Introduction. Tendon ruptures are a common injury and often require surgical intervention to heal. A refixation is commonly performed with high-strength suture material. However, slipping of the thread is unavoidable even at 7 knots potentially leading to reduced compression of the sutured tendon at its footprint. This study aimed to evaluate the biomechanical properties and effectiveness of a novel dynamic high-strength suture, featuring self-tightening properties. Method. Distal biceps tendon rupture tenotomies and subsequent repairs were performed in sixteen paired human forearms using either conventional or the novel dynamic high-strength sutures in a paired design. Each tendon repair utilized an intramedullary biceps button for radial fixation. Biomechanical testing aimed to simulate an aggressive postoperative rehabilitation protocol stressing the repaired constructs. For that purpose, each specimen underwent in nine sequential days a daily mobilization over 300 cycles under 0-50 N loading, followed by a final destructive test. Result. After the ninth day of cyclic loading, specimens treated with the dynamic suture exhibited significantly less tendon elongation at both proximal and distal measurement sites (-0.569±2.734 mm and 0.681±1.871 mm) compared to the conventional suture group (4.506±2.169 mm and 3.575±1.716 mm), p=0.003/p<0.002. Gap formation at the bone-tendon interface was significantly lower following suturing using dynamic suture (2.0±1.6 mm) compared to conventional suture (4.5±2.2 mm), p=0.04. The maximum load at failure was similar in both treatment groups (dynamic suture: 374± 159 N; conventional suture: 379± 154 N), p=0.925. The predominant failure mechanism was breakout of the button from the bone (dynamic suture: 5/8; conventional suture: 6/8), followed by suture rupturing, suture unraveling and tendon cut-through. Conclusion. From a biomechanical perspective, the novel dynamic high-strength suture demonstrated higher resistance against gap formation at the bone tendon interface compared to the conventional suture, which may contribute to better postoperative tendon integrity and potentially quicker functional recovery in the clinical setting

Dislocation after total hip replacement (THR) is a devastating complication. Risk factors include patient and surgical factors. Mitigation of this complication has proven partially effective. This study investigated a new innovating technique to decrease this problem using rare earth magnets. Computer simulations with design and magnetic finite element analysis software were used to analyze and quantitate the forces around hip implants with embedded magnets into the components during hip range of motion. N52 Neodymium-Iron-Boron rare earth magnets were sized to fit within the existing acetabular shells and the taper of a hip system. Additionally, magnets placed within the existing screw holes were studied. A 50mm titanium acetabular shell and a 36mm ceramic liner utilizing a taper sleeve adapter were modeled which allowed for the use of a 12mm × 5mm magnet placed in the center hole, an 18mm × 15mm magnet within the femoral head, and 10mm × 5mm magnets in the screw holes. Biomechanical testing was also performed using in-vitro bone and implant models to determine retention forces through a range of hip motion. The novel system incorporating magnets generated retentive forces between the acetabular cup and femoral head of between 10 to 20 N through a range of hip motion. Retentive forces were stronger at the extreme position hip range of motion when additional magnets were placed in the acetabular screw holes. Greater retentive forces can be obtained with specially designed femoral head bores and acetabular shells specifically designed to incorporate larger magnets. Mechanical testing validated the loads obtained and demonstrated the feasibility of the magnet system to provide joint stability and prevent dislocations. Rare earth magnets provide exceptional attractive strength and can be used to impart stability and prevent dislocation in THR without the complications and limitations of conventional methods

Although bone morphogenetic protein 2 (BMP-2) has been FDA-approved for spinal fusion for decades, its disadvantages of promoting osteoclast-based bone resorption and suboptimal carrier (absorbable collagen sponge) leading to premature release of the protein limit its clinical applications. Our recent study showed an excellent effect on bone regeneration when BMP-2 and zoledronic acid (ZA) were co-delivered based on a calcium sulphate/hydroxyapatite (CaS/HA) scaffold in a rat critical-size femoral defect model. Therefore, the aim of this study was to evaluate whether local application of BMP-2 and ZA released from a CaS/HA scaffold is favorable for spinal fusion. We hypothesized that CaS/HA mediated controlled co-delivery of rhBMP-2 and ZA could show an improved effect in spinal fusion over BMP-2 alone. 120, 8-week-old male Wistar rats (protocol no. 25-5131/474/38) were randomly divided into six groups in this study (CaS/HA, CaS/HA + BMP-2, CaS/HA + systemic ZA, CaS/HA + local ZA, CaS/HA + BMP-2 + systemic ZA, CaS/HA + BMP-2 + local ZA). A posterolateral spinal fusion at L4 to L5 was performed bilaterally by implanting group-dependent scaffolds. At 3 weeks and 6 weeks, 10 animals per group were euthanized for µCT, histological staining, or mechanical testing. µCT and histological results showed that the CaS/HA + BMP-2 + local ZA group significantly promoted bone regeneration than other treated groups. Biomechanical testing showed breaking force in CaS/HA + BMP + local ZA group was significantly higher than other groups at 6 weeks. In conclusion, the CaS/HA-based biomaterial functionalized with bioactive molecules rhBMP-2 and ZA enhanced bone formation and concomitant spinal fusion outcome. Acknowledgements: Many thanks to Ulrike Heide, Anna-Maria Placht (assistance with surgeries) as well as Suzanne Manthey & Annett Wenke (histology)

Aims. Several artificial bone grafts have been developed but fail to achieve anticipated osteogenesis due to their insufficient neovascularization capacity and periosteum support. This study aimed to develop a vascularized bone-periosteum construct (VBPC) to provide better angiogenesis and osteogenesis for bone regeneration. Methods. A total of 24 male New Zealand white rabbits were divided into four groups according to the experimental materials. Allogenic adipose-derived mesenchymal stem cells (AMSCs) were cultured and seeded evenly in the collagen/chitosan sheet to form cell sheet as periosteum. Simultaneously, allogenic AMSCs were seeded onto alginate beads and were cultured to differentiate to endothelial-like cells to form vascularized bone construct (VBC). The cell sheet was wrapped onto VBC to create a vascularized bone-periosteum construct (VBPC). Four different experimental materials – acellular construct, VBC, non-vascularized bone-periosteum construct, and VBPC – were then implanted in bilateral L4-L5 intertransverse space. At 12 weeks post-surgery, the bone-forming capacities were determined by CT, biomechanical testing, histology, and immunohistochemistry staining analyses. Results. At 12 weeks, the VBPC group significantly increased new bone formation volume compared with the other groups. Biomechanical testing demonstrated higher torque strength in the VBPC group. Notably, the haematoxylin and eosin, Masson’s trichrome, and immunohistochemistry-stained histological results revealed that VBPC promoted neovascularization and new bone formation in the spine fusion areas. Conclusion. The tissue-engineered VBPC showed great capability in promoting angiogenesis and osteogenesis in vivo. It may provide a novel approach to create a superior blood supply and nutritional environment to overcome the deficits of current artificial bone graft substitutes. Cite this article: Bone Joint Res 2023;12(12):722–733

The December 2023 Shoulder & Elbow Roundup³⁶⁰ looks at: Clavicle fractures: is the evidence changing practice?; Humeral shaft fractures, and another meta-analysis…let’s wait for the trials now!; Hemiarthroplasty or total elbow arthroplasty for distal humeral fractures…what does the registry say?; What to do with a first-time shoulder dislocation?; Deprivation indices and minimal clinically important difference for patient-reported outcomes after arthroscopic rotator cuff repair; Prospective randomized clinical trial of arthroscopic repair versus debridement for partial subscapularis tears; Long-term follow-up following closed reduction and early movement for simple dislocation of the elbow; Sternoclavicular joint reconstruction for traumatic acute and chronic anterior and posterior instability.

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This study aimed to establish the optimal fixation methods for calcaneal tuberosity avulsion fractures with different fragment thicknesses in a porcine model.

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Mechanical stimulation is a key factor in the development and healing of tendon-bone insertion. Treadmill training is an important rehabilitation treatment. This study aims to investigate the benefits of treadmill training initiated on postoperative day 7 for tendon-bone insertion healing.

Integrin α2β1 is one of the major transmembrane receptors for fibrillary collagen. In native bone we could show that the absence of this protein led to a protective effect against age-related osteoporosis. The objective of this study was to elucidate the effects of integrin α2β1 deficiency on fracture repair and its underlying mechanisms. Standardised femoral fractures were stabilised by an intramedullary nail in 12 week old female C57Bl/6J mice (wild type and integrin α2. -/-. ). After 7, 14 and 28 days mice were sacrificed. Dissected femura were subjected to µCT and histological analyses. To evaluate the biomechanical properties, 28-day-healed femura were tested in a torsional testing device. Masson goldner staining, Alizarin blue, IHC and IF staining were performed on paraffin slices. Blood serum of the animals were measured by ELISA for BMP-2. Primary osteoblasts were analysed by in/on-cell western technology and qRT-PCR. Integrin α2β1 deficient animals showed earlier transition from cartilaginous callus to mineralized callus during fracture repair. The shift from chondrocytes over hypertrophic chondrocytes to bone-forming osteoblasts was accelerated. Collagen production was increased in mutant fracture callus. Serum levels of BMP-2 were increased in healing KO mice. Isolated integrin deficient osteoblast presented an earlier expression and production of active BMP-2 during the differentiation, which led to earlier mineralisation. Biomechanical testing showed no differences between wild-type and mutant bones. Knockout of integrin α2β1 leads to a beneficial outcome for fracture repair. Callus maturation is accelerated, leading to faster recovery, accompanied by an increased generation of extra-cellular matrix material. Biomechanical properties are not diminished by this accelerated healing. The underlying mechanism is driven by an earlier availability of BMP-2, one main effectors for bone development. Local inhibition of integrin α2β1 is therefore a promising target to accelerate fracture repair, especially in patients with retarded healing

Recently, a new suture was designed to minimize laxity in order to preserve consistent tissue approximation while improving footprint compression after tendon repair. The aims of this study were: (1) to compare the biomechanical competence of two different high strength sutures in terms of slippage and failure load, (2) to investigate the influence of both knots number and different media (air, saline and fat) on the holding capacity of the knots. Alternating surgical knots of two different high-strength sutures (group1: FibreWire; group2: DynaCord; n = 105) were tied on two roller bearings with 50N tightening force. Biomechanical testing was performed in each medium applying ramped monotonic tension to failure defined in terms of either knot slippage or suture rupture. For each group and medium, seven specimens with either 3, 4, 5, 6, or 7 knots each were tested, evaluating their knot slippage and ultimate load to failure. The minimum number of knots preventing slippage failure and thus resulting in suture rupture was determined in each group and medium, and taken as a criterium for better performance when comparing the groups. In each group and medium failure occurred via suture rupture in all specimens for the following minimum knot numbers: group1: air – 7, saline – 7, fat – 7; group2: air – 6; saline – 4; fat – 5. The direct comparison between the groups when using 7 knots demonstrated significantly larger slippage in group1 (6.5 ± 2.2 mm) versus group2 (3.5 ± 0.4 mm) in saline (p < 0.01) but not in the other media (p ≥0.52). Ultimate load was comparable between the two groups for all three media (p ≥ 0.06). The lower number of required knots providing sufficient repair stability, smaller slippage levels and identical suture strength, combined with the known laxity alleviation effect demonstrate advantages of DynaCord versus FibreWire

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It has been established that mechanical stimulation benefits tendon-bone (T-B) healing, and macrophage phenotype can be regulated by mechanical cues; moreover, the interaction between macrophages and mesenchymal stem cells (MSCs) plays a fundamental role in tissue repair. This study aimed to investigate the role of macrophage-mediated MSC chondrogenesis in load-induced T-B healing in depth.

Restoration a joint's articular surface following degenerative or traumatic pathology to the osteochondral unit pose a significant challenge. Recent advances have shown the utility of collagen-based scaffolds in the regeneration of osteochondral tissue. To provide these collagen scaffolds with the appropriate superstructure novel techniques in 3D printing have been investigated. This study investigates the use of polyɛ-caprolactone (PCL) collagen scaffolds in a porcine cadaveric model to establish the stability of the biomaterial once implanted. This study was performed in a porcine cadaveric knee model. 8mm defects were created in the medial femoral trochlea and repaired with a PCL collagen scaffold. Scaffolds were secured by one of three designs; Press Fit (PF), Press Fit with Rings (PFR), Press Fit with Fibrin Glue (PFFG). Mobilisation was simulated by mounting the pig legs on a continuous passive motion (CPM) machine for either 50 or 500 cycles. Biomechanical tensile testing was performed to examine the force required to displace the scaffold. 18 legs were used (6 PF, 6 PFR, 6 PFFG). Fixation remained intact in 17 of the cohort (94%). None of the PF or PFFG scaffolds displaced after CPM cycling. Mean peak forces required to displace the scaffold were highest in the PFFG group (3.173 Newtons, Standard deviation = 1.392N). The lowest peak forces were observed in the PFR group (0.871N, SD = 0.412N), while mean peak force observed in the PF group was 2.436N (SD = 0.768). There was a significant difference between PFFG and PFR (p = 0.005). There was no statistical significance in the relationship between the other groups. PCL reinforcement of collagen scaffolds provide an innovative solution for improving stiffness of the construct, allowing easier handling for the surgeon. Increasing the stiffness of the scaffold also allows press fit solutions for reliable fixation. Press fit PCL collagen scaffolds with and without fibrin glue provide dependable stability. Tensile testing provides an objective analysis of scaffold fixation. Further investigation of PCL collagen scaffolds in a live animal model to establish quality of osteochondral tissue regeneration are required

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As has been shown in larger animal models, knee immobilization can lead to arthrofibrotic phenotypes. Our study included 168 C57BL/6J female mice, with 24 serving as controls, and 144 undergoing a knee procedure to induce a contracture without osteoarthritis (OA).

The Adams-Berger reconstruction is an effective technique for treating distal radioulnar joint (DRUJ) instability. Graft preparation techniques vary amongst surgeons with insufficient evidence to support one technique over another. Our study evaluated the biomechanical properties of four graft preparation techniques. Extensor tendons were harvested from fresh frozen porcine trotters obtained from a local butcher shop and prepared in one of three configurations (n=5 per group): tendon only; tendon prepared with non-locking, running suture (2-0 FiberLoop, Arthrex, Naples, FL) spaced at 6 mm intervals; and tendon prepared with suture spaced at 12 mm intervals. A fourth configuration of suture alone was also tested. Tendons were allocated in a manner to ensure comparable average diameters amongst groups. Biomechanical testing occurred using custom jigs simulating radial and ulnar tunnels attached to a Bose Electroforce 3510 mechanical testing machine (TA Instruments). After being woven through the jigs, all tendons were sutured end-to-end with 2-0 PROLENE suture (Ethicon). Tendons then underwent a staircase cyclic loading protocol (5-25 Newtons [N] at 1 hertz [Hz] for 1000 cycles, then 5-50 N at 1 Hz for 1000 cycles, then 5-75 N at 1 Hz for 1000 cycles) until graft failure; if samples did not fail during the protocol, they were then loaded to failure. Samples were visually inspected for mode of failure after the protocol. A one-way analysis of variance was used to compare average tendon diameter; post-hac Tuhey tests were used to compare elongation and elongation rate. Survival to cyclic loading was analyzed using Kaplan-Meier survival curves with log rank. Statistical significance was set at a = 0.05. The average tendon diameter of each group was not statistically different [4.17 mm (tendon only), 4.33 mm (FiberLoop spaced 6 mm), and 4.30 mm (FiberLoop spaced 12 mm)]. The average survival of tendon augmented with FiberLoop was significantly higher than tendon only, and all groups had significantly improved survival compared to suture only. There was no difference in survival between FiberLoop spaced 6 mm and 12 mm. Elongation was significantly lower with suture compared to tendon augmented with FiberLoop spaced 6 mm. Elongation rate was significantly lower with suture compared to all groups. Modes of failure included rupture of the tendon, suture, or both at the simulated bone and suture and/or tendon interface, and elongation of the entire construct without rupture. In this biomechanical study, augmentation of porcine tendons with FiberLoop suture spaced at either 6 or 12 mm for DRUJ reconstruction significantly increased survival to a staircase cyclic loading protocol, as suture material was significantly stiffer than any of the tendon graft configurations

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A number of anti-retroviral therapies (ART) have been implicated in potentially contributing to HIV-associated bone disease. The aim of this study was to evaluate the effect of combination ART on the fracture healing process.

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To verify whether secretory leucocyte protease inhibitor (SLPI) can promote early tendon-to-bone healing after anterior cruciate ligament (ACL) reconstruction.

Abstract. Introduction. All-tissue quadriceps tendon (QT) is becoming an increasingly popular alternative to hamstrings tendon (HT) and bone-tendon-bone (BTB) autograft for anterior cruciate ligament (ACL) reconstruction. The relatively short graft length however dictates that one, or both, ends rely on suture fixation. The strength of this construct is therefore extremely important. This study evaluates whether the use of a novel fixation technique can improve the tensile properties of the construct compared to a Krackow suture, and a looped tendon (suture free) gold standard. Methods. Eighteen porcine flexor tendons were tested, across three groups; suture-tape Krackow, looped tendon, and the novel ‘strain suture’. Biomechanical testing simulated the different stages of ACL graft preparation and loading (60N preload for 10 minutes, 10 cycles from 10N to 75N, and 1000 cycles from 100N to 400N). Elongation and load to failure were recorded, and stiffness calculated for each construct. Results. The mean elongation was significantly improved for the strain suture compared to the suture tape Krackow for preload, 10 cycle and 1000 cycle testing protocols respectively (1.36mm vs 4.93mm, p<001; 0.60mm vs 2.72mm, p<0.001; 2.95mm vs 29.08mm, p<0.001). Compared with the looped tendon, the strain suture demonstrated similar results for preload and 10 cycle elongation, but greater elongation during the 1000 cycle stage. Stiffness of the latter two constructs was similar. Conclusions. Augmentation of the suture fixation using this novel technique provides a construct that is significantly superior to currently practised suture techniques, and similar in elongation and stiffness to a looped graft

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Alcoholism is a well-known detrimental factor in fracture healing. However, the underlying mechanism of alcohol-inhibited fracture healing remains poorly understood.

Cemented total hip replacement (THR) provides excellent outcomes and is cost-effective. Polished taper-slip (PTS) stems demonstrate successful results and have overtaken traditional composite-beam (CB) stems. Recent reports indicate they are associated with a higher risk of postoperative periprosthetic femoral fracture (PFF) compared to CB stems. This study evaluates risk factors influencing fracture characteristics around PTS and CB cemented stems. Data were collected for 584 PFF patients admitted to eight UK centres from 25/05/2006-01/03/2020. Radiographs were assessed for Unified Classification System (UCS) grade and Arbeitsgemeinschaft für Osteosynthesefragen/Orthopaedic Trauma Association (AO/OTA) type. Statistical comparisons investigated relationships by age, gender, and stem fixation philosophy (PTS versus CB). The effect of multiple variables was estimated using multinomial logistic regression to estimate odds ratios (OR) with 95% confidence intervals (CI). Median (IQR) age was 79.1 (72.0–86.0) years, 312 (53.6%) patients were female, and 495 (85.1%) stems were PTS. The commonest UCS grade was type B1 (278, 47.6%). The commonest AO/OTA type was spiral (352, 60.3%). Metaphyseal-split fractures occurred only with PTS stems with an incidence of 10.1%. Male gender was associated with a five-fold reduction in odds of a type C fracture (OR 0.22, 95% CI 0.12 to 0.41, p<0.001) compared to a type B fracture. CB stems were associated with significantly increased odds of transverse fracture (OR 9.51, 95% CI 3.72 to 24.34, p <0.001) and wedge fracture (OR 3.72, 95% CI 1.16 to 11.95, p <0.05) compared to PTS stems. This is the largest study investigating PFF characteristics around cemented stems. The commonest fracture types are B1 and spiral fractures. PTS stems are exclusively associated with metaphyseal-split fractures, but their incidence is low. Males have lower odds of UCS grade C fractures compared to females. CB stems had higher odds of bending type fractures (transverse and wedge) compared to PTS stems. Biomechanical testing is needed for validation and investigation of modifiable factors which may reduce the risk of unstable fracture patterns requiring complex revision surgery over internal fixation

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Rotator cuff (RC) tears are common musculoskeletal injuries which often require surgical intervention. Noninvasive pulsed electromagnetic field (PEMF) devices have been approved for treatment of long-bone fracture nonunions and as an adjunct to lumbar and cervical spine fusion surgery. This study aimed to assess the effect of continuous PEMF on postoperative RC healing in a rat RC repair model.

Patients undergoing revision surgery of a primary total hip arthroplasty often exhibit bone loss and poor bone quality, which make achieving stable fixation and osseointegration challenging. Implant components coated in porous metals are used clinically to improve mechanical stability and encourage bone in-growth. We compared ultra-porous titanium coatings, known commercially as Gription and Porocoat, in an intra-articular model by press-fitting coated cylindrical implants into ovine femoral condyles and evaluating bone in-growth and fixation strength 4, 8 and 16 weeks post-operatively. Bilateral surgery using a mini-arthrotomy approach was performed on twenty-four Dorset-Rideau Arcott rams (3.4 ± 0.8 years old, 84.8 ± 9.3 kg) with Institutional Animal Care Committee approval in accordance with the Canadian Council on Animal Care. Cylindrical implants, 6.2 mm in diameter by 10 mm in length with surface radius of curvature of 35 mm, were composed of a titanium substrate coated in either Porocoat or Gription and press-fit into 6 mm diameter recipient holes in the weight-bearing regions of the medial (MFC) and lateral (LFC) femoral condyles. Each sheep received 4 implants; two Gription in one stifle (knee) and two Porocoat in the contralateral joint. Biomechanical push-out tests (Instron ElectroPuls E10000) were performed on LFCs, where implants were pushed out relative to the condyle at a rate of 2 mm/min. Force and displacement data were used to calculate force and displacement at failure, stiffness, energy, stress, strain, elastic modulus, and toughness. MFCs were fixed in 70% ethanol, processed undecalcified, and polished sections, approximately 70 µm thick (Exakt Micro Grinding system) were carbon-coated. Backscattered electron images were collected on a scanning electron microscope (Hitachi SU3500) at 5 kV and working distance of 5 mm. Bone in-growth within the porous coating was quantified using software (ImageJ). Statistical comparisons were made using a two-way ANOVA and Fisher's LSD post-hoc test (Statistica v.8). Biomechanical evaluation of the bone-implant interface revealed that by 16 weeks, Gription-coated implants exhibited higher force (2455±1362 N vs. 1002±1466 N, p=0.046) and stress (12.60±6.99 MPa vs. 5.14±7.53 MPa, p=0.046) at failure, and trended towards higher stiffness (11510±7645 N/mm vs. 5010±8374 N/mm, p=.061) and modulus of elasticity (591±392 MPa vs. 256±431 MPa, p=0.61). Similarly, by 16 weeks, bone in-growth in Gription-coated implants was approximately double that measured in Porocoat (6.73±3.86 % vs. 3.22±1.52 %, p=0.045). No statistically significant differences were detected at either 4 nor 8 weeks, however, qualitative observations of the exposed bone-implant interface, made following push-out testing, showed more bony material consistently adhered to Gription compared to Porocoat at all three time points. High variability is attributed to implant placement, resulting from the small visual window afforded during surgery, unique curvatures of the condyles, and presence of the extensor digitorum longus tendon which limited access to the LFC. Ultra-porous titanium coatings, know commercially as Gription and Porocoat, were compared for the first time in a challenging intra-articular ovine model. Gription provided superior fixation strength and bone in-growth, suggesting it may be beneficial in hip replacement surgeries where bone stock quality and quantity may be compromised