Pretic-I was a safe and effective artificial cervical disc prosthesis--a retrospective and comparative study with 5-year follow-up

Background The newly designed cervical disc prosthesis, Pretic-I, had been finished its limited clinical use for over 5 years. At a short-term follow-up of 2 years, we obtained satisfactory clinical results. The long-term clinical efficacy and safety of Pretic-I will now be analyzed. Methods Peri-operative parameters included intra-operative blood loss, operation time, off-bed time. Clinical parameters included visual analogue scale (VAS) for arm and neck, neck disability index (NDI), and Japanese Orthopaedic Association (JOA) score. Radiological parameters included C2–7 Cobb angle, Shell angle, and the range of motion (ROM) of C2–7, functional segment unit (FSU), and adjacent FSU. The CDA-related complications included adjacent segment degeneration (ASDeg), adjacent segment disease (ASDis), heterotopic ossification (HO), prosthesis subsidence, prosthesis displacement, and dysphagia. Results A total 64 patients from two independent centers received a single-level CDA with Discover (n = 32) and Pretic-I (n = 32), and all of patients finished a 5-year follow-up. There’re no significant differences between two groups in peri-operative parameters. The clinical parameters improved greatly in Pretic-I group (p<0.0001), and there’s no statistical difference from Discover group. Furthermore, Pretic-I could slightly improve the cervical curvature (15.08 ± 11.75 to 18.00 ± 10.61, p = 0.3079) and perfectly maintain the Shell angle (3.03 ± 3.68 to 2.23 ± 4.10, p = 0.1988), cervical ROM (52.48 ± 14.31 to 53.30 ± 11.71, p = 0.8062) and FSU ROM (12.20 ± 4.52 to 10.73 ± 4.45, p = 0.2002). The incidence of high-grade HO (Grade III-IV) at the final follow-up was significantly lower in Pretic-I group than in Discover group (12.50% vs. 34.38%, p = 0.0389, Statistical Power = 95.36%). The incidences of other CDA-related complications in Pretic-I group were also well-accepted, comparable to the Discover group, without significant differences. Conclusion CDA with Pretic-I demonstrated a well-accepted and sustained clinical outcome, with a significantly lower incidence of high-grade HO. This newly designed prosthesis is expected to become an alternative choice for cervical disc prosthesis in the future.

Comparison of Pretic-I Versus Discover Disc Arthroplasty As Treatment for Single-level Cervical Disc Degenerative Disease With 5-year Follow-up

Background: The newly designed cervical disc prosthesis, Pretic-I, had been finished its limited clinical use for over 5 years. At a short-term follow-up of 2 years, we obtained satisfactory clinical results. The long-term clinical efficacy and safety of Pretic-I will now be analyzed. Methods: Peri-operative parameters included intra-operative blood loss, operation time, off-bed time. Clinical parameters included visual analogue scale (VAS) for arm and neck, neck disability index (NDI), and Japanese Orthopaedic Association (JOA) score. Radiological parameters included C2-7 Cobb angle, Shell angle, and the range of motion (ROM) of C2-7, functional segment unit (FSU), and adjacent FSU. The CDA-related complications included adjacent segment degeneration (ASDeg), adjacent segment disease (ASDis) , heterotopic ossification (HO), prosthesis subsidence, prosthesis displacement, and dysphagia.Results: A total 64 patients from two independent centers received a single-level CDA with Discover (n=32) and Pretic-I (n=32), and all of patients finished a 5-year follow-up. There’re no significant differences between two groups in peri-operative parameters. The clinical parameters improved greatly in Pretic-I group (p＜0.0001), and there’s no statistical difference from Discover group. Furthermore, Pretic-I could slightly improve the cervical curvature (15.08±11.75 to 18.00±10.61, p=0.3079) and perfectly maintain the Shell angle (3.03±3.68 to 2.23±4.10, p=0.1988), cervical ROM (52.48±14.31 to 53.30±11.71, p=0.8062) and FSU ROM (12.20±4.52 to 10.73±4.45, p=0.2002). The incidence of high-grade HO (Grade III-IV) at the final follow-up was significantly lower in Pretic-I group than in Discover group (12.50% vs. 34.38%, p=0.0389, Statistical Power=95.36%). The incidences of other CDA-related complications in Pretic-I group were also well-accepted, comparable to the Discover group, without significant differences.Conclusion: CDA with Pretic-I demonstrated a well-accepted and sustained clinical outcome, with a significantly lower incidence of high-grade HO. This newly designed prosthesis is expected to become an alternative choice for cervical disc prosthesis in the future.

Prospective Multicenter Trial of Cervical Arthroplasty With the ROTAIO® Cervical Disc Prosthesis

ObjectiveAnterior Cervical Discectomy and Arthroplasty (ACDA) is an established treatment for degenerative cervical disc disease and seems to be an alternative to fusion in minimizing the risk of Adjacent Segment Disease (ASD). The ROTAIO® cervical disc prosthesis is a novel unconstrained implant with a variable center of rotation aiming at physiological motion. The objective of this multicenter prospective trial was to evaluate clinical outcome and complications within 2 years.Material and Methods120 patients (72 females and 48 males with a median age of 43.0 years; range: 23 to 60 years) underwent ACDA (ROTAIO®, SIGNUS Medical, Alzenau, Germany) and were prospectively followed for 24 months. Preoperative complaints were mainly associated with radiculopathy (n=104) or myelopathy (n=16). There were 108 monosegmental and 12 bisegmental procedures including 6 hybrid constructs. Clinical outcome was evaluated at 3, 12 and 24 months by the Visual Analogue Scale (VAS) for head, neck and arm pain, the Neck Disability Index (NDI), the Work Limitation Questionnaire (WL-26), the Patient`s Satisfaction Index (PSI) and a Quality of Life Questionnaire (SF-36). The Nurick Score, the Modified Japanese Orthopaedic Association Score (mJOA) plus a Composite Success Rate have been additionally applied. Finally, complications, the patient`s overall satisfaction and the amount of analgesics were assessed. ResultsHighly significant clinical improvements were observed according to NDI and VAS (p<0.0001 (arm); p<0.001 (neck); p=0.002 (head)) at all postoperative time points. Analgetic medication could be reduced after 3 months in 91.3%, after 12 months in 87.1% and after 24 months in 95.2% of patients. Doctor`s visits for cervical spine problems have been reduced in 93.8% after 24 months.Patient`s overall satisfaction was high after 3, 12 and 24 months with 83.5%, 78.4% and 79.1% of patients, while 4.1%, 6.8% and 7.0% respectively were not satisfied. The composite success rate was 77.5% after 12 months and 76.9% after 24 months. There were no major complications in this series. Slight subsidence of the prosthesis was observed in 2 patients and 3 patients demonstrated fusion after 24 months. 2 patients developed symptomatic foraminal stenosis, so that implant removal and fusion was performed.ConclusionThe ROTAIO® cervical disc prosthesis is a safe and efficient treatment option for symptomatic degenerative disc disease demonstrating excellent clinical results at 2 years. Outcome proves to be stable over time with very low revision rates.

Low Wear Debris Compliant Mechanism Cervical Disc Prosthesis

The device outlined in this paper is 3D printable cervical disc prosthesis that uses a compliant mechanism to behave biomechanically like a natural cervical intervertebral disc. The device is DMLS printed out of biocompatible titanium as a single part, and can be manufactured to the custom length, width, height, and lordotic angle desired for the patient. The device has 6 degrees of freedom for flexion, extension, and lateral bending. The device has 0.83 mm of max compression with a compressive stiffness of 473.1 N/mm. The device consists of compliant mechanism with two plates fused on the top and bottom. The mechanism is essentially two perpendicular beams fused at their midpoints. The beams act as rotational as well as compressive springs. This allows the rotational and compressive range of motion. This design is intended to minimize the production of wear debris, which is a problem with prosthetics. It also provides the ability for a disc prosthesis to be easily custom manufactured for the patient.

Does index level sagittal alignment determine adjacent level disc height loss?

OBJECTIVEThe authors sought to compare the effect of index level sagittal alignment on cephalad radiographic adjacent segment pathology (RASP) in patients undergoing cervical total disc arthroplasty (TDA) or anterior cervical discectomy and fusion (ACDF).METHODSThis was a retrospective study of prospectively collected radiographic data from 79 patients who underwent TDA or ACDF and were enrolled and followed prospectively at two centers in a multicenter FDA investigational device exemption trial of the Bryan cervical disc prosthesis used for arthroplasty. Neutral lateral radiographs were obtained pre- and postoperatively and at 1, 2, 4, and up to 7 years following surgery. The index level Cobb angle was measured both pre- and postoperatively. Cephalad disc degeneration was determined by a previously described measurement of the disc height/anteroposterior (AP) distance ratio.RESULTSSixty-eight patients (n = 33 ACDF; n = 35 TDA) had complete radiographs and were included for analysis. Preoperatively, there was no difference in the index level Cobb angle between the ACDF and TDA patients. Postoperatively, the ACDF patients had a larger segment lordosis compared to the TDA patients (p = 0.002). Patients who had a postoperative kyphotic Cobb angle were more likely to have undergone TDA (p = 0.01). A significant decrease in the disc height/AP distance ratio occurred over time (p = 0.035), by an average of 0.01818 at 84 months. However, this decrease was not influenced by preoperative alignment, postoperative alignment, or type of surgery.CONCLUSIONSIn this cohort of patients undergoing TDA and ACDF, the authors found that preoperative and postoperative sagittal alignment have no effect on RASP at follow-up of at least 7 years. They identified time as the only significant factor affecting RASP.