Tangent sign - A reliable predictor of risk for tendon re-rupture in rotator cuff repair

Abstract

PURPOSE OF THE STUDY Repair techniques for rotator cuff injury are currently well advanced. However, the risk of re-rupture, particularly when severe damage to the tendons has been repaired, is still high. The causes of failure can be due to the extent of injury, a repair done on a highly degenerated tendon with diminished viability or ischaemic damage to the tendon tissue resulting from suture material. The aim of the study was to ascertain the reliability of the tangent sign, a commonly used indicator of the degree of suprasupinatus muscle atrophy, in the prediction of risk for tendon re-rupture in the post-operative period. MATERIAL AND METHODS In 2011 the rotator cuff torn tendons were repaired by the method of double- ow suture in 37 patients. The surgery was done by an open technique using the deltoid-splitting approach. A pre-operative magnetic resonance image (MRI) of the shoulder was obtained in all patients and each was assessed by a competent independent radiology specialist with a focus on the extent of a tendon lesion and the tangent sign. At 2-year follow-up, the results of repeated MRI were evaluated in view of the state of repaired tendons and, if a re-tear was found, its relation to the original suture and its extent in the sagittal plane were determined. The pre- and post-operative MRI findings were compared to find out how the presence or absence of a tangent sign befor surgery relates to the incidence of supraspinatus tendon re-rupture at 2 years after surgery. The results were statistically analysed using Student's t-test and the Chi-square test. RESULTS Of the 37 shoulders, in the pre-operative period, a tangent sign was identified in 21 (56.8%). The average size of a rotator cuff tear was 29.3 mm for the whole group. For the shoulders with no tangent sign, the average value was 21.8 mm, for those with a tangent sign present, it was 39.6 mm. At 2-year follow-up, no tear was found in the patients in whom pre-operative MRI showed no tangent sign while re-tears were recorded in 18 of 21 shoulders (85.7%) with a tangent sign present before surgery. On the average, the re-rupture had 40.8 mm in size and, in all cases, it occurred at the site of tendon re-insertion into the greater tubercle. These results were statistically significant (p < 0.01). DISCUSSION In repair of injury to the tendons of the rotator cuff muscles, emphasis is currently placed on a thorough pre-operative examination. MRI is an important part of the diagnostic procedure because it provides a detailed image of the muscle as a whole. Although great advances have recently been made in both the diagnostic and surgical techniques, the incidence of tendon re-rupture within a few years of the procedure is still high. CONCLUSION Our results show that the presence of a tangent sign detected by pre-operative MRI examination of the shoulder can be an important predictor of failure in rotator cuff repair and can also turn attention to the selection of an alternative technique to be used.