In vivopatellar kinematics during total knee arthroplasty

Abstract

Patellar maltracking after total knee arthroplasty often results in complications, including anterior knee pain, instability and impingement, and is therefore better resolved intraoperatively. Many factors can affect patellar kinematics during knee replacement, including component position, implant design, joint alignment, and soft tissue tensions. However, to our knowledge, the impact of arthroplasty on patellar kinematics has not been previously reported in vivo. A computer-assisted surgery (CAS) system was developed to measure the pre-arthroplasty patellar kinematics, display the distance between this path and the surface of the planned femoral component, and compare the post-arthroplasty path to the pre-arthroplasty path. Three surgeons from three centers used this CAS system to measure the in vivo pre-and post-arthroplasty kinematics of 18 patients. There was a small, but consistent, proximal shift in the tibial joint lines (mean: 4.2 mm), resulting in pseudo patella-baja, i.e., relatively more distal contact of the patella on the femoral component. This led to significant changes in proximodistal and anteroposterior patellar positioning as well as patellar flexion following arthroplasty (p50.008). Mediolateral shift, tilt and internal/external spin had the greatest magnitudes of change (mean: 4.1 mm, 4.6 and 4.6 , respectively) relative to their mean pre-arthroplasty ranges (averaging 2.1 mm, 5.8 and 5.8 , respectively); however, these changes were distributed almost equally medially and laterally, indicating no surgical bias in any one direction. Female patients had more lateral tilt on average than male patients throughout flexion (p50.004 post-arthroplasty, p50.03 prearthroplasty, in later flexion), as well as other kinematic differences; there may therefore be potential for improving overall kinematic results by focusing on gender differences during research, design and surgery. This study demonstrated the feasibility of using a CAS system to measure patellofemoral kinematics. Intraoperative awareness of patellar tracking, including knowledge of the tibiofemoral joint line, could have an impact on the surgical plan and thereby improve the postoperative outcome.

Computer‐assisted patellar resection system: Development and insights

“…Since the use of a bone screw to attach the marker array to the bone was considered undesirable due to the time required and the potential to cause fracture, other attachment methods should be sought out. Although patellar bone screws were used to attach marker arrays in kinematic studies [17][18][19] and are commonly used to attach marker arrays to other bones, concerns over the risk of fracture in thinner patellae would prevent widespread use. Use of a commercially available patellar marker array allowed us to test the feasibility of the system, but the attachment will need to be improved before clinical implementation.…”

Computer-assisted patellar resection for total knee arthroplasty

“…A drawback of the current system is that it uses a bone screw to attach the baseplate. Patellar bone screws have been used clinically in kinematic studies [16]; however, a non-invasive attachment mechanism, which is currently under development, would increase acceptance of the system.…”

“…A marker array was then attached to the baseplate such that the three markers faced the localizer when the patella was everted. The baseplate and marker array system had been used clinically with the Praxim system to study patellar kinematics [16]. At the end of each cadaveric experiment, the metal marker array base was replaced with an acrylic base having the same dimensions, such that the base appeared in the postoperative CT scans without creating metal artefacts.…”

“…The flat, arrow-shaped baseplate portion of the patellar marker array, with three shallow spikes on the bottom [11,16], was screwed securely into the bone using a screw 3 mm in diameter and 9 mm long positioned at the center of the patellar anterior surface. A marker array was then attached to the baseplate such that the three markers faced the localizer when the patella was everted.…”

Patellaposition und Patellofemoralarthrose nach unikompartimentellem Kniegelenkersatz

“…Sowohl Veränderungen der Patellaverkippung und/oder lateralisation können potenti ell zu einem vorderen Knieschmerz oder einem Impingement nach endoprotheti scher Versorgung führen [3].…”