AUTHOR AND EDITOR INFORMATION

Section 1 of 11  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Outcome And Prognosis
• Future And Controversies
• References

INTRODUCTION

Section 2 of 11  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Outcome And Prognosis
• Future And Controversies
• References

Multiple techniques are available for reconstruction of the anterior cruciate ligament (ACL). Controversy certainly exists as to which autograft is best and which methods of placement and fixation should be used.

Instances exist in which autograft is not available because of multiple reconstructions or combined ligament injuries. In addition, after discussing the advantages and drawbacks of the various graft materials available, patients may choose not to use autograft material. In these situations, other graft sources must be considered. This article deals with the grafts available and is aimed at providing the reader with an increased confidence in choosing from various materials. This article does not cover surgical indications or techniques, as other articles in this publication address these issues.

For excellent patient education resources, visit eMedicine's Foot, Ankle, Knee, and Hip Center. Also, see eMedicine's patient education articles Knee Injury and Knee Pain.

Related e-Medicine topics:
Bone Graft Substitute Materials

Related Medscape topics:
Resource Center  Joint Disorders
Allograft vs. Autograft in ACL Reconstruction
Role of Allografts in Primary ACL Reconstruction
Utility of Routine Cultures of ACL Allograft Tissue Questioned

History of the Procedure

The supremacy of free bone-patellar tendon-bone autograft was briefly challenged in the 1970s and 1980 by proponents of artificial ligaments in the form of Gore-Tex and Proplast. Poor experiences with these nontissue substitutes led surgeons to choose other graft materials, including allografts. This trend was accelerated after Jackson and others developed the technique of arthroscopically assisted ACL reconstructions during the mid 1980s.¹

Problem

The obvious issue is, What is the better choice when both autografts and allografts are available to the surgeon and patient?² See Indications for a discussion of the advantages and disadvantages of autografts and allografts.

INDICATIONS

Section 3 of 11  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Outcome And Prognosis
• Future And Controversies
• References

Certainly, the use of autografts presents some disadvantages. One is the need to add an incision to sacrifice important tissue. The other is the imposition of iatrogenic hardships, including patellofemoral symptoms, especially with bone-patella tendon-bone grafts that can hinder rehabilitation and can contribute to range-of-motion loss, arthrofibrosis, and patella baja. Reported cases of patellar tendon rupture and patellar fracture also cause concern. For hamstring constructs, 2 strand grafts are neither as strong nor as stiff as desired, and 4-strand grafts can affect knee-flexion torque when both semitendinosus and gracilis are harvested.³

Overall, concern with soft-tissue fixation continues to be a challenge, although advances are being made in this regard. Allografts would appear to be a rational choice. Their benefits include the sparing of autogenous tissue and the morbidity associated with their harvest, small incisions, shorter surgical times, and a larger choice of tissue types and sizes. This is especially important in revision cases in which bone may be deficient.

Shino⁴ and Noyes independently reported good results using allografts in the 1980s, as have Yoldas⁵ and Lawhorn in 2003.⁶ So, why is the allograft not the universal choice? Offsetting the list of allograft benefits is a litany of potential disadvantages, which include a potential for disease transmission, delayed incorporation, and decreased ultimate strength relative to autograft counterparts . Allografts also add another thousand dollars or so to the cost of a reconstruction. The actual surgical technique, including tunnel placement, tensioning, and fixation methods, should be similar for autografts and allografts. Therefore, the 3 major clinical factors to consider in assessing allograft use are potential disease transmission (see Workup), ultimate graft strength (see Treatment), and additional cost of the  allografts.^{7, 8, 9}

RELEVANT ANATOMY

Section 4 of 11  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Outcome And Prognosis
• Future And Controversies
• References

See Surgical therapy.

CONTRAINDICATIONS

Section 5 of 11  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Outcome And Prognosis
• Future And Controversies
• References

While no true contraindications seem to apply to the use of allografts, some reports indicate that chronic instabilities tend to do better with autografts.

WORKUP

Section 6 of 11  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Outcome And Prognosis
• Future And Controversies
• References

Lab Studies

• The American Association of Tissue Banks has set standards since 1984 for allograft use. Its publication has been revised and updated 6 times, most recently in 1996. It sets the minimum standards for procurement and processing of allogenic tissue. Potential donors undergo a series of examinations in addition to the physical examination, which include medical, social, and sexual histories. Any history of unprotected sex or exposure to a communicable disease results in an automatic rejection, as does other diseases.
• • On physical examination, abnormalities are sought, including signs of infectious disease. Routine blood and tissue cultures are obtained and examined for antibodies associated with HIV 1 and HIV 2, hepatitis, syphilis, and lymphoma. A major concern is the timing of HIV antibody production in an infected individual. This window averages 25 days but can be as long as 6 months. To decrease the risk of missing unconverted donors, many tissue banks do a polymerized chain reaction (PCR) to detect viral antigens. This decreases the window to about 19 days with a confidence level of 95%. It adds approximately $120 to the overall cost of the graft. This decreases the risk of viral transmission.^{10, 11}
  • Grafts can be harvested using aseptic or clean techniques. If a clean technique is used, a secondary sterilization process is needed. Heat or high-dose radiation can be used to kill virus particles, but this alters and weakens the collagen structure. Ethylene oxide, although excellent in removing microorganisms, was the culprit in earlier reports of poor allograft outcomes due to chemical residue resulting in synovitis and graft failures. The most common technique is that of sterile harvest, antibiotic soaks, low-dose radiation, and storage by either freeze drying, freezing, or the newest technique, cryopreservation, which may cause less damage to the tissue during processing.^{12, 13, 14}
  • What is the risk of viral transmission, and should it cause concern? In 1989, Buck et al calculated a 1 in 1.5 million chance of HIV transmission in screened donors.¹⁵ Later, this was lowered to approximately 1 in 10-20 million based on unpublished calculations by tissue bank workers. Moreover, no cases of transmitted viral disorders have been documented since the advent of the laboratory standards established more than a decade ago.

TREATMENT

Section 7 of 11  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Outcome And Prognosis
• Future And Controversies
• References

Surgical therapy

A major advantage of allografts is that there are a greater variety of tissues available for reconstruction. Bone-patellar tendon-bone has been used most commonly, and although some advocate its use in primary cases, most are used in revisions. Its popularity stems from its 2 bony attachment sites, which ease fixation. Achilles tendon is also available, but it is used more commonly in posterior cruciate ligament (PCL) reconstruction due to its size, length, relative ease of insertion, and accommodation to being split into 2 bundles as part of an increasing trend for PCL reconstruction. Hamstring, tensor fascia lata, and other tissues, such as anterior and posterior tibial tendons, have also been used with varying success.¹⁶ Rene Verdonk of Belgium has reported good success in revisions with these tibial tendons with up to an 8-year follow-up.

Following proper thawing or rehydration and implantation, the incorporation of both autograft and allograft follows a similar sequence. The original structure acts as a scaffold for revascularization, cell repopulation, and remodeling. However, the timing of events varies, as the remodeling and maturation process is prolonged by as much as 50% for allografts. Grafts are weakest during this vascularization and maturation period. This has implications for the stresses that these tissues can withstand in the postoperative period.

Once remodeling is complete, implanted allografts appear histologically similar to native ACL. However, this does not necessarily translate into strength or stability. Shino⁴ showed histologic maturity at 18 months, while Arnozky¹⁷ showed dog allograft histologically resembling normal ACLs at 1 year. Using a goat model, Drez¹⁸ and Jackson^{9, 12} independently showed similarities with native ACL at 26 weeks. Although it is now understood that the goat model is not applicable to humans regarding time of incorporation, Drez showed the maximum load-to-failure of allografts to be 43% of the native ACL, and Jackson showed this failure to be 27% of native ACL versus 62% for autografts.

COMPLICATIONS

Section 8 of 11  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Outcome And Prognosis
• Future And Controversies
• References

Infection following any surgical procedure is certainly one of the accepted, yet feared, complications. Recently, however, significant publicity has surrounded 3 infections and subsequent deaths following orthopedic allograft transplants.¹⁹

The strain level that damages grafts and the strain level necessary for graft development are not presently known. Proper graft placement certainly plays a critical role. Specifically for allograft, the hydration status or how well thawed a graft is must be considered. If the graft is not allowed to fully recover from its frozen or freeze-dried state, postoperative tensioning and strain characteristics may drastically change soon after surgery.

OUTCOME AND PROGNOSIS

Section 9 of 11  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Outcome And Prognosis
• Future And Controversies
• References

Long-term published clinical studies comparing allografts to autografts are few. Indelicato²⁰ and Shelton²¹ all showed generally good results in comparison of the tissues. In another study, an overall trend of fewer patellofemoral symptoms and better range of motion with allografts was noted. Shelton described a trend of increased pivot glide with allograft, which was not statistically significant. Although happy with their allograft results, they all remained cautious with their outlook, echoing the sentiments of Beynnon that it may take years to see a pattern for overall failure for any graft type. ²²

Beynnon theorizes that the initial and 2- to 3-year outcome studies may not accurately assess longer-term results.²³ He showed that reestablishing AP stability is not a predictor of future graft behavior. Using strain gauges in autograft reconstructions, he showed that strain characteristics established at the time of surgery was a more powerful predictor of long-term results. Grafts that varied most from normal strain patterns in the early postoperative period showed long-term failure. This is disturbing when recent bench studies have shown that tensioning allografts in the human cadaver knee to fully achieve AP joint stability increased forces in the graft at all angles of flexion.

Authors have long proclaimed dangerous strain and shearing in terminal extension. Of particular note, the good results that  Indelicato²⁰ and Shelton²¹ achieved all predated the era of accelerated rehabilitation protocols popularized by Shelbourne.²⁴ In fact, the allograft protocols included limited arcs and crutch weightbearing for up to 12 weeks.

With all of this in mind and knowing that allografts take longer to remodel and mature, the following question remains: Should there be concern with allografts in general and specifically in relation to recent trends in accelerated rehabilitation? Although Shelbourne has not suggested this, should his autograft axiom be applied? It allows activity based on the status of rehabilitation and not on graft biology. Alternatively, should these patients be restricted as is commonly done in grafts without bone plugs due to fixation concern? This question is especially important with the potential earlier aggressive rehabilitation and return to activity that allografts allow due to the decreased morbidity compared with autografts.

FUTURE AND CONTROVERSIES

Section 10 of 11  

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Outcome And Prognosis
• Future And Controversies
• References

The risks of disease transmission would seem to have become infinitely small, but, as evidenced by fatal infections noted already, this risk has not been reduced to zero. It is imperative that the surgeon constantly monitors the source of his or her grafts and has a very specific protocol of response in the face of an adverse surgical outcome when infection is a possible diagnosis.

With a supply of safe graft materials, other than a national graft shortage or insurers or the hospital denying coverage for the additional costs, strength and long-term results become the main concern.

The information above indicates the need to protect these grafts from aggressive early rehabilitation. Protection may include limited weightbearing and stresses placed across the joint. However, no data are available to support this protocol, and prospective comparative studies are needed. For primary cases, weighing the risk of outright allograft failure due to tissue weakness against the morbidities of autograft harvest still leaves the surgeon with a difficult decision. No clear answer exists.

Far from ideal, allografts offer a material off the shelf with a relatively good record. Although prospective long-term results are unknown, many patients have done well clinically with this procedure as a primary reconstruction. However, with improved soft-tissue fixation, tripled semitendinosus without gracilis and Quad tendon grafts are becoming more appealing, as they offer strong autograft materials without the problems associated with patella tendon. For revisions and situations in which no autograft material is available, it offers hope where none might otherwise exist.

REFERENCES

Section 11 of 11

• Authors and Editors
• Introduction
• Indications
• RELEVANT ANATOMY
• Contraindications
• Workup
• Treatment
• Complications
• Outcome And Prognosis
• Future And Controversies
• References

1. Jackson DW, Grood ES, Arnoczky SP, et al. Freeze dried anterior cruciate ligament allografts. Preliminary studies in a goat model. Am J Sports Med. Jul-Aug 1987;15(4):295-303. [Medline].
2. Eriksson E. Auto- or allograft for ACL-reconstruction?. Knee Surg Sports Traumatol Arthrosc. Jun 2007;15(6):689. [Medline].
3. Edgar CM, Zimmer S, Kakar S, Jones H, Schepsis AA. Prospective Comparison of Auto and Allograft Hamstring Tendon Constructs for ACL Reconstruction. Clin Orthop Relat Res. Jun 25 2008;[Epub ahead of print]. [Medline].
4. Shino K, Inoue M, Horibe S, et al. Maturation of allograft tendons transplanted into the knee. An arthroscopic and histological study. J Bone Joint Surg Br. Aug 1988;70(4):556-60. [Medline].
5. Yoldas EA, Sekiya JK, Irrgang JJ, Fu FH, Harner CD. Arthroscopically assisted meniscal allograft transplantation with and without combined anterior cruciate ligament reconstruction. Knee Surg Sports Traumatol Arthrosc. May 2003;11(3):173-82. [Medline].
6. Lawhorn KW, Howell SM. Scientific justification and technique for anterior cruciate ligament reconstruction using autogenous and allogeneic soft-tissue grafts. Orthop Clin North Am. Jan 2003;34(1):19-30. [Medline].
7. Bolano L, Kopta JA. The immunology of bone and cartilage transplantation. Orthopedics. Sep 1991;14(9):987-96. [Medline].
8. Bullis DW, Paulos LE. Reconstruction of the posterior cruciate ligament with allograft. Clin Sports Med. Jul 1994;13(3):581-97. [Medline].
9. Jackson DW, Simon TM, Kurzweil PR, Rosen MA. Survival of cells after intra-articular transplantation of fresh allografts of the patellar and anterior cruciate ligaments. DNA-probe analysis in a goat model. J Bone Joint Surg Am. Jan 1992;74(1):112-8. [Medline].
10. Bottenfield S, Caspari RB, Hurwitz RL, Asselmeier MA. HIV transmission via allograft organs and tissues. Sports Med Arthroscopy Rev. 1993;1:42-46.
11. Simonds RJ, Holmberg SD, Hurwitz RL, et al. Transmission of human immunodeficiency virus type 1 from a seronegative organ and tissue donor. N Engl J Med. Mar 12 1992;326(11):726-32. [Medline].
12. Jackson DW, Windler GE, Simon TM, et al. Intraarticular reaction associated with the use of freeze-dried, ethylene oxide-sterilized bone-patella tendon-bone allografts in the reconstruction of the anterior cruciate ligament. Am J Sports Med. Jan-Feb 1990;18(1):1-10; discussion 10-1. [Medline].
13. Langer F, Czitrom A, Pritzker KP, Gross AE. The immunogenicity of fresh and frozen allogeneic bone. J Bone Joint Surg Am. Mar 1975;57(2):216-20. [Medline].
14. Rihn JA, Irrgang JJ, Chhabra A, Fu FH, Harner CD. Does irradiation affect the clinical outcome of patellar tendon allograft ACL reconstruction?. Knee Surg Sports Traumatol Arthrosc. Sep 2006;14(9):885-96. [Medline].
15. Buck BE, Malinin TI, Brown MD. Bone transplantation and human immunodeficiency virus. An estimate of risk of acquired immunodeficiency syndrome (AIDS). Clin Orthop. Mar 1989;(240):129-36. [Medline].
16. Ozer H, Selek HY, Turanli S, Atik SO. Failure of primary ACL surgery using anterior tibialis allograft via transtibial technique. Arthroscopy. Sep 2007;23(9):1026. [Medline].
17. Arnoczky SP, Warren RF, Ashlock MA. Replacement of the anterior cruciate ligament using a patellar tendon allograft. An experimental study. J Bone Joint Surg Am. Mar 1986;68(3):376-85. [Medline].
18. Drez DJ Jr, DeLee J, Holden JP, et al. Anterior cruciate ligament reconstruction using bone-patellar tendon- bone allografts. A biological and biomechanical evaluation in goats. Am J Sports Med. May-Jun 1991;19(3):256-63. [Medline].
19. Centers for Disease Control and Prevention (CDC). Update: allograft-associated bacterial infections--United States, 2002. MMWR Morb Mortal Wkly Rep. Mar 15 2002;51(10):207-10. [Medline].
20. Indelicato PA, Bittar ES, Prevot TJ, Woods GA, Branch TP, Huegel M. Clinical comparison of freeze-dried and fresh frozen patellar tendon allografts for anterior cruciate ligament reconstruction of the knee. Am J Sports Med. Jul-Aug 1990;18(4):335-42. [Medline].
21. Shelton WR, Papendick L, Dukes AD. Autograft versus allograft anterior cruciate ligament reconstruction. Arthroscopy. Aug 1997;13(4):446-9. [Medline].
22. van Arkel ER, de Boer HH. Survival analysis of human meniscal transplantations. J Bone Joint Surg Br. Mar 2002;84(2):227-31. [Medline].
23. Beynnon BD, Johnson RJ, Fleming BC, Stankewich CJ, Renström PA, Nichols CE. The strain behavior of the anterior cruciate ligament during squatting and active flexion-extension. A comparison of an open and a closed kinetic chain exercise. Am J Sports Med. Nov-Dec 1997;25(6):823-9. [Medline].
24. Shelbourne KD, Nitz P. Accelerated rehabilitation after anterior cruciate ligament reconstruction. Am J Sports Med. May-Jun 1990;18(3):292-9. [Medline].

Article Last Updated: Jul 8, 2008