This is the first study to evaluate the diagnostic and therapeutic impact of SPECT/CT in patients with unspecific hand and wrist pain. This clinical situation is particularly challenging for the clinician because of the unsatisfying therapeutic options which can be offered to the patient. In this study, SPECT/CT proved not only to detect more lesions than clinical examination and conventional imaging prior to SPECT/CT, but also to detect metabolic and osseous changes which have been evaluated as the possible reason for the clinical symptoms. Thus, SPECT/CT might be integrated in a diagnostic algorithm as a problem solving tool when clinical examination and conventional imaging (plain radiographs, planar bone scan, as well as partly CT and MRI) fail to detect the cause of the patient's symptoms.
Currently, there are only a few studies available which investigated the diagnostic usefulness of SPECT/CT, partly compared with other imaging modalities. However, no other study has investigated this anatomical area in such a specific patient population, and none of the other studies investigated the specific therapeutic impact.
In a study by Hirschmann and co-workers, the value of SPECT/CT in patients with pain after surgical treatment of knee osteoarthritis was evaluated
. They found that SPECT/CT showed its highest value in establishing the suspected diagnosis for the clinician by displaying the specific anatomical location of the suspected pathology. Only a small number of patients were investigated. However, this basic ability of SPECT/CT, also in other specific anatomical areas, e.g., the hindfoot, has been investigated in several other studies as well
[4, 6, 7]. Even-Sapir and co-workers found in a large cohort with 76 patients that SPECT/CT is able to detect significantly more lesions than conventional imaging workup
. Additionally, the specific localization of the metabolic activity was a major advantage concerning diagnostic confidence, thus potentially sparing additional imaging and costs. Improved diagnostic value was found to be as high as 58% concerning the final diagnosis. In comparison, in our study, a slightly smaller but more specific patient population was investigated, while the latter mentioned study investigated patients with nonspecific planar bone scan findings. Based on our highly selective patient population, the diagnostic improvement was not as high as in the latter study; however, the diagnostic improvement was in the range of other studies with SPECT/CT. Linke et al. conducted a large study with 71 patients with skeletal disorders and found that the addition of the CT information was followed by a diagnostic change in approximately one third of all patients in various skeletal conditions, e.g., re-classifications from osteoarthritis to fracture and suspected osteomyelitis to osteoarthritis
In our study, SPECT/CT also detected significantly more lesions than plain radiography as well as planar bone scan, and the increase in lesion detectability yielded approximately 20% compared to planar bone scan and even more compared to plain radiography. In fact, CT revealed various bone disorders, such as joint narrowing, subchondral cysts, etc. However, often, osteoarthritic and postoperative changes do not cause pain. The metabolic aspect of SPECT/CT is able to demonstrate the focus of activated osteoarthritis or pathologic bone alteration. Additionally, we could confirm the abovementioned results that SPECT/CT offers more precise localization, and thereby, the clinically suspected diagnosis was confirmed in the additional 14% of our patients. However, we did not account this for therapeutic impact because the intended therapy has not been changed based on the SPECT/CT results. In another study by Hirschmann et al., the level of activation on SPECT/CT correlated significantly with the stage of osteoarthritis seen on plain radiographs
. However, no correlation was observed between the degree of bony deformation and the detected activity as well as between activation and signs of osteoarthritis on CT scans. Overall, even if there was (partly) severe bony deformation in keeping with morphological signs of osteoarthritis, the degree of morphological deformation did not correlate well with the clinical symptoms of the patients. Thus, the amount of uptake/level of activation was found to be more useful in the determination of the actual disease status than morphological imaging alone. In our study, radiographs were negative in several cases, while SPECT/CT found pathologies responsible for the pain syndrome. However, we additionally found several lesions where plain radiography or CT showed bony pathologies without increased uptake and/or there were additional, more subtle lesions which were found responsible for the clinical symptoms. This might be especially important for patients with severe osteoarthritic wrists (SLAC or SNAC) where it can be impossible to determine which of the numerous lesions is currently active by means of morphological imaging. SPECT/CT also has shown to be valuable in related indications, e.g., evaluation of bone vitality
There are only very few studies currently available in the literature which evaluated the change in therapy based on SPECT/CT findings. In our study, we added the evaluation of therapeutic impact based on an interdisciplinary discussion between our institute and the department of hand surgery. As mentioned, in 19 out of 51 patients, significant influence on therapy was observed. Of these, SPECT/CT findings led to surgical treatment in the majority of patients. Especially in those cases, the prior imaging findings have been discreet on plain radiography. On conventional bone scan, the exact anatomical localization was difficult to identify, thus lacking a clear-cut diagnosis. Our results do not completely endorse the findings of the study of Gnanasegaran et al. where SPECT/CT provided additional diagnostic information in 81% of patients with unexplained foot pain or postoperative disorders
. Thereupon, patient management was changed in 62%. Those differences might be explained by the more standardized imaging procedures in our patient population as well as by the much more specific patient population. However, post-therapeutic evaluations might be an additional example where SPECT/CT might have a future in as a standard diagnostic tool, because MRI is often impaired in those cases due to prominent contrast media uptake post-operatively. According to the overview of Scharf, old and new injuries in these special cases only could be ruled out with SPECT/CT because the ability to localize activity within a bone or at an articular surface allows for differentiation between fractures and joint disease
Our study has several limitations. Firstly, evaluating the therapeutic impact was conducted retrospectively. However, it was jointly evaluated together with the hand surgeons in our hospital, and it was evaluable based on the patients' charts which therapy was indeed changed based on the results of the SPECT/CT. SPECT/CT also had false positive findings in ten patients. These were neglected based on the clinical findings by the treating surgeon after discussion with the imaging specialist. Thus, SPECT/CT always has to be considered in a clinical context as a whole, and the clinical examination should certainly not be neglected when evaluating multimodality images. Not all patients had totally the same imaging scheme prior to SPECT/CT. All patients had X-rays and planar bone scan to compare with (from the combined SPECT/CT procedure), but only half of our study population had MRI. However, all patients had unspecific hand and wrist pain at the time point of the SPECT/CT. The results of the direct comparison of SPECT/CT vs. MRI concerning lesion detection and characterization have already been published
. In that study, we mainly found a higher sensitivity of the MRI concerning lesion detection, but a higher specificity of SPECT/CT in depicting the clinically relevant lesions. Thus, our study presented here concentrated on the diagnostic impact on therapy rather than on diagnostic accuracy. SPECT/CT, as a combined metabolical/anatomical imaging modality, is methodically impaired concerning soft tissue evaluation, e.g., tendons, sheaths, as well as fibrous tissue. However, new concepts already demonstrated that even in SPECT/CT, truly combined radiological/metabolical imaging is possible - even with intra-articular contrast media
. Radiation is certainly a topic not to neglect. However, in our study, we used a middle-dose CT with 80 mA in a FOV of 40 cm which can be considered a ‘justifiable’ dose, especially in the extremities.