| Summary: | Purpose. To measure the transverse acetabular ligament (TAL) anteversion in hips with severe deformity, using fluoroscopy–computed tomographic navigation. Methods. 31 hips in 10 men and 19 women aged 40 to 78 (mean, 58.7) years who underwent total hip arthroplasty for primary osteoarthritis (n=6) or osteoarthritis secondary to developmental hip dysplasia (n=19) or congenital hip dislocation (n=6) were included. The severity of hip dislocation was classified according to the Crowe classification; 15 hips were grade 1, 7 were grade 2, 3 were grade 3, and 6 were grade 4. The TAL anteversion was measured using fluoroscopy–computed tomographic navigation. The difference in TAL anteversion between non-dislocated hips (Crowe grade 1, n=15) and dislocated hips (Crowe grades 2–4, n=16) was compared. Results. In all 31 hips, the TAL could be visualised intra-operatively. No patient reported severe pain, early wear, loosening, or dislocation after 2 years. The mean TAL anteversion and inclination angles measured by the navigation system were 26.5° (SD, 8.9°; range, 8°–42°) and 41.5° (SD, 4.6°; range, 32°–49°), respectively. 22 of the 31 hips were in the safe zone. TAL anteversion in non-dislocated and dislocated hips was not significantly different. Inter- and intra-observer mean absolute differences in TAL anteversion were 0.3° and 0.4°, respectively. Conclusion. The TAL is a useful anatomic landmark for total hip arthroplasty in dislocated hips.
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