Efficacy of Transection-Free Patellar Tendon Imbrication Technique for the Correction of Patella Alta.

BACKGROUND

Addressing patella alta often involves a distalization of the tibial tubercle with an osteotomy. Yet such osteotomies have several potential complications, including nonunion, fracture, and hardware irritation. In addition, tibial tubercle osteotomies are contraindicated in children because of the presence of an open tibial tubercle apophysis.

PURPOSE/HYPOTHESIS: The primary aim of this study was to quantify the change in the Caton-Deschamps Index (CDI) and the maximum patellar tendon elongation achieved with cyclic loading with a novel transection-free patellar tendon imbrication method in cadaveric specimens. The authors hypothesized that the imbrication technique would achieve at least 1 cm of shortening and an improvement in CDI by 0.30 from pre- to postoperative imaging.

STUDY DESIGN

Controlled laboratory study.

METHODS

Ten fresh-frozen skeletally mature cadaveric knees without a history of knee surgery were used for the laboratory portion of the study. A pulley system was utilized to suspend 45 N (10 lb) from the quadriceps tendon to mimic physiological loading of the quadriceps tendon. Seven figure-of-8 high-molecular-weight polyethylene sutures were placed in the patellar tendon and tied sequentially. The patellar tendon was measured with a ruler to assess pre- and postimbrication tendon length. Computed tomography scans were obtained both before and after imbrication, and the change in CDI was calculated. To assess patellar tendon elongation, the tibia and patella were fixed to a servohydraulic load frame using custom fixtures, and the patellar tendon was dynamically loaded between 50 and 400 N at 0.5 Hz for 500 cycles. Statistical significance was determined at a value <.05.

RESULTS

In the cadaveric specimens, there was a significant decrease in patellar tendon length from pre- to postimbrication (47.2 ± 7.0 mm vs 36.8 ± 7.2 mm; < .001), with a mean patellar tendon shortening of 10.4 ± 0.97 mm. There was also a significant decrease in the CDI from pre- to postimbrication, with a mean change in CDI of 0.33 ± 0.09 ( = .014). The mean maximum patellar tendon elongation was 3.9 ± 1.7 mm after 500 cycles.

CONCLUSION

The novel transection-free patellar tendon imbrication technique can be used to reduce patellar tendon length and CDI at time zero. This technique may be useful in skeletally immature patients with incompletely ossified tibial tubercle apophyses.

CLINICAL RELEVANCE

The transection-free patellar tendon imbrication technique can be used in skeletally immature patients to correct patella alta without risking potential growth arrest due to the presence of an open tibial tubercle apophysis. Moreover, this technique avoids potential complications of distalizing tibial tubercle osteotomies for the correction of patella alta in skeletally mature patients, including nonunion, fracture, and hardware irritation.