TY - JOUR
T1 - Improved quadriceps' mechanical advantage in single radius TKRs is not due to an increased patellar tendon moment arm
AU - Ward, T. R.
AU - Pandit, H.
AU - Hollinghurst, D.
AU - Moolgavkar, P.
AU - Zavatsky, A. B.
AU - Gill, H. S.
AU - Thomas, N. P.
AU - Murray, D. W.
PY - 2011
Y1 - 2011
N2 - Single femoral radius TKRs have been reported to improve quadriceps' mechanical advantage, leading to enhanced patient function. An increased patellar tendon moment arm (PTMA) has been cited as the main feature leading to improved quadriceps' mechanical advantage. However, these designs often incorporate a recessed trochlea which alters the patellar mechanism and may contribute to improved quadriceps' mechanical advantage. This study simultaneously measured the PTMA using two and three dimensional methods, as well as quadriceps forces (QF), patellofemoral kinematics and tibiofemoral kinematics in a motion analysis laboratory during an open chain leg extension activity. Six cadaveric knees were tested in the normal state and after implantation of three different single femoral radius TKR designs: cruciate retaining, posterior stabilised and rotating platform posterior stabilised (Stryker, Newbury, UK). QFs in the TKRs were between 15% and 20% lower than normal between 60 degrees and 70 degrees flexion. The increase in PTMA was insufficient to explain the reduced QF in the TKRs. The patellar flexion angle (PFA) of the TKRs was lower than normal at knee flexion angles greater than 50 degrees , probably as a result of the recessed trochlea. A simple patellar model demonstrated that the reduced PFA may explain a large proportion of the reduction in QF after single radius TKR.
AB - Single femoral radius TKRs have been reported to improve quadriceps' mechanical advantage, leading to enhanced patient function. An increased patellar tendon moment arm (PTMA) has been cited as the main feature leading to improved quadriceps' mechanical advantage. However, these designs often incorporate a recessed trochlea which alters the patellar mechanism and may contribute to improved quadriceps' mechanical advantage. This study simultaneously measured the PTMA using two and three dimensional methods, as well as quadriceps forces (QF), patellofemoral kinematics and tibiofemoral kinematics in a motion analysis laboratory during an open chain leg extension activity. Six cadaveric knees were tested in the normal state and after implantation of three different single femoral radius TKR designs: cruciate retaining, posterior stabilised and rotating platform posterior stabilised (Stryker, Newbury, UK). QFs in the TKRs were between 15% and 20% lower than normal between 60 degrees and 70 degrees flexion. The increase in PTMA was insufficient to explain the reduced QF in the TKRs. The patellar flexion angle (PFA) of the TKRs was lower than normal at knee flexion angles greater than 50 degrees , probably as a result of the recessed trochlea. A simple patellar model demonstrated that the reduced PFA may explain a large proportion of the reduction in QF after single radius TKR.
UR - http://www.scopus.com/inward/record.url?scp=84865349110&partnerID=8YFLogxK
UR - http://www.ncbi.nlm.nih.gov/pubmed/22001289
UR - http://dx.doi.org/10.1016/j.knee.2011.07.006
U2 - 10.1016/j.knee.2011.07.006
DO - 10.1016/j.knee.2011.07.006
M3 - Article
VL - 19
SP - 564
EP - 570
JO - The Knee
JF - The Knee
IS - 5
ER -