Dislocations

What is a Dislocation?

A dislocation is an injury whereby the two surfaces of a joint become separated.  The causes are usually one of:

• a road traffic accident
• an awkward fall
• trapping a foot / leg in a hole / fence whilst jumping or running.

Such an injury is VERY disabling and the patient is usually unable to put much, if any, weight on the affected leg.

Which joints dislocate?

Any joints can dislocate, sometimes in association with fractures, especially fractures of the parts of the bone where ligaments attach that then make the joint unstable.  At Weighbridge Referral Centre we see fractures of many different joints but the two most common ones are those of the hip and the hock (ankle).

Dislocation of the Hip

This is usually the result of being hit by a car.  Patients with this injury tend to stand with no weight on the leg, hold the leg partially flexed and turned inwards.  Although these signs are typical of hip dislocation they can be mimicked by other injuries and so X-rays are required to make sure the problem is a dislocation and there are no complicating issues before any treatment is attempted.  In most cases it is possible, under general anaesthetic, to put the ball of the hip joint back into the socket but in only about 50% of these will it stay in place whilst the supporting tissue heal.
If the hip cannot be reduced by manipulation or will not stay in place and keeps “popping out” then there are a number of options:

• If a hip is left dislocated then the level of pain will reduce over a few weeks and a dog will regain some use in the limb.  The outlook in this situation is better in the cat where although use of the limb will never be normal it can be quite satisfactory.
• It is generally possible to replace the ball into the socket surgically and then secure it there using one of several techniques (see below).
• If it is not possible to replace the ball of the hip into the socket, or the ball has been badly damaged by the injury (unusual but possible) then it may be better to consider removal of the ball (a femoral head and neck excision) or performance of a total hip replacement.  Both of these techniques are explained more fully towards the end of the information under Osteoarthritis.

What techniques are used to treat dislocation of the hip at Weighbridge Referral Centre?
A number of techniques are used depending on factors such as

• The size of the patient
• For how long the hip has been dislocated
• The presence of any complicating factors such as fractures
• How much support can be regained for the hip by suturing the damaged tissues

The commonest technique currently used at this Centre for uncomplicated hip dislocations that have been present for only a few days is that of a “Toggle”.  This involves replacement of the normal ligament from the socket to the ball with a strand of nylon (or similar material) anchored to the pelvis with a toggle (a little like the principle used to fasten a duffle coat) and then passed down a tunnel created in the ball of the hip and down the neck of the ball.  This artificial ligament is not expected to last forever, but long enough to allow the tissues around the hip to heal and provide the required support to prevent re-dislocation.  The healing process takes in the order of 4-6 weeks.
After surgery dogs are allowed as much lead exercise (on a short leash) as they can tolerate – increasing the duration of walks as they recover.  But they are not allowed freedom around the house or the garden, with no access to furniture or free access to stairs (can be walked up and down these if required, but not allowed to run up and down them at will).  When not on the end of a lead they should be restricted to a pen or small room containing no furniture and with a non-slip floor.  In the case of cats, they are restricted to pen/cage rest for one month with some supervised activity.  Once 4-6 weeks has passed it is usually possible to steadily increase activity levels, with re-introduction of off lead exercise, over the next month or two.

How successful is surgery in returning these dogs to normal levels of activity?
Unfortunately, none of the techniques currently available are able to offer a 100% chance of full recovery.  Of the uncomplicated cases seen at Weighbridge Referral Centre, about 90% will regain good or excellent function in the leg.

Dislocation of the Hock (Ankle)

This is usually the result of either being hit by a car or else putting the foot in a hole whilst running.  The dogs are unable to take weight on the leg.  There is usually a very definite abnormal alignment of the foot with respect to the leg and there may be wounds around the ankle, particularly if a car has been involved.  Although it is usually quite obvious that a dislocation is present it is necessary to take X-rays to assess the full extent of the damage since fractures are usually present as well.

Treatment of these dislocations has to take into account three concerns:

• Any wounds that might need dressing changes for a few to several weeks
• The stability of the joint once it has been put back into alignment
• Any damage to the joint surface itself that might compromise any return to function

In some cases it is possible to put the joint back into alignment and then hold it there in a splint or cast for about 8 weeks whilst the supporting ligaments heal.  This may be difficult to manage if wounds need regular attention since every time the cast is removed to redress the wound any movement of the joint will damage the tissue repair that is taking place.  Hence it is probably better to stabilise the joint surgically as this will help with easier management of the wound without damaging the repair process.  If the joint surface is badly damaged (fractured or loss of cartilage from the surface) then it is highly likely lameness will continue even if the joint can be successfully stabilised – because of rapid onset arthritis.  As a result, such cases might be better treated by surgically fusing the joint (arthrodesis) and more details of this can be found towards the end of the information under Osteoarthritis.

How are dislocated hock joints usually stabilised at Weighbridge Referral Centre?
Some cases are treated with a simple cast but most of those sent to us have severe injuries where such measures would be inadequate.

Surgical stabilisation of the hock (ankle) might involve repairing the damaged ligaments or replacing them with a material such as nylon anchored either around bone screws with washers or else through special screws drilled into the bones that have an “eye” in their heads through which the nylon can be placed.  After such surgery the repair needs protecting whilst healing gets underway and this usually means keeping the joint in a splint or cast for 6-8 weeks.

         

In some cases, where the wounds are very extensive it is inadvisable to put such foreign material into the wounds because they can encourage infection.  In those cases it may be necessary to stabilise the joint with an external frame created by placing pins into the bones above and below the joint and then connecting these together with bars on the outside of the leg.  This allows easy access to any wounds and also makes keeping a bandage on the leg very easy because it grips on the frame!

After treatment of a dislocation using any of these methods the joint is often very stiff and it is usual for a programme of physiotherapy to be recommended once the cast or external frame has been removed.

How successful is treatment in returning these dogs to normal levels of activity?
Unfortunately, the hock joint is less forgiving than the larger joints such as the hip.  Following injury a number will remain mildly unstable or stiff after successful treatment to stabilise them.  It is difficult to place an accurate figure on the likelihood of success because the amount of damage caused by a dislocation is extremely variable.  An educated guess for the average patient would be in the order of a 75-80% chance of regaining good function in the leg.