Mid-Thoracic Vertebral Compression Fracture after Mini-Trampoline Exercise: A Case Series of Seven Patients

Abstract

Background and Objectives: Home-based training exercise gained popularity during the coronavirus disease 2019 pandemic era. Mini-trampoline exercise (MTE) is a home-based exercise that utilizes rebound force generated from the trampoline net and the motion of the joints of the lower extremities. It is known to be beneficial for improving postural balance, stability, muscle strength and coordination, bone strength, and overall health. However, we encountered several patients with mid-thoracic vertebral compression fractures (VCFs) following regular MTE, which was never reported previously, despite having no history of definite trauma. This study aims to report mid-thoracic VCFs after regular MTE and arouse public attention regarding this spinal injury and the necessity of appropriate prior instructions about the correct posture. Patients and Methods: All consecutive patients diagnosed with acute VCFs following regular MTE were included. We collected data on patient demographics, history of MTE, characteristics of symptoms, and radiological findings such as the location of fractures and anterior vertebral body compression percentage. Results: Seven patients (one man and six women) and ten fractures (T5 = 1, T6 = 3, T7 = 2, and T8 = 4) were identified. Symptoms started 2.57 ± 1.13 weeks after the beginning of regular MTE. All patients reported that they were never properly instructed on the correct posture. They also stated that they were exercising with a hunchback posture and insufficient joint motion of the lower extremities while holding the safety bar with both hands, which resulted in increased peak vertical force along the gravity z-axis in the mid-thoracic area and consequent mid-thoracic VCFs. Conclusions: Mid-thoracic VCFs can occur following regular MTE even without high-energy trauma in case of improper posture during exercise. Therefore, public attention on mid-thoracic VCFs following MTE and the appropriate prior instructions are imperative.

Keywords: case series; compression fracture; mini-trampoline; thoracic vertebrae.

Figure 1

The calculation of anterior vertebral body compression percentage (AVCP). H₁ represents the anterior vertebral body height (AVH) of the above vertebra. H, AVH of the index vertebra. H₂, AVH of the below vertebra. AVCP = 100 ∗ [(H₁ + H₂)/2 − H]/(H₁ + H₂)/2.

Figure 2

The 65-year-old (Patient 1) and 63-year-old (Patient 2) female patients diagnosed with acute mid-thoracic vertebral compression fracture (VCF) following mini-trampoline exercise (MTE). (A) Sagittal fat suppression T2-weighted MR image of Patient 1 showing VCF with bone marrow edema involving T8 (white arrowhead). (B) Sagittal fat suppression T2-weighted MR image of Patient 2 showing VCF with bone marrow edema involving T6 (white arrow). (C,D) The last follow-up X-ray showing well-maintained vertebral bodies without significant height loss (black arrowhead).

Figure 3

A 53-year-old (Patient 6) female patient diagnosed with acute T6 and T7 vertebral compression fracture (VCF) following mini-trampoline exercise (MTE). (A) Sagittal fat suppression T2-weighted MR image showing VCF with bone marrow edema involving T6 and T7 (white arrowheads). (B) The last follow-up X-ray showing well-maintained vertebral bodies without significant height loss (black arrowheads).

Figure 4

(A) Mini-trampoline exercise (MTE) with sufficient joint motion of the lower extremities and maintaining spinal angle. (B) MTE with insufficient joint motion of the lower extremities and a hunchback posture.

Figure 5

Schematic representation of the gravity z-axis (Gz) force on the inclined vertebrae being decomposed into shearing (Fs) and compressive (Fc) forces, resulting in a vertebral compression fracture.