Implant design affects markers of bone resorption and formation in total hip replacement

Titanium nanotopography enhances mechano-response of osteocyte three-dimensional network toward osteoblast activation

The bone turnover capability influences the acquisition and maintenance of osseointegration. The architectures of osteocyte three-dimensional (3D) networks determine the direction and activity of bone turnover through osteocyte intercellular crosstalk, which exchanges prostaglandins through gap junctions in response to mechanical loading. Titanium nanosurfaces with anisotropically patterned dense nanospikes promote the development of osteocyte lacunar-canalicular networks. We investigated the effects of titanium nanosurfaces on intercellular network development and regulatory capabilities of bone turnover in osteocytes under cyclic compressive loading. MLO-Y4 mouse osteocyte-like cell lines embedded in type I collagen 3D gels on titanium nanosurfaces promoted the formation of intercellular networks and gap junctions even under static culture conditions, in contrast to the poor intercellular connectivity in machined titanium surfaces. The osteocyte 3D network on the titanium nanosurfaces further enhanced gap junction formation after additional culturing under cyclic compressive loading simulating masticatory loading, beyond the degree observed on machined titanium surfaces. A prostaglandin synthesis inhibitor cancelled the dual effects of titanium nanosurfaces and cyclic compressive loading on the upregulation of gap junction-related genes in the osteocyte 3D culture. Supernatants from osteocyte monolayer culture on titanium nanosurfaces promoted osteocyte maturation and intercellular connections with gap junctions. With cyclic loading, titanium nanosurfaces induced expression of the regulatory factors of bone turnover in osteocyte 3D cultures, toward higher osteoblast activation than that observed on machined surfaces. Titanium nanosurfaces with anisotropically patterned dense nanospikes promoted intercellular 3D network development and regulatory function toward osteoblast activation in osteocytes activated by cyclic compressive loading, through intercellular crosstalk by prostaglandin.

Comparison of Bone Turnover Biomarkers in Serum and Urine Measured on an Automated Analytical Platform

BACKGROUND

Matched serum and urine samples from patients who had total hip replacement were used to assess serum-validated immunoassay reagents for use in urine.

METHODS

Samples were evaluated by an automated electrochemiluminescent immunoassay (cobas e411; Roche Diagnostics) for C-terminal telopeptide of type I collagen isoform β (β-Crosslaps), osteocalcin N-terminal midfragment (N-MID OC), N-terminal propeptide of type I collagen (PINP), and interleukin 6 (IL-6). Spike and recovery experiments were utilized to assess urinary matrix effects. Correlations between serum and both raw and creatinine-corrected urinary measures were assessed. Short-term precision was assessed.

RESULTS

Spike and recovery experiments indicated minimal matrix effects of urine for the β-Crosslaps assay. Potential matrix effects were observed for the other analytes because N-MID OC and IL-6 tended to be slightly overrecovered, whereas PINP was underrecovered. There were strong correlations between serum β-Crosslaps and raw (Spearman ρ [rs] = 0.725, P < 0.0001) and creatinine-corrected (rs = 0.793, P < 0.0001) urinary measures and moderate correlations between serum N-MID OC and raw (rs = 0.582, P < 0.0001) and creatinine-corrected (rs = 0.482, P < 0.0001) urinary measures. PINP was not detected in urine, and no significant serum-urine correlations were found for IL-6. Short-term precision for urinary levels of β-Crosslaps, N-MID OC, and IL-6 were 1.6%, 6.3% and 14.4%, respectively.

CONCLUSIONS

Urinary measurements of β-Crosslaps and N-MID OC assays were correlated with serum measurements and had good short-term precision. Urinary PINP was not detectable. IL-6 can be measured in urine using this technology, but the levels did not correlate with serum levels, and the short-term precision was variable.

Customizable Implant-specific and Tissue-Specific Extracellular Matrix Protein Coatings Fabricated Using Atmospheric Plasma

Progression in implant science has benefited from ample amount of technological contributions from various disciplines, including surface biotechnology. In this work, we successfully used atmospheric plasma to enhance the biological functions of surgical implants by coating them with extracellular matrix proteins. The developed collagen and laminin coatings demonstrate advantageous material properties. Chemical analysis by XPS and morphological investigation by SEM both suggested a robust coating. Contact angle goniometry and dissolution study in simulated body fluid (SBF) elicited increased hydrophilicity and physiological durability. Furthermore, these coatings exhibited improved biological interactions with human mesenchymal and neural stem cells (NSCs). Cell adhesion, proliferation, and differentiation proved markedly refined as shown by enzymatic detachment, flow cytometry, and ELISA data, respectively. Most importantly, using the pathway-specific PCR array, our study discovered dozens of deregulated genes during osteogenesis and neurogenesis on our newly fabricated ECM coatings. The coating-induced change in molecular profile serves as a promising clue for designing future implant-based therapy. Collectively, we present atmospheric plasma as a versatile tool for enhancing surgical implants, through customizable implant-specific and tissue-specific coatings.

Particle-induced osteolysis is not accompanied by systemic remodeling but is reflected by systemic bone biomarkers

Particle-induced osteolysis is caused by an imbalance in bone resorption and formation, often leading to loss of implant fixation. Bone remodeling biomarkers may be useful for identification of osteolysis and studying pathogenesis, but interpretation of biomarker data could be confounded if local osteolysis engenders systemic bone remodeling. Our goal was to determine if remote bone remodeling contributes to biomarker levels. Serum concentrations of eight biomarkers and bone remodeling rates at local (femur), contiguous (tibia), and remote (humerus and lumbar vertebra) sites were evaluated in a rat model of particle-induced osteolysis. Serum CTX-1, cathepsin K, PINP, and OPG were elevated and osteocalcin was suppressed in the osteolytic group, but RANKL, TRAP 5b, and sclerostin were not affected at the termination of the study at 12 weeks. The one marker tested longitudinally (CTX-1) was elevated by 3 weeks. We found increased bone resorption and decreased bone formation locally, subtle differences in contiguous sites, but no differences remotely at 12 weeks. Thus, the skeletal response to local particle challenge was not systemic, implying that the observed differences in serum biomarker levels reflect differences in local remodeling.

Implant placement increases bone remodeling transiently in a rat model

To examine bone remodeling following implant placement, 88 female Sprague-Dawley rats underwent either sham ovariectomy (sham-ovx) or ovariectomy (ovx) at 4.5 months. At 11 months, 17 baseline control animals were euthanized, while 71 rats received bilateral intramedullary femoral implants. Implanted rats were randomized to 4-, 8-, or 12-week follow-up times. Microcomputed tomography was used to assess cortical area and trabecular architecture in all rats. Dynamic and static histomorphometry were performed in a subset to examine the trabecular and endocortical bone in the distal femoral metaphysis adjacent to the implant and the periosteal surface at the midshaft superior to the implant (n = 59). Implantation did not affect bone volume in either sham-ovx or ovx rats compared to baseline controls. Implant placement significantly increased mineralizing surface, mineral apposition rate, and bone formation rate in both sham-ovx and ovx rats at the trabecular and endocortical surfaces at four and sometimes 8 weeks, with a return to baseline values by 12 weeks. At the periosteal surface, implant placement increased bone formation at 4 weeks with a return to baseline levels by 8 weeks. Thus, implant placement increases bone remodeling transiently without affecting bone volume in sham-ovx and ovx rats.

Proximally versus fully porous-coated femoral stems: a multicenter randomized trial

There are two broad-based categories of cementless femoral component designs: proximally porous-coated and fully porous-coated. While both have been widely used, there remains debate regarding differences in clinical outcome scores, relative incidence of thigh pain, and development of stress shielding. We investigated these variables in a multicenter prospective randomized blinded clinical trial of 388 patients from three centers: 198 patients had a proximally porous-coated tapered cementless femoral component and 190 patients had a fully porous-coated cementless femoral component. A minimum followup of 2 years (mean, 6.7 years; range, 2.0-8.65 years) was available in 367 of the 388 patients (95%). We observed no differences in age at surgery, body mass index, or preoperative clinical outcome scores (WOMAC, SF-12, Harris hip score, UCLA activity, thigh pain) with the two groups. We determined serial bone density changes in a subcohort of 72 patients from two of the three centers. The postoperative clinical outcome scores were similar at all followup intervals, and we observed no differences in the incidence of thigh pain at any time. Bone density reduction in Gruen Zone 7 was greater with the fully coated stem than the proximally coated stem (24% versus 15% reduction, respectively). Both fully and proximally coated stems performed well, with no clinical differences at 2 years' followup, except in bone mineral density evaluations.

LEVEL OF EVIDENCE

Level I, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Biological options to enhance periprosthetic bone mass

There is a potential for the use of pharmacological agents to enhance the quality of bone around a total hip or knee prosthesis, reducing the risk of implant failure or periprosthetic fracture. Bisphosphonates are currently used for the management of postmenopausal osteoporosis and recent investigations also suggest a potential role for the management of postoperative periprosthetic bone loss. Current evidence suggests that the short-term gains may not be sustained in the long term. Teriparatide and parathyroid hormone 1-84 have been licensed to treat postmenopausal osteoporosis and may also be investigated for the potential to enhance periprosthetic bone mass. In addition, other agents such as calcitonin and strontium ranelate, non-anabolic agents such as doxycycline, and recombinant OPG adeno-associated virus (rAAV) gene therapy, may in the future provide solutions for enhancing periprosthetic bone mass.

Predictive value of a preoperative biochemical bone marker in relation to bone remodeling after cementless total hip arthroplasty

To identify the factors predicting proximal bone resorption of the femur after cementless total hip arthroplasty (THA), we studied 24 postmenopausal women with osteoarthritis. Periprosthetic bone mineral density (BMD) measurements of the seven Gruen zones were determined with dual-energy X-ray absorptiometry at 3 wk, 6, 12, and 18 mo after operation. The greatest decrease in BMD (13.2%) was found in zone 7 at 18 mo. At 18 mo, preoperative serum bone alkaline phosphatase was associated univariately with BMD loss in zones 1 (r = 0.407, p = 0.048) and 7 (r = 0.543, p = 0.006) and urinary N-telopeptide cross-linked collagen type I (NTX) was associated univariately with that in zone 7 (r = 0.520, p = 0.009). Patient age correlated with BMD loss in zone 7 (r = 0.425, p = 0.039). Multiple regression analysis identified a significant relationship between the BMD loss and patient age and NTX in zone 7 at 18 mo (r2 = 0.422, p = 0.001). We conclude that preoperative bone markers are significant predictors of bone remodeling after THA with the particular implants used in our study.