[A study of the neurologic risk in tendino-muscular advancement of supra-spinatus and infra-spinatus in the repair of large rotator cuff rupture].

PURPOSE OF THE STUDY

An anatomical study by Warner et al. (1992) showed that an advancement of supra and infra-spinatus of more than 3 cm could be deleterious for the suprascapular nerve or its branches. In pathological conditions, the limit of possible advancement could even be less than 3 cm. The authors wanted to know whether this technique, which they use for the repair of large rotator cuff tears, could have neurological effects in surgical practice.

MATERIAL

24 shoulders among 24 patients having had a rotator cuff repair using a musclar advancement have been studied. In 13 cases only the supraspinatus had been advanced, and in 11 cases both supra and infraspinatus have been advanced.

METHODS

The suprascapular nerve status has been studied postoperatively by EMG. EMG was performed at a mean 8.5 months follow-up. Motor unit potentials were studied at rest and after maximal contraction. Electro-stimulation at Erb's point was used to evaluate muscular latency. All repairs have been controlled by opaque arthrography, and a CT scan grading of muscular fatty degeneration was performed. In 19 cases EMG had also been performed preoperatively.

RESULTS

At revision, 17 EMG were considered normal. In one case there was an impairment of the first primary trunk, already noticed preoperatively. Only 6 EMG anomalies probably related to surgery have been noticed, although the width of the tear in the coronal plane was nearly always of more than 3 cm. 4 of these 6 shoulders had been explored preoperatively by EMG, and were recorded as normal before surgery. Electric impairment was limited to the supraspinatus in 3 cases (increase of muscular latency after single advancement in two cases, polyphasic motor unit potential after double advancement in one case), to the infraspinatus in one case (polyphasic motor unit potentials recorded in the infraspinatus after single advancement of the supraspinatus), and concerned both muscles in 2 cases (increase of muscular latencies after double advancement).

DISCUSSION

Muscular advancement was usually performed for tears of more than 2.5 cm wide, and so should be deleterious for suprascapular nerve, according to Warner et al. studies. But in most cases no neurological impairment could be observed in surgical practice. This could be due to the fact that the gap to repair is due not only to a loss of substance in the tendons but also to muscular retraction. In a first step, the muscular release allows to correct this muscular retraction ("muscular" advancement). The advancement remaining then to be performed is about 2 cm wide ("tendino-muscular" advancement).

CONCLUSION

It appears that in surgical practice supra and infraspinatus advancement threatens only moderatly the suprascapular nerve or its branches, even if the width of the tear is greater than 3 cm. Postoperative immobilization in slight lateral elevation further reduces the importance of this advancement.