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2000 Publications

DOES INITIAL GRAFT TENSION DURING ACL RECONSTRUCTION AFFECT THE RESTORATION OF STATIC KNEE STABILITY?DOES INITIAL GRAFT TENSION DURING ACL RECONSTRUCTION AFFECT THE RESTORATION OF STATIC KNEE STABILITY?by Nicholas SJ, D'Amato MJ, Hershman EB, McHugh MP, Tyler TF, Gleim GW, Kolstad KNicholas Institute of Sports Medicine and Athletic Trauma, New York, NY - last modified 2013-02-10 00:00
American Orthopaedic Society for Sports Medicine: Specialty Day. Orlando, FL, March 18, 2000.

 

Introduction: Despite a number of in vitro cadaver studies, no consensus has been reached regarding 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 the present study was to (1) determine the inter- and intra-surgeon variability in initial graft tension, and (2) prospectively randomize patients into low or high tension groups and document the postoperative change in static knee stability in a double-blind fashion.

Methods: Graft tension at the time of fixation was measured for three surgeons (A,B,C) each of whom performed 10 ACL reconstructions. Surgeons A and B were experienced (attendings) and surgeon C was inexperienced (a resident).

Graft tension was compared between surgeons and the coefficient of variation in tension was computed for each surgeon. Graft tension was measured with a load cell attached by sutures to the bone plug of a patellar tendon autograft.

For the controlled graft tension study, 43 patients undergoing bone-patellar tendon-bone autograft ACL reconstructions by a single surgeon (A) were randomized into high (17 men, 3 women) and low (16 men, 7 women) tension groups. Arthrometric measurements of anterior tibial displacement (ATD) were made preoperatively and one week following surgery (KT-1000 manual maximum side-side difference).

Additionally, knee joint effusion and range of motion were documented. Both the patient and the examiner were blinded to group assignments. Results are reported as mean+/-SEM.

Results: Graft Tension was lower (P<0.05) for surgeon B (47.9+/-1.4 N) compared with surgeons A (82.8+/-4.7 N) and C (71.4+/-7.0 N). The coefficient of variation was higher for surgeon C (31.1%) compared with surgeon A (18.1%) and surgeon B (9.1%) (P<0.05). Based on the inter-surgeon values for graft tension (AvB), a high tension of 90 N and a low tension of 45 N were used for the randomized groups.

Reconstructive surgery reduced side-side difference in ATD from 6.3+/-0.4 mm to 1.4+/-3.2 mm (P <0.001), but this effect was different between tension groups. Surgery reduced ATD by 5.3+/-0.6 mm in the "high" group compared with only 3.4+/-0.5 mm in the "low" group (P <0.01). Side-side difference in ATD one week following surgery was related to loss of extension (r=-0.31, P <0.05) and preoperative side-side difference in ATD (r=0.47, P<0.001), but was unaffected by knee joint effusion (P=0.61).

When corrected for the confounding effects of extension loss and preoperative side-side difference in ATD (analysis of covariance), patients in the "high" group had 0.6+/-0.5 mm side-side difference in ATD one week following surgery, compared with 2.3+/-0.4 mm for patients in the "low" group (P<0.05).

Conclusions: No previous study has demonstrated an effect of initial graft tension during ACL reconstruction on early postoperative measures of knee stability. Patients set at a high tension had greater postoperative static knee stability than patients set at a low tension.

Since measurements were made only one week following surgery, this effect can be attributed to the mechanical constraints imposed at the time of surgery rather than to subsequent stress on the graft.

Low graft tension at the time of fixation will result in early postoperative laxity. These data strongly suggest that ACL grafts should be fixed in high tension in order to avoid excessive postoperative laxity.