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Penn Orthopaedic Surgery Studies Plan to Assess Joint Replacement Technique, Outcomes Using Robotics


A proposed research program at Penn Orthopaedics will leverage the remarkable precision and accuracy of robotic technology for hip and knee surgery.

Typically, the foundation for clinical practice guidelines and recommendations originate in a rigorous review of clinical studies. These guidelines, in turn, constitute the framework for clinical decision-making and best practices in medicine and surgery.

Fulfilling the Promise of Robotic Hip and Knee Surgery, Penn Orthopaedics Seeks Answers in Research

A current review of the NIH Library of Medicine's PubMed registry yields fewer than 10 clinical and randomized controlled trials of robotic hip and knee surgery performed in the last decade. Of these, the majority have been performed outside of the United States — particularly studies of robotic knee surgery.

Of studies performed in the US, almost all were prospective cohort studies, and most were short-term in small populations. Importantly, none compared robotic joint replacement surgery to conventional joint replacement, nor sought to determine what the precise measurements of robotic approaches can contribute to optimal approach and best practices for joint replacement surgery on the whole.

Thus, robotic hip and knee replacement programs in the United States have very little relevant clinical trial information to rely on — an issue of interest to the surgeons at Penn Orthopaedics, where robotic surgery is among the options for hip and knee replacement.

"We've had a very positive experience with robotic surgery," says surgeon T. David Tarity, MD, FAAOS, FAAHKS, who performs robotic joint replacement surgery at Penn Orthopaedics.

"But the absence of available study reports means that much of what we know about the advantages of robotic surgery — the precision measurements, the cuts precise to a fraction of a millimeter and alignment positioning within a fraction of a degree — hasn't been studied in the context of universal benefit to patients undergoing joint replacement surgery."

New Trials on the Horizon

To address these disparities, the robotic surgeons at Penn Orthopaedics are planning a series of trials using the ultra-precise measurement capabilities of cutting-edge robotic joint replacement technology to clarify questions about surgical technique in robotic surgery.

Eventually, the team hopes to also provide data on efficacy, long-term outcomes and other areas of interest to orthopaedic joint replacement specialists, including the application of knowledge obtained during robotic surgery to determine optimal surgical approaches for all joint replacements, robotic or conventional.

"Robotic platforms offer us a wealth of information that can be used in many ways to tease out the true difference makers for optimal hip and knee replacement outcomes, whether traditional manual instrumented or robotic-assisted" explains Dr. Tarity.

"This data should allow us to be more effective at delivering joint replacements to all patients with end stage arthritis with less complications."

The research will be made possible by leveraging this remarkable level of precision and accuracy available with the robotic technologies at Penn Orthopaedics.

In addition to investigations based on clinical experience, planned studies will involve more formalized platforms, including the use of the Human Performance Lab at the Penn Musculoskeletal Center. The facility is instrumented with gait analysis, force plates and other data sources that will allow surgeons to determine whether significant differences exist in ambulation after robotic knee replacement versus conventional knee replacement.

Other areas of interest have to do with the association of surgical technique and outcomes. For example, Dr. Tarity explains, many patients at Penn present with complex cases after having been refused elsewhere.

"For these complicated populations, the robot may be able to provide some validation for what we've learned in conventional instrument surgery through study, experience and expertise," Dr. Tarity continues.

"One of the questions we'd like to answer is whether changing certain target alignments makes a difference in outcomes," Dr. Tarity says. "This is now possible because alignment is an integrated and reproducible factor in robotic surgery."

The proposed studies might also shed light on certain questions that have plagued hip and knee surgery for eons — including post-surgical dislocation and infection during recovery.

But the chief question, according to Dr. Tarity, is what opportunities there are for improvement and optimization in hip and knee replacement.

"How can we do better?" Dr. Tarity says. "That's the question we'd really like to answer."

As proposed, the studies will begin in the next year or so with observational investigations and expand to more traditional studies, including, possibly, conventional comparative investigations.

Robotic Joint Replacement Technologies at Penn

Penn Orthopaedics offers access to two robotic systems for partial and total knee replacement and total hip replacement: Stryker's Mako Robotic Arm-Assisted System and Smith and Nephew's NAVIO.

The Mako System is used for partial and total knee arthroplasty (TKA) as well as total hip arthroplasty (THA); the NAVIO System is designed for unicompartmental (partial) knee arthroplasty and TKA.

The Mako robotic arm-assisted surgery system employs a preoperative CT scan and three-dimensional planning to size and orientate implants prior to bone resection. The capacity of the Mako System to achieve bone resection and final limb coronal and sagittal alignment on the basis of preoperative planning is exceptionally high.

In a recent study, (94.29%) of bone resections were within 1mm of the plan. Mean absolute difference in final limb coronal alignment was 0.78° (0.78), with 78.13% being ?1.00° of the plan, and 100% being ?3.00° of the plan.

NAVIO handheld robotics are designed to improve alignment, stability and proprioception, which may contribute to implant survival.

Currently, the NAVIO Surgical System is the only handheld robotic technology for knee arthroplasty. The system incorporates an intuitive CT-free registration and patient-specific planning process.

In a 2020 prospective study of the NAVIO System in 63 patients who underwent TKA, the mean difference between robotic achieved and postoperative limb alignment was 1.24°. The mean difference between planned and achieved component placement in coronal and sagittal plane for tibia was 0.33° and 0.66° and for femur was 0.62° and 0.30°, respectively.


Penn Medicine, Philadelphia, PA 800-789-7366 © , The Trustees of the University of Pennsylvania

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