Lumbar interspinous spacers: a systematic review of clinical and biomechanical evidence.

STUDY DESIGN Systematic review. OBJECTIVE To evaluate the current biomechanical and clinical evidence available on the use and effectiveness of lumbar interspinous devices and to recommend indications for their use. SUMMARY OF BACKGROUND DATA Lumbar interspinous spacers (ISPs) have recently become popular as an alternative treatment for lumbar degenerative disease. Several spacers are currently available in the market and there have been various proposed indications. The relevant biomechanical and clinical papers are analyzed. METHODS A systematic review of clinical and biomechanical studies was done using the following key words: interspinous implants, interspinous devices, interspinous spacers, dynamic stabilization, X-STOP, Coflex, Wallis, DIAM. The database inclusions were MEDLINE, CINAHL (Cumulative Index to Nursing and Allied Health Literature), and PubMed. The main outcome measure was clinical outcome assessment based on validated patient-related questionnaires. Biomechanical studies were analyzed to evaluate the effects of ISPs on the kinematics of the spine. The methodology of the clinical studies was also analyzed. RESULTS Largest number of studies has been with the X-STOP device. The biomechanical studies with all the devices showed that ISPs have a beneficial effect on the kinematics of the degenerative spine. Apart from 2 randomized controlled trials, the other studies with the X-STOP device were not of high methodologic quality. Nevertheless, analysis of these studies showed that X-STOP may improve outcome when compared to nonoperative treatment in select group of patients aged 50 or over, with radiologically confirmed lumbar canal stenosis and neurogenic claudication, who have improvement of their symptoms in flexion. Studies on the other devices show satisfactory outcome to varying degrees. However, due to small number and poor design of the studies, it is difficult to clearly define indications for their use in lumbar degenerative disease. CONCLUSION Lumbar ISPs may have a potential beneficial effect in select group of patients with degenerative disease of the lumbar spine. However, further good quality trials are needed to clearly outline the indications for their use.