Use of ultrasonography to evaluate the dynamics of the infrapatellar fat pad after anterior cruciate ligament reconstruction: a feasibility study.

PURPOSE: There has been no specific study on the quantitative morphological changes that occur in the infrapatellar fat pad (IPFP) after anterior cruciate ligament (ACL) reconstruction. We used ultrasonography to evaluate the dynamics of the IPFP in knees after ACL reconstruction using the contralateral knees as controls.

METHODS: We enrolled 31 patients 3 months after they underwent ACL reconstruction. The thickness of the superficial part of the IPFP was measured using longitudinally oriented ultrasound images of the anterior part of both knees at 90° and 10° flexion. We then used these data to calculate the ratio of the change in thickness.

RESULTS: At 90° knee flexion, the superficial part of the IPFP was significantly thinner in the reconstructed knees (9.3 ± 3.4 mm) than in the contralateral knees (11.8 ± 4.6 mm). The thickness change ratio was significantly smaller in the reconstructed knees (188.6 ± 64.7%) than in the contralateral knees (249.7 ± 73.8%).

CONCLUSION: When assessed 3 months after ACL reconstruction, the thickness of the superficial part of the IPFP at 90° knee flexion and the thickness change ratio of the IPFP were both significantly lower in the reconstructed knees than in the contralateral knees.