Effect of size and location of simulated lytic lesions on the structural properties of human vertebral bodies, a micro-finite element study

Liu

BMC Musculoskelet Disord

et al. 2020

Background: Thoracolumbar burst fractures can be treated with posterior short-segment fixation. However, no classification can help to estimate whether the healed vertebral body will have sufficient stability after implant removal. We aimed to develop a Healing Pattern Classification (HPC) to evaluate the stability of the healed vertebra based on cavity size and location. Methods: Fifty-two thoracolumbar burst fracture patients treated with posterior short-segmental fixation without fusion and followed up for an average of 3.2 years were retrospectively studied. The HPC was divided into 4 types: type I-no cavity; type II-a small cavity with or without the violation of one endplate; type III-a large cavity with or without the violation of one endplate; and type IV-a burst cavity with the violation of both endplates or the lateral cortical shell. The intraobserver and interobserver intraclass correlation coefficients (ICCs) of the HPC were assessed. The demographic characteristics and clinical outcomes of the cohort were compared between the stable group (types I and II) and the unstable group (types III and IV). Logistic regression was conducted to evaluate risk factors for unstable healing. Results: The intraobserver and interobserver ICCs of the HPC were 0.86 (95% CI = 0.74-0.90) and 0.77 (95% CI = 0.59-0.86), respectively. While the unstable healing group (types III and IV) accounted for 59.6% of the patients, most of these patients were asymptomatic. The preoperative Load Sharing Classification (LSC) comminution score may predict the occurrence of unstable healing (OR = 8.4, 95% CI = 2.4-29.7). Conclusions: A reliable classification for assessing the stability of a healed vertebra was developed. With type I and II healing, the vertebra is considered stable, and the implant can be removed. With type III healing, the vertebra may have healing potential, but the implant should not be removed unless type II healing is achieved. With type IV healing, the vertebra is considered extremely unstable, and instrumentation should be maintained. Assessing the LSC comminution score preoperatively may help to predict unstable healing after surgery.

Section: Introductionmentioning

confidence: 92%

Section: Hpcmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Healing pattern classification for thoracolumbar burst fractures after posterior short-segment fixation

Liu

BMC Musculoskelet Disord

et al. 2020

“…The cut-off for a small/large cavity was set according to Costa et al's research, which suggests that a lytic lesion larger than approximately 1/3 of the vertebral body volume may have a significant impact on the structural properties of the vertebral body [16]. Therefore, vertebrae with HPC type I/II healing were considered stable, and those with HPC type III/IV healing were considered unstable.…”

Section: Hpcmentioning

confidence: 99%

Healing Pattern Classification for Thoracolumbar Burst Fractures after Posterior Short-segment Fixation

Liu

et al. 2020

Preprint

Background: Thoracolumbar burst fractures can be treated with posterior short-segment fixation. However, no classification can help to estimate whether the healed vertebral body will have sufficient stability after implant removal. We aimed to develop a Healing Pattern Classification (HPC) to evaluate the stability of the healed vertebra based on cavity size and location.Methods: Fifty-two thoracolumbar burst fracture patients treated with posterior short-segmental fixation without fusion and followed up for an average of 3.2 years were retrospectively studied. The HPC was divided into 4 types: type I - no cavity; type II - a small cavity with or without the violation of one endplate; type III - a large cavity with or without the violation of one endplate; and type IV - a burst cavity with the violation of both endplates or the lateral cortical shell. The intraobserver and interobserver intraclass correlation coefficients (ICCs) of the HPC were assessed. The demographic characteristics and clinical outcomes of the cohort were compared between the stable group (types I and II) and the unstable group (types III and IV). Logistic regression was conducted to evaluate risk factors for unstable healing.Results: The intraobserver and interobserver ICCs of the HPC were 0.86 (95% CI=0.74-0.90) and 0.77 (95% CI=0.59-0.86), respectively. While the unstable healing group (types III and IV) accounted for 59.6% of the patients, most of these patients were asymptomatic. The preoperative Load Sharing Classification (LSC) comminution score may predict the occurrence of unstable healing (OR=8.4, 95% CI=2.4-29.7).Conclusions: A reliable classification for assessing the stability of a healed vertebra was developed. With type I and II healing, the vertebra is considered stable, and the implant can be removed. With type III healing, the vertebra may have healing potential, but the implant should not be removed unless type II healing is achieved. With type IV healing, the vertebra is considered extremely unstable, and instrumentation should be maintained. Assessing the LSC comminution score preoperatively may help to predict unstable healing after surgery.

“…To assist surgeons in the decision-making process, several biomechanical studies have shown that the modifications associated with simulated metastatic lesions (and the consequent risk of instability) are to a large extent related to biomechanical factors [10][11][12]. In fact, vertebral fracture in case of tumors is possibly triggered by the limited mechanical strength of neoplastic tissue, and by the stress concentrations occurring around tumor lesions.…”

Section: Introductionmentioning

confidence: 99%

Assessing the Mechanical Weakness of Vertebrae Affected by Primary Tumors: A Feasibility Study

et al. 2020

Patients spend months between the primary spinal tumor diagnosis and the surgical treatment, due to the need for performing chemotherapy and/or radiotherapy. During this period, they are exposed to an unknown risk of fracture. The aim of this study was to assess if it is possible to measure the mechanical strain in vertebrae affected by primary tumors, so as to open the way to an evidence-based scoring or prediction tool. We performed biomechanical tests on three vertebrae with bone tumor removed from patients. The tests were designed so as not to compromise the standard surgical and diagnostic procedures. Non-destructive mechanical tests in combination with state-of-the-art digital image correlation allowed to measure the distribution of strain on the surface of the vertebra. Our study has shown that the strains in the tumor region is circa 3 times higher than in the healthy bones, with principal strain peaks of 40,000/−20,000 microstrain, indicating a stress concentration potentially triggering vertebral fracture. This study has proven it is possible to analyze the mechanical behavior of primary tumor vertebrae as part of the clinical treatment protocol. This will allow building a tool for quantifying the risk of fracture and improving decision making in spine tumors.