Does Age Affect Surgical Outcomes in Patients with Degenerative Cervical Myelopathy?: Results from the Prospective, Multicenter AOSpine International Study on 479 Patients
Authors: Nakashima Hiroaki , Tetreault Lindsay , Nagoshi Narihito , Nouri Aria , Fehlings Michael 
Published: April 2016

Introduction

Currently, the global population is experiencing a shift in its age structure. With this aging of the population, clinicians worldwide will be required to manage an increasing number of patients with degenerative cervical myelopathy (DCM). However, there is controversy whether surgical decompression is equally effective and safe in elderly patients as it is in younger patients. This study aims to determine whether age truly is an independent predictor of surgical outcome and to provide evidence to guide practice and decision-making.

Material and Methods

A total of 479 symptomatic DCM patients were prospectively enrolled in the CSM-International study at 16 centers. Our sample was divided into a younger (<65years) and elderly (≥65years) group. Each subject was neurologically examined at baseline and 24-months postoperatively and evaluated using a variety of functional outcome measures, including the Neck Disability Index (NDI), SF-36 physical component summary (PCS) and mental component summary (MCS), and the modified Japanese Orthopaedic Association scale (mJOA). A mixed model analytic approach was used to evaluate differences in these outcome measures between groups. We first created an unadjusted model between age and surgical outcome and then developed two adjusted models that accounted for variations in 1) baseline characteristics and 2) both baseline and surgical factors.

Results

Of the 479 patients, 360 (75.16%) were < 65 years and 119 (24.84%) were ≥65 years. There were no significant differences in gender ( p = 0.82) or duration of symptoms ( p = 0.82) between the two age groups. However, elderly patients had a significantly higher number of co-morbidities ( p < 0.0001). In addition, elderly patients were functionally more impaired preoperatively based on the mJOA ( p < 0.0001) and Nurick ( p < 0.0001) scales and had a lower SF-36 PCS ( p = 0.048). The majority of younger patients (64.96%) underwent anterior surgery, whereas the preferred approach in the elderly group was posterior (58.62%) ( p < 0.0001). Elderly patients had a greater number of decompressed levels (4.14 ± 1.30) than younger patients (3.50 ± 1.23) ( p < 0.0001). Three hundred and eight-nine patients (81.21%) attended their 24-month follow-up appointment. Younger patients achieved a higher postoperative mJOA ( p < 0.0001) and a lower Nurick score ( p < 0.0001) than elderly patients. SF-36 PCS scores were also significantly higher in the younger group ( p = 0.033). There were no significant differences in postoperative NDI or SF-36 MCS between age groups. After adjustments for patient and surgical characteristics, these differences in postoperative outcome scores decreased but remained significant. On average, elderly patients had a significantly longer length of postoperative hospital stay (12.99 ± 13.56 days) than younger patients (9.53 ± 8.67 days) ( p = 0.0086). There were no significant differences between the two age groups with respect to rates of perioperative complications ( p = 0.47).

Conclusion

Older age is an independent predictor of functional status in patients with DCM. However, patients over 65 with DCM still achieve functionally significant improvement after surgical decompression. Potential explanations for this lower functional outcomes in older patients include that the elderly 1) increased degenerative pathology, including a decrease in number of anterior horn cells and number of myelinated fibers 2) co-morbidities, 3) reduced physiological reserves and 4) age-related changes to the spinal cord.