Abstract
Introduction
The diagnosis, disease severity and outcome assessment of spinal claudication depend on patient's subjective report. In the past, the gold standard for diagnosing and screening for troubling spinal claudication was lacking. Quantify severity of claudication by standing and walking tolerance test used to be the best measure but was tedious. Simple quantitative test is lacking. The present study uses 6-minute walk test (6MWT) to solve these problems.
Material and Methods
Patients suspicious of spinal claudication were prospectively tested on standing and walking ability. Time when symptom becomes intolerable constituted the tolerance time. They were tested on distance (6MWD) they can maximally walk on level ground in shuttle between a 15m-distance in 6 minute; and screened for standing and walking instability with Tinetti score. Patients underwent surgery were monitored. The study was conducted in 2 stages. The first stage is a pilot study on a small group of patients which aim to establish the correlation among the different tests modality; standing tolerance test, walking tolerance test, 6 minute walk test, tinetti gait and balance test. After the best correlated tests modalities were found, the study was modified. The standing tolerance test and the 6 minute walk test were performed on a larger group of patients to generate sizable database.
Results
Since 2004, 1182 patients were included. The age-matched 6MWD correlate with 20 minute standing tolerance well with sensitivity and specificity above 0.7. Using ROC curve, 6MWD that distinguish 20 minute claudication tolerance are: 392m (age: 41–50); 377m (age: 51–60); 330m (age: 61–70); 267m (age: 71–80); 236m (age: 81–90). These findings agreed with the findings of another study on the reference values of 6MWD for normal Chinese subjects. That study showed that the minimal value of 6MWD for normal Chinese adults of different age groups was 330m. For those who underwent surgery, their standing and walking tolerance significantly improved in first 3 months but not later. The balance and gait score improved significantly only after 3 months post-operatively. The 6MWD increased significantly at both 3 and 6 months post-operatively, implying that 6MWD is more sensitive in picking up changes.
Conclusion
6-minute walk test is a simple, practical method in screening for spinal claudication. The age matched 6MWD for incapacitating claudication was found. The 6-minute walk test also provides useful quantitative data for disease progression and treatment outcome monitoring. In the present study, we were able to demonstrate that 6MWD increased significantly at 3 months post-operative period comparing to pre-operative status and at 6 months post-op comparing to 3 months post-op period. The improvement of 6MWD was a reflection of improvement of walking tolerance and standing tolerance since both tolerance time increased significantly at 3 months after surgery. The improvement from 3 months to 6 months post-op was on the other hand a reflection of the improvement in gait pattern and balance ability instead, since only the 6MWD, Tinetti balance and gait score improved significantly during this period.