Acetabular component positioning using anatomic landmarks of the acetabulum.
BACKGROUND
The acetabular cup should be properly oriented to prevent dislocation and to reduce wear. However, achieving proper cup placement is challenging with potentially large variations of cup position. We propose a new technique to position the acetabular cup.


OBJECTIVE
We used this technique, then determined actual cup position and subsequent dislocation rate.


METHODS
We measured acetabular abduction (α°) and anteversion (β°) on preoperative CT scans in 46 patients (50 hips) scheduled for THA. During the operation, we identified the transverse acetabular notch (TAN) and anterior acetabular notch (AAN), a notch at the anterior acetabular margin. We then marked two reference points for 40° abduction at the acetabular rim: the superior point, which is opposite the TAN, and the inferior point at |α - 40| mm inside (when α was > 40°) or outside the TAN (when α was < 40°). We also marked two reference points for 15° anteversion: the posterior point opposite the AAN and the anterior point at |β - 15| mm inside (when β was < 15°) or outside the AAN (when β was > 15°). During cup insertion, we aligned cup abduction to the line between the superior and inferior points and cup anteversion to the line between the anterior and posterior points. We measured cup abduction and anteversion and evaluated the dislocation rate. One patient was lost to followup before 60 months; the minimum followup for the other 45 patients was 60 months (mean, 62.8 months; range, 60-65 months).


RESULTS
The mean cup abduction was 40° (range, 32°-47°) and the mean cup anteversion was 17° (range, 8°-25°). No dislocation occurred postoperatively in 49 hips (45 patients) for a minimum of 5 years followup.


CONCLUSIONS
We obtained adequate cup position with our method and none of 45 patients (49 hips) had dislocation.


METHODS
Level IV, therapeutic study. See Guidelines for Authors for a complete description of level of evidence.
Department of Orthopaedic Surgery, Chung-Ang University College of Medicine, Seoul, South Korea.
Yong-Chan
YC
Ha
Jeong Joon
JJ
Yoo
Young-Kyun
YK
Lee
Jin Young
JY
Kim
Kyung-Hoi
KH
Koo
D000077:Acetabulum / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D000328:Adult; D000368:Aged; D059925:Anatomic Landmarks; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000295:instrumentation*; D001696:Biomechanical Phenomena; D005260:Female; D006617:Hip Dislocation / Q000209:etiology; D006621:Hip Joint / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011474:Prosthesis Design; D016059:Range of Motion, Articular; D020127:Recovery of Function; D013997:Time Factors; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome; D055815:Young Adult