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Patients who have patellofemoral instability or patellofemoral arthritis that is localized to certain portions of the patellofemoral joint (kneecap), may be candidates for a tibial tubercle osteotomy. In this circumstance, the tibial tubercle is either elevated or moved distally (away from the center) and elevated to try to restore a more normal position of the patella, or to unload the patella from an area of arthritis on the trochlea or distal pole of the patella.
A thorough work-up is necessary to determine which patients may be candidates for a tibial tubercle osteotomy. In patients with patellar instability and patella alta, who also have a tibial tubercle-trochlear groove (TT-TG) distance of 2 cm or greater, a tibial tubercle osteotomy may be indicated. In addition, for patients who have an articular cartilage resurfacing procedure of the distal half of their patella, or the medial or lateral portions of the trochlear groove, may also be candidates for tibial tubercle osteotomy.
In a tibial tubercle osteotomy, the tibial tubercle and the patellar tendon are detached and moved to a pre-calculated new position on the anterior tibia. Usually, this involved moving the tibial tubercle distally or distally and medially. The moved tubercle is held in place by two screws and washers. Usually, patients have a secure fixation which allows for early knee motion of up to 90 degrees of knee flexion.
A thorough workup is necessary to determine the underlying pathology and determine where the tibial tubercle will need to be transferred.
With this procedure, patients need to be non-weight-bearing for 6 weeks and the osteotomy itself can take up to 4 months to heal before significant stress can be placed across the quadriceps mechanism in order to make sure that they do not go on to have a full fracture of their tibia. This complication is rare, a sudden fall or stress to the knee could put the area of the tibial tubercle osteotomy under significant stress, which could lead to a fracture. A Tibial tubercle osteotomy is generally considered a higher level/ salvage type procedure.
A tibial tubercle osteotomy involves moving the tibial tubercle to a different location, almost always due to some underlying kneecap problem. Often, it involves a complete detachment of the tibial tubercle, along with the patellar tendon that is attached to it, and moving it either further down the tibia (due to patella alta or a high-riding kneecap) or moving it more to the inside (medially) because of an increased tibial tubercle to trochlear groove distance (TT-TG) or some treatable lateral patellofemoral compartment arthritis.
Patients who need a tibial tubercle osteotomy surgery usually have underlying kneecap instability or lateral patellofemoral compartment arthritis. In these circumstances, a workup to include a long leg alignment x-ray to see if a patient is malaligned in a significant amount of valgus (knock kneed), as well as plain x-rays to ensure that there is no significant arthritis, supplemented with an MRI scan to determine the amount of arthritis and shape of the trochlea, as well as a CT scan to determine the patient’s tibial tubercle to trochlear groove distance (TT-TG) would be indicated.
It is important to ensure that a proper workup has been determined as to how far distally (down the tibia) or medially (towards the inside of the tibia) the tibial tubercle must be moved in order to obtain the best surgical outcomes.
Patients who have a high tibial tubercle to trochlear groove (TTTG) distance of 20 millimeters or more that do need to have a medial patellofemoral ligament reconstruction (MPFL) are generally felt to need a tibial tubercle osteotomy. In addition, patients with a high-riding patella (called patella alta) also need a workup with varying measurement techniques when they do undergo kneecap instability surgery to determine how far distal the tibial tubercle should be moved to have it better seated within the trochlear groove.
A tibial tubercle osteotomy involves detaching the tibial tubercle from its attachment on the tibia (shinbone) concurrent with its patellar tendon attachment. Depending upon whether it is treating concurrent kneecap instability or osteoarthritis, the tibial tubercle will be moved a set amount distally down the tibia and/or medially on the tibia to best position the tibial tubercle to address these pathologies. The tibial tubercle is then secured back to the tibia, most commonly using cannulated screws and washers, to provide a solid fixation of the tibial tubercle until there is appropriate time for it to heal.
Most patients who have a tibial tubercle osteotomy require 6 weeks of nonweightbearing to ensure that the tibial tubercle heals appropriately. X-rays are usually obtained at the 6-week point after surgery to ensure that there has been an appropriate amount of healing of the tibial tubercle to judge whether further advancement in their weightbearing program can be performed. In some cases, there may be a longer period of nonweightbearing required, such as after a revision tibial tubercle osteotomy, or in cases where a thinner shell of tibial tubercle was transferred.
The success rate for a tibial tubercle osteotomy depends upon its underlying reason for the tibial tubercle transfer. For cases that are performed concurrent with a medial patellofemoral ligament reconstruction (MPFL), the success rate for the surgery is felt to be greater than 80%. For a tibial tubercle osteotomy that is performed with a cartilage resurfacing procedure, or with the treatment of lateral patellofemoral joint arthritis, the success rate is dependent upon the cartilage resurfacing technique and the amount of arthritis that is present. In general, it is felt that the success rate can be between 70-80% for up to 5 years.