Relative contribution of the nail and plate to a nail-plate construct for comminuted distal femoral fractures.

The purpose of this study was to assess the biomechanical contributions of the nail and the plate individually to a complete nail-plate construct in the setting of comminuted distal femur fractures. For this biomechanical study, comminuted extra-articular distal femur fractures were created in 24 synthetic osteoporotic femur models. These were then split into three groups: the nail-only group, the plate-only group, and the nail-plate group. After fixation, each specimen underwent sequential axial and torsional loading, and axial and torsional stiffness were calculated and compared. The addition of a nail to a plate-only construct increased axial stiffness by 19.7% and torsional stiffness by 59.4%. The plate-only group and nail-plate group both demonstrated significantly greater axial and torsional stiffness than the nail-only group at all levels of axial and torsional load. (p < 0.001) At 1000 and 2000 N of cyclic loading, the nail-plate group demonstrated significantly greater axial stiffness than the plate-only group (p ≤ 0.018). The nail-plate group demonstrated greater torsional stiffness than the plate-only groups at all levels of torsional loading (p < 0.001). In osteoporotic comminuted distal femur fracture models, most of the axial stiffness in a nail-plate construct comes from the plate. While the combination of the two constructs is not fully additive, the plate contributes the majority of the axial and torsional stiffness in a nail-plate construct. The supplementation of the plate with a nail primarily helps to increase resistance to rotational forces. Level of Evidence: III.

Evidence for cemented TKA and THA based on a comparison of international register data.

BACKGROUND: Hip and knee implants can either be fixed without cement, press-fit, or with bone cement. Real-world data from arthroplasty registers, as well as studies provide a broad database for the discussion of cemented versus uncemented arthroplasty procedures. OBJECTIVE: What does current evidence from international arthroplasty registries and meta-analyses recommend regarding cemented or cementless fixation of hip and knee implants? METHODS: A recommendation is generated by means of direct data comparison from the arthroplasty registries of eight countries (USA, Germany, Australia, UK, Sweden, Norway, New Zealand, Netherlands), the comparison of 22 review studies and meta-analyses based on registry data, as well as an evaluation of recommendations of healthcare systems from different nations. For this purpose, reviews and meta-analyses were selected where the results were statistically significant, as were the annual reports of the arthroplasty registries that were current at the time of writing. RESULTS: For knee arthroplasties, long survival time as well as lower risk of revision can be achieved with the support of cemented fixation with antibiotic-loaded bone cement. In patients aged 70 years and older, cemented fixation of hip stem implants significantly reduces risk of intraoperative or postoperative periprosthetic fracture (quadruple). This applies both to elective total hip arthroplasties and to hemiarthroplasty after femoral neck fractures. Antibiotic-loaded bone cement significantly (p = 0.041) reduces the risk of periprosthetic infection, especially in patients with femoral neck fractures. CONCLUSION: Total knee replacement with antibiotic-loaded bone cement is well established internationally and is evidence-based. Registry data and meta-analyses recommend cemented fixation of the hip stem in older patients. In Germany, USA and Australia these evidence-based recommendations still must be transferred to daily practice.

[Comparison of polymethyl methacrylate skull implant fixation by three types of titanium fasteners]. / Sravnenie sposobov fiksatsii implantov cherepa iz polimetilmetakrilata tremya vidami titanovykh krepezhei.

OBJECTIVE: To evaluate mechanical strength of three methods of polymethyl methacrylate skull implant fixation in two experimental models. MATERIAL AND METHODS: The first experiment was performed on a plastic model that was as close as possible to bone in structural characteristics. The second experiment was performed on a biological specimen (a ram's head). We assessed the quality of implant fixation to bone window edges by craniofixes, ties and microscrews and lateral intercortical screws. RESULTS: Craniofixes are feasible for small flat flaps, but not advisable for wide highly curved implants. They are also the most expensive method of fixation. Implant fixation by ties and microscrews is a universal method comparable in price to craniofix. Lateral intercortical fixation is effective both for small flat implants and wide implants with large curvature. However, this method is not always applicable. CONCLUSION: Combined fixation by lateral intercortical screws and ties allows for the most effective fixation while reducing the overall price of consumables.

Is Tibial Bone Mineral Density Related to Sex, Age, Preoperative Alignment, or Fixation Method in Primary Total Knee Arthroplasty?

BACKGROUND: Cementless total knee arthroplasty (TKA) has regained interest for its potential for long-term biologic fixation. The density of the bone is related to its ability to resist static and cyclic loading and can affect long-term implant fixation; however, little is known about the density distribution of periarticular bone in TKA patients. Thus, we sought to characterize the bone mineral density (BMD) of the proximal tibia in TKA patients. METHODS: We included 42 women and 50 men (mean age 63 years, range: 50 to 87; mean body mass index 31.6, range: 20.5 to 49.1) who underwent robotic-assisted TKA and had preoperative computed tomography scans with a BMD calibration phantom. Using the robotic surgical plan, we computed the BMD distribution at 1 mm-spaced cross-sections parallel to the tibial cut from 2 mm above the cut to 10 mm below. The BMD was analyzed with respect to patient sex, age, preoperative alignment, and type of fixation. RESULTS: The BMD decreased from proximal to distal. The greatest changes occurred within ± 2 mm of the tibial cut. Age did not affect BMD for men; however, women between 60 and 70 years had higher BMD than women ≥ 70 years for the total cut (P = .03) and the medial half of the cut (P = .03). Cemented implants were used in 1 86-year-old man and 18 women (seven < 60 years, seven 60 to 70 years, and four ≥ 70 year old). We found only BMD differences between cemented or cementless fixation for women < 60 years. CONCLUSIONS: To our knowledge, this is the first study to characterize the preoperative BMD distribution in TKA patients relative to the intraoperative tibial cut. Our results indicate that while sex and age may be useful surrogates of BMD, the clinically relevant thresholds for cementless knees remain unclear, offering an area for future studies.

Restoring implant fixation strength in osteoporotic bone with a hydrogel locally delivering zoledronic acid and bone morphogenetic protein 2. A longitudinal in vivo microCT study in rats.

Osteoporosis poses a major public health challenge, and it is characterized by low bone mass, deterioration of the microarchitecture of bone tissue, causing a consequent increase in bone fragility and susceptibility to fractures and complicating bone fixation, particularly screw implantation. In the present study, our aim was to improve implant stability in osteoporotic bone using a thermoresponsive hyaluronan hydrogel (HA-pNIPAM) to locally deliver the bisphosphonate zoledronic acid (ZOL) to prevent bone resorption and bone morphogenetic protein 2 (BMP2) to induce bone formation. Adult female Wistar rats (n = 36) were divided into 2 treatment groups: one group of SHAM-operated animals and another group that received an ovariectomy (OVX) to induce an osteoporotic state. All animals received a polyetheretherketone (PEEK) screw in the proximal tibia. In addition, subgroups of SHAM or OVX animals received either the HA-pNIPAM hydrogel without or with ZOL/BMP2, placed into the defect site prior to screw implantation. Periprosthetic bone and implant fixation were monitored using longitudinal in vivo microCT scanning post-operatively and at 3, 6, 9, 14, 20 and 28 days. Histological assessment was performed post-mortem. Our data showed that pure hydrogel has no impact of implant fixation The ZOL/BMP2-hydrogel significantly increased bone-implant contact and peri-implant bone fraction, primarily through reduced resorption. STATEMENT OF CLINICAL SIGNIFICANCE: Local delivery of ZOL and BMP2 using a biocompatible hydrogel improved implant stability in osteoporotic bone. This approach could constitute a potent alternative to systemic drug administration and may be useful in avoiding implant loosening in clinical settings.

Fixation strength of swelling copolymeric anchors in artificial bone.

Fixation with suture anchors and metallic hardware for osteosynthesis is common in orthopedic surgeries. Most metallic commercial bone anchors achieve their fixation to bone through shear of the bone located between the threads. They have several deficiencies, including stress-shielding due to mechanical properties mismatch, generation of acidic by-products, poor osteointegration, low mechanical strength and catastrophic failure often associated with large bone defects that may be difficult to repair. To overcome these deficiencies, a swelling porous copolymeric material, to be used as bone anchors with osteointegration potential, was introduced. The purpose of this study was to investigate the fixation strength of these porous, swelling copolymeric bone anchors in artificial bone of various densities. The pull-out and subsidence studies indicate an effective fixation mechanism based on friction including re-fixation capabilities, and minimization of damage following complete failure. The study suggests that this swelling porous structure may provide an effective alternative to conventional bone anchors, particularly in low-density bone.

Stability of lumbar vertebrae with lumbar spondylolisthesis after lumbar fusion and implant internal fixation / 中国组织工程研究

BACKGROUND:The purpose of the treatment of lumbar spondylolisthesis is to reconstruct the spine sequence and vertebral stability, relieve nerve compression, and achieve permanent lumbar fusion. OBJECTIVE:To explore the restore of vertebral stability of the lumbar spondylolisthesis patients after lumbar fusion and implant internal fixation. METHODS:The lumbar spondylolisthesis was often divided into dysplastic, isthmic, degenerative, traumatic and pathological with Wiltse classification. The slip degree of upper vertebra relative to lower vertebra on the lumbar X-ray film was divided into five grades, and then the appropriate treatment method was selected according to the classification, grading and specific circumstances of the lumbar spondylolisthesis patients. RESUTLS AND CONCLUSION:The strong fusion and internal fixation and the rigid connection between implants and vertebra are often used to stabilize the spine and correct deformities with high bone fusion rate, thus reducing pseudoarticulation formation. Dynamic fusion and internal fixation can distribute the load conduction of rigid internal fixation with elastic material or micro-devices, thus reducing stress shielding and adjacent segment stress concentration. Dynamic non-fusion and internal fixation can change the load transfer mode of spinal motion segment, inhibit spinal movement and prevent adjacent segment degeneration, in order to make the instable lumbar spine reach its normal activity characteristics, and achieve dynamic reconstruction of lumbar sequence. Lumbar isthmus defects directly repaired with graft is suitable for the young adult with the symptoms of lumbar spondylolisthesis and without degenerative disc disease. There is no consistent option on which materials and position is suitable for graft in the lumbar spondylolisthesis patients, as wel as which methods for fusion and implant internal fixation can achieve ideal effect.