Twelve horses met the criteria to be included in the study, (6 geldings, 4 mares, 2 stallions) with a median age of 5.5 y (mean 6.3, range: 3 to 12 y). Of these 12 horses; 8 were Quarter horses, 2 Appaloosas, 1 Paint, and 1 Thoroughbred. Six horses were used for barrel racing, 5 for roping and/or reining, and 1 was used for racing (). The hospital breed distribution is 50% Quarter horses and hospital use distribution is 30% western performance events. Three of the horses sustained an injury to the collateral ligament while performing, and 9 were injured while they were in a stall or turned out to pasture/paddock.
The median lameness score was 4.0/5 (mean 3.5, range: 2–4/5). The median duration of clinical signs prior to presentation was 5 d (mean 8.8 d, range: 1 to 28 d). On clinical examination, 9 horses were lame in the right hind limb and 3 were lame in the left hind limb. The ligaments that were damaged included the long lateral collateral ligament (7 cases), long medial collateral ligament (3 cases), and both medial and lateral long collateral ligaments (2 cases). Specific information on lameness and ligaments injured are outlined in . Damage to the short oblique collateral ligaments was not found in any of the cases.
Each horse withdrew the limb and held the tarsus in flexion when minimal digital pressure was applied over the damaged collateral ligament. All horses resisted manipulation of the tarsus (flexion, medial, and lateral bending force) and had some degree of periarticular edema with marked edema focused around the damaged collateral ligament. Subjectively, 8 horses had severe effusion and 4 horses had moderate effusion within the tarsocrural joint.
Bacterial culture and sensitivity performed were performed for 2 cases, one of which was negative (case 6) and the other was positive for Streptococcus (case 8). Cytology was not performed in any of the cases.
All cases had radiographic evidence of soft tissue thickening, with marked thickening focused around the injured collateral ligament. Ten of the 12 horses had no significant articular abnormalities within the tarsocrural joint during the radiographic examination performed at the time of presentation. Radiographic findings within each tarsocrural joint are described in . Three horses had evidence of osteoarthritis within the tarsometatarsal and distal intertarsal joint.
Follow-up radiographs were taken between 30 d and 240 d following the initial examination. Four of the 6 horses with follow-up radiographs had signs of progressive osteoarthritis at the time of follow-up examination ().
All horses had evidence of thickened synovium, fibrinous loculations, and/or coagulated blood and hyperechoic swirling synovial fluid within the tarsocrural joint (). The damaged collateral ligament in each case had moderate diffuse fiber pattern disruption that extended the length of the ligament, along with increased cross-sectional area compared with the contralateral limb (). None of the injured collateral ligaments had complete disruption of the fibers within the ligament. Cartilage irregularity was seen on the medial trochlear ridge in case 7. During arthroscopic surgery, a full-thickness cartilage erosion was seen on this area of the medial trochlear ridge.
Ultrasound image showing hyperechoic synovial fluid/fibrin within a plantar pouch of a tarsocrural joint (outlined by white arrows).
Transverse section of a medial collateral ligament showing moderate fiber damage within the ligament. The white arrow is pointing to the damaged portion of the ligament.
Of the 7 horses that had follow-up ultrasonography, horses of cases 4, 3, 9, and 11 had a normal collateral ligament fiber pattern at 80, 90, 120, and 120 d, respectively, following the initial examination. Three of the 7 horses with follow-up examinations had collateral ligaments that remained larger than the tarsocrural collateral ligament on the contralateral limb. At 90 d following the initial examination, case 2 had a 50% improvement in fiber pattern and 75% improvement in cross-sectional area. The case 7 horse had 50% improvement in fiber pattern at 190 d, along with roughening of the medial trochlear ridge of the talus. The case 12 horse had 80% improvement in fiber pattern at 120 d. The other 6 horses were lost to ultrasound follow-up due to the owner declining further evaluation of the horse.
Treatment and outcome
Twelve horses were hospitalized for a median of 6.5 d (mean 5.6 d, range: 4 to 17 d) during the study period (). Nine of 12 horses were medicated with procaine penicillin G and gentamicin sulfate while they were hospitalized. After 4 d of treatment with procaine penicillin G and gentamicin sulfate, the case 8 horse was switched to enrofloxacin because clinical signs became more severe. The remaining horse (case 3) received only gentamicin sulfate. outlines the treatment details per case. The horses of cases 11 and 12 did not receive any systemic antibiotics.
Each horse received systemic phenylbutazone and a DMSO/nitrofurazone sweat wrap over the affected tarsocrural joint for 3 to 10 d, starting the day of presentation. Three horses (cases 2, 3, 8) had a single joint lavage of the affected tarsocrural joint with lactated Ringer’s solution. One horse (case 2) had the joint lavage 2 wk prior to arthroscopic surgery and 1 horse (case 8) had the joint lavage 3 d prior to arthroscopic surgery.
Local antimicrobial therapy is summarized in . Six horses received intra-articular injections of amikacin sulfate. Following minimal improvement with intra-articular injections of amikacin sulfate, the horses of cases 6 and 8 received regional limb perfusion with cefotaxime initially, followed by imipenem and cilastatin.
Extracorporeal shock wave therapy over the damaged collateral ligaments was performed in 3 cases (cases 4, 7, and 12). The horse of case 4 had 1 treatment 14 d following the initial injury. The horse of case 7 had 2 treatments at 30 d and 60 d following the initial injury. The horse of case 12 had 1 treatment 60 d following the initial injury.
Arthroscopic lavage and debridement of the tarsocrural joint was performed on 8 of 12 horses. Median duration of time from injury to surgery was 14 d (mean 14.4 d, range: 1 to 28 d) (). Serosanguinous synovial fluid, fibrin, and blood clots were flushed and debrided from the tarsocrural joint in all 8 horses that had arthroscopic surgery (). There was widespread cartilage thinning and fibrillation within the tarsocrural joint in all 8 horses. Six of 8 horses had focal full thickness cartilage erosions and/or bone fragments removed during the initial arthroscopic surgery (; ). Synovial proliferation along with a tear in the joint capsule over the collateral ligament and fraying of the collateral ligament were seen during arthroscopic surgery in each case. The horses of cases 2 and 6 had a second arthroscopic surgery to remove additional fibrin and fibrillated cartilage (). Following the second arthroscopic surgery, the horse of case 6 was hospitalized for 17 d and received phenylbutazone for 10 d. The horse of case 2 was hospitalized for 2 d and received phenylbutazone for 4 d. Systemic and local antimicrobial therapy for these 2 cases is outlined in .
Arthroscopic surgery findings
Arthroscopic intra-operative photograph of a tarsocrural joint with a significant amount of fibrin and synovial proliferation. White arrows point to fibrin tags within the joint.
Arthroscopic intra-operative photograph of a full-thickness cartilage erosion on the medial malleolus. The white arrow outlines the full thickness cartilage erosion.
In total, 12 horses were discharged from the hospital with instructions to have strict stall rest for 30 to 120 d, along with ultrasound examinations every 30 to 60 d. Thirty days of stall rest with 15 min of daily hand walking began once the horses had an 80% improvement in lameness, along with significant sonographic improvement in the fiber pattern of the damaged collateral ligament. Following stall rest with hand walking, horses were turned out in a 30′ × 30′ paddock for 30 d and then 30 d of increasing exercise under saddle. The horses of cases 4 and 5 were discharged with instructions to administer doxycycline hylate (Doxycylcine; West-Ward) 10 mg/kg BW, PO, BID, for 4 and 10 d, respectively. The horses of cases 6 and 8 were discharged with instructions to administer chloramphenicol (Viceton Biomeda, Le Sueur, Minnesota, USA), 50 mg/kg BW, PO, TID for 7 and 14 d, respectively.
At the time of follow-up 4 horses were athletically sound (). The horse of case 3 went back to its previous level of performance 3 mo following the initial presentation; it was retired after 6 mo of performance due to a carpal injury. Seven horses with follow-up for more than 3 y were retired due to tarsocrural joint lameness despite strict stall rest, and remained pasture sound at the time of follow-up (). The horse of case 10 was still in convalescence 60 d after injury, and the horse of case 8 was euthanized due to a persistent severe lameness in the affected tarsus 30 d following the initial presentation.
Three of the 4 horses that returned to their previous level of performance were grade 3/5 lame and had moderate effusion at presentation; all 4 horses had been seen within 24 h of the initial injury. Six of 7 horses that did not have a positive outcome were grade 4/5 lame and all 7 horses had severe tarsocrural joint effusion.