| Clinical Profile |
| Findings |
| Normal Tendon |
| Rupture of the Tendon |
| Etiology |
| Clinical Features |
| On MRI |
| Treatment |
| Suggested Reading |
 |
| Clinical Profile |
| Findings |
| Normal Tendon |
| Rupture of the Tendon |
| Etiology |
| Clinical Features |
| On MRI |
| Treatment |
| Suggested Reading |
|
Patient gave a H/O trauma followed by pain and swelling of the left ankle joint.
There is a discontinuity of the Achilles tendon with intervening areas of
intermediate signal intensity on the T1W images which turn hyperintense on the T2W and
GRASS images, which would represent fluid. The proximal fragment is frayed and retracted
and the distal fragment is lax. This would represent a complete tear of the tendon. Soft
tissue edema (hyperintense signal on the T2W images) around the ankle joint is noted.
The Achilles tendon is the largest tendon in the body. It is formed by a confluence of the tendons of the gastrocnemius and soleus muscles. It inserts onto the posterior aspect of the calcaneum. It assists in plantar flexion of the foot. The Achilles tendon does not have a synovial sheath.
On MRI: |
The Achilles tendon shows uniform hypointense signal on all pulse sequences. On axial images, the tendon is is elliptic with with a mildly concave or flat anterior surface and convex posteriorly. Occasionally mild anterior lobulations are seen and they are usually bilaterally symmetrical. On the sagittal images it is seen as a cord extending from the gastrocnemius-soleus muscle complex to the posterior calcaneum. Anterior to it is the pre-Achilles fat pad.
Acute rupture usually occurs when the foot is suddenly dorsiflexed against the contracting triceps surae group. This may occur during an unexpected strenuous effort or sudden stretching of the tendon. In trained athletes it may happen once muscular exhaustion sets in.
In nonathletic people, there is usually a predisposing condition. They may rupture both tendons simultaneously. The following may cause weakening of the connective tissue and collagen fibres:
Gout
Rheumatoid Arthritis
Systemic lupus erythematosus
Diabetes Mellitus
Hyperparathyroidism
Chronic renal failure
Long-term use of steroids
Rupture usually occurs 2 to 6 cm superior to it's insertion. This site has
decreased vascularity and is also the region where the most superficial fibres of the
tendon run horizontally. Local steroid injections may also cause ruptures.
Patients usually present with pain, local swelling and inability to raise up on their
tows on the affected side. In complete tears, a palpable defect may be noted. Occasionally
the gap may not be felt and the patient may be able to plantar flex the foot with the
toes. Also differentiation from venous thrombosis and plantaris and gastrocnemius tears
may not be possible. In 25% of patients tear of the Achilles tendon may be missed. Imaging
may be performed with soft tissue radiography, USG, CT or MRI. MRI is the most useful and
is helpful in following the healing process.
Partial Rupture:
There is partial continuity of a portion of the tendon fibres on at least one sagittal section. There is no tendinous gap.
The tendon may be thickened and usually exhibits focal areas of intermediate signal intensity on the T1W images and increased signal intensity on the T2W images due to edema and/or hemorrhage.
It may be difficult to differentiate between tendinitis and partial tears as the two often coexist. In uncomplicated chronic tendinitis there is focal or diffuse thickening of the tendon without increased intrasubstance signal intensity.
Complete Rupture:
There is discontinuity of the tendon (unless the tendon edges are overlapping) with intervening fluid, fat or hemorrhage.
The proximal fragment is retracted with fraying. The distal fragment is lax and buckled. Sagittal images help in ascertaining the distance between the two fragments.
Hemorrhage, edema and inflammation may be seen in the peritendinous soft tissues. There may be fluid collection in the paratenon anterior to the tendon.
Retracted tendons usually require surgery.
The proliferating ends assume a bulbous contour and it increases with greater tendon diastasis. Intratendinous fluid spaces may be seen at a three to six months interval following conservative or surgical repair. Healed tendons (at the end of one year) are usually thickened without associated increased signal intensity.
A tendon repaired with a polymer of lactic acid (PLA) shows a thickened tendon with moderate signal intensity streaks, which may mimic a tendon rerupture.
Rerupture of tendon is more frequent in patients treated conservatively. Such reruptures should be treated surgically.
Occasionally the tendon may get infected after surgery.