Biomechanical comparison of strategies to adjust axial stiffness of a hybrid fixator

Comparison between Areas of Bone Visualization Using Radiolucent Hybrid Fixator Frames and Graphically Simulated Metallic Frames: An Ex Vivo Study

The objective of this study is to evaluate the difference between the amount of bone visible with the superimposition of a radiolucent hybrid external fixator and a graphically simulated metallic frame. Eighteen frames were applied to eighteen bone specimens. The fracture area (FA), the radiolucent area (RLA) and the radiopaque area (ROA) inside the FA were calculated for each construct on both postoperative views. The ratio between the RLA and FA and between the ROA and FA was used to evaluate the amount of bone visible in the FA with a radiolucent and a radiopaque fixator, respectively. Finally, the areas of RLA and ROA were compared using the Wilcoxon test and Friedman test to evaluate the effect of the radiolucent material on the amount of bone visible. Differences were considered significant if p < 0.5. In every specimen p was <0.5. The amount of bone visible was significantly higher with the radiolucent frame compared to the radiopaque frame. Based on the results of this study, the use of radiolucent materials can be a valuable option for external fixation, in order to decrease the radiographic interference of the frame, allowing better assessment of fracture reduction and bone healing on postoperative radiographs.

Pes varus correction in dachshunds with mini hybrid external skeletal fixators

AIM

To evaluate the clinical and radiographic outcome of pes varus deformity correction in dachshunds managed with acute medial opening wedge osteotomy of the distal tibia and stabilised with a mini hybrid external skeletal fixator (HESF).

METHODS

Surgical correction involved a transverse osteotomy over the premeasured location at the distal tibia and application of a IMEX mini HESF. All corrections were evaluated using centre of rotation and angulation methodology.

RESULTS

Medical records and radiographies of 20 dachshunds (28 pes varus corrections) were reviewed. All osteotomies healed and fixators were removed between 6 and 12 weeks. Lameness resolved in 18 dachshunds (90%) and significantly improved in two dachshunds (10%). Lateral patella luxation (LPL) was detected in 11/28 (39.2%) of the involved pelvic limbs, all of which resolved following pes varus correction. Mean frontal plane alignment (FPA) of the normal and abnormal tibiae were 12.3° valgus (range: 4°-18°) and 25° Varus (range: 16°-41°) respectively. Angular correction ranged between 30° and 50° (Mean: 39°) and the mean post-operative FPA was 13° valgus (range: 5°-21°).

CLINICAL SIGNIFICANCE

Pes varus deformity in dachshunds can be corrected by medial opening wedge osteotomy of the distal tibia stabilised by HESF. Single-session bilateral pes varus corrections can also be performed with minimal morbidity. LPL was commonly detected in dogs with pes varus deformity and all resolved spontaneously following pes varus correction alone.

Open Tibial Fracture in a Non-Compliant Patient: A Case Report

Open tibial fractures represent the most frequent fractures of long bones, comprising approximately 1.9% of all fractures. Although locked intramedullary nailing is the gold standard for treating closed and unstable tibia diaphyseal fractures, for most exposed fractures, an external fixator can first be used, followed by conversion through an intramedullary nail. The present report describes the case of a 17-year-old male who presented with a complex multi-segmented displaced tibia fracture, type 42-C3, with exposure of IIIB type according to the Gustilo–Anderson classification, and with an attached disrupted fracture of peroneal malleolus, type 44-B2. External fixation was the preferred treatment method. Before the definitive surgical treatment, the patient had a second accident that caused refracture and damage to the soft tissues and external fixation system. This prolonged the time estimated for the conversion from the external fixator to the intramedullary nail. The reported case shows the use of various treatment steps with different timelines and an intervention with vacuum-assisted closure therapy for soft tissue healing as well as subsequent intramedullary nailing in order to reach the definitive healing of a non-compliant patient. These combined methods achieved an acceptable reduction and good stability of such a complex fracture.

Open Tibial Fracture in a Non-Compliant Patient: A Case Report

Open tibial fractures represent the most frequent fractures of long bones, comprising approximately 1.9% of all fractures. Although locked intramedullary nailing is the gold standard for treating closed and unstable tibia diaphyseal fractures, for most exposed fractures, an external fixator can first be used, followed by conversion through an intramedullary nail. The present report describes the case of a 17-year-old male who presented with a complex multi-segmented displaced tibia fracture, type 42-C3, with exposure of IIIB type according to the Gustilo-Anderson classification, and with an attached disrupted fracture of peroneal malleolus, type 44-B2. External fixation was the preferred treatment method. Before the definitive surgical treatment, the patient had a second accident that caused refracture and damage to the soft tissues and external fixation system. This prolonged the time estimated for the conversion from the external fixator to the intramedullary nail. The reported case shows the use of various treatment steps with different timelines and an intervention with vacuum-assisted closure therapy for soft tissue healing as well as subsequent intramedullary nailing in order to reach the definitive healing of a non-compliant patient. These combined methods achieved an acceptable reduction and good stability of such a complex fracture.

Evaluation of the accuracy of a veterinary dynamometric wire tensioner

OBJECTIVES

The purpose of this study was to determine the accuracy of a commonly used veterinary wire tensioner.

METHODS

Wire tension was measured using a load cell after each of five tensioners were used to tension each of six wires to the 66, 84, and 118 mm ring settings in an adjustable custom testing fixture. Each tensioner then experienced simulated aging and testing was repeated. Percentage error was calculated for each ring size, before and after tensioner aging. Measured tension values were compared to manufacturer reported tension values for each ring size using a one-sample two-way t-test; p <0.05 was considered significant.

RESULTS

Compared to the manufacturer reported values, measured wire tension values were significantly lower for 66 mm and 84 mm rings and significantly higher for 118 mm rings, before and after simulated aging. Mean wire tension values did not significantly differ between individual wire tensioners.

CLINICAL SIGNIFICANCE

The tensioners tested achieved significantly different wire tension values than those reported by the manufacturer. This discrepancy could lead to under-tensioning and allowing excessive movement at a fracture site or over-tensioning, leading to wire breakage. We recommend tensioning wires at least to the recommended line on the device for 66 mm and 84 mm rings and at most to the recommended line for 118 mm rings. Further studies are needed to evaluate other veterinary wire tensioners and to develop a calibration method for these devices in practice.

Evaluation of sixty-eight cases of fracture stabilisation by external hybrid fixation and a proposal for hybrid construct classification

Background

Hybrid external fixation (HEF) is an emerging technique for fracture stabilization in veterinary orthopedics, but its use has been reported in few papers in the veterinary literature. The linear and circular elements that form hybrid fixators can be connected in a very high number of combinations, and for this reason just referring to HEF without any classification is often misleading about the actual frame structure. The aim of this study was to retrospectively evaluate fracture stabilization by HEF in 58 client-owned dogs and 8 cats, and to extend the already existing classification for hybrid constructs to include all frame configurations used in this study and potentially applicable in clinical settings. Animal signalment, fracture classification, surgical procedure and frame configuration were recorded. Complications, radiographic, functional and cosmetic results were evaluated at the time of fixator removal.

Results

Sixty-eight fractures in 58 dogs and eight cats were evaluated. Two dogs had bilateral fractures. Fifty-one percent were radio-ulna, 34% tibial, 9% humeral, 3% femoral and 3% scapular fractures. One ring combined with one or two linear elements was the most widely employed configuration in this case series. Radiographic results at the time of frame removal were excellent in 59% of the cases, good in 38% and fair in 3%, while functional and cosmetic results were excellent in 69% of the cases, good in 27% and fair in 4%.

Conclusions

HEF is a useful option for fracture treatment in dogs and cats, particularly for peri and juxta-articular fractures. It can be applied with a minimally invasive approach, allows adjustments during the postoperative period and is a versatile system because of the large variety of combinations that can fit with the specific fracture features. The classification used enables to determine the number of linear and circular elements used in the frame.