60. Surgery for spinal stenosis in achondroplasia: causes of reoperation and reduction of risks

BACKGROUND CONTEXT

Individuals with achondroplasia are prone to symptomatic spinal stenosis requiring surgery. However, the optimal surgical management remains unknown. There is no data on the revision rate or causes of revision in patients with achondroplasia who have undergone previous spine surgery.

PURPOSE

The purpose of this study was to review the patients with achondroplasia who have undergone surgery for spinal stenosis to determine the rate of revision, review the causes of revision and determine if spinal construct was related to the need for revision.

STUDY DESIGN/SETTING

A retrospective review was conducted 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 SAMPLE

Thirty-three surgeries from 130 patients.

OUTCOME MEASURES

Type of surgery was placed into four categories: decompression only without fusion, decompression with a short fusion (T10 or distal for the upper instrumented vertebra [UIV])(short fusion) decompression with a long fusion (T9 or proximal as the UIV) (long fusion) and decompression with a long fusion and interbody caudally (interbody). Need for revision (binary), cause of the revision (proximal junctional kyphosis, pseudarthrosis and symptomatic stenosis/recurrence of stenosis) and previous revision (binary) were also documented

METHODS

Patient demographics, surgical dates, indications for surgery and type of surgery were recorded. Descriptive statistics were calculated. Statistical analysis was performed using R (R Core Team 2022, Vienna, Austria.). Fisher's exact test was used to determine if an association existed between construct type and need for revision as well as revision causes. Pairwise comparisons were again performed using Fisher's Exact test but with a Bonferroni correction. Multivariate logistic regression was performed to determine if any of the construct types could predict the need for revision and/or cause of revision. Odds ratios were calculated based on significant findings in the Fisher's Exact test and logistic regression coefficients. Significance was set at p < 0.05.

RESULTS

Thirty-three of the 130 (21.5%) patients with achondroplasia required spinal stenosis surgery. Twenty-four individuals who met the criteria were selected for analysis. The initial spine surgery was at an average age of 18.7 years (SD 10.1 years). Nine patients (37.5%) required revision surgeries, 3 required multiple revisions. Five of 9 (55.6%) of the revisions had primary surgery at an outside institution. Revision surgeries were due to caudal pseudarthrosis (8), proximal junctional kyphosis (PJK) (7), and new neurological symptoms (7). Short fusions (T10 or distal) had a significantly higher likelihood of developing proximal junctional kyphosis, with an odds ratio of 31.2 (p = 0.007, 95% CI 1.6-2479.6). Additionally, short fusions without a caudal interbody were more likely to develop caudal pseudarthrosis when compared to long without a caudal interbody (p = 0.044). To date, none of the initial cases that had long fusions with caudal interbody required a revision for distal pseudarthrosis.

CONCLUSIONS

In patients with achondroplasia, rate of surgery for spinal stenosis is 21.5% and the risk of revision is 37.5% 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 long fusion with use of interbody cage at the caudal level in all patients to reduce risks of revision.

FDA Device/Drug Status

This abstract does not discuss or include any applicable devices or drugs.