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Abstract Presented at the 29th Annual Meeting of the Arthroscopy Association of North America| Volume 26, ISSUE 6, SUPPLEMENT , e18, June 01, 2010

Contact Area and Pressure Changes in the Medial Compartment of the Knee in Horizontal Cleavage Tears of the Medial Meniscus (SS-36)

      Introduction

      Horizontal meniscus tears are challenging and the surgeon has to decide whether to repair, resect either of the upper or lower leaf of the tear, or do a segmental meniscectomy. There is currently no biomechanical data to support either method of treatment. We present a human cadaveric biomechanical study to investigate the changes in the contact area and pressure distribution at the medial tibial plateau of the knee, following the management of a simulated horizontal cleavage tear.

      Methods

      7 fresh frozen human cadaveric knees are used. A medial parapatellar arthrotomy is made to expose the medial compartment of the knee. A contoured template of a pressure-sensitive film is placed between the meniscus and the surface of the medial tibial plateau, to capture changes in contact area and pressure. A compression load of 740N and 1100N is applied and maintained for 5 seconds, before unloading. The medial compartment is divided into 13 Regions of Interest; 7 beneath the medial meniscus (M1 to M7), 3 in a transition zone (T1 to T3), and 3 in the exposed surface not covered by the meniscus (E1 to E3). A densitometer is used to record the intensity of the color change, indicative of the mean applied pressure. Each template is also digitized and the average contact area calculated. A horizontal cleavage tear of the medial meniscus is created. The specimens are loaded and imprints taken under the following groups: 1) horizontal cleavage tear alone, 2) repair with two vertical mattress sutures, 3) meniscectomy of the upper leaf, 4) meniscectomy of the lower leaf, and 5) segmental meniscectomy of the cut region.

      Results

      The mean total contact area measured in the medial compartment after each experiment showed no significant change (p=0.68) when compared to the intact condition. In the presence of a horizontal cleavage tear, there is no significant change in the location of the contact area and mean contact pressure, even after repair with sutures. Following upper leaf meniscectomy, there is an increase in the mean pressure by 57% in the ROI of M4 and M5 (Scheffe, p=0.19). Between upper and lower leaf meniscectomies, upper leaf meniscectomy leads to a significant increase in pressure in ROI M4 by about 100% (Scheffe, p<0.001), and in ROI M5 by about 130% (Scheffe, p<0.001). Lower leaf meniscectomy leads to a 2 times increase in pressure in ROI M6 at the posterior horn of the medial meniscus (Scheffe, p=0.003). Segmental meniscectomy leads to a shift in the contact area, and increases the mean contact pressure by 3.5 times in ROI E2 and T2

      Conclusion

      This study indicates that segmental meniscectomy results in more direct unprotected cartilage-to-cartilage contact. The best treatment for a horizontal cleavage tear of the meniscus will be to repair it. If repair is not possible, a meniscectomy of the lower leaf of the tear will be the next best alternative.