Long-term comparison of mobile-bearing vs fixed-bearing total knee arthroplasty.

Few published reports have been published regarding a comparison of the long-term outcomes between mobile- (MB) and fixed-bearing component designs for knee arthroplasty. The minimum 10-year clinical and radiologic follow-up of an unselected consecutive series of 89 patients (107 knees) who were randomized to have one of these different designs for primary arthroplasty was done. Twenty-six patients (30 knees) who had a fixed-bearing design and 24 patients (33 knees) who had an MB prosthesis were available for follow-up. Two MB knees were revised for aseptic loosening of a tibial component in one and femoral component fracture in the other. In patients who did not have revision surgery, there were no differences between the groups with respect to mean Knee Society scores, knee flexion, or pain scores.

Acetabular component positioning using the transverse acetabular ligament: can you find it and does it help?

BACKGROUND: Several studies have reported that the transverse acetabular ligament (TAL) can be used to orient the acetabular component during total hip arthroplasty and that it can be identified in nearly all patients. QUESTIONS/PURPOSES: We attempted to determine how often the TAL could be identified during primary THA and its accuracy as a guide for acetabular component positioning. METHODS: In a prospective series of 63 patients (64 hips) undergoing primary THA, two surgeons attempted to identify the TAL and, if it was found, to use it for acetabular component orientation. Patients in whom the TAL was identified served as the study group and the ligament was used for cup orientation in those patients; the remaining patients in whom the ligament could not be identified served as a control group and had free-hand cup positioning. Anteversion was determined by radiographic measurement from true lateral views. RESULTS: The TAL was identified in only 30 hips (47%) and was more likely to be found in patients who did not have inferior acetabular osteophytes. Acetabular position was not improved using this ligament for reference. CONCLUSIONS: The TAL could not be routinely identified at surgery and when used for cup orientation it was no more accurate for cup positioning than free-hand technique.

Titanium particles modulate expression of Toll-like receptor proteins.

The role of Toll-like receptors (TLRs) responding to microbial remnants, indolent biofilms or cellular byproducts in aseptic loosening of joint replacements is unknown. Thus, the effect of titanium (Ti) particles on TLR protein levels was evaluated. To create a model of particle-induced inflammation, an intramedullary stainless steel rod with and without Ti particles was bilaterally placed in the femora of 14 mice. The animals were sacrificed at 2 or 10 weeks postoperatively and paraffin-embedded femur sections were evaluated for TLR1, 2, 4, 5, 8, and 9 proteins using immunohistochemistry. Decrease in the number of TLR immunoreactive cells was observed between weeks 2 and 10 in both settings. Furthermore, in the presence of Ti particles, the numbers of TLR immunoreactive cells were lower than in the presence of rod only at both time points, suggesting downregulation of TLR expression by Ti-particles per se. Accordingly, in a short-term 24 h stimulation, downregulation of TLR4 mRNA (p < 0.02) was observed in vitro in RAW 264.7 cells challenged with Ti particles. Results suggest that after an initial inflammatory stage, TLRs are downregulated in response to Ti particles, possibly to inhibit excessive inflammation, although TLR downregulation might at the same time render tissues more susceptible to pathogens.

Validation and quantification of an in vitro model of continuous infusion of submicron-sized particles.

Wear particles produced from total joint replacements have been shown to stimulate a foreign body and chronic inflammatory reaction that results in periprosthetic osteolysis. Most animal models that simulate these events have used a single injection of particles, which is not representative of the clinical scenario, in which particles are continuously generated. The goal of this study was to evaluate the feasibility of an osmotic pump for the continuous delivery of clinically relevant submicron-sized particles over an extended period of time. Blue-dyed polystyrene particles and retrieved ultra-high molecular weight polyethylene (UHMWPE) particles, both suspended in mouse serum, were loaded into an Alzet mini-osmotic pump. Pumps were attached to vinyl tubing that ended with hollow titanium rods, simulating a metal implant, which was suspended in a collection vessel. The number of particles collected was evaluated over 2- and 4-week time periods. Delivery of both the polystyrene and UHMWPE particles was feasible over pump concentrations of 10(9) to 10(11) particles per pump. Furthermore, delivery efficiency of polystyrene particles decreased with increasing initial particle concentration, whereas delivery efficiency of UHMWPE particles increased slightly with increasing initial particle concentration. For UHMWPE, approximately one-third of the particles in the pump were collected at 4 weeks. This in vitro study has quantified the efficiency of a unique particle pumping system that may be used in future in vivo investigations to develop a murine model of continuous particle infusion.

Mouse femoral intramedullary injection model: technique and microCT scan validation.

The murine femoral intramedullary injection model is frequently used to examine the in vivo effects of biomaterials or cancer cells. The surgical technique includes a knee arthrotomy with patellar dislocation for intramedullary access. This study examined a less invasive surgical approach of direct injection of particles via the transpatellar tendon without patellar dislocation. By using polymethylmethacrylate injection and microCT scan, we found that, compared with the traditional technique, this new approach was more reproducible, less time consuming, and achieved identical volumes of intramedullary injections. Animal morbidity and the biomechanics of the joints were also improved as a result of the simplified procedure. Furthermore, our study suggested that an intramedullary volume in excess of 10 microL can lead to major vascular filling and so should be avoided.

Histomorphometric analysis of the intramedullary bone response to titanium particles in wild-type and IL-1R1 knock-out mice: a preliminary study.

Aseptic loosening of implants following total joint arthroplasty remains a major cause of implant failure. Particulate debris generated primarily from wear results in inflammatory mediated periprosthetic osteolysis. Titanium is a commonly utilized metal in joint arthroplasty and titanium debris induces the production of the pro-inflammatory cytokine IL-1. To further elucidate the role of IL-1, this study examined the response of murine femora to the presence of titanium particles following implantation of an intramedullary rod in mice lacking the receptor for IL-1. We hypothesized that the inflammatory effects of wear debris on bone would be mitigated in IL-1R1 deficient mice with a resultant decrease in resorption. Femora receiving titanium particles demonstrated a marked inflammatory response in wild-type mice with increased endocortical resorption, periprosthetic membrane formation, and significant histomorphometric changes. Femora exposed to titanium particles in the knockout mice also demonstrated osteolysis with irregular deposition of trabecular bone and increased cortical porosity. The persistence of inflammation and osteolysis, despite the lack of functional IL-1R1, suggests a multi-factorial role for IL-1 in the proinflammatory cascade resulting from wear debris. This intramedullary murine model provides the ability to evaluate and quantify the proinflammatory cascade in an in vivo model approximating prosthesis failure.

Utility of judet oblique x-rays in preoperative assessment of acetabular periprosthetic osteolysis: a preliminary study.

Anteroposterior (AP) x-rays provide limited information about size and location of acetabular osteolytic lesions after total hip arthroplasty (THA). In the study reported here, we sought to determine the utility of oblique (Judet) x-rays in preoperative assessment of acetabular lesions. AP, anterior (obturator), and posterior (iliac oblique) x-rays of 10 patients (10 hips) who underwent revision THA were evaluated retrospectively. Mean osteolytic area was 790 mm2 (SD, 520 mm2) on anterior oblique x-rays and 384 mm2 (SD, 396 mm2) on AP x-rays (P = .005). Mean osteolytic area on posterior oblique x-rays was 512 mm2 (SD, 430 mm2) (P = .34). Judet x-rays were useful in determining size and location of acetabular osteolysis.

UHMWPE wear debris upregulates mononuclear cell proinflammatory gene expression in a novel murine model of intramedullary particle disease.

BACKGROUND: We examined the effects of ultra-high molecular weight polyethylene (UHMWPE) particles on mononuclear cell proinflammatory gene expression in a novel murine model. We hypothesized that mononuclear cell gene transcription of tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1beta), interleukin-6 (IL-6) and macrophage chemoattractant protein-1 (MCP-1) would be upregulated by the addition of polyethylene particles in this murine intramedullary rod model. MATERIAL AND METHODS: The model involved a stainless steel Kirschner wire inserted retrograde with a line-to-line fit in bilateral femora of C57bl/6 mice. Additionally, the right femora were injected with 3 x 10(9) UHMWPE particles. Mononuclear marrow cells were isolated by bone marrow aspiration and Ficoll-Paque centrifugation at 2, 4 and 10 weeks post-surgery. Total RNA was isolated and real-time RT-PCR was performed to quantify gene expression. Histological specimens of explanted femora were also analyzed to track the changes in periprosthetic tissue. RESULTS: UHMWPE particles stimulated gene transcription in mononuclear cells when examined at 2, 4 and 10 weeks post-surgery, compared to the rod-only group. Relative levels of IL-1beta and MCP-1 mRNA increased in a linear fashion over the 10-week time-course. IL-6 mRNA showed increased expression which peaked at 4 weeks. TNF-alpha mRNA expression was variable and reached a minimum at 4 weeks. The addition of UHMWPE particles stimulated ingress of macrophages and multinuclear cells of macrophage origin to the bone-implant interface. INTERPRETATION: In this model, a single bolus of UHMWPE particles had a long-term effect on gene transcription in mononuclear cells which perpetuated a chronic inflammatory state. This murine model of intramedullary particle-induced inflammation simulates periprosthetic events associated with implant wear in humans, and may contribute to a more mechanistic understanding of wear-debris associated prosthesis failure.

Interleukin-1 modulates periprosthetic tissue formation in an intramedullary model of particle-induced inflammation.

UNLABELLED: Interleukin-1 (IL-1) is a proinflammatory cytokine that has been implicated in wear-debris associated total joint replacement failure. We hypothesized that the absence of the IL-1 type-1 receptor would mitigate the inflammatory response to titanium particles and decrease periprosthetic inflammatory tissue in a murine intramedullary rod model. METHODS: An intramedullary rod with and without commercially pure titanium particles was placed in the femora of 24 wild type mice (WT) and 24 mice lacking a functional type-1 receptor to IL-1. Femora were analyzed histologically and by ELISA of organ culture explant supernatants. RESULTS: The presence of titanium particles in WT mice stimulated increased expression of interleukin-6 (IL-6) and macrophage chemoattractant protein-1 (MCP-1) relative to rod only controls. In contrast, IL-6 and MCP-1 expression were diminished in IL-1r1-KO mice exposed to titanium particles. Additionally, the formation of a periprosthetic fibro-inflammatory membrane in IL-1r1-KO mice was blunted at 2 weeks when compared to that in wild-type mice. Inflammatory changes and the quality of periprosthetic bone of IL-1r1-KO mice was similar to WT mice in response to titanium particles. CONCLUSIONS: These results implicate IL-1 as an important modulator in the local inflammatory response to intramedullary titanium particles. MCP-1 appears to be significantly modulated in IL-1r1-KO mice in response to titanium particles. This may be responsible, in part, for the diminished periprosthetic membrane observed in IL-1r1-KO mice at 2 weeks. Expansion of this murine model of intramedullary particle-induced inflammation to other gene targets may contribute to a more mechanistic understanding of wear-debris associated prosthesis failure.

Proinflammatory mediator expression in a novel murine model of titanium-particle-induced intramedullary inflammation.

Wear debris from total joint replacement prostheses is implicated in periprosthetic osteolysis and implant loosening. The pathophysiology of this biological process remains unclear. Animal models of particle-induced osteolysis have proven useful in the study of specific tissue responses to wear debris. However, existing in vivo murine models of particle-mediated inflammation do not permit analysis of cortical bone degradation. This study describes a murine model of particle disease using an intramedullary rod in the mouse femur to parallel the clinical situation. The model consists of placing a 10-mm-long Kirschner wire retrograde in both femurs of C57b1/6 male mice via a medial parapatellar arthrotomy. Phagocytosable titanium particles were also implanted unilaterally to replicate generation of wear debris. Mice were sacrificed at 2, 10, and 26 weeks and whole femurs were cultured for 72 h. Levels of interleukin-6, monocyte chemotactic protein-1, and macrophage colony stimulating factor were assayed by ELISA. Transverse histological sections, at the level of the implant, were taken and stained with hematoxylin and eosin (H&E). Results demonstrated increased expression of proinflammatory mediators at 2 weeks in femora with rod and particles compared to femora with rods alone. Destruction of the endosteum was evident at 2, 10, and 26 weeks in the femora with titanium. This novel murine model of particle-induced intramedullary inflammation may facilitate cost-effective genetic studies and offers investigators a simple, clinically relevant intramedullary model to readily examine the pathogenesis of particle-mediated periprosthetic osteolysis.

Human interleukin-1-induced murine osteoclastogenesis is dependent on RANKL, but independent of TNF-alpha.

Although interleukin-1 (IL-1) has been implicated in the pathogenesis of inflammatory osteolysis, the means by which it recruits osteoclasts and promotes bone destruction are largely unknown. Recently, a cytokine-driven, stromal cell-free mouse osteoclastogenesis model was established. A combination of macrophage colony stimulating factor (M-CSF) and receptor activator of NFkappaB ligand (RANKL) was proven to be sufficient in inducing differentiation of bone marrow hematopoietic precursor cells to bone-resorbing osteoclasts in the absence of stromal cells or osteoblasts. This study utilizes this model to examine the impact of human IL-1beta on in vitro osteoclastogenesis of bone marrow progenitor cells. We found that osteoclast precursor cells failed to undergo osteoclastogenesis when treated with IL-1 alone. In contrast, IL-1 dramatically up-regulated osteoclastogenesis by 2.5- to 4-folds in the presence of RANKL and M-CSF. The effect can be significantly blocked by IL-1 receptor antagonist (p < 0.01). Tumor necrosis factor-alpha (TNF-alpha) was undetectable in the culture medium of differentiating osteoclasts induced by IL-1. Adding exogenous TNF-alpha neutralizing antibody had no influence on the IL-1-induced effect as well. These results show that in the absence of stromal cells, IL-1 exacerbates osteoclastogenesis by cooperating with RANKL and M-CSF, while TNF-alpha is not involved in this IL-1-stimulated osteoclast differentiation pathway.