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The indications for lumbar and cervical disc replacement
The Spine Journal 4 (2004) 177S–181S
The indications for lumbar and cervical disc replacement Paul C. McAfee, MD St. Joseph Hospital, Scoliosis and Spine Center, O’Dea Medical Building 104, 7505 Osler Drive, Towson, MD 21204, USA
Abstract
Although cervical and lumbar disc replacements are in their spinal surgical infancy with regard to clinical application, the indications are already delineated. Lumbar disc arthroplasty is indicated for one- or two-level discogenic mechanical back pain primarily in the absence of radiculopathy. In contrast, cervical disc replacement can be readily applied in patients presenting with neurologic deficit, radiculopathy or myelopathy because the approach and anterior spinal cord decompression are identical for anterior cervical disc replacement and traditional Smith-Robinson cervical decompression. In addition, the application of more complex spinal osteotomies, revision of pseudarthroses and deformity correction are much more applicable to the cervical arthroplasty procedures. This is because even the most experienced vascular access surgeon has difficulty with the formidable revision through a repeat anterior lumbar procedure, whereas most experienced cervical spinal surgeons are familiar with repeat anterior cervical approaches. The end result is that surgeons will have more trepidation with multilevel lumbar arthroplasties, especially those presenting in conjunction with neurologic symptoms. At the current time radiculopathy is an exclusion criteria for the four prospective Investigational Device Exemption (IDE) Food and Drug Administration (FDA) studies on lumbar disc replacement, whereas cervical radiculopathy is an inclusion criteria for the major IDE FDA investigations of cervical arthroplasties. 쑖 2004 Elsevier Inc. All rights reserved.
Keywords:
Lumbar arthroplasty; Indications for disc replacement; Cervical disc replacement; Lumbar
Lumbar disc replacement The lumbar artificial disc is an alternative to arthrodesis. Its purpose is to restore the basic motion of the intervertebral segment and to protect the adjacent levels against unphysiologic loading. Two prostheses with nonrandomized designs placed in uncontrolled studies have over 10-year follow-up results in Europe [1]. Huang et al. [2] have reported 35 patients with the ProDisc Artificial Total Lumbar Disc Replacement (Synthes, Inc., Paoli, PA) inserted in 50 vertebral levels. Five different investigators, Lemaire (France), David (France), Ross (England), Zeegers (Netherlands) and the
FDA device/drug status: investigational/not approved (Charite´ and PCM disk). Support in whole or in part was received from Cervitech/Johnson & Johnson. Author PCM acknowledges a financial relationship (consultant for Johnson & Johnson; stockholder for Cervitech), which may indirectly relate to the subject of this manuscript. Corresponding author. Scoliosis and Spine Center, O’Dea Medical Building 104, 7505 Osler Drive, Towson, MD 21204, USA. Tel.: (410) 3378888; fax: (410) 823-4833. E-mail address: [email protected] (P.C. McAfee) 1529-9430/04/$ – see front matter doi:10.1016/j.spinee.2004.07.003
쑖 2004 Elsevier Inc. All rights reserved.
originator Bu¨ttner-Janz (East Germany) have each performed large series of SB Charite´ (DePuy Spine, Raynham, MA) disc replacement and presented long-term follow-up studies. Fritzell et al. [3] won the 2001 Volvo Award by proving that patients with discogenic pain have better outcomes after successful spinal fusions rather than continued conservative treatment. They performed a randomized controlled trial from the Swedish Lumbar Spine Study Group with 2-year follow-up by an independent observer. A total of 294 patients were referred to 19 spinal centers, randomized blindly into four treatment groups, nonsurgical groups (N⫽72) versus three surgical fusion techniques, which were reported together (N⫽222). Disability assessed by the Oswestry Scale was reduced by 25% in the surgical group versus 6% among the nonsurgical group. The “net back to work rate” was significantly in favor of surgical treatment: 36% versus 13% (p⫽.002). The early complication rate in the surgical group was 17%. As a result of the study of Fritzell et al., the current prosthetic disc replacement trials in the United States randomize and compare results with interbody fusions as opposed to nonoperative care, which would be much more difficult for patients
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P.C. McAfee / The Spine Journal 4 (2004) 177S–181S
to accept. The Frizell et al. study is the benchmark that the major disc replacement trials use as a comparison. The SB Charite´ Food and Drug Administration (FDA) study randomized against stand-alone anterior BAK interbody fusion [4]. The remaining devices, such as the MAVERICK Artificial Disc (Medtronic Sofamor Danek, Inc., Memphis, TN), the ProDisc-L and the FlexiCore (SpineCor, Inc., Summit, NJ) randomize against interbody fusions supplemented with posterior instrumentation and fusion or stand-alone anterior interbody cages with bone morphogenetic protein (BMP)-2. Therefore, the most accurate way of determining the indications for each of these devices would be to identify patients who are indicated for the comparative control arm of the respective Investigational Device Exemption (IDE) studies. An overall summary of the current indications for lumbar disc replacement is listed below. Lumbar inclusion criteria are the following: • Can be used in males or females • Age 18 to 60 years, optimally below age 50 years • Symptomatic degenerative disc disease or lumbar spondylosis with objective evidence of degenerative disc disease by computed tomography or magnetic resonance imaging. Some specific radiographic findings included vacuum disc sign, high intensity zone signal, Modic changes, degenerative cyst formation and marginal vertebral body osteophyte formation. • All patients should be studied with a provocative discogram performed by an independent radiologist or anesthesiologist who is not part of the surgical team. To be positive, the discogram should demonstrate concordant pain reproduction and use at least one control level that is not painful and does not reproduce the patient’s symptoms. Degenerative disc disease is defined as discogenic back pain with degeneration of the disc as confirmed by history and radiographic studies with one or more of the following factors: 1. Contained herniated nucleus pulposus 2. Paucity of facet joint degeneration changes 3. Decrease of intervertebral disc height of at least 4 mm and/or 4. Scarring/thickening of annulus fibrosis with osteophytes indicating osteoarthritis. • Only single or two intervertebral level disc disease at L3–L4, L4–L5 or L5–S1. • Nonradicular leg pain or back pain in the absence of nerve root compression (ie, resulting from disc herniation) as determined by magnetic resonance imaging or computed tomography scan without lateral recess stenosis. The only exception to this is that in carefully selected cases neuroforaminal stenosis can be corrected by disc replacement restoring the intervertebral disc height and increasing the neuroforaminal height. • Postlaminectomy syndrome is a good indication. Patients with prior lumbar discectomy.
• The lumbar disc replacement can be used for end-stage type disc disease and symptomatology rather than a primary treatment. All patients should exhaust and fail a minimum of 6 months of conservative, nonoperative treatments. These include physical therapy, facet joint injections, epidural steroids, acupuncture, back school, behavior modification, ultrasound, anti-inflammatory medications, analgesic medications, muscle relaxants, lumbosacral stabilization therapy, orthotic management and other nonoperative attempts at reducing the mechanical back disability. Patients are excluded from the ongoing FDA trials if they had undergone a previous attempted fusion procedure anywhere in the thoracolumbar spine. After approval, no doubt a major indication for lumbar disc replacements will be in adjacent segment disease—patients with symptomatic degeneration adjacent to lumbar fusions [5]. Patients with osteopenia should be excluded, and high-risk patients in this category, such as women after oophorectomy, should undergo dual-energy X-ray absorptiometry scans to demonstrate an absence of osteopenia. Other exclusion criteria for the lumbar spine should be 1) objective evidence of nerve root compression, 2) straight leg raise producing pain below the knee, 3) spinal fracture, spondylolysis, spondylolisthesis, scoliosis, spinal tumor or severe facet joint arthrosis or 4) being more than one standard deviation greater than normal body weight.
Cervical disc replacement The indications for anterior cervical disc replacement are the same as for anterior cervical decompression: radiculopathy or myelopathy caused by either one or two levels of anterior cervical compression [6–8]. Most surgeons would agree that a patient presenting with a compressive lesion causing arm weakness, paresthesia and unremitting radicular pain with or without lower extremity hyperactive reflexes requires anterior cervical decompression. The only difference of opinion is what to do after anterior surgical spinal cord or nerve root decompression. The goals are to restore the intervertebral disc height and neuroforaminal height to prevent recurrence of neurologic compression. Prevention of symptomatic adjacent segment disease Robbins and Hilibrand [5] and Hilibrand et al. [9] have focused attention on cervical adjacent segment disease. They chronicled 374 patients having a total of 409 anterior cervical arthrodeses followed for up to 21 years after Bohlman performed a Smith-Robinson anterior cervical fusion. They found symptomatic adjacent segment disease occurring at a relatively constant incidence of 2.9% per year (range, 0.0% to 4.8% per year). New disease was defined as new onset of myelopathy or radiculopathy significant enough to require surgery. Survivorship analysis projected that 25.6% of the
P.C. McAfee / The Spine Journal 4 (2004) 177S–181S
patients (95% confidence interval, 20% to 32%) who had an anterior cervical arthrodesis would have new disease at an adjacent level within 10 years after the operation. The most likely levels to develop adjacent segment disease were C5–C6 and C6–C7. In light of this compelling evidence, a major role of cervical disc replacement will be adjacent to already established cervical fusions with adjacent segment spinal compression—herniated nucleus pulposis, cervical spondylosis and focal cervical spinal stenosis. Cervical inclusion criteria Cervical inclusion criteria are the following: • Cervical degenerative disc disease requiring surgical treatment at one to three levels for symptoms or signs of cervical radiculopathy and/or myelopathy, with or without axial neck pain [6–8,10,11]. • Requires surgical treatment at one to three levels from C3 to T1 that has failed conservative treatment lasting at least 6 weeks for any one or more of the following: 1) disc herniation with radiculopathy, 2) spondylotic radiculopathy, 3) disc herniation with myelopathy or 4) spondylotic myelopathy. • The focal compressive lesion must be documented by computed tomography, myelography or magnetic resonance imaging. • The patient must have an abnormal neurologic sign indicative of radiculopathy or myelopathy: abnormal reflex, sensation or motor strength in a corroborative dermatome or myotome. • 18 to 65 years of age.
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Twenty-three patients underwent a total of 32 Porous Coated Motion (PCM) (Cervitech, Inc., Rockaway, NJ) cervical arthroplasties from C3–C4 to C6–C7: single level, 15 cases; double level, 7 cases; and three levels, 1 case (Fig. 1). Indications were 16 patients with radiculopathy and 7 patients with cervical myelopathy. The neural decompression was a standard Smith-Robinson type anterior cervical decompression followed by cervical arthroplasty—“press-fit” in 29 cases (Fig. 2), and 3 cases with Kleippel-Feil syndrome had the fixed variety of PCM with supplemental screw fixation of both components. At 9-month follow-up, all patients were neurologically intact (Fig. 3). Three had been done as outpatient procedures, two endoscopically through a 1-inch incision, 12 involved a hospital stay of less than 24 hours, and all patients were discharged in under 48 hours. Mean estimated blood loss was 113 cc (range, less than 50 to 850 cc). Mean length of
Cervical exclusion criteria Cervical exclusion criteria are the following: • Ankylosing spondylitis, rheumatoid arthritis, ossification of posterior longitudinal ligament or diffuse idiopathic skeletal hyperostosis • Insulin-requiring diabetes mellitus • Prior cervical spinal infection • Chronic steroid use or a medical condition requiring chronic steroid administration • Morbid obesity • Pregnancy • Axial neck pain as the solitary symptom. (Note: In contrast, a patient undergoing lumbar disc replacement who is an ideal candidate has isolated mechanical back pain and no lower extremity symptoms or signs.) Illustrative clinical cervical study Preliminary clinical results of a cervical disc replacement using conventional conservative biomaterials (ultrahigh molecular weight polyethylene and cobalt-chromium-molybdenum) were analyzed [12–15].
Fig. 1. Three-level Porous Coated Motion (PCM) cervical arthroplasty. (A) This 40-year-old man presented with cervical spondylitic myelopathy and three-level disease with myelomalacia at C3–C4, C5–C6 and C6–C7. He was ambulatory but demonstrated weakness in all four extremities. (B) The anteroposterior and lateral cervical radiographs 6 months postoperative PCM three-level disc replacement. He was neurologically intact with 30 degrees of motion from C3–C4 to C6–C7.
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Fig. 2. This 39-year-old woman had previously undergone a cervical cage arthrodesis procedure at C3–C4 and C6–C7 highlighting the need for no additional restriction of motion. (Top) Unfortunately, she was locked in a kyphotic position with herniated discs at the both intermediate levels. The sagittal magnetic resonance imaging shows two levels of disc herniation that corresponded to her left arm radiculopathies at C4–C5 and C5–C6. (Bottom left) The lateral radiograph of her cervical spine shows that the “lordotic” cages at C3–C4 and C6–C7 in fact contributed to her disabling cervical kyphosis as well as disc space collapse at C4–C5 and C5–C6. (Bottom middle) After Porous Coated Motion cervical replacement and anterior releases at C5–C6 and C4–C5, her bilateral radicular pain resolved and her neck was in a more physiologically lordotic position with successful kyphosis correction. (Bottom right) The corresponding anteroposterior view.
surgery was 90.7 minutes (range, 35 to 150 minutes). No reoperations were required, no infections occurred, and no removal of implants was necessary. Oswestry, visual analog scale (VAS) and Odoms outcome measures were comparable to historical data of anterior cervical discectomy and fusion with plates, cervical cages and preliminary reports of other cervical disc replacements. Twenty-three of 32 cases (71.9%) had 15 points or more improvement over preoperative Oswestry Neck Disability Index. Nineteen of 23 patients (82.6%) had greater than 20% improvement on VAS. The Cervical Spine Disability Questionnaire and Treatment Intensity Questionnaire demonstrated 25% or more improvement in 17 of 23 patients (73.9%). Operative-level intervertebral range-of-motion was quantified on flexion-extension plain films, and segmental motion was corroborated with dynamic fluoroscopy at 3 and 6 months after surgery.
All 32 prostheses in 23 patients demonstrated successful ingrowth with no evidence of loosening. Three cases had been performed adjacent to prior anterior cervical discectomy and fusion procedures. The preserved cervical motion in the patients with Kleippel-Feil syndrome was important; as Crockard and Stevens [16] has shown, cervical motion is important to assist in chewing in this class of patients. One patient had 3 mm of anterior subluxation of the components in the first 3 months but was clinically asymptomatic with 10 degrees of flexion-extension range of motion.
Conclusions Lumbar arthroplasty is applied to patients with chronic disabling mechanical back pain, whereas cervical arthroplasty is most appropriate in patients presenting with cervical radiculopathy or myelopathy. The revision of cervical
P.C. McAfee / The Spine Journal 4 (2004) 177S–181S
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References
Fig. 3. This 29-year-old man sustained a fracture subluxation at C4–C5, which healed after anterior cervical plating. Unfortunately, the plate was too long, spanned unnecessary cervical levels and resulted in mechanical pain, trapezius spasm and C5–C6 radicular symptoms. (A) The spine is fused at C4–C5 at the site of the prior trauma, but the plate immobilized C3–C4 and C5–C6 unnecessarily. Magnetic resonance imaging did show some disc material still present at C3–C4 and a herniated disc at C5–C6. (B) Lateral and anteroposterior radiographs after plate removal and anterior cervical disc replacement at C3–C4 and C5–C6. The patient had a full neurologic recovery and over 15 degrees of recovered flexion and extension motion.
arthroplasty approaches are already part of an experienced spinal surgeon’s armamentarium. In contrast, even the most technically advanced vascular access surgeon will have his or her hands full with a revision lumbar arthroplasty approach [17]. This consideration will have a major impact on the primary indications for cervical and lumbar arthroplasties after FDA approval and more widespread implantations.
[1] McAfee PC. Artificial disc prosthesis: the Link SB Charite´. In: Kaech DL, Jinkins JR, editors. Spinal Restabilization Procedures. New York: Elsevier Science BV, 2002:299–310. New York: Elsevier Science BV, 2002:299–310. [2] Huang RC, Giraldi FP, Cammisa FP, Tropianl P, Marnay T. Longterm flexion-extension range of motion of the Prodisc total disc replacement. J Spinal Dis Techniques 2003;16:435–40. [3] Fritzell P, Hagg O, Wessberg P, Noldwall A, and the Lumbar Spine Study Group. Chronic low back pain and fusion: a comparison of three surgical techniques. A prospective multicenter randomized study from the Swedish Lumbar Spine Study Group. Spine 2002;27: 1131–41. [4] McAfee PC, Fedder IL, Saiedy S, Shucosky EM, Cunningham BW. Experimental design of total disk replacement—experience with a prospective randomized study of the SB Charite´. Spine 2003;28: S153–62. [5] Robbins MM, Hilibrand AS. Post-arthrodesis adjacent segment degeneration. In: Vaccaro A, Anderson DG, Crawford A, Benzel E, Regan J, editors. Complications of pediatric and adult spinal surgery. Philadelphia, PA: Lippincott, 2003. [6] Anderson PA, Rosler DM, Rouleau JP, Bryan VE. Evaluation of the inflammatory response to the Bryan Cervical Disk Prosthesis in a caprine model. Eur Spine J 2002;11:S36. [7] Bryan VE. Cervical motion segment replacement. Eur Spine J 2002; 11:S92–7. [8] Cummins BH, Robertson JT, Gill SS. Surgical experience with an implanted artificial cervical joint. J Neurosurg 1998;88:943–8. [9] Hilibrand AS, Carlson GD, Palumbo MA, Jones PK, Bohlman HH. Radiculopathy and myelopathy at segments adjacent to the site of a previous anterior cervical arthrodesis. J Bone Joint Surg 1999;81A: 519–28. [10] Cunningham BW, Gordon JD, Dmietriev AE, Hu N, McAfee PC. Biomechanical evaluation of total disk arthroplasty: and in-vitro human cadaveric model. Paper presented at: International Meeting of Advanced Spinal Technologies (IMAST); May 8–10, 2002; Montreaux, Switzerland. [11] Pointillart V. Cervical disk prosthesis in humans. Spine 2001;26: E90–2. [12] Lewis GL. Properties of crosslinked ultra-high-molecular-weight polyethylene. Biomaterials 2001;22:371–401. [13] McAfee PC, Cunningham BW, Devine JD, Williams Eric, Yu-Yahiro J. Classification of heterotopic ossification (HO) in artificial disk replacement. Proceedings of the 17th Annual Meeting of the North American Spine Society in Montreal Canada. Spine J 2002;2:94S. [14] McAfee PC, Cunningham BW, Dmitriev A, Hu NB, Kim SW, Cappuccino A, Pimenta LH. Cervical disk replacment—porous coated motion prosthesis. A comparative biomechanical analysis showing the key role of the posterior longitudinal ligament. Spine 2003;28:S196–85. [15] McAfee PC, Cunningham BW, Orbegoso CM, Sefter JC, Dmitriev AE, Fedder IL. Analysis of porous ingrowth in intervertebral disc prostheses. A non-human primate model. Spine 2003;28:332–40. [16] Crockard HA, Stevens JM. Craniovertebral junction abnormalities in inherited disorders: part of the syndrome caused by the disorder? Eur J Pediatr 1995;154:504–12. [17] White AA, Panjabi MM. Kinematics of the spine. In: White AA, Panjabi MM, editors. Clinical biomechanics of the spine. Philadelphia: JB Lippincott, 1990:86–125.
The indications for lumbar and cervical disc replacement Paul C. McAfee, MD St. Joseph Hospital, Scoliosis and Spine Center, O’Dea Medical Building 104, 7505 Osler Drive, Towson, MD 21204, USA
Abstract
Although cervical and lumbar disc replacements are in their spinal surgical infancy with regard to clinical application, the indications are already delineated. Lumbar disc arthroplasty is indicated for one- or two-level discogenic mechanical back pain primarily in the absence of radiculopathy. In contrast, cervical disc replacement can be readily applied in patients presenting with neurologic deficit, radiculopathy or myelopathy because the approach and anterior spinal cord decompression are identical for anterior cervical disc replacement and traditional Smith-Robinson cervical decompression. In addition, the application of more complex spinal osteotomies, revision of pseudarthroses and deformity correction are much more applicable to the cervical arthroplasty procedures. This is because even the most experienced vascular access surgeon has difficulty with the formidable revision through a repeat anterior lumbar procedure, whereas most experienced cervical spinal surgeons are familiar with repeat anterior cervical approaches. The end result is that surgeons will have more trepidation with multilevel lumbar arthroplasties, especially those presenting in conjunction with neurologic symptoms. At the current time radiculopathy is an exclusion criteria for the four prospective Investigational Device Exemption (IDE) Food and Drug Administration (FDA) studies on lumbar disc replacement, whereas cervical radiculopathy is an inclusion criteria for the major IDE FDA investigations of cervical arthroplasties. 쑖 2004 Elsevier Inc. All rights reserved.
Keywords:
Lumbar arthroplasty; Indications for disc replacement; Cervical disc replacement; Lumbar
Lumbar disc replacement The lumbar artificial disc is an alternative to arthrodesis. Its purpose is to restore the basic motion of the intervertebral segment and to protect the adjacent levels against unphysiologic loading. Two prostheses with nonrandomized designs placed in uncontrolled studies have over 10-year follow-up results in Europe [1]. Huang et al. [2] have reported 35 patients with the ProDisc Artificial Total Lumbar Disc Replacement (Synthes, Inc., Paoli, PA) inserted in 50 vertebral levels. Five different investigators, Lemaire (France), David (France), Ross (England), Zeegers (Netherlands) and the
FDA device/drug status: investigational/not approved (Charite´ and PCM disk). Support in whole or in part was received from Cervitech/Johnson & Johnson. Author PCM acknowledges a financial relationship (consultant for Johnson & Johnson; stockholder for Cervitech), which may indirectly relate to the subject of this manuscript. Corresponding author. Scoliosis and Spine Center, O’Dea Medical Building 104, 7505 Osler Drive, Towson, MD 21204, USA. Tel.: (410) 3378888; fax: (410) 823-4833. E-mail address: [email protected] (P.C. McAfee) 1529-9430/04/$ – see front matter doi:10.1016/j.spinee.2004.07.003
쑖 2004 Elsevier Inc. All rights reserved.
originator Bu¨ttner-Janz (East Germany) have each performed large series of SB Charite´ (DePuy Spine, Raynham, MA) disc replacement and presented long-term follow-up studies. Fritzell et al. [3] won the 2001 Volvo Award by proving that patients with discogenic pain have better outcomes after successful spinal fusions rather than continued conservative treatment. They performed a randomized controlled trial from the Swedish Lumbar Spine Study Group with 2-year follow-up by an independent observer. A total of 294 patients were referred to 19 spinal centers, randomized blindly into four treatment groups, nonsurgical groups (N⫽72) versus three surgical fusion techniques, which were reported together (N⫽222). Disability assessed by the Oswestry Scale was reduced by 25% in the surgical group versus 6% among the nonsurgical group. The “net back to work rate” was significantly in favor of surgical treatment: 36% versus 13% (p⫽.002). The early complication rate in the surgical group was 17%. As a result of the study of Fritzell et al., the current prosthetic disc replacement trials in the United States randomize and compare results with interbody fusions as opposed to nonoperative care, which would be much more difficult for patients
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P.C. McAfee / The Spine Journal 4 (2004) 177S–181S
to accept. The Frizell et al. study is the benchmark that the major disc replacement trials use as a comparison. The SB Charite´ Food and Drug Administration (FDA) study randomized against stand-alone anterior BAK interbody fusion [4]. The remaining devices, such as the MAVERICK Artificial Disc (Medtronic Sofamor Danek, Inc., Memphis, TN), the ProDisc-L and the FlexiCore (SpineCor, Inc., Summit, NJ) randomize against interbody fusions supplemented with posterior instrumentation and fusion or stand-alone anterior interbody cages with bone morphogenetic protein (BMP)-2. Therefore, the most accurate way of determining the indications for each of these devices would be to identify patients who are indicated for the comparative control arm of the respective Investigational Device Exemption (IDE) studies. An overall summary of the current indications for lumbar disc replacement is listed below. Lumbar inclusion criteria are the following: • Can be used in males or females • Age 18 to 60 years, optimally below age 50 years • Symptomatic degenerative disc disease or lumbar spondylosis with objective evidence of degenerative disc disease by computed tomography or magnetic resonance imaging. Some specific radiographic findings included vacuum disc sign, high intensity zone signal, Modic changes, degenerative cyst formation and marginal vertebral body osteophyte formation. • All patients should be studied with a provocative discogram performed by an independent radiologist or anesthesiologist who is not part of the surgical team. To be positive, the discogram should demonstrate concordant pain reproduction and use at least one control level that is not painful and does not reproduce the patient’s symptoms. Degenerative disc disease is defined as discogenic back pain with degeneration of the disc as confirmed by history and radiographic studies with one or more of the following factors: 1. Contained herniated nucleus pulposus 2. Paucity of facet joint degeneration changes 3. Decrease of intervertebral disc height of at least 4 mm and/or 4. Scarring/thickening of annulus fibrosis with osteophytes indicating osteoarthritis. • Only single or two intervertebral level disc disease at L3–L4, L4–L5 or L5–S1. • Nonradicular leg pain or back pain in the absence of nerve root compression (ie, resulting from disc herniation) as determined by magnetic resonance imaging or computed tomography scan without lateral recess stenosis. The only exception to this is that in carefully selected cases neuroforaminal stenosis can be corrected by disc replacement restoring the intervertebral disc height and increasing the neuroforaminal height. • Postlaminectomy syndrome is a good indication. Patients with prior lumbar discectomy.
• The lumbar disc replacement can be used for end-stage type disc disease and symptomatology rather than a primary treatment. All patients should exhaust and fail a minimum of 6 months of conservative, nonoperative treatments. These include physical therapy, facet joint injections, epidural steroids, acupuncture, back school, behavior modification, ultrasound, anti-inflammatory medications, analgesic medications, muscle relaxants, lumbosacral stabilization therapy, orthotic management and other nonoperative attempts at reducing the mechanical back disability. Patients are excluded from the ongoing FDA trials if they had undergone a previous attempted fusion procedure anywhere in the thoracolumbar spine. After approval, no doubt a major indication for lumbar disc replacements will be in adjacent segment disease—patients with symptomatic degeneration adjacent to lumbar fusions [5]. Patients with osteopenia should be excluded, and high-risk patients in this category, such as women after oophorectomy, should undergo dual-energy X-ray absorptiometry scans to demonstrate an absence of osteopenia. Other exclusion criteria for the lumbar spine should be 1) objective evidence of nerve root compression, 2) straight leg raise producing pain below the knee, 3) spinal fracture, spondylolysis, spondylolisthesis, scoliosis, spinal tumor or severe facet joint arthrosis or 4) being more than one standard deviation greater than normal body weight.
Cervical disc replacement The indications for anterior cervical disc replacement are the same as for anterior cervical decompression: radiculopathy or myelopathy caused by either one or two levels of anterior cervical compression [6–8]. Most surgeons would agree that a patient presenting with a compressive lesion causing arm weakness, paresthesia and unremitting radicular pain with or without lower extremity hyperactive reflexes requires anterior cervical decompression. The only difference of opinion is what to do after anterior surgical spinal cord or nerve root decompression. The goals are to restore the intervertebral disc height and neuroforaminal height to prevent recurrence of neurologic compression. Prevention of symptomatic adjacent segment disease Robbins and Hilibrand [5] and Hilibrand et al. [9] have focused attention on cervical adjacent segment disease. They chronicled 374 patients having a total of 409 anterior cervical arthrodeses followed for up to 21 years after Bohlman performed a Smith-Robinson anterior cervical fusion. They found symptomatic adjacent segment disease occurring at a relatively constant incidence of 2.9% per year (range, 0.0% to 4.8% per year). New disease was defined as new onset of myelopathy or radiculopathy significant enough to require surgery. Survivorship analysis projected that 25.6% of the
P.C. McAfee / The Spine Journal 4 (2004) 177S–181S
patients (95% confidence interval, 20% to 32%) who had an anterior cervical arthrodesis would have new disease at an adjacent level within 10 years after the operation. The most likely levels to develop adjacent segment disease were C5–C6 and C6–C7. In light of this compelling evidence, a major role of cervical disc replacement will be adjacent to already established cervical fusions with adjacent segment spinal compression—herniated nucleus pulposis, cervical spondylosis and focal cervical spinal stenosis. Cervical inclusion criteria Cervical inclusion criteria are the following: • Cervical degenerative disc disease requiring surgical treatment at one to three levels for symptoms or signs of cervical radiculopathy and/or myelopathy, with or without axial neck pain [6–8,10,11]. • Requires surgical treatment at one to three levels from C3 to T1 that has failed conservative treatment lasting at least 6 weeks for any one or more of the following: 1) disc herniation with radiculopathy, 2) spondylotic radiculopathy, 3) disc herniation with myelopathy or 4) spondylotic myelopathy. • The focal compressive lesion must be documented by computed tomography, myelography or magnetic resonance imaging. • The patient must have an abnormal neurologic sign indicative of radiculopathy or myelopathy: abnormal reflex, sensation or motor strength in a corroborative dermatome or myotome. • 18 to 65 years of age.
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Twenty-three patients underwent a total of 32 Porous Coated Motion (PCM) (Cervitech, Inc., Rockaway, NJ) cervical arthroplasties from C3–C4 to C6–C7: single level, 15 cases; double level, 7 cases; and three levels, 1 case (Fig. 1). Indications were 16 patients with radiculopathy and 7 patients with cervical myelopathy. The neural decompression was a standard Smith-Robinson type anterior cervical decompression followed by cervical arthroplasty—“press-fit” in 29 cases (Fig. 2), and 3 cases with Kleippel-Feil syndrome had the fixed variety of PCM with supplemental screw fixation of both components. At 9-month follow-up, all patients were neurologically intact (Fig. 3). Three had been done as outpatient procedures, two endoscopically through a 1-inch incision, 12 involved a hospital stay of less than 24 hours, and all patients were discharged in under 48 hours. Mean estimated blood loss was 113 cc (range, less than 50 to 850 cc). Mean length of
Cervical exclusion criteria Cervical exclusion criteria are the following: • Ankylosing spondylitis, rheumatoid arthritis, ossification of posterior longitudinal ligament or diffuse idiopathic skeletal hyperostosis • Insulin-requiring diabetes mellitus • Prior cervical spinal infection • Chronic steroid use or a medical condition requiring chronic steroid administration • Morbid obesity • Pregnancy • Axial neck pain as the solitary symptom. (Note: In contrast, a patient undergoing lumbar disc replacement who is an ideal candidate has isolated mechanical back pain and no lower extremity symptoms or signs.) Illustrative clinical cervical study Preliminary clinical results of a cervical disc replacement using conventional conservative biomaterials (ultrahigh molecular weight polyethylene and cobalt-chromium-molybdenum) were analyzed [12–15].
Fig. 1. Three-level Porous Coated Motion (PCM) cervical arthroplasty. (A) This 40-year-old man presented with cervical spondylitic myelopathy and three-level disease with myelomalacia at C3–C4, C5–C6 and C6–C7. He was ambulatory but demonstrated weakness in all four extremities. (B) The anteroposterior and lateral cervical radiographs 6 months postoperative PCM three-level disc replacement. He was neurologically intact with 30 degrees of motion from C3–C4 to C6–C7.
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Fig. 2. This 39-year-old woman had previously undergone a cervical cage arthrodesis procedure at C3–C4 and C6–C7 highlighting the need for no additional restriction of motion. (Top) Unfortunately, she was locked in a kyphotic position with herniated discs at the both intermediate levels. The sagittal magnetic resonance imaging shows two levels of disc herniation that corresponded to her left arm radiculopathies at C4–C5 and C5–C6. (Bottom left) The lateral radiograph of her cervical spine shows that the “lordotic” cages at C3–C4 and C6–C7 in fact contributed to her disabling cervical kyphosis as well as disc space collapse at C4–C5 and C5–C6. (Bottom middle) After Porous Coated Motion cervical replacement and anterior releases at C5–C6 and C4–C5, her bilateral radicular pain resolved and her neck was in a more physiologically lordotic position with successful kyphosis correction. (Bottom right) The corresponding anteroposterior view.
surgery was 90.7 minutes (range, 35 to 150 minutes). No reoperations were required, no infections occurred, and no removal of implants was necessary. Oswestry, visual analog scale (VAS) and Odoms outcome measures were comparable to historical data of anterior cervical discectomy and fusion with plates, cervical cages and preliminary reports of other cervical disc replacements. Twenty-three of 32 cases (71.9%) had 15 points or more improvement over preoperative Oswestry Neck Disability Index. Nineteen of 23 patients (82.6%) had greater than 20% improvement on VAS. The Cervical Spine Disability Questionnaire and Treatment Intensity Questionnaire demonstrated 25% or more improvement in 17 of 23 patients (73.9%). Operative-level intervertebral range-of-motion was quantified on flexion-extension plain films, and segmental motion was corroborated with dynamic fluoroscopy at 3 and 6 months after surgery.
All 32 prostheses in 23 patients demonstrated successful ingrowth with no evidence of loosening. Three cases had been performed adjacent to prior anterior cervical discectomy and fusion procedures. The preserved cervical motion in the patients with Kleippel-Feil syndrome was important; as Crockard and Stevens [16] has shown, cervical motion is important to assist in chewing in this class of patients. One patient had 3 mm of anterior subluxation of the components in the first 3 months but was clinically asymptomatic with 10 degrees of flexion-extension range of motion.
Conclusions Lumbar arthroplasty is applied to patients with chronic disabling mechanical back pain, whereas cervical arthroplasty is most appropriate in patients presenting with cervical radiculopathy or myelopathy. The revision of cervical
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References
Fig. 3. This 29-year-old man sustained a fracture subluxation at C4–C5, which healed after anterior cervical plating. Unfortunately, the plate was too long, spanned unnecessary cervical levels and resulted in mechanical pain, trapezius spasm and C5–C6 radicular symptoms. (A) The spine is fused at C4–C5 at the site of the prior trauma, but the plate immobilized C3–C4 and C5–C6 unnecessarily. Magnetic resonance imaging did show some disc material still present at C3–C4 and a herniated disc at C5–C6. (B) Lateral and anteroposterior radiographs after plate removal and anterior cervical disc replacement at C3–C4 and C5–C6. The patient had a full neurologic recovery and over 15 degrees of recovered flexion and extension motion.
arthroplasty approaches are already part of an experienced spinal surgeon’s armamentarium. In contrast, even the most technically advanced vascular access surgeon will have his or her hands full with a revision lumbar arthroplasty approach [17]. This consideration will have a major impact on the primary indications for cervical and lumbar arthroplasties after FDA approval and more widespread implantations.
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