Morphologic changes in fresh-frozen meniscus allografts over 1 year: a prospective magnetic resonance imaging study on the width and thickness of transplants.

BACKGROUND

Little is known about morphologic changes in the remodeling period after human meniscal allograft transplantation (MAT).

HYPOTHESIS

The gross structure of meniscal transplants may be altered significantly in width and thickness during early remodeling periods.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

Thirty-one patients who underwent MAT (9 medial and 22 lateral menisci) between 2008 and 2009 were prospectively evaluated by serial magnetic resonance imaging scans 2 days, 6 weeks, and 3, 6, and 12 months after surgery. At each time point, the width and thickness of the menisci were measured. The relative degree of shrinkage after 1 year was categorized as minimal (<10%), mild (10%-25%), moderate (25%-50%), or severe (>50%). The Lysholm score and Tegner activity level were used for clinical outcome scales.

RESULTS

More apparent changes were observed at mid-body rather than at the posterior horn. Meniscal width at the mid-body decreased to 89% (P < .01), whereas thickness increased to 115% (P < .01) at 12 months. Shrinkage was observed for 3 months after MAT, but there were no significant changes thereafter. The thickness of the meniscal peripheral rim did not change before 3 months but increased afterward, for up to 1 year. Of the 31 patients, 20 (64.5%) had minimal shrinkage, 6 (19.4%) had mild shrinkage, 5 (16.1%) had moderate shrinkage, and none had severe shrinkage over 1 year. In the 5 cases of moderate shrinkage, the reduction occurred progressively for 1 year. However, the relative morphologic changes did not correlate with clinical outcome scales at postoperative 1 and 2 years (P > .05). The preoperative alignment deviation, cartilage status (Outerbridge grade), age, gender, amount of extrusion, and time from previous meniscectomy did not affect the degree of shrinkage.

CONCLUSION

Gross morphologic alterations, as determined by width and thickness, were observed during the first postoperative year. Substantial shrinkage at the mid-body occurred progressively for 1 year in 16.1% of the cases. No association was found between morphologic changes and short-term clinical outcomes.