Summary

Hybrid HTO can be performed for the patients suffering from relatively severe knee osteoarthritis with varus deformity those who open-wedge HTO are not applicable without minding the leg length change.

Abstract

Background

Open-wedge high tibial osteotomy(HTO) is a reliable procedure for knee osteoarthritis and knee osteonecrosis. However, in severe osteoarthritis case, alternative operation procedure is required because of the weak point of open-wedge HTO

Purpose

The aim of this study is to assess the clinical results and surgical complications of the novel closed wedge high tibial osteotomy (Hybrid HTO) in our hospital. Hybrid HTO is a novel closed wedge HTO procedure reported by Ryohei Takeuchi et al .
MATERIAL & METHODS:
26 knees in 19 consecutive patients who were underwent Hybrid HTO with an internal plate fixator were assessed. JOA Score (Japan Orthopedic Association Knee Score) was used to evaluate the functional results.
Radiological parameters consisted of femorotibial angle (aFTA), posterior tibial slope angle (PTS), mechanical axis deviation (%MA) , medial proximal tibial angle(MPTA)
, the angle between the ground surface and distal tibial plafond, and Caton-index for checking patella height. The ratio of the leg length (RLL) between the operated side and the opposite side of each patient was calculated before and after surgery. In 9 knees of all 26 knees, articular cartilage in medial femorotibial joint and patellofemoral joint was evaluated by arthroscopy before and about 12 months after HTO according to ICRS grading system. In all cases operative complications were recorded.

Results

Duration of follow-up was 12.5±5.2 months. Mean JOA Score improved 44.8 ±3.2 to 87.5 ±4.0 points (P<0.001). Mean aFTA was corrected 186.9±2.5° pre-operatively to 170.3±1.4°post-operatively (P<0.001). Mean %MA was corrected 4.5±11.5% pre-operatively to 61.6±3.8% post-operatively (P<0.001). Mean PTS decreased significantly 4.8±1.6° pre-operatively to 3.1±2.1° post-operatively (P<0.001). Mean the angle between the ground surface and distal tibial plafond decreased significantly 7.9±1.6° preoperatively to 1.67±1.5° post-operatively(P<0.001). Mean MPTA increased significantly 81.9±2.3° preoperatively to 93.5±4.3° post-operatively(P<0.001). Mean Caton-index did not change 0.82±0.14 pre-operatively to 0.81±0.12 post- operatively (P=0.23). ICRS grade in medial femorotibial joint improved in 9 of 9 knees (100.0%). ICRS grade in patellofemoral joint did not change in 9 of 9 cases (100.0%) . Mean RLL did not change 0.993±0.010 pre-operatively to 0.991±0.008 post- operatively (P=0.84).
Operative complications are non-union of the osteotomy site 2knees of 1case (7.7%) , Methicillin-resistant Staphylococcus aureus (MRSA) infection 1knee of 1 case (3.8%), Pseudoaneurysm formation in the posterior tibial artery just after plate removal 1knee of 1 case (3.8%), deep peroneal nerve injury 1knee of 1 case (3.8%).

Discussion

& CONCLUSIONS:
From the result of this study, Hybrid HTO leads to significant improvements in radiographic parameters and knee function. Coronal alignment of the ankle joint became more parallel after Hybrid HTO, while MPTA became larger after Hybrid HTO. In general, closed wedge HTO tends to shorten the leg length, however Hybrid HTO did not significantly influence the leg length of the patients. Hybrid HTO can be performed for the patients suffering from relatively severe knee osteoarthritis with varus deformity those who open-wedge HTO are not applicable without minding the leg length change. Hybrid HTO is thought to be a convincing choice for serious knee osteoarthritis with varus deformity.