# Intertrochanteric and Subtrochanteric Femur Fractures

## Overview

Intertrochanteric and subtrochanteric fractures are extracapsular hip fractures of the proximal femur. Unlike femoral neck fractures, avascular necrosis is not a major concern because the extracapsular location preserves the blood supply to the femoral head. Treatment is almost always surgical, as nonoperative management carries unacceptable morbidity and mortality. The key surgical decision is selecting the appropriate implant based on fracture stability and pattern.

## Intertrochanteric Fractures

### Anatomy and Biomechanics

The fracture line extends from the greater to the lesser trochanter through the intertrochanteric region, which is primarily cancellous bone with a good blood supply and therefore high union potential. The deforming forces include the iliopsoas pulling the lesser trochanter (causing the proximal fragment to flex), the abductors pulling the greater trochanter, and the shaft adducting. The calcar femorale is a dense cortical strut in the posteromedial femoral neck, and its integrity is a key determinant of fracture stability.

### Classification

#### AO/OTA Classification

In this system, 31A1 denotes a simple pertrochanteric (two-part, stable) fracture, 31A2 a multifragmentary pertrochanteric (comminuted, unstable) fracture, and 31A3 an intertrochanteric or reverse obliquity pattern.

#### Evans/Jensen Classification

This classification divides fractures into stable and unstable patterns based on cortical contact after reduction. Unstable patterns include those with posteromedial comminution, lateral wall incompetence, and reverse obliquity.

#### Key Concept: Lateral Wall Competency

The lateral wall is the lateral cortex of the proximal fragment. An intact lateral wall prevents excessive medialization of the shaft. When the fracture line exits through the lateral cortex at or above the level of the vastus ridge, the lateral wall is considered incompetent. A lateral wall fracture, whether present or at risk, changes the implant choice from a sliding hip screw to a cephalomedullary nail.

### Stable vs. Unstable Patterns

A stable pattern is a simple two-part fracture with an intact posteromedial cortex and intact lateral wall. Unstable patterns include those with posteromedial comminution (loss of calcar buttress), lateral wall fracture or incompetence, subtrochanteric extension, or reverse obliquity.

<image>Intertrochanteric fracture classification showing stable 2-part pattern versus unstable comminuted pattern with lateral wall incompetence</image>

### Treatment

| Fracture Pattern | Recommended Implant | Rationale |
|-----------------|-------------------|-----------|
| Stable 2-part (intact lateral wall, intact posteromedial cortex) | Sliding Hip Screw (SHS/DHS) | Allows controlled collapse; cost-effective; reliable |
| Unstable (posteromedial comminution) | Cephalomedullary Nail (short) | Shorter lever arm; load-sharing; protects lateral wall |
| Lateral wall fracture/incompetence | Cephalomedullary Nail (short) | SHS contraindicated; prevents medialization |
| Reverse obliquity | Cephalomedullary Nail (long) | SHS contraindicated (cannot resist medialization) |
| Subtrochanteric extension | Cephalomedullary Nail (long) | Must span entire fracture zone |

#### Sliding Hip Screw (SHS/DHS)

The sliding hip screw is the gold standard for stable intertrochanteric fractures. It works through a lag screw in the femoral head with a side plate, allowing controlled sliding and collapse at the fracture site to achieve compression. It is cost-effective, reliable, and allows controlled collapse to reach stability. The tip-apex distance (TAD) should be kept below 25 mm, measured as the sum of distances from the screw tip to the apex of the femoral head on AP and lateral views. The lag screw should sit in a center-center or center-inferior position on both views, and a four-hole side plate is used for most fractures. The sliding hip screw is contraindicated for unstable patterns, lateral wall fractures, reverse obliquity, and subtrochanteric extension.

#### Cephalomedullary Nail (CMN)

Cephalomedullary nails are preferred for unstable intertrochanteric fractures. Examples include the Gamma nail, PFNA, TFN, and InterTAN. These devices offer a shorter lever arm because they are intramedullary, provide load-sharing rather than load-bearing fixation, protect the lateral wall, and can accommodate subtrochanteric extension. A short nail is adequate for most intertrochanteric fractures without subtrochanteric extension, while a long nail is indicated for subtrochanteric extension, pathologic bone, ipsilateral shaft fracture, or reverse obliquity. Lag screw options include a single screw with an antirotation pin or blade, a dual integrated screw (InterTAN) that resists rotation and the Z-effect, and a helical blade (PFNA) that compacts bone and may achieve better purchase in osteoporotic bone.

#### Tip-Apex Distance (TAD)

The TAD is the critical predictor of lag screw cutout. When the TAD is below 25 mm, the cutout rate is less than 2%, but it increases significantly above that threshold. The calcar-referenced TAD (CalTAD) is a newer measurement that may better predict cutout.

### Reduction Techniques

Closed reduction is performed on the fracture table under fluoroscopy using traction, internal rotation, and slight abduction. An acceptable reduction restores the neck-shaft angle, achieves cortical contact on both AP and lateral views, and corrects rotation. Clamp-assisted and percutaneous reduction tools are used for difficult reductions. Achieving "positive medial cortical support," where the medial cortex of the shaft sits just inside the femoral neck in slight valgus, improves stability.

<image>Sliding hip screw (SHS) construct for stable intertrochanteric fracture and cephalomedullary nail for unstable pattern</image>

## Subtrochanteric Fractures

### Definition

Subtrochanteric fractures occur within 5 cm below the lesser trochanter, a zone of high mechanical stress that experiences significant bending and torsional forces. These fractures are more challenging to reduce and fix than intertrochanteric fractures.

### Deforming Forces

The proximal fragment is flexed by the iliopsoas, abducted by the gluteus medius and minimus, and externally rotated by the short external rotators. The distal fragment is adducted by the adductors and shortened by the quadriceps and hamstrings. Understanding these deformities is essential for achieving reduction.

### Classification

The Russell-Taylor classification, based on piriformis fossa and lesser trochanter involvement, is less commonly used today. A descriptive classification is preferred, characterizing the fracture by length, comminution, and proximal extension into the intertrochanteric region.

### Treatment

#### Cephalomedullary Nail (Long)

A long cephalomedullary nail spanning the entire femur to the level of the metaphyseal flare distally is the standard treatment for subtrochanteric fractures. Trochanteric entry nails are preferred by most surgeons because the entry point is easier and avoids the risk of AVN associated with piriformis entry. The hip should be started in flexion, adduction, and internal rotation to correct the proximal fragment deformity. The "kickstand" technique, placing a bump under the ipsilateral buttock, can help. Reduction aids include a Schanz pin in the proximal fragment as a joystick, percutaneous clamps, and blocking (Poller) screws. Eccentric reaming into the lateral cortex must be avoided as it weakens the construct. Cerclage wires are used for fracture reduction; although there is concern about devascularization, they are commonly used without apparent healing problems.

#### Plate Fixation

Plate fixation is rarely first-line for subtrochanteric fractures because it is less biomechanically favorable. Indications include failed nailing, a narrow medullary canal, and significant proximal deformity preventing nail passage. The 95-degree angled blade plate was historically the gold standard before modern nails. Proximal femoral locking plates and MIPO technique are alternatives but technically demanding.

### Complications

Nonunion occurs in 5 to 15% of cases, higher than intertrochanteric fractures due to the high mechanical stress in this region. Malunion in varus, flexion, and external rotation results from inadequate control of the proximal fragment. Hardware failure, including screw cutout and nail breakage at the fracture site, can occur from stress concentration.

## Atypical Femoral Fractures

### Association with Bisphosphonates

Prolonged bisphosphonate use (more than 3 to 5 years) is associated with atypical subtrochanteric and diaphyseal fractures, and similar fractures have been reported with denosumab. The mechanism involves oversuppression of bone remodeling, which leads to accumulation of microdamage and reduced bone toughness.

### ASBMR Criteria (Major Features -- All Must Be Present)

The fracture must be located along the femoral diaphysis from just distal to the lesser trochanter to just proximal to the supracondylar flare. It must result from minimal or no trauma, show a transverse or short oblique pattern, and be non-comminuted or minimally comminuted. Complete fractures extend through both cortices and may have a medial spike, while incomplete fractures involve only the lateral cortex. Minor features include localized periosteal reaction on the lateral cortex, generalized increase in cortical thickness, bilateral prodromal symptoms, bilateral fractures, and delayed healing.

### Clinical Features

Patients often report prodromal thigh or groin pain from a stress reaction for weeks to months before the fracture. Radiographs may show lateral cortical beaking. Bilateral involvement occurs in up to 28% of cases, so the contralateral femur should always be imaged.

### Management

Complete fractures are treated with cephalomedullary nailing using a long nail, the same as for standard subtrochanteric fractures, although healing may be delayed. Incomplete fractures with lateral cortex stress reaction are managed initially with protected weight-bearing and teriparatide (anabolic therapy). Prophylactic nailing is considered if pain persists or the fracture line progresses despite conservative measures. The bisphosphonate should be discontinued (drug holiday), and teriparatide should be started to promote bone remodeling and healing.

### Bisphosphonate Drug Holiday

A drug holiday is considered after 3 to 5 years of bisphosphonate therapy, depending on fracture risk assessment. The residual effect of alendronate persists for 2 to 3 years after discontinuation, while zoledronic acid maintains its effect for up to 5 years. Therapy is resumed if fracture risk increases based on DEXA monitoring. The balance to consider is that the risk of atypical fracture is very low in absolute terms, while the risk of osteoporotic fracture is much higher.

<image>Atypical femoral fracture showing characteristic transverse fracture pattern with lateral cortical beaking and periosteal thickening</image>

## Clinical Pearls

For intertrochanteric fractures, the lateral wall must be assessed before choosing an implant; if it is compromised, a cephalomedullary nail should be used instead of a sliding hip screw. A TAD below 25 mm is non-negotiable, as most screw cutouts are preventable with proper screw positioning. In subtrochanteric fractures, the proximal fragment deformity of flexion, abduction, and external rotation should be anticipated, and the patient positioned accordingly before attempting reduction. Blocking (Poller) screws are invaluable in subtrochanteric nailing, as they redirect the nail path and improve reduction. Always ask about bisphosphonate use in any low-energy femoral shaft or subtrochanteric fracture, because atypical fractures require a different management approach and the contralateral femur must be evaluated. Early weight-bearing as tolerated after intertrochanteric fracture fixation is safe and recommended, as prolonged non-weight-bearing increases deconditioning and complication rates in the elderly. Cement augmentation of lag screws through cannulated screws is an emerging technique for severely osteoporotic bone and may reduce cutout.

## References
- Baumgaertner MR, et al. The value of the tip-apex distance in predicting failure of fixation of peritrochanteric fractures of the hip. *JBJS Am*. 1995;77(7):1058-1064.
- Haidukewych GJ. Intertrochanteric fractures: ten tips to improve results. *JBJS Am*. 2009;91(3):712-719.
- Shane E, et al. Atypical subtrochanteric and diaphyseal femoral fractures: second report of a task force of the ASBMR. *J Bone Miner Res*. 2014;29(1):1-23.
- Palm H, et al. Completeness of the Arbeitsgemeinschaft fur Osteosynthesefragen/Orthopaedic Trauma Association fracture classification for intertrochanteric fractures. *JBJS Am*. 2012.
- Hak DJ, et al. Subtrochanteric femur fractures. *JAAOS*. 2010;18(3):170-180.