GONIOMETRIC EXTERNAL FIXATOR CH-N FOR STA BILIZATION OF HIGH TIBIAL OSTEOTOMY FOR VARUS DEFORMITY

Introduction The authors present technique and results of a new extern al fixator, the << goniometric >> external fixator CH-N for osteosynth esis of high tibial osteotomy for arthritic varus knee deformity on 86 kness (75 patients). Materials and methods 86 knees in varus deformit y with degenerative arthritis of the medial compartment (56 females an d 16 males - age 63 +/- 8 years) were treated for 5 years (1989-1993) by high tibial osteotomy stabilized by a << goniometric >> external fi xator CH-N. Results Clinical results were 65,9 per cent excellent, 17, 1 per cent good, 11,8 per cent fair and 5,2 per cent poor 1 year after osteotomy (86 cases analyzed), changing in 60 per cent excellent, 22, 3 per cent good, 9,1 per cent fair and 8,5 per cent at 3 years follow- up (61 cases). Radiological results were The preoperative mechanical a xis of 13 degrees +/- 5 degrees in varus transformed to 4 degrees +/- 2 degrees in valgus at consolidation and to 2,5 degrees +/- 3 degrees in valgus at one year follow-up. At 3 years follow-up we founded a new loss of correction of 1 degrees (mean) in 22 per cent of cases (61 ca ses). Subchondral density decreased in 91 per cent of cases (86 cases) one year after and in 82 per cent of cases, 3 years after the osteoto my (61 cases). In 12 per cent of cases we found a decrease of the over correctional angle of the varus deformity 1 year after, and in 22 per cent of cases 3 years after. Two cases needed total knee arthroplasty 4 years after ostcotomy. Postoperatively, in 86 per cent of cases we d id not found increase in both clinical and radiological (pathological) findings of the patellofemoral joint one year after, and in 75 per ce nt of cases 3 years after. Discussion The principle of this special << goniometric >> external fixator is based on the << goniometric >> cen tral joint in the frontal plane, this allows to guide the screws durin g osteotomy in the predesigned position and to control the correction during and after the procedure, in contrary to the others current syst em either internal or external. Any faulty correction can be modified. With its distal screwing axis, it allows axial dynamization. There ar e only some but not serious inconveniences due to the application of p ins (temporary neuromuscular problems and pin-track infections.