Abstract
The results of PLLA screws for ACL reconstruction have demonstrated no significant clinical differences when compared to metallic screws up to two years. However, studies examining PLLA-HA screws are lacking, as are medium term outcomes of bioresorbable screws. This study aims to compare the clinical outcome of ACL reconstruction with a PLLA-HA to a titanium screw, and to assess the extent of resorption of the PLLA-HA screw at two and five years after ACL reconstruction.
Forty patients were randomised to receive either a PLLA-HA or titanium RCI interference screw for ACL reconstruction. Both examiners and patients were blinded to screw type. Patients were prospectively reviewed at 24 and 60 months after surgery with full IKDC assessment, Instrumented Ligament Testing, Lysholm knee score. MRI scans were performed at two and five years following surgery.
Five years after surgery, one patient with a titanium screw had an ACL graft rupture and had undergone revision surgery. Of the remaining 39 patients, 38 (97%) were reviewed at five years. There was no significant difference between the two groups in the volume of the tibial (p=0.89) or femoral (p=0.22) tunnels at five years. Significant screw resorbtion at five years was seen in 77% on the tibial side and 88% on the femoral side in the PLLA group. Good ossification was evident on five year MRI in 94% of the tibial screws and 56% of the femoral screws. In the PLLA-HA group peri tunnel bone marrow oedema was present in 35% of patients on the tibial side and 53% of patients on the femoral side at five years. There was no peri-tunnel bone marrow oedema evident in the titanium group. Peri-graft ganglion cyst was evident on MRI scan on the tibial side in 24% of patients from the PLLA-HA group and 18% of the titanium group (p=0.67). There was no significant difference between the PLLA-HA group and the titanium group on any of the other clinical parameters including IKDC subjective knee score (mean 93), symptoms, range of motion, instrumented ligament laxity (mean 1.8 mm) or overall IKDC grade (90% normal or nearly normal).
ACL reconstruction with PLLA-HA bioabsorbable screws affords comparable clinical and subjective results to titanium screws at five years after surgery. Significant progression of PLLA HA screw resorption occurs between two and five years, with over 75% of screws demonstrating some resorption by five years. However, complete resorption was only evident in a small number of patients. ACL reconstruction with a PLLA HA screw has excellent clinical outcomes and progressive screw resorption and ossification is evident at five years.
