title: Densitometric kneecap changes after unilateral knee arthroplasty.
abstract: OBJECTIVE
  To assess bone density of kneecaps in subjects with femoro-tibial prosthesis before and after surgery by means of DEXA examination.
  
  
  METHODS
  We examined 34 patients with unilateral femoro-tibial prosthesis, 20 healthy subjects of the same age and non-carriers of knee replacement and 14 healthy young adult subjects. All the data sets were analysed by two radiologists (AS and AM). The coincidence of the results between the two specialists was evaluated by means of Cohen's Kappa index and the results were considered statistically significative if p value is < of 0.05.
  
  
  RESULTS
  The values of patellar BMD in the group of 34 patients, were: a minimum of 0.386 g/cm(2) (K = 0.879, p = 0.0012), a maximum 1.707 g/cm(2) (K = 0.886, p = 0.0016). The comparison between the left and right knee showed the following data: minimum difference 0.034 g/cm2 (K = 0.901, p = 0.0015), maximum difference of 0.622 g/cm(2) (K = 0.908, p = 0.0017), the average was found to be of 0.277 g/cm(2) (K = 0.894, p = 0.0018). But this difference tends to decrease 6 months after surgery. In the group of healthy young adults, we obtained the following values: a minimum of 0.782 g/cm(2) (K = 0.907, p = 0.0025), maximum 1.503 g/cm(2) (K = 0.932, p = 0.0012). Between both knees, the difference was minimal 0.006 g/cm(2) (K = 0.951, p = 0.0035) and maximum 0.096 g/cm(2) (K = 0.926, p = 0.0007) with an average difference of 0.058 g/cm(2) (K = 0.954, p = 0.0026). In the group of healthy subjects of the same age and non-carriers of knee replacement the values were average higher. A maximum value of 1.134 g/cm(2) (K = 0.894, p = 0.0028) and a minimum value of 0.944 g/cm(2) (K = 0.892, p = 0.0023) were found; between both knees a minimum difference of 0.010 g/cm(2) (K = 0.918, p = 0.0047) and a maximum of 0.090 g/cm(2) (K = 0.937, p = 0.0017) were found, with an average difference of 0.052 g/cm(2) (K = 0.956, p = 0.0024).
  
  
  CONCLUSIONS
  DEXA examination of the patellar is recommended as a supplementary study to the clinical and radiological standard exams because it is able to provide additional information to determine when to intervene surgically, on the basis of patellar bone density values.
authors.affiliation: Department of Radiology, Sapienza University of Rome, Rome, Italy. flavio.barchetti@live.it.
authors.forename: F
authors.initials: F
authors.lastname: Barchetti
authors.forename: A
authors.initials: A
authors.lastname: Stagnitti
authors.forename: N
authors.initials: N
authors.lastname: Al Ansari
authors.forename: V
authors.initials: V
authors.lastname: De Marco
authors.forename: S
authors.initials: S
authors.lastname: Montechiarello
authors.forename: V
authors.initials: V
authors.lastname: Forte
authors.forename: V
authors.initials: V
authors.lastname: Noce
authors.forename: M
authors.initials: M
authors.lastname: Glorioso
authors.forename: V
authors.initials: V
authors.lastname: Sorrentino
authors.forename: G
authors.initials: G
authors.lastname: Barchetti
authors.forename: E
authors.initials: E
authors.lastname: Pasqualitto
authors.forename: A
authors.initials: A
authors.lastname: Marini
authors.forename: M
authors.initials: M
authors.lastname: Marini
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation; D015519:Bone Density; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007720:Knee Prosthesis; D008297:Male; D010329:Patella / Q000000981:diagnostic imaging*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D015203:Reproducibility of Results; D016896:Treatment Outcome