Orthopedic Surgery Mock Exam - Set B3CDB8

In anterior-posterior compression (APC) injuries, the internal pudendal and obturator arteries are the most commonly injured arterial branches due to disruption of the anterior ring. Conversely, in lateral compression injuries and fractures extending through the greater sciatic notch, the superior gluteal artery is the most frequently injured.

The anterolateral ligament (ALL) originates posterior and proximal to the lateral femoral epicondyle and inserts on the proximal tibia midway between Gerdy's tubercle and the fibular head. It acts as a secondary restraint to internal tibial rotation and the pivot shift phenomenon.

Ceramic-on-ceramic (CoC) bearings possess excellent scratch resistance and have the lowest linear and volumetric wear rates among the available bearing surfaces, significantly reducing the incidence of wear particle-induced osteolysis. However, they carry a unique risk of squeaking and catastrophic ceramic component fracture.

In the setting of cervical spondylotic myelopathy, T1 hypointensity on MRI represents permanent structural damage to the spinal cord (myelomalacia, necrosis, or cavitation) and is a strong independent predictor of poor clinical outcomes and limited neurologic recovery following decompression. T2 hyperintensity alone can represent reversible edema.

Patients with endocrine disorders (such as hypothyroidism, growth hormone deficiency) or renal osteodystrophy are at a significantly elevated risk for bilateral slipped capital femoral epiphysis (SCFE). In these populations, prophylactic pinning of the contralateral hip is highly recommended, regardless of their chronological age.

SLAC Stage I involves the radial styloid and distal scaphoid. Stage II involves the entire radioscaphoid joint. Stage III involves the capitolunate joint. The radiolunate joint is typically spared in SLAC wrists. Proximal row carpectomy (PRC) or four-corner fusion with scaphoid excision are appropriate for Stage II, but PRC is contraindicated in Stage III due to capitolunate arthritis.

The patient is presenting with acute Charcot arthropathy (Eichenholtz stage 0 or 1). The clinical picture mimics infection, but the lack of an ulcer or systemic signs points to Charcot. The mainstay of initial treatment during the acute inflammatory phase is immobilization (usually via total contact casting) and non-weight-bearing to arrest the destructive process and prevent further deformity.

The clinical, radiographic, and histologic descriptions are classic for synovial sarcoma. Synovial sarcoma is characterized by the specific chromosomal translocation t(X;18)(p11;q11), which results in the SYT-SSX fusion gene. This molecular marker is highly sensitive and specific for confirming the diagnosis.

Titanium and its alloys owe their high biocompatibility and excellent corrosion resistance to the spontaneous formation of a thin, passive, adherent oxide layer (primarily titanium dioxide, TiO2) on their surface when exposed to air or bodily fluids. This inert layer prevents further oxidation and interaction with the surrounding biological environment.

In active, independent older adults with displaced femoral neck fractures, total hip arthroplasty (THA) is associated with better functional outcomes, less long-term groin pain (no acetabular cartilage wear), and lower long-term reoperation rates compared to hemiarthroplasty. This comes at the expense of a higher initial risk of dislocation, longer surgical times, and increased blood loss.

The coracohumeral ligament (CHL) originates on the base of the coracoid process and blends into the rotator interval, inserting onto the greater and lesser tuberosities. It is a primary static restraint to inferior translation and external rotation of the humerus when the shoulder is in an adducted position.

In a posterior-stabilized (PS) TKA, 'cam jump' or dislocation of the cam-post mechanism typically occurs in deep flexion. The primary cause of this phenomenon is a loose flexion gap (often combined with insufficient posterior tibial slope or a small femoral component). This laxity allows the femur to translate anteriorly relative to the tibia in deep flexion, clearing the post.

The TLICS system allocates points based on morphology, neurologic status, and posterior ligamentous complex (PLC) integrity. For neurologic status: intact = 0, nerve root = 2, complete cord injury = 2, incomplete cord injury/cauda equina = 3. This patient has an incomplete deficit (3 points). With morphology being a burst fracture (2 points), the score is at least 5, which strongly favors operative intervention.

The Ponseti method dictates that clubfoot deformities should be corrected in the specific order summarized by the mnemonic CAVE: Cavus (corrected first by elevating the first ray to supinate the forefoot), Adductus, Varus, and finally Equinus (which often requires a percutaneous Achilles tenotomy as the final step).

Trigger finger is caused by a size mismatch between the flexor tendon (often with a reactive nodule) and the retinacular sheath, primarily at the A1 pulley. The A1 pulley is located palmar to the metacarpophalangeal (MCP) joint. The A2 pulley is over the proximal phalanx, and the A3 pulley is over the PIP joint.

An intermetatarsal angle (IMA) greater than 13-15 degrees represents a moderate-to-severe deformity. A proximal osteotomy (e.g., Ludloff, crescentic, or proximal chevron) combined with a distal soft tissue release provides superior corrective power for larger IMAs. Distal osteotomies are reserved for mild deformities (IMA < 13 degrees). A Lapidus is indicated if first ray hypermobility is present.

Osteoid osteoma is a benign bone-forming tumor characterized by a radiolucent nidus usually less than 1.5-2 cm in diameter. The cells within the nidus produce very high levels of prostaglandins, particularly PGE2. This causes profound local vasodilation and severe pain, explaining the classic symptom of night pain that is rapidly and dramatically relieved by NSAIDs or aspirin.

Secondary fracture healing involves endochondral ossification. During the soft callus phase, the hematoma is replaced by fibrocartilage, predominantly composed of Type II collagen synthesized by proliferating chondrocytes. This cartilaginous template is later calcified (involving Type X collagen) and finally replaced by woven bone (Type I collagen produced by osteoblasts) during the hard callus phase.

The standard two-incision technique for lower leg fasciotomy involves an anterolateral incision and a posteromedial incision. The anterolateral incision is placed between the tibial crest and the fibula, providing access to release the anterior and lateral compartments. The posteromedial incision allows for release of the superficial and deep posterior compartments.

The femoral origin of the medial patellofemoral ligament (MPFL) is a critical landmark for anatomic reconstruction (often referenced radiographically as Schöttle's point). Anatomically, it is located in a saddle-shaped depression between the medial epicondyle (distal/anterior) and the adductor tubercle (proximal/posterior).

Preservation of dorsal ulnar sensation indicates the compression is distal to the dorsal ulnar sensory branch (which arises proximal to the wrist), localizing the lesion to Guyon's canal. Guyon's canal is divided into three zones: Zone 1 is proximal to the bifurcation and contains both motor and sensory fibers; Zone 2 contains only the deep motor branch; Zone 3 contains only the superficial sensory branch. Mixed motor and sensory deficits localize to Zone 1.

BMPs are members of the TGF-beta superfamily. They initiate intracellular signaling cascades by binding to specific Type I and Type II transmembrane serine/threonine kinase receptors, which leads to the phosphorylation and activation of intracellular Smad proteins.

Denosumab is a fully human monoclonal antibody that binds to RANKL (Receptor Activator of Nuclear factor Kappa-B Ligand). By binding RANKL, it prevents it from interacting with the RANK receptor on osteoclasts and osteoclast precursors, thereby profoundly inhibiting osteoclast formation, function, and survival.

Hyperflexion in a Pavlik harness can lead to femoral nerve palsy, presenting as decreased active knee extension. The standard initial management for a clinically evident femoral nerve palsy in this setting is to temporarily remove the harness to allow for neurologic recovery, rather than continuing or tightening the straps.

Trunnionosis, or mechanically assisted crevice corrosion at the modular head-neck junction, has been most commonly observed in combinations utilizing a large cobalt-chrome (CoCr) femoral head on a titanium alloy stem due to galvanic and fretting corrosion mechanics.

The PCL consists of two main bundles: the anterolateral (AL) bundle and the posteromedial (PM) bundle. The AL bundle is the larger of the two and is tight in flexion and lax in extension. Conversely, the smaller PM bundle is tight in extension and lax in flexion.

While the anterior inferior tibiofibular ligament (AITFL) is typically the first to tear in a syndesmotic injury, biomechanical studies demonstrate that the posterior inferior tibiofibular ligament (PITFL) provides the greatest proportion of strength (approximately 42%) to the syndesmosis, making it the strongest stabilizer.

Optimal placement of a pelvic binder is centered directly over the greater trochanters. Placing the binder too high (e.g., iliac crests or ASIS) reduces its biomechanical efficacy in closing the pelvic volume and can paradoxically open the true pelvis further.

In L5-S1 isthmic spondylolisthesis, the exiting L5 nerve root is most commonly compressed within the neural foramen by fibrocartilaginous tissue of the pars defect, resulting in L5 radiculopathy (pain, weakness in EHL, and sensory changes in the first dorsal web space).

SNAC staging: Stage I involves the radial styloid and distal scaphoid. Stage II involves the entire radioscaphoid fossa. Stage III involves the capitolunate (midcarpal) joint. Because the entire radioscaphoid joint is arthritic but midcarpal is spared, this is Stage II. Proximal row carpectomy (PRC) or four-corner fusion are standard recommended treatments.

Catterall's 'head-at-risk' signs include: Gage's sign (a V-shaped radiolucency in the lateral portion of the epiphysis/metaphysis), calcification lateral to the epiphysis, lateral subluxation of the femoral head, a horizontal physis, and metaphyseal cysts.

A knee that is tight in flexion but balanced in extension requires a maneuver that exclusively increases the flexion gap. When using an anterior referencing system, decreasing the femoral component size selectively decreases the posterior condylar offset (thinner posterior cut), which enlarges the flexion space without altering the extension space.

The superficial zone of articular cartilage is characterized by the highest water content, lowest proteoglycan content, and densely packed collagen fibers that are oriented parallel to the joint surface to resist sheer stress.

A 'floating shoulder' refers to a double disruption of the superior shoulder suspensory complex, most classically represented by an ipsilateral fracture of the glenoid neck and a fracture of the clavicle shaft, thereby functionally isolating the glenohumeral joint from the axial skeleton.

While both biceps tenotomy and tenodesis yield similarly good outcomes regarding pain relief and function, simple tenotomy has a significantly higher rate of cosmetic deformity (the 'Popeye' muscle bulge) and occasional cramping, compared to tenodesis.

A classic and pathognomonic finding of a Lisfranc injury on an AP radiograph is any step-off or malalignment of the medial border of the second metatarsal base with the medial border of the middle cuneiform. They should form a perfectly continuous line in a normal foot.

The classic presentation of an osteoid osteoma is night pain relieved by NSAIDs, characterized radiographically by a radiolucent nidus with surrounding sclerosis. Radiofrequency ablation (RFA) is the standard of care for definitive minimally invasive treatment when medical management fails.

A Stener lesion occurs when the distal attachment of the thumb ulnar collateral ligament (UCL) completely avulses and retracts proximally, becoming displaced superficial to the adductor pollicis aponeurosis. This aponeurosis interposes between the torn UCL ends, preventing native healing and necessitating surgical repair.

Chance fractures (flexion-distraction injuries of the spine) are highly associated with lap-belt use in motor vehicle accidents. They carry a very high rate (up to 40-50%) of concomitant intra-abdominal visceral injuries, particularly to hollow viscous organs like the small bowel.

Tranexamic acid (TXA) is a synthetic analog of the amino acid lysine. It acts as an antifibrinolytic agent by reversibly binding four to five lysine receptor sites on plasminogen, which prevents plasmin from binding to and degrading fibrin, thereby stabilizing the blood clot.