Role of Kinesiotherapy in the Prevention of Heterotopic Ossification: A Systematic Review

Physical and psychosocial outcomes among burn-injured people with heterotopic ossification: A burn model system study

INTRODUCTION

Heterotopic ossification (HO), or ectopic bone formation in soft tissue, is a not so rare and poorly understood debilitating sequela of burn injury. Individuals developing HO following burn injuries to their hands often experience reductions in mobility, significant contractures, and joint pain. This study identifies demographic characteristics of individuals who develop HO and compares their physical and psychosocial outcomes to the general burn population.

METHODS

Participant demographics, injury characteristics, and PROMIS-29 scores across three time points (discharge, six- and 12- months after injury) were extracted from the Burn Model System National Longitudinal Database representing participants from 2015-2022. Mixed-effects linear regression models were used to compare PROMIS scores across all three longitudinal measurements. Models were adjusted for age, sex, race/ethnicity, HO status, and burn size.

RESULTS

Of the 861 participants with data concerning HO, 33 were diagnosed with HO (3.8% of participants). Most participants with HO were male (n = 24, 73%) and had an average age of 40 + /- 13 years. Participants with HO had significantly larger burn size (49 +/-23% Total Body Surface Area (TBSA)) than those without HO (16 +/-17%). Participants with HO reported significantly worse physical function, depression, pain interference and social integration scores than those without HO. After adjusting for covariables, participants with HO continued to report statistically significantly worse physical function than those without HO. Although physical functioning was consistently lower, the two populations did not differ significantly among psychosocial outcome measures.

CONCLUSIONS

While HO can result in physical limitations, the translation to psychosocial impairments was not evident. Targeted treatment of HO with the goal of maximizing physical function should be a focus of their rehabilitation.

LEVEL OF EVIDENCE

2b TYPE OF STUDY: Symptom Prevalence Study.

Heterotopic Ossification around the Elbow Revisited

Heterotopic ossification (HO) is the process of ectopic bone formation in the periarticular soft tissues and is usually formed in the elbow, hip and knee joint as a complication of trauma, burns, brain injury or surgical procedures. The development of HO around the elbow joint can cause a severe limitation of range of motion (ROM) and may affect daily activities of the patient. Treatment of ectopic bone formation around the elbow is a challenge for many surgeons. Non-operative treatment usually fails to restore the ROM of the elbow joint; thus, surgery is necessary to restore the function of the joint. In the past, many surgeons suggested that a delayed excision of HO, until maturation of the ectopic bone, is the best option in order to avoid any possible recurrence. However, many authors now suggest that this delay may lead to complications such as muscular atrophy and formation of soft tissue contractures that can cause a greater impairment of elbow function; thus, early excision is a better option and can better restore the elbow ROM. We performed a literature research of articles that investigated which is the best time of HO excision and we also evaluated if the tethering effect of HO can lead to a greater impairment of the elbow function. We found numerous studies suggesting that a limitation in ROM of the elbow can appear from the tethering of the ectopic bone formation and not only from primary HO. Concerning the HO excision, there were no significant differences between patients who underwent delayed and early excision, concerning the recurrence rate of HO around the elbow. Patients who underwent early excision had better restoration of elbow ROM; thus, early excision, combined with a rehabilitation program, is reported to be the best option for these patients.

Effect of mechanical stimulation on tissue heterotopic ossification: an in vivo experimental study

Background: Heterotopic ossification of tendons and ligaments (HOTL) is a common clinical condition characterized by the absence of discernible features and a lack of effective treatment. In vitro experiments have demonstrated that mechanical stimulation can induce cell differentiation toward osteogenesis, thereby promoting heterotopic ossification. Currently, there are few experimental designs aimed at inducing ligament stretching in mice, and the mechanism of heterotopic ossification may not entirely mirror that observed in clinical cases. Therefore, there is an urgent imperative to develop a novel and feasible animal model. Methods: In this study, all the Enpp1 gene deficiency mice (a mouse model with heterotopic ossification of multiple ligaments) were divided into three groups: the control group, the spinal brake group, and the hyperactive group (treadmill training group). An external spinal fixation device was designed to restrict mice's spinal flexion and extension at 6 weeks of age. The brace was adjusted weekly according to the changes in the size of the mice. Additionally, treadmill training was used to increase activity in the spinal ligaments and Achilles tendons of the mice. Micro-CT scanning and HE staining were performed at 12, 20, and 28 W to evaluate the degree of ossification in the spinal ligament and Achilles tendon. What's more, As one of the mechanical stimulation transduction signals, YAP plays a crucial role in promoting osteogenic differentiation of cells. Immunofluorescence was utilized to assess YAP expression levels for the purpose of determining the extent of mechanical stimulation in tissues. Results: Our findings showed that a few ossification lesions were detected behind the vertebral space of mice at 8 weeks of age. Spinal immobilization effectively restricts the flexion and extension of cervical and thoracic vertebrae in mice, delaying spinal ligament ossification and reducing chronic secondary spinal cord injury. Running exercises not only enhance the ossification area of the posterior longitudinal ligament (PLL) and Achilles tendons but also exacerbate secondary spinal cord injury. Further immunofluorescence results revealed a notable increase in YAP expression levels in tissues with severe ossification, suggesting that these tissues may be subjected to higher mechanical stimulation. Conclusion: Mechanical stimulation plays a pivotal role in the process of heterotopic ossification in tissues. Our study provided valid animal models to further explore the pathological mechanism of mechanical stimulation in HOTL development.