Purpose of the study: The aim of this prospective clinical study was to assess outcome after anterior retroperitoneal interbody arthrodesis for L5-S1 discopathy. We used a cage filled with an autologous corticocancellous graft and plate fixation.
Materials and methods: Forty patients with low back pain unresponsive to medical treatment for more than six months were included in this series. We noted the clinical signs and radiculalgia. Patients were assessed preoperatively, postoperatively, at one year and at last follow-up using the Oswestry score and a visual analog scale (VAS). The plain X-rays disclosed 30 cases of discopathy (16 primary and 14 postdiscectomy) and 10 cases of spondylolisthesis by L5 isthmic lysis (three Meyerding grade 0 and seven grade 1). MRI revealed signs of disc degeneration in all cases with a black disc or modification of the endplate signals (Modic type 1 in 23 and type 2 in 13). The anterior retroperitoneal approach was used in all cases for complete discectomy, arthrodesis with cage insertion and an autologous corticocancellous graft harvested from the iliac bone and fixation using a triangular plate (Pyramid, Medtronic, Memphis TN). Clinical and radiographic follow-up data were available at six weeks and three, six and 12 months in addition to last follow-up. A follow-up using MRI was performed in the event of complications.
Results: The population was composed of 25 women and 15 men, mean age 44 years and eight months (range 29-693 years). Thirteen patients presented radiculalgia. There were no vascular or gastrointestinal complications with the anterior approach. Bone healing was achieved at one year in 38 patients (95%). The mean Oswestry score improved from 52 to 16% and the mean VAS from 7.8 to 1.83 at 18 months follow-up. All occupationally-active patients but one resumed their former activity at mean 4.7 months. There were no sexual complications in this series. Low back pain persisted in three patients and five developed transient facet joint symptoms. Two patients developed secondary radiculalgia. We noted two cases of nonunion, in one grade 1 spondylolisthesis and in one grade 1 spondlylolisthesis (with revision for complementary posterior arthrodesis and a good outcome at latest follow-up).
Discussion and conclusion: Anterior L5-S1 interbody fusion with a cage filled with a corticocancellous autograft fixed with a plate provides good clinical and radiographic results for the stabilization of painful discopathy. The results have been good for isolated L5-S1 discopathy and for grade 0 spondylolisthesis. The limit for this technique would appear to be grade 1 spondylolisthesis with a degraded disc. Performed via an anterior retroperitoneal approach, this method is a good alternative to the classical posterior approach, enabling very low morbidity.