Surgical Options for Patellar Stabilization in the Skeletally Immature Patient

Robot-Assisted Individualized Medial Patellofemoral Ligament Reconstruction in Skeletally Immature Patients With Recurrent Patellar Dislocation: A Single-Center Retrospective Study

Background

The surgical treatment of patellar instability in children and adolescents can be challenging, as successful surgical techniques used in adults may pose a risk to the open growth plate when applied in this younger population.

Purpose

To review a series of adolescent patients with recurrent patellar dislocation who underwent robot-assisted individualized medial patellofemoral ligament (MPFL) reconstruction.

Study Design

Case series; Level of evidence: 4.

Methods

This retrospective clinical study included 76 patients with recurrent patellar dislocation who underwent MPFL reconstruction by a robot-assisted technique or adductor magnus sling technique from June 2018 to August 2022. All patients were divided into the robot-assisted group (42 patients) or the adductor magnus sling group (34 patients). In both groups, a semitendinosus autograft was used for the MPFL reconstruction. In the robot-assisted group, the graft was fixed to the femur using an interference screw. In the adductor magnus sling group, the graft was loped around the adductor magnus. During the surgery, the distance between Schoettle point and the medial distal femoral physis, along with the simulated angle range of the bone tunnel and the optimal angle, was recorded in the robot-assisted group using an intraoperative 3-dimensional navigation system. The clinical results were evaluated using preoperative and postoperative functional scores and imaging.

Results

All patients returned for follow-up at a mean of 39.7 ± 9.8 months after surgery. The mean age of the patients was 13.3 years (range, 10-16 years). The Schoettle points were all located below the medial distal femoral physis, with a mean distance of 6.48 ± 1.78 mm from Schoettle points to the medial distal femoral physis. The angle range of the bone tunnel was achieved by targeting a mean of 8.6° to 23.4° anteriorly and 10.9° to 17.8° distally, with the optimal angles being 14.6° anteriorly and 13.5° distally. No patients experienced recurrent patellar instability after surgery; however, the functional scores in the robot-assisted group were slightly higher than those in the traditional adductor magnus sling group (International Knee Documentation Committee score: 93.2 ± 6.2 vs 86.1 ± 7.9; Lysholm score: 90.0 ± 8.1 vs 85.9 ± 7.3; Kujala score: 87.8 ± 6.8 vs 83.0 ± 8.8; all P < .05) at the last follow-up. All the patients had normal patellar tracking, except for 3 patients (8.8%) in the adductor magnus sling group. None of the patients exhibited subsequent growth deformity or any evidence of physeal invasion.

Conclusion

The intraoperative robotic navigation system confirmed that the Schoettle point can be safely positioned in patients with open epiphyses. The robot-assisted design of individualized anatomic reconstruction of the MPFL using a forward distal oblique bone tunnel is safe and effective, demonstrating good clinical outcomes.

A Cadaveric Study of the Sagittal Patellar Insertion of the Medial Patellofemoral Ligament in Children: Implications for Reconstruction

BACKGROUND

Patellofemoral instability is a common problem, and medial patellofemoral ligament (MPFL) reconstruction is a standard treatment approach for recurrent instability. The accurate restoration of anatomy in MPFL reconstruction is essential. While coronal-plane anatomy of the MPFL patellar insertion has been previously reported, sagittal-plane anatomy has not been widely studied.

PURPOSE

To evaluate the sagittal patellar insertion of the MPFL in pediatric specimens to guide future anatomic reconstruction.

STUDY DESIGN

Descriptive laboratory study.

METHODS

A total of 11 pediatric cadaveric knee specimens were dissected. The patella and sagittal MPFL insertion were evaluated. The maximal anterior-posterior patellar width, distance from the posterior patella to the posterior MPFL insertion, distance from the medial patellar articular cartilage edge to the MPFL insertion, maximal MPFL thickness, and distance from the anterior MPFL insertion to the anterior patella were measured. The proportion of patellar coverage by the sagittal MPFL insertion footprint was calculated.

RESULTS

The pediatric knee specimens had a mean age of 9.3 ± 1.4 years (range, 6-11 years). The mean maximal transverse patellar width was 19.0 ± 2.7 mm (range, 13.7-22.7 mm). The mean posterior patella-to-posterior MPFL distance was 10.5 ± 1.6 mm (range, 7.7-12.6 mm). The mean patellar articular cartilage edge-to-MPFL distance was 2.3 ± 0.6 mm (range, 1.5-3.5 mm). The mean maximal MPFL thickness was 4.0 ± 0.9 mm (range, 2.6-5.5 mm). The mean anterior MPFL-to-anterior patella distance was 4.4 ± 1.1 mm (range, 2.6-5.8 mm). The sagittal MPFL insertion footprint spanned a mean of 21.0% (range, 16.1%-29.7%) of the medial patella.

CONCLUSION

This study, utilizing skeletally immature cadaveric specimens, demonstrated that the sagittal MPFL insertion consistently resided in the anterior third of the patella, averaging 21% of the total sagittal patellar width. Additionally, the distance from the MPFL insertion to the medial patellar articular cartilage edge showed minimal variation, representing a consistent intraoperative landmark for MPFL graft placement.

CLINICAL RELEVANCE

This research characterized MPFL insertion anatomy on the medial patella in the sagittal plane. This knowledge provides a clear target area for anatomic graft placement during MPFL reconstruction.

Combined Medial Patellofemoral Ligament and Medial Quadriceps Tendon Femoral Ligament Reconstruction With Semitendinosus Allograft for Pediatric Patients With First-Time Patella Dislocation Yields Low Failure Rates and Improved Functional Outcomes Compared With Nonoperative Treatment

PURPOSE

To evaluate the clinical outcomes of nonoperative versus operative treatment, consisting of combined medial patellofemoral ligament and medial quadriceps tendon femoral ligament (MPFL/MQTFL) reconstruction, for first-time patellar dislocation in the skeletally immature population through a standardized, rigorous approach.

METHODS

This consecutive retrospective cohort was composed of all skeletally immature patients who sustained a first-time patellofemoral dislocation. Patients were grouped into nonoperative management (bracing and physical therapy) and operative management (MPFL/MQTFL reconstruction) cohorts. The primary outcome, failure, was defined as subsequent dislocation or subluxation. Additional outcomes included demographics, risk factors for patellofemoral instability, functional outcomes (Kujala and Pediatric International Knee Documentation Committee scores), return to sports, and complications. Minimum follow-up was 2 years. A correlation analysis attempted to identify potential associations between failure and risk factors.

RESULTS

In total, 142 consecutive patients were included with 90 patients in the nonoperative group and 52 patients in the operative group. Failure rates differed by intervention; those receiving operative management had significantly lower failure rates than conservative management (15.4% vs 58.8%, P < .0001). Kujala and Pediatric International Knee Documentation Committee scores were significantly greater in the operative group compared with the nonoperative group (91.5 ± 7.8 vs 82.5 ± 12.1, P < .0001 and 89.0 ± 9.3 vs 78.4 ± 12.9, P < .0001, respectively). Tegner activity level was also greater in the operative group (6.0 ± 1.4 vs 4.0 ± 1.4, P < .0001). Return to sport was significantly greater for those in the operative group (88.5% vs 66.2%, P < .001). Return to same level of activity was achieved in greater percentage of patients treated surgically (91.3% vs 69.6%, P = .0075). Complication rates were more frequent in the operative group compared with the nonoperative group (11.5% vs 1.1%, P < .001).

CONCLUSIONS

MPFL/MQTFL reconstruction in skeletally immature patients with first-time patellofemoral dislocation demonstrated lower failure rates and improved functional outcomes at a minimum 2-year follow-up compared with nonoperative management.

LEVEL OF EVIDENCE

Level III, retrospective cohort study.

Physeal Sparing Approaches for MPFL Reconstruction

PURPOSE OF REVIEW

To update and concepts for pediatric physeal-sparing patellofemoral stabilization surgery.

RECENT FINDINGS

Recent studies have demonstrated positive results in patellofemoral stabilization in pediatric populations with physeal-sparing techniques that limit the potential for physeal damage. Comprehensive analysis remains limited by population and technique heterogeneity. Physeal-sparing patellofemoral stabilization, most significantly through physeal-sparing reconstruction of the medial patellofemoral ligament complex remains a viable option for pediatric patients with recurrent patellofemoral instability.

Return to sports and short-term follow-up of 101 cases of medial patellofemoral ligament reconstruction using gracilis tendon autograft in children and adolescents

INTRODUCTION

An acute patellofemoral dislocation is the most common acute knee injury in children. Recent studies suggest up to 40% of immature patients may develop recurrent instability. MPFL reconstruction has become a mainstay for the treatment of patellofemoral instability. Aim of the recent study is to show our experiences of MPFL reconstruction in patellar instability in immature patients using a gracilis autograft in respect to return to sport, growth plate disorders and short-term results.

MATERIALS AND METHODS

A total of 101 patients (50 females, 51 males) were included in this retrospective study. Mean age at time of operation was 14.8 ± 1.6 years. Primary outcome measures included patient satisfaction, Kujala score, recurrent instability, return to normal activity, return to sports, clinical leg axis and complications. Mann-Whitney U test was used for statistical analysis and alpha was set at p < 0.05 to declare significance.

RESULTS

At a mean follow-up of 32.0 ± 12.1 months 90/101 patients could be followed-up. 84% of all patients were satisfied or very satisfied with the result at latest follow-up. 86.6% of all patients were able to return to sports, 2.3% had a relevant deviation of the clinical leg axis, but symmetrical. In sum complication rate was 2.9%. Redislocation rate was 0.9% (1/101). Kujala Score improved significantly from 47.1 preoperatively to 85.3 postoperatively (p < 0.01).

CONCLUSION

Anatomic MPFL reconstruction using gracilis tendon allograft tissue is a safe procedure in children and adolescents with low risk of recurrent instability.

Osteochondral Fractures in Acute Patellar Dislocations in Adolescents: Midterm Results of Surgical Treatment

Background:

Osteochondral fractures (OCFs) are common injuries during acute patellar dislocation (APD), carrying a high risk of early joint deterioration if left untreated. The recommended approach is reduction and stable fixation; however, data on the results of such treatment are limited.

Purpose:

To evaluate midterm results of fixation of APD-related OCFs in adolescents and to identify predictive factors for poor outcomes.

Study Design:

Case series; Level of evidence, 4.

Methods:

This was a retrospective analysis of adolescent patients who underwent internal fixation of APD-related OCFs between 2004 and 2015 at a single tertiary pediatric trauma center. The primary outcome variables included Knee injury and Osteoarthritis Outcome Score (KOOS), patient satisfaction (0-10 scale), and sports participation compared with preoperative level. Secondary outcome variables included relationship between final results and OCF location (patellofemoral vs tibiofemoral), surgical delay (>6 weeks), and patellar instability after OCF fixation. OCF healing was evaluated using magnetic resonance imaging (MRI).

Results:

Included were 40 patients (19 female, 21 male) with 42 OCFs (29 patellar OCFs, 13 lateral femoral condyle OCFs). The median patient age at surgery was 14.5 years (interquartile range [IQR], 13-15.5 years), and median follow-up was 76 months (IQR, 52.5-95 months). Recurrence of patellar instability occurred in 27.5% of patients. Median overall KOOS was 93.8 (IQR, 90.8-97.6); KOOS–Symptoms, 92.9 (IQR, 85.7-96.4); KOOS–Pain, 97.2 (IQR, 91.7-100); KOOS–Activities of Daily Living, 100 (IQR, 97.1-100); KOOS–Sports, 90 (IQR, 80-100); and KOOS–Quality of Life, 78.1 (IQR, 56.2-87.5). Median satisfaction score was 8 (IQR, 8-9), and 16 patients (40%) returned to sports participation at their preinjury level. MRI scans revealed a 100% rate of bone healing. Abnormalities exceeding the fracture area were evident on MRI scans in 86.5% of patients. Recurrence of patellar instability (even after surgical fixation) and unstable patella at final follow-up were independent predictors of worse results after OCF fixation.

Conclusion:

In the current study, reduction and internal fixation for APD-related OCF in adolescents yielded favorable midterm outcomes. Recurrence of dislocation and persistent patellar instability jeopardized clinical results.

[Tibial tubercle osteotomy in children and adolescents]

Patellofemoral instability (PFI) is one of the most common knee pathologies in children and adolescents. The high risk of re-dislocation necessitates a targeted risk analysis. A high-riding patella and a changed pulling direction of the extensor apparatus, which can be determined from the TTTG distance, are the main risk factors of PFI, also in a young population. The indication for surgical treatment, which is increasingly based on evidence, does not differ significantly from that of adults. However, due to the risk of disturbance of the growth plates, tibial tubercle osteotomy cannot be performed with open physis, which means that the surgical techniques must be adapted to the circumstances. A correction of a high-riding patella and an increased TTTG distance is possible with distal soft tissue procedures without impairing the growth plates, even in children and adolescents, and leads to better results compared with isolated MPFL reconstructions if the cut-off values of risk factors are exceeded and the indication is correct.

Increased tibiofemoral rotation on MRI with increasing clinical severity of patellar instability

PURPOSE

Tibiofemoral rotation through the knee joint, specifically relative external tibial rotation, has been identified as a potential contributing factor to patellar instability. The purpose of this study is to investigate the relationship between severity of instability with degree of tibiofemoral rotation in three clinical cohorts: fixed or obligatory dislocators (in which the patella either is constantly laterally dislocated or laterally dislocates with every instance of knee flexion, respectively), standard traumatic instability patients, and normal controls.

METHODS

A retrospective study was performed with three cohorts from April 2009 to February 2019: fixed or obligatory dislocators, standard traumatic instability patients, and controls with normal magnetic resonance imaging (MRI) of the knee. All fixed or obligatory dislocation patients from the study time frame were analyzed; controls and standard traumatic instability patients were randomly selected. Inclusion criteria were age under 18 years and qualifying diagnosis; exclusion criteria were outside institution MRI and previous MPFL reconstruction or tibial tubercle osteotomy. Tibiofemoral rotation was measured blindly on initial axial MRI using the posterior femoral and tibial condylar lines. Tibial tubercle to trochlear groove distance (TT-TG) was measured. Intraclass correlation coefficient (ICC) was calculated among four measurers.

RESULTS

A total of 100 patients were included, 20 fixed or obligatory dislocators, 40 standard traumatic instability patients, and 40 controls. Median age was 13.2 years (range 10-17 years), with 55 females. Age was significantly higher in the standard traumatic instability group than both the control (p < 0.001) and fixed or obligatory dislocator groups (p = 0.003). ICC for TT-TG and tibiofemoral rotation were 0.92 and 0.96, respectively. Fixed or obligatory dislocator patients averaged 8.5° external tibiofemoral rotation, standard traumatic instability patients 1.6° external tibiofemoral rotation, and controls 3.8° internal tibiofemoral rotation. Both tibiofemoral rotation and TT-TG were highest in the fixed or obligatory dislocator cohort, followed by the standard traumatic instability cohort, and lowest in the controls (p < 0.0001 for tibiofemoral rotation and TT-TG). Multivariate analysis showed no correlation between age and tibiofemoral rotation.

CONCLUSIONS

Measurement of tibiofemoral rotation was reproducible with excellent interrater reliability. The degree of tibiofemoral rotation is correlated with severity of patellar instability, with the greatest external tibiofemoral rotation in fixed or obligatory dislocator patients, followed by standard traumatic instability patients, and slight internal tibiofemoral rotation in controls. High external tibiofemoral rotation may be an important pathoanatomic factor in fixed or obligatory dislocators, and with further understanding may become a prognostic factor or surgical target.

LEVEL OF EVIDENCE

III.

Anterior and distal tunnel orientation for anatomic reconstruction of the medial patellofemoral ligament is safer in patients with open growth plates

PURPOSE

In patients with open growth plates, the direction of tunneling that avoids distal femoral physis (DFP) damage in anatomic reconstructions of the medial patellofemoral ligament (MPFL) has been a topic of discussion. The objective of this study was to determine the ideal orientation for anatomic reconstructions of MPFL tunneling that minimized DFP damage while avoiding breaching the intercondylar notch.

METHODS

Eighty magnetic resonance images of patients aged 10 through 17 were obtained, randomly sampled from the institutional database. A de novo software was developed to obtain 3D models of the distal femur and DFP. In each model, the anatomical insertion point of the MPFL was determined as defined by Stephen. A 20-mm-depth drilling was simulated, starting from the insertion point at every possible angle within a 90° cone using 5-, 6- and 7-mm drills. Physeal damage for each pair of angles and each drill size was determined. Damage was expressed as a percentage of total physis volume. Statistical analysis was conducted using Student's t test and one-way ANOVA.

RESULTS

Maximum physeal damage (5.35% [4.47-6.24]) was obtained with the 7-mm drill when drilling 3° cephalic and 15° posterior from insertion without differences between sexes (n.s.). Minimal physeal damage (0.22% [0.07-0.37]) was obtained using the 5-mm drill aimed 45° distal and 0° anteroposterior, not affected by sex (n.s.). Considering intra-articular drilling avoidance, the safest zone was obtained when aiming 30°-40° distal and 5°-35° anterior, regardless of sex.

CONCLUSION

Ideal femoral tunnel orientation, avoiding physeal damage and breaching of the intercondylar notch, was obtained when aiming 30°-40° distal and 5°-35° anterior, regardless of sex. This area is a safe zone that allows anatomic MPFL reconstruction of patients with an open physis.

Stepwise Lengthening of the Quadriceps Extensor Mechanism for Severe Obligatory and Fixed Patella Dislocators

We introduce an algorithm of independently performing vastus lateralis lengthening followed by Z lengthening of the rectus and intermedius portion of the quadriceps tendon to treat fixed and obligatory patellar instability in the pediatric population. Performing this procedure in conjunction with medial patellofemoral ligament reconstruction minimizes subsequent episodes of instability without creating extensor mechanism weakness or contracture.

High failure rate 10.8 years after vastus medialis transfer and lateral release (Green's quadricepsplasty) for recurrent dislocation of the patella

PURPOSE

In adolescent patients with recurrent patellar dislocation, the Green's quadricepsplasty stabilizes the patella in a combination of a lateral release, a transfer of the medial head of the quadriceps onto the lateral part of the patella and an imbrication of the medial patellar retinaculum and joint capsule. This study aimed to evaluate the long-term performance, considering re-dislocations and functional outcomes. We hypothesized a high failure rate in the long term.

METHODS

In this single surgeon and single center study 26 knees in 23 patients (mean age 14.2 years; 4-22 years, 18 females) with recurrent patellofemoral dislocation underwent a vastus medialis transfer, medial reefing and lateral release as it was described by Green in 1965 with a mean follow-up 10.8 years (6-24 years). Clinical assessment was carried out with an IKDC-score (international knee documentation committee) and a self-assessment for each knee separately. The radiologic evaluation included measurement of the patella height, the grade of trochlear dysplasia and the sulcus angle.

RESULTS

In 12 of 26 cases (46.2%) the patella did not re-dislocate after vastus medialis transfer and lateral release. In 11 of 26 cases (42.3%), the patients described the function of their knees as normal or nearly normal according to IKDC after the surgical treatment without any re-dislocation. In 14 of 26 cases (53.8%), the patella re-dislocated. 7 of these 14 cases underwent a revision operation. Re-dislocations occurred after a mean interval of 21 months after the index procedure. In only 2 of 26 cases (7.7%) the patients returned to sports.

CONCLUSION

Green's procedure to stabilize patellofemoral instabilities results in a high failure rate on the long-term and low subjective assessments. We do not recommend performing vastus medialis transfer, medial imbrication and lateral release as a standalone technique.

LEVEL OF EVIDENCE

IV.

Anchor-Based Femoral Fixation for Physeal-Sparing Medial Patellofemoral Ligament Reconstruction: A Time-Zero Biomechanical Comparison With Tenodesis Screw Fixation

BACKGROUND

Open physes and trochlear/notch geometries in pediatric patients limit the safe corridor for femoral interference screw graft fixation during medial patellofemoral ligament (MPFL) reconstruction. Accordingly, interest is increasing in anchor-based fixation, but biomechanical validation is deficient.

PURPOSE

To compare anchor-based and tenodesis screw femoral fixation of MPFL grafts in a time-zero biomechanical model.

STUDY DESIGN

Controlled laboratory study.

METHODS

Twenty-seven fresh-frozen porcine distal femurs were potted for testing in an electromechanical load frame, while bovine tendons were used for MPFL grafts. Reconstructions were performed with 1 of 3 femoral fixation strategies: 4.5-mm biocomposite double-loaded threaded anchor (DLA group), 3.9-mm biocomposite knotless threaded anchor (KA group), or traditional 7 × 23-mm biocomposite tenodesis screw (TS group). For testing, femoral specimens were oriented and secured in the mechanical testing apparatus such that actuator tensile pull re-created the normal MPFL trajectory. Specimens underwent 10 cycles of 5- to 15-N loading at 1-Hz preconditioning, followed by 1000 cycles of 10- to 50 N-loading at 1 Hz. After cyclic loading, all specimens were loaded to failure at 305 mm/min. The average cyclic construct stiffness, displacement, and load-to-failure data between the 3 groups were compared using analysis of variance (ANOVA) with the significance level set at P < .05.

RESULTS

Average cyclic construct stiffnesses were comparable across groups per repeated-measures ANOVA analysis: 68.3 ± 6.3, 71.4 ± 6.4, and 74.3 ± 7.9 N/mm for TS, DLA, and KA groups, respectively (at cycle 1000). Average construct displacements at cycles 100 and 1000 were significantly less in the anchor versus tenodesis screw groups per ANOVA and Tukey post hoc analysis: 7.7 ± 4.2 mm for the TS group versus 3.7 ± 0.4 and 4.3 ± 0.6 mm for the DLA and KA groups, respectively (at cycle 1000). There was no significant difference in ultimate failure loads between the anchor and tenodesis screw groups, but 3 of 9 TS constructs failed at loads below the average failure load of the native MPFL.

CONCLUSION

Compared with the tenodesis group, anchor-based fixation produced constructs with equivalent cyclic stiffnesses, improved load-displacement characteristics, and had less failure load variability in the porcine cadaveric model.

CLINICAL RELEVANCE

Femoral fixation of the MPFL graft with a single anchor (4.5 or 3.9 mm threaded) is a viable alternative to traditional tenodesis screw fixation.

Medial Patellofemoral Ligament Reconstruction and Nonanatomic Stabilization Techniques in Skeletally Immature Patients

Patellar instability is a common cause of knee disability in children and adolescent, with a high recurrence rate. When conservative treatment fails, surgical options should be considered. The femoral insertion of the medial patellofemoral ligament (MPFL) is in close proximity to the distal femoral growth plate and precautions should be taken to avoid injuries to the physis. Anatomical features of the MPFL complex, with focus on the relationship between femoral MPFL attachment and femoral physis, are discussed together with surgical tips to avoid injuries to the growth plates. The aim of this article is to review the recent literature regarding MPFL reconstruction and other stabilization techniques for patellofemoral instability in skeletally immature patients, focusing on the different surgical options available. These can be classified as anatomical versus nonanatomical, proximal versus distal realignments, or based on the graft used: free graft and pedicled graft (quadriceps, patellar tendon, hamstring, and adductor magnus).

[Patellofemoral instability in children and adolescents]

Dislocation of the patella is one of the most common knee injuries in childhood and adolescence. After detailed clinical and radiological clarification, conservative functional treatment with special orthotic devices is most commonly applied in patients with a primary dislocation without concomitant injuries; however, the redislocation rate after conservative treatment has been reported in the literature to be between 35% and 70%, depending on the risk factors present. Therefore, numerous surgical treatment options exist which are sometimes again associated with high redislocation rates and others can lead to early arthrosis of the patellofemoral joint when used indiscriminately. Many scientific contributions on the topic notably in the last two decades have increased the understanding of patellofemoral instability. The comprehensive knowledge of the causes for a persisting instability of the patella has made the treatment more efficient and precise but also more complex.

Surgical Management of Patellofemoral Instability in the Skeletally Immature Patient

Compared with skeletally mature patients, skeletally immature patients are at a higher risk of acute traumatic patellar dislocation. Surgical treatment is the standard of care for patients with recurrent instability and requires important and technically challenging physeal considerations. Physeal-sparing medial patellofemoral ligament reconstruction is the treatment of choice for these patients, replacing older nonanatomic extensor mechanism realignment techniques. Implant-mediated guided growth is an important adjunct to correct genu valgum angular deformities that contribute to patellar instability. Patient-specific surgical techniques and proper surgical indications are crucial for successful outcomes.

Patellar Instability in the Skeletally Immature

PURPOSE OF REVIEW

This review will focus on the evaluation and management of patellar instability in the developing patient.

RECENT FINDINGS

A large number of surgical techniques have been described to prevent recurrent patellofemoral instability in the pediatric population, including both proximal and distal realignment procedures. The wide variety of treatment options highlights the lack of agreement as to the best surgical approach. However, when a comprehensive exam and workup are paired with a surgical plan to address each of the identified abnormalities, outcomes are predictably good. Patellar instability is a common knee disorder in the skeletally immature patient that presents a unique set of challenges. Rates of re-dislocation in pediatric and adolescent patients are higher than in their adult counterparts. Careful consideration of the physeal and apophyseal anatomy is essential in these patients. While the majority of primary patellar instability events can be treated conservatively, multiple events often require surgical intervention.

High rate of recurrent patellar dislocation in skeletally immature patients: a long-term population-based study

PURPOSE

Patellar dislocation can occur in isolation or be associated with chronic instability. The goals of this study are to describe the rate and factors associated with additional patellar instability events (ipsilateral recurrence and contralateral dislocation), as well as the development of patellofemoral arthritis in patients who are skeletally immature at the time of first patellar dislocation.

METHODS

The study included a population-based cohort of 232 skeletally immature patients who experienced a first-time lateral patellar dislocation between 1990 and 2010. A chart review was performed to collect information related to the initial injury, treatment, and outcomes. Subjects were followed for a mean of 12.1 years to determine the rate of subsequent patellar dislocation (ipsilateral recurrence or contralateral dislocation) as well as clinically significant patellofemoral arthritis.

RESULTS

104 patients had ipsilateral recurrent patellar dislocation. The cumulative incidence of recurrent dislocation was 11% at 1 year, 21.1% at 2 years, 37.0% at 5 years, 45.1% at 10 years, 54.0% at 15 years, and 54.0% at 20 years. Patella alta (HR 10.6, 95% CI 3.6, 36.1), TT-TG ≥ 20 mm (HR 18.7, 95% CI 1.7, 228.2), and trochlear dysplasia (HR 23.7, 95% CI 1.0, 105.2) were associated with recurrence. Similarly, 18 patients (7.8%) had contralateral patellar dislocation. The cumulative incidence of patellofemoral arthritis was 0% at 2 years, 1.0% at 5 years, 2.0% at 10 years, 10.1% at 15 years, 17% at 20 years, and 39.0% at 25 years. Osteochondral injury was associated with arthritis (HR 25.7, 95% CI 6.2, 143.8). There was no association with trochler dysplasia (HR 1.2, 95% CI 0.2, 5.0), recurrent patellar instability (HR 1.2, 95% CI 0.2, 7.2), gender (HR 1.3, 95% CI 0.3, 5.6), or patellar-stabilizing surgery (HR 0.7, 95% CI 0.2, 3.5) and arthritis.

CONCLUSION

Skeletally immature patients had a high rate of recurrent patellar instability that was associated with structural abnormalities such as patella alta,TT-TG ≥ 20 mm, and trochlear dysplasia. Approximately 10% of patients experienced a contralateral dislocation and 20% of patients developed arthritis by 20 years following initial dislocation. Osteochondral injury was associated with arthritis.

LEVEL OF EVIDENCE

Retrospective case series, Level IV.

Medial patellofemoral ligament and medial patellotibial ligament reconstruction in children: preliminary results

OBJECTIVE

The aim of this study was to evaluate the reconstruction of the medial patellofemoral ligament associated with the medial patellotibial ligament in skeletally immature patients.

METHOD

This is a case series study in patients with patellar instability with open physis. In total, seven patients were evaluated: four males and three females were operated using the proposed technique. Patients with open physis who had more than two episodes of recurring patellar dislocation were included. No patients underwent additional procedures. The distance from the anterior tibial tuberosity to the trochlea grove (TT-TG) was measured in all patients. On physical examination, the inverted J-sign, the apprehension sign, and the knee range of motion parameters were used in the pre- and post-operative period. In addition, the Kujala and Lysholm scores were applied before and 12 months after surgery. The results were analyzed with the Wilcoxon test.

RESULTS

The mean age of the patients was 11.28 in both genders. Comparing the data of the pre- and post-operative period, the inverted J-sign was present in six patients (85.7%) vs. absent in one (14.3%). The apprehension sign was absent in cases in the postoperative period; the range of motion was 117.85 ± 8.09 vs. 148.57 ± 3.77. The Kujala score was 42.57 ± 8.9 vs. 88.57 ± 5.09 and the Lysholm scores were classified as excellent or good in 28.6% and 71.4%, respectively.

CONCLUSION

The combined reconstruction of the medial patellofemoral ligament combined with the medial patellotibial ligament in skeletally immature patients with predisposing factors, presents satisfactory results without episodes of recurrence or residual subluxation; according to these preliminary results, it should be considered as a treatment option.

Evaluation of the Tibial Tubercle to Posterior Cruciate Ligament Distance in a Pediatric Patient Population

BACKGROUND

Evaluation of distal extensor mechanism alignment continues to evolve in children with patella instability. Prior studies support the use of the tibial tubercle to trochlear groove (TT-TG) distance but limitations exist for this measurement including: changes in the TT-TG distance with knee flexion, difficulty with finding the deepest part of a dysplastic trochlea, and limitations regarding identification of the site of the anatomic abnormality. The tibial tubercle-posterior cruciate ligament (TT-PCL) distance has been introduced as an alternative measure to address the shortcomings in the TT-TG distance by quantifying the position of the TT independent of the trochlea and with respect to the tibia only. The objectives of this study were to (1) confirm that TT-PCL measurements in the pediatric population are reliable and reproducible; (2) determine whether normal TT-PCL distance changes with age; and (3) compare TT-PCL distances in patients with and without patellar instability to assess its utility in the workup of pediatric patellar instability.

METHODS

All knee magnetic resonance imaging performed for patients from birth to 15.9 years of age at our institution between December 2004 and February 2012 were retrospectively collected (total 566). Eighty-two patients had patellar instability and 484 patients did not have patellar instability. Two magnetic resonance imaging reviewers measured TT-PCL distance on T2-weighted axial images in a blinded manner. Intraobserver and interobserver agreement was measured. Correlation between TT-PCL distance and age as well as group differences between mean TT-PCL distances was evaluated.

RESULTS

Intraobserver and interobserver agreement was excellent (0.93) and very good (0.80), respectively. The mean TT-PCL distance was 20.1 mm with a range of 5.8 to 32.1 mm. The mean age was 12.6 years with a range of 0.8 to 15.9 years. The average TT-PCL distance was 21 mm for the instability group and 19.9 mm for the control group. TT-PCL distance increased significantly as subject age increased; however, there was no significant measurement difference shown between the patellar instability group and the control group.

CONCLUSIONS

TT-PCL distance increased with age in the pediatric population but did not correlate with recurrent patella instability in this pediatric cohort.

LEVEL OF EVIDENCE

Level III-diagnostic.

Influence of graft source and configuration on revision rate and patient-reported outcomes after MPFL reconstruction: a systematic review and meta-analysis

PURPOSE

The purpose of this systematic review and meta-analysis was to determine the influence of graft source (allograft vs. autograft) and configuration (single-limbed vs. double-limbed) on failure rate and disease-specific patient-reported outcome (Kujala score) after medial patellofemoral ligament (MPFL) reconstruction for patellar instability.

METHODS

A systematic review of PubMed, Scopus, and the Cochrane Library was performed. A total of 31 studies met inclusion/exclusion criteria and were used to extract cohorts of patients who underwent ligament reconstruction with various allograft, autograft, single-limbed, and double-limbed constructs. Failure rates and postoperative improvements in Kujala scores were compared between cohorts using inverse-variance weighting in a random-effects analysis model and appropriate comparative statistical analyses (Chi-squared and independent samples t tests).

RESULTS

A total of 1065 MPFL reconstructions were identified in 31 studies. Autograft reconstructions were associated with greater postoperative improvements in Kujala scores when compared to allograft (32.2 vs. 22.5, p < 0.001), but there was no difference in recurrent instability (5.7 vs. 6.7 %, p = 0.74). Double-limbed reconstructions were associated with both improved postoperative Kujala scores (37.8 vs. 31.6, p < 0.001) and lower failure rate (10.6 vs. 5.5 %, p = 0.030).

CONCLUSION

MPFL reconstructions should be performed using double-limbed graft configurations. While autograft tendon may be associated with higher patient-reported outcomes in the absence of associated connective tissue disorders or ligamentous laxity, patient factors and allograft processing techniques should be carefully considered when selecting an MPFL graft source, as revision rates were no different between graft sources.

LEVEL OF EVIDENCE

IV.

An Algorithmic Approach to the Management of Recurrent Lateral Patellar Dislocation

High-level evidence supports nonoperative treatment for first-time lateral acute patellar dislocations. Surgical intervention is often indicated for recurrent dislocations. Recurrent instability is often multifactorial and can be the result of a combination of coronal limb malalignment, patella alta, malrotation secondary to internal femoral or external tibial torsion, a dysplastic trochlea, or disrupted and weakened medial soft tissue, including the medial patellofemoral ligament (MPFL) and the vastus medialis obliquus. MPFL reconstruction requires precise graft placement for restoration of anatomy and minimal graft tension. MPFL reconstruction is safe to perform in skeletally immature patients and in revision surgical settings. Distal realignment procedures should be implemented in recurrent instability associated with patella alta, increased tibial tubercle-trochlear groove distances, and lateral and distal patellar chondrosis. Groove-deepening trochleoplasty for Dejour type-B and type-D dysplasia or a lateral elevation or proximal recession trochleoplasty for Dejour type-C dysplasia may be a component of the treatment algorithm; however, clinical outcome data are lacking. In addition, trochleoplasty is technically challenging and has a risk of substantial complications.

Medial patellofemoral ligament (MPFL) reconstruction improves radiographic measures of patella alta in children

BACKGROUND

Patellofemoral instability has previously been associated with patella alta. The purpose of this study was to evaluate adolescents undergoing MPFL reconstruction for standardized indices of patellar height on pre- and post-operative radiographs to determine if these radiographic parameters change after MPFL reconstruction.

METHODS

Twenty-seven children (mean age 14.9years old) who underwent MPFL reconstruction without a distal realignment procedure were evaluated pre- and post-operatively for Insall-Salvati Ratio, Modified Insall-Salvati Ratio, and Caton-Deschamps Index by three blinded raters. Intrarater reliability and interrater reliability were calculated for each index, and means of each were compared pre- and post-operatively to determine if MPFL reconstruction was associated with improved patellar height.

RESULTS

All three indices of patellar height indicated that there was patella alta present in this cohort preoperatively. Furthermore, all three measures were significantly improved postoperatively (paired t-tests, P<0.001 for all) to within normal childhood ranges. Interrater reliability was excellent for both the Insall-Salvati Ratio (ICC=0.89) and Caton-Deschamps Index (ICC=0.78), and adequate for the Modified Insall-Salvati Ratio (ICC=0.57); intrarater reliability was excellent for all three (ICCs: 0.91, 0.82, 0.80 respectively).

CONCLUSIONS

MPFL reconstruction in children using hamstring autograft was associated with consistently improved patellar height indices to within normal childhood ranges. This associated improvement of patellar height as measured on a lateral radiograph may subsequently improve patellofemoral mechanics by drawing the patella deeper and more medially into the trochlear groove.

LEVEL OF EVIDENCE

Level 4.

Medial patellofemoral ligament reconstruction using hamstring autograft in children and adolescents

We introduce an anatomic reconstruction technique for the medial patellofemoral ligament using a free hamstring autograft in skeletally immature patients. We dock the 2 ends of the graft in the superior-medial patella using sockets and secure the femoral graft attachment in a socket tunnel distal to the physis. This technique minimizes the risk of injury to the growth plate and still enables accurate and successful anatomic positioning of the hamstring autograft.