Analysis of partial bundle anterior cruciate ligament tears- diagnosis and management with ACL augmentation

Partial ACL tears are increasingly recognized in young active patients. They can evolve into complete tears. Controversy exists regarding the need to spare intact ACL bundle as it has its advantages considering biomechanical strength, blood supply and proprioception. The current study determined the challenges in partial ACL tear management and assessed the functional outcomes.

Twenty consecutive patients with partial ACL tears were studied. Inclusion criteria were: age 16-45yrs and patients operated for partial ACL tear. Exclusion criteria were: combined ACL-PCL injuries, associated collateral injuries, complete ACL tear, chondral defect or bony malalignment and patients with radiographic signs of arthritis. 'Partial' tear was defined as continuous fibers from native tibial ACL footprint to native femoral ACL footprint in arthroscopy. Clinical and radiological assessment was done to evaluate anteromedial(AM) or posterolateral(PL) bundle tears. We used the term "ACL-augmentation" without disturbing the intact bundle or preserving the intact fibers as much as possible. Functional scoring was done using Lysholm score. Standard post-operative protocols were followed. Statistical analysis was done using SPSS software.

Mean age of patients was 31.2 years. Physically active age group (<30yrs) included 62.5% patients. Males were 87.5%. Pain and instability were the presenting complaints in 75% and 70% respectively. Average duration of presentation since injury was 4.2 months. Sports activities were the most common mode of injury (45%) followed by road traffic accidents (37.5%). Anterior drawer test was positive in 40%, pivot shift in 35% and Lachman test was positive in 65%. On arthroscopy, 65% had AM bundle tears and 35% had PL bundle tears. The intact bundle was found lax in 13% cases. Associated meniscal tear was present in 28% patients. Stiff knee was the most common post-operative complaint. Preoperative Lysholm knee score of 74.5 improved to 87.7 at 12months (p < 0.001). Around 97.5% of the patients reported outcomes as good and fair.

The treatment strategy needs to be individualized. The ACL augmentation needs more systematic and accurate placement of portals while sparing the intact ACL fibers. For AM bundle, tibial tunnel entry point is about 1-2 cm medial to tibial tuberosity. For PL bundle, it is about 3-4 cm medial to tibial tuberosity to protect the AM bundle. Long term studies with greater number of subjects are required.