Estimating the Plain and Negative Tendonography techniques for evaluating injured tendon in Rabbit

 

Muhammad Majeed*, Aseel K. Hussein

¹Veterinary College, Baghdad University

²MSc Student, Veterinary College, Baghdad University

 

ABSTRACT:

Plain tendonography is not very common choice for diagnosis tendon defects however; using contrast agent in last few decades to raise the ability of identifying the abnormalities of the tendon was increased. The aim of this study was to compare two techniques, the plain and negative tendonography on identifying the defects of the injured tendon in rabbit model.

Tendon injury was induced in ten adult rabbits by external trauma then a radiological examination of the injured tendon was examined at 0,14, 28, 42 and 56 days after inducing injury using two techniques, a plain and negative tendonography.

The results showed that the abnormalities of the tendon and adjacent structure recognized in both of the two groups in early stage after injury however, the changes were significantly clearer in negative tendonography in comparison to the plain tendonography.

 

 

 

 

 

INTRODUCTION:

A tendonography is a term used to describe the radiological examination of the tendon using plain radiograph or radiograph with contrast agents. The latter may increase the visualization of the tendon for diagnosis the tendon defects like tendonitis, tendovaginitis and contracture ligaments. Recently, the technique is widely replaced by ultrasonography, CT (Computed tomography) and MRI (Magnetic resonance imaging) since they invented (1 and 2).

 

Normal tendon is bright white color having fibroblastic texture. Tendons have different shapes; they may be flattened ribbons, rounded cord or strap-like bands (3).

 

Tendon is composed of fascicles which are consisted of aligned fibrils. These fibrils are composed initially by a triple helix polypeptide chain, tropocollagen, which is produced at the level of fibroblast and released into the extracelluar space uniting into sub-fibrils then fibrils. The shape of arranging these proteins within the matrix is named as hierarchic arrangement as described by researchers (4-6).

 

Five types are given for the surrounding structures of the tendons namely fibrous sheath or retinacula, reflection pulleys, synovial sheath, peritendinous or paratenon and tendon bursae (7). Others had a simpler classification as epitenon or paratenon (8). Both of Peritenon or Epitenon carry the intrinsic vascular, lymphatic and nerve supply to the internal structure of the tendon (9). On the other hands, the extrinsic blood supply is carried by the Mesotenon. The Paratenon covers the non-sheathed  tendon and allows for gliding and supplying the extrinsic blood supply and acting as a synovial sheath in area of local pressure (10). These blood supplies enter the tendon by intrinsic systems at both of musculotendinous junction and osteotendinous insertion while, extrinsic system in paratenon or synovial sheath (11) and vessels may connect between the peritendinous, interatendinous and vascular networks at the level of endotenon septa (12). The nutrition in tendons that had no synovial sheath relays on extrinsic components of the vasculature by entering the vessels the paratenon transversely composing a network like shape (13).

 

Both of sympathetic and Para-sympathetic nerve fibers innervate the tendon and originate from cutaneous, peritendious and muscular tissues. Nerve fibers enter the endotenon septa at the level of myotendinous junction however, the reality of termination of the nerve endings reaches the surface of actual tendon only and do not penetrate it (14).

 

The calcaneal tendon, which is called common calcaneal tendon or Achilles tendon, is generally defined as the compound structure that consists of all the structures adhered to the tuber calcanei of the calcaneal bone (15). As an anatomical nomenclature, The Achilles tendon is the term used in the laboratory workers which is referred to calcaneal tendon or tendo calcaneus (16). The calcaneal tendon is composed of tendons arise from gastrocnemius, superficial digital flexor muscles, semitendinosus muscle, gracilis muscle, and biceps femoris muscle (15). The soleus muscle and its tendon are negligible in the rabbit therefore; the rabbit of Achilles tendon represents distinctive gross anatomical and MRI features especially for mechanical testing or a comparative model to human (17).

 

Tenosynovitis is inflammation of the tendon sheath. Peritendnitis is inflammation about the tendon with or without a sheath. Inflammatory changes around a tendon may be manifested as fluid accumulation within the tendon sheath and synovial proliferation or scarring. Both tenosynovitis and peritendinitis have overlapping radiographic appearance.

 

Tendonitis is a result of acute trauma or overuse that leads to inflammation within the tendon while, degeneration and partial or complete rupture is a consequence of long standing of tendonitis. The acute one is usually resulted when the tendon face a sudden force as it is often noticed in Achilles tendon rupture while; a degenerative process leads to chronic spontaneous rupture. Either of those cases shows almost similar features on images by representing a range of the process of tendon degeneration while, severe disruption of the normal morphology of the tendon may be reveled partial rupture (18). On tendonography, a fusiform enlargement and irregularity of the tendon also are comparable (2 and 18).

The flow of the contrast media is discontinued when there is rupturing in the tendon as it was seen using tendograms the irregularity may be associated with tendon hypertrophy and sheath irregularity may in partial rupture. It is found that the age of the tendon ruptured is defined the type of matrix occupies the gap like fluid, fat or scar tissue (18). Xeroradiography is rarely used in calcaneal disorder (18).

 

On the other hand, tendons are described using ultrasonography, computed tomography and magnetic resonance imaging techniques (19). Ultrasonic measurement of the tendon thickness has been proposed as a useful, non-invasive tool for identifying tendon defects (2).

 

The contrast media are used for identifying tendonitis, tendovaginitis and contracture of the palmer and planter annular ligaments of correlated bones (2 and 20). Negative contrast agent x-ray technique, which is literally called air tenogram, is used for separating tendons’ sheaths and ligaments for better visualization of correlated defects (2).

 

The aim of this study was to compare between using two methods, the plain tendonography and negative tendonography for identifying the defects of the Achilles tendon and adjacent structures.

 

MATERIALS AND METHODS:

This study included 10 apparently normal adult rabbits. The calcaneal tendon injury was induced using external trauma in all the rabbits by introduce a local compression on the calcaneal tendon proximal to the location of calcaneal tuberosity in an equal strength and duration. The compressed area was clinically identified just after inducing the damage. All the groups were left without treatment for the whole study.

 

Clinical signs were recorded during the study period and the animals were examined after 0 time (this was calculated as 3 days after inducing injury), 14, 28, 42, 56 days for the progress of tendon injury using radiological protocols as below:

1.  Plain tendonography group: 

calcaneal tendon was examined using plain tendonography.

2.  Negative tendonography group:

The calcaneal tendon was examined using negative tendonography. The site of the ankle was prepared surgically then a dose of 6ml/kg of air was injected directly to the subcutaneous tissue of the ankle and massage was made just before x-ray examination time.

 

RESULTS AND DISCUSSION:

CLINICAL FINDINGS:

All the animals of the study showed palpable compression just after inducing the injury replaced gradually by swelling area and become advance about 24hrs after inducing the injury. The area was painful which was identified by the lameness and the animal was not been able to stand on it or use it during walking. The pain firstly reduced and ended by the end of the first week however, the swelling gradually decreased and disappeared by the end of the fourth weeks of inducing the injury. It was found that if the tendon suffered from an acute trauma, the animal would not been able to use the limb and cannot bear the weight. Furthermore, the animal postural and continuity of having the swelling may help confirming the chronic Achilles tendon injury (21)

 

Radiological features of Achilles tendon:

On lateral view of plain radiograph, the tendon showed to have well defined edge described as a radiopaque cord shape compared to the adjacent structures which mainly determined by triangular radiolucent structure (fat pad). The calcaneal tendon has well-defined edges with recognized pre Achilles fat pad on the lateral view (Figure 1). The pad has a radiolucent, well demarcated shape defined by the flexor halluces longus anteriorly, while by the Achilles tendon posteriorly and calcaneal tuberosity inferiorly. A group of researchers found that the fat pad which is located anteriorly to Achilles tendon has a very clear shape demarcated by Achilles tendon posteriorly (22 and 23).

 

At zero-time, the plain radiograph showed a thickened area at the site of the injury associated with slight loss of the normal radiolucent appearance of fat pad due to  the trauma (Figure 2-A). Variable changes were seen in man Achilles tendon when they examined using x-ray examination by researchers including thickening of the tendon and reducing the normal appearance of the fat pad according to a study (22 and 24). While using negative tendonography, the changes of the affected part of the tendon was clearer as the contrast increased between the fat pad and the anterior edge of the tendon however, no extra signs were identified in comparison to the plain radiograph (Figure 2-B). Using negative tendonography usually increases the contrast by which the tendon is well identified in comparison to the plain technique (2)

 

Figure 1: Radiological appearance of Achilles tendon on lateral view of the rabbit ankle using plain radiography shows (A) normal features of the tendon and (B) Achilles tendon suffer from compressed pressure on the tendon

 

Figure 2: Lateral view plain radiograph of a tendon represents Achilles tendon 3 days after inducing injury (Zero-time). (a) The radiograph shows thickening in the tendon at the site of injury associated with variable degree of losing the opacity of the fat pad anterior to the tendon. (B) The negative contrast agent (air) increase the opacity between the anterior edge of the tendon and the affected pad at the site of trauma

 

After two weeks of inducing the injury the signs were continued in both of plain and negative tendonography. On the other hand, by four weeks period time, the plain radiograph shows slight return of the fat pad to its normal appearance and at this stage the radiolucent features of the fat pad is gradually return to normal (Figure 3). The thickening of the tendon also started to be reduced when 4/5 of the total group showed to have thickened tendon. On the other hands, using negative contrast agent showed reduce the inflammation however, all the cases of this group were still had visible changes within the tendon size and texture. Increase the contrast when air used as negative contrast agent was proven by researchers for identifying the defects within the soft tissues (2). The inflammation of the fat pad on the other side started to reduce by returning the normal appearance (the triangular radiolucent shape) in this stage (Figure 3).

 

Figure 3: Lateral view plain radiograph representing the shape of the tendon and adjacent structures after four weeks of inducing defects. Note the cordlike shape of the tendon which indicate slight thickening of the tendon at the site of injury. (B) The thickening of the tendon started to reduce and the fat pad normal appearance (radiolucent) started to be seen again

 

A continuity of reducing the tendon defects was seen during this stage in both groups however, the signs of defects were still clearer in negative tendonography group in comparable to the plain group which might be explained by the high contrast that the negative tendonography may reveal ().

 

When the percentage of the results was calculated for stage of the two groups, the abnormalities associated with the tendon itself were still seen in the negative tendonography in comparison to the plain one at the four and six weeks (Table 1 and Figure 7).

 

Table 1: This table represents the percentage of existence of the thickened Achilles tendon after inducing injury during the whole study

 

 

Figure 3: 3D line shows the percentage of presence of thickened (or any other abnormalities with the tendon) tendon during the whole study in (Plain) plain tendonography and (Negative) negative using air tendonography. Note that the thickened tendon was recognized in the two groups till the second weeks

 

On the other hands, the abnormalities of the fat pad showed to be correlated to the defects of the tendon itself. when the contrast were compared between stages of each group, the fat pad showed to return to its normal opacity by time, however, the negative tendonography had better visualization to determine the defects of the pad in comparison to the plain one. in negative tendonography, the adhesion between the Achilles tendon and the fat pad showed to be clearer in this group. This might be due to increase the contrast (air has very radiolucent appearance in comparison to the fat which has abnormities due to the trauma) that gave better ability to distinguish between structures (Table-2 and figure-8).

 

It is concluded that using a contrast agent for tendonography increase the possibility of identifying the defects of Achilles tendon and its adjacent structures then increase the possibility of treating them in field.

 

Table 2: This table shows the percentage of affected fat pad of each group. Note that apparently the fat pad showed to be normal-has radiolucent appearance and sharp edges in most of the cases at the weeks four and six while, negative tendonography had a visible defects characterized mostly by adhesions.

 

 

Figure 4: A 3D line graph reveals the percentage of the effected fat pad within each group.

 

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Accepted on 26.05.2017        © RJPT All right reserved