SICOT

Scientific Debate

Autograft for Primary ACL Reconstruction: HS or BPTB?

The choice of graft for primary anterior cruciate ligament (ACL) reconstruction can be either an autograft, allograft or synthetic. However, an autograft is universally recognised as the gold standard for primary reconstruction and the common options include hamstring (HS) and bone-patellar tendon-bone (BPTB) grafts. In this article, the benefits of each autograft will be discussed.
 

Choice of Autograft for Primary ACL Reconstruction: Hamstrings are the better option

Anterior cruciate ligament (ACL) reconstruction surgery is an excellent procedure to restore knee joint stability following rupture of the native ACL. Autograft is universally recognised as the gold standard for primary reconstruction and the common options include bone-patellar tendon-bone (BPTB) and hamstring (HS) grafts. HS grafts generally refers to the combination of the gracilis and semitendinosus tendons which are harvested and looped-over, usually creating a 4-strand graft (though the number of strands may be increased or decreased). The benefits of HS over BPTB autografts will be discussed in the first part of this article.

Most proponents of HS grafts cite post-operative anterior knee pain as the primary reason for avoiding a BPTB. In a Cochrane systematic review of over 1600 ACL reconstructions, BPTB grafts were shown to have significantly higher anterior knee problems compared to HS, especially in the early post-operative period (<3 months) [1]. Rates of anterior knee pain following BPTB grafts between 20-49% have been reported in the literature. In contrast, anterior knee pain following HS grafts generally range between 5-15% [2,3].

Donor site morbidity, particularly neuropraxia and sensitivity following damage of the infrapatellar branch of the saphenous nerve (IPBSN) has a higher incidence in BPTB patients compared to HS. Authors generally agree that a vertical incision poses a greater risk of injury to the IPBSN; which is commonly the case when harvesting the BPTB graft with nerve injury reported as high as 59% [4]. Rates of nerve injury following HS graft harvesting with vertical incisions have been reported at 39.7% and this risk is further reduced to 14.9% when a horizontal incision is used [5]. During surgery, the nerve is generally visible as it crosses the pes anserinus and can be protected during hamstring harvest, further minimising the risk of injury.

The risk of developing osteoarthritis (OA) is another concern for surgeons and one of the reasons why ACL reconstruction is advocated to minimise knee instability and, therefore, reduce the risk of OA in the future. Many studies have demonstrated increased knee laxity following HS grafts compared to BPTB in the short and medium term though these differences were generally small [6]. Interestingly, the rates of developing OA in the long term have been reported as being higher in the BPTB group by some authors [7,8]. It remains unclear as to why these differences exist as there are potentially many factors that contribute to OA development apart from graft choices alone (e.g. meniscal injury, sub-chondral fractures, post-operative rehabilitation, etc.).

From a technical point of view, accurate tunnel placements are crucial in the successful outcome following ACL reconstruction. The recent shift towards an anteromedial approach for improved anatomical femoral tunnel preparations compared to older, trans-tibial techniques generally result in greater graft obliquity and, hence, increased graft length [9].  HS grafts are more forgiving in adjusting for appropriate lengths and, therefore, the risk of graft length mis-match is reduced. BPTB grafts generally have fixed tendon lengths and further discrepancies exist in cases of patella alta and patella baja.

BPTB proponents commonly cite autograft osteo-integration as an important factor for graft choice. Orthopaedic basic science tells us that bone-to-bone healing occurs quicker than soft tissue-to-bone healing. Older literature have shown that hamstring fixation methods (suspensory fixation, ties-over-button) allows micro-motion between the tendon-bone interface, leading to decreased anchorage of Sharpey’s fibres, lower fibro-cartilaginous consolidation and increased tunnel widening (particularly on the femoral side) [10]. More recent articles have suggested ways to overcome these pitfalls by employing anatomical tunnel positioning and modifications to the post-operative rehabilitation (lower intensity) in patients having HS grafts which improve soft tissue osteo-integration and give rise to equivalent clinical outcomes, despite suspensory fixation [11,12].

Economic considerations may also influence graft options. An interesting paper by Genuario et al, using a decision tree model, compared cost-effectiveness of graft choices (HS, BPTB and allograft) with an incremental ratio of $50,000/quality-adjusted life year (QALY) as the threshold. They found that HS grafts were the least costly and most effective (considering for anterior knee pain and post-operative instability) compared to BPTB (allografts were the most costly among the three options) [13].

In summary, HS grafts remain an excellent choice in ACL reconstruction surgery as per the reasons mentioned above. Further benefits also include improved knee extension in the short term and a lower incidence of patella fractures compared to BPTB grafts [14,15]. However, it is important to note that most studies show similar successful long-term outcomes following either graft choices [6,16]. The final decision should remain based on individual patient characteristics and the surgeons own experience.

1. Mohtadi NG, Chan DS, Dainty KN, Whelan DB. Patellar tendon versus hamstring tendon autograft for anterior cruciate ligament rupture in adults. Cochrane database Syst Rev. 2011 Jan;(9):CD005960.
2. Ibrahim SA-R, Al-Kussary IM, Al-Misfer ARK, Al-Mutairi HQ, Ghafar SA, El Noor TA. Clinical evaluation of arthroscopically assisted anterior cruciate ligament reconstruction: patellar tendon versus gracilis and semitendinosus autograft. Arthroscopy. 2005 Apr;21(4):412–7.
3. Poolman RW, Abouali JAK, Conter HJ, Bhandari M. Overlapping systematic reviews of anterior cruciate ligament reconstruction comparing hamstring autograft with bone-patellar tendon-bone autograft: why are they different? J Bone Joint Surg Am. 2007 Jul;89(7):1542–52.
4. Portland GH, Martin D, Keene G, Menz T. Injury to the infrapatellar branch of the saphenous nerve in anterior cruciate ligament reconstruction: comparison of horizontal versus vertical harvest site incisions. Arthroscopy. 2005 Mar;21(3):281–5.
5. Papastergiou SG, Voulgaropoulos H, Mikalef P, Ziogas E, Pappis G, Giannakopoulos I. Injuries to the infrapatellar branch(es) of the saphenous nerve in anterior cruciate ligament reconstruction with four-strand hamstring tendon autograft: vertical versus horizontal incision for harvest. Knee Surg Sports Traumatol Arthrosc. 2006 Aug;14(8):789–93.
6. Xie X, Liu X, Chen Z, Yu Y, Peng S, Li Q. A meta-analysis of bone-patellar tendon-bone autograft versus four-strand hamstring tendon autograft for anterior cruciate ligament reconstruction. Knee. 2015 Mar;22(2):100–10.
7. Pinczewski LA, Lyman J, Salmon LJ, Russell VJ, Roe J, Linklater J. A 10-year comparison of anterior cruciate ligament reconstructions with hamstring tendon and patellar tendon autograft: a controlled, prospective trial. Am J Sports Med. 2007 Apr;35(4):564–74.
8. Leys T, Salmon L, Waller A, Linklater J, Pinczewski L. Clinical results and risk factors for reinjury 15 years after anterior cruciate ligament reconstruction: a prospective study of hamstring and patellar tendon grafts. Am J Sports Med. 2012 Mar;40(3):595–605.
9. Bowers AL, Bedi A, Lipman JD, Potter HG, Rodeo SA, Pearle AD, et al. Comparison of anterior cruciate ligament tunnel position and graft obliquity with transtibial and anteromedial portal femoral tunnel reaming techniques using high-resolution magnetic resonance imaging. Arthroscopy. 2011 Nov;27(11):1511–22.
10. Höher J, Möller HD, Fu FH. Bone tunnel enlargement after anterior cruciate ligament reconstruction: fact or fiction? Knee Surg Sports Traumatol Arthrosc. 1998 Jan;6(4):231–40.
11. Iorio R, Vadalà A, Argento G, Di Sanzo V, Ferretti A. Bone tunnel enlargement after ACL reconstruction using autologous hamstring tendons: a CT study. Int Orthop. 2007 Feb;31(1):49–55.
12. Xu Y, Ao Y, Wang J, Yu J, Cui G. Relation of tunnel enlargement and tunnel placement after single-bundle anterior cruciate ligament reconstruction. Arthroscopy. 2011 Jul;27(7):923–32.
13. Genuario JW, Faucett SC, Boublik M, Schlegel TF. A cost-effectiveness analysis comparing 3 anterior cruciate ligament graft types: bone-patellar tendon-bone autograft, hamstring autograft, and allograft. Am J Sports Med. 2012 Feb;40(2):307–14.
14. Ageberg E, Roos HP, Silbernagel KG, Thomeé R, Roos EM. Knee extension and flexion muscle power after anterior cruciate ligament reconstruction with patellar tendon graft or hamstring tendons graft: a cross-sectional comparison 3 years post surgery. Knee Surg Sports Traumatol Arthrosc. 2009 Feb;17(2):162–9.
15. Stein DA, Hunt SA, Rosen JE, Sherman OH. The incidence and outcome of patella fractures after anterior cruciate ligament reconstruction. Arthroscopy. Jan;18(6):578–83.
16. Webster KE, Feller JA, Hartnett N, Leigh WB, Richmond AK. Comparison of Patellar Tendon and Hamstring Tendon Anterior Cruciate Ligament Reconstruction: A 15-Year Follow-up of a Randomized Controlled Trial. Am J Sports Med. 2016 Jan;44(1):83–90.

Bone patella tendon graft for ACL reconstruction: the “gold standard” graft for ACL reconstruction

What is the best graft for primary ACL reconstruction? The optimal graft choice for primary anterior cruciate ligament (ACL) reconstruction remains controversial. The choice of graft can be either an autograft, allograft or synthetic. However, autograft is currently the main choice of graft for primary ACL reconstruction which is mainly either the hamstring (semi tendinosus and gracilis) or the bone-patellar tendon-bone (BPTB) graft [1].

In choosing the optimal graft for patients undergoing ACL reconstruction, the surgeon needs to consider various factors such as the duration in return to play, the risk of re-rupture and complications associated with using the autograft.

The main advantages of using BPTB graft is graft incorporation. Tomita et al showed that graft incorporation is better with bone-to-bone healing compared to tendon-to-bone healing [2]. A more recent study also shows similar results [3]. The biology of graft incorporation, which involves osteonecrosis, occurs at the graft-tunnel interface, followed by creeping substitution and incorporation into surrounding host bone. Complete incorporation of the bone graft to the host bone is expected by 6 weeks postoperatively [4]. In comparison to the hamstring graft, the process of incorporation takes approximately 12 weeks, in which the hamstring graft demonstrated reduced ultimate failure load compared to the BPTB graft [5].

Another added advantage in using the BPTB graft is the ability for early post-operative rehabilitation.  The risk of graft rupture is a concern for early post-operative rehabilitation. It has been shown that the BPTB graft is superior in comparison to the native ACL in terms of ultimate tensile load, cross-sectional area and stiffness [6]. Thus, the BPTB provides intrinsic biomechanical advantage. When used in combination with rigid aperture fixation such as interference screw fixation, early post-operative rehabilitation can be initiated.

In terms of graft strength, studies have shown that both hamstrings and BPTB tendon grafts are stronger than native ACL. However, the strength of hamstring tendon grafts depends on the number of graft strands. Reinhart et al showed that only the 4-strand hamstring was statistically insignificantly different when compared to BPTB grafts where the 2-strand graft is significantly weaker than the BPTB [7].

Also, the incidence of tunnel widening have been reported with the use of hamstring grafts [8]. It is understood that tunnel widening may be caused by a variety of factors and whether its presence may or may not affect clinical outcome is still debateable. However, it may affect revision ACL surgery where a large tunnel may prevent a revision tunnel to be created in the optimum position in which a two-stage revision may be required.  

Clinically, BPTB autografts have been used for ACL reconstruction for years with excellent results at long-term follow-up [9]. In a recent Cochrane review comparing patellar tendon to hamstring autografts, the review showed that static stability testing such as Lachman, Pivot Shift, and instrumented laxity favoured BPTB grafts over hamstring grafts [10].  A systematic review of level I studies found a higher risk of failure in hamstring autografts compared with BPTB autografts, and only 1 of 5 studies found a higher risk of anterior knee in the BPTB autografts group of patients [7].

However, in the end, the optimum clinical outcome is based on the need of the patient, the experience of surgeons and choice of the graft. Both grafts, whether it be the hamstring or BPTB graft, have been reliable and with long-term clinical outcome results. 

1. Reinhardt KR, Hetsroni I, Marx RG. Graft selection for anterior cruciate ligament reconstruction: a level I systematic review comparing failure rates and functional outcomes. Orthop Clin North Am 2010;41:249-262
2. Tomita F, Yasuda K, Mikami S, Sakai T, Yamazaki S, Tohyama H. Comparisons of intraosseous graft healing between the doubled flexor tendon graft and the bone-patellar tendonbone graft in anterior cruciate ligament reconstruction. Arthroscopy 2001;17:461-476.
3. Gulotta LV, Rodeo SA. Biology of autograft and allograft healing in anterior cruciate ligament reconstruction. Clin Sports Med 2007;26:509-524.
4. Panni AS, Milano G, Lucania L, Fabbriciani C. Graft healing after anterior cruciate ligament reconstruction in rabbits. Clin Orthop Relat Res 1997:203-212
5. Tomita F, Yasuda K, Mikami S, Sakai T, Yamazaki S, Tohyama H. Comparisons of intraosseous graft healing between the doubled flexor tendon graft and the bone-patellar tendon-bone graft in anterior cruciate ligament reconstruction. Arthroscopy 2001;17:461-476.
6. Chan DB, Temple HT, Latta LL, Mahure S, Dennis J, Kaplan LD. A biomechanical comparison of fan-folded, single-looped fascia lata with other graft tissues as a suitable substitute for anterior cruciate ligament reconstruction. Arthroscopy 2010;26:1641-1647.
7. Reinhardt KR, Hetsroni I, Marx RG. Graft selection for anterior cruciate ligament reconstruction: a level I systematic review comparing failure rates and functional outcomes. Orthop Clin North Am 2010;41:249-262.
8. L'Insalata JC, Klatt B, Fu FH, Harner CD. Tunnel expansion following anterior cruciate ligament reconstruction: a comparison of hamstring and patellar tendon autografts. Knee Surg Sports Traumatol Arthrosc 1997;5:234-238.
9. Moller E, Weidenhielm L, Werner S. Outcome and knee-related quality of life after anterior cruciate ligament reconstruction: a long-term follow-up. Knee Surg Sports Traumatol Arthrosc 2009;17:786-794.
10. Mohtadi NG, Chan DS, Dainty KN, Whelan DB. Patellar tendon versus hamstring tendon autograft for anterior cruciate ligament rupture in adults. Cochrane Database Syst Rev 2011;9:CD005960.