Aims

The ulna is an extremely rare location for primary bone tumours of the elbow in paediatrics. Although several reconstruction options are available, the optimal reconstruction method is still unknown due to the rarity of proximal ulna tumours. In this study, we report the outcomes of osteoarticular ulna allograft for the reconstruction of proximal ulna tumours.

Despite its intrinsic ability to regenerate form and function after injury, bone tissue can be challenged by a multitude of pathological conditions. While innovative approaches have helped to unravel the cascades of bone healing, this knowledge has so far not improved the clinical outcomes of bone defect treatment. Recent findings have allowed us to gain in-depth knowledge about the physiological conditions and biological principles of bone regeneration. Now it is time to transfer the lessons learned from bone healing to the challenging scenarios in defects and employ innovative technologies to enable biomaterial-based strategies for bone defect healing. This review aims to provide an overview on endogenous cascades of bone material formation and how these are transferred to new perspectives in biomaterial-driven approaches in bone regeneration.

Cite this article: T. Winkler, F. A. Sass, G. N. Duda, K. Schmidt-Bleek. A review of biomaterials in bone defect healing, remaining shortcomings and future opportunities for bone tissue engineering: The unsolved challenge. Bone Joint Res 2018;7:232–243. DOI: 10.1302/2046-3758.73.BJR-2017-0270.R1.

Elastic stable intramedullary nailing (ESIN) is generally acknowledged to be the treatment of choice for displaced diaphyseal femoral fractures in children over the age of three years, although complication rates of up to 50% are described. Pre-bending the nails is recommended, but there are no published data to support this. Using synthetic bones and a standardised simulated fracture, we performed biomechanical testing to determine the influence on the stability of the fracture of pre-bending the nails before implantation. Standard ESIN was performed on 24 synthetic femoral models with a spiral fracture. In eight cases the nails were inserted without any pre-bending, in a further eight cases they were pre-bent to 30° and in the last group of eight cases they were pre-bent to 60°. Mechanical testing revealed that pre-bending to 60° produced a significant increase in the stiffness or stability of the fracture. Pre-bending to 60° showed a significant positive influence on the stiffness compared with unbent nails. Pre-bending to 30° improved stiffness only slightly.

These findings validate the recommendations for pre-bending, but the degree of pre-bend should exceed 30°. Adopting higher degrees of pre-bending should improve stability in spiral fractures and reduce the complications of varus deformity and shortening.

Several techniques are available for the treatment of displaced fractures of the neck of the radius in children. We report our experience in 14 children treated by indirect reduction and fixation using an elastic stable intramedullary nail. The patients were followed up for a mean of 28 months. One developed asymptomatic avascular necrosis. The rest had excellent results. One had a neuropraxia of the posterior interosseous nerve, which recovered within six weeks. We advocate elastic stable intramedullary nailing for the closed reduction and fixation of these fractures in children.

Aim: To compare the biomechanical properties of paired flexible steel and titanium nails in simulated transverse fractures of synthetic composite bones. Methods: Steel and titanium nails (3mm diameter) were individually used in pairs of divergent configuration to study torsion, cantilever bending (anteroposterior and lateral), and axial loading properties of adolescent synthetic composite tibiae model (10mm diameter). Properties of the intact bone, simulated fresh fracture with nails and simulated healing fracture with nails were studied. Instron 4303 universal testing machine was used to study axial loading. Applying fibreglass layers around the fracture with epoxy resin simulated fracture healing with callus formation. Results: Steel and titanium nails maintained good alignment of fracture fragments. Both the nails demonstrated very poor stability of fresh fractures in torsion loading. Steel nail/bone construct was 57% stronger than Titanium nail/bone construct under similar testing conditions during fracture healing (p< 0.05) but still < 50% stiffness of intact bone. In bending tests, both types of nails showed < 10% of the stiffness of intact bone in fresh fractures (p< 0.05). Mediolateral stiffness was better than anteroposterior stiffness. In fracture healing, the bending stiffness of both types of nail/bone constructs was > 50% that of intact bone. Axial stiffness of both nails was more than bending or torsion stiffness implying that fracture fragments play a significant role in the stability of the fracture. Although both types of nail/bone constructs demonstrated similar stiffness results in fresh and healing fractures, steel nails performance was statistically better than Titanium nails in all loading tests (p< 0.05). Conclusion: Fractures fixed with either type of flexible nails should be supplemented with splints or plaster for a short duration until callus formation. Flexible nails should be used with caution in comminuted fractures, over weight patients since they may not provide adequate stability or allow early mobilization. Additional research with cadaver bones may provide further insight into the performance of the flexible nails

As there is little information on the factors that influence fracture union following intramedullary nailing of the tibia we retrospectively investigated patient-, injury- and treatment-related factors in 161 patients with closed or grade I open fractures of the tibial diaphysis. The patients were reviewed until clinical and radiological evidence of union at a mean of 13.3 months (4 to 60). Multivariate statistical analysis using a Cox proportional hazards model showed that the risk of failure of union increased by 2.38 times for highly comminuted fractures, by 3.14 times when nail dynamisation was applied, and by 1.65 times when the locking screws failed. In fractures with no or only minimal comminution the risk of nonunion increased if the post-reduction gap was ≥ 3 mm.

We report our experience using an inflatable intramedullary nail in 20 diaphyseal humeral fractures. The nail is introduced without reaming and does not require proximal and distal locking, because it allows radial stabilisation of the fracture. The tip of the nail must be inserted 5 cm beyond the fracture line. Since April 2002 we have applied 20 “Fixion” nails in 19 patients with humeral fractures. This is a stainless steel nail with a circular cross section reinforced by four bars, which can be inflated by saline solution through a dedicated pump. The average age of the 19 patients was 35.6 years, 15 were males and four female. Among these, 17 were closed fractures, three fractures open degree 1 (Gustilo Anderson class.). According to the AO classification, eight fractures were type A1 and A2, 10 were type A3 and two type B2. Nine fractures required reaming. Passive mobilisation is allowed 5 days after surgery, followed by active mobilisation 3 weeks later. Eighteen of the twenty fractures consolidated in an average time of 3.5 months. Two of 20 cases showed delayed union at 4 weeks and were treated by increasing the immobilisation period. Final healing without complications in these cases was observed at 5 months. No peripheral neurological complications were observed. “Fixion” nail is a new, easy method of intramedullary nailing. It helps to reduce operating time and in our experience it did not show any complications. It must be reserved for simple diaphyseal fractures where it is possible to achieve good stability and complete union

In order to define the operative indications, we compared the post-operative complications, time of consolidation, incidence of compartment syndrome, and fat embolism in centro medullary nails made from two different metals. This study includes approximately 234 centro medullary nails (TARGON System) used for treatment of diaphysal fractures of the leg or femur after a skiing injury. Steel nails were used before 1998 and titanium nails after 1998. The time of consolidation was the same for steel nails and titanium reamed nails. We remain faithful to limited reaming which avoids destruction of bone, and cortical and exothermic damage, but enables easier insertion of the titanium nail for leg fractures and bone grafts in sitù. The incidence of compartment syndrome with use of a titanium nail is reduced threefold. Regarding femoral fracture, the insertion of the nail without wire is more complicated and the operative stage is extended by 25%. The time of consolidation is the same for titanium or steel nails, and there were no failures with either type. However, we advise using titanium reamed nails for leg fractures and steel reamed nails for femoral fractures. If there is a suspicion of fat embolism, it is better to use femoral titanium nails