The use of radionuclide bone scanning in the diagnosis of tibial ‘stress’ fractures in the horse: a review of five cases.

This research paper discusses the use of radionuclide bone scanning in detecting tibial stress fractures in horses, particularly in five two-year-old thoroughbred horses that developed sudden hindlimb lameness after moderate to fast exercise.

Overview of the Study

• The researchers investigated five cases of two-year-old Thoroughbreds that started to show signs of hindlimb lameness after undertaking moderate to fast exercise. The main focus of the study was the application of radionuclide bone scanning, using a handheld scintillation detector following an injection of Technetium-99m methylene diphosphonate (Tc99 MDP), which helps in the identification of tibial stress fractures.

Findings

• During the investigation, they found that the radionuclide bone scanning allowed for the detection of stress fractures that were missed or undetectable through normal radiological examination. These radiological findings were subtle and mostly confined to new bone and callus growth at the fracture site.
• In two of the horses, these signs took several weeks to develop and become noticeable. However, in the other three horses, these signs were already present at the onset of lameness, suggesting that there had been ongoing bone damage or pathology before the fracture occurred.
• What remained consistent through all five cases was the location of the most evident radiological signs – the proximal lateral tibia some 8 to 9 cm from the femoro-tibial joint surface.
• The detection of five cases of tibial fractures in one racing season led the researchers to believe that this condition has been underdiagnosed in the clinic prior to the availability of bone scanning.

Conclusion

• The study highlights the importance and effectiveness of radionuclide bone scanning in diagnosing tibial stress fractures in horses. This improved detection method might aid in early diagnosis and prevention of severe bone injuries in race horses, thereby avoiding any unnecessary suffering and possibly extending their racing careers.