SEPTEMBER 2008 SPINAL IMPLANTS: DR8 PEDICLE SCREW SYSTEM HEALTH TECHNOLOGY ASSESSMENT SECTION MEDICAL DEVELOPMENT DIVISION MINISTRY OF HEALTH MALAYSIA 016/08
DISCLAIMER Technology review is a brief report, prepared on an urgent basis, which draw on restricted reviews from analysis of pertinent literature, on expert opinion and / or regulatory status where appropriate. They are not subjected to an external review process. While effort has been made to do so, this document may not fully reflect all scientific research available. Additionally, other relevant scientific findings may have been reported since completion of the review. Please contact: htamalaysia@moh.gov.my, if you would like further information. Health Technology Assessment Section, Medical Development Division Ministry of Health Malaysia Level 4, Block E1, Precinct 1 Federal Government Administrative Centre 62590 Putrajaya Tel: 603 88831246 Fax: 603 8883 1230 Available at the following website: http://www.moh.gov.my ii
Prepared by: Dr Izzuna Mudla bt Mohamed Ghazali Principal Assistant Director Health Technology Assessment Section Ministry of Health Malaysia Reviewed by: Datin Dr Rugayah bt Bakri Deputy Director Health Technology Assessment Section Ministry of Health Malaysia iii
EXECUTIVE SUMMARY Pedicle screw spinal systems are multiple component devices, made from a variety of materials, including alloys such as 316L stainless steel, 316LVM stainless steel, 22Cr-13Ni-5Mn stainless steel, Ti-6Al-4V, and unalloyed titanium that allow the surgeon to build an implant system to fit the patient's anatomical and physiological requirements. DR8 TM Dual Rod Pedicle Screw System is locally produced and made of medical grade quality titanium or medical grade quality stainless steel. The screws are made in different sizes to accommodate patients individual needs. DR8 TM Dual Rod Pedicle Screw System has not received FDA approval. It can be classified as Class III medical device. According to the manufacturer this device has been used in some hospitals in Malaysia. There are two types of screw; Fixed Angle Screw (FAST) and Variable Angle Screw (VAST) System. Both systems used open screw concept with top loading locking mechanism which allows easier insertion of rod diameters (from 5.5mm to 6mm); secured via 3 contact points fixation between the rod and the screw. The screws come in 4 different diameters; 4.6mm, 5.6mm, 6.6mm and 7.6mm, and available in different lengths from 25mm to 55mm with 5mm increment. There was insufficient evidence to support the safety, effectiveness and cost-effectiveness of DR8 TM Pedicle Screw System, thus more clinical research is warranted. Based on this review, DR8 TM Pedicle Screw System cannot be recommended to be used until more evidence on its safety and effectiveness is obtained. iv
SPINAL IMPLANTS: DR8 PEDICLE SCREW SYSTEM 1. INTRODUCTION Back disorders encompass a spectrum of conditions, from those of acute onset and short duration to lifelong disorders, and include osteoarthritis, disc degeneration, osteoporosis, and common low back pain. The prevalence of many of these disorders increases markedly with age, and many of the disorders are affected by lifestyle factors, such as obesity and certain types of physical activity. 1 In the US population, the third National Health and Nutrition Examination Survey (NHANES III) (1988-1994) estimated that the 12-month period prevalence of back pain episodes lasting for at least 1 month was 17.8%. In the adult Greek population, the 1-month prevalence of back pain has been estimated as 32%. 1 In Malaysia, a cross sectional study among 330 doctors at Kuala Lumpur Hospital revealed that 59.2% of them developed low back pain during their working life. 2 Back disorders can be managed either surgically or non-surgically. The reasons for surgery include deformity, pain, neurological dysfunction and functional impairment. The pedicle screw which is sometimes used as an adjunct to spinal fusion surgery provides a means of gripping a spinal segment. The screw themselves do not fixate the spinal segment, but act as firm anchor points that can then be connected with a rod. 3 Boucher, in 1959, has been credited as being the first to use pedicle screws but it was Roy-Camille, in the late 1970s, who was the first to use screws and hooks and connecting them with rods or plates. In 1983, Arthur Steffee patented the VSP spinal fixation system. 4 The early pedicle screw fixation systems utilized rather thick rods to support the screws as shown below. An internal bone growth stimulator is shown at the top of the image. Not only were the rods difficult to bend at surgery but they tended to exert significant adverse stress on the screws and adjacent spinal segments. Complications involving nerve compression or injury associated with the placement of pedicle screws still occur in approximately 8-15% of cases. 4 There are many brands of pedicle screw in the market. DR8 TM Pedicle Screw System is produced by a local company, Delphax Corporation Berhad. This review was requested by the Director of Medical Development Division, Ministry of Health Malaysia following a request for a meeting by the company. 1
2. OBJECTIVES The objective of this review is to determine the safety, effectiveness and costeffectiveness of DR8 TM Pedicle Screw System for spinal implants. 3. TECHNICAL FEATURES Pedicle screw spinal systems are multiple component devices, made from a variety of materials, including alloys such as 316L stainless steel, 316LVM stainless steel, 22Cr- 13Ni-5Mn stainless steel, Ti-6Al-4V, and unalloyed titanium that allow the surgeon to build an implant system to fit the patient's anatomical and physiological requirements. Such a spinal implant assembly consists of a combination of anchors (e.g., bolts, hooks, and/or screws); interconnection mechanisms incorporating nuts, screws, sleeves, or bolts; longitudinal members (e.g., plates, rods, and/or plate/rod combinations); and/or transverse connectors. 5 According to Food and Drug Administration (FDA), pedicle screw spinal systems can be either classified as Class II (special controls) or Class III medical device depending on the intended usage (Appendix 3). DR8 TM Dual Rod Pedicle Screw System is made of medical grade quality titanium or medical grade quality stainless steel. The screws are made in different sizes to accommodate patients individual needs. DR8 TM Dual Rod Pedicle Screw System has not received FDA approval. It can be classified as Class III medical device. According to the manufacturer this device has been used in some hospitals in Malaysia. There are two type of screws; Fixed Angle Screw (FAST) and Variable Angle Screw (VAST) System. Both systems used open screw concept with top loading locking mechanism which allows easier insertion of rod diameters (from 5.5mm to 6mm); secured via 3 contact points fixation between the rod and the screw. The screws come in 4 different diameters; 4.6mm, 5.6mm, 6.6mm and 7.6mm, and available in different lengths from 25mm to 55mm with 5mm increment. The FAST system features an open-type slot for the purpose of securing and stabilizing different rod diameters whereas the VAST system features an open-type slot with the ability of 25 degrees angulation at 360 degrees for the purpose of securing and stabilizing different rod diameters. 2
Figure 1. DR8 Variable Angled Screw (VAST) and Fixed Angled Screw (FAST) System A locking mechanism is delivered with a single nut that attaches the rod to the screw. The dorsal end component of the Plug Head breaks off automatically from the proximal part at about 80-100 pound torque upon final tightening. The rod has cylindrical smooth surface and available in 5.5mm and 6mm diameters. The length of the rod is 480 mm. The nexus connector stabilizes the construct by means of 2 J-Hooks connected to the 2 adjacent rods via a slotted bar. 3
SURGICAL TECHNIQUE 6 SCREW INSERTION The FAST or VAST Screws are inserted into the L4-S1 pedicles once the pedicles and the appropriate screw diameters and lengths are determined. FAST Screws: The FAST Screw Driver is used to insert the Fixed Angled Screws. Ensure the short horizontal-bar end is fully engaged or seated into the head of the screw before the threaded sleeve is applied onto the head of the screws. When fully inserted, the screws should be extended by 50% to 80% into the vertebral body and ensured that they are parallel to the end plate. VAST Screws: The Screw Driver is used to insert Variable Angled Screws. Ensure the hex end is fully engaged or seated into the head of ROD the screw INSERTION before the threaded sleeve is applied onto the head Appropriate of the screws. rod diameter is determined and cut to the desired length. The French Bender is used to bend the rod to fit the desired spinal contours. The Rod Holder is used for optimal rod insertion. NUT APPLICATION After the rod is placed at the base of the screw head, the Plug Head is positioned at the tip of the screw head using the Nut Starter. If required, the Rod Pusher or Rod Introducer is used to position the rod into the screw head. The Rod Reducer is used for reduction when the rod is not fully seated on the head of the screw. 4
COMPRESSION/DISTRACTION The compression or the distraction is performed when necessary. Care must be taken in placing the instruments securely against the body of the screws and not against the Plug Head. In both procedures, the Plug Head is tightened on one side of the segment, while the other Plug Head remains loose. The compression or the distraction will thus occur against that of the tightened screw. FINAL TIGHTENING The final tightening is performed with the Final Nut Driver and the Anti-Torque Driver. The Anti-Torque Driver is placed over a screw head resting on the rod, while the Final Nut Driver is inserted through the cannulation of the Anti-Torque Driver. Upon final tightening of the Plug Head with the Final Nut Driver, the dorsal end component of the Plug Head breaks off automatically from the proximal part at about 80 to 100 pound torque. CONNECTOR-TECHNIQUE Following the final tightening of the screws and rods, the distance between the two rods is measured and a bar is cut to the required length. For both the distraction and compression positioning, the J-Hook components of the Nexus are placed onto the rods, one on each opposite side. The bar is then positioned in between the J-Hook components and the rods and set screws are tightened. 5
4. METHODOLOGY 4.1 SEARCH METHODS Literature were searched through electronic databases which included Medline, Cochrane Library, Science Direct, Ebscohost and general databases such as Google and Yahoo. The search strategy used the terms, which were either used singly or in various combinations: Spinal implants OR Pedicle screw OR DR8 Pedicle screw, effectiveness OR efficacy, safety OR safe OR adverse effect* OR harm* effect*, cost effectiveness OR cost analysis OR econom*. There was no limitation in the search. 4.2 SELECTION OF STUDIES INCLUDED /EXCLUDED For effectiveness, only human studies were included in this review. Only systematic reviews of randomized controlled trials and randomized controlled trials were included. Animal study and observational studies were excluded. As for safety assessment, all studies on DR8 Pedicle screw were included. A critical appraisal of all relevant literature was performed using Critical Appraisal Skills Programme (CASP) checklists and the evidence graded according to the US/Canadian Preventive Services Task Force Level of Evidence (Harris 2001). 5. RESULTS AND DISCUSSION There was no scientific evidence retrieved on DR8 TM Pedicle Screw System. Reports provided by the manufacturer will be used for discussion in the safety assessment. 5.1 SAFETY There was no evidence retrieved on the safety of DR8 TM Pedicle Screw System. Lonstein et. al. conducted a retrospective review of all pedicle-screw procedures that were done by the group from January 1, 1984 to December 31, 1993. They concluded that there were few problems associated with the insertion of screws, provided that the surgeon is experienced and adheres to the principles and details of the operative technique. 7 Delphax titanium screw and rods conformed to that of a grade Ti-6AI-4V or UNS R56401. The titanium screw has undergone mechanical testing and conformed to the required standard. It has been assessed in laboratory for cytotoxicity using a mammalian cell line as the target cells. The results showed no cytotoxic response at a concentration of 100% under the condition of the test. 8 Animal study conducted to assess toxicity of the titanium screw using mice showed that there was no death or remarkable change in body weight and no adverse reaction was observed following the administration of the extract of titanium screw. 9 Pyrogen test had been conducted and showed that spinal screw was found to be nonpyrogenic under the condition of the test. 10 6
5.2 EFFICACY/EFFECTIVENESS There was no evidence retrieved on efficacy of DR8 TM Pedicle Screw System. 5.3 COST EFFECTIVENESS There was no evidence retrieved on cost-effectiveness of DR8 TM Pedicle Screw System. However, the price is claimed to be lower compared to imported spinal implants. 6. CONCLUSION There were insufficient evidence on safety, effectiveness and cost-effectiveness of DR8 TM Pedicle Screw System. Thus more clinical research is warranted. 7. RECOMMENDATION Based on this review, DR8 TM Pedicle Screw System cannot be recommended to be used until more evidence on its safety and effectiveness is obtained. 7
8. REFERENCES 1. Manek NJ, MacGregor AJ. Epidemiology of Back Disorders: Prevalence, Risk Factors, and Prognosis. Curr Opin Rheumatol. 2005;17(2):134-140. 2. Jabar M. The Prevalence of Low Back Pain Among Doctors of Hospital Kuala Lumpur. NCD Malaysia. 2005;4(2):4-9. 3. Ullrich PF. pedicle screws for spine fusion. Retrieved from Spine-Health (http://spinehealth.com) on 3 February 2009. 4. Pedicle Screw Segmental Instrumentation. In: The Burton Report. February 2009 edition. Volume VIII. Retrieved from http://www.burtonreport.com/infspine/surgstabilpedscrews.htm on 1 February 2009. 5. 21CFR888.3070. Pedicle screw spinal system. In: Subpart D--Prosthetic Devices. Code of Federal Regulation.[Revised as of April 1, 2008]. 6. DR8 Dual-rod Pedicle Screw System. Delphax Corporation Berhad, 2006. (Brochure) 7. Lonstein JE, Denis F, Perra JH et al. Complications Associated with Pedicle Screws. The Journal of Bone And Joint Surgery. 1999;81:1519-1528. (Abstract) 8. MTT Assay For Cytotoxicity Of Medical Device. Test Report No. MB-MTA-66-06. Mediamal Testing & Consultancy Services(MTES), 9 Mei 2006. 9. Systemic Toxicity Test (Animal study). Test Report No. MB-234-STT-06. Mediamal Testing & Consultancy Services(MTES), 9 Mei 2006. 10. Pyrogen Test (Animal study). Study report no: MB-PYRO-67-06. Mediamal Testing & Consultancy Services(MTES), 20 April 2006. 8