Achieving mechanical support of the inferomedial region of the proximal humerus seems to be important for maintaining fracture reduction. Locked plates in general do not appear to be a panacea for these fractures and are unable to support the humeral head alone from a lateral tension-band position. However, there are several factors that are in the surgeon's control that may improve the mechanical environment. Achieving an anatomic or slightly impacted stable reduction, as well as meticulously placing a superiorly directed oblique locked screw in the inferomedial region of the proximal fragment, may achieve more stable medial column support and allow for better maintenance of reduction.

Many syndesmoses were malreduced on CT scan but went undetected by plain radiographs. Radiographic measurements did not accurately reflect the status of the distal tibiofibular joint in this series of ankle fractures. Furthermore, postreduction radiographic measurements were inaccurate for assessing the quality of the reduction. Although we did not seek to correlate functional outcomes, the known morbidity of postoperative syndesmotic malreduction should lead to heightened vigilance for assessing accurate syndesmosis reduction intraoperatively.

Significant evidence exists that trauma to a joint produced by a single impact load below that which causes subchondral bone fracture can result in permanent damage to the cartilage matrix, including surface fissures, loss of proteoglycan, and cell death. Limited information exists, however, on the effect of a varying impact stress on chondrocyte biophysiology and matrix integrity. Based on our previous work, we hypothesized that a stress-dependent response exists for both the chondrocyte's metabolic activity and viability and the matrix's hydration. This hypothesis was tested by impacting bovine cartilage explants with nominal stresses ranging from 0.5 to 65 MPa and measuring proteoglycan biosynthesis, cell viability, and water content immediately after impaction and 24 hours later. We found that proteoglycan biosynthesis decreased and water content increased with increasing impact stress. However, there appeared to be a critical threshold stress (15-20 MPa) that caused cell death and apparent rupture of the collagen fiber matrix at the time of impaction. We concluded that the cell death and collagen rupture are responsible for the observed alterations in the tissue's metabolism and water content, respectively, although the exact mechanism causing this damage could not be determined.

No abstract

No abstract