History of external skeletal fixation

Use of external fixators in developing countries: a short socioeconomic analysis

The use of external fixators (EFs) dates back to 377 BC Hippocrates’ time, and it has a wide range of orthopaedic applications. External fixator has expanded its use in the management of fractures and other musculoskeletal conditions. It is widely used all over the world to manage complex musculoskeletal injuries. It has many advantages as compared to internal fixation in some trauma scenarios. However, the cost of the external fixators presents a dilemma to the healthcare system in developing countries. The goals of this review article are to explain the importance of EFs in developing countries in managing fractures, to determine the problems encountered at present during external fixation by developing countries, to identify solutions that could be used to address these issues, expand the use of external fixation into other domains of treatment, the impact of COVID-19 pandemic on fracture management based on existing literature. In conclusion, EFs are very expensive, researches have been conducted to overcome these barriers in developing countries. However, there are limitations in implementing in developing countries. It is important to have affordable and clinically acceptable EFs available in developing countries.

Effect of Bidirectional Insertion of External Skeletal Fixation Pins on Axial Pullout Strength in Canine Cadaveric Bone

OBJECTIVE

 The aim of this study was to evaluate the effect of bidirectional insertion on axial pullout strength of tapered run out (TRO), traditional negative profile (TNP) and positive profile (PP) pins.

STUDY DESIGN

 Cadaveric adult canine tibiae were harvested. Tapered run out pins (Group 1) were inserted unidirectionally to the desired position; bidirectionally past the desired position, then withdrawn to the desired position (Group 2); and bidirectionally as described for Group 2, repeated twice (Group 3). Traditional negative profile pins (Group 4-6) and PP pins (Group 9-11) were placed in the same manner. Tapered run out (Group 7), TNP (Group 8) and PP pins (Group 12) were driven unidirectionally such that the shaft of the pin violated the cis-cortex. A servohydraulic testing machine extracted the pins and measured axial peak pullout strength.

RESULTS

 Positive profile pins had significantly greater pullout strength than TRO and TNP pins placed unidirectionally to the desired position. Method of insertion had no effect on peak pullout strength of TNP pins. TRO and PP pins inserted unidirectionally to the desired position had significantly greater peak pullout strengths than insertion bidirectionally or if the shaft of the pin violated the cis-cortex.

CONCLUSION

 The authors recommend that pins used for external skeletal fixation should be placed unidirectionally to the desired position with fluoroscopic guidance, intra-operative depth gauge measurements or measurements from preoperative radiographs. Repositioning pins results in loss of peak pullout strength with TRO and PP pins.

The tell-tale thigh

A body of a 91-year-old donor underwent whole-body CT scanning before being transferred for use in an anatomical dissection course. Metallic objects were detected in the thigh muscles, extensive bone abnormalities were found in the left femur and the diaphysis of the left femur was 50% wider than that of the right diaphysis. History revealed that the body donor had been seriously wounded at the end of World War II by a rocket explosion. His multiple fractures and lesions had not been surgically treated either in an Austrian military hospital or in a French prisoner of war camp. The patient suffered for almost 70 years from this violation of the Geneva Conventions. In the light of current armed conflicts, the present case is an example of how one injustice can result in severe, lifelong medical consequences. It also shows that the history behind a wounded thigh can have an enormous impact on teaching ethics to today's medical students.

In vitro biomechanical testing of different configurations of acrylic external skeletal fixator constructs

OBJECTIVE

To evaluate the in vitro biomechanical properties of four different configurations of acrylic external skeletal fixator constructs.

MATERIALS AND METHODS

Simulated bone constructs were prepared using two segments of 20 mm ultra-high-density polyethylene rods with a gap of 5 mm. The full pins (1.5 mm) were passed through the proximal and distal segments of ultra-high-density polyethylene rods, in the same plane, parallel to each other in configuration U, and were crossed in the M1, M2 and C configurations at a 90° angle to each other. Configuration U was a single bilateral uniplanar construct, M1 was a double orthogonal bilateral construct, M2 was a double orthogonal bilateral construct with proximal and distal connecting articulations, and C was a double orthogonal bilateral construct with proximal and distal circumferential articulations. Temporary scaffolds of different external skeletal fixator configurations were constructed using commercially available polyvinyl chloride pipes (20 mm) connected and secured to the fixation pins at a fixed distance from the rods. Acrylic powder (polymer) mixed with liquid (monomer) was poured into the pipes and allowed to solidify to form the side bars and rings. The external skeletal fixator constructs were then subjected to axial compression, cranio-caudal three-point bending and torsion (n = 4 each) using a universal testing machine. Mechanical parameters, namely stress, strain, modulus of elasticity, stiffness and bending moment of fixator constructs, were determined from load-displacement curves.

RESULTS

Configuration U was the weakest and configuration C was the strongest under all the testing modes. Under compression, the M1, M2 and C configurations were similar. Under bending, a significant difference was observed among the uniplanar, multiplanar and circular configurations with no difference between M1 and M2. However, under torsion, all the external skeletal fixator configurations differed significantly.

CLINICAL SIGNIFICANCE

The freeform external skeletal fixator using acrylic as a replacement for a metallic bar may be useful to treat bone fractures and luxations in small animals, as it is mechanically strong, lightweight, economical, and pins can be passed from any direction depending upon the clinical situation.

The relevance of threaded external skeletal fixation pin insertion speed in canine bone with and without predrilling

OBJECTIVES

The effects of insertion speed in revolutions per minute (RPM) and pilot hole predrilling for placement of threaded external skeletal fixation pins on temperature and morphological damage in cortical bone were evaluated. The null hypothesis states that insertion speed and predrilling will have no significant effect on temperature and morphological damage.

METHODS

Fixation pins were inserted into cadaveric canine femurs at speeds of 700 RPM and 150 RPM, with and without pre-drilling. Temperature was measured at each cortex 0.5 mm and 3.0 mm from each insertion site. Samples were examined grossly and by scanning electron microscopy for evidence of morphological damage. Data were analysed for maximum temperature, temperature increase, sites above thermal necrosis thresholds, microcracks, thread quality and gross damage.

RESULTS

Predrilling had a significant effect on maximum temperature, temperature increase, sites exceeding necrosis thresholds, microcracks, thread quality and gross damage. Speed of insertion had no significant effect on any of the measured parameters following predrilling, but had a significant effect on thread quality without predrilling.

CLINICAL SIGNIFICANCE

Our results fail to reject the null hypothesis concerning insertion speed, which had no significant effect on thermal damage, and minimal effect on morphological damage, which was negated by predrilling. Our results reject the null hypothesis concerning predrilling and support the practice of predrilling fixation pin insertion sites.

Treatment of comminuted tibial shaft fractures in four dogs with the use of interlocking nail connected with type I external fixator

The treatment of comminuted tibial shaft fractures in canine patients is burdened by significant risk which involves bone healing complications, such as delayed bone union. Complications may result from iatrogenic damage to blood vessels during fracture stabilization. To minimize this risk, treatment methods increasingly often rely on the concept of biological osteosynthesis. One of such methods involves the treatment of fractures with the use of new hybrid fixator consisted of an interlocking nail connected with type I external fixator. Connection of the nail with external fixator has been recently developed to maximize treatment efficiency. This manner of stabilization increases bone-fixator construct strength on forces acting in the place of fracture. It also enables fracture fixation with minimal damage of the blood supply of bone fragments. This article describes surgical procedure of stabilization of comminuted tibial bone fractures in four dogs by the use of interlocking nail connected with external fixator type I, discusses and evaluates the results of clinical treatment with the involvement of the said fixator. To control bone consolidation process the radiograms were taken in 6 and 8 week of healing. In all cases, the reviewed methods of clinical treatment were successful in producing bone union after eight week of healing. During the whole period of observations no complication was observed. In all cases the intramedullary nail were left in the medullary canal after the healing process was finished. The fixator supported quick restoration of limb function after treatment.

Treatment of canine and feline diaphyseal radial and tibial fractures with low-stiffness external skeletal fixation

The healing of 62 cases of radial and tibial fractures treated with low-stiffness Kirschner-Ehmer external skeletal fixation frames (frame types 1a, 1a plus intramedullary pin [1aIMP], 1b and 2b) was evaluated. The mean time to clinical union was 65 days. All cases treated with 1b, 2b or 1aIMP frames healed. Four of 25 cases treated with 1a frames failed to heal due to premature pin loosening; these failures were in heavier patients than 1a cases which healed (P=0.041). Complications occurred in 40 of 62 cases, and were more common in cases treated with type 2b frames. Pin loosening was the most frequent complication (35 cases) and most commonly involved the most proximal pin (P<0.001). In type 2b frames, full pins loosened more frequently than half pins (P<0.001). This study indicates that canine and feline fractures can heal readily when treated with these frames, suggesting that more rigid type 2a or type 3 frames are unnecessary in the majority of cases. Increased morbidity compared with the use of more rigid frames need not be expected, but 1a frames should be avoided in heavier patients.

A mechanical comparison of veterinary linear external fixation systems

OBJECTIVE

To compare the fixation rigidity of recently developed external fixation systems (EFSs) to that of the traditional Kirschner-Ehmer (KE) system.

STUDY DESIGN

In vitro biomechanical study.

SAMPLE POPULATION

Five different EFSs (KE, Secur-U, small SK carbon fiber, small SK titanium, large SK carbon fiber) were assembled into 7 frame geometries to stabilize Delrin plastic rods with a 1-cm gap.

METHODS

External skeletal fixation (ESF) constructs were tested in axial compression, torsion, medial-lateral bending, and cranial-caudal bending. Testing was conducted within the elastic range of each fixator. Mean stiffness in each mode was determined from the slope of the linear portion of the load-deformation curve. Comparison of stiffness values of each EFS within each loading mode and frame type was performed with 1-way analysis of variance (P <.05).

RESULTS

Mean stiffness values were significantly higher for the large SK EFS in all frame types compared with KE but were equal in torsional stiffness in the double-bar type 1a frame. The small SK EFS with titanium connecting bar had greater stiffness than the KE in all modes for frame types Ia, Ia-accessory bar, and II-modified. No overall difference was detected between the KE EFS and the small SK with carbon fiber rod. The stiffness of the Secur-U type Ia frame with augmentation plate was significantly greater than the KE type Ia with accessory bar.

CONCLUSIONS

The newer external fixation systems evaluated in this study provided fixation rigidity equal to or greater than that of the KE system.

CLINICAL RELEVANCE

EFSs with increased frame rigidity should permit the use of less complex frame designs while providing fracture stability.

Use of IMEX SK-circular external fixator hybrid constructs for fracture stabilization in dogs and cats

Complex long-bone fractures with short juxta-articular fracture segments can be difficult to manage. Recently, IMEX Veterinary, Inc., began producing titanium hybrid rods that can be secured to ring components of the IMEX circular external skeletal fixation system to create SK-circular hybrids. In this case series, SK-circular hybrids were used to stabilize long-bone fractures (two femoral, one humeral, and three tibial fractures) with short distal bone segments in three dogs and three cats with body weights ranging from 1.9 to 15 kg (mean, 6.7 kg; median, 5.4 kg). Although three cases required surgical revision, animals ambulated well and all fractures obtained union. Time to radiographic union ranged from 62 to 137 days (mean, 90 days; median, 84 days). The functional outcome was considered excellent in all six cases.

Recent advances in external skeletal fixation

While the use of external skeletal fixation was once associated with substantial postoperative morbidity, clinical and experimental studies have led to technological advances and modifications in application techniques that have greatly improved the results obtained with this treatment modality. The past decade saw numerous advances in external skeletal fixator implants, components and instrumentation, including improvements in fixation pin design, and the development of new linear external skeletal fixation systems and economical circular external skeletal fixation systems specifically engineered for use in dogs and cats. In addition, a greater understanding of fixator biomechanics and the pathobiology of the bone-fixation pin interface have improved fixator application practices. This article reviews many of the more significant recent advances in external skeletal fixation.

External skeletal fixation. Linear fixators

Linear external skeletal fixators offer some unique advantages over other fixation systems; they are biomechanically versatile, minimize surgical trauma to the fracture environment, and allow for simple staged disassembly to help promote bone healing. Historically, the use of linear external skeletal fixators has been reported to result in numerous complications, primarily related to the pin-bone interface. External skeletal fixators have experienced a resurgence in the past two decades. Increased knowledge of proper pin insertion techniques and advancements in pin design have greatly enhanced the longevity of the pin-bone interface, resulting in fewer complications. This article reviews some of the potential advantages of linear external skeletal fixators and principles of application to help strengthen the pin-bone interface and minimize complications.

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.

Use of external skeletal fixators in the repair of femoral fractures in cats

This paper reports the results of fixation of 35 femoral fractures in cats using an external skeletal fixator alone or in combination with supplementary devices. All the fractures healed. The average time to fixator removal was eight weeks and two days. The external skeletal fixator offers a method of repairing many types of femoral fractures in cats allowing sound orthopaedic principles to be maintained and producing a successful outcome.

A comparison of acute pull-out strength between two-way and one-way transfixation pin insertion for external skeletal fixation in canine bone

This study tested the hypothesis that two-way insertion of an external skeletal fixator transfixation pin would weaken the pin-bone interface. Smooth and partially threaded (end) transfixation pins were placed in tibiae of 32 cadavers by slow speed drilling or hand placement through a predrilled pilot hole. In one bone of each tibial pair, pins were inserted 2 cm beyond the distal cortex and retracted to a predetermined position (two-way). In the contralateral limb, the pins were inserted in one forward motion to the predetermined position (one-way). The peak force (Newtons) required to extract the pins (pull-out strength) axially at a rate of 1 mm/sec was determined by using a universal testing machine. A significant (p < .05) decrease in pull-out strength was found in pins placed by two-way insertion (674 +/- 410) as opposed to one-way insertion (766 +/- 432). The results of this in vitro study suggest that one-way insertion should be used clinically to decrease weakening of the pin-bone interface and prevent possible failure of external fixators. A significantly greater pull-out strength was found for threaded pins placed in the proximal diaphysis (1459 +/- 330 Newtons) compared to the distal metaphysis (873 +/- 297 Newtons).