anterior cruciate ligament reconstruction surgery, graft choice, intraarticular xenografts, biological synthetic collagen grafts
Anterior cruciate ligament (ACL) reconstruction surgery
Ask a sports injury question now! We've just launched a new feature called "Questions".
Which type of graft is appropriate for each individual patient?
Reconstruction of the anterior cruciate ligament (ACL) is the surgical treatment of choice as direct primary repair of the ligament has been shown to result in persistent laxity and instability of the knee(1). The aim of reconstruction (described in the last issue of SIB) is to restore stability of the knee without restricting its other functions, especially motion.
Intraarticular anterior cruciate ligament reconstruction requires a graft. These grafts may be autograft (the patient's own tissue), allograft (tissue taken from another person - usually a deceased donor) or synthetic. In addition, experimental work is being undertaken on xenografts and biological synthetic collagen grafts.
The choice of graft
The choice appears vast (table 1) but in practice only autografts using hamstring tendons and central third bone patella tendon bone (BPTB) are routinely used with good outcomes(2). These are generally harvested from the injured knee but have also been taken from the uninjured knee with very good results(3). There is little to choose between patellar tendon and hamstring grafts in the long term(4). The surgeon who undertakes anterior cruciate ligament reconstruction regularly (and there is an argument that this operation is all too frequently performed by people who don't do it regularly enough) should be familiar with both techniques and select the graft to suit the patient.
BPTB or hamstring graft - the rationale for graft selection
No one graft is applicable for every patient. There are strong advocates for each type. The choice should be made according to the individual patient since the use of either graft has specific advantages and disadvantages (see tables 2 and 3).
BPTB grafts should be avoided in patients who have kneeling professions or who participate in jumping sports such as netball with much eccentric loading. In addition, those patients with pre-existing anterior knee pain or patellofemoral problems should not receive BPTB grafts.
We tend to avoid hamstring grafts in patients with recent medial side injuries or with chronic medial instability. Also, hamstring grafts should be avoided in very heavy patients who need accelerated rehabilitation, or in athletes who require hamstring dominance (running backwards a great deal).
It may be necessary to tailor the choice of graft depending on associated reconstruction; for example, if combining the anterior cruciate ligament reconstruction with a posterior cruciate ligament (PCL) or posterolateral corner reconstruction.
Iliotibial tract graft
A graft from the iliotibial tract has satisfactory mechanical properties and results in less anterior knee pain. However, there is a long lateral operative scar, a risk of herniation of the quadriceps muscle and interference with an important lateral stabiliser of the knee(22).
Quadriceps tendon graft
The quadriceps tendon graft is thick with good biomechanical properties(7,8). Although it may be associated with less anterior knee pain, graft harvesting is technically difficult and results in an unsightly scar. Postoperatively, the donor quadriceps strength is significantly decreased even after one year(9).
Allografts
Allografts provide the graft material in a freeze-dried, fresh-frozen, irradiated or preserved state. There is a great deal of debate over whether these processes affect the mechanical properties of the graft(23,24,25,26). Other issues such as disease transmission, processing to decrease antigenicity and storage should also be considered before using 'off the shelf' allografts, which may be abnormally long or bulky(27). Nevertheless, in the complex revision scenario, allograft availability may be invaluable. We tend to favour fresh frozen non irradiated BPTB or Achilles allograft for revision cases and for specific cases where standard grafts are indicated.
Synthetic grafts
Once in vogue in the 1970s, synthetic ligaments (carbon fibre, polyester, Dacron) are not currently recommended for routine primary intraarticular knee reconstruction(11,12,13,14,15,28) as their long-term follow-up results are unacceptable. Synthetic grafts have been shown to be stiff with poor elastic properties and induce foreign body reactions, resulting in increased infection rates. They are expensive and should be avoided.
Xenografts
Early results using xenografts (tissues from other species) in animal and human studies have been disappointing. The xenograft does not integrate well with the host tissue and appears to be associated with extreme intraarticular wear and synovitis(29,30). Xenograft rejection is also a problem. Recent animal studies have concentrated on immunologically modifying the xenograft in an attempt to decrease the immune rejection problem(31).
The future - 'biological' grafts
Tissue engineering offers the possibility of replacing damaged human ligaments with engineered ligament tissues(32). Attempts are being made to culture in vitro ligament tissues by seeding human anterior cruciate ligament and medial collateral ligament (MCL) cells onto synthetic biodegradable polymer fibre scaffolds. Research is also active on anterior cruciate ligament fibroblast-seeded collagen scaffolds for anterior cruciate ligament reconstruction(33,34,35).
It is likely that in the future, tissue-engineered ligaments will include growth factors to accelerate and promote revascularisation of the graft and healing of the bone blocks or tendinous tissue to the bone tunnels. This hopefully should enable patients to return to work and sport more quickly(22).
Complications of anterior cruciate ligament reconstruction
The most common complications include failure to regain full extension or flexion (due to malpositioning of the tunnels used to pass the graft), anterior knee pain (whichever graft type is used), graft impingement (again due to poor tunnel positions) and graft failure (either traumatic as a result of a new injury or due to inappropriate rehabilitation).
Other complications include infection, thrombophlebitis, skin necrosis, haemarthrosis, sensory nerve damage, reflex sympathetic dystrophy and arthrofibrosis.
Finally, it must be appreciated that the anterior cruciate ligament is a living anatomical structure with its own blood supply and innervation, including proprioception. No substitute graft can fulfil these functions(36); but with appropriate rehabilitation athletes regularly return to their previous level of function.
Alex Watson and Fares Haddad
References
1. Orthopaedic Review, 22 (11), pp1213-1223, 1993
2. American Journal of Sports Medicine, 28 (1), pp124-130, 2000
3. American Journal of Sports Medicine, 28 (5), pp651-658, 2000
4. American Journal of Sports Medicine, 27 (4), pp444-454, 1999
5. American Journal of Sports Medicine, 23 (5), pp593-596, 1995
6. Scand J Med Sci Sports, 11 (1), pp16-22, 2001
7. American Journal of Sports Medicine, 27 (1), pp27-34, 1999
8. Arthroscopy, 11 (2), pp252-254, 1995
9. J Trauma, 46 (4), pp678-682, 1999
10. Biomaterials, 21 (23), pp2461-2474, 2000
11. American Journal of Sports Medicine, 21 (3), pp367-373, 1993
12. Injury, 25 (7), 443-445, 1994
13. Knee Surgery, Sports Trauma, Arthroscopy, 1 (2), pp71-75, 1993
14. Journal of Biomedical Materials Research, 48 (4), pp534-549, 1999
15. Knee Surgery, Sports Trauma, Arthroscopy, 4 (3), pp132-136, 1996
16. American Journal of Sports Medicine, 16 (4), pp321-326, 1988
17. J Biomech Eng, 123 (2), pp62-169, 2001
18. J Orthop Sci, 5 (6), pp585-592, 2000
19. American Journal of Sports Medicine, 24 (5), pp698-701, 1996
20. Knee Surg Sports Traumatol Arthrosc, 9 (3), pp51-154, 2001
21. Arthroscopy, 16 (7), pp763-767, 2000
22. Journal of Bone and Joint Surgery, 83B (5), pp625-634, 2001
23. J Biomech Eng, 118 (1), pp56-61, 1996
24. Knee Surgery, Sports Traumatology, Arthroscopy, 6 (4), pp224-230, 1998
25. International Orthopaedics, 21 (2), pp93-97, 1997
26. Arthroscopy, 17 (1), pp9-13, 2001
27. Arthroscopy, 11 (4), pp475-477, 1995
28. American Journal of Sports Medicine, 25 (30), pp288-293, 1997
29. Clin Orthop, 236, pp270-278, 1988
30. Journal of Bone and Joint Surgery, 69A (6), pp860-864, 1987
31. Transplantation, 65 (12), pp1577-1583, 1998
32. Tissue Engineering, 5 (5), pp443-452, 1999
33. Journal of Orthopaedic Research, 18 (4), pp557-564, 2000
34. Journal of Orthopaedic Research, 16 (4), pp414-420, 1998
35. Journal of Biomedical Materials Research, 29 (11), pp1363-1371, 1995
36. BASK Instructional Lecture 1, 8 (1), pp69-72, 2001
Intraarticular anterior cruciate ligament reconstruction requires a graft. These grafts may be autograft (the patient's own tissue), allograft (tissue taken from another person - usually a deceased donor) or synthetic. In addition, experimental work is being undertaken on xenografts and biological synthetic collagen grafts.
The choice of graft
The choice appears vast (table 1) but in practice only autografts using hamstring tendons and central third bone patella tendon bone (BPTB) are routinely used with good outcomes(2). These are generally harvested from the injured knee but have also been taken from the uninjured knee with very good results(3). There is little to choose between patellar tendon and hamstring grafts in the long term(4). The surgeon who undertakes anterior cruciate ligament reconstruction regularly (and there is an argument that this operation is all too frequently performed by people who don't do it regularly enough) should be familiar with both techniques and select the graft to suit the patient.
BPTB or hamstring graft - the rationale for graft selection
No one graft is applicable for every patient. There are strong advocates for each type. The choice should be made according to the individual patient since the use of either graft has specific advantages and disadvantages (see tables 2 and 3).
BPTB grafts should be avoided in patients who have kneeling professions or who participate in jumping sports such as netball with much eccentric loading. In addition, those patients with pre-existing anterior knee pain or patellofemoral problems should not receive BPTB grafts.
We tend to avoid hamstring grafts in patients with recent medial side injuries or with chronic medial instability. Also, hamstring grafts should be avoided in very heavy patients who need accelerated rehabilitation, or in athletes who require hamstring dominance (running backwards a great deal).
It may be necessary to tailor the choice of graft depending on associated reconstruction; for example, if combining the anterior cruciate ligament reconstruction with a posterior cruciate ligament (PCL) or posterolateral corner reconstruction.
Iliotibial tract graft
A graft from the iliotibial tract has satisfactory mechanical properties and results in less anterior knee pain. However, there is a long lateral operative scar, a risk of herniation of the quadriceps muscle and interference with an important lateral stabiliser of the knee(22).
Quadriceps tendon graft
The quadriceps tendon graft is thick with good biomechanical properties(7,8). Although it may be associated with less anterior knee pain, graft harvesting is technically difficult and results in an unsightly scar. Postoperatively, the donor quadriceps strength is significantly decreased even after one year(9).
Allografts
Allografts provide the graft material in a freeze-dried, fresh-frozen, irradiated or preserved state. There is a great deal of debate over whether these processes affect the mechanical properties of the graft(23,24,25,26). Other issues such as disease transmission, processing to decrease antigenicity and storage should also be considered before using 'off the shelf' allografts, which may be abnormally long or bulky(27). Nevertheless, in the complex revision scenario, allograft availability may be invaluable. We tend to favour fresh frozen non irradiated BPTB or Achilles allograft for revision cases and for specific cases where standard grafts are indicated.
Once in vogue in the 1970s, synthetic ligaments (carbon fibre, polyester, Dacron) are not currently recommended for routine primary intraarticular knee reconstruction(11,12,13,14,15,28) as their long-term follow-up results are unacceptable. Synthetic grafts have been shown to be stiff with poor elastic properties and induce foreign body reactions, resulting in increased infection rates. They are expensive and should be avoided.
Xenografts
Early results using xenografts (tissues from other species) in animal and human studies have been disappointing. The xenograft does not integrate well with the host tissue and appears to be associated with extreme intraarticular wear and synovitis(29,30). Xenograft rejection is also a problem. Recent animal studies have concentrated on immunologically modifying the xenograft in an attempt to decrease the immune rejection problem(31).
The future - 'biological' grafts
Tissue engineering offers the possibility of replacing damaged human ligaments with engineered ligament tissues(32). Attempts are being made to culture in vitro ligament tissues by seeding human anterior cruciate ligament and medial collateral ligament (MCL) cells onto synthetic biodegradable polymer fibre scaffolds. Research is also active on anterior cruciate ligament fibroblast-seeded collagen scaffolds for anterior cruciate ligament reconstruction(33,34,35).
It is likely that in the future, tissue-engineered ligaments will include growth factors to accelerate and promote revascularisation of the graft and healing of the bone blocks or tendinous tissue to the bone tunnels. This hopefully should enable patients to return to work and sport more quickly(22).
Complications of anterior cruciate ligament reconstruction
The most common complications include failure to regain full extension or flexion (due to malpositioning of the tunnels used to pass the graft), anterior knee pain (whichever graft type is used), graft impingement (again due to poor tunnel positions) and graft failure (either traumatic as a result of a new injury or due to inappropriate rehabilitation).
Other complications include infection, thrombophlebitis, skin necrosis, haemarthrosis, sensory nerve damage, reflex sympathetic dystrophy and arthrofibrosis.
Finally, it must be appreciated that the anterior cruciate ligament is a living anatomical structure with its own blood supply and innervation, including proprioception. No substitute graft can fulfil these functions(36); but with appropriate rehabilitation athletes regularly return to their previous level of function.
Alex Watson and Fares Haddad
References
1. Orthopaedic Review, 22 (11), pp1213-1223, 1993
2. American Journal of Sports Medicine, 28 (1), pp124-130, 2000
3. American Journal of Sports Medicine, 28 (5), pp651-658, 2000
4. American Journal of Sports Medicine, 27 (4), pp444-454, 1999
5. American Journal of Sports Medicine, 23 (5), pp593-596, 1995
6. Scand J Med Sci Sports, 11 (1), pp16-22, 2001
7. American Journal of Sports Medicine, 27 (1), pp27-34, 1999
8. Arthroscopy, 11 (2), pp252-254, 1995
9. J Trauma, 46 (4), pp678-682, 1999
10. Biomaterials, 21 (23), pp2461-2474, 2000
11. American Journal of Sports Medicine, 21 (3), pp367-373, 1993
12. Injury, 25 (7), 443-445, 1994
13. Knee Surgery, Sports Trauma, Arthroscopy, 1 (2), pp71-75, 1993
14. Journal of Biomedical Materials Research, 48 (4), pp534-549, 1999
15. Knee Surgery, Sports Trauma, Arthroscopy, 4 (3), pp132-136, 1996
16. American Journal of Sports Medicine, 16 (4), pp321-326, 1988
17. J Biomech Eng, 123 (2), pp62-169, 2001
18. J Orthop Sci, 5 (6), pp585-592, 2000
19. American Journal of Sports Medicine, 24 (5), pp698-701, 1996
20. Knee Surg Sports Traumatol Arthrosc, 9 (3), pp51-154, 2001
21. Arthroscopy, 16 (7), pp763-767, 2000
22. Journal of Bone and Joint Surgery, 83B (5), pp625-634, 2001
23. J Biomech Eng, 118 (1), pp56-61, 1996
24. Knee Surgery, Sports Traumatology, Arthroscopy, 6 (4), pp224-230, 1998
25. International Orthopaedics, 21 (2), pp93-97, 1997
26. Arthroscopy, 17 (1), pp9-13, 2001
27. Arthroscopy, 11 (4), pp475-477, 1995
28. American Journal of Sports Medicine, 25 (30), pp288-293, 1997
29. Clin Orthop, 236, pp270-278, 1988
30. Journal of Bone and Joint Surgery, 69A (6), pp860-864, 1987
31. Transplantation, 65 (12), pp1577-1583, 1998
32. Tissue Engineering, 5 (5), pp443-452, 1999
33. Journal of Orthopaedic Research, 18 (4), pp557-564, 2000
34. Journal of Orthopaedic Research, 16 (4), pp414-420, 1998
35. Journal of Biomedical Materials Research, 29 (11), pp1363-1371, 1995
36. BASK Instructional Lecture 1, 8 (1), pp69-72, 2001
