Effects of vertebroplasty on endplate subsidence in elderly female spines

Abstract

<jats:sec> <jats:title>OBJECT</jats:title> <jats:p>The aim in this study was to quantify the effects of vertebroplasty on endplate subsidence in treated and adjacent vertebrae and their relationship to endplate thickness and underlying trabecular bone in elderly female spines.</jats:p></jats:sec> <jats:sec> <jats:title>METHODS</jats:title> <jats:p>Vertebral compression fractures were created in female cadaveric (age range 51–88 years) thoracolumbar spine segments. Specimens were placed into either the control or vertebroplasty group (n = 9/group) such that bone mineral density, trabecular microarchitecture, and age were statistically similar between groups. For the vertebroplasty group, polymethylmethacrylate bone cement was injected into the fractured vertebral body under fluoroscopy. Cyclic compression (685–1370 N sinusoid) was performed on all spine segments for 115,000 cycles. Micro-CT scans were obtained before and after cyclic loading to quantify endplate subsidence. Maximum subsidence was compared between groups in the caudal endplate of the superior adjacent vertebra (SV<jats:sub>cau</jats:sub>); cranial (TV<jats:sub>cra</jats:sub>) and caudal (TV<jats:sub>cau</jats:sub>) endplates of the treated vertebra; and the cranial endplate of the inferior adjacent vertebra (IV<jats:sub>cra</jats:sub>). In addition, micro-CT images were used to quantify average endplate thickness and trabecular bone volume fraction. These parameters were then correlated with maximum endplate subsidence for each endplate.</jats:p></jats:sec> <jats:sec> <jats:title>RESULTS</jats:title> <jats:p>The maximum subsidence in SV<jats:sub>cau</jats:sub> endplate for the vertebroplasty group (0.34 ± 0.58 mm) was significantly (p &lt; 0.05) greater than for the control group (−0.13 ± 0.27 mm). Maximum subsidence in the TV<jats:sub>cra</jats:sub>, TV<jats:sub>cau</jats:sub>, and IV<jats:sub>cra</jats:sub> endplates were greater in the vertebroplasty group, but these differences were not significant (p &gt; 0.16). Increased subsidence in the vertebroplasty group manifested locally in the anterior region of the SV<jats:sub>cau</jats:sub> endplate and in the posterior region of the TV<jats:sub>cra</jats:sub> and TV<jats:sub>cau</jats:sub> endplates (p &lt; 0.10). Increased subsidence was observed in thinner endplates with lower trabecular bone volume fraction for both vertebroplasty and control groups (R<jats:sup>2</jats:sup> correlation up to 62%). In the SV<jats:sub>cau</jats:sub> endplate specifically, these 2 covariates aided in understanding subsidence differences between vertebroplasty and control groups.</jats:p></jats:sec> <jats:sec> <jats:title>CONCLUSIONS</jats:title> <jats:p>Bone cement injected during vertebroplasty alters local biomechanics in elderly female spines, resulting in increased endplate disruption in treated and superior adjacent vertebrae. More specifically, bone cement increases subsidence in the posterior regions of the treated endplates and the anterior region of the superior caudal endplate. This increased subsidence may be the initial mechanism leading to subsequent compression fractures after vertebroplasty, particularly in vertebrae superior to the treated level.</jats:p></jats:sec>

Cement injection and postoperative vertebral fractures during vertebroplasty

“…Vertebroplasty is commonly used to treat OVCF because it is simple, offers little trauma, and affords pain relief [10, 11]. Multiple studies of adjacent vertebral fractures in patients undergoing vertebroplasty indicate that bone cement volume contributes to refracture risk [7, 12–14]. Kwon’s group reported [8] that as much bone cement as possible should be used to treat OVCF, and the volume of the vertebral body exceeds 27.8% of the transfusion volume, recovery is optimal.…”

“…These studies do not consider the long-term consequences and subsequent adjacent vertebral fractures. Excessive injection of bone cement increases the stiffness of the vertebral body, which can cause fracture and increase the risk of bone cement leakage [7, 17].…”

“…However, some patients have immediate post-operative fractures of the adjacent vertebral body, and this is undesirable [2–5]. It is likely that the distribution of cement and the injection volume cause vertebral stiffness, which can cause refractures [6, 7].…”

“…Current data suggest that bone cement injection volume and pain relief were positively correlated, so cement volumes exceeding the vertebral body volume were used for 27.8% of treated patients [8]. However, we now know that excessive bone cement volumes can increase the risk of bone cement leakage and increase vertebral body stiffness, causing adjacent vertebral fractures [7, 9]. Therefore, the bone cement injection volume should be optimized.…”

Gradual Height Decrease of Augmented Vertebrae after Vertebroplasty at the Thoracolumbar Junction

“… 16) Cemented vertebrae had a lower elastic modulus, but there was no significant effect on the frequency or severity of an induced fracture within the vertebrae. 15) Pneumaticos et al 18) reported that there is no difference in the compressive load of failure between augmented and non-augmented fractured vertebrae. These mechanisms may induce recollapse of augmented vertebrae as well as non-augmented fractured vertebrae.…”