Arthrodesis of the Ankle.

About 90 % of all cases of painful posttraumatic ankle arthritis can be very successfully treated with a minor invasive ankle arthrodesis technique by using a small anterior approach and a fixation with four 6. 5 mm screws of which the posteromedial and transfibular one are inserted percutaneously. The results with this standardized procedure have been reported previously as excellent and good in a mid-term run of 6 years (34). This technique leads to a high union rate of 99% (92 of 93) with rapid bone healing within 8 ± 2 weeks, it causes a low minor complication rate of 8 % and enables a significant increase of the AOFAS ankle/hindfoot score (17) from 36 preoperatively to 85 postoperatively as well as a midtarsal movement of 24° ± 16°. In some cases of ankle arthritis due to chronic syndesmotic instability a 5th screw is additionally used to compress the reamed espace claire for regaining a stable ankle fork. A 5th screw is used also in case of necessary shortening of the fibula or in cases of idiopathic ankle arthritis with gross varus deformity when a transfibular approach becomes necessary instead of the anterior approach. About 10% of ankle arthrodesis need different procedures like in cases of malunited ankle or pilon fractures with low grade infection, larger bony defects due to resection of necrotic bone, due to primary bone loss in open fractures or due to secondary bone loss in failed ankle replacement cases. They need usually a two stage procedure with primary debridement and temporary joint transfixation and secondary anterior double plate fixation with autogenous bone grafting. In case of critical anterior soft tissues a posterolateral approach with a bladeplate-fixation is performed. In the very rare cases of severe ankle infection a three stage procedure is recommended with a radical necrectomy of infected soft tissues or dead bone and/or combined with taking biopsies, filling the defects with Gentamycin-PMMA- beads and stabilizing the reamed joint with a threaded compression Charnley fixator in the first stage. A re-debridement in the second stage might need additionally a permanent lavage with sensitive antibiotics according to the probes and in the third stage a third debridement with finally autogeneous bonegrafting is done. Key words: ankle arthrodesis, anterior, posterolateral, transfibular ankle approach, 4- to 5-screw fixation technique, double plate fixation, autogeneous bonegrafting, Charnley compression fixator.