Aims. This study aims to enhance understanding of clinical and radiological consequences and involved mechanisms that led to corrosion of the Precice Stryde (Stryde) intramedullary lengthening nail in the post market surveillance era of the device. Between 2018 and 2021 more than 2,000 Stryde nails have been implanted worldwide. However, the outcome of treatment with the Stryde system is insufficiently reported. Methods. This is a retrospective single-centre study analyzing outcome of 57 consecutive lengthening procedures performed with the Stryde nail at the authors’ institution from February 2019 until November 2020. Macro- and microscopic metallographic analysis of four retrieved nails was conducted. To investigate observed corrosion at telescoping junction, scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDX) were performed. Results. Adjacent to the nail’s telescoping junction, osteolytic changes were observed in bi-planar radiographs of 20/57 segments (35%) after a mean of 9.5 months (95% confidence interval 7.2 to 11.9) after surgery. A total of 8/20 patients with osseous alterations (40%) reported rest and ambulation pain of the lengthened segment during consolidation. So far, 24 Stryde nails were retrieved and in 20 (83%) macroscopic corrosion was observed at the nail’s telescoping junction. Before implant removal 11/20 radiographs (55%) of lengthened segments with these 20 nails revealed osteolysis. Implant retrieval analysis by means of SEM showed pitting and crevice corrosion. EDX detected chromium as the main metallic element of corrosion. Conclusion. Patients are exposed to the risk of implant-related osteolysis of unclear short- and long-term clinical consequences. The authors advocate in favour of an early implant removal after osseous consolidation. Cite this article: Bone Joint Res 2021;10(7):425–436

Peri-prosthetic osteolysis and subsequent aseptic loosening is the most common reason for revising total hip replacements. Wear particles originating from the prosthetic components interact with multiple cell types in the peri-prosthetic region resulting in an inflammatory process that ultimately leads to peri-prosthetic bone loss. These cells include macrophages, osteoclasts, osteoblasts and fibroblasts. The majority of research in peri-prosthetic osteolysis has concentrated on the role played by osteoclasts and macrophages. The purpose of this review is to assess the role of the osteoblast in peri-prosthetic osteolysis. In peri-prosthetic osteolysis, wear particles may affect osteoblasts and contribute to the osteolytic process by two mechanisms. First, particles and metallic ions have been shown to inhibit the osteoblast in terms of its ability to secrete mineralised bone matrix, by reducing calcium deposition, alkaline phosphatase activity and its ability to proliferate. Secondly, particles and metallic ions have been shown to stimulate osteoblasts to produce pro inflammatory mediators in vitro. In vivo, these mediators have the potential to attract pro-inflammatory cells to the peri-prosthetic area and stimulate osteoclasts to absorb bone. Further research is needed to fully define the role of the osteoblast in peri-prosthetic osteolysis and to explore its potential role as a therapeutic target in this condition. Cite this article: Bone Joint J 2013;95-B:1021–5

The most frequent cause of failure after total hip replacement in all reported arthroplasty registries is peri-prosthetic osteolysis. Osteolysis is an active biological process initiated in response to wear debris. The eventual response to this process is the activation of macrophages and loss of bone. Activation of macrophages initiates a complex biological cascade resulting in the final common pathway of an increase in osteolytic activity. The biological initiators, mechanisms for and regulation of this process are beginning to be understood. This article explores current concepts in the causes of, and underlying biological mechanism resulting in peri-prosthetic osteolysis, reviewing the current basic science and clinical literature surrounding the topic

Aims. The aim of this study was to present the first retrieval analysis findings of PRECICE STRYDE intermedullary nails removed from patients, providing useful information in the post-market surveillance of these recently introduced devices. Methods. We collected ten nails removed from six patients, together with patient clinical data and plain radiograph imaging. We performed macro- and microscopic analysis of all surfaces and graded the presence of corrosion using validated semiquantitative scoring methods. We determined the elemental composition of surface debris using energy dispersive x-ray spectroscopy (EDS) and used metrology analysis to characterize the surface adjacent to the extendable junctions. Results. All nails were removed at the end of treatment, having achieved their intended lengthening (20 mm to 65 mm) and after regenerate consolidation. All nails had evidence of corrosion localized to the screw holes and the extendable junctions; corrosion was graded as moderate at the junction of one nail and severe at the junctions of five nails. EDS analysis showed surface deposits to be chromium rich. Plain radiographs showed cortical thickening and osteolysis around the junction of six nails, corresponding to the same nails with moderate – severe junction corrosion. Conclusion. We found, in fully united bones, evidence of cortical thickening and osteolysis that appeared to be associated with corrosion at the extendable junction; when corrosion was present, cortical thickening was adjacent to this junction. Further work, with greater numbers of retrievals, is required to fully understand this association between corrosion and bony changes, and the influencing surgeon, implant, and patient factors involved. Cite this article: Bone Jt Open 2021;2(8):599–610

Background. We have previously described the relationship between wear rates of MOM components and soft tissue necrosis. In this study we investigated the link between wear rates, metal ion concentrations and osteolysis. Methods. All unilateral patients who underwent revision of hip resurfacings at our centre were included. Retrieved components were analysed using a coordinate measuring machine to determine total volumetric material loss and rates of wear. Given the accuracy of the wear calculations (which we have previously published), wear rates were considered “abnormal” if ≥3mm. 3. /yr. ROC curves were constructed to determine a Co concentration which would be clinically useful to detect abnormal wear. During revision, the presence/absence of osteolysis was documented. Results. There were 65 patients in total (mean time to revision was 41 months (2 to 98). 60 patients had suffered ARMD. 2 hips were revised for infection, 1 for osteolysis and 1 due to a loose cup and 1 for unexplained pain. A blood cobalt concentration >5µg/l was found to be 100%(62.2–100) specific and 94.4%(84.2–98.6) sensitive for the detection of abnormal wear. All patients with wear rates greater than 12mm. 3. /yr (n=21) were found to have osteolysis (the minimum total loss of material in this group of patients was 16mm3). ROC analysis showed that a blood cobalt ≥44.6µg/l was 97.2% specific for the detection of this rate of wear. 3 of the 21 patients with these rates of wear were asymptomatic. They decided on revision after discussion with the surgeon. Two were revised following acute femoral collapse but were completely pain free prior to these events. Conclusion. These data suggest that a blood cobalt concentration of 5µg/l can reliably identify an abnormally wearing resurfacing prosthesis. Elevated metal ion concentrations are associated with osteolysis, even in the absence of symptoms

Aims. Limb-lengthening nails have largely replaced external fixation in limb-lengthening and reconstructive surgery. However, the adverse events and high prevalence of radiological changes recently noted with the STRYDE lengthening nail have raised concerns about the use of internal lengthening nails. The aim of this study was to compare the prevalence of radiological bone abnormalities between STRYDE, PRECICE, and FITBONE nails prior to nail removal. Methods. This was a retrospective case series from three centres. Patients were included if they had either of the three limb-lengthening nails (STYDE, PRECICE, or FITBONE) removed. Standard orthogonal radiographs immediately prior to nail removal were examined for bone abnormalities at the junction of the telescoping nail parts. Results. In total, 306 patients (168 male, 138 female) had 366 limb-lengthening nails removed. The mean time from nail insertion to radiological evaluation was 434 days (36 to 3,015). Overall, 77% of STRYDE nails (20/26) had bone abnormalities at the interface compared with only 2% of FITBONE (4/242) and 1% of PRECICE nails (1/98; p < 0.001). Focal osteolysis in conjunction with periosteal reaction at the telescoping interface was only observed in STRYDE nails. Conclusion. Bone abnormalities at the interface of telescoping nail parts were seen in the majority of STRYDE nails, but only very rarely with FITBONE or PRECICE nails. We conclude that the low prevalence of radiological changes at the junctional interface of 242 FITBONE and 98 PRECICE nails at the time of nail removal does not warrant clinical concerns. Cite this article: Bone Joint J 2021;103-B(11):1731–1735

Aims. Distraction osteogenesis with intramedullary lengthening devices has undergone rapid development in the past decade with implant enhancement. In this first single-centre matched-pair analysis we focus on the comparison of treatment with the PRECICE and STRYDE intramedullary lengthening devices and aim to clarify any clinical and radiological differences. Methods. A single-centre 2:1 matched-pair retrospective analysis of 42 patients treated with the STRYDE and 82 patients treated with the PRECICE nail between May 2013 and November 2020 was conducted. Clinical and lengthening parameters were compared while focusing radiological assessment on osseous alterations related to the nail’s telescopic junction and locking bolts at four different stages. Results. Osteolysis next to the telescopic junction was observed in 31/48 segments (65%) lengthened with the STRYDE nail before implant removal compared to 1/91 segment (1%) in the PRECICE cohort. In the STRYDE cohort, osteolysis initially increased, but decreased or resolved in almost all lengthened segments (86%) after implant removal. Implant failure was observed in 9/48 STRYDE (19%) and in 8/92 PRECICE nails (9%). Breakage of the distal locking bolts was found in 5/48 STRYDE nails (10%) compared to none in the PRECICE cohort. Treatment-associated pain was generally recorded as mild and found in 30/48 patients (63%) and 39/92 (42%) in the STRYDE and PRECICE cohorts, respectively. Temporary range of motion (ROM) limitations under distraction were registered in 17/48 (35%) segments treated with the STRYDE and 35/92 segments (38%) treated with the PRECICE nail. Conclusion. Osteolysis and periosteal reaction, implant breakage, and pain during lengthening and consolidation is more likely in patients treated with the STRYDE nail compared to the PRECICE nail. Temporary ROM limitations during lengthening occurred independent of the applied device. Implant-related osseous alterations seem to remodel after implant removal. Cite this article: Bone Joint J 2023;105-B(1):88–96

In older patients (>75 years of age), with an intact rotator cuff, requiring a total shoulder replacement (TSR) there is, at present, uncertainty whether an anatomic TSR (aTSR) or a reverse TSR (rTSR) is best for the patient. This comparison study of same age patients aims to assess clinical and radiological outcomes of older patients (≥75 years) who received either an aTSR or a rTSA. Consecutive patients with a minimum age of 75 years who received an aTSR (n=44) or rTSR (n=51) were prospectively studied. Pre- and postoperative clinical evaluations included the ASES score, Constant score, SPADI score, DASH score, range of motion (ROM) and pain and patient satisfaction for a follow-up of 2 years. Radiological assessment identified glenoid and humeral component osteolysis, including notching with a rTSR. Postoperative improvement for ROM and all clinical assessment scores for both groups was found. There were significantly better patient reported outcome scores (PROMs) in the aTSR group compared with the rTSR patients (p<0.001). Both groups had only minor osteolysis on radiographs. No revisions were required in either group. The main complications were scapular stress fractures for the rTSR patients and acromioclavicular joint pain for both groups. This study of older patients (>75 years) demonstrated that an aTSR for a judiciously selected patient with good rotator cuff muscles can lead to a better clinical outcome and less early complications than a rTSR

Hip and knee arthroplasty (HKA) are two of the most successful orthopaedic procedures. However, one major complication necessitating revision surgery is osteolysis causing aseptic loosening of the prosthesis. JAK-STAT has been demonstrated to influence bone metabolism and can be regulated by microRNA (miRNA). Adult patients with osteolysis or aseptic loosening undergoing revision HKA were recruited. Age and gender matched patients undergoing primary hip or knee arthroplasty were our controls. Samples of bone, tissue and blood were collected and RNA isolation was performed. The best quality samples were used for RNA-sequencing. Data analysis was performed using RStudio and Galaxy to identify differentially expressed genes. Western blotting of IL6 was used to confirm protein expression. Five circulating miRNA were identified which had 10 differentially expressed genes in bone and 11 differentially expressed genes in tissue related to the JAK-STAT pathway. IL6 in bone and EpoR in bone were highly significant and IL6 in tissue, MPL in bone, SOCS3 in tissue, JAK3 in bone and SPRED1 in bone were borderline significant. Western blot results demonstrated up-expression of IL6 in bone tissue of revision patients. Periprosthetic osteolysis and aseptic loosening can be attributed to miRNA regulation of the JAK-STAT pathway in osteoblasts and osteoclasts, leading to increased bone resorption. These findings can be used for further experiments to determine utility in the clinical setting for identifying diagnostic markers or therapeutic targets

The benefits of HXLPE in total knee arthroplasty (TKA) have not been as evident as total hip arthroplasty (THA). A systematic review and meta-analysis to assess the impact of highly-crosslinked polyethylene (HXLPE) on TKA outcomes compared to conventional polyethylene (CPE) is described. All studies comparing HXLPE with CPE for primary TKA were included for analysis. The minimum dataset included revision rates, indication for revision, aseptic component loosening and follow-up time. The primary outcome variables were all-cause revision, aseptic revision, revision for loosening, radiographic component loosening, osteolysis and incidence of radiolucent lines. Secondary outcome measures included postoperative functional knee scores. A random-effects meta-analysis allowing for all missing data was performed for all primary outcome variables. Six studies met the inclusion criteria. In total, there were 2,234 knees (1,105 HXLPE and 1,129 CPE). The combined mean follow-up for all studies was 6 years. The aseptic revision rate in the HXLPE group was 1.02% compared to 1.97% in the CPE group. There was no difference in the rate of all-cause revision (p = 0.131), aseptic revision (p = 0.298) or revision for component loosening (p = 0.206) between the two groups. Radiographic loosening (p = 0.200), radiolucent lines (p = 0.123) and osteolysis (p = 0.604) was similar between both groups. Functional outcomes were similar between groups. The use of HXLPE in TKA yields similar results for clinical and radiographic outcomes when compared to CPE at midterm follow-up. HXLPE does not confer the same advantages to TKA as seen in THA

Hip resurfacing arthroplasty (HRA) is a bone conserving alternative to total hip arthroplasty. We present the early 1 and 2-year clinical and radiographical follow-up of a novel ceramic-on-ceramic (CoC) HRA in a multi-centric Australian cohort. Patient undergoing HRA between September 2018 and April 2021 were prospectively included. Patient-reported outcome measures (PROMS) in the form of the Forgotten Joint Score (FJS), HOOS Jr, WOMAC, Oxford Hip Score (OHS) and UCLA Activity Score were collected preoperatively and at 1- and 2-years post-operation. Serial radiographs were assessed for migration, component alignment, evidence of osteolysis/loosening and heterotopic ossification formation. 209 patients were identified of which 106 reached 2-year follow-up. Of these, 187 completed PROMS at 1 year and 90 at 2 years. There was significant improvement in HOOS (p< 0.001) and OHS (p< 0.001) between the pre-operative, 1-year and 2-years outcomes. Patients also reported improved pain (p<0.001), function (p<0.001) and reduced stiffness (p<0.001) as measured by the WOMAC score. Patients had improved activity scores on the UCLA Active Score (p<0.001) with 53% reporting return to impact activity at 2 years. FJS at 1 and 2-years were not significantly different (p=0.38). There was no migration, osteolysis or loosening of any of the implants. The mean acetabular cup inclination angle was 41.3° and the femoral component shaft angle was 137°. No fractures were reported over the 2-year follow-up with only 1 patient reporting a sciatic nerve palsy. There was early return to impact activities in more than half our patients at 2 years with no early clinical or radiological complications related to the implant. Longer term follow-up with increased patient numbers are required to restore surgeon confidence in HRA and expand the use of this novel product. In conclusion, CoC resurfacing at 2-years post-operation demonstrate promising results with satisfactory outcomes in all recorded PROMS

Polyimide (MP-1, MMATech, Haifa, Israel), is a high performance aerospace thermoplastic used for its lubricity, stability, inertness and radiation resistance. A wear resistant thin robust bearing is needed for total hip arthroplasty (THR). After independent laboratory testing, in 2006, the author used the material as a bearing in two Reflection (Smith and Nephew, USA) hip surgeries. The first, a revision for polyethylene wear, survives with no evidence of wear, noise, new osteolysis or complications related to the MP-1 bearing after 16 yrs. The second donated his asymptomatic MP-1 hip at 6.5yrs for post-mortem examination. There were no osteoclasts, cellular reaction bland in contrast to that of polyethylene. In 2013 a clinical study with ethical committee approval was started using a Biolox Delta (Ceramtec, Germany) head against a polyimide liner in 97 patients. MMATech sold all liners, irradiated: steam 52:45. Sixteen were re-machined in New Zealand. Acetabular shells were Delta PF (LIMA, Italy). The liner locked by taper. The cohort consisted of 46:51 M:F, and ages 43 to 85, mean 65. Ten received cemented stems. For contralateral surgery, a ceramic or polyethylene liner was used. Initial patients were lower demand, later, more active patients, mountain-biking and running. All patients have on-going follow up, including MP-1 liner revision cases. There has been no measurable wear, or osteolysis around the acetabular components using weight-bearing radiographs. Squeaking within the first 6 weeks was noted in 39 number of cases and subtle increase in palpable friction, (passive rotation at 50 degrees flexion), but then disappeared. There were 6 revisions, four of which were related to cementless Stemsys implants (Evolutis, Italy) fixed distally with proximal linear lucencies in Gruen zones 1 and 7, and 2 and 6. No shells were revised and MP-1 liners were routinely changed to ceramic or polyethylene. The liners showed no head contact at the apex, with highly polished contact areas. There were no deep or superficial infections, but one traumatic anterior dislocation at 7 years associated with 5 mm subsidence of a non-collared stem. The initial squeaking and increased friction was due to the engineering of the liner / shell composite as implanted, not allowing adequate clearance for fluid film lubrication and contributed to by shell distortion during impaction. The revised bearings were “equatorial” rather than polar, and with lack of wear or creep this never fully resolved. Where the clearance was better, function was normal. The “slow” utilization was due to my ongoing concern with clearances not being correct. The revision of 4 Stemsys stems, tribology issues may have contributed, but non “MP-1” / Stemsys combinations outside this study have shown the same response, thought to be due to de-bonding of the hydroxyapatite coating. With correct engineering and clearances, a 3.6 mm thick MP-1 bearing, a surface Ra<0.5, steam sterilized, shows no appreciable wear, and with confidence, can be used as a high performance THR bearing

Polyethylene wear-debris induced inflammatory osteolysis is known as the main cause of aseptic loosening and long term revision total hip arthroplasty. Although recent reports suggest that antioxidant impregnated ultra-high molecular weight polyethylene (UHMWPE) wear-debris have reduce the osteolytic potential in vivo when compared to virgin UHMWPE, little is known about if and/or how PE rate of oxidation affects osteolysis in vivo. We hypothesized that oxidized UHMWPE particles would cause more inflammatory osteolysis in a murine calvarial bone model when compared to virgin UHMWPE. Male C57BL/6 eight weeks old received equal amount of particulate debris overlaying the calvarium of (n=12/group): sham treatment (no particles), 2mg (6,75×107 particles/mg) of endotoxin-free UHMWPE particles (PE) or of endotoxin-free highly oxidized-UHMWPE (OX) particles. In vivo osteolysis was assessed using high resolution micro-CT and inflammation with L-012 probe dependent luminescence. At day 10, calvarial bone was examined using high resolution micro-CT, histomorphometric, immunohistochemistry analyses and qRT-PCR to assess OPG, RANK, RANK-L, IL-10, IL-4, IL-1b and TRAP genes expression using the protocol defined by individual TaqManTM Gene Expression Assays Protocol (Applied Biosystems). In vivo inflammation was significantly higher in the OX (1.60E+06 ± 8.28E+05 photons/s/cm2) versus PE (8.48E+05 ± 3.67E+05) group (p=0.01). Although there was a statistically significant difference between sham (−0.27% ± 2.55%) and implanted (PE: −9.7% ± 1.97%, and OX: − 8.38% ± 1.98%) groups with regards to bone resorption (p=0.02), this difference was not significant between OX and PE (p = 0.14). There was no significant difference between groups regarding PCR analyses for OPG, RANK, RANK-L, IL-10, IL-4, IL-1b and TRAP (p = 0.6, 0.7, 0.1, 0.6, 0.3, 0.4, 0.7 respectively). Bone volume density was significantly decreased in PE (13.3%±1.2%) and OX (12.2%±1.2%) groups when compared to sham (15%±0.9%) (p < 0 .05). Histomorphometric analyses showed a significantly decreased Bone Thickness/Tissue Thickness ratio in the implanted group (0.41±0.01 mm and 0.43±0.01 mm) compared to sham group (0.69± 0.01) (p < 0 .001). However, there were no significant difference between OX and PE (p = 0.2). Our findings suggest that oxidized UHMWPE particles display increased inflammatory potential. Results were not significant regarding in vivo or ex vivo osteolysis. As antioxidant-diffused UHMWPE induce less inflammation activity in vivo, the mechanism by which they cause reduced osteolysis requires further investigation

Abstract. Background. Although tantalum is a well recognised implant material used for revision arthroplasty, little is known regarding the use of the same in primary total hip arthroplasty. Methods. A literature search was performed to find all relevant clinical studies until March 2020, which then underwent a further selection criteria. The inclusion criteria was set as follows: Reporting on human patients undergoing primary total hip arthroplasty; Direct comparison between tantalum acetabular cups with conventional acetabular cups. for use in primary total hip arthroplasty; Radiological evaluation (cup migration, osteointegration); Clinical (functional scores, need for subsequent revision, patient-reported outcomes; Post-operative complications; Reporting findings in the English Language. After a thorough search a total of six studies were included in the review. The primary outcome. measures were clinical outcomes, implant migration, change in bone mineral density and rate of revision and infection. Results. Tantalum was found superior to titanium with regards to fewer radiolucencies, survivorship, osteointegration, decreased osteolysis and mechanical loosening. No significant difference in radioisometric analysis, bone mineral density or Harris Hip Score was found. Revision and infection rates were found to be significantly lower in tantalum group at 10 years from pooled data of national joint registry. Conclusion. The use of tantalum can be reserved for cases of high risk of failure or mechanical loosening, where failure of a contralateral joint occurred as it carries lower risk of failure and infection. Further studies with longer follow-up would be useful in drawing further conclusions

This study aimed to analyze the effect of two different techniques of cement application: cement on bone surface (CoB) versus cement on bone surface and implant surface (CoBaI) on the short-term effect of radiolucent lines (RLL) in primary fully cemented total knee arthroplasties (TKA) with patella resurfacing. 379 fully cemented TKAs (318 patients) were included in this monocentric study. Preoperative and postoperative at week 4 and 12 month after surgery all patients had a clinical and radiological examination and were administered the Oxford Knee Score (OKS). Cement was applied in two different ways among the two study groups: cement on bone surface (CoB group) or cement on bone surface and implant surface (CoBaI group). The evaluation of the presence of RLL or osteolysis was done as previously described using the updated Knee Society Radiographic Evaluation System. The mean OKS and range of motion improved significantly in both groups at the 4-week and 12-month follow-up, with no significant difference between the groups (CoB vs. CoBaI). RLL were present in 4.7% in the whole study population and were significantly higher in the CoBaI group (10.5%) at the 4-week follow-up. At the 12-month follow-up RLL were seen in 29.8% of the TKAs in the CoBaI group, whereas the incidence was lower in the CoB group (24.0% (n.s.)). There were two revisions in each group. None of these due to aseptic loosening. Our study indicated that the application of bone cement on bone surface only might be more beneficial than onto the bone surface and onto the implant surface as well in respect to the short-term presence of RLL in fully cemented primary TKA. The long-term results will be of interest, especially in respect to aseptic loosening and might guide future directions of bone cement applications in TKA

Prosthetic joint infection (PJI) is a complex disease that causes significant damage to the peri-implant tissue. Developing an animal model that is clinically relevant in depicting this disease process is an important step towards developing novel successful therapies. In this study, we have performed a thorough histologic analysis of peri-implant tissue harvested post Staphylococcus aureus (S. aureus) infection of a cemented 3D-printed titanium hip implant in rats. Sprague-Dawley rats underwent left hip cemented 3D-printed titanium hemiarthroplasty via posterior approach under general anesthesia. Four surgeries were performed for the control group and another four for the infected group. The hip joint was inoculated with 5×10. 9. CFU/mL of S. aureus Xen36 prior to capsule closure. The animals were scarified 3 weeks after infection. The femur was harvested and underwent micro-CT and histologic analysis. Hematoxylin and eosin (H&E), as well as Masson's trichrome (MT) stains were performed. Immunohistochemistry (IHC) using rabbit antibody for S. aureus was also used to localize bacterial presence within femur and acetabulum tissue . The histologic analysis revealed strong resemblance to tissue changes in the clinical setting of chronic PJI. IHC demonstrated the extent of bacterial spread within the peri-implant tissue away from the site of infection. The H&E and MT stains showed 5 main features in infected bone: 1) increased PMNs, 2) fibrovascular inflammation, 3) bone necrosis, and 4) increased osteoclasts 5) fibrosis of muscular tissue and cartilage. Micro CT data showed significantly more osteolysis present around the infected prosthesis compared to control (surgery with no infection). This is the first clinically relevant PJI animal model with detailed histologic analysis that strongly resembles the clinical tissue pathology of chronic PJI. This model can provide a better understanding of how various PJI therapies can halt or reverse peri-implant tissue damage caused by infection

The benefit of using acetabular screws in primary total hip arthroplasty (THA) has been questioned in recent years. The disadvantages of using screws include increased operative time, risk of injury to surrounding neurovascular structures and metal ware breakage. Recent large registry studies have reported that screws do not confer a protective effect against acetabular loosening or the presence of osteolysis. Other studies have even described an increased risk of aseptic acetabular loosening with the selective use of screws. We report findings from a multicentre cohort study. This large cohort study compared clinical outcomes between primary acetabular components that were inserted with and without screws. Independent variables included the presence (or absence) of screws, the total number of screws used and the cumulative screw length (CSL). Outcome measures included all-cause revision, acetabular component revision and acetabular component loosening. Statistical software (Stata/IC 13.1 for Mac [64-bit Intel]) was used to conduct all statistical analyses. A p-value < 0 .05 taken to be significant. There were 4,583 THAs performed in total. Screws were used in 15.9% (n=733). At a mean follow-up of 5.2 years, the all-cause revision rate in the screw cohort was 1.5% compared to 0.83% in the no screw cohort (p=0.085). There was no difference in acetabular component revision rates for screws (3/733, 0.41%) versus no screws (12/3,850, 0.31%) (p=0.439). The rate of acetabular loosening noted during the time of revision surgery was significantly higher when screws were used in the index procedure (2/733, 0.2%) compared to the no screw cohort (1/3,850, 0.02%) (p=0.017). There was no difference in outcomes when stratifying by the number of screws used or the cumulative screw length. Primary acetabular components do not require screws for fixation. All cause revision rates and acetabular component revision rates are comparable for the screw and the no screw cohorts. The rate of acetabular component loosening, as observed during revision surgery, is significantly higher when screws are used in the index total hip replacement

Introduction. The Oxford Unicompartmental Knee Replacement (OUKA) is the most popular unicompartmental knee replacement (UKR) in the New Zealand Joint Registry with the majority utilising cementless fixation. We report the 10-year radiological outcomes. Methods. This is a prospective observational study. All patients undergoing a cementless OUKA between May 2005 and April 2011 were enrolled. There were no exclusions due to age, gender, body mass index or reduced bone density. All knees underwent fluoroscopic screening achieving true anteroposterior (AP) and lateral images for radiographic assessment. AP assessment for the presence of radiolucent lines and coronal alignment of the tibial and femoral components used Inteliviewer radiographic software. The lateral view was assessed for lucencies as well as sagittal alignment. Results. 687 OUKAs were performed in 641 patients. Mean age at surgery was 66 years (39–90yrs), 382 in males and 194 right sided. 413 radiographs were available for analysis; 92 patients had died, 30 UKRs had been revised and 19 radiographs were too rotated to be analysed the remainder were lost to follow-up. Mean radiograph to surgery interval was 10.2 years (7.1–16.2yrs). RLLs were identified in zone 1 (3 knees), zone 2 (2 knees), zone 3 (3 knees), zone 5 (3 knees), zone 6 (2 knees) and zone 7 (42 knees). No RLL had progressed, and no case had any osteolysis or prosthesis subsidence. Alignment in the coronal plane: mean 2.90° varus (9.30° varus - 4.49° valgus) of the tibial component to the tibial anatomic axis and the femoral component in mean 4.57° varus (17.02° varus - 9.3° valgus). Sagittal plane posterior tibial slope was a mean 6.30° (0.44° -13.60° degrees) and mean femoral component flexion of 8.11° (23.70° flexion – 16.43° extension). Conclusion. The cementless OUKA demonstrates stable fixation with low revision rates at our centre supporting results earlier published by the design centre

Aim. To make an inoculum for induction of Implant-Associated Osteomyelitis (IAO) in pigs based on bacterial aggregates resembling those found on the human skin, i.e. aggregates of 5–15 µm with low metabolic activity. The aggregates were evaluated and compared to a standard planktonic bacterial inoculum. Method. The porcine Staphylococcus aureus strain S54F9 was cultured in Tryptone Soya Broth for seven days. Subsequently, the culture was filtered through cell strainers with pore sizes of 15 µm and 5 µm, respectively. The fraction of 5–15 µm aggregates in the top of the 5 µm filter was collected as the aggregate-inoculum. The separation of aggregates into different size fractions was evaluated by light microscopy. The metabolism of the aggregate-inoculum and a standard overnight planktonic inoculum was evaluated with isothermal microcalorimetry. In total, six female minipigs were allocated into three groups (n=2), receiving different inoculums. Group A: overnight planktonic inoculum; 10. 4. CFU S. aureus (S54F9), Group B: seven days old 5–15 µm aggregate-inoculum; 10. 4. CFU S. aureus (S54F9), Group C: saline. All inoculums were placed in a pre-drilled implant cavity in the right tibia of the pig and a sterile stainless-steel implant was inserted. The pigs were euthanized seven days after surgery. Postmortem macroscopic pathology, microbiology, computed tomography and histopathology were performed. Results. The separation of aggregates into different size fractions was done successfully by the filtering method. Isothermal microcalorimetry showed, a delayed Time-to-peak metabolic activity of the aggregate-inoculum compared to the planktonic inoculum. S. aureus was isolated from subcutis, bone and implants from all animals in groups A and B. Both group A animals showed osteomyelitis at gross inspection with suppuration and sequestration, while groups B and C animals had no macroscopic lesions. From CT scans, both group A animals also showed positive signs of osteomyelitis, i.e., osteolysis, while only one animal in group B did, and none in group C. Histopathological examination of the bones showed more extensive inflammation in group A animals compared to those in group B, which showed more osteoid formation. Conclusions. Formation and separation of low metabolism bacterial aggregates into different size fractions was possible. The aggregates can be used as inoculum in the porcine IAO model, with microbiological re-isolation from both implants and tissue. Furthermore, the aggregates caused a less aggressive IAO, than the planktonic counterparts. Using aggregated bacteria as inoculum appears to be more relevant to the clinical situation of infecting bacteria

Introduction. Stryde® lengthening nail has been recently withdrawn because of concerns about osteolysis and other bone lesions that have been observed early after implantation. The present study analyses the incidence and features of these bone lesions in our patients. Materials and Methods. This is a retrospective review of a series of patients from two centres specializing in limb reconstruction. Inclusion criteria was a history of surgery with Stryde® lengthening nail with more than one year follow-up available. All postoperative x-rays were and clinical notes were reviewed. Results. 36 patients with 75 bone segments were included. 11 (30.5%) patients and 32 (42.6%) bone segments were without any lesion. In 3 (8.3%) patients and 3 (4%) segments, osteolytic lesions only were noticed. 11(30.5%) patients and 14 (18.6%) segments had combined lytic lesions and periosteal reaction or cortical thickening. 12 (33.3%) patients and 26 (34.6%) segments developed only periosteal reaction or cortical thickening. 54.8% of patients with bilateral nailing had bilateral lesions. 52% of the patients with bone lesions reported late onset of pain after the completion of the lengthening. The average earliest interval that any of the lesions was noticed was 10.2 months post-surgery. Conclusions. Patients with Stryde® nails should be monitored clinically and radiologically at regular intervals until removal. The early failure and withdrawal of Precise Stryde® nail, is a significant event in the field of limb reconstruction; this study adds useful data to the growing pool of published data related to the this event