Radius/Ulna Fractures

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Radius/Ulna Fractures

Laurent P. Guiot and Reunan P. Guillou

14.1 Introduction

Traumatic radius and ulna (antebrachial) fractures are common in dogs and cats and often require surgical treatment for optimal outcome (Figure 14.1). The current standard‐of‐care techniques involve open reduction of the fracture and placement of either a bone plate (applied on the cranial or medial radial surfaces) or closed reduction with an external skeletal fixator (ESF) [13]. The choice of implants is dictated by patient size, fracture configuration, and surgeon preference. In particular, locking plates have recently become an attractive alternative to conventional plating for the treatment of radius and ulna fractures. In this chapter, we will review specificities of locking plate application for traumatic antebrachial fractures, including the types of approaches and fracture reduction techniques that can be used with this type of implant.

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Figure 14.1 Medio‐lateral (a) and cranio‐caudal (b) radiographic images of a radius‐ulna fracture treated with a splint for 16 weeks. There is a hypertrophic nonunion with moderate periosteal proliferation on the cranial aspect of the proximal radial fragment and obliteration of the medullary cavity at the fracture ends.

Conventional osteosynthesis (CO) of radius fractures has been associated with fair to good clinical outcomes with reported healing times of 54–90 days. Unfortunately, complication rates of up to 48%, including delayed healing, infection, pin track drainage (when using ESF) and implant failure, have been reported (Figure 14.2) [49]. Furthermore, 25% of these complications are severe and include catastrophic failure of the repair and nonunions. These shortcomings likely result from a combination of factors, including poor fracture biology and inappropriate mechanical environment. As a result, longer healing times may be expected, and, accordingly, relatively strong bone plates are often used in an attempt to prevent implant fatigue failure before bone union occurs [8, 10, 11]. This strategy, however, may result in significant osteopenia of the bone underneath the plate and increases the risk of secondary fracture. This risk is further potentiated with the use of open approaches that disrupt fracture biology, and during which relatively short plates are typically used, creating stress concentration at the proximal aspect of the plate.

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Figure 14.2 Construct failures in a dog (a, b) and a cat (c, d) with distal radius and ulna fractures. The short bone plate used in the dog failed through a screw hole adjacent to the fracture site, despite its adequate thickness. Fatigue failure can be explained by the high stress concentration at the level of the fracture site due to the short working length of the plate that functioned as a bridging implant in this case where a small defect was present on the caudal radial cortex postoperatively. In the cat (c, d), the bone fractured just proximal to the bone plate. This failure is partly explained by an abrupt change in construct strength and stiffness at the level of the plate extremity. This phenomenon is commonly observed in small‐breed animals with distal radius‐ulna fractures, where a short bone plate is selected. Note the presence of four holes beneath the plate on the lateral projection (c) corresponding to drill holes and subsequent repositioning of the bone plate due to suboptimal initial fracture reduction.

Direct surgical approach of the fracture during CO has a negative impact on periosteal vascularization, and the use of conventional bone plates may further deplete the viability of the periosteum [12, 13]. The importance of periosteal vascularization during bone healing is critical in all breeds, but may be more so in small and toy breeds due to the paucity of endosteal and medullary supply [14]. It has been reported that in dogs less than 6 kg, internal fixation or external coaptation are associated with complication rates ranging from 54% to 83% [15, 16]. In these cases, the use of locking implants could prove advantageous, as they significantly reduce damage to the periosteum, while providing mechanical advantages compared to standard plates. The preservation of periosteal blood supply should favor early formation of a callus and expedite healing of the fracture while limiting osteonecrosis under the bone plate. Faster bone healing may, in turn, allow for the safe use of relatively smaller implants, as the required implant fatigue life is decreased. While studies are lacking to support these hypotheses, it is our belief that locking implants have the potential to mitigate complications associated with internal fixation of radius fractures in all patients, and particularly in toy‐breed dogs. The use of these implants in combination with adherence to biological osteosynthesis principles will likely offset some of the complications seen in CO of antebrachial fractures.

14.2 Biological Osteosynthesis in R‐U Fracture Repair

Biological osteosynthesis principles emphasize preservation of the soft tissue envelope surrounding a fracture site to optimize bone healing capability [17]. When these principles are used to apply a bone plate, it is often referred to as minimally invasive plate osteosynthesis (MIPO) (Figure 14.3). While MIPO can be performed using conventional implants, locking plates are specifically designed for biological applications, and their full benefit is attained when used in combination with these techniques.

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Figure 14.3 Preoperative radiograph (a), intraoperative images (b, c) and postoperative radiographs (d) of a radius and ulna fracture treated using minimally invasive plate osteosynthesis (MIPO) in a dog. A distraction frame using partial rings and two motors was secured to the radius with one transverse K‐wire per fragment (b). Two small approaches to the proximal and distal radial metaphyseal regions were made on the cranial radial surface. A 2.0 locking compression plate was inserted into an epiperiosteal tunnel over the cranial radial surface (c). The extensor tendons were preserved during the procedure. Immediate postoperative radiographs (d) show adequate restoration of alignment and apposition. The plate bone ratio (PBR) is high (82%), and the plate screw density is low (0.4).

Available literature on biological osteosynthesis for the treatment of antebrachial fractures in dogs is very limited and includes one cadaveric anatomical study, a short comparative study using bone plates, and retrospective case series using ESF [1822]. Our clinical experience suggests that MIPO of radius and ulna fractures is possible in a variety of patient sizes and represent an effective fixation method that could replace traditional techniques in the future. It is generally agreed by clinicians that the advent of locking implants facilitates MIPO in various fracture patterns but that the lack of direct observation of the fracture site during surgery makes restoration of alignment more challenging.

14.3 Reduction Techniques for Radius Fractures Stabilized with a Locking Plate

While it is possible to achieve and maintain the anatomical alignment with two bone forceps applied to the radial metaphyses through the small incisions used in MIPO, the forceps often impede the application of a bone plate, and they require constant manual control by a scrubbed assistant [23, 24]. In addition, locking implants require specific drilling guides that must adequately engage the locking mechanism of the plate in order to allow proper screw insertion. If the reduction instrumentation interferes with the drill‐guides, there is a risk of malpositioning the screw, which would negatively affect construct properties.

Alternatives to direct fragment manipulation with bone‐holding forceps include the placement of a temporary distraction frame/device, the application of toothed reduction handles, and the use of a hanging leg technique or a traction table. The first two techniques provide direct control over the bone, as they anchor into the radius at locations remote from final fixation. Their downside is that they do result in minor trauma to the bone when compared to the latter two options. Nevertheless, we prefer the use of a distraction frame as our standard reduction technique for radius/ulna fractures for several reasons. First and foremost, the damage created to the bone and surrounding tissues is minimal, as the frame uses small‐sized, percutaneously inserted Kirschner wires (K‐wires) applied to metaphyseal regions. Next, it allows for progressive, controlled distraction of the fracture site and permits adjustments in varus/valgus, rotation and pro‐recurvatum as necessary. Finally, it does not interfere with the placement of a locking plate if applied properly (Figure 14.4).

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Figure 14.4

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Jun 13, 2021 | Posted by in SUGERY, ORTHOPEDICS & ANESTHESIA | Comments Off on Radius/Ulna Fractures
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