Fractures of the forearm (radius or ulna or both) in children have traditionally been immobilised in plaster of Paris (POP) but synthetic cast materials are becoming more popular. There have been no randomised studies comparing the efficacy of these two materials. The aim of this study was to investigate which cast material is superior for the management of these fractures. We undertook a single-centre prospective randomised trial involving 199 patients with acute fractures of the forearm requiring general anaesthesia for reduction. Patients were randomised by sealed envelope into either a POP or synthetic group and then underwent routine closed reduction and immobilisation in a cast. The patients were reviewed at one and six weeks. A satisfaction questionnaire was completed following the removal of the cast. All clinical complications were recorded and the cast indices were calculated. There was an increase in complications in the POP group. These complications included soft areas of POP requiring revision and loss of reduction with some requiring re-manipulation. There was an increased mean padding index in the fractures that lost reduction. Synthetic casts were preferred by the patients. This study indicates that the clinical outcomes and patient satisfaction are superior using synthetic casts with no reduction in safety. Cite this article: Bone Joint J 2013;95-B:1285–9

Aims. Acute and chronic injuries of the interosseus membrane can result in longitudinal instability of the forearm. Reconstruction of the central band of the interosseus membrane can help to restore biomechanical stability. Different methods have been used to reconstruct the central band, including tendon grafts, bone-ligament-bone grafts, and synthetic grafts. This Idea, Development, Exploration, Assessment, and Long-term (IDEAL) phase 1 study aims to review the clinical results of reconstruction using a synthetic braided cross-linked graft secured at either end with an Endobutton to restore the force balance between the bones of the forearm. Methods. An independent retrospective review was conducted of a consecutive series of 21 patients with longitudinal instability injuries treated with anatomical central band reconstruction between February 2011 and July 2019. Patients with less than 12 months’ follow-up or who were treated acutely were excluded, leaving 18 patients in total. Preoperative clinical and radiological assessments were compared with prospectively gathered data using range of motion and the abbreviated version of the Disabilities of the Arm, Shoulder and Hand questionnaire (QuickDASH) functional outcome score. Results. Of the 18 patients (nine male, nine female) who met the inclusion criteria, the median follow-up was 8.5 years (interquartile range (IQR) 5.6 to 10). Their mean age was 49 years (SD 11). The mean extension improved significantly from 38° (SD 15°) to 24° (SD 9°) (p = 0.027), with a mean flexion-extension arc change from 81° (SD 27°) to 93° (SD 30°) (p = 0.172) but with no forearm rotational improvement (p = 0.233) at latest follow-up. The QuickDASH functional score improved significantly from 80 (SD 14) to 52 (SD 26) following reconstruction (p = 0.031), but generally the level of disability remains high. Radiological assessment showed no progression of proximal migration of the radius, with a stable interbutton distance and ulnar variance from immediate postoperative radiograph to the latest follow-up. Conclusion. Central band interosseus membrane reconstruction using a synthetic braided cross-linked graft can improve patient-rated arm function and range of motion, but significant functional deficits remain in patients with chronic injuries. Cite this article: Bone Joint J 2024;106-B(2):182–188

Abstract. Introduction. The Syn-VAR RCT is the first of its kind comparing hamstrings autograft v synthetic neoligament for MPFL reconstruction. Our aim is to evaluate short and long term patient related outcomes measures (PROMs) following synthetic / autologous MPFL reconstruction in a heterogenous cohort of patients with recurrent patellar instability. Method. 20 patients meeting inclusion criteria were recruited and randomised. Standardised surgery was performed by a single surgeon in Altnagelvin Hospital with data collected over 3 years from 2016. Kujala score was the primary outcome measure with data captured preoperatively and 12 weeks/2 years postoperatively. Secondary outcomes included four other validated scores and complications including Norwich Patellar Instability, Lysholm, IKDC and Banff. Results. 20 patients with an average age of 19 included 9 females and 11 males. At 12 weeks and 2 years Kujala improvement in the hamstring group was 18 and 32 (both p<0.05) compared to the synthetic group where the increase was 2 and 20 (p<0.05). All secondary score improvements at 2 years were significant (p<0.05) with no difference in any score at all time intervals when comparing both groups (p<0.05). Discussion. Our RCT validates the non-inferiority of synthetic MPFL reconstruction as a treatment for restoring patellar stability in a small heterogenous group with positive long term data and minimal morbidity. With no hamstring harvesting offering a reduction in theatre time with this offers a safe, efficient and viable alternative with reduced morbidity

Introduction. The purpose of this study was to analyse the efficacy and complications associated with the use of Calcium Sulphate synthetic bone graft in a paediatric population. There are no published articles on the use in children. Materials & Methods. A retrospective review was undertaken of the notes, microbiology, and X-Rays of 17 cases (in 15 patients) of calcium sulphate use in paediatric patients. As well as patient demographic data, data collected included indication, use of additional agents (antibiotics), return to theatre, and wound complications. Major complications were also assessed for. Results. There were 17 cases, in 15 patients, in our case series where calcium sulphate synthetic bone graft was used. The average patient age was 12.0 years (range 5 years – 17 years). Indications for use included likely infection (12), possible infection (3), and 2 elective finger cases (enchondroma and osteotomy). The humerus was the most common target site (5), followed by the femur (4), tibia (3), calcaneum (2), finger (2) and metatarsal (1) also included. There were positive intra-operative microbiology samples for eleven cases (Staphylococcus aureus and Staphylococcus epidermidis). Antibiotics were used in all cases except the elective finger surgery, and choice ranged between vancomycin, gentamicin, or a combination of both. Two patients required return to theatre for management of ongoing deep infection, although one case was later deemed to be non-infective osteomyelitis. Seven patients had undergone debridements prior to the definitive one with calcium sulphate (5 without Calcium Sulphate, 2 with Calcium Sulphate). Three patients experienced wound issues in the form of discharge/leakage, all were managed with dressings and did not require return to theatre. Conclusions. Calcium Sulphate synthetic bone graft, with addition of antibiotics, is an efficacious treatment in the paediatric population and is not associated with any major complications. Wound discharge should be observed for, and patients/parents warned about this, but only as per the adult population

Aims. Our objective was to conduct a systematic review and meta-analysis, to establish whether differences arise in clinical outcomes between autologous and synthetic bone grafts in the operative management of tibial plateau fractures. Methods. A structured search of MEDLINE, EMBASE, the online archives of Bone & Joint Publishing, and CENTRAL databases from inception until 28 July 2021 was performed. Randomized, controlled, clinical trials that compared autologous and synthetic bone grafts in tibial plateau fractures were included. Preclinical studies, clinical studies in paediatric patients, pathological fractures, fracture nonunion, or chondral defects were excluded. Outcome data were assessed using the Risk of Bias 2 (ROB2) framework and synthesized in random-effect meta-analysis. The Preferred Reported Items for Systematic Review and Meta-Analyses guidance was followed throughout. Results. Six studies involving 353 fractures were identified from 3,078 records. Following ROB2 assessment, five studies (representing 338 fractures) were appropriate for meta-analysis. Primary outcomes showed non-significant reductions in articular depression at immediate postoperative (mean difference -0.45 mm, p = 0.25, 95%confidence interval (CI) -1.21 to 0.31, I. 2. = 0%) and long-term (> six months, standard mean difference -0.56, p = 0.09, 95% CI -1.20 to 0.08, I. 2. = 73%) follow-up in synthetic bone grafts. Secondary outcomes included mechanical alignment, limb functionality, and defect site pain at long-term follow-up, perioperative blood loss, duration of surgery, occurrence of surgical site infections, and secondary surgery. Mean blood loss was lower (90.08 ml, p < 0.001, 95% CI 41.49 to 138.67) and surgery was shorter (16.17 minutes, p = 0.04, 95% CI 0.39 to 31.94) in synthetic treatment groups. All other secondary measures were statistically comparable. Conclusion. All studies reported similar methodologies and patient populations; however, imprecision may have arisen through performance variation. These findings supersede previous literature and indicate that, despite perceived biological advantages, autologous bone grafting does not demonstrate superiority to synthetic grafts. When selecting a void filler, surgeons should consider patient comorbidity, environmental and societal factors in provision, and perioperative and postoperative care provision. Cite this article: Bone Jt Open 2022;3(3):218–228

Introduction/Purpose. A randomized clinical trial of first MTP joint hemiarthroplasty with a synthetic cartilage implant demonstrated equivalent pain, function and safety outcomes to first MTP joint arthrodesis at 2 years. Recognizing that many hemiarthroplasty and total toe implants have initially good results that deteriorate over time, the purpose of this study was to prospectively assess the safety and efficacy outcomes for the synthetic cartilage implant population and to determine if the excellent outcomes were maintained at >5 years. Methods. One hundred nineteen patients were evaluated at 5+ years; 23 could not be reached for follow-up, but implant status was available for 7 of these subjects. Patients completed a pain visual analogue scale (VAS) and Foot and Ankle Ability Measure (FAAM) Sports and Activities of Daily Living (ADL) scores, preoperatively and at 2, 6, 12, 26, 52, 104 and 260 weeks postoperatively. Minimal clinically important differences are: ≥30% difference for pain VAS, 9 points for FAAM Sports, and 8 points for FAAM ADL. Great toe active dorsiflexion, weight-bearing radiographs, secondary procedures, and safety parameters were evaluated. Results. Of 119 patients available at mean 5.8 years follow-up (SD ±0.7; range: 4.4–8.0), 9 underwent implant removal and conversion to fusion in years 2–5, leaving 106 patients. The implant survival rate was 92.4% at 5.8 years. Pain and function outcomes at 5.8 years were similar to those at 2 years. VAS Pain, FAAM Sports, ADL Scores were maintained or improved at 5.8 years. No evidence of avascular necrosis, device migration or fragmentation was observed. There were no unanticipated safety events through 5.8 years. Ninety-three (93%) percent would have the procedure again. Conclusion. The synthetic cartilage hemiarthroplasty implant continues to demonstrate safety and efficacy for the treatment of advanced first MTP joint osteoarthritis with evidence of therapeutic effect and acceptable safety profile at 5.8 years

Our objective was to conduct a systematic review and meta-analysis, comparing differences in clinical outcomes between either autologous or synthetic bone grafts in the operative management of tibial plateau fractures: a traumatic pattern of injury, associated with poor long-term functional prognosis. A structured search of MEDLINE, EMBASE, The Bone & Joint and CENTRAL databases from inception until 07/28/2021 was performed. Randomised, controlled, clinical trials that compared autologous and synthetic bone grafts in tibial plateau fractures were included. Preclinical studies, clinical studies in paediatric patients, pathological fractures, fracture non-union or chondral defects were excluded. Outcome data was assessed using the Risk of Bias 2 (ROB2) framework and synthesised in random-effect meta-analysis. Preferred Reported Items for Systematic Review and Meta-Analysis guidance was followed throughout. Six comparable studies involving 352 patients were identified from 3,078 records. Following ROB2 assessment, five studies (337 patients) were eligible for meta-analysis. Within these studies, more complex tibia plateau fracture patterns (Schatzker IV-VI) were predominant. Primary outcomes showed non-significant reductions in articular depression at immediate postoperative (mean difference −0.45mm, p=0.25, 95% confidence interval (95%CI): −1.21-0.31mm, I. 2. =0%) and long-term (>6 months, standard mean difference −0.56, p=0.09, 95%CI: −1.20-0.08, I. 2. =73%) follow-up in synthetic bone grafts. Secondary outcomes included mechanical alignment, limb functionality, defect site pain, occurrence of surgical site infections, secondary surgery, perioperative blood loss, and duration of surgery. Blood loss was lower (90.08ml, p<0.001, 95%CI: 41.49-138.67ml, I. 2. =0%) and surgery was shorter (16.17minutes, p=0.04, 95%CI: 0.39-31.94minutes, I. 2. =63%) in synthetic treatment groups. All other secondary measures were statistically comparable. Our findings supersede previous literature, demonstrating that synthetic bone grafts are non-inferior to autologous bone grafts, despite their perceived disadvantages (e.g. being biologically inert). In conclusion, surgeons should consider synthetic bone grafts when optimising peri-operative patient morbidity, particularly in complex tibial plateau fractures, where this work is most applicable

Aims. The Cartiva synthetic cartilage implant (SCI) entered mainstream use in the management of first metatarsophalangeal joint (MTPJ) arthritis following the positive results of large trials in 2016. Limited information is available on the longer-term outcomes of this implant within the literature, particularly when independent from the originator. This single-centre cohort study investigates the efficacy of the Cartiva SCI at up to five years. Methods. First MTPJ arthritis was radiologically graded according to the Hattrup and Johnson (HJ) classification. Preoperative and sequential postoperative patient-reported outcome measures (PROMs) were evaluated using the Manchester-Oxford Foot Questionnaire (MOXFQ), and the activities of daily living (ADL) sub-section of the Foot and Ankle Ability Measure (FAAM). Results. Patients were followed up for a mean of 66 months (SD 7.1). Of an initial 66 cases, 16 did not return PROM questionnaires. A total of six failures were noted, with survival of 82%. Overall, significant improvement in both objective scores (MOXFQ and FAAM ADL) was maintained versus preoperatively: 18.2 versus 58.0 (p > 0.001) and 86.2 versus 41.1 (p > 0.001), respectively. The improvement was noted to be less pronounced in males. Subjective scores had deteriorated since early follow-up, with an interval decrease in patient satisfaction from 89% to 68%. Furthermore, a subset of cases demonstrated clinically important interval deterioration in objective scores. However, no specific patient factors were found to be associated with outcomes following analysis. Conclusion. This study represents the longest-term independent follow-up in the literature. It shows reassuring mid-term efficacy of the Cartiva SCI with better-than-expected survival. However, deterioration in scores for a subset of patients and lower satisfaction may predict ongoing failure in this group of patients. Additionally, males were noted to have a lower degree of improvement in scores than females. As such, ongoing observation of the SCI to assess durability and survivability, and identify predictive factors, is key to improving patient selection. Cite this article: Bone Jt Open 2024;5(9):799–805

Objectives. Cartiva synthetic cartilage implant (SCI) is licenced for use in management of symptomatic hallux rigidus in several countries including the UK. As for now, there are no independent comparative series for treatment of hallux rigidus utilising polyvinyl alcohol implants. Study design and methods. Patients at a single centre with symptomatic hallux rigidus who underwent Cartiva SCI implant procedure were identified. First metatarsophalangeal joint arthritis was radiographically graded according to the Hattrup and Johnson (HJ) classification. Pre-operative and post-operative patient-reported outcomes were evaluated using the Foot and Ankle Ability Measure (FAAM) activities of daily living subscale and the Manchester-Oxford Foot Questionnaire (MOXFQ). Results. 66 patients (19M, 47F) (43R and 23L) were followed up for an average of 14 months (min=2, max=36). 17 patients suffered from HJ2/moderate arthritis and 49 patients with grade HJ3/severe arthritis. Post-operative mean FAAM scores showed statistically significant improvement (p< 0.0001). Patients reported a 40% increase in functionality during activities of daily living. All 3 MOXFQ Domain scores improved significantly (p< 0.02). The Index score improved by 28 points (p< 0.0001). There was no correlation between length of follow up or age and PROMs (r=0.129). No statistical difference was demonstrated between sexes. However clinically, males and older patients exhibit better outcomes. There was a 89.4% patient satisfaction with the use of Cartiva. Conclusions. Our study shows excellent results with statistically significant improvements in functional outcomes, and promising short-term follow-up with low early revision rates. Pain in particular was significantly reduced. One third of patients developed post-operative stiffness requiring a manipulation under anaesthesia. Patient selection is key. Additional imaging may be required to assess sesamoid osteoarthritis. At 3 years the implant has demonstrated to be safe and efficacious in the management of hallux rigidus. Durability and survivability of the implant will continue to be studied in this cohort

Introduction. To determine if elite athletes can return to professional sport after MCL or posterolateral (PLC) reconstruction using LARS ligaments. The secondary aims are to demonstrate the safety and efficacy of LARS by reporting sport longevity, subsequent surgeries, and complications. Methods. A retrospective review of all extra-articular knee ligament reconstructions, utilising a LARS synthetic ligament, by 3 sports knee surgeons between 2013 and 2020 was undertaken. All elite athletes aged over 16 years and a minimum of 2 years post reconstruction were included. No LARS were used for ACL reconstructions, and they were excluded if a LARS ligament was used for a PCL reconstruction. Return to play (RTP) was defined as competing at professional level or national/ international level in amateur sport. Results. Sixty-four (84.2%) MCL reconstructions and 12 (15.8%) PLC reconstructions were included. 52 (68.4%) underwent concomitant autograft cruciate(s) reconstruction including 6 (7.8%) bicruciate reconstructions. The mean age was 25.1 years (SD +/− 4.50). 35 (46.1%) were footballers and 35 (46.1%) were rugby players. Sixty-seven athletes (88.2%) returned to elite sport, 7 (9.2%) did not RTP and RTP status was unknown for 2 (2.6%) (Figure 1). 65 out of 67 (97.0%) RTP at the same/higher Tegner level. 56 (83.6%) and 20 (57.1%) were still playing at 2- and 5-years post-surgery Six (7.9%) players required further surgery due to irritation from the metal fixation implants. One had an inflammation adjacent to the synthetic material at the femoral end and the other cases involved the tibial staples. All six cases were able to RTP. One athlete, following bicruciate /MCL surgery had the LARS removed due to laxity. There was one MCL re-rupture, sustained while jumping, 4 years after returning to football. Conclusions. Utilising LARS in extra-articular knee ligament reconstructions allows 88.2% of athletes with a variety of knee ligament injuries to return to elite sport. The results compare well regarding RTP, complication, and revision rates with the published evidence for other types of MCL and PLC grafts. This, coupled with 57% of athletes still playing 5 years post-surgery suggests the LARS is safe and effective in these cases. For any figures or tables, please contact authors directly

Introduction. There are over ½ million total knee replacement (TKR) procedures performed each year in the United States and is projected to increase to over 3.48 million by 2030. Concurrent with the increase in TKR procedures is a trend of younger patients receiving knee implants (under the age of 65). These younger patients are known to have a 5% lower implant survival rate at 8 years post-op compared to older patients (65+ years), and they are also known to live more active lifestyles that place higher demands on the durability and functional performance of the TKR device. Conventional TKR designs increase articular conformity to increase stability, but these articular constraints decrease patient range of knee motion, often limiting key measures of femoral rollback, A/P motion, and deep knee flexion. Without this articular constraint however, many patients report TKR “instability” during activities such as walking and stair descent, which can significantly impede confidence of movement. Therefore, there is a need for a TKR system that can offer enhanced stability while also maintaining active ranges of motion. Materials and Methods. A novel knee arthroplasty system has been designed that uses synthetic ligament systems that can be surgically replaced, to provide ligamentous stability and natural motion to increase the functional performance of the implant. A computational anatomical model (AnyBody) was developed that incorporated ligaments into an existing Journey II TKR. Ligaments were modeled and given biomechanical properties from literature. Simulated A/P drawer tests and knee flexion were analyzed for 2,916 possible cruciate ligament location and length combinations to determine the effects on the A/P stability of the TKR. A physical model was then constructed, and the design was verified by performing 110 N A/P drawer tests under 710 N of simulated body weight. Results and Discussion. As ACL insertion location moved posteriorly on the femur, it was found to decrease ACL ligament strain, enabling a higher range of flexion. In general, as ACL and PCL length increased, the A/P laxity of the TKR system increased linearly. Range of motion was found to be more dependent on ligament attachment location, and laxity was more dependent on ligament length. In this work, TKR stability was clearly affected by changes in synthetic ligament length and location. When comparing the laxity between a TKR with and without ligaments, the TKR with synthetic ligaments experienced significantly less displacement than a TKR without synthetic ligaments. Conclusions. The stability of a TKR can be increased while maintaining range of motion by incorporating synthetic ligaments into its design. The effectiveness of the ligaments was clearly dependent on two factors: length and location. It is imperative to the success of the implant to obtain the correct lengths and locations because improper placement or length can impact the outcome significantly. These results emphasize the need for a knee replacement that incorporates synthetic ligaments, with calibrated location and lengths, to significantly influence stability and possible kinematic performance of the TKR system, and potentially influencing long-term functional outcomes

Introduction. There are over one-half million total knee replacement (TKR) procedures performed each year in the United States and is projected to increase to over 3.48 million by 2030. Concurrent with the increase in TKR procedures is a trend of younger patients receiving knee implants (under the age of 65). These younger patients are known to have a 5% lower implant survival rate at 8 years post-op compared to older patients (65+ years), and they are also known to live more active lifestyles that place higher demands on the durability and functional performance of the TKR device. Conventional TKR designs increase articular conformity to increase stability, but these articular constraints decrease patient range of knee motion, often limiting key measures of femoral rollback, A/P motion, and deep knee flexion. Without this articular constraint however, many patients report TKR “instability” during activities such as walking and stair descent, which can significantly impede confidence of movement. Therefore there is a need for a TKR system that can offer enhanced stability while also maintaining active ranges of motion. Materials and Methods. A novel knee arthroplasty system was designed that uses synthetic ligament systems that can be surgically replaced, to provide ligamentous stability and natural motion to increase the functional performance of the implant. Using an anatomical knee model from the AnyBody software, a computational model that incorporated ligaments into an existing Journey II TKR was developed. Using the software ligaments were modeled and given biomechanical properties developed from equations from literature. Simulated A/P drawer tests and knee flexion test were analyzed for 2,916 possible cruciate ligament location and length combinations to determine the effects on the A/P stability of the TKR. A physical model was constructed, and the design was verified by performing 110 N A/P drawer tests under 710 N of simulated body weight. Results and Discussion. As ACL insertion location moved posteriorly on the femur, it was found to decrease ACL ligament strain, enabling a higher range of flexion. In general, as ACL and PCL length increased, the A/P laxity of the TKR system increased linearly. Range of motion was found to be more dependent on ligament attachment location, and laxity was more dependent on ligament length. In this work, TKR stability was clearly affected by changes in synthetic ligament length and location. When comparing the laxity between a TKR with and without ligaments, the TKR with synthetic ligaments experienced significantly less displacement than a TKR without synthetic ligaments as seen in Figure 1. Conclusions. This study shows that the stability of a TKR can be increased while maintaining range of motion by incorporating synthetic ligaments into this design. The effectiveness of the ligaments was clearly dependent on two factors: length and location, with incorrect lengths and locations significantly impairing ranges of motion. These results verify that a knee replacement can incorporate synthetic ligaments, and that with calibrated location and lengths, they can significantly influence stability and possible kinematic performance of the TKR system, and potentially influencing long-term functional outcomes. For any figures or tables, please contact the authors directly

Introduction. Concerning biomechanical research, human specimens are preferred to achieve conditions that are close to the clinical situation. On the other hand, synthetic femurs are used for biomechanical testing instead of fresh-frozen human femurs, to create standardized and comparable conditions. A new generation of synthetic femurs is currently available aiming to substitute the validated traditional one. Structural femoral properties of the new generation have already been validated, yet a biomechanical validation is missing. The aim of our study was to analyse potential differences in the biomechanical behaviour of two different synthetic femoral designs by measuring the primary rotational stability of a cementless femoral hip stem. Methods. The cementless SL-PLUS® standard stem (size 6, Smith&Nephew Orthopaedics AG, Rotkreuz, Swizerland) was implanted in two groups of synthetic femurs. Group A consists of three 2. nd. generation femurs and group B consists of three 4. th. generation femurs (both: size large, composite bone, Sawbones® Europe, Malmö, Sweden). Using an established method to analyse the rotational stability, a cyclic axial torque of ±7.0 Nm along the longitudinal stem axis was applied. Micromotions were measured at defined levels of the bone and the implant. The calculation of relative micromotions at the bone-implant interface allowed classifying the rotational implant stability. Results. Lowest relative micromotions were located near the isthmus for both designs (2. nd. 3.47 ± 1.43 mdeg/Nm and 4. th. 5.97 ± 0.39 mdeg/Nm), whereas highest relative micromotions were located at distal tip for both designs (2. nd. 8.42 ± 1.38 mdeg/Nm and 4. th. 8.40 ± 0.39 mdeg/Nm). No statistically significant differences were found between 2. nd. and 4. th. generation femurs in the distal part (2. nd. 8.42 ± 1.38 mdeg/Nm and 4. th. 8.40 ± 0.39 mdeg/Nm; p>0.05), but proximally (2. nd. 3.63 ± 1.10 mdeg/Nm vs. 4. th. 6.55 ± 1.27 mdeg/Nm; p<0.05). Compared to the 2. nd. generation, the 4. th. generation femur resulted in less absolute micromotions and less standard deviation of micromotions. Discussion. Compared to other implant designs, the SL-PLUS® stem resulted in low relative motions regardless the used synthetic femur. Within the two distal measuring levels, no significant differences could be observed. Proximally, at the level of the Trochanter minor, mean relative motions nearly doubled from group A to B. However, the anchorage principle of the SL-PLUS® stem was still similar in both synthetic femurs. Qualitatively, both synthetic femurs revealed a proximal fixation of the stem. Although the values of relative motion slightly differs, 4. th. generation synthetic femurs are suitable to achieve similar results for measuring the primary stability of cementless femoral hip stems compared to 2. th. generation synthetic femurs. Future measurements with human specimens should validate weather one of the synthetic bone models is closer to the human situation. Within this study we could show that the new 4. th. generation synthetic femur designs could qualitatively give comparable results to older synthetic bone models regarding biomechanical tests, like primary stability measurements on cementless hip stems

Introduction. The objective of this study was to determine if a synthetic bone substitute would provide results similar to bone from osteoporotic femoral heads during in vitro testing with orthopaedic implants. If the synthetic material could produce results similar to those of the osteoporotic bone, it could reduce or eliminate the need for testing of implants on bone. Methods. Pushout studies were performed with the dynamic hip screw (DHS) and the DHS Blade in both cadaveric femoral heads and artificial bone substitutes in the form of polyurethane foam blocks of different density. The pushout studies were performed as a means of comparing the force displacement curves produced by each implant within each material. Results. The results demonstrated that test material with a density of 0.16 g/cm. 3. (block A) produced qualitatively similar force displacement curves for the DHS and qualitatively and quantitatively similar force displacement curves for the DHS Blade, whereas the test material with a density of 0.08 g/cm. 3. (block B) did not produce results that were predictive of those recorded within the osteoporotic cadaveric femoral heads. Conclusion. This study demonstrates that synthetic material with a density of 0.16 g/cm. 3. can provide a good substitute for cadaveric osteoporotic femoral heads in the testing of implants. However we do recognise that no synthetic material can be considered as a definitive substitute for bone, therefore studies performed with artificial bone substrates may need to be validated by further testing with a small bone sample in order to produce conclusive results

Aim. There is growing evidence that bacteria encountered in periprosthetic joint infections (PJI) form surface-attached biofilms on prostheses, as well as biofilm aggregates embedded in synovial fluid and tissues. However, models allowing the investigation of these biofilms and the assessment of their antimicrobial susceptibility in physiologically relevant conditions are currently lacking. To address this, we developed a synthetic synovial fluid (SSF) model and we validated this model in terms of growth, aggregate formation and antimicrobial susceptibility testing, using multiple PJI isolates. Methods. 17 PJI isolates were included, belonging to Staphylococcus aureus, coagulase negative staphylococci, Cutibacterium acnes, Pseudomonas aeruginosa, enterococci, streptococci, Candida species and Enterobacterales. Growth and aggregate formation in SSF, under microaerophilic or anaerobic conditions, were evaluated using light microscopy. The biofilm preventing concentration (BPC) and minimum biofilm inhibitory concentration (MBIC) of relevant antibiotics (doxycyclin, rifampicin and oxacillin) were determined for the staphylococcal strains (n=8). To this end, a high throughput approach was developed, using a fluorescent viability resazurin staining. BPC and MBIC values were compared to the minimum inhibitory concentration (MIC) obtained with conventional methods. Results. The SSF model allowed all isolates to grow well under microaerophilic or anaerobic conditions. When cultured in SSF, all isolates formed biofilm aggregates, varying in size and shape along different species. A susceptibility testing method based on measuring resazurin-derived fluorescence was successfully developed, allowing high throughput determination of the BPC and the MBIC in SSF. For all staphylococci cultured in SSF a reduced susceptibility to the tested antibiotics was observed when compared to susceptibility data obtained in general medium. For rifampicin and doxycyclin the BPC was consistently higher than the MIC (two- to fourfold dilution difference for rifampicin and four- to sixfold dilution difference for doxycyclin). For oxacillin the MIC equaled the BPC for two isolates, while for the other isolates the BPC was higher than the MIC (two- to fourfold dilution difference). Expectedly, the MBIC was higher than the BPC and differences with the MIC were even more pronounced for all antibiotics tested (differences of six- to fourteenfold dilutions were observed). Conclusion. Our data indicate that the in vitro SSF model could provide more insight in how PJI-related pathogens form biofilms in physiologically relevant conditions. The BPC and MBIC were consistently and substantially higher than MIC. This model could be a valuable addition to evaluate the antimicrobial susceptibility in biofilms in a PJI context. Sources of funding: FWO-Vlaanderen (grant G066523N)

Abstract. Objectives. Meniscus allograft and synthetic meniscus scaffold (Actifit. ®. ) transplantation have shown promising outcomes for symptoms relief in patients with meniscus deficient knees. Untreated chondral defects can place excessive load onto meniscus transplants and cause early graft failure. We hypothesised that combined ACI and allograft or synthetic meniscus replacement might provide a solution for meniscus deficient individuals with co-existing lesions in cartilage and meniscus. Methods. We retrospectively collected data from 17 patients (16M, 1F, aged 40±9.26) who had ACI and meniscus allograft transplant (MAT), 8 patients (7M, 1F, aged 42±11) who underwent ACI and Actifit. ®. meniscus scaffold replacement. Other baseline data included BMI, pre-operative procedures and cellular transplant data. Patients were assessed by pre-operative, one-year and last follow-up Lysholm score, one-year repair site biopsy, MRI evaluations. Results. In the MAT group, the final post-operative evaluation was 7±4.5 years. The mean pre-operative Lysholm score was 49±17, rose to 66.6±16.4 1 year post-op and dropped to 58±26 at final evaluation. Four of the 17 patients had total knee replacements (TKRs) at average 6.4 years after treatment. In the Actifit. ®. group, the final post-operative assessment was 5.6±2.7years. The pre-operative Lysholm score was 53.7±21.3, increasing to 72.8±15.2 at 1 year and 70.4±27.6 at final clinical follow-up. None of the patients in the Actifit® group had received TKRs. Conclusions. Both MAT and Actifit. ®. groups were effective in improving patients symptoms and knee function according to one-year post-operative assessments. However, the knee function of patients in MAT group dropped at final follow-up, whereas the Actifit® group maintained their knee function. These preliminary findings warrant further investigations, to include more patients and alongside comparisons to ACI alone and allograft/Actifit. ®. alone as comparator groups before accurate conclusions may be drawn on the comparative efficacy of each technique. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

Introduction. Low back pain (LBP) is a worldwide leading cause of disability. This preclinical study evaluated the safety of a combined advanced therapy medicinal product developed during the European iPSpine project (#825925) consisting of mesendoderm progenitor cells (MEPC), derived from human induced pluripotent stem cells, in combination with a synthetic poly(N-isopropylacrylamide) hydrogel (NPgel) in an ovine intervertebral disc degeneration (IDD) model. Method. IDD was induced through nucleotomy in 4 adult sheep, 5 lumbar discs each (n=20). After 5 weeks, 3 alternating discs were treated with NPgel (n=6) or NPgel+MEPC (n=6). Before sacrifice, animals were subjected to: MRI of lumbar spines (disc height and Pfirmann grading); blood sampling (hematological, biochemical, metabolic and lymphocyte/monocytes immunological). After 3 months the sheep were sacrificed. The spines were processed for: macroscopic morphology (Thompson grading), microscopic morphology (Histological grading), and glycosaminoglycan content (GAG, DMMB Assay). Furthermore, at sacrifice biodistribution of human MEPC was assessed by Alu-sequences quantification (qPCR) from three tissue samples of heart, liver, spleen, brain, lungs, and kidneys, and PBMCs collected to assess activation of systemic immune cells. To each evaluation, appropriate statistical analysis was applied. Result. Flow cytometry showed no induction of systemic activation of T cells or monocytes. Alu quantification did not give detection of any cells in any organ. Disc height index was slightly increased in discs treated with NPgel+MEPC. Pfirmann's and Thompson's classification showed that treatment with NPgel or NPgel+MEPC gave no adverse reactions. Histological grading showed similar degeneration in vertebrae treated with NPgel+MEPC or with NPgel alone. The amount of GAG was significantly increased in the nucleus pulposus following treatment with NPgel+MEPC compared to NPgel alone, in which a decrease was observed compared to untreated discs in both nucleus pulposus and annulus fibrosus. Conclusion. This study showed the safety of both NPgel+MEPC and NPgel treatments

Introduction: In the 1970’s, ‘viscosupplementation’ with hyaluronan was proposed as a potential treatment for OA with the idea that it would improve joint lubrication. However, despite studies showing its ability to reduce pain, the fact that the resident time within a joint (48 hours) is much less than its clinical effect (several months) along with pharmacological effects on chondroctyes and synoviocytes has confirmed that injected hyaluronan acts as a pharmaceutical rather than as a lubricant as originally thought. In this regard, the effects of inert synthetic lubricants on arthritic joints have not previously been adequately investigated. This study examines the effect of injecting an inert synthetic lubricant, perfluoroalkylether (PFAE16350), as a mechanical joint lubricant to prevent the development of osteoarthritis in a surgically induced model of osteoarthritis in the adult guinea pig. Materials & Methods: Osteoarthritic changes were initiated in the hind knee joint of 12 adult male Dunkin-Hartley guinea-pigs by excision of the medial meniscus and anterior cruciate ligament. After wound closure, the animals were randomly assigned to 1 of 2 groups: (1) Single intra-articular injection of 1ml synthetic, sterile lubricant (PFAE16350) or (2) Control group with single intra-articular injection of 1ml 0.9% sterile saline. At 9 weeks after surgery, after sacrifice, knee arthrotomy was performed, the presence of synthetic lubricant noted and the articular cartilages examined for macroscopic evidence of osteoarthritis. These cartilages were then fixed, embedded, sectioned, stained and graded histologically for osteoarthritis according to a modified Mankin scoring system. Immunohistochemical studies were performed to assess for any inflammatory or cytotoxic effect by the lubricant. Results: All guinea-pigs remained healthy and mobile throughout the study. Subjective macroscopic assessment of the medial tibial plateau osteophyte was noted to be larger and the articular surface more roughened in the control cases compared to the lubricated cases. Synthetic lubricant was noted at arthrotomy in all cases where it was injected. Guinea-pig joints treated with the synthetic lubricant showed a mean modified Mankin score of 3.0 points compared with the guinea-pig joints treated with saline where the median modified Mankin score was 8.5 points (p< 0.001). There was no evidence of an inflammatory or cytotoxic response by immunohistochemical studies. Discussion: This study has confirmed that inert synthetic perfluoroalkylether lubricants can remain in the articular space for prolonged periods and inhibit the development of osteoarthritis without initiating an inflammatory response. Synthetic lubricants such as PFAE16350 warrant further investigation for potential use in osteoarthritis

Abstract. Introduction. The aim of this study was to determine if elite athletes could return to professional sport after MCL or PLC reconstruction using LARS ligaments and to demonstrate the safety and efficacy of LARS by reporting sport longevity, subsequent surgeries and complications. Methods. A retrospective review of all extra-articular knee ligament reconstructions in elite athletes utilising LARS ligaments by 3 knee surgeons between January 2013 and October 2020 was undertaken. Return to play (RTP) was defined as competing at professional level or national/ international level in amateur sport. Results. Sixty-four (84.2%) MCL and 12 (15.8%) PLC reconstructions utilising LARS in elite athletes were included. 52 (68.4%) underwent concomitant cruciate(s) reconstruction. The mean age was 25.1 years (SD +/− 4.50. Most were football (35, 46.1%) or rugby players (35, 46.1%). Sixty-seven athletes (88.2%) RTP with 65 (97.0%) of these playing at the same or higher Tegner level. 56 (83.6%) and 20 (57.1%) were still playing at 2 and 5 years post-surgery. Six (7.9%) players (5 of whom RTP) required further surgery relating to the LARS / metalwork and there was one case of adverse local inflammatory reaction to the synthetic material. There was one MCL re-rupture, sustained 4 years after RTP. Conclusion. Utilising LARS in extra-articular knee ligament reconstructions allows 88.2% of athletes, with a variety of knee ligament injuries, to return to elite sport. The low morbidity rates coupled with 57% of athletes still playing 5 years post-surgery suggests the LARS is safe and effective in these cases

Summary Statement. The tensile properties of a number of synthetic fibre constructs and porcine MCLs were experimentally determined and compared to allow the selection of an appropriate synthetic collateral ligament model for use in a kinematic knee simulator. Introduction. As patient expectations regarding functional outcomes of total knee arthroplasty rise the need to assess the kinematics of new implants in vitro has increased. This has traditionally been done using cadaveric models, which can demonstrate high physiological relevance but also substantial inter-specimen variability. More recently there has been a shift towards the use of in silico and non-cadaveric methods. Such methods require significant simplifications of the joint and the modelling of soft tissue structures such as the collateral ligaments. Collateral ligaments are often modelled in in silico studies but have not, in the published literature, been modelled in in vitro knee kinematic simulators. Tensile testing of ligament tissue, to provide reference data, and the subsequent analysis of potential synthetic analogues was carried out. The overall aim of the study was to develop a synthetic ligament analogue for use in kinematic knee simulators. Methods. Porcine MCLs were chosen as these are of a similar size and are a readily available alternative to human ligaments. Six porcine knee specimens were sourced and the MCLs dissected by an orthopaedic registrar. Testing was carried out on an Instron MTS fitted with a 5kN load cell. Each specimen was subjected to 5 pre-conditioning loading cycles before cross-sectional and length measurements were made. Each specimen was then cyclically loaded from 0–200N for 30 cycles before being loaded to failure at a rate of 100mm/min. Ten potential synthetic analogues were also assessed using the same procedure: the Lars 80 (Corin Ltd) synthetic ligament reconstruction system and a selection of readily available synthetic constructs. Results. The porcine specimens demonstrated 6% ± 1% strain (mean ± standard error) after 30 cycles of loading, and a tensile stiffness of 100 N/mm ± 8.9 N/mm. The results of the load to failure tests also indicated a substantial toe region and highlighted the substantial variability associated with cadaveric specimens. The Lars system demonstrated a tensile stiffness of nearly 9 times that of the porcine specimens. However, non-parametric Mann-Whitney U analyses indicated that three of the synthetic samples did not have statistically significantly different tensile stiffness values compared to the porcine specimens (p < 0.05). Of these samples, the polyester braided cord demonstrated the longest and most physiologically relevant toe region. All of the polyester load-displacement traces fell within the range demonstrated by the porcine specimens. Discussion/Conclusion. The tensile properties of the porcine specimens analysed were similar to those reported in in the literature for human ligaments1. Porcine MCLs are thus a fair model of human collateral ligaments and were a suitable reference material for the selection of a synthetic analogue. The tensile testing carried out in the present study indicated that commercially available synthetic ligaments are over engineered in terms of strength and inappropriate for use in kinematic analysis. However, a polyester braided cord did demonstrate appropriate basic mechanical properties and would be appropriate as an analogue model on kinematic knee rigs