The Effect of Cast Immobilization on Meniscal Healing

A 1.5-cm longitudinal, full-thickness incision was made in the vascularized portion of the medial meniscus in 20 adult dogs and anatomically repaired. Postoperatively, the animals were either placed in a long leg cast (N = 9) or mobilized immediately (N = 11). The animals were sacrificed at 2 weeks (6 dogs), 4 weeks (6 dogs), or 10 weeks (8 dogs). Five medial menisci from the nonop erated side were used as controls. Collagen content was measured using a digital image analysis system, and the collagen percentage in the repair tissue in each postoperative treatment group was compared. In the 2-week and 4-week groups, there was no statistically significant difference in the percentage of collagen be tween those animals immobilized versus those that had early mobilization. The animals in the 10-week group that were mobilized had a significantly greater collagen percentage in the healing meniscal incision than those that were cast immobilized (44.6% ± 10% versus 27.0% ± 11 %, P < 0.0001). There was no significant difference in the collagen percentages between the mo bilized 10-week group and the contralateral control me nisci group. All other menisci had a decreased collagen percentage compared with the controls. Prolonged im mobilization decreases collagen formation in healing menisci. Thus, our results suggest that patients under going isolated meniscal repair either be immediately mobilized after surgery or immobilized for short periods only.