Clinical usefulness of single photon emission tomography/computed tomography with stress analysis in early diagnoses of stem instability of noncemented hip arthroplasty

Objective Hip pain arising from implant instability is generally caused by repetitive stress injury, which subsequently leads to induction or exacerbation of abnormal metabolism of bone around the implant. single photon emission tomography/computed tomography (SPECT-CT) has advantages in localizing areas of increased tracer uptake that reflects such abnormal bone metabolism. Therefore, we investigated whether the application of SPECT/CT with stress analysis can be an effective practice in evaluating the instability of stem in noncemented hip arthroplasty or not. Method In total 16 patients were collected for unexplained painful hip arthroplasties. When physical examination and blood tests were unremarkable, radiographs were inconclusive and bone scan indicated increased scintigraphic uptake at the proximal part and at the tip of the stem; SPECT/CT was performed. Stem stability was assessed by measuring whether there was consistency between the increased scintigraphic uptake and the direction of the stress around the implant along with the location of the prosthesis. Result Among the 16 symptomatic hips, 9 hips showed the stability of the stem, 3 hips showed the stem instability and 4 hips showed the acetabular loosening with the stem stability. With the application of SPECT/CT with stress analysis, 15 out of 16 (93.7%) cases were found to have the change in the diagnoses, and managements were implemented in 11 out of 16 (68.7%) cases. When comparing before and after SPECT/CT, there was no significant association in clinical diagnosis and management (Pearson chi- square test = 4.61 and 1.33, P = 0.33 and 0.25). Conclusion SPECT/CT combined with stress analysis can be a useful tool in early diagnosis of stem instability and can assist surgeons in subsequent management and decision implementation when other radiographic imagings are inconclusive.