Soft-tissue Driven Patient Specific Alignment in Total Knee Arthroplasty: Early Experience

Patient specific alignment (PSA) is a soft-tissue driven technique for total knee arthroplasty (TKA) which adjusts the bony cuts around a preserved soft-tissue envelope, minimizing soft-tissue releases. It has documented improved patient satisfaction and outcomes. Combining the mechanical alignment (MA) philosophy of neutral mechanical bony cuts and overall alignment, with the kinematic alignment (KA) philosophy of measured resection to restore the native joint line, the PSA bony cuts are made within an acceptable alignment boundary, allowing some deviation from mechanically neutral alignment in favor of a balanced knee. The joint line is oriented according to soft-tissue tension throughout range of motion (ROM), without altering the native hip-knee-ankle angle and overall limb alignment. The underlying assumption is that soft tissues do not contract in the concavity of a deformity, but may stretch on the convex side.

Utilizing navigation and computer software and eventually robotics, a soft-tissue tension curve is generated throughout ROM. Initial resections are planned, built on the foundation of KA, in order to create a balanced tension curve, but with resections performed within acceptable MA boundaries. Once the navigated tibial cut is completed, all remaining osteophytes are removed, an articulating soft-tissue tensor is placed with the patella reduced, and the final tension curve is generated again throughout ROM. Before cutting bone, the femoral resection plan is adjusted with regard to varus/valgus alignment, proximal/distal and anterior/posterior position, flexion/extension, and internal/external rotation in order to achieve a symmetrically balanced tension curve. Navigation then guides accurate femoral resections. We report our early experience, learning curve, technique, and associated pearls and pitfalls with PSA in 67 TKAs (64 patients, 37 females, 27 males) with mean age of 71 (R 55-90) implanted between 2/25/20 ad 8/3/21, utilizing the DePuy Attune Rotating Platform Tibial and Cruciate Retaining Femoral components, with posterior cruciate sacrifice.