Chemical denervation with botulinum neurotoxin a improves the surgical manipulation of the muscle-tendon unit: an experimental study in an animal model

Botulinum Toxin Intervention in Cerebral Palsy-Induced Spasticity Management: Projected and Contradictory Effects on Skeletal Muscles

Spasticity, following the neurological disorder of cerebral palsy (CP), describes a pathological condition, the central feature of which is involuntary and prolonged muscle contraction. The persistent resistance of spastic muscles to stretching is often followed by structural and mechanical changes in musculature. This leads to functional limitations at the respective joint. Focal injection of botulinum toxin type-A (BTX-A) is effectively used to manage spasticity and improve the quality of life of the patients. By blocking acetylcholine release at the neuromuscular junction and causing temporary muscle paralysis, BTX-A aims to reduce spasticity and hereby improve joint function. However, recent studies have indicated some contradictory effects such as increased muscle stiffness or a narrower range of active force production. The potential of these toxin- and atrophy-related alterations in worsening the condition of spastic muscles that are already subjected to changes should be further investigated and quantified. By focusing on the effects of BTX-A on muscle biomechanics and overall function in children with CP, this review deals with which of these goals have been achieved and to what extent, and what can await us in the future.

Canadian Physicians' Use of Perioperative Botulinum Toxin Injections to Spastic Limbs: A Cross-sectional National Survey

Objective

To investigate the practice patterns of Canadian physicians who use perioperative botulinum toxin (BoNT) injections to improve surgical outcomes on spastic limbs.

Design

A cross-sectional national survey composed of an invitation email and an 18-item questionnaire was disseminated by a national physical medicine and rehabilitation (PMR) society to 138 physician members involved in spasticity management.

Setting

Not applicable.

Participants

Twenty-five percent of the participants (N=34) fully completed the survey.

Interventions

Not applicable.

Main Outcome Measures

Participants completed an online questionnaire that examined the practice patterns and surgical outcomes associated with perioperative BoNT injections.

Results

The majority (n=21; 84%) of Canadian physicians who inject BoNT perioperatively to improve outcomes of surgeries performed on spastic limbs are specialists in PMR practicing in academic settings. Most respondents (74%) used BoNT injections for perioperative treatment for patients with limb spasticity undergoing surgery. Of those surveyed, 65% of physicians used BoNT preoperatively, 21% used BoNT intraoperatively, and 24% used BoNT postoperatively.Of the physicians who performed BoNT injections preoperatively, 6% performed BoNT injections 7 to 12 weeks preoperatively, 32% performed BoNT injections 4 to 6 weeks preoperatively, 47% performed BoNT injections 2 to 3 weeks preoperatively, and 15% performed BoNT injections 0 to 1 week preoperatively. The majority of physicians (85%) responded that injecting BoNT perioperatively may improve a patient's surgical outcome and all of the participants (100%) stated that BoNT did not contribute to any perioperative complications or adverse effects. Qualitative responses emphasized that successful outcomes from the perioperative BoNT were linked to enhanced collaboration with surgeons and that more research is needed to determine the optimal timing of perioperative BoNT.

Conclusion

Canadian physicians, mostly PMR specialists, administer perioperative BoNT to improve outcomes of surgeries performed on spastic limbs. The optimal timing for perioperative BoNT was suggested to be 2 to 3 weeks before the surgery by 47% of survey respondents. All participating physicians responded that perioperative BoNT did not contribute to any known perioperative complications or adverse events. This study highlights the importance of conducting more robust research to better understand optimal timing for perioperative BoNT injection, enhancing collaboration between physicians and surgeons, and increasing awareness of perioperative BoNT when planning for surgeries on spastic limbs.

Perioperative Botulinum Toxin Injections to Enhance Surgical Outcomes in Patients With Spasticity: Preoperative, Intraoperative, and Postoperative Case Reports

Spasticity causes an array of disabilities, which in turn may lead to the need for surgical intervention. Spasticity itself may also negatively affect surgical outcomes. This report reviews the potential benefit of perioperative (before, during, or after surgery) botulinum toxin (BoNT) injections for 3 patients with spasticity due to spinal cord injury, stroke, or multiple sclerosis. We discuss perioperative BoNT in 3 time periods: preoperatively, intraoperatively, and postoperatively. The cases demonstrate the use of perioperative BoNT in decreasing pain, improving wound healing, and improving surgical outcomes. We conclude by discussing the potential use of perioperative BoNT for surgical interventions in patients with spasticity and the need for further high-quality research in this field.

Peri-operative Botulinum Neurotoxin injection to improve outcomes of surgeries on spastic limbs: A systematic review

Our objective was to systematically review literature regarding the rationale and current evidence for peri-operative Botulinum Neurotoxin (BoNT) injection to improve outcomes of surgeries on spastic limbs. We conducted a systematic search of databases MEDLINE, EMBASE, and Cochrane Central Register of Controlled until March 2020, using the PRISMA guidelines. After assessing all titles and abstracts against inclusion criteria, full texts were reviewed for studies of potential interest. The inclusion criteria were studies on humans with any study design, published in all languages. Participants had to have underlying limb spasticity and be scheduled to undergo surgery on one or more spastic limb(s). BoNT had to be administered peri-operatively to improve surgical outcomes and not solely for the purpose of alleviating spasticity. The risk of bias was evaluated using the Physiotherapy Evidence Database (PEDro) scoring system for randomized controlled trials (RCTs) and the Downs and Black tool for RCTs and non-randomized trials. Further, the level of evidence was evaluated using a five-level scale (simplified form of Sackett). Five studies met our inclusion criteria comprising a total of 90 participants, of both pediatric and adult age groups, with underlying limb spasticity, who received BoNT perioperatively to improve outcomes of the surgeries performed on spastic limbs. Interventions were intramuscular BoNT injection prior to, at the time of, or after surgery on a spastic limb for the purpose of improving surgical outcomes, and not solely for alleviating muscle spasticity. Outcome measures were surgical success/failure, post-operative pain and analgesic use, sleep quality, adverse events, spasticity control e.g. Modified Ashworth Scale. Our literature search yielded 5 articles that met the inclusion criteria. Current evidence supports peri-operative injection of BoNT to improve outcomes of surgeries performed on spastic limbs. There is level 1 evidence that BoNT administered pre-operatively is effective for reducing pain, spasticity, and analgesic use in pediatric patients with cerebral palsy (CP). This is supported by level 4 evidence from a retrospective case series. Level 5 evidence from case reports highlights the potential for the use of BONT in the peri-operative period. There is level 1 evidence that BoNT administered intra-operatively is not effective for reducing pain and analgesic use in pediatric patients with CP. This lack of benefit may reflect sub-optimal timing of injections, different methods of injection, different timing of the primary outcome measure, and/or differences in adjunctive therapies, but further research is required.

Tendinosis-like changes in denervated rat Achilles tendon

Background

Tendon disorders are common and lead to significant disability and pain. Our knowledge of the ‘tennis elbow’, the ‘jumpers knee’, and Achilles tendinosis has increased over the years, but changes in denervated tendons is yet to be described in detail. The aim of the present study was to investigate the morphological and biochemical changes in tendon tissue following two weeks of denervation using a unilateral sciatic nerve transection model in rat Achilles tendons.

Methods

Tendons were compared with respect to cell number, nuclear roundness, and fiber structure. The non-denervated contralateral tendon served as a control. Also, the expression of neuromodulators such as substance P and its preferred receptor neurokinin-1 receptor, NK-1R, was evaluated using real-time qRT-PCR.

Results

Our results showed that denervated tendons expressed morphological changes such as hypercellularity; disfigured cells; disorganization of the collagen network; increased production of type III collagen; and increased expression of NK-1R.

Conclusion

Taken together these data provide new insights into the histopathology of denervated tendons showing that denervation causes somewhat similar changes in the Achilles tendon as does tendinosis in rats.

Botulinum neurotoxin-A in idiopathic chondrolysis: a report of two cases

Two cases of idiopathic chondrolysis were treated by botulinum neurotoxin-A injections, with a favorable outcome. The treatment consisted of botulinum neurotoxin-A injections, followed by an intensive rehabilitation program. No surgery was needed. Both patients were symptom-free and showed an extremely satisfactory range of motion. Radiographs indicated reconstitution of the joint space in both cases. We believe that botulinum neurotoxin-A injections combined with an intensive rehabilitation program may be considered a new potential management modality and is worth attempting and studying when one considers the results of previously published reports.

Age-related changes affect rat rotator cuff muscle function

BACKGROUND

The influence of age on rotator cuff function and muscle structure remains poorly understood. We hypothesize that normal aging influences rotator cuff function, muscle structure, and regulatory protein expression in an established rat model of aging.

METHODS

Seventeen rats were obtained from the National Institute on Aging. The supraspinatus muscles in 11 middle-aged (12 months old) and 6 old (28 months old) rats were studied for age-related changes in rotator cuff neuromuscular function by in vivo muscle force testing and electromyography (EMG). Changes in muscle structure and molecular changes were assessed with quantitative immunohistochemistry for myogenic determination factor 1 (MyoD) and myogenic factor 5 (Myf5) expression.

RESULTS

Old animals revealed significantly decreased peak tetanic muscle force at 0.5 N and 0.7 N preload tension (P < .05). The age of the animal accounted for 20.9% of variance and significantly influenced muscle force (P = .026). Preload tension significantly influenced muscle force production (P < .001) and accounted for 12.7% of total variance. There was regional heterogeneity in maximal compound motor action potential (CMAP) amplitude in the supraspinatus muscle; the proximal portion had a significantly higher CMAP than the middle and distal portions (P < .05). The expression of muscle regulatory factors MyoD and Myf5 was significantly decreased in old animals compared with middle-aged animals (P < .05).

CONCLUSIONS

The normal aging process in this rat model significantly influenced contractile strength of the supraspinatus muscle and led to decreased expression of muscle regulatory factors. High preload tensions led to a significant decrease in force production in both middle-aged and old animals.

The science of rotator cuff tears: translating animal models to clinical recommendations using simulation analysis

PURPOSE

The purpose of this article is to review basic science studies using various animal models for rotator cuff research and to describe structural, biomechanical, and functional changes to muscle following rotator cuff tears. The use of computational simulations to translate the findings from animal models to human scale is further detailed.

METHODS

A comprehensive review was performed of the basic science literature describing the use of animal models and simulation analysis to examine muscle function following rotator cuff injury and repair in the ageing population.

RESULTS

The findings from various studies of rotator cuff pathology emphasize the importance of preventing permanent muscular changes with detrimental results. In vivo muscle function, electromyography, and passive muscle-tendon unit properties were studied before and after supraspinatus tenotomy in a rodent rotator cuff injury model (acute vs chronic). Then, a series of simulation experiments were conducted using a validated computational human musculoskeletal shoulder model to assess both passive and active tension of rotator cuff repairs based on surgical positioning.

CONCLUSION

Outcomes of rotator cuff repair may be improved by earlier surgical intervention, with lower surgical repair tensions and fewer electromyographic neuromuscular changes. An integrated approach of animal experiments, computer simulation analyses, and clinical studies may allow us to gain a fundamental understanding of the underlying pathology and interpret the results for clinical translation.

Botulinum Neurotoxin A injections influence stretching of the gastrocnemius muscle-tendon unit in an animal model

Botulinum Neurotoxin A (BoNT-A) injections have been used for the treatment of muscle contractures and spasticity. This study assessed the influence of (BoNT-A) injections on passive biomechanical properties of the muscle-tendon unit. Mousegastrocnemius muscle (GC) was injected with BoNT-A (n = 18) or normal saline (n = 18) and passive, non-destructive, in vivo load relaxation experimentation was performed to examine how the muscle-tendon unit behaves after chemical denervation with BoNT-A. Injection of BoNT-A impaired passive muscle recovery (15% vs. 35% recovery to pre-stretching baseline, p < 0.05) and decreased GC stiffness (0.531 ± 0.061 N/mm vs. 0.780 ± 0.037 N/mm, p < 0.05) compared to saline controls. The successful use of BoNT-A injections as an adjunct to physical therapy may be in part attributed to the disruption of the stretch reflex; thereby modulating in vivo passive muscle properties. However, it is also possible that BoNT-A injection may alter the structure of skeletal muscle; thus modulating the in vivo passive biomechanical properties of the muscle-tendon unit.

The effect of botulinum neurotoxin-A on blood flow in rats: a potential mechanism for treatment of Raynaud phenomenon

PURPOSE

Botulinum neurotoxin-A (BoNTA) is used to treat several disorders, including Raynaud phenomenon. Recent investigations cite toxin-induced increases in blood flow, but no mechanism for BoNTA's actions is proposed. This study hypothesized that local application of BoNTA causes arteriolar vasodilation through sympathetic blockade and results in increased blood flow.

METHODS

Microvascular effects of BoNTA were assessed using a rat cremaster preparation. Cremaster microvascular diameters were measured in the muscle before and after treatment with the muscle paralytic agent gallamine triethiodide. Preparations were then treated with one of the following: BoNTA (4, 6, or 10 units), BoNTA dilution vehicle, or denatured BoNTA. Arteriolar diameters were measured repeatedly over the observation period. Additional preparations were treated with either tetrodotoxin or prazosin and rauwolscine before BoNTA to confirm that the observed vasodilatory responses were the result of sympathetic neural inhibition.

RESULTS

The BoNTA application resulted in a significant dose-dependent vasodilation (13% to 15%) of observed cremaster arterioles. Control treatments did not cause vasodilation. Both tetrodotoxin and prazosin/rauwolscine treatments elicited similar vasodilatory effects, with no additional vasodilation elicited by BoNTA. Addition of sodium nitroprusside following BoNTA elicited further vasodilation. In addition, systemic arterial pressure was unaffected by the local administration of BoNTA.

CONCLUSIONS

Local application of BoNTA results in arteriolar dilation that yields an approximate 69% increase in blood flow, without changing systemic arterial pressure. A BoNTA-mediated vasodilation through sympathetic blockade is a likely mechanism to explain the increase in blood flow reported after treatment with the toxin.

CLINICAL RELEVANCE

The ability of BoNTA to inhibit sympathetic nervous input reduces vasoconstriction, which is the most likely mechanism for improvement seen in Raynaud phenomenon patients following BoNTA injection.

Evaluation of in vivo rotator cuff muscle function after acute and chronic detachment of the supraspinatus tendon: an experimental study in an animal model

BACKGROUND

Surgical repair of large chronic rotator cuff tears can be technically demanding because it requires manipulation of a muscle-tendon unit that is scarred, retracted, and stiffer than normal, all of which contribute to increased tension at the repair site. The purpose of the present study was to characterize the in vivo rotator cuff muscle-tendon unit function after acute and chronic injury at surgically relevant preload tensions.

METHODS

Sixty-two Sprague-Dawley rats were divided into a healthy, uninjured (control) group (n = 22), an acute injury group (n = 20), and a chronic injury group (n = 20) and underwent in vivo muscle force testing and electromyographic testing of the supraspinatus muscle-tendon unit at various preload tensions.

RESULTS

Preload tension affected the maximum supraspinatus muscle contractile force in all groups (p < 0.05). At the peak tension required to repair an acute tear, there was a 28% to 30% reduction in maximum tetanic contraction amplitude in all groups (p < 0.05). At the peak tension required to repair a chronic tear, there was a 40% to 53% reduction in maximal tetanic contraction amplitude in all groups (p < 0.05). The uninjured (control) group showed increased muscle endurance (p < 0.05) in comparison with the acute injury and chronic injury groups at all preload tensions. The chronic injury group showed reduced compound motor action potential amplitude (p < 0.05).

CONCLUSIONS

Both the acute and chronic injury groups demonstrated functional impairment related to increasing preload tensions. Higher repair tensions, associated with the chronic injury setting, resulted in greater functional impairment. The present study also demonstrates an association between increased time from rotator cuff tendon injury and impaired in vivo rotator cuff muscle electromyographic findings.