Comparison of rotary stability after anterior cruciate ligament reconstruction between single-bundle and double-bundle techniques
Isawa T, Okasaki K, Tashiro Y, Matsubara H, Miura H, Matsuda S, Hashizume M, & Iwamoto Y. Am J Sports Med. 2011; 39: 1470: doi:10.1177/0363546510397172.
Management of anterior cruciate ligament (ACL) tears commonly involves undergoing surgery to reconstruct the ligament.  New surgical techniques have evolved over the years for ACL reconstruction, and one of the newer techniques gaining attention is the double-bundle technique.  The theory behind the double bundle technique is that this technique will more accurately replicate the anatomy and function of the original ACL.  The purpose of this study was to compare rotary stability of the single-bundle versus the double-bundle reconstruction with medial hamstring autografts. This study included 23 consecutive patients treated with a single-bundle reconstruction (average age = 26, all female) and 25 consecutive patients receiving a double-bundle reconstruction (average age = 27, 17 female).  The same surgical team performed all of the surgeries. All participants underwent the same post-surgical rehabilitation program, and were permitted to return to play after 9 months. The average time to follow up was comparable, however the ranges were slightly different between groups (single = 13.6 months [range: 8-26 months], double = 12.3 months [range: 8-14 months]). Outcome measures were anterior translation (with a KT-2000), Lysholm knee scores (knee symptoms), physical activity level (Tegner Activity Score), pivot shift test, and rotary stability. Rotary instability was assessed in a horizontal open MRI with the knee in 10 degrees of flexion with a valgus stress while an examiner pushed the tibia anteriorly and internally. The research staff then measured the anterior displacement of the tibia in the medial and lateral compartments (see Okazaki K 2007 for more details). The double-bundle technique resulted in better anterior stability (average = 2.2 mm) when compared to the single-bundle technique (average = 1.2 mm). The double-bundle technique also yielded better rotary stability (average = 1.2 mm) when compared to the single-bundle technique (average = 4.1 mm). The presence of a positive pivot shift was less common in knee with the double-bundle technique (16%) compared to the single-bundle technique (43%), but this was not statistically significant. The findings of this study demonstrate that the double-bundle technique produced better biomechanical results than the single-bundle technique. However, the two patient groups had similar physical activity levels and knee symptoms at follow-up.     
This study is important because it quantitatively supports the potential superiority of the double-bundle technique in re-establishing rotary stability as well as anterior translation stability.  The findings of this study reaffirm previous studies that used nonquantitative methods.  The authors acknowledge some limitations of this study, including the high female to male ratio, the range in time to follow up was different between groups, the relatively short follow-up time (1 year), and that the tunnel placement technique utilized was popular in the last decade but has since evolved. Furthermore a larger sample size and randomizing participants would help reduce biases between groups and improve the comparisons between the two approaches. At the time of 1 year follow-up, there were no differences in perceived outcome between the two groups. It would be interesting to follow these cohorts longer to evaluate their long-term outcomes (e.g., failure rates, function). As surgical techniques evolve, it is important to not only understand the immediate short-term results (apparent biomechanical superiority of the double-bundle technique), but also the long-term results (possible failure rates, influence on osteoarthritis development).
Written by: Nicole Cattano
Reviewed by: Jeffrey Driban