Howard A. Paul

An image-directed robotic system for precise orthopaedic surgery

The authors have developed an image-directed robotic system to augment the performance of human surgeons in precise bone machining procedures 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. The first generation system described in this paper was used in a successful veterinary clinical trial on 26 dogs needing hip replacement surgery. It was the basis for subsequent development of a second-generation system that is now in human clinical trials. >

Development of a surgical robot for cementless total hip arthroplasty.

The long-term success of cementless total hip arthroplasty (THA) may depend on bone ingrowth into the porous-fixation surfaces of the implant. The ingrowth process is facilitated when the surgeon achieves a satisfactory fit for the prosthesis. Clinically or roentgenographically visible failure and persistent thigh pain after cementless THA remain significant problems, both of which may be alleviated by more precise preparation of the femoral canal and selection of an appropriately sized prosthesis. The objective of this study was to obtain an exact fit for the prosthesis through the use of an image-directed surgical robot for femoral canal preparation.

A surgical robot for total hip replacement surgery

The authors describe a robotic surgical system that has been designed to create femoral cavities that are precisely shaped and positioned for implantation of uncemented prostheses. This robotics system creates cavities with a dimensional accuracy more than 50 times greater than broached cavities, exceeds the tolerances to which implants are manufactured, and does not produce gaps that prevent bone ingrowth. A canine study was undertaken to evaluate the prosthesis fit and placement achieved by employing a surgical robot to prepare the femur. This study compared the results achieved on 15 dogs undergoing total hip replacement with manual broaching techniques and 25 dogs undergoing robotically assisted surgery. Among the 25 dogs, which ranged in age from 2/sup 1///sub 2/ to 11 years, there were no deaths, no infections, and no intraoperative complications. Human applications of this technique are also considered.<<ETX>>

Development of a surgical robot for cementless total hip replacement

The combination of robotics and medical imaging may soon provide orthopaedic surgeons with a tool that significantly increases the precision of cementless total hip replacement operations and directly links preoperative planning with surgical execution. Twenty-six successful robot-assisted operations have been performed on dogs and the first clinical trials on human patients have recently taken place.

Management of bone loss in revision total hip arthroplasty using custom cementless femoral components

Forty-seven consecutive revision total hip arthroplasties were performed using porous ingrowth custom-made prostheses designed from plain radiographs and computed tomography scans. At an average follow-up period of 30 months (range, 2-4 years), one revision has been required for loosening. The average Harris pain score was 39 and the average total score was 84 at the last follow-up evaluation. Complications included nine cases (19%) with intraoperatively detected fractures of the proximal femur treated with cerclage wires and seven cases (15%) with subsidence greater than 3 mm. There were no postoperative infections and only two dislocations. At the time of surgery local particulate bone graft was used in all cases. Thirty-four percent required structural graft to restore bone stock; no case required grafting for prosthesis stability. Management of bone loss in total hip arthroplasty using a custom cementless prosthesis appears to provide an attractive alternative to massive bone grafting.

Robotic total hip replacement surgery in dogs

Approximately half of over 120000 total hip replacement operations performed annually in the United States use cementless implants. The standard method for preparing the femoral cavity for such implants improves the use of mallet-driven handheld broach whose shape matches that of the desired implant. In vitro experiments have supported the possibility that more accurate (and efficacious) results can be achieved by using a robot to machine the cavity. The authors are developing a second-generation system suitable for use in an operating room, targeted at clinical trials on dogs needing hip implants. A description is given of the background, objectives, architecture, and surgical procedure for this system. Also provided are brief descriptions of key results from earlier experiments and planned future work.<<ETX>>

Efficacy of bone staples for fixation

Summary: The pull-out strength of two types of bone staples (A, Techmedica; B, Richards) was evaluated in a canine model and compared with a control of 6.5 mm cancellous bone screw (Synthes). Fifteen adult mongrel dogs were divided into three groups of five animals each. The implants were placed in the lateral femoral condyle and proximal humerus on the right side at time zero, and on the left side 3 weeks later. The dogs were killed at 6 weeks. In addition a third site, the tibial tubercle, was used to examine the effectiveness of each device for patellar tendon reattachment. The strength of the reattached patellar tendon was measured and compared with a control intact patellar tendon insertion. The pull-out loads from bone of the two staple types are not statistically different. The displacement to failure, however, was found to be 71% greater (p < 0.007), and the work to failure 128% greater (p < 0.010) for staple A as compared with staple B. This may be of clinical relevance in avoiding staple back-out. Both staples were inferior to the screw for pull-out load displacement and work to failure (p < 0.0001). All reattached tendons were significantly weaker (mean 202 N) than the intact tendon (mean 1,448 N) regardless of implant type. The dissected specimens uniformly showed necrosis of the tendon under the implant. Healing was by massive scar formation surrounding the implant.

Orlhodock - An Image Driven Orthopaedic Surgical Planning System

The OrthoDock (Orthopaedic Docking) system allows a surgeon to interactively manipulate a graphic representation of a prosthetic in 3d image data in order to determine optimum selection and position. Precise position and orientation information, both relative and absolute, of the prosthesis in the tissue is determined by using integrated graphics and image processing. The system is the 3d image processing portion of the robotic surgery system known as RoboDoc 111.

The calcar bone graft

A canine model was developed to investigate the use of an autogeneic iliac bone graft to treat the calcar deficiency commonly found at the time of revision surgery for femoral component loosening. Five large male mixed-breed dogs had bilateral total hip arthroplasty staged at three-month intervals, and were sacrificed at six months. Prior to cementing the femoral component, an experimental calcar defect was made, and a bicortical iliac bone graft was fashioned to fill the defect. Serial roentgenograms showed the grafts had united with no resorption. Technetium-99 bone scans showed more uptake at three months than at six months in the graft region. Disulfine blue injection indicated all grafts were perfused at both three and six months. Thin section histology, fluorochromes, and microradiographs confirmed graft viability in all dogs. Semiquantitative grading of the fluorochromes indicated new bone deposition in 20%-50% of each graft at three months and 50%-80% at six months. Although the calcar bone graft was uniformly successful in this canine study, the clinical application of this technique should be evaluated by long-term results in humans.