EVALUATION OF 99MTC-DPD-SPECT-CT FOR LOCALIZATION OF SYMPTOMATIC OSTEOARTHRITIS IN DEGENERATIVE HINDFOOT AND MIDFOOT JOINTS

Abstract

Introduction: Determination of the origin of chronic foot pain in osteoarthritis (OA) is challenging since clinical examination of the foot faces a complex anatomy with several joints, osseous, and non-osseous structures contributing to the symptoms. Non-invasive imaging methods (Rx, CT, MRI) show a poor correlation with pain degree. Studies using functional imaging based on the detection of activated osteoblasts with 99mTc-Dicarboxypropandiphosphate (DPD) to indicate painful facet joints show promising results, but so far no evaluation for chronic OA pain conditions in foot joints has been conducted and the diagnostic potential was limited due to poor spatial resolution of the scintigraphic assessment.

Single Photon Emission Computed Tomography – Computed Tomography (SPECT-CT) combines metabolic information with an exact anatomical localization. We hypothesised that diagnostic infiltration with a local anaesthetic of a painful hindfoot or midfoot joint showing 99mTc-DPD-uptake in SPECT-CT, leads to a positive OA pain response.

Methods: 26 patients with chronic OA pain and radiological signs of OA in a hindfoot or midfoot joint (27 feet) were included. Plain radiography was performed to detect degenerative changes and to rule out pathologies different from OA. Pain status was measured by Visual Analogue Scale (VAS). AOFAS hindfoot/midfoot score and SF-36–score were documented. All patients received a 99mTc-DPD SPECT-CT (Symbia T2, Siemens). The localisation of 99mTc-DPD-uptake and consequently the site of infiltration were defined. The infiltration was performed with a local anaesthetic (bupivacaine) and iodine solution under CT-guidance with exact documentation of the contrast media deposit by CT. Pain status was assessed directly post-infiltration. Pain relief in responders was defined as reduction of VAS-score > 50% immediately after infiltration, partial response as reduction of < 50%.

Results: Infiltration was performed in 26 hindfoot joints and 5 midfoot as indicated by 99mTc-DPD-uptake in SPECT-CT. Subsequent CT control scans showing contrast media depot confirmed exact successful infiltration in all indicated joints. In 22 patients an immediate significant (p< 0.01) postinterventional pain reduction of VAS more than 50% was observed. Mean VAS before infiltration was 5.77 (range 2–10; SD 2.22) and 0.82 (range 0–4; SD 1.26) immediately after infiltration. Two patients showed a partial response and one patient showed no pain resolution after infiltration.

Conclusion: The results show a significant correlation of uptake and pain resolution after infiltration allowing precise identification of OA hindfoot joints as pain inducing foci. SPECT-CT offers good prediction of outcome after infiltration improving the localisation of the pain inducing joint, thus aiding in pre-operative planning.