NEUROLOGIC RISK IN SUPRA-SPINATUS AND INF RA-SPINATUS TENDINO-MUSCULAR ADVANCEMENT FOR THE REPAIR OF LARGE ROTATOR CUFF TEARS

Purpose of the study An anatomical study by Warner et al. (1992) showe d that an advancement of supra and infra-spinatus of more than 3 cm co uld be deleterious for the suprascapular nerve or its branches. In pat hological conditions, the limit of possible advancement could even be less than 3 cm. The authors wanted to know whether this technique, whi ch they use for the repair of large rotator cuff tears, could have neu rological effects in surgical practice. Material 24 shoulders among 24 patients having had a rotator cuff repair using a muscular advancemen t have been studied. In 13 cases only the supraspinatus had been advan ced, and in 11 cases both supra and infraspinatus have been advanced. Methods The suprascapular nerve status has been studied postoperativel y by EMG. EMG was performed at a mean 8,5 months follow-up. Motor unit potentials were studied at rest and after maximal contraction. Electr o-stimulation at Erb's point was used to evaluate muscular latency. Al l repairs have been controlled by opaque arthrography, and a CT scan g rading of muscular fatty degeneration was performed. In 19 cases EMG h ad also been performed preoperatively. Results At revision, 17 EMG wer e considered normal. In one case there was an impairment of the first primary trunk, already noticed preoperatively. Only 6 EMG anomalies pr obably 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 t hese 6 shoulders had been explored preoperatively by EMG, and were rec orded as normal before surgery. Electric impairment was limited to the supraspinatus in 3 cases (increase of muscular latency after single a dvancement 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 adva ncement of the supraspinatus), and concerned both muscles in 2 cases ( increase of muscular latencies after double advancement). Discussion M uscular advancement was usually performed for tears of more than 2,5 c m wide, and so should be deleterious for suprascapular nerve, accordin g to Warner et al. studies. But in most cases no neurological impairme nt could be observed in surgical practice. This could be due to the fa ct that the gap to repair is due not only to a loss of substance in th e tendons but also to muscular retraction. In a first step, the muscul ar 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 threaten s only moderatly the suprascapular nerve or its branches, even if the width of the tear is greater than 3 cm. Postoperative immobilization i n slight lateral elevation further reduces the importance of this adva ncement.