# A novel image-based classification system for atlantoaxial deformity caused by mucopolysaccharidosis type IVA: an efficacy evaluation

## TL;DR

This paper introduces a new classification system for spinal deformities in a rare genetic disorder, showing it is reliable and useful for guiding treatment.

## Contribution

A novel classification system for atlantoaxial deformities in type IVA mucopolysaccharidosis with validated reliability and clinical utility.

## Key findings

- The new classification system showed high inter- and intra-observer agreement (k-values of 0.773 and 0.792).
- Surgical plans based on the classification were effective and safe, with high fusion success rates and minimal complications.

## Abstract

Retrospective Study.

Type IVA mucopolysaccharidosis (MPS) is often associated with atlantoaxial deformity, and lacks a unified surgical treatment standard or classification system. We examined the value and clinical applicability of a new classification system for atlantoaxial deformities caused by type IVA MPS.

In this single-center retrospective clinical study, we analyzed 85 patients with type IVA MPS admitted between 2018 and 2022. Using the new classification system, the patients were classified as MPS A, B, C, and D according to pathological and imaging characteristics. Intra- and interobserver consistency tests were conducted by 10 independent observers. Subsequent clinical treatment was guided by the new classification system. Demographic, surgical, and clinical data were collected.

Thirty-nine patients with MPS A, fifteen with MPS B, seven with MPS C, and twenty-four with MPS D were included. The inter- and intra-observer k-values were 0.773 and 0.792, respectively. During the study period, seven patients with MPS A converted to MPS D, and five underwent subsequent surgery. Two patients with MPS B converted to MPS D and underwent surgery. Two patients with MPS C underwent atlantoaxial reduction and fusion fixation, and one underwent simple posterior arch resection of the atlas. Among 33 patients who underwent posterior atlantoaxial reduction and fusion fixation, 32 achieved bone fusion. Short-term complications comprised 1 case of mortality, 1 case of postoperative airway obstruction, 1 case of pain at the iliac bone graft donor site, and 2 cases of delayed wound healing. During the long-term follow-up period, no serious surgical complications have been observed to date, and the mADI value and ASIA scores of all patients improved to varying degrees.

The new classification system has a high reliability and clinical guidance value for diagnosis and treatment planning. The surgical plans adopted based on this diagnostic classification were effective and safe.