Evaluation of carpal canal pressure in carpal tunnel syndrome

Evaluation of Carpal Canal Pressure in Carpal Tunnel Syndrome Ikki Hamanaka, MD, Ichiro Okutsu, MD, Kieko Shimizu, Yoshio Takatori, MD, Setsuo Ninomiya, MD, Tokyo, Japan Preoperative electrophysiologic testing and intraoperative carpal canal pressure measurements were performed on 957 hands in 647 patients with clinical signs of carpal tunnel syndrome. Fifty-five symptomatic hands in 48 patients were normal in both distal sensory latency and distal motor latency preoperatively. Carpal canal pressure was, however, significantly elevated compared to control data in all 55 hands. After complete subcutaneous release of the carpal canal using the Universal Subcutaneous Endoscope system, carpal canal pressure was reduced to within the normal control range. Clinical symptoms of carpal tunnel syndrome improved in all 55 hands. Postoperative electrophysiologic data remained within normal range in patients who agreed to receive electrophysiologic examinations. (J Hand Surg 1995;20A:848-854.)

Diagnosis of carpal tunnel syndrome is based on clinical signs and/or electrophysiologic tests such as distal sensory latency (DSL) and distal motor latency (DML), which have been considered to be the most reliable methods of confirming the diagnosis of carpal tunnel syndrome. Some patients who are clinically diagnosed as having carpal tunnel syndrome, however, show normal electrophysiologic test results. In a retrospective study we determined whether clinical symptoms and elevated carpal canal pressure are sufficient to diagnose carpal tunnel syndrome in patients with normal electrophysiologic test results.

Materials and Methods From June 1986 to May 1993, 957 hands in 647 consecutive patients who had been diagnosed as having carpal tunnel syndrome from clinical signs were seen at the Japanese Red Cross Medical Center. From the Departmentof Orthopaedic Surgery,Japanese Red Cross Medical Center, and the Departmentof Neurology,Institute of Brain Research, Facultyof Medicine,Universityof Tokyo,Tokyo,Japan. Receivedfor publicationNov.2, 1992;acceptedin revisedformFeb. 7, 1995. No benefitsin any formhavebeenreceivedor will be receivedfroma commercialpartyrelateddirectlyor indirectlyto the subjectof thisarticle. Reprint requests: Ikki Hamanaka, MD, Departmentof Orthopaedic Surgery,JapaneseRed CrossMedicalCenter,4-1-22, Hiroo,Shibuya-ku, Tokyo150,Japan.

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The Journal of Hand Surgery

This group consisted o f 385 hands in 253 men and 572 hands in 394 women, with a mean age of 53.9 years (range, 21-87). There were 163 right and 174 left hands in patients with unilateral clinical signs of carpal tunnel syndrome. There were 310 patients with clinical signs of bilateral carpal tunnel syndrome. In 299 hands (210 patients), there was no apparent cause o f the carpal tunnel syndrome; in 629 hands (414 patients), it was caused by hemodialysis for chronic renal failure; and in 29 hands (23 patients), it was caused by either diabetes mellitus, rheumatoid arthritis, pregnancy, or trauma. Initial diagnosis o f carpal tunnel syndrome was based on clinical symptoms, ''2 sensory disturbance of the median nerve distribution area, median nerve percussion test at the wrist, 2 Phalen's test, 2 manual muscle testing (MMT), and muscle atrophy of the abductor pollicis brevis muscle. Electrophysiologic tests were performed preoperatively in all cases and postoperatively in cases where patients agreed to receive them. The electrophysiologic investigation included evaluation o f DSL, DML, and motor nerve conduction velocity of the median and ulnar nerves using the Medelec ms-6 (Nihon Denki-Sanei, Tokyo, Japan) or Mystro ms-25 (Nihon Denki, Tokyo, Japan) system. The normal range of DSL was < 3.4 ms, and DML, < 4.2 ms. 3

The Journal of Hand Surgery / Vol. 20A No. 5 September 1995 849 Preoperative and postoperative carpal canal pressure measurements were performed in resting and power active grip positions with a continuous infusion technique (Figs. 1, 2). ' This was conducted under local anesthesia and without a pneumatic tourniquet in the operating room. A 14-gauge or 18-gauge Angiocath (Desert Medical, Sandy, UT), a P-50 transducer (Gould H.B. Medical Products, Oxnard, CA) with an F-100J flushing device (American Edward Laboratories, Irvine, CA) or a DPT-6003 transducer with flushing device (Peter Von Berg Medizintechnik GMBH, Kirchseeon/Eglharting, Germany and Kawasumi Laboratories, Tokyo, Japan), and a monitor (Nihon Kohden, Tokyo, Japan) were used. The operative procedure and measurement have been described elsewhere? '~-7 As a control, pressure in the carpal canal was also measured in 31 patients (19 men, 12 women) with a mean age of 37.9 years (range, 18 to 67) in whom hand surgery was being performed for conditions unrelated to carpal tunnel syndrome) Based on Pascal's law, which shows that the diameter of an Angiocath does not affect the relative internal pressure, data from our original 16-patient control group, in which an 18-gauge Angiocath 1 catheter was used, were combined with additional data from a more recent 15-patient group in which a 14-gauge Angiocath was used. It was determined from our data that carpal canal control pressure was 15.0 +_ 10.3 mmHg (range, 1-38 mmHg) in the

Figure 1. Preoperative endoscopic view of the carpal canal. (TCL, transverse carpal ligament; Arrow, tip of the catheter, F, flexor tendon.)

resting position and/or 135.0 + 80.3 mmHg (range, 18-250 mmHg) with power active grip. Preoperative and postoperative values of carpal canal pressure in patients who had clinical signs of carpal tunnel syndrome were statistically analyzed using the unpaired ttest with the control group. A comparative statistical analysis was also done using the unpaired t-test, comparing patients who had normal electrophysiologic test results and elevated carpal canal pressure (55 hands, 48 patients) and patients who had abnormal electrophysiologic test results and elevated carpal canal pressure (902 hands, 599 patients) in terms of age, type of employment (Fig. 3), and hand dominance. Operations were performed in all patients when the carpal canal pressure was 15 mmHg or more in resting position and/or 135 mmHg or more with power active grip. Subjective complaints of tingling sensations were recorded. Sensory disturbance was measured using a 3-g algesiometer for pain sensation and a 2-g von Frey hair for touch sensation. Muscle power of the abductor pollicis brevis muscle was tested by manual muscle testing.

Results Patients With Normal Electrophysiologic Test Results and Elevated Carpal Canal Pressure Normal values for DSL and DML were shown in 55 (in 48 patients) of the 957 hands (5.7%). This group consisted of 17 men (17 hands) and 31 women (38 hands), with a mean age and 1 SD of 50.1 + 10.45 years (range, 22-70). All patients were righthanded. There were 17 right and 24 left hands in patients with unilateral clinical signs of carpal tunnel syndrome. There were seven patients with clinical signs of bilateral carpal tunnel syndrome. The cause of carpal tunnel syndrome was not apparent in 16 hands (15 patients); in 36 hands (30 patients), it was hemodialysis for chronic renal failure; in 2 hands (2 patients), rheumatoid arthritis; and in 1 hand, diabetes mellitus. The mean preoperative DSL and 1 SD was 2.59 _+ 0.35 ms (range, 1.78-3.40). The mean preoperative DML and 1 SD was 3.69 +_0.37 ms (range, 2.70-4.20). Twenty of 48 patients (23 hands) agreed to undergo postoperative electrophysiologic tests, and all 23 hands retained normal DSL and DML. The mean postoperative DSL and 1 SD was 2.24 +_ 0.33 ms (range, 1.54-2.80). The mean postoperative DML and 1 SD was 3.35 +_0.46 ms (range, 2.60-4.00).

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Hamanakaet al. / Carpal Canal Pressurein CTS

Figure 2. Measurements of carpal canal pressure were performed with continuous infusion technique: (A) in resting position; (B) with power active grip.

OTHER !2 LABORER 2 MONK MANUFACTURER 2 DOMESTIC HELPER

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DOMESTIC HELPER1 - ~ TAILOR 1 ~...~- " ~ (% OF PATIENTS) BARBER 1 ~

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(% OF PATIENTS)

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A Figure 3. Work type. (A) Patients with normal electrophysiologic test results and elevated carpal canal pressure (55 hands, 48 patients). (B) Patients with abnormal electrophysiologic test results and elevated carpal canal pressure (902 hands, 599 patients).

The Journal of Hand Surgery / Vol. 20A No. 5 September 1995

851

Table 1. Preoperative Carpal Canal Pressure

Normal electrophysiologic test results (n = 55) Abnormal electrophysiologic test results (n = 902)

Control (n = 31) Elevated (n = 957)

Resting Position (15.0 + 10.3 mmHg)

Power Active Grip (135.0 + 80.3 mmHg)

43.1 + 24.6*

167.2 + 79.4

60.3 _+ 31.9"

177.4 _+ 33.0*

*Significant difference positive: Unpaired t-test p < .01

Preoperative mean pressure of the carpal canal and 1 SD was 43.1 + 24.6 mmHg (range, 3-131) in resting position and 167.2 + 79.4 mmHg (range, 1-250) with power active grip. Preoperative data in resting position were significantly higher than control data (resting, p < .01); however, data for power active grip were not significantly different from control data (Table 1, Fig. 4A). Postoperative mean pressure of the carpal canal and 1 SD was 4.9 + 3.6 mmHg (range, 0-14) in resting position and 42.7 + 54.5 mmHg (range, 0-233) with power active grip. These data are within normal limits and significantly lower than control data (resting, p < .01; power active grip, p < .01) (Fig. 4A). All 55 hands had experienced tingling sensations preoperatively. Every patient in this group was clinically evaluated postoperatively. The mean period and 1 SD until disappearance of tingling sensations was 28,3 + 74.6 days (range, 0-489). Tingling sensations disappeared within 17 months in all 55 hands. The mean period and 1 SD until disappearance of sensory disturbance in both pain and touch sensation was 51.4 + 89.4 days (range, 1-483). Sensory disturbance disappeared within 17 months in all 55 hands. Muscle power of the abductor pollicis brevis muscle was improved or remained the same as before surgery in all 55 hands (Table 2).

T a b l e 2. R e c o v e r y o f A b d u c t o r Pollicis B r e v i s M u s c l e With N o r m a l E l e c t r o p h y s i o l o g i c Results*

Before Operation 0 1 2 3 4 5 *n = 55

0

1

After Operation 2 3 4

5

1 1 1

1 9 29 13

Patients With Abnormal Electrophysiologic Test Results and Elevated Carpal Canal Pressure Abnormal DSL and/or DML were shown in 902 (in 599 patients) of the 957 hands (94.3%). This group consisted of 236 men (368 hands) and 363 women (534 hands), with a mean age and 1 SD of 54.0 + 10.7 years (range, 21-87). In this group 596 of the 599 patients were right-handed. The mean age, type of employment (Fig. 3), and hand dominance of patients in this group were not significantly different from that of patients with normal electrophysiologic test results. There were 146 right and 150 left hands in patients with unilateral clinical signs of carpal tunnel syndrome. There were 303 patients with clinical signs of bilateral carpal tunnel syndrome. The cause of carpal tunnel syndrome was not apparent in 283 hands (195 patients); in 593 hands (384 patients), it was hemodialysis for chronic renal failure; in 14 hands (10 patients), rheumatoid arthritis; in 8 hands (6 patients), diabetes mellitus; in 2 hands (2 patients), pregnancy; and in 2 hands (2 patients), trauma. The mean preoperative DSL and 1 SD was 4.34 +_ 2.08 ms (range, 1.90-17.6, n = 548; undetectable, n = 354). The mean preoperative DML and 1 SD was 7.24 _+ 2.80 ms (range, 2.45-30.4, n = 831; undetectable, n = 71). The mean postoperative DSL and 1 SD was 2.99 + 0.57 ms (range, 1.70-5.20). The mean postoperative DML and 1 SD was 4.37 _+ 1.04 ms (range, 1.95-11.0) in 902 hands (599 patients). Preoperative mean pressure of the carpal canal and 1 SD deviation was 60.3 _+ 31.9 mmHg (range, 2-251) in resting position, and 177.4 +_ 33.0 mmHg (range, 11-251) with power active grip. These data are significantly higher than control data (resting, p < .01; power active grip, p < .01) (Table 1, Fig. 4B). Postoperative mean pressure was 5.7 + 4.6 mmHg (range, 0-33) in resting position and 47.8 + 52.1 mmHg (range, 0-269) with power active grip. This data is within normal limits, significantly lower than

Hamanaka et al. / Carpal Canal Pressure in CTS

852

mmHg 2.50 200 150

100' ~L

PREOP

CO~

CARPAL CANAL PRESSURE/ A / POSITION

...."37.....~P~t~ RESTING P O W E R ACTIVE GRIP

mmHg 250 200

iiiiiiiii!i!iiiiii!i

150

lii il

100 -

CARPAL CANAL PRESSLIRE/ / POSITION B

~..-~....~op. RESTING

POWER ACTIVE GRIP

Figure 4. Mean pressures in the carpal canal. (A) Patients with normal electrophysiologic test results and elevated carpal canal pressure (55 hands, 48 patients). (B) Patients with abnormal electrophysiologic test results and elevated carpal canal pressure (902 hands, 599 patients). control data (resting, p < 0.1; power active grip, p < .01) (Fig. 4B), and not significantly different from Table 3. Recovery of Abductor Pollicis Brevis Muscle With Normal Electrophysiologic Test Results* Before Operation

0

1

0

14

After Operation 2 3 4

12

16

11

1

3

2

2

2 3 4 5

1'

4 2' 1'

10 11 1~

4

5

33 19 11 40 20 128 14 271 1*'s 187 3

* n = 821

t Cervical radiculopathy due to cervical spondylosis. :~ Amyloidosis due to long-term hemodialysis.

preoperative and postoperative data of patients with normal electrophysiologic test results and elevated carpal canal pressure. All 902 hands had experienced tingling sensations preoperatively. Postoperative clinical evaluation data are based on only those patients who presented for follow-up examinations and do not represent 100% of the group. The mean period and 1 SD until disappearance of tingling sensations was 43.0 + 70.4 days (range, 0--758). The mean period and 1 SD until disappearance of sensory disturbance in both pain and touch sensation was 79.5 + 167.9 days (range, 1-2037). Muscle power of the abductor pollicis brevis muscle was improved or remained the same as before surgery in 815 of the 821 hands that were evaluated postoperatively. The remaining 6 cases became worse (Table 3).

The Journal of Hand Surgery / Vol. 20A No. 5 September 1995

Discussion Carpal tunnel syndrome is an entrapment neuropathy that is caused by compression of the median nerve due to a variety of reasons. 8-1~ Symptomatic pain and tingling sensations are clinical problems and are caused by compression of the narrow sensory nerve fiber groups. Electrophysiologic tests may measure the conduction velocity of the large nerve fiber groups and not reflect the real condition of a compressed nerve. Kimura and Ayyar 11 reported that 4.1% of their patients showed clinical signs of having carpal tunnel syndrome but had normal DSL and DML. In our experience, this type of patient accounted for 5.7% of the group. In these cases, differential diagnosis of other diseases, for example, cervical radiculopathy, and carpal tunnel syndrome is difficult. Recent studies have revealed that carpal canal pressure measurement is useful for diagnosing carpal tunnel syndrome because it monitors the condition of the carpal canal directly. 1,7,12-17 Preoperative carpal canal pressure in those patients in this study with normal electrophysiologic results was significantly higher than control in resting position, but not with power active grip. Patients in this group also required a significantly shorter period for clinical recovery. This may be due to these patients having experienced median nerve compression of shorter duration or lesser degree. Preoperatively, patients with abnormal electrophysiologic results showed higher carpal canal pressure than control in both positions. There is a high possibility that the degree of power exercised with power active grip position varies according to the individual's personality, muscular strength, and exertion. There was a high standard deviation in these data among patients with normal and abnormal electrophysiologic results and elevated carpal canal pressure. It is necessary, therefore, to consider elevated carpal canal pressure in resting position and/or with power active grip as significant. The maximum postoperative carpal canal pressure with power active grip in one case was 233 mmHg. This is the only postoperative datum in this study that exceeded control data. We feel this is the result of remaining palmar aponeurosis in one initial case. We have since learned to perform complete release of the carpal canal until carpal canal pressure is within normal limits.

853

Muscle power of the abductor pollicis brevis became worse postoperatively in 6 hands in the 902hand group. All 6 of these patients' carpal tunnel syndromes were caused by hemodialysis for chronic renal failure. Postoperatively, amyloid may have been continuously deposited in the released carpal canals, causing carpal canal pressure to increase and compressing the median nerve. This would cause abductor pollicis brevis muscle power to decrease. One of these patients was suffering from a double lesion of cervical radiculopathy as well as carpal tunnel syndrome. All patients in this series presented with complaints of intolerable clinical symptoms. All patients with both clinical symptoms of carpal tunnel syndrome and higher than normal carpal canal pressure in at least one position were managed surgically and showed satisfactory recovery postoperatively. Thus, no data on the natural evolution of the condition in this type of patient are available. Patients who present with mild clinical symptoms and show electrophysiologic results within normal limits can be managed conservatively. In cases where patients complain of severe or intolerable symptoms of carpal tunnel syndrome and show electrophysiologic results within normal limits, carpal canal pressure measurement is useful to confirm the clinical diagnosis prior to complete endoscopic release of the carpal canal. If the necessary equipment and conditions are available in an office setting, the procedure can easily be performed there, using only local anesthesia without endoscopic observations.

References 1. Okutsu I, Ninomiya S, Hamanaka I, Kuroshima N, Inanami H. Measurement of pressure in the carpal canal before and after endoscopic management of carpal tunnel syndrome. J Bone Joint Surg 1989;71A:679-83. 2. Phalen GS. The carpal tunnel syndrome: seventeen years' experience in diagnosis and treatment of 654 hands. J Bone Joint Surg 1966;48A:211-28. 3. Genba K, Sonoh M, Okutsu I, Hamanaka I, Nishiyama K, Ohtsubo K. Endoscopic management of carpal tunnel syndrome in long-term hemodialysis patients. J Jpn Nephrol Assoc 1990;23:393-8. 4. Okutsu I, Ninomiya S, Takatori Y, Ugawa Y. Endoscopic management of carpal tunnel syndrome. Arthroscopy 1989;5:11-8. 5. Okutsu I, Ninomiya S, Natsuyama M, et al. Subcutaneous operation and examination under universal endoscope. J Jpn Orthop Assoc 1987;61:491-8. 6. Okutsu I, Hamanaka I, Ninomiya S, Takatori Y, Shimizu K, Ugawa Y. Results of endoscopic management of carpaltunnel syndrome in long-term haemodialysis versus idiopathic patients. Nephrol Dial Transplant 1993; 8:1110-4.

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7. Okutsu I, Ninomiya S, Takatori Y, et al. Results of endoscopic management of carpal tunnel syndrome. Orthop Rev 1993;22:81-7. 8. Kimura I, Sekino H, Ayyar DR, Kimura N, Saso S, Makino M. Carpal tunnel syndrome in patients on long-term hemodialysis. Tohoku J Exp Med 1986;148: 257-66. 9. Dorwart BB. Carpal tunnel syndrome: a review. Semin Arthritis Rheum 1984;14:134-40. 10. Stevens JC, Beard CM, O'Fallon WM, Kurland LT. Conditions associated with carpal tunnel syndrome. Mayo Clin Proc 1992;67:541-8. 11. Kimura I, Ayyar DR. The carpal tunnel syndrome: electrophysiological aspects of 639 symptomatic extremities. Electromyogr Clin Neurophysiol 1985 ;25:151-64. 12. Tanzer RC. The carpal-tunnel syndrome: a clinical and anatomical study. J Bone Joint Surg 1959;41A:626-34.

13. Gelberman RH, Hergenroeder PT, Hargens AR, Lundborg GN, Akeson WH. The carpal tunnel syndrome: a study of carpal canal pressures. J Bone Joint Surg 1981 ;63A:380-3. 14. Gelberman RH, Szabo RM, Mortensen WW. Carpal tunnel pressures and wrist position in patients with Colles' fractures. J Trauma 1984;24:747-9. 15. Wemer CO, Elmqvist D, Ohlin P. Pressure and nerve lesion in the carpal ttmnel. Acta Orthop Scand 1983;54: 312-6. 16. Kongsholm J, Olerud C. Carpal tunnel pressure in the acute phase after Colles' fracture. Arch Orthop Trauma Surg 1986; 105:183-6. 17. Lundborg G, Gelberman RH, Convery MM, Lee YF, Hargens AR. Median nerve compression in the carpal tunnel: functional response to experimentally induced controlled pressure. J Hand Surg 1982;7:252-9.