Lower Extremity Deformity Correction & TKA Biomechanics for ABOS Board Review | Part 4

A 65-year-old man presents with end-stage knee osteoarthritis and a remote history of a midshaft femur fracture treated nonoperatively, leaving him with a symptomatic coronal plane deformity. When planning a primary total knee arthroplasty (TKA), what is the generally accepted maximum limit of extra-articular coronal plane femoral deformity that can be managed safely with intra-articular bone cuts and soft-tissue balancing?

During a primary total knee arthroplasty, the surgeon inadvertently places the femoral component in 5 degrees of internal rotation relative to the surgical transepicondylar axis. What is the most likely biomechanical consequence of this malpositioning?

When correcting a lower extremity diaphyseal angular deformity, what is the biomechanical consequence of performing an opening wedge osteotomy at a level proximal to the Center of Rotation of Angulation (CORA), while maintaining the Axis of Correction of Angulation (ACA) at the osteotomy site?

A 45-year-old patient is undergoing correction of a diaphyseal tibial angular deformity. The surgeon plans an osteotomy at a level distant from the Center of Rotation of Angulation (CORA). According to the principles of deformity correction, what is the inevitable geometric consequence of fully realigning the mechanical axis with this technique?

During a total knee arthroplasty (TKA) gap balancing procedure, the surgeon notes that the knee is well-balanced and symmetric in extension, but symmetrically tight in 90 degrees of flexion. Which of the following is the most appropriate step to achieve balanced gaps?

A surgeon is performing a medial opening wedge high tibial osteotomy (HTO) for a 40-year-old active male with medial compartment osteoarthritis and varus alignment. To prevent altering the patient's sagittal plane kinematics, how should the anterior gap compare to the posterior gap at the osteotomy site?

Which of the following biomechanical effects is most strongly associated with joint line elevation during a revision total knee arthroplasty?

A 65-year-old woman with advanced primary knee osteoarthritis undergoes a posterior-stabilized (PS) TKA. The surgeon inadvertently internally rotates the tibial component. What is the most likely biomechanical consequence of this malrotation?

In the application of an Ilizarov circular frame for tibial lengthening, which of the following modifications will most significantly increase the axial stiffness of the construct?

A patient with a severe 25-degree valgus knee deformity and a completely incompetent medial collateral ligament (MCL) presents for TKA. Which of the following implant constraints is most appropriate?

During a TKA, a measured resection technique is utilized. The surgeon uses the surgical transepicondylar axis (sTEA) to establish femoral component rotation. Which of the following best describes the sTEA?

A patient undergoes distraction osteogenesis using an Ilizarov frame. Six weeks post-operatively, radiographs show a lucent zone in the regenerate without evidence of bridging callus. The distraction rate is 1.0 mm per day. What is the most appropriate management for this delayed consolidation?

A 55-year-old male presents with a symptomatic extra-articular distal femoral varus deformity of 15 degrees located 5 cm proximal to the joint line. If the surgeon decides to correct this entirely with an intra-articular bone cut during a TKA, what is the most significant risk?

In a posterior-stabilized (PS) TKA, at approximately what angle of flexion does the cam on the femoral component typically engage the tibial post to initiate posterior femoral rollback?

A patient presents with 'patellar clunk syndrome' two years following a TKA. Which implant characteristic and kinematic phase are most classically associated with this condition?

During a TKA for a severe varus deformity, the medial compartment remains tight in full extension but is well balanced in flexion. Which structure should be incrementally released next to specifically address the tight extension gap?

A patient undergoes a medial closing wedge distal femoral osteotomy (DFO) for a valgus deformity. Which of the following is an expected biomechanical consequence of this specific procedure compared to a lateral opening wedge DFO?

Increasing the posterior slope of the tibial bone cut during a TKA will have which of the following effects on the flexion and extension gaps?

When utilizing the 'lengthening over a nail' (LON) technique for lower extremity deformity correction, what is the primary biomechanical and clinical advantage over traditional isolated Ilizarov lengthening?

A patient with a complex multi-planar tibial deformity is treated with a hexapod circular external fixator (e.g., Taylor Spatial Frame). What is the fundamental biomechanical advantage of this system over a traditional Ilizarov frame?

In an excessively thick (overstuffed) patellar component during TKA, which of the following postoperative complications is most directly expected?

A 16-year-old male with a history of infantile Blount's disease presents with a complex proximal tibial deformity. What is the classic pathoanatomic triad of the tibial deformity in this condition?

During pre-operative templating for a TKA on a patient with a 20-degree valgus deformity, the surgeon plans a lateral parapatellar approach. To preserve patellar viability, which critical arterial supply must the surgeon attempt to protect?

During a primary total knee arthroplasty (TKA), the joint is perfectly balanced in extension but demonstrates a tight flexion gap. Which of the following is the most appropriate corrective action?

Internal rotation of the tibial component in a primary total knee arthroplasty primarily leads to which of the following postoperative complications?

A 65-year-old patient presents with end-stage knee osteoarthritis and a 15-degree midshaft femoral varus deformity. When planning a primary TKA using an intra-articular resection alone to correct the mechanical axis, which of the following compromises must be accepted?

During a medial opening-wedge high tibial osteotomy (HTO), the surgeon aims to correct a varus deformity. If the osteotomy gap is opened disproportionately wider anteriorly than posteriorly, what is the most significant biomechanical consequence?

In deformity correction planning, the Center of Rotation of Angulation (CORA) is determined by the intersection of the proximal and distal anatomical axes. If an osteotomy and hinge are placed exactly at the CORA, what is the biomechanical result during angular correction?

Intraoperatively during a TKA, a surgeon finds the knee is tight in full extension but perfectly balanced in 90 degrees of flexion. Which of the following is the most appropriate next step to balance the knee?

Mechanical Axis Deviation (MAD) of the lower extremity is standardly defined as:

A patient with severe osteoarthritis and an 18-degree varus deformity is evaluated for TKA. Preoperative imaging reveals a Joint Line Convergence Angle (JLCA) of 6 degrees (opening laterally). How does this affect preoperative bone resection planning?

A patient has significant anterior bowing of the femoral diaphysis. If a standard intramedullary alignment guide is utilized during primary TKA, what is the most likely error in the distal femoral resection?

Which of the following frame modifications will most effectively INCREASE the axial stability of a circular external fixator applied to the tibia?

During revision TKA, the joint line is inadvertently elevated by 10 mm. Which of the following biomechanical consequences is most likely to occur?

A 45-year-old patient presents with knee pain and a 10-degree valgus alignment. Radiographs reveal a mechanical Lateral Distal Femoral Angle (mLDFA) of 81 degrees and a medial Proximal Tibial Angle (mPTA) of 87 degrees. What is the most appropriate corrective osteotomy?

According to Paley's rules of deformity correction, if an osteotomy is performed at a level different from the Center of Rotation of Angulation (CORA) but the hinge is placed exactly at the CORA (Rule 2), what is the expected outcome?

In a native knee, posterior femoral rollback during deep flexion is primarily driven by the interaction of the posterior cruciate ligament (PCL) and the geometry of the tibial plateau. In a standard posterior-stabilized (PS) total knee arthroplasty, how is this kinematic mechanism mechanically replicated?

When planning a deformity correction, the surgeon places the osteotomy at a different level than the Center of Rotation of Angulation (CORA), but the Axis of Correction of Angulation (ACA) passes directly through the CORA. Which of the following describes the resultant alignment according to Paley's rules?

A 58-year-old patient with severe knee osteoarthritis has an extra-articular varus deformity of the proximal tibial diaphysis due to a malunited fracture. What is the generally accepted threshold of extra-articular coronal plane tibial deformity beyond which a simultaneous or staged corrective osteotomy is recommended over intra-articular compensatory resection during TKA?

A surgeon evaluates a patient with chronic anterior knee pain and a feeling of instability following a primary total knee arthroplasty. A CT scan reveals the tibial component is placed in 15 degrees of internal rotation relative to the medial third of the tibial tubercle. What is the expected patellofemoral complication?

A patient with significant distal femoral diaphyseal anterior bowing (procurvatum deformity) undergoes standard primary TKA using a traditional long intramedullary femoral alignment guide. If uncorrected, this diaphyseal deformity will most likely cause the femoral component to be placed in:

During a cruciate-retaining (CR) total knee arthroplasty, the surgeon notes that the anterior aspect of the tibial tray lifts off the bone during deep flexion prior to securing the trial component. What is the most appropriate next step in management?

According to the principles of deformity correction, if the Axis of Correction of Angulation (ACA) and the osteotomy are both located away from the Center of Rotation of Angulation (CORA), what is the resultant biomechanical effect on the mechanical axis after angular correction?

A patient is undergoing deformity correction for a mid-diaphyseal tibial varus deformity. If the osteotomy is performed at a level proximal to the Center of Rotation of Angulation (CORA), but the Axis of Correction of Angulation (ACA) is maintained exactly at the CORA, what is the expected geometric outcome of the limb?

During primary total knee arthroplasty, the use of a standard straight intramedullary (IM) alignment guide in a femur with an excessive anterior sagittal bow can lead to which of the following intraoperative errors?

During a gap-balancing technique for total knee arthroplasty, the surgeon notes that the extension gap is perfectly balanced and rectangular, but the flexion gap is asymmetric, being tighter on the medial side than the lateral side. Which of the following femoral component adjustments will correct this mismatch without altering the extension gap?

A patient presents with persistent anterior knee pain and recurrent lateral patellar subluxation 1 year after a primary total knee arthroplasty. CT scan evaluation is most likely to reveal which of the following component malrotations?

A patient with a 15-degree diaphyseal valgus deformity of the femur is scheduled for a primary total knee arthroplasty (TKA). If the surgeon attempts to correct this entirely with an intra-articular standard cut perpendicular to the mechanical axis of the femur, what is the most likely consequence on the distal femoral resection?

What is the primary biomechanical consequence of elevating the joint line during a revision total knee arthroplasty?

When performing an osteotomy to correct a tibial deformity, the surgeon places the osteotomy and the Axis of Correction of Angulation (ACA) at a level distant from the Center of Rotation of Angulation (CORA). According to Paley's rules, what is the expected geometric outcome?

During a primary PCL-substituting (PS) TKA, the trial reduction demonstrates a perfectly balanced extension gap, but the flexion gap is excessively tight, limiting flexion to 85 degrees. Which of the following is the most appropriate next step to balance the knee?

According to current orthopedic consensus, what is the generally accepted threshold of extra-articular coronal plane tibial deformity beyond which a simultaneous or staged extra-articular osteotomy is typically recommended during TKA?

Which of the following technical errors during the placement of TKA components is most likely to increase the Q-angle and precipitate lateral patellar maltracking?

In a cruciate-retaining (CR) total knee arthroplasty, cutting excessive posterior slope into the proximal tibia will most directly result in which of the following biomechanical outcomes?

A 70-year-old female undergoes TKA for a fixed 15-degree valgus deformity. During trial reduction, the knee is perfectly balanced in 90 degrees of flexion, but the lateral compartment remains asymmetrically tight in full extension. Which structure should be selectively released next?

A patient with a severe mechanical axis deviation is evaluated for deformity correction. Radiographs demonstrate a mechanical Lateral Distal Femoral Angle (mLDFA) of 98 degrees and a Medial Proximal Tibial Angle (MPTA) of 87 degrees. What is the primary source of the patient's deformity?

When setting the rotational alignment of the tibial component during primary TKA, aligning the center of the tibial tray to the medial third of the tibial tubercle serves to optimize patellofemoral mechanics primarily by:

When programming a six-axis hexapod frame for complex lower extremity deformity correction, which of the following represents a strictly defined "mounting parameter"?

Patellar clunk syndrome is a recognized complication of total knee arthroplasty. It is most heavily associated with which specific TKA design feature and technical factor?

If an intra-articular correction is attempted for a severe diaphyseal varus deformity located 3 cm proximal to the knee joint line during a primary TKA, what is the most likely surgical consequence?

Anterior femoral notching during primary TKA most significantly increases the biomechanical risk of which postoperative complication?

In a severe varus knee undergoing TKA, the patient has a residual 15-degree flexion contracture after appropriate distal femoral and proximal tibial bone resections. The flexion gap is appropriately balanced. What is the most appropriate next step to correct the contracture?

In the kinematic alignment philosophy for TKA, the primary goal for coronal plane alignment differs from traditional mechanical alignment by:

A 68-year-old female undergoes primary total knee arthroplasty for severe valgus osteoarthritis. The surgeon aggressively resects the distal femur to correct the deformity and balances the extension gap by utilizing a thicker tibial polyethylene insert. This technique inadvertently elevates the joint line by 8 mm. What is the primary biomechanical consequence of this joint line alteration?

A 40-year-old male presents with a symptomatic diaphyseal varus deformity of the tibia.

Surgical planning dictates that an osteotomy will be performed exactly at the Center of Rotation of Angulation (CORA). To avoid any translational displacement of the mechanical axis, the Axis of Correction of Angulation (ACA) is placed directly on the convex cortex of the deformity. Which of the following correctly describes the resulting geometric correction?

During a primary total knee arthroplasty using a posterior referencing system, trial components are inserted. Evaluation reveals that the knee is well-balanced and stable in full extension, but demonstrates 4 mm of symmetric laxity in 90 degrees of flexion. The patellar tracking is central, and the joint line is at the anatomic level. What is the most appropriate intraoperative modification to achieve optimal gap balancing?

A 45-year-old active male is undergoing a medial opening wedge high tibial osteotomy (HTO) distal to the tibial tubercle for medial compartment osteoarthritis with varus malalignment. What is the most common expected secondary biomechanical effect on the extensor mechanism if the osteotomy gap is opened symmetrically without altering the posterior tibial slope?

A surgeon is performing a primary posterior-stabilized total knee arthroplasty. To optimize patellofemoral tracking, the femoral component is externally rotated 3 degrees relative to the posterior condylar axis. What is the primary biomechanical effect of this rotation on the flexion and extension gaps?

When correcting a multi-apical tibial deformity, the surgeon plans an osteotomy at a site anatomically distant from the Center of Rotation of Angulation (CORA) but places the Axis of Correction of Angulation (ACA) exactly at the CORA. Which of the following best describes the resulting alignment?

A 68-year-old woman with advanced knee osteoarthritis has a concomitant extra-articular diaphyseal tibial varus deformity from a malunited fracture. When considering a single-stage intra-articular correction during TKA, what is the maximum recommended angular deformity of the tibia in the coronal plane before an extra-articular osteotomy is generally indicated to prevent excessive joint line obliquity?

During a revision total knee arthroplasty, the joint line is inadvertently elevated by 8 mm compared to the native knee. What is the most likely biomechanical consequence of this joint line elevation on the extensor mechanism?

While balancing a primary total knee arthroplasty, the surgeon finds that the joint is symmetrically tight in extension but perfectly balanced in flexion. Which of the following maneuvers is the most appropriate next step to achieve a balanced knee?

If the tibial component is inadvertently placed in excessive internal rotation during a primary total knee arthroplasty, what is the predictable consequence on patellofemoral kinematics?

When evaluating a patient for lower extremity deformity correction, how is the mechanical axis deviation (MAD) objectively measured on standing full-length anteroposterior radiographs?

In a cruciate-retaining total knee arthroplasty, what is the primary role of the intact posterior cruciate ligament (PCL) during deep knee flexion?

A 45-year-old active patient with symptomatic isolated lateral compartment osteoarthritis and a mechanical valgus alignment of 12 degrees undergoes a medial closing-wedge distal femoral osteotomy. Which of the following is an expected biomechanical outcome of this specific osteotomy technique compared to a lateral opening-wedge technique?

When performing a primary TKA on a patient with a significant diaphyseal varus bowing of the femur, utilizing a standard intramedullary alignment rod that traverses the entire diaphysis without accounting for the bow will most likely result in which of the following errors?

According to Paley's principles of deformity correction, how is the Center of Rotation of Angulation (CORA) geometrically defined on an anteroposterior radiograph of a deformed long bone?

Increasing the posterior slope of the tibial component during a cruciate-retaining primary total knee arthroplasty has which of the following primary biomechanical effects?

A 72-year-old female presents with end-stage osteoarthritis and a malunited midshaft tibia fracture. When planning a primary total knee arthroplasty, what is the generally accepted maximum limit of extra-articular coronal plane tibial deformity that can be managed safely with an intra-articular compensatory bone cut alone?

In the principles of lower extremity deformity correction, if the Axis of Correction of Angulation (ACA) is placed at a different level than the Center of Rotation of Angulation (CORA), what is the inevitable geometric consequence?

During a revision total knee arthroplasty, the surgeon utilizes a thicker tibial polyethylene insert and thick distal femoral augments, resulting in a joint line elevation of 12 mm. What is the most likely biomechanical consequence of this alteration?

A surgeon is performing a primary total knee arthroplasty using an anterior referencing system for the femoral component. If the femoral measurement falls exactly between two sizes and the surgeon elects to downsize the component, what is the immediate biomechanical consequence?

To optimize patellar tracking in a patient with a mildly increased Q-angle undergoing primary total knee arthroplasty, which intraoperative adjustment of the femoral component is most appropriate?

A 50-year-old male undergoes a medial opening wedge high tibial osteotomy (HTO) for isolated medial compartment osteoarthritis. If the osteotomy gap is opened equally at the anterior and posterior cortices, what unintended biomechanical change is most likely to occur?

During the trial reduction phase of a posterior-stabilized total knee arthroplasty, the knee is found to be excessively tight in both full extension and 90 degrees of flexion. What is the most appropriate next step to balance the knee?

When setting the rotation of the tibial component in a total knee arthroplasty, referencing off the medial third of the tibial tubercle rather than internally rotating the tray avoids which of the following complications?

The Paley multiplier method is frequently used to predict limb length discrepancy at skeletal maturity. This predictive method is primarily based on which of the following parameters?

In a cruciate-retaining total knee arthroplasty, paradoxical anterior translation of the femur on the tibia during deep flexion is most directly caused by:

A patient with a severe proximal tibial varus deformity requires an extra-articular osteotomy. The Center of Rotation of Angulation (CORA) is located in the proximal metaphysis. If a dome osteotomy is performed with the Axis of Correction of Angulation (ACA) perfectly aligning with the CORA, what is the geometric result?

An orthopedic surgeon is analyzing a long-leg radiograph to plan a deformity correction.

The mechanical axis line of the proximal segment and the mechanical axis line of the distal segment intersect at a specific point. What term strictly defines this intersection?