title: Quadriceps force during knee extension in different replacement scenarios with a modular partial prosthesis.
abstract: BACKGROUND
  Previous biomechanical studies have shown that bi-cruciate retaining knee replacement does not significantly alter normal knee kinematics, however, there are no data on the influence of a combined medial and patellofemoral bi-compartimental arthroplasty. The purpose of this in vitro study was to evaluate the effect of different replacement scenarios with a modular partial knee replacement system on the amount of quadriceps force required to extend the knee during an isokinetic extension cycle.
  
  
  METHODS
  Ten human knee specimens were tested in a kinematic knee simulator under (1) physiologic condition and after subsequent implantation of (2) a medial unicondylar and (3) a trochlear replacement. An isokinetic extension cycle of the knee with a constant extension moment of 31 Nm was simulated. The resulting quadriceps extension force was measured from 120° to full knee extension.
  
  
  RESULTS
  The quadriceps force curve described a typically sinusoidal characteristic before and after each replacement scenario. The isolated medial replacement resulted in a slightly, but significantly higher maximum quadriceps force (1510 N vs. 1585 N, P = 0.006) as well as the subsequent trochlear replacement showed an additional increase (1801 N, P = 0.008). However, for both replacements no significant difference to the untreated condition could be detected in mid-flexion (10-50°).
  
  
  CONCLUSIONS
  When considering a bi-compartimental replacement an increase of required maximum quadriceps force needed to extend the knee has to keep in mind. However, the close to physiological movement in mid-flexion suggests that patients with a bi-crutiate retaining arthroplasty might have an advantage in knee stability compared to total knee arthroplasty.
authors.affiliation: Department of Orthopaedic Surgery, Hannover Medical School, Anna-von-Borries-Str. 3, 30625 Hannover, Germany. Electronic address: tilman.calliess@ddh-gruppe.de.
authors.forename: Tilman
authors.initials: T
authors.lastname: Calliess
authors.affiliation: Department of Orthopaedic Surgery, Hannover Medical School, Anna-von-Borries-Str. 3, 30625 Hannover, Germany.
authors.forename: Ssuheib
authors.initials: S
authors.lastname: Schado
authors.affiliation: Department of Orthopaedic Surgery, Hannover Medical School, Anna-von-Borries-Str. 3, 30625 Hannover, Germany.
authors.forename: Berna I
authors.initials: BI
authors.lastname: Richter
authors.affiliation: Department of Orthopaedic Surgery, Hannover Medical School, Anna-von-Borries-Str. 3, 30625 Hannover, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Becher
authors.affiliation: Department of Orthopaedic Surgery, Hannover Medical School, Anna-von-Borries-Str. 3, 30625 Hannover, Germany.
authors.forename: Marco
authors.initials: M
authors.lastname: Ezechieli
authors.affiliation: Department of Orthopaedic Surgery, Hannover Medical School, Anna-von-Borries-Str. 3, 30625 Hannover, Germany.
authors.forename: Sven
authors.initials: S
authors.lastname: Ostermeier
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology* / Q000601:surgery; D007720:Knee Prosthesis; D008297:Male; D053580:Muscle Strength / Q000502:physiology*; D052097:Quadriceps Muscle / Q000503:physiopathology* / Q000601:surgery; D016059:Range of Motion, Articular / Q000502:physiology*
keywords: Arthroplasty; Biomechanics; In-vitro; Partial knee replacement; Patellofemoral; Quadrizeps force; Unicondylar knee replacement