Risk Factors of Nonunion After Acute Osteoporotic Vertebral Fractures

A Prospective Multicenter Cohort Study

Hiroyuki Inose, MD, PhD; Tsuyoshi Kato, MD, PhD; Shoichi Ichimura, MD, PhD; Hiroaki Nakamura, MD, PhD; Masatoshi Hoshino, MD, PhD; Daisuke Togawa, MD, PhD; Toru Hirano, MD, PhD; Yasuaki Tokuhashi, MD, PhD; Tetsuro Ohba, MD, PhD; Hirotaka Haro, MD, PhD; Takashi Tsuji, MD, PhD; Kimiaki Sato, MD, PhD; Yutaka Sasao, MD, PhD; Masahiko Takahata, MD, PhD; Koji Otani, MD, DMSc; Suketaka Momoshima, MD, PhD; Masato Yuasa, MD, PhD; Takashi Hirai, MD, PhD; Toshitaka Yoshii, MD, PhD; Atsushi Okawa, MD, PhD

Disclosures

Spine. 2020;45(13):895-902. 

In This Article

Abstract and Introduction

Abstract

Study Design: Prospective cohort study.

Objective: To characterize a patient population with nonunion after acute osteoporotic vertebral fractures (OVFs) and compare the union and nonunion groups to identify risk factors for nonunion.

Summary of Background Data: While OVFs are the most common type of osteoporotic fracture, the predictive value of a clinical assessment for nonunion at 48 weeks after OVF has not been extensively studied.

Methods: This prospective multicenter cohort study included female patients aged 65 to 85 years with acute one-level osteoporotic compression fractures. In the radiographic analysis, the anterior vertebral body compression percentage was measured at 0, 12, and 48 weeks. Magnetic resonance imaging (MRI) was performed at enrollment and at 48 weeks to confirm the diagnosis and union status. The patient-reported outcome measures included scores on the European Quality of Life-5 Dimensions (EQ-5D), a visual analogue scale for low back pain, and the Japanese Orthopaedic Association Back Pain Evaluation Questionnaire (JOABPEQ) at 0, 12, and 48 weeks.

Results: In total, 166 patients completed the 12-month follow-up, 29 of whom had nonunion. Patients with nonunion at 48 weeks after OVF had lower EQ-5D and JOABPEQ walking ability, social life function, mental health, and lumbar function scores than those with union at 48 weeks after injury. The independent risk factors for nonunion after OVF in the acute phase were a diffuse low type pattern on T1-weighted MRI and diffuse low and fluid type patterns on T2-weighted MRI. The anterior vertebral body compression percentage and JOABPEQ social life function scores were independent risk factors at 12 weeks.

Conclusion: A diffuse low type pattern on T1-weighted MRI and diffuse low and fluid type patterns on T2-weighted MRI were independent risk factors for nonunion in the acute phase. Patients who have acute OVFs with these risk factors should be carefully monitored for nonunion.

Level of Evidence: 2

Introduction

Because vertebral fractures are the most common type of osteoporotic fracture, the number of osteoporotic vertebral fractures (OVFs) increases as the population ages. Indeed, the Rotterdam study showed that while the incidence of vertebral fractures was 7.8/1000 person-years at ages 55 to 65 years, the incidence increased to 19.6/1000 person-years at ages of 75 years or older for women.[1] In the acute stage, OVFs cause severe back pain, disabilities in activities of daily living, and deterioration of the quality of life (QOL). For most patients with OVFs, pain levels and QOL gradually improve as bony union is achieved.[2] However, if bony union fails, continuous lower back pain, deterioration of QOL, and even neurological deficits attributable to nerve compression can occur.[3] Accordingly, operative interventions such as vertebroplasty, spinal decompression, and instrumentation surgery are performed for patients with such nonunions to reduce back pain and the risk of developing further spinal deformities. However, these procedures have disadvantages of procedural complications and may increase the risk of fracture in the adjacent vertebrae.[4] Moreover, while some reports have shown the usefulness of radiological findings for predicting delayed union (3–6 mo after injury),[3,5,6] there are few reports that have investigated the risk factors for nonunion (48 wks or longer after injury). Therefore, improved identification methods for patients at high risk of nonunion after OVF are needed so that preventive measures can be implemented to decrease the incidence of this complication.

The purpose of this prospective multicenter study was to characterize a patient population with nonunion after acute OVFs and to compare the union and nonunion groups to identify risk factors associated with nonunion, with a focus on patient-reported outcome measures and radiographic assessments to identify cut-off values for these risk factors.

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