MONTREAL — The combination of single photon emission CT and regular CT can be used to analyze mechanical and anatomical knee joint alignment and how they may affect the loading pattern of the knee, according to research presented here at the International Cartilage Repair Society World Congress 2012.
“Single photon emission computed tomography (SPECT) with CT gives you a good impression of where the pathology in the subchondral bone is happening — where the tracer uptake is, precisely,” Markus P. Arnold, MD, PhD, of Bruderholz, Switzerland, said. “It is two modalities combined in one: the 3-D information of the biological processes and the activity of the bone is the SPECT, and the anatomical 3-D structure information is the CT.”
Arnold and his colleagues retrospectively studied 104 knees in 76 patients, noting the maximum intensity for each femoral, tibial and patellar joint compartment. They also examined anterior-posterior and lateral weightbearing radiographs to calculate Kellgren-Lawrence osteoarthritis scores and used long leg radiographs to determine the anatomical and mechanical alignment of each leg. These alignments were labeled varus, valgus or neutral.
Markus P. Arnold
The anatomical and mechanical alignments were then correlated with tracer uptake for each area of interest, along with the Kellgren-Lawrence scores.
The investigators identified significant correlations between tracer uptake on the medial compartment, and the anatomical and mechanical varus alignment of the knee. They could also identify similar significant correlations with tracer uptake on the lateral compartments.
Furthermore, Arnold added, those patients with higher Kellgren-Lawrence scores were found to have higher tracer uptake values in corresponding joint compartments.
“Intensity of tracer uptake in the medial compartment — and this is also true for the lateral compartment — significantly correlates with the anatomical and mechanical varus and valgus alignment,” Arnold said. “This new modality helps us to get more insight.”
Hirschmann MT, Arnold MP, Friederich NF, Rasch H. Does the mechanical alignment correlate with the tracer uptake pattern and intensity in SPECT/CT? A retrospective series on 104 knees. Paper #11.4.7. Presented at the International Cartilage Repair Society World Congress 2012. May 12-15. Montreal.