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SUTURE O F THE MUSCULOSPIRAL NERVE SUTURE OF THE MUSCULOSPIRAL NERVE: 315 THREE CASES. BY CAPTAIN GWYNNE \YILLIAMS, R.A.M.C. (T.), LONDON. THEfollowing cases show t h e completeness with which motor recovery takes place a f t e r suture of the musculospiral nerve, a n d accord with t h e general impression as to the results of suture of this particular nerve. T h e y are brought forward because t h e y show t h e r a t e of recovery of t h e nerve and-by t h e order in which recovery of t h e muscles t a k e s place-emphasize t h e progressive down-growth of t h e axis-cylinder. T h e y a r e also p u t forth as offering a hypothesis to explain t h e difference i n t h e results of suture i n t h e musculospiral as opposed t o other nerves. The technique of t h e operation has i n every case been quite simple, t h e nerve ends being brought together without a n y tension by a single catgut suture through t h e substance of t h e nerve. T h e line of suture has been wrapped round with subcutaneous fat. Precautions were t a k e n t o prevent a n y tension on t h e union until a m o n t h had elapsed. In all cases t h e muscles paralyzed were relaxed b y an extension splint. I n Cases 1 a n d 3 t h e fingers were kept extended from t h e first ; b u t i n Case 2 t h i s was n o t done until t h e radial extensors had recovered; this helped to prevent the stiffness of the metacarpophalangeal joints, which is liable t o occur as a result of prolonged extension of t h e fingers even when massage and movements are used daily. I n Case 1 n o other treatment was carried out, b u t in Cases 2 and 3 massage a n d galvanism were employed. Case 1.-J. BI., age 15, came under my care at University College Hospital, on Oct. 2, 1916, having cut his right arm just above the elbow-joint a month before. The wound was not quite healed, and there was complete musculospiral paralysis. The muscles were relaxed by an extension splint, but no recovery having taken place by Dec. 24, 1916, the nerve was explored. OPERATIOlrT.-The ends of the nerve were separated by about one inch ; they were freshened, and sutured with catgut, the line of suture being wrapped in subcutaneous fat. The radial extensors recovered by April 12, 1917. I did not see the patient again until May 14, when the extensors of the fingers had recovered. On June 10 the extensor longus pollicis showed definite voluntary movements. The after-treatment consisted entirely of relaxation, since the patient was unable t o attend for massage and galvanism. Case 2.-B. Gunshot wound, March 23, 1917, involving the right musculospiral in the middle of the upper arm. The wound took some time t o heal. OPmcATroN.-Sept. 3. The nerve was found t o be completely interrupted ; both ends were freshened, and sutured with catgut, the line of suture being wrapped in subcutaneous fat. The patient was not seen by me for some time, but says that he noticed recovery of the wristdrop a t the end of Feb., 1918. I saw him on March 4, and the radial extensors had recovered. On May 7 I received a report from Dr. Murray Levick t h a t there was voluntary movement in the extensor communis digitornm and the extensor ossis metacarpi pollicis, but not in the extensor longus pollicis. On .June 25, the latter muscle showed definite voluntary movement, but was not very strong. The after-treatment consisted of relaxation, massage, and galvanism. Case 3.-J. S. AI. Gunshot wound, Nov. 5 , 1916, involving the musculospiral and musculocutaneous ncrves a t the outlet of the axilla on the left side. No suppuration. OPEnATION.-Jan. 6, 1917. The musculospiral was found t o be completely interrupted by scar tissue ; this was excised and the nerve sutured with catgut, the suture line being covered by a sheath of subcutaneous fat. The musculocutaneous was fixed by scar tissue, from which it was released, and the nerve wrapped in fat. Movement in the biceps was first noticed on Feb. 22, 1917. I n July, movement was suspected in the extensors of the wrist, and by the middle of September the hand could be supported, the extensor carpi radialis longior acting well. Extension of the little finger was noticed by Dec. 1.5 ; by Christmas the middle and ring fingers had recovered, and the index began t o move about Jan. 16, i.e., a year after the operation. At the end of February there was a faint sign of movement in the extensor longus pollicis. These facts as t o recovery have been sent me by the patient from Australia ; I have not seen them myself. The treatment was relaxation, massage, and galvanism. It will be seen t h a t recovery took place most quickly in Case 1, where t h e lesion was most peripheral, and t h a t i t was slower when t h e lesion was higher up. T h u s t h e distance 316 THE BRITISH JOURNAL O F SURGERY of the line of suture from the elbow-joint, which corresponds roughly with the entrance of the branches into the radial extensors, was in Case 1 one inch, in Case 2 three inches, and in Case 3 seven inches, while recovery was noticed in these muscles in three and a half, six, and eight months respectively. The next group of muscles t o show recovery is the extensor communis digitorum, which the posterior interosseous nerve supplies immediately it has passed through the supinator brevis ; the times of recovery in this muscle group being five, eight, and twelve months. The last muscle to recover in each case was the extensor longus pollicis, in six, ten, and fourteen months respectively ; the nerve t o this muscle is a long branch which enters the muscle about 5 in. distal to the elbow-joint. Circumstances have necessarily rendered any more exact investigation of these cases difficult ; but the facts that have been presented show that recovery in any muscle is proportional t o the distance of the lesion from the entry of the nerve into the muscle, and that the rate of growth of the axis-cylinder is about one inch in a month. These three are the only cases of suture of the musculospiral nerve which I have been able to follow up in any way, and at first I was surprised at the completeness of their recovery, since there was no difference in the technique of the operation which was in any way likely to account for their success. Secondary suture of a nerve has always been regarded as unsatisfactory, and i t seemed extraordinary that three consecutive cases should succeed. Reports of cases from other sources soon showed that suture of the musculospiral nerve gave very satisfactory results, so there must be some reason why the musculospiral nerve differs from other trunks such as the median and ulnar, where the recovery is very seldom complete. The only difference in the after-treatment, usually carried out was that in the case of the ulnar and median it was very difficult t o relax the muscles of the hand satisfactorily ; I tried various devices, but without success. I therefore conclude that it must be the composition of the nerve that made the difference. The musculospiral trunk is almost entirely motor, the sensory distribution being not only small in area, but the area is, relative t o the median and ulnar, of slight importance, so that the sensory nerve fibres are probably very few. Any given axis-cylinder starting out from the upper end of the divided musculospiral nerve is almost certain t o find its way down a motor path ; whereas with a mixed nerve, such as the ulnar, if we presume that the motor and sensory fibres are equal in number, the chances of a motor or sensory fibre finding its proper destination are about 50 per cent. There is no evidence that a motor fibre can pick out a motor path, or a sensory fibre a sensory path, and it would be expected that each fibre would take the path that was nearest. The deduction from this would be t h a t a purely motor nerve or a purely sensory nerve should recover almost completely after a satisfactory suture, and in a mixed nerve the recovery might reach completeness if the approximation of the sections of the nerve was topographically accurate ; but unless this rather improbable condition of affairs was brought about, the sensory and motor recovery would both be partial. Further, it might be said that if the suture of a purely motor nerve fails on one occasion, there seems no reason why it should not be undertaken again, unless it can be shown that there is a time limit after which the axis-cylinders will not grow down the nerve peripheral t o the section. The results in a mixed nerve might be improved if it %-ere possible, by knowledge of the topographical arrangement of the various nerve bundles in a trunk, to approximate the ends more accurately: it is possible t o do this roughly in the upper part of the sciatic, but it is doubtful if it could be done in the median or ulnar, displaced as they frequently are by dense scar tissue. The proof of this hypothesis would require an extensive series of observations on the relative motor and sensory composition of nerve trunks and the results of suture. Light would be thrown on the question by cases of suture of the facial and hypoglossal nerves. If shown t o be true, it would be an important factor in determining the prognosis of nerve injuries. I have t o thank Colonel Bruce Porter for permission to publish Cases 2 and 3, which came under my observation at the 3rd London General Hospital.