Computer-assisted minimally invasive treatment of osteochondrosis dissecans of the talus.

OBJECTIVE

Revascularization of areas of necrosis in the talus and stimulation of bone regeneration whilst protecting the talar hyaline cartilage using computer-assisted minimally invasive drilling or retrograde cancellous bone relining of the osteochondrotic zone.

INDICATIONS

Osteochondrosis dissecans of the talus, Berndt & Harty stages I-III.

CONTRAINDICATIONS

Osteochondrosis dissecans of the talus, Berndt & Harty stage IV. General contraindications such as poor skin and soft-tissue conditions or poor general condition.

SURGICAL TECHNIQUE

Before the operation: fitting a removable cast for the ankle (ankle fixation cast), then computed tomography of the ankle with the ankle fixation cast fitted. Planning the site of the central Kirschner wire in the talus using a navigation system in the laboratory. Adjusting and locking the aiming device. Intraoperative procedures: fitting the sterilized ankle fixation cast. Retrograde placement of the 2.4-mm Kirschner wire through the locked aiming device. Check on the position of the Kirschner wire using an image intensifier. Arthroscopy of the ankle; further parallel holes may then be drilled depending on the findings or retrograde cancellous bone grafting may be performed by harvesting cancellous bone from the calcaneus.

POSTOPERATIVE MANAGEMENT

For retrograde drilling/parallel drilling: 1 week of partial weight bearing at 30 kg. For retrograde cancellous bone grafting: 4 weeks of partial weight bearing at 15 kg, then 2 more weeks of partial weight bearing at 30 kg. Physiotherapy.

RESULTS

From December 1999 to January 2005, 41 patients with osteochondrosis dissecans of the talus were selected for computer-assisted treatment by retrograde drilling or retrograde cancellous bone grafting. In 39 of the 41 patients, the osteochondral lesion-as verified by postoperative magnetic resonance imaging (MRI)-was accessed, i.e., the drilled hole led to the lesion. In two cases, irreparable flaws in the materials were discovered intraoperatively, so that the above method was only performed on 39 patients. The 1-year results for the first 15 patients treated with retrograde drilling/parallel drilling and concomitant ankle arthroscopy without retrograde cancellous bone graft are presented here based on the follow-up MRI (position of drill hole, assessment of vitality of the area of osteochondritis) and a clinical score. The four women and eleven men were, on average, 34.1 years old (14-55 years). In the radiologic comparison of the pre- and postoperative stages of the osteochondritis dissecans, 46.7% of patients showed an improvement in the Berndt & Harty stage. 40.0% showed the same osteochondrosis dissecans stage in the postoperative MRI, and in 13.3% it deteriorated by one grade. In the clinical follow-up examination, the AOFAS Score averaged 88.9 points.