26 Microsurgical Open Vertebroplasty and Kyphoplasty

Chapter 26 26 Microsurgical Open Vertebroplasty and Kyphoplasty

B.M.Boszczyk,M.Bierschneider,B.Robert,H.Jaksche

26.1 with the virtues of applying VP to more complex frac- Terminology turesinopensurgery.

Vertebroplasty (VP) and kyphoplasty (KP) are percutaneous methods of injecting polymethylmethacry- 26.4 late (PMMA) into fractured osteoporotic vertebral Advantages bodies with the aim of immediate stabilisation and pain relief. PMMA is injected at low viscosity directly Amongst the advantages of open surgical VP, as pro- into the cancellous bone in the VP technique [8]. KP posed by Wenger and Markwalder [17], are the de- differs from VP in that a contrast-filled, inflatable bal- compression of compromised neural structures and loon is inserted into the vertebral body, allowing a de- the control over the spinal canal during the injection gree of fracture reduction and leaving a cavity behind of the augmentation material. As the most commonly after withdrawal which is filled with high-viscosity used augmentation material is still PMMA, which has PMMA [7]. the potential of inflicting thermal damage to neural structures besides mechanical compression once cured [10, 15, 16], the ability to immediately remove 26.2 extruded PMMA from the spinal canal bears obvious Surgical Principle advantages. The application of microsurgical principles to the technique of Wenger and Markwalder has The rationale behind applying spinal microsurgical led to the development of the microsurgical unilateral principles to the vertebral augmentation techniques interlaminar approach for VP and KP [3–5], which (VP and KP) is the advantage of achieving both neural minimises soft tissue trauma while maintaining the decompression and vertebral stabilisation with mini- assets of spinal decompression and control during mal approach-related trauma. For selected indications augmentation. Furthermore, as the interlaminar ap- this method enables a less invasive treatment of severe proachallowsaccesstothevertebralbodiesofboth osteoporotic and neoplastic fracture types with neural adjacent vertebrae, augmentation of neighbouring compromise that are traditionally stabilised with open vertebrae can be performed through the same ap- implant-related reconstruction [2]. proach when required. The thoracolumbar junction VP or KP for traumatic fractures in non-osteoporot- and entire lumbar spine are accessible with this tech- ic vertebrae are not considered in this chapter. nique. For the spinal surgeon accustomed to microsurgical procedures this method allows the expansion of VP and 26.3 KP to more complex cases, involving neurological com- History pression or severe posterior wall fragmentation, that are unsuitable for percutaneous treatment. No addi- The introduction of percutaneous augmentation tech- tional specialised instruments are needed for the ap- niques, VP in 1987 by Galibert et al. [6] and KP in 2000 proach as these are the same as for conventional micro- by Wong et al. [18], has added highly effective proce- discectomy or decompression. dures to the armament of the spinal surgeon faced with For carefully selected indications, microsurgical VP osteoporotic and neoplastic vertebral fractures. While and KP fill the gap between percutaneous augmenta- several reviews have focused on the remarkable clinical tion and open reconstruction with implants. success of the percutaneous application of these meth- odstouncomplicatedfractures[1,8,9,11],onlythe publication by Wenger and Markwalder [17] has dealt 26 Microsurgical Open Vertebroplasty and Kyphoplasty 231

26.5 bral collapse or incomplete burst fracture types with Disadvantages varying degrees of neural encroachment. In the classification system by Magerl et al. [12] the fractures there- Due to the narrowing of the spinal canal in the midtho- fore suitable for augmentation are the A1.1 (endplate racic spine, this technique is essentially limited to the impression), A1.2 (wedge fracture), A1.3 (vertebral col- thoracolumbar junction and lumbar spine. Above the lapse) and A3.1 (incomplete burst fracture) types. thoracolumbar junction resection of the medial pedicle wall may be necessary to avoid exerting pressure on the spinal cord during intraspinal tool placement. 26.7 As proficiency in microsurgical decompression of Contraindications the spinal canal without laminectomy and facetectomy 26.7.1 is mandatory for this method, spinal surgeons unac- Thoracic Fractures customed to such techniques may need to accept a con- siderable learning curve. Furthermore, the surgeon The microsurgical interlaminar approach has been must be able to deal with lesions of the dura and ex- used extensively at lumbar and thoracolumbar levels. truded PMMA through a very limited exposure of the However, only a small number of fractures of the mid- spinal canal. thoracic spine have been treated [5]. Here the space available between the spinal cord and the pedicle is the limiting factor and resection of the medial pedicle wall 26.6 may be necessary to allow tool placement without dan- Indications ger of neural compression. Severe osteoporotic fractures of the upper thoracic spine (T1–4) are infrequent 26.6.1 and have as yet not been treated with this microsurgical Considerations for Microsurgical Augmentation method. Four conditions affecting the thoracolumbar and lumbar spine lead to the consideration of microsurgical VP 26.7.2 or KP: Type B and C Fractures 1. Osteoporotic vertebral fractures with symptomatic Thesefracturetypesrequireadditionalposteriorin- fragment-induced compression of neural struc- strumentation in order to stabilise their inherent flex- tures ion and rotation instability characteristics. 2. Osteolytic vertebral tumours with symptomatic or rapidly progressing neoplastic compression of neural structures 26.7.3 3. Osteoporotic vertebral fractures or osteolytic tu- Laminectomy mours with severe compromise of the posterior The extent of required decompression and vertebral vertebral wall, judged to bear a high risk of epidu- body augmentation must be evaluated realistically with ral PMMA leakage respect to the surgical goal that is achievable with this 4. Osteoporotic vertebral fractures in the setting of technique. When complete laminectomy becomes nec- preexisting symptomatic spinal stenosis requiring essary, especially at the thoracolumbar levels, posterior decompression instrumentationshouldbeadded.Thisisrecommend- ed as the resection of the posterior tension band leads 26.6.2 to load transfer to the anterior column, where adjacent Type A Fractures vertebral bodies weakened through osteoporosis or tumour metastasis may fail. Thecharacterofthefractureandthequalityofbone must be assessed during the preoperative evaluation. In osteoporotic vertebrae with rarefied trabecular struc- 26.8 ture, fractures tend to result in varying degrees of verte- Patient’s Informed Consent bral body collapse with possible retropulsion of the posterior wall into the spinal canal. In contrast to fractures Beside the general considerations for spinal surgery, in non-osteoporotic vertebrae, splitting or severe frag- the following points should be discussed: mentation occur less frequently. While mild vertebral 1. Approach-related injury of the neural structures collapse is ideal for percutaneous augmentation, the ma- and dura with the possibility of neurological dete- jority of osteoporotic fractures requiring microsurgical rioration and cerebrospinal fluid fistula augmentation will be characterised by complete verte- 232 Thoracic/Thoracolumbar Spine – Fractures

2. Injury of abdominal or thoracic viscera and vessels al side is accomplished by “crossing over” the thecal sac through anterior vertebral perforation with VP or as described in Chapter 44. Resection of the facet joint KP instruments and laminae should be as sparing as possible. Once the 3. PMMA extrusion into the spinal canal with neuro- lateral edge of the thecal sac is reached, it is gently un- logical compromise dermined using a curved dissector and carefully mobi- 4. PMMA leakage into the venous system with the po- lised medially (3–4 mm) to expose the lateral aspect of tential of lethal pulmonary embolism or paradox the posterior vertebral wall. The thecal sac may be re- cerebral embolism tracted cranial or caudal to the segmental nerve root in 5. Conversion to complete laminectomy and instru- accordance with the morphology of the fracture mentation if adequate decompression cannot be (Fig. 26.1a–c). It should be appreciated that, in contrast achieved microsurgically to non-traumatic spinal stenosis, the compression usu- 6. Lowered fracture threshold of adjacent vertebrae in ally arises from anterior to the thecal sac due to posteri- the presence of severe osteoporosis or wall retropulsion. An attempt may be made to gently impact retropulsed bone in fresher fractures, however in severely osteoporotic bone the situation may be ag- 26.9 gravated by further fissuring of the posterior wall, es- Surgical Technique pecially if the fracture is already partially consolidated. This is undesirable as any additional fissures will in- 26.9.1 crease the risk of epidural cement leakage during aug- Microsurgical Interlaminar Vertebroplasty mentation. and Kyphoplasty ThetipofaVPcannulaorKPtrocarmaynowbeset The operation is performed under general anaesthesia. on the posterior vertebral wall lateral to the thecal sac. The patient is placed prone on a spine frame or cush- Theplacementmaybeoverorunderthe“shoulder”of ions with legs extended. Osteoporotic patients must be the segmental nerve (Fig. 26.1b, c). This is done visual- treated very gently to avoid rib fractures. As lateral ly, verifying that the thecal sac is not violated. The angle fluoroscopy will be needed for the vertebral augmenta- of the instrument is adjusted in accordance with the lat- tion after the decompression has been completed, the eral fluoroscopy view and is tapped into the vertebral position of the C-arm should be taken into account dur- body aiming for the anterior midline of the vertebral ing the initial positioning and draping of the patient. body. While the VP cannula is introduced into the ante- The vertebral body or bodies to be treated is/are locali- rior third of the vertebral body, the KP trocar is placed sedwiththeC-arm.Thelevelofthecompressedneural just beyond the posterior vertebral wall and a hand structures and the morphology of the fracture dictates drillisadvancedtocreateachannelfortheplacement which interlaminar space is to be approached, i.e. cra- of the kyphoplasty balloon. A biopsy may optionally be nial or caudal of the lamina of the affected vertebral taken at this point. If VP is to be performed, contrast body. When adjacent vertebrae are to be treated, the medium may optionally be injected in order to assess common interlaminar space is chosen as this will allow any leakage pathways from the vertebral body. Ideally, augmentation of both vertebral bodies through the the vertebral body will fill as a cloud before the contrast same approach. A longitudinal midline skin incision is medium dissipates. Very rapid paravertebral or epidu- centred above the spinous processes of the targeted in- ral drainage should prompt the surgeon to either read- terlaminar space. In single or adjacent levels, an inci- just the placement of the cannula (without reperfora- sion of 5–7 cm is usually sufficient. Subcutaneous dis- ting the posterior vertebral wall) or inject the augmen- section exposes the thoracolumbar fascia at its inser- tation material very slowly under live fluoroscopy. For tion to the spinous processes. The fascia is incised lon- KP, the balloon is inflated gradually (Fig. 26.2a) until gitudinally, close to the spinous processes on the side the desired effect of cavity formation and, as far as pos- with the predominating neurological symptoms or sible, fracture reduction is achieved. The balloon is more severe disruption of the posterior wall. The para- withdrawn, leaving a cavity to be filled with PMMA. vertebral musculature is detached medially and gently ForbothtechniquesPMMAisinjectedinsmallpor- retracted, exposing the interlaminar space. The spinal tions (approximately 0.5 ml) into the vertebral body us- canal is opened by longitudinally dividing the ligamen- ing frequent fluoroscopic control. KP allows PMMA to tum flavum and resecting the bony rims of the superior be introduced into the cavity at high viscosity and inferior laminae using punches. As with any intra- (Fig. 26.2b) while the viscosity for VP must be lower in spinal procedure, care is taken not to injure the dura. order to allow for trabecular distribution. The injection Decompression of the thecal sac and segmental is discontinued once sufficient filling of the vertebral nerve root is accomplished by piecemeal removal of li- body has been achieved or leakage is detected. The epi- gamentum flavum, laminae and medial portion of the dural space may be inspected at any time during the zygapophyseal joint. Decompression of the contralater- procedure, allowing extruded PMMA to be removed 26 Microsurgical Open Vertebroplasty and Kyphoplasty 233

Fig. 26.1. a Illustration of the interlaminar fenestra- tion, unilaterally exposing the thecal sac, thereby pro- viding access for the decompression of the neural structures. b The entry point to the superior verte- b bral body (X)throughthe posterior wall is exposed by gentle retraction of the thecal sac. c The correspond- ing entry point to the inferior vertebral body (X)is reachedbygentlyretracting the shoulder of the exiting nerve root a

from under the thecal sac may be difficult. Bleeding from the vertebral body usually subsides after the injection of PMMA. Tool placement does not differ from osteoporotic fractures, however in kyphoplasty the balloon will expand predominantly into the region of the osteolysis. In cases with posterior wall infiltration (see also Fig. 26.3), careful attention must therefore be di- rected towards recognising any tendency of increased posterior wall retropulsion. During augmentation, PMMA will follow the path of least resistance in the Fig. 26.2. a Illustration of a single kyphoplasty balloon placed osteolytic bone and leakage may occur unexpectedly. convergently into the vertebral body through the interlaminar Thisisespeciallytrueforvertebraethathavereceived approach in an axial view. b After removal of the balloon the radiation,wherepartsofthecancellousbonemaybe remaining cavity is cautiously filled with high-viscosity bone cement filled with dense fibrous tissue.

26.9.3 before it is fully cured. After the augmentation has been Avoiding Complications During Augmentation completed, the instruments are withdrawn and the woundisclosedinlayersintheusualfashionafterirri- The single most important element in detecting leak- gation. age is the lateral fluoroscopy view. Often only a very fine trail of PMMA will initially be seen either posterior to the vertebral body, indicating epidural leakage, or 26.9.2 anterior to the vertebral body, indicating venous embo- Considerations for Vertebral Tumours lism. The entire circumference of the vertebral body The treatment of neoplastic lesions with this technique should therefore be visualised on the monitor. Saving is more demanding than the treatment of osteoporotic an image before injection as reference is helpful in dif- fractures. Essentially, the decompression is performed ferentiating superimposed artefacts from real leakages. in the same manner, although removal of tumour mass Injection should be interrupted immediately whenever 234 Thoracic/Thoracolumbar Spine – Fractures

Fig. 26.3. a Sagittal T2-weighted MRI revealing osteolytic infiltration of the L5 vertebral body with extension to the spinal canal. b Axial T2-weighted MRI demonstrating the right-sided neoplastic neural compression. c Sagittal CT reconstruction at 7 month follow-up showing maintenance of vertebral body c height. d Axial CT of L5 at 7 month follow-up showing the central PMMA placement and slender right-sided hemilaminectomy

26.9.4 leakage is suspected. As PMMA cures more quickly Vertebroplasty or Kyphoplasty within the warm body environment, further injection may be attempted after 1 or 2 minutes. This will, how- Asreviewoftheliteratureshowsthatpainreliefand ever, only be possible with slow-curing cement and in biomechanical stability resulting from both procedures kyphoplasty requires the withdrawal of the cement ap- arecomparable[4],otherfactorsneedtobetakeninto plication cannula (not the working cannula) in order to account in the choice between these techniques. Frac- maintain cement injectability. Extruded PMMA is usu- ture reduction and restoration of vertebral body height ally easily removed from the epidural space as long as it may be achieved through kyphoplasty, however severe is of a pasty consistency. PMMA usually does not ad- loss of height and an older fracture age may limit these here to the dura. Subligamentary deposits, however, effects to a minimum [5]. The most valuable consistent may be impossible to remove. Although smaller depos- effect achievable through kyphoplasty in this setting is its are unlikely to cause any neural damage, the spinal the markedly reduced rate of leakage [5, 14] through canal may be irrigated to dissipate heat during curing the injection of high-viscosity PMMA into the pre- in such an event. formedcavity,evenincaseswithsignificantposterior wall disruption. 26 Microsurgical Open Vertebroplasty and Kyphoplasty 235

26.10 60–70% in an investigation and review by Nguyen et Postoperative Care al. [13]. Although very severe fractures with a high degree of fragmentation, or such requiring complete la- Immediate postoperative care does not differ from that minectomy, will continue to demand conventional sur- for isolated microsurgical decompression. As the verte- gical reconstruction, the reduced invasiveness and bral body is stabilised as soon as the PMMA is fully complication rate of the described microsurgical aug- cured (approximately 20 minutes), patients may be mo- mentation techniques justify considering these meth- bilised on the day of the procedure and do not routinely ods as a first-line approach whenever feasible. require bracing. As the surgical goal is accomplished with the decompression of the neural structures and stabilisation of the vertebral body, postoperative atten- 26.12 tion should be focused on the treatment of the primary Results and Conclusion disease leading to the fracture (osteoporosis or malig- nancy). Theresultsofthefirst24patients(21womenand3 men; mean age 75.5 years; range 57–91 years) with a total of 34 severe osteoporotic vertebral fractures treat- 26.11 ed from 2000 to 2002 with microsurgical interlaminar Hazards, Pitfalls and Complications VP or KP have been published in detail [5]. There were seven type A1.1 (see also Fig. 26.4), six type A1.2, ten To date we have experienced no major complications type A1.3, one type A2.2 and ten type A3.1 fractures with these methods. In a series published on our first 24 (see also Fig. 26.5). osteoporotic patients [5], there were two approach-re- Case example 1 (Fig. 26.3): This 67-year-old patient lated dural lacerations. These were sutured and sealed developed progressive low back pain and right-sided with fibrin glue without evidence of cerebrospinal fluid foot drop following osteolytic prostate cancer metasta- fistula at follow-up. The vertebral arch fractured in one sis to the spine (Fig. 26.3a, b). Decompression of the L5 patient during decompression without clinical conse- nerve root was performed through the L5/S1 interlami- quence and one patient suffered perioperative rib frac- nar space. Impingement of the L5 nerve root at the tures which healed during the follow-up period. Signif- shoulder made a slight hemilaminectomy necessary. icant epidural leakage of PMMA requiring removal oc- Central augmentation by kyphoplasty in the load-bear- curred in five patients. This was achieved before the ing area was achieved (Fig. 26.3c, d). At 7 month follow- exothermic curing phase. Minor subligamentary leak- up the patient has only minor low back pain with re- age was not removed. In total, the leakage in patients solvingfootdropandiscapableofextendedhiking. treated with VP amounted to 73% while the respective Case example 2 (Fig. 26.4): This 85-year-old patient rate for KP was 39%. Here, leakage was defined as any presented with an acute onset of low back pain centred breach of the vertebral cortical shell, regardless of mag- over L4 and pronounced neurogenic claudication with nitude, and was assessed from the postoperative com- hypaesthesia of the L5 dermatomes bilaterally. Preop- puted tomography scan. In these complex fractures KP erative evaluation revealed a new mild endplate im- was found to provide a greater level of control over the pression fracture of L4 (type A1.1) along with multiseg- injected PMMA than VP. mental spinal stenosis (Fig. 26.4a, b). Interlaminar de- Significant prevertebral PMMA leakage occurred in compression of L3/L4 and L4/L5 was performed from a patient treated for metastasis of a bronchial carcino- the left with “cross-over” decompression to the right. ma after the anterior cortex was inadvertently perforat- In order to treat the mild endplate impression fracture, ed with the VP trocar. The leakage, which collected PMMAwasinjectedasvertebroplastybelowtheL4su- close to the vertebral body, had no clinical effect. In an- perior endplate (Fig. 26.4c, d) via a vertebroplasty can- other patient, treated for breast carcinoma metastasis, nula introduced through the posterior wall of L4. Post- significant PMMA leakage occurred under the posteri- operatively, back pain had markedly subsided and the or longitudinal ligament during VP which could not be claudication improved. removed. Presumably as a consequence of radiation of Case example 3 [3](Fig. 26.5): This 79-year-old pa- the spine, the dura was strongly adherent to the sur- tient suffered an incomplete burst fracture of L1 rounding structures and prevented adequate mobilisa- (type A3.1) (Fig. 26.5a) after a fall and presented with tion for removal of the cement. The spinal canal was ir- severe back pain but without neurological deficit. Due rigated during curing of the cement and no neurologi- to a recent history of septic knee endoprosthesis and cal deficit was found postoperatively. pulmonary embolism, anterior reconstruction was de- The overall complication rate for osteoporotic frac- clined. Percutaneous kyphoplasty was also declined tures with neurological deficits treated by conventional due to the severe disruption of the posterior wall with reconstructivesurgerywasfoundtobeashighas increased risk of PMMA leakage or bone retropulsion. 236 Thoracic/Thoracolumbar Spine – Fractures

d Postoperative lateral radiograph with evident PMMA filling below the superior endplate of L4

Fig. 26.4. a Preoperative sagittal CT-myelogram reconstruction revealing a mild superior endplate impression of L4 type A1.1. b Axial CT-myelogram demonstrating the predominantly left-sided spinal stenosis at L3/L4. c Postoperative AP radiograph showing the PMMA augmentation below the endplate of L4

b dysesthesia or numbness in five of eight patients with preoperative deficits. Radicular pain improved in all butonepatient,whowasfoundtohavepersistentnerve An L1/L2 interlaminar approach (Fig. 26.5b) allowed root impingement and has undergone an extended de- the placement of the kyphoplasty balloon parallel to compression since. With meticulous haemostasis, the the inferior endplate (Fig. 26.5c), below the fractured average intraoperative blood loss in patients without portion of the posterior wall. Inflation of the balloon bleeding disorders was below 100 ml, an amount com- achieved a degree of height restoration (Fig. 26.5d) and parable to solitary microsurgical spinal decompres- allowedcontrolledfillingofthevertebralbody sion. The actual augmentation procedure (i.e. in addi- (Fig. 26.5e, f). Control over the spinal canal was main- tion to the decompression) was found to add tained throughout the procedure. In the event of ce- 10–40 minutes to the operation time, depending upon ment leakage, this could have been promptly removed. the complexity of the fracture and the use of VP or KP. At 18 month follow-up the patient is free of thoraco- Even with KP, an improvement of kyphosis of 10° or lumbar back pain despite moderate subsidence of the more was the exception in these severely injured verte- vertebral body (Fig. 26.5g). brae with a fracture age of at least 4 weeks and was only These patients were followed postoperatively for an reached in two patients. In these severely osteoporotic average of 9.5 months (range 1–31 months). During patients a total of seven new fractures occurred during this period there was no progressive olisthesis or sign the follow-up period, only three of which were, howev- of instability attributable to the decompression. The er, adjacent to augmented vertebrae. Two of the adja- majority of patients showed significant improvement cent fractures required augmentation. of both back and leg pain (improvement of preopera- Although clinical experience with the techniques tive back and radicular pain was excellent in seven, described here is still limited, the two main compo- good in ten, fair in five patients and poor in one pa- nents of microsurgical decompression and vertebral tient). The patient with poor outcome had a symptom- augmentation are each established methods. Combin- atic adjacent fracture at the time of follow-up. Neuro- ing microsurgical decompression with VP or KP allows logical follow-up revealed an improvement in motor the treatment of severe osteoporotic fractures associat- power in five of eight patients and an improvement of ed with neurological deficits that are not sufficiently 26 Microsurgical Open Vertebroplasty and Kyphoplasty 237

e fg Fig. 26.5. a Sagittal T2-weighted MRI revealing an incomplete burst fracture of L1 type A3.1 with a large retropulsed fragment of the posterior wall. b Placement of a single kyphoplasty balloon via an L1/L2 interlaminar approach. c Placement of the kyphoplasty balloon parallel to the inferior endplate through the posterior wall after gently retracting the thecal sac. d Inflation of the kyphoplasty balloon and restoration of vertebral height. e Postoperative CT showing containment of PMMA within the vertebral body. f Lateral postoperative radiograph revealing superior endplate support by PMMA. g Lateral radiograph at 18 month follow- up revealing moderate subsidence of L1 238 Thoracic/Thoracolumbar Spine – Fractures

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