ABOS Part I Comprehensive Review - Batch 47

Question 1

A 55-year-old male presents with chronic right knee pain and a progressive varus deformity. A full-length standing radiograph is obtained, as shown below. The mechanical axis of the lower limb is measured to pass 25 mm medial to the center of the kne

Accepted Answer

The patient has a varus deformity, and the MAD indicates a significant pathological malalignment.

Question 2

A 30-year-old female presents with a progressive genu valgum deformity. Preoperative planning reveals a Mechanical Lateral Distal Femoral Angle (mLDFA) of 95 degrees. All other joint orientation angles (MPTA, JLCA, LDTA) are within normal limits. Bas

Accepted Answer

Distal femur

Question 3

A surgeon is planning a complex limb reconstruction for a patient with a post-traumatic angular deformity of the tibia. After drawing the proximal and distal mechanical axes of the deformed bone, they identify the point where these two lines intersec

Accepted Answer

The Center of Rotation of Angulation (CORA), which is the geometric apex of the deformity and dictates the transverse bisector line.

Question 4

A 40-year-old patient requires correction of a uniapical diaphyseal femoral varus deformity. The surgeon's goal is to achieve a pure angular correction without any translation at the osteotomy site, ensuring maximal bone-on-bone apposition for rapid

Accepted Answer

Rule One: Osteotomy and hardware hinge (ACA) are both placed at the CORA.

Question 5

A 7-year-old child presents with a severe congenital tibial deformity where the CORA is precisely located at the open proximal tibial physis. The surgeon needs to correct the angular deformity while preserving the growth plate. Which of Paley's Osteo

Accepted Answer

Rule Two, placing the hardware hinge (ACA) at the physis (CORA) but performing the osteotomy in the healthy metaphysis, resulting in planned translation at the osteotomy site.

Question 6

Following a complex femoral osteotomy, a patient's postoperative full-length radiograph shows that while the angular deformity appears visually corrected, the mechanical axis of the limb remains significantly deviated, and there is a noticeable step-

Accepted Answer

Rule Three was violated, leading to iatrogenic translation of the bone ends AND failure of the mechanical axes to realign.

Question 7

A 25-year-old patient presents with a significant genu varum deformity and a 2 cm limb length discrepancy (shortening) in the affected limb. The surgeon plans a gradual correction using an external fixator. To address both the angular deformity and t

Accepted Answer

An angular correction with distraction, where the hinge is placed on the bisector line but more convex than the convex cortex (out in space).

Question 8

A 60-year-old patient with severe osteoarthritis and a varus knee deformity requires a high tibial osteotomy. The surgeon plans an acute correction using a locking plate, aiming for primary bone healing under compression. The patient has no significa

Accepted Answer

A closing wedge osteotomy with the hinge on the concave cortex, resecting a wedge of bone.

Question 9

A surgeon is reviewing a patient's preoperative planning for a complex multiapical deformity of the femur. The planning software has identified multiple CORAs along the bone. According to Paley's methodology, what is the most appropriate approach to

Accepted Answer

Address each CORA individually with separate osteotomies and hinges, or perform a single, carefully calculated compromise osteotomy.

Question 10

Which of the following statements best encapsulates the ultimate goal of Paley's geometric principles in lower extremity deformity correction?

Accepted Answer

To restore normal mechanical alignment and joint orientation through meticulous, mathematically sound preoperative planning.

ABOS Part I Orthopaedic Deformity Correction, Limb Reconstruction & Gait Analysis Review | Part 21914

ABOS Part I Orthopaedic Review: Paley's Principles of Deformity Correction & Limb Alignment | Part 21912

Key Takeaway