Introduction

Foot lameness can be acute or chronic and is often bilateral. Regionalising pain in the area is also challenging because of the complexity of the anatomy in this area and the transfer of pain from adjacent areas, including but not limited to the navicular area and hoof itself. Therefore, diagnostic imaging is essential to confirm the site or sites of disease and pathology, and offer a treatment plan to the owner, including providing a more accurate prognosis. In this regard, foot lameness is probably one of the most common clinical presentations for equine veterinarians and at the same time is often the most challenging to provide an accurate diagnosis and effective treatment plan for. Good quality imaging is an essential part of piecing together this oftentimes complex picture.

Imaging includes at a minimum digital radiography, but oftentimes also ultrasound, scintigraphy and/or MRI/ CT scanning, all of which offer varying limitations and benefits depending on the disease process present, availability, costs, and the owner’s expectations. Corrective shoeing is also normally paramount in effectively managing foot lameness in horses and getting your farrier and vet to work together will be critical.

Osteoarthritis of the DIP Coffin Joint

Osteoarthritis (OA) of the DIP (coffin) joint has significant implications. Once radiographic evidence of marked OA is present, the management of horses at a high level of athletic performance can be challenging. So, as with any joint, early detection of joint disease and earlier intervention and management will have a greater impact on sustaining athletic performance.

Synovitis is one of the early signs of joint disease and varying degrees of synovial proliferation and synovial membrane thickening can be well identified with ultrasound and MRI. In addition, joint capsule thickening as a result of capsulitis, oftentimes indicating chronicity, can be well distinguished with these modalities. Digital radiography, with an appropriate window and level, can demonstrate soft tissue swelling associated with the dorsal recess of the DIP joint by evaluating the skin contour on the lateromedial view.

CT images using a soft tissue window can reveal skin contour and can also provide useful information about joint capsule thickening and synovial proliferation versus effusion, and contrast arthrography will further characterise these findings. Enthesophyte formation at joint capsule attachments will be evident on radiographs, ultrasound, MRI, and CT. Ultrasound will be limited to the joint capsule attachments, which can be visualised proximal to the coronary band1.

On radiographs, OA is characterised by periarticular osteophyte formation of the joint margins. Care though must be taken in interpretation due to normal anatomic variations in some cases, and especially of the extensor process. Unfortunately articular cartilage damage or loss resulting in joint space narrowing of the DIP joint does not typically become radiographically evident until severe changes have occurred. Further, large areas of full thickness articular cartilage defects can be present in the DIP joint with a radiographically normal joint space width. Therefore it often requires other imaging modalities to diagnose early articular cartilage damage and more subtle subchondral bone loss. These modalities may have limited availability in some countries or locations so the veterinarian is often required to offer a treatment plan without fully understanding the full extent of the disease(s) in play. MRI imaging is increasing our understanding in this regards and especially with a view to offering owners a better estimate of the expected outcomes from treatment.

Osteoarthritis of the PIP Pastern Joint

OA of the PIP (pastern) joint is readily recognised by periarticular osteophyte formation (bone spurs) with proliferative bone, although again care must be taken with over-interpretation as small osteophytes in the absence of other indicators of joint disease, particularly in the hindlimb, can be an incidental or relatively minor finding.

The PIP joint has a greater tendency to develop subchondral bone lysis secondary to OA compared to other joints (because it is a ‘low-motion’ joint). Thus, chronic advanced OA of the PIP joint can be manifested by focal or multifocal areas of subchondral lysis and joint space narrowing. Subchondral bone cysts can be seen in both young horses with minimal or no evidence of OA and in mature horses with more advanced joint disease.

Treatment of Foot Lameness with Arthramid® Vet

Treatment of foot lameness in horses due to osteoarthritis has traditionally included rest, controlled exercise, corrective shoeing, nutraceuticals (including glucosamine, epiitalis, hyaluronic acid, and PSGAG’s), NSAID’s (non-steroidal anti-inflammatory drugs), and any combination of the above, along with intra-articular medication including with corticosteroids or biotechnological substances such as stem cells, platelet rich plasma, and autologous conditioned serum (IRAP).

2.5% polyacrylamide (PAAG) hydrogel (Arthramid® Vet) is novel and has shown a higher success rate and to be longer lasting than other treatments for OA in the horse. In published studies, Bathe et al (2016), treated 20 sport horses, all with persistent lameness despite previous treatments with corticosteroids. The average lameness duration was 15 months and average lameness score was 3/10. 10 horses had arthritic changes evident radiologically, 18 underwent MRI examination and all had OA changes. Long term (median 12 months) follow-up was available in 18 cases; 12/18 (67%) returned to full function, and 3/18 improved but to a lower level, with only 3/18 failing to improve. The authors noted that this success rate and long-term duration of effect was significant given the severity of the cases and that they had been non-responsive to other treatments.

Jannsen et al (2012) also published a case series of 12 horses with DIP joint lameness due to OA. All were diagnosed by nerve blocks and intra-articular analgesia as well as radiological and MRI-findings. Again, all horses had been treated unsuccessfully previously with intra-articular treatments including hyaluronic acid, corticosteroids, and/or autologous conditioned serum (IRAP). Six months after treatment with Arthramid® Vet 8/12 (67%) of the horses treated were still sound, and 2 horses showed at least some improvement, with only 2 horses being non-responsive.

Arthramid® Vet is administered by a veterinarian directly into the joint. Once inside the joint it adheres to the synovial membrane and creates a long-term “bio-scaffold” structure within the soft tissues of the joint capsule itself, augmenting the membrane and supporting better joint function.

Over the next 2 to 4 weeks Arthramid® Vet becomes fully integrated into the synovial membrane through the ingrowth of blood vessels and collagen fibres. Augmentation of the synovial membrane results in;
• Progressive relief from pain
• Enhanced, more elastic joint capsule
• Improved shock absorption and load bearing ability of the joint
• Proliferation of synovial cells which are responsible for producing synovial (joint) fluid

After veterinary treatment with Arthramid® Vet owners should rest the horse for 48 hours and plan a reduced workload (not galloping or competing) for up to 4-6 weeks. This is also a good time to introduce any corrective shoeing that may be required. Veterinarians may also consider the use of NSAID’s at this stage to manage the acute pain for the first 7 to 10 days and while full integration of the Arthramid® Vet is allowed to occur. A follow up visit at 4 to 6 weeks is advisable to assess the response to treatment. For further details please consult our User Guide or Contact Us.

Conclusion

Arthramid® Vet is clinically proven effective and long lasting and offers veterinarians and owners an alternative treatment enabling a shift away from the use of corticosteroids in the treatment of foot related lameness associated with osteoarthritis in horses.

Dr Jason Lowe
Equine Veterinarian.

References 

1. Frisbie, D., Werpy, N., Kawcak, C., and Barrett, M. (2016). Specifics of anatomy, clinical diagnosis, imaging diagnosis, and treatment by region; Distal Limb. In Joint Disease in the Horse, 2nd edn., Ed: C. McIlwraith, D. Frisbie, C. Kawcak, and P. van Weeren, Elsevier, St. Louis. pp. 281-301.
2. Bathe, A.P., Read, R.M. and Briggs, C (2016) Intra-articular polyacrylamide hydrogel for the treatment of 20 horses with non-responsive osteoarthritis of the interphalangeal joints: a prospective study. Veterinary Orthopaedic Society 43rd Annual Conference Abstract, USA.
3. Janssen, I., Koene, M. and Lischer, C. (2012) Intra-articular application of polyacrylamide hydrogel as a treatment of osteoarthritis in the distal interphalangeal joint: case series with 12 horses. Pferdeilkunde 28(6), 650-656.