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Case History
35 year old healthy male involved in a motor vehicle accident sustaining severe open clean Grade III B left distal femur fracture. The fracture involves articular surface in a T-shaped pattern with metaphyseal comminution (Figure 1) and (Figure 2). Associated injuries include an ipsilateral open Grade II both bone forearm fracture. There were no other significant injuries.
Treatment Options
Treatment options included: 1) transarticular external fixation for a period of 7 - 10 days to allow soft tissue healing followed by delayed definitive internal fixation, 2) alternative plate fixation using a fixed 95 degree angled blade plate, condylar buttress plate, or a dynamic condylar screw (DCS), 3) a retrograde locked intramedullary nail, or 4) small wire fixator such as Hybrid or Ilizarov configuration.
Operative Stabilization
Initial management of this patient involved resuscitation of general status, reduction and splinting of extremities, initiation of intravenous antibiotics and preparation for operative intervention. Patient received a left lower extremity angiogram to rule out arterial injury after evaluation of initial radiographs reveal significant displacement and fracture of supracondylar femur. An intraoperative reduction is achieved and a DCS condylar screw is placed for stabilization (Figure 3) and (Figure 4). The reduction is short, in valgus and clinically internally rotated. The distal femur is medially displaced and mechanical axis of extremity now lies lateral to the center of the knee. The condylar screw position is in varus to the knee axis resulting in a valgus deformity when engaged with the fixed angle side 90 degree side plate. Patient was started on physical therapy and makes progress however fracture site remains painful. Surgeon feels that hardware could be source of pain and hardware is removed (Figure 5) and (Figure 6). The patient continues to have pain, feels his knee is unstable, is unable to ambulate on extremity and it remains short, internal rotation and in valgus and has only 30 degrees of knee flexion. Note that patella articulating with distal end of proximal fragment on lateral radiograph (Figure 6). Intraoperative reduction is achieved by take down of the nonunion, freeing of the scar tissue and removal of the DCS implant. Realignment of the condylar fragment to the correct anatomic position is accomplished by lengthening the nonunion and stabilization with an interfragmentary lag screw. Temporary stability is achieved with AO Weber clamps (Figure 7). Final fixation, correction of deformities and eventually healing is achieved by using an AO condylar buttress plate (Figure 8) and (Figure 9).
Salvage Principles
Salvage principles involve realignment of the extremity by take down of the nonunion site, reduction in the amount of valgus deformity, lateralization of the distal femur with respect to the proximal shaft, lengthening of the nonunion and stable definitive fixation of the nonunion. Restoration of length and the patello-femoral articulation is critical to improve knee function. With the placement of a DCS in either the proximal or distal femur, the surgeon creates a hole in the metaphyseal fragment that makes secondary reconstructive surgery more difficult. Realignment of the nonunion site in this patient requires initial correction of posterior displacement of the condylar fragment (Figure 7) by the use of AO clamps. Lateralization and reduction of valgus are controlled by the choice of implant used to stabilize the femur. There are several implants that can be used to solve this problem. The classic 95 degree fixed angle blade plate is an excellent implant in this situation but requires reasonable bone stock and may require grafting of the DCS hole to achieve plate stability in the condylar fragment. It is contra-indicated with osteoporosis. Alternative implants include the condylar buttress plate and retrograde femoral nail. The choice of implant does not include using another DCS screw with a longer side plate. This is a common mistake made by surgeons who fail to recognize the etiology of the fixation failure. The original DCS screw placement in this patient is incorrect and resulted in the medial displacement, internal rotation and valgus position of the reduction (Figure 2) and (Figure 3). Using another DCS with a longer plate requires using the condylar screw preventing correction of the deformity. The best choice in this clinical situation is the condylar buttress plate or the fixed angled 95 degree blade plate. The condylar buttress plate by correct contouring achieved a correction in the medial displacement, internal rotation, posterior displacement and reduction in the valgus malalignment. It provides excellent fixation through the use of multiple screws in the condylar fragment and easily overcomes the bone stock deficiency created by the drilling of the DCS condylar screw hole. The condylar screw hole can be filled with bone bank allograft in an attempt to restore distal femur bone stock. The condylar buttress plate is an excellent device but requires restoration of length to achieve a correct reduction. If the extremity is left short, the condylar buttress will result in an excessive valgus reduction of the distal femur.
Summary
The DCS is a common implant used in treating distal and proximal metaphyseal fractures of the femur. It has several potential complications if inserted incorrectly. Common malalignment problems associated with the DCS include shortening, medial displacement, internal rotation and valgus angular deformity. The valgus deformity occurs from inaccurate placement of the drill guide summation wire. Once the condylar fragments are drilled with the DCS step reamer the resultant reduction deformity cannot be corrected. Internal rotation of the extremity is also a common deformity with the DCS and may result from lack of attention to guide wire placement by the surgeon.. The surgeon must correctly place the summation guide wire to offset these deformities. Another common complication of using plate devices in general is lack of restoration of extremity length and correct achievement of the lower extremity mechanical axis. The use of indirect reduction techniques incorporating distraction of the fracture site in addition to mastering the skills of condylar fracture reduction techniques is critical in preventing shortening and angular deformity of these fractures.