The demographic shift in numerous societies around the globe has led spine surgeons to focus on the diagnosis and treatment of osteoporotic vertebral body compression fractures, which are associated with debilitating pain, functional decline, and impaired mobility. Previous studies have demonstrated greater morbidity and significantly higher overall mortality rates of patients who have sustained vertebral compression fractures in comparison with age-matched controls1. Secondary negative effects of vertebral compression fracture include an altered kyphotic sagittal alignment, chronic back pain, and decreased pulmonary capacity.
Conservative measures including pain management, temporary bed rest, narcotics, and/or extension bracing represent a first line of treatment. Patients for whom conservative treatment fails or cases with progressive/advanced collapse of the vertebral body and instability of the spine may need reconstructive surgical procedures with posterior stabilization and, possibly, anterior column reconstruction. However, the risks of surgery, including perioperative complications, must be expected to increase significantly with increasing patient age, particularly when more invasive surgical strategies including instrumentation are chosen2-5.
Conversely, early mobilization has been associated with reduced morbidity and improved survival following other types of skeletal fractures in elderly patients. In order to reduce the morbidity rate associated with vertebral compression fractures, the main focus of the treatment strategy should be on pain reduction and mobilization at the earliest possible stage.
Recently, minimally invasive percutaneous techniques with vertebral body bone cement augmentation have gained popularity. Cement application may be achieved with prior balloon dilation (kyphoplasty) or without it (vertebroplasty). Both techniques combine the advantages of immediate fracture stabilization, pain reduction, early mobilization, and possibly partial correction of the sagittal imbalance.
Most noteworthy are the data in a recently published survival analysis highlighting significantly improved survival rates of patients who had been treated surgically with cement augmentation for vertebral compression fractures in comparison with those who had received conservative treatment; these improved rates were found regardless of age, sex, the number of vertebral fractures, or comorbidities6. The authors concluded that rather aggressive management should be considered for patients who have refractory and intractable back pain if they otherwise would require hospitalization to control these symptoms of vertebral compression fracture.
It is crucial to assess patient safety as well as appropriate mid-term and long-term results in the evaluation of any surgical technique. For a subset of elderly patients, however, the major clinical relevance falls within the immediate posttraumatic period following a vertebral compression fracture, during which early mobilization and, if surgery is required, minimal perioperative trauma are paramount for the patient’s survival. Despite well-justified demands for long-term follow-up data from an evidence-based-medicine point of view, from the patient’s perspective the short-term results are as decisive as the five to ten-year follow-up data in a cohort of eighty-year-olds. Therefore, a mere comparison of mid-term and long-term results may be misleading in the discussion of adequate treatment options for vertebral compression fracture.
These facts highlight the advantages of currently available percutaneous cement augmenting techniques, which have led to their widespread application. These advantages include immediate fracture stabilization, pain relief, and mobilization of the patient by means of a minimally invasive procedure with short operating times and virtually negligible blood loss. Considering the vast number of affected patients, the evaluation of these new percutaneous cement augmenting techniques is of utmost importance. In this respect, Werner et al. are to be congratulated for providing the first analysis of the effectiveness of vertebral body stenting by comparing it with a well-established and widely accepted balloon kyphoplasty procedure.
One of the goals of vertebral body stenting was to improve patient safety and reduce the risk of cement leakage by formation of a cavity for cement application, as occurs with balloon kyphoplasty. Another hypothetical goal of vertebral body stenting is to resist advanced or progressive collapse of the vertebral body and to prevent the loss of correction that is seen following removal of the balloon used for balloon kyphoplasty. The paucity of currently available data on vertebral body stenting, due to its recent introduction to the market, does not allow any definite conclusions regarding whether vertebral body stenting can live up to its expectations and accomplish the above-mentioned hypothetical goals.
The results presented by Werner et al. demonstrated no significant difference between vertebral body stenting and balloon kyphoplasty with regard to cement leakage, radiation exposure time, or neurological sequelae. The fact that similar rates of cement leakage were observed is not surprising as both techniques rely on the production of a cavity before cement application.
In comparison with kyphoplasty, vertebral body stenting includes an additional surgical step for stent insertion and dilation, which technically is not challenging for any surgeon who is familiar with the balloon kyphoplasty technique but which may be associated with its own specific and technique-related pitfalls. Difficulties involving incomplete stent dilation may be encountered, as described by the authors. Stent opening may be sensitive to implant placement (i.e., too lateral to the vertebral body cortex), type of fracture, level of fracture (thoracic vertebrae are smaller than lumbar vertebrae), and fracture age (bone too sclerotic in older fractures), one point that was only partially evaluated in the study by Werner et al. Anterior dislodgement with stent penetration of the anterior vertebral body cortex may bring the sharp edges of the stent into immediate contact with vascular structures. This raises questions about revision strategies following vertebral body stenting procedures since posterior removal of a (partially) opened or even unopened stent may be technically impossible. These aspects were confirmed by the authors’ results, which revealed significantly higher material-related complications in the vertebral body stenting cohort. It should, however, be noted that none of the material-related complications imposed any substantial threat to patient safety. Furthermore, discrepancies in cement leakage rates can be attributed to the different types of cement that were used in the different groups rather than to the surgical technique, a problem that compromises the comparison between the two cohorts.
Finally, the authors did not observe any advantage of vertebral body stenting over balloon kyphoplasty with regard to kyphosis correction, which was one of the main aims of its market introduction. Future studies should therefore delineate whether there is one particular subset of fractures that is at increased risk of re-subsidence, and for which vertebral body stenting may thus have advantages over other types of cement augmenting techniques. The current study, however, did not reveal any particular advantage of vertebral body stenting over a standard balloon kyphoplasty technique.
The adoption of vertebral body stenting by spine surgeons will similarly depend on the additional implant-related costs as well as the local reimbursement system, which may vary substantially among countries. Werner et al. provided a provisional cost analysis, but it focused only on immediate and direct implant-related expenditures. The considerable prevalence of material-related complications, however, led to the use of multiple sets of vertebral body stenting implants in the same patient, which significantly raised the overall costs. This fact should be included in any upcoming detailed analysis of direct and indirect expenditures. Finally, as Werner et al. pointed out, they compared the overall costs of vertebral stenting with a rather cost-intensive balloon kyphoplasty system. This may direct the surgeon’s choice toward cheaper alternatives, including less costly balloon kyphoplasty or vertebroplasty systems.
In summary, use of percutaneous cement augmenting techniques has substantially improved treatment of vertebral compression fractures, with reduced overall morbidity and mortality rates as well as immediate pain relief and mobilization of the patients. Modifications of the surgical technique, changes in the cement application process, and modified cement materials will ultimately result in further improvements, particularly for patients with debilitating pain and those who do not respond to conservative therapy.
Additional studies and larger cohorts will be required to establish the real effectiveness and value of each of these techniques, and the series of questions raised will be the key factor for further improvements of a recently introduced vertebral body stenting technique before it may find general acceptance and widespread application among the spine community.