Occasionally, patellar pain is amenable to surgery. In the next two parts of this course we will discuss several procedures, which may sometimes be carried out in combination with one another.
These procedures include -
- surgery for patellar malalignment
- surgery to slow established patello-femoral arthritis
- patellar resurfacing (partial patellar replacement)
- patellectomy (removing the patella)
The first and last topics are minefields of mismanagement, and the bane of the lives of many thousands of patients. I expect you to follow up any of the other causes of peri-patellar pain via the reading links already given in the relevant sections.
In this part of the course I have a few key messages for you to take away with you. Here is the first key message -
Surgery for patellar mal-alignment may involve -
- releasing tight structures on the lateral side (lateral release/lateral retinacular release)
- tightening incompetent structures on the medial side (medial reefing, repositioning of the VMO, reconstruction of the medial patellofemoral ligament)
- repositioning the tibial tubercle
The first two are called 'proximal' realignments, as the surgery is on side of the knee cap towards the head. The third one is called a 'distal' realignment, as it is on the side of the kneecap towards the foot. The end result of each of these procedures is to decrease the Q angle.
[Reprinted with permission, The Adult Knee, Chapters 59-60, Lippincott Williams & Wilkins, 2003.]
Releasing tight structures on the lateral side
A 'lateral release' is an operation to cut the lateral retinaculum.
Lateral release is the workhorse of patellar re-alignment surgery. The concept behind it is simple: if the patella is tilted and/or displaced to the side as a result of a tight lateral retinaculum, cut the retinaculum! Such a maneuver should allow the kneecap to assume a more normal position. But in the absence of a tight lateral retinaculum, a lateral retinacular release offers few if any benefits.
There are two standard ways of doing this procedure -
- 'open' lateral release
- 'arthroscopic' lateral release
In the open technique the surgeon cuts down from the skin side, whereas in the arthroscopic technique the surgeon cuts up from inside the knee.
It is important that the surgeon checks the mobility of the patella before and during the procedure, so that the tilt is corrected. Also, the cut must not extend up and damage the vastus lateralis (of the quads), or the patella may be rendered unstable. Also, 'bleeders' must be stopped so that the knee does not fill up with blood after the procedure (haemarthrosis).
Tightening incompetent structures on the medial side
Note - these three procedures, and the lateral release procedure we have already discussed, are all called 'proximal' realignment procedures, to distinguish them from the bone operations to move the tibial tuberosity (which are called 'distal' realignment procedures).
'Proximal' means 'on the aspect towards the head', while 'distal' means 'on the aspect towards the feet'.
Three main procedures are used to tighten up the medial side of the patella -
- medial reefing
- repositioning of the VMO
- reconstruction of the medial patellofemoral ligament
If the medial retinaculum is lax and contributes to the poor position of the patella, it can be divided and then tightened the same way a tailor might tighten a garment.
Repositioning of the VMO
A 'VMO advancement' moves the bottom end (distal end) of the VMO muscle down and towards the outer side (distally and laterally) to improve its mechanical efficiency.
The procedure is often done together with medial reefing.
Reconstruction of the medial patellofemoral ligament (MPFL)
This procedure is reserved for patients who suffer from instability. When the patella dislocates, the MPFL can be stretched and/or torn. The creation of a new MPFL can restore stability to the patella. This operation is the newest in a long line of operations designed to keep a kneecap from sliding off to the side. Ideally, a reconstruction of the MPFL will stabilize the kneecap without over-tightening it. Over-tightening can lead to arthritis, a late complication associated with some of the older operations.
Repositioning of the tibial tubercle
The very first recorded operation for patellar pain or instability was described by César Roux in the late 19th century. His operation was we would call today a 'distal' re-alignment, i.e. a re-alignment operation that takes place distal to the kneecap. Specifically, this means moving the patellar tendon, and this is most commonly done by moving the tibial tuberosity (the part of the shin bone to which the tendon attaches).
Like all patellar procedures, tibial tuberosity transfers have each had their day in the sun. Maquet in Belgium described a transfer of the tibial tuberosity in the anterior direction. This made the tuberosity more prominent, i.e. it would stick out. This was designed to take pressure off the kneecap and therefore diminish pain.
Tibial tuberosity transfers (Maquet, Elmslie-Trillat, Fulkerson)
Elmslie in England and Trillat in France described moving the tibial tuberosity medially (towards the inside), a variation of Roux's procedure. This diminished the tendency of a patella to slide laterally (to the outside). Cox popularized the operation in the United States.
[Image reprinted with permission, The Adult Knee, Chapters 59-60, Lippincott Williams & Wilkins, 2003.]
Fulkerson in the United States combined these two transfers by slanting the bony cut of the tuberosity. The result is a displacement that is half way between a Maquet and an Elmslie-Trillat. There is some anterior displacement and some medial displacement. The specific slant of the cut determines whether there will be more anterior or medial displacement.
The indications for each of these tibial tuberosity transfer procedures are very much in the eye of the beholder.
None of these operations is magical.The only absolute is that a lateral retinacular release is indicated only when the lateral retinaculum is overly tight.
The distal re-alignments diminish the Q angle when they move the tt medially. The Maquet doesn't affect the Q angle, and the proximal re-alignment give the appearance of increasing the Q angle, since the patella moves medially. This is a question that often comes up at meetings. I answer by saying that the true Q angle is unmasked when the patella is centered.