An RODC must read:
ROBODOC Clinical Trial Status
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Robodoc Clinical Results:
Domestic Multi-Center Trial
European Trial
William L. Bargar, M.D., Dr. med. Andre Bauer, Anthony DiGioia, M.D., Roderick Turner, M.D., Jeffery K. Taylor, M.D., Joseph McCarthy, M.D., Dana Mears, M.D.
Abstract
Integrated Surgical Systems has developed an image-directed robotic system to augment the performance of human surgeons in orthopaedic surgery, initially targeted at cementless total hip replacement surgery. The total system consists of an interactive CT-based presurgical planning component and a surgical system consisting of a robot, redundant motion monitoring, and man-machine interface components. In Vitro experiments conducted with this system have demonstrated an order-of magnitude improvement in implant fit and placement accuracy, compared to standard manual preparation techniques. Twenty-six successful robot-assisted operations have been performed on dogs and fifty-one robot-assisted operations have been performed in a US FDA-authorized clinical trial on humans. In European trials conducted at the Berufsgenossenschaftliche Unfallklinik (BGU) 120 human patients have been successfully operated.
Introduction and Background
The long term success of cementless total hip replacement has been attributed in part to how well the femoral component fits the femur. Appropriate fit can be accomplished by choosing the correct size and type of implant, positioning the implant appropriately in the femur, and preparing the implant-bone interface accurately. In 1992 the concept was introduced of using CT-scan image data, a pre-op planning computer workstation, and a robot arm with a high speed milling device, (the ROBODOC© Surgical Assistant System) in an effort to improve these three aspects of cementless total hip replacement. The effort has evolved chronologically in four phases:
Phase I--Limited Feasibility Study 1986-87
Phase II--In Vitro Development 1987-89
Phase III--In Vivo Development 1989-91
Phase IV--Clinical Applications (US) 1991-present
In Phase I an automated machine language was applied successfully to tasking an industrial robot to mill simplified shapes in synthetic bone. In Phase II an imaging system was developed based upon 3D registered data that retains pixel size accuracy for registration. Also a computer workstation was developed to preplan prosthesis selection and positioning. Human and canine cadaver bones were milled in vitro using a modified industrial robot to accuracy's equal to or better than implant tolerances. In Phase III specifications were developed for a surgical robot designed to operate in the sterile OR environment. A canine study of 26 patients was successfully performed. The improved precision was verified. No untoward risks were identified.
In Phase IV a ten patient human feasibility study was completed in California. No unforeseen risks were identified. All surgeries were successfully completed. A 300 patient randomized multi-center trial in the United States is under way. We are now reporting the interim results of that study.
Method
Patients to be included in the domestic study had to be candidates for cementless total hip replacement. In general this meant that they were usually younger, more active and/or overweight than usual total hip replacement patients. Specific inclusion and exclusion criteria were utilized.
The inclusion criteria is: the patient has severely disabled joint(s) due to primary or secondary degenerative osteo, rheumatoid, or post-traumatic arthritis; avascular necrosis of the femoral head; or acute femoral neck fracture. The patient is able to understand and is willing to comply with the requirements of the study, the patient is eligible to receive the total hip replacement systems validated for use with the ROBODOC Surgical Assistant System, the patient must be at least 21 years of age, but no older than 80 years of age, and lastly, the patient signs an informed consent document specific to this study. The exclusion criteria is: the patient has an active systemic infection or any active local infection in or near the operative hip joint or near the distal femur, the patient requires a revision of a previous total hip replacement, the patient has a metallic implant in the operative hemi-pelvis or femur, which may interfere with scanning or operations, the patient has a pathological skeletal condition (severe osteoporosis, Paget's disease, or renal osteolystrophy), the patient has a knee width measuring greater than 18 cm and/or a femur length measuring less than 30 cm on the operative limb, the patient has any systemic illness or physical impairment which would render him/her unable to perform post-op rehabilitation, the patient has a significant mental disorder, is pregnant, is obese (as defined by 1983 Metropolitan Life Standards), is a prisoner or transient, has a history of drug/alcohol abuse within 12 months prior to screening for study entry, or if the patient refuses blinded randomization into the study.
After the informed consent was obtained the patients were then randomized into either the Control Group or the ROBODOC Group.
Three centers have contributed to this study to date, Each center had 2-4 surgeons participating. As of January 1, 1995, ninety-four patients (51 ROBODOC, 43 control) have completed a minimum 3 months follow-up.
The average age was 52 for the ROBODOC Group and 55 for the Control Group. There were 40 males and 11 females in the ROBODOC Group. In the Control Group there were 33 males and 10 females. Osteoarthritis predominated in both groups with 54% in the ROBODOC group and 58% in the Control Group. Avascular necrosis comprised 21% of the ROBODOC Group and 15% of the Control Group.
The patients were evaluated using the modified Harris Hip Scale, the Hip Society Rating System and the SF-36 Health Survey. Surgical time, blood loss, and length of stay were also monitored. The post-op radiographs were evaluated by the principal investigators using strict criteria to determine the following: the correctness of implant size, the appropriateness of the implant position and the presence of any reaming artifacts. Two different implants have been used so far in the study, the Osteolock (Howmedica) and the AML (Depuy). Patients were grouped by implant type and reviewed separately according to implant specific criteria.
Results
The modified Harris Hip Score at 3 months averaged 72.0 for the ROBODOC group and 68.0 for the control group (NS). The average surgery time was longer for the ROBODOC group (266 minutes vs. 125 minutes, >.0001). Average length of stay was not significantly different (7.00 days ROBODOC vs. 7.16 days control). The SF-36 mean scales scores are equivalent in all categories but Role Emotional for which there is no interpretation. Complications included (ROBODOC vs. Control): intraoperative femoral fractures (0 vs. 2), post-op dislocations (3 vs. 2), DVT (I vs. 1), PE (0 vs. I), partial sciatic nerve palsy (1 vs. 2), and death secondary to CVA (1 vs. O). Dr. Charles Engh's, Anderson Clinic, Arlington, VA., and Dr. William Bargar's, Sutter General, Sacramento, CA., radiographic review of the AML's showed significant differences. Comparing ROBODOC to control: correct size (100% vs. 78%), correct position (97% vs. 61%) and reaming defects (3% vs. 14%). These differences are significant at p<.05 level (Chi-Sq.).
Discussion
Clinical comparisons (e.g. Harris Score) at this short follow-up did not show any significant differences. The radiographic review did, however, show improvements in sizing, and positioning in the ROBODOC group. These factors have been shown to be surrogate indictors of long term outcome and suggest an improvement for long term clinical results using this technique.
Application to total knee replacement and use and revision total hip replacement have begun. Collaborative efforts have also been initiated to develop other non-orthopaedic applications.
The successful linking of the fields of imaging and robotics has resulted in a new tool for precision in surgery. The original application of this device to cementless total hip replacement has shown the technology to be of benefit. It is through the development of additional applications that this new category of testing of surgical "smart tools" will allow the operating room of the future to provide improved outcomes that make this technology cost effective.
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Addendum: European Trial
In 1991, first contacts between the Berufsgenossenschaftliche Unfallklinik Frankfurt am Main and Integrated Surgical Systems (ISS) in Sacramento, the developers of ROBODOC, were established. Since that time, parallel to the ongoing Phase 2 and 3 study in the US, transition of this technology to the European market was discussed and planned.
Apart from the FDA approval, German regulations required the T?V testing of the System, which, contrary to the FDA procedure, did not challenge the efficacy of the system, but put emphasis on its technical safety. Regarding the System as a tool in the surgeons control, its use and evaluation of its benefits were left to the surgeon's judgment.
The major issue in the transfer of ROBODOC to Germany was the different surgical approach. While many American surgeons operate total hips through a posterior approach, with the patient in a lateral decubitus position, most German and European surgeons prefer the anterior-lateral approach. The patient is positioned supine on the OR table. Extensive testing led to modifications of the fixator arm of the robot, the bone motion monitor and the lower leg holder. Pins were placed and found in a different orientation, so software had to be adapted.
After obtaining T?V certification, the System was installed at the BGU in Frankfurt in July 1994. The first two cases, performed in the same week, had to be aborted due to inaccurate CT data. These cases nevertheless proved the safety of the system. The computer detected an error in table motion of the "somewhat dated" scanner during pin finding. Lacking accuracy in pin data, the computer refused to complete the procedure. The first successful surgery was performed in August 1994. Subsequently 124 cases were attempted, 120 of these cases were successfully completed. Two cases had to be aborted due to pin loosening. One case had to be canceled due to a limitation identified in the software which could not accommodate a deformed trochanter. Another was canceled due to a non critical software bug. All these cases could be completed by hand, although the preoperatively planned implant sizes could not be manually executed by the surgeon.
Results
The series of 120 successfully operated patients showed no major complications related to the use of the robot. While, OR time in the first 15 cases averaged 180 minutes, the 105 succeeding patients were operated in an average time of 120 minutes, and the fastest cases took 99 minutes. The overall complication rate was lower than in comparable cementless series previously published. While BETTIN 1993 reported a 33.7% rate, EHALL published in 1992 a 16.6% rate. BGU's rate of complications was 11.6%. This included a 3.3% rate of deep vein thrombosis, a 3.3% rate of pulmonary embolism, a 2.5% rate of nerve palsy and a 2.5% rate of postoperative dislocation. No fractures occurred, a rather common complication in cementless hip replacement. In all robot cases, the preoperatively chosen implant could be implanted, and postoperative x-rays showed that positioning of the implant was performed with a high degree of exactness when related to the preoperative plan. Consequently, immediate full weight bearing was recommended to the patients instead of, as is common at the BGU in cementless hip procedures, walking on crutches for ten weeks.
The series of 120 patients in Germany showed that robot assisted surgery can be performed without exposing the patients to any specific risks; that postoperative complications are lower then in comparative series; that OR times, once the initial learning phase is over, are not intolerably long; that exact transformation of preoperative planning gives strength to the hope, that a better long-term result can be achieved than in standard manual procedures
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