14.1 Introduction

The use of stifle orthoses in dogs with cruciate pathology is gaining popularity in both preoperative and postoperative patients as well as those that are unable to undergo surgery. While significant numbers of orthoses are being recommended and prescribed in lieu of surgery, no clinical data exist to support the efficacy of these orthotics as a replacement for surgical repair [1, 2]. Additionally, our understanding of the impact of orthoses on joint function in companion animals is limited, with very few studies focused on the dog stifle. The majority of information available to clinicians on orthoses is limited to other joints [3–7] or review articles [2, 8].

Critical evaluation of the effects on stifle function following orthoses application is limited to two studies that assessed the joint motion and one study that evaluated paw pressure before and after orthosis application. The first study utilized a computerized simulation to assess the impact of an orthosis on virtual joint motion [9]. The second study evaluated joint motion and other temporospatial variables in a group of normal dogs with and without a stifle orthosis [10]. Finally, a small retrospective case series evaluated paw pressure in dogs wearing stifle orthoses but did not evaluate joint function specifically [11].

Unfortunately, there is even less information available on complications experienced by dogs wearing stifle orthoses. One recent survey examined owner satisfaction with orthoses and did document some common complications [12], the vast majority of which involved skin lesions as a result of wearing the orthosis. However, complications that have not been addressed previously are the potentially unintended impact of stifle orthosis use on the adjacent joints and associated soft tissues [10].

In this chapter we will explore the available evidence for the use of stifle orthoses in dogs, paying particular attention to their impact on the restoration of joint motion, clinical use in injured limbs, and associated complications.

14.2 Stifle Orthoses Construction

The construction of orthoses is important and depending on changes in the components and/or composition, it can impart varying degrees of stability to the underlying joint. Orthosis can vary from rigid to semi‐rigid, and flexible. These varying degrees of stability can be affected by the material from which the body of the orthosis (i.e., “frame”) is made as well as the type of moveable joint (hinge) or in some cases the absence of a moveable joint [2, 9].

14.2.1 Stifle Orthosis Frame

The majority of stifle orthoses frames used in dogs are made from a rigid material and are custom designed from a cast or mold to fit an individual limb. These frames are formed using various materials, including thermosetting plastics that are molded into a permanent shape after heating or various forms of thermoforming plastics (e.g., thermoplastic) which soften when heated, harden when cooled, and can be reheated and reshaped numerous times (Figure 14.1) [13]. Orthoses can be made without a moveable joint to restrict motion or more commonly with some form of hinge joint to allow varying degrees of joint motion. The fabrication of a custom orthosis can require a period of weeks before it is available for patient use. However, these orthoses are designed to an individual patient’s specifications. The currently available clinical data on stifle orthosis function in dogs are centered around custom‐fit orthoses [9–11].

Alternatively, off‐the‐shelf stifle orthoses are also available. The frames of these types of orthoses are prefabricated and produced in select sizes (small, medium, large, etc.). This can allow an in‐hospital and semicustomizable fit due to the integration of heat‐moldable material and other adjustable components within the orthosis frame (Figure 14.1). Off‐the‐shelf orthoses have the benefit of allowing quick and repeated frame customization and may prove beneficial for those patients who experience changes in limb size (e.g., during the postsurgical and rehabilitation period). However, in the authors’ experience, off‐the‐shelf orthoses often require more extensive in‐hospital adjustments to provide adequate fit and function, as compared to custom orthoses, and this may lead to more complications, especially skin issues. Unfortunately, most veterinarians have limited experience and/or expertise in orthosis fitting and adjustment, making it challenging to obtain the level of fit that a custom‐made orthotic can provide.

To date, a comparison between custom‐made and off‐the‐shelf stifle orthoses in dogs has not been performed. Therefore, for those patients where optimal orthosis fit and function is required, a custom‐made orthosis represents the best available option.

14.2.2 Moveable Joint Options with Stifle Orthoses

Orthosis movement is achieved with the placement of a joint between the thigh frame (i.e., femoral component) and the crus frame (i.e., tibial component). Various types of moveable joints have been utilized in stifle orthoses. The two most common types of joints are a rigid single‐axis hinge joint and a more “rubberized” flexible joint often referred to as a polymer flexure joint (Figure 14.2). The type of joint present in an orthosis directly impacts the overall support imparted to the braced joint and thus its range of motion (ROM). Additionally, rigid single‐axis hinge joints may have adjustable stops that allow clinicians to selectively restrict joint flexion and extension and flexible joints are available in varying degrees of stiffness.

The available research regarding the impact of joint type on stifle orthosis motion is limited. A small unpublished kinematic study evaluating normal dogs wearing two different stifle orthoses with differing joints (metal hinge joint versus flexible joint) found differences in overall orthosis motion (Figure 14.2). While flexion and extension of the orthosis were similar, a more profound difference was seen in the other planes of motion (internal/external rotation and abduction/adduction). A notable difference occurred during internal/external rotation of the orthosis, with more profound internal rotation during maximum joint flexion, corresponding with the typical screw‐home mechanism of the femoral‐tibial joint. Similar findings were reported in a recent computerized simulation [9]. That study found that hinge stiffness impacted internal rotation, with stiffer hinges allowing less internal rotation and less stiff hinges allowing more.

It is possible that cranial cruciate ligament‐deficient dogs with more profound rotational instability (e.g., “pivot shift”) either before or after surgery may benefit from an orthosis with increased stiffness, especially to internal rotation. Unfortunately, the ideal hinge stiffness for a cranial cruciate‐insufficient dog using an orthosis in lieu of surgery or post surgery is unknown.

14.3 Stifle Orthoses and Owner Perception

According to a recent survey‐based study, the perception of owners of dogs who had orthoses to manage cranial cruciate ligament (CCL) rupture was good and indicated that they may provide some benefit [12]. That study found that 85% of owners who chose an orthosis as the primary treatment for CCL rupture in their dogs were satisfied with that decision and would make the same choice again. Interestingly, this was similar to those who chose surgical treatment with tibial plateau leveling osteotomy (TPLO) as indicated by a 90% satisfaction rate. However, those who chose surgery with TPLO were significantly more likely to rate that treatment as “excellent, very good, or good” compared to those owners who chose to use an orthosis as the primary means of joint stabilization. Additionally, owners of dogs who underwent surgical stabilization were more likely to report that their dogs had “mild or no lameness” following treatment. An additional study found that the three most common reasons for owners electing an orthosis in lieu of surgery in dogs with CCL rupture were: (i) dislike the idea of the surgery/too invasive; (ii) age of the dog; (iii) cost of surgery [1].

Overall, owner perception of orthoses as a treatment for CCL rupture is good, but the clinical results are inferior to TPLO. Most owners who choose orthoses over surgical correction do so based on patient‐related concerns or for financial reasons [1].

14.4 Stifle Orthoses and Weight Bearing

Limited information is available regarding the impact of stifle orthoses on weight bearing in dogs with CCL rupture. Currently, there is only one study that has evaluated dynamic weight bearing in dogs with CCL rupture and treated with orthoses [11]

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