INTRODUCTION:
Osteoporotic vertebral fracture (OVF) is the most common fragility fracture and generally have a good prognosis. In conservative treatment of OVF, it has been reported that 9.8-19.6% develop nonunion or pseudoarthrosis, and these are main factor contributing to residual low back pain (LBP). However, the definition of pseudoarthrosis varies among previous reports, and many of them focused on static factor such as vertebral vacuum cleft. This study aimed to prospectively investigate the incidence of pseudarthrosis using our definition and its impact on clinical outcomes following conservative treatment of OVF.
METHODS:
This study is a prospective multicenter cohort study conducted in eight hospitals. The inclusion criteria as follow: 1) acute single OVF occurring within 3 weeks, 2) aged >60 years, and 3) follow-up period for 12-months. A total of 134 patients met the inclusion criteria with a mean age was 79.4±7.2 years. Patient characteristics, patient reported outcomes measures (PROMs), and radiographic findings (X-ray, CT, MRI) were evaluated at baseline, 3-months, and 12-months. The PROMs included a visual analogue scale (VAS) for low back pain (LBP), the Oswestry disability index (ODI), and the Japanese Orthopaedic Association back pain evaluation questionnaire (JOABPEQ). Conventional pseudarthrosis (CP group) was defined as the presence of intravertebral vacuum cleft on CT. CP group was divided into two groups, 1) unstable P (UP); vertebral kyphotic angle (VKA) of 3 degrees or more between sitting and supine positions, 2) stable P (SP) group; VKA less than 3 degrees and presence of bony bridge with adjacent vertebra. Continuous data with skewed distribution were analyzed using the Mann–Whitney U test after normality was assessed using the Shapiro–Wilk test. Fisher’s exact or chi-square tests were used to assess for categorical variables. PROMs at baseline and 12-months were compared using the Wilcoxon signed-rank test. Statistical analyses were performed using JMP version 15.
RESULTS:
The CP group was found in 18.7% (25 patients) at 12 months. UP group was found in 6.7% (9 patients). There was no significant difference in JOABPEQ (except for walking ability) between the CP and non-CP group. No significant difference was observed in VAS for LBP (30.1 vs 24.7, p=0.58) and ODI (32.2 vs 26, p=0.21) between the CP group and the non-CP group at 12 months. However, the UP group had significantly higher VAS for LBP (49.3 vs 23.8, p=0.03) and tended to be higher ODI (38.4 vs 27.9, p=0.17) than the non-UP group at 12-months (49.3 vs 23.8, p=0.03). In JOBPEQ, walking ability, and social life function at 12-months were significantly worse in the UP group than in the non-UP group. A logistic regression analysis revealed that high-signal change on T2WI was identified as an independent prognostic factor (odds ratio 11.5, 95% confidence interval 1.8-74.9, p=0.01) associated with UP.
DISCUSSION:
Conventional pseudoarthrosis was found in 18.7%, and unstable pseudoarthrosis evaluating vertebral instability and bony bridge was found in 6.7%. Unstable pseudoarthrosis demonstrates more clinical importance by PROMs than conventional pseudoarthrosis.