EQUINE VETERINARY EDUCATION / AE / MAY 2015


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Case Report


Treatment of a Standardbred racehorse for septic infraspinatus and intertubercular bursitis caused by haematogenous bacterial spread


P. O’Sullivan*, T. Gudehus†, L. Kamm‡ and I. S. Bridge‡ Troytown Grey Abbey Equine Veterinary Services, Kildare, Ireland; †Pferdeklinik Leichlingen, Germany; and ‡Veterinary Associates Equine and Farm, Karaka New Zealand.


*Corresponding author email: ptosval@gmail.com Keywords: horse; intertubercular bursitis; infraspinatus bursitis; bursoscopy


Summary This report describes the diagnosis and treatment of synovial sepsis of the infraspinatus and intertubercular (bicipital) bursae. The origin of infection was considered to be haematogenous spread from an ipsilateral foot abscess. The horse responded well to treatment and returned to full athletic function.


Introduction


Lameness originating from the shoulder region in horses is relatively uncommon. Diseases of the biceps tendon and intertubercular bursa have been reported and treatment options previously described in detail (Gough and McDiarmid 1998; Hawe and McDiarmid 1999; Fugaro and Adams 2002). Septic conditions are most commonly caused by a traumatic incident but the possibility of haematogenous spread to this synovial structure has also been recognised (Adams and Blevins 1989). Sepsis of the infraspinatus bursa has also been reported (Whitcomb et al. 2006). The anatomical arrangement of the soft tissue structures of


the shoulder region is complex. The infraspinatus bursa (ISB) is a small synovial structure located between the caudal portion of the greater (lateral) humeral tubercle and the long portion of the tendon of insertion of the infraspinatus muscle which traverses the caudal part of the greater tubercle and attaches further craniodistally on the humerus (Getty 1975). The intertubercular bursa (ITB) is located between the


tendon of origin of the biceps brachii muscle (biceps tendon) and cranial humerus. This bursa envelops both medial and lateral margins of the biceps tendon. The biceps tendon is bilobed in the region of the bursa and interdigitates with the underlying greater, intermediate and lesser humeral tubercles. The bursa terminates just proximal to the deltoid tuberosity of the humerus (McIlwraith et al. 2005). This case involves a racehorse with synovial sepsis of the ITB and ISB. Diagnosis and treatment are discussed.


Case history A 4-year-old Standardbred gelding in full race training was presented for investigation of acute onset right forelimb lameness (grade 4/5: AAEP score). The horse had raced 5 days prior to presentation. Routine clinical examination including application of hoof testers identified severe pain on palpation of the sole. The shoe was removed and following superficial debridement of the medial aspect of the white line, a superficial subsolar abscess with malodorous purulent material was identified. Minimal undermining of the sole was observed. The abscess was further debrided by removal of a 0.5 cm


portion of sole to allow adequate drainage. The foot was placed in a light bandage to prevent gross contamination and phenylbutazone (4.4 mg/kg bwt i.v. s.i.d.) was administered. No further anti-inflammatory or antimicrobial treatment was initiated. Two days after initiation of treatment, no lameness was


evident at a walk and the horse was very slightly lame on the right forelimb (grade 1/5: AAEP) when trotted in a straight line on a hard surface. Replacement of the shoe and gradual reintroduction of walking exercise was recommended. Four days following initial presentation the horse was re-evaluated following deterioration in lameness. Moderate right forelimb lameness (grade 3/5: AAEP) was again noted.


Clinical examination


Clinical examination of the foot and lower limb was unremarkable and no response noted following application of hoof testers. A painful response to digital pressure was noted over the lateral aspect of the greater tubercle of the humerus. Otherwise manipulation of the proximal limb was not resented. The biceps tendon was not sensitive to palpation or manipulation. No evidence of external trauma was present and the horse was subsequently treated as previously with phenylbutazone (4.4 mg/kg bwt i.v. s.i.d.). The severity of lameness increased within the next 24 h with the horse becoming reluctant to bear full weight on the limb (grade 4/5: AAEP).


Radiographic examination of the shoulder region including mediolateral and craniomedial-caudolateral radiographs of the scapulohumeral joint, cranioproximal-craniodistal skyline projections of the humeral tubercles and tangential views of the deltoid tuberosity did not identify any significant abnormalities. Ultrasonographic examination identified mixed echogenic distention of the ISB with no abnormal findings of the scapulo-humeral joint, biceps tendon or ITB noted. Ultrasound-guided synoviocentesis of the ISB was attempted but synovial fluid could not be aspirated. (Schneeweiss et al. 2012) A tentative diagnosis of septic infraspinatus bursitis was


made, with haematogenous localisation following spread from the ipsilateral foot abscess considered the most likely source of infection.


Case management


Antimicrobial treatment was initiated (procaine benzylpenicillin 22.000 iu/kg bwt i.m. b.i.d. and gentamicin 6.6 mg/kg bwt i.v. s.i.d.). The horse was hospitalised for further treatment and monitoring. Endoscopic examination and


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