The architecture within which cells reside is key to mediating their specific functions within the body. In this study, we use melt electrospinning writing (MEW), a recently developed 3D printing technology unique in its ability to generate ECM like fibres and control their deposition, to fabricate cell micro-environments with various fibrous architectures to study their effect on human stem cell behaviour. We designed, built and optimised a MEW apparatus and used it to fabricate four different platform designs of 10.4±2μm fibre diameter, with angles between fibres on adjacent layers of 90°, 45°, 10° and R (random). Characterisation was conducted via scanning electron microscopy (SEM) imaging and tensile testing, and human skeletal stem cells (hSSCs) were seeded to scaffolds to study the effect of architecture on cell morphology and mechanosensing. Cell morphology was significantly altered between groups, with cells on 90° scaffolds having a lower aspect ratio, greater spreading, greater cytoskeletal tension and nuclear YAP expression. Long term cell culture studies were then conducted to determine the differentiation potential of scaffolds in terms of alkaline phosphatase activity, collagen and mineral production. Across these studies, an increased cell spreading in 3-dimensions is seen, with decreasing alignment of architecture correlated with enhanced osteogenesis, as seen by significant fold increases in ALP (2.8), collagen (2.5) and calcium (3.6) in the 90° scaffold architecture compared to 10°. This study therefore highlights the critical role of fibrous architecture in regulating stem cell behaviour with implications for tissue engineering and disease progression

Introduction. Cemented stems have shown 90–100% survivorship when coupled with polyethylene acetabular component. This study aims to compare cemented stem behaviour in combination with large metal on metal (MOM) vs. metal on poly (MOP) bearings. Patients and Methods. 100 patients were recruited into a single centre RCT (we required 40 in each group for power .90 to confirm stem subsidence of >0.5mm at 2 years; p< 0.05). Recruits were randomized to MOP (28mm) or MOM femoral heads with CPCS cemented femoral stem. Assessments included X-rays (AP pelvis), Harris Hip Scores, blood metal ion levels and patient questionnaires (WOMAC, SF-36, satisfaction questionnaire). Evaluations were done pre-operatively and 3, 12 and 24 months post operatively; blood metal ion measures at 1 year. Results. There were 50 patients in each arm of study matched for age (64 ± 8.5) and BMI (29.04 ±5.5). There was no difference in femoral stem subsidence at 2 years 1.34 (±1.3) and 1.4 (±1.2) mm for MOM and MOP respectively (p=0.88). There was significant improvement in HHS from pre-op to 3 months: 41 to 87 for MOM and 44 to 86 for MOP (p=0.00). This was maintained with no difference between groups at 2 years (p=0.74). Similar pattern was seen for WOMAC and SF-36 scores for both groups at 2 years (p>0.05). Increased blood Cobalt and Chromium levels were observed in 17% and 0% for MOM and MOP group. MOM group reported better patient satisfaction for overall (91% vs. 79%), pain relief (82% vs 66%) and improvement in ADL activities (94% vs.70%) at 2 years. Conclusions. There were no significant differences between groups for stem behavior, clinical and patient reported outcomes. Despite higher patient satisfaction reported by MOM patients, increased metal ion levels had raised concerns regarding the use of MOM bearings with cemented stems for primary THR

The aim of this study was to investigate the possible benefit of large-head metal-on-metal bearing on a stem for primary hip replacement compared with a 28 mm diameter conventional metal-on-polyethylene bearing in a prospective randomised controlled trial. We investigated cemented stem behaviour between these two different bearings using Einzel-Bild-Röntgen-Analyse, clinical and patient reported measures (Harris hip score, Western Ontario and McMaster Universities osteoarthritis index, Short Form-36 and satisfaction) and whole blood metal ion levels at two years. A power study indicated that 50 hips were needed in each group to detect subsidence of > 5 mm at two years with a p-value of < 0.05. . Significant improvement (p < 0.001) was found in the mean clinical and patient reported outcomes at two years for both groups. Comparison of outcomes between the groups at two years showed no statistically significant difference for mean stem migration, clinical and patient reported outcomes; except overall patient satisfaction which was higher for metal-on-metal group (p = 0.05). Metal ion levels were raised above the Medicines and Healthcare products Regulatory Agency advised safety level (7 µg per litre) in 20% of the metal-on-metal group and in one patient in metal-on-polyethylene group (who had a metal-on-metal implant on the contralateral side). Two patients in the metal-on-metal group were revised, one for pseudotumour and one for peri-prosthetic fracture. . Use of large modular heads is associated with a risk of raised whole blood metal ion levels despite using a proven bearing from resurfacing. The head-neck junction or excess stem micromotion are possibly the weak links warranting further research

Purpose: The long-term outcome of the Harris-Galante 1 (HGP1) stem is a controversial issue. A randomised study reported by Thanner (AOS 1999) mentioned a 72% survival at ten years, basically related to femoral osteolysis observed in 18% of the cases with mechanical failure requiring revision in 20%. We studied the clinical and radiological outcome of 191 HGP1 stems reviewed at a mean 12.5 years.

Material: This prospective study included a consecutive series of 181 patients (191 hips) 101 men and 80 women, mean age 62.1 years (range 19–83). Indication for arthroplasty was primary hip degeneration (80%), or osteonecrosis (14.6%). A metal-backed polyethylene cup and a 28 mm head were inserted in 86% of the cases. At review, 41 patients had died (43 hips), two were lost to follow-up, and x-rays were available for 109. Mean follow-up was 150.2±15.3 months.

Methods: The Postel Merle d’Aubigné (PMA) and Harris (HHS) scores were recorded for all patients. Position and quality of bone fixation were analysed. Stem migration was calculated on the different x-rays by calculating the distance between the centre of the head and the summit of the greater trochanter. Lucent lines (Gruen), osteolysis and the ARA score were noted. The SOFCOT 1997 radioclinical classification was used. Actuarial survival curves were plotted taking stem revision as the endpoint. Quantitative data were compared with the chi-square test.

Results: One patient died on day three. There were three displacements. The PMA pain score improved from 2.5 to 5.6 and the HHS improved from 52.5 to 85.6 points. The stem was perfectly aligned in 80 cases, and presented a varus deviation ≤ 3° in 26 cases. A change in the initial alignment was noted in three cases and stem impaction in 14. Eleven revisions were necessary for fibrous fixation (n=5), pain (n=2), femoral malposition, (n=1), fracture of the femur during the operation (n=1, and diaphyseal osteolysis (n=1). Finally, there were no radiographic anomalies for 69 hips (class A), radiographic anomalies without clinical expression for 34 (class B), basically because of severe osteolysis of the calcar (n=6), and stress shielding in zone 1A-B. Three hips caused pain without a detectable radiographic anomaly (class C), only one hip was in class D because of the poor clinical and radiological result. The 15-year actuarial survival taking stem revision as the endpoint was 89.5±3.7%.

Discussion: The 5% rate of unstable fibrous fixation observed in this series is very different from the 16% reported by Garcia Cimbrelo (2001). There was only one case of femoral shaft osteolysis limited to zone 3 which required revision, contrasting with the 16% (Thanner) and 24% (Garcia Cimbrelo) reported for shorter follow-ups.

Conclusion: With an 89.5% mid-term survival, the Harris Gallante 1 femoral stem has provided good clinical results and a solid fixation due to the proximal porous coating on the titanium. Although rare, stem failure was observed during the first six years of implantation.

After cemented total hip arthroplasty (THA) there may be failure at either the cement-stem or the cement-bone interface. This results from the occurrence of abnormally high shear and compressive stresses within the cement and excessive relative micromovement. We therefore evaluated micromovement and stress at the cement-bone and cement-stem interfaces for a titanium and a chromium-cobalt stem. The behaviour of both implants was similar and no substantial differences were found in the size and distribution of micromovement on either interface with respect to the stiffness of the stem. Micromovement was minimal with a cement mantle 3 to 4 mm thick but then increased with greater thickness of the cement. Abnormally high micromovement occurred when the cement was thinner than 2 mm and the stem was made of titanium. The relative decrease in surface roughness augmented slipping but decreased debonding at the cement-bone interface. Shear stress at this site did not vary significantly for the different coefficients of cement-bone friction while compressive and hoop stresses within the cement increased slightly