12.1 Introduction

Apart from pain and mobility impairment, vertebral compression fractures (VCFs) result in deformities that in the long term can cause potential systemic complications as well as increased chance of future vertebral fractures of either the adjacent vertebral segments or other vertebral bodies.

One of the indications for use of intraosseous implants is the attempt to correct the kyphotic angle. Mechanical effects of kyphosis include decreased thoracic and abdominal space, anterior shift of the craniothoracic center of gravity, and a compensatory counterkyphotic stance with subsequent clinical consequences such as decreased appetite with resultant nutritional impact, frailty, increased future VCF risk, and secondary chronic back pain due to constant paraspinal muscular contraction. ^{1 – 4} With current evidence, it is clear that percutaneous vertebroplasty and balloon kyphoplasty (BKP) are more efficient than conservative therapy for the management of painful fractures, prolonging survival, and preventing morbidity in these patients. ¹ Use of vertebral implants, combined with cement injection, is intended to provide analgesic and stabilizing effects along with kyphotic angle correction and vertebral height restoration. Correction of the kyphotic angle may be associated with optimal spinal alignment, paraspinal muscle relaxation, a more upright posture, and reduced pain along with a significantly higher improvement in function and quality of life. ^{4 , 5}

Another potential use of the intraosseous implants is to provide stabilization of the fracture along with the improved sagittal alignment to optimize and decrease the stress on the adjacent vertebral bodies. The prospect of stabilizing the vertebral body by using vertebroplasty or even kyphoplasty might be associated with a higher risk of refracture due to the less optimal restoration of the vertebral height. ^{1 , 6} In fractures where simple augmentation is contraindicated, the use of an alternative material with different mechanical properties than polymethyl methacrylate (PMMA) can have an additive effect to normalize the spinal compression forces.

The purpose of this chapter is to describe the most commonly used vertebral implants and the implantation procedures associated with placing these implants. The advantages and disadvantages of different products will be addressed.

12.2 The Implants

Vertebral implants for fracture treatment include stents, jacks, polyether ether ketone (PEEK) cages, and fracture reduction systems. Indications for implants include osteoporotic or traumatic fractures as well as primary or metastatic neoplastic spine disease. ^{6 , 7} The contraindications are similar to those for standard vertebral augmentation techniques, including asymptomatic fractures, pain relief with conservative therapy, local or systemic infection, severe coagulopathy, and severe cardiorespiratory disease. ^{6 , 7}

Vertebral body stenting (VBS): VBS is a minimally invasive percutaneous technique during which an expandable cobalt–chromium device is deployed inside the vertebral body (▶Fig. 12.1). The stent access kit includes guidewires, trocars, and working sleeves, drill and blunt plungers, vertebral body balloons and inflation system, vertebral body catheters and stents, as well as cement and a cement delivery system. The balloons and stents are available in three sizes; size selection is based on the preoperative planning via computed tomography scan. Usually, the stents are nonretrievable once expanded.

SpineJack: The concept of SpineJack is to achieve a superoinferior restoration of the vertebral body including cortical rings and end plates. The expansion of the implant is progressive and can be maintained until the cement is injected (▶Fig. 12.2). Additionally, in order to best fit for each fracture’s shape and patient’s anatomy, it is possible to expand the implant under the most compressed portion of the VCF. The access kit for spine jack implant includes trocar, Kirschner’s wire, reamer and template, the implant introduction system, and the cement delivery system. Once Spine Jack is expanded, there is no retrieval of the implant.

Osseofix: Osseofix (Alphatec Spine, Carlsbad, CA) is an intravertebral expandable titanium mesh cylinder (▶Fig. 12.3). During expansion, the surrounding trabecular bone is compacted and the vertebral height is partially restored and the kyphotic deformity decreased. ⁷ The implant acts as scaffold augmenting the vertebral fracture stabilization and creating channels for subsequent cement injection. Osseofix is indicated for compression fractures at the T6–L5 levels. Once Osseofix is expanded, there is no retrieval of the implant.

VerteLift: This is a nitinol implant of different sizes and configurations in order to fit each fracture and patient. The implant also has the feature of being able to be repositioned. This nitinol implant is composed of super-elastic struts designed for vertebral end plate support and fracture reduction, which is maintained until bone cement is injected (▶Fig. 12.4). During cement injection, the polymer flows around and through the struts interdigitating with the cancellous bone.

KIVA system: This is a spiraled coiled PEEK-OPTIMA implant loaded with 15% barium sulfate (▶Fig. 12.5). The implant has a distal marker and is indicated for treatment of thoracic and lumbar spinal fractures (T6–L5 levels). The access kit of the KIVA system includes needles, guide pins, a working cannula, a deployment system containing the nitinol coil, and the PEEK polymer cage as well as a cement delivery system. During the expansion of the nitinol coil, the system is retrievable and repositionable. Once the PEEK material is deployed, there is no possibility of withdrawal. The most commonly used percutaneous vertebral implants are listed in ▶Table. 12.1.