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New developments in orthopaedics

Options available for the diagnosis and treatment of orthopaedic disease in animals continue to advance and evolve

19 February 2020, at 2:00pm

One of the more significant developments over the past 10 to 20 years has been the development of joint arthroscopy. As well as facilitating minimally invasive surgical techniques, arthroscopy has greatly increased our understanding of some of the complex pathology commonly encountered in the patients that we treat. Arthroscopy is now extremely commonplace; however, the quality of the digital imaging systems available continues to progress and the ultra-high definition systems now available have facilitated more precise surgical technique and improved clinical decision making, in what can be highly complex cases.

Arthroscopy is most commonly performed in the elbow joint and although, sadly, there is no current consensus on the most appropriate treatment for the multiple pathologies encountered, the ability to record and store high-quality digital images has been of huge benefit in improving our understanding of this complex condition. Additionally, showing owners detailed video footage of the procedures that have been carried out increases their own understanding, improves postoperative compliance and anecdotally at least, results in improved clinical outcomes.

Osteochondrosis dissecans (OCD) is a relatively common condition encountered in small animals, particularly in large and giant breeds. The condition involves a failure of endochondral ossification, resulting in regions of excessively thick articular cartilage. At the deepest layers of the abnormal cartilage the cartilage becomes necrotic and can split; eventually a fissure line appears, and joint fluid subsequently underruns the dead cartilage flap, resulting in large defects within the joint. The exposure of the subchondral bone releases a cascade of inflammatory mediators and results in significant progression of osteoarthritis and degenerative joint disease. Previously, these cartilage flaps were removed arthroscopically, and the necrotic tissue debrided, to encourage infilling with fibrocartilage. Fibrocartilage, however, is a poor substitute for articular cartilage, and over recent years joint resurfacing has now become the gold standard for the treatment of OCD lesions.

OCD is most commonly seen in the shoulder and many dogs can do well clinically with standard debridement; however, with lesions affecting the central and medial portions, severe osteoarthritis can still develop. Our preferred treatment for the vast majority of these lesions, especially in high-performance and sporting dogs, is the use of synthetic osteochondral grafts. The grafts include a mesh titanium base which encourages bony ingrowth and a highly resistant inert polyurethane surface which not only restores the topography of the affected joint, but also seals the subchondral bone from the release of the inflammatory mediators. We now commonly place these grafts in the shoulder (Figures 1A and 1B), elbow (Figure 1C) and stifle (Figure 1D).

One of the major difficulties of resurfacing procedures in the elbow is achieving adequate exposure, as the graft needs to be placed at 90 degrees to the joint surface. Initially, access was either by osteotomy of the medial epicondyle or by transection of medial collateral ligament, both of which were associated with significant morbidity. A more recent approach to preserve these structures has greatly improved the success of the osteochondral grafting when performed in the elbow. Advances are continuing in the treatment of end stage osteoarthritis in the elbow and we are eagerly awaiting the release of the newest iteration of an elbow replacement system which we hope will revolutionise the treatment of this debilitating condition, as has been the case with total hip replacement (THR), now considered a routine procedure in referral practice. The author’s preference is to use non-cemented implants where possible as this negates the potential risk for de-bonding of the cement from either the bone or the implant in the medium to longer term. Initially, hip replacement was only available for medium-sized dogs weighing approximately 25kg or larger; however, technology has advanced such that size is no longer a limiting factor and we have successfully performed hip replacement on a 2kg Chihuahua (Figures 2A and B) and a 90kg Caucasian Shepherd Dog (Figure 3).

The UK’s first total ankle replacement has just been successfully carried out and although there are currently few indications, a handful of successful total shoulder replacements have also been performed.

Perhaps one of the most exciting advances of recent times is the use of 3D printing and the use of computer-assisted design (CAD) software for the manufacture of custom-made drill guides, cutting guides and even custom-made implants. These guides and implants are based on high-definition 3D CT scans. This technology has revolutionised the treatment of complex limb deformity cases as well as a variety of complex spinal conditions, such as a 1.09kg Chihuahua with severe atlantoaxial subluxation (Figure 4A) who received surgery with custom-made 3D-printed guides (Figures 4B and C). Figure 5 shows the images taken from CAD software which were used to plan the exact trajectories to achieve optimal bone purchase with bone stock of less than 1.5mm.

The use of these guides primarily reduces the risk for breach of the spinal canal when placing implants into the vertebral bodies. In cases of complex limb deformity, the procedures can be planned virtually, and specific cutting guides can be made to facilitate accurate limb realignment. The use of life-size 3D prints of the limb in question also facilitates preoperative contouring of implants, greatly reducing surgical time. Custom 3D implants can be manufactured in particularly complex cases.

It is an exciting time for veterinary orthopaedics and collaboration between orthopaedic and neurosurgeons has greatly improved the treatment in a variety of spinal conditions. We are currently developing the use of specific guides as a new treatment for lumbosacral foraminal stenosis which involves making a precise iliac osteotomy with subsequent reduction using custom 3D-printed guides. It is also pleasing that the collaboration between human and veterinary orthopaedic surgeons is increasing all the time and the use of instruments using lasers to aid precise osteotomies is an exciting thought for the future.