2009 Marshall Urist Young Investigator Award: how often do patients with high-flex total knee arthroplasty use high flexion?
Although high-flexion TKA designs aim to safely accommodate deep flexion, it is unknown how often patients use deep flexion outside the laboratory. We used a validated smart-activity monitor to document the prevalence of knee flexion greater than 90 degrees in 20 consecutive patients (21 knees) who had high-flexion TKAs, at a minimum of 2 years' followup. Patients wore the device continuously for a mean of 35.7 +/- 0.5 hours. The 21 knees flexed more than 90 degrees for an average of 10 +/- 3.8 minutes (0.5%). Activities performed with flexion greater than 90 degrees were, on average, 70% in single-limb stance, 12% moving from sitting to standing, 8% walking, 7% moving from standing to reclining, 2% stepping, 0.9% moving from lying to standing, and 0.1% running. Eight knees flexed greater than 120 degrees for an average of 2.2 minutes (range, 0.2-15 minutes), or 0.1% of the testing time. Activities performed with flexion greater than 120 degrees were, on average, 90% in single-limb stance, 6% moving from sitting to standing, 3% walking, 0.6% moving from standing to reclining, 0.3% stepping, and 0.1% moving from lying to standing. Peak flexion used at any time during testing was, on average, 84% +/- 11% of maximum postoperative flexion (125 degrees +/- 12 degrees). These patients rarely used deep flexion.


METHODS
Level IV, therapeutic study.
Huddleston
James I
JI
Department of Orthopaedic Surgery, Stanford University Medical Center, 300 Pasteur Drive, R-149, Stanford, CA 94305-5341, USA. jhuddleston@stanford.edu
Scarborough
Donna Moxley
DM
Goldvasser
Dov
D
Freiberg
Andrew A
AA
Malchau
Henrik
H
D000203:Activities of Daily Living; D000368:Aged; D019645:Arthroplasty, Replacement, Knee; D001363:Awards and Prizes; D001696:Biomechanical Phenomena; D004582:Electronics, Medical / Q000295:instrumentation; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007719:Knee Joint / Q000502:physiology* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000295:instrumentation / Q000379:methods; D009043:Motor Activity / Q000502:physiology*; D020370:Osteoarthritis, Knee / Q000601:surgery*; D016059:Range of Motion, Articular / Q000502:physiology*