Summary

Pressure between the two boudles of ACL in native intact anterior cruciate ligament (ACL) and ACL grafts of double bundles ACL reconstruction (DB-ACLR) with different tunnel placements were measured and compared, in which PR-ACLR shows to be more corresponded with the physiological condition

Abstract

Objective

To determine the amount and dynamic change regularity of the impingement pressure between the anteromedial bundle (AMB) and posterolateral bundle (PLB) in native intact anterior cruciate ligament (ACL) and ACL grafts of double bundles ACL reconstruction (DB-ACLR) with different tunnel placements, so as to clarify the impingement conditions between the two boudles of ACL grafts after DB-ACLR.

Methods

Fifteen fresh-frozen nonpaired human cadaver knees were randomly divided into three groups according to the specimen number: native intact ACL (NI-ACL), preserved remnants DB-ACLR (PR-ACL) which was performed according to fiber orientation with ACL remnants preserved, and bony landmark DB-ACLR (BL-ACL) which was performed according to surrounding bony landmarks with ACL completely cleared. Impingement pressure between the AMB and PLB were measured in the three groups respectively by pressure sensors which were tailored and inserted into AMB and PLB according to the shape of the contact surface. Contact pressure between the AMB and PLB at different flexion angles (full range of motion from the maximum extension to maximum flexion, performed measurement every 15 angles) was measured used Tekscan pressure sensor test system.

Results

The amount and change regularity of impingement pressure were similar in NI-ACL group and PR-ACL group: Within the flexion range of 120 degrees of the knee joint, quantity of impingement pressure showed no significant change in both groups (P >0.05), the maximum, minimum and average pressure showed as follows respectively: 10.04±0.86N (0.14±0.02MPa), 8.42±0.92N (0.12±0.01MPa), 9.52±0.87N (0.13±0.02MPa) (NI-ACL group); 10.33±0.68N (0.14±0.01MPa), 9.11±0. 97N (0.13±0.02MPa), 9.75±0.93N (0.14±0.05MPa) (PR-ACL group). While impingement pressure rapidly increase when the flexion range exceed 120 degrees, which showed significant difference with datas within the flexion range of 120 degrees (P <0.05). The maximum, minimum and average pressure showed as follows respectively: 27.04±2.39N (0.38±0.08MPa), 20.52±1.98N (0.29±0.03MPa), 23.78±2.26N (0.29±0.03MPa) (NI-ACL group); 28.13±2.46N (0.40±0.05MPa), 22.35±2.01N (0.31±0.04MPa), 25.24±2.33N (0.35±0.03MPa) (PR-ACL group). Impingement pressure in BL-ACL group showed no regularity within the whole range of knee joint motion, which showed significant difference in all pressure datas. The maximum, minimum and average pressure within the knee joint flexion range of 120 degrees showed as follows respectively: 28.13±2.82N(0.39±0.05MPa), 9.36±1.28N(0.13±0.02MPa), 19.05±2.73N(0.27±0.04MPa). When the flexion range exceed 120 degrees, the maximum, minimum and average pressure showed as follows respectively: 39.53±3.12N (0.56±0.06MPa), 32.35±2.12N (0.45±0.04MPa), 35.94±2.56N (0.50±0.05MPa). There was no significant difference in the maximum, minimum and average impingement pressure between the NI-ACL group and PR-ACL group within the whole range of knee joint motion (P >0.05). In addition to the minimum pressure, maximum, and average impingement pressure of were significantly higher than that of NI - ACL and PR-ACL group within the flexion range of 120 degrees (P <0.05). While the maximum, minimum and average pressure showed significant difference with that of NI - ACL and PR-ACL group when the flexion range exceed 120 degrees (P < 0.05).

Conclusion

1. Impingement pressure between AMB and PLB is small and show little change within the flexion range of 120 degrees under physiological condition .While the pressure increase rapidly when the flexion range exceed 120 degrees. It should be ensured that the pressure between AMB and PLB stay small within the knee joint flexion range of 120 degrees at least, otherwise it may lead to pathological impingement between AMB and PLB, developing innto graft wear or rerupture. 2.Compared to BL-ACLR, pressure between grafts of PR-ACLR shows to be more corresponded with the physiological condition, which can be attributed to higher levels accordance with native anatomy and biomechanical mechanism of AMB with PLB.