Background
From January 2017 - August 2019, I worked as a Biomechanics and Orthopedic Surgery R&D Engineer at the Orthopaedic Trauma Institute, an orthopedic surgery clinic and research facility at the University of California, San Francisco. I was the principal engineer on more than two dozen laboratory and clinical studies on topics ranging from the mechanical behavior of implanted devices to post-surgical outcomes to the use of 3D printing as a diagnostic and treatment tool. My work was published five times in domestic and international medical journals and featured in poster presentations at several conferences. You can read a brief description of each published paper below; follow the link in each section to view the full text.
Augmenting Long-Bone Fixation with Mini-fragment Plates
Full Title: “The influence of mini-fragment plates on the mechanical properties of long-bone plate fixation.”
Mini-fragment plates are small orthopedic fixation plates often used to provisionally stabilize a fracture while a surgeon applies a larger, definitive fixation plate. However, the surgeon must then decide whether to remove the smaller plates or leave them in place, based on how they think the small plates will mechanically influence the fixation construct. The construct must stabilize the fracture enough to allow for sufficient healing, but must also not be too stiff, as this can also impede the healing process. We tested two humerus fracture models in torsion and 4-point bending, with and without the added mini-fragment plates, to determine how the extra plates influence the constructs’ mechanical properties. We found that the extra plates statistically increase torsional stiffness and 4-point bending stiffness under certain loading conditions.
Detecting Compartment Syndrome Using Ultrasound
Compartment syndrome is a rare but very serious traumatic or post-surgical complication in which pressure builds up in a muscle compartment, disrupting blood flow to the area. If not treated in a timely manner, compartment syndrome can cause nerve and blood vessel damage, limb loss, or even death. Diagnosis of compartment syndrome is inconsistent and often depends on subjective factors or invasive measurement procedures. We induced elevated compartment pressures in a cadaver model by introducing fluid to the muscle compartment. Using an ultrasound transducer combined with a pressure sensing transducer, we measured the size of the compartment and the pressure required to flatten its superficial membrane. We found that both the compartment measurement and the pressure required to flatten it correlated very well with intracompartmental pressure, indicating a potential for clinical use of ultrasound in the diagnosis of compartment syndrome.
Assessment of Hip Replacement in Treating Fractures
Full Title: “Acetabulum cup stability in an early weight-bearing cadaveric model of geriatric posterior wall fractures.”
Elderly patients who experience hip fractures often suffer negative recovery outcomes due to restricted activity post-injury. Total hip replacement surgery has been suggested as a possible treatment that may allow for earlier weight-bearing activities following certain types of hip fractures. However, the implant must be stable enough to prevent failure of the fixation construct and damage to the bone and surrounding tissue. We created a semicircular hip fracture in cadaveric pelvis specimens and performed a total hip replacement procedure. To test stability, we cyclically loaded the implant at typical walking forces and measured its motion using optical markers. Our results showed implant motion below the defined threshold, indicating support for the practice of early weight-bearing activity following total hip replacement as a treatment for these fractures.
Stable Areas for Screw Fixation in Hip Replacement
Hip fractures are a common injury in the elderly population, but the best treatment methods are still unclear. Total hip replacement surgery is an increasingly common treatment for these injuries, but a fractured hip socket does not represent an optimal location for implanting a prosthetic cup. We used CT scans of fractured pelvises to determine common stable areas for implanting an artificial socket, as well as anatomical corridors that are available for screw fixation. We identified the most common fracture type, stable joint surfaces, and available bone corridors, which may aid in the development of fixation strategies for hip fractures.
Comparing 3D Printed and Traditional Casts
Full Title: “A biomechanical comparison of fiberglass casts and 3 dimensional printed, open-latticed, ventilated casts.”
In recent years, most advances in the treatment of wrist fractures have come through surgical techniques and post-surgical rehabilitation, rather than through non-operative management. Traditional fiberglass casts are often bulky and uncomfortable, and interfere with hygiene by forcing patients to avoid getting the area wet. Developments in 3D scanning and 3D printing facilitate the creation of anatomically specific casts utilizing a ventilated design to increase patient comfort. We created a standardized wrist fracture model in cadaver specimens and subjected them to biomechanical tests simulating activities of daily use. Our results demonstrated statistically comparable results in terms of fracture fragment motion between specimens fitted with a 3D printed cast and those given a fiberglass cast. This provided support for a randomized clinical trial comparing the two casting techniques.