High reliability in digital planning of medial opening wedge high tibial osteotomy, using Miniaci's method

Pre-operative planning is essential in high tibial osteotomy (HTO). Miniaci's method employs Mikulicz's weight-bearing line and is advantageous because the point of mechanical loading is related to the known degenerative condition of the knee. Miniaci's geometrical method has been modified for an opening wedge and described for use with a digital picture archiving and communications system viewer. Reliability for this method was hypothesised to be equivalent to published reliability for landmark-based commercial software and independent of observer experience.

Twenty-four patients awaiting HTO had standardised long-leg radiographs. Mikulicz's weight-bearing line was projected through the lateral compartment of the knee at Fujisawa's point. The correction angle was generated at the hinge point subtending the current and proposed ankle centres. The opening wedge was plotted to measure an opening distance. Observations were recorded twice by three observers. Agreement was reported as intraclass correlation coefficients with 95 % confidence intervals.

Intra-rater agreement was excellent for the correction angle (0.965-0.985) and opening distance (0.928-0.980). If no set hinge point was used, then the inter-rater reliability was 0.986 for the correction angle and 0.984 for the opening distance. There was no discernible pattern demonstrating improved reliability from the experienced observer.

Reliability is comparable to commercially based landmark software and independent of observer experience. This makes such geometrical pre-operative planning accessible to surgeons who perform HTO with insufficient frequency to justify the investment in commercial software.

Diagnostic study, Level II.