Auxiliary osseous findings in fetlocks of non-racing sports horses with sagittal groove disease of the proximal phalanx on low-field magnetic resonance imaging.

BACKGROUND: Sagittal groove disease of the proximal phalanx in equine athletes is commonly considered a bone stress injury. Repetitive hyperextension of the fetlock under high load is thought to contribute to its development. Concurrent changes are often reported in the dorsal sagittal ridge of the third metacarpus/metatarsus (MC3/MT3). OBJECTIVES: To describe the spectrum of associated osseous abnormalities that are present in the fetlock in a large group of horses diagnosed with sagittal groove disease on low-field magnetic resonance imaging (MRI). STUDY DESIGN: Retrospective, cross-sectional. METHODS: MRI images of horses diagnosed with sagittal groove disease at Equitom Equine Clinic between March 2014 and March 2023 were evaluated using semi-quantitative grading schemes and a sagittal groove disease MRI classification system. RESULTS: MRIs of 132 limbs were evaluated, predominantly from warmbloods used for showjumping (n = 83) and dressage (n = 18). Osseous densification and bone oedema-like signal grades were higher in the dorsal sagittal ridge than palmarly/plantarly (p < 0.001 and p < 0.05, respectively). Grades of both osseous densification and bone oedema-like signal in the dorsal sagittal ridge did not significantly differ between the different sagittal groove disease MRI classifications (both p > 0.05). MAIN LIMITATIONS: Inclusion based on original MRI reports, absence of control group, small numbers within some grading groups hindering statistical analyses. CONCLUSIONS: Findings support the aetiological theories of chronic bone-stress due to loaded fetlock hyperextension however the severity of osseous changes of the dorsal sagittal ridge does not appear to be associated with the severity of sagittal groove disease classification.

HISTORIAL: La enfermedad del surco sagital (SGD) de la falange proximal en equinos atletas, es considerada comúnmente como un lesión de hueso por estrés. Se piensa que la hiperextensión repetitiva del nudo bajo alta carga contribuye a su desarrollo. Cambios concurrentes ocurren menudo en la cresta sagital dorsal del tercer metacarpo/metatarso (MC3/MT3). OBJETIVOS: Describir el espectro de anomalías óseas asociadas que están presentes en el nudo en un gran grupo de caballos diagnosticados con SGD por imágenes de resonancia magnética de baja frecuencia (MRI). DISEÑO DEL ESTUDIO: Retrospectivo, transversal. MÉTODOS: Imágenes de MRI de caballos diagnosticados con SGD en la Clínica Equina Equitom de Marzo 2014 a Marzo 2023, fueron evaluadas usando esquemas de graduación semi­cuantitativos y un sistema de clasificación de SGD MRI. RESULTADOS: MRIs de 132 extremidades fueron evaluadas, proveniente principalmente de caballos de sangre caliente (Warmblood) usados para salto (n = 83) y adiestramiento (n = 18). Densificación ósea y los grados de las señales parecidas al edema de hueso, eran mayores en la cresta sagital dorsal que en palmar/plantar (p < 0.001 y p < 0.05, respectivamente). Los grados de tanto la densificación ósea como de la señal parecida al edema óseo en la cresta sagital, no difirieron significativamente entre las clasificaciones SGD MRI (ambos p > 0.05). LIMITACIONES PRINCIPALES: Inclusión basada en los informes de MRI originales, ausencia de grupo de control, numero pequeño dentro de algunos de los grupos por graduación lo que no permitió hacer análisis estadísticos. CONCLUSIONES: Los hallazgos apoyan las teorías etiológicas del estrés óseo crónico debido a la hiperextensión del nudo bajo carga, sin embargo la severidad de los cambios óseos de la cresta sagital dorsal no parecen estar asociada con la severidad de la clasificación SGD.

Low-field magnetic resonance imaging of sagittal groove disease of the proximal phalanx in non-racing sport horses.

BACKGROUND: Injuries of the sagittal groove of the proximal phalanx (P1) in equine athletes are considered to predominantly occur due to chronic bone stress overload. OBJECTIVES: To describe the range of abnormalities that is present in the sagittal groove in a large group of horses diagnosed with sagittal groove disease (SGD) on low-field MRI. STUDY DESIGN: Retrospective, cross-sectional. METHODS: Medical records were searched to identify initial MRI images of horses diagnosed with SGD and these were blindly evaluated using a semi-quantitative grading scheme and novel SGD MRI classification system reflecting potential pathways of pathological progression and severity of stress injury. RESULTS: A total of 132 limbs from 111 horses were included in the study; predominantly warmbloods competing in showjumping (n = 83) and dressage (n = 18). SGD MRI classifications were: 0 (normal, n = 0), 1 (small subchondral defect, n = 2), 2 (osseous densification, n = 28), 3 (subchondral microfissure with osseous densification, n = 7), 4 (bone oedema-like signal within the subchondral ± trabecular bone and ± subchondral microfissure or demineralisation, n = 72), 5 (incomplete macrofissure/fracture, n = 23) and 6 (complete fracture, n = 0). Classification 4c (bone oedema-like signal with demineralisation) and 5 had higher proportions in the plantar third of hindlimbs (3% and 10%, respectively) compared with forelimbs (0% and 0%, respectively). SGD classification and extent of bone oedema-like signal were not significantly different between lame (n = 116) and non-lame limbs (n = 16) (both p > 0.05). Periosteal new bone and oedema-like signal were identified (either confidently or suspected) at the dorsoproximal aspect of P1 in 25% and 39% of limbs, respectively. MAIN LIMITATIONS: Inclusion via diagnoses in original MRI reports, variable clinical history, small size of some classification groups. CONCLUSIONS: The presence or absence of lameness is not a dependable measure of the severity of SGD. The periosteal oedema-like signal of P1 has not previously been described in MRI of SGD and further supports the concept of bone stress injury.

Single energy metal artifact reduction performs better than virtual monoenergetic dual-energy reconstruction in CT of the equine proximal phalanx.

Metal artifacts in CT negatively impact the evaluation of surgical implants and the surrounding tissues. The aim of this prospective experimental study was to evaluate the ability of a single energy metal artifact reduction (SEMAR™, Canon) algorithm and virtual monoenergetic (VM) dual-energy CT (DECT) scanning techniques to reduce metal artifacts from stainless steel screws surgically inserted into the equine proximal phalanx. Seven acquisitions of 18 cadaver limbs were performed on a Canon Aquilion One Vision CT scanner (Helical +SEMAR, Volume +SEMAR, Standard Helical, Standard Volume and VM DECT at 135, 120, and 105 keV) and reconstructed in a bone kernel. Blinded subjective evaluation performed by three observers indicated a significant effect of acquisition in both adjacent tissues (P < 0.001) and distant tissues (P < 0.001) and the best metal artifact reduction was seen with Helical +SEMAR and Volume +SEMAR. The subjective overall preference of CT acquisition type was (1) Helical +SEMAR, (2) Volume +SEMAR, (3) VM DECT 135 keV, (4) VM DECT 120 keV, (5) VM DECT 105 keV, (6) Standard Helical, (7) Standard Volume (P < 0.001). Unblinded objective evaluation performed by one observer showed that VM DECT 120 keV, Helical +SEMAR, and Volume +SEMAR performed similarly and were objectively the best at reducing blooming artifact. Overall, the best metal artifact reduction was obtained with SEMAR, followed by VM DECT. However, VM DECT performance varies with energy level and was associated with decreased image quality in distant tissues and artifactual overcorrection of metal artifacts at high energy levels.

Follow-Up Magnetic Resonance Imaging of Sagittal Groove Disease of the Equine Proximal Phalanx Using a Classification System in 29 Non-Racing Sports Horses.

Evolution of magnetic resonance imaging (MRI) findings in horses with sagittal groove disease (SGD) of the proximal phalanx is relatively sparsely described. This retrospective, descriptive, longitudinal study describes the findings of sequential low-field MRI fetlock examinations in horses with SGD of the proximal phalanx using a classification system. Twenty-nine horses were included, predominantly warmbloods used for show jumping (79%). For 29 limbs re-examined during the initial rehabilitation period, classification remained constant (n = 18), increased (n = 2), decreased (n = 7), and fluctuated (n = 2). Notably, two limbs with initial classification 4b (bone oedema-like signal with subchondral microfissure) and one with 4c (bone oedema-like signal with subchondral demineralisation) progressed to classification 5 (incomplete macrofissure/fracture), highlighting their potential as prodromal or imminent fissure pathology. Following conservative (n = 28) and surgical (n = 1) treatment, 86% of the horses re-entered full training and competition with a mean ± sd recovery time of 9.4 ± 4.4 months. In total, 20% of horses in the study subsequently presented for repeat MRI due to recurrent lameness after resuming full work, with classification that was the same (n = 2), increased (n = 2), or decreased (n = 2) compared with the last scan. This study underscores the variability in progression of SGD MRI findings, emphasising the need for further larger-scale research into patterns of progression.