MCQs – Hip Recon 4

Modern Study Review (AI-Generated)

High-Yield Summary

This topic is a staple of the Royal College exam, focusing heavily on hip pathology imaging, surgical anatomy, osteotomy biomechanics, and fracture management. The single most important clinical trade-off is the choice of osteotomy type (varus vs. valgus) based on preoperative hip range of motion, particularly abduction and adduction limitations, which dictate postoperative function and complication risk. While the exam favors classical imaging signs and fixed safe zones for screw placement, modern practice increasingly integrates advanced imaging and individualized surgical planning. Understanding vascular anatomy and biomechanics remains critical to avoid complications such as avascular necrosis and gait abnormalities.

High-Yield Decision Matrix

Active Recall Q&A

AVN Imaging

Q: What is the earliest MRI finding in avascular necrosis (AVN) on T1-weighted images?
A: A single-density line (low signal) representing separation of normal and ischemic bone.
Related Pearl: This line precedes other imaging signs and is critical for early AVN diagnosis before structural collapse.

Q: What does the “double-line sign” on T2 MRI images in AVN represent?
A: A second, high signal intensity line within the low signal line, indicating hypervascular granulation tissue.
Related Pearl: The double-line sign is pathognomonic for AVN and helps differentiate it from other femoral head lesions.

Acetabular Screw Placement

Q: What is the safest zone for screw placement in the acetabulum?
A: The posterosuperior quadrant.
Related Pearl: Avoiding anterosuperior and anteroinferior zones prevents injury to the external iliac vessels and obturator artery, respectively.

Q: Which acetabular zones should be avoided for screw placement due to vascular risk?
A: Anterosuperior (external iliac vessels), anteroinferior (obturator artery), and if possible, posteroinferior (sciatic notch).
Related Pearl: Knowledge of pelvic vascular anatomy is essential to prevent catastrophic hemorrhage during fixation.

Acetabular Protrusio

Q: Which diseases are commonly associated with acetabular protrusio?
A: Rheumatoid arthritis, Paget’s disease, Marfan’s syndrome, and homocystinuria.
Related Pearl: These systemic diseases alter bone remodeling, leading to medial displacement of the acetabulum.

Q: Is acetabular protrusio seen in neurofibromatosis?
A: No, it is not typically seen in neurofibromatosis.
Related Pearl: Differentiating causes of protrusio aids in diagnosis and management planning.

Chiari Osteotomy

Q: What is the indication for a Chiari osteotomy?
A: Coxa magna with lateral extrusion of the femoral head.
Related Pearl: Chiari osteotomy is a salvage procedure aimed at improving hip stability and load distribution.

Q: What are the goals of Chiari osteotomy in developmental dysplasia of the hip (DDH)?
A: To medialize the hip and improve the weightbearing surface through capsular metaplasia.
Related Pearl: This procedure is reserved for salvage cases where conventional reconstruction is not feasible.

Osteotomy for Osteoarthritis

Q: What is the purpose of performing an osteotomy in osteoarthritis of the hip?
A: To medialize the joint reaction forces around the hip.
Related Pearl: Medialization reduces joint contact stress, potentially delaying arthroplasty.

Developmental Dysplasia of the Hip (DDH)

Q: In untreated adult DDH, which is worse: a poorly formed pseudoacetabulum from mild subluxation or a high riding dislocation with a well-formed pseudoacetabulum?
A: A poorly formed pseudoacetabulum from mild subluxation is worse.
Related Pearl: A well-formed pseudoacetabulum allows better load transmission despite dislocation.

Q: What is the recommended management for a young adult with asymptomatic high riding dislocated hips?
A: Observation; do nothing.
Related Pearl: Surgery is not indicated without symptoms due to risks outweighing benefits.

Osteoporosis of the Hip

Q: In hip osteoporosis, which trabeculae are the last to be lost?
A: The primary compressive trabeculae.
Related Pearl: Preservation of these trabeculae maintains some structural integrity under load.

Osteotomy Planning and Biomechanics

Q: Why is limited abduction a concern when planning a varus osteotomy of the hip?
A: Because varus osteotomy adducts the femur relative to the proximal fragment, worsening abduction deficit.
Related Pearl: Preoperative range of motion assessment is critical to avoid postoperative functional impairment.

Q: Why is limited adduction a concern when planning a valgus osteotomy of the hip?
A: Because valgus osteotomy abducts the femur relative to the proximal fragment, worsening adduction deficit.
Related Pearl: This can leave the leg stuck in abduction, causing patient dissatisfaction.

Q: How does a varus osteotomy affect the abductor lever arm and joint reaction force?
A: It increases the abductor lever arm, decreases abductor force, and reduces joint reaction force.
Related Pearl: Reduced joint reaction force can slow osteoarthritis progression but may weaken abductor function.

Q: What is a common complication of varus osteotomy related to the abductor muscles?
A: Abductor muscle shortening causing limp and greater trochanter prominence; may require trochanteric advancement.
Related Pearl: Trochanteric advancement restores abductor tension and improves gait mechanics.

Q: How does a valgus osteotomy affect the abductor lever arm and joint reaction force?
A: It decreases the abductor lever arm, increases abductor force, and increases joint reaction force.
Related Pearl: Increased joint reaction force may accelerate cartilage wear if not balanced by improved joint congruency.

Q: What is the overall purpose of osteotomies around the hip besides biomechanical changes?
A: To increase joint surface contact and decrease unit load on cartilage.
Related Pearl: This can reduce pain and delay the need for total hip arthroplasty.

Q: When is a valgus osteotomy indicated in cases of femoral head deformity?
A: When the head loses sphericity and extrudes laterally (e.g., Perthes disease, AVN) to medialize weightbearing and reduce pain.
Related Pearl: Medializing the weightbearing zone decreases the moment arm of body weight, improving joint mechanics.

Hip Trauma and Fracture Management

Q: Which type of hip fracture has the highest incidence of complications?
A: Subtrochanteric fractures due to medial buttress comminution.
Related Pearl: These fractures are biomechanically unstable and prone to nonunion.

Q: What is the main blood supply responsible for healing femoral neck fractures in adults?
A: The lateral epiphyseal artery.
Related Pearl: Preservation of this vessel is critical to prevent avascular necrosis after fracture.

Q: Which muscle tendon can be interposed in the joint after a posterior hip dislocation?
A: The iliopsoas tendon.
Related Pearl: Interposition can block reduction and requires surgical attention.

Q: Do Pipkin I femoral head fractures always require surgery?
A: No, they do not necessarily require surgical treatment.
Related Pearl: Non-displaced Pipkin I fractures can be managed conservatively with good outcomes.

Classic Clinical Notes

• The earliest finding in AVN is a single-density line (low signal) on T1 that presumably represents the separation of normal and ischemic bone. On T2 images, a second, high signal intensity line can be found within this line – this is believed to represent hypervascular granulation tissue and is called the double-line sign. Note that the “double line sign” is seen on T2 images.

• The safest zone to put a screw into the acetabulum is posterosuperior; avoid anterosuperior (external iliac vessels), anteroinferior (obturator artery) and if possible the posteroinferior (sciatic notch).

• Acetabular protrusio is seen with rheumatoids, Paget’s, Marfans, homocystinuria (looks like Paget’s). It is not seen in neurofibromatosis.

• Indications for Chiari – coxa magna with lateral extrusion of the head.

• In DDH, the Chiari is a salvage operation that hopes to both medialize the hip, and improve the weightbearing surface via metaplasia of the capsule.

• The purpose of doing an osteotomy for surgical treatment of OA is to medialize the joint reaction forces around the hip.

• In an adult with untreated DDH, a poorly formed pseudoacetabulum from mild subluxation is worse than a high riding dislocation that articulates in a well formed pseudoacetabulum.

• In a young adult with asymptomatic high riding dislocated hips – do nothing.

• In osteoporosis of the hips, the last trabeculae to be lost are the primary compressive.

• When planning a varus osteotomy of the hip, if the patient has limited ABDUCTION, be worried. By doing the varus osteotomy, you adduct their femur relative to the proximal fragment – if they have limited abduction, they’ll never be able to abduct their femur much past midline.

• Conversely, when planning a valgus osteotomy of the hip, if the patient has limited ADDUCTION, again, be worried. By doing the valgus osteotomy, you are abducting their femur relative to their proximal fragment. If they have limited adduction, their leg will be stuck out in abduction, and they won’t be able to bring it to midline – this’ll piss them off just a tad.

• In terms of thinking about varus and valgus osteotomies of the hip:

• In general: varus osteotomy increases the lever arm of the abductors (and may ever so slightly decrease the lever arm of the body weight by medializing the contact point of the hip) – the force of the abductors is less, and hence, the joint reaction force (the vector sum of the body weight force and the abductor force) is LESS.

• The problem is that the abductor muscles are shortened, and may be shortened to the point where they are ineffective at holding up the GT – results in a limp! You may have to rectify this by advancing their trochanter. It also increases the prominence of the GT because it has been lateralized.

• In general: valgus osteotomy, you decrease the lever arm of the abductors (and may ever so slightly increase the lever arm of the body weight by lateralizing the contact point of the hip) – the force of the abductors is more, and hence, the joint reaction force (the vector sum of the body weight force and abductor force) is MORE.

• The thing to remember though is that the osteotomies are done not just for joint biomechanics, but also to increase joint surface contact and thus decrease unit load on the cartilage. Often, when the head loses its sphericity and extrudes laterally a bit (Perthes, AVN), the weightbearing characteristics of the joint can be improved with a valgus osteotomy. If the weightbearing is happening primarily along the superolateral aspect of the joint, a valgus osteotomy may medialize the primary point of weightbearing, thus DECREASING the moment arm of the body weight. By bringing inferior osteophytes to articulate with one another, you may decrease the unit load on the remaining cartilage and thus have less pain.

• Some Hip Trauma:

• Subtrochanteric fractures have the highest incidence of complication because of medial buttress comminution.

• The main blood supply for healing a femoral neck fracture in adults is the lateral epiphyseal artery.

• Iliopsoas can be interposed in the joint after a posterior hip dislocation.

• Pipkin I type fractures do not necessarily have to be treated with surgery.

Last Updated on January 25, 2026 by Christian Veillette