title: Assessment of in vivo loading history of the patellofemoral joint: a study combining patellar position, tilt, alignment and bone SPECT/CT.
abstract: OBJECTIVE
  The current study investigates whether patella height and tilt or leg alignment influence the intensity values as well as the distribution pattern of single photon emission computerized tomography/computerized tomography (SPECT/CT) tracer uptake in the patellofemoral joint.
  
  
  METHODS
  99mTc-HDP-SPECT/CT and radiographs of consecutive 84 knees were prospectively obtained. Lateral radiographs were analyzed in terms of patellar height, Insall-Salvati index and modified Insall-Salvati index. Skyline views were analyzed for Laurin's lateral patellofemoral angle. On long-leg radiographs, the mechanical leg alignment was classified as varus, valgus or neutral. SPECT/CT was analyzed for each anatomical region using a previously validated SPECT/CT localization and grading algorithm. Mean, standard deviation, minimum and maximum of grading for each area of the localization scheme were recorded. Nonparametric Spearman's correlations were used to correlate patellar height, lateral patellar angle and leg alignment with the tracer uptake intensity. Chi-square statistics were used for categorical data (p < 0.05).
  
  
  RESULTS
  A patella baja correlated significantly with higher SPECT/CT tracer uptake in all patellar and lateral femoral regions (p < 0.001). A higher lateral patellar tilt correlated significantly with higher tracer uptake in the superior lateral femoral parts and the tibial tubercle. In mechanically varus aligned knees, there was significantly higher SPECT/CT tracer uptake on the medial and in valgus knees on the lateral part of the patellofemoral joint (p < 0.05).
  
  
  CONCLUSIONS
  As the intensity and distribution of the SPECT/CT significantly correlated with patella baja and patellar tilt, SPECT/CT might be considered as imaging modality for evaluating patients with patellofemoral disorders and for follow-up of patients after patellofemoral realignment procedures.
  
  
  METHODS
  Diagnostic study, Level II.
authors.affiliation: Department of Orthopaedic Surgery and Traumatology, Kantonsspital Baselland-Bruderholz, 4101, Bruderholz, Switzerland.
authors.forename: Stephan N
authors.initials: SN
authors.lastname: Schön
authors.forename: Faik K
authors.initials: FK
authors.lastname: Afifi
authors.forename: Helmut
authors.initials: H
authors.lastname: Rasch
authors.forename: Felix
authors.initials: F
authors.lastname: Amsler
authors.forename: Niklaus F
authors.initials: NF
authors.lastname: Friederich
authors.forename: Markus P
authors.initials: MP
authors.lastname: Arnold
authors.forename: Michael T
authors.initials: MT
authors.lastname: Hirschmann
mesh_terms: D000328:Adult; D018771:Arthralgia / Q000175:diagnosis*; D017760:Bone Malalignment / Q000175:diagnosis; D004164:Diphosphonates; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging; D006801:Humans; D008297:Male; D008875:Middle Aged; D015609:Organotechnetium Compounds; D010329:Patella / Q000002:abnormalities / Q000000981:diagnostic imaging*; D057071:Patellofemoral Joint / Q000002:abnormalities / Q000000981:diagnostic imaging*; D011859:Radiography; D019275:Radiopharmaceuticals; D013977:Tibia / Q000000981:diagnostic imaging; D015899:Tomography, Emission-Computed, Single-Photon
chemical_list: D004164:Diphosphonates; D015609:Organotechnetium Compounds; D019275:Radiopharmaceuticals; C060491:technetium Tc 99m hydroxydiphosphonate