Aperius interspinous implant versus open surgical decompression in lumbar spinal stenosis

Background context: Few studies have analyzed the results of an interspinous distraction device in patients with lumbar spinal stenosis. It is still unknown whether the outcomes of an interspinous implant are related to the severity of stenosis.

Purpose: To determine the success rate of the Aperius implant and open decompression with the aim of defining better the indications for the two modalities of treatment.

Study design: Comparison of two cohorts of patients with moderate or severe stenosis treated with the Aperius or by open decompression.

Patient sample: The sample comprises 36 patients who had the Aperius implant and 35 who underwent open decompression, both groups followed prospectively. In the two cohorts, central or lateral stenosis was present in similar proportions, and in both, the patients had pure intermittent claudication or symptoms at rest and on walking. In both groups, preoperative diagnosis was made by magnetic resonance imaging (MRI).

Outcome measures: Patients of both groups were evaluated with the Zurich Claudication Questionnaire (ZCQ) and Oswestry Disability Index. The results were rated as good or poor based on the ZCQ.

Methods: The patients of both cohorts were evaluated at 1 month and 3, 6, and 12 months after operation, the final follow-up being carried out at least 2 years after surgery. Severity of stenosis was determined based on preoperative MRI scans. In 17 patients of the Aperius group, MRI studies were repeated at the 6-month or final follow-up and compared with the preoperative studies.

Results: Of the patients in the Aperius group, six had removal of the implant and open surgical decompression at 2 to 17 months after operation; these patients were considered to have a poor result. At the final follow-up, the result was rated as good in 47% of all patients who had had the Aperius implant. The percentage of good outcomes was 60% in moderate stenosis and 31% in severe stenosis. When considering all not reoperated patients, 57% had good outcomes; however, if only the scores in the patient satisfaction domain of the ZCQ were considered, 67% of these patients were somewhat satisfied with the result of Aperius. No significant relationship was found between patients with pure intermittent claudication and those with leg symptoms also at rest. In 71% of cases in which preoperative and postoperative MRIs were compared, no significant change in size of the spinal canal was found after operation, whereas in the remaining patients a slight increase in size of the canal was detected. In the open decompression cohort, the results were good in 80% of cases and poor in 20%. The outcomes were satisfactory in 69% of moderate stenosis, with no significant difference with the similar subgroup of the Aperius series. In severe stenosis, the 89% rate of good results was significantly higher than in the severe Aperius subgroup (p<.0001).

Conclusions: The Aperius interspinous implant is poorly indicated for severe lumbar stenosis, which is significantly improved only in a small minority of cases, whereas decompression procedures ensure high chances of good results. The implant may be indicated for selected patients with moderate stenosis. The outcomes of the Aperius are not influenced by the type of clinical presentation of lumbar stenosis.