Influence of an interdental full pin on stability of an acrylic external fixator for rostral mandibular fractures in dogs
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Abstract Objective —To determine total stiffness and gap stiffness of an external fixation system in a canine mandibular fracture gap model incorporating a full interdental pin as the only point of rostral fixation in a bilateral type-I external fixator. Sample Population —10 canine mandibles. Procedure —Bilateral mandibular ostectomies were performed between premolars 3 and 4. A type-I external fixator incorporating a full interdental pin was placed to stabilize a 0.5-cm fracture gap. Four pin configurations (intact mandibular bodies with fixator; ostectomized mandibular bodies and complete fixator; ostectomized mandibular bodies with caudal pins of rostral fragment cut; ostectomized mandibular bodies with all pins of rostral fragment cut) were tested in dorsoventral bending 5 times on each mandible. The full interdental pin remained intact in all configurations. Total stiffness and gap stiffness were determined for each configuration on a materials testing machine. Results —Total stiffness of intact mandibles was significantly greater than that of ostectomized mandibles, regardless of external fixator configuration. However, total stiffness and gap stiffness were not significantly different among different external fixator configurations applied to ostectomized mandibles. Conclusion and Clinical Relevance —External fixator configurations with only the full interdental pin engaging the rostral fragment were as stiff as configurations that had 2 or 4 additional pins in the rostral fragment for the applied loads. External fixators for rostral mandibular fractures may be rigidly secured with rostral fragment implants applied extracortically, avoiding iatrogenic trauma to teeth and tooth roots. ( Am J Vet Res 2001;62:576–580)Keywords:
Interdental consonant
Mandible (arthropod mouthpart)
Mandibular fracture
Abstract Objective —To determine total stiffness and gap stiffness of an external fixation system in a canine mandibular fracture gap model incorporating a full interdental pin as the only point of rostral fixation in a bilateral type-I external fixator. Sample Population —10 canine mandibles. Procedure —Bilateral mandibular ostectomies were performed between premolars 3 and 4. A type-I external fixator incorporating a full interdental pin was placed to stabilize a 0.5-cm fracture gap. Four pin configurations (intact mandibular bodies with fixator; ostectomized mandibular bodies and complete fixator; ostectomized mandibular bodies with caudal pins of rostral fragment cut; ostectomized mandibular bodies with all pins of rostral fragment cut) were tested in dorsoventral bending 5 times on each mandible. The full interdental pin remained intact in all configurations. Total stiffness and gap stiffness were determined for each configuration on a materials testing machine. Results —Total stiffness of intact mandibles was significantly greater than that of ostectomized mandibles, regardless of external fixator configuration. However, total stiffness and gap stiffness were not significantly different among different external fixator configurations applied to ostectomized mandibles. Conclusion and Clinical Relevance —External fixator configurations with only the full interdental pin engaging the rostral fragment were as stiff as configurations that had 2 or 4 additional pins in the rostral fragment for the applied loads. External fixators for rostral mandibular fractures may be rigidly secured with rostral fragment implants applied extracortically, avoiding iatrogenic trauma to teeth and tooth roots. ( Am J Vet Res 2001;62:576–580)
Interdental consonant
Mandible (arthropod mouthpart)
Mandibular fracture
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Objective:To assess the efficacy of introral open reduction of mandibular body fractures using a 2.0-mm titanium miniplate rigid fixation without maxillomandibular fixation(MMF). Method:47 mandibular fractures in 29 patients were included in this study. A Triangular maxillomandibular wire fixation in bilateral molars and incisor regions and interdental wire fixation beside the fracture lines were adapted after manual reduction prosoperatively. After the mandibular arch has been returned to premorbidity and fixed primarily, a transoral mucoperiosteal incision was made to reveal the fracture lines and fragments, one or two 2.0-mm titanium miniplate were adapted along Champy's lines of ideal osteosynthesis and secured with 8.0-mm monocortical screws after the bone fragments have been reduced appropriately.Panoramic radiograph and clinical examination were applied one day and three months after the operation to exhibit bone union and occlusion . The other complications were also assessed. Result: All patients displayed satisfactory occlusion and bone union without evident complications. Conclusion: A transoral 2.0-mm miniplate rigid fixation after a temporary triangular maxillomandibular wire fixation and interdental wire fixation beside the fracture lines was appropriate to mandibular fractures. MMF was not nessesory.
Interdental consonant
Mandibular fracture
Osteosynthesis
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Interdental consonant
Mandibular fracture
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Maxillomandibular fixation (MMF) is usually used to treat double mandibular fractures. However, advancements in reduction and fixation techniques may allow recovery of the premorbid dental arch and occlusion without the use of MMF. We investigated whether anatomical reduction and microplate fixation without MMF could provide secure immobilization and correct occlusion in double mandibular fractures.Thirty-four patients with double mandibular fractures were treated with open reduction and internal fixation without MMF. Both fracture sites were surgically treated. For bony fixations, we used microplates with or without wire. After reduction, each fracture site was fixed at two or three points to maintain anatomical alignment of the mandible. Interdental wiring was used to reduce the fracture at the superior border and to enhance stability for 6 weeks. Mouth opening was permitted immediately.No major complications were observed, including infection, plate exposure, non-union, or significant malocclusion. Five patients experienced minor complications, among whom the only one patient experienced a persistant but mild malocclusion with no need for additional management.This study showed that double mandibular fractures correction with two- or three-point fixation without MMF simplified the surgical procedure, increased patient comfort, and reduced complications, due to good stability and excellent adaptation.
Interdental consonant
Mandibular fracture
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Mandible (arthropod mouthpart)
Bony union
Mandibular fracture
Mandibular angle
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Mandibular fracture
Bite force quotient
Mandible (arthropod mouthpart)
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New composite hybrid fixators for fracture stabilization using single or multiple rings with monolateral bars and half-pin fixation may provide clinical advantages such as reduced bulk and easier skin access. However, the mechanical properties of these fixators are difficult to estimate from numerous design parameters. Addressing this problem the following research questions were asked: (1) Do composite hybrid fixators have similar stiffness properties to clinically proven triple-ring fixators; (2) How does the fixation mechanism affect the stiffness properties of external fixators, and, (3) Are there interferences between ring number and fixation method? An experimental study was done on simulated metaphyseal tibial fractures and stiffness of 12 fixators was measured for different loading conditions. The results showed that triple-ring fixators provide approximately 20% stiffer properties than double-ring and single-ring fixators. No influence of ring number on the AP bending properties was found and different fixation methods were associated with large differences in fixator stiffness, whereas significant interferences were found between ring number and fixation method. Although the mechanical properties investigated in the current study cannot predict directly the clinical performance of these fixators, the stiffness data provide useful information for making decisions regarding the treatment of fractures using external fixation.
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Clinical and experimental studies have shown that several mechanical factors influence the fracture healing process. One such factor, interfragmentary movement, is affected by loading and the stiffness of the fixation device. This study evaluated the stiffness of different external fixation devices for a rat femoral fracture model, using in vitro and analytical methods. The contribution to the stiffness of the fixation construct was dominated by the flexibility of the pins in relation to their offset, diameter, and material properties. The axial stiffness increased with decreasing offset and increasing pin diameter. Titanium pins resulted in significantly lower axial stiffness compared to stainless steel pins of the same design. The fixator body material and fixator length had a less pronounced influence on fixation stiffness. Mechanically characterized external fixation devices will allow in vivo study of the fracture healing process utilizing pre-calculated fracture fixation stiffness. These characterized fixation devices will allow controlled manipulation of the axial and shear interfragmentary movement to achieve a flexible fixation resulting in callus formation compared to a more rigid fixation limiting callus formation in a rat femoral fracture model.
Biomechanics
Limiting
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Background Despite the published clinical evidence of the implementation of external fixation of proximal femoral osteotomies, there is lack of specific laboratory justification. Methods Two groups of 5 adult composite femur constructs of varus proximal femoral osteotomy were tested under incremental and cyclical loading of up to 600N along the mechanical axis. Five were fixed with a blade plate and another 5 with a monolateral external fixator. Load versus displacement curves were produced, and passive stiffness of all constructs was calculated. The described loading regime aimed to simulate the initial postoperative state and provide data for the assessment of vertical intrinsic passive stiffness in partial weight-bearing conditions. Results Although the blade plate constructs showed higher average stiffness, this was not statistically significant [F(1,8)=1.712, P=0.23]. No construct failed. No failure or plastic deformation was observed under the described loading regime. Conclusions Vertical intrinsic passive stiffness in partial weight-bearing conditions during the initial postoperative period can be considered satisfactory subsequent to unilateral external fixation of a varus intertrochanteric osteotomy. Clinical Relevance The results support the hypothesis that external fixation is a biomechanically sound alternative to internal fixation of varus intertrochanteric osteotomies, in selected patients.
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To describe a novel fixation of open, unstable, unilateral mandibular fractures applying a locking compression plate as an external skeletal fixator (ESF-LCP).Four horses and one dromedary.Short case series.Animals presented with unstable, open, unilateral fractures of the mandible. Fracture fixation was performed under general anesthesia. A 4.5/5.5 narrow LCP was applied externally above the level of the skin and combined with intraoral tension band wiring.Fracture fixation was achieved successfully using an ESF-LCP. Minimal tissue manipulation was required during application and removal of the construct. The ESF-LCPs provided adequate access to the wounds at the fracture site, were well tolerated, and did not interfere with any objects in the animals' environment. Mild drainage at the screw-skin interface developed in all cases, requiring early implant removal due to surgical site infection in one case. The use of longer plates was associated with superficial pressure necrosis of the skin in the masseter area in two cases. Implants were removed after 3 to 12 weeks, and the long-term functional outcome after 11 to 41 (median 13) months was good in all cases.Stabilization of mandibular fractures with ESF-LCP led to good outcomes in this case series. The use of longer plates positioned more caudally and in a ventrolateral position seemed associated with surgical site infection and pressure necrosis of the skin.Use of a locking compression plate as an external skeletal fixator seems to offer a viable alternative to treat unilateral mandibular fractures, especially when these are open and/or infected.
Mandibular fracture
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