HOW EFFECTIVE IS THE “GUIDED MOTION” OF MODERN TOTAL KNEE REPLACEMENTS?

BH van Duren; H Pandit; S Tilley; M Price; HS Gill; DW Murray; NP Thomas

doi:10.1302/1358-992X.94BSUPP_XXIX.BASK2011-102

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Knee

HOW EFFECTIVE IS THE “GUIDED MOTION” OF MODERN TOTAL KNEE REPLACEMENTS?

British Association for Surgery of the Knee (BASK)

BH van Duren
H Pandit
S Tilley
M Price
HS Gill
DW Murray
NP Thomas

HOW EFFECTIVE IS THE “GUIDED MOTION” OF MODERN TOTAL KNEE REPLACEMENTS?

van Duren B, Pandit H, Tilley S, et al. HOW EFFECTIVE IS THE “GUIDED MOTION” OF MODERN TOTAL KNEE REPLACEMENTS?. Orthop Procs. 2012;94-B(SUPP_XXIX):102-102. doi:10.1302/1358-992X.94BSUPP_XXIX.BASK2011-102

van Duren, BH, et al. “HOW EFFECTIVE IS THE “GUIDED MOTION” OF MODERN TOTAL KNEE REPLACEMENTS?.” Orthopaedic Proceedings, vol. 94-B, no. SUPP_XXIX, 2012, pp. 102-102., https://doi.org/10.1302/1358-992X.94BSUPP_XXIX.BASK2011-102

van Duren, B., Pandit, H., Tilley, S., Price, M., Gill, H., Murray, D., & Thomas, N. (2012). HOW EFFECTIVE IS THE “GUIDED MOTION” OF MODERN TOTAL KNEE REPLACEMENTS?. Orthopaedic Proceedings, 94-B(SUPP_XXIX), 102-102. https://doi.org/10.1302/1358-992X.94BSUPP_XXIX.BASK2011-102

van Duren, B., Pandit, H., Tilley, S., Price, M., Gill, H., Murray, D. et al. (2012) “HOW EFFECTIVE IS THE “GUIDED MOTION” OF MODERN TOTAL KNEE REPLACEMENTS?.” Orthopaedic Proceedings, 94-B(SUPP_XXIX), pp. 102-102. Available at: https://doi.org/10.1302/1358-992X.94BSUPP_XXIX.BASK2011-102

van Duren, BH, H Pandit, S Tilley, M Price, HS Gill, DW Murray, and NP Thomas. “HOW EFFECTIVE IS THE “GUIDED MOTION” OF MODERN TOTAL KNEE REPLACEMENTS?.” Orthopaedic Proceedings 94-B, no. SUPP_XXIX (2012): 102-102. https://doi.org/10.1302/1358-992X.94BSUPP_XXIX.BASK2011-102

van Duren B, Pandit H, Tilley S, Price M, Gill H, Murray D, et al. HOW EFFECTIVE IS THE “GUIDED MOTION” OF MODERN TOTAL KNEE REPLACEMENTS?. Orthop Procs. 2012 Jul 1;94-B(SUPP_XXIX):102-102. https://doi.org/10.1302/1358-992X.94BSUPP_XXIX.BASK2011-102

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Abstract

Introduction

Traditional TKR designs exhibit abnormal and unpredictable kinematics: with posterior subluxation in extension and anterior slide with flexion. These can contribute to restricted knee flexion and reduced quadriceps efficiency. Newer designs attempt to provide “guided motion” with the aim of mimicking normal knee kinematics. The Journey (Smith & Nephew) BCS TKR incorporates both an anterior and a posterior cam/post mechanism while Triathlon PS TKR (Stryker) incorporates a posterior cam/post mechanism. This study compares the in-vivo kinematics of these two designs and compares it with normal knee.

Methods

Knee kinematics of 10 patients with Journey-BCS TKR and 11 patients with Triathlon PS TKR; all with excellent clinical outcome (average age: 65) were analysed. Patients underwent fluoroscopic assessment of the knee during a step-up and deep knee bend exercise. 2D fluoroscopic images were recorded. Data was analysed for patella tendon angle (PTA) and contact points using a 3D model fitting technique. This data was compared to normal knee kinematics (n=20).

Results

The average maximum KFA achieved by the implant groups was 125° (Journey), 114° (Triathlon) and 141° for the normal group. The average angle of anterior cam/post engagement was 13° knee flexion angle (KFA) and the posterior cam/post mechanism at 45° KFA for Journey and 63° for Triathlon. For the Journey, in the step-up exercise both medial and lateral condylar contact points translated anteriorly with extension. For the lunge both condylar contact points translated posteriorly. Triathlon knees exhibited a medial pivot motion. The PTA for Journey showed a similar trend to normal knees.

Conclusions

In the Journey TKR, both anterior and posterior cam-post mechanisms engaged and helped produce consistent femoral translation throughout knee flexion without paradoxical movement. This was similar to normal knee kinematics albeit with slight offset. The Triathlon produced posterior translation but did not completely eliminate paradoxical movement.