Comparison of a reverse-transverse cross pin technique with a same side cross pin type II external skeletal fixator in 89 dogs

The objective of this study was to determine whether a novel reverse-transverse cross pin insertion technique could increase the stability of type II external skeletal fixators (ESF) in dogs compared with an alternate, same side cross pin ESF. Reverse-transverse cross pin technique and type II ESFs same side cross pin technique were applied and compared among subjects. Two of 42 ESFs (4.8%) applied with the reverse-transverse cross pin technique and 39 of 47 ESFs (83%) applied with the same side cross pin technique were subjectively unstable at the time of fixator removal (P < 0.001). The same side cross pin ESFs had significantly more pin tract new bone formation than the reverse-transverse ESFs (P = 0.038). In summary, this approach may provide a method of treating a variety of musculoskeletal conditions and soft tissue cases, which reverse-transverse cross pin ESFs are tolerated in dogs for a variety of conditions

Static versus dynamic loads as an influence on bone remodelling

Bone remodelling activity in the avian ulna was assessed under conditions of disuse alone, disuse with a superimposed continuous compressive load, and disuse interrupted by a short daily period of intermittent loading. The ulna preparation is made by two submetaphyseal osteotomies, the cut ends of the bone being covered with stainless steel caps which, together with the bone they enclosed, are pierced by pins emerging transcutaneously on the dorsal and ventral surfaces of the wing. The 110 mm long undisturbed section of the bone shaft can be protected from functional loading, loaded continuously in compression by joining the pins with springs, or loaded intermittently in compression by engaging the pins in an Instron machine. Similar loads (525 n) were used in both static and dynamic cases engendering similar peak strains at the bone's midshaft (-2000 x 10-6). The intermitent load was applied at a frequency of 1 Hz during a single 100 second period per day as a ramped square wave, with a rate of change of strain during the ramp of 0.01 per second

A more patient-friendly use of circular fixators in deformity correction

PURPOSE: The evaluation of a construction that allows the exchange of circular and unilateral external fixators on the same fixation pins to the bone in outpatient circumstances during bone lengthening and alignment procedures. METHODS: Nine children were treated with this concept. After bone lengthening and alignment, the circular fixators were exchanged for unilateral fixators in the outpatient clinic to hold the position of the bony parts during the consolidation phase. RESULTS: The decrease of time needed to use the circular fixator during the treatment was considered to be an improvement in comfort. CONCLUSIONS: The concept of using both a circular and a unilateral external fixator in a construction that allows the exchange of the external fixators in outpatient circumstances combines the advantages of both systems, and creates more options in the different stages of bone deformity correction. Patient comfort is increased by the decrease of time needed to use the circular fixator

Postoperative complications associated with external skeletal fixators in cats

OBJECTIVES: The objective of this study was to quantify complications associated with external skeletal fixators (ESFs) in cats and to identify potential risk factors. METHODS: A retrospective review of medical records and radiographs following ESF placement was performed. RESULTS: Case records of 140 cats were reviewed; fixator-associated complications (FACs) occurred in 19% of cats. The region of ESF placement was significantly associated with complication development. Complications developed most frequently in the femur (50%), tarsus (35%) and radius/ulna (33%). Superficial pin tract infection (SPTI) and implant failure accounted for 45% and 41% of all FACs, respectively. SPTI occurred more frequently in the femur, humerus and tibia, with implant failure more frequent in the tarsus. No association between breed, age, sex, weight, fracture type (open vs closed), ESF classification, number of pins per bone segment, degree of fracture load sharing, and the incidence or type of FAC was identified. No association between region of placement, breed, age, sex, weight, fracture type (open vs closed), ESF classification, number of pins per bone segment, fracture load sharing and the time to complication development was identified. CONCLUSIONS AND RELEVANCE: Complication development is not uncommon in cats following ESF placement. The higher complication rate in the femur, tarsus and radius/ulna should be considered when reviewing options for fracture management. However, cats appear to have a lower rate of pin tract infections than dogs

About the development of external fixators applied in emergency surgery

At first, the doctors mentioned their own medical experience with treatment of complex pelvic injury in patients with polytrauma and give reasons for necessity of early stabilization of pelvic fractures by means of external fixation, especially with continuous hemorrhage into lesser pelvis region and the retroperitoneum. Afterwards, they used damage control surgery methods including selective embolization. However, this article is focused also on the design of external fixators applied in traumatology and orthopaedics (i.e. skills of engineers). These fixators can be used in the treatment of open and unstable (i.e. complicated) fractures of pelvis and its acetabulum. Two versions (i.e. old and new) are compared. Numerical modelling (i.e. Finite Element Method), together with CAD modelling, experiments, material engineering, and nanotechnology are presented as a support for developing of a new design of external fixators.Nejprve, lékaři zmiňují své vlastní lékařské zkušenosti s léčbou komplexního poranění pánve u pacientů s polytraumaty a udávají důvody pro neodkladnou včasnou stabilizaci pánevních zlomenin pomocí zevních fixátorů, obzvláště u plynulého krvácení do nižších oblastí pánve a retroperitonea. Potom využívají metod “damage control surgery” včetně selektivní embolizace. Nicméně, tento článek je také zaměřen na design nových externích fixátorů aplikovaných v traumatologii a ortopedii (tj. zkušenosti inženýrů). Tyto fixátory mohou být využívány v léčbě otevřených a nestabilních (tj. komplikovaných) zlomenin pánve a acetabula. Dvě verze fixátorů (tj. stará a nová) jsou porovnány. Počítačové modelování (tj. metoda konečných prvků), společně CAD sw, experimenty, materiálovým inženýrstvím a nanotechnologií jsou prezentovány jako podpora vývoje nových konstrukcí zevních fixátorů

Rigidity of unilateral external fixators - A biomechanical study

Introduction: External fixation is the primary choice of temporary fracture stabilisation for specific polytrauma patients. Adequate initial fracture healing requires sufficient stability at the fracture site. The purpose of this study was to compare the rigidity of the Dynafix DFS®Standard Fixator (4 joints) with the Orthofix ProCallus Fixator®(2 joints), which differ in possibilities for adapting the configuration for clinical needs. Materials and methods: Both devices were tested 10 times in a standardised model. In steps of 10 N, loading was increased to a maximum of 160 N in parallel, transversal and axial direction (distraction and compression). Translation resultant and rotation resultant were calculated. Results: With a force of 100 N in parallel direction the mean translation resultant (Trmean) of the Dynafix DFS®Standard Fixator (6.65 ± 1.43 mm) was significantly higher than the ProCallus Fixator®(3.29 ± 0.83 mm, p < 0.001; Student's t-test). With a maximum load of 60 N in transverse direction the Trmeanof the Dynafix DFS®Standard Fixator was significantly lower (8.14 ± 1.20 mm versus 9.83 ± 0.63 mm, p < 0.005). Translation was significantly higher with the Dynafix DFS®Standard Fixator, for both distraction (2.13 ± 0.32 mm versus 1.69 ± 0.44 mm, p < 0.05) and compression (1.55 ± 1.08 mm versus 0.15 ± 0.33 mm, p < 0.005). The mean rotation resultant (Rrmean) at 160 N distraction was lower for the Dynafix DFS®Standard Fixator (0.70 ± 0.17° versus 0.97 ± 0.21°, p < 0.005). Conclusions: Both fixators were most sensitive to transverse forces. The Dynafix DFS®Standard Fixator was less rigid with parallel and axial forces, whereas transverse forces and rotation at distraction forces favoured the Dynafix DFS®Standard Fixator. Repeated heavy loading did not influence the rigidity of both devices

External fixator configurations in tibia fractures: 1D optimization and 3D analysis comparison

The use of external fixation devices in orthopedic surgery is very common in open tibial fractures. A properly applied fixator may improve the healing process while one improperly applied might delay the healing process. The several external fixator systems used in clinical today, can be categorized into uniplanar–unilateral, uniplanar–bilateral, biplanar and multiplanar. The stability on the fracture focus and, therefore, the fracture healing process, is related with the type of external fixator configuration that is selected. The aim of this study is to discuss the principles for the successful application of unilateral–uniplanar external fixation, the assembly of its components, for the case of a transverse fractures using computational models. In this context, the fixation stiffness characteristics are evaluated using a simplified 1D finite element model for the tibia and external fixator. The beams are modeled with realistic cross-sectional geometry and material properties instead of a simplified model. The VABS (the Variational Asymptotic Beam Section analysis) methodology is used to compute the cross-sectional model for the generalized Timoshenko model, which was embedded in the finite element solver FEAP. The use of Timoshenko beam theory allows accounting for several kinds of loads, including torsion moments. Optimal design is performed with respect to the assembly of fixator components using a genetic algorithm. The optimization procedure is based on the evaluation of an objective function, which is dependent on the displacement at the fracture focus. The initial and optimal results are compared by performing a 3D analysis, for which different three-dimensional finite element models are created. The geometrical model of a tibia is created on the basis of data acquired by CAT scan, made for a healthy tibia of a 22 year old male. The 3D comparison of the 1D optimal results show a clear improvement on the objective function for the several load cases and, therefore, it is shown that appropriate selection of the external fixator geometrical features can lead to an improvement on the stability of the external fixator. The results obtained show that the optimal position of the side beam and the first pin should be as close as possible to the bone interface and as close as possible to the fracture focus, respectively. Concerning the second pin, it should be placed away from the first pin in case of flexion loads, to axial and torsion loads the second pin should be placed near the first pin

Leg Lengthening With a Motorized Nail in Adolescents: An Alternative to External Fixators?

Leg lengthening by external fixation is associated with various difficulties. We evaluated eight adolescent patients who underwent leg lengthening with a motorized intramedullary lengthening device. We asked whether this method could reduce the time of hospitalization and rehabilitation and whether the incidence of complications commonly associated with external fixators could be reduced. We compared our preliminary results with those from other reports, with a focus on leg length achieved, time of rehabilitation, and rate of complications. The average leg-length discrepancy was 3.8cm (range, 3-5cm). The average lengthening distance was 3.8cm (range, 2.9-4.7cm). In six patients, leg lengthening was combined with successful correction of the mechanical axis alignment. The consolidation index averaged 26days/cm (range, 19-41days/cm). The average hospital stay was 9.6days. No bone or soft tissue infections were observed. In comparison to other studies (1.0-2.8 complications/patient), our results suggest that the difficulties commonly associated with external fixators can be reduced with this method. It also allows good angular correction in patients with mechanical axis deviation. These features combined with a short time of hospitalization and rehabilitation make it a promising procedure for limb lengthening. Level of Evidence: Level IV Therapeutic study. See the Guidelines for Authors for a complete description of levels of evidenc

Informování o konstrukci externího fixátoru pro léčení zlomenin pánve a acetabula

Main point in this contribution is the design of external fixators applied in traumatology and orthopaedics. These fixators can be used in the treatment of open and unstable (i.e. complicated) fractures of pelvis and its acetabulum. Numerical modelling (i.e. Finite Element Method), together with CAD modelling, experiments, material engineering, and nanotechnology are presented as a support for developing of a new design of external fixators.Hlavním bodem článku je návrh externích fixátorů aplikovaných v traumatologii a ortopedii. Tyto fixátory mohou být používány pro léčení otevřených a nestabilních (komplikovaných) zlomenin pánve a acetabula. Obory numerické modelování (Metoda konečných prvků), společně s modelováním v CAD, experimenty, materiálové inženýrství a nanotechnologie vytváří v dnešní době podporu pro vývoj nových směrů v konstrukci externích fixátorů