Failure of the Wallis interspinous implant to lower the incidence of recurrent lumbar disc herniations in patients undergoing primary disc excision

Background: Ipsilateral recurrent disc herniation after lumbar discectomy is a significant problem in the management of lumbar disc disease and may necessitate repeat surgical intervention. A population-based study in Finland found that about 14% of all primary lumbar discectomies required additional surgical interventions. Interspinous devices, which have been shown to unload the posterior anulus, may reduce the Occurrence of recurrent herniations. We report our short-term experience with the use of the Wallis device in the management of patients with lumbar disc herniation undergoing primary disc excision. Patients and Methods: Thirty-seven consecutive patients (23 males and 14 females, average age 36y) underwent primary lumbar disc excision followed by fixation of the segment with the Wallis implant during a period of I year. Indications for implanting the Wallis device were a Voluminous disc herniation and preservation of at least 50% of disc space height. Surgery was performed at level L4-5 in most patients. Average follow-up after Surgery was 16 months (range 12 to 24). The last 14 patients were also evaluated by the preoperative and postoperative Oswestry Disability Index (ODI) questionnaire, the SF-36 Survey, and by a visual analog scale (VAS) for back and leg pain. Results: The average ODI dropped from 43 to 12.7. The average VAS for back pain dropped from 6.6 tol.4 and the average Vas for leg pain dropped from 8.2 to 1.5. Five patients (4 males and I female) with relapsing leg pain were diagnosed by contrast-enhanced magnetic resonance imaging as suffering from recurrent herniation (5/37, 13%). All reherniations occurred at level L4-5 level between I and 9 months after the index surgery. Two of the 5 patients Subsequently underwent additional discectomy and fusion. Summary: The current Wallis implant is probably incapable of reducing the incidence of recurrent herniations, but it still may be useful in patients with discogenic back pain due to early degenerative disc disease.