The Case for Hamstring Anterior Cruciate Ligament Reconstruction




Abstract


Surgeons have a choice of grafts when anterior cruciate ligament (ACL) reconstruction is necessary. Among all available graft types, the literature clearly shows the superiority of autograft versus allograft or synthetic.1–4 It is our opinion that, except in rare circumstances, there is no indication for allograft or synthetic. Once it is decided to use autograft, which is the best choice? Far and away, the two most commonly used autografts are 4-strand HS, which has the highest worldwide and US usage rate, and patellar tendon (BTB) grafts, which come in second. Quadriceps tendon (QT) grafts are the only other autografts with significant clinical usage. This chapter will present the case for using hamstring (HS) grafts.




Keywords

Autograft, donor site morbidity, four-strand hamstring, graft strength, infection, stability, stiffness

 




Keywords

Autograft, donor site morbidity, four-strand hamstring, graft strength, infection, stability, stiffness

 




Introduction


Surgeons have a choice of grafts when anterior cruciate ligament (ACL) reconstruction is necessary. This chapter will present the case for using hamstring (HS) grafts. Among all available graft types, the literature clearly shows the superiority of autograft versus allograft or synthetic. It is our opinion that, except in rare circumstances, there is no indication for allograft or synthetic. Once it is decided to use autograft, which is the best choice? Far and away, the two most commonly used autografts are four-strand HS, which has the highest worldwide and US usage rate, and bone-patellar tendon-bone (BPTB or BTB) grafts, which come in second. Quadriceps tendon (QT) grafts are the only other autografts with significant clinical usage.


The most important factor in deciding which of these three grafts to use is the experience and skill of the individual surgeon, and overall good results can be expected with each of these grafts in the hands of a skilled surgeon. Decreased skill with graft harvest and fixation can produce a subpar result with a good graft. Conversely, a skilled and creative surgeon can adjust fixation and rehabilitation to minimize the weaknesses and maximize the strengths of a given graft.


When considering which autograft to use, the primary considerations are as follows:



  • 1.

    Stability rates


  • 2.

    Graft strength


  • 3.

    Donor site morbidity


  • 4.

    Anterior knee pain


  • 5.

    Risk of subsequent arthritis


  • 6.

    Risk of infection


  • 7.

    Stiffness



Each will be considered individually throughout this chapter.


Some studies have shown differences in tunnel widening with various graft-fixation combinations, but no study has shown any adverse consequence of tunnel widening, and therefore that parameter will not be considered here. (Further discussion of tunnel widening can be found in Chapter 131 .) Time to graft tunnel healing has been cited by some; however by 4 months postoperatively, all grafts have achieved graft tunnel healing that exceeds graft strength, rendering this parameter a nonfactor in ultimate failure rates. The following discussion will compare HS to BTB. QT has been used successfully, but there is insufficient data in the literature to compare it to the other grafts.




Stability Rates


Meta-analysis has clearly shown that HS grafts and BTB have similar postoperative stability rates. This is the most important parameter. This rate has also been shown to be similar in men and women. It is important to consider only four-strand HS grafts when assessing stability. In the early days of ACL reconstruction, two-strand HS grafts were used and fixation was subpar. However, since the 1990s stability rates for HS grafts have met or exceeded those of BTB grafts. The thought was also disseminated in the early days of anterior cruciate ligament reconstruction (ACLR) that HS grafts were weaker because they did not heal as strongly in the tunnel as BTB. However, ultimate graft tunnel pullout strength has been shown to be equal between all autografts. When graft tunnel healing strength exceeds interstitial graft strength, it ceases to matter as a factor in failure, since failure will then occur in the substance of the graft. HS graft achieves this ultimate strength by 3 months postoperatively, before patients are returned to full activity. BTB achieves this ultimate strength a few weeks sooner, but this is of no clinical significance since the ultimate strengths are the same and are achieved early on in the rehabilitation phase by both grafts.


Conclusion


Stability rates are equal after HS and BTB reconstruction.




Graft Strength


A four-strand HS graft is clearly stronger than a 10-mm BTB graft in a given patient, by a factor of at least 50% (see Chapter 13 ) for a given patient. HS graft strength can be further enhanced by using a five- or six-strand HS graft (see also Chapter 24 ). When harvesting the semitendinosus (ST) and gracilis (GR) tendons, it is usual to obtain a length of at least 25 cm, and often much more. Since only about 16 cm is generally used for each graft, there is usually extra tendon that is discarded. This extra can be used to produce an even stronger graft of five or six strands, if need be. The author indeed uses an extra strand of ST when performing revision cases or in unusually large patients.


A number of papers have been written about the possibility of a HS graft being too small for a given patient. This, however, is not a valid concern. As with BTB, smaller tendons are found in smaller people, but the HS graft is always stout enough to serve as a sufficiently strong graft for a given patient. Some studies have seemed to find a higher failure rate if the graft is not at least 6 cm in diameter. The author has not found this to be the case. However, if surgeons are worried, they can always add an extra strand as described previously. Indeed the only two known failures in the author’s extensive 25-year experience using exclusively four-strand HS grafts were in large athletic males with large tendons. It is important to realize that in the studies on graft strength that showed greater strength of HS versus BTB, the graft strengths were normalized against the patient’s own ACL. HS, BTB, and quadriceps tendon have been shown to be far stronger than the native ACL, even accounting for an expected loss of ultimate tendon graft after ligamentization is complete.


Conclusion


HS graft is stronger than BTB.




Donor Site Morbidity and Weakness


Virtually no donor site morbidity has been found after HS harvest. However, patellar fractures, which has been seen in several National Football League players, and patellar tendon rupture, while uncommon, are a known and devastating sequela of BTB harvest. It is important to be familiar with a posterior approach to HS harvest to avoid cutting the HS graft short. However, with proper attention to technique, an adequate graft length should be achieved in all cases.


Weakness of the quadriceps is common after BTB harvest and can be difficult to overcome since the weakness occurs directly as a result of the BTB harvest. Additionally, the extensor mechanism exercises needed to correct this weakness can often aggravate the relatively common anterior knee pain seen after BTB ACLR. Indeed this problem has spawned the relatively common practice of harvesting the BTB graft from the contralateral knee.


Persisting weakness after HS harvest, however, is usually completely correctable. This is partially achieved by the semimembranosus hypertrophying to compensate for the loss of the ST. Additionally, the ST regrows and reattaches on the proximal tibia in 95% of patients by 1 year after surgery (see Chapter 30 ). The only persisting weakness seen after HS graft occurs when measurements are taken with the knee beginning in 90 degrees of flexion. However, this range of motion is only used in non-weight-bearing activities and is thus of no clinical or functional significance.


Conclusion


There is more donor site morbidity with BTB.




Anterior Knee Pain


The incidence of anterior knee pain has been found to be consistently higher after BTB than HS grafts (see also Chapter 136 ). The fact that the patellar tendon and patella are both being violated for BTB graft is the obvious explanation. Patients from Asian countries, where cross-legged sitting or kneeling are often a prominent part of the culture, tend to favor HS grafts because of their lower incidence of anterior knee pain (see ).


Thus patients with prior anterior knee pain symptoms and patients who need to engage in kneeling, squatting, stair climbing, or jumping are all patients for whom the HS graft is a safer alternative.


Conclusion


Anterior knee pain is more common after BTB than HS.

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Aug 21, 2017 | Posted by in ORTHOPEDIC | Comments Off on The Case for Hamstring Anterior Cruciate Ligament Reconstruction
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