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James R. Kasser, MD
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Third Session
Moderator: James R. Kasser, MD
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| Andreas Gomoll, MD |
Daniel Estok, MD |
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A Nanocomposite Bone Cement
Andreas Gomoll, MD
Advisor: Thomas S. Thornhill, MD
Discussor: Daniel Estok, MD
Bone cement consists of a liquid and powder components. The powder components are determined, in part, by the size of the particles present in the powder. Conventional radiopacifier particles range from 1-3 µm, but go on to form aggregates that range from 50-400 µm. These aggregates allow for flaws in the matrix of cement that subsequently allow for crack propagation and ultimate failure. In this work Dr. Gomoll proposes the use of nanoparticles,
those particles on the order of 100nm, for use in the construction of bone cement. He used scanning electron microscopy and x-ray scattering methods to determine that nanoparticles have an approximately 10-fold increase in covered surface area (due to decreased aggregation). Additionally, he analyzed the strength of the composite under various loading conditions and found that the number of cycles required for failure was increased over 200% with nanoparticles. It is hoped that nanoparticles can be used in bone cement to help implant survivorship.
Dr. Estok was pleased to see that the work on bone cement continues, and thanked Dr. Gomoll for his elegant study. He questioned Dr. Gomoll on whether the technique of cementing was as important as the material used. Dr. Gomoll pointed out that nanocement would provide increased strength and could perhaps make up for lacking technique so that a wider array of surgeons could obtain more consistent and better results.
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| Jeremy Moses, MD |
Arthur Boland, MD |
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In-Vivo Tibiofemoral Articular Cartilage Contact Patterns Following Anterior Cruciate Ligament Rupture.
Jeremy Moses, MD
Advisor: Thomas Gill, MD
Discussor: Arthur Boland, MD
ACL rupture is common among Americans, with as many as 80,000 people between the age of 15-45 suffering an ACL rupture every year. The contact stresses in the knee in ACL deficient knees can lead to several problems
in the knee including meniscal pathology, chondral injuries, and osteoarthritis
(OA). It is felt that the altered kinematics of the knee are the linchpin in understanding how this process occurs. In this work Dr. Moses uses a new technique to determine the contact stresses in ACL deficient knees and proposes
how these may be responsible for both the acute and chronic pathology seen in this condition. Dr. Moses proposed a novel scheme whereby MRI images were combined with orthogonal, kinematic, fluoroscopic images of the knee to determine the contact points seen in knee motion both with and without an ACL. He found that ACL deficient knees have contact points that are more lateral in the medial compartment of the knee. This, in turn, can be used to help explain many of the pathological findings with respect to OA, chondral injuries and meniscal tears found in ACL deficient knees. While the data did not demonstrate long term benefits of ACL repair with respect to OA and chondral injury, it did show improvement in meniscal tear rates.
Dr. Boland noted that Dr. Moses provided an excellent review of an extensive body of literature and complemented him on the use of this new and innovative technique. He inquired as to the feasibility of adding different degrees of freedom, for example internal and external rotation, to the schema. Dr. Moses responded that such work is already in progress.
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| Eric Rightmire, MD |
David Lhowe, MD |
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Managing acute infections after open reduction internal fixation (ORIF) of fractures: Can they be treated with hardware in place?
Eric Rightmire, MD
Advisor: Mark Vrahas, MD
Discussor: David Lhowe, MD
Many orthopedic surgeons treat infection after an ORIF by leaving the hardware in place and treating the patient with suppressive antibiotics until the fracture has healed. Isolated case series and reports have claimed as much as a 95% success rate with this regimen. Dr. Rightmire sought to determine if this regimen worked well for acute infection. Additionally he sought to determine the risk factors for treatment failure and to suggest any alternate treatments in such a case. He examined 81 fractures with acute postop infections and analyzed them in terms of fracture type/classification,
hardware type, and organism involved. He showed that healing of the fracture with hardware in place was only 59%, far less than that reported in the literature. Moreover he showed that of those with hardware left in after union, 34% progressed to later infection. Interestingly he showed that smokers
had 4-fold higher risk of hardware failure every month.
Dr. Lhowe noted that this was a very clinically relevant investigation and that not a week goes by on the trauma service where this question isn’t addressed. He recognized that studies such as this that involve heterogeneous
populations, different surgeons, and no set protocol make drawing statistically significant conclusions difficult at best. He felt that this study could likely change practice habits such that many surgeons should consider removing hardware after union irrespective of supposed sterility of the fracture.
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