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 The wire was withdrawn proximally in 5-mm increments and into the forearm until pressure was below 10 mm Hg.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.     

Carpal tunnel pressure alters median nerve function in a dose-dependent manner: a rabbit model for carpal tunnel syndrome.

BACKGROUND: An in vivo animal model for carpal tunnel syndrome (CTS) is presented which allows for graded application of pressure to the median nerve within the carpal canal. We hypothesized that such pressure would cause electrophysiologic changes in the median nerve in a dose-related manner, with NCS/EMG changes consistent with CTS in humans. METHODS: In 40 New Zealand white rabbits, ranging from 2 to 2.5 kg, angioplasty catheters were placed in the carpal tunnel in the forepaws and pressures ranging from 50 to 80 mmHg applied to one side while the contralateral side served as the control and remained uninflated. Pressure was applied until a 15% increase in distal motor latency was obtained for 2 consecutive weeks by nerve conduction studies. RESULTS: All the experimental limbs exhibited a 15% increase in distal motor latency. None of the control limbs showed a significant increase in distal motor latency. In the experimental animals the 15% delay was achieved in approximately 4-5 weeks in the 50-70 mmHg groups and in approximately 1 week in the 80 mmHg group. CONCLUSION: This new animal model for CTS demonstrates a direct cause and effect relationship between carpal tunnel pressure and median nerve dysfunction. We anticipate that this in vivo model with clinically relevant outcomes will facilitate identification of injury mechanisms, and will serve as a basis for future development of novel interventions and treatments.     

The anatomical site of constriction of the median nerve in patients with severe idiopathic carpal tunnel syndrome

During open carpal tunnel release in patients with severe idiopathic carpal tunnel syndrome, an area of constriction in the substance of the median nerve is frequently noted. In a prospective study of 30 patients, the central point of the constricted part of the nerve was determined intraoperatively and found to be, on average, 2.5 (range 2.2-2.8)cm from the distal wrist crease. This point always corresponded to the location of the hook of the hamate bone. These intraoperative findings were compared with the "narrowest" point of the carpal canal as determined by anatomical and radiological studies in the literature.     

Carpal arch and median nerve changes during radioulnar wrist compression in carpal tunnel syndrome patients

The purpose of this study was to investigate the morphological changes of the carpal arch and median nerve during the application of radiounlarly directed compressive force across the wrist in patients with carpal tunnel syndrome. Radioulnar compressive forces of 10 N and 20 N were applied at the distal level of the carpal tunnel in 10 female patients diagnosed with carpal tunnel syndrome. Immediately prior to force application and after 3 min of application, ultrasound images of the distal carpal tunnel were obtained. It was found that applying force across the wrist decreased the carpal arch width (p < 0.001) and resulted in increased carpal arch height (p < 0.01), increased carpal arch curvature (p < 0.001), and increased radial distribution of the carpal arch area (p < 0.05). It was also shown that wrist compression reduced the flattening of the median nerve, as indicated by changes in the nerve's circularity and flattening ratio (p < 0.001). This study demonstrated that the carpal arch can be non‐invasively augmented by applying compressive force across the wrist, and that this strategy may decompress the median nerve providing symptom relief to patients with carpal tunnel syndrome. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1234–1240, 2016.     

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.     

Carpal tunnel and transverse carpal ligament stiffness with changes in wrist posture and indenter size

This study investigated the effects of loading and posture on mechanical properties of the transverse carpal ligament (TCL). Ten fresh‐frozen cadaver arms were dissected to expose the TCL and positioned in the load frame of a servo‐hydraulic testing machine, equipped with a load cell and custom made indenters. Four cylindrical indenters (5, 10, 20, and 35 mm) loaded the TCL in three wrist postures (30° extension, neutral and 30° flexion). Three loading cycles with a peak force of 50 N were applied at 5 N/s for each condition. The flexed wrist posture had significantly greater TCL stiffness (40.0 ± 3.3 N/mm) than the neutral (35.9 ± 3.5 N/mm, p = 0.045) and extended postures (34.9 ± 2.8 N/mm, p = 0.025). TCL stiffness using the 10 and 20 mm indenters was larger than the 5 mm indenter. Stiffness was greatest with the 20 mm indenter, which had the greatest indenter contact area on the TCL. The 35 mm indenter covered the carpal bones, compressed the carpal tunnel and produced the lowest stiffness. The complexity of the TCL makes it an important part of the carpal tunnel and the mechanical properties found are essential to understanding mechanisms of carpal tunnel syndrome. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 29:1682–1687, 2011     

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.     

Two cases of endoscopic management of carpal tunnel syndrome in macrodactyly patients.

Some cases of carpal tunnel syndrome in macrodactyly patients have been reported. We performed endoscopic carpal canal release on two unilateral macrodactyly patients suffering from bilateral carpal tunnel syndrome. We measured carpal canal pressure before performing endoscopic surgery using the Universal Subcutaneous Endoscope system to confirm median nerve compression. We diagnosed median nerve compression in each patient due to the high preoperative carpal canal pressure. Carpal canal pressure immediately decreased to within normal range following release of both the flexor retinaculum and the distal holdfast fibres of the flexor retinaculum. One patient recovered to within normal in terms of sensory disturbances and abductor pollicis brevis muscle strength. The other patient showed improvement in terms of sensory disturbance, however, muscle power did not recover because this patient had suffered from carpal tunnel syndrome for ten years. Endoscopic carpal canal release and decompression surgery was effective for carpal tunnel syndrome in both macrodactyly patients.     

Results of treatment of carpal tunnel syndrome with associated hourglass deformity of the median nerve

Two hundred twenty-seven successive cases of carpal tunnel syndrome confirmed by abnormal electrodiagnostic studies were reviewed. All cases underwent open carpal tunnel release by a single surgeon over a 3-year period. Thirty-two hands (14% of all cases) in 29 patients demonstrated an hourglass deformity at the time of surgery. Electrodiagnostic tests revealed no evidence of any other type of peripheral neuropathy in any patient. Postoperative electrodiagnostic studies were obtained in all cases on completion of therapy. The length of the follow-up period averaged 11 months (range, 3-35 months). The duration of preoperative symptoms ranged from 2 years to more than 10 years. Twenty-eight of the 32 hands (88%) with hourglass deformities demonstrated subjective clinical improvement or complete resolution of symptoms. Chronicity of symptoms and electrophysiologic severity did not correlate with the presence of the hourglass deformity. Presence of hourglass compression of the median nerve in carpal tunnel syndrome is therefore not a negative prognostic indicator.     

Median nerve deformation and displacement in the carpal tunnel during index finger and thumb motion

The purpose of this study was to investigate the deformation and displacement of the normal median nerve in the carpal tunnel during index finger and thumb motion, using ultrasound. Thirty wrists from 15 asymptomatic volunteers were evaluated. Cross‐sectional images during motion from full extension to flexion of the index finger and thumb were recorded. On the initial and final frames, the median nerve, flexor pollicis longus (FPL), and index finger flexor digitorum superficialis (FDS) tendons were outlined. Coordinate data were recorded and median nerve cross‐sectional area, perimeter, aspect ratio of the minimal‐enclosing rectangle, and circularity in extension and flexion positions were calculated. During index finger flexion, the tendon moves volarly while the nerve moves radially. With thumb flexion, the tendon moves volarly, but the median nerve moves toward the ulnar side. In both motions, the area and perimeter of the median nerve in flexion were smaller than in extension. Thus, during index finger or thumb flexion, the median nerve in a healthy human subject shifts away from the index finger FDS and FPL tendons while being compressed between the tendons and the flexor retinaculum in the carpal tunnel. We are planning to compare these data with measurements in patients with carpal tunnel syndrome (CTS) and believe that these parameters may be useful tools for the assessment of CTS and carpal tunnel mechanics with ultrasound in the future. Published by Wiley Periodicals, Inc. J Orthop Res 28:1387–1390, 2010     

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.     

掌部小切口治疗腕管综合征

目的介绍应用新型掌部小切口行腕管松解术。方法对确诊为腕管综合征的68例(89侧)患者采用新型掌部小切口行腕管松解术,该切口为纵行、位于鱼际纹尺侧2～3mm、长约2.0～2.5cm,近端不超过远侧腕横纹。结果经术后6个月随访,所有患者症状均消失,拇短展肌肌力、握力、捏力、皮肤感觉功能均明显改善,术前术后差异在统计学极具显著意义(P<0.001)。本组无任何神经血管并发症,无1例出现腕掌部瘢痕疼痛。结论本切口具有安全、损伤小、直视下松解腕管并同时可行正中神经内松解和尺管松解、手术瘢痕小等诸多优点,是腕管松解术的一种新型、可靠的手术入路。     

The Modified Ultrasound-Guided Distal-to-Proximal Carpal Tunnel Injection With Median Nerve Hydrodissection: A Retrospective Safety Review of 827 Procedures

Objective: The aim of this report is to describe a new ultrasound guided technique for carpal tunnel injection and median nerve hydrodissection using distal to proximal approach. Methods: From 2015 to 2019, 827 consecutive injections by distal-to-proximal approach were included using coding information to check for post-procedural skin hypopigmentation, hematoma, seroma, nerve injury, or vascular injury. Results: There were no occurrences of post-procedural skin-hypopigmentation, hematoma or seroma formation, or neurovascular injury. Conclusions: The distal approach carpal tunnel injection is a safe and effective method. It may directly inject the medication into carpal tunnel to avoid skin hypopigmentation from steroid side effect with previous report method, also it may release adhesion of median nerve with surrounding soft tissue by hydrodissection. It helps median nerve compression at outlet of carpal tunnel.     

The 'yellow fat sign' - a reliable indicator of the completeness of carpal tunnel release

Carpal tunnel syndrome is the commonest nerve compression syndrome and longitudinal division of the transverse carpal ligament to release the median nerve remains one of the most commonly performed procedures. This may be undertaken by plastic, orthopaedic, general or neurosurgeons. However, incomplete division of this ligament remains a cause of persistent symptoms. In this paper we draw attention to an anatomical landmark at the distal end of the tunnel, visualisation of which indicates complete release.     

The use of diagnostic ultrasound in carpal tunnel syndrome

PURPOSE: Traditional evaluation of suspected carpal tunnel syndrome (CTS) involves a thorough history, physical examination, and nerve conduction velocity studies (NCS). Ultrasound is used widely in Europe and has gained acceptance in the United States in the diagnosis of various musculoskeletal disorders. The purpose of this study was to document the ultrasonographic measurement difference in median nerve size between patients with CTS and controls and to correlate these findings with NCS findings, thereby allowing us to test the validity of ultrasound as a diagnostic modality for CTS. METHODS: Forty-four wrists in 26 CTS patients and 86 wrists in 43 asymptomatic volunteers were imaged using a real-time ultrasound scanner with a 12/5 MHz linear-array transducer. The cross-sectional area of the median nerve was measured at the level of the distal wrist crease in both CTS patients and controls. All CTS patients had NCS. The ultrasonographic median nerve area was compared for the 2 groups and correlation analysis between ultrasonographic nerve sizes and NCS findings was performed. RESULTS: The average cross-sectional area of the median nerve at the distal wrist crease was 9 mm(2) in asymptomatic volunteers and 14 mm(2) in CTS patients. For the CTS patients the Pearson correlation coefficient between ultrasound nerve measurement and NCS values was 0.37, suggesting that higher values of ultrasound measurements are associated with abnormal NCS findings. CONCLUSIONS: Our results indicate that high-resolution ultrasound is informative in the evaluation of CTS and shows enlargement of the median nerve at the distal wrist crease in symptomatic patients. Therefore it is a reliable modality for imaging the wrist in patients with CTS. In addition ultrasound is well tolerated and safe. TYPE OF STUDY/LEVEL OF EVIDENCE: Diagnostic, Level I.     

急性腕管综合征的手术治疗

目的:探讨急性腕管综合征的手术治疗方法和效果。方法:对14例急性腕管综合征患者的手术方法进行分析总结,手术主要是切开腕横韧带,清除积血和炎性渗出物及致压物,解除粘连,彻底松解正中神经和血管受压。结果:切口均Ⅰ期愈合,手部肿胀于1周内消退,神经症状逐渐恢复,完全恢复正常时间2~45 d,平均15 d。随访6个月~1年,无一例复发,患手功能良好。结论:对急性腕管综合征患者,经短时间观察和保守治疗无效,早期手术可获得满意疗效。     

Median nerve deformation and displacement in the carpal tunnel during finger motion

The objective of this study was to evaluate the correlations between deformation and displacement of median nerve and flexor tendons during finger motion in the carpal tunnel for both carpal tunnel syndrome (CTS) patients and healthy controls. Sixty‐two wrists of 31 asymptomatic volunteers and fifty‐one wrists of 28 idiopathic CTS patients were evaluated by ultrasound. The displacement of the median nerve and the middle finger flexor digitorum superficialis (FDS) tendon, as well as area, perimeter, aspect ratio of a minimum enclosing rectangle, and circularity of the median nerve were measured in finger extension and flexion positions. Deformation indices were defined as the ratios of indices in finger extension and flexion positions. The correlations between displacement and deformation indices were evaluated. There were significant correlations between nerve palmar–dorsal displacement and deformation indices (p < 0.05). The aspect ratio deformation index showed the strongest correlation to palmar–dorsal displacement of the nerve (?0.572, p < 0.01). This study showed that there is a relationship between median nerve deformation indices and nerve palmar–dorsal displacement in the carpal tunnel. Since the highest correlations were between palmar–dorsal nerve displacement direction and aspect ratio deformation index, these parameters may be helpful to understand the pathophysiology of CTS. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31:1876–1880, 2013

     

Intraoperative changes in motor nerve conduction latency in carpal tunnel syndrome

A prospective study of 47 patients with 51 hands treated for carpal tunnel syndrome by surgical release of the deep transverse carpal ligament was performed using intraoperative motor nerve conduction latency measured over a standard distance across the carpal tunnel both before and after release of the ligament. The results of intraoperative conduction latencies indicated a dramatic and immediate reduction in the conduction latency across the carpal canal in all but seven patients, two of whom had diabetes. When the results were subjected to statistical analysis, they were significant (P is equal to 0.00001). Although further studies are indicated, these data suggest that a rapidly reversible mechanical or metabolic block, such as ischemia in the segment of the median nerve, may be responsible for the symptoms of carpal tunnel syndrome.     

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     

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