Tibial plafond fractures: limited internal fixation and a hybrid external fixator.
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Adult↗
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Advantages and disadvantages of pinless external fixation.
The AO pinless external fixator (PEF) uses trocar tipped clamps to grip the outer tibial cortex rather than pins to transfix it. Its main advantage is to avoid further contamination of the medullary canal in open tibial fractures where a nail may subsequently be used. We tested the anatomical safety of this device and its effect on plastic surgical procedures compared with a standard unilateral external fixator (UEF).The PEF and UEF were placed on two amputated limbs which were then dissected. Structures at risk were traced on ten cadaver limbs. We found that important anatomical structures were endangered by the PEF and that safe zones could not always be defined. The UEF avoided these structures. Plastic surgical approaches were made more difficult by the PEF which imposed limitations on local flap design and endangered the arterial perforators which supply them. We conclude that safety is compromised by the PEF because margins for error are small. It poses additional problems in soft tissue reconstruction and highlights the need for co-operation between plastic surgical and orthopaedic teams in choice of fixation device.
Cadaver↗
Evaluation of fracture predilection in the calcaneus after external fixator pin removal.
OBJECTIVES/HYPOTHESIS: External fixators have been advocated for the treatment of intra-articular fractures of the distal tibia, so-called "pilon" or "plafond" fractures. Current recommendations include placement of external fixator pins, which vary in diameters up to six millimeters, in the talus and calcaneus. Removal of a relatively large pin may create a large defect in the bone, theoretically increasing fracture predilection with weight bearing. The objective was to compare the compressive load at failure of intact and formerly instrumented calcanei. It was hypothesized that the pin hole defect would not lead to a clinically significant difference in compressive load at failure. STUDY DESIGN: A biomechanical evaluation of randomized matched pairs of cadaveric calcanei. METHODS: Fresh human calcanei were harvested, embedded in casting compound, and tested pairwise. Among pairs of calcanei, one served as the control, and the other was drilled with a 6.0-mm pin in the posterior portion. The pin was removed before biomechanical evaluation. Testing was performed in compression under displacement control on a hydraulic materials testing system. RESULTS: There was a 22% reduction in compressive load at failure (p = 0.021) of the drilled versus intact specimens. Compared with intact calcanei, defect calcanei had a compressive failure load much closer to forces that might be encountered with walking and running. CONCLUSIONS: The six-millimeter-pin defect is a significant stress riser, and protected, progressive weight bearing after pin removal should be recommended.
Aged↗
The use of upper limb external fixation in paediatric trauma.
External fixation is an alternative method of treatment for paediatric fractures of the upper extremity. We report our experience of the management of 23 children with an average age of 10 years 1 month and review the literature. The method is indicated for second and third degree open fractures, open multiply injured patients and severely comminuted fractures. External fixation has proved unequalled for correction of limb deformities and lengthening procedures.
Adolescent↗
Mechanical comparison of two external fixator clamp designs.
OBJECTIVE: To compare two external fixation clamp designs for their ability to resist movement of a fixation pin in relation to the connecting rod. STUDY DESIGN: Two designs of external fixator clamps were attached to connecting rods mounted on a jig for mechanical testing. Fixator pins were placed perpendicular to the connecting rod. A mechanical testing machine was used to deflect each 3.2-mm pin at a distance that was 25 mm from the center of the clamp bolt. Both clamp designs were tightened to 4.4, 6.1, and 7.8 newton-meters (N x m) torque, and loads were applied in a position ramp through 4 mm and resisting loads were measured. Two clamp orientations were used during load application, such that the deflection of the pin tended to tighten the clamp bolt or tended to loosen the clamp bolt. The tests were videotaped to determine mode of failure. Comparisons of the load/displacement curves for the two external fixator clamp designs were made using nonlinear equational curve fitting methods. The resultant plateau and rise coefficients were compared using analysis of variance. RESULTS: Slippage of the pin in relation to the clamp occurred with the Kirschner-Ehmer clamp tightened to 4.4, 6.1, and 7.8 N x m, and slipping of the pin in relation to the clamp occurred with the experimental clamp design tightened to 4.4 and 6.1 N x m but not to 7.8 N m. At 7.8 N x m, the 3.2-mm pin deformed plastically with the experimental clamp design. Increasing the torque of the clamp bolt resulted in superior plateau coefficients for both clamp designs. At each level of tightness and in each clamp orientation to applied pin load, the experimental clamp design provided greater plateau coefficients than did the Kirschner-Ehmer clamp design. At 7.8 N x m of tightness, the Kirschner-Ehmer clamp and bolt bent, whereas only slight plastic deformation of the experimental clamp design occurred. CONCLUSIONS: The experimental external fixator clamp was more secure in resisting fixator pin movement at all levels of tightening compared with the Kirschner-Ehmer-type external fixator clamp. At 7.8 N x m of tightening, the new clamp design did not allow slippage of the pin within the clamp. CLINICAL SIGNIFICANCE: The experimental external fixator clamp should result in greater rigidity of fixator configurations, in addition to providing design features that allow addition of a clamp between two installed clamps, sleeved predrilling of pilot holes for all pins, measurement of pin depth, and placement of positive profile pins at all sites.
Animals↗
[External fixator: surgical technique, pinless fixator, change in procedure].
External Fixation-Technique: The advantages of external over internal fixation are as follows: a) endosteal and periosteal blood supply is undisturbed, b) "low-tech" equipment may be used, c) secondary adjustments are possible and d) easy implant removal. These benefits however are outweighed by the main disadvantages of long term external fixation i.e. pin complications and delayed union of fractures. Better understanding of postoperative management and careful application of screws of improved design will lead to better results. Today's standard applications of external fixation for tibial fractures is a unilateral fixator, using Schanz screws. The pin-bone interface is the most critical site of all external fixation. By avoiding heat necrosis (low temperature drilling) and preventing micro motion at the pin-bone interface (by applying bending- or more recently radial-preload), pin complications such as infection and loosening can be reduced. Two Schanz screws are inserted into each main fragment and are connected with one short tube per fragment. The fracture is then reduced by using these tubes as handles. After reduction a third tube connects the first two by means of two tube-to-tube clamps. This type of fixation will easily allow for three dimensional secondary corrections of alignment. Approximately three weeks following the injury some motion at the fracture site will stimulate callus formation. This can be achieved by destabilisation, dynamisation or "active stimulation" of the fracture site [2]. Pinless fixator: The pinless external fixator holds the fragments firmly with pointed clamps that penetrate about one millimeter into cortical bone without entering and contaminating the medullary canal.(ABSTRACT TRUNCATED AT 250 WORDS)
Equipment Design↗
Open tibial fractures: faster union after unreamed nailing than external fixation.
Unreamed intramedullary nailing is an alternative to external fixation in the treatment of open tibial fractures. We compared a prospective series of thirty-one patients managed with a solid nail with static interlocking without intramedullary reaming, with a retrospective series of thirty-one patients managed by external fixation. The protocol for soft tissue treatment was the same throughout the study period. Most fractures were caused by high energy trauma and included Grade I to III B injuries. The fracture wound infection rate was equal in both groups; there were two deep and three superficial infections in the nail group and three deep and two superficial infections in the external fixation group. In addition, eleven patients in the external fixation group had severe pin track infections. The mean time to union was five months in the nail group and eight months in the external fixation group. The incidence of delayed union was twice as high in the external fixation group as in the nail group. The number of surgical procedures performed to promote union was three times higher in the external fixation group. The malunion rate did not differ between the groups. Although the treatment groups are not fully comparable, the results indicate that intramedullary nailing is superior to external fixation in the treatment of most open tibial fractures.
Adolescent↗
Flexible external fixation for craniodorsal coxofemoral luxations in dogs.
An external fixator consisting of two Ellis pins connected by a flexible band was developed and evaluated as a treatment for craniodorsal coxofemoral luxations in dogs. The technique for closed application of the fixator without injury to the coxofemoral joint or sciatic nerve was developed in six dog cadavers. The coxofemoral joints were then surgically destabilized and the limbs were manipulated through a full range of motion to assess the efficacy of the fixator in maintaining joint reduction. The fixator maintained joint reduction and stability after a surgically created craniodorsal luxation except when the femur was externally rotated 90 degrees. A flexible external fixator was then applied unilaterally in four healthy dogs. The dogs tolerated the fixator well and were bearing weight on the limb within 2 days after surgery; the range of motion was not limited by the fixator. The efficacy of a flexible external fixator in maintaining joint reduction after craniodorsal coxofemoral luxation was then evaluated in eight large dogs. The right coxofemoral joint in each dog was luxated surgically by removal of the dorsal joint capsule and transection of the ligament of the head of the femur and deep gluteal muscle. The joint was reduced and the fixator pins were applied in a closed fashion. In four dogs, a flexible external band was applied to the pins. Luxation did not reccur in these four dogs. The bands were not applied initially in four control dogs. Luxation occurred in three of the four control dogs within 24 hours of surgery. The joints that luxated were reduced and the flexible bands applied. Luxation did not recur after the bands were in place. The dogs tolerated the external fixators well, were bearing weight within 2 days of surgery, and walking with only minimal lameness 5 days after surgery. Luxation of the coxofemoral joints did not occur during the 2-week period in which the fixators were in place. The joints remained stable 1 week after removal of the fixators, at which time the dogs were euthanatized. Necropsy evaluation identified inflammation surrounding the pins and fibrous thickening of the dorsal joint capsule. The flexible external fixators were applied closed, maintained reduction of the coxofemoral joint after replacement of a craniodorsal luxation, and allowed weight bearing and limb usage soon after surgery. The flexible external fixator has several advantages over other methods of treating craniodorsal coxofemoral luxations. Complications noted in this study included pin tract drainage, pin loosening, and disruption of the flexible bands.
Animals↗
[The echographic follow-up of patients treated with an external fixator in childhood and adolescence].
In the last few years external fixation has started to be extensively used in pediatric orthopedics and traumatology and ultrasound (US) monitoring has been adopted. The role of US was investigated in a study on 64 patients aged 2 to 30 years treated from November, 1989, to December, 1993. Some patients underwent several interventions with different methods and therefore belong to more than one of the three considered groups. In case of surgical lengthening (group A), the role of US was investigated in a study on 54 patients aged 2 to 26 years. The following variables were studied with US: diastasis entity, stump axis and the evolution of regenerated tissue within 10 days of the beginning of lengthening (first follow-up), at 20 days (second follow-up) and at 30 days (third follow-up). Ilizarov and Wagner fixators and one external fixation reduction fixator were used on 54 patients in 83 segments (43 femurs, 39 tibias and 1 humerus). In all, 104 corticotomies were performed. In fractures treated with external fixators (group B), US allowed the study of the hematoma surrounding the lesion and of its progressive evolution from fibrous tissue to bone callus, within 30 days of external fixation (first follow-up), at 60 days (second follow-up) and at 90 days (third follow-up). Eight patients were treated. The segments treated were 9 femurs and 2 tibias, 11 fixators in all. Patients age ranged 9 to 19 years. Five patients underwent corrective osteotomies with external fixators (group C), in which group US follow-up exams were not standardized. For all 252 US examinations, performed in real time, an Acuson 128 unit with a 5-MHz linear probe was used and anterior, median and lateral longitudinal scans were acquired.
Adolescent↗
Treatment of non-union of the humerus using the Orthofix external fixator.
An Orthofix monolateral axial external fixator was used to treat 31 patients with non-union of the humeral shaft, 30 of whom had been previously treated surgically. In seven cases the non-union was hypertrophic and one of these cases had been treated by simple fixation anol compression, the others by fixation, bone grafting and decortication; in 20 cases the non-union was hypotrophic and had been treated by fixation and decortication with bone grafting. The remaining four cases had septic non-union, treated by debridement of the focus of infection and fixation, followed in three cases by a bone graft and osteomuscular decortication once the infection had been eradicated. The fracture site consolidated in all patients in a mean time of 4.9 months. Five patients required further surgery: three in the group with infected non-union and two who had had a new bone graft and application of the external fixator, one because of a refracture (the patient was receiving chronic treatment with antimitotic agents) and one because of persistent non-union. There were no major complications (e.g. radial nerve palsy, joint stiffness, deep infection), and only six cases of pin track infection (5% of the screws implanted). The authors believe that this method is reliable, effective and low risk provided that the patient is cooperative; furthermore, the monolateral axial external fixator is tolerated well and allows movement of the shoulder and elbow throughout the period of treatment.
Adolescent↗
Suitability of external fixators for use in the tropics.
External fixation systems proved to decrease the osteomyelitis rate in patients in the tropics compared with internal stabilization. This study was designed to show how external fixators being used for treatment of patients in industrial countries compare with cheap alternatives regarding their suitability for the application in tropical countries. Eleven external fixation systems were compared for stability, cost, weight, variability, handling, and capability of being produced locally. Stiffness, slipping moment, and irreversible deformation were determined in material testing machines. The technically best fixators are expensive and cannot be manufactured locally. The inexpensive constructs lack variability and stability. When cost is not a problem, the Synthes model is recommended. With some restrictions in mechanical stability and variability, the Pfeifer Fixator II and a wooden model offer inexpensive and locally producible alternatives. These results may help to select an external fixation device to meet local needs and possibilities in tropical countries.
Biomechanical Phenomena↗
External fixator pin design.
The integrity of the bone-pin interface is the critical link in the stability of external fixation systems. External fixation pins placed in cancellous metaphyseal bone frequently loosen over time, resulting in fixation failure and an increased risk of infection. To design an external fixation pin with optimal bone-metal interface strength in cancellous bone, a systematic study of various thread design features was performed. Combinations of pitch, tooth profile, and minor diameter in 5 mm self-tapping half pins were evaluated in coaxial pullout testing using a fresh bovine cancellous bone. A significant increase in pullout strength was found with a decrease in minor diameter. No statistical differences were found in pullout strength attributable to thread profile and pitch. There were no significant interactions between minor diameter and tooth profile or minor diameter and pitch. The data obtained suggest significantly greater holding power in cancellous bone can be achieved by using an external fixation pin with a smaller minor diameter or a larger interference. Additional pullout testing of five commercially available external fixator pins was performed. Of these, the two pins with the largest interference demonstrated greater pullout strength. Therefore, within a range of acceptable major diameters and adequate minor diameters for the torsional strength requirements, an optimal interference for cancellous pin application may exist and it may well be larger than that present in currently available external fixation pins.
Animals↗
The role of external fixation in pelvic disruptions.
External fixation has a definite role in the management of pelvic fractures. Biomechanically, it is not useful for maintaining reduction of the unstable, vertically migrating pelvis and must be used with some other form of treatment, such as traction, spica cast, or internal fixation. In vertically stable fractures, that is, rotationally unstable fractures, the anteroposterior and lateral compression injuries, the external fixator should probably be the first course of treatment.
Adult↗
Structural stiffness and reducibility of external fixators placed in malalignment and malrotation.
OBJECTIVE: To determine the structural stiffness and reducibility of various external fixators placed in malalignment and malrotation. DESIGN: Uniform testing of all external fixator configurations. SETTING: Orthopaedic biomechanical laboratory. METHODS: Thirteen external fixators from different manufacturers, in a total of fifteen configurations, were studied. All external fixators were applied to a malreduction jig initially, and a subsequent anatomic reduction was then attempted. If an anatomic reduction was possible, the structural stiffness of those fixators was determined. If anatomic reduction was not possible, the external fixator was removed and reapplied to an anatomically reduced model, and then structural stiffness was determined. RESULTS: Six of the thirteen external fixator configurations allowed an anatomic reduction after placement on a malreduction model. The other nine external fixator configurations would not allow for an anatomic reduction. All the external fixator configurations were biomechanically tested in anteroposterior bending, lateral bending, axial load, and torsion. Each fixator had its own structural stiffness and is reported. CONCLUSIONS: Some external fixators will not allow for an anatomic reduction once placed in malalignment and malrotation without repositioning of the fixator pins. External fixator configurations (i.e., single-pin, dual-pin, and multipin barclamps) affect structural stiffness. Structural stiffness widely varied among the external fixators. Proper external fixator selection will enable early fracture immobilization in malalignment and malrotation in suboptimal conditions (e.g., wartime conditions or a civilian disaster), with subsequent external fixator adjustment for an anatomic reduction.
Biomechanical Phenomena↗
Treatment of tibial defect and bone nonunion with limb shortening with external fixator and reconstituted bone xenograft.
OBJECTIVE: To explore the effect of external fixator and reconstituted bone xenograft (RBX) in the treatment of tibial bone defect, tibial bone nonunion and congenital pseudarthrosis of the tibia with limb shortening. METHODS: Twenty patients (13 males and 7 females) with tibial bone defect, tibial bone nonunion or congenital pseudarthrosis of the tibia with limb shortening were treated with external fixation. Two kinds of external fixators were used: a half ring sulcated external fixator used in 13 patients and a combined external fixator in 7 patients. Foot-drop was corrected at the same time with external fixation in 4 patients. The shortened length of the tibia was in the range of 2-9 cm, with an average of 4.8 cm. For bone grafting, RBX was used in 12 patients, autogenous ilium was used in 3 patients and autogenous fibula was implanted as a bone plug into the medullary canal in 1 case, and no bone graft was used in 4 patients. RESULTS: All the 20 patients were followed-up for 8 months to 7 years, averaging 51 months. Satisfactory function of the affected extremities was obtained. All the shortened extremities were lengthened to the expected length. For all the lengthening area and the fracture sites, bone union was obtained at the last. The average healing time of 12 patients treated with RBX was 4.8 months. CONCLUSIONS: Both the half ring sulcated external fixator and the combined external fixator have the advantages of small trauma, simple operation, elastic fixation without stress shielding and non-limitation from local soft tissue conditions, and there is satisfactory functional recovery of affected extremities in the treatment of tibial bone defects, tibial bone nonunion and congenital pseudarthrosis of the tibia combined with limb shortening. RBX has good biocompatibility and does not cause immunological rejections. It can also be safely used in treatment of bone nonunion and has reliable effect to promote bone healing.
Adolescent↗
Structural stiffness of the Hoffmann simple anterior tibial external fixation frame.
Tibial external fixation frames were constructed on aluminum tube simulating tibia bone. A 20-mm gap was left at the fracture site in order to measure the structural stiffness of the frame rather than the aluminum tube. The performance of the frames were experimentally evaluated and quantified using tests which simulated the loading conditions encountered in normal walking. These included axial compression, anteroposterior (AP) bending, lateral bending and torsional loading of the frame. The parameters studied were (a) number of fixation pins, (b) number of connecting rods and (c) location of clamps on the pins. Four constants were evaluated from these tests using various structural configurations of the frames; these resulted in four stiffness coefficients in compression, AP bending, lateral bending and torsion. Stiffnesses of various frames with different geometric configurations were compared by comparing their appropriate stiffness coefficients. Such comparison can set forth a quantitative guideline in selecting a suitable frame configuration for the type of injury and condition of fracture pattern. This type of quantitative analysis can also be useful in modifying the frame during the postoperative bone healing process.
Equipment Design↗
Which external fixation device?
Seven external fixation frames which are used for the treatment of fractures have been evaluated. The features of these devices are presented and some of the advantages and disadvantages of each are described.
Bone Nails↗
Limb lengthening with the Ilizarov external fixator.
The Ilizarov External Fixator is used to lengthen or widen bones, to correct angular or rotational defects, or to immobilize fractures. This article discusses techniques of application and care of the device; physiology and mechanics of limb lengthening and bone regeneration; and nursing strategies to achieve patient compliance and prevent complications.
Bone Lengthening↗