The Role of the Proximal Segment in Peripheral Nerve Regeneration

The peripheral nervous system is designed to connect the orchestrations of brain and spinal cord to the rest of the body. In addition, it connects the outside world and that same brain, gathering information from numerous sensory organs in our skin and from our other “senses”. Injury to a nerve subsequently results in impairment of function as well as impairment of that information gathering system. In order to restore the damage, a series of complex changes is triggered in the cell body and the axon, all aimed at restoring motor and sensory function. However, different parts of the peripheral nervous system have different responses to injury. It is possible to distinguish three different parts: The cell body, the proximal segment and the distal segment. Proximal to the lesion, in the cell body and the proximal segment, the aim is to reconnect the axon to its effector organ as soon as possible. Distal to the lesion everything is aimed at creating an environment that allows reconnection of axons to happen. In order to accomplish this, the nerve proceeds through a number of morphological and electrophysiological changes. Although maybe not directly obvious, those morphological transformations after injury are reflected in electrophysiological changes. Previous research demonstrated changes in peak-peak amplitude of compound nerve action signals in the proximal segment after nerve transection and reconstruction45−48. However, the mechanisms involved however, are still unclear. The aim of this thesis is to explore the changes in the proximal segment and to clarify possible modifications to the proximal segment influencing repair

Ultrasound imaging of the rabbit peroneal nerve

Ultrasound imaging of peripheral nerves is increasingly used in the clinic for a wide range of applications. Although yet unapplied for experimental neuroscience, it also has potential value in this research area. This study explores the feasibility, possibilities and limitations of this technique in rabbits, with special focus on peripheral nerve regeneration after trauma. The peroneal nerve of 25 New Zealand White rabbits was imaged at varying time intervals after a crush lesion. The ultrasonic appearance of the nerve was determined, and recordings were validated with in vivo anatomy. Nerve swelling at the lesion site was estimated from ultrasound images and compared with anatomical parameters. The peroneal nerve could reliably be identified in all animals, and its course and anatomical variations agreed perfectly with anatomy. Nerve diameters from ultrasound were related to in vivo diameters (p < 0.001, R2 = 77%), although the prediction interval was rather wide. Nerve thickenings could be visualized and preliminary results indicate that ultrasound can differentiate between neuroma formation and external nerve thickening. The value of the technique for experimental neuroscience is discussed. We conclude that ultrasound imaging of the rabbit peroneal nerve is feasible and that it is a promising tool for different research areas within the field of experimental neuroscience

An early diagnostic tool for diabetic peripheral neuropathy in rats

The skin's rewarming rate of diabetic patients is used as a diagnostic tool for early diagnosis of diabetic neuropathy. At present, the relationship between microvascular changes in the skin and diabetic neuropathy is unclear in streptozotocin (STZ) diabetic rats. The aim of this study was to investigate whether the skin rewarming rate in diabetic rats is related to microvascular changes and whether this is accompanied by changes observed in classical diagnostic methods for diabetic peripheral neuropathy. Computer-assisted infrared thermography was used to assess the rewarming rate after cold exposure on the plantar skin of STZ diabetic rats' hind paws. Peripheral neuropathy was determined by the density of intra-epidermal nerve fibers (IENFs), mechanical sensitivity, and electrophysiological recordings. Data were obtained in diabetic rats at four, six, and eight weeks after the induction of diabetes and in controls. Four weeks after the induction of diabetes, a delayed rewarming rate, decreased skin blood flow and decreased density of IENFs were observed. However, the mechanical hyposensitivity and decreased motor nerve conduction velocity (MNCV) developed 6 and 8 weeks after the induction of diabetes. Our study shows that the skin rewarming rate is related to microvascular changes in diabetic rats. Moreover, the skin rewarming rate is a non-invasive method that provides more information for an earlier diagnosis of peripheral neuropathy than the classical monofilament test and MNCV in STZ induced diabetic rats

Investigating the mechanical shear-plane between core and sheath elements of peripheral nerves

The mechanical architecture of rat sciatic nerve has been described as a central core surrounded by a sheath, although the way in which these structures contribute to the overall mechanical properties of the nerve is unknown. We have studied the retraction responses of the core and sheath following transection, together with their tensile properties and the interface between them. Nerves were harvested and maintained at their in situ tension and then either transected entirely, through the sheath only, or through an exposed section of the core. The retraction of each component was measured within 5 min and again after 45 min. Post mortem loss of retraction was tested 0 min or 60 min after excision. For fresh nerves, immediate retraction was 12.68% (whole nerve), 5.35% (sheath) and 4% (core), with a total retraction of 15%, 7.21% and 5.26% respectively. For stored nerves, immediate retraction was 5.33% (whole nerve) and 5.87% (sheath), with an extension of 0.78% for core, and a total retraction of 6.71% and 7.87% and an extension of 1.74%, respectively. Tensile extension and pullout force profiles were obtained for the sheath, the core and the interface between them. These showed a consistent hierarchy of break strengths that would, under increasing load, result in failure of the interface, then the core and finally the sheath. These data reflect the contributions of material tension and fluid swelling pressure to total retraction, and the involvement of an energy-dependent process that runs down rapidly post mortem. This study increases our understanding of the composite nature of peripheral nerve tissue architecture and quantifies the material properties of the distinct elements that contribute to overall mechanical function

Palmaris longus interposition in revision surgery for recurrent and persistent carpal tunnel syndrome: a case series

Contains fulltext : 220192.pdf (Publisher’s version ) (Open Access)Carpal tunnel syndrome (CTS) is the most frequently operated neurological disorder of the hand. Incidence of patients remaining symptomatic has been reported up to 30% after primary release. Revision surgery remains challenging although multiple surgical options have been described. In this case series a simple novel technique, the palmaris longus interposition, is described for the treatment of recurrent and persistent CTS. Patients who underwent PLI between October 2013 and 2018 and without underlying neurological or hand disorders severely affecting the operated hand were eligible for inclusion. All were preoperatively diagnosed with recurrent or persistent CTS based on clinical assessment. Eighteen patients with 20 operated hands consented to the study. Patient characteristics were retrospectively reviewed, including nerve conduction studies and ultrasound scans. Patients were postoperatively asked to classify their symptoms as resolved, improved, not improved or worsened. In addition, postoperative symptom severity and functional status were assessed using the Boston Carpal Tunnel Questionnaire. Ten hands showed recurrent symptoms while the other 10 showed persistent symptoms. The average follow-up was 15 months. No improvement was reported in 5 hands, whereas improvement or complete relief of symptoms was reported in 15 hands. The mean total score of the Boston Carpal Tunnel Questionnaire postoperatively was 2.29 and ranged between 1.26 and 4.32. These results suggest that using the palmaris longus tendon as interposition graft between the leaves of the flexor retinaculum may be a suitable technique for the management of patients with mild to moderate symptoms of recurrent and persistent CTS. Further research should investigate whether this technique has better outcome compared to other procedures

Adipose-derived stem cells inhibit the contractile myofibroblast in Dupuytren's disease.

Item does not contain fulltextBACKGROUND: In an attempt to provide minimally invasive treatment for Dupuytren's disease, percutaneous disruption of the affected tissue followed by lipografting is being tested. Contractile myofibroblasts drive this fibroproliferative disorder, whereas stem cells have recently been implicated in preventing fibrosis. Therefore, the authors tested the role of stem cells in modulating myofibroblast activity in Dupuytren's disease. METHODS: The authors compared the effect of co-culturing Dupuytren's myofibroblasts with either adipose-derived or bone-marrow-derived stem cells on isometric force contraction and associated levels of alpha-smooth muscle actin mRNA and protein expression. The authors also tested the effect of these stem cells on Dupuytren's myofibroblast proliferation and assessed whether this was mediated by cell-to-cell contact or by a paracrine mechanism. RESULTS: Addition of adipose-derived stem cells to Dupuytren's myofibroblasts reduced the contraction of the latter, with a corresponding reduction of alpha-smooth muscle actin protein expression, probably through a dilution effect. In contrast, bone marrow-derived stem cells increased myofibroblast contractility. In addition, adipose-derived stem cells inhibit myofibroblast proliferation and mediate these effects by soluble factors, influenced by cell-to-cell contact-dependent signaling. CONCLUSION: Adipose-derived stem cells inhibit the contractile myofibroblast in Dupuytren's disease, and these findings lend support to the potential benefit of lipografting in conjunction with aponeurotomy as a novel strategy for the treatment of Dupuytren's disease.01 november 201

Robert Mathys Finger prosthesis of the proximal interphalangeal joint: a retrospective case series of 19 joints in 17 patients

Item does not contain fulltextINTRODUCTION: The Robert Mathys (RM) Finger is a hinged type of arthroplasty for the metacarpophalangeal and proximal interphalangeal (PIP) joint that compensates ligament instability. The aim of this study is to evaluate the outcomes and complications of RM Finger arthroplasty of the PIP joint. MATERIALS AND METHODS: A retrospective case series of 19 RM Finger arthroplasties of the PIP joint in 17 patients was performed with a median follow-up of 36 months. The active range of motion (AROM) was measured pre-operatively, at the 6-week follow-up, at the termination of hand therapy, and at the final follow-up. Complications were recorded, as well as pain on a visual analog scale (VAS), stability, deformity, pinch strength, the Michigan Hand Outcomes Questionnaire (MHQ), and the Patient Global Index of Improvement Questionnaire. RESULTS: One implant fracture occurred. Another patient had an amputation due to stiffness. For the remaining joints, AROM was 61 degrees . One joint mobilization under local anesthesia, one arthrolysis and two extensor tendon reconstructions were also necessary. Pain at the follow-up was 1.2 on the VAS. Relative pinch strength was 69%. Joint stability was restored in all fingers, although one joint had an ulnar deviation of 15 degrees . Eight fingers developed a snapping phenomenon, of which five had a swan neck deformity. One finger had an extension lag with a Boutonniere deformity. MHQ scores were less compared to the unaffected hand. Fifteen patients rated their outcome as improved compared to their pre-operative condition. CONCLUSIONS: RM Finger arthroplasty of the PIP joint restores joint stability with AROM improvement, and with low pain, although it has a high rate of complications. LEVEL OF EVIDENCE: IV

[Marjolin ulcer; malignant degeneration in a chronic wound]

Item does not contain fulltextBACKGROUND: A chronic ulcerating wound may turn malignant. The term 'Marjolin ulcer' is used to describe any skin malignancy which develops in an area of chronic ulceration, irritation or inflammation. It is generally a squamous cell carcinoma. CASE DESCRIPTION: A 66-year-old woman was admitted urgently due to pain and signs of infection in wounds on her back which she had had for six to seven years. The patient had sustained wounds to her back as a result of a hot water scalding at the age of two. These wounds had healed and scarred. Pathological examination of three punch biopsies taken from the margins of the largest ulcer indicated a squamous cell carcinoma; a Marjolin ulcer was diagnosed. CONCLUSION: If a patient has chronic skin lesions associated with non-healing ulcers, especially after sustaining burn injuries as a child, pathological examination is indicated. This can allow a potential skin malignancy to be identified and treated at as early a stage as possible

An anatomical study on the effectiveness of Arthrex Mini TightRope((R)) ligament reconstruction in an unstable trapeziometacarpal joint

Item does not contain fulltextINTRODUCTION: Laxity in the trapeziometacarpal (TMC) joint is a debilitating condition usually affecting a young population. It can be treated operatively with ligament reconstruction. The purpose of this study was to determine the effectiveness of the Arthrex Mini TightRope((R)) in reinforcing the stabilizing ligaments in an unstable TMC joint without decreasing the range of motion of the thumb. This method was compared with the "gold standard" published by Eaton and Littler in 1973. MATERIALS AND METHODS: Six fresh frozen arms from five cadavers were included. TMC joint laxity was measured on stress view radiographs as the ratio of the radial subluxation (RS) of the first metacarpal in relation to the trapezium, by the first metacarpal articular width (AW) (as described by Wolf in 2009). Measurements of the pre- and post-operative range of motion (ROM) were performed and compared. RESULTS: Both the Arthrex Mini TightRope((R)) and the Eaton-Littler stabilization improved the stability of the TMC joint. The pre-operative laxity value (ratio RS/AW) of 0.27 was significantly (P = 0.02) improved by each of the surgical interventions (Eaton-Littler RS/AW = 0.05 and Tightrope RS/AW = 0.09). The pre- and post-operative range of motion was not significantly different by each of the surgical interventions. There were no significant differences between the two stabilizing methods regarding laxity or range of motion. CONCLUSION: The Arthrex Mini TightRope((R)) provided a good stabilization method for the TMC joint in this anatomical model without compromising the range of motion