title: Factors predicting quadriceps femoris muscle atrophy during the first 12weeks following anterior cruciate ligament reconstruction.
abstract: BACKGROUND
  Factors predicting quadriceps femoris muscle (QF) atrophy during the early period after arthroscopic ACL reconstruction have not been extensively studied. It is also yet to be confirmed whether muscle atrophy is a key determinant of postoperative QF weakness.
  
  
  METHODS
  Mean changes in QF volume, MVIC torque and isometric endurance time were analysed in 25 patients prior to and at four and 12 weeks after surgery. A multivariable regression model of change in QF volume was made from combination of several parameters of preoperative QF size and strength and postoperative joint recovery. The impact of QF atrophy on muscle weakness was evaluated with univariate regression and MVIC torque to volume ratio at postoperative week only.
  
  
  RESULTS
  The model of QF volume change was significant (P<0.01) only at postoperative week 4, explaining 57% of its variation, where isometric endurance time had a negative and knee extension ROM deficit a positive weight. Change in QF volume explained (P<0.05) 46% of the MVIC torque variation at postoperative week 12. A significant change (P<0.05) in QF MVIC torque to volume ratio was observed at postoperative week 12.
  
  
  CONCLUSIONS
  Good prediction of QF atrophy in the first postoperative month can be made from studied variables, with isometric endurance and knee extension ROM deficit being the most significant contributors. The atrophy explained a large part of QF muscle weakness, whereas factors contributing to the remaining portion need further research.
authors.affiliation: Department of Physiotherapy, Faculty of Health Sciences, University of Ljubljana, Slovenia.
authors.forename: T
authors.initials: T
authors.lastname: Grapar Žargi
authors.affiliation: Department of Orthopaedic Surgery, University Medical Centre Ljubljana, Slovenia.
authors.forename: Matej
authors.initials: M
authors.lastname: Drobnič
authors.affiliation: Department of Physiotherapy, Faculty of Health Sciences, University of Ljubljana, Slovenia.
authors.forename: Renata
authors.initials: R
authors.lastname: Vauhnik
authors.affiliation: Department of Radiology, University Medical Centre Ljubljana, Slovenia.
authors.forename: Jadran
authors.initials: J
authors.lastname: Koder
authors.affiliation: Department of Physiotherapy, Faculty of Health Sciences, University of Ljubljana, Slovenia. Electronic address: alan.kacin@zf.uni-lj.si.
authors.forename: Alan
authors.initials: A
authors.lastname: Kacin
mesh_terms: D000328:Adult; D059549:Anterior Cruciate Ligament Reconstruction / Q000009:adverse effects*; D001182:Arthroscopy; D005260:Female; D006801:Humans; D008297:Male; D018908:Muscle Weakness; D009133:Muscular Atrophy / Q000209:etiology* / Q000473:pathology*; D011446:Prospective Studies; D052097:Quadriceps Muscle / Q000473:pathology*; D012307:Risk Factors
keywords: Joint swelling; Knee extension ROM; Muscle endurance; Quadriceps muscle atrophy; Semitendinosus–gracilis autograft; Volitional muscle activation