Rapidly destructive coxarthrosis (RDC) is rare and develops unusual clinical course. Recent studies suggest multiple possible mechanisms of the development of RDC. However the exact mechanism of RDC is still not clear. The difficulty of the study on RDC is attributed to its rareness and the fact that the data before the onset of RDC is normally unavailable. In this report, we presented the patient having the radiographic data before the onset who had rapid osteoarthritis (OA) development after contralateral THA, which meets the current criteria of RDC. We thought that the increased posterior tilt of the pelvis after THA reinforced the stress concentration at pre-existed anterior acetabular cyst, thereby the destruction of the cyst was occurred. As a result the rapid OA was developed. We think that there is the case of rapid osteoarthritis developing due to alternating load concentration by posterior pelvic tilt on preexisting anterior acetabular cyst such as our patient among the cases diagnosed as RDC without any identifiable etiology. The recognition of sagittal alignment changes and anterior acetabular cyst may play important role in prediction and prevention of the rapid hip osteoarthritis development similar to RDC.
Rapidly destructive coxarthrosis (RDC) was firstly described by Postel and Kerboull in 1970 [
An 80-year-old female had a total hip arthroplasty (THA) on her right hip due to chronic osteoarthritis of the hip for 7 years. At the time of right THA, she had no symptoms on her left hip. However, 2 months after right THA, she started to have left hip pain without any trauma. Gradually left hip pain was deteriorated, as a result left THA was performed 10 months after right THA. After right THA, the patient had no minor trauma such as falls or standing firmly. There were no clinical signs and results of blood test indicating the systematic autoimmune disorder and the infection.
Concerning the radiographic evaluation, standard X-ray of the hip and CT scan were obtained. At the time of right THA, left hip was showing enough joint space with aectabular cyst at anterior part (Figures
Consequent X-ray of the hip. At the time of right THA, left hip had enough joint space with bone cyst at anterior acetabulum ((a), (b); white arrow). Postoperative X-ray (c). 8 months after right THA, left hip had the end stage of osteoarthritis (black arrow; (d)).
Sagittal plane of CT. Before right THA, enough joint space with the bone cyst at anterior part of the acetabulum (a). Before Left THA, narrowing joint space with destruction of the bone cyst at anterior part of the acetabulum. Femoral head is also flattened with subchondral sclerotic changes due to osteoarthritis development (b).
MRI of T1 weighted image (a) and T2 weight image (b) showed no abnormality of the left hip.
For sagittal alignment assessment, full-length standing lateral radiograph was used; in brief the subject stood in a relaxed position, with the arms folded across the chest to minimize variation due to the effects of trunk posture on the lumbosacral junction [
Alignment change assessment using the standing lateral X-ray. The pelvic tilt was defined as the angle between the vertical line and the anterior pelvic plain, which was constructed by the line passing through the midpoint of the bilateral anterior iliac spines and the midpoint of the bilateral pubic tubercles. At the time of right THA (a), the pelvic tilt angle was 4°. At the time of left THA, the pelvic tilt angle was 11°. The pelvic was tilted posteriorly about 6°.
Left THA was performed under general anesthesia. The intra-articular joint fluid was sent for the microorganisms examination (the standard culture revealed negative). After left THA, no complication was observed.
Postel and Kerboull firstly described RDC in English literature in 1970 [
Recent studies suggest multiple possible mechanism of the development of RDC. Yamamoto and Bullough reported that SIF of the femoral head occurs in elderly women with osteopenia, and they speculated that insufficiency fracture resulting from osteopenia might lead to rapid breakdown of the hip joint [
In this report, we presented the patient who had rapid OA development, which meets the current criteria of RDC after contralateral THA. We thought that the increased posterior tilt of the pelvis after THA reinforced the stress concentration at pre-existed anterior acetabular cyst, thereby the destruction of the cyst was occurred. As a result the rapid OA was developed (Figure
Schema of the estimated mechanism of rapid osteoarthritis changes in our case.
In general, pelvic posterior tilt increases according to the ages due to the decrease of the lumbar lordosis and back muscle weakness [
Concerning the bone cyst, even though many studies have been performed on the mechanism of development of the bone cyst, the exact mechanism is still not clear. There is the hydrodynamic theory [
We think that there is the case of rapid osteoarthritis developing due to alternating load concentration by posterior pelvic tilt on preexisting anterior acetabular cyst such as our patient among the cases diagnosed as RDC without any identifiable etiology. The recognition of sagittal alignment changes and anterior acetabular cyst may play important role in prediction and prevention of the rapid hip osteoarthritis development similar to RDC.
The authors declare that there is no conflict of interests regarding the publication of this paper.
The authors would like to thank Dr. Kaoru Tashiro for his cooperation in analyzing the sagittal alignment change.