ORIGINAL ARTICLE

Sung-Gon Kim Æ Hisashi Kurosawa

Keishoku Sakuraba Æ Hiroshi Ikeda Æ Shunji Takazawa

The effect of initial graft tension on postoperative clinicaloutcome in anterior cruciate ligament reconstructionwith semitendinosus tendon

Received: 23 November 2004 / Published online: 28 September 2005� Springer-Verlag 2005

Abstract Introduction: The goal of this study is toestablish the influence of tensioning the graft duringanterior cruciate ligament (ACL) reconstruction, with asemitendinosus tendon graft, on postoperative stability.Type of study: Prospective controlled clinical trial.Material and methods: Forty-eight patients were ran-domly allocated to three groups in which three differenttensions, 8, 12, or 15 kg force, was applied on thereconstructed ACL during the operation. The patientswere observed for 1 year or more after surgery (min.1 year, max. 2 years 8 months). Clinical outcome wasevaluated using the visual analogue scale, anterior kneelaxity (using the KT2000 arthrometer) and the torque ofthe knee extensor. Results: Postoperatively, the averageside-to-side differences in anterior laxity were 1.3 mm inthe 8 kg group, 2.1 mm in the 12 kg, and 2.4 mm in the15 kg group. The visual analogue scale averaged 84, 83,and 79 mm, respectively. There were no significant dif-ferences among the three groups. There were also nosignificant differences between the groups for musclestrength recovery during isokinetic and isometric con-traction at 1 year postoperatively. Conclusion: Therewere no significant differences among the groups insubjective clinical results, anterior laxity, and kneeextensor strength in the ACL reconstructions that usedthe autogenous semitendinosus tendon graft.

Keywords Anterior cruciate ligament ÆReconstruction Æ Hamstrings Æ Initial tension

Introduction

There have been few studies about the optimal initialgraft tension at the time of reconstruction of the anteriorcruciate ligament (ACL). Some tension should be ap-plied to the graft in order to remove the slack, but strongtensions have been reported to be harmful in animalmodels [1]. Overtensioned grafts may not only lead to alimitation of the range of the motion, but also damagethe articular surface. Yasuda et al. [14] reported that arelatively high initial tension (upto 80 N) reduces thepostoperative anterior laxity of the knee joint after ACLreconstruction, using the doubled autogenous hamstringtendons connected in series with the Leeds-Keio artifi-cial ligament. However, the clinical results of using morethan 80 N in initial tension are unidentified. Since highertension (80 N) can lead to lesser A–P laxity in the study,a better result may be obtained in the case of usingtension of more than 80 N. The aim of this study is toinvestigate the effects of the graft initial tension on theclinical outcome after ACL reconstruction with a semi-tendinosus tendon.

Materials and methods

Patients who, between July 1999 and September 2001,underwent ACL reconstruction using the autogenoussemitendinosus tendon were prospectively randomizedinto three groups for graft initial tension of 8 kgf(78.5 N), 12 kgf (117.7 N), and 15 kgf (147.1 N),respectively. The randomization was accomplished usingthe remainder obtained when dividing the patient’shospital ID number by three. 12 of the 60 patients in-volved in the study were excluded, thus leaving a studysample of 48 patients. Five patients with an age of over40 years at surgery were excluded and seven patientscould not be followed up periodically throughout thestudy. They were observed for 1 year or more aftersurgery. In the 8 kg group, there were 16 patients (11male and 5 female) with an average age of 27.1 years at

S.-G. Kim (&) Æ H. Kurosawa Æ H. Ikeda Æ S. TakazawaDepartment of Orthopaedics, Juntendo University,2-1-1 Hongo, Tokyo, JapanE-mail: s-kim@med.juntendo.ac.jpTel.: +81-3-38133111Fax: +81-3-38133428

K. SakurabaDepartment of Sports Medicine,School of Sports and Health Science,Juntendo University, Chiba, Japan

Arch Orthop Trauma Surg (2006) 126: 260–264DOI 10.1007/s00402-005-0045-x

the time of surgery. In the 12 kg group, there were 16patients (11 male and 5 female) with an average ageof 22.6 years. In the 15 kg group, there were 16patients (7 male and 9 female) with an average age of23.7 years. The time from injury to surgery averaged30±38 months for the 8 kg group, 18±23 months forthe 12 kg group, and 19±23 months for the 15 kggroup. There were no significant differences in the age,gender, surgical time from injury, follow up period andassociated meniscus injury among the groups (Table 1).

Operative procedure

The semitendinosus tendon was harvested using a ten-don stripper through a longitudinal incision over the pesanserinus. The tendon was folded 5 times (penta-ST)and was connected with extension polyester tapes of3 mm in width (Telos, Tokyo, Japan) at the distal andproximal ends of the tendon loop. During the connec-tion with the tapes, the graft was stretched with amanual max tension (Fig. 1a). The graft was securedwith a small metal button that was introduced through asmall incision on the lateral thigh at the femur side.Thereafter, the graft was pulled by a custom-madespring tensiometer that holed the extension tape(Fig. 1b), and the knee was guided from full flexion tofull extension for three cycles with the chosen tension.The graft was fixed using a double stapling technique at30� of knee flexion, after resetting the tension. Thediameter of the graft substance averaged 9.2±0.9 mmfor the 8 kg group, 9.8±0.8 mm for the 12 kg group,and 9.4±0.9 mm for the 15 kg group. There were nosignificant differences among these groups. For postop-erative rehabilitation, the same protocol was used in theinitial 4 months and followed by athletic rehabilitation.

Clinical assessments

Subjective clinical evaluation was performed using the100 mm visual analogue scale with ‘completely normal’at the 100 mm end and ‘severely abnormal’ at the 0 mmend [7]. The anterior knee laxity, range of motion, andthe torque of the knee extensor were measured

12 months after the surgery. Instrumented Lachmantests were performed using the KT2000 arthrometer(MEDmetric Corporation, San Diego, CA, USA) at30 lbs. The isokinetic concentric torque, at 60� per sec-ond, and the isometric torque, at 60� flexion of the kneeextensor, were measured with a BIODEX dynamometer(BIODEX Medical Systems, Shirley, NY, USA).

Statistical analysis

Statistical analysis was carried out using the Student’st-test for multiple comparisons. Spearman’s rank cor-relation was used for relationship between the A–Plaxity difference and the initial tension. P-values lessthan 0.05 were considered to indicate statistical sig-nificance.

Results

There were no significant differences in the preoperativevisual analogue scale and side-to-side anterior dis-placement differences in a KT2000 among the groups(Table 1).

Postoperatively, the average side-to-side differencesin anterior laxity were 1.3±1.4 mm in the 8 kg group,2.1±1.9 mm in the 12 kg, and 2.4±2.2 mm in the 15 kg(Fig. 2).

The postoperative visual analogue scale averaged 84,83, and 79 mm, respectively (Fig. 3). Although, rela-tively, the 8 kg group had less postoperative anteriorlaxity and indicated better results in visual analoguescale, there were no significant differences among threegroups.

There was no significant tendency between eachgroup (Table 2) with respect to the muscle strengthrecovery during isokinetic and isometric contraction at1 year postoperatively.

Eight patients had more than a 3 mm side-to-sidedifference, postoperatively. There were two in the 8 kggroup (one man, one woman), three in the 12 kg group(three men), and three in the 15 kg group (one man, twowomen) (Fig. 4). No patient had a limitation of therange of motion over 5 degrees.

Table 1 Preoperative patientdata. There were no significantdifferences in these data amongthe groups

Group 8 kg 12 kg 15 kg

Number of patients 16 16 16Man : moman 11:5 11:5 7:9Average of age at surgery 27.1 22.6 23.7Follow up period (month) 16.3 15.8 18.8Visual analogue scale (means ± S.D., mm) 30±25 36±24 37±17A–P laxity (mean ± S.D., mm) 5.6±1.9 5.0±2.0 6.3±2.6Meniscus injuryMedial 6 6 6Lateral 5 6 3Bilateral 3 3 5

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Discussion

Initial tension of the graft has been considered one of themost important factors for clinical results after ACLreconstruction. However, there has been no consensus asto the optimal tension that is to be used since grafttensioning is highly variable, intraoperatively, amongsurgeons [5]. Yasuda et al. [14] reported that, in theACL reconstruction with a hamstring tendon graft, the

postoperative laxity in the tension at 80 N was signifi-cantly less than at 20 N. Therefore, the authors recom-mend applying 80 N of tension to the grafts. However,they described that an initial tension of 80 N was notexcessively high for both the autogenous semitendinosusand gracilis tendon grafts. Yoshiya et al. [16] reportedthat the different amounts of tension (25 and 50 N), inthe ACL reconstruction using bone-patellar tendon-bone, did not lead to detectable differences in clinicalresults, subjectively or objectively. Another prospectivestudy by van Kampen et al. [17] did not find any

Fig. 1 a The semitendinosustendon folded five times, whichis connected with extensionpolyester tapes. b A custom-made spring tensiometer, whichholds the extension tape thatpulls the graft

Fig. 2 The postoperative side-to-side difference in A–P laxitymeasured with KT2000 arthrometer. There were no significantdifferences among these groups. (P-values were 0.20 in 8–12 kg,0.11 in 8–15 kg, and 0.67 in 12–15 kg)

Fig. 3 One hundred millimeter visual analogue scale as subjectiveclinical evaluation. There were no significant differences amongthese groups

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significant difference in the laxity, IKDC level, Lysholmscore, or non-weight bearing radiographs, one year afterACL reconstruction with a 20 or 40 N tension to thebone-patellar tendon-bone graft. They prefered to ten-sion the graft with a maximum of 20 N in order tominimize the risk of graft degradation as well as reducethe risk of overconstraining the knee joint. The magni-tude of graft tensioning should be tissue specific [4],because optimal tensions may be related to the graftstiffness and this will be complicated by the differingstiffness of fixation methods. Differences of the type ofgraft may account for the inconsistency between them.Heis and Paulos [8] described the application of aweaker tension to the bone-patellar tendon-bone graft,while a stronger tension was deemed necessary for thehamstring graft.

In our study, two women had more than 6 mm side-to-side difference, postoperatively, in the 15 kg group(Fig. 3). The optimal initial graft tension may be dif-ferent for men and women. A high initial tension mayincrease the risk of A–P laxity for women, but the effectof the graft tension on sex differences is still unknown.

Some studies have demonstrated that the graft withhigher tension had inferior failure loads, when comparedwith grafts with lower tension [10, 12]. In a canine model[15], focal myxoid degeneration was found in the highlytensioned knee. Amis [1, 2] reported that increasingACL graft tension subluxates the tibia posteriorly, so ahigh tension increases the risk of high cartilage contactstresses and also risks the range of motion loss caused byoverconstraining the knee [13]. Conversely, other

experimental studies showed that a higher initial grafttension resulted in improved histological and biome-chanical parameters [11]. In our study, no patient had alimitation of the range of motion over 5�, due to over-constraining of the knee; so 15 kg, for the initial tension,may not be too high. It is known that the viscoelasticcreep phenomenon reduces the initial graft tensionshortly after fixation [3, 6, 9]. Our study suggests thatinitial graft tension, of within 8–15 kg, gives littleinfluence to the postoperative clinical outcome.

Conclusion

There were no significant differences among the groupsin subjective clinical results, anterior laxity, and kneeextensor strength in the ACL reconstructions using theautogenous semitendinosus tendon graft.

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Table 2 Knee extensor muscle strength recovery 1 year after surgery. The mean postoperative peak torque was compared with theuninjured side (percentage). The isokinetic torque was measured during concentric contraction. There were no significant differencesamong these groups

Group 8 kg 12 kg 15 kg

Isokinetic contraction (60�/s) 81.3±17.0 85.2±10.9 86.4±21.1Isometric contraction (60�s flexion) 90.9±18.0 91.3±11.7 88.8±8.4

Fig. 4 Scattergram of side-to-side laxity difference. White pointsshowed men and black points showed women. There was nosignificant correlation between the side-to-side laxity difference andthe magnitude of initial tension among three groups (P=0.0531)

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