Osteochondral Autograft Plugs versus Paste Graft: Morselization Increases Chondral Matrix Production.

Objective: Patients undergoing articular cartilage paste grafting have been shown in studies to have significant improvement in pain and function in long-term follow-ups. We hypothesized that impacting of osteochondral autografts results in higher chondrocyte matrix production versus intact osteochondral autograft plugs.

Design: This institutional review board-approved study characterizes the effects of impacting osteochondral plugs harvested from the intercondylar notch of 16 patients into a paste, leaving one graft intact as a control. Cell viability/proliferation, collagen type I/II, SOX-9, and aggrecan gene expression via qRT-PCR (quantitative reverse transcription-polymerase chain reaction) were analyzed at 24 and 48 hours. Matrix production and cell morphology were evaluated using histology.

Results: Paste samples from patients (mean age 39.7) with moderate (19%) to severe (81%) cartilage lesions displayed 34% and 80% greater cell proliferation compared to plugs at 24 and 48 hours post processing, respectively ( = 0.015 and = 0.021). qRT-PCR analysis yielded a significant ( = 0.000) increase of aggrecan, SOX-9, collagen type I and II at both 24 and 48 hours. Histological examination displayed cell division throughout paste samples, with accumulation of aggrecan around multiple chondrocyte lacunae.

Conclusions: Paste graft preparation resulted in increased mobility of chondrocytes by matrix disruption without loss of cell viability. The impaction procedure stimulated chondrocyte proliferation resulting in a cellular response to reestablish native extracellular matrix. Analysis of gene expression supports a regenerative process of cartilage tissue formation and contradicts long-held beliefs that impaction trauma leads to immediate cell death. This mechanism of action translates into clinical benefit for patients with moderate to severe cartilage damage.