Does lateral lift-off occur in static and dynamic activity in a medially spherical total knee arthroplasty? A pulsed-fluoroscopic investigation.

OBJECTIVES: The medially spherical GMK Sphere (Medacta International AG, Castel San Pietro, Switzerland) total knee arthroplasty (TKA) was previously shown to accommodate lateral rollback while pivoting around a stable medial compartment, aiming to replicate native knee kinematics in which some coronal laxity, especially laterally, is also present. We assess coronal plane kinematics of the GMK Sphere and explore the occurrence and pattern of articular separation during static and dynamic activities. METHODS: Using pulsed fluoroscopy and image matching, the coronal kinematics and articular surface separation of 16 well-functioning TKAs were studied during weight-bearing and non-weight-bearing, static, and dynamic activities. The closest distances between the modelled articular surfaces were examined with respect to knee position, and proportions of joint poses exhibiting separation were computed. RESULTS: Overall, 1717 joint poses were analyzed. At a 1.0 mm detection threshold, 37 instances of surface separation were observed in the lateral compartment and four medially (p < 0.001). Separation was activity-dependent, both laterally and medially (p < 0.001), occurring more commonly during static deep flexion in the lateral compartment, and during static rotation in the medial compartment. Lateral separation occurred more frequently than medial during kneeling (7/14 lateral vs 1/14 medial; p = 0.031) and stepping (20/1022 lateral vs 0/1022 medial; p < 0.001). Separation varied significantly between individuals during dynamic activities. CONCLUSION: No consistent association between closest distances of the articular surfaces and knee position was found during any activity. Lift-off was infrequent and depended on the activity performed and the individual knee. Lateral separation was consistent with the design rationale. Medial lift-off was rare and mostly in non-weight-bearing activities.Cite this article: S. Key, G. Scott, J.G. Stammers, M. A. R. Freeman†, V. Pinskerova, R. E. Field, J. Skinner, S. A. Banks. Does lateral lift-off occur in static and dynamic activity in a medially spherical total knee arthroplasty? A pulsed-fluoroscopic investigation. Bone Joint Res 2019;8:207-215. DOI: 10.1302/2046-3758.85.BJR-2018-0237.R1.

Delivering a quality-assured fracture liaison service in a UK teaching hospital-is it achievable?

UNLABELLED: To determine whether new national guidance on the specifications of a fracture liaison service are realistically deliverable, 1 year of data on the performance of such a service were audited. Audit targets were mostly met. This audit demonstrates that these standards are deliverable in a real world setting. INTRODUCTION: UK service specifications for a fracture liaison service (FLS) have been produced (National Osteoporosis Society, NOS) to promote effective commissioning and delivery of the highest quality care to patients with fragility fractures. How deliverable these standards are has not as yet been methodically reported. Our FLS was modelled on the ten NOS standards; performance was audited after 1 year to determine whether these standards could be delivered and to describe the lessons learnt. METHODS: Performance was audited against the NOS FLS Service Standards, with management based on the Fracture Risk Assessment Tool (FRAX®), the four-item Falls Risk Assessment Tool (FRAT), National Institute for Health and Care Excellence (NICE) and the National Osteoporosis Guideline Groups (NOGG) guidance. Data were recorded prospectively on a database. The FLS commenced in May 2014, was fully operational in August 2014 and data were captured from 1 September 2014 to 1 September 2015. RESULTS: The FLS detected 1773 patients and standards were largely achieved. Most, 94 %, patients were seen within 6 weeks, 533 DXA requests were generated, 804 outpatient FRAT assessments were recorded (134 required falls intervention) and 773 patients had bone treatments started. On follow-up at 3 months, between 78-79 % were still taking medication. CONCLUSIONS: Preliminary evaluation of a FLS implemented according to UK NOS standards demonstrates that the model is practical to apply to a large teaching hospital population. Collection and review of outcome and cost effectiveness data is required to determine the performance of this model in comparison with existing models.

Advanced wear of an Oxinium™ femoral head implant following polyethylene liner dislocation.

Oxinium™ (Smith & Nephew, Memphis, TN, US) has been used in hip arthroplasty since 2003. The surface coating is hard and provides low wear rates but if this surface coating is damaged, the soft metal core is at risk of accelerated wear. Previous reports have described accelerated wear following intra and postoperative hip dislocation. We report a case of advanced wear of an in situ Oxinium™ femoral head implant following a cracked acetabular liner. The liner had disengaged from the titanium shell, allowing the Oxinium™ head to articulate directly with the shell. The disengaged liner led to dislocation of the Oxinium™ head, with associated pronounced wear of the head and the acetabular cup. The patient had a successful revision procedure. We advise close follow-up of patients with Oxinium™ implants, especially if associated with dislocation and closed reduction.

The impact of trauma centre designation on open tibial fracture management.

INTRODUCTION: The British Orthopaedic Association/British Association of Plastic, Reconstructive and Aesthetic Surgeons guidelines for the management of open tibial fractures recommend early senior combined orthopaedic and plastic surgical input with appropriate facilities to manage a high caseload. The aim of this study was to assess whether becoming a major trauma centre has affected the management of patients with open tibial fractures. METHODS: Data were obtained prospectively on consecutive open tibial fractures during two eight-month periods: before and after becoming a trauma centre. RESULTS: Overall, 29 open tibial fractures were admitted after designation as a major trauma centre compared with 15 previously. Of the 29 patients, 21 came directly or as transfers from another accident and emergency deparment (previously 8 of 15). The time to transfer patients admitted initially to local orthopaedic departments has fallen from 205.7 hours to 37.4 hours (p=0.084). Tertiary transferred patients had a longer hospital stay (16.3 vs 14.9 days) and had more operations (3.7 vs 2.6, p=0.08) than direct admissions. As a trauma centre, there were improvements in time to definitive skeletal stabilisation (4.7 vs 2.2 days, p=0.06), skin coverage (8.3 vs 3.7 days, p=0.06), average number of operations (4.2 vs 2.3, p=0.002) and average length of hospital admission (26.6 vs 15.3 days, p=0.05). CONCLUSIONS: The volume and management of open tibial fractures, independent of fracture grade, has been directly affected by the introduction of a trauma centre enabling early combined senior orthopaedic and plastic surgical input. Our data strongly support the benefits of trauma centres and the continuing development of trauma networks in the management of open tibial fractures.

Delayed diagnosis of pseudoaneurysm formation in a patient with diaphyseal aclasis.

A 15 year old boy, with known diaphyseal aclasis, presented with a swollen left leg. The diagnosis of popliteal pseudoaneurysm, a known and well understood vascular complication, was delayed due to presentation suggestive of a chondrosarcoma. In this age group, sarcomatous change is more common and a potentially sinister complication of diaphyseal aclasis. Following a sarcoma MDT referral, the correct diagnosis was confirmed by ultrasound and CT angiogram. This case identifies one of the largest, non-ruptured popliteal pseudoaneurysms reported and illustrates an unusual complication of a rare orthopaedic genetic condition, which is potentially limb threatening.

The knee in full flexion: an anatomical study.

There has been only one limited report dating from 1941 using dissection which has described the tibiofemoral joint between 120 degrees and 160 degrees of flexion despite the relevance of this arc to total knee replacement. We now provide a full description having examined one living and eight cadaver knees using MRI, dissection and previously published cryosections in one knee. In the range of flexion from 120 degrees to 160 degrees the flexion facet centre of the medial femoral condyle moves back 5 mm and rises up on to the posterior horn of the medial meniscus. At 160 degrees the posterior horn is compressed in a synovial recess between the femoral cortex and the tibia. This limits flexion. The lateral femoral condyle also rolls back with the posterior horn of the lateral meniscus moving with the condyle. Both move down over the posterior tibia at 160 degrees of flexion. Neither the events between 120 degrees and 160 degrees nor the anatomy at 160 degrees could result from a continuation of the kinematics up to 120 degrees . Therefore hyperflexion is a separate arc. The anatomical and functional features of this arc suggest that it would be difficult to design an implant for total knee replacement giving physiological movement from 0 degrees to 160 degrees .

Fatty acid balance studies in preterm infants fed formula milk containing long-chain polyunsaturated fatty acids (LCP) II.

A milk formula (Prematil-LCP) containing long-chain polyunsaturated fatty acids (LCP) and with a fatty acid profile closely resembling breast milk has recently been introduced for preterm infants. A double-blind randomized controlled trial was performed comparing fatty acid absorption from Prematil-LCP (n=10) and standard Prematil (n=10). Formula-fed preterm infants underwent 3 d fat balances (once full enteral feeds were established) along with a parallel human milk fed group (n=11). Plasma samples were taken on the last day. Median total fat excretion (absorption, %) was 2.34g kg(-1) (82.0), 2.64g kg(-1) (82.9) and 1.65g kg(-1) (87.8) with Prematil, Prematil-LCP and human milk feeding, respectively. This reflected differences in the excretion and absorption of long-chain saturated fatty acids. All groups excreted detectable LCP. LCP disappearance was higher in infants fed human milk than in those fed Prematil-LCP, particularly for n-6 LCP (p < 0.01). Nevertheless, excreted LCP equated to < 30% dietary intake, with Prematil-LCP feeding. Plasma lipid fatty acid composition reflected differences in dietary LCP intake.

Fatty acid balance studies in term infants fed formula milk containing long-chain polyunsaturated fatty acids.

Long-chain polyunsaturated fatty acids (LCP) are thought to be required for optimal nervous system development in the newborn. A commercial milk formula containing LCP (Aptamil-LCP) with a fatty acid profile closely resembling breast milk, has recently been introduced for term infants. The absorption of fatty acids in term infants was examined in a double-blind randomized controlled trial comparing Aptamil-LCP (n = 20) and standard Aptamil (n = 20). Formula-fed newborn infants were studied from birth for 14 d. Fat balances (3 d) were performed from d 10. A 3-d stool collection was performed from d 10 in a parallel breastfed group (n = 21). Plasma samples were taken on d 6. Median fat excretion (mg kg[-1]) was 897.1, 615.0 and 355.2 with Aptamil, Aptamil-LCP and breastfeeding, respectively. The median total fat absorption coefficient in Aptamil-LCP-fed infants was higher than in those fed standard Aptamil (p < 0.01). These findings were accounted for by differences in the excretion and absorption of long-chain saturated fatty acids (C14:0, C16:0 and C18:0). Higher fat excretion was associated with bulkier and firmer stools. Only trace amounts of LCP were detected in the stools of all groups. This accounted for less than 4% of dietary intake in Aptamil-LCP-fed infants. No differences in the utilization of LCP from Aptamil-LCP and breast milk feeding were apparent. Plasma phospholipid fatty acid composition data reflected differences in dietary LCP intake. Thus, PL LCP levels were highest in the breastfed infants and lowest in the Aptamil-fed infants, with values for the Aptamil-LCP-fed group falling in between.

Fetal lipoproteins and placental release of esterified lipids.

An in vitro incubation technique was used to examine the release of lipids from the rabbit placenta. Free fatty acid, but not phospholipid or triacylglycerol, was released into the incubation media. In a second series of experiments, the addition of lipids to the umbilical circulation was studied in situ in the placenta of anaesthetized rabbits at late gestation. Each placenta was perfused from the fetal side in turn with two different perfusate solutions, either 4% bovine albumin solution or rabbit plasma. The rabbit plasma contained the appropriate carriers (lipoproteins) for esterified lipids, whereas the 4% albumin solution did not. The effluent perfusates were remarkably similar in free fatty acid concentration and composition, which closely matched the maternal free fatty acid profiles. The concentrations and fatty acid composition of the perfusate triacylglycerol and phospholipid fractions were unchanged by passage through the placenta, whether perfused with 4% albumin or with rabbit plasma. With this system, no evidence could be found for the addition of esterified lipids to the umbilical circulation in the rabbit despite the provision of appropriate carriers on the fetal side of the placenta.

Effect on placental transfer of exogenous lipid administered to the pregnant rabbit.

The transfer of lipids across the placenta was measured after infusion of an emulsion of triacylglycerol and phospholipid (intralipid) into 10 anesthetized rabbits. Maternal and umbilical venous and arterial samples were collected at 10-min intervals. All samples were analyzed for concentration and fatty acid composition of FFA, triacylglycerol, and phospholipid fractions. At the end of the infusion period of intralipid, there was a significant increase in the maternal concentrations of total triacylglycerol (p < 0.01) and of total phospholipid (p = 0.01) but not of total FFA (p > 0.05). Maternal plasma triacylglycerol and phospholipid altered in composition to match that of the infused Intralipid by the end of the infusion. Despite the significant rise in maternal triacylglycerol and phospholipid concentrations, the umbilical vein-artery difference for these lipid fractions remained unchanged and very low. In contrast, the umbilical vein-artery difference for FFA (p < 0.02) rose gradually throughout the experiments. There was no significant change in the fatty acid composition of the maternal FFA, but the fatty acid composition of the umbilical vein-artery difference for FFA changed to reflect the composition of Intralipid. These experiments show that exogenous triacylglycerol and phospholipid dramatically alter the lipid fractions presented to the placenta in the maternal plasma but do not cross the placenta intact. However, the composition of the FFA crossing the placenta is modulated to become more similar to that of the exogenous lipid.

Fetal and maternal plasma lipids in chronically catheterized mares in late gestation: effects of different nutritional states.

The effects of different nutritional states on plasma lipid concentrations have been examined in pregnant mares and their fetuses. Maternal and fetal arterial catheters were inserted into 12 pony mares between 244-303 days' gestation (term 320-360 days) and observations made from 5 days following the insertion of catheters. After recovery from surgery maternal and fetal arterial samples were withdrawn from 7 mares with normal feeding patterns (Group IA), from four of these mares at the end of a 30 h fast and 3 h later following refeeding (Group IB) and six mares who failed to re-establish normal feeding patterns (Group II). The fatty acid concentrations and composition of the plasma free fatty acid (FFA), triacylglycerol and phospholipid fractions were analysed. Maternal FFA, triacylglycerol and phospholipid concentrations were significantly raised in the fasted (Group IB) and under-fed (Group II) mares. Fetal concentrations of FFA and phospholipid increased significantly in the group of under-fed (Group II) mares but not in the fasted (Group IB) mares. In the fetal plasma the proportions of polyunsaturated fatty acids derived from essential fatty acids in the FFA and phospholipid fractions were much higher than those in the mare. In the fasted (IB) and under-fed (II) groups the relative amounts of the polyunsaturated fatty acids in each fraction remained unchanged (P > 0.05). These results show a short fast or prolonged undernutrition result in raised maternal plasma lipid concentrations which in turn can effect the total amount of lipid in the fetal circulation. However any increases in polyunsaturated fatty acids in the fetus (e.g. in Group II) are unlikely to come from the maternal circulation; likely sources of these fatty acids are the placenta or fetal tissues.

Release of lipid from the equine placenta during in vitro incubation.

An in vitro incubation technique was used to examine release of lipids from the equine placenta. Placental tissue was obtained at term (n = 5, term = 320-365 days) and earlier in gestation (n = 8, mean = 266 days). Term placentae were incubated at two temperatures, 4 degrees C (control) and 37 degrees C for 2 h. Pre-term placentae were incubated at 37 degrees C with two different concentrations of fatty acid in the medium. Tissues and media were analysed for their lipid concentrations. Term and pre-term placentae released free fatty acid (FFA) and phospholipid into the incubation medium during incubation at 37 degrees C. Long chain polyunsaturated fatty acids derived from the essential fatty acids were released into the media. The fatty acid profiles of the lipids released during incubation more closely resembled those of fetal plasma than maternal plasma lipids as measured in previous studies. These data are consistent with the view that the equine placenta is a source of both FFA and phospholipid for the fetus and that the placenta may provide long chain polyunsaturated fatty acids for the fetal foal.

Placental transfer of free fatty acids: importance of fetal albumin concentration and acid-base status.

Free fatty acids (FFA) are the main class of naturally occurring lipids transferred across the placenta, irrespective of species. In order to study the importance of fetal plasma albumin concentration and pH on placental transfer of FFA, in situ perfusion of the rabbit placenta in late gestation was used as an experimental model. Increasing albumin concentration on the fetal side of the placenta from 1 to 6% significantly increased transfer of FFA across the placenta. However, alteration of the umbilical perfusate pH in the range 7.0-7.5 had no significant effect.

Two different low birth weight formulae compared.

The performance of two different, commercially available, low birth weight formulae feeds was compared in preterm infants. The aim of the study was to determine the effect of compositional differences on tolerance, stool frequency and consistency, fat balance and weight gain. Inborn infants with birth weight less than 1500 g were randomised at birth to receive Prematil or Osterprem. Thirty infants received more than 900 ml/kg per week of designated formula alone during a total of 70 weeks of study. Three day fat balance was performed on 23 infants. Osterprem contains 40% more fat than Prematil. The composition of this fat is different in that Osterprem contains no medium chain triglycerides (MCT) compared to 30% in Prematil. Clinical evaluation demonstrated that Osterprem is associated with a significantly higher mean energy intake compared to Prematil (3442 and 3127 kJ/kg per week) but mean weight gain is not significantly different (123 and 112 g/kg per week). Mean stool frequency is higher on Osterprem (20.5 and 14.5 stool/week) and the consistency of stools firmer. This is attributable to a higher mean fat output (2.3 and 0.9 g/kg per day) secondary to the higher fat content of the feed and lower mean absorption (71.6 and 83.5%). Both feeds are well tolerated. The study also confirms that absorption of unsaturated fatty acids is inversely proportional to chain length.

New aerosol delivery system for neonatal ventilator circuits.

There is mounting evidence that a variety of drugs delivered as aerosols are likely to be of benefit in neonatal units. To avoid many of the problems associated with the use of jet nebulisers in ventilator circuits, a chamber was designed to be used in conjunction with a metered dose inhaler (MDI). The dimensions (4 cm x 11 cm) were chosen in an attempt to maximise drug delivery. In vitro studies were subsequently performed in order to determine the optimum operating conditions. Sodium cromoglycate delivered via this system was collected on a filter placed between the tip of an endotracheal tube and a model lung. The dose delivered was determined by means of an ultraviolet spectrophotometric assay. Using a Draeger Babylog 8000 ventilator it was found that drug delivery as maximised by actuating the device just before the inspiratory cycle when the chamber was placed adjacent to the endotracheal tube and by using a long (one second) inspiratory time. Under these conditions 1.5-2% of the original dose was deposited upon the filter at tidal volumes of 11-22 ml. When considered in terms of body weight this is many times the equivalent dose delivered to adults from an MDI. Effective drug delivery to the filter was confirmed using a radiolabelled aerosol. Radiolabelled studies delivering aerosol to the lungs of intubated rabbits demonstrated that deposition aerosol was distributed uniformly between lobes when corrected for the weight of each lobe. In conclusion, the device appears likely to deliver significant, reproducible quantities of drug to the lower respiratory tract while being simple to use.

Evaluation of techniques for delivery of steroids to lungs of neonates using a rabbit model.

Little is known about delivery of aerosolised steroids to neonatal patients undergoing assisted positive pressure ventilation and after extubation. A rabbit model has been established to investigate factors influencing drug delivery. Beclomethasone dipropionate, in a metered dose inhaler, was radiolabelled with technetium 99m. The mass median aerodynamic diameter of the aerosol was 3.3 (2.0) microns and the impactor measurements confirmed that the technetium distribution corresponded with that of the drug particles. The metered dose inhaler was actuated into a collapsible spacer that was used to ventilate and deliver aerosol to anaesthetised rabbits by a tracheostomy. From each actuation of the drug 2.9 (0.4)% of the aerosol deposited in the trachea and main bronchi and 1.2 (0.4)% in the lung. When the drug was delivered by a spacer device, with face-mask attachment, to rabbits breathing freely through a tracheostomy, aerosol deposition increased to 4.4 (2.1)% in the trachea and main bronchi and 1.9 (0.9)% in the lung lobes. The maximum change in systolic blood pressure after administration of aerosol by the collapsible spacer was a decrease of 13%. The methods described may prove useful for the delivery of inhaled steroids to neonatal patients likely to develop bronchopulmonary dysplasia.

Effects of altering umbilical flow and umbilical free fatty acid concentration on transfer of free fatty acids across the rabbit placenta.

The transfer of free fatty acids across the placenta perfused in situ was studied in anaesthetized rabbits in late gestation. In the first series of experiments, umbilical flow rate was varied between 0.6 and 4.0 ml/min in nine rabbits. Although increasing umbilical flow rate significantly decreased the free fatty acid concentration in the umbilical venous effluent (P = 0.0001), placental clearance of free fatty acids from the maternal circulation was not significantly changed by alterations in umbilical flow rate. In the second series of experiments, the materno-fetal free fatty acid concentration gradient was varied between + 1.58 mmol/l and -2.81 mmol/l in eight rabbits. There was a significant relationship between increasing materno-fetal gradient and increasing transfer of free fatty acids across the placenta (P less than 0.001). Moreover, net transfer of free fatty acids into the umbilical circulation was observed even with zero concentration gradient. Net transfer of free fatty acids from fetus to mother occurred when umbilical arterial free fatty acid concentration exceeded maternal arterial concentration by 1.3 mmol/l.

Maternal and umbilical venous plasma lipid concentrations at delivery in the mare.

The concentrations and fatty acid composition of the plasma free fatty acid, triacylglycerol and phospholipid fractions were determined in maternal and umbilical cord vein blood samples taken at delivery from 17 mares. Maternal and umbilical vein plasma free fatty acid concentrations were of a similar order and a positive correlation was found between the two levels suggesting that the equine placenta is permeable to fatty acid. Substantial amounts of the essential fatty acids and their longer chain derivatives were seen in both umbilical vein plasma free fatty acid and phospholipid fractions supporting this view. Certain long chain polyunsaturated derivatives of the essential fatty acids found in the umbilical venous plasma phospholipid fraction were not seen in the maternal circulating lipids. The precursor fatty acids were readily available to both foetal and placental tissues and therefore must have been elongated and incorporated into phospholipid by either or both. Very small amounts of the essential fatty acids were found in adipose stores in the newborn foal and virtually no fat stores at all in the newborn foal liver.

Maternal to fetal transfer of free fatty acids in the in situ perfused rabbit placenta.

The transfer of free fatty acids (FFA) across the placenta perfused in situ was studied in anaesthetised rabbits in late gestation. [14C]Palmitic acid and antipyrine were infused into 11 pregnant rabbits and samples collected for up to 90 min from the mother and the umbilical vessels. Levels of total FFA, radioactivity and antipyrine, a marker of placental integrity, were measured. Net FFA flux across the placenta increased with maternal FFA concentrations, confirming observations made using different methods. The specific activity of [14C]palmitic acid in perfusate also related to maternal levels and indicated that almost half of the FFA crossing the rabbit placenta must be derived from sources other than circulating maternal FFA. The composition of the perfusate FFA had a profile similar to that of circulating maternal FFA, except for an increase in a number of long chain, polyunsaturated fatty acids. These findings are consistent with maternal triacylglycerol as the other fatty acid source, with the placenta adding the longer chain, polyunsaturated fatty acids.

High arachidonic acid levels in the cord blood of infants of mothers on vegetarian diets.

1. Maternal and umbilical cord plasma samples were collected from forty-seven Asian women, twenty-eight life-long vegetarians and seventeen non-vegetarians, during delivery of their babies. The concentrations and fatty acid profiles of the plasma free fatty acid and triacylglycerol fractions were determined. 2. There were no significant differences between the levels of free fatty acid and triacylglycerol in either maternal or cord plasma from vegetarian compared with non-vegetarian Asian women. The fatty acid profiles of the lipid fractions in the two groups were similar. Total plasma free fatty acid levels in the maternal circulation correlated with umbilical cord levels. 3. The levels of linoleic acid in the maternal plasma free fatty acid fraction of the Asian women were much higher than previous reports on mixed populations of European women. In the Asian women arachidonic acid concentrations in both maternal and umbilical circulations were over four times higher than those reported for women unselected for race and diet.