34th Annual Scientific Meeting proceedings

These cases can be challenging because of the difficulty in obtaining an accurate diagnosis pre-operatively and are often something of ‘lucky dip’ as to precisely what pathology will be found within the sheath at surgery. Many cases are chronic at presentation as they are often not dramatically lame and conservative & medical management is often being tried first. This presents the complication of additional fibrosis to the surgery. Cases may be challenging if they are a revision surgery, if there is somewhat complex or challenging anatomy in that case, or if there are multiple pathologies present. They can also be challenging to neophytes as they can be technically challenging to get good access and visualisation because of the restrictions to ‘scope placement because of the limb and foot. A high level of skill and experience can make procedures more successful but the risk of complications is still high, as we discuss later. 

Clinical signs can often be enough to localise pathology to the tendon sheath, although diagnostic local analgesia can be used in addition. Ultrasonography is the main stay of imaging but the accurate differentiation of pathologies can be challenging. MRI examination is often unhelpful as many pathologies are below the range of resolution of standing MRI. Positive contrast tenograms can be helpful in assessing the presence or absence of a manica flexoria tear and positive contrast computed tomography offers even greater utility in assessing pathologies.

The majority of surgeons find operating in lateral recumbency to be most successful. The surgical sites should be well exposed with as little draping as possible to enable as free movement of the arthroscope relative to the limb and the foot as possible. A tourniquet can be extremely helpful in manica flexoria cases and a pneumatic tourniquet, although not quite as effective, has the advantage of that it can be placed and only inflated if necessary. There is often not much need for a large number of instruments but in my opinion a good synovial resector is essential. Radiofrequency devices are popular with some surgeons, but I try to use it sparingly in this site. devices in addition.

I was recently involved in the study where we described the findings in horses undergoing repeat tenoscopy for treatment of non-septic tenosynovitis of the digital flexor tendon sheath in 20 cases (Bathe & Lynch VOS 2025). All cases had persistent or recurrent lameness after the first surgery and the majority of the cases had had a DDFT lesion initially and in 2/3rd  of these there was recurrent/progression of the original tear. Adhesions and annular ligament constriction were also found, and another 1/3rd of the cases had new DDFT lesions, some of which were deemed to be high iatrogenic. Cases initially treated for sepsis of the DFTS tended to have adhesions or iatrogenic tendon damage. It is also possible to damage the lateral palmar nerve during portal placement. This damage does not appear to respond well to medical management, unlike neuritis cases following neurectomy, & surgical removal of the affected nerve is sometimes necessary.

It is not uncommon that damage to the SDFT occurs during ‘scope placement through the basisesamoid portal. In complex cases where the palpable landmarks are not very clear or there is marked constriction from the annular ligament, it can be preferable to place the initial scope portal more proximally and to make the universal portal under directed visualisation. This approach will be demonstrated. Care should be taken to be as atraumatic as possible during surgical manipulation and extreme caution with the use of radiolucency devices is advised. The degree of debridement of a DDFT tear is a matter of judgement. Similar to debridement of articular cartilage lesions,  with experience a more conservative approach tends to be taken. However it is important to make sure that full extent of the DDFT tear is assessed and treated, as distal reflective granulomas can be missed. If there is any evidence of compression from the annular ligament, then this should be transected. I have certainly had cases where this has not been done initially, which have had persistent lameness, which has resolved after subsequent surgical decompression. If I am concerned about the likelyhood of adhesion formation I will instil hyaluronic acid at the end of surgery and I have not identified any flares associated with this. Controlled walking exercise from soon after surgery can help restrict adhesion formation but early excessive exercise should be avoided. Although intrathecal treatments can be used to try an minimise the risk of adhesion formation there needs to be a balance between the number of injections performed into the tendon sheath, as it is a relatively delicate and sensitive area and the number of repeated injections should be minimised. In my experience the use of biologics such as IRAP or A2M post-operatively can be associated with a better outcome, particularly in horses with an intended fast return to exercise.