Page 24 - ISAKOS 2021 Newsletter Volume 1

CURRENT CONCEPTS
The Osteochondral Lesion: Management Options Now and Going Forward
Ceramics and bioglass overcome some of the drawbacks of metals as they are osteoconductive and inductive, allowing for bonding to the adjacent native bone tissues. The implant porosity and degradation rate also can be titrated during manufacturing, but these materials are brittle and may fracture when mechanically loaded. These subchondral material alternatives must be combined with a chondral component in order to make a complete osteochondral unit.
Currently Available Osteochondral Implants with Clinical Results
At present, only three multiphasic osteochondral implants have undergone clinical trials: (1) MaioRegen (Fin-Cermica Faenza SpA), (2) TruFit (Smith and Nephew, Andover, MA, USA), and (3) Agili-C (Cartilheal Ltd, Kfar Sava, Israel). MaioRegen and TruFit have been studied more extensively than Agili-C, for which clinical trials are presently ongoing.
A recent systematic review of 16 clinical studies on the use of MaioRegen, a triphasic scaffold, included 471 subjects with International Cartilage Regeneration and Joint Preservation Society (ICRS) grade-III and IV lesions2. The authors of the review reported significant clinical improvement in 13 studies at 24 months of follow-up. Two studies involving histological analysis showed no residual scaffold, with a strong presence of type-II collagen and proteoglycan content in the regenerate, indicating implant resorption and an adequate regenerative tissue response. Complications included 2 cases of partial implant detachment, 2 cases of graft hypertrophy, and 52 cases of minor complications (e.g., joint stiffness and swelling). Sixteen failures were documented in the review.
In another systematic review, Verhaegan et al. reported that TruFit, a biphasic, synthetic scaffold made of polylactide- coglycolide copolymer and calcium sulphate, showed clinical benefit up to 12 months, beyond which two studies showed worsening3. Complications included failure of osseous ingrowth, fissured lesions on the regenerate surface, and histological evidence of subchondral cysts. TruFit appeared to have issues with biodegradability and integration and requires further improvement before further clinical application.
Agili-C, the most recently developed implant, consists of modified aragonite with hyaluronic acid and a bone phase of calcium carbonate. Preclinical data have shown excellent cell recruitment and biocompatibility. A hemicondylar aragonite implant was implanted in a caprine model, resulting in good chondral and subchondral regeneration, excellent integration, and no adverse effects at 12 months. In a case study, a 47-year-old patient underwent treatment with Agili-C and reported significant functional improvement with radiographic evidence of hyaline cartilage regeneration over the entire defect with good bone integration at 2 years4.
22 ISAKOS NEWSLETTER 2021: VOLUME I
Sequential radiographs suggested that the entire implant was replaced with cartilage and bone by means of creeping substitution. A more recent study of 5 talar osteochondral lesions showed good cartilage fill and reported no adverse effects at 26 months, indicating that Agili-C may be a safe option for osteochondral lesion treatment5.
Future Directions
Osteochondral lesions have not had an adequate clinical / surgical solution. As tissue-engineering techniques and understanding of cellular differentiation mechanisms improve, research is inching closer to an answer. The clinical results associated with MaioRegen and Agili-C are encouraging, and we hope that such implants will be successful treatment options in the future. Further biological options such as TEC also look promising. With further well-designed trials and results being awaited, OATs and OCA remain techniques with respectable outcomes as long as their specific indications and limitations are noted.
References
1. Shimomura K, Moriguchi Y, Ando W, Nansai R, Fujie H, Hart DA, et al. Osteochondral repair using a scaffold-free tissue-engineered construct derived from synovial mesenchymal stem cells and a hydroxyapatite-based artificial bone. Tissue Eng - Part A. 2014;20(17– 18):2291–304. 2. D’Ambrosi R, Valli F, De Luca P, Ursino N, Usuelli F. MaioRegen Osteochondral Substitute for the Treatment of Knee Defects: A Systematic Review of the Literature. J Clin Med. 2019; 3. Verhaegen J, Clockaerts S, Van Osch GJVM, Somville J, Verdonk P, Mertens P. TruFit Plug for Repair of Osteochondral Defects—Where Is the Evidence? Systematic Review of Literature. Cartilage. 2015; 4. Kon E, Drobnic M, Davidson PA, Levy A, Zaslav K, Robinson D. Chronic posttraumatic cartilage lesion of the knee treated with an acellular osteochondral-regenerating implant: Case history with rehabilitation guidelines. J Sport Rehabil. 2014; 5. Drobni M, Kolar M, Verdonk P, Vannini F, Robinson D, Shabshin N, et al. Complex Osteochondral Lesions of the Talus Treated With a Novel Bi-Phasic Aragonite-Based Implant. J Foot Ankle Surg. 2020;