The superficial digital tendon runs along the back side of the
Achilles’ heel.
After sustaining a tear to the tissues that hold this tendon in
place, the tendon can dislocated of to the side of the heel bone
which frequently will produce a popping sound. In addition, the
patient will be lame on the affected limb.
Surgery is recommended to treat this condition
The prognosis is very favorable for these patients.
Anatomy
The Achilles’ tendon consists of a series of tendons that
attach onto the calcaneus bone (Achilles’ heel) and the superficial
digital flexor tendon (SDF) tendon that passes directly over the
back side of the Achilles’ tendon and then attaches onto the bones
of the toes in the hind paw.
See illustration right which demonstrates the anatomy of the
tendons that extend over the back side of the hock (key: SDF =
superficial digital flexor tendon; G = gastrocnemius tendon; B =
biceps femoris tendon). Take note that the biceps femoris and
gastrocnemius tendons attach directly onto the calcaneus bone,
whereas the SDF tendon runs over the calcaneous bone. The SDF
tendon tendon is held in place by tough tissue along both sides of
the tendon called retinaculum.
Pathology
Trauma is the most common inciting cause for a tear of the
retinaculum which holds the SDF tendon in place.
In some cases, the shape of the end of the calcaneous bone may
be abnormal which causes the tendon to naturally dislocate without
trauma. This problem is seen most commonly in Shelties.
When the tendon pops off the side of the bone, pain results and
the dog may cry out or become acutely nonweight-bearing
Signs of SDF tendon luxation
Sudden onset of lameness
Intermittent severe lameness with interposed periods of mild
lameness
An intermittent popping sound may be heard each time the tendon
dislocates
Swelling over the back point of the hock (Achilles’ heel) is
common
Diagnosis
The diagnosis of the SDF tendon luxation is made on physical
examination in which the tendon can be popped back and forth over
the Achilles’ heel (see below left)
Radiographs may be recommended to rule out fractures or other
problems with the bones. Usually the only finding is swelling over
the Achilles’s tendon (see below right)
Preop blood work is generally done to ensure that your pet is
in good internal health for anesthesia
Treatment
An incision is made over the site of the torn retinaculum and
the tear is identified (photo below left)
The torn retinaculum is sutured (photo below right)
Below is a video clip that shows the tendon luxating during
surgery and suturing of the tendon.
Care at home
Exercise must be limited for 2 months.
A soft padded bandage is applied to the hind limb for a period
of 2 weeks. A splint may also be used to support the repair during
the healing period.
Pain medications and a nonsteroidal anti-inflammatory likely
will be prescribed.
Prognosis
Most patients that have a simple traumatic tear of the
retinaculum respond very well to the surgery and regain normal
function of the limb.
Dogs that have an abnormally shaped tip of the calcaneus bone
may be more prone to recurrence of the luxation.
