Increased patellar bone tracer uptake in preoperative SPECT/CT before medial opening high tibial osteotomy correlates with inferior clinical outcome

Purpose The purpose of this study was to investigate whether specific bone tracer uptake (BTU) patterns on preoperative SPECT/CT could predict which patients with varus alignment and medial overload would particularly benefit from medial opening-wedge high tibial osteotomy (MOWHTO). It was the hypothesis that an increased preoperative BTU relative to the reference BTU of the femur on SPECT/CT in the lateral and patellar compartments of the knee are predictive factors for inferior clinical outcome and that the clinical outcome correlates with the extent of alignment correction. Methods Twenty-three knees from 22 patients who underwent MOWHTO for medial compartment overload were investigated preoperatively using Tc-99m-SPECT/CT. BTU was quantified and localised to specific joint areas according to a previously validated scheme. Pre- and postoperative mechanical alignment was measured. Clinical outcome was assessed at a median of 24 months (range 11–30) after MOWHTO by collecting the WOMAC score. Results Significant correlations between BTU in the patellar area and the total WOMAC score and its subcategories pain and stiffness were found. Thus, BTU in the 1sPat area (superior lateral patellar compartment) correlated with total WOMAC (rho = 0.43, p = 0.04), pain subcategory (rho = 0.43, p = 0.04), and stiffness subcategory (rho = 0.59, p = 0.003). No significant correlations were found between alignment correction, age, gender and WOMAC. Conclusion This study highlights the role of preoperative SPECT in modern knee surgery to obtain information about the loading pattern on different compartments of the knee. Despite the limited number of participants, the present study shows that a preoperative SPECT/CT scan can help the treating surgeons to identify patients who may be at risk of inferior clinical outcome if an MOWHTO is considered, as an elevated BTU in the patellar region on preoperative SPECT/CT appears to be a potential risk factor for postoperative pain and stiffness. Level of evidence Level III.

Good correlation of the maximal relative bone tracer uptake in SPECT/CT and intraoperative findings of chondral lesions graded with the ICRS

Aims and Objectives: It is a pertinent question if SPECT/CT is able to reflect the cartilage status of the knee. Hence, it was the purpose of this study to evaluate the correlation between maximal relative bone tracer uptake (mrBTU) of preoperative SPECT/CT and intraoperative findings of chondral lesions assessed with the International Cartilage Repair Society (ICRS) scoring. Materials and Methods: Thirty-three consecutive patients (male: female=11: 22; mean age ± standard deviation 61±15) with bi- or tri-compartmental osteoarthritis of the knee who underwent SPECT/CT before total knee arthroplasty (TKA) were included. The knee was divided into 11 anatomical regions. In each region, mrBTU values were calculated twice by two observers within a six weeks interval. The intraclass correlation coefficient (ICC) was calculated and mean values were used. Intraoperatively, for every region the cartilage status with regards to ICRS score was assessed. A non-parametrical Spearman’s correlation was performed. A factor analysis was performed on mrBTU and ICRS scores (p<0.05). Results: The ICC presented excellent correlations. The Spearman’s correlation performed separately on mrBTU and ICRS scores showed diffuse significant correlations which were especially strong between regions of the same knee compartment (p < 0.01). The Spearmann correlation calculated between rmBTU and IRCS scores evidenced very strong correlations on the medial femoral condyle, on the ventral two third of the medial tibia plateau (p < 0.01) and good correlations on the proximal femoral trochlea and on the medial patellar facet (p < 0.05). Conclusion: A highly significant correlation between SPECT/CT and intraoperative findings was demonstrated. The use of an objective measure as the rmBTU for osteoarthritis could overcome the limit of the subjectivity of MRI findings.