SUBTROCHANTERIC

FRACTURES

EPIDEMIOLOGY

Subtrochanteric fractures account for approximately 10% to 30% of all hip fractures, and they can affect persons of all ages.

There is a greater incidence of bimodal distribution in individuals 20 to 40 years of age and in persons older than 60 years of age.

ANATOMY

A subtrochanteric femur fracture is a fracture between the lesser trochanter and a point 5 cm distal to the lesser trochanter.

The subtrochanteric segment of the femur is subject to high biomechanical stresses. The medial and posteromedial cortices are the sites of high compressive forces, whereas the lateral cortex experiences high tensile forces (Fig. 31.1).

The subtrochanteric area of the femur is composed mainly of cortical bone. Therefore, there is less vascularity in this region and the potential for healing is diminished as compared with intertrochanteric fractures.

The deforming muscle forces on the proximal fragment include abduction by the gluteus, external rotation by the short rotators, and flexion by the psoas. The distal fragment is pulled proximally and into varus by the adductors (Fig. 31.2).

Mechanism of Injury

Low-energy mechanisms: Elderly individuals sustain a minor fall in which the fracture occurs through osteoporotic bone.

High-energy mechanisms: Younger adults with normal bone sustain injuries related to motor vehicle accidents, gunshot wounds, or falls from a height.

• Ten percent of higher energy subtrochanteric fractures result from gunshot injuries.

Pathologic fracture: The subtrochanteric region is also a frequent site for pathologic fractures, accounting for 17% to 35% of all subtrochanteric fractures.

CLINICAL EVALUATION

Patients involved in high-energy trauma should receive full trauma evaluation.

Patients typically are unable to walk and have varying degrees of gross deformity of the lower extremity.

Hip motion is painful, with tenderness to palpation and swelling of the proximal thigh.

Because substantial forces are required to produce this fracture pattern in younger patients, associated injuries should be expected and carefully evaluated.

Field dressings or splints should be completely removed, with the injury site examined for evidence of soft tissue compromise or open injury.

A significant volume of blood from hemorrhage can be lost into the thigh. In turn, the patient should be monitored for hypovolemic shock, with invasive monitoring as necessary.

Provisional field splinting should be converted to a traction pin until definitive fixation to limit further soft tissue damage and hemorrhage.

A careful neurovascular examination is important to rule out associated injuries, although neurovascular compromise related to the subtrochanteric fracture is uncommon.

RADIOGRAPHIC EVALUATION

An anteroposterior (AP) view of the pelvis and AP and lateral views of the hip and femur should be obtained.

One should assess the entire femur, including the knee.

Associated injuries should be evaluated and, if suspected, appropriate radiographic studies ordered.

A contralateral femoral radiograph is helpful to determine femoral length in highly comminuted fractures.

CLASSIFICATION

Russe l-Taylor (Commonly Used)

This was created in response to the development of first-generation and second-generation (cephalomedullary) interlocked nails as a guide to implant choice (may be obsolete now).

Type I: Fractures with an intact piriformis fossa:

A: The lesser trochanter is attached to the proximal fragment (Fig. 31.3).

B: The lesser trochanter is detached from the proximal fragment.

Type II: Fractures that extend into the piriformis fossa:

A: Have a stable medial construct (posteromedial cortex)

B: Have comminution of the piriformis fossa and lesser trochanter, associated with varying degrees of femoral shaft comminution

Orthopaedic Trauma Association Classification of Subtrochanteric Fractures See Fracture and Dislocation Classification Compendium at http://www.ota.org/compendium/compendium.html.

TREATMENT

Nonoperative (Historical)

This involves skeletal traction in the 90/90-degree position followed by spica casting or cast bracing.

This is reserved only for those elderly individuals who are not operative candidates and for children.

Nonoperative treatment generally results in increased morbidity and mortality in adults, as well as in nonunion, delayed union, and malunion with varus angulation, rotational deformity, and shortening.

Operative

Operative treatment is indicated in most subtrochanteric fractures.

Implants

Interlocking Nail

First-generation (centromedullary) nails are indicated for subtrochanteric fractures with both trochanters intact.

Second-generation cephalomedullary (i.e., reconstruction) nails are indicated for all fractures, especially those with loss of the posteromedial cortex; may be trochanteric or piriformis starting types.

Second-generation nails can also be used for fractures extending into the piriformis fossae; trochanteric types are recommended.

With use of an intramedullary (IM) nail, one must monitor for the nail exiting posteriorly out of the proximal fragment. One must also monitor for the common malalignment of varus and flexion of the proximal fragment. Distally, anterior perforation can occur due to mismatch in radius of curvature between the nail and femur.

Ninety-Five Degree Fixed Angle Device

The 95-degree fixed angle plates are best suited for fractures involving both trochanters; an accessory screw can be inserted beneath the fixed angle blade or screw into the calcar to increase proximal fixation (Fig. 31.4).

These devices function as a tension band when the posteromedial cortex is restored.

A dynamic condylar screw is technically easier to insert than a blade plate.

Proximal femur precontoured locking plates are a newer alternative to traditional fixed angle plates and screws.

One must take care not to devitalize the fracture fragments during fracture reduction and fixation.

Sliding Hip Screw

This implant is a poor choice for subtrochanteric fractures and should not be used.

Bone Grafting

Indirect reduction techniques have decreased the need for bone grafting because fracture fragments are not devascularized to the same extent as in open reduction.

If needed, the bone graft should be inserted through the fracture site, usually before plate application.

Open Subtrochanteric Fractures

These are rare, almost always associated with either penetrating injury or high-energy trauma from a motor vehicle accident or a fall from a height.

Treatment consists of immediate surgical debridement and osseous stabilization.

COMPLICATIONS

Loss of Fixation

With plate and screw devices, implant failure usually occurs secondary to screw cutout from the femoral head and neck in patients with osteopenic bone or plate breakage.

With interlocked nails, loss of fixation is commonly related to failure to lock the device statically, comminution of the entry portal, or use of smaller diameter nails. Cephalomedullary nails tend to

fail when healing does not occur. The nail tends to fail by fatiguing through the lag screw hole in the nail (Fig. 31.5).

Fixation failure involves removal of hardware, revision internal fixation with either plate and screws or an interlocked nail, and bone grafting.

Nonunion

This may be evident by a patient’s inability to resume full weight bearing within 4 to 6 months.

This may be associated with inadequate fracture reduction in varus.

Nonunion usually is accompanied by deformity of the fracture.

Nonunions that develop following IM nailing can be treated by implant removal followed by repeat reaming and placement of a larger diameter IM nail.

Correction of varus or flexion deformity is critical to success of nonunion surgery for subtrochanteric fracture nonunions.

Malunion

The patient may complain of a limp, leg length discrepancy, or rotational deformity.

Coxa varus is mainly the result of the uncorrected abduction deformity of the proximal segment caused by the hip abductors.

A valgus osteotomy and revision internal fixation with bone grafting are the usual treatment for a varus malreduction.

Leg length discrepancy is a complex problem that is more likely to occur following a fracture with extensive femoral shaft comminution stabilized with a dynamically locked, rather than a statically locked, nail.

Malrotation may occur with use of plate and screws or an IM nail if the surgeon is not alert to this potential complication.