Subtrochanteric Fractures

The zone. The subtrochanteric region runs from the lesser trochanter to 5cm distally, or to the isthmus. It is the zone of highest mechanical stress in the entire femur: the transition from cancellous to cortical bone, where the bending moment is at its maximum.

View larger

Who. The age distribution is bimodal. Young adults break it in high-energy trauma, with a male predominance; the elderly break it in low-energy falls, through pathological bone or as an atypical fracture, with a female predominance. Subtrochanteric fractures are 10-15% of proximal femoral fractures, and atypical fractures are increasing in incidence (bisphosphonate awareness). Knowing who breaks it, and how, guides suspicion of the underlying cause.

Mechanism. The mechanism helps distinguish the standard traumatic fracture from the atypical one:

• High-energy (young): motor vehicle accidents, motorcycle crashes, falls from height and sporting injuries; associated polytrauma is common
• Low-energy (elderly): a fall from standing height, minimal trauma or a spontaneous fracture, a fracture through a metastasis, or an atypical bisphosphonate-associated fracture
• Atypical: associated with over 5 years of bisphosphonate use, preceded by prodromal thigh pain for weeks to months, and may occur with minimal or no trauma

Risk factors. They guide investigation and treatment planning:

• Standard fractures: high-energy trauma, osteoporosis, metastatic bone disease, primary bone tumours, metabolic bone disease
• Atypical fractures: bisphosphonate use over 5 years, glucocorticoids, proton pump inhibitors, diabetes mellitus, rheumatoid arthritis, and Asian ethnicity (slightly higher risk)

The deforming muscles. Once the fracture has disrupted the lever arm, the proximal fragment is controlled by the gluteal abductors and iliopsoas, and each muscle group pulls a fragment its own way:

• Iliopsoas, on the lesser trochanter, flexes the proximal fragment 30-60 degrees
• The short external rotators, intertrochanteric, externally rotate it
• Gluteus medius and minimus, on the greater trochanter, abduct it
• The adductors, on the linea aspera, adduct the distal fragment

FEAR. The proximal fragment ends up Flexed, Externally rotated and Abducted, and the R is the reduction: match the leg to the proximal fragment by flexing the hip, abducting it and externally rotating slightly.

View larger

The blood supply. The periosteal supply comes from perforating branches of the profunda femoris and feeds the outer third of the cortex; it is preserved with minimal soft-tissue stripping. The endosteal supply is the nutrient artery, also from the profunda femoris, which enters the posterior cortex and feeds the inner two-thirds. Reaming disrupts it.

Why it matters. Surgery here balances biology against mechanics. Avoid excessive periosteal stripping, and accept that reaming, although it disrupts the endosteal supply, promotes a healing response.

The mechanics. The medial cortex is loaded in compression and the lateral cortex in tension, so any implant must resist high bending forces. An intramedullary nail does this better than a plate: it is load-sharing, sits on a shorter lever arm to the fracture, resists the bending moment effectively and allows early weight-bearing. A plate is load-bearing and has a higher failure rate, and a short nail creates a stress riser distally. Biomechanics is why the cephalomedullary nail is superior to plating in this region.

Russell-Taylor decides the nail entry point, Seinsheimer describes the complexity and stability of the pattern, and the ASBMR criteria identify the atypical fracture that needs modified management.

View larger

History. The history sorts the fracture into traumatic, atypical or pathological, and that decides the workup. After a high-energy injury, associated injuries are common. The questions that matter in the others:

• Atypical: minimal trauma (a fall from standing) or a spontaneous fracture, prodromal thigh pain, glucocorticoid use, and the bisphosphonate history, asking the duration specifically
• Pathological: known malignancy, weight loss, night sweats, previous radiation, and a history of metabolic bone disease

Examination. The limb is shortened and externally rotated, the thigh swollen from significant blood loss, and the patient unable to weight bear; ecchymosis may be delayed. The position of the proximal fragment is difficult to assess clinically, but note any rotational or angular deformity and whether the fracture is open or closed.

Neurovascular status. Record the dorsalis pedis and posterior tibial pulses, sciatic nerve function, and motor and sensory function in the foot, and assess the thigh compartments.

Trauma survey. A high-energy injury gets an ATLS assessment, with a search for ipsilateral injuries (the floating knee), spine clearance, and the chest and abdomen in polytrauma.

Flags that change the treatment. Contralateral thigh pain means checking the other femur. On the radiograph, a transverse pattern with lateral beaking flags an atypical fracture and a lytic lesion flags a pathological one, where biopsy before definitive fixation should be considered.

Radiographs. Three sets of films:

• Full-length femur, AP and lateral, which must show the hip and the knee
• AP pelvis, for comparison and the proximal extent
• Contralateral femur, if an atypical fracture is suspected

Read them for the pattern and comminution, the proximal and distal extent, piriformis fossa involvement (Russell-Taylor), the canal diameter for nail sizing, and atypical features such as lateral beaking.

CT and MRI. CT is for complex patterns, planning in difficult cases, assessing proximal extension and evaluating a pathological fracture. MRI or a bone scan evaluates a stress fracture or an incomplete contralateral fracture, and characterises a pathological lesion if metastatic disease is suspected. The choice follows the clinical suspicion and the needs of surgical planning.

Recognising the atypical fracture. The pattern is transverse or short oblique, starting at the lateral cortex, with beaking or thickening of the lateral cortex, generalised cortical thickening, and little comminution despite the mechanism. The change is often visible on radiographs before the fracture completes.

View larger

View larger

View larger

The atypical workup. A radiograph of the contralateral femur is mandatory (bilateral in 28%), with MRI if an incomplete fracture is suspected. The metabolic screen is vitamin D, calcium, PTH, phosphate and bone turnover markers (P1NP, CTX). Endocrinology is involved for bone-health optimisation, alternative osteoporosis treatment and monitoring during healing.

Preoperative planning. Measure the canal diameter at the isthmus for the nail diameter, the femoral length for the nail length, and the neck-shaft angle, and assess the entry point. Review Russell-Taylor for the entry point and Seinsheimer for pattern complexity, then plan the reduction strategy from the pattern. The equipment:

• Long cephalomedullary nail
• Reduction aids: clamps, K-wires, cerclage
• Blocking screw set
• Fracture table or radiolucent table
• Fluoroscopy (C-arm)

Algorithm

View larger

Goals. Anatomical alignment in length, rotation and axis; stable fixation that allows early mobilisation; biology preserved where possible; and the underlying cause addressed if the fracture is pathological or atypical.

The implant. The cephalomedullary nail is the gold standard, for the mechanical reasons above. A long nail is preferred because it protects the entire femur and prevents a distal stress riser; a short nail is only for the truly isolated subtrochanteric fracture, which is rare. The diameter is chosen for the canal.

The entry point. Piriformis entry is for Russell-Taylor type I only. Trochanteric entry is required for type II and suitable for any type, most modern nails are designed for it, and the entry point is specific to the nail.

Plates. A plate is not first-line. The blade plate or proximal femoral locking plate is reserved for salvage and revision. Plates had higher failure rates historically, and as load-bearing devices they bring more complications. Pooled, the evidence favours the nail, the Kuzyk systematic review finding that intramedullary implants reduce operative time and fixation failure (Evidence Base).

The atypical fracture before and at surgery. Stop the bisphosphonate immediately, image the contralateral femur, optimise vitamin D and calcium, and refer to endocrinology. At operation, open reduction is often required, proximal and distal fixation must both be secure, and bone graft is considered: local, from the iliac crest or with the reamer-irrigator-aspirator (RIA).

After surgery. Expect delayed healing compared with standard subtrochanteric fractures: counsel the patient, protect weight-bearing for longer and extend follow-up for union. Endocrinology stays involved for long-term bone health, with vitamin D and calcium supplementation. Consider teriparatide (a PTH analogue) postoperatively; the evidence that it advances healing is observational and inconsistent (Evidence Base).

The other femur. If it shows a stress fracture, nail it prophylactically before it completes. If there is only a prodrome, protect weight-bearing and monitor closely with serial imaging.

Intraoperative. Malreduction is the most common complication and the most preventable: varus, procurvatum or rotational malreduction, prevented by reducing before reaming. Iatrogenic fracture occurs at the entry point or distally during nail insertion; adequate reaming and the correct entry point prevent it, and it may need additional fixation. Hardware malposition means a malpositioned lag screw, a short nail creating a stress riser, or inadequate distal locking.

Nonunion. Historically 10-20%, improved with modern cephalomedullary nails. The risk factors are comminution, infection, varus and an atypical fracture, and the treatment is exchange nailing with bone graft.

Malunion. Varus is the most common, deviating the mechanical axis, and may require corrective osteotomy.

Implant failure. The nail breaks at the fracture site, or the lag screw cuts out, less commonly than in intertrochanteric fractures. It is usually related to nonunion.

Infection. Under 1% for closed fractures and higher for open ones. Treatment is debridement, antibiotics and possible implant exchange.

View larger

View larger

Late. These affect long-term quality of life and may require intervention:

• Chronic pain: thigh pain from the nail, which may require nail removal after union, and heterotopic ossification around the entry point
• Limb length discrepancy: from malreduction or bone loss; a shoe lift if under 2cm, lengthening if severe
• Refracture: after implant removal, through the stress riser at the screw holes
• Functional limitation: hip stiffness, knee stiffness (with an associated injury), and abductor weakness from the approach

The first two weeks. Check the wounds at 48 hours and remove drains at 24-48 hours once the output is below 50mL. Physiotherapy starts on day 1; early mobilisation reduces complications and improves outcomes in elderly patients. Analgesia is multimodal, opioids are weaned as tolerated, and regional blocks are considered for enhanced recovery.

Thromboprophylaxis. This is a high-risk injury. Chemical prophylaxis runs for a minimum of 4-6 weeks, LMWH preferred (enoxaparin 40mg daily), with mechanical prophylaxis (TED stockings and intermittent pneumatic compression) and early mobilisation.

Weight-bearing. It depends on the fracture pattern and the stability of fixation. Most cephalomedullary fixation allows touch weight-bearing or weight-bearing as tolerated, and a simple pattern with good fixation can bear weight as tolerated. Comminuted or complex patterns are toe-touch, and comminuted or unstable ones may require protected weight-bearing for 6-8 weeks; progress follows healing.

Follow-up. The reviews and what each is for:

• 2 weeks: wound check, suture removal and radiograph
• 6 weeks: clinical and radiological review; progress weight-bearing
• 12 weeks: radiograph and assessment of union and progression to full weight-bearing
• 6 months: confirm union

The 6- and 12-week radiographs look for callus formation and implant position, and for signs of varus collapse or implant failure.

Rehabilitation. Progressive strengthening, range of motion at the hip and knee, gait training as weight-bearing progresses, and hydrotherapy once the wound has healed.

Warning signs. Watch for:

• Increasing pain, suggesting nonunion or hardware failure
• Wound complications
• Progressive shortening (varus collapse)
• New-onset thigh pain (implant irritation or failure)

Union and return to activity. Union is clinical (full weight-bearing without pain) and radiological (bridging callus on 3 cortices), and takes 4-6 months on average. Light activities resume at 3 months and full unrestricted activity once united, although high-impact activities may be limited long-term. Driving is typically permitted at 6-8 weeks if right-sided and automatic.

The long term. Review annually until implant removal is considered, assessing leg length and watching for late complications. Removal is not routinely recommended; consider it for symptoms such as thigh pain or prominent hardware, delay it a minimum of 18-24 months after union, and warn of refracture through the screw holes.

Prognostic factors. A simple fracture pattern, an adequate reduction, a long cephalomedullary nail, a young and healthy patient and good bone quality are favourable. Comminution, varus malreduction, an atypical fracture (delayed healing), an open fracture and osteoporosis are unfavourable.

Global Epidemiology

Subtrochanteric fractures account for approximately 10-15% of proximal femoral fractures, with a bimodal distribution: high-energy injuries in young men and low-energy, osteoporotic or atypical fractures in older women. Atypical femoral fractures are strongly associated with antiresorptive therapy but remain rare in absolute terms.

These figures derive from the Swedish nationwide cohort of Schilcher and colleagues (DOI) and the second ASBMR Task Force report (DOI).

Guideline & Society Positions

Registry & Practice Variation

National hip-fracture registries and arthroplasty/trauma registries (including the AOANJRR in Australia, the National Hip Fracture Database in the UK, and equivalent Scandinavian registries that generated the atypical-fracture risk estimates above) consistently show cephalomedullary nailing as the dominant fixation method for subtrochanteric and reverse-oblique patterns. Practice variation persists in entry point (trochanteric versus piriformis), routine use of cerclage/open reduction adjuncts, and weight-bearing protocols.