- Case report
- Open Access
Inhalant abuse of 1,1-difluoroethane (DFE) leading to heterotopic ossification: a case report
© Little et al; licensee BioMed Central Ltd. 2008
- Received: 13 August 2008
- Accepted: 30 October 2008
- Published: 30 October 2008
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.
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.
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.
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.
- Heterotopic Ossification
- Diffuse Idiopathic Skeletal Hyperostosis
- Proximal Humerus Fracture
- Myositis Ossificans
- Resection Arthroplasties
First described in 1883 by German physician Riedel, heterotopic ossification (HO) is defined as the formation of mature, lamellar bone within soft tissues other than the periosteum [1–3]. There are three recognized etiologies of HO: (1) traumatic – following fractures, dislocations, or operative procedures, (2) neurogenic – occurring after closed head injuries, insults to the spinal cord, or central nervous system infections, and (3) genetic (i.e. myositis ossificans progressiva – a rare, autosomal dominant disease) [1, 2]. Although there are no definitively documented causal factors, HO is presumably the result of "the inappropriate differentiation of pluripotential mesenchymal cells into osteoblastic stem cells" . Individuals over the age of 60, males, patients with previous HO bone, hypertrophic osteoarthritis, ankylosing spondylitis, diffuse idiopathic skeletal hyperostosis (DISH), prior hip surgery, and surgical risk factors place the patient at a higher risk for the formation of HO [1, 2].
In the present case, we identify rapid pathogenic bone formation at multiple sites in a patient without any other significant risk factors except the abuse of an inhaled substance. Misuse or abuse of such compressed gases can result in difficulty breathing, alteration of the heart's electrical activity (irregular pulse, palpitations, inadequate circulation), abnormal kidney function, central nervous system depression, and death [4–8]. Neither literature nor material safety data sheets propose any skeletal risks related to overexposure or intentional abuse of 1,1-difluoroethane (DFE). To the knowledge of the authors, there is no existing literature suggesting the abuse of halogenated aliphatic aerosol propellants as a contributing factor to pathologic bone formation.
To rule out any signs or factors that may have contributed to HO in the patient, we reviewed pertinent medical, social and surgical history. However, the patient does not have a history of any of the contributing genetic disorders (fibrodysplasia ossificans progressiva, progressive osseous heteroplasia, or Albright's hereditary osteodystrophy). While HO may also be a result of the trauma, we do not believe that this is the case here. The patient did undergo ORIF for a displaced fracture dislocation of the acetabulum and displaced proximal humerus. Subsequent surgeries included hardware removal and resection arthroplasties in both areas. However, all recommended precautions to reduce the risk of HO were taken: atraumatic surgical techniques, careful excision, thorough irrigation and debridement, and administration of antibiotic prophylaxis. Additionally, the pathologic bone formation was not evident in any radiographs until 6 months following the initial injuries and 3 months after his resection surgery. This is long outside the 4–6 week window in which HO starts to appear on plain radiographs .
The final recognized cause of HO formation is neurogenic with either an insult to the central nervous system (CNS) including spinal trauma and head injuries or neurologic conditions such as encephalitis, meningitis, myelitis, tetanus, brain tumors, epidural abscess, or subarachnoid hemorrhage . Campos et al. hypothesize that the formation of HO in neurogenic injuries may be related to proprioception dysfunction. Perhaps because of "mixed signals," stimuli that were intended to strengthen tissue resistance resulted in HO .
There was minor evidence of this patient sustaining any neurogenic injuries as a result of the motor vehicle accident. The patient's Glascow Coma Score (GCS) was a 15 upon arrival to the emergency department, and his head was found to be normal with no swelling, ecchymosis, tenderness, lesions, abrasions, or lacerations. However, one of the hazardous health effects related to the inhalation of high concentrations of halogenated aliphatic aerosol propellants is damage to the CNS [4–8]. Furthermore, the most commonly found chemical ingredient in dusting sprays is DFE. Some of the side effects of DFE were apparent when the patient displayed metabolic abnormalities and high blood pressure during his final surgery, which could not be attributed to anything other than his increased abuse of DFE.
While the patient had some risk factors (male, fracture with dislocation) [1, 2], the authors feel that the biggest influence may have been the exorbitant inhalation of DFE. This substance may have exacerbated or accelerated any predisposition the patient had to developing HO.
HO following trauma and surgical intervention is not uncommon [1–3]. What is unusual in this case is the rate at which the pathological bone formation appeared, which was three months after the Girdlestone resection arthroplasties. In addition, radiographs obtained when the patient first presented did not reveal any HO at the time. 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. Interestingly, the HO is not limited to the areas where the resection arthroplasties were performed (although they are most abundant here), but it is present throughout the body.
Written informed consent was obtained by the patient for publication of this case report.
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