MCQs – Hip Recon 1

Modern Study Review (AI-Generated)

High-Yield Summary

This topic is a staple of the Royal College exam, focusing heavily on hip osteotomies, femoral neck fractures, avascular necrosis (AVN), obturator nerve anatomy, and surgical approaches to the pelvis and hip. The single most important clinical trade-off often tested is the management of femoral neck stress fractures based on cortex involvement—lateral cortex fractures mandate surgical fixation, whereas medial cortex fractures allow conservative management. While classic exam answers emphasize fixation or prosthesis for Pipkin II fractures, modern practice increasingly considers patient age and biological fixation techniques. Understanding detailed neurovascular anatomy in surgical approaches is critical to avoid iatrogenic injury.

High-Yield Decision Matrix

Active Recall Q&A

Hip Osteotomy & Fractures

Q: What is the effect of a valgus intertrochanteric osteotomy on the gluteus medius lever arm?
A: It decreases the lever arm of the gluteus medius.
Related Pearl: Decreasing the lever arm reduces abductor strength, potentially causing Trendelenburg gait.

Q: How does a varus intertrochanteric osteotomy affect the gluteus medius lever arm?
A: It increases the lever arm of the gluteus medius.
Related Pearl: Increasing the lever arm enhances abductor efficiency but may increase joint reaction forces, risking joint degeneration.

Q: What is the recommended treatment for most Pipkin II fractures that are not anatomically reduced?
A: They should be fixed surgically, or an endoprosthesis performed if the patient is elderly.
Related Pearl: Anatomical reduction is critical to prevent post-traumatic arthritis in femoral head fractures.

Q: Which side of femoral neck stress fractures is more worrisome, and what is the treatment if the lateral cortex is involved?
A: The lateral tension side is more worrisome; if the lateral cortex is involved, surgical fixation is required.
Related Pearl: Lateral cortex involvement predisposes to displacement due to tensile forces, increasing risk of fracture propagation.

Q: How should femoral neck stress fractures involving only the medial cortex be managed?
A: Feather weightbearing can be started.
Related Pearl: Medial cortex fractures are compression-sided and more stable, allowing conservative management.

Avascular Necrosis (AVN)

Q: What are the four most common associations for avascular necrosis of the hip?
A: Alcoholism, corticosteroids, trauma, and idiopathic causes.
Related Pearl: These factors disrupt blood supply to the femoral head, leading to osteonecrosis.

Q: What additional conditions can precipitate avascular necrosis?
A: Hemoglobinopathies, Gaucher’s disease, Caisson’s disease, hematologic neoplasia, SLE, organ transplantation, pancreatitis, irradiation, hyperuricemia, and pregnancy.
Related Pearl: Systemic diseases and treatments impair microcirculation and bone viability, increasing AVN risk.

Q: In a 28-year-old pregnant woman with hip pain, what is the diagnostic and initial management approach?
A: Obtain an MRI to diagnose AVN and initiate feather weightbearing until delivery.
Related Pearl: MRI is safe in pregnancy and sensitive for early AVN detection; conservative management reduces progression risk.

Obturator Nerve Anatomy & Function

Q: Describe the course and innervation of the anterior branch of the obturator nerve.
A: It passes through adductor brevis, then between adductor brevis and longus, supplying adductor longus, brevis, and gracilis.
Related Pearl: Injury to this branch affects thigh adduction and medial compartment function.

Q: What muscles does the posterior branch of the obturator nerve supply?
A: It pierces obturator externus, supplies it, then runs behind adductor brevis between brevis and magnus, supplying the adductor portion of adductor magnus.
Related Pearl: The ischiocondylar part of adductor magnus is innervated by the tibial sciatic nerve, not this branch.

Q: After obturator neurectomy, which part of adductor magnus remains functional and why?
A: The ischiocondylar part remains because it is innervated by the tibial branch of the sciatic nerve.
Related Pearl: This part acts as a thigh extensor and medial rotator but also contributes to adduction.

Q: What is the innervation and function of the pectineus muscle?
A: Innervated by the femoral nerve; it adducts the thigh and lies proximally in the same plane as adductor longus.
Related Pearl: Pectineus is a key adductor spared in obturator nerve injuries.

Surgical Approaches & Neurovascular Anatomy

Q: In the ilioinguinal approach, what does the interval lateral to the lacuna musculorum expose?
A: The iliac crest, iliac fossa, anterior column, and sacroiliac joint posteriorly.
Related Pearl: This exposure is critical for anterior pelvic and acetabular fracture fixation.

Q: What structures are exposed by the interval between the lacuna musculorum and lacuna vasorum in the ilioinguinal approach?
A: The pelvic brim, anterior column, quadrilateral plate, and posterior column.
Related Pearl: This interval allows access to the entire anterior column and quadrilateral surface.

Q: What is exposed medial to the lacuna vasorum after mobilizing the spermatic cord?
A: The superior pubic ramus and symphysis pubis; beware of the corona mortis.
Related Pearl: Injury to the corona mortis can cause significant hemorrhage during pelvic surgery.

Q: Why must the iliopectineal fascia be incised after mobilizing the lacuna musculorum in the ilioinguinal approach?
A: To access the quadrilateral plate; otherwise, structures beneath the inguinal ligament cannot be mobilized.
Related Pearl: The iliopectineal fascia separates muscular and vascular compartments; cutting it improves surgical exposure.

Q: Which nerve exits above the piriformis muscle, and what is the consequence of its injury?
A: The superior gluteal nerve; injury causes weakness of gluteus medius, minimus, and tensor fascia lata.
Related Pearl: Superior gluteal nerve injury leads to Trendelenburg gait due to abductor weakness.

Q: What neurovascular structures are located 2 cm above the piriformis?
A: The superior gluteal artery and nerve.
Related Pearl: Precise knowledge of this anatomy prevents iatrogenic injury during posterior hip approaches.

Q: List the nerves and vessels located 8 cm below the piriformis.
A: Sciatic nerve, posterior femoral cutaneous nerve, inferior gluteal artery and nerve, nerve to obturator internus, internal pudendal artery, nerve to quadratus femoris, pudendal nerve.
Related Pearl: These structures are vulnerable during posterior hip and gluteal surgeries.

Q: What is the most common nerve injury in the anterior Smith-Peterson approach?
A: Injury to the lateral femoral cutaneous nerve.
Related Pearl: This causes meralgia paresthetica, presenting as anterolateral thigh numbness or dysesthesia.

Classic Clinical Notes

• A valgus intertrochanteric osteotomy would decrease the lever arm of gluteus medius. Similarly, a varus intertrochanteric osteotomy would increase the lever arm.

• Most Pipkin II fractures that are not reduced anatomically should be fixed, or an endoprosthesis performed if in elderly.

• Stress fractures of the femoral neck – more worrisome on the lateral tension side than on the medial compression side. If the fracture has any involvement of the lateral cortex, then fix. If the fracture involves just the medial cortex, you can start with feather weightbearing.

• 4 most common associations for avascular necrosis include alcoholism, corticosteroids, and trauma; the fourth is idiopathic. The other precipitating conditions include hemoglobinopathies, Gaucher’s disease, Caisson’s disease, hematologic neoplasia, SLE, organ transplantation, pancreatitis, irradiation, hyperuricemia, and pregnancy.

• In a 28 year old pregnant woman who develops hip pain – the clue is that she is pregnant and may have AVN – get an MRI to make the diagnosis, then probably treat with feather weightbearing until child is born.

• Obturator nerve – anterior and posterior branches. Anterior branch passes through adductor brevis and then between adductor brevis and longus, and supplies longus, brevis, and gracilis. Posterior branch pierces obturator externus and supplies it, then runs down behind adductor brevis between brevis and magnus. It supplies the adductor portion of magnus (the rest of magnus – the ischiocondylar part – is supplied by tibial branches of the sciatic).

• If you were to do an obturator neurectomy, the ischiocondylar part of the adductor magnus would remain because it is innervated by the sciatic nerve, and although it is more of a thigh extendor and medial rotator, it would probably also adduct the limb. Pectineus is innervated by the femoral nerve and lies proximally but in the same plane as adductor longus – it adducts the thigh as well.

• In the ilioinguinal approach, the interval between the iliopsoas & lateral cutaneous femoral nerve (the lacuna musculorum) and the external iliac artery/vein & lymphatics (the lacuna vasorum) will expose the quadrilateral plate. Lateral to the lacuna musculorum gives you exposure to the iliac crest, fossa, anterior column, and SI joint at the back. Between the lacuna musculorum and vasorum exposes the pelvic brim all the way along the anterior column back to the SI joint, the quadrilateral plate, and the posterior column. Medial to lacuna vasorum is the spermatic cord, and once this is mobilized, the entire superior pubic ramus and symphysis pubis is exposed (watch for corona mortis).

• Important to remember that after mobilizing the lacuna musculorum, you need to incise the iliopectineal fascia to access the quadrilateral plate. The iliopectineal fascia separates the lacuna musculorum from the vasorum and unless you cut it, you will never be able to mobilize the structures beneath the inguinal ligament.

• The nerve exiting above piriformis is the superior gluteal – cutting it will result in weakness of gluteus medius, gluteus minimus, and tensor fascia lata.

• ABOVE piriformis: superior gluteal artery and nerve 2 above
• BELOW piriformis: sciatic nerve 8 below

posterior femoral cutaneous nerve
inferior gluteal artery and nerve
nerve to obturator internus
internal pudendal artery
nerve to quadratus femoris
pudendal nerve

• In the anterior Smith Peterson approach, the most common injury is to the lateral femoral cutaneous nerve.

Last Updated on January 25, 2026 by Christian Veillette