The healing of an autogenous osteochondral graft and a full thickness cartilage defect in the canine talus: compared by functional, radiographic and histological assessment

Abstract

A circular (5.5mm diameter) full thickness cartilage defect was created on the medial ridge of the talus in twelve skeletally mature dogs. In six dogs the articular surface of the lesion was repaired using an osteochondral graft obtained from the ipsilateral manus. The graft (Digit I, 1st phalanx, distal articular surface and diaphysis) was contoured to obtain a press fit in the drilled talar recipient site. In six dogs the lesion was not treated and healed by fibrous tissue replacement. Functional assessment (lameness, hock range of motion, joint stability, joint crepitus and mid-femoral muscle circumference) was completed preoperatively and at postoperative weeks 2 through 20. Radiographic assessment (periarticular soft tissue width, joint space width, osteophyte formation and graft incorporation) was completed preoperatively and at postoperative weeks 0, 6, 12 and 20. To facilitate the histologic assessment the tissues were stained with toluidine blue and hematoxylin and eosin. Histologic assessment of the articular surface on the operated talus (lesion, graft, and junctional area), ipsilateral tibia and contralateral talus was completed using a modification of the Mankin grading system. Subchondral bone was examined to assess graft viability and incorporation. Analysis of the ordinal data was completed using a Mann-Whitney rank sum test.

All dogs were fully weight bearing by postoperative week 7. One of six grafted dogs demonstrated a weight bearing lameness at postoperative week 20. The non-grafted dogs showed significantly better clinical function at postoperative week 6 (P=0.036). No significant difference in functional assessment was demonstrated at postoperative week 20 (P=0.136). Normal range of motion was measured in all dogs by the sixth postoperative week. Minimal crepitus was observed in 1 ungrafted dog and 3 grafted dogs. Joint stability remained normal in all dogs. Disuse muscle atrophy occurred in all dogs; however, atrophy had resolve by the 20th postoperative week. Immediate postoperative radiographic assessment demonstrated a significant difference between the ungrafted and grafted groups (P=0.005). No significant difference was noted at postoperative weeks 6, 12 or 20. All grafts appeared radiographically incorporated by postoperative week 12. All grafts restored joint surface congruity while 3 of 6 ungrafted lesions demonstrated poor articular congruity evidenced by a visual and palpable step defect. Four of six grafts partially retained normal hyaline cartilage resulting in significantly lower Mankin grades (P=0.014). No significant histologic differences between groups were demonstrated when the opposing tibia and junctional areas were examined.

Talar reconstruction using a phalangeal osteochondral graft is a viable surgical procedure. This data demonstrates that normal articular and subchondral architecture are more closely approximated by osteochondral reconstruction than fibrous by tissue repair.