Quantitative analysis of the ACL and PCL using T1rho and T2 relaxation time mapping: an exploratory, cross-sectional comparison between OA and healthy control knees.

BACKGROUND: Quantitative magnetic resonance imaging (MRI) methods such as T1rho and T2 mapping are sensitive to changes in tissue composition, however their use in cruciate ligament assessment has been limited to studies of asymptomatic populations or patients with posterior cruciate ligament tears only. The aim of this preliminary study was to compare T1rho and T2 relaxation times of the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) between subjects with mild-to-moderate knee osteoarthritis (OA) and healthy controls. METHODS: A single knee of 15 patients with mild-to-moderate knee OA (Kellgren-Lawrence grades 2-3) and of 6 age-matched controls was imaged using a 3.0 T MRI. Three-dimensional (3D) fat-saturated spoiled gradient recalled-echo images were acquired for morphological assessment and T1ρ- and T2-prepared pseudo-steady-state 3D fast spin echo images for compositional assessment of the cruciate ligaments. Manual segmentation of whole ACL and PCL, as well as proximal / middle / distal thirds of both ligaments was carried out by two readers using ITK-SNAP and mean relaxation times were recorded. Variation between thirds of the ligament were assessed using repeated measures ANOVAs and differences in these variations between groups using a Kruskal-Wallis test. Inter- and intra-rater reliability were assessed using intraclass correlation coefficients (ICCs). RESULTS: In OA knees, both T1rho and T2 values were significantly higher in the distal ACL when compared to the rest of the ligament with the greatest differences in T1rho (e.g. distal mean = 54.5 ms, proximal = 47.0 ms, p < 0.001). The variation of T2 values within the PCL was lower in OA knees (OA: distal vs middle vs proximal mean = 28.5 ms vs 29.1 ms vs 28.7 ms, p = 0.748; Control: distal vs middle vs proximal mean = 26.4 ms vs 32.7 ms vs 33.3 ms, p = 0.009). ICCs were excellent for the majority of variables. CONCLUSION: T1rho and T2 mapping of the cruciate ligaments is feasible and reliable. Changes within ligaments associated with OA may not be homogeneous. This study is an important step forward in developing a non-invasive, radiological biomarker to assess the ligaments in diseased human populations in-vivo.

Growth Kinetics and Atomistic Mechanisms of Native Oxidation of ZrSxSe2-x and MoS2 Crystals.

A thorough understanding of native oxides is essential for designing semiconductor devices. Here, we report a study of the rate and mechanisms of spontaneous oxidation of bulk single crystals of ZrSxSe2-x alloys and MoS2. ZrSxSe2-x alloys oxidize rapidly, and the oxidation rate increases with Se content. Oxidation of basal surfaces is initiated by favorable O2 adsorption and proceeds by a mechanism of Zr-O bond switching, that collapses the van der Waals gaps, and is facilitated by progressive redox transitions of the chalcogen. The rate-limiting process is the formation and out-diffusion of SO2. In contrast, MoS2 basal surfaces are stable due to unfavorable oxygen adsorption. Our results provide insight and quantitative guidance for designing and processing semiconductor devices based on ZrSxSe2-x and MoS2 and identify the atomistic-scale mechanisms of bonding and phase transformations in layered materials with competing anions.

Effectively Measuring Exercise-Related Variations in T1ρ and T2 Relaxation Times of Healthy Articular Cartilage.

BACKGROUND: Determining the compositional response of articular cartilage to dynamic joint-loading using MRI may be a more sensitive assessment of cartilage status than conventional static imaging. However, distinguishing the effects of joint-loading vs. inherent measurement variability remains difficult, as the repeatability of these quantitative methods is often not assessed or reported. PURPOSE: To assess exercise-induced changes in femoral, tibial, and patellar articular cartilage composition and compare these against measurement repeatability. STUDY TYPE: Prospective observational study. POPULATION: Phantom and 19 healthy participants. FIELD STRENGTH/SEQUENCE: 3T; 3D fat-saturated spoiled gradient recalled-echo; T1ρ - and T2 -prepared pseudosteady-state 3D fast spin echo. ASSESSMENT: The intrasessional repeatability of T1ρ and T2 relaxation mapping, with and without knee repositioning between two successive measurements, was determined in 10 knees. T1ρ and T2 relaxation mapping of nine knees was performed before and at multiple timepoints after a 5-minute repeated, joint-loading stepping activity. 3D surface models were created from patellar, femoral, and tibial articular cartilage. STATISTICAL TESTS: Repeatability was assessed using root-mean-squared-CV (RMS-CV). Using Bland-Altman analysis, thresholds defined as the smallest detectable difference (SDD) were determined from the repeatability data with knee repositioning. RESULTS: Without knee repositioning, both surface-averaged T1ρ and T2 were very repeatable on all cartilage surfaces, with RMS-CV <1.1%. Repositioning of the knee had the greatest effect on T1ρ of patellar cartilage with the surface-averaged RMS-CV = 4.8%. While T1ρ showed the greatest response to exercise at the patellofemoral cartilage region, the largest changes in T2 were determined in the lateral femorotibial region. Following thresholding, significant (>SDD) average exercise-induced in T1ρ and T2 of femoral (-8.0% and -5.3%), lateral tibial (-6.9% and -5.9%), medial tibial (+5.8% and +2.9%), and patellar (-7.9% and +2.8%) cartilage were observed. DATA CONCLUSION: Joint-loading with a stepping activity resulted in T1ρ and T2 changes above background measurement error. EVIDENCE LEVEL: 2 TECHNICAL EFFICACY STAGE: 1 J. MAGN. RESON. IMAGING 2020;52:1753-1764.

Three-Dimensional Surface-Based Analysis of Cartilage MRI Data in Knee Osteoarthritis: Validation and Initial Clinical Application.

BACKGROUND: Traditional quantitative analysis of cartilage with MRI averages measurements (eg, thickness) across regions-of-interest (ROIs) which may reduce responsiveness. PURPOSE: To validate and describe clinical application of a semiautomated surface-based method for analyzing cartilage relaxation times ("composition") and morphology on MRI, 3D cartilage surface mapping (3D-CaSM). STUDY TYPE: Validation study in cadaveric knees and prospective observational (cohort) study in human participants. POPULATION: Four cadaveric knees and 14 participants aged 40-60 with mild-moderate knee osteoarthritis (OA) and 6 age-matched healthy volunteers, imaged at baseline, 1, and 6 months. FIELD STRENGTH/SEQUENCE: 3D spoiled gradient echo, T1 rho/T2 magnetization-prepared 3D fast spin echo for mapping of T1 rho/T2 relaxation times and delayed gadolinium enhanced MRI of cartilage (dGEMRIC) using variable flip angle T1 relaxation time mapping at 3T. ASSESSMENT: 3D-CaSM was validated against high-resolution peripheral quantitative computed tomography (HRpQCT) in cadaveric knees, with comparison to expert manual segmentation. The clinical study assessed test-retest repeatability and sensitivity to change over 6 months for cartilage thickness and relaxation times. STATISTICAL TESTS: Bland-Altman analysis was performed for the validation study and evaluation of test-retest repeatability. Six-month changes were assessed via calculation of the percentage of each cartilage surface affected by areas of significant change (%SC), defined using thresholds based on area and smallest detectable difference (SDD). RESULTS: Bias and precision (0.06 ± 0.25 mm) of 3D-CaSM against reference HRpQCT data were comparable to expert manual segmentation (-0.13 ± 0.26 mm). 3D-CaSM demonstrated significant (>SDD) 6-month changes in cartilage thickness and relaxation times in both OA participants and healthy controls. The parameter demonstrating the greatest 6-month change was T2 relaxation time (OA median %SC [IQR] = 8.8% [5.5 to 12.6]). DATA CONCLUSION: This study demonstrates the construct validity and potential clinical utility of 3D-CaSM, which may offer advantages to conventional ROI-based methods. LEVEL OF EVIDENCE: 2. TECHNICAL EFFICACY STAGE: 2. J. Magn. Reson. Imaging 2020;52:1139-1151.

Photoconductive mechanism of IR-sensitive iodized PbSe thin films via strong hole-phonon interaction and minority carrier diffusion.

Photoconductive PbSe thin films are highly important for mid-infrared imaging applications. However, the photoconductive mechanism is not well understood so far. Here we provide additional insight on the photoconductivity mechanism using transmission electron microscopy, x-ray photoelectron microscopy, and electrical characterizations. Polycrystalline PbSe thin films were deposited by a chemical bath deposition method. Potassium iodide (KI) was added during the deposition process to improve the photoresponse. Oxidation and iodization were performed to sensitize the thin films. The temperature-dependence Hall effect results show that a strong hole-phonon interaction occurs in oxidized PbSe with KI. It indicates that about half the holes are trapped by KI-induced self-trapped hole centers (Vk center), which results in increasing dark resistance. The photo Hall effect results show that the hole concentration increases significantly under light exposure in sensitized PbSe, which indicates the photogenerated electrons are compensated by trapped holes. The presence of KI in the PbSe grains was confirmed by I 3d5/2 core-level x-ray photoelectron spectra. The energy dispersive x-ray spectra obtained in the scanning transmission electron microscope show the incorporation of iodine during the iodization process on the top of PbSe grains, which can create an iodine-incorporated PbSe outer shell. The iodine-incorporated PbSe releases electrons to recombine with holes in the PbSe layer so that the resistance of sensitized PbSe is about 800 times higher than that of PbSe without the iodine-incorporated layer. In addition, oxygen found in the outer shell of PbSe can act as an electron trap. Therefore, the photoresponse of sensitized PbSe is from the difference between the high dark resistance (by KI addition and iodine incorporation) and the low resistance after IR exposure due to electron compensation (by electron traps at grain boundary and electron-hole recombination in KI hole traps).

Clinical and Radiological Outcomes in Robotic-Assisted Total Knee Arthroplasty: A Systematic Review and Meta-Analysis.

BACKGROUND: The aim of this systematic review is to determine if robotic-assisted total knee arthroplasty (RATKA) results in improved clinical and radiological outcomes, and to elucidate the breadth and depth of studies conducted on this topic. METHODS: A Preferred Reporting Items for Systematic Reviews and Meta-Analyses systematic review was conducted using 4 databases (MEDLINE, EMBASE, Cochrane, and Web of Science) to identify all clinical studies that investigate clinical or radiological outcomes using RATKA. The Critical Appraisal Skills Program checklist for cohort studies was employed for critical appraisal and evaluation of all 22 studies that met the inclusion criteria. RESULTS: All studies reviewed determined that knee arthroplasty improved clinical outcomes. Twelve studies found statistically better clinical outcomes with RATKA compared with conventional TKA, whereas 9 studies found no difference. One study did not assess clinical outcomes. When assessing radiological outcomes, 14 studies reported that RATKA resulted in more consistent and accurate postoperative mechanical alignment, whereas 2 studies reported no difference. Six studies did not assess radiological outcomes. CONCLUSION: Although knee arthroplasty is one of the most commonly performed orthopedic operations, the level of patient satisfaction varies. The meta-analyses conducted in our systematic review shows that RATKA results in greater improvements in postoperative Hospital for Special Surgery score and Western Ontario and McMaster Universities scores compared to conventional TKA. Furthermore, it shows that RATKA results in more accurate postoperative alignment of prostheses. These together can explain the improved postoperative outcomes. More randomized controlled trials must be conducted before this technique is integrated into routine clinical practice.

Titanium contacts to graphene: process-induced variability in electronic and thermal transport.

Contact resistance (R C) is a major limiting factor in the performance of graphene devices. R C is sensitive to the quality of the interface and the composition of the contact, which are affected by the graphene transfer process and contact deposition conditions. In this work, a linear correlation is observed between the composition of Ti contacts, characterized by x-ray photoelectron spectroscopy, and the Ti/graphene contact resistance measured by the transfer length method. We find that contact composition is tunable via deposition rate and base pressure. Reactor base pressure is found to effect the resultant contact resistance. The effect of contact deposition conditions on thermal transport measured by time-domain thermoreflectance is also reported. Interfaces with higher oxide composition appear to result in a lower thermal boundary conductance. Possible origins of this thermal boundary conductance change with oxide composition are discussed.

Serialized holography for brand protection and authentication.

The problems presented by counterfeit products and documentation are discussed. Limitations of existing holograms for anti-counterfeit applications are described. We describe the advantages of full holographic serialization and the requirements in terms of materials and techniques for mass production of true serialized holograms. These requirements having been met, we report for the first time the mass production of fully serialized holograms. The novelty of the approach consists of the direct use of the product manufacturer's information as the object in a holographic recording system along with a self-processing photopolymer and modular optical system to facilitate mass production of truly serialized volume holograms. Various types of serialized holograms for overt and covert authentication are described. We discuss briefly the application of Optrace's manufacturing methods for future generation holographic devices.

MoS2 P-type transistors and diodes enabled by high work function MoOx contacts.

The development of low-resistance source/drain contacts to transition-metal dichalcogenides (TMDCs) is crucial for the realization of high-performance logic components. In particular, efficient hole contacts are required for the fabrication of p-type transistors with MoS2, a model TMDC. Previous studies have shown that the Fermi level of elemental metals is pinned close to the conduction band of MoS2, thus resulting in large Schottky barrier heights for holes with limited hole injection from the contacts. Here, we show that substoichiometric molybdenum trioxide (MoOx, x < 3), a high work function material, acts as an efficient hole injection layer to MoS2 and WSe2. In particular, we demonstrate MoS2 p-type field-effect transistors and diodes by using MoOx contacts. We also show drastic on-current improvement for p-type WSe2 FETs with MoOx contacts over devices made with Pd contacts, which is the prototypical metal used for hole injection. The work presents an important advance in contact engineering of TMDCs and will enable future exploration of their performance limits and intrinsic transport properties.

Hole selective MoOx contact for silicon solar cells.

Using an ultrathin (∼ 15 nm in thickness) molybdenum oxide (MoOx, x < 3) layer as a transparent hole selective contact to n-type silicon, we demonstrate a room-temperature processed oxide/silicon solar cell with a power conversion efficiency of 14.3%. While MoOx is commonly considered to be a semiconductor with a band gap of 3.3 eV, from X-ray photoelectron spectroscopy we show that MoOx may be considered to behave as a high workfunction metal with a low density of states at the Fermi level originating from the tail of an oxygen vacancy derived defect band located inside the band gap. Specifically, in the absence of carbon contamination, we measure a work function potential of ∼ 6.6 eV, which is significantly higher than that of all elemental metals. Our results on the archetypical semiconductor silicon demonstrate the use of nm-thick transition metal oxides as a simple and versatile pathway for dopant-free contacts to inorganic semiconductors. This work has important implications toward enabling a novel class of junctionless devices with applications for solar cells, light-emitting diodes, photodetectors, and transistors.

The Segond Fracture as a Vital Diagnostic Tool for Anterior Cruciate Ligament Injury in Acute Settings: A Case Report.

A Segond fracture is a specific type of avulsion fracture involving the lateral aspect of the proximal tibia adjacent to the tibial plateau. Segond fractures are indicative of ligamentous injury in the knee. In this case report, a 29-year-old male delivery driver presented to the ED with acute onset right knee pain after losing control of his motorbike at low speed. Examination revealed significant effusion and medial and lateral joint line tenderness. An anterior-posterior radiograph of the knee showed a Segond fracture. Subsequent MRI confirmed a full-thickness anterior cruciate ligament (ACL) rupture and medial collateral ligament (MCL) tear. Despite surgical reconstruction options, the patient chose conservative management. At eight-week follow-up, he demonstrated satisfactory progress. This case highlights the diagnostic significance of Segond fractures in identifying ligamentous damage in the knee without the availability of MRI. It also highlights the feasibility of non-operative management in some instances.

A Pilot Survey Study of Anterior Cruciate Ligament Injuries in Female University Athletes.

Introduction Female sports players are at increased risk of soft tissue knee injuries (STKIs) compared to their male counterparts. Injury prevention programs effectively reduce the incidence of anterior cruciate ligament (ACL) knee injuries. This pilot study, therefore, aimed to examine the prevalence, type, and management of STKIs within a population of female university sports players at the University of Cambridge. Additionally, this study aimed to examine the perceived risk of ACL injuries and knowledge of long-term complications, alongside participation and attitudes towards injury prevention programs. Methodology A survey was distributed to women's university sports teams at the University of Cambridge. Information was gathered on participant demographics and sporting history. Relevant medical history, including joint laxity, connective tissue disorders, and previous knee injuries, was also collected. Participant involvement in and attitudes towards injury prevention programs were evaluated. Results Data from eighty-five participants (n = 85) were collected, all of whom were female. Forty-two percent of participants had sustained a previous knee injury, of which the majority (44%) were ACL injuries. In the ACL-injured group, 38% (n=6) had undergone ACL reconstructive surgery, 44% (n=7) had received only physiotherapy, and 19% (n=3) had received no form of treatment. Only 44% of these participants sustaining an ACL injury reported a return to the same level of post-injury sport. Seventy-two percent of respondents felt they were at increased risk of ACL injury compared to males. Most participants (87%) did not follow an injury prevention program, but 95% expressed a willingness to enroll in one. Conclusions This pilot study indicates that most knee injuries in female university athletes in this cohort at Cambridge University are ACL injuries, with a considerable number being managed conservatively. The low rate of return to pre-injury sporting levels highlights the significant impact of ACL injuries on athletic careers. This study demonstrates results similar to previous studies on the broader population. However, due to the pilot nature of the research and limited statistical power, the results should be interpreted with caution before transposing to the wider population. Further investigation is required into why many of these ACL-injured female athletes were managed conservatively and whether this finding is mirrored in their male counterparts. Despite recognizing their higher risk than males, participants displayed low engagement in injury prevention programs, indicating a gap between awareness and action. The willingness to participate in prevention programs suggests the potential for improved engagement through targeted interventions. Future research should focus on identifying and addressing specific barriers to participation in injury prevention programs and exploring the reasons behind the preference for conservative management of ACL injuries. Additionally, expanding the sample size and including a more diverse athletic population would enhance the generalizability of the findings.

The patient with a painful knee.

Knee pain encompasses a wide array of differential diagnoses and can often pose a diagnostic challenge, as it can have traumatic or non-traumatic causes. A good clinical history, assessment and anatomical knowledge gives a strong foundation to narrow down the diagnosis, and understanding the correct imaging modality and findings further informs correct and timely management. This article reviews various disease processes including fractures, inflammatory, infective and neoplastic causes, and discusses the assessment and various imaging modalities to aid diagnosis in both primary and secondary care.

Research priorities of members of the British Association for Surgery of the Knee.

Aims: This study aims to identify the top unanswered research priorities in the field of knee surgery using consensus-based methodology. Methods: Initial research questions were generated using an online survey sent to all 680 members of the British Association for Surgery of the Knee (BASK). Duplicates were removed and a longlist was generated from this scoping exercise by a panel of 13 experts from across the UK who provided oversight of the process. A modified Delphi process was used to refine the questions and determine a final list. To rank the final list of questions, each question was scored between one (low importance) and ten (high importance) in order to produce the final list. Results: This consensus exercise took place between December 2020 and April 2022. A total of 286 clinicians from the BASK membership provided input for the initial scoping exercise, which generated a list of 105 distinct research questions. Following review and prioritization, a longlist of 51 questions was sent out for two rounds of the Delphi process. A total of 42 clinicians responded to the first round and 24 responded to the second round. A final list of 24 research questions was then ranked by 36 clinicians. The topics included arthroplasty, infection, meniscus, osteotomy, patellofemoral, cartilage, and ligament pathologies. The management of early osteoarthritis was the highest-ranking question. Conclusion: A Delphi exercise involving the BASK membership has identified the future research priorities in knee surgery. This list of questions will allow clinicians, researchers, and funders to collaborate in order to deliver high-quality research in knee surgery and further advance the care provided to patients with knee pathology.

Future research priorities for soft-tissue knee injuries.

Aims: To identify unanswered questions about the prevention, diagnosis, treatment, and rehabilitation and delivery of care of first-time soft-tissue knee injuries (ligament injuries, patella dislocations, meniscal injuries, and articular cartilage) in children (aged 12 years and older) and adults. Methods: The James Lind Alliance (JLA) methodology for Priority Setting Partnerships was followed. An initial survey invited patients and healthcare professionals from the UK to submit any uncertainties regarding soft-tissue knee injury prevention, diagnosis, treatment, and rehabilitation and delivery of care. Over 1,000 questions were received. From these, 74 questions (identifying common concerns) were formulated and checked against the best available evidence. An interim survey was then conducted and 27 questions were taken forward to the final workshop, held in January 2023, where they were discussed, ranked, and scored in multiple rounds of prioritization. This was conducted by healthcare professionals, patients, and carers. Results: The top ten included questions regarding prevention, diagnosis, treatment, and rehabilitation. The number one question was, 'How urgently do soft-tissue knee injuries need to be treated for the best outcome?'. This reflects the concerns of patients, carers, and the wider multidisciplinary team. Conclusion: This validated process has generated ten important priorities for future soft-tissue knee injury research. These have been submitted to the National Institute for Health and Care Research. All 27 questions in the final workshop have been published on the JLA website.

A systematic review of anterior cruciate ligament primary repair rehabilitation.

BACKGROUND: Rehabilitation after surgery of the injured anterior cruciate ligament (ACL) is crucial for satisfactory outcomes. Many trials have investigated this process after ACL reconstruction. The treatment of acute ACL ruptures with a repair technique has recently regained interest, although very little information is available about appropriate rehabilitation for such patients. The objective of this review was to evaluate studies on rehabilitation following ACL repair. METHODS: A systematic review of the literature following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines was conducted for patients undergoing a rehabilitation programme after ACL repair. The review has been registered on the International Prospective Register of Systematic Reviews (PROSPERO, Registration number: CRD42020173450). Elements of rehabilitation care we included in our strategy are postoperative bracing, home-based rehabilitation, strengthening exercises, proprioception and neuromuscular training. We searched PubMed, CINAHL, EMBASE, and the Cochrane Library for randomised trials of any form investigating rehabilitation protocols after repair of the injured ACL. Two reviewers independently assessed eligibility of trials. RESULTS: No trials were included. Available literature of lower evidence was included for discussion. CONCLUSIONS: No information is available from randomised trials to indicate whether there is any difference between rehabilitation protocols for patients who have undergone primary ACL repair.

Comparison of Exeter stem offset size for total hip arthroplasty between males and females: A retrospective series of 780 hips.

Background: Many orthopaedic surgeons use a 'standard' stem offset length, typically 37.5 mm and 44 mm for females and males respectively, in total hip arthroplasty. With increasingly personalized surgery, 'standard' one-size-fits-all stem lengths may be outdated. This study aims to test whether pre-operative templating affects stem length choice and whether 'standard' stem sizes are therefore outdated. Methods: We performed a retrospective chart review of all total hip arthroplasty patients using Stryker's Exeter cemented femoral hip system in our centre between 2016 and 2020. Demographic and surgical data were collected. Data from surgeons who templated pre-operatively were compared to data from those who did not. Results: 780 patients were included (309 male, 471 female), average age 71.4 years (range 23-96). We found a significant difference between male and female offset lengths; more males had an offset length of 44 mm and more females had an offset length of 37.5 mm (p = 0.004). Among surgeons who did not template pre-operatively, 20.6% of female patients and 10.3% of male patients had other 'non-standard' offset lengths. Among surgeons who did template pre-operatively, the proportion of both female and male patients who had other 'non-standard' offset lengths was significantly higher (43.1% and 23.4%, respectively p < 0.05). Conclusions: The difference between templating and non-templating surgeons' stem choice revealed significant individual variability between males and females. 'Standard' offset lengths for males and females were still used in the majority of our cohort. However, with the emergence of mainstream robotic arthroplasty, we feel that pre-operative templating has become a minimum standard.

A Study Investigating Whether BMI Is Associated With Acetabular Bone Size: Big Bones or a Big Myth?

Background There is a common conception held by patients with a high body mass index (BMI) that they have "big bones". Some people hold the assumption that their weight is attributed to larger bone stock rather than adipose tissue. It was the suspicion of the surgeons at our unit that this is often not the case. We therefore conducted a study investigating if there is any association between BMI and acetabular bone size. Methods We conducted a retrospective chart review of all patients undergoing total hip arthroplasty using the Trident acetabular system from Stryker at our tertiary level 1 trauma centre between September 2016 and August 2020. Patient demographic and surgical data were collected, and the association of BMI, height, and weight, with acetabular cup size was investigated using Pearson's correlation coefficient and chi-square test for independence. Results A total of 418 patients were included in this study (52.4% female; age: 20-93 years; mean age: 62.51 years), with a mean BMI of 29.55 kg/m2(range: 14.95-52.32 kg/m2). A weak positive association between BMI and cup size, which was statistically significant (r = 0.107; n = 418; p = 0.02). The chi-square test for independence was used to study the association between obesity and cup size (large vs small), which demonstrated no significant difference (p = 0.08). There was a moderately strong positive association between height and cup size (r = 0.551; n = 418; p < 0.01). There was a weak positive association between weight and cup size, which was statistically significant (r = 0.355; n = 418; p < 0.01). Conclusion Our study suggests that there is indeed a weakly positive linear association between BMI and cup size among total hip arthroplasty patients. This effect was, however, more significant for height and weight, and there was no significant association between obese and non-obese groups with small versus large cup size implanted. We therefore conclude that clinically there is no significant relationship between obesity and acetabular bone size and that the "big bones" claim is indeed fallacious.

The Joint-Specific BACH classification: A predictor of outcome in prosthetic joint infection.

BACKGROUND: There is currently no commonly accepted method of stratifying complexity of prosthetic joint infection (PJI). This study assesses a new classification, the Joint-Specific, Bone involvement, Anti-microbial options, Coverage of the soft tissues, Host status (JS-BACH) classification, for predicting clinical and patient reported outcomes in PJI. METHODS: Patients who received surgery for PJI at two centres in the UK between 2010 and 2015 were classified using JS-BACH as 'uncomplicated', 'complex' or 'limited treatment options'. Patient reported outcomes were recorded at 365-days following the index operation and included the EuroQol EQ-5D-3L index score and the EQ-visual analogue score (VAS). Clinical outcome data were obtained from the most recent follow-up appointment. FINDINGS: 220 patients met the inclusion criteria. At 365-days following the index operation, patients with 'uncomplicated' PJI reported similar EQ-index scores (0.730, SD:0.326) and EQ-VAS (79.4, SD:20.9) compared to the age-matched population. Scores for 'uncomplicated' PJI were significantly higher than patients classified as having 'complex' (EQ-index:0.515 SD:0.323, p = 0.012; EQ-VAS:68.4 SD:19.4, p = 0.042) and 'limited treatment options' PJI (EQ-index:0.333 SD:0.383, p < 0.001; EQ-VAS:60.2, SD:23.1, p = 0.005). The median time to final follow-up was 4.7 years (inter-quartile range 2.7-6.7 years) where there were 74 cases (33.6%) of confirmed recurrence. Using death as a competing risk, the Cox proportional-hazards ratio of recurrence for 'complex' versus 'uncomplicated' PJI was 23.7 (95% CI:3.23-174.0, p = 0.002) and having 'limited options' verses 'uncomplicated' PJI was 57.7 (95% CI:7.66-433.9, p < 0.001). INTERPRETATION: The JS-BACH classification can help predict likelihood of recurrence and quality of life following surgery for PJI. This will aid clinicians in sharing prognostic information with patients and help guide referral for specialist management of PJI.