Long-term survivorship of an exchangeable-neck hip prosthesis with a Ti-alloy/Ti-alloy neck-stem junction.

INTRODUCTION: Breakage of exchangeable-neck (EN) and adverse local tissue reactions (ALTRs) to neck-stem junction (NSJ) damage products are responsible for increasing the revision rate of EN hip prostheses. We investigated the survivorship of an EN hip prosthesis including a NSJ with both components made of titanium alloy (Ti-alloy/Ti-alloy) to assess whether, and to what extent, EN breakage and NSJ damage affected implant survivorship. MATERIALS AND METHODS: Using data from a hip replacement registry, we determined survivorship of 2857 EN prostheses. Long-offset configurations of head and EN were implanted in heavy (> 90 kg) patients only in 23 hips. We investigated under which conditions EN breakages or ALTRs occurred. We also measured titanium (Ti) and vanadium (V) blood concentrations in 24 patients with a unilateral well-working prosthesis. RESULTS: The 17-year survival rates for any reason and aseptic loosening of any component were 88.9% (95%CI 87.5-90.1; 857 hips at risk) and 96.9% (95%CI 96.0-97.6), respectively. There were two cases of EN breakage and one case of ALTR (metallosis), due to rim-neck impingement, out of 276 revisions. After an average period of 9.8 years (range 7.8-12.8 years), the maximum Ti and V blood concentrations in patients with a well-working prosthesis were 5.0 µg/l and 0.16 µg/l, respectively. CONCLUSION: The present incidence of EN breakage or ALTR is lower than those reported in other studies evaluating EN hip prosthesis survivorship. This study suggests that (i) the risk of EN breakage is reduced by limiting the use of long-offset configurations in heavy patients and (ii) Ti-alloy/Ti-alloy NSJ damage products do not promote ALTR nor significantly alter the rate of implant loosening. Since design decisions and implant configuration determine the NSJ strength, the NSJ strength in working conditions must be thoroughly investigated to proper define the clinical indications for any EN design.

Satisfactory clinical and radiologic outcomes with a new shorter and modular stem for end-stage hip osteoarthritis: an international prospective multicentre pilot study.

INTRODUCTION: This multicenter prospective cohort study aimed to assess the safety and clinical and radiologic performance of the CLS® BreviusTM Stem with Kinectiv® Technology. MATERIAL AND METHODS: A total of 222 consecutive subjects, recruited in five different centers, qualifying for primary total hip arthroplasty (THA), were enrolled in the study. All the subjects received the CLS® BreviusTM Stem with Kinectiv® Technology. All the enrolled study subjects underwent pre-operative clinical and radiographic evaluation. Additionally, all subjects underwent post-operative clinical, functional and radiographic evaluations at 6 months and 1, 2, 3, and 5 years. These evaluations included implant survival, pain and functional performance (Harris Hip Score [HHS], University of California, Los Angeles [UCLA] Activity Score, Oxford Hip Score), subject quality-of-life (EQ-5D), radiographic parameters, complications, and concentration of metal ions (aluminum and titanium) in blood. RESULTS: No revisions were performed during the follow-up period. Of the 222 patients, only 76 completed the 5-year follow-up. Only 7 and 5 patients had aluminum and titanium 5-year evaluations, respectively. All the clinical parameters showed an overall improvement in the overtime measured with ANOVA for repeated measures; furthermore, the clinical scores showed a statistically significant improvement at 5 years with respect to pre-operative value (p < 0.001). Aluminum and titanium showed no variation for repeated measures at different time points (p > 0.05). A total of six complications were reported, of which only two were hip-related. CONCLUSIONS: The function of the CLS® BreviusTM Stem with Kinectiv® Technology indicated that subject well-being significantly increased following THA regardless of age, gender, BMI, previous surgery, primary diagnosis, and lifestyle.

Mid-term outcomes of a partial 2-stage approach in late chronic periprosthetic hip infections.

INTRODUCTION: Late chronic periprosthetic infections (LCPIs) are worrisome complications of primary hip arthroplasties. The gold standard procedure is the 2-stage revision. 1-stage exchange is gaining popularity in order to reduce the invasivity of the former technique. A partial 2-stage exchange technique, retaining fixed components, may overcome some of the drawbacks of the previous techniques, allowing a much easier reconstruction step. METHODS: 28 patients with a LCPI after a primary total hip arthroplasty underwent a first removal stage: the loosened component was removed (23 cups and 5 stems) and the fixed component, with no local signs of infection, was retained. An antibiotic hand molded spacer was positioned in 16 cases. After a mean time of 8 months and a tailored antimicrobial therapy, the spacer was removed and the implant was revised. RESULTS: The mean follow-up was 5 years. The HHS score was 82.7. 4 cases failed (2 patients presenting a septic relapse after revision and 2 patients undergoing Girdlestone arthroplasty), achieving a survival rate of 83.4% at 5 years. 2 patients were unwilling to perform a further procedure and did not proceed to the second stage. All the other patients had no clinical, radiological, laboratory signs of septic relapse. CONCLUSIONS: The partial 2-stage approach seems a promising technique for LCPI in selected cases, with good infection control. It allows an easier revision by sparing the fixed components. Larger case series and longer follow-ups are needed to confirm the results and identify the limits of this approach.

Squeaking and other noises in patients with ceramic-on-ceramic total hip arthroplasty.

INTRODUCTION: Noise in ceramic-on-ceramic (CoC) total hip arthroplasty (THA) is a potential symptom of abnormal bearing wear. Squeaking and other prosthetic hip noises are multi-factorial phenomena that can be analysed and may provide prognostic information. METHODS: 46 patients with noisy CoC bearings were investigated using X-ray, computed tomography and joint fluid analysis, and classified into either high or low risk of ceramic liner fracture groups according to previously published guidelines. Noise events from the bearings of 16 high risk cases which were subsequently revised were compared with 30 patients in the low risk control group who did not undergo revision. Noise events were analysed for their physical characteristics using a standardised protocol and classified as either low frequency and short duration 'clicking' or long duration and high frequency 'squeaking'. RESULTS: The peak frequency of squeaking during forward walking was significantly higher for patients in the case group who were revised, compared with the control group. The patient-reported onset of squeaking (46 months postoperatively) was earlier than short-noise emissions (82 months). In the standardised sequence of movements, short-noise always occurred more frequently than squeaking. Small heads (28 mm) were more likely to develop short-noise, while large heads (⩾32 mm) were more likely to develop squeaking. DISCUSSION: Noise evaluation may provide additional value for predicting failure of CoC bearings, though some questions should be better investigated in a dedicated prospective trial.

What are the influencing factors on hip and knee arthroplasty survival? Prospective cohort study on 63619 arthroplasties.

BACKGROUND: Body mass index is used by the World Health Organization to classify obesity. While obesity influences the onset of arthritis and type-2 diabetes, its effect on implant survival is still open to debate, with conflicting results from clinical and registry studies, as well as meta-analyses. Other known factors such as gender or diabetes status could ponderate or mask the effect of BMI on implant survival. HYPOTHESIS: Our hypothesis was BMI influenced hip and knee arthroplasty survival, when results were made independent of gender and diabetes status. PATIENT AND METHODS: A registry study was designed on 30733 Total Hip Arthroplasties (THA), 28483 Total Knee Arthroplasties (TKA), 3754 Uni compartmental Knee Arthroplasties (UKA) and 649 Hinged Knee arthroplasties (HK), from 01/01/2003 to 31/12/2015. Mean follow-up was 5.5 years. Diabetes status was added to the model. Each arthroplasty survival was tested for age at implantation, gender, diabetes status, implant characteristics and specifically BMI, taking into account gender and diabetes status. RESULTS: Gender had a strong influence on arthroplasty results. Age also influenced arthroplasty survival, especially aseptic loosening; a young age would lower implant survival. Diabetes had an influence in hip survival, but its influence on septic loosenings in TKA wasn't proven (p=0.065). A mobile liner and/or a cruciate retaining knee were factors increasing the risk of revision. Weight influenced THA survival, especially aseptic loosening, but didn't have a measurable effect in any other arthroplasty. BMI was not found to influence any arthroplasty survival, whatever the endpoint, when diabetes and gender were taken into account. DISCUSSION: Gender, age and diabetes influenced survival of the lower limb arthroplasties, whereas BMI did not. Only weight did influence THA results and should be used instead of BMI. CONCLUSION: Studies on arthroplasty survival should systematically mention gender and diabetes status and beware of potential group incomparability. LEVEL OF EVIDENCE: III, cohort study.

Ischemia-Modified Albumin Expression: Is there a Difference between Male and Female Subjects?

BACKGROUND: Ischemia-modified albumin (IMA) derives from naive albumin, modified in the binding region of bivalent ions, as cobalt and iron. The cobalt, released from some types of hip prosthesis seems to be metabolized differently in males and females but the iron ion is more prevalent than cobalt and is detectable in the healthy population. Our aim was to verify if there are any gender- and age-related differences in IMA concentrations and if IMA correlates with cobalt and iron-related proteins. METHODS: IMA, albumin, iron, ferritin, transferrin, and cobalt were measured in 50 men and 50 women divided into two age/fertility-homogeneous groups. RESULTS: Men < 45-years-old showed a statistically significant lower IMA concentration than men ≥ 45 and fertile and menopausal women. Considering all the population studied, IMA does not seem to be correlated with age and is distributed differently by gender; also, Co distribution was different between males and females. CONCLUSIONS: IMA did not correlate with cobalt, iron, ferritin, and transferrin in any group, except for fertile women where IMA presented a statistically significant correlation with serum iron values. Minor expression of IMA in young males together with the results obtained on serum iron in fertile females, could explain the higher accumulation of circulating Co in women compared to men and their different cobalt metabolism.

Unilateral versus bilateral total knee arthroplasty: A registry study on survival and risk factors.

BACKGROUND: Bilateral cases, representing at least 25% of total knee arthroplasties (TKA), could convey a statistical bias linked to dependency. Registries allow exploring this issue, susceptible to question surgeon validated protocols. Do bilateral total knee arthroplasties behave differently than unilateral knees in terms of implant survival? HYPOTHESIS: Bilateral TKA have a better survival than unilateral TKA. PATIENTS AND METHODS: A number of 14,652 bilateral and 27,440 unilateral TKAs were compared. Influencing factors were tested with hazard ratios applied on bilateral knees. RESULTS: Bilateral knees had a better survival (p<0.001). Delay between first and second side surgeries had an influence on survival of the first knee: if below a year, the first knee survival was superior to the second knee; more than three years between both arthroplasties significantly decreased the survival of the first implant. If the first knee was revised, the hazard ratio for revision of the second implant was 3.5. DISCUSSION: Series should include separate evaluations of bilateral cases, because they have a better survival than unilateral knees. A long delay between both knee replacements could impact both implant survivals. Level of Evidence III, Cohort Comparative Study.

Component positioning and ceramic damage in cementless ceramic-on-ceramic total hip arthroplasty.

BACKGROUND: In ceramic-on-ceramic (CoC) total hip arthroplasty (THA), component positioning demonstrated to influence the bearing damage: however the connection between angles and clinical outcomes at long-term follow-ups is currently lacking. Aims of this study were: the computer tomography (CT) assessment of component positioning in CoC THAs; the correlation analysis between positioning and ceramic damage; the identification of safe zones. METHODS: 91 consecutive post-operative CT scans including two types of CoC implants, with a mean follow-up of 12 ± 4.4 years, were evaluated. III generation (74.2%) and IV generation (25.8%) CoC surfaces were included. The angle measurements (cup abduction, anteversion, cup tilt, stem antetorsion, sacral slope) were automated using a CT-based software. The combined anteversion was assessed as well as the cup-neck position at -15°, 0°, 45° and 90° of flexion. Ceramic damage was diagnosed using synovial fluid analyses and radiological criteria. RESULTS: 63.7% of THAs was inside the cup abduction target 30°-45° and 68.1% was inside the cup anteversion target 5°-25°. 19 patients (20.9%) showed signs of ceramic damage. High cup abduction and high cup-neck 45° minimum angle (which stood for high abduction and extreme combined version) significantly correlated with ceramic damage. No demographical features apart III generation ceramic bearings influenced the results. No safe zones could be detected. CONCLUSIONS: In CoC THA, no safe zones can be described. However it is important to avoid cup inclination over 45° and a combination of steep cup and extreme combined version.

The influence of bearing surfaces on periprosthetic hip infections: analysis of thirty nine thousand, two hundred and six cementless total hip arthroplasties.

PURPOSE: Periprosthetic hip infection (PHI) is a devastating complication. The association between PHI and bearing surfaces as well as patient-related factors has been recently investigated, with contradictive outcomes. The dataset of Emilia-Romagna region Registry for Orthopaedic Prosthetic Implants (RIPO) has been assessed to investigate, if the bearing choice influenced the risk of septic loosening occurrence. METHODS: RIPO data about 39,206 cementless total hip arthroplasties (THA), collected since 2003, were analysed. Age, gender, BMI, diabetes and bearing surfaces were evaluated. The end point of the study was the revision of at least a single component due to sepsis. RESULTS: Adjusted and unadjusted survival rates showed that ceramic-on-ceramic (COC) implants had the lower incidence of PHIs, whereas metal-on-metal (MOM) THAs were significantly more prone to infection. In MOM cohort, stemmed implants were involved in 28 out of 30 cases. Among the demographical features and comorbid conditions, only diabetes statistically influenced the rate of sepsis. CONCLUSIONS: Bearing surfaces influenced the rate of PHI; in particular, stemmed MOM implants were at higher risk, probably due to metal debris consequent to taperosis. Despite the preliminary results, stemmed MOM THAs should be used with care, and diabetic patients should be warned about increased septic risks.

Cementless Total Hip Arthroplasty in Crowe III and IV Dysplasia: High Hip Center and Modular Necks.

BACKGROUND: Total hip arthroplasty (THA) in severe developmental dysplasia of the hip (DDH) is a challenging procedure. The most used techniques involve anatomic cup positioning, augmentation femoral osteotomy. However, anatomic cup positioning is not always feasible in severe DDH and osteotomy nonunion may ensue. The purpose of the study was to assess the survivorship, the hip score results, the radiological parameters (fixation, loosening, component position) of a large cohort of patients with Crowe III and IV DDH, treated with high hip center and modular necks THAs. METHODS: Eighty-four THAs in Crowe III and IV DDH were evaluated, achieving a final follow-up of 15.1 years. All the patients were treated with the same cementless implant (modular necks and ceramic-on-ceramic coupling) and the same approach (high cup placement with slight medialization). The patients were clinically evaluated (Harris Hip score and Merle d'Aubigne and Postel score). A radiographic evaluation was performed, analyzing the orientation of the cup. RESULTS: Eighty patients were available at the last follow-up. The clinical scores were good at the final follow-up. Two sciatic lesions occurred: one patient fully recovered. The overall survivorship was 90.5% at 15 years: only 2 cases of aseptic loosening were reported. The mean center of rotation height was 33 ± 8 mm and the medialization was 30 ± 5 mm. CONCLUSION: A high cup placement with slight medialization is a valid technique in DDH patients. A good restoration of the offset, ceramic-on-ceramic coupling and a porous socket may provide durable results, overcoming the effects of increasing joint reaction forces related to high cup placement.

Short Stems Versus Conventional Stems in Cementless Total Hip Arthroplasty: A Long-Term Registry Study.

BACKGROUND: Short stems in total hip arthroplasty (THA) have recently gained increasing popularity, allowing mini-invasive exposures and bone-sparing approaches. However, long-term studies and recommendations for the routine use are not available. The aim of this report was to compare the survival rates and the reasons for revision of short stems versus conventional stems in cementless THAs, in a registry-based population. METHODS: The Registry of Prosthetic Orthopedic Implants (RIPO) was inquired about cementless THAs performed since 2000 to 2016. The stems were divided into short (<12 cm) and conventional ones, and then, classified according to the classification by Feyen and Shimmin: short stems with neck-retaining osteotomy (group A: 1684 hips), short stems with standard osteotomy (group B: 2727 THAs), and conventional stems (group C: 57,359 cases). Demographics, survivorships, and reasons for revision were investigated and compared. RESULTS: Short stems were preferentially implanted in younger patients and normal morphologies. Short and conventional stems showed comparable survival rates at long-term follow-up (>90% at 15 years). The rates of stem aseptic loosening, intraoperative fractures, and periprosthetic fractures were similar in the 3 groups. Group B had higher rates of revisions due to primary instability (early dislocations and impingement-related events; P < .05). Revisions due to pain were nonsignificantly higher in group B. CONCLUSION: Short stems are reliable implants at long-term follow-up. The comparison with conventional stems showed no additional risk of premature aseptic loosening and intraoperative and periprosthetic fractures. However, the high rate of revisions due to pain and, mostly, primary instability should be investigated in clinical trials.

Is Cross-Linked Polyethylene an Improvement Over Conventional Ultra-High Molecular Weight Polyethylene in Total Knee Arthroplasty?

BACKGROUND: Reducing polyethylene (PE) wear by increasing the cross-linking encouraged surgeons to hope for increased total knee arthroplasty (TKA) survival rates. Different methods of manufacturing cross-linked polyethylene (XLPE) were introduced, following promising in vitro results. Is there a measurable effect of cross-linking on TKA survival? METHODS: A registry study was conducted, focusing on fixed tibial inserts in primary TKA. Conventional PE represented 87% of the liners, 10% were cross-linked and 2% were antioxidant PE. Sixty-four percent of the liners were posterior-stabilized (PS). Survival of the different PE groups and survival of the main XLPE available were successively compared. We also looked for differences in the same brand implant groups with regard to PE type, as well as differences between cruciate retaining and PS knees. RESULTS: No differences were found when looking at survival for any cause or for aseptic loosening only (P = .96). When comparing the XLPE available, X3 was found to have a better survival than Prolong or Smith & Nephew XLPE (P = .036). When the same implants and X3 or conventional PE were used, no difference could reach a statistical significance. With Zimmer LPS Flex, Prolong XLPE was even associated with a lower survival compared with conventional PE. On Stryker implants, only the Cox regression model allowed highlighting a difference between X3 XLPE and conventional PE, only in PS knees. CONCLUSION: Increasing the cross-linking seems to only have a low effect, if any, on knee arthroplasty survival. Differences between brands could be found; the manufacturing process could play a role.

Total Knee Replacement in Young Patients: Survival and Causes of Revision in a Registry Population.

BACKGROUND: The incidence of total knee replacements (TKRs) in young patients is increasing. Few reports described encouraging results and acceptable survival rates. However, many concerns still persist, in particular about the high rates of infection and aseptic loosening. Aim of this article was to investigate the survival of TKRs in patients aged 45 years or younger in a registry population. METHODS: The Emilia-Romagna registry RIPO was enquired about TKRs in patients ≤45 years; 238 TKRs were evaluated at a mean follow-up of 5.4 years (range 0-15.6 years), examining the features of the patients involved, the survival rate, and the reasons for revision of the knee implants. RESULTS: The TKRs were generally performed in men, in private hospitals, and almost in half of the cases for other causes rather than primary osteoarthritis. The mean age was 40 years. Bicompartmental, cemented posterior-stabilized implants with fixed bearing were preferred. The survival rate was higher than 90% in the first 7 years, and then it decremented. The choice of implant did not apparently influence the survivorship. The final outcomes were acceptable, substantially in line with the previous literature about young patients. Twenty-one revisions occurred (8.8%), in particular 8 cases for aseptic loosening and 7 TKRs for infection. The rate of revision was higher than in overall population and even in some young cohorts. CONCLUSION: TKRs in patients aged 45 years or younger seem a promising procedure, although the high rates of septic and aseptic loosening should be carefully evaluated. Prospective, well-designed studies are required to confirm and investigate these preliminary findings.

3rd generation alumina-on-alumina in modular hip prosthesis: 13 to 18 years follow-up results.

INTRODUCTION: Ceramic-on-ceramic (CoC) couplings are alternative bearings surfaces that have been reported to reduce osteolysis, wear debris and aseptic loosening compared to the use of polyethylene. Early experiences with ceramics had poor results, but they have led to many improvements in the manufacture and design of subsequent implants. METHODS: We analysed medical files of 300 CoC total hip arthroplasty (THA) with a modular neck performed during period 1995-2000 by a single surgeon for a minimum follow-up of 13 years, evaluating clinical and radiological outcome. RESULTS: The mean clinical Merle d'Aubigne and Postel hip score at the final follow-up is 17.4, against a preoperative value of 11.4. Overall survivorship with an endpoint of revision is 93.2% (95% CI, 89.0%-97.3%) at 15 years, while considering only prosthesis failures related to aseptic loosening and ceramic breakage, survival rate at 15 years is 97.2% (95% CI, 94.8%-100%). We observed complications that led to revision surgery in 11 patients (4%) (periprosthetic fractures, liner ruptures, septic loosening of the implant, aseptic loosening of the cup, aseptic loosening of the stem). The occurrence of squeaking is low (1.6%, 4 cases) and we analysed the characteristics of these patients. DISCUSSION: Our study shows an excellent long term survivorship of third generation alumina CoC THA. We reiterate the importance to have a stable implant to maximise the advantage of ceramic and to avoid complications.

In vivo response of heme-oxygenase-1 to metal ions released from metal-on-metal hip prostheses.

Metal ion release and accumulation is considered to be a factor responsible for the high failure rates of metal-on-metal (MoM) hip implants. Numerous studies have associated the presence of these ions, besides other factors, including a hypoxia­like response and changes in pH due to metal corrosion leading to the induction of the oxidative stress response. The aim of the present study was to verify whether, in patients with a MoM hip prosthesis, mRNA and protein expression of HMOX­1 was modulated by the presence of metal ions and whether patients without prostheses exhibit a different expression pattern of this enzyme. The study was conducted on 22 matched pairs of patients with and without prostheses, for a total of 44 samples. Ion dosage was determined using inductively coupled plasma mass spectrometry equipped with dynamic cell reaction. HMOX­1 gene expression was quantified by reverse transcription-quantitative polymerase chain reaction and HMOX­1 protein expression was analyzed using an enzyme-linked immunosorbent assay. The results demonstrated that although there were significant differences in the metallic ion concentrations amongst the two groups of patients, there was no correlation between circulating levels of cobalt (Co) and chromium (Cr), and HMOX­1 gene and protein expression. Additionally, there was no significant difference in the protein expression levels of HMOX­1 between the two groups. In conclusion, it was demonstrated that circulating Co and Cr ions released by articular prosthetics do not induce an increase in HMOX­1 mRNA and protein expression at least 3.5 years after the implant insertion. The present study suggests that involvement of HMOX­1 may be excluded from future studies and suggests that other antioxidant enzymes, including superoxide dismutase, glutathione peroxidase and reductase should be investigated.

Radiological identification of Zweymüller-type femoral stem prosthesis in revision cases.

INTRODUCTION: Since 1979 the number of patients treated with femoral stems has continued to grow, as well as the number of stems with features similar to the Zweymüller prosthesis produced by different companies. Identification can be problematic in case requiring revision. In the present paper, we present an overview of morphometric differences between the different stem designs, which can be useful for radiologic identification in revision cases. METHODS: By doing some research on the Internet of specialized sites and worldwide literature, we searched for all femoral stems agreeing with Zweymüller principles (cementless, straight, tapered, rectangular cross-sectioned femoral stems). RESULTS: We found 26 different stems from different companies producing or having produced in the past the Zweymüller-type femoral stems for hip prosthesis. DISCUSSION: Accurate preoperative identification of the Zweymüller femoral stem type may be of critical importance to eventual outcomes following revision surgery. Each manufacturer has different instruments specific to the removal of their primary implants, and ensuring they are available can simplify the revision procedure significantly. Exact pre-operative planning is also necessary for selecting the correct ball head in cases where a stem is well-fixed and can be left in situ. The commonly used notation "Eurocone 12/14" provides no information about the actual taper angle. Whenever the stem is left in situ, the exact specifications of the taper must therefore be obtained from the manufacturer in order to use a metal sleeve that precisely fits it and the ball head. Failure to do so may result in severe complications, such as metallosis. In cases where it is not possible to identify the taper angle, the surgeon may even consider removal of the stem, though this significantly increases the surgical procedure's invasiveness. Only a single, uniform standard taper, such as that offered until 1994 by CeramTec, can solve these issues in the future. CONCLUSION: The survival rate of the Zweymüller stems after ten years was 96 % and the complication rate was very low. Pre-operative identification of the femoral implant is of considerable importance for planning and correctly implementing revision procedures.

Suturing the myotendinous junction in total hip arthroplasty: A biomechanical comparison of different stitching techniques.

BACKGROUND: The repair of the myotendinous junction following total hip arthroplasty is challenging as this region is the weakest part of the muscle structure. This study investigated the mechanical behaviour and the mode of failure of different suturing techniques of the myotendinous junction. A new asymmetrical stitch was compared to two widely used techniques, i.e. the simple stitch (two loops in parallel) and the figure-of-eight stitch. METHODS: The ovine triceps brachii myotendinous junction was selected as the experimental model. Each technique was sewn in muscle belly on one side and in a polyester belt (no-tendon configuration) or in thin tendon (full configuration) on the other side. The former was chosen to determine the grasping power of the stitch on the muscle despite the tendon quality, the latter to simulate a very thin gluteus medius tendon. FINDINGS: The new stitch showed a higher ultimate strength (+40%) compared to the two controls in the no-tendon configuration. In the full configuration, no significant increase was observed, although failure of the new stitch always occurred at the tendon side. Furthermore, the new stitch does not alter the stiffness of repair. INTERPRETATION: The new stitch has a higher grasping power on muscle belly than the single passing-through stitches thanks to the multiple fixation points, which better distribute the load in the tissue. However, such performance can be fully exploited only in the presence of good quality tendons.

European Society of Biomechanics S.M. Perren Award 2014: Safety factor of the proximal femur during gait: a population-based finite element study.

It has been suggested that the mechanical competence of the proximal femur is preserved with respect to physiological loading conditions rather than accidental overloading, but the consequences of this adaptation for fracture risk in the elderly remain unclear. The goal of the present study was to analyse the safety factor of the human femur in the two most frequent daily activities, level walking and stair climbing, and to understand the dependence, if any, of this safety factor on age, volumetric bone mineral density (vBMD), and gender. To this aim, a finite element study was performed on 200 subjects (116 women and 84 men), spanning a large range of age (23-84 years) and vBMD levels (T-score from 0 to -3.59). For the first time, finite element models that included a subject-specific description of the anatomy and mineral density distribution of each bone were coupled with a personalisation of the loads acting on the proximal femur during movement, including the action of the muscles and their variability across the population. The results demonstrate that the human proximal femur is characterised by a high safety factor (on average five, never reaching fracture threshold), even in the presence of advanced age and low mineral content. These results corroborate the hypothesis that the relationship between loading and mechanical competence is generally preserved in the elderly population for the most frequent motor activities, walking and stair climbing. Interestingly, a decrease of the safety factor was observed with increasing lifespan and reduced mineral content in women but not in men.