Intermediate Clinical Outcome of Bryan Cervical Disc Replacement for Degenerative Disk Disease and Its Effect on Adjacent Segment Disks

Transcription

1 Intermediate Clinical Outcome of Bryan Cervical Disc Replacement for Degenerative Disk Disease and Its Effect on Adjacent Segment Disks Chen Ding, MD; Ying Hong, BS; Hao Liu, MD; Rui Shi, MD; Tao Hu, MD; Tao Li, MD abstract Full article available online at Healio.com/Orthopedics. Search: The purpose of this study was to determine the intermediate clinical and radiographic outcomes of Bryan Cervical Disc (Medtronic Sofamor Danek, Inc, Memphis, Tennessee) replacement for the treatment of cervical degenerative disk disease and its effect on adjacent levels. Between November 2004 and December 2007, thirty-four patients (38 disks) underwent Bryan Cervical Disc replacement in the authors hospital. The authors retrospectively analyzed the records of 32 patients who completed follow-up. Outcome data were collected preoperatively; at 3, 12, 24 months postoperatively; and at last follow-up, which ranged from 32 to 69 months (average, 49.4 months). Clinical outcome, radiographic outcome, adjacent segment degeneration, complications, and reoperations were evaluated. The SF-36 physical component, SF-36 mental component, Neck Disability Index, Japanese Orthopaedic Association score, and neck/arm pain visual analog pain scale scores were all improved significantly at each postoperative time point compared with preoperative values (P,.05), but no statistically significant differences were noted between postoperative time points (P..05). The postoperative flexion extension range of motion of the operative site and adjacent segments were not significantly different from the preoperative values (P..05) and were approximately the same for each postoperative time point (P..05). A new degeneration scoring system demonstrated that approximately 23% of the adjacent levels displayed mild degeneration at last follow-up. However, degeneration did not affect the clinical outcomes. Prosthesis-related complications were rare, and no reoperations were performed. Bryan Cervical Disc replacement achieves satisfactory mid-term clinical and radiographic outcomes. The authors observed the progression of adjacent segment degeneration postoperatively, although no degradation of clinical outcomes occurred. Drs Ding, Liu, Shi, Hu, and Li are from the Department of Orthopedic Surgery, and Mr Hong is from the Operating Room, West China Hospital, Sichuan University, Chengdu, Sichuan, People s Republic of China. Drs Ding, Liu, Shi, Hu, and Li and Mr Hong have no relevant financial relationships to disclose. Dr Ding and Mr Hong contributed equally to this study. Correspondence should be addressed to: Hao Liu, MD, Department of Orthopedic Surgery, West China Hospital, Sichuan University, No. 37 Wai Nan Guo Xue Xiang, Chengdu, Sichuan , People s Republic of China (liuhao6304@163.com). doi: / A C Figure: Preoperative magnetic resonance image showing C5-C6 disk herniation (A). Neutral lateral radiograph at 48-month follow-up showing normal prosthesis position (B). Dynamic radiograph showing that the prosthesis preserved a certain range of motion (C). Magnetic resonance image at 48-month follow-up showing upper and lower adjacent disks with no herniation (D). B D JUNE 2012 Volume 35 Number 6 e909

2 Anterior cervical diskectomy and fusion was first described by Smith and Robinson 1 in the 1950s. Over the past 50 years, anterior cervical diskectomy and fusion has been commonly regarded as the gold standard of surgical treatment of cervical degenerative disk disease. 2 Although anterior cervical diskectomy and fusion yields excellent clinical outcomes and high fusion rates, 3,4 interbody fusion of the cervical spine sacrifices the mobility of the operative segment and results in hypermobility and abnormal increased intradiskal stress at the upper and lower adjacent segments. 5,6 This phenomenon could accelerate the degeneration of adjacent levels and lead to the recurrence of neurological symptoms. 7,8 Long-term follow-up of patients after anterior cervical diskectomy and fusion suggests that obvious radiographic changes existed at adjacent segments, including anterior or posterior osteophyte formation, disk space narrowing, and endplate sclerosis. 9,10 In addition, anterior cervical diskectomy and fusion leads to complications, such as pseudarthrosis, chronic pain at the harvest donor site, and adverse events in anterior plates. 11,12 Because of these anterior cervical diskectomy and fusion specific disadvantages, nonfusion methods in spine surgery are developing rapidly. One of these methods is cervical total disk replacement. In recent years, cervical total disk replacement has become increasingly popular worldwide as an alternative to spinal fusion. It is designed to restore disk height and physiological motion at the operative segment and maintain normal intradiskal stress at adjacent segments after thorough anterior diskectomy. This theoretically decreases the risk of adjacent segment disease, which is usually observed in patients after spinal fusion. 13 It also avoids other complications associated with anterior cervical diskectomy and fusion and allows an earlier return to normal cervical function. Early clinical experiences of cervical total disk replacement are described in the literature, and most of them are positive However, the follow-up periods of these studies are short, and data regarding mid-term results are lacking. Furthermore, it is unclear whether cervical total disk replacement reduces the occurrence of adjacent segment disease. In the current retrospective study, the authors describe the mid-term clinical and radiographic outcomes of consecutive patients with cervical degenerative disk disease who underwent Bryan Cervical Disc (Medtronic Sofamor Danek, Inc, Memphis, Tennessee) replacement in their hospital and assess the effect of Bryan Cervical Disc replacement on adjacent segment disks. Materials and Methods Between November 2004 and April 2007, a total of 38 Bryan Cervical Discs were implanted in 34 patients at the authors institution. Two patients were lost to follow-up, and the remaining 32 patients, who complied with follow-up, comprised the study cohort. Patients were evaluated preoperatively; at 3, 12, and 24 months postoperatively; and at last follow-up, which ranged from 32 to 69 months (average, 49.4 months). Thirty-two patients were followed up for 32 months, 30 patients for 36 months, 18 patients for 48 months, and 3 patients for 60 months. Preoperative imaging studies included static and dynamic plain radiographs of the cervical spine, 3-dimensional computed tomography (CT), and magnetic resonance imaging (MRI). Plain radiographs were used to evaluate the cervical alignment, degeneration, and range of motion (ROM) of the index segment. Three-dimensional CT was used to observe the posterior osteophyte and facet joint degeneration of the index segment. Magnetic resonance imaging was used to determine the level of disk herniation and neural compression. The inclusion criteria were: (1) single-, 2-, or 3-level degenerative disk disease between C3-T1 confirmed by radiographic evaluation and leading to symptomatic myelopathy or radiculopathy; (2) age between 18 and 65 years; and (3) poor remission of symptoms after at least 3 months of conservative treatment. Exclusion criteria were advanced kyphotic deformity, instability or loss of ROM at the index segment, facet joint arthropathy, spinal stenosis, advanced osteoporosis, ankylosing spondylitis, rheumatoid arthritis, infection, trauma, tumor, and pregnancy. Surgical Technique All surgeries were performed by the same senior spine surgeon (H.L.). Under general anesthesia, a patient was fixed with the neck in the neutral position. A standard Smith-Robinson approach was used to expose the pathologic segment. Next, the pathologic disk, including the pulpy nucleus and annulus fibrosus, was removed. After anterior diskectomy, the disk space was distracted in a parallel way by the Caspar distractor, and the distraction was maintained once the height of the intervertebral space reached 8.5 mm. The center of the disk space was determined by a simple gravitational referencing system. A system of levels and protractors defined the uncovertebral joints and found the center. After confirming the center of the disk space, a milling fixture was anchored to the vertebral bodies to precisely control the locations of the powered cutting instruments, which prepared the vertebral body endplates for the placement of the prosthesis. The milled endplates were exactly matched to the geometry of the implant s convex outer surface to provide immediate stability. The residual disk material, osteophytes, and posterior longitudinal ligament were then completely removed to achieve thorough decompression of the nerve root or spinal cord. A sterile saline lubricant was injected into a chosen suitable Bryan Cervical Disc, which was later inserted into the prepared intervertebral space. Plain radiographs confirmed appropriate placement of the prosthesis. Finally, a plasma drainage device was placed before closure of the incision. e910 Healio.com The new online home of ORTHOPEDICS Healio.com/Orthopedics

3 Bryan Artificial Cervical Disc Replacement Ding et al Postoperative Management The plasma drainage device was conventionally extracted 1 to 2 days postoperatively. The patient could leave the bed and begin physiological action of the cervical spine under a doctor s supervision 4 to 5 days postoperatively. A cervical collar was used for the first 4 weeks. All patients took celecoxib 200 mg twice daily for 2 weeks postoperatively and did targeted exercises to strengthen the neck and back muscles. Radiographic Variable Data Collection Surgical and outcome data were collected for each patient. Outcomes were evaluated preoperatively; at 3, 12, and 24 months postoperatively; and at last follow-up. Surgical data collected included operative time, blood loss, length of hospital stay, and time needed before resuming work. Clinical outcomes were measured by physical and mental SF-36, Neck Disability Index, Japanese Orthopedic Association score, neck/arm pain visual analog scale scores, and Odom s scale. Radiographic assessment included static and dynamic cervical radiographs. Device stability was assessed by observing the migration, excursion, and subsidence of the device on neutral lateral radiographs. The flexion extension of operative, upper, and lower adjacent segments were determined by assessment of flexion extension radiographs. Measurements on digital radiographs were performed with ACDSee Canvas 11 software (ACD Systems, Seattle, Washington). The disk space angle of the operative segment was taken and defined as the angle formed by the natural endplates preoperatively and by the shells of the prosthesis postoperatively. The sum of the disk space angle at full flexion and extension was used to calculated the ROM of the operative and adjacent segments. Adjacent segment degeneration was assessed by an objective and quantitative scoring system based on neutral lateral radiographs. 17 The overall degeneration score consists of 3 variables: height loss, anterior osteophytes, and endplate sclerosis (Table 1). The score ranges from 0 (no degeneration) to 9 (severe degeneration) points. Radiographic measurements were performed by 2 observers (C.D., T.H.). Each of them measured 3 times, and the mean value was used for analysis. Complications and reoperations were also recorded. Statistical Analysis Statistical analysis was performed using SPSS version 16.0 software (SPSS, Inc, Chicago, Illinois). Continuous variables were presented as mean6sd. Preoperative data and follow-up data were compared using 1-way analysis of variance. A value of P,.05 was considered statistically significant. Table 1 Scoring System of Cervical Disk Degeneration 1. Height loss a 0% 0 Middle disk height compared with normal middle disk height at an adjacent level 2. Anterior osteophytes with respect to anteroposterior diameter of corresponding vertebral body Points 25% 1 >25% to 50% 2 >50% to 75% 3 >75% 4 No osteophytes 0 1/8 anteroposterior diameter 1 >1/8-1/4 anteroposterior diameter 2 >1/4 anteroposterior diameter 3 3. Endplate sclerosis No sclerosis 0 Detectable 1 Definite 2 Overall degree of disk degeneration b Grade 0, no degeneration 0 Grade 1, mild degeneration 1-3 Grade 2, moderate degeneration 4-6 Grade 3, severe degeneration 7-9 a Middle disk height compared with normal middle disk height at an adjacent level. b Cervical disk degeneration grade is determined by adding the points from categories 1, 2, and 3. Results Of the 32 patients, 19 were men and 13 were women. Mean age was 44.1 years (range, years), and mean preoperative history was 20.7 months (range, months). Twenty-eight patients received single-level replacement, and 4 received bi-level replacement. The Bryan Cervical Disc was implanted at C3-C4 in 1 patient, C4-C5 in 4 patients, C5-C6 in 19 patients, C6-C7 in 4 patients, C4-C5 and C5-C6 in 1 patient, and C5-C6 and C6-C7 in 3 patients. The preoperative symptoms and signs were myelopathy in 13 patients, radiculopathy in 15 patients, and mixed cervical spondylosis in 4 patients. Surgical Data Surgery was successfully performed in all patients. Mean operative time was minutes (range, minutes), average blood loss was ml (range, ml), and average length of hospital stay and time needed to return to work were 12.4 days and 32.6 days, respectively. No perioperative complications occurred. JUNE 2012 Volume 35 Number 6 e911

4 Clinical Outcome Comparison of postoperative with preoperative data indicated statistically Table 2 Pre- and Postoperative SF-36, NDI, JOA, and VAS Scores Follow-up Score Preoperative 3 mo 12 mo 24 mo Final SF-36 PCS MCS NDI JOA VAS Neck pain Arm pain Abbreviations: JOA, Japanese Orthopaedic Association; MCS, mental component; NDI, Neck Disability Index; PCS, physical component score; VAS, visual analog pain scale score. Table 3 Pre- and Postoperative Flexion Extension Ranges of Motion of Operative and Adjacent Segments a Follow-up Segment Preoperative 3 mo 12 mo 24 mo Final Operative Upper adjacent Lower adjacent a Data presented as mean degrees. 1A 1B 1C 1D 1E Figure 1: Preoperative magnetic resonance image showing C5-C6 disk herniation (A). Forty-eight-month follow-up neutral lateral radiograph showing a normal prosthesis position (B), flexion extension radiograph showing that the prosthesis preserved a certain range of motion (C, D), and magnetic resonance image showing upper and lower adjacent disks with no herniation (E). significant improvement in quality of life and each aspect of patient function for all of the clinical outcome measures (Table 2). No outcome measure showed a statistically significant difference between any 2 postoperative time points (P..05). According to Odom s scale, the outcome was excellent in 19 patients, good in 8 patients, fair in 4 patients, and poor in 1 patient at last follow-up, meaning that 84.4% of the patients had a good to excellent outcome rating. Radiographic Outcome Flexion extension cervical radiographs showed that all 36 implanted devices remained mobile at last follow-up (Table 3). No statistically significant difference existed between the preoperative and postoperative data for the operative segment and its upper and lower adjacent segments (P..05), or between any 2 postoperative time points (P..05). Radiographic outcomes showed that the Bryan Cervical Disc preserved normal ROM of the operative and adjacent segments (Figures 1, 2). At the early follow-up time points, anterior prosthesis migration.2 mm was detected in 5 patients. When this phenomenon was detected, the patients used a neck collar and received radiographic examination more frequently. At 12-month follow-up, the authors noted the imaging of bone ingrowth into the endplates, and no further migration had occurred. The patients had no vascular or neurological complications, and the ROM of these 5 disks was preserved (Figure 3). No prosthesis subsidence or excursion occurred, and each prosthesis had achieved stabilization at last follow-up. According to the new scoring system of disk degeneration, the mean preoperative scores were at the upper and at the lower adjacent segments. At 12-month follow-up, 1 upper adjacent disk, which did not manifest any sign of degeneration preoperatively, had new formation of an anterior osteophyte. The degeneration scores of the upper and lower adjacent segments increased significantly, e912 Healio.com The new online home of ORTHOPEDICS Healio.com/Orthopedics

5 Bryan Artificial Cervical Disc Replacement Ding et al to and , respectively, at 24 months postoperatively (P,.05) and to and , respectively, at last follow-up (P,.05) (Table 4). Eight (25%) upper and 7 (22%) lower adjacent disks displayed new degeneration or progression of initial degeneration at last follow-up. However, the degeneration did not affect the mid-term clinical outcome (Figure 4). Complications Throat discomfort and dysphagia were reported in 6 patients. All of the symptoms were transient and disappeared within 2 weeks with no treatment. One patient who received C4-C5 and C5-C6 disk replacement suffered from persistent radicular pain and right upper extremity weakness, which did not respond to nonsteroidal anti-inflammatory drugs and physical therapy. This patient had a poor outcome according to Odom s scale. The cohort had no vascular or neurological complications, cerebrospinal fluid leakage, local hematoma, heterotopic ossification, or spontaneous fusion. No reoperations were performed after an average follow-up of 49.4 months. Discussion For.50 years, anterior cervical diskectomy and fusion has been the surgery of choice for cervical myelopathy and radiculopathy that does not respond to conservative treatment. 2 The application of an anterior cervical plate has increased the fusion rate, especially in multilevel fusion. 18 However, despite its safety and effectiveness, anterior cervical diskectomy and fusion may result in adjacent segment degeneration in the long term, which has caused concern among spine surgeons. Biomechanical studies show motion compensation and increased intradiskal stress at the segments adjacent to the fusion site after anterior cervical diskectomy and fusion, 5,6,19 which is believed to cause symptomatic adjacent segment disease and may necessitate reoperation. Long-term 2A 2B 2C 2D 2E Figure 2: Preoperative magnetic resonance image showing C5-C6 and C6-C7 disk herniation (A). Fortyeight-month follow-up lateral radiograph showing kyposis in the cervical spine; both prostheses had normal position (B) and preserved a certain range of motion (C, D). Forty-eight-month follow-up magnetic resonance image showing upper and lower adjacent disks with no herniation (E). 3A 3B 3C 3D 3E Figure 3: Postoperative neutral lateral radiographs showing the prosthesis in normal position 1 week postoperatively (A), 1.5-mm of anterior migration at 3-month follow-up (B), 1.5-mm of anterior migration at 6-month follow-up (C), 3.5-mm anterior migration at 12-month follow-up (D), and 3.5-mm anterior migration at 48-month follow-up (E). clinical studies also report a high rate of radiographic changes at the segments immediately adjacent to the fusion site (Table 5). Katsuura et al 20 followed 42 patients with anterior cervical fusion for an average of 9.8 years and reported that half of the patients had radiographic degenerative changes at adjacent segments. Hilibrand et al 21 reported that symptomatic adjacent Table 4 Degeneration Score of Upper and Lower Adjacent Segments Follow-up Segment Preoperative 12 mo 24 mo Final Points, N Upper adjacent Lower adjacent segment disease occurred at an average incidence of 2.9% per year after anterior cervical diskectomy and fusion and predicted an incidence of 25.6% within 10 years after fusion. However, it has not been shown whether adjacent segment degeneration is attributable to the biomechanical effects of fusion or is a result of the natural history of cervical degeneration. JUNE 2012 Volume 35 Number 6 e913

6 As an alternative to anterior cervical diskectomy and fusion, cervical total disk replacement theoretically preserves the normal kinematics and biomechanics of the cervical spine and consequently decreases the occurrence of adjacent segment disease. Since Goffin et al 14 first reported the successful application of the Bryan Cervical Disc in 2002, the satisfactory short-term clinical results of cervical total disk replacement with the Bryan Cervical Disc have been generally acknowledged However, few studies have reported mid- or long-term results. Garrido et al 22 reported functional outcomes at 48-month follow-up for 21 patients who received Bryan Cervical Disc replacement and 26 patients who received anterior cervical diskectomy and fusion. Their outcome data suggested improved outcome measures for both cohorts, with no degradation of the outcome measures from 24 to 48 months. Six reoperations were performed in the anterior cervical diskectomy and fusion cohort and 1 was performed in the Bryan Cervical Disc cohort. Of the 6 reoperations in the anterior cervical diskectomy and fusion cohort, 3 were for adjacent segment disease, whereas the reoperation in the Bryan Cervical Disc cohort was for adjacent segment disease. 22 Goffin et al 23 completed a 4- and 6-year follow-up study of 98 patients who received single-level (89 cases) or bi-level (9 cases) Bryan Cervical Disc replacement and found that the postoperative SF-36 physical and mental components, Neck Disability Index score, and neck/ 4A 4B 4C 4D 4E Figure 4: Preoperative (A) and postoperative neutral lateral radiographs at 12 (B), 24 (C), 36 (D), and 48 (E) months of a patient who received a C5-C6 Bryan Cervical Disc replacement (Medtronic Sofamor Danek, Inc, Memphis, Tennessee). The anterior osteophyte enlarged gradually at the upper adjacent segment. The lower adjacent segment showed enlargement of the anterior osteophyte and endplate sclerosis. arm pain visual analog pain scale scores were significantly better than the preoperative scores, and that the 4- and 6-year clinical results were consistent with, if not better than, the 1- and 2-year postoperative results. Four reoperations were performed at the operative segment, and 4 were performed at an adjacent segment. 23 Similarly, in the current study, the neurological symptoms of most patients were markedly relieved postoperatively. The SF-36 physical and mental components, Neck Disability Index, Japanese Orthopaedic Association score, and neck/arm pain visual analog pain scale scores were improved significantly at each follow-up visit (P,.05). The Odom s scale good to excellent outcome rate was 84.4% at last follow-up. Thus, the short-term satisfactory results postoperatively appear to be sustained in the mid term. However, the neurological improvement is mainly due to thorough decompression, not the application of a Bryan Cervical Disc. Compared with spinal fusion, cervical total disk replacement is thought to maintain more physiologic motion at the operative and adjacent segments, likely reducing the risk of adjacent segment degeneration. The radiographic outcomes of several multicenter, randomized, controlled investigational device exemption trials have demonstrated that operative segment ROM was preserved and adjacent segment ROM was unaltered after cervi- Study Table 5 Literature Review of Adjacent Segment Degeneration After Anterior Cervical Diskectomy and Fusion Year No. of Patients No. of M/F Mean Age, y Treated Level: No. Average Follow-up Degeneration, % (No.) Degree of Degeneration Katsuura et al / :23; 2:17; 3:2 9.8 y 50 (21) Neurological deterioration in 8 patients; 3 reoperations Hilibrand et al / :343; 2:28; 3:2; 4:1 Not stated, maximum of 21 y Average annual incidence, 2.9%; incidence of 25.6% within 10 years 29 reoperations Garrido et al / :26 48 mo Not stated 3 reoperations Kim et al / :26; 2:28 20 mo (22) No symptoms e914 Healio.com The new online home of ORTHOPEDICS Healio.com/Orthopedics

7 Bryan Artificial Cervical Disc Replacement Ding et al cal total disk replacement. 24,25 The results of the current study also suggest that the kinematics of operative and adjacent segments could be well maintained by cervical total disk replacement with the Bryan Cervical Disc in the mid term. The Bryan Cervical Disc has proven to be stable in the mid and long term. However, some cases of unstable devices have been reported. In the first published article about the Bryan Cervical Disc, Goffin et al 14 reported that device migration.2 mm was ascertained in 1 patient and suspected in another, but no migration.3 mm was found. Tian et al 26 detected 2-mm anterior device migration in 1 patient of 50 with Bryan Cervical Discs. In the current study, the authors observed device stability on neutral lateral radiographs and found.2 mm of anterior migration of the prosthesis in 5 cases during early followup. The authors recommended that those patients use a neck collar to restrict the motion of the cervical spine, and no further migration occurred after 12 months of follow-up. The patients had no symptoms, and the function of the devices was preserved. No prosthesis subsidence or excursion occurred in this cohort. Possible reasons for migration include inappropriate movement of the cervical spine at an early stage, insufficient milling of the upper and lower endplates, and the smaller size of the implanted disk. The protective effect of cervical total disk replacement on adjacent segment disks has not been confirmed by previous studies. Kim et al 27 reported that 6 (23.07%) patients in their single-level anterior cervical diskectomy and fusion cohort developed radiographic adjacent changes, compared with 5 (12.82%) in the single-level Bryan Cervical Disc cohort. They observed radiographic adjacent changes in 16 (57.14%) patients in the bilevel anterior cervical diskectomy and fusion cohort and 4 (33.33%) patients in the bi-level Bryan Cervical Disc cohort. Walraevens et al 28 assessed the progression of adjacent segment degeneration for up to 8 years after Bryan Cervical Disc replacement using the quantitative scoring system. They reported that the degeneration score of the upper adjacent segment increased significantly at 4-, 6-, and 8-year follow-up compared with the preoperative score (P,.01), as did the score for the lower adjacent segment at 4- and 6-year follow-up (P,.01). At 6 and 8 years postoperatively, 48% and 44% of patients, respectively, had new degeneration or progression of initial degeneration at adjacent segments. Four of 85 patients needed a reoperation at an adjacent segment. 24 In the current study, the authors also found that the degeneration scores of the upper and lower adjacent segments at 24 and 48 months were significantly different from the preoperative scores: approximately one-fourth of upper and lower adjacent disks had evidence of progression at last follow-up. The degeneration mainly manifested as new formation or enlargement of an anterior osteophyte. Although no degradation occurred in clinical outcome measures after 24-month follow-up and no reoperations were performed, the authors observed the development of adjacent segment degeneration after cervical total disk replacement in this study, and a long-term follow-up is required to determine whether and when the presence of degeneration will be translated symptomatically. Heterotopic ossification or spontaneous fusion after cervical total disk replacement has been reported by many authors. 29,30 In contrast, the authors of the current article encountered no explicit heterotopic ossification or spontaneous fusion during follow-up. The authors surmise several reasons for this result. First, they intraoperatively ensured that the upper and lower endplates were parallel after implanting the Bryan Cervical Discs. This step prevented the anterior and posterior edges of the endplates from getting too close so the motion of the Bryan Cervical Disc was restricted and osteophyte bridging was facilitated. Second, they completely removed residual disk material, osteophytes at the posterior edge, and the posterior longitudinal ligament, which may function as the starting point for formation of heterotopic ossification. Third, they washed the operative region repeatedly to prevent the adhesion of bone debris. Heterotopic ossification may be prevented by improved surgical technique. Finally, the authors regularly administered nonsteroidal anti-inflammatory drugs to patients for 2 weeks postoperatively because they are reported to reduce the incidence of heterotopic ossification. Conclusion The current study demonstrated that Bryan cervical disc replacement has a good mid-term clinical and radiographic outcome. Adjacent segment degeneration was also observed after this procedure. However, some limitations exist to the current study. It lacked a control group, the sample size was small, and some kinematic parameters, such as lateral bending and axial rotation ROM, were not measured. A prospective, randomized controlled, long-term follow-up study is needed to evaluate the long-term outcomes and effect on adjacent levels of cervical total disk replacement with the Bryan cervical disc. References 1. Smith GW, Robinson RA. The treatment of certain cervical-spine disorders by anterior removal of the intervertebral disc and interbody fusion. J Bone Joint Surg Am. 1958; 40(3): Bohlman HH, Emery SE, Goodfellow DB, et al. Robinson anterior cervical discectomy and arthrodesis for cervical radiculopathy. Long-term follow-up of one hundred and twenty-two patients. J Bone Joint Surg Am. 1993; 75(9): Heidecke V, Rainov NG, Burkert W. Anterior cervical fusion with the Orion locking plate system. Spine. 1998; 23(16): Caspar W, Geisler FH, Pitzen T, Johnson TA. Anterior cervical plate stabilization in one- and two-level degenerative disease: overtreatment or benefit? J Spinal Disord. 1998; 11(1): Fuller DA, Kirkpatrick JS, Emery SE, Wilber RG, Davy DT. A kinematic study of the JUNE 2012 Volume 35 Number 6 e915

8 cervical spine before and after segmental arthrodesis. Spine (Phila Pa 1976). 1998; 23(15): Eck JC, Humphreys SC, Lim TH, et al. Biomechanical study on the effect of cervical spine fusion on adjacent-level intradiscal pressure and segmental motion. Spine (Phila Pa 1976). 2002; 27(22): Goffin J, Geusens E, Vantomme N, et al. Long-term follow-up after interbody fusion of the cervical spine. J Spinal Disord Tech. 2004; 17(2): Robertson JT, Papadopoulos SM, Traynelis VC. Assessment of adjacent-segment disease in patients treated with cervical fusion or arthroplasty: a prospective 2-year study. J Neurosurg Spine. 2005; 3(6): Baba H, Furusawa N, Imura S, Kawahara N, Tsuchiya H, Tomita K. Late radiographic findings after anterior cervical fusion for spondylotic myeloradiculopathy. Spine (Phila Pa 1976). 1993; 18(15): Ishihara H, Kanamori M, Kawaguchi Y, Nakamura H, Kimura T. Adjacent segment disease after anterior cervical interbody fusion. Spine J. 2004; 4(6): Summers BN, Eisenstein SM. Donor site pain from the ilium. A complication of lumbar spine fusion. J Bone Joint Surg Br. 1989; 71(4): Brown CA, Eismont FJ. Complications in spinal fusion. Orthop Clin North Am. 1998; 29(4): Dmitriev AE, Cunningham BW, Hu N, Sell G, Vigna F, McAfee PC. Adjacent level intradiscal pressure and segmental kinematics following a cervical total disc arthroplasty: an in vitro human cadaveric model. Spine (Phila Pa 1976). 2005; 30(10): Goffin J, Casey A, Kehr P, et al. Preliminary clinical experience with the Bryan cervical disc prosthesis. Neurosurgery. 2002; 51(3): Murrey D, Janssen M, Delamarter R, et al. Results of the prospective, randomized, controlled multicenter Food and Drug Administration investigational device exemption study of the Prodisc-C total disc replacement versus anterior discectomy and fusion for the treatment of 1-level symptomatic cervical disc disease [published online ahead of print September 6, 2008]. Spine J. 2009; 9(4): Heller JG, Sasso RC, Papadopoulos SM, et al. Comparison of BRYAN cervical disc arthroplasty with anterior cervical decompression and fusion: clinical and radiographic results of a randomized, controlled, clinical trial. Spine (Phila Pa 1976). 2009; 34(2): Walraevens J, Liu B, Meersschaert J, et al. Qualitative and quantitative assessment of degeneration of cervical intervertebral discs and facet joints [published online ahead of print November 13, 2008]. Eur Spine J. 2009; 18(3): Rihn JA, Lawrence J, GaRihn JA, et al. Adjacent segment disease after cervical spine fusion. Instr Course Lect. 2009; 58: Schwab JS, Diangelo DJ, Foley KT. Motion compensation associated with singlelevel cervical fusion: where does the lost motion go? Spine (Phila Pa 1976). 2006; 31(21): Katsuura A, Hukuda S, Saruhashi Y, Mori K. Kyphotic malalignment after anterior cervical fusion is one of the factors promoting the degenerative process in adjacent intervertebral levels. Eur Spine J. 2001; 10(4): 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 Am. 1999; 81(4): Garrido BJ, Taha TA, Sasso RC. Clinical outcomes of Bryan cervical disc arthroplasty a prospective, randomized, controlled, single site trial with 48-month follow-up. J Spinal Disord Tech. 2010; 23(6): Goffin J, van Loon J, Van Calenbergh F, Lipscomb B. A clinical analysis of 4- and 6-year follow-up results after cervical disc replacement surgery using the Bryan Cervical Disc Prosthesis. J Neurosurg Spine. 2010; 12(3): Sasso RC, Best NM, Metcalf NH, Anderson PA. Motion analysis of bryan cervical disc arthroplasty versus anterior discectomy and fusion: results from a prospective, randomized, multicenter, clinical trial. J Spinal Disord Tech. 2008; 21(6): Kelly MP, Mok JM, Frisch RF, et al. Adjacent segment motion after anterior cervical discectomy and fusion versus ProDisc-c cervical total disk arthroplasty: analysis from a randomized, controlled trial. Spine. 2011; 36(15): Tian W, Han X, Liu B, et al. Clinical and radiographic results of cervical artificial disc arthroplasty: over three years followup cohort study. Chin Med J (Engl). 2010; 123(21): Kim SW, Limson MA, Kim SB, et al. Comparison of radiographic changes after anterior cervical diskectomy and fusion versus Bryan disc arthroplasty in single and bi-level cases [published online ahead of print January 6, 2009]. Eur Spine J. 2009; 18(2): Walraevens J, Demaerel P, Suetens P, et al. Longitudinal prospective long-term radiographic follow-up after treatment of single-level cervical disk disease with the Bryan cervical disc. Neurosurgery. 2010; 67(3): Leung C, Casey AT, Goffin J, et al. Clinical significance of heterotopic ossification in cervical disc replacement: a prospective multicenter clinical trial. Neurosurgery. 2005; 57(4): Lee JH, Jung TG, Kim HS, Jang JS, Lee SH. Analysis of the incidence and clinical effect of the heterotopic ossification in a single-level cervical artificial disc replacement. Spine J. 2010; 10(8): e916 Healio.com The new online home of ORTHOPEDICS Healio.com/Orthopedics