Piero Volpi (ed.)Arthroscopy and Sport Injuries10.1007/978-3-319-14815-1_7

7. Return to Sport (General Aspects)

Ryan R. Sullivan¹, Antony Hazel¹, Sarunas Skadas¹ and Pietro M. Tonino¹

(1)

Department of Orthopaedic Surgery and Rehabilitation, Loyola University Medical Center, 2160 S. First Ave, Maguire Building Suite 1700, Maywood, IL 60153, USA

Ryan R. Sullivan

Email: rysullivan@lumc.edu

Antony Hazel

Email: ahazel@lumc.edu

Sarunas Skadas

Email: sskadas@lumc.edu

Pietro M. Tonino (Corresponding author)

Email: ptonino@lumc.edu

Keywords

ACL reconstructionReturn to sportCriteria/goal-based progression through rehabilitationPhysical recovery following ACL reconstructionPsychological recovery following ACL reconstruction

7.1 Introduction

As the population has become more active, anterior cruciate ligament (ACL) injuries have become more common. More and more individuals are choosing ACL reconstruction in order to attempt to return to their previous functional level. Much of the previous research regarding ACL reconstruction has revolved around optimizing surgical variables. A new focus has arisen attempting to determine when patients are ready to return to full activity. ACL grafts continue to mature after one year which is well past the time when most athletes are cleared to return [1, 2]. A balance exists in trying to allow for one’s biology to recover and heal from surgery while minimizing the time off. The following chapter explores the multiple factors that contribute to one’s ability to return to sport and the current tools available that can assist in making an accurate determination of an athlete’s readiness.

7.2 Physical Recovery

Successful recovery from ACL reconstruction begins with prehabilitation. Prior to surgery, the goals are to reduce swelling, inflammation, and pain which can limit knee range of motion (ROM) and inhibit muscle activation. Knee ROM is optimized with emphasis on full knee extension; and muscle strength maximized to help prevent atrophy [3, 4]. This is important for minimizing postoperative complications such as arthrofibrosis and persistent muscle weakness [3–6].

After surgery, the focus of rehabilitation is to regain strength, dynamic control, and functional stability on the injured extremity. Mechanical and dynamic knee stability is an important indicator of the ability to protect the healing graft. Before initiating specific sport training, certain milestones must be met to verify that the above have been achieved.

The patient’s history and physical exam are important in assessing stability. Patients often report episodes of “giving way” in the affected extremity when laxity is present. The pivot shift test and Lachman’s maneuver can also identify laxity within the grafts and thus patients who may be susceptible to reinjury [7, 8]. Increased laxity is important to recognize because it may be associated with altered contact loading of the articular surfaces and inferior structural properties of the graft [4, 9].

There are other more functional means to assess stability and a “knee at risk.” The squat and hold is one such test, requiring the athlete to hold a one-legged stance position with the knee in flexion to accentuate any residual strength deficits in the injured limb. Balance tests on an unstable platform can be used to assess overall postural stability and neuromuscular control deficits.

After sufficient knee stability has been demonstrated, patients progress to more advanced assessments that are designed to evaluate strength, coordination, functional stability, and comparison between the injured and uninjured limbs. These factors are indicators of neuromuscular control, which along with biomechanical asymmetry is a main contributor to primary and secondary ACL injury risk when deficient [7, 10–12].

Test results are often reported using a limb symmetry index (LSI), which is a ratio comparing the injured limb to the uninjured limb. Normative data on healthy subjects has shown an LSI of 85 % or greater to be consistent with normal strength and function, and most researchers report an LSI result of 85–90 % for each individual test as satisfactory to allow return to sport [5, 10, 13].

The assessment of strength is a key component when making the decision for return to sport [7, 10, 14–16]. Adequate quadriceps strength is necessary for force generation and attenuation about the knee as well as for function and gait restoration [10, 17]. Hamstring strength is critical for knee stabilization and landing mechanics [10, 15, 16, 18–20]. Strength can be measured with isokinetic knee flexion and extension tests, squats, and leg press. The ratio of hamstring to quadriceps (H:Q) strength within the injured limb is an important indicator of the hamstrings’ ability to decrease anterior tibial displacement and shear generated by the anterior pull of the quadriceps, subsequently reducing ACL strain and injury risk [10, 15, 18–20]. The H:Q ratio is a main determinant for primary ACL injury risk and also correlates to self-reported knee function [10, 21].

Hip abduction strength can also be assessed as it influences initial contact and knee valgus angles during drop-landing tasks. Altered hip kinematics and excessive knee valgus angles predict secondary ACL injury after reconstruction [12]. Power measurements can also be employed as a more specific gauge of the use of strength in sports, as the rapid production of force is important for performance and injury protection [22].

The restoration of neuromuscular control after ACL reconstruction depends not only on muscle strength but also on dynamic knee stability and limb performance symmetry, which aid in attaining successful functional, subjective, and return-to-sport outcomes [8, 10, 14, 23–25].

Hop tests are frequently instituted as a reliable measure of dynamic stability, reflecting integration of neuromuscular control, strength and power, endurance, and confidence in the limb [26]. Single-leg hop tests correlate with quadriceps strength, limb stability, subjective outcomes, and return-to-sport outcomes [14, 23, 24, 27–31]. Athletes who attain hop test results greater than 85 % of the contralateral extremity are significantly more likely to return to pre-injury level of sports at 1 year [32]. Frequently used hop tests include single-limb hop for distance, single-limb crossover hop for distance, single-limb triple hop for distance, single-limb timed hop for distance, and single-limb vertical power hop.

Additional studies have found that hop testing under fatigued conditions affords a more sensitive way to detect persistent functional limitations. In one study, only two-thirds of athletes performed satisfactorily under fatigued conditions at 1 year following ACL reconstruction despite demonstrating greater than 90 % hop capacity when not fatigued [33]. A single-leg hop test at 11 months postoperatively preceded by pre-exhaustion exercise has been shown to increase the sensitivity of the single-leg hop. One study reported a greater than 90 % success rate under non-fatigued conditions which declined to 68 % demonstrating abnormal hop symmetry following a pre-exhaustion exercise protocol [34]. Testing after the lower extremity is fatigued to failure may be more pertinent measure of endurance, replicating the events during sports participation.

A battery of tests possesses a greater ability than any single test alone to discriminate between injured and non-injured sides [35–37]. A prospective cohort study [35] found that at 24 months postoperatively, rates of attaining a 90 % LSI for strength and hop test batteries were 48 and 44 %, respectively, compared to more than 90 % when the tests were evaluated individually. When combining the strength and hop test batteries, success rates were only 22 %. The combination of single-leg hop for distance, vertical jump, and side hop was found to possess a sensitivity of 91 % and accuracy of 88 % for detecting abnormal limb symmetry in patients who underwent ACL reconstruction 6 months previously [37]. In another study, evaluating a strength test battery of knee extension, knee flexion, and leg press was found to be more sensitive compared with any of the three tests individually. Eighty-six percent of patients had abnormal limb symmetry in knee extension at 6 months postoperatively, along with 42 % of patients in knee flexion and 61 % in leg press [36]. When combined, 95 % of patients did not meet the requirements of greater than 90 % LSI for all three tests. Another group found that test sensitivity improved from 52 to 62 % by using two hop tests rather than one [38].

In addition to objective measures, subjective self-evaluation of knee function is an important determinant of an athlete’s ability to return to sport. Self-reporting of knee function, instability, and knee symptoms such as pain and swelling are often the factors most strongly associated with return-to-sport status [23, 39, 40]. There are numerous instruments used to assess subjective outcomes in patients with knee injuries, such as the commonly used scales International Knee Documentation Committee (IKDC) Subjective Knee Form, Lysholm knee scale, and the Cincinnati knee score. These scales are reliable and valid for evaluation of postoperative symptoms, function, and sports activity after an ACL reconstruction [7, 41–43]. The IKDC is effective and responsive to changes in perceived function over time [7, 44, 45].

7.3 Psychological Recovery

Many athletes who achieve normal knee function following reconstruction are unable to return to pre-injury levels because of psychological factors [46]. Up to 30 % of athletes who do not return report fear of reinjury as the primary reason [40, 46, 47]. Psychological readiness to return to sport may lag behind physical readiness. Return prior to psychological readiness can lead to worsening psychological state as well as decreased performance and subsequent reinjury [48–50]. Recognition of maladaptive psychological processes that may negatively affect an athlete’s rehabilitation is therefore essential.

There are a number of tools for assessing psychological recovery after ACL reconstruction. One of the most widely used postsurgical psychological assessments is the Tampa Scale of Kinesiophobia (TSK), which measures fear of movement and reinjury [47, 51]. The TSK and its shortened version more specific to ACL-reconstructed athletes is a survey that demonstrates prognostic value in ACL-reconstructed athletes, predicting return to sport within 12 months when measured at 4 months postoperatively [48, 51]. Another scale, the 12-item ACL-Return to Sport after Injury (ACL-RSI), measures frustration, fear, and confidence. The value of ACL-RSI is that it can be used preoperatively as well as at 4–6 months postoperatively as a predictor of return to sport within 12 months [48, 50, 52]. Other assessment scales measure additional psychological aspects such as the emotional response to injury, an athlete’s self-efficacy, confidence, motivation, perception of control, and pain-catastrophizing behavior. These are important determinants of rehabilitation effort, perceived and actual rehabilitation outcomes, objective and subjective knee function, and return to pre-injury sports activity level [51, 53, 54].

Surgeons need to recognize these psychological issues in order to understand the postoperative recovery process and counsel the athlete as needed as they attempt a return to sport. Screening for maladaptive psychological responses to identify at-risk athletes should be performed early on so that psychological recovery can parallel physical rehabilitation. Interventions that may positively influence psychological recovery include peer modeling, relaxation, guided imagery, goal setting, provision of clear postoperative and rehabilitation instructions, and improvement of coping skills and self-efficacy beliefs [55]. Future research into improving psychological readiness should include further development of interventions specific to ACL reconstruction rehabilitation to provide standardized instruments for improving rehabilitation and return to sport.

7.4 Discussion

Historically, return-to-sport clearance has been based on time from surgery. Many athletes received clearance around the 6-month time point to allow for postoperative healing while progressing through rehabilitation [10, 25]. However, athletes recover and progress through rehabilitation at variable rates. When assessed after sports participation, many athletes demonstrate functional deficits that are independent of time from surgery [56]. Therefore, the return-to-sport decision should be based on the individual athlete’s recovery and monitored using specified objective and subjective criteria. Objective data should be used to ensure that the athlete possesses adequate knee strength and stability to protect the healing graft and safely return to sport. These measures help guide the athlete to provide a goal-oriented rehabilitation. These criteria include achievement of symmetrical joint motion, strength, and functional performance between the injured and uninjured limbs, as well as subjective and psychological scores within the norm, prior to return to sport.

Different centers have studied the benchmarks required for an athlete to return to sport. One group advocates return to sport when full ROM is achieved, hop and strength test results are at least 85 % of the uninjured extremity, the hamstring/quadriceps strength ratio is less than 15 % difference compared to the uninjured side, and the patient tolerates sport-specific activities with no increase in pain or swelling [57]. Another proposes criteria including a LSI of 90 % for strength and functional testing as well as a score of 90 % on two self-reported outcome measures. They saw 40 % of ACL-reconstructed athletes cleared for return to practice at 6 months and 73 % cleared at 12 months [5]. Those who did not meet criteria continued rehabilitation, focusing on areas in which they were deficient. It is important to note that although correlations exist between strength and stability testing with subjective and functional outcomes, there is a lack of data directly associating success in these areas with reduced risk of reinjury upon return to sport. Tests that accurately define adequate neuromuscular control are not clear [7, 10]. It is conceivable that normal strength and function promote neuromuscular control and graft protection leading to lower reinjury rate; therefore current testing methods evaluate these factors. However, future outcome research is needed to correlate successful strength and functional indices with lower risk of reinjury.

The ability to return to sport following ACL reconstruction requires the restoration of physical function and psychological readiness in addition to specific patient, sport, injury, and rehabilitation factors. Premature return to sport may predispose the patient to further injury, with incidence of reinjury to the graft or rupture of the contralateral ACL ranging from 6 to 32 % [10]. For athletes who successfully return to activity, one in four will go on to a second knee injury [10]. Of the many risk factors for graft injury or contralateral ACL injury, history of ACL reconstruction and return to high-level competitive pivoting/cutting/jumping sports are among the greatest contributors [10, 11, 58]. Primarily implicated in this increased risk is the asymmetric and impaired neuromuscular control and lower extremity biomechanics that both lead to and result from the initial ACL injury [10–12]. Injury prevention programs emphasizing neuromuscular training to reduce these modifiable impairments can potentially reduce the rate of ACL injuries by up to 50 % [59]. Plyometric testing such as drop vertical jumps and tuck jumps can be used to assess abnormalities in neuromuscular control, balance, symmetrical limb loading, force contribution, and force attenuation [5, 7, 10]. This allows observation of asymmetries in lower extremity positioning and movement as well as detrimental biomechanics such as decreased knee flexion and valgus knee angles upon landing that increase ACL shear and strain forces and risk of ACL injury [11, 12, 20, 60]. The evaluator can then direct the correction of these deficiencies and improvement of technique and limb symmetry [5, 7, 12]. Incorporating serial functional and strength testing is essential to decrease the risk of secondary ACL injury and upon reintegration into sport.

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