accumulation. The American Society for Bone and Mineral Research (ASBMR) criteria for an AFF include a location anywhere from just distal to the lesser trochanter to just proximal to the supracondylar flare. Major features include a transverse or short oblique fracture line, origin at the lateral cortex, noncomminuted or minimally comminuted morphology, and localized periosteal or endosteal thickening of the lateral cortex (beaking) at the fracture site.

Question 3

A 12-year-old obese boy is diagnosed with a unilateral left-sided slipped capital femoral epiphysis (SCFE). In which of the following scenarios is prophylactic percutaneous in situ pinning of the contralateral right hip most strongly indicated?

Explanation

Prophylactic pinning of the contralateral hip in SCFE is controversial for idiopathic cases but is strongly recommended for patients with endocrine disorders (such as hypothyroidism, panhypopituitarism) or metabolic bone diseases (like renal osteodystrophy), as well as those undergoing prior radiation therapy to the pelvis. These patients have a significantly higher risk (up to 100% in some metabolic conditions) of developing a subsequent contralateral slip compared to the general idiopathic SCFE population. Other factors favoring prophylactic pinning include younger age (open triradiate cartilage) and follow-up unreliability.

Question 4

Bone morphogenetic protein-2 (BMP-2) has potent osteoinductive properties and is utilized in various orthopedic fusion procedures. The intracellular signaling cascade initiated by BMP-2 binding to its cell surface serine/threonine kinase receptors relies primarily on the phosphorylation and activation of which of the following molecules?

Explanation

Bone morphogenetic proteins (BMPs) belong to the TGF-beta superfamily. When BMP-2 binds to its heterodimeric serine/threonine kinase receptors (Type I and Type II), it phosphorylates intracellular receptor-regulated Smad proteins (R-Smads), specifically Smad 1, 5, and 8. These phosphorylated R-Smads then form a complex with the common-partner Smad (co-Smad), Smad 4, which translocates to the nucleus to regulate the transcription of osteogenic genes (e.g., Runx2, Osterix). Wnt signaling relies on beta-catenin, while RANKL utilizes the NF-kappaB pathway.

Question 5

A 14-year-old boy completes a course of neoadjuvant chemotherapy followed by wide surgical resection of a conventional high-grade osteosarcoma of the distal femur. Pathological analysis of the resected tumor is performed. Which of the following is considered the most significant independent prognostic factor for long-term survival in this patient?

Explanation

In the management of osteosarcoma, the degree of tumor necrosis induced by neoadjuvant chemotherapy, as assessed in the definitive surgical resection specimen, is the most powerful and reliable predictor of disease-free and overall survival. A "good response" is classically defined as ≥90% tumor necrosis (Huvos grade III or IV) and correlates with a significantly better prognosis compared to a "poor response" (<90% necrosis). Initial tumor size and stage at presentation are also important, but post-chemotherapy necrosis remains the gold standard prognostic indicator for localized disease.

Question 6

Female athletes face a higher incidence of noncontact anterior cruciate ligament (ACL) tears compared to their male counterparts. Which of the following anatomical or biomechanical factors is recognized as increasing the risk of ACL injury in female athletes?

Explanation

Risk factors for noncontact ACL injuries in females include biomechanical, anatomical, and hormonal components. Biomechanically, females tend to demonstrate increased dynamic knee valgus and land with the knee in a more extended position, heavily loading the ACL. Anatomical risk factors include a narrow intercondylar notch (decreased notch width index), an increased Q-angle, and an increased posterior tibial slope. Additionally, females often have a decreased hamstring-to-quadriceps strength ratio (quadriceps dominance), which increases anterior tibial translation force during deceleration.

Question 7

A 24-year-old professional rugby player sustains an injury to his right ring finger when he grabs an opponent's jersey. He presents with an inability to actively flex the distal interphalangeal (DIP) joint. Radiographs show a large bony avulsion fragment from the volar base of the distal phalanx resting at the level of the proximal interphalangeal (PIP) joint. According to the Leddy and Packer classification, what type of flexor digitorum profundus (FDP) avulsion injury is this?

Explanation

The Leddy and Packer classification categorizes FDP tendon avulsions ('Jersey finger') based on the level of tendon retraction and the presence of a bony fragment. Type I involves retraction of the tendon into the palm; blood supply is severely compromised, requiring repair within 7-10 days. Type II involves retraction to the level of the PIP joint, held by the intact vinculum longum. Type III involves a large bony avulsion fragment that catches at the A4 pulley (level of the middle phalanx/PIP joint), preventing further proximal retraction. Type IV (added by Smith) is a bony avulsion from the distal phalanx with the tendon avulsed off the bony fragment itself.

Question 8

A 45-year-old male presents with a Levine-Edwards Type II Hangman's fracture (traumatic spondylolisthesis of the axis) following a high-speed motor vehicle collision. Radiographs demonstrate bilateral pars interarticularis fractures of C2 with significant anterior translation and angulation of C2 on C3. What is the classic proposed mechanism for this specific injury pattern?

Explanation

Hangman's fractures are classified by Levine and Edwards. Type I fractures involve <3 mm translation and no angulation; they result from hyperextension-axial loading. Type II fractures involve significant translation and angulation; the mechanism is initial hyperextension and axial loading (causing the pars fractures) followed immediately by severe flexion and compression (causing disruption of the C2-C3 disc and posterior longitudinal ligament, leading to translation/angulation). Type IIA involves marked angulation with minimal translation, caused by flexion-distraction. Type III involves bilateral pars fractures with associated bilateral C2-C3 facet dislocations, caused by flexion-compression.

Question 9

A 60-year-old male who underwent a primary total hip arthroplasty (THA) with a ceramic-on-ceramic bearing surface two years ago presents with a loud, high-pitched squeaking noise coming from his hip during certain movements, particularly bending and rising from a chair. Which of the following is the most significant biomechanical risk factor for developing squeaking in this type of bearing?

Explanation

Squeaking is a well-documented complication unique to hard-on-hard bearing surfaces, most notably ceramic-on-ceramic (CoC) THA. The primary etiology of CoC squeaking is disruption of the fluid film lubrication leading to stripe wear, which is most commonly caused by edge loading. Edge loading typically results from malposition of the acetabular component, such as excessive anteversion or steep inclination (abduction angle), or from micro-separation during the swing phase of gait. Component impingement or third-body wear can also contribute, but edge loading due to cup malposition is the predominant biomechanical risk factor.

Question 10

A 72-year-old diabetic male develops a chronic periprosthetic joint infection of his knee. Cultures yield Methicillin-Resistant Staphylococcus aureus (MRSA). The resistance of this organism to beta-lactam antibiotics (e.g., oxacillin, methicillin, cephalosporins) is primarily mediated by the expression of the mecA gene. What is the direct functional consequence of the mecA gene product?

Explanation

Methicillin resistance in Staphylococcus aureus is mediated by the acquisition of the staphylococcal cassette chromosome mec (SCCmec) element, which contains the mecA gene. The mecA gene encodes for penicillin-binding protein 2a (PBP2a), a transpeptidase that has a significantly reduced binding affinity for beta-lactam antibiotics. This allows the bacterium to continue cell wall synthesis (peptidoglycan cross-linking) even in the presence of beta-lactams. Beta-lactamase production causes penicillin resistance (but not methicillin resistance). Efflux pumps and altered porins are common resistance mechanisms in Gram-negative bacteria. Ribosomal methylation is the mechanism for macrolide resistance (erm gene).

Question 11

A 3-month-old female is being treated for developmental dysplasia of the hip (DDH) with a Pavlik harness. During a follow-up visit, the parents report that the child has stopped actively extending her right knee. On examination, the infant lacks active knee extension, and the patellar reflex is absent on the right. What positioning error in the Pavlik harness is the most likely cause of this complication?

Explanation

The patient is presenting with a femoral nerve palsy, which is the most common nerve injury associated with Pavlik harness use. Femoral nerve palsy occurs secondary to excessive hip flexion, which causes compression or stretch of the femoral nerve against the inguinal ligament or the brim of the pelvis. The hallmark sign is decreased or absent active knee extension. Treatment is to loosen or temporarily remove the anterior straps to decrease hip flexion, which usually leads to spontaneous recovery. Excessive hip abduction is the risk factor for avascular necrosis (AVN) of the femoral head.

Question 12

A 45-year-old male sustains a high-energy Schatzker Type IV tibial plateau fracture following a fall from a height. Radiographs show a fracture of the medial tibial plateau. Which of the following specific anatomical mechanisms and associated soft-tissue injuries makes this fracture pattern particularly dangerous?

Explanation

A Schatzker Type IV tibial plateau fracture involves the medial plateau. It is typically a high-energy injury resulting from varus and axial loading. The medial plateau is anatomically larger and stronger than the lateral plateau, so fractures here require more energy. A characteristic sub-variant is the posteromedial shear fragment. Displacement of this posteromedial fragment is extremely hazardous due to its proximity to the popliteal artery as it exits the popliteal fossa beneath the soleus arch. Popliteal artery injury or intimal tear must be meticulously ruled out via thorough vascular examination and ABI/CT angiography if suspected.

Question 13

A 28-year-old professional baseball pitcher presents with chronic shoulder pain. MRI arthrogram reveals a Partial Articular-Sided Supraspinatus Tendon Avulsion (PASTA) lesion. Nonoperative management has failed. Intraoperatively, the tear is assessed to involve 60% of the normal footprint depth. What is the most appropriate surgical management?

Explanation

A PASTA lesion is a partial-thickness articular-sided tear of the rotator cuff (most commonly the supraspinatus). The classic treatment algorithm dictates that if the tear involves less than 50% of the tendon footprint depth (typically <3-6 mm), debridement alone is indicated. However, if the tear involves greater than 50% of the footprint, the standard of care is surgical repair. This can be achieved either by completing the tear to a full-thickness tear and performing a standard repair, or by performing an in situ transtendon repair, which preserves the intact bursal-sided fibers.

Question 14

A 35-year-old construction worker presents with chronic radial-sided wrist pain. Radiographs demonstrate scaphoid nonunion advanced collapse (SNAC). There is significant arthritis at the radioscaphoid joint and the scaphocapitate joint, but the capitolunate joint and the radiolunate facet are radiographically spared. What stage of SNAC wrist does this represent, and what is a standard surgical option?

Explanation

SNAC wrist stages map the progression of arthritis following scaphoid nonunion. Stage I involves arthritis isolated to the radial styloid and the distal scaphoid. Stage II involves the entire radioscaphoid fossa and the scaphocapitate joint. Stage III involves periscaphoid arthritis extending to the capitolunate joint. The radiolunate joint is characteristically spared in all stages because the lunate maintains a concentric spherical relationship with the lunate fossa. For a Stage II SNAC wrist (radioscaphoid and scaphocapitate arthritis), a Proximal Row Carpectomy (PRC) is a viable option as long as the capitolunate joint is preserved. Scaphoid excision with four-corner fusion is also an option for Stage II and is the treatment of choice for Stage III (where PRC is contraindicated due to capitate head arthritis).

Question 15

During a total knee arthroplasty (TKA) on a patient with a severe, fixed valgus deformity, the surgeon notes that the extension gap remains unacceptably tight on the lateral side after initial bony cuts. To balance the knee, a stepwise lateral soft tissue release is planned. Which of the following structures is considered the primary restraint to valgus stress in extension, and is typically released to open a tight lateral extension gap without affecting the flexion gap?

Explanation

In TKA balancing for a valgus knee, one must distinguish between structures that affect the extension gap versus the flexion gap. The Iliotibial (IT) band is tight primarily in extension and acts as a major restraint to valgus stress when the knee is extended. Releasing or pie-crusting the IT band will open the lateral extension gap with minimal effect on the flexion gap. Conversely, the popliteus tendon is a major restraint in flexion; releasing it opens the flexion gap. The Lateral Collateral Ligament (LCL) affects both the flexion and extension gaps symmetrically. Therefore, for a tight lateral extension gap specifically, the IT band (and posterolateral capsule) is targeted.

Question 16

A 55-year-old female presents with severe neurogenic claudication and L5 radiculopathy. Radiographs reveal a Meyerding Grade 2 isthmic spondylolisthesis at L5-S1. She has failed 6 months of conservative management. What is the most appropriate surgical intervention?

Explanation

Isthmic spondylolisthesis (lytic defect in the pars interarticularis) most commonly occurs at L5-S1. In adults who fail conservative treatment and exhibit radiculopathy (commonly L5 root compression in the foramen by the fibrocartilaginous pars defect/Gill body) or neurogenic claudication, decompression alone (Gill procedure) has an unacceptably high rate of progressive slip and instability. The standard of care is decompression of the nerve roots combined with a posterior or transforaminal instrumented fusion of L5 to S1. Direct pars repair is reserved for young patients (children/adolescents) with normal disc spaces and minimal slip (Grade 1).

Question 17

Orthopedic implants and connective tissues exhibit viscoelastic properties. Which of the following statements provides the most accurate biomechanical definition of 'stress relaxation'?

Explanation

Viscoelastic materials exhibit time-dependent responses to loading. 'Stress relaxation' is defined as the progressive decrease in internal stress over time when the material is held at a constant strain (deformation). An example is the decreasing tension in a tightened ligament graft over time. Option 1 defines 'creep', which is the progressive increase in strain (deformation) over time when subjected to a constant stress (load). Option 2 defines 'hysteresis'. Option 3 describes the yield point. Option 4 describes fatigue failure.

Question 18

A 25-year-old male sustains a comminuted fracture of the tibial diaphysis. In the emergency department, he complains of severe pain out of proportion to the injury, especially with passive stretch of his toes. His blood pressure is 120/70 mmHg. Intracompartmental pressure measurements are obtained. Which of the following thresholds represents an absolute indication for emergency four-compartment fasciotomy?

Explanation

The diagnosis of acute compartment syndrome is primarily clinical, but intracompartmental pressure monitoring is critical in obtunded or polytrauma patients, or when the clinical picture is ambiguous. The most universally accepted objective criterion for performing a fasciotomy is a Delta P (ΔP) of less than 30 mmHg. Delta P is calculated as the patient's Diastolic Blood Pressure minus the Intracompartmental Pressure. Utilizing an absolute compartment pressure threshold (e.g., >30 or >40 mmHg) without accounting for the patient's systemic blood pressure can lead to both under-diagnosis in hypotensive patients and over-diagnosis in hypertensive patients.

Question 19

A 6-year-old boy presents to the emergency department after falling from monkey bars. He has a severely displaced, completely off-ended extension-type supracondylar humerus fracture (Gartland Type III). On examination, his hand is warm and pink, capillary refill is less than 2 seconds, but there is no palpable radial pulse. What is the most appropriate next step in management?

Explanation

The patient has a "pink, pulseless" hand in the setting of a Gartland III supracondylar fracture. The brachial artery is frequently kinked, tethered, or placed in spasm over the proximal fracture fragment rather than completely transected. The standard of care for a pink, pulseless hand is to proceed urgently to the operating room for closed reduction and percutaneous pinning (CRPP) of the fracture. In the vast majority of cases, reduction of the fracture relieves the vascular kinking and restores the pulse. Vascular exploration is only indicated if the hand remains pulseless and becomes poorly perfused (cold/white) after successful fracture reduction and pinning.

Question 20

A 15-year-old male presents with a painful mass in the mid-diaphysis of his humerus. Radiographs show a permeative, "moth-eaten" lytic lesion with an "onion skin" periosteal reaction. Biopsy reveals small, round, blue cells. Molecular genetic testing is performed. Which of the following chromosomal translocations is the hallmark of this malignancy?

Explanation

The clinical and radiographic presentation is classic for Ewing sarcoma. Ewing sarcoma is a small round blue cell tumor characterized genetically by the t(11;22)(q24;q12) translocation in >90% of cases. This translocation fuses the EWS gene on chromosome 22 with the FLI1 gene on chromosome 11, creating the EWS-FLI1 fusion protein, which acts as an aberrant transcription factor driving oncogenesis. t(9;22) is the Philadelphia chromosome (CML). t(X;18) is seen in synovial sarcoma. t(2;13) is characteristic of alveolar rhabdomyosarcoma. t(12;16) is seen in myxoid liposarcoma.

Question 21

A hemodynamically unstable 45-year-old male is brought to the trauma bay after a severe motorcycle crash. A pelvic binder is applied for an anterior-posterior compression (APC) III pelvic ring injury. FAST examination is negative. Despite massive transfusion protocol, the patient remains persistently hypotensive. What is the most appropriate next step in management?

Explanation

In a hemodynamically unstable patient with a pelvic fracture, a negative FAST scan, and a properly placed pelvic binder, persistent shock is typically due to retroperitoneal venous or cancellous bone bleeding. Preperitoneal pelvic packing is the immediate treatment of choice in extremis to mechanically tamponade the bleeding. Angiography may follow if packing fails to control arterial bleeding.

Question 22

A 35-year-old male presents with chronic, progressive right hip pain. Radiographs reveal a well-defined lytic lesion in the proximal femur epiphysis with central calcifications. Biopsy demonstrates sheets of cells with abundant clear cytoplasm, distinct cytoplasmic borders, and an underlying cartilaginous matrix. What is the most appropriate definitive treatment?

Explanation

The clinical and histological description is classic for clear cell chondrosarcoma, a rare, low-grade malignant cartilage tumor that preferentially involves the epiphysis of long bones (especially the proximal femur or humerus). Despite being low-grade, it has an unacceptably high local recurrence rate with intralesional curettage alone; therefore, wide surgical resection is the standard of care.

Question 23

A 42-year-old heavy laborer presents with progressive wrist pain. Radiographs reveal a scaphoid nonunion advanced collapse (SNAC) pattern with severe arthritic changes at the radioscaphoid and capitolunate joints, but the radiolunate joint is perfectly preserved (SNAC Stage III). He desires pain relief but needs to return to heavy manual labor. Which of the following is the most appropriate surgical option?

Explanation

SNAC Stage III involves arthritis of both the radioscaphoid and capitolunate joints. Proximal row carpectomy (PRC) relies on an intact, cartilage-covered capitate head to articulate with the lunate fossa; therefore, capitate arthritis is an absolute contraindication to PRC. Four-corner arthrodesis with scaphoid excision removes the arthritic joints while preserving the pristine radiolunate articulation, providing durable pain relief and strength for a heavy laborer.

Question 24

A 3-year-old girl is evaluated for worsening bilateral genu varum. Standing radiographs demonstrate a metaphyseal-diaphyseal angle (MDA) of 18 degrees and depression of the medial tibial metaphysis with a distinct medial beak. According to the Langenskiöld classification of infantile Blount's disease, at which stage does the proximal tibial epiphysis fuse with the metaphysis to form a frank medial physeal bar?

Explanation

The Langenskiöld classification stages the progressive radiographic changes in infantile Blount's disease. Stage VI is the final and most severe stage, characterized by complete fusion of the medial aspect of the epiphysis to the metaphysis, forming a permanent bony physeal bar that requires surgical resection and corrective osteotomy.

Question 25

A 68-year-old patient undergoes a primary total hip arthroplasty (THA). Over the next 6 months, the patient experiences recurrent anterior hip dislocations. Which of the following combinations of component positioning is the most likely biomechanical cause of these recurrent anterior dislocations?

Explanation

Anterior dislocation in THA is typically the result of excessive combined anteversion (i.e., excessive acetabular anteversion coupled with excessive femoral anteversion). This position causes the femoral head to lever out of the front of the socket during hip extension and external rotation.

Question 26

A 50-year-old male presents with acute severe right-sided neck pain that radiates down his arm to his middle finger. Neurological examination reveals marked weakness in elbow extension and wrist flexion, as well as an absent triceps reflex. A herniated nucleus pulposus is suspected at which of the following cervical disc levels?

Explanation

The patient's findings (weakness in elbow extension and wrist flexion, absent triceps reflex, and sensory changes in the middle finger) are classic for a C7 radiculopathy. In the cervical spine, nerve roots exit above their corresponding pedicle. Therefore, the C7 nerve root is compressed by a posterolateral disc herniation at the C6-C7 level.

Question 27

A 22-year-old soccer player sustains a non-contact twisting injury to his left knee. Radiographs in the emergency department reveal an avulsion fracture of the lateral aspect of the proximal tibia (Segond fracture). In addition to an anterior cruciate ligament (ACL) rupture, which of the following capsuloligamentous structures is specifically avulsed to create this fracture?

Explanation

A Segond fracture is a cortical avulsion off the anterolateral proximal tibia. It is pathognomonic for an ACL tear and represents an avulsion of the anterolateral capsule and the anterolateral ligament (ALL). The ITB inserts on Gerdy's tubercle, which is located more anteriorly.

Question 28

During fracture healing, bone morphogenetic proteins (BMPs) play a crucial role in osteoinduction by directing mesenchymal stem cells to differentiate into osteoblasts. Which of the following BMPs is FDA-approved for use in acute open tibial shaft fractures treated with an intramedullary nail?

Explanation

Recombinant human BMP-2 (rhBMP-2, commercial name Infuse) is currently FDA-approved for the treatment of acute, open tibial shaft fractures stabilized with an intramedullary nail, as well as for anterior lumbar interbody fusions (ALIF). rhBMP-7 (OP-1) previously had a humanitarian device exemption for recalcitrant tibial nonunions.

Question 29

A 55-year-old diabetic male with peripheral neuropathy presents with a markedly swollen, warm, and erythematous left foot. Pulses are bounding. Radiographs demonstrate acute periarticular fragmentation, bony debris, and early subluxation at the tarsometatarsal joints. According to the Eichenholtz classification of Charcot neuroarthropathy, which stage does this represent?

Explanation

The Eichenholtz classification of Charcot arthropathy includes three main stages (plus a more recently recognized Stage 0). Stage I is the Development/Fragmentation phase, characterized clinically by a red, hot, swollen foot and radiographically by bony debris, fragmentation, and joint subluxation/dislocation. Stage II is Coalescence (absorption of fine debris, early fusion), and Stage III is Consolidation (remodeling and stable deformity).

Question 30

A 32-year-old female sustains a closed distal-third spiral fracture of the humeral shaft (Holstein-Lewis fracture). On initial examination in the emergency department, she has a complete radial nerve palsy. What is the most appropriate initial management of the nerve injury?

Explanation

A primary radial nerve palsy in the setting of a closed humeral shaft fracture (including the Holstein-Lewis type) has a high rate of spontaneous recovery (70-90%). The standard of care is observation and supportive splinting (e.g., dynamic extension splint). Surgical exploration is generally indicated for open fractures, associated vascular injuries, or secondary nerve palsies that develop after closed reduction.

Question 31

During arthroscopic stabilization for a 20-year-old athlete with recurrent anterior shoulder instability, the surgeon visualizes an anterior capsulolabral injury. The labrum and the anterior band of the inferior glenohumeral ligament (IGHL) are stripped off the glenoid and medially displaced along the scapular neck, but the anterior periosteal sleeve remains intact. This lesion is most accurately classified as which of the following?

Explanation

An ALPSA (Anterior Labroligamentous Periosteal Sleeve Avulsion) lesion occurs when the anterior labrum and IGHL are avulsed and displace medially along the scapular neck, but the underlying periosteum remains intact. A classic Bankart lesion involves a complete tear of the labrum and periosteum. A Perthes lesion has an intact periosteum but the labrum is non-displaced.

Question 32

A 12-year-old obese boy presents with an acute-on-chronic slipped capital femoral epiphysis (SCFE) of his left hip. In which of the following clinical scenarios is prophylactic percutaneous pinning of the contralateral right hip most strongly indicated?

Explanation

While prophylactic pinning of the contralateral hip in SCFE remains controversial in idiopathic cases, it is strongly indicated in patients with underlying endocrine or metabolic disorders (e.g., hypothyroidism, renal osteodystrophy, growth hormone deficiency). These patients have an exceedingly high risk (often approaching 100%) of bilateral involvement.

Question 33

A 65-year-old female returns to the clinic 8 months after a posterior-stabilized (PS) total knee arthroplasty. She reports a painful catching and popping sensation in her anterior knee when extending the leg from a flexed position. What is the most likely etiology of her symptoms?

Explanation

The patient is describing 'patellar clunk syndrome,' which classically occurs in posterior-stabilized (PS) total knee replacements. It is caused by the formation of a fibrosynovial nodule on the undersurface of the quadriceps tendon/superior pole of the patella. During knee extension from a flexed position, this nodule catches in the intercondylar box of the femoral component, producing a painful 'clunk'.

Question 34

A 28-year-old carpenter suffers a deep laceration to the volar aspect of his index finger. Surgical exploration reveals complete transection of both the flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP) tendons within the fibro-osseous sheath, between the proximal edge of the A1 pulley and the FDS insertion. This injury is located in which flexor tendon zone?

Explanation

Flexor tendon Zone II, historically called 'no man's land' due to the poor surgical outcomes of the past, extends from the proximal edge of the A1 pulley to the insertion of the FDS tendon on the middle phalanx. Both the FDS and FDP travel tightly together within the fibro-osseous sheath in this zone.

Question 35

A 68-year-old man presents with bilateral leg pain, heaviness, and cramping that predictably worsens with walking. Which of the following historical findings most reliably helps to differentiate neurogenic claudication (due to lumbar spinal stenosis) from vascular claudication?

Explanation

Neurogenic claudication is exacerbated by lumbar extension (which decreases the cross-sectional area of the spinal canal) and relieved by lumbar flexion, such as sitting or leaning forward (the 'shopping cart sign'). Vascular claudication is related to muscle ischemia during activity and is typically relieved rapidly by simply stopping the activity (standing still), without requiring a change in spine posture.

Question 36

A 45-year-old pedestrian is struck by a motor vehicle and sustains a severe right knee injury. Radiographs and CT imaging demonstrate a bicondylar fracture involving both the medial and lateral tibial plateaus, with complete dissociation of the articular surfaces from the underlying tibial diaphysis. According to the Schatzker classification, what is the grade of this fracture?

Explanation

The Schatzker classification divides tibial plateau fractures into six types. Schatzker V is a bicondylar fracture but maintains continuity between the epiphysis/metaphysis and the diaphysis. Schatzker VI involves a bicondylar fracture with complete metaphyseal-diaphyseal dissociation, separating the articular block from the shaft.

Question 37

In the manufacturing of modern highly cross-linked ultra-high-molecular-weight polyethylene (UHMWPE) for total joint arthroplasty, what is the primary biomechanical and chemical purpose of adding vitamin E (alpha-tocopherol) to the polymer?

Explanation

Irradiation is used to heavily cross-link UHMWPE to reduce wear, but it leaves behind free radicals. Over time, these free radicals can react with oxygen in vivo, leading to oxidative degradation, embrittlement, and failure. Vitamin E (alpha-tocopherol) is a potent antioxidant added to scavenge these free radicals, neutralizing them without needing secondary thermal treatments (like remelting) which can reduce mechanical strength.

Question 38

A 35-year-old recreational athlete sustains an acute closed Achilles tendon rupture. He discusses treatment options and ultimately elects for non-operative management utilizing an early functional rehabilitation protocol. Based on modern randomized controlled trials, how do the outcomes of this non-operative approach compare to surgical repair?

Explanation

Historically, non-operative management with prolonged cast immobilization was associated with higher re-rupture rates compared to surgery. However, modern level I studies (e.g., Willits et al.) have demonstrated that non-operative management utilizing early weight-bearing and functional rehabilitation protocols results in equivalent re-rupture rates and functional outcomes to surgical repair, while entirely avoiding surgical complications such as infection and wound breakdown.

Question 39

A 30-year-old female presents with severe knee pain. Imaging reveals an eccentric, expansile lytic lesion in the distal femoral epiphysis that extends down to the subchondral bone. Biopsy confirms a Giant Cell Tumor (GCT) of bone. To reduce tumor size, minimize surgical morbidity, and limit recurrence, the multidisciplinary tumor board recommends preoperative therapy with a systemic agent that directly targets the RANK ligand. Which of the following drugs is indicated?

Explanation

Giant Cell Tumor of bone is driven by neoplastic stromal cells that secrete large amounts of RANK ligand, which recruits and activates the osteoclast-like giant cells responsible for the massive bone destruction. Denosumab is a human monoclonal antibody that binds to RANKL, inhibiting this pathway. It is highly effective in treating GCT, inducing ossification of the tumor and making complex joint-salvage surgeries feasible.

Question 40

A 6-week-old infant is diagnosed with Developmental Dysplasia of the Hip (DDH) and is subsequently placed in a Pavlik harness for treatment. The treating physician must carefully adjust the straps to maintain the hips in approximately 100 degrees of flexion and safe abduction. If the anterior straps are pulled too tight, causing hyperflexion of the hips beyond 120 degrees, which of the following complications is most likely to occur?

Explanation

In the application of a Pavlik harness, hyperflexion of the hips (>120 degrees) can compress the femoral nerve against the inguinal ligament, leading to an iatrogenic femoral nerve palsy (presenting as decreased quadriceps function/loss of active knee extension). Conversely, excessive forced abduction is classically associated with avascular necrosis (AVN) of the femoral head.

Question 41

A 6-week-old female is undergoing treatment for developmental dysplasia of the hip (DDH) with a Pavlik harness. During a follow-up visit, the parents note she has stopped kicking her left leg. Examination reveals decreased active extension of the left knee but normal ankle movements. What is the most likely iatrogenic cause of this presentation?

Explanation

Hyperflexion of the hip in a Pavlik harness can compress the femoral nerve against the inguinal ligament, leading to a femoral nerve palsy. This manifests clinically as decreased active knee extension. It is generally treated by adjusting the harness to reduce the degree of hip flexion. Excessive abduction is notoriously associated with avascular necrosis (AVN) of the femoral head, not isolated femoral nerve palsy.

Question 42

When utilizing a posteromedial approach for the open reduction and internal fixation of a posterior shearing tibial plateau fracture, the deep surgical interval is created between which two muscular structures?

Explanation

The classic posteromedial approach to the tibial plateau relies on developing the interval between the pes anserinus tendons (anteriorly/medially) and the medial head of the gastrocnemius (posteriorly). The medial gastrocnemius is retracted laterally along with the popliteal neurovascular bundle to expose the posterior joint capsule and posteromedial tibia.

Question 43

During the harvest of a hamstring autograft for an anterior cruciate ligament (ACL) reconstruction, care must be taken to avoid injury to a cutaneous nerve that supplies sensation to the anteromedial aspect of the lower leg. This nerve is a direct terminal branch of which of the following nerves?

Explanation

The saphenous nerve is at high risk of iatrogenic injury during hamstring graft harvest, which can result in anteromedial leg numbness or a painful neuroma. The saphenous nerve is the largest and longest cutaneous terminal branch of the femoral nerve.

Question 44

In the progression of Scaphoid Nonunion Advanced Collapse (SNAC), which of the following carpal articulations is characteristically spared from osteoarthritic changes until the terminal stages of the disease process?

Explanation

In both SLAC (Scapholunate Advanced Collapse) and SNAC wrists, the radiolunate joint is uniquely spared from early osteoarthritic changes. This is due to the concentric, spherical articulation of the lunate within the lunate fossa of the distal radius, which continues to distribute compressive loads evenly despite the loss of carpal stability. SNAC progression typically begins at the radial styloid-scaphoid articulation, moves to the entire radioscaphoid joint, and then involves the capitolunate joint.

Question 45

Ossification of the posterior longitudinal ligament (OPLL) is a frequent cause of cervical myelopathy, particularly in East Asian populations. Which of the following genes has been most strongly associated with the pathogenesis of OPLL?

Explanation

Mutations and polymorphisms in the ENPP1 (ectonucleotide pyrophosphatase/phosphodiesterase 1) gene have been strongly linked to the development of OPLL. ENPP1 is a key regulator of bone mineralization and inorganic pyrophosphate levels; altered expression contributes to the ectopic ossification seen in OPLL.

Question 46

A 55-year-old active male presents with an audible 'squeaking' sound originating from his total hip arthroplasty (THA), performed 3 years ago. He is asymptomatic and denies pain. Radiographs show a ceramic-on-ceramic bearing surface. What surgical factor is most consistently associated with the generation of this noise?

Explanation

Squeaking is a specific, known complication of ceramic-on-ceramic THA bearings. The strongest biomechanical predictor for squeaking is component malposition, specifically high acetabular inclination (a 'steep cup' usually >45-50 degrees) or abnormal version. This geometry leads to edge loading, a loss of the fluid film lubrication, micro-separation, and subsequent stripe wear that generates the acoustic phenomenon.

Question 47

A 22-year-old male presents with dull, aching thoracic back pain that is not significantly relieved by NSAIDs. CT imaging demonstrates a 3.5 cm expansile, lytic lesion in the posterior elements of T11 with a thin sclerotic rim. Histology reveals interlacing trabeculae of woven bone lined by prominent osteoblasts in a highly vascular stroma. What is the most likely diagnosis?

Explanation

The clinical presentation, anatomic location (posterior elements of the spine), size (>2 cm), and histologic appearance (woven bone, prominent osteoblasts, vascular stroma) are diagnostic of osteoblastoma. Osteoid osteoma shares identical histology but is defined clinically and radiographically as being smaller (typically <1.5-2.0 cm) and the pain is classically dramatically relieved by NSAIDs.

Question 48

According to Perren's strain theory of bone healing, what is the maximum interfragmentary strain environment that will permit primary (contact) bone healing to occur via osteoclast cutting cones?

Explanation

Perren's strain theory dictates that primary (direct) bone healing, characterized by Haversian remodeling and osteoclast cutting cones without intermediate cartilage formation, requires absolute stability. This corresponds to an interfragmentary strain of less than 2%. Strains between 2% and 10% permit secondary healing (endochondral ossification/callus), while strains greater than 10% result in fibrous nonunion.

Question 49

A patient undergoes a percutaneous repair of an acute Achilles tendon rupture. Postoperatively, he complains of burning pain, numbness, and tingling along the lateral border of his foot. Which nerve was most likely entrapped or injured during the surgical procedure?

Explanation

The sural nerve is highly vulnerable to injury or suture entrapment during percutaneous, minimally invasive, or even open Achilles tendon repairs. It courses proximally to distally, crossing from medial to lateral over the Achilles tendon approximately 10-12 cm proximal to the calcaneal insertion, and provides sensation to the posterolateral distal leg and lateral aspect of the foot.

Question 50

During an anterior (ilioinguinal) surgical approach to the pelvic ring for an acetabular fracture, life-threatening hemorrhage can occur if a vascular structure known as the 'corona mortis' is inadvertently lacerated. This vascular anomaly represents an anastomosis between which two vascular systems?

Explanation

The corona mortis ('crown of death') is an important vascular anastomosis (arterial, venous, or both) connecting the external iliac system (commonly via the inferior epigastric vessels) with the obturator system (internal iliac). It is located on the posterior aspect of the superior pubic ramus and is highly susceptible to injury during anterior approaches to the acetabulum.

Question 51

In the digital flexor tendon pulley system of the hand, which two annular pulleys are biomechanically the most critical to preserve during surgery in order to prevent bowstringing of the flexor tendons?

Explanation

The A2 and A4 pulleys are the major annular pulleys of the digits. The A2 pulley originates from the periosteum of the proximal phalanx, and the A4 pulley originates from the middle phalanx. Biomechanically, they are the most critical structures in maintaining the mechanical advantage of the flexor tendons; isolated loss of either, or certainly both, leads to severe bowstringing and loss of active flexion arc.

Question 52

Which of the following patients presenting with a unilateral slipped capital femoral epiphysis (SCFE) has the strongest clinical indication for prophylactic in-situ pinning of the contralateral, asymptomatic hip?

Explanation

Prophylactic pinning of the contralateral hip in SCFE is strongly recommended for patients presenting with an underlying endocrine or metabolic disorder (e.g., hypothyroidism, renal osteodystrophy, growth hormone supplementation). These atypical patients have an extraordinarily high risk (approaching 100% in some series) of developing bilateral disease compared to the idiopathic adolescent population.

Question 53

A 68-year-old man presents with bilateral leg pain and fatigue when walking. He notes the symptoms resolve quickly when he sits down or leans over a shopping cart. To formally differentiate neurogenic claudication from vascular claudication, a bicycle test (van Gelderen test) is performed. Which outcome is characteristic of neurogenic claudication secondary to lumbar spinal stenosis?

Explanation

In the van Gelderen bicycle test, a patient with neurogenic claudication can pedal longer and with less leg pain when the lumbar spine is flexed (leaning forward), because this posture increases the cross-sectional area of the spinal canal and neural foramina. In contrast, patients with vascular claudication experience ischemia-induced pain based on muscle work, regardless of spinal posture.

Question 54

A patient who underwent a primary posterior stabilized (PS) total knee arthroplasty 18 months ago presents with anterior knee pain and a painful 'catching' or 'popping' sensation when extending the knee from a flexed position. What is the most likely pathophysiologic mechanism for this specific complication?

Explanation

This is the classic presentation of 'patellar clunk syndrome,' a complication seen almost exclusively in posterior stabilized (PS) TKA designs. It is caused by the formation of a proliferative fibrous nodule at the superior pole of the patella or distal quadriceps tendon. As the knee extends from flexion, this nodule catches in the intercondylar box (cam mechanism) of the femoral component, popping out with an audible or palpable clunk.

Question 55

In the surgical management of recurrent anterior shoulder instability, what is the primary biomechanical objective of the arthroscopic Remplissage procedure?

Explanation

The Remplissage (French for 'to fill') procedure involves tenodesis of the infraspinatus tendon and posterior joint capsule into a large, engaging (off-track) Hill-Sachs lesion. The primary biomechanical goal is to prevent the bony defect from engaging the anterior glenoid rim during external rotation and abduction, effectively converting an intra-articular defect into an extra-articular one.

Question 56

A 6-year-old boy is brought to the emergency department after falling off monkey bars. Radiographs reveal a completely displaced extension-type supracondylar humerus fracture (Gartland Type III). On examination, the child's hand is warm and pink with brisk capillary refill, but the radial pulse is not palpable. What is the most appropriate initial management?

Explanation

For a 'pulseless, pink hand' in the setting of a displaced supracondylar humerus fracture, the standard of care is urgent closed reduction and percutaneous pinning (CRPP). The pulselessness is often due to kinking, compression, or spasm of the brachial artery over the fracture fragments. Reduction usually restores flow. If the hand remains pink and well-perfused post-reduction, even without a palpable pulse, close observation is recommended over routine surgical exploration.

Question 57

In orthopedic biomechanics, stress shielding around an implant is largely determined by the mismatch in stiffness between the implant material and the host bone. Which of the following values best approximates the modulus of elasticity (Young's modulus) of normal human cortical bone?

Explanation

The modulus of elasticity (stiffness) of cortical bone is approximately 15-20 GPa. For comparison, cancellous bone is much more flexible (0.1-2 GPa). Titanium alloys used in orthopedics have a modulus around 110 GPa, and Stainless Steel/Cobalt-Chrome alloys are around 200-220 GPa. The large difference between metal implants and cortical bone is the primary driver of stress shielding.

Question 58

A 24-year-old athlete sustains a severe midfoot injury. Radiographs demonstrate widening between the first and second metatarsal bases and a small bony avulsion fragment in this interval, commonly known as the 'Fleck sign.' This avulsed fragment represents the attachment of the Lisfranc ligament, which originates on which of the following bones?

Explanation

The Lisfranc ligament is a stout, interosseous ligament that is crucial for midfoot stability. It originates on the lateral aspect of the medial cuneiform and inserts on the medial aspect of the base of the second metatarsal. The 'Fleck sign' represents a bony avulsion of this ligament, usually from the second metatarsal base, indicating a severe disruption of the Lisfranc complex.

Question 59

Giant cell tumor of bone (GCTB) is a locally aggressive benign tumor. In cases where surgery is morbid and systemic therapy with Denosumab is utilized, what specific molecular interaction is being targeted by this medication?

Explanation

Denosumab is a fully human monoclonal antibody that specifically binds to RANKL (Receptor Activator of Nuclear factor Kappa-B Ligand). In GCTB, the neoplastic mononuclear stromal cells overexpress RANKL, which recruits and activates the reactive, bone-resorbing multinucleated giant cells. By inhibiting RANKL, Denosumab breaks this cycle, preventing giant cell formation and halting osteolysis.

Question 60

During the surgical decompression of the ulnar nerve for cubital tunnel syndrome, multiple potential sites of anatomic compression must be addressed. Which of the following represents the most proximal potential site of ulnar nerve entrapment in the arm?

Explanation

The Arcade of Struthers is a thin fascial band extending from the medial head of the triceps to the medial intermuscular septum, located approximately 8 cm proximal to the medial epicondyle. It represents the most proximal potential site of ulnar nerve compression. Note: The Ligament of Struthers is a distinct structure associated with the supracondylar process that can compress the median nerve, not the ulnar nerve.

Question 61

The primary cell responsible for particle-induced osteolysis in total hip arthroplasty responds most vigorously to polyethylene wear particles of what size?

Explanation

Macrophages are the primary cells responsible for the biological response to polyethylene wear debris, leading to osteolysis. The most biologically active particles are submicron in size, specifically in the 0.1 to 1.0 µm range. Particles of this size are readily phagocytosed, triggering the release of pro-inflammatory cytokines (like TNF-alpha, IL-1, IL-6) that stimulate osteoclastogenesis.

Question 62

A 25-year-old male presents with a deep, slow-growing soft tissue mass in his foot. Biopsy reveals a biphasic tumor with both epithelial and spindle cell components. Which chromosomal translocation is most characteristic of this lesion?

Explanation

The clinical and histological description (biphasic tumor with epithelial and spindle cells in a young adult's distal extremity) is classic for synovial sarcoma. Synovial sarcoma is characterized by the t(X;18) translocation, resulting in the SYT-SSX fusion gene. Options 0, 2, 3, and 4 refer to Ewing sarcoma, myxoid liposarcoma, alveolar rhabdomyosarcoma, and extraskeletal myxoid chondrosarcoma, respectively.

Question 63

A 22-year-old elite baseball pitcher complains of posterior shoulder pain during the late cocking phase of throwing. Physical examination reveals a positive apprehension test that is relieved by a relocation maneuver. MRI arthrogram is likely to show a SLAP tear along with what other pathology?

Explanation

This presentation describes internal impingement, which is a common cause of posterior shoulder pain in overhead throwing athletes. During extreme abduction and external rotation (late cocking phase), the articular surface of the posterior rotator cuff (supraspinatus/infraspinatus) becomes impinged between the greater tuberosity and the posterosuperior glenoid labrum. This leads to articular-sided partial cuff tears and posterosuperior labral lesions (often manifesting as SLAP tears).

Question 64

A patient presents with an inability to form an 'OK' sign, instead demonstrating a flat, pulp-to-pulp pinch. Sensation in the hand is completely normal. Which of the following muscles is innervated by the affected nerve?

Explanation

The clinical sign described (inability to flex the IP joint of the thumb and DIP joint of the index finger) is classic for Anterior Interosseous Nerve (AIN) syndrome. The AIN is a pure motor branch of the median nerve and innervates the flexor pollicis longus (FPL), the radial half of the flexor digitorum profundus (FDP to index and middle fingers), and the pronator quadratus.

Question 65

A 45-year-old man presents with neck pain radiating down his right arm. Examination reveals weakness in wrist extension, a diminished brachioradialis reflex, and numbness over the dorsal web space of the thumb and index finger. Which cervical nerve root is most likely affected?

Explanation

The C6 nerve root provides motor innervation for wrist extension and elbow flexion (along with C5), mediates the brachioradialis reflex, and supplies sensation to the radial aspect of the forearm, thumb, and index finger. A C5 radiculopathy affects shoulder abduction and the biceps reflex; C7 affects triceps and wrist flexion; C8 affects finger flexion; and T1 affects finger abduction.

Question 66

In a patient presenting with a unilateral slipped capital femoral epiphysis (SCFE), which of the following is considered an absolute indication for prophylactic in situ pinning of the contralateral asymptomatic hip?

Explanation

Prophylactic pinning of the contralateral hip in SCFE is strongly indicated for patients with underlying endocrine disorders (such as hypothyroidism, panhypopituitarism, renal osteodystrophy), patients previously treated with radiation therapy, and typically in children presenting at a young age (< 10 years). These patients have an exceptionally high risk of developing a contralateral slip.

Question 67

In a posterior pelvic ring disruption involving a severe sacroiliac joint dislocation, which arterial vessel is most vulnerable to direct injury and represents the most common source of major pelvic arterial hemorrhage?

Explanation

In unstable pelvic ring fractures with posterior disruption (e.g., severe sacroiliac joint dislocation or sacral fractures), the superior gluteal artery is the most frequently injured artery. It exits the pelvis through the greater sciatic notch in close proximity to the sacroiliac joint. Anterior ring fractures (like pubic rami fractures) are more associated with obturator or internal pudendal artery injuries, or the corona mortis.

Question 68

The primary Lisfranc ligament, critical for midfoot stability, connects which two osseous structures?

Explanation

The Lisfranc ligament is an interosseous ligament that originates from the lateral surface of the medial cuneiform and attaches to the medial aspect of the base of the second metatarsal. It is the largest and most crucial ligament for maintaining the stability of the tarsometatarsal joint complex. There is no ligamentous connection between the base of the first and second metatarsals.

Question 69

Which of the following femoral stem designs in total hip arthroplasty is most closely associated with extensive proximal stress shielding of the femur?

Explanation

Stress shielding occurs according to Wolff's law when the mechanical load is bypassed away from the bone and absorbed by the implant. Fully porous-coated cylindrical stems achieve extensive diaphyseal (distal) fixation. Because the stem rigidly loads the bone distally, the proximal femur is 'shielded' from stress, leading to proximal bone resorption (stress shielding). Proximally coated or tapered wedges rely on proximal loading, thereby minimizing this effect.

Question 70

Tranexamic acid (TXA) is widely utilized in orthopedic surgery to minimize perioperative blood loss. What is its primary mechanism of action?

Explanation

Tranexamic acid is a synthetic analog of the amino acid lysine. It acts as an antifibrinolytic by reversibly binding to the lysine binding sites on plasminogen molecules. This prevents plasminogen from binding to fibrin, thereby inhibiting its activation into plasmin and preventing the breakdown of existing blood clots.

Question 71

A 14-year-old female gymnast presents with progressive lower back pain. Radiographs demonstrate an isthmic spondylolisthesis at L5-S1 with 60% anterior translation of L5 on S1. According to the Meyerding classification, what grade is this slip, and what is the generally recommended definitive surgical management?

Explanation

The Meyerding classification grades the degree of anterior translation: Grade I (0-25%), Grade II (26-50%), Grade III (51-75%), Grade IV (76-100%), and Grade V (>100% or spondyloptosis). A 60% slip is Grade III. High-grade slips (III, IV, V) in symptomatic adolescents are generally unstable and require stabilization via fusion (usually L5-S1 or L4-S1 with instrumentation). Pars repairs (e.g., Buck's, Scott wiring) are reserved for symptomatic Grade I slips or spondylolysis without significant slip.

Question 72

During surgical approach to the flexor tendon sheath in the hand, care is taken to preserve specific annular pulleys to prevent bowstringing of the flexor tendons. Which combination of pulleys is biomechanically considered the most critical to preserve?

Explanation

The flexor tendon sheath contains five annular (A) and three cruciate (C) pulleys. The A2 pulley (over the proximal phalanx) and A4 pulley (over the middle phalanx) are thick, robust, and biomechanically critical for preventing bowstringing of the flexor tendons. Their preservation or reconstruction is essential for maintaining efficient finger flexion mechanics.

Question 73

A 55-year-old man is diagnosed with a conventional Grade II chondrosarcoma of the proximal femur. What is the most appropriate definitive surgical management?

Explanation

Conventional chondrosarcoma is notoriously resistant to both chemotherapy and radiation. Thus, surgical resection is the primary modality of treatment. While Grade I (atypical cartilaginous tumors) in the appendicular skeleton can sometimes be managed with extended curettage, Grade II and Grade III (high-grade) conventional chondrosarcomas require wide en bloc resection to minimize local recurrence. Reconstruction follows.

Question 74

A patient develops an inability to actively flex the interphalangeal joint of the thumb 6 months after a volar locked plating procedure for a distal radius fracture. This complication is most commonly associated with which surgical error?

Explanation

Rupture of the flexor pollicis longus (FPL) tendon is a recognized and dreaded complication of volar plating of distal radius fractures. It most commonly occurs due to attrition of the tendon rubbing against the prominent distal edge of a plate placed distal to the 'watershed line' (the bony prominence on the volar aspect of the distal radius). Overpenetration of dorsal screws risks extensor tendon rupture (often EPL).

Question 75

Which type of osteosynthesis provides absolute stability, resulting in primary (direct) bone healing without the formation of a visible fracture callus?

Explanation

Primary (direct) bone healing occurs under conditions of absolute stability (no interfragmentary strain) and direct bone contact. It involves direct Haversian remodeling across the fracture without intermediate callus formation. Compression plating of a transverse fracture provides this absolute stability. Nailing, bridge plating, external fixation, and casting provide relative stability, leading to secondary bone healing (with endochondral ossification and visible callus).

Question 76

In the Ponseti method for correcting idiopathic clubfoot, what is the correct anatomical sequence of deformity correction?

Explanation

The Ponseti method follows a strict, step-wise sequence for clubfoot correction, easily remembered by the acronym CAVE: Cavus (corrected by elevating the first ray), Adductus, Varus (adductus and varus corrected simultaneously by abducting the midfoot with counter-pressure on the lateral head of the talus), and finally Equinus (corrected last, often requiring a percutaneous Achilles tenotomy).

Question 77

A 55-year-old female presents with stage IIb adult-acquired flatfoot deformity (posterior tibial tendon insufficiency), characterized by flexible flatfoot and more than 40% uncovering of the talonavicular joint. Which of the following surgical procedures is most appropriate?

Explanation

Adult-acquired flatfoot Stage II is a flexible deformity. Stage IIa has minimal forefoot abduction, typically managed with a medial displacement calcaneal osteotomy (MDCO) and FDL transfer. Stage IIb features significant forefoot abduction (> 40% talonavicular uncovering), which necessitates an additional lateral column lengthening (e.g., Evans osteotomy) to correct the forefoot abduction, along with MDCO and FDL transfer. Stage III (rigid) requires arthrodesis (e.g., triple).

Question 78

According to the Schatzker classification for tibial plateau fractures, a bicondylar fracture involving both the medial and lateral plateaus is classified as which type?

Explanation

The Schatzker classification separates tibial plateau fractures into six types: I (lateral split), II (lateral split-depression), III (lateral pure depression), IV (medial plateau), V (bicondylar plateau), and VI (plateau with diaphyseal-metaphyseal dissociation). A bicondylar fracture without complete dissociation from the diaphysis is a Type V.

Question 79

During a total knee arthroplasty, the surgeon utilizes gap balancing. Evaluation reveals that the extension gap is symmetric and rectangular. However, the flexion gap is asymmetric: tight medially and loose laterally. What is the most appropriate surgical maneuver to balance the knee?

Explanation

A tight medial/loose lateral flexion gap with a balanced extension gap implies an isolated asymmetry in flexion. Externally rotating the femoral component moves the medial posterior femoral condyle anteriorly (decreasing its thickness) and the lateral posterior condyle posteriorly (increasing its thickness). This effectively loosens the tight medial side and tightens the loose lateral side in flexion, without altering the symmetric extension gap. Releasing the MCL would inappropriately open the medial side in extension as well.

Question 80

In a patient presenting with suspected cauda equina syndrome secondary to a massive L4-L5 disc herniation, which urodynamic finding is most characteristic of the resulting neurogenic bladder?

Explanation

Cauda equina syndrome causes compression of the lumbosacral nerve roots below the conus medullaris, constituting a lower motor neuron (LMN) lesion. This disruption of the parasympathetic outflow (S2-S4) to the bladder results in a flaccid, areflexic bladder (detrusor areflexia). Consequently, the bladder fails to contract, leading to urinary retention, large volumes, and eventually overflow incontinence. Hyperreflexia and dyssynergia are characteristics of upper motor neuron (UMN) lesions (above the conus).

Question 81

A 45-year-old female presents with the inability to actively extend her thumb interphalangeal joint 3 months after undergoing open reduction and internal fixation of a distal radius fracture with a volar locking plate. Radiographs reveal a healed fracture with a prominent screw protruding through the dorsal cortex. What is the most likely diagnosis?

Explanation

Extensor pollicis longus (EPL) rupture is a known complication of distal radius fractures treated with volar plating. It typically occurs due to mechanical attrition and friction over prominent dorsal screws that protrude past the dorsal cortex.

Question 82

A 6-year-old boy falls from monkey bars and sustains a completely displaced extension-type supracondylar humerus fracture. On examination, his hand is warm, pink, and well-perfused, but the radial pulse is absent. What is the most appropriate next step in management?

Explanation

In a pediatric supracondylar humerus fracture with a "pink, pulseless" hand, the initial step is emergent closed reduction and percutaneous pinning to realign the anatomy and relieve vascular kinking. Arterial exploration is generally reserved for hands that remain poorly perfused (white and pulseless) after a satisfactory reduction.

Question 83

A 45-year-old man presents with right lower extremity weakness and radicular pain radiating to the dorsum of his foot following heavy lifting. MRI reveals a massive posterolateral disc herniation at the L4-L5 level. Which of the following physical examination findings is most likely to be present?

Explanation

A posterolateral disc herniation at the L4-L5 level most commonly compresses the traversing L5 nerve root. L5 radiculopathy typically presents with weakness in the extensor hallucis longus (EHL) and altered sensation over the first dorsal web space.

Question 84

A 15-year-old boy presents with progressive knee pain and a palpable mass in the distal femoral diaphysis. Radiographs demonstrate a permeative, destructive bone lesion with an "onion skin" periosteal reaction. Biopsy confirms small round blue cells. Which of the following cytogenetic abnormalities is most characteristic of this tumor?

Explanation

The clinical presentation, "onion skin" periosteal reaction, and small round blue cell histology are characteristic of Ewing sarcoma. This tumor is strongly associated with the t(11;22) chromosomal translocation, which creates the EWS-FLI1 fusion protein.

Question 85

A 60-year-old male presents with worsening clumsiness in his hands, frequent falls, and a wide-based gait. During physical examination, flicking the volar surface of the distal phalanx of the middle finger results in rapid reflex flexion of the thumb and index finger. What is this clinical sign called?

Explanation

The Hoffmann sign is a classic upper motor neuron reflex elicited by flicking the nail of the middle finger, causing flexion of the thumb and index finger. It is a key clinical finding indicating spinal cord compression in cervical spondylotic myelopathy.

Question 86

A 35-year-old man sustains a closed spiral fracture of the tibial shaft. In the emergency department, his blood pressure is 110/70 mmHg. He is complaining of severe, unrelenting pain out of proportion to the injury. Which of the following compartment pressure measurements represents the most widely accepted absolute threshold for performing an emergent fasciotomy?

Explanation

The most widely accepted threshold for diagnosing acute compartment syndrome and indicating fasciotomy is a delta pressure (diastolic blood pressure minus compartment pressure) of less than 30 mmHg. Relying on an absolute pressure threshold can result in unnecessary surgeries or missed diagnoses in hypotensive patients.

Question 87

A 40-year-old manual laborer presents with chronic wrist pain. Radiographs demonstrate a chronic, ununited scaphoid waist fracture with secondary degenerative changes. According to the Scaphoid Nonunion Advanced Collapse (SNAC) progression pattern, which joint is typically the first to demonstrate arthritic changes?

Explanation

In the SNAC wrist progression, degenerative arthritic changes occur in a highly predictable sequence. Arthritis first develops at the articulation between the distal scaphoid fragment and the radial styloid (radioscaphoid joint).

Question 88

A 3-month-old female is being treated with a Pavlik harness for developmental dysplasia of the hip (DDH). During a follow-up visit, the parents note that the infant is no longer actively extending her left knee, though she moves her ankle and toes normally. Which of the following is the most likely cause of this finding?

Explanation

Femoral nerve palsy is a known complication of Pavlik harness treatment and is typically caused by excessive hip hyperflexion compressing the nerve against the inguinal ligament. It manifests as decreased active quadriceps function (lack of active knee extension) and resolves with adjustment of the flexion straps.

Question 89

A 22-year-old football player sustains an axial load to a plantarflexed foot resulting in midfoot pain. Examination shows plantar ecchymosis. Radiographs reveal widening of the space between the first and second metatarsal bases. The primarily injured ligament in this scenario connects which of the following structures?

Explanation

The Lisfranc ligament is a critical stabilizing interosseous ligament of the midfoot. It originates on the lateral aspect of the medial cuneiform and inserts onto the medial aspect of the base of the second metatarsal.

Question 90

An infant is born with bilateral idiopathic clubfeet (talipes equinovarus). The orthopedic surgeon elects to begin treatment using the Ponseti method of serial casting. What is the correct sequence of deformity correction in this method?

Explanation

The Ponseti method requires sequential correction of the clubfoot deformities using the CAVE mnemonic: Cavus, Adductus, Varus, and finally Equinus. The first step involves elevating the first ray to correct the forefoot cavus, which aligns the forefoot with the midfoot.

Question 91

A 28-year-old male is involved in a motor vehicle collision and sustains a traumatic posterior dislocation of the right hip. Which specific nerve division is most frequently injured in association with this specific dislocation?

Explanation

Sciatic nerve injury occurs in approximately 10-20% of posterior hip dislocations. The peroneal (fibular) division is particularly susceptible to stretch and compression injuries due to its more lateral, superficial position and its tight distal tethering at the fibular head.

Question 92

A 19-year-old male presents with severe, progressive mid-tibial pain that is worse at night and dramatically relieved by over-the-counter ibuprofen. Radiographs demonstrate a diaphyseal cortical thickening with a small radiolucent nidus. What is the primary mechanism by which non-steroidal anti-inflammatory drugs (NSAIDs) relieve pain in this condition?

Explanation

The clinical presentation is classic for an osteoid osteoma. The dramatic pain relief with NSAIDs is highly characteristic, as the central nidus produces large amounts of prostaglandin E2 (PGE2), which is directly inhibited by cyclooxygenase blockers.

Question 93

A 40-year-old "weekend warrior" feels a sudden pop in the back of his heel while playing basketball. Examination reveals a palpable gap and a positive Thompson test. If this is a classic acute Achilles tendon rupture, in which anatomic region did the rupture most likely occur?

Explanation

Acute Achilles tendon ruptures most frequently occur in a relatively hypovascular "watershed" zone. This area is anatomically located approximately 2 to 6 cm proximal to the tendon's insertion on the calcaneus.

Question 94

A 32-year-old carpenter presents with a swollen, painful index finger 3 days after a puncture wound. Suspecting pyogenic flexor tenosynovitis, the examining physician assesses for Kanavel's cardinal signs. Which of the following is one of these classic signs?

Explanation

Kanavel's four cardinal signs of flexor tenosynovitis include fusiform (sausage-like) swelling of the digit, a flexed resting posture, severe pain with passive extension, and tenderness along the entire flexor tendon sheath.

Question 95

A 40-year-old male presents with the inability to actively flex the interphalangeal joint of his right thumb and distal interphalangeal joint of his index finger. Passive wrist extension results in spontaneous, symmetric flexion of the thumb and all digits. What is the most likely diagnosis?

Explanation

The presence of spontaneous flexion of the thumb and index finger during passive wrist extension confirms an intact tenodesis effect, ruling out a tendon rupture. The specific weakness of the flexor pollicis longus and flexor digitorum profundus to the index finger indicates Anterior Interosseous Nerve (AIN) syndrome.

Question 96

When selecting metallic alloys for orthopedic implants, engineers often consider the modulus of elasticity to minimize stress shielding of the surrounding bone. Which of the following implant materials has a modulus of elasticity that most closely approximates that of cortical bone?

Explanation

Titanium and its alloys have a modulus of elasticity that is much closer to that of cortical bone compared to stiffer metals like cobalt-chromium or stainless steel. This property helps ensure better load sharing and reduces the risk of long-term stress shielding and bone resorption.

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