OTA 1999 Posters

Improved Clinical Outcome and Limb Mechanical Axis with the Use of a Femoral Distractor for Fractures of the Lateral Tibial Plateau

Brian D. Solberg, MD; Michael R. Baumgaertner, MD; Jeffrey Sumner, MD, Yale University, School of Medicine, Dept. of Orthopaedics, New Haven, CT

Purpose: To compare the radiographic and functional outcomes of patients with isolated lateral tibial plateau fractures (OTA 41:B1-B3) treated with or without a femoral distractor at intermediate follow-up (mean 44 months).

Methods: Retrospective review of clinical records, radiographs and examination in a clinic setting was conducted on thirty-two patients with isolated lateral tibial plateau fractures (OTA 41:B1-B3) requiring open reduction and internal fixation treated at our institution between June 1992 and July 1995. The distraction group (group A) consisted of seventeen patients treated using a femoral distractor at the time of reduction, the control group (group B) included nineteen patients that were treated without the use of a distraction device. Four patients were lost to follow-up. Clinical outcome was based on the Knee Society clinical score at latest clinic evaluation. Radiographs were evaluated pre-operatively, immediately after surgery and at latest follow-up for joint depression (step-off), tibio-femoral angle (mechanical axis), and tibial metaphyseal-diaphyseal angle.

Results: There was no difference between groups with regard to pre- and post-operative joint depression (18.7 mm vs. 17.8 mm p=0.69) and no patient had more than 1 mm of residual step-off at latest follow-up. Similarly, there was no difference between the two groups with regard to pre-operative mechanical axis (p=0.79) or pre-operative tibial-metaphyseal axis (p=0.82). There was a significant difference in postoperative tibial metaphyseal-diaphyseal angle with 2.8° varus in the distraction group and 0.3° valgus in the control group (p<0.0001). Moreover, postoperative mechanical axis differed significantly between the distraction group (6.3° valgus) and the control group (8.0° valgus) (p=0.001).

Twelve patients in the distraction group had an excellent outcome and four patients had a good outcome at a mean follow-up of 44 (9-71) months, while, in the control group, four patients rated excellent, nine good and three fair at mean follow-up of 45 (31-62) months (p=0.761). Patients in the distraction group had a significantly better clinical outcome with an average knee score of 92 vs. 88 for the control (p=0.03).

Discussion: Various anatomic studies have documented a slight varus (3 degree) orientation of the proximal tibia (joint line) relative to the shaft. Restoration of this subtle varus slope alters the mechanical axis shifting the center from the lateral to the medial compartment. The use of a femoral distractor at the time of reduction neutralizes joint reactive forces on the joint and allows for a more anatomic restoration of mechanical limb axis. This subtle restoration appears to favorably alter clinical outcome at intermediate follow-up.

Conclusion: The use of a femoral distractor during reduction of lateral tibial plateau fractures (OTA 41:B1-B3) results in a more accurate restoration of the subtle varus orientation of the proximal tibia. This leads to a better overall outcome at intermediate follow-up.