The function of proprioceptors in bone organization: a possible explanation for neurogenic heterotopic ossification in patients with neurological damage

Neurogenic heterotopic ossification in the upper limb

Neurogenic heterotopic ossifications (NHOs) are periarticular ectopic ossifications that frequently develop after a central nervous system injury, most often a traumatic one. They limit range of motion and cause pain, interfering with limb positioning and function, whether active or passive. Highly described in the lower limbs, NHOs can also develop in the upper limb, with specific characteristics depending on their location. This article provides a summary of the diagnostic and therapeutic management of NHOs in the upper limb, based on the current literature.

The role and mechanisms of polycomb repressive complex 2 on the regulation of osteogenic and neurogenic differentiation of stem cells

The stem cells differentiate into osteoblasts or neurocytes is the key process for treatment of bone‐ or neural tissue‐related diseases which is caused by ageing, fracture, injury, inflammation, etc Polycomb group complexes (PcGs), especially the polycomb repressive complex 2 (PRC2), act as pivotal epigenetic regulators by modifying key developmental regulatory genes during stem cells differentiation. In this review, we summarize the core subunits, the variants and the potential functions of PRC2. We also highlight the underlying mechanisms of PRC2 associated with the osteogenic and neurogenic differentiation of stem cells, including its interaction with non‐coding RNAs, histone acetyltransferases, histone demethylase, DNA methyltransferase and polycomb repressive complex 1. This review provided a substantial information of epigenetic regulation mediated by PRC2 which leads to the osteogenic and neurogenic differentiation of stem cells.

Association of α2-HS Glycoprotein with Neurogenic Heterotopic Ossification in Patients with Spinal Cord Injury

Background

The aim of this study was to explore the relationship between the α₂-HS glycoprotein concentrations in serum and the occurrence of neurogenic heterotopic ossification (NHO) in patients with spinal cord injury (SCI).

Material/Methods

During the period between January 2011 and January 2012, 75 patients (67 male) with paraplegia caused by spinal cord injury were enrolled. The patients were divided into 2 groups in accordance with the occurrence of heterotopic ossification based on the results high-frequency ultrasound on the bilateral hip joint. The levels of α₂-HS glycoprotein, C-reactive protein (CRP), D-dimer, and bone morphogenetic protein (BMP) were detected by ELISA.

Results

We found a significant decrease of α₂-HS glycoprotein in SCI patients with NHO compared to SCI patients without NHO. In contrast, a significant elevation of serum calcium, D-dimer, BMP, and CRP was observed in SCI patients with NHO. The degree of maturity of NHO did not influence the level of α₂-HS glycoprotein. Multivariate liner regression analysis showed that the level of serum α₂-HS glycoprotein was correlated with CRP and spasticity.

Conclusions

The decreased level of α₂-HS glycoprotein may be related to the formation of neurogenic heterotopic ossification in patients with spinal cord injury. Our results suggest that α₂-HS glycoprotein might be a risk factor for NHO in patients with SCI.

Heterotopic ossification of the shoulder after central nervous system lesion: indications for surgery and results

BACKGROUND

Heterotopic ossification (HO) of the shoulder after central nervous system damage has seldom been studied.

MATERIALS AND METHODS

We performed a single-center retrospective study from 1993 to 2009 including patients who underwent surgery for troublesome shoulder HO. Demographic data, HO location, surgical approach, preoperative and postoperative shoulder range of motion, etiologies, and postoperative complications were collected from patients' files.

RESULTS

We found 19 shoulder HOs in 16 patients (traumatic brain injury in 11, spinal cord injury in 2, stroke in 1, and cerebral anoxia in 2). The data in 2 files were incomplete and were therefore not used. HO locations around the joint were anteroinferomedial in 4 (21.1%), posteroinferomedial in 5 (26.3%), encircling in 3 (15.8%), superior in 1 (5.3%), and mixed (2 associated HOs that are not encircling) in 6 (31.6%). The surgical approaches were as follows: deltopectoral, 5 (26.3%); Neer, 3 (15.8%); posterior, 5 (26.3%); axillary, 1 (5.3%); Martini, 2 (10.5%); posterior associated with deltopectoral, 2 (10.5%); and Neer (superolateral) associated with deltopectoral, 1 (5.3%). The mean range of motion increased significantly (gain at follow-up of 69°, 60°, and 13° in forward elevation, abduction, and lateral rotation, respectively). Regarding postoperative complications, there was 1 case of capsulitis and 1 reoperation for insufficient excision (because of hemorrhage during surgery). There were no other side effects.

CONCLUSION

Anatomic relations with nerves and vessels, as well as limited range of motion, require a case-by-case surgical approach, a preoperative scan (looking for a gutter), and sometimes, electromyography. Surgical indications depend on the degree of loss of function or hygiene, control of comorbid factors, and discussion with the patient and his or her family.

Troublesome heterotopic ossification after central nervous system damage: a survey of 570 surgeries

Background

Heterotopic ossification (HO) is a frequent complication after central nervous system (CNS) damage but has seldom been studied. We aimed to investigate features of HO for the first time in a large sample and the rate of early recurrence of HO in terms of the time of surgery.

Methodology/Principal Findings

We retrospectively analyzed data from an anonymous prospective survey of patients undergoing surgery between May 1993 and November 2009 in our institution for troublesome HO related to acquired neurological disease. Demographic and HO characteristics and neurological etiologies were recorded. For 357 consecutive patients, we collected data on 539 first surgeries for HO (129 surgeries for multiple sites). During the follow-up, recurrences requiring another surgery appeared in 31 cases (5.8% [31/539]; 95% confidence interval [CI]: 3.8%–7.8%; 27 patients). Most HO requiring surgery occurred after traumatic brain injury (199 patients [55.7%]), then spinal cord injury (86 [24.0%]), stroke (42 [11.8%]) and cerebral anoxia (30 [8.6%]). The hip was the primary site of HO (328 [60.9%]), then the elbow (115 [21.3%]), knee (77 [14.3%]) and shoulder (19 [3.5%]). For all patients, 181 of the surgeries were performed within the first year after the CNS damage, without recurrence of HO. Recurrence was not associated with etiology (p = 0.46), sex (p = 1.00), age at CNS damage (p = 0.2), multisite localization (p = 0.34), or delay to surgery (p = 0.7).

Conclusions/Significance

In patients with CNS damage, troublesome HO and recurrence occurs most frequently after traumatic brain injury and appears frequently in the hip and elbow. Early surgery for HO is not a factor of recurrence.

Bedside ultrasound in early diagnosis of neurogenic heterotopic ossification in patients with acquired brain injury

OBJECTIVE

To illustrate ultrasound (US) and power Doppler US (PDUS) aspects of neurogenic heterotopic ossification (NHO) in consecutive patients with severe acquired brain injury, to evaluate the role of bedside US and PDUS in early diagnosis of NHO, to study incidence and outcome of NHO in this neurorehabilitative setting.

METHODS

Ninety-two consecutive patients with severe acquired brain injury underwent clinical and laboratory screening to pose suspect of NHO. In 6/92 patients bedside US examination confirmed the clinical suspect of NHO. US diagnosis of NHO was then confirmed by other imaging methods. All affected patients started therapy with indometacin, disodium etidronate, 6-methylprednisolone and they were followed-up for 1 year to evaluate the outcome.

RESULTS

The incidence of NHO in this setting was 6.5% (only one patient with multifocal involvement). In hip NHO US demonstrated the classical pattern of zone phenomenon, and PDUS demonstrated vascular signals within mineralized NHO and in the outer hypoechoic area. No vascular signal was observed in the central hypoechoic core. In knee and elbow NHO only a heterogeneously hypoechoic mass or hyperechoic mineralized mass were respectively evident, with vascular signals within the lesions at PDUS. Spectral wave analysis (SWA) demonstrated low resistance vessels in NHO. After 1 year of therapy only one patient showed a severe ankylosis of the hips.

CONCLUSIONS

Bedside US is a safe, cheap and useful tool in diagnosis of NHO and it allows to start therapy in early stages of NHO formation. PDUS adds data about neoangiogenetic activity of early NHO.

Risk factors of heterotopic ossification in traumatic spinal cord injury

OBJECTIVE: Heterotopic ossification (HO) is a complication of the spinal cord injury (SCI). It can result in anchylosis, harming the rehabilitation and quality of life. Previous publications had not elucidated the relation between possible independent variables, the aim of this study. METHOD: From 230 patients with SCI, admitted in 1998 at Hospital SARAH Brasilia, 33 with HO (14.3%; CI95% 10.1-19.6) were compared with 33 controls. The risk factors had been tested in bivariate analysis and in a model of logistic regression. RESULTS: Spasticity (odds ratio=3.8; CI95% 1.15-12.30), number of pressure ulcers (2.1; CI95% 1.08-3.89) and time lapsed since the injury (1.1; CI95% 1.02-1.24) were independently associated with HO. There was a confounder effect among these variables, without interaction. CONCLUSION: Spasticity, pressure ulcer and time of injury are associated with HO in spinal cord injury. The first two factors can be prevented and treatable.

Inhalant abuse of 1,1-difluoroethane (DFE) leading to heterotopic ossification: a case report

Background

Heterotopic ossification (HO) is the formation of mature, lamellar bone within soft tissues other than the periosteum. There are three recognized etiologies of HO: traumatic, neurogenic, and genetic. Presently, there are no definitively documented causal factors of HO. The following factors are presumed to place a patient at higher risk: 60 years of age or older, male, previous HO, hypertrophic osteoarthritis, ankylosing spondylitis, diffuse idiopathic skeletal hyperostosis, prior hip surgery, and surgical risk factors.

Case presentation

A 33-year-old male, involved in a motor vehicle crash, sustained an irreducible acetabulum fracture/dislocation, displaced proximal humerus fracture, and an impacted pilon fracture. During the time of injury, he was intoxicated from inhaling the aerosol propellant used in "dust spray" cans (1,1-difluoroethane, C₂H₄F₂). Radiographs identified rapid pathologic bone formation about the proximal humeral metaphysis, proximal femur, elbow, and soft tissue several months following the initial injury.

Discussion

The patient did not have any genetic disorders that could have attributed to the bone formation but had some risk factors (male, fracture with dislocation). Surgically, the recommended precautions were followed to decrease the chance of HO. Although the patient did not have neurogenic injuries, the difluoroethane in dusting spray can cause damage to the central nervous system. Signals may have been mixed causing the patient's body to produce bone instead of tissue to strengthen the injured area.

Conclusion

What is unusual in this case is the rate at which the pathological bone formation appeared, which was long outside the 4–6 week window in which HO starts to appear. The authors are not certain as to the cause of this rapid formation but suspect that the patient's continued abuse of inhaled aerosol propellants may be the culprit.