2015 ISAKOS Biennial Congress ePoster #1310
Biomechanical Comparison of Anatomic All-Inside Two, Three and Four Socket Anterior Cruciate Ligament Reconstructions – An In Vitro Robotic Study
Breck R. Lord, MA, MBBS, MRCS, London UNITED KINGDOM
Bhushan Sabnis, FRCS, Basingstoke UNITED KINGDOM
Hadi El Daou, PhD, London UNITED KINGDOM
Adrian J. Wilson, MBBS BSc FRCS, London UNITED KINGDOM
Andrew A. Amis, PhD, FREng, DSc, London UNITED KINGDOM
Biomechanics Group, Imperial College London, London, UNITED KINGDOM
FDA Status Cleared
Summary: . There is a lack of research that compares the efficacy of ACL reconstruction techniques in the context of all-inside surgery using total suspensory fixation. We present a novel 3-socket approach for anatomic all-inside double-bundle reconstruction, using a single bifurcating hamstrings graft: the TriLInk (TL) technique. Knee kinematics were evaluated using a 6 degree-of-freedom robotic system.
Evidence from cadaveric and clinical biomechanical studies has suggested improved kinematic restoration using double-bundle (DB) anterior cruciate ligament (ACL) reconstruction techniques, however, DB surgery is technically challenging. There is a lack of research that compares the efficacy of ACL reconstruction techniques in the context of all-inside surgery using total suspensory fixation. A novel 3-socket approach for anatomic all-inside double-bundle reconstruction, using a single bifurcating hamstrings graft, was evaluated: the TriLInk (TL) technique. Complete suspensory fixation enables differential tensioning on the femur, aiming to replicate native ACL behaviour. A single tibial socket simplifies the technique whilst conserving bone stock. The hypothesis of the present study was that the TL technique would show improved kinematic restoration compared to anatomic single-bundle (SB) and more closely resemble that of DB surgery.
Nine cadaveric knees were used to evaluate the kinematics of the intact, ACL-deficient, SB, TL and DB ACL reconstructions in each knee. Femoral sockets were positioned, using the validated ‘Direct-Measurement’ technique, in the centre of the entire femoral attachment or of the posterolateral and anteromedial bundles, as appropriate. The tibial socket(s) was positioned similarly, in accordance with validated bony landmarks. The graft tensioning method used a Rolimeter® to match the intact anterior-posterior (AP) laxity at 30° flexion. Using a 6 degree-of-freedom robotic system, AP knee laxity was measured with 90N force. Rotational laxity was measured with 5Nm internal and external torques. Tests were performed at 0°, 30°, 60° and 90° flexion. A simulated pivot-shift test of combined 8 Nm valgus and 4Nm internal rotation tibial torques was performed at 0°, 15°, 30° and 45° flexion.
Outcomes were analysed with a two-way repeated-measures ANOVA with Bonferroni corrected post testing. Differences were considered statistically significant when P = <0.05.
Every all-inside reconstruction was statistically similar to the intact. Tibial rotation/anterior translation in response to pivot-shift reported significant differences between ASB versus DB at 15° (1.55°vs-0.24°), 30° (1.29°vs 0.07°, 0.95mm vs -0.59mm) and 40° (1.14mm vs 0.11mm). No significant differences were found during anterior, internal/external tibial loading.
The all-inside technique is proficient at restoring native knee kinematics. Although there is a trend towards improved stability with TL and DB when compared to SB during the simulated pivot shift, there is no significant difference suggesting superiority of DB or TL over the SB technique. However, this is time-zero data, and the reconstructions may differ under cyclic rehabilitation and functional loading in-vivo. Future work would explore the efficacy of the TL technique in high demand patients with large femoral footprints, with greater native ACL anisometry, and an explosive pivot shift.