ABOS Part I Comprehensive Review - Batch 1

Question 1

A 62-year-old male presents with progressive right knee pain, worse with activity. Full-length standing AP radiographs reveal a Mechanical Axis Deviation (MAD) of 15mm medial to the center of the knee joint. The surgeon suspects a varus deformity ori

Accepted Answer

C. Medial Proximal Tibial Angle (MPTA)

Question 2

A 30-year-old competitive runner presents with chronic anterior knee pain and a feeling of instability, particularly during deceleration. MRI reveals a chronic Anterior Cruciate Ligament (ACL) deficiency. Preoperative planning for an ACL reconstructi

Accepted Answer

D. Posterior Proximal Tibial Angle (PPTA)

Question 3

A 10-year-old male presents with a progressive genu valgum deformity. Preoperative radiographs are obtained for planning a distal femoral osteotomy. When drawing the sagittal plane joint orientation line for the distal femur in this pediatric patient

Accepted Answer

C. The line should be drawn exactly where the growth plate (physis) exits anteriorly and posteriorly.

Question 4

A 55-year-old female undergoes a full-length standing AP radiograph of her lower extremities as part of a workup for knee osteoarthritis. The radiograph reveals a Mechanical Axis Deviation (MAD) of 12mm lateral to the center of the knee joint. The su

Accepted Answer

C. Mechanical Lateral Distal Femoral Angle (mLDFA)

Question 5

A 40-year-old male presents with chronic ankle pain and progressive varus deformity of the ankle, leading to medial gutter impingement. Preoperative planning for a supramalleolar osteotomy (SMOT) requires precise measurement of the frontal plane ankl

Accepted Answer

C. Lateral Distal Tibial Angle (LDTA)

Question 6

A 28-year-old female presents with a Trendelenburg gait and chronic hip pain. Radiographs reveal a femoral neck-shaft angle of 115°. Based on Paley's principles, what is the most likely diagnosis and its direct biomechanical consequence?

Accepted Answer

D. Coxa vara, leading to a shortened limb and abductor weakness.

Question 7

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 s

Accepted Answer

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

Question 8

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

Accepted Answer

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.

Question 9

A 35-year-old male presents with chronic posterior ankle pain and limited plantarflexion. Radiographic evaluation reveals an Anterior Distal Tibial Angle (ADTA) of 70°. Based on the case, what is the most likely sagittal plane deformity and its clini

Accepted Answer

D. Ankle recurvatum, leading to posterior impingement and loss of plantarflexion.

Question 10

A 50-year-old patient with a history of hip trauma presents with a Trendelenburg gait and reports difficulty with abductor strength. Radiographs show a high-riding greater trochanter relative to the femoral head. Which of the following angles, as def

Accepted Answer

B. Mechanical Lateral Proximal Femoral Angle (mLPFA)

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

Orthopedic Surgery Board Exam Review: Lower Limb Deformity, Paley's Principles & TKA | Part 22006

Key Takeaway