Abstract
The purpose of this study was to quantify tibial tunnel enlargement at 3-, 6- and 12-months post-anterior cruciate ligament reconstruction (ACLR), and evaluate the magnitude of tunnel widening with use of a Poly (L-lactic Acid) interference screw (PLLA (Bioscrew XtraLok, Conmed, New York)) compared to a Poly (L-lactic Acid) + tricalcium phosphate interference screw (PLLA+TCP (GENESYS Matryx screw comprised of microTCP and 96L/4D PLA, Conmed, New York)).
This was a prospective randomized controlled trial with two parallel groups. Eighty unilateral ACL-deficient participants awaiting ACLR surgery were recruited between 2013 and 2017 from the clinic of a sole fellowship trained orthopaedic surgeon. Patients had to be skeletally mature and less than 45 years old, with no concomitant knee ligament injuries requiring surgery, chondromalacia, or previous history of ipsilateral knee joint pathology, surgery or trauma to the knee.
Participants were randomized intra-operatively into either the PLLA or PLLA+TCP tibial interference screw fixation group. Study time points were pre-, 3-, 6-, and 12-months post ACLR. Participants underwent x-rays with a 25 mm calibration ball, IKDC knee assessment, and completed the ACL-Quality of Life score (ACL-QOL) at each visit.
Measurement (mm) of the most proximal and distal extents as well as the widest point of the tibial tunnel were taken using efilm (IBM Watson Health) and were standardized relative to the calibration ball. A contrast inverter was used to determine clear borders based on contrast between normal and drilled bone. In addition, a subjective evaluation of the tunnel was conducted looking for bowing of the borders of the tunnel or change in tunnel shape, categorizing the tunnel as widened or not widened.
Differences between groups at each time point were evaluated using independent t-tests corrected for multiple comparisons. Tunnel width was also compared as a percentage of actual screw size at 12-months post-operative. Categorical data were compared using Fisher's Exact Test. Forty participants were randomized to each group with mean age (SD) of 29.7 (7.6) and 29.8 (9.1), for PLLA and PLLA+TCP, respectively. There were no differences between groups in age, gender or ACL-QOL.
There were no differences found between groups at any time point in either tunnel width measurements or tunnel width as a percentage of actual screw size. The greatest difference between groups was noted in the measurement of the widest point on lateral x-ray view with a mean difference of 11%. Based on subjective evaluation of tunnel shape, three participants had visible widening in the PLLA group, and two in the PLLA+TCP group (p=NS).
No differences in tunnel widening were identified between ACL reconstruction patients using a PLLA interference screw compared to a PLLA+TCP screw for tibial fixation up to 12-months post-operative.
