Tetraplegia in a patient with huge heterotopic ossification of the hip joint after total hip arthroplasty: addition or reinforcement of handicaps.

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To the Editor: Heterotopic ossification (HO) used to be common after total hip arthroplasty (THA) (15–60% occurrence rate),1–5 but it has now become rather rare with the evolution of surgical and device technology. Several factors have been associated with HO occurrence after THA: certain surgical approaches,3,5 previous ectopic bone formations,2 hypertrophic osteoarthritis,2 ankylosing spondylitis,2,4 and diffuse idiopathic skeletal hyperostosis (DISH).6,7 This report is a case of a patient who was hospitalized 10 years after hip arthroplasty with huge HO of the right hip and cervical arthritis-related incomplete tetraplegia. An 81-year-old man who had a THA of the right hip 10 years before was referred to our hospital for gait rehabilitation. He had lost range of motion 3 years after surgery. A right hip contracture in extension was diagnosed. Radiographs showed a mature right hip HO fully surrounding the joint and severe osteoarthritis of the left hip joint (Figure 1). The patient was also diagnosed with fourth cervical spine spastic incomplete motor and sensory tetraplegia. Magnetic resonance imaging of the neck showed cervical myelopathy due to compressive mid-cervical spondylosis, without syrinx. To determine the role of the left hip arthritis in his disability and whether he could walk if his hip pain were decreased, 10 mL of 2% lidocaine was injected in the left hip joint. The hip pain was relieved, but spasticity of the left leg, which had been concealed by the hip pain, appeared. Two days later, edema of both wrists appeared. Bilateral wrist radiographs showed neuropathic joints, but no calcification of the ligaments of the hands, which is often seen in DISH, was noted. Four months later, urinary incontinence appeared. Urodynamics confirmed a central neurogenic bladder. Treatment with nonsteroidal antiinflammatory drugs was not effective, and weaning from corticosteroids, which decreased the hip pain, was impossible. The patient's autonomy and good humor improved after he began to use an electric wheelchair. Pelvic x-ray shows right hip heterotopic ossification and severe arthritis in the left hip. HO after THA is classified by local inflammatory signs, remaining range of motion, and Brooker's radiological criteria (extent of calcification in the muscles).1 In this patient, there were no signs of inflammation, range of motion was totally absent, and the HO was Brooker's Class IV. This was concluded to be a most severe case of mature HO. The rate of occurrence of Class IV HO is less than 2%;1 even so, limited functional restriction is reported. This patient had severe arthritis of the left hip that combined with the HO of his other hip to cause severe disability. His activities of daily living score was 1 out of 6. The patient had suffered from cervical pain and cervicobrachial neuralgia for a long time. Tetraplegia is a common cause of HO, and it could have facilitated the occurrence of HO in this patient, but it is difficult to ascertain whether a milder stage of tetraplegia existed before the THA surgery, because this patient did not complain of motor or sensory symptoms before surgery. Other factors causing HO, such as ankylosing spondylitis and DISH, were not present. Laminectomy to release the spinal cord compression may have been useful considering his response to corticosteroid drugs. Releasing the ankylosis of the right hip joint would have improved his posture and decreased the stress on his neck while seated, which was for more than 8 hours each day, but reports show that HO relapse is common.3,5 Moreover, removal of the THA stem along with the cement and the HO will cause unavoidable bleeding during surgery. Such surgery should not be undertaken without first informing the patient in detail about the risk of death or relapse and about the expected results. In this case, chronic bronchitis combined with ventilatory restriction due to the tetraplegia made anesthesia risky. Thus, corticosteroid therapy, which proved to be effective, was the only option. There are no reports on the long-term use of corticosteroids in patients with cervical arthritis and paraplegia. This patient acquired diabetes mellitus, possibly induced by the long-term corticosteroid therapy. HO itself usually causes little functional impairment, but when combined with other causes of deficiency, HO may result in a significant handicap, making it appear as if the causes of the deficiency are reinforcing the handicap. In conclusion, the THA in this patient may have triggered the huge HO around the right hip, and the inactivity caused by the cervical spondylosis with tetraplegia may have promoted it.