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2. Trauma MCQs

Practice Set 142 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 2821

Topic: Lower Extremity Trauma

While performing a medial opening wedge high tibial osteotomy (HTO) for a coronal varus deformity, the surgeon inadvertently opens the anterior gap more than the posterior gap. What is the expected iatrogenic effect in the sagittal plane?

. Decreased posterior tibial slope causing a recurvatum effect
. Increased posterior tibial slope causing a procurvatum effect
. Decreased mPDFA
. Increased mPDFA
. Pure axial translation of the tibia

Correct Answer & Explanation

. Increased posterior tibial slope causing a procurvatum effect

Explanation

Opening the anterior cortex more than the posterior cortex in an HTO tilts the tibial plateau posteriorly. This increases the posterior tibial slope, which is an apex anterior (procurvatum) morphologic change, increasing strain on the ACL.

Question 2822

Topic: 2. Trauma

A patient has a distal femoral diaphyseal fracture malunion with an apex anterior (procurvatum) deformity. The surgeon performs an osteotomy at the distal metaphysis (away from the diaphyseal CORA) and places the hinge at the osteotomy site. According to Paley's Rule 3, what is the biomechanical outcome?

. Pure angular correction
. Correction of angulation but creation of a secondary parallel translation deformity
. Restoration of collinearity of the mechanical axis
. Complete correction of both angulation and translation
. Creation of an intra-articular step-off

Correct Answer & Explanation

. Correction of angulation but creation of a secondary parallel translation deformity

Explanation

Paley's Rule 3 states that when the osteotomy and the hinge are both located away from the CORA, angular correction occurs but a secondary translation deformity is created (the proximal and distal axes become parallel but not collinear).

Question 2823

Topic: 2. Trauma

When correcting a severe distal femoral apex posterior (recurvatum) deformity with an anterior opening wedge osteotomy, what is a crucial patellofemoral biomechanical change that the surgeon must anticipate?

. Medialization of the tibial tubercle
. Decreased patellofemoral contact pressures
. Increased patellofemoral contact pressures and potential patella infera mechanics
. Spontaneous correction of patellar tilt
. Iatrogenic patella alta

Correct Answer & Explanation

. Increased patellofemoral contact pressures and potential patella infera mechanics

Explanation

An anterior opening wedge osteotomy at the distal femur effectively lengthens the anterior column, which can alter the extensor mechanism vector, increasing patellofemoral contact pressures and functionally tightening the extensor mechanism.

Question 2824

Topic: Lower Extremity Trauma

Historically, single-level pelvic support osteotomies were largely abandoned due to significant complications. Dr. Paley's modern double-level PSO technique overcame these limitations. What was the primary biomechanical failure of the historical single-level PSO that the double-level technique specifically addressed?

. Inability to tension the abductor muscles effectively.
. Failure to create a stable bony abutment against the pelvis.
. Creation of severe knee valgus and unacceptable Mechanical Axis Deviation (MAD).
. High rates of non-union at the osteotomy site.
. Inability to correct limb length discrepancy.

Correct Answer & Explanation

. Creation of severe knee valgus and unacceptable Mechanical Axis Deviation (MAD).

Explanation

Correct Answer: CThe case clearly states: 'The historical failure—creating a stable hip at the expense of a catastrophically malaligned knee—has been definitively solved.' It further elaborates that a proximal valgus osteotomy stabilizes the hip but forces the distal femur into severe valgus, shifting the mechanical axis far lateral to the knee center. This 'guarantees the rapid onset of lateral compartment knee arthritis and severe limb shortening.' The modern double-level PSO, by adding a distal osteotomy, specifically addresses and corrects this unacceptable Mechanical Axis Deviation (MAD) and knee valgus, while also allowing for limb length correction. Options A and B are incorrect as single-level PSO did stabilize the hip and tension abductors. Options D and E were complications but not the primary biomechanical failure that led to its abandonment and the development of the double-level technique.

Question 2825

Topic: Pelvic & Acetabular Trauma

A 7-year-old male presents with a complex left hip deformity following a prior Salter osteotomy for severe Developmental Dysplasia of the Hip (DDH). Preoperative planning requires establishing a reliable pelvic horizontal reference line. On the AP pelvis radiograph, the triradiate cartilages appear asymmetric due to premature closure on the previously operated side. Which of the following anatomical landmarks is the MOST reliable for establishing the pelvic horizontal line in this specific patient?

. Iliac crests
. Acetabular teardrops
. Center of the triradiate cartilages
. Inferior aspects of the sacroiliac (SI) joints
. Superior margins of the pubic symphysis

Correct Answer & Explanation

. Inferior aspects of the sacroiliac (SI) joints

Explanation

Correct Answer: DThe case explicitly states that in skeletally immature patients, the triradiate cartilage is an excellent landmark,provided the pelvis has not been subjected to a prior osteotomy or asymmetric premature closure. In complex revision cases, such as this patient with a prior Salter osteotomy leading to asymmetric triradiate cartilages, the surgeon must abandon the triradiate cartilage and revert to the more stable, universally applicable adult landmarks: the inferior SI joints or the sacral foramina. The inferior SI joints are described as the 'Gold Standard' due to their robustness, central location, and minimal affection by lateralized acetabular or iliac wing pathology. Iliac crests and acetabular teardrops are often distorted by the primary pathology or previous surgeries. The pubic symphysis is less reliable for a horizontal reference due to its variability and potential for rotation.

Question 2826

Topic: 2. Trauma

A 30-year-old patient presents with a severe proximal femoral varus deformity. After establishing a true Pelvic Horizontal Line on a full-length standing radiograph, the next critical step in Paley's planning method is to define the Proximal Mechanical Axis (PMA). How is the PMA correctly drawn for hip deformity correction?

. A line drawn along the anatomical axis of the deformed femoral neck.
. A line connecting the center of the greater trochanter to the center of the femoral head.
. A line drawn perfectly perpendicular (90 degrees) to the established Pelvic Horizontal Line, passing through the true geometric center of the acetabulum.
. A line extending proximally from the center of the knee joint, parallel to the femoral shaft.
. A line connecting the anterior superior iliac spine (ASIS) to the center of the femoral head.

Correct Answer & Explanation

. A line drawn perfectly perpendicular (90 degrees) to the established Pelvic Horizontal Line, passing through the true geometric center of the acetabulum.

Explanation

Correct Answer: CThe case emphasizes that the Proximal Mechanical Axis (PMA) represents the ideal, corrected orientation of the proximal femur. It is drawn as a line 'perfectly perpendicular (90 degrees) to the established Pelvic Horizontal Line' and 'must pass directly through the true geometric center of the acetabulum (or the center of the femoral head, but only if the head is concentrically reduced within a normal acetabulum).' This conceptual leap is paramount: the PMA does not follow the patient's existing, deformed femoral neck or proximal shaft, but rather represents a theoretical ideal for alignment relative to a level pelvis. Options A, B, D, and E describe either anatomical axes of the deformed bone or incorrect reference points, which would lead to inaccurate planning.

Question 2827

Topic: 2. Trauma

A 25-year-old patient presents with a post-traumatic malunion of the proximal femur, resulting in a multi-planar deformity. Preoperative planning involves identifying the Center of Rotation of Angulation (CORA). Which of the following statements accurately describes the CORA in the context of Paley's deformity correction principles?

. The CORA is always located at the site of the previous fracture or osteotomy.
. It is the point where the anatomic axis of the proximal segment intersects the anatomic axis of the distal segment.
. The CORA is the precise point in 2D or 3D space where the deformity is centered, defined by the intersection of the proximal and distal axis lines of a deformed bone.
. Performing an osteotomy away from the CORA will always result in a pure angular correction without any translation.
. The CORA is primarily used to determine the optimal length of the fixation device, not the osteotomy level.

Correct Answer & Explanation

. The CORA is the precise point in 2D or 3D space where the deformity is centered, defined by the intersection of the proximal and distal axis lines of a deformed bone.

Explanation

Correct Answer: CThe CORA (Center of Rotation of Angulation) is a fundamental concept in Paley's principles. It is defined as the precise point in 2D or 3D space where the deformity is centered, geometrically identified by the intersection of the proximal and distal axis lines of a deformed bone. Identifying the CORA is crucial because it dictates the optimal level for the corrective osteotomy to achieve the desired correction with or without intentional translation.Option A is incorrectbecause while the CORA may coincide with a previous fracture or osteotomy site, it is not always the case. The CORA is a geometric construct derived from the current alignment, not necessarily the historical site of injury.Option B is incorrectbecause the CORA is defined by the intersection of themechanical(or sometimes anatomic, depending on the specific axis used for measurement) axis lines of the deformed bone, not just the anatomic axes, especially in the context of the proximal femur where the mechanical axis is paramount for lower extremity alignment.Option D is incorrectbecause performing an osteotomy away from the CORA, while keeping the hinge at the CORA (Paley's Rule 2), will induce a calculated translation along with angular correction. If the hinge is also away from the CORA (Paley's Rule 3), it results in an unintentional and uncorrected secondary translation deformity.Option E is incorrectbecause the CORA is primarily used to determine the optimal level and type of osteotomy (e.g., opening, closing, translation) to achieve the desired angular and translational correction, not solely the length of the fixation device.

Question 2828

Topic: 2. Trauma

A 45-year-old male presents with a debilitating varus malunion of a previously fused right hip, causing significant functional limb shortening and an abductor lurch gait. Preoperative planning for a corrective osteotomy is initiated. Referring to the provided image, specifically diagram (b), what is the crucial first step in defining the axes for locating the CORA in this hip fusion varus malunion?

. Draw the distal mechanical axis (DMA) from the center of the ankle to the center of the knee.
. Identify the anatomic axis of the femoral shaft.
. Establish the horizontal line of the pelvis using the inferior SI joints.
. Measure the Neck Shaft Angle (NSA) of the fused hip.
. Determine the Joint Line Convergence Angle (JLCA) of the ipsilateral knee.

Correct Answer & Explanation

. Establish the horizontal line of the pelvis using the inferior SI joints.

Explanation

Correct Answer: CThe case content explicitly states, 'The First Commandment: Establish the Horizontal Line of the Pelvis' and for hip fusion planning, 'Step-by-Step Guide to Finding the CORA in Hip Fusion: 1. Establish the Pelvic Horizontal: First, establish the horizontal line of the pelvis using the inferior SI joints (or sacral foramina/triradiate cartilages if distorted).' This is the foundational step for all subsequent measurements and axis definitions, as illustrated by the horizontal line at the top of diagram (b) in the provided image.Option A is incorrectbecause drawing the DMA is a subsequent step after establishing the pelvic horizontal and the proximal mechanical axis.Option B is incorrectbecause while the anatomic axis can be a reference, the planning for hip fusion malunion primarily relies on mechanical axes relative to the pelvis.Option D is incorrectbecause the Neck Shaft Angle is not relevant for a fused hip, as the neck and shaft are part of a rigid, fused unit, and the goal is to reorient the entire limb relative to the pelvis.Option E is incorrectbecause the JLCA is a measure of knee joint parallelism and is not the initial step in defining the CORA for a proximal femoral fusion malunion, although it might be assessed later to rule out multiapical deformity.

Question 2829

Topic: 2. Trauma

Following the initial planning steps for the hip fusion varus malunion described in the previous question, the surgeon proceeds to define the proximal and distal mechanical axes. As depicted in diagram (b) of the provided image, the ideal proximal axis (red line) is drawn perpendicular to the pelvic horizontal, passing through the center of the acetabulum. The current distal mechanical axis (blue line) is extended proximally. Where is the CORA typically located for this type of deformity, as shown in the diagram?

. Within the femoral neck, proximal to the greater trochanter.
. At the level of the knee joint, indicating a compensatory deformity.
. In the subtrochanteric region of the femur.
. Within the acetabulum, at the center of the fused femoral head.
. Distal to the knee joint, in the proximal tibia.

Correct Answer & Explanation

. In the subtrochanteric region of the femur.

Explanation

Correct Answer: CThe case content explicitly states, 'In a typical varus malunion of a fused hip, the CORA will be located in the subtrochanteric region.' This is clearly illustrated in diagram (b) of the provided image, where the intersection of the ideal proximal axis (red line) and the current distal mechanical axis (blue line) occurs in the subtrochanteric area of the femur. This location is critical for planning the osteotomy.Option A is incorrectbecause while some proximal femoral deformities have a CORA in the femoral neck, a varus malunion of a fused hip typically shifts the CORA more distally due to the nature of the collapse.Option B is incorrectbecause the CORA is the apex of the deformity in the affected bone, not typically at a distant joint like the knee, unless there is a multiapical deformity involving the knee itself.Option D is incorrectbecause the acetabulum/fused femoral head is the reference point for the proximal axis, but the CORA for the angular deformity is the intersection of the two axes, which is typically distal to this point in a varus malunion.Option E is incorrectbecause the CORA for a proximal femoral deformity would not be located in the tibia unless there was a separate, unaddressed tibial deformity.

Question 2830

Topic: 2. Trauma

A 30-year-old patient requires a corrective osteotomy for a diaphyseal femoral deformity with a clearly defined CORA located in the mid-shaft. The surgeon plans to perform the osteotomy precisely at this CORA. According to Paley's osteotomy rules, what is the expected outcome of this surgical approach?

. The osteotomy will result in a calculated translation along with angular correction.
. The osteotomy will create an unintentional secondary translation deformity.
. The osteotomy will achieve pure angular correction with zero translation.
. The osteotomy will primarily address leg length discrepancy without angular correction.
. The osteotomy will require an external fixation device for stability, regardless of the CORA location.

Correct Answer & Explanation

. The osteotomy will achieve pure angular correction with zero translation.

Explanation

Correct Answer: CThis scenario describes Paley's Osteotomy Rule 1: 'The osteotomy and the axis of correction (hinge) both pass through the CORA.' The application of this rule states that it 'is the ideal scenario, resulting in pure angular correction with zero translation. The bone ends simply pivot open or closed.' This is the most straightforward method of correction when the CORA is in an accessible location.Option A is incorrectbecause calculated translation along with angular correction occurs when the osteotomy is at a different level than the CORA, but the hinge remains at the CORA (Paley's Rule 2).Option B is incorrectbecause unintentional secondary translation deformity occurs when both the osteotomy and the hinge are at a different level than the CORA (Paley's Rule 3), which is considered a planning error.Option D is incorrectbecause while osteotomies can address LLD, the primary outcome of Rule 1 is angular correction. LLD correction might be a secondary effect of angular correction or require additional specific techniques (e.g., lengthening).Option E is incorrectbecause the choice of internal or external fixation depends on many factors (stability, bone quality, patient factors), not solely on the CORA location or the application of Rule 1. Rule 1 can be performed with internal fixation (e.g., plating or nailing).

Question 2831

Topic: 2. Trauma

During preoperative planning for a complex proximal femoral deformity, a resident proposes an osteotomy where the bone cut is made at the subtrochanteric level, and the planned hinge for correction is placed at the mid-diaphysis. However, the calculated CORA for the deformity is located in the intertrochanteric region. If this plan is executed, which of Paley's osteotomy rules would be violated, and what would be the most likely consequence?

. Rule 1; the correction would be unstable and prone to nonunion.
. Rule 2; the correction would result in an intentional, calculated translation.
. Rule 3; the correction would result in an unintentional and uncorrected secondary translation deformity.
. Rule 1; the correction would achieve perfect angular alignment with zero translation.
. Rule 2; the correction would only address the leg length discrepancy.

Correct Answer & Explanation

. Rule 3; the correction would result in an unintentional and uncorrected secondary translation deformity.

Explanation

Correct Answer: CThis scenario describes a violation of Paley's Osteotomy Rule 3: 'The osteotomy and the axis of correction (hinge) are at a different level than the CORA.' The text explicitly states that 'This is a planning error. By placing the hinge away from the CORA, the surgeon inadvertently creates an unintentional and uncorrected secondary translation deformity. This shifts the mechanical axis away from the target, creating a new malalignment (often a zigzag deformity). Rule 3 should always be avoided in planned deformity correction.'Option A is incorrectbecause while instability and nonunion are potential complications of any osteotomy, the specific consequence of violating Rule 3 is the creation of an uncorrected translation deformity, not necessarily inherent instability.Option B is incorrectbecause Rule 2 involves a calculated translation, but only when the hinge is still at the CORA, which is not the case here.Option D is incorrectbecause Rule 1 achieves perfect angular alignment with zero translation by placing both the osteotomy and hinge at the CORA, which is not what is described in the question.Option E is incorrectbecause Rule 2 is for angular and calculated translational correction, and the scenario describes a violation of Rule 3, leading to unintended consequences.

Question 2832

Topic: 2. Trauma

A 55-year-old patient with a history of a failed hip arthrodesis presents with a severe varus malunion. The surgeon is performing digital templating for a corrective osteotomy. After establishing the pelvic horizontal and drawing the ideal proximal mechanical axis (PMA) perpendicular to it, the next critical step, assuming no distal deformities, is to draw the Distal Mechanical Axis (DMA) line. What is the correct method for drawing the DMA line in this specific context?

. From the center of the femoral head to the center of the knee joint.
. Bisecting the mid-diaphysis of the femur and extending proximally.
. From the center of the ankle joint through the center of the knee joint, then extended proximally up the femoral shaft.
. Perpendicular to the pelvic horizontal, passing through the greater trochanter.
. Connecting the two most prominent points of the medial and lateral femoral condyles.

Correct Answer & Explanation

. From the center of the ankle joint through the center of the knee joint, then extended proximally up the femoral shaft.

Explanation

Correct Answer: CThe case content, under 'Step-by-Step Guide to Finding the CORA in Hip Fusion,' explicitly states for Step 4: 'Draw the Distal Mechanical Axis (DMA) Line: Assuming no distal deformity, the DMA line is thecurrentmechanical axis of the distal limb. It is drawn from the center of the ankle joint through the center of the knee joint, and then extended proximally up the femoral shaft.' This is clearly illustrated by the blue line in diagram (b) of the provided image.Option A is incorrectbecause this describes the general mechanical axis of the lower extremity, but for a fused hip, the DMA is specifically drawn from the ankle through the knee and extended proximally to intersect the PMA.Option B is incorrectbecause bisecting the mid-diaphysis defines the anatomic axis, not the mechanical axis, which is crucial for deformity correction.Option D is incorrectbecause this describes a line that is not the mechanical axis and would not be used to define the CORA in this context.Option E is incorrectbecause connecting the femoral condyles defines the knee joint line, which is used in conjunction with the mechanical axis, but is not the DMA itself.

Question 2833

Topic: Lower Extremity Trauma

During the consolidation phase of distraction osteogenesis, plain radiographs reveal a wide, radiolucent gap in the center of the regenerate bone that is failing to mineralize. What is the most appropriate initial management strategy?

. Immediate autologous bone grafting
. Compression of the regenerate using the "accordion technique"
. Empiric intravenous antibiotics
. Exchange of the external fixator to an intramedullary nail
. Increasing the daily rate of distraction

Correct Answer & Explanation

. Compression of the regenerate using the "accordion technique"

Explanation

Poor or delayed regenerate mineralization is highly responsive to the "accordion technique." This process involves alternating cycles of compression and distraction to intensely stimulate local osteogenesis and accelerate mineralization.

Question 2834

Topic: 2. Trauma

What is the specific biomechanical effect on the hip joint reaction force following a successfully executed pelvic support osteotomy?

. It drastically increases joint reaction force by medializing the femoral shaft
. It lateralizes the abductor lever arm, thereby doubling the joint reaction force
. It bypasses the native hip joint entirely, transferring weight-bearing forces directly to the ischium
. It increases shear forces anteriorly across the sacroiliac joint
. It restores normal joint reaction forces by centralizing the femoral head

Correct Answer & Explanation

. It bypasses the native hip joint entirely, transferring weight-bearing forces directly to the ischium

Explanation

A PSO deliberately abandons the incompetent native hip articulation. It creates a bony fulcrum against the pelvis (ischium), effectively bypassing the hip and directly transferring weight-bearing forces from the femur to the pelvis.

Question 2835

Topic: 2. Trauma

Historically, single-level pelvic support osteotomies (e.g., Schanz osteotomy) were frequently abandoned due to poor long-term outcomes. What was the primary biomechanical failure associated with the single-level technique?

. Progressive hip flexion contracture
. Nonunion of the osteotomy site
. Severe varus deformity at the knee
. Ipsilateral knee osteoarthritis secondary to uncorrected valgus mechanical axis deviation
. Avascular necrosis of the femoral head

Correct Answer & Explanation

. Ipsilateral knee osteoarthritis secondary to uncorrected valgus mechanical axis deviation

Explanation

A single-level PSO creates a massive valgus angulation in the proximal femur to support the pelvis, severely shifting the mechanical axis laterally. This uncorrected valgus mechanical axis deviation leads to oblique knee joint forces and early, severe knee osteoarthritis.

Question 2836

Topic: 2. Trauma
A 9-year-old boy sustained a mid-shaft femoral fracture at age 6, which was treated with intramedullary nailing. He now presents with a 1.5 cm LLD, with the fractured limb being longer. Serial measurements over the last year show no further increase in discrepancy, indicating a stable difference. This LLD progression pattern, characterized by an initial increase followed by a plateau, is most commonly associated with which Shapiro type and etiology?
. Type 1; congenital short femur.
. Type 2; dynamic neuromuscular disorder.
. Type 3; overgrowth following a pediatric femoral shaft fracture.
. Type 4; Legg-Calvé-Perthes disease.
. Type 5; juvenile idiopathic arthritis.

Correct Answer & Explanation

. Type 3; overgrowth following a pediatric femoral shaft fracture.

Explanation

The case explicitly states that the Type 3 pattern is classically associated with the overgrowth phenomenon following a pediatric femoral shaft fracture. This pattern begins with an upward slope (increasing discrepancy due to hyperemia and stimulated growth) which then plateaus as the fracture consolidates and the hyperemic response subsides.

Question 2837

Topic: Lower Extremity Trauma

An 11-year-old girl with a skeletal bone age of 11 years has a 3.0 cm leg length discrepancy due to a left femoral overgrowth. Utilizing the Menelaus method, what is the most appropriate timing to perform a right distal femoral epiphysiodesis to equalize her leg lengths at maturity?

. Immediately at bone age 11
. Wait until bone age 12
. Wait until bone age 12.5
. Wait until bone age 13
. Perform a proximal tibial epiphysiodesis instead

Correct Answer & Explanation

. Immediately at bone age 11

Explanation

Using the Menelaus method, girls mature at 14 years. At bone age 11, she has 3 years of growth remaining. The distal femur grows at 1 cm/year (3 years x 1 cm/year = 3 cm). Immediate epiphysiodesis of the distal femur is indicated.

Question 2838

Topic: Lower Extremity Trauma



A 14-year-old boy is evaluated for a lower extremity deformity. Radiographs show a mechanical axis deviation (MAD) of 40 mm medial to the knee center. The mechanical Lateral Distal Femoral Angle (mLDFA) is 88 degrees (normal 85-90) and the Medial Proximal Tibial Angle (MPTA) is 75 degrees (normal 85-90). Where is the primary source of the deformity?

. Proximal femur
. Distal femur
. Intra-articular knee ligaments
. Proximal tibia
. Distal tibia

Correct Answer & Explanation

. Proximal tibia

Explanation

The normal mLDFA indicates the distal femur is properly aligned. The abnormally low MPTA identifies a varus deformity originating in the proximal tibia, which drives the medial mechanical axis deviation.

Question 2839

Topic: 2. Trauma

A 6-year-old boy sustained a midshaft femur fracture treated with flexible intramedullary nailing. To counsel the parents on expected leg length discrepancy due to fracture overgrowth, when should they expect the maximum amount of overgrowth to occur?

. Within the first 3 months
. Between 6 and 9 months
. Between 18 and 24 months
. During the adolescent growth spurt
. Immediately after hardware removal

Correct Answer & Explanation

. Between 18 and 24 months

Explanation

Post-traumatic femoral overgrowth in children typically peaks at 18 to 24 months following the fracture. The most rapid phase occurs in the first year, driven by post-traumatic hyperemia.

Question 2840

Topic: Lower Extremity Trauma

A 12-year-old girl with a projected LLD of 3.5 cm at skeletal maturity is scheduled for a percutaneous epiphysiodesis. Based on the Green-Anderson growth data, what is the accepted average rate of growth per year from the distal femur and proximal tibia?

. Distal femur 6 mm/yr; Proximal tibia 10 mm/yr
. Distal femur 10 mm/yr; Proximal tibia 6 mm/yr
. Distal femur 12 mm/yr; Proximal tibia 8 mm/yr
. Distal femur 8 mm/yr; Proximal tibia 12 mm/yr
. Distal femur 10 mm/yr; Proximal tibia 10 mm/yr

Correct Answer & Explanation

. Distal femur 10 mm/yr; Proximal tibia 6 mm/yr

Explanation

The distal femur grows at approximately 10 mm (3/8 inch) per year, and the proximal tibia grows at about 6 mm (1/4 inch) per year. This rule of thumb is critical for timing an epiphysiodesis.

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