Identifying and Exposing the Proximal Biceps in Its Groove: The "Slit" Technique.

Proximal biceps tendon pathology is a common source of shoulder symptoms. Thus, visualization of the entire extent of the biceps tendon is often required for both diagnostic and therapeutic purposes. Accurately recognizing the presence and extent of biceps pathology intraoperatively is made more difficult, however, due to the extra-articular location of a significant portion of the biceps tendon as it courses within the bicipital groove. Unfortunately, identification of the biceps groove in the subacromial space is often challenging due to the lack of visual and tactile landmarks. A technique that facilitates efficient and reliable bicipital groove identification and biceps tendon visualization along its entire course within the groove is presented.

Biomechanical analysis of pedicle screws in osteoporotic bone with bioactive cement augmentation using simulated in vivo multicomponent loading.

STUDY DESIGN: Biomechanical analysis of bioactive cements augmenting pedicle screw resistance to loosening in osteoporotic synthetic bone. OBJECTIVE: To simulate in vivo loading-loosening of pedicle screws in osteoporotic vertebrae; and to compare biomechanical efficacy of the following bioactive cements: calcium phosphate (CP), calcium sulfate (CS), and proprietary mixture (M). SUMMARY OF BACKGROUND DATA: Pedicle screw instrumentation in osteoporotic spines is limited by poor bone-screw interface strength, resulting in screw loosening fixation failure. Previous in vivo studies evaluated augmented pedicle screw resistance to pure pullout, not simulating in vivo loading/failure. METHODS: A pedicle screw-instrumented osteoporotic thoracic vertebra subjected to combined pullout, transverse, moment loading was simulated. Unconstrained 3-dimensional screw motion relative to vertebra was optically measured during quasi-static, and dynamic loading. RESULTS: Augmented groups (CP, CS, M) produced (P < 8.0E-07) higher quasi-static failure initiation force (61.2,45.6, 40.3 N) than those by the nonaugmented group (21.0 N), with no significant difference in small screw displacement up to these loads. Nonaugmented screw motion after failure initiation was primarily rotation (toggle-migration) with minimal pullout until the screw tip contacted the superior endplate, followed by more prominent screw pullout. Augmented screw motion (with cement remaining intact on screw) was similar, but with eventual bone fracture anterior to the pedicle region. Dynamic loading produced similar failure initiation force and screw motion. CONCLUSION: We believe our test protocol produced screw loosening failure similar to that observed clinically, and that it has the ability to detect differences in failure initiation force and failure modes to compare short-term efficacy of screw augmentation techniques. All cements improved screw resistance to failure. The CP > CS > M failure initiation force (P < 0.006) was because of differences in cement distribution. Animal studies may be required to characterize the remodeling activity of bioactive cements and their longer term efficacies.