Kiva System in the Treatment of Vertebral Osteoporotic Compression Fractures

Published on 11/04/2015 by admin

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38 Kiva System in the Treatment of Vertebral Osteoporotic Compression Fractures

Luis M. Rosales

KEY POINTS

• The Kiva system is useful for the reduction and the treatment of pathologic compression fractures of the vertebral body that may result from osteoporosis, in segments T10 to L5 of the spine.

• The Kiva system device preserves cancellous architecture using a percutaneously introduced PEEK (Poliether etherKetone) implant in a continuous loop to form a nesting, cylindrical column.

• The implant is delivered over a removable guide wire to provide structural support to the vertebral body. A vertical displacement of the column results in endplate re-elevation and fracture reduction.

• Bone cement is delivered through the lumen of the implant, which provides contained interdigitation into the cancellous bone, thus stabilizing the fracture and minimizing the risk of extravasation.

• The Kiva system achieves an improvement in analog pain scales and Oswestry Disability Index (ODI) and has no adverse effects from components.

Introduction

Vertebral compression fractures (VCFs) have a high incidence in the elderly population and are the most common fractures in osteoporotic bones. The majority present without a history of major trauma.¹ The incidence of VCF is increased in patients with a prior vertebral compression fracture, with studies indicating that nearly 20% of patients who have an osteoporotic VCF will develop a second fracture within a year of the first.² Not only do these fractures cause significant morbidity in terms of pain, loss of mobility, and kyphosis, but the relative risk of death after a vertebral fracture is nearly nine times greater than in people without a vertebral fracture.²

Percutaneous vertebroplasty (PVP) was introduced in France in 1984 by Galibert and Deramond as a treatment for a malignant aggressive hemangioma.¹ It is a therapeutic procedure performed to reduce pain and perhaps to stabilize vertebral lesions. Subsequently PVP was used to treat painful lesions such as hemangiomas, metastasis, multiple myeloma, and osteoporotic fractures. Today most patients undergoing PVP suffer from vertebral osteoporotic compression fractures. PVP is generally seen as a safe and efficient procedure for treatment of painful osteoporotic fractures.

Vertebral augmentation using balloon kyphoplasty and vertebroplasty ³ is traditionally performed with polymethyl methacrylate (PMMA) cement. Clinical studies have demonstrated the efficacy of both methods in reducing fracture-related pain.^2,⁴ However, there have also been reports of complications: extrusion of cement into surrounding tissue, vascular embolism in the corresponding vascular system, adverse systemic reactions to unpolymerized toxic monomers, and thermal damage to adjacent structures. The two latter complications are specific to PMMA. For this reason, and because PMMA does not become osseointegrated, attempts have been increasingly made in recent years to explore the possibilities of alternative cements by looking into biomaterials based on calcium phosphate (CaP). The properties of such bone cements, however, would have to fit a specific profile that takes into account the following parameters: setting behavior, mechanical fitness, and biological behavior.

There is a new vertebral augmentation device, the Kiva VCF Treatment System (Benvenue Medical, Santa Clara, Calif.), that can be used in the treatment of patients sustaining painful VCFs. Unlike the traditional balloon kyphoplasty procedure that pushes cancellous bone peripherally to form a repository for bone cement, the Kiva device preserves cancellous architecture using a percutaneously introduced Poliether etherKetone implant in a continuous loop to form a nesting, cylindrical column. The implant is delivered over a removable guide wire to provide structural support to the vertebral body, and it is a conduit for bone void filler placement. Vertical displacement by the column results in endplate re-elevation and fracture reduction. Bone cement is delivered through the lumen of the implant, which provides contained interdigitation into the cancellous bone thus stabilizing the fracture and minimizing the risk of extravasation.

Indications

The Kiva system is indicated for the management of pathological compression fractures of the vertebral body that may result from osteoporosis, in segments T10 to L5 of the spine. It can also used to treat benign or malignant lesions, by creating a transpedicular channel through which a PEEK implant is inserted into the vertebral body.

Contraindications

Contraindications include the following:

• Infection, systemic or local, at the surgical site

• Any medical condition that would preclude the patient from having surgery or would impede the benefit of surgery

• Pathology at the index level(s) (e.g., cancer)

• Neurologic signs or symptoms related to the compression fracture

• Previous surgical treatment for a vertebral body compression fracture

• Index level(s) vertebral body collapse to the degree that access to the vertebral body is not feasible

Precautions

Precautions that should be taken include the following:

• Failure to observe recommendations may contribute to serious patient injuries.

• Avoid contact with the sharp distal tip of the Osteo Coil wire.

• If the device appears damaged, do not use. Discard or return to the manufacturer. This device is intended for single use only.

• This device must be deployed under fluoroscopic guidance. Failure to use fluoroscopic guidance could result in serious patient injuries.

Description of the Device

The Kiva system is packaged as a single-use, sterile device incorporating an implantable PEEK distraction sleeve. It is a surgical instrument designed to provide percutaneous access and channel creation in the cancellous bone of the spine followed by delivery of a PEEK distraction sleeve implant into that channel. The Kiva system consists of five primary components:

1. Nitinol Kiva coil track. (Kiva coil track is a guide wire made of nitinol).

2. Stainless steel deployment with a PEEK liner

3. Polycarbonate deployment handle (Figure 38-1)

4. PEEK distraction sleeve implant made of PEEK-OPTIMA with 15% BaSO₄

5. PMMA bone cement delivery needle

FIGURE 38-1 Kiva handle.

The “shape memory” nitinol coil track is preset into a loop shape and it can be temporarily straightened into a cannula for deployment into cancellous bone. Once the cannula is positioned in the cancellous bone, the Kiva coil track is then advanced forward out of the cannula. The surgeon controls the amount of coil track wire deployment with the use of the handle, which allows for 2-mm increments per quarter turn of the coil track deployment knob. Upon exiting the cannula, the coil track regains its loop shape as it channels through the cancellous bone. Once channel creation is complete, the radiopaque PEEK-OPTIMA implant is advanced over the nitinol Kiva coil track and into the channel using the implant deployment knob on the deployment handle.

Clinical Presentation and Evaluation

Material and Methods

Twenty-two patients with radiologically confirmed VCFs between T10 and L5 underwent treatment with the Kiva device for persistent back pain symptoms. Study eligibility required a back pain visual notestyle scale (VAS) score of 5, fracture age less than 6 months, and Oswestry Disability Index (ODI) score of 30%. Patient-reported outcomes (VAS, ODI) were repeated at 3 and 12 months.

Results

Patients in to the study group (n = 22) had a mean age of 70.4 years, and 95.5 % were women. Mean pain scores declined from 7.6 to 2.8 (p < .0001). Mean ODI scores declined from 61.0% to 31.7% (p < .0001). There were no device-related adverse events.

Operative Technique

The procedure should be performed under strict aseptic conditions. The treating physician can administer prophylactic antibiotics according to usual practice. The patient is placed on the table in prone position and subjected to sedation according to the ACR Standard for sedation and analgesia in adults. Conscious sedation is induced by intravenous administration of fentanyl and midazolam (Versed) or other medications (e.g., propofol) in accordance with the preference of the treating physician. The patient’s vital signs must be monitored during the procedure. If needed, oxygen can be administered by nasal cannula, controlling the breath. Standard fluoroscopy is used to locate the body or the vertebral bodies to be treated and to place the needle to correctly. A 1-inch, 25-gauge needle is used to create a blister to administer subcutaneous bupivacaine 0.25%. Then a 2-inch, 25-gauge needle under fluoroscopic guidance is inserted at the site of the blister and introduced to the periosteum of the pedicle. The periosteum is then infiltrated with 6 to 7 ml bupivacaine 0.25%. A small incision is made in the skin over the pedicle, and the access needle is placed for a transpedicular approach.

The vertebral body is accessed with a cannula, using a standard transpedicular vertebral access technique, always through the right pedicle of the vertebra. With the Kiva handle in the vertebral body, the coil track is advanced using the coil track deployment knob, located on the right hand side of the deployment handle.

1. Using imaging guidance, insert the deployment cannula into the access site and through the cancellous bone. Position the cannula to deploy the Kiva coil track centrally in the anterior column.

2. Rotate the coil track deployment knob on the deployment handle forward slowly to incrementally control to the deployment of the Kiva coil track in the cancellous bone. After one-half turn, check fluoroscopic image for proper orientation of the Kiva coil track exiting the cannula (Figure 38-2).

3. If the Kiva coil track is not oriented in the proper plane or at to the proper position, retract the coil track back into the cannula and reposition the cannula to achieve a more optimal orientation.

4. Repeat steps 2 and 3 until the Kiva coil track is oriented at an optimum plane and position.

5. Using imaging guidance, continue to deploy the Kiva coil track making sure to check the fluoroscope image often (Figure 38-3).

6. Using imaging guidance, continue to deploy the Kiva coil track until the full length of the wire is reached or until the desired number of loops are deployed into a symmetrical stacked toroidal shaped coil.

FIGURE 38-2 Percutaneously introduced nitinol Kiva coil (guide wire) advanced through a deployment cannula.

FIGURE 38-3 The nitinol Kiva coil is advanced fully coiled within the cancellous portion of the fractured vertebral body.

Deployment of the Distraction Sleeve

The radiopaque PEEK-OPTIMA implant is advanced using the distraction sleeve implant deployment knob located on the lefthand side of the deployment handle. The radiopaque PEEK-OPTIMA implant can only be advanced forward, and it may not be retracted once advanced.

1. Once the coil track has been adequately deployed into the cancellous bone, using imaging guidance, advance the radiopaque PEEK-OPTIMA implant over the coil track and into the channel created by the coil track (Figure 38-4).

2. Monitor advancement of the radiopaque PEEK-OPTIMA implant using anteroposterior and lateral fluoroscopy to ensure proper advancement of the distraction sleeve implant.

3. Using imaging guidance, continue advancing the distraction radiopaque PEEK-OPTIMA implant until it reaches the end of the coil track or until resistance is encountered (Figure 38-5).

4. Using imaging guidance assess the position of both the coil and the implant. If any loop of the coil track has opened up to a larger diameter compared to the other coil loops, retract additional lengths of the coil in quarter to half-turn increments until all the loops of the coil track have a uniform diameter.

5. Using imaging guidance, slowly advance the coil in half-turn increments until either the full length of the wire is reached or until or until one of the wire loops begins to open up into a larger diameter than the other loops.

6. Using imaging guidance, advance the distraction implant.

7. Continue to advance the distraction sleeve implant until resistance is encountered or until one of the wire loops beginning to open up to a larger diameter than the other coil track loops.

8. At this point, the implant deployment is complete (Figure 38-6). Remove the coil track completely by rotating the coil track deployment knob backward until the coil track is fully retracted in the deployment handle (Figure 38-7).

9. Retract the distraction sleeve implant pusher completely by rotating the distraction sleeve implant deployment handle backward until the pusher wire is completely retracted into the deployment handle.

10. Disconnect the flexible connector at the end of the deployment handle from the deployment cannula by releasing the tab on the connector switch.

FIGURE 38-4 Radiopaque PEEK-OPTIMA Implant is delivered progressively over the removable Kiva coil.

FIGURE 38-5 A continuous loop forms a nesting, cylindrical column, providing vertical displacement that results in endplate elevation and fracture reduction.

FIGURE 38-6 Fluoroscopic image illustrating the deployment of the implant over the removable Kiva coil in a continuous loop, properly positioned within the vertebral body.

FIGURE 38-7 After removal of the Kiva coil, the implant is fully deployed and it serves as a conduit for bone cement placement.

Injecting Pmma Bone Cement

1. Insert the PMMA bone cement delivery needle through the deployment cannula and advance the needle until the distal tip of the needle engages the lumen of the distraction sleeve implant.

2. Once the tip of the needle has engaged the lumen of the implant, ensure that the bone cement delivery needle is steadily inserted into the implant by rotating the needle back and forth while it is applying gentle forward pressure to the needle.

3. The distraction sleeve implant and vertebral body are now ready for delivery of bone cement. Use bone cement approved for use in the spine (Figure 38-8, A and B).

FIGURES 38-8 AP and lateral fluoroscopic images show contained interdigitation of cement into the adjacent cancellous bone, minimizing the risk of cement extravasation, and the fracture is fully stabilized in situ. (A) Lateral and (B) AP view of the fluoroscopic images, show the PEEK implant filled with bone cement in the center of the vertebral body.

Postoperative Care

No special postoperative care is needed. After the procedure, the patient can stand up, either the same day or the day after.

Complications and Avoidance

This procedure, although performed percutaneously, has the risks of any procedure of vertebroplasty, including infection, bleeding, and neurological complications. With careful technique, these potential complications can be avoided.

Conclusions and Discussion

These findings, albeit short-term, suggest robust and consistent clinical improvement for pain and function outcomes, following this novel vertebral augmentation procedure in patients with painful VCFs. Clinically relevant gains were realized early postoperatively and maintained through follow-up. The device could be deployed and implanted without adverse events, with improvement in VAS pain scores (p = .0002) and ODI scores (p < .0001), with the following overall clinical success criteria: 2-point improvement in VAS and 15-point improvement in ODI. Two cases of cement extravasations occurred without clinical manifestations.

Although the PMMA cement has proved useful in these procedures, biodegradable vertebroplasty materials are being tested. Arecent report ⁵ showed for the first time that there is no difference in clinical and morphologic outcomes after kyphoplasty using either CaP cement (Calcibon) or conventional PMMA material in patients with painful osteoporotic vertebral fractures for at least 3 years of follow-up. There was no significant difference with regard to postoperative pain reduction or the improvement of mobility between the CaP and PMMA groups. Furthermore, there was a comparable height restoration of the fractured vertebral bodies, and no significant difference in the number of vertebral follow-up fractures during the 3-year study period. In daily routine, PMMA is used for the internal stabilization of vertebral fractures by kyphoplasty. However, PMMA is not biodegradable and heals with a fibrous tissue layer around the implant. Therefore CaP cement materials have been developed, which are biodegradable by osteoclastic resorption and allow a direct osseous integration of the entire surface of the implant, whereby a slow replacement by normal bone tissue seems possible.

Vertebroplasty is widely accepted as an effective, minimally invasive procedure, and is becoming the standard of care for the management of painful osteoporotic VCFs. Significant pain relief has been reported in 78% to 95% of patients suffering from osteoporotic VCFs. However, very few articles in the literature have focused on those patients who failed to respond to the initial PV. Although one study reported that a repeat PVP performed on previously treated vertebral levels for recurrent pain might offer therapeutic benefits (these patients experienced pain relief for 8 to 167 days after the initial PV), we are not aware of any studies on the use of repeat PVs in patients whose pain does not resolve after the initial treatment.⁵

References

1. Rousing R., Andersen Mikkel O., Jespersen Stig M., Thomsen K., Lauritsen J. Percutaneous vertebroplasty compared to conservative treatment in patients with painful acute or subacute osteoporotic vertebral fractures: three-months follow-up in a clinical randomized study. Spine. 2009;34(13 June 1,):1349-1354.

2. Becky Benz K., John Gemery M., John McIntyre J., Clifford Eskey J. Value of immediate preprocedure magnetic resonance imaging in patients scheduled to undergo vertebroplasty or kyphoplasty. Spine. 2009;34(6 March 15):609-612.

3. Blattert Thomas R., Jestaedt L., Weckbach A. Suitability of a calcium phosphate cement in osteoporotic vertebral body fracture augmentation: a controlled, randomized, clinical trial of balloon kyphoplasty comparing calcium phosphate versus polymethylmethacrylate. Spine. 2009;34(2 January 15):108-114.

4. He Shi-Cheng, Gao-Jun Teng, Gang Deng, Wen Fang, Jin-He Guo, Guang-Yu Zhu, Guo-Zhao Li. Repeat vertebroplasty for unrelieved pain at previously treated vertebral levels with osteoporotic vertebral compression fractures. Spine. 2008;33(6 March 15):640-647.

5. Grafe Ingo A., Baier M., Nöldge G., Weiss C., Da Fonseca K., Hillmeier J., Libicher M., Rudofsky G., Metzner C., Nawroth P., Meeder P.-J., Kasperk C. Calcium-phosphate and polymethylmethacrylate cement in long-term outcome after kyphoplasty of painful osteoporotic vertebral fractures. Spine. 2008;33(11 May 15):1284-1290.