Pedicle Screw Fixation in Osteoporotic Lumbar Spine

This is a prospective, observational single-center study. The osteoporotic patients requiring pedicle screw fixation for lumbar degenerative diseases are prospectively enrolled and followed up. This study mainly focuses on the most common osteoporosis-related surgical complications, which are pedicle screw loosening and the failure of lumbar fusion. The global and local bone mineral density(BMD) are evaluated with DXA, vertebral CT Hounsfield units(HU) before the surgery. The mechanical strength of the bone mass within the screw trajectory is also measured with a customized device during the surgery. We explored the effect of BMD on the pedicle screw loosening rate and fusion rate. In addition, the patients undergoing lumbar fixation with conventional pedicle screws without the use of bone cement are compared with those undergoing the fixation augmented with bone cement. The objective is to offer more detailed clinical evidence to guide the use of pedicle screw augmentation techniques in osteoporotic patients.

Pedicle screw fixation is a widely used technique for the surgical treatment of degenerative lumbar diseases, which can stabilize the spine before solid fusion and restore spinal balance. However, because of population aging and the high rate of osteoporosis in the elderly with lumbar degenerative diseases, the pedicle screw loosening has become a frequently reported complication. The bone-screw interface in osteoporotic spine is unstable, leading to reduced pull-out force and cut-out force.

Previous studies have widely reported the bone cement augmentation techniques used to directly strengthen the pedicle screws. It has been proved that cement-augmented pedicle screw fixation is associated with lower loosening rate and higher fusion rate. However, the use of cement can lead to cement leakage and pulmonary embolism, and need extra cost. Therefore, it is very important to identify the correlation between degree of osteoporosis and screw loosening risk , and to establish the indications for cement augmentation in osteoporotic patients.

The osteoporotic patients requiring posterior lumbar fusion with pedicle screw fixation are prospectively enrolled and followed up. The researchers will invite appropriate patients to participate in the study after their surgical plans are determined. General patients data are collected after informed consent, such as age, gender, weight, height, bone mineral density measured in T-scores and Hounsfield units, the mechanical strength of the bone mass within the screw trajectory, detailed surgical plans, and etc. They are followed up at 3, 6, 12, and 24 months according to our clinical routine, including lumbar x-ray and certain questions about the clinical outcomes. In addition, this study requires the patients to have lumbar CT scans because its advantage in judging the fusion status. In addition, the ODI and VAS scores are also routinely recorded.

The patients undergoing conventional pedicle screw fixation without cement augmentation are compared with those undergoing the fixation augmented with bone cement. The primary endpoints are the loosening rate and fusion rate at 12 months follow-up. The secondary endpoints are the loosening rate and fusion rate at other time point of follow-up , and the clinical outcomes(ODI and VAS) at every follow-up. We also explored the correlation between the BMD information measured with different methods and the patients outcomes, in order to find the high-risk patient group.

Eligibility Criteria:
Inclusion Criteria:

* aged≥ 50 years old
* lumbar degenerative diseases requiring lumbar fusion with pedicle screw fixation, such as degenerative lumbar spinal stenosis, degenerative lumbar spondylolisthesis and etc.
* no response to nonoperative treatment of at least 3 months
* osteoporosis diagnosed by any method for bone mineral density evaluation, such as DXA, QCT, or vertebral Hounsfield units
* informed consent

Exclusion Criteria:

* no lumbar CT scans within 3 months before the surgery
* no dual energy x-ray absorptiometry within 6 months before the surgery
* history of lumbar fusion surgery
* cervical myelopathy, thoracic spinal stenosis, motor neuron disease, tuberculosis of spine, spinal tumor