We Need to Talk about Lumbar Total Disc Replacement STEPHEN BEATTY Int J Spine Surg 2018, 12 (2) 201-240 doi: https://doi.org/10.14444/5029 http://ijssurgery.com/content/12/2/201 This information is current as of September 29, 2021. Email Alerts Receive free email-alerts when new articles cite this article. Sign up at: http://ijssurgery.com/alerts The International Journal of Spine Surgery 2397 Waterbury Circle, Suite 1, Aurora, IL 60504, Phone: +1-630-375-1432 © 2018 ISASS. All RightsDownloaded Reserved. from http://ijssurgery.com/ by guest on September 29, 2021 International Journal of Spine Surgery, Vol. 12, No. 2, 2018, pp. 201–240 https://doi.org/10.14444/5029 ÓInternational Society for the Advancement of Spine Surgery We Need to Talk about Lumbar Total Disc Replacement STEPHEN BEATTY, MD Institute of Health Sciences, Waterford Institute of Technology, Waterford, Republic of Ireland ABSTRACT Background: Replacement of a diseased lumbar intervertebral disc with an artificial device, a procedure known as lumbar total disc replacement (LTDR), has been practiced since the 1980s. Methods: Comprehensive review of published literature germane to LTDR, but comment is restricted to high- quality evidence reporting implantation of lumbar artificial discs that have been commercially available for at least 15 years at the time of writing and which continue to be commercially available. Results: LTDR is shown to be a noninferior (and sometimes superior) alternative to lumbar fusion in patients with discogenic low back pain and/or radicular pain attributable to lumbar disc degenerative disease (LDDD). Further, LTDR is a motion-preserving procedure, and evidence is emerging that it may also result in risk reduction for subsequent development and/or progression of adjacent segment disease. Conclusions: In spite of the substantial logistical challenges to the safe introduction of LTDR to a health care facility, the procedure continues to gain acceptance, albeit slowly. Clinical Relevance: Patients with LDDD who are considering an offer of spinal surgery can only provide valid and informed consent if they have been made aware of all reasonable surgical and nonsurgical options that may benefit them. Accordingly, and in those cases in which LTDR may have a role to play, patients under consideration for other forms of spinal surgery should be informed that this valid procedure exists. TDR Keywords: lumbar artificial disc replacement, lumbar total disc replacement, lumbar disc arthroplasty, lumbar disc degenerative disease, lumbar fusion, lumbar discectomy, informed consent INTRODUCTION important to appreciate that AFs, ND, and DH are radiologically evident in 39% to 76%, 48% to The most satisfactory definition for lumbar 85%, and 27% to 67% of asymptomatic patients, degenerative disc disease (LDDD) is ‘‘a condition respectively.7 where a damaged lumbar vertebral disc causes LDDD can present with low back pain (LBP), chronic pain in the lumbar region and/or leg sciatica, or both. LBP attributable to LDDD is (sciatica),’’ and the underlying disc changes include described as discogenic, is principally midline and annular fissure, degeneration of the nucleus pul- immediate paraspinous in the lumbar area, and is 1 posus, and herniation. Annular fissures (AFs) are aggravated by sitting and flexion.8 Discogenic back separations of annular fibers from their attachment pain is primarily mechanical in nature and is the to the vertebral bone and are classed as concentric, result of internal disruption (ND and AFs), leading 1 radial, or transverse. Nuclear degeneration (ND) to the inability of the nucleus pulposus to properly manifests in a wide array of changes, including bear the compression load and consequential and (but not restricted to) desiccation, fibrosis, and inappropriate diversion of this load to the posterior 2–5 narrowing of the disc space. A disc is described annulus.9–11 However, there may also be a chemical as herniated if there is localized displacement of component to discogenic LBP, as inflammatory disc material beyond the limits of the interverte- agents contained in degraded matrix materials can bral disc space, and disc herniation (DH) is stimulate and facilitate nociception.12 classified as protrusion or extrusion.1 Of note, The term sciatica (or lumbar radiculopathy) the presence of disc tissue extending beyond the refers to pain that radiates from the buttock down edges of the ring apophyses, throughout the along the course of the sciatic nerve,13 and circumference of the disc, is referred to as bulging neuroradiologic studies report that 87% of cases and is not considered a form of herniation.6 It is are associated with lumbar DH,14 the remainder Downloaded from http://ijssurgery.com/ by guest on September 29, 2021 Patients with LDDD Who Are Seeking Surgical Advice Must Be Informed of LTDR being either of extraspinal or of unknown origin.15 sonably premised on the observation that only The sciatic nerve is the largest nerve in the human surgery has been shown to benefit pain relief and a body,16 and disturbances anywhere along its course composite of condition-specific outcomes in the can give rise to symptoms; in the case of DH, short, medium, and long term.27,28 Nevertheless, it mechanical compression (distortion) of the nerve should be acknowledged that many patients will root below the affected disk is the putative cause,16 continue to experience mild to moderate symptoms although the chemical impact of inflammatory 5 years after surgery.29 17 cytokines may also contribute to symptoms. In the absence of DH, it is difficult to comment Sciatica attributable to DH is typically aggravated on the natural history of LDDD because of the lack by any Valsalva maneuver and is not always of correlation between evident disease and symp- 16 accompanied by LBP. Weakness and muscle toms,30–32 with the inevitable consequence that wasting of the affected limb is seen in less than half prospective studies are limited to a subgroup of 16 of cases, and foot drop is rare, reflecting the view symptomatic patients. Furthermore, LDDD and its that sensory fibers of the sciatic nerve may be more progression are not a mere function of age, because 18 sensitive to compression than its motor fibers genetic background33–35 and environmental factors because the dorsal roots of spinal nerves that (ie, mechanical, such as compressive loading, shear subserve nociception are unmyelinated and of small stress, and vibration)12 profoundly influence the risk diameter (C group peripheral nerves), whereas for the condition and its progression, and any motor function is subserved by fibers that are correlation is further confounded by the observation myelinated and of large diameter (A group periph- 19 that the presence of LDDD at a given level appears eral nerves). Most clinical tests devised to ascer- to be self-initiating and self-propagating at the tain whether the reported sciatica is attributable to 36–38 39 same and at adjacent levels. Notwithstanding lumbar DH are a variation of the straight-leg raising the imperfect association between age and LDDD, a test, which is sensitive (90%) but not specific.20 A relationship does exist,40 reflected in and attribut- few days after the onset of symptoms, electromyog- able to an age-related decline in the water41,42 and raphy and nerve conduction studies reveal a macromolecule43 content of intervertebral discs; topographic distribution of muscular denervation accordingly, LDDD should be viewed as a chronic corresponding to a nerve root, thereby confirming a and progressive condition. radiculopathy.16 Disc herniation is the result of ND in the In the majority of cases, sciatica resolves sponta- 44 neously within 3 months of onset.16,21 Recovery presence of AF, and sciatica attributable to DH may be facilitated with physical therapy aimed at can improve substantially with a nonsurgical approach, resulting in a good or excellent outcome enhancing control of the transversus abdominis and 45–47 multifidus muscles, thereby stabilizing the spine, in 85% to 90% of cases. Indeed, a recent and although the value of such regimes is difficult to systematic review reports that magnetic resonance measure.16 Epidural injections of glucocorticoids imaging–confirmed spontaneous regression of lum- are associated with short-term decrease in leg pain bar DH occurs in 96%, 79%, and 41% of but not with a decrease in need for subsequent sequestered, extruded, and protruded cases, respec- 48 surgery.22–24 Attempts to identify clinical and tively. However, the relationship between clinical psychological variables of prognostic value in improvement and radiologic evidence of spontane- patients with sciatica have been unrewarding.25 ous resorption of herniated disc material is less 47 For example, of four studies considering the clear. predictive value of duration of symptoms, only Beyond the self-initiating and self-propagating one21 reported a longer duration to be associated nature of LDDD at the same and adjacent levels, with a poor outcome in cases of conservatively LDDD also appears to cause vertebral body treated sciatica.25 Notwithstanding the favorable changes49 and osteoarthritis of the facet joints.50 natural history of symptoms in most cases, a Furthermore, nerve root enhancement on contrast- substantial proportion of patients with recalcitrant enhanced magnetic resonance imaging, indicative of and disabling sciatica are offered spinal surgery with peridural fibrosis,51,52 is evident in many unoperated a view to more effectively and more rapidly