Summary

We prospectively evaluated the influence of infrapatellar fat pad (IPFP) preservation on anterior knee pain (AKP) in 34 patients who underwent arthroscopic ACL reconstruction. The amount of IPFP resection was calculated using MRI before and 6 months after surgery. AKP was assessed using Kujala score. In this study, IPFP resection around the intercondylar area had no significant effect.

Abstract

Introduction

Anterior knee pain (AKP) is one of the major complications that interrupts rehabilitation after anterior cruciate ligament (ACL) reconstruction. The infrapatellar fat pad (IPFP) plays various roles in the knee, such as serving as a vascular supply, providing cushion for the patellar tendon, and secreting inflammatory factors. Damage to the IPFP during arthroscopy may cause AKP. However, no studies have showed correlation the amount of IPFP resection during arthroscopy with AKP. This study aimed to evaluate the influence of IPFP preservation on AKP in ACL reconstruction.

Methods

We prospectively assessed 34 injured ACLs that were randomly selected to undergo intercondylar IPFP resection to better visualize ACL or preservation. The size of total IPFP and the posterior part, divided along a line connecting the vertical and horizontal clefts, were calculated using a sagittal MRI at the center of intercondylar fossa of femur. The preservation rate of total IPFP was defined as the ratio of the total IPFP size at 6 months postoperatively compared to the preoperative total size. The resorption rate of the posterior portion was calculated by subtracting the 6-month postoperative ratio from the preoperative ratio as it relates to the total IPFP size. As clinical evaluation, the Kujala score to assess AKP at 3 and 6 months postoperatively and International Knee Documentation Committee (IKDC) score and Knee injury and Osteoarthritis Outcome Score (KOOS) at 1 year were used. The significance level set at p <0.05.

Results

There were 17 patients in each group; all underwent ACL reconstruction using the semitendinosus tendon. There were no differences in the mean age, sex, height, body weight, or time from MRI to surgery between the groups. Both groups had 10 meniscus tears. There were significant differences in the preserving rate of total IPFP size and the resorption rate of posterior part between the resection and preservation groups (80.0 ± 8.3% and 86.1 ± 12.4%, p = 0.022; 13.0 ± 5.5% and 3.8 ± 4.3%, P < 0.001 respectively). There was no significant difference in clinical evaluations between the resection group and the preservation group: the Kujala score were 74.3 ± 9.1 and 75.6 ± 12.2 at 3 months postoperatively (p = 0.727) and 90.2 ± 6.5 and 91.1 ± 9.0 at 6 months (p =0.360) respectively; IKDC score were 93.5 ± 5.9 and 90.9 ± 9.8 (p = 0.833) ; KOOS were 96.6 ± 3.5 and 94.6 ± 5.9 (p = 0.449). No cases had more than a 10-degree loss of knee extension compared to the healthy side at 6 months postoperatively.

Conclusions

The size of the IPFP, particularly the posterior part, decreased more in the resection group than that in the preserved group at 6 months after surgery. The posterior part of IPFP has richer vascular supply and more substance-P nerves that cause pain. Damage to the posterior part may cause AKP. However, this study suggests that IPFP resection around the intercondylar area to better visualize ACL had no effect in the early postoperative period.