It is incredibly stressful when your pet suffers an injury that results the inability to walk properly on their back legs also known as hindlimb lameness. While there can be many causes, one less common but serious condition to consider is a Superficial Digital Flexor (SDF) luxation.
What is an SDF Luxation?
Superficial Digital Flexor (SDF) luxation is a cause of hindlimb lameness that is typically traumatic in nature. It occurs when the SDF tendon slips out of its normal position, moving to the outside of the calcaneus (the point of the ankle/hock), which disrupts the joint’s normal mechanics. This condition is more commonly seen in active breeds, with Collies and Shetland Sheepdogs being particularly susceptible.
Clinical Signs: What to Look for
- Intermittent to persistent hindlimb lameness, which often gets worse with exercise
- An audible or palpable “popping” sensation when the hock moves
- Visual displacement of the tendon laterally as your pet walks
- Pain when the hock is touched or manipulated
- Swelling around the ankle (calcaneus)
- Tendency to hold the affected limb in a partial bent (flexion) position when standing
- In chronic cases that have gone untreated, the tendon and surrounding tissues may thicken
Diagnosis
A diagnosis begins with a comprehensive orthopedic examination by a veterinarian. This includes checking the tarsal (hock) range of motion, feeling for discomfort on direct palpation, and observing the tendon luxating. Radiographs (x-rays) are also used to visualize the surrounding soft tissue swelling and help to rule out other hock conditions. In more subtle cases, next steps may include a musculoskeletal ultrasound.
Treatment: Why Surgery is the Best Option
For this specific injury, conservative (non-surgical) management is typically not successful. Surgery is the most common and effective method of treatment. The surgical procedure typically includes the reconstruction of the retinaculum, which is the band of tissue that surrounds the tendon.
Post-Operative Care and Recovery
A dedicated recovery plan is crucial for a successful outcome.
- Rest: Your pet will need strict rest during the healing period. Pain medications, anti-inflammatories, and sedatives will be prescribed as indicated.
- Splinting: The limb will be supported by external coaptation, often with a splint, for a period of 3-6 weeks.
- Rehabilitation: Upon removal of the splinted bandage, a progressive rehabilitation protocol is initiated with passive range of motion exercises, controlled weight-bearing exercises, and a gradual return to full activity over a 3-4 month period.
Prognosis for Recovery
Early surgical intervention typically results in good to excellent outcomes with success rates of 85-95% reported. Prognosis is more guarded in chronic cases with extended damage to the tendon, cases with simultaneous joint disease, and working/sporting dogs requiring return to peak performance. Most dogs return to normal function within 4-6 months.