Femoral Component Malrotation Produces Quadriceps Weakness and Impaired Ambulatory Function following Total Knee Arthroplasty: Results of a Forward-Dynamic Computer Model

AbstractProper placement of the prosthetic components is believed to be an important factor in successful total knee arthroplasty (TKA). Implant positioning errors have been associated with postoperative pain, suboptimal function, and inferior patient-reported outcome measures. The purpose of this study was to investigate the biomechanical effects of femoral component malrotation on quadriceps function and normal ambulation. For the investigation, publicly available data were used to create a validated forward-dynamic, patient-specific computer model. The incorporated data included medical imaging, gait laboratory measurements, knee loading information, electromyographic data, strength testing, and information from the surgical procedure. The ideal femoral component rotation was set to the surgical transepicondylar axis and walking simulations were subsequently performed with increasing degrees of internal and external rotation of the femoral component. The muscle force outputs were then recorded for the quadriceps musculature as a whole, as well as for the individual constituent muscles. The quadriceps work requirements during walking were then calculated for the different rotational simulations. The highest forces generated by the quadriceps were seen during single-limb stance phase as increasing degrees of femoral internal rotation produced proportional increases in quadriceps force requirements. The individual muscles of the quadriceps displayed different sensitivities to the rotational variations introduced into the simulations with the vastus lateralis showing the greatest changes with rotational positioning. Increasing degrees of internal rotation of femoral component were also seen to demand increasing quadriceps work to support normal ambulation. In conclusion, internal malrotation of the femoral component during TKA produces a mechanically disadvantaged state which is characterized by greater required quadriceps forces (especially the vastus lateralis) and greater quadriceps work to support normal ambulation.</jats:p

Patients, pictures, and privacy: managing clinical photographs in the smartphone era

It is easy to capture and share clinical photographs and x-ray images using modern smartphones. This technology affords health-care providers the ability to rapidly collaborate and facilitate care for their patients. This improvement, however, has increased concerns regarding patient privacy and the safeguarding of protected health information. Health-care providers should understand the deidentification process for patient photographs because this process fundamentally changes the expectations and requirements for how providers are to handle this information. Properly deidentified patient photographs (and other data) are no longer considered identifiable protected health information and are not subject to the handling requirements mandated by the Health Insurance Portability and Accountability Act. This article addresses patient privacy concerns attendant to the acquisition, transmission, and sharing of clinical photographs among health-care providers. It provides guidelines for providers seeking to minimize the risk of noncompliance with privacy requirements as they adopt these new technologies into their practices. Keywords: Photograph, Smartphone, Privacy, Health Insurance Portability and Accountability Act, Deidentificatio