The effect of storage medium tonicity on osteochondral autograft plug diameter.

PURPOSE: The purpose of this study was to investigate the effect of differing storage medium on osteochondral plug diameter.
METHODS: Four storage conditions were evaluated: air, hypotonic solution (sterile water), isotonic saline solution (0.9% sodium chloride), and hypertonic saline solution (3.0% sodium chloride). Four osteochondral plugs were acquired (4.5-mm harvesting system) from each of 10 fresh calf femurs and randomized to 1 of 4 storage media (N = 40). Micro-computed tomography was used to evaluate the precise diameter of each plug. After a time 0 scan, each plug was placed in a designated storage medium and rescanned at 3 time points over approximately 1 hour. A region of interest was identified from approximately 1 to 6 mm proximal to the tidemark. Custom software automatically calculated the diameter of each plug.
RESULTS: The time 0 plug diameter (mean ± 95% confidence interval) for all specimens was 4.66 ± 0.01 mm. There were no significant differences between any of the groups at the baseline scan. There were also no significant differences between the time 0 and subsequent scans of the unsubmerged specimens. However, all of the liquid solutions (hypertonic, isotonic, and hypotonic) resulted in a significant increase in diameter from their baseline scans (P < .05), indicating that a cause may be increased extracellular matrix fluid pressure.
CONCLUSIONS: Placing an osteochondral plug in a liquid solution increased the diameter of the subchondral bone. Size increase from the storage medium appeared to level off within 14 minutes after placement in solution. CLINICAL RELEVANCE: Increases in diameter of the plug may alter the ease of insertion of the graft, possibly increasing contact pressure on cartilage during plug implantation. Copyright Â