A novel system improves preservation of osteochondral allografts

Abstract

Background: Osteochondral allografting is an option for successful treatment of large articular cartilage defects. Use of osteochondral allografting is limited by graft availability, often because of loss of chondrocyte viability during storage.

Questions/purposes: The purpose of this study was to compare osteochondral allografts implanted in canine knees after 28 days or 60 days of storage for (1) initial (1 week) safety and feasibility; (2) integrity and positioning with time (12 weeks and 6 months); and (3) gross, cell viability, histologic, biochemical, and biomechanical characteristics at an endpoint of 6 months.

Methods: With Institutional Animal Care and Use Committee approval, adult dogs (n=16) were implanted with 8-mm cylindrical osteochondral allografts in the lateral and medial femoral condyles of one knee. Osteochondral allografts preserved for 28 or 60 days using either the current tissue bank standard-of-care (SOC) or a novel system (The Missouri Osteochondral Allograft Preservation System, or MOPS) were used, creating four treatment groups: SOC 28-day, MOPS 28-day, SOC 60-day, and MOPS 60-day. Bacteriologic analysis of tissue culture and media were performed. Dogs were assessed by radiographs and arthroscopy at interim times and by gross, cell viability, histology, biochemistry, and biomechanical testing at the 6-month endpoint.

Results: With the numbers available, there was no difference in infection frequency during storage (5% for SOC and 3% for MOPS; p=0.5). No infected graft was implanted and no infections occurred in vivo. MOPS grafts had greater chondrocyte viability at Day 60 (90% versus 53%; p=0.002). For 60-day storage, MOPS grafts were as good as or better than SOC grafts with respect to all outcome measures assessed 6 months after implantation.

Conclusions: Donor chondrocyte viability is important for osteochondral allograft success. MOPS allows preservation of chondrocyte viability for up to 60 days at sufficient levels to result in successful outcomes in a canine model of large femoral condylar articular defects.

Clinical relevance: These findings provide a promising development in osteochondral allograft technology that can benefit the quantity of grafts available for use and the quality of grafts being implanted.

Figures

Fig. 1

This study design flow chart shows the process used to test and analyze the SOC and MOPS groups. SOC = standard-of-care; MOPS = The Missouri Osteochondral Allograft Preservation System; OCAs = osteochondral allografts.

Fig. 2

This intraoperative image shows 8-mm osteochondral allografts preserved by either SOC (left) or MOPS (right) and implanted in the medial and lateral femoral condyles of dogs using the press-fit method of a commercially available allograft system.

Fig. 3A–D

The radiographic appearances of the knees of (A) Dog 1 and (B) Dog 5 immediately after implantation of osteochondral allografts are shown. These radiographs show the appearances of the knees of (C) Dog 1 and (D) Dog 5 6 months after implantation of osteochondral allografts into the medial and lateral femoral condyles. For both of these dogs, MOPS-60 grafts were placed in the medial femoral condyles and SOC-60 grafts were placed in the lateral femoral condyles. Osseous integration of SOC and MOPS grafts is apparent based on the loss of radiolucency at the graft margins. There was no radiographic evidence for failure of osseous integration for any graft.

Fig. 4A–F

Corresponding (A) SOC-60 and (B) MOP-60 arthroscopic, (C) SOC-60 and (D) MOP-60 histologic (Stain, toluidine blue; original magnification, ×2); and (E) SOC-60 and (F) MOP-60 cell viability (Stain, calcein-AM/ SYTOX® blue; original magnification, ×4) images show the appearance of osteochondral allografts stored for 60 days before implantation in the femoral condyles of dogs and assessed 6 months after surgery. The arrowheads designate the graft-host junction in each image. Osteochondral allografts stored using MOPS for 60 days before implantation were consistently better than those stored using the current SOC for tissue banks based on the subjective arthroscopic appearance of the articular cartilage surface, histologic scoring, and chondrocyte viability. SOC = standard-of-care; MOPS = The Missouri Osteochondral Allograft Preservation System.

Fig. 5

Mean ± SD values for GAG content of articular cartilage from osteochondral allografts (MOPS [n = 7] and SOC [n = 7]) stored for either 28 or 60 days before implantation and assessed 6 months after implantation were compared with values for site-matched normal articular cartilage from the contralateral limbs (n = 14; Native). GAG content was significantly (p 

Fig. 6

Mean ± SD values for ortho-hydroxyproline content of articular cartilage from osteochondral allografts (MOPS [n = 7] and SOC [n = 7]) stored for either 28 or 60 days before implantation and assessed 6 months after implantation were compared with values for site-matched normal articular cartilage from the contralateral limbs (n = 14; Native). There were no differences in collagen content in native cartilage compared with cartilage from SOC and MOPS 28-day or 60-day grafts at 6 months (p = 0.28 and 0.21, respectively. OHP = ortho-hydroxyproline; SOC = standard-of-care; MOPS = The Missouri Osteochondral Allograft Preservation System.

Fig. 7A–B

Mean ± SD for (A) instantaneous tissue modulus (Ey) and (B) dynamic modulus (G) of articular cartilage from osteochondral allografts (MOPS [n = 7] and SOC [n = 7]) stored for either 28 or 60 days before implantation and assessed 6 months after implantation were compared with values for site-matched normal articular cartilage from the contralateral limbs (n = 14; Native). Native and MOPS-60 were significantly higher (p < 0.05) than SOC-60. SOC = standard-of-care; MOPS = The Missouri Osteochondral Allograft Preservation System.