Despite the growing success for osteochondral allograft (OCA) transplantation in treating large articular cartilage lesions in multiple joints, associated revision and failure rates are still higher than desired. While immunorejection responses have not been documented, the effects of the host's immune responses on OCA transplantation failures have not been thoroughly characterized. The objective of this study was to systematically review clinically relevant peer-reviewed evidence pertaining to the immunology of OCAs to elucidate theragnostic strategies for improving functional graft survival and outcomes for patients undergoing OCA transplantation. This systematic review of Cochrane Central Register of Controlled Trials, the Cochrane Database of Systematic Reviews, MEDLINE, PubMed, and EMBASE suggests that host immune responses play key roles in incorporation and functional survival of OCA transplants. OCA rejection has not been reported; however, graft integration through creeping substitution is reliant on host immune responses. Prolonged inflammation, diminished osteogenic potential for healing and incorporation, and relative bioburden are mechanisms that may be influenced by the immune system and contribute to undesirable outcomes after OCA transplantation. Based on the safety and efficacy of OCA transplantation and its associated benefits to a large and growing patient population, basic, preclinical, and clinical osteoimmunological studies on OCA transplantation that comprehensively assess and correlate cellular, molecular, histologic, biomechanical, biomarkers, diagnostic imaging, arthroscopic, functional, and patient-reported outcome measures are of high interest and importance.

Background: Meniscal allograft transplantation (MAT) has been developed as a treatment for meniscal deficiency. Despite promising outcomes, there are no real-time methods to evaluate graft survivorship and predict functional outcomes. Hypothesis: Assessment of serum and urine biomarkers could be used to develop biomarker panels—prognostic (1- and 3-month postsurgical time points) and diagnostic (6-month time point)—based on strong associations with clinically relevant outcome metrics obtained 6 months after surgery. Study Design: Descriptive laboratory study. Methods: Twelve adult purpose-bred research hounds were included and underwent medial meniscal release to induce meniscal deficiency. Three months after meniscal release surgery, medial menisci were replaced with fresh-frozen meniscus (n = 4), fresh meniscus (n = 4), or fresh meniscotibial osteochondral allograft (n = 4) such that a spectrum of pain and functional outcomes could be anticipated. Serum and urine from all dogs were collected preoperatively and at 1, 3, and 6 months after MAT surgery. Dogs were assessed for pain-related and functional outcomes at the same time points. To develop a prognostic panel of biomarkers, biomarker data from the 1- and 3-month post-MAT surgery time points were used to model 6-month clinical outcomes. A diagnostic panel of biomarkers was developed using data from the 6-month post-MAT surgery to model 6-month clinical outcomes. Primary outcomes for pain and function were visual analog scale (VAS) and operated limb percentage total pressure index (%TPI), respectively. Using random subject effects, linear mixed models were used to develop prognostic biomarker panels, and linear fixed-effect models were used to develop diagnostic biomarker panels, with variance explained for each panel reported ( R2) along with individual biomarker relationships. Results: Across prognostic biomarker panels, a panel including serum IL-6, IL-8, IL-10, and IL-18 was fit for the primary functional outcome, operated limb %TPI ( R2 = 0.450), whereas a panel including serum CTX-II and OPG was fit for the primary pain-related outcome, VAS ( R2 = 0.516). Across diagnostic biomarker panels, a panel including serum MMP-1 and MMP-3 and urine PINP and TIMP-1 was fit for %TPI ( R2 = 0.863). Separately, a panel including urine CTX-I, CTX-II, IL-8, MMP-2, and TIMP-1 was fit as diagnostic biomarkers for the VAS for pain ( R2 = 0.438). Conclusion: Biomarker panels of selected serum and/or urine proteins can model clinically relevant metrics for function and pain in a preclinical model of MAT. Clinical Relevance: Biomarker panels could be used to provide real-time diagnostic and prognostic data regarding outcomes after MAT.

Osteochondral allograft (OCA) transplantation has been largely successful in treating symptomatic articular cartilage lesions; however, treatment failures persist. While OCA biomechanics have been consistently cited as mechanisms of treatment failure, the relationships among mechanical and biological variables that contribute to success after OCA transplantation have yet to be fully characterized. The purpose of this systematic review was to synthesize the clinically relevant peer-reviewed evidence targeting the biomechanics of OCAs and the impact on graft integration and functional survival toward developing and implementing strategies for improving patient outcomes. The Cochrane Central Register of Controlled Trials, the Cochrane Database of Systematic Reviews, MEDLINE, PubMed, Cumulative Index to Nursing and Allied Health (CINAHL), Google Scholar, and EMBASE were searched to identify articles for systematic review. This review of relevant peer-reviewed literature provided evidence that the biomechanics related to OCA transplantation in the knee have direct and indirect effects on functional graft survival and patient outcomes. The evidence suggests that biomechanical variables can be optimized further to enhance benefits and mitigate detrimental effects. Each of these modifiable variables should be considered regarding indications, patient selection criteria, graft preservation methodology, graft preparation, transplantation, fixation techniques, and prescribed postoperative restriction and rehabilitation protocols. Criteria, methods, techniques, and protocols should target OCA quality (chondrocyte viability, extracellular matrix integrity, material properties), favorable patient and joint characteristics, rigid fixation with protected loading, and innovative ways to foster rapid and complete OCA cartilage and bone integration to optimize outcomes for OCA transplant patients.