A prospective randomised controlled trial to assess the efficacy of dynamic stabilisation of the lumbar spine with the Wallis ligament.

PURPOSE: This prospective randomised control study is to demonstrate whether or not there is a clinical benefit from inserting a Wallis implant on the functional recovery of patients who have undergone lumbar decompression surgery.

METHOD: Sixty consecutive patients with an average age of 58 years (34-81) who were selected for primary lumbosacral decompression were randomly assigned into two groups with equal number of patients, decompression alone or decompression with Wallis implant. The patients had an average follow-up of 40 months. Patients were assessed by visual analogue scale (VAS) (Boonstra et al., Int J Rehabil Res 31:165-169, 2008; Price et al., Pain 17:45-56, 1983) pain score for back and leg pain, and the Oswestry Disability Index questionnaire (ODI) (Smeets et al., Arthritis Care Res (Hoboken) 63:S158-S173, 2011).

RESULTS: The results in both the groups did not reveal a significant difference in the clinical outcome assessment of back pain score or ODI. With the Wilcoxon two-sample test, no difference in median values was achieved (p value 0.0787 for ODI and p value 0.1926 for back pain). The average ODI in the Wallis group dropped from 50.93 to 29.11. The average VAS for the Wallis group back pain dropped from 7.79 to 4.22.

CONCLUSION: The Wallis implant is a safe medical device. This study revealed a reduction in pain and functional disability in patients treated with decompression surgery for lumbar stenosis, with or without Wallis. The Wallis group improved more, but it was not statistically significant. The risk of complications is lower than other interspinous devices.