The influence of femoral technique for graft placement on anterior cruciate ligament reconstruction using a skeletally immature canine model with a rapidly growing physis

Anterior Cruciate Ligament Reconstruction in Skeletally Immature Patients Using an All-Epiphyseal Technique: A Prospective Cohort Study

Background

Transphyseal techniques are the most commonly used for anterior cruciate ligament (ACL) reconstruction in children. To mitigate the risk of growth disturbance, the tunnels should be positioned as vertically and centrally as possible in relation to the physis, potentially compromising the anatomic orientation of the graft and, therefore, its isometry. A graft rupture is frequent in this age group. Even though all-epiphyseal techniques have not clearly demonstrated better isometry, the authors propose an epiphyseal technique that aims for favorable anatomy, and therefore isometry, while avoiding physeal damage in young children with ACL ruptures.

Purpose

To present the results of a modified all-epiphyseal technique in prepubertal patients, evaluating knee function, graft survival, and joint and growth protection.

Study Design

Case series; Level of evidence, 4.

Methods

A total of 74 skeletally immature patients with a traumatic ACL rupture underwent a physeal preserving technique using a semitendinosus-gracilis tendon graft fixed with intra-epiphyseal resorbable interference screws in the femur and tibia, along with associated minimal notchplasty. Preoperative, intraoperative, and postoperative assessments included clinical knee stability and meniscal status, magnetic resonance imaging, isometry measurements, comparative laximetry measurements with stress radiography using the Lerat method, full-length standing radiography, measurements of the axes of the lower limbs, Tegner and Lysholm scores, and patient satisfaction.

Results

From 2004 to 2014, a total of 74 patients met our inclusion criteria and were followed up for a mean of 4.1 years (range, 2-7 years). Of these patients, 91.9% had an excellent/good postoperative Lysholm score, with similar preoperative and postoperative Tegner activity scores. Intraoperative isometry showed an intratunnel graft excursion <3 mm during extension in 95.9% of cases. Abnormal clinical laxity was observed in 4.1% at final follow-up, with an improvement in side-to-side laxity of 4.8 mm. There were 3 patients who experienced graft failure, with the salvage procedure employing a transphyseal technique in 1 patient. Meniscal tears occurred in 27.0%, with concomitant repair yielding a healing rate of 87.5%. No physeal alterations were observed, except for a tendency toward subtle overgrowth in the affected limb. Also, 90.5% of patients were satisfied or very satisfied with the outcome.

Conclusion

The proposed all-epiphyseal technique in skeletally immature patients demonstrated excellent overall results with a low incidence of reruptures and meniscal degeneration, without relevant alterations related to growth.

Midterm Outcomes of Hybrid Transepiphyseal ACL Reconstruction With Soft Tissue Quadriceps Tendon Autograft in Skeletally Immature Athletes

Background

Substantial developments in physeal-sparing surgical techniques for anterior cruciate ligament (ACL) reconstruction (ACLR) have demonstrated safety and efficacy in treating skeletally immature patients. However, outcomes using all-soft tissue quadriceps tendon (QT) autograft in this population are unknown.

Purpose

To evaluate outcomes including return to sport (RTS) and reinjury risk in skeletally immature patients ≥2 years after undergoing hybrid transepiphyseal ACLR using QT autograft.

Study Design

Case series; Level of evidence, 4.

Methods

A consecutive series of skeletally immature patients who underwent primary QT autograft ACLR using a hybrid transepiphyseal technique with ≥2 years of follow-up were retrospectively analyzed. Outcomes included RTS (primary), ability to return to preinjury level of competition, and subsequent ipsilateral/contralateral knee injury (secondary).

Results

A total of 50 patients were identified and contacted, of which 40 (80.0%) (35 male; mean age, 12.6 years [range, 9.4-16.0 years]) completed the survey at 5.7 ± 2.8 years (range, 2.0-11.5 years) postoperation. Of those, 26 (65.0%) were competitive middle/high school athletes and 18 (45.0%) competed in ≥2 sports. At a mean of 10.6 ± 2.3 months (range, 6-17 months) postoperatively, 37 patients (92.5%) returned to unrestricted sports participation, and 35 patients (87.5%) resumed competition at their preinjury level. Five patients required subsequent ipsilateral knee surgery for ACL revision (n = 2; 5.0%), meniscal injury (n = 2; 5.0%), or symptomatic hardware (n = 1; 2.5%) after a mean of 4.4 ± 1.7 years (range, 2.8-7.1 years). Three patients (7.5%) sustained a subsequent contralateral ACL injury, and 1 patient sustained a contralateral posterior cruciate ligament sprain.

Conclusion

Findings of this study suggest that midterm outcomes of patients treated with hybrid transepiphyseal ACLR using QT autograft are promising, with a high and expedited RTS and relatively low graft tear risk.

Graft Type and Diameter Are Predictors of Reinjury After Transphyseal Anterior Cruciate Ligament Reconstruction in Pediatric and Adolescent Patients

Purpose

To report the rate of anterior cruciate ligament (ACL) graft failure by physis status (open, closing, closed) and to analyze which factors were associated with higher risk of ACL graft failure.

Methods

Patients younger than 18 years who underwent transphyseal ACL reconstruction (ACLR) between 2000 and 2018 at a single institution were reviewed at minimum 2 years after ACLR. Patient records were reviewed for anthropometrics, surgical techniques, and ACL graft failure. Patients were subsequently stratified based on physis status (open, closing, closed) and analyzed.

Results

A total of 272 patients (mean age of 15.4 ± 1.3 years) were assessed. The transtibial technique was used in 63.6% of cases. A hamstring autograft was used exclusively in the open physis group. A patellar tendon autograft was used in 65.9% of patients with a closing physis and 80.9% of patients with a closed physis. The overall graft failure rate was 13.2%, with a contralateral ACL injury rate of 11.0%. Kaplan-Maier analysis by physis status showed different injury free from ACL reinjury (P < .001). An open physis was associated with increased risk of ACL reinjury (hazard ratio, 5.2; P < .001) when compared to a closed physis. A closing physis presented a higher hazard ratio but was not statistically significant (hazard ratio, 2.6; P = .08). Hamstring graft type (P = .03) and lower graft diameter (P = .04) were significantly related to higher ACL reinjury after adjusting for physis status.

Conclusions

Transphyseal ACLR is a safe procedure in pediatric patients. The rate of reinjury was 13.2%. This rate decreases with skeletal maturity, use of patellar tendon autograft, and a larger graft diameter.

Level of Evidence

Level III, retrospective cohort study.

Assessing the effect of physeal biopsy on angular deformity in a rabbit model

Obtaining a biopsy of the physis in a pediatric/juvenile could provide the ability to diagnose and manage children with physeal abnormalities. However, it has not yet been determined whether a physeal biopsy procedure affects angular deformity. We employed a rabbit model to collect biopsies of the distal femoral and proximal tibial physes on anesthetized, 8-week old New Zealand rabbits. The contralateral limb served as a control. At 8 (n = 5) and 16 (n = 5) weeks postbiopsy, animals were euthanized. Micro-computed tomography (CT) was employed to estimate percentage of the physis biopsied and assess structural abnormalities resulting from biopsy. Bone samples were embedded in polymethylmethacrylate and analyzed. The percentage of physis sampled was ≤1.5% of the total femoral physis while all but one of the tibiae had ≤2.3% removed. There were no iatrogenic clinical or radiographic deformities (frontal or sagittal). Micro-CT and histological analysis suggested that physeal defects had signs of healing that did not lead to subsequent angular deviation. A defect caused by physeal biopsy may not lead to angular deformity. Long-term data could help determine the safety and efficacy of collecting biopsies for histological analyses. Advanced imaging may demonstrate a detailed picture of anatomic or structural alteration of a given physis, but provides no functional information. The diagnostic and therapeutic information that could be gleaned from one or more serial biopsy samples could be invaluable in decision making and clinical management (e.g. skeletal dysplasias and metabolic conditions), so long as subsequent deformity is not a future possibility.

Delayed reconstruction and high BMI z score increase the risk of meniscal tear in paediatric and adolescent anterior cruciate ligament injury

PURPOSE

The purpose of this study was to identify epidemiologic risk factors for secondary meniscal tears in paediatric and adolescent patients who sustain an anterior cruciate ligament (ACL) tear. The hypothesis was that delayed reconstruction and elevated BMI z score, increase the risk for secondary meniscal tears.

METHODS

A prospective, descriptive and analytical study of consecutively accrued children and adolescents with an ACL tear was performed. One hundred and sixty subjects (114 males and 46 females) were identified between 2006 and 2015 at one institution. The age range was between 7 and 19 years. Fifteen parameters were recorded and analysed: age at initial trauma, initial trauma circumstance, sex, BMI z score, affected side, type of sport, Tegner score, athletic level, time to MRI, time to first referral, time to surgery, age at surgery, attempted non-operative treatment, operative report and associated meniscal tear. These meniscal lesions could be diagnosed by an MRI and / or during surgery.

RESULTS

Out of the 160 cases, 143 were treated surgically and 17 cases non-operatively. Median corrected BMI z score was 0.5 (range - 1.8 to 4.7). 41.9% had one or more meniscal lesions. 55 patients were initially treated non-operatively, of which 39 patients were secondarily operated. There was a positive relationship between meniscal lesion and: BMI z score (p = 0.0364), attempted non-operative treatment (p = 0.001) and time to surgery (p = 0.002). The median time to ACL reconstruction was 229 days for patients with secondary meniscal lesions.

CONCLUSIONS

Patients with ACL tears treated non-operatively developed secondary meniscal lesions requiring delayed surgical management. There was a positive correlation between BMI z score and secondary meniscal lesions. Thus, early ACL reconstruction is advocated in young athletes.

LEVEL OF EVIDENCE

Retrospective comparative study, Level III.

International Olympic Committee Pediatric ACL Injury Consensus Group, Ardern CL, Ekås G, Grindem H, Moksnes H, Anderson AF, Chotel F, Cohen M, Forssblad M, Ganley TJ, Feller JA, Karlsson J, Kocher MS, LaPrade RF, McNamee M, Mandelbaum B, Micheli L, Mohtadi NG, Reider B, Roe JP, Seil R, Siebold R, Silvers-Granelli HJ, Soligard T, Witvrouw E, Engebretsen L. 2018 International Olympic Committee Consensus Statement on Prevention, Diagnosis, and Management of Pediatric Anterior Cruciate Ligament Injuries

In October 2017, the International Olympic Committee hosted an international expert group of physical therapists and orthopaedic surgeons who specialize in treating and researching pediatric anterior cruciate ligament (ACL) injuries. The purpose of this meeting was to provide a comprehensive, evidence-informed summary to support the clinician and help children with ACL injury and their parents/guardians make the best possible decisions. Representatives from the following societies attended: American Orthopaedic Society for Sports Medicine; European Paediatric Orthopaedic Society; European Society for Sports Traumatology, Knee Surgery, and Arthroscopy; International Society of Arthroscopy, Knee Surgery and Orthopaedic Sports Medicine; Pediatric Orthopaedic Society of North America; and Sociedad Latinoamericana de Artroscopia, Rodilla, y Deporte. Physical therapists and orthopaedic surgeons with clinical and research experience in the field and an ethics expert with substantial experience in the area of sports injuries also participated. This consensus statement addresses 6 fundamental clinical questions regarding the prevention, diagnosis, and management of pediatric ACL injuries. Injury management is challenging in the current landscape of clinical uncertainty and limited scientific knowledge. Injury management decisions also occur against the backdrop of the complexity of shared decision making with children and the potential long-term ramifications of the injury.

2018 International Olympic Committee consensus statement on prevention, diagnosis and management of paediatric anterior cruciate ligament (ACL) injuries

In October 2017, the International Olympic Committee hosted an international expert group of physiotherapists and orthopaedic surgeons who specialise in treating and researching paediatric ACL injuries. Representatives from the American Orthopaedic Society for Sports Medicine, European Paediatric Orthopaedic Society, European Society for Sports Traumatology, Knee Surgery & Arthroscopy, International Society of Arthroscopy Knee Surgery and Orthopaedic Sports Medicine, Pediatric Orthopaedic Society of North America and Sociedad Latinoamericana de Artroscopia, Rodilla y Deporte attended. Physiotherapists and orthopaedic surgeons with clinical and research experience in the field, and an ethics expert with substantial experience in the area of sports injuries also participated. Injury management is challenging in the current landscape of clinical uncertainty and limited scientific knowledge. Injury management decisions also occur against the backdrop of the complexity of shared decision-making with children and the potential long-term ramifications of the injury. This consensus statement addresses six fundamental clinical questions regarding the prevention, diagnosis and management of paediatric ACL injuries. The aim of this consensus statement is to provide a comprehensive, evidence-informed summary to support the clinician, and help children with ACL injury and their parents/guardians make the best possible decisions.

2018 International Olympic Committee consensus statement on prevention, diagnosis and management of paediatric anterior cruciate ligament (ACL) injuries

In October 2017, the International Olympic Committee hosted an international expert group of physiotherapists and orthopaedic surgeons who specialise in treating and researching paediatric anterior cruciate ligament (ACL) injuries. Representatives from the American Orthopaedic Society for Sports Medicine, European Paediatric Orthopaedic Society, European Society for Sports Traumatology, Knee Surgery and Arthroscopy, International Society of Arthroscopy Knee Surgery and Orthopaedic Sports Medicine, Pediatric Orthopaedic Society of North America, and Sociedad Latinoamericana de Artroscopia, Rodilla y Deporte attended. Physiotherapists and orthopaedic surgeons with clinical and research experience in the field, and an ethics expert with substantial experience in the area of sports injuries also participated. Injury management is challenging in the current landscape of clinical uncertainty and limited scientific knowledge. Injury management decisions also occur against the backdrop of the complexity of shared decision-making with children and the potential long-term ramifications of the injury. This consensus statement addresses six fundamental clinical questions regarding the prevention, diagnosis, and management of paediatric ACL injuries. The aim of this consensus statement is to provide a comprehensive, evidence-informed summary to support the clinician, and help children with ACL injury and their parents/guardians make the best possible decisions.

Regenerative Medicine Approaches for the Treatment of Pediatric Physeal Injuries

The physis, or growth plate, is a cartilaginous region at the end of children's long bones that serves as the primary center for longitudinal growth and characterizes the immature skeleton. Musculoskeletal injury, including fracture, infection, malignancy, or iatrogenic damage, has risk of physeal damage. Physeal injuries account for 30% of pediatric fractures and may result in impaired bone growth. Once damaged, cartilage tissue within the physis is often replaced by unwanted bony tissue, forming a "bony bar" that can lead to complications such as complete growth arrest, angular or rotational deformities, and altered joint mechanics. Children with a bony bar occupying <50% of the physis usually undergo bony bar resection and insertion of an interpositional material, such as a fat graft, to prevent recurrence and allow the surrounding uninjured physeal tissue to restore longitudinal bone growth. Clinical success for this procedure is <35% and often the bony bar and associated growth impairments return. Children who are not candidates for bony bar resection due to a physeal bar occupying >50% of their physis undergo corrective osteotomy or bone lengthening procedures. These approaches are complex and have variable success rates. As such, there is a critical need for regenerative approaches to not only prevent initial bony bar formation but also regenerate healthy physeal cartilage following injury. This review describes physeal anatomy, mechanisms of physeal injury, and current treatment options with associated limitations. Furthermore, we provide an overview of the current research using cell-based therapies, growth factors, and biomaterials in the different animal models of injury along with strategic directions for modulating intrinsic injury pathways to inhibit bony bar formation and/or promote physeal tissue formation. Pediatric physeal injuries constitute a unique niche within regenerative medicine for which there is a critical need for research to decrease child morbidity related to this injurious process.

Magnetic Resonance Imaging Evaluation of Physeal Violation in Adolescents After Transphyseal Anterior Cruciate Ligament Reconstruction

PURPOSE

To quantify and compare the amount and location of physis violation of the distal femur and proximal tibia after transphyseal anterior cruciate ligament (ACL) reconstruction in skeletally immature patients.

METHODS

This study included 19 patients with open physes of the distal femur and proximal tibia who underwent ACL reconstruction with tibialis anterior allografts. Physeal tunnel volume and location on the growth plate, as well as obliquity to the growth plate, were measured by 3-dimensional postoperative magnetic resonance imaging of the distal femur and proximal tibia.

RESULTS

The percentage of physeal violation (ratio of the tunnel to the entire growth plate area) was similar for the distal femur and proximal tibia (3.95% vs 3.65%, P = .582). There were no differences in tunnel obliquity to the growth plate in the coronal (56.1° vs 71.6°, P = .061) and sagittal (85.9° vs 74.9°, P = .092) planes. The distal femoral tunnel was located 6.2% (17.2% vs 23.4%, P = .001) more peripherally in the anteroposterior direction and 9.7% (27.1% vs 36.8%, P < .001) more peripherally in the mediolateral direction than was the tibial tunnel.

CONCLUSIONS

The mean percentages of physeal violation of tunnel creation during ACL reconstruction in adolescent patients were 3.95% for the distal femur and 3.65% for the proximal tibia. Moreover, femoral tunnels were located more peripherally on the growth plate than were tibial tunnels, in both the anteroposterior and mediolateral directions.

LEVEL OF EVIDENCE

Level IV, case series.

All-Inside, All-Epiphyseal Anterior Cruciate Ligament Reconstruction in Skeletally Immature Athletes: Return to Sport, Incidence of Second Surgery, and 2-Year Clinical Outcomes

BACKGROUND

Anterior cruciate ligament (ACL) injuries in skeletally immature athletes are increasing.

PURPOSE

To evaluate the 2-year clinical outcomes of all-inside, all-epiphyseal ACL reconstruction in skeletally immature athletes with 3 to 6 years of remaining growth, with a focus on return to sport and the incidence of second surgery.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Twenty-three skeletally immature athletes were prospectively evaluated after all-epiphyseal ACL reconstruction utilizing a hamstring autograft. The athletes' age, sex, sport, mechanism of injury, radiographs, and magnetic resonance imaging (MRI) findings were noted. The evaluation included a physical examination, KT-1000 arthrometer measurements, isokinetic testing, and validated outcome scores. Standing radiographs and spoiled gradient recalled echo MRI scans were obtained at 6, 12, and 24 months postoperatively. A quality of movement assessment and return-to-sport performance analysis were also performed.

RESULTS

Of the 23 athletes, 6 were female (mean age, 11.3 years), and 17 were male (mean age, 12.6 years). At a minimum follow-up of 2 years (range, 24-45 months), the mean International Knee Documentation Committee score was 94.6 ± 4.9, the mean Lysholm score was 97.9 ± 4.0, the mean Marx activity rating scale score was 13.4 ± 3.6, and the mean Hospital for Special Surgery Pediatric Functional Activity Brief Scale score was 23.9 ± 7.0. Lachman and pivot-shift test results were negative in all patients. The mean side-to-side difference on the KT-1000 arthrometer was 0.9 ± 0.5 mm and less tight on the operated side. No significant growth disturbances were noted; however, 6 athletes had a leg-length discrepancy of more than 5 mm (range, 6-18 mm). Two patients had overgrowth in the femur of more than 15 mm (16 mm and 18 mm). Two athletes (8.7%) required second surgery. The mean time to return to unrestricted activity was 13.5 months (range, 8-22 months).

CONCLUSION

The all-inside, all-epiphyseal ACL reconstruction technique using a hamstring autograft demonstrates excellent subjective and objective clinical outcomes in skeletally immature athletes without physeal arrest.

Paediatric ACL repair reinforced with temporary internal bracing

PURPOSE

Instability following non-operative treatment of anterior cruciate ligament (ACL) rupture in young children frequently results in secondary chondral and/or meniscal injuries. Therefore, many contemporary surgeons advocate ACL reconstruction in these patients, despite the challenges posed by peri-articular physes and the high early failure rate. We report a novel management approach, comprising direct ACL repair reinforced by a temporary internal brace in three children.

METHODS

Two patients (aged 5 and 6 years) with complete proximal ACL ruptures and a third (aged seven) with an associated tibial spine avulsion underwent direct surgical repair, supplemented with an internal brace that was removed after 3 months.

RESULTS

Second-look arthroscopy, examination and imaging at 3 months confirmed knee stability and complete ACL healing in all cases. Normal activities were resumed at 4 months, and excellent objective measures of function, without limb growth disturbance, were noted beyond 2 years.

CONCLUSION

ACL repair in young children using this technique negates the requirement and potential morbidity of graft harvest and demonstrates the potential for excellent outcome as an attractive alternative to ACL reconstruction, where an adequate ACL remnant permits direct repair.

LEVEL OF EVIDENCE

IV.

Histological changes of semitendinosus autograft after anterior cruciate ligament reconstruction in an immature rabbit model

Introduction

The anterior cruciate ligament (ACL) injury is one of the most common in the knee. Tendons can be used as alternative grafts for ACL repair, with tendon “ligamentization” often reported in literature. The purpose of this study was to evaluate the morphological and histological changes occurring in a semitendinosus tendon (ST) during ACL reconstruction in growing rabbits.

Materials and methods

Twenty-one 8-week-old New Zealand white rabbits, weighing about 1500 g underwent reconstructive surgery on the right knee. In two cases the left knee was used to verify the normal microstructure of the ACL and ST in rabbits. The rabbits were then randomly divided into seven groups and sacrificed at 1, 4, 6, 8, 12, 24 and 48 weeks after surgery. The specimens were evaluated under light microscopy to analyze the changes in the intra-articular tract of the graft. The evidence of necrosis, neovascularization and organization of the collagen fibers were investigated.

Results

One month after surgery, numerous disorganized fibroblasts and collagenous fibers were identified. A marked reduction of cellular necrosis was observed in the early phase of the neo-ligament healing process. After 4 weeks, these fusiform-like cells became more rounded. By 8 weeks, the collagen fibers had become aligned in parallel with newly formed capillaries and highly differentiated fibroblasts. At 24 and 48 weeks the transplanted tendon differed histologically from both tendon and ligament.

Conclusions

The data of the present study showed that ligamentization did not occur until at least 24 months post-operatively and, during healing, the grafted tendon assumed a unique micro-architecture that was a middle between a tendon and a ligament.

The ACL reconstruction in pediatric age has become more frequent in these past recent years. The use of semitendinosus graft with preservation of its distal attachment should be the gold standard in skeletally immature patients.

Surgical-experimental principles of anterior cruciate ligament (ACL) reconstruction with open growth plates

Objective

To review surgical and animal experimental studies performed with open growth plates in relation with pediatric anterior cruciate ligament (ACL) reconstruction.

Backround

When it comes to the treatment of ACL injured children, there is a lack of current international guidelines, leaving the treating physicians with a therapeutic dilemma. A variety of surgical and animal experimental studies have been undertaken over the last decades in relation with open growth plates and ACL-reconstruction.

Method

Based on our own previous animal experimental data, we highlighted 15 specific points concerning pediatric ACL-reconstruction and reviewed additional literature concerning these individual items.

Results

Pediatric ACL-reconstruction could be proven to be safe in animal models. Growth abnormalities, risk factors and factors, which were specifically related to biological healing processes in children, were identified. From them surgical principles for safe pediatric ACL replacements can be deducted. Applying these principles through a correct technical execution of surgery may prevent clinically significant growth changes.

Conclusion

Over the last 2 decades it has been shown that a technically correct pediatric ACL reconstruction has little risk in creating clinically significant growth abnormalities. Animal experiments support this hypothesis despite the fact that the gained knowledge cannot be fully generalized to humans. More long time follow-up is needed to fully understand the complete risk factors related to ACL surgery with open growth plates.

Electronic supplementary material

The online version of this article (doi:10.1186/s40634-015-0027-z) contains supplementary material, which is available to authorized users.

Factors predictive of concomitant injuries among children and adolescents undergoing anterior cruciate ligament surgery

BACKGROUND

The timing of treatment for pediatric anterior cruciate ligament (ACL) injuries remains controversial. The risks of delaying reconstruction and the differences between age groups are poorly defined.

PURPOSE

To investigate factors that contribute to the prevalence and severity of concomitant chondral and meniscal injuries among patients aged 14 to 19 years versus those aged ≤14 years at the time of ACL reconstruction. The hypothesis was that concomitant injuries would be more prevalent in older versus younger subjects. Also, a delay in surgery would be predictive of the presence and severity of concomitant knee injuries requiring additional operative procedures.

STUDY METHODS

Cohort study; Level of evidence, 3.

METHODS

All subjects who underwent primary ACL reconstruction at a single tertiary pediatric hospital between 2005 and 2012 were retrospectively reviewed. The location, severity, and treatment of all concomitant knee injuries were recorded. Chi-square tests were used to compare the prevalence of chondral and meniscal injuries in the older (age, 14-19 years; n = 165) versus younger (age, ≤14 years; n = 66) cohorts. A multivariable logistic regression analysis was used to identify factors related to the presence of a concomitant injury that required additional treatment. Kaplan-Meier analyses were used to explore the relation between time to surgery and meniscal injury severity.

RESULTS

There was a significant relationship between time to surgery and the development of an irreparable meniscal injury (P < .05 for all) in both the younger and older groups. Time to surgery correlated with severity of chondral injury in the younger cohort (P = .0343) but not in the older cohort (P = .8877). In the younger cohort, only a delay in surgery >3 months (odds ratio [OR] = 4.8; 95% CI, 1.7-14.4; P = .0027) was significantly predictive of the presence of an injury that required additional operative procedures. In the older patients, a return to activity before surgery (OR = 3.8; 95% CI, 1.52-11.9; P = .0034) and obesity (OR = 2.5; 95% CI, 1.1-7.4; P = .0381) were significantly predictive of an injury that required additional operative procedures.

CONCLUSION

Compared with younger subjects, the prevalence of concomitant knee injuries as well as the need for additional operative procedures was greater among older subjects. A delay to surgery correlated with increased severity of injury among both older and younger populations. A delay in surgery >3 months was the strongest predictor of the development of a concomitant injury in the younger cohort. A return to activity and obesity were significantly related to the presence of a concomitant knee injury in the older cohort.

Platelet-rich plasma for enhancing surgical rotator cuff repair: evaluation and comparison of two application methods in a rat model

PURPOSE

Platelet-rich plasma (PRP) is a natural concentrate of autologous growth factors now being widely tested in different fields of medicine for its potential in enhancing the regeneration of tissue with low healing potential. However, studies of PRP in enhancing rotator cuff repair have been contradictory, perhaps because of how PRP is administered. The purpose of this study is to evaluate the effect of PRP and compare two different application methods of PRP on rotator cuff healing.

METHODS

The supraspinatus tendons of 48 mature, male Wistar-Albino rats were detached from their insertion on the humerus. The animals were divided into four groups: (1) no repair, (2) primary repair, (3) repair plus PRP injections into the tendon-bone interface, and (4) repair plus PRP absorbed from a sponge carrier to the tendon-bone interface. The tendons were evaluated biomechanically and histologically at week 8.

RESULTS

Cuffs repaired with PRP had significantly greater mean (SD) load-to-failure rates [11.1 (6.5) and 11.6 (3.9) N; P < 0.05] and stiffness [3.5 (2.3) and 1.6 (0.75) N; P < 0.05] than did cuffs repaired without PRP. The groups receiving PRP did not differ significantly on these variables. Histological evaluation showed no significant differences among the four groups.

CONCLUSIONS

The application of PRP, independent of the application method, significantly improved biomechanical properties at the rotator cuff tendon-bone interface. The type of application, injection or absorption from a sponge did not influence the effect of PRP on rotator cuff healing.

Transphyseal anterior cruciate ligament reconstruction in the skeletally immature: follow-up to a minimum of sixteen years of age

BACKGROUND

The evidence in favor of early surgical treatment of anterior cruciate ligament (ACL) injuries in children is increasing. However, the controversy regarding the safety of such a procedure in young athletes with wide open physes remains unresolved.

METHODS

We reviewed prospectively collected outcome data on consecutive patients who had undergone transphyseal ACL reconstruction at either (1) an age of less than fourteen years and Tanner stage 1 or 2, or (2) an age of less than twelve years and Tanner stage 3. Children who had less than four years of follow-up, who were younger than sixteen years at the time of final follow-up, or who had been at Tanner stage 4 at the time of surgery were excluded. Twenty-eight of the thirty-two included patients had been at Tanner stage 1 or 2 at the time of surgery, and the remaining four had been at Tanner stage 3 but had been younger than twelve years of age. The mean age at the time of the surgery was 11.25 years (range, 9.5 to 14.0 years; median, 12.1 years). The mean duration of follow-up was 72.3 months (range, forty-eight to 129 months; median, seventy-two months).

RESULTS

The mean Lysholm score improved from 71.5 preoperatively to 95.86 postoperatively (p < 0.0001). The mean Tegner activity scale score improved from 4.03 to 7.66 (p < 0.0001), which was comparable with the preinjury score of 8.0. One patient had a mild valgus deformity with no functional disturbance, and none had a limb-length discrepancy. One rerupture occurred, but all other patients had a good or excellent outcome.

CONCLUSIONS

This case series indicates good long-term results of ACL reconstruction with use of a transphyseal technique in young children.

Effects of suture choice on biomechanics and physeal status after bioenhanced anterior cruciate ligament repair in skeletally immature patients: a large-animal study

PURPOSE

The objective of this study was to assess the effect of absorbable or nonabsorbable sutures in bioenhanced anterior cruciate ligament (ACL) repair in a skeletally immature pig model on suture tunnel and growth plate healing and biomechanical outcomes.

METHODS

Sixteen female skeletally immature Yorkshire pigs were randomly allocated to receive unilateral, bioenhanced ACL repair with an absorbable (Vicryl) or nonabsorbable (Ethibond) suture augmented by an extracellular matrix-based scaffold (MIACH). After 15 weeks of healing, micro-computed tomography was used to measure residual tunnel diameters and growth plate status, and biomechanical outcomes were assessed.

RESULTS

At 15 weeks postoperatively, there was a significant difference in tunnel diameter with significantly larger diameters in the nonabsorbable suture group (4.4 ± 0.3 mm; mean ± SD) than in the absorbable group (1.8 ± 0.5 mm; P < .001). The growth plate showed a significantly greater affected area in the nonabsorbable group (15.2 ± 3.4 mm(2)) than in the absorbable group (2.7 ± 0.8 mm(2), P < .001). There was no significant difference in the linear stiffness of the repairs (29.0 ± 14.8 N/mm for absorbable v 43.3 ± 28.3 N/mm for nonabsorbable sutures, P = .531), but load to failure was higher in the nonabsorbable suture group (211 ± 121.5 N) than in the absorbable suture group (173 ± 101.4 N, P = .002). There was no difference between the 2 groups in anteroposterior laxity at 30° (P = .5117), 60° (P = .3150), and 90° (P = .4297) of knee flexion.

CONCLUSIONS

The use of absorbable sutures for ACL repair resulted in decreased physeal plate damage after 15 weeks of healing; however, use of nonabsorbable sutures resulted in 20% stronger repairs.

CLINICAL RELEVANCE

Choice of suture type for ACL repair or repair of tibial avulsion fractures may depend on patient skeletal age and size, with absorbable sutures preferred in very young, small patients at higher risk with physeal damage and nonabsorbable sutures preferred in larger, prepubescent patients who may place higher loads on the repair.

All-epiphyseal, all-inside anterior cruciate ligament reconstruction technique for skeletally immature patients

Anterior cruciate ligament (ACL) injuries are an increasingly recognized problem in the juvenile population. Unfortunately, outcomes with conservative treatment are extremely poor. Adult reconstruction techniques are inappropriate to treat skeletally immature patients because of the risk of physeal complications, including limb-length discrepancy and angular deformities. "Physeal-sparing" reconstruction techniques exist, but their ability to restore knee stability is not well understood. We describe an all-epiphyseal ACL reconstruction for use in skeletally immature patients. This is an all-inside technique with the femoral tunnel drilled retrograde and the tibial tunnel drilled retrograde; both tunnels are entirely within the epiphysis. Fixation of the hamstring autograft is achieved with soft-tissue buttons on both the femur and tibia. We present case examples for 2 patients who underwent the all-inside, all-epiphyseal reconstruction and our postoperative rehabilitation protocol. We present a novel surgical technique for an all-inside, all-epiphyseal ACL reconstruction in skeletally immature patients.

Management of anterior cruciate ligament injuries in skeletally immature individuals

Anterior cruciate ligament (ACL) injuries in skeletally immature individuals remain a challenge for the child, the parents, orthopaedic surgeons, and physical therapists. The main challenges are the potential risk of recurrent instability, secondary injuries following nonoperative treatment, and the risks involved with surgical treatment due to the vulnerability of the epiphyseal growth plates. We first present the physiological background for considerations that must be made when advising on treatment alternatives for skeletally immature individuals after ACL injury. The implications of continuous musculoskeletal development for treatment decisions are emphasized. No randomized controlled trials have been performed to investigate outcomes of different treatment algorithms. There is no consensus in the literature on clinical treatment decision criteria for whether a skeletally immature child should undergo transphyseal ACL reconstruction, physeal sparing ACL reconstruction, or nonoperative treatment. Additionally, well-described rehabilitation programs designed for either nonoperative treatment or postoperative rehabilitation have not been published. Based on the currently available evidence, we propose a treatment algorithm for the management of ACL injuries in skeletally immature individuals. Finally, we suggest directions for future prospective studies, which should include development of valid and reliable outcome measures and specific rehabilitation programs.

Treatment of anterior cruciate ligament injury in skeletally immature patients

The incidence of ACL tears is rising in the pediatric and adolescent populations as these individuals succumb to traumatic and nontraumatic athletic injuries. Management of this condition in the skeletally immature patient poses a challenge and is controversial. Operative reconstruction carries the concern for damage to the physis with resultant limb length inequality and angular joint deformity but provides stability to the knee and allows return of function in most patients. On the other hand, nonoperative treatment has been shown to carry an increased risk of meniscal and articular cartilage damage and is difficult from a compliance standpoint in this demographic. For the majority of skeletally immature patients, operative treatment is recommended as it has shown good clinical and functional results with minimal risk of growth disturbance. This paper aims to address the natural course of ACL injuries in the skeletally immature patient, treatment options with associated complications, and current preventative strategies.

Growth plate disturbance after transphyseal reconstruction of the anterior cruciate ligament in skeletally immature adolescent patients: an MR imaging study

BACKGROUND

There are concerns of potential growth disturbance after transphyseal reconstruction of the anterior cruciate ligament in skeletally immature patients. The authors used magnetic resonance (MR) imaging to evaluate growth disturbance and associated physeal abnormalities after index surgery.

METHODS

We retrospectively reviewed the follow-up MR imaging studies of 43 patients who underwent transphyseal reconstruction of the anterior cruciate ligament using a soft-tissue graft at the mean age of 14.8 years (range, 12.4 to 16.5 y). Mean time from surgery to follow-up MR imaging was 16 months (range, 6 to 36 mo). Bone tunnel to growth plate cross-sectional area ratios were calculated as percentages. Focal growth disturbances were assessed in the follow-up MR images in terms of physeal tenting, the presence of a focal bone bridge, an asymmetric growth arrest line of Harris, and metaphyseal extension of physeal cartilage. Physeal angles with respect to the longitudinal axes of the corresponding bones were measured in preoperative MR images and compared with those measured in follow-up images. Premature physeal closure was assessed using the proximal fibular growth plate as an internal control. Clinically, growth disturbances were assessed with physical examinations regarding standing pelvic heights and alignments of the lower extremities.

RESULTS

The bone tunnel to growth plate ratio was < 3% for proximal tibia and distal femur. A focal bone bridge was observed in 5 patients-4 at the tibial physis and 1 at the femoral physis. Physeal angles did not change significantly during follow-up in either the coronal or sagittal plane. Earlier physeal closure than other physes was observed in 2 proximal tibiae. Clinically, there were no perceived growth disturbances.

CONCLUSIONS

MR imaging revealed that focal physeal disruption developed after index procedure in 5 of 43 adolescent patients (11.6%) without a perceived clinical growth disturbance. The results suggest that transphyseal reconstruction of the anterior cruciate ligament may not be a benign procedure that can be applied safely to younger children with substantial growth remaining.

LEVEL OF EVIDENCE

Retrospective Case Series, Therapeutic Level IV.

Volumetric injury of the distal femoral physis during double-bundle ACL reconstruction in children: a three-dimensional study with use of magnetic resonance imaging

BACKGROUND

Double-bundle anterior cruciate ligament (ACL) reconstruction was developed to produce a more "anatomic" reproduction of the anteromedial and posterolateral bundles of the ACL. The purpose of this study was to determine the volume of injury to the physis during double-bundle ACL reconstruction in children with open physes.

METHODS

Magnetic resonance images (MRIs) of ten knees of children were converted into three-dimensional models. Computer-aided design/computer-aided manufacturing software placed drill-holes of 6, 7, 8, and 9 mm in diameter in these models, simulating tunnels in the femur used for anatomic double-bundle ACL reconstruction. Computer-aided design/computer-aided manufacturing software was used to calculate the total physeal volume and the volume of physis that was removed by creation of the tunnels. The ratio of the physeal volume that had been removed to the total physeal volume was subsequently determined.

RESULTS

With use of 6, 7, 8, and 9-mm-diameter drill-holes in the femur, the average physeal volume removed, as a percentage of the total physeal volume, was 1.5%, 2.0%, 2.5%, and 2.9%, respectively, for the anteromedial tunnels; 2.2%, 2.9%, 3.6%, and 4.2% for the posterolateral tunnels; and 3.7%, 4.8%, 5.7%, and 6.5% for the anteromedial and posterolateral tunnels combined. The volume of physeal damage caused by the posterolateral drill-holes was greater than that produced by the anteromedial drill-holes in all subjects.

CONCLUSIONS

Drill-hole placement during ACL reconstruction produces a zone of physeal injury. Double-bundle techniques substantially increase the volume of injury to the physis, which appears to increase the risk of abnormal growth in the distal femoral physis following this surgical procedure.

Transphyseal anterior cruciate ligament reconstruction in a skeletally immature knee using anterior tibialis allograft

Anterior cruciate ligament (ACL) injury in the skeletally immature individual is being recognized with increasing frequency. Nonoperative treatment of ACL injuries in skeletally immature patients have not been favorable. Surgical treatment options for complete ACL tears include primary ligament repair, extraarticular tenodesis, transphyseal reconstruction, partial transphyseal reconstruction, and physeal-sparing reconstruction. The advantage of transphyseal reconstruction is placement of the graft tissue in an isometric position, which provides better results, according to the literature. The potential disadvantage is angular or limb-length discrepancy caused by physeal violation. Controversy exists in allograft selection about whether bone or soft tissue passes into physes. The use of standard tunnels provides reliable results, but carries the risk of iatrogenic growth disturbance from physeal injury.This article presents 4 cases of transphyseal ACL reconstruction using anterior tibialis allograft in skeletally immature patients that had satisfactory functional outcomes with no growth disturbances. This is the first report of transphyseal ACL reconstruction using anterior tibialis allograft in skeletally immature patients in the English-speaking literature. All patients underwent transphyseal ACL reconstruction using anterior tibialis tendon allograft. None of the patients had angular deformities. No early physeal arrest was measured between the preoperative and postoperative radiographs. At last follow-up, the results of the Lachman test were normal for 3 patients and nearly normal for 1 patient. All patients demonstrated full range of knee motion (comparing the reconstructed knee to the contralateral knee). The results of the pivot-shift test were normal for 3 patients and nearly normal for 1 patient. No patients reported giving way.

Treating anterior cruciate ligament tears in skeletally immature patients

PURPOSE

To systematically review the current evidence for conservative and surgical treatment of anterior cruciate ligament (ACL) tears in skeletally immature patients.

METHODS

A systematic search of PubMed, CINAHL, EMBASE, CCTR, and CDSR was performed for surgical and/or conservative treatment of complete ACL tears in immature individuals. Studies with less than six months of follow-up were excluded. Study quality was assessed and data were collected on clinical outcome, growth disturbance, and secondary joint damage.

RESULTS

We identified 48 studies meeting the inclusion criteria. Conservative treatment was found to result in poor clinical outcomes and a high incidence of secondary defects, including meniscal and cartilage injury. Surgical treatment had only very weak evidence for growth disturbance, yet strong evidence of good postoperative stability and function. No specific surgical treatment showed clearly superior outcomes, yet the studies using physeal-sparing techniques had no reported growth disturbances at all.

CONCLUSIONS

The current best evidence suggests that surgical stabilization should be considered the preferred treatment in immature patients with complete ACL tears. While physeal-sparing techniques are not associated with a risk of growth disturbance, transphyseal reconstruction is an alternative with a beneficial safety profile and a minimal risk of growth disturbance. Conservative treatment commonly leads to meniscal damage and cartilage destruction and should be considered a last resort.

LEVEL OF EVIDENCE

Level IV, systematic review of Level II, III, and IV studies.

Correlation of magnetic resonance imaging and histologic examination of physeal bars in a rabbit model

BACKGROUND

The formation of a physeal bony bridge, or bar, is frequently observed in pediatric patients after trauma and is visualized using magnetic resonance imaging (MRI). No study to date has validated the indirect MRI bar area measurements with direct measurements.

PURPOSE

To create a physeal bar using a radiofrequency (RF) ablation technique in a rabbit model and to validate an indirect measurement of the bar area from MRIs with direct histologic measurements.

METHODS

An epiphysiodesis procedure was performed on the proximal tibial growth plates of 15 skeletally immature rabbit knees using radiofrequency ablation. The rabbits were euthanized 6 weeks postoperatively and volumetric ex vivo MRIs of the knees were acquired. The physeal bar area was calculated from a 3-dimensional reconstruction of the segmented MRIs and from matching histologic sections of the tibia.

RESULTS

A physeal bar was successfully created in all the rabbits. A strong correlation, r=0.83 (P=0.0001), was found between the MRI and histologic surface area measurements. The mean bar area from MRI measurements was 35.0 ± 20.8 mm² (mean ± SD), and the mean bar area from histologic measurements was 29.8 ± 16.1 mm².

CONCLUSIONS

This study found excellent correlation between the MRI and histologic physeal bar area measurements. The measurement differences that were found may be attributed to histologic specimen preparation and the geometry chosen to model the physis.

CLINICAL RELEVANCE

The results of this study allow for the quantitative evaluation of in vivo human physes in future studies and development of predictive models for limb length discrepancy.

Valgus and flexion deformity after reconstruction of the anterior cruciate ligament in a skeletally immature patient

Anterior cruciate ligament reconstruction in children with open physes is still a topic of debate. We report a unique case of growth disturbance in valgus and flexion of the distal femoral epiphysis, after an ACL reconstruction in a 14.5-year-old boy. The Clocheville technique using the patellar tendon was performed. The femoral tunnel and tibial groove were both positioned above the growth plates. Eighteen months after ACL reconstruction, the patient had to be re-operated on for a valgus and flexion deformity of the femoral epiphysis. The clinical, radiological and aesthetic results were satisfactory. The angular deformity was caused by the fact that either the femoral tunnel was too close to the posterolateral femoral growth plate or an excessive eccentric traction of the graft in relation to the central point of the knee.

Transphyseal anterior cruciate ligament reconstruction in patients with open physes

PURPOSE

The purpose of this study was to evaluate the clinical outcomes of transphyseal anterior cruciate ligament (ACL) reconstruction in patients with open physes.

METHODS

Transphyseal ACL reconstruction was performed in 26 patients with open tibial and femoral physes (physis >2 mm) by use of autogenous quadrupled hamstrings as grafts. Meniscal tearing was found in 65.3% of the patients. Partial chondral defect injury on the medial femoral condyle was found 6 months after injury in only 2 patients (7.69% of all patients). The mean follow-up period was 45 +/- 18.3 months. Clinical outcomes were evaluated by use of the International Knee Documentation Committee score and Lysholm Knee Scoring Scale, and the anteroposterior stability was objectively measured by use of KT-1000 arthrometer (MEDmetric, San Diego, CA). Possible length and angular discrepancies were observed by conventional radiography in a long film and scanograms of the lower limbs.

RESULTS

The mean length discrepancy between the operated lower limb and the contralateral limb was 1.2 +/- 3.2 mm (range, -7 to 7 mm). The mean angular deviation difference between the lower limbs was 0.46 degrees +/- 1.1 degrees . New traumatic injuries developed in 3 patients, in whom surgical revision was performed; 1 patient underwent a late meniscectomy. The mean difference in KT-1000 measurement was 2.0 +/- 1.0 mm. The mean subjective International Knee Documentation Committee score was 91.5 +/- 5.7, and the mean score on the modified Lysholm scale was 93.5 +/- 4. Of the patients, 3 (11.2% of all patients) could not return to the same level of physical activity as before injury.

CONCLUSIONS

ACL reconstruction by use of the transphyseal technique in an immature skeleton with a hamstring autograft, with careful attention being paid to the technique, resulted in good clinical outcomes and no growth abnormalities.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

Double-bundle anterior cruciate ligament reconstruction in a skeletally immature adolescent athlete

We present a technique for double-bundle anterior cruciate ligament (ACL) reconstruction in a 14-year-old female athlete. The patient presented with anterolateral knee rotatory instability following a traumatic injury suffered while practicing judo. The clinical examination revealed positive Lachman and pivot shift tests with no accompanying meniscal pathology. Roentgenograms revealed open physes, and magnetic resonance imaging scans confirmed an isolated midsubstance ACL tear without cartilaginous injury. The decision was made to anatomically reconstruct the ACL because the athlete wished to continue competitive judo. Autologous hamstring tendons were harvested for double-bundle ACL repair. Following arthroscopic retrograde femoral and antegrade tibial tunnel placement, the ligaments were secured using interference screws within the femoral and tibial epiphysis. Postoperative Lachman and pivot shift tests were negative.

Hindlimb growth after a transphyseal reconstruction of the anterior cruciate ligament: a study in skeletally immature sheep with wide-open physes

BACKGROUND

There is a lot of controversy in the recent literature with regard to the optimal treatment of anterior cruciate ligament (ACL) injuries during growth. Iatrogenic growth disturbance due to physeal damage is a potential complication, forcing many orthopaedic surgeons to treat these injuries conservatively.

HYPOTHESIS

It is possible to perform a fully transphyseal ACL reconstruction in an ovine model with wide-open physes without creating growth disturbances.

STUDY DESIGN

Descriptive laboratory study.

MATERIALS AND METHODS

Four-month-old skeletally immature sheep underwent a transphyseal ACL reconstruction of the right knee. The surgical technique followed the criteria known to be essential to avoid growth disturbances in humans; the tibial tuberosity was spared to prevent a genu recurvatum, thermal damage to the growth plates was avoided, the physes were perforated with a small-diameter drill in the center of the growth plate, a soft tissue graft was used, graft fixation was achieved far away from the growth plates, the perforated growth plates were filled by the soft tissue graft, and the graft was moderately pretensioned before fixation. The left knee served as a control. A computer-assisted evaluation of long radiographs (frontal and sagittal plane) of the exarticulated hindlimbs was performed to exactly evaluate the limb alignment, joint orientation, and leg length. The animals were sacrificed in groups of 6 after 3, 6, 12, and 24 weeks.

RESULTS

No angular deformities or leg-length discrepancies occurred after this transphyseal ACL reconstruction procedure throughout the remaining growth.

CONCLUSION

This large-animal study supports the clinical observation that it is possible to perform an ACL reconstruction without creating growth disturbances as long as a number of key principles are followed.

CLINICAL RELEVANCE

Previous animal studies argued against ACL reconstruction in skeletally immature patients. This large-animal study provides support for early operative treatment of ACL ruptures even in young patients with open physes.

Histologic and biomechanical analysis of anterior cruciate ligament graft to bone healing in skeletally immature sheep

PURPOSE

It was our aim to establish an animal model and to investigate the tendon graft-to-bone and physis healing process in skeletally immature sheep after reconstruction of the anterior cruciate ligament (ACL).

METHODS

Thirty-two immature sheep aged 4 months underwent a fully transphyseal ACL reconstruction by use of a soft-tissue graft. The animals were subsequently killed after 3, 6, 12, and 24 weeks and analyzed histologically and biomechanically.

RESULTS

There was a transient hypertrophy of the physis tissue at the passing site of the graft. Anchoring Sharpey-like fibers evolved as early as 3 weeks after surgery. A strong expression of collagen III messenger ribonucleic acid within the first 6 weeks preceded this anchoring process. The maximum load to failure of the tendon graft in the reconstructed knees initially decreased to 37.8 +/- 17.8 N after 3 weeks and was restored to 522.9 +/- 113 N after 24 weeks. Tendon graft stiffness was restored to 86% when compared with the control knees.

CONCLUSIONS

The early anchoring by Sharpey fibers was found at 3 weeks with continued maturation to 24 weeks. This development of anchoring fibers corresponded to that of biomechanical strength, starting with 5% of the normal knee at 3 weeks and then 15.2% at 6 weeks, 41.2% at 12 weeks, and 69% at 24 weeks. Tendon graft-to-bone and physis healing in skeletally immature sheep is further characterized by a transient hypertrophy of the physis cartilage. The physis recovers well from the trauma of drilling and placement of a soft-tissue graft. The early development of Sharpey-like fibers results in a solid integration of the graft into bone in a timely manner.

CLINICAL RELEVANCE

ACL reconstruction in skeletally immature individuals is still controversial. This study describes in detail the histologic and biomechanical stages of tendon graft healing to the bone and physis. These data enrich the existing knowledge of previous studies in adult sheep and may provide a basis for further research in the controversial field of ACL reconstruction during growth.