Do Metaphyseal Cones and Stems Provide Any Biomechanical Advantage for Moderate Contained Tibial Defects in Revision TKA? A Finite-Element Analysis Based on a Cadaver Model.

BACKGROUND: Satisfactory management of bone defects is important to achieve an adequate reconstruction in revision TKA. Metaphyseal cones to address such defects in the proximal tibia are increasingly being used; however, the biomechanical superiority of cones over traditional techniques like fully cementing the implant into the defect has not yet been demonstrated. Moreover, although long stems are often used to bypass the defects, the biomechanical efficacy of long stems compared with short, cemented stems when combined with metaphyseal cones remains unclear. QUESTIONS/PURPOSES: We developed and validated finite-element models of nine cadaveric specimens to determine: (1) whether using cones for addressing moderate metaphyseal tibial defects in revision TKA reduces the risk of implant-cement debonding compared with cementing the implant alone, and (2) when using metaphyseal cones, whether long, uncemented stems (or diaphyseal-engaging stems) reduce the risk of implant-cement debonding and the cone-bone micromotions compared with short, cemented stems. METHODS: We divided nine cadaveric specimens (six male, three female, aged 57 to 73 years, BMI 24 to 47 kg/m2) with standardized tibial metaphyseal defects into three study groups: no cone with short (50-mm) cemented stem, in which the defect was filled with cement; cone with short (50-mm) cemented stem, in which a metaphyseal cone was implanted before cementing the implant; and cone with long, diaphyseal-engaging stem, which received a metaphyseal cone and the largest 150-mm stem that could fit the diaphyseal canal. The specimens were implanted and mechanically tested. Then, we developed and validated finite-element models to investigate the interaction between the implant and the bone during the demanding activity of stair ascent. We quantified the risk of implant debonding from the cement mantle by comparing the axial and shear stress at the cement-implant interface against an experimentally derived interface failure index criterion that has been previously used to quantify the risk of cement debonding. We considered the risk of debonding to be minimal when the failure index was below 10% of the strength of the interface (or failure index < 0.1). We also quantified the micromotion between the cone and the bone, as a guide to the likelihood of fixation by bone ingrowth. To this end, we assumed bone ingrowth for micromotion values below the most restrictive reported threshold for bone ingrowth, 20 µm. RESULTS: When using a short, 50-mm cemented stem and cement alone to fill the defect, 77% to 86% of the cement-implant interface had minimal risk of debonding (failure index < 0.1). When using a short, 50-mm cemented stem with a cone, 87% to 93% of the cement-implant interface had minimal debonding risk. When combining a cone with a long (150-mm) uncemented stem, 92% to 94% of the cement-implant interface had minimal debonding risk. The differences in cone-bone micromotion between short, cemented stems and long, uncemented stems were minimal and, for both configurations, most cones had micromotions below the most restrictive 20-µm threshold for ingrowth. However, the maximum micromotion between the cone and the bone was in general smaller when using a long, uncemented stem (13-23 µm) than when using a short, cemented stem (11-31 µm). CONCLUSION: Although the risk of debonding was low in all cases, metaphyseal cones help reduce the biomechanical burden on the implant-cement interface of short-stemmed implants in high-demand activities such as stair ascent. When using cones in revision TKA, long, diaphyseal-engaging stems did not provide a clear biomechanical advantage over short stems. Future studies should explore additional loading conditions, quantify the interspecimen variability, consider more critical defects, and evaluate the behavior of the reconstructive techniques under repetitive loads. CLINICAL RELEVANCE: Cones and stems are routinely used to address tibial defects in revision TKA. Despite our finding that metaphyseal cones may help reduce the risk of implant-cement debonding and allow using shorter stems with comparable biomechanical behavior to longer stems, either cones or cement alone can provide comparable results in contained metaphyseal defects. However, longer term clinical studies are needed to compare these techniques over time.

The association between intracompartmental pressure and skeletal muscle recovery after tibial diaphyseal fractures: an ambispective cohort study.

BACKGROUND: Due to the special anatomy of the lower leg, tibial diaphyseal fracture causes increased intracompartmental pressure (ICP). Not only is this increased ICP the manifestation of skeletal muscle injury, but it induces further deterioration of the injury. The aim of this study was to assess the association between short-term ICP elevation and long-term skeletal muscle recovery after severe limb trauma. METHODS: In this single-center ambispective cohort study, we retrospectively screened and recruited a cohort of tibial diaphyseal fracture patients with integrated ICP data during the early post-traumatic period, and performed a prospective observational study to evaluate their skeletal muscle recovery through long-term follow-up and MR imaging after the removal of the implants. We analyzed the association between ICP elevation and skeletal muscle recovery using statistical methods. RESULTS: A total of 46 patients with healed fractures underwent intramedullary nail removal and MR imaging. The absolute values of the Pearson product-moment correlation coefficients between various ICP parameters and the cross-sectional area ratio (CSAR) ranged from 0.588 to 0.793, and the correlation coefficients between the ICP parameters and the average T2-weighted signal intensity ratio (T2SIR) varied from 0.566 to 0.775. Statistically significant associations were observed between the ICP parameters and the MR imaging parameters when simple linear regression analysis was performed. Among the ICP parameters, the accumulated ΔP (ΔP = diastolic blood pressure minus ICP) had the highest determination coefficient and explained 62.1% and 59.1% of the variance in CSAR and T2SIR, respectively. CONCLUSIONS: Short-term ICP elevation was associated with long-term skeletal muscle recovery following tibial diaphyseal fracture, especially for ICP data that integrated time factors. LEVEL OF EVIDENCE: Level 3.

Numerical investigation of mechanical behavior of human femoral diaphysis in normal and defective geometry: experimental evaluation.

Failure and major reoperation after internal fixation (IF) in mature femoral bones are common and proper selection of fixation method may reduce the rate of reoperations. Investigating the mechanical behavior of the human femoral diaphysis, this article studies effect of mechanical properties and geometry of the bone on selection of IF method. To this aim, we calculated the bone mineral density in human femurs, and then, using computed tomography scan, we obtained geometry and nonhomogeneous properties of the bone. Finite element (FE) models of osteotomised femurs were reinforced using four types of screws with a locking compression plate (LCP). We performed buckling and 4-point bending simulations, and results of these simulations represent critical buckling loads, maximum von Mises stresses, and strains around the screws and the central defect. To evaluate FE analysis, we employed the compressive experiments and compared load vs. displacement curves with FE results. Results corresponding to intact, osteotomised, and reinforced states are compared together, and the effect of cortical and unicortical screws in LCPs is studied. The FE results showed that application of identical prophylactic IF for two persons with identical injuries in the same conditions bring quite inverse results. As a consequence, evaluation of osteoporosis, elastic modulus, and morphometric data are required before fixation and screw selection. Besides, for short diaphysis, unicortical screws have maximum strengthening factor in bending. While for long samples, these types of screws can be the worst option, application of cortical screws results to maximum strength in comparison with other types.

Fixation of delayed distal radial fracture involving metaphyseal diaphyseal junction in adolescents: a comparative study of crossed Kirschner-wiring and non-bridging external fixator.

BACKGROUND: Conservative treatment remains the preferred choice for distal radius fracture in children. However, loss of reduction is problematic, especially in an older child. Crossed Kirschner-wires is widely used to treat distal radius fracture in adolescents. This study aimed to compare the application of crossed Kirschner-wiring (KW) and non-bridging external fixator (EF) for the treatment of delayed distal radial fracture involving metaphyseal diaphyseal junction (MDJ) in adolescents. METHODS: Between January 2012 to January 2017, 146 (male = 101, female = 45) patients in EF group and 117 (male = 76, female = 41) in KW group, were reviewed retrospectively. Preoperative data were collected from the hospital database, and postoperative clinical outcomes data were collected during the follow-up visits. We used SPSS for data analysis. RESULTS: There existed no significant difference between EF and KW regarding sex, body weight, fracture side, duration from injury to surgery. The duration of surgery was significantly shorter in EF (30.5 ± 6.1 min) than the KW group (44.6 ± 9.4 min), P < 0.001. The number of intraoperative X-ray images was significantly lower in EF (6.5 ± 1.1) than KW (11.8 ± 2.3), P < 0.001. The incidence of tendon irritation is significantly higher in the KW (19.7%) than the EF group (0%), P < 0.001. The residual angulation on the AP view was higher in KW (3.8 ± 2.3, degrees) than the EF group (2.5 ± 1.6, degrees), P < 0.001. The volar tilting is better in EF (6.6 ± 1.1, degrees) than the KW group (1.0 ± 1.5, degrees), P < 0.001. However, the functional outcomes of the wrist showed no significant difference between EF and KW group, P = 0.086. CONCLUSION: The EF was superior to KW in the treatment of radial MDJ fractures in adolescents. The EF displayed shorter duration of surgery, less tendon irritation, and better radiographic outcomes than the KW. However, the cost-effect analysis remains to be investigated, because the EF is more expensive than KW.

Three-dimensional Volumetric Filling Ratio Predicts Stress Shielding in Short-stem Anatomic Total Shoulder Arthroplasty.

INTRODUCTION: Three-dimensional (3-D) CT volumetric filling ratio (VFR) is a better predictor of proximal humerus stress shielding after short-stem anatomic total shoulder arthroplasty (aTSA) than using plain radiographs. METHODS: Forty-four patients with short-stem aTSAs, preoperative CT scans, and a minimum 3-year radiographic follow-up were included. Patients were divided into group A (stress shielding) and group B (no stress shielding) based on the radiographic analysis. Standard implant filling ratios were measured on plain radiographs. The 3-D VFR of the metaphyseal and diaphyseal segments of the aTSA stem was measured using MIMICS (Materialise). The area under a receiver operator characteristic curve was used to determine the predictive strength of the 3-D VFR method. RESULTS: The average age and radiographic follow-up was 69 years and 44 months. Group A had 19 patients and statistically higher filling ratios using 3-D VFR method than group B, whereas no notable differences were found between the groups using standard techniques. The 3-D VFR had an area under a receiver operator characteristic curve of 92%, which supports it as a good predictor of stress shielding. CONCLUSIONS: These methods enable early identification of patients at risk for stress shielding and can also be valuable in improving humeral stem designs. LEVEL OF EVIDENCE: Level III. Case-control study.

Marrow adipose tissue in adolescent girls with obesity.

BACKGROUND: Marrow adipose tissue (MAT) is increasingly recognized as an active and dynamic endocrine organ that responds to changes in nutrition and environmental milieu. Compared to normal weight controls, adolescent girls with anorexia nervosa have higher MAT content, which is associated with impaired skeletal integrity, but data are limited regarding MAT content in adolescents with obesity and how this interacts with bone endpoints. OBJECTIVE: To evaluate (i) MAT content in adolescents with obesity compared to normal-weight controls, (ii) the association of MAT with bone endpoints, and (iii) whether these associations of MAT are affected by body weight. METHODS: We assessed MAT, bone endpoints, and body composition in 60 adolescent girls 14-21 years old: 45 with obesity (OB) and 15 normal-weight controls (NW-C). We used (i) DXA to assess areal bone mineral density (aBMD) at the lumbar spine and total hip, and total body fat and lean mass, (ii) proton magnetic resonance spectroscopy (1H-MRS) to assess MAT at the 4th lumbar vertebra and femur, and MRI to assess visceral (VAT) and subcutaneous adipose tissue (SAT), (iii) high resolution peripheral quantitative CT (HR-pQCT) to assess volumetric BMD (vBMD), (iv) individual trabeculae segmentation to evaluate trabecular bone (plate-rod morphology), and (v) finite element analysis to assess stiffness (a strength estimate) at the distal radius and tibia. RESULTS: Groups did not differ for age or height. Weight, BMI, and areal BMD Z-scores at all sites were higher in the OB group (p<0.0001). MAT was lower in OB at the femoral diaphysis (p= <0.0001) and the lumbar spine (p=0.0039). For the whole group, MAT at the lumbar spine and femoral diaphysis was inversely associated with BMI, total fat mass, lean mass, and VAT. Even after controlling for body weight, independent inverse associations were observed of femoral diaphyseal and lumbar MAT with total tibial vBMD, and of lumbar MAT with radial trabecular vBMD. CONCLUSION: Adolescent girls with obesity have lower MAT than normal-weight controls despite having an excess of total body fat. These findings confirm that MAT is regulated uniquely from other adipose depots in obesity. MAT was inversely associated with vBMD, emphasizing an inverse relationship between MAT and bone even in adolescent girls with obesity.

The effects of focal brain damage on fracture healing: An experimental rat study.

OBJECTIVES: This study aims to investigate whether the motor cortex (MC) or the somatosensory cortex (SC) is more active during the course of bone healing after traumatic brain injury (TBI). MATERIALS AND METHODS: Thirty-three male Wistar albino rats (age, 8 to 10 months; weighing, 250 to 300 g) were randomized into three groups as the control group, MC damage group and SC damage group. Two rats from each brain damage group were sacrificed to verify the locations of the cortical injuries. Callus formation, callus/diaphysis ratios, and serum alkaline phosphatase (ALP) levels were measured at one, three and six weeks. RESULTS: The increases in callus masses in the control, MC, and SC groups were statistically significantly different between one and three weeks (p<0.05). Although this increase in the MC and SC groups was significant compared to the control group at the end of one week, no statistically significant difference was found between the MC and SC groups (p>0.05). There was a statistically significant difference in callus/diaphysis ratio between control, MC and SC groups in favor of MC group only at one week (p<0.05). The increase in serum ALP levels at three weeks was statistically significantly different in the MC and SC groups compared to the control group and significantly higher in the MC group compared to the SC group (p<0.05). CONCLUSION: There is a possible relationship between enhanced fracture healing after TBI and damage in the MC. Motor cortex plays a more active role on fracture healing in TBI.

Finite element modelling of the developing infant femur using paired CT and MRI scans.

Bone finite element (FE) studies based on infant post-mortem computed tomography (CT) examinations are being developed to provide quantitative information to assist the differentiation between accidental and inflicted injury, and unsuspected underlying disease. As the growing skeleton contains non-ossified cartilaginous regions at the epiphyses, which are not well characterised on CT examinations, it is difficult to evaluate the mechanical behaviour of the developing whole bone. This study made use of paired paediatric post mortem femoral CT and magnetic resonance imaging (MRI) examinations at two different stages of development (4 and 7 months) to provide anatomical and constitutive information for both hard and soft tissues. The work aimed to evaluate the effect of epiphyseal ossification on the propensity to shaft fractures in infants. The outcomes suggest that the failure load of the femoral diaphysis in the models incorporating the non-ossified epiphysis is within the range of bone-only FE models. There may however be an effect on the metaphysis. Confirmation of these findings is required in a larger cohort of children.

Zoledronate and Raloxifene combination therapy enhances material and mechanical properties of diseased mouse bone.

Current interventions to reduce skeletal fragility are insufficient at enhancing both the quantity and quality of bone when attempting to improve overall mechanical integrity. Bisphosphonates, such as Zoledronate (ZOL), are used to treat a variety of bone disorders by increasing bone mass to decrease fracture risk, but long-term use has been shown in some settings to compromise bone quality. Alternatively, Raloxifene (RAL) has recently been demonstrated to improve tissue quality and overall mechanical properties in a cell-independent manner by binding to collagen and increasing tissue hydration. We hypothesized that a combination of RAL and ZOL would improve mechanical and material properties of bone more than either monotherapy alone by enhancing both quantity and quality. In this study, wildtype (WT) and heterozygous (OIM+/-) male mice from the Osteogenesis Imperfecta (OI) murine model were treated with either RAL, ZOL, or both from 8 weeks to 16 weeks of age. Using the OIM model allows for investigation of therapeutic effects on a quality-based bone disease. Combination treatment resulted in higher trabecular architecture, cortical mechanical properties, and cortical fracture toughness in diseased mouse bone. Two fracture toughness properties, which are direct measures of the tissue's ability to resist the initiation and propagation of a crack, were significantly improved with combination treatment in OIM+/- compared to control. There was no significant effect on fracture toughness with either monotherapy alone in either genotype. Following the mass-based effects of ZOL, trabecular bone volume fraction was significantly higher with combination treatment in both genotypes. Combination treatment resulted in higher ultimate stress in both genotypes. RAL and combination treatment in OIM+/- also increased resilience compared to the control. In conclusion, this study demonstrates the beneficial effects of using combination drug treatments to increase bone mass while simultaneously improving tissue quality, especially to enhance the mechanical integrity of diseased bone. Combination therapies could be a potential method to improve bone health and combat skeletal fragility on both the microscopic and macroscopic levels.

Sclerostin antibody reduces long bone fractures in the oim/oim model of osteogenesis imperfecta.

Osteogenesis imperfecta type III (OI) is a serious genetic condition with poor bone quality and a high fracture rate in children. In a previous study, it was shown that a monoclonal antibody neutralizing sclerostin (Scl-Ab) increases strength and vertebral bone mass while reducing the number of axial fractures in oim/oim, a mouse model of OI type III. Here, we analyze the impact of Scl-Ab on long bones in OI mice. After 9 weeks of treatment, Scl-Ab significantly reduced long bone fractures (3.6 ±â€¯0.3 versus 2.1 ±â€¯0.8 per mouse, p < 0.001). In addition, the cortical thickness of the tibial midshaft was increased (+42%, p < 0.001), as well as BMD (+28%, p < 0.001), ultimate load (+86%, p < 0.05), plastic energy (+184%; p < 0.05) and stiffness (+172%; p < 0.01) in OI Scl-Ab mice compared to OI vehicle controls. Similar effects of Scl-Ab were observed in Wild type (Wt) mice. The plastic energy, which reflects the fragility of the tissue, was lower in the OI than in the Wt and significantly improved with the Scl-Ab treatment. At the tissue level by nanoindentation, Scl-Ab slightly increased the elastic modulus in bones of both OI and Wt, while moderately increasing tissue hardness (+13% compared to the vehicle; p < 0.05) in Wt bones, but not in OI bones. Although it did not change the properties of the OI bone matrix material, Scl-Ab reduced the fracture rate of the long bones by improving its bone mass, density, geometry, and biomechanical strength. These results suggest that Scl-Ab can reduce long-bone fractures in patients with OI.

A comparative evaluation of tibial metaphyseal-diaphyseal angle changes between physiologic bowing and Blount disease.

The purpose of this study was to estimate the rate of spontaneous improvement in tibial metaphyseal-diaphyseal angle (TMDA) in physiologic bowing in comparison to that in Blount disease and to provide reference values of TMDA for monitoring patients with highly suspected to have Blount disease.We retrospectively reviewed patients with physiologic bowing meeting the following criteria:(1) TMDA greater than 9° before 36 months of age at initial evaluation;(2) two or more standing long bone radiographs available; and(3) follow-up conducted up to resolution of deformity.Patients with Blount disease had(1) more than 2 standing long bone radiographs obtained before 36 months of age and(2) underwent no treatment during the period in which these images were obtained.TMDA measurements were obtained from 174 patients with physiologic bowing and 32 patients with Blount disease. Rates of TMDA improvement were adjusted by multiple factors using a linear mixed model, with sex and laterality as fixed effects and age and individual patients as the random effects.In the physiologic bowing group, TMDA improved significantly, by 3° per 6 months and by 6° per year. Changes in TMDA were not significant in the Blount disease group.Knowing the rate of TMDA change can be helpful for physicians seeking to monitor infants with suspected as having Blount disease with a high TMDA and to avoid unnecessary repeat radiographic evaluations.

Effects of Hole Diameter on Torsional Mechanical Properties of the Rabbit Femur.

OBJECTIVE: The aim of this study was to evaluate and compare the effect of three clinically applicable screw hole diameters on rabbit femoral torsional structural properties. SAMPLE: Eighteen pairs of skeletally mature New Zealand White rabbit femora (36 bones). MATERIALS AND METHODS: Femora with a bicortical hole at mid-diaphysis from one of the 3-drill bit sizes, 1.1 mm, 1.5 mm, 2.0 mm, and intact bones were studied. Each bone was bi-axially loaded in a servo-hydraulic load frame with the bone positioned so the neutral axis of torsion was aligned with the centre of the bone diaphysis. Axial compression to 35% body weight was applied to represent compression at stance, and rapid external torsion was applied to failure. Torque and angular deformation data were plotted for each test, with pre-yield and post-yield stiffnesses derived. Yield and failure torques and angles were determined, along with calculated yield, failure and post-yield energies. RESULTS: Failure torque was reduced compared with that of intact bone; weakened by 37% in 1.1-mm hole models, 53% in 1.5-mm hole models and 65% in 2.0-mm hole models. The torque angular deformation curves lacked plastic deformation. CONCLUSIONS AND CLINICAL RELEVANCE: This study demonstrates the unique, brittle biomechanics of rabbit bone. Based on data from other species that strength loss of no more than 50% is acceptable when placing orthopaedic implants, no defect greater than 1.1 mm (15% bone diameter) is recommended in rabbit femora.

The impact of the third fragment features on the healing of femoral shaft fractures managed with intramedullary nailing: a radiological study.

INTRODUCTION: Femoral shaft fractures with third fragments have a high non-union rate, which may reach 14%. This study aims to assess the impact of the radiological features of the third fragment, evaluated on post-operative X-rays, on the outcome of femoral shaft fractures type 32-B managed with intramedullary nailing, in order to obtain an algorithm which could predict the fracture healing time. MATERIALS AND METHODS: We have retrospectively evaluated a series of 52 patients. On post-operative X-rays, four radiological parameters were evaluated: the third fragment angle, the fracture gap, the third fragment size, and the mean third fragment displacement. All the patients underwent a radiologic follow-up at one, two, three, six, nine and 12 months post-operatively, to assess the bone healing. The patients were then divided into three groups, according to the fracture healing time: within six months (group A), between six and 12 months (group B), or fracture non-union after 12 months (group C). RESULTS: In 28 patients, out of 52 (53.85%), the fracture healing was observed at 6-month follow-up; in 18 patients, out of 52 (34.62%), the fracture healed within 12 months after trauma; and in six patients, out of 52 (11.54%), no fracture healing was observed at 12-month follow-up. The mean third fragment size was significantly different in each group (p < 0.05), while the mean third fragment displacement was significantly higher in group C, compared with group A (p = 0.0006) and group B (p = 0.0027). In group B, a positive correlation was found between the fracture healing time and the mean third fragment size (R = 0.594, p = 0.036); in group C, the fracture union time was positively related to the third fragment size (R = 0.689, p = 0.013) and the mean third fragment displacement (R = 0.7107, p = 0.006). Regression analysis showed that the third fragment size and the mean third fragment displacement are the most important features which affect the fracture healing time. CONCLUSIONS: The third fragment size (cutoff 40 mm) is the leading parameter to influence the fracture healing within or in more than six months. The mean third fragment displacement (cutoff 12 mm); on the other hand, impacts on the fracture delayed rather than absent healing.

A comparative biomechanical study on different fixation techniques in the management of transverse metaphyseal-diaphyseal junction fractures of the distal humerus in children.

BACKGROUND: Metaphyseal-diaphyseal junction (MDJ) fractures of the distal humerus are problematic to reduce and more susceptible to post-operative complications. This biomechanical study was designed to compare Kirschner wires (KW), lateral external fixation, and elastic stable intramedullary nails (ESIN) in simulated transverse MDJ fractures of various heights. METHOD: Sagittally oblique, transverse MDJ fractures were created in fourth-generation composite bone models at three levels: high, mid, and low fractures, respectively, and then fixed with either Kirschner wires, lateral external fixation (EF), or ESIN respectively and tested in extension, flexion, valgus, varus, internal, and external rotations. RESULTS: In the high fractures, ESIN had better overall stiffness than the other techniques. In the mid groups, three crossed pinning (1-medial and 2-lateral pins) had the best overall stiffness, followed by two crossed pinning (1-medial and 1-lateral pins). In the low fractures, three crossed pinning was superior to all other techniques. Two crossed pinning and three -lateral pinning techniques yielded comparable stiffness in the low fracture model. CONCLUSIONS: From a biomechanical perspective, ESIN provides the best overall stability for fractures located in the upper region of the MDJ, while percutaneous pinning is superior in stabilizing fractures of the lower region. Two lateral and one medial pins make the most stable crossed pinning construct for these fractures.

Bone fragility after spinal cord injury: reductions in stiffness and bone mineral at the distal femur and proximal tibia as a function of time.

Computed tomography and finite element modeling were used to assess bone structure at the knee as a function of time after spinal cord injury. Analyzed regions experienced degradation in stiffness, mineral density, and content. Changes were well described as an exponential decay over time, reaching a steady state 3.5 years after injury. INTRODUCTION: Spinal cord injury (SCI) is associated with bone fragility and an increased risk of fracture around the knee. The purpose of this study was to investigate bone stiffness and mineral content at the distal femur and proximal tibia, using finite element (FE) and computed tomography (CT) measures. A cross-sectional design was used to compare differences between non-ambulatory individuals with SCI as a function of time after injury (0-50 years). METHODS: CT scans of the knee were obtained from 101 individuals who experienced an SCI 30 days to 50 years prior to participation. Subject-specific FE models were used to estimate stiffness under axial compression and torsional loading, and CT data was analyzed to assess volumetric bone mineral density (vBMD) and bone mineral content (BMC) for integral, cortical, and trabecular compartments of the epiphyseal, metaphyseal, and diaphyseal regions of the distal femur and proximal tibia. RESULTS: Bone degradation was well described as an exponential decay over time (R2 = 0.33-0.83), reaching steady-state levels within 3.6 years of SCI. Individuals at a steady state had 40 to 85% lower FE-derived bone stiffness and robust decreases in CT mineral measures, compared to individuals who were recently injured (t ≤ 47 days). Temporal and spatial patterns of bone loss were similar between the distal femur and proximal tibia. CONCLUSIONS: After SCI, individuals experienced rapid and profound reductions in bone stiffness and bone mineral at the knee. FE models predicted similar reductions to axial and torsional stiffness, suggesting that both failure modes may be clinically relevant. Importantly, CT-derived measures of bone mineral alone underpredicted the impacts of SCI, compared to FE-derived measures of stiffness. TRIAL REGISTRATION: ClinicalTrials.gov (NCT01225055, NCT02325414).

The relationship between maternal and child bone density in Nigerian children with and without nutritional rickets.

We found a positive relationship between bone density in Nigerian children with and without rickets and that of their mothers. After treatment, children with rickets had greater bone density than children without rickets, indicating that children genetically programmed to have greater bone density may have a higher risk of rickets. INTRODUCTION: To determine the relationship between bone density in children with and without rickets and that of their mothers METHODS: Using an unmatched case-control design, forearm areal bone mineral density (aBMD) was measured in 52 and 135 Nigerian children with and without rickets and their mothers, respectively. We performed multivariate linear regression analyses to assess the relationship between maternal and child aBMD Z-scores. RESULTS: Forearm aBMD Z-scores in children were associated with maternal aBMD Z-scores at metaphyseal (effect estimate 0.23; 95% CI 0.08 to 0.37) and diaphyseal (effect estimate 0.16; 0.01 to 0.30) sites, after adjustment for rickets in the child, child's age and sex, height-for-age Z-score, and weight-for-age Z-score. In the adjusted model, rickets was inversely associated with child's aBMD Z-score at the diaphyseal site only (- 0.45, - 0.65 to - 0.24). The positive relationship between maternal and child aBMD Z-scores was marginally greater in children with rickets (slope 0.56, r = 0.47) than without rickets (slope 0.19, r = 0.20) at the diaphyseal site only (P = 0.06 for interaction) but not at the metaphyseal site (slopes 0.35 and 0.30, respectively, P = 0.48). After treatment with calcium for 6 months, metaphyseal aBMD Z-scores were greater in children with treated rickets (effect estimate 0.26; 95% CI 0.02 to 0.49) than in those without rickets. CONCLUSION: In Nigerian children with and without rickets, forearm aBMD Z-scores were positively associated with maternal aBMD Z-scores. Active rickets in the child marginally modified the relationship at the diaphyseal site only. After treatment, children with rickets had greater metaphyseal aBMD Z-scores than children without rickets.

Biomechanical Analysis of a Novel Intercalary Prosthesis for Humeral Diaphyseal Segmental Defect Reconstruction.

OBJECTIVE: To study the biomechanical properties of a novel modular intercalary prosthesis for humeral diaphyseal segmental defect reconstruction, to establish valid finite element humerus and prosthesis models, and to analyze the biomechanical differences in modular intercalary prostheses with or without plate fixation. METHODS: Three groups were set up to compare the performance of the prosthesis: intact humerus, humerus-prosthesis and humerus-prosthesis-plate. The models of the three groups were transferred to finite element software. Boundary conditions, material properties, and mesh generation were set up for both the prosthesis and the humerus. In addition, 100 N or 2 N.m torsion was loaded to the elbow joint surface with the glenohumeral joint surface fixed. Humeral finite element models were established according to CT scans of the cadaveric bone; reverse engineering software Geomagic was used in this procedure. Components of prosthetic models were established using 3-D modeling software Solidworks. To verify the finite element models, the in vitro tests were simulated using a mechanical testing machine (Bionix; MTS Systems Corporation, USA). Starting with a 50 N preload, the specimen was subjected to 5 times tensile (300 N) and torsional (5 N.m) strength; interval time was 30 min to allow full recovery for the next specimen load. Axial tensile and torsional loads were applied to the elbow joint surface to simulate lifting heavy objects or twisting something, with the glenohumeral joint surface fixed. RESULTS: Stress distribution on the humerus did not change its tendency notably after reconstruction by intercalary prosthesis whether with or without a plate. The special design which included a plate and prosthesis effectively diminished stress on the stem where aseptic loosening often takes place. Stress distribution major concentrate upon two stems without plate addition, maximum stress on proximal and distal stem respectively diminish 27.37% and 13.23% under tension, 10.66% and 11.16% under torsion after plate allied. CONCLUSION: The novel intercalary prosthesis has excellent ability to reconstruct humeral diaphyseal defects. The accessory fixation system, which included a plate and prosthesis, improved the rigidity of anti-tension and anti-torsion, and diminished the risk of prosthetic loosening and dislocation. A finite element analysis is a kind of convenient and practicable method to be used as the confirmation of experimental biomechanics study.

Association between leg bowing and serum alkaline phosphatase level regardless of the presence of a radiographic growth plate abnormality in pediatric patients with genu varum.

When children around 2 years of age show leg bowing and diseases are ruled out based on radiographic findings without conducting blood tests, they are classified as "physiologic" genu varum. Since whether or not physiologic genu varum is associated with bone metabolism is unclear, this study was conducted to clarify the association between genu varum and bone metabolism in children. Thirty-five pediatric patients with genu varm who visited our out-patient clinic were enrolled. While two of the 35 children had nutritional rickets, showing abnormalities on both blood test (ALP, ≥1000 IU/L; iPTH, >65 pg/mL and 25(OH)D, ≤20 ng/mL) and radiographs (such as cupping, fraying or splaying), five of 35 children showed abnormalities on blood tests but not radiographs. While metaphyseal-diaphyseal angle (MDA) correlated with serum 25-hydroxy vitamin D (r = -0.35, p = 0.04) and magnesium (r = -0.36, p = 0.04), MDA and femorotibial angle (FTA) correlated with alkaline phosphatase (r = 0.43, p = 0.01 and r = 0.51, p = 0.006, respectively). A ridge regression analysis adjusted for age and body mass index indicated that ALP was associated with MDA and FTA. A logistic regression analysis adjusted for age and BMI indicated that higher ALP influenced an MDA >11°, which indicates the risk for the progression of genu varum (odds ratio 1.002, 95% confidence interval 1.0003-1.003, p = 0.021). The higher ALP (+100 IU), the higher risk of an MDA >11° (odds ratio 1.22). In conclusion, genu varum is associated with the alkaline phosphatase level regardless of the presence of radiographic abnormalities in the growth plate in children.

Minimally Invasive Distal Metatarsal Diaphyseal Osteotomy (DMDO) for Chronic Plantar Diabetic Foot Ulcers.

BACKGROUND: The aims of this prospective study were first to evaluate the safety and effectiveness of minimally invasive distal metatarsal diaphyseal osteotomies (DMDOs) for treating a consecutive series of diabetic patients with chronic plantar diabetic foot ulcers (CPDFUs) and second to assess their clinical-functional and radiographic outcomes. METHODS: A consecutive series of patients affected by diabetes mellitus with CPDFUs, not responsive to previous nonoperative management, underwent DMDO. The CPDFUs were evaluated using the University of Texas Diabetic Wound Classification System (UTDWC). Demographic parameters, Foot & Ankle Society (AOFAS) scores, visual analog scale (VAS) scores, healing times, and complications were recorded. Maestro et al criteria and bone callus formation were analyzed radiologically. Statistical analysis was carried out ( P < .05). Thirty consecutive enrolled patients with a mean age of 66.7 (range, 53-75) years presented 35 CPDFUs with a mean diameter of 16.3 mm and a mean duration of 10.3 months. The most frequent grade of the UTDWC was IIIB (42.9%). RESULTS: All ulcers recovered with a mean healing time of 7.9 ± 4.0 (range, 4-17) weeks. AOFAS scores improved significantly from 55.3 to 81.4 points ( P < .001). At a mean follow-up of 25.3 months (range, 18-71), no cases of ulcer recurrence were recorded, while a major complication or a wound infection required longer healing time. CONCLUSION: Minimally invasive DMDO was a safe and effective method in promoting CPDFU healing, regardless of the grade of severity, by the reduction of the high plantar pressure under the metatarsal heads. This technique improved functional and radiographic outcomes with few complications. LEVEL OF EVIDENCE: IV, case series.

Factors that predict instability in pediatric diaphyseal both-bone forearm fractures.

The aim of this study was to determine the factors that may predict failure of closed reduction and casting of diaphyseal forearm fractures in children. Demographic and radiographic data of children with closed reduction and casting of these fractures in the emergency department were evaluated. Of 174 patients with adequate follow-up to union, 19 (11%) required a repeat procedure. Risk factors for repeat reduction included translation of 50% or more in any plane, age more than 9 years, complete fracture of the radius, and follow-up angulation of the radius more than 15° on lateral radiographs or of the ulna more than 10° on anteroposterior radiographs.