Radiographic analysis of movements of the acetabulum and the femoral head after Salter innominate osteotomy.
BACKGROUND
Salter innominate osteotomy (SIO) is widely used to improve the coverage of the femoral head in dysplastic acetabulum, but the geometric change after osteotomy and its effect on the outcome have not been well elucidated.


METHODS
Pelvic radiographs of the 90 hips in 86 patients who underwent SIO for the treatment of acetabular dysplasia were reviewed and the movement of the distal fragment and the shift of the femoral head after SIO were analyzed. On the basis of the anteroposterior radiographs of the pelvis in a supine position taken at 5 weeks after operation, various parameters including an open-wedged angle at the osteotomy site (lateral rotation angle, LRA), lateral displacement of the distal fragment (distance d), and the ratio of the bilateral obturator foramen heights (the ratio of obturator heights, ROH), were measured. Improvement in the center-edge angle (CEA) and acetabular index (AI) after SIO was correlated with the LRA, distance d, and ROH. Horizontal and vertical distances from the pubic symphysis to the center of the femoral head were also measured from preoperative and postoperative pelvic radiographs and changes in the position of the femoral head were calculated. For the patients who were followed until skeletal maturity, final radiographic results were also assessed according to the Severin classification.


RESULTS
The average improvement of the CEA and AI after SIO was 19.6 and 13.3 degrees, respectively. The average value of the LRA, distance d, and ROH were 30.2 degrees, 4.07 mm, and 73.0%, respectively. The LRA and distance d positively and the ROH negatively correlated with the improvement of the CEA and AI. The center of the femoral head moved an average of 7.06 mm caudally and 3.11 mm medially after SIO. Thirty-six hips (40%) in 36 patients were available for follow-up until skeletal maturity. The radiographic outcome was good (Severin I or II) in 33 hips and poor (Severin III) in 3 hips. Preoperative CEA was relatively smaller in a poor group. Greater improvement of the CEA during postoperative follow-up was observed in a good group.


CONCLUSIONS
Favorable coverage of the femoral head was obtained after SIO by shifting the center of the femoral head caudally and medially as well as rotating the distal fragment anterolaterally. SIO is a very effective procedure in improvement of the dysplastic acetabulum for the hips with round and spherical femoral head.


METHODS
Therapeutic studies, level III (retrospective study).
Kitoh
Hiroshi
H
Department of Orthopaedic Surgery, Nagoya University School of Medicine, Nagoya, Aichi, Japan. hkitoh@med.nagoya-u.ac.jp
Kaneko
Hiroshi
H
Ishiguro
Naoki
N
D000077:Acetabulum / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000601:surgery*; D002648:Child; D002675:Child, Preschool; D005260:Female; D005270:Femur Head / Q000000981:diagnostic imaging* / Q000503:physiopathology; D006617:Hip Dislocation / Q000503:physiopathology / Q000601:surgery*; D006621:Hip Joint / Q000000981:diagnostic imaging; D006801:Humans; D008297:Male; D010027:Osteotomy; D011184:Postoperative Period; D011859:Radiography; D012189:Retrospective Studies; D016896:Treatment Outcome