Summary

Comparison of radiological and functional outcomes of high tibial osteotomy between two principles of pre-operative planning

Abstract

Objective

High tibial osteotomy (HTO) is a useful alternative to knee replacement in the relatively young and active patient with medial compartment osteoarthritis. Careful pre-operative planning is required to attain the desired correction of mechanical axis. It is also important to prevent excessive proximal tibial valgus in order to avoid adverse outcomes. The objective of this study was to compare the radiological and functional outcomes of HTO by two different principles of pre-operative planning.

Methods

A total of 100 patients (109 knees), 67 (71 knees) under surgeon 1 and 33 (38 knees) under surgeon 2 were retrospectively studied. Surgeon 1 used 'Miniaci' method for planning with focus on achieving Mikulicz point at 62.5% (principle 1). Surgeon 2 employed planning software (TraumaCad) and tried to keep the mechanical medial proximal tibial angle (mMPTA) < 930 (principle 2). Mikulicz point and mMPTA were compared on long leg radiographs, taken before and 3 months post surgery. Under correction was defined as Mikulicz point < 50 % and over correction as > 70 %. Functional outcomes were determined using Oxford Knee Score (OKS), Knee Injury and Osteoarthritis Outcome Score (KOOS) and EQ5D5L pre-operatively, at 1 and 2 year follow up.

Results

Pre-operative Mikulicz point, mMTPA and functional scores were comparable between the groups. Mean post-operative mMPTA was significantly higher in group 1 (93.95 (SD 2.76)) compared to group 2 (92.13 (SD 2.37)) (p=0.01). In Group 1, 81.7 % patients had post-operative correction between 50-70% compared to 65.8 % in group 2. But this was not statistically significant (p=0.06). However, there were significant number of under corrections in group 2 (32.4 %) in comparison to group 1 (9.8 %) (p=0.003). Mean OKS and KOOS improved significantly in both the groups after surgery, while EQ5D improved only in group 1.

Conclusion

The conservative approach (principle 2) of planning for an HTO appears to be effective in preventing excessive valgus at the proximal tibia, but with a higher possibility of under correction. Though not statistically significant, there appears to be a trend towards the principle 1 being more consistent in achieving the desired correction. The functional outcomes showed more positive trend with principle 1. A longer follow up is needed to study the long-term implications of these principles.