Total hip replacement (THR) in young patients has been associated to higher revision rates than in older population. Different conditions may lead to end-stage arthritis of the hip in these patients. We compared the clinical and radiological outcome of two different groups of young and very young patients who underwent a ceramic-on-ceramic THR. 120 hips were prospectively followed for a mean of 10.4 years (range, 5 to 17). 38 patients (46 hips) were less than 30 years old (group 1), and, 68 (74 hips) were between 31 and 40 years old (group 2). Weight (p<0.001) and physical activity level were greater in group 2 (p<0.001). Preoperative function (p=0.03) and range of mobility (p=0.03) were worse in group 1. Primary osteoarthritis was not found in any case. Rheumatoid juvenile arthritis was the most frequent diagnosis in group 1 and avascular necrosis of the femoral head in group 2. A femoral funnel-shaped type 1 according to Dorr was more frequent in group 2 (p=0.04). The same ceramic-on-ceramic uncemented THR was used in all cases. Screws for cup fixation were only used when strictly needed. We analysed the clinical results according to the Merle-D´Aubignè and Postel scale, the postoperative radiological reconstruction of the hip and the radiological appearance of cup loosening. Kaplan-Meier survivorship analysis was used to estimate the cumulative probability of not having a revision surgery. Screw use required to obtain a secured interference fit of the acetabular component was found more frequently in group 1 (p=0.01). Postoperative pain (p=0.002) and function (p=0.002) were better in group 1. Mean acetabular abduction angle of the cup was greater in group 1 (p=0.03) and reconstruction to the hip rotation center according to Ranawat (p=0.01) was better in group 2. Placement of the acetabular component inside the Lewinnek´s zone and stem position were similar in both groups. No hips were revised due to complications related to ceramic or to stem loosening. Three cups were revised for aseptic loosening in group 1 and four in group 2. The survival rate for cup aseptic loosening at 15 years was 92.3% (95% CI: 83.7 to 100) for group 1 and 93.1% (95% CI: 85.3 to 99.9) for group 2 (Log rank, p=0.88). Ceramic-on-ceramic uncemented THR is an excellent option for young and very young patients. Despite worse preoperative conditions in patients under the age of 30 years, a similar clinical outcome was found in this series

It is known that the gait dynamics of elderly substantially differs from that of young people. However, it has not been well studied how this age-related gait dynamics affects the knee biomechanics, e.g., cartilage mechanical response. In this study, we investigated how aging affects knee biomechanics in a female population using subject-specific computational models. Two female subjects (ages of 23 and 69) with no musculoskeletal disorders were recruited. Korea National Institute for Bioethics Policy Review Board approved the study. Participants walked at a self-selected speed (SWS), 110% of SWS, and 120% of SWS on 10 m flat ground. Three-dimensional marker trajectories and ground reaction forces (Motion Analysis, USA), and lower limbs’ muscle activities were measured (EMG, Noraxon USA). Knee cartilage and menisci geometries were obtained from subjects’ magnetic resonance images (3T, GE Health Care). An EMG-assisted musculoskeletal finite element modeling workflow was used to estimate knee cartilage tissue mechanics in walking trials. Knee cartilage and menisci were modeled using a transversely isotropic poroviscoelastic material model. Walking speed in SWS, 110%, and 120% of SWS were 1.38 m/s, 1.51 m/s, and 1.65 m/s for the young, and 1.21 m/s, 1.34 m/s and 1.46 m/s for the elderly, respectively. The maximum tensile stress in the elderly tibial cartilage was ~25%, ~33%, and ~32% lower than the young at SWS, 110%, and 120% of SWS, respectively. These preliminary results suggest that the cartilage in the elderly may not have enough stimulation even at 20% increases in walking speed, which may be one reason for tissue degeneration. To enhance these findings, further study with more subjects and different genders will investigate how age-related gait dynamics affects knee biomechanics. Acknowledgments: Australian NHMRC Ideas Grant (APP2001734), KITECH (JE220006)

Management of ankle arthritis in young patients is challenging. Although ankle arthrodesis gives consistent pain relief, it leads to loss of function and adjacent joint arthritis. Ankle joint distraction (AJD) has been shown to give good outcomes in adults with osteoarthritis or post-traumatic arthritis. The efficacy in children or young adults and those with juvenile idiopathic arthritis is less well evidenced. Clinical notes and radiographs of all patients (n=6) managed with AJD in one tertiary referral centre were retrospectively reviewed. Radiographs were taken pre-surgery, intra-operatively, 1 month following frame removal and at the last follow up, tibiotalar joint space was assessed using ImageJ software. Measurements were taken at the medial, middle and lateral talar dome using frame components as reference. Radiographic data for patients with a good clinical outcome was compared with those who did not. At time of surgery mean age was 16.1 years (12 – 25 years). Mean follow up was 3.4 years (1.5 – 5.9 years). Indications were juvenile idiopathic arthritis (4) post-traumatic (1) and post-infective arthritis (1). Three patients at last follow up had a good clinical outcome. Two patients required revision to arthrodesis (1.3 and 2.4 years following distraction). One patient had spontaneous fusion. One patient required oral antibiotics for pin site infection. Inter-observer reliability was 95%. Mean joint space was 1.17mm (SD = 0.87mm) pre-operatively which increased to 6.72mm (SD = 2.23mm) at the time of distraction and 2.09mm (SD = 1.14mm) at the time of removal. At one-year follow up, mean joint space was 1.96mm (SD = 1.97mm). Outcomes following AJD in this population are variable although significant benefits were demonstrated for 50% of the patients in this series. Radiographic joint space preoperatively did not appear to be associated with need for arthrodesis. Further research in larger groups of young patients is required

Introduction and Objective. Scaphoid waist fractures (SWF) are notable in upper limb trauma and predominantly occur in young men. Morbidities associated with SWF include fracture non-union, premature arthritis and humpback deformity. Delayed treatment and non-adherence to fracture immobilisation increases likelihood of these complications. There is evidence that men engage in negative health behaviours such as delayed help-seeking. The Scaphoid Waist Internal Fixation for Fractures Trial (SWIFFT) conducted interviews in individuals who had sustained a SWF. Although SWIFFT showed multiple social determinants for the overall injury and healing experience, a key factor this novel study considers is age and sex. This study aimed to analyse interview data from young male participants in SWIFFT to help distinguish the experience of SWF in young men, through exploring the influence of masculinity. Materials and Methods. A purposive sample of 12 young male participants were selected from SWIFFT. These participants were enrolled from a possibility of 13 different centres across Britain. There were 17 semi-structured interviews produced from these participants, and this was thought to be sufficient for data saturation. These interviews were evaluated through deductive thematic analysis with an open-coding approach, with respondents’ experiences being compared against themes documented in men's health literature. The “Braun and Clarke (2006) Six Phases of Thematic Analysis” methodology was adopted to perform this. Results. There were three thematic models developed in the data set, which then were further divided into subthemes. Model 1: Negative Health Behaviour Prior to Treatment, model 2: Feeling Frail and model 3: Need for Speed. Model 1 corroborated that participants were inclined to sustain the injury as a result of risk-taking and would subsequently hesitate to seek treatment. Model 2 indicated that as a result of the injury, respondents were unable to engage in physical activities and activities of daily living. Respondents exercised caution to varying extents after sustaining a SWF. Model 3 highlighted that interviewees were prone to non-adherence with fracture immobilisation and in hindsight resumed employment prematurely. Conclusions. The findings of this study demonstrate that masculinity is significantly influential on the experience of SWF in young men. This was indicated through the results of thematic analysis strongly corresponding with behaviours established in men's health literature. Educational interventions could be of value in addressing behaviours observed in this population group, such as delayed help-seeking and non-compliance with fracture immobilisation. Further work in patient education and concordance with treatment after sustaining a SWF may be beneficial to longer term outcomes. In turn, this may reduce complications associated with SWF in young men

Mesenchymal stromal cells (MSC) have been proposed as an emerging cell therapy for bone tissue engineering applications. However, the healing capacity of the bone tissue is often compromised by patient's age and comorbidities, such as osteoporosis. In this context, it is important to understand the impact of donor age on the therapeutic potential of MSC. Importantly, the impact on donor age is not restricted to cells themselves but also to their microenvironment that is known to affect cell function. The extracellular matrix (ECM) has an important role in stem cell microenvironment, being able to modulate cell proliferation, self-renewal and differentiation. Decellularized cell-derived ECM (dECM) has been explored for regenerative medicine applications due to its bioactivity and its resemblance to the in vivo microenvironment. Thus, dECM offers the opportunity not only to develop microenvironments with customizable properties for improvement of cellular functions but also as a platform to study cellular niches in health and disease. In this study, we investigated the capacity of the microenvironment to rescue the impaired proliferative and osteogenic potential of aged MSC. The goal of this work was to understand if the osteogenic capacity of MSC could be modulated by exposure to a dECM derived from cells obtained from young donors. When aged MSC were cultured on dECM derived from young MSC, their in vitro proliferative and osteogenic capacities were enhanced. Our results suggest that the microenvironment, specifically the ECM, plays a crucial role in the osteogenic differentiation capacity of MSC. dECM might be a valuable clinical strategy to overcome the age-related decline in the osteogenic potential of MSC by recapitulating a younger microenvironment, attenuating the effects of aging on the stem cell niche. Overall, this study opens new possibilities for developing clinical strategies for elderly patients with limited bone formation capacity who currently lack effective treatments. Acknowledgements: The authors thank FCT for funding through the project DentalBioMatrix (PTDC/BTM-MAT/3538/2020) and to the research institutions iBB (UIDB/04565/2020 and UIDP/04565/2020) and Associate Laboratory i4HB (LA/P/0140/2020)

The modified Hedgehog technique was previously used to reattach pure chondral shear-off fragments in the pediatric knee. In the modified Hedgehog technique, the calcified side of chondral fragments is multiple times incised and trimmed obliquely for an interlocking fit in the defect site. Fibrin glue with or without sutures is subsequently applied to fix the fragment to the defect. This preliminary report further elucidates the potential of the technique by evaluation of its application in young adults using patient reported outcome measures (PROMs) and high-field Magnetic Resonance Imaging (MRI) as outcome measures. Three patients with a femoral cartilage defect (2 medial, 1 lateral), and a concomitant pure chondral corpus liberum were operatively treated by the modified Hedgehog technique. Age at surgery ranged from 20.6–21.2 years, defect size ranged from 3.8–6.0 cm2. Patients were evaluated at three months and one year after surgery by PROMs and 7.0T MRI. PROMs included the Internation Knee Documentation (IKDC), Knee Injury and Osteoarthritis Outcome Score (KOOS) and Visual Analog Scale (VAS) questionnaires. 7.0T MRI (Magnetom, Siemens Healthcare, Erlangen, Germany) using a 28-channel proton knee coil (QED, Electrodynamics LLC, Cleveland, OH) included a proton density weighted turbo spin-echo sequence with fat suppression to assess morphological tissue structure andgagCEST imaging to measure the biochemical tissue composition in terms of glycosaminoglycans (GAG). Twelve months after surgery all patients reported no pain and showed full range of motion. While PROMs at three months showed large variability between patients, one year after surgery the scores were consistently improved. Over time, morphological MRI visualized improvements in integration of the cartilage fragment with the surrounding cartilage, which was supported by biochemical MRI showing increased GAG values at the defect edges. Statistics were not applied to the results because of the small sample size. The modified Hedgehog technique in young adults with an acute onset caused by a pure chondral corpus liberum can be considered promising. The improved PROM results over time were supported by 7.0T MRI that visualized improvements in tissue structure and biochemical composition. Inclusion of more patients in future studies would allow statistical analysis and more conclusive results. The etiology of loosening and time between onset of symptoms and surgery for successful graft integration may differ between pediatric and young adult patients and is subject for future studies

Introduction. A deep squat (DS) is a challenging motion at the level of the hip joint generating substantial reaction forces (HJRF). During DS, the hip flexion angle approximates the functional range of hip motion. In some hip morphologies this femoroacetabular conflict has been shown to occur as early as 80° of hip flexion. So far in-vivo HJRF measurements have been limited to instrumented hip implants in a limited number of older patients performing incomplete squats (< 50° hip flexion and < 80° knee flexion). Clearly, young adults have a different kinetical profile with hip and knee flexion ranges going well over 100 degrees. Since hip loading data on this subgroup of the population is lacking and performing invasive measurements would be unfeasible, this study aimed to report a personalised numerical model solution based on inverse dynamics to calculate realistic in silico HJRF values during DS. M&M. Fifty athletic males (18–25 years old) were prospectively recruited for motion and morphological analysis. DS motion capture (MoCap) acquisitions and MRI scans of the lower extremities with gait lab marker positions were obtained. The AnyBody Modelling System (v6.1.1) was used to implement a novel personalisation workflow of the AnyMoCap template model. Bone geometries, semi-automatically segmented from MRI, and corresponding markers were incorporated into the template human model by an automated nonlinear morphing. Furthermore, a state-of-the-art TLEM 2.0 dataset, included in the Anybody Managed Model Repository (v2.0), was used in the template model. The subject-specific MoCap trials were processed to compute squat motion by resolving an overdeterminate kinematics problem. Inverse dynamics analyses were carried out to compute muscle and joint reaction forces in the entire body. Resulting hip joint loads were validated with measured in-vivo data from Knee bend trials in the OrthoLoad library. Additionally, anterior pelvic tilt, hip and knee joint angles were computed. Results. A preliminary set of results (20 out of 50 subjects) was analysed. The average HJRF was 3.42 times bodyweight at the peak of DS (95% confidence interval: 2.99 – 3.85%BW). Maximal hip and knee flexion angles were 113° (109.7°–116.8°) and 116° (109.4 – 123.0°) respectively. The anterior pelvic tilt demonstrated a biphasic profile with peak value of 33° (28.1° – 38.4°). Discussion. A non-invasive and highly personalised alternative for determining hip loading was presented. Consistently higher HJR forces during DS in young adults were demonstrated as opposed to the Orthoload dataset. Similarly, knee and hip flexion angles were much higher, which could support the increase in HJRF. We can conclude that DS hip kinetics in young adults clearly differ from the typical total hip arthroplasty population

The response of the muscle is critical in determining the functional outcome of limb lengthening. We hypothesised that muscle response would vary with age and therefore studied the response of the muscles during tibial lengthening in ten young and ten mature rabbits. A bromodeoxyuridine technique was used to identify the dividing cells. The young rabbits demonstrated a significantly greater proliferative response to the distraction stimulus than the mature ones. This was particularly pronounced at the myotendinous junction, but was also evident within the muscle belly. Younger muscle adapted better to lengthening, suggesting that in patients in whom a large degree of muscle lengthening is required it may be beneficial to carry out this procedure when they are young, in order to achieve the optimal functional result

The diagnosis and treatment of hip disease in young adults has rapidly evolved over the past ten years. Despite the advancements of improved diagnostic skills and refinement of surgical techniques, the psychosocial impact hip disease has on the young adult has not yet been elucidated. This observational study aimed to characterise the functional and psychosocial characteristics of a group of patients from our young hip clinic. 49 patients responded to a postal questionnaire which included the Oswestry Disability Index (ODI) and Hospital Anxiety and Depression Scale (HADS). Median age was 20 years (range 16-38) with a gender ratio of 2:1 (female: male). The most common diagnoses were Perthes' disease and developmental hip dysplasia. More than half of our patients had moderate to severe pain based on the Visual Analogue Scale (VAS) and at least a moderate disability based on the ODI. Thirty-two percent of patients were classified as having borderline to abnormal levels of depression and 49% of patients were classified as having borderline to abnormal levels of anxiety based on the HADS. Comparison of the ODI with the VAS and HADS anxiety and depression subscales showed a significant positive correlation (p<0.05). Multiple regression showed the ODI to be a significant predictor of the HADS anxiety and depression scores (regression coefficient 0.13, 95% confidence interval 0.06 to 0.21, p<0.05). This study highlights the previously unrecognised psychosocial effects of hip disease in the young adult. A questionnaire which includes HADS may be of particular value in screening for depression and anxiety in young people with physical illness. This study also highlights that collaboration with psychologists and other health care providers may be required to achieve a multidisciplinary approach in managing these patients

Introduction. Subchondral insufficiency fracture of the femoral head (SIF) is a recently proposed concept. It is generally seen in elderly people, however, some young adults have also been reported to suffer from this fracture. The purpose of this study was to investigate the clinical results of a transtrochanteric anterior rotational osteotomy (ARO) performed in young adults with SIF. Methods. This study focused on young SIF cases (age range from 10 to 29 years). Five patients were diagnosed to have SIF at our institution and conservative treatment was initially performed. The symptoms resolved in 1 case while the other 4 cases showed progression of a collapse. In these 4 cases, ARO was performed, since the fractured area was located in the anterosuperior portion of the femoral head. The average age of the patients was 22 years (range, 16 to 29 years) at the time of surgery, consisting of 2 men and 2 women. Results. All cases were followed-up and the average follow-up period was 3.4 years (range, 1.8 to 6.8 years). The average preoperative Harris hip score was 67 points, which improved to an average of 93 points at the latest follow-up. Radiographically, the fractured lesion healed and no progression of a collapse was observed in any of the 4 cases. Conclusion. In the majority of SIF cases, only the anterosuperior portion of the femoral head is involved by the fracture. When considering the optimal surgical treatments for SIF, ARO may be one of the useful options, especially for the treatment of young patients

Intermittent parathyroid hormone (iPTH 1–34) increases bone formation via modelling and remodelling mechanisms and as such is used to treat osteoporosis. The actions of iPTH on mesenchymal stem cell (MSCs) may underpin a further treatment option. We isolated bone marrow derived MSCs from young (WT) and ovarectomized senile (OVX) rats, investigating the effect of intermittent and continuous PTH administration on migration to SDF-1, proliferation and osteogenic differentiation. MSCs were harvested from the femora of 6–10week old WT rats and 10–13month old OVX rats. Cells were cultured with 25,50 and 100nmMol of PTH 1–34 added to osteogenic media either continuously or intermittently for 6hours in every 72hour cycle. ALP and Alizarin Red assessed osteogenic differentiation, and Alamar Blue- proliferation. Cells were seeded in a Boyden chamber to quantify SDF-1 migration. A student t-test was used to analyse results, and a p value<0.05 considered significant. ALP and Alizarin Red were significantly increased for WT and OVX groups at 50nmMol of iPTH. Continuous administration at all concentrations reduced calcium phosphate deposition by day 21 in all groups. In comparison to cells cultured in osteogenic media, 50nmMol of iPTH led to significantly higher ALP and Alizarin Red measurements up to days 10 and 7 respectively (figure 1). There was no change in proliferation between the groups, and PTH had no effect (figure 2.). WT MSCs not only had improved osteogenic differentiation, but also showed increased migration to SDF-1 in comparison to OVX groups. iPTH led to further increases in migration of both OVX and WT cells. iPTH increases the osteogenic differentiation and migration of MSCs from both young and ovarectomised rats, though this effect is not dose dependent. Ultimately, the role of iPTH on MSCs may lead to improved bone formation and cell homing capacity-particularly in the context of osteoporosis

Intermittent parathyroid hormone 1–34 (teriparatide) is the N-fragment terminal of the intact hormone, currently in clinical use to treat osteoporosis. Unlike anti-catabolic agents such as bisphosphonates, PTH 1–34 not only affects the osteoclast, but also up regulates bone formation via both modelling and remodelling mechanisms. The actions of iPTH on mesenchymal stem cell differentiation (MSCs) may underpin a further method in the treatment of osteoporosis specifically, and for fracture healing in general. Stem cells from older female osteoporotic animals have reduced activity and poorer osteogenic potential; additionally, their migration to and retention at sites of increased bone turnover are reduced in comparison to cells from younger animals. The aim of this study was to isolate bone marrow derived MSCs from both young Wild Type (WT) and ovarectomized senile (OVX) rats, then to investigate and compare the effect of pulsatile and continuous PTH administration on migration to SDF-1, proliferation and osteogenic differentiation. MSCs were harvested from the femora of 6–9week Wistar rats, and from 10–13month ovarectomized rats with established osteopenia. Cells were cultured with 25, 50 and 100nmMol of PTH 1–34 added to osteogenic media either continuously or in a pulsatile fashion for 6 hours in every 72hour cycle. ALP and Alizarin Red were used to assess the optimal concentration of PTH for osteogenic differentiation. Subsequently, proliferation was assessed with Alamar Blue and cells were seeded in a Boyden chamber to quantify the migration to SDF-1. As the data was parametric a student t-test was used to analyse results, and a p value < 0.05 was considered significant. ALP and Alizarin Red parameters were significantly increased for both WT and OVX groups at 50nmMol of pulsatile PTH in comparison to groups cultured in 25 or 100nmMol. Continuous administration at all concentrations led to reduced calcium phosphate deposition by day 21 in all groups. Interestingly, in comparison to cells cultured in osteogenic media, 50nmMol of pulsatile PTH lead to statistically significant higher ALP and Alizarin Red measurements up to day 10 and 14 respectively in WT cells, and days 10 and 21 in OVX cells. The proliferation rate normalised against DNA was similar for both OVX and WT rats at all-time points. PTH administration did not effect cell proliferation in any group. WT MSCs not only had improved osteogenic differentiation, but also showed increased migration to SDF-1 in comparison to OVX groups. Pulsatile PTH led to further increases in migration of both OVX and WT cells. Intermittent PTH increases the osteogenic diffrentiation and migration of MSCs from both young and ovarectomised rats, though importantly this effect is not dose dependent. Ultimately, the role of PTH 1–34 on MSCs may lead to improved bone formation and cell homing capacity-particularly in the context of osteoporosis

Background

Although there are predictive equations that estimate the total fat mass obtained from multiple-site ultrasound (US) measurements, the predictive equation of total fat mass has not been investigated solely from abdominal subcutaneous fat thickness. Therefore, the aims of this study were; (1) to develop regression-based prediction equations based on abdominal subcutaneous fat thickness for predicting fat mass in young- and middle-aged adults, and (2) to investigate the validity of these equations to be developed.

Summary Statement. In young, active patients cementless THR demonstrates excellent prosthetic stability by RSA and outstanding clinical outcomes at 5 years using a tapered titanium femoral stem, crosslinked polyethylene liners and either titanium or tantalum shells. Introduction. Early femoral implant stability is essential to long-term success in total hip replacement. Radiostereometric analysis (RSA) provides precise measurements of micromotion of the stem relative to the femur that are otherwise not detectable by routine radiographs. This study characterised micromotion of a tapered, cementless femoral stem and tantalum porous-coated vs. titanium acetabular shells in combination with highly cross-linked UHMWPE or conventional polyethylene liners using radiostereometric analysis (RSA) for 5 years following THR. Patients and Methods. This IRB-approved, prospective, double randomised, blinded study, involved 46 patients receiving a primary THR by a single surgeon. Each patient was randomised to receive a titanium (23) (Trilogy, Zimmer) or tantalum (23) (Modular Tantalum shell, Zimmer) uncemented hemispheric shell and either a highly-crosslinked or conventional polyethylene liner. Tantalum RSA markers were implanted in each patient. All patients had a Dorr A or B femoral canal and received a cementless, porous-coated titanium tapered stem (M/L Taper, Zimmer). All final femoral broaches were stable to rotational and longitudinal stress. RSA examinations, Harris Hip, UCLA, WOMAC, SF-12 scores were obtained at 10 days, 6 months, and annually through 5 years. Results. All patients demonstrated statistically significant improvement in Harris Hip, WOMAC, and SF-12 PCS scores post-operatively. Evaluation of polyethylene wear demonstrated that median penetration measurements were significantly greater in the conventional compared to the HXPLE liner cohorts at 1 year through 5 years follow-up (p<0.003). At 5 years, conventional liners showed 0.38 ± 0.05mm vertical wear whereas HXLPE liners showed 0.08 ± 0.02mm (p<0.003). Evaluation of the femoral stems demonstrated that the rate of subsidence was highest in the first 6 months (0.09mm/yr), with no other detectable motion through 5 years. Two outlying patients had significantly higher stem subsidence values at 6 months (0.7 mm and 1.0mm). One stem stabilised without further subsidence after 6 months (0.7mm), and the other stem stabilised at 1 year (1.5mm). Neither patient has clinical evidence of loosening. Evaluation of acetabular shells demonstrated less median vertical translation in tantalum than titanium shells at each time-point except at 3-years follow-up, however due to large standard errors, there was no significant difference between the two designs (p>0.05). These large standard errors were predominantly caused by two outliers, neither of which had clinical evidence of loosening. Discussion/Conclusion. In this RSA study of young THR patients, cementless tapered femoral stems, highly crosslinked polyethylene liners, and tantalum or titanium acetabular shells all demonstrated excellent performance through 5 years follow-up. Highly crosslinked polyethylene liners demonstrated significantly less wear than conventional liners. The femoral stem showed excellent stability through 5 years, with no clinical or radiologic episodes of failure. The small amount of micromotion seen is less than that previously reported for similar tapered, cementless stems and approaches the accuracy of RSA (0.05mm). Both acetabular shells demonstrated excellent stability with minimal micromotion at 5 years without significant differences in migration. All patients demonstrated significant clinical improvement in pain and function and additional RSA evaluation of these patients is planned

Abstract

Objectives. Whilst gait speed is variable between healthy and injured adults, the extent to which speed alone alters the 3D in vivo knee kinematics has not been fully described. The purpose of this prospective study was to understand better the spatiotemporal and 3D knee kinematic changes induced by slow compared with normal self-selected walking speeds within young healthy adults. Methods. A total of 26 men and 25 women (18 to 35 years old) participated in this study. Participants walked on a treadmill with the KneeKG system at a slow imposed speed (2 km/hr) for three trials, then at a self-selected comfortable walking speed for another three trials. Paired t-tests, Wilcoxon signed-rank tests, Mann-Whitney U tests and Spearman’s rank correlation coefficients were conducted using Stata/IC 14 to compare kinematics of slow versus self-selected walking speed. Results. Both cadence and step length were reduced during slow gait compared with normal gait. Slow walking reduced flexion during standing (10.6° compared with 13.7°; p < 0.0001), and flexion range of movement (ROM) (53.1° compared with 57.3°; p < 0.0001). Slow walking also induced less adduction ROM (8.3° compared with 10.0°; p < 0.0001), rotation ROM (11.4. °. compared with 13.6. °. ; p < 0.0001), and anteroposterior translation ROM (8.5 mm compared with 10.1 mm; p < 0.0001). Conclusion. The reduced spatiotemporal measures, reduced flexion during stance, and knee ROM in all planes induced by slow walking demonstrate a stiff knee gait, similar to that previously demonstrated in osteoarthritis. Further research is required to determine if these characteristics induced in healthy knees by slow walking provide a valid model of osteoarthritic gait. Cite this article: N. Mannering, T. Young, T. Spelman, P. F. Choong. Three-dimensional knee kinematic analysis during treadmill gait: Slow imposed speed versus normal self-selected speed. Bone Joint Res 2017;6:514–521. DOI: 10.1302/2046-3758.68.BJR-2016-0296.R1

Background

Individual illness perceptions have been shown to be important influences on clinical outcomes for low back, yet significant others' illness perceptions are rarely explored, particularly in relation to work disability.

Unicompartmental knee arthroplasty (UKA) is associated with a higher risk of revision compared with total knee arthroplasty (TKA). The outcomes of knee arthroplasty are typically presented as implant survival or incidence of revision after a set number of years, which can be difficult for patients and clinicians to conceptualise. We aimed to calculate the ‘lifetime risk’ of revision for UKA as a more relatable estimate of risk projection over a patient's remaining lifetime, and make comparisons to TKA. All primary UKAS performed from 1999 to 2019 (n=13,481) captured by the New Zealand Joint Registry (NZJR) were included. The lifetime risk of revision was calculated and stratified by age, gender and American Society of Anesthesiologists (ASA) status. The lifetime risk of revision for UKA was highest in the youngest patients (46-50 years; 40.4%) and lowest in the oldest patients (86-90 years; 3.7%). Lifetime risk of revision was higher for females (range 4.3%-43.4% cf. males 2.9%-37.4%) and patients with higher ASA status (ASA 3-4 range 8.8%-41.2% cf. ASA 1 1.8%-29.8%), regardless of age. The lifetime risk of UKA was two-fold higher than TKA (ranging from 3.7%-40.4% UKA, 1.6%-22.4% TKA) across all age groups. Increased risk of revision in the younger patients was associated with aseptic loosening in both males and females, and pain in females. Periprosthetic joint infections (PJI) accounted for 4% of all UKA revisions, in contrast to 27% for TKA; risk of PJI was higher for males than females for both procedures. The lifetime risk of revision is a more meaningful measure of arthroplasty outcomes and can aid with patient counselling prior to UKA. Findings from this study show the increased lifetime risk of UKA revision for younger patients, females and those with higher ASA status.

Regeneration of bone defects in elderly patients is limited due to the decreased function of bone forming cells and compromised tissue physiology. Previous studies suggested that the regenerative activity of stem cells from aged tissues can be enhanced by exposure to young systemic and tissue microenvironments. The aim of our project was to investigate whether extracellular matrix (ECM) engineered from human induced pluripotent stem cells (hiPSCs) can enhance the bone regeneration potential of aged human bone marrow stromal cells (hBMSCs). ECM was engineered from hiPSC-derived mesenchymal-like progenitors (hiPSC-MPs), as well as young (<30 years) and aged (>70 years) hBMSCs. ECM structure and composition were characterized before and after decellularization using immunofluorescence and biochemical assays. Three hBMSCs of different ages were cultured on engineered ECMs. Growth and differentiation responses were compared to tissue culture plastic, as well as to collagen and fibronectin coated plates. Decellularized ECMs contained collagens type I and IV, fibronectin, laminin and < 5% residual DNA, suggesting efficient cell elimination. Cultivation of young and aged hBMSCs on the hiPSC-ECM in osteogenic medium significantly increased hBMSC growth and markers of osteogenesis, including collagen deposition, alkaline phosphatase activity, bone sialoprotein expression and matrix mineralization compared to plastic controls and single protein substrates. In aged BMSCs, matrix mineralization was only detected in ECM cultures in osteogenic medium. Comparison of ECMs engineered from hiPSC-MPs and hBMSCs of different ages suggested similar structure, composition and potential to enhance osteogenic responses in aged BMSCs. Engineered ECM induced a higher osteogenic response compared to specific matrix components. Our studies suggest that aged BMSCs osteogenic activity can be enhanced by culture on engineered ECM. hiPSCs represent a scalable cell source, and tissue engineering strategies employing engineered ECM materials could potentially enhance bone regeneration in elderly patients

Unicompartmental knee arthroplasty (UKA) has a higher risk of revision than total knee arthroplasty, particularly for low volume surgeons. The recent introduction of robotic-arm assisted systems has allowed for increased accuracy, however new systems typically have learning curves. The objective of this study was to determine the learning curve of a robotic-arm assisted system for UKA.

Methods A total of 152 consecutive robotic-arm assisted primary medial UKA were performed by five surgeons between 2017 and 2021. Operative times, implant positioning, reoperations and patient-reported outcome measures (PROMS; Oxford Knee Score, EuroQol-5D, and Forgotten Joint Score) were recorded.

There was a learning curve of 11 cases with the system that was associated with increased operative time (13 minutes, p<0.01) and improved insert sizing over time (p=0.03). There was no difference in implant survival (98.2%) between learning and proficiency phases (p = 0.15), and no difference in survivorship between ‘high’ and ‘low’ usage surgeons (p = 0.23) at 36 months. There were no differences in PROMS related to the learning curve. This suggested that the learning curve did not lead to early adverse effects in this patient cohort.

The introduction of a robotic-arm assisted UKA system led to learning curves for operative time and implant sizing, but there was no effect on patient outcomes at early follow- up. The short learning curve was independent of UKA usage and indicated that robotic-arm assisted UKA may be particularly useful for low-usage surgeons.