Despite the growing success of OCA transplantation in treating large articular cartilage lesions in multiple joints, revisions and failures still occur. While preimplantation subchondral drilling is intended to directly decrease allograft bioburden and has been associated with significant improvements in outcomes after OCA transplantation, the effects of size, number, and spacing of subchondral bone drill sites have not been fully evaluated. This study aimed to investigate the effects of drill size with or without pulse-lavage of OCA subchondral bone by quantifying remnant marrow elements using histomorphometry. With IRB and ACUC approvals, human and canine OCAs were acquired for research purposes. Portions of human tibial plateau OCAs acquired from AATB-certified tissue banks that would otherwise be discarded were recovered and sectioned into lateral and medial hemiplateaus (n=2 each) with a thickness of 7 mm. Canine femoral condyles and tibial plateaus were split into lateral and medial components with a thickness of 7 mm (n=8). Using our clinical preimplantation preparation protocol, holes were drilled into the subchondral bone of each condyle and hemiplateau OCA using either 1.6 mm OD or 3.2 mm OD drill bits from the cut surface to the cortical subchondral bone plate. One femoral condyle and one hemiplateau per drill bit size were pulse-lavaged while the corresponding OCAs were not. The mean total %-fill remaining marrow elements for each treatment group was calculated. Little to no quantifiable bone marrow element retention was noted to remain within the subchondral bone of human or canine OCA specimens after subchondral drilling of allograft bone with either drill bit size evaluated and with or without pulse-lavage. The %-fill was consistent across zones, ranging from 1-5%. This project was designed to provide a preliminary histologic evaluation of the effects of drill size on OCA preimplantation preparation efficacy based on amount of remaining bone marrow elements in human and canine femoral condyle and tibial plateau specimens. Based on these initial findings, choice of drill bit size for OCA subchondral drilling may need to be based on the associated biomechanical effects rather than effects on donor bone marrow element removal

Aim. Prosthetic joint infection (PJI) presents the second most common complication of total joint arthroplasty (TJA). Accumulating evidence suggests that up to 20% of aseptic failures are low-grade PJI. However, there is still no single test to reliably diagnose all PJI. In his thesis, Mazzucco emphasized the viscosity differences between normal, osteoarthritic, and rheumatic synovial fluid. Similarly, a recent study by Fu et al. reported significantly lower viscosity in patients with PJI compared to the aseptic failure cohort. The primary aim of our study was to determine whether synovial fluid viscosity is a more reliable diagnostic criterion for PJI compared to the synovial fluid cell count with differential and serum C-reactive protein (CRP) levels. Method. We prospectively analyzed the viscosity of synovial fluid samples obtained during TJA of hip and knee joint revision procedures. We sampled 2.5–5 mL of synovial fluid for viscosity measurement. The samples were centrifuged (4 min at 7000 rpm) and the resulting supernatant was immediately transferred into the Ostwald viscometer. Viscosity was derived from the time required for a given volume of synovial fluid to pass the viscometer at 20 °C. The synovial fluid samples were also analysed for their cell count with differential and serum CRP was measured. The definite diagnosis of PJI was established on basis of EBJIS criteria. For the viscosity, the threshold for detecting PJI was set at 65 seconds. Results. Between December 2020 and March 2021, we analyzed 12 knee and 11 hip TJA revision samples. These included 14 septic and 9 aseptic synovial fluid samples. The average viscometer time in the PJI group was 31s (range 20–48s) compared to 247s (range 68–616s) in the group of aseptic revision procedures. The specificity and sensitivity of our viscosity measurements were 100%. The sensitivity and specificity of cell count was 100% and 85.7%, for the synovial fluid differential they were 100% and 85.7%, and for the CRP they were 88.9% and 71.4%, respectively. Conclusions. Our study is the first to report a significant difference in synovial fluid viscosity between the PJI and the aseptic cohort. It points towards the diagnostic superiority of viscosity measurements over conventional synovial fluid cell count, synovial fluid differential, and serum CRP levels. Albeit currently limited by small sample size, the study remains ongoing

Aims

Treatment outcomes for methicillin-resistant Staphylococcus aureus (MRSA) periprosthetic joint infection (PJI) using systemic vancomycin and antibacterial cement spacers during two-stage revision arthroplasty remain unsatisfactory. This study explored the efficacy and safety of intra-articular vancomycin injections for PJI control after debridement and cement spacer implantation in a rat model.

Aims

Unicompartmental knee arthroplasty (UKA) is a bone-preserving treatment option for osteoarthritis localized to a single compartment in the knee. The success of the procedure is sensitive to patient selection and alignment errors. Robotic arm-assisted UKA provides technological assistance to intraoperative bony resection accuracy, which is thought to improve ligament balancing. This paper presents the five-year outcomes of a comparison between manual and robotically assisted UKAs.

Aims

The Mathys Affinis Short is the most frequently used stemless total shoulder prosthesis in the UK. The purpose of this prospective cohort study is to report the survivorship, clinical, and radiological outcomes of the first independent series of the Affinis Short prosthesis.

The inmate population is a unique cohort with several healthcare-related challenges. International studies have demonstrated higher rates of infectious diseases, chronic diseases and psychiatric disorders in inmates when compared to general population. However, little is known about the outcomes following total joint arthroplasty in this population. This retrospective chart review aims to outline the differences in clinical outcomes after hip and knee total joint arthroplasty in the Kingston inmate population compared to the national population standard. A list of all inmate inpatient hospital visits with diagnostic/procedure codes pertaining to total joint arthroplasty within the last ten years was obtained through a computer-based search of the Kingston General Hospital Discharge Abstract Database(DAD). The patient charts were reviewed and demographic and outcome data pertinent to our study was collected. Data was compiled using Excel and imported into IBM SPSS for descriptive analysis. Twenty male inmate patients underwent 24 primary Total Hip Arthroplasties(THA) or Total Knee Arthroplasties(TKA) and one medial unicompartmental knee arthroplasty from May 2003 to January 2013. The average age was 58 with mean Body Mass Index(BMI) of 34. Median American Society of Anesthesiologist(ASA) score was 3 and mean Charlston Comorbidity Index was 3.92. The rates of HCV and HIV were 35%(n=5) and 0%, respectively. Average length of stay from time of initial procedure was 4.2 days. The overall revision rate was 24% (n=6). Reasons for revision included deep prosthetic infection (50%, n=3), aseptic loosening (17%, n=1), arthrofibrosis (17%, n=1) and late periprosthetic fracture (17%, n=1). Infection rates were reported at 16% (n=4); 75% of which were deep prosthetic infections requiring revision surgery. Other complications included ST-elevation myocardial infarction(STEMI) (n=1), and postoperative knee stiffness requiring manipulation under anesthesia(MUA) (n=1). Compared to Correctional Services Canada(CSC) data on male inmate health in 2012, our study population demonstrated a higher rate of HCV (35% vs. 9.4%), diabetes (30% vs. 4.2%) and overall cardiovascular and respiratory comorbidities. This may reflect the higher rate of comorbidities associated with osteoarthritis, such as BMI>25, which was evident in 95% of our study population vs. 64.5% in Canadian inmates. Total joint revision rates in our inmate study population was 24%, which is higher than the 2014 Canadian Joint Replacement Registry's yearly revision rate of 8.7% in THA and 5.2% in TKA. Our study population also demonstrated infection as the leading cause for revision at 50%, compared to 14.5% for THA and 19.6% for TKA in the general Canadian population. Further study of the complex biopsychosocial risk factors in the inmate population is warranted to better define pre-surgical risk assessment criteria

Periprosthetic joint infections are one of the most dreaded and complex complications of total joint arthroplasty, with fungal infection accountting for less than 1% of the cases. Treatment is challenging due to the lack of scientific evidence. We report a case of a Candida albicans total hip arthroplasty (THA) infection and performed a review of the literature. We report a case of a 79 year old women with an early THA infection (less of one month) from the primary surgery. She presented with pain and serous drainage from the operative wound and for that was submited to surgical debridement and revision of polyethilene. Cultures where taken (steril) and empirical vancomicin and rifampicin treatment was initiated. Because of persistent complains and drainage, the patient was submitted to another surgery. Cultures were taken at the time of surgery. A cement spacer impregnated with gentamicin was placed after implant removal. Cultures isolated Candida albicans. In light of this new evidence fluconazole was added to the previous scheme. After introduction of fluconazole, the clinical evolution was good. Drainage stoped 1 week after, and the wound closed. The inflammatory markers became normal shortly after. Leg pain became better. The patient was given oral suppressive treatment with fluconazole and was discharged, weight bearing as tolerated. A total of 4 mouths of treatment is programmed with close follow-up, untill the second staged revision is programmed. Prosthetic fungal infections are rare with most of the published articles being case reports. A substantial delay in diagnosis may occur because culture results are sometimes interpreted as contamination and there is a need for obtaining multiple samples, prolonged culture, and special staining. The best results are being reported with a long period of oral antifungal treatment and a two staged joint revision but there is an absence of standardized clinical and evidence-based treatment guidelines

Prosthetic joint infections (PJI) caused by Streptococcus species are relatively common. The aim of our study was to assess outcome after treatment for early and late PJI with Streptococcus species after a follow-up of two years. For this study we retrospectively included all patients with primary or revision total knee arthroplasty (TKA) or total hip (THA) arthroplasty, a minimum of two periprosthetic tissue cultures positive for Streptococcus species and a minimum follow-up of one year. According to international guidelines patients were classified as having early or late PJI. All patients with an early PJI were treated according to a standard treatment protocol, i.e. debridement and retention of the prosthesis, followed by adequate antibiotic therapy. Patients with late PJI underwent a debridement followed by adequate antibiotic therapy or joint revision. Patients’ hospital records were reviewed and we evaluated the status of the original prosthesis after an infection. Forty cases were included; 24 early and 16 late PJI. For early PJI, open debridement was performed in all patients, after a mean of 19 (range: 9 – 80) days. At final follow-up 21 prostheses (88%) were still in situ and without clinical signs of infection. Eight cases (41%) of late PJI were successfully treated with debridement and retention. Nine patients (59%) underwent a one- or two-stage revision. At final follow-up 16 patients (100%) with late PJI had a prosthesis in situ. Streptococcus dysgalactiae species accounted for more than 50% of the early infections, followed by Streptococcus agalactiae with 30%. In case of PJI with Streptococcus species open debridement and retention of the prosthesis should be performed followed by adequate and long-term antibiotic treatment. As expected, the retention rate for early PJI is much higher than that for late PJI

The surgical treatment of unicompartmental knee osteoarthritis remains controversial. This study aims to compare the medium-term outcomes of age and gender matched patients treated with unicompartmental knee replacement (UKR) and total knee replacement (TKR). We retrospectively reviewed pain, function and total knee society scores (KSS) for every UKR and age and gender matched TKR in NHS Tayside, with up to 10 years prospective data from Tayside Arthroplasty Audit Group. KSS was compared at 1, 3 and 5 years. Medical complications and joint revision were identified. Kaplan-Meier with revision as end-point was used for implants survival analysis. 602 UKRs were implanted between 2001 and 2013. Preoperative KSS for pain and total scores were not significantly different between UKRs and TKRs whereas preoperative function score was significantly better for UKRs. Function scores remained significantly better in UKRs from preoperative until 3 years follow up. Further analysis revealed no statistically significant difference in the change of function scores in both groups over time. There was a trend for TKRs to perform better than UKRs in pain scores. Total KSS for both groups were not significantly different at any point of the 5-year study. Fewer medical complications were reported in the UKR group. Kaplan-Meier analysis showed a survival rate of 93.7% in UKRs and of 97% in TKRs (Log rank p-value = 0.012). The revision rate for UKR was twice as much as TKR. The theoretical advantages of UKR are not borne out by the findings in this study other than immediate postoperative complications

Background. Total Knee Replacement (TKR) is technically demanding, time consuming and has higher complication rates in super obese (BMI>45) patients. Bariatric surgery can be considered for such patients prior to TKR although its effect on complications is unknown. Methods. All patients who underwent bariatric surgery and a TKR in the NHS in England between 2005 and 2009 were included. Hospital episode statistics data in the form of OPCS, ICD10 codes were used to establish 90-day DVT, PE and mortality rates (inpatient and outpatient). In addition, readmission to orthopaedics, joint revision and ‘return to theatre for infection’ rates were also established. Code strings for each patient were examined in detail to ensure the correct gastric procedures were selected. Fifty-three patients underwent bariatric surgery then TKR (44-1274 days) (group 1). Thirty-one patients underwent TKR then bariatric surgery (33-1398 days) (group 2). Results. In the 53 patients that underwent bariatric surgery first there was 1 DVT, no PE and 1 death at 90 days following knee replacement. There were no orthopaedic readmissions within one year of TKR, no revision at 18 months and no knee washouts for infection. In the 31 patients that underwent TKR first there were no DVT, PE or deaths at 90 days. There were four orthopaedic readmissions (12%) within 30 days of TKR and two infections of the knee replacement. Overall, one-year infection rate and readmission were higher if TKR was performed prior to the bariatric surgery. The statistical analysis is difficult due to small number of patients. Conclusions. This data suggests that timing of bariatric surgery appears to be crucial. Although complication rates appear high in patients who undergo both procedures, performing bariatric surgery first appears to reduce that risk of local complications

The use of new megaprosthesis for massive bone loss is an option for the replacement of skeletal segments. There are several clinical scenarios that can be associated with this situation including severe trauma with multiple failed osteosynthesis with a non union or with a previous prosthetic replacement of a neighbouring joint; multiple revision of arthroplasty with or without infections or large resections of tumours. The aim of this work is to evaluate retrospectively both clinical and radiological outcomes and any complications in patients treated with megaprosthesis in SEPTIC BONE DEFECTS in our Hospital from February 2012 to January 2015. From February 2012 to January 2014 a total of 20 patients were treated with mono-and bi-articular megaprosthesis subdivided as follows: 4 proximal femur, 11 distal femur, 3 total femur, 1 total humerus and 1 proximal humerus. Clinical and serial radiographic evaluations were performed at 6 weeks, 3, 6, 12, 18 and 24 months. Blood parameters with CRP and ESR were monitored for at least 2 months. The mean follow-up of patients was about 24.4 months (range 5 months to 31 months). The mean age of the patients was 53 years (range 37–80years). Of the patients 20, 9 were female and 11 were male. The aetiology was: 11 septic non unions, 3 infected TKA, 4 infected THR and 2 infected tumor prostheses. We have evaluated retrospectively both clinical and radiological outcomes of 20 patients. They had large bone defects that threatened the viability of the limb. They were treated with megaprosthesis. Although the mean length of follow-up was only 24.4 months they showed encouraging clinical results, with good articulation of the segments, no somato-sensory or motor deficit and acceptable functional recovery. There were three cases of dislocation, one case with rifampicin toxicity, one case with acute prosthetic infection (case that needed debridement and one case with chronic oral antimicrobial. Megaprosthesis provides a valuable opportunity to restore functionality to patients with highly disabling diseases. The number of complications is not depreciable

Finger arthroplasty lacks the success seen with hip and knee joint replacements. The Van Straten Leuwen Poeschmann Metal (LPM) prosthesis was intended for the proximal interphalangeal (PIP) joints. However revision rates of 30% after 19 months were reported alongside massive osteolysis. Three failed LPM titanium niobium (TiNb) coated cobalt chrome (CoCr) components were obtained- two distal and one proximal. All three components were analysed using an environmental scanning electron microscope (ESEM). This gave the chemical composition of the surface to determine if the TiNb surface coating was still intact. The distal components were analysed using a ZYGO non-contact profilometer (1nm resolution) with the proximal component unable to be analysed due to its shape. ZYGO analysis gave the roughness average (Ra) of the surface and determined the presence of scratches, pitting and other damage. Images obtained from both the ZYGO and the ESEM indicated that the surfaces of all components were heavily worn. On the articulating surfaces of both distal components unidirectional scratching was dominant, while the non-articulating surface showed multidirectional scratching. The presence of unidirectional scratching suggested two-body wear, whilst the multidirectional scratching on the non-articulating surface of the distal component suggested that trapped debris may have caused three-body wear. The ESEM chemical analysis showed that in some regions on the distal component the TiNb coating had been removed completely and in other areas it had been scratched or penetrated. On the proximal component the TiNb coating had been almost completely removed from the articulating surfaces and was only present in small amounts on the non-articulating surfaces. There was little evidence of bone attachment to the titanium coating which was intended to help provide fixation. ESEM images showed the coating had been removed in some sections where there was minimal scratching, suggesting this scratching did not impact significantly in the coating removal. Therefore here the main cause of coating removal may have been corrosion, although scratching may have also have played a part. The osteolysis reported clinically may have been linked to the wear debris from the failed coating

The number of joint revision surgeries is rising, and the complexity of the cases is increasing. In 58% of the revision cases, the acetabular component has to be revised. For these indications, literature decision schemes [Paprosky 2005] point at custom pre-shaped implants. Any standard device would prove either unfeasible during surgery or inadequate in the short term. Studies show that custom-made triflanged implants can be a durable solution with good clinical results. However, the number of cases reported is few confirming that the device is not in widespread use. Case Report. A patient, female 50 yrs old, diagnosed having a pseudotumor after Resurfacing Arthroplasty for osteo-arthritis of the left hip joint. The revision also failed after 1 y and she developed a pelvic discontinuity. X-ray and Ct scans were taken and sent to a specialized implant manufacturer [Mobelife, Leuven, Belgium]. The novel process of patient-specific implant design comprises three highly automated steps. In the first step, advanced 3D image processing presented the bony structures and implant components. Analysis showed that anterior column was missing, while the posterior column was degraded and fractured. The acetabular defect was diagnosed being Paprosky 3B. The former acetabular component migrated in posterolateral direction resulting in luxation of the joint. The reconstruction proposal showed the missing bone stock and anatomical joint location. In the second step, a triflanged custom acetabular metal backing implant was proposed. The bone defect (35ml) is filled with a patient-specific porous structure which is rigidly connected to a solid patient-specific plate. The proposed implant shape is determined taking into account surgical window and surrounding soft tissues. Cup orientation is anatomically analyzed for inclination and anteversion. A cemented liner fixation was preferred (Biomet Advantage 48mm). Screw positions and lengths are pre-operatively planned depending on bone quality, and transferred into surgery using jig guiding technology (Materialise NV, Leuven, Belgium). In the third step, the implant design was evaluated in a fully patient-specific manner in dedicated engineering (FEA) software. Using the novel automated CT-based methodology, patient-specific bone quality and thickness, as well as individualised muscle attachments and muscle and joint forces were included in the evaluation. Implants and jig were produced with Additive Manufacturing techniques under ISO 13485 certification, using respectively Selective Laser Melting (SLM) techniques [Kruth 2005] in medical grade Ti6Al4V material, and the Selective Laser Sintering technique using medical grade epoxy monomer. The parts were cleaned ultrasonically, and quality control was performed by optical scanning [Atos2 scanning device, GOM Intl. AG, Wilden, Switzerland]. Sterilization is performed in the hospital. CONCLUSION. A unique combination of advanced 3D planning, patient-specific designed and evaluated implants and drill guides is presented. This paper illustrates, by means of a clinical case, the novel tools and devices that are able to turn reconstruction of complex acetabular deficiencies into a reliable procedure

Introduction: Total hip arthroplasty (THA) has proven to be a highly successful procedure, but with its increased use there are an increasing number of joints requiring revision. A number of those patients requiring revision present with a severe loss of femoral bone stock around the failed femoral hip implant, which makes conventional revision techniques difficult or impossible. Materials and Methods: We have followed a consecutive series of forty-nine revisions THA (45 patients), performed for severe femoral bone loss using anatomic specific proximal femoral allografts longer than five centimetres. The patients mean age at the time of the index surgery was 63 (32–86) years. The patients were followed for a mean of 8.4 (5.2–16.6) years, with a five-year minimum follow-up. Results: The mean Harris Hip Score improved from 42.9 points preoperatively to 76.9 points at the last review. Fort-three of the hips (88%) had a successful outcome. Kaplan-Meier survivorship analysis predicted 83% rate of survival at 17 years. Six hips (12.2%) were further revised: four for non-union and aseptic failure of the implant, one for infection, and one for host step-cut fracture. Radiographicly, junctional union was observed in 44 hips (90%). Asymptomatic non-union of the greater trochanter were noticed in three hips (6.1%). Moderate allograft resorption was observed in five hips (10.2%), none were full-thickness graft resorption. The complications include trochanteric escape in three hips, host step-cut fractures in two hips, and four dislocations. Conclusion: We conclude that the good medium-term results with the use of large anatomic-specific femoral allografts justify their continued use in cases of revision hip arthroplasty with severe bone stock loss

We investigated the use of PCR (the Polymerase Chain Reaction) to detect the presence of infection in a group of patients undergoing revision arthroplasty for loose TJR (total joint replacement), compared to internationally agreed criteria used as the ‘gold standard’ for infection. We prospectively tested samples taken from 108 patients undergoing revision arthroplasty (76 hips, 32 knees). Antibiotics were omitted prior to obtaining samples. DNA was extracted by 2 methods – a previously published technique (reference) and a commercial extraction kit (Qiagen. ®. ). PCR involved amplification of an 882 base pair segment of the universal bacterial 16S RNA gene. During revision arthroplasty multiple specimens were taken from around the joint for microbiological and histological examination and the presence or absence of pus was noted. The patient was deemed to be infected if one of the following criteria was found: presence of a sinus pre-operatively; 2 or more intra-operative cultures positive for the same organism; an acute inflammatory response on histology; pus in the joint at revision. Using the published DNA extraction technique PCR had a sensitivity of 50%, specificity of 93%, positive predictive value of 67% and negative predictive value of 88%. Using commercial extraction the sensitivity improved to 60%, specificity to 98%, positive predictive value to 90% and negative predictive value to 90%. The previous report stated that PCR had a high sensitivity but a low specificity for detecting low grade infection. However, when using the published technique we found the opposite results – a moderate sensitivity and a high specificity. Introduction of a new DNA extraction technique improved the sensitivity. The refined PCR technique had a high accuracy, but further work is needed to improve sensitivity before we would recommend this method for routine clinical use

Aim: To assess medium term results of MOJE arthroplasty for degenerative Hallux Rigidus. Materials and Methods: Patients over 18 years of age with symptomatic degenerative hallux rigidus, with at least three years follow up were included in the study. Patients who had previous surgery for hallux rigidus were excluded. A press fit Moje ceramic on ceramic prosthesis was implanted using the standard technique. Patients were non-weight bearing for the initial two weeks followed by physiotherapy according to the Moje protocol. All patients were assessed radiologically and clinically using the AOFAS (American Orthopaedic Foot and Ankle Society) and Foot Function Index (FFI – R, short form) as the primary outcome measure and a Visual Analogue Pain score (VAS) as the secondary outcome measure. Radiological assessment was carried out independently by two authors. Prosthesis loosening was defined as more than 5mm subsidence (sum of proximal and distal components), implant tilting and presence of osteolytic lesions. Revision of arthroplasty was taken as an end point to define failure. Results: 27 Moje replacements of the first metatarso-phalangeal joint in 25 patients operated by one surgeon were included in the study. There were 22 female and 3 male patients with a mean age of 61 (range: 48–83). Mean preoperative range of movement (sum of dorsi and plantar flexion) was 310 (range: 10–65). Mean preoperative FFI – R score was 100 (range: 53–183); mean preoperative AOFAS score was 45 (range: 28–64); mean preoperative VAS was 8 (range: 3–10). The average follow up was 49 months (range: 36–60). There were no wound complications. Postoperatively, 5 joints (19%) required closed manipulation and 3 joints (11%) required open arthrolysis to improve the range of movement. Three joints (11%) drifted into valgus, two of them requiring a corrective Akin osteotomy of the proximal phalanx. One patient (4%) required open reduction for dislocation and one patient required excision of the medial sesamoid for persistent pain. In all, 12 replacements (44%) were symptomatic enough to require a further procedure. None of the joints required revision. The mean postoperative range of movement was 350 (range: 15–60, p=0.85, Relative Risk=1.069, 95% Confidence Interval: 0.72–1.59). There was improvement in postoperative FFI–R score (mean: 41, Range: 27–66, p=0.007, RR=0.53, 95% CI: 0.34–0.83), AOFAS score (mean: 83, range: 68–100, p=0.07, RR: 1.5, 95% CI: 0.98–2.38) and VAS (mean: 1, range: 0–5, p=0.04, RR: 0.80, 95% CI: 0.0.66–0.97). Radiologically, there were signs of loosening of prosthesis in 4 joints (15%) without an adverse outcome in pain and functional scores. Discussion: There is a high incidence of stiffness requiring further surgical procedure to improve the range of movement following this replacement. Although pain and function scores improve with Moje arthroplasty, patients should be counselled that their range of movement may not improve and annual long-term clinical and radiological surveillance would be necessary to assess the integrity of this prosthesis. Further studies including larger number of patients with longer follow up are required to assess the long-term results of this procedure

Pre-revision detection of infection in failed total joint replacements (TJR) is essential to allow appropriate management planning. Unfortunately, low-grade infection is often difficult to detect. The use of molecular biology may offer increased sensitivity in this setting. We have analysed the use of the Polymerase Chain Reaction (PCR) to diagnose infection in pre-operative aspirates in a group of patients undergoing revision arthroplasty. We prospectively tested 50 aspirates in 50 patients with failed TJR (34 hips and 16 knees). Antibiotics were omitted for 2 weeks prior to aspiration. The aspirate was sent for microbiological culture in aerobic and anaerobic conditions. An aliquot was retained for PCR analysis which involved DNA extraction then amplification of an 882 base pair segment of the Universal 16S RNA gene. In 33 patients who subsequently underwent revision arthroplasty multiple specimens were taken from around the joint for microbiological and histological examination and the presence or absence of pus was noted. The patient was deemed to be infected if one of these criteria was found: 2 or more intra-operative cultures positive for the same organism; an acute inflammatory response on histology; pus in the joint at revision . 1. . PCR was positive in 29 cases. Aspiration microbiology was positive in 13 cases. Of the 33 cases revised, 15 patients were deemed to be infected using the previously established criteria, described above. Compared to preoperative aspiration microbiology PCR had a sensitivity of 92% and specificity of 54%. Compared to the published criteria for infection, PCR was 93% sensitive and 61% specific. If rheumatoid cases are excluded the specificity improves to 71%. It was concluded that PCR has the ability to amplify very small amounts of target DNA. The apparently high false positive rate compared to aspiration microbiology may indicate that PCR is picking up DNA from contaminating or non-viable organisms (treated or phagocytosed), giving poor specificity. However, microbiology is known to have poor sensitivity on pre-operative aspiration samples, and some of the microbiology results may be false negative. Compared to the criteria for infection after revision our results for PCR are more encouraging, especially for non-rheumatoid patients. These patients are part of an ongoing study to identify the most reliable criteria for pre-operative diagnosis of infection in total joint replacement

Detection of infection in total joint replacements (TJR) is notoriously difficult. Ideally the diagnosis should be known before revision arthroplasty is undertaken. The level of C-reactive protein (CRP) is one readily available test. Sanzen et al. reported sensitivity of 78% and specificity of 100% for CRP in distinguishing infection in 23 infected TJRs and 33 non-infected TJRs undergoing revision, using a cut off of 2mg/dl. 1. However, they used only intra-operative cultures as the standard to compare the CRP against. We have analysed the reliability of CRP to diagnose infection pre-operatively in a group of patients undergoing revision arthroplasty, using the following criteria as the reference standard for infection: 2 or more intra-operative cultures positive for the same organism; presence of acute inflammatory response on histology; presence of pus in the joint at revision (1/3 positive indicates true infection), as described by Hanssen et al. 2. The results of CRP and the operative investigations of 26 patients undergoing revision arthroplasty (15 hips and 11 knees) were studied prospectively. In our unit CRP is assayed in mg/dl serum by an automated machine. During revision arthroplasty, multiple specimens were taken from around the joint for microbiological and histological examination. Microbiological cultures were carried out on solid media and broth in aerobic and anaerobic conditions. Histological analysis assessed the level of neutrophils present in the tissue. The presence or absence of pus was noted. The results were analysed graphically and a cut off level of CRP was then chosen for analysis of reliability. Thirteen patients were infected and 13 were not. Eleven of the 13 infected patients had a CRP greater than 2 mg/dl, and 10 of the 13 non-infected patients had a CRP less than 2 mg/dl. Using 2 mg/dl as a cut off, CRP had a sensitivity of 85% and a specificity of 77%. If 4mg/dl is taken as the threshold for infection, then CRP is 100% specific but only 61% sensitive. CRP is a useful investigation in the diagnosis of infection in joint replacements. However we have shown that a cut off of 2mg/dl is not 100% specific for non-infected patients. Increasing the threshold improves the specificity, but reduces the sensitivity. Unfortunately there is no single investigation that is 100% accurate in this setting. CRP results must be interpreted in the light of the clinical picture and other investigations. These patients are part of an ongoing study to identify the most reliable criteria for diagnosing the presence of infection in total joint replacement