Statistical shape analysis and computational modeling reveal novel relationships between tibiofemoral bony geometry and knee mechanics in young, female athletes.

Young female athletes participating in sports requiring rapid changes of direction are at heightened risk of suffering traumatic knee injury, especially noncontact rupture of the anterior cruciate ligament (ACL). Clinical studies have revealed that geometric features of the tibiofemoral joint are associated with increased risk of suffering noncontact ACL injury. However, the relationship between three-dimensional (3D) tibiofemoral geometry and knee mechanics in young female athletes is not well understood. We developed a statistically augmented computational modeling workflow to determine relationships between 3D geometry of the knee and tibiofemoral kinematics and ACL force in response to an applied loading sequence of compression, valgus, and anterior force, which is known to load the ACL. This workflow included 3D characterization of tibiofemoral bony geometry via principal component analysis and multibody dynamics models incorporating subject-specific knee geometries. A combination of geometric features of both the tibia and the femur that spanned all three anatomical planes was related to increased ACL force and to increased kinematic coupling (i.e., anterior, medial, and distal tibial translations and internal tibial rotation) in response to the applied loads. In contrast, a uniplanar measure of tibiofemoral geometry that is associated with ACL injury risk, sagittal plane slope of the lateral tibial plateau subchondral bone, was not related to ACL force. Thus, our workflow may aid in developing mechanics-based ACL injury screening tools for young, active females based on a unique combination of bony geometric features that are related to increased ACL loading.

Botulinum Toxin as an Adjunctive Therapy for Immobilization of a Distal Humerus Fracture in Parkinson's Disease-Associated Psychosis: A Case Report.

BACKGROUND Attainment of extremity immobilization in orthopedic trauma patients experiencing psychosis is often uniquely challenging. Many fractures, including those of the distal humerus, require a period of immobilization postoperatively to optimize fracture healing. Patients with Parkinson's disease have also been shown to have lower rates of union after fracture compared to the general population. The combination of Parkinson's disease and associated psychosis requires heightened attention to those parameters that may hinder fracture healing, such as inadequate immobilization of the fracture. Botulinum toxin has previously been described as a potential adjunctive therapy for fracture immobilization but has not yet been described in the setting of distal humerus fractures. CASE REPORT A 75-year-old woman with Parkinson's disease-associated psychosis presented 2 weeks after open reduction and internal fixation of a distal third humeral shaft fracture due to failure of fixation and episodes of violent hallucinations. The patient underwent irrigation and debridement, and revision open reduction and internal fixation. Given her uncontrolled hallucinations, intramuscular botulinum toxin injections were given to the right triceps, biceps, and brachialis muscles to aid in the immobilization of the right extremity and protect the surgical site during the perioperative period. The patient subsequently followed up at the clinic 3 months postoperatively with ongoing fracture healing, evidenced by bridging callous and bone formation on radiographs, as well as a return of motion to the extremity. CONCLUSIONS Botulinum toxin may be a safe and effective adjunct for fracture immobilization in patients who are difficult to immobilize and have high fixation failure risk.