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Patella dislocation altered load distribution on medial and lateral compartments
Load distribution on the medial and lateral compartments were altered with dislocation of the patella and subsequent lateralization of the extensor mechanism during total knee arthroplasty, according to study results.
Researchers used intraoperative load sensors to record medial and lateral compartment loads in 56 well-balanced total knee arthroplasties. With the patella in four different positions, including dislocated and not everted, dislocated and everted, located, and located and secured with two retinacular sutures, researchers recorded loads in full extension, relaxed extension and at 45° and 90° of flexion at full gravity-assisted flexion.
Results showed lower loads in the medial compartment when the patella was dislocated, while higher loads were observed when the patella was relocated in the femoral trochlea with and without provision closure of the medial retinaculum. Regardless of the position of the extensor mechanism, researchers found the highest medial compartment loads when the knee was held in full extension. Researchers also noted a substantial reduction of medial compartment loads from full extension to relaxed extension.
Throughout range of motion, a bimodal loading pattern was found in the lateral compartment, as well as a significant difference in lateral compartment loads with different patellar positions at each flexion angle, according to study results.
Researchers found a difference in load differential when the patella was held in the trochlea than when the patella was dislocated. Although the loads throughout range of motion shifted from the medial to the lateral compartment regardless of the patella position, results showed a higher shift of loads to the lateral compartment when the patella was dislocated.
According to study results, the absolute load differential between compartments detected with a reduced patellofemoral articulation differed from that observed with a dislocated patella. Researchers noted significantly higher absolute load differentials with a dislocated patella vs. a reduced patellofemoral articulation at 45° and 90° of flexion.
When the knee was in full extension, total loads of the knee were highest, according to study results. Researchers also found the patellar position did not affect the sum of loads when the knee was held at full and relaxed extension. – by Casey Tingle
Disclosures: Schnaser reports no relevant financial disclosures. Please see the full study for a list of all other authors’ relevant financial disclosures.