Anatomic Reduction and Monosegmental Fusion in the Treatment of Severe Developmental Spondylolisthesis

Introduction: The choice of surgical techniques for the treatment of severe developmental spondylolisthesis remains controversial. Fusion in situ is recommended by many authors. Despite reports of good clinical results, the pseudarthrosis rate is high. In addition, progression of deformity of already consolidated fusion masses and even neurologic compromise as late sequel have been described. To overcome these disadvantages partial reduction and fusion was performed. The purpose of the current study was to review a series of almost complete reduction of severe developmental L5/S1 spondylolistheses (Meyerding 3 to 5). The operative technique comprised reduction by temporary instrumentation of L4 and monosegmental fusion.

Material and Methods: 27 patients were operated upon between 1997 and 2001. Mean age at time of surgery was 16.7 years (range 9 to 29 years). Reduction was performed using temporary instrumentation of L4. Intersomatic fusion of L5/S1 was achieved either by an anterior approach or by a TLIF procedure. Mean follow-up time was 3.8 years (2.0 to 6.8 yrs.). Radiographic measurements were taken from radiographs of the entire spine in a standing position. Clinical outcome was evaluated by the SRS 30 outcome score.

Results: Slippage averaged 74% preoperatively (range, 50 to 100%) and was corrected to 10% (0 to 23%). Sacral inclination: 35° (3 to 57°) preop., 47° (28 to 63°) postop. Slip angle: 37° (12 to 75°) preop., 8° (-14 to 27°) postop. Segmental kyphosis/lordosis L5/S1: 20° (-8 to 61°) preop., -9° (-26 to 18°) postop. Pelvic incidence was 72° (47 to 89°). L5-incidence improved from 70° (34 to 113°) to 50° (24 to 81°). There were no pseudarthrosis. One patient had a superficial wound infection. Six patients developed L 5 root lesions. Five of these completely resolved, but one remained sensory symptomatic at latest follow up. Decompensation of the L4/5 level occurred in two patients and lead to fusion of this level.

Discussion: Anatomic reduction with monosegmental fusion allows for normalization of the complex impairment of the sagittal profile in developmental spondylolisthesis. The local deformity, mainly the anterior dislocation of L5 and the lumbosacral kyphosis, are corrected with a minimum of functional restriction. Thus, the overall sagittal profile of the spine is restored.