Knee cruciate substitute tendon graft

Arthroscopy: The Journal of Arthroscopic & Related Surgery Online

October 1999, Supplement 1 • Volume 15 • Number 7

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Knee Cruciate Substitute Tendon Graft Abstracts

These are the abstracts of the papers presented at the Second Biennial Meeting of The International Society of Arthroscopy, Knee Surgery and Orthopaedic Sports Medicine, Washington, DC, May 29- June 3, 1999.

1. No Increase of the Mechanical Properties of Patellar Tendon Grafts After Twisting.

Thomas Muellner, R. Reihsner O. Kwasny R. Schabus V. Vecsei

M.D.

Knee Cruciate Substitute Tendon Graft

Purpose: The aim of this study was to investigate whether the twisting of a patellar tendon (PT) graft improves or reduces its mechanical properties. Method: 27 pairs of 10mm cadaveric PT grafts (donor's mean age: 27y + 8y) were tested at a strain rate of 10% / min. For each pair, the left specimen served as an unmanipulated control while the right specimen was either left untwisted (A), twisted +90 ° (B), or twisted-90 ° (C). All avulsion failures (n=l 1 ) were excluded from the data. The following mechanical properties were evaluated: Ultimate load (N), failure strain (%), stiffness (N/mm), and the energy to failure (kNmm). The collagen content

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was calculated following the tensile testing from the dry-weight of the ligamentous portion of the specimen (1, 2), in order to make a comparison between the specimens possible. Statistical analysis was performed with a blocked analysis of variance with blocking on specimens using the statistical software package SAS (3). Results: Higher ultimate load values than previously reported were obtained for both the twisted and untwisted specimens. The values obtained for the left and right specimens from Group A were 4014 +319N and 3973+245 N, from Group B 3613+207N and 3891+147N, and from Group C 3997+278N and 4415+507N (Fig 1). No statistical significant differences were found for all mechanical properties and for the collagen content (p>0.2). Conclusion: Neither the presence of a twist, nor the direction of the twist were found to increase the ultimate load of the 10mm cadaveric patellar tendon graft as previously published by Cooper et al (4). The mean ultimate load obtained from the excluded avulsion failures is similar to the values Cooper et al. (4) obtained for their specimens and may explain the higher ultimate load values of the midsubstance ruptures obtained in our study. Significance: Recommendation for twisting can not be assessed to its mechanical properties. References: 1. Hooley CJ et al: J Biomechanics (1980);13:521-282; 2. Ellis DG: J Biomechanics (1969);2:175-186 3. SAS (1990) SAS/STAT User's Gide; 4. Cooper DE et al: Am J Sports Med (1993);21:818-24

44~ . . . . . . .

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2. Patellar vs. Hamstring Tendons in ACL Reconstruction: A Meta-Analysis.

Michael J. Yunes, B.A. John C. Richmond, M.D. Eric A. Engels, M.D., M.P.H. Leo A. Pinczewski


Introduction: Meta-analysis is a systematic method for statistical analyses that allows compilation of combined data from various independent studies. This allows one to better assess the potential benefits of various treatments. Purpose: Currently, both semi-tendinosus/gracilis (ST&G) and patellar tendons (PAT) are used for ACL reconstruction with little critical data comparing the respective outcomes. We conducted a meta- analyses (M-A) using randomized control trials (RCT's) to determine if there are differences between the two methods. Our hypothesis was that, while both surgical techniques have potential for excellent results, there are differences in outcomes between these techniques. Method: We searched the MEDLINE database, from 1980 to the present, for all RCT's comparing ST&G vs. PAT for ACL reconstruction. To supplement these results, a comprehensive review was

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completed by the senior author as well as a review of references from all potential papers. We included RCT's that: 1) compared ST&G with PAT and 2) used standard evaluation techniques including a minimum 2 year follow-up. Relevant data were extracted and pooled using the computer program Meta- Analyst (v. 0.989 © J. Lau). Outcomes evaluated are presented in the table below. Results: Four studies fulfilled our inclusion criteria. One of the studies contained two similar methods of PAT reconstruction; the data from these methods were pooled.

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ~E -J


Conclusions: These results demonstrate significant differences between PAT and ST&G reconstructions, with PAT reconstructed patients having nearly a 20% greater chance of having a statically stable knee (as measured by KT) and returning to pre-injury levels. Due to significant heterogeneity, loss of motion in extension could not be pooled. While there may be advantages in peri- operative morbidity with ST&G, it is at the cost of increased long-term laxity and lower activity levels.

3. Endoscopic Anterior Cruciate Ligament Reconstruction: Quadrupled Hamstring Tendon Versus Patellar Tendon Autograft.

Frank A. Cordasco, M.D. Timothy P. Char#on, M.D. David Rojer, M.D.


The published results following endoscopic ACL reconstruction using a central third patellar tendon (PT) autograft combined with an accelerated rehabilitation program demonstrate predictable and reliable restoration of stability and the ability to return to pre-injury level of activity. Preliminary studies using a quadrupled semitendinosus and gracilis (ST/G) autograft have demonstrated comparable results with improved techniques to enhance strength and biologic fixation. The purpose of the study is to prospectively evaluate 30 endoscopic ACL reconstructions using PT autograft and 30 ACL reconstructions using ST/G autograft, with respect to stability, function, and patient satisfaction. The groups were matched for age, sex, chronicity, level of activity, degree of injury, and meniscal/ chondral injury. Patients with multiple ligament injuries were excluded. All patients had an endoscopic ACL reconstruction performed by the same surgeon. The PT autografts were secured with interference screws. The ST/G autografts were secured on the femoral side with endobuttons (15) or crosspins (15), and on the tibial side with staples or a screw with a soft tissue washer. All patients were available for follow-up and were assessed clinically, arthrometrically (KT-1000), and using the Lysholm score



and International Knee Documentation Committee (IKDC)form. The average age in the PT group was 30 and in the ST/G group was 32. Lachman and pivot shift tests were 0 or 1 in all but two patients (1 PT, 1 ST/G). KT-1000 testing was less than 3mm MMD in 58 patients. Mean Lysholm score was 94% in the PT and 92% in the ST/G groups. IKDC scores revealed 28/30 PT and 27/30 ST/G rated normal or nearly normal. One patient in the ST/G group ruptured the graft in the early postoperative period during a fall from a height. There were no significant differences between the PT and ST/G groups with respect to clinical assessment, KT-1000 findings, Lysholm or IKDC scores. All patients would undergo the procedure again. This study demonstrates no significant differences in clinical stability, function, ability to return to sport, or patient satisfaction in two groups undergoing endoscopic ACL reconstruction using PT or ST/G autografts.

4. Biomechanical and Histological Comparisons of Intraosseous Graft Healing in Anterior Cruciate Ligament Reconstruction-Doubled Flexor Tendon Graft Versus Bone- Patellar Tendon-Bone Graft.

Fumihisa Tomita, M.D. Kazunori Yasuda, M.D., Ph.D. Shuji Yamazaki, M.D. Harukazu Tohyama, M.D


Purpose: To biomechanically and histologically compare intraosseous graft healing between the doubled flexor tendon (FT) graft and the bone-patellar tendon-bone (BTB) graft in anterior cruciate ligament (ACL) reconstruction. Methods: Twenty beagle dogs were used. For each animal, the right and left knees underwent ACL reconstruction using the doubled FT graft having a diameter of 4 mm and the BTB graft having a width of 4 mm, respectively. A 4-mm drill hole was made in the tibia through the insertion of the ACLº Each end of the graft was tethered to a screw-post with two sutures. Animals were sacrificed at 3, 6 and 12 weeks. Biomechanically, pull-out tests of the graft-tibia complex were performed after the sutures tethering each graft to the tibia were cut. Histologically, 5 sites within the tibial tunnel were evaluated with light and polarized light microscopy. Results: (1) At 3 weeks, all grafts were pulled out from the tunnel. The maximum load of the FT graft was significantly less than that of the BTB graft. At 6 weeks, the FT graft was pulled out in 3 of 5 knees, and the BTB graft was pulled out with a small fragment of the bone plug in 3 knees. There were no significant differences in the maximum load between the two grafts. At 12 weeks, all grafts were torn in the tendon substance. (2) Histologically, collagen fibers connecting the graft to the bone formed at the FT graft-bone interface at 3 weeks, and increased at 6 weeks. New bone formation appeared at the BTB graft-bone interface at 3 weeks, and gradually progressed at 6 weeks. However, the bone plug remained necrotic at 6 weeks. Conclusion: Intraosseous healing mechanism and the mechanically weakest site are significantly different between the two grafts. The maximum load of the FT graft was significantly less than that of the BTB graft at 3 weeks, while there were no significant differences between the two grafts at 6 weeks.

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Significance: The FT and BTB grafts are equivalently useful after 6 weeks in terms of intraosseous graft healing.

Figure. The maximum load of the graft-tibia complex at 3, 6, and 12 weeks.

300-

200"

100"

"•BTB

§ p<.OOl(vs FT 3W)

0" 3W 6W 12W


5. Resultant Forces in the BPTB-Graft.

Stefan Rupp, M.D. Thomas Hopf, M.D. Thomas Hess, M.D. Dieter Kohn, M.D


Objective: The objective of this study was to measure the resultant force in the human BPTB-graft after reconstruction of the ACL under various conditions in vitro. Methods: Seven fresh frozen cadaver lower extremities were used. Force measurement was done with a quartz force transducer mounted in a specially designed load cell. The effect of passive extension movement, quadriceps pull, varus torque and valgus torque on the resultant force in the ligament was investigated. Results: Passive extension of the joint generated a rapid increase of force in the graft between 30 and 0 degrees of flexion, reaching its maximum (128 + 25 N) at full extension. When quadriceps pull was applied to extend the joint resultant force began to increase at 50 degrees of flexion and reached its maximum (219 + 25 N) at full extension (Fig).

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250

2OO Z

150

&~ 100 iiii i i 0 10 20 30 40 50 60 70 80 90

knee flexion angle O


Additional resistance applied at the level of the ankle joint generated an additional load of the graft. Increase of forces in the ligament resulted from both varus and valgus applied moments. Conclusion: Successful reconstruction of the ACL requires the understanding of forces applied to the graft during normal joint function. The knowledge of forces loading the graft may be an important basis to judge security of various methods of graft fixation during early rehabilitation comparing these data to pull-out forces assessed in cadaver studies.

6. Prospective Evaluation of ACL Reconstruction Using Doubled Semitendinosus and Gracilis Rigidly Fixed to Bone.

Francesco Giron, M.D. Paolo Agile#i, M.D. Alfred V.J. Simeone, M.D. Giovanni Zaccherotti, M.D.

Knee Cruciate Substi tute Tendon Graft

Material: Fourty-seven patients with an isolated complete ACL injury (injury-surgery interval 19 months, range 1-156) were included. We personally reviewed 43 patients, at the 5 and 12 months follow-up. Two patients were lost, one had a rerupture in the mid-substance at 3 months while playing soccer and the fourth had had a knee fracture in an accident. The average age at surgery was 28 (range 17-48). Technique: The semitendinosus and gracilis tendons were harvested with special strippers: the average length after preparation was 25 (21-32) and 28 cm (24-33) respectively. The femoral tunnel was drilled first with the knee in maximum flexion through the antero-medial portal. The position of the K. wire was checked fluoroscopically with intraoperative lateral views and only positions less than 30% from the back were accepted or the K. wire was repositioned. The tibial K. wire was introduced using the one step guide (Arthrotek) which references off the roof of the notch in extension to avoid impingement. The fixation of the graft was by means of a Mitek anchor in the femur with the 2 tendons looped around the slot in the anchor, and with the an RCI screw, supplemented with a spiked washer and a bicortical screw in the tibia. The RCI screw was inserted to achieve a more anatomical level of fixation on tibial side. The 4 strands of the graft were individually tensioned and fixed at 25 ° after



cycling. Rehabilitation was moderately accelerated and without braces. Sports were resumed after 5 months. Method: We used the IKDC form in all the patients; KT-1000 and Cybex testing for concentric isokinetic strength were performed in 40 patients with a normal controlateral knee at the 2 follow-up. Results: At 5 months range of motion was complete in all the patients and 7% of them complained of some pain. The KT ssd was 2.2 mm at 30 Ibs (range 0-5 mm) and 58% of the patients had less than 3 mm. Quadriceps deficits were 23%, 21% and 16%, flexors deficits were 11%, 11%, and 9% at 60°/sec, 120°/sec and 180°/sec respectively. At 12 months pain was present in 6%, no patients had giving way. The KT ssd had remained the same, apart from one case with 6 mm after a reinjury during soccer. Only this latter patient has a pivot shift glide, the remainder were negative. Quadriceps deficits were 5%, 6%, 5.5% and flexors deficits were 5.5%, 7%, 5% at the three torques. Conclusion: We believe that the D-STG graft, with strong fixation to bone, can give excellent results similar if not better than the so called gold standard patellar tendon.

7. Correlation of Insertion Torque, Load at Failure and Bone Density Utilizing a Soft Tissue Interference Screw With Free Central Quadriceps Tendon Graft in ACL Reconstruction.

Brian J. Donahue, M.D. Brian P. McKeon, M.D. Danyel J. Tarinelli, B.E. John P. Fulkerson, M.D.


Introduction: The use of free tendon grafts without bone plugs, including central quadriceps tendon (CQT), is an excellent graft alternative in cruciate reconstruction. The purpose of this study is to evaluate the correlation of insertion torque of a soft tissue bioabsorbable interference screw (Bio- Interference Screw, Arthrex, Naples, FL) to the peak load at failure of the graft and bone density. Methods: Sixteen free CQT grafts (9x7mm) were harvested from 8 fresh frozen elderly cadaveric knees and fixed in porcine (N=8) or cadaveric (N=8) proximal tibias with an 8mm screw. Mean bone densities (gm/cm 2) of all porcine and cadaveric proximal tibias were measured by DXA scan prior to drilling 8mm tunnels. A cannulated torque screw driver was utilized to obtain screw insertion torque for all specimens. The constructs were then mounted on the MTS, preloaded to 25 Newtons (N) and loaded to failure in tensile mode at a rate of 2mm/sec. Data was analyzed with a linear regression and 2 way ANOVA test. Results: The mean insertion torque was 12.69 in-lbs (range 3.40 to 30.20 in-lbs). The mean peak load at failure was 309 N (23 to 716 N). The mean bone density was 1.04 gm/cm 2 (0.51 to 1.68 gm/cm2). The correlation of insertion torque to peak load at failure and mean bone density was r=0.83 and r=0.86 respectively. Conclusions: Our results demonstrate a high correlation between the insertion torque of the screw tested and both peak load at failure and mean bone density. Secure initial fixation of CQT grafts can be obtained with the Bio-lnterference Screw, provided there is adequate bone density and insertion torque.



8. The Biomechanics of a New Bone-Patellar Tendon-Bone Graft Interference Fixation Device.

Helmut Seitz, M.D. Vilmos Vecsei, M.D. Wolfgang Pichl, Ph.D. Wolfgang A. Menth-Chiari, M.D.


Purpose: A metal spreadable metal bolt [Howmedica GmbH, Kiel, Germany, (28 mm long and spreadable from 5 to 7 mm)] with non-tapping threads was developed to avoid the inherent pitfalls and complications associated with interference screws. Method: 48 knee specimens from 24 donors were obtained at autopsy. A bone-patellar tendon-bone (BPTB) graft was taken from the central third of the PT of each knee. The BPTB grafts were 9 mm in width with attached bone plugs measuring 25 mm in length, 9.5 mm in width, and 7 mm in depth. In 24 single femur and tibia specimens tunnels 10 mm in diameter were drilled. The autogenous plugs from the patellae were anchored in the femoral tunnels, the plugs from the tibial tubercles in the tibial canals using spreading bolts. After implantation of the spreading bolts 12 femur and 12 tibia specimens were dissected to measure the divergence of the bolts. The shafts of 12 femur- and 12 tibia-specimens were mounted in the materials testing machine (Instron TM 1253).


The constructs were loaded to failure at a displacement rate of 100 mm/min. The linear load in N, the maximum load at failure in N, and the stiffness in N/mm was determined for each sample. The mode of failure of each specimen was noted by visual inspection. Results: No problems occurred as a result of the insertion of the spreading bolts. The linear load was 920 + 283 N for the femoral site and 635 + 247 N for the tibial fixation site. Bone plug pullout was the mode of failure in all specimens.

' a --




Conclusion and Significance: This biomechanical analysis indicates that the spreading bolt is a reasonable alternative to interference screws.

9. Concentric/Eccentric Hamstrings to Quadriceps Torque Ratios Described as a Function of Knee Flexion Angle.

Thomas D. Rosenberg, M.D. Kathleen Definer, M. S. Rob Motl, M.S. Steve Johnson, Ph.D.


Introduction: Traditionally, isokinetic strength is reported as the ratio of maximum hamstrings torque to maximum quadriceps torque, regardless of knee angle. We have previously shown that the hamstrings to quadriceps torque ratio (H/Q ratio) varies as a function of knee flexion angle. The H/Q ratio is most commonly reported for concentric motion; however, in situations such as landing from a jump, the quadriceps are eccentrically activated while the hamstrings respond concentrically. The purpose of this research was to describe the concentric hamstrings to eccentric quadriceps torque ratio (con/ecc H/Q) as a function of knee flexion angle and to compare it to a concentric/concentric knee angle specific H/Q ratio (con/con H/Q). Methods: Thirty-four active women with an average age of 27 + 8 years were tested concentrically and eccentrically on a Cybex 6000 isokinetic dynamometer at an angular velocity of 60°/sec. The protocol was reviewed by the hospital's Institutional Review Board, and all subjects gave informed consent prior to enrollment in the study. A familiarization protocol was performed one week prior to data collection on all subjects. H/Q torque ratios were computed at 20, 30, 40, 50, 60, 70, and 80 degrees of knee flexion using 1) concentric-only data (con/con H/Q ratio) and 2) concentric hamstrings and eccentric quadriceps data (con/ecc H/Q ratio). These ratios were compared statistically using a repeated measures ANOVA.

Figure 1. Comparison of knee angle specific con/ con and con/ecc H/Q ratios.



o+~ 4- +

0.8 +! '0,7 ~

(1.6,1. O5 t

0.4 ~i

;.. [:-:°G;G~;~t

%",% , L.-'-con/ccc H/Q~

0.3 ! ~ :i ; ~ ~ 'r "~"

lo 20 30 4o so 6o 70 ao Knee flexion (deg)


Results: A graph depicting knee angle specific con/con H/Q ratios and con/ecc H/Q ratios is shown in Figure 1. Note that the con/ecc H/Q ratio is considerably lower in the 40 to 60 degree range of knee flexion than the con/con H/Q ratio (p < 0.01). Conclusion and Significance: The comparably low con/ecc H/Q ratio at middle angles of knee flexion demonstrates that the quadriceps can generate more torque than the hamstrings throughout this range of knee motion. Such imbalance may predispose the knee to injury. A program to train the hamstrings in these areas of knee flexion may lessen this injury risk.

10. ACL Graft Pretension Required to Restore Normal Laxity and Kinematics for Graft Fixation Complexes (GFC) of Different Stiffnesses.

Paul Eager, B. S. Stephen M. Howell, M.D. Maury L. Haft, Ph.D.


Introduction: The restoration of normal laxity and kinematics at 30 degrees of flexion with an anterior cruciate ligament (ACL) reconstruction requires that the pretension of the graft at 0 degrees of flexion be selected based on the stiffness of the femur-FM-graft-FM-tibia complex (GFC). Since the stiffness of the GFC is known to vary widely because of variability in the stiffness of the fixation methods, the purpose of this study was to determine the graft pretension required to restore normal laxity and kinematics for five GFCs that replicate the range of stiffness used clinically. Methods and Materials: Normal laxity, defined as the difference in tibial displacement on the femur between 225 N of anterior load and 1N of posterior load, and normal kinematics, defined as the tibial position relative to the femur at 1N of posterior load and 1 and 225 N of anterior load were determined for 7 human knees (fresh-frozen) at 30 degrees of flexion using a six degree of freedom knee testing machine. The knee was then reconstructed using a double-looped semitendinosus and gracilis graft that was fixed inside the femoral tunnel over a rigid transverse fixation bar and connected to the load cell by a series of interchangeable springs of different stiffnesses (24, 82, 151, 211,327 N/mm). Pretensions of 20, 100,200, 300, and 400 N were applied to the graft at 0 degrees of flexion. The

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laxity and kinematics were determined at 30 degrees of flexion for 25 combinations of pretension and GFC stiffnesses and compared to that of the normal knee. Results: The A-P laxity of the intact knee averaged 11.5 + 2.0 mm. The average translation of the tibia on the femur was 3.4 + 1.6 mm between 1 N of posterior load to 1 N of anterior load that was defined as the "free-play" of the knee. Pretensioning the graft 20N or more for all of the GFC complexes limited the free-play and overconstrained the knee. The reduction in free-play was more extensive as either the pretension or the stiffness of the graft-fixation-bone complex increased. The restoration of normal anterior laxity required the proper balance between the pretension applied at 0 degrees of flexion and the stiffness of the graft-fixation-bone complex. Less pretension was required as the stiffness of the graft-fixation-bone complex increased (i.e. a 300 N of pretension was required for a GFC stiffness of 24 N/mm and 20 N for a GFC of 211 N/mm). The normal kinematics of the knee (i.e. normal limit of anterior motion at 1 and 225 N and normal limit of posterior motion at 1 N) were not be restored eventhough normal anterior laxity was restored for GFC of stiffness 24, 82, 151, 211 N/mm with a pretension of 300,200, 100, and 20 N respectively. Discussion: The penalty for applying any pretension to the graft at 0 degrees of flexion is abnormal kinematics with a reduction in the free-play of the knee and overlimitation of the normal anterior limits of motion. Higher pretension (i.e. 300N) required for a low stiffness GFC (i.e. 24 N/mm) may exceed the ability of the fixation method to resist slippage under cyclic load and failure. In contrast, GFC with the stiffness of the normal ACL (i.e. 211 N/mm) required lower pretension (20 N) which current fixation methods are capable of withstanding. Restoring normal free play and the normal limit of anterior translation at 225N (i.e. normal kinematics) may require an ACL GFC with stiffness similar to the normal ACL and insertion of the graft with some slackness at 0 degrees of flexion.

11. Tibial Tunnel Enlargement Following ACL Reconstruction With Patellar Tendon AutograftmA Prospective Study Using CT Scan.

Christian Fink, M.D. Karl Peter Benedetto, M.D. Michael Zapp, C.M. Christian Hoser, M.D.


Purpose: Radiographic expansion of bone tunnels following various ACL reconstruction techniques have been noted. It was the aim of this prospective study to get better understanding of the etiology and the clinical significance of this process. Therefore changes of the tibial tunnel in patients who underwent endoscopic ACL reconstruction with bone-patellar tendon-bone autograft (interference screw fixation) have been monitored over a period of two years using subsequent CT scans. Materials and Methods: 30 patients (20 male, 10 female; mean age 26.8 + 4.6) were included in the study and evaluated clinically (IKDC, Lysholm, Tegner Score, KT 1000) pre operative as well as 6 weeks(w), 3 months(m), 6, 12 and 24 m following surgery. At 1 and 6 w, as well as 3, 6, 12 and 24 m post-op a spiral CT scan of the knee using helical transversal acquisition in 5mm sections with secondary reformation and reconstructions was obtained. To characterize the shape of the tibial tunnel five diameters (DI: at the tibia plateau, D4: at the tip of the bone block/screw, D2: 33% of D1 to D4. D3: 66% of D1 to D4 and DS: -33% D1 to D4) have been measured in coronar and sagittal planes.

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Results: In all planes expansion of the tibial tunnel was found to be greatest in D2 and D3 (Tab. 1), resulting in a "pear-shaped" appearance of the tunnel.

A t al | dJamd.,v:r~ .~ub.~ql=¢a~ tam,e l {~l~a iisiel,~ is gre~te~: (:p<lk85) wRhir= the I ~ t 6 ~'eekt~ - - f i f l l ew iag surgery . (1 w post * O - f~ ~ : 17•9=+ 6•2 %, 6"4" - 3 m{~, lhs : 4 .8 +- 2.4 %, 3 m - (~: m : 4.7= + 0 . 5 ~ , 6 m * ~ pe~=': 4.3± 1.1%, t ~'ea~ • 2 y~ar~: J .4± &4%. Ne c~)rrdathm h~tweea tunnt~l expa nlsicm alll~ d inlcal pa rame te r s (t:.g. ]u~ily~ sytnpt(m~) ('o~lld l~e Ik'l ~'cl t'~,


Discussion: If tunnel expansion would simply be a mechanical effect one would expect its greatest diameter at the tibia plateau level (D1) ("cone shaped tunnel"). Since the tibial tunnel in our study appears "pear-shaped," fluid leakage might be the important cofactor. This is further supported by the finding, that the highest amount of tunnel enlargement takes place in the early (until 6 weeks) postoperative phase, there swelling is most frequently present. Although no negative effects of tunnel expansion on the early clinical results was found, it could become a problem in revision surgery. Therefore modifications of our current operative technique have to be considered.

12. The Effect of Graft Fixation Techniques on Tunnel Widening in Hamstring ACL Reconstruction.

Mark Clatworthy John Bartlett Stephen Howell J.L Insalata F. Fu C. Harner


Introduction: It has been proposed that tunnel widening in hamstring ACL reconstructions is related to the stiffness of the fixation method and how closely the graft is fixed to the joint line. Constructs which include tape and/or suture have been shown to have permanent elongation up to 5mm (the bungy cord effect). The resultant excessive graft motion has been suggested as an aetiology for tunnel widening. Purpose: The purpose of this study was to determine if the amount of tunnel widening is related to the stiffness of the fixation method and the distance between the point of fixation and the articular surface of the joint• Method: Four fixation methods were evaluated. Two groups had more elastic fixation. Thirty subjects were reconstructed using an endobutton and tape (femur) and sutures tied to a post (tibia) and thirty eight subjects were reconstructed with a mitek anchor and tape (femur) and two staples (tibia)• Two groups had more rigid fixation. Forty eight were subjects reconstructed with a bone mulch screw (femur) and staples (tibia) and thirty one subjects with two screws and soft tissue washers (femur) and a post (tibia). Tunnel widening was determined using standardized AP and lateral roentgenograms which were scanned, digitized, adjusted for magnification and measured with Scion Image software.

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Results: Tunnel widening occurred with all the fixation methods. The least tunnel widening occurred in the endobutton and sutures to a post construct where two bungy cords were present and a there was a greater distance between point of fixation and the articular surface of the joint (ANOVA p=<0.02). There was no difference between the other methods. Fixing the graft closer to the joint resulted in increased tunnel widening (t test p=<0.002). Conclusion: Tunnel widening occurs with both elastic and rigid fixation methods. Tunnel widening can not be avoided by fixing the graft closer to the joint or eliminating the suture bridge. Significance: Graft tunnel motion does not appear to be the sole cause of tunnel widening in hamstring ACL reconstruction.

13. The Effect of Graft-Tunnel Diameter Disparity on Intraosseous Graft Healing in Anterior Cruciate Ligament Reconstruction Using Doubled Flexor Tendon or Bone- Patellar Tendon-Bone Graft.

Shuji Yamazaki, M.D. Kazunori Yasuda, M.D., Ph.D. Fumihisa Tom#a, M.D. Harukazu Tohyama, M.D.


Purpose: To biomechanically and histologically clarify the effect of graft-tunnel diameter disparity on intraosseous graft healing in ACL reconstruction using the doubled flexor tendon (FT) graft or the bone- patellar tendon-bone (BTB) graft. Methods: Twenty-eight adult beagle dogs were divided into two groups, Groups T and L, of 14 animals each. In each animal, anatomical ACL reconstruction was performed using the doubled FT graft having a diameter of 4 mm in the right knee, and using the BTB graft having a width of 4 mm in the left knee. In Group T, a bone tunnel having a diameter of 4 mm was drilled in the tibia. In Group L, a bone tunnel having a diameter of 6 mm was drilled in the tibia. In each group, 7 animals were sacrificed at 3 and 6 weeks. Pull-out tests of the graft-tibia complex and histological examinations were performed at each period. Results: Regarding the FT graft, histologically, the collagen fibers connecting the tendon to the bone further increased in the graft-bone gap, and became more dense in Group L than in Group T at each period. Mechanically, there were no significant differences in the maximum load between Groups T and L at each period (Fig. 1). Concerning the BTB graft, although new bone formation appeared at the posterior aspect of the bone plug in each group, the plug remained necrotic at 6 weeks. The maximum load of Group L was significantly lower than that of Group T at 6 weeks (Fig. 2). Conclusion: The graft-tunnel diameter disparity of 2 mm (67%) did not significantly affect the pull-out strength of the FT graft. This result is explained by the histological findings. This study implied that, for the FT graft, the graft-tunnel diameter disparity can be compensated by activities of fibroblasts and osteoblasts. Significance: Graft-tunnel diameter disparity within 2 mm is acceptable in ACL reconstruction using the FT graft.

http://www2.us.elsevierhealth.com/inst/serve?a...rt&group Knee +Cruciate +Substitute +Tendon +Graft (13 of 14) [12/13/2007 12:00:28 PM]


Fig. 1: The maximum load (N) of the FT graft-tibia complex.

Fig. 2: The maximum load (N) of the BTB graft- tibia complex.

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http://www2~us~e~sevierhea~th~c~m/inst/serve?a.~rt&gr~u~=Knee+~ru~iate+Substitute+Tend~n+Graft (14 of 14) [12/1 3/2007 12: 00:28 PM]

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Knee cruciate substitute tendon graft

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