34th Annual Scientific Meeting proceedings

Introduction
Lameness originating in the shoulder of the horse is rare but trauma to the shoulder region can result in a myriad of consequences to the bones, joints and soft tissues of the region, usually manifesting as lameness characterised by a markedly shortened cranial phase of the stride. Comprehensive evaluation of the shoulder is limited by its proximity to the body and the overlying muscles make the presence of swelling difficult to discern and palpation of specific structures difficult.  Hence, the careful use of imaging, while also challenging for this area, is an important requirement for an accurate diagnosis. Conventional imaging is still possible though and routine radiography of the area includes a lateromedial radiograph with the affected limb drawn forward so that the shoulder joint overlaps the trachea to improve visualisation.  Additional oblique views are possible where the most frequently taken are the craniomedial-caudolateral and cranioproximal-craniodistal flexed oblique views in the standing horse.  Ultrasonography is extremely useful for this area as the area is conveniently accessible for the clinician and ultrasound can be used to evaluate the soft tissue structures (such as the bicipital tendon and bursa), identify effusion within the bursa and shoulder joint, but also identify bony pathology difficult to see on the limited radiographic views.  Advanced cross-sectional imaging has been limited by the size of the joint and the proximity of the thorax adjacent to the shoulder.  However, gamma scintigraphy is well suited to identify osseous trauma in this area and is logically used to evaluate markedly lame horses where no pathology has been identified in the distal limb.  Most recently, with the newer CT machines (such as the Qalibra helical CT), it has become possible to image the shoulder under general anaesthesia, when intra-synovial contrast can also be used identify intra-synovial pathology.

Specific conditions

Fractures
One of the most common traumatic fractures involves the deltoid tuberosity, that occur mostly in association with kicks to the shoulder when horses are together at pasture.  These fractures can be missed on lateromedial radiographs and require craniomedial-caudolateral or caudolateral-craniomedial oblique projections to identify them.  Ultrasound can identify these fractures very readily along with any associated damage to the bicipital tendon and bicipital (intertubercular) bursa (rare).  Treatment is local debridement and wound management and horses do well with this approach [1].  Other fractures include supraglenoid tubercle fractures, fractures of the scapular spine and neck, and the proximal humerus [2]. Ultrasound is again helpful to identify the presence of these fractures, although more limited in determining its exact configuration. Fractures of the proximal humerus and scapula can treated conservatively, if appropriate, or by lag screw fixation (proximal humerus), or plates (scapula[3]) although displaced fractures are challenging in adult horses.  Supraglenoid tubercle fractures are amenable to lag screw fixation if not comminuted [4], with a bicipital tenectomy suggested as improving outcome [5].  More recently locking plates have also been used to treat these fractures [6-8]. Only small case numbers are available in the literature to judge prognosis but younger and smaller horses can do well.

Other osseous abnormalities
Proximal humeral osteitis, possibly associated with trauma, is a rare condition of uncertain aetiopathogenesis.  Only scattered case reports [9-12] exist describing this condition. Horses have either been treated surgically or euthanased because the prognosis has been considered as poor.  This author has seen three cases with forelimb lameness of varying severity.  Imaging revealed new bone on the axial margins of the cranial part of the lateral (greater) tuberosity, causing indentation of the overlying bicipital tendon, and effusion within the bicipital bursa.  None of the cases were septic.  The first case was managed successfully by debriding the abnormal new bone tenoscopically but subsequent cases were managed equally successfully using intra-thecal corticosteroid medication.

Shoulder joint trauma
Luxation/subluxation of the shoulder joint has been described in the literature after severe falls, but in low numbers and generally with a poor prognosis [13].  One case at the Royal Veterinary College Equine Referral Hospital has been recently successfully reduced under general anaesthesia with a return to soundness.

Shoulder dysplasia occurs in miniature horses and, while likely to be a growth dysplasia [14], they rarely present until the animals are mature with sudden onset lameness. Such a scenario suggests that trauma superimposed on the presence of dysplasia results in chronic subluxation and, frequently severe, osteoarthritis.  Medical treatment is usually unsuccessful and euthanasia is often elected by the owners because of the severity of the lameness.  Shoulder arthrodesis is an alternative treatment that can reduce morbidity successfully [15].

While developmental osseous cyst-like lesions are found in the shoulder joint, similar lesions, most likely traumatic in origin, are found in the intermediate tubercle of the proximal humerus [16].   They are usually associated with bicipital bursitis.  They can be treated successfully by arthroscopic/bursoscopic debridement but also possibly by intra-synovial medication, at least in the short term.

Soft tissue traumatic injuries
These include aspetic and septic bicipital bursitis and bicipital tendinopathy.  Septic bicipital bursitis is often associated with penetrating injuries and can be managed successfully by bursoscopic lavage [17, 18].  Bicipital tendinopathy can be traumatic or possibly an over-strain injuryand is associated with bicipital bursitis and distension. Management is usually conservative, although bicipital tenotomy has been described for the management of both septic and aseptic bicipital tendinopathy combined within bicipital bursitis and proximal humeral osteitis [11, 19]. Medial displacement of the bicipital tendon, while resembling a traumatic lesion, is usually the result of congenital dysplasia of the intermediate and medial tubercles [20].

Acknowledgements
Dr. Kate Hanousek, European College of Sports Medicine and Rehabilitation resident, Dr. Pius Spiesshofer, European College of Veterinary Surgeons resident, Prof. Andy Fiske-Jackson, and the other equine surgeons and imaging team at the Royal Aeterinary College. Professor Michael Schramme, University of Lyon.

References

1. Fiske-Jackson, A.R., et al., Diagnosis, management, and outcome in 19 horses with deltoid tuberosity fractures. Vet Surg, 2010. 39(8): p. 1005-10.
2. Dyson, S., Sixteen fractures of the shoulder region in the horse. Equine Vet J, 1985. 17(2): p. 104-10.
3. Kidd, J.A., L. Lamas, and F.M. Henson, Repair of a longitudinal scapular fracture in a horse. Vet Surg, 2007. 36(4): p. 378-81.
4. Dart, A.J. and J.R. Snyder, Repair of a supraglenoid tuberosity fracture in a horse. J Am Vet Med Assoc, 1992. 201(1): p. 95-6.
5. Bleyaert, H.F. and J.B. Madison, Complete biceps brachii tenotomy to facilitate internal fixation of supraglenoid tubercle fractures in three horses. Vet Surg, 1999. 28(1): p. 48-53.
6. Frei, S., et al., Fixation of supraglenoid tubercle fractures using distal femoral locking plates in three Warmblood horses. Vet Comp Orthop Traumatol, 2016. 29(3): p. 246-52.
7. Frei, S., et al., Evaluation of the optimal plate position for the fixation of supraglenoid tubercle fractures in warmbloods. Vet Comp Orthop Traumatol, 2017. 30(2): p. 99-106.
8. Ahern, B.J., et al., Supraglenoid tubercle fractures repair with transverse locking compression plates in 4 horses. Vet Surg, 2017. 46(4): p. 507-514.
9. Scilimati, N., et al., Multimodal Diagnostic Imaging to Identify Septic Apophysitis of the Proximal Humerus in a Thoroughbred Foal. J Equine Vet Sci, 2021. 101: p. 103448.
10. Bohn, A., M. Papageorges, and B.D. Grant, Ultrasonographic evaluation and surgical treatment of humeral osteitis and bicipital tenosynovitis in a horse. J Am Vet Med Assoc, 1992. 201(2): p. 305-6.
11. Fugaro, M.N. and S.B. Adams, Biceps brachii tenotomy or tenectomy for the treatment of bicipital bursitis, tendonitis, and humeral osteitis in 3 horses. J Am Vet Med Assoc, 2002. 220(10): p. 1508-11, 1475.
12. Booth, T.M., Lameness associated with the bicipital bursa in an Arab stallion. Vet Rec, 1999. 145(7): p. 194-8.
13. Semevolos, S.A., et al., Shoulder joint luxation in large animals: 14 cases (1976-1997). J Am Vet Med Assoc, 1998. 213(11): p. 1608-11.
14. Boswell, J.C., et al., Radiological study to evaluate suspected scapulohumeral joint dysplasia in Shetland ponies. Equine Vet J, 1999. 31(6): p. 510-4.
15. Semevolos, S.A., J.P. Watkins, and J.A. Auer, Scapulohumeral arthrodesis in miniature horses. Vet Surg, 2003. 32(5): p. 416-20.
16. Ramzan, P.H., Osseous cyst-like lesion of the intermediate humeral tubercle of a horse. Vet Rec, 2004. 154(17): p. 534-6.
17. Vatistas, N.J., et al., Infection of the intertubercular bursa in horses: four cases (1978-1991). J Am Vet Med Assoc, 1996. 208(9): p. 1434-7.
18. Spiesshofer, P., et al., Septic inflammation of the bicipital bursa: clinical, imaging, and surgical findings in nine horses. J Am Vet Med Assoc, 2023. 261(9): p. 1380-1387.
19. Melly, V. and P. Baia, Standing biceps brachii tenectomy to treat chronic bicipital tendinopathy associated with bursal fibrosis and humeral adhesions in a Quarter Horse gelding. Equine Vet Educ. 33: p. 393-399.
20. Coudry, V., A.K. Allen, and J.M. Denoix, Congenital abnormalities of the bicipital apparatus in four mature horses. Equine Vet J, 2005. 37(3): p. 272-5.