12.54 Supracondylar fractures of the femur

Supracondylar fractures in their true sense are non-articular distal metaphyseal femoral fractures. However, they may extend into the intercondylar (epiphyseal) region of the femur which in turn is usually intra-articular.

Results of treatment of these fractures are dictated by numerous factors, including pre-injury state of the knee, severity of the injury, and associated injuries. The presence of femoral implants such as intramedullary devices or total knee prosthesis also dictates management and outcome of these complex fractures.

The incidence of distal femoral fractures ranges from 4% of all femoral fractures in patients over 16 years, and 31% when hip fractures are excluded. These fractures predominantly occur in two patient groups: 84% mainly in elderly females with osteoporosis, average age 65 years and injury due to moderate-energy trauma; and the remainder mainly in young men due to high-energy trauma.

The detailed anatomy of the distal femur can be found in any standard textbook of anatomy. The transition zone between the distal diaphysis and the femoral condyles makes up the supracondylar area (Figure 12.54.1). At this point the metaphysis flares, especially on the medial side. Anteriorly, the patella articulates with the condyles in the trochlear groove. Between the two condyles posteriorly, there is the intercondyloid notch. On the medial aspect, there is the prominent adductor tubercle at the point of maximum flare of the metaphysis.

The distal femur serves as origin and insertion to several powerful muscles and ligaments. After a fracture these muscles usually cause characteristic deformities (Figure 12.54.1).

The mechanical and anatomical axes of the femur differ. The mechanical axis passes through the head of the femur and the middle of the knee joint, and subtends an angle of 3 degrees from the vertical. The anatomical axis is an average of 9 degrees valgus to the vertical axis. The axis of the knee joint is parallel to the horizontal (Figure 12.54.2). During fixation of these fractures all attempts should be made to restore these relationships. Approximately 10cm above the knee joint, the femoral artery passes into the popliteal fossa as it emerges from the adductor canal in the adductor magnus.

Like any other bone in the body, the distal femur is also affected by osteoporosis which causes thinning of the cortices and expansion of the medullary cavity resulting in decreased bone stock and increased bone fragility. This is believed to contribute significantly to the age-related increase of distal femoral fractures, especially in elderly women, from minor trauma such as falls.

Patients with supracondylar femur fractures who have been involved in high-energy trauma, frequently sustain both remote life-threatening (head, chest, and major vascular) and other local injuries. Soft tissue structures in and around the knee (skin, joint surface, menisci, cruciate, and collateral ligaments) are no exception. The incidence of associated vascular injury is low. The popliteal artery is more often at risk when an associated posterior dislocation of the knee occurs. Other associated fractures include condyles, tibial plateau, patella, ipsilateral femoral shaft and tibial shaft fracture creating a ‘floating knee’. Ipsilateral acetabular, femoral head and neck fractures, and hip dislocation should be actively sought to avoid overlooking these frequently missed associated injuries.

About 5–10% of these fractures are complicated by an open wound.

Most supracondylar fractures occur with the knee flexed. At low energy in the elderly, the patient usually stumbles and falls onto the knee. The high-energy injuries are usually dashboard injuries in motor vehicle collisions where the flexed knee impacts the dashboard. These high-energy injuries are often open and associated with a multiply injured young patient.

Figure 12.54.1 shows characteristic fracture displacement after injury.

Several classification systems have been proposed, however, the AO/OTA classification is the most comprehensive. This classification is useful in determining treatment and prognosis. It is based on the location and pattern of the fracture and considers all fractures within the distal femur (Figure 12.54.3). Type A fractures involve the distal shaft only with varying degrees of comminution. Type B fractures are condylar fractures; type B1 is a sagittal split of the lateral condyle, type B2 is a sagittal split of the medial condyle, and type B3 is a coronal plane fracture. Type C fractures are T-condylar and Y-condylar fractures; type C1 fractures have no comminution, type C2 fractures have a comminuted shaft fracture with two principal articular fragments, and type C3 fractures have intra-articular comminution.

Initial evaluation is performed using ATLS^® guidelines to ensure life-threatening injuries are identified and prioritized. The history of injury is usually either motor vehicle collision in a young person or a fall onto a flexed knee in an elderly person. The knee will be swollen and deformed. Evidence of neurological deficit, vascular injury, compartment syndrome, open fractures, and previous surgery (knee replacement in the elderly) should be identified.

Plain radiographs should include anteroposterior and lateral views of the entire limb, especially in high-energy trauma to rule out more proximal or distal associated fractures or dislocations. These should be repeated after initial reduction and application of traction or splint. The latter radiographs often supply more information about the anatomy of the fracture. Radiographs of the normal or uninvolved opposite femur may be taken for comparison to help in preoperative planning.

CT scans are used when further evaluation is necessary for surgical planning especially when intra-articular extension is noted or suspected. Coronal plane fractures coexist in a significant proportion of patients and if posterior fractures are approached through a medial or lateral parapatellar approach it will lead to extensive incisions and soft tissue stripping.

MRI is used only occasionally to evaluate the knee ligaments prior to definitive surgical intervention.

If vascular injury is suspected, Doppler pulse recording of the popliteal and distal pulses should be documented. In dislocation and gross displacement, consideration should be given to performing arteriography.

Whenever there is a clinical suspicion of compartment syndrome, especially in an obtunded patient, compartment pressure monitoring is indicated.

The femur should have been splinted prior to transportation. On arrival in the emergency department ATLS^® guidelines dictate early prioritization and management of associated injuries. Following treatment of life threatening injuries, urgent limb-threatening injuries (vascular, compartment syndrome) are then managed. Management of open injuries is described in Chapter 12.7. In patients with severe multiple injuries, damage control orthopaedics may be appropriate. This usually entails using external fixators for the initial rapid stabilization of fractures, along with soft tissue care such as decompression of compartment syndrome and wound debridement (Figure 12.54.4). Definitive fracture fixation and complex reconstructive work can then be performed when the patient is physiologically stable.

Undisplaced fractures in elderly, high-risk patients may be treated in a cast brace. Subsequent displacement is an indication for fixation.

The principles of management of these injuries follows that of any long-bone fracture involving the metaphyseal region, namely anatomical reconstruction of the articular surface if involved and accurate realignment in all axes of the metadiaphyseal segment. The introduction of anatomical precontoured locking plates has greatly facilitated this task. The development of submuscular percutaneous plating, indirect reduction techniques, and limited arthrotomies allows the uninjured tissues to remain relatively inviolate (Figure 12.54.5).

Modern techniques require familiarity with all surgical options, see Box 12.54.1.

The priority flow of definitive management of these fractures begins with articular reduction and absolute stability of the joint reduction, and metaphyseal/diaphyseal bridging with either an intramedullary or extramedullary implant (relative stability), taking care to use a soft tissue sparing technique.

Antegrade and retrograde intramedullary nailing are usually preferred for A type fractures (extra-articular) or simple C fractures in the hands of enthusiastic proponents of nailing. Conventional plating using the blade plate, dynamic condylar screw, and condylar buttress plate have been reported extensively. The new millennium has seen several reports of the growing use of internal fixators or locked plates, coupled with minimally invasive techniques of application (Figure 12.54.5).

There is considerable confusion regarding the use of locked plates through open and percutaneous approaches, and the number, sequence, placement, and type of screws used in fixation of these fractures. The influence of permutations of these variables on the type of healing achieved is debated. Clarity is sought on the degree of construct stiffness required to optimize rapid callus formation, and the influence of screw type and position on the stiffness of the construct.

Alignment of the meta/diaphyseal segment remains of paramount importance, and single pass image intensifier screening is relatively inaccurate in judging long-bone alignment. The use of a ‘horizontal plumb line’ such as a diathermy cable or proprietary Perspex sheets with fine radio-opaque wires embedded helps get the ‘big picture’.

Some locked internal fixators have cut-outs to allow screw placement to reconstitute the articular block. The placement of the screws requires meticulous planning. Despite this, certain complex fracture patterns may have bone loss/fracture lines in these locations, preventing optimum entry point use. An easy option is to introduce the lag screws from the medial side, taking care to avoid prominent medial metal.

Reduction is greatly aided by large pointed clamps. Special minimally invasive osteosynthesis instrument sets are commercially available to facilitate reduction and provisional stabilization. The large ball-pointed clamps from the pelvic and acetabular set are very useful in obtaining a hold on the articular block. Manual traction, the use of ankle strap distraction over a bolster, reduction triangles, and the use of completely radiolucent pelvic surgery table are invaluable in any attempt to obtain minimally invasive reduction and fixation.

Management of open fractures is described in Chapter 12.7.

In the acute fracture setting, ligamentous injuries are very difficult to detect clinically. Most are due to fracture propagation with avulsion of the ligaments (collateral and cruciate) from the distal femur, especially in type C fractures. Magnetic resonance imaging (MRI) scans may also be difficult to interpret at this time. With good fracture reduction and fixation along with functional bracing, most of these ligaments heal. The knee is further evaluated at the time of fracture healing when any necessary ligament reconstruction can be undertaken.

Patella fractures are managed in the standard fashion with accurate reduction and stable fixation to assure patellofemoral joint congruity. These are usually addressed at the same time as the fixation of the distal femur fracture. With extensive comminution of the patella, a partial or total patellectomy may have to be undertaken.

An ipsilateral proximal femur fracture is also usually repaired at the same time. Most other associated fractures such as tibial plateau, tibial shaft, and ipsilateral acetabular fractures are usually repaired in a timely manner as patient fitness for surgery allows. In the case of a ‘floating knee’ (distal femur fracture and ipsilateral tibial shaft fracture) some surgeons may elect to fix both fractures under one anaesthesia or delay the tibial fixation depending on the patient’s fitness.

A vascular injury is an emergency, and should therefore for treated well within 6h to avoid an ischaemic limb disaster. After repair of the vessels, a fasciotomy should be carried out to avoid compartment syndrome from reperfusion. Fracture stabilization is necessary to protect the repair.

Repair of nerve injuries if necessary should be undertaken as soon as possible, but is not an emergency.

Loss of articular cartilage is treated according to the patient’s age and feasibility of carrying out a reconstruction. In the young patient, the defect, if large, should be reconstructed when the acute injury has settled.

In the elderly, for a previously symptomatic arthritic knee that has sustained a complex articular fracture, a case can be made for a primary stemmed, stabilized, or partially constrained knee replacement. Multifragmentary metaphyseal fracture patterns (A3) can be spanned or replaced with modular segments.

Extensive comminution of the metaphyseal region requires judgement to obtain accurate alignment in all three axes, as well as regain leg length. This may require screening the opposite leg to match the length.

Periprosthetic supracondylar femur fractures following total knee arthroplasty are an infrequent, but devastating, complication. Because of the poor results of non-operative management, internal fixation of these fractures is recommended. Depending on the fracture pattern and the type of prosthesis, these fractures may be fixed with retrograde intramedullary nailing or open reduction and internal fixation. If the prosthesis is loose then it is recommended to perform a revision using the appropriate implant after careful planning (Figure 12.54.6).

Internal fixation of type A fractures commences with immediate postoperative mobilization of the knee. In A1 fractures, early touch weight bearing progressing to weight bearing to tolerance over 4–6 weeks with the help of walking aids.

A2 and A3 fractures with significant metaphyseal comminution partially weight bear until early signs of callus formation, concentrating on range of movement and quadriceps exercises.

Articular fractures (B and C) are mobilized with immediate range of movement exercises and touch weight bearing for 10–12 weeks.

Tenuous fixation leading to subsequent immobilization is likely to lead to stiffness and non-union, and is best revised early to allow compliance with immediate unrestrained access by the physiotherapist.

Failure to achieve pre-accident levels of form and function in the affected limb is partly determined by the nature of the injury. The iatrogenic component (Box 12.54.2) of this complication relates to infection, malunion, non-union, hardware failure, and stiffness.

All of these are directly related in some degree to imperfections in the treatment algorithm.

This is a common injury in the fragile elderly population, and myocardial infarctions, chest infections, and deep wound infections are the commonest afflictions.

Malunion, non-union, and hardware failure may require reoperation.

The outcome following treatment of supracondylar fractures of the femur is multifactorial (Box 12.54.3).

The authors could find only one randomized controlled trial of operative (dynamic condylar screw) versus non-operative management (Thomas’ splint with a Pearson knee flexion attachment) of displaced fractures of the distal femur. Fewer complications, shorter length of stay, and better outcomes demonstrated the clear advantages of internal fixation.

Antegrade intramedullary nailing for supracondylar and intercondylar fractures is accomplished by either percutaneous or open reduction of the articular surface and fixation with screws followed by nailing. Ninety-four per cent good or excellent results are reported as is a good range of knee movement.

Retrograde nails are also extensively reported in these fractures with favourable results.

In a review of publications between 1989 and 2005 operative treatment results in a 32% reduction in the risk of a poor result. They also concluded that experienced surgeons significantly reduce the risk of revision surgery. They could find no evidence of difference between implants in predisposing these fractures to non-unions, infections, and fixation failures.

Improved implant technology coupled with the general acceptance of soft tissue preservation principles in trauma surgery have made fixation of these difficult fractures in a fragile population less onerous. The economics of today’s health care and the gradual erosion of traditional nursing skills dictate that this trend will continue and fixation of undisplaced supracondylar fractures in elderly osteopenic people will pose a lesser risk than nursing them in bed.