Does minimally invasive total knee arthroplasty improve isokinetic torque?
BACKGROUND
Less invasive dissection of the extensor apparatus, one of the aspects of minimally invasive surgical (MIS) TKA, might result in less reduction of postoperative quadriceps strength. However, it is unclear whether MIS is associated with less strength reduction.


OBJECTIVE
We asked whether knee strength (extensor or flexor torque) would be greater in patients having a MIS TKA compared with patients having a standard TKA and whether knee scores, alignment, ROM, tourniquet and operating times, and hospital length of stay were improved.


METHODS
We prospectively recruited 52 patients awaiting MIS or standard TKA, matched for age, weight, height, BMI, sex, and surgically treated side, but not randomized. Isokinetic tests were performed preoperatively and postoperatively to obtain peak values of extensor and flexor torque. Postoperative-to-preoperative ratios and the extensor-flexor torque ratio also were calculated.


RESULTS
Mean baseline extensor torques were 57 Nm and 53 Nm for MIS and standard TKAs, respectively. At 8 weeks postoperatively, absolute values of the mean postoperative knee extensor torque also were similar: 47 and 45 Nm for patients with MIS and standard TKAs, respectively. The postoperative-to-preoperative ratios were 0.8 for extensor and flexor torque in both groups. The extensor-flexor torque ratios were similar between groups.


CONCLUSIONS
Our data suggest a less invasive dissection of the extensor apparatus involved in MIS TKA does not enhance postoperative quadriceps strength.


METHODS
Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
Department of Orthopaedic Surgery, Innsbruck Medical University, Anichstrasse 35, 6020 Innsbruck, Austria. michael.liebensteiner@i-med.ac.at
Michael C
MC
Liebensteiner
Martin
M
Krismer
Arnold
A
Koller
Barbara
B
Semenitz
Eckart
E
Mayr
D000368:Aged; D019645:Arthroplasty, Replacement, Knee; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D007592:Joint Diseases / Q000601:surgery*; D007719:Knee Joint / Q000502:physiology* / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D019060:Minimally Invasive Surgical Procedures; D019415:Torque