Evaluating factors affecting patellar component fixation strength in total knee arthroplasty.

Complications related to the patellofemoral joint after total knee arthroplasty (TKA) represent up to 50% of TKA reoperations. Shear forces across the knee produce wear and occasionally result in failure of fixation of all-polyethylene patellar components. We conducted a study to evaluate the effect of 2 factors on the shear strength of patellar component fixation: time between cement mixing and application of the patellar component, and amount of pressure applied during implantation. Fifty-four patellae were harvested from 27 cadavers and were prepared as for a TKA, allowing 3 different amounts of time for the cement to set or cure before application, and using 3 different pressures. The patellae were mounted and tested for fixation strength with a materials testing machine. Fixation was significantly stronger (P = .006) at 42 pounds of pressure after curing the cement for 8 minutes (compared with 2 minutes) and was significantly stronger (P = .005) after 2 minutes of curing at 42 pounds of pressure (compared with 62 pounds of pressure). We concluded that allowing the cement to cure while cementing the femoral and tibial components does not jeopardize fixation of the patellar component and that excessive compression of a patellar clamp may weaken fixation.

Distraction lengthening of the thumb following replantation.

Distraction lengthening is one of several surgical reconstructive methods used to obtain length of an amputated digit and to improve function. However, the use of this technique following replantation is a relatively new concept. A case of a 32-year-old male who sustained a traumatic amputation of his left nondominant thumb and index finger is described. The injury and the replantation surgery each resulted in a significant amount of bone loss from the thumb. Nine months following the replantation, distraction osteogenesis was utilized to lengthen the thumb and to improve both function and cosmesis.