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 degrees ; on postoperative radiographs it was 11.7 +/- 5.7 degrees 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.