Predictors of outcome in the quadriparetic nonambulatory myelopathic patient with rheumatoid arthritis: a prospective study of 55 surgically treated Ranawat class IIIb patients.

The functional results of surgery in patients with myelopathic nonambulatory rheumatoid arthritis (Ranawat Class IIIb) are often disappointing, with high rates of postoperative morbidity and mortality. The authors therefore undertook a detailed investigation of a cohort of 55 Ranawat Class IIIb patients (11 men and 44 women) with a mean age of 64.7 years who were recruited prospectively over a 10-year period (1983-1993), to determine what factors may accurately predict a good surgical outcome. Only 14 patients (25.5%) were judged to have had a favorable outcome as determined by an improvement to Ranawat Class I or II or an improvement of at least 0.5 points in the Stanford Health Assessment Questionnaire disability index. The early postoperative mortality rate was high (12.7%) in this group and almost one-quarter of the patients were dead within 6 months. These poor results mirror those already published in the existing literature. Univariate analysis revealed that age (p = 0.02), degree of vertical translocation (p = 0.05), and, more importantly, spinal cord area (p = 0.006) were significant predictors of outcome. Multiple logistic regression analysis showed that spinal cord area (p = 0.026) was, in fact, the major determinant of outcome and, indeed, of long-term survival (p = 0.001). The mean spinal cord area of those patients not achieving a good outcome was 44 mm2. The atlantodens interval (ADI) was not shown to be a significant outcome determinant, which may be explained by the correlation between an increasing vertical translocation and a decreasing ADI (r = 0.4, p = 0.01). Furthermore, as the degree of vertical translocation increased, the space available for the cord was observed to decrease (p = 0.003) commensurate with a reduction in spinal cord area (p = 0.02). Together, these findings strongly argue for earlier surgical intervention, before the development of vertical translocation, permanent neurological damage, and spinal cord atrophy can occur.