Summary

The majority of patients consented for the BEAR-MOON study are successfully enrolled in the study based on intra-operative findings, but a small minority fail intra-operative screening.

Abstract

Background

Bridge-Enhanced ACL Repair (the BEAR technique) has shown promising results in preclinical testing with lower rates of osteoarthritis, and in initial safety cohort and small clinical trials. The BEAR-MOON multi-center randomized non-inferiority clinical trial is being conducted to compare the BEAR technique against ACL reconstruction with patellar tendon autograft.

Purpose

The purpose of this study is to present the intra-operative findings from the BEAR-MOON cohort and report on the patients excluded from enrollment based on intra-operative findings.

Methods

All patients consented for the BEAR-MOON study were included. Demographic data (age, sex, ethnicity, and time from injury to surgery), baseline PROMs (IKDC, KOOS, AKPS, and Marx activity scale), physical exam (range of motion, Lachman, and pivot shift), and intra-operative findings (length of tibial ACL stump and percent of tibial footprint attachment intact) were collected. The group of patients who were excluded from enrollment in the study based on intra-operative findings were compared to the patients who were successfully enrolled at the time of surgery.

Results

One hundred patients have been consented for the BEAR-MOON study. Ninety-one patients have been evaluated for enrollment intra-operatively; 84 have been successfully enrolled and 7 have failed intra-operative screening. Of the 84 patients enrolled, the mean ACL stump length was 17.3 ± 4.26; 77 patients had 75-100% of the tibial footprint attachment intact while 7 patients had 50-75% intact. Of the 7 patients who failed intra-operative screening, the mean ACL stump length was 10.9 ± 4.56; 4 patients had 75-100% of the tibial footprint attachment intact while 1 patient had 50-75% intact, and the remaining two had less than 50% intact. The reasons for intra-operative screening failure were ACL tibial stump less then 10mm (3 patients), tibial footprint attachment less than 50% intact (2 patients), concomitant bucket handle meniscus tear (1 patient), and tibial stump too frayed to repair (1 patient). There was no difference between groups of enrolled and failed enrollment patients in terms of demographics, including age (32.9 ± 9.30 vs. 32.1 ± 12.47), sex, and time from injury to surgery (40.4 ± 7.83 vs. 42.1 ± 7.03 days). There was also no difference between groups in terms of physical exam findings and PROMs, except a difference in Marx scores (11.0 ± 4.75—enrolled vs. 13.3 ± 2.75—failed (p-value=0.04)).

Conclusion

The majority of patients consented for the BEAR-MOON study are successfully enrolled in the study based on intra-operative findings, but a small minority fail intra-operative screening. This is most commonly because the tibial stump is too short or too much of it is not intact at the tibia; the findings do not seem to be affected by age, sex, or time from injury to surgery. This is important information to share pre-operatively with patients considering undergoing the BEAR procedure, and surgeons should be prepared with a back-up plan if the ACL does not appear acceptable for the BEAR procedure at the time of surgery.