Comparison of Poly-L-Lactic Acid and Poly-L-Lactic Acid/Hydroxyapatite Bioabsorbable Screws for Tibial Fixation in ACL Reconstruction: Clinical and Magnetic Resonance Imaging Results

Abstract

BackgroundThe purpose of this study was to compare the clinical and radiological results of 2 different tibial fixations performed using bioabsorbable screws with added hydroxyapatite (HA) and pure poly-L-lactic acid (PLLA) screws in anterior cruciate ligament (ACL) reconstruction.MethodsA total of 394 patients who underwent arthroscopic ACL reconstruction between March 2009 and June 2012 were retrospectively reviewed. Of those, 172 patients who took the radiological and clinical evaluations at more than 2 years after surgery were enrolled and divided into 2 groups: PLLA group (n = 86) and PLLA-HA group (n = 86). Both groups were assessed by means of the Lysholm score, International Knee Documentation Committee (IKDC) subjective knee score, and Tegner activity score. Stability was evaluated using the KT-2000 arthrometer. Magnetic resonance imaging was performed to evaluate tibial tunnel widening, screw resorption, osteoingeration, and foreign body reactions.ResultsThe PLLA-HA group showed significant reduction in the extent of tibial tunnel widening and foreign body reactions and significant increase in screw resorption compared to the pure PLLA group (p < 0.001 for both). In contrast, postoperative Lysholm score, Tegner activity score, IKDC score, and side-to-side difference on the KT-2000 arthrometer showed no significant differences between groups (p = 0.478, p = 0.906, p = 0.362, and p = 0.078, respectively). The PLLA group showed more significant widening in the proximal tibial tunnel than the PLLA-HA group (p = 0.001). In the correlation analysis, proximal tibial tunnel widening revealed a positive correlation with knee laxity (r = 0.866) and a negative correlation with Lysholm score (r = −0.753) (p < 0.01 for both).ConclusionsThe HA added PLLA screws would be advantageous for tibial graft fixation by reducing tibial tunnel widening, improving osteointegration, and lowering foreign body reactions. Even though no clinically significant differences were noted between the pure PLLA group and PLLA-HA group, widening of the proximal area of the tibial tunnel showed a tendency to increase knee laxity measured using the KT-2000 arthrometer.

Bone Tunnel Enlargement With Non-Metallic Interference Screws in Acl Reconstruction

“…In our study, the screw with biocomposite (TCP) showed a 36.83% enlargement of the tibial tunnel, close to studies with addition of HA. 4 , 18 However, in the group with pure PLDL, enlargement of the tibial tunnel (35.24%) was slightly lower than the TCP group, unlike most studies. 4 , 17 , 18 …”

“…It is believed that the addition of biocomposites, such as tricalcium phosphate (TCP) and hydroxyapatite (HA) in PLDL, can accelerate the process of graft incorporation with improved conversion to cancellous bone which reduces acidity during degradation. 17 Lee 4 using MRI, compared the enlargement of the tibial tunnel between PLDL with hydroxyapatite (HA) and pure PLDL screws and found a smaller tibial tunnel enlargement (27.4% x 41.3%), similar to Robinson 18 who also found a smaller tibial tunnel enlargement using CT, 29.9% with the addition of HA to PLDL compared to pure PLDL 46%. In our study, the screw with biocomposite (TCP) showed a 36.83% enlargement of the tibial tunnel, close to studies with addition of HA.…”

“…The material of the absorbable interference screw can influence the enlargement of the bone tunnel due to formation of an inflammatory process during its absorption. 4 Moisala 6 found that PLDL compared with metal screws led to greater enlargement of the femoral tunnel. The average widening of the tunnels within the three types of interference screws evaluated in our study showed that PEEK, a bioinert material with no absorption, led to a smaller tunnel expansion, but it was statistically similar to biomaterials, such as PLDL and TCP.…”

“…The interference screw is still the most widely used fixation, 2 and is made from many different types of materials, such as titanium, bioinert materials such as polyether-ethyl ketone (PEEK), and bioabsorbable materials, such as poly-lactic acid (PLDL) that may be associated with biocomposites, such as hydroxyapatite (HA), and tricalcium phosphate (TCP), each with their advantages and disadvantages. 3 , 4 , 5 …”

“…Metal (titanium) interference screws, although widely used due to their lower cost, have some disadvantages such as the difficulty of being removed in a revision surgery 3 , 4 and the presence of artifacts in magnetic resonance imaging (MRI) that may hamper a correct interpretation, which directed several surgeons to opt for screws made of bioinert materials and biomaterials. 5 …”