Changes in digital flexor tendon mechanics after endoscopic and open carpal tunnel releases in cadaver wrists

Trigger Fingers After Open Carpal Tunnel Release

Trigger finger (TF) and carpal tunnel syndrome (CTS) are common conditions often occurring together with an unclear relationship. While some studies conclude that TFs occur as a result of carpal tunnel release (CTR), others have not established a causal relationship. Our purpose was to evaluate the prevalence and timing of TF development in the same hand after open CTR in our population. This was a retrospective review of 497 patients undergoing open CTR by a single surgeon. Two hundred twenty-nine charts were analysed for age, gender, handedness, BMI, workers' compensation status, and background disease. We analysed the specific digit involved and timing to development of triggering after CTR. Thirty-one patients developed triggering after CTR (13.5%). Mean age was 52.5 (14.0) years. Follow-up ranged from 1 to 53 months with a median follow-up of 6 months (interquartile range = 2-13). The thumb was the most common to trigger (42.22%), followed by the ring 24.44%, middle 22.22%, little 8.89%, and index fingers 2.22%. Trigger thumb occurred at 3.5 months (3.6) post-operatively, while other digits triggered at 7.5 months (4-10.25) after surgery (P = .022). No risk factors were associated with TF development. Our results suggest that a trigger thumb develops more frequently and earlier than other trigger digits after an open CTR. Further study is needed to clarify the mechanisms involved and may enable specific treatment such as local anti-inflammatory medication following CTR. We suggest educating prospective carpal tunnel surgery patients to high risk of triggering following CTR.

Ultrasound assessment of the effectiveness of carpal tunnel release on median nerve deformation

To assess the biomechanical effect of carpal tunnel release (CTR), we evaluated the deformation and displacement patterns of the median nerve before and after CTR in carpal tunnel syndrome (CTS) patients. Sixteen wrists of 14 idiopathic CTS patients who had open CTR and 26 wrists of 13 asymptomatic volunteers were evaluated by ultrasound. Cross-sectional images of the carpal tunnel during motion from full finger extension to flexion were recorded. The 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, determined by the flexion-extension ratio for each parameter, were compared before and after CTR. After CTR, the deformation indices of perimeter and circularity became significantly larger and the aspect ratio became significantly smaller than those before CTR (p < 0.05). Those differences were more obvious when comparing the values between the patients before CTR and the controls. Since the deformation indices after CTR are similar to the patterns of normal subjects, the surrounding structures and environment of the median nerve may be normalized upon CTR. This may be a way to tell how the median nerves recover after CTR.

A handy review of carpal tunnel syndrome: From anatomy to diagnosis and treatment

Carpal tunnel syndrome (CTS) is the most commonly diagnosed disabling condition of the upper extremities. It is the most commonly known and prevalent type of peripheral entrapment neuropathy that accounts for about 90% of all entrapment neuropathies. This review aims to provide an outline of CTS by considering anatomy, pathophysiology, clinical manifestation, diagnostic modalities and management of this common condition, with an emphasis on the diagnostic imaging evaluation.

Transverse carpal ligament and forearm fascia release for the treatment of carpal tunnel syndrome change the entrance angle of flexor tendons to the A1 pulley: the relationship between carpal tunnel surgery and trigger finger occurrence

PURPOSE

The appearance of trigger finger after decompression of the carpal tunnel without a preexisting symptom has been reported in a few articles. Although, the cause is not clear yet, the loss of pulley action of the transverse carpal ligament has been accused mostly. In this study, we planned a biomechanical approach to fresh cadavers.

METHODS

The study was performed on 10 fresh amputees of the arm. The angles were measured with (1) the transverse carpal ligament and the distal forearm fascia intact, (2) only the transverse carpal ligament incised, (3) the distal forearm fascia incised to the point 3 cm proximal from the most proximal part of the transverse carpal ligament in addition to the transverse carpal ligament. The changes between the angles produced at all three conditions were compared to each other.

RESULTS

We saw that the entrance angle increased in all of five fingers in an increasing manner from procedure 1 to 3, and it was seen that the maximal increase is detected in the middle finger from procedure 1 to procedure 2 and the minimal increase is detected in little finger.

DISCUSSION

Our results support that transverse carpal ligament and forearm fascia release may be a predisposing factor for the development of trigger finger by the effect of changing the enterance angle to the A1 pulley and consequently increase the friction in this anatomic area.

CLINICAL RELEVANCE

This study is a cadaveric study which is directly investigating the effect of a transverse carpal ligament release on the enterance angle of flexor tendons to A1 pulleys in the hand.

Current concepts of carpal tunnel syndrome: pathophysiology, treatment, and evaluation

The current concepts of carpal tunnel syndrome (CTS) with respect to its pathophysiology, treatment, and evaluation are discussed. With regard to the pathophysiology of idiopathic CTS, biomechanical studies to determine the kinematics of the flexor tendon, and the median nerve inside the carpal tunnel may provide valuable insights. Different degrees of excursion between the flexor tendons and the median nerve could cause strain and microdamage to the synovial tissue; this has been microscopically observed. A biomechanical approach for elucidating the events that trigger the development of CTS seems interesting; however, there are limitations to its applications. Endoscopic carpal tunnel release (ECTR) is a useful technique for achieving median nerve decompression. However, it is not considered superior to conventional open carpal tunnel release in terms of fast recovery of hand function. Unless the effect of inserting a cannula into the diseased carpal tunnel on the median nerve function is quantitatively elucidated, ECTR will not be regarded as a standard procedure for relieving the median nerve from chronic compression. The treatment of CTS should be evaluated on the basis of patient-oriented questionnaires as well as conventional instruments because these questionnaires have been validated and found to be highly responsive to the treatment. It should be noted that nerve conduction studies exclusively evaluate the function of the median nerve, whereas patient-oriented questionnaires take into account not only the symptoms of CTS but other accompanying pathologies as well, such as flexor tenosynovitis. In Japan, the number of CTS patients is expected to rise; this may be attributed to a general increase in the life-span of the Japanese and increase in the number of diabetic patients. Thus, more efforts should be directed toward elucidating the pathophysiology of so-called idiopathic CTS, so that new treatment strategies can be established for CTS of different pathologies.

Relative longitudinal motion of the finger flexors, subsynovial connective tissue, and median nerve before and after carpal tunnel release in a human cadaver model

PURPOSE

The normal gliding environment in the carpal tunnel is complex. The median nerve and flexor tendons are surrounded by a multilayered subsynovial tissue. To date, observations of the relative motions of the flexor tendon, median nerve and multilayered subsynovial tissue have been through a surgically released open carpal tunnel. The purpose of this study was to compare the motions of these tissues in an intact and open carpal tunnel.

METHODS

We measured the relative motion of the middle finger flexor digitorum superficialis tendon, its surrounding subsynovial connective tissue (SSCT) and the median nerve in 8 human cadavers. The flexor retinaculum was used as a fixed reference point. The motions were compared for simulated isolated middle finger and simulated fist motion as measured fluoroscopically in the closed carpal tunnel and directly in the open carpal tunnel.

RESULTS

While the simulated isolated finger motion produced significantly less SSCT and median nerve motion (p<.05), there was no difference in flexor digitorum superficialis, SSCT, or nerve motion when comparing the fluoroscopic measurements in the closed carpal tunnel with the direct visual measurements in the open carpal tunnel.

CONCLUSIONS

Relative motion of the flexor tendons, SSCT, and median nerve within the carpal tunnel follows a certain pattern, which may indicate the physiological state of the SSCT. This relative motion pattern was not affected by flexor retinaculum release.

Carpal tunnel syndrome and development of trigger digit

Although the coexistence of carpal tunnel syndrome and trigger digit in the same hand is well documented, the interactive relationship between them is unclear. This study was conducted to examine the factors that may impact on the development of trigger digit in the hand with idiopathic carpal tunnel syndrome. One hundred and eighty-one patients were enrolled. Their gender, age, dominant side, severity of carpal tunnel syndrome, history or presence of trigger digit, and treatment type were recorded. The patients were evaluated for the presence of trigger digit at 1, 3, 6 and 12 months after surgery or the initial evaluation. Two hundred and sixty-five hands in 152 patients were included in the final assessment. Logistic regression analysis revealed that surgery was a significant risk factor for the onset of trigger digit and may accelerate development of trigger digit when carpal tunnel syndrome was mild to moderate, but not when it was severe. In severe disease, other unknown factors, such as hypertrophy of the flexor tenosynovium, may mask the effect of surgery.