Current Surgical Versus Conservative Management in the Treatment of Osteochondritis Dissecans

Take Home Message: Conservative versus surgical options for the treatment of various entities of osteochondritis dissecans (OCD) exist. Treatment options when clinical signs a represent include conservative and surgical options for femoropatellar, metacarpophalangeal/metatarsophalangeal and glenohumeral OCD depending on the nature of the lesion. In the tarsocrural joint, arthroscopic surgery is recommended for all cases accompanied by clinical signs. Treatment of radiographic lesions of OCD in yearlings is also practiced but must be accompanied with transparency with regard to those manipulations.

The paper reviews current knowledge on conservative versus surgical options for the treatment of osteochondrosis entities in the horse. Clinical and radiographic signs of each significant osteochondrosis entity in the horse are presented, followed by the value of conservative treatment versus arthroscopic surgery options as well as the results for each option with the various entities. The entities presented in detail include, osteochondritis dissecans (OCD) of the femoropatellar, tarsocrural, metacarpophalangeal and me tatarsophalangeal, and glenohumural articulations. The various treatment options for subchondral cystic lesions of the medial femoral condyle are detailed with evidence for the value of various treatments and subchondral cystic lesions in other locations are briefly reviewed.

I. INTRODUCTION

Osteochondritis dissecans (OCD) is arguably the most important entity within the developmental orthopaedic disease complex. It is a common cause of lameness in young athletic horses and is the most frequent condition of the complex requiring surgical intervention. Osteochondritis dissecans has been classically considered as a manifestation of osteochondrosis.¹ Rejno and Stromberg² described the first stages of osteochondrosis as a disturbance of cellular differentiation in the growing cartilage, and the second as involving the process of basal forces within the joint, giving rise to fissures in the damaged cartilage. The terms osteochondrosis, osteochondritis dissecans and osteochondrosis dissecans have been regularly used as synonyms, but this is misleading. Poulos³ distinguished them as follows: osteochondrosis is the disease, osteochondritis is the inflammatory response to the disease, and OCD is the condition in which a flap (an area of cartilage or osteochondral separation) can be demonstrated. This is a simple but appropriate representation.

Subchondral bone cysts or subchondral cystic lesions (SCLs) were also proposed by Stromberg and Rejno⁴ as a manifestation of osteochondrosis. It is usually assumed that SCLs showing up clinically in the first two years of life are indeed manifestations of osteochondrosis. However, they represent quite a different disease than OCD. Examination of the lining of enucleated SCLs in the medial femoral condyle showed that they produce increased levels of PGE₂, neutral metalloproteinases, and nitric oxide (NO), and that there was enhanced osteoclastic resorption activity attributable to the tissue.⁵ In situ hybridization of sections of fibrous tissue of SCLs showed that mRNA of IL-1β was upregulated at the periphery of the cystic lesion and IL-6 was upregulated in the fibrin tissue of the center.⁶ Other work showed that SCLs could be produced after 5mm wide, 3mm deep defects were created in the subchondral bone plate at the central weight-bearing area of the medial femoral condyle,⁷ leading to an alternative pathogenesis for clinical disease in older horses.

Based on the well-recognized association between osteochondrosis and both OCD and SCLs, the options for surgical management will be presented for both clinical entities. Figure 1 illustrates the proposed pathways of osteochondrosis leading to both OCD and SCLs.
 

II. OSTEOCHONDRITIS DISSECANS (OCD)

Disease Manifestations

Three categories of OCD lesions are recognized:

1. Those showing clinical and radiographic signs
2. Those showing clinical signs without radiographic (but arthroscopic) signs
3. Those showing radiographic, but no clinical signs.

Data from the first two categories of disease have been tabulated from the most commonly affected joints from the author’s surgical case reports⁸ and are typically cases referred for surgery. The relative incidence of clinical signs vs. radiographic lesions also has been documented in the femoropatellar joint by McIntosh and McIlwraith.⁹ The third category of radiographic lesions has become increasingly important because of the common use of pre-sale radiographs of yearlings.^10,11

The condition affects the articular (joint) cartilage, and often involves the subchondral bone beneath the cartilage surface (Fig 2A). Generally, a dissecting lesion develops that involves cartilage, or cartilage and bone, and the dissection plane ultimately reaches the joint surface.^1,8 It is theorized that clinical signs develop when the joint surface is reached by the dissecting lesions. Sometimes the OCD fragments can detach and become a loose body, or joint mouse. In most instances however, the fragments remain loosely attached to the bone of origin, but the debris that is released into the joint from the flap results in synovitis or joint inflammation and the clinical signs Osteochondritis dissecans can affect a number of joints, but the most commonly involved are the femoropatellar, tarsocrural and fetlock joints. Shoulder joints also are affected, but less frequently. Each of these entities will be discussed separately.
 

Osteochondritis Dissecans of the Femoropatellar joint

The femoropatellar joint is one of the principal joints affected with OCD. Although stifle OCD can be diagnosed in almost any breed, it seems to be more common in Thoroughbreds than in other breeds (Table 1).¹² Approximately 60% of affected horses are one year of age or younger when the condition becomes symptomatic, and younger animals that develop clinical signs often have more severe changes within the joint (Table 2).¹² However, radiographic lesions are sometimes identified in older horses in which no clinical signs have ever been observed.

Clinical and Radiographic Signs

Animals usually present with a sudden onset of joint swelling and lameness. A recent increase in the level of exercise is sometimes part of the history. [...]