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The effect of wedge and slope angles on knee contact pressure and kinematics in medial opening wedge high tibial osteotomy Black, Marianne Susan


Introduction: Medial opening-wedge high tibial osteotomy (HTO) is a surgical procedure intended to shift load from the medial to the lateral compartment of the knee. The 10-year success rates of HTO are variable. One factor affecting success may be how effectively the procedure corrects alignment in the coronal plane (wedge angle) and sagittal plane (slope angle). The objective of this study was to determine the effect of changing tibial slope for a range of tibial wedge angles in medial opening wedge HTO on knee joint contact pressure location and kinematics during continuous loaded flexion/extension. Methods: The accuracy and repeatability of Novel pliance capacitive pressure sensors were measured under relevant compressive forces using a materials testing system (Instron ElectroPuls E10000). Seven male cadaveric knee specimens (mean age 62 (14)) cycled through simulated squatting. Tibiofemoral and patellofemoral kinematics were measured using an infrared (Optotrak Certus) motion tracking system. Contact pressure was measured using capacitive pressure sensors (Novel Pliance). This assessment was repeated for seven clinically relevant combinations of wedge and slope. Results: The capacitive pressure sensors had a maximum error of 13 ± 2.1% when applying force across the entire sensor. Significant differences (p<0.05) were found between all tibiofemoral and patellofemoral kinematic parameters and contact pressure parameters measured for all wedge and slope combinations. An increase in slope from neutral to 5° resulted in 7mm of anterior translation of the centre of pressure on the medial compartment for a 15° wedge (p<0.000). Increasing the wedge angle resulted in anterior translation of the tibia relative the femur (p<0.000). Increasing the wedge angle to 7.5° resulted in a reduction in the proportion of load in the medial compartment by 17% (p<0.001). Conclusion: Knee kinematics and contact pressure are altered as a result of changes to the wedge and slope of the osteotomy. There is a large focus on the effect of the coronal plane correction in HTO, but the sagittal plane correction also plays an important role in contact pressure at the tibiofemoral joint.

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