title: Quadriceps force in relation of intrinsic anteroposterior stability of TKA design.
abstract: OBJECTIVE
  Decreased quadriceps strength and fatigue is suspected to be one of the contributing factors for anterior knee pain and malfunction after total knee arthroplasty (TKA). The purpose of this in vitro study was to investigate the amount of quadriceps force required to extend the knee isokinetically after TKA in dependence of different prosthesis designs and the state of the posterior cruciate ligament (PCL).
  
  
  METHODS
  Eight fresh frozen human knee specimens underwent testing in a kinematic device simulating an isokinetic knee extension cycle from 120° of flexion to full extension. The quadriceps force was measured after implantation of a cruciate retaining (CR) TKA (Genesis II, Smith&Nephew, Memphis, TN, USA) applying a conventional CR (11 mm) and a highly conforming (deep dished, DD) polyethylene (PE) inlay consecutively before and after resection of the PCL. Finally, tests were repeated with a posterior-stabilized (PS) design.
  
  
  RESULTS
  Simulating a physiological knee extension, no significant differences in the average quadriceps force were detected between the cruciate preserving inlays (CR 1,146.57 ± 88.04 N, DD 1,150.19 ± 97.54 N, P = 0.86) as long as the PCL was intact. After resection of the PCL, the required quadriceps force increased significantly for both designs (CR 1,203.17 ± 91.51 N, P < 0.01 and DD 1,191.88 ± 80.07 N, P < 0.03). After implantation of the posterior stabilized femoral component quad force decreased to its initial levels with forces significantly lower compared to the PCL deficient knees provided with a CR or DD (PS 1,130.91 ± 107.88 N, P < 0.01) inlay. With a deficient PCL there were no statistical differences for the DD design in comparison with CR in mean quad forces (CR 1,203.17 ± 91.51 N vs. DD 1,191.88 ± 80.07 N, P = 0.50) nor in peak forces (CR 1,729.44 ± 161.86 N, DD 1,688.66 ± 123.18 N, P = 0.17).
  
  
  CONCLUSIONS
  At intact PCL peak quad forces and mean forces beyond 70° of flexion could be shown to be significantly lower with a PS TKA design in comparison with cruciate preserving designs such as CR and DD. In the PCL deficient knee quad forces with a highly conforming implant (DD) and CR were significantly higher than with a PS TKA. The use of PS implants in all PCL deficient knees seems to be advisable
authors: Department of Orthopedics and Rheumatology, University Hospital Marburg, Baldingerstrasse, 35043 Marburg, Germany. heyse@med.uni-marburg.de
authors: Thomas Jan
authors: TJ
authors: Heyse
authors: Christoph
authors: C
authors: Becher
authors: Nadine
authors: N
authors: Kron
authors: Sven
authors: S
authors: Ostermeier
authors: Christof
authors: C
authors: Hurschler
authors: Markus D
authors: MD
authors: Schofer
authors: Susanne
authors: S
authors: Fuchs-Winkelmann
authors: Carsten O
authors: CO
authors: Tibesku
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee; D001696:Biomechanical Phenomena; D002102:Cadaver; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000502:physiology*; D008297:Male; D018763:Muscle Fatigue / Q000502:physiology; D052097:Quadriceps Muscle / Q000502:physiology*