Improvement in functional gait parameters following corrective thoracolumbar surgery in children affected by Mucopolysaccharidosis 1 (Hurler syndrome)

Abstract

Objective: Thoracolumbar kyphosis is a common indication for spinal surgery in children with Mucopolysaccharidosis. Functional outcome of spinal surgical intervention has never been published in patients with this rare disease. We present a cohort of patients with Mucopolysaccharidosis 1(Hurler syndrome) who underwent thoraco-lumbar spinal deformity correction and functional outcome assessed by pre-operative and post-operative gait analysis. This study represents the first attempt at presenting a functional assessment of surgical outcome in any Mucopolysaccharidosis subtype.

Methods: A retrospective analysis of prospectively collected data was carried out from 11 children diagnosed with this subtype of Mucopolysaccharidosis. All patients underwent thoracolumbar kyphosis correction between the years 2013 to 2016. Gait assessment was performed using GAITRite™ electronic walkway pre-operatively and post-operatively within 9 to 24 months from the index surgery. Walking distance, cadence and gait velocity were the three spatio-temporal parameters analysed. Wilcoxon signed rank test was used to analyse the data and P-Value ≤0.05 was deemed significant.

Results: There was a statistically significant improvement in walking distance in 9 out of 11 patient post-operatively with a mean increase of 232.06 cms (P = 0.05). There was marginal improvement in cadence by 6.33 steps/min post-operatively (P-value 0.79). Gait velocity also showed a marginal increase by 8.73 cms/sec post-operatively (P-value 0.32).

Conclusion: The results of our study suggest that correction of thoracolumbar kyphosis in children with Mucopolysaccharidosis 1 resulted in a significant improvement of walking distance with a trend towards improved gait in the other parameters. Post-operative change in cadence was not statistically significant suggesting that physiological maturation of gait had minimal effect in the specified post-operative assessment timeframe. This study emphasizes that outcomes of spinal surgery in children with Mucopolysaccharidosis 1 should be determined by functional measures aiming to maintain or improve quality of life.

Keywords: Functional outcome; Gait; Kyphosis; Mucopolysaccharidosis 1; Spinal surgery.

Fig. 1

Pre-operative radiograph of thoracolumbar spine showing high lumbar kyphosis- Lateral view

Fig. 2

Post-operative radiograph of the same patient after correction of thoracolumbar kyphosis- Lateral view

Fig. 3

Identification of quadrilaterals, midline of foot and the line of progression using the walkway- Image reproduced with permission from CIR Systems, Inc. GAITRite Electronic walkway technical reference (WI-02-15. Rev. L 5/6/2013)

Fig. 4

Box and Whisker plot comparing pre-operative and post-operative walking distance (cms)

Fig. 5

Box and Whisker plot comparing pre-operative and post-operative cadence (steps/min) and gait velocity (cms/sec)