Orthopedic Surgery Board Review: ABOS Part I & AAOS OITE MCQ Cases | Part 21553

Correct Answer: C

In younger, active individuals, allograft ACL reconstructions have been consistently shown to have a significantly higher failure rate compared to autograft reconstructions. While inadequate fixation and tunnel malposition (femoral or tibial) are common causes of graft failure, the choice of allograft in a young, high-demand athlete is a major contributing factor to reinjury. Meniscal pathology, while impacting long-term knee health, is not directly associated with the primary cause of graft re-tear.

Correct Answer: A

A staged revision is primarily indicated when the existing tunnels from the previous ACL reconstruction are too wide, preventing reliable graft fixation, or if their position significantly compromises the accurate placement of new tunnels for the revision ACL. In such cases, the initial stage involves removing hardware and bone grafting the tunnels to allow for healing and consolidation, followed by the definitive revision reconstruction at a later date. A vertical femoral tunnel can often be addressed in a single stage by creating a new, anatomically correct tunnel. Retained hardware can typically be removed during a single-stage procedure. The type of prior graft (autograft vs. allograft) or the presence of a meniscal tear does not inherently necessitate a staged approach.

Correct Answer: C

Graft impingement in the intercondylar notch, leading to a loss of terminal knee extension, is most commonly caused by an anteriorly placed tibial tunnel. If the tibial tunnel is too anterior, the graft will be taut and impinge against the roof of the intercondylar notch during knee extension. Femoral tunnel position primarily affects rotational stability and anterior translation, not typically terminal extension impingement. A tibial tunnel that is too posterior would lead to graft laxity rather than impingement. The type of graft (autograft or allograft) does not inherently affect the risk of impingement based on tunnel placement.

Correct Answer: C

Septic bursitis is an infection of the bursa, often presenting with signs of inflammation and systemic symptoms. Findings highly suggestive of septic bursitis include fever (>37.8°C), a significant temperature difference over the bursa compared to surrounding skin (>2.2°C), and overlying skin lesions (e.g., cellulitis, abrasions). Significant local erythema is also a classic sign of infection. Pain with passive range of motion of the knee, however, is more characteristic of an intra-articular process (e.g., arthritis, meniscal tear) rather than an isolated bursitis, whether septic or aseptic. Bursitis pain is typically worse with direct pressure or active motion involving the bursa.

Correct Answer: D

For isolated PCL injuries, especially those with minimal posterior translation, non-operative management is often successful. The primary focus of rehabilitation is quadriceps strengthening. The quadriceps muscle provides an anteriorly directed force on the tibia, which can dynamically stabilize the knee and counteract the posterior laxity caused by the PCL injury. Hamstring strengthening, while important for overall knee health, can exacerbate posterior translation. Strict immobilization can lead to stiffness and atrophy. Open chain exercises may place undue stress on the PCL. Surgical reconstruction is typically reserved for higher-grade PCL injuries or combined ligamentous injuries.

Correct Answer: B

An acutely locked knee with a firm endpoint and normal radiographs strongly suggests a mechanical block to motion, most commonly a meniscal tear (e.g., bucket-handle tear) or a loose body. An MRI is the gold standard imaging modality for evaluating the integrity of the menisci, articular cartilage, and identifying loose bodies, providing crucial information for diagnosis and surgical planning. Corticosteroid injections or oral anti-inflammatories will not address a mechanical block. While a long-leg splint might provide comfort, it does not advance the diagnosis or treatment. Attempting a closed reduction without a clear diagnosis from MRI could be inappropriate or ineffective if the block is due to a large meniscal tear or loose body.

Correct Answer: D

The female athlete triad is a syndrome characterized by three interrelated components: 1) Low energy availability (with or without disordered eating), 2) Menstrual dysfunction (e.g., amenorrhea), and 3) Low bone mineral density (e.g., osteoporosis). Abulia refers to a lack of will or initiative and is a neurological or psychological symptom not directly part of the triad. Low energy availability is now recognized as the underlying cause that links disordered eating to menstrual dysfunction and low bone mineral density.

Correct Answer: D

Stress fractures are classified by their risk of progression to complete fracture or nonunion. High-risk locations include the superior femoral neck, anterior tibial diaphysis, navicular, base of the fifth metatarsal, and the neck of the talus. These sites are prone to tensile forces or poor blood supply, making them more susceptible to complications. The calcaneus, medial malleolus, first metatarsal, and inferior femoral neck are generally considered lower to intermediate risk sites.

Correct Answer: B

The primary goal of a preparticipation physical examination is to identify life-threatening conditions or conditions that may predispose an athlete to injury or illness during sports. A history of Long QT syndrome, exertional shortness of breath (suggesting asthma or cardiac issues), missed or absent menses (a component of the female athlete triad, indicating potential bone health issues), and prior heat stroke (indicating susceptibility to heat illness) are all significant red flags that require further evaluation before sports participation. A healed long-bone fracture, while important to review for any residual deficits, is generally the least worrisome of the options, assuming it has healed without complications and full function has been restored.

Correct Answer: D

Hypertrophic cardiomyopathy (HCM) is the most common cause of sudden cardiac death in young athletes. It is an inherited condition characterized by abnormal thickening of the heart muscle, particularly the left ventricle, which can obstruct blood flow and lead to dangerous arrhythmias during physical exertion. While coronary artery abnormalities, Long QT syndrome, Commotio cordis (a blunt chest trauma causing ventricular fibrillation), and Marfan syndrome (which can lead to aortic dissection) are all causes of sudden cardiac death in athletes, HCM accounts for the largest proportion of these tragic events.

Correct Answer: D

The patient is a 7-year-old girl weighing 35 kg with a diaphyseal femur fracture. According to the provided guidelines for femur fracture treatment by age, flexible intramedullary nails are the optimal choice for children aged 6-8 years. While a spica cast is an option for this age group, flexible nailing is generally preferred for its benefits to the patient and family, allowing for earlier mobilization and easier care. Lateral trochanteric intramedullary nails are typically reserved for children 9 years of age or older, those weighing over 49 kg, or those with length-unstable fractures, none of which apply to this patient. External fixation is usually reserved for severely comminuted or open fractures, or in the setting of damage control orthopaedics, which is not indicated here. Traction followed by delayed spica casting is a less preferred option compared to flexible nailing for this age and weight.

Correct Answer: B

The goal for flexible intramedullary nail fixation of a femur fracture is to achieve approximately 80% canal fill. The patient's femoral isthmus measures 7.5 mm. To calculate the appropriate nail size, we need to find two nails whose combined diameter is 80% of 7.5 mm. 80% of 7.5 mm is 0.80 * 7.5 mm = 6.0 mm. Therefore, using two 3-mm nails (3 mm + 3 mm = 6 mm) will achieve exactly 80% canal fill. Option A (two 2.5-mm nails = 5 mm) would result in 67% canal fill (5/7.5), which is less than ideal and could lead to fixation failure. Option C (one 3.0-mm and one 3.5-mm nail = 6.5 mm) would result in 87% canal fill (6.5/7.5), which is greater than 80% and increases the risk of complications, as does using nails of different sizes which can contribute to loss of reduction and malalignment. Option D (two 3.5-mm nails = 7 mm) would result in 93% canal fill (7/7.5), which is too high. Option E (one 2.5-mm and one 3.0-mm nail = 5.5 mm) would result in 73% canal fill (5.5/7.5), which is also suboptimal.

Correct Answer: C

The most common complication associated with flexible intramedullary nailing for pediatric femur fractures is pain or irritation at the insertion sites, typically around the knee where the nails exit the bone. This is often due to the ends of the nails irritating the surrounding soft tissues. Studies have shown relatively low rates of infection, significant bleeding, and loss of reduction (especially with length-stable fractures) when proper surgical technique is employed. Delayed union or nonunion is also a rare complication in pediatric femur fractures treated with flexible nails. To minimize the risk of insertion site irritation, it is suggested that the nails be left no more than 25 mm out of the bone.

Correct Answer: C

Children between the ages of 2 and 10 years are at the highest risk for ipsilateral overgrowth following a femoral shaft fracture. While the reported range of overgrowth can be broad (approximately 4 to 25 mm), the average amount of overgrowth observed in this age group is typically around 9 mm. Therefore, stating that there is no risk of overgrowth at this age (Option A) or that it only occurs in children under 2 or over 10 (Option E) is incorrect. Options B and D either underestimate or overestimate the average amount of overgrowth commonly seen in this specific age range.

Correct Answer: B

Tibial tubercle fractures occur more commonly in adolescents who have a history of Osgood–Schlatter disease. Osgood–Schlatter disease is an overuse injury characterized by repetitive strain across the tibial tubercle apophysis, which can weaken the apophysis and predispose it to avulsion fractures. While a direct causal relationship is not always definitively proven, the association is well-recognized. Patellofemoral syndrome involves anterior knee pain related to overuse but is not a direct risk factor for tibial tubercle avulsion. Sinding-Larsen–Johansson syndrome is similar to Osgood–Schlatter but affects the inferior pole of the patella, not the tibial tubercle. Patellar tendonitis is inflammation of the patellar tendon and is not specifically linked to an increased risk of tibial tubercle fractures. Chondromalacia patellae refers to softening of the articular cartilage of the patella and is unrelated to tibial tubercle fractures.

Correct Answer: B

Tibial tubercle fractures, particularly displaced ones, carry a significant risk of developing an isolated anterior compartment syndrome. This is primarily due to injury to the recurrent anterior tibial artery, which is located in close proximity to the tibial tubercle and can be damaged during the fracture event or subsequent swelling. The anterior tibial artery itself is a larger vessel but the recurrent branch is more directly involved in the local vascularity around the tibial tubercle. The medial inferior geniculate artery supplies the knee joint but is not the primary vessel implicated in compartment syndrome with this specific fracture. The lateral compartment and fibular artery are not typically involved in compartment syndrome secondary to a tibial tubercle fracture.

Correct Answer: D

For a displaced Type III tibial tubercle fracture in an adolescent, an open reduction is necessary to achieve anatomical alignment. Closed reduction with casting or pinning (Options A and B) is insufficient for displaced fractures of this type. While pinning (Option C) can be used, screw fixation is generally preferred over pins or sutures in larger adolescents due to the significant pulling forces exerted by the quadriceps and to provide more stable fixation, allowing for earlier range of motion. Furthermore, Type III fractures are associated with a risk of intra-articular pathology (e.g., meniscal injury, soft tissue incarceration), making an arthrotomy (or arthroscopy) essential to ensure anatomical joint surface reduction and address any associated injuries. Suture fixation (Option E) might be considered in very young adolescents with concerns about growth plate integrity, but screw fixation is superior for stability in older adolescents where the growth plate is already closing.

Correct Answer: B

The radiograph depicts a Tillaux fracture, which is a transitional ankle fracture in adolescents involving an avulsion of the anterolateral distal tibial epiphysis. This fragment remains attached to the anterior inferior tibiofibular ligament (AITFL), which is one of the primary syndesmotic ligaments of the ankle. Chopart injuries involve the midtarsal joint, not the distal tibia. The Chaput fragment is another eponym for the same fracture piece attached to the AITFL, but it is more commonly used in adult ankle fractures. The anterior talofibular ligament (ATFL) is the most commonly injured ligament in lateral ankle sprains, not typically involved in a Tillaux fracture.

Correct Answer: B

Classically, a triplane fracture of the distal tibia presents with a characteristic radiographic appearance: it appears as a Salter–Harris II fracture on lateral radiographs (sagittal view) and as a Salter–Harris III fracture (which corresponds to the Tillaux fragment) on coronal imaging (anteroposterior or AP view). This unique combination reflects the fracture's involvement of the physis, epiphysis, and metaphysis in different planes. Therefore, option B accurately describes this classic presentation. Other combinations of Salter-Harris classifications on these views do not represent the typical triplane fracture pattern.

Correct Answer: D

A residual articular diastasis of greater than 2 mm after reduction of a triplane fracture is generally considered an indication for surgical intervention to minimize the risk of abnormal joint contact forces and subsequent degenerative changes. This patient has a residual articular gap of >4 mm, clearly indicating the need for surgery. While surgical approaches vary, a common and effective method involves reducing the articular surface and fixing it with all-epiphyseal lag screws placed perpendicular to the fracture line in an extraphyseal and extra-articular manner. Given that the patient has a large metaphyseal fragment, additional fixation with lag screws placed across this metaphyseal spike (in addition to epiphyseal screws) would optimize fracture fixation and stability. Therefore, a construct involving lag screws in both the epiphyseal and metaphyseal fragments is the most comprehensive and appropriate surgical approach. Continued immobilization (Option A) is not indicated due to the significant residual displacement. Physeal-spanning compression plates (Option E) are generally not indicated for these fractures due to the risk of physeal arrest.

Correct Answer: C

The patient's history of the finger being tightly flexed at the moment of laceration is a critical detail in flexor tendon injuries. When a flexor tendon is lacerated in a flexed position, the distal stump remains near the laceration site. However, once the finger is extended (as it would be during examination or initial wound care), the proximal tendon stump retracts significantly due to the pull of the muscle belly in the forearm. This retraction can be substantial, often pulling the stump proximal to the A1 pulley, into the palm, or even into the distal forearm. Therefore, surgical planning must account for the need for a more extensive proximal exploration, potentially requiring a counter-incision in the palm, to retrieve the retracted proximal tendon stump. This phenomenon is a well-known challenge in Zone II flexor tendon repairs.

Option A is incorrect; while digital nerve injuries are common, the position of the finger at injury primarily affects tendon retraction, not necessarily increasing nerve stretch risk. Option B is incorrect; a flexed position does not inherently lead to a partial laceration; a sharp knife can still cause a complete transection. Option D is incorrect; while some pulleys might be less taut, the primary implication is tendon retraction. Option E is incorrect; the timing of repair (primary vs. delayed) is dictated by the time from injury and wound conditions, not solely by the finger's position at injury, although significant retraction can make primary repair more challenging if delayed too long.

Correct Answer: C

For acute penetrating injuries to the hand, particularly those involving flexor tendons, the primary concern for infection is typically skin flora, most commonly Staphylococcus aureus and Streptococcus species. A first-generation cephalosporin, such as Cefazolin, provides excellent coverage against these common gram-positive organisms and is generally well-tolerated. The case specifically mentions the administration of a first-generation cephalosporin, aligning with standard practice for clean-contaminated wounds.

Option A (Vancomycin and Piperacillin-Tazobactam) would be overly broad for an initial empiric choice in this scenario, typically reserved for more severe infections, immunocompromised patients, or those with specific risk factors for MRSA or polymicrobial infections (e.g., human/animal bites, farm injuries). Option B (Ciprofloxacin and Metronidazole) targets gram-negative and anaerobic bacteria, which are not the primary concern for a clean knife injury. Option D (Clindamycin and Gentamicin) is also a broad-spectrum combination, with gentamicin covering gram-negatives and clindamycin covering anaerobes and some gram-positives, but Cefazolin is simpler and usually sufficient. Option E (Doxycycline) is not a first-line empiric choice for acute penetrating hand injuries.

Correct Answer: C

The image shows a laceration on the volar aspect of the middle finger. The clinical findings are key: complete inability to actively flex both the PIP (proximal interphalangeal) and DIP (distal interphalangeal) joints. The FDS tendon is primarily responsible for PIP flexion, and the FDP tendon is responsible for DIP flexion. Loss of both indicates a complete transection of both tendons. The laceration location 'over the middle phalanx' places the injury squarely in Flexor Tendon Zone II, which extends from the A1 pulley to the FDS insertion on the middle phalanx. The diminished sensation along the radial digital nerve is a common associated injury but does not change the primary tendon diagnosis.

Option A is incorrect because an FDP avulsion (Jersey finger) typically presents with an inability to flex the DIP joint, but PIP flexion (FDS) would be intact. Zone I is distal to the FDS insertion, involving only the FDP. Option B is incorrect because a partial FDS laceration would likely present with weakness, not complete loss, of PIP flexion, and Zone III is in the palm. Option D is incorrect because an isolated digital nerve laceration would cause sensory deficits but preserve active tendon function. Zone IV is at the wrist. Option E is incorrect because an extensor tendon laceration would affect finger extension, not flexion, and Zone V is at the MCP joint level on the dorsal aspect.

Correct Answer: B

The case explicitly states that the radial digital nerve was found to be approximately 80% transected during surgical exploration, confirming the clinical suspicion of a severe partial laceration. A two-point discrimination of 8 mm is abnormal and indicates a significant sensory deficit. In the setting of an open wound and a clear clinical deficit, a digital nerve laceration, whether partial or complete, warrants immediate surgical exploration and microsurgical repair. Performing this repair during the same surgical setting as the flexor tendon repair is the standard of care. This allows for primary repair, which generally yields the best outcomes, and avoids the complications of delayed repair such as nerve retraction and scar tissue formation.

Option A is incorrect; while some very minor neuropraxic injuries might recover, a significant laceration (80% transection) will not spontaneously recover adequate function. Option C is incorrect; delayed nerve grafting is reserved for cases where primary repair is not possible due to significant nerve gap or chronic injury. Option D is incorrect; corticosteroids are not indicated for nerve lacerations. Option E is incorrect; NCS/EMG are typically used for chronic nerve compression or entrapment neuropathies, not for acute, open lacerations where the diagnosis is clinically evident and confirmed by exploration.

Correct Answer: C

The case explicitly states the primary indications for plain film radiography in the setting of a sharp penetrating injury: 1) Exclusion of Foreign Bodies (e.g., metallic shards, glass), and 2) Assessment of Osseous Integrity (e.g., phalangeal fractures, cortical nicking, bony avulsions). While the patient reported a knife injury, it's crucial to rule out other potential foreign bodies or associated bony trauma that might complicate the repair or recovery. The radiographs in this patient demonstrated normal osseous architecture and no foreign bodies.

Option A is incorrect; radiographs are not effective for assessing tendon retraction or gap formation, which are soft tissue structures. Option B is incorrect; radiographs cannot evaluate the integrity of annular pulleys. Option D is incorrect; the anatomical zone of injury is determined clinically by the laceration's location relative to anatomical landmarks and tendon function deficits. Option E is incorrect; while soft tissue swelling can be noted on radiographs, it's not the primary indication, and other imaging modalities or clinical examination are better for quantifying soft tissue changes.

Correct Answer: C

The clinical presentation of intact active PIP flexion but absent active DIP flexion, combined with a bony avulsion fragment from the volar base of the distal phalanx on radiographs, is pathognomonic for a Flexor Digitorum Profundus (FDP) avulsion, commonly known as a Jersey Finger. The FDP tendon inserts onto the volar base of the distal phalanx, and its avulsion results in the loss of DIP flexion. The intact PIP flexion indicates that the FDS tendon, which inserts on the middle phalanx and flexes the PIP joint, is functional.

Option A is incorrect because a complete Zone II FDS and FDP laceration would result in the loss of both PIP and DIP flexion. Option B is incorrect because a partial FDP laceration would typically present with weakened, but not completely absent, DIP flexion. Option D is incorrect because an isolated digital nerve laceration would primarily cause sensory deficits, not a loss of active tendon function. Option E is incorrect because an extrinsic flexor muscle belly injury would likely affect multiple digits or present with more diffuse weakness, and the specific bony avulsion points away from this diagnosis.

Correct Answer: C

The case explicitly states that the profound advantage of WALANT in Zone II repairs is the ability to communicate with the conscious patient intraoperatively. This allows the surgeon to ask the patient to actively flex and extend the digit after the tendon repair is complete. This provides real-time assessment of the repair construct's strength, direct observation of tendon gliding through the pulleys, and immediate identification and resolution of any triggering or catching before wound closure. This intraoperative validation is a hallmark benefit that significantly contributes to optimizing outcomes and preventing complications like adhesions or impingement.

Option A is incorrect; while WALANT can be efficient, its primary advantage is not necessarily faster anesthetic onset or reduced overall operative time compared to other methods. Option B is incorrect; a Certified Hand Therapist is crucial for postoperative rehabilitation regardless of the anesthesia technique. Option D is incorrect; while epinephrine provides hemostasis, the primary mechanism for infection prevention is sterile technique and prophylactic antibiotics, not the anesthetic itself. Option E is incorrect; while WALANT can be more cost-effective, the most significant clinical advantage highlighted in the case for Zone II repair is the intraoperative assessment.

Correct Answer: C

The case clearly outlines the dual functions of the epitendinous suture: 'The epitendinous suture serves two critical functions: it increases the overall tensile strength of the repair by 20-30%, and it neatly tucks in the exposed collagen fibrils at the tendon ends, creating a smooth surface that minimizes gliding resistance and prevents postoperative adhesions.' While the core suture provides the bulk of the initial tensile strength, the epitendinous suture significantly augments it and, crucially, creates a smooth interface that reduces friction and adhesion formation within the tight fibro-osseous sheath of Zone II.

Option A is incorrect; the core suture provides the majority of the tensile strength, not the epitendinous suture. Option B is incorrect; the Quadrigia effect is prevented by ensuring end-to-end repair without excessive shortening, not directly by the epitendinous suture. Option D is incorrect; revascularization occurs through diffusion and the vincula, not primarily through the epitendinous suture. Option E is incorrect; even with a robust repair, early active motion protocols still require protective splinting to prevent rupture during the initial healing phase.

Correct Answer: C

The case explicitly details the critical positioning for the dorsal blocking splint: 'Wrist: 20 to 30 degrees of palmar flexion. Metacarpophalangeal (MCP) Joints: 50 to 70 degrees of flexion. Interphalangeal (PIP and DIP) Joints: Full extension (neutral).' This specific position places the flexor tendons in a relaxed state, minimizing tension on the repair site while still allowing for controlled, protected active extension within the splint and passive or place-and-hold flexion exercises as part of an Early Active Motion (EAM) protocol.

Options A, B, D, and E describe incorrect or suboptimal splint positions that would either place excessive tension on the repair, limit necessary motion, or not adequately protect the healing tendons.

Correct Answer: D

The scenario described, where the repaired middle finger achieves full flexion but the adjacent, uninjured ring and small fingers are unable to achieve full flexion, is the classic presentation of the Quadrigia effect. As explained in the case, 'The Flexor Digitorum Profundus muscle has a common muscle belly in the proximal forearm that gives rise to the tendons of the middle, ring, and small fingers. Because these tendons act in concert, over-advancing the FDP tendon during repair (typically by more than 1 cm) will artificially shorten that specific tendon. When the patient attempts to make a fist, the shortened repaired tendon reaches maximum excursion early, physically blocking the common muscle belly from contracting further. This prevents the adjacent, uninjured fingers from achieving full flexion.'

Option A is incorrect; Lumbrical Plus finger presents as paradoxical PIP extension when attempting to grip, not a blocking of adjacent fingers. Option B is incorrect; tendon adhesions would primarily limit active flexion of the repaired finger, not block adjacent uninjured fingers. Option C is incorrect; a tendon rupture would result in a loss of active flexion in the repaired finger, not a blocking effect on adjacent digits. Option E is incorrect; intrinsic muscle contracture would typically affect MCP flexion and IP extension, not specifically block adjacent FDP function in this manner.

Anterior placement of the tibial tunnel leads to graft impingement against the intercondylar roof (Blumensaat's line) during terminal extension. This biomechanical conflict typically presents as a significant loss of extension and potential graft attrition.

A femoral tunnel placed too anteriorly (non-anatomic) results in the graft tightening significantly as the knee flexes. This "captures" the joint and severely limits knee flexion, often requiring revision surgery if conservative management fails.

The PCL consists of the larger anterolateral (AL) bundle and the smaller posteromedial (PM) bundle. The AL bundle is tight in flexion, whereas the PM bundle is tight in extension.

An increase in external rotation greater than 10 degrees at 30 degrees of flexion, with symmetric rotation at 90 degrees, indicates an isolated posterolateral corner (PLC) injury. If rotation is increased at both 30 and 90 degrees, a combined PLC and PCL injury is present.

The PCL consists of the anterolateral (AL) and posteromedial (PM) bundles. The larger AL bundle is tightest in knee flexion, whereas the smaller PM bundle is tightest in knee extension.

An increase in external rotation of more than 10 degrees at 30 degrees of flexion, but not at 90 degrees, indicates an isolated posterolateral corner (PLC) injury. Increased external rotation at both 30 and 90 degrees indicates a combined PLC and PCL injury.

The revascularization and proliferation phase of graft healing typically occurs between 6 and 12 weeks postoperatively. During this time, the graft undergoes necrosis and subsequent revascularization, resulting in its weakest biomechanical state.

A complete meniscal root tear disrupts the circumferential hoop stresses that normally distribute axial loads. Biomechanically, this derangement results in increased contact pressures equivalent to a total meniscectomy.

Schöttle's point is the radiographic landmark for the femoral origin of the MPFL. It is located 1 mm anterior to the posterior cortex line, 2.5 mm distal to the posterior origin of the medial femoral condyle, and proximal to the medial epicondyle.

The patient has a "Cyclops lesion," which is a localized form of anterior arthrofibrosis that blocks terminal extension. Histologically, it is composed of a dense nodule of fibrovascular and granulation tissue.

An increased posterior tibial slope increases anterior tibial translation under axial loading, significantly raising the risk of ACL rupture. Other risk factors in females include a narrow intercondylar notch and increased Q angle.

The middle genicular artery pierces the posterior capsule to supply the cruciate ligaments and the synovial fold of the intercondylar notch. The inferior and superior genicular arteries primarily supply the menisci and joint capsule.

Increasing the posterior tibial slope forces the tibia anteriorly, straining the ACL. Therefore, in an ACL-deficient knee undergoing HTO, decreasing the posterior slope helps protect the future graft by minimizing anterior tibial translation.

Approximately 70% to 80% of knee OCD lesions occur on the lateral aspect of the medial femoral condyle. This classic location is often remembered by the mnemonic "LAME" (Lateral Aspect Medial Epicondyle/Condyle).

An anteriorly placed tibial tunnel causes the graft to impinge against the roof of the intercondylar notch (Blumensaat's line) during knee extension. This results in a mechanical block to terminal extension and potential early graft failure.

A femoral tunnel placed too far anteriorly (shallow) is non-anatomic. This positioning causes the graft to artificially tighten as the knee goes into flexion and become abnormally loose in full extension.

Extensive literature demonstrates that the use of allografts in young (under 25), highly active patients results in a significantly higher failure rate (up to 3-4 times higher) compared to autografts. Slower biologic incorporation is the primary reason for this failure.

An ABI < 0.9 after a knee dislocation is highly suspicious for a vascular injury, most commonly to the popliteal artery. The gold standard for further evaluation in a hemodynamically stable patient with an abnormal ABI is a CT angiogram.

The Segond fracture is an avulsion of the anterolateral ligament (ALL) from its tibial insertion, located just posterior to Gerdy's tubercle. It is highly specific for an underlying ACL rupture.

At 0 degrees, the posterior capsule and cruciate ligaments act as secondary restraints to valgus stress. At 25-30 degrees of flexion, these secondary restraints are relaxed, and the sMCL becomes the primary restraint, providing ~80% of the valgus stability.

The deep (radial) zone of articular cartilage contains the largest diameter collagen fibrils oriented perpendicular to the joint line. It also possesses the highest concentration of proteoglycans, providing maximal resistance to compressive forces.

The saphenous nerve (specifically the infrapatellar branch and the main trunk) runs medially and is highly vulnerable during the posteromedial approach used for inside-out medial meniscal repairs. Dissection must carefully stay anterior to the medial head of the gastrocnemius to protect it.

An LSI of >90% on functional hop testing (along with symmetric quadriceps strength >90%) is widely accepted as the minimal criteria before clearing an athlete to return to high-risk, pivoting sports post-ACL reconstruction.

An anteriorly placed femoral tunnel creates a graft that is relatively loose in extension but progressively tightens as the knee flexes. This typically results in a restriction or complete loss of deep knee flexion, or it may lead to graft stretching and failure if flexion is forced.

A vertically placed femoral tunnel (e.g., high in the notch at the 12 o'clock position) may adequately restore anteroposterior translation (yielding a negative Lachman test). However, it fails to control rotational forces, clinically manifesting as a persistent, high-grade pivot shift.

A staged ACL revision is indicated when significant tunnel widening (typically >14-15 mm) or tunnel coalition compromises the structural integrity needed for new graft fixation. Bone grafting to fill the defects followed by a period of healing is required before the final reconstruction.

Ramp lesions are longitudinal tears of the peripheral meniscocapsular attachment of the posterior horn of the medial meniscus. They are frequently obscured from standard anterior portals and are best evaluated using a trans-notch view or a dedicated posteromedial portal.

Young patient age (particularly under 20 years) and returning to high-level pivoting sports are the strongest independent predictors of ACL graft failure. While graft choice can influence outcomes, age consistently shows the highest correlation with reinjury and failure.

The common peroneal nerve is the most frequently injured nerve in multiligament knee injuries, particularly those with a PLC disruption. The pathomechanism is typically a stretch or traction injury (neuropraxia or axonotmesis) secondary to severe varus and hyperextension forces.

An increase of >10 degrees in external rotation at 30 degrees of flexion, with normal rotation at 90 degrees, indicates an isolated posterolateral corner (PLC) injury. If increased external rotation is present at both 30 and 90 degrees, it signifies a combined PLC and PCL injury.

The clinical presentation and MRI findings describe a 'cyclops lesion', which is localized arthrofibrosis anterior to the ACL graft. Arthroscopic excision is the definitive treatment and reliably restores terminal knee extension.

Schöttle's point is the radiographic landmark for the femoral origin of the MPFL. On a strict lateral radiograph, it is found 1 mm anterior to the posterior cortex line, 2.5 mm distal to the posterior origin of the medial femoral condyle, and proximal to Blumensaat's line.

A knee flexion contracture greater than 15 degrees is a significant relative contraindication to a high tibial osteotomy, as the procedure cannot effectively correct sagittal plane deformity and patients do poorly. Other contraindications include tricompartmental OA and inflammatory arthritis.

A tear at the posterior root of the medial meniscus detaches the meniscus from its bony anchor, completely disrupting load-sharing hoop stresses. Biomechanically, this results in altered tibiofemoral contact pressures equivalent to a total meniscectomy.

The popliteal artery is at substantial risk during posterior lateral meniscus repairs (both all-inside and inside-out techniques) because it runs centrally in the popliteal fossa, immediately posterior to the joint capsule.

In the setting of a knee dislocation, an ABI of less than 0.9 strongly suggests an underlying vascular injury, even if pulses are palpable. CT angiography is the gold-standard diagnostic step to define the injury and guide surgical intervention.

The primary blood supply to the ACL is the middle genicular artery, which branches directly off the popliteal artery and pierces the posterior joint capsule to supply the cruciate ligaments and synovial fold.

Anterior placement of the femoral tunnel during ACL reconstruction results in a graft that becomes excessively tight in flexion. This biomechanical mismatch typically causes a loss of knee flexion and can eventually lead to graft stretching or failure.

A complete posterior root tear of the medial meniscus disrupts the circumferential hoop stresses, leading to meniscal extrusion. This results in biomechanical changes equivalent to a total meniscectomy, characterized by decreased contact area and significantly increased peak contact pressures.

High-dose terminal irradiation (greater than 2.0 to 2.5 Mrad) is used to sterilize allografts but significantly alters their structural properties. This leads to a dose-dependent decrease in biomechanical strength and a higher risk of clinical graft failure.

The radiograph demonstrates a Segond fracture, which is an avulsion fracture of the anterolateral proximal tibia. This finding is highly pathognomonic for an anterior cruciate ligament (ACL) tear and represents avulsion of the anterolateral complex.

The dial test evaluates for posterolateral corner (PLC) and PCL injuries. Asymmetry of greater than 10 degrees at 30 degrees of flexion, which normalizes at 90 degrees, indicates an isolated PLC injury. Combined PLC and PCL injuries typically show increased external rotation at both 30 and 90 degrees.

The femoral origin of the MPFL is located in the saddle region between the medial epicondyle and the adductor tubercle. Radiographically, Schöttle's point is used to identify this anatomic location to ensure proper graft isometry during reconstruction.

In prepubescent patients (Tanner stage 1 or 2) with significant growth remaining, physeal-sparing ACL reconstruction techniques, such as an iliotibial band extra-articular tenodesis, are recommended. Transphyseal techniques carry an unacceptable risk of iatrogenic growth arrest or angular deformity in this age group.

For knee dislocations, an ABI greater than 0.9 with normal palpable pulses indicates a very low likelihood of a flow-limiting vascular injury. The standard of care is admission for serial physical and neurovascular examinations for 24 to 48 hours.

The anterolateral bundle is the larger and biomechanically dominant bundle of the PCL, and it is tightest in knee flexion. Single-bundle PCL reconstructions aim to recreate this anterolateral bundle to restore the primary restraint against posterior tibial translation.

Bone-patellar tendon-bone (BTB) autografts are associated with a higher incidence of donor site morbidity, specifically anterior knee pain and pain with kneeling, compared to hamstring autografts. Hamstring grafts are more associated with temporary deep flexion weakness and saphenous nerve paresthesias.