Postotic laterosensory canal and pterotic branch homology in catfishes

Morphology of the postotic laterosensory canal was surveyed across loricarioid and outgroup catfishes in order to resolve conflicting statements regarding homology and phylogenetic significance of intrinsic character variation. A pterotic branch is widespread among catfishes and has been identified as a synapomorphy for siluriforms, but its presence in loricarioid catfishes has been disputed. In contrast to previous statements that absence of a pterotic branch is synapomorphic for loricarioids, we confirm the presence of a pterotic branch in Nematogenys inermis and other trichomycterids, callichthyids, and loricariids. The pterotic branch is secondarily absent in scoloplacids and astroblepids. We present criteria for establishing homology of the pterotic branch and review character state optimization schemes on the currently accepted phylogeny. The postotic region of loricariids is further specialized in having an expanded swimbladder capsule that incorporates the trunk lateral line canal and has a lateral opening covered by a greatly expanded pterotic complex. The trunk lateral line enters the swimbladder capsule mesial to the pterotic lateral wall and passes anteromedially as a fleshy tube before forming the postotic canal in the pterotic, a morphology reported previously for a single loricariid representative. Variation in the relative extent and topographic position of postotic canal branches and other morphologies is diagnostic of certain loricariid taxa, suggesting a rich character complex of potential utility in phylogeny reconstruction.     

Homology and evolution of the opercular series in the loricarioid catfishes (Pisces: Siluroidei)

Aspects of the morphology of the opercular region of siluroids (catfishes) were examined to determine the homologies of the opercular bones of loricarioid catfishes, a diverse monophyletic neotropical group. Homology of the component structures was inferred by examination of three criteria: (1) functional relations to the jaw abduction mechanism of primitive halecostome fishes; (2) positional relations to the bones of the suspensorium and the path of the preopercular laterosensory canal; and (3) pattern of development of the preopercular canal and lateral cheek plates of loricarioid catfishes. The majority of siluroids have lost one or more of the preopercular canal exit branches to the skin surface present in most primitive siluroids. A number of specializations of the canal pathway and components of the opercular series have occurred in loricariids. Trichomycterids have the preopercular canal reduced to a short branch from the pterotic. Callichthyids share the presence of a preopercular canal with primitive siluroids, but have lost the communication of the canal between the preopercle and pterotic bones. Callichthyids and scoloplacids share one additional loss of a preopercle exit. The second of two subopercular elements of astroblepids is homologous with the interhyal. Astroblepids and loricariids have lost one additional preopercle exit, the interoperculo-mandibular ligament and the corresponding biomechanical couple for lower jaw abduction. Loricariids have probably lost the interopercle as well. These derived features of loricariids and astroblepids are viewed as specializations for a particular feeding behaviour: scraping algae and detritus from the substratum.     

Advanced squamous cell carcinoma involving both upper and lower lips and oral commissure with simultaneous reconstruction by local flap: a case report

Introduction

Squamous cell carcinoma is one of the most common malignant tumors of the skin and oral mucosa. However, squamous cell carcinoma involving near total upper and lower lip and oral commissure is rarely seen in the English literature. Simultaneous reconstruction of the upper and lower lips has been inconclusive and presents a challenge to the surgeon. We report such a case and outline our simultaneous reconstruction with local flaps. To the best of our knowledge this has never been reported.

Case presentation

A 73-year-old Thai woman presented with a large rapidly growing squamous cell carcinoma involving the upper lip, lower lip, left oral commissure and left cheek. En bloc resection of upper lip, lower lip, left oral commissure and buccal region was performed. Left radical neck dissection and right modified neck dissection were performed. Reconstruction of the upper lip with a left nasolabial-cheek cervicofacial rotational-advancement flap and right cheek advancement with perialar crescent flap was performed. The lower lip was reconstructed with bilateral labiomental advancement flaps.

Conclusions

Squamous cell carcinoma can grow rapidly and spread along the orbicularis oris muscle and across the oral commissure to the opposite lip. In advanced cancer, multimodal treatment is necessary. No gold standard in the reconstruction of both upper and lower lips has been established. We report the case of an advanced squamous cell carcinoma involving both the upper lip, lower lip, left oral commissure and buccal area and simultaneous reconstruction with local flap coverage that, to the best of our knowledge, has never been reported.     

Design, construction and modularity of pressure-fit acetabular cups]

To enable a comparison of different pressfit acetabular cups objective criteria are essential. The aim of this study is to describe the design features of this type of cup and to analyse currently available cups. 30 implants were systematically measured and analysed. The mean surface roughness (Ra) was determined and configurations established with the light section technique. For further evaluation the cups were transversely sectioned. The cups are made of pure titanium, titanium alloy or polyethylene coated with titanium. Five implants take the form of monoblocks. The configuration is predominately (n = 25) flattened spherical. The size of eight cups corresponds to the outer diameter, 19 cups have a larger outer diameter (overdimensioning), 3 cups have a smaller outer diameter (underdimensioning). The magnitude of overdimensioning is, on average, 1.9%. 9 cups are provided with plugs, hollow cylinders, fins or rings as outer stabilizers. Surface roughness achieved with corundum blasting is 6.8 microns. Titanium porous-coated implants have a surface roughness of 21-32 microns. 24 cups have polyethylene inserts, most of which are snap-fixed with equatorial lips. For 16 cups, full-ceramic inserts are available. 4 cups have a metal insert. Titanium implants with structured or HAC-coated surfaces have become the accepted standard for cementless acetabular cup implantation. Together with ceramic, metal, or modified polyethylene inserts they meet the requirement for permanent osteo-integrative stability.     

Suckermouth armored catfish resolve the paradox of simultaneous respiration and suction attachment: a kinematic study of Pterygoplichthys disjunctivus

Suckermouth armored catfishes (Loricariidae) use their suckermouth for inspiration, feeding, and attachment to substrates. The sucker consists of a pre-valvular cavity, formed by a modified lip disc, and is separated from the larger post-valvular buccal cavity by a muscular oral valve. The combination of respiration and suction attachment seems paradoxal, as a properly functioning suction device would need a sucker without leakage (yet inspiration must occur via the sucker), and continuous subambient pressure in the sucker cavity (even during expiratory mouth floor elevation). In the loricariid Pterygoplichthys disjunctivus, the anatomy of the suckermouth structures was examined, and a kinematic analysis was performed to acquire insights into how respiration and attachment are combined. High-speed external and X-ray recordings show that suckermouth attachment influences respiratory parameters such as decreasing excursion amplitudes of mouth floor elements, and the way water enters the mouth via furrows in the lip disc. Respiration, however, continues during attachment and is not blocked. Our data show that the muscular oral valve actively separates the post-valvular buccal cavity from the pre-valvular sucker cavity. Volume changes of this pre-valvular cavity are opposite to those of the post-valvular cavity and assure sucker function even during expiration. These volume changes are caused by movements of the lower lip, the lower jaws, and the oral valve. The lateral inflow furrow openings, controlled by the maxillary barbels, can occur unilaterally. Morphological and kinematic data also show that the opercle is anatomically and functionally decoupled from the gill opening.     

Transforming growth factor-beta3 promotes mesenchymal cell proliferation and angiogenesis mediated by the enhancement of cyclin D1, Flk-1, and CD31 gene expression during CL/Fr mouse lip fusion

BACKGROUND: Cleft lip with or without cleft palate is the most common congenital anomaly in the craniofacial region. Knowledge of the molecular mechanisms behind normal lip fusion can contribute to better intervention and improved functional clinical outcome. Transforming growth factor-beta3 (TGF-beta3) has been implicated in lip morphogenesis. Therefore, we hypothesized that TGF-beta3 functions during lip fusion through regulation of angiogenesis and mesenchymal cell cycle progression during early developmental stages. METHODS: To test this hypothesis we used the CL/Fraser mouse model, which has a high incidence of cleft lip. Lips isolated from embryonic day (ED) 11.5 mouse embryos were allowed to develop in serum-free organ cultures in the presence or absence of TGF-beta3. The lips that developed in these cultures fused in 2 days. RESULTS: During normal development, we detected positive immunoreactions for TGF-beta3 at the site of fusion. We also detected mesenchymal cells that were immunopositive for Flk-1 and CD31, which are markers for endothelial cell precursors. Exogenous TGF-beta3 accelerated lip fusion in culture. This enhancement was associated with an increase in the number of capillary blood vessels in the lips cultured in the presence of TGF-beta3, in comparison with controls. In tandem, TGF-beta3 increased the level of expression of both Flk-1 and CD31. Our data suggest that an elevated level of TGF-beta3 may promote angiogenesis in developing lips that is mediated by increased Flk-1 and CD31 expression. We also detected increased cyclin D1 expression (a marker for cell proliferation) in the presence of TGF-beta3, which suggests that TGF-beta3 promoted cell proliferation. CONCLUSIONS: TGF-beta3 promoted cell proliferation and angiogenesis in lip mesenchymal tissues. These events led to enhanced lip fusion in the presence of TGF-beta3.     

A comparative analysis of healing of surgical cleft lip corrected in utero and neonates.

We studied the healing process in surgically created cleft lips in fetal mice and compared it with that in newborn mice with cleft lips. Our purpose was to determine the time for optimal healing, defined as minimal scarring, for a repaired cleft lip. Full-thickness paramedian lip incisions were made in NMRI mice in utero, in 2- and 4-day-old neonates, and in adults (n = 10 in each experimental and control group). The healing process was studied by biochemical analysis of hyaluronic acid and hydroxyproline content in the repaired cleft tissue. We found that the production of hyaluronic acid remained stable during the healing period and was similar in all experimental groups. However, there was an unexplained but consistent depression in the hyaluronic acid content of fetal tissue 2 days after repair. Hydroxyproline was present in the fetal healing tissue, but in a low concentration, starting 4 days after surgical incision of the lip. The production of hydroxyproline in 2-day-old neonates was similar to that in the fetuses throughout the healing period (p less than 0.0005). However, the production of hydroxyproline increased in 4-day-old neonatal and adult tissues. In conclusion, we found an optimal healing period for mice with minimal collagen production in the late fetal stage, and this lasted 2 days after birth.     

Ontogeny of the catfish pectoral-fin spine (Teleostei: Siluriformes)

The characteristic and morphologically variable pectoral-fin spine of catfishes (order Siluriformes) has been well-investigated based on later developmental stages (juveniles and adults) but information on the earliest life stages are lacking. Here, we document the ontogeny of pectoral-fin spines in four siluroid (Ictalurus punctatus, Noturus gyrinus, Silurus glanis and Akysis vespa) and two loricarioid catfishes (Corydoras panda and Ancistrus sp.). To further our understanding of pectoral-fin spine development, we also examined adult and juvenile specimens representing 41 of the currently 43 recognized families of catfishes. Development of the pectoral-fin spine is similar in all catfishes and resembles the development of a typical soft fin ray. Fusion between hemitrichia of the anteriormost lepidotrichium occurs proximally first, forming the spine proper, with growth of the spine occurring through the subsequent fusion of developing distal hemitrichial segments that comprise the spurious ray. The variation of pectoral-fin spine morphology observed is largely attributed to the presence/absence of five traits, which either develop as part of the hemitrichial segments that are added to the distal tip of the spine during growth (distal rami, anterior/posterior serrae) or develop independent of these segments (denticuli and odontodes).     

TESTING HISTORICAL HYPOTHESES OF MORPHOLOGICAL CHANGE: BIOMECHANICAL DECOUPLING IN LORICARIOID CATFISHES

The “decoupling hypothesis” has been proposed as a mechanistic basis for the evolution of novel structure and function. Decoupling derives from the release of functional constraints via loss of linkages and/or repetition of individual elements as redundant design components, followed by specialization of one or more elements. Examples of apomorphic decoupling have been suggested for several groups of organisms, however there have been few empirical tests of explicit statements concerning functional and morphological consequences of decoupling. Using the loricarioid catfishes, we tested one particular consequence of decoupling, the prediction that clades possessing decoupled systems having increased biomechanical complexity will exhibit greater morphological variability of associated structures than outgroups having no such decoupled systems. Morphometric procedures based on interlandmark distances were used to quantify morphological variance at three levels of design at successive nodes in the loricarioid cladogram. Additional landmark-based procedures were used to localize major patterns of shape change between clades. We report significantly greater within-group morphometric variance at all three morphological levels in those lineages associated with decoupling events, confirming our predictions under the decoupling hypothesis. Two of 12 comparisons, however, yielded significant variance effects where none were predicted. Localization of the major patterns of shape change suggests that disassociation between morphological and functional evolution may contribute to the lack of fit between variance predictions and decoupling in these two comparisons.     

Ontogeny of the jaw and maxillary barbel musculature in the armoured catfish families Loricariidae and Callichthyidae (Loricarioidea,Siluriformes), with a discussion on muscle homologies

The neotropical loricarioid catfishes include six families, the most species‐rich of which are the Callichthyidae and the Loricariidae. Loricariidae (suckermouth armoured catfishes) have a highly specialized head morphology, including an exceptionally large number of muscles derived from the adductor mandibulae complex and the adductor arcus palatini. Terminology of these muscles varies among the literature, and no data exist on their ontogenetic origin. A detailed examination of the ontogeny of both a callichthyid and a loricariid representative now reveals the identity of the jaw and maxillary barbel musculature, and supports new hypotheses concerning homologies. The adductor mandibulae muscle itself is homologous to the A1‐OST and A3′ of basal catfishes, and the A3′ has given rise to the newly evolved loricariid retractor veli as well. The A2 and A3″ have resulted in the retractor tentaculi of Callichthyidae and the retractor premaxillae of Loricariidae. Thus, these two muscles are shown to be homologous. In Loricariidae, the extensor tentaculi consists of two separate muscles inserting on the autopalatine, and evidence is given on the evolutionary origin of the loricariid levator tentaculi (previously and erroneously known as retractor tentaculi) from the extensor tentaculi, and not the adductor mandibulae complex. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 155 , 76–96.     

Epithelium of lips and associated structures of the Indian major carp,Catla catla

Structural organization of the epithelium of the lips and associated structures of the Indian major carp,Catla catla, is described. The upper lip is thin and is associated on its dorsal side with a membranous fold of skin and the rostral cap. In contrast, the lower lip is thick and very conspicuous. It is associated on its ventral side with a fold of skin between it and the ventral head skin. The lower lip is divided into a non-projectile portion, a projectile portion and an intermediate groove region. The projectile portion remains folded covering a part of the ventral head skin when the mouth is closed. Their role in relation to the formation of the characteristic feeding tube is discussed. The epithelium of the lips and associated structures is stratified in nature and is composed of the epithelial cells, mucous cells, club cells, lymphocytes and the taste buds. The mucous cells are small, few or even absent and do not appear to secrete profusely at the surfaces of the upper and the lower lips. This suggests that the lips inCatla catla, which feeds on micro-organisms, do not need extra lubrication for protection against abrasion during feeding. In the epithelium at the folds of skin, the voluminous mucous cells secrete profusely and provide extra lubrication to their surface. This reduces the resistance to surface drag during stretching and enables the jaws to protrude with increasing efficiency and swiftness. The club cells are developed additionally to complement the mucous cells in the rostral cap and the upper lip epithelium. Their primary function appears protective in some way, which needs further confirmation. The taste buds, though few in the lower lip, are located in a good number in the upper lip on the characteristic epithelial papillae-like projections, and are projected at the surface. These have been associated with the acute gustatory sense of the fish. The taste buds are absent on the folds of skin where they may not be of much significance.     

A mechanical bottleneck explains the variation in cup growth during FcγR phagocytosis

Phagocytosis is the process by which cells internalize particulate material, and is of central importance to immunity, homeostasis and development. Here, we study the internalization of immunoglobulin G‐coated particles in cells transfected with Fcγ receptors (FcγRs) through the formation of an enveloping phagocytic cup. Using confocal microscopy, we precisely track the location of fluorescently tagged FcγRs during cup growth. Surprisingly, we found that phagocytic cups growing around identical spherical particles showed great variability even within a single cell and exhibited two eventual fates: a cup either stalled before forming a half‐cup or it proceeded until the particle was fully enveloped. We explain these observations in terms of a mechanical bottleneck using a simple mathematical model of the overall process of cup growth. The model predicts that reducing F‐actin concentration levels, and hence the deforming force, does not necessarily lead to stalled cups, a prediction we verify experimentally. Our analysis gives a coherent explanation for the importance of geometry in phagocytic uptake and provides a unifying framework for integrating the key processes, both biochemical and mechanical, occurring during cup growth.     

Primary reconstruction of complex midfacial defects with combined lip-switch procedures and free flaps.

Free flaps are generally the preferred method for reconstructing large defects of the midface, orbit, and maxilla that include the lip and oral commissure; commissuroplasty is traditionally performed at a second stage. Functional results of the oral sphincter using this reconstructive approach are, however, limited. This article presents a new approach to the reconstruction of massive defects of the lip and midface using a free flap in combination with a lip-switch flap. This was used in 10 patients. One-third to one-half of the upper lip was excised in seven patients, one-third of the lower lip was excised in one patient, and both the upper and lower lips were excised (one-third each) in two patients. All patients had maxillectomies, with or without mandibulectomies, in addition to full-thickness resections of the cheek. A switch flap from the opposite lip was used for reconstruction of the oral commissure and oral sphincter, and a rectus abdominis myocutaneous flap with two or three skin islands was used for reconstruction of the through-and-through defect in the midface. Free flap survival was 100 percent. All patients had good-to-excellent oral competence, and they were discharged without feeding tubes. A majority (80 percent) of the patients had an adequate oral stoma and could eat a soft diet. All patients have a satisfactory postoperative result. Immediate reconstruction of defects using a lip-switch procedure creates an oral sphincter that has excellent function, with good mobility and competence. This is a simple procedure that adds minimal operative time to the free-flap reconstruction and provides the patient with a functional stoma and acceptable appearance. The free flap can be used to reconstruct the soft tissue of the intraoral lining and external skin deficits, but it should not be used to reconstruct the lip.     

Divergent regulation of Wnt-mediated development of the dorsomedial and ventrolateral dermomyotomal lips

The dermomyotome is the dorsal compartment of the somite which gives rise to multiple cell fates including skeletal muscle, connective tissue, and endothelia. It consists of a pseudostratified, roughly rectangular epithelial sheet, the margins of which are called the dermomyotomal lips. The dermomyotomal lips are blastema-like epithelial growth zones, which continuously give rise to resident dermomyotomal cells and emigrating muscle precursor cells, which populate the subjacent myotomal compartment. Wnt signaling has been shown to regulate both dermomyotome formation and maintenance of the dermomyotomal lips. Whereas the epithelialization of the dermomyotome is regulated via canonical, β-catenin-dependent Wnt signaling, the downstream signaling mechanisms suppressing epithelial-mesenchymal transition (EMT) in the mature dermomyotomal lips have been unknown. Here, we present evidence that dermomyotomal lip sustainment is differentially regulated. Whereas the dorsomedial dermomyotomal lip is maintained by canonical Wnt signaling, development of the ventrolateral dermomyotomal lip is regulated by non-canonical, PCP-like Wnt signaling. We discuss our results in the light of the different developmental prerequisites in the dorsomedial and ventrolateral lips, respectively, thus providing a new perspective on the regulation of dermomyotomal EMT.     

A long-term, controlled-outcome analysis of in utero versus neonatal cleft lip repair using an ovine model.

Successful open repair of a cleft lip in utero has the advantage of scarless wound healing in the fetus. Unfortunately, no long-term outcome studies have been performed to evaluate the efficacy of these repairs. Moreover, no study to date has compared the long-term results of an in utero cleft lip repair to a similar, control-matched, newborn cleft repair. This study was performed to evaluate the 9-month outcome of in utero cleft lip surgery compared with an identical cleft lip repair performed on infant lambs. In utero epithelialized cleft lips were created through an open hysterotomy in sixteen 65-day-old fetal lambs (term = 140 days) using methods described by Longaker et al. Eight of 16 animals underwent subsequent in utero repair of these clefts at 90 days gestational age. The repair of the remaining eight animals was delayed until 1 week postpartum. At 9 months, the animals were analyzed for changes in lip contour and for the degree of scarring by hematoxylin and eosin and Masson's trichrome collagen staining. Two animals in each group died from preterm labor. Of the animals that survived to term, all repaired lips had some degree of abnormality postoperatively. One of six lips repaired in utero dehisced before delivery. Three of six neonatal repairs dehisced in the first postoperative month. In the remaining animals with intact lip repairs, the vertical lip height on the repaired side was an average of 9 to 12 mm shorter than the normal lip in both the in utero and neonatally repaired animals. Phenotypically, the postnatally repaired animals had more lip distortion and visible notching. Histologically, the in utero repair was scarless and the neonatal repairs had scar throughout the entire vertical height of the lip with an associated loss of hair in this region. Maxillary growth was also evaluated. There was no inhibition of maxillary growth in the animals that underwent in utero cleft lip repair. However, in the neonatal repair group, significant maxillary retrusion was evident. Compared with the cleft side of the maxilla, horizontal growth was decreased by 11 percent (p = 0.01). Compared with the intrauterine repair group, there was a 17-percent decrease in horizontal maxillary width (p = 0.01). Straight-line in utero repair of a cleft lip produces a better long-term result in terms of maxillary growth than a similar repair performed postnatally in the ovine model. There was no diminution in maxillary growth in the animals treated in utero. Histologically, in utero repair of clefts was indeed scarless. However, both lip repairs produced lips that were significantly shorter than their contralateral noncleft sides. This degree of lip shortening would require a secondary lip revision, thereby defeating the purpose of performing an intrauterine repair. Comparisons now need to be made between in utero and neonatal repairs using a Millard-type rotation advancement technique before intrauterine treatment can be considered to be more beneficial than our current treatment modalities.     

喀斯特山区粗裂地钱风兜亚种冬季芽胞杯的形态多样性特征及芽胞传播观察

芽胞杯是地钱属特有的无性繁殖器官,关于其冬季形态特征及繁殖传播的行为研究较少。现以贵州喀斯特山区常见的粗裂地钱风兜亚种（Marchantia paleacea subsp.diptera）为代表,在最冷的冬季1月份,对其芽胞杯、杯内芽胞产量及传播方式进行野外定点观察和采样分析。结果显示：（1）冬季芽胞杯形态多样。根据其颜色和杯内芽胞特点将其划分为4个生长时期：未成熟期（透明）、成熟期（绿色）、衰退期（紫色）和衰亡期（紫黑色）,反映了冬季芽胞杯生长发育的不同阶段。（2）各生长时期的芽胞杯数量不同,表现出有序的凋亡特征。在统计的708个芽胞杯中,4个时期芽胞杯数量分别为62、209、254和183个,且不同时期的芽胞杯内芽胞的平均产量明显不同,不同时期单杯芽胞的平均产量分别为42、131、87和0 个;（3）冬季芽胞杯及芽胞在配子体上的密度较高,每平方米分别达到10 139和754 889个;（4）除春夏季常见的被雨滴敲打传播外,通过重力作用传播是冬季芽胞的一种重要传播方式。冬季粗裂地钱风兜亚种配子体上的芽胞杯处在不同的生长时期,形成的芽胞仍十分丰富,这对该物种适应喀斯特山区最冷月严苛环境条件具有积极的意义。     

In situ sampling of small volumes of soil solution using modified micro-suction cups

Two modified designs of micro-pore-water samplers were tested for their capacity to collect unbiased soil solution samples containing zinc and citrate. The samplers had either ceramic or polyethersulfone (PES) suction cups. Laboratory tests of the micro-samplers were conducted using (a) standard solutions with zinc and citrate concentrations that can be found in the rhizosphere and (b) two soils with contrasting texture. The results showed that both suction cups were inert with respect to citrate and zinc: they did not affect the concentrations of the two ions in freshly prepared and directly sampled standard solutions. Both micro-suction cups removed most microorganisms by filtration, though the PES cups were more effective in this respect. This filtering by the suction cups allowed for relatively accurate analysis of citrate in solutions containing microorganisms. These capacities, together with their small size and small dead volume, make the two micro-pore-water samplers highly suitable for sampling of rhizosphere soil solutions although further testing with other organic acids and trace metals may be needed.     

An optical method for determining deformation and form changes in polyethylene surfaces of explanted acetabular cups of hip endoprostheses]

AIM: Most methods used for the determination of volumetric wear of polyethylene cups are based on the assumption that the head of the prosthesis penetrates the cup in "cylindrical" fashion. The new accurate optical method is independent of this disputable assumption. METHOD: The articulating surface of the cup is scanned with light and a data set of 60,000 pixels obtained in this way is stored in a computer. Data obtained from used cups were compared with those obtained from unused cups. The volumetric wear was calculated directly by threefold integration. To assess the changes in surface shape, the data are fitted by an ellipsoid whose long axis defines the mean direction of load. A total of 18 retrieved and 3 unused cups of different types were studied. RESULTS: The unused acetabular cups deviated only slightly from ideal hemispheres. The surfaces showed rotational symmetry, and an undulation having an amplitude of 0.1 mm between dome and equator. For all explanted cups, the assumption of cylindrical penetration of the head into the polyethylene was shown not to represent the true situation. The cup expands in all directions, and the volumetric wear is underestimated by 50% with the traditional methods. The data suggest that long-term survival may be jeopardized when the main direction of loading is centered on the dome of the cup. Ceramic heads were associated with smaller rates of volumetric wear. CONCLUSION: The new optical method is characterised by short measuring times, precision and simple application. Analysis of the wear patterns of polyethylene components using this technique may contribute to a further understanding of the complex mechanisms of aseptic loosening.     

Primary stability of cement-free press-fit acetabulum cups. In vitro displacement studies]

The initial stability of 6 different hemispherical press-fit titanium acetabular cups was investigated by lever-out tests using a foam model. Each cup was implanted in a standardised manner into machined PVC-foam blocks with an underreaming of 1/2/3 mm, and levered out 5 times. A computer recorded the load-displacement curves. Both insertion forces and lever-out forces increased with increasing press-fit from 1 to 2 mm. With underreaming of 2 mm, insertion forces varied between 9 and 34 Nm, and lever-out torques between 13 and 23 Nm. The cup made up of multi-layer irregular titanium wire mesh had the highest initial stability of all the cups tested. 3 mm underreaming was associated with insertion difficulties, so that lever-out is difficult to compare with that with 1 and 2 mm. The amount of contact on the equatorial rim, where we saw the most attrition after lever-out, is the most important factor for determining the lever-out torque. The quality of the PVC foam blocks, the accuracy of reaming, and the definition of cup insertion are very important parameters for test reproduction. Since the trials were conducted under laboratory conditions, translation of the results to the intraoperative situation should be undertaken only with certain reservations.