Summary

Our study indicate that on an individual basis, the Tibial Tubercle-Trochlear groove distance in patients suffering from recurrent lateral patellar dislocation may both decrease and increase during the growth spurt.

Abstract

Background

Increased Tibial Tubercle-Trochlear Groove Distance (TT-TG) is a risk factor for recurrent lateral patella dislocations (RLPD). Population studies have demonstrated that the TT-TG increases gradually during growth until skeletal maturity in healthy subjects, but the change in TT-TG distance on an individual basis during adolescence in patients with RLPD has previously not been investigated. The purpose of this study was to measure the TT-TG distance in mature and skeletally immature RLPD patients over a three-year period.

Method

13 patients with open physes (mean age 13 years) and 12 adult patients (mean age 25 years) with RLPD were recruited from a prospective randomized control trial. The TT-TG distance was measured on MRI at baseline and three years later. The change in TT-TG distance and Insall-Salvati ratio (ISR) was compared between the two groups.

Results

The change in TT-TG distance from baseline to the three-year follow up was greater in the patients with open physes (2.9 mm, 95% Confidence Interval (CI) 2.1 – 3.7) compared to the skeletally mature patients (1.3 mm, 95% CI 0.6 – 2.0, p=0.004). Furthermore, the change in TT-TG distance in the patients with open physes could both increase and decrease. The change in ISR was also greater in the patients with open physes (0.09 (95% CI (0.04 – 0.14) vs 0.03 (95% CI 0.016 – 0.049, p=0.028).

Conclusion

Our study indicate that on an individual basis, the TT-TG distance in patients suffering from RLPD may both decrease and increase during the growth spurt. This contradicts the current concept that the TT-TG distance increases gradually during growth. This is important information to consider when treating adolescents with RLPD, particularly when bony correction surgery is contemplated.