Hasan Raza Mohammad1, Stefano Campi2, David Murray2, Stephen Mellon2. 1. Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences (NDORMS), University of Oxford, Oxford, UK. Electronic address: hasanmohammad@doctors.org.uk. 2. Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences (NDORMS), University of Oxford, Oxford, UK.
Abstract
BACKGROUND: Tibial plateau fracture is an important complication of cementless Oxford unicompartmental knee replacement. The press fit between the keel and the bone's keel slot is responsible for primary fixation and also contributes to fracture risk. This study investigates whether the fracture risk could be reduced without compromising primary fixation, by using different instruments to widen the keel slot. METHODS: Keel slots were made in polyurethane blocks (n = 60) using the standard keel cut saw blade or a new blade that was 0.2 mm wider, with adjuvant use of the cemented pick or a prototype rasp. A tibial component was pushed into and pulled out of the slots using a Dartec materials testing machine. It was assumed that the 'push-in' force was related to the risk of fracture and 'pull-out' force was related to fixation. Reproducibility studies with 10 different tibial components were undertaken. RESULTS: The new blade required significantly lower push-in forces than the standard blade (789 N SD 130, 1411 N SD 180; P < 0.001), but the pull-out forces were not different (240 N SD 47, 230 N SD 56; P > 0.999). With the standard blade the pick decreased the push-in (818 N SD 318; P < 0.001) and pull-out (128 N SD 58; P < 0.001) forces, but the rasp had no effect. With the new blade the pick had no effect, but the rasp increased the push-in force (1390 N SD 202; P < 0.001). CONCLUSIONS: This study suggests the fracture risk will be reduced with the new blades, with no compromise in fixation. If the new blades are used routine use of the cemented pick appears to be of no benefit.
BACKGROUND: Tibial plateau fracture is an important complication of cementless Oxford unicompartmental knee replacement. The press fit between the keel and the bone's keel slot is responsible for primary fixation and also contributes to fracture risk. This study investigates whether the fracture risk could be reduced without compromising primary fixation, by using different instruments to widen the keel slot. METHODS: Keel slots were made in polyurethane blocks (n = 60) using the standard keel cut saw blade or a new blade that was 0.2 mm wider, with adjuvant use of the cemented pick or a prototype rasp. A tibial component was pushed into and pulled out of the slots using a Dartec materials testing machine. It was assumed that the 'push-in' force was related to the risk of fracture and 'pull-out' force was related to fixation. Reproducibility studies with 10 different tibial components were undertaken. RESULTS: The new blade required significantly lower push-in forces than the standard blade (789 N SD 130, 1411 N SD 180; P < 0.001), but the pull-out forces were not different (240 N SD 47, 230 N SD 56; P > 0.999). With the standard blade the pick decreased the push-in (818 N SD 318; P < 0.001) and pull-out (128 N SD 58; P < 0.001) forces, but the rasp had no effect. With the new blade the pick had no effect, but the rasp increased the push-in force (1390 N SD 202; P < 0.001). CONCLUSIONS: This study suggests the fracture risk will be reduced with the new blades, with no compromise in fixation. If the new blades are used routine use of the cemented pick appears to be of no benefit.
Authors: Lena Keppler; Steffen Klingbeil; Alexander Martin Keppler; Johannes Becker; Christian Fulghum; Björn Michel; Kilian Voigts; Wolfgang Reng Journal: BMC Musculoskelet Disord Date: 2022-06-21 Impact factor: 2.562
Authors: Hasan R Mohammad; James A Kennedy; Stephen J Mellon; Andrew Judge; Christopher A Dodd; David W Murray Journal: J Orthop Surg Res Date: 2020-01-31 Impact factor: 2.359