Extensor Mechanism Realignment
Other popular names
Who does it affect?
Anyone. In some patients this tendency is greater than others due to their own individual body shape and bony anatomy. In others it may be due to injury.
Why does it happen?
Disorders of the patello-femoral joint, that is the articulation between the undersurface of the patella and the front of the femur (the trochlea groove), are very common.
They can be broadly divided into two groups – patella instability and pain. Patella instability is where the patella dislocates or subluxes (partially dislocates).
In everyone the pull of the quadriceps muscles tends to pull the patella laterally. Some patients are pre-disposed to subluxation or dislocation and can dislocate their patella for the first time with less severe, and for some patients, even trivial trauma. Some patients without such a pre-disposition can sustain a more severe injury that causes the patella to dislocate.
A combination of pain, swelling, instability and tenderness which may be localised or extended depending upon the injury.
The diagnosis is often clear with a knowledge of lateral dislocation of the patella followed by marked pain and swelling. On examination there is tenderness over the stretched MPFL.
After the pain and swelling of the acute injury has settled, abnormal lateral movement of the patella is often apparent and patients are often very apprehensive when the patella is moved laterally (patella apprehension).
An MRI scan is occasionally used to confirm the diagnosis and to identify any other injuries in the acutely painful and swollen knee following a dislocation.
All patients need a period of rest and rehabilitation following the acute injury. This should include a program of physiotherapy to regain a full range of movement and improve muscle function around the knee.
Many patients are able to prevent further episodes of subluxation or dislocation by performing exercises taught though a physiotherapy programme aimed at improving the ability of the quadriceps, in particular, the function of the VMO (vastus medialis obliquitis) muscles to prevent patella dislocation.
Unfortunately some patients continue to experience patella instability symptoms despite a properly performed exercise programme and these patients can require surgery to prevent further episodes of dislocation.
This type of surgery, performed under general anaesthetic, usually involves altering the position of the tibial tuberosity to which the patella tendon is attached. This alters the angle of ‘pull’ of the quadriceps muscles on the patella for patients in whom this pull is likely to cause dislocation of the patella.
The operation involves an 8cm incision in addition to the arthroscopic incisions over the lateral aspect of the upper shin just below the knee. The tibial tubersoity is cut, moved medially and held in its new position with screws.
You are likely to spend 1 or 2 nights in hospital. Protection of the knee is required for up to 6 weeks and a rehabilitation programme for around 3 months.
The anaesthetic will wear off after approximately 6 hours. Simple analgesia (pain killers) usually controls the pain and should be started before the anaesthetic has worn off.
You will go home in a splint and on crutches. Take the splint off only for a bath or shower. Carry out simple quadriceps tensioning exercises. Touch weight-bearing only. Keep the wound covered and clean and dry (leave the dressing alone).
- 2 weeks: post-op appointment and dressing removed.
- 2-4 weeks: Progress weightbearing on crutches and gentle range of movement exercises and quadriceps contraction exercises. Increase weightbearing as tolerated. Brace off for exercises, showering and at rest.
- 4-6 weeks: expect 0-50º movement, comfortable protected weightbearing. Use crutches or brace as tolerated. Progress quadriceps strength. Become independently mobile.
- 6 weeks: 0-90º of flexion. Comfortable with short walking. Straight leg control. To have an x-ray if had bony surgery. Attend regular physiotherapy. Begin more advanced rehabilitation including step-ups, bike, mini-trampoline, and swimming.
- 8 weeks: Progress strength exercises with light resistance; include step machine, single knee bends, mini-trampoline (jumps).
- 10 weeks: progress agility on step-ups, short runs, stop starts, increased strength.
- 12 weeks: progress sports specific drills and activities.
All of these time parameters are minimum if progress is as expected.
Return to normal routine
Bathing and showering
The wounds should be kept clean and dry until the wound has sealed. Showering is fine and the waterproof dressings can be changed afterwards. Bathing is best avoided until the wounds are sealed, typically 10 days after surgery.
In summary, whilst the wounds are wet - keep them dry and when the wounds are dry, you can get them wet!
Surgery is followed by a prolonged course of physiotherapy. This requires a commitment to undertake this rehabilitation in order to achieve the best possible result (at least half an hour per day for 6 months). It is vitally important to stay within the post-operative activity restrictions an physiotherapy guidelines to avoid damaging stretching your reconstructed ligament.
Return to work
The timing of your return to work depends on the type of work and your access, however, the following is a general guide:
- Desk work: as soon as pain allows and you can travel easily to and from work (2 weeks)
- Light duties: if the job allows partial use of crutches or limited walking (2-5 weeks). If the job involves standing for prolonged walking, bending, lifting, stairs but no squatting (7-8 weeks)
- Heavy duties: full squatting, heavy lifting, digging, in and out of heavy machinery, ladder work etc (3-4 months)
When you can walk without crutches or a limp and be in control of your vehicle (about 8 weeks).
No operation is without risk. Complications that can occur include:
These risks include:
- Infection of the bone or joint (<1%)
- Blood clots which can be minor (0.25%) or serious, even fatal (1/5000)
- Anaesthetic risk is extremely low.
- Others: rarely nerve damage, vessel damage, poor skin healing, tethering, urinary tract infection, drug reactions and other possible unexpected outcomes can occur.
- Recurrent dislocation can occur in around 10% of patients.
- Re-current dislocation can still occur but the risk of this is probably less than 10%
All these risks are uncommon and in total, the chance of being worse off in the long term is about or less than 1%.