Postoperative Rehabilitation for Pediatric and Adolescent Anterior Cruciate Ligament Reconstruction

Jessica Graziano

With sports participation and specialization on the rise, intrasubstance tears of the anterior cruciate ligament (ACL) in children are now being seen with greater frequency.¹,² The literature has recently reported on the steady increase in ACL injury in the skeletally immature athlete and has extensively reported on the high incidence in the adolescent female athlete.³,⁴,⁵ Early specialization, maturation, high-risk movement patterns, and an inadequate strength base all contribute to increased injury rates as well as impact postoperative recovery and decision making.²,⁴,⁶,⁷,⁸,⁹

Postoperative rehabilitation involves progressing athletes through phases of strength and functional mobility as well as addressing growth-related changes that impact postural alignment. In addition, young athletes are returning to higher levels of play with demands for peak performance at earlier ages, causing subsequent higher rates of revision anterior cruciate ligament reconstructions (ACLR).²,¹⁰ Movement patterns play a critical role in ACL injury because they may influence anterior tibial shear force, which strains the ACL.³,⁴,⁸ Therefore, emphasis should be placed on refining movement skills in the final phase of rehabilitation to reduce reinjury risk.

THE EFFECT OF GRAFT SELECTION ON REHABILITATION

In order to reduce reinjury rates, postoperative progression should consider not only the individual’s strength but also differences in graft selection and fixation strength. If an athlete is advanced to activities involving excessive loading of the knee, such as plyometrics and running, prior to adequate healing time or without an appropriate strength base to meet the demands of the activity, delayed healing and elongation of the graft may lead to chronic instability.¹¹

The most commonly used graft tissues in young athletes are autogenous patellar bone-tendon-bone¹²,¹³ and autogenous hamstring tendons.¹⁴,¹⁵,¹⁶ Bone-to-bone healing in the osseous tunnel for patellar tendon grafts occur in approximately 8 weeks. Healing of tendon to bone for hamstring autografts takes approximately 12 weeks.¹⁷,¹⁸ Therefore, our rehabilitation progression for hamstring or semitendinosus grafts tends to be less aggressive, and return to running, plyometrics, and sports is slightly slower.¹⁹ In addition, it is important to note that the graft’s strength may reach its weakest point at approximately 6 to 8 weeks postoperatively secondary to graft remodeling.¹⁹,²⁰,²¹,²² Although controlled loading in the early phases is important to enhance ligament and tendon healing, excessive loading can damage the healing graft and lead to graft elongation.²¹,²²,²³,²⁴,²⁵ Unfortunately, there is limited data in humans that makes determining timing and optimal loading on healing ACL reconstructions difficult to determine.²³,²⁴,²⁵

Multiple techniques for surgical stabilization of the ACL-deficient knee in young athletes have been described. The guidelines to be discussed are a criterion-based progression and take into account general graft healing and incorporate strategies to address physiologic changes incurred by growth and maturation. Surgeon preference for range of motion (ROM) and weight bearing should be respected in the initial acute phase.

REHABILITATION CONSIDERATIONS FOR THE PEDIATRIC AND ADOLESCENT ATHLETE

Advances in graft reconstruction techniques and fixation methods have significantly improved surgical success with ACLR for young athletes.²⁵,²⁶,²⁷,²⁸ Therefore, the potential for an athlete to return to play without reinjury has shifted to be more determined by differences in rehabilitation than by surgical procedure.¹¹,²⁷,²⁸,²⁹

Successful functional outcomes critically depend on a scientifically based rehabilitation program that considers graft healing with respect to joint loading to prevent graft elongation. In addition, outcomes depend on the effects of growth spurts and maturation that have been associated with deficits in core strength, coordination, and neuromuscular control secondary to increased bony lever arms and changes in center of body mass.³,⁶,⁹ A patient may demonstrate proper alignment and neuromuscular control with movement in the early phases of rehabilitation but may need to revisit a movement later on secondary to a growth spurt that affected their center of mass as well as body awareness and alignment.³,⁶

The guidelines to be discussed are the Hospital for Special Surgery’s (HSS) ACLR guidelines for the all-epiphyseal technique with hamstring autograft. Special considerations regarding the autogenous patellar tendon graft will be presented for the adolescent population. This is a criterion-based progression, which respects general graft healing and incorporates strategies to address physiologic changes incurred by this special population to improve quality of movement. The decision to return to play is made as a collaborative team effort with the physician, physical therapist, trainer, and coach and is based on both qualitative and quantitative data regarding sports readiness. Surgeon preference for ROM and weight bearing should be respected in the initial acute phase as well as concomitant injury.

POSTOPERATIVE PHASE 1 (WEEKS 0 TO 4): PROTECTION PHASE

Rehabilitation begins immediately after surgery. Patients typically remain in the hospital overnight for observation to allow for control of activity level, pain, and swelling and ensure appropriate start of rehabilitation. If apprehensive with ROM exercises, a continuous passive motion machine is initiated from 0 to 45 degrees while the patient is at the hospital. The initial postoperative visit is vital in establishing a rapport and trust with the patient and their caregivers. Children may be anxious and guarded secondary to pain; therefore, trust needs to be established to create an optimal therapeutic environment.

Rehabilitation in the first month places significant emphasis on protection of the surgical repair, prevention of muscle inhibition caused by effusion, and prevention of postsurgical complications such as arthrofibrosis. The goals are regaining knee extension to 0 degrees, progressive weight bearing, controlling postoperative effusion, gradually restoring flexion ROM, and progressing quadriceps reeducation (Table 12.1).

TABLE 12.1 Phase 1: Protection Phase (Weeks 0-4)

Goals

Knee extension to 0 degrees
Flexion ROM ˜90 degrees
Control postoperative effusion/pain
Straight-leg raise without quadriceps lag
WBAT with crutches

Criteria to Progress into Phase 2

Zero degrees of knee extension
Improved quadriceps strength with ability to perform a straightleg raise without a quadriceps lag
At least 90 degrees of flexion ROM
Able to demonstrate unilateral (involved limb) weight bearing pain-free

Treatment Recommendations

Modalities for Postoperative Pain and Effusion

Controlling postoperative pain and effusion is crucial secondary to their role in muscle inhibition.³⁰,³¹,³² Treatment options for swelling include cryotherapy and joint compression through the use of compression wrap. Cryotherapy, electrical stimulation, and passive range of motion (PROM) may reduce pain.¹⁹,³² In contrast, ultrasound should not be used on the skeletally immature athlete’s joint secondary to contraindications on growth plates.³²

The speed of weight-bearing progression and joint loading may affect pain and swelling. In general, we recommend our patients stay out of school for 3 to 5 days to minimize pain and effusion as well as use bilateral upper extremity crutches for at least 4 weeks to control loading of the knee joint.

Bracing and Ambulation

Advanced fixation techniques allow for immediate weight bearing. Postoperatively, partial weight bearing is instructed with a hinged brace locked in extension to emphasize full knee extension and assist while the quadriceps is inhibited.¹⁷,³³,³⁴ Studies have demonstrated improved functional knee scores and proprioception with brace use after surgery.³³,³⁴

The athletes are advancing to weight bearing as tolerated (WBAT) with an assistive device over the next 2 weeks. Mechanical loading of the knee is progressed with the use of an assistive device over the first 4 to 6 weeks to allow the knee joint to acclimate to increased loads with minimal pain and effusion.

Brace education is reviewed on the initial visit with both the patient and caregiver secondary to its importance for graft protection and maintenance of knee extension ROM. The clinician should encourage frequent brace checks throughout the day as the brace may loosen and slide distally, facilitating a flexed knee gait, which may cause loss of knee extension.

Range of Motion

ROM may begin immediately secondary to graft placement in the native footprint of the ACL²⁷ and is strongly encouraged to minimize the effects of immobilization such as excessive collagen formation.³⁵,³⁶,³⁷ Full passive knee extension is emphasized while flexion is gradually restored. Extension is critical for normalized gait.³⁸ Flexion contractures cause excessive loading on the patellofemoral joint, leading to pain and quadriceps weakness.³⁸,³⁹

Specific exercises targeted toward achieving knee extension are supine hamstring stretches, gastrocnemius stretches with a towel, and towel roll extension. For towel roll extensions, a towel roll is placed under the patient’s heel/ankle while lying supine with a low-load, long-duration stretch.

Flexion ROM is gradually progressed and depends on the individual’s response to surgery as well as apprehension and age. Constant reassurance should be provided to the child that no damage will occur with ROM exercises. If persistent effusion exists, ROM may advance at a slower pace. ROM should progress gradually in phase 1 rather than aggressively at the expense of increased pain, effusion, and apprehension delaying recovery.

Figure 12.1. Short crank bike being used for ROM, strength, and endurance in phase 1.

Patient and caregiver are instructed on performing seated active-assisted knee flexion/passive extension exercises three to five times per day. When approximately 80 degrees of flexion ROM is achieved, a short crank bike (140 to 180 mm) may be used to develop endurance, strength, and ROM (Fig. 12.1). The shorter crank allows patients to cycle full circles prior to achieving appropriate ROM necessary to start on a standard bike (170 mm).

Patella Mobilizations

Patella mobilizations are performed to minimize decreased ROM and quadriceps inhibition.³⁹ Loss of mobility may result secondary to excessive scar tissue adhesions along the medial and lateral, fat pad retinacula, and harvesting the patellar tendon for the graft.³⁹,⁴⁰ If patellar mobility is lost, infrapatellar contractures may result in ROM complications and difficulty with quadriceps activation.³⁹,⁴⁰,⁴¹ Mobilizations are performed in both the medial/lateral and superior/inferior directions, especially for those with a patellar tendon autograft. Superior mobility of the patella is required for complete knee extension and inferior glides for flexion.³⁹,⁴⁰,⁴¹

Strengthening

Reestablishing voluntary quadriceps control is crucial. Quadriceps setting with a towel roll under the knee is used for reeducation and, when combined with neuromuscular electrical stimulation, has been found to be more efficient than exercise alone to improve strength.⁴² Once patients demonstrate good quad contraction, they are progressed to straight-leg raises with the brace locked until sufficient quadriceps control is demonstrated. When no quadriceps lag is demonstrated, they may perform straight-leg raises without the brace. When achieved with appropriate endurance, the brace may be unlocked for ambulation.

We recommend incorporating closed kinetic chain (CKC) leg press when ROM is greater than 90 degrees of flexion and quadriceps control improves. Leg press is performed bilaterally inside a pain-free arc (70 to 75 degrees) and advanced to a unilateral exercise using greater ROM in later phases. Closed kinetic exercises are used for strengthening in the early phases, as they have been shown to minimize stress to the ACL.¹⁹,²⁰

Proximal hip strength is crucial for stability as well as reducing loads at the knee.²,⁸,¹¹ Progressive resistance exercise can be performed with cuff weights and isotonic exercises. In later phases, core and proximal hip strength will be crucial for ensuring minimal valgus loading with dynamic activities.

Neuromuscular Training

Neuromuscular training is emphasized because balance deficits have been identified following ACL reconstruction as well as extensive reports in the literature regarding neuromuscular deficits being a risk factor for injury.³,⁸,⁴³,⁴⁴ A rocker board can be used as soon as the patient is 50% weight bearing. Training starts with basic weight shifting in both the medial/lateral direction. A Biodex Balance System (Biodex Medical Systems, Shirley, NY) tends to be fun for young patients and may be used to demonstrate weight shifting and weight bearing (Fig. 12.2). In addition, wall squats may be performed for joint repositioning and weight bearing as well. In later phases, squats may be progressed to unstable surfaces such as a tilt board once the patient exhibits good postural control and lower extremity alignment on solid surfaces.

Figure 12.2. Weight shifting and balance training being performed by an adolescent on the Biodex Balance System.

POSTOPERATIVE PHASE 2 (WEEKS 4 TO 8): INTERMEDIATE PROTECTION PHASE

In phase 2, the graft is not optimal. The literature has reported that the graft undergoes a period of necrosis, revascularization, and remodeling. Graft strength decreases during this period of necrosis and gradually increases as it remodels.¹²,¹⁴,¹⁶,⁴⁵ Constant reinforcement with activity modification is required to ensure the individual does not push past his or her physiologic capabilities injuring the graft.

The goals are continued emphasis on protection of the surgical repair, controlled effusion, flexion ROM, good patellar mobility, normalized gait, and the ability to ascend a 6- to 8-in step (height dependent) pain-free with good control (Table 12.2).

Treatment Recommendations

Modalities

Cryotherapy continues to be emphasized secondary to gradually increased loads to the joint with activity as well as to minimize quadriceps inhibition. Electrical stimulation for quadriceps reeducation should be discharged at this time secondary to improved quadriceps contraction.

Bracing and Ambulation

As quadriceps strength improves and the patient demonstrates the ability to perform a straight-leg raise without a quadriceps lag, he or she may change to a postoperative brace as per the surgeon’s preference. The brace serves as a reminder to the individual and his or her friends to avoid activities that may risk reinjury. Mechanical loading of the knee is progressed during this phase, and the athlete is advanced off of crutches by 6 to 8 weeks, pending normalized gait and extension ROM. We have found that if progressed off of crutches too quickly and without sufficient quad control, patients are at risk of losing knee extension secondary to ambulating on a flexed knee.

TABLE 12.2 Phase 2: Moderate Protection Phase (Weeks 4-8)

Goals

Gradually improve knee flexion ROM
Restore patellar mobility
Minimize postoperative pain and effusion
Normalize gait pattern without assistive device
Able to ascend a 6-8-in step with good control

Criteria to Progress into Phase 3

ROM (0-130 degrees)
Ability to ascend a 6-8-in step (height dependent) with good control
Minimal to no joint effusion
Normalized gait

Range of Motion

Flexion is gradually progressed to full flexion by 8 to10 weeks postoperatively. This can be achieved by progressing the athlete from seated active-assisted range of motion (AAROM) knee flexion to wall slides (Fig. 12.3A) and a stair stretch (Fig. 12.3B). The clinician should monitor these exercises to ensure compliance with repetitions and sets as well as quality of performance. As ROM progresses from 110 to 115 degrees, cycling is advanced to a standard 170-mm ergometer. Low-peak strain values have been demonstrated on the ACL with stationary cycling.⁴⁵,⁴⁶

Strengthening

As ROM and strength continues to improve, additional CKC exercises are added such as squats, leg press, advanced neuromuscular activities, and unilateral CKC exercises. Weight on the leg press is progressed and determined by the athlete’s physiologic capabilities as well as quality of movement. Despite popular belief that weight training affects growth plates in children, studies have demonstrated no adverse effects.⁴⁷ In contrast, strength training has demonstrated a reduction in the number and severity of knee injuries in adolescent athletes.⁴⁸,⁴⁹,⁵⁰,⁵¹,⁵² It is recommended that a clinician supervise children at all times while on equipment to ensure safety as well as appropriate weight, repetitions, and quality of movement.⁴⁷ Children should be educated to perform movements slowly and controlled with equal weight acceptance to translate over to functional activities.

Figure 12.3. Flexion ROM progression. A. Wall slides used for obtaining flexion ROM. The stretch is held by the uninvolved leg for approximately 5 seconds. Then the uninvolved limb is used to slide the leg back up the wall. B. Stair stretch being performed by an adolescent with 5- to 8-second holds for flexion ROM.

Squats are progressed from wall slides to free squats. Wall squats and barbell squats have been shown to be effective and safe regarding tensile loads on the ACL. Weight-bearing squats have been reported to have an ACL tensile load of 50 N versus non-weight-bearing knee extensions demonstrating 150 N.²⁰,⁵³,⁵⁴ Quality of movement is key to avoid adverse loading of the ACL as well as develop compensatory movement patterns. Anterior knee translation beyond the toes may increase ACL loading during squatting exercises.²⁰,⁵⁴ Studies have demonstrated improved lower extremity alignment with verbal feedback and direct supervision in young athletes.²,⁵⁵,⁵⁶ The use of a chair gives the child a cue to sit back and use a hip strategy to prevent anterior knee translation (Fig. 12.4). A mirror may be used for visual feedback if the individual presents with an asymmetrical weight shift. For children who present with weak gluteal musculature and resultant valgus, TheraBands may be used above the knee to activate hip abductors. In addition, it should be understood that the child has potentially never learned proper squatting technique and the clinician may be the first to teach him or her.

Figure 12.4. Demonstration of impact of cueing on hip strategy A. A patient performing a squat with a knee strategy and anterior knee translation beyond the toes. B. Same child using a hip strategy after successfully correcting her squat by sitting back into a chair as a cue.

Unilateral CKC exercises are added such as contralateral hip abduction and extension with a TheraBand to activate gluteus medius early on as well as address single-leg weight bearing. Forward step-ups are gradually progressed with various step heights for strengthening based on proper alignment and technique. Retrograde treadmill ambulation is used with progressive inclines to facilitate quadriceps strengthening pending patient age and coordination.⁵⁷ Proximal hip strengthening exercises are continued and advanced as ROM allows, such as clamshells, bilateral lower extremity bridging, and lateral band walking.

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