Anterior Cruciate Ligament Injuries P

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Introduction

An anterior cruciate ligament (ACL) injury represents one of the most dra- matic events in the career of a soccer player. This ligament acts as a restrain to the anterior tibial translation during twisting, jumping, and cutting manoeuvres. In case of a tear, it cannot heal, and surgical reconstruction is mandatory to recover the full function of the knee and allow the player to go back to the game. Unfortunately, we still do not know if restoration of ade- quate function of the knee changes the long-term destiny of this injury.

Nevertheless, the increased number of people of both genders and all ages involved in soccer activities around the world, changes in rules with a pro- gressive increase in the speed of the game, and the great diffusion of this sport activity, mainly in Europe, has turned the ACL in the most extensively studied ligament of the body. In this chapter, we try to concentrate on what we currently know about ACL injuries in terms of incidence, risk factors, nat- ural history, clinical evaluation, surgical treatment, and outcome results.

Incidence

Up to one fifth of football injuries involve the knee joint [1]. In most cases,

sprains or overuse injuries are encountered; however, major injuries such as

ACL tears are not infrequent, and they seriously affect a player’s career, with

both short- and long-term consequences. Bjordal et al. [2] retrospectively

reviewed ACL injuries that occurred in their local community in Norway over

a period of 10 years to 176 players involved in organised football. An overall

incidence of 0.063 injuries per 1,000 game hours was recorded. Women had a

significantly higher incidence (0.1 injuries per 1,000 game hours) than men

(0.05). Overall, ACL injury incidence during training was significantly lower

(0.013) than during games (0.063). Giza et al. [3] in professional female foot-

ball players observed as well that the risk of ACL injury is doubled in games with respect to training. Gwinn et al. [4] calculated the incidence of ACL injury in all US Naval Academy midshipmen over 6 years both at a profes- sional and amateur level. In intercollegiate football, the male injury rate was 0.08 per 1,000 athletic exposures and was 9 times inferior to women’s risk.

When intramural coed soccer was examined, male injury risk was higher (0.3 injuries per 1,000 exposures), and the female/male ratio inferior (6x), thus suggesting that a specific training at a higher level protects the knee joint.

Arendt and Dick [1] examined a larger sample consisting of 739 National Collegiate Athletic Association (NCAA) football teams over a 5-year period (1989–1993). ACL injury incidence in men was 0.13 and was significantly lower than in women (0.31). The same group of researchers [5] more recent- ly extended their investigation on the same sample teams to year 2002. A 13- year time interval was therefore examined. In the final year of the study peri- od, ACL injury incidence in men was significantly lower (0.07 injuries per 1,000 h exposure) than in the first year (0.12). This trend was not observed in women, which in 2002 still showed an incidence of 0.28 injuries per 1,000 h of exposure.

Mechanism of Injury

Most ACL lesions in football are caused by non-contact injuries. Agel et al. [5]

in a 13-year study period found the incidence of non-contact injuries to vary from 28% to 85% in men and from 42% to 70% in women, with an average of 58% and 50% non-contact injuries for women and men, respectively. This dif- ference was statistically significant. Other investigators [2] in a smaller sam- ple found non-contact injuries to be 54% and 42% in men and women, respectively. Non-contact injuries are usually the result of a deceleration such as the one that occurs when a player wants to change direction. In this situa- tion, increased quadriceps contraction induces an anterior force, and if the tibia is externally rotated and a valgus moment is present, the ACL is partic- ularly at risk. A concomitant meniscal or medial collateral ligament lesion is likely to occur in such conditions.

An exclusively non-contact soccer injury mechanism is knee hyper-exten-

sion resulting from missing the ball while kicking. Contact injuries, on the

other hand, are mainly the result of tackling. Bjordal et al. [2] in their series

found that 58% and 42% of ACL injuries were due to tackling in women and

men, respectively. In men, most tackles (64%) were from the side. In women,

ACL injuries were due both to side (44%) and front (32%) tackles.

Risk Factors

The clear identification of ACL injury risk factors in football players is attrac- tive in the attempt to set up prevention strategies. At the same time, this task is quite challenging, as large series would be necessary to be prospectively examined, and the incidence of ACL injuries in football is quite limited [6].

Risk factors can be easily distinguished into modifiable and non-modifiable.

The main non-modifiable ACL injury risk factor is gender. As previously dis- cussed, female football players are at higher risk of experiencing an ACL injury during their career. A more narrow intercondylar notch, hormonal influences, and inadequate neuro-muscular control have been considered responsible of the higher propensity of female players to injuries [7]. The exact role and mechanism of hormones on the ACL has not been clarified, and controversial results have been presented. On the other hand, in recent years, great attention has been dedicated to understanding the neuro-muscu- lar control differences between men and women with the attempt to set up interventional strategies to prevent non-contact injuries. Women athletes have been found to have different landing and cutting patterns from men. In particular, women have the tendency to land with the knee more extended than do men, and in cutting manoeuvres, the knee is in a more extended, externally rotated, and valgus position than in men [8]. The recognition of these patterns should help to prevent injuries by instructing athletes and cor- recting their movement patterns.

Among non-modifiable risk factors is the importance of previous injuries, which has been emphasised by some. Arnason et al. [9] analysed injury data of 306 football players over one season in Iceland and recorded 5 ACL injuries with an overall incidence of 0.15 per 1,000 h of exposure. Though with multi- variate analysis no clear risk factor could be isolated due to the paucity of ACL lesions, players who sustained knee sprains had a significantly positive history of previous injuries. Chomiak et al. [10] followed 398 football players from the Czech Republic for 1 year and found that previous injuries or a pre- existing knee instability are predisposing factors to new knee injuries. In their series they also found that less-experienced soccer players had a higher incidence of ACL injuries.

Among the modifiable risk factors, the only significant correlation has

been identified with shoe design. Lambson et al. [11] compared 4 types of

football shoes and evaluated the incidence of ACL tears among 3,119 high

school football players during the 1989–1991 competitive seasons. They

found that longer, irregular peripheric cleats produced significantly higher

torsional resistance than the other designs with flatter cleats and were asso-

ciated with a significantly higher ACL injury rate.

Clinical Evaluation

A good diagnosis starts by obtaining a good history. ACL injury in most situ- ations is a major traumatic event with a characteristic history. The athlete usually describes the knee as “coming apart”, and in most cases, the injury type is non-contact. An audible “pop” is heard or felt in about 50% of cases.

An effusion secondary to bleeding occurs within 6–12 h after the injury; full weight bearing and full extension of the knee are usually difficult [12]. In acute injuries, physical examination could be difficult due to knee pain. The examiner should avoid performing potentially painful and unnecessary com- ponents of full knee examination and should concentrate only on ligament examination. A comfortable and relaxed patient is essential. We suggest eval- uating the uninjured knee first to gain patient confidence and obtain a base- line for comparison. The Lachman test is considered the most reliable and reproducible investigation method to confirm an ACL injury. In an acute set- ting and when performed correctly, this test has a sensitivity of 87–98% for detecting an ACL tear [13]. An increased anterior tibial translation and a soft or absent end point compared with the opposite healthy knee can confirm the ACL injury. Another important test is the pivot-shift test. However, creating this can be difficult in an acute setting secondary to patient guarding. This test can provide additional confirmation of ACL injury, however.

After the ACL has been evaluated, the collateral ligaments, the posterior cruciate ligament, and the menisci need to be assessed for injury. In some cases, the status of the ACL may remain in question at the conclusion of a detailed history and examination. In these cases, it is helpful to reduce pain and swelling and to re-evaluate the knee several days later. Imaging should include standard weight-bearing anteroposterior (AP) view, a lateral view, and a patellofemoral Merchant view. Most often, plain x-rays are normal;

however, an avulsion or an osteochondral fracture may be seen. A Segond fracture may be seen on AP view and is considered highly predictive of an ACL injury. Magnetic resonance imaging (MRI) usually is not needed to eval- uate an acute knee injury because of the accuracy of the history and physical examination. More important than confirming an ACL injury is the addition- al information that can be obtained with regard to the menisci, the subchon- dral bone, and the other ligamentous structures. In chronic ACL-deficient knees, an MRI can detect associated meniscal injuries or a new bone bruise from a recent giving way.

Natural History

Several studies have attempted to define the disability, associated pathologies,

and degenerative changes of the knee after an isolated untreated lesion of the

ACL. However, this is a controversial issue because most studies do not reflect the true natural history of the ACL-deficient knee due to the fact that only symptomatic knees have been observed and followed up. Moreover, many studies have short or incomplete follow-ups, without objective documenta- tion, or flawed by inconsistent and varying treatment between cases.

Nevertheless, even in studies where the documentation is incomplete, impor- tant information can be obtained regarding functional impairment, incidence of associated injuries, and effectiveness of rehabilitation regimens.

A recent review of the literature [14] considering only studies with more than 5-years follow-up, revealled that radiographic degenerative arthritis sig- nificantly increases after all knee injuries compared with the uninjured joint of the same patient. Partial or total ruptures of the ACL without major con- comitant injuries seem to increase the risk 10-fold (15–20% incidence of degenerative arthritis) compared with an age-matched, un-injured popula- tion. Thus, an ACL injury combined with a significant meniscal tear or other knee ligament injuries results in knee arthritis in most patients. Ten to 20 years after ACL injury, knee arthritis often presents a slight joint-space nar- rowing and usually is not associated with major clinical symptoms. The pro- gression of the arthritis is slow, and in some cases, the condition seems to remain stable. Time is an important determinant for the degree of arthritis, and other significant symptoms requiring treatment may be delayed and only encountered more than 30 years from the initial trauma. However, it must be noted that in the case of ACL injury, most patients are not able to return to the un-restricted pre-injury level of function and complain of pain, swelling, and giving-way symptoms during sports activities [15–17].

In “cutting-sports performers”, such as soccer players, the persistence of sports activity at the same intensity level is a high risk factor for additional ipsilateral knee lesions, most commonly meniscal or cartilage tears, with a dramatic increase in the incidence of early degenerative arthritis [18]. Von Porat el al. [19], evaluating 154 soccer athletes 14 years after an anterior cru- ciate injury, found that only 8% were still participating in organised soccer;

80% reported reduced activity level, and of these, the majority (69%) report- ed the knee injury as the cause. No difference in radiographic outcome was determined between those treated within or without surgery. Radiographic changes were found in 78% of the injured knees, and of these, radiographic osteoarthritis equivalent to Kellgren and Lawrence’s grade 2 was seen in 41%.

Male soccer players have an increased risk of knee osteoarthritis [18– 21].

Injuries to the menisci and the cruciate ligaments are believed to be the main

reason for this, but when injuries are excluded, a relation between elite soccer

and osteoarthritis persists [21]. This means that a player who returns to soc-

cer after an ACL injury has an even higher risk of osteoarthritis both because

of soccer itself and because of the injury.

Treatment of the Injury

A unified treatment approach to ACL injuries is yet to be defined. Young and motivated athletes most often desire to recover pre-injury sport activity and are unable to do so unless surgical reconstruction allows them to achieve rea- sonable knee stability. Older and recreational athletes often prefer to decrease their activity level, thus avoiding giving-way episodes, and to postpone surgi- cal reconstruction, which will keep them away from work for a protracted time.

Unfortunately, whether a conservative or a surgical treatment is used, the natural history of an ACL-deficient knee seems to show that occasional episodes of giving way are still present in all patients and that it is not possi- ble to prevent early joint degeneration in about one half of those knees. Thus, at the present time, counselling patients as to the most appropriate treatment can only be based on factors that are known to place the knee at risk for fur- ther injury and relating those factors to the individual patient.

Many patients who tear the ACL will elect not to undergo reconstruction.

For the skeletally immature athlete, this decision is only a temporary one. The adult, however, may have few limitations during sport or daily living activities and may feel no need to undergo surgical treatment. The main key for the appropriate treatment is the patient’s desire and motivation to recover soccer activity at the same level as prior to the knee injury.

Regardless of the situation, the initial management of an acute ACL tear involves decreasing the patient’s pain and swelling, followed by restoring full range of motion with rest, ice, isometric, and extension exercises.

Strengthening exercises, with closed kinetic chain rehabilitation programs, begin once extension is restored and flexion exceeds 110°. In the last phase of the rehabilitation program, the patient is progressively introduced to activi- ties that are believed to be safe based on the patient’s confidence and knee stability. Returning to high-risk activities usually is not possible without sus- taining additional giving-way episodes.

Surgical treatment is reserved for those players who want to continue playing soccer. The goals of ACL reconstruction are to re-establish a normal knee with full range of motion, good stability, and strength and to prevent additional meniscal and/or chondral damage. To achieve those goals, a great variety of surgical techniques have been developed throughout the last 40 years. The most popular is single-bundle intra-articular ACL reconstruction with tibial and femoral bony tunnels. This technique aims to recreate one of the two major fibre bundles of the ACL: the anteromedial (AM) bundle. This is the most isometric bundle of the native ACL and shows quite constant ten- sion behaviour throughout the range of motion.

Several different type of grafts have also been employed for ACL recon-

struction, and actually, the most accepted ones are autografts – including the central third of the patellar tendon, the quadriceps tendon, and the hamstring tendons – and fresh-frozen allografts, represented by the central third of the patellar tendon and the tibialis anterior tendon. Based on the allograft employed, a wide variety of fixation methods have been introduced to achieve rigid fixation of the graft to the bone. However, apart from the technique employed, the main principles for a successful ACL reconstruction are a graft showing biomechanical properties similar to those of the native ACL, a pre- cise placement of the bony tunnels, and a strong and rigid fixation of the graft in the correct tension.

Despite the high rate of satisfactory results achieved with the single-bun- dle technique, and though successful in reducing the anterior drawer, recent- ly, several investigators [22–26] have complained about the inability of this type of reconstruction to completely restore the rotational laxity and avoid the pivot-shift phenomenon. Single-bundle reconstruction has been devel- oped in an attempt to replicate the function of the more isometric AM bun- dle. In this reconstruction technique, the femoral tunnel is close to the roof of the femoral inter-condylar notch. Consequently, it is also close to the axis of axial rotation of the tibia; thus, the graft is insufficient to resist externally applied rotatory loads. Recent laboratory studies using different investigation devices [22–26] demonstrated that the single-bundle reconstruction is cer- tainly effective in restoring tibiofemoral anterior laxity in response to a tibial anterior translation force, but it is not so effective in reducing the coupled anterior tibial translation and rotation resulting from a combined tibial val- gus and internal rotation torque. Based on these findings, it has been sug- gested that both the AM and the posterolateral (PL) bundles should be recon- structed. The PL bundle resists the majority of the anterior draw force in the native ACL [27] and in ACL reconstructions [28] when the knee is almost fully extended.

Laboratory studies comparing single-bundle to double-bundle ACL reconstruction have reported a significant superiority of the double-bundle reconstruction in restoring normal anterior tibial translation and avoiding the pivot-shift phenomenon [28–30]. Unfortunately, to date in the literature, all clinical studies [31–33] have failed to demonstrate a clear improvement in terms of anterior knee stability, incidence of residual pivot-shift, and postop- erative proprioceptive function. Double-bundle ACL reconstruction is cer- tainly an appealing technique, but further studies are needed to support its routine clinical use.

Postoperative rehabilitation is as important as the surgical technique to achieve a stable knee. An adequate rehabilitation program should emphasise rapid recovery of the full range of motion, fighting with pain and swelling.

Usually, the graft needs about 2–3 months to incorporate into the bone, and

the remodelling process allows the graft to sustain vigorous loads only after 6 months from surgery. Strengthening exercises should start when the full range of motion has been recovered and the swelling has disappeared. It is important to avoid exercises that could apply excessive tension on the graft.

In the first postoperative month, it is safe to start with isometric exercises; in the second postoperative month, it is possible to introduce close kinetic chain exercises; at the beginning of the third postoperative month, open kinetic chain exercises can be gradually added. For soccer players, return to sport- specific training should not be allowed until up to the fourth or fifth month postoperatively while return to competition should be delayed to the sixth or eighth month postoperatively based on the grade of knee stability and mus- cular strength recovered.

Outcome Results

A vast number of studies reporting outcome results of ACL reconstruction have been published in the literature. While after an ACL injury the return rate to cutting sports is low with conservative treatment [16, 17], the mid- to long-term results of operative treatment with the central third of the patellar tendon and hamstring tendon autografts are good with regard to stability improvement and the ability to return to demanding knee activities [34–36].

Most reports on ACL reconstructions, however, deal with heterogeneous pop- ulations, with varying demands on knee function and different levels of sport performance. Soccer players represent a homogeneous group with similar and high demands on knee function, and only few papers [37, 38] report out- come results of ACL reconstruction in this sport category.

In a questionnaire survey of ACL injuries reported to Swedish insurance

companies, Roos et al. [38] found that only 26% of ACL-reconstructed players

were still active in soccer after 7 years, and none of the élite players were

active at the same level. Interestingly, there was no difference in the return

rate to soccer after either surgical or conservative treatment. The majority of

players give up the sport for social reasons, and this is very likely 7 years after

an injury. More recently, Bak et al. [37], evaluating 132 soccer players who

underwent primary ACL reconstruction with an iliotibial band autograft,

found that the majority of players (68%) were still active at a median of 4

years after reconstruction, and only 11% of those who were not active at the

follow-up claimed that knee problems were the cause. Moreover, evaluating

gender differences, an unacceptable rerupture rate was seen in female soccer

players. Women participating in cutting sports are subjected to a significant-

ly higher risk of sustaining an ACL injury than are men [5] and are therefore

probably also at higher risk of graft failure.

Long-term radiographic analysis showed no differences between men and women in terms of osteoarthritis risk. More than 10 years from ACL injury, both genders showed an high prevalence of either radiographic or sympto- matic knee osteoarthritis. Lohmander et al. [39], investigating 103 female soc- cer players 12 years after an ACL injury, reported that 82% had radiographic changes in their index knee, and 51% fulfilled the criteria for radiographic knee osteoarthritis. Seventy-five percent reported having knee-related symp- toms that affected their quality of life, and 42% were considered to have symptomatic radiographic knee osteoarthritis. Slightly more than 60% had undergone reconstructive surgery of the ACL. Using multi-variate analyses, surgical reconstruction was found to have no significant influence on knee symptoms. Von Porat et al. [19], in a cohort of 154 male soccer players 14 years after the initial ACL injury, found radiographic changes in 78% of injured knees. No difference on radiographic outcome was determined between those treated with or without surgery. Only 12 (8%) of the 154 par- ticipants were still participating in organised soccer.

Conclusion

Soccer is the most popular sport worldwide with around 200 million licensed players according to the Federation of International Football Associations (FIFA). However, this is a high-risk sports activity for the integrity of the ACL.

Many factors have been recognized that increase the risk of ACL injury, par- ticularly in women. The only consistent solution to regain knee stability and to return to the sport at the pre-injury activity level is surgical reconstruc- tion. However, reconstruction, though effective in restoring short-term knee function, is not able to prevent long-term joint degeneration. Efforts should be made to obtain a precise definition of the injury mechanism and how to prevent it. Today, prevention represents the only chance to guarantee a soccer player a long career.

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