Degenerative problems of the hip in patients
with childhood and adult onset neuromuscular disorders can be challenging
to treat. Many orthopaedic surgeons are reluctant to recommend total
hip replacement (THR) for patients with underlying neuromuscular
disorders due to the perceived increased risks of dislocation, implant loosening,
and lack of information about the functional outcomes and potential
benefits of these procedures in these patients. Modular femoral
components and alternative bearings which facilitate the use of
large femoral heads, constrained acetabular components and perhaps
more importantly, a better understanding about the complications
and outcomes of THR in the patient with neuromuscular disorders,
make this option viable. This paper will review the current literature
and our experience with THR in the more frequently encountered neuromuscular
disorders. Cite this article:
Arthritis of the hip is a relatively common problem in patients with neuromuscular disorders due to muscle imbalance around the hip from weakness, paralysis, contractures and spasticity. Neuromuscular disorders such as cerebral palsy, Parkinson's disease, poliomyelitis, previous cerebrovascular accident (CVA) and Charcot arthropathy have been considered by many to be relative contraindications to total hip arthroplasty (THA). The presence of certain anatomic abnormalities (excessive femoral anteversion, acetabular dysplasia, leg length discrepancy (LLD) and coax valga) and significant soft tissue contractures, muscle imbalance, and muscular weakness make THA a challenging surgical procedure in this patient population, and can predispose to dislocation and poor functional outcome following surgery. THA can, however, result in substantial pain relief and functional improvement in patients with significant hip arthritis and neuromuscular disorders, and can be safely performed, provided certain technical considerations are addressed. The patient's motor strength and functional status (ambulatory vs. “sitter”) should be carefully assessed pre-operatively, since both of these factors may affect the choice of surgical approach and component position. Significant soft tissue contractures should be released at the time of surgery. Although these can be frequently performed “open,” percutaneous adductor tenotomy is occasionally necessary for patients with significant adduction contractures. Patients requiring significant soft tissue releases may benefit from 6 weeks of bracing to allow soft tissues to heal in appropriately and minimize risk of dislocation during this period of time. Use of modular femoral components that allow for correction of excessive femoral anteversion, should be considered in patients with coexistent dysplasia and neuromuscular disease (i.e. CP or polio). Large femoral head components should also be considered in patients with increased risk factors for dislocation. Despite their obvious theoretical advantages, the use of large head metal on metal THAs should be used with extreme caution in view of growing concerns about these devices. Although constrained acetabular liners are associated with an increased risk of mechanical failure, their use should be strongly considered in patients with significant motor weakness or major soft tissue deficiencies. Meticulous soft tissue closure of the capsule of the hip is recommended, especially when performing THA through a posterior approach. Patients with neuromuscular disorders associated with spasticity and involuntary movements need to be optimally treated medically prior to and indefinitely after THA. There are limited reports of outcomes following THA in patients with neuromuscular disorders, however some generalisations based on underlying diagnosis can be made. Patients with cerebral palsy and polio frequently have acetabular dysplasia, excessive femoral anteversion and LLD, and although durability does not seem to be a major concern, dislocation and instability is relatively common and needs to be addressed. Durability and instability do not appear to be major concerns in patients with
