Occur in a zone extending from the lesser trochanter to 5cm distal to the lesser trochanter.
Extension into the intertrochanteric region is common with therse fractures.
More difficult to treat than intertrochanteric fractures due to the powerful muscle forces acting on the fragments as well as the stress in this region.
In young patients they are due to high-energy trauma or pathologic fracture.
10% of high-energy fractures are due to gun shot wounds.
In the elderly, they are often low energy injuries involving osteoporotic bone.
Pathologic fractures account for 17-35% of all subtrochanteric fractures.
Fractures at this site may be a result of screw placement for a previous femoral neck fracture, if the inferior screw is placed too low.
These fractures occur at the cortico-cancellous junction.
The high composition of cortical bone and the decreased vascularity impairs the capacity for healing of these fractures compared to the abundant cancellous bone of the intertrochanteric region of the hip.
The proximal fragment is usually flexed and externally rotated by the pull of the iliopsoas and short external rotators, and abducted by the pull of the gluteus medius and minimus.
The distal fragment is adducted and shortened by the pull of the adductors leading to a varus and procurvatum fracture alignment.
Patients typically present with pain unable to ambulate with deformity of the proximal thigh.
A relationship between long-term Alendronate use and subtrochanteric fractures has been established.
An AP pelvis, internal rotation AP and cross-table lateral of the affected hip should be obtained.
Patients with low-energy fractures who have been on long-term bisphosphonate therapy should have contralateral femur imaging to rule out impending fractures.
The limb should be stabilized with skeletal traction, initially.
Nonoperative treatment should only be employed in those whom surgery is deemed very high risk.
Surgical stabilization is the standard of care.
Intramedullary nail fixation is the pref2242ed treatment.
Most patients should not fully bear weight for the first 6-8 weeks.
Incidence of nonunion occurs in 0-8% of cases.