27 Percutaneous Kyphoplasty in Traumatic Fractures

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27 Percutaneous Kyphoplasty in Traumatic Fractures

G. Maestretti, P. Otten

27.1 Terminology

Kyphoplasty: This term describes a new method of percutaneous restoration of the shape of vertebral bodies with the aim of correction of a traumatic kyphotic deformity.

IBT: Inflatable bone tamp.

VAS: Visual analogue scale.

CPC: Calcium phosphate cement.

27.2 Surgical Principle

27.2.1 Introduction

Ninety percent of all spinal fractures occur in the thoracolumbar region, and 66 % are compression fractures of type A (A1 35 %, A2 3.5 % A3 27.5 %). Type A fractures involve mainly the vertebral body: the posterior column is only insignificantly injured, if at all. The height of the vertebral body is reduced and the posteri- or ligamentous complex is intact. Translation into the sagittal plane does not occur. These type of injuries are caused typically by axial compression with or without flexion. The incidence of neurological injuries goes up to approximately 32 % in burst fractures (type A3) [13].

Although it is a very common fracture, there is no consensus as to a standardised treatment with various opinions regarding the most appropriate treatment for those fractures without neurological deficit and this re- mains a subject of controversy.

Internal fixation offers the possibility of immediate stability and correction of the deformity with the potential visual decompression of neurological structures when needed. With non-operative care, brace or body casts, the same possibility of stabilisation with less correction of the deformity is given [14, 17, 18]. Recent studies comparing long-term results in the treatment of burst fractures found the same results with lesser morbidity for non-operative treatments [21]. Failures after pedicle screw fixation and specifically after removal of instrumentation or after conservative management are possi-

bly due to lesions of the disc and are later due to disc degeneration with decreased anterior column support.

Restoration of vertebral height and preservation of the endplate may prevent the secondary risk of kyphotic deformation and so decrease the risk of chronic pain.

In this respect kyphoplasty is an improved technique for the reduction of fractures, for vertebral body height restoration and cement augmentation in the treatment of painful osteoporotic compression fractures with a decreased complication rate compared to vertebroplasty [8, 12].

New calcium phosphate cements which have a good resistance and stability under compression can now be used in association with kyphoplasty, and thus provide a new alternative treatment in non-pathological type A fractures. With this new, mini-invasive percutaneous technique we now have the potential to obtain clinical results comparable with the classic surgical treatment but with less surgical trauma to the patient [1, 19, 20].

27.2.2

Surgical Principle of Kyphoplasty

In the standard kyphoplasty procedure, an inflatable bone tamp (IBT) or balloon is used to restore the vertebral body height and correct the spinal deformities before cementation. The similarities of the technique to vertebroplasty are only in the use of a percutaneous in- trabody cannula for the cement injection. However, it gives a number of potential advantages, such as a lower risk of cement extravasation, and can help towards a better restoration of the vertebral height.

A cannula is introduced into the vertebral body, through a trans- or extrapedicular approach, and is fol- lowed by the insertion of an inflatable balloon. The IBT is inflated, under permanent control of pressure and volume and a cavity is created inside the vertebral body. As the IBT is progressively increasing in volume, the superior endplate is elevated with restoration of the original vertebral body height.

Deflation and removal of the balloon leaves a cavity in the restored vertebral body. This cavity is filled with a very viscous cement, either with direct injection or, even better, with a prefilled 1.5-ml bone filler device under

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low pressure. Filling is performed under continuous lateral fluoroscopic guidance. Higher cement viscosity, lower pressure injection and compacted bone around the cavity reduces the risk of cement extravasation. The procedure can be performed under general anaesthesia or under local anaesthetics with intravenous sedation.

The patient may be discharged from the hospital on the day of the procedure.

27.3 History

Kyphoplasty was developed independently of vertebroplasty in the 1980s, by an orthopaedic surgeon looking for a minimally invasive surgical procedure to address the pain and deformity of vertebral compression fractures (VCFs) following orthopaedic principles: anato- my restoration and solid fixation while minimising tissue disruption.

The first balloon kyphoplasty procedure for osteoporotic VCFs was performed by Dr M. Reiley in Berke- ley, California, in 1998. The CE mark was obtained in February 2000.

The idea to use this technique to treat traumatic fractures in young patients appeared in three European groups independently of each other. The first kyphoplasty procedure with calcium phosphate cement was performed in Belgium by Prof. P. Vanderschot in July 2002. At the same time two other groups started with the same technique in Switzerland (G. Maestretti and P.

Otten) and in Germany (H. Hillmeier).

The first advisory team meeting, regrouping the Ky- phon trauma group, was held in Belgium in March 2003 to better define the indications and lay the foundations of a standard technique.

27.4 Advantages

The advantages of this minimally invasive technique are an almost immediate return to daily activities, dis- appearance of pain, minimal operative risks and good biomechanical stability of the fractured vertebra.

Blood loss being minimal, this could be a first-choice technique in polytraumatised patients needing short- term spine stability, thus improving nursing in ICU without any risk of secondary lesions.

This technique enables normal mobilisation after 6 h, depending on residual pain, without a brace. Pa- tients can be discharged from the hospital the same day as the operation. Compared to conservative management with braces, patients suffer less inconvenience and there is better reduction of the fracture and better control of pain under load. Compared to standard sur-

gery, this technique offers a lower risk of morbidity al- lowing a quicker return to work and sport.

27.5 Disadvantages

This technique is an operation preferably performed under general anaesthesia although it is a minimally invasive technique and it necessitates extensive use of fluoroscopy. The technique uses the same approach as a kyphoplasty in osteoporotic fractures but the cement application is difficult. This is mainly due to a short crystallisation time, which makes it difficult to apply and necessitates a long learning curve. The initial cost is high, due to the price of IBTs, but we believe this cost is balanced out by a short hospitalisation time and a faster return to work.

27.6 Indications

The trauma group reached a consensus about the following indications:

Traumatic fractures type A1, A3.1, A2 and A3.2 in- volving vertebral bodies from T5 to L5, without any neurological deficit, with at least 15° of deformity Traumatic fractures type A3.1, A3.2 in which the posterior fragment in the canal does not cause any neurological deficit

Traumatic fractures type A2 and A3.2 only with a split less than 2 mm

May be considered in fractures of type B associated with posterior instrumentation

27.7 Contraindications

Contraindications are given for high thoracic levels, cervical fractures, fractures of type A2 with a split larg- er than 2 mm and fractures of type A3.3 and type C.

Pathological fractures should not be treated with this technique.

27.8 Surgical Technique

27.8.1

Kyphoplasty Technique

Compared with the standard kyphoplasty for osteoporotic fractures, there are some differences to consider in the treatment of traumatic fractures for young pa-

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tients. First, the preoperative planning must include clinical examination, plain X-rays, a CT scan and sometimes an MRI to exclude type B fractures. This allows a better classification of the fracture and correct planning for the ideal trajectory of the cannulas. The planning ensures the best possible reduction of the fracture without increasing the risk of bone fragment displacement in the canal in type A3 fractures. An MRI examination is useful in defined cases, especially to exclude a type B fracture.

We recommend general anaesthesia in these proce- dures, to allow a possible switch to an open procedure in case of an unsatisfactory reduction. A radiolucent operating table is recommended and the patient is po- sitioned in slight lordosis, so facilitating the reduction of the fracture and sometimes already reducing the fracture. A good fluoroscopic C-arm must be at hand and able to perform AP and lateral images.

After correct definition of the involved level, Jamshi- di cannulas are placed under fluoroscopy either trans- or extrapedicularly, according to the preoperative CT planning. The choice of the trans- or extrapedicular method depends on the level and size of the pedicles.

The cannula has to perforate the posterior cortical wall and penetrate a few millimetres into the vertebral body.

Guide pins are then introduced and X-rays must be taken, both in AP and lateral views, to ensure there is no perforation of the endplates and that the trajectory is parallel to the fractured endplate. Correct position- ing of the guide pins (and then the IBT) depends on the trajectory and angulations of the fracture. A space of at least a few millimetres must be left under the superior endplate and the fracture line. Contact of the IBT and cement with the disc space must be avoided.

The working cannulas are introduced, foraging of the vertebral body is performed and two IBTs are placed (Fig. 27.1). The size of IBT must be chosen with regard to the vertebral body size, the amount of reduction needed and the type of fracture. For example, in an A3 fracture a 4-cc balloon is preferred and placed in the anterior third portion of the vertebra, minimising the risk of a posterior fragment displacement in the canal.

Each IBT is connected to a syringe filled with radio- opaque medium (Fig. 27.2). The syringe is also connected to a pressure transducer (giving pressure in atm

Fig. 27.1. Position of IBT in vertebral body

Fig. 27.2. Inflation of IBT

or psi). Simultaneous inflating of both IBTs is performed to 50 psi, and then the internal guide is removed. The IBTs are progressively inflated by 0.5-ml augmentation, under constant fluoroscopy with control of pressure and volume.

In cases of fractures in young patients, high pres- sures of 300 psi are quickly obtained with a low volume of IBT. In these cases you have to take time to let the pressure diminish while the balloons expand, with pro- gressive displacement of trabeculae and correction of fracture. When the volume reaches 1.5 cc, an AP view is performed to further check the position of the IBTs. If the position is optimal, inflation is performed until a correct reduction is obtained. Operative time is pro- portional to the age, type of the fracture and deformity and it may take up to 1.5 h. Maximal pressure of 400 psi and total volume must not be exceeded as there is risk of rupturing the balloons.

When satisfied with the reduction, both IBTs are removed and the cavity is cemented. Calcibon is held in a fridge and mixed just before use, so as to delay the crystallisation time. Mixing is always performed by pour- ing the liquid first and then adding the powder, and it takes 60 seconds to obtain a viscous consistency. Can- nulas, 1.5 cc in volume, are prefilled quickly, and the distal end is obtruded with bone wax to protect the cement from early contact with blood. Filling of the vertebral body starts in the anterior part and goes posteriorly, under constant fluoroscopy, paying special attention to the posterior fragment in type A3 fractures (Figs. 27.3, 27.4). This phase is short and takes a maximum of 3 min. Crystallisation is completed within a few minutes, cannulas are removed, a final fluoroscopy check is performed and the skin is sutured.

Fig. 27.3. Filling of the vertebral body starts anteriorly

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Fig. 27.4. Completed cementing of vertebral body

27.8.2

Calcium Phosphate Cements

Calcium phosphate cements (CPCs) consist of a powder containing one or more solid compounds of calcium and/or phosphate salts and a liquid that can be wa- ter or aqueous solution [3]. If the powder and the liquid are mixed in an appropriate ratio, they form a paste that at room or body temperature sets by entanglement of the crystals precipitated within the paste [2, 4]. The mass does not set for several minutes and is, depending on the liquid/powder ratio, injectable via a syringe [9, 10]. One of the most important characteristics of CPCs is that they are supposed to be osteoconductive and de- gradable [6, 7, 15, 16].

Although numerous reports on in vitro and in vivo investigation dealing with CPCs have been published, there are still some problems to overcome. These mainly involve the setting time, the compressive strength reached after setting and the degradation rate of the cement in vivo [5]. A relatively long time for the material to harden in situ was reported for Bone Source cement.

Blood and tissue fluids, which come in contact with the cement shortly after initial placement, can significantly delay the final setting time of some cements. Alpha- BSM and Cementek harden after 20 – 40 min, which renders them impractical. Regarding strength, Norian SRS, Alpha-BSM and Cementek hardly develop a compressive strength that equals the maximum strength of trabecular bone [5]. Resorption of Bone Source is poor- ly documented.

A CPC that is mainly composed of alpha-tricalcium phosphate (alpha-Ca3(PO4)2) and dicalcium (CaHPO4) has also been developed and improved. This alpha- TCP cement was originally called Biocement D in 1998, but is now marketed under the name Calcibon. Animal studies were performed from August 1999 to May 2000, and use as a graft substitute in humans started in July 2000. The CE mark was obtained in December 2002. Mixed at a liquid to powder ratio of 0.35:1, it has a cohesion time of 1 min, an initial setting time of 2 – 3 min, a final setting time of 7.5 min at 37°C and a maximal compressive strength of 60 MPa reached at 3 days. The cement is composed of a cement powder

that contains 61 % alpha-TCP, 26 % CaHPO4, 10 % CaCO3and 3 % precipitated hydroxyapatite. The cement liquid is a 4 % aqueous solution of Na2HPO4. The cement paste hardens as a CDHA trough hydrolysis of the alpha-TCP:

3 Ca₃(PO₄)₂+ H₂O – CA₉(HPO₄) (PO₄) 5OH To be injectable via a syringe, the liquid to powder ratio in Calcibon was set between 0.3:1 and 0.4:1. Cell culture studies using fibroblast and human bone marrow oste- oprogenitors showed that the substance is not cytotoxic and stimulates differentiation of osteoblasts. Osteoclast response to the cement in tissue culture showed that the material was reabsorbed by the osteoclasts [11].

27.9 Postoperative Care

Depending on the residual pain, mobilisation can start as of the 6th postoperative hour. For 2 weeks we advise not to lift any load, and any physical effort is to be avoided.

Gentle decontracting massages are prescribed, with isometric muscular reinforcement. Standard advice for a good back posture is given by a physiotherapist. After 2 weeks, the patient may return to work and take part in sport. Delays are due to residual post-traumatic muscle contraction.

27.10 Results

27.10.1 Clinical Example

This young 25-year-old female, manual worker, fell at work from a height of 3 metres. She was admitted in emergency with acute low back pain, and an isolated L1 fracture (Fig. 27.5). VAS was initially at 9. CT scan con- firmed a type A3.2 fracture with 22° of deformity (Figs.

27.6, 27.7). A Calcibon kyphoplasty was performed under general anaesthesia at day 2. Postoperative plain X-rays with the patient upright (Fig. 27.8) and a CT scan (Figs. 27.9, 27.10) at 24 h show the reduction of the fracture. The patient was discharged after 48 h, and resumed the work after 4 weeks, without any pain. At 1-year X-ray control shows a deformity of 6° (Fig. 27.11).

27.10.2 Clinical Results

From August 2002 to August 2003, 28 patients, with a mean age of 45 years, with 33 acute traumatic vertebral type A fractures were treated.

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Fig. 27.5. Preoperative plain X-rays

Fig. 27.6. Preoperative CT scan, axial

Fig. 27.7. Preoperative CT scan, lateral

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Fig. 27.8. Postoperative plain X-rays (standing)

Fig. 27.9. Postoperative CT scan, axial

Fig. 27.10. Postoperative CT scan, lateral

All patients were evaluated with plain X-rays preoperatively and also after 24 h, 7 days, and 2, 6 and 12 months. A preoperative CT scan was always performed which was also done after 24 h and 1 year. Clini- cal examinations with VAS, Roland Morris disability score evaluations, are performed preoperatively, after 7 days, and after 2, 6 and 12 months. The operative pro-

cedures were performed in a general manner, under general anaesthesia. The type of fractures were 3 A1.1, 21 A1.2, 7 A3.1 and 2 A3.2. The mean surgery time was 60 min, the final pressure of the IBT was 233 psi and the mean volume of Calcibon injected was 6.8 ml.

The mean initial kyphosis was 17°, and reduction obtained preoperatively was to a mean of 5°. We noticed

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Pre Per-op 24h 7 d 2 m 6 m 12 m 25

22.5 20 17.5 15 12.5 10 7.5 5 2.5 0

0

Pre 7 d 2 m 6 m 12 m 10

8

6

4

2

0 Fig. 27.11. X-rays at 1 year

Fig. 27.12. Kyphosis angles in degrees

a gradual loss of correction from a mean of 6° at 24 h to a mean of 10° at the last follow-up (Fig. 27.12). The mean preoperative segmental kyphosis was 4°, perioperative correction was to –6°, 24 h after surgery it was –1° with a mean of 4° at the last follow-up. The height restoration (Beck index) was 0.70 preoperative, corrected to 0.90 perioperative, 0.87 24 h after surgery and 0.84 at the last follow-up without clinical significance. The VAS score demonstrated a decrease over time from a mean of

Fig. 27.13. Visual analogue scale

8.7 preoperative, to 3.1 at 7 days and 1 at the last follow- up (Fig. 27.13). Roland Morris disability scores demonstrated a similar improvement over time from a mean of 5 at 7 days to a mean of 2 at the last follow-up.

All patients with vertebral fractures as sole medical problems were discharged from the hospital within

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48 h. All active patients returned to work within 3 months.

27.10.3 Complications

We noticed two anterior wall perforations by cannulas, six leakages in the disc space and one posteriorly in the spinal canal without any clinical significance. These leakages certainly occurred through fracture lines as we never noticed any leakage in veins or pulmonary embolism. No long-term complications were noticed.

27.11 Critical Evaluation

The standard treatment of thoracolumbar vertebral fractures type A is still debated. Conservative treatment does not restore the spine balance and due to the loss of anterior height this may lead to acceleration of disc degeneration and loss of anterior support.

Open surgical therapy with instrumentation carries definite risks, is destructive for muscles, but helps to restore the vertebral height, thus preventing the long- term chronic pain sometimes seen in posttraumatic kyphotic deformations. Kyphoplasty is a new technique in the treatment of osteoporotic fractures resis- tant to conservative therapy, and seems to be superior to vertebroplasty as the risk of complications, such as cement leakage and venous embolism, is less.

Our study demonstrates that kyphoplasty in the treatment of some thoracolumbar fractures compares well with the standard therapies. A rapid decrease in pain, early discharge from the hospital and the high rate of early return to normal daily activities and work is especially appealing. The tendency to lose the correction obtained after the operation justifies a long-term analysis. This long-term loss of correction has also been described with posterior instrumentation. Only long-term follow-up will tell if this technique can be used as a standard alternative therapy of acute thoracolumbar fractures, and determine which kinds of fracture should be treated this way.

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Lumbar Spine

Low Back Pain (Ch.28) . . . 249

Disc (Ch.29 – 39) . . . 260

Disc Reconstruction (Ch.40 – 43) . . . 364

Spinal Stenosis (Ch.44) . . . 397

Fusion (Ch.45 – 48) . . . 409

Dynamic Stabilization (Ch.49 – 51) . . . 459