Received: 2 November 2023 | Accepted: 8 November 2023 DOI: 10.1111/eve.13922
C L INI C A L COMMENTA RY
Rib fractures in horses Yvonne S. Hall
Correspondence: Yvonne S. Hall Email:
suzy.hall@theleh.co.uk
| Russell Parker Liphook Equine Hospital, Forest Mere , Liphook, Hampshire , UK
The case report by (Jimenez-Rihuete et al., 2024 ) describes an in- teresting case of rib fracture in a racehorse with an attributable hindlimb lameness. This case is the first to suggest that caudal rib fractures are a cause of hindlimb lameness and peri-regional diag- nostic analgesia of a rib fracture can be used to alleviate hindlimb lameness. A recent retrospective study (Hall et al., 2022 ) reported 73
horses diagnosed with a rib fracture of which 56% (41/73) presented due to poor performance with a fewer number of horses presenting with lameness as a primary complaint (21/73). Undoubtedly rib frac- tures are painful in the acute stages of injury, with the most common site for rib fracture in a horse being dorsally (5-15 cm from the cos- tovertebral junction) on the 18th rib (Hall et al., 2022 ). In this study, not all horses with caudal rib fractures were found to have lameness; those that were lame had a variable pattern of lameness. All of the horses which underwent diagnostic analgesia were found to have lameness independent to the rib fracture. However, only a small per- centage of horses underwent diagnostic analgesia, a limitation of a retrospective study. An alternative retrospective case series of 50 rib fractures
(Wylie & Head, 2016 ) reported 5 fractures of the first rib which all occurred in racing Thoroughbreds (age 2–7 years with a median age of 3), all of which had ipsilateral forelimb lameness. In the absence of a traumatic incident, the authors suggested that fractures of the 1st rib may represent fatigue fracture pathology associated with training. A similar aetiology is possible for caudal rib fractures but is considered unlikely as this injury is not over-represented in racing Thoroughbreds compared with a general population of horses and trauma remains the most likely cause. Ribs can be imaged in detail with nuclear scintigraphy given the
relatively small amount of overlying soft tissue. Orthogonal images (lateral, dorsal and oblique) should be used to localise the region, extent, pattern and origin of increased radiopharmaceutical uptake. Nuclear scintigraphy is highly sensitive in identifying osteoblas- tic activity but has low specificity for identifying the nature of the pathological process. Fractures show increased radiopharmaceutical
See Related article: https:// doi. org/ 10. 1111/ eve. 13904 . Equine Vet Educ. 2024;36:285–287.
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uptake within 24–72 h post-injury, making nuclear scintigraphy highly sensitive in the acute stage of disease versus radiographic signs which may not be seen for around 7–10 days unless the fracture is displaced. The appearance of a fracture on nuclear scintigraphy in- cludes 5–7 days of diffuse intense uptake, 1–4 weeks of focal intense uptake (Figure 1 ) and then a gradual decrease of radiopharmaceuti- cal uptake over the next 6–12 months. This prolonged visibility on scintigraphy means that is difficult to age a fracture based on scin- tigraphy alone. Ultrasonography is potentially more suitable to mon- itor fracture healing and identify those cases which are non-healing and require intervention. Costochondral junctions normally have a moderately increased radiopharmaceutical uptake on nuclear scin- tigraphy and should not be mistaken for a rib fracture (Figure 1 ). The caudal ribs overly the kidney (Figure 1 ) but in most instances have a mild to moderate diffuse region of increased radiopharmaceutical uptake. The use of furosemide 1 h before imaging has been advo- cated to improve soft tissue clearance and improve image count to background ratio. This was evaluated in a recent study where 1 mg/ kg furosemides was administered intravenously 1 h post 99 m Tc- HDP administration and the image quality was assessed subjectively and semi-quantitively. There was no significant difference in image quality or radiation dose rate to handler, with a minimum distance of 30 cm distance having the most effect on reducing the handler dose rate by 65% (Mageed et al., 2021 ). Ultrasonographic examination is highly sensitive and specific in
identifying rib fractures (Hall et al., 2022 ). If a rib fracture is sus- pected in the initial stages of examination, then survey ultraso- nographic examination of the ribs is recommended, especially the caudal ribs. However, rib fractures rarely result in focal localising pain on palpation and so even a detailed clinical examination may be unrewarding. Ultrasonography of the ribs is a simple technique; clipping is not required and discontinuity and callus within the lat- eral cortex of the ribs is easy to identify (Figure 2 ) but should not be confused with the costochondral junction (Figures 3 and 4 ). The costochondral junction is identified by the presence of hypoechoic cartilage and it should be noted that the margins of adjacent ribs
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