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 percu- taneous 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 princi- ples 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 classifi- cation 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 frac- tures 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 lum- bar 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 tu- mour 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 pos- terior 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