Clinical Case Study - Subcapital Intracapsular Fracture of the Neck of Femur

Question 1: Classify the types of fracture of the neck of the femur

A. By Anatomical Site (location along the neck)

B. By Displacement - Garden Classification (most widely used)

• Garden I - Undisplaced/incomplete; valgus-impacted; trabecular lines in femoral head angled relative to acetabulum
• Garden II - Complete, undisplaced; trabecular lines collinear with acetabulum
• Garden III - Complete, partially displaced with varus angulation; trabecular lines misaligned
• Garden IV - Completely displaced; head is free within acetabulum and realigns itself

C. By Angle of Fracture Line - Pauwels Classification

• Type I - Angle ≤ 30° (mostly horizontal, stable, good prognosis)
• Type II - Angle 30-50° (intermediate)
• Type III - Angle > 50° (nearly vertical, greatest shear forces, poor prognosis, high risk of nonunion)

Question 2: Anatomical basis of lateral rotation and shortening

• The iliopsoas, gluteus maximus, obturators, piriformis, and short external rotators all insert on or near the greater trochanter and the proximal femur.
• After the fracture, these muscles pull the distal fragment (shaft + lower limb) into external rotation unopposed, because the femoral head remains locked in the acetabulum.
• The foot therefore falls into external rotation - classically lying flat against the bed.

• The iliopsoas inserts on the lesser trochanter and pulls the shaft proximally.
• The adductors (adductor magnus, longus, brevis, gracilis, pectineus) pull the shaft medially and proximally.
• With loss of bony continuity at the neck, there is no resistance to upward displacement of the shaft, so the greater trochanter rides up and the limb shortens.
• Shortening can be confirmed clinically by Bryant's triangle and Nelaton's line - both show elevation of the greater trochanter.

Question 3: How is the length of the lower limb measured?

True (Absolute) Limb Length

• Measured from the anterior superior iliac spine (ASIS) to the medial malleolus of the same side using a tape measure.
• This measures the actual bony length of the limb.
• Both limbs must be placed in identical positions (parallel to each other) before measurement.

Apparent (Relative) Limb Length

• Measured from the umbilicus (or xiphisternum) to the medial malleolus.
• This detects apparent shortening caused by pelvic tilt, adduction/abduction deformity, or scoliosis - not just bony shortening.
• In fracture neck of femur, both true and apparent shortening are present.

Question 4: Possible complication of subcapital intracapsular fracture

Avascular Necrosis (AVN) of the Femoral Head

• The blood supply to the femoral head travels via retinacular vessels closely applied to the femoral neck (branches of the medial and lateral circumflex femoral arteries).
• In a subcapital intracapsular fracture - especially displaced fractures (Garden III and IV) - these retinacular vessels are torn, cutting off the blood supply to the femoral head.
• AVN occurs in 15-35% of patients with displaced intracapsular fractures.
• The risk is greatest in Garden type 3 and 4 fractures.

Other complications include:

1. Non-union - failure of the fracture to heal (common because the femoral head has poor blood supply even before AVN)
2. Malunion - heals in a bad position
3. Late osteoarthritis - due to joint damage and altered mechanics
4. Deep vein thrombosis / pulmonary embolism - due to immobility in this elderly population (high mortality)
5. Haemorrhage/shock - significant blood loss at fracture site
6. Implant failure - if managed surgically

Question 5: Clinical implications of the neck-shaft angle

Clinical significance:

• The neck-shaft angle determines the biomechanical forces acting across a fracture. A more vertical fracture line (higher Pauwels angle combined with a varus neck-shaft angle) leads to greater shear forces at the fracture site, making fixation unstable and increasing risk of non-union.
• After fracture or surgical repair, the goal is to restore the normal neck-shaft angle to ensure proper abductor function and avoid Trendelenburg gait.
• Coxa vara (reduced neck-shaft angle) causes: relative shortening of the limb, inefficient hip abductors, Trendelenburg limp, and increased stress on the femoral neck.