A hemicallotasis method has been developed utilizing an external fixator as high tibial osteotomy (HTO), and satisfactory results of this method with the external fixator have been reported. This external fixator has a universal joint that moves in all directions. We have recently designed a hemicallotasis device for this operation.
HTO for the knee with varus deformity utilizing the hemicallotasis method was performed on 44 knees. The patients had a mean age at operation of 65 years (range 49-82 years), a mean follow-up period of 68 months (range 36-119 months), and a mean preoperative knee score of 66 points (range 27-90 points).
The operated knees had a mean knee score at the final follow-up of 86 points (range 51-98 points), but the mean range of knee motion was not changed as follows. Before surgery, the mean flexion was 129 degrees (range 90-150 degrees) and the mean extension was -5 degrees (range -30 to 0 degrees), whereas at the final follow-up, the corresponding values were 127 degrees (range 85-150 degrees) and -4 degrees (range -25 to 0 degrees), respectively. Radiographically, the femorotibial joint was classified as grade 2 in 9 knees, grade 3 in 21 knees, and grade 4 in 14 knees according to the classification of osteoarthritis (Kellgren and Laurence). The patellofemoral joint was also classified as grade 1 in 39 knees, grade 2 in 2 knees, and grade 3 in 3 knees. The mean femorotibial angle was 184 degrees (4 degrees varus) before surgery, 169 degrees (11 degrees valgus) after pin extraction, and was maintained at the final follow-up. The complications of this method were relatively few and consisted of pin-tract infection (8 knees), deep vein thrombosis (3 knees), and delayed union (2 knees). No peroneal nerve palsy or compartment syndrome was encountered. No knee was converted to total arthroplasty. However, administration of analgesics was necessary in ten knees at the final follow-up.
The hemicallotasis method easily determined the angle of correction even in the knees with ligamentous laxity. Nevertheless, one of the major demerits of this method was a longer period of application of the external fixator. The level of evidence was level IV (case series).