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Computed Tomography With Implant Movement Analysis in the Work-Up of Painful Total Hip Prostheses
Thomas R Listopadzki1, K Keely Boyle2, Scott R Nodzo2
1Department of Orthopaedics, Jacobs School of Medicine and Biomedical Science, University at Buffalo, The State University of New York at Buffalo, Buffalo, New York.
Background:
Diagnosing aseptic loosening following total hip arthroplasty is challenging. Computed tomography (CT)-guided implant movement analysis (CT-IMA) overlays two CT scans of a stressed total hip prosthesis to evaluate for micromotion. The purpose of this study was to evaluate this technology in identifying clinically stable and unstable total hip prostheses.
Methods:
Plain radiographs and CT-IMA scans of 80 patients with painful total hip prostheses were evaluated. Standard radiographs demonstrating 1- to 2-mm circumferential radiolucent lines within the modified Gruen, or Delee and Charnley zones, or subsidence were considered loose. A CT-IMA scan demonstrating implant motion > 0.5 mm was generally considered loose. Patients were categorized by implant stability based on plain radiographs and CT-IMA scans. Hip Dysfunction and Osteoarthritis Outcome Score for Joint Replacement (HOOS, JR) scores were calculated for each group from the initial to the final follow-up. Statistical analysis was performed with two-tailed paired t-tests.
Results:
There were 66 patients who were categorized into the radiographically Stable-IMA Stable group (Group 1), six into the radiographically Loose-IMA Stable group (Group 2), and eight into the radiographically Loose-IMA Loose group (Group 3). Within Group 1, HOOS, JR scores improved from 49.5 ± 18.4 to 64.2 ± 18.9 (P = 0.004). The 14 patients who underwent revision surgery had well-fixed components. Within Group 2, HOOS, JR scores improved from 57.7 ± 19.7 to 69.1 ± 21.5 (P = 0.01). The two patients who underwent revision surgery had well-fixed components. Within Group 3, HOOS, JR scores improved from 45.5 ± 18.1 to 71.8 ± 15.4 (P = 0.04). The seven patients who underwent revision surgery had loose components and one patient was lost to follow-up.
Conclusions:
A CT-IMA better identified patients who had stable total hip prostheses than standard radiographs, demonstrating its value in the workup of a painful total hip prosthesis.
