33rd Annual Scientific Meeting proceedings

This presentation is focusing on the most common osteochondral (OC) lesions in the femoropatellar, tarsocrural and metacarpo/metatarsophalangeal joints. Osteochondritis dissecans (OCD) lesions of the stifle and hock, dorsal osteochondral fragments (DOF) and plantar/ palmar osteochondral (POF) of the fetlock joints are included. The discussion is trying to summarize the current knowledge and attempting to answer the question of whether these lesions should be all addressed surgically, or if conservative treatment can be a valid option.

Osteochondral lesions are common in young horses, with a prevalence over 50 % in certain populations (1). These fragments are commonly identified in pre-purchase examinations in young individuals or during lameness investigations, requiring prognostic and therapeutic decisions from veterinarians. Clinical symptoms vary; joint effusions and lameness are often recognized, but many horses with lesions are asymptomatic.

While we seem to have a consensus in operating on horses with obvious clinical symptoms, the need for surgery in asymptomatic animals is still debated. It has been advocated that it is unnecessary to remove some lesions, and in some cases, “preventative” surgery has been declared to be an unfair and selfish act from surgeons.

When making decision to choose surgical or conservative treatment, many aspects should be considered. One must agree that performing surgery is a responsibility and is not without risks; therefore, where conservative treatment is a valid option, it should be considered and possibly prioritized. Obvious advantages with conservative treatment are lower costs, no risk of anesthesia related complications and surgical site infections, and no stress and trauma for the patient. However, overall costs related to delayed surgery can be increased compared to the price of prophylactic intervention (15). Also, surgical treatment can be more disruptive later in the middle of the horse’s athletic career. Conservative treatments are always palliative as resolution of lesions cannot be expected, except in very young individuals in the tarsocrural and stifle joints before eight months of age (16).

It is well known in both human and veterinary medicine that OCD lesions are a common cause of joint effusion, lameness and are a potential cause of osteoarthritis (2,3). Incongruent joint surfaces and loose fragments in the joints induce inflammation that with time can result in joint destruction and irreversible changes on the cartilage.

OCD lesions in horses are most common in the tarsocrural joints and this is probably the reason why this joint has been studied most extensively. The inflammatory response to OCD lesions and presence of biomarkers for cartilage destruction has been documented in horses with or without clinical symptoms (4, 5, 6, 7). It has also been shown that surgical intervention (fragment removal and debridement) can improve clinical symptoms and early, prophylactic removal of OC fragments can result in an equally successful athletic career compared to horses without OCD (8,9). Early removal of dorsal fragments also has been advocated and associated with racing success in the fetlock joints(15). While excision and debridement is the most common procedure to treat lesions of the lateral trochlea in the stifle (10), reattachment techniques of OCD fragments has been also implemented, resulting in not just clear improvement of clinical symptoms and reaching intended use (11,22) but even complete resolution of the OC defects in most cases (12).

While larger defects in the stifle and tarsocrural joints are widely recommended to be treated surgically, fragment removal in the fetlock joints is still debated. It has been shown that Thoroughbred racehorses may train and race with dorsal fragments following conservative treatment during their racing career (13). Also, the necessity of POF fragment removal in Standardbreds has been questioned (14). However, there are several publications that still argue for the potential risk for nonsurgical treatment in these cases and it has been noticed that these fragments can contribute to OA changes in the fetlock joints in older individuals (19, 20).

It is a common suggestion to operate horses only with obvious clinical signs; however, asymptomatic horses often start to show effusion or lameness when training or competition is initiated (17). By the onset of clinical symptoms, the joints may already be damaged (OA) and these defects do not change or heal after surgery (15). Many high-performance horses can cope with substantial inflammation and cartilage erosion that might not show as decreased performance for a long time. Despite these horses still performing to a high level, this does not necessary mean that they do not experience some discomfort, particularly between races. Therefore, in the author’s opinion, treatment success evaluated only through racing results (starts, earnings and speed..) should be carefully interpreted. In addition to these results, animal welfare aspects should also be considered, even if these measures are hard to evaluate.

Bilateral OC lesions and multiple joint involvement with OC fragments is common (1). Often symmetric lesions show asymmetric symptoms and coexisting lesion in other joints can be asymptomatic. In those cases, to operate only the symptomatic joints can be hard to defend in common practice.

The intended use of athletes is an important factor. While racehorses can cope with certain lesions during their relatively short racing career, dressage horses or show jumpers competing for a much longer time might not.

Lesion size, fragment complexity, mobility and secondary changes on cartilage can have an important prognostic value, however these parameters cannot be accurately evaluated with traditional diagnostic imaging techniques. For accurate diagnosis and treatment, arthroscopic surgery is needed. In addition, during arthroscopic evaluation, undiscovered lesions can be found in less common places, for instance on more proximal edge of the distal intermediate ridge, the plantar aspect of the tibia or the abaxial surface of the lateral talus trochlea (21, 23).

It has been questioned whether it is fair to remove fragments “only to facilitate” selling of yearlings. Even if we disregard the potential preventive value of surgery, we must consider the fact that in our profession we indeed make a service for owners too. However, removing fragments can serve these horses in a different way as well, since if those individuals cannot be sold, they may not be needed. Therefore, with a surgical procedure we might “save a life” or at least successful athletic career.

We seem to have consensus on the following: that larger defects in high motion joints and affected joints with obvious symptoms, particularly in athletes, should be operated. However, many horses can still cope with certain fragments for a long period. Veterinarians should evaluate many aspects, risks and benefits, when deciding treatment strategies for certain individuals with particular lesions.

References

1. Lykkjen et al.: Osteochondrosis and osteochondral fragments in Standardbred trotters: Prevalence and relationshipsEquine Veterinary Journal 44 (2012) 332–338
2. McIlwraith:Surgical versus conservative management of osteochondrosis; The Veterinary Journal 197 (2013) 19–28
3. Accadbled et al.: Osteochondritis dissecans of the knee; Orthopaedics & Traumatology: Surgery & Research 104 (2018) S97–S105
4. Brink et al. Association between clinical signs and histopathologic changes in the synovium of the tarsocrural joint of horses with osteochondritis dissecans of the tibia. Am J Vet Res 2010;71:47–54.
5. de Grauw et al.: Cartilage-derived biomarkers and lipid mediators of inflammation in horses with osteochondritis dissecans of the distal intermediate ridge of the tibia; AJVR, Vol 67, No. 7, July 2006
6. Verwilghen et al.: Relationship between arthroscopic joint evaluation and the levels of Coll2-1, Coll2-1NO2, and myeloperoxidase in the blood and synovial fluid of horses affected with osteochondrosis of the tarsocrural joint; Osteoarthritis and Cartilage 19 (2011) 1323e1329
7. Machado et al.: Synovial fluid chondroitin sulphate indicates abnormal joint metabolism in asymptomatic osteochondritic horses; Equine Veterinary Journal 44 (2012) 404–411
8. Brink et al.: 2009. Lameness and effusion of the tarsocrural joints after arthroscopy of osteochondritis dissecans in horses. Veterinary Record 165, 709–712.
9. McCoy et al.: Short- and long-term racing performance of Standardbred pacers and trotters after early surgical intervention for tarsal osteochondrosis; Equine Veterinary Journal 47 (2015) 438–444
10. Foland et al.: Arthroscopic surgery for osteochondritis dissecans of the femoropatellar joint of the horse Equine Vet J 24:419–423, 1992
11. Nixon et al.: Arthroscopic reattachment of osteochondritis dissecans lesions using resorbable polydioxanone pins; Equine vet. J. (2004) 36 (5) 376-383
12. H. Wilderjans; Personel communication
13. Ramzan et al.:  Career outcome of Thoroughbred racehorses with metacarpo/ metatarsophalangeal joint dorsal chip fracture managed nonsurgically and surgically: A retrospective cohort study; Equine Vet J. 2020;52:823–831.
14. Carmalt et al.: Racing performance in Standardbred trotting horses with proximal palmar/plantar first phalangeal fragments relative to the timing of surgery; Equine Veterinary Journal 47 (2015)
15. Colón et al.: Qualitative and quantitative documentation of the racing performance of 461 Thoroughbred racehorses after arthroscopic removal of dorsoproximal first phalanx osteochondral fractures (1986–1995); Equine vet. J. (2000) 32 (6) 475-481
16. Dik et al.: Radiographic development of osteochondral abnormalities in the hock and stifle of Dutch Warmblood foals, from age 1 to 11 months. Equine Veterinary Journal, Suppl. 31, 9–15, 1999.
17. McIlwraith CW. : Clinical aspects of osteochondritis dissecans. In: McIlwraith CW, Trotter GW, eds. Joint disease in the horse. Philadelphia: WB Saunders Co, 1996;369–374
18. Steinheimer, D.N., McIlwraith, C.W., Park, R.D., Steyn, P.F., 1995. Comparison of radiographic subchondral bone changes with arthroscopic findings in the equine femoropatellar and femorotibial joints: A retrospective study of 72 joints (50 horses). Veterinary Radiology 36, 478–484
19. Declercq et al.: Dorsoproximal proximal phalanx osteochondral fragmentation in 117 Warmblood horses, Vet Comp Orthop Traumatol 2009; 22: 1–6
20. Goldkuhl et al.: Evaluation of cartilage injury in horses with osteochondral fragments in the metacarpo/metatarsophalangeal joint: A study on 823 arthroscopies, Equine Vet J. 2023;1–10.
21. McIlwraith CW. : Surgical versus conservative management of osteochondrosis; The Veterinary Journal 197 (2013) 19–28
22. Sparks et al.: Arthroscopic reattachment of osteochondritis dissecans cartilage flaps of the femoropatellar joint: Long-term resultsEquine vet. J. (2011) 43 (6) 650-659
23. Author´s observation