Segmental carpal canal pressure in patients with carpal tunnel syndrome

PURPOSE: To clarify which part of the median nerve is the most compressed and to compare carpal canal pressure with the latency of the sensory nerve potential and the duration of symptoms. METHODS: Fifteen patients with idiopathic carpal tunnel syndrome were studied using a pressure guidewire system to record canal pressure. The wire was introduced from the distal end of the carpal canal to 2 cm proximal to the distal wrist crease (DWC) and then retracted in 5-mm increments using an image intensifier to guide the progress. A nerve conduction study was performed, and all patients were asked how long the symptoms lasted. RESULTS: Carpal canal pressure was significantly higher 5 to 15 mm distal to the DWC. The most compressed point was 10 mm distal to the DWC, with a pressure of 44.9 +/- 26.4 mm Hg. The correlation coefficient between the highest canal pressure and the latency was 0.393 and between highest canal pressure and duration of symptoms was 0.402. CONCLUSIONS: Our study showed that the most compressed part of the median nerve in the carpal canal is 10 mm distal to the DWC. The carpal canal pressure was related to the latency and to the duration of symptoms.     

Fingertip loading and carpal tunnel pressure: Differences between a pinching and a pressing task

Carpal tunnel syndrome may be caused by repeated or sustained elevated carpal tunnel pressure. This study examined the relationship between carpal tunnel pressure, posture, and fingertip load. In 20 healthy individuals, carpal tunnel pressure was measured with a catheter inserted into the carpal tunnel of the dominant hand and connected to a pressure transducer. With the wrist in a pressure-neutral position, the subjects pressed on a force transducer with the index finger to levels of 0, 5, 10, and 15 N. They then pinched the transducer at the same levels of force. For both fingertip-loading postures, the carpal tunnel pressure increased with increasing fingertip load. Carpal tunnel pressures were significantly greater (p < 0.015) for the pinching task (14.2, 29.9, 41.9, and 49.7 mm Hg [1.89, 3.99, 5.59, and 6.63 kPa] for 0, 5, 10, and 15 N force levels, respectively) than for simple finger pressing (7.8, 14.1, 20.0, and 33.8 mm Hg [1.04, 1.88, 2.67, and 4.51 kPa]). This study indicates that although the external load on the finger remained constant between the two tasks, the internal loading, as measured by carpal tunnel pressure, experienced a near 2-fold increase by using a pinch grip. These findings should be given consideration in designing work tasks and tools because relatively low fingertip forces, especially in a pinch grip, elevate carpal tunnel pressures to levels that, if prolonged, may lead to the development or exacerbation of carpal tunnel syndrome.     

Basal joint arthroplasty decreases carpal tunnel pressure

Background

There is a well-documented association between carpal tunnel syndrome (CTS) and thumb carpometacarpal (CMC) arthritis, and these conditions commonly coexist. We have observed that patients who have previously undergone thumb basal joint arthroplasty (BJA) seem rarely to present subsequently with CTS. Our hypothesis is that BJA decreases the pressure within the carpal tunnel.

Methods

Twenty-eight patients (6 with coexistent CTS) undergoing BJA were enrolled in the study. The pressure within the carpal tunnel immediately before and after BJA was measured using a commercially available pressure monitor device (Stryker STIC; Kalamazoo, MI). In patients with concomitant CTS undergoing both BJA and carpal tunnel release (CTR), the pressure was measured after BJA but prior to release of the transverse carpal ligament.

Results

The pressure within the carpal tunnel decreased after BJA in all patients. There were 3 patients with stage II arthritis, 15 patients with stage III arthritis, and 10 patients with stage IV arthritis. The mean pressure prior to BJA among all patients was 23.9 mmHg and decreased to 11.0 mmHg after BJA. Patients with concomitant CTS had a mean pre-BJA pressure of 26.5 mmHg, which decreased to 7.3 mmHg after BJA.

Conclusions

BJA decompresses the carpal tunnel and decreases the pressure within. In patients with concomitant CTS, the BJA alone (without additional release of the transverse carpal ligament) decreases the carpal tunnel pressure. Further study is warranted to determine the need for discrete release of the transverse carpal ligament in patients with CTS who are undergoing BJA.

Level of Evidence

Level II, diagnostic.     

Effect of wrist posture on carpal tunnel pressure while typing

Long weekly hours of keyboard use may lead to or aggravate carpal tunnel syndrome. The effects of typing on fluid pressure in the carpal tunnel, a possible mediator of carpal tunnel syndrome, are unknown. Twenty healthy subjects participated in a laboratory study to investigate the effects of typing at different wrist postures on carpal tunnel pressure of the right hand. Changes in wrist flexion/extension angle (p = 0.01) and radial/ulnar deviation angle (p = 0.03) independently altered carpal tunnel pressure; wrist deviations in extension or radial deviation were associated with an increase in pressure. The activity of typing independently elevated carpal tunnel pressure (p = 0.001) relative to the static hand held in the same posture. This information can guide the design and use of keyboards and workstations in order to minimize carpal tunnel pressure while typing. The findings may also be useful to clinicians and ergonomists in the management of patients with carpal tunnel syndrome who use a keyboard. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:1269–1273, 2008     

Relationship of carpal canal contents volume to carpal canal pressure in carpal tunnel syndrome patients

Forty patients long-term haemodialysis with a second recurrence of carpal tunnel syndrome and concomitant loss of flexor tendon function due to flexor adhesions were treated by excision of the flexor digitorum superficialis tendons. During the procedure the carpal canal pressure was measured using a continuous infusion technique. The preoperative mean carpal canal pressure was 81 (SD, 53)mmHg. After removal of all the flexor digitorum superficialis tendons, the carpal canal pressure decreased to 10 (SD, 8)mmHg. The clinical symptoms of carpal tunnel syndrome were relieved and hand strength and finger motion were improved in all patients.     

Intraneural median nerve pressure in carpal tunnel syndrome

In order to determine whether endoscopic carpal tunnel release decompresses the median nerve, we measured the intraneural median nerve pressure pre- and postoperatively in 55 hands. The median nerve pressure was significantly reduced postoperatively.     

Measurement of carpal canal and median nerve pressure in patients with carpal tunnel syndrome

Carpal tunnel syndrome is a compression neuropathy wherein the median nerve is compressed inside of the carpal canal. Its diagnosis is made clinically, electrophysiologically, and sometimes by carpal canal pressure measurement. The objective of surgical management of this condition is the decompression of the median nerve. We usually measure carpal canal pressure preoperatively and postoperatively using a continuous infusion technique for diagnoses as well as for postoperative evaluation of decompression following our Universal Subcutaneous Endoscope system procedure. To evaluate whether our procedure effectively decompressed the median nerve, we measured intraneural pressure preoperatively and postoperatively in the resting position, with active power grip, and in the Okutsu test position. Correlation between the carpal canal pressure and intraneural median nerve pressure was statistically analyzed using the Kendall rank correlation coefficient (n = 157 hands). A significant correlation was present preoperatively in resting position and postoperatively with active power grip and in the Okutsu test position. Because of this correlation, we conclude that our endoscopic operative procedure effectively decompresses the median nerve and that simple carpal canal pressure measurement is sufficient to confirm diagnoses and to evaluate the status of postoperative decompression.     

Area and shape changes of the carpal tunnel in response to tunnel pressure

Carpal tunnel mechanics is relevant to our understanding of median nerve compression in the tunnel. The compliant characteristics of the tunnel strongly influence its mechanical environment. We investigated the distensibility of the carpal tunnel in response to tunnel pressure. A custom balloon device was designed to apply controlled pressure. Tunnel cross sections were obtained using magnetic resonance imaging to derive the relationship between carpal tunnel pressure and morphological parameters at the hook of hamate. The results showed that the cross‐sectional area (CSA) at the level of the hook of hamate increased, on average, by 9.2% and 14.8% at 100 and 200 mmHg, respectively. The increased CSA was attained by a shape change of the cross section, displaying increased circularity. The increase in CSA was mainly attributable to the increase of area in the carpal arch region formed by the transverse carpal ligament. The narrowing of the carpal arch width was associated with an increase in the carpal arch. We concluded that the carpal tunnel is compliant to accommodate physiological variations of the carpal tunnel pressure, and that the increase in tunnel CSA is achieved by increasing the circularity of the cross section. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 29:1951–1956, 2011     

Carpal tunnel pressure in patients with carpal tunnel syndrome due to long-term hemodialysis

We studied carpal tunnel pressure and outcome of endoscopic carpal tunnel release in 42 patients (53 hands) with carpal tunnel syndrome (CTS) and receiving long-term hemodialysis. We compared these results with those of 41 patients (49 hands) with idiopathic CTS. Pressure was measured peroperatively: first, before dilation of the carpal tunnel; second, after dilation but before release of the transverse carpal ligament; and third, after completion of the release. In patients receiving long-term hemodialysis, the highest pressures were 76.9, 56.0, and 7.8 mmHg respectively. In patients with idiopathic CTS, pressures were 68.8, 44.1, and 4.0 mmHg respectively. The clinical outcome was inferior in patients receiving long-term hemodialysis.     

Pathomechanics of peripheral nerve loading. Evidence in carpal tunnel syndrome.

Peripheral nerve injury is a common occurrence, with carpal tunnel syndrome (CTS) receiving the most attention. Nerve dysfunction associated with compression syndromes results from an interruption or localized interference of microvascular function due to structural changes in the nerves or surrounding tissues. This article reviews the physiologic, pathophysiologic, and histologic effects of compressing peripheral nerves in animal models, and then examines the evidence for similar processes in humans using CTS as a model.     

Measurement of pressure in the carpal canal before and after endoscopic management of carpal tunnel syndrome

In forty-six patients who had carpal tunnel syndrome, a technique of continuous infusion, given under local anesthesia and without a pneumatic tourniquet, was used to measure pressures in the carpal canal before and after endoscopic release of the transverse carpal ligament (retinaculum flexorum manus). Pressures were similarly measured in sixteen subjects in a control group. The mean preoperative pressures were significantly higher in the patients who had carpal tunnel syndrome than in the patients in the control group when the pressures were measured under four conditions: with the wrist in the resting position, with active grip, and with maximum passive extension and flexion of the wrist. The mean pressures improved significantly postoperatively and were in the range of values that were found under each condition for the control group. Measurement of pressure in the carpal canal before and after operation may be useful in diagnosing carpal tunnel syndrome and in determining the effectiveness of endoscopic management.     

Verification of the pressure provocative test in carpal tunnel syndrome.

Three provocative tests (pressure, Phalen's test, and Tinel's sign) were studied in 30 patients with carpal tunnel syndrome and 30 control subjects. The pressure provocative test had a sensitivity of 100%. In contrast, Phalen's test was 88% sensitive and Tinel's sign only 67% sensitive. The pressure provocative test is a sensitive indicator of median nerve compression at the wrist with a faster reaction time than Phalen's test (mean time of 9 seconds vs 30 seconds). It is an appropriate provocative test in patients with stiff or painful wrists when wrist flexion is restricted.     

Investigation of segmental carpal tunnel pressure in patients with idiopathic carpal tunnel syndrome--is it necessary to release the distal aponeurotic portion of the flexor retinaculum in endoscopic carpal tunnel release surgery?

Segmental carpal tunnel pressure was measured in 12 hands of 11 idiopathic carpal tunnel syndrome patients before and after two-portal endoscopic carpal tunnel release. We aimed to determine at which part of the carpal tunnel the median nerve could be compressed, and to evaluate whether carpal tunnel pressure could be reduced sufficiently at all segments of the carpal tunnel after the surgery. Pressure measurements were performed using a pressure guide wire. The site with the highest pressure corresponded to the area around the hamate hook; the pressure in the area distal to the flexor retinaculum could be pathogenically high (more than 30 mmHg) before the surgery. The two-portal endoscopic carpal tunnel release achieved sufficient pressure reduction in all segments of the carpal tunnel when the flexor retinaculum and the fibrous structure between the flexor retinaculum and the palmar aponeurosis were completely released.     

Compartment pressure in the carpal tunnel in distal fractures of the radius

In a prospective controlled study, carpal tunnel tissue pressures were determined in a group of 56 patients with distal dislocated fractures of the radius at initial presentation, immediately prior to and after reduction, and 1, 2, 4, 12, and 24 h after reduction. Depending on the severity of the trauma and delay to presentation at the hospital, initial measurements revealed raised pressure averaging 23 mmHg, which further increased during reduction to 44 mmHg. After 4 h the average pressure was 37 mmHg, and it then dropped to 26 mmHg after 12 h. For anatomical reasons the median nerve is quite vulnerable in the region of the wrist joint. Chronic pressure here may cause carpal tunnel syndrome. Acute pressure in the carpal tunnel, which according to our investigations represents a distinct compartment, results in an overt compartment syndrome. The possibility of a direct relationship between markedly elevated tunnel pressure and the development of Sudeck's dystrophy is discussed.     

Electromyographic evaluation after endoscopic carpal tunnel release in idiopathic carpal tunnel syndrome

The purpose of this study was to electromyographically evaluate results in patients with carpal tunnel syndrome (CTS) who underwent endoscopic carpal tunnel release (ECTR). The subjects were 26 patients with idiopathic CTS (37 hands) who were followed for at least 6 months after ECTR. To compare results informatively, hands were classified into four groups: those with normal distal motor latency (DML) and sensory conduction velocity (SCV) were classified as group A, those with normal DML and abnormal SCV as group B, those with an abnormal DML and normal SCV as group C, and those with abnormal DML and SCV as group D. All but one of the hands were classified as group D on the basis of preoperative electromyographic evaluation, while one was classified as group C. The mean preoperative obtainable DML and SCV values were 7.2 m and 27.3 m/s, respectively. Postoperatively, 12 hands were in group A, 8 hands in group B, 2 hands in group C, and 15 hands in group D. The mean DML and SCV values at final follow-up were 4.3 ms and 40.8 m/s, respectively. Of the 25 hands with muscle atrophy before surgery, 6 hands were in group A, 5 hands were in group B, 1 hand was in group C, and 13 hands were in group D at final follow-up. Thenar muscle atrophy and denervation potentials were present before surgery in 13 of the 15 hands classified as group D at the final follow-up. Received for publication on June 23, 1998; accepted on Oct. 30, 1998     

Endoscopic carpal tunnel release

Endoscopic carpal tunnel release is not a procedure to be taken lightly. Like many surgical procedures, it is a demanding exercise that requires exacting knowledge of the anatomy of the hand, attention to detail, and the ability to manipulate three-dimensional objects while observing them in two dimensions on a video screen. In the hands of well trained surgeons, ECTR provides patients with a safe, predictable solution to their carpal tunnel sydrome that will allow them a rapid return to normal activities with minimal postoperative discomfort.