Aim

Staphylococcus epidermidis has emerged as an important opportunistic pathogen causing orthopedic device-related infections (ODRIs). In this prospective clinical and laboratory study, we have investigated the association of genome variation and phenotypic features of the infecting S. epidermidis isolate with the clinical outcome of the infected patient.

There are multiple proximal prosthetic geometries available for a surgeon to select when humeral head replacement is indicated for four-part proximal humerus fractures. We compared different proximal prosthetic geometries in stable and unstable fracture patterns, with a standard tuberosity fixation method.

Simulated four-part fractures were created with an oscillating saw in six synthetic shoulder models. Three different proximal prosthetic geometries used polymetylmethacrelate (PMMA) – a smooth circular shape (SCS), a diamond shape (DS) and an irregular multiple fin shape (IMFS) prostheses. A standardised fixation method using vertical, and horizontal straps along with a medial based cerclage strap was performed. Passive motion was then carried out using a robotic articulator. Interfragmentary displacement was measured from tuberosity to tuberosity as well as tuberosity to shaft using mercury strain gauges.

The least amount of interfragmentary motion occurred when an IMFS was used in a stable fracture pattern. This geometry provided more interfragmentary stability even with the unstable fracture pattern than the DS or SCS. The least stable construct was the SCS prosthesis with an unstable fracture pattern.

Prosthetic geometry does affect stability of tuberosity reconstruction in proximal humerus fractures. An irregular shaped prosthesis augments the fixation construct. When using a smooth prosthetic design a stable fracture pattern must be achieved to prevent excessive interfragmentary motion. A smooth prosthetic design for tuberosity reconstruction is not recommended.

Introduction: Whether or not to resurface the patella in total knee replacement (TKR) is controversial. One concern is the possibility of progression of the arthritis in the patellofemoral joint that has not been resurfaced when exposed to the stress of articulating with the femoral component.

Methods: The cohort comprised six knees for Trac TKA (Biomet). The assessment involved the use of an electronic sensor system(Iscan, Tekscan). The readings were taken on an anaesthetised patient, during surgery. A tourniquet was not used. A subvastus operative approach was used.

Results: The contact area and contact stress increased with flexion with and without the femoral component in place. We measured no increase in patellar stress when the patella that had not been resurfaced articulated with the femoral component.