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Abstracts Presented at the 7th Biennial Congress of the International Society of Arthroscopy, Knee Surgery, and Orthopaedic Sports Medicine| Volume 28, ISSUE 9, SUPPLEMENT , e357-e358, September 01, 2012

Paper 39: Acetabular Labral Tear in Japanese Patients

      Abstract

      Introduction

      The acetabular labral tear normally develops in a hip with some form of bony structural abnormality such as acetabular retroversion or decreased offset of head-neck junction. Most tears have been observed laterally and anteriorly in western countries. However, 70∼90% of osteoarthritis in Japanese patients develop from acetabular dysplasia. Literature from Japan reported posterior labral tears were common. These factors suggest that there could be some different clinical feature between acetabular labral tears in Japanese and the ones in western people. Furthermore, to the best of our knowledge, quantitative assessment of intermediate term postoperative clinical results of arthroscopic partial limbectomy has not been reported.
      The purpose of this paper was to reveal frequency of bony structural abnormality, the most frequent portion of the acetabular labral tear, and quantitative intermediate term clinical results of the arthroscopic partial limbectomy in Japanese patients.

      Cases and Methods

      We performed arthroscopic partial limbectomy in 63 hip joints of 63 patients (7 joints of 7 males and 56 joints of 56 females) aged between 13 and 86 (mean; 47.8) years at examination. The follow up period ranged between 48 months and 72 months (mean; 62).
      The radiographical findings, arthroscopic findings, and clinical results of these patients were investigated. Modified Harris' hip scoring system (mHHS)by Byrd were obtained for preoperative and postoperative clinical assessment.

      Results

      Plain radiography showed no abnormality in 42 joints, acetabular dysplasia in 19 joints, and decreased offset of head-neck junction in 2 joints. In the 42 joints without abnormality on plain radiographs, arthroscopy confirmed only labral tear in 28 joints, both labral tear and diffuse articular cartilage degeneration in 13 joints, and both labral tear and small chondral damage in 1 joint. 13 joints with both labral tear and diffuse articular cartilage degeneration were diagnosed as primary osteoarthritis. In the 19 joints with acetabular dysplasia on plain radiographs, CE angle ranged between 11 degrees and 18 degrees (mean;16). In 18 of 19 joints showing acetabular dysplasia, only labral tears were confirmed, and both labral tear and delamination of articular cartilage in 1 joint. In 2 joints with decreased offset of head-neck junction, labral tear and delamination of the articular cartilage were confirmed.
      In all joints, acetabular labral tear confirmed either anterior or lateral part of the acetabular rim.
      In 29 joints with no abnormality on radiographs and only labral tear or labral tear with chondral damage in arthroscopic findings, mHHS improved from mean score of 52.5 before surgery to mean score of 93.5 after surgery. In 19 joints showed acetabular dysplasia on radiographs, mHHS improved from mean score of 67.3 before surgery to mean score of 90.2 after surgery. In 13 joints diagnosed as primary osteoarthritis, mHHS improved from mean score of 63 before surgery to mean score of 86.2 after surgery. In 2 joints with decreased offset of head-neck junction, mHHS improved only for a few months.

      Discussions

      Acetabular retroversion and decreased offset of head-neck junction are thought to be major cause of acetabular labrum tear. However, In our cases no acetabular retroversion and only 2 joints with decreased head-neck junction were confirmed. The reason for this discrepancy is not clear. The fact that frequency of slipping upper femoral head in Japanese is reported to be less than that in western people might be one of the reasons.
      Early articles with small study groups from Japan reported that labral tears frequently occur posteriorly unlike recent reports with large series of cases from Europe and the U.S.A. in which most tears have observed laterally and anteriorly. The cause of this discrepancy may reflect unique aspects of population, may be aberrant due to small study groups, or different way of life among countries might contribute to them. However our study in 63 Japanese cases supported the reports from Europe and the U.S.A.
      Long term clinical results of arthroscopic partial limbectomy are unknown. Our study revealed that in the normal shaped hip with or without chondral degeneration and mild dysplasia, arthroscopic partial limbectomy will assume good clinical results in intermediate term. However long term clinical outcomes was unknown.

      Conclusions

      Unlike the reports from western countries, normal shaped hip was the most frequent in Japanese patients with acetabular labrum tear. The reason for this discrepancy is not clear. Anterior and superior parts of acetabular rim are the most frequent portion where labrum tear occurs even in Japanese. In the normal shaped hip with or without chondral degeneration and mild dysplasia, arthroscopic partial limbectomy will assume good clinical results within 4years after arthroscopic partial limbectomy.