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2. Trauma MCQs

Practice Set 148 of 640

This practice set contains high-yield board review questions covering key concepts in 2. Trauma. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 2941

Topic: Lower Extremity Trauma

A 48-year-old female presents with chronic knee pain. Radiographs show a mechanical axis that passes 10 mm lateral to the center of the knee joint. The mLDFA is 80°, and the MPTA is 87°. The Joint Line Convergence Angle (JLCA) is 1°. Which of the following statements accurately describes the primary deformity and its implications?

. The patient has a proximal tibial varus deformity, leading to medial compartment overload.
. The patient has a distal femoral valgus deformity, leading to lateral compartment overload.
. The deformity is primarily intra-articular, indicated by the normal mLDFA and MPTA.
. The JLCA suggests significant medial collateral ligament laxity.
. The mechanical axis deviation is within normal limits, requiring no surgical intervention for alignment.

Correct Answer & Explanation

. The patient has a distal femoral valgus deformity, leading to lateral compartment overload.

Explanation

Correct Answer: BThe mechanical axis passing 10 mm lateral to the center of the knee indicates a negative MAD, which signifies a valgus alignment. This valgus alignment leads to lateral compartment overload. To identify the source, we look at the joint orientation angles: the mLDFA is 80°. The normal mLDFA range is 85° to 90°. An mLDFA less than 85° indicates a distal femoral valgus deformity. The MPTA is 87°, which is normal (85° to 90°), ruling out a proximal tibial deformity. The JLCA of 1° is also normal (0° to 2°), suggesting no significant ligamentous laxity or cartilage loss contributing to joint line opening. Therefore, the primary deformity is a distal femoral valgus, causing lateral compartment overload.Option A is incorrectbecause the mechanical axis is lateral (valgus), not medial (varus), and the MPTA is normal, ruling out proximal tibial varus.Option C is incorrectbecause the mLDFA is abnormal, indicating a bony deformity in the distal femur, not primarily an intra-articular issue.Option D is incorrectbecause a JLCA of 1° is normal. A JLCA > 2° would suggest ligamentous laxity or cartilage loss.Option E is incorrectbecause a MAD of 10 mm lateral is outside the normal range (4-8 mm medial), indicating significant valgus malalignment.

Question 2942

Topic: Lower Extremity Trauma

A 28-year-old athlete presents with left knee pain and a progressive genu valgum deformity. A full-length standing AP radiograph is obtained, as shown below. Based on the principles of deformity analysis, where is the primary anatomical location of the angular deformity in this patient?

. Primarily in the distal femur, indicated by an increased mechanical lateral distal femoral angle (mLDFA).
. Primarily in the proximal tibia, indicated by a decreased medial proximal tibial angle (MPTA).
. Primarily in the distal femur, indicated by a decreased mLDFA.
. Primarily in the proximal tibia, indicated by an increased MPTA.
. Equally distributed between the femur and tibia, resulting in a neutral joint line.

Correct Answer & Explanation

. Primarily in the distal femur, indicated by a decreased mLDFA.

Explanation

Correct Answer: CThe image shows a genu valgum deformity. To determine the primary location of the deformity (femoral vs. tibial), one assesses the mechanical axis deviation and the joint line orientation. In genu valgum, the mechanical axis passes lateral to the knee. The mLDFA (normal 87° ± 3°) measures the angle between the mechanical axis of the femur and the distal femoral joint line. A decreased mLDFA (e.g., 80° or less) indicates a valgus deformity originating in the distal femur. The MPTA (normal 87° ± 3°) measures the angle between the mechanical axis of the tibia and the proximal tibial joint line. An increased MPTA (e.g., 95° or more) indicates a valgus deformity originating in the proximal tibia. Visually, the image suggests that the distal femur is angled more laterally relative to the femoral shaft, while the tibial plateau appears relatively horizontal. Therefore, a decreased mLDFA, indicating a valgus deformity of the distal femur, is the most likely primary location. An increased mLDFA (Option A) would indicate femoral varus. A decreased MPTA (Option B) would indicate tibial varus. An increased MPTA (Option D) would indicate tibial valgus. Option E is incorrect as there is clear malalignment.

Question 2943

Topic: Lower Extremity Trauma

A 50-year-old patient presents with medial compartment knee pain and a varus deformity. A close-up radiograph of the knee is shown below. To accurately quantify the angular deformity and plan a corrective osteotomy, which of the following measurements is most critical for determining the contribution of the proximal tibia to the overall malalignment?

. Mechanical lateral distal femoral angle (mLDFA).
. Medial proximal tibial angle (MPTA).
. Joint line convergence angle (JLCA).
. Anatomical lateral distal femoral angle (aLDFA).
. Posterior tibial slope (PTS).

Correct Answer & Explanation

. Medial proximal tibial angle (MPTA).

Explanation

Correct Answer: BThe image shows a close-up of a knee joint, likely with a varus deformity given the clinical context. To determine the contribution of the proximal tibia to the overall malalignment, the Medial Proximal Tibial Angle (MPTA) is the most critical measurement. The MPTA is formed by the intersection of the mechanical axis of the tibia and the medial aspect of the tibial plateau. A normal MPTA is 87° ± 3°. In a varus deformity originating from the proximal tibia, the MPTA will be decreased (e.g., <84°). The mLDFA (Option A) assesses the distal femur. The JLCA (Option C) indicates joint space narrowing or opening but does not directly quantify bone deformity. The aLDFA (Option D) uses the anatomical axis, which is less relevant for mechanical alignment. The PTS (Option E) is measured on a lateral radiograph and relates to sagittal plane alignment, not coronal plane varus/valgus.

Question 2944

Topic: 2. Trauma

A 30-year-old male presents with a complex post-traumatic deformity of the right femur. Preoperative planning involves a long AP radiograph of the entire lower extremity. To accurately assess the femoral deformity and plan for intramedullary fixation, the surgeon must understand the relationship between the anatomic and mechanical axes of the femur. What is the typical angle subtended between the anatomic and mechanical axes of a normal femur, and what is its clinical significance?

. A. 0 degrees; they are parallel, simplifying intramedullary nailing.
. B. Approximately 3 degrees; important for assessing hip joint congruity.
. C. Approximately 6 degrees; crucial for understanding the divergence between IM guides and load-bearing axis.
. D. Approximately 10 degrees; primarily relevant for patellofemoral tracking.
. E. Varies widely; making it unreliable for consistent surgical planning.

Correct Answer & Explanation

. C. Approximately 6 degrees; crucial for understanding the divergence between IM guides and load-bearing axis.

Explanation

Correct Answer: CThe case explicitly states, 'In the femur, however, the two axes are distinctly different... This divergence forms the Anatomic-Mechanical Angle (AMA), which normally subtends an angle of about 6 degrees (range 5-7°).' It further emphasizes, 'Understanding this relationship is vital for accurate planning, especially when utilizing intramedullary guides for fracture fixation, deformity correction, or total knee arthroplasty, as these instruments follow the anatomic axis, not the load-bearing mechanical axis.' Therefore, a 6-degree angle is typical, and its significance lies in the divergence between the physical bone axis (followed by IM guides) and the functional load-bearing axis.Incorrect Options:A. 0 degrees; they are parallel, simplifying intramedullary nailing:This is incorrect. The text states they are distinctly different in the femur. In the tibia, they are nearly parallel, but not the femur.B. Approximately 3 degrees; important for assessing hip joint congruity:The typical angle is 6 degrees, not 3. While hip mechanics are involved, the primary significance highlighted is for IM instrumentation.D. Approximately 10 degrees; primarily relevant for patellofemoral tracking:The typical angle is 6 degrees, not 10. Patellofemoral tracking is influenced by other factors like Q-angle and rotational alignment, not directly by the AMA.E. Varies widely; making it unreliable for consistent surgical planning:The text provides a specific normal range (5-7°), indicating it is a consistent and reliable measurement for planning.

Question 2945

Topic: Lower Extremity Trauma

A 70-year-old female presents with severe valgus deformity of her left knee. Preoperative planning involves measuring joint orientation angles. Her mLDFA is measured at 80°, and her MPTA is 87°. The Mechanical Axis Deviation (MAD) is 18 mm lateral. Based on these measurements and the Paley method, what is the primary anatomical source of this patient's valgus malalignment?

. A. Proximal tibial varus deformity
. B. Distal tibial valgus deformity
. C. Proximal femoral varus deformity
. D. Distal femoral valgus deformity
. E. Combined proximal tibial and distal femoral varus deformity

Correct Answer & Explanation

. D. Distal femoral valgus deformity

Explanation

Correct Answer: DThe case defines normal values for joint orientation angles: mLDFA (Mechanical Lateral Distal Femoral Angle) is normally 88° (range 85°-90°), and MPTA (Medial Proximal Tibial Angle) is normally 87° (range 85°-90°).The patient's mLDFA is 80°. The case states, 'An mLDFA < 85° signifies a distal femoral valgus deformity.' This measurement is significantly below the normal range, indicating a valgus deformity originating from the distal femur.The patient's MPTA is 87°. This value falls within the normal range (85°-90°), indicating that there is no significant proximal tibial deformity contributing to the malalignment.Given the 18 mm lateral MAD (consistent with valgus malalignment) and the specific angle measurements, the primary source of the valgus deformity is the distal femur.Incorrect Options:A. Proximal tibial varus deformity:This would be indicated by an MPTA < 85°, which is not present (MPTA is 87°).B. Distal tibial valgus deformity:This would be indicated by an abnormal LDTA, which is not provided, but the primary deformity is clearly identified in the femur.C. Proximal femoral varus deformity:This would be indicated by an abnormal LPFA or NSA, which are not provided, but the mLDFA points to a distal femoral issue.E. Combined proximal tibial and distal femoral varus deformity:This is incorrect. The MPTA is normal, ruling out proximal tibial deformity, and the femoral deformity is valgus, not varus.

Question 2946

Topic: Lower Extremity Trauma

A 35-year-old active duty soldier sustained a complex tibial shaft fracture that healed with significant angulation and translation. Preoperative planning for corrective osteotomy involves identifying the Center of Rotation of Angulation (CORA). Which of the following best describes the CORA and its significance in surgical planning?

. A. The point where the anatomic axis of the proximal segment intersects the anatomic axis of the distal segment, indicating the ideal site for intramedullary nail insertion.
. B. The perpendicular distance from the mechanical axis to the center of the knee, quantifying the global limb malalignment.
. C. The point of intersection of the proximal mechanical axis and the distal mechanical axis of the deformed bone segment, dictating the ideal osteotomy site and hinge position.
. D. The angle between the distal femoral joint line and the femoral mechanical axis, defining the orientation of the knee joint.
. E. The point where the ground reaction force passes through the limb during the single-leg stance phase, representing the load-bearing line.

Correct Answer & Explanation

. C. The point of intersection of the proximal mechanical axis and the distal mechanical axis of the deformed bone segment, dictating the ideal osteotomy site and hinge position.

Explanation

Correct Answer: CThe case defines the CORA precisely: 'The CORA is defined as the point of intersection of the proximal mechanical axis and the distal mechanical axis of the deformed bone segment.' It further emphasizes its significance: 'Finding the CORA is the absolute key to surgical planning because it dictates the biomechanical reality of the deformity. It tells the surgeon exactly where the osteotomy should ideally be performed and how the correction hinge must be positioned.'Incorrect Options:A. The point where the anatomic axis of the proximal segment intersects the anatomic axis of the distal segment, indicating the ideal site for intramedullary nail insertion:While anatomic axes are used for IM nailing, the CORA is defined by mechanical axes and is for angular deformity correction, not IM nail insertion site.B. The perpendicular distance from the mechanical axis to the center of the knee, quantifying the global limb malalignment:This describes the Mechanical Axis Deviation (MAD), not the CORA.D. The angle between the distal femoral joint line and the femoral mechanical axis, defining the orientation of the knee joint:This describes the Mechanical Lateral Distal Femoral Angle (mLDFA), not the CORA.E. The point where the ground reaction force passes through the limb during the single-leg stance phase, representing the load-bearing line:This describes the mechanical axis of the lower extremity, not the CORA.

Question 2947

Topic: Lower Extremity Trauma

A 40-year-old male presents with a 10-year history of progressive right knee pain and a varus deformity. Standing long AP radiographs show a Mechanical Axis Deviation (MAD) of 15 mm medial to the center of the knee. His MPTA is 80°, and his mLDFA is 88°. Which of the following statements accurately describes the significance of these findings according to the Paley method?

. A. The normal MPTA indicates that the deformity is primarily located in the distal femur.
. B. The 15 mm medial MAD is within the normal physiological range, suggesting no significant malalignment.
. C. The mLDFA of 88° indicates a distal femoral valgus deformity contributing to the overall varus.
. D. The primary source of the varus malalignment is a proximal tibial varus deformity, as evidenced by the MPTA.
. E. The deformity is multiapical, requiring complex spatial frame correction due to both femoral and tibial involvement.

Correct Answer & Explanation

. D. The primary source of the varus malalignment is a proximal tibial varus deformity, as evidenced by the MPTA.

Explanation

Correct Answer: DLet's break down the measurements based on the case:MAD of 15 mm medial:The case states, 'Normal Alignment: The mechanical axis normally passes 1 to 8 mm medial to the exact center of the knee.' A MAD of 15 mm medial is significantly outside this normal range, indicating varus malalignment.MPTA of 80°:The normal MPTA is 87° (range 85°-90°). An MPTA < 85° signifies a proximal tibial varus deformity. This patient's 80° MPTA clearly indicates a proximal tibial varus deformity.mLDFA of 88°:The normal mLDFA is 88° (range 85°-90°). This patient's mLDFA is perfectly normal, indicating no distal femoral deformity.Therefore, the primary source of the varus malalignment is a proximal tibial varus deformity.Incorrect Options:A. The normal MPTA indicates that the deformity is primarily located in the distal femur:The MPTA of 80° isabnormal, indicating a proximal tibial deformity. The mLDFA is normal, ruling out a distal femoral deformity.B. The 15 mm medial MAD is within the normal physiological range, suggesting no significant malalignment:This is incorrect. The normal range for MAD is 1-8 mm medial. 15 mm medial is significant varus malalignment.C. The mLDFA of 88° indicates a distal femoral valgus deformity contributing to the overall varus:An mLDFA of 88° is normal. A distal femoral valgus deformity would be indicated by an mLDFA < 85°.E. The deformity is multiapical, requiring complex spatial frame correction due to both femoral and tibial involvement:Since the mLDFA is normal, there is no femoral deformity. The deformity is primarily uni-apical in the proximal tibia.

Question 2948

Topic: Lower Extremity Trauma

When evaluating a full-length standing lower extremity radiograph for deformity correction, the surgeon measures the angle between the mechanical axis and the anatomical axis of the femur (AMA). In a normally aligned lower extremity, what is the expected approximate value of this angle?

. 1 degree
. 3 degrees
. 7 degrees
. 11 degrees
. 15 degrees

Correct Answer & Explanation

. 7 degrees

Explanation

The anatomic-mechanical angle (AMA) of the femur normally averages 7 degrees (range 5 to 9 degrees). This angle reflects the mechanical axis running from the femoral head center to the knee center, while the anatomic axis follows the medullary canal of the femoral shaft.

Question 2949

Topic: 2. Trauma

In a limb lengthening procedure utilizing an intramedullary nail and an external fixator (Lengthening Over a Nail), a corticotomy is performed. The surgeon waits 7 days before initiating distraction. What is the primary biological purpose of this latency period?

. To allow resolution of soft tissue edema
. To permit the formation of a soft callus and vascular ingrowth
. To prevent deep vein thrombosis
. To allow the periosteum to completely reattach
. To minimize the risk of hardware failure

Correct Answer & Explanation

. To permit the formation of a soft callus and vascular ingrowth

Explanation

The latency period (typically 5-7 days) allows for early hematoma organization, soft callus formation, and essential revascularization at the corticotomy site. Distracting immediately disrupts this fragile early healing phase and significantly increases the risk of nonunion.

Question 2950

Topic: Lower Extremity Trauma

A 42-year-old male undergoes a high tibial osteotomy (HTO) for medial compartment osteoarthritis. The surgeon aims to shift the mechanical axis to the Fujisawa point to optimize load distribution. Where is the Fujisawa point located on the tibial plateau?

. Exactly at the center of the tibial plateau (50%)
. 62.5% from the medial edge of the tibial plateau
. 37.5% from the medial edge of the tibial plateau
. 75% from the medial edge of the tibial plateau
. 62.5% from the lateral edge of the tibial plateau

Correct Answer & Explanation

. 62.5% from the medial edge of the tibial plateau

Explanation

The Fujisawa point is located approximately 62-62.5% across the width of the tibial plateau, measured from medial to lateral. Shifting the mechanical weight-bearing axis to this point optimally unloads the medial compartment while protecting the lateral compartment from rapid breakdown.

Question 2951

Topic: 2. Trauma

A patient presents with a severe varus deformity of the knee. Radiographs show a mechanical axis deviation (MAD) of 40 mm medial to knee center, normal mechanical lateral distal femoral angle (mLDFA), and a normal medial proximal tibial angle (MPTA). The joint line convergence angle (JLCA) is 12 degrees. What does this indicate regarding the source of the deformity?

. Diaphyseal bowing of the tibia
. Diaphyseal bowing of the femur
. Ligamentous laxity or cartilage loss leading to intra-articular deformity
. Metaphyseal malunion of the proximal tibia
. Combined femoral and tibial extra-articular deformities

Correct Answer & Explanation

. Ligamentous laxity or cartilage loss leading to intra-articular deformity

Explanation

The joint line convergence angle (JLCA) measures the angle between the distal femoral and proximal tibial articular surfaces (normal 0-2 degrees). An increased JLCA with normal bony metaphyseal angles (mLDFA and MPTA) indicates the varus deformity is purely intra-articular, typically due to asymmetric cartilage loss or collateral ligament laxity.

Question 2952

Topic: 2. Trauma

A 14-year-old patient is undergoing tibial lengthening. The surgeon implements a distraction rate of 2.0 mm per day, divided into four increments. After four weeks, radiographs show a large radiolucent gap with no visible mineralized regenerate. What is the most likely consequence of this distraction protocol?

. Premature consolidation
. Hypertrophic nonunion
. Poor regenerate formation leading to delayed union or nonunion
. Increased incidence of pin tract infections
. Rapid intramembranous ossification with excellent bone stock

Correct Answer & Explanation

. Poor regenerate formation leading to delayed union or nonunion

Explanation

The ideal rate of distraction is approximately 1 mm per day in a rhythm of 0.25 mm every 6 hours. A distraction rate that is too fast (e.g., 2.0 mm/day) typically results in poor regenerate formation, leading to delayed union or atrophic nonunion.

Question 2953

Topic: Lower Extremity Trauma

A 30-year-old female presents with bilateral knee pain. Full-length standing radiographs reveal a mechanical axis deviation (MAD) falling 25 mm medial to the center of the right knee. Joint orientation measurements demonstrate a mechanical lateral distal femoral angle (mLDFA) of 96° and a medial proximal tibial angle (MPTA) of 87°. Where is the primary site of deformity?

. Proximal tibia
. Distal femur
. Intra-articular (joint line convergence)
. Diaphysis of the tibia
. Hip joint

Correct Answer & Explanation

. Distal femur

Explanation

The normal mLDFA is 87°±3° and normal MPTA is 87°±3°. An mLDFA of 96° indicates a significant varus deformity in the distal femur. Since the MPTA is normal, the deformity is localized to the femur.

Question 2954

Topic: 2. Trauma

A 55-year-old man presents with a symptomatic varus knee deformity. Radiographic evaluation shows a joint line convergence angle (JLCA) of 6° with medial narrowing, whereas his contralateral asymptomatic knee has a JLCA of 1°. The mLDFA is 88° and MPTA is 86°. Which of the following is the most appropriate interpretation of these findings?

. The varus deformity is primarily driven by a malunited femoral shaft fracture.
. The deformity is primarily intra-articular, likely due to medial compartment cartilage loss or ligamentous laxity.
. He requires an opening wedge high tibial osteotomy to correct the bony malalignment.
. The measurements indicate an extra-articular diaphyseal tibial deformity.
. The JLCA is within normal physiological limits for a 55-year-old.

Correct Answer & Explanation

. The deformity is primarily intra-articular, likely due to medial compartment cartilage loss or ligamentous laxity.

Explanation

The normal JLCA is 0° to 2°. A JLCA of 6° indicates an intra-articular source of the varus thrust, usually related to medial cartilage loss or lateral collateral ligament laxity, rather than an extra-articular bony deformity (supported by normal mLDFA and MPTA).

Question 2955

Topic: 2. Trauma

A 28-year-old male presents with a distal third femoral valgus deformity post-trauma. The mLDFA is 75°. To correct the mechanical axis and restore limb length, the surgeon chooses a lateral opening wedge distal femoral osteotomy. Where should the hinge of this osteotomy be functionally placed to minimize unintended translation?

. Medial cortex of the distal femur at the level of the CORA.
. Lateral cortex of the distal femur at the level of the CORA.
. Center of the medullary canal 5 cm proximal to the CORA.
. Anterior cortex to prevent sagittal plane shifts.
. At the level of the adductor tubercle regardless of the CORA.

Correct Answer & Explanation

. Medial cortex of the distal femur at the level of the CORA.

Explanation

For a lateral opening wedge osteotomy to correct a valgus deformity, the mechanical hinge must be placed on the intact medial cortex (concave side of the deformity) exactly at the level of the CORA (Rule 1). This yields pure angular correction without translation.

Question 2956

Topic: 2. Trauma

A patient with a diaphyseal tibial nonunion and a 4 cm limb length discrepancy is treated with bone transport using an external fixator. After the transport dock is complete, the surgeon assesses the 'regenerate' bone in the distraction gap. What is the radiologic term for the distinct radiodense line seen at the center of the active regenerate gap during distraction?

. Zone of provisional calcification
. Fibrous interzone
. Central growth plate
. Zone of remodeling
. Ischemic core

Correct Answer & Explanation

. Fibrous interzone

Explanation

In the distraction gap, there are typically two zones of mineralization advancing toward the center, separated by a radiolucent central band known as the fibrous interzone. This is the active site of collagen synthesis and early mineralization.

Question 2957

Topic: 2. Trauma

A 45-year-old male presents with a symptomatic varus deformity of his right tibia following a malunited fracture. Preoperative planning identifies the Center of Rotation of Angulation (CORA). According to the rules of osteotomy, if the osteotomy and the axis of correction of angulation (ACA) are both placed exactly at the CORA, what is the expected geometric outcome of the correction?

. Complete correction of angulation with parallel translation of the mechanical axis.
. Complete correction of angulation with no translation of the mechanical axis.
. Partial correction of angulation with simultaneous limb lengthening.
. Correction of angulation but creation of a secondary apex-anterior translation.
. Incomplete angular correction due to hinge interference.

Correct Answer & Explanation

. Complete correction of angulation with no translation of the mechanical axis.

Explanation

According to Paley's Rule 1 of osteotomy, when both the osteotomy and the ACA are placed at the CORA, the mechanical axes will realign perfectly without any translation. This principle is fundamental for restoring normal limb alignment without introducing secondary deformities.

Question 2958

Topic: Lower Extremity Trauma

A 32-year-old female is evaluated for right knee pain. Standing full-length radiographs show a mechanical axis deviation (MAD) of 20 mm medial to the center of the knee. The mechanical lateral distal femoral angle (mLDFA) is 96 degrees, and the mechanical proximal tibial angle (MPTA) is 87 degrees. What is the primary source of the patient's deformity?

. Distal femoral valgus
. Proximal tibial varus
. Distal femoral varus
. Ligamentous laxity of the medial collateral ligament
. Proximal tibial valgus

Correct Answer & Explanation

. Distal femoral varus

Explanation

The normal mLDFA is approximately 87 degrees (range 85-90). An mLDFA of 96 degrees indicates a varus deformity of the distal femur, while the MPTA of 87 degrees is normal. Therefore, the medial mechanical axis deviation is driven entirely by the distal femur.

Question 2959

Topic: 2. Trauma

A surgeon is planning a corrective osteotomy for a tibial diaphyseal malunion.

Due to poor soft tissue quality at the CORA, the surgeon chooses to perform the osteotomy 4 cm distal to the CORA, but places the hinge (ACA) exactly at the CORA. Which of the following describes the resulting deformity correction according to Paley's Rules?

. The mechanical axis will be completely realigned with no translation.
. The mechanical axis will realign, but translation will occur at the osteotomy site.
. The mechanical axis will remain uncorrected with isolated lengthening.
. A secondary angular deformity will be created, requiring a second osteotomy.
. The mechanical axis will overcorrect into valgus without translation.

Correct Answer & Explanation

. The mechanical axis will realign, but translation will occur at the osteotomy site.

Explanation

This scenario describes Paley's Rule 2. When the osteotomy is made away from the CORA but the ACA remains at the CORA, the mechanical axis is fully corrected but translation necessarily occurs at the osteotomy site.

Question 2960

Topic: Lower Extremity Trauma

During distraction osteogenesis utilizing an Ilizarov frame, a patient's post-operative radiographs at 4 weeks show an 'hourglass' shaped regenerate with a very narrow central zone. What is the most appropriate next step in management?

. Increase the rate of distraction to 1.5 mm per day.
. Decrease the rate of distraction or perform a temporary compression.
. Immediately bone graft the regenerate site.
. Remove the frame and place an intramedullary nail.
. Maintain the current rate but decrease the frequency of distractions.

Correct Answer & Explanation

. Decrease the rate of distraction or perform a temporary compression.

Explanation

An 'hourglass' or tapering regenerate indicates poor bone formation, usually due to a distraction rate that is too fast for the patient's osteogenic potential. Decreasing the rate of distraction, or temporarily compressing the site, stimulates osteogenesis and improves the regenerate caliber.

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