Are Quadruple Hamstrings the New Gold Standard?

John Theodoropoulos, M.D., FRCSC
William Osler Health Centre
Brampton, ON

The current ideal graft for Anterior Cruciate Ligament (ACL) reconstruction is subject to debate. The use of central third Bone-Patellar Tendon-Bone (BPTB) grafts have historically been considered the gold standard. Notwithstanding the advantages of high initial strength and bone-to-bone healing seen with BPTB grafts for ACL reconstruction, there are some shortcomings. These are harvest site morbidity and include anterior knee pain, pain on kneeling, loss of extension and patellar fracture leading surgeons to seek an alternative graft.

One of these graft alternatives is the use of hamstring tendons (Semitendinosus and Gracilis). This began with the use of double hamstring grafts (2HT) and eventually quadruple hamstrings grafts (4HT) in ACL reconstruction. The advantages of using 4HT grafts included ease of harvest, less anterior knee pain, less extension loss and equal strength and stability. Unfortunately, despite the recent increase in the number of randomized control trials and meta-analysis studies comparing the two graft choices, the answer to which graft choice is superior has yet to be answered.

One of the initial criticisms in the use of 4HT grafts was that of lower strength compared to BPTB. The concerns of graft strength have been shown to be invalid. Data from studies by both Noyes and Harner 1,2 have shown that 4HT grafts are stronger (4090 N versus 2900 N) and stiffer (776 N/mm versus 685 N/mm) than BPTB grafts as well as the native ACL (2160 N).

As a result of improved fixation techniques, concerns of pull-out strength and stability have also been shown to be invalid. A recent meta-analysis by Prodromos3, comparing stability between the two grafts (4HT and BPTB) found that the 4HT, using modern fixation techniques, was more stable (80% within 2mm of contra-lateral knee using KT 1000) than the BPTB technique using modern soft tissue fixation on the tibia and EndoButton (Smith and Nephew) fixation the femur. Another recent study showed no difference in stability between 4HT and BPTB as defined by Lachman, pivot shift and KT 1000 side-to-side difference > 5 mm.4

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This brings us to the issue of graft fixation. This is a valid concern as it takes twice as long (10-12 weeks) to get soft tissue to bone healing as it does bone-to-bone healing (six weeks). Fortunately, HT graft fixation has improved over the last ten years. Initially HT were fixed with staples, this evolved to the use of EndoButton, crosspins and finally interference screw fixation. Currently many studies have shown that the pullout strength of interference screw fixation in soft tissue grafts was similar to that of BPTB.5,6 In a recent review of the literature, Goldblatt found that there was no difference in risk of failure between the graft types when interference screws were used for both tibial and femoral fixation.4

Two less recent meta-analysis studies have shown evidence to the contrary. Freedman et al7 found higher graft failure in the use of hamstring grafts, as well as higher patient satisfaction. They also found a higher incidence of knee pain in BPTB versus HT ACL reconstruction. Yunes8 also found less laxity and a higher chance of return to sport in the BPTB group. Unfortunately, some of the studies included in both of these meta-analyses included the use of double hamstring (2HT) and older fixation techniques.

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Two recent studies have attempted to keep all the confounding variables equal and look only at graft type. In a recent randomized controlled study comparing outcome scores, stability and knee pain in BPTB versus 4HT using the same fixation technique (interference screw), the only difference found was kneeling pain.9 A similar study by Shaieb et al10 found the BPTB group had a higher incidence of anterior knee pain and more patients with loss of motion compared to the 4HT, again using similar fixation techniques.

One interesting study by Pinczewski also found a higher incidence of anterior knee pain and more notably an increase in early osteoarthritic changes in the BPTB group. Unfortunately, this study was nonrandomized and needs to be investigated further before any judgment can be made regarding degenerative joint disease and graft selection in ACL reconstruction.11

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As you can see, the literature is immense and the question still remains unanswered. The previous concerns of inferior stability using hamstring grafts were a result of the now obsolete use of 2HT grafts and older fixation techniques. Currently, with modern fixation techniques, both the BPTB and 4HT surgical techniques and outcomes are similar. The graft choice is determined by what the surgeon and the patient are comfortable with after educating themselves as to the potential morbidity associated with each graft type.

My personal choice is the use of the 4HT graft. It is simple and reproducible with minimal harvest morbidity. Hamstring graft harvest can be done through a very small three centimetre vertical incision over the pes anserinus insertion two centimetres medial to the tibial tubercle. The tendons are usually palpable through the skin and allow for centralization of the incision. The tendons are identified, the sartorius fascia incised and the tendons delivered out of the wound while incising any attachments to the gastrocnemius musculature. When the tendons are delivered three to four centimetres out of the wound, usually all of the attachments have been released. An open tendon stripper is used leaving the distal tendon attached to bone (Figure 1). A gentle pull on the tendon and concomitant push on the tendon stripper prevents any tendon amputation (rarely a problem). The remainder of the procedure is done similar to BPTB technique. After cycling, the graft is tensioned. Currently, I do not use a tensioner (other than brute force) prior to insertion of the tibial screw, although many new tensioners on the market show promise in achieving appropriate initial tension. The graft is fixed using an EndoButton (Smith and Nephew, Figure 2) on the femoral side and an Xtralock Screw (Linvatec, Figure 3) on the tibial side. If purchase with the tibial fixation is a concern, a screw and washer is added and the individual hamstring strands are wrapped around a post and tied using high strength suture (Figure 4). It is important to whipstitch high strength suture (Herculon, Linvatec) or Fibrewire (Arthrex) on both ends of the tendon on the tibial side to prevent suture breakage and inadvertent cutting during interference screw fixation (Figure 5).

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An ideal graft would have no donor site morbidity and early secure fixation to allow for accelerated rehabilitation and rapid return to pre-injury activity level. Using modern surgical fixation techniques, similar clinical results are achieved with both the 4HT and BPTB grafts. Potential advantages of the use of 4HT over BPTB are reduced donor site morbidity with less anterior knee pain and kneeling pain. The ultimate decision on which graft to use is based on surgeon preference and comfort with the technique. A surgeon should be skilled in both techniques and have a thorough knowledge of the current literature to inform a patient when selecting a graft.
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References

1. Noyes F.R., Butler D.L., Grood E.S. Zernicke R.F., Hefzy M.S. Biomechanical Analysis of Human Ligament Grafts Used in Knee Ligament Repairs and Reconstructions. Journal of Bone and Joint Surgery American 1984. 66(3): p. 344-352.

2. Harner D.L. Brown C.H., Steiner M.E., Hecker A.T., Hayes W.C. Hamstring Tendon Grafts for Reconstruction of the Anterior Cruciate Ligament: Biomechanical Evaluation Of The Use of Multiple Strands and Tensioning Techniques. Journal of Bone and Joint Surgery American 1999. 81(4): p. 549-557.

3. Prodromos C.C., Joyce B.T., Shi K., Keller B.L. A Meta-Analysis of Stability After Anterior Cruciate Ligament Reconstruction as a Function of Hamstring Versus Patellar Tendon Graft and Fixation Type. Arthroscopy 2005. 21(10): p. 1202.e1-1202.e9.

4. Goldblatt J.P., Fitzsimmons S.E., Balk E., Richmond J.C. Reconstruction of the Anterior Cruciate Ligament: Meta-analysis of Patellar Tendon Versus Hamstring Tendon Autograft. Arthroscopy 2005. 21(10): p. 791-803.

5. Corry I.S., Webb J.M., Clingeleffer A.J., Pinczewski L.A. Arthroscopic Reconstruction of the Anterior Cruciate Ligament: A Comparison of Patellar Tendon Autograft and Four Stranded Hamstring Tendon Autograft. American Journal of Sports Medicine 1999. 27(4): p. 444-454.

6. Wagner M., Kaab N.J., Schallock J., Haas N.O., Weiler A. Hamstring Tendon Versus Patellar Tendon Anterior Cruciate Ligament Reconstruction Using Biodegradable Interference Fit Fixation A Prospective Matched-Group Analysis. American Journal of Sports Medicine 2005. 33(9): p. 1327-1336.

7. Freedman K.B., DAmato M.J., Nedeff D.D., Kaz A., Bach B.R. Arthroscopic Anterior Cruciate Ligament Reconstruction: A Meta-analysis Comparing Patellar Tendon and Hamstring Tendon Autografts. American Journal of Sports Medicine, 2003. 31(1): p. 2-11.

8. Yunes M., Richmond J.C., Engels E.A., Pinczewski L.A. Patellar Versus Hamstring Tendons in Anterior Cruciate Ligament Reconstruction: A Meta-analysis. Arthroscopy, 2001. 17(3): p. 248-257.

9. Ejerhe L., Kartus J., Sernet N., Kohler K. Patellar Tendon or Semitendinosus Tendon Autografts for Anterior Cruciate Ligament Reconstruction? A Prospective Randomized Study With A Two-Year Follow-up. American Journal of Sports Medicine 2003. 31(1): p. 19-25.

10. Shaieb M.D., Kan D.M., Chang S.K., Marumoto J.M., Richardson A.B., A Prospective Randomized Comparison of Patellar Tendon Versus Semitendinosus and Gracilis Tendon Autograft for Anterior Cruciate Ligament Reconstruction. American Journal of Sports Medicine 2002. 30(2): p. 214-220.

11. Pinczewski L.A., Deehan D.J., Salmon L.J., Russel V.J., Clingeleffer A.A. A Five-Year Comparison of Patellar Tendon Versus Four-Strand Hamstring Tendon Autograft for Arthroscopic Reconstruction of the Anterior Cruciate Ligament. American Journal of Sports Medicine 2002. 30(4): 523-536.

 

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