Polylactide (LTS) causes less inflammation response than polydioxanone (PDS): a meniscus repair model in sheep

Background Incidence of meniscus injury has increased in today's active society. Arthroscopical refixation yields better results than partial meniscectomy. The best healing rates are achieved by sutures. As non-degradable sutures are permanent foreign bodies, slow absorbable materials are needed. A slow degradable suture with high concentration of polylactide acid, the so-called "long-term suture" (LTS, Panacryl), has been suggested to produce a higher inflammatory response than conventional polymer sutures [Vicryl, Dexon or polydioxanone (PDS)]. The aim of the study was to assess LTS for meniscus repair after a traumatic lesion and to evaluate immunological response, biodegradation and healing. Methods In 24 randomised sheep, a radial tear of the medial meniscus was sutured by either PDS or LTS. Twelve sham-operated animals served as control. Half of the sheep were killed after 6 months, the other half after 12 months. The medial and lateral meniscus, synovial membrane, articular cartilage and ascendant lymph nodes up to the kidney were examined. Joint effusion was evaluated by MRI. Results The synovial membrane was significantly thinner in the LTS group (6 months 85 +/- 10 mu m, 1 year 100 +/- 28 mu m) than in the PDS group (6 months 165 +/- 10 mu m, 1 year 175 +/- 23 mu m, P < 0.001) and the controls (6 months 150 +/- 17 mu m, 12 months 192 +/- 21 mu m, P < 0.001). The joint effusion was higher in the PDS than in the LTS group after 6 months, and tended to be higher in controls. In controls, effusion tended to be higher than in the LTS group. In all medial departments, osteoarthritis evolved much more intensely than in the lateral knee departments (P < 0.01). Bilateral lymph nodes from the groin up to the kidneys were larger (crosscut area) after 6 months in the controls (2.28 +/- 0.7 mm(2)) and PDS treated animals (2.3 +/- 0.7 mm(2)) than in the LTS group (1.3 +/- 0.3 mm(2), P < 0.001). After 1 year, node size differed significantly between controls and animals from the LTS group (1.98 +/- 0.4 mm(2) vs. 1.5 +/- 0.2 mm(2), P < 0.05), and between animals from the PDS and the LTS group (2.5 +/- 0.1 mm(2) vs. 1.5 +/- 0.2 mm(2), P < 0.001). Conclusion The polylactide thread LTS causes less immunological reaction and synovitis than a polydioxanone suture (PDS). Clinical relevance: LTS may serve as an alternative to PDS for repair of slow healing structures such as tendons and menisci.