PRE-OPERATIVE FACTORS AND TREATMENT OUTCOME FOLLOWING CARPAL TUNNEL RELEASE G-Z YU, J. C. FIRRELL

and T-M TSAI

From the Christine M. Kleinert Institute for Hand and Micro Surgery, Louisville, Kentucky, USA

The outcome of carpal tunnel release was evaluated retrospectively in 60 hands of 53 patients followed for six to 33 months (median ten months). Outcome was considered good in 27% (pain, weakness, and numbness were essentially resolved); fair in 42% (most of the symptoms improved); and poor in 32% (symptoms persisted or worsened). Patients whose pre-operative work activity was considered physically strenuous were associated with a slightly but significantly poorer outcome (60% good or fair) compared to those in light work or with no employment (89% good or fair). Proportionately fewer patients returned to their original work when they previously engaged in strenuous activity, ranging from 27% for those using air guns to 80% in light work. It appears that the highest chance of a poor outcome from carpal tunnel release occurs in patients who have either associated symptoms of thoracic outlet syndrome or physically strenuous work activities. Journal of Hand Surgery

(British Volume, 1992)

17B : 646-650

(median ten months, range six to 33 months). This resulted in the analysis of data from 53 patients (60 hands). Ages ranged from 20 to 83 years, with a median of 46 years, although the age group with the highest prevalence was between 30 and 39 years. 22 were males and 31 female. Most of the patients (28 out of 53) had been treated conservatively by us without success for a median time of two months before proceeding to surgery. Most of the remainder had conservative treatment B, , splinting, changing elsewhere, including vitamin work habits if they were suspect as causative factors, steroid injection, and non-steroidal anti-inflammatory drugs. Only patients with long-standing symptoms (more than six months), significant thenar atrophy, sensory loss, or following adequate conservative treatment underwent surgery.

Carpal tunnel syndrome has been diagnosed and treated more frequently in recent decades. Release of the flexor retinaculum was first reported in 1933, (Learmonth, 1933) and this still remains the surgical treatment of choice. Despite many reports on the efficacy of conservative and surgical treatment, there have always been groups of patients who have not responded well. It seems possible that pre-existing factors in a patient’s history or in the aetiology itself may not only contribute to the onset of the syndrome but may also influence the outcome of the surgical treatment. Several causative factors have been implicated in carpal tunnel syndrome, among them repetitive strain injuries related to certain work activities. It is unknown whether this subgroup of patients has a better or worse surgical outcome than those without any obvious workrelated trauma. It is also unknown whether the eventual outcome is related to the presence of other associated health conditions, such as thoracic outlet compression and arthritis. Another question relating to the outcome is whether the duration and severity of symptoms has any relationship with the outcome of treatment. We performed a retrospective analysis of patients following surgical carpal tunnel release, paying particular attention to the duration of symptoms, obesity, deficits in nerve conduction velocity, the presence of other health conditions, and occupation. The purpose of this analysis was to determine if any link could be found between these pre-existing conditions and the outcome of treatment.

Surgical procedure The following surgical technique was used: after an axillary block (in most cases) and under tourniquet control, a 4 to 6 cm longitudinal incision was made along the hypothenar border from the proximal palm to the wrist crease. If the incision needed to cross the wrist crease, it was extended in a zig-zag fashion. After the palmar fascia was divided, the transverse carpal ligament was sectioned under direct observation. A superficial synovectomy was performed if synovial hypertrophy was observed, and the median nerve was traced to the motor branch. An epineurotomy was performed if the nerve showed severe constriction by the compression. The flexor retinaculum was reconstructed in the last three years of the study period. Before the wound was closed, the tourniquet was deflated to check for haemostasis, and 1 ml of Celestone was placed into the canal. The wound was closed using interrupted sutures without drainage. Post-operatively, the wrist was immobilized using a volar plaster splint in mild dorsiflexion for two weeks.

METHODS Patient population We reviewed the records of patients who were treated by carpal tunnel release by one surgeon between September 1979 and July 1988. We only included patients who had been assessed at least six months post-operatively 646

OUTCOME

FOLLOWING

CARPAL

TUNNEL

RELEASE

Criteria for analysis Our pre-operative analyses concentrated on the following factors to determine if any could be shown to affect the surgical outcome : (1) duration of symptoms; (2) obesity; (3) deficit in nerve conduction velocity; (4) associated health conditions; and (5) occupation. We reviewed the weights of patients to determine if obesity predisposed to a poor outcome of treatment. Body mass index (BMI) was used to measure obesity (Krupp, Schroeder and Tierney, 1987) with weight expressed in kilograms and height in metres : BMI=v

Weight Height2

Normal body mass index was defined as 20 to 25, mildly obese as 25 to 30, moderately obese as 30 to 40 and severely obese as greater than 40. Measurements of nerve conduction velocity in the median nerve were completed prior to treatment in 59 hands. Multiple associated health conditions were noted in our study group, including thoracic outlet compression, arthritis, and diabetes. We graded occupations as follows : (1) heavy work, i.e. strenuous physical labour or the use of air tools or power saws; (2) medium work, involving repetitive manual work; (3) light work, involving clerical or custodial work; or (4) minimal work, referring to the activity level of retired people or to non-repetitive work, including those at home. 23 patients with 28 affected hands performed heavy work prior to treatment; 13 patients (14 hands) were in medium work, eight patients (nine hands) did light work, and nine patients (nine hands) did minimal work. We considered both the heavy and medium work categories to be physically strenuous (42 hands) and the light and minimal categories not to be physically strenuous (18 hands). Subjective criteria for outcome of treatment were based on the resolution of symptoms of numbness, pain, and weakness. If all the symptoms resolved, the result was good. If most of the symptoms improved, the result was fair. If symptoms persisted or were not satisfactorily improved, the result was poor. Information on the work status of these patients was derived from their records.

RESULTS Post-operatively, 16 of 60 hands (27%) had good results, 25 of 60 (42%) had fair results, and 19 of 60 (32%) had poor results. The change in surgical technique to include reconstruction of the flexor retinaculum did not seem to influence the final outcome of the study regarding alleviation of symptoms. In this group of patients, 42 carpal tunnels were released without reconstruction of the flexor retinaculum and 16 with. The success rate in the pre-reconstruction group was 11 (26%) good, 17 (40%) fair, and 14 (33%) poor. This compared with 4 (25%)

647

good, 8 (50%) fair, and 4 (25%) poor with ligament reconstruction. This difference was not significant. Duration of symptoms The duration of symptoms prior to the first visit ranged from 0.25 to 72 months, with a median of six months. If the time for conservative therapy is added, only three out of 19 hands (16%) had a good result following surgery in patients with symptoms for less than six months, compared to 12 out of 33 hands (36%) with a good result for those with longer duration. 42% of the hands had fair results with less than six months duration of symptoms, as did 42% of hands with longer duration. There were proportionately more poor results in the less-than-sixmonth group (42%) compared to those with longer duration (21%). However, these differences in outcomes were not statistically significant. Obesity In our study, seven patients (eight hands) were moderately obese, ten patients (13 hands) mildly obese, and 35 patients (38 hands) of normal weight. None of the 52 patients with records of both weight and height could be classified as severely obese. Mild to moderate obesity did not appear to relate to the outcome of treatment. For patients at or less than their ideal weight, 71% of their affected hands obtained a good or fair result compared to 64% for patients who were mild to moderately obese. Nerve conduction velocity There were no significant trends observed in the data to indicate that a severe nerve conduction deficit was related to a poorer result (Table 1). Associated conditions Additional health problems recorded in the study population were as follows, in order of frequency of occurrence : injuries to the forearm, wrist, or hand (13 patients, 17 hands), arthritis (12 patients), trigger finger (nine patients, 12 hands), thoracic outlet compression (ten patients), hypertension (nine patients), diabetes (six patients), pronator teres syndrome (five patients), previously treated carpal tunnel syndrome (five patients), Table l-Pre-operative treatment outcome

nerve conduction velocity evaluations

related to

Treatment outcome

Normal

Mild deficit

Moderate and severe de&it

Good Fair Poor

4 (31%) 6 (46%) 3 (23%)

4 (19%) 10 (48%) -l (33%)

8 (40%) 4 (20%) 8 (40%)

Total

13

21

20

THE

648

cubital tunnel syndrome (three patients), Dupuytren’s contracture (three patients), neck, shoulder, or upper arm injury (three patients), tennis elbow (two patients), FCR tendinitis (two patients), ganglion (one patient), Guyons’s canal syndrome (one patient), radial tunnel syndrome (one patient), rheumatoid arthritis (one patient), de Quervain’s disease (one patient), cardiac instability (one patient), hepatitis (one patient), and peptic ulcer (one patient). Patients with poorer outcomes tended to have a higher incidence of multiple health problems. We reviewed the incidence of these health problems in the various outcome groups to see if any had a higher association with a poor outcome. Table 2 shows the results for health problems that occurred three or more times. A statistically higher incidence of a poor outcome was seen only for patients with thoracic outlet compression. Only two extremities out of a possible 41 in the good or fair outcome group had associated thoracic outlet compression (7%) while eight extremities out of a total of 19 in the poor outcome group had this (42%) (P= 0.009). Thus, patients additionally diagnosed with thoracic outlet compression in this series had an 80% chance of a poor outcome. Next in line for a poor result were patients with recurrent carpal tunnel syndrome. There were five of these and only two had a good outcome, while three had a poor outcome (not statistically significant). Table 2-Associated

conditions as related to treatment outcome Treatment outcome (hands)

Thoracic outlet compression Recurrent carpal tunnel syndrome Arthritis Forearm/wrist and hand injuries Trigger finger Diabetes Cubital tunnel syndrome Neck, shoulder, or upper arm injury Hypertension Pronator teres Dupuytren’s

Good and fair (41)

Poor (19)

2

8

2 6

3 6

> 0.05 >0.05

9 8 4

8 4 2

>0.05 >0.05 >0.05

2

1

>0.05

2 7 4 3

1 2 1 0

>0.05 >0.05 >0.05 > 0.05

P value

0.009

JOURNAL

OF HAND

Table 3-Job

Physically strenuous jobs were related to a higher incidence of fair and poor treatment outcomes (Table 3). 17 out of 42 hands in the strenuous category had a poor outcome, compared to only two out of 18 hands in the non-strenuous category. Despite this statistically better

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1992

type as related to treatment outcome Treatment outcome (hands)

Occupation*

Good

Fair

Poor

Physically strenuous Heavy Medium

I 3

11 4

10 I

Not physically Light Home

5 1

2 8

2 0

strenuous

* “Home” means retired people or housewives. “Light” means clerical office workers. “Medium” means repetitive, assembly line workers. “Heavy” means manual labourers and those using power tools. The physically strenuous job group had significantly more poor results than the not physically strenuous job group (P=O.O2,Fisher’s exact test). The distribution of possible outcomes for the four job types were significantly different (chi-squared test, 3 x 4 contingency table, P=O.OZ).There was no statistically significant difference between heavy and medium or between “light” and “home”.

outcome for those with a less strenuous occupation preoperatively, the distinction between specific jobs was not apparent. Thus, patients in the heavy work category preoperatively had a 64% chance of a good or fair outcome, but those in the medium category averaged 50% good or fair results. Those in light work had a 78% chance of a good or fair outcome. All those in the home environment (homemakers and retired people) had a good or fair outcome. Although the higher prevalence of a poor outcome in the heavy work category seems clear, this group also had a statistically higher prevalence of thoracic outlet compression, which was also found to be strongly associated with a higher chance of a poor outcome (see above). Of the 42 hands in the physically strenuous job category, ten (24%) had thoracic outlet compression, while of the 18 hands in the non-strenuous group, none had thoracic outlet compression (Table 4). If cases with thoracic outlet compression are excluded from the analysis, there were 72% good and fair results in the strenuous group compared to 89% in the non-strenuous group. This difference is not statistically significant (P = 0.19). Table 4--Incidence

Job type

SURGERY

of thoracic outlet compression

as related to specilk

job type Job type

Thoracic outlet compression

Total

Heavy Medium Air gun Saw Light Home Retired

2 4 3 1 0 0 0

18 14 8 2 9 3 6

The physically strenuous job types of “heavy”, “medium”, “air gun”, and “saw” had a higher incidence of extremities with thoracic outlet compression (10/42) than the remaining non-physically strenuous job types (O/18) (Fisher’s exact test, P=O.Ol)

OUTCOME

FOLLOWING

CARPAL TUNNEL

649

RELEASE

Return to work

In 44 patients there was information about work before the operation and at follow-up. For those previously doing heavy work, 15 out of 23 (65%) returned to their original employment. In the medium work group, 8 out of 13 (62%) returned to their original work. In the light work group all eight patients returned to work (100%). Some patients changed to restricted duty, either permanently or before returning to their original work. Others chose to change jobs after returning to their regular job. The median time to return to restricted duties was 2.6 months and to regular work was 4.6 months. A number of patients did not return to either in the time period studied. Seven patients changed jobs between 2.6 months and 20 months post-operatively. DISCUSSION The patients studied were not preselected in any way and represent a review of those treated by one surgeon over a nine-year period, with at least six months post-operative follow-up. The sample did not include patients who only required conservative treatment, indicating that symptoms were severe enough to make carpal tunnel release the appropriate treatment. The age distribution was similar to that reported in many other studies, but was generally younger than the reviews of Phalen (1966) and Tountas et al (1983). The median duration of conservative treatment was similar to the national median from the data of Duncan et al (1987). Duration of symptoms

One curious finding of this study was that patients with duration of symptoms less than six months had a slightly lower chance of good recovery. However, our series was small and the reasons for this finding remain unclear. Possibly, patients with less severe or intermittent symptoms may wait longer before seeking treatment, while patients with severe symptoms are more likely to seek treatment early. Paine and Polyzoidis (1983) reported that in patients with a long symptomatic history, recent worsening was often the reason to seek surgical relief. Other factors that may explain why patients with symptoms of less than six months duration have a better treatment outcome include a patient’s psychological profile and the question of secondary gain. Further study in this area is needed. Nau et al (1988) reported that painful nocturnal paraesthesiae occurred in patients with a short history and were a good prognostic feature. They also reported that the severity of paresis and wasting was dependent on the duration of symptoms before operation. Most of their patients with symptoms of long duration also had severe compression. Our indications for surgery still follow the guideline of operation within one year of the onset of conservative

treatment. However, it can be seen that a poor prognosis does not necessarily result from long-term symptoms of carpal tunnel syndrome. Our data may serve to reopen the question, since patients with a delay to surgery of more than six months form the onset of symptoms showed as good a rate of recovery as those having the release performed less than six months from the onset of symptoms.

Obesity

Ditmars and Houin (1986) discussed the concept that obesity can cause compression within the carpal tunnel. Our data suggests that a higher proportion of carpal tunnel patients may be obese (33%) compared to the national average (25%), (Krupp et al, 1987) but it is not appropriate to draw conclusions without considering the demographics of the local population. We did not demonstrate that being obese had any remarkable effect on the outcome of the surgery.

Nerve conduction velocity

Pre-operative nerve conduction velocities taken across the wrist are considered useful for diagnostic purposes. It would seem logical to expect that a more severe deficit would be indicative of a more severe nerve lesion, yet the outcome of surgery was apparently no different for patients with severe neurophysiological deficits than for those with none (Table 1). Nerve conduction velocity evaluation should probably be considered an added diagnostic tool only. Many surgeons consider it to be insufficiently specific or sensitive to act as a sole diagnostic measure in carpal tunnel syndrome. Luchetti et al (1988) reported that the prognostic value of either pre- or intra-operative sensory conduction velocities was low. Nau et al (1988) reported that nerve conduction velocity measurements were more useful for confirming that the nerve has been adequately decompressed (by improvement after operation) than for prognostic value. However, in cases where the preoperative nerve conduction velocity is normal, this cannot be done. In our study, pre-operative nerve conduction velocity did not predict any outcomes.

Associated health conditions

Many authors (Phalen, 1966; Tountas, et al, 1983; Ditmars and Houin, 1986; Browne and Snyder, 1975) have reported that carpal tunnel syndrome is often accompanied by associated conditions, but the correlation between these and the results of treatment has not been mentioned. Although patients with other complicating conditions would be expected to have generally poorer health and perhaps less tolerance of the carpal tunnel syndrome, the only one that had a statistically

650

high association with a poor outcome was thoracic outlet compression. All such cases were in the physically strenuous work category. Although no conclusion can be drawn regarding cause and effect of job type and thoracic outlet compression, it is possible that the poor outcome of treatment seen in these patients may be because of the strenuous work that the patient was doing.

Occupation

The significantly higher rate of poor outcome for patients in the physically strenuous job category has not previously been clearly documented. Tountas et al (1983) separated their patients into two groups : work-related and non-work-related. Poor results were much higher in the former (11.1 ‘A)than in the latter (3.5%). These results are qualitatively the same as ours and imply that their job intensity may have caused more permanent damage or that there may be related problems requiring treatment, for example, the double crush syndrome. We have shown a distinction between light and strenuous work and the ultimate outcome. The light work and homemaker group in our study had an 11% poor recovery rate, while the medium and heavy group had a 40% poor recovery rate. We should interpret these results cautiously since patients used to doing more strenuous work may have other reasons for their hands to be worse post-operatively. For those in more strenuous occupations, the poorer outcome was also reflected in the lower rate of return to their original work. Some of these changed jobs and found employment, but a certain percentage did not find any work. Again, it is important to note that this information does not indicate a cause-and-effect relationship between the type of job and the outcome of treatment. A physically stressful job is likely to put more pressure on the nerve and potentially irritate it. Following surgery this would still be the case. It is encouraging to note that a number of people who were previously unable to work did manage to return even when the job was stressful, indicating successful treatment. While surgical release may not be the final universal cure for carpal tunnel syndrome, it has a high rate of success in relieving most symptoms in patients who have previously been unresponsive to conservative treatment.

THE JOURNAL

OF HAND SURGERY

VOL. 17B No. 6 DECEMBER

1992

CONCLUSION

This study may help the prediction of outcome in patients undergoing carpal tunnel release. The generally lower success rate in those engaged in strenuous labour suggests that a change of occupation may help, but those with thoracic outlet compression may require some other form of treatment. Our data suggest that waiting longer before surgery may not necessarily be detrimental, although this concept needs to be verified. This would give more opportunity for conservative treatment to work. Although nerve conduction velocity measurements are useful to confirm the diagnosis, a severe nerve conduction deficit should not necessarily be considered as an indication of poor outcome of surgical treatment. The trends seen in this retrospective study can only be fully validated by a prospective study that carefully follows patients pre-operatively and post-operatively. The associations of poorer treatment outcome with occupation and/or thoracic outlet compression described here should be evaluated closely in such a study. References BROWNE, E. 2. and SNYDER, C. C. (1975). Carpal tunnel syndrome caused by hand injuries. Plastic and Reconstructive Surgery, 56: 1: 41-43. DITMARS, D. M. and HOUIN, H. P. (1986). Carpal tunnel syndrome. Hand Clinics, 2: 3: 525-532. DUNCAN, K. H., LEWIS, R. C., FOREMAN, K. A. and NORDYKE, M. D. (1987). Treatment of carpal tunnel syndrome by member of the American Society for Surgery of the Hand: results of a questionnaire. Journal of Hand Surgery, 12A : 3 : 384-391. KRUPP, M. A., SCHROEDER, S. A. and TIERNEY, L. M. (1987). Current MedicalDiagmsisand Treatment. Norwalk, Connecticut, Los Altos, Appleton &Lange, California. LEARMONTH, J. R. (1933). The principle of decompression in treatment of certain diseases of peripheral nerves. Surgical Clinics of North America, 13: 905-913. LUCHETTI, R. SCHOENHUBER, R. and LANDI, A. (1988). Assessment of sensory nerve conduction in carpal tunnel syndrome before, during and after operation. Journal of Hand Surgery, 13B: 4: 386-390. NAU, H. E., LANGE, B. and LANGE, S. (1988). Prediction of outcome of decompression for carpal tunnel syndrome. Journal of Hand Surgery, 13B: 4: 391-394. PAINE, K. W. E. and POLYZOIDIS, K. S. (1983). Carpal tunnel syndrome: decompression using the Paine retinaculotome. Neurosurgery, 59: 10311036. PHALEN, G. S. (1966). The carpal-tunnel syndrome. Journal of Bone and Joint Surgery, 48A: 2: 211-228. TOUNTAS, C. P., MACDONALD, C. J., MEYERHOFF, J. D. and BIHRLE, D. M. (1983). Carpal tunnel syndrome. A review of 507 patients. Minnesota Medicine, 66: 8: 479-482. Acceptedafter revision: 19 February Tsu-MinTsai, Center Plaza,

1992 MD, Christine M. Kleinert Institute for Hand and Micro Surgery, One Medical Suite 800,225 Abraham Flexner Way, Louisville, Kentucky 40202, USA.

Q 1992 The British

Society

for Surgery

of the Hand