Patella Stabilisation
What is patella stabilisation surgery?
Instability of the patella (kneecap) can cause pain and prevent normal activities due to apprehension that it will dislocate. A stabilisation procedure is performed to change the patella's tracking and strengthen the soft tissues that prevent it from dislocating.
The medial patellofemoral ligament acts as a restraint to the patella dislocating outwards. The tibial tuberosity is a bony prominence at the front of the knee where the patella tendon inserts. The trochlea is a groove in the femur bone that accommodates the kneecap. When the trochlea is dome-shaped (rather than a groove), it is called trochlea dysplasia.
Although many procedures fall under this category, the two most commonly performed are a medial patellofemoral ligament (MPFL) reconstruction and a tibial tuberosity osteotomy. A trochleoplasty is rarely required in cases of severe trochlea dysplasia.
What is involved in MPFL reconstruction surgery?
The steps involved in MFPL reconstruction surgery include:
Diagnostic knee arthroscopy
2-3 small (< 1cm) portals are created to allow passage of a camera and surgical tools within the knee joint. The whole joint is inspected for damage and to confirm the patella is out of its normal groove.
Graft harvest
This involves taking one hamstring tendon (usually gracilis) to reconstruct the MPFL ligament.
Creation of bone tunnels
Tunnels are created in the patella (kneecap) and the femur to allow for passage of the graft. The positions of the tunnels are confirmed using X-rays to ensure accuracy.
Graft passage and tensioning
The hamstring graft is then passed through the bone tunnels and tensioned until the patella is in a normal position within the groove of the femur. The graft is held in position using screws and suture anchors.
What is involved in tibial tuberosity surgery?
The steps involved in a tibial tuberosity transfer include:
Performing the osteotomy
An oscillating saw is used to detach the tibial tuberosity, which has the patella tendon attached to it.
Repositioning of osteotomy fragment
Depending on your pre-operative scans, a plan is calculated on how much the tibial tuberosity will be pulled down and medially.
Fixation of the osteotomy fragment
Once the tibial tuberosity has been moved to its new position, it is held in place using a low-profile plate and accompanying screws. This will stabilize the fragment and allow it to heal.
What is involved in trochleoplasty surgery?
The steps involved in a trochleoplasty include:
Detachment of the cartilage flap
A thin 3-5mm flap cartilage over the trochlea is detached from the underlying bone.
Reshaping
The bone under the trochlea cartilage is reshaped from a dome to a v-shaped groove to allow space for the kneecap to sit in.
Reattachment of the cartilage flap
The cartilage flap is now pushed down over the newly created v-shaped trochlea. This is held in place with suture tape and bone anchors.
Release of the tight lateral tissue
Often, in severe trochlea dysplasia, the tissues on the knee's outside (lateral) aspect are tight. As part of the trochleoplasty, the lateral tissues are sown in a lengthened position to release the tension and allow the kneecap to sit properly within the trochlea groove.
What is my follow-up schedule after the operation?
Approximately 2-4 weeks of leave from work is required for a desk-based job.
2 weeks
The wound dressings will be removed, and the wound will be reviewed to ensure it has healed. At this stage, the sutures will also be removed.
8 weeks
The range of motion in the knee will be assessed. You are expected to be able to fully straighten the knee and bend it more than ninety degrees. If a tibial tuberosity osteotomy or trochleoplasty is performed, an X-ray is taken at this stage to ensure the osteotomy site has healed.
4 months
The patella will be assessed for stability. The knee should have a full range of motion but may have residual swelling around it. Return to sports will commence from 4-6 months post-operatively. If things have progressed as expected, this will be the final appointment.
Frequently Asked Questions
What are the risks of having patella stabilisation surgery? +
General complications of MPFL reconstruction surgery can include:
Infection
The risk is less than 1 in 400 of developing an infection. This can occur despite using a sterile surgical technique and giving pre-operative intravenous antibiotics.
If the infection involves only the wound (superficial), it may just need treatment with a course of antibiotics.
If a deep knee joint infection occurs, it may require more surgery to wash out the knee as well as intravenous antibiotics.
Bleeding
Bleeding can occur around the arthroscopic port sites or into the knee joint itself. This is usually self-limiting but on rare occasions will require re-operation to wash out the accumulated blood.
Deep vein thrombosis
Clots can occur in the deep veins of the leg that may dislodge and occlude the arteries in the lungs. DVT presents as leg pain and swelling after your operation. The diagnosis is confirmed with an ultrasound scan and, depending on the type of DVT, may require treatment with blood thinners.
Specific complications of MPFL reconstruction surgery can include:
Recurrent instability
This can occur due to trauma, graft failure, or a failure to address other anatomical abnormalities that predispose to patella dislocation. This may need a revision stabilisation procedure.
Patella fracture
The bone tunnels created in the patella may weaken the bone and cause it to fracture. This is a rare complication and usually requires surgical repair of the fracture.
Stiffness
The knee can become stiff after surgery due to the formation of scar tissue. This stiffness usually resolves with physiotherapy but can sometimes persist. If the knee is not bending or straightening adequately 6-8 weeks post-operatively, a manipulation procedure may be required. This involves putting the patient to sleep and pushing on the knee in order to break the scar tissue.
Anterior knee pain
The cause of anterior knee pain after MPFL reconstruction can be multifactorial. Causes include cartilage damage on the undersurface of the patella, suboptimal bone tunnel position, or presence of an abnormally shaped femoral groove (trochlear dysplasia).
Patellofemoral joint osteoarthritis
A long-standing history of patellofemoral instability, especially in conjunction with an abnormally shaped femoral groove (trochlear dysplasia), will predispose the patient to arthritic changes within this joint.
Do I need patellofemoral stabilisation surgery for my first patella dislocation? +
In the first instance of patella dislocation, it is worthwhile working with an experienced physiotherapist to see if strengthening the thigh muscles can control the instability.
1 out of 5 patients have recurrent patella dislocations. There are several risk factors that may contribute to re-dislocation of the patella. They include patients with hyper laxity, an abnormally shaped groove for the patella (trochlear dysplasia), a high-riding patella (patella alta) or patients with alignment or rotational abnormalities in the lower limbs.
If the patella dislocates more than once, it is likely to be a recurring problem due to the aforementioned anatomical abnormalities. In this situation, patella stabilisation surgery should be considered.
Will patellofemoral stabilisation surgery affect my teenagers growth plates? +
Patella dislocation usually presents in growing adolescents. This means that the growth plates around the knee are still active. Performing certain types of surgery like a tibial tubercle osteotomy or a trochleoplasty will significantly damage the growth plate. Avoiding surgery till their growth has stopped is recommended. At this stage the appropriate combination of surgery can be performed. If non-operative management is not feasible then an MPFL reconstruction can be performed to help with the instability. Even then there is still a small, but acceptable risk of damaging the growth plate in the femur during this procedure.
When can I return to playing sport? +
Most patients return to sports 4-6 months after patella stabilisation surgery. This depends on the individuals' muscle strength and balance which should be assessed by an experienced sports physiotherapist.
When can I drive after an patella stabilisation surgery? +
You will not be able to drive for 6 weeks following a tibial tubercle osteotomy and/or MPFL reconstruction surgery. You must be off strong painkillers, be walking without crutches and have a relatively painfree range of motion in the affected knee before your commence driving.
When can I swim after patella stabilisation surgery? +
The wound should be kept dry for two weeks following the operation. Once the wound healing is reviewed at your 2-week post-operative consultation you will be able to shower with no wound dressings on. Participating in pool based rehabilitation or swimming is not recommended for 4 weeks after your operation as it may increase the risk of infection.
Is patellofemoral instability associated with developing knee arthritis ? +
Unfortunately recurrent patella dislocations as an adolescent and young adults increases the risk of developing patellofemoral arthritis in adulthood. It is uncertain whether patella stabilisation surgery will reduce this risk.