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Biomechanics & Biomaterials MCQs

Practice Set 9 of 88

This practice set contains high-yield board review questions covering key concepts in Biomechanics & Biomaterials. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 161

Topic: Biomechanics & Biomaterials

A 62-year-old male presents with progressive right knee pain, worse with activity. Full-length standing AP radiographs reveal a Mechanical Axis Deviation (MAD) of 15mm medial to the center of the knee joint. The surgeon suspects a varus deformity originating from the proximal tibia. Based on Paley's principles, which of the following angles, if found to be abnormal, would most directly confirm a proximal tibial varus deformity and guide a high tibial osteotomy (HTO)?

. A. Mechanical Lateral Distal Femoral Angle (mLDFA)
. B. Lateral Distal Tibial Angle (LDTA)
. C. Medial Proximal Tibial Angle (MPTA)
. D. Posterior Proximal Tibial Angle (PPTA)
. E. Neck-Shaft Angle (NSA)

Correct Answer & Explanation

. C. Medial Proximal Tibial Angle (MPTA)

Explanation

Correct Answer: CThe correct answer is C, the Medial Proximal Tibial Angle (MPTA). The case describes a patient with medial Mechanical Axis Deviation (MAD) and a suspicion of proximal tibial varus. According to Paley's principles, the MPTA is the cornerstone of tibial alignment in the frontal plane. A normal MPTA ranges from 85° to 90° (average ~87°). An MPTA of less than 85° specifically indicates tibia vara, which is a proximal tibial varus deformity. High Tibial Osteotomies (HTOs) are designed to correct this angle, typically restoring it to a normal or slightly valgus alignment (e.g., 89-90°) to offload the medial compartment.Option A (mLDFA)is the mechanical Lateral Distal Femoral Angle. While critical for overall limb alignment, it assesses distal femoral alignment (normal 85-90°). An abnormality here would indicate a femoral deformity, not a proximal tibial one.Option B (LDTA)is the Lateral Distal Tibial Angle. This angle assesses distal tibial alignment in the frontal plane (normal 86-92°). An abnormality here would indicate a deformity at the ankle level, not the proximal tibia.Option D (PPTA)is the Posterior Proximal Tibial Angle. This angle assesses the sagittal plane alignment (posterior tibial slope) of the proximal tibia (normal 77-84°). While important for knee kinematics, it does not directly quantify frontal plane varus/valgus deformity.Option E (NSA)is the Neck-Shaft Angle. This angle assesses the frontal plane alignment of the proximal femur (normal 124-136°). It is unrelated to knee or tibial deformities.

Question 162

Topic: Biomechanics & Biomaterials

A 45-year-old male with medial compartment knee osteoarthritis undergoes a medial opening wedge high tibial osteotomy (HTO). Postoperatively, the patient experiences anterior knee pain. Radiographs reveal an unintended increase in the posterior tibial slope. Which surgical error most likely caused this outcome?

. Over-distraction of the anterior cortex relative to the posterior cortex
. Over-distraction of the posterior cortex relative to the anterior cortex
. Placement of the hinge too anteriorly
. Placing the osteotomy distal to the tibial tubercle
. Failure to release the superficial medial collateral ligament

Correct Answer & Explanation

. Over-distraction of the anterior cortex relative to the posterior cortex

Explanation

In an opening wedge HTO, the posterior tibial cortex is naturally wider than the anterior cortex. If the anterior aspect is opened symmetrically or more than the posterior aspect, the posterior tibial slope unintentionally increases, which alters knee kinematics and strains the ACL.

Question 163

Topic: Biomechanics & Biomaterials

A 45-year-old active male is undergoing a high tibial osteotomy (HTO) for medial compartment osteoarthritis and varus deformity. The surgeon chooses a medial opening wedge HTO. To prevent unintended alterations in the sagittal plane knee kinematics, how should the anterior and posterior gaps of the osteotomy compare?

. The anterior gap should be roughly equal to the posterior gap.
. The anterior gap should be approximately half the size of the posterior gap.
. The anterior gap should be twice the size of the posterior gap.
. The anterior gap should be maximally opened while the posterior gap remains closed.
. The posterior gap should be grafted while the anterior gap is stabilized with a plate.

Correct Answer & Explanation

. The anterior gap should be approximately half the size of the posterior gap.

Explanation

Because the proximal tibia is naturally triangular and narrower anteriorly, opening the anterior and posterior gaps equally will inadvertently increase the posterior tibial slope. To maintain the native slope, the anterior opening gap should be approximately 50% of the posterior gap.

Question 164

Topic: Biomechanics & Biomaterials

In the context of external fixation biomechanics, when utilizing half-pins to augment a circular frame, the bending stiffness of the pin is highly dependent on its core diameter. According to biomechanical principles, the bending stiffness is proportional to the radius raised to which power?

. Second power (r^2)
. Third power (r^3)
. Fourth power (r^4)
. Fifth power (r^5)
. It is inversely proportional to the radius.

Correct Answer & Explanation

. Fourth power (r^4)

Explanation

The bending stiffness of a pin or screw is proportional to the area moment of inertia, which for a solid cylinder is a function of the radius to the fourth power (r^4). Therefore, small increases in core diameter exponentially increase the pin's stiffness.

Question 165

Topic: Biomechanics & Biomaterials

A 22-year-old patient is undergoing correction of a severe proximal tibial procurvatum deformity (apex anterior). If left uncorrected, how does a diaphyseal procurvatum deformity of the tibia mechanically affect knee kinematics?

. It functionally increases the posterior tibial slope, potentially increasing ACL strain and causing a knee flexion contracture.
. It functionally decreases the posterior tibial slope, predisposing to PCL insufficiency.
. It forces the knee into recurvatum during weight-bearing.
. It restricts internal rotation of the tibia during the screw-home mechanism.
. It uniformly decreases patellofemoral contact pressures.

Correct Answer & Explanation

. It functionally increases the posterior tibial slope, potentially increasing ACL strain and causing a knee flexion contracture.

Explanation

An apex anterior deformity (procurvatum) of the tibia tilts the knee joint line such that the effective posterior tibial slope is increased. This alters knee kinematics by increasing anterior tibial translation forces, putting stress on the ACL and potentially leading to a functional flexion contracture.

Question 166

Topic: Biomechanics & Biomaterials
A surgeon is considering a 'compensatory strategy' for a patient with a 20° FFD caused by 10° femoral procurvatum and 10° soft tissue contracture, as depicted in Panel (iii) of the provided diagram. Which of the following statements accurately describes the outcome and implications of this compensatory approach?
. A 10° femoral extension osteotomy is performed, restoring the PDFA to normal, and the remaining 10° FFD is corrected by soft tissue release.
. A 20° femoral extension osteotomy is performed, making the leg clinically straight but resulting in an intentionally overcorrected (increased) PDFA.
. A 20° femoral extension osteotomy is performed, making the leg clinically straight and restoring the PDFA to a normal value of 83°.
. A 10° soft tissue release is performed, and the remaining 10° FFD is corrected by a femoral extension osteotomy, leaving the PDFA undercorrected.
. This approach is considered the gold standard as it avoids soft tissue releases and minimizes surgical complexity.

Correct Answer & Explanation

. A 20° femoral extension osteotomy is performed, making the leg clinically straight but resulting in an intentionally overcorrected (increased) PDFA.

Explanation

As described in the case and illustrated in Panel (iii) of the diagram, the compensatory strategy involves performing a larger osteotomy than anatomically required to correct the osseous deformity. In this specific example (20° FFD, 10° bone, 10° soft tissue), a 20° femoral osteotomy is performed. This single osseous intervention makes the leg clinically straight (0° extension) but leaves the joint with an intentionally abnormal, overcorrected PDFA (e.g., if normal is 83° and initial was 74°, a 20° correction would make it 94°, which is recurvatum). This approach 'compensates' for the soft tissue contracture by overcorrecting the bone.

Question 167

Topic: Biomechanics & Biomaterials

A 70-year-old patient undergoes a distal femoral osteotomy for correction of a 15° fixed flexion deformity. Postoperatively, the patient continues to experience significant anterior knee pain, a persistent crouched gait, and reports difficulty with terminal knee extension. Radiographs show that the coronal alignment is excellent, but the sagittal plane correction resulted in a PDFA of 90°. Based on the case's discussion, what is the most likely underlying cause of the patient's persistent symptoms?

. Inadequate correction of a coronal plane deformity, leading to persistent mechanical axis deviation.
. Overcorrection of the femoral procurvatum, resulting in iatrogenic femoral recurvatum and altered knee kinematics.
. Undercorrection of the soft tissue contracture, leading to persistent hamstring tightness.
. Development of a new tibial procurvatum deformity due to compensatory loading.
. Avascular necrosis of the distal femur, causing pain and limited range of motion.

Correct Answer & Explanation

. Overcorrection of the femoral procurvatum, resulting in iatrogenic femoral recurvatum and altered knee kinematics.

Explanation

Correct Answer: BThe normal PDFA is 83° (range 79° to 87°). A postoperative PDFA of 90° indicates an overcorrection of the femoral procurvatum, resulting in iatrogenic femoral recurvatum (a posterior bow). As highlighted in the case, overlooking sagittal plane malalignment or creating an iatrogenic one can lead to persistent anterior knee pain, abnormal kinematics, and profound patient dissatisfaction, even with a perfectly executed coronal correction. Femoral recurvatum would place increased stress on the anterior knee structures and alter the normal passive extension moment, contributing to the crouched gait and difficulty with terminal extension.Option A is incorrectas the question states coronal alignment is excellent.Option C is incorrectbecause while undercorrection of soft tissue can cause FFD, the specific finding of a 90° PDFA points to an osseous overcorrection as the primary issue here, which itself can cause pain and kinematic problems.Option D is incorrectbecause while compensatory loading can occur, the direct and immediate cause of symptoms with a 90° PDFA is the iatrogenic femoral recurvatum.Option E is incorrectas avascular necrosis is a serious complication but is not directly indicated by the described symptoms and radiographic finding of an abnormal PDFA; the symptoms are more consistent with biomechanical malalignment.

Question 168

Topic: Biomechanics & Biomaterials

Following a successful valgus knee realignment with a distal femoral osteotomy, a patient reports persistent lateral knee pain despite good radiographic correction of the mechanical axis. On examination, the patient has tenderness over the lateral epicondyle and pain with varus stress. What is the most likely cause of this persistent pain?

. Nonunion of the osteotomy site.
. Overcorrection leading to medial compartment overload.
. Development of patellofemoral instability.
. Iliotibial band (ITB) friction syndrome due to altered biomechanics.
. Recurrence of the valgus deformity.

Correct Answer & Explanation

. Iliotibial band (ITB) friction syndrome due to altered biomechanics.

Explanation

Correct Answer: DIliotibial band (ITB) friction syndrome is a known complication or cause of persistent pain after valgus knee realignment. The osteotomy changes the biomechanics of the knee, potentially altering the tension and tracking of the ITB over the lateral femoral epicondyle. This can lead to inflammation and pain, especially with activities involving repetitive knee flexion and extension. Tenderness over the lateral epicondyle and pain with varus stress (which can tension the ITB) are classic signs.Option A is incorrectbecause nonunion would typically present with more diffuse pain, instability, and often radiographic signs of failed healing, not localized lateral epicondyle tenderness.Option B is incorrectbecause overcorrection leading to medial compartment overload would cause medial knee pain, not lateral knee pain.Option C is incorrectbecause patellofemoral instability would typically present with anterior knee pain, catching, or giving way, not primarily lateral epicondyle tenderness.Option E is incorrectbecause recurrence of the valgus deformity would lead to a return of lateral compartment pain due to loading, but the question states 'good radiographic correction of the mechanical axis' and points to specific lateral epicondyle tenderness.

Question 169

Topic: Biomechanics & Biomaterials

A 32-year-old female with chronic ACL insufficiency and a varus-procurvatum deformity of the proximal tibia is undergoing an anterior opening-wedge high tibial osteotomy. How will correcting the procurvatum (increasing the posterior tibial slope) affect her knee biomechanics?

. It will increase anterior tibial translation, worsening ACL instability
. It will decrease anterior tibial translation, stabilizing the ACL-deficient knee
. It will have no effect on sagittal plane translation
. It will isolate stress to the lateral collateral ligament
. It will decrease patellofemoral joint reaction forces

Correct Answer & Explanation

. It will increase anterior tibial translation, worsening ACL instability

Explanation

Increasing the posterior tibial slope increases the anterior translation force on the tibia during weight-bearing. In an ACL-deficient knee, this exacerbates anterior instability, making an anterior closing-wedge (slope-decreasing) osteotomy more appropriate.

Question 170

Topic: Biomechanics & Biomaterials

A 40-year-old patient with chronic LCL laxity and a varus knee deformity is undergoing surgical planning. The surgeon is considering an acute fibular head advancement to tighten the lateral structures. Based on the case, what is the most significant limitation or risk associated with this acute correction technique?

. The technique is only applicable for valgus deformities, not varus knees.
. It allows for precise, unlimited correction potential without risk of overtensioning.
. There is a high risk of iatrogenic injury to the common peroneal nerve due to extensive dissection.
. It requires a long period of external fixation, increasing patient morbidity.
. The procedure is associated with rapid bone healing at the fibular osteotomy site, leading to premature fusion.

Correct Answer & Explanation

. There is a high risk of iatrogenic injury to the common peroneal nerve due to extensive dissection.

Explanation

Correct Answer: CThe case discusses acute fibular head advancement and explicitly lists its limitations and risks: 'While conceptually simple, acute advancement carries significant risks and inherent limitations: High Risk to the Peroneal Nerve: The procedure requires extensive, meticulous dissection around the fibular neck, placing the common peroneal nerve at extremely high risk for traction injury (neurapraxia), entrapment, or outright transection.'Option A is incorrectbecause fibular head advancement is discussed in the context of LCL laxity, which is typically associated with varus knees and lateral thrust.Option B is incorrectbecause the text states, 'Limited Correction Potential: The amount of advancement is strictly restricted by the compliance of the surrounding neurovascular and muscular tissues. You can only pull the fibular head so far before tension on the nerve becomes critical.' It also mentions 'Stress Relaxation: The viscoelastic nature of ligamentous tissue means that acutely tightened ligaments tend to stretch out and relax over time, potentially leading to recurrent laxity and failure of the reconstruction,' implying that precise, durable overtensioning is difficult.Option D is incorrectbecause acute correction techniques typically do not involve prolonged external fixation; that is a characteristic of gradual correction methods.Option E is incorrectbecause the primary concern with acute advancement is nerve injury and limited correction, not premature fusion. Bone healing is generally desired, but the method's drawbacks outweigh this.

Question 171

Topic: Biomechanics & Biomaterials

Following a medial opening wedge high tibial osteotomy to correct a severe varus deformity, the patient exhibits persistent knee extension lag and complains of anterior knee pain. What intraoperative technical error is most likely responsible for this complication?

. Overcorrection of the mechanical axis into 4 degrees of valgus.
. Failure to release the superficial medial collateral ligament distally.
. Distalization of the tibial tubercle leading to patella baja.
. Inadvertent lateral cortical hinge fracture.
. Use of a gap ratio that increased the posterior tibial slope.

Correct Answer & Explanation

. Distalization of the tibial tubercle leading to patella baja.

Explanation

A medial opening wedge HTO elongates the proximal tibia. If the osteotomy is proximal to the tibial tubercle, it relative distalizes the patella, creating patella baja. This alters patellofemoral kinematics, often leading to anterior knee pain and extensor lag.

Question 172

Topic: Biomechanics & Biomaterials

A 68-year-old male with symptomatic medial compartment knee osteoarthritis and a varus deformity is observed during gait analysis. The physical therapist notes that the patient consistently walks with a 'toe-out' gait pattern, characterized by excessive external rotation of the lower limb. Based on the biomechanical principles discussed in the case, what is the most likely reason for this compensatory gait alteration?

. A. To increase the adductor moment arm, thereby increasing medial compartment load for stability.
. B. To shift the ground reaction vector (GRV) further away from the center of the knee joint, increasing pain.
. C. To reduce the adductor moment arm by placing the GRV closer to the center of the knee joint, providing symptomatic relief.
. D. To increase internal rotation of the lower limb, which is a natural response to varus.
. E. To compensate for a primary hip abductor weakness, unrelated to the knee deformity.

Correct Answer & Explanation

. C. To reduce the adductor moment arm by placing the GRV closer to the center of the knee joint, providing symptomatic relief.

Explanation

Correct Answer: CThe case content explains that patients with severe compartmental overload subconsciously alter their gait kinematics to manipulate the Ground Reaction Vector (GRV) and reduce pain. A 'toe-out' gait, achieved by excessive external rotation of the lower limb, physically places the GRV closer to the center of the knee joint. This effectively reduces the adductor moment arm, which is directly proportional to a reduction in the medial compartment load, providing the patient with temporary symptomatic relief.Option A is incorrectbecause a toe-out gait aims to reduce, not increase, the adductor moment arm to offload the painful medial compartment.Option B is incorrectbecause a toe-out gait places the GRV closer to the center of the knee, thereby reducing the adductor moment and pain, not increasing it.Option D is incorrectbecause a toe-out gait involves external rotation, not internal rotation. A 'toe-in' gait involves internal rotation and would increase the adductor moment, exacerbating medial compartment pain.Option E is incorrectbecause while hip abductor weakness can cause gait abnormalities, the toe-out gait in this context is described as a specific compensation for knee compartmental overload, directly manipulating the GRV relative to the knee.

Question 173

Topic: Biomechanics & Biomaterials

The ultimate goal of any reconstructive orthopedic procedure for lower extremity deformities, as emphasized by the Paley principles, extends beyond achieving a pristine static postoperative radiograph. Which of the following best encapsulates the overarching objective of such surgical interventions?

. A. To achieve perfect anatomical alignment on static radiographs, regardless of functional outcome.
. B. To minimize surgical time and reduce hospital stay, prioritizing efficiency over long-term function.
. C. To restore fluid, efficient, and pain-free gait, optimizing kinematics and preserving native joint function.
. D. To ensure the patient can bear full weight immediately post-surgery, even with residual pain.
. E. To replace the native joint with an arthroplasty as the primary solution for all deformities.

Correct Answer & Explanation

. C. To restore fluid, efficient, and pain-free gait, optimizing kinematics and preserving native joint function.

Explanation

Correct Answer: CThe very first paragraph of the teaching case sets the tone: 'For the orthopedic reconstructive surgeon, the final arbiter of success is not the pristine, static postoperative radiograph, but the fluid, efficient, and pain-free gait of the patient in motion.' It further states that the ultimate goal is 'the complete restoration of biomechanical function,' and that rigorous application of Paley principles aims to 'restore normal biomechanics, optimize kinematics, and ultimately save the native joint from premature arthroplasty.' This clearly emphasizes functional, dynamic outcomes over static radiographic appearance.Option A is incorrectbecause the case explicitly states that static radiographs are not the 'final arbiter of success'; functional gait is.Option B is incorrectbecause while efficiency is important, it is not the overarching objective. The primary goal is long-term functional restoration and pain relief.Option D is incorrectbecause immediate full weight-bearing is not the ultimate goal; pain-free, efficient gait is, which may or may not involve immediate full weight-bearing depending on the procedure.Option E is incorrectbecause the Paley principles are specifically highlighted as a means to perform 'joint-preserving osteotomies that restore normal biomechanics... and ultimately save the native joint from premature arthroplasty,' making arthroplasty a secondary, not primary, solution for many deformities.

Question 174

Topic: Biomechanics & Biomaterials

When measuring a patient's lower extremity alignment parameters, the Joint Line Congruency Angle (JLCA) is found to be 6 degrees, opening laterally. What is the most likely clinical correlate to this radiographic finding?

. Normal knee joint kinematics
. Medial compartment cartilage loss or lateral ligament laxity
. Lateral compartment cartilage loss or medial ligament laxity
. Fixed valgus deformity of the distal femur
. Normal physiologic bowing of the tibia

Correct Answer & Explanation

. Medial compartment cartilage loss or lateral ligament laxity

Explanation

A normal JLCA is 0 to 2 degrees. A JLCA that opens laterally implies that the medial joint space is abnormally narrowed or the lateral side is widened, typically indicating medial compartment cartilage wear or lateral ligamentous laxity.

Question 175

Topic: Biomechanics & Biomaterials



A 19-year-old male requires correction of a complex distal tibial deformity characterized by varus, procurvatum, internal rotation, and 2 cm of shortening. The surgeon elects to use a hexapod circular fixator (e.g., Taylor Spatial Frame). What is the primary biomechanical advantage of this device over a traditional Ilizarov frame for this multidimensional deformity?

. It relies strictly on manual hinge placement at the exact CORA for successful angular correction.
. It allows simultaneous correction of all six degrees of freedom utilizing a virtual hinge and software program.
. It eliminates the risk of pin-tract infections due to the use of hydroxyapatite-coated wires exclusively.
. It requires a faster distraction rate (2.0 mm/day) because the frame struts are inherently dynamic.
. It negates the need for an osteotomy if the deformity is within 5 centimeters of the joint line.

Correct Answer & Explanation

. It allows simultaneous correction of all six degrees of freedom utilizing a virtual hinge and software program.

Explanation

The Taylor Spatial Frame (hexapod system) utilizes computer software to create a 'virtual hinge' in space. This allows for the simultaneous, gradual correction of complex deformities in all six degrees of freedom (angulation, translation, and rotation across all planes) without requiring complex, physical hinge adjustments.

Question 176

Topic: Biomechanics & Biomaterials
A 30-year-old construction worker sustains a Rockwood Type III AC joint separation. Understanding the biomechanics of the AC joint is crucial for treatment planning. Which of the following statements accurately describes the primary role of the coracoclavicular (CC) ligaments in AC joint stability?
. They primarily resist anterior and posterior shear forces at the AC joint.
. They are the main stabilizers against superior translation of the clavicle.
. They provide the majority of horizontal stability to the AC joint.
. The conoid ligament primarily resists anterior displacement, while the trapezoid resists posterior displacement.
. They form part of the coracoacromial arch, preventing superior humeral head migration.

Correct Answer & Explanation

. They are the main stabilizers against superior translation of the clavicle.

Explanation

The coracoclavicular (CC) ligaments (conoid and trapezoid) are the primary vertical stabilizers of the AC joint. They provide approximately 70-80% of the vertical stability, resisting superior translation of the clavicle relative to the acromion.

Question 177

Topic: Biomechanics & Biomaterials

When performing an anatomic coracoclavicular ligament reconstruction using a tendon graft, restoring the functional biomechanics of the joint requires routing the graft properly. Which of the following best describes the structural restraint roles of the native CC ligaments?

. Trapezoid resists anterior translation; Conoid resists posterior translation.
. Conoid resists superior and anterior displacement; Trapezoid resists compression to the acromion.
. Both ligaments primarily resist anterior-posterior translation over superior-inferior.
. Trapezoid primarily resists superior displacement; Conoid primarily resists medial displacement.
. Conoid provides static stability; Trapezoid acts solely as a dynamic stabilizer.

Correct Answer & Explanation

. Conoid resists superior and anterior displacement; Trapezoid resists compression to the acromion.

Explanation

The conoid ligament acts as the primary restraint to superior and anterior displacement of the clavicle. The trapezoid ligament provides resistance to axial compression, resisting medial displacement of the acromion under the clavicle.

Question 178

Topic: Biomechanics & Biomaterials

When comparing the Taylor Spatial Frame (TSF) to a traditional classic Ilizarov frame for correcting a multiplanar deformity, what is the primary biomechanical and functional advantage of the hexapod system?

. It requires fewer half-pins for adequate stability
. It allows for simultaneous correction of 6 degrees of freedom without requiring frame modifications
. It primarily utilizes tensioned wires, avoiding the need for half-pins entirely
. It prevents pin-tract infections by using hydroxyapatite-coated struts
. It eliminates the need for a latency period prior to distraction

Correct Answer & Explanation

. It allows for simultaneous correction of 6 degrees of freedom without requiring frame modifications

Explanation

The TSF is a hexapod frame that allows simultaneous correction of angulation, translation, and rotation (6 degrees of freedom) through software-guided strut adjustments, avoiding the need to rebuild the frame.

Question 179

Topic: Biomechanics & Biomaterials

The ultimate goal of Dr. Paley's single-cut oblique osteotomy method for combined angulation and rotation deformities, as described in the case, is to achieve which of the following?

. To simplify surgical planning by eliminating the need for advanced imaging.
. To allow for sequential correction of angulation followed by rotation in separate surgical stages.
. To restore the patient's mechanical axis, optimize joint orientation, and return physiologic limb function to prevent early-onset osteoarthritis.
. To primarily correct cosmetic deformities without significant biomechanical impact.
. To achieve limb shortening in cases of severe overgrowth.

Correct Answer & Explanation

. To restore the patient's mechanical axis, optimize joint orientation, and return physiologic limb function to prevent early-onset osteoarthritis.

Explanation

Correct Answer: CThe introduction of the case explicitly states the ultimate goal: 'The ultimate goal? Restoring the patient's mechanical axis, optimizing joint orientation, and returning physiologic limb function to prevent early-onset osteoarthritis.'Option A is incorrectbecause the method emphasizes meticulous preoperative planning, including advanced imaging like CT version studies, not eliminating them.Option B is incorrectbecause the core principle of the single-cut oblique osteotomy is to correctbothangulation and rotationsimultaneouslywith one elegant cut, moving beyond sequential or separate corrections.Option D is incorrectbecause while cosmetic improvement may be a secondary benefit, the primary focus is on restoring normal biomechanics and preventing long-term joint degeneration.Option E is incorrectbecause limb shortening is not the primary or universal goal of this method; the focus is on correcting alignment and rotation.

Question 180

Topic: Biomechanics & Biomaterials

A surgeon plans a medial opening wedge high tibial osteotomy (HTO) for a patient with medial compartment osteoarthritis. If the osteotomy is performed proximal to the tibial tubercle, what is the most predictable effect on the patellofemoral joint?

. Increased patellar height (patella alta).
. Decreased patellar height (patella baja).
. Lateral subluxation of the patella.
. Medial subluxation of the patella.
. No change in patellofemoral kinematics.

Correct Answer & Explanation

. Decreased patellar height (patella baja).

Explanation

A medial opening wedge HTO performed proximal to the tibial tubercle increases the distance between the tibial tubercle and the joint line. This effectively decreases the patellar height relative to the joint, leading to patella baja (infera).

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