Measurement of Tibial Orientation Helps Select the Optimal Insert Thickness to Personalize PCL Tension in a Medial Ball-in-Socket TKA

Abstract

As the conformity of a medial ball-in-socket total knee arthroplasty (TKA) provides intrinsic anterior-posterior (A-P) stability, surgeons cannot rely on the manual examination of sagittal laxity to identify the optimal insert thickness. Instead, the present study determined whether measuring tibial axial orientation in extension and 90° flexion with an insert goniometer could identify the optimal thickness that, when implanted, provides high postoperative function. In twenty-two patients that underwent unrestricted caliper-verified kinematic alignment (KA) with a PCL retaining implant, two surgeons measured tibial orientation in extension and 90° flexion with 10, 11, 12, and 13 mm thick insert goniometers. Each TKA had one insert thickness that restored either the maximum external tibial orientation in extension, the maximum internal tibial orientation at 90° flexion, or both relative to 1 mm thinner and thicker inserts. In addition, the 6-month median [interquartile range] Forgotten Joint Score of 73 (54–87) and Oxford Knee Score of 42 (38–45) indicated high satisfaction and function. In conclusion, surgeons using a medial ball-in-socket TKA design can measure external tibial orientation in extension and internal tibial orientation at 90° flexion with an insert goniometer. Furthermore, implanting an insert with the thickness that provided the maximum orientation values resulted in high postoperative function, thereby personalizing PCL tension.

Similar Recovery Rate for Patients Aged between 50 and 89 Years That Go Home on the Surgery Day and Self-Administer Their Rehabilitation after Kinematically Aligned Total Knee Arthroplasty

“…We excluded those with prior fractures of the knee, inflammatory or septic arthritis, or lower extremity neurologic disorders. Each was treated with cemented components using an insert with a medial ball-in-socket with flat lateral articulation conformity, implanted with posterior cruciate ligament retention (GMK SpheriKA, Medacta International, Castel San Pietro, Switzerland, www.medacta.com, accessed on 5 November 2023) [12][13][14][15].…”

“…Best-fitting the anatomic baseplate parallel to the cortical rim of the tibial resection set I-E rotation [20]. The optimum insert thickness satisfied the criteria of maximizing passive external tibial orientation in extension and internal tibial orientation in 90 • flexion as measured by an insert goniometer [14]. After making the femoral and tibial resections, the posterior medial and lateral femur were injected with 20 cc of 0.2% ropivacaine using a 20-gauge spinal needle to reduce injury to neurovascular structures.…”