The correlation of correction magnitude and tibial slope changes following open wedge high tibial osteotomy

We investigated whether there is a correlation between coronal plane correction magnitude and tibial slope in patients treated with medial open wedge high tibial osteotomy (OWHTO) and also measured changes in patellar height. Thirty-four knees treated with for varus deformities were retrospectively reviewed and the follow-up period of the patients was averaged 24.1 months. Preoperative and postoperative measurements of the Hospital for Special Surgery (HSS) score, Insall–Salvati index, posterior tibial slope angle, mechanical axis deviation, proximal medial tibial angle (PMTA) was used to determine. All patients had a significant increase in their HSS score postoperatively (P < 0.0001). There was no significant correlation between the differences in patellar heights (P = 0.368). The mechanical axis deviation was altered by a mean of 25.5 ± 10.9 mm and the difference was statistically significant (P < 0.05). The mean posterior tibial slope angle on preoperative radiographs was 9.0 ± 5.1°; on postoperative radiographs it was 11.7 ± 5.7° and the difference was statistically significant (P < 0.007). Seventeen knees (50%) demonstrated postoperative posterior tibial slope angle increases; 7 knees (21%) had a decrease in this angle, while 10 knees (29%) showed no change. Statistical analyses revealed that the mechanical axis deviation was not correlated with change in tibial slope (P = 0.837). Although we could not find a correlation between tibial slope change and the amount of coronal correction, 50% of our patients demonstrated increased tibial slope.