Quantitative magnetic resonance imaging detects changes in meniscal volume in vivo after partial meniscectomy.

Background: Quantifying changes in meniscal volume in vivo before and after partial meniscectomy (PM) could help elucidate the mechanisms involved in osteoarthritis development after meniscal injury and its surgical treatment. Purpose/

Hypothesis: To determine whether quantitative magnetic resonance imaging (qMRI) can detect the immediate reduction in meniscal volume created by PM, while ruling out changes in unresected structures. We hypothesized that qMRI would be reliable for determining meniscal volume within the repeated images of unresected menisci. Additionally, we expected no significant difference in volume between the uninjured menisci of the injured knees and the same menisci of the uninjured knees.

Study Design: Cohort study (Diagnosis); Level of evidence, 2.

Methods: Ten subjects with meniscal tears were evaluated with 3-T MRI before and after arthroscopic PM. Manual segmentation was used to create models of the menisci and to determine the preoperative and postoperative meniscal volumes for each subject. The responsiveness and reliability of qMRI for determining meniscal volume in vivo were evaluated using these measurements. We expected a decrease in volume of the resected menisci, but not in the uninjured menisci, after surgery.

Results: The mean preoperative volume of the injured menisci was significantly greater than the mean postoperative volume (2896 +/- 277 vs 2480 +/- 277 mm(3); P = .000). There was no significant difference between the mean preoperative and postoperative volumes of the uninjured menisci (2687 +/- 256 vs 2694 +/- 256 mm(3); P = 1.000).

Conclusion: Manual segmentation demonstrated a significant reduction in the volume of the surgically resected menisci after PM, but no significant change in the volume of unresected meniscal tissue, indicating that the manual segmentation method is responsive.

Clinical Relevance: This approach offers a novel, reliable method to study the relationship between the volume of meniscal tissue removed during PM and subsequent patient outcomes during long-term clinical studies.