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.

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.

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.

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.

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.

Soft tissue dissection in placement of reference markers during computer aided total hip arthroplasty.

OBJECTIVE: During computer navigated hip arthroplasty, impingement of soft tissues on reference markers (RMs) may cause errors in the navigation process. The aim of this study was to investigate the effect of such soft tissue impingement during limb movement on the stability of different RMs. MATERIALS AND METHODS: The stability of one- and two-screw RM systems inserted using three different levels of soft tissue dissection was analyzed in fresh cadaver lower limbs. All tests were done with RMs inserted in both the distal-anterior femur and the distal-lateral femur. RESULTS: Rotations of less than 0.15 degrees and translations of less than 0.4 mm occurred in most test combinations. The combination that showed the greatest instability was when a stab incision was used to insert a screw in the distal-lateral femur (translation: 0.73 +/- 0.05 mm; rotation: 0.25 +/- 0.05 degrees ) (p < 0.001). This instability occurred in both single- and double-screw RMs (p = 0.21). CONCLUSIONS: Reference markers can be placed in the anterior distal femur through stab incisions without resulting in significant impingement during limb movement. When RMs are placed in the lateral distal femur, impingement may occur from the fascia lata. Release of the fascia lata 1 cm either side of the screw prevents significant impingement. Wide skin incision is unnecessary in any location.

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.

Conversion of bilateral hip and knee ankylosis to total joint replacements.

We present a 25-year-old patient with juvenile rheumatoid arthritis and ankylosis of both hips and both knees treated by staged bilateral hip and knee arthroplasty. She was followed up for 18 months. We discuss the pre-operative planning, surgical details and post-operative rehabilitation.

Arthrodesis of the distal interphalangeal joint: description of a new technique and clinical follow-up at 2 years.

INTRODUCTION: Arthrodesis of the distal interphalangeal joint (DIPJ) is an accepted operative procedure to treat osteoarthritis, instability and joint deformity. There is a wide spectrum of recommended operative techniques including cerclage wires, headless screws, bio-resorbable pins and lag screws. Lag screw fixation remains one of the most accepted methods of fixation; however, problems can occur in particular subsidence of the screw head leading to loss of compression and prominence of the screw head in the finger tip necessitating removal. We describe here a new technique of DIPJ arthrodesis that avoids these problems. METHODS AND PATIENTS: The technique is described here in detail, and clinical results are given for 18 joints (17 patients) followed-up at a mean 24 months (range 6-44). RESULTS: Mean post-operative DASH score was 15. There were no cases of non-union; only four complications were seen, one case of nail growth disturbance and one of early screw breakage necessitating revision. Two infections necessitated early hardware removal although both arthodesis were united. CONCLUSION: The technique is simple and reliable giving consistent clinical results.

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.

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.

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 Lubinus patellofemoral arthroplasty: a series of 17 cases.

INTRODUCTION: The Lubinus patellofemoral arthroplasty was introduced in our institution in 1994. The first 17 patients were followed-up in order to identify the short-term outcome for this prosthesis. MATERIALS AND METHODS: The average age at surgery was 66 years (range 37-82 years). The mean follow-up was 19 months. The indications for surgery were strictly limited to radiographically proven primary osteoarthritis affecting only the patellofemoral joint (13) and secondary arthritis due to maltracking, subluxation (3) or trauma to the patella (1). At review, the range of movement and Lysholm and Tegner scores were recorded and radiographs obtained. Patients were also asked if their outcome was satisfactory or unsatisfactory. RESULTS: At review, only 9 (53%) knees were classified as satisfactory by the patients. Further surgery had been carried out in 6 cases (35%) including revision to total knee arthroplasty in 4 (24%). Other complications included clicking and subluxation in 3 cases (18%), extension block in 3 (18%) and infection in 1 (6%). Progression of osteoarthritis to involve other compartments occurred in 2 cases (12%). CONCLUSIONS: Many of these early problems are related to the unforgiving nature of the prosthesis on insertion. These poor early results have led us to stop using the prosthesis.