Summary

Novel osteotomy fixed with a DFN for genu valgum correction

Abstract

Introduction

Genu valgum when left untreated can lead to lateral compartment osteoarthritis apart from being a cosmetic problem.The valgus deformity more often than not lies in the femur. Lateral opening wedge osteotomy is a popular technique to correct these deformities and fixation techniques vary from plates to intramedullary nails. We describe an osteotomy technique fixed with a distal femoral nail in a small subset of patients with follow up.
Materials & Methods: Patients with a genu valgum deformity that were a minimum of 18 yrs were included in the study. A pre operative standing Hip Knee Ankle Xray (HKA) was done to quantify the deformity by measuring the femoro tibial angle. The technique involved first making a 6 cm anterior midline incision with lateral parapatellar approach to the distal femur. The entry point was made and the guide pin introduced perpendicular to the distal femoral condyles, confirming it with a fluoroscopic image. The point where the guide wire touches the cortex medially is the level of the osteotomy. A 2cm lateral incision was made at this level. An osteotome was introduced through this incision and the osteotomy performed such that after penetrating the lateral cortex, the osteotome is advanced to the anterior, medial and posteromedial cortices, that are weakened while widening the lateral window. There was a distinct change in the tone of the osteotome when it touches these cortices, apart from fluoroscopic guidance. Once weakened, a valgus force was exerted completing the osteotomy. This caused the proximal segment to collapse into the distal segment. The canal was then reamed to the appropriate diameter and nail introduced in the same direction perpendicular to the femoral condyles. It was locked distally with 3 screws and proximally with one screw. Patients were kept non-weight bearing for 6 weeks and then partial weight bearing with a walker from 6 weeks to 3 months. A standing Hip Knee Ankle X ray was done at 3 months to confirm the final alignment

Results

There were 6 patients, 3 bilateral and two unilateral cases of genu valgum. Mean age was 23.4 yrs (Range 19-30yrs), Mean BMI 25.24 with a mean pre op femoro-tibial angle of 9.56 degrees valgus underwent a distal femoral osteotomy at the cortico-cancellous junction of the femur. The mean post op femoro tibial angle was 2.5 degrees varus (Range 1-3 degrees varus), Mean Tegner score of 5.5 (4-8) and Mean Lysolhm Score of 85.6 (Range 69-95) at a mean 18.8 months follow up. One patient needed a manipulation under anesthesia at 6 weeks. No other complications were reported.
Statistical Analysis: Analysis was done using SPSS version 22 software. The means and ranges of pre op femoro tibial angle, post op femoro tibial angle, age, BMI, follow up, Tegner score and Lysolhm score were done

Conclusions

This minimally invasive technique of performing a complete osteotomy and stabilising it with a distal femoral nail gives good results with a low complication rate in this subset of patients.