PAST LETTERS FROM THE PRESIDENT
Yasunari
Hiranuma, Takashi Atsumi, Kenichi Yamano, Yasushi Takemura,
Satoshi Tamaoki, Yasuhiro Asakura, Eiji Kato, Minoru Watanabe
Department of Orthopaedic Surgery, Fujigaoka Hospital, Showa University School of Medicine, Yokohama, Japan
Purpose:
We evaluated antero-posterior instability of the hip with osteonecrosis
immediately after anterior rotational osteotomy using Dynamic CT and investigated
the relationship between the instability and developing marginal osteophyte
of the femoral head postoperatively.
Patients
and Methods: 23 hips of 21 patients with non-traumatic osteonecrosis
undergoing anterior rotational osteotomy were subjected. There were 2
women and 19 men with mean age of 39 at operation. All patients were followed
up for more than 2 years (mean: 4). The etiologic factors were steroids
administration in 10, alcoholic abuse in 12, and both in 1. According
to the staging system by the Japanese Ministry of Health, Labor, and Welfare,
there were 11 hips in stage 3a (collapse is less than 3 mm), 9 in 3b (collapse
is 3 mm or greater), and 3 in stage 4. Dynamic CT, taking in both neutral
and 45 degrees flexion position, studied antero-posterior shift of the
femoral head. In addition, we observed marginal osteophyte with more than
2 mm in size on follow-up A-P radiograph.
Results: Seven hips (30%) with 5 hips in stage 3b and
2 hips in stage 4 showed instability. Marginal osteophyte was shown in
8 hips including all of 7 hips with the instability. However these hips
had no joint narrowing.
Conclusions: From these results, hip instability immediately after anterior rotational osteotomy occurs in case with an extensive necrotic lesion and marked collapse preoperatively. Developing marginal osteophyte may prevent the instability.