The biological response to orthopaedic wear debris is central to peri-prosthetic tissue inflammation and osteolysis, through mechanisms that include local inflammatory cytokine production. In particular, interleukin-1 beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha|) are generated in high quantities following monocyte accumulation in periprosthetic inflammatory tissue, and these cytokine combine with other inflammatory mediators to trigger osteolysis. Since the precise mechanisms involved in debris-associated inflammation remain unclear, it is important to understand how wear debris particles initially interact with inflammatory cells. We have previously demonstrated that the severity of the inflammation response is influenced by the size, shape, and quantity of particles accumulated in tissues. The current in vitro and in vivo results indicate that heat-shock protein (Hsp) expression is elevated when monocytes are exposed to wear debris particles. We have also addressed the mechanisms by which heat-shock protein 60 (Hsp60) positively modulates inflammatory cytokines via Toll-like receptor-4 (TLR4) signal transduction pathway on mononuclear cells. Furthermore, down-regulation of TLR4 expression using antisense oligonucleotides targeted to TLR4 mRNA suppressed cytokine production in both exogenous Hsp60 and particles stimulated cultures. Collectively, these data indicate that monocytic Hsp60 is an additional inducible immunoregulatory mediator in response to particle-induced cell stress.

Forty-two intra-articular calcaneus fractures underwent open reduction and internal fixation with a low profile, titanium plate with a shape similar to the lateral aspect of the calcaneus. All 42 fractures healed without complication. There were no cases of hardware breakage. None of the patients were noted to have a loss of reduction. The plates were applied without bending and molded to the side of the calcaneus with tightening of the screws. No patient complained of symptomatic hardware during the follow-up period. With postoperative plain radiographs, the reduction was judged as anatomic in 35 patients, less than a 2 mm step off in six patients, and one patient with greater than 2 mm step off. Use of this new plate allows for easy application as it does not require contouring, is well tolerated without complaints of hardware prominence, and none of the hardware broke prior to fracture union.