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PubMed1992

Biomechanical consequences of callus development in Hoffmann, Wagner, Orthofix and Ilizarov external fixators.

A theoretical analysis by a finite elements model (FEM) of some external fixators (Hoffmann, Wagner, Orthofix and Ilizarov) was carried out. This study considered a logarithmic progress of callus elastic characteristics. A standard configuration of each fixator was defined where design and application characteristics were modified. A comparison among standard configurations and influence of every variation was made with regard to displacement and load transmission at the fracture site. An experimental evaluation of standard configurations was performed with a testing machine. After experimental validation of the theoretical model was achieved, an application of physiological loads which act on a fractured limb during normal gait was analysed. A minimal contribution from an external fixator to the total rigidity of the bone-callus-fixator system was assessed when a callus showing minimum elastic characteristics had just been established. Insufficient rigidity from the fixation devices to assure an adequate immobilization during the early stages of fracture healing was verified. However, regardless of the external fixator, callus development was the overriding element for the rigidity of the fixator-bone system.

Biomechanical Phenomena↗

PubMed1987

External fixation of complex carpal dislocations: a preliminary report.

In ten cases of complex carpal fracture dislocations an external fixator between the radius and the second or third metacarpals was used as an adjunct to open reduction and internal fixation. The external fixator facilitates reduction, ligamentous repair, and internal fixation of the carpal bones. Furthermore, continuous postoperative distraction of the wrist maintains a stable reduction of the carpus permitting cast free after treatment and early active motion of the neighboring joints. This method is particularly useful for carpal stabilization when combined injuries of the same extremity coexist.

Adult↗

PubMed1990

[Stabilization of open tibial fracture by an external fixator. Advantages through supplemental screw osteosynthesis].

One hundred thirty-two open tibial shaft fractures were treated by unilateral external fixation. In order to evaluate the usefulness of supplemental lag screw fixation, we compared forty-four reexamined fractures in which only external fixation was utilized with fifty-five reexamined fractures, stabilized with supplemental lag screws and external fixation. We did not find significant differences in time to full-weight bearing (17.1 vs. 15.6 weeks), time to union (18.7 vs 18.0 weeks), incidence of delayed union [as defined by time to union over 32 weeks (10.9% vs. 11.4%)], incidence of osteomyelitis (5.4% vs. 4.5%), or incidence of malunion [axial malalignment greater than 5 degrees (12.7% vs. 11.4%)]. Clinically significant differences were found demonstrating a twofold increase in refracture rate in the group with supplemental lag screws (10.9% vs. 4.5%) and requiring twice as many bone grafting procedures to achieve union (65.5% vs. 29.5) than did the group treated by external fixation alone. Therefore we do not recommend the routine use of supplemental lag screw fixation.

Adolescent↗

PubMed1991

[External fixator as primary and definitive treatment of tibial fracture with severe soft tissue damage].

The initial treatment of choice of fractures with severe soft tissue damage of the leg is the stabilization with an external fixator. After successful healing the question arises whether to continue the initial treatment with the external fixator to bone union or to change the initial concept by an internal fixation. Our experience with 62 fractures of the tibia (follow-up of 59 fractures) from 1985 to 1989 shows that 72% of the fractures were healed by the external fixator alone. Delayed union or pseudoarthrosis occurred in 17% and were mostly treated by late internal fixation. An analysis of the fracture types (new AO classification) did not show certain fracture types, that did not respond to the external fixator treatment alone. We conclude that the reason for a delayed union or pseudoarthrosis is less a morphological than a biological one. We recommend the first and final external fixator as treatment for fractures with severe soft tissue damage of the leg.

External Fixators↗

PubMed1979

External fixation devices in fractures of the leg.

External fixation devices, of which there are many types, represent a new and extremely effective method of fixation in fractures of the leg. These are extremely common, frequently severe and often complicated by a variety of other lesions. The usefulness of this method lies in the fact that they can be applied immediately with minimal additional trauma, and the fracture can be immobilised whilst leaving the damaged area uncovered and thus available to carry out repairs and reconstruction of the soft tissues. Mobilisation of the patient is not impeded, and they can be replaced by other more traditional methods as and when these may become more appropriate. The author presents his own views based on some ten years experience with external fixation devices in traumatology, with special reference to fractures of the tibia.

Bone Nails↗

PubMed1990

Tibia nonunions treated by interlocked nailing: increased risk of infection after previous external fixation.

Eighteen patients, mean age 36 years (range of 22-76 years), with tibia-shaft nonunions were treated with interlocked nailing. There were 12 nonunions originally treated with either cast, lag screws, plate, or Ender nails (nine closed, two open grade I and one grade II injury). The remaining six nonunions, all open fractures (five grade II and one grade III injury) initially received external fixation. After removal of the fixator, 72 days postinjury (range of 58-111 days), there was a delay of 218 days (range of 112-449 days) before the nailing procedure in those patients primarily treated with external fixation. All 12 nonunions not primarily treated with external fixation healed without complications after nailing within 17 weeks (range of 12-24 weeks). All six nonunions primarily treated with external fixation had temporary pin-tract infections, which healed after pin extraction. Two of the nonunions healed without any complication, whereas four developed intramedullary infection with the same bacteria as from the pin-tract site. Although the number of patients is small in this report, there is an apparently high incidence of intramedullary infection in the group originally treated with external fixation. The sequential procedure of external fixation followed by intramedullary nailing is, therefore, not recommended in the treatment of open tibia fractures.

Adult↗

PubMed1989

Mechanical performance of pin clamps in external fixators.

Insufficient holding strength on a pin within a clamp may result in the diminution of the overall fixation rigidity as well as pin movement at the pin-bone interface. In this study the holding strength of pin fixation clamps in two representative external fixators (Hoffmann and Orthofix) was evaluated by determination of the torque resistance of pins within a clamp. In the standard Hoffman clamp, the pin-clamping effect was satisfactory in the symmetric two-, three-, and four-pin configurations, whereas the standard Orthofix clamp provided higher holding strength in the symmetric two- and three-pin configurations. All other pin configurations in both clamps resulted in a high variation of pin torsional resistance, and sometimes one of the pins registered low or had no resistance to torsion. The results indicated that the holding power of the clamps was adequate only if certain guidelines were followed at the time of external fixator application. An instrumented torque wrench may be helpful to assess the pin-fastening strength within the clamp. This wrench should also be used to introduce appropriate and uniform tightening torques to the pin clamp screws. However, these results do not apply to those fixators in which each pin will be tightened individually.

Fracture Fixation↗

PubMed1991

Ankle arthrodesis. A comparison of internal and external fixation.

The authors reviewed the results of ankle arthrodesis in 68 ankles in 66 patients. The average follow-up period of the patients was five years (range, two to ten years). There were 40 ankles in which internal fixation was used and 28 ankles in which external fixation was used. The two groups were compared to determine the effect of mode of stabilization on outcome. Outcome was measured by time to union, development of complications, and clinical follow-up result. The groups were similar in regards to gender, age, and preoperative diagnosis. The external fixation group had a significantly higher prevalence of complications, including non-union, delayed union, and infection, than the internal fixation group. It was concluded that ankle arthrodesis with internal fixation is better tolerated and has fewer complications than techniques that use external fixation.

Adult↗

PubMed1992

Vascular injury from external fixation: case reports.

The incidence of vascular injury from external fixation of fractures was studied retrospectively in two surgical departments during the period 1985-1990. A total of 1231 fractures of the lower limb were treated. External fixation was used in the initial stabilization of 28 femoral and 93 tibial fractures. In this series of 121 fractures four iatrogenic vascular injuries were seen: two arterial thromboses with distal ischemia and two incidents of the formation of a false aneurysm with bleeding along a pin. The diagnosis was made by angiography. Surgical intervention was necessary in all four cases. In one patient the injury resulted in amputation of the distal portion of the foot.

Adult↗

PubMed1992

The effect of wire configuration on the stability of the Ilizarov external fixator.

The stability of the basic unit for fixation of the Ilizarov external fixation system was tested in several loading modes. The effects of varying the number of wires and the orientation of wire placement were studied. The fixation units were mounted on a plastic, simulated, long bone and tested by loading in several directions. The Ilizarov fixation ring was found to be relatively stiff in axial compression and torsion. Its stiffness in this mode was directly proportional to the number of wires in the system and independent of the configuration of wire placement. Loading in bending and in shear provided much lower levels of stiffness, and this was dependent on the angles formed between the wires. The addition of a wire at a minimum distance of 4 cm from the primary ring significantly improved bending stiffness. The use of opposed olive wires also improved shear stiffness.

Equipment Design↗

PubMed1991

Induction and prevention of pin loosening in external fixation: an in vivo study on sheep tibiae.

In external fixation of fractures, pin loosening is a major concern. Preloading the pins is generally done to ensure their stability within the bone cortex. The effect of radial preload and bending preload in reducing resorption at the pin/bone interface was tested. Schanz screws were fixed to live sheep tibiae using a pneumatically operated external fixator frame. Evaluation was based on radiological observation and fluorochrome histology using sequential labels. Though not completely absent, bone resorption was minimal in the radial preload group, compared with the two other groups. More important, the bone-to-pin contact surface in the radial preload group was found to be almost intact after 5 weeks. In this study, radial preload appears to be superior to bending preload in terms of minimizing the problems of pin loosening.

Animals↗

PubMed1992

Biomechanical evaluation of the Pinless external fixator.

In open fractures especially in those with severe soft tissue damage, fracture stabilisation is best achieved by using external fixators. There are some intrinsic complications which occur during classical external pin fixation. To overcome the problem of pin track infection and vascular damage from drilling, the Pinless external fixator was developed. It is based on the idea of a forceps with trocar points, which only penetrate the bone cortex superficially. The function of the device was tested in two mechanical trials and two in vitro tests in which one pinless clamp was put under a controlled load of 50 N, 150 cycles/day and studied over a 5 week period in sheep. The loads and time range of the experiment were chosen to simulate a temporary fracture stabilisation in a patient not bearing weight. The main question to be answered was whether the Pinless external fixator would be able to maintain stable fixation. Furthermore, it was to determine the changes at the trocar-to-bone interface. The clamp was found to maintain 72% of the initially applied clamping force after 5 weeks of in vivo application and it was found to be tight at removal. Some decrease of clamping force was found during the first 20 days and then the force tended to level off. There was no slippage nor did the clamp penetrate the cortex. There were no obvious signs of infection around the trocar-holes and in the bacterial tests no pathological cultures were grown. Histology revealed very localised bone reactions, the indentation caused by the trocar tips being only 1.2 mm deep. The study concludes, as far as could be ascertained from these tests, that it is safe to use pinless external fixation for temporary fracture fixation.

Animals↗

PubMed1990

[External fixator in the district hospital].

Follow-up checks were performed on 59 cases of external fixation between 1 and 9 years after operation. Complications are not severe, and all patients of this group finally had achieved a good or very good functional end result. External fixator is found a favourite method for use in an ordinary hospital as the author's. The criteria of indication particularly found a new evaluation. The need of giving the external fixator in accurately defined instability is emphasized.

Adult↗

PubMed1987

Comminuted Colles' fractures treated with external fixation.

In a prospective series of 75 patients the results of early external fixation of comminuted intraarticular Colles' fractures were studied. Comparison was made to a control group of 32 patients treated with plaster cast fixation. The groups were equal with regard to age, sex and fracture type. The treatment consisted of reduction in general anaesthesia or arm block followed by the application of a small external fixation device. The fixation lasted for five weeks after which the patients were allowed free exercises. For evaluation at the one year follow up the following variables were used: Radiographic appearance. Healing in of the styloid process of the ulna. Subjective evaluation according to the Lidström score. Objective evaluation including range of motion and grip strength. In all follow up variables the treatment group was significantly better than the control group. The prognosis of conservatively treated comminuted intraarticular Colles' fractures is poor. The results of after external fixation are, however, very encouraging and the method can be recommended.

Adult↗

PubMed1989

[External fixation for open fractures of the femur].

32 cases of severe open fractures of the femur were treated by external fixation in 1 lateral plane with either the Wagner apparatus or the A.O. tubular system. 2/3 of the cases were war injuries and 1/3 were due to traffic accidents. In 1 case the broken limb was severely burned. In half the cases external fixation was changed for P.O.P. or internal fixation because of pin tract infection or delayed union. There were no non-unions or amputations, but 1 case had chronic post-traumatic osteomyelitis. We conclude that the method of choice for 3rd degree open fractures of the femur is external fixation. In the case of severe multitrauma and complex wounds with vascular injury or burns, external fixation is mandatory.

Femoral Fractures↗

PubMed1990

External fixation or plaster cast for severely displaced Colles' fractures? Prospective 1-year study of 46 patients.

In a prospective randomized study of 47 severely displaced Colles' fractures, 23 had external fixation and 24 had a dorsal plaster cast. Five fractures in the plaster-cast group redislocated and were externally fixed at rereduction after the 11-day follow-up. Three patients in the external-fixation group had a noncomplicated pin-tract infection, and 1 patient had a transient sensory disturbance arising from the cutaneous branch of the superficial radial nerve. After 1 year, the patients allocated to primary external fixation had a better radiographic and functional end result; according to Lidström's grading, 19/22 were excellent or good after external fixation as compared with 12/19 after plaster-cast treatment.

Adult↗

PubMed1989

Treatment of open fractures of the tibial shaft: Ender nailing versus external fixation. A randomized, prospective comparison.

A randomized, prospective study comparing Ender nailing with external fixation for open fractures of sixty-three tibiae (sixty patients) was undertaken. Ender nailing proved to be at least as effective as external fixation with respect to seven parameters: time to union, tibial alignment, total number of operations, ranges of motion of the knee and ankle, pain, presence of infection, and complications. Ender nailing is a safe alternative to external fixation for grade-I and grade-II open fractures. It should not be used for comminuted fractures, which might shorten about the nails.

Adolescent↗

PubMed1987

Anatomic factors in the femoral implantation of the Ilizarov external fixator.

Ilizarov's method of external fixation with compression or distraction for lesions of the limbs demonstrates new possibilities in osteogenesis. Its performance with double horizontal pinning on several external rings calls for precautions to avoid lesions of the vessels, nerves and joints. This study, based on anatomic sections radiographed after opacification of the arterial system, makes it possible to propose rules for insertion of the pins. Insertion of the anteromedial pins of the thigh should be made 2 cm in front of the line of projection of the femoral artery, between the middle of the inguinal ligament and the posterior margin of the medial condyle. Insertion of the posterolateral thigh pins should be made 2 cm lateral to the line of projection of the sciatic nerve, between the center of the ischiotrochanteric interval, the apex of the popliteal fossa and the posterior aspect of the head of the fibula.

Bone Nails↗