Aims: The aim of this study was to independently evaluate the short-term clinical and functional outcomes of patients selected for non-operative management of ACL injuries using the Cross Brace Protocol (CBP), to further define the effectiveness of this protocol and identify predictors of success.
Methods: This was a prospective study evaluating the short-term outcomes of patients selected for CBP management following isolated grade 3 ACL rupture, as confirmed on 3T MRI. Selection for CBP management was determined by patient suitability assessed by T.C. based on MRI findings, clinical criteria, and patient preference for non-operative treatment. Baseline characteristics were recorded including MRI rupture classification. At 3-months, ACL healing was assessed and those with unfavourable healing were deemed unsuccessful with CBP. At 9 months, ligament laxity (Dyneelax Robotic Knee Arthrometer, Genourob, France) and Return to Sport (RTS) functional limb testing were assessed (including range of motion, strength, Y-Balance test, and Hop tests). 12-month evaluation included Patient Reported Outcome Measures (PROMs); Tegner Activity Score (TAS), International Knee Documentation committee (IKDC), and Lysholm Knee Scale (LKS). Additionally, 12-month MRI findings, conversion to surgery and recurrent ACL injury were also observed.
Results: 133 patients were recruited between April 2024 and March 2025 who sustained an ACL rupture and deemed suitable to commence the CBP. The mean (SD) baseline characteristics were determined for this cohort: age 34 (11.6), gender 66% female, side of injury 55% left, and pre-injury Tegner Score 7.3 (1.8). At 3-months 6 participants (5%) showed no evidence of healing and converted to surgery. At 9-months, laxity measures showed an absolute displacement difference at 200N of 1.18 (1.1) mm between the healthy and injured knees, range of motion showed a small, but significant deficit in both flexion and extension (p = 0.007 and p = 0.004 respectively), and quadricep strength was significantly lower, although clinically insignificant (p < 0.001). At 12-months, MRI grades of healing were again assessed, and PROMs were evaluated: TAS 5.7 (1.8), IKDC 74.6 (9.2) and LKS 93.0 (7.9). 6 participants (5%) sustained a subsequent injury and re-rupture within 12 months, leading to a total of 12 (9%) of the CBP cohort requiring conversion to surgery. Those requiring surgery were significantly younger (p = 0.002) and had higher pre-injury TAS (p = 0.04). MRI rupture types were not predictive of re-rupture within 12-months in this cohort.
Conclusion: The Cross Brace Protocol provides an additional non-operative option for ACL injuries and may be associated with satisfactory anatomical and functional healing for certain patient groups. Patients selected as suitable for CBP demonstrated acceptable PROMs, re-rupture rates, and ligament laxity. Positive results were associated with older individuals and lower pre-injury functional demands. Continued research of this novel intervention is required to observe longer term follow-up and further evaluate its effectiveness compared to ACL reconstruction and other non-operative strategies.
