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Ankle diastasis or "High ankle sprain"

Pre-Operation

The right ankle is being subjected to an eversion type injury, which is a common cause of a diastasis injury
Distal tibiofibular joint and supporting ligaments
X-rays demonstrating a diastasis injury to a left ankle
MRI (coronal views) demonstrates damage to the inter-osseous membrane and ligament
MRI (axial views) demonstrating AITFL rupture and partial tear of the PITFL

This injury is a far less common than the usual ankle sprain, and is more severe with potentially worse long term outcomes if it goes un-treated. It is commonly referred to as a “high ankle sprain” as the damage is higher than the use ankle injury.

 

The mechanism of injury may be similar to that of the common ankle sprain (where the ankle goes into inversion) but with greater force. This is common in all twisting and pivoting sports. Another mechanism of injury is when the ankle is forced into eversion and external rotation. This is common in all codes of football. Dr. Porter also sees this injury from wrestling, combat sports, motocross, mountain biking, skiing and snow-boarding.

 

Following the injury, most patients are not able to continue participating. If they are struggling to walk they often present to an A&E department on the day of the injury. Here an x-ray is performed which may be normal in the presence of a less severe injury (or dynamic diastasis), or may show the separation between the two leg bones just above the ankle joint in more severe cases (a static diastasis).

 

The best treatment that the A&E department can offer the patient is to perform the preliminary investigations (x-rays), put the patient in a fracture boot or back slab, give them crutches, ask them to remain non-weight, commence a blood thinner to prevent thrombosis, if appropriate, and refer them for sub-specialist review. An A&E discharge summary can be used as a referral to see Dr. Porter.

 

If the x-rays are normal, an MRI is often requested. This will confirm the diagnosis, confirm the presence of other ligament and / or bone or cartilage injuries, and assist with operative planning.

Operation

Arthroscopic view of the diastasis injury. The probe is demonstrating the laxity at the distal tibiofibular joint.
This is the post-operative x-ray of a left ankle following fixation of the diastasis using 2 x suture button devices

Although the ankle may improve with non-operative treatment (strict non-weight-bearing cast immobilization for 8 weeks), if there is any residual widening of the joint, this results in early degeneration within the ankle joint. For this reason, Dr. Porter will usually recommend surgery, particularly in young active patients, professional athletes and performing artists.

 

The surgery to fix the diastasis is performed in an operating theatre, with the patient under a general anaesthetic with x-ray control.

 

The goal of surgery is to hold the two bones together and allow the ligaments to heal in this position. For this reason and arthroscopy (key-hole) surgery is often performed at the same time, to check there are no soft tissues blocking attempts to pull the bones together.

 

Current technology allows the diastasis to be corrected and held in the correct position until the ligaments healing, as a minimally invasive  procedure under x-ray control. Some surgeons and centres will use screws to hold the bones together. The ankle will not move until these screws are removed or until they break. Some surgeons, hospitals and medical centres recommend the screws are left in place and allowed to break. This is not Dr. Porter’s policy. Depending upon where the screws break they can also cause problems. For these reasons Dr. Porter using a “tight-rope” technique. The devices is passed across the distal tibiofibular joint (DTFJ) in a manner similar to the screws, and consists of two titanium buttons joined by suture material which has the same tensile strength as stainless steel. When the device is tightened the two bones are pulled together. The advantages of this system are that the patient can begin non-weight-bearing ankle movements immediately following surgery (and therefore less fibrosis and scarring results), and the device does not have to be removed.

 

The only advantage of screws is that the operation is cheaper, but the American Academy of Orthopaedic Surgeons has made a strong recommendation that a tight rope (or “suture button”) should be used in preference to screws in the interest of patient outcome. It is also cost effective.

Potential
complications

Despite our best attempts, potential complications are a risk with any injury or surgical procedure. You need to be aware of these rare potential complications.

The more common ones are listed here, but please ask the surgeon if there are any you are particularly concerned about.

1. Infection

Despite the best sterile techniques, there is a low risk of wound infections (1%) and even lower risk of deep infection (fraction of 1%). These can usually be treated with a course of antibiotics, but some may need to have the wound washed out in an operating theatre.

2. Thrombo-embolism

Any lower limb injury, and / or surgery performed, carries a risk of DVT (clotting in the leg veins). Most patients will be on a low dose of a blood thinner to reduce the risk of this occurring. This may be an injection or a tablet.

3. Post-operative stiffness / fibrosis

This is unusual but can occur following major ankle injuries, such as those involving the distal tibiofibular joint, especially if there was also a fracture. The best treatment is prevention with early range of motion work while non-weight-bearing. On occasions this may require a repeat arthroscopic or key-hole procedure to remove the fibrous tissue

4. Nerve injury

There may be an area of numbness distal to the incision, where the skin nerves are cut to gain access to the ankle. However this is rarely a significant problem, and it only involves the skin, and does not affect any muscles.

5. Bleeding

Veins may be damaged during the surgical exposure, but this causes bruises only and these resolve with time. On rare occasions a small artery may be damaged, especially if it is an "aberrant" artery running in an unusual location. A collection of blood, hematoma or "pseudo aneurysm" may for and this would may have to be removed during a return to theatre.

6. Compartment syndrome

This is a rare complication which can occur following trauma and / or surgery. The swelling within the leg builds up to the point that it reduces blood flow into the leg. This can become a serious limb threatening complication, if not dealt with promptly. It manifest as an increasing, severe, throbbing pain and tightness in the leg. It requires surgical treatment, which includes release of the tight connective tissue enclosing the compartments of the leg.

7. Recurrence

The incidence of this of this is rare following surgical repair of a diastasis. However the operation cannot make the injured joint bullet-proof, and a repeated high impact could undo the surgical repair, but this is rare.

Post-Operation

Following surgery the patient is not allowed to put any weight on the operate ankle / foot, until 6 weeks post-surgery, and is allowed to partial weight bear up to 50% body weight for the following 2 weeks. At 8 weeks post-surgery the patient can progress to full weight bearing as long as pain free to do so.

 

Formal physiotherapy will be continued until at least 3 months post-surgery. return to full sport / activity  can vary from 3-6 months depending upon the severity of the injury and the sport / activity concerned.

Rehab / Physio

This is the boot that the patient should be placed in. It is important to wear the correct boot. A short ankle boot is not used for this injury as it does not provide sufficient immobilisation of the injured joint

The post-operative guidelines and protocol are available by clicking on the link below. This is a printable PDF format and can be taken to the treating physiotherapist. The patient will also be given a copy on the day of surgery.

https://www.cosm.net.au/wp-content/uploads/2020/07/Ankle-or-foot-fracture-or-diastasis.pdf