Case Series With Histopathologic and Radiographic Analyses Following Failure of Fresh Osteochondral Allografts of the Talus.
BACKGROUND
Fresh osteochondral allografting of the talus is one treatment option for large chondral defects. Following positive early term results, failure rates of up to 35% have been reported. A retrieval study was performed to characterize failed talar allografts.


METHODS
Failed fresh osteochondral allografts of the talus were retrieved on revision. Cases of deep infection were excluded. After tissue fixation, samples were decalcified, embedded, and stained with Safranin-O/Fast Green, osteocalcin, tumor necrosis factor alpha (TNF-α), CD4, CD8, and CD68. Slides were graded according to the modified Mankin scoring system or severity scale. Medical record review was performed.


RESULTS
Eight allografts (7 patients) were retrieved from patients, following an average term of implantation of 31 months (range, 12-58). There were 3 types of allografts in this series (hemidome, n=5; segmental, n=2; bipolar, n=1). Reasons for transplantation were post-traumatic arthritis or osteonecrosis; reasons for revision were graft failure/collapse, nonunion, progressive arthritis, and/or pain. Prior to revision, all grafts exhibited collapse and subchondral lucencies. At the graft host interface, Safranin-O staining demonstrated substantial loss of sulfated glycosaminoglycans, Osteocalcin immunostaning was nearly absent, CD68 (indicating osteoclast activity) was predominantly exhibited, and CD4+ helper T cells as well as CD8+ cytotoxic T cells and NK cells-cell types commonly implicated in allogeneic organ transplant rejection-were found in high concentrations. TNF-α was present throughout the graft.


CONCLUSIONS
A histopathologic analysis of 8 retrieved, failed talar allografts was performed. Graft failure appeared to be primarily biologic, with an extensive loss of viable cartilaginous and osseous tissue at the graft-host interface. This study provides the first evidence of a potential CD4+ and CD8+ lymphocyte-mediated failure mechanism in fresh osteochondral allografts that were revised following collapse.


METHODS
Level IV, case series.
Department of Orthopaedic Surgery, Beaumont Health System, Royal Oak, MI, USA.
Ryan Joseph
RJ
Pomajzl
Department of Orthopaedic Research, Beaumont Health System, Royal Oak, MI, USA erin.baker@beaumont.edu.
Erin Ann
EA
Baker
Department of Orthopaedic Research, Beaumont Health System, Royal Oak, MI, USA.
Kevin Charles
KC
Baker
Department of Orthopaedic Research, Beaumont Health System, Royal Oak, MI, USA.
Mackenzie Marie
MM
Fleischer
Department of Orthopaedic Research, Beaumont Health System, Royal Oak, MI, USA.
Meagan R
MR
Salisbury
Department of Orthopaedic Research, Beaumont Health System, Royal Oak, MI, USA.
Dylan M
DM
Phillips
Department of Orthopaedic Surgery, Beaumont Health System, Royal Oak, MI, USA.
Paul Thomas
PT
Fortin
D064591:Allografts / Q000503:physiopathology*; D016025:Bone Transplantation / Q000379:methods*; D002357:Cartilage Diseases / Q000473:pathology*; D002358:Cartilage, Articular / Q000473:pathology*; D005500:Follow-Up Studies; D006801:Humans; D010020:Osteonecrosis / Q000503:physiopathology / Q000601:surgery*; D011446:Prospective Studies; D013628:Talus / Q000601:surgery*; D014184:Transplantation, Homologous / Q000379:methods*
collapse; failure; osteochondral allograft; talar allograft; talus