Article
Ball-in-socket medial conformity with posterior cruciate ligament retention neither limits internal tibial rotation and knee flexion nor lowers clinical outcome scores after unrestricted kinematically aligned total knee arthroplasty
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Authors
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Alexander Nedopil
- Adventist Health Lodi Memorial, Julius-Maximilians-Universität Würzburg, University of California, Davis, Lodi, United States
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Stephen Howell
- Department of Mechanical Engineering, University of California, Davis, Davis, United States
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Maury Hull
- Department of Mechanical Engineering, University of California, Davis, Davis, United States
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Maximilian Rudert
- Orthopädische Klinik, König-Ludwig-Haus, Orthopädisches Zentrum für Muskuloskelettale Forschung, Lehrstuhl für Orthopädie der Universität Würzburg, Würzburg, Germany
| Published: | October 23, 2023 |
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Outline
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Objectives: For a tibial insert with ball-in-socket medial conformity, PCL retention, and flat lateral articular surface (B-in-S MC+PCL), this study determined whether internal tibial rotation and knee flexion were limited and clinical outcome scores were lower during weight-bearing activities relative to an insert with intermediate (i.e. less than ball-in-socket) medial conformity (I MC+PCL). Figure 1 [Fig. 1]
Methods: Twenty-five patients were treated with bilateral unrestricted, caliper-verified kinematic alignment (KA) TKA with an I MC+PCL insert and B-in-S MC+PCL insert in opposite knees. Each patient performed weight-bearing deep knee bend, step-up, and chair rise under single-plane fluoroscopy. Analysis following 3D model-to-2D image registration determined internal tibial rotation. For each TKA, knee flexion was measured and patients completed clinical outcome scoring questionnaires.
Results: Internal tibial rotation did not differ between conformities during chair rise and step-up (p=0.3419 and 0.1030, respectively). During deep knee bend, internal tibial rotation between 90º and maximum flexion was 3º greater in the B-in-S MC+PCL group (18° vs 15º) (p=0.0290). Mean knee flexion (p=0.3115) and median FJS, OKS, and WOMAC scores (p=0.2100, 0.2154, and 0.4542, respectively) did not differ between conformities (Table 1 [Tab. 1])
Conclusion: An insert with ball-in-socket medial conformity, which maximizes AP stability, did not limit internal tibial rotation and knee flexion and did not lower patient-reported outcomes when implanted with unrestricted caliper-verified KA and PCL retention. These results suggest that surgeons treating patients interested in high-level and athletic activities could use ball-in-socket medial conformity and PCL retention to restore AP stability like the native knee.
