Clinical Outcomes With the Prestige II Cervical Disc
Object: A prospective, randomized clinical trial was conducted to compare the Prestige II Cervical Disc with anterior decompression and fusion for the treatment of single-level degenerative disease. Standardized clinical outcome measures and radiographic examinations were used at prescribed postoperative intervals to compare the treatment groups.
Methods: Patients with symptomatic single-level cervical disc disease who met the inclusion/exclusion criteria defined in the protocol were randomized to receive the Prestige II disc or iliac crest autograft fusion. All patients underwent a standardized neurological and radiographic examination and completed outcomes questionnaires (Neck Disability Index and Short Form–36) preoperatively and at each postoperative interval (6 weeks and 3, 6, 12, and 24 months). Two independent radiologists reviewed all x-ray films and assessed motion at the treated level and adjacent segments. Standard statistical methods were used to compare all outcome measures.
Preliminary results in 55 patients enrolled in the study are presented. Several patients have reached the final (24-month) follow-up interval. Clinical and radiographic results are encouraging, with significant improvement seen in both treatment groups. Radiographic results show that the Prestige II disc maintains motion at the treated level without adjacent-segment compromise.
Conclusions: Cervical spine arthroplasty is an exciting and rapidly developing surgical treatment option. An objective comparison with fusion is important to advance this option. This is the first prospective randomized trial in which cervical arthroplasty is compared with fusion. The preliminary results from this limited number of patients indicate that the Prestige II disc is potentially a viable alternative to fusion for primary cervical disc disease; however, further clinical studies with larger sample sizes will be required to show statistical equivalence.
Cervical arthroplasty is an exciting and rapidly advancing treatment option for spine surgeons. The rationale behind motion-sparing spinal implants is based primarily on the growing evidence that spinal fusion may contribute to adjacent-segment degeneration. For example, Hilibrand, et al., reported adjacent-segment disease in approximately 25% of patients with single-level ACDFs 10 years after the initial procedure.
In a radiographic study, Wigfield, et al., reported significantly increased motion at levels adjacent to an anterior cervical fusion when compared with segments adjacent to a level treated with the Prestige Cervical Disc System. In a biomechanical cadaveric study, DiAngelo, et al., reported statistically significant differences in motion seen at levels adjacent to a simulated fusion when compared with intact specimens and those implanted with the Prestige artificial cervical disc.
Goffin and coauthors investigated radiological evidence of new or progressive adjacent-segment spondylosis 5 years after anterior fusion. They found evidence of spondylotic progression in 92% of their 180 patients, with a correlation between the radiological findings and clinical deterioration. Most recently, Kulkarni, et al., reported a magnetic resonance imaging short-term follow-up study conducted after cervical corpectomy and fusion. Accelerated spondylotic changes adjacent to the fused segment were recognized in 75% of the 44 patients studied.
Prior to scientifically conducted investigations such as these, many spine surgeons theorized about the effects of fusion on adjacent-segment disease based on their own clinical experience. For decades, surgical procedures have been refined to facilitate anterior decompression of the cervical spinal cord and the exiting nerve roots, and these procedures became the mainstay of surgical treatment of cervical disease. Nevertheless, it was also recognized that after a simple anterior cervical discectomy, a spontaneous fusion of the treated segment can appear in up to 90% of cases. To prevent cervical kyphosis after discectomy, primary stabilization procedures became more important to maintain the sagittal balance of the cervical spine. Many treatment options now exist for internal fixation of the cervical spine; these range from traditional bone grafting with a tricortical iliac crest autograft to allografts or synthetic spacers filled with autograft or recombinant human bone morphogenetic protein–2.
The clinical outcome after an anterior cervical decompression and fusion procedure for either a cervical disc herniation or spondylosis is very satisfactory and has be come the gold standard. As we become more aware of the possible long-term effects of cervical arthrodeses on the adjacent-segment degeneration, however, it seems appropriate and justified to investigate new treatment options such as cervical arthroplasty. The goal of these new devices is preservation of motion of the functional spinal unit after a successful decompression of the neurological structures. It must be demonstrated that the maintenance of motion will last over an extended time period and that the adjacent segments undergo lesser degenerative changes compared with those in the fusion group. Our study is a first attempt to formulate some answers to the open questions regarding cervical arthroplasty.
Bristol–Cummins Disc. In the late 1980s, British neurosurgeon Brian Cummins became increasingly frustrated by the number of adjacent-segment surgeries he was performing in patients he had previously treated with ACDF. Cummins was determined to develop a solution and began collaborating with a medical engineer at his institution, Frenchay Hospital in Bristol, United Kingdom. The final design featured a ball-and-socket mechanism, which was placed into the disc space and fixed to the anterior cervical spine by bone screws driven through anterior phalanges into the adjacent VBs (Fig. 1). The ball component was slightly smaller than the socket, which allowed for slight translatory movements. The devices were manufactured from No. 316 stainless steel in the Frenchay Hospital machine shop. The Bristol–Cummins disc was designed to be implanted using a standard Smith–Robinson technique.
(Enlarge Image)
Computer drawing showing the Bristol–Cummins disc.
In 1991 Cummins received Ethics Committee approval to begin implanting the devices in patients with end-stage cervical disease who had undergone multiple previous cervical fusions, in an attempt to stop the cascade of subsequent fusions and maintain some motion in these severe cases. In all, 22 devices were implanted in 20 patients. The results were reported in 1998 and it was demonstrated radiographically that the device continued to function, with good clinical outcomes in the majority of patients. Additionally, when 16 of the patients were evaluated again in 2003, radiographic examinations performed for this long-term follow up demonstrated that the device still functioned 12 years postoperatively (JT Robertson, unpublished data).
The Bristol–Cummins device showed clinical viability in principle despite its obvious engineering shortcomings. The device was too large for the majority of patients, with an interbody height of 11 mm and an anterior phalange height of 14 mm each. At least one device was manufactured out of specification, with the ball being larger than the socket. Several screw breakages were reported; however, weaker fenestrated titanium screws were used in many cases. Additionally, a galvanic reaction between the stainless steel implant and the titanium screws may have caused further material weakening. One of the devices was explanted because of improper sizing and persistent pain. Evaluation of the explanted device showed virtually no wear. Many issues associated with use of the Bristol– Cummins disc are clearly related to the extreme biomechanical environment seen in the end-stage patients who were treated with the device on an ethics committee–approved humanitarian basis.
The Bristol–Cummins experience paved the way for cervical arthroplasty by showing that a metal-on-metal ball-and-socket device could relieve pain while maintaining motion at the treated level over a long-term follow-up duration.
Prestige I Disc. In 1998, a prospective observational clinical trial was initiated on a refined version of the Bristol–Cummins disc known as the Prestige I (Fig. 2) artificial cervical disc (Medtronic Sofamor Danek, Memphis, TN). The objective of the study was assessment of the safety and stability of the device once implanted as well as the preservation of motion in the cervical spine after decompression and arthroplasty. The 15 patients who were enrolled had either radiculopathy or myelopathy and radiologically confirmed cervical disc herniation or posterior VB osteophytes. Eligibility for the study required that patients had undergone previous surgery at an adjacent level, had congenital fusion, or displayed radiological evidence of adjacent-level DDD. After anterior decompressive surgery all patients received the Prestige I implant. Follow-up visits were required until 2 years postsurgery and included clinical examination, radiological assessment, and evaluation of the patients by questionnaires. The authors could demonstrate that all devices maintained motion over time at the treated levels, with reestablishment of the disc height. The procedure was considered safe and the implant was stable with no dislocation of the components. Two screws broke with no clinical consequences, but no screws pulled out. Data obtained at 24 months compared with preoperative data from the questionnaires indicated improvement in all aspects of the patients' function and quality of life. The study's sample size was too small for any clinical changes to reach statistical significance.
(Enlarge Image)
Computer drawing showing the Prestige I disc.
The pilot study was successful and allowed for pursuit of further development and the application of the device on a larger scale.
Object: A prospective, randomized clinical trial was conducted to compare the Prestige II Cervical Disc with anterior decompression and fusion for the treatment of single-level degenerative disease. Standardized clinical outcome measures and radiographic examinations were used at prescribed postoperative intervals to compare the treatment groups.
Methods: Patients with symptomatic single-level cervical disc disease who met the inclusion/exclusion criteria defined in the protocol were randomized to receive the Prestige II disc or iliac crest autograft fusion. All patients underwent a standardized neurological and radiographic examination and completed outcomes questionnaires (Neck Disability Index and Short Form–36) preoperatively and at each postoperative interval (6 weeks and 3, 6, 12, and 24 months). Two independent radiologists reviewed all x-ray films and assessed motion at the treated level and adjacent segments. Standard statistical methods were used to compare all outcome measures.
Preliminary results in 55 patients enrolled in the study are presented. Several patients have reached the final (24-month) follow-up interval. Clinical and radiographic results are encouraging, with significant improvement seen in both treatment groups. Radiographic results show that the Prestige II disc maintains motion at the treated level without adjacent-segment compromise.
Conclusions: Cervical spine arthroplasty is an exciting and rapidly developing surgical treatment option. An objective comparison with fusion is important to advance this option. This is the first prospective randomized trial in which cervical arthroplasty is compared with fusion. The preliminary results from this limited number of patients indicate that the Prestige II disc is potentially a viable alternative to fusion for primary cervical disc disease; however, further clinical studies with larger sample sizes will be required to show statistical equivalence.
Cervical arthroplasty is an exciting and rapidly advancing treatment option for spine surgeons. The rationale behind motion-sparing spinal implants is based primarily on the growing evidence that spinal fusion may contribute to adjacent-segment degeneration. For example, Hilibrand, et al., reported adjacent-segment disease in approximately 25% of patients with single-level ACDFs 10 years after the initial procedure.
In a radiographic study, Wigfield, et al., reported significantly increased motion at levels adjacent to an anterior cervical fusion when compared with segments adjacent to a level treated with the Prestige Cervical Disc System. In a biomechanical cadaveric study, DiAngelo, et al., reported statistically significant differences in motion seen at levels adjacent to a simulated fusion when compared with intact specimens and those implanted with the Prestige artificial cervical disc.
Goffin and coauthors investigated radiological evidence of new or progressive adjacent-segment spondylosis 5 years after anterior fusion. They found evidence of spondylotic progression in 92% of their 180 patients, with a correlation between the radiological findings and clinical deterioration. Most recently, Kulkarni, et al., reported a magnetic resonance imaging short-term follow-up study conducted after cervical corpectomy and fusion. Accelerated spondylotic changes adjacent to the fused segment were recognized in 75% of the 44 patients studied.
Prior to scientifically conducted investigations such as these, many spine surgeons theorized about the effects of fusion on adjacent-segment disease based on their own clinical experience. For decades, surgical procedures have been refined to facilitate anterior decompression of the cervical spinal cord and the exiting nerve roots, and these procedures became the mainstay of surgical treatment of cervical disease. Nevertheless, it was also recognized that after a simple anterior cervical discectomy, a spontaneous fusion of the treated segment can appear in up to 90% of cases. To prevent cervical kyphosis after discectomy, primary stabilization procedures became more important to maintain the sagittal balance of the cervical spine. Many treatment options now exist for internal fixation of the cervical spine; these range from traditional bone grafting with a tricortical iliac crest autograft to allografts or synthetic spacers filled with autograft or recombinant human bone morphogenetic protein–2.
The clinical outcome after an anterior cervical decompression and fusion procedure for either a cervical disc herniation or spondylosis is very satisfactory and has be come the gold standard. As we become more aware of the possible long-term effects of cervical arthrodeses on the adjacent-segment degeneration, however, it seems appropriate and justified to investigate new treatment options such as cervical arthroplasty. The goal of these new devices is preservation of motion of the functional spinal unit after a successful decompression of the neurological structures. It must be demonstrated that the maintenance of motion will last over an extended time period and that the adjacent segments undergo lesser degenerative changes compared with those in the fusion group. Our study is a first attempt to formulate some answers to the open questions regarding cervical arthroplasty.
Bristol–Cummins Disc. In the late 1980s, British neurosurgeon Brian Cummins became increasingly frustrated by the number of adjacent-segment surgeries he was performing in patients he had previously treated with ACDF. Cummins was determined to develop a solution and began collaborating with a medical engineer at his institution, Frenchay Hospital in Bristol, United Kingdom. The final design featured a ball-and-socket mechanism, which was placed into the disc space and fixed to the anterior cervical spine by bone screws driven through anterior phalanges into the adjacent VBs (Fig. 1). The ball component was slightly smaller than the socket, which allowed for slight translatory movements. The devices were manufactured from No. 316 stainless steel in the Frenchay Hospital machine shop. The Bristol–Cummins disc was designed to be implanted using a standard Smith–Robinson technique.
(Enlarge Image)
Computer drawing showing the Bristol–Cummins disc.
In 1991 Cummins received Ethics Committee approval to begin implanting the devices in patients with end-stage cervical disease who had undergone multiple previous cervical fusions, in an attempt to stop the cascade of subsequent fusions and maintain some motion in these severe cases. In all, 22 devices were implanted in 20 patients. The results were reported in 1998 and it was demonstrated radiographically that the device continued to function, with good clinical outcomes in the majority of patients. Additionally, when 16 of the patients were evaluated again in 2003, radiographic examinations performed for this long-term follow up demonstrated that the device still functioned 12 years postoperatively (JT Robertson, unpublished data).
The Bristol–Cummins device showed clinical viability in principle despite its obvious engineering shortcomings. The device was too large for the majority of patients, with an interbody height of 11 mm and an anterior phalange height of 14 mm each. At least one device was manufactured out of specification, with the ball being larger than the socket. Several screw breakages were reported; however, weaker fenestrated titanium screws were used in many cases. Additionally, a galvanic reaction between the stainless steel implant and the titanium screws may have caused further material weakening. One of the devices was explanted because of improper sizing and persistent pain. Evaluation of the explanted device showed virtually no wear. Many issues associated with use of the Bristol– Cummins disc are clearly related to the extreme biomechanical environment seen in the end-stage patients who were treated with the device on an ethics committee–approved humanitarian basis.
The Bristol–Cummins experience paved the way for cervical arthroplasty by showing that a metal-on-metal ball-and-socket device could relieve pain while maintaining motion at the treated level over a long-term follow-up duration.
Prestige I Disc. In 1998, a prospective observational clinical trial was initiated on a refined version of the Bristol–Cummins disc known as the Prestige I (Fig. 2) artificial cervical disc (Medtronic Sofamor Danek, Memphis, TN). The objective of the study was assessment of the safety and stability of the device once implanted as well as the preservation of motion in the cervical spine after decompression and arthroplasty. The 15 patients who were enrolled had either radiculopathy or myelopathy and radiologically confirmed cervical disc herniation or posterior VB osteophytes. Eligibility for the study required that patients had undergone previous surgery at an adjacent level, had congenital fusion, or displayed radiological evidence of adjacent-level DDD. After anterior decompressive surgery all patients received the Prestige I implant. Follow-up visits were required until 2 years postsurgery and included clinical examination, radiological assessment, and evaluation of the patients by questionnaires. The authors could demonstrate that all devices maintained motion over time at the treated levels, with reestablishment of the disc height. The procedure was considered safe and the implant was stable with no dislocation of the components. Two screws broke with no clinical consequences, but no screws pulled out. Data obtained at 24 months compared with preoperative data from the questionnaires indicated improvement in all aspects of the patients' function and quality of life. The study's sample size was too small for any clinical changes to reach statistical significance.
(Enlarge Image)
Computer drawing showing the Prestige I disc.
The pilot study was successful and allowed for pursuit of further development and the application of the device on a larger scale.
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