Effect of medial opening wedge high tibial osteotomy on intraarticular knee and ankle contact surface pressures
Suero EM, Hawi N, Sabbagh Y, Westphal R, Wahl FM, Krettek C, Citak M, Liodakis E
Objective: High tibial osteotomy (HTO) is a commonly used surgical technique for treating moderate osteoarthritis (OA) of the medial compartment of the knee by shifting the center of force towards the lateral compartment. Previous studies have documented the effects of HTO on the biomechanics of the knee. However, the effects of the procedure on the contact pressures within the ankle joint have not been well described.
Methods: A medial, L-shaped opening wedge high tibial osteotomy was performed on eight cadaveric lower leg specimens. A previously developed stainless-steel device with integrated load cell was used to axially load the leg. Pressure-sensitive sensors were used to measure intraarticular contact pressures. Intraoperative changes in alignment were monitored in real time using computer navigation. Baseline measurements were taken for each leg in its native alignment. An axial loading force was applied to the leg in the caudal-craneal direction and gradually ramped up from 0 to 550 N. Intraarticular contact pressure (kg) and contact area (mm2) data were collected.
Multiple linear regression models were constructed to estimate changes in contact pressure and contact surface area in the medial and lateral compartments of the knee and in the ankle, in response to 5º, 10º and 15º changes in mechanical alignment.
Results and conclusion: Small changes in mechanical alignment (5º) resulted in a nonsignificant 11.7% increase in lateral compartment contact pressures compared to the intact leg (P>0.05). However, larger changes in alignment correction resulted in a 76.4% increase in contact pressures at 10º and a 152.9% increase at 15º (P<0.05). In the medial compartment, a 27.1% increase in pressure at 5º was followed by a 21.3% decrease at 10º and a 49.4% decrease at 15º. These changes were not statistically significant (P >0.05).
The intraarticular surface contact area did not significantly change in the lateral compartment (P>0.05). In the medial compartment, a 5º change in alignment resulted in a 9.4% increase in contact area (P<0.05). A change in alignment of 10º resulted in a 6.2% decrease in contact area (P>0.05), while a 15º change in alignment resulted in a significant 28.1% decrease in contact area (P<0.05). A 5º change in mechanical alignment did not significantly alter intraarticular ankle pressures (P>0.05). However, larger corrections decreased contact pressures by 27.0% at 10º (P<0.05) and by 23.6% at 15º (P>0.05).
Significant reductions in contact area were observed after each step of alignment correction: 12.3% at 5º (P<0.05); 21.6% at 10º (P<0.05); and 26.5% at 15º (P<0.05).
We conclude that small valgus realignment of the proximal tibia does not significantly alter the biomechanics of the ankle. However, moderate-to-large changes in proximal tibial alignment result in significantly decreased tibiotalar contact surface area and in changes in intraarticular ankle pressures.
Deutscher Kongress für Orthopädie und Unfallchirurgie (DKOU 2014). Berlin, 28.-31.10.2014. Düsseldorf: German Medical Science GMS Publishing House; 2014. DocWI43-625
Published: October 13, 2014
© 2014 Suero et al.
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