Tibial tubercle osteotomy with distalization may effectively treat patellar instability
According to recently published results, tibial tubercle osteotomy with concomitant distalization resulted in positive radiographic, clinical and functional outcomes in the treatment of patients with patellar instability and patella alta.
Researchers from the University of São Paulo in Brazil analyzed 25 patients (31 knees) who underwent tibial tubercle osteotomy with distalization (TTO-d) for patellar instability and patella alta between 2013 and 2019. Patients were followed up for a mean of 2.62 years.
According to the study, researchers assessed radiological outcomes using the Caton-Deschamps index (CDI), tibial tubercle-trochlear groove (TT-TG) distance and amount of distalization. They assessed clinical and functional outcomes using the J-sign measurement, apprehension test, Tegner activity level and Kujala score. In addition, researchers factored in postoperative complications and two commonly cited consequences of TTO-d: anterior knee pain and chondral degeneration.
Overall, 71% of patients saw a complete resolution of anterior knee pain, and no cases of osteotomy nonunion were reported. Investigators found one instance of patellar instability recurrence and two cases of painful hardware, according to the study.
After reviewing radiological results, researchers found a mean CDI change of 1.37 preoperatively to 1.02 postoperatively, a mean TT-TG distance of 16.15 mm and a mean amount of distalization of 8.80 mm. Researchers also noted the J-sign improved in 96.8% of cases, the apprehension test was negative in all cases, the median Kujala score increased from 52 to 77 and the median Tegner activity level improved from 3 to 4.
Researchers expressed no basis for concern that the procedure causes anterior knee pain and chondral degeneration, and concluded that “TTO-d appears to be a safe and efficient procedure with low complication rates, providing an additional tool for the personalized treatment of patellar instability.”
Perspective
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I enjoyed reading “Tibial turbercle osteotomy with distalization is a safe and effective procedure for patients with patella alta and patellar instability” by Leite and colleagues. This case series out of Brazil is a well-done study highlighting an important consideration in patellofemoral instability surgery.
Patella alta is clearly a primary risk factor for patella instability since the patella enters the trochlear groove later in flexion. I have been performing distalization in conjunction with tibia tubercle osteotomy for more than 10 years in patients with severe patella alta (CD ratio > 1.3) and chronic patellar instability. Similar to this paper, patients have had been pleased with a stable, pain-free knee.
My concerns with this technique have always centered around patellofemoral contact pressure in relationship to patella cartilage damage. This paper showed persistent pain correlated with patellar cartilage defect severity. This compares to my experience.
In addition to patella cartilage defect severity, it is important to keep patella cartilage defect location in mind when processing these cases. A common objection to tubercle distalization is concern for nonunion or failed osteotomy healing. They had no cases of nonunion. Again, this is consistent with our experience at Iowa. A long (>6 cm) thick (>8 mm) fragment has good bony surface area for healing and is stable. We perform distalization tubercle osteotomy similarly to Leite and colleagues, but do like to place an autograft or synthetic bone graft substitute between the proximal tibia bumper and the fragment for stability and to more closely calculate the exact amount of distalization.
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