ANALYSIS OF THE ULTRASONOGRAPHIC SUPERFICIAL DIGITAL FLEXOR TENDONS IMAGE IN HALF-BRED HORSES

Radomir Henklewski¹, Maciej Janeczek², Aleksander Chrószcz², Norbert Pospieszny², Kornel Ratajczak^1
1 Department and Clinic of Veterinary Surgery, Wrocław University of Environmental and Life Sciences, Poland
² Department of Biostructure and Animal Physiology, Wrocław University of Environmental and Life Sciences, Poland

ABSTRACT

The investigations were carried out on 3.5 years old 20 half-bred horses. The measurements were made during an active race training. The ultrasonographic examination of SDFT (superficial digital flexor tendon) was carried out with a linear transducer 6-8 Mhz. The averaged values of cross-sectional area measurements were 92.36 mm² at level A, 95.23 mm² at level B and 105.59 mm² at level C. The results were statistically analyzed with t-Student test.

Key words: superficial digital flexor tendon, ultrasonography, locomotor system, horse.

INTRODUCTION

The diseases of locomotor system are the most important issue in animals, used in sport, the same as the locomotor diseases of sportsmen [3,20]. The examinations carried out in United Kingdom proved, the locomotor system injuries in 43–46% referred to tendons injuries [20]. None of them (except bone tissue) heals by first intention, therefore the accurate diagnosis of locomotor system tissues injuries plays the most important role in proper treatment and further convalescence [3]. Magnetic resonance imaging (MRI), tomography, scyntygraphy, ultrasonography and tenoscopy are commonly used in tendons imaging [5,6,12,14,15,23]. Tendons play the great role in load-transfer between muscles and bones [13,22]. According to the tendons architecture, we can divide them in two groups: energy storing tendons and positional tendons. First of them are used not only in passive energy-transfer generated by skeletal muscles, but also in potential energy-storing further released as kinetic energy [1,4,20]. The superficial digital flexor tendon (SDFT) belongs to the energy storing tendons. The most incidence of SDFT traumas arise from biomechanical changes in horse's limb connected with its function [14]. The ultrsonographic assessment of tendon injuries can be based on 5 criteria similar to Roentgen signs in radiology – alterations in echogenicity, size, margination, shape and position. The most important for precise diagnosis are changes in echogenicity and size, usually assessed subjectively, therefore the objective criteria of measurements can be useful [19]. The aim of this study was precise description of normal ultrasonographic SDFT image in half-bred horses.

MATERIAL AND METHODS

The investigations were carried out in 20 half-bred horses 3,5 years old. All evaluated horses were free of tendon/ligament disorders as determinated by physical examination. The investigations were made during an active race training. Before the ultrasonographic examination, the metacarpal region in both forelimbs were prepared by close-clipping, soaking in hot water with soap and then covering with acoustic gel. The ultrasound unit Anser 485 with the 6–8 Mhz linear array probe and a stand-off pad was used during imaging. The images were recorded using the thermal printer Mitsubishi P 91 E.

During the ultrasonographic examination both forelimbs were full-loaded. The transverse images were obtained from judged by Strőnberg [21] and Ying-Ling [24] criteria levels. The SDFT circumference and the cross-sectional area were measured by tracing around the outline of the tendon using the dedicated software application. The SDFT means was preformed using appropriate t-Student test.

RESULTS

The exanimated tendons were less echogenic than skin and more echogenic than subcutaneous tissue. The echogenicity of SDFT and deep digital flexor tendon (DDFT), located below, was the same. It occurred no echogenicity differences at all examinated SDFT cross-sectional area levels. The ultrasonographic transverse and sagittal SDFT image has got homogenous echogenicity. The cross-sectional area of SDFT was oval-shaped at A level, it becomes flatten out at B level and it was the most visible at C level. SDFT becomes semilunar bent-shape enclosing the palmar surface of DDFT (Fig. 1, 2 ,3 ). The cross-sectional area increases in distal forelimb course. The averaged values of cross-sectional area measurements were 92.36 mm² at level A 95.23 mm² at level B and 105.59 mm² at level C (Table 1). The statistical analysis proved statistical significance between cross-section areas on level A and C, and between B and C (Table 1).

Fig. 1. The SDFT at A level

Fig. 2. The SDFT at B level

Fig. 3. The SDFT at C level

Table 1. Measurements of the CSA (cross section area) of the superficial digital flexor tendons A, B, – the difference between the mean value of measurements is statistically significant p ≤ 0,01

	A	B	C
mean value (mm2)	92.36A (max – 105, min – 75) SD – 8.1	95.23B (max – 102, min – 88) SD – 3.85	105.59AB (max – 120, min – 97) SD – (6.08)

DISCUSSION

The ultrasonography of locomotor system undoubtedly plays an irreplaceable role in human and veterinary medicine. Diagnostic ultrasonography provides a safe, noninvasive, easy-access and precise imaging method [10,11]. Our investigations proved the same echogenicity of SDFT and deep digital flexor tendon (DDFT) located below. The same results obtained other authors [1,2,3]. It is commonly used in horse orthopedics to assess an injuries SDFT, to visualize the morphology of soft tissue structure and the repair-processes monitoring [2,7,16,17]. Gillis et al. [8] described the normal sonographic image and thickness of SDFT at levels (A, B, C) in 50 Arabian bred horses free of tendon/ligament disorders as determinated by clinical examination. Çelimli et al. [2] proved, the cross-sectional area, circumference and width of SDFT increases in distal forelimb course and the thickness of SDFT shown decreasing value. Our investigations proved above mentioned results in the cross-sectional area of SDFT. In case of any inflammatory state and during tendon injuries the ultrasonographic images are strongly correlated with changes observed during histopathological examination. The investigated SDFT images are aechogenic or strongly hypoechogenic in ultrasonographic visualization during the acute inflammations and the extravasations of blood.  The heteroechogenic or hyperechogenic areas of SDFT in ultrasonographic examination were caused by the chronic inflammations, fibrosis and intratendon scars [16]. It occurred, the first manifestation of inflammarory process, expanding in SDFT, is an increase of SDFT cross-sectional area and their circumference. The ultrasonography makes possible the visualization of SDFT adaptation process during increasing training effort and training optimization [9,24]. Many authors raise the question of results repetition, especially the measurements assessed in ultrasonographic examination. In Pickersgill et al. [18], no significant differences in ultrasonographic SDFT image analysis carried out by other persons. Simultaneously the various level of transverse image during examination have direct effect on assessed results. The ultrastructure of investigated tendon affect their ultrasonographic image. Therefore the most important, for accurate measurement, is the proper use of linear array probe. Even small array probe deflection effects significantly on the echogenicity of investigated tissues [6,17]. Ii is proved, more influence of breed and training on the ultrasonographic image and measurement values than age, weight and size of all free of tendon/ligament disorders animals [2].

CONCLUSIONS

Ultrasound investigations of the superficial digital flexor tendon can be a useful tool in horse's locomotor system diagnosis. The echogenisity of SDFT and the deep digital flexor tendon was similar and clearly differs from surrounding tissues. The results of all cross-sectional area levels echogenicity for SDFT was the same. Probably, the introduced methods of SDFT examination will be helpful in clinical examination of locomotor system disorders.

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Accepted for print: 15.10.2009

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Radomir Henklewski
Department and Clinic of Veterinary Surgery,
Wrocław University of Environmental and Life Sciences, Poland
Pl. Grunwaldzki 51, 50-336 Wrocław, Poland

Maciej Janeczek
Department of Biostructure and Animal Physiology,
Wrocław University of Environmental and Life Sciences, Poland
Kożuchowska 1/3, 51-631 Wrocław, Poland
Phone: 71 32 05 744
email: janeczekm@poczta.onet.pl

Aleksander Chrószcz
Department of Biostructure and Animal Physiology,
Wrocław University of Environmental and Life Sciences, Poland
Kożuchowska 1/3, 51-631 Wrocław, Poland

Norbert Pospieszny
Department of Biostructure and Animal Physiology,
Wrocław University of Environmental and Life Sciences, Poland
Kożuchowska 1/3, 51-631 Wrocław, Poland

Kornel Ratajczak
Department and Clinic of Veterinary Surgery,
Wrocław University of Environmental and Life Sciences, Poland
Pl. Grunwaldzki 51, 50-336 Wrocław, Poland

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