34th Annual Scientific Meeting proceedings

Navicular bursoscopy was first described in 1999 [1], one of the later equine synovial structures to be examined endoscopically. Initially the “direct” approach was used. This involved guiding the endoscope along the dorsal margin of the deep digital flexor tendon and relying on blunt force to penetrate the navicular bursa. This technique could be challenging, and subsequent investigation has confirmed that it frequently results in iatrogenic trauma to the navicular bone and the deep digital flexor tendon (in 66% and 71% of cases in a post mortem study) [2]. It has also been shown that the direct approach is often not direct at all, and involvement of the distal interphalangeal joint or digital flexor tendon sheath occurred in 45% of cases [3]. These authors showed that this frequency could be reduced by directing the endoscope distally, rather than axially, in the first instance [3].

The transthecal approach to the navicular bursa was first described in 2003 [4]. This approach has become more widely used [5]. The approach involves establishing a portal in the distal digital flexor tendon sheath, with the endoscope dorsal to the deep digital flexor tendon. The distal margin of the tendon sheath is then dissected along the dorsal margin of the tendon, using sharp dissection or electrosurgery, until entry to the navicular bursa is achieved. Comparison of the direct and transthecal approach actually suggested better visibility with a direct approach, though this was for ipsilateral structures and the authors did not consider arthroscopic “good practice” of swapping arthroscope and instrument portals around [6].

Endoscopy of the navicular bursa was originally described for the treatment of contamination or sepsis, typically following penetration of the bursa by a nail or other foreign object. This condition had long been recognised as a devastating injury to the horse [7]. Initial reports were very encouraging with 75% return to soundness and 63% return to athletic activity [1]. Sadly, though inevitably, these results were not borne out by greater numbers. In 2013 a multicentre study suggested that the prognosis with 95 horses was 56% survival and only 35% return to athletic activity  [8]. A few years later another paper suggested remarkable results with the old fashioned “streetnail” or bursotomy treatment, with 100% survival and 70% return to athletic activity (admittedly with a limited number of athletic horses, the majority being broodmares or other retired animals) [9].

The use of bursoscopy both for diagnosis and treatment of “navicular disease” or whatever term is preferred for lameness which is localised to the foot, potentially the palmar part of the foot, has also been investigated [10]. In one large series the same authors reported 114 horses which underwent bursoscopy [5]. In 22 cases, no pathology was identified, probably confirming what is known about the lack of specificity of nerve blocks of the horse’s foot [11]. The authors reported a successful outcome with 53 horses of which 37 returned to original levels of activity [5]. The percentages of these cases are difficult to interpret – is it of 92 horses with identified intra bursal pathology (58% and 40%) or of 114 horses which underwent bursoscopy (46% and 32%) [5].

A more recent paper compared Magnetic Resonance Imaging findings with bursoscopic findings and ultimate outcome [12]. Previous authors had described collagenous tissue which recoiled from the dorsal border of the deep digital flexor tendon into the proximal navicular bursa, and noted that these masses could be removed [10]. The latter study used the term “synovial mass” to describe these lesions, and showed excellent correlation between a hyperintense lesion associated with the dorsal border of the deep digital flexor tendon and such a lesion at bursoscopy. Disappointingly these authors did not report an encouraging prognosis. Ultimately they suggested that 18 (30%) of horses returned to their previous levels of performance. The authors noted that this is comparable to the success rate reported with conservative management of deep digital flexor tendonitis [13], and thus questioned the value of surgery. Other authors have confirmed that dorsal fibrillation lesions of the deep digital flexor tendon on MRI and at bursoscopy have a good correlation [14].

It can be concluded that the evidence for navicular bursoscopy following traumatic penetration of the navicular bursa is compelling, if not overwhelming. However, the evidence for bursoscopy for “navicular disease”* is limited. It may be that the surface lesions visible at bursoscopy are less significant for pain and ultimately lameness than lesions within the tendon itself.

References

1. Wright, I.M., Phillips, T.J. and Walmsley, J.P. (1999) Endoscopy of the navicular bursa: A new technique for the treatment of contaminated and septic bursae. Equine Veterinary Journal 31, 5–11.
2. Haupt, J.L. and Caron, J.P. (2010) Navicular Bursoscopy in the Horse: A Comparative Study: Navicular Bursoscopy in the Horse. Veterinary Surgery no-no.
3. Kane-Smyth, J., Taylor, S.E., García, E.C. and Reardon, R.J.M. (2016) Frequency of Penetration of the Digital Flexor Tendon Sheath and Distal Interphalangeal Joint Using a Direct Endoscopic Approach to the Navicular Bursa in Horses: Frequency of Inadvertent Synovial Penetration in Navicular Bursa Endoscopy. Veterinary Surgery 45, 380–385.
4. Rossignol, F. and Perrin, R. (2003) Tenoscopy of the navicular bursa: Endoscopic approach and anatomy. Journal of Equine Veterinary Science 23, 258–265.
5. Smith, M.R.W. and Wright, I.M. (2012) Endoscopic evaluation of the navicular bursa: Observations, treatment and outcome in 92 cases with identified pathology: Endoscopic evaluation of the navicular bursa in 92 cases. Equine Veterinary Journal 44, 339–345.
6. Mählmann, K., Koch, C. and Bodó, G. (2015) Diagnostic endoscopy of the navicular bursa using a needle endoscope by direct or transthecal approach: A comparative cadaver study: Diagnostic Needle Endoscopy of the Navicular Bursa. Veterinary Surgery 44, 816–824.
7. Richardson, G.L., O’Brien, T.R., Pascoe, J.R. and Meagher, D.M. (1986) Puncture Wounds of the Navicular Bursa in 38 Horses A Retrospective Study. Vet Surgery 15, 156–160.
8. Findley, J.A., Pinchbeck, G.L., Milner, P.I., Bladon, B.M., Boswell, J., Mair, T.S., Suthers, J.M. and Singer, E.R. (2014) Outcome of horses with synovial structure involvement following solar foot penetrations in four UK veterinary hospitals: 95 cases: Outcome of synovial foot penetration. Equine Vet J 46, 352–357.
9. Suarez‐Fuentes, D.G., Caston, S.S., Tatarniuk, D.M., Kersh, K.D. and Ferrero, N.R. (2018) Outcome of horses undergoing navicular bursotomy for the treatment of contaminated or septic navicular bursitis: 19 cases (2002–2016). Equine Vet J 50, 179–185.
10. Smith, M.R.W., Wright, I.M. and Smith, R.K.W. (2007) Endoscopic assessment and treatment of lesions of the deep digital flexor tendon in the navicular bursae of 20 lame horses. Equine Veterinary Journal 39, 18–24.
11. Schumacher, J., Schramme, M.C., Schumacher, J. and DeGraves, F.J. (2013) Diagnostic analgesia of the equine digit: Diagnostic analgesia of the equine digit. Equine Veterinary Education 25, 408–421.
12. Giorio, M.E., Graham, R.J., Berner, D., O’Neill, H.D. and Bladon, B.M. (2024) Presence and size of synovial masses within the navicular bursa correlate well between magnetic resonance imaging and bursoscopy and have a guarded prognosis. Equine Veterinary Journal 56, 982–988.
13. Cillán-García, E., Milner, P.I., Talbot, A., Tucker, R., Hendey, F., Boswell, J., Reardon, R.J.M. and Taylor, S.E. (2013) Deep digital flexor tendon injury within the hoof capsule; does lesion type or location predict prognosis? Veterinary Record 173, 70–70.
14. Maleas, G., Werpy, N., Joostens, Z., Bladon, B., Gerlach, K. and Mageed, M. (2025) Diagnostic performance of ultrasonography, bursography and standing magnetic resonance to detect navicular intrabursal pathology in horses with foot pain. Equine Veterinary Journal evj.14530.