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Chapter V RECOVERY OF SENSORY FUNCTION Y. T. Oestcr and Loyal Davis A. INTRODUCTION In keeping with the guiding interests of the study as a whole, the objective of the sensory studies was two-fold: (1) to provide a more adequate and unbiased description of the final level of sensory return following injuries well defined as to extent and anatomic structure; and (2) to utilize differ- ential sensory recovery as an analytic tool for evaluating the effects of characteristics of the nerve injury, of any associated injuries, and of various details in their management. One cannot expect the content of routine clinical records, much less those of war injuries, to be commensurate in their detail and perfection with observations made years after the injury in accordance with a specific research protocol and in comparatively leisurely fashion. The practical objectives and the limitations of the base- line and interim observations, therefore, have guided the selection of sensory tests to be performed at follow-up and have directed interest away from many more basic problems in neurophysiology which might other- wise have been studied. From among specific sensory tests considered to be technically feasible and relatively reliable, a battery has been chosen to provide a representative picture of sensory performance at follow-up. To this description of sensory performance has been added a careful ana- tomic description of the original injury, with emphasis upon complete sutures. Sensory regeneration is not, therefore, studied here in its longi- tudinal aspect; rather it is assumed that a maximum return of sensation had occurred in each case prior to the follow-up examination, usually 4 or 5 years after definitive operation. Nor are the quality and extent of the sensory loss, either at injury or at follow-up, mapped in detail, as in earlier studies (24, 59, 60, 76). Finally, and purely as a matter of editorial convenience, the painful sensations of which patients complained either spontaneously or on examination and the limitation of function by sensory deficit are discussed in other chapters. The organization of the present chapter parallels that of chapter III on motor recovery. There is first a methodological part concerned with the selection of the specific tests of sensory function and with their tech- niques and instrumentation. The basic, descriptive portrayal of sensory status at follow-up is contained in a separate section which, unlike its counterpart in the motor chapter, is separate from the analysis of the 241

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effects of certain characteristics of the nerve lesion itself, a separation enforced by the greater number of individual modalities requiring discus- sion here. Two final parts follow the organization of the motor chapter in detail, one on the influence of associated injuries, infections, and ther- apeutic procedures, the other on the apparent effect of certain technical aspects in the surgical management of peripheral nerve injuries. In preparing the tabulation plan for the sensory chapter, consideration was given to the possibility that the correlation between motor and sensory regeneration might be so high as to render unnecessary any study of the details of surgical management beyond that contemplated in the motor chapter. However, preliminary tabulations suggested that such was not the case and the tables underlying the present chapter follow very closely the pattern described in chapter I, including the detail of the injury- operation groups. The greater complexity and variety of the sensory determinations, as contrasted with the motor, render difficult the task of writing a single, unified chapter representing the work of all five peripheral nerve centers. In many ways it would have been more adequate, and certainly more satisfying for the workers in each center, to have analyzed and reported upon their own data. However, the original plan of the entire study was predicated upon a common, integrated analysis and it is on that basis that the present chapter proceeds. Conspicuously absent from it are the results of many special sensory studies made in individual centers, espe- cially Chicago, where the sensory examination was most complete. It is hoped that the ancillary data may be presented in subsequent reports from individual centers. B. METHODS OF EVALUATING SENSORY RECOVERY At the initial January 1947 conference it was pointed out that there then existed very little information on the specific level of sensory return, by modality, which could be expected following injuries of known extent, and that both practical and scientific interests would be served by the careful assessment of individual modalities. However, since a large-scale, cooperative survey was being planned, and it was agreed that uniform, comparable examinations should be made routinely, it was plain that the standard examination must not be overly elaborate, and that individual follow-up centers should be encouraged to supplement the standard examination with additional determinations of their own choosing in the light of their special interests. Emphasis was, therefore, placed on the more reliable and more objective aspects of sensory response to stimulation, and many tests originally proposed for the standard examination were not chosen. Moreover, when the time came to prepare a code for the statistical analysis, it was realized that the handling of data on areas of sensory loss would present difficulties, and that the most reliable observations were those pertaining to the area of isolated nerve supply (autonomous zone). 242

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Accordingly, the mapping of total areas of diminished or absent sensibility was discontinued except in individual centers, notably Chicago, where there were special interests in the material. The Chicago center also made some observations on the loss of sensory response to temperature and to vibration. At the January 1947 conference tentative agreement was reached on the content of the sensory examination, as follows: Mapping of area of loss of touch. Mapping of area of loss of sensitivity to temperature. Mapping of area of loss of superficial pain sensation. Determination of deep pain response at tip of fingers and toes. Mapping of two-point sensitivity. Tinel's sign. At the first planning conference in November 1947 the above list was confirmed, and the standard forms thereafter designed for the project called for specific mapping of areas of sensory loss. The Chicago center printed these forms with provision for an additional distinction between areas of diminished touch (or superficial pain) response and areas of complete loss. At the Chicago conference in January 1949 it was decided to abstract from the sensory examination only the superficial pain and touch thresholds for the autonomous zones, together with the pain and touch responses to deep pressure, and to summarize sensory regeneration on the basis of the scale developed by workers associated with the British Medical Research Council (68). The tests of temperature sensation and two-point discrimination, and the determination of Tinel's sign, were dropped from the list of standard sensory tests. Later, as trial coding proceeded, the group was persuaded to add to the abstract for statistical purposes tests of position sense and localization of stimuli, although these had been omitted from the original protocol. 1. Pain. Pain was considered in terms of deep pain resulting from pressure, as on the tips of fingers and toes, and of superficial pain resulting from graded pinprick. The superficial pain threshold was determined by means of Lewey's spring algesiometers (42) which were made and calibrated at the same source. The examiner applied the pointed end of this instrument to the appropriate area and exerted steady, gentle force. The end-point was read in grams/mm2 pressure. The observations on the autonomous zone were scaled as follows for analysis: a. No sensation of pain. b. Deep pressure pain only. c. Superficial pain sensation to 40 gin./mm1. d. Superficial pain sensation to 30 gm./mm'. e. Superficial pain sensation to 20 gm./mm1. /. Superficial pain sensation to 10 gm./mm2. g. Superficial pain sensation to 6 gm./mm1. h. Superficial pain sensation to<[6 gm./mm'. 243

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Although the Chicago charts, and the early charts of the other centers, contain further data of undeniable value on the extent of any deficit in pain sensibility, the data on the autonomous zone are surely the most reproducible, especially since examiners were loath to block adjacent nerves. The five centers were compared, prior to the statistical analysis, on the basis of completely sutured nerves, completely divided at injury, and with no associated nerve injury. The proportions with thresholds of 10 gm or less were compared for sutures of median, ulnar, radial, and peroneal, and with thresholds of 30 gm. or less for the tibial, and appeared to be reasonably homogeneous except that New York ratings were much les* favorable on peroneal sutures. Although the specifications for selecting the cases for these comparisons were so rigorous that the number of cases per center was not large, and in consequence the comparisons are not very powerful in the statistical sense, at least gross comparability of examinations seemed assured. Later, when all the ratings of individual centers were compared in more detail, it became plain that the centers did vary con- siderably in their use of the categories "no pain sensation," "deep pressure pain only," and threshold below 6 gm. Also one center (Chicago) almost never observed thresholds of 30 gm., 20 gm., and 6 gm. and concentrated its readings on the other categories of the classification. 2. Touch Touch was approached in parallel fashion. Dr. Lewey devised a care- fully standardized series of von Frey hairs, also made centrally and cal- ibrated at the Philadelphia center, which all follow-up centers employed. Although the Chicago observations, and those made early in the other cen- ters, extended to mapping the entire area of loss or diminution in touch sensibility, when the material was coded for statistical analysis attention was confined to the autonomous zones. The following scale was used: 0. No sensation, or threshold in excess of 50 gm./mm' 1. Deep pressure felt with 50 gm./mm' 2. Deep pressure felt with 35 gm./mm' 3. Deep pressure felt with 25 gm./mm2 4. Superficial pressure felt with 16 gin./mm' 5. Superficial pressure felt with 5 qm./mnv 6. Superficial pressure felt with 3 gin./mm' 7. Superficial pressure felt with <3 gm./mm1 The study of center variation in rating touch thresholds was made along the lines already described in connection with the pain threshold, and considerable center variation was found for each of the four nerves sampled (median, ulnar, tibial, and peroneal). The only systematic feature of this variation was the greater tendency of one center (San Francisco) to report thresholds of 3 gm. and a lesser tendency to report "no sensation, or threshold in excess of 50 gm." In addition, however, the Chicago center almost never reported thresholds of 50, 35, 16, and 3 gm. Consideration was given to the possibility of analyzing the touch data by center, but since 244

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only one center deviated in a gross way, and accounted for only about 13 percent of the data, this was not done. One member of the study group (Dr. Lyons) has questioned the ability of the examiners to distinguish reliably between pain and touch reinnerva- tion, pointing out that it is very rare in this material (about 1.7 percent) that examiners reported no pain sensation in the presence of some touch sensibility. He also suggested that there may have been many instances in which regenerated superficial or even deep pain fibers were stimulated by the examiner and their reponse interpreted as sensation of touch or deep pressure. No statistical validation procedure seems applicable here, but the relationship between pain and touch assessments on median, ulnar, peroneal, and tibial nerves is shown in table 131. It will be seen there that 104/684 or 15 percent of the cases with a pain response were considered to have no touch response in contrast to the figure of 1.7 percent already given for absent pain sensitivity in the presence of a touch response. Table 131.—Correlation Between Pain and Touch Assessments, Median, Ulnar, Peroneal, and Tibial Nerves Pain response Touch response Absent Present Total Abse n t 83 104 10 93 Present 580 684 Total 187 590 777 3. Position Sense The test of position sense consisted of asking the subject to locate the postion of the moved part, screened from his view. The following rough scale was used in classifying the observations for statistical analysis: 0. No position sense 1. Position sense present but reduced 2. Position sense normal. Unfortunately, the test was performed only about half the time, and in one center (Chicago) almost never. The center comparison was confined to ulnar sutures of the set previously defined, and the resulting variation, exhibited in table 132, seemed sufficient to deny the ratings any real value in the subsequent analyses; accordingly the data are not presented here. 4. Localization Estimation of the patient's ability (without visual help) to localize stimuli applied to the affected autonomous zone was also a late addition to the standard sensory examination. If no significant pain or sensory 245

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Table 132.—Center Variation in Reporting of Position Sense Number of lesions, by position sense Follow-up center Absent Reduced Normal Total A. Complete sutures on ulnar ' Boston 8 4 7 19 New York 2 2 17 21 Philadelphia 15 34 28 77 San Francisco 2 28 4 34 Total 27 68 56 151 B. All nerves, all types of lesion, all operations 31 21 124 176 New York 37 24 154 215 Philadelphia 157 264 390 811 San Francisco 12 246 58 316 Total 237 555 726 1*518 1 Injury produced complete nerve division, and no other nerve was injured on the same limb. perception existed, there was so obviously no ability to localize that many examiners did not even code this observation. For example, at the Philadelphia center, where localization was actually tested in about half of the cases, table 133 shows the relation between the performance of the test and the results obtained in tests on the pain and touch thresholds. With some pain or touch sensation, a stimulus, either pain or touch, was chosen, which was easily perceived. In other words, the test was one of localization of touch, where possible, and otherwise consisted in pain localization. When the observations on localization were abstracted for statistical study they were classified as follows: 0. Absent localization. 1. Split sensation. 2. Normal localization. Localization was tested in less than half the cases, and presence of anesthesia played a large role in the examiner's decision whether to perform the test. Unfortunately, when the observations were coded for statistical analysis all cases not tested were lumped together as unknowns, so that the material as coded cannot be used except in conjunction with the results of tests on pain and touch thresholds. Quite significant center variation was ob- 246

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served; the percentages with normal localization, for example, are 31, 39, 60, and 62 for the 4 centers, on a range of 178 to 468 cases. Although the variation is less extreme than that observed for position sense, it is nevertheless too large to permit pooling of data with impunity. For these reasons the observations on localization possess only very limited useful- ness and their presentation in the following section has been limited to the data from a single center, Philadelphia. Table 133.—Percentage of Cases Tested for Localization in Relation to Results of Pain and Touch Stimulation, Complete Sutures on Median, Ulnar, Tibial, and Sciatic-Tibial Nerves Examined at Philadelphia Follow-up Center Number of lesions studied Localization test performed Pain threshold Touch threshold Number Percent None, or 50 gm. or None, or 50 gm. or >50 gm... less . . 91 47 7 168 9 11 29 3 118 0 12 62 43 70 0 40 gm. or less >50 gm... less Unknown on either pain or touch. Total 322 161 50 5. Modified British Summary of Sensory Regeneration The summary of sensory regeneration was adapted from a scale de- veloped by the Nerve Injuries Committee of the Medical Research Council of Great Britain (68, 70), and consists of the following rubrics: 0. Absence of sensibility in the autonomous zone. 1. Recovery of deep cutaneous pain sensibility within the autonomous zone. 2. Recovery of superficial pain sensibility. 3. Recovery of some degree of superficial cutaneous pain and touch sensibility within the autonomous zone. 4. Return of superficial pain and touch sensibility throughout autonomous zone, with overreaction and inability to localize stimulus. 5. Return of superficial cutaneous pain and touch sensibility throughout autonomous zone, with disappearance of any overresponsc. 6. Return of sensibility as above with the addition that there is some recovery of two-point discrimination within the autonomous zone. 7. Complete recovery. A precise comparison with the British classification is made in table 140, below. The modified British summary of sensory regeneration was adopted at the Chicago conference not only for its value as a summarizing device but also as a possible bridge between the results of the two studies. Exploration of center variation prior to tabulation did not extend to this 247

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sensory summary, it having been supposed that any derived summary would merely have the characteristics of its components. Subsequent to the tabulation of the sensory data, however, the centers were compared as to their use of the British classification; 1,924 completely sutured nerves with no associated nerve injury were studied. The observed variation was very discouraging and had it been discovered prior to tabulation and analysis the material of each center would have been studied separately. Table 134 includes the comparative data on the median and ulnar; results with the tibial and sciatic-tibial were no better. Table 134.—Comparison of Follow-up Centers as to Classification of Sensory Recovery on Basis of British Summary, Completely Sutured Nerves With No Associated Nerve Injuries Percentage distribution of cases by British sum- mary Total Center Not more Pain and Pain and number than re- touch, with touch, with of nerves turn of overreaction no over- Total superficial and inabil- response pain (0, ity to local- (5, 6, 7) i l,2)i ize (3, 4) i Median sutures Boston 24 0 40 0 36 0 100 0 ,0 57 1 32 1 10 7 99. 9 28 New York 24.3 63.6 12. 1 100.0 107 Philadelphia 26.9 31.9 41. 2 100.0 119 San Francisco 4.0 48.0 48.0 100.0 5O Ulnar sutures 27.5 44. 9 27 5 99.9 69 67. 3 28.8 3.8 99.9 52 New York 35. 3 49.7 15.0 100.0 153 Philadelphia 34.8 16.7 48.5 100.0 204 7 9 50 6 41 6 100 1 89 1 These numbers define the grouping more specifically, in terms of the classification on p. 247. 6. Sensory Evidence of Anatomic Regeneration In each case a judgment was also made as to evidence of any anatomic regeneration of sensory fibers; similar assessments were made on the basis of the voluntary motor and the electrical tests, it will be recalled. Prior to 241

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tabulation, statistical tests on the homogeneity of the five centers were con- fined to the proportion coded as having any evidence of anatomic regenera- tion, and these suggested that the centers were sufficiently homogeneous. Later, at the time the centers were compared as to their use of the British summary of sensory regeneration, the matter was restudied with specific attention to evidence of anatomic regeneration of sensory fibers and quite significant variation found, as may be seen in table 135. Two centeis seem to deviate excessively from the rest, Chicago in the direction of report- ing lower sensory return and San Francisco in the opposite direction, if the cases examined by the five centers are in fact homogeneous to begin with. Table 135.—Comparison of Follow-up Centers as to Percentage of Completely Sutured Lesions With Any Evidence of Anatomic Regeneration of Sensory Fibers, Nerves With JVb Associated Nerve Injury on Same Limb Percentage with evidence of regeneration, by nerve Center Median Ulnar Tibial Sciatic- tibia! Boston 87.5 71.4 91.7 85.7 96.2 80.6 76.4 90.7 86.3 95.6 100.0 58.6 96.7 88.6 100.0 81.3 50.0 Ohirago ....*..* New York 75.4 74.6 90.0 Philadelphia Total 88.2 87.3 85.6 73.6 The same pattern of deviation is evident in table 134 on the British sum- mary of sensory regeneration, and suggests the need for some consideration of any independent evidence of the homogeneity of the cases themselves, as contrasted with the sensory evaluations, as has been assumed. Study of the modified British summary of motor regeneration tends to confirm this assumption of homogeneity; no absolute confirmation is, of course, possible since the cases are different, but in comparison with an average rank of 3.0 which would be expected from 5 centers with homogeneous material the Chicago cases have an average rank of 2.5 and San Francisco 2.8 among all 5 centers, where the averaging is done over nerves.1* "Each center was ranked 1, 2, 3, 4, or 5 in order of relative excellence of results on each nerve (M, U, R, P, SP, and ST, only T being omitted for paucity of cases), and the 6 ranks thus obtained for each center were averaged; in entirely homogeneous material each center would have an expected average rank of 3.0, the average of ranks 1,2,3, 4, and 5. 403980—57- -18 249

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7. Sources of Error In view of the essentially subjective nature of sensation, each and every determination requires the active cooperation of the subject under study. His status in respect to fatigue, willingness to cooperate, and immediate response to his environment, all combine to influence clinical observations on sensory performance. But in addition to these sources of variation, the evidence is that in this study the examiners themselves probably varied greatly in their interpretation of the patients' reactions to sensory stimuli. Of all the clinical observations and assessments abstracted for statistical study, only that on pain is surely adequate for direct pooling of data from the various centers. Since the extent of examiner-variation was not fully appre- ciated until after the main analysis had been completed on the pooled data it was not possible to extend the analysis to the individual centers to the extent desired. One result is that the effect of characteristics of the nerve injury, of associated injuries, and of variables in the management of the nerve injury, may be analyzed best on the basis of the pain threshold, but the observations on touch and the British classification have also been used. To the extent that variation among the study centers cooperating in the present investigation may be representative of variation among the general- ity of skilled neurological observers, however, the fact that the group of examiners was as large as five provides some assurance that their examina- tions will yield an average picture of all possible examinations, rather than one unduly influenced by a particular point of view. Although examiners were asked to extend their sensory examination to all 7 major nerves (M, U, R, P, T, SP, and ST), and observations on all 7 appear in the present chapter, chief reliance must of course be placed upon the median, ulnar, tibial, and sciatic-tibial injuries. For the radial, peroneal, and sciatic-peroneal the anatomic pattern of sensory supply varies so greatly from one individual to the next, both quantitatively and qualitatively, that the lack of earlier assessments of comparable extent and quality robs the follow-up examination of any real precision in the indi- vidual case. Indeed trained observers who look for early evidence of sensory regeneration following nerve injury have learned that no conclu- sions can be drawn from the degree of sensation present in the so-called autonomous zones of these nerves. On the other hand, the fact of great individual variation in the autonomous zones does not necessarily deny these nerves a role in any statistical analysis on the effects of characteristics of injury and of details of treatment, because there can be no reason to assume any correlation between individual aberrations in pattern of nerve supply and the nature of the lesion or the choice of treatment. Individual variation in the autonomous zones may be considered a random variable in such statistical analyses, tending to obscure the significance of any variation which may derive from the characteristics of injury and treat- ment. Since the statistical analysis is very largely concerned with ascer- taining whether particular factors influence individual modalities in some 250

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general way common to all nerves, It has seemed unnecessarily restrictive to exclude the radial, peroneal, and sciatic-peroneal entirely and better to use them for whatever independent data they might contain. To the extent that the autonomous zones for radial and peroneal nerves are smaller than average, or even absent, examiners may be expected to exaggerate the frequency with which sensory fibers have regenerated. However, the data may be used to derive estimates of the likelihood of sensory return, it seems probable that such estimates will be unduly high, but to an un- known extent. Comparisons between these nerves and others, therefore, will not be reliable, although high-low comparisons within each of them may be. A true high-low difference might well be obscured by the error of observation arising out of individual variation in autonomous zones. In view of the interest which attaches to comparisons of lysed and sutured lesions and in view of the presumably incomplete nature of most lesions subjected merely to neurolysis, all cases of this type were reviewed " at the end of the project for positive evidence of sensory loss at the time of operation. C. DESCRIPTION OF SENSORY RECOVERY FOLLOWING COMPLETE NERVE SUTURE To avoid any bias which might result from the inclusion of possibly atypical cases, the tables for this section were restricted to the representa- tive sample defined in chapter I (p. 9). The scheme of presentation places emphasis upon the modality of sensation, the injured nerve, and the follow-up center (where necessary), in that order. 1. Pain For all the complete sutures in the representative sample, without regard to site of injury, extent of injury, presence of associated nerve injury, etc., table 136 provides a summary of findings by nerve. Subject to the qualifi- cations already mentioned, these data are presented as a factual summary of the major findings of the study with respect to deep-pressure and super- ficial pain. They constitute as good an estimate as one might hope to have of the ultimate level of pain sensibility following peripheral nerve suture in young males. Table 136 is comparable to table 49 in the motor chapter (pp. 88-89), which distributes each sample of affected muscles as to ultimate power following suture. As will be shown by the subsequent analysis, the special features of the wounds incurred by the men studied here, and the fact that they were received in battle, appear to have so little influence upon the ultimate extent of sensory regeneration that one cannot doubt the representativeness of the results as a sample of all peri- pheral nerve injuries in young males, provided they were treated by suture in the modern manner. 17 New York and Philadelphia cases were reviewed at those centers, Boston, Chicago, and San Francisco cases by personnel of the NRC Follow-up Agency. 251

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Table 181.—Bulb Suture and Recovery of Pain Response in Autonomous %pne at Follow-up, All Complete Sutures, by Nerve Lesions with no special features Lesions first treated by bulb suture Statis- tical Nerve Percentage with pain threshold of 10 gm. or less ' Percentage with pain threshold of 10 gm. or less ' tests ' Number Number Median 191 141 156 121 37.2 29.1 44.9 33.1 33.3 22. 1 18.0 23 25 26 10 10 12 11 30.4 32.0 38.5 30.0 10.0 25.0 18.2 NS NS NS NS NS NS NS Ulnar Radial Tibial 57 131 100 Sciatic-tibial 1 Among all examined cases, including those classified as "hypesthesia, unmeasured." 1 Result of statistical tests (two-tailed) abbreviated as follows: NS—Not significant. 7. Character of Nerve Ends at Definitive Suture The prognostic significance of the surgeon's description of nerve ends, following resection and freshening, was sought in the eventual sensory re- covery of pure lesions on the median,ulnar, peroneal, and tibial, but none was found. Pain, touch, and British summary were studied for each nerve, but with generally negative results as illustrated in table 182 for pain. Table 182.—Surgeon's Description of Nerve Ends at Definitive Suture and Re- covery of Pain Response in Autonomous %pne at Follow-up, Pure Lesions on the Median, Ulnar, Peroneal, and Tibial Both distal and proximal ends normal Other Statis- tical tests1 Nerve Percentage with pain thresholds of 10 gm. or less ' Percentage with pain thresholds of 10 gm. or less i Number Number 97 199 29.9 36.7 36.8 27.3 30 62 31 46.7 33.9 22.6 23.8 NS NS NS NS Ulnar 68 44 Tibial 21 1 Among all examined lesions, including those classified as "hypesthesia, unmeasured." 1 Results of statistical tests (two-tailed) abbreviated as follows: NS—Not significant. 300

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8. Tension Upon Suture Line The observations on tension are technically less satisfactory than most observations concerned with the details of management, as already noted. Only pure lesions on the median, ulnar, peroneal, and tibial nerves were studied as to the possible effect of tension upon sensory recovery. Pain, touch, and the British summary of sensory recovery were all included in these studies, but for none of the sensory indices was the variation associated with differences in tension of a magnitude which achieved statistical significance. The data on pain are presented in table 183 as representative of the findings. The lesions classified as having no tension are those in which the operator's report specifically stated that tension was minimal; cases in which the operator made no reference to tension were not used in the analysis. Table 183.—Surgeon's Description of Tension on Definitive Suture Line and Recovery of Pain Response in Autonomous %pne at Follow-up, Pure Lesions on the Median, Ulnar, Peroneal, and Tibial Nerves No tension Moderate or severe tension Statis- tical test « Nerve Percentage with pain threshold of 10 gm. or less l Percentage with pain threshold of 10 gm. or less ' Number Number Median 74 187 111 35.1 34.8 29.7 19 35 18 36.8 25.7 50.0 NS NS NS Ulnar Peroneal plus tibial i Among all examined cases, including those classified as "hypesthesia, unmeasured." ' Results of statistical tests (two-tailed) abbreviated as follows: NS=Not significant. 9. Suture Material As was observed in the initial study of motor recovery, there at first appeared to be marked differences in sensory return when lesions were grouped according to the material used in the definitive suture. Lesions sutured with silk appeared no different from those sutured with fine tantalum wire, but both were definitely superior to those on which the plasma glue technique was employed. Table 184 presents a summary of these initial comparisons on definitive sutures for "pure" lesions. As was shown in chapter III, however, the plasma glue series is not comparable with the tantalum and silk series in two major respects: (a) plasma glue sutures were generally done at longer intervals after injury; and (b) definitive plasma glue sutures were more often second or subsequent sutures. 301

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Table 184.—Suture Material at Definitive Operation and Sensory Recovery, Pure Lesions Only, by Nerve Tantalum Silk Plasma glue Statis- Nerve tical No. of Percent No. of Percent No. of Percent tests' lesions supe- lesions supe- lesions supe- rior ' rior ' rior * A. Pain threshold Median 106 34. 9 38 47.4 25 8.0 ** Ulnar 257 35.4 80 22. S 29 27.6 NS Peroneal 91 29.7 42 42.9 + -f NS Tibial 59 27. 1 27 29.6 + + NS B. Touch threshold Median 107 31.8 38 52.6 25 8.0 ** Ulnar 258 30.2 77 32.5 29 27.6 NS Peroneal 91 34. 1 42 33.3 + + NS Tibial 59 27. 1 27 25.9 + + NS C. British summary Median 108 32 4 38 36. 8 25 4.0 ** Ulnar 262 32 8 80 28.7 30 10.0 * Peroneal 94 25.5 42 28.6 + + NS Tibial 60 16 7 28 14 3 + + NS 1 Superior is defined as follows: Pain: superficial pain felt with 10 gm. or less, among all tested* including any with "hypalgesia, unmeasured." Touch: superficial pressure felt with 5 gm. or less, among all tested, including any with "hypesthcsia, unmeasured." British summary: Both superficial pain and touch present, no overresponse. 1 Results of statistical tests abbreviated as follows: NS=Not significant. * ^significant at .05 level. **-=significant at .01 level. + Too few cases to tabulate. Since sensory recovery is unrelated to interval from injury to suture, the only controls which appear necessary are that the groups be defined by the suture materials used at the first operation and examined at the New York Center where all the plasma glue patients were seen. Controlled comparisons of this nature were made for median and ulnar nerves, and are summarized in table 185. Since it has already been shown that asso- ciated nerve lesions do not affect examiners' evaluations of sensory recovery, 302

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table 185 is not confined to pure nerve lesions as is table 184, and there is actually a net gain in the number of plasma glue median sutures available for study. The use of these additional controls does not dissipate all the evidence of poorer sensory return following plasma glue suture, for the touch response of the median nerve continues to be inferior, but otherwise all the differentials of table 184 appear greatly reduced in table 185, and to such an extent that the only tenable conclusion is that sensory recovery following plasma glue suture is probably no different from that seen after sutures with tantalum and silk. Table 185.—Suture Material at First Operation and Sensory Recovery, All Median and Ulnar Lesions Studied at New York Center Tantalum or silk Plasma glue Statistical tests' Nerve No. of Percent No. of lesions Percent superior ' lesions superior ' A. Pain threshold Median 72 31.9 29 20.7 NS Ulnar 114 26. 3 27 22.2 NS Total 186 28.5 56 21.4 NS B. Touch threshold Median 72 26.4 29 6.9 NS Ulnar 114 21. 1 28 28.6 NS Total . . 186 23 1 57 17 5 NS C. British summary Median 71 54.9 29 69.0 NS Ulnar 115 52.2 28 50.0 NS Total 186 53 2 57 59 6 NS "As in table 184. ' Results of statistical tests abbreviated as follows: NS = Not significant. 10. Use of Cuff About one-third of the definitive sutures were protected by cuffs, almost always those made of tantalum foil. In only about 7 percent of the cases was it unknown whether a cuff was employed. All seven major nerves 303

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were studied for variation in sensory recovery associated with the use of cuffs, and the selection was not limited to pure lesions. Pain, touch, and the British summary of sensory recovery were utilized in these compari- sons, and in each index the observed variation appeared to exceed that expected from a random process. Table 186 provides a summary of the observations on pain, and although for only 1 of the 7 nerves is the dis- crepancy statistically significant, it will be noted that in every comparison there is a differential in the same direction. When all seven tests are taken in combination it is clear that the evidence in favor of the cuff is statis- tically quite significant. Analysis of the touch response also provides fairly strong evidence in favor of the cuff (table 187). In one of the individual comparisons the discrepancy between the percentages with superior touch response attains statistical significance, and although for the ulnar the direction of the difference is counter to the rest, when all 7 tests are combined the overall probability is found to be <^*01. The evidence from the British summary of sensory recovery is even more definite. Table 188 distributes each nerve-cuff group according to a coarse grouping of the British scale. Almost uniformly the sutures accom- plished with the aid of cuffs look better at both ends of the scale. Table 186.—Use of Cuff at Definitive Suture and Recovery of Pain Response in Autonomous %pne at Follow-up, by Nerve No cuff used Cuff used Nerve Percentage with pain threshold of 10 gin. or less ' Percentage with pain threshold of 10 gm. or less J Statis- tical tests ' Number of lesions Number of lesions Median 211 322 145 125 71 125 99 35.1 30.1 43.4 29.6 25.4 14.4 14.1 119 194 104 43.7 33.5 48.1 36.8 34.3 28.9 22.5 NS NS Ulnar Radial NS NS NS Peroneal 38 35 97 71 Tibial Sciatic-peroneal * Sciatic-t ibial NS All tests combined ** 1 Among all examined cases, including those classified as "hypesthesia, unmeasured." 1 Results of statistical tests (two-tailed) abbreviated as follows: NS—Not significant. *—Significant at .05 level. **—Significant at .01 level. 304

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Table 187.—Use of Cuff at Definitive Suture and Recovery of Touch Response in Autonomous %pne at Follow-up, by Nerve No Cuff used Cuff used Nerve Percentage with touch threshold of 5 gm. or less i Percentage with touch threshold of 5 gm. or less ' Statis- tical Number of lesions Number of lesions tests 2 Median 213 323 143 125 71 125 99 35.7 31.6 121 193 105 39 35 98 73 45.5 29.5 52.4 38.5 31.4 22.4 20.5 NS NS NS NS NS * Ulnar Radial 44. 1 26.4 21.1 10.4 13.1 Peroneal Tibial Sciatic-peroneal Sciatic-tibial NS All tests combined ** 1 Among all examined lesions, including those classified as "hypalgesia* unmeasured." ' Results of statistical tests (two-tailed) abbreviated as follows: NS—Not significant. *—Significant at .05 level. **—Significant at .01 level. As noted in chapter III, the decision to employ a cuff is probably related to characteristics of the case which have a bearing upon nerve regeneration. When a controlled motor comparison of cases with and without cuff was done by restricting the analysis to lesions with most favorable prospects for recovery (no associated injuries, short gaps, and fairly early time of operation), the advantage of cases with cuff disappeared. Accordingly, the same selection was made here and tables 186 and 187 were repeated. Unlike motor recovery, sensory recovery is not appreciably affected by these restrictions; a larger sampling variation is introduced by the fact of smaller numbers of cases, but no systematic shift appears in either the group with, or the group without, cuffs. In consequence, lesions with tantalum foil again appear to have recovered more fully than those without, although the margin of advantage is less certain and more variable in this smaller amount of material. Table 189 contains these data; statistical tests were done only on the totals for all nerves since each nerve is repre- sented by so few cases, and both for pain and touch lead to the rejection of the hypothesis that cases with cuff are no better than those without. 305

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Table 188.—Use of Cuff at Definitive Suture and British Classification of Sensory Recovery at Follow-up, by Nerve Percentage distribution as to British classi- fication of sensory recovery At most superficial pain and touch with overreaction and inability to localize At least superficial pain and touch with disappear- ance of over- response Number of lesions Nerve and use of cuff No sen- sation or deep pain Total Median: No cuff 23.9 21.7 49.1 46.7 27.1 100.1 100. 1 218 120 Cuff 31.7 Ulnar: No cuff 31.4 24.1 38.7 47.2 29.9 28.6 100.0 99.9 328 199 Cuff Radial: No cuff 21.5 10.2 34.2 44.3 49.1 100.0 100.0 149 108 Cuff 40.7 Peroneal: No cuff 39.1 25.6 38.3 43.6 22.7 30.8 100.1 100.0 128 39 Cuff Tibial: No cuff 50.0 25.0 38.9 52.8 11.1 100.0 100.0 72 36 Cuff 22.2 Sciatic-peroneal : No cuff 55.1 45.0 37.0 39.0 7.9 16.0 100.0 100.0 127 100 Cuff Sciatic-tibia!: No cuff 59.0 49.3 35.0 36.0 6.0 14.7 100.0 100.0 100 Cuff 75 11. Use of Stay Suture Among all complete sutures, 67 percent were performed without resort to the stay suture, 22 percent with the stay suture, and in 11 percent the operation report was unclear or silent on the subject. As was noted in the roster-comparisons appearing in chapter II, stay sutures were much less often placed on sutures in the representative sample than on other sutures. To avoid this source of bias, therefore, the study of stay suture was confined to the representative sample of sutures, all of which are from the Army Registry and within the sampling area. Only the nerves of the upper extremity were studied, and the British summary of sensory recovery was used to provide the criterion. As may be seen in table 190, this limited study provides no evidence of any effect upon sensory return. 306

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Table 189.—Percentage of Sutured Lesions With Superior Pain and Touch Thresholds1 in Relation to Use of Tantalum Cuff, by Nerve, for Lesions Selected *for Favorable Outcome Nerve sutured Number of lesions Percentage with superior pain thres- hold Percentage with superior touch threshold No cuff Cuff No Cuff P« No cuff Cuff P» cuff Median 11 21 33 18 10 10 19 17 27.3 29.0 26.1 11.1 20.0 16.0 23.1 57. 1 39.4 38.9 30.0 50.0 26.3 23.5 38.5 28.1 30.4 27.8 20.0 16.0 15.4 45.5 28. 1 61.1 27.3 50.0 15.8 23.5 Ulnar 31 23 18 10 25 26 Radial Peroneal Tibial Sciatic-peroneal Sciatic-tibial . . Total 144 128 22.2 38.3 <.01 24.5 34.9 .034 1 As defined in tables 186 and 187. 1 Having no associated injuries, short gaps, and moderate intervals from injury to suture. ' Probability obtained in statistical test of percentages. Table 190.—British Summary of Sensory Recovery and Use of Stay Suture at Definitive Suture, Nerves of the Upper Extremity Number of lesions Percentage with superior sensory return l Nerve Stay suture Median None 217 30.4 Any . 49 34.7 Total 266 31.2 Ulnar 360 30.0 77 28.6 Total 437 29.7 Radial None 169 55.0 Anv 52 42.3 Total 221 52. 1 1 Defined as groups 5, 6* and 7 in table 169, i. e., at least return of superficial pain and touch without overresponse. 307

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12. Training of Surgeon Trained neurosurgeons performed about 45 percent of the definitive operations, general surgeons with wartime training in neurosurgery about 33 percent, and surgeons with essentially no special neurosurgical training the remaining 22 percent. The analysis of variation in sensory recovery associated with these differentials in neurosurgical training was done on pure lesions managed by complete suture. Pain recovery, touch recovery, and the British summary of sensory recovery were all employed as measures of functional sensory return, but for none of them was any evidence found that neurosurgical training, thus defined, was associated with differentials in sensory recovery. Table 191 presents a summary of the pain data to exemplify this analysis. Table 191.—Neurosurgical Training and Recovery of Pain Response in Autonomous %one Following Definitive Suture on Pure Nerve Lesions, by Nerve Neurosurgical training Nerve Trained neuro- surgeon General surgeon with neurosur- gical training Essentially un- trained in neurosurgery Statis- tical tests' Number of cases Percentage with pain thresholds of 10 grn. or less ' Number of cases Percentage with pain thresholds of 10 gm. or less ' Number of cases Percentage with pain thresholds of 10 gm. or less * Median 73 129 56 37 30.1 27.9 33.9 29.7 53 150 54 36 47.2 33.3 35.2 25.0 51 100 32 27.5 36.0 25.0 29.4 NS NS NS NS Ulnar Peroneal Tibial 17 1 Among all examined cases, including those classified as "hypesthesia, unmeasured." 1 Results of statistical tests (two-tailed) abbreviated as follows: NS=Not significant. 13. Summary Despite the difficulties inherent in arguing from the fact ol group dif- ferences to the effect of specific forms of treatment when treatment groups are defined by clinical considerations alone, sensory recovery at follow-up has been used as a criterion for exploring the possible influence of the variety of details on treatment abstracted from operation reports in military records of treatment. In general the results obtained here differ greatly from those presented in the motor chapter, so much so in fact that the difficulty is not one of interpreting variation in the light of treatment 308

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differences but rather one of determining whether the observed variation is within the limits of a random process. The following characteristics appear not to be associated with significant variation in sensory recovery: Days from injury to definitive suture. Echelon (Z/I or overseas) of definitive suture. Length of surgical gap at definitive suture. Resort to bulb suture as a preliminary procedure prior to definitive suture. Operator's gross evaluation of nerve ends after freshening. Operator's report of tension on definitive suture-line. Suture material. Use of stay suture. Level of formal neurosurgical training of operator. In marked contrast to the analysis of motor recovery, it is extremely significant that the analysis here yields no evidence that time from injury to suture influenced sensory recovery in any way. The only elements of surgical treatment which were found to be asso- ciated with variation in sensory recovery, by the criterion of statistical significance used here, are: a. Transposition and mobilization of nerves in the lower extremity were followed by considerably poorer recovery of touch sensibility, but appeared to have no effect upon recovery of pain. In the upper extremity no such variation was seen. b. Sutured nerves about which tantalum foil cuffs were placed appear to have definitely superior recovery of both pain and touch sensibility, even after some effort at insuring the inherent comparability of the treatment groups in the light of factors present at suture which might be considered to have prognostic value. 309

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