OTA 1997 Posters - Tibia Fractures

The Anterior-T Frame External Fixator: A Treatment Option for High Energy Proximal Tibia Fractures

George K. Bal, MD, Jens R. Chapman, MD, M. Bradford Henley, MD, Stephen Benirschke, MD, B. Claudi, MD

Tacoma, Washington, USA

Purpose: Treatment of high energy proximal tibia fractures poses difficulties due to extensive soft tissue damage, displacement of articular fragments, and fracture comminution. Recent reports have shown promising results with hybrid external fixation combined with limited internal fixation. The purpose of this study is to evaluate a simple, inexpensive technique for stabilizing high energy proximal tibia fractures using percutaneous methods.

Methods: All proximal tibia fractures treated at Harborview Medical Center from July, 1992 to January, 1996 were reviewed. There were 38 fractures in 36 patients treated with an anterior T-frame external fixator. The operative technique involved indirect, or minimal open, reduction. If necessary, joint reduction was maintained with percutaneous, cannulated interfragmentary screws. The external fixator was assembled with standard 5.0 mm half pins and conventional external fixator components (Synthes, USA, Paoli, PA 19301). A single half pin was placed anterior to posterior into both medial and lateral plateau fragments, and a transverse bar used to connect them. Two 5.0 mm half pins were then inserted into the tibial diaphysis, and a vertical bar, with proximal extension, placed over the two pins. The proximal fragment is then reduced on the shaft, and a 5.0 mm half pin placed from anterior-inferior to posterior-superior. This pin is connected to the vertical bar. The vertical and transverse bars are then connected together, stabilizing the fracture in a reduced position. Postoperative care consisted of standard pin site care, active knee motion as soon as soft tissue injuries allowed, and progressive weight bearing based on radiographic signs of healing.

Results: We identified 36 patients with 38 fractures treated with an anterior T-frame external fixator. Three patients died during the initial hospitalization, one patient required an amputation for a Type IIIC injury which failed revascularization. This left 32 patients with 34 fractures. There were 25 bicondylar split fractures with meta-diaphyseal extension (Schatzker Type VI), and 9 complex proximal tibia fractures. Twenty-one fractures were closed, 13 open: 2 Type 1, 7 Type IIIA, 3 Type IIIB, and 1 Type IIIC. The average Injury Severity Score was 16 (range 9-34). Follow-up averaged 24 months (range 5-50 months). Average time to healing was 5 months (range 3-12 months). There were 9 (26%) complications: three pin tract infections, one septic arthritis, one manipulation under anesthesia, one DVT, one non-union, one symptomatic malunion(11 degrees valgus), and one refractured through the distal diaphyseal pin tract. All patients eventually healed. The average Harris Knee Score was 85 for pain (range 75-100), and 83 for function (range 50-100). All patients achieved full knee extension. Average flexion was 125 degrees (range 100-145). The proximal tibial joint surface was an average of 4.5 degrees valgus (range 3 degrees varus to 11 degrees valgus) and 6.75 degrees posterior slope (range 212 degrees).

All patients working prior to their injury had returned to work at latest follow-up.

Discussion: Operative treatment of complex proximal tibia fractures has shown mixed results. Various reports have shown infection rates of 2.2 to 87% with open reduction and internal fixation, and shown late amputation rates of 4% and 10%. Recently, more discussion has arisen concerning combined internal and external fixation of high energy proximal tibia fractures. Reports of limited internal fixation with external fixation of proximal tibia fractures have shown reduced rates of infection and improved functional outcome. The two constructs typically described involve limited internal fixation (compression screws, or small plate), and either a unilateral, medial, external fixator, or a hybrid frame fixator. The primary concern with these constructs is complications related to proximal pin placement. The proximal, medial pins enter near, or even through, the pes anserinus complex.

Discussion: During knee flexion and extension, the pes anserinus tendons cause tissue movement around the pins and greatly increase the risk of infection. Pin site complications have ranged from 5 to 100% in published reports. Loss of extension may also be related to tethering or impingement of the pes anserinus. Flexion contracture rates of up to 17% have also been reported with these constructs. A secondary concern involves the complexity and cost of these frames. Hybrid frames require individual equipment sets, with specialized instruments, and can be complicated to assemble: A standard hybrid fixator configuration: 2 tension wires, 3 half pins, 2 semi-circular frames, 7 wire/pin clamps, and 3 connecting rods. The anterior T-frame external fixator was first described in 1991. The two main advantages of the anterior T-frame fixator are the pin placement, and simplicity of the frame. The pin sites are all anterior, which minimizes the risk of pin tract complications and pes anserinus tethering/impingement. We report a pin tract complication rate of 11%, and no flexion contractures, which compares favorably with previous studies. Our patient population had a high rate of associated lower extremity injuries (62%), yet the Harris Knee scores 85 for pain and 83 for function are also comparable to other published reports. The anterior T-frame external fixator is relatively easy to assemble and does not require a special instrument or implant set. The fixator can be assembled from easily available large external fixator components: five 5.0 mm half pins, 1 connecting rod, 1 transverse bar, 5 clamp bodies, and a universal joint.

Conclusion: The anterior T-frame external fixator, with percutaneous internal fixation, is a versatile, effective method for initial stabilization of high energy proximal tibia fractures. The frame is simple, inexpensive, and can be used for definitive treatment, thus avoiding some of the possible complications associated with hybrid or medial frame constructs.