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Load bearing at the menisco-femoral joint: an in vitro study in the canine knee (SS-22)

      The purpose of this study was to determine the contact areas (CA) and local contact stresses (LCS) at the canine menisco-femoral joint during ROM, and to determine the influence of a partial or total meniscectomy. Materials: Both knees of 3 hound-type canines were tested in a universal testing machine, configured for an axial-load of 90–120 N. Measurement of CA and LCS was done at 30°, 50°, and 70° and with intact menisci, after partial meniscectomy, and after total meniscectomy. Pressure distribution was estimated using pressure sensitive film inserted above the menisci. Results: Medial meniscus at 50°: the average CA decreased from 2.1 cm2 in the intact knee, to 1.6 cm2 after partial meniscectomy, to 0.5 cm2 after total meniscectomy; the average LCS increased from 1.3 MPa in the intact knee, to 1.7 MPa after partial meniscectomy, to 2.1 MPa after total meniscectomy. Medial meniscus at 30°: the average CA decreased from 1.7 cm2 in the intact knee, to 1.3 cm2 after partial meniscectomy, to 0.4 cm2 after total meniscectomy; the average LCS increased from 1.2 MPa in the intact knee, to 1.5 MPa after partial meniscectomy, to 2.5 MPa after total meniscectomy. Medial meniscus at 70°: the average CA decreased from 2.4 cm2 in the intact knee, to 1.7 cm2 after partial meniscectomy knee, to 0.5 cm2 after total meniscectomy; the average LCS remained at 1.7 MPa in the intact knee and after partial meniscectomy, but increased to 2.3 MPa after total meniscectomy. Lateral meniscus at 50°: the average CA decreased from 3.3 cm2 in the intact knee, to 2.4 cm2 after partial meniscectomy knee, to 0.7 cm2 after total meniscectomy; the average LCS remained at 1.5 MPa in the intact knee and after partial meniscectomy, but increased to 2.9 MPa after total meniscectomy. Lateral meniscus at 30°: the average CA decreased from 3.0 cm2 in the intact knee, to 2.3 cm2 after partial meniscectomy, to 0.5 cm2 after total meniscectomy; the average LCS remained at 1.3 MPa in the intact knee and after partial meniscectomy, but increased to 2.4 MPa after total meniscectomy. Lateral meniscus at 70°: the average CA decreased from 3.2 cm2 in the intact knee, to 2.4 cm2 after partial meniscectomy, to 0.8 cm2 after total meniscectomy; the average LCS increased from 1.4 MPa in the intact knee, to 1.6 MPa after partial meniscectomy, to 2.9 MPa after total meniscectomy. These differences were statistically significant (P < .05). Conclusions: Partially excised menisci offer a sufficient “spacer effect” to protect the femoral cartilage. The contact area and local contact stress differ minimally, both in the intact knee and after partial meniscectomy, when tested with low loads during physiologic gait. A dramatic decrease of contact area followed by an increase of local contact stress was noted after total meniscectomy.