Aims

The aims of this study were to evaluate the morphology of the ankle in patients with an osteochondral lesion of the talus using 3D CT, and to investigate factors that predispose to this condition.

Introduction: Clinical experience has shown that addressing variations in bone morphology is important in the development of successful hip implant designs. Numerous studies of femoral bone morphology have been published utilizing various techniques. This study has developed a method which consistently measures large quantities of 3-dimensional digital femura geometry segmented from computed tomography (CT) scans and can accurately make anatomical measurements from these images. Methods: CT images of left femora on five hundred fifty six left femura (57% male, 43% female), consisting of 69% Caucasian, 16% Asian and 14% unknown were analyzed. The average age was 66 years, ranging from 40 to 93 years. Segmentation of the outer cortical, inner cortical, and marrow boundaries were consistently performed over all CT scans. The positions identified on the reference bone are transformed to the equivalent position on the clinical bone images, from which the dimensional data is extracted and stored. The mediolateral width (MLW), medial offset (MO) and lateral offset (LO) were measured in 10mm increments, ranging from 20mm above the lesser trochanter (LT) to 130mm below the lesser trochanter. The canal flare index was defined as a ratio of the mediolateral width at a section 20mm above the lesser trochanter to the mediolateral width at the isthmus level. Results: The mean mediolateral width at 20mm above the lesser trochanter was 47.0 ± 4.5 (35.1–61.8; n=556). Noble reported 45.4 ± 5.3 (31.0–60.0; n=200), Husmann reported in a neck oriented study 46.3 ± 6.9 (27.6–63.6; n=310) and Laine reported 47.1 ± 4.9 (n=50). The mean medial offset at a section 20mm above the lesser trochanter was 25.1 ± 2.9 (16.7–33.4). In the study by Husmann, a mean of 25.0 ± 5.2 (9.4–45.5) was reported. The mean canal flare index was 4.49 ±.8. Noble reported a mean canal flare index of 3.80 ±.074, Husmann 3.81 ±.83 and Laine 4.3 ±.93. Discussion: In general, the study showed minor differences to published data of proximal bone morphology. However, this more powerful study has shown that there is a higher mean canal flare index than determined by Noble and a similar mean canal flare index as determined by Laine. As reported by Laine, the canal flare index varies significantly with the placement of measurements in the canal. In this study the measurements were performed in a plane oriented by the femoral neck as a hip stem would be placed. The CFI over the isthmus width showed a greater correlation than previously shown by Noble. The novel software tool allows for anatomical measurements that can be applied to an unlimited population size enabling further applications and studies

INTRODUCTION. Understanding bone morphology is essential for successful computer assisted orthopaedic surgery, where definition of normal anatomical variations and abnormal morphological patterns can assist in surgical planning and evaluation of outcomes. The proximal femur was the anatomical target of the study described here. Orthopaedic surgeons have studied femoral geometry using 2D and 3D radiographs for precise fit of bone-implant with biological fixation. METHOD. The use of a Statistical Shape Model (SSM) is a promising venue for understanding bone morphologies and for deriving generic description of normal anatomy. A SSM uses measures of statistics on geometrical descriptions over a population. Current SSM construction methods, based on Principal Component Analysis (PCA), assume that shape morphologies can be modeled by pure point translations. Complicated morphologies, such as the femoral head-neck junction that has non-rigid components, can be poorly explained by PCA. In this work, we showed that PCA was impotent for processing complex deformations of the proximal femur and propose in its place our Principal Tangent Component (PTC) analysis. The new method used the Lie algebra of affine transformation matrices to perform simple computations, in tangent spaces, that corresponded to complex deformations on the data manifold. RESULTS. Both PCA and PTC were applied to the proximal femur dataset, from which selected femurs were reconstructed using the accumulation of components. PCA was deemed to have failed to reconstruct the surfaces because it required 65 components to achieve high coverage of the dataset. An important observation was that the head-neck junction was the most difficult section in the femur, requiring more components than other anatomical regions to reconstruct. This finding is consistent with the surgical observation that deformations occur in this junction for abnormal hip morphologies. PTC was successful in recovering 100% of the medical data using the only the first 5 components. We note that the encoding of deformation in PTC accounting for the performance increase. PTC outperformed PCA on the dataset in descriptive compactness. CONCLUSION. A standard SSM construction method was not adequate for analysing proximal femur surfaces because it could not easily model the complexity of non-rigid deformations at the head-neck junction. Principal tangent components, a novel method for using exponential maps on manifolds, accurately reconstructed the anatomical surfaces with very few components. Future work may include extending these concepts to describe joint diseases based on the shape of surfaces derived from volumetric data, such as CT or MRI. In conclusion, we have shown that differential geometry may be provide new insights to computational anatomy applications

Introduction. The first carpometacarpal (CMC) joint is the second most common joint of the hand affected by degenerative osteoarthritis (OA). 1. Laxity of ligamentous stabilizers that attach the first metacarpal bone (MC1) and the trapezium bone (TZ), notably the volar anterior oblique ligament (AOL), has been associated with cartilage wear, joint space narrowing, osteophyte formation, and dorsal-radial CMC subluxation. 2. In addition, the proximal-volar end of the MC1 has a bony prominence known as the palmar lip (PL) that adds conformity to this double-saddle joint, and is thought to be a supplemental dorsal stabilizer. Currently, no study has looked at the changes to the 3D shape and relative positions of these structures with OA. Methods. CT scans of patients with clinically diagnosed CMC OA (n=11, mean age 73 [60–97], 8 females) and CT scans of ‘normal’ patients with no documented history of CMC OA (n=11, mean age 37 [20–51], 6 females) were obtained with the hand in a prone position. 3D reconstructions of the MC1 and TZ bones were created, and each assigned a coordinate system. 3. The long axis of the MC1 and the proximal-distal axis of the TZ were established, and the location where they intersected the CMC articular surface was defined as their articular center points, X and O, respectively (Figure 1). Using the TZ as a fixed reference, we calculated the relative position of X in the dorsal-ventral and radial-ulnar directions. A two sample t-test was performed to compare the normal and OA groups. In addition, the distal position of the PL relative to X was recorded. Results. The dorsal position of the MC1 relative to the TZ was significantly greater (p=0.002) in the OA group compared with the normal group, with mean dorsal positions of 7.1 and 3.2mm, respectively (Figure 2). The distal position of the PL relative to X was also significantly greater (p=0.001) in the OA group when compared with the normal group, with mean positions of 5.8 and 1.9mm, respectively (Figure 3). Discussion. Dorsal migration of the MC1 in the OA group would suggest a compromised AOL, known to be elongated or absent intraoperatively. Without a sufficient AOL, the PL was positioned more distally in the OA group, as the load on the PL during extension activities could possibly exceed cartilage strength resulting in subchondral bone remodeling and further joint degeneration. We did not observe radial migration of the MC1 bone possibly due to the presence of bony osteophytes that can reduce abduction-adduction function in OA patients. 4. The relationship discovered between OA and changes to bone morphology and relative bone positions of the CMC joint may provide further insight into the natural progression of this disease

Bone strength is influenced by bone quality besides its density. This study aimed to evaluate the effects of teriparatide on changes of bone strength as well as trabecular and cortical bone microstructures at femoral neck in female ovariectomized (OVX) rats. Eighteen female Wister rats were divided into three groups: the sham control, OVX and treatment (Tx) groups. All of them were sacrificed after 3-month intermittent teriparatide intervention in Tx group. All left femurs were removed and scanned using micro-CT and followed by mechanical test for each femoral neck. Regarding micro-CT, four trabecular parameters including bone volume fraction (BV/TV), trabecular thickness (TbTh), trabecular separation (TbSp), and trabecular number (TbN) and three cortical parameters including volumetric bone mineral density (vBMD), cortical cross-sectional area (CtAr) and cortical thickness (CtTh) were measured at femoral neck region. All data were analyzed and was presented as median ± SEM. The mean bone strength of femoral neck significantly decreased in OVX group when compared to the control group (p < 0.05) and was significantly restored in Tx group (p < 0.01). Regarding the trabecular parameters, the BV/TV and TbTh significantly decreased in OVX group while compare to Tx group. However, no significant difference was observed in TbSp and TbN between the groups. Regarding the cortical parameters, CtTh was significantly greater in Tx group than that in OVX group (p<0.01). As our findings, intermittent teriparatide can improve the deteriorated bone strength of femoral neck due to ovarian deficiency via changing both trabecular microarchitecture and cortical morphology.

Aims

Cementless unicompartmental knee arthroplasty (UKA) has advantages over cemented UKA, including improved fixation, but has a higher risk of tibial plateau fracture, particularly in Japanese patients. The aim of this multicentre study was to determine when cementless tibial components could safely be used in Japanese patients based on the size and shape of the tibia.

The lateral wall thickness (LWT) in trochanteric femoral fractures is a known predictive factor for postoperative fracture stability. Currently, the AO/OTA classification uses a patient non-specific measure to assess the absolute LWT (aLWT) and distinguish stable A1.3 from unstable A2.1 fractures based on a threshold of 20.5 mm. This approach potentially results in interpatient deviations due to different bone morphologies and consequently variations in fracture stability. Therefore, the aim of this study was to explore whether a patient-specific measure for assessment of the relative LWT (rLWT) results in a more precise threshold for prediction of unstable fractures. Part 1 of the study evaluated 146 pelvic radiographs to assess left-right symmetry with regard to caput-collum-angle (CCD) and total trochanteric thickness (TTT), and used the results to establish the rLWT measurement technique. Part 2 reevaluated 202 patients from a previous study cohort to analyze their rLWT versus aLWT for optimization purposes. Findings in Part 1 demonstrated a bilateral symmetry of the femur regarding both CCD and TTT (p ≥ 0.827) allowing to mirror bone's morphology and geometry from the contralateral intact to the fractured femur. Outcomes in Part 2 resulted in an increased accuracy for the new determined rLWT threshold (50.5%) versus the standard 20.5 mm aLWT threshold, with sensitivity of 83.7% versus 82.7% and specificity 81.3% versus 77.8%, respectively. The novel patient-specific rLWT measure can be based on the contralateral femur anatomy and is a more accurate predictor of a secondary lateral wall fracture in comparison to the conventional aLWT. This study established the threshold of 50.5% rLWT as a reference value for prediction of fracture stability and selection of an appropriate implant for fixation of trochanteric femoral fractures

Osteoarthritis (OA) is the leading cause of pain and disability worldwide and is characterized by the degenerative changes of articular cartilage. Joint loading is required for cartilage maintenance; however, hyper-physiologic loading is a risk factor for OA. Mechanosensitive ion channels Piezo1 and Piezo2 synergistically transduce hyper-physiologic compression of chondrocytes, leading to chondrocyte death and onset of OA. This injury response is inhibited by Piezo channel loss of function, however the mechanistic role of Piezo channels in vivo is unknown. We examined the hypothesis that deletion of Piezo in chondrocytes will protect mice from joint damage and pain-related behaviors following a surgical destabilization of the medial meniscus (DMM), investigating a key mechanistic and mechanobiological role of these channels in the pathogenesis of OA. Aggrecan-Cre Piezo1 and Piezo1/2 knockout mice ((Agc)1-CRE. ERT2. ;Piezo1. fl/fl. Piezo2. fl/fl. ) were generated and given a 5-day Tamoxifen regimen at 12-weeks of age (n=6–12/group/sex). Cre-negative mice served as controls. At 16-weeks, mice received DMM surgery on the left knee. 12-weeks following DMM prior to sacrifice, activity and hyperalgesia were measured using spontaneous running wheels and a small animal algometer. Structural changes in bone, cartilage, and synovium were characterized using microCT, histology, and Modified Mankin Score criteria. Knockout of Piezo1/2 channels was chondroprotective in both sexes following DMM surgery as demonstrated by reduced Modified Mankin Score compared to control animals. Piezo1 KO was chondroprotective in only female mice, indicating a sexually dimorphic response. Piezo1 and Piezo1/2 KO was protective against pain in male mice, while females displayed no differences compared to controls. No changes were observed in bone morphology. Chondrocyte-specific Piezo1/2 knockout protects the knee joint from structural damage, hyperalgesia and functional deficits in a surgical model of PTOA in male and female mice, illustrating the importance of Piezo channels in response to injury in vivo. Future work aims to interrogate potential sexually dimorphic responses to cartilage damage and investigating Piezo2 KO mice

Introduction and Objective. Type 2 diabetes mellitus (T2DM), and the often concurrent obesity, causes metabolic changes that affect many organs and tissues, including bone. Despite a normal or even higher bone mineral density (BMD), T2DM has often been associated with a higher fracture risk, indicating a compromised bone quality. In this work, we use a novel congenic leptin receptor-deficient BioBreeding Diabetes Resistant rat (BBDR.cg.lepr.cp) to investigate the impact of T2DM and obesity on bone morphology and architecture at the microscale. Materials and Methods. Two different anatomical locations, i.e., femur and cranium, were studied combining micro-computed X-ray tomography (micro-CT) with scanning electron microscopy (SEM). Micro-CT data were examined using advanced image analysis tools in three-dimensions (3D). Results. Both parietal bones and femurs were smaller, i.e., thinner and shorter, respectively, in diabetic animals compared to healthy controls. Image analysis of the sagittal suture revealed a reduced suture width and length in diabetic animals, suggesting an altered bone apposition rate. Histomorphometry analysis from micro-CT data highlighted differences in microstructure of both trabecular and cortical femur between diabetic and healthy rats. In particular, bone volume fraction (BV/TV) was lower in the T2DM group, while trabecular spacing (Tb.Sp) was increased, overall indicating a higher porosity in diabetic trabecular bone. SEM revealed the presence of extended portions of hyper-mineralized cartilage in the distal femur of the diabetic animals. Conclusions. Micro-CT analyses, combined with SEM imaging, suggest that T2DM impacts bone growth and remodelling, in turn leading to differences in the structural organization at the microscale

Known risk factors for early periprosthetic femur fracture (PFF) following total hip arthroplasty (THA) include poor bone quality, surgical approach and cementless implants. The association between femoral component size and alignment and the risk of early PFF is not well described. We evaluated radiographic parameters of femoral component sizing and alignment as risk factors for early PFF. From 16,065 primary cementless THA, we identified 66 cases (0.41%) of early PFF (<90 days from index THA) at a single institution between 2016–2020. The stem was unstable and revised in all cases. We matched 60 cases of early PFFs (2:1) to 120 controls based on femoral component model, offset, surgical approach, age, BMI, and sex. Mean age was 67 years; 60% were female. Radiographic assessment of preoperative bone morphology and postoperative femoral component parameters including stem alignment, metaphyseal fill, and medial congruence with the calcar. A multivariable logistic regression was built to identify radiographic risk factors associated with early PPF. Markers of poor preoperative bone quality including canal calcar ratio (p=0.003), canal flare index (p<0.001), anteroposterior canal bone ratio (CBR) (p<0.001) and lateral CBR (p<0.001) were statistically associated with PFF. Valgus alignment (23% versus 12%) (p<0.001) was more prevalent in the PFF group compared to controls, as well as varus alignment of the implant (57% versus 43%). Distance between the medial aspect of the implant and the calcar was greater in cases of PFF (2.5 mm versus 1.4 mm) (p<0.001). Multivariate analysis demonstrated that valgus implant alignment (Odds Ratio (OR) 5) and medial implant-calcar incongruity (OR 2) increased the risk of early PFF. Medial implant-calcar incongruity and valgus alignment of the femoral component were risk factors for early PFF following cementless THA after controlling for age, sex, BMI, approach, proximal femoral morphology, and implant design

Knee laxity following anterior cruciate ligament (ACL) injury is a complex phenomenon influenced by various biomechanical and anatomical factors. The contribution of soft tissue injuries – such as ligaments, menisci, and capsule – has been previously defined, but less is known about the effects of bony morphology. (Tanaka et al, KSSTA 2012) The pivot shift test is frequently employed in the clinical setting to assess the combined rotational and translational laxity of the ACL deficient knee. In order to standardise the maneuver and allow for reproducible interpretation, the quantitative pivot shift test was developed. (Hoshino et al, KSSTA 2013) The aim of this study is to employ the quantitative pivot shift test to determine the effects of bone morphology as determined by magnetic resonance imaging (MRI) on rotatory laxity of the ACL deficient knee. Fifty-three ACL injured patients scheduled for surgical reconstruction (36 males and 17 females; 26±10 years) were prospectively enrolled in the study. Preoperative magnetic resonance imaging (MRI) scans were reviewed by two blinded observers and the following parameters were measured: medial and lateral tibial slope, tibial plateau width, femoral condyle width, bicondylar width, and notch width. (Musahl et al. KSSTA 2012). Preoperatively and under anaesthesia, a quantitative pivot shift test was performed on each patient by a single experienced examiner. An image analysis technique was used to quantify the lateral compartment translation during the maneuver. Subjects were classified as “high laxity” or “low laxity” based upon the median value of lateral compartment translation. (Hoshino et al. KSSTA 2012) Independent t-tests and univariate logistic regression were used to investigate the relationship between the pivot shift grade and various features of bone morphology. Statistical significance was set at p<0.05. A high inter-rater reliability was observed in all MRI measurements of bone morphology (ICC=0.72–0.88). The median lateral compartment translation during quantitative pivot shift testing was 2.8mm. Twenty-nine subjects were classified as “low laxity” (2.8mm). The lateral tibial plateau slope was significantly increased in “high laxity” patients (9.3+/−3.4mm versus 6.1+/−3.7mm; p<0.05). No other significant difference in bone morphology was observed between the groups. This study employed an objective assessment tool – the quantitative pivot shift test – to assess the contribution of various features of bone morphology to rotatory laxity in the ACL deficient knee. Increased lateral tibial plateau slope was shown to be a significant independent predictor of high laxity. These findings could help guide treatment strategies in patients with high grade rotatory laxity. Further research into the role of tibial osteotomies in this sub-group is warranted

Evaluating musculoskeletal conditions of the lower limb and understanding the pathophysiology of complex bone kinematics is challenging. Static images do not take into account the dynamic component of relative bone motion and muscle activation. Fluoroscopy and dynamic MRI have important limitations. Dynamic CT (4D-CT) is an emerging alternative that combines high spatial and temporal resolution, with an increased availability in clinical practice. 4D-CT allows simultaneous visualization of bone morphology and joint kinematics. This unique combination makes it an ideal tool to evaluate functional disorders of the musculoskeletal system. In the lower limb, 4D-CT has been used to diagnose femoroacetabular impingement, patellofemoral, ankle and subtalar joint instability, or reduced range of motion. 4D-CT has also been used to demonstrate the effect of surgery, mainly on patellar instability. 4D-CT will need further research and validation before it can be widely used in clinical practice. We believe, however, it is here to stay, and will become a reference in the diagnosis of lower limb conditions and the evaluation of treatment options. Cite this article: Bone Joint J 2021;103-B(5):822–827

Abstract. Objectives. Over 1% of the global population suffers with ankle osteoarthritis (OA), yet there is limited knowledge on the changes to subchondral bone with OA. In other joints, it has been shown that bone becomes osteosclerotic, with fewer, thicker trabeculae that become hypomineralised, causing an increased apparent bone volume fraction (BV/TV). Microstructural alterations reduce overall joint strength, which may impact the success of late-stage surgical interventions, such as total ankle arthroplasty (TAA). Previous ankle studies have evaluated changes to cartilage, bone plate and bone morphology with OA, hence this study aimed to characterise changes to trabecular architecture. Methods. Three ankle joints were isolated from non-diseased cadaveric feet (three males: 43, 50 and 57 years, MEEC 18-027). Cylindrical subchondral bone specimens (N=6, 6.5 mm Ø) were extracted from the tibial plafond. Osteoarthritic bone samples (N=6, distal tibia) were sourced from local patients (three males: 65, 58 and 68 years, NREC 07/Q1205/27) undergoing TAA surgery. Specimens were imaged using µCT at a 16 µm isotropic resolution (µCT-100 ScanCo Medical). Virtual cores of bone (6.5 mm Ø) were extracted from the image data of the osteoarthritic specimens and trimmed to a height of 4 mm. BoneJ was used to evaluate key morphological indices: BV/TV; anisotropy (DA); trabecular thickness (Tb.Th); trabecular density (Conn.D) and ellipsoid factor (EF) which characterises rod/plate geometry. Differences between the two groups of specimens were evaluated using a t-test with Bonferroni correction. Results. Significant increases in BV/TV and Tb.Th (p<0.01) were observed with OA compared to non-diseased. Differences in EF showed a shift to more rod-dominated structure with OA, but this was not significant. No significant differences to DA and Conn.D were observed. Conclusions. The results of this study agree with trends observed in other OA joints, but would benefit from a larger sample size. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Introduction. The ability to create patient-specific implants (PSI) at the point-of-care has become a desire for clinicians wanting to provide affordable and customized treatment. While some hospitals have already adopted extrusion-based 3D printing (fused filament fabrication; FFF) for creating non-implantable instruments, recent innovations have allowed for the printing of high-temperature implantable polymers including polyetheretherketone (PEEK). With interest in FFF PEEK implants growing, it is important to identify methods for printing favorable implant characteristics such as porosity for osseointegration. In this study, we assess the effect of porous geometry on the cell response and mechanical properties for FFF-printed porous PEEK. We also demonstrate the ability to design and print customized porous implants, specifically for a sheep tibial segmental defect model, based on CT images and using the geometry of triply periodic minimal surfaces (TPMS). Methods. Three porous constructs – a rectilinear pattern and gyroid/diamond TPMSs – were designed to mimic trabecular bone morphology and manufactured via PEEK FFF. TPMSs were designed by altering their respective equation approximations to achieve desired porous characteristics, and the meshes were solidified and shaped using a CAD workflow. Printed samples were mCT scanned to determine the resulting pore size and porosity, then seeded with pre-osteoblast cells for 7 and 14 days. Cell proliferation and alkaline phosphatase activity (ALP) were evaluated, and the samples were imaged via SEM. The structures were tested in compression, and stiffness and yield strength values were determined from resulting stress-strain plots. Roughness was determined using optical profilometry. Finally, our process of porous structure design/creation was modified to establish a proof-of-concept workflow for creating PSIs using geometry established from segmented sheep tibia CT images. Results. ALP activity measurements of the porous PEEK samples at 7 and 14 days were significantly greater than for solid controls (p < 0.001 for all three designs, 14 days). No difference between the porous geometries was found. SEM imaging revealed cells with flat, elongated morphology attached to the surface of the PEEK and into the pore openings, with filopodia and lamellipodia extensions apparent. mCT imaging showed average pore size to be 545 ± 43 µm (porosity 70%), 708 ± 64 µm (porosity 68%), and 596 ± 94 µm (porosity 69%) for the rectilinear, gyroid, and diamond structures, respectively. The average error between the theoretical and actual values was −16.3 µm (pore size) and −3.3 % (porosity). Compression testing revealed elastic moduli ranging from 210 to 268 MPa for the porous samples. Yield strengths were 6.6 ± 1.2 MPa for lattice, 14.8 ± 0.7 MPa for gyroid, and 17.1 ± 0.6 for diamond. Average roughness ranged from 0.8 to 3 µm. Finally, we demonstrated the ability to design and print a fully porous implant with the geometry of a sheep tibia segment. Assessments of implant geometrical accuracy and mechanical performance are ongoing. Discussion. We created porous PEEK with TPMS geometries via FFF and demonstrated a positive cellular response and mechanical characteristics similar to trabecular bone. Our work offers an innovative approach for advancing point-of-care 3D printing and PSI creation

Evaluate precisely and reproducibly tridimensional positioning of bone tunnels in anterior cruciate ligament reconstructions (ACL). To propose biplanar stereoradiographic imaging as a new reference in tridimensional evaluation of ACL reconstruction (ACLR). Comparing knee 3D models issued from EOStm low-irradiation biplanar X-Ray with those issued from computed tomography (CT-Scan) high definition images will allow a bone morphological description of a previously unseen precision. We carried out the transfer of 3D models from EOStm X-Ray images obtained from 10 patients in the same reference frame with models issued from CT-Scan. Two evaluators reconstructed both pre-operative and post-operative knees, using two different stereoradiographic projections, for a total of 144 knee 3D models from EOStm. A surface analysis by distance mapping allowed us to know the differences or errors between the homologous points of the EOStm and CT reconstructions, the latter being our “bronze-standard”. At the femur, we obtained a mean (95% confidence level) error of 1.5 mm (1.3–1.6) between the EOStm models compared to the Arthro-CT segmentations when using AP-LAT incidences, compared to 1 mm (1.0 – 1.1) with oblique projections. For the tunnels placement analysis, the total radius difference between EOStm and Arthro-CT's femoral tunnel apertures was 0.8 mm (0.4–1.2) in AP-LAT and 0.6 mm (0.0–1.2) in oblique views. These femoral apertures positioning on EOStm models were within 4.3 mm (3.0–5.7) of their homologues on CT-Scan models, 4.6 mm (3.5–5.6) with the oblique views. Furthermore, 9.3o (7.2–11.4) of difference in direction between femoral tunnels from EOStm models and CT reconstructions is obtained with AP-LAT projections, 8.3o (6.6–10) with obliques views. Measures of these parameters were also performed at the tibia. According to the intra and inter-reproducibility analysis of our knee 3D models, EOStm biplanar X-Ray images prove to be fast, efficient and precise in the design of ACLR 3D models with respect to CT-Scan. Our results also propose the recourse of oblique stereoradiographic projections for the realization of knee 3D models. These models will be subjects of further analysis and will allow us eventually to propose a new frame of reference guiding the positioning of the tunnels in the ACLR

Aims. Little is known about the risk factors that predispose to a rupture of the posterior cruciate ligament (PCL). Identifying risk factors is the first step in trying to prevent a rupture of the PCL from occurring. The morphology of the knee in patients who rupture their PCL may differ from that of control patients. The purpose of this study was to identify any variations in bone morphology that are related to a PCL. Patients and Methods. We compared the anteroposterior (AP), lateral, and Rosenberg view radiographs of 94 patients with a ruptured PCL to a control group of 168 patients matched by age, sex, and body mass index (BMI), but with an intact PCL after a knee injury. Statistical shape modelling software was used to assess the shape of the knee and determine any difference in anatomical landmarks. Results. We found shape variants on the AP and Rosenberg view radiographs to be significantly different between patients who tore their PCL and those with an intact PCL after a knee injury. Overall, patients who ruptured their PCL have smaller intercondylar notches and smaller tibial eminences than control patients. Conclusion. This study shows that differences in the shape of the knee are associated with the presence of a PCL rupture after injury. A smaller and more sharply angled intercondylar notch and a more flattened tibial eminence are related to PCL rupture. This suggests that the morphology of the knee is a risk factor for sustaining a PCL rupture. Cite this article: Bone Joint J 2019;101-B:1058–1062

Aims

This study reports the results of 38 total hip arthroplasties (THAs) in 33 patients aged less than 50 years, using the JRI Furlong hydroxyapatite ceramic (HAC)-coated femoral component.

INTRODUCTION. It is generally accepted that strong hammering is necessary for the press fit fixation of a joint prosthesis. In this regard, large stress must remain within bone tissues for a long period. This residual stress is, however, some different from the feasible mechanical stimuli for bone tissues because that is stationary, continuous and directed from within outward unlike physiological conditions. The response on this residual stress, which may induce the disorder of the fixation of implant, has not been discussed, yet. In the present study, we designed an experimental method to exert a stationary load from inside of a femur of a rat by inserting a loop spring made from a super elastic wire of titanium alloy. Response of the femur was assessed by bone morphology mainly about the migration of the wire into the bone twelve weeks after the implantation. MATERIALS AND METHODS. We developed a method using a loop spring made of super elastic wire of titanium alloy, which can maintain sufficient magnitude of stress in a rat femur during the experimental period. The loop spring was fabricated with a wire of 0.4 mm diameter before the quenching process. Eleven Wistar rats of ten weeks old were used for the experiments. The loop spring was inserted the right femur, as shown in Figure 1. The left femur was remained intact. The compressive load was added from within outward of bone marrow when the spring was compressed with the insertion into a bone marrow of a rat femur, as shown in Figure 2. The average contact stress was calculated by dividing the elastic force by the spring and bone contact area. The contact stress was distributed from 62 to 94 MPa, which are sufficiently lower than the yield stress of cortical bone [1]. The assessment of bone morphology around the implanted loop spring was performed by micro-CT imaging after the twelve weeks of cage activity. RESULTS. To assess the migration of the spring in the femur, we measured the distance from the endocortical surface to the periphery of the spring, on the micro CT image, as shown in Figure 3. Apparent migration of the spring wire was observed on nine specimens among the eleven. Deep migration over 0.3 mm was observed at three cases. DISCUSSION. The migration of the wire in cortical bone was accompanied with the bone resorption on the surface of the wire toward outside. Therefore, the present findings suggest that stationary load at the implant surface can induce endosteal bone resorption and prosthesis dislocation and protrusion. CONCLUSION. We developed a method for configuring a stationary stress field in a rat femur using a loop spring with the super elasticity. It was found that stationary stress about 70 MPa can induce bone resorption

Objectives. An important measure for the diagnosis and monitoring of knee osteoarthritis is the minimum joint space width (mJSW). This requires accurate alignment of the x-ray beam with the tibial plateau, which may not be accomplished in practice. We investigate the feasibility of a new mJSW measurement method from stereo radiographs using 3D statistical shape models (SSM) and evaluate its sensitivity to changes in the mJSW and its robustness to variations in patient positioning and bone geometry. Materials and Methods. A validation study was performed using five cadaver specimens. The actual mJSW was varied and images were acquired with variation in the cadaver positioning. For comparison purposes, the mJSW was also assessed from plain radiographs. To study the influence of SSM model accuracy, the 3D mJSW measurement was repeated with models from the actual bones, obtained from CT scans. Results. The SSM-based measurement method was more robust (consistent output for a wide range of input data/consistent output under varying measurement circumstances) than the conventional 2D method, showing that the 3D reconstruction indeed reduces the influence of patient positioning. However, the SSM-based method showed comparable sensitivity to changes in the mJSW with respect to the conventional method. The CT-based measurement was more accurate than the SSM-based measurement (smallest detectable differences 0.55 mm versus 0. 82 mm, respectively). Conclusion. The proposed measurement method is not a substitute for the conventional 2D measurement due to limitations in the SSM model accuracy. However, further improvement of the model accuracy and optimisation technique can be obtained. Combined with the promising options for applications using quantitative information on bone morphology, SSM based 3D reconstructions of natural knees are attractive for further development. Cite this article: E. A. van IJsseldijk, E. R. Valstar, B. C. Stoel, R. G. H. H. Nelissen, N. Baka, R. van’t Klooster, B. L. Kaptein. Three dimensional measurement of minimum joint space width in the knee from stereo radiographs using statistical shape models. Bone Joint Res 2016;320–327. DOI: 10.1302/2046-3758.58.2000626

Aims

The aim of the study was to investigate whether the primary stability of press-fit acetabular components can be improved by altering the impaction procedure.

Aims

It is important to analyze objectively the hammering sound in cup press-fit technique in total hip arthroplasty (THA) in order to better understand the change of the sound during impaction. We hypothesized that a specific characteristic would present in a hammering sound with successful fixation. We designed the study to quantitatively investigate the acoustic characteristics during cementless cup impaction in THA.

Aims

The rationale for exacting restoration of skeletal anatomy after unstable ankle fracture is to improve outcomes by reducing complications from malunion; however, current definitions of malunion lack confirmatory clinical evidence.

Aims

It is important to analyze objectively the hammering sound in cup press-fit technique in total hip arthroplasty (THA) in order to better understand the change of the sound during impaction. We hypothesized that a specific characteristic would present in a hammering sound with successful fixation. We designed the study to quantitatively investigate the acoustic characteristics during cementless cup impaction in THA.

Aims

This study aimed to establish the optimal fixation methods for calcaneal tuberosity avulsion fractures with different fragment thicknesses in a porcine model.

Introduction:. Although cementless total hip arthroplasty (THA) is well accepted, the optimal femoral component design remains unknown. Among early complications, loosening and periprosthetic fracture persist and are related to implant design. The purpose of this study is to compare the anatomic fit and early subsidence of two different stem designs: a modern, short taper-wedge design and a traditional fit-and-fill design. Methods:. A retrospective cohort study of 129 consecutive cementless THAs using two different femoral stems was performed. A modern taper-wedge stem was used in 65 hips and a traditional proximal fit-and-fill stem was used in 64 hips. Radiographic analysis was performed at preoperative, immediate postoperative and 1-month postoperative intervals. The radiographic parameters of bone morphology via the canal-flare index, implant subsidence at 1 month, sagittal alignment, and the “anatomic fit” metrics of canal fill and associated gaps were measured and recorded. Results:. There were no differences between groups in patient demographics (p > 0.4), and in bone morphology via the canal-flare index (p = 0.6) with numbers available. The mean subsidence was less in the taper-wedge design at 0.27 mm compared to 1.1 mm in the fit-and-fill stem (p < 0.0001). Subsidence greater than 2 mm occurred in 26 of 64 fit-and-fill stems (41%) compared to 1 of 65 taper-wedge implants (1.5%). The percentage fill at all levels measured was greater in the taper-wedge design (p < 0.0001). The taper-wedge design was inserted a mean of 2.7° sagittal extension compared to 0.4° in the fit-and-fill design (p < 0.0001). Conclusion:. Despite being shorter in length, the taper-wedge design demonstrates greater axial stability and less subsidence compared to a traditional fit-and-fill stem. The optimized proximal femoral fit inherent in this anatomic-based taper-wedge design is likely responsible for the minimal subsidence. The clinical implication of greater extension in the sagittal plane is unknown and longer-term clinical follow up is warranted

Aims

This study investigated the effects of β-caryophyllene (BCP) on protecting bone from vitamin D deficiency in mice fed on a diet either lacking (D-) or containing (D+) vitamin D.

Pre-existing hip pathology such as femoroacetabular impingement is believed by some, to have a direct causal relationship with osteoarthritis of the hip. The strength of this relationship remains unknown. We investigate the prevalence of abnormal bone morphology in the symptomatic hip on the pre-operative anteroposterior pelvic radiograph of consecutive patients undergoing hip resurfacing. Rotated radiographs were excluded. One hundred patients, of mean age 53.5 years were included (range 33.4–71.4 years, 32% female). We examined the films for evidence of a cam-type impingement lesion (alpha angle >50.5°, a pistol grip, Pitt's pits, a medial hook, an os acetabuli and rim ossification), signs of acetabular retroversion or a pincer-type impingement lesion (crossover sign, posterior wall sign, ischial sign, coxa profunda, protrusio, coxa vara, Tonnis angle < 5°), and hip dysplasia (a Tonnis acetabular angle >14° and a lateral centre-edge angle of Wiberg <20°). Pre-existing radiographic signs of pathology were present in a large proportion of hips with low grade (Tonnis grade 1–2) arthritis. There is a group of patients who presented with more advanced osteoarthritis in which we suspect abnormal bone morphology to be a causative factor but, for example, neck osteophytes obscure the diagnosis of a primary cam lesion. Our findings corroborate those of Harris and Ganz. Impingement is radiographically detectable in a large proportion of patients who present with early arthritis of the hip, and therefore we agree that it is a likely pre-cursor for osteoarthritis. Treatments directed at reducing hip impingement may stifle the progression of osteoarthritis

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)

Aims

To develop an early implant instability murine model and explore the use of intermittent parathyroid hormone (iPTH) treatment for initially unstable implants.

Introduction:. Subchondral bone density (SBD) distribution is an important parameter regarding that may be important when considering implant stability. This parameter is a reflection of the loading experienced by the joint throughout the lifetime and may be useful in pre-surgical planning and implant design. Clinically, the question of the glenoid surface preparation for TSA/RSA remains controversial, despite numerous published studies on glenoid bone morphology. To address this question, there exists a need to develop a 3D quantitative method capable of analyzing the complex glenoid bone morphology at different depths from the surface. Computed tomographic osteoabsoptiomery (CT-OAM) evaluates SBD based on the Housfield Unit (HU) value of each pixel. In this pilot study, we aimed to analyze SBD distribution of the glenoid at different depths by means of CT-OAM in male TSA subjects. Materials and Methods:. A study group of twenty male TSA patients (61–69y.o) were included in this study. Each subject obtained a pre-operative CT scan following a standardized protocol on the same CT scanner (1.25 mm slice thickness). Resultant DICOM 2D images were processed in custom-written program (VC++) and the surface of every glenoid was manually traced from the axial slices. Care was taken during the manual tracing process to exclude osteophytes and cyst formations from the resultant surface. Values of HU at every selected pixel on the surface of the glenoid were recorded. Subsequently, the layer of pixels at a 0.5 mm distance from the previous surface was virtually scraped and the HU values of new layer of pixels were recorded. This routine was repeated up to a depth of 5 mm from the glenoid surface, taking measurements on 11 virtual 3D surfaces with a thickness of 0.5 mm. Mean SBD distribution was reported for each layer and differences were compared using ANOVA and Fisher's post-hoc test. Results:. Apparent differences in mean SBD distribution were identified at every measured depth from the glenoid surface (Fig. 1). Significant differences (Tab.1) were identified between the middle range of studied surfaces (2.5–4.5 mm) when compared to the superficial (0–1.5 mm, p < 0.0001) and deep layers (5 mm, p < 0.0001). The maximum mean value of HU (1635.9 ± 35.5) was measured at 3.5 mm depth and the minimum value of HU was measured on the surface of the glenoid (1445.8 ± 31.3). Discussion:. The stability of the glenoid component in TSA prostheses is highly dependent on the SBD distribution. Controversy among orthopaedic surgeons exists regarding the depth of reaming required to prepare an arthritic glenoid. Extensive reaming may lead to the violation of the support provided by the denser subchondral bone; however, optimal match between the bone and glenoid component undersurface is highly desirable. This study demonstrates that the density of the bone is sustained up to a depth of approximately 4.5 mm from the glenoid surface, suggesting that an increased reaming may be favorable without compromising bony support

Periprosthetic fractures around the femur during and after total hip arthroplasty (THA) remain a common mode of failure. It is important therefore to recognise those factors that place patients at increased risk for development of this complication. Prevention of this complication, always trumps treatment. Risk factors can be stratified into: 1. Patient related factors; 2. Host bone and anatomical considerations; 3. Procedural related factors; and 4. Implant related factors. Patient Factors. There are several patient related factors that place patients at risk for development of a periprosthetic fracture during and after total hip arthroplasty. Metabolic bone disease, particularly osteoporosis increases the risk of periprosthetic fracture. In addition, patients that smoke, have long term steroid use or disuse, osteopenia due to inactivity should be identified. A metabolic bone work up and evaluation of bone mineralization with a bone densitometry test can be helpful in identifying and implementing treatment prior to THA. Pre-operative Host Bone and Anatomic Considerations. In addition to metabolic bone disease the “shape of the bone” should be taken into consideration as well. Dorr has described three different types of bone morphology (Dorr A, B, C), each with unique characteristics of size and shape. It is important to recognise that not one single cementless implant may fit all bone types. The importance of templating a THA prior to surgery cannot be overstated. Stem morphology must be appropriately matched to patient anatomy. Today, several types of cementless stem designs exist with differing shape and areas of fixation. It is important to understand via pre-operative templating which stem works best in what situation. Procedural Related Factors. There has been a resurgence in interest in the varying surgical approaches to THA. While the validity and benefits of each surgical approach remains a point of debate, each approach carries with it its own set of risks. Several studies have demonstrated increased risk of periprosthetic fractures during THA with the use of the direct anterior approach. Risk factors for increased risk of periprosthetic fracture may include obesity, bone quality and stem design. Implant Related Factors. As mentioned there are several varying cementless implant shapes and sizes that can be utilised. There is no question that cementless fixation remains the most common mode of fixation in THA. However, one must not forget the role of cemented fixation in THA. Published results on long term fixation with cemented stems are comparable if not exceeding those of press fit fixation. In addition, the literature is clear that cemented fixation in the elderly hip fracture patient population is associated with a lower risk of periprosthetic fracture and lower risk of revision. The indication and principles of cemented stem fixation in THA should not be forgotten

Introduction. Glenoid loosening, still a main complication for shoulder arthroplasty, was suggested to be related implant design, surgical aspects, and also bone quality. However, typical studies of fixation do not account for heterogeneity in bone morphology and density which were suggested to affect fixation failure. In this study, a combination of cyclic rocking horse tests on cadaver specimens and microCT-based finite element (microFE) analysis of specimens of a wide range of bone density were used to evaluate the effects of periprosthetic bone quality on the risks of loosening of anatomical keeled or pegged glenoid implants. Methods. Six pairs of cadaveric scapulae, scanned with a quantitative computer tomography (QCT) scanner to calculate bone mineral density (BMD), were implanted with either cemented anatomical pegged or keeled glenoid components and tested under constant glenohumeral load while a humeral head component was moved cyclically in the inferior and superior directions. Edge displacements were measured after 1000, 4000 and 23000 test cycles, and tested for statistical differences with regards to changes or implant design. Relationships were established between edge displacements and QCT-based BMD below the implant. Four other specimens were scanned with high-resolution peripheral QCT (82µm) and implanted with the same 2 implants to generate virtual models. These were loaded with constant glenohumeral force, varying glenohumeral conformity and superior or inferior load shifts while internal stresses at the cement-bone and implant-cement interfaces were calculated and related to apparent bone density in the periprosthetic zone. Results. Mean displacements at the inferior and superior edges showed no statistical difference between keeled and pegged designs (p>0.05). Compression and distraction were however statistically different from the initial reference measurement at even 1000 and 4000 cycles for both implant designs (p<0.05). For both implant designs, superior and inferior distractions were generally highest at each measurement time in specimens where BMD below the lifting edge was lower, showing a trend of increased distraction with decreased BMD. Moreover, the microFE models predicted higher bone and cement stresses for specimens of lower apparent bone density. Finally, highest peak stresses were located at the cement-bone interface, which seemed the weaker part of the fixation. Discussion. With this combined experimental and numerical study, it was shown that implant distraction and stresses in the cement layer are greater in glenoids of lower bone density for both implant designs. This indicates that fixation failure will most likely occur in bone of lower density, and that fixation design itself may play a secondary role. These results have important impact for understanding the mechanisms of glenoid component failure, a common complication of total shoulder arthroplasty

Introduction. The origins of the uncemented tapered wedge hip stem design currently offered by several orthopaedic device companies can be linked back to the cemented Straight Mueller type stem design first used in 1977. The design, a wedge shape with a taper angle of 6 degrees, maintains a single medial curvature for all sizes and increases laterally in the width to accommodate different size femurs. Although evolutionary improvements have been made over the years the basic body geometry of the stem has stayed mainly unchanged with excellent clinical survivorship. Over the past decade, the demographics of hip replacement have changed, with a large increase in younger male patients in the age range of 40 to 60 years. In this study the femoral fit of a novel tapered stem, designed to fit a wide array of patient types, is compared to a standard predicate tapered stem design. Methods. A bone morphology study was performed on a patient population of 556 patients using three dimensional digital data from CT-scans. To characterize the fit of the stem designs we analyzed the ratio of a distal (60mm below lesser trochanter) and a proximal (10mm above lesser trochanter) cross section. The same measurements were taken with the standard tapered stem design and the novel tapered stem design, with a given constant implantation height of 20mm above the lesser trochanter. The fit of the stems was classified as Type 1, where there was both proximal and distal engagement, Type 2, proximal engagement only, Type 3, distal engagement only. The distal and proximal engagement, Type 1, was specified with a maximum engagement difference of 2mm proximal to distal. Results. The standard tapered stem showed a well balanced distal to proximal ratio in the median sizes. However, with increasing stem size the distal engagement increases. The novel tapered stem design showed a well balanced proximal to distal ratio throughout the complete size range. With respect to Type 3 fit classification the novel tapered stem design showed a reduced percentage of distal engagements (2.8%) compared to the predicate standard stem (17.2%). In the 40 to 60 year old male group the distal engagements for the standard stem increases (28.2%), whereas the distal engagements for the novel stem remains unchanged (1.3%). Discussion. The cementless, tapered wedge stem design is used in large numbers globally due to its ease of use and reproducibility. However, changing patient demographics and associated bone morphology represents a challenge for existing designs to achieve a proximal fit. The novel tapered stem design presented here was adapted to these influencing factors by optimizing the proximal to distal ratio with respect to the whole patient group resulting in a particularly marked improvement in proximal fit in the male 40–60 age group compared to predicate stem designs

Aims

The aim of this study was to determine whether total hip arthroplasty (THA) for chronic hip pain due to unilateral primary osteoarthritis (OA) has a beneficial effect on cognitive performance.

Aims. The aim of this study was to identify patient- and surgery-related risk factors for sustaining an early periprosthetic fracture following primary total hip arthroplasty (THA) performed using a double-tapered cementless femoral component (Bi-Metric femoral stem; Biomet Inc., Warsaw, Indiana). Patients and Methods. A total of 1598 consecutive hips, in 1441 patients receiving primary THA between January 2010 and June 2015, were retrospectively identified. Level of pre-operative osteoarthritis, femoral Dorr type and cortical index were recorded. Varus/valgus placement of the stem and canal fill ratio were recorded post-operatively. Periprosthetic fractures were identified and classified according to the Vancouver classification. Regression analysis was performed to identify risk factors for early periprosthetic fracture. Results. The mean follow-up was 713 days (1 to 2058). A total of 48 periprosthetic fractures (3.0%) were identified during the follow-up and median time until fracture was 16 days, (interquartile range 10 to 31.5). Patients with femoral Dorr type C had a 5.2 times increased risk of post-operative periprosthetic fracture compared with type B, while female patients had a near significant two times increased risk over time for post-operative fracture. Conclusion. Dorr type C is an independent risk factor for early periprosthetic fracture, following THA using a double tapered cementless stem such as the Bi-Metric. Surgeons should take bone morphology into consideration when planning for primary THA and consider using cemented femoral components in female patients with poor bone quality. Cite this article: Bone Joint J 2017;99-B:451–7

Cemented total hip replacements (THR) are widely used and are still recognized as the gold standard by which all other methods of hip replacements are compared. [. 1. ]. Long-term results of cemented total hip replacements show that the revision rate due to aseptic loosening could be as high as 75.4% [. 2. ]. Moreover, high stresses developed in the cement mantle of reconstructed hips can lead to premature failure of the constructs [. 3. ]. Surgical fixation techniques vary considerably [. 4. ]. The aim of this study was to investigate the performances of different surgical fixation techniques of hip implants for patients with different body mass indices, bone morphology and bone quality, using finite element (FE) methods. Anatomically correct reconstructed hemi-pelves were created, using CT-Scan data of the Visible Human Data set, downloaded to Mimics V8.1 software, where poly-lines of cancellous and cortical bones were created, and exported to I-Deas 11.0 FE package, where the econstructed hemi-pelvis was simulated. Accurate 3D model of the hemi-pelvis was scaled up and down to create hemi-pelves of acetabular sizes of the following diameters: 46 mm, 52 mm, and 58 mm. Following sensitivity analyses, element sizes ranging from 1–3 mm were used. Material properties of the bones, implants and cement were taken from literature [. 5. –. 7. ]. Bones of poor quality were simulated by a reduction in the elastic modulii of the cortical bone by 50%, the cancellous bone by 10 % and the subchondral bone by 50% [. 5. ]. The nodes at the sacro-iliac joint areas and the pubic support areas were fixed. A compressive force of 3 times body weight was simulated at the hip joint. The nodes between the cancellous and subchondral bones were merged. Contact elements were used at the subchondral bone and cement mantle interface and between the femoral head implant and acetabular component. Dynamic in vitro tests, simulating forces acting on a hip joint during a gait cycle, were carried out on reconstructed synthetic bones, positioned on an Instron 8874 hydraulic machine, to verify the FE models. The volume of cement stressed at different levels in groups of 0–1 MPa, 1–2 MPa and up to 11 and above MPa were calculated. Results of FE analyses showed that. an increase in the body mass index from 20 to 30 generated an increase in the tensile stress level in the cement mantle;. lower tensile and shear stresses developed in thicker cement mantles. For a 46mm acetabular size, peak tensile stresses decreased from 10.32MPa to 8.14MPa and peak shear stresses decreased from 5.36MPa to 3.67MPa when cement mantle thickness increased from 1mm to 4mm. A reduction in the bone quality would result in an increase of approximately 45% in the cement mantle stresses. Results of in-vitro tests show that an increase in the cement mantle thickness improved fixation, corroborating with the FE results. Performances of fixation techniques depend on the patient’s bone mass index, bone quality, bone morphology

A critical bone defect may be more frequently the consequence of a trauma, especially when a fracture occurs with wide exposure, but also of an infection, of a neoplasm or congenital deformities. This defect needs to be treated in order to restore the limb function. The treatments most commonly performed are represented by implantation of autologous or homologous bone, vascularized fibular grafting with autologous or use of external fixators; all these treatments are characterized by several limitations. Nowadays bone tissue engineering is looking forward new solutions: magnetic scaffolds have recently attracted significant attention. These scaffolds can improve bone formation by acting as a “fixed station” able to accumulate/release targeted growth factors and other soluble mediators in the defect area under the influence of an external magnetic field. Further, magnetic scaffolds are envisaged to improve implant fixation when compared to not-magnetic implants. We performed a series of experimental studies to evaluate bone regeneration in rabbit femoral condyle defect by implanting hydroxyapatite (HA), polycaprolactone (PCL) and collagen/HA hybrid scaffolds in combination with permanent magnets. Our results showed that ostetoconductive properties of the scaffolds are well preserved despite the presence of a magnetic component. Interestingly, we noticed that, using bio-resorbable collagen/HA magnetic scaffolds, under the effect of the static magnetic field generated by the permanent magnet, the reorganization of the magnetized collagen fibers produces a highly-peculiar bone pattern, with highly-interconnected trabeculae orthogonally oriented with respect to the magnetic field lines. Only partial healing of the defect was seen within the not magnetic control groups. Magnetic scaffolds developed open new perspectives on the possibility to exploiting magnetic forces to improve implant fixation, stimulate bone formation and control the bone morphology of regenerated bone by synergically combining static magnetic fields and magnetized biomaterials. Moreover magnetic forces can be exploited to guide targeted drug delivery of growth factors functionalized with nanoparticles

Bone loss continues to be a clinical and therapeutic problem. Bone reconstruction of osseous defects is a challenge after fracture and traumatic injuries, infections and tumors. The common objective is to regenerate bone morphology and function. Several techniques have been developed to promote bone formation, but the advent of new biomaterials allows us to take an entirely different approach to the treatment of bone voids. However, the use of bone substitutes should be considered carefully, as not all biomaterials behave the same way in humans. Calcium phosphate ceramics are osteoconductive materials that promote bone regeneration. The aim of this study was to retrospectively evaluate the clinical, radiographic and histological results of bone loss treated with an adjunct injectable biphasic bone substitute (BBS). We analysed the results of patients with fractures and a bone defect that were treated using an injectable BBS (calcium sulfate + hydroxyapatite) and those that were treated using the same bone substitute with antibiotic (gentamicin and/or vancomycin). Patient outcome was evaluated clinically and radiographically. In 9 cases samples for histological analysis were obtained. From July 2009 to May 2015, 126 cases (cs) on 111 patients (pt) (calcaneus: 53 cs, 47 pt; tibia: 32 cs, 30 pt; Femur: 14 cs, 9 pt, Elbow: 5 cs, 5 pz; humerus 2 cs, 2 pz; wrist 7cs, 7pz; forearm 6 cs, 4 pz; foot 2 cs, 2 pz; Phalanx 5 cs, 5 pt) were treated at our hospital with a BBS. The mean follow-up was 15 months, and bone ingrowth was assessed at 1, 2, 3, 6 and 12 months by X-ray. In all cases, the calcium sulphate phase of the BBS dissolved within 4–6 weeks, and new bone formation was observed at 6 months. On six patients large bone was treated with a revision surgery (autologous cancellous bone graft combined with BBS and antibiotic). No complications were reported. The 9 histological samples confirmed gradual remodeling and regeneration of the bone substitute over time. This biomaterial is versatile, offers a good augment for hardware and bone alignment, is biocompatible and osteoconductive, and has allowed us to manage significant bone voids. Histological analysis of samples from the tibia, ulna and calcaneus have confirmed the ability of this bone substitute to remodel into bone

Biomechanical interpretations of bone adaptation in biological reconstructions following bone tumors would be crucial for orthopedic oncologists, particularly if based on quantitative observations. This would help to plan for surgical treatments, rehabilitative programs and communication with the patients. In particular, outcomes of the Capanna technique, which combines bone allograft and vascularized fibula autograft, lead to stable and durable reconstructions [1, 2], and different remodeling patterns have been described [3] as a response to mechanical loading. However, there are several events that are not understood and require a biomechanical interpretation, as the evolution patterns can evolve towards conditions that threaten the strength of the reconstruction. We aimed to (i) analyze the biomechanical adaptation of a femoral reconstruction after Ewing sarcoma, in terms of morphological and densitometric evolution of bone from CT data, internal loads acting on the bone during movement, mechanical competence of the reconstruction, and (ii) relate in-progress bone resorption to the mechanical stimulus induced by different motor activities. Eight CT datasets of a patient (8 yrs at surgery using the Capanna technique) during 76-month follow-up were available. The evolution of bone morphology, density and moments of inertia was quantified. At the last control, the patient underwent gait analysis (walking, chair rise/sit, stair ascent/descent, squat). We created a multiscale musculoskeletal and finite element model from CT scans and motion analysis data at the end of follow-up, using state-of-the-art modeling workflows [4, 5], to analyze muscle and joint loads, and to compare the mechanical competence of the reconstructed bone with the contralateral limb, in the current real condition and in a possible revision surgery that removed proximal screws. Although there were no reconstruction complications and osteo-fusion with intense remodeling between allograft and autograft was shown, there was a progressive decrease in allograft cortical thickness and density. There were strategies of muscle coordination that led to differences in joint loads between limbs more marked in more demanding motor activities, and generally larger in the contralateral limb. The operated femur presented a markedly low ratio of physiological strain due to load-sharing with the metal implant, particularly in the lateral aspect. A possible revision surgery removing the three most proximal screws would help restore a physiological strain configuration, while the safety of the reconstruction would not be threatened. We suggest that bone resorption is related to load-sharing and to the internal forces exerted during movement, and the mechanical stimulus should be improved by adopting modifications in the surgical treatment and by promoting physical therapy aimed at specific muscle strengthening

There is a critical need for safe innovation in total joint replacements to address the demands of an ageing yet increasingly active population. The development of robust implant designs requires consideration of uncertainties including patient related factors such as bone morphology but also activity related loads and the variability in the surgical procedure itself. Here we present an integrated framework considering these sources of variability and its application to assess the performance of the femoral component of a total hip replacement (THR). The framework offers four key features. To consider variability in bone properties, an automated workflow for establishing statistical shape and intensity models (SSIM) was developed. Here, the inherent relationship between shape and bone density is captured and new meshes of the target bone structures are generated with specific morphology and density distributions. The second key feature is a virtual implantation capability including implant positioning, and bone resection. Implant positioning is performed using automatically identified bone features and flexibly defined rules reflecting surgical variability. Bone resection is performed according to manufacturer guidelines. Virtual implantation then occurs through Boolean operations to remove bone elements contained within the implant's volume. The third feature is the automatic application of loads at muscle attachment points or on the joint contact surfaces defined on the SSIM. The magnitude and orientation of the forces are derived from models of similar morphology for a range of activities from a database of musculoskeletal (MS) loads. The connection to this MS loading model allows the intricate link between morphology and muscle forces to be captured. Importantly, this model of the internal forces provides access to the spectrum of loading conditions across a patient population rather than just typical or average values. The final feature is an environment that allows finite element simulations to be run to assess the mechanics of the bone-implant construct and extract results for e.g. bone strains, interface mechanics and implant stresses. Results are automatically processed and mapped in an anatomically consistent manner and can be further exploited to establish surrogate models for efficient subsequent design optimization. To demonstrate the capability of the framework, it has been applied to the femoral component of a THR. An SSIM was created from 102 segmented femurs capturing the heterogeneous bone density distributions. Cementless femoral stems were positioned such that for the optimal implantation the proximal shaft axis of the femurs coincided with the distal stem axis and the position of the native femoral head centre was restored. Here, the resection did not affect the greater trochanter and the implantations were clinically acceptable for 10000 virtual implantations performed to simulate variability in patient morphology and surgical variation. The MS database was established from musculoskeletal analyses run for a cohort of 17 THR subjects obtaining over 100,000 individual samples of 3D muscle and joint forces. An initial analysis of the mechanical performance in 7 bone-implant constructs showed levels of bone strains and implant stresses in general agreement with the literature

Introduction. Range of motion (ROM) simulation of the hip is useful to understand the maximum impingement free ROM in total hip arthroplasty (THA). In spite of a complex multi-directional movement of the hip in daily life, most of the previous reports have evaluated the ROM only in specific directions such as flexion-extension, abduction-adduction, and internal - external rotation at 0° or 90° of hip flexion. Therefore, we developed ROM simulation software (THA analyzer) to measure impingement free ROM in any positions of the hip. Recent designs of the hip implants give a wider ROM by increasing the head diameter and then, bone to bone impingement can be a ROM limit factor particularly in a combination of deep flexion, adduction and internal rotation of the hip. Therefore, the purpose of this study were to observe an individual variation in the pattern of the bone impingement ROM in normal hip bone models using this software, to classify the bone impingement ROM mapping types and to clarify the factors affecting the bone impingement type. Methods. The subjects were 15 normal hips of 15 patients. Three dimensional surface models of the pelvis and femur were reconstructed from Computer tomography (CT) images. We performed virtual hip implantation with the same center of rotation, femoral offset, and leg length as the original hips. Subsequently, we created the ROM mapping until bone impingement using THA analyzer. We measured the following factors influenced on the bone impingement map patterns; the neck shaft angle, the femoral offset, femoral anteversion, pelvic tilt, acetabular anteversion, sharp angle, and CE angle. These factors were compared between the two groups. Statistical analysis was performed with Mann-Whitney U test, and statistical significance was set at P<0.05. Results. According to the borderline of ROM at the flexion-internal rotation corner on the bone impingement map, the hips were classified into two groups; group-A showed more than 45° of the borderline slope at the flexion-internal rotation corner and the remaining hips were group-B. (Fig.1). There were 7 hips in group-A and 8 hips in group-B. Femoral offset was 36.8±2.2 mm in group-A and 30±2.7 mm in group-B. Femoral anteversion was 32±6.4° in-group A and 43 ±4.8° in group-B. There were statistically significant differences in the femoral offset and femoral anteversion between the groups. There were no significant differences in the other factors. Discussion. The results of this study showed various ROM map patterns even in normal hips and we classified them into two groups. An increased femoral offset or a decreased femoral anteversion revealed an early impinge in internal rotation. ROM until bone impingement is affected by the individual bone morphology. However, it is not easy to evaluate bony ROM in complex hip positions. THA analyzer shows the impingement position visually on the map and it is easy to understand the hip positions with reduced ROMs. Conclusion. There are two patterns on the bony ROM map in normal hips, and an early impinge in internal rotation occurred by increasing the femoral offset or decreasing the femoral anteversion. For figures/tables, please contact authors directly.

Osteoarthritic (OA) changes to the bone morphology of the proximal tibia may exhibit load transfer patterns during total knee arthroplasty not predicted in models based on normal tibias. Prior work highlighted increased bone density in transverse sections of OA knees in the proximal-most 10mm tibial cancellous bone. Little is known about coronal plane differences, which could help inform load transfer from the tibial plateau to the tibial metaphysis. Therefore, we compared the cancellous bone density in OA and cadaveric (non-OA) subjects along a common coronal plane. This study included nine OA patients (five women, average age 59.1 ± 9.4 years) and 18 cadaver subjects (four women, average age 39.5 ± 14.4 years). Patients (eight with medial OA and one with lateral OA) received pre-operative CT scans as standard-of-care for a unicompartmental knee replacement. Cadavers were scanned at our institution and had no history of OA which was confirmed by gross inspection during dissection. 3D reconstructions of each proximal tibia were made and an ellipse was drawn on the medial and lateral plateau using a previously published method. A coronal section (Figure 1) to standardize the cohort was created using the medial ellipse center, lateral ellipse center, and the tibial shaft center 71.5mm from the tibial spine. On this section, profile lines were drawn from the medial and lateral ellipse centers, with data collected from the first subchondral bone pixel to a length of 20mm. The Hounsfield Units (HU) along each profile line was recorded for each tibia; a representative graphical distribution is shown in Figure 2. The Area Under the Curve (AUC) was calculated for the medial and lateral sides, which loosely described the stiffness profile through the region of interest. To determine differences between the medial and lateral subchondral bone density, the ratio AUC[medial] / AUC[lateral] was compared between the OA and cadaver cohorts using a two-sample t-test. Data from the sole lateral OA patient was mirror-imaged to be included in the OA cohort. The majority of the OA patients appeared to have higher subchondral bone density on the affected side. Figure 3 compares the medial and laterals sides of each group using the AUC ratio method described above. For the cadaver group the AUC was 1.2 +/− 0.22, with a median of 1.1 [0.9 1.6], smaller than the mean AUC for the OA group, which was 1.4 +/− 0.39, with a median of 1.6 [0.93 2.1]. The p-value was 0.06. The increased density observed in OA patients is consistent with asymmetric loading towards the affected plateau, resulting in localized remodeling of cancellous bone from the epiphysis to metaphysis. From the coronal plane, bone was often observed in OA patients bridging the medial plateau to the metaphyseal cortex. Although the cadaver subjects were normal from history and gross inspection, some subjects exhibited early bone density changes consistent with OA. Future work looks to review more OA scans, extend the work to the distal femur, and convert the HU values to bone elastic moduli for use in finite element modelling

Background. Constitutional knee varus increases the risk of medial OA disease due to increase in the knee adduction moment and shifting of the mechanical axis medially. Hueter-Volkmann's law states that the amount of load experienced by the growth plate during development influences the bone morphology. For this reason, heightened sports activity during growth is associated with constitutional varus due to added knee adduction moment. In early OA, X-rays often show a flattened medial femoral condyle extension facet (EF). However, it is unknown whether this is a result of osteoarthritic wear, creep deformation over decades of use, or an outcome of Hueter-Volkmann's law during development. A larger and flattened medial EF can bear more weight, due to increased load distribution. However, a flattened EF may also extrude the meniscus, leading meniscus degeneration and joint failure. Therefore, this study aimed to investigate whether varus knees have flattened medial EFs of both femur and tibia in a cohort of patients with no signs yet of bony attrition. Methods. Segmentation and morphology analysis was conducted using Materialise software (version 8.0, Materialise Inc., Belgium). This study excluded knees with bony attrition of the EFs based on Ahlbäck criteria, intraoperative findings, and operation notes history. Standard reference frames were used for both the femur and tibia to ensure reliable and repeatable measurements. The hip-knee-angle (HKA) angle defined varus or valgus knee alignment. Femur: The femoral EFs and flexion facets (FFs) had best-fit spheres fitted with 6 repetitions. (Fig1). Tibia: The slopes of the antero-medial medial tibial plateau were approximated using lines. (fig2). Results. 72 knees met the inclusion and exclusion criteria. The average age was 59 ± 11 years. The youngest was 31 and the oldest 84 years. Thirty-three were male and 39 were female. There was good intra- and inter-observer reliability for EF sphere fitting. Femur: The results demonstrated that the medial femoral condyle EF is flattened in knees with constitutional varus, as measured by the Sphere Ratios between the medial and lateral EF (varus versus straight: p = 0.006), and in the scaled values for the medial EF sphere radius (varus versus straight: p = 0.005). There was a statistically significant, moderate and positive correlation between the medial femoral EF radius, and the medial femoral EF-FF AP offset. (fig3). Tibia: There was a statistically significant difference between the steepness of the slopes of the medial tibial plateau EF in varus and valgus knees, suggesting varus knees have a less concave (flatter) medial EF. (fig3). Conclusions. In comparison to straight knees, varus knees have flattened medial EFs in both femur and tibia. As this was the case in knees with no evidence of bony attrition, this could mean flattened medial EFs may be a result of medial physis inhibition during development, due to Hueter-Volkmann's law. Flattened medial EFs may increase load distribution in the medial compartment, but could also be a potential aetiology in primary knee OA due to over extrusion of the medial meniscus and edge loading

Constitutional knee varus increases the risk of medial OA disease due to increase in the knee adduction moment and shifting of the mechanical axis medially. Hueter-Volkmann’s law states that the amount of load experienced by the growth plate during development influences the bone morphology. For this reason, heightened sports activity during growth is associated with constitutional varus due to added knee adduction moment. In early OA, X-rays often show a flattened medial femoral condyle extension facet (EF). However, it is unknown whether this is a result of osteoarthritic wear, creep deformation over decades of use, or an outcome of Hueter-Volkmann’s law during development. A larger and flattened medial EF can bear more weight, due to increased load distribution. However, a flattened EF may also extrude the meniscus, leading meniscus degeneration and joint failure. Therefore, this study aimed to investigate whether varus knees have flattened medial EFs of both femur and tibia in a cohort of patients with no signs yet of bony attrition. Segmentation and morphology analysis was conducted using Materialise software (version 8.0, Materialise Inc., Belgium). This study excluded knees with bony attrition of the EFs based on Ahlbäck criteria, intraoperative findings, and operation notes history. Standard reference frames were used for both the femur and tibia to ensure reliable and repeatable measurements. The hip-knee-angle (HKA) angle defined varus or valgus knee alignment. Femur: The femoral EFs and flexion facets (FFs) had best-fit spheres fitted with 6 repetitions. Tibia: The slopes of the antero-medial medial tibial plateau were approximated using lines. Results 72 knees met the inclusion and exclusion criteria. The average age was 59 ± 11 years. The youngest was 31 and the oldest 84 years. Thirty-three were male and 39 were female. There was good intra- and inter-observer reliability for EF sphere fitting. Femur: The results demonstrated that the medial femoral condyle EF is flattened in knees with constitutional varus, as measured by the Sphere Ratios between the medial and lateral EF (varus versus straight: p = 0.006), and in the scaled values for the medial EF sphere radius (varus versus straight: p = 0.005). There was a statistically significant, moderate and positive correlation between the medial femoral EF radius, and the medial femoral EF-FF AP offset. Tibia: There was a statistically significant difference between the steepness of the slopes of the medial tibial plateau EF in varus and valgus knees, suggesting varus knees have a less concave (flatter) medial EF. Conclusions In comparison to straight knees, varus knees have flattened medial EFs in both femur and tibia. As this was the case in knees with no evidence of bony attrition, this could mean flattened medial EFs may be a result of medial physis inhibition during development, due to Hueter-Volkmann’s law. Flattened medial EFs may increase load distribution in the medial compartment, but could also be a potential aetiology in primary knee OA due to over extrusion of the medial meniscus and edge loading

Deformity can be associated with significant bone loss, ligament laxity, soft-tissue contractures, distortion of long bone morphology, and extra-articular deformity. Correction of varus, valgus, or flexion deformity requires soft tissue releases in conjunction with bone cuts perpendicular to the long axes of the femur and tibia. Cruciate-retaining or -substituting implants can be used based on surgeon preference if the ligaments are well balanced. However, in presence of severe deformity, additional measures may be warranted to achieve alignment and balance. TKA then becomes a more challenging proposition and may require the surgeon to perform extensive releases, adjunct osteotomies and deploy more constrained implants. Merely enhancing constraint in the implant however without attending to releases and extra-articular correction may not suffice. Certain myths in deformity correction will be presented. Technical tips with regard to preoperative planning, i.e., whether intra-articular correction alone will suffice or extra-articular correction is required, will be highlighted. Surgical principles and methods of performing large releases, reduction osteotomy, lateral epicondylar sliding osteotomy, sliding medial condylar osteotomy, and closed wedge diaphyseal/metaphyseal osteotomy concomitantly with TKA will be illustrated with examples. Technique of performing TKA with concomitant extra-articular deformity resulting from coronal bowing of femoral or tibial diaphysis, malunited fractures, prior osteotomies, and stress fractures will be presented. The techniques reported can successfully restore alignment, pain-free motion, and stability without necessarily using more constrained implants

Introduction. Migration of the trial femoral head is a rarely occurring complication of total hip arthroplasty (THA) performed using the anterolateral approach (ALA). This migration of the trial femoral head under the rectus femoris is extremely risky because of the anatomical situation. Analyzing the morphological character of a case of migration may help us to avoid this risk. Objective. We analyzed the three-dimensional bone morphology using computed tomography (CT) scan images to investigate the physiological characteristics of five migration cases. Methods. We examined 108 patients (21 men, 87 women, 113 hips) who underwent THA via the ALA. The average patient age was 62.9 (range: 30–87) years and average body mass index was 24.4 (range: 18.0–36.0) kg/m2. The exclusion criteria were dysplastic coxarthroses greater than Crowe type II, previous fractures, previous hip operations, and muscle disease. Three-dimensional models of the pelvis and femur were made using ZedHip software® (Lexi, Tokyo, Japan). The anterior superior iliac spine on the affected side (A) and contralateral side (A’), anterior inferior iliac spine (I), and greater trochanter tip (G) were noted in these models. The distances A–I, I–G, and A–G and the angle formed by AA’ and AI were measured (Figure 1, 2). Each hip was classified by the presence (group M) or absence (group N) of migration during surgery. A Fisher's exact probability test, Student's t-test, and Welch's t-test were used to compare the two groups, and p-values less than 0.05 were considered significant. Results. In 5 of the 113 hips, the trial femoral heads migrated under the rectus femoris and were removed safely. No significant differences were found between the gender, height, weight, or BMI of the groups. The average A–I distance was 32.3±3.0 mm (mean±SD) in group M and 39.4±10.4 mm in group N; I–G was 52.2±8.2 mm in group M and 59.7±10.6 mm in group N; and A–G was 64.3±10.3 mm in group M and 76.3±12.3 mm in group N. The average angle formed by AA’ and AI was 50.5±5.8°. Significant differences between the two groups were found for the distances A–I and A–G. Conclusions. In 4.4% of cases, the trial femoral heads migrated under the rectus femoris, which creates a risk for serious complications because major nerve and blood vessels are located nearby. The tendency for migration was expected to be related to the balance between soft tissues. In this study, we found that migration tends to occur in patients with shorter distances between A and I, and A and G. The trial head should be dislocated more carefully in those patients

Deformity can be associated with significant bone loss, ligament laxity, soft-tissue contractures, distortion of long bone morphology, and extra-articular deformity. Correction of varus, valgus, or flexion deformity requires soft tissue releases in conjunction with bone cuts perpendicular to the long axes of the femur and tibia. Cruciate-retaining or -substituting implants can be used based on surgeon preference if the ligaments are well balanced. However, in presence of severe deformity, additional measures may be warranted to achieve alignment and balance. TKA then becomes a more challenging proposition and may require the surgeon to perform extensive releases, adjunct osteotomies and deploy more constrained implants. Merely enhancing constraint in the implant, however, without attending to releases and extra-articular correction may not suffice. Pre-operative planning, i.e., whether intra-articular correction alone will suffice or extra-articular correction is required, will be highlighted. Surgical principles and methods of performing large releases, reduction osteotomy, lateral epicondylar sliding osteotomy, sliding medial condylar osteotomy, and closed wedge diaphyseal/metaphyseal osteotomy concomitantly with TKA will be illustrated with examples. Results of a large series of TKA with extra-articular deformity resulting from coronal bowing of femoral or tibial diaphysis, malunited fractures, prior osteotomies, and stress fractures will be presented. The techniques reported can successfully restore alignment, pain-free motion, and stability without necessarily using more constrained implants

Aims

Aseptic loosening is a leading cause of uncemented arthroplasty failure, often accompanied by fibrotic tissue at the bone-implant interface. A biological target, neutrophil extracellular traps (NETs), was investigated as a crucial connection between the innate immune system’s response to injury, fibrotic tissue development, and proper bone healing. Prevalence of NETs in peri-implant fibrotic tissue from aseptic loosening patients was assessed. A murine model of osseointegration failure was used to test the hypothesis that inhibition (through Pad4^-/- mice that display defects in peptidyl arginine deiminase 4 (PAD4), an essential protein required for NETs) or resolution (via DNase 1 treatment, an enzyme that degrades the cytotoxic DNA matrix) of NETs can prevent osseointegration failure and formation of peri-implant fibrotic tissue.