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Background: Pseudotumors are sterile inflammatory lesions found in the soft tissues surrounding metal-on-metal (MOM) and metal-on-polyethylene hip arthroplasties. In patients with MOM hip arthroplasties, pseudotumors are thought to represent an adverse reaction to metal wear debris. However, the pathogenesis of these lesions remains unclear. Currently, there is inconsistent evidence regarding the influence of adverse cup position and increased wear in the formation of pseudotumors.Questions/purposes: We therefore determined whether pseudotumor formation was associated with (1) adverse cup position, (2) raised metal ion levels, and (3) increased wear rates of the retrieved components.Methods: We retrospectively reviewed all 352 patients for whom we had retrieved specimens from revisions of a current-generation MOM hip prosthesis between February 2008 and September 2010; of these, 105 met our inclusion criteria. We used multivariate logistic regression analysis to compare acetabular orientation, metal ion levels before revision, and component wear rates between patients with (n = 72) and without (n = 33) pseudotumors, according to findings on metal artifact reduction sequence MRI.Results: The proportion of patients demonstrating evidence of a pseudotumor in well-positioned hips was similar to those with adverse cup positions (67% and 66%, respectively). Patients revised with pseudotumors had similar whole-blood metal ion levels and component wear rates to those who were not revised.Conclusions: Pseudotumors were not associated with increased wear or metal ion levels, suggesting patient susceptibility is likely to be more important. [ABSTRACT FROM AUTHOR]

Background: The Trident II Tritanium acetabular shell is additively manufactured (3D printed), based on the established Trident 'I' Tritanium shell, produced using conventional methods; this study characterised their differences., Methods: We obtained 5 Trident I (T1) and 5 Trident II (T2) shells sized 52 mm, 54 mm (n = 3) and 60 mm. We measured their: mass, shell-liner engaging surface roughness, roundness, wall thickness, the depth of the bone-facing porous layer, porosity, and the number, volume and location of structural voids., Results: The mass varied by up to 13.44 g. The T1 and T2 shells had a median internal roughness of 0.18 μm and 0.43 μm, (p < 0.001) and the median departure from roundness was 6.9 μm and 8.9 μm, (p < 0.001). The 54 mm and 60 mm T2 shell walls were 37% and 29% thinner than their T1 counterparts (p < 0.01). The T2 shells had irregular porous structures, shallower in depth by 11-27% (p < 0.001) than T1 shells, which had repeating mesh units; the overall porosity was comparable (54%). All T2 shells had between 115 and 3415 structural voids, compared with two T1 shells containing 21 and 31 voids. There was no difference in the depth of the porous layer for the 54 mm T2 shells (p = 0.068), whilst T1 shells did show variability (p < 0.01). Both groups showed a variability in surface roughness and roundness (p < 0.01)., Conclusion: This is the first study to compare shells from a single manufacturer, produced using conventional and additive methods. This data will help interpret the performance of the 3D printed Trident II as longer-term clinical data is generated., (© 2024. The Author(s).)

Three-dimensional printing is a rapidly growing manufacturing method for orthopaedic implants and it is currently thriving in several other engineering industries. It enables the variation of implant design and the construction of complex structures which can be exploited in orthopaedics and other medical sectors. In this review, we develop the vocabulary to characterise 3D printing in orthopaedics from terms defined by industries employing 3D printing, and by fully examining a 3D-printed off-the-shelf acetabular cup (Fig. 1). This is a commonly used 3D-printed implant in orthopaedics, and it exhibits a range of prominent features brought about by 3D printing. The key features and defects of the porous and dense regions of the implant are clarified and discussed in depth to determine reliable definitions and a common understanding of characteristics of 3D printing between engineers and medical experts in orthopaedics. Despite the extensive list of terminology derived here, it is clear significant gaps exist in the knowledge of this field. Therefore, it is necessary for continued investigations of unused implants, but perhaps more significantly, examining those in vivo and retrieved to understand their long-term impact on patients and the effects of certain features (e.g. surface-adhered particles). Analyses of this kind will establish an understanding of 3D printing in orthopaedics and additionally it will help to update the regulatory approach to this new technology.

Study Design: Multicentre comparative analysis of explanted Spine Magnetically Controlled Growing Rods (MCGRs)., Objectives: MAGEC X, the latest commercially available generation, was recalled in 2020 due to the risk of post-implantation separation of an actuator end-cap component. Currently, the supply of all MAGEC rods was temporarily suspended in the UK and the EU. Objective of this study is to compare the performance of the MAGEC X MCGR to the earlier MAGEC 1.3 design iteration, by means of retrieval analysis., Methods: Fifteen of both MAGEC X and MAGEC 1.3 rods were consecutively collected from five different hospitals following removal surgery and matched by time to removal. Clinical and implant data was collected for all MCGRs. Analysis comprised visual assessments of external damage, plain radiograph evaluations, force and elongation testing, MAGEC X end-cap torque testing and disassembly. Mann-Whitney U tests were used to statistically compare groups., Results: Rod distraction reached in vivo was significantly higher in the MAGEC 1.3 ( P = .002). There was no statistically significant difference in the total external damage score ( P = .870), maximum force produced ( P = .695) or distraction reached during force test ( P = .880). No pin fracture was detected. Elongation of stroke was mildly higher ( P = .051) for the MAGEC X implants. One MAGEC X had evident end cap component loosening. Internal damage scores were mildly lower in the MAGEC X group., Conclusion: MAGEC X showed similar performance results than the previous design iteration MAGEC 1.3. End-cap component loosening was observed, with no major consequences on the internal mechanism., Competing Interests: Declaration of Conflicting InterestsThe author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: Authors HH and AH receive institutional support from NuVasive to independently collect and analyse retrieved MAGEC rods. Authors MS, ST and EB use MAGEC rods in their clinical practice.

Background: Three-dimensional computed-tomography (3D-CT) planning for primary Total Hip Arthroplasty (THA) typically uses the external femoral surface; as a result, it is difficult to predict the prosthetic femoral version (PFV) for uncemented femoral stems that press-fit to the internal surface of the bone. Cemented fixation allows the surgeon to adjust the version independent of the internal femoral anatomy. We aimed to better understand the effect of the fixation type on PFV., Methods: This was a case series study including a total of 95 consecutive patients (106 hips), who underwent uncemented (n = 81 hips) and cemented (n = 25 hips) primary THA using the posterior approach. The surgeon aimed for a PFV of 20°. Our primary objective was to compare PFV in both groups; our secondary objective was to evaluate the clinical outcomes., Results: The mean (± SD) PFV was 13° (± 9°) and 23° (± 8°) for the uncemented and cemented THA groups (P < 0.001), respectively. In the uncemented THA group, 36% of the patients had a PFV of < 10°. In the cemented THA group, this clinically important threshold dropped to 8%. Similarly, the Bland-Altman (BA) plots showed wider 95% limits of agreement for the uncemented group. Satisfactory clinical outcomes were recorded., Conclusion: We found that the PFV was more clinically acceptable, for the posterior surgical approach, in the cemented group when compared to the uncemented group. Both THA groups reported high variability indicating the need to develop surgical tools to guide the PFV closer to the surgical target., (© 2023. The Author(s).)

CT is the principal imaging modality used for the pre-operative 3D planning and assessment of total hip arthroplasty (THA). The image quality offered by CT has a radiation penalty to the patient. Higher than necessary radiation exposure is of particular concern when imaging young patients and women of childbearing age, due to the greater risk of radiation-induced cancer in this group. A harmonised low-dose CT protocol is needed, evidenced by the huge variability in the 17 protocols reviewed. The majority of the protocols were incomplete, leading to uncertainty among radiographers when performing the scans. Only three protocols (20%) were optimised for both 'field of view' and image acquisition parameters. 10 protocols (60%) were optimised for 'field of view' only. These protocols included imaging of the relevant landmarks in the bony pelvis in addition to the knees - the reference for femoral anteversion. CT parameters, including the scanner kilovoltage (kV), milliamperage-time product (mAs) and slice thickness, must be optimised with a 'field of view' that includes the relevant bony landmarks. The recommended kV and mAs values were very wide ranging from 100 to 150 and from 100 to 250, respectively. The large variability that exists amongst the CT protocols illustrates the need for a more consistent low-dose CT protocol for the planning of THA. This must provide an optimal balance between image quality and radiation dose to the patient. Current CT scanners do not allow for measurements of functional pelvic orientation and additional upright imaging modalities are needed to augment them.

Objectives: This study aims to quantitatively evaluate whether there are muscle mass differences between male and female recreational cyclists and compare muscle quality and body composition in the pelvis region between two well-matched groups of fit and healthy male and female adults., Methods: This cross-sectional study involved 45 female and 42 male recreational cyclists. The inclusion criteria for both groups were to have cycled more than 7000 km in the last year, have an absence of injuries and other health problems, have no contraindication to MRI, and be 30-65 years old. Our main outcome measures were fat fraction, as a measure of intramuscular fat (IMF) content, and volume of the gluteal muscles measured using Dixon MRI. The gluteal subcutaneous adipose tissue (SAT) volume was evaluated as a secondary measure., Results: We found that there were no gender differences in the IMF content of gluteus maximus (GMAX, p=0.42), gluteus medius (GMED, p=0.69) and gluteus minimus (GMIN, p=0.06) muscles, despite women having more gluteal SAT (p<0.01). Men had larger gluteal muscles than women (p<0.01), but no differences were found when muscle volume was normalised by body weight (GMAX, p=0.54; GMED, p=0.14; GMIN, p=0.19)., Conclusions: Our study shows that despite the recognised hormonal differences between men and women, there is gender equivalence in the muscle mass and quality of the gluteal muscles when matched for exercise and body weight. This new MRI study provides key information to better understand gender similarities and differences in skeletal muscle and body composition., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2023. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

The management of massive acetabular defects at the time of revision hip surgery is challenging. Severe pelvic bone loss and the heterogeneity and quality of the remaining bone stock can compromise the fixation and mechanical stability of the implant., Methods: We reviewed a database of consecutive patients who had undergone acetabular reconstruction with the use of a custom 3D-printed implant with a dual-mobility bearing for the treatment of Paprosky type-3B defects between 2016 and 2019. Functional and radiological outcomes were assessed., Results: A total of 26 patients (17 women and 9 men) with a minimum follow-up of 36 months (median, 53 months; range, 36 to 77 months) were identified. The median age at surgery was 69 years (range, 49 to 90 years), and 4 patients had pelvic discontinuity. The cumulative implant survivorship was 100%. The median Oxford Hip Score improved significantly from 8 (range, 2 to 21) preoperatively to 32 (range, 14 to 47) postoperatively (p = 0.0001). One patient had a transient sciatic nerve palsy, 1 hip dislocated 6 months postoperatively and was managed nonoperatively, and 1 infection recurred. No patient had a fracture. Radiographic evaluation showed bone ingrowth at the bone-implant interface in 24 patients (92%) at ≥12 months of follow-up and showed no evidence of implant loosening or migration at the latest follow-up (3 to 6 years)., Conclusions: Excellent functional improvement, implant survivorship, and osseointegration were recorded in the patient cohort. Accurate preoperative planning and the adoption of custom 3D-printed implants showed promising results in complex revision hip surgery., Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence., Competing Interests: Disclosure: The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article (http://links.lww.com/JBJSOA/A512)., (Copyright © 2023 The Authors. Published by The Journal of Bone and Joint Surgery, Incorporated. All rights reserved.)

The placement of acetabular implant components determines the short- and long-term outcomes of total hip replacement (THR) and a number of tools have been developed to assist the surgeon in achieving cup orientation to match the surgical plan. However, the accuracy and precision of 3D-CT for the measurement of acetabular component position and orientation is yet to be established. To investigate this, we compared measurements of cobalt chrome acetabular components implanted into 2 different bony pelvic models between a coordinate measuring Faro arm and 3 different low dose CT images, including 3D-CT, 2D anterior pelvic plane (APP) referenced CT and 2D scanner referenced (SR) CT. Intra-observer differences were assessed using the Intraclass correlation coefficient (ICC). The effect of imaging the pelvis positioned in 3 different orientations within the CT scanner was also assessed. The measured parameters were the angles of inclination and version. 3D-CT measurements were found to closely match the "true values" of the component position measurements, compared with the 2D-CT methods. ICC analysis also showed good agreement between the coordinate measuring arm (CMA) and 3D-CT but poor agreement between the 2D SR method, in the results from two observers. When using the coordinate system of the CT scanner, the measurements consistently produced the greatest error; this method yielded values up to 34° different from the reference digitising arm. However, the difference between the true inclination and version angles and those measured from 3D APP CT was below half a degree in all cases. We concluded that low radiation dose 3D-CT is a validated reference standard for the measurement of acetabular cup orientation., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Henckel, Ramesh, Hothi, Richards, Di Laura and Hart.)

Background: Implantation of the femoral component with suboptimal version is associated with instability of the reconstructed hip joint. High variability of Prosthetic Femoral Version (PFV) has been reported in primary Total Hip Arthroplasty (THA). Three-dimensional (3D) Patient-Specific Instrumentation (PSI) has been recently developed and may assist in delivering a PFV within the intended range. We performed a pilot study to better understand whether the intra-operative use of a novel PSI guide, designed to deliver a PFV of 20°, results in the target range of PFV in primary cemented THA., Methods: We analysed post-operative Computed-Tomography (CT) data of two groups of patients who underwent primary cemented THA through posterior approach; 1. A group of 11 patients (11 hips) for which the surgeon used an intra-operative 3D-printed stem positioning guide (experimental) 2. A group of 24 patients (25 hips) for which the surgeon did not use the guide (control). The surgeon aimed for a PFV of 20°, and therefore the guide was designed to indicate the angle at which the stem was positioned intra-operatively. PFV angles were measured using the post-operative 3D-CT models of the proximal femurs and prosthetic components in both groups. Our primary objective was to compare the PFV in both groups. Our secondary objective was to evaluate the clinical outcome., Results: Mean (± SD) values for the PFV was 21.3° (± 4.6°) and 24.6° (± 8.2°) for the experimental and control groups respectively. In the control group, 20% of the patients reported a PFV outside the intended range of 10° to 30° anteversion. In the experimental group, this percentage dropped to 0%. Satisfactory clinical outcome was recorded in both groups., Conclusion: The intra-operative use of a PSI PFV guide helped the surgeon avoid suboptimal PFV in primary cemented THA. Further studies are needed to evaluate if the PSI guide directly contributes to a better clinical outcome., (© 2023. The Author(s).)

Physical activity and a healthy lifestyle are crucial factors for delaying and reducing the effects of sarcopenia. Cycling has gained popularity in the last decades among midlife men. While the cardiovascular benefits of cycling and other endurance exercises have been extensively proved, the potential benefits of lifelong aerobic exercise on muscle health have not been adequately studied. Our aim was to quantify the benefits of cycling in terms of muscle health in middle-aged men, using magnetic resonance imaging. We ran a cross-sectional study involving two groups of middle-aged male adults (mean age 49 years, range 30-65) that underwent Dixon MRI of the pelvis. The groups consisted of 28 physically inactive (PI) and 28 trained recreational cyclists. The latter had cycled more than 7000 km in the last year and have been training for 15 years on average, while the PI volunteers have not practiced sports for an average of 27 years. We processed the Dixon MRI scans by labelling and computing the fat fraction (FF), volume and lean volume of gluteus maximus (GMAX) and gluteus medius (GMED); and measuring the volume of subcutaneous adipose tissue (SAT). We found that the cyclists group had lower FF levels, a measure of intramuscular fat infiltration, compared to the PI group for GMAX (PI median FF 21.6%, cyclists median FF 14.8%, p < 0.01) and GMED (PI median FF 16.0%, cyclists median FF 11.4%, p < 0.01). Cyclists had also larger GMAX and GMED muscles than the PI group (p < 0.01), after normalizing it by body mass. Muscle mass and fat infiltration were strongly correlated with SAT volume. These results suggest that cycling could help preserve muscle mass and composition in middle-aged men. Although more research is needed to support these results, this study adds new evidence to support public health efforts to promote cycling., (© 2023. The Author(s).)

Edge-wear in acetabular cups is known to be correlated with greater volumes of material loss; the location of this wear pattern in vivo is less understood. Statistical shape modelling (SSM) may provide further insight into this. This study aimed to identify the most common locations of wear in vivo, by combining CT imaging, retrieval analysis and SMM. Shape variance was described in 20 retrieved metal-on-metal acetabular surfaces. These were revised after a mean of 90 months, from 13 female and seven male patients. They were positioned with a mean inclination and anteversion of 53° and 30°, respectively. Their orientation, in vivo, was established using their stabilising fins, visible in pre-revision CT imaging. The impact of wear volume, positioning, time, gender and size on the in vivo location of wear was investigated. These surfaces had a mean wear volume of 49.63 mm 3 . The mean acetabular surface displayed superior edge-wear centred 7° within the posterosuperior quadrant, while more of the volumetric wear occurred in the anterosuperior quadrant. Components with higher inclination had greater superior edge-wear scars, while a relationship was observed between greater anteversion angles and more posterosuperior edge-wear. This SSM method can further our understanding of hip implant function, informing future design and may help to refine the safe zone for implant positioning.

Femoral neck osteotomy creates a critical anatomical landmark for surgeons performing primary Total Hip Arthroplasty (THA); it affects the final height and position of the femoral component. Patient Specific Instrumentation (PSI) has been developed to guide the osteotomy. We aimed to assess the accuracy of a patient-specific (PS) femoral osteotomy guide in primary THA using three-dimensional (3D) computed tomography (CT) analysis. We included pre- and post-operative CT data of 103 THAs. All patients underwent 3D planning to define the optimal femoral neck osteotomy level. Our primary objective was to quantify the discrepancy between the achieved and planned osteotomy level; our secondary objective was to evaluate the clinical outcome. The median (Interquartile Range—IQR) discrepancy between the achieved and planned osteotomy level was 0.3 mm (−1 mm to 2 mm). We found a strong positive correlation between the planned and achieved osteotomy level (R2 = 0.9, p < 0.001). A satisfactory clinical outcome was recorded. Our findings suggest that surgeons can use 3D-printed PS guides to achieve a femoral neck osteotomy with a high level of accuracy to the plan.

Background: 3D printed patient-specific titanium acetabular cups are used to treat patients with massive acetabular defects. These have highly porous surfaces, with the design intent of enhancing bony fixation. Our aim was to characterise these porous structures in commercially available designs., Methods: We obtained 12 final-production, patient-specific 3D printed acetabular cups that had been produced by 6 manufacturers. High resolution micro-CT imaging was used to characterise morphometric features of their porous structures: (1) strut thickness, 2) the depth of the porous layer, (3) pore size and (4) the level of porosity. Additionally, we computed the surface area of each component to quantify how much titanium may be in contact with patient tissue. Statistical comparisons were made between the designs., Results: We found a variability between designs in relation to the thickness of the struts (0.28 to 0.65 mm), how deep the porous layers are (0.57 to 11.51 mm), the pore size (0.74 to 1.87 mm) and the level of porosity (34 to 85%). One manufacturer printed structures with different porosities between the body and flange; another manufacturer had two differing porous regions within the body of the cups. The cups had a median (range) surface area of 756.5 mm 2 (348 - 1724)., Conclusions: There is a wide variability between manufacturers in the porous titanium structures they 3D print. We do not currently know whether there is an optimal porosity and how this variability will impact clinically on the integrity of bony fixation; this will become clearer as post market surveillance data is generated., (© 2022. The Author(s).)

Background: Titanium, which is known to be a highly biologically inert element, is one of the most commonly used metals in orthopaedic implants. While cobalt and chromium blood metal ion testing is routinely used in the clinical monitoring of patients with metal-on-metal hip implants, much less is known about the levels of titanium in patients with other implant types. The aim of this study was to better understand the normal ranges of blood titanium levels in patients implanted with large and sliding titanium constructs by comparison with reference levels from conventional titanium hips., Methods: This study examined data collected from 136 patients. Over a period of 24 months, whole blood samples were collected from 41 patients implanted with large titanium implants: long (range 15 to 30 cm) spine rods with a sliding mechanism ("spine rods", n = 18), long bone tumour implants ("tumour implants", n = 13) and 3D-printed customised massive acetabular defect implants ("massive acetabular implants", n = 10). This data was compared with standard, uncemented primary titanium hip implants ("standard hips", 15 cm long) (n = 95). Clinical, imaging and blood titanium levels data were collected for all patients and compared statistically between the different groups., Results: The median (range) of blood titanium levels of the standard hip, spine rods, femoral tumour implants and massive acetabular implants were 1.2 ppb (0.6-4.9), 9.7 ppb (4.0-25.4), 2.6 ppb (0.4-104.4) and 5.7 ppb (1.6-31.5) respectively. Spine rods and massive acetabular implants had significantly greater blood titanium levels compared to the standard hips group (p < 0.001)., Conclusion: This study showed that titanium orthopaedic implants that are large and/or have a sliding mechanism have higher blood titanium levels compared to well-functioning, conventionally sized titanium hips. Reassuringly, the increased levels did not appear to induce adverse metal reactions. This study provides useful baseline data for future studies aimed at assessing blood titanium levels as a biomarker for implant function., (© 2022. The Author(s).)

Background: With the Persona® knee system a novel anatomic total knee design was developed, which has no pre-coating, whereas the predecessor knee system is pre-coated with polymethylmethacrylate (PMMA). Joint registry data have shown no decrease in risk of aseptic revision of PMMA pre-coated tibial components compared with non-pre-coated implants. The aim of this retrieval study was to compare the amount of cement adhesions, geometry and surface features between the two knee designs and to correlate them with the underlying reason for revision surgery., Methods: Retrieval analysis was performed of 15 NexGen® and 8 Persona® fixed-bearing knee implants from the same manufacturer retrieved from two knee revision centres. A photogrammetric method was used to grade the amount of cement attached to the tibial tray backside. The geometry and dimensions of the tibial trays, tray projections and peripheral lips were measured using digital callipers and compared between the two different designs. To measure the surface roughness on the backside of the tibial tray, a contact profilometer was used. To investigate differences between the two designs statistical analyses (t-test) were performed., Results: All Persona® trays showed evidence of cement adhesion with a % area of 75.4%; half of the NexGen® trays had cement adhesions, with a mean value of 20%. There was a significant difference in the percentage of area covered by cement between the two designs (p < 0.001). Results from the contact profilometer revealed that Persona® and NexGen® tray backsides showed a similar lateral (1.36 μm and 1.10 μm) and medial (1.39 μm and 1.12 μm) mean surface roughness with significant differentiation (p < 0.05) of the lateral and medial roughness values between the two designs. Persona® stems showed a significantly higher mean surface roughness (1.26) compared to NexGen® stems (0.89; p < 0.05)., Conclusion: The novel anatomic knee system showed significantly more cements adhesions and a higher surface roughness which was most likely attributed to the most obvious design and coating alteration of the tibial tray. This study provides first retrieval findings of a novel TKA design recently introduced to the market., (© 2022. The Author(s).)

Background: SPECT/CT distribution patterns in patients with total knee replacements have previously been correlated with factors such as time of implantation, implant type and alignment. It is unknown, however, if an increased and more extended bone tracer uptake (BTU) in SPECT/CT, representing loading of the joint, correlates with findings from retrieval studies. The aim of this study was to further understand this subject., Materials and Methods: 62 retrieved TKA were included. SPECT/CT was performed prior to revision. Quantitative and qualitative medio-lateral comparisons of BTU intensity and distribution in the tibia were performed. Retrieval analysis was performed with a micro-CT method to assess the thickness differences between medial and lateral sides of polyethylene inserts with symmetrical designs., Results: In the subgroup of TKA with asymmetrical SPECT/CT distribution, there was a significant correlation between retrieval and medical imaging data ( p = 0.0355): patients showing a more extended BTU in the medial compartment also had a significantly thinner insert in the medial compartment, and vice versa in the lateral side., Conclusion: This is the first study comparing BTU distribution patterns and retrieval findings. Our results support the hypothesis that SPECT/CT is able to identify bone activity due to implant position and loading.

Background: With the Persona® knee system a new polyethylene formulation incorporating vitamin-E which aims to reduce oxidation and maintain wear resistance was introduced. Although in-vitro studies have demonstrated positive effects of the vitamin-E antioxidants on UHMWPE, no retrieval study has looked at polyethylene damage of this system yet. It was the aim to investigate the in-vivo performance of this new design, by comparing it with its predecessor in retrieval analysis., Methods: 15 NexGen® and 8 Persona® fixed-bearing implants from the same manufacturer (Zimmer Biomet) were retrieved from two knee revision centres. For retrieval analysis, a macroscopic analysis of polyethylene using a peer-reviewed damage grading method was used (Hood-score). The roughness of all articulating metal components was measured using a contact profilometer. The reason(s) for TKA revision were recorded. Statistical analyses (t-test) were performed to investigate differences between the two designs., Results: The mean Hood score for Persona® inserts was 109.3 and for NexGen® 115.1 without significant differences between the two designs. Results from the profilometer revealed that Persona® and NexGen® femoral implants showed an identical mean surface roughness of 0.14 μm. The Persona® tibial tray showed a significantly smoother surface (0.06 μm) compared to the NexGen® (0.2 μm; p < 0.001). Both Hood score and surface roughness were influenced by the reasons for revision (p < 0.01)., Conclusions: The bonding of the antioxidant vitamin-E to the PE chain used in the novel Persona® knee system does not reduce in-vivo surface damage compared to highly crosslinked PE without supplemented vitamin-E used in its predecessor knee system NexGen®. However, the Persona® titanium alloy tibial tray showed a significantly smoother surface in comparison to the NexGen® titanium alloy tibial tray. This study provides first retrieval findings of a novel TKA design and may help to understand how the new Persona® anatomic knee system performs in vivo., (© 2021. The Author(s).)

We aimed to determine if gluteus maximus (GMAX) fat infiltration is associated with different levels of physical activity. Identifying and quantifying differences in the intramuscular fat content of GMAX in subjects with different levels of physical activity can provide a new tool to evaluate hip muscles health. This was a cross-sectional study involving seventy subjects that underwent Dixon MRI of the pelvis. The individuals were divided into four groups by levels of physical activity, from low to high: inactive patients due to hip pain; and low, medium and high physical activity groups of healthy subjects (HS) based on hours of exercise per week. We estimated the GMAX intramuscular fat content for each subject using automated measurements of fat fraction (FF) from Dixon images. The GMAX volume and lean volume were also measured and normalized by lean body mass. The effects of body mass index (BMI) and age were included in the statistical analysis. The patient group had a significantly higher FF than the three groups of HS (median values of 26.2%, 17.8%, 16.7% and 13.7% respectively, p < 0.001). The normalized lean volume was significantly larger in the high activity group compared to all the other groups (p < 0.001, p = 0.002 and p = 0.02). Employing a hierarchical linear regression analysis, we found that hip pain, low physical activity, female gender and high BMI were statistically significant predictors of increased GMAX fat infiltration., (© 2021. The Author(s).)

Aims: Acetabular edge-loading was a cause of increased wear rates in metal-on-metal hip arthroplasties, ultimately contributing to their failure. Although such wear patterns have been regularly reported in retrieval analyses, this study aimed to determine their in vivo location and investigate their relationship with acetabular component positioning., Methods: 3D CT imaging was combined with a recently validated method of mapping bearing surface wear in retrieved hip implants. The asymmetrical stabilizing fins of Birmingham hip replacements (BHRs) allowed the co-registration of their acetabular wear maps and their computational models, segmented from CT scans. The in vivo location of edge-wear was measured within a standardized coordinate system, defined using the anterior pelvic plane., Results: Edge-wear was found predominantly along the superior acetabular edge in all cases, while its median location was 8° (interquartile range (IQR) -59° to 25°) within the anterosuperior quadrant. The deepest point of these scars had a median location of 16° (IQR -58° to 26°), which was statistically comparable to their centres (p = 0.496). Edge-wear was in closer proximity to the superior apex of the cups with greater angles of acetabular inclination, while a greater degree of anteversion influenced a more anteriorly centred scar., Conclusion: The anterosuperior location of edge-wear was comparable to the degradation patterns observed in acetabular cartilage, supporting previous findings that hip joint forces are directed anteriorly during a greater portion of walking gait. The further application of this novel method could improve the current definition of optimal and safe acetabular component positioning. Cite this article: Bone Joint Res  2021;10(10):639-649.

The accuracy of the implant's post-operative position and orientation in reverse shoulder arthroplasty is known to play a significant role in both clinical and functional outcomes. Whilst technologies such as navigation and robotics have demonstrated superior radiological outcomes in many fields of surgery, the impact of augmented reality (AR) assistance in the operating room is still unknown. Malposition of the glenoid component in shoulder arthroplasty is known to result in implant failure and early revision surgery. The use of AR has many promising advantages, including allowing the detailed study of patient-specific anatomy without the need for invasive procedures such as arthroscopy to interrogate the joint's articular surface. In addition, this technology has the potential to assist surgeons intraoperatively in aiding the guidance of surgical tools. It offers the prospect of increased component placement accuracy, reduced surgical procedure time, and improved radiological and functional outcomes, without recourse to the use of large navigation or robotic instruments, with their associated high overhead costs. This feasibility study describes the surgical workflow from a standardised CT protocol, via 3D reconstruction, 3D planning, and use of a commercial AR headset, to AR-assisted k-wire placement. Post-operative outcome was measured using a high-resolution laser scanner on the patient-specific 3D printed bone. In this proof-of-concept study, the discrepancy between the planned and the achieved glenoid entry point and guide-wire orientation was approximately 3 mm with a mean angulation error of 5°.

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: No studies have focused on magnetic resonance imaging (MRI) of the hips of marathoners, despite the popularity and injury risks of marathon running., Purpose: To understand the effect of preparing for and completing a marathon run (42 km) on runners' hip joints by comparing MRI findings before and after their first marathon., Study Design: Case-control study; Level of evidence, 3., Methods: A total of 28 healthy adults (14 males, 14 females; mean age, 32.4 years) were recruited after registering for their first marathon. They underwent 3-T MRI of both hips at 16 weeks before (time point 1) and 2 weeks after the marathon (time point 2). After the first MRI, 21 runners completed the standardized, 4 month--long training program and the marathon; 7 runners did not complete the training or the marathon. Specialist musculoskeletal radiologists reported and graded the hip joint structures using validated scoring systems. Participants completed the Hip disability and Osteoarthritis Outcome Score (HOOS) at both imaging time points., Results: At time point 1, MRI abnormalities of the hip joint were seen in 90% of participants and were located in at least 1 of these areas: labrum (29%), articular cartilage (7%), subchondral bone marrow (14%), tendons (17%), ligaments (14%), and muscles (31% had moderate muscle atrophy). At time point 2, only 2 of the 42 hips showed new findings: a small area of mild bone marrow edema appearance (nonweightbearing area of the hip and not attributable to running). There was no significant difference in HOOS between the 2 time points. Only 1 participant did not finish the training because of hip symptoms and thus did not run the marathon; however, symptoms resolved before the MRI at time point 2. Six other participants discontinued their training because of non-hip related issues: a knee injury, skin disease, a family bereavement, Achilles tendon injury, illness unrelated to training, and a foot injury unrelated to training., Conclusion: Runners who completed a 4-month beginner training program before their first marathon run, plus the race itself, showed no hip damage on 3-T MRI scans., Competing Interests: The authors declared that there are no conflicts of interest in the authorship and publication of this contribution. This research study was funded by patient donations and supported by researchers at the National Institute for Health Research University College London Hospitals Biomedical Research Centre. Support was also received from The London Clinic, The Maurice Hatter Foundation, The RNOH Charity, The Rosetrees Trust, and The Stoneygate Trust. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto., (© The Author(s) 2021.)

Aims: The main advantage of 3D-printed, off-the-shelf acetabular implants is the potential to promote enhanced bony fixation due to their controllable porous structure. In this study we investigated the extent of osseointegration in retrieved 3D-printed acetabular implants., Methods: We compared two groups, one made via 3D-printing (n = 7) and the other using conventional techniques (n = 7). We collected implant details, type of surgery and removal technique, patient demographics, and clinical history. Bone integration was assessed by macroscopic visual analysis, followed by sectioning to allow undecalcified histology on eight sections (~200 µm) for each implant. The outcome measures considered were area of bone attachment (%), extent of bone ingrowth (%), bone-implant contact (%), and depth of ingrowth (%), and these were quantified using a line-intercept method., Results: The two groups were matched for patient sex, age (61 and 63 years), time to revision (30 and 41 months), implant size (54 mm and 52 mm), and porosity (72% and 60%) (p > 0.152). There was no difference in visual bony attachment (p = 0.209). Histological analysis showed greater bone ingrowth in 3D-printed implants (p < 0.001), with mean bone attachment of 63% (SD 28%) and 37% (SD 20%), respectively. This was observed for all the outcome measures., Conclusion: This was the first study to investigate osseointegration in retrieved 3D-printed acetabular implants. Greater bone ingrowth was found in 3D-printed implants, suggesting that better osseointegration can be achieved. However, the influence of specific surgeon, implant, and patient factors needs to be considered. Cite this article: Bone Joint Res  2021;10(7):388-400.

Objectives: To determine and compare the health status of hip joints of individuals undertaking various lengths of long-distance running and of those who are not running., Methods: Fifty-two asymptomatic volunteers underwent bilateral hip 3.0 Tesla MRI: (1) 8 inactive non-runners; (2) 28 moderately active runners (average half a marathon (21 km)/week) and (3) 16 highly active runners (≥ marathon (42 km)/week). Two musculoskeletal radiologists reported the hip MRI findings using validated scoring systems. Study participants completed a Hip disability and Osteoarthritis Outcome Score (HOOS) questionnaire to indicate their perceived hip function., Results: The MRI findings show that there were no significant differences among inactive non-runners, moderately active runners and highly active runners in the amount of labral abnormalities (p=0.327), articular cartilage lesions (p=0.270), tendon abnormalities (p=0.141), ligament abnormalities (p=0.519). Bone marrow oedema was significantly more common in moderately active runners than in non-runners and highly active runners (p=0.025), while small subchondral cysts were more common in runners than in non-runners (p=0.017), but these were minor/of small size, asymptomatic and did not indicate specific exercise-related strain. Articular cartilage lesions and bone marrow oedema were not found in highly active runners. HOOS scores indicate no hip symptoms or functional problems among the three groups., Conclusion: The imaging findings were not significantly different among inactive non-runners, moderately active runners and highly active runners, in most hip structures, suggesting that long-distance running may not add further damage to the hip joints., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2021. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: 3D Surgical planning has become a key tool in complex hip revision surgery. The restoration of centre of rotation (CoR) of the hips and leg length (LL) are key factors in achieving good clinical outcome. Pelvic imaging is the gold standard for planning and assessment of LL. We aimed to better understand if 3D planning is effective at equalising LL when large acetabular defects are present., Materials and Methods: This was a prospective case study of 25 patients. We report the analysis of pre-operative LL status and planned LL restoration measured on CT, in relation to the achieved LL measured post-operatively in functional, weight bearing position. Our primary objective was the assessment of restoration of CoR as well as the anatomical and functional LL using biplanar full-length standing low-dose radiographs; our secondary objective was to evaluate the clinical outcome., Results: Pre-operative intra-pelvic discrepancy between right and left leg was a mean of 28 mm (SD 17.99, min = 3, max = 60 mm). Post-operatively, the difference between right and left vertical femoral offset (VFO), or CoR discrepancy, was of 7.4 mm on average, significantly different from the functional LL discrepancy (median = 15 mm), p = 0.0024. Anatomical LLD was a median of 15 mm. In one case there was transient foot drop, one dislocation occurred 6 months post-operatively and was treated by closed reduction, none of the patients had had revision surgery at the time of writing. Mean oxford hip score at latest follow up was 32.1/48., Discussion: This is the first study to investigate limb length discrepancy in functional position after reconstruction of large acetabular defects. We observed that VFO is not an optimal surrogate for LL when there is significant bone loss leading to length inequality, fixed flexion of the knee and abduction deformity., Conclusions: Although challenging, LLD and gait abnormalities can be greatly improved with the aid of an accurate surgical planning. Surgeons and engineers should consider the integration of EOS imaging in surgical planning of reconstruction of large acetabular defects.

Three-dimensional (3D) pre-operative planning in total hip arthroplasty (THA) is being recognized as a useful tool in planning elective surgery, and as crucial to define the optimal component size, position and orientation. The aim of this study was to systematically review the existing literature for the use of 3D pre-operative planning in primary THA.A systematic literature search was performed using keywords, through PubMed, Scopus and Google Scholar, to retrieve all publications documenting the use of 3D planning in primary THA. We focussed on (1) the accuracy of implant sizing, restoration of hip biomechanics and component orientation; (2) the benefits and barriers of this tool; and (3) current gaps in literature and clinical practice.Clinical studies have highlighted the accuracy of 3D pre-operative planning in predicting the optimal component size and orientation in primary THAs. Component size planning accuracy ranged between 34-100% and 41-100% for the stem and cup respectively. The absolute, average difference between planned and achieved values of leg length, offset, centre of rotation, stem version, cup version, inclination and abduction were 1 mm, 1 mm, 2 mm, 4°, 7°, 0.5° and 4° respectively.Benefits include 3D representation of the human anatomy for precise sizing and surgical execution. Barriers include increased radiation dose, learning curve and cost. Long-term evidence investigating this technology is limited.Emphasis should be placed on understanding the health economics of an optimized implant inventory as well as long-term clinical outcomes. Cite this article: EFORT Open Rev 2020;5:845-855. DOI: 10.1302/2058-5241.5.200046., Competing Interests: ICMJE Conflict of interest statement: AJH reports receipt of a grant to UCL from Medacta. The other authors declare no conflict of interest relevant to this work., (© 2020 The author(s).)