Trans-rectal ultrasound
Findings:
- The sacrum is caudodorsally rotated from the level of the lumbosacral junction. At the level of the sacrococcygeal junction, the Cd1 vertebra is severely ventrally displaced in relation to the sacrum (yellow bracket). The margins of the sacrococcygeal junction are moderately irregular. At this level, several small osseous fragments are identified (asterisk), and multiple are surrounded by hypoechoic fluid (blue arrows).
Conclusions:
- Chronic sacrococcygeal luxation with draining tracts and possible sequestrums.
Pre-op radiographs:
The Cd1 vertebra is severely ventral displaced in relation to the sacrum. The opposing endplates of the caudal sacrum and Cd1 are severely flattened in an oblique plane with moderate osseous proliferation along the margins. Ventral to the Cd1 cranial endplate a small poorly defined and rounded osseous body is identified –> findings are compatible with chronic sacrococcygeal luxation and suspected fragmentation.
The caudal endplate of Cd3 is moderately irregularly marginated –> concerns for osteomyelitis.
Procedure:
Resection of remaining coccygeal vertebrae (1-3):
- The coccygeal vertebrae were successfully dissected free of all soft tissue attachments and resected without complication. Several fragments of bone within their own draining tracts were obtained and submitted for culture and sensitivity.
Culture and sensitivity:
- Aerobic : streptococcus equi ssp. Zooepidemicus (90%); B-hemolytic staphylococci (<1%)
- Anaerobic : Bacteroides fragilis (95%); Gram negative bacilli (5%)
Post-op radiographs:
The coccygeal vertebrae have been removed. The margins of the caudal ventral aspect of the last sacral vertebra remains smooth and ill-defined.
The previously described osseous proliferation along the dorsal aspect of the sacral segment is now reduced in size and smooth.
A deep gas-filled cavity is noted ventrally to the caudal aspect of the sacrum. A Penrose drain is superimposed with this cavity in one of the views.
The dorsal wall of the rectum this ventrally deviated at this level.
A little bit more…
- Sacrococcygeal luxation and sacral fractures in horses are rare and poorly described.
- Injuries are most often secondary to backing-up into an object, sitting down suddenly, falling over backwards or landing on the tail. Injuries may also be iatrogenic, such as from lifting a patient by the tail when repositioning under general anaesthesia (McMaster et al.)
- A gross morphological change to the pelvic anatomy is often observed, such a boney protuberance/enlargement. Fracture or luxation in this region may also be palpable (Butler et al., Kearney et al).
- Loss of tail tone, progressing into tail and anus paralysis may be observed due to damage to the cauda equina (Butler et al., Kearney et al., McMaster et al.)
- Of the few reported, ventral displacement of the luxation/fracture seems prevalent (may be due to the pull of the pelvic musculature) (Collatos et al., Butler et al.).
- The tail has been speculated to be used for counterbalance during athletic activities, although some riders report no changes pre- and post- amputation (Collatos et al.).
- Some horses may develop tailhead puritis due to concurrent caudal equine neuritis, or regional inflammation from trauma or post amputation (Collatos et al.).
- Lateral radiographs of the sacrum may allow visualization of fracture, especially if more caudally located, or sacrococcygeal luxation. In some instances, nuclear scintigraphy and/or trans-rectal ultrasound are necessary to identify changes to the sacrum (Kearney et al.).
- In horses with cauda equina syndrome, surgical decompression of fractured/luxated vertebrae, epidural corticosteroids and physical therapy may be considered (McMaster et al.).
References:
- Collatos C, Allen D, Chambers J, Henry M. Surgical treatment of sacral fracture in a horse. Journal of the American Veterinary Medical Association. 1991 Mar 1;198(5):877-9.
- McMaster M, Munsterman A, Albanese V. Traumatic coccygeal luxation and distal amputation of the tail of an Appaloosa mare. Equine Veterinary Education. 2016 Sep;28(9):497-502.
- Kearney EM, Trostle SS. Inability to lift the tail in a Thoroughbred gelding. Journal of the American Veterinary Medical Association. 2023 Aug 18;1(aop):1-2.
- Butler JA, Colles CM, Dyson S, Kold S, Poulos P. Clinical radiology of the horse. Oxford: Blackwell science; 2000 Jan 11.
