Between 2003 and 2007, 99 knees in 77 patients underwent opening wedge high tibial osteotomy. We evaluated the effect of initial stable fixation combined with an artificial bone substitute on the mid- to long-term outcome after medial opening-wedge high tibial osteotomy (HTO) for medial compartmental osteoarthritis or spontaneous osteonecrosis of the knee in 78 knees in 64 patients available for review at a minimum of five years (mean age 68 years; 49 to 82). The mean follow-up was 6.5 years (5 to 10). The mean Knee Society knee score and function score improved from 49.6 (sd 11.4, 26 to 72) and 56.6 (sd 15.6, 5 to 100) before surgery to 88.1 (sd 12.5, 14 to 100) and 89.4 (sd 15.6, 5 to 100) at final follow-up (p <  0.001) respectively. There were no significant differences between patients aged ≥ 70 and < 70 years. The mean standing femorotibial angle was corrected significantly from 181.7° (sd 2.7°, 175° to 185°) pre-operatively to 169.7° (sd 2.4°, 164° to 175°) at one year’s follow-up (p < 0.001) and 169.6° (sd 3.0°, 157° to 179°) at the final follow-up (p = 0.69 vs one year).

Opening-wedge HTO using a stable plate fixation system combined with a bone substitute is a reliable procedure that provides excellent results. Although this treatment might seem challenging for older patients, our results strongly suggest that the results are equally good.

Cite this article: Bone Joint J 2014;96-B:339–44.

The efficacy of an imageless navigation system in acetabular cup orientation during total hip arthroplasty (THA) is well known. We evaluated the accuracy of placement of the cup and stem and leg extension length with the imageless navigation system.

Radiographic evaluation was performed in 69 consecutive patients (75 joints) who underwent primary THA from January 2009 to December 2010. Evaluation of the cup inclination angle (CI), cup anteversion angle (CA), leg extension length (L) and stem anteversion angle (SA) was carried out. SA was evaluated in 21 patients who underwent CT scan after surgery. The accuracy of imageless navigation system was evaluated by comparison of the navigation values obtained during surgery with the radiographic or CT measured values.

Good correlation was found between the navigation values and the radiographic or CT measured values in CI (P<0.001, r² = 0.579), CA (P<0.001, r² = 0.607), L (P<0.001, r² = 0.775), and SA (P<0.001, r² = 0.834). The mean absolute difference between navigation and radiograph or CT was 3.3 degrees (range 0.1 to 9.9 degrees) in CI, 4.6 degrees (0.1 to 11.4 degrees) in CA, 3.2mm (0.7 to 8.3) in L, and 3.6 degrees (0.1 to 10 degrees) in SA.

The results of this study demonstrated that imageless navigation shows good accuracy not only in cup implantation angle but also in leg extension length and in stem anteversion angle according to radiographic and CT evaluation. We conclude that imageless navigation is a useful tool for performing accurate surgery for THA.