Larger Head Size Research Articles

Earlier detection of hypochondroplasia: A large single-center UK case series and systematic review.

Hypochondroplasia (HCH) is a rare autosomal dominant skeletal dysplasia condition caused by FGFR3 mutations leading to disproportionate short stature. Classically HCH presents in toddlers or school-age children, as limb-to-trunk disproportion and is often mild and easily overlooked during infancy. We report experiences from a single-center UK HCH-cohort of 31 patients, the rate of antenatal HCH detection in our cohort (13/31, 41.9%) and describe relevant case-data for this subset of 13 patients. Inclusion criteria were patients with confirmed molecular HCH diagnosis (by age 3 years) and presenting with short long-bones or large head size on antenatal ultrasound scan. We then conducted a systematic literature review using PUBMED and MEDLINE, analyzing patients with HCH and related antenatal findings. Antenatally suspected (with subsequent molecular confirmation) HCH has been reported 15 times in the literature (2004-2019). Key markers (consistent in both groups) included reduced; femur length, humeral length and increased; biparietal diameter and head circumference. HCH is increasingly detected both antenatally and in infancy, contrary to previous descriptions. This is likely due to greater HCH awareness, improved imaging, and easier molecular testing. Thus, one should consider HCH outside the classical presenting period. Studying the natural history of younger patients with HCH is important with the advent of several targeted FGFR3 therapies currently in trials for Achondroplasia, that may soon be trialed in HCH.

Abstract 5779: The association of instrument assisted deliveries and the development of childhood brain tumors: A matched case control study

Abstract Background: Pediatric brain tumors are the second most common type of childhood cancer and have the highest mortality rate among all pediatric cancer types. New information on potentially preventative measures would be of great value. Previous studies have suggested that instrument-assisted delivery (forceps and vacuum) may be associated with an increased risk for childhood brain tumors. The goal of this study was to determine if there was an association of exposure to instrument-assisted deliveries with childhood brain tumors in Denmark. We additionally examined risk with emergency or planned cesarean section. Methods: This was a matched case-control study with childhood brain tumor cases in Denmark diagnosed from 1978-2013. Cases were identified from the Danish Cancer Registry. Birth outcomes, maternal procedures and covariates were obtained from the Danish Medical Births Register and the nationwide Hospital Register. A total of 3,698 brain tumor cases were recruited and 25 controls were matched to each case based on child's sex and birth year (N=89,554). We used conditional logistic regression to determine associations of delivery instruments types with various childhood brain tumors. Results: Compared to children birthed by spontaneous vaginal delivery, children who later developed ependymomas (N=136) had a greater likelihood of having been delivered by vacuum assisted deliveries (OR=1.69, 95% CI 1.01-2.83). An overall increased risk for cesarean section with any CNS tumor (OR= 1.20, 95% CI 1.06-1.36) dropped to 1.10 when we limited the age range to 4 or older (N=1,087). This suggests no clear increased risk for cancer with cesarean section, as there is a possibility that the CNS tumor was present before birth and influenced a larger head size, thus requiring a cesarean section. Planned cesarean and emergency cesarean section were not related to risk increases. While the use of forceps was rare in this population (1.2% in controls), we could not confirm previously reported associations with astrocytoma (OR=0.84), though there was a weak increase for ependymoma with wide confidence intervals (OR=2.69, 95% CI 0.77, 9.38). Conclusions: Based on objective data, the findings in our study suggest that there might be an association between vacuum assisted deliveries and ependymomas. Our data did not support a strong association of childhood brain tumors with cesarean sections. Citation Format: Karen Yeh, Johnni Hansen, Julia E. Heck. The association of instrument assisted deliveries and the development of childhood brain tumors: A matched case control study [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5779.

The Calpain Gene is Correlated With Metal-on-Metal Hip Replacement Failures

BackgroundMetal-on-metal (MOM) total hip arthroplasty is associated with unacceptable failure rates secondary to metal ion reactions. Efforts to identify which patients will go on to failure have been limited; recently, there has been a suggestion for a potential genetic basis for the increased risk of revision in MOM hip replacements (MOMHRs). The purpose of this study is to determine whether certain immunologic genotypes are predictive of the need for revision in patients with MOM total hip implants. MethodsThis is a case-control study of all patients undergoing primary MOMHR between September 2002 and January 2012 with a minimum of 5-year follow-up. Our investigational “case” cohort was comprised of patients who underwent revision for MOMHR for a reason other than infection. A single-nucleotide polymorphism (SNP) array analysis was performed to identify a potential genetic basis for failure. ResultsThirty-two patients (15 case and 17 control) were included in our analysis. All patients in the revision group had a chief complain of pain; revision patients were more likely to have a posterior approach (P = .01) and larger head size (P = .04) than nonrevision patients. No patient or implant characteristics were independently associated with revision in a multivariate analysis. Patients with SNP kgp9316441 were identified as having an increased odds of revision for MOM failure (P < .001). ConclusionThis study identified an SNP, kgp9316441, encoding proteins associated with inflammation and macrophage activation. This SNP was associated with significantly increased odds of revision for MOMHR. Future studies are warranted to validate this gene target both in vitro and in vivo. Level of EvidenceIII.

Ten years on: increased metal ion levels in a cohort of patients who underwent uncemented metal-on-polyethylene total hip arthroplasty.

We have previously demonstrated raised cobalt and chromium levels in patients with larger diameter femoral heads, following metal-on-polyethylene uncemented total hip arthroplasty. Further data have been collected, to see whether these associations have altered with time and to determine the long-term implications for these patients and our practice. Patients from our previous study who underwent Trident-Accolade primary total hip arthroplasties using a metal-on-polyethylene bearing in 2009 were reviewed. Patients were invited to have their cobalt and chromium levels retested, and were provided an Oxford Hip Score. Serum ion levels were then compared between groups (28 mm, 36 mm, and 40 mm heads) and over time. Metal ion levels were repeated in 33 patients. When comparing the results of serum metal ion levels over time, regardless of head size, there was a significant increase in both cobalt and chromium levels (p < 0.001). Two patients with larger head sizes had undergone revision arthroplasty with evidence of trunnion damage at surgery. Two patients within the 40 mm subgroup had metal ion levels above the MHRA (Medicines and Healthcare Products Regulatory Agency) threshold for detailed investigation. The increase in cobalt and chromium, when comparing the 36 mm and 40 mm groups with those of the 28 mm group, was not significant (36 mm vs 28 mm; p = 0.092/p = 0.191; 40 mm vs 28 mm; p = 0.200/p = 0.091, respectively). There was no difference, between femoral head sizes, when comparing outcome as measured by the Oxford Hip Score. This study shows an increase in cobalt and chromium levels over time for all modular femoral head sizes in patients with metal-on-polyethylene bearings, with two patients demonstrating ion levels above the MHRA threshold for failure, and a further two patients requiring revision surgery. These results may have clinical implications regarding longer term follow-up of patients and future implant choice, particularly among younger patients. Cite this article: Bone Joint J 2020;102-B(7):832-837.

Large Diameter Head in Primary Total Hip Arthroplasty: A Systematic Review.

The literature around use of Large Diameter Heads (LDH) is abundantly available for revision Total Hip Arthroplasty (THA) but is lacking for primary uncomplicated THA. This systematic review was undertaken to synthesize data around primary THA involving LDH and analyze the associated complications (dislocation, volumetric wear, implant survivorship and functional score) along with reported effects on range of motion (ROM), patient reported outcomes and impingement rate/groin pain. A PRISMA compliant systematic review was done using extensive search in PubMed database, along with offline search looking for the literature published in English language between 2008 and 2018. The articles providing data on the use of large diameter heads (LDH) (36mm or larger) on various bearing surfaces were collected. This included robust national joint registries of different countries. Narrative approach to data synthesis was used. A total of 23 papers met our inclusion criteria, including six national joint registries. It was observed that LDH had significantly low dislocation rates, excellent implant survival rate as per Kaplan-Meier survivorship (> 90% at five years). Surgical approaches, except Minimally Invasive Surgery (MIS), did not increase any risk of dislocation as long as it was meticulously repaired. There was no significant improvement in any functional scores or improved ROM. LDH of 32-36mm are now commonly used in primary THA and is accepted as a popular size. The beneficial effects of a large head size are negated beyond 38mm. The most favored size for LDH THA, therefore, is 36mm contrary to the older literature favoring 28mm.

Complications and re-revisions after revisions of 528 metal-on-metal hips because of adverse reaction to metal debris

Background and purpose — There is limited amount of evidence about optimal revision indications, technique, and implants when performing revision surgery for metal-on-metal (MoM) hip replacements due to adverse reaction to metal debris (ARMD). We assessed which factors are related to re-revisions and complications after a revision of MoM hip arthroplasty because of ARMD. We also aimed to provide information on optimal implants for these revisions.Patients and methods — 420 MoM total hip arthroplasties (THA) and 108 MoM hip resurfacings were implanted and later revised at our institution. We used Cox regression to analyze the factors associated with re-revisions and complications after a revision for ARMD.Results — A re-revision was performed on 27 THAs (6%) and 9 resurfacings (8%). The most common indication for re-revision was recurrent dislocation (20 hips, 4%). Complications not leading to re-revision were seen in 21 THAs (5%) and 6 resurfacings (6%). The most common complication was dislocation treated with closed reduction in 13 hips (2%). Use of revision head size > 36mm was associated with decreased risk for dislocations. Presence of pseudotumor, pseudotumor grade, pseudotumor size, or the choice of bearing couple were not observed to affect the risk for re-revision. Non-linear association was observed between preoperative cobalt and risk for re-revision.Interpretation — As dislocation was the most frequent post-revision complication, large head sizes should be used in revisions. Because size or type of pseudotumor were not associated with risk of re-revision, clinicians may have to reconsider, how much weight is put on the imaging findings when deciding whether or not to revise. In our data blood cobalt was associated with risk for re-revision, but this finding needs further assessment.

Recovery of activity level following total hip arthroplasty in patients less than 60 years of age.

Total hip arthroplasty (THA) is a useful treatment for pain relief and functional improvement. THA indications now include younger, more active patients, with improved implant design and bearing materials. We aimed to investigate daily activity level and return to work after THA, about which limited information is available. Moreover, differences in patient background and clinical parameters including size of femoral head and surgical approach were evaluated. A multicentre survey was carried out in patients below 60 years, undergoing THA between 2007 and 2012, at least 1 year after surgery. Primary THA patients with osteoarthritis, avascular necrosis, rheumatoid arthritis, hip dysplasia, and no history of postoperative complications were included. The questionnaire included daily activity and occupation levels before and after surgery. University of California, Los Angeles (UCLA) activity score and occupational classification index were defined, and statistical analysis was performed. The mean preoperative UCLA score in 204 patients was 4.55 which improved to 6.17 after surgery. Pre- as well as postoperative UCLA scores in males were significantly higher than that in females. No differences were observed in other parameters. Return to work rate in males was 94.4%; significantly higher than that in females (52.3%). Younger patients with large head THA were more likely to return to work. Most patients showed improved activity levels. Satisfaction levels were higher in young males with large femoral head size. Patients with a higher preoperative work level are expected to have a higher return to work rate.

Morphological variation of Ahaetulla prasina (Boie, 1827) (Squamata: Colubridae) in Indonesia, with an expanded description of the species

Since Leviton (1967) argued that genus Ahaetulla needed to extensively review, we started to examine the most common Ahaetulla species in Indonesia, A. prasina. This study aims to explain the morphological variation and analyses pattern of A. prasina population from Sumatra, Java, Kalimantan and Sulawesi mainland. This study was carried out by manually counting and measuring the characteristics of 64 A. prasina specimens belongs to Museum Zoologicum Bogoriense (MZB) collections on 2016. All morphological characters have analysed using PCA, homogeneity test and one way anova test. The results shown there have variation in meristic characters as the adaptation pattern due to environmental condition and sexual dimorphism. In contrast, the morphometric characters shown that there no significant and slightly variation within population in these mainlands. Kalimantan population has larger head size than others and assumed as an adaptation towards its prey. This evidence proved that A. prasina is a snake species which successfully adapt in various environment types.

The prevalence of elevated-rim polyethylene liner use in primary total hip arthroplasty in the New York State metropolitan area.

In existing radiographic studies on primary total hip arthroplasty (THA) examining the spino-pelvic effect on THA instability, there is no control of the type of polyethylene liner used, which may be a significant confounder of the results. We sought to determine the prevalence of the use of elevated liners in primary THA using regional implant company sales data. A total of 12,528 liners were analyzed, demonstrating that the overall regional percentage use of lipped liner use is high and varies inversely with larger head sizes. This prevalence data suggests that it is important to consider the use of lipped liners as a confounding variable that should not be overlooked in radiographic studies analyzing cup position and THA instability.

Direct current stimulation-induced synaptic plasticity in the sensorimotor cortex: structure follows function

BackgroundNon-invasive direct current stimulation (DCS) of the brain induces functional plasticity in vitro and facilitates motor learning across species. The effect of DCS on structural synaptic plasticity is currently unknown. ObjectiveThis study addresses the effects and the underlying mechanisms of anodal DCS on structural plasticity and morphology of dendritic spines in the sensorimotor cortex (M1/S1). MethodsA DCS electrode setup was combined with a chronic cranial window over M1/S1 in transgenic Thy1-GFP mice, to allow for in vivo 2-photon microscopy and simultaneous DCS. Contralateral electrical forepaw stimulation (eFS) was used to mimic the second synapse specific input, a previously shown requirement to induce functional plasticity by DCS. Changes in spine density and spine morphology were compared between DCS/eFS and sham, as well as two control conditions (sham-DCS/eFS, DCS/sham-eFS). Furthermore, the role of BDNF for stimulation-induced changes in spine density was assessed in heterozygous Thy1-GFP x BDNF+/- mice. ResultsCombined DCS/eFS rapidly increased spine density during stimulation and changes outlasted the intervention for 24 h. This effect was due to increased survival of original spines and a preferential formation of new spines after intervention. The latter were morphologically characterized by larger head sizes. The DCS-induced spine density increase was absent in mice with reduced BDNF expression. ConclusionPrevious findings of DCS-induced functional synaptic plasticity can be extended to structural plasticity in M1/S1 that similarly depends on a second synaptic input (eFS) and requires physiological BDNF expression. These findings show considerable parallels to motor learning-induced M1 spine dynamics.

Large head ceramic-on-ceramic bearing in primary total hip arthroplasty: average 3-year follow-up of a multicentre study

Surgeons are increasingly using larger femoral head sizes in total hip arthroplasty (THA) to improve stability and reduce the rate of dislocation, 1 of the leading causes of revision surgery. Large ceramic head sizes up to 48 mm can now be used with monoblock acetabular components. National registries have shown promising results at short-term with large diameter ceramic-on-ceramic THA, with very low revision rates.This study reports on the average 3-year follow up of a press-fit monoblock large diameter acetabular shell with a pre-assembled ceramic liner, with emphasis on the radiographic outcome, complications related to the implantation of the cup, and the patient's clinical outcome. 170 hips in 169 patients were reviewed at an average 38 ± 5.8 months following surgery. The radiographic review revealed no acetabular cup loosening, no osteolysis and no cup migration. 1 acetabular cup was revised for malposition. The patient clinical outcome and the satisfaction rate were excellent. At 3 years, 7.1% of patients complained of groin pain and 3.5% spontaneously reported hip joint generated noise. 1 patient sustained a non-recurrent traumatic hip dislocation 2 years post surgery. New technology should be introduced cautiously on the market. This is especially true for the large diameter ceramic monoblock acetabular component used in this study since it involves a new acetabular component design. At short term, we have not identified new modes of failure with this implant. Longer follow-up is still needed to assess the safety of large ceramic bearing in THA.

Multivariate analysis of risk factors for re-dislocation after revision for dislocation after total hip arthroplasty.

The treatment for recurrent dislocation of a total hip arthroplasty is surgical using varied techniques and technologies to reduce the chances of re-dislocation and re-revision. The goal of this study is to compare operative techniques to reduce re-dislocation and re-revision in revision hip arthroplasty due to recurrent dislocations. A retrospective study of revision hip arthroplasties done due to recurrent dislocation prior to 01 January 2014. Electronic physician and provincial health records were used to collect patients' initial and follow-up data. Treatment failure was defined as either aseptic re-revision or re-dislocation without revision. Time to event was considered as the re-revision date or the date of second dislocation when the latter endpoint was used. Of 379 operations, 88 (23.2%) had aseptic repeat revision or recurrent dislocation. Of these: 66 (75.0%) due to dislocation with re-revision; 10 (11.4%) due to dislocation with no re-revision surgery; 5 (5.7%) due to aseptic loosening of components; 3 (3.4%) due to osteolysis; 3 (3.4%) due to pseudotumour; and 1 (1.1%) due to periprosthetic fracture. The following factors increase risk of failure: the use of augmented-liners (lipped, oblique and high-offset liners; HR = 1.68, 95% CI, 1.05-2.69), periprosthetic femur fracture (HR = 2.80, 95% CI, 1.39-8.21) and pelvic discontinuity (HR = 3.69, 95% CI, 1.66-8.21). Femur head sizes 36-40 mm are protective (HR = 0.54, 95% CI, 0.31-0.86). In abductor dysfunction the use of focal constrained liners decreases the risk of failure (HR = 0.13, 95% CI, 0.018-0.973). Larger head sizes and focal constrained liners (abductors dysfunction) should be used and fully constrained liners and augmented-liners should be avoided in a revision hip arthroplasty due to recurrent dislocations.

The anatomy of the syncervical of Auroraceratops (Ornithischia: Ceratopsia), the oldest known ceratopsian syncervical

The Early Cretaceous basal neoceratopsian dinosaur Auroraceratops rugosus was described based on a single skull recovered from the Gonpoquan Basin in northwestern Gansu Province, China. The genus is now known from cranial and postcranial remains representing at least 80 individuals, many of which come from the neighboring Yujingzi Basin, with an age of Aptian to earliest Albian (126-115 Ma). Among the new material were four syncervicals, representing the phylogenetically and temporally earliest occurrence of a syncervical in Ceratopsia. The anatomy of the syncervical matches that described in leptoceratopsids and protoceratopsids, with the first segment formed from a small atlas centrum, a much larger atlantal intercentrum, and a splint-like, divided atlantal neural arch. The axis bears a large hatchet-shaped neural spine and facets for a double-headed cervical rib. The centra of the first three cervical vertebrae and the first two intercentra are fused, though the boundaries of the individual elements are discernable. The relatively early temporal and phylogenetic appearance of a syncervical supports recent work that shows that the syncervical of ceratopsians is unrelated to the larger head size and cranial ornamentation characteristic of later appearing ceratopsian clades.Citation for this article: Li, D., E. M. Morschhauser, H. You, and P. Dodson. 2019. The anatomy of the syncervical of Auroraceratops (Ornithischia: Ceratopsia), the oldest known ceratopsian syncervical; pp. 69–74 in Hailu You, Peter Dodson, and Eric Morschhauser (eds.), Auroraceratops rugosus (Ornithischia, Ceratopsia) from the Early Cretaceous of northwestern Gansu Province, China. Society of Vertebrate Paleontology Memoir 18. Journal of Vertebrate Paleontology 38(Supplement). DOI: 10.1080/02724634.2018.1510411.

Cervical Spine Evaluation in Pediatric Trauma: A Review and an Update of Current Concepts.

The clinical presentation and diagnostic workup in pediatric cervical spine injuries (CSI) are different from adults owing to the unique anatomy and relative immaturity. The current article reviews the existing literature regarding the uniqueness of these injuries and discusses the current guidelines of radiological evaluation. A PubMed search was conducted using keywords “paediatric cervical spine injuries” or “paediatric cervical spine trauma.” Six hundred and ninety two articles were available in total. Three hundred and forty three articles were considered for the review after eliminating unrelated and duplicate articles. Further screening was performed and 67 articles (original articles and review articles only) related to pediatric CSI were finally included. All articles were reviewed for details regarding epidemiology, injury patterns, anatomic considerations, clinical, and radiological evaluation protocols. CSIs are the most common level (60%–80%) for pediatric Spinal Injuries (SI). Children suffer from atlantoaxial injuries 2.5 times more often than adults. Children's unique anatomical features (large head size and highly flexible spine) predispose them to such a peculiar presentation. The role of National Emergency X-Ray Utilization Study, United State (NEXUS) and Canadian Cervical Spine Rule criteria in excluding pediatric cervical injury is questionable but cannot be ruled out completely. The minimum radiological examination includes 2- or 3-view cervical X-rays (anteroposterior, lateral ± open-mouth odontoid views). Additional radiological evaluations, including computerized tomography (CT) and magnetic resonance imaging (MRI) are obtained in situations of abnormal physical examination, abnormal X-rays, inability to obtain adequate X-rays, or to assess cord/soft-tissue status. The clinical criteria for cervical spine injury clearance can generally be applied to children older than 2 years of age. Nevertheless, adequate caution should be exercised before applying these rules in younger children. Initial radiographic investigation should be always adequate plain radiographs of cervical spine. CT and MRI scans should only be performed in an appropriate group of pediatric patients.

Capsular Ligament Function After Total Hip Arthroplasty

Background:The hip joint capsule passively restrains extreme range of motion, protecting the native hip against impingement, dislocation, and edge-loading. We hypothesized that following total hip arthroplasty (THA), the reduced femoral head size impairs this protective biomechanical function.Methods:In cadavers, THA was performed through the acetabular medial wall, preserving the entire capsule, and avoiding the targeting of a particular surgical approach. Eight hips were examined. Capsular function was measured by rotating the hip in 5 positions. Three head sizes (28, 32, and 36 mm) with 3 neck lengths (anatomical 0, +5, and +10 mm) were compared.Results:Internal and external rotation range of motion increased following THA, indicating late engagement of the capsule and reduced biomechanical function (p < 0.05). Internal rotation was affected more than external. Increasing neck length reduced this hypermobility, while too much lengthening caused nonphysiological restriction of external rotation. Larger head sizes only slightly reduced hypermobility.Conclusions:Following THA, the capsular ligaments were unable to wrap around the reduced-diameter femoral head to restrain extreme range of motion. The posterior capsule was the most affected, indicating that native posterior capsule preservation is not advantageous, at least in the short term. Insufficient neck length could cause capsular dysfunction even if native ligament anatomy is preserved, while increased neck length could overtighten the anterior capsule.Clinical Relevance:Increased understanding of soft-tissue balancing following THA could help to prevent instability and improve early function. This study illustrates how head size and neck length influence the biomechanical function of the hip capsule in the early postoperative period.

Variation in Use of Postoperative Precautions and Equipment Following Total Hip Arthroplasty: A Survey of the AAHKS and CAS Membership

BackgroundA traditional method to reduce dislocation risk following total hip arthroplasty involves prescribing postoperative precautions and ambulatory equipment to patients. The purpose of this study was to determine the prevalence of postoperative precaution and equipment use among North American arthroplasty surgeons for patients undergoing primary total hip arthroplasty. MethodsWe conducted a survey of American Association of Hip and Knee Surgeons and Canadian Arthroplasty Society members using an electronic questionnaire format to determine how often precautions and equipment were prescribed, and whether their use was associated with surgical approach and other surgeon demographics. ResultsOf the respondents, 44% universally prescribed precautions while 33% never prescribed precautions. Use of the posterolateral approach, surgeon experience, and larger head size use were significantly associated (P < .01) with precaution and equipment use. Direct anterior approach surgeons were significantly less likely to prescribe precautions (P < .0001) and significantly less likely to prescribe equipment (P < .0001). ConclusionAlthough postoperative precautions continue to be used to some degree by the majority of members, their consumption of healthcare resources through utilization of additional care providers and purchasing of equipment, known association with reduced patient satisfaction, and lack of supporting evidence make them a target for future scrutiny.

Have large femoral heads reduced prosthetic impingement in total hip arthroplasty?

Prosthetic impingement is implicated in dislocation after total hip arthroplasty (THA). While use of larger diameter femoral heads reduces the incidence of dislocation, the effect of larger heads upon impingement rate is unknown. We assessed retrieved THA components for evidence of impingement to determine if large femoral heads reduced the rate of impingement in primary THA and what factors might influence impingement. Liners from 97 primary THAs retrieved at revision arthroplasty were scored for evidence of impingement, defined as wear or deformation on the rim of the component. Component inclination and version were measured from anteroposterior and cross-table lateral radiographs. Independent of revision diagnosis, 77% of liners demonstrated evidence of impingement. Impingement was less prevalent and less severe as head size increased. Severe impingement was observed in 50% of the liners with 28-mm heads, 15% of liners with 32-mm heads, and 21% of liners with 36-mm heads. Regardless of head size, 76% of liners revised for instability demonstrated impingement. Decreased head-neck ratio, use of an elevated liner, increased length of implantation, and increased version were associated with increased severity of impingement. We showed that larger head sizes are associated with decreased incidence of impingement on retrieved acetabular liners when compared to smaller head sizes. Larger heads have reduced but not eliminated impingement, which remains a potential source of instability.

Comparison of head size and bite force in two sister species of parrotbills

BackgroundBrain size is associated with morphological evolution and behavioral flexibility because animals with large brain size tend to utilize new resources and colonize novel environments more successfully. Therefore, animals with larger brain size should possess larger distribution ranges. Brain size is strongly positively correlated with head size in birds, but also with prey size and vocalizations, because individuals with large heads eat large food items and produce high frequency calls.MethodsTo test if there exists an association between head morphology and bite performance, we compared head size and bite force in two sympatric sister species of parrotbills, Ashy-throated Parrotbill (Paradoxornis alphonsianus) and Vinous-throated Parrotbill (P. webbianus), which both originated from the Himalayan area, but differ significantly in their distribution ranges.ResultsIn Guizhou, southwestern China, the Ashy-throated Parrotbill with a restricted distribution range had smaller heads whilst the Vinous-throated Parrotbill with a large distribution range had larger heads. However, there were no differences in head size between Ashy-throated Parrotbills and allopatric populations of Vinous-throated Parrotbills (Jiangxi and Hebei). Furthermore, the tendency of variation in bite force was opposite to that in head size with populations with larger head size having weaker bite force.ConclusionsWe showed that there are no differences in head size between the Ashy-throated Parrotbill and allopatric populations of Vinous-throated Parrotbill, which provides evidence for the hypothesis that differences in head size in the Guizhou populations of two sister species are probably the result of local adaptation rather than species-specific. Our study has implications for avian dispersal and adaption related to head size such as diet ecology and vocalizations.

An apparently non-swinging tentorium in the Diplopoda (Myriapoda): comparative morphology of the tentorial complex in giant pill-millipedes (Sphaerotheriida).

The presence of a swinging tentorium is a key apomorphy of Myriapoda, but this character has been studied in detail in only few species. Here the tentorium, i.e., the peristomatic skeleton of the preoral chamber, is comparatively studied in three species of the millipede order Sphaerotheriida Brandt, 1833. Since dissections of the fragile tentorial components proved to be difficult, despite the large head size, they were analysed mainly in situ via micro-computed tomography. Our results confirm previous observations of large differences in the tentorial construction in the giant pill-millipedes compared to chilognathan diplopods. The tentorium of Sphaerotheriida consists of a curved, plate-like epipharyngeal bar with distal projections, an elongate and thin hypopharyngeal bar, and a plate-like triangular posterior process; a transverse bar is absent. Only seven muscles attach at the tentorium in giant pill-millipedes, including two antennal muscles and two muscles of the gnathochilarium. Within the order Sphaerotheriida, the composition of the tentorium and its muscular equipment seems to be conserved, except for some variability in the shape of the epipharyngeal bar. As the transverse bar has been considered essential for the mobility of the tentorium in myriapods, its absence in Sphaerotheriida may indicate that their tentorium is not capable of performing a swing. Loss of tentorial mobility may also pertain to the order Glomerida Brandt, 1833, inferred here from the absence of a posterior process. An apparently immobile tentorium in Glomerida and Sphaerotheriida can straightforwardly be correlated with transformations of the head related to their ability of volvation. The different transformations of the tentorium, here hypothesised to cause immobility, may support current assumptions that the ability of volvation evolved convergently in Glomerida and Sphaerotheriida. This conclusion, however, still requires more detailed studies of the head anatomy in Glomerida and Glomeridesmida Cook, 1895.

A rescue method for a large femoral trial head trapped into the cup during direct anterior total hip arthroplasty without using a fracture table

Minimal invasive direct anterior approach (DAA) is an established procedure for total hip arthroplasty (THA). THA via DAA with a larger head size has been reported to reduce the risk of postoperative dislocation. Additionally, variations of the technique exist among different surgeons. Many surgeons prefer a standard surgical table to a fracture table because a standard surgical table less interfere the use of fluoroscopy and facilitates measuring leg length. Here, we presented a rare complication during THA via DAA with a 36 mm large head using a standard surgical table. A 59-y-old woman was diagnosed of bilateral dysplastic hip. The first (right) THA via DAA was done smoothly but a significant postoperative leg length discrepancy (LLD) was noted. To precisely evaluate the LLD in the second (left) THA via DAA, we used a standard surgical table. Intraoperatively, during the last trial reduction, the 36 mm trial head was trapped into the cup and could not be re-dislocated. In the meantime, the surgical table is not helpful for anterior traction to dislocate the head. Then, we decided to chisel the trial head and perform a controlled cracking on the calcar using an osteotome for further sub-siding the stem. Finally, the THA was completed smoothly and the patient did not complain a subjective LLD anymore. We suggest that surgeons should be aware of the slightly different length between the trial stem and the real stem, and should be careful about the selection of head size and type of surgical table in THA via DAA.