Patella dislocation Surgery – Soft Tissue Vs Bony
Patella dislocation surgery (stabilisation surgery) requires a thorough understanding of the underlying cause for patella ‘instability’. There is not one operation that will ‘fix’ all scenarios, and Dr. Smith will discuss the options available, based on your individual causes for the ‘instability’
Procedures designed to address patella instability can be thought of as:
Soft Tissue procedures
These procedures are designed to ‘reconstruct’ or ‘tighten’ the medial (inner) soft tissue restraints of the patella (kneecap). Or, to ‘release’ the tight lateral (outer) soft tissues that are pulling the kneecap out of position.
The most common bony procedure involves re-positioning the tibial tuberosity. The tibial tuberosity is the area of bone on the tibia (shin bone) that the patella tendon attaches to. The medical term for this procedure is “Tibial tubercle osteotomy”
Soft Tissue Procedures
The medial patellofemoral ligament (MPFL) is a band of tissue that connects the medial (inner) side of the kneecap to the femur (thigh bone). The MPFL is responsible for keeping the patella in its groove, when the leg is bent in the range from 0-30 degrees.
When a patient experiences a kneecap dislocation, the knee cap typically dislocates to the outside of the knee, causing a rupture of the MPFL.
Simply repairing the MPFL with sutures has little role to play in this condition, as there is good evidence that this does not reduce the rate of subsequent dislocations.
A ‘Reconstruction’ is performed whereby a ‘donor tendon’, typically a single small hamstring tendon (gracilis), is taken from the inside of the knee, and fashioned into a ‘new’ MPFL. This ‘reconstruction’ can be performed in isolation, or combined with a ‘tibial tubercle osteotomy’ (see below).
A small incision is made on the upper inside of the shin bone, and the gracilis (small hamstring tendon) is removed. A second small incision is made on the inside of the kneecap and two ‘tunnels’ are created in the kneecap, to position the ends of the hamstring tendon. Finally, a small incision is made over the inner side of the end of the thigh bone (femur) and this hamstring tendon is secured into position using a screw.
Xray is used to confirm the accurate position of this fixation. This reconstruction provides restraint to the kneecap coming out of position. The wounds are closed and a bandage is applied
You are able to go home the following day and usually spend a short period of time in a brace and on crutches.
A lateral release involves using key hole surgery to release the tight outer structures of the knee. This procedure is not always required, however it may be added to the MPFL reconstruction (see above) if needed.
Tibial Tubercle Osteotomy
As part of the preoperative detailed assessment, you will undergo a specialised CT scan to check your bony anatomy. When your ‘Tibial tubercle’ is significantly mal-positioned, you will require an ‘osteotomy’ as part of your procedure. The purpose of this ‘osteotomy’ is to re-position the tubercle, and allow normal patella tracking. This procedure may be combined with a MPFL reconstruction (see above) in some situations.
An incision is made alongside the tibial tubercle. The patella tendon is protected, and using a small saw, the tuberosity is partially released. This allows for it to be translated across into a better position. Typically this is in the order of 10mm. The bone fragment (tubercle) is then held in its new position with the use of 2 screws.
Following this procedure, a period of knee splint and crutch use is required.