Objectives. The role of mechanical stress and transforming growth factor beta 1 (TGF-β1) is important in the initiation and progression of osteoarthritis (OA). However, the underlying molecular mechanisms are not clearly known. Methods. In this study, TGF-β1 from osteoclasts and knee joints were analyzed using a co-cultured cell model and an OA rat model, respectively. Five patients with a femoral neck fracture (four female and one male, mean 73.4 years (68 to 79)) were recruited between January 2015 and December 2015. Results showed that TGF-β1 was significantly upregulated in osteoclasts by cyclic loading in a time- and dose-dependent mode. The osteoclasts were subjected to cyclic loading before being co-cultured with chondrocytes for 24 hours. Results. A significant decrease in the survival rate of co-cultured chondrocytes was found. Terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labelling (TUNEL) assay demonstrated that mechanical stress-induced apoptosis occurred significantly in co-cultured chondrocytes but administration of the TGF-β1 receptor inhibitor, SB-505124, can significantly reverse these effects. Abdominal administration of SB-505124 can attenuate markedly articular cartilage degradation in OA rats. Conclusion. Mechanical stress-induced overexpression of TGF-β1 from osteoclasts is responsible for chondrocyte apoptosis and cartilage degeneration in OA. Administration of a TGF-β1 inhibitor can inhibit articular cartilage degradation. Cite this article: R-K. Zhang, G-W. Li, C. Zeng, C-X. Lin, L-S. Huang, G-X. Huang, C. Zhao, S-Y. Feng, H. Fang. Mechanical stress contributes to osteoarthritis development through the activation of transforming growth factor beta 1 (TGF-β1). Bone Joint Res 2018;7:587–594. DOI: 10.1302/2046-3758.711.BJR-2018-0057.R1

Wear is an important factor in the long term success of total knee arthroplasty. Therefore, wear testing methods and machines become a standard in research and implant development. These methods are based on two simulation concepts which are defined in standards ISO 14243-1 and 14243-3. The difference in both concepts is the control mode. One is force controlled while the other has a displacement controlled concept. The aim of this study was to compare the mechanical stresses within the different ISO concepts. Furthermore the force controlled ISO was updated in the year 2009 and should be compared with the older which was developed in 2001. A finite element model based on the different ISO standards was developed. A validation calculated with kinematic profile data of the same implant (Aesculap, Columbus CR) in an experimental wear test setup (Endolap GmbH) was done. Based on this model all three different ISO standards were calculated and analysed. Validation results showed Pearson correlation for anterior posterior movement of 0.3 and for internal external rotation 0.9. Two main pressure maximums were present in ISO 14243-1:2001 (force controlled) with 17.9 MPa and 13.5 MPa for 13 % and 48 % of the gait cycle. In contrast ISO 14243-1:2009 (force controlled) showed three pressure maximums of 18.5 MPa (13 % of gait cycle), 16.4 MPa (48 % of gait cycle) and 13.2 MPa (75 % of gait cycle). The displacement controlled ISO (14243-3:2014) showed two pressure maximums of 16.0 MPa (13 % of gait cycle) and 17.2 MPa (48 % of gait cycle). The adapted force controlled ISO of the year 2009 showed higher mechanical stress during gait cycle which also might lead to higher wear rates. The displacement controlled ISO leads to higher mechanical stress because of the constraint at the end of the stance phase of the gait cycle. Future studies should analyse different inlay designs within these ISO standards

In this study we used subject-specific finite element analysis to investigate the mechanical effects of rotational acetabular osteotomy (RAO) on the hip joint and analysed the correlation between various radiological measurements and mechanical stress in the hip joint. We evaluated 13 hips in 12 patients (two men and ten women, mean age at surgery 32.0 years; 19 to 46) with developmental dysplasia of the hip (DDH) who were treated by RAO. Subject-specific finite element models were constructed from CT data. The centre–edge (CE) angle, acetabular head index (AHI), acetabular angle and acetabular roof angle (ARA) were measured on anteroposterior pelvic radiographs taken before and after RAO. The relationship between equivalent stress in the hip joint and radiological measurements was analysed. The equivalent stress in the acetabulum decreased from 4.1 MPa (2.7 to 6.5) pre-operatively to 2.8 MPa (1.8 to 3.6) post-operatively (p < 0.01). There was a moderate correlation between equivalent stress in the acetabulum and the radiological measurements: CE angle (R = –0.645, p < 0.01); AHI (R = –0.603, p < 0.01); acetabular angle (R = 0.484, p = 0.02); and ARA (R = 0.572, p < 0.01). The equivalent stress in the acetabulum of patients with DDH decreased after RAO. Correction of the CE angle, AHI and ARA was considered to be important in reducing the mechanical stress in the hip joint. Cite this article: Bone Joint J 2015;97-B:492–7

The meniscus is a fibrocartilaginous tissue that plays an important role in controlling the complex biomechanics of the knee. Many histological and mechanical studies about meniscal attachment have been carried out, and medial meniscus (MM) root repair is recommended to prevent subsequent cartilage degeneration following MM posterior root tear. However, there are only few studies about the differences between meniscus root and horn cells. The goal of this study was to clarify the differences between these two cells. Tissue samples were obtained from the medial knee compartments of 10 patients with osteoarthritis who underwent total knee arthroplasty. Morphology, distribution, and proliferation of MM root and horn cells, as well as gene and protein expression levels of Sry-type HMG box (SOX) 9 and type II collagen (COL2A1) were determined after cyclic tensile strain (CTS) treatment. Horn cells had a triangular morphology, whereas root cells were fibroblast-like. The number of horn cells positive for SOX9 and COL2A1 was considerably higher than that of root cells. Although root and horn cells showed similar levels of proliferation after 48, 72, or 96 h of culture, more horn cells than root cells were lost following 2-h CTS (5% and 10% strain). SOX9 and COL2A1 mRNA expression levels were significantly enhanced in horn cells compared with those in root cells after 2- and 4-h CTS (5%) treatment. This study demonstrates that MM root and horn cells have distinct characteristics and show different cellular phenotypes. Our results suggest that physiological tensile strain is important for activating extracellular matrix production in horn cells. Restoring physiological mechanical stress may be useful for promoting healing of the MM posterior horn

Objectives. In total hip arthroplasty (THA), the cementless, tapered-wedge stem design contributes to achieving initial stability and providing optimal load transfer in the proximal femur. However, loading conditions on the femur following THA are also influenced by femoral structure. Therefore, we determined the effects of tapered-wedge stems on the load distribution of the femur using subject-specific finite element models of femurs with various canal shapes. Patients and Methods. We studied 20 femurs, including seven champagne flute-type femurs, five stovepipe-type femurs, and eight intermediate-type femurs, in patients who had undergone cementless THA using the Accolade TMZF stem at our institution. Subject–specific finite element (FE) models of pre- and post-operative femurs with stems were constructed and used to perform FE analyses (FEAs) to simulate single-leg stance. FEA predictions were compared with changes in bone mineral density (BMD) measured for each patient during the first post-operative year. Results. Stovepipe models implanted with large-size stems had significantly lower equivalent stress on the proximal-medial area of the femur compared with champagne-flute and intermediate models, with a significant loss of BMD in the corresponding area at one year post-operatively. Conclusions. The stovepipe femurs required a large-size stem to obtain an optimal fit of the stem. The FEA result and post-operative BMD change of the femur suggest that the combination of a large-size Accolade TMZF stem and stovepipe femur may be associated with proximal stress shielding. Cite this article: M. Oba, Y. Inaba, N. Kobayashi, H. Ike, T. Tezuka, T. Saito. Effect of femoral canal shape on mechanical stress distribution and adaptive bone remodelling around a cementless tapered-wedge stem. Bone Joint Res 2016;5:362–369. DOI: 10.1302/2046-3758.59.2000525

1. When cortisone is administered to rabbits there is early rapid resorption of bone and a partial inhibition of new bone formation. After a few days the effect becomes less obvious, so that, if observations are made at later stages, the results may be ascribed then to simple inhibition of bone growth. 2. The effect of mechanical stress has been studied in the jaw. When tooth movement is induced mechanically there is, in ordinary circumstances, a resorption of bone on the side to which the tooth is moving (the "pressure" side) and bone formation on the opposite side (the "tension" side). After administration of cortisone there is increased resorption on the "pressure" side and there is greater resorption of connective tissues here. On the "tension" side there is resorption and inhibition of bone formation. 3. In the areas of stress, when cortisone is administered, collagen fibres are no longer in apposition, being separated by spaces presumably filled with altered ground substance; this kind of change may be responsible for many of the observed phenomena. 4. A.C.T.H. does not produce a demonstrable resorptive effect on bone or connective tissue until it has been administered for periods longer than is required for cortisone (three weeks); even then the change is not pronounced. 5. In the guinea pig there is slight delay in bone formation with large doses of both cortisone and A.C.T.H., but no significant bone resorption occurs

Aims. The presence of facet tropism has been correlated with an elevated susceptibility to lumbar disc pathology. Our objective was to evaluate the impact of facet tropism on chronic lumbosacral discogenic pain through the analysis of clinical data and finite element modelling (FEM). Methods. Retrospective analysis was conducted on clinical data, with a specific focus on the spinal units displaying facet tropism, utilizing FEM analysis for motion simulation. We studied 318 intervertebral levels in 156 patients who had undergone provocation discography. Significant predictors of clinical findings were identified by univariate and multivariate analyses. Loading conditions were applied in FEM simulations to mimic biomechanical effects on intervertebral discs, focusing on maximal displacement and intradiscal pressures, gauged through alterations in disc morphology and physical stress. Results. A total of 144 discs were categorized as ‘positive’ and 174 discs as ‘negative’ by the results of provocation discography. The presence of defined facet tropism (OR 3.451, 95% CI 1.944 to 6.126) and higher Adams classification (OR 2.172, 95% CI 1.523 to 3.097) were important predictive parameters for discography-‘positive’ discs. FEM simulations showcased uneven stress distribution and significant disc displacement in tropism-affected discs, where loading exacerbated stress on facets with greater angles. During varied positions, notably increased stress and displacement were observed in discs with tropism compared to those with normal facet structure. Conclusion. Our findings indicate that facet tropism can contribute to disc herniation and changes in intradiscal pressure, potentially exacerbating disc degeneration due to altered force distribution and increased mechanical stress. Cite this article: Bone Joint Res 2024;13(9):452–461

Military personnel operating on high speed marine craft are exposed to Whole-Body Vibration (WBV). Additionally planing craft operate at speeds with minimal contact of the hull with warer making the crew vulnerable to mechanical shock. An association between Low Back Pain (LBP) and exposure to WBV has been extensively reported in civilian literature. LBP is reported by military personnel operating on planing craft leading to downgrades and potential discharge. There is a clear need to understand the impact prolonged exposure has on our population operating these craft. We performed a bibliographical search of the PubMed database for records using a combination of keywords. Abstracts were screened for relevance and references cited in retrieved papers reviewed. There is no consensus in the literature on the potentially pivotal pathological process behind the association. Evidence from professional driving suggests current safe operating exposure levels require review to protect against long-term damage however with little evidence concerning the unique environment in which boats crews operate, the parity of these environments require investigation to allow direct comparison. Due to the prevalence of LBP in this population a need exists to establish the pathological process and add to the evidence base driving safe operating exposure levels.

A recently developed parametric geometrical finite element model (p-FEM) was adapted to the specific hip geometric measurements of a group of patients with slipped capital femoral epiphysis (SCFE). The objective was to analyze the stress distribution in the growth plate of these patients and to evaluate differences for those patients who developed bilateral disease.

Different geometric parameters were measured in the healthy proximal femur of 18 adolescents (mean age, 12,1 yr) with unilateral SCFE and in 23 adolescents matched in age without hip disease (control group). Five patients developed SCFE in the contralateral side during follow-up. Different geometric measurements were taken from hip conventional X-ray studies. The p-FEM of the proximal femur permits modifications of different geometrical parameters, therefore the X-ray measurements taken from each patient were applied to the model obtaining a subject-specific model for each case. In each model, different mechanical situations such as walking, stairs climbing and sitting were simulated by applying loads on the femoral head corresponding to each own weight. The risk for growth plate failure was estimated by the Tresca, von Misses and Rankine stresses.

In summary, the models shows important differences between the stresses computed at the healthy femurs of patients with unilateral SCFE and femurs that further underwent bilateral SCFE. So, the 95% confidence interval of the percentage of volume of the growth plate subjected to stresses higher than 2MPa was almost similar for the control group and patients with unilateral SCFE. However, those patients who developed bilateral disease had statistically significant large physeal areas with more than 2.0 MPa (p< 0.005). Stresses were also strongly dependent on the geometry of the proximal femur, especially on the posterior sloping angle of the physis and the physeal sloping angle.

In spite of simplifications of the developed p-FEM, this tool has been able to show the influence of femur geometry in growth plate stresses and to predict the sites where growth plate starts to fail.

Introduction. Mechanical loading has been hypothesized to play an important role in the development, remodeling and in diseases of many skeletal tissues, including cartilage. In order to study the metabolic response of cartilage to physical forces, in vitro systems have often been used because of the precise control with which mechanical loads can be applied. We developed a new mechanical loading system, in which we were able to load the intact femoral condyle in order to preserve the native cartilage/subchondral bone structure. This system represents a more ‚in vivo‘ situation than cartilage explants or chondrocyte cell culture systems. Our approach focused on changes in mRNA expression of type II collagen, type VI collagen, and aggrecan in loaded versus adjacent unloaded cartilage in order to analyse the early response of chondrocytes to well-defined mechanical stresses. Methods. Femoral condyles were obtained from two-year-old cows. The integrity of the cartilage surface was controlled by staining with safranin O. The femoral condyles were compressed in an Instron 8501 material testing machine. Cyclic compression pressure was applied for 2000 cycles in a sinusoidal waveform of 0. 5 Hz-frequency with a peak stress of 0. 2 to12. 5 MPa. Following loading, full depth cartilage sections were cut out and one half immediately frozen in liquid nitrogen for RNA isolation and the other half soaked in 4% paraformaldehyde for paraffin embedding. As control, the adjacent unloaded cartilage was collected and treated in the same way. Total RNA was isolated and changes in mRNA expression were quantitated by competitive quantitative PCR, using an internal standard of a C-terminal truncated version of the corresponding genes. The PCR-reactions were separated by agarose gel electrophoresis and amplified fragments quantified using video-densitometry analysis. The results were expressed as the ratio of mRNA from loaded to unloaded cartilage. Results. Cyclic compression with peak stresses of 12. 5, 6. 3, 2. 5 and 0. 6 MPa lead to a two-fold decrease in the mRNA expression of type II collagen and aggrecan and a threefold decrease of type VI collagen, in consideration of the intra-assay variability of about 30%. Compression with peak stresses of 0. 3 and 0. 2 MPa lead to a three-fold increase of the mRNA expression of type II collagen, a four-fold increase of aggrecan and a slight decrease of type VI collagen. Low compression strength leads to an increase of the mRNA expression of the major components of cartilage, type II collagen and aggrecan, whereas high loading leads to a decrease of the mRNA expression. Conclusion. The results show that our system can be used to analyze early responses of chondrocytes to well-defined mechanical stresses in an intact cartilage/bone-system and therefore will enable us to investigate the role of physiological and non-physiological high loading on the induction of cartilage degradation and regeneration in joint trauma and osteoarthritis. Since the cartilage/bone samples are incubated in medium during the experiment, this system will also offer us the opportunity to investigate additives to the medium as potential pharmacological therapeutics in osteoarthritis

Abstract. Source of Study: London, United Kingdom. This intervention study was conducted to assess two developing protocols for quadriceps and hamstring rehabilitation: Blood Flow Restriction (BFR) and Neuromuscular Electrical Stimulation Training (NMES). BFR involves the application of an external compression cuff to the proximal thigh. In NMES training a portable electrical stimulation unit is connected to the limb via 4 electrodes. In both training modalities, following device application, a standardised set of exercises were performed by all participants. BFR and NMES have been developed to assist with rehabilitation following lower limb trauma and surgery. They offer an alternative for individuals who are unable to tolerate the high mechanical stresses associated with traditional rehabilitation programmes. The use of BFR and NMES in this study was compared across a total of 20 participants. Following allocation into one of the training programmes, the individuals completed training programmes across a 4-week period. Post-intervention outcomes were assessed using Surface Electromyography (EMG) which recorded EMG amplitude values for the following muscles: Vastus Medialis, Vastus Lateralis, Rectus Femoris and Semitendinosus. Increased Semitendinosus muscle activation was observed post intervention in both BFR and NMES training groups. Statistically significant differences between the two groups was not identified. Larger scale randomised-controlled trials are recommended to further assess for possible treatment effects in these promising training modalities

Low back pain is the single most common cause for disability in individuals aged 45 years or younger, it carries tremendous weight in socioeconomic considerations. Degenerative aging of the structural components of the spine can be associated with genetic aspects, lifetime of tissue exposure to mechanical stress & loads and environmental factors. Mechanical consequences of the disc degenerative include loss of disc height, segment instability and increase the load on facets joints. All these can lead to degenerative changes and osteophytes that can narrow the spinal canal. Surgery is indicated in patients with spinal stenosis who have intractable pain, altered quality of life, substantially diminished functional capacity, failed non-surgical treatment and are not candidates for non-surgical treatment. The aim was to determine the reasons for refusal of surgery in patients with established degenerative lumber spine pathology eligible for surgery. All patients meeting the study criteria, patients older than 18 years, patients with both clinical and radiological established symptomatic degenerative lumbar spine pathology and patients eligible for surgery but refusing it were recruited. Questionnaire used to investigate reasons why they are refusing surgery. Results 59 were recruited, fifty-one (86.4 %) females and eight (13.6 %) males. Twenty (33.8 %) were between the age of 51 and 60 years, followed by nineteen (32.2 %) between 61 and 70 years, and fourteen (23.7 %) between 71 and 80 years. 43 (72 %) patients had lumber spondylosis complicated by lumber spine stenosis, followed by nine (15.2 %) with lumbar spine spondylolisthesis and four (6.7 %) had adjacent level disease. 28 (47.4 %) were scared of surgery, fifteen (25.4 %) claimed that they are too old for surgery and nine (15.2 %) were not ready. Findings from this study outlined that patients lack information about the spinal surgery. Patients education about spine surgery is needed

Objective. Excessive mechanical stress on synovial joints causes osteoarthritis (OA) and results in the production of prostaglandin E2 (PGE2), a key molecule in arthritis, by synovial fibroblasts. However, the relationship between arthritis-related molecules and mechanical stress is still unclear. The purpose of this study was to examine the synovial fibroblast response to cyclic mechanical stress using an in vitro osteoarthritis model. Method. Human synovial fibroblasts were cultured on collagen scaffolds to produce three-dimensional constructs. A cyclic compressive loading of 40 kPa at 0.5 Hz was applied to the constructs, with or without the administration of a cyclooxygenase-2 (COX-2) selective inhibitor or dexamethasone, and then the concentrations of PGE2, interleukin-1β (IL-1β), tumour necrosis factor-α (TNF-α), IL-6, IL-8 and COX-2 were measured. Results. The concentrations of PGE2, IL-6 and IL-8 in the loaded samples were significantly higher than those of unloaded samples; however, the concentrations of IL-1β and TNF-α were the same as the unloaded samples. After the administration of a COX-2 selective inhibitor, the increased concentration of PGE2 by cyclic compressive loading was impeded, but the concentrations of IL-6 and IL-8 remained high. With dexamethasone, upregulation of PGE2, IL-6 and IL-8 was suppressed. Conclusion. These results could be useful in revealing the molecular mechanism of mechanical stress in vivo for a better understanding of the pathology and therapy of OA. Cite this article: Bone Joint Res 2014;3:280–8

Varus malalignment increases the susceptibility of cartilage to mechanical overloading, which stimulates catabolic metabolism to break down the extracellular matrix and lead to osteoarthritis (OA). The altered mechanical axis from the hip, knee to ankle leads to knee joint pain and ensuing cartilage wear and deterioration, which impact millions of the aged population. Stabilization of the remaining damaged cartilage, and prevention of further deterioration, could provide immense clinical utility and prolong joint function. Our previous work showed that high tibial osteotomy (HTO) could shift the mechanical stress from an imbalanced status to a neutral alignment. However, the underlying mechanisms of endogenous cartilage stabilization after HTO remain unclear. We hypothesize that cartilage-resident mesenchymal stem cells (MSCs) dampen damaged cartilage injury and promote endogenous repair in a varus malaligned knee. The goal of this study is to further examine whether HTO-mediated off-loading would affect human cartilage-resident MSCs' anabolic and catabolic metabolism. This study was approved by IACUC at Xi'an Jiaotong University. Patients with medial compartment OA (52.75±6.85 yrs, left knee 18, right knee 20) underwent open-wedge HTO by the same surgeons at one single academic sports medicine center. Clinical data was documented by the Epic HIS between the dates of April 2019 and April 2022 and radiographic images were collected with a minimum of 12 months of follow-up. Medial compartment OA with/without medial meniscus injury patients with unilateral Kellgren /Lawrence grade 3–4 was confirmed by X-ray. All incisions of the lower extremity healed well after the HTO operation without incision infection. Joint space width (JSW) was measured by uploading to ImageJ software. The Knee injury and Osteoarthritis Outcome Score (KOOS) toolkit was applied to assess the pain level. Outerbridge scores were obtained from a second-look arthroscopic examination. RNA was extracted to quantify catabolic targets and pro-inflammatory genes (QiaGen). Student's t test for two group comparisons and ANOVA analysis for differences between more than 2 groups were utilized. To understand the role of mechanical loading-induced cartilage repair, we measured the serial changes of joint space width (JSW) after HTO for assessing the state of the cartilage stabilization. Our data showed that HTO increased the JSW, decreased the VAS score and improved the KOOS score significantly. We further scored cartilage lesion severity using the Outerbridge classification under a second-look arthroscopic examination while removing the HTO plate. It showed the cartilage lesion area decreased significantly, the full thickness of cartilage increased and mechanical strength was better compared to the pre-HTO baseline. HTO dampened medial tibiofemoral cartilage degeneration and accelerate cartilage repair from Outerbridge grade 2 to 3 to Outerbridge 0 to 1 compared to untreated varus OA. It suggested that physical loading was involved in HTO-induced cartilage regeneration. Given that HTO surgery increases joint space width and creates a physical loading environment, we hypothesize that HTO could increase cartilage composition and collagen accumulation. Consistent with our observation, a group of cartilage-resident MSCs was identified. Our data further showed decreased expression of RUNX2, COL10 and increased SOX9 in MSCs at the RNA level, indicating that catabolic activities were halted during mechanical off-loading. To understand the role of cartilage-resident MSCs in cartilage repair in a biophysical environment, we investigated the differentiation potential of MSCs under 3-dimensional mechanical loading conditions. The physical loading inhibited catabolic markers (IL-1 and IL-6) and increased anabolic markers (SOX9, COL2). Knee-preserved HTO intervention alleviates varus malalignment-related knee joint pain, improves daily and recreation function, and repairs degenerated cartilage of medial compartment OA. The off-loading effect of HTO may allow the mechanoregulation of cartilage repair through the differentiation of endogenous cartilage-derived MSCs

Hip instability is one of the most common complications after total hip arthroplasty (THA). Among the possible techniques to treat and prevent hip dislocation, the use of constrained liners is a well-established option. However, there is concern regarding the longevity of these devices due to higher mechanical stress caused by limited hip motion. The primary aim of this paper is to analyze the failure rate of a specific constrained liner in a series of consecutive cases. This study is a retrospective consecutive case series of THA and revision hip arthroplasty (RHA), in which a constrained polyethylene insert was used to treat or prevent hip instability. Patients were divided in 3 different groups (THA for hip fracture, THA for osteoarthrosis, and RHA). Survival analysis was performed for failure, defined as at least one episode of hip dislocation or radiographical signs of acetabular loosening. Logistical regression was used to investigate risk factors for failure. A total of 103 patients were included in the study. Fourteen patients (13,6%) were THA for osteoarthrosis, 60 (58,3%) were THA for hip fracture, and 29(28,2%) were RHA. The median follow-up was 28 months (ranging 12 − 173 months). Failure occurred in 4 cases (3,9%) comprehending 2 dislocations (1,9%) and 2 early acetabular loosening (1,9%). Amongst the groups, there were no cases of failures in the THA due to osteoarthrosis, in the THA for hip fracture there were 3 cases (5%) and in the RHA one case (3,4%). Failure-free survival was not statistically different between groups. There were no risk factors statistically related to failure. The use of constrained acetabular insert to prevent or treat instability achieved an adequate survival time with a low rate of complications. Further studies are necessary to corroborate our findings

Biomechanical analysis is important to evaluate the effect of orthopaedic surgeries. CT-image based finite element method (CT-FEM) is one of the most important techniques in the computational biomechanics field. We have been applied CT-FEM to evaluate resorptive bone remodeling, secondary to stress shielding, after total hip arthroplasty (THA). We compared the equivalent stress and strain energy density to postoperative BMD (bone mineral density) change in the femur after THA, and a significant correlation was observed between the rate of changes in BMD after THA and equivalent stress. For periacetabular osteotomy cases, we investigated mechanical stress in the hip joint before and after surgery. Mechanical stress in the hip joint decreased significantly after osteotomy and correlated with the degree of the acetabular coverage. For arthroscopic osteochondroplasty cases, we examined mechanical strength of the proximal femur after cam resection using CT-FEM. The results suggested that both the depth and area of the resection at the distal part of femoral head-neck junction correlated strongly with fracture risk after osteochondroplasty. This talk consists of our results of clinical application studies using CT-FEM, and importance of application of CT-FEM to biomechanical studies to assess the effect of orthopaedic surgeries

Introduction and Objective. Anterior cruciate ligament reconstruction (ACLR) with tendon autografts is the “gold standard” technique for surgical treatment of ACL injuries. Common tendon graft choices include patellar tendon (PT), semitendinosus/gracilis “hamstring” tendon (HT), or quadriceps tendon (QT). Healing of the graft after ACLR may be affected by graft type since the tissue is subjected to mechanical stresses during post-operative rehabilitation that play important roles in graft integration, remodeling and maturation. Abnormal mechanical loading can result in high inflammatory and degradative processes and altered extracellular matrix (ECM) synthesis and remodeling, potentially modifying tissue structure, composition, and function. Because of the importance of load and ligamentization for tendon autografts, this study was designed to compare the differential inflammatory and degradative metabolic responses to loading by three tendon types commonly used for autograft ACL reconstruction. Materials and Methods. With IRB approval (IRB # 2009879) and informed patient consent, portions of 9 QT, 7 PT and 6 HT were recovered at the time of standard of care ACLR surgeries. Tissues were minced and digested in 0.2 mg/ml collagenase solution for two hours and were then cultured in 10% FBS at 5% CO. 2. , 37°C, and 95% humidity. Once confluent, cells were plated in Collagen Type I-coated BioFlex® plates (1 × 10. 5. cells/well) and cultured for 2 days prior to the application of strain. Then, media was changed to supplemented DMEM with 2% FBS for the application of strain. Fibroblasts were subjected to continuous mechanical stimulation (2-s strain and 10-s relaxation at a 0.5 Hz frequency) at three different elongation strains (mechanical stress deprivation-0%, physiologic strain-4%, and supraphysiological strain-10%). 9. for 6 days using the Flexcell FX-4000T strain system. Media was tested for inflammatory biomarkers (PGE2, IL-8, Gro-α, and MCP-1) and degradation biomarkers (GAG content, MMP-1, MMP-2, MMP-3, TIMP-1, and TIMP-2). Significant (p<0.05) difference between graft sources were assessed with Kruskal-Wallis test and post-hoc analysis. Results are reported as median± interquartile range (IQR). Results. Differences in Inflammation-Related Biomarker Production (Figure 1): The production of PGE2 was significantly lower by HT fibroblasts compared to both QT and PT fibroblasts at all timepoints and strain levels. The production of Gro-α was significantly lower by HT fibroblasts compared to QT at all time points and strain levels, and significantly lower than PT on day 3 at 0% strain, and all strain levels on day 6. The production of IL-8 by PT fibroblasts was significantly lower than QT and HT fibroblast on day 3 at 10% strain. Differences in Degradation-Related Biomarker Production (Figure 2): The production of GAG by HT fibroblasts was significantly higher compared to both QT and PT fibroblasts on day 6 at 0% strain. The production of MMP-1 by the QT fibroblasts was significantly higher compared to HT fibroblasts on day 3 of culture at all strain levels, and in the 0% and 10% strain levels on day 6 of culture. The production of MMP-1 by the QT fibroblasts was significantly higher compared to PT fibroblasts at in the 0% and 4% strain groups on day 3 of culture. The production of TIMP-1 by the HT fibroblasts was significantly lower compared to PT fibroblasts on day 3 of culture. Conclusions. The results of this study identify potentially clinically relevant difference in the metabolic responses of tendon graft fibroblasts to strain, suggesting a lower inflammatory response by hamstring tendon fibroblasts and higher degradative response by quadriceps tendon fibroblasts. These responses may influence ACL autograft healing as well as inflammatory mediators of pain in the knee after reconstruction, which may have implications regarding graft choice and design of postoperative rehabilitation protocols for optimizing outcomes for patients undergoing ACL reconstruction. For any figures or tables, please contact the authors directly

Introduction. The low-contact stress (LCS) knee prosthesis is a mobile-bearing design with modifications to the tibial component that allow for meniscal-bearing (MB) or rotating-platform (RP). The MB design had nonconstrained anteroposterior and rotational movement, and the RP design has only nonconstrained rotational movement. The anterior soft tissues, including patellar tendon (PT), prevent anterior dislocation of the MB. The PT may consistently be exposed to overstressing. Therefore, we hypothesized that the PT thickness and width in MB prosthesis revealed more morphological changes than those of RP prosthesis due to degeneration of the PT induced by much mechanical stress of the MB movement. To confirm this hypothesis, we analyze the PT thickness and width induced by mobile-bearing inserts. Objectives. Sixty LCS prostheses in 30 patients were analyzed. The average follow-up time was 61 months. MB prosthesis was used on one side of the knee and RP prosthesis was used on the contralateral side of the knee. All patients were chosen from group with no clinical complication, and all had achieved passive full extension and at least 90°of flexion. The average Hospital for Special Surgery Score was 94.6 ± 2.7. Methods. We measured the thickness and width of PT at joint line level, which were confirmed by sagittal section using ultrasound in knee extension between MB and RP design prosthesis. Results. The mean thickness of PT was 4.7 mm (1.2) with MB and 4.7 mm (1.0) with RP design prosthesis. The mean width of PT was 30.6 mm (3.2) with MB and 31.3 mm (3.5) with RP design prosthesis. No significant differences were found between both groups. Conclusion. The current results showed that the PT thickness and width in MB prosthesis did not reveal more morphological changes than those of RP prosthesis due to degeneration of the PT induced by much mechanical stress of the MB movement. The possible reasons are the following: (1) We did not remove infra-patellar fat pad, which might play shock absorber of mechanical stress from MB, and prevent from significant degeneration of PT, (2) MB inserts did not stimulate the middle of the PT directly, unlike LCS A/P-Glide inserts, and might come into contact with the both ends of the PT and (3) MB inserts did not move so as to cause degeneration in the PT

Background. Medical applications of nanotechnology are promising because it allows the surface of biomaterial to be tailored to optimise the interfacial interaction between the biomaterial and its biological environment. Such interfaces are of interest in the domain of orthopaedic surgery as they could have anti-bacterial functions or could be used as drug delivery systems. The development of orthopaedics is moving towards better integration of biology in implants and surgical techniques, but the mechanical properties of implanted materials are still important for orthopaedic applications. During clinical implantation, implants are subjected to large mechanical stresses. In order to obtain the best performance during clinical use, mechanical properties of implants need to be investigated and understood. Method. We modified the topography of commercial titanium orthopaedic screws using electrochemical anodization in a 0.4 wt% hydrofluoric acid solution to produce titanium dioxide nanotube layers. The morphology of the nanotube layers were characterised using scanning electron microscopy. The mechanical properties of the nanotube layers were investigated by screwing and unscrewing an anodized screw into several different types of human bone while the torsional force applied to the screwdriver was measured using a torque screwdriver. The range of torsional force applied to the screwdriver was between 5 and 80 cN·m. Independent assessment of the mechanical properties of the same surfaces was performed on simple anodized titanium foils using a triboindenter. Results. The fabricated nanotube layers can resist mechanical stresses close to those found in clinical situations. Conclusion. The mechanical characteristics of this surface treatment appear to be sufficiently robust to withstand realistic clinical operating conditions that our in vitro experiments were designed to simulate. These results show that the nanotube layers remain intact after the implantation process. This may allow for the exciting possibility of nanotubes being loaded with molecules. Level of Evidence. II

Introduction: Two second generation highly crosslinked UHMWPEs have been cleared by the FDA for clinical use in the United States: sequentially crosslinked UHMWPE (X3™ UHMWPE, Stryker Inc., Mahwah, NJ, USA) and α-tocopherol stabilized UHMWPE (E-Poly™ UHMWPE, Biomet, Inc., Warsaw, IN, USA). Both have been shown to be oxidatively stable under standardized aging methods (ASTM F2003); however, these conventional aging methods did not consider the effect of mechanical loading on the oxidative behavior of the materials. By coupling the adverse effects of thermal aging and mechanical stress, we sought to investigate if either material was prone to environmental stress cracking (ESC). We hypothesize that the residual free radicals remaining in sequentially crosslinked PE will lead to oxidative degradation in this adverse test; furthermore, we hypothesized that the α-tocopherol infused in E-Poly™ will continue to protect the highly crosslinked PE even under such unfavorable conditions. Materials and Methods: Three materials were tested:. Conventional: UHMWPE gamma sterilized in inert,. SXL: sequentially irradiated and annealed UHMWPE irradiated to a cumulative dose of 100kGy (33 kGy irradiation + 8 hour annealing in air, repeated 3 times) and gas plasma sterilized, and. E-Poly: UHMWPE irradiated to 100kGy, stabilized with α-tocopherol, and gamma sterilized in inert. Four specimens from each group were subjected to a reciprocating mechanical stress of 10 MPa at a frequency of 0.5 Hz in an environmental chamber maintained at 80°C. Control samples were placed in the chamber but not subjected to cyclic mechanical stress. When a visible crack was observed on a sample’s surface or when a sample fractured, it and its corresponding control sample were analyzed by FTIR to quantify oxidation. Results: All conventional specimens, half (2 of 4) of the SXL specimens, and none of the E-Poly specimens failed prior to the completion of 1,530,000 cycles (5 weeks of testing at 0.5 Hz). Cyclic loading had an adverse effect on the oxidation of the conventional and the SXL groups; the peak oxidation levels were higher in the cyclically loaded samples as compared to the control samples removed at the same time which were not loaded, likely due to an increase in chain scission induced by the mechanical load. The E-Poly specimens did not fail during the 5 weeks of testing, and FTIR did not reveal detectable oxidation in either control or loaded samples. Discusssion and conclusion: Though the sequential processing of SXL creates a material with a lower free radical content compared to once-annealed material, it still yields a material prone to oxidation under extreme conditions, raising questions about its long-term oxidative stability. E-Poly™, protected by α-tocopherol, continues to exhibit high oxidation resistance even under adverse conditions

The structure and extracellular matrix composition of the interface are complex and allow for a gradual mechanical stress transfer between tendons and bone. In this study, biphasic silk fibroin scaffolds designed to mimic the gradient in collagen molecule alignment present at the interface. The scaffolds had two different pore alignments: anisotropic at the tendon side and isotropic at the bone side. Total porosity ranged from 50–80% and the majority of pores were <100–300 µm. Young's modulus varied from 689–1322 kPa. In addition, human adMSC were cultured on the scaffolds to evaluate the effect of pore morphology on cell proliferation and gene expression. Biphasic scaffolds supported cell attachment and influenced cytoskeleton organization depending on pore alignment. In addition, the gene expression of tendon, enthesis and cartilage markers significantly changed in each region of the scaffolds. We functionalized those scaffolds with heparin and explored their ability to deliver TGF-β2 and GDF5. TGF-β2 and pore anisotropy synergistically increased the expression of tendon/ligament markers and collagen I protein content. The combined delivery of TGF-β2 and GDF5 enhanced the expression of cartilage markers and collagen II protein content on substrates with isotropic porosity, whereas enthesis markers were enhanced in areas of mixed anisotropic/isotropic porosity

In recent years, novel therapies for intervertebral disc (IVD) regeneration have been developed that are based on the delivery of cells, biomaterials or bioactive molecules. The efficacy of these biological therapies depends on the type and degree of IVD degeneration. Whole organ culture bioreactors provide an attractive platform for pre-clinical testing of IVD therapeutics, since the cells are maintained within their native extracellular matrix, and the endplate remains intact to fulfil its function. Moreover, defined regimes of mechanical stress are applied to the IVD, representing either physiological or degenerative, detrimental loading. Different degrees of degeneration can be induced by high load, low nutrition, enzyme injection, and/or mechanical damage; while recent organ culture models also implement an inflammatory component. Using whole organ culture models, we found that mesenchymal stem cell injection into nucleotomized IVDs had an anabolic effect on the IVD cells. Furthermore, hyaluronan hydrogels were beneficial for cell delivery and mechanical support. We also found that anti-inflammatory treatment could partially prevent the induction of cytokines in an inflammatory model. However, chemokine delivery did not induce a significant repair response in an annulus fibrosus defect. In line with 3R principles, relevant ex-vivo models are essential to reliably test biological IVD treatments

Previous studies have shown that low-density, rod-like trabecular structures develop in regions of low stress, whereas high-density, plate-like trabecular structures are found in regions of high stress. This phenomenon suggests that there may be a close relationship between the type of trabecular structure and mechanical properties. In this study, 160 cancellous bone specimens were produced from 40 normal human tibiae aged from 16 to 85 years at post-mortem. The specimens underwent micro-CT and the microstructural properties were calculated using unbiased three-dimensional methods. The specimens were tested to determine the mechanical properties and the physical/compositional properties were evaluated. The type of structure together with anisotropy correlated well with Young’s modulus of human tibial cancellous bone. The plate-like structure reflected high mechanical stress and the rod-like structure low mechanical stress. There was a strong correlation between the type of trabecular structure and the bone-volume fraction. The most effective microstructural properties for predicting the mechanical properties of cancellous bone seem to differ with age

[Introduction]. It is said that the mechanical stress is a main factor to advance degenerative osteoarthritis. Therefore, to keep the joint stability is very important to minimize mechanical stress. Methods to evaluate bone-related factor are almost established, especially in hip dysplasia. On the other hand, it is unclear how much each soft tissue contribute to the joint stability. In this study we evaluated the soft tissue contribution for hip joint stability by distraction testing using MTS machine. [Materials & Methods]. We used seven fresh frozen hips from four donors, whose race was all western and reason of death was not related to hip disease in all cases. Average age of them at death was 83 years old. Mean average weight and height were each 52 kg and 162 cm. We retrieved hemi pelvis and proximal femur which kept hip joint intact. We removed all other soft tissue except iliofemoral ligament, pubofemoral ligament, ischiofemoral ligament and capsule. The hemi-pelvis mounted on angular-changeable fixator and the femur fixed to MTS machine (Figure 1). XY sliding table was used to minimize the horizontal direction stress during distraction. MTS machine was set to pull the femur parallel to its shaft by 0.4 mm/sec velocity against pelvis after 10N compression and to keep 5 mm distance for 5 seconds. We measured the force at 1 mm, 3 mm, 5 mm distraction. In case the joint was dislocated, the maximum force just before dislocation was recorded. The specimen was changed its posture as neutral (flexion0° abduction0° external rotation0°), flexion (flexion60° abduction0° external rotation0°), abduction (flexion0° abduction30° external rotation0°) and extension (extension20° abduction0° external rotation0°). Each position was measured in six sequential conditions, which are normal, Incised iliofemoral ligament, Circumferentially incised capsule, resected capsule, labral radial tear and resected labrum. After measurement joint surface was observed to evaluate the joint condition. [Results]. We excluded the one specimen two hips by osteoarthritic change of joint surface. The average force needed for 5 mm distraction in normal condition at neutral, flexion, extension and abduction posture was each 95.8N, 52.7N, 162.8N and 94.2N. The force was biggest in extension posture and smallest in flexion posture. The force was statistically reduced from 95.8N to 31.5N after iliofemoral ligament incision in neutral position. The force was also statistically reduced from 145.6N to 31.9N after Circumferential capsule incision in extension posture (Figure 2). In all posture, traction force was reduced after capslotomy and all hip dislocated in all cases. [Discussion]. We could conclude that iliofemoral ligament works much in neutral and extension posture, and capsule helps its work in extension more than in neutral posture. We have reported the zona orbicularis will be important as joint stabilizer before. Capsule including zona orbicularis makes hip joint more stable in any posture because dislocation happened easily after capsule resection in all posture

Introduction: In a photoelasticimetric model Ondrouch suggested a correlation between stress in arthritic joints, microfractures and bone cysts. Other authors believe in a causative role of access of joint ßuid to bone in periarticular osteolysis. In our opinion mechanical stress induced by cartilage defects induces microfractures followed by cystic bone degradation. Materials and Methods: A þnite element analysis using the well described parameters for cancellous and cortical bone as also cartilage was performed. Several typical situations of localized and general cartilage pathologies were calculated in a schematic hip joint situation. Results: A signiþcant impact of cartilage defect size and resulting stress distribution correlating well to cystic lesions of patients with osteoarthritis of the hip could be shown. In localized cartilage defects max. stress was calculated at the rims of the lesions in the subchondral bone. Assuming a situation with an allready preformed cyst either in the acetabulum or the femoral head, further enlargement of the cyst will appear due to a maximal stress at the rims of the lesions. Femoral lesions have a comparable small tendency to grow, thereas acetabular lesions will grow rapidly. Discussion and Conclusion: These þndings þt very well with the clinical observations. Cartilage lesions inducing microfractures by mechanical stress may be able to explain the process of subchondral cyst formation. A process involving osteoclasts and myxomatous cells within the bone marrow seems to be a subsequent mechanism of remodelling and formation of myxomatous cyst content

Aims

Circular RNA (circRNA) is involved in the regulation of articular cartilage degeneration induced by inflammatory factors or oxidative stress. In a previous study, we found that the expression of circStrn3 was significantly reduced in chondrocytes of osteoarthritis (OA) patients and OA mice. Therefore, the aim of this paper was to explore the role and mechanism of circStrn3 in osteoarthritis.

The amount of bone loss due to implant failure, loosening, or osteolysis can vary greatly and can have a major impact on reconstructive options during revision total knee arthroplasty (TKA). Massive bone loss can threaten ligamentous attachments in the vicinity of the knee and may require use of components with additional constraint to compensate for associated ligamentous instability. Classification of bone defects can be helpful in predicting the complexity of the reconstruction required and in facilitating preoperative planning and implant selection. One very helpful classification of bone loss associated with TKA is the Anderson Orthopaedic Research Institute (AORI) Bone Defect Classification System as it provides the means to compare the location and extent of femoral and tibial bone loss encountered during revision surgery. In general, the higher grade defects (Type IIb or III) on both the femoral and tibial sides are more likely to require stemmed components, and may require the use of either structural graft or large augments to restore support for currently available modular revision components. Custom prostheses were previously utilised for massive defects of this sort, but more recently have been supplanted by revision TKA component systems with or without special metal augments or structural allograft. Options for bone defect management are: 1) Fill with cement; 2) Fill with cement supplemented by screws or K-wires; 3) Morselised bone grafting (for smaller, especially contained cavitary defects); 4) Small segment structural bone graft; 5) Impaction grafting; 6) Porous metal cones or sleeves 7) Massive structural allograft-prosthetic composites; 8) Custom implants. Of these, use of uncemented highly porous metal metaphyseal cones in combination with an initial cemented or partially cemented implant has been shown to provide versatile and highly durable results for a range of bone defects including those previously requiring structural bone graft. The hybrid fixation combination of both cement and cementless fixation of an individual tibial or femoral component has emerged as a frequent and often preferred technique. Initial secure and motionless interfaces are provided by the cemented portions of the construct, while subsequent bone ingrowth to the cementless porous metal portions is the key to long term stable fixation. As bone grows into the porous portions there is off loading and protection of the cemented interfaces from mechanical stresses. While maximizing support on intact host bone has been a longstanding fundamental principle of revision arthroplasty, this is facilitated by the use of metaphyseal cones or sleeves in combination with initial fixation into the adjacent diaphysis. Preoperative planning is facilitated by good quality radiographs, supplemented on occasion by additional imaging such as CT. Fluoroscopically controlled x-ray views may assist in diagnosing the loose implant by better revealing the interface between the implant and bone and can facilitate accurate delineation of the extent of bone deficiency present. Part of the preoperative plan is to ensure adequate range and variety of implant choices and bone graft resources for the planned reconstruction allowing for the potential for unexpected intraoperative findings such as occult fracture through deficient periprosthetic bone. While massive bone loss may compromise ligamentous attachment to bone, in the majority of reconstructions, the degree of revision implant constraint needed for proper balancing and restoration of stability is independent of the bone defect. Thus, some knees with minimal bone deficiency may require increased constraint due to the status of the soft tissues while others involving very large bone defects, especially of the cavitary sort, may be well managed with minimal constraint

Anterior cruciate ligament (ACL) reconstruction is the current standard of care for ACL tears. However, the results are not consistently successful, autografts or allografts have certain disadvantages, and synthetic grafts have had poor clinical results. The aim of this study was to determine the efficacy of tissue engineering decellularized tibialis tendons by recellularization and culture in a dynamic tissue bioreactor. To determine if recellularization of decellularized tendons combined with mechanical stimulation in a bioreactor could replicate the mechanical properties of the native ACL and be successfully used for ACL reconstruction in vivo. Porcine tibialis tendons were decellularized and then recellularized with human adult bone marrow-derived stem cells. Tendons were cultured in a tissue bioreactor that provided biaxial cyclic loading for up to 7 days. To reproduce mechanical stresses similar to hose experienced by the ACL within the knee joint, the tendons were subjected to simultaneous tension and torsion in the bioreactor. Expression of tendon-specific genes, and newly synthesized collagen and glycosaminoglycan (GAG) were used to quantify the efficacy of recellularization and dynamic bioreactor culture. The mechanical strength of recellularized constructs was measured after dynamic stimulation. Finally, the tissue-engineered tendons were used to reconstruct the ACL in mini-pigs and mechanical strength was assessed after three months. Dynamic bioreactor culture significantly increased the expression of tendon-specific genes, the quantity of newly synthesized collagen and GAG, and the tensile strength of recellularized tendons. After in vivo reconstruction, the tensile strength of the tissue-engineered tendons increased significantly up to 3 months after surgery and were within 80% of the native strength of the ACL. Our translational study indicates that the recellularization and dynamic mechanical stimuli can significantly enhance matrix synthesis and mechanical strength of decellularized porcine tibialis tendons. This approach to tissue engineering can be very useful for ACL reconstruction and may overcome some of the disadvantages of autografts and allografts

Osteoarthritis (OA) is a highly prevalent degenerative joint disorder characterized by joint pain and physical disability. Aberrant subchondral bone induces pathological changes and is a major source of pain in OA. In the subchondral bone, which is highly innervated, nerves have dual roles in pain sensation and bone homeostasis regulation. The interaction between peripheral nerves and target cells in the subchondral bone, and the interplay between the sensory and sympathetic nervous systems, allow peripheral nerves to regulate subchondral bone homeostasis. Alterations in peripheral innervation and local transmitters are closely related to changes in nociception and subchondral bone homeostasis, and affect the progression of OA. Recent literature has substantially expanded our understanding of the physiological and pathological distribution and function of specific subtypes of neurones in bone. This review summarizes the types and distribution of nerves detected in the tibial subchondral bone, their cellular and molecular interactions with bone cells that regulate subchondral bone homeostasis, and their role in OA pain. A comprehensive understanding and further investigation of the functions of peripheral innervation in the subchondral bone will help to develop novel therapeutic approaches to effectively prevent OA, and alleviate OA pain.

Cite this article: Bone Joint Res 2022;11(7):439–452.

Objectives. Enhanced micromotions between the implant and surrounding bone can impair osseointegration, resulting in fibrous encapsulation and aseptic loosening of the implant. Since the effect of micromotions on human bone cells is sparsely investigated, an in vitro system, which allows application of micromotions on bone cells and subsequent investigation of bone cell activity, was developed. Methods. Micromotions ranging from 25 µm to 100 µm were applied as sine or triangle signal with 1 Hz frequency to human osteoblasts seeded on collagen scaffolds. Micromotions were applied for six hours per day over three days. During the micromotions, a static pressure of 527 Pa was exerted on the cells by Ti6Al4V cylinders. Osteoblasts loaded with Ti6Al4V cylinders and unloaded osteoblasts without micromotions served as controls. Subsequently, cell viability, expression of the osteogenic markers collagen type I, alkaline phosphatase, and osteocalcin, as well as gene expression of osteoprotegerin, receptor activator of NF-κB ligand, matrix metalloproteinase-1, and tissue inhibitor of metalloproteinase-1, were investigated. Results. Live and dead cell numbers were higher after 25 µm sine and 50 µm triangle micromotions compared with loaded controls. Collagen type I synthesis was downregulated in respective samples. The metabolic activity and osteocalcin expression level were higher in samples treated with 25 µm micromotions compared with the loaded controls. Furthermore, static loading and micromotions decreased the osteoprotegerin/receptor activator of NF-κB ligand ratio. Conclusion. Our system enables investigation of the behaviour of bone cells at the bone-implant interface under shear stress induced by micromotions. We could demonstrate that micromotions applied under static pressure conditions have a significant impact on the activity of osteoblasts seeded on collagen scaffolds. In future studies, higher mechanical stress will be applied and different implant surface structures will be considered. Cite this article: J. Ziebart, S. Fan, C. Schulze, P. W. Kämmerer, R. Bader, A. Jonitz-Heincke. Effects of interfacial micromotions on vitality and differentiation of human osteoblasts. Bone Joint Res 2018;7:187–195. DOI: 10.1302/2046-3758.72.BJR-2017-0228.R1

The April 2024 Spine Roundup³⁶⁰ looks at: Lengthening behaviour of magnetically controlled growing rods in early-onset scoliosis: a multicentre study; LDL, cholesterol, and statins usage cause pseudarthrosis following lumbar interbody fusion; Decision-making in the treatment of degenerative lumbar spondylolisthesis of L4/L5; Does the interfacing angle between pedicle screws and support rods affect clinical outcomes after posterior thoracolumbar fusion?; Returning to the grind: how workload influences recovery post-lumbar spine surgery; Securing the spine: a leap forward with s2 alar-iliac screws in adult spinal deformity surgery.

The August 2024 Foot & Ankle Roundup³⁶⁰ looks at: ESWT versus surgery for fifth metatarsal stress fractures; Minimally invasive surgery versus open fusion for hallux rigidus; Diabetes and infection risk in total ankle arthroplasty; Is proximal medial gastrocnemius recession useful for managing chronic plantar fasciitis?; Fuse the great toe in the young!; Conservative surgery for diabetic foot osteomyelitis; Mental health and outcome following foot and ankle surgery.

Aims

Osteoarthritis (OA) is a common degenerative joint disease. The osteocyte transcriptome is highly relevant to osteocyte biology. This study aimed to explore the osteocyte transcriptome in subchondral bone affected by OA.

Aims

The aim of this study was to investigate the incidence and characteristics of instrumentation failure (IF) after total en bloc spondylectomy (TES), and to analyze risk factors for IF.

Aims

Postoperative complication rates remain relatively high after adult spinal deformity (ASD) surgery. The extent to which modifiable patient-related factors influence complication rates in patients with ASD has not been effectively evaluated. The aim of this retrospective cohort study was to evaluate the association between modifiable patient-related factors and complications after corrective surgery for ASD.

Aims

Knee osteoarthritis (OA) involves a variety of tissues in the joint. Gene expression profiles in different tissues are of great importance in order to understand OA.

Aims

The purpose of this study was to evaluate the mid-term outcomes of autologous matrix-induced chondrogenesis (AMIC) for the treatment of larger cartilage lesions and deformity correction in hips suffering from symptomatic femoroacetabular impingement (FAI).

Aims

Osteoarthritis (OA) is a prevalent joint disorder with inflammatory response and cartilage deterioration as its main features. Dihydrocaffeic acid (DHCA), a bioactive component extracted from natural plant (gynura bicolor), has demonstrated anti-inflammatory properties in various diseases. We aimed to explore the chondroprotective effect of DHCA on OA and its potential mechanism.

Aims

This study aimed, through bioinformatics analysis and in vitro experiment validation, to identify the key extracellular proteins of intervertebral disc degeneration (IDD).

Aims

This study aimed to explore the biological and clinical importance of dysregulated key genes in osteoarthritis (OA) patients at the cartilage level to find potential biomarkers and targets for diagnosing and treating OA.

Hip osteoarthritis (OA) is a disorder of high socio-economic relevance. The causes of hip osteoarthritis are multifactorial; however, the epidemiological literature regularly cites occupational tasks, such as heavy lifting and carrying, as a risk factor for the development of hip OA. The level of mechanical stresses upon the hip joint caused by occupational tasks remain largely unclear, however. This project sought to quantify the levels of stresses upon the hip joint during occupational tasks. In particular we were interested in comparing load as well as stress levels from everyday activities with occupational tasks typically performed by blue collar workers. Sectors and occupational activities presenting a high potential for stress upon the hip joint were identified by means of a survey conducted among accident insurance institutions. Lifting, carrying and load transfer (25 to 50 kg), ladder climbing and stair climbing (without additional load and with an additional load of 25 kg) were selected from among these sectors and activities for the purpose of the study. Laboratory measurements were performed in which motion capturing and a range of force measurement apparatus were used to record and evaluate the performance of the selected tasks by 12 skilled workers from a number of sectors. multi-body simulation was used to calculate the stress in the form of hip-joint contact forces. The contact pressures and their geometric distribution on the cartilage surfaces of the hip joint were then calculated from these results by means of finite-element analysis. This produced an indicator for the strain upon the hip joint. The highest hip-joint forces, at (637±148)% of the body weight, occurred during handling of the 50 kg load. This corresponded to 1.7 times the stress arising during walking, at (368±78)% of the body weight. Significantly higher hip-joint forces compared to those arising during walking were observed for the carrying of loads of 40 kg and 50 kg, the handling of loads of 25 kg, 40 kg and 50 kg, and stair climbing with an additional load of 25 kg. Maximum contact pressures of 24.1 MPa were computed during the finite-element analysis (lifting of 50 kg); only very small regions of the joint surface were however affected by these high pressures. During walking, the maximum pressure reached 15 MPa. The results obtained provide a quantitative overview of the strains upon the hip joint during occupational and everyday tasks. They constitute an aid to future quantitative exposure assessments in a range of sectors and occupational fields, and thus contribute to improving estimation of the relevance of stresses of occupational origin to the incidence of hip OA

In addition to mechanical stresses, an inflammatory mediated association between obesity and knee osteoarthritis (OA) is increasingly being recognised. Adipokines, such as adiponectin and leptin, have been postulated as likely mediators. Clinical and epidemiological differences in OA by race have been reported. What contributes to these differences is not well understood. In this study, we examined the profile of adipokines in knee synovial fluid (SF) and the gene expression profile of the infra-patellar fat pad (IFP) by race among patients with end-stage knee OA scheduled for knee arthroplasty. Age, sex, weight and height (used to derive body mass index (BMI)) and race (White, Asian and Black) were elicited through self-report questionnaire prior to surgery. SF and IFP samples were collected at the time of surgery. Adipokines (adiponectin and leptin) were examined in the SF using MAGPIX Multiplex platform. IFP was profiled using Human Adipogenesis PCRArray and genes of interest were further validated via quantitative relative RT-PCR using Student's t-test. Overall differences in adiponectin and leptin concentrations were tested across race. Linear regression modeling was used to investigate the association between adiponectin and leptin concentrations (outcomes) and race (predictor; referent group: White), adjusting for age, sex and BMI. 67 patients (18 White, 33 Asian, 16 Black) were included. Mean SF adiponectin concentration was greatest in Whites (1175.05 ng/mL), followed by Blacks (868.53 ng/mL) and Asians (702.23 ng/mL) (p=0.034). The mean SF leptin concentration was highest in Blacks (44.88 ng/mL), followed by Whites (29.86 ng/mL) and Asians (20.18 ng/mL) (p=0.021). Regression analysis showed Asians had significantly lower adiponectin concentrations compared to Whites (p<0.05). However, leptin concentrations did not differ significantly by race after adjusting for covariates. Testing of the IFP, using the Adipogenesis PCRArray, showed significant higher expression of LEP gene (leptin, p=0.03) in Asians (n=4) compared to Whites (n=4). There appears to be important racial differences in the SF adiponectin profile among individuals with end-stage knee OA. Differential gene expression in the IFP across racial groups could be a potential contributory source for the noted SF variations. Further work to determine the source and function of adipokines in knee OA pathophysiology across racial groups is warranted

Introduction. Wear and survival of total joint replacements do not depend on the duration of the implant in situ, but rather on the amount of its use, i.e. the patient's activity level [1]. With this in mind, the present study was driven by two questions: (1) How does total knee replacement (TKR) respond to the simulation of daily highly demanding activities? (2) How does implant size affect wear response of total knee replacement (TKR)?. Materials & Methods. Two sets of the same total knee prosthesis (TKP), different in size (#2 and #6), equal in design, were tested on a three-plus-one knee joint simulator for two million cycles using a highly demanding daily load waveform [2], replicating a stair-climbing movement. The results were compared with two sets of TKP previously tested with the ISO level walking task. Gravimetric and micro-Raman spectroscopic analyses were carried out on the polyethylene inserts. Visual comparison with in vivo explants was carried out and digital microscopy was used to characterize the superficial structure of all the TKPs and explanted components. Results. The average volumetric loss of the UHMWPE inserts tested for 2Mc under ISO standard level walking were 21.36 ±1 mm3 and 41 ±2 mm3 for the size #2 and size #6, respectively. The average volumetric mass loss after two million cycles for the size #2 under the stair climbing simulation was 44 ±6 mm3. Microscope examinations showed some deep scratches along the flexion/extension movements for all the components. A decrease in crystallinity, induced by mechanical stress was observed on all polyethylene components and was quantitatively confirmed by the orthorhombic fraction αo value. Conclusion. These preliminary results showed that under more severe conditions for size #2, the material properties change according to a different wear mechanism and a decrease in crystallinity occurs. Under the ISO 14243-2 load profile, an increase in crystallinity was observed; whereas under the more demanding conditions, a decrease in crystallinity occurs. Analyses on the size #6 component are in progress

Aims

Pelvic incidence (PI) is considered an important anatomical parameter for determining the sagittal balance of the spine. The contribution of an abnormal PI to hip osteoarthritis (OA) remains controversial. In this study, we aimed to investigate the relationship between PI and hip OA, and the difference in PI between hip OA without anatomical abnormalities (primary OA) and hip OA with developmental dysplasia of the hip (DDH-OA).

Osteoarthritis (OA) is a degenerative disease resulting from progressive joint destruction caused by many factors. Its pathogenesis is complex and has not been elucidated to date. Advanced glycation end products (AGEs) are a series of irreversible and stable macromolecular complexes formed by reducing sugar with protein, lipid, and nucleic acid through a non-enzymatic glycosylation reaction (Maillard reaction). They are an important indicator of the degree of ageing. Currently, it is considered that AGEs accumulation in vivo is a molecular basis of age-induced OA, and AGEs production and accumulation in vivo is one of the important reasons for the induction and acceleration of the pathological changes of OA. In recent years, it has been found that AGEs are involved in a variety of pathological processes of OA, including extracellular matrix degradation, chondrocyte apoptosis, and autophagy. Clearly, AGEs play an important role in regulating the expression of OA-related genes and maintaining the chondrocyte phenotype and the stability of the intra-articular environment. This article reviews the latest research results of AGEs in a variety of pathological processes of OA, to provide a new direction for the study of OA pathogenesis and a new target for prevention and treatment.

Cite this article: Bone Joint Res 2022;11(5):292–300.

Knee osteoarthritis (OA) affects an estimated 250 million people worldwide, with a cure yet to be found. Consequently, there is an urgent need to improve our understanding of OA physiopathology. While knee OA has long been mostly described as a loss of cartilage thickness (CTh) and research has focused on this characteristic, the role of bone alterations is rapidly gaining in interest. Analyzing subchondral bone mineral density (sBMD) is particularly interesting because this could inform on the mechanical environment at the knee. However, there is a paucity of data on sBMD in literature mainly because of the lack of prior methods to measure this parameter. A method for 3D sBMD assessment based on computed tomography (CT) scans was recently proposed, thus allowing testing for sBMD differences in knee OA. This study aimed at comparing non-OA and medial OA knees in terms of tibial sBMD and CTh. Specifically, it was hypothesized that sBMD and CTh differ with OA. Ten knees with severe medial OA and 10 matched non-OA knees were analyzed after ethical approval (50% male; 60 ± 3 years old). The arthro-CT scans of the 20 knees were segmented using custom software to build 3D mesh models of the tibial bone and cartilage. CTh maps were obtained by calculating the distance between cartilage and bone meshes, while sBMD maps were calculated based on the intensity of the CT in the first 3mm of bone. For each knee, the average CTh and sBMD values over the entire medial and lateral compartments were calculated and used to determine the medial-to-lateral (M/L) CTh and sBMD ratios. Unpaired t-tests and receiver operating characteristic (ROC) were used for statistical analysis. The M/L sBMD ratio was significantly higher in OA compared to non-OA knees (1.14 ± 0.04 vs. 1.08 ± 0.03; p<0.01), whereas the CTh ratio was not significantly different between groups (0.70 ± 0.21 vs. 0.85 ± 0.10; p=0.06). No significant differences were found between OA and non-OA knees for the average medial CTh and sBMD (p>0.4). High classification performance was obtained for the sBMD ratio and low performance for the average sBMD in the medial compartment (areas under the ROC curve of 0.9 and 0.6, respectively). CTh ratio and medial compartment average provided medium classification performances (areas under the curve of 0.7). This study showed that sBMD differed between non-OA and severe medial OA knees and that sBMD M/L ratio was more sensitive to OA severity than CTh variables. These results brought new insights into the pathogenesis of knee OA, by supporting the idea that sBMD is altered with OA and suggesting that sBMD could play a role in disease development. Indeed, the mechanical stresses on the cartilages are related to the mechanical characteristics of the bones. Indirectly, this study also demonstrated the value of arthro-CT scans to simultaneously assess sBMD and CTh. Additional studies with larger cohorts of patients at different stages of the disease are necessary to better understand when changes in sBMD occur

Introduction. Acute poliomyelitis is a very rare disease in western countries, however the remnant of the pathology can be find among the adult patients. In poliomyelitis, sensation is normal and patients may suffer from painful etiologies. Total knee arthroplasty (TKA) with non-hinged or semi hinged prosthesis systems may be a good options to relief the pain in poliomyelitic patients, however the knee remains unstable. Using the hinged system implant may be the good option to resolve the late. Although the main concern in case of hinged implant usage is the mechanical stress which is directly transferred to the bone surface in contact with the implant. This may leads to implant mobilization and consequently failure. Methods and Materials. From 2004 to 2014, 14 TKA were performed in poliomyelitic patients with secondary knee pain. All patients were presented with extensor compartment hyposthenia and reduced antigravity function. In all patients a third generation rotating hinged knees (RHK) implant system (Zimmer, Warsaw, IN, USA) was applied. Bilateral TKA was performed in only one case. The mean age at the time of surgery was 56 years (ranged 48–77). Mean follow-up was 60 months (24–112). Results Due to post-operative infection, one patient underwent knee arthrodesis and excluded from the study. In one case, patellar fracture occurred 3 month following the surgery and treated non-surgically. Pain relief was observed in all patients following the surgery without any major complication. Mean objective score according to knee society knee scoring system was improved from 28 (16–51) preoperatively to 79 (72–88) postoperatively. Mean functional score was improved from 24 (5–35) preoperatively to 66 (50–70) postoperatively. At last follow up the mean range of motion was 90° (75°−100°). Following radiographic control at last follow-up all implants was stable without any sign of failure such as mobilization, radiolucency line or osteolysis. Conclusion. Providing stable knee implant system is the most important factor in addition to pain relief in case of poliomyelitic patients with knee pain. In our experience, third generation RHK supplied satisfactory clinical results in poliomyelitic patients supplying good implant stability without interfere with existing intrinsic stability of the lower limb. We believe that good results were achieved due to particular specification of RHK implant including mild 3° of hyperextension and weight distribution mode in which 95% transfer to polyethylene insert and only 5% to hinged compartment that help to restore the stability in such a particular patients also in case of late post-polio syndrome

Introduction. Modern hip replacements all have encapsulated the design concept of proximal modularity. The factors contributing to the increased wear and corrosion at the taper junction are trunnion geometry, surface characteristics, head size, impaction forces, and material coupling. This study maps the inferior and superior region of the trunnion and bore to provide a visual identification of the corrosion severity. The corrosion/wear generated inferiorly and superiorly at the bore and trunnion will be quantified to understand how corrosion is affected by mechanical stresses in relation to anatomical orientation. Methodology. Three neck tapers generated from bar stock containing a threaded trunnion Ti-6Al-4V and 3× 32mm femoral heads (Co-Cr-Mo) with a +4 offset manufactured by Signature Orthopaedics were used within this study. Rectangular Rozzette strain gauges (Tokyo Sokki Kenkyujo Co., Ltd.) were adhered onto the inferior and superior sections of the neck section. The tapers were fatigued in accordance to ISO 7206 at 5Hz for 5 million cycles at 37 degrees Celsius in phosphate buffered saline. The tapers were sectioned from the center of the femoral head to split both trunnion and bore into superior and inferior components. SEM imaging of all surface areas for each component, per taper (4) was done under ×100 magnification. The images were used to quantify the corrosion present across the surface area using a MATLAB based program called Histomorph. To obtain a visual observation of the variation of corrosion across the bore and trunnion the proximal, medial, and distal regions were mapped together for both the superior and inferior sections. Results. The superior region of the trunnion had a dominant tensile strain in comparison to the inferior region, which had a dominant compressive strain. Corrosion/wear of the inferior section of the trunnion was significantly higher (p<0.05) in comparison to the superior section (Figure 1). The bore had more corrosion/wear on the superior side in comparison to the inferior side however the difference was not significant. The mapping of the trunnion shows corrosion/wear along the whole length of the inferior side and dominantly at the distal region for the superior side (Figure 2 & 3). The superior section of the trunnion had higher corrosion/wear damage across the center and distal regions of the trunnion. The subdivision of the superior section reveals that the majority of the distal section contains higher wear/corrosion damage. However the central region also has sufficient corrosion/wear extending across the width of the bore. Conclusion. The corroded regions have shown that the type of stress present on the regions of the taper junction determines the severity of corrosion. The inferior section of the trunnion under compressive stress has significantly (p<0.05) higher corrosion/wear in comparison to the superior section dominated by tensile stress

Aims

This study reports updates the previously published two-year clinical, functional, and radiological results of a group of patients who underwent transfibular total ankle arthroplasty (TAA), with follow-up extended to a minimum of five years.

Aims

In the repair of condylar cartilage injury, synovium-derived mesenchymal stem cells (SMSCs) migrate to an injured site and differentiate into cartilage. This study aimed to confirm that histone deacetylase (HDAC) inhibitors, which alleviate arthritis, can improve chondrogenesis inhibited by IL-1β, and to explore its mechanism.

The development of spinal deformity in children with underlying neurodisability can affect their ability to function and impact on their quality of life, as well as compromise provision of nursing care. Patients with neuromuscular spinal deformity are among the most challenging due to the number and complexity of medical comorbidities that increase the risk for severe intraoperative or postoperative complications. A multidisciplinary approach is mandatory at every stage to ensure that all nonoperative measures have been applied, and that the treatment goals have been clearly defined and agreed with the family. This will involve input from multiple specialities, including allied healthcare professionals, such as physiotherapists and wheelchair services. Surgery should be considered when there is significant impact on the patients’ quality of life, which is usually due to poor sitting balance, back or costo-pelvic pain, respiratory complications, or problems with self-care and feeding. Meticulous preoperative assessment is required, along with careful consideration of the nature of the deformity and the problems that it is causing. Surgery can achieve good curve correction and results in high levels of satisfaction from the patients and their caregivers. Modern modular posterior instrumentation systems allow an effective deformity correction. However, the risks of surgery remain high, and involvement of the family at all stages of decision-making is required in order to balance the risks and anticipated gains of the procedure, and to select those patients who can mostly benefit from spinal correction.

Epidemiological studies have shown that accumulated mechanical stress is a risk factor for the development of osteoarthritis (OA). This debilitating progressive clinical condition affects a broad spectrum of patients and will ultimately lead to definitive arthroplasty surgery as the endpoint treatment option in many cases. The aim of this study is to establish a graded murine model of OA by medial meniscotibial destabilisation of the knee joint and in phase two, to investigate the migration and engraftment of radioisotope labeled mesenchymal stem cells (MSCs) at varying points of disease progression. The first phase of the study was to establish the murine model, an Irish first. All procedures were performed aseptically under general anaesthesia via a midline medial parapatellar approach on a murine fracture table. Microsurgical dissection was performed through necropsy analysed layers to the joint space and the meniscotibial ligament identified and transected. Validated histopathological analysis was performed at two, four, eight and twelve weeks postoperatively. The results showed a gradation of OA changes from mild unicondylar changes at two weeks, moderate unicompartmental change at four, severe unicompartmental change at eight and severe bicompartmental change at twelve weeks post-operatively. In vivo Bazooka-Single Photon Emission Computed Tomography (SPECT) (Phase 2) imaging studies are currently ongoing following the model establishment

Summary Statement. Intra-articular injection of humanised monoclonal anti-VEGF antibody (Bevacizumab, Avastin®) in a osteoarthritis rabbit model is related to positive restorative effects in terms of histopathologic evaluation. Introduction. Vascular endothelial growth factor (VEGF) is generally undetectable in adult human articular cartilage under physiological conditions. Upon exposure to pathological stimulation such as inflammation, hypoxia or accumulating mechanical stress, VEGF would be up regulated in hypertrophic chondrocytes of arthritic cartilage leading to osteophyte formation, disregulation of chondrocyte apoptosis and induction of catabolic factors, including matrix metalloproteinases (MMPs). This in vivo study aims to investigate the potential role of VEGF inhibition to treat Osteoarthritis (OA), through intra-articular injection of Bevacizumab, a humanised monoclonal anti-VEGF antibody, in a OA rabbit model. Methods. OA was induced in twelve adult male New Zealand rabbits surgically by monolateral Anterior Cruciate Ligament Transection (ACLT). The rabbits were randomly divided into two equal groups (experimental and control). Intra-articular injections of Bevacizumab or saline (control) were given 4 weeks after ACLT and were administered once a week for 4 time. Animal were sacrificed at 2 and 3 month time point an knee analyzed histologically and grossly. Histopathological variables such as the number of fibroblasts and inflammatory cells, collagenous matrix deposition, synovial hyperplasia, granulation tissue formation, vascular proliferation were evaluated. Results:The macroscopic evaluation of the knee in the experimental group revealed smooth joint surfaces of articular cartilage and no osteophyte formation compared to the control group that showed marked arthritis including synovial hypertrophy and osteophyte formation. Histologic assessment demonstrated, in the experimental group, significantly higher scores concerning number of microvessels, synovial hyperplasia, macrophage infiltration, collagenous matrix deposition, chondrocytes proliferation and apoptosis compared to the control group. Conclusion. In conclusion, VEGF modulation via intra-articular injection of Bevacizumab in a rabbit model of knee OA, resulted in reduction of articular cartilage degeneration through setting up an appropriate environment that prevent chondrocyte hypertrophy, apoptosis and osteophytes formation by blocking the intrinsic VEGF catabolic pathway, endochondral ossification, and the extrinsic VEGF-induced vascular invasion. VEGF-signaling inhibtion through Bevacizumab represent a potential way to treat OA

Aims

Varus-valgus constrained (VVC) devices are typically used in revision settings, often with stems to mitigate the risk of aseptic loosening. However, in at least one system, the VVC insert is compatible with the primary posterior-stabilized (PS) femoral component, which may be an option in complex primary situations. We sought to determine the implant survivorship, radiological and clinical outcomes, and complications when this VVC insert was coupled with a PS femur without stems in complex primary total knee arthroplasties (TKAs).

Introduction. Total knee arthroplasty (TKA) implant systems offer a range of sizes for orthopaedic surgeons to best mimic the patient's anatomy and restore joint function. From a biomechanical perspective, the challenge on the TKA implants is affected by two factors: design geometry and in vivo load. Larger geometry typically means more robust mechanical structure, while higher in vivo load means greater burden on the artificial joint. For an implant system, prosthesis geometry is largely correlated with implant size, while in vivo load is affected by the patient's demographics such as weight and height. Understanding the relationships between implant size and patients' demographics can provide useful information for new prosthesis design, implant test planning, and clinical data interpretation. Utilizing a manufacturer supported clinical database, this study examined the relationships between TKA patient's body weight, height, and body mass index (BMI) and the received implant size of a well-established implant system. Methods. A multi-site clinical database operated by Exactech, Inc. (Gainesville, FL, USA) was utilized for this study. The database contains patient information of Optetrak TKA implant recipients from over 30 physicians in US, UK, and Colombia since 1995. Nine implant sizes (0, 1, 2, 2.5, 3, 3.5, 4, 5 and 6) are seen in the database, while size 0 was excluded due to very low usage. Taking primary TKA only, a total of 2,713 cases were examined for patient's body weight, height, BMI, and their relationships with the implant size. Results. Both patient's weight and height strongly correlate with implant size (R. 2. »0.95 for both parameters with a linear regression). On average, the increase of one implant size corresponds to an increase of 7.4 kg in patient's weight and 7.0 cm in patient's height (Figure 1). However, there is almost no dependency between patient's BMI and implant size (R. 2. <0.05), and the regression line is almost flat (k=-0.08) (Figure 1). Discussion. Based on the Exactech database, this study revealed that TKA patients' weight and height increase close-to-linearly with implant size, but BMI stays fairly constant. These relationships are not all intuitive mathematically, and are likely simplified representations of higher order functions within the particular variable ranges. The most interesting finding was the independence of BMI on implant size, which provides a favorable validation of the geometry design and size selection of the Optetrak implant system. BMI (kg/m. 2. ) has the same unit dimension as stress (N/m. 2. ) excluding the constant g (9.8 N/kg). Since implant geometry is generally proportional to patient height, and joint force is generally proportional to patient weight, the mechanical stress imposed on the implant would be generally proportional to patient's BMI. The fact that BMI stays constant across sizes indicates that the implant system would experience a similar level of stress across all sizes, which has been previously observed in femorotibial contact stress analyses on the Optetrak system. This study showed that a heavier TKA patient statistically tends to receive a larger implant which, depending on implant design, will provide larger contact area and compensate for the higher load

Disc degeneration starts as an avascular necrosis. In the lower lumbar area the discs deteriorate early because of mechanical stresses. During certain early periods of degenerative changes a mechanical disorder between the annulus and the posterior longitudinal ligament may cause tiredness and pain. When the disc is completely degenerated and has lost its physical properties backache disappears

Introduction. There is no published series described change in bone mineral density (BMD) after ankle replacement. We present the results of a prospective study examining the effect of total ankle replacement (TAR) upon local bone mineral density (BMD). Aim. To design a method and assess the effect of TAR loading on local ankle bones, by analysing the BMD of different area around ankle before and after Mobility TAR. Methods. 23 patients undergoing Mobility ankle arthroplasty for osteoarthritis had preoperative bone densitometry scans of the ankle, repeated at 1 and 2 years after surgery. BMD of 2 cm. 2. areas around ankle were measured. Pre- and postoperative data were compared. Results: Mean BMD within the lateral malleolus decreased significantly from 0.5g/cm. 2. to 0.42g/cm. 2. (17%, P > 0.01), at 1 & 2 years postoperatively. Mean BMD within medial malleolus decreased slightly from 0.67g/cm. 2. to 0.64 g/cm. 2. at the same period. However BMD at medial side metaphysic of tibia increased by 7%. There was little increase in BMD in tibia just proximal to implant and at talus. Discussion and Conclusion. Absence of stress shielding around distal tibia, just proximal to tibial component and talus indicates that ankle replacements implanted within the accepted limits for implant alignment, load distal tibia and talus. However, there was stress shielding over the lateral malleolus resulting in decreased BMD in lateral malleolus. Increase BMD at tibial metaphysis, proximal to medial malleolus indicates an increase in mechanical stress which may explain occasional postoperative stress fracture of medial malleolus or medial side ankle pain

Aims

Some patients presenting with hip pain and instability and underlying acetabular dysplasia (AD) do not experience resolution of symptoms after surgical management. Hip-spine syndrome is a possible underlying cause. We hypothesized that there is a higher frequency of radiological spine anomalies in patients with AD. We also assessed the relationship between radiological severity of AD and frequency of spine anomalies.

We applied joint distraction using an Ilizarov apparatus in 11 patients with post-traumatic osteoarthritis of the ankle to try to delay the need for an arthrodesis. Distraction for three months resulted in clinical improvement in pain and mobility for a mean of two years, with an increase in the joint space. We considered that these effects may be produced by the absence of mechanical stress on the cartilage combined with the intra-articular hydrostatic pressures during distraction. We measured these pressures during walking with distraction, and found levels very similar to those reported to improve osteoarthritic cartilage when applied in vitro

Summary Statement. Increased Dkk-1 signaling is associated with OA occurrence and joint microenvironment damage. Interruption of Dkk1 action is beneficial to improve OA knees. Introduction. Osteoarthritis (OA) is a leading cause of disability and healthcare financial burden for total knee arthroplasty, rehabilitation, and disability. Inappropriate mechanical stress, immunological, or biochemical regulation reportedly disturbs homeostasis among cartilage, synovium and subchondral bone microstructure that contributes to OA pathogenesis. Control of joint-deleterious factor action is an emerging strategy to ameliorate OA-induced joint deterioration. Dickkopf-1 (Dkk-1) is a potent inhibitor for Wnt/β-catenin signaling regulation of tissue development and remodeling in physiological or pathological contexts. Dkk-1 also acts as a master deleterious factor that represses osteoblast differentiation capacity and bone repair. Associations among Dkk-1 expression, chondrocyte fate, synovial fibroblast behavior or OA incidence are merit of characterization. Patients & Methods. Cartilage, synovial tissue and fluid were harvested from informed consent OA patients underwent arthroplasty and patient with knee injuries without OA changes as controls. Primary chondrocyte cultures and synovial fibroblasts were treated with inflammatory cytokines or Dkk-1 antisense oligonucleotide or monoclonal antibodies. Knees in experimental animals were subjected to anterior cruciate ligament transection- or intra-articular collagenase injection to induce OA. Joint inflammation, integrity and subchondral bone microstructure in knees as well gait profiles were quantified using 2-deoxyglucose-probed near-infrared in vivo image, µCT, catwalk and histomorphometric analyses. Results. In clinical vignettes, patients with end-stage OA knee had higher abundances of Dkk-1 in cartilage, synovial tissue, and synovial fluid compared to control patients. Disruption of DKk-1 signaling ameliorated the promoting effects of inflammatory cytokines on the survival and cartilage matrix synthesis in primary cartilage chondrocyte cultures. Of interest, Dkk-1 neutralization attenuated the excessive angiogenic activities and matrix metalloproteinase secretion in primary synovial fibroblasts of OA knees. Dkk-1 modulation of survival or metabolic activities in chondrocytes and synovial fibroblasts were through β-catenin-dependent and -independent signaling pathways. Moreover, increased Dkk-1 expression in lesion sites and sera was associated with the incidence of femoral head osteonecrosis. Loss of Dkk-1 action alleviated bone cell apoptosis in osteonecrotic bone microenvironments. In experimental OA knee models, knockdown of Dkk-1 alleviated articular cartilage damage as evidenced by improved Mankin score in OA knees. Dkk-1 disruption also alleviated the adverse effects of OA on subchondral bone exposure and loss of trabecular bone volume and mineral acquisition in injured joints. Loss of Dkk-1 function reduced joint inflammation, vessel number, leukocyte infiltration in synovium compartment of OA joint and improved gait profiles of affected limbs. Conclusion. Dkk-1 signaling is associated with the OA knee occurrence and accelerates apoptosis, matrix degradation and angiogenic activities in chondrocytes and synovial fibroblasts of OA joint. Dkk-1 interference alleviates the promoting effects of OA on cartilage, synovial and subchondral bone remodeling. Blocking the deleterious actions of Dkk-1 in joint microenvironment will be a prospective molecular regime beneficial for retarding excessive joint deterioration in OA knees

Aim: Cementation of tibial implants in total knee arthroplasty is a gold-standard considering the high loosening rates of cementless implants. In contrast, only sparse data exist regarding unicondylar arthroplasty due to limited use. In this study, we compare cemented with cementless unicondylar knee arthroplasty and aim to define both clinical and radiological differences in treatment outcome. Materials and Methods: In a retrospective study, 106 patients who had undergone a medial unicondylar replacement were examined after a mean postoperative period of 8 years. Of these, 42 patients (median age 81±7 years) had received a cemented and 64 (median age 73±7 years) a cementless knee arthroplasty by the same surgeon while 7 patients were deceased or could not be reached. Well-established clinical (VAS, HSS, KSS, UCLA, WOMAC) and quality of life (SF-36) scores were used to evaluate treatment outcome. X-rays were performed to evaluate periprosthetic loosening zones, according to Ewald’s criteria. Results: The cementless patient group presented significantly better clinical scores (HSS, KSS, UCLA, WOMAC), except in the Visual Analogue Scale (VAS) for pain assessment. The quality of life was significantly better in the cementless group except in the subgroups concerning physical function, vitality and social role, which resembled normal population. Moreover, radiographic analysis using antero-posterior X-rays revealed significantly more and larger periprosthetic loosening areas in tibial zone 2 in the cementless group. Conclusion: The inferior clinical results characterising the cemented group could be attributed to the higher mean age. Regarding the radiological loosening zones, we did not detect any differences in the techniques of fixation, although physical activity and mechanical stresses were higher in the cementless group

Uncemented double-mobility acetabular cups, first used in the late 1970s as a solution to recurrent hip dislocations, have proved efficient in reducing dislocation rates while preserving an important range of motion. The low wear-rate and low mechanical stress on the bone to cup interface enhances survival. New instrumentation has permitted design changes that improve the dislocation coverage of the cup (upper part of the cup) and reduce the risk of impingement with the femoral stem (lower part of the cup). Indications for the use of double-mobility cups have increased. They include primary total hip arthroplasty in relatively unstable hips, in which cases we use the Avantage® press-fit or 3P cup with an AURA II anatomical uncemented or cemented stem, dysplasia (in congenital high dislocations we use the press-fit or 3P or revision cup with an AURA revision stem, and in dysplasia we use small AURA II or Vectra or CMK dysplastic stems), muscular deficiency, in which Avantage® cups can be used with AURA II or revision stems, resection prosthesis or ARMEL calcar prosthesis, etc.)

The reconstruction of lower limb defects after oncological reconstructions is still a problem in limb salvage surgery. Large bony defects need to be treated with sound and durable reconstructions. During recent decades, the life expectancy of patients affected with cancer has improved considerably because of advances in chemotherapy, immunotherapy, hormonal treatment and radiotherapy. This improvement requires greater reliability in the reconstructive procedure in order to avoid mechanical failure during prolonged survival of the patient. The author experience with modular megaprosthesis by Link (megasystem C) allowed us to present a rapid, effective and functional solution. From June 2001 to December 2007 225 patients have been operated with a megaprosthesis C for tumoral resection. The new megaprosthesis C by Link represents a wide-ranging system that can afford a large variety of reconstructions in the inferior limb, from very short replacement of 5 cm in proximal femur, to a total femur and proximal tibia replacement. Modularity is represented by 1 cm increase in length. The different options of cemented and not cemented stem may be used with intraoperative decision. In cemented stem a rough collar seals the osteotomy and prevents polyethylene debris from entering the femoral canal by inducing a scar tissue around the stem entrance (so-called purse-string effect). Moreover in patients with solitary lesions and very good prognosis an allograft-prosthesis composite can be performed with improved clinical results on walking and function. Of the 225 patients that underwent tumoral resection and reconstruction with a modular megaprosthesis approximately 43% (97 cases) were operated for metastatic disease. Among these cases 55 cases were proximal femoral recontructions, 39 cases were distal femoral reconstructions and 3 cases were proximal tibial reconstructions. All cases were performed with cemented stems. We experienced a 7% of postoperative infections, 2% of dislocations of proximal femoral prosthesis and 3% of mechanical failures. While infections and dislocation rates were in the average for this surgery, mechanical failures were relatively high. We should consider that in patients with relatively long resections and muscle deficiency the mechanical stress exerted on the prosthesis can explain this kind of mechanical failure. However the new design of morse tapers have annulled these problems

Summary. Shear stress and hydrostatic effects on the hMSCs early mechano gene response were similar. For the same magnitude gene response, the hydrostatic compression (1.5×10. 5. Pascal) is a 200000 times greater than the force exerted by shear stress (0.7 Pascal). Introduction. In the lab, a perfusion bioreactor designed to automate the production of bone constructs was developed. The proof of concept was established in a large animal model of clinical relevance. The cells perfused in the bioreactor are likely to perceive 2 types of stresses: shear stress and hydrostatic pressure. Optimization of this bioreactor implies a better understanding of the effects of these forces on the cells in order to have better proliferation and differentiation. An understanding of the response of one cell layer submit to various strength is relevant. The primary objective of this study was to test the hypothesis that hMSCs have the fundamental ability to distinguish between different types of mechanical signals as evidenced by distinct gene expression. The effect of shear stress on one cell layer cultures of hMSCs will be evaluated using a commercially available system called Ibidi. For the hydrostatic pressure as there is no commercial device available, our group has developed a prototype capable of delivering a well-defined mechanical loading to cells in culture. Validation of the techniques: In order to validate the systems (shear stress and cyclic pressure apparatus) used in this study, we have used an osteocytes-like cell line, MLO-Y4. When stimulated by a 30 minutes PFF at 7 dyn/cm. 2. or hydrostatic compression at 1.5 bar, cells responded by producing NO in the culture media. NO release after mechanical stimulation of hMSCs: hMSCs were subjected to increased PFF (7 to 42 dyn/cm. 2. ) for 30 minutes. This stimulation resulted in an increased release of NO in the media compared to non-stimulated cells (p<0.05). Interestingly the level of NO was maximal at 7 dyn/cm. 2. and decreased with higher flow rate. Similar observation was made after hMSCs stimulation by hydrostatic pressure for 30 minutes: a peak of NO release at 1.5 bar was observed. Early gene expression of known mechano-sensitive genes: Gene expression analysis immediately after stimulation (PFF or hydrostatic compression) was performed on a range of known mechano-sensitive genes: NOS2, PTGS2, PTGES, IER3 and EGR1. Immediately after stimulation by PFF at 7 dyn/cm. 2. or hydrostatic pressure at 1.5 bars, the expression of all the genes of interest appear to be up regulated in stimulated cells. Conclusions. In the present study, hMSCs cells responses to two different treatments, shear stress and hydrostatic pressure, were monitored in parallel to study the difference in sensitivity to both mechanical stresses. Both systems used ensure a stable and reproducible strain condition in a well-controlled environment. We demonstrated that the shear stress and the hydrostatic pressure effects on the hMSCs were similar. We note that, for the same magnitude response, force exerted by the hydrostatic compression (1.5×10. 5. Pascal) on the cells is a 200000 times greater than the force exerted by shear stress (0.7 Pascal). This shows that the direct effect of hydrostatic compression on the hMSCs is negligible compared to the shear stress

INTRODUCTION:. Proximally coated femoral stems have been designed to address the shortcomings of fully coated femoral stems including proximal femoral stress shielding. The design improvements leading to more optimized proximal femoral loading condition in the “Neck preserving stems” have increased the popularity of such implants (e.g., Minihip). Neck preserving stems depict better biological outcomes compared to more traditional stems . 1. by utilizing more natural mechanical stress/strain distribution over the femur. These stems provide significant reduction in both torsional and bending moments at the stem/bone interface. This reduction may result in decreasing the micromotion and failure of osseointegration . 1. Figure 1 demonstrates the differences between the cutting areas of a neck preserving versus traditional stem. The Minihip stem demonstrate a curved structure that is designed to match the shape of the femoral neck. The stability of the implant is achieved in the femoral neck and intertrochanteric area of the proximal femur. Further investigations are needed to establish a solid ground for the outcome of these stem in total hip arthroplasty (THA). OBJECTIVES:. The current study was conducted to report the short-term clinical outcome of the THA by using Minihip neck preserving stem. METHODS:. In the current study the short-term clinical outcomes of the patients in the patients who were treated by Minihip THA is analyzed. All patients were evaluated via Hip Disability and Osteoarthritis Outcome Score (HOOS). In addition we explored the effect of obesity on the perceived difficulty of surgery performance. A multinomial logistic regression was used in addition to a multivariate repeated ANCOVA was performed to determine significance of the demographics (i.e., BMI, Height, Weight, Age, and Gender). The signed consent was obtained from each participant. RESULTS:. 26 of the patients reported their symptoms to evaluate the HOOS (20 male, 6 female, Age 61.7 ± 8.5 years and BMI of 27.5 ± 3.88). Six patients demonstrated obesity (BMI>30). Post-operative data were collected at a mean followup time of 3 months. The results indicated significantly higher HOOS in individuals during postop depicting better quality of life (F(1, 25) = 186.695, p < .001), lower pain (F(1,25) = 249.317, p < .001), and higher activity level (F(1,25) = 202.233, p < .001). The increase in the performance of the patients however was not affected by the obesity of the individuals. We have also explored the effect of BMI on the difficulty of the surgery perceived by the surgeon and found that the surgeries were more difficult in obese patients (p = .023). CONCLUSION:. In this pilot study we have demonstrated that Minihip has the potential to exhibit excellent short-term clinical outcome in THA. In our study all individuals reported better quality of life after receiving the surgery. Future study should be conducted on comparing the differences in the outcome of the THA between commonly used implants and neck preserving stems

Introduction. Adverse Local Tissue Reactions (ALTR) have been reported in association with both wear and corrosion. Tissue reactions have been reported in association with corrosion at CoCr head-CoCr neck, CoCr head-TiAl6V4 neck, and CoCr modular neck on beta-titanium (TMZF) stem junctions. The current abstract reports on 3 cases of ALTR in association with CoCr modular necks on convention titanium (TiAl6V4) stem junctions. Case 1. A 67 year old male (87 kg, 1.73 m, BMI 29.1) presented with new onset hip irritation 11 months after surgery. Radiographs show no abnormalities. Further investigation revealed the following: ESR = 95, CRP = 5, Cr level = 1.0, Co level = 4.1, leukocyte transformation testing = highly reactive to nickel. Hip aspiration was culture negative with 11,250 wbc. Metal artifact reduction MR showed cystic local reaction in the region of the greater trochanter. Case 2. A 52 year old male (89 kg, 1.83 m, BMI 26.5) presented with new onset hip irritation 30 months after surgery. Radiographs show no abnormalities. Further investigation revealed the following: ESR = 7, CRP = 5.4, Cr level = 2.1, Co level = 4.8, leukocyte transformation testing = reactive to nickel. Hip aspiration was culture negative with 3995 wbc. Metal artifact reduction MR showed cystic local reaction in the region of the iliopsoas. Case 3. A 52 year old male (104 kg, 1.85 m, BMI 30.1) presented with new onset hip irritation 26 months after surgery. Radiographs show no abnormalities. Further investigation revealed the following: ESR = 33, CRP = 34.9, Cr level = 1.0, Co level = 3.7, leukocyte transformation testing = no reactivity to any of the biomaterials. Hip aspiration was culture negative with 3,780 wbc. Metal artifact reduction MR showed cystic local reaction in the region of the iliopsoas. Discussion. All three of these patients are scheduled for revision surgery. All three had ceramic-ceramic bearings. We have experience with 1029 ceramic-ceramic THA with fixed neck conventional titanium and modular titanium neck implants with minimum 2 yr f/u and have never diagnosed an adverse reaction in any of these patients. It is possible that corrosion at the CoCr neck on TiAl6V4 stem junction is the root cause of these reactions. Although the incidence of diagnosed reactions is roughly 1%, it appears that the use of CoCr at any junction under significant mechanical stress can result in adverse local tissue reaction and therefore should either be avoided or used with great caution and compelling indications

The concept that fluid percolating through bone matrix is the basis for mechanotransduction of stress stimuli to modeling and remodeling has proved challenging. 4. Traditional solid mechanical models in which piezoelectricity is the mechanotransduction process are more intuitive to orthopaedic practitioners nurtured on the fundamentalism of Wolff’s “Law”. However, the scientific evidence from Anderson and Ericksson. 1. , Piekarski and Munro. 5. , and Hillsley and Frangos. 3. strongly support a bone fluid flow (BFF) paradigm, which, when coupled with the Utah paradigm of Frost. 2. forms the most scientifically validated explanation to date of osteon response to mechanical stress in vivo. In order to make this explanation more intuitive we have developed a metaphorical rendering of the model. The rendering adds an extension to include our current model for the effects of skeletal muscle contraction on the basic multicellular unit (BMU). In the metaphor, cortical bone is the continent nation HaroldFrostland. Its cities are fed by waterways which serve as metaphors for each of the fluid transporting pathways from arteries to inter-collagen spaces of bone matrix. Bounding the continent are oceans wherein underwater earthquakes—metaphors for skeletal muscle contractions—generate solitary pressure waves (tsunamis) and a ripple effect in continental waterways. Critical for penetration by and effectiveness of such solutions is that flow resistance in the waterways must allow pressure buildup. Locks/valves serve to provide this resistance. When pressure is sufficient filtration at transfer points—metaphors for where nutrient exchange occurs--is enhanced. By this means, muscle contraction enhances delivery of fluid not only to bone cells; but around them as well, stimulating mechanotransduction

Biochemical changes in the articular cartilage of the knees of mature dogs, one with natural and four with surgically induced osteoarthritis, have been investigated. The four dogs were killed three, six, nine and forty-eight weeks after division of the right anterior cruciate ligament, the left knees serving as controls. The cartilage of the joints operated on was thicker and more hydrated than the control cartilage; the proteoglycans were more easily extracted and had higher galactosamine/glucosamine molar ratios. The proportion of proteoglycans firmly associated with collagen, and hence not extractable, diminished before fibrillation was demonstrable by indian ink staining of the surface. These biochemical changes were present throughout the entire cartilage of the joints operated on of the dogs killed more than three weeks later, and of the dog with natural osteoarthritis. The results suggest that in response to altered mechanical stresses the chondrocytes synthesise proteoglycans that contain more chondroitin sulphate relative to keratin sulphate than normally, as in immature articular cartilage

Introduction. Malalignment of lower limb is a common feature in patients with osteoarthritis (OA). This, either cause or effect of OA, is known to alter the normal anatomy of knee and affects progression of wear and tear in mechanically stressed compartment. We investigated the relationship of mechanical axis to wear and tear in varus, neutral and valgus knees. Materials and Methods. A retrospective analysis of 136 consecutive patients, with OA, who underwent total knee replacement using computer navigation. The thickness of medial and lateral cuts of distal femur and proximal tibia were recorded. Pre-op coronal deformity was assessed using long leg radiographs and Femoral Tibial Mechanical Angle (FTMA) calculated. Patients were evaluated as one group and three subgroups based on preop varus, neutral or valgus lower limb alignment. Student t test and Pearson's correlation coefficient were used for statistical analysis. Results. When considered as a whole group (136 patients) there was a significant difference between the medial and lateral cuts on both femoral and tibial side (p <0.001). We also found a significant negative correlation between FTMA and femoral lateral cut (r = −0.45). In varus group (103 patients) tibial medial and lateral cuts were significantly different (p<0.05) while there was no significant difference in femoral medial and lateral cuts. In valgus group (n=23) there was a significant difference between the femoral medial and lateral cuts (p<0.0001) while no significant difference was found between tibial medial and lateral cuts. Intergroup comparison showed that there was a significant difference between the varus and valgus group with regards to femoral medial cut, femoral lateral cut and tibial medial cut (all p<0.01). There was no significant difference between the tibial lateral cut between the varus and valgus group. We found a significant negative correlation between tibial lateral cut and FTMA in valgus group (r=-0.68). Discussion. In both varus and neutral group tibial lateral cut was more as compared to medial cut and this difference was significant while there was no significant difference between femoral medial and tibial cuts. This emphasises the point that in varus and neutral knees tibial side wear is responsible for causing the deformity as compared to femoral. There was no significant difference in tibial lateral cut between varus and valgus group. In valgus knees femoral side is responsible for producing malalignment rather than tibial side and less amount of lateral femur removal is required but amount of lateral tibial removal is not significantly different. This study shows that varus deformity is mainly a tibial phenomenon while valgus deformity mainly occurs in femur. Surprisingly, approximately a mean 9 mm of lateral tibial cut was required, irrespective of whether the patient had varus, neutral or valgus preop lower limb alignment

The clinical, radiographic and pathological features of eighty-eight cases of histologically verified intra-osseous ganglia in eighty-three patients are described. All were located in the subchondral bone adjacent to a joint and most frequently involved the hip, the ankle (medial malleolus), the knee and the carpal bones. Forty-seven of the eighty-three patients were male and all the patients were between fourteen and seventy-three years of age, with an average age of forty-one years. There are two fundamental types of intra-osseous ganglia, one apparently arising by penetration of juxta-osseous ganglion into the underlying bone, a mechanism proved in fourteen of our eighty-eight cases (16 per cent); in the remaining seventy-four cases, the ganglion cyst was primarily intra-osseous ("idiopathic"). The initial cause of the intramedullary mucoid degeneration is discussed. We believe that mechanical stress and repeated minor trauma near the surface of the bone may lead to intramedullary vascular disturbance with consequent foci of aseptic bone necrosis. The revitalisation of these areas causes fibroblastic proliferation, followed by mucoid degeneration of the connective tissue, possibly due to some unknown local factor. Curettage or excision is usually effective, and recurrence (only four cases) is exceptional

Bone fixation plates are routinely used in corrective and reconstructive interventions. Design of such implants must take into consideration not only good surface fit, but also reduced intra-operative bending and twisting of the implant itself. This process increases mechanical stresses within the implant and affects its durability and the functional outcome of the surgery. Wound exposure and anaesthesia times are also reduced. Current population-based designs consider the average shape of a target bone as a template to pre-shape the implant. Other studies try to enhance the average design by optimising surface metrics in a statistical shape space. This could ensure a low mean distance between the implant and any bone in the population, but does not reduce neither the maximum possible distances nor directly the mechanical forces needed to fit the implant to the specific patient. We propose a population-based study that considers the bending and torsion forces as metrics to be minimised for the design of enhanced fixation plates. Our aim is to minimise the necessary intra-operative deformations of the plates. In our approach, we first propose to represent a fixation plate by dividing it into discrete sections lengthwise and fitting a plane to each section. The number of sections depends on the size of the implant and anatomical location. It should be small enough to capture the anatomical curvatures, but large enough not to be affected by local noise in the surface. Surface patches corresponding to common locations for plate fixations are extracted from 200 segmented computed tomography (CT) images. In this work, distal lateral femoral patches are considered. A statistical shape model of the patches is then computed and a large population of 2,197 instances is generated, evenly covering the natural statistical variation within the initial population. These instances are considered as both bone surfaces and potential new designs of the contact surface of the fixation plate. The key formulation of our solution is to examine the effect of deforming each section of the implant on the rest of the sections and compute the amount of bending and torsion needed to shape one patch to another. Each instance of the population is fitted to all others and the maximum bending and torsion angles are recorded. A similar process was applied for the mean of the population. The goal is to pick from the population the shape that simultaneously minimises the bending and torsion angles. The maximum required bending was reduced from 25.3® to 19.3® (24.72% reduction), whereas the torsion component was reduced from 12.4® to 6.2® (50% reduction). The method proposed in this abstract enhances the current state-of-the-art in orthopaedic implant design by considering the mechanical deformations applied to the implant during the surgery. The obtained results are promising and indicate a noticeable improvement over the standard pre-contouring to the population mean. We plan to further validate the method and as a future outlook, we intend to test the approach in real surgical scenarios

Aims

The aim of this study was to identify factors associated with poor outcome following coccygectomy on patients with chronic coccydynia and instability of the coccyx.

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Limb-lengthening nails have largely replaced external fixation in limb-lengthening and reconstructive surgery. However, the adverse events and high prevalence of radiological changes recently noted with the STRYDE lengthening nail have raised concerns about the use of internal lengthening nails. The aim of this study was to compare the prevalence of radiological bone abnormalities between STRYDE, PRECICE, and FITBONE nails prior to nail removal.

Introduction: Avascular necrosis (AVN) of bone is a process that is characterized pathologically by bone marrow ischemia and eventual death of trabecular bone. Following the development of the disease with the remodeling process, the microstructure and corresponding mechanical properties of the trabecular bone changes in different regions with different intensities. Eventually, the lesion leads to collapse of the femoral head and destruction of the hip joint. The most striking finding is the direct relationship between mechanical stress and the progressive collapse of the necrotic region. This study investigated the differences in the mechanical properties from the trabecular bone of the different regions in AVN of the femoral head using microfinite element models. Materials and Methods: A 20mm cylindrical core sample was obtained from the necrotic zone of the human femoral head with pre-collapse disease throughout the overall head under the fluoroscope and then was scanned using Micro-CT. Region of interest (ROI) was determined in the necrotic, the reactive, and the sub-reactive zone respectively, which were created with the hexahedron mesh model; finite element analysis was performed. Results: The histomorphology and FE-analysis of three zones revealed that the parameters of Tb. Th, BV/TV, reaction force, ultimated stress, and elastic modulus increase obviously in the reactive zone. Discussion: The authors conclude that obvious increases of the parameters and the stress concentration in the reactive zone are due to the adaptive remodeling of trabeculae in the boundary zone between the necrotic and the normal zone

Introduction:. The mechanical stresses and strains surrounding orthopaedic implants can influence bone resorption and formation, micro-fracture, and consequently implant fixation or loosening. Experimental measurement of these internal parameters is generally not feasible. Computational predictions by finite element modeling are promising, but until recently have been limited to assuming the surrounding cancellous bone as a continuous volume, without modeling individual trabeculae. A recent study demonstrated errors in bone-implant stiffness exceeding 100% when using this continuum assumption [1]. Conversely, recently micro-finite element computer models have been built from high resolution imaging of trabecular bone. In the present study we developed such models of central pegs cemented into cadaveric glenoids. We hypothesized that additional applied cement would lead to stronger implant fixation, but less physiologic strains in the trabeculae. Methods:. Two cadaveric specimens were implanted, with the applied cement volume in the Specimen 2 approximately double that of Specimen 1. The specimens were imaged by micro-computed tomography (vivaCT 40, Scanco, Switzerland) with a resolution of 12 microns. Images were filtered and resampled, then imported in Mimics (Materialise, Belgium) for semi-automated segmentation and 3D reconstruction based on our laboratory's published methods. Finite element models containing 1.7 to 1.8 million elements having sides of 0.1 mm were generated by a direct image voxel-to-element approach [2] (Fig. 1). The material properties of cement and bone were assumed linear elastic (bone: E = 3.5 GPa, cement: E = 3.0 GPa, and implant (UHMWPE): E = 1.3 GPa), and interfaces were assumed fully bonded. All outer walls of the bone were fixed, and a downward force of 250 N was applied to the implant peg. Simulations were run using Abaqus (Simulia, Pawtucket RI) on a 32-core, 1 TB-memory server at PSU's High Performance Computing Systems. Results:. Specimen 1 had 254 mm. 3. cement measured in the model, whereas Specimen 2 had 535 mm. 3. Strain energy density was less for Specimen 2 for bone underneath the implant, but similar between specimens for bone around the implant sides (Figs 2 and 3), providing initial indication of complex effects of cement volume on peri-implant strains. In Specimen 2 a slightly larger volume of cement (8.6 vs. 6.8 mm. 3. ) was exposed to von Mises stresses exceeding 10 MPa. Discussion:. This study is novel in its prediction of stresses and strains down to the level of individual glenoid trabeculae surrounding a cemented implant. In this pilot investigation we found that bone embedded in the cement mantle is subject to low strains, whereas the bone immediately surrounding the cement mantle is subject to abnormally high strains, with both cement technique and trabecular architecture likely influencing results. The study is limited by the lack of application of more complex loads and boundary conditions. Future work includes modeling of additional specimens and statistical analyses, and investigation of the roles of cement stiffness and peg design in dictating peri-implant bone strains

Introduction: Osteoarthritis is the most common joint disease in the world. Biochemical and genetic factors as well as mechanical stress contribute to lesions in the cartilage. The present study analyses the effect of b-Endorphin on the cells of articular cartilage. Materials and methods: We used rat articular cartilage for the study. After tripsinizing the cartilage and isolating the chondrocytes the cells were cultured in a culture medium. B-Endorphin was dissolved in the culture medium at concentrations of 1 and 10 mM. Only the culture medium was added to the control wells. Naloxone 1 mM was added for co-treatment with b-Endorphin and naloxone. Thirty minutes later, b-Endorphin was added, thus blocking its receptors. Results: We studied the effect of this procedure on chondrocytes’ proliferating activity and on the proteoglycan synthesis of the extracellular matrix. An increase was observed in the incorporation of 3H-Thymidine, which in turn reflected an increase in the chondrocytes’ proliferating activity. In addition, 35S incorporation analyses were made of cultures which assessed proteoglycan synthesis which showed an increase in the extracellular-matrix forming activity. Differences between the groups with b-endorphin, b-endorphin + naloxone and the control group were found to be highly significant (p< 0.01). Conclusions: B-endorphin has a stimulating effect upon chondrocytes and proteoglycans present in the extracellular matrix in culture. These stimulating effects are mediated by the interaction with a specific opioid receptor, present in the articular cartilage cells. It may be conceived that trophic stimulation of cartilage cells in the early stages of the disease might partly mitigate the loss of joint surface

Introduction: Mechanical complications following lumbar fixation are due to the combination of various factors related to morphology, pathology, and surgery. The aim of this study was to provide a patient-specific Finite Element Model of the lumbar spine for the simulation of surgical strategies, and to use it as a predictive tool aiming to detect and reduce preoperatively the risks of mechanical complications. Materials & Methods: A pre-existing 3D personalized FEM of the lumbar spine was used. Posterior implants and main degenerative pathologies were also modelled. After in vitro validation based on 24 specimens and 4 different instrumentations, the model was used to simulate real cases. Applied loads were based on patient characteristics (weight, imbalance). Simulation results included mechanical stresses in the discs and within the implants. Clinical consistency of the simulations was tested through the gathering of clinical data for 66 patients instrumented with lumbo-sacral rigid screw-rod systems. Two subsets were considered: “mechanical successes” (53), and “mechanical failures” (13, including 11 screw breakage and 2 screw loosening). Blind comparison was then performed between these observed clinical outcomes and numerical simulations results. Results & Discussion: Among the 66 patients, simulation results highlighted specific behaviours for 9 patients for which mechanical loads on implants were significantly higher. All of these 9 patients were actual “mechanical failures”. None of the actual “mechanical successes” were associated with “abnormal” simulation results. Conclusion: This is the first time finite element simulations helped predicting 9 failures out of 13 observed among a total of 66 patients. This is a promising step towards the possibility to use FEM as a clinically relevant simulation tool for surgery planning

Reaming intramedullary nailing, possibly associated with autologous bone grafting, is an effective procedure for the treatment of uninfected non-union and limited post-traumatic segmental bony defects. The main purpose of the treatment is to remove the causes responsible for the pathological evolution of fracture healing and to create proper vascular and mechanical conditions in the lesion site. Hypertrophic non-union, which is considered a biologically active pathological condition, can be effectively treated by reaming of the medullary canal and by introducing a new nail of a larger diameter locked in a dynamic configuration; the purpose of this procedure is to help osteogenic compressive forces at the non-union site. In contrast, for the treatment of atrophic non-union it is necessary to avoid all mechanical stresses on the non-union site and give a new proper biological input. Cancellous and cortical-cancellous autologous bone grafting has undoubtedly well-known osteoinduc-tive and osteoconductive properties as well as introducing new osteogenic bone marrow cells to the non-union site. Non-union site exposure, essential to remove pathological tissues and to open medullary canal, must be performed by gently dissecting the soft tissues to lower the infection risk and to save the periosteal vascularisa-tion. The authors report their experience using locked reamed intramedullary nailing combined with cancellous and/or cortical-cancellous autologous bone grafts for the treatment of uninfected non-union, non-biologically active delayed union and limited post-traumatic bony defects in 15 cases. Based on our experience, such a procedure is reliable and with excellent biological and mechanical properties, as all of the lesions healed at the end of the treatment without complications. In these “bone callus” diseases, which always provide clinical and psychological discomfort, this procedure has demonstrated good results and, because of this, in our series, has also been used for the treatment of delayed union

Aims: Hydroxyapatite coatings have been proven to improve the osteointegration of metal implants however they are not stable and they might delaminate from the metal surface when challenged by the mechanical stresses experienced by the implant. Therefore, efforts of different researchers are being devoted to find more stable coatings or surface treatments that could replace HA. In particular, spontaneous calcium phosphate deposition on titanium surfaces from aqueous electrolyte containing calcium and phosphate ions, such as simulated body fluid solutions, has been observed and is believed to be related to the excellent bonding capability in contact with bone tissue. In the present study, a new multiphase anodic spark deposition (ASD) method combined with chemical etching is presented It has been optimized and such modified titanium surface exhibited high mineralisation potential, selective protein adsorption, quicker and more intensive osteoblasts adhesion and differentiation. Such treatements was labelled BioSpark™ and consisted in a thick calcium-phosphate-doped oxide film growth on the titanium bulk. This oxide layer exhibits anatase lattice, micro-porosity and a thin nano-roughened texture. Methods: The effect of this process, was investigated invitro and in vivo in cortical and spongy bone of 12 adult sheep. Histomorphometric and microhardness measurement were carried out at each experimental time (4, 8, 12 weeks) to quantify the bone-to-implant contact around the implants, the bone ingrowth as well as the newly bone hardness and bone maturation index. Results: Data suggests that the BioSpark treatment produces a modification of the Ti surface, which represents good bioactivity and may be suitable for achieving a stable implant osseointegration. Conclusions: Such surface modification treatments was applied in the last two years on dental implants with great success and is now being tested in human being for histological studies. In the future, it will be applied on orthopaedic prostheses devices in order to improve device osteintegration. The data demonstrate that this type of surface improves the material osteointegration potential when compared to conventional surfaces while offering high mechanical stability

Zirconia (ZrO2) on Polyethylene (PE) has been used for18 years. However, a majority of clinical results expressed caution, citing surprisingly high wear and osteolysis. The most recent clinical study (Walters 2004) reports 20% higher wear with ZrO2/PE compared to CoCr/PE The PE wear may be the result of increased surface roughness of the ball, due to zirconia transformation from tetragonal to monoclinic phase. Impingement of metal cup backing on zirconia may result in high stress that drives the transformation. Our objective was to simulate the conditions most likely to transform the zirconia ball surface. In phase one, the rim of a titanium cup was loaded against a zirconia ball with a static load range of 0.01kN to 10kN to simulate impingement-dislocation stress. The ball was cleaned with acid, ultrasonic cleaning, and then observed under SEM. Ball sections were made for XRD study. In phase two, the zirconia balls were pressure stressed in a hip simulator (static load range of 1kN to 4kN) for 600 cycles. Wear studies follow. In phase one, the rim of a titanium cup was loaded against a zirconia ball with a static load range of 0.01kN to 10kN to simulate impingement-dislocation stress. The ball was cleaned with acid, ultrasonic cleaning, and then observed under SEM. Ball sections were made for XRD study. In phase two, the zirconia balls were pressure stressed in a hip simulator (static load range of 1kN to 4kN) for 600 cycles. Wear studies follow. Pressure alone does not appear to transform zirconia in the articular surface. The phase two simulator studies include combinations of mechanical stress, environmental aging (autoclave) and lubricants (air, water, serum). The role of the heavy metal transfer may actually protect the zirconia surface from transformation phenomena

Aim: Many risk factors for DDH are well documented. This study was undertaken to investigate whether multiple pregnancy is a risk factor for developmental dysplasia of hips. Method: During a 10-year period from 1989 to 1998, 39826 newborn babies had their hips scanned. Of these, 1022 (2.6%) babies were non-singletons. Inclusion criteria for our study were all non-singletons, who had their hips scanned in the þrst week after birth. We analyzed the results of their hip scans and calculated the risk for developing DDH either alone or with other risk factor and other variables like the gender, mode of delivery, birthweight and the length of pregnancy. Results: Of the 1022 babies, 825 (80.7%) had their hips scanned in the þrst week. M: F: 49.6%: 50.4%. We had 397 sets of twins, 9 sets of triplets and 1 set of quadruplet. 78% of this group had a normal presentation. 21% (181) of these babies were breech. There was no family history associated with any of the multiple births. Ultrasound abnormality was seen in 30 hips (1.8%). 1 patient had Pavlik harness treatment for persistent ultrasound abnormality. No signiþcant correlation was seen in the gender or in the length of pregnancy. Conclusion: Though it is a general impression that the hips of the non-singletons are under high mechanical stress during pregnancy and would be expected to have a relatively high incidence of DDH, from our study it is evident that the risk is no greater than the normal singletons

The treatment of bone metastases is usually palliative and aims to achieve adequate control of pain, to prevent and resolve compression of the cord in lesions of the spine and to anticipate or stabilise pathological fractures in the appendicular skeleton. In selected cases the complete resection of an isolated bone metastasis may improve the survival of the patient. During recent decades, the life expectancy of patients affected with metastatic carcinoma has improved considerably because of advances in chemotherapy, immunotherapy, hormonal treatment and radiotherapy. This improvement requires greater reliability in the reconstructive procedure in order to avoid mechanical failure during prolonged survival of the patient. The author experience with modular megaprosthesis by Link (megasystem C) allowed us to present a rapid, effective and functional solution. From June 2001 to December 2007 225 patients have been operated with a megaprosthesis C for tumoral resection. The new megaprosthesis C by Link represents a wide-ranging system that can afford a large variety of reconstructions in the inferior limb, from very short replacement of 5 cm in proximal femur, to a total femur and proximal tibia replacement. Modularity is represented by 1 cm increase in length. The different options of cemented and not cemented stem may be used with intraoperative decision. In cemented stem a rough collar seals the osteotomy and prevents polyethylene debris from entering the femoral canal by inducing a scar tissue around the stem entrance (so-called purse-string effect). Moreover in patients with solitary lesions and very good prognosis an allograft-prosthesis composite can be performed with improved clinical results on walking and function. Of the 225 patients that underwent tumoral resection and reconstruction with a modular megaprosthesis approximately 43% (97 cases) were operated for metastatic disease. Among these cases 55 cases were proximal femoral recontructions, 39 cases were distal femoral reconstructions and 3 cases were proximal tibial reconstructions. All cases were performed with cemented stems. We experienced a 7% of postoperative infections, 2% of dislocations of proximal femoral prosthesis and 3% of mechanical failures. While infections and dislocation rates were in the average for this surgery, mechanical failures seemed relatively high. However in patients with relatively long resections and muscle deficiency the mechanical stress exerted on the prosthesis can explain this kind of mechanical failure

Purpose: Acetabular revision has become a challenging situation due to the importance of bone stock loss encountered in SOFCOT stage III acetabula. The number of failures due to loosening are explained by the strong mechanical stress on the bone grafts or inadequate restitution of the rotation centre of the hip. The purpose of this study was to evaluate mid-term results of the Kerboull support used to achieve anatomic recentring of the hip and progressive weight bearing on the bone grafts. Material and methods: This retrospective series included 54 acetabular revisions performed for stage III loosening between 1989 and 1996. A Kerboull support was used in all cases. The patients were assessed with the Postel Merle d’Aubigné score and radiographically on plain pelvis films in order to search for recurrent loosening or arthroplasty failure. The log rank test was used to compare actuarial survival. Results: The series included 62% women. Mean age was 62.3 years (33–87). This was the first revision for 78% and a second or more revision for 22%. The preoperative Postel Merle d’Aubligné score was 9.18 points. This score was 12.3 postoperatively, 15.6 at one year, 15.5 at five years and 14.8 at last follow-up. Dislocation was the most frequent complication, with 55% occurring on cups more than 46° oblique. Grafts were considered radiographically integrated in 58% of the cases. There were 5.5% failures due to migration, 13.8% due to fracture of the superior screw. The actuarial survival was 97.4% at three years, 94.7% at four years, 89.2% at five years and 73% at seven and ten years. Conclusion: On the basis of these good short-, mid- and long-term clinical and radiographic results, we recommend Kerboull support for the treatment of stage III acetabular loosening

Aims

Interleukin (IL)-1β is one of the major pathogenic regulators during the pathological development of intervertebral disc degeneration (IDD). However, effective treatment options for IDD are limited. Suramin is used to treat African sleeping sickness. This study aimed to investigate the pharmacological effects of suramin on mitigating IDD and to characterize the underlying mechanism.

Background. High re-rupture rates following repairs of rotator cuff tears (RCTs) have resulted in the increased use of repair grafts to act as temporary scaffolds to support tendon healing. It has been estimated that thousands of extracellular matrix repair grafts are used annually to augment surgical repair of rotator cuff tears. The only mechanical assessment of the suitability of these grafts for rotator cuff repair has been made using tensile testing only, and compared grafts to canine infraspinatus. As the shoulder and rotator cuff tendons are exposed to shearing as well as uniaxial loading, we compared the response of repair grafts and human rotator cuff tendons to shearing mechanical stress. We used a novel technique to study material deformation, dynamic shear analysis (DSA). Methods. The shear properties of four RCT repair grafts were measured (Restore, GraftJacket, Zimmer Collagen Repair and SportsMesh). 3mm-sized biopsy samples were taken and subjected to DSA using oscillatory deformation under compression to calculate the storage modulus (G') as an indicator of mechanical integrity. To assess how well the repair grafts were matched to normal rotator cuff tendons, the storage modulus was calculated for 18 human rotator cuff specimens which were obtained from patients aged between 22 and 89 years (mean age 58.8 years, with 9 males and 9 females). Control human rotator cuff tendons were obtained from the edge of tendons during hemiarthoplasties and stabilisations. A 1-way ANOVA of all of the groups was performed to compare shear properties between the different commercially available repair grafts and human rotator cuff tendons to see if they were different. Specific comparison between the different repair grafts and normal rotator cuff tendons was done using a Dunn's multiple comparison test. Results. We report a significant difference in the shear moduli of all four rotator cuff repair grafts (P<0.0001, 1 way ANOVA, Kruskall-Wallis test). 2 of the grafts, Zimmer Collagen Repair and SportMesh, were not significantly different when compared to rotator cuff tendons and were found to have comparable shear mechanical properties (P > 0.05, Dunn's multiple comparison test). The other repair grafts, GraftJacket and Restore, had a significantly lower storage modulus when compared to human rotator cuff tendons. Conclusions. With increasing numbers of repairs of rotator cuff tears, and augmentation of these repairs, there is a need to understand the mechanical and biological properties of the both repair grafts and the tendons they are designed to augment. At present there is no clear definition of the ideal mechanobiological properties of rotator cuff repair patches. Current rotator cuff repair grafts display a wide variation in their shear mechanical properties, and how closely they are matched to the mechanical properties of human rotator cuff tendons. It is hoped that this study may help to guide surgeons in deciding on the most appropriate rotator cuff tendon repair graft

INTRODUCTION. Osteoarthritis (OA) can be artificially simulated ex vivo on healthy articular cartilage (AC) samples by use of proteolytic enzymes. In this article we will present preliminary analyses of the physical degradation of AC when subjected to alternating mechanical stresses. Since AC damage due to OA is believed to be mechanically induced, the first step towards the realisation of an improved understanding of degenerative behaviour of AC under physiological loading conditions is to perform ex vivo tests which mimic such conditions at best. METHODS. Porcine AC was subjected to biochemical stimulation or left as native AC. Biochemical degradation was performed using combinations of trypsin and Matrix Metalloproteinases (MMPs) to induce the loss of proteoglycan and collagen. A comparison of the biochemical and mechanical properties, topography and difference in response to mechanical damage between the digested AC and healthy AC was made using White Light Interferometry (WLI), Atomic Force Microscopy (AFM) and mechanical testing. The mechanical damage was induced by subjecting AC to shear under physiological and non physiological conditions. The AC was mechanically tested in a Phosphate Buffered Saline (PBS) bath. After mechanical testing, biochemical analysis of the collagen and aggrecan content of the tissue and PBS present in the bath during the mechanical test was performed. Collagen content was determined by measurement of the amount of hydroxyproline (HPRO), and aggrecan content by the amount of glycosaminoglycans (GAG). The mechanical test was either performed on healthy (native) AC or on AC which had first been digested. RESULTS AND DISCUSSION. After mechanical testing, very small collagen damage and a very high ECM damage in the native AC following the mechanical test was observed. This seems to be in line with the development of AC damage during OA; the first part of the AC structure to be affected and damaged is the ECM. The collagen is believed to be more stable and degrades both mechanically and chemically only after the ECM has started degrading. Another possible explanation for this could be the fact that the collagen is able to resist shear stresses very well due to the fibrils being aligned parallel to the surface hence limiting the onset of damage. In the digested AC, both ECM and collagen damage are considerably higher since both parts of the structure have already been partially degraded. Experiments have also shown a dramatic decrease of interstitial fluid pressurisation in the digested samples hence exposing the solid constituent of AC to further degradation during mechanical testing. This could shed light on the nature of the progression of OA. CONCLUSIONS. This study allows us to better understand damage in AC and its effect on biomechanical, structural, biochemical properties and on the mechanical response of the tissue at physiological conditions. Future work will also include the use of Atomic Force Microscopy in order to characterise the surface and evaluate local mechanical properties using force – indentation curves. Mechanical stimulation of living AC in order to induce biochemical changes in the tissue due to abnormal stresses and strains on the chondrocytes will also be investigated

The morbidity associated with tendinopathy is a costly burden on our health system. Recent investigations in our laboratory have shown that alterations in mechanical stress cause significant changes in tendon expression of key matrix molecules and proteolytic enzymes including the aggrecanase molecules, (e.g. ADAMTS-5). Here, we investigate the biomechanical consequences of such altered tensile stress in tail tendons from mice with and without deletion of the ADAMTS-5 gene. Tail tendons from 12 week old C57BL6 wild type and ADAMTS-5 knock-out mice were immediately snap frozen (ex vivo), or cultured stress deprived for 120 hours in DMEM/10% FCS (eight tendons per group). Material properties including maximum stress, strain and elastic modulus were determined for each tendon in uniaxial tension to failure at a constant strain rate of 1.0 mm/second (10% strain/second) on an Instron 8874 servo-hydraulic testing apparatus. Significant differences between groups were determined with Kruskal-Wallis one-way analysis of variance, followed by Mann-Whitney U test with Benjamini-Hochberg post-hoc corrections for multiple comparisons. Stress deprivation for 120 hours led to a significant increase in maximum stress for both the wild type (~150% increase, p = 0.0008) and ADAMTS-5 deficient (~100%, p = 0.0033) mice when compared to ex vivo tendon. Stress deprivation led to a 100% increase in elastic modulus compared to ex vivo for the wild type tendons (p = 0.0033) but failed to increase this parameter in the ADAMTS-5 deficient mice. When the effect of stress deprivation of the ADAMTS-5 deficient mice was directly compared to the wild type stress deprived tendons, a 35% decrease in elastic modulus was found (p = 0.021). We have shown for the first time that deletion of an aggrecanase molecule significantly decreases the material properties of tendon. Alterations in the expression of the aggrecanase molecules may play a role in the development and progression of tendinopathy through their ability to modulate the metabolism of aggrecan [. 1. ]. Previous research in our laboratory has shown that aggrecanase expression is markedly up-regulated by stress deprivation. This finding in combination with the results of the present study suggest that the aggrecanase molecules may provide a future therapeutic target for the treatment tendinopathy

Introduction: Packaging of Muscolo-Skeletal Tissues (MST) stored at −80°C must assure safety and sterility in order to minimize any risk of bacterial contamination and/or mechanical failure. Polymeric bags demonstrated problem of integrity at −80°C; gamma ray sterilisation induce oxidation decreasing mechanical properties, whereas Ethylene Oxide (EtO) does not. Antioxidant biocompatible additive, as Vitamin E, could improve mechanical resistance. Objectives: Based on a previous paper presented at EATB 2005 congress, to analyse mechanico-chemical properties of plastic bags routinely used in MST Banks and new samples in order to identify and solve possible problems arising from the chemical composition and/or sterilisation. Materials and Methods: Five different polymeric sterile bags used in three International Banks (three gamma and two EtO sterilised) and four experimental sample, manufactured on purpose from a Linear Low Density PolyEthylene (LLDPE) 150 microns thick films (EtO and e-beam sterilised), two added of Vitamin E, were analysed. Impact resistance was evaluated both on frozen and unfrozen material (in oven at 37°C); results were related to chemical composition, Tg, sterilisation and Fourier Transformed InfraRed Spectroscopy (FTIR). Results: Three samples routinely used (one gamma and one EtO) showed severe macroscopic modification (glassy behaviour) at frozen temperature with no resistance to any mechanical stress Two samples (EtO) did not resist to mechanical tests at frozen state. The four experimental LLDPE, EtO and e-beam sterilised, resisted to mechanical tests. FTIR analysis confirmed the chemical composition declared by the commercial film: pure LLDPE, without any toxic additive and LLDPE with vitamin E. Discussion: Packaging must use polymers with adeguate glass transition temperature (Tg) in order to maintain at −80° the rubbery state, not stiff nor fragile (not to pass to glassy state). High energy radiation oxidize polymer and decrease their mechanical resistance. LLDPE combine low Tg of the amorphous phase and low crystallinity, resulting in good mechanical properties at working temperature and at −80°C. Addition of Vitamin E protect against oxidation. EtO sterilisation does not modify the structure. Conclusion: A LLDPE added of Vitamin E, sterilised by EtO and e-beam could improved packaging and storage of tissues at −80°C, with increased resistance to oxidation

Aims

Osteoarthritis (OA) is a disabling joint disorder and mechanical loading is an important pathogenesis. This study aims to investigate the benefits of less mechanical loading created by intermittent tail suspension for knee OA.

Osteointegration of HA coated devices is well demonstrated. An abundant experimental material exists, allowing to describe the various properties of HA (early osteointegration, sealing effect, gap healing effect, etc…). Various side-effects have been described (third body wear of HA debris, delamination of the proximal coating etc…). Thus controversy still exists, despite a more and more convincing clinical experience. The role of human retrievals is therefore crucial to determine the exact role of all these parameters in the natural life of the implant throughout the years. 49 human well-functioning explants have been retrieved during systemic autopsies in elderly patients previously operated for a displaced fracture of the neck with a Corail® implant. Delays of implantation vary from 5 days to 10 years. All these specimens have been processed for optical microscopy, electronic microscopy with backscattering. This constitutes the longest report on one single implant and the retrievals are evenly distributed over this ten-year period. Several histomorphometric parameters were measured in the different Gruen’s zones: cortical bone density, cortical bone thickness, density of endosteal bone. 3 steps are recognized:. Bone formation around the implant appears early after surgery. Multiple units of bone formation go to coalescence as soon as 6 weeks and develop thereafter, leading to osteointegration. Bone remodelling reorganizes the architecture of connecting trabeculae according to the mechanical stresses resulting from the presence of the implant. Compression areas are generally the seat of broad and interconnected trabeculae, whereas tensile stresses areas display the presence of long, thin, unconnected and often parallel trabeculae. Very broad and short trabeculae are often seen at the level of the corners. Coating resorption is seen in every specimen beyond one year of implantation, predominantly in the areas with less bone coverage. Release of HA particles in the joint cavities was never encountered. Some metallic particles, originating from the femoral ball are commonly seen in the polyethylene. HA particles (presumably scratched off the prosthesis during insertion?...) have never been identified in the heterotopic ossifications. We conclude that the osteointegration of the Corail stems is a reliable phenomenon with a reproducible sequence of events. It lasts even after the disappearance of the coating in a 5–10 years period. The presence of the stem provokes a remodelling of the cortices but the presence of a total coating and its longer duration at the level of the tip does not induce a disappearance of the proximal bone or a loose of the proximal fixation

Full thickness defects of articular cartilage have a poor capacity for biological repair and often progress to osteoarthritis. Various surgical techniques have been developed to overcome the inability of chondrocytes to heal injured cartilage. Arthroscopic lavage and debridement offer temporary symptomatic relief whereas marrow-stimulating techniques like drilling, microfracture and abrasion arthroplasty yield poor quality fibro-cartilage that is incapable of withstanding the mechanical stresses to which healthy articular cartilage is subjected. We present our experience using the osteochondral graft transfer technique in the treatment of isolated Outerbridge grade 4 lesions of the knee. The study includes nineteen patients with a mean age of 29 years (range 17 to 40) presenting with symptomatic lesions of the knee with a mean defect size of 2.4cm (0.8 to 6). At a mean follow-up of 20 months (6 to 40) our results showed a significant improvement in patient function by a mean of 46 points or a 23% mean improvement as assessed by the Knee Society Score (P< 0.0001; One sample t-test). Similarly there was significant improvement in the Brittberg scores with a mean improvement by 2 clinical grades (p< 0.0001; Wilcoxon Rank test). Quality of life scores as measured by the Short Form 36 were dramatically improved by a mean of 24 points (p< 0.0001; Wilcoxon Rank test). In addition, there was significant reduction in pain post-operatively (p< 0.0001; Wilcoxon Rank test) with patients describing a mean improvement of 6 points as measured on the visual analogue chart. A significant number of patients (84.2%) were able to return to active sporting levels by 6 months (p< 0.0001;McNemar Change test). The results of the osteochondral graft transfer technique, at relatively short-term follow-up, are encouraging with a high percentage of subjective satisfaction. This procedure proved to be a reliable and valid solution for treating isolated osteochondral defects of the knee, providing functional and durable cartilage that is critical to joint function

Introduction: The management of periprosthetic osteolysis is a challenging problem in revision hip arthroplasty. Filling acetabular bone defects with structural allografts resulted in early failure due to resorption of the graft. The application in combination with reinforcement rings should promote bone incorporation as a result of reduced mechanical stresses. This study evaluates the long-term results in the treatment of acetabular deficiencies using bulk allografts supported with a Burch-Schneider Anti-Protrusio Cage (APC). Materials and Methods: From January 1992 to December 1995, 69 consecutive patients underwent revision surgery following periprosthetic osteolysis and aseptic loosening of the cup. Acetabular bone loss included IIIA and IIIB types according to Paproski classification. 12 patients died for unrelated causes with a well-functioning total hip arthroplasty in situ. 3 cases were lost at follow-up. The study group consisted of 56 hips in 54 patients. There were 11 males and 43 females, aged from 33 to 84 years (medium 65). Average follow-up was 11.7 years, ranging from 10 to 14.4. Surgical procedure included filling acetabular bone defects with bulk allografts supported with a Burch-Schneider APC which was fixed with screws to the iliac bone. A poly-ethylene cup was finally cemented into the metal cage. Deambulation was allowed one week after surgery, but weightbearing was delayed two months. Clinical evaluation was determined using Harris hip score (HHS). The stability of the acetabular implant was assessed according to Gill criteria. The progression of the bone graft was evaluated using Gross grading. Results: 2 patients developed deep infection that was treated by resection-arthroplasty. Aseptic loosening of acetabular cage following an extensive resorption of bone graft was observed in 6 cases and 3 of them underwent rerevision. X-ray signs of graft incorporation occurred in 48 hips. Average HHS values of 30 (range, 11 to 81) and 75 (range, 28 to 100) points were assessed respectively in the preoperative time and at follow-up. Discussion and Conclusions: In severe acetabular bone deficiencies the application of reinforcement rings in combination with massive allografts has been advocated in order to prevent bone graft resorption and cup loosening. Burch-Schneider Anti-Protrusio Cage is able to protect the graft spanning bone defects and promoting augmentation of periprosthetic bone stock. With an aseptic failure rate of 8.9% and a total survival rate of 85.7% at an average of 11.7 years, the use of APC and structural allograft proved out to be an effective procedure in the long-term reconstructive treatment of extensive loss of acetabular bone stock

Purpose: To evaluate and compare the effect of arthroscopic depridement and lavage versus arthroscopic lavage only as a treatment in osteoarthritis of the knee. Type of Study: A prospective study. Material and Methods: 500 patients ( mean age 58 years ) were available for 6 years follow-up after arthroscopy of the knee as a treatment of osteoarthritis refractory to conservative treatment. 250 patients were treated with debridement and lavage and 250 patients were treated with lavage only. Osteoarthritis of the knee is a common cause of knee pain. The pain from osteoarthritis is due to synovitis, capsular and ligamentous inflammation, and subchondral bone pain because cartilage has no nerves. Degenerative arthritis is usually the end result of mechanical stress inflicted on the articular cartilage, either through a suddenly applied single load or through the cumulative effect of multiple or repetitive loads leads to breakdown of the articular cartilage. The treatment of knee pain due to osteoarthritis of the knee includes conservative treatment such as rest, weight loss, physical therapy, nonsteroidal anti-inflammatory drugs, Cox-II inhibitors, nutritional supplements, steroid injections, Viscosupplementation, and surgical treatment such as arthroscopy, osteotomy or arthroplasty. With failure of conservative treatment, arthroscopic debridement and lavage is the treatment of choice for such patients. Results: Arthroscopic debridement and lavage performed in earlier stages of osteoarthritis of the knee resulted in significant reduction of pain for long period of time. In advanced stages of osteoarthritis, patients experienced less pain relief for shorter period of time. Debridement and lavage was superior to lavage only at 6 years in reduction of pain. In my group 93.8% (91.2% of the lavage group and 96.4% of the debridement group) were satisfied at 6 months and felt better than before their surgery, at 3 years 45.6% (35.6% of the lavage group and 55.6% of the debridement group) felt better, and at 6 years 30.2% (22.8% of the lavage group and 37.6% of the debridement group) felt better after the arthroscopic procedure. Conclusions: Arthroscopic debridement and lavage of painful osteoarthritic knees has a better outcome than lavage only for the same treatment, however patients must be made aware that the procedure is not curative and that it is quite possible that they will need further surgery in the future. Arthroscopic surgery (debridement and lavage or even lavage only) is reasonably successful temporizing and palliative procedure. However, the patient must be informed about the prospects of success, the benefits, the alternative and the risks of that procedure

Introduction: The use of anterior vertebral staples in the fusionless correction of scoliosis has received increased attention in recent literature. Several animal studies have shown stapling to be effective in modulating vertebral growth. In 2005 Betz (1) published the only clinical series to date. Despite the increasing volume of literature suggesting the efficacy of this treatment, little is known about it’s biomechanical consequences. In 2007 Puttlitz (2) measured the change in spinal range of motion after staple insertion in a bovine model. They found a small but statistically significant decrease in range of motion in axial rotation and lateral bending. The clinical significance of this is questionable as the differences were only a few degrees over three vertebral levels. A well designed biomechanical evaluation of the effects of staple insertion on spinal stability is needed. The aim of this study was to evaluate the effect of insertion of a laterally placed anterior vertebral staple on the stiffness characteristics of a single motion segment. Methods: Four-pronged shape memory alloy staples were inserted into fourteen individual bovine thoracic motion segments. A displacement controlled six degree-of-freedom robotic facility was used to test control and staple constructs through a pre-determined range of motion in flexion, extension, lateral bending, and axial rotation. All data were synchronised with robot position data and filtered using moving average methods. The stiffness in each condition was calculated in units of Nm/degree of rotation. Paired t-tests were used to compare results. Results: Stiffness measurements in the control condition correlated with previously published measures (3). A significant decrease in stiffness (p< 0.05) following staple insertion was found in flexion, extension, lateral bending away from the staple, and axial rotation away from the staple. Stiffness for axial rotation towards the stapled side was significantly greater than for away. A near significant increase in lateral bend stiffness away from the staple compared with towards was also seen. Discussion: These results suggest that staple insertion consistently decreased stiffness in all directions of motion. This is contrary to the results of Puttlitz (2), which reported a reduced range of motion (i.e. increased stiffness) for some motions using moment-controlled testing. This decrease in stiffness could not be explained by changes in anatomy or tissue properties between specimens, as each stapled motion segment was compared with its own intact state. Addition of the staple would intuitively be expected to increase motion segment stiffness, however we suggest that the staple prongs may cause sufficient disruption to the vertebral bodies and endplates to slightly reduce overall stiffness. Hence, growth modulation may be achieved through physical disruption of the endplate, rather than static mechanical stress. Further research is planned to investigate the proportion of load carried by the staple during spinal movement and the anatomical effect of the staple on the physis. In conclusion, anterior vertebral stapling causes a slight but significant decrease in the stiffness of treated motion segments

Aims

It has been hypothesized that proximal radial neck resorption (PRNR) following press-fit radial head arthroplasty (RHA) is due to stress-shielding. We compared two different press-fit stems by means of radiographs to investigate whether the shape and size of the stems are correlated with the degree of PRNR.

Purpose: The purpose of this study was to analyse mechanical failures involving dismonted osteosynthesis materials implanted to fix pertrochanteric or subtrochanteric fractures with a dynamic hip screw (DHS), a Gamma nail, or a plate nail system (STACA). Material and methods: Our cohort included 16 patients among a series of 350 patients who had been treated with 240 DHS, 80 Staca nailplates, and 30 Gamma nails between 1996 and 1999. We used the Ender classification for the x-ray analysis and the Cuny criteria which describe the most common causes of dismounted material. Results: According to the defined criteria, 70/350 osteosynthesis assemblies (20%) were considered insufficient on the immediate postoperative x-rays and eventually dismounted in 16 patients. Two of these patients had major osteopaenia according to the Singh criteria and ten underwent revision because of poor clinical tolerance. These patients had six DHS (3 “swinging” cervical nails, two dismounted plates, and one screw protruding into the joint space). A protruding screw was the problem for the eight Staca nail-plates. Two Gamma nails had a “swinging” screw. These cases of dismounted material were predominantly observed in patients with Ender grade 5, 7 and 8 pertrochanteric fractures. Discussion: Our analysis of these cases revealed several important factors: 1) the quality of the fracture reduction with restitution of the medial pillar of the per-trochanteric mass; 2) central anchoring in the femoral head essential for stable fixation; 3) superior stability of the DHS in grade 1 and 6 fractures due to the greater projected surface improving hold in cancellous bone. Inversely, for subtrochanteric fractures (grade 7 and 8), centromedulary shaft anchoring with a Gamma nail reduces mechanical stress in varus and thus the risk of “swinging” screws. Finally, the monoblock construct of the Staca nail-plate, which does not have the dynamic potential of the DHS and the Gamma nail, raises a risk of protrusion, particularly in case of “internal rotation” fractures with major metaphyseal comminution (grades 4 and 5). This latter type of fixation is however very effective for simple pertrochanteric fractures with minimal comminution (grades 1 to 3). Conclusion: Material dismounting results from a series of factors related both to the material used and to the operative technique. We thus reserve the Staca nail-plate for grade 1 to 3 fractures in the Ender classification, the DHS for grades 1 to 6 and the nail-screw fixation for subtrochanteric (grade 7 and 8) fractures

In an experimental study in rabbits, bone and cartilage regeneration could be achieved with a new class of resorbable bio-implants. These implants consist of an open porous structure made from polylacitdes and an open porous fleece made from polyglactin/polydioxanon. Both layers were not separated from each other, thus allowing mesenchymal cells to penetrate freely from bone into both the bone substitute and the cartilage substitute layer. It could be shown that ostochondral defects of 4mm diameter and 6mm depth in the condyle of the knee of rabbits healed by the process of mesenchymal cell differentiation into osteocytes and chondrocytes triggered by mechanical load induction only. Evaluation of the newly formed cartilage by light microscopy and immunohistology showed hyaline like features. However, in many clinical cases chondral defects occur without substantial accompanying bone loss. In these situations, reconstruction of the cartilage defects only seems to be sufficient. However, fixation of such fleeces onto the bone is difficult. On one hand, adherence of the fleece to the underlying bone is crucial, on the other hand an open connection from the bone to the fleece must be accomplished in order to allow mesenchymal cells to penetrate the fleece. Therefor, any kind of glue fixation is not appropriate. To overcome this problem, a new fixation method was developed which allows a safe connection of the fleece onto the bone while providing an open contact of the fleece to the bone marrow for unhampered migration of mesenchymal cells. The new “Cartilage patches” consist of a fleece (serving as the cartilage substitute layer) made from polyglactin/polydioxanon which had proven its applicability in the above mentioned experiments. Fixation of fleece was achieved by “darts” which were glued onto the fleece. The darts were made from polylacitdes, thus providing sufficient mechanical stability in the bone. During operation, small holes are cut into the bone by a special instrument. The holes are located in such a way that the darts of the cartilage patch fit into them, such resulting in a stable fixation of the fleece onto the underlying bone. Blood containing mesenchymal cells from the bone marrow is able to flow from the holes into the fleece. In a biomechanical analysis the adherence of the cartilage patches were tested with respect to shear resistance and pull-out stabillity. The results of the tests show that the new cartilage patches withstand the mechanical stress exerted onto articular surfaces and can serve as a new class of cartilage substitute layers. In an animal experiment the applicability of the cartilage patches in reconstruction of cartilage defects in the knee joint of sheep will be proven

Aims

The Mathys Affinis Short is the most frequently used stemless total shoulder prosthesis in the UK. The purpose of this prospective cohort study is to report the survivorship, clinical, and radiological outcomes of the first independent series of the Affinis Short prosthesis.