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The management of the skeletally immature athlete sustaining injury to the anterior cruciate ligament and other knee structures provides multiple challenges for both the treating clinicians and parents of the injured child. The diagnostic process and subsequent decision making present additional complexities because of the developmental anatomy and the potential for disturbance of normal growth patterns by some surgical interventions. In the following case report, the course to appropriate management of a young athlete is detailed, including the contributions of imaging results. The reconstructive options available to orthopedic surgeons and the patient's post‐operative progression are also briefly discussed. Rehabilitation practitioners require an understanding of the unique issues present when providing care for pediatric and adolescent athletes with knee injuries in order to assist in optimal decision making in the phases during which they are involved.
5 (Single Case Report)
Management of patients with injuries to the anterior cruciate ligament (ACL) of the knee has become one of the most studied topics in musculoskeletal medicine and rehabilitation. Estimates are that approximately two million people worldwide experience ACL injuries annually.1 Although precise data are not available, an estimated 125,000 to 200,000 ACL reconstructions annually occur in the United States alone.2 Children and adolescent athletes account for 0.5% to 3.0% of all ACL injuries and the rate at which these injuries are occurring in these populations is increasing.3‐6 American football athletes are known to have the greatest relative risk for sustaining knee injuries, followed closely by girl's soccer. When ACL injuries are specifically considered, however, girl's sports of soccer, basketball, and volleyball all have a higher rate of injuries proportionally than football.7
While differential diagnosis must consider other pathologies such as meniscal tears, osteochondral injuries, tibial spine fractures, other ligament injuries, or epiphyseal fractures, individuals with ACL injuries often have those same pathologies and others as accompanying injuries.5 Young individuals with ACL tears have been reported to have concurrent meniscal injuries in 69% of the cases.8 The younger patient with the acute ACL injury often sustains a lateral meniscus tear at the time of the original trauma, while the young person with the chronically ACL deficient knee will be at risk for developing a medial meniscus tear.9 If reconstruction of the ACL is delayed beyond 12 weeks, the risk for irreparable meniscal injury significantly increases.10 Thus, efficient early management of the skeletally immature person suspected of having an ACL injury is imperative. Recent work continues to delineate the importance of the meniscus as a “chondral protective” structure with much poorer long‐term outcomes occurring in those patients who have sustained meniscal injury and meniscectomy, either in isolation or accompanying other structural injury.11
Optimal diagnosis and management of ACL injuries in pediatric and adolescent athletes presents a particularly complex problem for the young person, their parents, and clinicians. Consideration of the immature skeleton of the pediatric or adolescent athlete adds further intricacy to the management decisions for providing the best care. Concern for disruption of normal growth, particularly limb length on the side of the affected knee, is the basis for this attention. The skeletally immature patient was once routinely treated with conservative measures in order to minimize the risk of disturbing normal growth, but this approach was found to have negative consequences as described in Janssen et al.11 Activity limitation, bracing, and exercise have proven largely unsuccessful in persons of this age group with ACL deficient knees with preventing meniscal injury and early onset of the degenerative cascade. Thus, surgical intervention is now generally considered to be the standard of care. Less clearly practiced, however, is how to best complete the diagnosis, reconstruction, and post‐operative rehabilitation of the skeletally immature athlete with an ACL injury. These topics are explored in this case report of a pediatric patient who sustained an ACL injury, with subsequent reconstruction, and rehabilitation.
During a youth football game, an eight year‐old athlete carried the ball toward the goal line, but was tackled prior to scoring a touchdown. During the contact that concluded the play, the young athlete experienced an injury to his right knee. He was observed to have planted his right foot to change directions in an attempt to avoid being tackled. While the right foot was planted and the left foot was moving toward a different direction, he was tackled by multiple opposing players, resulting in his trunk rotating to the left left on his fixed right lower extremity. He remained down on the field of play momentarily, reporting to his father “My knee popped. I think it's broke [sic].” He was held from further competition during the game and treated with the application of ice to his knee. Effusion of the injured joint, as reported by his parents, was evident within 30 minutes. Within two days, the effusion and pain had largely resolved and his gait was approaching normal, without the use of an assistive devices. With squatting, running, and higher demand activities, however, his parents noticed a tendency for him to use compensatory mechanics for his right lower extremity. Although he returned to school with improving mobility, the parents sought medical ‐consultation first with a pediatrician, who then referred the patient to an orthopedic surgeon for evaluation. Radiography and a clinical examination were completed, but the initial orthopedic consultation did not yield diagnosis of a significant injury. The recommendation by the orthopedist was to allow the athlete to return to his prior activity level as indicated by his comfort level. The parents, dissatisfied with the outcome of the orthopedic assessment, sought an additional opinion. Further evaluation was completed by a family medicine physician with certification in sports medicine. This physician's clinical examination immediately raised suspicion of an ACL injury by the presence of a positive Lachman's test. Radiographs and magnetic resonance imaging (MRI) were promptly completed with a tear of the ACL being visualized along with suspicion of a lateral meniscus injury. The radiographs revealed no bony abnormality and the open physes of the femur, tibia, and fibula (Figures 1 and and2)2) were readily identifiable. The MRI revealed complete disruption of the ligament at the lateral wall of the femoral notch (Figure 3) and a lateral meniscus tear (Figure 4).
With surgical consultation being recommended by this physician, the parents were able to obtain an immediate assessment by another orthopedic surgeon. The next consultation sought by the parents for their son with an orthopedic surgeon resulted in the recommendation for ACL reconstruction using an allograft and a post‐operative period of immobilization. An additional opinion was later offered by a pediatric orthopedic surgeon, who ordered bone age studies to supplement the MRI in the decision‐making process. This physician recommended an all epiphyseal reconstruction to minimize risk to the growth plates using a hamstring autograft. He also discussed with the parents alternative reconstruction techniques, including an iliotibial extra‐articular reconstruction and an adult‐type reconstruction crossing the growth plates. Still yet another opinion was sought by the parents because of the apparently conflicting information provided in the prior consultations. The fourth orthopedist, known for helping develop the all epiphyseal reconstruction, offered a similar recommendation for an all epiphyseal technique using a hamstring autograft. After extensive deliberation, the parents chose for their son the all epiphyseal autograft technique under the care of the orthopedic surgeon offering the final consultation.
Clinicians should have an elevated index of suspicion for a ligamentous injury in the young athlete who presents with a traumatic hemarthrosis or reporting this to have occurred immediately after the injury.5 Although joint effusion is a nonspecific sign, most ACL and meniscus injuries are accompanied by knee effusion.12,13 Effusion may also be present with Salter‐Harris fractures and, thus, indicate the need for further investigation.12
Among clinical examination procedures, the Lachman's test, the pivot shift, and the anterior drawer test are most frequently used to evaluate for ACL injury. In a recently published meta‐analysis, the Lachman's test was determined to have the best combined psychometric values for identifying acute, complete ACL ruptures.14 The sensitivity and specificity were each calculated to be 81%. An earlier meta‐analysis found the sensitivity and specificity values to be greater at 85% and 94%, respectively.15 In the more recent study, the values increased if the patient was examined under anesthesia, which points to the potential complication of apprehension by the patient interfering with examination procedure and interpretation of the results. Particular analysis of the diagnostic value of Lachman's test and other clinical examination procedures in pediatric and adolescent athletes has not been thoroughly studied. Only one investigation has closely considered the accuracy of clinical examination and diagnostic imaging for ACL tears specifically in this younger group of individuals with the results indicating comparable diagnostic accuracy as adults.16 Many studies routinely include younger persons in their study populations, but do not stratify the data based on age.
Other clinical examination procedures, particularly the pivot shift and anterior drawer tests, have been found to have less diagnostic accuracy than Lachman's test. The pivot shift maneuver has very high specificity, but low sensitivity, limiting its clinical utility.14,15 The anterior drawer test also has significantly less sensitivity than Lachman's test, particularly in the assessment of acute injuries, but may have greater diagnostic value in the presence of chronic ACL deficiency.14,15
The commonly used clinical examination procedures for identifying meniscus tears have questionable clinical utility and also have had limited evaluation specifically in pediatric or adolescent patients. The clinical tests, particularly if flexion of the knee is not permitted by the patient, may not allow for a valid examination. Reliance on the clinical examination procedures to detect or rule out meniscus injuries may be imprudent, in light of the diagnostic accuracy of such procedures being reported as low as 29 to 59%.17 Experienced examiners using a modified McMurray's Test have been reported to have only moderate diagnostic accuracy in younger persons.16 Additionally, a history of trauma, often including a rotary mechanism, is a common attribute in the history as the degenerative tears later in life would be very unlikely. In addition to effusion, snapping and giving away are also common signs of meniscus injury.9 Thus, the history and subjective reports by the patient may be as informative as the clinical examination.
Early clinical examination following acute knee trauma may have limited diagnostic value and MRI often reveals ACL injuries not initially detected.18 MRI is generally acknowledged to be the optimal imaging modality for identifying ligamentous, tendinous, cartilaginous surface, and subchondral bone injuries of the knee. Given the known propensity for meniscus and ACL injuries to be concurrent in a majority of skeletally immature athletes, suspicion of one injury should routinely include concern for concomitant injury. With a suggestive history or any clinical exam findings consistent with ACL or meniscus injury, diagnostic imaging is indicated to visualize the tissues suspected of involvement.
According to the American College of Radiology (ACR) Appropriateness Criteria, the topic of “Acute Trauma to the Knee” includes recommendations for persons of all ages (excluding infants). Within the rating system of the ACR Appropriateness Criteria are numerical scales pertaining to the most or least indicated imaging. The highest value of 9 is consistent with most indicated imaging and 1 is the lowest value or least indicated imaging. Among the variants listed for “Acute Trauma to the Knee,” based on clinical presentation are two guidelines that may be applicable for individuals suspected of having ACL or meniscus injuries. Variant 2 of “Patient of any age (excluding infants); fall or twisting injury, with one or more of the following: focal tenderness, effusion, inability to bear weight ‐ First study” recommends radiographs of the knee with a 9 rating followed by MRI at 5. This guideline is supplemented by Variant 3 or “Patient any age (excluding infants); fall or twisting injury with either no fracture or a Segond fracture seen on a radiograph, with one or more of the following: focal tenderness, effusion, inability to bear weight. Next study,” which indicates MRI (without contrast) as being the preferred imaging with a rating of 9.19
Distinct from the tibial eminence fracture often occurring in young athletes, a Segond fracture is a small avulsion fracture often visualized along the lateral joint line on anterior‐posterior view radiographs. This avulsion is usually of a small fragment of the middle third of the lateral tibial rim. While an atypical radiographic finding, Segond fractures are often associated with the presence of ACL injuries. Thus, the presence of such a finding on radiographs should raise suspicion of an ACL injury and indicates the need for MRI.13,20
In the skeletally immature, overall MRI detection of ACL tears has been observed to demonstrate as high as 95% sensitivity and 88% specificity with arthroscopic exposure serving as the comparison standard.21 Other investigations have reported ‐values as low as 64% to 78% sensitivity, while maintaining high specificity at 94% to 100%.22,23 The lower sensitivity reported in some investigations has been attributed to inexperience with assessment of the anatomy of that age group, difficulty with interpretation because of smaller and developmental anatomy, and the relatively higher proportion of incomplete tears in this age being more difficult to identify.16
Injury patterns of the ACL may also vary considerably related to age. Tibial eminence avulsion fractures are most common during puberty, partial thickness tears among adolescents before skeletal maturity, and complete tears after skeletal maturity. While much attention has been focused on the ACL injury rate in female athletes, ACL injuries are also very common in young males during the period of open physes in the form of tibial eminence avulsions or incomplete tears. In a recent report of American high school sports injury data, ACL injuries accounted for 12.25% of all recorded injuries in male athletes.7 The predominance of female ACL injuries occurs later as skeletal maturation continues.13,24
The accuracy of MRI results compared to intra‐operative findings for meniscus tears for children and adolescent persons has been inconsistently reported. The accuracy of MRI in detecting meniscus tears in adolescents may be comparable to that in adults.13 Major et al2 evaluated individuals aged 11 to 17 years with a mean age of 15 and compared the results of MRI interpretations to those of adults. The results were similar across the age groups. The sensitivities to medial and lateral meniscus tears were calculated to be 92% and 93%, respectively, with specificities at 87% and 95%, respectively. Other investigations suggest less diagnostic accuracy in pediatric patients, probably because of the developmental changes present in the meniscus in those skeletally immature. Sensitivities as low as 50% to 62% have been reported with lower accuracy in those under age 12.9,16 The normally greater vascularity of the meniscus in children can cause enhancement within the mid‐substance of the meniscus, thus, mimicking a tear and complicating the interpretation.17
In addition to meniscal injury, the medial collateral ligament may also be concurrently injured at the time of ACL trauma. Discontinuity of the fibers of the medial collateral ligament and edema are often seen in association with tears of the ACL because of the valgus stress of the pivot shift‐like mechanism of trauma.13 Because of the potential for the history and the clinical examination of the patient to not correspond with the imaging findings as read by a radiologist, some orthopedic surgeons believe that the physician conducting the examination should also be the interpreter of the diagnostic imaging.25
Anterior cruciate ligament reconstruction and rehabilitation in skeletally immature athletes is more complex than in adults and those with closed physes. Trauma or orthopedic interventions may disrupt the physes and create bony bridges resulting in a reduction of bone length or angulation.26 The long bones of the knee account for approximately 65% of potential lower extremity growth as the distal femur accounts for 37% and the proximal tibia for 28%.27,28 The threat of injury to the growth plates of the femur and tibia resulting from the reconstructive procedure and subsequent life‐long limb length discrepancy is particularly important in decision making for pediatric patients. For those sustaining injuries prior to the interval of maximum growth in early adolescence, the potential effect may be of even greater magnitude.
Among the factors considered by orthopedic surgeons in selecting the best reconstructive procedure for the pediatric or adolescent patient is the physiologic age and potential for growth. For the patient in this case report, radiographs were completed to establish his bone age (Figure 5). At the time of the completion of this radiograph, a bone age of eight years (96 months) was determined. His chronological age was actually eight years and seven months (103 months) or 1.4 standard deviations below the mean, but within normal limits (<2.0 standard deviations). This methodology of determining bone age was established by Greulich and Pyle and considers the pattern of epiphyses and bone development of the hand and wrist.29 The actual radiographs of the individual are compared in an atlas to those of established standards of bone development. Once established for the individual patient, the actual bone age must be a consideration in the choice of operative procedures to minimize the risk of growth disruption. The use of Tanner staging based on sexual ‐characteristics has also been employed by surgeons in order to classify their patients' physiologic age for consideration prior to undergoing knee reconstruction procedures.30
The available surgical procedures for the skeletally immature patient who has sustained and ACL tear are generally categorized as physeal sparing, transphyseal, and partial transphyseal reconstructions.5 Conventional transphyseal tunnels for the graft anchors (as used in those with closed growth plates) have been described, but presumably contain the greatest risk of physis injury and growth disturbance. The extent of this risk, however, is not precisely known. Variations on these techniques in which only one physis is affected with the stabilization have also been reported.31 Theoretically, extra‐articular reconstruction, sparing the physis, provides a method to restore joint stability and maximally avoid risk of growth disturbance. Extra‐articular reconstructions, however, have a history of variable outcomes.5 The technique used in the young athlete in this report is a physeal sparing technique in which the bone tunnels for the hamstring graft were placed only through the femoral and tibial epiphyses.32
Some surgeons recommend the type of technique based on the child's or adolescent's physiologic or bone age. Chicorell et al5 recommend physeal‐sparing combined intra/extra‐articular reconstruction with ITB for the pre‐pubescent patient at Tanner Stage 1 or 2 (Males: ≤12 years, Females: ≤11 years). For adolescents with growth remaining at Tanner Stage 2 or 3 (Males 13‐16 years, Females 12‐14 years), a transphyseal reconstruction using a hamstrings graft and metaphyseal fixation is recommended. For Tanner stage 5 (Males >16 years, Females >14 years), an adult‐type reconstruction with interference screw is recommended. This strategy is advocated to minimize threat of disruption of epiphysis and subsequent interference with growth potential. Similarly, other surgeons suggest the lower limit to perform an adult type ACL reconstruction in which the physes would likely be closed is over 14 years for females and over 16 years for males.33
In an anatomical study based upon 31 patients 10 to 15 years of age, Kercher et al34 determined that less than 3% injury occurs when drilling an 8‐millimeter tunnel across the physis. They further proposed that a vertical tunnel has minimal effect, but the tunnel diameter is critical to minimize the magnitude of physis violation. Interference screws can be placed safely in order to avoid the physis, but require careful planning. Their work was similar in nature to that of other investigators who proposed that less than 7% in the frontal plane and 1% in the transverse plane of the femoral physes were affected as a result of a femoral only transphyseal procedure, presumably offering little risk for growth disturbance.31
Kennedy et al35 recently tested three simulated pediatric ACL reconstructions using six cadaveric specimens, evaluating for the magnitude of anterior tibial translation and the pivot shift. The all epiphyseal technique improved stability, but did not restore the knee to pre‐injury ACL laxity as compared to the extraphyseal iliotibial band (ITB) technique. Greater residual laxity compared to the pre‐injury state was present in the all epiphyseal and transtibial over‐the‐top techniques. The ITB technique, however, actually excessively constrained the rotational component of the knee motion compared to the intact status. Interpretation of these findings must be with caution because of the limited scope of the study.
In a meta‐analysis derived from 55 published reports, Frosch et al36 determined the overall rate of significant limb length discrepancies or malalignment complications to be 1.8%. Transphyseal reconstruction was associated with a significantly lower risk of leg‐length differences or varus‐valgus deviations (1.9%) compared with physeal‐sparing techniques (5.8%), but had a higher risk of re‐rupture (4.2% vs. 1.4%). The authors of the meta‐analysis offered the explanation of the technical challenges of the surgery and the fragility of the growth plate for the apparently counter‐intuitive findings of the physeal sparing techniques having higher risk of leg length discrepancies. One must also consider the selection of physeal sparing procedures in younger patients with inherently greater risk of growth disturbance because of their age. The collective data also suggested bone–patellar tendon–bone grafts are less likely to fail, but had higher risks of leg‐length differences and varus‐valgus deviations than the hamstrings grafts (3.6% vs. 2.0%). A critical analysis must also include acknowledgment that direct comparisons of techniques in clinical trials have not yet occurred. Thus, no single technique has been determined to be clinically superior, in part because all reported data are in small case series with only short‐term follow‐up.37 Direct comparison studies of the techniques with long‐term outcomes will be required to determine if one technique yields best results.
Approximately eight weeks following the injury, the young athlete underwent surgical reconstruction of his right knee. The intra‐operative findings were consistent with the imaging and clinical examination findings. The ACL was observed to be completely ruptured and had markedly atrophied in the two month interval between injury and surgery (Figure 5). The suspected lateral meniscus tear was also confirmed to be present (Figure 6). An all epiphyseal technique was completed to reconstruct his right ACL using a quadruple hamstring graft comprised of the semitendinosus and gracilis tendons (Figure 7). The unstable intrasubstance tear of the lateral meniscus was repaired using an inside‐out technique (Figure 8). The articular cartilage of his tibiofemoral joint was explored during the surgical exposure and was found to be normal. The ACL reconstruction along with the meniscus repair, although technically challenging, were completed without complication, according to the surgeon's report. Dr. Allen F. Anderson MD (Nashville, TN) has provided the video of the surgical procedure used for the subject of this case report. The link to this video is available at www.ijspt.org and the authors invite you view the surgery to expand your understanding of this complex procedure.
Post‐operative care and the rehabilitative progression for the skeletally immature athlete are similar to that of adults undergoing other grafting procedures, albeit with greater initial precautions and a more conservative progression. The rehabilitative protocol for this patient, as preferred by the orthopedic surgeon, required an immediate post‐operative period of non‐weight‐bearing for six weeks for protection of the epiphyses (with bone tunnels) and meniscus repair while working on recovery of knee range of motion and muscle activation throughout the affected lower extremity. He initiated formal physical therapy the day of the surgery while still in the hospital and continued with regular supervised outpatient visits the same week, while also completing multiple exercises at home under the supervision of his parents. He began progression to weight–bearing activities at six weeks post‐operatively and discontinued using crutches after 12 weeks. He completed a total of 29 physical therapy visits over a seven month period, fully recovering his range of motion, regaining his strength, and demonstrating only minimal residual quadriceps atrophy. At approximately eight months after surgery, the treating therapist compared the athlete's involved lower extremity to the uninvolved with multiple functional tests, including the single leg hop for distance, single leg vertical jump, triple hop for distance, and single leg diagonal hop for distance. He was judged by the therapist to have comparable function in the involved lower extremity. Circumferential thigh measures indicated the affected limb to have only minor remaining atrophy. Clearance for return to participation in sports occurred one month later during a follow‐up visit to the orthopedic surgeon. While approved to return to high level activities by the physician, wear of a protective brace for one to two years was recommended.
The specific rehabilitation procedures and his progression are not the focus of this report. Greenberg et al38 have provided details of a similar post‐operative rehabilitation protocol used in their case report describing an eight year‐old having also undergone an all epiphyseal ACL reconstruction. The authors discuss criteria for return to participation and functional testing. Readers are referred to the Greenberg et al paper for specific details on the rehabilitation progression in that young athlete and decision making for return to sports participation.
During the course of rehabilitation of the young athlete described in this case report, follow‐up visits were completed with his orthopedic surgeon. Radiographs were obtained during these visits to assess for hardware integrity, the continued presence of open physes, and any suggestion of developing varus or valgus angulation or other malalignment.13 Figures 10 and and1111 are examples of the follow‐up radiographs completed to monitor his progress, taken nine months post‐operatively in this instance. Note the presence of the bone tunnels in the epiphyses and the open epiphyses in both the tibia and femur. More sophisticated imaging is usually reserved for individuals in whom knee radiographs indicate the need for further investigation, the clinical examination suggests angulation or asymmetry, or individuals who are having complications or functional impairments attributable to the involved knee.5 Should additional imaging be indicated, MRI would likely be chosen to further investigate the knee. MRI can evaluate in more detail than plain radiographs, the integrity of the graft, hardware loosening, and post‐operative complications, including ganglion cyst formation, graft impingement, and arthrofibrosis. MRI may also give greater detail as to the possible presence of bony bridges spanning the physes. MRI can also demonstrate fluid characteristics within the joint, allow visualization of synovial hypertrophy, and reveal intra‐articular loose bodies.39
That autumn, nine months following the surgery and only a few weeks after being cleared by the physician, the young athlete, then nine years of age, returned to playing football. He initially completed non‐contact football training drills and gradually increased his activity level toward that demanded in practice and games. With his return to higher level activities, he wore a brace specifically for protection of knee and the ACL graft. The use of a brace intended to protect the reconstructed knee during sports activities has been advocated for one to two years following reconstruction in skeletally immature athletes.5 Although there are no outcome studies for the use of bracing specifically in pediatric or adolescent patients having had reconstructive procedures, the benefits may include improved proprioception and greater confidence.40 He also returned to participation in basketball in the winter and baseball the following spring and summer. He is currently playing successfully in his second season of football since the reconstructive procedure and rehabilitation. He continues to wear a supportive brace with this activity, now his second because of growth. His mother reports that he is experiencing no symptoms and is having no difficulty with the involved knee during participation in sports or other activities. His only complaint is mild tenderness with direct pressure over the tibial screw site (see Figures 10 and and1111 for location). Although specific radiographic measures have not been undertaken to examine for overall limb length, there are no indications for suspicion of limb length inequality based on the post‐operative knee radiographs or observations of impairment of functional performance.
Clinicians evaluating skeletally immature patients with traumatic onset of knee pain must be aware of the injury patterns that occur in pediatric and adolescent athletes. Practitioners must also be knowledgeable of the limitations of routinely used clinical examination procedures for suspected pathologies of the anterior cruciate ligament and menisci, particularly in younger individuals. Indications for imaging coupled with an understanding of the most appropriate imaging based on the patient's presentation is also required. While those involved with the care of pediatric and adolescent athletes having undergone reconstructive knee procedures must obviously have expertise in the rehabilitation process, an understanding of the pre‐operative and post‐operative medical management of such patients may allow for improved care by a greater comprehension of the patient's experiences and the decisions required by the parents and the physicians during the entire sequence of events prior to rehabilitation.