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 »  Abstract
 »  Introduction
 »  Material and methods
 »  Results
 »  Discussion
 »  References

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Year : 2001  |  Volume : 49  |  Issue : 1  |  Page : 37-40

Neurogenic heterotopic ossification : a diagnostic and therapeutic challenge in neurorehabilitation.


Department of Neurology, National Institute of Mental Health and Neurosciences, Bangalore - 560029, India.

Correspondence Address:
Department of Neurology, National Institute of Mental Health and Neurosciences, Bangalore - 560029, India.

  »  Abstract

Heterotopic ossification (HO) is an important cause of restriction in range of movements and secondary motor disability following neurotrauma, orthopaedic interventions and burns. It has not received focussed attention in non-traumatic neurological disorders. In a prospective study of 377 patients, on medical problems in neurological rehabilitation setting, 15 subjects (3.97%) had neurogenic heterotopic ossification. Their clinical diagnosis was: transverse myelitis (7), neurotuberculosis (4), traumatic myelopathy (2) and stroke (2). Hip (10), knee (4) and elbow joints (1) were involved. The risk factors included urinary tract infection (15), spasticity (6), pressure sores (13) and deep venous thrombosis (DVT) (6). The initial diagnosis was often other than HO and included DVT (3), haematoma (2) and arthritis (2). ESR and serum alkaline phosphatase levels were elevated in all but one subject. The diagnosis of HO was established using X-rays, CT Scan and three-phase bone scan. Following treatment with non-steroidal anti-inflammatory drugs, the range of motion improved in only four patients. HO resulted in significant loss of therapy time during rehabilitation. High index of suspicion about this complication is necessary for early diagnosis and prompt intervention.

How to cite this article:
Taly A B, Nair K P, Jayakumar P N, Ravishankar D, Kalaivani P L, Indiradevi B, Murali T. Neurogenic heterotopic ossification : a diagnostic and therapeutic challenge in neurorehabilitation. Neurol India 2001;49:37-40


How to cite this URL:
Taly A B, Nair K P, Jayakumar P N, Ravishankar D, Kalaivani P L, Indiradevi B, Murali T. Neurogenic heterotopic ossification : a diagnostic and therapeutic challenge in neurorehabilitation. Neurol India [serial online] 2001 [cited 2021 Sep 27];49:37-40. Available from: https://www.neurologyindia.com/text.asp?2001/49/1/37/1304




   »   Introduction Top

Formation of mature lamellar bone in soft tissue is
known as heterotopic ossification (HO). There are
four forms of HO viz neurogenic HO (NHO), myositis
ossificans, hereditary HO and HO after burns.[1] The
neurogenic HO is mostly reported after trauma to
central nervous system and is an important cause of
disability in neurological rehabilitation. Several
factors, both hereditary and acquired, have been
implicated in the pathogenesis of NHO. However,
their exact role is far from clear. The primary
neurological deficits may modify the clinical features
of HO. Therefore, its diagnosis is often delayed and
requires high index of suspicion. This report describes
patients with NHO, seen at neurological rehabilitation
unit, National Institute of Mental Health and
Neurosciences, Bangalore, India.


   »   Material and methods Top

Fifteen subjects from a prospective study[2] of medical
problems in neurological rehabilitation unit, who had
clinical and radiological evidence of NHO, form the
basis of this report. Detailed history regarding trauma,
surgery, onset and evolution of neurological
symptoms and interval between the onset of
neurological deficits and features suggesting NHO
was recorded. Location, aetiology and severity of the
neurological lesion was noted. American Spinal Injury
Association (ASIA) impairment scale was used to
describe the completeness of the spinal cord lesion.3
Risk factors for NHO like deep venous thrombosis
(DVT), spasticity, pressure sores and urinary tract
infection were documented. Clinical features of HO,
namely decreased range of motion (ROM) at the
affected joint, fever, erythema at the involved site,
localised soft tissue swelling and warmth were looked
for. Laboratory investigations, including erythrocyte
sedimentation rate (ESR), serum alkaline phosphatase
(SAP) levels, X-rays, computerised axial tomography
scans, ultra-sonography and bone scans, were
reviewed. Therapeutic response to drugs was also
evaluated.

   »   Results Top

During this study, among 377 patients who were
admitted to neurological rehabilitation unit, 15
patients (3.97%) had clinical and radiological
evidence of NHO. Among 13 subjects with spinal
cord disorders, the lesion was complete (ASIA grade
- A) in nine patients and incomplete (ASIA grade - B)
in four. Neurosurgical procedures of the spine were
carried out in four patients. Two patients had Pott's
spine, one had traumatic myelopathy and one had
negative exploration for suspected tumour. In
addition, one patient each had hemiplegia due to
vasculitis and quadriparesis due to cerebral venous
thrombosis. The initial symptoms of NHO were: pain
(8), swelling (11) [Figure - 1] and restricted ROM (15).
The concomitant risk factors were DVT (6), spasticity
(6), pressure sores (13) and urinary tract infection
(15). Erythrocyte sedimentation rate (ESR) was
elevated in all and ranged between 30 mm and 115
mm during first hour. Serum alkaline phosphatase
(SAP) levels were elevated in all except one subject.
Initial plain X-rays of the involved joints were normal
in eight subjects, however serial X-rays showed NHO
in seven of them [Figure - 2] and [Figure - 3]. In one subject with
normal X-rays, bone scan revealed NHO.
Computerised tomographic (CT) scan, done in two
subjects, revealed calcification around hip joints
[Figure - 4]. Eleven patients were treated with indomethacin,
two patients each received diclofenac
sodium and ibuprofen. Range of motion exercises and
active physiotherapy were stopped till all signs of
inflammation subsided and ESR and alkaline
phosphatase returned to normal levels. Range of
motion improved in four subjects, three of whom had
received indomethacin and one diclofenac sodium.


   »   Discussion Top

NHO is often regarded as a complication of traumatic
brain and spinal cord injuries[1],[5],[6] and its incidence,
among them, varies from 16% to 53%. However, its
incidence in non-traumatic neurological disorders is
not known. In the present series, 15 of the 377 patients
(3.97%) admitted to neurological rehabilitation unit
developed this complication. NHO is reported to be
more common among patients with cervical cord
injury, but in the current series only two patients had
cervical myelopathy. Bravo-Payno et al also did not
find any significant association between the level of
SCI and NHO.[7] Hip, knee and elbow joints have
predilection for HO.[6] The distal joints are usually
spared except in burns.[1] In the current study, hip
joints were the most frequently affected (n=10).
Among four subjects with knee joint involvement,
three had bilateral affection. Early manifestations of
NHO may mimic DVT, arthritis, haematoma,
infection and tumour. Only in eight instances NHO
was considered as the first diagnosis. Awareness and
high index of suspicion are essential for early
diagnosis. Pain is the most common symptom of
NHO,5 however, it may be absent, as in our cases, due
to severe sensory deficits associated with the primary
neurological disease. Limitation of range of motion,
the most common sign of HO, was present in all and
should arouse suspicion among care givers.
Elevation of level of alkaline phosphatase is a
hallmark of NHO8 and is considered a sensitive,
convenient and inexpensive investigation for early
detection. Some authors even recommend empirical
treatment for NHO based on SAP levels.[5] However,
these levels may be elevated in patients with hepatic
dysfunction, fractures and bone tumours. Whenever
possible, the diagnosis of HO should be confirmed by
other investigations. ESR of more than 35 mm in first
hour is reported to be an early indicator of NHO.
However, it has low specificity as it may be raised due
to concomitant conditions like pressure sore and
urinary tract infection. Despite these limitations, both
the tests are very frequently used for assessing the
activity of NHO.[1]
Plain X-rays are helpful in the diagnosis and
monitoring the progression of NHO1 but may be
negative during early stages. In the present study, Xrays
were initially normal in eight patients and it was
only on serial study that calcification was
demonstrated. NHO may involve soft tissue structures
like blood vessels and nerves near the joint.[4],[9] CT,
being more sensitive, helps in early detection of NHO
and delineation of bone from soft tissues. In two of
our patients, CT clearly defined the extent of soft
tissue involvement. The 'gold standard' for the
diagnosis is three-phase bone scan.[1] This was done in
two subjects and revealed NHO in one patient with
negative X-rays. The limitations of this test are cost,
radiation and lack of easy availability of this facility.
Ultrasonography is believed to be useful in the early
diagnosis of HO and differentiation of HO from
primary bone tumours, haematomas and abscess.[6],[10]
However, it was not carried out routinely in our
patients.
Risk factors for NHO include DVT, spasticity, severe
trauma, pressure sores, complete spinal cord injury,
urinary tract infection and vigorous physiotherapy.
[1],[5],[7] Rapid and frequent stretching of spastic
limbs can result in traumatic muscle tears. Cassar-
Pullincino et al observed muscle necrosis,
haemorrhage and cellular proliferation in the central
hypoechogenic zone surrounded by an intermediate
echogenic zone of osteoblast and immature bone. The
outer zone consisted of mature bone with trabecular
pattern.[11] Bodley et al also observed early bone
formation and macrophages containing haemosiderin
in NHO.[10] These studies suggest that microtrauma
might be contributory to its pathogenesis.[10],[11] Deep
venous thrombosis is considered a risk factor as well
as a complication of NHO.[4],[7],[9] In the present series,
six patients had DVT and in two of them DVT
preceded heterotopic ossification.
Management of NHO is difficult and includes
disodium etidronate, indomethacin, physical therapy,
radiation, surgery, verapamil and warfarin.[1],[4],[5],[12],[13],[14]
Once the process of bone formation is complete, the
response to treatment is poor. The aim of medical
treatment, thus, is to prevent NHO in high risk
patients and to avert recurrence after surgery.
Diphosphonates interfere with the conversion of
amorphous calcium phosphate to hydroxyapatite
crystals,[1],[5] and is used in dosage 20 mg/kg/day for
three to six months for prophylaxis of NHO. Their
side effects include fracture of long bones, fever,
myalgia, leucopaenia, bone pains and rebound
ossification. Indomethacin inhibits prostaglandin
synthetase and reduces inflammation. This decreases
the mesenchymal cell proliferation and interferes with
new bone formation. Among 11 patients, who
received indomethacin, range of motion improved in
three. Role of ROM exercises is controversial as it
may increase the inflammation and accelerate bone
formation.[5] Some authors recommend ROM to
maintain the mobility of the joint and prevent
ankylosis while others prefer to treat them with
'benign neglect'.[1] Radiation prevents the conversion
of precursor cells to bone forming cells. Once NHO is
established, radiation therapy is said to be ineffective
but may have role in preventing recurrence after
surgery.[1],[5] Surgical removal of the ectopic bone tissue
is indicated only after six months of conservative
therapy and is often a difficult procedure. It is
contraindicated if there is any clinical or laboratory
evidence (raised ESR and SAP level) of active NHO.
In conclusion, this report highlights the occurrence of
NHO in a variety of neurological and neurosurgical
disorders in a rehabilitation setting. Unsupervised
vigorous exercises may contribute to the formation of
NHO. Lack of awareness and absence of pain due to
primary neurological disorder account for delay in the
diagnosis. Once, fully formed, there is no effective
treatment. Thus, unexplained swelling or reduction in
ROM of joints of paretic limbs, rapid ESR and
elevated SAP levels should warrant a search for HO.
Treatment includes rest to the affected limb in acute
phase and indomethacin and diphosphonates till signs
of inflammation subside and ESR and SAP levels
return to normal. Early detection and prompt
intervention are essential for disability limitation.
 

  »   References Top

1.Buschlbacher R : Heterotopic ossification : A Review. Crit Revs Phys Rehabil Med 1992; 4 : 199-213.  Back to cited text no. 1    
2.Taly AB, Kalaivani PL, Sivaraman Nair KP et al : Medical problems in neurological rehabilitation setting. Paper presented at 24th Annual National Conference of Indian Association of Physical Medicine and Rehabilitation Hyderabad, India 1996.  Back to cited text no. 2    
3.Ditunno Jr JF, Young W, Donovan WH et al : The international standards booklet for neurological and  Back to cited text no. 3    
4.functional classification of spinal cord injury. Paraplegia 1994; 34 : 70-80.  Back to cited text no. 4    
5.Colachis SC, Clinchot DM, Venesy D : Neurovascular complications of heterotopic ossification following spinal cord injury. Paraplegia 1993; 31 : 51-57.  Back to cited text no. 5    
6.Garland DE : A clinical perspective on common forms of acquired heterotopic ossification. Clin Orthop1991; 263 : 13-29.  Back to cited text no. 6    
7.Snoecx M, DeMuynck D, VanLaene M : Association between muscle trauma and heterotopic ossification in spinal cord injured patients. Reflections on causal relationships and diagnostic value of ultrasonography. Paraplegia 1995, 33 :464-468.  Back to cited text no. 7    
8.Bravo-Payno P, Esclarin A, Arzoz T et al : Incidence and risk factors in the appearance of heterotopic ossification in spinal cord injury. Paraplegia 1992; 30 : 740-745.  Back to cited text no. 8    
9.Kurer MHJ, Khoker MA, Dandona P : Human osteoblast stimulation by sera from paraplegic patients with heterotopic ossifications. Paraplegia 1992; 30 : 165-168.  Back to cited text no. 9    
10.Colachis SC, Clinchot DM : The association between deep venous thrombosis and heterotopic ossification in patients with acute traumatic spinal cord injury. Paraplegia 1993; 31 :507-512.  Back to cited text no. 10    
11.Bodley R, Jamous A, Short D : Ultrasound in early diagnosis of heterotopic ossification in patients with spinal injuries. Paraplegia1993; 31 : 500-506.  Back to cited text no. 11    
12.Cassar-Pullincino VN, McClelland M, Badwan DA et al : Sonographic diagnosis of heterotopic bone formation in spinal injury patients. Paraplegia 1993; 31 : 40-50.  Back to cited text no. 12    
13.Biering-Sorensen F, Tondevold E : Indomethacin and disodium etidronate for prevention of recurrence of  Back to cited text no. 13    
14.heterotopic ossification after surgical resection. Two case reports. Paraplegia 1993; 31 : 513-515.  Back to cited text no. 14    
15.Sharma R, Kumar D, Goyal HC et al : Heterotopic ossification in patients with spinal cord injury. Ind J Phys Med Rehab 1996; 7 : 10-16.  Back to cited text no. 15    
16.Taly AB, Nair KPS, Veerendrakumar M et al : Heterotopic ossification in non- traumatic myelopathies. Spinal cord 1999; 37 : 47-49.  Back to cited text no. 16    

 

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