Approach to Inflammatory Arthritis – Knee Arthritis
– successful arthroplasty in rheumatoid knees is largely attributable to their low demand and limited rehab goals
– again, be aware that bone turnover may be higher in peri-articular bone and may compromise fixation
– all inflammatory arthropathies may have significant ligament and soft-tissue contractures and concomitant muliplanar deformity – be prepared to do significant soft tissue releases, ligament balancing, and be ready for the possibility that their will be residual instability requiring more constrained prosthesis.
– extensive ligament release may make for an overly large flexion gap where the collaterals are most slack – in extension, the collaterals tighten and stability is more readily achieved.
Strategies to deal with the flexion/extension mismatch – with normal extension gap, but large flexion gap
– release the PCL – although this might make it worse in that releasing the PCL tends to increase the flexion gap more than the extension gap. Nonetheless, it is probably easier to balance the knee with this gone.
– you can cut more off the distal femur and insert a bigger poly space – be aware that this elevates the joint line though!
– you can upsize the component and add posterior condyle augments to close down the flexion space – this will not change the joint line, but may require you to adjust all your components.