INFLUENCE OF THE HUMERAL NOTCH ON THE RESULTS OF ARTHROSCOPIC CURE OF ANTERIOR SHOULDER INSTABILITY: A RADIOGRAPHIC AND COMPUTED TOMOGRAPHIC STUDY

Abstract

Purpose: This study was conducted to analyse the importance of the Malgaigne notch and its position on standard x-rays taken in internal rotation or on arthroscan in patients treated for anterior instability of the shoulder. Our purpose was to search for criteria perdictive of outcome of arthroscopic stabilisation of the shoulder joint using the Bankart method.

Material and methods: Fifty-four patients were reviewed to determine the postoperative Duplay score. Mean follow-up was 68 months (32–100). Mean age at surgery was 29 years. We divided the patients into three populations as a function of preoperative symptoms: population A two dislocations or more, population B one dislocation then episodes of subluxation, population C no dislocation but pain. We divided this population according to the Duplay score. Group 1 patients had a fair or poor outcome, Group 2 patients had a good or excellent outcome. We reviewed 54 radiograms using patterns of increasing size (mm by mm) to assess the radius of the humeral head and the depth of the notch. We evaluate the reproducibility of this method by comparing the readings of ten senior orthopaedic surgeons. There were no false positives or false negatives. Variance of the measures taken by the ten surgeons was 0.67 at 1.31 mm, a small variance. We compared the ratio between the radius of the humeral head and the depth of the notch in the different groups.

Results: The Malgaigne notch was significantly deeper in population A (19%) than in population B (14%) or population C (14.3%). This suggests that the size of the notch has an effect on symptomatology of shoulder instability. The notch was also significantly deeper in group 1 patients (fair or poor outcome) (21%) than in group 2 (good or excellent outcome) (16%) (p=0.05).

Discussion: Beyond a threshold set at 15%, there were 54% fair or poor results. The position of the notch in height was significantly different in population A compared with populations B and C (p=0.01). It appears to be higher in case of true recurrent dislocation. We did not demonstrate any statistical link between the position of the notch on the CT scan and surgical outcome. This study demonstrates the importance of information on the internal rotation images in choosing the proper type of surgery for shoulder instability.