## 1 Introduction  
A vertebral compression fracture (VCF) is a subsidence of a vertebra, a subsidence that occurs in the anterior part of the vertebral body. Radiologically, the vertebrae take on a cuneiform appearance.  
Since two-thirds of the anterior column of the spine supports three-quarters of the body's weight, a compression fracture of the vertebra involves the compression of the anterior body with the preservation of the posterior vertebral wall and the posterior elements of the vertebra.  
Fractures predominantly occur at the T12-L1 level and, to a lesser extent, at the T7-T8 vertebrae. The risk of subsequent fracture increases by 5-10 times once the first osteoporortic fracture occurs.  
Most compression fractures of the spine result from primary (age-related) or secondary (drug-related) osteoporosis (a reduction in bone mass and a deterioration of the micro-architecture of bone tissue that increases its fragility).  
For these patients with osteoporosis, low-intensity stress on the spine generated by daily activities, minor trauma, can lead to a vertebral compression fracture [1]. Also, some malignant diseases (cancer) can be another cause of this type of fracture, as well as some traumas.  
The treatment of VCFs has seen rapid progress in recent years. Starting from conservative, noninvasive methods (based on prescribed drug treatment, bed rest, medical recovery procedures, etc.), we switched to minimally invasive, percutaneous methods, of which their primary action is the injection of cement into the body of the verteba (vertebroplasty, 1984 and kyphoplasty, 1998). In the last 15 years, combined treatment methods using implants and cement have appeared for the treatment of VCFs.  
The percutaneous treatment of VCFs began with [PERSON]'s method of treating vertebral angiomas [1]. These results led to using vertebplasty to treat this type of fracture. After some time, a new method appeared, namely, kyphoplasty [1,2], with derived variants [3]. The results were compared to those of the previous percutaneous treatment method, vertebplasty. After another period, combined treatment methods appeared [4], which included implants and cement, such as SpineJack (SJ) [5], the Osseofix(r) Spinal System [6], and the Kiva VCF System [7]. These new methods' performances were also compared against the performance of the previous one, namely, kyphoplasty (KP) [8; 9; 10; 11]. Until now, both KP and SJ have proven their effectiveness in treating VCFs both in terms of restoring vertebral height and of alleviating patient symptoms.  
Given the spread of their use and the demonstrated results, the KP and SJ methods can be considered references in VCF treatment. Thus, it is natural that any new method that may appear should have its results measured against those of these reference methods. Below are brief descriptions of the two methods:  
* Kyphoplasty consists of inserting a balloon into the body of the verteba, inflating it, and creating a cavity by moving the bone fragments to their original position or by yielding the cancellous bone tissue (especially if the cause of the fracture is osteoporosis); the cavity is formed in a somewhat random fashion, following the principle of least resistance against the pressure inside the balloon. The resulting cavity is filled with cement [1];
* the procedure using the SpineJack system promises to restore the height of the verteba \"like never before\" by inserting an expandable implant into the body of the verteba (very similar to a car jack), which in turn creates a cavity, following the expansion action of the two arms for pushing the two bony plates of the verteba to the initial position; this time, the cavity is created as a result of the mechanical action, in a controlled direction (up-down), given the orientation of the implant [5].