title: Quadriceps strength impairment in the mid- to long-term follow-up period after total knee arthroplasty.
abstract: OBJECTIVE
  Quadriceps strength impairment after total knee arthroplasty (TKA) continues to be a concern. However, most studies of quadriceps strength have short-term follow-up periods. Whether quadriceps strength impairment occurs in the long-term follow-up period after TKA remains unclear. The purpose of this study was to compare the quadriceps strength between posterior cruciate ligament-retaining (CR) and substituting (PS) design mobile-bearing TKA (1) in the same patients after an average of 10 years and (2) between TKA patients and age-matched controls.
  
  
  METHODS
  A prospective, quasi-randomized design was used. Thirty-four patients (68 knees) who underwent bilateral TKA (CR on one side and PS on the other) were followed for a minimum of 5 years, and 35 age-matched controls (70 knees) were evaluated. A handheld dynamometer was used to measure quadriceps isometric strength. For each patient, the maximum value of three trials was used. The ratio of muscle strength to body weight (MS/BW ratio; N/kg) was used to evaluate outcomes.
  
  
  RESULTS
  The median MS/BW ratio was 3.3 (range 1.4-10.5) for CR 3.4 (range 0.9-9.3) for PS, and 4.6 (range 0.4-8.8) for controls. The MS/BW ratio did not differ between prosthesis designs, but was significantly smaller in both CR (p = 0.020) and PS (p = 0.024) than in controls.
  
  
  CONCLUSIONS
  Posterior cruciate ligament-retaining TKA does not confer a substantial advantage an average of 10 years postoperatively. In addition, quadriceps strength, as measured using a hand-held dynamometer, was significantly lower in both TKA patient groups than in age-matched controls. Clinically, the results of this study indicate that quadriceps-strengthening exercises should be continued in the long term after TKA.
  
  
  METHODS
  II.
authors.affiliation: Ishii Orthopaedic and Rehabilitation Clinic, 1089 Shimo-Oshi, Gyoda, Saitama, 361-0037, Japan. ishii@sakitama.or.jp.
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Ishii
authors.affiliation: Ishii Orthopaedic and Rehabilitation Clinic, 1089 Shimo-Oshi, Gyoda, Saitama, 361-0037, Japan.
authors.forename: Hideo
authors.initials: H
authors.lastname: Noguchi
authors.affiliation: Ishii Orthopaedic and Rehabilitation Clinic, 1089 Shimo-Oshi, Gyoda, Saitama, 361-0037, Japan.
authors.forename: Junko
authors.initials: J
authors.lastname: Sato
authors.affiliation: Ishii Orthopaedic and Rehabilitation Clinic, 1089 Shimo-Oshi, Gyoda, Saitama, 361-0037, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Sakurai
authors.affiliation: Division of Information Science and Biostatistics, Niigata University Graduate School of Medical and Dental Sciences, 1 Asahimachi Dori Niigata, Niigata, 951-8520, Japan.
authors.forename: Shin-Ichi
authors.initials: SI
authors.lastname: Toyabe
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects* / Q000379:methods; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D053580:Muscle Strength / Q000502:physiology*; D053581:Muscle Strength Dynamometer; D016119:Posterior Cruciate Ligament / Q000601:surgery; D011446:Prospective Studies; D011474:Prosthesis Design; D052097:Quadriceps Muscle / Q000503:physiopathology* / Q000601:surgery; D013997:Time Factors
keywords: A hand-held dynamometer; Long-term follow-up; PCL-retaining TKA; PCL-substituting TKA; Quadriceps strength