| Part 1 The clinical outcomes and the neck moving ability of Bryan Cervical Disc replacement for cervical spondylosisObjective: Cervical spondylosis is a common disease in clinical spine work. Since the 1950s, ACDF has proved stable and efficient to treatment the cervical spondylosis, and become the gold standard of surgery treatment for cervical disorders. But, reports have indicated that the fusion between vertebras can induces compensatory activity and stress load in adjacent segments increasedly, which is significantly related to the degenerative changes in adjacent segments. Furthermore, some scholars have also observed that long-term AS appears in postoperative rehabilitation in some patients, such as neck stiffness, pain, and limited mobility. In theory, artificial cervical disc replacement can maintain the movement of the surgery segment, and can reduce the incidence of postoperative degenerative changes of adjacent segments. So artificial cervical disc replacement is a procedure widely performed in clinical treatment for cervical spondylosis. The study was designed to analyze the clinical outcomes of Bryan artificial cervical disc replacement in teratment for cervical spondylosis.Methods: From October 2004 to April 2006, 22 patients underwent Bryan cervical disc replacement (replacement group), including 13 men and 9 women. Their ages ranged from 33 to 54 years (mean, 43.3 years). The course of disease was 1-21 months (mean, 6 months). 16 of the patients suffered from cervical myelopathy, and 6 patients were cervical radiculopathy. Twenty patients underwent single-level arthroplasty and two were bi-level. During the same periods, 30 patients underwent ACDF (fusion group),including 17 men and 13 women. Their ages ranged from 35 to 64 years (mean, 50.3 years). The course of disease was 1-23 months (mean, 7 months). 19 of the patients suffered from cervical myelopathy, and 11 patients were cervical radiculopathy. 26 patients underwent single-level arthroplasty and 4 were bi-level. Follow-ups for all the patients were performed at 1 week, 3 months, 6 months, 12 months, and 24 months after the surgery. In each follow-up, dynamic X-ray was performed to observe the stability of prothesis, the range of motion (ROM) of operated segments in replacement group, and the status of fusion in control group. The neurologic recovery rate, the changes of cervical curvature in the operated segments, the total range of motion, and the incidence of AS were analyzed.Results: All the patients were followed up for 24-42 months (30.6 months on average). There were no graveness complications happening during and after operation in both groups. There were no complications of prosthesis bit shifting and amotio in replacement group. All patients in control group exhibited a bony fusion on X-ray films 6 months after surgery, without loose, dislocation or breakage of plate and bolt.①The patients'clinical symptoms of radiculopathy were obviously relieved and the curative effect was satisfactory in two groups of nerve root cervical syndrome. In both groups of cervical spondylotic myelopathy, the patients'JOA scores at the postoperative follow-up increased obviously compared with preoperative scores (P<0.01), and there was no statistically significant difference between the two groups before the operation and at final follow-up (P > 0.05).②In replacement group, one case developed spontaneous fusion 2 years postoperatively, and the motion at operated level of the rest cases were preserved (preoperative 7.32°±0.55°, postoperative 6.21°±0.46°, P > 0.05).③There was no significant difference in ROMs of adjacent segments in replacement group before and after surgery (P>0.05). There was significant difference in control group, ROM was increased obviously postoperative compared with the preoperative (P<0.05).④Before the operation, the rate of kyphosis in replacement group was 13.64% and 13.33% in control group, there was no statistically significant difference (P>0.05). At final follow-up, the rate of kyphosis in replacement group was 9.09% and 40.00% in control group, there was statistically significant difference between the two groups (P<0.05).⑤In replacement group, ROM was 48.8°±14.4°before the operation and 44.5°±13.6°at the final follow-up, there was no statistically significant difference (P>0.05). In control group, ROM was 49.2°±15.1°before the operation and 35.8°±10.9°at the final follow-up, it was obviously lower than preoperative (P<0.01).⑥The rate of postoperative neck AS was 18.18% in group A and 46.67% in group B, and the difference was statistically significant (P<0.05).Conclusion: Compared with traditional anterior cervical discectomy and fusion, Bryan cervical disc replacement for cervical spondylosis can not only achieve good clinical outcomes but also maintain the ROM of the operated segment. Moreover, it can avoid the increase activity of adjacent segments and the decrease of total ROM of cervical spine. It can also maintain the curvature of operated segment and reduce the incidence of the postoperative neck AS.Part 2 Clinical and radiologic outcomes of modified techniques in Bryan cervical disc arthroplastyObjective: Aggravation of kyphosis is a known challenge after arthroplasty. Reports have indicated that the risk of axial symptoms after anterior cervical discectomy is significantly related to the presence of cervical kyphosis. Disc insertion angle and overmilling have been reported to be factors resulting in kyphosis; however, few studies have performed techniques to avoid these factors. This prospective study was designed to determine whether the modified techniques of Bryan cervical disc arthroplasty can prevent these adverse outcomes. In particular, kyphosis and clinical outcomes were analyzed.Methods: Modified techniques include changes in disc insertion, reducing the overmilling of endplates, ensuring the anterior borders are at the same horizontal line, and obtaining an accurate fit for the prosthesis size. The techniques described in the product monograph were performed in 20 patients (control group), and the modified techniques were performed in 29 patients (investigational group). Clinical and radiologic (radiograph) follow-ups for all the patients were performed before and after surgery (2 years). Disability and pain were assessed using the self-administered modified Oswestry NDI and the VAS to assess neck and arm pain. SF-36 outcome measures were obtained for both the physical component as well as the mental component. The change of functional spinal unit angle between the two groups was compared.Results: For all of the following functional outcomes measures, both groups demonstrated statistically significant improvement compared with preoperative values. There was no deterioration in either group. There was no statistically significant difference between the two groups in regards to preoperative scores and postoperative scores with the exception of neck pain VAS and FSU angle changes. The mean neck pain VAS before surgery was 73.45 (control) and 74.53 (investigational). Two-year follow-up scores were 22.1 (control) and 14.79 (investigational) (P = 0.0013). After surgery, 14 of 20 patients in the control group developed a tendency toward kyphosis of the FSU in the neutral position (range: - 9°to 13°, mean: -1.1°±5.05), and none of the 29 patients in the investigational group developed kyphosis of the FSU in the neutral position (range: 0°–10°, mean: 3.79°±2.90) (P = 0.0007). There were no intraoperative complications, no vascular or neurologic complications, no spontaneous fusions, and no device failures or explantations.Conclusion: Postoperative kyphosis of an operative level can be redressed and neck pain can be prevented by the modified techniques of Bryan cervical disc arthroplasty. Part 3 Efficacy and safety of the cervical posterior longitudinal ligament resection in Bryan cervical disc arthroplastyObjective: Bryan cervical disc arthroplasty can be used to restore and maintain the mobility and function of the involved cervical spinal segments. The efficiency of the PLL resection in anterior cervical decompression and fusion has been demonstrated. However, there is no clinical report comparing PLL removal and preservation in Bryan cervical disc arthroplasty. A retrospective investigation was designed to investigate the efficacy and safety of the cervical PLL resection in Bryan cervical disc arthroplasty.Methods: Thirty-one patients undergoing Bryan cervical disc implantation only in one level from August 2006 to January 2009 were investigated in this study. Cervical PLL was preserved in 14 patients (including 7 males and 7 females, with the mean age of 44.6 years) and removed in 17 patients (including 9 males and 8 females, with the mean age of 46.1 years). The clinical (JOA score, VAS score for neck and arm pain) and radiologic parameters (the FSU angle and ROM) were compared between the two groups.Results: No significant differences were found in terms of age, affected segment, gender, follow-up period, operation time and bleeding amount between the two groups. Clinical parameters demonstrated that the PLL removed group had statistically significant (P<0.05) improvements as assessed by JOA score and VAS arm pain score. However, neck pain relief was similar in both groups (P>0.05). There were no significant differences between the two groups with regard to the increase of FSU angle and ROM (P>0.05). No severe complication was found in the two groups.Conclusion: Removal of the cervical PLL was beneficial for the clinical outcomes and achieved a similar effect on the angle and ROM of the affected segment as preservation of the cervical PLL. Removal of the cervical PLL during Bryan cervical disc arthroplasty is safe and feasible.
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