Real time monitoring of carbon dioxide levels in surgical helmet systems worn during hip and knee arthroplasty.

Background: Orthopaedic surgical helmet systems (SHS) rely on an intrinsic fan to force clean external air over the wearer. Carbon dioxide (CO2) is produced through aerobic metabolism and can potentially accumulate inside the SHS. Levels above 2500 ppm have previously been shown to affect cognitive and practical function. Maximum Health and Safety Executive (HSE) 8-h exposure limit is 5000 ppm. There is a paucity of data on real-world CO2 levels experienced during arthroplasty surgery whilst wearing a SHS. Objectives: To determine intra-operative levels of CO2 experienced within SHS. Methods: CO2 levels were continuously recorded during 30 elective arthroplasties, both primary and revision. Data was recorded at 0.5Hz throughout the procedure utilising a Bluetooth CO2 detector, worn inside a surgical helmet worn with a toga gown. Five surgeons contributed real time data to the study. Results: The average CO2 level across all procedures was 3006 ppm, with 23 of the cases measured within the surgeons' helmets having a mean above 2500 ppm, but none having a mean above 5000 ppm. For each procedure, the time spent above 2500 and 5000 ppm was calculated, with the means being 72.6 % and 5.4 % respectively. Minimum fan speed was associated with only a marginally higher mean CO2 value than maximum fan speed. Discussion: The use of surgical helmet systems for elective orthopaedic surgery, can result in CO2 levels regularly rising to a point which may affect cognitive function. Conclusion: Further research is needed to corroborate these findings however, we recommend that future designs of SHS include active management of exhaust gases, possibly returning to Charnley's original design principles of the body exhaust system.

The Impact of Frailty and Deprivation on the Likelihood of Receiving Primary Total Hip and Knee Arthroplasty among People with Hip and Knee Osteoarthritis.

BACKGROUND: Among people with hip and knee osteoarthritis (OA), increasing deprivation is associated with reduced likelihood of receiving hip and knee arthroplasty (THA, TKA). OBJECTIVES: To assess whether higher levels of frailty in the most deprived neighbourhoods explains the association between greater neighbourhood deprivation and reduced likelihood of receiving THA and TKA among people with hip and knee OA. DESIGN: Longitudinal cohort study. SETTING: Linked primary and secondary care electronic medical records and national mortality data. PARTICIPANTS: 104,913 individuals with incident hip OA and 216,420 with incident knee OA. MEASUREMENTS: Frailty was assessed using a frailty index and categorised as fit, mild, moderate, and severe frailty. Neighbourhood deprivation was assessed using the index of multiple deprivation (IMD). RESULTS: Compared to those in neighbourhoods in the least deprived quintile of IMD, those in neighbourhoods in the fourth and fifth quintile of IMD (most deprived), respectively, were less likely to receive THA, adjusted subhazard ratio (95% CI), 0.90 (0.87, 0.93) and 0.77 (0.74, 0.80), over a mean follow up of 4.4 years, with similar results for TKA. Higher levels of frailty at OA diagnosis were associated also with reduced likelihood of receiving THA and TKA. The association, however, between deprivation and likelihood of receiving THA and TKA could not be explained by increased levels of frailty among those living in the most deprived areas. CONCLUSIONS: Further work is needed to understand why those in the most deprived areas are less likely to receive THA and TKA.

National Joint Registry recorded untoward intraoperative events during primary total hip arthroplasty: an investigation into the data accuracy, causal mechanisms and attributability.

INTRODUCTION: Untoward intraoperative events occurring during total hip arthroplasty are recorded by the National Joint Registry through Minimum Data Set (MDS) forms. This data may be used to assess the safety of implants. The aim of this study is to evaluate the accuracy of the untoward intraoperative events, assess the mechanism and ascertain whether these events were attributable to the implants inserted. METHODS: A retrospective analysis was undertaken of primary total hip arthroplasties performed between 2005 and 2018 in which an untoward intraoperative event was recorded. RESULTS: Of 12,802 primary hip replacements, 64 patients (0.5%) had untoward intraoperative events recorded on the MDS form. In 43 of 64 cases, the intraoperative untoward event recorded on the MDS form matched the operation notes. Among these 43 cases, in 30 (69%) patients the intraoperative event could be attributed to the implant recorded. In the remaining 13 (31%) cases, the events recorded could not be attributed to the implant. In six cases, the untoward events were attributed to implants used to manage the events rather than the implants which caused them. In seven cases, the untoward events were related to surgical technique rather than to the implant or instrumentation. CONCLUSIONS: Our analysis highlights that all untoward intraoperative events recorded on the NJR form are not implant related or attributable to the implant inserted. Provision should be made on the MDS form to clarify whether a particular untoward intraoperative event was related to the implant inserted.

Does the publication of NICE guidelines for venous thromboembolism chemical prophylaxis influence the prescribing patterns of UK hip and knee surgeons?

INTRODUCTION: We assessed the practice of surgeons regarding venous thromboembolism (VTE) chemical prophylaxis for total hip replacement (THR) and total knee replacement (TKR), before and after issuing of updated National Institute for Health and Care Excellence (NICE) guidance in 2018. METHODS: A survey, circulated through the British Hip Society and regional trainee networks/collaboratives, was completed by 306 UK surgeons at 187 units. VTE chemical prophylaxis prescribing patterns for surgeons carrying out primary THR (n=258) and TKR (n=253) in low-risk patients was assessed after publication of 2018 NICE recommendations. Prescribing patterns before and after the NICE publication were subsequently explored. RESULTS: Following the new guidance, 34% (n=87) used low-molecular-weight heparin (LMWH) alone, 33% (n=85) aspirin (commonly preceded by LMWH) and 31% (n=81) direct oral anticoagulants (DOACs: with/without preceding LMWH) for THR. For TKR, 42% (n=105) used aspirin (usually monotherapy), 31% (n=78) LMWH alone and 27% (n=68) DOAC (with/without preceding LMWH). NICE guidance changed the practice of 34% of hip surgeons and 41% of knee surgeons, with significantly increased use of aspirin preceded by LMWH for THR (before=25% vs after=73%; p<0.001), and aspirin for TKR (before=18% vs after=84%; p<0.001). Significantly more regimens were NICE guidance compliant after the 2018 update for THR (before=85.7% vs after=92.6%; p=0.011) and TKR (before=87.0% vs after=98.8%; p<0.001). CONCLUSION: Over one-third of surveyed surgeons changed their VTE chemical prophylaxis in response to 2018 NICE recommendations, with more THR and TKR surgeons now compliant with latest NICE guidance. The major change in practice was an increased use of aspirin for VTE chemical prophylaxis.

Modified conventional gait model vs. Six degrees of freedom model: A comparison of lower limb kinematics and associated error.

BACKGROUND: The conventional gait model (CGM) is commonly utilised within clinical motion analysis but has a number of inherent limitations. To overcome some of these limitations modifications have been made to the CGM and six-degrees of freedom models (6DoF) have been developed. RESEARCH QUESTION: How comparable are lower limb kinematics calculated using modified CGM and 6DoF models and what is the error associated with the output of each model during walking? METHODS: Ten healthy males attended two gait analysis sessions, in which they walked at a self-selected pace, while a 10-camera motion capture system recorded lower limb kinematics. Hip, knee and ankle joint kinematics in all three anatomical planes were calculated using a modified CGM, with medial anatomical markers and a three-dimensional foot added, and 6DoF. Mean absolute differences were calculated on a point-by-point basis over the walking gait cycle and interpreted relative to a 5° threshold to explore the comparability of model outputs. The standard error of the measurement (SEM) was also calculated on a point-by-point basis over the walking gait cycle for each model. RESULTS: Mean absolute differences above 5° were reported between the two model outputs in 58-86% of the walking gait cycle at the knee in the frontal plane, and over the entire walking gait cycle at the hip and knee in the transverse plane. SEM was typically larger for the modified CGM compared to the 6DoF, with the highest SEM values reported at the knee in the frontal plane, and the hip and the knee in the transverse plane. SIGNIFICANCE: Caution should be taken when looking to compare findings between studies utilising modified CGM and 6DoF outside of the sagittal plane, especially at the hip and knee. The reduced SEM associated with the 6DoF suggests this modelling approach may be preferable.

The microbiology of the infected knee arthroplasty.

We describe the results of a retrospective analysis of patients with microbiologically proven infection, who underwent revision TKA between 1994 and 2008. Of the 121 patients included in the study, 61 (50%) were male and 60 (50%) were female. The mean age was 71 (range 42-88) years. The most common organisms identified were Coagulase negative Staphylococcus (CNS) (49%) and Staphylococcus aureus (SA) (13%). The prevalence of CNS appears to be increasing, while that of SA and other organisms is decreasing. Vancomycin and teicoplanin were the most effective antibiotics with overall sensitivity rates of 100% and 96%, respectively. The results of our theoretical model suggest that gentamicin combined with vancomycin is the most effective empirical regimen. Staphylococcal species are the most common organisms encountered in deep infection of the knee. Gentamicin combined with vancomycin offers the most comprehensive protection and potentially allows for infected knee arthoplasties to be treated with a one-stage procedure.

Results of total aponeurectomy for Dupuytren's contracture in 61 patients: a retrospective clinical study.

INTRODUCTION: Many surgical techniques have been advocated to treat Dupuytren's contracture. Partial fasciectomy is often performed to treat the whole spectrum of Dupuytren's disease. METHOD: We have reviewed the effectiveness of total aponeurectomy performed on 61 patients [10 women and 51 men (male:female ratio 5.1:1) with a mean age of 63.0 (range 42-79 years) and a mean follow-up of 3.45 years (range 1.03-6.39 years)]. RESULTS: Post-operative complications including haematoma, seroma or necrosis were found in 13.8% of the patients. Recurrence of contracture occurred in 10.8% of the patients and 4.6% of the operated patients presented with a nerve lesion. Nerve irritation occurred in 6.2% of the patients. The mean DASH-score was 3.85 (range 0-52.5). Family pre-disposition was an important risk factor for Dupuytren's disease with 44.3% of patients having a positive family history. CONCLUSION: We suggest that total aponeurectomy is a promising alternative to partial fasciectomy with low risk for a recurrence and slightly increased risk for a nerve lesion.

Strain imparted during impaction grafting may contribute to bony incorporation: an in vitro study of the release of bmp-7 from allograft.

In order to investigate the osteoinductive properties of allograft used in impaction grafting and the effect of strain during impaction on these properties, we designed an in vitro experiment to measure strain-related release of bone morphogenetic protein-7 (BMP-7) from fresh-frozen femoral head allograft. A total of 40 10 mm cubes of cancellous bone were cut from ten samples of fresh-frozen femoral head. The marrow was removed from the cubes and the baseline concentrations of BMP-7 were measured. Specimens from each femoral head were allocated to four groups and subjected to different compressive strains with a material testing machine, after which BMP-7 activity was reassessed. It was present in all groups. There was a linear increase of 102.1 pg/g (95% confidence interval 68.6 to 135.6) BMP-7 for each 10% increase in strain. At 80% strain the mean concentration of BMP-7 released (830.3 pg/g bone) was approximately four times that released at 20% strain. Activity of BMP-7 in fresh-frozen allograft has not previously been demonstrated. This study shows that the freezing and storage of femoral heads allows some maintenance of biological activity, and that impaction grafting provides a source of osteoinductive bone for remodelling. We have shown that BMP-7 is released from fresh-frozen femoral head cancellous bone in proportion to the strain applied to the bone. This suggests that the impaction process itself may contribute to the biological process of remodelling and bony incorporation.

Why fine-wire fixators work: an analysis of pressure distribution at the wire-bone interface.

Tensioned fine-wire external fixator systems have been used successfully for the treatment of fractures, mal-unions and for limb lengthening for many years. When used in metaphyseal bone, this type of fixator has a lower loosening rate than half-pin fixators. The differing mechanical properties of these fixator systems have been investigated extensively; however, most studies have centered on the mechanical properties of the fixator as a whole. Our knowledge of the interactions occurring at the interface between implant and bone remains sparse. In order to investigate this interaction, we devised a simple experimental model to characterise the distribution of pressure in cancellous bone surrounding a tensioned wire under loading conditions. Comparison was then made to a similar model of a half-pin fixator. Pressure was measured using pressure sensitive film at various distances away from the implant-bone interface. Static, single cycle loading of the model was performed with a Universal Testing Machine. Pressure distribution in the fine-wire model was found to occur in three regions: polar, beam loading and uniform. Polar patterns were seen closest to the wire with pressure concentrated at the entry and exit points of the wire. Beam loading was seen at a distance of 1.5 mm from the wire and pressure reached a uniform distribution at 4.0 mm. Most of the pressure measured was less than 2 MPa, which is less than the yield strength of cancellous bone (2-7 MPa). Higher loads produced higher stresses but the distribution pattern was similar. In contrast, the half-pin model showed far higher pressures (20 MPa), which were present deeper in the bone specimen. These results further our understanding of the biomechanics of fine-wire fixators and may explain the lower loosening rate of this type of fixator when compared to half-pin fixators used in metaphyseal bone.

The prophylaxis and treatment of heterotopic ossification following lower limb arthroplasty.

Heterotopic ossification following joint replacement in the lower limb occurs in 3% to 90% of cases. Higher grades of heterotopic ossification can result in significant limitation of function and can negate the benefits of joint replacement. The understanding of the pathophysiology of this condition has improved in recent years. It would appear to be related to a combination of systemic and local factors, including over-expression of bone morphogenetic protein-4. There is currently little evidence to support the routine use of prophylaxis for heterotopic ossification in arthroplasty patients, but prophylaxis is recommended by some for high-risk patients. Radiotherapy given as one dose of 7 Gy to 8 Gy, either pre-operatively (< four hours before) or post-operatively (within 72 hours of surgery), appears to be more effective than indometacin therapy (75 mg daily for six weeks). In cases of prophylaxis against recurrent heterotopic ossification following excision, recent work has suggested that a combination of radiotherapy and indometacin is effective. Advances in our understanding of this condition may permit the development of newer, safer treatment modalities.

Reference marker stability in computer aided orthopedic surgery: a biomechanical study in artificial bone and cadavers.

INTRODUCTION: In computer assisted orthopaedic surgery, rigid fixation of the Reference Marker (RM) system is essential for reliable computer guidance. A minimum shift of the RM can lead to substantial registration errors and inaccuracies in the navigation process. Various types of RM systems are available but there is little information regarding the relative stabilities of these systems. The aim of this study was to test the rotational stability of three commonly used RM systems. MATERIALS AND METHODS: One hundred and thirty Synbones and 15 cadavers were used to test the rotational stability of three different RM systems (Schanz' screw, RM B and RM C adjustment systems). Using a specially developed testing device, the peak torque sustained by each RM system was assessed in various anatomical sites. RESULTS: Comparison of means for Synbone showed that the RM C was the most stable (mean peak torque 5.60 +/- 1.21 Nm) followed by the RM B system (2.53 +/- 0.53 Nm) and the RM A (0.77 +/- 0.39 Nm) (p<0.01). The order of stability in relation to anatomical site was femoral shaft, distal femur, tibial shaft, proximal tibia, anterior superior iliac spine, iliac crest and talus. Results from the cadaver experiments showed similar results. Bi-cortical fixation was superior to mono-cortical fixation in the femur (p<0.01) but not the tibia (p=0.22). CONCLUSION: The RM system is the vital link between bone and computer and as such the stability of the RM is paramount to the accuracy of the navigation process. In choosing RM systems for computer navigated surgery surgeons should be aware of their relative stability. Anatomical site of RM placement also affect the stability. Mono-cortical fixation is generally less stable than bi-cortical.

A 28-year clinical and radiological follow-up of alumina ceramic-on-crosslinked polyethylene total hip arthroplasty: a follow-up report and analysis of the oxidation of a shelf-aged acetabular component.

AIMS: Our aim in this study was to describe a continuing review of 11 total hip arthroplasties using 22.225 mm Alumina ceramic femoral heads on a Charnley flanged femoral component, articulating against a silane crosslinked polyethylene. PATIENTS AND METHODS: Nine patients (11 THAs) were reviewed at a mean of 27.5 years (26 to 28) post-operatively. Outcome was assessed using the d'Aubigne and Postel, and Charnley scores and penetration was recorded on radiographs. In addition, the oxidation of a 29-year-old shelf-aged acetabular component was analysed. RESULTS: The mean clinical outcome scores remained excellent at final follow-up. The mean total penetration remained 0.41 mm (0.40 to 0.41). There was no radiographic evidence of acetabular or femoral loosening or osteolysis. There was negligible oxidation in the shelf-aged sample despite gamma irradiation and storage in air. CONCLUSION: These results highlight the long-term stability and durability of this type of crosslinked, antioxidant containing polyethylene when used in combination with a small diameter alumina ceramic femoral head. Cite this article: Bone Joint J 2017;99-B:1286-9.

Chondroprotection by urocortin involves blockade of the mechanosensitive ion channel Piezo1.

Osteoarthritis (OA) is characterised by progressive destruction of articular cartilage and chondrocyte cell death. Here, we show the expression of the endogenous peptide urocortin1 (Ucn1) and two receptor subtypes, CRF-R1 and CRF-R2, in primary human articular chondrocytes (AC) and demonstrate its role as an autocrine/paracrine pro-survival factor. This effect could only be removed using the CRF-R1 selective antagonist CP-154526, suggesting Ucn1 acts through CRF-R1 when promoting chondrocyte survival. This cell death was characterised by an increase in p53 expression, and cleavage of caspase 9 and 3. Antagonism of CRF-R1 with CP-154526 caused an accumulation of intracellular calcium (Ca2+) over time and cell death. These effects could be prevented with the non-selective cation channel blocker Gadolinium (Gd3+). Therefore, opening of a non-selective cation channel causes cell death and Ucn1 maintains this channel in a closed conformation. This channel was identified to be the mechanosensitive channel Piezo1. We go on to determine that this channel inhibition by Ucn1 is mediated initially by an increase in cyclic adenosine monophosphate (cAMP) and a subsequent inactivation of phospholipase A2 (PLA2), whose metabolites are known to modulate ion channels. Knowledge of these novel pathways may present opportunities for interventions that could abrogate the progression of OA.

International metal-on-metal multidisciplinary teams: do we manage patients with metal-on-metal hip arthroplasty in the same way? An analysis from the International Specialist Centre Collaboration on MOM Hips (ISCCoMH).

AIMS: There are many guidelines that help direct the management of patients with metal-on-metal (MOM) hip arthroplasties. We have undertaken a study to compare the management of patients with MOM hip arthroplasties in different countries. METHODS: Six international tertiary referral orthopaedic centres were invited to participate by organising a multi-disciplinary team (MDT) meeting, consisting of two or more revision hip arthroplasty surgeons and a musculoskeletal radiologist. A full clinical dataset including history, blood tests and imaging for ten patients was sent to each unit, for discussion and treatment planning. Differences in the interpretation of findings, management decisions and rationale for decisions were compared using quantitative and qualitative methods. RESULTS: Overall agreement between the orthopaedic centres and the recommended treatment plans for the ten patients with MOM hip implants was moderate (kappa = 0.6). Full agreement was seen in a third of cases, however split decisions were also seen in a third of cases. Units differed in their interpretation of the significance of the investigation findings and put varying emphasis on serial changes, in the presence of symptoms. DISCUSSION: In conclusion, the management of raised or rising blood metal ions, cystic pseudotumours and peri-acetabular osteolysis led to inconsistency in the agreement between centres. Coordinated international guidance and MDT panel discussions are recommended to improve consensus in decision making. TAKE HOME MESSAGE: A lack of evidence and the subsequent variation in regulator guidance leads to differences in opinions, the clinical impact of which can be reduced through a multi-disciplinary team approach to managing patients with MOM hip implants. Cite this article: Bone Joint J 2016;98-B:179-86.

The use of a novel bone allograft wash process to generate a biocompatible, mechanically stable and osteoinductive biological scaffold for use in bone tissue engineering.

Fresh-frozen biological allograft remains the most effective substitute for the 'gold standard' autograft, sharing many of its osteogenic properties but, conversely, lacking viable osteogenic cells. Tissue engineering offers the opportunity to improve the osseointegration of this material through the addition of mesenchymal stem cells (MSCs). However, the presence of dead, immunogenic and potentially harmful bone marrow could hinder cell adhesion and differentiation, graft augmentation and incorporation, and wash procedures are therefore being utilized to remove the marrow, thereby improving the material's safety. To this end, we assessed the efficiency of a novel wash technique to produce a biocompatible, biological scaffold void of cellular material that was mechanically stable and had osteoinductive potential. The outcomes of our investigations demonstrated the efficient removal of marrow components (~99.6%), resulting in a biocompatible material with conserved biomechanical stability. Additionally, the scaffold was able to induce osteogenic differentiation of MSCs, with increases in osteogenic gene expression observed following extended culture. This study demonstrates the efficiency of the novel wash process and the potential of the resultant biological material to serve as a scaffold in bone allograft tissue engineering.

Alar haematoma.

We present two cases of alar haematoma. This is a very rare complication of nasal trauma, and only two cases have been described previously. One case presented late and did not undergo surgical drainage and has a persistent cosmetic deformity. We recommend early surgical drainage when possible.

Oculomotor nerve palsy following submucosal diathermy to the inferior turbinates.

Submucosal diathermy to the inferior turbinates is a common surgical procedure performed to improve the nasal airway. We present the case of a previously well six-year-old boy who underwent submucosal diathermy and developed the unusual complication of a left oculomotor nerve palsy. The possible aetiology is discussed.

The current state of bearing surfaces in total hip replacement.

We reviewed the literature on the currently available choices of bearing surface in total hip replacement (THR). We present a detailed description of the properties of articulating surfaces review the understanding of the advantages and disadvantages of existing bearing couples. Recent technological developments in the field of polyethylene and ceramics have altered the risk of fracture and the rate of wear, although the use of metal-on-metal bearings has largely fallen out of favour, owing to concerns about reactions to metal debris. As expected, all bearing surface combinations have advantages and disadvantages. A patient-based approach is recommended, balancing the risks of different options against an individual's functional demands.

Group B streptococci as an unusual cause of septic arthritis of the hip: association with childbirth.

Group B streptococci (GBS) birth canal colonisation in pregnant women and women of child-bearing age is well known. The recognition and incidence of infections caused by these organisms in non-pregnant and elderly adults are increasing. Clinical manifestations of GBS infections can range from simple skin and soft tissue infections to fatal meningitis in newborns. GBS as a cause of septic arthritis of the hip associated with pregnancy is previously unreported. We report a case of septic arthritis of the hip joint caused by GBS in a 30-year-old woman with a history of recent childbirth. Delay in recognition and lack of timely appropriate treatment of this condition henceforth led to severe destruction of the joint, requiring ultimate reconstruction of the joint with cemented total hip arthroplasty. This case report highlights the atypical presentation and rapidly destructive nature of this infection with catastrophic consequences.

Two stage revision knee arthroplasty for infection with massive bone loss. A technique to achieve spacer stability.

We report a technique for the intra-operative production of an antibiotic-impregnated cement spacer, reinforced with an intramedullary nail. The spacer is designed for use in cases where significant bone loss and/or ligamentous instability prevent the formation of a stable joint when using a conventional spacer during a two-stage revision knee arthroplasty. This technique has been performed in eleven patients. Nine patients have subsequently undergone a second-stage procedure. Two patients died of unrelated causes before a second-stage could be performed. In all but one case, the infection has been successfully eradicated and patients remain infection free at a mean follow-up of 32 months (range 21-64 months). We believe that the described technique is an effective alternative to the traditional spacer, in patients with significant bone loss and/or ligamentous instability. It delivers antibiotics locally, while producing a mechanically stable joint, on which the patient can mobilise, maintaining leg length and tissue tensions.