ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION WITH A COMPOSITE GRAFT BONE-PATELLAR TENDON-BONE/LIGAMENT AUGMENTATION DEVICE

ROBERT E. HUNTER, MD

The ligament augmentation device (LAD) (3M, St Paul, MN) was developed in the late 1970s by John Kennedy of Canada for augmentation of the Marshall/Macintosh reconstruction. The Canadian experience with polypropylene in that setting showed statistical improvement over the nonaugmented reconstruction. This study was repeated in a United States trial and confirmed the findings of Kennedy and Roth. Since then, LAD has been used in a variety of clinical settings with both autogenous and allograft tissue. Through the early 1990s over 14,000 devices have been implanted in the United States and 60,000 have been implanted worldwide. The purpose of this paper is to review the basic science data associated with the LAD, the clinical experience with its use, and the investigator's preferred surgical technique for implantation with a bone-patellar tendon-bone autograft. KEY WORDS: anterior cruciate ligament, synthesis, knee, graft

The use of synthetics for anterior cruciate ligament (ACL) reconstruction is not a particularly new concept. The first synthetic ACL reconstruction was described by Corner 1 in 1914 when he used silver wire to reconstruct an ACL deficient knee. The patient, described in a case report, was hospitalized for 3 weeks, and at discharge from the hospital had regained 90 ° of flexion and was "much pleased." After that early interest in synthetic reconstruction there was a period of relative quiet, other than experimental animal work.

Interest was rekindled in synthetic devices in the late 1970s, including Kennedy's 2 early work with the ligament augmentation device (LAD). Research that extended through the 1980s was focused in three distinct areas of synthetic use: (1) Prosthetics, defined as products that when implanted served to provide an immediate and per- manent substitution for the ligament replaced (eg, Gore- Tex graft). (2) Scaffolds, defined as a product that pro- vided immediate and complete stability, but whose long- term success demanded creeping substitution via mature collagen (eg, Leeds-Keio scaffold). (3) Stints, a product used to augment the strength or fixation of autogenous tissue until healing allowed independent tissue function (eg, LAD).

From the Department of Orthopaedics, University of Colorado, Health Sciences Center, Denver; and Orthopaedic Associates of As- pen and Glenwood, Aspen, CO.

Address reprint requests to Robert E. Hunter, MD, Orthopaedic Associates of Aspen and Glenwood, 100 E Main St, Suite 101, Aspen, CO 81611.

Copyright © 1995 by W. B. Saunders Company 1060-1872/95/0303-0008505.00/0

LAD is braided polypropylene manufactured as a con- tinuous fiber and heat sealed at both ends to avoid un- raveling. It exists in either a 6- or 8-mm width and var- ies in length from 8 to 21 cm. It has a strength to failure of 1,530 to 2,000 N (6- v 8-ram width), and a stiffness that is slightly more than a normal ACL. Strain to failure is 22%. Under cyclic loads ranging from 50 to 500 N, the augmentation device shows a 3% creep after 1,000,000 cycles. Fatigue under the same testing situation is 9%. When subjected to bending loads, the fatigue is increased to 23% after 10,000,000 cycles. 3"4

When Kennedy 2 first began experimenting with the LAD in the late 1970s, he used the material to augment the Marshall/Macintosh reconstruction technique and felt his early results were promising. In 1985, Roth s re- viewed Kennedy's clinical experience and found that there was a statistical improvement in stability over nonaugmented reconstruction with minimal complica- tions and concluded that LAD enhanced the results of this technique.

From the strength of that experience, a United States clinical trial was begun in 1983 comparing a nonaug- mented with an augmented Marshall/Macintosh recon- struction. The study was a multicenter, prospective, nonrandomized project and showed the same clinical re- sult. There was a statistical improvement in stability and complications continued to be minimal. 6 Based on the United States clinical trial, the Food and Drug Ad- ministration approved the augmentation device for use as an augmentation to the Marshall/Macintosh procedure in 1987. In 1985, a second United States clinical trial was begun in 20 centers using autogenous tissues in the form of iliotibial band, semitendinosis, or bone-patellar ten-

182 Operative Techniques in Sports Medicine, Vol 3, No 3 (July), 1995:pp182-186

don-bone (BPTB). This was a prospective, nonrandom- ized study. Inclusion criteria included a positive pivot shift phenomenon, a KT-1000 arthrometer (MedMetric, San Diego, CA) showing an involved minus normal side difference of greater than or equal to 5 mm, no evidence of contralateral knee pathology, and no surgical interven- tion for either the collateral ligaments or the posterior cruciate ligament. Criteria for success were developed combining both motion and stability. 7

The results showed that the augmentation group was statistically superior to the nonaugmented group at 3, 6, and 12 months after surgery with no statistical difference in the two groups thereafter. However, there continued to be a trend toward higher success in the augmented population. This statistical improvement applied to all three autogenous tissues. Analysis of the data showed that the improved success was based on enhanced post- operative motion associated with LAD augmentation in both the acute and chronic setting. In no circumstance was there a shown enhancement in stability between augmented and nonaugmented knees.

The complication rate in this population of 721 knees was small, with an overall infection rate of 1.4%, an as- piration rate of 3.7%, and a need to retention the graft in 0.5%. Explant of the LAD for any reason occurred in 3.1%, with 1.2% caused by rupture and an additional 1% caused by recurrent laxity.

In 1991, Hunter et al 8 presented their clinical results with 75 patients who had undergone a BPTB/LAD com- posite graft ACL reconstruction. Follow up was a min- imum of 24 months. The pivot shift phenomenon was found to be normal in 92%, Lachman's was less than or equal to mild in 95%, and the KT-1000 arthrometer mea- surements showed less than or equal to 5-mm side-to- side difference in 90%, with less than 3-mm side-to-side difference in 82%. Extension loss was greater than 5 ° in 5%, and no patient experienced greater than 10 ° of loss. Effusion was found to be present in 4% with none re- ported greater than mild. Overall failure rate was 5% for recurrence of grade III laxity.

Bartlett repor ted his experience in 1991. He con- structed a s tudy consisting of three groups: group I, BPTB; group II, BPTB augmented with an extra-articular Ellison procedure; and group III, a BPTB augmented with the LAD. His results show group I to be better than group II, which in turn was superior to group III. His conclusion was that the LAD did not appear to enhance the postoperative result. 9

In 1992, Noyes et al 1° presented their experience with an allograft augmented with the LAD. Their overall fail- ure rate was 28% with or without augmentation. Only 70% of the LAD group was actually studied because of a study design that stipulated that only those patients who returned for release of the augmentation were included in the study. The KT-1000 arthrometer results showed the LAD group to be superior to the control group up to 6 months postoperatively with no difference in the two groups thereafter. Additional treatment for lost exten- sion was reported in 2% of the augmented group, and 8% in the control group.

In 1993, Barrett et al n presented their clinical experi-

ence with an autograft BPTB reconstruction augmented with the LAD. Seventy-five patients were available for review with an average follow up of 24 months. The study was a prospective nonrandomized assessment of 25 patients who had undergone LAD augmentation, compared with 50 patients who constituted the control g roup . A " h o t d o g " t e c h n i q u e p o p u l a r i z e d by Gaechter 12 was used for the reconstruction with interfer- ence fit screws for fixation. There was no statistical ad- vantage to the LAD in his study and the complication rate was significantly higher. He concluded that LAD did not appear to be of value in his clinical experience.

The investigator performs ACL reconstruction using 10 basic steps. These are as follows:

1. Diagnostic exam 2. Meniscus management 3. Notchplasty 4. Graft harvest S. Pin placement 6. Hole drilling 7. Chest tube test 8. Composite graft preparation 9. Graft passage 10. Graft fixation.

Other than steps 8 and 9, all aspects of the technique are identical to the nonaugmented reconstruction and, therefore, only the composite graft preparation and graft passage will be reviewed.

After the BPTB graft is harvested, the bone ends are trimmed to fit the appropriate spacer. It is important that the bone pass relatively freely through the spacer because additional space will be occupied by the LAD. The investigator uses a graft width of 8 to 9 mm and, in some smaller knees, 7 mm. Two 7/64-in holes are drilled in the patellar and tibial bone plugs. A LAD, matching the length of the bone-tendon-bone preparation, is se- lected. On the bone plug that is to be passed through the tibia and into the femur, LAD is placed on the ante- rior surface and aligned flush with end of the bone. A 0 Ethibond suture (Ethicon, Somerville, NJ) is used to fix LAD directly to the bone with the knot tied over LAD (Fig 1, top inset). Once fixed, a No. 5 Ethibond suture is passed through each bone hole and the overlying LAD (Fig 1, center). On the opposite end a No. 2 Ethibond suture is passed through the distal-most hole in the bone plug and the overlying LAD, creating a "figure eight" loop (Fig 2). The "figure eight" loop is fixed to one end of the tension board. The No. 5 Ethibond is knotted with a slip knot and attached to the other end of the tension board and a load of 15 pounds is applied to the composite graft. Equal tension to both the BPTB and the LAD components is created by virtue of the equilibrium allowed by the "figure eight" loop (Fig 3). With the pre- tension in place, a 2-0 vicryI suture is used to "tubularize" the LAD within the patellar tendon with the tubulariza- tion extending from one bone plug to the other. With each pass, the needle passes through both the LAD and the overlying tendon, thereby insuring that the LAD/ tendon relationship will be maintained once the preten- sion is released (Fig 3, inset). After tubularization, a No.

ACL RECONSTRUCTION 183

Fig 1. (top inset) On the bone plug that will ultimately be passed through the tibia and into the femur, the LAD is aligned flush with the end and fixed in place with a single nonabsorbable suture. (center) A #5 nonabsorbable suture is passed through each bone hole and the overlying LAD. A slip knot (bottom inset) can be placed in the suture to allow fixation to the tension board. Once the graft has been pre- pared the knot can be pulled out without damage to the su- ture material.

5 Ethibond suture is passed through each hole in the tibial bone plug and the overlying LAD. The tension is released, and the No. 2 Ethibond suture used for tension- ing is removed (Fig 4).

After holes have been drilled in the tibia and the femur and the edges carefully radiused, the graft is ready for passage. The composite graft is passed through the tib- ial hole and up into the femoral hole with a cancellous surface of the bone plug facing anterior and the LAD posterior. Thus, as the graft enters the femoral hole, the synthetic material is protected from the abrasive wear that could occur along the anterior border of the femoral hole. As the tibial bone plug is engaged into the tibia, the graft is rotated 180 ° such that the cancellous surface of the bone plug is posterior and LAD lies anterior. In this way, the LAD is protected from the abrasive posterior surface of the tibial hole. In a right knee the graft is

Fig 3. The graft is fixed to the tension board using sutures through the bone plugs and overlying LAD. A 15# load is applied. The "figure eight" loop (Fig 2) allows equilibrium between the synthetic and autogenous tissue. (inset) A 2-0 absorbable suture is used to "tubularize" the tendon around the LAD. The suture is passed through the tendon and LAD to ensure LAD/autogenous tissue orientation once the ten- sion is released. Tubularization extends from one bone plug to the other.

rotated counterclockwise, and in a left knee this rotation is clockwise (Fig 5). This creates a graft that has an ap- pearance very similar to a normal ACL with an antero- medial and posterolateral component. In addition, this creates a graft whose strength is approximately 30% stronger than a nonrotated graft.13

Although fixation can be performed in a variety of ways, the investigator prefers interference fit screws. The screws must be placed along the side wall of the cancellous bone plug thereby avoiding cutting of the syn- thetic material as the screw is implanted. This allows for compression of the synthetic material and the bone plug against the side wall of both the femoral and tibial holes (Fig 6).

At this point there is no compelling evidence to suggest that the LAD is necessary for use in every case. How- ever, there are selected situations where the investigator believes the LAD can be of value as a supplement to the normal reconstruction technique. When using a 7- to 8- mm bone-tendon-bone graft, tissue strength is a concern. Although initially stronger than a normal ACL, the an- ticipated weakening because of the normal resorption process could result in failure or elongation before final maturation. 13 Therefore, it is a recommendation that with grafts smaller than 9 mm, the LAD be used as pro- tection against plastic deformation during this vulnerable healing period.

In situations where the bone plug is inadvertently bro- ken at the time of harvest, the LAD serves as a method of bridging this weakened junction while the bone has a

Fig 2. A #2 nonabsorbable suture is passed through the dis- tal-most hole of the bone plug that will ultimately be fixed in the tibia and then through the overlying LAD.

Fig 4. #5 Nonabsorbable sutures are passed through each hole in the distal bone plug and overlying LAD. Once com- pleted, the tension is released and the #2 "figure eight" su- ture is removed.

184 ROBERT E. HUNTER

Fig 5. The graft is passed through the tibia into the femur. In the femur the cancellous surface of the bone is anterior and the LAD posterior. In the tibia, the bone plug is rotated 180 ° with the cancellous surface posterior and the LAD anterior.

chance to heal over the first 4 to 8 weeks . The hams t r ing graft , a l t h o u g h i nc r ea s ing in p o p u l a r i t y , has s h o w n mixed resul ts as a t issue source in chronic ACL deficient knees. 14 For that r eason the inves t igator r e c o m m e n d s augmen ta t i on wi th the LAD in an effort to suppo r t that t issue in the chronic setting. A subse t of pa t ients w h o presen t wi th hyper lax i ty is a relative indicat ion for addi- t ional a u g m e n t a t i o n in an effort to avoid the predictable s t retching of the recons t ruc t ion dur ing the heal ing phase .

Allograft ACL recons t ruc t ion cont inues to be an area of interest bu t the resul ts have b e e n s h o w n to be poorer than autograf t t issue. 15 This reflects the s lower heal ing and incorpora t ion rate, the lower recovery of ul t imate graft s t rength, and the possibil i ty of a low-level rejection p h e n o m e n o n . Because of this de lay in incorpora t ion and u l t imate s t r eng th reduc t ion , LAD a u g m e n t a t i o n , w h e n used appropr ia te ly , could be an advan tage .

The final area w h e r e the inves t iga tor has used the LAD augmen ta t i on f requent ly is in older knees (greater than 50 years old). As N o y e s 1° and others 164s have shown, age and disuse are i m p o r t a n t factors in predic t ing BPTB s t reng th wi th significant r educ t ion in s t r eng th in the older knee. A u g m e n t a t i o n has been of value in this sit- ua t ion to protec t this w e a k e r tissue.

The LAD has a large clinical t rack record hav ing been imp lan ted in grea ter t han 60,000 knees a r o u n d the wor ld , and in excess of 14,000 knees in the Uni ted States. This clinical exper ience has s h o w n conclusively that the LAD is safe. There has b e e n no series of repor t ing p rob lems wi th chronic synovit is , art icular cartilage damage , partic- ulate debris, or regional t ransfer of part iculate material . Infect ion rates have b e e n consis tent wi th n o n a u g m e n t e d popula t ions and compl ica t ions have been kep t to an ac- ceptable level. H o w e v e r , it r e m a i n s unc lear h o w to mos t effectively use the LAD f rom the s t andpo in t of sur- gical technique and clinical setting. In this era of cost con ta inment , the cost /benefi t ratio to any synthet ic device m u s t be carefully w e i g h e d and appl ied to each clinical -use.

f

* J

J/ t

. . . . . a~

Fig 6. The interference screw is placed along the sidewall of the bone plug thereby avoiding damage to the LAD or su- tures. Once the screws are in place and the knee has been tested for full range of motion and stability the #5 nonab- sorbable sutures can be removed.

REFERENCES

1. Corner EM: Notes of a case illustrative of an artificial anterior cru- ciate ligament demonstrating the action of that ligament. Proc R Soc Med 7:120-121, 1914

2. Kennedy JC: Application of prosthetics to anterior cruciate ligament reconstruction and repair. Clin Orthop 172:125-128, 1983

3. McPherson GK, Mendenhall HV, Gibbons DF, et al: Experimental mechanical and histologic evaluation of the Kennedy Ligament Augmentation Device. Clin Orthop 196:168-195, 1985

4. Mendenhall HV, McPherson GK, Gibbons DF, et al: Histological and mechanical evaluation of the ligament augmentation device. Trans Am Soc Artif Intern Organs 29:314-317, 1983

5. Roth JH, Kennedy JC, Lockstadt H, et al: Polypropylene braid aug- mented and nonaugmented intraarticular anterior cruciate ligament reconstruction. Am J Sports Med 13:321-336, 1985

6. Daniel DM, Woodward EP, Losse GM, et al: The Marshall/ Macintosh anterior cruciate ligament reconstruction with the Kennedy Ligament Augmentation Device: Report of the United States clinical trials, in Freidman MJ, Ferkel RD (eds): Prosthetic Ligament Reconstruction of the Knee. Philadelphia, PA, Saunders, 1988, pp 71-78

7. Hunter RE, Van Kampen C: A Composite Graft ACL Reconstruc- tion: A Prospective Multi~Center Study. Presented at the Second AOSSM/JOSSM Trans-Pacific Meeting. Maui, HI, March 20-25, 1993

8. Hunter R, Mittun P: ACL reconstruction with patellar-tendon LAD composite graft. Presented at the Annul Meeting of the Arthroscopy Association of North America. San Diego, CA, April, 1991

9. Bartlett J: Anterior cruciate ligament autografts and augmentation. Presented at the Combined Annual Meeting of the Australian and New Zealand Orthopaedic Associations. Christchurch, New Zealand, September 1991

10. Noyes FR, Barber SD: The effect of a ligament-augmentation device on allograft reconstructions for chronic ruptures of the anterior cru- ciate ligament. J Bone Joint Surg [Am] 74:960-973, 1992

11. Barrett GR, Field LD: Comparison of patella tendon versus patella tendon/Kennedy ligament augmentation device for anterior crudate ligament reconstruction: Study of results, morbidity, and complica- tions. Arthroscopy 9:624-632, 1993

12. Gaechter A: Anterior cruciate reconstruction through a transliga-

ACL RECONSTRUCTION 185

mentous approach, in Jakob RP, Staubli H-U (eds): The Knee and The Cruciate Ligaments, Springer-Verlag, Germany, 1992, pp 384- 388

13. Cooper DE, Deng XH, Burstein AL, et al: The strength of the central third patellar tendon graft. A biomechanical study. Am J Sports Med 21:818-823, 1993

14. Sgaglione NA, Del Pizzo W, Fox JM, et al: Arthroscopically assisted anterior cruciate ligament reconstruction with the pes anserine ten- dons. Comparison of results in acute and chronic ligament defi- ciency. Am J Sports Med 21:249-256, 1993

15. Paulos L: ACL surgery using allograft tissues. Presented at the 9th

International SCOI Symposium, Update 1994, New Perspectives in Arthroscopy and Sports Medicine. Palm Springs, CA, March 16-19, 1994

16. Noyes FR, Grood ES: The strength of the anterior cruciate ligament. Age and species-related changes. J Bone Joint Surg [Am] 58:1074- 1082, 1976

17. Noyes FR, Torvik PJ, Hyde WB, et al: Biomechanics of ligament failure II. An analysis of immobilization, exercise and recondition- ing effects in primates. J Bone Joint Surg [Am] 58:1406-1418, 1974

18. Butler DL, Grood ES, Noyes FR, et al: On the interpretation of our anterior cruciate ligament data. Clin Orthop 196:26-34, 1985

186 ROBERT E. HUNTER