The effect of time after shear injury on the subsynovial connective tissue and median nerve within the rabbit carpal tunnel

Establishing the electrophysiological feasibility of the rabbit median nerve as an experimental model for carpal tunnel syndrome

BACKROUND

Rabbits are appropriate models for experimental carpal tunnel syndrome (CTS) studies. This study aimed to explore whether the distribution and innervation area of the nerves supplying the thenar muscles of rabbits are similar to those in humans using anatomical, electrophysiological, and histopathological methods.

NEW METHOD

20 New Zealand rabbits were used to establish reference conduction values for the median and ulnar nerves. Median nerve denervation was performed on the left forelimb of six rabbits, and changes were assessed 33 days post-surgery. Normative data from healthy rabbits were compared with those from denervated rabbits, and comparisons were made between the right and left forelimbs of the denervated rabbits. Thenar and interosseous (2nd, 3rd, and 4th) muscles were used for histopathology. Dissections focused on the thenar muscles and branches of the median and ulnar nerves.

RESULTS

Thenar muscles were 2.5-3 mm in width and 7-8 mm in length), innervated by both the median and ulnar nerves. Normative latency and amplitude values of 1.85 ± 0.30 ms and 7.71 ± 3.50 mV for the median nerve and 1.85 ± 0.19 ms and 6.14 ± 2.50 mV for the ulnar nerve, respectively. Denervation reduced thenar muscle CMAP amplitude (2.51 ± 2.16 mV, p = 0.047) on ulnar nerve stimulation, indicating dual innervation. The median sensory nerve conduction latency (2.55 ± 0.20 ms) was successfully performed for the first time. Histopathological analysis revealed localized atrophy and degenerative changes in the denervated thenar muscles.

COMPARISON WITH EXISTING METHODS

The new method including novel normative data will significantly enhance the evaluation of CTS in experimental rabbit models, paving the way for more accurate and reliable future research.

CONCLUSION

The innervation patterns of rabbit thenar muscles were similar to those in humans. This data can aid CTS understanding in rabbit models.

Comparison of the establishment of a rabbit model of carpal tunnel syndrome under ultrasound-guided and landmark-guided methods

A simple and feasible rabbit model of carpal tunnel syndrome (CTS) was established using an animal experimental study. Twenty-four New Zealand white rabbits were randomized into a normal group (Group C), a glucose injection model group (Groups N-M) and an ultrasound-guided injection model group (Groups U-M). Each group consisted of 8 rabbits.Electrophysiological and ultrasound examinations were performed before sampling. Hematoxylin-eosin (H&E) staining and electron microscopy were performed to observe the neuropathological changes. During electrophysiological testing 1 week after modeling, the amplitudes of the sensory nerve conduction velocity (SNCV), distal motor latency (DML) and compound muscle action potential (CMAP ) in the U-M group were significantly different compared to the C group and the N-M group (P < 0.05). Five weeks after modeling, the amplitudes of the SNCV, DML and CMAP in the U-M group and the C group were significantly different (P < 0.05). These differences were statistically significant compared to the DML and CMAP in the N-M group (P < 0.05), and the changes in these parameters were more significant than the results 1 week after modeling (P < 0.05). The difference in CMAP amplitude between the N-M group and C group was statistically significant (P < 0.05), but the other parameters were not significantly different (P > 0.05). Compared to the original modeling method, four injections of 0.3 ml of 10% glucose solution under ultrasound guidance reduced the time required to establish the disease model and increased the stability of the model. Therefore, this technique is a simple and feasible method for establishing a model of rabbit carpal tunnel syndrome.

Bilateral Idiopathic Carpal Tunnel Syndrome: Clinical-Functional Characterization and Efficacy of Two Combined Postoperative Physiotherapeutic Treatments

OBJECTIVE

To evaluate the efficacy of combined association instrument myofascial mobilization (IASTM) and stretching in patients with idiopathic bilateral carpal tunnel syndrome (CTS) operated on one hand and to analyze the response of the operated (OH) and non-operated (NH) hand according to the sequence of therapies. Research on these parameters has not yet been found in the literature.

METHODS

Randomized controlled crossover study with 43 participants using the objective and subjective outcome variables. Patients were randomly assigned to two groups: starting with stretching followed by IASTM and starting with IASTM followed by stretching. Then patients underwent surgery on the hand with more severe involvement and physical therapy rehabilitation was started 30 days after for a period of 4 weeks. After the 1-week interval the participants who started with stretching were referred to IASTM and vice versa, following the same previous patterns. The outpatient reassessments took place at 3 to 6 months. Crossover ANOVA and effect sizes were used as analysis methods.

RESULTS

Time was the most significant outcome for all variables both during therapies and at 6-month follow-up. Regarding response to the combined therapies between OH and NH, there were differences for both OH and NH, with the greatest impact on NH for the palmar grip and VAS variables. The treatment sequences were significant for pain on the NH and mental SF-12, suggesting that starting with IASTM followed by stretching had a superior outcome for these outcomes.

CONCLUSION

The combination of IASTM with stretching, used in the postoperative period of bilateral idiopathic CTS, proved to be supplementary, with significant results and large effect sizes for most of the outcomes assessed, both during the time of application of the therapies and in the 6-month follow-up for both hands, and may constitute a viable therapeutic alternative for this population.

A Correlation between Upper Extremity Compressive Neuropathy and Nerve Compression Headache

BACKGROUND

Compressive neuropathies of the head/neck that trigger headaches and entrapment neuropathies of the extremities have traditionally been perceived as separate clinical entities. Given significant overlap in clinical presentation, treatment, and anatomical abnormality, the authors aimed to elucidate the relationship between nerve compression headaches and carpal tunnel syndrome, and other upper extremity compression neuropathies.

METHODS

One hundred thirty-seven patients with nerve compression headaches who underwent surgical nerve deactivation were included. A retrospective chart review was conducted and the prevalence of carpal tunnel syndrome, thoracic outlet syndrome, and cubital tunnel syndrome was recorded. Patients with carpal tunnel syndrome, cubital tunnel syndrome, and thoracic outlet syndrome who had a history of surgery and/or positive imaging findings in addition to confirmed diagnosis were included. Patients with subjective report of carpal tunnel syndrome/thoracic outlet syndrome/cubital tunnel syndrome were excluded. Prevalence was compared to general population data.

RESULTS

The cumulative prevalence of upper extremity neuropathies in patients undergoing surgery for nerve compression headaches was 16.7 percent. The prevalence of carpal tunnel syndrome was 10.2 percent, which is 1.8- to 3.8-fold more common than in the general population. Thoracic outlet syndrome prevalence was 3.6 percent, with no available general population data for comparison. Cubital tunnel syndrome prevalence was comparable between groups.

CONCLUSIONS

The degree of overlap between nerve compression syndromes of the head/neck and upper extremity suggests that peripheral nerve surgeons should be aware of this correlation and screen affected patients comprehensively. Similar patient presentation, treatment, and anatomical basis of nerve compression make either amenable to treatment by nerve surgeons, and treatment of both entities should be an integral part of a formal peripheral nerve surgery curriculum.

Muscle Fascia Changes in Patients with Occipital Neuralgia, Headache, or Migraine

SUMMARY

In an ongoing effort to understand the pathogenesis of occipital neuralgia/headache/migraine, it is critical to describe the anatomical/tissue changes encountered during surgery. Greater occipital nerve anatomical studies mainly focus on the greater occipital nerve course through muscle/fascial planes and interaction with the occipital vessels. However, structural soft-tissue changes have not been described in detail. Anecdotally, trapezius fascia is thickened at the greater occipital nerve trigger site. This study further investigates this observation. Patients undergoing greater occipital nerve decompression surgery were enrolled prospectively in this observational study (n = 92). Tissue changes were recorded intraoperatively. The resulting data were examined. Trapezius fascia was more than 3 mm thick and appeared fibrotic in 86 patients (94 percent), whereas semispinalis muscle appeared normal in all subjects. The greater occipital nerve was macroscopically abnormal, defined as edematous, flattened, and discolored in 29 cases (32 percent). The occipital artery interacted significantly with the greater occipital nerve in 88 percent of cases. The authors conclude that the tissue structure is abnormal in patients undergoing greater occipital nerve decompression surgery. This is the first study that describes the prevalence of thickened and fibrotic appearing trapezius fascia at the occipital trigger site, a phenomenon encountered in the vast majority of patients (94 percent). This structural anomaly has a resemblance to thickened fascial tissues seen in other nerve compression syndromes, and could be related to microtrauma/overuse or actual trauma in the head and neck region.

Median nerve conduction studies in rabbits

BACKGROUND

When planning nerve conduction studies using animal models, the sciatic nerve is often used and the upper extremity nerves are not preferred due to the size of laboratory animals. This study aimed to present the method and mean values of median nerve conduction studies in laboratory rabbits. Fifty-five six-month-old male New Zealand white rabbits weighing 2 to 2.5 kg were included in nerve conduction studies performed under anesthesia. The compound muscle action potential amplitude and distal latency values were recorded for the median motor nerve with the electrodes placed on the flexor digitorum superficialis muscle and tendon.

RESULTS

A total of 110 median nerves were evaluated. The mean amplitude of the median nerve was 30.6 ± 6.8, mV the median nerve distal latency was 1.3 ± 0.2 ms, and the mean intensity of stimulation inducing a response was 2.5 ± 1 mA.

CONCLUSIONS

The mean values obtained by the median motor nerve conduction method in this study can act as a guide for future nerve interventions undertaken in the upper extremities.

Development of a hyperelastic material model of subsynovial connective tissue using finite element modeling

Carpal tunnel syndrome (CTS) is one of the most common disorders of the hand. Assessment of carpal tunnel tissue mechanical behavior, especially that of the subsynovial connective tissue (SSCT), is important to better understand the mechanisms of CTS. The aim of this study was to develop a hyperelastic material model of human SSCT using mechanical test data and finite element modeling (FEM). Experimental shear test data of SSCT from 7 normal subjects and 7 CTS patients collected in a prior study was used to define material response. Hyperelastic coefficients (μ and α) from the first-order Ogden material property definition were iteratively solved using specimen-specific FEM models simulating the mechanical test conditions. A typical Ogden hyperelastic response for the normal and CTS SSCT was characterized by doing the same with data from all samples averaged together. The mean Ogden coefficients (μ/α) for the normal cadaver and CTS patient SSCT were 1.25×10(-5)MPa/4.51 and 1.99×10(-6)MPa/10.6, respectively when evaluating coefficients for individual specimens. The Ogden coefficients for the typical (averaged data) model for normal cadaver and CTS patient SSCT were 1.63×10(-5)MPa/3.93 and 5.00×10(-7)MPa/9.55, respectively. Assessment of SSCT mechanical response with a hyperelastic material model demonstrated significant differences between patient and normal cadaver. The refined assessment of these differences with this model may be important for future model development and in understanding clinical presentation of CTS.

Transforming growth factor-β (TGF-β) expression is increased in the subsynovial connective tissue in a rabbit model of carpal tunnel syndrome

Carpal tunnel syndrome (CTS) is an idiopathic disease that results from increased fibrosis of the subsynovial connective tissue (SSCT). A recent study found overexpression of both transforming growth factor-β (TGF-β) and connective tissue growth factor (CTGF) in the SSCT of CTS patients. This study investigated TGF-β and CTGF expression in a rabbit model of CTS, in which SSCT fibrosis is induced by a surgical injury. Levels of TGF-β1 and CTGF at 6, 12, 24 weeks after injury were determined by immunohistochemistry A significant increase in TGF-β1 and a concomitant significant increase in CTGF were found at 6 weeks, in addition to higher cell density compared to normal (all p<0.05), Interestingly, CTGF expression was reduced at 12 and 24 weeks, suggesting that an initial insult results in a time limited response. We conclude that this rabbit model mimics the fibrosis found in human CTS, and may be useful to study pathogenetic mechanisms of CTS in vivo.