Scott Lovald

Orthopaedic Biomaterials in Research and Practice, Second Edition

This work offers an explanation of clinical phenomena related to the intrinsic properties of natural and fabricated biomaterials relevant to orthopaedic practice. It covers such central aspects of biomaterials as properties of tissues and of fabricated materials as well as the interaction between natural and fabricated materials. This work is designed to serve as a course textbook for orthopaedic residents and as a self-instructional review for both the orthopaedist in-training and candidates for board exams. It should also be useful as an introductory source of information for the medical student or practitioner who lacks primary engineering training.

Complications, mortality, and costs for outpatient and short-stay total knee arthroplasty patients in comparison to standard-stay patients.

The purpose of the present study is to determine the differences in cost, complications, and mortality between knee arthroplasty (TKA) patients who stay the standard 3-4 nights in a hospital compared to patients who undergo an outpatient procedure, a shortened stay or an extended stay. TKA patients were identified in the Medicare 5% sample (1997-2009) and separated into the following groups: outpatient, 1-2 days, 3-4 days, or 5+ days inpatient. At two years, costs associated with the outpatient and the 1-2 day stay groups were

Biomechanical Optimization of Bone Plates Used in Rigid Fixation of Mandibular Fractures

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Patient selection in outpatient and short-stay total knee arthroplasty.

1967 lower than the 3-4 day stay group, respectively. Out to 2 years, the outpatient and 1-2 day stay groups reported less pain and stiffness, respectively, though the 1-2 day group also had a higher risk for revision.

Comparison of Plate-Screw Systems Used in Mandibular Fracture Reduction: Finite Element Analysis

PURPOSE To design and optimize a bone plate for fractures of the mandibular body that will provide maximum fracture stability with minimal implanted volume and patient intrusion. The design will be driven by the unique biomechanics specific to this fracture location. MATERIALS AND METHODS A finite element model of a fractured human mandible was created using tomography scans. Material properties were assigned to the cortical bone, cancellous bone, and dental region. Boundary conditions included simulating a unilateral molar clench and incisal loading. The bone plate design process included a shape optimization routine and design parameter analysis using the model. The optimized bone plate design was finally compared with standard bone plate configurations based on stress and strain measures. RESULTS For incisal loading, the newly designed InterFlex II plate has 69% of the fracture strain and only 34% of the plate stress of an 8-hole strut plate. For unilateral molar loading, those numbers improve even further to 59% and 27%, respectively. InterFlex II plate stresses are less than or equal to the paired plate configuration, and fracture strain is within 10% of the corresponding paired plate strain under both loading scenarios. In terms of mechanical performance, InterFlex II is in the same class as the commonly used paired plate configuration, despite having only 55% of the implanted volume. CONCLUSION A design process focused on shape and design variable optimization can produce bone plates that provide maximum fracture stability with minimum implanted volume.

Liposomal Bupivacaine: A Comparative Study of More Than 1000 Total Joint Arthroplasty Cases

The purpose of the current study is to identify patients who are at high risk for rehospitalization, revision, complications, and mortality after outpatient and short-stay total knee arthroplasty (TKA). The Medicare 5% limited data set sample was used to identify patients with a TKA procedure who were treated in an outpatient setting or who were discharged within 1 or 2 days in the hospital setting. Rehospitalization risk increased with higher Charlson score (i.e., poorer health status), older patients, inpatients (vs. outpatients), patients not receiving a femoral nerve block, earlier (vs. recent) year of surgery, and those with a recent history of heart failure. The findings of this study suggest that existing comorbidities, particularly heart failure, have the greatest effect on event risk after outpatient and short-stay TKA. The information obtained from this study should assist with patient selection for TKA performed on an outpatient basis.

Biomechanical optimization of bone plates used in rigid fixation of mandibular symphysis fractures.

A finite element model of the human dentate mandible has been developed to provide a comparison of fixation systems used currently for fracture reduction. Volume domains for cortical bone, cancellous bone, and teeth were created and meshed in ANSYS 8.0 based on IGES curves created from computerized tomography data. A unilateral molar clench was loaded on the model with a fracture gap simulated along the symphysis. Results based on Von Mises stress in cortical and cancellous bone surrounding the screws, and on fracture surface spatial fixation, show some relative differences between different screw-plate systems, yet all were judged to be appropriate in their reduction potential.

Mortality, Cost, and Health Outcomes of Total Knee Arthroplasty in Medicare Patients

Pain after total joint arthroplasty (TJA) can be severe and difficult to control. A single-dose local analgesic delivers bupivacaine in a liposomal time-release platform. In 2248 consecutive patients with hip and knee arthroplasty, half (Pre) were treated using a well-established multimodal analgesia, including periarticular injection (PAI), and half had the PAI substituted for a liposomal bupivacaine injection technique (Post). Pain scores were significantly lower for patients in the Post group for both hip and knee procedures. A large series of patients who had TJA experienced pain relief after the introduction of liposomal bupivacaine as part of an established multimodal protocol.

Biomechanical Analysis of Mandibular Angle Fractures

PURPOSE To design and optimize a bone plate for fractures of the mandibular symphysis that will provide maximum fracture stability with minimal implanted volume and patient intrusion. The design will be driven by the unique biomechanics specific to this fracture location. MATERIALS AND METHODS A finite element model of a fractured human mandible was created using computed tomography scans. The boundary conditions included simulating molar, canine, and incisal loading. The bone plate design process included a shape optimization routine and design parameter analysis using the model. The optimized bone plate design was finally compared with standard bone plate configurations according to stress and strain measures. RESULTS Compared with the miniplate combination, the InterFlex III plate, with the same thickness and just 14% more implanted volume, had only 55% of the plate stress and 25% less fracture strain under the strongest loads considered by the model. Compared with the band/fracture plate combination, the InterFlex plate had 88% of the fracture strain and 74% of the plate stress, despite having only 60% of the plate volume. CONCLUSIONS The results have demonstrated that the new optimized plate is a hybrid of fixation hardware with the small profile of the smallest miniplate configuration and the superior fixation strength and safety that exceeds that of the larger fracture plate configuration.

Mechanical design optimization of bioabsorbable fixation devices for bone fractures.

There are little data that quantify the long term costs, mortality, and downstream disease after Total Knee Arthroplasty (TKA). The purpose of this study is to compare differences in cost and health outcomes between Medicare patients with OA who undergo TKA and those who avoid the procedure. The Medicare 5% sample was used to identify patients diagnosed with OA during 1997-2009. All OA patients were separated into non-arthroplasty and arthroplasty groups. Differences in costs, mortality, and new disease diagnoses were adjusted using logistic regression for age, sex, race, buy-in status, region, and Charlson score. The 7-year cumulative average Medicare payments for all treatments were