Cartilage lesions often undergo irreversible progression due to low self-repair capability of this tissue. Tissue engineered approaches based in extrusion bioprinting of constructs loaded with stem cell spheroids may offer valuable alternatives for the treatment of cartilage lesions. Human mesenchymal stromal cell (hMSC) spheroids can be chondrogenically differentiated faster and more efficiently than single cells. This approach allows obtaining larger tissues in a rapid, controlled and reproducible way. However, it is challenging to control tissue architecture, construct stability, and cell viability during maturation. In this study we aimed at the development of a reproducible bioprinting process followed by post-bioprinting chondrogenic differentiation procedure using large quantities of hMSC spheroids encapsulated in a xanthan gum-alginate hydrogel. Multi-layered constructs were bioprinted, ionically crosslinked, and chondrogenically differentiated for 28 days. The expression of glycosaminoglycan, collagen II and IV were observed. After 56 days in culture, the bioprinted constructs were still stable and show satisfactory cell metabolic activity with profuse extracellular matrix production. These results showed a promising procedure to obtain 3D cartilage-like constructs that could be potential use as stable chondral tissue implants for future therapies.

Acknowledgments: The National Council for Scientific and Technological Development (CNPq, Brazil – Grants # 314 724/2021-4, 307 829/2018-9, 430 860/2018-8, 142 050/2018-0 and 465 656/2014-5), the Coordination for the Improvement of Higher Educational Personnel (CAPES, Brazil – PrInt 88 887.364849/2019-00 and PrInt 88 887.310405/2018-00), the Fund for Support to Teaching, Research and Extension from the University of Campinas (FAEPEX/UNICAMP, Brazil – Grants # 2921/18, 2324/21), and the European Union's Horizon 2020 JointPromise project – Precision manufacturing of microengineered complex joint implants, under grant agreement 874 837 are acknowledged for the financial support of this study.

Osteoarthritis (OA) of the equine distal interphalangeal joint (DIPJ) is a common cause of lameness. MicroRNAs (miRNAs) from biofluids such as plasma and synovial fluid make promising biomarker and therapeutic candidates.

The objectives of this study are (1) Identify differentially expressed (DE) miRNAs in mild and severe equine DIPJ OA synovial fluid samples and (2) Determine the effects of DE miRNAs on equine chondrocytes in monolayer culture.

Synovial fluid samples from five horses with mild and twelve horses with severe DIPJ OA were submitted for RNA-sequencing; OA diagnosis was made from MRI T2 mapping, macroscopic and histological evaluation. Transfection of equine chondrocytes (n=3) was performed using the Lipofectamine® RNAiMAX system with a negative control and a miR-92a mimic and inhibitor. qPCR was used to quantify target mRNA genes.

RNA-seq showed two miRNAs (miR-16 and miR-92a) were significantly DE (p<0.05). Ingenuity Pathway Analysis (IPA) identified important downstream targets of miR-92a involved in the pathogenesis of osteoarthritis and so this miRNA was used to transfect equine chondrocytes from three donor horses diagnosed with OA. Transfection was successfully demonstrated by a 1000-20000 fold increase in miR-92a expression in the equine chondrocytes. There was a significant (p<0.05) increase in COMP, COL3A1 and Sox9 in the miR-92a mimic treatment and there was no difference in ADAMTS-5 expression between the miR-92 mimic and inhibitor treatment.

RNA-seq demonstrated miR-92a was downregulated in severe OA synovial fluid samples which has not previously been reported in horses, however miR-92a is known to play a role in the pathogenesis of OA in other species. Over expression of miR-92a in equine chondrocytes led to significantly increased COMP and Sox9 expression, consistent with a chondrogenic phenotype which has been identified in human and murine chondrocytes.

A primary goal of revision Total Knee Arthroplasty (rTKA) is restoration of the Joint Line (JL) and Posterior Condylar Offsets (PCO). The presence of a native contralateral joint allows JL and PCO to be inferred in a way that could account for patient-specific anatomical variations more accurately than current techniques. This study assesses bilateral distal femoral symmetry in the context of defining targets for restoration of JL and PCO in rTKA.

566 pre-operative CTs for bilateral TKAs were segmented and landmarked by two engineers. Landmarks were taken on both femurs at the medial and lateral epicondyles, distal and posterior condyles and hip and femoral centres. These landmarks were used to calculate the distal and posterior offsets on the medial and lateral sides (MDO, MPO, LDO, LPO respectively), the lateral distal femoral angle (LDFA), TEA to PCA angle (TEAtoPCA) and anatomic to mechanical axis angle (AAtoMA). Mean bilateral differences in these measures were calculated and cases were categorised according to the amount of asymmetry.

The database analysed included 54.9% (311) females with a mean population age of 68.8 (±7.8) years. The mean bilateral difference for each measure was: LDFA 1.4° (±1.0), TEAtoPCA 1.3° (±0.9), AAtoMA 0.5° (±0.5), MDO 1.4mm (±1.1), MPO 1.0mm (±0.8). The categorisation of asymmetry for each measure was: LDFA had 39.9% of cases with <1° bilateral difference and 92.4% with <3° bilateral difference, TEAtoPCA had 45.8% <1° and 96.6% <3°, AAtoMA had 85.7% <1° and 99.8% <3°, MDO had 46.2% <1mm and 90.3% <3mm, MPO had 57.0% <1mm and 97.9% <3mm.

This study presents evidence supporting bilateral distal femoral symmetry. Using the contralateral anatomy to obtain estimates for JL and PCO in rTKA may result in improvements in intraoperative accuracy compared to current techniques and a more patient specific solution to operative planning.

Constrained acetabular inserts provide a solution for both complex primary and revision hip arthroplasty, but there have been ongoing concerns for high risk of failure and their longevity. The Stryker® Trident acetabular insert is pre-assembled with its constrained ring. We believe this to be the largest series of constrained acetabular inserts with a minimum of 5 year follow-up.

We retrospectively reviewed all Stryker® Trident ‘All-Poly’ constrained acetabular inserts cemented into bone in our unit between 2008 and 2016. We collated demographic details and reviewed all patients’ radiographs and clinical notes. Indications for surgery, latest Oxford Hip Scores (OHS) and clinical and radiographic complications were identified.

117 consecutive Stryker® Trident ‘All-Poly’ constrained inserts were cemented into bone in 115 patients during the study period with a mean age of 80 (47–97). Most common indications for surgery were recurrent dislocation (47), complex primary arthroplasty (23), revision arthroplasty (19) and failed hemiarthroplasty (12). 41 patients required revision of the acetabular component only. Follow-up was a minimum of 5 years (mean 8.6, range 5–13). There were three 30-day mortalities and six 1-year mortalities. The mean latest OHS was 37 (24–45). Four cups failed in three patients, one at the cement-bone interface, two at the cement-prosthesis interface and one at the bipolar interface. These were treated conservatively in three patient and with excision arthroplasty in one patient. There were four peri-prosthetic fractures, one Vancouver C distal femur fracture treated conservatively and three Vancouver B1 fractures, two treated conservatively and one treated with open reduction internal fixation. There was breakage of one constrained ring with no adverse effects and one superficial wound infection requiring oral antibiotics only.

This series demonstrated that despite the elderly and complex nature of these patients’ clinical situations, constrained acetabular inserts offer a useful and pragmatic solution, with relatively low complications, including in our series a cup failure rate of 3% and peri-prosthetic fracture rate of 3%.

This study aimed to verify the accuracy of the DIERS Formetric Scan when assessing vertebral rotation of the apical vertebrae in Adolescent Idiopathic Scoliosis (A.I.S) patients, to determine whether the DIERS Formetric Scans can be used instead of or alongside radiographs when assessing A.I.S patients.

Both the radiographs and the DIERS Formetric Scans of 60 Preoperative A.I.S patients. All patients included in our study had predominant thoracic curves using the Lenke classification method, Cobb angle range 33° – 85°. Each radiograph was categorised into groups according to the severity of Nash-Moe rotation score of the apical vertebrae. Three groups were formed Nash-Moe +1 (20 patients), Nash-Moe +2 (27 patients), Nash-Moe +3 (13 patients). Each result was then compared to the maximal rotation analysed by the DIERS Formetric Scan, which took place on the same day as the radiographs. The results were then assessed using a Pearson Correlation Coefficient and a One-Way ANOVA with Post-Hoc Tukey HSD Analysis.

The Nash-Moe +1 Group scored a mean maximal rotation of 14.65° ±6.56 (11.82 – 17.48) (95% Confidence Interval), Nash-Moe +2 mean maximal rotation was 19.6° ±7.1 (16.92 – 22.28) and Nash-Moe +3 scored 21.53° ±8.9 (16.99 – 26.37). The Pearson Correlation Coefficient of this assessment was +0.342 (p value 0.07) demonstrating a weak positive correlation. The One-Way ANOVA analysis with Post-Hoc Tukey HSD analysis. The results of this analysis was an F value score of +4.115 (p Value 0.021) for the overall One-Way ANOVA test. The Post-Hoc Tukey HSD tests demonstrate that there is a statistical difference between Group 1 and Group 3 (p value 0.030) but there is no statistical difference between Group 1 and Group 2 (p value 0.068) as well as no statistical difference between Group 2 and Group 3 (p value 0.716).

DIERS Formetric Scan assessment of vertebral rotation shows a positive correlation with the Nash-Moe method. This allows us to rely on the Formetric scans and thus a possible reduction in radiographs when assessing A.I.S, this reduces the exposure to ionising radiation in A.I.S patients.

Aim

Our aim was to compare the Wilkins'-modified Gartland classification and AO classifications of supracondylar humeral fracture with respect to: -Inter-observer reliability; Association of fracture-grade with radiological quality of reduction; Association of fracture-grade with complications.

Introduction: The Resurfacing Hip has been increasingly popular for younger patients. Femoral neck fractures are still the main complication. The problems associated with cement such as thermal necrosis, cement debris and lack of long-term biological fixation, combined with the general use of cementless fixation in young patients invite the question whether a cementless component can be used for resurfacing hip replacement. Given that the cement may reinforce the femoral head preventing collapse, an additional question regarding the effect of bone density in cemented and cementless fixation can be asked. The hypotheses of the study are that:

High bone density will increase the yield point and stiffness of the femoral head and therefore improve the implant fixation.

Materials and Methods: Thirty-six femoral head specimens were obtained from consented patients receiving routine hip arthroplasty. The heads were stored frozen at −20oC until use. pQCT was used to analyse trabecular bone density within each head. Specimens were ranked according to bone density and were assigned to high and low bone density groups. Cemented and cementless fixations were then alternatively assigned to individual heads in each group. Thus the 4 groups included in the study were: High density cemented, high density cementless, low density cemented, and low density cementless. Implantation of Birmingham resurfacing hips was carried out according to recommended surgical procedures. For cementing groups, surgical simplex P bone cement was used. Each sample was potted in a cylindrical polyethylene block for testing. A compressive load up to 5 or 10 KN using a Hounsfield Universal Testing Machine were applied on each sample at a rate of 1 mm min-1. Load versus displacement graphs were plotted for all tests. Yield point and stiffness were measured for each sample.

Results:

For yield point, there is no significant difference between cemented or cementless resurfacing (4169 ± 1420 N vs. 3789 ± 1461 N; P = 0.434). However, the high density heads provide a significantly higher yield point than low density heads (4749 ± 1145 N vs. 3208 ± 1287 N; P = 0.01).

Discussion: Bone density plays an important role in resurfacing hip arthroplasty. Higher bone density will reduce the incidence of fractures comparing with lower density. Therefore, resurfacing THR for the older patients and those with sub-optimal bone density should be used with caution. Consequently, it is suggested that a bone density scan should be routinely applied for those patients who are considered for resurfacing hip replacement. There is no difference between the cemented and cementless fixation in reducing femoral head failure, though cement will increase the stiffness of the bone. The study suggests that cementless resurfacing hip could be an alternative design with its clinical advantages of long-term osseointegration if implant is coated with bio-active materials.