Computer assisted valgus osteotomy in osteoarthritic genu varum : results of the axial correction in a casecontrol study of 56 cases

This study aimed to evaluate the resulting mechanical axis in 28computer assisted valgus osteotomies (group A) and to comparethem to 28 classical osteotomies (group B) being randomly chosenin a total of 140 osteotomies operated on between January 1997 andDecember 2000.The groups were entirely comparable regarding age, gender, operatedside, osteoarthritis grading (modified Ahlback’s grades) andaxial deformity in varus (group A: 173.3° +/- 3.80° - 160° to 178°;group B: 172.8° +/- 3.18 – 164° to 178°) as measured on a long legXray (HKA angle).Fifty two cases involved a high tibial opening valgus osteotomyfixed by a tricalcic phosphate wedge (Biosorb*) and a T- shapedAO plate, whereas the 4 remaining cases (2 in group A, 2 in groupB) associated a high tibial medial opening osteotomy to a lateralfemoral closing osteotomy because of a genu varum superior to 15°.The operation aimed to obtain a mechanical axis between 182° and186°. The achieved axial correction has been controlled in all theknees at three months with a long leg Xray.In group A, the mean postoperative HKA angle wa s 183.4° +/- 0.99(181 to 185°) and 184° +/- 2.28 (181 to 189°) in group B. Thus, theaim has been achieved for 96% in group A and for 71% in group B,a statistically significant difference in absolute value (p = 0.0248)as well as in comparison of standard deviations (p = 0.0015).