A PROSPECTIVELY RANDOMIZED DOUBLE-LIMB STUDY ON THE EFFECT OF INITIAL GRAFT TENSION ON KNEE STABILITY FOLLOWING ACL RECONSTRUCTION.

Nicholas SJ, D'Amato MJ, McHugh MP, Tyler TF, Kolstad K, Gleim GW

Nicholas Institute of Sports Medicine and Athletic Trauma, New York, NY

At present there is no consensus on the amount of graft tension needed to recreate normal knee mechanics while providing the ideal biologic milieu for graft healing. In practice, few surgeons control for the degree of tension placed on the graft at the time of fixation. The purpose of this study was to examine the effect of high versus low initial graft tension on surgical outcome following ACL reconstruction. Thirty patients undergoing bone-patellar tendon-bone autograft ACL reconstruction by a single surgeon were randomized into High (12 men, 3 women) and Low (9 men, 6 women) tension groups. Grafts were set at 90 N or 45 N based on a pilot study documenting variability in graft tension for two experienced surgeons. Arthrometric measurements (KT-1000 manual maximum) of anterior tibial displacement (ATD) and knee ROM were made pre-op, 1 week post-op and six months post-op. Knee Outcome Scores were collected pre-op and 6 months post-op and a single leg hop test was performed 6 months post-op. Both the patient and the examiner were blinded to group assignments. Results are reported as mean+/-SD. Patients in the High tension group had less ATD than patients in the Low tension group (p=0.018): 1 week post-op 0.2+/-2.2 mm vs. 2.0+/-2.2 mm; 6 months post-op 1.6+/-2.1 mm vs. 3.4+/-2.1 mm. Three patients had >5mm side-side difference in ATD (surgical failure) and all were in the Low tension group. Only one patient (High tension) had less ATD on the involved side (overconstrained). Knee ROM was not different between groups: in the Low tension group no patients lacked >=5° extension and four patients lacked >=5° flexion; in the High tension group two patients lacked >=5° extension and one patient lacked >=5° flexion. KOS scores (Low=86+/-9, High=90+/-9) and hop test deficits (Low=13+/-15%, High=17+/-9%) were not different between groups at 6 months. In conclusion, initial graft tension clearly affected static knee stability following ACL reconstruction. A graft tension of 90 N provided greater stability without overconstraining the knee while a graft tension of 45 N resulted in residual laxity, with three patients categorized as surgical failures. Since differences were apparent at 1 week post-op, this effect can be attributed to the mechanical constraints imposed at the time of surgery rather than to subsequent stress on the remodeling graft. These data highlight the importance of documenting graft tension during ACL reconstruction. We strongly suggest that ACL grafts should be fixed in high tension in order to avoid excessive postoperative laxity.

American Orthopaedic Society for Sports Medicine: Specialty Day. San Francisco, CA, March 3, 2001.