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Purpose: Bone single photon emission computed tomography (SPECT)/CT is considered as beneficial in unhappy patients with pain, stiffness or swelling after total knee arthroplasty (TKA). The purpose of this study was to identify typical patterns of bone tracer uptake (BTU), distribution and intensity values in patients after TKA. The above findings were correlated with the type and fixation of TKA, the time from TKA and intraoperative findings at revision surgery. Methods: A total of 100 knees of 84 consecutive patients (mean age ± SD 70 ± 11years) after TKA with persistent knee pain were prospectively included. All patients underwent clinical examination, standardized radiographs and 99mTc-hydroxymethane diphosphonate (HDP) SPECT/CT as part of a routine diagnostic algorithm. The diagnosis before and after SPECT/CT and final treatment were recorded. TKA component position was determined on 3-D reconstructed images. Intensity and anatomical distribution of BTU was determined. Maximum intensity values were recorded as well as ratios in relation to the proximal midshaft of the femur. Univariate analyses (chi-square test, Pearson's correlation and t test for independent samples) were performed (p < 0.05). Results: SPECT/CT changed the clinical diagnosis and final treatment in 85/100 (85%) knees. Intraoperative findings confirmed the preoperative SPECT/CT diagnosis in 32/33 knees (97%). TKA loosening as well as progression of patellofemoral osteoarthritis (OA) was correctly diagnosed in 100% of knees. Typical patterns of BTU for specific pathologies were identified. Loose femoral TKA components significantly correlated with increased BTU at the lateral femoral regions (p < 0.05). Loose tibial TKA components significantly correlated with increased BTU at all tibial regions (p < 0.05) and around the tibial peg (p > 0.01). Conclusion: The diagnostic benefits of SPECT/CT in patients after TKA have been proven. Typical pathology-related BTU patterns were identified, which will

Purpose: The purpose was to prospectively evaluate the outcome, in particular the SPECT/CT bone tracer uptake (BTU) after high tibial osteotomy (HTO) due to symptomatic varus malalignment. It was the hypothesis that the BTU after HTO decreases in the medial compartment, clinical outcome and the degree of correction correlates with BTU and asymptomatic patients after HTO reveals a significantly decreased BTU in the medial subchondral areas. Methods: Twenty-two consecutive patients with 23 knees undergoing medial opening-wedge HTO for medial compartment overloading were assessed pre- and postoperatively (12 and/or 24months) using Tc-99m-HDP-SPECT/CT including our 4D-SPECT/CT protocol. BTU was quantified and localized to specific biomechanically relevant joint areas. Maximum absolute and relative values (mean±standard deviation, median and range) for each area were recorded. Pre- and postoperative mechanical alignment was measured. At 24months after HTO, the WOMAC score was used. Results: A significant decrease of BTU in the medial subchondral zones after HTO was found (preoperatively to 12 and 24months postoperatively, p<0.01). BTU normalized in all asymptomatic patients within 24months. This decrease was partly seen in the lateral compartments, but significantly higher in the medial compartments (p<0.0001). A significant increase of the BTU was noted in zones directly adjacent to the plate or within the osteotomy zone (p<0.01). Decreased BTU was observed in osteotomy zones at 24months postoperatively following higher uptake values at 12months postoperatively. The average valgus correction of the tibiofemoral angle was 5.9°±2.8°. Less stiffness correlated significantly with a higher decrease in BTU (p<0.05). Higher postoperative BTU significantly correlated with more pain (p<0.05). No statistical significant associations between BTU and alignment correction were found. Conclusion: In patients with medial compartment, overloading due to varus malalignment HTO led to a