Cementless total knee replacement (TKR) is at the present date a controversial topic. Aim of the study was to compare the effect on tibial periprosthetic bone mineral density (BMD) between different implant materials and designs. During the two-year period between January 2005 and December 2006, we analysed data of 45 patients who underwent consecutively cementless TKR (49 implants) at our Institution for primary osteoarthritis. Data was divided in 2 groups: A) 26 implants with tantalium tibial component (Zimmer NexGen Trabecular Metal. TM. Monoblock); B) 23 implants with porous titanium tibial component (Lima MultiGen. TM. ). Data was comparable per sex, age, BMI, post-op alignment, post-op KSS > 75, absence of major post-op complications. Standard AP x-rays were taken 4 months post-op and 8 years post-op. In order to quantify the reduction of BDM, we determined using ImageJ (an open source software) the Mean Grey Value (MGV) of a specific area on the 4 months- and 8 yrs-postop AP x-rays. Group A and Group B had an average MGV variation of, respectively, 11.79% and 10.51%; there was no statistically significant difference between the two groups. Reduction of BMD in a TKR is known to be a biomechanical response to load and it is conditioned by the alignment of the components and their design. Our study shows that the different materials (porous titanium vs. tantalium), in relation to the different implant design, have a similar effect on the surrounding bone. The overall results show a valid osseointegration in both group of patients

Femoral stem design affects periprosthetic bone mineral density (BMD), which may impact long term survival of cementless implants in total hip arthroplasty (THA). The aim of this study was to examine proximal femoral BMD in three morphologically different uncemented femoral stems designs to investigate whether one particular design resulted in improved preservation of BMDMethods: 119 patients were randomised to receive either a proximally coated dual taper wedge stem, a proximally coated anatomic stem or a fully coated collarless triple tapered stem. All surgeries were performed via the posterior approach with mobilization on the day of surgery. Dual energy x-ray absorptiometry scans (Lunar iDXA, GE Healthcare, Madison, WI) assessed BMD across the seven Gruen zones pre-operatively, and post-operatively at 6-weeks, 1-year, and 2-years and compared to the unoperated contralateral femur as a control. Patient reported outcome measures of pain, function and health were also included at these corresponding follow-ups. BMD increased in zones one (2.5%), two (17.1%), three (13.0%), five (10%) and six (17.9%) for all stems. Greater preservation of BMD was measured on the lateral cortex (zone 2) for both the dual taper wedge and anatomic stems (p = 0.019). The dual taper wedge stem also demonstrated preservation of BMD in the medial calcar (zone 7) whilst the anatomic and triple taper stem declined in this region, however this was not statistically significant (p = 0.059). BMD decreased on average by 2.1% inthe mid-diaphysis region, distal to the stem tip (zone 4) for all implants. All stems performed equivalently at final follow-up in all patient reported outcome measures. This study demonstrated maintenance of femoral BMD in three different cementless femoral stem designs, with all achieving excellent improvements in patient reported outcomes. There was no significant stress shielding observed, however longer follow-up is required to elucidate the impact of this finding on implant survivorship

Introduction. The fixation of press-fit orthopaedic devices depends on the mechanical properties of the bone that is in contact with the implants. During the press-fit implantation, bone is compacted and permanently deformed, finally resulting in the mechanical interlock between implant and bone. For the development and design of new devices, it is imperative to understand these non-linear interactions. One way to investigate primary fixation is by using computational models based on Finite Element (FE) analysis. However, for a successful simulation, a proper material model is necessary that accurately captures the non-linear response of the bone. In the current study, we combined experimental testing with FE modeling to establish a Crushable Foam model (CFM) to represent the non-linear bone biomechanics that influences implant fixation. Methods. Mechanical testing of human tibial trabecular bone was done under uniaxial and confined compression configurations. We examined 62 human trabecular bone samples taken from 8 different cadaveric tibiae to obtain all the required parameters defining the CFM, dependent on local bone mineral density (BMD). The derived constitutive rule was subsequently applied using an in-house subroutine to the FE models of the bone specimens, to compare the model predictions against the experimental results. Results. The crushable foam model provided an accurate simulation of the experimental compression test, and was able to replicate the ultimate compression strength measured in the experiments [Figure 1]. The CFM was able to simulate the post-failure behavior that was observed in the experimental specimens up to strain levels of 50% [Figure 2]. Also, the distribution of yield strains and permanent displacement was qualitatively very similar to the experimental deformation of the bone specimens [Figure 3]. Conclusion. The crushable foam model developed in the current study was able to accurately replicate the mechanical behavior of the human trabecular bone under compression loading beyond the yield point. This advanced bone model enables realistic simulations of the primary fixation of orthopaedic devices, allowing for the analysis of the influence of interference fit and frictional properties on implant stability. In addition, the model is suitable for failure analysis of reconstructions, such as the tibial collapse of total knee arthroplasty. For any figures or tables, please contact the authors directly

To explore a novel machine learning model to evaluate the vertebral fracture risk using Decision Tree model and train the model by Bone Mineral Density (BMD) of different compartments of vertebral body. We collected a Computed Tomography image dataset, including 10 patients with osteoporotic fracture and 10 patients without osteoporotic fracture. 40 non-fracture Vertebral bodies from T11 to L5 were segmented from 10 patients with osteoporotic fracture in the CT database and 53 non-fracture Vertebral bodies from T11 to L5 were segmented from 10 patients without osteoporotic fracture in the CT database. Based on the biomechanical properties, 93 vertebral bodies were further segmented into 11 compartments: eight trabecular bone, cortical shell, top and bottom endplate. BMD of these 11 compartments was calculated based on the HU value in CT images. Decision tree model was used to build fracture prediction model, and Support Vector Machine was built as a compared model. All BMD data was shuffled to a random order. 70% of data was used as training data, and 30% left was used as test data. Then, training prediction accuracy and testing prediction accuracy were calculated separately in the two models. The training accuracy of Decision Tree model is 100% and testing accuracy is 92.14% after trained by BMD data of 11 compartments of the vertebral body. The type I error is 7.14% and type II error is 0%. The training accuracy of Support Vector Machine model is 100% and the testing accuracy is 78.57%. The type I error is 17.86% and type II error is 3.57%. The performance of vertebral body fracture prediction using Decision Tree is significantly higher than using Support Vector Machine. The Decision Tree model is a potential risk assessment method for clinical application. The pilot evidence showed that Decision Tree prediction model overcomes the overfitting drawback of Support Vector Machine Model. However, larger dataset and cohort study should be conducted for further evidence

In conventional DXA (Dual-energy X-ray Absorptiometry) analysis, pixel bone mineral density (BMD) is often averaged at the femoral neck. Neck BMD constitutes the basis for osteoporosis diagnosis and fracture risk assessment. This data averaging, however, limits our understanding of localised spatial BMD patterns that could potentially enhance fracture prediction. DXA region free analysis (RFA) is a validated toolkit for pixel-level BMD analysis. We have previously deployed this toolkit to develop a spatio-temporal atlas of BMD ageing in the femur. This study aims first to introduce bone age to reflect the overall bone structural evolution with ageing, and second to quantify fracture-specific patterns in the femur. The study dataset comprised 4933 femoral DXA scans from White British women aged 75 years or older. The total number of fractures was 684, of which 178 were reported at the hip within a follow-up period of five years. BMD maps were computed using the RFA toolkit. For each BMD map, bone age was defined as the age for which the L2-norm between the map and the median atlas at that age is minimised. Next, bone maps were normalised for the estimated bone age. A t-test followed by false discovery rate (FDR) analysis was applied to compare between fracture and non-fracture groups. Excluding the ageing effect revealed subtle localised patterns of loss in BMD oriented in the same direction as principal tensile curves. A new score called f-score was defined by averaging the normalised pixel BMD values over the region with FDR q-value less than 1e–6. The area under the curve (AUC) was 0.731 (95% confidence interval (CI)=0.689–0.761) and 0.736 (95% CI=0.694–0.769) for neck BMD and f-score. Combining bone age and f-score improved the AUC significantly by 3% (AUC=0.761, 95% CI=0.756–0.768) over the neck BMD alone (AUC=0.731, 95% CI=0.726–0.737). This technique shows promise in characterizing spatially-complex BMD changes, for which the conventional region-based technique is insensitive. DXA RFA shows promise to further improve fracture prediction using spatial BMD distribution

The effect of an advanced porous surface morphology on the mechanical performance of an uncemented femoral knee prosthesis was investigated. Eighteen implants were inserted and then pushed-off from nine paired femurs (Left legs: advanced surface coating; right legs: Porocoat® surface coating as baseline). Bone mineral density (BMD) and anteroposterior dimension were measured, which both were not significantly different between groups. The insertion force was not significantly different, but push-off force was significantly higher in the advanced surface coating group (P = 0.007). BMD had direct relationship with the insertion force and push-off force (p < 0.001). The effect of surface morphology on implant alignment was very small. We suggest that the surface properties create a higher frictional resistance thereby providing a better inherent stability of implants featuring the advanced surface coating

Bones are thought to become fragile with advancing age due to a loss of mass and structure. However, there are important aspects of bone fragility and fracture that cannot be explained simply by a loss of bone: 30% of all patients told they have healthy bone based on bone mineral density (BMD) measurements go on to fracture. It has been suggested that increased fracture risk might also be due to ageing at the nanoscale, which might deteriorate the overall mechanical properties of a bone. However, it is not clear how mechanics at the level of the collagen-mineral matrix relate to mechanical properties of the whole bone, or whether nano-mechanics contribute to fracture risk. In order to answer these questions our group is developing state of the art methods for analysing the structure and function of the collagen mineral matrix under loading. To image the collagen mineral matrix we obtained beam time on a synchrotron particle accelerator at the Diamond Light Source (Didcot, UK). Electrons are accelerated to near light speed by powerful electromagnets, then slowed to create high energy monochromatic X-Ray beams. Through a combination of X-Ray computed tomography and X-Ray diffraction we have been able to image the collagen/mineral matrix. Furthermore, using in situ loading experiments it has been possible to visualise collagen fibrillar sliding and mineral crystal structure. Our group is analysing how age related changes in nano-structure affect bone mechanical behaviour. As well as comparing fragility fracture patients with ‘healthy’ age matched controls to investigate whether ageing at the nano-scale could increase fracture risk. We are also assessing the effect of common treatments for bone fragility (e.g. bisphosphonate) on nano-mechanics. Unfortunately the expense and high radiation dose associated with synchrotron imaging prevents the technology from being adapted for patients. Therefore the next step will be to identify and test tools that can be used to indirectly assess bone chemistry and mechanical properties at point of care (e.g. laser spectroscopy and indentation). The data could be used to improve the diagnosis, monitoring and treatment of bone fragility

Introduction. Trabecular Titanium is a biomaterial characterized by a regular three-dimensional hexagonal cell structure imitating trabecular bone morphology. Components are built via Electron Beam Melting technology in aone- step additive manufacturing process. This biomaterial combines the proven mechanical properties of Titanium with the elastic modulus provided by its cellular solid structure (Regis 2015 MRS Bulletin). Several in vitro studies reported promising outcomes on its osteoinductive and osteoconductive properties: Trabecular Titanium showed to significantly affect osteoblast attachment and proliferation while inhibiting osteoclastogenesis (Gastaldi 2010 J Biomed Mater Res A, Sollazzo 2011 ISRN Mater Sci); human adipose stem cells were able to adhere, proliferate and differentiate into an osteoblast-like phenotype in absence of osteogenic factors (Benazzo 2014 J Biomed Mater Res A). Furthermore, in vivo histological and histomorphometric analysis in a sheep model indicated that it provided bone in-growth in cancellous (+68%) and cortical bone (+87%) (Devine 2012 JBJS). A multicentre prospective study was performed to assess mid-term outcomes of acetabular cups in Trabecular Titanium after Total Hip Arthroplasty (THA). Methods. 89 patients (91 hips) underwent primary cementless THA. There were 46 (52%) men and 43 (48%) women, with a median (IQR) age and BMI of 67 (57–70) years and 26 (24–29) kg/m2, respectively. Diagnosis was mostly primary osteoarthritis in 80 (88%) cases. Radiographic and clinical evaluations (Harris Hip Score [HHS], SF-36) were performed preoperatively and at 7 days, 3, 6, 12, 24 and 60 months. Bone Mineral Density (BMD) was determined by dual-emission X-ray absorptiometry (DEXA) according to DeLee &Charnley 3 Regions of Interest (ROI) postoperatively at the same time-points using as baseline the measureat 1 week. Statistical analysis was carried out using Wilcoxon test. Results. Median (IQR) HHS and SF-36 improved significantly from 48 (39–61) and 49 (37–62) preoperatively to 99 (96–100) and 76 (60–85) at 60 mo. (p≤0.0001). Radiographic analysis showed evident signs of bone remodelling and biological fixation, with presence of superolateral and inferomedial bone buttress, and radial trabeculae in ROI I/II. All cups resulted radiographically stable without any radiolucent lines. The macro-porous structure of this biomaterial generates a high coefficient of friction (Marin 2012 Hip Int), promoting a firm mechanical interlocking at the implant-bone interface which could be already observed in the operating room. BMD initially declined from baseline at 7 days to 6 months. Then, BMD slightly increased or stabilized in all ROIs up to 24 months, while showing evidence of partial decline over time with increasing patient' age at 60 months, although without any clinical significance in terms of patients health status or implant stability. Statistical significant correlations in terms of bone remodeling were observed between groups of patients on the basis of gender and age (p≤0.05). No revision or implant failure was reported. Conclusions. All patients reported significant improvements in quality of life, pain relief and functional recovery. Radiographic evaluation confirmed good implant stability at 60 months. These outcomes corroborate the evidence reported on these cups by orthopaedic registries and literature (Perticarini 2015 BMC Musculoskelet Disord; Bistolfi 2014 Min Ortop)

Introduction. We report a case which total knee arthroplasty (TKA) was able to be performed on schedule for the patient with occult fracture of proximal tibia which seemed to have occurred three months prior to the surgery, and has healed in short period of time by the use of Teriparatide. Case report. The patient is 84-year-old female, having right knee pain for past 7 years. Her knee pain increased by passive extension maneuver that was done by a bonesetter 3 months prior to the surgery. On her initial visit, the X-ray finding was severe medial osteoarthritis, and femorotibial angle (FTA) in the upright film was 197°, but there was no other disorder including fracture. Since the bone mineral density (BMD) of affected femoral neck was 62%YAM, and affected lateral femoral condyle as well as lateral tibial condyle seemed very porotic, we started using daily 20μg Teriparatide injection from 3 months prior to the surgery. Proximal tibial fracture was presented in the X-ray taken on the day before surgery, but since adequate bone union has already been formed, surgery was performed on schedule. Tibial implant with long stem was used for just to be certain. Thanks to the Teriparatide, the condition of cancellous bone in cut surface was excellent, and reaming of the tibia through fracture area felt very solid. Discussion. Proximal tibial fracture that occurred just before TKA is very rare. The fracture in this case was probably due to the maneuver done by the bonesetter. Teriparatide is indicated when osteoporosis is severe and the patient is at risk for fracture. We also indicate Teriparatide for the patients whose femoral neck BMD is very low and severe valgus knee or varus knee is present. Unloaded side of femoral or tibial condyle is usually very porotic in such a case. In our case, the fracture was so called fragility fracture which was found incidentally the day before surgery, but TKA could be done on schedule since adequate callus has been formed by the use of Teriparatide which started 3 months prior to the surgery

Orthopaedic surgeons are astounded with the strength of bone found in Polynesians. Furthermore the rate at which new Polynesian bone over-grows metal fixation of a recent fracture is impressive. Studies demonstrate that Polynesians have a higher Bone Mineral Density (BMD) than age and weight matched Europeans in NZ (1, 2). In addition, Polynesians have a lower incidence of hip fractures when compared to other ethnic groups (3). This suggests that the higher BMD or other inherent differences must account for the lower incidence of hip fractures in Polynesians. The aim of this study was to identify (if any) a difference in osteoblast mitosis between European and Polynesian bone. Samples were collected from 13 patients that had joint replacements in accordance with the MCNZ ethics approval. The bone is processed and osteoblasts cultured in the lab to 50% confluence. The cells are then tagged with Propidium Iodide. Using Fluorescence-Activated Cell Sorting (or FACS) the number of osteoblasts in the different phases of the cell cycle are counted. The percentage of cells in G0/G1, S and G2/M phase can be determined by entering the FACS data into a program called mod-fit. This study shows that Polynesians have a greater proportion of cells undergoing replication (i.e S-phase) than their European counterparts. Incidentally we have also shown that the proportion of cells undergoing mitosis lowers with age irrespective of ethnicity

INTRODUCTION. Loosening is a major cause for revision in uncemented hip prostheses due to insufficient primary stability. Primary stability after surgery is achieved through press-fit in an undersized cavity. Cavity preparation is performed either by extraction (removing bone) or compaction (crushing bone) broaching. Densification of trabecular bone has been shown to enhance primary stability in human femora; however, the effect of clinically used compaction and extraction broaches on human bone with varying bone mineral density (BMD) has not yet been quantified. The purpose of this study was to determine the influence of the broach design and BMD on the level of densification at the bone-cavity interface, stem seating, the bone-implant contact area and the press-fit achieved. METHODS. Paired human femora (m/f=11/12, age=60±18 y) were scanned with quantitative computed tomography (QCT, Philips Brilliance 16) before broaching, with the final broach, after its removal and after stem implantation. Compaction broaching (n=4) was compared in an in situ (cadaver) study against extraction broaching with blunt tooth types (n=3); in an ex situ (excised femora) study, compaction broaching was compared against extraction broaching with sharp tooth types (n=8 each). QCT data were resampled to voxel sizes of 1×1×1 mm (in situ) and 0.5×0.5×1 mm (ex situ). Mean trabecular BMD of the proximal femur was determined. The cavity volumes were segmented in the post-broach images (threshold: −250 mgHA/cm3, Avizo 9.2) and a volume of interest (VOI) of one-voxel thickness was added around the cavity to capture the interfacial bone. VOIs were transferred to the pre-broach image and bone densification was calculated within each VOI as the increase from pre- to post-broach image (MATLAB). Detailed surface data sets of broaches and stems were collected with a 3D laser-scanner (Creaform Handyscan 700) and aligned with the segmented components in the CT scans (Fig. 1). Stem seating was defined as the difference between the top edge of the stem coating and the final broach. Distance maps between the stem and cavity surface were generated to determine the bone-implant contact area and press-fit. All parameters were analysed between 5 mm distal to the coating and 1 cm distal to the lesser trochanter and analysed with related-samples Wilcoxon signed rank and Spearman's correlation tests (IBM SPSS Statistics 22). RESULTS. Trabecular BMD ranged from 81 to 221 mgHA/cm3. Densification was higher with compaction compared to sharp (p=0.034), but not blunt extraction broaching (p=1.000). Proximal bone-implant contact area, press-fit and stem seating did not differ between broaching methods. Bone-implant contact area and bone densification increased with trabecular BMD (rs=0.658, p=0.001 and rs=0.443, p=0.034), press-fit with stem seating (rs=0.746, p<0.001) and contact area with bone densification (rs=0.432, p=0.039). DISCUSSION. Sharp extraction broaching reduces densification at the bone-cavity interface, but does not affect the press-fit or contact area. Trabecular BMD was positively associated with contact area, and stem seating with press-fit. Future studies will aim to link these findings to primary stability and influence on periprosthetic fractures. For any figures or tables, please contact authors directly

Bone remodeling effects is a significant issue in predicting long term stability of hip arthroplasty. It has been frequently observed around the femoral components especially with the implantation of prosthesis stem. Presence of the stiffer materials into the femur has altering the stress distribution and induces changes in the architecture of the bone. Phenomenon of bone resorption and bone thickening are the common reaction in total hip arthroplasty (THA) which leading to stem loosening and instability. The objectives of this study are (i) to develop inhomogeneous model of lower limbs with hip osteoarthritis and THA and (ii) to predict the bone resorption behavior of lower limbs for both cases. Biomechanical evaluations of lower limbs are established using the finite element method in predicting bone remodeling process. Lower limbs CT-based data of 79 years old female with hip osteoarthritis (OA) are used in constructing three dimensional inhomogenous models. The FE model of lower limbs was consisted of sacrum, left and right ilium and both femur shaft. Bond between cartilage, acetabulum and femoral head, sacrum and ilium were assumed to be rigidly connected. The inhomogeneous material properties of the bone are determined from the Hounsfield unit of the CT image using commercial biomedical software. A load case of 60kg body weight was considered and fixed at the distal cut of femoral shaft. For THA lower limbs model, the left femur which suffering for hip OA was cut off and implanted with prosthesis stem. THA implant is designed to be Titanium alloy and Alumina for stem and femoral ball, respectively. Distribution of young modulus of cross-sectional inhomogeneous model is presented in Fig. 2 while model of THA lower limbs also shown in Fig. 2. Higher values of young modulus at the outer part indicate hard or cortical bone. Prediction of bone resorption is discussed with the respect of bone mineral density (BMD). Changes in BMD at initial age to 5 years projection were simulated for hip OA and THA lower limbs models. The results show different pattern of stress distribution and bone mineral density between hip OA lower limbs and THA lower limbs. Stress is defined to be dominant at prosthesis stem while femur experienced less stress and leading to bone resorption. Projection for 5 years follow up shows that the density around the greater tronchanter appears to decrease significantly

Introduction. Fixation patterns of cementless stem were known as proximal or distal part. Distal fixation was seen in fully porous coated stem and stress shielding of the proximal femur was indicative. These phenomena did not lower the clinical results, but technical difficulties were more and more in revision surgery because of infection or dislocation. There was lot of reports that alendronate was effective for treatment of osteoporosis by induction of apoptosis in osteoclasts. We can expect alendronate to modify the bone quality around the stem after cementless THA. Objectives. We studied prospectively that quantitative computed tomography (QCT) measured bone mineral density around the stem between alendronate group and control. We tried to clarify that stress shielding after cementless THA can be prevented by use of alendronate or not. Materials and methods. From September 2011, 60 patients underwent total hip arthroplasty with cementless stems. Thirty patients took alendronate (35mg/week) after surgery (Group A) and remaining 30 patients were control (Group C). Between two groups, gender, age at surgery, diagnosis and body mass index were similar. Two types of stem were used as Zweimuller type or taperlock type. Just after THA, femoral shaft divided by Gruen zone measured bone mineral density (BMD) with QCT and forearm also measured BMD by DEXA. Following examination was performed at 6 months, 12 months and 24 months after surgery. Results. Gender of two groups was as follow: four males and twenty-six females in Group A and two males and twenty-eight females in Group C. The age at surgery was 67.6+7.9y in group A and 62.5+13.3y in group C. Zweimuller type was used for 18 patients and taperlock type was used for 12 patients in group A. Zweimuller type was used for 14 patients and taperlock type was used for 16 patients in group C. BMD of forearm were not different between two groups and it meant that bone quality and osteoporosis of groups was similar. On the other hands, femoral BMD of group A was higher than that of group C. Especially BMD of group C was relatively low in zone 1 and 7. Conclusion. Weekly use of alendronate (35mg) might be useful for preventing stress shielding after cementless THA

Purpose. The purpose of this study was to evaluate periprosthetic bone mineral density (BMD) changes around a cementless short tapered-wedge stem and determine correlations between BMD changes and various clinical factors, including daily activity, after total hip arthroplasty (THA) with a short tapered-wedge stem. Methods. The study included 65 patients (65 joints) who underwent THA with a TriLock stem. At baseline, and 6, 12, and 24 months postoperatively, BMDs of the seven Gruen zones were evaluated using dual-energy X-ray absorptiometry. Correlations were determined between BMD changes and clinical factors, including the Harris hip score, body mass index, University of California at Los Angeles (UCLA) activity rating score, age at surgery, and initial lumbar BMD. Results. Minimal BMD changes were noted in the distal femur (Gruen zones 3, 4, and 5). However, significant BMD loss was noted in zone 7 at each time point. BMD loss was also noted in zone 1 at 6 and 12 months postoperatively, but BMD recovered after 18 months. Significant positive correlations were noted between BMD changes and the UCLA activity rating score in zones 1, 6, and 7. Additionally, negative correlations were noted between BMD changes and initial spine BMD in zones 2 and 3. Table legends. Table 1 Background of the patients. Table 2 Bone mineral density changes (%) at 6, 12, and 24 months postoperatively in the seven Gruen zones. Columns represent mean ± standard deviation. ※indicates P < 0.05 compared with baseline bone mineral density. Table 3 Correlations between periprosthetic bone mineral density changes and clinical factors (the Harris hip score, body mass index, University of California at Los Angeles activity rating score, age at surgery, and initial lumbar bone mineral density) in the seven Gruen zones at 24 months postoperatively. Correlation coefficients and P-values are presented. Boldface indicates P < 0.05. Conclusion. Periprosthetic BMD was maintained in the proximal femur, especially Gruen zone 1, with a short tapered stem. Daily activity may reflect improvements in periprosthetic bone quality after THA with a short tapered stem; however, this stem is not recommended in patients with low bone quality. To view tables, please contact authors directly

Purpose. The study aim was to assess how the periprosthetic bone density of the MiniHip™ changed in the course of the first year. Is there a correlation between the decrease in bone density with CCD angle or stem size? Are there other variables influencing the changes in bone density?. Material and Methods. 62 patients aged 25–78 years (34 women, 28 men) were implanted with a MiniHip total hip replacement during 2011 and 2012 through an anterolateral minimally invasive (ALMI) approach. Pre-operative diagnosis was osteoarthritis in 49 patients, dysplasia in 7, femoral necrosis in 4 and femoral neck fracture in 2 cases. As a primary variable the periprosthetic bone mineral density (BMD) was measured postoperatively within the first 2 weeks as a baseline measurement. Follow-up measurements were performed at 3, 6 and 12 months postoperatively. Statistical analysis was conducted to show any differences. Results. There is an initial post-operative loss of BMD in the first 3 months due to surgery and inactivity, with a significant decrease in the periprosthetic BMD proximally in Gruen Zones 1 (10.05%), 2 (12.37%) and 7 (10.05%) and distally in Gruen Zone 4 (6.9%). The density in the remaining Gruen regions also decreased but was not significant. In the following 3 months, the decrease in this Gruen regions continues without being significant. But after 6 months the bone mineral density shows a regeneration. At 12 months compared with the 6 months results there is an increase in BMD in Gruen Zones 1 (5.09%) and 7 (2.82%), also an increase in Gruen Zone 3 (1.75%) and 4 (1.78%) [Fig. 1]. A significant correlation between stem size and proximally bone loss in Gruen zones 1 & 7 was seen. In Gruen zone 1, there is also a correlation between bone loss and femoral neck angle, whereas this correlation was not significant in Gruen zone 7, but showing the same tendency. The analysis of covariables showed no dependencies of the results to sex, diagnosis or bearing surfaces. Conclusion. The MiniHip shows a loss of bone mineral density immediately post-operatively. After the initial decrease there was an increase especially in the proximal Gruen zones 1 and 7. Compared to other cementless short stems there was a lower bone density decrease [Fig. 2]. MiniHip™ loads the proximal femur in a more physiological way, which may preserve more bone in zones 1 and 7

The advantages of unicompartmental knee arthroplasty (UKA) include its bone preserving nature, lower relative cost and superior functional results. Some temporary pain has been reported clinically following this procedure. Could this be related to bone remodeling? A validated bone remodeling algorithm may have the answers…. A 3D geometry of an intact human cadaveric tibia was generated using CT images. An all poly unicompartmental implant geometry was positioned in an inlay and onlay configuration on the tibia and the post-operative models created. An adaptive bone remodeling algorithm was used with finite element modeling to predict the bone remodeling behavior surrounding the implant in both scenarios. Virtual DEXA images were generated from the model and bone mineral density (BMD) was measured in regions of interest in the AP and ML planes. BMD results were compared to clinical results. The bone remodelling algorithm predicted BMD growth in the proximal anterior regions of the tibia, with an inward tendency for both inlay and onlay models. Looking in the AP plane, a maximum of up to 7% BMD growth was predicted and in the ML plane this was as high as 16%. Minimal BMD loss was observed, which suggests minimal disturbance to the natural bone growth following UKA. Positron emission tomography (PET) scans showed active hot spots in the antero- medial regions of the tibia. These results were consistent with the finite element modeling results. Bone remodeling behavior was found to be sensitive to sizing and positioning of the implant. The adaptive bone remodeling algorithm predicted minimal BMD loss and some BMD growth in the anterior region of the tibia following UKA. This is consistent with patient complaint and PET scans

We investigated the effect of adjuvant and neoadjuvant chemotherapy regimens on the tibial regenerate after removal of the external fixator in a rabbit model of distraction osteogenesis using New Zealand white rabbits. Forty rabbits were randomly distributed into two groups. In the neoadjuvant group, half of the rabbits received 1mg/kg cisplatinum & 2mg/kg adriamycin at eight weeks of age followed by 1mg/kg cisplatinum & 4mg/kg adriamycin at ten weeks of age. The remaining ten received an identical volume of normal saline using the same regimen. The adjuvant group differed only in the timing of the chemotherapy infusion. Half received the initial infusion ten days prior to the osteotomy, with the second infusion four days following the osteotomy. Again, the remaining ten rabbits received an identical volume of normal saline using the same regimen. This produced an identical interval between infusions and identical age at osteotomy in both groups. All rabbits underwent a tibial osteotomy at 12 weeks of age. Distraction started 24hours after osteotomy at a rate of 0.75mm a day for 10 days, followed by 18 days without correction to allow for consolidation of the regenerate. At week 16 there was no difference in Bone Mineral Density (BMD), Bone Mineral Content (BMC) or volumetric Bone Mineral Density (vBMD) in the adjuvant group. Neoadjuvant chemotherapy appears to have a significant detrimental effect on BMD, vBMD and BMC. Despite this there were no significant alterations in the mechanical properties of the regenerate. Histologically there was a trend for increased cortical thickness in the control groups compared to intervention however this did not prove statistically significant. In conclusion, adjuvant chemotherapy may be more beneficial for cases where distraction osteogenesis is being considered to replace segmental bone loss after tumour excision

Vitamin D is vital for bone health because it assists in the absorption and utilisation of calcium. Vitamin D deficiency may predispose individuals to developing osteoporosis and subsequent osteoporotic fracture. There are various studies in elderly females with hip fractures correlating the low bone mineral density (BMD) with vitamin D levels. But very few studies have evaluated the influence on elderly males. Therefore this study was conducted. All male patients aged more than 50 years presenting to orthopaedic department, in JIPMER, Puducherry, with either fracture neck of femur or intertrochanteric fracture were included. Serum vitamin D level was assessed in them and BMD of both the hips was evaluated by DEXA scan. The vitamin D levels, T-scores, Z-scores were then analysed and correlated. Of the total 41 patients evaluated 21 (51%) had fracture neck of the femur and 20 (49%) patients had intertrochanteric fractures. We found that 11 (26.8%) patients had osteoporosis, 17 (41.5%) had osteopenia, and 13 (31.7%) had normal values. The mean value of total T-scores on fracture side was −1.55 and on no fracture side was −1.88. Among them 9 (22%) patients had vitamin D level <20 ng /mL, 15 (36%) had levels between 20ng–30ng/mL and 17 (41%) had >30ng/mL. Total T-score and Z-score on fracture side and no fracture side showed no correlation with vitamin D (p value >0.05) in these patients. We found significant osteoporosis in both neck and trochanteric regions on both fracture and no fracture sides, yet we had some patients with trochanteric fracture and some with neck fracture on only one side. In view of this other factors like mode of injury, velocity of injury, muscle wasting might have contributed significantly to the type of fracture and side involved. The BMD was found to be lower in patients with neck of femur fracture compared to intertrochanteric fracture, but no correlation was found between vitamin D and BMD scores at neck and trochanteric region. From this study it appears that there is no direct relationship between the vitamin D level and BMD in elderly males with hip fractures. It may emphasise that in male patients with hip fractures vitamin D may not have critical role in development of osteoporosis. The treatment of such patients with vitamin D supplements to prevent hip fractures is still debatable. However further studies in very large groups and controls may bring more light on this subject

Bone mineral density (BMD) and bone mineral content (BMC) have not been previously assessed in unicompartmental knee replacement (UKR). We studied the early bone changes beneath the uncemented Oxford medial UKR. Our hypothesis was that this implant should decrease the shear stresses across the bone-implant interface and result in improved BMD and BMC beneath the tibial component. Using the Lunar iDXA and knee specific software we developed 7 regions of interest (ROI) in the proximal tibia and assessed 38 patients with an uncemented Oxford UKR at 2 years. We measured the replaced knee and contralateral unreplaced knee using the same ROI and compared the BMD and BMC. The initial precision study in 20 patients demonstrated high precision in all areas. There were 12 males and 16 females with an average age of 65.8 years (46–84 years). ROI 1 and 2 were beneath the tibial tray and had significantly less BMC (p=0.023 and 0.001) and BMD (p=0.012 and 0.002). ROI 3 was the lateral tibial plateau and this area also had significantly less BMC (p=0.007) and BMD (p=0.0001). ROI 4 and 5 immediately below the tibial keel had no significant change. These changes were independent of gender and age. These results were surprising in that the universal loss of BMC and BMD suggested that bone loading of the proximal tibia was not improved even after a UKR. The better BMD and BMC adjacent to the keel confirms other studies that show improved bone in-growth around keels and pegs in the uncemented tibial component. A prospective longitudinal study has been developed to compare BMD and BMC changes over time to see whether these changes are dynamic

Introduction. Resorptive bone remodeling secondary to stress shielding has been a concern associated with cementless total hip arthroplasty (THA). At present, various types of cementless implants are commercially available. The difference in femoral stem design may affect the degree of postoperative stress shielding. In the present study, we aimed to compare the difference in bone mineral density (BMD) change postoperatively in femurs after the use of 1 of the 3 types of cementless stems. Methods. Ninety hips of 90 patients who underwent primary cementless THA for the treatment of osteoarthritis were included in this study. A fit-and-fill type stem was used for 28 hips, a tapered-rectangular Zweymüller type stem was used for 32 hips, and a tapered-wedge type stem was used for 30 hips. The male/female ratio of the patients was 7/21 in the fit-and-fill type stem group, 6/26 in the tapered-rectangular Zweymüller type stem group, and 6/24 in the tapered-wedge type stem group. The mean age at surgery was 59.9 (39–80) in the fit-and-fill type stem group, 61.7 (48–84) in the tapered-rectangular Zweymüller type stem group and 59.6 (33–89) in the tapered-wedge type stem group. To assess BMD change after THA, we obtained dual-energy X-ray absorptiometry scans preoperatively and at 6, 12, 24, and 36 months postoperatively. Results. There were no differences in demographic data, such as gender, age at surgery, and body mass index, among the 3 groups (Table1). In terms of BMD change after THA, no differences were observed in Gruen zones 1–5 among the 3 groups during the 3-year follow-up. The BMD in Gruen zone 6 was maintained in the tapered-wedge type stem group, but decreased by 5% in the fit-and-fill type stem group and by 20% in the tapered-rectangular Zweymüller type stem group (p < 0.01). The BMD loss in Gruen zone 7 was observed in all stem types; however, the BMD loss at 36 months in the tapered-wedge type stem group (−15%) was significantly less than that of the other 2 groups (the fit-and-fill type stem group: −29%; the tapered-rectangular Zweymüller type stem group: −30%; p < 0.001 for both groups) (Figure). Discussion and Conclusion. A difference in postoperative BMD loss was observed among the 3 stem designs. This may be a result of the different fixation concept associated with each stem design. In the present study, we compared the postoperative BMD change after THA among a fit-and-fill type stem, a tapered-rectangular Zweymüller type stem, and a tapered-wedge type stem. BMD in the medial-proximal femur was maintained 3 years after THA in the group with the tapered-wedge type stem, which is fixed in a more proximal part of the femur compared to the other stems