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Data assessing femoral stems may be influenced by grouping together matt and polished stems, despite their differing reported survivorship. The aim of this study is to assess the difference in revision rates between commonly used cemented and cementless stems when polished tapered stems are assessed independently of matt stems.Australian Orthopaedic Association National Joint Replacement Registry data from 1999 to 2019 were used to assess difference in revision rates between the 5 most commonly implanted femoral cemented and cementless stems for osteoarthritis. Cemented matt femoral stems, stems using line-to-line cementing techniques and procedures using non-cross-linked polyethylene, large head (32 mm) metal-on-metal bearing surfaces or exchangeable necks were excluded. Cumulative percent revision was used to help compare survivorship between stems.There were 201,889 total hip replacements meeting the inclusion criteria, of which 50.0% were cemented and 50.0% cementless. Cemented stems had a lower rate of revision at all time points compared to cementless stems. This was most significant during the first 2 weeks (hazard ratio 0.48, 95% confidence interval 0.40-0.58, P.001) compared to 2 weeks postoperatively and onwards (hazard ratio 0.85, 95% confidence interval 0.81-0.90, P.001). A subanalysis of head size, bearing type, and surgeon volume further supported the use of a cemented stem.Commonly used cemented polished tapered stems have a lower revision rate when compared to commonly used cementless prostheses, and are recommended in all age groups for both low-volume and high-volume surgeons especially when head size 32 mm or smaller is used.

Background To report clinical outcomes and survival at a minimum of 10 years of a consecutive series of uncemented total hip arthroplasty (THA) with fourth-generation ceramic-on-ceramic (CoC) bearings and determine the incidence of articular noises, their risk factors, and impact on quality of life (QoL). Methods From a series of 456 CoC THAs, there were 25 revisions, 38 deceased, and 36 lost to follow-up. The remaining 357 hips were assessed at 11.1 ± 0.7 years (range, 10-14) using the Forgotten Joint Score, Oxford Hip Score, and a questionnaire on articular noises. Kaplan-Meier survival was calculated, and multivariable analysis was performed to determine associations between articular noise and patient/surgical factors. Results The 10-year survival was 96.3% for the cup, 96.5% for the stem, and 94.2% for all components. The Forgotten Joint Score was 79 ± 26 (range, 0-100), and Oxford Hip Score was 16 ± 7 (range, 12-60). The mean impact of articular noises on QoL was 1.8 ± 2.9 (range, 0-9): considered negligible in 60 hips (16%), moderate in 27 hips (7%), and severe in only 13 hips (4%). Multivariable analyses revealed that the incidence of articular noise decreased with age (odds ratio [OR], 0.94; P = .001), body mass index (OR, 0.85; P = .001), and in hips implanted with 32-mm (vs 36 mm) heads (OR, 0.18; P = .030). Conclusion Of 100 hips (28%) that reported some articular noises 10 years after CoC THA, the impact of articular noises on QoL was negligible for most patients. Although larger heads can improve mobility and reduce risks of dislocations, surgeons must be aware that increasing head size could also increase risks of articular noises, notably in young and active patients.

Nine simply supported reinforced concrete beams of dimensions 150 × 150 × 700 mm have been tested to study the anchorage behavior of installed headed bars. The variables included the size of the added head plate, debonded length and loading type. Therefore, four head areas 28*28, 32*32, 35*35 and 38*38 mm, three debonded lengths 0, 300 and 600 mm and two loading types (one-point load and two-point load) are used in this research. The test results of load failure values, type of failure and deflection for eight beams provided with plate head and one beam of the non-head bar are being obtained. It was found that the value of load failure increased with using higher plate head size and lower debonding length. Furthermore, the percentages of decrease in deflection for beams that have head net size Anh/Ab (2.9, 4, 5, and 6) are 29%, 36%,38% and 44% respectively, and 12% and 55% when beams with debonding length 300 and 600 mm compared with beams of full bonded (zero debonded length). While the load failure for beams tested under two-points load was greater than beams which were tested under one-point load.

Background Decompressive craniectomy (DC) is a widely used treatment for refractory high intracranial pressure (ICP). While the Brain Trauma Foundation guidelines favor large DC, there remains a lack of consensus regarding the optimal size of DC in relationship to the patient's head size. The aim of this study is to determine the optimal size of DC to effectively control refractory ICP in traumatic brain injury and to measure that size with a method that takes into consideration the patient's head size. Methods All cases of unilateral DC performed to control refractory increased ICP due to cerebral edema during a 7½-year period were included. Demographic and injury-related data were collected by retrospective chart review. The patients were categorized in 2 groups: 21 patients with a “small flaps” and 9 patients with a “large flap.” Results Two groups had similar preoperative characteristics. The amount of cerebrospinal fluid drained and the doses of hyperosmolar therapy given were not different between the 2 groups. The postoperative ICP was significantly lower for the large craniectomy flap group: 13.3 mm Hg confidence interval 99% [12.7, 13.8] versus 16.9 mm Hg confidence interval 99% [16.5, 17.2] (P = 0.01), and this difference was maintained for 96 hours postoperatively. Conclusions Better ICP control was achieved in patients who underwent a large decompressive craniectomy (ratio >65%) when compared with smaller craniectomy sizes. The proposed method of measuring the craniectomy size, to our knowledge, is the first to take into account the patient's head size and can be easily measured intraoperatively.

The cementless Corail is one of the most commonly used stems in total hip arthroplasty (THA). The aim of this study was to investigate whether there was a difference in revision rate for smaller stems.All primary THA procedures recorded by the Australian Joint Replacement Registry from September 1999 to December 2017 performed for osteoarthritis using the Corail stem, a cementless acetabular cup, modern bearing surfaces (ceramic/ceramic, ceramic/cross-linked polyethylene, and metal/cross-linked polyethylene), and 28 mm, 32 mm, and 36 mm head sizes were included. The primary outcome measure was femoral component revision. Data were analyzed and adjusted for age, gender, and head size. Further analysis investigated the effects of surgical approach.There was 41,265 primary THAs recorded. The cumulative percent revision (CPR) at 13 years was 7.7% (5.5, 10.7) for stem sizes 8 and 9 and 3.0% (2.4, 3.8) for sizes 10-20 (P.001). When adjusted for age and gender, the sizes 8 and 9 collared (hazard ratio [HR]: 6.22 [3.84-10.06], P.001) and collarless (HR: 3.28 [2.41-4.45], P.001) had a higher CPR than the collared and collarless size 10-20. The size 8 and 9 stems performed with an anterior approach had the highest CPR (HR: 14.44 [6.21-33.56], P.001). The main reason for revision of size 8 and 9 femoral stems was loosening (65.2%, compared to 31.5% for 10-20 femoral stems).Smaller Corail stems have 4 times the rate of revision compared with the larger femoral sizes with loosening being the most common diagnosis. This is most evident when using an anterior approach.

In vitro models of arthroplasty enable pre-clinical testing and inform clinical decision making. Repeated-measures comparisons maximise resource efficiency, but their validity without testing order randomisation is not known. This study aimed to identify if there were any large testing order effects for cadaveric models of knee and hip arthroplasty. First, the effect of testing order on total knee arthroplasty (TKA) biomechanics was assessed. Extension moments for TKAs (N = 3) implanted into the native knee (TKA-only) were compared to a dataset of TKAs (N = 24) tested after different combinations of partial knee arthroplasty (TKA-last). The effect of repeatedly testing the same knee five times over 36 h on patellofemoral and tibiofemoral kinematics was also quantified. Second, the effect of testing order on capsular ligament function after total hip arthroplasty (THA) was assessed. Randomisation was removed from a previously published dataset to create increasing and decreasing head size groups, which were compared with t-tests. All three TKA-only extension moments fell within the 95% CI of the TKA-last knees across the full range of knee flexion/extension. Repeated testing resulted in root-mean-squared kinematics errors within 1 mm, 1°, or 5% of total range of motion. Following THA, smaller head-size resulted in greater laxity in both the increasing (p = 0.01) and decreasing (p 0.001) groups. Testing order did not have large effects on either knee or hip arthroplasty biomechanics measured with in vitro cadaveric models.

Transcranial magnetic stimulation (TMS) and transcranial electric stimulation (TES) are increasingly popular methods to noninvasively affect brain activity. However, their mechanism of action and dose-response characteristics remain under active investigation. Translational studies in animals play a pivotal role in these efforts due to a larger neuroscientific toolset enabled by invasive recordings. In order to translate knowledge gained in animal studies to humans, it is crucial to generate comparable stimulation conditions with respect to the induced electric field in the brain. Here, we conduct a finite element method (FEM) modeling study of TMS and TES electric fields in a mouse, capuchin monkey, and human model. We systematically evaluate the induced electric fields and analyze their relationship to head and brain anatomy. We find that with increasing head size, TMS-induced electric field strength first increases and then decreases according to a two-term exponential function. TES-induced electric field strength strongly decreases from smaller to larger specimen with up to 100x fold differences across species. Our results can serve as a basis to compare and match stimulation parameters across studies in animals and humans.HIGHLIGHTSTranslational research in brain stimulation should account for large differences in induced electric fields in different organismsWe simulate TMS and TES electric fields using anatomically realistic finite element models in three species: mouse, monkey, and humanTMS with a 70 mm figure-8 coil creates an approximately 2-times weaker electric field in a mouse brain than in monkey and human brains, where electric field strength is comparableTwo-electrode TES creates an approximately 100-times stronger electric field in a mouse brain and 3.5-times stronger electric field in a monkey brain than in a human brain

Background and purpose Gender disparities in auditory brainstem response (ABR) results have been reported but the exact reasons remain controversial. Difference in head size between genders has been suggested but the literature is lacking, particularly at threshold levels. In this short communication, we compared ABR results between males and females with comparable head sizes at supra-threshold and threshold levels. Materials and methods In this comparative study, of 58 healthy young adults, 30 of them (17 females and 13 males) with comparable head sizes underwent the standard ABR testing. Wave V latencies and ABR thresholds were determined and analyzed accordingly. Results At the supra-threshold level, significantly shorter wave V latencies were found in females than in males (p = 0.029). This difference was substantive (d = 0.86) and persisted even when the head size was included in the analysis (p = 0.032). In contrast, no significant differences in ABR thresholds were found between genders (p > 0.05). Conclusions Significant gender differences in ABR results among young adults were only found at the supra-threshold level, which were not related to the head size. Based on the study outcomes, gender-specific normative data for ABR are still beneficial for clinical applications, particularly when recording ABR at high stimulation levels.

Objective The new direct gradual cranial expansion surgical technique has been used to treat children with postshunt microcephaly and slit ventricle syndrome. To evaluate the feasibility of this new surgical treatment, we studied intracranial pressure (ICP) in microcephalic children with developmental delay. Methods Mean ICP, age, sex, head size, and developmental assessments were compared in 24 microcephalic children with developmental delay who had had continuous ICP monitoring. Results Children studied included 9 boys and 15 girls with a mean age of 4.9 ± 2.0 years. Mean ICP was 18.7 ± 8.6 mm Hg. Children with high ICP had significantly lower age and higher B wave ratios than children with low ICP. There were no statistically significant differences in developmental scores and head sizes between children with high ICP and children with low ICP. In multiple linear regression analysis, we observed significantly increased risk of mean ICP elevation by B wave ratio and developmental score and decreased risk of mean ICP elevation by age, but not significantly increased risk of mean ICP elevation by head circumferences (z score). Conclusions Our findings suggest that a portion of microcephalic children with developmental delay have high ICP that cannot be expected from head sizes, and high ICP has decreasing tendency with age.

Exposure to low frequency and radiofrequency electromagnetic fields at low intensities poses a significant health hazard that has not been adequately addressed by national and international organizations such as the World Health Organization. There is strong evidence that excessive exposure to mobile phone-frequencies over long periods of time increases the risk of brain cancer both in humans and animals. The mechanism(s) responsible include induction of reactive oxygen species, gene expression alteration and DNA damage through both epigenetic and genetic processes. In vivo and in vitro studies demonstrate adverse effects on male and female reproduction, almost certainly due to generation of reactive oxygen species. There is increasing evidence the exposures can result in neurobehavioral decrements and that some individuals develop a syndrome of "electro-hypersensitivity" or "microwave illness", which is one of several syndromes commonly categorized as "idiopathic environmental intolerance". While the symptoms are non-specific, new biochemical indicators and imaging techniques allow diagnosis that excludes the symptoms as being only psychosomatic. Unfortunately standards set by most national and international bodies are not protective of human health. This is a particular concern in children, given the rapid expansion of use of wireless technologies, the greater susceptibility of the developing nervous system, the hyperconductivity of their brain tissue, the greater penetration of radiofrequency radiation relative to head size and their potential for a longer lifetime exposure.

Background Bearing surface wear and osteolysis are major factors limiting the durability of total hip arthroplasty (THA). Second generation annealed highly cross-linked polyethylene (HXLPE) and ceramics were introduced to THA for their excellent wear rates. However, there is little data comparing the wear rates of metal and ceramic heads on second generation HXLPE. Methods Sixty patients who received a noncemented THA with a 32- or 36-mm delta ceramic head were matched with 60 THAs with a 32- or 36-mm metal head based on gender, head size, follow-up, and University of California, Los Angeles activity score. Linear and volumetric wear rates were measured. Results At mean 6-year follow-up, the mean linear wear rates were 0.012 mm/y (standard deviation [SD] 0.045; 95% confidence interval [CI] 0.001-0.024) and 0.018 mm/y (SD 0.025; 95% CI 0.012-0.025) for the ceramic and metal groups, respectively (P = .724). The mean volumetric wear rates for the ceramic and metal head groups were 11.9 (SD 43.0; 95% CI 0.7-23.0) and 17.3 (SD 23.9; 95% CI 11.1-23.4), respectively. No significant differences were detectable in either the mean linear or volumetric wear rates (P = .380 and P = .398, respectively). Conclusion Second generation HXLPE had low wear rates and we were unable to detect a significant difference in wear rates with 32- or 36-mm metal and ceramic heads. We believe that this is due to the excellent tribological properties of second generation HXLPE. We continue to use ceramic as standard of care because of issues of trunnionosis with metal heads.

The Concrete Capacity Design (CCD) method, which was first proposed in 1995, has since been adopted in design standards worldwide because of its accuracy and simplicity. With advancements in concrete technology and construction industry, there are new applications whereby the behaviour of anchors cannot be predicted by the original formulation of the CCD method. This paper intends to provide a comprehensive review of the recent research on tensile behaviour of single cast-in headed anchors failing due to a concrete cone failure mode without the influence of concrete edge. The review includes, but is not limited to, studies on the effect of deep embedment of anchors, anchor head size, variation in size and shape of concrete aggregates, prestressed concrete, fibre-reinforced concrete, high strength concrete, lightweight concrete, as well as age of concrete at the time of loading on behaviour of anchors. Where discrepancy is found in the literature, critical review is presented through an in-depth examination of available results. In addition to recent modified (CCD) prediction models, older models are also presented for a better demonstration of how prediction models have evolved over the past five decades. The paper concludes with a detailed list of identified knowledge gaps in the area and proposals for future work.

Background Decreased fretting and corrosion damage at the taper interface of retrieved ceramic-on-polyethylene total hip arthroplasty (THA) implants has been consistently reported; however, resultant fretting corrosion as a function of femoral head size and taper geometry has not been definitively explained. Methods Eight cohorts were defined from 157 retrieved THA implants based on femoral head composition (n = 95, zirconia-toughened alumina, ZTA vs n = 62, cobalt-chromium alloy, CoCr), head size (n = 56, 32mm vs n = 101, 36mm), and taper geometry (n = 84, 12/14 vs n = 73, V40). THA implants were evaluated and graded for taper fretting and corrosion. Data were statistically analyzed, including via a 23 factorial modeling. Results Factorial-based analysis indicated the significant factors related to both resultant (summed) fretting and corrosion damage were head material and taper geometry; head material–taper geometry interaction was also a significant factor in resultant corrosion damage. Lower rates of moderate-to-severe fretting and corrosion damage were exhibited on ZTA heads (ZTA = 13%, CoCr = 38%), smaller heads (32mm = 18%, 36mm = 26%), and 12/14 tapers (12/14 = 13%, V40 = 35%). ZTA+32mm heads demonstrated the lowest rates of moderate-to-severe fretting and corrosion damage (12/14 = 2%, V40 = 7%), whereas CoCr heads with V40 tapers demonstrated the greatest rates of moderate-to-severe damage (32mm = 47%, 36mm = 59%). Conclusion In this series, retrieved implants with ZTA, 32-mm heads paired with 12/14 tapers exhibited lower rates of moderate-to-severe damage. Factorial analysis showed head material, taper geometry, and their interactions were the most significant factors associated with resultant damage grades. Isolating implant features may provide additional information regarding factors leading to fretting and corrosion damage in THA. Level of Evidence IV (case series).

Head-related traits are economically important in fish because they will essentially affect fillet yields. Bighead carp (Hypophthalmichthys nobilis) is an important aquaculture fish, and interestingly its head has higher culinary and market values than its fillet in China. In this study, using 776 bighead carp individuals and high-throughput SNP genotyping technology, we performed genome-wide association study (GWAS) to identify genomic regions and candidate genes potentially associated with head-size and head-shape traits such as head length (HL), head width (HW), head height (HH), head length/head height ratio (HL/HH), head length/head width ratio (HL/HW) and head length/body length ratio (HL/BL). The morphometrics of most of these traits were significantly correlated (P

Background Dislocation is a leading cause of revision after primary total hip arthroplasty (THA). While more common in the first few years post procedure, dislocation can occur at any time. This study investigated the difference in late dislocation in ceramic on ceramic bearings compared to metal on polyethylene and ceramic on polyethylene bearings in THA. Methods Data was used from the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) and the cumulative percent revision (CPR) for dislocation was estimated using the Kaplan-Meier method for the different bearing surfaces. There were 192,275 THA included in the study with 101,915 metal on cross linked polyethylene (MoXLPE), 30,256 ceramic on cross linked polyethylene (CoXLPE), and 60,104 ceramic on ceramic (CoC). Results The CPR for dislocation at 13 years for MoXLPE, CoXLPE and CoC groups was 1.2 (95% CI 1.1- 1.3), 1.0 (95% CI 0.7- 1.4) and 0.9 (95% CI 0.8-1.1) respectively. There was an increased risk of revision for dislocation for MoXLPE compared to CoXLPE and CoC. When stratified for head size there was no difference in the risk of revision for dislocation between MoXLPE, CoXLPE and CoC in the 28mm and 32mm head sizes. With head sizes 36mm, MoXLPE had a higher rate of dislocation compared to other materials. Conclusion Bearing surface has little impact on revision for dislocation.

Sequentially crosslinked and annealed polyethylene (SXL) is a second generation highly crosslinked polyethylene that has been available for joint replacement with clinical success. The purpose of this study is to characterize SXL cups through an analysis of almost 14 years of historical in vitro wear simulation data. Three characteristics were evaluated in this study (1) Wear rate, (2) linear penetration and (3) shelf-life effect on wear. Specimens were SXL acetabular cups with internal diameters ranging from 22 mm to 44 mm, and thicknesses ranging from 3.9 mm to 19.6 mm. All cups were tested for 1–5 million cycles. Wear rates were tested for normality and suspected outliers were tested using the generalized extreme studentized deviate (ESD). A total of 290 samples were evaluated, which included suspected outliers. After ESD statistical outlier removal, distribution was non-normal and the range of wear rates was −4.3 to 8.2 mm3/mc, with a mean of 1.8±1.6 mm3/mc and median of 1.6 mm3/mc. Individual bearing sizes and thicknesses reveal non-normal distributions for the 22 mm, 32 mm, and 40mm groups and for the 10 mm thickness group. The sample with the highest calculated linear penetration rate, 22.2 μm/mc, was for a 22 mm bearing size with 19.6 mm thickness. Before and after outlier removal, regression results of bearing size, thickness, and shelf age produce linear coefficients of correlation, R2 Published clinical data performance at 5 years documented with 32 mm bearings show clinical values ranging from 0.008 mm/yr to 0.015 mm/yr. The 32 mm bearing size represents 127 samples in this data set, and the mean calculated linear penetration is 0.008 mm/mc. This value compares favorably to the reported penetration values, assuming that 1 million hip wear simulation cycles approximates closely to one year of in-vivo cycles. In addition, wear analysis showed no effect of shelf-life on wear and maintained its low wear characteristics regardless of polyethylene thickness or head size.

Because of improvements in ceramic materials and manufacturing, the incidence of ceramic failures has decreased over time. Recent concerns with corrosion have contributed to an increase in ceramic ball head utilization. The purpose of this study is to report the incidence of modern alumina bearing failures from a single major ceramic manufacturer in nearly 6 million hip implants and to identify trends in the modes of failure of these implants.Beginning in the year 2000, CeramTec AG (Plochingen, Germany) began a comprehensive program for reporting and gathering failure data on its products. From January 1, 2000, to December 31, 2013, over 3.2 million pure alumina (PA) and 2.78 million alumina matrix composite (AMC) ceramic ball heads were implanted worldwide. During this period, there were 672 PA and 28 AMC femoral head fractures. The fractures were analyzed with respect to time to failure, head size, and implant factors.The incidence of clinical fractures of modern PA femoral heads and AMC femoral heads was 1 in 5000 (0.0201%) and 1 in 100,000 (0.0010%), respectively (P.0001). The majority of implant failures (80%) occurred within 48 months following surgery (P.01). Fractures were usually associated with specific events such as trauma, mismatched components, and dislocations. Large-diameter PA heads were associated with a lower rate of fracture compared to smaller-diameter femoral heads (0.0316% for 28-mm heads vs 0.0080% for heads 32 mm or greater [P.01]). Similar trends were observed with AMC heads. The neck lengths of the femoral ball heads were also a factor: a short-taper 28-mm ball head was more likely to fracture compared to other neck lengths (P.01).Modern PA ceramic heads are reliable with extremely low risk of fracture. The reliability is even better with AMC heads.

A copy number variant (CNV) of 16p11.2, which encompasses 30 genes, is associated with developmental and psychiatric disorders, head size and body mass. The genetic mechanisms that underlie these associations are not understood. To elucidate the effects of genes on development, we exploited the quantitative effects of CNV on craniofacial structure in humans and model organisms. We show that reciprocal deletion and duplication of 16p11.2 have characteristic “mirror” effects on craniofacial features that are conserved in human, rat and mouse. By testing gene dosage effects on the shape of the mandible in zebrafish, we show that the distribution of effects for all individual genes is consistent with that of the CNV, and some combinations have non-additive effects. Our results suggest that, at minimum, one third of genes within the 16p11.2 region influence craniofacial development, and the facial gestalt of each CNV represents a product of 30 dosage effects.

Background Aseptic loosening and periprosthetic osteolysis are frequent complications in total hip arthroplasty requiring revision surgery. Highly cross-linked polyethylene (HXLPE) implants have improved wear resistance, permitting larger femoral heads. However, such implants may experience surface cracking, mechanical failure, and oxidative damage. Vitamin E-infused HXLPE (VEPE) implants were therefore developed to reduce oxidation without compromising mechanical strength. We addressed the following questions: (1) Does femoral head size affect the midterm annual polyethylene wear rates of VEPE acetabular cups? (2) Does femoral head size affect the midterm migration rates of VEPE acetabular cups? (3) Are clinical outcomes affected by femoral head size? Hypothesis Annual wear rate, migration rate, and clinical outcomes of VEPE acetabular cups are independent of femoral head size. Patients and methods This was a prospective, multicentre, observational study of patients that underwent total hip arthroplasty. Hips were grouped according to the size of femoral head implanted (28 mm, 32 mm, and 36 mm). We determined annual wear rate and migration rate of VEPE acetabular cups using the Einzel-Bild-Rontgen-Analyse software. Clinically, we assessed the Harris Hip Score and visual analog score for pain and satisfaction. Results We followed 253 patients (267 hips) for a mean of 55.0 ± 20.6 months in the 28 mm, 46.2 ± 21.4 months in the 32 mm, and 43.8 ± 22.6 months in the 36 mm group. The annual wear rate was 0.025 mm per year from 1 year to the last follow-up and remained similar between the groups (p > 0.05). Also, mean two-dimensional migration rates did not exceed 0.05 mm from 2 years to the last follow-up and remained similar between the groups (p = 0.355). Finally, clinical outcomes also did not differ between the groups (p > 0.05). Two patients required revision surgery. Discussion Femoral head size did not influence midterm annual wear rate, migration rate, and clinical outcomes of VEPE acetabular cups. Furthermore, wear and cup migration rates were below the reported values leading to osteolysis and aseptic loosening. Nevertheless, studies with extended follow-up periods will be necessary to confirm these results in the long term. Level of evidence IV.

Background We report on the midterm linear and volumetric wear of highly cross-linked polyethylene (HXLPE) and survivorship of 2 prospective young total hip arthroplasty (THA) cohorts that differed by the size of ceramic femoral head used: 28 vs 32 mm. Methods We prospectively analyzed 220 consecutive primary THAs in patients aged ≤50 years who received a cementless THA with a ceramic femoral head on HXLPE liner (C-HXLPE). There were 101 patients (46%) with 28-mm heads and 119 patients (54%) who received 32-mm heads at a mean follow-up of 5.5 years (range, 60-109 months). Wear was calculated using Martell Software. Results The 28-mm C-HXLPE cohort demonstrated average linear and volumetric wear of 0.020 mm/y (standard deviation [SD], 0.074; 95% CI, 0.003-0.037) and 18.775 mm 3 /y (SD, 21.743; 95% CI, 13.773-23.778) compared with 0.032 mm/y (SD, 0.087; 95% CI, 0.013-0.050]) and 29.847 mm 3 /y (SD, 35.441; 95% CI, 22.294-37.401) in the 32-mm C-HXLPE group. Subgroup analysis by gender and head size discovered significantly greater wear in females with 32-mm heads compared with 28-mm heads in both linear (0.01, 95% CI = −0.014 to 0.033 vs 0.048, 95% CI = 0.022-0.074 mm/y, P = .004) and volumetric wear (14.11, 95% CI = 8.957-19.271] vs 29.71, 95% CI = 17.584-41.840] mm 3 /y, P = .009). We found a 96% (95% CI = 92.30%-97.94%]) survivorship by Kaplan-Meier analysis at minimum 5 years with no failures because of osteolysis. Conclusions Ceramic on HXLPE demonstrates extremely low wear properties in young patients at midterm follow-up. We identified a gender-dependent difference in wear based on head size, with 32-mm heads being associated with increased wear in females.

Despite the increasing usage of thin and high strength steel roof battens in the roof structures of low-rise buildings, recent cyclones and storms have shown that they prematurely fail at their screw fastener connections to the rafters or trusses due to the screw heads pulling through the batten bottom flanges. Such pull-through failures can lead to catastrophic failures of the entire roofing systems as observed during recent high wind events. Therefore a detailed experimental study consisting of both small scale and full scale tests was undertaken to investigate the pull-through failures of roof battens under wind uplift loading in relation to many critical parameters such as screw fastener tightening, roof batten geometry, batten thickness, steel grade, screw fastener head size and screw fastener location. Effects of underside surface and edge details of the screw fastener head, and screw fastener types were also considered. This paper presents the details of the tests conducted in this study and the pull-through failure load results obtained from them. Finally it presents the details of suitable design rules and capacity reduction factors developed in this study that can be used to accurately determine the design pull-through capacities of steel roof battens under wind uplift loads.

A lack of uniformity of broccoli heads in practice leads to the need for multiple hand harvests which increase production costs significantly. Decisions about harvest operations have to take economic aspects and existing price fluctuations into account. For planning of cutting and optimization of harvesting a forecast of the exact amount of harvestable heads per date is necessary. A model for growth, development and variability is presented here. Heading and variation in time to heading were considered in a piecewise linear regression model in response to temperature combined with one stochastic subroutine to describes the occurring variability. This model was implemented into a growth model to validate the hypothesis that variation in heading can explain the variation in head size. For this task a dry matter production and portioning model for cauliflower was used and reparameterised for broccoli growth and improved through implementation of dynamic LUE and SLA parameters. The model was positively evaluated using independent field data. The model explains on average 79% (22–94%) of the measured variability in head size at final harvest by variation in heading. For prediction of harvest dates a harvest criterion of 500 g fresh weight with a stem part of 0–10 cm is defined. To maximise reaping percentages of individual harvests and for optimisation of harvest operations the model calculates percentages of harvestable heads per date. Simulations showed that harvest percentages not less than 80% can be archived by 1.8 selective hand harvests on average.

Background: Ceramic-on-ceramic (COC) total hip arthroplasty (THA) has gained popularity since improvements in wear characteristics and longevity. Whether large ceramic femoral heads (≥36 mm) have increased postoperative range of motion (ROM) and a lower dislocation rate is not clear. This study aimed to compare functional outcomes and early complications between large-head (≥36 mm) and smaller-head (≤32 mm) COC prostheses with a minimum follow-up of 12 months. Methods: A total of 95 consecutive uncemented COC THAs were performed in 90 patients between January 2012 and July 2013. Of these, 49 patients (smaller-head group) received third generation and 41 patients (large-head group) received fourth generation COC prostheses. Harris hip score (HHS), Western Ontario and McMaster Universities Arthritis index (WOMAC), and ROM of the hip pre- and post-operatively were compared, as well as the presence of early complications. Results: Postoperative HHSs (88.4 vs. 89.3, p = 0.34) and WOMAC scores (12.0 vs. 11.0, p = 0.111) were not different between the groups. Postoperative flexion ROM was lower in the smaller-head group (98.8° vs. 106.1°, p

Recent data indicate that the contemporary prevalence of dislocation after primary total hip arthroplasty is up to 5- to 10-fold greater in those patients with spinal deformities that lead to stiffness and/or significant pelvic tilt. Moreover, the interplay between the hip and spine is complex, dynamic, and changes over the lifetime of a patient. Finally, the interplay is not fully understood. As such, consideration should be given to the use of dual-mobility constructs in this cohort of patients given the increased effective head size, combined with the dual articulation before hard impingement.

The effects of large heads on stresses at the THA trunnion–head junction and their impact on tribocorrosion/metal ion release remain controversial. A 12/14 3D-model of a stem with different head sizes was investigated. Material properties of titanium were assigned to the trunnion and cobalt–chrome/alumina to the heads. A load simulating walking single-leg stand phase was applied to the head. A total contact head–trunnion interface was assumed. The area underneath the junction underwent significant elevations in stresses as head size increased from 28- to 40-mm. Maximum principal stress doubled between 28 and 40-mm heads, regardless of head material. Stress levels had a direct correlation to head diameter. Stress increases observed using increasingly larger heads will probably contribute to head–trunnion tribocorrosion and ion release.

Previous findings on normal sexual dimorphism in hippocampal volume have not always been consistent. This study investigated gender differences in hippocampal volume using different head-size correction strategies. T1-weighted MR images were collected in 99 healthy, Caucasian, university students (66 female subjects; mean age: 23.1 ± 2.3, range: 19-31 years). Sexual dimorphism in hippocampus was investigated by automated MRI volumetry and voxel-based morphometry (VBM) using both general linear model (GLM) and proportion head-size correction strategies. Absolute hippocampal volumes were larger in men than women. After adjusting for head-size, the proportion method indicated larger hippocampi in women than men, while no gender differences were found using the GLM approach. Investigating absolute hippocampal volumes in 15 head-size matched pairs of males and females indicated no gender differences. We suggest that there is no sexual dimorphism in hippocampal size and the apparent gender differences found by the proportion method may have more to do with head-size than with sex. The GLM and proportion head-size correction strategies are not interchangeable and may yield different results. The importance of the present findings is mostly related to scientific reproducibility across MRI volumetry or VBM studies.

The effects of articular head size on the wear losses of the metal insert and articular head for a metal-on-metal bearing were examined using a hip simulator manufactured to satisfy ISO 14242-1. The wear properties of metal-on-metal and metal-on-polyethylene bearings were also compared under the same conditions. The total wear losses of the metal insert and articular head decreased with increasing diameter of the metal insert in the range from 28 to 44 mm. The total wear loss was greater for a diameter of 48 mm than for a diameter of 44 mm. When the articular metal insert diameter was smaller than 44 mm, the wear loss was reduced because the contact surface pressure increased with increasing metal insert diameter. However, the increase in wear loss observed for the 48-mm-diameter insert might have been due to the considerable increase in the rotation moment with increasing insert diameter. The tendency of decreasing contact pressure calculated using the Hertzian contact stress equation nearly conformed to the change in wear loss. On the other hand, the wear loss of an artificial hip joint consisting of a cross-linked ultrahigh-molecular-weight polyethylene insert (UHMWPE) and a Co–Cr–Mo articular head was small.

Use of larger diameter femoral heads has been popularised in total hip arthroplasty (THA). Recent studies have implicated larger femoral heads in early failure. We evaluated what effect the size of the femoral head had on the early functional outcome in order to determine the optimal head size for the maximal functional outcome. There were 726 patients who underwent elective THA and were divided into 3 groups according to head size then compared with respect to functional outcome scores and dislocation rates. This study failed to show that increasing the size of the femoral head significantly improved the functional outcome at 1 year after total hip arthroplasty but that the use of a 36 mm or greater femoral head did reduce the dislocation rate.

Adult green turtles (Chelonia mydas) are unusual relative to other sea turtles in that they are predominately herbivorous. This herbivorous diet is reflected in the serrated morphology of their beak, bite performance and the relative morphometrics of their heads. Recent bite performance data in loggerhead turtles (Caretta caretta), which are known for their durophagous capability, have demonstrated that bite force is correlated with head morphometrics. The objective of this study was to characterize bite force in green turtles and correlate bite performance with head and carapace morphometrics. We predicted that maximum bite force in green turtles would be less in magnitude relative to loggerheads, but would be positively correlated with head morphometrics. Therefore, mass, straight carapace length, straight carapace width, greatest head width, height, and length were collected with bite force from free-ranging green turtles from Punta Abreojos, Baja California Sur, Mexico and Otsuchi, Japan. Subjects ranged from 10.9 to 48 kg, with straight carapace length and width ranged from 40.6 cm to 71.9 cm (mean = 56.3 ± 8.5 cm) and from 33.5 cm to 55.9 cm (mean = 44.8 ± 5.7 cm), respectively. A bite force apparatus was used to collect bite performance from subjects. The maximum bite force was 303 N. Mean head width, head height, and head length were 8.7 ± 1.2, 8.2 ± 1.1, and 11.5 ± 1.5 cm, respectively. Bite force was lower in magnitude than reported for loggerhead turtles as predicted but still strong enough to process algal and plant matter, as well as crush many hard prey items. Simultaneous measurements of body and head size, and the use of non-linear reduced major axis regression, show that bite force scaled isometrically relative to body size and head size. Simple correlation showed that all logged transformed morphometrics were good predictors of logged bite performance, but an AICc-based weighted regression showed that body mass, followed by head width and head height, were better predictors of bite force than carapace size.

In brain volumetric studies, intracranial volume (ICV) is often used as an estimate of pre-morbid brain size as well as to compensate for inter-subject variations in head size. However, if the estimated ICV is biased by for example gender or atrophy, it could introduce errors in study results. To evaluate how two commonly used methods for ICV estimation perform, computer assisted reference segmentations were created and evaluated. Segmentations were created for 399 MRI volumes from 75-year-old subjects, with 53 of these subjects having an additional scan and segmentation created at age 80. ICV estimates from Statistical Parametric Mapping (SPM, version 8) and Freesurfer (FS, version 5.1.0) were compared to the reference segmentations, and bias related to skull size (approximated with the segmentation measure), gender or atrophy were tested for. The possible ICV related effect on associations between normalized hippocampal volume and factors gender, education and cognition was evaluated by normalizing hippocampal volume with different ICV measures. Excellent agreement was seen for inter- (r=0.999) and intra- (r=0.999) operator reference segmentations. Both SPM and FS overestimated ICV. SPM showed bias associated with gender and atrophy while FS showed bias dependent on skull size. All methods showed good correlation between time points in the longitudinal data (reference: 0.998, SPM: 0.962, FS: 0.995). Hippocampal volume showed different associations with cognition and gender depending on which ICV measure was used for hippocampal volume normalization. These results show that the choice of method used for ICV estimation can bias results in studies including brain volume measurements.

Modular femoral stem systems decouple leg length, offset, and version. The hip ROM and type of impingement for 162 femoral head/neck combinations were measured at four extreme hip positions in a Sawbones pelvis and femur to identify constructs that lead to early impingement. Hip ROM increased in all positions with increasing head size and neck length. We identified a new type of impingement created by the build-up of the proximal femoral stem: femoral stem on acetabular liner impingement. Seventy percent of neutral neck options achieved our definition of acceptable ROM. In general, when utilizing a modular femoral stem, surgeons can minimize impingement by choosing the longest femoral neck that does not over-lengthen the limb, using the largest femoral head accommodated by the cup, and avoiding neck version unless the cup or stem is malaligned.

Visual evoked potentials (VEPs) are known to be influenced by several biological variables, including sex. In adult populations studies using conventional high-contrast checkerboard have shown that females display larger amplitudes and shorter latencies than males. To date, few studies have been conducted in children; the available data suggests that girls display significantly larger amplitudes than boys but the effect on latency is absent or negligible. We investigated sex-related VEP differences in 149 school-age (11.3 ± 0.6 years) children from Northern Quebec using several VEP protocols: achromatic pattern-reversal VEPs at high (95%) and low contrast (30%, 12% and 4%), as well as motion-onset VEPs and isoluminant pattern-reversal VEPs. Girls showed significantly larger amplitudes in achromatic VEPs for most of the contrast levels as well as in N2 response to motion-onset. No significant difference was found regarding the amplitude of isoluminant VEPs. In addition, girls showed shorter latencies for the achromatic N75 and a trend (p

Accurate assessment of canine hearing is essential to decrease the incidence of hereditary deafness in predisposed breeds and to substantiate hearing acuity. The Brainstem Auditory Evoked Response (BAER) is a widely accepted, objective test used in humans and animals for estimation of hearing thresholds and deafness diagnosis. In contrast to humans, testing and recording parameters for determination of normal values for canine hearing are not available. Conflicting information concerning breed and head size effects on canine BAER tests are major contributors preventing this normalization. The present study utilized standard head measurement techniques coupled with BAER testing and recording parameters modeled from humans to examine the effect canine head size and breed have on BAER results. Forty-three adult dogs from fourteen different breeds had head size measurements and BAER tests performed. The mean latencies compared by breed for waves I, II, III, IV, and V were as follows: 1.46±0.49 ms, 2.52±0.54 ms, 3.45±0.41 ms, 4.53±0.83 ms and 5.53±0.43 ms, respectively. The mean wave I-V latency interval for all breeds was 3.69 ms. All dogs showed similar waveform morphology, structures, including the presence of five waves occurring within 11 ms after stimulus presentation and a significant trough occurring after Wave V. All of the waveform morphology for our subjects occurred with consistent interpeak latencies as shown by statistical testing. All animals had diagnostic results within the expected ranges for each wave latency and interwave interval allowing diagnostic evaluation. Our results establish that neither differences in head size nor breed impact determination of canine BAER waveform morphology, latency, or hearing sensitivity for diagnostic purposes. The differences in canine head size do not have a relevant impact on canine BAERs and are not clinically pertinent to management or diagnostic decisions.

The potential for corrosion at the modular head-neck junction in total hip arthroplasty has been well described, however the associated biological implications have recently received increasing clinical attention. Taper corrosion has been reported in patients with metal-on-polyethylene bearing surfaces, but it has also been recognized as an increasing cause of failure in patients with large head metal-on-metal hip replacements. Mechanical factors such as taper geometry, stem design, head size, or neck length may play a role in the etiology of taper corrosion. It can produce a range of clinical symptoms including pain, weakness, and instability that result from adverse local tissue reactions. While systemic effects have been reported, these remain poorly understood at present. A diagnostic algorithm to taper corrosion is provided, and treatment options are reviewed.

Hemispherical uncemented components have become the most frequently inserted components for acetabular revision. Reliable osseous fixation following press fit insertion with supplemental screw fixation has been achieved even in cases with significant acetabular deformities. Modular polyethylene liners have increased intraoperative flexibility with options for modifying head size, offset, and inclination. Cementable polyethylene liners allow independent positioning of the shell and articular surface and may reduce backside wear and facilitate improved liner positioning. Dislocation and infection remain leading complications after acetabular revision surgery.

A deburring tool for intersecting holes is proposed. The tool has a hemispherical cutter head mounted on a pivoted shaft which is loaded against the burr edge by a set of springs. The cutter head is inserted into an intersecting hole up to the burr edge and is subsequently rotated counterclockwise with a return stroke. The cutter head size is selected such that the cutter head has maximum accessibility to the three dimensional burr edge. The cutting edge is designed to maintain proper ranges of rake angle and relief angle during deburring. The efficiency of the tool in terms of deburring speed is verified by a set of deburring tests on Al6061-T6. The measured depth of cut on the burr edge confirms the complete removal of burrs.

We describe a scaling method for templating digital radiographs using conventional acetate templates independent of template magnification without the need for a calibration marker. The mean magnification factor for the radiology department was determined (119.8%; range, 117%-123.4%). This fixed magnification factor was used to scale the radiographs by the method described. Thirty-two femoral heads on postoperative total hip arthroplasty radiographs were then measured and compared with the actual size. The mean absolute accuracy was within 0.5% of actual head size (range, 0%-3%) with a mean absolute difference of 0.16 mm (range, 0-1 mm; SD, 0.26 mm). Intraclass correlation coefficient showed excellent reliability for both interobserver and intraobserver measurements with intraclass correlation coefficient scores of 0.993 (95% CI, 0.988-0.996) for interobserver measurements and intraobserver measurements ranging between 0.990 and 0.993 (95% CI, 0.980-0.997).

Head size markedly differs among individuals. To our knowledge, there have been no studies that systematically investigated the effect of head size on diffusion tensor measures of the brain. The purpose of this study was to evaluate the effect of head size or total intracranial volume on diffusion tensor measures (FA and MD). A total of 821 normal subjects (304 females and 517 males) were included in this study. We investigated the effect of total intracranial volume on FA and MD mainly using tract-based spatial statistics (TBSS). There were a number of regions where FA or MD was significantly correlated with total intracranial volume. There was no significant interaction between total intracranial volume and sex. The results indicate that total intracranial volume significantly influences diffusion tensor measures such as FA and MD. The possible explanations of the relationship between diffusion tensor measures and total intracranial volume may be 'partial volume effects' or micro-architectural differences related to head size. When total intracranial volumes are significantly different between groups, it may be necessary to control for total intracranial volume in the statistical analysis, depending on the hypothesis being tested.

In this study, numerical simulation of anchor bolt pullout in plain concrete by a heterogeneous numerical model is presented. The heterogeneity of the concrete material was modeled by randomly assigning strength and elastic modulus to the elements according to Weibull's distribution. The ongoing debonding process was obtained, including crack initiation, crack propagation and formation of the concrete cone. The numerical results indicate that there is a strong size effect on failure resistance of the concrete cone. By increasing the anchor head size, peak pullout load and the volume of concrete cone increase. The peak pullout load and the volume of concrete cone also increase with the increasing of embedded length. With this heterogeneous numerical model, the asymmetrical crack patterns and the crack branching observed in tests is obtained. Moreover, asymmetrical crack and crack branching were easy to occur with lower homogeneity index. The numerical results agreed well with the experimental investigations.

Smaller head sizes and head/cup ratios make cups smaller than 50 mm and larger than 58 mm, more prone to dislocation. Using computer modeling, we compared average head sizes and posterior horizontal dislocation distance (PHDD) in two 78-patient matched cohorts. Cup sizes were small (≤ 50 mm) or large (≥ 58 mm). The control cohort had conventional fixed bearing prostheses, while the experimental cohort had anatomical dual mobility (ADM) hip prostheses. ADM cups have larger average head sizes and PHDD than traditional fixed bearing prostheses by 11.5 mm and 80% for cups ≤ 50 mm, and 16.3 mm and 90% for cups ≥ 58 mm. Larger head sizes and increased head/cup ratio may allow the ADM prosthesis to reduce the incidence of dislocation.

Femoral head sizes greater than 32 mm are more prevalent with current total hip arthroplasty. We hypothesized that linear wear rates of Durasul highly cross-linked polyethylene would not differ with different head sizes. We also compared the range of motion of the hip. Ninety-four consecutive arthroplasties in 84 patients were studied for a mean 3.6 ± 0.7 years. There was no statistical difference in linear wear rates and annual or total penetration rates when 28-mm and 32-mm heads were compared to 38-mm and 44-mm heads. Volumetric wear was 12.4 mm 3 /y higher with bigger heads. Range of motion did not differ. Larger femoral head sizes show no evidence of an accelerated wear pattern when used with Durasul.

Glenohumeral instability after total shoulder arthroplasty is a potential complication observed after primary arthroplasty. The following review discusses anterior, posterior, superior, and inferior instability, as well as the respective clinical presentations and treatment algorithms. Many factors are associated with the various types of instability: glenoid size and version, humeral retroversion and height, humeral head size, soft-tissue balancing, and rotator cuff integrity. Avoidance of these problems requires proper planning and intraoperative technique during the index procedure, as well as early recognition and treatment of any postoperative instability.

The purpose of this study was to determine if the use of both a larger femoral head size and a posterior capsular repair would lead to a decreased incidence of dislocation following revision total hip arthroplasty (THA). Two hundred forty-two consecutive revision THAs with posterolateral approach were performed between 2000 and 2005. Group 1 had 132 revision THAs with posterolateral approach and 28-mm head size without posterior capsule repair. Group 2 had 100 revision THAs with a 32-mm head size and repair of the remaining hip capsule. There were no statistically significant differences in the two groups. Group 1 had 14 dislocations (10.6%). Group 2 had 3 dislocations (2.7%) (P < .05). Based on the results of this retrospective review, the authors recommend the use of both larger femoral head sizes and repair of any posterior capsular tissue available in patients undergoing revision hip arthroplasty.

The purpose of this study was to quantify the effects of femoral offset and head size on range of motion (ROM) after total hip arthroplasty. Modular prostheses were implanted into 11 cadaveric hips using a posterolateral approach and tested for ROM with 3 different offsets and 5 different femoral head sizes. Increasing the femoral offset to 4 and 8 mm resulted in 21.1 degrees and 26.7 degrees of improved flexion, and 13.7 degrees and 21.2 degrees of improved internal rotation, respectively. The ROM improved in a head size-dependent manner primarily because of increasing the jumping distance of the femoral head rather than delaying any impingement. In contrast, the effectiveness of femoral offset was driven by delayed osseous impingement.

Many patients undergoing total hip resurfacing arthroplasty present with reduced anterior femoral neck concavity as a part of the degenerative process. Painful hip impingement may develop or persist after hip resurfacing when the retained femoral neck abuts against the metallic acetabular component or the anterior acetabular bony wall. We report on two cases of painful postoperative hip impingement after hip resurfacing, in one of whom anterior neck-contouring osteoplasty restored pain-free range of motion (ROM). To restore natural hip ROM, surgeons performing hip total hip resurfacing arthroplasty should aim to reproduce the normal femoral head-neck offset ratio. Femoral head-neck offset restoration can be achieved by proper femoral component positioning (especially optimal translation), by femoral neck osteoplasty or by increasing femoral component head size appropriately.

Summary Femoral head size remains one of the most controversial and oft debated aspects of hip replacement surgery. Sir John Charnley set the debate in motion in his paper on Low Friction Arthroplasty with the emphasis on finding the ideal head size to reduce friction and therefore, it was thought, wear. As our understanding of tribology improved and with the development of more wear-resistant materials, the emphasis has shifted towards finding the ideal size to improve joint stability. The ability to use large diameter heads has provided an opportunity to expand the indications for total hip arthroplasty to include trauma and younger patients.

Fluctuating temperatures (FTs) influence hatchling phenotypes differently from constant temperatures (CTs) in some reptiles, but not in others. This inconsistency raises a question of whether thermal fluctuations during incubation always play an important role in shaping the phenotype of hatchlings. To answer this question, we incubated eggs of Naja atra under one CT (28 °C, CT), two temperature-shift [cold first (CF) and hot first (HF) in which eggs were first incubated at 24 or 32 °C and then at the other, each for 20 days, and finally at 28 °C until hatching], and one FT thermal regimes. Female hatchlings were larger in snout–vent length but smaller in tail length, head size than male hatchlings from the same-sized egg; female hatchlings had more ventral scales than did male hatchlings. The FT and HF treatments resulted in shorter incubation lengths. Tail length was greatest in the CT treatment and smallest in the FT treatment, with the CF and HF treatments in between; head width was greater in the CT treatment than in the other three treatments. Other examined hatchling traits did not differ among treatments. The observed morphological modifications cannot be attributed to the effect of thermal fluctuations but to the effect of temperatures close to the upper and lower viable limits for the species. Our results therefore support the hypothesis that hatchling phenotype is not altered by thermal fluctuation in species with no phenotypic response to incubation temperature within some thresholds.

Data collected by Hooton (1939) on 676 inmates held at the Concord Reformatory in Massachusetts include both anthropometric measures and IQ scores. In this study a sample ( N = 238) was drawn to assess the nonparametric correlation between measures of head size and IQ. Head length ( r = .13), breadth ( r = .15), height ( r = .14), circumference ( r = .15) and calculated volume ( r = .20) correlated with IQ. Two measures of body size also correlated with IQ; height ( r = .22) and sitting height ( r = .19).

Larger femoral head size reduces the incidence of hip dislocation, which is a major complication after total hip arthroplasty. However, acetabular liner wear is a function of contact area and therefore head size. Larger heads also reduce liner thickness and there is a general concern about increased wear. This study evaluates the influence of polyethylene thickness and femoral head size on the wear performance of sequentially cross-linked acetabular inserts. A sequential cross-linking and annealing process for treating ultra-high molecular weight polyethylene (UHMWPE) has been developed (X3 ® , Stryker Orthopaedics). This material was compared to conventional UHMWPE in hip simulator wear testing. Liners varying from 32 mm to 52 mm in diameter and 3.8–7.9 mm in thickness were evaluated here. An MTS (Eden Prairie, MN) multi-station hip simulator was used for wear testing. All components were tested at 1 Hz under a joint reaction profile (2450 N maximum) and 50% diluted Alpha Calf Fraction Serum (Hyclone, Logan, UT). Results show no statistically significant effect of head size or liner thickness on wear rate of sequentially cross-linked liners. Analysis shows poor correlation between head size and wear rate ( R 2 = 0.2751), and between liner thickness and wear rate ( R 2 = 0.0055). An average of all tested sizes show a reduction of 96% in wear rate compared to control. The excellent wear performance of the sequentially cross-linked liners studied here increases the potential for use of large head components in total hip arthroplasty.