Kyphoplasty for all?

Abstract

The Interventional treatment of Vertebral Compression Fractures (VCFs) has undergone tremendous and expected evolution since its inception by Herve Deramond in the 1980s. Vertebroplasty was the first type of intervention that demonstrated tremendous success in managing the pain associated with VCFs. This allowed the patient to regain physical activity, which was previously restricted due to pain, which improved the quality of life and prevented further advancement of osteoporosis due to subsequent immobility. First performed in 1998, an additional type of intervention named Kyphoplasty was introduced by an orthopaedic surgeon in the US and marketed by Kyphon Corporation (acquired by Medtronic in 2009). The primary difference from vertebroplasty was the introduction of balloon bone tamps via steering bone cannulas into each hemi vertebra to allow creation of bilateral bone voids and potential elevation of the depressed endplates (fracture reduction). This allows the application of the PMMA cement to be performed in a low pressure (compaction) fashion versus vertebroplasty, which is a high pressure system of cement application to the vertebral body. This distinct difference is postulated as the reason why there is a higher cement extravasation/ embolization rate in vertebroplasty (20-40%) versus Kyphoplasty (7-9%). The majority of the reported complications was related to the cement extravasation/embolization and includes radicular neuropathies, pulmonary emboli, renal emboli, femoral neuralgia with sciatica, neurological deficit and posterior column deficit with proprioception loss. The symptomatic complication rate is 1.6- 3.0% for vertebroplasty and 0-0.3% for Kyphoplasty. The cement extravasation can also increase patient mortality, extend hospital stay and may even require open surgical removal of symptomatic extravasated cement. Pathological vertebral fractures, with particular emphasis on myelomas, are primarily treated with Kyphoplasty, which is supported by the research literature. This is because of the unpredictability of the integrity of the vertebral body due to the invasive, destructive nature of the neoplasm. Cortical margins may or may not be intact and, therefore, the risk of cement extravasation/ embolization increases. Kyphoplasty allows the creation of the bone voids and subsequent low pressure application of the thicker cement into these voids with fine control reducing the risk of leakage from the confines of the vertebral body. With retropulsed fragments, there is a relative contraindication to use of vertebroplasty because of the risk of displacing the fragment further posteriorly and causing cord/nerve root compression. On the other hand, Kyphoplasty has never been shown to ever displace a fragment posteriorly. In fact, reduction of the pressure caused by the compression with elevation of the more anterior fracture endplates has many times been shown to pull the fragment anteriorly into a more anatomic position. This suggests Kyphoplasty is a safer and therefore more clinically useful procedure than vertebroplasty in these situations. The procedure of vertebroplasty has evolved so that a unipedicle approach with as steep an angle as possible toward the midline is preferred. This unfortunately raises the risk of breaching the medial wall of the pedicle as the operator attempts to get as medial and close to the midline as possible in order to facilitate uniform distribution of cement into both sides of the vertebrae. This steep angulation is not necessary in Kyphoplasty as it is a bipedicle approach and the ideal location for the cannulas and balloon tamps is in each mid hemivertebrae. Initial comparisons of vertebroplasty versus Kyphoplasty suggested that the additional cost of Kyphoplasty did not warrant the additional potential benefits. As the complexity of the vertebroplasty kits and cement have increased, so have the kit costs. On the other hand, the costs of Kyphoplasty have actually decreased over time due to refinement of the access trocars and balloon tamps with reduction of the number of steps and subsequent kit supplies as a result. In some markets, the costs are very comparable currently. Initially, Kyhoplasty patients were mandated (arbitrarily) by Medicare in US to be inpatient status requiring an overnight hospital stay and subsequent costs. This has been rescinded and the vast majority is now out-patient procedures and who can go home two hours after the procedure. These two changes make both procedures quite comparable from a cost standpoint. Another advantage of Kyphoplasty is the ease and completeness of acquiring bone biopsies at the time of the procedure. Since many multiple myeloma patients are surreptitiously diagnosed as a result of bone biopsy at the time of spine intervention, the ability to obtain high quality specimens is critical. Vertebroplasty accesses only one half of the vertebral body typically. Kyphoplasty allows biopsies to be obtained from both sides of the vertebrae. The access cannulas entering the posterior margin of the vertebral body in Kyphoplasy are slightly larger in diameter and a dedicated coaxial bone biopsy device supplied by Kyphon produces excellent, long core, continuous specimens from both sides. This aids in the early detection of multiple myeloma patients allowing them prompt evaluation and subsequent treatment; therefore, we have a low threshold for biopsy at the time of the procedure as finding patients like these is of tremendous value. The ease of doing the biopsies bilaterally through the introducer cannulas in Kyphoplasty helps with this decision making process. In summary, I would suggest that any procedure that can be performed more safely, give the same or better results, has greater depth of indications, potentially produces better diagnostic pathologic material and has similar costs is the correct choice for treatment. For all of these reasons, I vote strongly in favor of Kyphoplasty for treatment of vertebral compression fractures