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acl reconstruction surgery, anterior cruciate ligament, reconstructive surgery, bone-patellar-tendon-bone reconstruction, Noyes's 'rule of thirds', patellar fracture, osteoarthrosis, ACL reconstruction with a semitendinosis, gracilis-semitendinosis-tendon technique, allograft reconstruction, synthetic replacement

ACL reconstruction surgery: how to choose the right acl reconstruction surgery when you have received terrible news about your knee

Sitting in your doctor's office, you learn the shocking truth: the MRI reveals that you have indeed ruptured the anterior cruciate ligament (ACL) in one of your knees. Your doctor is staring at you, waiting for you to make some decisions. Do you want reconstructive surgery? If so, what kind of surgery? Who should actually perform the op? Are you content with the surgeon provided by the NHS, or will you do some research and find just the right person, regardless of financial cost?

While you ponder these options, other important considerations cross your mind, too: should you strengthen your leg muscles before the surgery in order to enhance post-operative recovery? What kind of after-surgery rehabilitative programme will be best?

Noyes's 'rule of thirds'
The decision about whether to have reconstructive surgery is not always clear-cut. The great knee expert F. R. Noyes attempted to aid the decision-making process by formulating his 'rule of thirds' (1). Basically, Noyes suggested that about one-third of individuals with an ACL-deficient knee could successfully return to unrestricted sports participation without reconstructive surgery, provided they used braces on their knees and embarked on a high-quality leg-strengthening programme. Another third could return to sports activity without surgery, provided they utilised braces and strengthening exercises – and reduced their level of participation (eg, trained and competed with lower intensity and volume than before). Finally, the last third of the ACL-deficient athletes would not be able to return to sporting activity because of chronic instability in the damaged knee; athletes in this last third would be those whom Noyes considered the best candidates for reconstructive surgery.

Note that Noyes's system involves a certain amount of anxiety-filled waiting, however: you recover from the pain and inflammation associated with your initial rupture, you carry out strengthening exercises and wear a brace, and nervously hope for the best. If you are a serious athlete, you will probably not want to play this game, especially since some research has indicated that Noyes's 33% success rate with the non-surgery option is too high. For example, one study detected instability in 87.5% of un-reconstructed knees (2). Contrast this with another study which found that 95% of individuals who had their ACLs reconstructed with patellar-tendon autografts had no 'giving way' or noticeable instability in their knees at all(3).

Indeed, if you hope to participate actively and aggressively in sports that involve running, particularly those that include sudden decelerations, high-impact landings, potential collisions with other athletes, and rapid changes of direction, ACL-restoration surgery is a near necessity. The ACL is a constrainer and controller of knee motion and provides stability to the knee; without an ACL, your knee is inherently unstable and is likely to 'give out' at a painful, inopportune moment. In addition, undergoing ACL reconstruction can reduce your risk of future cartilage damage (4) and osteoarthritic changes in your knee joint, in addition to improving your overall performances.

Deciding not to have surgery
The decision not to have surgery can also sometimes be easy. If you are a relatively low-level weekend cricketer, for example, you may opt for a brace and special hamstring exercises, instead of the surgeon's knife, especially if you decide to reduce your overall aggressiveness as you move around the cricket pitch. If you are an elite cyclist and you have accidentally ruptured your ACL while playing a pick-up game of basketball or volleyball, you may decide that you do not need surgery at all, since the ACL does not play an essential role in the mechanics of cycling. You can cut out the 'cross-training' and continue your high-level cycling career, once the symptoms of your acute injury have subsided.

And deciding to have it
If you do decide to have your ACL reconstructed, you should be aware that there are several different ways in which it can be restored. The most commonly used surgical techniques are as follows:

(a) The ACL reconstruction with a bone-patellar-tendon-bone autograft.
This is the most commonly used reconstructive procedure and is sometimes referred to as the 'gold standard' of ACL restoration. Basically, the middle third of the patellar tendon (the tendon which runs through your kneecap and connects with the front of the tibia below) is cut from the patella down to the tibia in the ACL-deficient knee; bone 'plugs' about 8mm deep which are naturally connected to this strip of tendon at both ends (the patella and tibia) are also removed along with the tendon. This strip of patellar tendon, with the bone plugs at either end, is then surgically fitted into the appropriate positions on the femur and tibia to mimic the location of a natural ACL.

A key advantage associated with the bone-patellar-tendon-bone autograft is its great strength, compared with other popular autografts. A normal ACL will fail when it is acted on by a force equal to 1725 Newtons, but a comparable mass of patellar tendon will not fail until the external force reaches about 2900 Newtons (5).

This is an important factor in general (naturally, an athlete does not want his/her brand-new ACL to be prone to rupture after it has been implanted), and it is particularly important during the four to six weeks which follow surgery. During that time period, the graft, regardless of the source of the grafted material, undergoes a great deal of necrosis (cell death), cellular re-population, and re-vascularisation (ingrowth of new blood vessels); in fact, some studies indicate that there may be no living cells at all left in the graft approximately two weeks after surgery.

Consequently, the graft is substantially weaker than it will be when these processes are completed, and the risk of re-rupture is relatively high. Thus, having the strongest-possible connective-tissue framework in place is imperative. Even if the bone-patellar-tendon-bone autograft temporarily loses 40% of its tensile strength during this re-modelling period, it will still be stronger than the original ACL (6).

Another plus – and the minuses
Another reason for the popularity of the bone-patellar-tendon-bone reconstruction is that ACL replacements sometimes don't 'take' very well, meaning they may lose their attachments to either the femur or tibia (or both) after surgery. However, the bone-patellar-tendon-bone technique usually avoids that problem, since the bony plugs are inserted into small, waiting craters in the femur and tibia, become intermeshed with the surrounding bone, and remain quite stable. Nonetheless, there are several disadvantages associated with bone-patellar-tendon-bone grafting.

These include an increased risk of patellar fracture and osteoarthrosis, difficulties in achieving full extension of the knee, and the potential for long-term pain in the patellar tendon and patellofemoral joint; individuals with existing patellofemoral pain or narrow patellar tendons are not considered good candidates for the procedure. Note a patellar-tendon ACL reconstruction is sometimes carried out without the bony plugs at either end of the strip of patellar tendon (instead, staples are used to attach the connective-tissue ends of the patellar tendon to the hopefully correct locations in the femur and tibia), but this technique is not believed to possess as much initial stability as the bony plug method.

(b) ACL reconstruction with a semitendinosis- and/or gracilis-tendon autograft.
In this procedure, the tendon(s) from the semitendinosis and/or gracilis muscles (from the hamstring group in the posterior upper portion of the leg) are cut out and then positioned within the knee as a substitute for the lost ACL.

A key advantage of using this procedure instead of the 'gold-standard' patellar-tendon reconstruction is that semitendinosis/gracilis autografts are associated with many fewer patellofemoral problems during post-surgery recovery (as you might expect, since the patella and its tendon are left alone during this restoration). Another good feature of semitendinosis/gracilis autografting is that the incision used for taking the semitendinosis and/or gracilis tendon(s) can also be used to create the tibial tunnel into which the new ACL will be attached, thus cutting down on the number of surgical wounds experienced by the patient. In addition, the semitendinosis and gracilis tendons are very simple to 'harvest' surgically, with a small amount of dissection needed and consequently little post-op morbidity at the site.

One of the drawbacks associated with this form of restoration is the potential for hamstring weakness, as you might expect, although certain studies have shown normal strength in donor hamstrings 22 months after surgery. There is some evidence to suggest that the semitendinosis and gracilis muscles can actually regenerate their tendons after they have been removed (7), which would certainly help to restore strength to the hamstring group (incidentally, research indicates that the removed section of patellar tendon from the patellar-tendon autograft also re-grows). In fact, hamstring problems related to ACL reconstruction are considered so manageable that an athlete may 'blow out' an ACL in one knee, have the surgeon use the semitendinosis tendon of that knee to replace the ACL, sever the new ACL at some later date, and then have the semitendinosis tendon of the other knee harvested to create yet another ACL, without extreme concern about the long-term functionality of either appendage's hamstring group.

Since the gracilis-semitendinosis-tendon technique seems to be so salubrious from both surgical-technique and recovery standpoints, why is it not the gold standard, instead of the patellar-tendon reconstruction? One key reason is that the gracilis and semitendinosis tendons are simply not as strong as the patellar tendon. Recalling that a normal ACL fails under a load of 1725 Newtons and a patellar-tendon replacement gives up the ghost at about 2900 Newtons, you will be appalled to learn that a semitendinosis graft substitute for the ACL falls apart at just 1200 Newtons, and the gracilis goes to pieces at a paltry load of only 860 Newtons (5).

True, maximal tensile strength should not be the only variable used to judge the effectiveness of a graft source, and some surgeons attempt to get around the gracilis/semitendinosis weakness by using both tendons for the graft, but the overwhelming strength difference between the patellar-tendon and gracilis/semitendinosis grafts is a factor for you to consider, especially if you are involved in sports which incorporate high speeds, cutting movements, sudden decelerations, and/or hard impacts with other competitors or simply with the ground or gym floor after explosive vertical leaps.

(c) Allograft reconstruction of the ACL.
In this technique, a cadaver is dissected to yield an ACL, the semitendinosis and/or gracilis tendons from the hamstrings, the bone-patellar-tendon-bone portion of the knee, an iliotibial band, or even an Achilles tendon; the removed tissue is then transplanted into the knee of the ACL-missing patient to serve as a substitute ACL. This technique is appealing for a couple of reasons. First, there is no donor-site morbidity at all for the athlete undergoing surgery – no painful incision in the patellar tendon or severing of a hamstring tendon to obtain the graft, for example. In addition, a large amount of strong, varied graft material can be harvested from the 'donor', who seldom seems to mind very much.

And the downside?
There is a potential disadvantage associated with allografting, however. Diseases may be transmitted from the cadaver to the athlete, including hepatitis and HIV-related ailments. Freezing the graft material prior to transplantation may significantly reduce the risk; one study estimated the likelihood of transmitting the HIV virus to be about one in 1.6 million when frozen tissue is utilised (8). However, it is clear that allografts are not always completely sterile; in one recent case, a serious, gangrenous infection developed in an individual who received an allograft for ACL reconstruction; the patient eventually had to have his leg amputated.

(d) Synthetic replacement of the ACL, eg, the creation of a prosthetic ligament.
The use of synthetic materials for ACL reconstruction became popular when it was realised that autografted ACLs were fairly weak and vulnerable for up to four months following surgery, with a relatively high risk for rupture and abnormal stretching (stretched-out ACLs, even though they are not completely disrupted, may provide little stabilising support for the knee); synthetic ACLs, in contrast, provide immediate, very strong stabilising support for the knee. In addition, the use of a synthetic replacement means that there will be no donor-site morbidity in the athlete, and the overall surgical process is straightforward and relatively easy. Gore-Tex, Dacron, carbon fibres, and polypropylene braids have been utilised to create artificial ACLs.

The snag
However, a key problem associated with synthetic ligaments is that they inevitably suffer from 'creep' – the unrecoverable elongation of a material over time after 'multiple cyclic loads' (in other words, a lot of use). Unfortunately, synthetic materials become less functional as time goes on, unlike autografts, which seem to become stronger after a three- to four-month period. Overall, synthetic ligaments have been linked with relatively high failure rates and persistent effusions within the knees of individuals receiving the devices.

Choosing a surgeon
As you might expect, there is considerable debate about which form of restoration is best overall, and investigations comparing the techniques have been published. For example, one study detected a 50% failure rate when hamstring tendons were used for ACL restoration, versus a 15% incidence of failure with patellar-tendon insertions (9).

The truth, however, is that no one technique is right for every ACL-deficient patient. As we have mentioned, athletes with existing patellofemoral troubles or narrow patellar tendons should not opt for the bone-patellar-tendon-bone procedure, despite its various strong points. Similarly, individuals with frequent hamstring injuries or hamstring weakness – and perhaps those who will ultimately place high maximal forces on their grafted ACLs – would not seem to be optimal candidates for a semitendinosis/gracilis autograft. You will simply have to work very carefully with your selected surgeon to determine which procedure is right for you.

Speaking of surgeons, how do you choose the right person for the job? The post-operative period is not fun; it is painful and demanding, so ACL reconstruction is not a surgery you will want to repeat too often, if at all. In addition, your future athletic career may well hinge on your choice, so approach your decision very, very carefully.

Naturally, if you receive your health care through the NHS in the UK, your GP (or Accident and Emergency Department, in some cases, depending on whom you consulted for treatment) would refer you to a local surgeon. In this case, you may not even see a surgeon who specialises in ACL reconstructions or even knee operations in general, as ACL replacement is sometimes regarded as general orthopaedic surgery. With all due respect to general orthopaedic surgeons, don't let this happen. Even a small mistake during the ACL restoration, a small misplacement of the graft attachment, for example, can make a big difference in how your knee will function following surgery – and in your future athletic career.

You need an absolutely expert ACL-restoration surgeon, someone who does a lot of reconstructions, who keeps up with the latest techniques, and who has a high success rate with his/her operations. You might have to bite the bullet and pay for surgery 'outside the system', to the tune of about £4000 or more, but remember that the money spent may be well worth it in the long run. A strong, stable knee is worth its weight in gold to the serious athlete.

Success rates
Of course, determining success rates for surgeons can be a difficult process. Although there are some surgical-outcome data available, individual-surgeon's achievement rates are not really available, and – as SIB's consulting surgeon, Dr. Fares Haddad, points out – quantifying outcomes within the NHS is very difficult, as patients do not attend follow-up as regularly as one would like, and the resources needed to collect the appropriate data are lacking.

So, you will have to begin an interview process, talking to as many knowledgeable people in the fields of sports medicine and physical therapy as possible. Most sports-medicine doctors have ideas about who are the best knee surgeons in the country, based on their experiences with patients of their own who have sought surgical remedies for their knee problems, as well as conversations with other doctors. Not surprisingly, those considered at the top of the game are not always the most famous, nor will they necessarily be the ones in the highest echelons of the British Association of Knee Surgery.

It is also a sensible idea to talk to serious athletes who have undergone ACL reconstructions. You should find out who did their operations, what restoration techniques were used, the seriousness of their post-surgery complications, and how quickly they were able to return to competition. Naturally, this latter factor will depend on the quality of the post-operative rehabilitation programme, too, so be careful not to pin the blame for a poor outcome on a surgeon, when a bad rehab programme may be the true culprit.

Points to bear in mind
Once you have comprised a list of surgeons who seem qualified to do your surgery, schedule appointments with them, and on the appointed day bring all of your medical records, including the MRI results for your knee. As you evaluate the surgeons, keep the following points in mind:

(1) Take note of how careful, thorough, and well-prepared the surgeon is during your meeting. The author of this article, who is currently missing the ACL in his right knee, was recently seen by a knee surgeon who was rumoured to be one of the 'top-10-ACL-replacement specialists' in the United States. The author innocently asked if it would be all right to carry out running workouts while he awaited his surgery, and the vaunted surgeon replied that running would be absolutely great, as long as the workouts were not very painful. The surgeon then added, 'You have to be careful, though, because if you do run you might develop some wear-and-tear damage in your knee'. The author's concern was that his X-rays and MRIs, both of which had been made available to the surgeon before the appointment, indicated that such wear-and-tear damage, including bone spurs on the femur and osteoarthritic changes in the cartilage capping the femur, was already present. As your author reasoned, if a surgeon cannot prepare himself properly and incorporate relevant information about a patient prior to an important meeting, how can one be confident that said surgeon will do so before he makes incisions and drills holes in one's knee?

(2) Sound out the surgeon concerning his/her views on post-surgery rehabilitation. True, surgeons generally don't get directly involved with the rehab process, but if he/she mentions that performing leg extensions from a seated position and conducting hamstring curls from a prone position will be a key part of the strength-recovery process, you may safely move on to the next surgeon on your list, since this individual has failed to stay up-to-date on the latest trends in rehabilitation, which include an emphasis on weight-bearing, closed-chain, functional activity, even for the recently ACL-restored patient. Although you might say that there is no reason why surgeons should stay up-to-date on such things, bear in mind that one principle of doctoring is that you care about what happens to your patient – including what happens following what may be a wonderful surgical intervention.

(3) Look for subtle – and sometimes not-so-subtle – clues about the surgeon's success rate and approach to his/her work. At another interview scheduled by the author of this article, one of the surgeons on his list began praising his own surgical prowess and popularity of same, noting that 'One of my patients, a well-known college volleyball player, has asked me to replace the ACL in her right knee four different times'. The surgeon literally glowed about the confidence placed in his dexterity, but your author had a slightly different interpretation of the situation.

(4) Ask your surgeon a probing question about ACL reconstructions to determine if he/she is mainly a plumber who repairs knees according to techniques learned during training or if he/she stays up to date on all the relevant issues pertaining to restorations. For example, you might ask how rehabilitation will differ depending on whether the patellar-tendon or hamstring graft is used (patellar permits aggressive strengthening to be carried out earlier) – or you might ask whether there is a significant maximal-strength difference between patellar and hamstring grafts (see above).

In terms of rehab facilities, most surgeons tend to utilise specific facilities and physiotherapists. The surgeon should give you a copy of the rehab protocol and ask you to visit the rehabilitation facilities, and – as mentioned – the surgeon should emphasise the great importance of functional and sport-specific strengthening, along with a relatively quick return to weight-bearing activity. To truly pass your test with flying colours, the surgeon should advise you to start the physiotherapy/rehabilitation (prehabilitation) well before your reconstruction.

The bottom line? If you do your homework properly, choose the right restoration technique and surgeon, and take extra care to functionally strengthen your leg before and after surgery, you should be able to convert your unstable, ACL-deficient knee into a structure which will allow you to perform at your highest level in your sporting activity.

Owen Anderson

(1) 'The Symptomatic Anterior Cruciate-Deficient Knee. Part II. The Results of Rehabilitation, Activity Modification, and Counseling on Functional Disability', J Bone Joint Surg, Vol. 65A, p. 163, 1983
(2) 'Follow-Up of the Acute Nonoperated Isolated Anterior Cruciate Ligament Tear', American Journal of Sports Medicine, Vol. 14(3), p. 205, 1986
(3) 'Reconstruction of the Chronically Insufficient Anterior Cruciate Ligament with the Central Third of the Patellar Tendon', J Bone Joint Surg, Vol. 73(A), p. 278, 1991
(4) Surgery of the Knee (Third Edition). Chapter 2: Anatomy. John Insall and W. Norman Scott, Eds., New York: Churchill Livingstone, p. 44, 2001
(5) 'Biomechanical Analysis of Human Ligament Grafts Used in Knee-Ligament Repairs and Reconstructions', J Bone Joint Surg Am, Vol. 66, p. 344, 1984
(6) The Lower Extremity and Spine in Sports Medicine. Volume 1, Chapter 39: Arthroscopic Cruciate Reconstruction. James Nicholas and Elliott Hershman, Eds., St. Louis, Mosby, p. 865, 1995
(7) 'Regeneration of the Semitendinosis and Gracilis Following Their Transection for Repair of the Anterior Cruciate Ligament', American Journal of Sports Medicine, Vol. 17, p. 709, 1989
(8) 'Human Immunodeficiency Virus Cultured from Bone: Implications for Transplantation', Clinical Orthopaedics, Vol. 251, p. 249, 1990
(9) 'Retrospective Direct Comparison of Three Intraarticular Anterior Cruciate Ligament Reconstructions', American Journal of Sports Medicine, Vol. 19(6), p. 596, 1991

acl reconstruction surgery, anterior cruciate ligament, reconstructive surgery, bone-patellar-tendon-bone reconstruction, Noyes's 'rule of thirds', patellar fracture, osteoarthrosis, ACL reconstruction with a semitendinosis, gracilis-semitendinosis-tendon technique, allograft reconstruction, synthetic replacement