Dislocation of large-diameter head metal-on-metal total hip arthroplasty and hip resurfacing arthroplasty
Miettinen, S. S. A., Mäkinen, T. J., Laaksonen, I., Mäkelä, K., Huhtala, H., Kettunen, J. S., & Remes, V. (2019).Hip
Introduction:
Dislocation of large-diameter head (LDH) metal-on-metal (MoM) total hip arthroplasty (THA) or hip resurfacing arthroplasty (HRA) is a rare complication. This study aimed to determine the incidence and risk factors for dislocation of LDH MoM THAs and HRAs.
Methods:
This retrospective analysis considered 4038 cementless LDH MoM THAs and HRAs, 3207 THAs in 2912 patients and 831 HRAs in 757 patients. The end of follow-up was revision due to dislocation. Incidence of dislocation was evaluated from this study population of 4038, and study groups were formed. The study was designed as a case-control study, and a threefold stratified randomised control group was formed. Demographic data were collected and radiological analyses were performed in the study groups.
Results:
There were 26/3207 (0.8%) early dislocations in the THA group, and 6/831 (0.7%) in the HRA group (p = 0.9). Most LDH THA dislocations occurred in a group with head size ⩽ 38 mm (18/26) (p < 0.001). In dislocated hips, there were more dysplastic acetabula and post-traumatic hips than in the control group (p = 0.036). In the dislocation group, the mean acetabulum component anteversion angle was 19.6° (standard deviation [SD] 13.4°) and in the control group it was 23.2° (SD 10.4°) (p = 0.006); 7/32 (21.8%) of dislocated THAs needed revision surgery, and mean time to revision from the index surgery was 1.2 (SD 2.6) years.
Discussion:
Dislocations occurred more often in THAs of head size ⩽ 38 mm and with a smaller anteversion angle of the acetabulum component. Hip dysplasia and post-traumatic osteoarthritis were more common in patients with dislocation.
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