Surgical Management of Spinal Deformities in Neurofibromatosis: A Correlation Between Modulation and Surgical Outcome

Children's Hospital Medical Center, Cincinnati, OH, USA

PURPOSE:
To critically analyze the influence of modulation of the outcome of surgical management of spinal deformities in NF1 and evaluate the effect of various dystrophic radiographic features.

MATERIALS & METHODS:
Clinical records, operative data and radiographic were reviewed on 39 patients (21 males 18 females) with Neurofibromatosis-1 who underwent a spinal fusion at our institutions between 1991 to 1996. The mean follow-up was 59 months. Deformities were categorized as either non dystrophic (n=9) when no radiographic dystrophic features were present, modulated (n=21) when a deformity acquired dystrophic features and dystrophic (n=9) when there were 3 or more dystrophic features present at the time of presentation. Nine radiographic features including vertebral wedging (n=18), vertebral rotation (n=12), lateral vertebral scalloping (n=1), spindled transverse processes (n=7), wide interpedicular distances (n=8), wide intervetebral foramina (n=5) and rib penciling n=28) were recorded to determine their influence on the surgical outcome. Spinal neurofibromas were present in 29 patients in this series. 11 patients underwent only a posterior spinal fusion while 28 patients had both anterior & posterior spinal fusion done. Exact Wilcoxon rank sum and Kruskal Walis rank sum tests were performed for statistical analysis.

RESULTS:
The mean preoperative deformity measured 68° for the non-dystrophic group, 75º for the modulators and 76º for the dystrophic group. Postoperatively the deformity measured at a mean of 43º for the non-dystrophic group, 48º for the modulators and 46º for the dystrophic group. At the final follow-up the mean deformity measured 49º in the non-dystrophic group, 62º for the modulators and 53º for the dystrophic variety (p=0.9). Five patients developed pseudoarthrosis in our series, 4 were modulators and one in the non dystrophic group. The Exact Wilcoxon rank sum test to determine the influence of dystrophic radiographic features on the surgical outcome failed to reach statistical significance for any of the above mentioned features individually. Presence of a spinal neurofibroma also failed to influence the surgical outcome by Exact Wilcoxon rank tests (p=0.961). Penciling of three ribs did significantly influence the outcome (p=0.015).

CONCLUSION:
Our results suggest that modulated deformities share the same risk of postoperative loss of correction following spinal fusion as seen in the dystrophic deformities. An increased incidence of pseudarthrosis was observed in the deformities showing modulation.