O2072: Surgery for Spinal Stenosis in Achondroplasia: Causes of Reoperation and Reduction of Risks

Background: Individuals with achondroplasia are prone to symptomatic spinal stenosis requiring surgery. Revision rates are thought to be high, however, the precise causes and rates of re-operation are unknown. The primary aim of this study was to investigate the causes that necessitate re-operation after the initial surgical intervention in individuals with achondroplasia and spinal stenosis. Additionally, we report on surgical techniques aimed at reducing the risks of these re-operations.

Methods: This was a retrospective review over an 8-year period of all patients with achondroplasia at a single institution that serves as a large referral center for patients with skeletal dysplasias. Patient demographics, surgical dates, indication for surgery and type of surgery were recorded. Type of surgery was placed into four categories: decompression only without fusion, decompression with a short fusion (T10 or below for the upper instrumented vertebrate [UIV]), decompression with a midlevel fusion (T7 – T9 as the UIV) and decompression with a long fusion (T2 – T4 as the UIV). Use of interbody fusion was also documented.

Results: In total, 148 patients were identified of which 33 underwent spinal surgery (22.2%) at a mean age of 17.6 years. 21 patients were included, 12 were excluded for lack of follow up or documentation. Sixteen revisions were performed on 9 patients (43%), 4 of whom required multiple revisions. Five (56%) of the revisions had primary surgery at an outside institution. 14 (67%) primary surgeries were done at our institution and 4 (29%) required revision. Some revisions were performed for multiple reasons. On average the time from initial surgery to revision was 1.9 years. The reasons for revisions included caudal pseudarthrosis (n=8), proximal junctional kyphosis (PJK) (n=7) and neurological symptoms (n=7).

Short fusions were more likely to development proximal junctional kyphosis with an odds ratio of 31.2 (p = 0.007, 95% CI 1.6 – 2479.6). Short fusions without a caudal interbody were also more likely to develop a caudal pseudoarthrosis when compared with long and mid-fusions without a caudal interbody (p = 0.044). Odds ratio could not be calculated as all the short fusions had a caudal pseudarthrosis.

Conclusion: In patients with achondroplasia, rate of surgery for spinal stenosis is 22% and the risk of revision is 43% and is primarily due to pseudarthrosis, PJK, and recurrent neurologic symptoms. Surgeons should consider discussing spinal surgery as part of the patient’s life plan and should consider wide decompression of the stenotic levels and fusion from T4-L4 with use of interbody cage at the caudal level in all patients to reduce risks of revision.