The relation of the femoral physis and the medial patellofemoral ligament

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.

Allografts for Medial Patellofemoral Ligament (MPFL) Reconstruction in Adolescent Patients with Recurrent Patellofemoral Instability: A Systematic Review

This systematic review updates the currently available evidence on medial patella-femoral ligament (MPFL) reconstruction using allografts. The outcomes were measured with patient-reported outcome measures (PROMs), redislocation and complication rates. This study was performed according to the 2020 PRISMA guidelines using the PubMed, Scopus, Web of Science databases, accessed in February 2023. Studies examining the clinical outcomes of MPFL reconstruction with allografts in adolescents and children with recurrent patellofemoral instability (PFI) were included. Data from three trials, including 113 surgical procedures in 121 children, were retrieved. 40% (48/121) of the included patients were girls. The mean age of the patients was 14.7 ± 0.8 years, and the mean follow-up length was 38.1 ± 16.5 months. With MPFL allograft reconstruction, the Kujala score improved by 14.7% (p < 0.0001) and the IKDC by 38.8% (p < 0.0001). The rate of dislocations was 5% (6 of 121), reoperation for instability was 11% (13 of 121), and subluxation was 2% (1 of 47). Conclusion: These results encourage the use of allografts for MPFL reconstruction in adolescent patients with recurrent patellofemoral instability. Though patellofemoral instability is common in clinical practice, the current literature lacks clinical evidence on allograft MPFL reconstruction. Additional high-quality investigations are required to properly establish the long-term advantages of allograft MPFL and its complication rate.

The Schöttle Point Is Consistently Located Distal to the Medial Femoral Physis in Pediatric Patients: A Digitally Reconstructed Radiographic Study

BACKGROUND

Significant controversy surrounds ideal tunnel position for medial patellofemoral ligament (MPFL) reconstruction (MPFLR) in the pediatric setting. The start point for femoral tunnel positioning (the Schöttle point) relative to the distal medial femoral physis is not well defined. Previous studies provide conflicting data regarding position of the MPFL origin and the Schöttle point relative to the distal femoral physis.

HYPOTHESIS

The Schöttle point would be consistently distal to the distal medial femoral physis.

STUDY DESIGN

Descriptive laboratory study.

METHODS

The institutional picture archiving and communication system was queried for computed tomography (CT) imaging studies of pediatric knees. Data were imported to an open-source image computing platform. True lateral digitally reconstructed radiographs and 3-dimensional (3D) renderings were generated, and the Schöttle point was registered in 3D space. Then, 3D distance measurements were obtained from the Schöttle point to the distal medial femoral physis.

RESULTS

A total of 49 pediatric knee CT scans were included. Mean age was 13.0 ± 2.3 years. Mean minimum distance from the medial physis to the Schöttle point was 9.9 ± 3.0 mm (range, 3.4-16.1 mm). In 49 of 49 cases (100%), the Schöttle point was distal to the physis. Using a 6-mm reaming diameter would result in 3 of 49 (6%) femurs having violation of the distal medial femoral physis. Moving the start point 3 mm distally would result in 0 of 49 (0%) sustaining physeal injury.

CONCLUSION/CLINICAL RELEVANCE

The Schöttle point is consistently distal to the distal medial femoral physis. The mean minimum distance from the Schöttle point to the physis on the medial cortex is 9.9 mm. The Schöttle point provides a safe and reliable radiographic landmark for pediatric MPFLR, although reaming diameter should be considered.

Interference screws vs. suture anchors for isolated medial patellofemoral ligament femoral fixation: A systematic review

PURPOSE

The present study aimed to systematically review and compare 2 femoral autograft fixation techniques, namely, interference screws and suture anchors, for isolated medial patellofemoral ligament reconstruction in patients with recurrent patellofemoral instability at mid- to long-term follow-up.

METHODS

A literature search was performed in September 2020. All studies reporting the outcomes of primary isolated medial patellofemoral ligament reconstruction for recurrent patellofemoral instability were considered for inclusion. Only studies reporting the type of femoral autograft fixation under examination were considered. Studies reporting data from patients with elevated tibial tuberosity-tibial groove, patella alta, and/or Dejour's trochlear dysplasia types C and D, were not included. Only articles reporting data with a minimum follow-up period of 18 months were considered.

RESULTS

Data from 19 studies (615 patients) were retrieved. The overall age was 24.4 ± 6.7 years (mean ± SD). The mean follow-up was 46.5 ± 20.9 months. There were 76 patients in the anchor group and 539 in the screw group. Comparability was found with regard to age and follow-up duration between the 2 study groups. There was comparability between the Kujala, Lysholm, and Tegner scores at baseline. At the last follow-up, no worthy differences were found in terms of mean Kujala (+2.1%; p = 0.04), Lysholm (+1.7%; p = 0.05), and Tegner (+15.8%; p = 0.05) scores. Although complications occurred almost exclusively in the screw cohort, no statistically significant difference was found.

CONCLUSION

Femoral autograft fixation through interference screws or suture anchors report similar clinical scores and rate of apprehension test, persistent joint instability, re-dislocations, and revisions. These results must be interpreted within the limitations of the present study.

Relationship of the Medial Patellofemoral Ligament Origin on the Distal Femur to the Distal Femoral Physis: A Systematic Review

BACKGROUND

The relationship between the medial patellofemoral ligament (MPFL) and the distal femoral physis has been reported in multiple studies.

PURPOSE

To determine the distance from the MPFL central origin on the distal femur to the medial distal femoral physis in skeletally immature participants.

STUDY DESIGN

Systematic review.

METHODS

A systematic review was performed according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Multiple databases were searched for studies investigating the anatomic origin of the MPFL on the distal femur and its relationship to the medial distal femoral physis in skeletally immature participants. Study methodological quality was analyzed with the Anatomical Quality Assessment tool, with studies categorized as low risk, high risk, or unclear risk of bias. Continuous variable data were reported as mean ± SD. Categorical variable data were reported as frequency with percentage.

RESULTS

Seven articles were analyzed (298 femurs, 53.7% male patients; mean age, 11.7 ± 3.4 years). There was low risk of bias based on the Anatomical Quality Assessment tool. The distance from the MPFL origin to the distal femoral physis ranged from 3.7 mm proximal to the physis to 10.0 mm distal to the physis in individual studies. Six of 7 studies reported that the MPFL origin on the distal femur lies distal to the medial distal femoral physis in the majority of specimens. The MPFL originated distal to the medial distal femoral physis in 92.8% of participants at a mean distance of 6.9 ± 2.4 mm.

CONCLUSION

The medial patellofemoral ligament originates distal to the medial distal femoral physis in the majority of cases at a mean proximal-to-distal distance of 7 mm distal to the physis. However, this is variable in the literature owing to study design and patient age and sex.

Comparison of Ligament Isometry and Patellofemoral Contact Pressures for Medial Patellofemoral Ligament Reconstruction Techniques in Skeletally Immature Patients

BACKGROUND

Adult medial patellofemoral ligament (MPFL) reconstruction techniques are not appropriate for the skeletally immature patient given the proximity of the distal femoral physis. Biomechanical consequences of reconstructions aimed at avoiding the physis have not been adequately studied.

PURPOSE

To quantify the biomechanical effects of MPFL reconstruction techniques intended for skeletally immature patients.

STUDY DESIGN

Controlled laboratory study.

METHODS

Four MPFL reconstruction techniques were evaluated using a computationally augmented cadaveric model: (1) Schoettle point: adult-type reconstruction; (2) epiphyseal: socket distal to the femoral physis; (3) adductor sling: graft wrapped around the adductor tendon; (4) adductor transfer: adductor tendon transferred to patella. A custom testing frame was used to cycle 8 knees for each technique from 10° to 110° of flexion. Patellofemoral kinematics were recorded using a motion camera system, contact stresses were recorded using Tekscan pressure sensors, and MPFL length was computed using an inverse kinematics computational model. Change in MPFL length, patellar facet forces, and patellar kinematics were compared using generalized estimating equation modeling.

RESULTS

Schoettle point reconstruction was the most isometric, demonstrating isometry from 10° to 100°. The epiphyseal technique was isometric until 60°, after which the graft loosened with increasing flexion. The adductor sling and adductor transfer techniques were significantly more anisometric from 40° to 110°. Both grafts tightened with knee flexion and resulted in significantly more lateral patellar tilt versus the intact state in early flexion and significantly higher contact forces on the medial facet versus the epiphyseal technique in late flexion.

CONCLUSION

In this cadaveric simulation, the epiphyseal technique allowed for a more isometric ligament until midflexion, when the patella engaged within the trochlear groove. The adductor sling and adductor transfer grafts became tighter in flexion, resulting in potential loss of motion, pain, graft stretching, and failure. Marginal between-condition differences in patellofemoral contact mechanics and patellar kinematics were observed in late flexion.

CLINICAL RELEVANCE

In the skeletally immature patient, using an epiphyseal type MPFL reconstruction with the femoral attachment site distal to the physis results in a more isometric graft compared with techniques with attachment sites proximal to the physis.

Is Diagnostic Arthroscopy at the Time of Medial Patellofemoral Ligament Reconstruction Necessary?

Background:

Although medial patellofemoral ligament (MPFL) reconstruction is well described for patellar instability, the utility of arthroscopy at the time of stabilization has not been fully defined.

Purpose:

To determine whether diagnostic arthroscopy in conjunction with MPFL reconstruction is associated with improvement in functional outcome, pain, and stability or a decrease in perioperative complications.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

Patients who underwent primary MPFL reconstruction without tibial tubercle osteotomy were reviewed (96 patients, 101 knees). Knees were divided into MPFL reconstruction without arthroscopy (n = 37), MPFL reconstruction with diagnostic arthroscopy (n = 41), and MPFL reconstruction with a targeted arthroscopic procedure (n = 23). Postoperative pain, motion, imaging, operative findings, perioperative complications, need for revision procedure, and postoperative Kujala scores were recorded.

Results:

Pain at 2 weeks and 3 months postoperatively was similar between groups. Significantly improved knee flexion at 2 weeks was seen after MPFL reconstruction without arthroscopy versus reconstruction with diagnostic and reconstruction with targeted arthroscopic procedures (58° vs 42° and 48°, respectively; P = .02). Significantly longer tourniquet times were seen for targeted arthroscopic procedures versus the diagnostic and no arthroscopic procedures (73 vs 57 and 58 min, respectively; P = .0002), and significantly higher Kujala scores at follow-up were recorded after MPFL reconstruction without arthroscopy versus reconstruction with diagnostic and targeted arthroscopic procedures (87.8 vs 80.2 and 70.1, respectively; P = .05; 42% response rate). There was no difference between groups in knee flexion, recurrent instability, or perioperative complications at 3 months. Diagnostic arthroscopy yielded findings not previously appreciated on magnetic resonance imaging (MRI) in 35% of patients, usually resulting in partial meniscectomy.

Conclusion:

Diagnostic arthroscopy with MPFL reconstruction may result in findings not previously appreciated on MRI. Postoperative pain, range of motion, and risk of complications were equal at 3 months postoperatively with or without arthroscopy. Despite higher Kujala scores in MPFL reconstruction without arthroscopy, the relationship between arthroscopy and patient-reported outcomes remains unclear. Surgeons can consider diagnostic arthroscopy but should be aware of no clear benefits in patient outcomes.

Long-term results of arthroscopic medial reefing for patellar instability

BACKGROUND

The purpose of the study was to investigate the long-term outcomes of the all-inside arthroscopic medial reefing (AAMR) procedure for patellar instability and the factors that affect successful outcome.

METHODS

In this retrospective study, AAMR with suture was performed in 16 knees of 15 patients who had at least one patellar dislocation and did not experience a decrease in pain and who did not have a major radiological bony abnormality. Preoperatively, Tegner and Lysholm scales were used; for the final evaluation Tegner, Lysholm, Kujala and Knee injury and Osteoarthritis Outcome Score (KOOS) were used.

RESULTS

The average age of the patients at the time of operation was 18 years (range: 11-36 years). The average follow-up time was 118.3 months (range: 85-143 months). Six of the 16 knees (37.5%) exhibited re-dislocation. Preoperatively, the mean Lysholm and Tegner were 66.5 and 4.0, respectively; and postoperatively increased to 89.3 (P = .001) and 4.66, respectively. At the final follow-up, mean Kujala was 89.3 (good), and mean KOOS was 91.4. In all patients with re-dislocation, fewer than four knots were used, and none of the patients with four knots exhibited re-dislocation. Re-dislocations occurred in two, two, one and one patients at two, three, five and eight years, respectively.

CONCLUSIONS

The AAMR technique is associated with minimal incisional scarring and an increase in functional scores. It is also associated with a high risk of re-dislocation compared with other methods. If the technique still needs to be used, despite the high re-dislocation rate, at least four knots should be applied.

Medial Patellofemoral Ligament Reconstruction and Lateral Retinacular Lengthening in the Skeletally Immature Patient

Patellar instability remains a ubiquitous and troublesome problem in orthopaedics and represents a challenge in the pediatric population. Reconstruction of the medial patellofemoral ligament (MPFL) has become a mainstay of patellar instability management in recent years. As with any procedure at or around the physes, there is concern among surgeons regarding safe placement of hardware and drilled tunnels. The authors describe a technique for anatomic MPFL reconstruction with the aid of fluoroscopic guidance to maintain a "safe zone" without violating the distal femoral physis. This technique allows for reliable MPFL reconstruction in the skeletally immature population with concomitant lateral lengthening, while requiring only minor deviations from the procedure in a skeletally mature patient.

Prediction of recurrence based on the patellofemoral morphological profile and demographic factors in first-time and recurrent dislocators

INTRODUCTION

Prediction of recurrence in first-time patellar dislocation is an unsolved mystery. The purpose of our study is to compare patellar instability patients and normal control groups with anatomical risk factors and validation of newer parameters patello-trochlear index (PTI) and tibial tuberosity-posterior cruciate ligament (TT-PCL) and also to find the significant risk factors that help to predict the recurrence of dislocation in first-time dislocators.

METHODS

This is a comparison study between 50 normal individuals as a control population (group-1) and 94 patients with patellar instability done between 2013 and 2017. Further, 94 patients (group-2) were divided into first-time dislocators (group-2A) and recurrent dislocators (group-2B) which include 39 and 55 patients, respectively. Demographic factors like age, sex, the age of the first dislocation, mechanism of injury, and laterality and MRI risk factors like trochlear dysplasia, patellar height, patellar malalignment, and lateralization of tibial tuberosity were statistically analyzed.

RESULTS

All parameters used to measure each MRI factors showed significant difference with p value < 0.0001 between group 1 and group 2 except PTI (0.035) and TT-PCL (0.036). While comparing demographic factors between first-time dislocators and recurrent dislocator groups, patients with first-time dislocation < 16 years of age (OR-3.6) and bilateral involvement are associated with recurrence and among MRI factors, trochlear dysplasia (odds ratio OR-12), patellar tilt (OR-0.2), and patella alta (OR-4.9) were known to be associated with higher chance of recurrence.

CONCLUSION

There is a significant difference in anatomic risk factors between normal and patellar instability knees. PTI and TT-PCL are less significant than the previous parameters. Age < 16 years, the presence of trochlear dysplasia, patella alta, and bilateral involvement have a significant role as prediction factors in a recurrent dislocation in both adolescents and adults.

Properties and Function of the Medial Patellofemoral Ligament: A Systematic Review

BACKGROUND

As the main passive structure preventing patellar lateral subluxation, accurate knowledge of the anatomy, material properties, and functional behavior of the medial patellofemoral ligament (MPFL) is critical for improving its reconstruction.

PURPOSE

To provide a state-of-the-art understanding of the properties and function of the MPFL by undertaking a systematic review and statistical analysis of the literature.

STUDY DESIGN

Systematic review.

METHODS

On June 26, 2018, data for this systematic review were obtained by searching PubMed and Scopus. Articles containing numerical information regarding the anatomy, mechanical properties, and/or functional behavior of the MPFL that met the inclusion criteria were reviewed, recorded, and statistically evaluated.

RESULTS

A total of 55 articles met the inclusion criteria for this review. The MPFL presented as a fanlike structure spanning from the medial femoral epicondyle to the medial border of the patella. The reported data indicated ultimate failure loads from 72 N to 208 N, ultimate failure elongation from 8.4 mm to 26 mm, and stiffness values from 8.0 N/mm to 42.5 N/mm. In both cadaveric and in vivo studies, the average elongation pattern demonstrated close to isometric behavior of the ligament in the first 50° to 60° of knee flexion, followed by progressive shortening into deep flexion. Kinematic data suggested clear lateralization of the patella in the MPFL-deficient knee during early knee flexion under simulated muscle forces.

CONCLUSION

A lack of knowledge regarding the morphology and attachment sites of the MPFL remains. The reported mechanical properties also lack consistency, thus requiring further investigations. However, the results regarding patellar tracking confirm that the lack of an MPFL leads to lateralization of the patella, followed by delayed engagement of the trochlear groove, plausibly leading to an increased risk of patellar dislocations. The observed isometric behavior up to 60° of knee flexion plausibly suggests that reconstruction of the ligament can occur at flexion angles below 60°, including the 30° and 60° range as recommended in previous studies.

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).

A Simple Method of Measuring the Distance From the Schöttle Point to the Medial Distal Femoral Physis With MRI

Background:

Medial patellofemoral ligament (MPFL) reconstruction is the treatment of choice for recurrent patellar instability in the skeletally immature patient. Avoiding the open physes during anatomic MPFL reconstruction is a challenge in this population.

Purpose:

To describe a novel method using magnetic resonance imaging (MRI) to determine the distance from the Schöttle point to the medial distal femoral physis among skeletally immature individuals with patellar instability.

Study Design:

Descriptive laboratory study.

Methods:

Preoperative MRI scans were analyzed from 34 patients with open distal femoral physes and lateral patellar instability. With the multiplanar reconstruction mode on a picture archiving and communication system (PACS), the location of the Schöttle point was determined according to previously reported distances from the posterior femoral cortical line and the posterior origin of the medial femoral condyle. This location was then extrapolated to the most medial sagittal slice on MRI showing the medial distal femoral physis. The distance was measured from this point to the most distal aspect of the physis.

Results:

The mean age of the study cohort was 13.6 years (range, 10.6-15.7 years); there were 13 males and 21 females. The mean distance from the medial distal femoral physis to the Schöttle point was 7.27 ± 1.78 mm. The Schöttle point was distal to the medial distal femoral physis in all cases. There was no significant correlation between age and mean distance in either the overall study population (r = 0.046, P = .798) or when stratified by sex (females, P = .629; males, P = .089). The distance between the Schöttle point and the medial distal femoral physis was shorter for females than for males (6.51 vs 7.71 mm, P = .043). After adjustment for age, females on average were 1.31 mm closer to the Schöttle point than were males (B = –1.31, P = .041).

Conclusion:

This technique can be used to determine the distance between the medial distal femoral physis and the Schöttle point. The Schöttle point was distal to the physis in all patients, and it was closer to the physis in skeletally immature females compared with age-matched males.

Clinical Relevance:

The long-term repercussions of improperly placed MPFL reconstruction include recurrent patellar instability, increased patellofemoral contact pressures and overtensioning of the ligament, and possibly patellofemoral arthritis. The current technique can be used preoperatively to determine the appropriate safe distance for drilling a socket distal to the physis.

Combined Reconstruction of the Medial Patellofemoral Ligament (MPFL) and Medial Quadriceps Tendon-Femoral Ligament (MQTFL) for Patellar Instability in Children and Adolescents: Surgical Technique and Outcomes

OBJECTIVES

A variety of surgical options exist to treat the challenging problem of recurrent patellar instability in children and adolescents. The goal of the current study is to describe a novel combined reconstruction technique of both the medial patellofemoral ligament (MPFL) and the medial quadriceps tendon-femoral ligament (MQTFL) and report patient outcomes of a single-surgeon series.

METHODS

All patients studied underwent simultaneous MPFL and MQTFL reconstruction for patellar instability using gracilis allograft. Demographic, clinical, and radiographic data were collected. Subjective outcomes were assessed for a minimum of 1 year postoperatively.

RESULTS

Twenty-five patients (27 knees), including 15 female and 10 male individuals with an average age of 15.0±2.2 years (range, 10.3 to 18.9), were included. Prior ipsilateral patellofemoral surgery had been performed in 6 of 25 (24%) patients. Simultaneous hemiepiphysiodesis for valgus deformity at the time of combined reconstruction was performed in 5 of 25 (20%) patients. Preoperative imaging showed a mean tibial tubercle-trochlear groove of 17.2±3.8, Caton-Deschamps Index (CDI) of 1.13±0.16, and trochlear dysplasia Dejour A/B [22/26 (85%)] or Dejour C/D [4/26 (15%)]. A total of 18 patients (19 knees, 72%) returned outcomes questionnaires at a mean 2.0±0.5 years after surgery. Mean Kujala, Pedi-IKDC, and Lysholm scores were 85.9±13.9, 81.5±15.2, and 84.3±13.5, respectively. Later revision procedure (tibial tubercle osteotomy) for recurrent patellar instability was required in 2 of 25 patients (8%) patients, and another patient reported persistent instability not requiring revision. Return to sports was possible in 10 of 13 self-reported athletes (77%) at a mean of 5.8±3.9 months (range, 2 to 15).

CONCLUSIONS

The present study describes a combined MPFL-MQTFL reconstruction technique with favorable short-term results. Although particularly useful in the skeletally immature patient where tibial tubercle osteotomy should be avoided and patellar fixation minimized, combined reconstruction may potentially be appropriate for older patients with patellofemoral instability as well. This technique more closely recreates the native anatomy of both the MPFL and MQTFL, may decrease the risk of patellar fracture, and can be useful in the revision setting.

LEVEL OF EVIDENCE

Level IV.

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.

Variation in the Medial Patellofemoral Ligament Origin in the Skeletally Immature Knee: An Anatomic Study

BACKGROUND

The medial patellofemoral ligament (MPFL) is frequently reconstructed to treat recurrent patellar instability. The femoral origin of the MPFL is well described in adults but not in the skeletally immature knee.

PURPOSE

To identify a radiographic landmark for the femoral MPFL attachment in the skeletally immature knee and study its relationship to the distal femoral physis.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Thirty-six cadaveric specimens between 2 and 11 years old were dissected and examined (29 male and 7 female). Metallic markers were placed at the proximal and distal borders of the MPFL femoral origin footprint. Computed tomography scans with 0.625-mm slices in the axial, coronal, and sagittal planes were used to measure the maximum ossified height and ossified depth. The measurements were used to describe the position of the midpoint MPFL attachment with respect to the posterior-anterior and distal-proximal dimensions of the femoral condyle on the sagittal view and to describe the distance from the physis to the femoral origin of the MPFL.

RESULTS

In 23 of 36 specimens, the femoral origin of the MPFL was distal to the physis. Thirteen of the 36 specimens had an MPFL origin at or proximal to the physis, with a more proximal MPFL origin consistently seen in older specimens. The distance of the MPFL origin to the physis ranged from 15.1 mm distal to the physis to 8.3 mm proximal to the physis. The mean midpoint of the MPFL femoral origin was located 3.0 ± 5.5 mm distal to the physis for all specimens. For specimens aged <7 years, the mean MPFL origin was 4.7 mm distal to the physis, and for specimens aged ≥7 years, the mean MPFL origin was 0.8 mm proximal to the femoral physis. The MPFL origin was more proximal and anterior for those aged ≥7 years and more distal and posterior for those aged <7 years.

CONCLUSION

Surgical reconstruction of the MPFL is a common treatment to restore patellar stability. There appears to be significant variability in the origin of the MPFL in skeletally immature specimens. This study demonstrated that the MPFL origin was more proximal and anterior with respect to the physis in the older age group. The MPFL origin footprint may be customized for different age groups.

CLINICAL RELEVANCE

This information shows anatomic variation of the MPFL origin with age, with older specimens having a footprint that was more proximal and anterior than younger specimens. Customization of the surgical technique might be considered based on patient age.

Evaluation of the Schöttle Technique in the Pediatric Knee

Background

The Schöttle point is commonly used for anatomic femoral tunnel placement during medial patellofemoral ligament (MPFL) reconstruction. This technique has not been previously validated in the skeletally immature patient, in whom femoral tunnel placement may put the distal femoral physis at risk of iatrogenic injury.

Hypothesis

Interobserver reliability for femoral tunnel placement will be higher in adult knees compared with pediatric knees.

Study Design

Cross-sectional study (diagnosis); Level of evidence, 3.

Methods

We selected 30 perfect lateral radiographs for this study: 20 from pediatric knees (mean patient age, 10 years; range, 8-11 years) and 10 from adult knees (mean patient age, 18.5 years; range, 18-23 years). Six observers with varying levels of clinical experience evaluated each radiograph and approximated the site of the MPFL femoral tunnel using the Schöttle technique. Intra- and interobserver reliabilities for femoral tunnel placement were evaluated. Statistical analysis was used to compare measurements.

Results

During initial interobserver measurements, the diameter of the composite perfect circles averaged 9.0 and 6.8 mm in adult and pediatric knees, respectively (P = .004). At repeat measurement, circles averaged 9.8 and 7.3 mm in adult and pediatric knees, respectively (P = .0001). Femoral tunnel placement intraobserver variance averaged 2.9 mm in adult knees (range, 1.9-4.0 mm) and 2.3 mm in pediatric knees (range, 1.9-2.9 mm). This difference was not significant (P = .14).

Conclusion

This study demonstrated that interobserver variance is actually greater in adult knees compared with pediatric knees, although interobserver variance was significantly different for both populations. Additionally, intraobserver variance is small on repeat measures, demonstrating that the Schöttle technique is reproducible for individual observers. Sources of this increased variance between observers are differences in agreement on the bony landmarks required for the Schöttle technique. Due to this variability in tunnel placement, we recommend caution when the Schöttle technique is used in pediatric knees to avoid iatrogenic injury to the distal femoral physis during femoral tunnel placement.

Medial patellofemoral ligament reconstruction: patient selection and perspectives

Patellofemoral instability is a painful and often recurring disorder with many negative long-term consequences. After a period of failed nonoperative management, surgical intervention has been used to reduce the incidence of patellar subluxation and dislocations. Medial patellofemoral ligament (MPFL) reconstruction successfully addresses patellofemoral instability by restoring the deficient primary medial patellar soft tissue restraint. When planning MPFL reconstruction for instability, it is imperative to consider the patient's unique anatomy including the tibial tuberosity-trochlear groove (TT-TG) distance, trochlear dysplasia, and patella alta. Additionally, it is important to individualize surgical treatment in the skeletally immature, hypermobile, and athletic populations.

Safe Drilling Paths in the Distal Femoral Epiphysis for Pediatric Medial Patellofemoral Ligament Reconstruction

BACKGROUND

Anatomic surgical reconstruction of the medial patellofemoral ligament (MPFL) has been popularized for the treatment of recurrent patellar instability in the skeletally immature population. Previous anatomic studies have found that the femoral attachment point of the MPFL is very close to the distal femoral physis.

PURPOSE

To establish the safe angles for drilling the distal femoral epiphysis for MPFL graft placement.

STUDY DESIGN

Descriptive laboratory study.

METHODS

A total of 23 cadaveric distal femoral epiphyses were scanned into high-resolution 3-dimensional images. Using computer-aided design, we identified and marked the femoral insertion site of the MPFL. Cylinders 8 mm in diameter were placed at varying angles to simulate the drill paths for placement of 6-mm interference screws with a 1-mm buffer. The distance from the MPFL footprint to where the tunnel first violated the physis, the intercondylar notch, or the distal cartilage was measured. We recorded the percentage of tunnels that caused violations before reaching 20 mm, the shortest length of a typical femoral tunnel socket.

RESULTS

Measurements indicated that 41% of tunnels angled distally less than 10° violated the physis, 40% of tunnels angled distally more than 10° but anteriorly less than 10° violated the notch, and 27% of tunnels angled distally and anteriorly more than 20° violated the distal femoral cartilage. At least 90% of the tunnels were safe at 20 mm when the drill was angled between 15° and 20° both anteriorly and distally.

CONCLUSION

Because of the anatomy of the distal femoral physis, drilling into the epiphysis from the MPFL attachment site at improper trajectories risks damage to sensitive structures. Angling the drill to an acceptable degree distally and anteriorly leads to less risk to the physis and notch, respectively, but angling too much leads to risk to the distal femoral cartilage. Small variations in the sagittal plane were better tolerated than variations in the coronal plane, so we recommend that more attention be paid to the radiographic anteroposterior view intraoperatively. It is safest to angle the drill distally and anteriorly approximately 15° to 20° in each plane from the MPFL attachment site.

CLINICAL RELEVANCE

During drilling into the distal femoral epiphysis at the MPFL origin in skeletally immature patients, angling the drill appropriately 15° to 20° both distally and anteriorly minimizes damage to the physis, notch, and distal femoral cartilage.

The Relationship of the Femoral Physis and the Medial Patellofemoral Ligament in Children: A Cadaveric Study

BACKGROUND

Young athletes sustain patellar dislocations in a variety of sports. The medial patellofemoral ligament (MPFL) is a critical structure that functions as an anatomic checkrein to help prevent lateral patellar dislocation. Reconstruction of this ligament is challenging in patients with open physes because of concerns about iatrogenic damage to the femoral physis.

PURPOSE

To evaluate the relationship of the distal femoral physis and the MPFL.

STUDY DESIGN

Descriptive laboratory study.

METHODS

In 15 cadaveric, pediatric knees (age, 7-11 years), markers were placed at the proximal/distal limits of the MPFL femoral attachment and were evaluated with computed tomography. The distance from the MPFL attachment midpoint to the most medial aspect of the distal femoral physis was measured.

RESULTS

The mean femoral width of the MPFL was 8.1 mm (range, 4.3-13.8 mm). The femoral MPFL midpoint was distal to the femoral physis in 11 specimens and proximal to the physis in 4 specimens. The most proximal portion of the MPFL femoral attachment extended above the medial physis in 7, was at the physis in 5, and was below the physis in 3 specimens. One specimen had the entire MPFL femoral attachment above the physis. For knees with the MPFL midpoint above the medial physis, the distance between the center of the MPFL and physis was 3.3 mm (range, 0.3-7.1 mm). For knees with the MPFL below the medial physis, the distance between the center of the MPFL and physis was -6.8 mm (range, -0.7 to -22.0 mm).

CONCLUSION

The relationship of the femoral attachment of the MPFL and the medial femoral physis shows some anatomic variation. In all cases, the MPFL is close to the medial femoral physis, but the midpoint of the MPFL is at, slightly above, or slightly below the physis.

CLINICAL RELEVANCE

The relationship of the MPFL femoral attachment footprint to the femoral physis in the skeletally immature patient is not well understood, and access to pediatric cadaveric tissue is very limited. This small series demonstrates that there is considerable variation in the relationship between the MPFL and distal femoral physis. This anatomic information may guide MPFL reconstruction technique in young patients and reduce the risk of iatrogenic physeal arrest on the femur.

The patellar insertion of the medial patellofemoral ligament in children: a cadaveric study

BACKGROUND

The purpose of this study was to evaluate the medial patellofemoral ligament (MPFL) patellar insertion in skeletally immature anatomic specimens.

METHODS

Nine pediatric cadaveric knee specimens were examined through gross dissection. Metallic markers were placed at the MPFL patellar insertion footprint. Computed tomographic scans for each specimen were analyzed. The MPFL insertion footprint width, patellar height, and patellar width were measured. The distance from the MPFL insertion footprint center to the midline of the patella was assessed. The proportion of the patella that the MPFL footprint inserted upon was calculated.

RESULTS

The mean width of the MPFL patellar insertion footprint was 12 mm (range, 8 to 18 mm). The mean patellar height was 31 mm (range, 20 to 48 mm). The mean patellar width was 27 mm (range, 21 to 39 mm). The center of the MPFL insertion footprint was found to be a mean 4.7 mm (range, -2 to 10.5 mm) above the midline of the patella, with insertion centers occurring both above and below the midline. The MPFL insertion footprint spanned a mean 41% (24% to 63%) of the longitudinal width of the patella.

CONCLUSIONS

Most adult studies report the MPFL insertion on the upper 1/2 to 2/3 of the patella. This series of skeletally immature subjects demonstrated that the center of the MPFL insertion was above and below the midpoint of the patella. The MPFL insertions of some of the younger specimens did extend into the distal 1/3 of the patella. The insertion of the older specimens was found in the proximal 2/3 of the patella, a similar location to most previous adult anatomic studies.

CLINICAL RELEVANCE

This research suggests that the MPFL insertion on the patella may be at slightly different locations in some skeletally immature subjects compared with adults. The specimens dissected in the present study showed more variability than previously published reports, with some insertions extending into the distal 1/3 of the patella in the youngest subjects. These dissections may be useful to surgeons performing MPFL reconstructions in skeletally immature patients.

Evaluation and management of patellar instability in pediatric and adolescent athletes

CONTEXT

The rising popularity and intensity of youth sports has increased the incidence of patellar dislocation. These sports-related injuries may be associated with significant morbidity in the pediatric population. Treatment requires understanding and attention to the unique challenges in the skeletally immature patient.

EVIDENCE ACQUISITION

PubMed searches spanning 1970-2013.

STUDY DESIGN

Clinical review.

LEVEL OF EVIDENCE

Level 5.

RESULTS

Although nonoperative approaches are most often suitable for first-time patellar dislocations, surgical treatment is recommended for acute fixation of displaced osteochondral fractures sustained during primary instability and for patellar realignment in the setting of recurrent instability. While a variety of procedures can prevent recurrence, the risk of complications is not minimal.

CONCLUSION

Patellar stabilization and realignment procedures in skeletally immature patients with recurrent patellar dislocation can effectively treat patellar instability without untoward effects on growth if careful surgical planning incorporates protection of growth parameters in the skeletally immature athlete.

The relationship of the femoral physis and the medial patellofemoral ligament in children: a cadaveric study

BACKGROUND

Patellar dislocations are common in skeletally immature athletes, and the medial patellofemoral ligament (MPFL) is an important primary restraint to lateral patellar translation. The relationship between the MPFL femoral origin footprint and femoral physis is unclear. The purpose of this study was to evaluate the MPFL femoral origin footprint and its relationship to the femoral physis in skeletally immature anatomic specimens.

METHODS

Six skeletally immature cadaver knee specimens were examined through gross dissection (group A: 1, 11, and 11 mo; and group B: 8, 10, and 11 y). Metallic markers were placed at the center of the MPFL femoral origin footprint. Computed tomography scans for each specimen were analyzed. The MPFL footprint width, and the vertical distances from the center and proximal extent of the MPFL footprint to the medial aspect of the physis were measured.

RESULTS

The mean width of the MPFL femoral origin footprint was 0.70 cm (0.48 to 1.09 cm) and 1.12 cm (1.03 to 1.29 cm) for groups A and B, respectively. The mean distance from the center of the MPFL origin footprint to medial aspect of the distal femoral physis was 0.90 cm (0.52 to 1.30 cm) and 0.40 cm (0.00 to 0.86 cm) distal to the physis for groups A and B, respectively. The mean distance from the proximal extent of the MPFL origin footprint to the medial aspect of the femoral physis was -0.55 cm (-0.28 to -1.03 cm) and 0.16 cm (-0.34 to 0.64 cm) for groups A and B, respectively.

CONCLUSIONS

All subjects were found to have a center of the MPFL origin footprint at or below the physis. The proximal extent of the MPFL origin footprint was found to extend above the physis in the 2 older specimens.

CLINICAL RELEVANCE

The relationship of the MPFL origin footprint to the femoral physis in the skeletally immature is not well understood. These dissections may be useful to surgeons performing MPFL reconstructions in skeletally immature patients.

The relationship of the medial patellofemoral ligament attachment to the distal femoral physis

BACKGROUND

No published study has ever described the relationship of the medial patellofemoral ligament (MPFL) attachment to the distal femoral physis in skeletally immature cadaveric specimens. As such, there continues to be much confusion about this relationship, which is important when considering MPFL reconstruction in the skeletally immature patient.

HYPOTHESIS

The MPFL footprint is distal to the medial border of the distal femoral physis.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Sixteen skeletally immature cadaveric specimens were used for this study. The average age of the specimens was 12 years (range, 10-15 years). The MPFL femoral attachment, adductor tubercle, and medial epicondyle were identified in all specimens, and the topography of the distal femoral physis was carefully described. Measurements were then taken of the distance from the medial aspect of the distal femoral physis to the MPFL femoral attachment and the horizontal distance from the MPFL femoral attachment to the point where a femoral tunnel would intersect the undulating femoral physis. All measurements were made with digital calipers.

RESULTS

The MPFL attachment was distal to the medial aspect of the femoral physis in all specimens. The MPFL attachment was an average of 8.5 mm distal to the medial aspect of the distal femoral physis. In the coronal plane, the undulating physis was 10.5 mm medial to the MPFL attachment. In all specimens, the undulations of the medial physis were concave directly posterior and lateral to the MPFL attachment and convex anterior to the MPFL attachment. Both the adductor tubercle and the medial epicondyle were also distal to the femoral physis in all specimens.

CONCLUSION

This study has confirmed the findings of others, who have shown that the MPFL femoral attachment lies distal to the medial aspect of the distal femoral physis. In addition, the study findings show that the MPFL femoral attachment is in very close proximity to the distal femoral physis.

CLINICAL RELEVANCE

To facilitate anatomic MPFL reconstruction, Schottle et al described a radiographic method to identify the MPFL femoral attachment on lateral radiographs in skeletally mature patients. Because of the complex physeal anatomy, much confusion exists concerning whether an MPFL femoral tunnel can be placed safely in the pediatric patient. The findings of this study suggest that anatomic MPFL reconstruction may be accomplished with a tunnel angled distally and anteriorly to avoid injury to the distal femoral physis.

Temporary hemiepiphysiodesis of the distal medial femur: MPFL in danger

INTRODUCTION

Temporary hemiepiphysiodesis (TH) with plate fixation is a well-accepted and common treatment for correcting leg malalignment in skeletally immature patients. The purpose of this study was to investigate any soft tissue damage caused during TH at the distal medial femur with a plate and two screws. We hypothesized that correct plate placement can affect the integrity of the medial stabilizing structures of the knee, especially the medial patellofemoral ligament (MPFL), the medial collateral ligament (MCL) or result in arthrotomy of the knee joint itself.

MATERIALS AND METHODS

In eight cadaveric knees of five adult humans a TH was performed with a plate and two cancellous screws at the distal medial femur using a standardized surgical technique. Subsequently the medial capsular and ligamentous structures were systematically exposed and assessed. Capsular and synovial tissue was also inspected for impingement by the plate or screws.

RESULTS

In all knees the MPFL was present. In two specimens the MPFL was intact and the plate was lying over the dorsal part of the MPFL close to the MCL. The MPFL was completely cut in two cases in the central part of the ligament. In four cases the MPFL was partially dissected or perforated by a screw and fixed to the femur by the plate. The MCL was intact and not impinged by the implant in any case. In total four of eight knees the capsule was transected or perforated by a screw or by a part of the plate, resulting in intraarticular implant placement.

CONCLUSIONS

Standard plate placement during TH on the distal medial femur frequently leads to damage to the MPFL, impingement of the MPFL, the capsular and synovial tissues or exposure of the knee joint.

Anchor proximal migration in the medial patellofemoral ligament reconstruction in skeletally immature patients

The medial patellofemoral ligament (MPFL) injury has been considered instrumental in lateral patellar instability after patellar dislocation. Consequently, the focus on the study of this ligament reconstruction has increased in recent years. The MPFL femoral anatomical origin point has great importance at the moment of reconstruction surgery, because a graft fixation in a non anatomical position may result in medial overload, medial subluxation of the patella or excessive tensioning of the graft with subsequent failure. In the pediatric population, the location of this point is highlighted by the presence of femoral physis. The literature is still controversial regarding the best placement of the graft. We describe two cases of skeletally immature patients in whom LPFM reconstruction was performed. The femoral fixation was through anchors that were placed above the physis. With the growth and development of the patients, the femoral origin point of the graft moved proximally, resulting in failure in these two cases.

Complications of medial patellofemoral ligament reconstruction in young patients

BACKGROUND

The medial patellofemoral ligament (MPFL) has been recognized as the primary restraint to lateral subluxation of the patella. Reconstruction of the MPFL for patellar instability has demonstrated early clinical success, but postoperative complications have rarely been reported, especially in young patients.

PURPOSE

To assess early complications (<3 years) of MPFL reconstruction in young patients.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

The charts and radiographs of all patients who underwent MPFL reconstruction between 2005 and 2011 were retrospectively reviewed to identify postoperative complications. A complication was considered major if the patient required hospitalization or further surgery. Each complication was analyzed to identify the technical factors related to it.

RESULTS

A total of 179 knees underwent MPFL reconstruction during the study period. There were 38 complications in 29 knees (16.2%), with 34 major and 4 minor. Major complications included recurrent lateral patellar instability (8 patients), knee motion stiffness with flexion deficits (8 patients), patellar fractures (6 patients), and patellofemoral arthrosis/pain (5 patients). Eighteen of 38 (47%) complications were secondary to technical factors and were considered preventable. Female sex and bilateral MPFL reconstructions were risk factors associated with postoperative complications.

CONCLUSION

Complications occurred in 16.2% of MPFL reconstruction surgeries for patellar instability in young patients, with almost half resulting from technical problems. Patients should be counseled preoperatively on the risk of potential complications.

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.

Predictors of recurrent instability after acute patellofemoral dislocation in pediatric and adolescent patients

BACKGROUND

Patellofemoral instability is common in the pediatric and adolescent population, yet prognosis after the first dislocation has been difficult to determine.

PURPOSE

To describe the demographics of pediatric and adolescent patients with a first-time patellofemoral dislocation and to determine predictors of recurrent instability.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

A search of the Mayo Medical Index database between 1998 to 2010 was performed, and 2039 patients were identified. Inclusion criteria were (1) age 18 years or younger, (2) no history of patellofemoral subluxation/dislocation of the affected knee, (3) radiographs within 4 weeks of the initial instability episode, and (4) a dislocated patella requiring reduction or convincing history/findings suggestive of acute patellar dislocation (effusion/hemarthrosis, tenderness along medial parapatellar structures, and apprehension with lateral patellar translation). Radiographs were evaluated for trochlear dysplasia (Dejour classification) and patella alta (Caton-Deschamps and Insall-Salvati indices). Skeletal maturity was graded based on the distal femoral and proximal tibial physes (open, closing, or closed).

RESULTS

A total of 222 knees (120 male [54.1%] and 102 female [45.9%]) in 210 patients with an average age of 14.9 years (range, 9-18 years), met the inclusion criteria. Twenty-four patients (10.8%) underwent early surgery. All others were initially treated nonoperatively. Of the 198 patients in this group, 76 (38.4%) had recurrent instability, and 39 (51.3%) of these required surgical treatment. Recurrent instability was associated with trochlear dysplasia (P < .01). Patients with both immature physes and trochlear dysplasia had a recurrence rate of 69% (33/48), with a hazard ratio of 3.3. Age, sex, body mass index, and patella alta were not statistically associated with recurrent instability.

CONCLUSION

Nonoperative treatment for first-time patellofemoral dislocation resulted in a 62% success rate. However, skeletally immature patients with trochlear dysplasia had only a 31% success rate with nonoperative management. Nearly half of patients with recurrent instability required surgical intervention to gain stability.

Anatomic reconstruction of the medial patellofemoral ligament in children and adolescents with open growth plates: surgical technique and clinical outcome

BACKGROUND

Recurrent lateral patellar dislocation is a common knee injury in the skeletally immature adolescent. Because of the open physis, operative therapy in children is challenging. This study presents the outcomes of a minimally invasive technique for anatomic reconstruction of the medial patellofemoral ligament (MPFL) in children that respects the distal femoral physis.

HYPOTHESIS

Anatomic reconstruction of the MPFL in children that maintains the distal femoral physis will prevent redislocation, preserve the distal femoral physis, and improve knee function.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Twenty-one consecutive patients with patellofemoral instability and open growth plates underwent anatomic reconstruction of the MPFL that maintained the distal femoral growth plate. Preoperative radiographic examination included AP and lateral views to assess patella alta and limb alignment. Magnetic resonance imaging was performed to evaluate trochlear dysplasia and tibial tubercle-trochlear groove (TT-TG) distance. Evaluation included preoperative and postoperative physical examination, Kujala score, and Tegner activity score.

RESULTS

The average age at the time of operation was 12.2 years (range, 10.3-13.9). The average follow-up after operation was 2.8 years after surgery (range, 2.0-3.6). No recurrent dislocation occurred, but 2 patients with high-grade trochlear dysplasia still had a positive apprehension sign. The Kujala score significantly improved from 72.9 (range, 37-87) preoperatively to 92.8 (range, 74-100) postoperatively (P < .01). The Tegner activity score decreased, but not significantly, from 6.0 (range, 3-9) preoperatively to 5.8 (range, 3-9) postoperatively (P = .48).

CONCLUSION

Anatomic reconstruction of the MPFL that respects the distal femoral physis in skeletally immature patients is a safe and effective technique for the treatment of patellofemoral instability and allows patients to return to sports without redislocation of the patella.

Galeazzi semitendinosus tenodesis for patellofemoral instability in skeletally immature patients

BACKGROUND

Numerous surgical treatments have been described to address subluxation or dislocation of the patella, but many are not suitable for the skeletally immature patient, as they risk injury to the proximal tibial physis or tibial tubercle apophysis. The Galeazzi semitendinosus tenodesis is a soft-tissue reconstruction technique designed to stabilize the patella without altering the femoral or the bony structures about the knee. We sought to determine if this semitendinosus tenodesis is a safe and effective treatment for patellofemoral instability in skeletally immature patients.

METHODS

We retrospectively analyzed the records of a population of skeletally immature patients who underwent semitendinosus tenodesis for patellofemoral instability at our institution from 1990 to 2006. Condition-specific outcome and function were prospectively collected, including the International Knee Documentation Committee (IKDC) score, Kujala Score, and Marx Activity Scale. Recurrent instability was defined as patient-reported postoperative subluxation, dislocation, or both.

RESULTS

Twenty-eight patients (34 total knees) were included in the study. Average follow-up was 70 months (range, 27 to 217 mo). Patients reported recurrent instability in 28 of the 34 knees (82%). Overall, 41% of patients had IKDC scores <70. Twelve knees (35%) were symptomatic enough to undergo subsequent surgery, but had similar mean IKDC (63), Kujala (81), and Marx Activity Scores (7.5) at long-term follow-up to those (IKDC 64, Kujala 79, Marx 8.2) who did not undergo additional surgeries (P=0.73, 0.88, 0.76, respectively). Complications included 1 superficial wound infection and 1 mild wound dehiscence.

CONCLUSIONS

Patellofemoral instability remains a challenging clinical problem, particularly in patients with open physes. The Galeazzi semitendinosus tenodesis is a safe procedure for patellofemoral instability in skeletally immature patients, but our long-term data suggest it may not be as successful as previously reported. Approximately 82% of patients experienced recurrent subluxation or dislocation despite surgical intervention, which may be due in large part to various predisposing factors, and there was a 35% rate of second surgeries. However, given the variability in techniques and reported results of patellofemoral stabilizing procedures in skeletally immature patients, the Galeazzi procedure may still be a reasonable way to temporize the difficult problem of patellar instability until patients reach skeletal maturity, when bony realignment procedures can be more safely used.

LEVEL OF EVIDENCE

Level IV, case series.

Effects of medial patellofemoral ligament reconstruction on patellar tracking

PURPOSE

Medial patellofemoral ligament (MPFL) reconstruction has been performed to treat recurrent patellar dislocation. However, the effects on patellar tracking have not been well documented, particularly in patients. The purpose of this study is to compare patellar tracking pattern and chondral status at MPFL reconstruction with those at second-look arthroscopy.

METHODS

Between 1999 and 2008, 71 patients with recurrent patellar dislocation underwent MPFL reconstruction using a double-looped semitendinosus tendon. Of these, 25 knees in 24 patients underwent second-look arthroscopy (at 6-26 months after initial surgery), forming the subject for the present study. No other surgical procedures such as tibial tuberosity transfer, lateral release, or osteotomy were performed in any patients. To assess the patellar tracking pattern, the position of the patella on femoral groove was evaluated arthroscopically during passive knee motion through lateral suprapatellar portal.

RESULTS

Before MPFL reconstruction, the patella in all patients was shifted laterally throughout the entire range of knee motion. Immediately after MPFL reconstruction, patellar malalignment was corrected in all cases. On second-look arthroscopy, two different patellar tracking patterns were observed. In 9 knees, the patella was located on the center of the femoral groove throughout the range of motion. Meanwhile, in the remaining 16 knees, the patella was shifted laterally at knee extension and migrated to the center of femoral groove with increased knee flexion. No significant deteriorations in chondral status were seen on second-look arthroscopy.

CONCLUSION

The present study revealed that not all improved patellar trackings after MPFL reconstruction remained intact at follow-up. Chondral status in patellofemoral joint was not aggravated by MPFL reconstruction.

LEVEL OF EVIDENCE

Therapeutic studies, Level IV.

The relation of the distal femoral physis and the medial patellofemoral ligament

PURPOSE

The purpose of this study was to analyse true lateral radiographs of children and adolescents to determine the relation of the origin of the MPFL and the distal femoral physis considering the complex anatomy of the physis. The hypothesis was that the femoral insertion of the MPFL is distal to the growth plate.

METHODS

Antero-posterior and true lateral radiographs from PACS computer records of 27 patients with a history of patellofemoral instability were assessed. To determine the femoral origin of the MPFL, the method by Schöttle et al. and the method by Redfern et al. were applied independently. On the anteroposterior radiograph, the distance between the medial most part of the physis and the central part of the physis was measured to quantify the concave curvature of the physis. To cross-reference the femoral insertion of the MPFL onto an ap view, the projected MPFL origin-physis distance was subtracted from the distance between the most medial part of the physis and the central part of the physis.

RESULTS

The projected median origin of the MPFL as measured on a lateral radiograph was located 3.2 mm (1.2-5.8 mm) proximal to the physis. The median distance between the most medial part of the physis and the physeal line on the anteroposterior radiograph was 9.9 mm (4.1-12.0 mm). Subtracting the two measured values, the median origin of the MPFL as seen on the ap view was 6.4 mm (2.9-8.5 mm) distal to the femoral physis.

CONCLUSION

Considering the concave curvature of the distal femoral physis, it can be assumed that the femoral insertion of the MPFL is distal to the femoral physis. As a too proximal insertion of the graft can cause unintentional tightening of the MPFL in knee flexion, these results have to be considered when performing reconstruction of the MPFL in children and adolescents with open growth plates.