Helical plating - a novel technique to increase stiffness in defect fractures.

Single-plate fixation bridging bone defects provokes nonunion and risks plate-fatigue failure due to under- dimensioned implants. Adding a helical plate to bridge the fracture increases stiffness and balances load sharing. This study compares the stiffness and plate surface strain of different constructs in a transverse contact and gap femoral shaft fracture model. Eight groups of six synthetic femora each were formed: intact femora; intact femora with lateral locking plate; contact and gap transverse shaft osteotomies each with lateral locking plate, lateral locking plate and helical locking plate, and long proximal femoral nail. Constructs underwent non-destructive quasi-static axial and torsional loading. Plate surface strain evaluation was performed under 200 N axial loading. Constructs with both lateral and helical plates demonstrated similar axial and torsional stiffness- independent of the contact or gap situations - being significantly higher compared to lateral plating (p < 0.01). Torsional stiffness of the constructs, with both lateral and helical plates in the gap situation, was significantly higher compared to this situation stabilised by a nail (p < 0.01). Plate surface strain dropped from 0.3 % in the gap situation with a lateral plate to < 0.1 % in this situation with both a lateral and a helical plate. Additional helical plating increases axial and torsional construct stiffness in synthetic bone and seems to provide well-balanced load sharing. Its use should be considered in very demanding situations for gap or defect fractures, where single-plate osteosynthesis provides inadequate stiffness for fracture healing and induces nonunion.

Mechanical Stimulation of Fracture Healing - Stimulation of Callus by Improved Recovery.

PURPOSE OF THE STUDY Mechanical stimulation plays an uncontested role in the surgical treatment of bone fractures. The effect of frequency, shape, amplitude and rise time of usually symmetrical mechanical stimuli is well known. The recovery period immediately after single pulses is potentially a critical period but has attracted little attention so far. The present study addresses the effect of extending the recovery period which may conceivably increase the efficacy of postoperative fracture management and physiotherapeutic intervention. MATERIAL AND METHODS The research method consisted of moving an isolated fragment of bone at a fixed amplitude followed by different recovery periods of between ten seconds and two hours between repeated single pulses. The amount of callus produced was observed radiologically and micro-radiologically and the material property of the healing unit was assessed by measuring the stiffness of the unit. RESULTS The result was that pulses applied after a recovery period of up to two hours produced abundant callus and a large increase of stiffness. Pulses applied after a recovery period of ten seconds produced only traces of callus and no increase of stiffness. The significant differences of mean values at 5 weeks were 74 mm2 vs. 13 mm2, and 31.5 MPa vs. 5.5 MPa, respectively. CONCLUSIONS The working hypothesis postulates a time-dependent change in tissue reaction to deformation in relation to the time allowed for recovery. Damage and consequent irritation inducing callus does not occur below the critical interval. The observed, unexpected lack of reaction to recovery intervals below 10 seconds may trigger the expectation that in postoperative physiotherapy loading at longer intervals would be preferable to activation at frequencies of locomotion. Key words: fracture healing, mechanical stimulation, callus.

How to Choose between the Implant Materials Steel and Titanium in Orthopedic Trauma Surgery: Part 2 - Biological Aspects.

BIOLOGICAL ASPECTS OF STEEL AND TITANIUM AS IMPLANT MATERIAL IN ORTHOPEDIC TRAUMA SURGERY The following case from the ICUC database, where a titanium plate was implanted into a flourishing infection, represents the clinical experience leading to preferring titanium over steel. (Fig. 1) (6). Current opinions regarding biological aspects of implant function. The "street" opinions regarding the biological aspects of the use of steel versus titanium as a surgical trauma implant material differ widely. Statements of opinion leaders range from "I do not see any difference in the biological behavior between steel and titanium in clinical application" to "I successfully use titanium implants in infected areas in a situation where steel would act as foreign body "sustaining" infection." Furthermore, some comments imply that clinical proof for the superiority of titanium in human application is lacking. The following tries to clarify the issues addressing the different aspects more through a practical clinical approach than a purely scientific one, this includes simplifications. Today's overall biocompatibility of implant materials is acceptable but: As the vast majority of secondary surgeries are elective procedures this allows the selection of implant materials with optimal infection resistance. The different biological reactions of stainless steel and titanium are important for this segment of clinical pathologies. Biological tole - rance (18) depends on the toxicity and on the amount of soluble implant material released. Release, diffusion and washout through blood circulation determine the local concentration of the corrosion products. Alloying components of steel, especially nickel and chromium, are less than optimal in respect to tissue tolerance and allergenicity. Titanium as a pure metal provides excellent biological tolerance (3, 4, 16). Better strength was obtained by titanium alloys like TiAl6V4. The latter found limited application as surgical implants. It contains Vanadium (9). Today's high strength titanium alloys contain well tolerated alloying components1 like Zr, Nb, Mo and Ta (ISO 5832-14) (7, 15). The corrosion rate of surgical implants is kept low by the passive layer formed when immerged in body fluids (13, 14). The passive layer may be locally destroyed, for instance, by mechanical fretting or by local corrosion conditions like in pitting; it is renewed by an electrochemical corrosion process which releases alloying components like Ni and Cr (Fig. 2) (10). The amount of soluble component may vary markedly depending on the local electrochemical conditions (see below).

The Potential of the ICUC® Documentation Concept to Improve Trauma Surgery.

Conventional documentation of surgical procedures using only pre- and postoperative X-ray images and possibly a few intra-operative pictures does not allow secondary analysis of the technical performance in detail. In particular, the quality of the handling of tissues and surgical tools cannot be judged «post hoc¼, i.e. after the end of the surgical procedure. The invasiveness of the surgical act cannot yet be quantified. Surrogate invasiveness indices have therefore been developed. Furthermore, conventional documentation does not allow evaluation of the proper use of the C-arm both technically and with regard to fluoroscopy time. Documentation that follows the ICUC® documentation concept includes all fluoroscopy shots and images covering all key portions of the entire surgical procedure by multiple still images or videos. In certain cases, such documentation can help to explain post-operative courses that might be difficult to understand based only on X-rays and written operation reports. Finally, the data included in ICUC® documentation are a valuable source for knowledge extraction. In addition, time saving is conceivable if operation reports can include images of the key stages of the procedure with a few additional comments dictated during the surgery. Key words: trauma surgery, ICUC® documentation concept.

How to Choose between the Implant Materials Steel and Titanium in Orthopedic Trauma Surgery: Part 1 - Mechanical Aspects.

When choosing between metal implants of different materials the surgeon mainly needs to balance the pros and cons of steel and titanium. Economic constraints often do not permit both to be kept in stock and it is necessary to decide beforehand which to choose. The arguments for the use of the "preferred metal" vary. The present paper elucidates the practical aspects based on the complex scientific background that has identified the differences between the two metals in their mechanical, electrochemical, biological and application behavior. The data presented here are intended to help the surgeon when he is confronted with different and often complex clinical situations and problems. The following is an overview of different aspects to help with selection of the proper material for the clinical application. The first part concerns mechanical aspects the second part the biological aspects. Both aspects are discussed with the practical application in mind. Nonmetallic implant materials have seen an increasing interest in the recent past. Plastic materials needed improvement to achieve good strength and avoid creep with loss of e.g. compression and minimizing leakage of chemicals.

Evolution of AO Fracture Treatment Part 1: the Internal Fixator.

Surgical fracture treatment has undergone an extensive evolution in the past decades. In the early days achieving solid healing in anatomically reduced position was the primary and nearly exclusive goal of fracture treatment. Since mainly Lambotte, Danis and Müller in Europe the focus of surgical fracture treatment shifted to achieving early recovery of the function of the injured limb with safe healing. Considering the shortcomings of the early fracture treatment helps understanding the evolution of surgical fracture treatment. The evolution of the biomechanical and biological principles of AO plate fixation are discussed as a model.

Balancing Success and Risk in Orthopedic Trauma Surgery: The Ridge-Walking between Sound Accepting "Good" and Risky Striving for "Better".

Immediate post-operative rating of surgical performance can be a valuable source of learning when trying to analyze the reasons for the difference between "work as planned" and "work as done". There are many reasons for the difference, but they can only be found if complete documentation of the surgical steps allows retrospective scrutiny. Documentation like ICUC1 provides this opportunity for scrutiny and may allow better understanding of some unexpected post-operative evolutions.

Fracture healing: fracture healing understood as the result of a fascinating cascade of physical and biological interactions. Part II.

Based on our own observations an explanation of the different factors influencing bone reaction is proposed. Special attention is given to the aspect of tissue deformation (strain). We propose thinking in terms of strain rather than of instability when contemplating tissue reaction. Considering the observed bone behavior should help improving the treatment of fractures and their complications.

Fracture healing: fracture healing understood as the result of a fascinating cascade of physical and biological interactions. Part I. An Attempt to Integrate Observations from 30 Years AO Research.

The choice of best procedure in fracture treatment relies on a proper understanding of tissue reactions to the prevailing mechanical and biological conditions. Investing time and effort is rewarding as it opens up access to a fascinating world and improves fracture treatment based on logical decision making. An intact bony skeleton enables mechanical functions of the human body such as locomotion. This function of the bone is made possible by its stiffness and strength, which allows bone to carry load without undergoing major deformation while remaining intact even under heavy loads. The shortcoming of bone as a strong and stiff material is its brittleness. Its brittleness prevents bone from bridging a fracture under unstable conditions. In spontaneous healing or healing under flxible fiation, a cascade of repair tissues stabilizes the fracture and allows for solid bony union. Excessive load fractures the bone. Disrupted bone loses its stiffness. Loss of stiffness and, consequently, loss of skeletal support disables the function of the limb. fracture healing is a ubiquitous and spontaneous process which restores stiffness as a prerequisite for mechanical function. Restoration of mechanical integrity requires that bone bridges and/or remodels the fracture site. If there is high initial tissue deformation (strain) at the fracture site, bone as a brittle material cannot bridge the gap. In spontaneous healing or healing under flxible fiation a cascade of consecutive phases of tissue differentiation are required to overcome this shortcoming of bone. The cascade increases tissue stiffness at the expense of tolerance to deformation until a low value of interfragmental strain is reached that then allows bone to form a solid bridge. The cascade of differentiation is impressive as a "reasonable" process with a goal. Therefore, bone healing is often considered as a rational process where the repair tissues are expected "to think and to act in order to achieve". we propose the observation of bone reactions without assuming that these reactions are guided by goal-oriented intelligence because the latter is non-existent. Observing the unexpected without having a preconceived opinion is a precondition for new insight. This approach avoids being misled into projecting one's own thinking into tissues that react without goal orientation. fracture healing is a repair process which requires induction and must be enabled. To get a feel for the problem we will fist address the mechanical properties of bone as the prerequisites for its mechanical functions. Then we will discuss which conditions induce and which enable the repair process. The following paper addresses a fascinating interplay between physical and biological processes that enable fractured bone to bridge solidly and remodel to regain its "pre-fracture" function and structure. no one of the different treatment modalities or healing patterns is best on its own. for a given situation the goal is to recover the function of the bone, limb and patient early and permanently by choosing the optimal procedure and implant. Understanding bone reactions permits a rational choice and replaces subjective predilection and monomania. The stability of the fiation and the blood supply are priority considerations, which must often be weighed against each other.

Biomechanical and biological aspects of defect treatment in fractures using helical plates.

The clinical case of figure 1 through figure 11 shows a series of impressive failures of plate fixation. The plates were repeatedly applied bridging a comminuted bone segment in a heavy patient. The biomechanical analysis elaborates why this happened and proposes an unconventional procedure to prevent this failure with a minimally invasive procedure. A plate bridging an open gap or a defect in a long bone diaphysis is exposed to full functional load. According to clinical observations such plate application often fails even without external load such as weight bearing. The plate risks to break through fatigue when exposed during a long time to cyclic loading. This type of failure has been observed even with broad plates as well in femoral as in tibiae. The first option to avoid such failure consists in protecting the plate by installing load sharing between plate and either bone or an additional implant. This reduces the load carried by the plate to a safe level. Load sharing with bone may be installed at surgery by establishing solid mechanical bridge between the two main fragments of the fractured bone. The optimal load sharing relies on a solid compressed contact between the main fragments. It can be established because the bone is able to take a large load which results in optimal protection of the plate. In the case of an extended comminuted bone segment it may be very difficult, traumatizing and inefficient to reconstruct the bone. In the present case it was impossible to establish load sharing through the bone. The second option protecting the plate is provided by callus bridging of the gap or defect. The formation of a solid callus bridge takes time but the fatigue failure of the plate also takes time. Therefore, the callus bridge may prevent a late fatigue failure. The surgeon may select one of several options: - Replacing the lack of bone support using a second plate which immediately alleviates plate loading. The drawback of application of a second conventional plate is the extent of surgical trauma at the critical site of healing. - Shingling and/or applying an autologous cancellous bone graft: This procedure provides initially no relevant load sharing but will do so after a couple of weeks. The mechanical coupling of the comparably soft graft and the main fracture fragments presents little problems. Applying a cortical bone graft: Such a graft does provide initial only small load sharing and does a less good job inducing callus than a cancellous graft. Furthermore, the coupling by callus between a somewhat rigid bone graft and the mobile main fracture fragments requires a solid maintained contact. If the cortical graft is fixed using implants with small contact area to the graft such as screws or cerclage loops, the local stress may be critical and the graft may break. When the cortical graft is fixed with cerclage wires the procedure must take into account the limited strength of the individual cerclage. Therefore multiple and well-spaced cerclages are required and may lead to success especially if an intramedullary component of the implant contributes to protection (6). The degree of unloading depends apparently on the stiffness of the material of the protecting splint. Though, more important is the effect of the dimensions of the splint. While titanium as a material is about 50% less stiff than steel, the thickness of the implant changes the stiffness with the third power. That is doubling the thickness results in eightfold increased stiffness. When considering the unloading by application of a second plate the leverage of the second plate plays an important role. The larger the distance between the axis of bending and the second implant the larger the protecting effect. The helical plate (2, 3, 7) as introduced by A.A.D. Fernandez offers biological and mechanical advantages. It can be applied without touching the fracture site maintaining the critical biology intact and provides mechanically efficient unloading. Its application is fairly simple: The helical plate is modified conventional long and small plate that is twisted between its ends about 90 degrees. The twist is applied using "bending irons" (4, 5, 8) whereby the force required is small and the exact degree of twist is not critical. Therefore the twist is applicable operating bending irons by hand. Assuming a situation where a plate bridging a defect or non-union has failed the broken plate is replaced by a similar implant: At the distal end of the bone fracture and opposite to the surgical approach a small incision allows to slide in the helical plate in such a way that proximally the plate ends on the same side of the limb as the replaced plate. Ideally the two plate ends meet and the application of the helical plate does not ask for an additional surgical exposure at this location. Otherwise a small minimally invasive exposure is required. The helical plate is then fixed to the main bone fragments using a couple of locked screws. The following case demonstrates the use and efficiency of the helical plate saving a situation where multiple attempts using conventional plates had failed. The successful final treatment of this case was performed by A. A. D. Fernandez.

Cerclage, evolution and potential of a Cinderella technology. An overview with reference to periprosthetic fractures.

Periprosthetic fractures are increasingly frequent. The fracture may be located over the shaft of the prosthesis, at its tip or below. The treatment of explosion fractures is difficult because the shaft blocks the application of implants, like screws, which need to penetrate the medullary cavity. The cerclage, as a simple periosteal loop, made of wire or more recently cable, does not only avoid the medullary cavity. Its centripetal mode of action is well suited for reducing and maintaining radially displaced fractures. Furthermore, the cerclage lends itself well for minimally invasive internal fixation. New insight challenges the disrepute of which the cerclage technology suffered for decades. The outcome of cerclage fixation benefits from an improved understanding of its technology, mechano-biology and periosteal blood supply. Preconceived and generally accepted opinions like "strangulation of blood supply" need to be re-examined. Recent mechanical evaluations demonstrate that the wire application may be improved but cable is superior in hand- ling, maintenance of tension and strength. Beside the classical concepts of absolute and relative stability a defined stability condition needs consideration. It is typical for cerclage. Called "loose-lock stability" it specifies the situation where a loosened implant allows first unimpeded displacement changing abruptly into a locked fixation preventing further dislocation.

Tissue deformation controlling fracture healing.

To achieve optimal flexibility in biological internal fracture fixation two questions require clarification: which biomechanical parameter controls healing and what are the boundary conditions thereof? Fracture movement interacts with callus and local stress and strain are influencing the reaction of the tissue cells. A linear gradient of strain was created inside a sheep tibia osteotomy using an active external fixator. The effect of different amounts of strain applied at 10 stimulation cycles/day on the occurrence of callus and on enabling osseous connection of the fragments was evaluated using micro-radiology to determine the amount of calcified new bone formation and its quality of gap bridging. A strong relation between level of strain and amount of callus was observed. Depending on the strain level different pattern of connections were seen. At the lowest investigated gap strain level of about 7% direct connection of the fragments within the gap occurred. Beyond 13% the callus only connected indirectly outside the gap. At over 36% callus did not connect the fragments anymore comparable to a situation in hypertrophic non-unions. The observed strong relation between interfragmentary strain and reduced osseous bridging may support the hypothesis that the elongation at rupture of connecting tissue plays an important role defining the upper limit for solid bridging. In planning fracture treatment, the amount of fracture mobility resulting in interfragmentary strain may play a crucial role to achieve solid healing.

[Optimizing the degree of fixation stability based on the strain theory]. / Optimierung der Stabilität flexibler Osteosynthesen mit Hilfe der Dehnungstheorie.

Elastic flexible internal fixation stabilizes the fracture using the principle of splinting. Foregoing absolute stability using compression serves to maintain the mechano-biological induction of fracture healing. It also serves to maintain the blood supply to soft tissues and bone. The healing pattern seen after flexible fixation corresponds to that of secondary bone healing. It starts early and requires less precision, which in turn helps to avoid iatrogenic damage during reduction and stabilization.Prognosis based alone on the degree of fracture mobility is inadequate because spontaneous healing can be observed in wild animals even with great mobility while in turn minimal instability of closely reduced fractures may result in delayed or non-union. The determining factor for tissue differentiation is not mobility but deformation (strain) of the repair tissue. While tissue strain depends on mobility, it depends even more so - and is all too often disregarded - on the distance between the moving fracture surfaces. Strain plays an important role when choosing the method of immobilisation and predicting an outcome, determining the induction and tolerance of the repair tissue.

Tissue reaction to implants of different metals: a study using guide wires in cannulated screws.

Cannulated screws, along with guide wires, are typically used for surgical fracture treatment in cancellous bone. Breakage or bending deformation of the guide wire is a clinical concern. Mechanically superior guide wires made of Co-Cr alloys such as MP35N and L605 may reduce the occurrence of mechanical failures when used in combination with conventional (316L stainless steel) cannulated screws. However the possibility of galvanic or crevice corrosion and adverse tissue reaction, exists when using dissimilar materials, particularly in the event that a guide wire breaks, and remains in situ. Therefore, we designed an experiment to determine the tissue reaction to such an in vivo environment. Implant devices were designed to replicate a clinical situation where dissimilar metals can form a galvanic couple. Histological and SEM analyses were used to evaluate tissue response and corrosion of the implants. In this experiment, no adverse in vivo effects were detected from the use of dissimilar materials in a model of a broken guide wire in a cannulated screw.

Absolute or relative stability in minimal invasive plate osteosynthesis of simple distal meta or diaphyseal tibia fractures?

INTRODUCTION: Minimal invasive plate osteosynthesis in simple distal meta or diaphyseal tibia fractures can be applied using absolute (lag screw and neutralisation plate; LSN) or relative stability (bridge plate; BP). The primary aim of the study was to compare time to radiological union and time to full weight bearing in the two groups (LSN vs. BP). Reduction was performed either percutaneously or by a minimally open approach (mini open). Secondary aim was to analyse the number of complications between both groups. METHODS: Retrospective single centre review of patients with a simple distal meta or diaphyseal tibia fracture operated with a Locking Compression Plate (LCP) between 2009 and 2015 in a Level one Trauma Centre. Postoperative radiographs were assessed in a standardised manner. Time to radiological fracture union and time to full weight bearing were observed. Callus index and postoperative complications were analysed. RESULTS: Fifty-seven patients with a minimum follow-up of 6 months were analysed. Forty-eight patients had a shaft (AO/OTA Type 42) and nine a distal tibia fracture (AO/OTA Type 43). Forty patients were treated with using the LSN concept and 17 patients with the BP concept. Median time to radiological fracture union was statistically significant shorter (p=0.04) in the LSN group with 19 weeks compared to 27 weeks in the BP-group. Time to full weight bearing was 10 weeks in both groups. A total (including implant removal) of 35 reoperations were performed in the LSN-group and 18 in the BP-group. Wound healing disorders (deep surgical site infections) were seen less the LSN group in 3/40 (7.5%) compared to the BP-group with 3/17 (17.6%). In the LSN group, there was no statistical difference in time to union or weight bearing between a percutaneous or mini open approach. CONCLUSION: Stable osteosynthesis of simple distal meta or diaphyseal tibia fractures leads to faster radiologic fracture healing without an increase in complications or number of revisions compared to bridge plating. If a percutaneous reduction is not feasible for the insertion of a lag screw, a mini-open approach does not lead to a delay in fracture healing.

Aspects of internal fixation of fractures in porotic bone. Principles, technologies and procedures using locked plate screws.

Fractures of the bones of elderly people occur more often and have a more important effect because of a generally diminished ability to coordinate stance and walking. These fractures occur at a lower level of load because of lack of strength of the porotic bone. Prompt recovery of skeletal support function is essential to avoid respiratory and circulatory complications in the elderly. To prevent elderly people from the risks of being bedridden, demanding internal fixation of fractures is required. The weak porotic bone and the high level of uncontrolled loading after internal fixation pose complex problems. A combination of several technical elements of design, application and aftercare in internal fixation are proposed. Internal fixators with locked screws improve the biology and the mechanics of internal fixation. When such fixators are used as elevated splints they may stimulate early callus formation because of their flexibility, the limit of flexibility being set by the demands of resistance and function of the limb. Our own studies of triangulation of locked screws have demonstrated their beneficial effects and unexpected limitations.

Effect of bone size, not density, on the stiffness of the proximal part of normal and osteoporotic human femora.

Proximal femur fractures in the elderly lead to a high rate of hospitalization. In studying the operative treatment of such fractures, it is first necessary to understand the relationship between the morphologic properties of this part of the femur (related to both geometry and density) and its mechanical properties. Numerous investigations showed that femoral strength correlates with bone mass; however, the dimension of the bones was not taken into account. We measured the relationship between the stiffness of the proximal femur under physiologic load and its geometry and density. Conventional x-rays and quantitative computed tomography (QCT) were carried out on pairs of human cadaver femora. Eight pairs were instrumented with strain gauges. Bones were subjected to an eccentric load that simulates moderate weight bearing (single-leg stance), and the strain parallel to the bone axis was plotted as a function of the load applied. An apparent bone stiffness was calculated as the ratio between the strain gradient within the section and the load applied. Strong correlation was found between x-ray densitometry and QCT. The bone stiffness also correlates strongly with the geometry (area) and slightly with bone mass; however, an unexpectedly low correlation was found between stiffness and density. We chose stiffness as a mechanical parameter (not strength) because it describes the "normal" bone behavior under load. Our results clearly demonstrate that the cross-sectional size of the bones must be taken into account when establishing the relationship between the mechanical characteristics of the bone and its morphology. In accordance with previous predictions, our results support that bone loss due to osteoporosis is compensated for by an increase in bone diameter.

Evaluation of soft tissue reactions at the interface of titanium limited contact dynamic compression plate implants with different surface treatments: an experimental sheep study.

Five types of limited contact dynamic compression plates (LC-DCPs) of pure titanium with different surface treatments and an electropolished stainless steel LC-DCP were tested. The surface roughness parameters and chemical surface conditions were determined and checked for probable surface contamination. After an implantation period of 3 months on long bones of sheep, the soft tissue adjacent to the plates was evaluated histomorphometrically. The difference in roughness parameters was statistically significant for most surface conditions. A correlation was found between the surface roughness of the implants and the thickness of the adjacent soft tissue layer. The thinnest soft tissue reaction layer with a good adhesion to the implant surface was observed for the titanium anodized plates with coarse surface. Smooth implants, in particular the electropolished stainless steel plates, induced statistically significant thicker soft tissue layers. Profilometer roughness measurements combined with scanning electron microscopy techniques were useful methods to characterize the surface morphology.