Aims. This study aimed to demonstrate the promoting effect of elastic fixation on fracture, and further explore its mechanism at the gene and protein expression levels. Methods. A closed tibial fracture model was established using 12 male Japanese white rabbits, and divided into elastic and stiff fixation groups based on different fixation methods. Two weeks after the operation, a radiograph and pathological examination of callus tissue were used to evaluate fracture healing. Then, the differentially expressed proteins (DEPs) were examined in the callus using proteomics. Finally, in vitro cell experiments were conducted to investigate hub proteins involved in this process. Results. Mean callus volume was larger in the elastic fixation group (1,755 mm. 3. (standard error of the mean (SEM) 297)) than in the stiff fixation group (258 mm. 3. (SEM 65)). Pathological observation found that the expression levels of osterix (OSX), collagen, type I, alpha 1 (COL1α1), and alkaline phosphatase (ALP) in the callus of the elastic fixation group were higher than those of the stiff fixation group. The protein sequence of the callus revealed 199 DEPs, 124 of which were highly expressed in the elastic fixation group. In the in vitro study, it was observed that a stress of 200 g led to upregulation of thrombospondin 1 (THBS1) and osteoglycin (OGN) expression in bone marrow mesenchymal stem cells (BMSCs). Additionally, these genes were found to be upregulated during the osteogenic differentiation process of the BMSCs. Conclusion. Elastic fixation can promote fracture healing and osteoblast differentiation in callus, and the ability of elastic fixation to promote osteogenic differentiation of BMSCs may be achieved by upregulating genes such as THBS1 and OGN. Cite this article: Bone Joint Res 2024;13(10):559–572

The August 2013 Children’s orthopaedics Roundup³⁶⁰ looks at: a multilevel approach to equinus gait; whether screening leads to needless intervention; salvage of subcapital slipped epiphysis; growing prostheses for children’s oncology; flexible nailing revisited; ultrasound and the pink pulseless hand; and slipping forearm fractures.

Introduction: The traditional methods for the treatment of femoral shaft fractures of children consists of closed reduction and either spica casting or fixation by external fixator. There are also reports on the treatment of such injuries by open reduction and internal fixation by plate. In the last years the method of minimal invasive fixation of such fractures with elastic nails became popular in children over 6–7 year old. The purpose of this paper is to present our experience with elastic nail fixation of femoral shaft fractures of children. Material and Methods: We present a series of 43 children aged 3–13 year old, mean age: 6.5y, follow-up 2–4 years, mean 2.5 years) with shaft fractures of the femur. 12 children were under 5 year of age. Seven of them were poly-trauma patients. There were no open fractures. Each patient was treated by closed reduction and percutaneous nail insertion under C-arm imaging intensifier control. Fixation was accomplished by a knee immobilizer alone. Early non-weight-bearing mobilization was encouraged until appearance of callus formation. Subsequently, weight-bearing was encouraged. Results: The results of all cases were excellent. All fractures were united within 7–14 weeks, with an average of 9 weeks. There were not any cases of femoral fractures through nail insertion. There was no decrease in the range of hip and knee motion. None of the patients had complications such as infection, malalignment or neurovascular injury. There was two cases of bursitis around the tip of the nail in the supracondylar region, which was resolved by early pin removal. Removal of the pins was done 6–9 months following operations. Conclusions: Closed reduction and minimal invasive fixation of femoral shaft fractures by use of Nancy Nails is safe, simple and useful in children with femoral shaft fractures, even in young children under the age of 5 years, and especially in cases of poly-trauma. This minimally invasive procedure allows for early mobilization with no loss of range of motion or associated complications

We report early major complications encountered following TEN fixation of femoral fractures in children.

A case series of four children aged 8– 16 years who had primary TEN fixation of isolated femoral diaphyseal fractures.

Three of the four patients had major complications. These were: significant knee stiffness requiring manipulation, haemarthrosis requiring washout and nail removal, loss of position and refracture. Two required revision to locked intramedullary nails without early complication.

In the skeletally immature child TEN fixation of femoral fractures has a significant major complication rate. This needs to be recognised when comparing TEN fixation with other treatment options.

Methods of treatment of femoral fractures still remain controversial in adolescent age when the patients are too young for adult-type stabilization. This study examines the possibilities for improving the mechanical parameters of the bone-nail interface in flexible intramedullary nailing.

Mathematical models, which simulate different fractures, have been created by using the finite elements method. The stabilizing construction with two 4,00 mm Ender nails was performed in two versions:

standard divergent “C” configuration (3 points of pressure);

Each version has been tested towards the deforming forces – bending in frontal and sagital plane; torsion and axial loading. Strength coefficient of the nails has been calculated as well as the stiffness of the configuration. The comparative analysis of the results found out that under the angular and torsional forces the mechanical parameters of the two types of configurations are equivalent. However, under axial loading, the divergent “S” configuration shows definitely better mechanical characteristics. The strength coefficient is 30% higher and the stiffness of the configuration is twice as strong. The specific intramedullary cohesion enables more considerable resistance towards the transverse displacement in telescoping of the fragments.

Proceeding from the presented data, it could be considered that the divergent “S” configuration creates much more sufficient length control. Its implementation in axial unstable femoral fractures could enable an earlier mobilization, respectively – an earlier weight-bearing loading.

Introduction: It has been proposed that tunnel widening in ACL reconstructions is due to excessive graft tunnel motion secondary to elastic fixation. Aim: To determine whether techniques which fix the graft closer to the joint (interference screws), eliminate the bungy cord and are stiffer will decrease tunnel widening. The clinical significance of tunnel widening is examined. Method: Two hundred and fifty nine patients were evaluated prospectively. Four fixation methods were evaluated. Sixty-nine were reconstructed using Endobuttons and staples (elastic fixation). Forty-eight were subjects reconstructed with a bone mulch screw and staples, 55 patients were reconstructed with metal interference screws and 87 with bioabsorbable interference screws. Patients underwent a clinical examination, IKDC, Cincinnati knee score and KT-1000 testing one year post-operatively. These factors were correlated with tunnel widening. Tunnel widening was determined using magnification adjusted AP and lateral radiographs using Scion Image software. Results: Tunnel widening occurred with all the fixation methods. Mean tunnel area increased 122% for the Bioscrew, 89% for the metal interference screw, 76% for the bone mulch screw and 36% for the Endobutton (ANOVA p=< 0.0001). Tunnel widening did not correlate with increased laxity, poor IKDC or Cincinnati knee scores. Conclusions: Tunnel widening occurred with both elastic and rigid fixation methods. Tunnel widening could not be avoided by fixing the graft closer to the joint or eliminating the ‘bungy cord’. Graft tunnel motion was not the sole cause of tunnel widening in ACL reconstruction. Tunnel widening did not correlate with poor outcome in the short term

The purpose of our study was to compare the mechanical nature of nails with different cross-sections in order to optimise the elasticity-stability ratio. There is no doubt that elastic intramedullary osteosynthesis is a successful choice for treating femoral shaft fractures in children. However, misalignment is a potential problem connected with stability of the fixation.

The mechanics of two types of nails with the same type of surface, but with different kind of cross sections – a circle (Ender) and an ellipse – was examined using the “finite elements” method.

The standard configuration of the two nails was put under four kinds of deforming forces: bending in the frontal plane and the sagital plane, torsion, and axial compression. Strength coefficient and stiffness were calculated in each particular situation.

In respect to angular stability (frontal plane) and axial compression, the mechanical characteristics of the two types of nails are similar. The stability of the elliptical nail is higher in bending in the sagital plane and in torsion. The elliptical implant has better intramedullary cohesion because the large half-axis is perpendicular to the sagital plane.

Nails with an elliptical cross section provide the opportunity for redistribution of stiffness. As a result, better mechanical properties are achieved. The elliptical cross section assures better intramedullary cohesion.