1. General Principles & Basic Science MCQs

A 22-year-old female undergoes a Bernese periacetabular osteotomy (PAO) for symptomatic hip dysplasia. Postoperatively, she demonstrates weakness in ankle dorsiflexion and great toe extension. Which nerve was most likely injured during the procedure?

A 5-year-old child presents with a severe limp. Radiographs reveal complete resorption of the right femoral head and neck with a high-riding trochanter (Choi type IV) as a sequela of neonatal MRSA septic arthritis. Which salvage procedure provides the most stable fulcrum for ambulation and equalizes leg length?

In evaluating a normal lower extremity via long standing radiographs, the mechanical axis deviation (MAD) is typically located in which position relative to the center of the knee joint?

When applying a circular external fixator to the proximal tibia, placing transverse wires carries a risk of neurovascular injury. To safely avoid the common peroneal nerve laterally, a lateral-to-medial wire should be optimally inserted in which manner?

When performing a corrective osteotomy for a uniplanar tibial deformity, what is the geometric consequence of placing the osteotomy and the hinge at a level distant from the Center of Rotation of Angulation (CORA)?

During preoperative planning for a distal femoral varus deformity, the mechanical lateral distal femoral angle (mLDFA) and the mechanical proximal tibial angle (mPTA) are measured. What are the normal population averages for these respective angles?

A patient with a multiplanar tibial deformity is treated with a hexapod external fixator. Following the initial correction schedule, a residual 5-degree varus deformity is noted. To generate a residual correction program, which of the following frame parameters MUST be updated in the software?

In the context of distraction osteogenesis via the Ilizarov method, what is the optimal latency period prior to initiating distraction after the corticotomy?

When performing a deformity correction, if the osteotomy and the axis of correction of angulation (ACA) are both located exactly at the center of rotation of angulation (CORA), what is the expected geometric outcome?

When performing a medial opening wedge high tibial osteotomy (HTO) for varus gonarthrosis, failing to make the anterior gap smaller than the posterior gap will typically result in which unintended sagittal plane deformity?

During a lower extremity deformity correction, the osteotomy is made proximal to the CORA, but the axis of correction of angulation (ACA) is placed exactly at the CORA. What is the resulting mechanical effect upon correction?

The Taylor Spatial Frame utilizes a specialized software program to calculate strut adjustments based on a 6-axis deformity analysis. Which of the following is NOT a required radiographic or clinical parameter for the software to generate a prescription?

When planning a corrective osteotomy for a lower extremity deformity, if the osteotomy is performed at a level different from the Center of Rotation of Angulation (CORA) but the correction axis passes through the CORA, what is the expected resulting deformity?

A 35-year-old female on chronic corticosteroids for SLE presents with groin pain. MRI reveals bilateral femoral head avascular necrosis (Ficat Stage II). What is the primary rationale for performing a core decompression?

When using a hexapod circular fixator for deformity correction, accurate data entry into the software is crucial. Which parameter specifically dictates the spatial relationship between the reference ring and the bone segment it attaches to?

According to the principles of deformity correction (Paley's Rule 1), if an osteotomy and the correction hinge are both placed exactly at the Center of Rotation of Angulation (CORA), what is the resulting effect on the bone segments after realignment?

When analyzing the mechanical axis of the lower extremity for deformity planning, what is the accepted normal range for the mechanical lateral distal femoral angle (mLDFA)?

A 14-year-old female undergoes femoral lengthening using distraction osteogenesis. During the consolidation phase, her surgeon calculates the External Fixator Index (EFI). How is the EFI defined?

When programming a Taylor Spatial Frame (hexapod fixator) for multiplanar lower extremity deformity correction, what does the "mounting parameter" mathematically communicate to the software?