External Skeletal Fixation Research Articles

Management of small infected tibial defects with antibiotic-impregnated autogenic cancellous bone grafting.

Between January of 1991 and December of 1993, 36 patients who had tibia fractures complicated by small infected tibia defects were treated at the authors' service. The group included 30 men and 6 women whose average age was 36.5 years (range, 18-72 years). The average follow-up period was 3.7 years. By using the Cierney-Mader staging classification of chronic osteomyelitis, 26 of 36 patients (72%) were stage 4A and 10 of 36 patients (28%) were stage 4B. Ten patients required muscle transfer. All patients were treated with a two-stage protocol. In the first stage, antibiotic-impregnated polymethylmethacrylate bead chains were used to obliterate the debrided osseous defect. In the second stage, the beads were removed, and the defects were reconstructed with antibiotic-impregnated autogenic cancellous bone graft. The time between the first and second stage was 2 to 8 weeks for patients without muscle transfer and 8 to 12 weeks for the patients with muscle transfer. The bone defects ranged from 2 to 4 cm. Wound healing and bony union were achieved in all patients. Only two patients had recurrent infections. The infection arrest rate was 94.4%. Minor pin tract infection of the external skeletal fixation was seen in two patients. Two patients developed skin rashes secondary to antibiotic therapy. Radiographs at an average follow-up of 3.7 years showed good consolidation and hypertrophy of grafted bones in all patients. After 3 to 5 years of follow-up, our results suggest that the use of impregnating antibiotics have no adverse effects on autogenic cancellous bone graft incorporation and may help to eliminate infection. This treatment protocol provided rapid recovery from osteomyelitis. The use of antibiotic-impregnated autogenic bone graft seems to be an effective and safe method for the management of small infected tibial defects.

Use of the modified acrylic external fixator in 54 dogs and 28 cats

This paper describes the use of acrylic resin instead of a Kirschner clamp for treating bone fractures. The technique is cheaper than using Kirschner external skeletal fixator and allows greater...

The importance of serial debridement and “second-look” procedures in high-energy ballistic and avulsive facial injuries

Facial gunshot and high-velocity avulsive injuries are a tremendous challenge to the reconstructive surgeon. The complexity of these injuries is represented by the potential for loss of mucosal lining, bone, and cutaneous covering, as well as the jeopardized relationships between the functional and aesthetic subunit of the head and neck region. Traditionally, wounds of this nature have been managed conservatively with initial débridement, external skeletal fixation, and delayed secondary reconstruction of the missing skeletal and soft-tissue components. In this review, a protocol designed to optimize the functional and aesthetic outcomes of the management of facial gunshot and avulsive wounds is presented. Treatment is divided into three distinct but overlapping phases. At the time of patient admission, a sequential and direct clinical and radiographic assessment is made to define the injury zones of the bone and soft tissue, as well as the zones of bone and soft-tissue loss. This is immediately followed by, wound stabilization in preparation for component tissue reconstruction within the first 7 to 10 days of admission. The goal is to anatomically reconstruct the skeletal buttresses and surround them with a stable vascularized lining and cutaneous envelop within the primary phase of wound healing, thereby avoiding reconstruction after secondary contraction has taken place.

Artrodese do joelho em cães pela fixação externa

Sete cães clinicamente sadios sofreram artrodese do joelho direito ou esquerdo. A imobilização foi realizada por meio de fixador externo com pinos de Steinmann e barras de acrílico autopolimerizável. Foram removidas todas as estruturas intra-articulares e seccionadas as superfícies articulares do fémur e da tíbia. Foi realizada enxertia com osso esponjoso autógeno entre os ossos e aplicada a imobilização mantendo o ângulo articular estabelecido no pré-operatório. Foi observado o retorno ao uso funcional do membro e foram feitos controles radiográficos no pós-operatório imediato, 30, 60 e 90 dias de evolução. Os aspectos da fusão articular foram avaliados macro e microscopicamente. Constatou-se que esse tipo de fixação promove retorno precoce ao uso do membro com desempenho funcional satisfatório, sendo eficiente para promover a artrodese da soldra.

Flexural and Torsional Analysis of Five Acrylics for Use in External Skeletal Fixation

SummaryMechanical testing of five acrylics was performed to evaluate material property differences that might affect their use as support rods in external skeletal fixation (ESF). Flexural and torsional analysis demonstrated that differences existed in the stiffness of the acrylics with polyethyl/polymethylmethacrylate products being the stiffest and a polyethylmethacrylate product being least stiff. Increasing the amount of inert filler also increased the stiffness. The inherent porosity of the individual acrylics did not have an effect on their mechanical properties. These differences in stiffness might affect fracture healing by affecting the amount of primary or secondary osteosynthesis that occurs.Different polymeric forms of acrylic possess mechanical properties that influence their stiffness. Based on flexural and torsional analysis, these properties may differ significantly and affect external skeletal fixator stiffness.Presented at the twenty-fourth annual meeting of the Veterinary Orthopedic Society, Big Sky, MT March 2-8, 1997.

Tarsocrural Arthrodesis: A Clinical Report Using a Circular External Fixator

SummaryArthrodesis is a well documented treatment option for comminuted intraarticular fractures, irreparable collateral ligament injuries, limb salvage for ischiatic nerve injury, and severe degenerative joint disease of the tarsocrural joint (1-6). Conservative splint or bandage application often results in a less than favorable outcome in the management of these types of injuries. Common techniques to achieve tarsocrural arthrodesis include divergent Steinmann pin placement, lag screw or compression plating and external skeletal fixation (1-5). This report describes a tarsocrural arthrodesis using a circular external fixation system to manage an open, severely contaminated, comminuted intra-articular fracture of the talus and calcaneous, with extensive soft tissue degloving injuries. The decision to use a circular external fixation system was based on its ability to (1) adequately stabilize the tibialtarsal region, (2) be applied with minimal soft tissue and vascular disruption, (3) allow adequate post-operative soft tissue wound management, and (4) be tolerated well by the patient allowing early weight bearing of the limb.Severe tarsocrural injuries were diagnosed on a four-year-old mixed breed dog including articular fractures of the tubercalcaneous, talus, fibula, multiple tarsal bones and the second metatarsal bone. A circular ring external fixator was used to arthrodese the joint. Twelve weeks following surgery the limb was functional without any mechanical gait alteration and with minimal to zero discomfort.

Backscattered Electron Imaging of the Calcified Tissues Present in Bone Healing

SummaryThe aspect of calcified tissues involved in fracture healing was studied by means of backscattered electron imaging. Bilateral transverse midshaft osteotomies were performed in the tibiae of 16 dogs. The osteotomies were reduced by means of a type II external skeletal fixator, and the clinical and radiographic course was assessed weekly until the moment of euthanasia, one, two, four and eight weeks after the operations. The osteotomized areas were removed and their structure examined in the scanning electron microscope, using backscattered electron images, to determine the general aspect of the extracellular matrix of the calcified tissues present. Four different tissues were observed: lamellar bone, woven bone, calcified cartilage and chondroid tissue. The backscattered electron contrast and fibre arrangement of the matrix, as well as the size and shape of the cellular lacunae, allow identification of the tissue. Chondroid tissue, which seems to have a leading role in the early phases of fracture healing, shows a characteristic pattern of a highly calcified and fibrous matrix with a large number of irregular and confluent cell lacunae.The morphological characteristics of the calcified tissues involved in fracture healing were studied by means of backscattered electron imaging. Lamellar bone, woven bone, calcified cartilage and chondroid tissue were the four calcified tissues observed during the healing process of canine midshaft tibial experimental fractures.

Microangiographic Pattern of Bone Healing in Canine Tibial Osteotomies Treated with Type II External Fixators

SummaryThe morphological aspects of the vascular response, which develops in the fracture-healing process of osteotomies treated with external fixators, were evaluated by means of microangiography. Bilateral transverse midshaft osteotomies were performed in the tibiae of 16 dogs. The osteotomies were reduced by means of a Type II external skeletal fixator, and the clinical and radiographic courses were assessed weekly until the moment of euthanasia. Four dogs each were euthanatized at one, two, four and eight weeks postoperatively. After heparinization and euthanasia both femoral arteries were perfused with micronized barium sulphate, and microangiograms were performed in decalcified mid-tibial sagittal slices. Initial intramedullary revascularization as well as gap supply were already observed in some one-week microangiograms, and they were well developed in all of the two-week microangiograms. A network of parallel extraosseous blood vessels, orientated perpendicularly to the cortical surface, first appeared in the two-week microangiograms. Four weeks after the osteotomy, the extraosseous network showed its greatest degree of development whereas in the eight-week microangiograms most of the osteotomies showed only some traces of the abovementioned vascular reaction. It can be concluded that the microangiographic pattern developed in external fixated osteotomies shows many similarities with those described in experimental fractures, reduced by other means, with the earlier development of all of the vascular phenomena being the most important difference.Microangiography was used to determine the morphological characteristics of the vascular response developed in the tibial experimental fractures healing process.

Bilateral Pes valgus Deformity in a Shetland Sheepdog

SummaryAn eight-month-old, 19.7 kg, male Shetland Sheepdog was diagnosed with a valgus deformity present in both hindlimbs. Anamnesis failed to reveal a traumatic incident to explain the deformities. Bilateral tibial osteotomies and placement of an external skeletal fixation were used in the correction of the defects. Several reports exist concerning angular limb deformities of the rear limb in Shetland Sheepdogs. These facts may represent a breed at risk for such defects.An eight-month-old Shetland Sheepdog with bilateral valgus deformities of the tibiotarsal joint was managed by staged bilateral corrective tibial osteotomies and placement of an external skeletal fixation. Reports of angular limb deformities of Shetland Sheepdogs are reviewed.

Staged management of infected humeral nonunion.

Fourteen patients with infected humeral nonunion complicated by sinus discharge were treated with a staged protocol consisting of (1) radical debridement with local antibiotic beads implantation, and (2) external skeletal fixation with autologous bone grafting. In the first stage, a thorough debridement and sequestrectomy were done. Antibiotic beads were used to obliterate the bone defect, and the wound was then directly closed. In the second stage, the bead chains were replaced with autogenous cancellous bone graft. Unilateral Hoffman external skeletal fixators were applied simultaneously. The mean follow-up period was 73.6 months (range, 29 months to 9 years). The length of time to achieve bony union ranged from 3.5 to 8 months (average, 4.3 months). Hoffman pin complication was found in two cases, which were then shifted to plate internal fixation. All the infections were eradicated, and the wounds healed without further skin graft or flap coverage. All the fractures achieved bony union except for one in a patient who died. Most patients acquired satisfactory function of elbow motion after removal of external fixation and physical therapy. The method of two-stage management was effective for infected humeral nonunion. Not only was the infection eradicated and osseous union achieved, but also the limb function and joint motion were preserved.

Epoxy Putty for Free‐Form External Skeletal Fixators

To evaluate the suitability of epoxy putty for use as a connecting beam material in a free-form external skeletal fixator. Mechanical evaluation of beams and the pin-material interface of commonly used methacrylates and the proposed epoxy putty. The apparent modulus, bending strength, and toughness of 10 beams of three methacrylates (Technovit, APEF System, Bone Cement) and three epoxy putties (Oatey Epoxy Putty, All-Metals PowerPoxy, and Plumber's PowerPoxy) were determined in three-point bending. The shear strength of smooth and roughened-shaft pins embedded in the three methacrylates and the Oatey Epoxy Putty was determined by pull-out testing. The epoxy putties had similar strength, greater apparent modulus, and reduced toughness when compared with the methacrylates. The shear strength of the smooth pin interface with the Oatey Epoxy putty was greater than that with the methacrylates. The interface with roughened pins was much stronger than that with smooth pins for all materials tested. Epoxy putty is a suitable material for free-form external fixators. It is easy to handle, inexpensive, and has suitable setting times and mechanical properties.

Open reduction and bone plate stabilization, compared with closed reduction and external fixation, for treatment of comminuted tibial fractures: 47 cases (1980–1995) in dogs

Objective To compare open reduction and bone plate fixation with closed reduction and external skeletal fixation as treatment for severely comminuted fractures of the tibia. Limb alignment, fracture reduction, operating time, hospitalization time, postoperative care, time to unrestricted activity, bone healing, complications, and number of surgical procedures were considered. Design Retrospective case series. Animals 47 dogs with severely comminuted fractures of the tibia treated with open reduction and bone plate application (22 dogs) or closed reduction and external fixation (25 dogs). Procedure Medical records of all dogs included in this study were reviewed. Postoperative and follow-up radiographs were evaluated by 2 independent observers. Results Differences were not found in hospitalization time, time to unrestricted activity, or time to earliest radiographic evidence of bone healing between dogs with fractures treated with a bone plate and dogs with fractures treated with an external fixator. Fractures treated with an external fixator had more caudal malalignment, and fractures treated with a bone plate had more valgus malalignment. Malalignments were determined not to be related to clinical problems. Dogs with fractures treated with an external fixator had shorter surgery times and more recheck examinations. Dogs with fractures treated with a bone plate had more complications. Clinical Implications Open reduction with bone plate fixation and closed reduction with external fixation were both effective for treatment of comminuted tibial fractures. External fixation was associated with shorter surgery time, but dogs required more extensive postoperative care. Bone plate fixation was associated with more complications. (J Am Vet Med Assoc 1997;211:1008–1012)

Management of large infected tibial defects with antibiotic beads local therapy and staged fibular osteoseptocutaneous free transfer.

Fifteen patients with tibial fractures complicated by large infected tibial defects were treated with a two-stage protocol. In the first stage, antibiotic-impregnated polymethylmethacrylate bead chains were used to obliterate the debrided osseous defect, and a meshed porcine skin was used for temporary wound coverage. In the second stage, the bead chains were removed, and the defects were reconstructed with a microvascularized fibular osteoseptocutaneous free transfer. The time between the first and second stages of treatment was 2 to 6 weeks. The bone defects ranged from 6 to 16 cm, and the skin defect areas ranged from 10 to 82 cm2. Wound healing and bony union were achieved in all 15 cases. An additional muscle flap or skin graft was required for only three patients with a large skin defect. Minor pin tract infections were seen in two patients. Stress fractures in three cases were successfully managed with bracing, external skeletal fixation or plating, and cancellous bone grafting. All of the most recent roentgenograms showed good consolidation and hypertrophy of grafted fibular bones. No recurrence of osteomyelitis was observed during an average follow-up period of 50 months (range, 36-86 months). We therefore conclude that this treatment protocol provides rapid recovery from osteomyelitis. The fibular osteoseptocutaneous graft is a useful method for the reconstruction of a large tibial defect, and it also offers the unique advantage of simultaneously reconstructing a moderate skin defect.

Dissipation of heat during polymerization of acrylics used for external skeletal fixator connecting bars.

To determine the amount of heat conducted by transfixation intramedullary pins (IP) and Kirschner wires (KW) during polymerization of acrylics used for external skeletal fixator (ESF) connecting bars. Thermal conduction was measured using thermistors applied to IP and KW surfaces during the polymerization phase of acrylics. Type II ESF were created from IP or KW placed into wooden dowels and plastic tubing used to create connecting bars filled with one of two types of acrylic (Acrylic Pin External Fixation System or Technovit, Jorgensen Laboratories, Loveland, CO). Thermistors were positioned on the acrylic column surface and on IP or KW surfaces 5 or 10 mm from the acrylic column. Five ESF test groups were created. The maximum temperature (Tmax) of the acrylic column (Tmax-A), IP (Tmax-IP), KW (Tmax-KW), and duration that Tmax-IP or Tmax-KW remained greater than or equal to 55 degrees C were calculated. All IP and KW thermistors placed 5 mm from acrylic columns reached mean temperatures greater than 50 degrees C and had peak temperature ranges greater than 55 degrees C compared with all IP and KW thermistors placed 10 mm from the acrylic columns in all groups. Thermistors placed 5 mm from the acrylic column in two groups maintained temperatures greater than 55 degrees C for greater than or equal to 0.5 minute. Acrylic columns positioned 5 mm from a thermistor on a IP or KW had the potential to reach or exceed temperatures that have been reported to cause thermal necrosis of tissues. Acrylic Pin External Fixation System or Technovit acrylic connecting bars used in ESF designs have the potential to cause thermal injury to soft and bony tissue by thermal conduction along transfixation pins or wires.

External skeletal fixation for stabilisation of comminuted humeral fractures in cats

Thirteen feline humeral fractures were stabilized using external skeletal fixation alone or in combination with supplementary devices. Eleven of the 13 fractures healed. Pins placed in the distal humerus should be angled to avoid the supracondylar foramen and radial nerve. An intramedullary pin in combination with external skeletal fixation is indicated for mildly comminuted reconstructable fractures. For severely comminuted humeral fractures, closed application of an external skeletal fixator may be preferable to open reduction and internal fixation to provide healing and is recommended as an alternative to amputation.

Biomechanics of the Gazi type pelvis external skeletal fixator.

External skeletal fixation is an alternative method of treatment to conventional therapy and open surgical procedures in pelvis fractures. The appropriate type of frame and the configuration of the connecting bars of these fixators are under investigation. In the Gazi type pelvis external fixator (GPEF) which has been developed, a 70 degree angulation is applied to the connecting bars of the anterior quadrangular frame. This configuration, which is expected to improve the stability of the posterior column of the pelvis, was evaluated biomechanically on a phantom with various types of pelvic fractures and separations. The results suggest that the GPEF effectively controls anterior column pelvis fractures such as unilateral pubic ramus fractures, unilateral ischium pubis rami fractures and symphysis pubis separations under vertical loads. The fixator is partially capable of stabilizing the posterior column; however, loads above 700 N cause separation at the fracture site. Further studies and clinical trials are essential to determine the GPEF's effectiveness in reducing blood loss and in providing stability at the posterior column.

Vascular Injury and Delayed Hemorrhage after Antebrachial External Skeletal Fixation in a Dog

SummaryA seven-month-old female Saluki was diagnosed with angular limb deformity due to premature closure of the left distal ulnar physis. Corrective radial osteotomy and ulnar ostectomy were performed, and the radius was stabilized with external skeletal fixation. Profuse haemorrhage occurred from the second medioproximal pin site two weeks after surgery. Removal of the pin resolved the hemorrhage. Early recognition and treatment of vascular injury secondary to vessel erosion after external skeletal fixation is necessary, as this is a serious complication. Appropriate pin placement in the radius will prevent this complication.Two weeks after application of an external skeletal fixator to the antibrachium of a seven-month-old Saluki profused haemorrhage occurred from one pin site. Surgical removal of the pin was necessary to arrest haemorrhage.

A Comparison of the Mechanical Properties of Two External Fixator Designs for Transarticular Stabilization of the Canine Hock

SummaryBiomechanical testing was performed on 20 canine tibiotarsal joints. The conventional transarticular external skeletal fixator (ESF) was applied to one rear limb while the alternative design using acrylic was applied to the contralateral rear limb. The mode of failure for all models was fracture of the phalanges at the point of fixation in the distal grip device.The mean stiffness for the acrylic design was 58.5 N/mm and for the conventional ESF 44.8 N/mm. The mean maximum load to failure for the acrylic design was 490.7 N, compared to 405.1 N for the conventional ESF. The angle of deformation at maximum for the acrylic apparatus was 0.45 degrees compared to 2.36 degrees for the standard ESF. The mean energy absorbed to maximum load was 1.92 N-m for the acrylic design and for the conventional ESF 2.69 N-m. This study indicated that the acrylic design was superior in maintaining immobilization across the tibiotarsal joint, indicated by the angle of deformation (p = 0.002) and was structurally comparable in stiffness (p = 0.295), maximum strength (p = 0.438), and total energy absorbed to failure (p = 0.276).The properties of an acrylic and a stainless steel external transarticular skeletal fixator were biomechanically evaluated. Biomechanical parameters evaluated included: maximum load to failure, stiffness, angle of deformation across the tibiotarsal joint, and energy absorbed to failure. The angle of deformation was less (p = 0.002) for the acrylic device. Based on this study, we conclude that the new acrylic design is structurally comparable to the conventional transarticular ESF and warrants clinical trials.

A Review of 116 Clinical Cases Treated with External Fixators

SummaryOne hundred and sixteen clinical cases (113 dogs) in which the external skeletal fixation was applied as the primary method of stabilization were reviewed. The 116 clinical cases were divided into the following groups: open fractures (41 cases); gunshot fractures (8 cases); comminuted fractures (11 cases); fractures affecting immature animals (11 cases); trans-articular application of external fixators (16 cases); corrective osteotomies (4 cases) and “simple” fractures (25 cases). History and signs of the animal (breed, age and weight), location and treatment of the fracture, healing time and functional recovery were evaluated in each case and discussed for every group. The mean healing time in the different groups ranged from 4.6 wks (immature animal’s fractures) to 13 wks (gunshot fractures). With reference to the functional recovery, in 14 cases (12.1%) the results were poor, in 57 cases (49.1%) the results were good and in 45 cases (38.3%) the results were excellent. The main complications observed were delayed union, non-union and osteomyelitis.One hundred and sixteen clinical cases of fractures (113 dogs) were treated with a »Meynard« external fixator. The cases were divided in 7 groups: open fractures, gunshot fractures, comminuted fractures, fractures affecting immature animals, trans-articular application of external fixators, corrective osteotomies and »simple« fractures. Each case is reviewed and a discussion is provided for each group.

Improved osseointeraction of calcium phosphate-coated external fixation pins. Studies in calves.

We investigated osseointeraction of solution-precipitated calcium phosphate (SPCP)-coated transfixation pins used in external skeletal fixation of a calf stable fracture model. One group (SPCP) received centrally-threaded transfixation pins which had SPCP coating; the other group (control) received identical, but not coated, pins. Radiographs were obtained 1 and 40 days after surgery and examined for evidence of osteolysis. Bone phase 99mTc-MDP studies were performed 6 and 28 days after surgery. Calves were killed 40 days after surgery and mechanical tests performed. Dual-energy x-ray absorptiometry (DEXA) and histomorphometric analyses were done. A smaller proportion of SPCP pins (5/24) had evidence of discharge during the study compared with control pins (21/24). A smaller proportion of SPCP pins (4%) had radiographic evidence of osteolysis compared with control pins (42%). Uptake of 99mTc-MDP was similar for SPCP and control calves. Uptake was significantly greater in bone segments showing radiographic evidence of osteolysis than in bone segments not having osteolysis. Yield stress (MPa) for axial displacement was similar in the treatment groups. Bone mineral density was less in SPCP pins. Affinity index and interface histologic score were greater and osteoclastic index less in SPCP calves. Coating of transfixation pins with solution-precipitated calcium phosphate improved the osseointeraction of pin and bone during this 40-day study.