Safety of interbody fusion in the elderly

Abstract

Lee D. Hieb, MD, FAAOS, David Stevens, PA-C, Yuma, AZ, USA; M. Mason Macenski, PhD, Minneapolis, MN, USAIntroduction: It is often thought that elderly patients undergoing spinal decompression are at little risk of developing late instability. However, our experience treating a large geriatric population indicates that symptomatic instability may develop and prove quite refractory to salvage. The morbidity of classic posterior fusions in the elderly has made it difficult to recommend “prophylactic” fusion. Our favorable experience using interbody fusion in younger patients caused us to expand this technique to our older population.Methods: Seventy-one consecutive patients 55 years or older underwent interbody stabilization by the primary author. In all but one case threaded titanium cages were used. These cases were then retrospectively reviewed for complication, length of stay, blood loss, and other aspects of surgery, as well as various measures of outcome. Age 55 years was chosen, because it was observed that by this age many of the comorbidities associated with the elderly (eg, osteoporosis, hypertension, coronary artery disease, etc.) have become established. Patients were followed up if they were at least 2 years postsurgery. Most patients presented with symptoms of high-grade spinal stenosis and had stabilization either for spondylolisthesis, segmental instability or for indirect decompression of “up-down” lateral recess stenosis. Neither low bone mineral density, calcification of the great vessels nor cigarette smoking were considered contraindications to surgery. Morbidly obese patients, however, were generally excluded. Radiographic and clinical follow-up was done at 1, 3 and 6 months, 1 and 2 years. Bone density testing was obtained at follow-up if not done before the procedure.Results: The cohort consisted of 19 men and 52 women, ranging in age from 55 to 85 years. Mean age was 67.9 years. Twenty-nine patients underwent anterior only fusion (anterior lumbar interbody fusion, ALIF), 12 posterior decompression and fusion (posterior lumbar interbody fusion, PLIF) and 30 combined anterior fusion posterior lumbar decompression. There were 37 one-level, 27 two-level and five three-level procedures performed. Four patients were anesthesia Class 1, 22 Class 2, 37 Class 3 and five Class 4. Average blood loss was as follows: anterior only surgery, 274 cc; posterior only, 579 cc; combined single setting anterior stabilization and posterior decompression, 347 cc. Only two major complications occurred. One patient who was moderately obese and a smoker developed a hernia at the site of the anterior retroperitoneal incision that required secondary repair. The second patient developed severe aspiration pneumonia while on the rehabilitation ward, 3 days after an uneventful two-level anterior lumbar fusion. This resulted in a prolonged intensive-care-unit stay; the patient went on to full recovery. Mean hospitalization was 3.9 days and was slightly longer for PLIF procedures than for ALIF or ALIF with concomitant posterior decompression. No cage migration occurred. One patient who was obese redeveloped some deformity of a spondylolisthesis, but this did not require treatment beyond temporary brace management. Subsidence proved difficult to measure. This was done by comparing the first with the last standing lumbar film, using the cage as an index of radiographic magnification. In those disc spaces where measurement was possible, settling averaged 2.9 mm. Bone mineral density, which ranged from a T score at −2.21 to +2.55, did not correlate with the degree or absence of settling of the disc space. Although clinical outcome was not the primary focus of this study, nearly all patients reported improved function. Of the four patients who were nonambulatory at the time of surgery, all became ambulatory, three using no assistive devices. Two patients who were very severely limited in their ambulation became unlimited ambulators postoperatively. As a whole, all outcome measures showed improvement. Patient mobility, pain scores for back and leg pain all significantly improved. Bowel and bladder complaints were reduced from 23.9% to 5.6% postoperatively.Our cohort included 83% smokers, four bedridden patients and many of anesthesia Class 3 or 4. Nevertheless, complication rate was low, and nearly all patients improved significantly. PLIF procedures resulted in more blood loss, were more challenging to perform and resulted in slightly longer hospitalization. Combining anterior interbody fusion with concomitant posterior decompression was better tolerated by patients, and easier to perform, especially for multilevel procedures. Patients were nearly all mobilized on the first postoperative day with only an abdominal binder (ALIF). Bowel recovery was the factor most likely to slow recovery in the ALIF patients. Subsidence, although much discussed, is in practice very difficult to quantitate. The bone density in our patients did clearly not predict the degree of settling. In sum, interbody fusion affords a safe and effective alternative for elderly patients at risk for instability.