Aims. A novel enhanced cement fixation (EF) tibial implant with deeper cement pockets and a more roughened bonding surface was released to market for an existing total knee arthroplasty (TKA) system.This randomized controlled trial assessed fixation of the both the EF (ATTUNE S+) and standard (Std; ATTUNE S) using radiostereometric analysis. Methods. Overall, 50 subjects were randomized (21 EF-TKA and 23 Std-TKA in the final analysis), and had follow-up visits at six weeks, and six, 12, and 24 months to assess migration of the tibial component. Low viscosity bone cement with tobramycin was used in a standardized fashion for all subjects. Patient-reported outcome measure data was captured at preoperative and all postoperative visits. Results. The patient cohort mean age was 66 years (SD seven years), 59% were female, and the mean BMI was 32 kg/m. 2. (SD 6 kg/m. 2. ). Mean two-year subsidence of the EF-TKA was 0.056 mm (95% confidence interval (CI) 0.025 to 0.086) versus 0.006 mm (95% CI -0.029 to 0.040) for the Std-TKA, and the two-year maximum total point motion (MTPM) was 0.285 mm (95% upper confidence limit (UCL) ≤ 0.363) versus 0.346 mm (95% UCL ≤ 0.432), respectively, for a mean difference of -0.061 mm (95% CI -0.196 to 0.074). Inducible displacement also did not differ between groups. The MTPMs between 12 and 24 months for each group was below the published threshold of 0.2 mm for predicting early aseptic loosening (p < 0.001 and p = 0.001, respectively). Conclusion. Both the enhanced fixation and the standard tibial implant design showed fixation with a predicted low risk of long-term aseptic loosening. Cite this article: Bone Jt Open 2024;5(1):20–27

Aims. The Exeter V40 femoral stem is the most implanted stem in the National Joint Registry (NJR) for primary total hip arthroplasty (THA). In 2004, the 44/00/125 stem was released for use in ‘cement-in-cement’ revision cases. It has, however, been used ‘off-label’ as a primary stem when patient anatomy requires a smaller stem with a 44 mm offset. We aimed to investigate survival of this implant in comparison to others in the range when used in primary THAs recorded in the NJR. Methods. We analyzed 328,737 primary THAs using the Exeter V40 stem, comprising 34.3% of the 958,869 from the start of the NJR to December 2018. Our exposure was the stem, and the outcome was all-cause construct revision. We stratified analyses into four groups: constructs using the 44/00/125 stem, those using the 44/0/150 stem, those including a 35.5/125 stem, and constructs using any other Exeter V40 stem. Results. In all 328,737 THAs using an Exeter V40 stem, the revision estimate was 2.8% (95% confidence interval (CI) 2.7 to 2.8). The 44/00/125 stem was implanted in 2,158 primary THAs, and the ten-year revision estimate was 4.9% (95% CI 3.6 to 6.8). Controlling for age, sex, year of operation, indication, and American Society of Anesthesiologists grade demonstrated an increased overall hazard of revision for constructs using the 44/00/125 stem compared to constructs using other Exeter V40 femoral stems (hazard ratio 1.8 (95% CI 1.4 to 2.3)). Conclusion. Although the revision estimate is within the National Institute for Health and Care Excellence ten-year benchmark, survivorship of constructs using the 44/00/125 stem appears to be lower than the rest of the range. Adjusted analyses will not take into account ‘confounding by indication’, e.g. patients with complex anatomy who may have a higher risk of revision. Surgeons and patients should be reassured but be aware of the observed increased revision estimate, and only use this stem when other implants are not suitable. Cite this article: Bone Joint J 2023;105-B(5):504–510

Periprosthetic joint infection (PJI) is one of the most dreaded complications after arthroplasty surgery; thus numerous approaches have been undertaken to equip metal surfaces with antibacterial properties. Due to its antimicrobial effects, silver is a promising coating for metallic surfaces, and several types of silver-coated arthroplasty implants are in clinical use today. However, silver can also exert toxic effects on eukaryotic cells both in the immediate vicinity of the coated implants and systemically. In most clinically-used implants, silver coatings are applied on bulk components that are not in direct contact with bone, such as in partial or total long bone arthroplasties used in tumour or complex revision surgery. These implants differ considerably in the coating method, total silver content, and silver release rates. Safety issues, such as the occurrence of argyria, have been a cause for concern, and the efficacy of silver coatings in terms of preventing PJI is also controversial. The application of silver coatings is uncommon on parts of implants intended for cementless fixation in host bone, but this option might be highly desirable since the modification of implant surfaces in order to improve osteoconductivity can also increase bacterial adhesion. Therefore, an optimal silver content that inhibits bacterial colonization while maintaining osteoconductivity is crucial if silver were to be applied as a coating on parts intended for bone contact. This review summarizes the different methods used to apply silver coatings to arthroplasty components, with a focus on the amount and duration of silver release from the different coatings; the available experience with silver-coated implants that are in clinical use today; and future strategies to balance the effects of silver on bacteria and eukaryotic cells, and to develop silver-coated titanium components suitable for bone ingrowth. Cite this article: Bone Joint J 2021;103-B(3):423–429

Aims. Periprosthetic joint infection (PJI) is a debilitating condition with a substantial socioeconomic burden. A novel autologous blood glue (ABG) has been developed, which can be prepared during surgery and sprayed onto prostheses at the time of implantation. The ABG can potentially provide an antimicrobial coating which will be effective in preventing PJI, not only by providing a physical barrier but also by eluting a well-known antibiotic. Hence, this study aimed to assess the antimicrobial effectiveness of ABG when impregnated with gentamicin and stem cells. Methods. Gentamicin elution from the ABG matrix was analyzed and quantified in a time-dependent manner. The combined efficiency of gentamicin and ABG as an anti-biofilm coating was investigated on titanium disks. Results. ABG-gentamicin was bactericidal from 10 μg/ml and could release bactericidal concentrations over seven days, preventing biofilm formation. A concentration of 75 μg/ml of gentamicin in ABG showed the highest bactericidal effect up to day 7. On titanium disks, a significant bacterial reduction on ABG-gentamicin coated disks was observed when compared to both uncoated (mean 2-log reduction) and ABG-coated (mean 3-log reduction) disks, at days 3 and 7. ABG alone exhibited no antimicrobial or anti-biofilm properties. However, a concentration of 75 μg/ml gentamicin in ABG sustains release over seven days and significantly reduced biofilm formation. Its use as an implant coating in patients with a high risk of infection may prevent bacterial adhesion perioperatively and in the early postoperative period. Conclusion. ABG’s use as a carrier for stem cells was effective, as it supported cell growth. It has the potential to co-deliver compatible cells, drugs, and growth factors. However, ABG-gentamicin’s potential needs to be further justified using in vivo studies. Cite this article: Bone Joint Res 2020;9(12):848–856

Aims. Bacteriophages infect, replicate inside bacteria, and are released from the host through lysis. Here, we evaluate the effects of repetitive doses of the Staphylococcus aureus phage 191219 and gentamicin against haematogenous and early-stage biofilm implant-related infections in Galleria mellonella. Methods. For the haematogenous infection, G. mellonella larvae were implanted with a Kirschner wire (K-wire), infected with S. aureus, and subsequently phages and/or gentamicin were administered. For the early-stage biofilm implant infection, the K-wires were pre-incubated with S. aureus suspension before implantation. After 24 hours, the larvae received phages and/or gentamicin. In both models, the larvae also received daily doses of phages and/or gentamicin for up to five days. The effect was determined by survival analysis for five days and quantitative culture of bacteria after two days of repetitive doses. Results. In the haematogenous infection, a single combined dose of phages and gentamicin, and repetitive injections with gentamicin or in combination with phages, resulted in significantly improved survival rates. In the early-stage biofilm infection, only repetitive combined administration of phages and gentamicin led to a significantly increased survival. Additionally, a significant reduction in number of bacteria was observed in the larvae after receiving repetitive doses of phages and/or gentamicin in both infection models. Conclusion. Based on our results, a single dose of the combination of phages and gentamicin is sufficient to prevent a haematogenous S. aureus implant-related infection, whereas gentamicin needs to be administered daily for the same effect. To treat early-stage S. aureus implant-related infection, repetitive doses of the combination of phages and gentamicin are required. Cite this article: Bone Joint Res 2024;13(8):383–391

Aims. Vertebral body tethering (VBT) is a non-fusion technique to correct scoliosis. It allows correction of scoliosis through growth modulation (GM) by tethering the convex side to allow concave unrestricted growth similar to the hemiepiphysiodesis concept. The other modality is anterior scoliosis correction (ASC) where the tether is able to perform most of the correction immediately where limited growth is expected. Methods. We conducted a retrospective analysis of clinical and radiological data of 20 patients aged between 9 and 17 years old, (with a 19 female: 1 male ratio) between January 2014 to December 2016 with a mean five-year follow-up (4 to 7). Results. There were ten patients in each group with a total of 23 curves operated on. VBT-GM mean age was 12.5 years (9 to 14) with a mean Risser classification of 0.63 (0 to 2) and VBT-ASC was 14.9 years (13 to 17) with a mean Risser classification of 3.66 (3 to 5). Mean preoperative VBT-GM Cobb was 47.4° (40° to 58°) with a Fulcrum unbend of 17.4 (1° to 41°), compared to VBT-ASC 56.5° (40° to 79°) with 30.6 (2° to 69°)unbend. Postoperative VBT-GM was 20.3° and VBT-ASC Cobb angle was 11.2°. The early postoperative correction rate was 54.3% versus 81% whereas Fulcrum Bending Correction Index (FBCI) was 93.1% vs 146.6%. The last Cobb angle on radiograph at mean five years’ follow-up was 19.4° (VBT-GM) and 16.5° (VBT-ASC). Patients with open triradiate cartilage (TRC) had three over-corrections. Overall, 5% of patients required fusion. This one patient alone had a over-correction, a second-stage tether release, and final conversion to fusion. Conclusion. We show a high success rate (95%) in helping children avoid fusion at five years post-surgery. VBT is a safe technique for correction of scoliosis in the skeletally immature patient. This is the first report at five years that shows two methods of VBT can be employed depending on the skeletal maturity of the patient: GM and ASC. Cite this article: Bone Jt Open 2022;3(2):123–129

Aims. This study aimed to examine the effects of tumour necrosis factor-alpha (TNF-α) on osteoblasts in metal wear-induced bone loss. Methods. TNF-α immunoexpression was examined in periprosthetic tissues of patients with failed metal-on-metal hip arthroplasties and also in myeloid MM6 cells after treatment with cobalt ions. Viability and function of human osteoblast-like SaOs-2 cells treated with recombinant TNF-α were studied by immunofluorescence, terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL) assay, western blotting, and enzyme-linked immunosorbent assay (ELISA). Results. Macrophages, lymphocytes, and endothelial cells displayed strong TNF-α immunoexpression in periprosthetic tissues containing metal wear debris. Colocalization of TNF-α with the macrophage marker CD68 and the pan-T cell marker CD3 confirmed TNF-α expression in these cells. Cobalt-treated MM6 cells secreted more TNF-α than control cells, reflecting the role of metal wear products in activating the TNF-α pathway in the myeloid cells. While TNF-α did not alter the immunoexpression of the TNF-receptor 1 (TNF-R1) in SaOs-2 cells, it increased the release of the soluble TNF-receptor 1 (sTNF-R1). There was also evidence for TNF-α-induced apoptosis. TNF-α further elicited the expression of the endoplasmic reticulum stress markers inositol-requiring enzyme (IRE)-1α, binding-immunoglobulin protein (BiP), and endoplasmic oxidoreductin1 (Ero1)-Lα. In addition, TNF-α decreased pro-collagen I α 1 secretion without diminishing its synthesis. TNF-α also induced an inflammatory response in SaOs-2 cells, as evidenced by the release of reactive oxygen and nitrogen species and the proinflammatory cytokine vascular endothelial growth factor. Conclusion. The results suggest a novel osteoblastic mechanism, which could be mediated by TNF-α and may be involved in metal wear debris-induced periprosthetic bone loss. Cite this article: Bone Joint Res 2020;9(11):827–839

Aims. Accumulated evidence indicates that local cell origins may ingrain differences in the phenotypic activity of human osteoblasts. We hypothesized that these differences may also exist in osteoblasts harvested from the same bone type at periarticular sites, including those adjacent to the fixation sites for total joint implant components. Methods. Human osteoblasts were obtained from the acetabulum and femoral neck of seven patients undergoing total hip arthroplasty (THA) and from the femoral and tibial cuts of six patients undergoing total knee arthroplasty (TKA). Osteoblasts were extracted from the usually discarded bone via enzyme digestion, characterized by flow cytometry, and cultured to passage three before measurement of metabolic activity, collagen production, alkaline phosphatase (ALP) expression, and mineralization. Results. Osteoblasts from the acetabulum showed lower proliferation (p = 0.034), cumulative collagen release (p < 0.001), and ALP expression (p = 0.009), and produced less mineral (p = 0.006) than those from the femoral neck. Osteoblasts from the tibia produced significantly less collagen (p = 0.021) and showed lower ALP expression than those from the distal femur. Conclusion. We have demonstrated for the first time an anatomical regional variation in the biological behaviours of osteoblasts on either side of the hip and knee joint. The lower osteoblast proliferation, matrix production, and mineralization from the acetabulum compared to those from the proximal femur may be reflected in differences in bone formation and implant fixation at these sites. Cite this article: Bone Joint Res 2021;10(9):611–618

Aims. A pragmatic multicentre randomized controlled trial, UK FROzen Shoulder Trial (UK FROST), was conducted in the UK NHS comparing the cost-effectiveness of commonly used treatments for adults with primary frozen shoulder in secondary care. Methods. A cost utility analysis from the NHS perspective was performed. Differences between manipulation under anaesthesia (MUA), arthroscopic capsular release (ACR), and early structured physiotherapy plus steroid injection (ESP) in costs (2018 GBP price base) and quality adjusted life years (QALYs) at one year were used to estimate the cost-effectiveness of the treatments using regression methods. Results. ACR was £1,734 more costly than ESP ((95% confidence intervals (CIs) £1,529 to £1,938)) and £1,457 more costly than MUA (95% CI £1,283 to £1,632). MUA was £276 (95% CI £66 to £487) more expensive than ESP. Overall, ACR had worse QALYs compared with MUA (-0.0293; 95% CI -0.0616 to 0.0030) and MUA had better QALYs compared with ESP (0.0396; 95% CI -0.0008 to 0.0800). At a £20,000 per QALY willingness-to-pay threshold, MUA had the highest probability of being cost-effective (0.8632) then ESP (0.1366) and ACR (0.0002). The results were robust to sensitivity analyses. Conclusion. While ESP was less costly, MUA was the most cost-effective option. ACR was not cost-effective. Cite this article: Bone Jt Open 2021;2(8):685–695

Objective. In the present study, we aimed to assess whether gelatin/β-tricalcium phosphate (β-TCP) composite porous scaffolds could be used as a local controlled release system for vancomycin. We also investigated the efficiency of the scaffolds in eliminating infections and repairing osteomyelitis defects in rabbits. Methods. The gelatin scaffolds containing differing amounts of of β-TCP (0%, 10%, 30% and 50%) were prepared for controlled release of vancomycin and were labelled G-TCP0, G-TCP1, G-TCP3 and G-TCP5, respectively. The Kirby-Bauer method was used to examine the release profile. Chronic osteomyelitis models of rabbits were established. After thorough debridement, the osteomyelitis defects were implanted with the scaffolds. Radiographs and histological examinations were carried out to investigate the efficiency of eliminating infections and repairing bone defects. Results. The prepared gelatin/β-TCP scaffolds exhibited a homogeneously interconnected 3D porous structure. The G-TCP0 scaffold exhibited the longest duration of vancomycin release with a release duration of eight weeks. With the increase of β-TCP contents, the release duration of the β-TCP-containing composite scaffolds was decreased. The complete release of vancomycin from the G-TCP5 scaffold was achieved within three weeks. In the treatment of osteomyelitis defects in rabbits, the G-TCP3 scaffold showed the most efficacious performance in eliminating infections and repairing bone defects. Conclusions. The composite scaffolds could achieve local therapeutic drug levels over an extended duration. The G-TCP3 scaffold possessed the optimal porosity, interconnection and controlled release performance. Therefore, this scaffold could potentially be used in the treatment of chronic osteomyelitis defects. Cite this article: J. Zhou, X. G. Zhou, J. W. Wang, H. Zhou, J. Dong. Treatment of osteomyelitis defects by a vancomycin-loaded gelatin/β-tricalcium phosphate composite scaffold. Bone Joint Res 2018;7:46–57. DOI: 10.1302/2046-3758.71.BJR-2017-0129.R2

Aims. This systematic review places a recently completed multicentre randomized controlled trial (RCT), UK FROST, in the context of existing randomized evidence for the management of primary frozen shoulder. UK FROST compared the effectiveness of pre-specified physiotherapy techniques with a steroid injection (PTSI), manipulation under anaesthesia (MUA) with a steroid injection, and arthroscopic capsular release (ACR). This review updates a 2012 review focusing on the effectiveness of MUA, ACR, hydrodilatation, and PTSI. Methods. MEDLINE, Embase, PEDro, Science Citation Index, Clinicaltrials.gov, CENTRAL, and the World Health Organization (WHO) International Clinical Trials Registry were searched up to December 2018. Reference lists of included studies were screened. No language restrictions applied. Eligible studies were RCTs comparing the effectiveness of MUA, ACR, PTSI, and hydrodilatation against each other, or supportive care or no treatment, for the management of primary frozen shoulder. Results. Nine RCTs were included. The primary outcome of patient-reported shoulder function at long-term follow-up (> 6 months and ≤ 12 months) was reported for five treatment comparisons across four studies. Standardized mean differences (SMD) were: ACR versus MUA: 0.21 (95% confidence interval (CI) 0.00 to 0.42), ACR versus supportive care: -0.13 (95% CI -1.10 to 0.83), and ACR versus PTSI: 0.33 (95% CI 0.07 to 0.59) and 0.25 (95% CI -0.34 to 0.85), all favouring ACR; MUA versus supportive care: 0 (95% CI -0.44 to 0.44) not favouring either; and MUA versus PTSI: 0.12 (95% CI -0.14 to 0.37) favouring MUA. None of these differences met the threshold of clinical significance agreed for the UK FROST and most confidence intervals included zero. Conclusion. The findings from a recent multicentre RCT provided the strongest evidence that, when compared with each other, neither PTSI, MUA, nor ACR are clinically superior. Evidence from smaller RCTs did not change this conclusion. The effectiveness of hydrodilatation based on four RCTs was inconclusive and there remains an evidence gap. Cite this article: Bone Jt Open 2021;2(9):773–784

Objectives. The aim of this study was to analyze drain fluid, blood, and urine simultaneously to follow the long-term release of vancomycin from a biphasic ceramic carrier in major hip surgery. Our hypothesis was that there would be high local vancomycin concentrations during the first week with safe low systemic trough levels and a complete antibiotic release during the first month. Methods. Nine patients (six female, three male; mean age 75.3 years (sd 12.3; 44 to 84)) with trochanteric hip fractures had internal fixations. An injectable ceramic bone substitute, with hydroxyapatite in a calcium sulphate matrix, containing 66 mg of vancomycin per millilitre, was inserted to augment the fixation. The vancomycin elution was followed by simultaneously collecting drain fluid, blood, and urine. Results. The antibiotic concentration in the drain reached a peak during the first six hours post-surgery (mean 966.1 mg/l), which decreased linearly to a mean value of 88.3 mg/l at 2.5 days. In the urine, the vancomycin concentration reached 99.8 mg/l during the first two days, followed by a logarithmic decrease over the next two weeks to reach 0 mg/l at 20 days. The systemic concentration of vancomycin measured in blood serum was low and decreased linearly from 2.17 mg/l at one hour post-surgery to 0 mg/l at four days postoperatively. Conclusion. This is the first long-term pharmacokinetic study that reports vancomycin release from a biphasic injectable ceramic bone substitute. The study shows initial high targeted local vancomycin levels, sustained and complete release at three weeks, and systemic concentrations well below toxic levels. The plain ceramic bone substitute has been proven to regenerate bone but should also be useful in preventing bone infection. Cite this article: M. Stravinskas, M. Nilsson, A. Vitkauskiene, S. Tarasevicius, L. Lidgren. Vancomycin elution from a biphasic ceramic bone substitute. Bone Joint Res 2019;8:49–54. DOI: 10.1302/2046-3758.82.BJR-2018-0174.R2

Limb alignment in total knee arthroplasty (TKA) influences periarticular soft-tissue tension, biomechanics through knee flexion, and implant survival. Despite this, there is no uniform consensus on the optimal alignment technique for TKA. Neutral mechanical alignment facilitates knee flexion and symmetrical component wear but forces the limb into an unnatural position that alters native knee kinematics through the arc of knee flexion. Kinematic alignment aims to restore native limb alignment, but the safe ranges with this technique remain uncertain and the effects of this alignment technique on component survivorship remain unknown. Anatomical alignment aims to restore predisease limb alignment and knee geometry, but existing studies using this technique are based on cadaveric specimens or clinical trials with limited follow-up times. Functional alignment aims to restore the native plane and obliquity of the joint by manipulating implant positioning while limiting soft tissue releases, but the results of high-quality studies with long-term outcomes are still awaited. The drawbacks of existing studies on alignment include the use of surgical techniques with limited accuracy and reproducibility of achieving the planned alignment, poor correlation of intraoperative data to long-term functional outcomes and implant survivorship, and a paucity of studies on the safe ranges of limb alignment. Further studies on alignment in TKA should use surgical adjuncts (e.g. robotic technology) to help execute the planned alignment with improved accuracy, include intraoperative assessments of knee biomechanics and periarticular soft-tissue tension, and correlate alignment to long-term functional outcomes and survivorship

Aims. Poly(methyl methacrylate) (PMMA)-based bone cements are the industry standard in orthopaedics. PMMA cement has inherent disadvantages, which has led to the development and evaluation of a novel silorane-based biomaterial (SBB) for use as an orthopaedic cement. In this study we test both elution and mechanical properties of both PMMA and SBB, with and without antibiotic loading. Methods. For each cement (PMMA or SBB), three formulations were prepared (rifampin-added, vancomycin-added, and control) and made into pellets (6 mm × 12 mm) for testing. Antibiotic elution into phosphate-buffered saline was measured over 14 days. Compressive strength and modulus of all cement pellets were tested over 14 days. Results. The SBB cement was able to deliver rifampin over 14 days, while PMMA was unable to do so. SBB released more vancomycin overall than did PMMA. The mechanical properties of PMMA were significantly reduced upon rifampin incorporation, while there was no effect to the SBB cement. Vancomycin incorporation had no effect on the strength of either cement. Conclusion. SBB was found to be superior in terms of rifampin and vancomycin elution. Additionally, the incorporation of these antibiotics into SBB did not reduce the strength of the resultant SBB cement composite whereas rifampin substantially attenuates the strength of PMMA. Thus, SBB emerges as a potential weight-bearing alternative to PMMA for the local delivery of antibiotics. Cite this article: Bone Joint Res 2021;10(4):277–284

Aims. The results of kinematic total knee arthroplasty (KTKA) have been reported in terms of limb and component alignment parameters but not in terms of gap laxities and differentials. In kinematic alignment (KA), balance should reflect the asymmetrical balance of the normal knee, not the classic rectangular flexion and extension gaps sought with gap-balanced mechanical axis total knee arthroplasty (MATKA). This paper aims to address the following questions: 1) what factors determine coronal joint congruence as measured on standing radiographs?; 2) is flexion gap asymmetry produced with KA?; 3) does lateral flexion gap laxity affect outcomes?; 4) is lateral flexion gap laxity associated with lateral extension gap laxity?; and 5) can consistent ligament balance be produced without releases?. Patients and Methods. A total of 192 KTKAs completed by a single surgeon using a computer-assisted technique were followed for a mean of 3.5 years (2 to 5). There were 116 male patients (60%) and 76 female patients (40%) with a mean age of 65 years (48 to 88). Outcome measures included intraoperative gap laxity measurements and component positions, as well as joint angles from postoperative three-foot standing radiographs. Patient-reported outcome measures (PROMs) were analyzed in terms of alignment and balance: EuroQol (EQ)-5D visual analogue scale (VAS), Knee Injury and Osteoarthritis Outcome Score (KOOS), KOOS Joint Replacement (JR), and Oxford Knee Score (OKS). Results. Postoperative limb alignment did not affect outcomes. The standing hip-knee-ankle (HKA) angle was the sole positive predictor of the joint line convergence angle (JLCA) (p < 0.001). Increasing lateral flexion gap laxity was consistently associated with better outcomes. Lateral flexion gap laxity did not correlate with HKA angle, the JLCA, or lateral extension gap laxity. Minor releases were required in one third of cases. Conclusion. The standing HKA angle is the primary determinant of the JLCA in KTKA. A rectangular flexion gap is produced in only 11% of cases. Lateral flexion gap laxity is consistently associated with better outcomes and does not affect balance in extension. Minor releases are sometimes required as well, particularly in limbs with larger preoperative deformities. Cite this article: Bone Joint J 2019;101-B:331–339

Aims. The objectives of this study were to assess the effect of anterior cruciate ligament (ACL) resection on flexion-extension gaps, mediolateral soft tissue laxity, maximum knee extension, and limb alignment during primary total knee arthroplasty (TKA). Methods. This prospective study included 140 patients with symptomatic knee osteoarthritis undergoing primary robotic-arm assisted TKA. All operative procedures were performed by a single surgeon using a standard medial parapatellar approach. Optical motion capture technology with fixed femoral and tibial registration pins was used to assess study outcomes pre- and post-ACL resection with knee extension and 90° knee flexion. This study included 76 males (54.3%) and 64 females (45.7%) with a mean age of 64.1 years (SD 6.8) at time of surgery. Mean preoperative hip-knee-ankle deformity was 6.1° varus (SD 4.6° varus). Results. ACL resection increased the mean extension gap significantly more than the flexion gap in the medial (mean 1.2 mm (SD 1.0) versus mean 0.2 mm (SD 0.7) respectively; p < 0.001) and lateral (mean 1.1 mm (SD 0.9) versus mean 0.2 mm (SD 0.6) respectively; p < 0.001) compartments. The mean gap differences following ACL resection did not create any significant mediolateral soft tissue laxity in extension (gap difference: mean 0.1 mm (SD 2.4); p = 0.89) or flexion (gap difference: mean 0.2 mm (SD 3.1); p = 0.40). ACL resection did not significantly affect maximum knee extension (change in maximum knee extension = mean 0.2° (SD 0.7°); p = 0.23) or fixed flexion deformity (mean 4.2° (SD 3.2°) pre-ACL release versus mean 3.9° (SD 3.7°) post-ACL release; p = 0.61). ACL resection did not significantly affect overall limb alignment (change in alignment = mean 0.2° valgus (SD 1.0° valgus; p = 0.11). Conclusion. ACL resection creates flexion-extension mismatch by increasing the extension gap more than the flexion gap. However, gap differences following ACL resection do not create any mediolateral soft tissue laxity in extension or flexion. ACL resection does not affect maximum knee extension or overall limb alignment. Cite this article: Bone Joint J 2020;102-B(4):442–448

Aims. Between 15% and 20% of patients remain dissatisfied following total knee arthroplasty (TKA). The SAIPH knee system (MatOrtho, Surrey, United Kingdom) is a medial ball and socket TKA that has been designed to replicate native knee kinematics in order to maximize the range of movement, stability, and function. This system is being progressively introduced in a stepwise fashion, with this study reporting the mid-term clinical and radiological outcomes. Patients and Methods. A retrospective review was undertaken of the first 100 consecutive patients with five-year follow-up following SAIPH TKA performed by the senior authors. The data that were collected included the demographics of the patients, clinical findings, the rate of intraoperative ligamentous release, patient-reported outcome measures (PROMS), radiological assessment, complications, and all-cause revision. Revision data were cross-checked with a national registry. Results. A total of 100 TKAs in 92 patients were included. Three patients died (three TKAs) and a further two TKAs were revised. Of the remaining 95 TKAs, five-year follow-up data were available for 81 TKAs (85%) in 87 patients. There were significant improvements in all PROMs and high satisfaction. The mean ROM at final follow-up was from 0° (full extension) to 124° flexion. There were seven major complications (7%): one infection, two deep vein thromboses, one cerebrovascular event, and two patients with stiffness requiring a manipulation under anaesthesia. Two patients required a lateral retinacular release to optimize patellar tracking in valgus knees; no additional ligament releases were performed in any patient. Radiological analysis demonstrated no evidence of implant-related complications. Conclusion. These results demonstrate satisfactory clinical and radiological outcomes at five years following a medial ball and socket TKA. The complication and revision rates are consistent with those previously reported for patients undergoing TKA. These results demonstrate the safety and efficacy of the SAIPH Knee TKA system and support its wider use

Aims. Optimal exposure through the direct anterior approach (DAA) for total hip arthroplasty (THA) conducted on a regular operating theatre table is achieved with a standardized capsular releasing sequence in which the anterior capsule can be preserved or resected. We hypothesized that clinical outcomes and implant positioning would not be different in case a capsular sparing (CS) technique would be compared to capsular resection (CR). Methods. In this prospective trial, 219 hips in 190 patients were randomized to either the CS (n = 104) or CR (n = 115) cohort. In the CS cohort, a medial based anterior flap was created and sutured back in place at the end of the procedure. The anterior capsule was resected in the CR cohort. Primary outcome was defined as the difference in patient-reported outcome measures (PROMs) after one year. PROMs (Harris Hip Score (HHS), Hip disability and Osteoarthritis Outcome Score (HOOS), and Short Form 36 Item Health Survey (SF-36)) were collected preoperatively and one year postoperatively. Radiological parameters were analyzed to assess implant positioning and implant ingrowth. Adverse events were monitored. Results. At one year, there was no difference in HSS (p = 0.728), HOOS (Activity Daily Life, p = 0.347; Pain, p = 0.982; Quality of Life, p = 0.653; Sport, p = 0.994; Symptom, p = 0.459), or SF-36 (p = 0.338). Acetabular component inclination (p = 0.276) and anteversion (p = 0.392) as well as femoral component alignment (p = 0.351) were similar in both groups. There were no dislocations, readmissions, or reoperations in either group. The incidence of psoas tendinitis was six cases in the CS cohort (6%) and six cases in the CR cohort (5%) (p = 0.631). Conclusion. No clinical differences were found between resection or preservation of the anterior capsule when performing a primary THA through the DAA on a regular theatre table. In case of limited visibility during the learning curve, it might be advisable to resect a part of the anterior capsule. Cite this article: Bone Joint J 2021;103-B(2):321–328

Aims. Microbiological culture is a key element in the diagnosis of periprosthetic joint infection (PJI). However, cultures of periprosthetic tissue do not have optimal sensitivity. One of the main reasons for this is that microorganisms are not released from the tissues, either due to biofilm formation or intracellular persistence. This study aimed to optimize tissue pretreatment methods in order to improve detection of microorganisms. Methods. From December 2017 to September 2019, patients undergoing revision arthroplasty in a single centre due to PJI and aseptic failure (AF) were included, with demographic data and laboratory test results recorded prospectively. Periprosthetic tissue samples were collected intraoperatively and assigned to tissue-mechanical homogenization (T-MH), tissue-manual milling (T-MM), tissue-dithiothreitol (T-DTT) treatment, tissue-sonication (T-S), and tissue-direct culture (T-D). The yield of the microbial cultures was then analyzed. Results. A total of 46 patients were enrolled, including 28 patients in the PJI group and 18 patients in the AF group. In the PJI group, 23 cases had positive culture results via T-MH, 22 cases via T-DTT, 20 cases via T-S, 15 cases via T-MM, and 13 cases via T-D. Three cases under ongoing antibiotic treatment remained culture-negative. Five tissue samples provided the optimal yield. Any ongoing antibiotic treatment had a relevant influence on culture sensitivity, except for T-DTT. Conclusion. T-MH had the highest sensitivity. Combining T-MH with T-DTT, which requires no special equipment, may effectively improve bacterial detection in PJI. A total of five periprosthetic tissue biopsies should be sampled in revision arthroplasty for optimal detection of PJI. Cite this article: Bone Joint Res 2021;10(2):96–104

Aims. Iliopsoas pathology is a relatively uncommon cause of pain following total hip arthroplasty (THA), typically presenting with symptoms of groin pain on active flexion and/or extension of the hip. A variety of conservative and surgical treatment options have been reported. In this retrospective cohort study, we report the incidence of iliopsoas pathology and treatment outcomes. Methods. A retrospective review of 1,000 patients who underwent THA over a five-year period was conducted, to determine the incidence of patients diagnosed with iliopsoas pathology. Outcome following non-surgical and surgical management was assessed. Results. In all, 24 patients were diagnosed as having developed symptomatic iliopsoas pathology giving an incidence of 2.4%. While the mean age for receiving a THA was 65 years, the mean age for developing iliopsoas pathology was 54 years (28 to 67). Younger patients and those receiving THA for conditions other than primary osteoarthritis were at a higher risk of developing this complication. Ultrasound-guided steroid injection/physiotherapy resulted in complete resolution of symptoms in 61% of cases, partial resolution in 13%, and no benefit in 26%. Eight out of 24 patients (who initially responded to injection) subsequently underwent surgical intervention including tenotomy (n = 7) and revision of the acetabular component (n = 1). Conclusion. This is the largest case series to estimate the incidence of iliopsoas pathology to date. There is a higher incidence of this condition in younger patients, possibly due to the differing surgical indications. Arthoplasty for Perthes' disease or developmental dysplasia of the hip (DDH) often results in leg length and horizontal offset being increased. This, in turn, may increase tension on the iliopsoas tendon, possibly resulting in a higher risk of psoas irritation. Image-guided steroid injection is a low-risk, relatively effective treatment. In refractory cases, tendon release may be considered. Patients should be counselled of the risk of persisting groin pain when undergoing THA. Cite this article: Bone Joint J 2021;103-B(2):305–308