MRI Anatomy of the Tibial ACL Attachment and Proximal Epiphysis in a Large Population of Skeletally Immature Knees: Reference Parameters for Planning Anatomic Physeal-Sparing ACL Reconstruction

Management of Anterior Cruciate Ligament Tears in Skeletally Immature Patients

PURPOSE OF REVIEW

Anterior cruciate ligament (ALC) tears are increasingly common in skeletally immature patients, as more children and adolescents participate in intensive sports training and specialization at increasingly younger ages. These injuries were historically treated nonoperatively, given concerns for physeal damage and subsequent growth disturbances after traditional ACL reconstruction techniques. However, there is now sufficient data to suggest superior outcomes with operative treatment, specifically with physeal-sparing and physeal-respecting techniques. This article reviews considerations of skeletal maturity in patients with ACL tears, then discusses surgical techniques, with a focus on their unique indications and outcomes. Additional surgical adjuncts and components of postoperative rehabilitation, which may reduce retear rates, are also considered.

RECENT FINDINGS

Current research shows favorable patient-reported outcomes and high return-to-sport rates after ACL reconstruction in skeletally immature patients. Graft rupture (ACL retear) rates are low, but notably higher than in most adult populations. Historically, there has been insufficient research to comprehensively compare reconstruction techniques used in this patient population. However, thoughtful systematic reviews and multicenter prospective studies are emerging to address this deficit. Also, more recent data suggests the addition of lateral extra-articular procedures and stringent return-to-sports testing may lower retear rates. Physeal-sparing and physeal-respecting ACL reconstructions result in stabilization of the knee, while respecting the growth remaining in children or skeletally immature adolescents. Future research will be essential to compare these techniques, given that more than one may be appropriate for patients of a specific age and skeletal maturity.

Pediatric anterior cruciate ligament tears and associated lesions: Epidemiology, diagnostic process, and imaging

The incidence of anterior cruciate ligament injuries in skeletally immature patients has increased in recent years. The gold standard treatment of this type of trauma in children is not yet established. Conservative management may underestimate the risk of new meniscal and chondral tears; on the other hand, a more interventional approach may expose the patient to iatrogenic damage to the growth plate. A correct approach to the skeletally immature patient with knee trauma is therefore essential to guide the decision-making process. This review article aims to present an update on the epidemiology and diagnostic process of pediatric patients with anterior cruciate ligament tears and possible associated injuries. Level of Evidence: V.

Anterior Cruciate Ligament Rupture in Skeletally Immature Patients

In the past 20 years, sports injuries in pediatric and adolescent athletes have increased dramatically, with anterior cruciate ligament (ACL) injuries accounting for more than 25% of all knee injuries at this age. Diagnosis is based on detailed clinical history, physical examination, and imaging assessment, where magnetic resonance imaging plays a central role. The growing immature skeleton presents specific characteristics, which require unique methods for surgical reconstruction, ideally avoiding the physes or minimizing the risk of damaging them. Specific rehabilitation protocols are needed, and these patients face a higher risk of recurrent and contralateral ACL injury. Nonsurgical treatment or delayed reconstruction has been associated with persistent instability, activity modifications, worst functional outcomes, and increased risk of irreparable injuries to menisci and articular cartilage. Consequently, surgical stabilization is the preferred treatment for most patients, despite the eventual risk of angular deformities or limb-length discrepancies due to iatrogenic physeal injury. A variety of surgical techniques have been described, depending on the skeletal maturity and growth remaining. Targeted prevention programs play a key role in reducing the risk of ACL injury, are easy to implement, and require no additional equipment. High-quality evidence supports its use in all pediatric athletes.

Transepicondylar Distance Can Predict Graft and Tunnel Length for Different Pediatric Anterior Cruciate Ligament Reconstruction Techniques: A Magnetic Resonance Imaging Study

PURPOSE

To find a correlation and mathematical formulas between a linear 2-dimensional (2D) magnetic resonance imaging (MRI) measurement around the knee and the length of the grafts and tunnels required for both all-inside-all-epiphyseal and Kocher-Micheli pediatric anterior cruciate ligament (ACL) reconstruction techniques.

METHODS

At time 0 and 30 days after, 2 observers measured: (1) on standard 2D knee MRI, 7 linear distances, representing morphologic measurements, such as transepicondylar distance (TD), and (2) on 3-dimensional (3D) MRI, 5 curved distances, corresponding to Kocher-Micheli and all-epiphyseal ACL reconstruction techniques. Intra- and interobserver reliability was tested for all measurements. The correlation between 2D and 3D measurements was tested. The 2D measurement with highest repeatability and reproducibility and with strongest correlation with 3D measurements was used to extract formulas to calculate the tunnel and graft length for the 2 techniques.

RESULTS

Seventy-six MRIs were used. The intra- and interobserver reliability of 2D measurement was high, with TD showing the highest reproducibility and repeatability. 3D measurements also showed good intra and inter-observer reliability. A linear correlation was found between 2D and 3D measurements, with TD showing the strongest correlation. TD was used to extract formulas to calculate graft or tunnel length for Kocher-Micheli and all-epiphyseal ACL reconstruction. All formulas were proven to be accurate. A reference chart was also created to be used in the surgical setting.

CONCLUSIONS

With specific formulas, TD can be used to calculate the length of the tunnels, intra-articular portion and graft length for an all-inside all-epiphyseal pediatric ACL reconstruction and the length of the iliotibial band required for the Kocher-Micheli technique.

CLINICAL RELEVANCE

The surgeon can use these formulas in pediatric ACL reconstruction preoperative planning, graft harvesting and tunnel drilling.

Intact PCL is a potential predictor of ACL graft size in the skeletally immature knee and other anatomic considerations for ACL reconstruction

PURPOSE

To develop a method for using an intact posterior cruciate ligament (PCL) as a predictor of anterior cruciate ligament (ACL) graft size and examine possible differences in tunnel length based on all-epiphyseal drilling method.

METHODS

One hundred one patients 5-18 years of age with magnetic resonance imaging (MRI) of the knee at an outpatient pediatric orthopaedic clinic from 2008 to 2020 were included. ACL and PCL coronal, sagittal, and length measurements were made in all patients. Tunnel length measurements were made in patients with open physes. Statistical analyses were performed to evaluate potential associations in patient bony or ligamentous measurements.

RESULTS

PCL sagittal width and PCL coronal width were statistically significant predictors of ACL sagittal width and ACL coronal width, respectively (p = 0.002, R = 0.304; p = 0.008, R = 0.264). The following equations were developed to calculate ACL coronal and sagittal width measurements from the corresponding measurement on an intact PCL; ACL Coronal Width (mm) = 6.23 + (0.16 x PCL Coronal Width); ACL Sagittal Width (mm) = 5.85 + (0.53 x PCL Sagittal Width). Mean tibial maximum oblique length (27.8 mm) was longer than mean tibial physeal sparing length (24.9 mm). Mean femoral maximum oblique length (36.9 mm) was comparable to mean femoral physeal sparing length (36.1 mm). Both were longer than mean femoral straight lateral length (32.7 mm).

CONCLUSION

An intact PCL is a predictor of native ACL size. Tunnel length differs based on chosen drilling method in all-epiphyseal technique.

LEVEL OF EVIDENCE

Diagnostic Level III.

All-Epiphyseal Physeal-Sparing Anterior Cruciate Ligament Reconstructive Surgery: A Study of 3-Dimensional Modeling to Characterize a Safe and Reproducible Surgical Approach

Purpose

The purpose of this study was to use 3-dimensional magnetic resonance imaging modeling of the skeletally immature knee to help characterize safe and reproducible tunnel positions, diameters, lengths, trajectories, and distances from anatomic landmarks and the physeal and articular cartilage for physeal-sparing anterior cruciate ligament (ACL) reconstructive surgery.

Methods

Magnetic resonance imaging from 19 skeletally immature knees with normal anatomy were gathered. The 3-dimensional models were created, and the relevant anatomic structures were identified. Cylinders simulating tunnel length, diameter and trajectory were superimposed onto the models, and descriptive measurements were performed.

Results

A safe position for the creation of an 8 mm diameter femoral tunnel was described in the lateral femoral condyle. The femoral tunnel length averaged 25.5 ± 2.6 mm. The bony entry point was located 3.8 ± 2.4 mm proximally and 12.7 ± 2.2 mm posteriorly to the lateral epicondyle. The shortest distance from the tunnel edge to the physis and femoral articular cartilage was 2.8 ± 0.7 mm and 3.7 ± 0.9 mm, respectively. The safe position for an 8 mm diameter tibial tunnel was also identified and described in the proximal tibia. The epiphyseal tibial tunnel length from the ACL footprint to the physis averaged 15.5 ± 1.6 mm. The proximal tibial epiphysis was found to accommodate a tibial crosspin measuring 63.5 ± 5.9 mm in length and 8.2 ± 1.5 mm in diameter without disrupting the physis or articular cartilage.

Conclusions

Three-dimensional modeling created from magnetic resonance imaging can help define important anatomic relationships for physeal-sparing ACL reconstructive surgery in skeletally immature knees and may assist in reducing the risk of injury to local anatomic structures.

Clinical Relevance

Knowledge of the anatomic relationships in skeletally immature knees serves as a valuable reference for surgeons performing physeal-sparing ACL reconstruction surgery.

Validated Pediatric Functional Outcomes of All-epiphyseal ACL Reconstructions: Does Reinjury Affect Outcomes?

BACKGROUND

Greater frequency and intensity level of sports participation may be contributing to an increasing incidence of anterior cruciate ligament (ACL) tears in skeletally immature athletes. Prior studies have assessed the functional outcomes of physeal-respecting ACL reconstruction in this patient population based on adult functional outcomes scoring systems; however, there is only sparse literature evaluating functional outcomes of this specific patient population. This study aimed to retrospectively evaluate a cohort of pediatric patients who had undergone all-epiphyseal ACL reconstruction (AEACLR) with a set of clinically validated, pediatric-specific patient-reported functional outcomes scores (PRFOS). We hypothesized that patients who had rerupture would have significantly lower outcomes scores compared with those who did not rerupture.

METHODS

This was a retrospective evaluation of AEACLR patients at a single, tertiary care, children's hospital within a period of 2 years and had >6 months of initial clinical postoperative follow-up. Those who consented to participation were provided an online combined survey including questions relating to demographics and rerupture as well as 3 validated pediatric PRFOS. Statistical analysis of the cohort demographics, PRFOS, and subgroup analysis of the rerupture group compared with the ACL intact patients was performed.

RESULTS

The mean functional outcome scores at a mean of 48.6 months from surgery demonstrated excellent return to functional activity (Mean International Knee Documentation Committee, 93.8; Pedi-Patient-Reported Outcomes Measurement Information System, 98.8; Pedi- Functional Activity Brief Score, 21.6). There was a 13% rerupture rate and rerupture patients had a significantly decreased Pedi-International Knee Documentation Committee (94.9 intact vs. 86.0 rerupture; P=0.001) and Pedi-Patient-Reported Outcomes Measurement Information System (99.4 intact vs. 95.4 rupture; P=0.001) scores.

CONCLUSIONS

AEACLR patients have excellent outcomes based on pediatric-specific PRFOS. Rerupture patients demonstrated a decrease in functional outcomes scores compared with intact ACL patients. The results demonstrate the efficacy of AEACLR as measured by pediatric-specific functional outcome scores for the treatment of ACL rupture in skeletally immature athletes.

LEVEL OF EVIDENCE

Level III-retrospective comparative study.

Extra-articular, Intraepiphyseal Drilling for Osteochondritis Dissecans of the Knee: Characterization of a Safe and Reproducible Surgical Approach

Background:

Osteochondritis dissecans (OCD) is an idiopathic focal condition affecting the subchondral bone of joints, and it is increasingly prevalent among the active young adult population. For lesions that have failed nonoperative management, transarticular drilling and extra-articular drilling are surgical options. Although the extra-articular approach preserves the articular cartilage, it is technically challenging and could benefit from a study of surgical approach.

Purpose:

To use 3-dimensional modeling of magnetic resonance imaging (MRI) scans from skeletally immature individuals to characterize safe tunnel entry points, trajectories, and distances from the physeal and articular cartilage along the course of the distal femoral epiphysis to the OCD target in their most common location of the medial femoral condyle (MFC).

Study Design:

Descriptive laboratory study.

Methods:

A total of 17 MRI scans from skeletally immature patients were used to create 3-dimensional models of the knee joint. Virtual representations of an OCD lesion were placed in the lateral aspect of the MFC; cylinders simulating tunnel length, diameter, and trajectory were superimposed onto the models; and measurements were taken.

Results:

Two safe tunnels were identified, 1 anterior and 1 posterior to the medial collateral ligament (MCL). The anterior tunnel had a diameter of 10.3 ± 1.4 mm, skin entry point of 16.9 ± 12.1 mm anterior and 7.1 ± 5.9 mm superior to the medial epicondyle, bony entry point of 12.1 ± 3.5 mm anterior and 2.4 ± 3.5 mm inferior to the medial epicondyle, and tunnel length of 31.8 ± 3.7 mm. The posterior tunnel had a diameter of 7.8 ± 1.8 mm, skin entry point of 9.4 ± 5.1 mm posterior and 26.0 ± 14.0 mm superior to the medial epicondyle, bony entry point of 8.6 ± 2.6 mm posterior and 5.1 ± 4.2 mm superior to the medial epicondyle, and tunnel length of 33.5 ± 4.5 mm.

Conclusion:

This anatomic characterization study identifies and defines 2 safe and reproducible tunnel approaches, 1 anterior and 1 posterior to the MCL, for drilling or creating tunnels to OCD lesions of the MFC in an extra-articular fashion.

Clinical Relevance:

The study findings provide valuable anatomic references for surgeons performing extra-articular drilling or tunneling of OCD lesions.

Three-dimensional isotropic magnetic resonance imaging can provide a reliable estimate of the native anterior cruciate ligament insertion site anatomy

PURPOSE

This study quantified the error in anterior cruciate ligament (ACL) insertion site location and area estimated from three-dimensional (3D) isotropic magnetic resonance imaging (MRI) by comparing to native insertion sites determined via 3D laser scanning.

METHODS

Isotropic 3D DESS MRI was acquired from twelve fresh-frozen, ACL-intact cadaver knees. ACL insertion sites were manually outlined in each MRI slice, and the resulting contours combined to determine the 3D insertion site shape. Specimens were then disarticulated, and the boundaries of the ACL insertion sites were digitized using a high-accuracy laser scanner. MRI and laser scan insertion sites were co-registered to determine the percent overlapping area and difference in insertion centroid location.

RESULTS

Femoral ACL insertion site area averaged 112.7 ± 17.9 mm² from MRI and 109.7 ± 10.9 mm² from laser scan (p = 0.345). Tibial insertion area was 134.7 ± 22.9 mm² from MRI and 135.2 ± 15.1 mm² from laser scan (p = 0.881). Percentages of overlapping area between modalities were 82.2 ± 10.2% for femurs and 81.0 ± 9.0% for tibias. The root-mean-square differences for ACL insertion site centroids were 1.87 mm for femurs and 2.49 mm for tibias. The MRI-estimated ACL insertion site centroids were biased on average 0.6 ± 1.6 mm proximally and 0.3 ± 1.9 mm posteriorly for femurs, and 0.3 ± 1.1 mm laterally and 0.5 ± 1.5 mm anteriorly for tibias.

CONCLUSION

Errors in ACL insertion site location and area estimated from 3D-MRI were determined via comparison with a high-accuracy 3D laser scanning. Results indicate that MRI can provide estimates of ACL insertion site area and centroid location with clinically applicable accuracy. MRI-based assessment can provide a reliable estimate of the native ACL anatomy, which can be helpful for surgical planning as well as assessment of graft tunnel placement.

What's New in Pediatric and Adolescent Anterior Cruciate Ligament Injuries?

BACKGROUND

Anterior cruciate ligament (ACL) tears in children and adolescent patients are being diagnosed and treated at an ever-increasing rates. We performed a review of recent literature regarding care of children and adolescent athletes with an ACL injury.

METHODS

PubMed database was searched for all papers related to treatment of children and adolescents with ACL injuries from October 1, 2012 to September 30, 2015, yielding 114 publications.

RESULTS

A total of 59 papers were found to have contributed important new findings. Papers were selected based on new findings in the following categories: epidemiology, anatomy, risk factors, sex disparity, prevention, surgical outcomes, timing and associated pathologies, and rehabilitation and return to sport.

CONCLUSIONS

Pediatric ACL injuries continue to rise and there are multiple surgical procedures that restore clinical function with good outcomes. Early surgical treatment is favored to prevent concomitant articular injuries. Early return to play can increase risk of reinjury and should be met with caution in this age group. Prevention strategies should be further studied and implemented in hopes of decreasing the incidence of this injury and the long-term potential damage.

LEVEL OF EVIDENCE

Level 4-titerature review.

Multiligament Knee Injuries in Older Adolescents: A 2-Year Minimum Follow-up Study

Background:

Multiligament knee injuries cause significant functional impairment. Adults undergoing anatomic reconstruction of multiligament knee injuries have excellent outcomes postoperatively. However, less is known about the outcomes in adolescent patients following multiligament reconstruction.

Purpose/Hypothesis:

We aimed to assess patient outcomes and failure rates following unstaged multiligament reconstruction in an adolescent population at a minimum 2-year follow-up. We hypothesized that outcomes of multiligament reconstruction in these patients would be comparable to previously reported outcomes in the adult population.

Study Design:

Case series; Level of evidence, 4.

Methods:

The study included patients who had undergone multiligament knee reconstruction at 19 years of age or younger and had at least 2 years of follow-up. All procedures were performed by the same surgeon. Exclusion criteria included patient age 14 years or younger at the time of surgery, open physes, prior ipsilateral meniscal or knee ligament surgery, or a tibial plateau fracture at the time of injury. Multiligament reconstruction was defined as a reconstruction of at least 1 cruciate ligament and at least 1 component of the posterolateral corner or the medial knee. Patients were evaluated according to Lysholm score, Tegner score, Short Form–12 physical component summary (SF-12 PCS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score, and postoperative patient satisfaction.

Results:

Twenty patients (mean age, 17.7 years; mean follow-up, 37.1 months) were included in this study. No patient required additional ligament surgery after the index surgery because of graft failure. The median preoperative Lysholm score was 49.5 (range, 18-90), and the median postoperative Lysholm score was 86 (range, 44-100) (P < .001). The median preoperative Tegner activity score was 2 (range, 0-9), and the median postoperative Tegner activity score was 6 (range, 2-10) (P = .012). The median SF-12 PCS improved from 40.5 preoperatively to a median of 56.1 postoperatively (P < .001). WOMAC total score improved from a median of 26.5 preoperatively to a median of 2 postoperatively (P < .001). Median postoperative patient satisfaction was 10 (range, 5-10).

Conclusion:

Single-stage multiligament knee reconstruction is a reliable procedure that improves knee function at 2-year follow-up in adolescent patients. Patient satisfaction was excellent, but longer follow-up in a larger series of patients is required to determine the long-term benefits of multiligament reconstruction in this patient population.

Variation in the shape of the tibial insertion site of the anterior cruciate ligament: classification is required

PURPOSE

To propose a classification system for the shape of the tibial insertion site (TIS) of the anterior cruciate ligament (ACL) and to demonstrate the intra- and inter-rater agreement of this system. Due to variation in shape and size, different surgical approaches may be feasible to improve reconstruction of the TIS.

METHODS

One hundred patients with a mean age of 26 ± 11 years were included. The ACL was cut arthroscopically at the base of the tibial insertion site. Arthroscopic images were taken from the lateral and medial portal. Images were de-identified and duplicated. Two blinded observers classified the tibial insertion site according to a classification system.

RESULTS

The tibial insertion site was classified as type I (elliptical) in 51 knees (51 %), type II (triangular) in 33 knees (33 %) and type III (C-shaped) in 16 knees (16 %). There was good agreement between raters when viewing the insertion site from the lateral portal (κ = 0.65) as well as from the medial portal (κ = 0.66). Intra-rater reliability was good to excellent. Agreement in the description of the insertion site between the medial and lateral portals was good for rater 1 and good for rater 2 (κ = 0.74 and 0.77, respectively).

CONCLUSION

There is variation in the shape of the ACL TIS. The classification system is a repeatable and reliable tool to summarize the shape of the TIS using three common patterns. For clinical relevance, different shapes may require different types of reconstruction to ensure proper footprint restoration. Consideration of the individual TIS shape is required to prevent iatrogenic damage of adjacent structures like the menisci.

LEVEL OF EVIDENCE

III.

Pediatric Anterior Cruciate Ligament Reconstruction: A Systematic Review of Transphyseal Versus Physeal-Sparing Techniques

BACKGROUND

Anterior cruciate ligament reconstruction is becoming more common in skeletally immature individuals, and it may be performed with transphyseal or physeal-sparing techniques. A number of studies have assessed the outcomes of these techniques, but there is a need to systematically evaluate the pooled data from these studies.

PURPOSE

To compare the differences in demographics and outcomes of transphyseal and physeal-sparing techniques by assessing (1) demographics, (2) incidence of growth disturbances, and (3) graft survivorship in the pediatric population.

STUDY DESIGN

Systematic review.

METHODS

A thorough review of 3 databases was performed to identify all studies that evaluated outcomes after pediatric reconstruction based on transphyseal or physeal-sparing techniques. After completing our search and cross-referencing for additional sources, 43 reports were identified for this review. Reports were analyzed for differences in demographics as well as incidence of leg-length discrepancies, angular deformities, and graft survivorship. After review of manuscripts, 27 studies were included for review (21 transphyseal and 6 physeal-sparing studies).

RESULTS

Those who had transphyseal reconstruction were more likely to be female (39% vs 20%; P = .0001), while those with the physeal-sparing surgery were younger (12 vs 13.5 years of age; P = .0001). The transphyseal and physeal-sparing cohorts demonstrated similar incidence rates of leg-length discrepancies (0.81% vs 1.2%, respectively; P = .64) and angular deformities (0.61% vs 0%, respectively; P = .36). The transphyseal and physeal-sparing cohorts also showed similar rates of rerupture (6.2% vs 3.1%, respectively; P = .11).

CONCLUSION

Although the study groups were not well matched with regard to age and sex, our results show that these surgical techniques have no differences in incidence of growth disturbances or graft survivorship. Younger males tend to undergo physeal-sparing reconstruction. Future research should focus on long-term outcome metrics with the physeal-sparing techniques, as there remains a paucity of studies regarding them.

Pediatric anterior cruciate ligament reconstruction outcomes

Treatment of pediatric anterior cruciate injuries have become an area of controversy sparking much debate about best management strategies. Delaying surgery until skeletal maturity has often been shown to result in unfavorable outcomes due to concomitant meniscal and chondral injuries in this population. There have been numerous techniques used to reconstruct the ACL in the skeletally immature patient; however, most studies are limited by small patient numbers and other methodological concerns. With recent publications reporting failure rates as high as 15-25 % and growth disturbances being uncommon but now reported within almost every technical category, patient and caregiver education become of paramount importance. Key principles will be outlined that may help to avoid some of the pitfalls that occur when dealing with this unique population.

Anterior cruciate ligament reconstruction in skeletally immature patients

The management of pediatric patients with an anterior cruciate ligament (ACL) tear can be a challenging endeavor for physicians, athletic trainers, coaches, and parents alike. In particular, the significant longitudinal growth that arises from the physes about the knee creates a unique set of circumstances that must be considered in this patient population. The purpose of this review is to provide a summary of the most recent current literature for the management of skeletally immature patients with an ACL tear.

Analysis of the Tibial Epiphysis in the Skeletally Immature Knee Using Magnetic Resonance Imaging: An Update of Anatomic Parameters Pertinent to Physeal-Sparing Anterior Cruciate Ligament Reconstruction

BACKGROUND

Physeal-sparing anterior cruciate ligament (ACL) reconstruction is being performed increasingly in skeletally immature knees.

PURPOSE

To determine normal values for the maximum oblique length and "safe" physeal-sparing length and their corresponding angular trajectories across the tibial epiphysis on reconstructed magnetic resonance images (MRIs) in children and adolescents.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

An electronic search for pediatric knee MR examinations from April 2003 to April 2013 was performed at our institution. A 3-dimensional system viewer was used to measure the maximum oblique length, physeal-sparing length, and their corresponding angular trajectories on reconstructed MRIs. Knees were stratified by age into 2 groups: group 1 consisted of boys <13 years and girls <12 years and group 2 consisted of older boys (13-14 years) and girls (12-14 years). Each cohort was further stratified by sex. Group 1 consisted of 36 knees (mean age, 10.9 years) and group 2 consisted of 59 knees (mean age, 13.6 years).

RESULTS

Significant differences existed for the maximum oblique length and its angular trajectory for the younger versus older cohort (22.2 ± 2.7 vs 23.8 ± 2.7 mm, P = .007; 42.0° ± 4.0° vs 39.4° ± 4.2°, P = .003) and for the physeal-sparing length and its angular trajectory (19.4 ± 2.8 vs 21.3 ± 2.9 mm, P = .001; 30.1° ± 4.1° vs 28.2° ± 4.5°, P = .042). In group 2, females had shorter maximal oblique length and physeal-sparing length than boys (22.7 ± 2.3 vs 25.0 ± 2.7 mm, P < .001; 20.3 ± 2.6 vs 22.4 ± 2.9 mm, P = .004).

CONCLUSION

The maximum oblique length across the tibial epiphysis is shorter than previously believed, measuring approximately 22 mm and approximately 24 mm for high- and intermediate-risk knees, respectively. However, "safe" physeal-sparing lengths were only approximately 19 mm and 21 mm for the younger and older cohorts, respectively. The angles corresponding to the maximum and safe lengths are more acute than commonly thought, measuring approximately 40° and 30°, respectively. All prepubescent knees and intermediate-risk females should receive careful attention before ACL reconstruction due to the relative smaller size of their tibial epiphyses.

CLINICAL RELEVANCE

Physeal-sparing ACL reconstruction is gaining acceptance as a surgical option for complete ACL tear in skeletally immature knees. Iatrogenic growth disturbance after violation of an open growth remains a real concern for surgeons tasked with providing operative management for the unstable pediatric knee. Inadvertent iatrogenic growth plate injury to the tibial physis has been shown to occur more commonly than surgeons would intend during physeal-sparing ACL reconstruction.