Introduction: Medial laxity is an important problem in knees with mono-compartmental gonarthrosis. Medial laxity can cause the progression of the gonarthrosis if it is left uncorrected. Therefore, managing of medial laxity during high tibial osteotomy is very important. In this study, the effect of openning focal-dome type osteotomy on the medial laxity was investigated.

Materials-Methods: Four knees of two cadavers (74-year-old male and 52-year-old female) were used in this study. For the creating pseudo-medial laxity in the knee, while total medial menisectomy was performed in two knees of male cadaver, 5 mm osteochondral resection of both joint surfaces of the medial femoral condyle and medial tibial plateau was performed in two knees of female cadaver.

Results: After creation of the pseudo-medial laxity, opening focal-dome type osteotomy extending to proximal to the insertion of superficial medial collateral ligament was applied with circular fixator in all knees and 15° valgus effect was applied on the osteotomy line by motor unit of the circular fixator. By applying 15° valgus effect on the osteotomy, average reduction of medial laxity was measured as 70% in all knees.

Conclusions: Opening focal-dome type osteotomy decreases medial laxity effectively by tightening the superficial medial collateral ligament.