Assessment of Cartilage Resected from Osteochondral Lesions of the Talus for Intraoperative Reimplantation

Abstract

Category: Basic Sciences/Biologics; Arthroscopy Introduction/Purpose: Osteochondral lesions of the talus (OLT) are frequently treated with microfracture and may be augmented with decellularized extracellular matrix or particulated juvenile cartilage. The damaged OLT cartilage is often discarded. Infrequently it is used as a source for autologous chondrocyte expansion and implantation in a subsequent procedure. This resected cartilage has demonstrated variable chondrocyte viability. The influence of cartilage type on chondrocyte viability, whether frayed fibrocartilage from in vivo repair or delaminated hyaline cartilage, remains unknown. Also, little has been reported on the use of the OLT cartilage as a source for immediate cartilage autograft. The purpose of this study is to evaluate chondrocyte quantity and viability from the excised cartilage of OLTs at the time of arthroscopic debridement and microfracture. Methods: Patients aged 18 to 65 undergoing arthroscopic debridement and microfracture of talar OLTs were included. IRB approval of the study protocol was obtained. At the time of ankle arthroscopy, the cartilage from the OLT was collected either by GraftNet™ Autologous tissue collector (GraftNet™ Autologous Tissue Collector, Arthrex; Naples, FL) or manual collection and mincing of the specimen with a scalpel. Chondrocytes were isolated by overnight digestion with 2% collagenase in tissue culture medium at 37°C. The isolated cells were stained with Trypan Blue and counted for total cell number and viability (%), using an automated cell counter. Data collection included patient age, size and location of the OLT, intraoperative surgeon assessment of cartilage type (hyaline cartilage, fibrocartilage, or mixed fibro-hyaline cartilage), histologic determination of cartilage type, weight of the specimen, and chondrocyte cell count and viability. Results: Fourteen OLT specimens were collected. The average size was 0.831 (SD ± 1.10) cm 2 , and average weight 0.19 (SD ± 0.17) grams. Overall, the average number of chondrocytes was 1.12 x106 (SD ± 1.13 x106) cells/mm 2 and 3.99 x106 (SD ± 3.28 x106) cells/gram. The average viability was 72.36% (SD ± 12.25%). Using histologic determination of cartilage type, in hyaline specimens (n = 8, 57.14%) we found 1.08 x106 (SD ± 0.85 x106) chondrocytes/cm 2 , 70.73% (SD ± 11.73 %) viability. In fibrocartilage specimens (n = 2, 14.29%) we found 0.37 x106 (SD ± 0.10 x106) chondrocytes/cm 2 , 78.08% (SD ± 22.03%) viability. In mixed cartilage specimens (n = 4, 28.57%) we found 1.58 x106 (SD ± 1.80 x106) cells/cm 2 , 72.78% (SD ± 11.79%) viability. (Table 1) Conclusion: We found OLT chondrocyte viability of 72.36%, with a trend toward greater chondrocyte concentration and similar viability comparing hyaline and fibro cartilage, respectively. Cartilage type was consistent between intraoperative and histologic assessment in all but four specimens. OLT cartilage has the potential to serve as an immediate intraoperative chondrocyte autograft source for enhancement of talus cartilage repair procedures, eliminating the risk of donor site morbidity and additional surgeries as in culture-based methods. Further study with more patients may shed light on the accuracy of intraoperative cartilage classification, and differences in chondrocyte quantity and viability between cartilage types.