Risk Factor For Patellar Instability Research Articles

Medial Patellofemoral Ligament Reconstruction With Growth Modulation in Children With Patellar Instability and Genu Valgum

Patellar instability is common in the second decade, and genu valgum is a risk factor for patellar instability. In skeletally immature patients, genu valgum can be gradually corrected using less-invasive, well-established, growth-modulation techniques. For skeletally immature patients with patellar instability and genu valgum, it would be desirable to address both instability and deformity. We describe our technique of physeal-respecting medial patellofemoral ligament reconstruction in skeletally immature patients using hamstring autograft and simultaneous transphyseal screw hemiepiphysiodesis to gradually correct genu valgum. The medial patellofemoral ligament reconstruction technique features posteromedial hamstring graft harvest, single patellar tunnel fixation without implant, and femoral attachment just below the distal femoral physis. The technique of growth modulation features percutaneous insertion of a single transphyseal screw through the distal medial femoral physis without interference with medial patellofemoral ligament graft placement. Our preliminary results have been encouraging with successful correction of genu valgum and satisfactory patellar stabilization without growth disturbances.

Relationship between Anatomical Risk Factors, Articular Cartilage Lesions, and Patient Outcomes Following Medial Patellofemoral Ligament Reconstruction.

The purpose of this study was (1) to determine which risk factors for patellar instability were associated with the presence of patellofemoral cartilage lesions and (2) to determine how cartilage lesion presence, size, and grade affect postoperative disease-specific quality of life. Preoperative, intraoperative, and postoperative demographic, anthropometric (body mass index, Beighton score, hip rotation), radiographic (crossover sign, trochlear bump), cartilage lesion morphology (presence, size, location, grade), and outcomes data (Banff Patella Instability Instrument 2.0 [BPII 2.0]) were prospectively collected from patients undergoing isolated medial patellofemoral ligament reconstruction. For all knees (n = 264), single and multivariable logistic regression was used to determine if any patellar instability risk factors affected the odds of having a cartilage lesion. In patients with unilateral symptoms (n = 121), single variable linear regression was used to determine if the presence, size, or ICRS (International Cartilage Regeneration & Joint Preservation Society) grade of cartilage lesions could predict the 12 or 24+ month postoperative BPII 2.0 score. A total of 84.5% of knees had patellofemoral cartilage lesions (88.3% involved the distal-medial patella). Trochlear dysplasia (high grade: odds ratio = 15.7, P < 0.001; low grade: odds ratio = 2.9, P = 0.015) was associated with the presence of a cartilage lesion. The presence, size, and grade of cartilage lesions were not associated with 12 or 24+ month postoperative BPII 2.0 scores. Trochlear dysplasia was a risk factor for the development of patellofemoral cartilage lesions in this patient population. Cartilage lesions most commonly involve the distal-medial patella. There was no significant relationship between patellofemoral cartilage lesion presence, size, or grade and postoperative BPII 2.0 scores in short-term follow-up.

Cartilage Restoration in the Patellofemoral Joint: Techniques and Outcomes

Focal chondral defects are common in the patellofemoral joint, particularly in young and active patients, and can significantly impair quality of life. The pathomechanism of cartilage lesions in the patellofemoral joint are multifactorial and can be divided into chronic repetitive microtrauma due to patellar maltracking and acute macrotrauma such as patellar dislocation. Numerous risk factors for patellar instability have been reported including trochlear dysplasia, patella alta, chronic lateral patellar static position, excessive lateral position of the tibial tuberosity, excessive internal rotation of femur/external rotation of tibia, and patholaxity of the medial patellofemoral ligament. Patients with patellofemoral chondral lesions typically present with anterior knee pain that is exacerbated by activity, patellar instability, and/or loss of motion. This is often accompanied by effusion, soft tissue swelling, giving way, crepitance, and loose body sensation. If conservative treatment fails, various surgical treatment options are available ranging from palliative (chondroplasty), over reparative (marrow stimulation techniques) to restorative (autologous chondrocyte implantation and particulated juvenile allograft cartilage), and reconstructive procedures (osteochondral transplantation). A thorough physical and imaging evaluation of the patient is crucial to detect concomitant pathologies and to eventually allow planning a comprehensive individual treatment approach for each patient that addresses both the chondral lesion and any associated pathology. Also, setting realistic expectations and elucidating patient's goals are important parts of a successful treatment. Following these principles, favorable outcomes and high satisfaction rates can be achieved after cartilage restoration in the PFJ.

The Reversed Dynamic Patellar Apprehension Test (ReDPAT) mimics anatomical complexity in lateral patellar instability

Aims and Objectives: To develop a dynamic physical examination test that functionally simulates actual patellar instability events and that mimics the range of patellar stabilizer insufficiency in an individual patient. Materials and Methods: Seventy-four consecutive patients (male/female 33/41; mean age 22±7 years) with recurrent lateral patellar instability and thirty controls (male/female 16/14; mean age 31±14 years) were prospectively evaluated using the reversed dynamic patellar apprehension test (ReDPAT). The examination starts with the knee flexed at 120°. The knee is then extended while the patella is translated laterally. The maneuver is stopped at first onset of a subjective apprehensive reaction, and the ReDPAT result is considered positive according to this knee joint flexion angle. Anatomical predisposition was assessed according to Dejour’s classification of trochlear dysplasia, tibial tuberosity-trochlear groove distance, tibial tuberosity-posterior cruciate ligament distance, patellar height, and varus/valgus malalignment. Results: The study group had an average of 3.4 ± 1.0 (1-6) anatomical risk factors for lateral patellar dislocation. Severe trochlear dysplasia (84%) and patella alta (49%) were the most common. Test sensitivity, specificity, and accuracy reached 97.3%, 90%, and 95.2%, respectively, and test-retest reliability was good (Pearson’s r 0.84; p&lt;0.0001). The ReDPAT results became positive at a mean knee flexion angle of 58°±17° (20°-90°). Knee flexion angle correlated significantly with the severity of trochlear dysplasia (p=0.018), valgus deformity (p=0.011), and the total number of anatomical risk factors (p=0.02). Conclusion: This study introduced the reversed dynamic patellar apprehension test as a reliable clinical examination tool in the assessment of lateral patellar instability. The results of this study indicate that the degree of knee joint flexion at which the provocative sense of apprehension becomes positive correlates with severity of trochlear dysplasia, valgus deformity and the total number of anatomical risk factors for patellar instability.

THE EFFECT OF TROCHLEAR DYSPLASIA ON COMMONLY USED RADIOGRAPHIC PARAMETERS TO ASSESS PATELLAR INSTABILITY

Background: Patellar instability (PI) is a relatively rare knee condition but most commonly occurs in children and adolescents. The etiology of PI is complex and multi-faceted. Trochlear dysplasia, patellar tilt, tibial tuberosity-trochlear groove (TT-TG) distance, and patella alta have all been cited as contributory factors. Some authors have postulated that trochlear dysplasia (TD) alters the patellofemoral joint such that several of these radiographic parameters are changed relative to the amount of TD present. However, methods to quantify TD have not reached universal agreement. The lateral trochlear inclination (LTI) is one measure that has been described to characterize and quantify trochlear morphology on axial MRI images. Recently, a modified technique for measuring LTI that references the femur’s posterior condylar axis has demonstrated near-perfect inter- and within-rater reliability (ICC: 0.971, 95% CI: 0.88 – 0.97) and may serve as a new method to reliably quantify TD. The purpose of this study was to evaluate this modified LTI measurement against historically used radiographic measures of PI including TT-TG distance, lateral patellar inclination (LPI) angle, and the Caton-Deschamps (CD) ratio. We hypothesized that lower LTI measurements (i.e. more dysplastic trochleas) would be associated with higher TT-TG distances, increased patellar tilt, more patella alta and vice versa. Methods: Patients aged nine to eighteen years who were treated for PI at our tertiary referral center between January 2014 and August 2017 were queried. Radiographs and MRI exams of the symptomatic knee were obtained for measurement. On MRI, LTI measurements were made using the novel technique with reference to the orientation of the fully-formed posterior condyles. LPI measurements were conducted using a novel technique where the angle of the widest portion of the patella is measured relative to the posterior femoral condyles (ICC = 0.885, 95% CI: 0.77 – 0.95). TT-TG distances were measured on MRI from both the proximal (pTT-TG) and distal (dTT-TG) extents of the trochlea. The CD ratio was measured on lateral radiographs. All measurements were made by three independent observers. A separate cohort was randomly selected from the original list for the same measurements on two occasions, at least two weeks apart. Inter- and intra-rater correlation coefficients were then calculated using this subgroup and regression analysis was performed using data from the entire cohort. Results: Sixty-five patients met inclusion criteria for this study, from which thirty were selected for reliability analysis. Average pTT-TG distance (15.7±4.5 mm) was not significantly different from dTT-TG distance (15.7±4.2 mm) (p=0.94). Good inter-rater reliability was found for both pTT-TG (ICC=0.78, 95% CI: 0.59-0.89) and dTT-TG (ICC=0.83, 95% CI: 0.66-0.91). Both measurements also had excellent within-rater reliability (ICC=0.95, 95% CI: 0.90-0.98 for pTT-TG; ICC=0.90, 95% CI: 0.80-0.95 for dTT-TG). Linear regression analysis showed LTI to have a weak but significant inverse correlation with both pTT-TG (r = -0.40, b=-0.15 mm, p&lt;0.001) and dTT-TG (r = -0.59, b=-0.21 mm, p&lt;0.001). LTI also showed moderate and significant inverse correlation with LPI (r = -0.69, b=-0.54degrees, p&lt;0.001). The average CD ratio was 1.3±0.3 (range 0.8-2.1). LTI did not show significant correlation with the CD ratio (r = -0.19, p=0.14). Moderate inter-rater reliability (ICC=0.62, 95% CI: 0.34-0.80) and high intra-rater reliability (ICC=0.82, 95% CI: 0.66-0.91) were found for CD ratio measurements. Conclusion/Significance: In our cohort, smaller LTI measurements (higher levels of dysplasia) were found to be significantly correlated with larger TT-TG measurements and greater patellar inclination angles which supports the notion that these radiographic measures are dependent variables relative to dysplasia and thus may not be consistent independent risk factors for patellar instability. Interestingly, pTT-TG and dTT-TG distances were not significantly different, suggesting that while TD tends to medialize the trochlear groove, once the groove is formed it proceeds distally in a fairly straight line. The CD ratio was not found to be correlated with dysplasia represented by LTI in this cohort which suggests that patellar height is independent of dysplasia. Taken together, the results of this study suggest that TD may be the principal anatomic risk factor for patellar instability and that the TT-TG and patellar tilt are altered secondary to TD. Patellar height did not have a correlation with TD and thus should be analyzed separately as to its role in patellar instability.

INCREASING HOSPITAL ADMISSIONS FOR PATELLAR INSTABILITY: A NATIONAL DATABASE STUDY FROM 2004-2017

Background: Patellar instability refers to subluxation or dislocation of the patella out of the trochlear groove of the femur. Patellar instability is classically thought to be most common in adolescent girls. Risk factors for patellar instability described in the literature include female sex, race, sports participation, personal or family history of patellar instability, ligamentous laxity, trochlear dysplasia, and other anatomic factors. However, the epidemiology of patellar instability is not fully characterized, as some studies have produced conflicting information or been drawn from limited populations. In this study, we used the Pediatric Health Information System (PHIS) database to examine trends in admissions for patellar instability throughout the United States. We believe that a national pediatric hospital database will help to illustrate trends in the epidemiology of patellar instability. We hypothesized that there would be an increasing rate of patellar instability admissions in recent years. Secondarily, we examined how demographic factors and insurance status relate to admissions for patellar instability. Methods: This study used Pediatric Health Information System (PHIS) which is a comprehensive administrative database in which more than 45 pediatric hospitals participate, including not-for-profit, freestanding, and tertiary care pediatric centers associated with the Children’s Hospital Association. Patients with ICD 9 &amp; 10 codes 8363, 8364, 71785, M221.0, S83.001, S83.002, S83.003, S83.004, S83.005, and S83.006, were abstracted from PHIS. We abstracted patient characteristics such as age, sex, race, primary source of payment, and discharge year, as well as hospital characteristics such as hospital city. We included all patients admitted with patellofemoral dislocations that were reported in the PHIS database between January 1, 2004 and April 30, 2017. A Shapiro-Wilk test was conducted to determine normality of the dataset, along with a subsequent Pearson correlation to examine the relationship between number of patellar dislocation admissions over the years studied, adjusted for number of hospitals in the study. The relationship between age at admission and sex was examined using a two sample T-test and a linear regression analysis. All statistical analyses were performed using IBM SPSS Statistics Software Version 23.0 (IBM Corp, Armonk, NY, USA). Statistical significance was set at p &lt; 0.05. Results: An estimated total of 25,413 admissions for patellar instability were identified by the search of the PHIS database; 15,444 (60.8%) were female patients and 9,966 (39.2%) were male. The adjusted number of admissions per reporting hospital significantly increased over the years studied (r=0.775, p&lt;0.001), from 14.5 admissions per reporting hospital in 2004 to 86.0 admissions per reporting hospital in 2016. Males were admitted for patellar instability at a significantly older age than females in the data extracted from the PHIS database (14.36 ± 0.23 vs. 13.58 ± 0.20 years, p&lt;0.001). Of all patellar instability admissions, 55.0% were white, 20.4% were black, 1.7% were Asian, and 22.9% were unknown race. A larger number of patellar instability admissions occurred in patients with insurance status other than Medicaid in every year that data was collected. Conclusions/Significance: Based on a PHIS database search, pediatric hospital admissions for patellar instability are steadily increasing. The majority of patients admitted for patellar instability are female, white, and have insurance other than Medicaid. Males admitted for patellar instability tended to be older than females admitted for the same. [Table: see text][Figure: see text][Figure: see text][Figure: see text][Figure: see text]

Simultaneous treatment for patellar instability and genu valgum in skeletally immature patients: a preliminary study.

Genu valgum is a risk factor for patellar instability. The study purpose was to report on preliminary results of medial patellofemoral ligament (MPFL) reconstruction and simultaneous growth modulation, in patients with patellar instability and genu valgum. A total of seven patients (eight knees) with MPFL reconstruction and medial transphyseal screw insertion for genu valgum correction were assessed using full-length radiographs. Genu valgum corrected from 13.1° to 3.7° at mean 11.7 months, without compromising patellar stability. One patient each had 6° overcorrection and 5° rebound valgus. Guided growth using transphyseal screw during MPFL reconstruction could achieve deformity correction without interference with MPFL graft placement.

Trochlear Dysplasia and Its Relationship to the Anterior Distal Femoral Physis.

Trochlear dysplasia is a known risk factor for patellar instability in adolescent patients. A spatial relationship between dysplastic trochlea and anterior distal femoral physis has not been established. The purpose of this study was to investigate this relationship. Our hypothesis was that the position of the dysplastic trochlea and trochlear bump would coincide with the anterior distal femoral physis and that the distance between them would increase with age. In a retrospective study, magnetic resonance images of adolescents with trochlear dysplasia were evaluated. Measurements performed included trochlear depth, trochlear bump size, proximal trochlea-physis distance, and trochlear bump-physis distance. Linear regression analyses were performed to correlate the variables with increasing age. In total, 175 knees (160 patients) with trochlear dysplasia were included. The mean trochlea-physis distance was 4.50 mm (SD=1.93) and it increased with age (slope=0.26; P<0.01). The lateral aspect of trochlea was proximal to the physis in 24 (13.7%) knees and was at the level of the physis in 31 (17.7%) knees. The size of trochlear bump increased with age (slope=0.15; P=0.01). The bump-physis distance increased with age (slope=0.41; P<0.01). The dysplastic trochlea is closely related to the anterior distal femoral physis. The distance between the dysplastic trochlea and femoral physis increases with age. The close relationship between proximal aspect of trochlea and anterior distal femoral physis should be considered when trochlear surgery is planned in skeletally immature patients. Level II.

Femoral trochlea does not remodel after patellar stabilization in children older than 10 years of age

Trochlear dysplasia is a major risk factor for patellar instability. It has been sparsely reported that the trochlea can remodel when patellar stabilization is performed in skeletally immature patients before the age of 10 years. It is not known whether trochlea can remodel significantly after the age of 10 years. The purpose of the study was to evaluate trochlear remodeling in skeletally immature patients after patellar stabilization surgery, with a focus on children older than 10 years of age. In a retrospective study, knee MRI of 21 patients who had undergone patellar stabilization surgery, were evaluated. Twenty of these 21 patients were older than 10 years of age at time of surgery. The measurements of cartilaginous and bony sulcus angles, trochlear depth, and cartilaginous trochlear bump were compared between preoperative and postoperative MRI, using paired t-tests. In 20 patients older than 10 years of age, the mean cartilaginous sulcus angle change between preoperative and postoperative axial MRI was not significant (2.2°±7.9°, P=0.6). The mean change in the bony sulcus angle value was not significant (3.6°±6.8°, P=0.07). Similarly, there was no significant change in trochlear depth (P=0.8), or size of the trochlear bump (P=0.1). For one patient under 10 years of age at the time of surgery, there was a 21° and a 15° improvement in cartilaginous and bony sulcus angle, respectively. There were no significant changes in the trochlear parameters and trochlear remodeling in patients older than 10 years of age. Patellar stabilization at a younger age (<10 years), may allow for trochlear remodeling. Level of Evidence: Level IV, case series.

Is femoral trochlear dysplasia related to global joint hypermobility?

BackgroundHypermobility is a known risk factor for patellar instability. In this study, we hypothesized that a significant relationship exists between global joint hypermobility and trochlear dysplasia. MethodsFollow-up patients from the shoulder department of our institution with global joint hypermobility (Group 1, n = 42) and healthy volunteers (Group 2, n = 42) without known knee complaints were included in our study. All participants underwent knee magnetic resonance imaging (MRI) for the evaluation of possible trochlear dysplasia, and the measurements included lateral trochlear inclination; trochlear facet asymmetry; the depth of the trochlear groove; condylar asymmetry; lateralization of the patella; sulcus angle; and the lateral, medial and central trochlear height. The Dejour classification was also assessed. ResultsThe age and gender distributions of the groups were similar (p > 0.05). The radiological evaluations revealed that the lateral trochlear inclination (p < 0.001), trochlear facet asymmetry (p < 0.001), depth of the trochlear groove (p < 0.001), lateralization of the patella (p < 0.001), sulcus angle (p < 0.001), and central trochlear height (p < 0.001) were significantly different between the two groups. The condylar asymmetry and lateral and femoral condylar height parameters were similar between the groups (p = 0.297, p = 0.890 and p = 0.521, respectively). According to the Dejour classification, 39 patients had dysplasia in Group 1, whereas dysplasia was detected in only 4 of the participants in Group 2. ConclusionsOur study revealed that most of the trochlear dysplasia criteria were met in patients with global joint hypermobility. In addition to a clinical patellofemoral examination, the precise radiological evaluation of the joint is beneficial in patellofemoral instability patients with concomitant hypermobility. Patient cohort of this study was consist of patients underwent shoulder surgery.

The reversed dynamic patellar apprehension test mimics anatomical complexity in lateral patellar instability

To develop a dynamic physical examination test that functionally simulates actual patellar instability events and that mimics the range of patellar stabilizer insufficiency in an individual patient. Seventy-eight consecutive patients (male/female 35/43; mean age 22 ± 7years) with recurrent lateral patellar instability and 35 controls (male/female 16/19; mean age 31 ± 14years) were prospectively evaluated using the reversed dynamic patellar apprehension test (ReDPAT). Anatomical predisposition was assessed according to Dejour's classification of trochlear dysplasia, tibial tuberosity-trochlear groove distance, tibial tuberosity-posterior cruciate ligament distance, patellar height, and varus/valgus malalignment. The study group had an average of 3.4 ± 1.0 (1-6) anatomical risk factors for lateral patellar dislocation. Severe trochlear dysplasia (84%) and patella alta (49%) were the most common. Test sensitivity and specificity was 93.7% (95% CI 0.8584-0.9791) and 88.2% (95% CI 0.7255-0.9670), respectively. The positive predictive value reached 94.9% (95% CI 0.8739-0.9859) and the negative predictive value was 85.7% (95% CI 0.6974-0.9519). The ReDPAT results became positive at a mean knee flexion angle of 58°±17° (20°-90°). Knee flexion angle correlated significantly with the severity of trochlear dysplasia (p = 0.018), valgus deformity (p = 0.011), and the total number of anatomical risk factors (p = 0.02). This study introduced the reversed dynamic patellar apprehension test as a reliable clinical examination tool in the assessment of lateral patellar instability. The results of this study indicate that the degree of knee joint flexion at which the provocative sense of apprehension becomes positive correlates with severity of trochlear dysplasia, valgus deformity and the total number of anatomical risk factors for patellar instability. This test indicates the patient-specific end of stable patellar tracking and the beginning of patellar stabilizer insufficiency. Therefore, this test might be helpful in deciding for or against a bony procedure in the treatment of patellar dislocation. II.

Clinical Results after Combined Distal Femoral Osteotomy in Patients with Patellar Maltracking and Recurrent Dislocations.

The purpose of this study is to analyze the clinical results after treatment of patellofemoral instability and maltracking caused by torsional or axial deformities of the lower extremity by combined distal femoral osteotomies (DFOs). We analyzed 31 DFOs (25 patients) with patellar maltracking and instability, treated in our clinic. Torsional angles and the leg axis in the frontal plane were measured preoperatively. Standardized scoring systems were determined pre- and postoperatively including a clinical examination. Nineteen cases of torsional and 12 cases of axis deformities were evaluated 27 (12-64) months postoperatively. Among those with torsional deformity, mean femoral torsion was -39.0 ± 8.8 degrees, tibial tuberosity to trochlear groove (TT-TG) 20.3 ± 4.5 mm. We performed 19 torsional (+11.4 ± 2.4 degrees) DFOs with medial patellofemoral ligament (MPFL) augmentation (n = 19), tibial tuberosity transfer (n = 14, 10.9 ± 6.0 mm), varus (n = 4, 3.3 ± 1.0 degrees), or valgus (n = 1, 7.0 degrees) correction. Among valgus deformities, the leg axis was 6.7 ± 2.3 degrees valgus and TT-TG 19.3 ± 5.0 mm. We performed 12 medially closing-wedge DFOs (7.6 ± 2.8 degrees) with MPFL augmentation (n = 12) and tibial tubercle transfer (n = 9, 11.4 ± 7.3 mm). Visual analogue pain scale improved from 6.2 to 1.5 (p = 0.000), Kujala score from 45.0 to 81.5 (p = 0.000), Lysholm score from 40.3 to 83.9 (p = 0.000), and Tegner score from 2.1 to 3.9 (p = 0.000). Preoperative cartilage damage significantly influences the postoperative functional outcome (Lysholm score) (p = 0.026) as well as the improvement in terms of the Kujala score (p = 0.045) in the overall collective. No redislocation was observed. Patellofemoral maltracking and instability in torsional and axis deformities can successfully be treated by combined DFOs with excellent clinical results. The coexistence of risk factors for patellar instability requires a combination of additional procedures to complement the osteotomy. Preoperative cartilage lesions significantly influence the clinical outcome.

The Growth of Trochlear Dysplasia During Adolescence.

Femoral trochlear dysplasia is a known risk factor for patellar instability. The growth pattern of the normal trochlea is known, but there have been no studies investigating the growth and development of the dysplastic trochlea. The purpose of this study was to assess the growth pattern of trochlear dysplasia in adolescents. In a retrospective analysis, magnetic resonance images of adolescents with patellar instability and trochlear dysplasia were evaluated. These images were measured for lateral and medial condylar height, trochlear height, cartilaginous and bony trochlear bump, and cartilaginous and bony sulcus angle. The type of trochlear dysplasia was classified as per Dejour classification. These measurements were plotted against age, and their growth patterns were evaluated using statistical methods. Of 235 knees with patellar instability, trochlear dysplasia was present in 175 knees (74% knees) and these were further analyzed. With increasing age, the mean lateral and medial condylar heights and mean trochlear height showed statistically significant increase (P<0.01). Cartilaginous trochlear bump (slope=0.15, P=0.013) and bony trochlear bump (slope=0.22, P<0.01) increased with age, with some reaching the pathologic value by age of 15.1 years. After age 11 years, there were no significant changes for cartilaginous and bony sulcus angles (cartilage: slope=0.03, P=0.96; bony: slope=-0.90, P=0.11). The mean cartilaginous sulcus angle was significantly greater than the mean bony sulcus angle (P<0.01). All Dejour types of trochlear dysplasia were present across all age groups. All linear measurements of trochlear dysplasia (condylar height, trochlear height, trochlear bump) increased with age. However, the shape of trochlear dysplasia, as reflected by sulcus angle and Dejour classification, did not change with increasing age. The shape of trochlear dysplasia is most likely a genetic predisposition and does not necessarily change during skeletal growth. Level II-diagnostic, cross-sectional.

Operative Repair of Medial Patellofemoral Ligament Injury Versus Knee Brace in Children With an Acute First-Time Traumatic Patellar Dislocation: A Randomized Controlled Trial

Background: A lateral patellar dislocation (LPD) is the most common traumatic knee injury with hemarthrosis in children. The redislocation rate is high. Varying operative and nonoperative treatments have been advocated with no consensus on the best treatment. Purpose: (1) To evaluate if arthroscopic-assisted repair of the medial patellofemoral ligament (MPFL) in patients with an acute first-time traumatic LPD would reduce the recurrence rate and offer better objective/subjective knee function compared with a knee brace without repair. (2) To study the presence of anatomic patellar instability risk factors (APIFs) and their association with a redislocation. Study Design: Randomized controlled trial; Level of evidence, 1. Methods: This was a prospective series of 74 skeletally immature patients aged 9 to 14 years (38 girls and 36 boys; mean age, 13.1 years) with a first-time traumatic LPD, with clinical examinations, radiographs, magnetic resonance imaging, and diagnostic arthroscopic surgery performed within 2 weeks of the index injury. The child was randomized to either (1) a knee brace (KB group) for 4 weeks and physical therapy or (2) arthroscopic-assisted repair (R group) of the MPFL with anchors, 4 weeks with a soft cast splint, and physical therapy. The follow-up time was 2 years. Results: The redislocation rate was significantly lower in the R group than in the KB group at final follow-up: 8 patients (22%) versus 16 patients (43%), respectively (P = .047). The Knee injury and Osteoarthritis Outcome Score for children sport/play and quality of life subscales had lower scores in the R group compared with the KB group; the significant differences were among those with redislocations. The mean Kujala score was excellent in the KB group (95.9) and good in the R group (90.9). An impaired Limb Symmetry Index (median, 83%) for concentric quadriceps torque at 90 deg/s was found only in the R group. Eighty-one percent of the study patients had ≥2 APIFs. Trochlear dysplasia (trochlear depth <3 mm) had the highest odds ratio for redislocations (2.35 [95% CI, 0.69-8.03]), with no significant association between APIFs and a redislocation. Conclusion: Operative repair of an MPFL injury in the acute phase in skeletally immature children with a primary traumatic LPD significantly reduced the redislocation rate but did not improve subjective or objective knee function compared with a knee brace without repair. The majority of the patients in both groups were satisfied with their knee function. There was a high representation of APIFs, which needs to be considered when evaluating the risk of redislocations. Registration: ISRCTN 39959729 (Current Controlled Trials).

3D Knee Trochlear Morphology Assessment by Magnetic Resonance Imaging in Patients With Normal and Dysplastic Trochleae.

Trochlear dysplasia is recognized as a significant risk factor for patellar instability, but current imaging modalities fail to allow full visualization and classification of the complex 3-dimensional (3D) anatomy of the trochlea. The purpose of this study was to elucidate primary differences in trochlear morphology between patients with and without patellar instability by utilizing 3D magnetic resonance imaging (MRI) reconstructions of the trochlea. An institutional review board-approved retrospective review included 24 patients with a diagnosis of patellar instability and an age-matched and sex-matched control population of 12 patients. 3D models of the femoral trochlea were created from MRI images and measurements were performed. 3D measurements were trochlear groove volume and surface area that were normalized to the femoral width. 2D measurements were performed throughout the length of the trochlea including the bony and cartilaginous sulcus angles as well as the bony and cartilaginous trochlear depths. Differences were also assessed between sex, skeletal maturity, and trochlear dysplasia severity. Surface topography of the trochlea varied significantly based on location with the trochlea becoming progressively more flat proximally away from the notch (P<0.05). Patients with patella instability had reduced trochlear volumes and trochlear depths compared with control patients (P<0.05). These differences were more pronounced with the cartilaginous measurements as well as more proximally within the trochlea. Patients with high-grade dysplasia had greater reductions in trochlear volumes and depth especially proximally in the trochlea (P<0.05). Once femoral size was standardized, minimal differences were observed based on sex or skeletal maturity (P>0.05). Novel 3D MRI reconstructions demonstrated that measurements of trochlear morphology varied significantly between patients with and without patellar instability. When trochlear dysplasia is present, it appears to affect the majority of the trochlear surface, but preferentially the proximal extent. Future trochlear dysplasia classification systems may benefit from assessment of articular cartilage surface measures rather than primarily osseous structure measurements. Level III-case-control prognostic study.

Increased internal femoral torsion can be regarded as a risk factor for patellar instability — A biomechanical study

BackgroundIncreased internal femoral torsion is regarded as a risk factor for patellar instability. Biomechanical investigations confirming this hypothesis are missing. MethodsEight fresh-frozen cadaver knees were tested on a specially designed simulator. Patellar motion and patellofemoral pressure were evaluated for 0°, 10°, and 20° of increased internal and external femoral torsion with native and with transected medial patellofemoral ligaments used to simulate patellar instability. A regression analysis was used for statistical analysis. FindingsIn native medial patellofemoral ligaments, there were no significant changes in mean or peak pressures for any torsional states (P≥0.07). At 20° increased internal femoral torsion, there was a significant center of force shift towards the lateral side (P=0.01). Patellar shift was directed laterally at low knee flexion angles up to 30°. Lateral patellar tilt increased significantly at 10° and 20° of increased internal femoral torsion (P≤0.004). In transected medial patellofemoral ligaments, mean pressure (P≤0.005) and peak pressure (P≤0.02) decreased significantly for all torsional states. There was a significantly greater lateral center of force shift with increased internal femoral torsion (P≤0.04). Lateral patellar tilt increased significantly (P<0.001). Patellar shift did not change significantly with increased internal femoral torsion (P≥0.30). InterpretationIn a native medial patellofemoral ligament, 20° of increased internal femoral torsion can be regarded as a significant risk factor for patellar instability. With an insufficient medial patellofemoral ligament, 10° of increased internal femoral torsion already represents a significant risk factor.

Anatomic patellar instability risk factors in primary lateral patellar dislocations do not predict injury patterns: an MRI-based study.

The primary goal was to describe the injury patterns in a population of primary (first time) lateral patellar dislocators (LPD) to lend clarity to commonly held notions about injury patterns in this population. A prospective study identifying patients presenting with LPD between 2008 and 2012. Inclusion criteria were a history and physical exam consistent with primary LPD, and an MRI consistent with the diagnosis without other significant ligamentous injury. On MRI, location of cartilage, medial patellofemoral ligament (MPFL) injury, and bone bruising were noted. Severity was categorized as partial or complete for MPFL and cartilage lesions. Anatomic patellar instability risk factors (patella alta, trochlear dysplasia, increased TT-TG, and lateral patella tilt) were recorded and compared to the injury patterns. This study involved 157 patients; 107 patients were skeletally mature. Of the 157 patients, 26 had surgery for this injury due to clinician-perceived need for cartilage debridement. MPFL injury severity was complete rupture (N = 69, 44%), partial (N = 67, 43%), and none (N = 19, 13%). MPFL injury location was isolated femoral (N = 16, 10%), isolated patella (N = 26, 17%), isolated mid-substance (0%), multiple locations (N = 95, 61%), and none (N = 20, 13%). Chondral injury location was patella (N = 67, 43%), lateral femoral condyle (N = 11, 7%), multiple locations (N = 53, 34%), and none (N = 26, 17%). A majority (61%) of patellar chondral lesions were at its inferomedial aspect; all medial patellar retinacular partial injuries involved the inferomedial aspect of the patella, consistent with the insertion of the medial patellotibial ligament (MPTL). Skeletally immature patients had a greater risk of isolated patellar MPFL and chondral injury. No clear relationship was found between/across the location and/or severity of bone bruising, MPFL, or chondral injury. Underlying anatomic patellar instability risk factors defined by MRI, do not predict injury patterns. MPFL and chondral injury, as well as bone bruising, are common following LPD. The medial patellotibial ligament is torn in patellar-based medial retinacular injuries, based on MRI injury location. Skeletal immaturity plays a role in the location of the injury pattern with isolated patellar-based MPFL/chondral injury being more common in the skeletally immature patient. Sex does not appear to be a factor in injury patterns after primary LPD. Knowledge of these injury trends will help focus the clinician in injury evaluation when managing primary patellar dislocations. Case series, Level IV.

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Trochlear dysplasia and patella alta are known risk factors for patellar instability, yet the relation between the two has not been well understood. Morphologic abnormalities such as trochlear dysplasia and patella alta are known to alter patellofemoral kinematics, whereas altered contact pressures, in turn, have been associated with the development of trochlear dysplasia. As our current treatments aim to correct these deformities through increasingly complex procedures such as trochleoplasty and tuberosity distalization, we should consider this relation and the potential for changing the course of developing such morphologic abnormalities earlier in life. Further studies on the developmental cause of this disorder may help guide future treatments in the management of patellar instability.

Morphology and Anatomic Patellar Instability Risk Factors in First-Time Traumatic Lateral Patellar Dislocations: A Prospective Magnetic Resonance Imaging Study in Skeletally Immature Children

Background: The incidence of primary lateral patellar dislocation (LPD) in children aged 9 to 14 years is 0.6 to 1.2 per 1000. Causation is assumed to be multifactorial, including anatomic variants of the patellofemoral (PF) joint that result in a higher risk of LPD. No publication has compared the morphology of the PF joint and anatomic patellar instability risk factors (APIFs) in a primary LPD population versus controls, defining children by skeletal maturity. Purpose: To characterize the PF morphology and APIFs (trochlear dysplasia, abnormal lateral patellar tilt, elevated tibial tubercle–trochlear groove [TT-TG] distance, patella alta) through magnetic resonance imaging (MRI) measurements in skeletally immature children with and without a primary LPD and to identify (potential) distinctive differences between these 2 groups. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A prospective series of 103 skeletally immature children aged 9 to 14 years with an MRI-confirmed primary LPD were matched with a control group of 69 children. The PF morphology and APIFs were assessed during a 2.5-year period with standardized MRI using sagittal and axial views. Results: In the LPD group, 79% had 2 to 4 APIFs compared with 7% in the control group. All major measurements of trochlear dysplasia were significantly different between the 2 groups. The mean central condylar height was significantly higher in the LPD group compared with the control group, resulting in a lower trochlear depth (2.3 vs 4.5 mm, respectively) and higher sulcus angle (156.7° vs 141.1°, respectively). The LPD group had significantly higher values of patellar height, Caton-Deschamps index (1.33 vs 1.15, respectively), lateral patellar tilt (21.1° vs 8.5°, respectively), and TT-TG distance (13.9 vs 9.8 mm, respectively) compared with the control group. The main divergent APIF was trochlear dysplasia (defined as trochlear depth <3 mm), seen in 74% of the LPD group compared with 4% of the control group. Elevated TT-TG distance as a single APIF was never present in the LPD group; patellar tilt was only seen in the LPD group. The most common APIF in the control group was patella alta (36%). Conclusion: There was a significant difference in mean values of all established APIFs between the children with a first-time LPD and the controls. Trochlear dysplasia was the main APIF, and together with lateral patellar tilt (≥20°), they had the strongest association with LPD.

Individual anatomical risk factors for patellar instability

Over the last two decades the management of patellofemoral instability has changed with the advent of the ability to define the variation in the anatomy of the patellofemoral joint and to put a number onto that variation. From this we are able to agree what is “normal” and what is pathological. The review by Dietrich et al. (1) looks at the key method for doing this, namely imaging. The problem with the patellofemoral joint is that there is little consensus internationally on terminology, details of the history, the relevant examination techniques (which to do, how to do them, and how to report them) (2), but there is consensus on which are the important anatomical abnormalities, how to image and what to measure (1,3). As a consequence there is a better understanding about the surgical interventions needed to correct the abnormalities, although not necessarily which patients require an operation and the timing of it (4).