Is There A Difference In Uni- And Multi-compartmental Knee Arthroplasty Kinematics?

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1 Is There A Difference In Uni- And Multi-compartmental Knee Arthroplasty Kinematics? Toshifumi Watanabe, MD, PhD 1, Stefan Kreuzer, MD, MS 2, Jennifer Amanda Christopher, BS 3, Michael Conditt, PhD 3, Brian H. Park, MSc 4, Alex Iorgulescu 4, Nicholas J. Dunbar 4, Scott A. Banks, PhD 4. 1 Tokyo Medical and Dental University, Tokyo, Japan, 2 University of Texas Health Science Center, Houston, TX, USA, 3 MAKO Surgical Corp, Fort Lauderdale, FL, USA, 4 University of Florida, Gainesville, FL, USA. Disclosures: T. Watanabe: None. S. Kreuzer: 1; Smith & Nephew, Synvasive, Corin U.S.A.. 2; Corin U.S.A.; Stryker; Mako; Medtronic; Zimmer. 3B; Corin U.S.A.; Stryker; MAKO; Medtronic. 4; MAKO, Innovative Orthopedic Technologies. 5; MAKO, Synvasive, Corin U.S.A. J.A. Christopher: 3A; MAKO Surgical. M. Conditt: 3A; MAKO Surgical. B.H. Park: None. A. Iorgulescu: None. N.J. Dunbar: None. S.A. Banks: 1; DJO Surgical, MAKO Surgical. 3B; DJO Surgical. 5; DJO Surgical, Exactech, MAKO Surgical, MatOrtho, Medacta. Introduction: There is great interest to provide reliable and durable treatments for one- and two-compartment arthritic degeneration of the cruciate-ligament intact knee. One approach is to resurface only the diseased compartments with discrete unicompartmental components, retaining the undamaged compartment(s) and the cruciate ligaments. However, placing multiple small implants into the knee presents a greater surgical challenge than total knee arthroplasty, and it is not certain natural knee mechanics can be achieved. The goal of this study was to compare in vivo kinematics in knees that received either medial unicompartmental, medial unicompartmental plus patellofemoral, or bi-unicondylar knee arthroplasty. Methods: Fifteen patients with 25 knee arthroplasties consented to participate in an I.R.B. approved study of knee kinematics with a bicruciate-retaining multicompartmental knee arthroplasty system. All subjects presented with knee OA, intact cruciate ligaments, and coronal deformity ranging from 7 varus to 4 valgus. All subjects received multicompartmental knee arthroplasty using haptic robotic-assisted bone preparation an average of 13 months (6-29 months) before the study. Eleven knees received a medial unicompartmental knee arthroplasty (muni), six knees received a medial UKA and patellofemoral (muni+pf) arthroplasty, and eight knees received medial and lateral bi-unicondylar arthroplasty (biuni). Subjects averaged 62 years of age and had an average body mass index of 30. Their average combined Knee Society Pain/Function score was 106±27 preoperatively and 170±27 at the time of the study. Knee range of motion averaged -3 to 121 preoperatively and -1 to 130 at the time of the study. Knee motions were recorded using video-fluoroscopy while subjects performed step-up/down and kneeling activities (Fig. 1). The three-dimensional position and orientation of the implant components and bones were determined using model-image registration techniques. A composite 3D model of bone and implants was created from the preoperative plan for each femoral and tibial segment. The AP locations of the medial and lateral condyles were determined by computing a distance map between the femoral condyle and the tibial articular surface, and taking the centroid of all surface points within a 1mm-3mm band with the point of closest approach. Condylar translations were normalized to the antero-posterior depth of each medial and lateral tibial articular surface, so that contact at the posterior margin would be 0% and the anterior margin 100%. Results: Knee kinematics during maximum flexion kneeling showed tibial internal rotation (least in biuni knees, p<0.05), and posterior lateral condylar translation (Table 1). All knees showed tibial internal rotation and posterior femoral condylar translation with flexion during the step activity (Fig. 2). Knees with muni and muni+pf arthroplasty showed an offset in tibial internal rotation, but the same amount of total rotation as the biuni knees. The muni+pf knees showed more anterior translation of the lateral condyle as the knee reached full extension, but there were no significant pair-wise differences comparing translations between any groups. Discussion: Knees with tricompartmental total arthroplasty usually sacrifice one or both cruciate ligaments and also exhibit kinematics differing from the normal knee. Tibiofemoral rotations are almost always significantly less than the normal knee, and often the femur translates forward with flexion over some portion of the motion arc. In contrast, knees with accurately-placed uni- or bi-compartmental arthroplasty exhibited stable knee kinematics consistent with intact and functioning cruciate ligaments. The patterns of tibiofemoral motion were more similar to natural knees than commonly has been observed in knees with total knee arthroplasty. Knees with biuni exhibit comparable condylar translations and rotations during step activities, but less axial rotation in kneeling, when compared to muni and muni+pf knees, where the native lateral compartment is intact. Significance: In knees with one- or two-compartment degenerative disease and intact cruciate ligaments, it may be possible to retain more natural knee function using accurately placed multicompartmental knee arthroplasty components. With small exceptions, the kinematics of knees with partial arthroplasty of the medial, medial plus patellofemoral, or both condylar compartments do not differ in a functionally significant manner

2 Acknowledgments: References: Table 1. Knee kinematics during maximum flexion kneeling Kinematic parameter muni (n=11) muni + PF (n=6) biuni (n=8) Knee Flexion (deg) 128 ± ± ± 10 Tibial Internal Rot (deg) 19 ± 7 18 ± 5 10 ± 5* Medial Translation (%) 40 ± ± ± 10 Lateral Translation (%) 10 ± ± ± 10

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4 ORS 2014 Annual Meeting Poster No: 0845

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