Median and ulnar nerve injuries

Abstract

Summary Although the clinical assessment of recovery after peripheral nerve injury has been well standardized since World War II, the interpretation of the findings is seriously limited by the subjective nature of the customary tests. The patient who is unwilling, unable or too young to co-operate defies accurate classification. The results of tests of response to pinprick and light touch bear little relation to the functional capacity of the hand. Tests of joint position sense and 2 point discrimination are more informative in this regard, but are often neglected because they are tedious to perform and require the intelligent and patient co-operation of the subject. Recent work by Moberg, suggesting that fingerprint tests of sweating could be used as an objective method of evaluating the return of functional sensibility in the hand and advocating the use of functional and objective tests, has led to a more critical appraisal of the results of nerve sutures. The nerve injuries treated since 1948 by 4 plastic surgeons in their public hospital and private practice have been reviewed, using conventional subjective tests, ninhydrin fingerprints and functional tests, in an attempt to investigate further the relationship between sudomotor function and sensory recovery and also to assess the results of the cases treated. Half of the patients were children under fourteen years of age. The common injury was a tidy distal laceration of the median and/or ulnar nerve, frequently complicated by significant tendon injuries. In this paper the results of 97 median or ulnar nerve sutures are presented and some observations on the results of other forms of nerve repair are reported. Motor recovery was always incomplete after ulnar nerve suture: the useful grade (M2+) was reached by all but one of the children and by two-thirds of the adults. Complete recovery of motor function was common after median suture in childhood: only 2 children failed to attain the useful grade (M 3) and half of the adults also reached this grade. The M.R.C. workers designated S2+, the grade which corresponds to return of touch and pain sensibility to the tips of the fingers but with persistent over-reaction to be the one which repaid suture, as indeed it is in terms of a protective type of sensibility. Only one child failed to reach this grade after median nerve repair and none after ulnar suture. More than three-quarters of the adults also reached this grade after median or ulnar suture. The recovery of tactile gnosis after median nerve repair is necessary for precision sensory function. The functional tests provided a useful method of assessing this faculty, recovery of which was good in children and very defective in adults, causing serious disability. After the repair of complete nerve injuries, normal or slightly impaired sweating, as shown by the fingerprint tests, corresponded closely to the return of tactile gnosis and some two point discrimination. In addition to the exceptions described by Moberg, the recovery of normal sweating after nerve grafting was unaccompanied by a corresponding recovery of tactile gnosis and precision sensory function. As an objective test, fingerprinting was also unreliable in the assessment of the results of partial nerve injuries. As Weir Mitchell and his colleagues observed almost a century ago, “incomplete injuries of the nerve supply give rise to the most variable consequences.” The relative uniformity of technique and management in this series and the predominance of tidy distal lesions, permitted the examination of the effect of some other factors on the results, particularly that of age. Nerve suture in childhood produced the most gratifying results. Provided that the repair was performed without undue delay, a good result was the rule. The results in adults were poor, particularly with regard to precision sensory function in median nerve injuries. In view of this, the use of island flap transfer is suggested in addition to median nerve suture in an attempt to restore precision sensory grip, especially when the dominant hand is affected. Post-operative sepsis was not a problem in the management of these civilian nerve injuries.- The importance of primary repair of concomitant tendon injuries is stressed, as poor results of tendon sutures are incompatible with good function in the hand. The timing of definitive nerve repair appeared relatively unimportant within a few months of injury but, especially in children, the advantages of primary repair were obvious.