Polylactide Carbonate Research Articles

Paper 284: Double Bundle Anterior Cruciate Ligament Reconstruction Using a Polylactide Carbonate (CALAXO) Osteoconductive Interference Screw

The purpose of this study was to describe our experience of the new Polylactide Carbonate (Calaxo) Osteoconductive interference screw (Smith & Nephew) when used for both femoral and tibial graft fixation in Double Bundle ACL reconstruction. Since May 2006, patients with an ACL deficient knee were reconstructed using the Double Bundle technique. All were followed prospectively and outcome data collected. Evidence of fixation failure was established subjectively by clinical examination (Pivot Shift) and objectively via KT-1000 arthrometer. Following ethical approval, post-operative CT scans (immediate and 12-18 months) were performed on five (a further 5 awaited) patients allowing assessment of tunnel dimensions/fill. Twenty nine patients (26 male, 3 female) with a mean age of 30 (range 18-47) were included. At last follow-up, no evidence of graft/fixation failure was found; KT-1000 mean side-side difference 1.4mm (range −3 to +6). All patients had a positive pivot shift preoperatively which was abolished postoperatively. Subjective IKDC score was significantly improved with a mean of 76.27% (SD 17.38) at last review compared with 54.02% (SD 17.86) preoperatively (t (22) = −5.37, p<0.05) One patient had a postoperative infection with no other complications reported. Radiologically the screws did not show complete resorption in 2 cases, with significant tunnel widening found on 3 cases. Some evidence of new bone formation was noted but not found to be significant. We have shown satisfactory clinical results with use of the Calaxo screw when used in Double Bundle ACL Reconstruction. However, radiologically the ostoeconductive properties of the screw shown in the pre-clinical animal model were not evident. This study helps illustrate that preclinical animal data cannot necessarily be translated into human practice. Surgeons should proceed with caution when using new biological implants tested purely in animal models. Although we have not had any cases of the reported adverse local soft tissue reaction associated with Calaxo, we support Smith & Nephew's decision to withdraw the screw from clinical use.

Double blinded randomised controlled trial of a polylactide carbonate (Calaxo) and tricalcium phosphate (Milagro ®) composite screws for tibial fixation in ACL reconstruction

Double blinded randomised controlled trial of a polylactide carbonate (Calaxo) and tricalcium phosphate (Milagro ®) composite screws for tibial fixation in ACL reconstruction

Magnetic resonance imaging appearance of anterior cruciate ligament reconstruction using Calaxo screws

Bioabsorbable interference screws are commonly used to secure the graft during anterior cruciate ligament (ACL) reconstruction, in part because they result in less image degradation on subsequent magnetic resonance imaging (MRI). However, some bioabsorbable screws are associated with abnormalities on MRI examination not reported with metallic interference screws. We describe a finding on knee MRI examination after ACL reconstruction using a polylactide carbonate (PLC) bioabsorbable screw that we believe to be previously unreported with any other bioabsorbable screws. The finding raised suspicion of hemorrhage or infection, neither of which were present clinically. Analysis of tissue from the tibial tunnel suggested an explanation for the MRI finding: calcite crystals. An additional five patients with knee MRI examinations after ACL reconstruction using a PLC screw were reviewed and correlated with clinical findings with four having similar imaging abnormalities present. The PLC (Calaxo screw, Smith and Nephew, Andover, MA) screw used in these patients has been recalled in the United States and Europe by the manufacturer after a greater than expected incidence of adverse reactions, and legal action may be pending.

Tibial tunnel widening after bioresorbable poly-lactide calcium carbonate interference screw usage in ACL reconstruction

Developing bio-absorbable interference screws for anterior cruciate ligament (ACL) reconstruction has proven to be a challenging task. The aim of this study was to investigate the osteogenetic response of poly-lactide carbonate (PLC) interference screws in ACL reconstruction in humans. Ten patients (median age, 28 years) underwent arthroscopic ACL reconstruction with semitendinosus/gracilis tendon graft and a PLC interference screw. The patients were scanned with a multi-slice CT scanner 2 weeks and 1 year postoperatively. Fourteen days postoperatively a mean tunnel widening of 78% [52%; 110%] was observed. At 1-year follow-up, the mean tunnel widening was 128% [84%; 180%]. No sign of bone replacement or bone ingrowth was observed. Factors such as accelerated rehabilitation, micro-motions, and early screw degradation might be responsible for this large tunnel widening. Our results demonstrate the difficulty in translation of preclinical data. This study illustrates the need for extensive preclinical investigation of new materials for clinical purposes.

The unpredictable material properties of bioabsorbable PLC interference screws and their adverse effects in ACL reconstruction surgery

The aim of this study was to look at the clinical outcome of polylactide carbonate (PLC) interference screws in knee ligament reconstruction surgery. We prospectively followed up 59 patients who underwent primary hamstring anterior cruciate ligament (ACL) reconstructions using PLC (Calaxo screw; Smith and Nephew, Andover, MA) screws to secure the graft in the tibial tunnel. The average age was 34 years (range 17-55 years, SD 8.93). Twenty-three (39%) patients presented with complications [synovitis in 15% (nine) patients, prominent tibial swelling in 34% (20) patients and both in seven patients]. In comparison, similar complications were not seen in two groups of 59 age and sex matched patients in whom PLLA (Bio RCI; Smith and Nephew, Andover, MA) screws or Titanium (RCI; Smith and Nephew, Andover, MA) screws were used by the same surgeon. The problems encountered in the PLC screw group did not adversely affect knee stability. Six patients underwent exploration of the tibial tunnel site. A sterile white cheesy substance was removed, leaving an empty tibial tunnel. The ACL graft was found to be well attached to tibial tunnel in all cases. The PLC screw diameter, surface area or tibial tunnel diameter did not have any correlation to the occurrence of complications. Two patients required multiple washouts, one of whom developed a deep infection. The degradation of PLC screws does not follow the gradual and controlled pattern demonstrated in the ovine model. The unpredictable screw degradation, and the reaction to it can lead to serious clinical consequences.

Tibial Cyst and Intra-Articular Granuloma Formation After Anterior Cruciate Ligament Reconstruction Using Polylactide Carbonate Osteoconductive Interference Screws

We report a case of sterile tibial cyst and intra-articular granuloma formation of the knee 6 months after a double-bundle anterior cruciate ligament reconstruction with bioabsorbable polylactide carbonate osteoconductive interference screws. The patient presented with increasing pain and swelling of the knee. Surgical exploration was performed, and 2 pretibial cavities were encountered, filled with remnants of the biodegradable screws and fibrinous material. Both sites underwent curettage, and the cavities were filled with allogeneic bone grafts. Arthroscopic evaluation of the knee showed an intact anterior cruciate ligament and a large granuloma formation anterior to the intercondylar notch in conjunction with the anteromedial tibial tunnel. Arthroscopic resection of the granuloma together with synovectomy was performed. To our knowledge, this is the first case report of this complication with polylactide carbonate screws.

Comparison of Poly-L-Lactide and Polylactide Carbonate Interference Screws in an Ovine Anterior Cruciate Ligament Reconstruction Model

The purpose of this study was to compare polylactide carbonate (PLC) interference screws with poly-L-lactide (PLLA) screws in an ovine anterior cruciate ligament reconstruction model. A PLC screw or PLLA screw was placed in the center of a 4-strand soft-tissue autograft fixating the graft within the tibial tunnel. Assessments were made at 6 and 12 weeks for fixation strength and at time points of 6, 12, 26, and 52 weeks via computed tomography and histology. No adverse or inflammatory reactions were noted for either material at any time point. Mechanical fixation strength increased from 6 to 12 weeks for both the PLC and PLLA screws, with no significant differences in fixation strength being found between the 2 groups. By 26 weeks, the PLC screw was partially replaced by new bone, a process that was completed by 52 weeks. The PLLA screws were intact and surrounded by a fibrous layer at 52 weeks with no obvious resorption. New bone formation within the tendon construct located in the bone tunnel proximal to the interference screw was also noted in the PLC screw group but was not observed in the PLLA group. This study has supported the hypothesis that this bioabsorbable composite has sufficient mechanical properties and strength retention to function successfully as an interference screw but also stimulates a biologic healing response, enabling replacement by bone and tunnel healing. This study shows both the satisfactory mechanical characteristics and osteoconductive nature of PLC used in an interference screw in an ovine anterior cruciate ligament reconstruction model.