Subtrochanteric fracture

A fracture within 5 cm below the lesser trochanter, where the femur carries its highest bending stresses: compression medially, tension laterally. The proximal fragment is pulled into flexion (iliopsoas), abduction (gluteus medius and minimus) and external rotation (short rotators), while the adductors draw the shaft medially. Reduction is therefore the difficult part of the operation. A growing share are atypical femoral fractures after long-term bisphosphonate or denosumab treatment.

Mechanism

Bimodal: high-energy trauma in young adults (often comminuted); low-energy falls in osteoporotic bone; pathological fractures (metastases, myeloma); atypical fractures with minimal or no trauma, often after weeks of prodromal thigh pain.

Clinical findings

• Thigh pain and deformity, unable to bear weight; the proximal thigh looks swollen and flexed.
• Ask about bisphosphonates or denosumab, prodromal thigh or groin pain, and a history of cancer.
• Atypical fracture: examine and image the other femur, which is involved (complete, incomplete or beaking only) in roughly a third of cases or more.

Imaging

• AP and lateral of the whole femur including hip and knee, plus AP pelvis.
• If an atypical fracture is suspected (thigh pain, bisphosphonates, transverse lateral break): full-length AP of the other femur, and MRI or isotope scan if it shows cortical beaking.
• CT or MRI and oncology staging if a pathological fracture is suspected.

• AP and lateral of the whole femur including hip and knee, plus AP pelvis.
• Atypical femoral fracture (ASBMR task force major features): minimal trauma, starts at the lateral cortex, essentially transverse (may turn oblique medially with a medial spike), non-comminuted, with localised periosteal or endosteal thickening (“beaking”) of the lateral cortex.
• Full-length films of the contralateral femur; MRI or isotope scan if the other side shows beaking or pain. CT or MRI to stage a suspected metastasis.

Classification

32A (subtroch)

Simple: A1 spiral, A2 oblique, A3 transverse, coded in the 32 shaft segment with the subtrochanteric zone.

32B / 32C

Wedge or multifragmentary patterns of the same zone.

Russell–Taylor

I: piriformis fossa intact (IA lesser trochanter intact, IB lesser trochanter detached). II: extension into the piriformis fossa / greater trochanter (IIA medial buttress intact, IIB medial comminution). Historically used to choose the nail entry.

Seinsheimer

I undisplaced; II two parts (transverse, spiral with the lesser trochanter on the proximal or distal fragment); III three parts; IV four or more; V with intertrochanteric extension.

Atypical femoral fracture

Incomplete (lateral cortical stress line, “dreaded black line”) or complete; subtrochanteric or diaphyseal.

Types shown in 3D

32A3 (subtroch)

Simple transverse (< 30°), 2–3 cm below the lesser trochanter. The classic deformity is clear: proximal fragment flexed, abducted and externally rotated; shaft adducted and shortened.

32A1 (subtroch)

Long spiral starting near the lesser trochanter. A cerclage cable helps hold the reduction while the nail is passed.

32B (subtroch)

Medial wedge: the posteromedial cortex, the main compression buttress, is broken. Without it the implant takes the full load: restore it if possible, otherwise use a long nail.

Atypical femoral fracture

Low-energy, transverse at the lateral cortex (where the cortex is thickened, “beaked”), turning oblique medially into a short medial spike, without comminution. Linked to long-term bisphosphonate or denosumab use. Image the other femur.

Treatment

Treatment of choice

Long cephalomedullary nail (reconstruction or trochanteric entry), after the deformity has been corrected: traction alone rarely reduces it. Use percutaneous clamps, a ball-spike pusher, joysticks or a mini-open approach with a cerclage cable to control the flexed, abducted proximal fragment before reaming. Avoid varus: it is the main cause of failure.

Plate

Proximal femoral locking plate or 95° blade plate when a nail cannot be used (e.g. distorted canal, existing implants). Higher rates of failure if the medial buttress is not restored.

Atypical femoral fracture

Stop the antiresorptive; check calcium, vitamin D and consider teriparatide. Complete fractures: long cephalomedullary nail, with care to avoid a varus, lateral-gap reduction (the bowed femur fits the nail poorly). Incomplete fracture with pain or a visible line on MRI: prophylactic nailing; painless, early lesions: protected weight bearing and close follow-up.

Pathological

Long cephalomedullary nail protecting the whole femur (or resection and endoprosthesis for solitary metastases, e.g. renal cell carcinoma, after embolisation). Radiotherapy afterwards.

Aftercare

Weight bearing as tolerated after a nail with good cortical contact; protected weight bearing for comminuted or plated fractures. Atypical fractures heal slowly: expect 6–12 months and watch the other side.

Complications

• Malreduction in varus, flexion and external rotation
• Non-union and implant failure (especially atypical fractures)
• Delayed union
• Contralateral atypical fracture
• Malrotation