Comparison of unilateral and bilateral percutaneous vertebroplasty for osteoporotic vertebral compression fractures: a systematic review and meta-analysis

Osteoporosis is an important health issue in ageing populations, characterized by low bone mass that leads to fragile bones and higher fracture risks [1, 2]. Osteoporosis and associated fractures are the cause of morbidity in older adults, and osteoporotic vertebral compression fracture (OVCF) is the most common one, which affects more than 200 million individuals worldwide [3]. It occurs more frequently than ankle, wrist, or hip fractures, and it may occur spontaneously just in a simple activity such as picking up something or just rising from a chair [4]. Patients with osteoporotic vertebral fractures (OVFs) suffer severe back pain for weeks to months, and spinal deformities, reduced pulmonary function, restriction of the abdominal and thoracic contents, impaired mobility, and clinical depression caused by OVCFs produce effects on patient quality of life [5‐8]. OVCFs can affect both the elderly male and female. Studies suggested that OVCFs are developed in 8% of women older than 50 years and 27% of men and women older than 65 years [9, 10].

OVCFs have traditionally been treated with bed rest, analgesic use, physical therapy, and antiresorptive medications. But these treatments are conservative managements which cannot reverse the kyphotic deformities, and also cause comorbidities including deep venous thrombosis, acceleration of osteopenia, respiratory problems, and emotional problems [4, 11]. Besides, because of the poor quality of osteoporotic bone, classical surgery with metal implants often fails and contributes to persistent back pain, neurological symptoms, and functional limitations [8, 12]. Percutaneous vertebroplasty (PVP), which was introduced by Galibert in 1984 for treating osteolytic metastasis, myeloma, and hemangioma [13], is a minimally invasive surgical procedure that has gained popularity as a new treatment of OVCFs. The procedure includes placing spinal needles into fractured vertebral bodies and injecting polymethylmethacrylate (PMMA) or other bone cements into the fractured vertebral body under radiological control to relieve pain and increase bone strength [14]. After the injection of the cement, pain pathways in the surrounding tissue seem to be altered in response to various stimulations. Mechanism stabilization of the fracture, such as thermal injury to the nerve endings, results in immediate pain relief [15]. It has been reported that PVP can produce immediate pain relief compared to conservative treatments [16].

PVP is one of the optimal treatments for OVCFs and provides rapid pain relief and stabilization of fractured vertebral bodies [17, 18], but the matter of surgical approach selection remains controversial. As a minimally invasive technique, the standard technique is typically carried out using the bipedicular approach [19, 20]. Some researchers believe that bilateral PVP is more superior for excellent pain relief, which is associated with symmetrical distribution of bone cement in the vertebral body [15, 21]. But in recent years, unilateral PVP is being increasingly used for the reduction of operation and radiation exposure time and the lower risk of cement leakage and complications [22, 23]. In theory, bilateral PVP shows increased surgery time and injected cement volume, and the risk of bone cement leakage is twice that of the unipedicular approach; on the other hand, unilateral PVP can reduce the operation time, surgery-associated complications, radiation exposure, and cost, and unilateral PVP can also achieve the same clinical results.

The aim of this meta-analysis is to examine the safety and effectiveness of unilateral percutaneous vertebroplasty for treatment of osteoporotic vertebral compression fractures compared with that of bilateral treatment. Owing to the inconsistent results of studies about shear bond strength, it is necessary to perform a systematic review and meta-analysis to study the difference of curative effects and complication rates of surgery between unilateral and bilateral PVP, which will undoubtedly increase surgeon confidence of both medical staffs and patients.

Excellent strategies for OVCFs are treatments with effective management of pain, short time of recovery, and no requirement of an extended nursing and rehabilitation care [37]. Longo et al. [38] had reported the evidence available on the conservative care for patients with OVCFs and focused on the role of the most commonly used spinal orthoses. But conservative management has not been standardized. Since percutaneous vertebroplasty was introduced more than 30 years ago, researchers extended to vertebral fractures. In the past decades, it has been proved that PVP is a safe and effective surgery. In these studies [17‐20], both unipedicular and bipedicular surgeries achieved satisfactory results and patients’ clinical outcome parameters were significantly improved and consistent compared to pre-surgical condition. Some have proved that compared with bilateral PVP, unilateral PVP surgery provides comparable restoration of vertebral body stiffness and therapeutic effects [39, 40]. In this meta-analysis, we compared the effectiveness between unilateral and bilateral PVP through VAS, ODI, surgery time, injected cement volume, and cement leakage outcome.

Owing to the cytotoxic effect of polymethylmethacrylate (PMMA), which is injected into the bones and causes damage to terminal nerve endings, and the immobility and inhibition of micro movement in the fractured fragment [41, 42], significant pain reduction was achieved in the PVP groups who suffered from thoracolumbar compression fractures [43]. VAS is a psychometric response scale used in questionnaires, which measures the subjective characteristics or attitudes that cannot be directly measured. Studies use VAS to estimate pain relief after PVP surgery compared with pre-operation. The meta-analysis suggested that there was no significant difference of the VAS score in the unilateral group and bilateral group, which means that the pain relief of the unilateral group is as much as that of the bilateral group. ODI is an index used by clinicians and researchers to quantify disability for low back pain. A score of 0 is equated with no disability and 100 is the maximum disability possible. The results showed that the ODI score of unilateral PVP was similar to that of bilateral PVP. Also, as we had expected, the bilateral surgery costs more time and more material than the unilateral surgery.

Although relatively safe and effective, PVP may cause complications including cement leakage, soft tissue damage, pedicle fracture, nerve injury, and spinal epidural hematoma [44]. Cement leakage is one of the most frequent complications of vertebroplasty. Symptoms of nerve irritation through compression of nerve roots may be caused by the leakage. It has been reported that pulmonary cement embolism (PCE) following vertebroplasty existed. Cement leakages of both unilateral and bilateral PVP are reported to be as high as 73% [9], but most leakages remain clinically asymptomatic, and even small quantities of leakage may have a significant clinical impact, which is often recognized by their clinical signs and symptoms such as chest pain, dyspnea, tachypnea, coughing, and sweating [45]. In this study, the total cement leakage rates of both groups were 25% (96/384) and 29.88% (101/338), respectively, but no statistically significant difference was observed. The results suggested that increased bone cement injection did not result in increased bone cement leakage rate, and it may be attributed to the nature of the high-viscosity bone cement itself.

Our results support the point that the unipedicular technique is a faster, lower risk alternative that provides a comparable spinal deformity correction than the bipedicular approach. It also increased the cost-effectiveness of the procedure for injecting less cement and cost less surgery time, which lowers the risk of surgery and morbidity.

However, this study has some limitations. In this study, we chose the random-effect model for high heterogeneities of the meta-analyses (I ² > 50%). The reasons for high heterogeneities were complex, including different surgical technologies used, varying types of fractures, pre-surgical medical status, and different follow-up times. Also non-RCT studies cause greater bias risks than RCT studies. Besides, the poor quality of some studies indicates that further well-designed and prospective studies are needed to determine the clinical outcomes, which this study did not cover.

Both unipedicular and bipedicular surgery are safe and effective treatments for OVCF. Although both punctures provide excellent pain relief and improvement of life quality, we encourage the use of the unipedicular approach as the preferred surgical technique for treatment of OVCFs due to less operation time, limited X-ray exposure, and minimal cement introduction and extravasation.