title: Do Chondral Lesions of the Knee Correlate with Bone Tracer Uptake by Using SPECT/CT?
abstract: OBJECTIVE
  To evaluate the correlation of bone tracer uptake as determined with single photon emission computed tomography (SPECT)/computed tomography (CT) and the size and severity of chondral lesions detected with magnetic resonance (MR) imaging of the knee.
  
  
  METHODS
  MR imaging and SPECT/CT images of 63 knee joints in 63 patients (mean age ± standard deviation, 49.2 years ± 12.7) with chondral or osteochondral lesions were prospectively collected and retrospectively analyzed after approval by the ethics committee. Chondral lesions were graded on MR images by using a modified Noyes grading scale (grade 0, intact; grade 1, fibrillations; grade 2, <50% defect; grade 3, >50% defect; and grade 4, grade three plus subchondral changes) and measured in two dimensions. Technetium 99m hydroxymethane diphosphonate SPECT/CT bone tracer uptake was volumetrically quantified by using validated software. Maximum values of each subchondral area (patellofemoral or medial and lateral femorotibial) were quantified, and a ratio was calculated in relation to a reference region in the femoral shaft, which represented the bone tracer uptake background activity. Grades and sizes of chondral lesions and bone tracer uptake were correlated by using an independent t test and analysis of variance (P < .05).
  
  
  RESULTS
  Bone tracer uptake was low (mean relative uptake, 1.64 ± 0.95) in knees without any present chondral lesion. In knees with grade 3 and 4 chondral lesions, the relative ratio was significantly higher (3.62 ± 2.18, P = .002) than in knees with grade 1 and 2 lesions (2.95 ± 2.07). The larger the diameter of the chondral lesion, the higher the bone tracer uptake. Higher grades of chondral lesions (grades 3 and 4) larger than 4 cm(2) (4.96 ± 2.43) showed a significantly higher bone tracer uptake than smaller lesions (<1 cm(2), 2.72 ± 1.43 [P = .011]; and 1-4 cm(2), 3.28 ± 2.15 [P = .004]).
  
  
  CONCLUSIONS
  SPECT/CT findings significantly correlate with the degree and size of chondral lesions on MR images. Grade 3 and 4 chondral lesions of the knee, as well as larger lesions, correlate with a high bone tracer uptake.
authors.affiliation: From the Department of Orthopaedic Surgery and Traumatology (M.D., M.T.H., J.R., E.T.) and Department of Radiology (A.F.), Kantonsspital Baselland-Bruderholz, Binningen, Switzerland; and Department of Radiology, University Hospital Basel, Petersgraben 4, 4031 Basel, Switzerland (A.H.).
authors.forename: Milos
authors.initials: M
authors.lastname: Dordevic
authors.affiliation: From the Department of Orthopaedic Surgery and Traumatology (M.D., M.T.H., J.R., E.T.) and Department of Radiology (A.F.), Kantonsspital Baselland-Bruderholz, Binningen, Switzerland; and Department of Radiology, University Hospital Basel, Petersgraben 4, 4031 Basel, Switzerland (A.H.).
authors.forename: Michael T
authors.initials: MT
authors.lastname: Hirschmann
authors.affiliation: From the Department of Orthopaedic Surgery and Traumatology (M.D., M.T.H., J.R., E.T.) and Department of Radiology (A.F.), Kantonsspital Baselland-Bruderholz, Binningen, Switzerland; and Department of Radiology, University Hospital Basel, Petersgraben 4, 4031 Basel, Switzerland (A.H.).
authors.forename: Jan
authors.initials: J
authors.lastname: Rechsteiner
authors.affiliation: From the Department of Orthopaedic Surgery and Traumatology (M.D., M.T.H., J.R., E.T.) and Department of Radiology (A.F.), Kantonsspital Baselland-Bruderholz, Binningen, Switzerland; and Department of Radiology, University Hospital Basel, Petersgraben 4, 4031 Basel, Switzerland (A.H.).
authors.forename: Anna
authors.initials: A
authors.lastname: Falkowski
authors.affiliation: From the Department of Orthopaedic Surgery and Traumatology (M.D., M.T.H., J.R., E.T.) and Department of Radiology (A.F.), Kantonsspital Baselland-Bruderholz, Binningen, Switzerland; and Department of Radiology, University Hospital Basel, Petersgraben 4, 4031 Basel, Switzerland (A.H.).
authors.forename: Enrique
authors.initials: E
authors.lastname: Testa
authors.affiliation: From the Department of Orthopaedic Surgery and Traumatology (M.D., M.T.H., J.R., E.T.) and Department of Radiology (A.F.), Kantonsspital Baselland-Bruderholz, Binningen, Switzerland; and Department of Radiology, University Hospital Basel, Petersgraben 4, 4031 Basel, Switzerland (A.H.).
authors.forename: Anna
authors.initials: A
authors.lastname: Hirschmann
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002358:Cartilage, Articular / Q000473:pathology*; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D007719:Knee Joint / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D011857:Radiographic Image Interpretation, Computer-Assisted; D015899:Tomography, Emission-Computed, Single-Photon; D014057:Tomography, X-Ray Computed