of success, but recurrence of neurological involvement and persistence of low-back pain led to an increasing number of failures. By 5 years this number had reached 27% of the available population pool, suggesting that the failure rate could reach 50% within the projected life expectancies of most patients. Of the 26 failures, 16 were secondary to renewed neurological involvement, which occurred at new levels of stenosis in eight and recurrence of stenosis at operative levels in eight. Reoperation was successful in 12 of these 16 patients, but two required a third operation. The incidence of spondylolisthesis at 5 years was higher in the surgical failures (12 of 26 patients) than in the surgical successes (16 of 64). Spondylolisthetic stenosis tended to recur within a few years following decompression. Because of age and associated illnesses, fusion may be difficult to achieve in this group. Post operative infection A small minority of lumbar surgical patients will develop a post operative infection. In most cases, this is a bad complication and does not bode well for eventual improvement or future employability. Reports from the surgical literature indicate an infection rate anywhere from 0% to almost 12%. The incidence of infection tends to increase as the complexity of the procedure and operating time increase. Usage of metal implants (instrumentation) tends to increase the risk of infection. Factors associated with an increased infection include diabetes mellitus, obesity, malnutrition, smoking, previous infection, rheumatoid arthritis, and immunodeficiency. Previous wound infection should be considered as a contraindication to any further spinal surgery, since the likelihood of improving such patients with more surgery is small. Antimicrobial prophylaxis (giving antibiotics during or after surgery before an infection begins) reduces the rate of surgical site infection in lumbar spine surgery, but a great deal of variation exists regarding its use. In a Japanese study, utilizing the Centers for Disease Control recommendations for antibiotic prophylaxis, an overall rate of 0.7% infection was noted, with a single dose antibiotic group having 0.4% infection rate and multiple dosage antibiotic infection rate of 0.8%. The authors had previously used prophylactic antibiotics for 5 to 7 postoperative days. Based on the Centers for Disease Control and Prevention guideline, their antibiotic prophylaxis was changed to the day of surgery only. It was concluded there was no statistical difference in the rate of infection between the two different antibiotic protocols. Based on the CDC guideline, a single dose