Botulinum Toxin-induced Muscle Paralysis Inhibits Heterotopic Bone Formation

Pioneering pain management with botulinum toxin type A: From anti-inflammation to regenerative therapies

In the present paper, a comprehensive review was conducted to evaluate the performance of botulinum toxin type A (BTX-A) in managing various types of pain, including myofascial, muscular temporomandibular joint pain, orofacial pain, chronic migraines, and more. Firstly, the mechanism of action and anti-inflammatory effects of BTX-A was introduced. Following this, recent advancements in BTX-A applications were discussed, with an emphasis on emerging combination therapies, regenerative medicine, and personalized treatment strategies. Unlike previous reviews, this study explored a broader spectrum of pain conditions and highlighted BTX-A's versatility and potential as a long-term, minimally invasive pain management option. Additionally, the importance of tailoring BTX-A treatment was emphasized through the integration of biomarkers, genetic factors, and optimized dosing regimens to enhance efficacy and minimize side effects. Novel combinations with regenerative therapies, such as stem cells and tissue engineering, were identified as promising avenues for joint and nerve repair, providing both symptomatic relief and tissue regeneration. Furthermore, digital health tools and artificial intelligence were suggested as innovative approaches to monitor treatment responses and optimize dosing protocols in real-time, advancing personalized pain management. Overall, this review underscores BTX-A's potential in comprehensive and patient-centered pain management and offers recommendations to guide future studies in optimizing BTX-A therapy.

Muscle-guided mapping of post-traumatic heterotopic ossification of the elbow: a novel computed tomography-based study

BACKGROUND

Heterotopic ossification (HO) involves abnormal bone formation in soft tissues near joints, commonly occurring after elbow trauma or surgery, leading to pain and functional limitations. Previous studies have primarily characterized HO distribution based on bony landmarks, lacking a detailed investigation into the characteristics of its distribution in periarticular soft tissue in post-traumatic elbows. This study aimed to (1) develop a muscle-guided classification system using computed tomography (CT) to map HO relative to elbow muscle-tendon units and (2) investigate correlations between HO location and severity.

METHODS

In a retrospective study, 56 patients with HO and elbow stiffness following trauma were analyzed. CT imaging was used to classify HO into 7 categories: Posterior - olecranon tip - triceps brachii; Posteromedial - medial gutter - flexor carpi ulnaris (PM-MG-FCU); Posterolateral - lateral gutter - anconeus; Medial - medial epicondylar - flexor muscles; Lateral - lateral epicondylar - extensor muscles; Anterior - humeroulnar joint - brachialis; and Anterior - humeroradial - supinator. HO severity was graded (1-3) based on CT morphology, and correlations between HO location and severity were assessed.

RESULTS

PM-MG-FCU was the most common HO location (67.9%). Significant correlations were found between HO severity and location, with higher rates of HO in grades 2 and 3, characterized by extensive mature bone formation and bone bridge development occurring in the posterolateral - lateral gutter - anconeus, posterior - olecranon tip - triceps brachii, and PM-MG-FCU.

CONCLUSION

The muscle-guided classification system effectively delineated HO distribution near elbow muscle-tendon units. HO locations surrounding the anconeus, triceps brachii, and flexor carpi ulnaris correlate with higher radiographic severity, providing valuable insights for treatment strategies.

Engineered myeloid precursors differentiate into osteoclasts and resorb heterotopic ossification in mice

Introduction

Heterotopic ossification (HO) occurs following orthopedic trauma, spinal cord injuries, brain trauma and limb amputations. Once symptomatic, HO causes pain, limited mobility and decreased quality of life. Current treatments are limited and have significant complications with high recurrence rates, underscoring the need for improved therapeutic interventions. Osteoclasts (OCs) are physiological bone resorptive cells that secrete enzymes and protons to degrade bone.

Methods

In this study, we describe the use of genetically engineered OCs as a novel cell therapy approach to treat HO. Inducible, engineered myeloid precursors (iRANK cells) treated with a chemical inducer of dimerization (CID) differentiated into TRAP+ multinucleated OCs and resorbed mineralized tissues in vitro.

Results

In vivo, BMP-2-induced murine HO lesions were significantly regressed following treatment using iRANK cells with concomitant systemic administration of CID. Moreover, many OCs were TRAP+, MMP9+, and GFP+, indicating that they differentiated from delivered iRANK cells.

Discussion

In summary, these data con rm the ability of engineered myeloid precursors to differentiate into OCs and resorb HO in vivo paving the way for OC delivery as a promising approach for HO treatment.

Neglecting Bone Health: A Critical Gap in Management of Muscle Spasticity with Botulinum Toxin in Spinal Cord Injury

Neuromuscular inhibitors have been quickly advanced from being used only for aesthetic purposes to being used as a treatment for musculoskeletal pain and muscle spasticity. This phenomenon stems from the diminished force exerted by muscles, which are essential for bone remodeling. In this context, it is hypothesized that botulinum toxin (BTX) might exert a direct influence on bone resorption. Although such treatments have the potential to provide patients with significant relief, bone loss occurring due to elective muscle paralysis has yet to be examined in clinical trials. The disuse model resulting from spinal cord injury, characterized by the absence of ground reaction and muscle forces, provides an ideal context for exploring the skeletal ramifications of intramuscular BTX injection. This approach enables an investigation into the intricate interplay between muscle and bone, encompassing the impact of spasticity on bone preservation, the potential positive and negative outcomes of BTX on bone metabolism, and the involvement of the autonomic nervous system in bone remodeling regulation. This paper presents a narrative review of research findings on the disturbance of the typical balance between muscles and bones caused by acute muscle paralysis from BTX, resulting in osteopenia and bone resorption.

The Role of Botulinum Neurotoxin A in the Conservative Treatment of Fractures: An Experimental Study on Rats

This paper explores the role of botulinum neurotoxin in aiding fracture recovery through temporary muscle paralysis. Specifically, it investigates the effects of botulinum neurotoxin-induced paralysis of the sternocleidomastoid muscle on clavicle fractures in rats. The research aims to assess safety, effectiveness, and the impact on fracture healing. Healthy male Albino Wistar rats were divided into four groups: clavicle fracture, botulinum neurotoxin injection, both, and control. Surgeries were conducted under anaesthesia, and postoperatively, animals were monitored for 28 days. Euthanasia and radiological assessment followed, examining fracture healing and muscle changes, while tissues were histopathologically evaluated. The modified Lane-Sandhu scoring system was used for the radiographic evaluation of clavicle fractures, and the results varied from complete healing to nonunion. Histopathological examination at 28 days postfracture showed fibrous tissue, mesenchymal cells, and primary callus formation in all groups. Despite varied callus compositions, botulinum neurotoxin administration did not affect clavicle healing, as evidenced by similar scores to the control group. Several studies have explored botulinum neurotoxin applications in fracture recovery. Research suggests its potential to enhance functional recovery in certain types of fractures. Theoretical benefits include managing muscle spasticity, aiding reduction techniques, and preventing nonunion. However, botulinum neurotoxin's transient effect and nonuniversal applications should be considered. The present study found that botulinum toxin had no clear superiority in healing compared to controls, while histological evaluation showed potential adverse effects on muscle tissue. Further research is essential to understand its risk-benefit balance and long-term effects.

Regional distribution prevalence of heterotopic ossification in the elbow joint: a 3D study of patients after surgery for traumatic elbow injury

BACKGROUND

Heterotopic ossification (HO) is a common complication after elbow fracture surgery and can lead to severe upper extremity disability. The radiographic localization of postoperative HO has been reported previously. However, there is no literature examining the distribution of postoperative HO at the three-dimensional (3D) level. This study aimed to investigate 1) the distribution characteristics of postoperative HO and 2) the possible risk factors affecting the severity of postoperative HO at a 3D level.

METHODS

A retrospective review was conducted of patients who presented to our institution with HO secondary to elbow fracture between 13 January 2020 and 16 February 2023. Computed tomography scans of 56 elbows before elbow release surgery were reconstructed in 3D. HO was identified using density thresholds combined with manual identification and segmentation. The elbow joint and HO were divided into six regions according to three planes: the transepicondylar plane, the lateral ridge of the trochlear plane, and the radiocapitellar joint and coronoid facet plane. The differences in the volume of regional HO associated with different initial injuries were analyzed.

RESULTS

Postoperative HO was predominantly present in the medial aspect of the capsule in 52 patients (93%), in the lateral aspect of the capsule in 45 patients (80%), in the medial supracondylar in 32 patients (57%), and in the lateral supracondylar, radial head, and ulnar region in the same number of 28 patients (50%). The median and interquartile range volume of total postoperative HO was 1683 (777-4894) mm3. The median and interquartile range volume of regional postoperative HO were: 584 (121-1454) mm3 at medial aspect of capsule, 207 (5-568) mm3 at lateral aspect of capsule, 25 (0-449) mm3 at medial supracondylar, 1 (0-288) at lateral supracondylar, 2 (0-478) at proximal radius and 7 (0-203) mm3 at the proximal ulna. In the subgroups with Injury Severity Score > or = 16, Gustilo-Anderson II, normal uric acid levels, elevated alkaline phosphatase, and body mass index > or = 24, the median HO volume exceeds that of the respective control groups.

CONCLUSION

The medial aspect of the capsule was the area with the highest frequency and median volume of postoperative HO among all initial elbow injury types. Patients with higher Gustilo-Anderson grade, Injury Severity Score, alkaline phosphatase or Body Mass Index had higher median volume of postoperative HO.

A microCT-based platform to quantify drug targeting

BACKGROUND

Heterotopic ossification (HO) is a frequent and debilitating complication of traumatic musculoskeletal injuries and orthopedic procedures. Prophylactic dosing of botulinum toxin type A (BTxA) holds potential as a novel treatment option if accurately distributed throughout soft-tissue volumes where protection is clinically desired. We developed a high-resolution, microcomputed tomography (microCT)-based imaging strategy to assess drug distribution and validated this platform by quantifying distribution achieved via a prototype delivery system versus a single-bolus injection.

METHODS

We injected an iodine-containing contrast agent (iodixanol 320 mg I/mL) into dissected rabbit musculature followed by microCT imaging and analysis. To contrast the performance of distributed versus bolus injections, a three-dimensional (3D) 64-cm3-printed soft-tissue holder was developed. A centered 2-cm3 volume of interest (VOI) was targeted with a single-bolus injection or an equal volume distributed injection delivered via a 3D-printed prototype. VOI drug coverage was quantified as a percentage of the VOI volume that was < 1.0 mm from the injected fluid.

RESULTS

The microCT-based approach enabled high-resolution quantification of injection distribution within soft tissue. The distributed dosing prototype provided significantly greater tissue coverage of the targeted VOI (72 ± 3%, mean ± standard deviation) when compared to an equal volume bolus dose (43 ± 5%, p = 0.031) while also enhancing the precision of injection targeting.

CONCLUSIONS

A microCT-based imaging technique precisely quantifies drug distribution within a soft-tissue VOI, providing a path to overcome a barrier for clinical translation of prophylactic inhibition of HO by BTxA.

RELEVANCE STATEMENT

This platform will facilitate rapid optimization of injection parameters for clinical devices used to effectively and safely inhibit the formation of heterotopic ossification.

KEY POINTS

• MicroCT provides high-resolution quantification of soft-tissue drug distribution. • Distributed dosing is required to maximize soft-tissue drug coverage. • Imaging platform will enable rapid screening of 3D-printed drug distribution prototypes.

The Action of Botulinum Toxin A on the Sternocleidomastoid Muscle: An Experimental Study on Rats

In this study, we aim to investigate the effective dose of botulinum neurotoxin A that results in paralysis of the sternocleidomastoid muscle for a minimum duration of 28 days in Wistar rats. This research is the first in a series of studies to investigate the value of botulinum toxin A in the healing of clavicle fractures through the temporary paralysis of the sternocleidomastoid. A surgical incision was made under general anaesthesia, and botulinum neurotoxin A in respective doses of 4 and 6 international units (IU) or normal saline in equivalent volumes were injected directly into the exposed muscle. Electromyography was conducted on days 0, 7, and 28 following substance administration to determine the extent of muscle paralysis. Electromyography on day 0 showed no paralysis in either group. Animals injected with neurotoxin all exhibited paralysis on days 7 and 28 that was weaker in the group injected with the smaller dose of 4 IU. One death occurred in the group injected with the higher dose (6 IU), whereas in the control group, no paralysis was seen. Botulinum neurotoxin A in a dose of 6 IU resulted in complete paralysis of the sternocleidomastoid in rats for a minimum of 28 days. A dose of 4 IU resulted in less potent paralysis but was safer in our research. Botulinum neurotoxin is a substance utilised in cosmetics and therapeutics for many years, yet research shows that its use can be expanded to target a wider range of pathologies. In this series of studies, we aim to explore the neurotoxin's applications on the treatment of clavicle fractures. To investigate this, we need to first establish the duration of its action on the sternocleidomastoid muscle.

Prophylaxis for Heterotopic Ossification Following Distal Biceps Tendon Repair

Heterotopic ossification (HO) is a possible complication of distal biceps tendon repair (DBTR). Several agents can prevent HO formation, although relatively few studies have investigated prophylaxis specifically after DBTR. The purposes of this study were to survey members of the American Shoulder and Elbow Surgeons (ASES) to determine (1) what percentage use HO prophylaxis after DBTR; (2) type, dosage, and duration of prophylaxis used; and (3) use of single-incision or double-incision surgical technique. An anonymous electronic survey was distributed to ASES members to determine the use of HO prophylaxis and DBTR technique. The survey included questions regarding the number of DBTRs performed annually; preferred surgical technique and implants; and type, dosage, and duration of HO prophylaxis used before, during, and after surgery. Descriptive statistics were used to analyze the results. Of 173 respondents, 98 (56.6%) performed 1 to 10 DBTRs per year, 65 (37.6%) performed 11 to 25 DBTRs per year, and 10 (5.8%) performed 26 to 50 DBTRs per year. A total of 131 (75.7%) preferred the single-incision technique, whereas 42 (24.3%) preferred the double-incision technique. A total of 94 (54.3%) performed DBTR using a metal button and interference screw, 35 (20.2%) through drill holes, 25 (14.5%) with suture anchors, and 19 (11.0%) with a metal button alone. A total of 132 (76.3%) respondents did not use HO prophylaxis, and 41 (23.7%) used nonsteroidal anti-inflammatory drugs following surgery. A total of 35 (85.4%) used indomethacin, 18 (51.4%) of whom preferred 75 mg/d for 3 to 4 weeks. Heterotopic ossification is a commonly reported complication following DBTR, especially with the double-incision technique. Prophylaxis with anti-inflammatory medications and suppressive modalities (radiation therapy) appear to reduce the incidence of HO. Despite these data, most surgeons (76.3%) do not use HO prophylaxis. Low annual volume of cases, lack of large-volume studies with outcome data, and the dominant use of the single-incision repair technique may explain this. [Orthopedics. 2021;44(4):e588-e592.].

The effect of traumatic brain injury on bone healing from a novel exosome centered perspective in a mice model

BACKGROUND

In patients with traumatic brain injury (TBI) combined with long bone fracture, the fracture healing is always faster than that of patients with single fracture, which is characterized by more callus growth at the fracture site and even ectopic ossification. Exosomes are nanoscale membrane vesicles secreted by cells, which contain cell-specific proteins, miRNAs, and mRNAs.

METHODS

In this study, we used exosomes as the entry point to explore the mechanism of brain trauma promoting fracture healing. We established a model of tibia fracture with TBI in mice to observe the callus growth and expression of osteogenic factors at the fracture site. Blood samples of model mice were further collected, exosomes in plasma were extracted by ultra-centrifugation method, and then identified and acted on osteoblasts cultured in vitro. The effects of exosomes on osteoblast differentiation at the cell, protein and gene levels were investigated by Western Blot and q-PCR, respectively. Furthermore, miRNA sequencing of exosomes was performed to identify a pattern of miRNAs that were present at increased or decreased levels.

RESULTS

The results suggested that plasma exosomes after TBI had the ability to promote the proliferation and differentiation of osteoblasts, which might be due to the increased expression of osteoblast-related miRNA in exosomes. They were transmitted to the osteoblasts at the fracture site, so as to achieve the role of promoting osteogenic differentiation.

CONCLUSION

The TBI-derived exosomes may have potential applications for promoting fracture healing in future.

THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE

Plasma exosomes early after TBI have the ability to promote osteoblast proliferation and differentiation. The mechanism may be achieved by miRNA in exosomes. Plasma exosomes may be used as breakthrough clinical treatment for delayed or non-union fractures.

Relationship between heterotopic ossification and traumatic brain injury: Why severe traumatic brain injury increases the risk of heterotopic ossification

Heterotopic ossification (HO) is a pathological phenomenon in which ectopic lamellar bone forms in soft tissues. HO involves many predisposing factors, including congenital and postnatal factors. Postnatal HO is usually induced by fracture, burn, neurological damage (brain injury and spinal cord injury) and joint replacement. Recent studies have found that patients who suffered from bone fracture combined with severe traumatic brain injury (S-TBI) are at a significantly increased risk for HO occurrence. Thus, considerable research focused on the influence of S-TBI on fracture healing and bone formation, as well as on the changes in various osteogenic factors with S-TBI occurrence. Brain damage promotes bone formation, but the exact mechanisms underlying bone formation and HO after S-TBI remain to be clarified. Hence, this article summarises the findings of previous studies on the relationship between S-TBI and HO and discusses the probable causes and mechanisms of HO caused by S-TBI. The translational potential of this article: A better understanding of the probable causes of traumatic brain injury-induced HO can provide new perspectives and ideas in preventing HO and may support to design more targeted therapies to reduce HO or enhance the bone formation.

Osteogenic programs during zebrafish fin regeneration

Recent advances in genomic, screening and imaging technologies have provided new opportunities to examine the molecular and cellular landscape underlying human physiology and disease. In the context of skeletal research, technologies for systems genetics, high-throughput screening and high-content imaging can aid an unbiased approach when searching for new biological, pathological or therapeutic pathways. However, these approaches necessitate the use of specialized model systems that rapidly produce a phenotype, are easy to manipulate, and amenable to optical study, all while representing mammalian bone physiologies at the molecular and cellular levels. The emerging use of zebrafish (Danio rerio) for modeling human disease highlights its potential to accelerate therapeutic and pathway discovery in the mammalian skeleton. In this review, we consider the potential value of zebrafish fin ray regeneration (a rapid, genetically tractable and optically transparent model of intramembranous ossification) as a translational model for such studies.