The role of retraction in direct nerve injury in total hip replacement: an anatomical study.

OBJECTIVES: Acetabular retractors have been implicated in damage to the femoral and obturator nerves during total hip replacement. The aim of this study was to determine the anatomical relationship between retractor placement and these nerves. METHODS: A posterior approach to the hip was carried out in six fresh cadaveric half pelves. Large Hohmann acetabular retractors were placed anteriorly, over the acetabular lip, and inferiorly, and their relationship to the femoral and obturator nerves was examined. RESULTS: If contact with bone was not maintained during retractor placement, the tip of the anterior retractor had the potential to compress the femoral nerve by passing superficial to the iliopsoas. If pressure was removed from the anterior retractor, the tip pivoted on the anterior acetabular lip, and passed superficial to the iliopsoas, overlying and compressing the femoral nerve, when pressure was reapplied. The inferior retractor pierced the obturator membrane in all specimens medial to the obturator nerve, with subsequent retraction causing the tip to move laterally, making contact with the nerve. CONCLUSION: Iliopsoas can only offer protection to the femoral nerve if the retractor passes deep to the muscle bulk. The anterior retractor should be reinserted if pressure is removed intra-operatively. Vigorous movement of the inferior retractor should be avoided. Cite this article: Bone Joint Res 2014;3:212-6.

An anatomic study of local infiltration analgesia in total knee arthroplasty.

BACKGROUND: Local infiltration analgesia (LIA) is a relatively novel technique developed for effective pain control following total knee arthroplasty (TKA), reducing requirements for epidural or parenteral postoperative analgesia. This study investigated the anatomical spread of an LIA used in TKA to identify the nerve structures reached by the injected fluid. METHODS: Six fresh-frozen cadaveric lower limbs were injected according to a standardised LIA technique with a solution of latex and India ink to enable visualisation. Wounds were closed and limbs placed flat in a freezer at -20°C for two weeks. Limbs were then either sliced or dissected to identify solution locations. RESULTS: Solution was found from the proximal thigh to the middle of the lower leg. The main areas of concentration were the popliteal fossa, the anterior aspect of the femur and the subcutaneous tissue of the anterior aspect of the knee. There was less solution in the lower popliteal fossa. The solution was found to reach the majority of nerves, with good infiltration of nerves supplying the knee. CONCLUSIONS: These results support the positive clinical outcomes with this LIA technique. However, the lack of infiltration into the lower popliteal fossa suggests more fluid or a different injection point could be used. The solution reaching the extensor muscles of the lower leg is likely to have no beneficial analgesic effect for a TKA patient. The LIA technique is already used in clinical practice following total knee arthroplasty. Results from this study show there may be scope to optimise the injection sites in LIA technique.

Computer-assisted measurements of coronal knee joint laxity in vitro are related to low-stress behavior rather than structural properties of the collateral ligaments.

The relationship between coronal knee laxity and the restraining properties of the collateral ligaments remains unknown. This study investigated correlations between the structural properties of the collateral ligaments and stress angles used in computer-assisted total knee arthroplasty (TKA), measured with an optically based navigation system. Ten fresh-frozen cadaveric knees (mean age: 81 ± 11 years) were dissected to leave the menisci, cruciate ligaments, posterior joint capsule and collateral ligaments. The resected femur and tibia were rigidly secured within a test system which permitted kinematic registration of the knee using a commercially available image-free navigation system. Frontal plane knee alignment and varus-valgus stress angles were acquired. The force applied during varus-valgus testing was quantified. Medial and lateral bone-collateral ligament-bone specimens were then prepared, mounted within a uni-axial materials testing machine, and extended to failure. Force and displacement data were used to calculate the principal structural properties of the ligaments. The mean varus laxity was 4 ± 1° and the mean valgus laxity was 4 ± 2°. The corresponding mean manual force applied was 10 ± 3 N and 11 ± 4 N, respectively. While measures of knee laxity were independent of the ultimate tensile strength and stiffness of the collateral ligaments, there was a significant correlation between the force applied during stress testing and the instantaneous stiffness of the medial (r = 0.91, p = 0.001) and lateral (r = 0.68, p = 0.04) collateral ligaments. These findings suggest that clinicians may perceive a rate of change of ligament stiffness as the end-point during assessment of collateral knee laxity.

Profile of the distal femur anterior cortex--a computer-assisted cadaveric study.

INTRODUCTION: Accurate positioning and sizing of the femoral component in total knee arthroplasty is important for stability and functional outcome. The purpose of the study was to evaluate the bony profiles of the distal anterior femoral cortex (AFC). MATERIALS AND METHODS: Anatomical bony landmarks on 50 adult cadaveric femora were collected. Critical points were used to identify the distal AFC surface. RESULTS: There were four anterior cortex profiles: (1) lateral side highest and medial side lowest (56%); (2) lowest height in median area (26%); (3) highest height in median area (14%); (4) medial side highest and lateral side lowest (4%). DISCUSSION: Anterior referencing in TKA needs to represent the anterior shape of the distal femoral cortex to prevent notching, femoro-patellar overstuffing or flexion gap mismanagement. Due to the variability of the AFC, surgeons have to carefully select the AFC landmark to be sure of avoiding complications.

'Time critical' rapid amputation using fire service hydraulic cutting equipment.

INTRODUCTION: Entrapped trauma victims require extrication, which, on rare occasions, may involve amputation of a limb. Standard extrication techniques sometimes fail or may be impossible, leading to the death of the entrapped victim. We propose that the use of fire service hydraulic cutting equipment can be used effectively to urgently amputate a limb, where conventional techniques are unusable. METHOD: The study aims to determine: (i) the potential use of this equipment to achieve expeditious life-saving amputations and (ii) the effect the fire service hydraulic cutting equipment has on the bony and surrounding soft tissues. Initially a porcine limb was used followed by fresh-frozen cadaveric lower limbs. We recorded the time, number of cuts, proximal fracture propagation and quality of bone cut when performing amputations at five levels. RESULTS: The experiment confirms that faster guillotine amputations in human cadaveric lower limb specimens can be achieved by using fire service hydraulic cutting equipment. Overall, the average time to complete an amputation in these ideal experimental circumstances at all five levels was quicker using the hydraulic cutting equipment. Either one or two cutting actions were required to achieve the amputation using fire service hydraulic cutting equipment. The degree and proximal extent of the comminution were greater using the fire service hydraulic cutting equipment. CONCLUSION: If circumstances and time constrains allow, a conventional amputation technique carried out by a trained medical practitioner would be preferable to the use of the fire service hydraulic cutting equipment. However, we feel that this technique could be used to perform emergent amputation under trained medical supervision, if it is felt that a standard amputation technique would take too long or the environment is too restrictive to perform a standard amputation safely.

Does the cranial suspensory ligament have a role in cryptorchidism?

The cranial suspensory ligament (CSL) is a fibromuscular structure anchoring the embryonic gonad to the posterior abdominal wall in male and female mammals. Its persistence in females is believed to be responsible for retaining the ovaries within the abdomen, while its regression in males permits testis descent. Embryonic loss of the CSL in males is believed to be an androgen-dependent event, and failure of this process has been proposed as a cause of cryptorchidism. The present study demonstrates that the nuclei of mesenchymal cells in the caudal part of the CSL are immunoreactively positive for androgen receptor. We examined the effects of exposure of the non-steroidal antiandrogen flutamide during the period from gestational day 10 to birth on the development of the CSL and on testis descent. Exposure of male Albino Swiss rats to the antiandrogen flutamide during this period resulted in feminization of the external genitalia and the suppression of growth of the testes and male reproductive tracts. In adulthood, testes were found to be located in diverse positions including normal scrotal (50%), intra-abdominal (10%) and ectopic suprainguinal (40%). The CSL of the testis persisted into adulthood in all flutamide-treated males, regardless of testis location. In all cases, the ligament consisted of bundles of smooth muscle fibres in the retroperitoneal fat of the posterior abdominal wall. These findings suggest that androgen blockade during embryonic development interferes with testicular descent, but that maldescent cannot be correlated with either the persistence of the CSL of the testis or its structure.

Anatomy of the motor nerve to the gracilis muscle and its implications in a one-stage microneurovascular gracilis transfer for facial reanimation.

BACKGROUND: The present study was conducted to investigate the anatomy of the motor nerve to the gracilis muscle (MNG) to provide the anatomical basis for harvesting a one-stage gracilis transfer with a long nerve for re-animation of the paralysed face. METHODS: An anatomical study was performed on 24 lower-limb specimens (from the pelvis down to the knee) from 12 embalmed cadavers. The MNG was dissected from the surface of the muscle to the obturator foramen. Two anatomical regions were defined in the course of the nerve. The first region includes the part of the nerve that can easily be reached through a standard incision in the medial aspect of the thigh, that is, from the surface of the muscle to the posterior border of the adductor brevis muscle and the second region from there to the obturator foramen. Measurements of both anatomical regions and the maximum length of the nerve were taken with a calliper. The anatomical relations of the nerve were also noted and photo-documented. RESULTS: The median maximum length of the MNG from the surface of gracilis to the posterior border of adductor brevis ('first anatomical region') was 7.7 cm (Range 6.3-10.5 cm); from there to the obturator foramen ('second anatomical region') the length was 3.7 cm (Range 2-6 cm), giving a median length of dissection of the nerve as 11.5 cm (Range 9.9-13.6 cm). Intraneural dissection of the MNG has to be performed proximally in the course of the nerve (the part corresponding to the second anatomical region), just where it runs inside the fascia over the obturator externus muscle. CONCLUSIONS: Over 10-cm length of the MNG can be obtained when dissected along the course of the nerve up to the obturator foramen. To achieve the maximum length, intraneural dissection must normally be performed after the nerve passes the posterior border of the adductor brevis. An endoscopic approach or extended proximal incision is recommended to easily reach the proximal part of the nerve as far as the obturator foramen.

Altered sirtuin expression is associated with node-positive breast cancer.

Sirtuins are genes implicated in cellular and organismal ageing. Consequently, they are speculated to be involved in diseases of ageing including cancer. Various cancers with widely differing prognosis have been shown to have differing and characteristic expression of these genes; however, the relationship between sirtuin expression and cancer progression is unclear. In order to correlate cancer progression and sirtuin expression, we have assessed sirtuin expression as a function of primary cell ageing and compared sirtuin expression in normal, 'nonmalignant' breast biopsies to breast cancer biopsies using real-time polymerase chain reaction (PCR). Levels of SIRT7 expression were significantly increased in breast cancer (P<0.0001). Increased levels of SIRT3 and SIRT7 transcription were also associated with node-positive breast cancer (P<0.05 and P<0.0001, respectively). This study has demonstrated differential sirtuin expression between nonmalignant and malignant breast tissue, with consequent diagnostic and therapeutic implications.

Deficits in the mid-brain raphe nuclei and striatum of the AS/AGU rat, a protein kinase C-gamma mutant.

The AS/AGU rat carries a recessive mutation (agu) in the gene coding for the gamma isoform of protein kinase C. The rat is characterized by disordered locomotion and progressive dysfunction of the nigrostriatal dopaminergic (DA) system. This dysfunction begins with a failure to release DA within the striatum and culminates in cell loss within the substantia nigra pars compacta. The present study examines another midbrain aminergic system with input to the basal ganglia, the serotonergic (5-HT) raphe-striatal system originating in the dorsal raphe nucleus. By 3 months after birth, there is a very substantial reduction in the extracellular levels of 5-HT in the dorsal caudate-putamen of the mutants compared with controls (c. 70%). This is accompanied by a proportional increase in the levels of the 5-HT metabolite 5-hydroxyindole acetic acid (5-HIAA). At a later age, there are reductions in whole tissue 5-HT (and increases in 5-HIAA) in both the striatum and the region containing the dorsal raphe nucleus, as well as numbers of 5-HT-immunoreactive cells in the dorsal raphe nucleus. The median raphe appears to be unaffected. The results are seen in terms of an initial dysfunction in transmitter release leading to cell death, perhaps through the formation of free radicals or neurotoxins.

Postnatal development of the reproductive system in the grey short-tailed opossum, Monodelphis domestica.

Postnatal phenotypic sex differentiation has been investigated in a laboratory marsupial, Monodelphis domestica, as part of a larger study to resolve apparent discrepancies between eutherian and marsupial mammals. These include the formation of sex-specific structures in marsupials prior to gonadal differentiation and the retention in both sexes of structures which are sex-specific in eutherians. The time-course and nature of differentiation was investigated in 131 specimens ranging in age from the day of birth to 56 days. Patent wolffian ducts extend to the urogenital sinus in both sexes at birth, while müllerian ducts are identified on day 1 and grow in a cranio-caudal direction to reach the urogenital sinus on day 6. The male müllerian duct shows signs of regression at its cranial end on day 10 and throughout its length on day 12; its lumen has completely disappeared by day 15. By this time the epididymis and vas deferens have developed from the wolffian duct; their histological differentiation occurs between days 26 and 56. Prostatic buds are identifiable in tissue surrounding the male urethra on day 14. In the female, the wolffian duct is larger than the müllerian duct until day 14; thereafter the wolffian duct begins to regress at its cranial end, disappearing by day 17, whereas the müllerian duct begins to enlarge, converging with its fellow at the urogenital sinus by day 19. Lateral vaginae, vaginal culs-de-sac, uteri and oviducts have differentiated from the müllerian ducts by day 25. Gonads of both sexes are elongated in shape at birth, attached along the medial aspect of the large mesonephroi in the abdominal cavity. However, from day 3 onwards the testis becomes more rounded than the ovary. Degeneration of the male mesonephros begins about day 10 and is almost completed by day 19; the female mesonephros is still relatively large at day 14 though it too has almost disappeared by day 19. By postnatal day 13 the abdominal phase of testis descent is underway and the inguinal phase begins at day 15. Testes have reached the scrotal sac by day 24 and achieve their final position at the base of the scrotum by day 28. In summary, postnatal reproductive tract development and gonadal descent has been examined in this important biomedical model, where differentiation of the wolffian and müllerian ducts takes place after gonadal differentiation, according to the normal eutherian pattern.

The role of androgens in development of the scrotum of the grey short-tailed Brazilian opossum ( Monodelphis domestica).

In eutherian mammals, sex differentiation is initiated by expression of the testis-determining gene on the Y chromosome. Subsequent phenotypic development of the reproductive tract and genitalia depends on the production of hormones by the differentiated testis. In marsupials the mechanisms of phenotypic development may vary from this pattern, as differentiation of the scrotal primordia has been shown to occur before that of the gonad. Thus, the development of the scrotum in the marsupial has been regarded as an androgen-independent process. We have sought to clarify the ontogeny of scrotal development and the appearance of androgen receptor immunoreactivity by examining Monodelphis domesticaembryos/pups from 1 day prior to birth until 2 days after birth. We have also used immunocytochemistry to determine the expression of the key steroidogenic enzyme 3beta-hydroxysteroid dehydrogenase as an indicator of when the developing gonad may be capable of synthesizing androgens. Expression of this enzyme was first detected in the gonads and adrenals of both sexes 1 day prior to birth and before the appearance of scrotal bulges. Androgen receptor immunoreactivity was detected in the scrotal anlagen of male opossum pups as early as 1 day following birth. This finding is significantly earlier than previous reports and coincides with the appearance 1 day after birth of distinct scrotal bulges. Androgen receptor immunoreactivity was also observed in the genital tubercles of male pups, but not female pups, 2 days after birth. These results suggest that androgens may play an important role in the development of the male genitalia at a much earlier stage than that indicated by previously published work and that scrotal development in this species may not be androgen-independent.

Pharmacological analysis of extracellular dopamine and metabolites in the striatum of conscious as/agu rats, mutants with locomotor disorder.

The as/agu rat is a spontaneously occurring mutation which exhibits locomotor abnormalities, reduced tyrosine hydroxylase levels in the substantia nigra and lower extracellular levels of dopamine. The animal could represent a model of some human locomotor disorders. High-potassium medium evoked a 460% rise of dopamine levels in control rats but double this in mutants. Amphetamine increased extracellular dopamine by 710% in controls and 1480% in mutants. Clorgyline produced a small increase of dopamine levels in controls but an 1170% increase in mutants. The uptake inhibitor nomifensine increased dopamine levels by 910% in controls but only 270% in mutants. After treatment with benserazide plus L-DOPA, an acute injection of L-DOPA evoked a release of dopamine which was twice as large in the as/agu rats compared with controls. The results show reduced extracellular dopamine in as/agu rats when the locomotor disorder is apparent, but there has been little loss of tyrosine hydroxylase. The responses to drugs are qualitatively different from those obtained using 6-hydroxydopamine.Overall, the effects of compounds affecting aminergic neurons suggest that one possible mechanism for the neuronal abnormality in as/agu rats is a defective regulation of dopamine release from striatal terminals.

The AS/AGU rat: a spontaneous model of disruption and degeneration in the nigrostriatal dopaminergic system.

The AS/AGU rat provides an alternative to experimentally produced laboratory models of basal ganglia disorders. This mutant is characterised by disturbances of movement including clumsy gait, whole body tremor, rigidity and difficulty in initiating movement. From an early age, there is a profound depletion of extracellular dopamine in the dorsal caudate-putamen as measured via in vivo microdialysis; levels are only 10-20% of those found in the parent Albino Swiss (AS) strain. Subsequently a depletion of whole tissue dopamine levels occurs and, later still, loss of dopaminergic cells in the substantia nigra pars compacta. The dysfunction in movement and the nigrostriatal dopaminergic system are clearly linked, since movement can be ameliorated by L-DOPA administration. Furthermore, there are depletions in glucose utilisation in several regions of the basal ganglia circuitry, including the substantia nigra pars compacta, the subthalamic nucleus and the ventrolateral thalamus. The AS/AGU rat represents a unique opportunity to investigate the intrinsic factors controlling the integrity of dopaminergic systems and the recent successful positional cloning of the agu gene will allow the molecular mechanisms underlying this interesting phenotype to be analysed.

Sex difference in target seeking behavior of developing cremaster muscles and the resulting first visible sign of somatic sexual differentiation in marsupial mammals.

Cremaster muscles are present in both male and female developing and adult marsupial mammals. They are complex structures and composed of several distinct bundles of striated muscle fibers provided with: (1) a distinct and extensive innervation; (2) a distinct blood vascular supply; (3) a distinct tendineous origin on the anterosuperior iliac spine; and (4) distinct target structures. The muscles thus seem to be separate anatomical entities and not a part of one or more of the layers of the ventral abdominal wall musculature. Cremaster muscles in males are elongated, are larger than in females, and for the most part are a component of the funiculus spermaticus. They insert on the distal part of the tunica vaginalis. The distal parts of the muscles in females are flattened ("fan shaped") and insert over a broad area on the dorsal borders of the mammary glands. Muscles in males have no relation whatsoever to the male mammary glandular rudiments. Muscles in females are attached at the base of the uterine round ligament. The remarkable sex difference in target structures of marsupial cremaster muscles becomes noticeable during perinatal life when outgrowing muscles take a different path in males and females. The initial appearance of this sexually dimorphic trait precedes the sexual differentiation of the genital ducts and external genitalia. In fetal males, the cremaster muscles grow in the direction of the site where scrotal bulges initially appear in the subcutaneous layers and later on the inguinal skin surface. They also take the gubernacular core of the ventral abdominal wall and the attached peritoneal epithelium with them during this outgrowth process. Consequently, this results in the development of a slitlike evagination of the abdominal lumen as the primary step to development of the processus vaginalis, while the testis and adjacent mesonephros and its duct are still attached to the posterior abdominal wall. In fetal females, the outgrowing cremaster muscles pass along the gubernacular core and, subsequently, this structure develops further as the tip (attached to the tubo-uterine junction) of the intra-abdominally protruding and further developing uterine round ligament. The female cremaster muscles grow further into caudal direction to shape a dorsal border of the developing mammary glands. The early onset of this sexually dimorphic outgrowth of cremaster muscles indicates that the "classical hormones" of sexual differentiation (anti-Müllerian hormone [AMH] and steroidal androgens) are not involved in this process. It could thus depend on primary genetic control with male development associated with the male-limited activity of genes on the Y-chromosomes and female development as the default process. Alternatively, the process in males could be under the control of an as yet unidentified third fetal testicular hormone involved in sexual differentiation processes which must then show an unexpectely early (i.e., perinatal) onset of its secretion.

Local cerebral glucose utilization in the AS/AGU rat: a mutant with movement disorders.

The AS/AGU mutant rat is characterized by a wide staggering gait and a movement disorder of the hindlimbs. Local cerebral glucose utilization in the brain was investigated using the [14C]2-deoxyglucose autoradiographic technique to map any functional alterations in the mutant AS/AGU (agu/agu) compared with Albino Swiss controls (+/+). Locomotor tests were also performed to confirm the phenotypic assignment of the animals. Statistically significant reductions in glucose utilization were apparent in 12 of the 44 regions examined in the AS/AGU animals. The regions showing the most significant differences (P < 0.01) from the control AS strain were the substantia nigra pars compacta (-23%) and medial geniculate body (-17%). Statistically significant decreases (P < 0.05 and P < 0.02) in glucose utilization ranging from -15 to -26% were also displayed in the superior colliculus superficial layer, auditory cortex, ventroposterior nucleus of the thalamus, molecular layer of the hippocampus, dentate gyrus, medial amygdaloid nucleus, median raphe nucleus, subthalamic nucleus, medial preoptic area of the hypothalamus and anterior hypothalamus. In no region studied was the mean value of glucose use in the AS/AGU rat greater than in the control animals. The results of this study complement previous behavioural and neurochemical characterization studies of this mutant, confirm that the disorder involves functional disturbances of the basal ganglia, and demonstrate the involvement of the limbic system and some sensory systems.

Extracellular levels of dopamine and its metabolite 3,4-dihydroxy-phenylacetic acid measured by microdialysis in the corpus striatum of conscious AS/AGU mutant rats.

The AS/AGU rat is a mutant derived from the Albino Swiss (AS) strain. It is characterized by an ungainly, staggering gait, hind limb rigidity, whole body tremor and, in older animals, difficulty in initiating movement. As and AS/AGU males aged three, six and nine months (n=6 per group) were used to estimate the levels of dopamine and its metabolites in the extracellular fluid of the caudate-putamen. The results indicate a profound loss of dopamine in the extracellular fluid at all age points examined, together with an increase in the concentration of the metabolite 3,4-dihydroxyphenylacetic acid. It is suggested that these changes reflect a defect of dopaminergic neuron function which may underlie the motor disorder seen in these animals.

Postnatal development of Leydig cells in the opossum (Monodelphis domestica): an immunocytochemical and endocrinological study.

This study involved characterization of Leydig cells of the opossum Monodelphis domestica, functionally by immunocytochemical identification of the enzyme 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) and by measurement of testosterone levels using RIA. Immunostaining for 3 beta-HSD was first detected in a few Leydig cells on Day 16, was increased by Day 24, reached a peak at 4 mo, and was present even in senescent (3 yr) animals. Plasma testosterone was first measurable (0.35 nM) at prepuberty (3.5 mo). Prior to that, plasma testosterone concentrations were uniformly below the level of detection (< 0.3 nM) in both sexes from Day 5 to 2.5 mo. By 4 mo (puberty), plasma testosterone levels in males had risen significantly to 1.53 +/- 0.35 nM, continuing to increase to 1.79 +/- 0.4 nM at 6 mo and peaking at 2.71 +/- 0.29 nM in the adult (1-2 yr). Ovarian testosterone concentrations were consistently lower than those in the testis, as were those of adrenals of both sexes. Thus the testis would appear to be the major source of androgen production throughout life in this species. Our immunocytochemical study suggests that in Monodelphis, puberty is reached at 4 mo, and this was further supported by a rise in circulating testosterone levels at this time.