Aims: Developing a new effective method of clavicle osteosynthesis. Methods: The K-wire is inserted along bone fragments (and bone autograft – in case of clavicle defect). Then K-wire is fixed near the breast-bone with the curved or threaded lug. External end of K-wire is strained in external fixation module. When having fracturing console pin with lug is inserted in acromion of frontal plane and is connected to K-wire with short bar. In cases of non-unions and defects two K-wire are inserted (through coracoid and acromion) sagittally. Both of them are strained in half-ring. The K-wire inserted along bone fragments is strained in half-ring (Patent of RF # 1657168). Results: 238 patients were treated by CoSF: 222 with fractures, 11 – with non-unions, 5 – with defects of clavicle. Complete restoration of shoulder function during of fixation period was registered in 86,1% patients (p< 0,001). Analysis has shown that the main reason of join stiffness were delayed operation. 13,6% of patients have been operated in more than two weeks the injury had occurred, when the contracture already appeared. Pin-tract infection were arised in 3,4% cases, pin-tract osteomyelitis – in 1% cases. Conclusions: Good and excellent results proved prospective of CoSF as well as improving this method

Introduction. The exact mechanisms leading to tendinopathies and tendon ruptures remain poorly understood while their occurrence is clearly associated with exercise. Overloading is thought to be a major factor contributing to the development of tendon pathologies. However, as animal studies have shown, heavy loading alone won't cause tendinopathies. It has been speculated, that malfunctioning adaptation or healing processes might be involved, triggering tendon tissue degeneration. By analysing the expression of the entirety of degrading enzymes (degradome) in pathological and non-pathological, strained and non-strained tendon tissue, the aim of this study was to identify common or opposite patterns in gene regulation. This approach may generate new targets for future studies. Materials and Methods. RNA was extracted from different tendon tissues: normal (n=7), tendinopathic (n=4) and ruptured (n=4) Achilles tendon; normal (n=4) and tendinopathic (n=4) posterior tibialis tendon; normal hamstrings tendon with or without subjection to static strain (n=4). The RNA was reverse transcribed, then pooled per group The expression of 538 protease genes was analysed using Taqman low-density array quantitative RT-PCR. To be considered relevant, changes had to be at least 4fold and measurable at a level below 36 Cts. Results. In general, there was little common regulation when exercised was compared with pathological tissue. The expression of PAMR1 and TNFαIP3 was upregulated with exercise (169-fold and 78-fold), Achilles tendinopathy (9724-fold and 7-fold) and Achilles tendon rupture (1809-fold and 10-fold), while DDI1, PSMB11 and PSH2 which were down-regulated with exercise were upregulated with Achilles pathology. Discussion. The newly found targets may deliver insights into the initiation and progression of tendon pathologies: PAMR1, a regeneration associated muscle protease which has been shown to be downregulated in Duchenne muscular dystrophy and upregulated in regenerating muscle fibers, might also be involved in tendon regeneration; TNFαIP3, which negatively regulates the NF-κB/pro-inflammatory pathway, could have anti-inflammatory function in tendon regeneration. PSMB11 and PSH2 are for the first time shown to be expressed in tendon and regulated in tendon pathology. Using this approach we were able to generate new targets and to add information on function, regulation and expression sites of recently identified proteins

Purpose: Trauma to the radial collateral ligaments requires the same attention as trauma to the ulnar ligaments. Damage is uncommon due to the particular anatomic position, but nevertheless a distinct clinical entity.

Material and methods: We report a retrospective analysis of 14 patients, eight who underwent emergency surgery and six with trauma sequelae. Mean follow-up was 22 months and mean age 37 years. Among the recent lesions, the pain score (scale from 1 to 5) was 4.5) and the instability score (scale from 1 to 3) was 3. Palmar subdislocation was 4.8 mm and laxity was 16.7°. Among the old lesions (> 1 month) the corresponding data were pain 3.3, instability 2.5, palmar sub-dislocation 4.2 mm, laxity 19.1°. Two patients had signs of osteoarthritis. At surgery, the phalanx and metacarpus were equally injured. Associated lesions (capsule, short abductor) were present in 78% of the patient. The radial collateral ligaments and the soft tissue were reinserted or retightened in all cases. One patients required arthrodesis due to cartilage damage.

Results: Among the recent injuries, 71% reached a good subjective result: amplitude loss (flexion/extension) was 17°, force was 75% and laxity was 5°. Two patients had palmar subdisloction. Among the older lesions, a good subjective result was achieved in 66%: loss of amplitude case 32°, force was 69% and laxity was 8°. Palmar subdislocation was 2 mm on the average. We had two cases of persistent dysaesthesia.

Discussion: Radial injury appears to be falsely benign because the Stener lesion is not found on this side of the metacarpophalange. The importance of the injury in these traumas is related to the vulnerability of the dorsal region of the medial collateral ligament and is probably the cause of poor outcome after surgery for older lesions with palmar dislocation which is difficult to correct. We advocate emergency surgery for a wide range of indications. We always operate major radial laxity (> 35°) or laxity associated with palmar subdislocation. For other cases, we use the anterior forced drawer view to disclose potential associated dorsal injury.

Aims

The aim of this study was to determine the risk of tibial eminence avulsion intraoperatively for bi-unicondylar knee arthroplasty (Bi-UKA), with consideration of the effect of implant positioning, overstuffing, and sex, compared to the risk for isolated medial unicondylar knee arthroplasty (UKA-M) and bicruciate-retaining total knee arthroplasty (BCR-TKA).

Aims

Periprosthetic hip fractures (PPFs) after total hip arthroplasty are difficult to treat. Therefore, it is important to identify modifiable risk factors such as stem selection to reduce the occurrence of PPFs. This study aimed to clarify differences in fracture torque, surface strain, and fracture type analysis between three different types of cemented stems.

Aims. Few studies have investigated potential consequences of strained surgical resources. The aim of this cohort study was to assess whether a high proportion of concurrent acute surgical admissions, tying up hospital surgical capacity, may lead to delayed surgery and affect mortality for hip fracture patients. Methods. This study investigated time to surgery and 60-day post-admission death of patients 70 years and older admitted for acute hip fracture surgery in Norway between 2008 and 2016. The proportion of hospital capacity being occupied by newly admitted surgical patients was used as the exposure. Hip fracture patients admitted during periods of high proportion of recent admissions were compared with hip fracture patients admitted at the same hospital during the same month, on similar weekdays, and times of the day with fewer admissions. Results. Among 60,072 patients, mean age was 84.6 years (SD 6.8), 78% were females, and median time to surgery was 20 hours (IQR 11 to 29). Overall, 14% (8,464) were dead 60 days after admission. A high (75. th. percentile) proportion of recent surgical admission compared to a low (25. th. percentile) proportion resulted in 20% longer time to surgery (95% confidence interval (CI) 16 to 25) and 20% higher 60-day mortality (hazard ratio 1.2, 95% CI 1.1 to 1.4). Conclusion. A high volume of recently admitted acute surgical patients, indicating probable competition for surgical resources, was associated with delayed surgery and increased 60-day mortality. Cite this article: Bone Joint J 2021;103-B(2):264–270

Despite the clinical relevance of back pain and intervertebral disc herniation, the lack of reliable models has strained their molecular understanding. We characterized the lumbar spinal phenotype of C57BL/6 and SM/J mice during aging. Interestingly, old SM/J lumbar discs evidenced accelerated degeneration, associated with high rates of disc herniation. SM/J AF's and degenerative human's AF transcriptomic profiles showed altered immune cell, inflammation, and p53 pathways. Old SM/J mice presented increased neuronal markers in herniated discs, thicker subchondral bone, and higher sensitization to pain. Dorsal root ganglia transcriptomic studies and spinal cord analysis exhibited increased pain and neuroinflammatory markers associated with altered extracellular matrix regulation. Immune system single-cell and tissue level analysis showed distinctive T-cell and B-cell modulation and negative correlation between mechanical allodynia and INF-α, IL-1β, IL2, and IL4, respectively. This study underscores the multisystemic network behind back pain and highlights the role of genetic background and the immune system in disc herniation disease. Acknowledgments: This study is supported by grants from the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) R01AR055655, R01AR064733, R01AR074813 to MVR

The suprascapular nerve is an ideal target for nerve blockade to alleviate shoulder pain given its widespread innervation to the shoulder girdle. Many techniques have been described. To widen the availability of this treatment we investigate whether an anatomical landmark technique can be easily learned by novice injectors to provide efficacious blockade. Five injectors were recruited with varying experience; from the novice medical student to an orthopaedic consultant. Five torsos (10 shoulders) were used. A single page of written instruction and illustration of the Dangoisse landmark technique was provided prior to injection of a Thiel embalmed cadaver bilaterally. A pre-mixed injectate with blue dye was used. Cadavers were dissected and the presence or absence of dye staining reported by 3 observers and a consensus agreement reached. Dissection demonstrated diffuse staining in the suprascapular fossa. 90% of shoulders were found to have adequate staining of the suprascapular nerve directly, or its distal branches, in a manner which would provide adequate anaesthesia. The inter-observer agreement was good (k = 0.73) for staining at the supraspinous fossa and excellent (k=0.87) for staining distally. The technique was easily performed by novice injectors with a 100% success rate. We demonstrate that this technique is reproducible by a range of clinicians to effectively provide anaesthesia of the SScN. The main risks are ineffective block (10% in this series) and of intravascular injection. Within a resource strained healthcare environment greater uptake of this technique is likely to be of benefit to a wider array of patients

Introduction. The enhanced recovery after surgery (ERAS) concept in arthroplasty surgery has led to a reduction in postoperative length of stay in recent years. Patients with prolonged length of stay (PLOS) add to the burden of a strained NHS. Our aim was to identify the main reasons. Methods. A PLOS was arbitrarily defined as an inpatient hospital stay of four days or longer from admission date. A total of 2,000 consecutive arthroplasty patients between September 2017 and July 2018 were reviewed. Of these, 1,878 patients were included after exclusion criteria were applied. Notes for 524 PLOS patients were audited to determine predominant reasons for PLOS. Results. The mean total length of stay was 4 days (1 to 42). The top three reasons for PLOS were social services, day-before-surgery admission, and slow to mobilize. Social services accounted for 1,224 excess bed days, almost half (49.2%, 1,224/2,489) of the sum of excess bed days. Conclusion. A preadmission discharge plan, plus day of surgery admission and mobilization on the day of surgery, would have the potential to significantly reduce length of stay without compromising patient care. Cite this article: Bone Joint Open 2020;1-8:488–493

Prophylactic augmentation is meant to reinforce the vertebral body (VB), but in some cases it is suspected to actually weaken it. To elucidate the biomechanical efficacy of prophylactic augmentation, the full-field three-dimensional strain distributions were measured for the first time inside prophylactic-augmented vertebrae. Twelve thoracic porcine vertebrae were assigned to three groups: 4 were augmented with bone cement for vertebroplasty (Mendec-Spine, Tecres), 4 were treated with another bone cement for vertebroplasty (Calcemex-Spine, Tecres) while the other 4 were tested untreated as a control. Destructive tests were carried out under axial compression, in a step-wise fashion (unloaded, 5%, 10% and 15% compression). At each loading step, μCT-images were acquired. The internal strain distribution was investigated by means of DVC analysis. Some augmented specimens were stronger than the respective control, while others were weaker. In most of the specimens, the strain distribution in the elastic regime (5% compression) seemed to predict the location of the micro-damage initiation before it actually became identifiable (at 10% and 15% compression). The measured strain had the same order of magnitude for all groups. However, in the control vertebrae, the highest strain would unpredictably appear at any location inside the VB. Conversely, for both augmentation groups, the highest strains were measured in the regions adjacent to the injected cement mass, whereas the cement-interdigitated-bone was less strained. Localization of high strains and failure was consistent between specimens, but different between the two cement types: with Mendec-Spine failure the highest strains were mainly localized at mid-height and at the same level where the cement mass was localized; with Calcemex-Spine failure the highest strains were mainly cranial and caudal to the cement mass. Both the micro-CT images, and the DVC strain analysis highlighted that:. The cement mass was less strained than any other regions in the vertebra. Failure never started inside the cement mass. This can be explained with the additional stiffening and reinforcement associated with the infiltration of the cement inside the trabecular bone. The highest strains and failure were localized in the bone adjacent to the cement-bone interdigitated region. This can be explained by the strain concentration between the cement-interdigitated bone (stiffer and stronger), and the adjacent non-augmented trabecular bone. The strain maps in the elastic regime and the localization of failure was different in the augmented vertebrae, when compared to the natural controls. This suggests an alteration of the load sharing in the augmented structure where the load is mostly carried by the cement region. The different localization of failure initiation between the two augmented groups could be explained by the different mechanical properties of the two cements. This study has demonstrated the potential of DVC in measuring the internal strain and failure in prophylactic-augmented vertebrae. It has been shown that failure starts inside the augmented VB, next to the injected cement mass. This can help establishing better criteria (in terms of localization of the cement mass) in order to improve clinical protocols for vertebroplasty surgical procedures

Objectives. Up to 40% of unicompartmental knee arthroplasty (UKA) revisions are performed for unexplained pain which may be caused by elevated proximal tibial bone strain. This study investigates the effect of tibial component metal backing and polyethylene thickness on bone strain in a cemented fixed-bearing medial UKA using a finite element model (FEM) validated experimentally by digital image correlation (DIC) and acoustic emission (AE). Materials and Methods. A total of ten composite tibias implanted with all-polyethylene (AP) and metal-backed (MB) tibial components were loaded to 2500 N. Cortical strain was measured using DIC and cancellous microdamage using AE. FEMs were created and validated and polyethylene thickness varied from 6 mm to 10 mm. The volume of cancellous bone exposed to < -3000 µε (pathological loading) and < -7000 µε (yield point) minimum principal (compressive) microstrain and > 3000 µε and > 7000 µε maximum principal (tensile) microstrain was computed. Results. Experimental AE data and the FEM volume of cancellous bone with compressive strain < -3000 µε correlated strongly: R = 0.947, R. 2. = 0.847, percentage error 12.5% (p < 0.001). DIC and FEM data correlated: R = 0.838, R. 2. = 0.702, percentage error 4.5% (p < 0.001). FEM strain patterns included MB lateral edge concentrations; AP concentrations at keel, peg and at the region of load application. Cancellous strains were higher in AP implants at all loads: 2.2- (10 mm) to 3.2-times (6 mm) the volume of cancellous bone compressively strained < -7000 µε. Conclusion. AP tibial components display greater volumes of pathologically overstrained cancellous bone than MB implants of the same geometry. Increasing AP thickness does not overcome these pathological forces and comes at the cost of greater bone resection. Cite this article: C. E. H. Scott, M. J. Eaton, R. W. Nutton, F. A. Wade, S. L. Evans, P. Pankaj. Metal-backed versus all-polyethylene unicompartmental knee arthroplasty: Proximal tibial strain in an experimentally validated finite element model. Bone Joint Res 2017;6:22–30. DOI:10.1302/2046-3758.61.BJR-2016-0142.R1

Ten RCTs published between 2000 and 2013 support treating distal radius buckle fractures and other low-risk distal radius fractures with a removable splint and with no orthopaedic follow-up. Application of this evidence has been shown to be variable and suboptimal resulting in unnecessary costs to a strained healthcare system. The Canadian evidence on this topic has been generated by subspecialist physicians working in paediatric hospitals. It is unclear what factors affect the dissemination of this information. We investigated the association of hospital type and physician type with the application of best-evidence treatment for low-risk distal radius fractures in children with the goal of improving our understanding of evidence diffusion in Ontario for this common injury. We performed a retrospective population-based cohort study using linked health care administrative data. We identified all children aged 2–14 treated in Ontario emergency departments from 2003–2015 with distal radius fractures with no reduction and no operation within a six week period. We excluded refractures and children with comorbidities. We evaluated the followup received – orthopaedic, general practitioner, or none. We examined the data for trends over time. Multivariable log binomial regression was used to quantify associations between hospital and physician type and best-evidence treatment. We adjusted for patient-related variables including age, sex, rural or urban location, and socioeconomic status. 70,801 fractures were analyzed. Best-evidence treatment was more likely to occur in a small (RR 1.86, 95%CI 1.72–2.01), paediatric (RR 1.16, 95%CI 1.07–1.26), or community (RR 1.13, 95%CI 1.06–1.20) hospital compared with treatment in a teaching hospital. Best-evidence treatment was more likely if initial management was by a paediatrician with additional emergency medicine training (RR 1.73, 95%CI 1.56–1.92) or paediatrician (RR 1.22, 95%CI 1.11–1.34). Paediatric and teaching hospitals have improved their use of best-evidence over time while other hospital types have stagnated or deteriorated. Paediatricians, paediatricians with additional emergency medicine training, and emergency medicine residency trained physicians have improved their use of best-evidence over time, while other physician types have stagnated or deteriorated. Overall, only 20% of patients received best-evidence treatment and 70% had orthopaedic follow-up. Significant over-utilization of resources for low-risk distal radius fractures continues decades after the first randomized trials showed it to be unnecessary. Physician type and hospital rurality are most strongly associated with best-evidence treatment. Physician types involved in generating, presenting, and publishing best-evidence for this fracture type are successfully implementing it, while others have failed to change their practices. Rural hospitals are excellent resource stewards by necessity, but are deteriorating over time. Our results strongly indicate the need for targeted implementation strategies to explicitly apply clinical evidence in clinical practice Canada-wide, with the goal of providing more cost-effective care for common children's fractures

Aim: This study was designed to investigate the nature and extent of tibial translation (TT) during open kinetic chain (OKC) and closed kinetic chain (CKC) activity; recent reports have suggested that the anterior cruciate ligament (ACL) may be strained to an equal amount during CKC and OKC exercise. Method: Fifteen unilaterally ACL deficient (ACLD) patients and six control subjects underwent fluoroscopic assessment while performing a passive extension exercise, an OKC resisted extension exercise, and a weight-bearing CKC exercise designed to reflect knee motion experienced during dynamic daily activity. Measurements of the patella tendon angle (the angle between the long axis of the tibia and the patella tendon) were obtained to calculate relative TT. Results: The results show that in ACL intact (ACLI) knees the CKC exercise caused greater anterior TT than the OKC exercise from 0 to 60° of knee flexion (p< 0.05). No difference between ACLI and ACLD knees was detected during the CKC exercise. Maximum weight-bearing (CKC) TT was 8±3 mm. The ACLD tibia during the OKC exercise translated more than the ACLI tibia, and to the same extent as the CKC exercise at 10 to 200 of knee flexion. The ACLI tibia during OKC exercise translated to a maximum of 3±4 mm at 1 0° knee flexion. Summary: This study has demonstrated that fluoroscopic analysis may be used to detect differences in the kinematics of ACLI and ACLD limbs during activity. It validates recent data demonstrating that the ACL may be strained during CKC exercise to an equal or greater amount than during OKC exercise, and shows that the ACLD knee kinematics are similar to the ACLI knee during CKC exercise. Factors other than the ACL may control the extent of maximal TT during weightbearing activity. This has important consequences for the development of rehabilitation regimes after ACL reconstruction. The commonly held assumption that CKC exercise will protect an ACL graft may not be valid

Whilst lateral ankle sprain is often considered a benign injury it represents between 3–5% of all A&E visits in the UK. The mechanical characteristics of ankle ligaments under sprain-like conditions are scarcely reported. The lateral collateral ankle ligaments were dissected from n=6 human cadaveric specimens to produce individual bone-ligament-bone specimens. An Instron Electropuls E10000 was used to uni-axially load the ankle ligaments in tension. The ligaments were first preconditioned between 2 N and a load value corresponding to 3.5% strain for 15 cycles and then strained to failure at a rate of 100%/s. The mean ultimate failure loads and their standard deviations for the anterior talofibular (ATFL), calcaneofibular (CFL) and posterior talofibular (PTFL) ligaments are 351.4±105.6 N, 367.8±76.1 N and 263.6±156.6 N, respectively. Whilst the standard deviation values are high they align with those previously reported for ankle ligament characterisation. The large standard deviations are partly due to the inherent variability of human cadaveric tissue but could also be due to varying previous activity levels of participants or a prior unreported ankle sprain. Although the sample size is relatively small the results were stratified to identify any potential correlations of age, BMI and weight with ultimate load. A strong Pearson correlation (r=0.919) was found between BMI and ultimate load of the CFL but a larger sample size is required to confirm a link. The ligament failure modes were observed and categorised as avulsion or intra-ligamentous failure. The ATFL avulsed from the fibula in five instances and intra-ligamentous failure occurred once. The CFL avulsed from the fibula twice and failed four times through intra-ligamentous failure. Finally, the PTFL avulsed from the fibula once, avulsed from the talus once and failed through intra-ligamentous failure in four instances. The results identify the forces required to severely sprain the lateral collateral ankle ligaments and their failure modes

25–40% of unicompartmental knee replacement (UKR) revisions are performed for unexplained pain possibly secondary to elevated proximal tibial bone strain. This study investigates the effect of tibial component metal backing and polyethylene thickness on cancellous bone strain in a finite element model (FEM) of a cemented fixed bearing medial UKR, validated using previously published acoustic emission data (AE). FEMs of composite tibiae implanted with an all-polyethylene tibial component (AP) and a metal backed one (MB) were created. Polyethylene of thickness 6–10mm in 2mm increments was loaded to a medial load of 2500N. The volume of cancellous bone exposed to <−3000 (pathological overloading) and <−7000 (failure limit) minimum principal (compressive) microstrain (µ∊) and >3000 and >7000 maximum principal (tensile) microstrain was measured. Linear regression analysis showed good correlation between measured AE hits and volume of cancellous bone elements with compressive strain <−3000µ∊: correlation coefficients (R= 0.947, R2 = 0.847), standard error of the estimate (12.6 AE hits) and percentage error (12.5%) (p<0.001). AP implants displayed greater cancellous bone strains than MB implants for all strain variables at all loads. Patterns of strain differed between implants: MB concentrations at the lateral edge; AP concentrations at the keel, peg and at the region of load application. AP implants had 2.2 (10mm) to 3.2 (6mm) times the volume of cancellous bone compressively strained <−7000µ∊ than the MB implants. Altering MB polyethylene insert thickness had no effect. We advocate using caution with all-polyethylene UKR implants especially in large or active patients where loads are higher

Objectives. Deep bone and joint infections (DBJI) are directly intertwined with health, demographic change towards an elderly population, and wellbeing. The elderly human population is more prone to acquire infections, and the consequences such as pain, reduced quality of life, morbidity, absence from work and premature retirement due to disability place significant burdens on already strained healthcare systems and societal budgets. DBJIs are less responsive to systemic antibiotics because of poor vascular perfusion in necrotic bone, large bone defects and persistent biofilm-based infection. Emerging bacterial resistance poses a major threat and new innovative treatment modalities are urgently needed to curb its current trajectory. Materials and Methods. We present a new biphasic ceramic bone substitute consisting of hydroxyapatite and calcium sulphate for local antibiotic delivery in combination with bone regeneration. Gentamicin release was measured in four setups: 1) in vitro elution in Ringer’s solution; 2) local elution in patients treated for trochanteric hip fractures or uncemented hip revisions; 3) local elution in patients treated with a bone tumour resection; and 4) local elution in patients treated surgically for chronic corticomedullary osteomyelitis. Results. The release pattern in vitro was comparable with the obtained release in the patient studies. No recurrence was detected in the osteomyelitis group at latest follow-up (minimum 1.5 years). Conclusions. This new biphasic bone substitute containing antibiotics provides safe prevention of bone infections in a range of clinical situations. The in vitro test method predicts the in vivo performance and makes it a reliable tool in the development of future antibiotic-eluting bone-regenerating materials. Cite this article: M. Stravinskas, P. Horstmann, J. Ferguson, W. Hettwer, M. Nilsson, S. Tarasevicius, M. M. Petersen, M. A. McNally, L. Lidgren. Pharmacokinetics of gentamicin eluted from a regenerating bone graft substitute: In vitro and clinical release studies. Bone Joint Res 2016;5:427–435. DOI: 10.1302/2046-3758.59.BJR-2016-0108.R1

Rotator cuff repair is performed to treat shoulder pain and disability. Failure of the tendon repair site is common; one strategy to improve healing is to enforce a period of post-operative immobilisation. Immobilisation may have unintended effects on tendon healing. Tenocytes under uniaxial strain form more organised collagen and up regulate expression of proliferative genes. Vitamin C (ascorbic acid), an anti-oxidant that is a co-factor for collagen synthesis, has also been reported to enhance collagen deposition and organisation. The purpose of this study was to compare human tenocyte cultures exposed to uniaxial cyclical strain with or without slow-release ascorbic acid (ascorbyl-2 phosphate) to determine their individual and combined effects on tissue remodelling and expression of tissue repair genes. Rotator cuff tissues were collected from degenerative supraspinatus tears from eight patients. Tenocytes were incorporated into 3D type I collagen culture matrices. Cultures were divided into four groups: 1) ascorbic acid (0.6mMol/L) + strain (1%–20% uniaxial cyclic strain at 0.1 Hz), 2) ascorbic acid unstrained, 3) strain + vehicle 4) unstrained + vehicle. Samples were fixed in paraffin, stained with picrosirius red and analysed with circular polarising light. A second set of cultures were divided into three groups: 1) 0.5mM ascorbic acid, 2) 1mM ascorbic acid, 3) vehicle cultured for 24, 72, 120 and 168 hours. Cell-free collagen matrix was used as a control. Tenocyte proliferation was assessed using the water soluble tetrazolium-1 (WST1) assay and f tissue repair gene expression (TGFB1, COL1A1, FN1, COLIII, IGF2, MMP1, and MMP13), were analysed by qPCR. The data were analysed using a Split model ANOVA with contrast and bonferroni correction and a one-way ANOVAs and Tukey's test (p<0.05 was significant). Our results indicated that unstrained cultures with or without exposure to slow release ascorbic acid exhibited greater picrosirius red birifringency and an increase in collagen fiber deposition in a longitudinal orientation compared to strained tenocytes. We found that slow release ascorbic acid promoted significant dose and culture-time dependent increases in tenocyte proliferation (p<0.05) but no obvious enhancement in collagen deposition was evident over cultures without ascorbic acid supplementation. Based on these data, applying strain to tenocytes may result in less organised formation of collagen fibers, suggestive of fibrotic tissue, rather than tendon remodelling. This may indicate that a short period of immobilisation post-rotator cuff repair is beneficial for the healing of tendons. Exposure to slow release ascorbic acid enhanced tenocyte proliferation, suggesting that supplementation with Vitamin C may improve tendon repair post-injury or repair. Future studies will assess levels of tissue repair-associated proteins as well as comparing traumatic and degenerative rotator cuff tears to healthy uninjured rotator cuff tissue

Aims

This study aimed to investigate the risk of postoperative complications in COVID-19-positive patients undergoing common orthopaedic procedures.

Introduction. Differing levels of tendon retraction are found in full-thickness rotator cuff tears. The pathophysiology of tendon degeneration and retraction is unclear. Neoangiogenesis in tendon parenchyma indicates degeneration. Hypoxia inducible factor 1(HIF) and vascular endothelial growth factor (VEGF) are important inducers of neoangiogenesis. Rotator cuff tendons rupture leads to fatty muscle infiltration (FI) and muscle atrophy (MA). The aim of this study is to clarify the relationship between HIF and VEGF expression, neoangiogenesis, FI, and MA in tendon retraction found in full-thickness rotator cuff tears. Methods. Rotator cuff tendon samples of 33 patients with full-thickness medium-sized rotator cuff tears were harvested during reconstructive surgery. The samples were dehydrated and paraffin embedded. For immunohistological determination of VEGF and HIF expression, sample slices were strained with VEGF and HIF antibody dilution. Vessel density and vessel size were determined after Masson-Goldner staining of sample slices. The extent of tendon retraction was determined intraoperatively according to Patte's classification. Patients were assigned to 4 categories based upon Patte tendon retraction grade, including one control group. FI and MA were measured on standardized preoperative shoulder MRI. Results. HIF and VEGF expression, FI, and MA were significantly higher in torn cuff samples compared with healthy tissue (p<0.05). HIF and VEGF expression, and vessel density significantly increased with extent of tendon retraction (p<0.04). A correlation between HIF/VEGF expression and FI and MA could be found (p<0.04). There was no significant correlation between HIF/VEGF expression and neovascularity (p>0.05). Conclusion. Tendon retraction in full-thickness medium-sized rotator cuff tears is characterized by neovascularity, increased VEGF/HIF expression, FI, and MA. VEGF expression and neovascularity may be effective monitoring tools to assess tendon degeneration

Summary Statement. Tendon micromechanics were investigated using 2 methods. When collagen deformation was measured directly, higher levels of inter-fibre sliding were observed than when tenocyte nuclei were tracked. This suggests that under high strain tenocytes become unattached from the collagen fibres. Introduction. Fibre extension and inter-fibre sliding have both been reported during tendon extension, but fibre sliding is believed to be the predominant mechanism in normal healthy tendon function. Fatigue damage is known to result in structural changes and reduced mechanical properties, but its influence on micromechanics is unknown. This work aimed:. 1. To investigate the effect of fatigue loading on bovine digital extensor fascicle micromechanics, comparing fibre extension and fibre sliding, hypothesising that the relative importance of these may change due to fatigue damage. 2. To compare two techniques for characterising micromechanics: bleaching of a grid to directly measure collagen deformation, and using the cells as fiducial markers of fibre movement. Methods. The tensional regions of healthy digital extensor tendons were removed within 24 hours of slaughter and frozen. Tendons were defrosted, hydrated and fascicles dissected and loaded into custom-designed chambers allowing the mechanical loading of fully hydrated tendon fascicles. Fascicles were loaded for 0, 300 or 900 cycles under creep conditions at a frequency of 1Hz and to a maximum applied stress of 25% of the mean UTS of the fascicles. Fascicles were stained using either Acridine Orange to stain the cell nuclei or DTAF solution to stain the collagen. After DTAF staining, a grid consisting of 4 squares of side 50 μm was photo-bleached using the FRAP system on a Leica TCS SP2 confocal scanning microscope. To investigate micromechanics, fascicles were secured in a uniaxial rig and strained in 2% increments to 10% total strain at a rate of 1%s. −1. Imaging was carried out at each increment and local strains calculated from grid deformation or nuclei movement. Results. No significant changes in micromechanics were observed with increasing numbers of creep cycles, as measured with either technique. This was despite quite significant matrix damage being observed particularly after 900 cycles. When using the grid deformation measure of strains, a continual increase in fibre sliding was seen above 4% applied strain, correlating with the levelling off of intra-fibre strains. This same move towards dominant fibre sliding was not observed with techniques using the nuclei as fiducial markers. Using the nuclei as markers consistently reported significantly lower levels of fibre sliding than those measured from grid deformation at strains of 6% and above, under all creep conditions. Discussion/Conclusion. The apparent absence of any effect of creep on the measured microstructural deformation may be a result of the localised nature of the measurement techniques. At sites where matrix structure broke down both the tracking of nuclei and the photo-bleaching of the grid proved problematic and it is these regions where the greatest degree of deformation would perhaps be expected, with remaining areas of the tissue stress-deprived. The smaller levels of fibre shear reported when measured through nuclei tracking suggests that the tenocytes may not be well adhered to the fibres and may be protected from some of the matrix deformation in response to loading