Stress protection by external fixation of the rabbit tibia

Osteopenia of the tibia and femur caused by an external fixator in the tibia was studied in 14 rabbits. Eight rabbits were treated with a complete unilateral external fixator in one tibia, whereas the other tibia served as a control. The other 6 animals had one leg operated on with inserting of all the pins but without the frame. This technique was chosen to compare osteopenia caused by stress protection and the effect of the pins. After 6 weeks, we found a 7 percent reduction in the bone mineral content in the tibial diaphyseal segment between the pins of the external fixator and no bone loss in the tibia that were operated on with only pins. In the femurs, there was a smaller decrease in the bone mineral content: respectively 3.2 percent (complete frame) and 2.9 percent (only pins). On all the operated on tibiae, there was an increase in the bone mineral content around the pins both proximally and distally.     

Piroxicam-induced reduction in osteopenia after external fixation of rabbit tibia

Twelve rabbits were treated with a unilateral external fixator in one tibia for 12 weeks, while the other tibia served as an intact control. Half of the animals were also treated with 10 mg/kg/day of piroxicam, given in two daily oral doses. Changes in bone mineral content were determined using single photon absorptiometry. After 12 weeks, we found a 3 percent decrease in the bone mineral content in the tibia of the animals treated with piroxicam versus 9 percent in the nonpiroxicam group (P = 0.04). In the femurs, there was an insignificant decrease in bone mineral, 2 percent (piroxicam) and 1 percent (nonpiroxicam) respectively. The results indicate that piroxicam may reduce the osteopenia caused by external fixation.     

Piroxicam-induced reduction in osteopenia after external fixation of rabbit tibia

Twelve rabbits were treated with a unilateral external fixator in one tibia for 12 weeks, while the other tibia served as an intact control. Half of the animals were also treated with 10 mg/kg/day of piroxicam, given in two daily oral doses. Changes in bone mineral content were determined using single photon absorptiometry. After 12 weeks, we found a 3 percent decrease in the bone mineral content in the tibia of the animals treated with piroxicam versus 9 percent in the nonpiroxicam group (P = 0.04). In the femurs, there was an insignificant decrease in bone mineral, 2 percent (piroxicam) and 1 percent (nonpiroxicam) respectively. The results indicate that piroxicam may reduce the osteopenia caused by external fixation.     

A study of external skeletal fixation systems for unstable pelvic fractures

This study was undertaken to determine the feasibility of constructing an anterior pelvic external fixator capable of resisting displacement of vertical shear fractures. Newly designed tapered thread pins for cancellous bone had better bone pin fixation and their greater 6-mm diameter provided more than twice the stiffness of Hoffmann 4-mm pins when tested in clusters. Using these pins and a more rigid anterior frame as one model, various pelvic fixators were tested to determine their resistance to vertical shear forces. These tests determined that this new fixator was 16 times stiffer than a Bonnel single anterior frame and five times stiffer than a double anterior frame (both constructed of Hoffmann components). Extrapolation from the data shows that 13 mm of posterior fracture displacement would occur with loads of one half body weight using the new fixator. Additionally it was noted that Hoffmann frames constructed with two 5-mm pins performed as well as those using three 4-mm pins.     

Stability of an ankle arthrodesis fixed by cancellous-bone screws compared with that fixed by an external fixator. A biomechanical study.

Twenty-three fresh-frozen human specimens were subjected to ankle arthrodesis and fixation with two cancellous-bone screws. The specimens were then subjected to four newton-meters of manually applied tibial torque, plantar flexion-dorsiflexion moment, and medial-lateral bending moment; relative rotation between the tibia and the talus was recorded for each mode of testing. A Calandruccio triangular compression device was then applied to threaded pins penetrating the tibia and talus, the screws were removed, and the test sequence was repeated. Tibiotalar motions recorded with both systems of fixation were markedly affected by the quality of the bone. When less than 2 degrees of total tibiotalar rotation was recorded in response to four newton-meters of manually applied internal-external tibial torque, all specimens demonstrated less torsional rotation with the screw fixation than with the external fixator. The mean rotations produced by medial-lateral bending moment were equivalent for both systems of fixation. When torsional rotations with the use of screw fixation were greater than 2 degrees, all specimens demonstrated more torsional rotation with the screws than with the external fixator, and all but one specimen had more medial-lateral rotation with the screws than with the fixator. For applied plantar flexion-dorsiflexion moment, twenty-two of the twenty-three specimens demonstrated more rotation with the Calandruccio fixator than with the screws; this was due in part to motion permitted at the hinge points of the frame itself.     

Bone and muscle mass after hip arthroplasty: A quantitative computed tomography study in 20 arthrosis cases

We performed a prospective, quantitative computed tomography (QCT) study of bone mineral density (BMD), cortical bone volume, bone mass and muscle volume in 20 patients who were operated on with cemented total hip arthroplasty because of unilateral arthrosis. Both extremities were measured preoperatively, 3 and 6 months after the operation by a single-energy computer tomograph equipped for bone mineral densitometry.

Preoperatively, we found a 25 percent decrease in muscle volume of the thigh on the arthrosis side compared to the contralateral side, but only a 6 percent decrease in bone mass, mainly of the cortical bone volume in the middle femur. In the cancellous bone of distal femur and proximal tibia there was a reduction in BMD of 11 and 14 percent, respectively, compared to the contralateral side. After 6 months, we found no changes in cortical bone mass, either on the operated femur or on the contralateral, control femur. The BMD of cancellous bone in distal femur and proximal tibia had not changed. However, the thigh muscle on the operated side showed a strong recovery; 6 months after the operation there was a 19 percent gain on the operated side.     

Complications of external fixation of open fractures of the tibia

Forty-two cases of open fractures of the tibia treated by external fixation are presented. Forty-three per cent of patients developed sepsis around one or more pins. Pin track sepsis occurred in 78 per cent of cases involving transfixion pins through muscle and bone but in only 17 per cent of cases using transcutaneous half-pins. Malalignment of more than 5 degrees in any plane was seen in 38 per cent of cases, almost half of which increased in plaster after removal of the fixator.     

Stress-protection after external fixation on the intact rabbit tibia

Bone loss due to the stress-protecting effect of a metal plate on intact bone is a well-known phenomenon. The purpose of the present study was to find whether a similar effect is caused by external fixation. External mini-fixation was applied on the intact rabbit tibial diaphysis of one leg. The other tibia served as control. The animals were sacrificed after 6 or 12 weeks, and both tibiae biomechanically tested in three-point bending. The bone mineral content was measured by photon absorptiometry. No significant changes in bone strength, stiffness or mineral content were found after 6 weeks. The strength and stiffness were significantly reduced after 12 weeks. The median strength and stiffness at that time were 87 and 88 per cent, respectively, in relation to the control bones. The mineral content in the bone segment which had been stabilized by external fixation was significantly reduced after 12 weeks (median 90 per cent of the values for the control bones). No significant change in the mineral content occurred at a level in the tibial diaphysis distal to the external fixation device. It is concluded that the stress-protecting effect caused by external mini-fixation on the rabbit tibia occurs later, and is less pronounced, than that caused by metal plates.     

Stability of external fixators used for knee arthrodesis after failed knee arthroplasty

Secondary arthrodesis as treatment for failed knee arthroplasty is being used increasingly. The usual method is sustained rigid external fixation. The fusion rate is low in cases with considerable metaphyseal bone loss and poor bone quality. Currently, the Hoffmann- Vidal fixator or comparable designs are preferred to the less stable Charnley single frame fixator. The standard Hoffmann- Vidal device uses only transverse percutaneous fixating pins and gives an anteroposterior bending stiffness that is considerably lower than the lateral bending stiffness. In the present study, external fixators were tested for stability in a material testing machine under standardized conditions using synthetic bones. The anteroposterior bending stiffness was significantly improved when sagittal pins connected to a ventral compression rod were added to a Hoffmann- Vidal fixator. Stiffness was still more improved when sagittal pins were connected to ventral frames as in a modification of the Hoffmann- Vidal or the similar Ace-Fischer fixator.     

The unilateral axial dynamic fixator study of its biomechanical property and clinical application

The home made UADF after Bastiani's pattern was mechanically tested in our lab on fracture of cadaveric femurs. For comparison, the same test was also carried out with conventional semicircular external fixator. The results showed that the rigidity and stability of fixation closely related with the diameter of the bone-pin used. The diameter of the treated pins used in UADF was one time larger than that of the round pin used in conventional semicircular external fixator. The compression rigidity of the former frame was 3.5 times stronger than that of the latter one; the extent of displacement of the fragments happened in the former frame was much less than that occurred in the latter one. Clinical Application of UADF. on fracture of tibia and fibula in 31, of femur in 8, knee arthrodesis and osteotomy of tibia and fibula one in each, brought bony healing on successfully. It is apparent that the UADF is multifunctional, universal and adaptable in use, leading to success.     

Internal stabilization after external fixation of fractures of the shaft of the tibia: sense or nonsense?

A series of 95 patients with fresh fractures of the shaft of the tibia, treated primarily with a Vidal-Adrey transfixation frame, was studied retrospectively. Only 20 fractures (21.0 per cent) attained clinical and radiological consolidation within 4 months after injury. Pseudarthrosis was seen in 12 patients (12.9 per cent). The external fixator was attached for an average time of 25.0 weeks. Pin loosening was seen in seven patients (7.3 per cent), minor pin track infection in nine (9.4 per cent) and major pin track infection in three (3.1 per cent). In 31 patients (32.6 per cent) a second operative procedure was necessary to accelerate fracture healing. In 17 patients an autologous bone graft was carried out with the external fixator in place. Internal stabilization was performed after removal of the external fixator frame in 14 cases, at an average time of 9.4 months after injury. In difficult fractures we feel that change from external to internal fixation should be performed earlier; it makes early removal of the fixator pins possible and prevents the problems associated with prolonged use of fixator frames. The internal fixation, eventually combined with a transplantation of cancellous autografts, creates a mechanical and biological stimulus for bone consolidation. Functional recovery may also be improved because of a shorter healing time.     

Antimicrobial efficacy of external fixator pins coated with a lipid stabilized hydroxyapatite/chlorhexidine complex to prevent pin tract infection in a goat model.

BACKGROUND: Pin tract infection is a common complication of external fixation. An antiinfective external fixator pin might help to reduce the incidence of pin tract infection and improve pin fixation. METHODS: Stainless steel and titanium external fixator pins, with and without a lipid stabilized hydroxyapatite/chlorhexidine coating, were evaluated in a goat model. Two pins contaminated with an identifiable Staphylococcus aureus strain were inserted into each tibia of 12 goats. The pin sites were examined daily. On day 14, the animals were killed, and the pin tips cultured. Insertion and extraction torques were measured. RESULTS: Infection developed in 100% of uncoated pins, whereas coated pins demonstrated 4.2% infected, 12.5% colonized, and the remainder, 83.3%, had no growth (p < 0.01). Pin coating decreased the percent loss of fixation torque over uncoated pins (p = 0.04). CONCLUSION: These results demonstrate that the lipid stabilized hydroxyapatite/chlorhexidine coating was successful in decreasing infection and improving fixation of external fixator pins.     

Limb lengthening and correction of deformity in the lower limbs of children with osteogenesis imperfecta

We performed limb lengthening and correction of deformity of nine long bones of the lower limb in six children (mean age, 14.7 years) with osteogenesis imperfecta (OI). All had femoral lengthening and three also had ipsilateral tibial lengthening. Angular deformities were corrected simultaneously. Five limb segments were treated using a monolateral external fixator and four with the Ilizarov frame. In three children, lengthening was done over previously inserted femoral intramedullary rods. The mean lengthening achieved was 6.26 cm (mean healing index, 33.25 days/cm). Significant complications included one deep infection, one fracture of the femur and one anterior angulation deformity of the tibia. The abnormal bone of OI tolerated the external fixators throughout the period of lengthening without any episodes of migration of wires or pins through the soft bone. The regenerate bone formed within the time which is normally expected in limb-lengthening procedures performed for other conditions. We conclude that despite the abnormal bone characteristics, distraction osteogenesis to correct limb-length discrepancy and angular deformity can be performed safely in children with OI.     

Modulation of the soft tissue reactions to percutaneous orthopaedic implants.

To evaluate soft tissue reactions and biofilm formation on percutaneous external fixator screws coated with diamond-like carbon (DLC) and hydroxyapatite (HA) coatings on stainless-steel (SS) pins in an ovine loaded osteotomy model, an Orthofix external fixator was used to stabilize a 3-mm tibial midshaft osteotomy with six tapered pins inserted into the right tibia of 32 skeletally mature Friesland ewes. Animals were divided into four groups; SS, fully coated HA, DLC, and HA-coated threads. At 10 weeks, specimens were harvested and the pins were removed en bloc to examine the interfaces between the surface coatings and the tissues. Fully coated HA pins had a significantly higher percentage of dermal contact with the pin surface than HA-coated threads (p=0.028). The presence of a biofilm was evident on all pin surfaces except DLC-coated pins. Significantly greater numbers of bacteria were present on fully coated HA and plain stainless-steel pins compared with DLC. The surface of DLC-coated pins had a significantly lower number of bacterial colonies compared to SS (p=0.028) and fully coated HA pins (p=0.005). Fully coated HA pins have greater dermal attachment to the pin surface than the other pin coatings investigated. DLC-coated pins have the potential to prevent biofilm formation and bacterial colonization that may reduce infection and consequent pin loosening. An external fixator pin that is partially coated with HA to encourage bone and soft tissue integration and with DLC to reduce biofilm formation is advocated.     

Stress-Protection After External Fixation on the Intact Rabbit Tibia

Bone loss due to the stress-protecting effect of a metal plate on intact bone is a well-known phenomenon. The purpose of the present study was to find whether a similar effect is caused by external fixation.

External mini-fixation was applied on the intact rabbit tibial diaphysis of one leg. The other tibia served as control. The animals were sacrificed after 6 or 12 weeks, and both tibiae biomechanically tested in three-point bending. The bone mineral content was measured by photon absorptiometry.

No significant changes in bone strength, stiffness or mineral content were found after 6 weeks. The strength and stiffness were significantly reduced after 12 weeks. The median strength and stiffness at that time were 87 and 88 per cent, respectively, in relation to the control bones. The mineral content in the bone segment which had been stabilized by external fixation was significantly reduced after 12 weeks (median 90 per cent of the values for the control bones). No significant change in the mineral content occurred at a level in the tibial diaphysis distal to the external fixation device.

It is concluded that the stress-protecting effect caused by external mini-fixation on the rabbit tibia occurs later, and is less pronounced, than that caused by metal plates.     

The small pin circular fixator for distal tibial pilon fractures with soft tissue compromise

A Monticelli-Spinelli small pin circular external fixator was used in combination with closed reduction or a limited open reduction internal fixation in five cases in an attempt to salvage a satisfactory result in distal tibia pilon fractures when associated soft tissue compromise prevented standard fixation with plates and screws. The small pin fixator enhances the ability to perform a closed reduction through a technique that uses distraction with pins in the tibia and calcaneus, combined with correction of angulation by tensioning wires with a stop nut. Small pin stabilization of these comminuted fractures allows early patient mobilization. The small diameter pins support the soft cancellous bone fragments. This technique attempts to combine the benefits of traction, external fixation, and limited internal fixation. We recommend this technique as a salvage procedure when plates and screws are contraindicated because of poor bone and soft tissue conditions.     

Accelerating bone formation and earlier healing after using demineralized bone matrix for limb lengthening in rabbits.

We studied the effects of grafting with demineralized bone matrix during lengthening of the tibia in young Japanese White rabbits. The demineralized bone matrix was made from frozen cortical bone harvested from other rabbits. A 5-mm gap was created in the tibial diaphysis by a subperiosteal osteotomy; a maximum of 20 mm (2-3 mm/day) of tibial lengthening was reached in a week with use of an external fixator. The control group of 20 rabbits did not receive an implant; the group of 21 experimental rabbits received an implant of demineralized bone matrix in the surgical gap. The control group failed to demonstrate radiographic callus 5 weeks after surgery, and nonunion was persistent after 1 year. In the group with demineralized bone matrix, new radiodensity was demonstrated within the lengthening gap at 3 weeks, with a gradual increase in bone density to 85% that of the intact tibia after 12 weeks. Bone union was seen within 1 year for all experimental animals for whom the external fixator was removed 8 weeks after the procedure. These bones showed normal bone structure histologically. The lengthening was carried out at a rapid distraction rate of 2-3 mm/day; therefore, this method allows for satisfactory bone formation at a faster rate than normal.     

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.     

Single local injection of recombinant fibroblast growth factor-2 stimulates healing of segmental bone defects in rabbits

The effects of a single local injection of recombinant human fibroblast growth factor-2 on the healing of segmental bone defects were evaluated in rabbits. One month after the external fixator originally designed for this experiment was installed in the tibia of the rabbit, a 3-mm bone defect was created by an osteotomy in the middle of the tibia and 0, 50, 100, 200, or 400 μg of fibroblast growth factor-2 in 100 μg of saline solution was injected into the defect. Injection of the growth factor increased the volume and mineral content of newly made bone at the defect in a dose-dependent manner with significant effects at Concentrations of 100 μg or greater. These significant effects were observed at 5 weeks and later. One hundred micro-grams of the growth factor increased the volume and mineral content of newly made bone by 95 and 36%, respectively, at 5 weeks. These results indicate that a single local injection of fibroblast growth factor-2 stimulates the healing of segmental defects. We speculate that such an injection could be clinically useful for the healing of fractures even when the fracture gap is rather large.     

A Novel technique of three-ring Ilizarov fixator frame in gap non-union of tibia

IntroductionGap non-union of tibia occurring mostly after trauma and many times complicated by infection, is a difficult problem to treat. The study aimed to assess the outcome of the three-ring construct of the Ilizarov fixator frame in the management of gap non-union of the tibia.MethodsThis retrospective study included 30 patients of gap non-union of tibia operated from April 2016 to March 2019 with a three-ring Ilizarov fixator frame and follow-up done till March 2021. The mean age was 39.27 (range 10–66) years. The results were assessed by the Association for the Study and Application of the Method of Ilizarov (ASAMI) criteria. MPTA, PPTA, and LDTA after removal of the frame were also measured.ResultsOut of the total 30 cases, all the patients showed complete union. The Ilizarov fixator was kept for an average period of 11.43 months and the mean defect size was 7.17 (range 2–12) cm. All patients were followed up for an average period of 39.36 (range 24–54) months. According to the ASAMI score bone/radiological results, 27 were classified as excellent, 2 as good, and 1 as poor. Functionally 28 were graded as excellent and the remainder as good. The normal ranges of MPTA, LDTA & PPTA were also achieved in a majority (80%) of patients.ConclusionOur results after using only a three-ring Ilizarov fixator frame are almost equivalent to earlier studies and have advantages such as less weight, better patient compliance, superior radiographic visualization, easy mobilization, and reduced costs. Ilizarov ring fixator remains an excellent treatment modality for tibial non-union with a defect, regarding bone union, deformity correction, infection eradication, limb-length achievement, and limb function.