Effects of static fingertip loading on carpal tunnel pressure

The purpose of this study was to explore the relationship between carpal tunnel pressure and fingertip force during a simple pressing task. Carpal tunnel pressure was measured in 15 healthy volunteers by means of a saline-filled catheter inserted percutaneously into the carpal tunnel of the nondominant hand. The subjects pressed on a load cell with the tip of the index finger and with 0, 6, 9, and 12 N of force. The task was repeated in 10 wrist postures: neutral; 10 and 20° of ulnar deviation; 10° of radial deviation; and 15, 30, and 45° of both flexion and extension. Fingertip loading significantly increased carpal tunnel pressure for all wrist angles (p = 0.0001). Post hoc analyses identified significant increases (p <0.05) in carpal tunnel pressure between unloaded (0 N) and all loaded conditions, as well as between the 6 and 12 N load conditions. This study demonstrates that the process whereby fingertip loading elevates carpal tunnel pressure is independent of wrist posture and that relatively small fingertip loads have a large effect on carpal tunnel pressure. It also reveals the response characteristics of carpal tunnel pressure to fingertip loading, which is one step in understanding the relationship between sustained grip and pinch activities and the aggravation or development of median neuropathy at the wrist.     

Basal joint arthroplasty and carpal tunnel release through a single incision: an in vitro study

PURPOSE: Carpal tunnel syndrome coexists with basal joint arthritis in a large percentage of patients. These 2 conditions are often treated surgically through separate incisions. The purpose of this cadaver study is to show the effect of trapeziectomy and transverse carpal ligament release from the scaphoid tubercle on carpal canal pressures. This technique may permit both problems to be addressed through the same Wagner incision. METHODS: In 4 fresh frozen cadaver limbs pressures in the carpal canal were elevated to 30 mm Hg through a percutaneously placed balloon. Pressures were measured using an 18-gauge sideport needle via a transducer. Trapeziectomy and release of the transverse carpal ligament from the scaphoid were performed in succession through a Wagner incision with canal pressures measured after each step. RESULTS: Carpal canal pressures decreased after trapeziectomy (mean, 7 mm Hg; range, 3-14 mm Hg) but did not return to baseline (0 mm Hg) until complete release of the ligament. CONCLUSIONS: Decompression of the carpal tunnel can be performed effectively through a Wagner incision during basal joint arthroplasty. This cadaver model shows reduction in the canal pressures after trapeziectomy and release of the transverse carpal ligament. This single-incision approach is attractive because it may decrease morbidity compared with a 2-incision approach in patients with concomitant carpal tunnel syndrome and basal joint arthritis.     

Finger flexor tendon forces are a complex function of finger joint motions and fingertip forces.

In vivo tendon forces provide a view inside the musculoskeletal system revealing muscle function and potential injury etiologies. The studies presented here measured the in vivo tendon force of the flexor digitorum superficialis of the long finger during open carpal tunnel release surgery in ten adult patients. Forces were measured during passive movement of the finger, isometric pinch, and dynamic tapping of the finger. The tendon forces during passive movement of the finger were the largest with the finger fully extended. During isometric pinch, tendon force was linearly related to fingertip force, and was on average 3.3 times larger than the fingertip force. During dynamic activities, however, the relationship between tip and tendon force was nonlinear and often remained elevated when the finger was moving but with no applied force. Tendon forces were the highest with the isometric finger pinch. In conclusion, tendon force is a completed function of both fingertip load and motion of the joints that the tendons cross. A comparison of these results with others published in the literature indicated that rehabilitation processes need to incorporate a systems approach rather than rely on one specific physiologic relationship to minimize finger flexor tendon forces.     

Carpal tunnel syndrome secondary to wrist and finger flexor spasticity

Ten patients with spastic wrist flexion deformities secondary to traumatic brain injury were evaluated for carpal tunnel syndrome. The angle of wrist flexion deformity averaged 75 degrees (range, 58 to 115 degrees). Nerve conduction studies demonstrated prolonged median motor and/or sensory latencies in all patients. Preoperative wick catheter measurements of carpal tunnel pressures in eight patients averaged 11 mm Hg in the resting position, 21 mm Hg in maximal wrist flexion, and 15 mm Hg in maximal extension. Each patient had carpal tunnel release with simultaneous wrist and finger flexor tendon releases or lengthenings. At surgery nine of the median nerves were constricted at the proximal edge of the transverse carpal ligament. The presence of normal carpal tunnel pressures and impingement of the median nerve at the proximal edge of the transverse carpal ligament indicates that the chronically flexed posture of the wrist resulted in median nerve compression, and this condition may be aggravated by underlying pressure from the spastic finger flexors.     

Dose-responsiveness of electrophysiologic change in a new model of acute carpal tunnel syndrome

This study was done to determine the dose-responsiveness during the development of acute pressure-induced median neuropathy in rabbits and to develop a new animal model of acute carpal tunnel syndrome. Twenty-three rabbits were used. Carpal tunnel syndrome was induced by infusing a controlled saline solution into the carpal tunnel of rabbits using a 21-gauge needle under general anesthesia to elevate the carpal tunnel pressure. The changes in the amplitude and latency of the compound muscle action potential obtained by abductor pollicis recording were observed after a complete conduction block, and after the release of pressure at various pressure levels. Pressures greater than 30 mm Hg applied to the carpal tunnel caused a remarkable electrophysiologic change. A higher pressure level resulted in a shorter time required for a complete conduction block and also for recovery after the release of pressure. Complete conduction block occurred between 40 and 50 minutes at a pressure of 100 mm Hg. The degree of recovery after a conduction block was related inversely to the pressure-time integrals. Our animal model reflects the pathophysiology of acute carpal tunnel syndrome and shows a regular dose-responsiveness during the development of acute pressure-induced neuropathy.     

Canal pressures before,during, and after endoscopic release for idiopathic carpal tunnel syndrome

A special transducer was used to measure in situ carpal tunnel pressures in 20 patients who had surgery for idiopathic carpal tunnel syndrome (CTS) by one-portal endoscopic section of the flexor retinaculum. Pressures were elevated initially. The pressures were maximal (mean, 93 mm Hg) with full passive wrist extension. Peaks of high pressures, on average 97 mm Hg, were recorded with the Agee (MicroAire, Charlottesville, VA) endoscopic device in the canal. Release of the endoscopic flexor retinaculum resulted in a marked decrease of the pressures.     

Single-portal endoscopic carpal tunnel release compared with open release : a prospective,randomized trial

BACKGROUND: Carpal tunnel syndrome is a common condition causing hand pain and numbness. Endoscopic carpal tunnel release has been demonstrated to reduce recovery time, although previous studies have raised concerns about an increased rate of complications. The purpose of this prospective, randomized study was to compare open carpal tunnel release with single-portal endoscopic carpal tunnel release. METHODS: A prospective, randomized, multicenter center study was performed on 192 hands in 147 patients. The open method was performed in ninety-five hands in seventy-two patients, and the endoscopic method was performed in ninety-seven hands in seventy-five patients. All of the patients had clinical signs or symptoms and electrodiagnostic findings consistent with carpal tunnel syndrome and had not responded to, or had refused, nonoperative management. Follow-up evaluations with use of validated outcome instruments and quantitative measurements of grip strength, pinch strength, and hand dexterity were performed at two, four, eight, twelve, twenty-six, and fifty-two weeks after the surgery. Complications were identified. The cost of the procedures and the time until return to work were recorded and compared between the groups. RESULTS: During the first three months after surgery, the patients treated with the endoscopic method had better Carpal Tunnel Syndrome Symptom Severity Scores, better Carpal Tunnel Syndrome Functional Status Scores, and better subjective satisfaction scores. During the first three months after surgery, they also had significantly (p < 0.05) greater grip strength, pinch strength, and hand dexterity. The open technique resulted in greater scar tenderness during the first three months after surgery as well as a longer time until the patients could return to work (median, thirty-eight days compared with eighteen days after the endoscopic release). No technical problems with respect to nerve, tendon, or artery injuries were noted in either group. There was no significant difference in the rate of complications or the cost of surgery between the two groups. CONCLUSION: Good clinical outcomes and patient satisfaction are achieved more quickly when the endoscopic method of carpal tunnel release is used. Single-portal endoscopic surgery is a safe and effective method of treating carpal tunnel syndrome.     

In vivo finger flexor tendon force while tapping on a keyswitch.

Force may be a risk factor for musculoskeletal disorders of the upper extremity associated with typing and keying. However, the internal finger flexor tendon forces and their relationship to fingertip forces during rapid tapping on a keyswitch have not yet been measured in vivo. During the open carpal tunnel release surgery of five human subjects, a tendon-force transducer was inserted on the flexor digitorum superficialis of the long finger. During surgery, subjects tapped with the long finger on a computer keyswitch, instrumented with a keycap load cell. The average tendon maximum forces during a keystroke ranged from 8.3 to 16.6 N (mean = 12.9 N, SD = 3.3 N) for the subjects, four to seven times larger than the maximum forces observed at the fingertip. Tendon forces estimated from an isometric tendon-force model were only one to two times larger than tip force, significantly less than the observed tendon forces (p = 0.001). The force histories of the tendon during a keystroke were not proportional to fingertip force. First, the tendon-force histories did not contain the high-frequency fingertip force components observed as the tip impacts with the end of key travel. Instead, tendon tension during a keystroke continued to increase throughout the impact. Second, following the maximum keycap force, tendon tension during a keystroke decreased more slowly than fingertip force, remaining elevated approximately twice as long as the fingertip force. The prolonged elevation of tendon forces may be the result of residual eccentric muscle contraction or passive muscle forces, or both, which are additive to increasing extensor activity during the release phase of the keystroke.     

Functional sensibility assessment. part II: Effects of sensory improvement on precise pinch force modulation after transverse carpal tunnel release

Patients with median nerve compression at the carpal tunnel often have poor sensory afferents. Without adequate sensory modulation control, these patients frequently exhibit clumsy performance and excessive force output in the affected hand. We analyzed precision grip function after the sensory recovery of patients with carpal tunnel syndrome (CTS) who underwent carpal tunnel release (CTR). Thirteen CTS patients were evaluated using a custom‐designed pinch device and conventional sensory tools before and after CTR to measure sensibility, maximum pinch strength, and anticipated pinch force adjustments to movement‐induced load fluctuations in a pinch‐holding‐up activity. Based on these tests, five force‐related parameters and sensory measurements were used to determine improvements in pinch performance after sensory recovery. The force ratio between the exerted pinch force and maximum load force of the lifting object was used to determine pinch force coordination and to prove that CTR enabled precision motor output. The magnitude of peak pinch force indicated an economic force output during manipulations following CTR. The peak pinch force, force ratio, and percentage of maximum pinch force also demonstrated a moderate correlation with the Semmes–Weinstein test. Analysis of these tests revealed that improved sensory function helped restore patients' performance in precise pinch force control evaluations. These results suggest that sensory information plays an important role in adjusting balanced force output in dexterous manipulation. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:1534–1539, 2009     

Pressure–morphology relationship of a released carpal tunnel

We investigated morphological changes of a released carpal tunnel in response to variations of carpal tunnel pressure. Pressure within the carpal tunnel is known to be elevated in patients with carpal tunnel syndrome and dependent on wrist posture. Previously, increased carpal tunnel pressure was shown to affect the morphology of the carpal tunnel with an intact transverse carpal ligament (TCL). However, the pressure–morphology relationship of the carpal tunnel after release of the TCL has not been investigated. Carpal tunnel release (CTR) was performed endoscopically on cadaveric hands and the carpal tunnel pressure was dynamically increased from 10 to 120 mmHg. Simultaneously, carpal tunnel cross‐sectional images were captured by an ultrasound system, and pressure measurements were recorded by a pressure transducer. Carpal tunnel pressure significantly affected carpal arch area (p < 0.001), with an increase of >62 mm² at 120 mmHg. Carpal arch height, length, and width also significantly changed with carpal tunnel pressure (p < 0.05). As carpal tunnel pressure increased, carpal arch height and length increased, but the carpal arch width decreased. Analyses of the pressure–morphology relationship for a released carpal tunnel revealed a nine times greater compliance than that previously reported for a carpal tunnel with an intact TCL. This change of structural properties as a result of transecting the TCL helps explain the reduction of carpal tunnel pressure and relief of symptoms for patients after CTR surgery. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31: 616–620, 2013     

Effect of grip type,wrist motion,and resistance level on pressures within the carpal tunnel of normal wrists

Elevated carpal tunnel pressure (CTP) has been associated with carpal tunnel syndrome. This study systematically evaluated the effect of wrist motion resistance and grip type on CTP during wrist motion typical of occupational tasks. CTP during four wrist motion patterns, with and without resistance, and with and without gripping, was measured in vivo in 14 healthy individuals. CTP measured during compound motions fell between that measured in the cardinal planes of wrist flexion/extension and radial/ulnar deviation. Generally, with no active gripping there was little pressure change due to wrist angular displacement or resistance level. However, concurrent active pinch or power grip increased CTP particularly in motions including extension. CTP typically did not increase during wrist flexion, and in fact often decreased. Extension motions against resistance when employing a pinch or power grip increase CTP more than motions with flexion. Results could help inform design or modification of wrist motion intensive occupational tasks. © 2014 The Authors. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:524–530, 2014.     

Effect of wrist position on power grip and key pinch strength following carpal tunnel decompression

Power grip and thumb key pinch strength were measured pre- and immediately postoperatively in 30 patients with carpal tunnel syndrome while the wrist was in flexion and extension. The carpal tunnel decompression was performed under local infiltration with 1% lignocaine. Grip strength decreased more in wrist flexion than in wrist extension. No difference was found in thumb pinch strength. The authors conclude that some of the immediate postoperative loss of grip strength in wrist flexion can be attributed to prolapse of flexor tendons out of the carpal tunnel in this position.     

Release of the transverse carpal ligament alone is associated with elevated pressure beneath the distal volar forearm fascia in a cadaver model of carpal tunnel syndrome

PURPOSE: The purpose of this study is to determine whether release of the distal volar forearm fascia (DVFF) is necessary at the time of median nerve decompression for carpal tunnel syndrome. METHODS: Five fresh-frozen cadaver specimens were mounted vertically with the hand dependent and a 2.27-kg weight suspended from the fingers. A pressure sensor wire was used to measure pressures starting just distal to the transverse carpal ligament (TCL). The wire was withdrawn proximally in 5-mm increments and into the forearm until pressure was below 10 mm Hg. An incision in the forearm was extended distally until the pressure sensor was found. The distance from this point to the distal volar wrist crease was measured. The TCL was released, keeping the DVFF intact, and the experiment was repeated. Paired t-tests determined whether there were statistically significant differences between measurements before and after TCL release. RESULTS: Average peak pressure under the intact TCL was 57.8 +/- 10.1 mm Hg. Average peak pressure under the DVFF with the TCL intact was 61.2 +/- 43.6 mm Hg. Following release of the TCL, average peak pressure beneath the TCL significantly decreased to 14.0 +/- 9.0 mm Hg, whereas average peak pressure at the intact DVFF increased to 64.8 +/- 48.7 mm Hg. Average locations where DVFF pressure became less than 10 mm Hg with an intact TCL and with released TCL were 4.30 +/- 1.8 cm and 4.00 +/- 1.8 cm proximal to the distal volar wrist crease, respectively. There was no significant difference between DVFF pressures before or after TCL release. CONCLUSIONS: In a cadaver model of carpal tunnel syndrome, release of the TCL alone is associated with persistent pressures >30 mm Hg in the region of the DVFF. Release of the TCL did not significantly change the location of the pressure drop-off under the DVFF.     

The clinical significance of the palmaris longus tendon in the pathophysiology of carpal tunnel syndrome

Carpal tunnel syndrome is associated with increased intracarpal canal pressure. The effect of tendon loading on intracarpal canal pressures is documented in biomechanical studies. Palmaris longus loading in wrist extension induces the greatest absolute increase in intracarpal canal pressure. Despite this fact, the palmaris longus is not yet a proven independent risk factor for the development of carpal tunnel syndrome. The purpose of this prospective clinical study was to assess and quantify the association between the presence of a palmaris longus tendon and carpal tunnel syndrome. Thirty-six carpal tunnel subjects with bilateral disease were compared with 36 controls. Each subject was clinically examined for the presence of the palmaris longus tendon. The prevalence of palmaris longus agenesis was significantly lower in the carpal tunnel group. The palmaris longus tendon is a strong independent risk factor for carpal tunnel syndrome.     

Prospective randomized comparison of single-incision and two-incision carpal tunnel release outcomes

Background

This study analyzes both the subjective and objective symptom and functional outcomes of patients who underwent either traditional single-incision or two-incision carpal tunnel release (CTR).

Methods

From 2008 to 2009, patients with isolated carpal tunnel syndrome were randomized to undergo either single-incision or two-incision CTR by a single surgeon at a university medical center. Pre-operatively, participants completed a Disabilities of the Arm, Shoulder, and Hand (DASH) Questionnaire, Brigham and Women's Carpal Tunnel Questionnaire (BWCTQ), as well as grip and pinch strength and Semmes–Weinstein monofilament sensation testing. At 2 weeks, 6 weeks and at least 6 months post-operatively, these measurements were repeated along with assessment of scar tenderness and pillar pain. Data were analyzed using SPSS version 20 software to perform non-parametric tests and Pearson's correlations. Significance was set at p?=?0.05.

Results

There was no statistically significant difference between the single- and two-incision CTR groups with respect to pre- and post-operative DASH scores, BWCTQ scores, grip strength, pinch strength, scar tenderness, or pillar pain. The only statistically significant difference was improved sensation by Semmes–Weinstein in the single-incision group in the second finger at 6 weeks post-operatively and in the third finger at 6 months post-operatively.

Conclusions

The preservation of the superficial nerves and subcutaneous tissue between the thenar and hypothenar eminences may account for reports of less scar tenderness and pillar pain among recipients of two-incision CTR compared to single-incision CTR in the early post-operative period. However, there is similar post-operative recovery and improvement in grip and pinch strength and sensation after 6+ months post-operatively.     

Flexor tendon forces: in vivo measurements.

S-shaped force transducers were developed for measurement of the forces along intact tendons. After calibration, the transducers were applied to the flexor pollicis longus and flexor digitorum superficialis and profundus tendons of the index finger in five patients operated on for treatment of carpal tunnel syndrome. The tendon forces generated during passive and active motion of the wrist and fingers were recorded. For pinch function, the amount of the applied load was measured with a special pinch meter. Tendon forces in the range of 0.1 to 0.6 kgf were measured during passive mobilization of the wrist. Tendon forces up to 0.9 kgf were present during passive mobilization of the fingers. Tendon forces up to 3.5 kgf were present during active unresisted finger motion. Tendon forces up to 12.0 kgf were recorded during tip pinch, with a mean applied pinch force of 3.5 kgf. These results have potential application in determining the amount of force that a tendon repair would have to resist during passive as well as active postsurgical mobilizations.     

Carpal tunnel syndrome with thenar atrophy: evaluation of the pinch and grip strength in patients undergoing surgical treatment

This aim of this study was to evaluate the progression of grip, tip pinch, key (lateral) pinch, and tripod pinch strengths in patients suffering from carpal tunnel syndrome with thenar atrophy following surgery. Between October 2008 and May 2010, 46 patients (49 hands) with carpal tunnel syndrome associated with thenar atrophy underwent surgery. Thenar atrophy was assessed by clinical inspection. Evaluations for grip strength and for tip, key, and tripod pinch strengths were made using a hydraulic hand dynamometer grip and a hydraulic pinch gauge, respectively. These measurements were taken before surgery and at 3 and 6 months after the procedure. When we compared the averages of all forces measured in the affected hand before the surgery with all forces measured at 3 months postoperative, we found no significant differences. However, after 6 months, we found significant differences for all four strength tests as compared with those measurements taken preoperatively and at the 3 month time point. Our results suggest that patients with thenar atrophy show increased grip strength and pinch strength by the sixth month after surgical treatment.     

Outcomes of open and endoscopic carpal tunnel release: a meta-analysis

Background

Currently, there are two genres of surgical treatment of carpal tunnel syndrome, open versus endoscopic. The goal of our study is to analyze published data by comparing outcomes of surgical treatment for carpal tunnel syndrome and determine if one approach is superior to the other (open versus endoscopic).

Methods

A meta-analysis of retrospective series of Carpal tunnel release including >20 patients, with results measuring outcomes based on at least six of the following nine parameters (paresthesia relief, scar tenderness, two-point discrimination, thenar muscle weakness, Semmes–Weinstein/SW monofilament testing, return to work time, grip and pinch strength, and complications).

Results

Endoscopic carpal tunnel approach showed statistically superior outcomes in eight of the nine categories investigated. Only in the category of complications (mean occurrence of 1.2 % in the open release versus 2.2 % in the endoscopic release group) was the endoscopic group inferior.

Conclusion

This suggests that the endoscopic release is superior to the open release, particularly in experienced hands.     

Carpal Tunnel Syndrome Impairs Thumb Opposition and Circumduction Motion

Background

Carpal tunnel syndrome is associated with sensory and motor impairments resulting from the compressed and malfunctioning median nerve. The thumb is critical to hand function, yet the pathokinematics of the thumb associated with carpal tunnel syndrome are not well understood.

Questions/purposes

The purpose of this study was to evaluate thumb motion abnormalities associated with carpal tunnel syndrome. We hypothesized that the ranges of translational and angular motion of the thumb would be reduced as a result of carpal tunnel syndrome.

Methods

Eleven patients with carpal tunnel syndrome and 11 healthy control subjects voluntarily participated in this study. Translational and angular kinematics of the thumb were obtained using marker-based video motion analysis during thumb opposition and circumduction movements.

Results

Motion deficits were observed for patients with carpal tunnel syndrome even though maximum pinch strength was similar. The path length, normalized by palm width of the thumb tip for the patients with carpal tunnel syndrome was less than for control participants (opposition: 2.2 palm width [95% CI, 1.8–2.6 palm width] versus 3.1 palm width [95% CI, 2.8–3.4 palm width], p < 0.001; circumduction: 2.2 palm width [95% CI, 1.9–2.5 palm width] versus 2.9 palm width [95% CI, 2.7–3.2 palm width], p < 0.001). Specifically, patients with carpal tunnel syndrome had a deficit of 0.3 palm width (95% CI, 0.04–0.52 palm width; p = 0.022) in the maximum position of their thumb tip ulnarly across the palm during opposition relative to control participants. The angular ROM also was reduced for the patients with carpal tunnel syndrome compared with the control participants in extension/flexion for the metacarpophalangeal (opposition: 34° versus 58°, p = .004; circumduction: 33° versus 58°, p < 0.001) and interphalangeal (opposition: 37° versus 62°, p = .028; circumduction: 41° versus 63°, p = .025) joints.

Conclusions

Carpal tunnel syndrome disrupts kinematics of the thumb during opposition and circumduction despite normal pinch strength.

Clinical Relevance

Improving understanding of thumb pathokinematics associated with carpal tunnel syndrome may help clarify hand function impairment associated with the syndrome given the critical role of the thumb in dexterous manipulation.