Evaluation of the donor site defect after harvesting the medial third of the patellar tendon in ACL reconstruction: An MRI study.

PURPOSE: Previous studies have reported magnetic resonance imaging (MRI) changes in the donor-site defect size following anterior cruciate ligament reconstruction (ACLR) using the middle third of the patellar tendon (mid-third patellar tendon ACLR); however, no corresponding reports exist for ACLR using the medial third of the patellar tendon (medial-third patellar tendon ACLR). This study aimed to assess the changes in donor-site defect size postoperatively in medial-third ACLR patients and hypothesized a clinically relevant MRI change within the first year.

METHODS

Twenty-two consecutive patients underwent MRI examinations to measure the donor-site defect size ('gap' signal) and laterally remaining tendon size ('normal tendon' signal) at two time points: 14 (±5) days and 7.9 (±2.0) months postoperatively. The primary outcome was the post-pre difference of the "gap" signal. Wilcoxon signed rank test assessed the post-pre difference of the 'gap' signal, while robust linear regression examined the effect of either age at surgery or follow-up time on the post-pre difference of the 'gap' signal.

RESULTS

The primary finding was a significant reduction in the 'gap' signal [-9.2 mm (95% CI: -12.3; -6.7)] between 2 weeks and ~8 months (p < 0.001). The 'normal tendon' signal did not change significantly [1.6 mm (95% CI: -0.5; 3.3), p = 0.237]. Age at surgery had a negative, statistically nonsignificant effect on donor-site 'gap' signal difference (-2.24 [95% CI: -5.59; 0.60], p = 0.106). In addition, follow-up time had a negative, statistically nonsignificant effect on donor-site 'gap' signal difference (-0.97 [95% CI: -2.98; 4.14], p = 0.571). Eight of 22 patients had no detectable 'gap' signal at 8 months.

CONCLUSION

The most important finding for this study is a significant decrease in the donor-site defect along with an undetectable 'gap' that was verified for ~36% of the sample at a minimum mean follow-up of ~8 months. The laterally remaining 'normal tendon' signal remained unchanged. Neither age at surgery nor follow-up time had an impact on the healing of the donor-site defect. From a clinical perspective our findings suggest that the medial-third patellar tendon autograft has a high healing capacity after harvesting, already at a mean follow-up of ~8 months.

LEVEL OF EVIDENCE: Level IV.