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3. Adult Reconstruction (Hip & Knee) MCQs

Practice Set 38 of 326

This practice set contains high-yield board review questions covering key concepts in 3. Adult Reconstruction (Hip & Knee). Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 741

Topic: 3. Adult Reconstruction (Hip & Knee)

What is the typical normal angle between the anatomic axis and the mechanical axis of the femur (AMA angle)?

. 0 degrees
. 3 degrees
. 7 degrees
. 12 degrees
. 15 degrees

Correct Answer & Explanation

. 7 degrees

Explanation

The normal anatomic-mechanical axis (AMA) angle of the femur is approximately 7 degrees (range 5-9 degrees). This relationship is critical when using intramedullary guides for deformity correction or arthroplasty.

Question 742

Topic: 3. Adult Reconstruction (Hip & Knee)

A patient undergoing tibial lengthening with a circular frame presents with a red, painful pin site that has purulent discharge but no radiographic evidence of osteolysis. According to the Checketts-burns classification, what is the most appropriate initial management?

. Immediate removal of the offending pin
. Oral antibiotics and increased local pin site care
. Intravenous antibiotics and hospital admission
. Surgical debridement of the pin tract
. Exchange of the pin for a larger diameter half-pin

Correct Answer & Explanation

. Oral antibiotics and increased local pin site care

Explanation

This scenario describes a superficial pin site infection (Checketts-burns Grade 2), lacking deep bone involvement. It is appropriately and effectively managed with oral antibiotics and aggressive local pin site care.

Question 743

Topic: Total Hip Arthroplasty (THA)

A 6-year-old girl has a congenital short femur with a current leg length discrepancy (LLD) of 3 cm. Using the Paley multiplier method, how is the predicted LLD at skeletal maturity most accurately calculated?

. By multiplying the current LLD by the age- and gender-specific multiplier.
. By adding 1 cm for each year of remaining skeletal growth.
. By multiplying the normal femur length by the multiplier and subtracting the short femur length.
. By comparing her current percentile on the Green-Anderson charts and extrapolating to age 16.
. By dividing the current LLD by the mother's height multiplier.

Correct Answer & Explanation

. By multiplying the current LLD by the age- and gender-specific multiplier.

Explanation

The Paley multiplier method simplifies the prediction of LLD at skeletal maturity by multiplying the patient's current LLD by an established, gender- and age-specific constant. This method has been shown to be highly accurate and does not require complex bone age calculations or growth chart plotting.

Question 744

Topic: Total Knee Arthroplasty (TKA)

A surgeon is planning a complex osteotomy for a multi-planar lower limb deformity using a hexapod circular external fixator. The patient has a combined distal femoral and proximal tibial deformity. To ensure accurate correction and prevent inducing secondary deformities, which of the following principles, as described in the case, is paramount when placing the hinge pins for the osteotomy?

. A. Hinge pins must be placed perpendicular to the mechanical axis of the limb.
. B. Hinge pins must be placed parallel to the anatomic axis of the bone.
. C. Hinge pins must be placed parallel to the joint orientation line of the adjacent joint.
. D. Hinge pins must be placed at the exact Center of Rotation of Angulation (CORA).
. E. Hinge pins must be placed to achieve a final Mechanical Lateral Distal Femoral Angle (mLDFA) and Medial Proximal Tibial Angle (MPTA) of 90 degrees.

Correct Answer & Explanation

. C. Hinge pins must be placed parallel to the joint orientation line of the adjacent joint.

Explanation

Correct Answer: CThe correct answer is C. Under the 'Surgical Pearls for Joint Orientation Mapping' section, the case explicitly states: 'When performing an opening or closing wedge osteotomy, the hinge pin must be perfectly parallel to the joint orientation line to prevent inducing an unwanted secondary deformity in the orthogonal plane.' This principle ensures that the correction occurs purely in the intended plane (e.g., frontal plane for varus/valgus) without inadvertently creating a deformity in the sagittal plane (e.g., flexion/extension).Option Ais incorrect. While the mechanical axis is crucial for overall alignment, hinge pins are oriented relative to the joint line to control the plane of correction, not necessarily perpendicular to the mechanical axis of the entire limb.Option Bis incorrect. Hinge pins are oriented relative to the joint line, not necessarily parallel to the anatomic axis of the bone, especially if the anatomic axis itself is deformed or if the osteotomy is near a joint.Option Dis incorrect. While the CORA is the apex of the deformity and the ideal location for an osteotomy, the hinge pins' orientation (parallel to the joint line) is a separate, critical principle for preventing secondary deformities, regardless of whether the osteotomy is precisely at the CORA or away from it (using Paley's rules).Option Edescribes the goal of traditional Mechanical Alignment in TKA, not a general principle for hinge pin placement in osteotomies. Furthermore, achieving 90-degree angles for mLDFA and MPTA might not be the goal for all osteotomies, especially if aiming for kinematic alignment or specific overcorrection.

Question 745

Topic: Total Knee Arthroplasty (TKA)

A 70-year-old patient is undergoing Total Knee Arthroplasty (TKA). The surgeon is debating between a traditional Mechanical Alignment (MA) approach and a Kinematic Alignment (KA) approach. Based on the case, what is the fundamental difference in how these two philosophies utilize joint orientation lines?

. A. MA aims to restore the patient's pre-arthritic joint orientation lines, while KA aims for a neutral Mechanical Axis Deviation (MAD).
. B. MA aims to cut the distal femur and proximal tibia perpendicular to their mechanical axes, while KA aims to restore the patient's pre-arthritic joint orientation lines.
. C. MA focuses on correcting the Neck-Shaft Angle (NSA), while KA focuses on the Lateral Distal Tibial Angle (LDTA).
. D. MA prioritizes sagittal plane alignment (e.g., PDFA), while KA prioritizes frontal plane alignment (e.g., MPTA).
. E. Both MA and KA aim to achieve an MPTA of 87° and an mLDFA of 88°.

Correct Answer & Explanation

. B. MA aims to cut the distal femur and proximal tibia perpendicular to their mechanical axes, while KA aims to restore the patient's pre-arthritic joint orientation lines.

Explanation

Correct Answer: BThe correct answer is B. The case clearly differentiates Mechanical Alignment (MA) and Kinematic Alignment (KA) in TKA. It states: 'Mechanical Alignment: Traditional TKA aims to cut the distal femur and proximal tibia perpendicular to their mechanical axes. This forces the mLDFA and MPTA to be exactly 90°.' In contrast, 'Kinematic Alignment: Modern KA techniques aim to restore the patient's pre-arthritic joint orientation lines. The surgeon intentionally cuts the tibia at an MPTA of 87° and the femur at an mLDFA of 87° to match the native anatomy...'Option Aincorrectly swaps the definitions. MA aims for a neutral MAD (by making mLDFA and MPTA 90°), while KA aims to restore native joint lines.Option Cis incorrect. NSA and LDTA are not the primary distinguishing factors between MA and KA; the focus is on the knee's frontal plane angles (mLDFA, MPTA).Option Dis incorrect. Both MA and KA consider both frontal and sagittal planes, but the fundamental difference lies in their approach to frontal plane joint orientation (perpendicular to mechanical axis vs. native joint line).Option Eis incorrect. While 87° and 88° are average normal values, MA specifically aims for 90° for both mLDFA and MPTA, which often alters the native joint line. KA aims to restore theindividual patient'spre-arthritic angles, which might be around these averages but are not rigidly set to them for all patients.

Question 746

Topic: 3. Adult Reconstruction (Hip & Knee)

A 70-year-old patient is undergoing a Total Knee Arthroplasty (TKA). The surgeon is using an intramedullary guide for the distal femoral cut. The diagram below shows the frontal plane joint orientation angles, which helps illustrate the relationship between different axes.

Based on Paley's '7-Degree Rule' and its application in TKA, what is the typical angular difference between the mechanical and anatomic axes of the femur, and how is this accounted for when using an intramedullary guide?

. A. 0°; the intramedullary rod is aligned with the mechanical axis.
. B. 7° (range 5-9°); the distal femoral cutting block is typically set to 5° or 7° of valgus to convert the anatomic axis cut to a mechanical axis cut.
. C. 7° (range 5-9°); the distal femoral cutting block is typically set to 5° or 7° of varus to convert the anatomic axis cut to a mechanical axis cut.
. D. 15°; the intramedullary rod is aligned with the anatomic axis, requiring a 15° valgus cut.
. E. 2°; the intramedullary rod is aligned with the mechanical axis, requiring a 2° varus cut.

Correct Answer & Explanation

. B. 7° (range 5-9°); the distal femoral cutting block is typically set to 5° or 7° of valgus to convert the anatomic axis cut to a mechanical axis cut.

Explanation

Correct Answer: BThe case highlights 'The 7-Degree Rule': 'The difference between the mechanical and anatomic axes of the femur is typically 7° (range 5-9°). This is why a standard distal femoral cutting block in Total Knee Arthroplasty (TKA) is usually set to 5° or 7° of valgus—it is converting the anatomic axis (the intramedullary rod) into a mechanical axis cut perpendicular to the load-bearing line.'Option A is incorrect; there is a significant difference between the two axes.Option C is incorrect; the correction is typically in valgus, not varus, to achieve a perpendicular cut to the mechanical axis.Option D is incorrect; the difference is 7°, not 15°.Option E is incorrect; the difference is 7°, not 2°, and the correction is valgus, not varus.

Question 747

Topic: Total Knee Arthroplasty (TKA)

A 65-year-old female presents for Total Knee Arthroplasty (TKA). She has a mid-diaphyseal femoral malunion with 25 degrees of varus deformity. Which of the following is the most appropriate management to achieve a stable, aligned knee?

. Standard intra-articular femoral resection with a 25-degree valgus cut
. Corrective femoral osteotomy staged before TKA
. Simultaneous TKA with unconstrained polyethylene
. Standard TKA with an offset stem bypassing the deformity
. Custom TKA implant with asymmetric condyles

Correct Answer & Explanation

. Corrective femoral osteotomy staged before TKA

Explanation

Extra-articular coronal plane deformities >20 degrees in the femur generally require a corrective osteotomy rather than compensatory intra-articular resection. Intra-articular correction of such large extra-articular deformities disrupts collateral ligament balance and joint line obliquity.

Question 748

Topic: Total Knee Arthroplasty (TKA)

During preoperative planning for a TKA in a patient with an accentuated lateral femoral bow, you note an abnormally large anatomic-mechanical angle (AMA) of the femur. How does an increased femoral bow typically alter the standard distal femoral cut if referencing the intramedullary axis?

. Requires a larger valgus cut angle than standard
. Requires a smaller valgus cut angle than standard
. Requires 0 degrees of valgus
. Requires a varus cut angle
. Has no effect on the intramedullary guide

Correct Answer & Explanation

. Requires a larger valgus cut angle than standard

Explanation

The Anatomic-Mechanical Angle (AMA) of the femur normally ranges from 5-7 degrees. In an accentuated lateral femoral bow, the anatomic axis diverges more from the mechanical axis, necessitating a larger valgus cut angle (e.g., 7-9 degrees) when using an intramedullary guide.

Question 749

Topic: Total Knee Arthroplasty (TKA)

A 65-year-old male undergoes TKA 15 years after a closing wedge high tibial osteotomy. He now has severe patella baja. Which of the following technical modifications is most appropriate to prevent patellar tendon avulsion during surgical exposure?

. Extensive lateral retinacular release
. Quadriceps snip
. V-Y quadricepsplasty
. Tibial tubercle osteotomy
. Proximal soft tissue release of the patellar tendon

Correct Answer & Explanation

. Tibial tubercle osteotomy

Explanation

Patella baja is common after closing wedge HTO, making patellar eversion difficult and dramatically increasing the risk of patellar tendon avulsion. A tibial tubercle osteotomy (TTO) safely improves exposure and allows for proximalization of the tubercle to correct the baja.

Question 750

Topic: Total Knee Arthroplasty (TKA)

In a type II valgus knee (with attenuated medial collateral ligament) undergoing TKA, what is the most appropriate component constraint if a lateral release leaves the knee unbalanced in flexion and extension?

. Cruciate retaining (CR)
. Posterior stabilized (PS)
. Constrained non-hinged (CCK)
. Rotating hinge
. Unicompartmental knee

Correct Answer & Explanation

. Constrained non-hinged (CCK)

Explanation

A type II valgus knee is defined by medial collateral ligament attenuation. If the knee cannot be balanced with soft tissue releases due to medial incompetence, a Constrained Condylar Knee (CCK) implant is required to provide coronal stability.

Question 751

Topic: Total Knee Arthroplasty (TKA)

A patient with osteoarthritis and a 15-degree varus deformity presents for TKA. Preoperative templating reveals an mPTA of 80 degrees and an mLDFA of 88 degrees. To achieve a neutral mechanical axis while restoring parallel joint lines, which technique is most appropriate?

. Standard distal femoral cut at 5 degrees valgus and standard tibial cut at 90 degrees to mechanical axis
. Under-resecting the medial tibia to leave it in varus
. Performing a lateral opening wedge DFO prior to TKA
. Standard tibial cut at 90 degrees and oversized asymmetric femoral component
. Standard femoral and tibial cuts combined with a massive medial epicondylar osteotomy

Correct Answer & Explanation

. Standard distal femoral cut at 5 degrees valgus and standard tibial cut at 90 degrees to mechanical axis

Explanation

The deformity is entirely in the proximal tibia (abnormal mPTA of 80; normal mLDFA of 88). Cutting the tibia perpendicular to its mechanical axis and the femur at its standard anatomic valgus angle, followed by medial release, will correct this extra-articular deformity intra-articularly without issue.

Question 752

Topic: Total Knee Arthroplasty (TKA)

During a TKA, the surgeon inadvertently cuts the proximal tibia with 15 degrees of posterior slope. What is the most likely biomechanical consequence of this error?

. Flexion instability with anterior subluxation of the femur on the tibia
. Extension gap laxity with recurvatum
. Tightness in flexion preventing more than 90 degrees of flexion
. Anterior lift-off of the tibial tray during walking
. Patellar clunk syndrome

Correct Answer & Explanation

. Flexion instability with anterior subluxation of the femur on the tibia

Explanation

Excessive posterior tibial slope functionally increases the flexion gap relative to the extension gap. This causes the femur to slide anteriorly (or tibia posteriorly) in deep flexion, leading to flexion instability.

Question 753

Topic: 3. Adult Reconstruction (Hip & Knee)

During Total Knee Arthroplasty (TKA) on a patient with a significant diaphyseal anterior bow of the femur, a standard long intramedullary alignment guide is utilized. If the anterior bow is not properly accounted for, what is the most likely consequence for the femoral component alignment?

. Extension of the femoral component
. Flexion of the femoral component
. Excessive valgus alignment
. Excessive varus alignment
. Internal rotation of the femoral component

Correct Answer & Explanation

. Excessive varus alignment

Explanation

A severe anterior bowing of the femoral diaphysis causes a straight intramedullary rod to pitch anteriorly at the distal end. This results in the cutting block being directed into flexion, leading to a flexed femoral component and potential notching or limited knee extension.

Question 754

Topic: Total Knee Arthroplasty (TKA)

A 68-year-old female with severe rheumatoid arthritis presents for TKA. Radiographs demonstrate a 25-degree valgus deformity. On clinical examination, there is a fixed valgus contracture, and the medial collateral ligament (MCL) is completely incompetent and attenuated (Krackow Type II). Which of the following implant choices is most appropriate?

. Cruciate-retaining (CR) TKA
. Posterior-stabilized (PS) TKA with lateral release
. Medial pivot TKA
. Constrained condylar knee (CCK) or rotating hinge TKA
. Standard CR TKA with simultaneous medial collateral ligament reconstruction

Correct Answer & Explanation

. Constrained condylar knee (CCK) or rotating hinge TKA

Explanation

A Krackow Type II valgus deformity is characterized by an incompetent/attenuated MCL. Standard unconstrained implants (CR, PS) will fail due to medial instability, requiring a higher level of constraint such as a CCK or rotating hinge prosthesis.

Question 755

Topic: Total Knee Arthroplasty (TKA)

A 55-year-old male is undergoing TKA 15 years after a previous opening wedge High Tibial Osteotomy (HTO). Which of the following technical challenges is most specifically anticipated as a direct consequence of the prior opening wedge HTO?

. Patella alta requiring proximal advancement of the tibial tubercle
. Excessive external rotation of the proximal tibia
. Patella baja and difficulty everting the patella during exposure
. Medial collateral ligament attenuation requiring a hinged prosthesis
. A significant valgus extra-articular deformity

Correct Answer & Explanation

. Patella baja and difficulty everting the patella during exposure

Explanation

Opening wedge HTOs (and closing wedge to a lesser extent) typically lower the joint line and can lead to secondary patella baja. This scarring and relative shortening of the patellar tendon make patellar eversion and adequate surgical exposure during subsequent TKA very challenging.

Question 756

Topic: Total Knee Arthroplasty (TKA)

In preparing the distal femur during a TKA for a severe fixed valgus deformity (15 degrees), the surgeon decides to set femoral rotation. If the posterior condylar axis is solely relied upon for referencing, what alignment error is most likely to occur?

. Excessive external rotation of the femoral component
. Excessive internal rotation of the femoral component
. Medialization of the femoral component
. Excessive flexion of the femoral component
. Hyperextension of the femoral component

Correct Answer & Explanation

. Excessive internal rotation of the femoral component

Explanation

Severe valgus deformities are classically associated with lateral femoral condyle hypoplasia. Referencing the posterior condyles directly in this setting will internally rotate the femoral component, adversely affecting patellofemoral tracking and flexion gap balance.

Question 757

Topic: Total Knee Arthroplasty (TKA)

A 60-year-old male with end-stage knee osteoarthritis presents with an extra-articular diaphyseal varus deformity of the femur following a prior fracture. The deformity is located 10 cm proximal to the joint line. At what degree of coronal plane angulation is a simultaneous or staged extra-articular corrective osteotomy typically recommended prior to or during TKA?

. Greater than 5 degrees
. Greater than 10 degrees
. Greater than 20 degrees
. Greater than 35 degrees
. Coronal deformities never require extra-articular osteotomy if computer navigation is used

Correct Answer & Explanation

. Greater than 20 degrees

Explanation

Intra-articular compensatory bone cuts during TKA can typically manage extra-articular femoral coronal deformities up to 20 degrees. Deformities >20 degrees in the femur (or >15 in the tibia) usually necessitate a staged or concurrent extra-articular osteotomy to avoid collateral ligament compromise.

Question 758

Topic: Total Knee Arthroplasty (TKA)

During TKA utilizing standard extramedullary tibial alignment guides, a patient is noted to have excessive anterior bowing of the tibial shaft. If the surgeon aligns the extramedullary guide parallel to the anterior tibial crest without fluoroscopic verification, what error is most likely to occur in the tibial bone cut?

. Excessive varus cut
. Excessive valgus cut
. Decreased (or reverse) posterior tibial slope
. Excessive posterior tibial slope
. Excessive internal rotation of the tibial tray

Correct Answer & Explanation

. Excessive posterior tibial slope

Explanation

The anterior crest of a bowed tibia curves anteriorly away from the mechanical axis. If the guide is placed parallel to this bowed crest, the cutting block pitches posteriorly, resulting in a cut with excessive posterior slope.

Question 759

Topic: Total Knee Arthroplasty (TKA)

A surgeon is evaluating a 55-year-old patient for a TKA. The patient has a severe extra-articular varus deformity of the proximal tibia. According to Wolff and Paley's recommendations for TKA in the setting of extra-articular deformity, an intra-articular compensatory cut becomes absolutely contraindicated (mandating an osteotomy) when the theoretical cut does what?

. Changes the posterior slope by 2 degrees.
. Requires more than 5 mm of medial polyethylene thickness.
. Demands the use of a posterior-stabilized (PS) implant.
. Violates the attachment of the patellar tendon.
. Compromises the collateral ligament insertions.

Correct Answer & Explanation

. Compromises the collateral ligament insertions.

Explanation

Intra-articular compensatory cuts for extra-articular deformities are limited by the anatomy of the knee. If the required bone cut is so severe that it would excise or irreparably compromise the origins or insertions of the collateral ligaments, an extra-articular osteotomy must be performed instead.

Question 760

Topic: 3. Adult Reconstruction (Hip & Knee)

A 65-year-old male with knee osteoarthritis and an old midshaft femur fracture malunion is being evaluated for a total knee arthroplasty (TKA). When assessing if his extra-articular diaphyseal femoral varus deformity can be managed strictly with an intra-articular bone resection during TKA, which of the following radiographic findings best confirms that an intra-articular correction is feasible without compromising collateral ligaments?

. The mechanical axis of the proximal femoral segment passes through the intercondylar notch of the knee.
. The mechanical lateral distal femoral angle (mLDFA) measures 92 degrees.
. The anatomic-mechanical angle of the femur measures exactly 5 degrees.
. The joint line convergence angle (JLCA) is less than 2 degrees.
. The mechanical axis of the entire lower extremity passes through the lateral compartment.

Correct Answer & Explanation

. The mechanical axis of the proximal femoral segment passes through the intercondylar notch of the knee.

Explanation

According to Paley's principles and guidelines for TKA in extra-articular deformity, if the mechanical axis of the proximal segment passes through the knee joint, an intra-articular cut can generally be safely performed. If it passes outside the knee, an extra-articular corrective osteotomy is typically required to avoid collateral ligament compromise.

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