Aims

The aims of this study were to determine the incidence and factors for developing periprosthetic joint infection (PJI) following hemiarthroplasty (HA) for hip fracture, and to evaluate treatment outcome and identify factors associated with treatment outcome.

Aims

Deep surgical site infection (SSI) remains an unsolved problem after hip fracture. Debridement, antibiotic, and implant retention (DAIR) has become a mainstream treatment in elective periprosthetic joint infection; however, evidence for DAIR after infected hip hemiarthroplaty is limited.

Aims. The aims of this study were to develop an in vivo model of periprosthetic joint infection (PJI) in cemented hip hemiarthroplasty, and to monitor infection and biofilm formation in real-time. Methods. Sprague-Dawley rats underwent cemented hip hemiarthroplasty via the posterior approach with pre- and postoperative gait assessments. Infection with Staphylococcus aureus Xen36 was monitored with in vivo photoluminescent imaging in real-time. Pre- and postoperative gait analyses were performed and compared. Postmortem micro (m) CT was used to assess implant integration; field emission scanning electron microscopy (FE-SEM) was used to assess biofilm formation on prosthetic surfaces. Results. All animals tolerated surgery well, with preservation of gait mechanics and weightbearing in control individuals. Postoperative in vivo imaging demonstrated predictable evolution of infection with logarithmic signal decay coinciding with abscess formation. Postmortem mCT qualitative volumetric analysis showed high contact area and both cement-bone and cement-implant interdigitation. FE-SEM revealed biofilm formation on the prosthetic head. Conclusion. This study demonstrates the utility of a new, high-fidelity model of in vivo PJI using cemented hip hemiarthroplasty in rats. Inoculation with bioluminescent bacteria allows for non-invasive, real-time monitoring of infection. Cite this article: Bone Joint J 2021;103-B(7 Supple B):9–16

Abstract. Background. Dislocation of a hip hemiarthroplasty is a devastating complication with a high mortality rate in elderly patients. Previous studies have suggested a higher dislocation rate in patients with neuromuscular conditions. In this study, we have reviewed our larger cohort of patients to identify whether there is any association between neuromuscular disorders and prosthetic dislocation in patients treated with hip hemiarthroplasty for femoral neck fractures. Patients and Methods. Our study is a retrospective analysis of data collected over 34 years for patients with intracapsular neck of femur fracture who underwent hip hemiarthroplasty. The study population is composed of four groups: patients with no neuromuscular disorders, patients with Parkinson's disease, patients with previous stroke, and patients with dementia. Results. A total of 3827 patients were treated with hip hemiarthroplasty. For the 3371 patients with no neuromuscular condition (Group I) the dislocation rate was 1.1%. 219 patients had Parkinsonism (Group II) with a dislocation rate of 3.2%, 104 patients had a previous stroke with weakness on the fracture side with a dislocation rate of 1.0% (Group III), and 984 patients had severe dementia with a dislocation rate of 1.8% (Group IV). The increased dislocation rate for those with Parkinson's disease was statistically significant (p=0.02) while none of the other neuromuscular conditions were statistically significant. Conclusion. Our study demonstrates an increased risk of dislocation after hemiarthroplasty for patients with Parkinson's disease in comparison to other groups. No increase was apparent for those with dementia or weakness from a previous stroke

Introduction and Objective. Dislocation of a hip hemiarthroplasty is a significant complication with a high mortality rate in elderly patients. Previous studies have shown a higher risk of dislocation in patients with neuromuscular conditions. In this study, we reviewed our larger cohort of patients to identify if there is a link between neuromuscular disorders and dislocation of hip hemiarthroplasty in patients with neuromuscular conditions. Materials and Methods. We have retrospectively analysed a single-centre data that was collected over 34 years for patients with intracapsular neck of femur fracture who underwent hip hemiarthroplasty. The study population was composed of four groups: patients with no neuromuscular disorders, patients with Parkinson's disease, patients with previous stroke, and patients with mental impairment. Results. A total of 3827 patients were included in the analysis. 3371 patients had no neuromuscular condition (Group I) with a dislocation rate of 1.1%. 219 patients had Parkinsonism (Group II) with a dislocation rate of 3.2%, 104 patients had a previous stroke with weakness on the fracture side with a dislocation rate of 1.0% (Group III), and 984 patients had severe mental impairment with a dislocation rate of 1.8% (Group IV). The increased dislocation rate for those with Parkinson's disease was statistically significant (p=0.02) while none of the other neuromuscular conditions were statistically significant. Conclusions. Our study has shown an increased risk of dislocation of hemiarthroplasty in patients with Parkinson's disease in comparison to other groups. No increase was apparent for patients with mental impairment or weakness from a previous stroke

Between 2016–2019, 4 patients developed hip infections post-hemiarthroplasty. However, between 2020–2021 (Covid-19 pandemic period), 6 patients developed hip infections following hip hemiarthroplasty. The purpose of the investigation is to establish the root causes and key learning from the incident and use the information contained within this report to reduce the likelihood of a similar incident in the future. 65 patients presented with a neck of femur fracture during Covid-19 pandemic period between 2020–2021, 26 had hip hemiarthroplasty of which 6 developed hip infections. Medical records, anaesthetic charts and post-hip infections guidelines from RCS and NICE were utilised. Proteus, Enterococci and Strep. epidermis were identified as the main organisms present causing the hip infection. The average number of ward moves was 4 with 90% of patients developing COVID-19 during their hospital stay. The chance of post-operative wound infection were multifactorial. Having had 5 of 6 patients growing enterococci may suggest contamination of wound either due to potential suboptimal hygiene measures, inadequate wound management /dressing, potential environmental contamination if the organisms (Vancomycin resistant enterococci) are found to be of same types and potential hospital acquired infection due to inadequate infection control measures or suboptimal hand hygiene practices. 3 of the 5 patients grew Proteus, which points towards suboptimal hygiene practices by patients or poor infection control practices by staff. Lack of maintenance of sterility in post op wound dressings alongside inexperience of the handling of post-operative wound in non-surgical wards; multiple ward transfers exceeding the recommended number according to trust guidelines especially due to pandemic isolation measures and COVID-19 infection itself had resulted in an increased rate of hip infections during the COVID-19 pandemic. Multidisciplinary team education and planned categorisation and isolation strategy is essential to minimise the rate of further hip infections during the pandemic period in future

Background. Hip Hemiarthroplasty is one of the commonest orthopaedic operation done in UK with recent NHFD data from 2017 report showing that 43% of the 77000 patients who presented to hospital had hemiarthroplasty. Literature suggests dislocation rate of 0.8% – 6.1% for Hip Hemiarthroplasty. Dislocation of hemiarthroplasty may lead to significant morbidity and mortality. Aim. To investigate if acetabular dysplasia has a significant association with hemiarthroplasty dislocation. Methodology. Retrospective multicentre review. Review of radiographs of patients receiving a hip hemiarthroplasty for a hip fracture measuring Acetabular index (sharp angle) and Lateral Centre edge angle(CEA). A large acetabular index and lower value for the center-edge angle suggest acetabular dysplasia. Measurements were made for 20 patients with dislocation and 20 patients without dislocation. Statistical assessment of the results with unpaired t test was performed. Results. Mean acetabular angle for those with dislocation was 42.65 degrees versus 37.8 for those without dislocation giving a p value of 0.000861. Mean Center-edge angle of those with dislocation was 26.1 degrees versus 37 for those without dislocation giving a p value of 0.000019. Conclusion. This study showed that the hemiarthroplasty dislocation group had higher acetabular index and Lower Center-edge angle compared to the hemiarthroplasty group without dislocation clearly demonstrating that acetabular dysplasia is implicated in the aetiology of hip hemiarthroplasty dislocation. Hence careful review of the pre-op X-rays for dysplastic features would benefit in making a sound management plan

Gram-negative prosthetic joint infections (GN-PJI) present unique challenges in management due to their distinct pathogenesis of biofilm formation on implant surfaces. To date, there are no animal models that can fully recapitulate how a biofilm is challenged in vivo in the setting of GN-PJI. The purpose of this study is to establish a clinically representative GN-PJI in vivo model that can reliably depict biofilm formation on titanium implant surface. We hypothesized that the biofilm formation on the implant surface would affect the ability of the implant to be osseointegrated. The model was developed using a 3D-printed, medical-grade titanium (Ti-6Al-4V), monoblock, cementless hemiarthroplasty hip implant. This implant was used to replace the femoral head of a Sprague-Dawley rat using a posterior surgical approach. To induce PJI, two bioluminescent Pseudomonas aeruginosa (PA) strains were utilized: a reference strain (PA14-lux) and a mutant strain that is defective in biofilm formation (DflgK-lux). PJI development and biofilm formation was quantitatively assessed in vivo using the in vivo imaging system (IVIS), and in vitro using the viable colony count of the bacterial load on implant surface. Magnetic Resonance Imaging (MRI) was acquired to assess the involvement of periprosthetic tissue in vivo, and the field emission scanning electron microscopy (FE-SEM) of the explanted implants was used to visualize the biofilm formation at the bone-implant interface. The implant stability, as an outcome, was directly assessed by quantifying the osseointegration using microCT scans of the extracted femurs with retained implants in vitro, and indirectly assessed by identifying the gait pattern changes using DigiGaitTM system in vivo. A localized prosthetic infection was reliably established within the hip joint and was followed by IVIS in real-time. There was a quantitative and qualitative difference in the bacterial load and biofilm formation between PA14 and DflgK. This difference in the ability to persist in the model between the two strains was reflected on the gait pattern and implant osseointegration. We developed a novel uncemented hip hemiarthroplasty GN-PJI rat model. This model is clinically representative since animals can bear weight on the implant. PJI was detected by various modalities. In addition, biofilm formation correlated with implant function and stability. In conclusion, the proposed in vivo GN-PJI model will allow for more reliable testing of novel biofilm-targeting therapetics

Introduction. Gram-negative prosthetic joint infections (GN-PJI) present unique challenges in management due to their distinct pathogenesis of biofilm formation on implant surfaces. The purpose of this study is to establish a clinically representative GN-PJI model that can reliably recapitulate biofilm formation on titanium implant surface in vivo. We hypothesized that biofilm formation on an implant surface will affect its ability to osseointegrate. Methods. The model was developed using 3D-printed titanium hip implants, to replace the femoral head of male Sprague-Dawley rats. GN-PJI was induced using two bioluminescent Pseudomonas aeruginosa strains: a reference strain (PA14-lux) and a mutant biofilm-defective strain (ΔflgK-lux). Infection was monitored in real-time using the in vivo imaging system (IVIS) and Magnetic Resonance Imaging (MRI). Bacterial loads on implant surface and in periprosthetic tissues were quantified utilizing viable-colony-count. Field-emission scanning-electron-microscopy of the explanted implants was used to visualize the biofilm formation at the bone-implant-interface. The implant stability, as an outcome, was directly assessed by quantifying the osseointegration in vitro using microCT scan, and indirectly assessed by identifying the gait pattern changes using DigiGait. TM. system in vivo. Results. Localized infection was established within the hip joint and was followed by IVIS in real-time. There was a quantitative and qualitative difference in the bacterial load and biofilm formation between PA14-lux and ΔflgK-lux. This difference in the ability to persist in the model between the two strains was reflected in the gait pattern and implant osseointegration. Conclusions. We developed a novel uncemented hip hemiarthroplasty, GN-PJI rat model. To date, the proposed in vivo biofilm-based model is the most clinically representative for GN-PJI since animals can bear weight on the implant and poor osseointegration correlates with biofilm formation. In addition, localized PJI was detected by various modalities. Clinical Relevance. The proposed in vivo GN-PJI model will allow for more reliable testing of novel biofilm-targeting therapeutics

Introduction. The hip hemiarthroplasty in posterior approach is a common surgical procedure at the femoral neck fractures in the elderly patients. However, the postoperative hip precautions to avoid the risk of dislocations are impeditive for early recovery after surgery. We used MIS posterior approach lately known as conjoined tendon preserving posterior (CPP) approach, considering its enhancement of joint stability, and examined the intraoperative and postoperative complications, retrospectively. Methods. We performed hip hemiarthroplasty using CPP approach in 30 patients, and hip hemiarthroplasty using conventional posterior approach in 30 patients, and both group using lateral position with the conventional posterior skin incision. The conjoined tendon (periformis, obturator internus, and superior/inferior gemellus tendon) was preserved and the obturator externus tendon was incised in CPP approach without any hip precautions postoperatively. The conjoined tendon was incised in conventional approach using hip abduction pillow postoperatively. Results. There was no difference between CPP approach group and conventional approach group in the mean age of patients (81.8 years, and 80.3 years, respectively), and in the mean operative time (68.8 minutes, and 64.9 minutes, respectively). In 4 cases of CPP approach, the avulsion fracture at femoral attachment of the conjoined tendon occured during hip reduction manoeuvres. No dislocations occured in both groups in the follow-up period (2 years). Discussion. Lately, the number of hip surgery in muscle sparing approach is increasing. However, in general, MIS approach induces the intraoperative complications, and requires the skillful procedure. The hip reduction manoeuvres would be more difficult in the CPP approach, than in conventional posterior approach, because the preserved conjoined tendon would inhibit hip reduction, considering those avulsion fractures of the femoral attachment. Nevertheless, CPP approach did not require no extended time compared to conventional approach, and no postoperative hip precautions. Due to these results, CPP approach could be a good MIS procedure including early recovery after surgery based on the enhancement of joint stability, excluding the difficulties in hip reduction manoeuvres. We could not show the difference in dislocation rate between two groups, because of small numbers. We are planning to increase the number of patients in the future study

Prosthetic joint infections (PJI) are devastating complications. Our knowledge on hip fractureassociated hemiarthroplasty PJI (HHA-PJI) is limited compared to elective arthroplasty. The goal of this study was to describe the epidemiology, risk factors, management, and outcomes for HHA-PJI. A population-based (465,000) multicentre retrospective analysis of HHAs between 2006-2018 was conducted. PJI was defined by international consensus and treatment success as no return to theatre and survival to 90 days after the initial surgical management of the infection. Univariate, survival and competing risk regression analyses were performed. 1852 HHAs were identified (74% female; age:84±7yrs;90-day-mortality:16.7%). Forty-three (2.3%) patients developed PJI [77±10yrs; 56% female; 90-day-mortality: 20.9%, Hazard-Ratio 1.6 95%CI 1.1-2.3,p=0.023]. The incidence of HHA-PJI was 0.77/100,000/year and 193/100,000/year for HHA. The median time to PJI was 26 (IQR 20-97) days with 53% polymicrobial growth and 41% multi-drug resistant organisms (MDRO). Competing risk regression identified younger age [Sub-Hazard-Ratio(SHR) 0.86, 95%CI 0.8-0.92,p<0.001], chronic kidney disease (SHR 3.41 95%CI 1.36-8.56, p=0.01), body mass index>35 (SHR 6.81, 95%CI 2.25-20.65, p<0.001), urinary tract infection (SHR 1.89, 95%CI 1.02-3.5, p=0.04) and dementia (SHR 9.4, 95%CI 2.89-30.58,p<0.001) as significant risk factors for developing HHA-PJI. When infection treatment was successful (n=15, 38%), median survival was 1632 days (IQR 829-2084), as opposed to 215 days (IQR 20-1245) in those who failed, with a 90-day mortality of 30%(n=12). There was no significant difference in success among debridement, excision arthroplasty or revision arthroplasty. HHA PJI is uncommon but highly lethal. All currently identified predictors are non-modifiable. Due to the common polymicrobial and MDRO infections our standard antibiotic prophylaxis may not be adequate HHA-PJI is a different disease compared to elective PJI with distinct epidemiology, pathogens, risk factors and outcomes, which require targeted research specific to this unique population

Introduction. Premature cessation of clopidogrel in certain patients with cardiac conditions is associated with an increased risk of recurrent coronary events. Such patients often present with proximal femoral fractures requiring surgical intervention. Our aim was to ascertain whether it is necessary to stop clopidogrel preoperatively to avoid postoperative complications following hip hemiarthroplasty surgery. Methods. A retrospective review of 102 patients with ongoing clopidogrel therapy and patients not on clopidogrel who underwent hip hemiarthroplasty for an intracapsular proximal femoral fracture was undertaken. Statistical comparison on pre- and postoperative haemoglobin (Hb), ASA grades, comorbidities, operative times, transfusion requirements, hospital length of stay (LOS), wound infection, haematoma and reoperation rates between the two groups was undertaken. Results. There were 50 patients in the clopidogrel group (CG) and 52 in the non-clopidogrel group (NCG). The mean age was 83 years. There was no difference with respect to ASA grade, comorbidities (except cardiac comorbidities), age, gender and operation times between the two groups. The mean preoperative Hb was 12.5 g/dl and 12.6 g/dl respectively in the CG and NCG (p=0.72). The mean postoperative Hb was 10.8 g/dl and 11.1 g/dl respectively in the CG and NCG (p= 0.37). 4 and 2 patients respectively required transfusions postoperatively in the CG and NCG (p= 0.37). A total of 8 and 5 units were utilised in the CG and NCG groups respectively (p= 0.54). There was no difference with respect to LOS, wound infection, haematoma and reoperation rates between the two groups postoperatively. Conclusion. Maintaining clopidogrel therapy throughout the perioperative period in high risk patients with intracapsular proximal femoral fractures is not associated with an increased risk of bleeding or complications following hip hemiarthroplasty surgery

Introduction and Objective. Interest for direct anterior approach (DAA) in hip hemiarthroplasty (HHA) has greatly increased in recent years, however which is the best surgical approach in hip replacement treating femoral neck fractures (FNFs) is already unclear. The aim of this study is to perform a radiographic and perioperative complications analysis by comparing the direct anterior approach (DAA) with the direct lateral approach (DLA) in patients treated with hemiarthroplasty for FNFs. Materials and Methods. Patients with FNFs surgically treated between 2016–2020 with HHA were enrolled. The radiographical outcomes of DAA and DLA are compared. Several peri-operative and post-operative variables were evaluated: mean surgery time, complications as periprosthetic fractures or episodes of dislocation, the average of post-operative diaphyseal filling of the stem (Canal Fill Index, CFI), the extent of heterotopic ossification (HO) (simplified Broker classification) and metadiaphiseal bone loss (Paprosky classification) within one year from surgery. Results. 86 patients underwent HHA by DAA and 80 patients by DLA. The two groups are qualitatively comparable. No statistically significate differences were showed in all variables analyzed (p>0.05). The average of surgical time of DAA were 61 minutes compared to 67 of DLA. No differences were showed in the post-operative CFI (DAA 0.71 ± 6.1; DLA 0.76 ± 13.5), the extent of the HO (DAA 79.07% low; DLA 75% low) and metadiaphiseal bone loss (DAA Grade I 91.86%; DLA Grade I 93.75%). Regarding perioperative complications, we have discovered only one periprosthetic fracture each group. Although there was no statistically significant difference, we highlighted a higher number of dislocations in the group of DLA (2 episodes vs no one). Conclusions. In this study we have shown that the DAA is an adequate surgical choice comparing with the classical DLA for FNFs treated with HHA. The analysis of our radiographic parameters and perioperative complications have not shown a significant difference between the two surgical approach. This study is limited by a purely radiographic analysis without addition of clinical parameters

The December 2023 Hip & Pelvis Roundup. 360. looks at: Early hip fracture surgery is safe for patients on direct oral anticoagulants; Time to return to work by occupational class after total hip or knee arthroplasty; Is there a consensus on air travel following hip and knee arthroplasty?; Predicting whether patients will achieve minimal clinically important differences following hip or knee arthroplasty; High-dose dual-antibiotic-loaded cement for hip hemiarthroplasty in the UK (WHiTE 8): a randomized controlled trial; Vitamin E – a positive thing in your poly?; Hydroxapatite-coated femoral stems: is there a difference in fixation?

Aims: Research was preformed including evaluation of early functional and radiographic results, six months after operative treatment of femoral neck fracture, using hemiarthroplasty and osteosynthesis, and late results, two years and more after operation. Methods: Clinical material comprehended two groups of hundred unselected patients each. Control exams included anamnestic data, and radiographic studies of treated hip. Data were stored in previously prepared research protocol according to applied functional and radiographic scoring systems. Results: Data were analized and compared between groups. Results of hip hemiarthroplasty showed direct influence of age, general state of health, size of prosthesis, use of cement and mode of rehabilitation on outcome of patients. Sex, social state, intercurrent diseases and length of operation showed no influence on outcome. Conclusions: According to this analysis hip hemiarthroplasty is a method of choice in cases of elder cathegory of patients, poor general health state, low mental capacity, short mobility and short life expectancy. In a younger patient group method of choice is ostheosynthesis or total hip prosthesis TKA – general

Recent National Institute for Health and Care Excellence (NICE) guidance has advised against the continued use of the Thompson implant when performing hip hemiarthroplasty and recommended surgeons consider using the anterolateral surgical approach over a posterior approach. Our objective was to review outcomes from a consecutive series of Thompson hip hemiarthroplasty procedures performed in our unit and to identify any factors predicting the risk of complications. 807 Thompson hip hemiarthroplasty cases performed between April 2008 and November 2013 were reviewed. 721 (89.3%) were cemented and 86 (10.7%) uncemented. 575 (71.3%) were performed in female patients. The anterolateral approach was performed in 753 (93.3%) and the posterior approach with enhanced soft tissue repair in 54 (6.7%). Overall, there were 23 dislocations (2.9%). Dislocation following the posterior approach occurred in 13.0% (7 of 54) in comparison to 2.1% (16 of 753) with the anterolateral approach (odds ratio (OR) 8.5 (95% CI 2.8 to 26.3) p < 0.001). Surgeon grade and patient history of cognitive impairment did not have a significant impact on dislocation rate. Patients were discharged home in 459 cases (56.9%), to a care home or other hospital in 273 cases (33.8%). 51.8% (338 of 653) returned home within 30 days. 75 died during their admission (9.3%). 30-day mortality was 7.1% and 1-year mortality was 16.6%. Intraoperative fracture occurred in 15 cases (1.9%) of which 14 were cemented. Superficial or deep infection occurred in 33 cases (4.1%). We recommend against the continued use of the posterior approach in hip hemiarthroplasty, as enhanced soft tissue repair did not reduce dislocation rates to an acceptable level. Our findings, however, demonstrate satisfactory results for patients treated with the Thompson hip hemiarthroplasty performed through an anterolateral approach. We suggest that the continued use of the Thompson implant in a carefully selected patient cohort is justifiable

Aim. To review the outcome of deep prosthetic infection in patients following hip hemiarthroplasty surgery. Method. A retrospective case-note analysis was performed of deep infection coded hip hemiarthroplasty patients between 2004–2009. Patients were selected when there was proven microbiology from deep wound swabs or tissue specimens. Results. Deep infection developed in 14 of 1428 hemiarthroplasties. The mean age at time of fracture was 83 (71–93). There was a 12:2 female to male ratio. Eleven of the 14 cases had an American Society of Anaesthesiologists (ASA) score of three or four. Eight infections were due to Staphylococcus aureus, of which 6 were due to MRSA, which accounted for 43% of infections overall. There was no significant correlation between pathogen and success of treatment. Eight of the 14 hips were treated with open debridement and washout with implant retention. This was successful in 4 hips (50%). Infection recurred in 4 hips, one of which was revised to total hip replacement. The remaining 3 hips with recurrent infection were treated with excision arthroplasty. Three of the 14 hips were treated initially with excision arthroplasty. One required a further debridement and another required 3 debridements to control infection following implant removal. In 2 hips, a single stage revision to total hip replacement was performed. One of these developed recurrent infection, which was treated successfully with open debridement and washout. In one hip, no further surgery was performed. The 90-day mortality for patients with infected hemiarthroplasty was 36%. Conclusion. Deep infection following hemiarthroplasty of the hip has serious consequences and high mortality at 90 days. In our study sample, recurrence of infection was common and at least half required multiple operations. This study highlights the importance of infection prevention to reduce the morbidity and mortality following hip fracture surgery

Introduction. Geometric variations of the hip joint can give rise to abnormal joint loading causing increased stress on the articular cartilage, which may ultimately lead to degenerative joint disease. In-vitro simulations of total hip replacements (THRs) have been widely reported in the literature, however, investigations exploring the tribology of two contacting cartilage surfaces, and cartilage against metal surfaces using complete hip joint models are less well reported. The aim of this study was to develop an in-vitro simulation system for investigating and comparing the tribology of complete natural hip joints and hemiarthroplasties with THR tribology. The simulation system was used to assess natural porcine hip joints and porcine hemiarthroplasty hip joints. Mean friction factor was used as the primary outcome measure to make between-group comparisons, and comparisons with previously published tribological studies. Method. In-vitro simulations were conducted on harvested porcine tissue. A method was developed enabling natural acetabula to be orientated with varying angles of version and inclination, and natural femoral heads to be potted centrally with different orientations in all three planes. Acetabula were potted with 45° of inclination and in the complete joint studies, natural femoral heads were anatomically matched and aligned (n=5). Hemiarthroplasty studies (n=5) were conducted using cobalt chrome (CoCr) heads mounted on a spigot (Figure 1), size-matched to the natural head. Natural tissue was fixed using PMMA (polymethyl methacrylate) bone cement. A pendulum friction simulator (Simulator Solutions, UK), with a dynamic loading regime of 25–800N, ± 15° flexion-extension (FE) at 1 Hertz was used. The lubricant was a 25% (v/v) bovine serum. Axial loading and motion was applied through the femoral head and frictional torque was measured using a piezoelectric transducer, from which the friction factor was calculated. Results. The correct anatomical orientation and positioning was achieved enabling in-vitro simulation testing to be conducted on hemiarthroplasty and complete hip joint samples for two-hours. Mean friction increased rapidly followed by a continued gradual increase to ≈0.03 ± 0.00 in the complete joints, with the hemiarthroplasty group plateauing at ≈0.05 ± 0.01 (Figure 2). Mean friction factor was significantly lower (t-test; p < 0.05) in the complete natural joint group. Discussion. An in-vitro simulation system for the natural hip joint with controlled orientation of the femur and acetabulum was successfully developed and used to measure friction in complete porcine hip joints and porcine hip hemiarthroplasties. A non-linear increase in friction indicative of biphasic lubrication was observed in both groups with slower exudation of fluid from the complete joints compared to the hemiarthroplasties, inferring a quicker move towards solid-phase lubrication. Higher friction in the hemiarthroplasties, which was similar to that measured in-vitro in metal-on-polyethylene THRs, was most likely due to variable clearances between the non-conforming spherical metal head and aspherical acetabulum, causing poorer congruity and distribution of the load. This could in time lead to abrasive wear and cartilage degradation. This methodology could have an important role when investigating associations between hip geometric variations, interventions for hip disease/pathology, and risk factors for cartilage degeneration

Hip fractures are frequent due to osteoporosis and old age. The incidence of the second hip fracture had been reported as 5–9%. Subcapital displaced fractures in the elderly are treated sometimes with hip hemiarthroplasty. Our aims was to evaluate patients with bilateral no simultaneous hip fracture treated with hemiarthroplasty at our institution. Material and methods.- Twenty-two patients, 19 women and 3 men, were evaluated with a mean age of 79 at the initial fracture and 82 at the subsequent fracture. In 13 the first fracture was on the left and 9 on the right. All were of Garden grade IV. One of the fractures occurred from 1994 to 2003. The mean hospital stay was 18 days for the first fracture and 14 for the second. The second fracture happened a mean of 4 years after the first one (1 month to 9 years). This report is based on 14 of these patients, with more than one-year follow-up. The others 8, 6 had died and 2 were missing. Results.- Walking capacity: previous to the first fracture 11 walked more than 1000 meters, 3 between 100 and 500 meters. Outdoors: after the first fracture 6 walked without help, 3 used one cane and 3 used a walker or two canes, and 2 were unable. After the second fracture 1 walked without help, 2 used one cane, 5 used two canes or walker and 6 were unable. Indoors: after the first fracture 12 walked without help, 2 were able with the help of one cane, 2 with two canes. After the second fracture 2 walked without help, 3 used one cane, 7 used two canes or walker and 2 were unable to walk. Dressing: all were independent before; after the first 12 and after the second 7. Bathing: 13 were independent before, after the first 9 and after the second 5. Feeding: all were independent before, after the first 11 and after the second 6. Toilet: 13 were independent before, after the first 9 and after the second 4. Shopping: 11 were independent before, after the first 5 and after the second 0. Housekeeping: 11 independent before, 1 with help and 2 unable, after the first 4 were independent, 5 need help and 5 unable, and after the second 1 was able, 3 with help and 11 unable after the second. Public transport: 3 were able and 11 unable before the fracture, after the first fracture 3 were able and 11 unable, after the second fracture none was able, 2 with help and 12 unable. Finances: 2 were able and 12 unable before the fracture, after the first fracture 2 were able and 12 unable, and after the second 2 with help and 12 unable. Eight were limping and 6 had groin pain. Conclusion.- Previous to the first fracture walking capacity was good in this age group. Following the first hemiarthroplasty patients deteriorate in their walking capacity and others activities of daily life and much so after the second one. Limping or groin pain was present in all after the second fracture with more than one year follow-up

Introduction: The objective of our study was to analyse the incidence of subsidence of an uncemented, hydroxyapatite coated, collarless prosthesis (Orthodynamics) and its impact on postoperative mobility in patients with fractured neck of femur. Methods: 22 sets of case notes and X Rays were available for patients treated with the Orthodynamics hemiarthroplasty between February and November 2005. The mean age was 78 years (range 61 – 91 years). Analysis of standardised anteroposterior radiographs in the immediate postoperative period and at a mean interval of 14 weeks (ranging from 6 weeks to 64 weeks) was undertaken. Subsidence was calculated by measuring the reduction in the distance between the tip of lesser trochanter and a fixed point on the prosthesis. Results: 18 of the 22 (81.8 %) cases showed subsidence of the prosthesis. The mean subsidence calculated was 9.1 millimetres (range 1 to 25 millimetres) and it showed no relationship to the postoperative interval at which it was calculated. Impact of subsidence on mobility state was assessed. Post operative mobility status was available for sixteen patients. Nine patients showed no change in the mobility at follow up. This group had a mean subsidence of 4.3 mm. Seven patients had a worsening of their mobility state. The mean subsidence in this group was 10.1 mm. Discussion: Our study shows significant subsidence of an uncemented, collarless, hydroxyapatite coated prosthesis used for hip hemiarthroplasty and an associated worsening of mobility. We suggest that further review of this prosthesis is done and other proven prostheses used for hip hemiarthroplasty after a fractured neck of femur