In Vivo Oxidation and Surface Damage in Retrieved Ethylene Oxide-sterilized Total Knee Arthroplasties

Background

Gas sterilization (eg, ethylene oxide [EtO] and gas plasma) was introduced for polyethylene to reduce oxidation due to free radicals occurring during radiation sterilization. Recently, oxidation has been observed in polyethylenes with undetectable levels of free radicals, which were expected to be oxidatively stable. It is unclear whether in vivo oxidation will occur in unirradiated inserts sterilized with EtO.

Questions/purposes

Methods

We collected 20 EtO-sterilized tibial inserts at revision surgeries. We assessed oxidative using Fourier transform infrared spectroscopy and mechanical properties using the small punch test. Surface damage was assessed using damage scoring techniques and micro-CT.

Results

Oxidation indexes were low and uniform between the regions. The subtle changes did not affect the mechanical properties of the polymer. The dominant surface damage modes included burnishing, abrasion, and third-body wear. There was no evidence of delamination in the retrievals.

Conclusions

The retrieved EtO-sterilized UHMWPE retrievals remained stable with respect to both oxidative and mechanical properties for up to 10 years in vivo. We did observe slight measurable amounts of oxidation in the inserts; however, it was far below levels that would be expected to compromise the strength of the polymer.

Clinical Relevance

Due to the stable oxidative and mechanical properties, EtO-sterilized tibial components appear to be an effective alternative to gamma-sterilized inserts, at least in short-term implantations.

     

Recent Advances in Understanding Bisphosphonate Effects on Bone Mechanical Properties

Purpose of the Review

Bisphosphonates have well-established effects on suppressing bone resorption and slowing bone loss, yet the effects on bone mechanical properties are less clear. We review recent data from pre-clinical and clinical experiments that assessed mechanical properties of bisphosphonate-treated specimens.

Recent Findings

Pre-clinical work has utilized new techniques to show reduced fatigue life and transfer of stress from the mineral to collagen. Several notable studies have examined mechanical properties of tissue from patients treated with bisphosphonates with mixed results. Pre-clinical data suggest effects on mechanics may be independent of remodeling suppression.

Summary

The direct effect of bisphosphonates on bone mechanics remains unclear but recent work has set a solid foundation for the coming years.

     

What Factors Influence the Biomechanical Properties of Allograft Tissue for ACL Reconstruction? A Systematic Review

Background

Allograft tissue is used in 22% to 42% of anterior cruciate ligament (ACL) reconstructions. Clinical outcomes have been inconsistent with allograft tissue, with some series reporting no differences in outcomes and others reporting increased risk of failure. There are numerous variations in processing and preparation that may influence the eventual performance of allograft tissue in ACL reconstruction. We sought to perform a systematic review to summarize the factors that affect the biomechanical properties of allograft tissue for use in ACL reconstruction. Many factors might impact the biomechanical properties of allograft tissue, and these should be understood when considering using allograft tissue or when reporting outcomes from allograft reconstruction.

Questions/purposes

What factors affect the biomechanical properties of allograft tissue used for ACL reconstruction?

Methods

We performed a systematic review to identify studies on factors that influence the biomechanical properties of allograft tissue through PubMed and SCOPUS databases. We included cadaveric and animal studies that reported on results of biomechanical testing, whereas studies on fixation, histologic evaluation, and clinical outcomes were excluded. There were 319 unique publications identified through the search with 48 identified as relevant to answering the study question. For each study, we recorded the type of tissue tested, parameters investigated, and the effects on biomechanical behavior, including load to failure and stiffness. Primary factors identified to influence allograft tissue properties were graft tissue type, sterilization methods (irradiation and chemical processing), graft preparation, donor parameters, and biologic adjuncts.

Results

Load to failure and graft stiffness varied across different tissue types, with nonlooped tibialis grafts exhibiting the lowest values. Studies on low-dose irradiation showed variable effects, whereas high-dose irradiation consistently produced decreased load to failure and stiffness values. Various chemical sterilization measures were also associated with negative effects on biomechanical properties. Prolonged freezing decreased load to failure, ultimate stress, and ultimate strain. Up to eight freeze-thaw cycles did not lead to differences in biomechanical properties of cadaveric grafts. Regional differences were noted in patellar tendon grafts, with the central third showing the highest load to failure and stiffness. Graft diameter strongly contributed to load-to-failure measurements. Age older than 40 years, and especially older than 65 years, negatively impacted biomechanical properties, whereas gender had minimal effect on the properties of allograft tissue. Biologic adjuncts show potential for improving in vivo properties of allograft tissue.

Conclusions

Future clinical studies on allograft ACL reconstruction should investigate in vivo graft performance with standardized allograft processing and preparation methods that limit the negative effects on the biomechanical properties of tissue. Additionally, biologic adjuncts may improve the biomechanical properties of allograft tissue, although future preclinical and clinical studies are necessary to clarify the role of these treatments.

Clinical Relevance

Based on the findings of this systematic review that emphasize biomechanical properties of ACL allografts, surgeons should favor the use of central third patellar tendon or looped soft tissue grafts, maximize graft cross-sectional area, and favor grafts from donors younger than 40 years of age while avoiding grafts subjected to radiation doses > 20 kGy, chemical processing, or greater than eight freeze-thaw cycles.

     

Bone-Albumin filling decreases donor site morbidity and enhances bone formation after anterior cruciate ligament reconstruction with bone-patellar tendon-bone autografts

Purpose

Donor site pain affects 32–43 % of patients after anterior cruciate ligament surgery when the autograft is freshly harvested bone-patellar tendon-bone tissue. Our aim was to compare functional and morphological differences between donor sites with and without serum albumin-coated bone allograft filling.

Methods

After harvesting and implanting the graft, the tibia site was filled with either fresh autologous cancellous bone enhanced with albumin-coated allograft or autologous bone alone. The patella site was filled either with albumin-coated allograft or with blood clot. Knee function was evaluated by the VISA, Lysholm and IKDC scores and a visual analog scale of pain during standing, kneeling and crouching after six weeks and six months. Computed tomography was performed at six months for morphological evaluation.

Results

At six weeks, both groups were still recovering from surgery and the overall knee function was still impaired but the functional scores were significantly higher in the Bone-Albumin group. The pain with crouching and kneeling was also lower as compared to controls. At six months, the knee function scores were close to normal, with a slight decrease in the controls. Pain at kneeling was still prominent in the controls, but significantly lower in the Bone-Albumin group. Computed tomography showed significantly smaller bone defects and higher bone density in the Bone-Albumin group.

Conclusions

Results from the present study indicate that donor site pain, a disturbing long-term side effect of bone-patellar tendon-bone surgery, is significantly reduced if bone buildup in the patella and the tibia is augmented by serum albumin-coated bone allografts.

     

Quantifying Massive Allograft Healing of the Canine Femur In Vivo and Ex Vivo: A Pilot Study

Background

Allograft integration in segmental osseous defects is unpredictable. Imaging techniques have not been applied to investigate angiogenesis and bone formation during allograft healing in a large-animal model.

Questions/purposes

We used dynamic contrast-enhanced (DCE)-MRI and cone beam (CB)-CT to quantify vascularity and bone volume in a canine femoral allograft model and determined their relationship with biomechanical testing and histomorphometry.

Methods

Femoral ostectomy was performed in three dogs and reconstructed with a 5-cm allograft and compression plate. At 0.5, 3, and 6 months, we performed DCE-MRI to quantify vascular permeability (Ktrans) and perfused fraction and CB-CT to quantify bone volume. We also performed posteuthanasia torsional testing and dynamic histomorphometry of the grafted and nonoperated femurs.

Results

DCE-MRI confirmed the avascular nature of allograft healing (perfused fraction, 2.08%–3.25%). CB-CT demonstrated new bone formation at 3 months (26.2, 3.7, and 2.2 cm³) at the graft-host junctions, which remodeled down at 6 months (14.0, 2.2, and 2.0 cm³). The increased bone volume in one subject was confirmed with elevated Ktrans (0.22) at 3 months. CB-CT-identified remodeled bone at 6 months was corroborated by histomorphometry. Allografted femurs recovered only 40% of their strength at 6 months.

Conclusions

CB-CT and DCE-MRI can discriminate differences in angiogenesis and bone formation in the canine allograft model, which has potential to detect a small (32%) drug or device effect on biomechanical healing with only five animals per group.

Clinical Relevance

These radiographic tools may have the potential to assess adjuvant effects on vascular invasion and new bone formation after segmental allograft transplantation.

     

Room temperature housing results in premature cancellous bone loss in growing female mice: implications for the mouse as a preclinical model for age-related bone loss

Summary

Room temperature housing (22 °C) results in premature cancellous bone loss in female mice. The bone loss was prevented by housing mice at thermoneutral temperature (32 °C). Thermogenesis differs markedly between mice and humans and mild cold stress induced by standard room temperature housing may introduce an unrecognized confounding variable into preclinical studies.

Introduction

Female mice are often used as preclinical models for osteoporosis but, in contrast to humans, mice exhibit cancellous bone loss during growth. Mice are routinely housed at room temperature (18–23 °C), a strategy that exaggerates physiological differences in thermoregulation between mice (obligatory daily heterotherms) and humans (homeotherms). The purpose of this investigation was to assess whether housing female mice at thermoneutral (temperature range where the basal rate of energy production is at equilibrium with heat loss) alters bone growth, turnover and microarchitecture.

Methods

Growing (4-week-old) female C57BL/6J and C3H/HeJ mice were housed at either 22 or 32 °C for up to 18 weeks.

Results

C57BL/6J mice housed at 22 °C experienced a 62 % cancellous bone loss from the distal femur metaphysis during the interval from 8 to 18 weeks of age and lesser bone loss from the distal femur epiphysis, whereas cancellous and cortical bone mass in 32 °C-housed mice were unchanged or increased. The impact of thermoneutral housing on cancellous bone was not limited to C57BL/6J mice as C3H/HeJ mice exhibited a similar skeletal response. The beneficial effects of thermoneutral housing on cancellous bone were associated with decreased Ucp1 gene expression in brown adipose tissue, increased bone marrow adiposity, higher rates of bone formation, higher expression levels of osteogenic genes and locally decreased bone resorption.

Conclusions

Housing female mice at 22 °C resulted in premature cancellous bone loss. Failure to account for species differences in thermoregulation may seriously confound interpretation of studies utilizing mice as preclinical models for osteoporosis.

     

Indications for prophylactic osteosynthesis associated with curettage in benign and low-grade malignant primitive bone tumors of the distal femur in adult patients: a case series

Background

The aim of the study was to evaluate whether the use of preventive osteosynthesis after curettage in benign and primitive low-grade malignant bone tumor localized in the distal femur in adult patients provides sufficient mechanical stability to the system as to allow weight-bearing and reduce the risk of postoperative fracture. Additionally, lower limb function after curettage and preventive osteosynthesis was evaluated.

Materials and methods

We analyzed twelve cases of benign and low-grade malignant bone lesions of the distal femur in adult patients treated in our orthopedic department between 2008 and 2011 with curettage, bone filling and preventive osteosynthesis. All patients were treated with curettage with the use of high-speed cutters, plus liquid nitrogen as local adjuvant in low-grade malignant lesions, and filling of the lesion with bone graft or allograft or acrylic cement, followed by osteosynthesis.

Results

No fractures or major complications were observed; good function of the knee was observed.

Conclusion

We recommend preventive osteosynthesis after curettage in patients with very large lesions (>5 cm, >60 cm³) or high functional requirements, in obese patients, and when local adjuvants are used.

Level of evidence

Level IV retrospective case-series study.

     

Surgical Revascularization Induces Angiogenesis in Orthotopic Bone Allograft

Background

Remodeling of structural bone allografts relies on adequate revascularization, which can theoretically be induced by surgical revascularization. We developed a new orthotopic animal model to determine the technical feasibility of axial arteriovenous bundle implantation and resultant angiogenesis.

Questions/purposes

We asked whether arteriovenous bundles implanted in segmental allografts would increase cortical blood flow and angiogenesis compared to nonrevascularized frozen bone allografts and contralateral femoral controls.

Methods

We performed segmental femoral allotransplantation orthotopically from 10 Brown Norway rats to 20 Lewis rats. Ten rats each received either bone allograft reconstruction alone (Group I) or allograft combined with an intramedullary saphenous arteriovenous flap (Group II). At 16 weeks, we measured cortical blood flow with the hydrogen washout method. We then quantified angiogenesis using capillary density and micro-CT vessel volume measurements.

Results

All arteriovenous bundles were patent. Group II had higher mean blood flow (0.12 mL/minute/100 g versus 0.05 mL/minute/100 g), mean capillary density (23.6% versus 2.8%), and micro-CT vessel volume (0.37 mm³ versus 0.07 mm³) than Group I. Revascularized allografts had higher capillary density than untreated contralateral femora, while vessel volume did not differ and blood flow was lower.

Conclusions

Axial surgical revascularization in orthotopic allotransplants can achieve strong angiogenesis and increases cortical bone blood flow.

Clinical Relevance

Poor allograft revascularization results in frequent complications of nonunion, infection, and late stress fracture. The presented technique of surgical revascularization could therefore offer a beneficial adjunct to clinical segmental bone allografting.

     

Die Masquelet-Technik zur Behandlung großer dia- und metaphysärer Knochendefekte

Objective

Treatment of large dia- and metaphyseal bone defects (>?3 cm) with two surgical interventions with an interval of 4–8 weeks.

Indications

Dia- and metaphyseal bone defects predominantly of the lower extremity.

Contraindications

Intraarticular bone defects, persisting bone infection or osteomyelitis, insufficient soft tissue coverage in the region of the bone defect, osteoporosis.

Surgical technique

First surgical intervention: thorough bone debridement and soft tissue coverage, implantation of a cement spacer into the bone defect for the induction of a synovial foreign-body membrane, internal or external fixation. Second surgical intervention: removal of the cement spacer and filling of the bone defect with autologous cancellous bone graft, optionally internal fixation after initial external fixation.

Postoperative management

Partial to full weight-bearing after the first surgical intervention depending on pain. Partial weight-bearing (max. 15 kg) after the second surgical intervention, until radiological signs of a remodeling of the regenerate bone occur. Usually no implant removal.

Results

A total of 6 patients (4 men, 2 women) aged 15–66 years with average bone defects of 7 cm (range 4–10 cm) were treated using the Masquelet technique. There were 2 aseptic femoral nonunions and 4 tibial nonunions (2 septic and 2 aseptic nonunions). One case was a periprosthetic tibial bone defect. Bone stabilization after debridement was performed using ring fixators on the tibia and an intramedullary nail and a locking plate on the femur, respectively. The second surgical intervention was performed after 6–9 weeks. In 3 of the 4 tibial cases, internal fixation was performed during this intervention. The iliac crest and the RIA (reamer–irrigator–aspirator) technique were used for cancellous bone grafting. Amputation after breakage of the plate was necessary in the patient with the periprosthetic bone defect. Nonunion at the docking site required cancellous bone grafting in 1 patient. All 5 patients were able to perform full weight-bearing without pain after 6 months. The Ilizarov fixator was removed 5 months after the second surgical intervention in a 15-year-old patient. None of the other implants were removed.

     

Effects of doxorubicin administration on bone strength and quality in sedentary and physically active Wistar rats

Summary

Doxorubicin (DOX) is used in pediatric cancer treatment. This study assessed the effects of 7 weeks of DOX and 10-week recovery on bone quality and biomechanical properties in sedentary and exercised Wistar rats. DOX decreases femur diaphysis radial growth and biomechanical properties. Some of these DOX effects were aggravated by exercise.

Introduction

Bone growth in pre-pubertal years critically influences adult fracture risk. DOX is widely used in the treatment of pediatric cancers, but there is limited evidence on its potential negative effects on bone growth. Exercise improves bone growth in children, but there is no evidence if it protects against DOX-induced bone toxicity. This study investigates the early and intermediate effects of a 7-week course of DOX on bone histomorphometry and strength in sedentary and exercised growing animal models.

Methods

Sixty-eight male Wistar rats (8 weeks) were treated with DOX (2 mg kg^?1) or vehicle for 7 weeks and afterward housed in standard cages or in cages with a running wheel and killed 2 or 10 weeks after last DOX administration. Femurs and blood were collected for assaying geometry, trabecular microarchitecture (histology), biomechanical properties (three-point bending and shearing of the femoral neck), bone calcium content and density (atomic absorption spectroscopy), and bone turnover markers (ELISA).

Results

DOX treatment reduced the femur diaphysis radial growth, with DOX-treated animals having a lower tissue area, cortical area, cortical thickness, and moment of inertia. DOX also decreased distal femur trabecular bone volume and trabecular number and increased trabecular separation. Femur diaphysis stiffness and maximum load were also reduced in past DOX-treated animals. Exercise was shown to worsen the effects of past DOX treatment on the femur diaphysis mechanical properties.

Conclusion

DOX negatively affects bone geometry, trabecular microarchitecture, and femur mechanical properties in growing Wistar rats. Exercise further aggravates the detrimental effects of past DOX treatment on bone mechanical properties.

     

Acetabular cortical and cancellous bone density and radiolucent lines after cemented total hip arthroplasty: a prospective study using computed tomography and plain radiography

Introduction

The aim of this prospective study was to evaluate load-transfer mechanisms and stress patterns of periacetabular cortical and cancellous bone after cemented total hip arthroplasty (THA) in vivo using computed tomography (CT) assisted osteodensitometry. In addition we analyzed the efficacy of CT in detecting radiolucent lines around the acetabular component compared to plain radiography.

Materials and methods

Twenty-two cemented acetabular cups were investigated using conventional sequential axial CT scans (Ø 8 days and 26 months post-OP) and plain radiography (Ø 5 days and 40 months post-OP). CT assisted osteodensitometry was used to determine cancellous and cortical bone bone density (BD). Radiolucent lines were evaluated using both CT and plain radiography.

Results

Significant BD loss at the time of follow-up was only detectable ventral to the cup (cortical bone: ?16%, P = 0.001; cancellous bone: ?31%, P = 0.001). The BD changes dorsal and cranial to the cup were not significant. Postoperatively no radiolucent lines were observed in the cement-bone interface by CT, while on plain radiography acetabular lucent lines were seen in 12 out of 22 cases.

Conclusion

CT-osteodensitometry has the technical ability to discriminate between cortical and cancellous bone structures with respect to strain-adapted remodeling: sufficient cancellous and cortical bone stock remained dorsal and cranial to the cup indicative of a balanced load transfer to these regions. CT-osteodensitometry has the potential to become an effective instrument for quality control in THA and the method of choice for in vivo determination of periprosthetic BD. In contrast, plain radiography is more suitable for the early detection of radiolucent lines compared to axial CT scans.

     

Large diaphyseal-incorporating allograft prosthetic composites: when,how, and why

Background

Proximal humeral bone loss in shoulder arthroplasty is a complex problem with a heterogeneous presentation. Different etiologies may contribute to varying degrees of severity in bone loss that dictate different treatment approaches.

Objectives

The purpose of this is article is to describe our technique for treatment of proximal humeral bone loss with proximal humeral allograft prosthetic composites (APC) and identify factors that may predict when larger allografts may be necessary.

Materials and methods

Ninety-nine patients were identified that had undergone reverse total shoulder arthroplasty with use of a proximal humeral allograft. Thirty-nine of these had large allografts that involved a significant portion of the diaphysis. Preoperative characteristics were examined to identify factors that may be associated with use of a larger diaphyseal-incorporating allograft.

Results

Well-fixed humeral stems could be treated with short metaphyseal allografts in 55 of 65 (85%) cases. Loose stems required longer diaphyseal-incorporating allografts in 28 of 31 (90%) cases, and these were commonly associated with periprosthetic fractures (n = 10), failed prior APC (n = 6), and infection (n = 5). Noncemented stems required diaphyseal grafts in 75% of cases, compared to cemented stems which required larger grafts in 34% of cases.

Conclusions

Proximal humeral bone loss in the setting of revision shoulder arthroplasty can be successfully managed with a reverse total shoulder and proximal humeral allograft. Larger allografts are frequently required for loose humeral stems, and noncemented stems appear more likely to require larger allografts than cemented stems.

     

Allograft augmentation in proximal humerus fractures

Objective

Achieve stable fixation to initially start full range of motion (ROM) and to prevent secondary displacement in unstable fracture patterns and/or weak and osteoporotic bone.

Indications

(Secondarily) displaced proximal humerus fractures (PHF) with an unstable medial hinge and substantial bony deficiency, weak/osteoporotic bone, pre-existing psychiatric illnesses or patient incompliance to obey instructions.

Contraindications

Open/contaminated fractures, systemic immunodeficiency, prior graft-versus-host reaction.

Surgical technique

Deltopectoral approach. Identification of the rotator cuff. Disimpaction and reduction of the fracture, preparation of the situs. Graft preparation. Allografting. Fracture closure. Plate attachment. Definitive plate fixation. Radiological documentation. Postoperative shoulder fixation (sling).

Postoperative management

Cryotherapy, anti-inflammatory medication on demand. Shoulder sling for comfort. Full active physical therapy as tolerated without pain. Postoperative radiographs (anteroposterior, outlet, and axial [as tolerated] views) and clinical follow-up after 6 weeks and 3, 6, and 12 months.

Results

Bony union and allograft incorporation in 9 of 10 noncompliant, high-risk patients (median age 63 years) after a mean follow-up of 28.5 months. The median Constant–Murley Score was 72.0 (range 45–86). Compared to the uninjured contralateral side, flexion was impaired by 13?%, abduction by 14?%, and external rotation by 15?%. Mean correction of the initial varus displacement was 38° (51° preoperatively to 13° postoperatively).

     

The challenge of non-union in subtrochanteric fractures with breakage of intramedullary nail: evaluation of outcomes in surgery revision with angled blade plate and allograft bone strut

Purpose

Subtrochanteric fractures have a bimodal age distribution. They usually require open reduction and internal fixation. Closed reduction and intramedullary nail fixation rate are increased for this type of fracture. As a result, the hardware breakage and non-union rate is high among such patients. Our purpose is to evaluate the outcomes of the role of blade plate and bone strut allograft in the management of subtrochanteric non-union by femoral nailing.

Materials and methods

We reported a group of 22 patients with subtrochanteric non-union, associated with breakage of the intramedullary nail with medial femoral allograft bone and lateral blade plate and wire (PS) s; and a group of 13 patients with subtrochanteric non-union, associated with breakage of the intramedullary nail treated with lateral blade plate and screws (CG). The chosen criteria to evaluate the two group during the clinical and radiological follow-up were the quality of life, measured by The Short Form (12) Health Survey (SF-12), the hip function and quality of life related to it, measured by the Harris Hip Score (HHS), bone healing, measured by Radiographic Union Score (RUS) by XR and CT at 1 year after the surgery, and postoperative complications. The evaluation endpoint was set at 12 months.

Results

The Bone healing measured by RUS occurred and also the full recovery before the first trauma measured by SF-12 and HHS are better in PS group. We only had three unimportant complications in PS while four breakage hardware in CG.

Conclusion

We conclude that in complicated non-unions, the use of blade plate and bone strut allograft has a definite positive role in the management of such cases.

     

Mechanical Characterization of Bone: State of the Art in Experimental Approaches—What Types of Experiments Do People Do and How Does One Interpret the Results?

Purpose of Review

The mechanical integrity of bone is determined by the direct measurement of bone mechanical properties. This article presents an overview of the current, most common, and new and upcoming experimental approaches for the mechanical characterization of bone. The key outcome variables of mechanical testing, as well as interpretations of the results in the context of bone structure and biology are also discussed.

Recent Findings

Quasi-static tests are the most commonly used for determining the resistance to structural failure by a single load at the organ (whole bone) level. The resistance to crack initiation or growth by fracture toughness testing and fatigue loading offers additional and more direct characterization of tissue material properties. Non-traditional indentation techniques and in situ testing are being increasingly used to probe the material properties of bone ultrastructure.

Summary

Destructive ex vivo testing or clinical surrogate measures are considered to be the gold standard for estimating fracture risk. The type of mechanical test used for a particular investigation depends on the length scale of interest, where the outcome variables are influenced by the interrelationship between bone structure and composition. Advancement in the sensitivity of mechanical characterization techniques to detect changes in bone at the levels subjected to modifications by aging, disease, and/or pharmaceutical treatment is required. As such, a number of techniques are now available to aid our understanding of the factors that contribute to fracture risk.

     

Acetabular reinforcement ring with additional hook improves stability in three-dimensional finite element analyses of dysplastic hip arthroplasty

Background

The stability of acetabulum reconstructions using reinforcement rings and hooks is important for successful replacement surgery. The objective of this study was to biomechanically determine the effects of the hook on stress and the related micromotions of the acetabular reinforcement ring during the immediate postoperative period.

Methods

Acetabular reinforcement ring models were developed using a nonlinear, three-dimensional, finite element method. Using a pre-prepared template, we constructed without-hook and bone graft models of varying volumes and material properties.

Results

The stress on the inferior margin of the acetabulum was higher in the with-hook model than in the without-hook model, especially with increased bone graft volumes, and the stiffness of the bone graft material was decreased. Relative micromotions in the without-hook model were higher than in the with-hook models. The highest relative micromotion was observed in the model with increased bone graft volume and lower stiffness of bone graft material.

Conclusions

In biomechanical analyses, the hook effectively dispersed stress and improved the initial fixation strength of the acetabular reinforcement ring.

     

Surgical Approach to Bone Metastases

Purpose of Review

The purpose of this review was to examine the recent changes in the surgical treatment of bone metastases and how the treatment paradigm has shifted with the improvement of adjuvant therapies. How surgery fits into the local and systemic treatment was reviewed for bone metastases in different areas.

Recent Findings

The more common use of targeted chemotherapies and focused high-dose radiation have altered the treatment paradigm of bone metastases.

Summary

Overall changes in the surgical treatment of bone metastases have been driven by an increased multidisciplinary approach to metastatic cancer and the awareness that one type of surgery does not work for all patients. The individual patient treatment goals dictate the surgical procedures used to achieve these goals. Advancements in adjuvant therapy-like radiation and more targeted chemotherapies have allowed for less invasive surgical approaches and therefore faster recoveries and reduced surgical morbidity for patients.

     

Proximal loading of the femur leads to low subsidence rates: first clinical results of the CR-stem

Introduction

A new femoral stem was developed with a design that leads to compression of cancellous bone in the calcar region which results in proximal loading. The cross-sectional design of the implant provides rotational stability.

Materials and methods

In the first clinical investigation ten patients underwent uncemented total hip arthroplasty between January 1999 and May 1999 using the CR-stem^® (Implantcast GmbH, Buxtehude, Germany). Results were investigated using the Harris-hip-score (HHS) and antero-posterior and lateral radiographs. Migration was evaluated with the EBRA-FCA-method with a follow-up of 7 years.

Results

We demonstrated a mean subsidence rate of 2.23 ± 1.13 mm 7 years after implantation thus providing basic data for extensive testing in a clinical environment.

Discussion

As small subsidence rates are regarded as predictor for superior long-term results in uncemented total hip arthroplasty according to the literature, the CR-stem shows promise for excellent long-term results.

     

A brief history of FRAX

Summary

This paper reviews the research programme that went into the development of FRAX® and its impact in the 10 years since its release in 2008.

Introduction

Osteoporosis is defined on the measurement of bone mineral density though the clinical consequence is fracture. The sensitivity of bone mineral density measurements for fracture prediction is low, leading to the development of FRAX to better calculate the likelihood of fracture and target anti-osteoporosis treatments.

Methods

The method used in this paper is literature review.

Results

FRAX, developed over an 8-year period, was launched in 2008. Since the launch of FRAX, models have been made available for 64 countries and in 31 languages covering more than 80% of the world population.

Conclusion

FRAX provides an advance in fracture risk assessment and a reference technology platform for future improvements in performance characteristics.