[Computer-assisted surgery-(CAS-)guided correction arthrodesis of the subtalar joint].

OBJECTIVE: Restoration of a stable and plantigrade foot in deformities at the hindfoot and concomitant degenerative changes at the subtalar joint.

INDICATIONS: Deformities at the hindfoot and concomitant degenerative changes at the subtalar joint.

CONTRAINDICATIONS: Active local infection or relevant vascular insufficiency.

SURGICAL TECHNIQUE: Prone position and posterolateral approach to the subtalar joint. Placement of dynamic reference bases in talus and calcaneus through stab incisions. Two-dimensional image acquisition for navigation. Definition of the axes of talus and calcaneus, and of the extent of correction. Exposure of the subtalar joint and removal of remaining cartilage. Computer- assisted surgery-(CAS-)guided correction and transfixation of the corrected position with two 2.5-mm Kirschner wires. Transplantation of autologous cancellous and cortical bone, if necessary. Three-dimensional (3-D) image acquisition for analysis of the accuracy of the correction and planning of the drillings for the screws. CAS-guided drilling and insertion of the screws. 3-D image acquisition for analysis of the accuracy of the correction implant position. Wound closure in layers.

POSTOPERATIVE MANAGEMENT: 15 kg partial weight bearing in an orthosis (e.g. Vacuped TM, OPED Inc., Valley, Germany) for 6 weeks, followed by full weight bearing in a stable standard shoe.

RESULTS: From September 1, 2006 to August 31, 2008, 26 correction arthrodeses were performed. The accuracy was assessed by intraoperative 3-D imaging. All achieved angles/translations were within a maximum deviation of 2°/2 mm when compared to the planned correction. Complications that were associated with CAS were not observed. In all 25 cases that completed 2-year follow-up, timely fusion was registered.