Aim

The duration of systemic antibiotic therapy following first-stage surgery is contentious. Our Institution's philosophy is to perform an aggressive debridement, use high concentration targeted antibiotics through cement beads and systemic prophylactic antibiotics alone. In the presence of significant soft tissue infection or microbiological diagnostic uncertainty; systemic antibiotics may be prescribed for 5 days whilst awaiting tissue culture results. The aim of this study was to assess the success of our philosophy in the management of PJI of the hip using our two-stage protocol.

The duration of systemic antibiotics following first-stage surgery is contentious. Our Institution's philosophy is to perform an aggressive debridement, high concentration of targeted antibiotics through cement beads and systemic prophylactic antibiotics alone. In the presence of significant soft tissue infection or microbiological diagnostic uncertainty; systemic antibiotics may be prescribed for 5 days whilst awaiting tissue culture results. The aim of this study was to assess the success of our philosophy for two-stage hip revision.

A retrospective review of our Institution's prospective database was performed to identify all intended two-stage hip revision procedures for PJI. All patients had a confirmed PJI as per MSIS 2013 criteria, minimum 5-years follow up and outcomes according to the MSIS working group outcome-reporting tool; then grouped into “successful” or “unsuccessful” (suppressive antibiotics, further revision for infection, death within 1 year).

383 intended two-stage hip revisions were identified; of which 299 met our inclusion criteria, in 289 patients (6 repeat ipsilateral two-stage, 4 bilateral two-stage). Median follow up was 10.7 years (IQR 6.3 – 15.0). 258 (86%) patients proceeded to 2^nd stage surgery. 91% success rate was observed for those patients who underwent reimplantation, although dropping to 86% when including the patients who did not proceed to second stage. The median duration of post-operative systemic antibiotics was 5 days (IQR 5–9). No significant difference was observed in patients who received either; < / = 48 hours (86%; n=70) compared to > 48 hours antibiotics (86%; n=229; p=0.96) or </= 5 days of antibiotics (88%; n=202) compared to > 5 days antibiotics (82%; p=0.38). A significant majority had gram-positive (88%) infection with 30% being polymicrobial. Greater success rates were observed with two-stage exchange or gram-positive PJI (86%); than for gram-negative PJI (81%) and polymicrobial infection (74%) (p=0.36). Fungal PJI was observed to have a significantly reduced rate of success (n=3; 33%; p=0.03).

Aggressive surgical debridement with high concentration, targeted local antibiotic delivery at time of first stage to manage PJI of the hip provides a high rate of success, responsible antibiotic stewardship and reduced hospital costs.

Aims

The aim of this study was to develop a single-layer hybrid organic-inorganic sol-gel coating that is capable of a controlled antibiotic release for cementless hydroxyapatite (HA)-coated titanium orthopaedic prostheses.

No single test is 100% sensitive and specific for the diagnosis of prosthetic joint infection. Joint aspiration is currently the only preoperative investigation that can establish the identity of the infecting organism and its antibiotic susceptibilities. Frequently when attempting to aspirate a joint a ‘dry tap occurs as fluid cannot be aspirated. In this situation, normal saline may be injected into the joint and then reaspirated to provide fluid for culture.

The aim of this study was to ascertain the diagnostic accuracy of culture of joint aspiratie with or without saline reaspiration in the event of a dry tap.

A retrospective analysis of 580 hip and knee aspirations in patients deemed to have moderate-high risk of infection and ultimately proceeded to revision arthroplasty over 12 years at a large quaternary referral centre where pre operative aspiration is routine.

Fluid was aspirated in 313 (54%) cases and dry taps in which saline injection reaspiration was performed occurred in 267 (46%) cases. Overall sensitivity and specificity of diagnostic aspiration were 84% (78–89%) and 85% (81–88%) respectively. Sensitivity and specificity of saline injection-reaspiration after dry tap were 87% (79–82%) and 79% (72–84%) compared to 81% (71–88%) and 90% (85–93%) for direct aspiration.

Pre operative joint aspiration and culture is a sensitive and specific test for the confirmation of diagnosis in patients at a moderate to high risk of prosthetic joint infection. Culture of saline injection-reaspiration also provides accurate diagnostic information in the event of a dry tap. Both methods allow susceptibility testing of relevant organisms and are therefore able to guide peri-operative and cement instilled antibiotic therapy.

Culture of pre operative joint aspirates provides sensitive and specific diagnostic information including antimicrobial susceptibility results.

Saline injection-reaspiration is a useful additional technique in those patients in whom fluid cannot be aspirated.

The management of periprosthetic joint infection is challenging and the duration of systemic antibiotic therapy whether it be during the interval phase or after reimplantation of a new prosthesis is controversial. We report our experience of managing chronic periprosthetic infection of the hip by the two stage exchange procedure.

Patients who were scheduled to undergo a two stage revision for chronic periprosthetic infection of the hip were identified from our prospective database.

Of 425 patients with microbiologically proven periprosthetic infection, 369 (87%) underwent a two stage procedure, leaving 56 patients who did not proceed to reimplantation. 41 of these were clinically infection free but for personal or medical reasons did not proceed. The remaining 15 had persistent infection. The mean age at the time of the first stage was 68 years (26 – 92 yrs). 256 (61%) patients were alive for review. The mean time between stages was 6.3 months with a mean follow up after the second stage was 65 months (range 5 to 276 months).

The success rate of a single 1^st stage debridement, confirmed by negative cultures at the time of second stage reimplantation was 94%. 19 patients underwent a repeat 1^st stage debridement and were classed as failures of the 1^st stage. At the time of final review, 340 (92%) patients were deemed infection free out of those who had completed a 2 stage exchange.

The duration of systemic antibiotic treatment after both the 1^st and 2^nd stages was divided into <48 hrs and >48 hours. There was no significant difference in the success of the 1^st stage procedure in patients who received < 48 hours (48% of the patients) as opposed to > 48 hours (p = 0.98, Chi Squared Test, Relative Risk 1.009). Similarly there was no difference in the overall success of the two stage procedure irrespective of the duration of antibiotic therapy with 76% of patients receiving <48hrs of antibiotics after the second stage.

Aggressive surgical debridement together with targeted local and short term systemic antibiotic therapy should be the mainstay of treatment in two stage revision surgery.

Introduction

Data on the outcome of THA in patients under the age of 30 years is sparse. There is a perceived reluctance to offer surgery to young patients on the basis of potential early failure of the implant. We aim to review our experience with THA in this group of patients to establish outcomes in a high volume specialist arthroplasty unit.

Introduction

Tantalum trabecular metal components are increasingly used to reconstruct major bone defects in revision arthroplasty surgery. It is known that some metals such as silver have antibacterial properties. Recent reports have raised the question as to whether Tantalum components are protective against infection in revision surgery. This is based on a retrospective, single institution review, of revision cases comparing tantalum with titanium acetabular implants, which reported a lower incidence of subsequent infection in the tantalum group.

This laboratory study aimed to establish if tantalum had any intrinsic antibacterial properties against planktonic bacteria or ability to inhibit biofilm formation.

Background

An extended trochanteric osteotomy (ETO) is a widely used approach for revision hip arthroplasty. Following an ETO it is common practice to use a long stemmed femoral prosthesis at the second stage to bypass the osteotomy. We propose that at the second stage, if the osteotomy has united, it is appropriate to use a standard length prosthesis, which preserves bone stock for any future revisions.

Introduction

Vancomycin is commonly added to acrylic bone cement during revision arthroplasty surgery. Proprietary cement preparations containing vancomycin are available but significantly more expensive. We investigated whether the antibiotic elution and mechanical strength of ‘home-made’ vancomycin containing bone cement was comparable to commercial vancomycin-impregnated cement.

Background and objectives

Local bone-related adverse events occur more frequently following metal-on metal hip resurfacing (MOMHR) versus convention total hip arthroplasty (THA). High local tissue levels of cobalt and chromium may contribute to impaired bone health, however the systemic effects on bone of exposure to elevated metal levels after MOMHR are unknown.

Measurements of biochemical markers of bone turnover have been explored as a diagnostic tool for the detection of osteolysis after THA, but their predictive value in individual subjects has been poor. One explanation for this low diagnostic utility is that the mechanism of bone resorption in osteolysis may be different to that occurring in other high bone turnover states, such as osteoporosis, where these markers were principally developed. The aim of this study was to examine the role of the biomarkers urinary ααCTX-I and serum CTX-MMP, that are released in pathological rather than physiological bone turnover states, for detecting periprosthetic osteolysis in a case control study of 23 subjects with osteolysis and 26 controls. All samples were collected between the hours of 0800 and 1000 following an overnight fast, and were assayed using standard techniques. The demographic characteristics of the subjects in both groups were similar. Serum CTX-MMP was greater in the osteolysis versus the control group (P=0.001). Urinary ααCTX-I was similar between osteolysis and control groups (P> 0.05). A cut-off value of 5.50ng/mL CTX-MMP had a sensitivity of 91% (95% CI: 72 to 99) and specificity of 69% (48 to 96) detecting osteolysis (P=0.001). The same cut-off had a sensitivity of 100% (100 to 100) and specificity of 63% (44 to 79) for detecting femoral osteolysis (P=0.0004), and a sensitivity of 89% (65 to 98) and specificity of 58% (39 to 75) for identifying pelvic osteolysis (P=0.014). Serum CTX-MMP shows promise for further investigation as a sensitive bio-marker for detecting periprosthetic osteolysis.

In this 2-year randomised clinical trial we examined whether cemented femoral prosthesis geometry affects the pattern of strain-adaptive bone remodelling in the proximal femur after THA. 128 patients undergoing primary THA were randomised to receive a Charnley (shape-closed, no taper), Exeter (force-closed, double-tapered) or C-stem (forced-closed, triple-tapered) prosthesis. All received a cemented Charnley cup. Proximal femoral BMD change over 2 years was measured by DXA. Urine and serum samples were collected at pre-operative baseline and over 1 year post-operatively. N-telopeptides of type-I-collagen (NTX) was measured in urine as a marker of osteoclast activity and Osteocalcin (OC) in serum as a maker of osteoblast activity. Clinical outcome using the Harris and Oxford hip scores, and prosthesis migration measured using digitised radiographs (EBRA-Digital) were measured over 2 years. The baseline characteristics of the subjects in each group were similar (P> 0.05). Decreases in femoral BMD were observed over the first year for all prosthesis designs. Bone loss was greatest (14%) in the proximal medial femur (region 7). The pattern and amount of bone loss observed was similar between all prosthesis designs (P> 0.05). Transient rises in both osteoclast (NTX) and osteoblast (OC) activity also occurred over year 1, and were similar in pattern in the 3 prosthesis groups (p> 0.05). All prostheses showed migration patterns that were true to their design type and similar improvements in clinical hip scores were observed over the 2 year study. Differences in the proposed mechanism of load transfer between prosthesis and host bone in force-closed versus shape-closed femoral prosthesis designs in THA are not major determinants of prosthesis-related remodelling.

Introduction: Polymorphisms within genes encoding bone regulatory cytokines influence individuals’ susceptibility to osteolysis after THA. We aimed to determine whether single nucleotide polymorphisms (SNPs) within these genes influence the severity of these osteolytic lesions in 272 patients with established aseptic loosening.

Methods: Assessment of osteolytic lesions was made from pre-revision radiographs in conjunction with direct visualisation in those subjects undergoing surgery. Osteolytic lesions were defined as linear (AAOS pelvic and femoral osteolysis classification grade 0) or expansile, in the presence of segmental or cavitary defects (AAOS grade 1 or greater). We analysed 11 SNPs in the pro-inflammatory cytokines IL-1A, IL-1B, IL-1RA, IL-6 and TNF; 2 SNPs within the FRZB gene, which modulates osteoblast function; and 6 SNPS in the RANK/RANKL/OPG pathway, that modulates osteoclast function.

Results: Femoral Osteolysis: Carriage of the IL-6 −174C allele was 60% in the expansile osteolysis group versus 80% in the linear osteolysis group (χ2 test p=0.007). Carriage of the OPG −163G allele was 34% in the expansile osteolysis group versus 18% in the linear group (χ2 test p=0.03). The odds ratios for expansile osteolysis associated with carriage of IL-6-174G and OPG −163G were 2.7 (1.3 to 5.7, p=0.008) and 2.3 (1.1 to 5.0, p=0.03) respectively.

Acetabular Osteolysis: No differences in SNP genotype were found between osteolysis groups.

Discussion: The IL-6-174G allele and the OPG-163G allele are over-represented in subjects with expansile femoral versus linear osteolysis, but do not relate to severity of pelvic osteolysis. These differences in association may reflect differences in the mechanism of osteolysis between the bone sites, however, replication of the results are required to confirm this differential association.

Introduction: Between 1990 and 2000 we reconstructed 123 hips in 110 patients using impaction bone grafting with frozen, morsellised irradiated femoral heads and cemented sockets. This review presents the medium to long term survivorship of irradiated allograft in acetabular reconstruction in our cohort of patients.

Patients and Methods: Patients were reviewed in out-patients. Radiographs were examined for union, lucency and component migration.

The mean age at revision with allograft was 64.3 years (26 to 97). 86 hips (70%) in 74 patients were reviewed both clinically and radiologically.

At the time of review 28 patients (29 hips) had died and 5 patients (5 hips) were lost to follow up. Of those patients who had died 18 hips had been followed up to a mean of 66 months (12–145). A further 3 hips were unable to attend for clinical review but had accurate implant-allograft survivorship data.

Their data were included in survivorship analysis to the time of last clinical review.

Results: There have been 19 revisions; 9 for infection, 7 for aseptic loosening and 3 for dislocation. In surviving acetabular reconstructions, union of the graft had occurred in 64 out of 67 hips (95.5%). Radiolucent lines at the bone cement interface were seen in 12 hips (17.9%; 9 in a single DeLee zone and 3 in multiple zones) but none were considered loose. Migration of the acetabular component greater than 5mm was seen in 3 hips (4.5%). Survivorship analysis using revision as an end point for all indications at 10 years was 83.3% (95% C.I. 68 to 89%) and 71.3% (95% C.I. 58 to 84%) at 15 years

Conclusion: Acetabular reconstruction using irradiated allograft and a cemented cup is an effective reliable technique with good results in the medium to long term comparable to series using non irradiated freshly frozen bone.

Introduction: Between 1987 and 1997 we implanted 319 primary hybrid total hip arthroplasties in 289 patients using the ‘Plasmacup’ (B. Braun Ltd, Sheffield) with a conventional metal on polyethylene articulation. We have observed a high revision rate with this implant recently and therefore undertook a clinical review of this cohort.

Patients and Methods: The indications for surgery were osteoarthritis (223), secondary arthritis (83), inflammatory arthritis (10), and others (3). 17 patients have died and 20 have been lost to follow up. Survival analysis was calculated using implant failure defined as revision (including liner exchange), and includes the censored patients outlined above. Assessment of complications in surviving implants was made using AP radiographs of the hip.

Results: The cup survival rate (Kaplan-Meier method) was 91% at 10 years (95%CI ± 4%) and 67% at 13 years (95%CI +/−9%). The stem survival rate was 96% at 10 years (95%CI +/−3%) and 87% at 13 years (95%CI +/−7%). The median wear in cup revisions for osteolysis was 2.4mm (IQR 1.0–3.2mm), and the median wear in surviving cups was 1.3 mm (IQR 0.8 1.9mm), and was an independent predictor of failure (Cox: p=0.001). There have been 57 revisions (35 cup only, 18 cup and stem, 4 stem only). Indications for revision were osteolysis or loosening (34), wear (18), and infection (5). In surviving cups (214), 29 have expansile acetabular osteolysis and 8 have linear osteolysis. In surviving stems (244), 14 have expansile osteolysis and 23 have linear osteolysis.

Conclusions: There is a high late failure rate of the plasma cup using a conventional metal on polyethylene articulation. Patients with this implant/bearing combination should be closely monitored, particularly after 10 years.

Introduction: The use of prolonged courses of parenteral or oral antibiotic therapy in combination with a two-stage exchange procedure in the management of the infected total hip arthroplasty is reported by many major series.

Methods: We present a series of 114 patients, all with microbiologically proven chronic deep infection, treated with a two-stage exchange with antibiotic loaded cement and where a prolonged course of antibiotic therapy has not been used. The mean follow-up for all patients is 74months (range 2–175months) with all surviving patients having a minimum 2 year follow-up.

Results: Infection was successfully eradicated in 100 patients (88%). The infection cure rate in our series is similar to that reported elsewhere where prolonged adjuvant antibiotic therapy was used.

Discussion: Using the technique described a prolonged course of systemic antibiotics does not appear to be necessary; the high costs of antibiotic administration, both to the patient and care facility are not incurred.

Introduction: There are few published reports outlining the outcome of those patients who have undergone revision hip arthroplasty surgery for recurrent infection.

From a consecutive series of 114 patients who had undergone a two-stage exchange without prolonged antibiotic therapy we report the outcome of those patients who continued to have persistent infection.

Methods: Fourteen patients were identified, all with microbiologically proven recurrent deep infection. Seven patients have undertaken further attempts at cure by a two-stage exchange and where again a prolonged course of antibiotic therapy was not routinely used. Infection was eradicated in six out of the seven patients (84%). The mean follow-up of this group is 90 months (range 25–150 months).

Results: From the initial series an overall cure rate of 93% was seen. The other patient has a pseudarthrosis.

Seven patients elected not to undergo a further two-stage revision. Five patients have retained their arthroplasty with lifelong suppressive antibiotic therapy. One has a pseudarthrosis and one disarticulation has taken place for inadequate tissue cover.

Discussion: This series would suggest that in patients willing to undertake further surgery in an attempt to eradicate infection they stand a good chance of a successful outcome.

Introduction: The concept that aseptic loosening is a function of polyethylene wear has led to the introduction of cross-linked polyethylene in THA. We studied the relationship between polyethylene wear rate and aseptic loosening to model the potential effects of wear-reducing strategies on the failure rate for each prosthetic component.

Methods: 350 subjects who had previously undergone Charnley THA were divided into 3 groups: Controls (n=273); isolated femoral stem looseners (n=43); and isolated cup looseners (n=34). Polyethylene wear was measured using a validated method (EBRA). The relationship between wear rate and loosening was examined using logistic regression analysis, and estimates of the effect of wear rate modulation made using odds-ratios (OR ).

Results: The median annual wear rate in the controls (0.07mm) was lower than both stem looseners (0.09mm, p=0.002) and cup looseners (0.18mm, p< 0.001). The OR of cup loosening increased 4.7 times per standard deviation (SD) increase in wear rate above the reference (control) population (p< 0.001). The OR of stem loosening increased 1.7 times per SD, but was not independent of other risk factors (p> 0.05). The potential reduction in risk of loosening was calculated using the following formula: (OR ^SD2)/(OR ^SD1), where 1 and 2 are the predicted mean z-score wear rates of modified versus conventional polyethylene. Thus, for a 25% or 50% reduction in wear rate, the incidence of cup loosening may reduce by 71% and 293%, respectively. The rate of stem loosening may reduce by 7% and 17%, respectively.

Discussion: The use of cross-linked-polyethylene has the potential for a major impact on the incidence of cemented cup loosening. However their effect on femoral stem loosening may be limited.

Introduction: Bone phenotype, such as osteoarthritis (OA) pattern and development of osteolysis or heterotopic ossification (HO) after THA, may be governed by genetic and environmental factors. We investigated whether single nucleotide polymorphisms within the gene encoding secreted-Frizzled Related Protein-3, FRZB Arg200Trp and FRZB Arg324Gly influence bone phenotype.

Methods: Genomic DNA was extracted from 609 subjects at a mean of 11 years following cemented THA for idiopathic osteoarthritis. Pre-operative OA was defined using The American College of Rheumatology criteria and post operative HO after primary THA was assessed using Brooker’s classification

Results: For FRZB Arg200Trp, minor allele carriage (MAC) was greater in subjects with pre-operative pelvic osteophytes (n=267) versus those without osteophytes (n=34) (MAC 27.9% versus 6.3%, Fisher’s exact test p=0.037). There were no associations with other radiographic criteria of OA. MAC was also higher in HO+ve subjects (n=291) versus HO-ve subjects (n=341), (MAC 21.7% versus 12.0%, χ² test p=0.063). Finally MAC was 14.2% in osteolysis +ve subjects (n=268) and 21.7% in osteolysis –ve subjects (n=341) (χ² test p=0.041).

The adjusted odds ratios for pelvic osteophytes and HO with carriage of the rare FRZB 200 variant were 4.34 (1.01–18.7 p=0.048) and 1.64 (1.05 to 2.54, p=0.028) respectively. The adjusted odds ratio for osteolysis was 0.62 (0.38 to 0.99 p=0.049).

There were no bone phenotype associations with the FRZB Arg324Gly variants.

Discussion: Carriage of the FRZB 200Trp allele is positively associated with osteophyte and HO formation and negatively associated with osteolysis, suggesting this locus may be a marker for pro-osteoblastic activity.

Introduction: Bone cements produced by different manufacturers vary in their mechanical properties and antibiotic elution characteristics. Small changes in the formulation of a bone cement, which may not be apparent to surgeons, may also affect these properties. The manufacturing method of Palacos bone cement with added gentamicin has recently changed. We have carried out a study to examine the mechanical characteristics and antibiotic elution of Schering-Plough Palacos (‘old’ version), Heraeus Palacos (‘new’ version) and Depuy CMW Smartset bone cements.

Methods: Schering-Plough Palacos R40G (contains 0.5g gentamicin per 40g mix), Heraeus Palacos R+G (contains 0.5g gentamicin per 40g mix) and Depuy-CMW Smartset GHV (contains 1g gentamicin per 40g mix) were used. 40g samples of the three cements with no additional vancomycin, 1g and 2g vancomycin were prepared by a standard method using vacuum mixing in a syringe. Antibiotic elution over a five week period was measured using an immunoassay method. Standard mechanical testing was carried out according to methods defined in ISO 5833.

Results: Both Heraeus Palacos and Smartset bone cements performed significantly better than Schering-Plough Palacos in terms of mechanical characteristics both with and without additional antibiotics. All cements show a deterioration in flexural strength with increasing addition of vancomycin although staying above ISO minimum levels. Both Heraeus Palacos and Smartset elute significantly more gentamicin cumulatively than Schering-Plough Palacos. Smartset elutes significantly more vancomycin cumulatively compared with Heraeus Palacos.

Discussion: Both Heraeus Palacos and Smartset Bone cements elute significantly more gentamicin than Schering-Plough Palacos with no deterioration in mechanical characteristics. Smartset also elutes significantly more vancomycin than Heraeus Palacos without adverse affect on mechanical characteristics. Although marketed as the ‘original’ Palacos, Heraeus Palacos has significantly altered mechanical and antibiotic elution characteristics compared with previous versions.