Tibialis anterior or posterior allograft anterior cruciate ligament reconstruction versus hamstring autograft reconstruction: an economic analysis in a hospital-based outpatient setting.

PURPOSE: To analyze and compare the direct costs, reimbursement rates, gross contribution margins, and operating room and recovery room times for anterior cruciate ligament (ACL) reconstructions with the use of soft-tissue allografts and autografts. We aimed to determine the financial impact of using allograft tissue for ACL reconstruction in a hospital-based outpatient setting. METHODS: Financial data from the facility billing database and operating room (OR) reports from the electronic medical record were queried to identify all patients undergoing arthroscopic ACL reconstruction during a 12-month period. A subset of patients who had isolated ACL reconstruction with or without simple meniscectomy or chondral debridement was identified as the study group. We compared 46 ACL reconstructions using tibialis anterior or posterior allografts and 50 ACL reconstructions using hamstring autografts. Facility direct cost, reimbursement rates, gross contribution margin, OR times, and other variables were compared. RESULTS: The facility mean direct cost for ACL reconstruction using allografts was $4,587, with a mean OR time of 92 minutes. The mean direct cost and OR time for ACL reconstruction using autografts were $3,849 and 125 minutes, respectively. Allograft ACL reconstructions were $738 more costly, and reimbursement was also higher. Allograft ACL reconstruction produced a 41.5% margin with a gross contribution margin of $3,248, whereas autografts had a reimbursement rate with a 45% margin with a gross contribution margin of $3,156. CONCLUSIONS: In this study the cost of allograft tissue used in ACL reconstruction was not offset by the savings realized from shorter OR and recovery room times. However, in a hospital-based outpatient setting, reimbursement covered the cost of the allograft, offsetting the additional expense. LEVEL OF EVIDENCE: Level III, retrospective comparative study for economic analysis.

Meshless Modeling of Deformable Shapes and their Motion.

We present a new framework for interactive shape deformation modeling and key frame interpolation based on a meshless finite element formulation. Starting from a coarse nodal sampling of an object's volume, we formulate rigidity and volume preservation constraints that are enforced to yield realistic shape deformations at interactive frame rates. Additionally, by specifying key frame poses of the deforming shape and optimizing the nodal displacements while targeting smooth interpolated motion, our algorithm extends to a motion planning framework for deformable objects. This allows reconstructing smooth and plausible deformable shape trajectories in the presence of possibly moving obstacles. The presented results illustrate that our framework can handle complex shapes at interactive rates and hence is a valuable tool for animators to realistically and efficiently model and interpolate deforming 3D shapes.

Meshless Animation of Fracturing Solids.

We present a new meshless animation framework for elastic and plastic materials that fracture. Central to our method is a highly dynamic surface and volume sampling method that supports arbitrary crack initiation, propagation, and termination, while avoiding many of the stability problems of traditional mesh-based techniques. We explicitly model advancing crack fronts and associated fracture surfaces embedded in the simulation volume. When cutting through the material, crack fronts directly affect the coupling between simulation nodes, requiring a dynamic adaptation of the nodal shape functions. We show how local visibility tests and dynamic caching lead to an efficient implementation of these effects based on point collocation. Complex fracture patterns of interacting and branching cracks are handled using a small set of topological operations for splitting, merging, and terminating crack fronts. This allows continuous propagation of cracks with highly detailed fracture surfaces, independent of the spatial resolution of the simulation nodes, and provides effective mechanisms for controlling fracture paths. We demonstrate our method for a wide range of materials, from stiff elastic to highly plastic objects that exhibit brittle and/or ductile fracture.