Abstract
BACKGROUND AND PURPOSE: CT micromotion analysis (CTMA) has been considered as an alternative to radiostereometry (RSA) for assessing early implant migration of orthopedic implants. We investigated the feasibility of CTMA to assess early migration and the progression of radiolucent lines in shoulder arthroplasties over 24 months using sequential low-dose CT scans. PATIENTS AND METHODS: 7 patients were included and underwent 9 primary total shoulder arthroplasties. We made CT scans preoperatively, within 1 week postoperatively, and after 3, 6, 12, and 24 months. At each follow-up, postoperative glenoid migration and any development of radiolucent lines were assessed. Clinical outcomes were recorded at all time points except within 1 week postoperatively. RESULTS: For the glenoid component, the median translation and median rotation were 0.00-0.10 mm and -1.53° to 1.05° at 24 months. Radiolucent lines could be observed around all glenoid components. The radiolucent lines developed from the periphery to the center of the implant for 6 glenoid components during follow-up. The Constant Score improved from a mean of 30 (21-51) preoperatively to 69 (41-88) at 24 months. INTERPRETATION: CTMA can be used to identify early migration and the development of radiolucent lines over time in glenoid components. Clinical trials with a larger sample size and longer follow-up are needed to establish the relationship between migration, radiolucent lines, loosening, and clinical outcome.