Lateral Trochlear Inclination Angle Research Articles

Evaluation of the relationship between trochlear and patellar morphology and patellar chondromalacia with magnetic resonance imaging

It was aimed to investigate the relationship between magnetic resonance imaging (MRI) measurements of trochlear and patellar morphology and grade 3-4 patellar chondromalacia. Grade 3-4 patellar chondromalacia group, and an age- and sex-matched control group with normal patellar joint cartilage were comprised. For trochlear morphology evaluation in MRI; sulcus angle, trochlear angle, lateral trochlear inclination angle and medial trochlear inclination angle were measured. For patellar morphology evaluation; patella trochlear ratio, insall-salvati ratio, modified Insall- Salvati ratio and Blackburne-Peel ratio were measured. Obtained measurements were statistically analyzed according to demographic characteristics. One hundred and twenty-five patients with chondromalacia and 125 controls participated. The sulcus angle and the trochlear angle were significantly higher in the patellar chondromalacia group (p<0.05). The lateral trochlear inclination angle was significantly less in the patellar chondromalacia group (p=0.011). There was no significant difference between the groups in terms of medial trochlear inclination angle (p=0.520). There was no significant difference between the groups in terms of patella-trochlear ratio (p=0.617). Insall-Salvati ratio was significantly higher in the patellar chondromalacia group (p=0.003). Modified Insall-Salvati ratio was significantly lower in the patellar chondromalacia group (p=0.001). The rate of Blackburne-Peel was significantly higher in the patellar chondromalacia group (p=0.004). Measurements of sulcus angle, trochlear angle, lateral trochlear inclination angle, Insall-Salvati ratio, modified Insall-Salvati ratio, Blackburne-Peel ratio have diagnostic value for grade 3-4 chondromalacia.

Using Dual-Orthogonal Fluoroscopy and CT to Assess the Relationship Between Knee Morphology and Patellar Kinematics in Patients With Patellofemoral Pain.

Patellofemoral pain (PFP) is one of the most common knee overuse injuries, with studies suggesting PFP as a precursor for early knee osteoarthritis. The etiology of PFP is multi-factorial; however, patellar mal-tracking has been regarded as a primary mechanism. Details of this multi-factorial mechanism have been unclear because of the limitations in evaluating in-vivo, three-dimensional (3D) patellofemoral joint movement during dynamic activities accurately. Alternatively, studies have demonstrated the high accuracy and repeatability of dual fluoroscopy and CT/MRI for measuring knee joint motion. This study uses dual fluoroscopy and CT to investigate the associations between joint morphology and patellar kinematics in healthy controls and subjects with PFP. Eight PFP females (29.7±10.6 years) and 10 healthy females (25.0±7.7 years) were recruited and screened by a sports medicine physician. CT imaging was performed on participants in a supine with the knee extended, and ankle and hip in neutral alignment. Dual-orthogonal fluoroscopy measured patellar movement while participants performed a lunge task. A calibration algorithm was used to register the 3D CT model to 2D fluoroscopy image to calculate the relative position and angles of the patella based on the clinical definition of patellar motion. Measures of patellar and trochlear morphology were generated and correlated to kinematic data. There was a significant difference in the patellar-to-trochlear width ratio; however, no other significant differences in CT morphology measurements were present between groups. For PFP patients in the weight-bearing extended position, there was a moderate positive correlation between the patellar-to-trochlear width ratio and medial-lateral patellar shift (τ = 0.643, p = 0.026). Healthy controls in this position demonstrated a moderate positive correlation between the lateral-trochlear inclination angle and medial-lateral patellar shift (τ = 0.600, p = 0.016) and moderate negative correlation between medial trochlear inclination angle and medial-lateral patellar shift (τ = -0.511, p = 0.040).The findings suggest that, for this cohort, there is correlation between morphology and patellar kinematics. Passive and active stabilizers likely have a role in mal-tracking.

Poster 139: Utilization of 3D Statistical Shape Modeling of Anatomic Variation Across a Cohort of Patella Instability Patients

Poster 139: Utilization of 3D Statistical Shape Modeling of Anatomic Variation Across a Cohort of Patella Instability Patients

Should isolated superolateral Hoffa's fat pad edema identified by MRI be reported or ignored in adolescent patients?

Background and objectiveThe presence of superolateral Hoffa's fat pad (SHFP) edema is associated with several morphometric measurements related to patellar alignment and trochlear morphology. Our aim is to evaluate management implications in adolescent patients with isolated superolateral Hoffa's fat pad edema on MRI. Materials and methodsRetrospective review of 117 adolescents with knee MRI (mean 14.8 years old) with isolated superolateral Hoffa's fat pad edema. Patients with edema were separated into two groups based on the number of MRI axial slices involved with edema: group 1 (G1) of 27 patients with 1 slice vs group 2 (G2) of 90 patients with 2 or more slices. A comparison control group was used (45 patients who had normal MRI knees). Data points included % referral for physical therapy (PT) or surgery, Hoffa's fat pad edema, tibial tubercle-trochlear groove (TT-TG) distance and lateral trochlear inclination (LTI) angle. Fisher's exact and independent t-tests, ANOVA and regression models were used for statistical analysis. ResultsThere is statistically significant difference between Hoffa's fat pad edema patients and control regarding PT referral with G1: 70%, G2: 76%, and control: 53% (p = 0.03). There is statistically significant difference between these groups regarding TT-TG measurements with higher values in edema groups; G1: 11.9 mm±4.1, G2 13 mm ±4.1, and control 8.7 mm±3.6, (p = 0.001). There was a statistically significant association between edema and increased TT-TG distance (p = 0.001) but not LTI angle (p = 0.2). ConclusionMRI identification of isolated superolateral Hoffa's fat pad edema is positively associated with TT-TG distance and its presence is associated with higher referral rates to physical therapy for patella maltracking.

Patellofemoral Anatomical Measurements on MRI in Patient with Suprapatellar Fat Pad Edema and Mass Effect.

To evaluate the impact of patellofemoral joint anatomical measurements of patients with anterior knee pain who were diagnosed with suprapatellar fat pad (SPFP) impingement syndrome (SP-FPIS) by magnetic resonance imaging (MRI). A prospective, descriptivestudy. Goztepe Education and Research Hospital, between March 2015 and June 2019. The study included 34 patients (Group 1) and 34 healthy volunteers (Group 2) who were referred to the radiology clinic with anterior knee pain; they underwent MRI and diagnosed with SP-FPIS. Twenty-three anatomical measurements such as SPFP cranio caudal length (CC), anteroposterior length (AP), oblique length (OBL), patellar length (PL), patellar tendon length (PTL), Insall Salvati Index (ISI), patellar cartilage distal-tibial tubercle (TT), patellar cartilage length (PCL), Modified Insall Salvati Index (MISI), patellotrochlear cartilage length (TCL), lateral trochlear inclination angle (LTI), etc. related to the morphological structure of SPFP and patellofemoral joint were evaluated and compared in both groups. The mean age of groups 1 and 2 was 45.62±10.87 and 41.47±11.98 years, respectively. There was a statistically significant difference in patients with SP-FPIS in PL, PT, TT, PC, MISI, TC, PTI, MF, PHY, PPI, MT, LTI, CC, AP, and OBL measurements compared with the control group (p<0.05). In the logistic regression analysis performed to evaluate the effect of statistically significant parameters on anterior knee pain, the probability of SP-FPIS increases 1.5 times as PTL increases among the groups, while the risk of SP-FPIS decreases 0.78 times as LTI decreases (p<0.05). There is a predisposing effect of PTL increase in SP-FPIS development, while LTI decrease has a protective effect. These results will guide future studies for the development and/or modification of treatment methods. Patellofemoral joint, Suprapatellar fat pad impingement syndrome, Anterior knee pain, Knee magnetic resonance imaging, Knee anatomy.

Unpacking the Tibial Tubercle–Trochlear Groove Distance: Evaluation of Rotational Factors, Trochlear Groove and Tibial Tubercle Position, and Role of Trochlear Dysplasia

Background: The tibial tubercle to trochlear groove (TT-TG) distance is often utilized for determining the surgical treatment for patients with patellar instability (PI). It is thought to directly represent the position of the TT on the tibia. Recent work has shown that the measurement of the TT-TG distance is multifactorial. Purpose: To investigate the relationship between relative tibial external rotation (rTER) and trochlear dysplasia (TD), as well as the location of the TG and TT in patients with and without PI, and to correlate these and other anatomic measurements with the TT-TG distance. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A total of 89 patients with PI who underwent magnetic resonance imaging were identified with 92 matched control patients. A standardized measurement protocol on axial magnetic resonance imaging determined rTER, the proximal and distal TG lateralization (pTGL and dTGL, respectively) ratios, and the TT lateralization (TTL) ratio. Other measures of interest included the lateral trochlear inclination angle, sulcus angle, and lateral patellar inclination angle. Univariate regression was used to determine the associations of TD (lateral trochlear inclination angle, sulcus angle) with rTER and the TG position, and multivariate regression was used to model associations among all the variables with the proximal and distal TT-TG distances. Results: rTER was significantly higher in the study group (P < .001), and univariate regression showed a significant association between dysplasia measures and rTER (P < .001). The pTGL ratio was lower in the study group (P = .025), but there was no difference in the dTGL ratio (P = .090) or the TTL ratio (P = .098) between the groups. There were no associations between dysplasia measures and the pTGL and dTGL ratios (P > .05). Multivariate regression showed that the proximal TT-TG distance is predicted by the sulcus angle, pTGL ratio, rTER, and TTL ratio (P < .05) and that the distal TT-TG distance is predicted by the lateral patellar inclination angle, dTGL ratio, sulcus angle, rTER, and TTL ratio (P < .05). Conclusion: rTER had a significant association with TD. The position of the proximal TG was more medial in patients with PI. There was no significant difference in the TTL ratio between patients with and without PI. The TT-TG distance was associated with multiple anatomic measures and was not solely predicated on the position of the TT.

Using a 3D handheld scanner to capture trochlear groove shape: proof of concept study.

Trochleoplasty is a surgical procedure used to treat patellar instability by modifying the trochlear groove. Analysis of the groove with a handheld scanner would enable accurate real-time planning and facilitate tailormade correction. We aimed to measure trochlear depth, sulcus angle, trochlear facet ratio, trochlear angle and lateral trochlear inclination angle and to establish inter- and intra-rater reliability for knee models to determine reliability and repeatability. The trochlear grooves of three knee models were scanned by two investigators. Three-dimensional reference models were created and surface-matched. Custom software was used to determine the desired parameters. The intraclass correlation coefficient (ICC) was used to determine test-retest reliability and the parameter results for each model that showed best reproducibility. There was good interobserver reliability (trochlear depth, 1.0mm; sulcus angle, 2.7°; trochlear angle, 4.0°; lateral trochlear inclination angle, 4.0°), except in the trochlear facet ratio (32.0%) of one knee model. With outliers removed, the ICC was moderate to excellent in 73.34% of measurements, with trochlear depth showing the best reproducibility. This feasibility study showed a handheld scanner in conjunction with supporting software can measure trochlear parameters with good to excellent inter- and intra-observer reliability.

Usefulness of three-dimensional computed tomography for patellofemoral measurement.

This study aimed to establish the normal values for knee patellofemoral alignment as measured using 3-dimensional computed tomography (3D CT), to standardize the technique, and to show the inter- and intra-observer reliability of this measurement. The present study included 62 asymptomatic volunteers (124 knees). 3D CT scanning was performed with each volunteer in the supine position with 15° of knee flexion, and consistent 3D axial images of the patellofemoral joint were obtained with alignment in the desired stereographic baseline direction in anterior-posterior, lateral, and axial rotations. Two independent observers measured patellofemoral alignment parameters, including the sulcus angle, congruence angle, lateral patellofemoral angle, condyle-patellar angle, and lateral trochlear inclination angle. Based on 3D CT measurement, the mean values of the parameters were 145.9° ± 9.2° for the sulcus angle, 12.6° ± 22.6° for the congruence angle, 9.2° ± 4.6° for the lateral patellofemoral angle, 14.1° ± 6.4° for the condyle-patellar (lateral facets) angle, -8.5° ± 8.4° for condyle-patellar (patellar axis) angle, and 16.5° ± 6.3° for the lateral trochlear inclination angle. A statistically significant difference was observed between men and women in the sulcus and condyle-patellar (patellar axis) angles (p = 0.045, 0.011, respectively). All parameters showed excellent inter- and intra-observer reliability. The normal values and ranges for patellofemoral alignment parameters were evaluated using 3D CT. The results of this study provide reference information that may facilitate diagnosis and treatment planning of patellofemoral disorders in skeletally mature non-pathologic patients. II.

Trochlear Dysplasia as Shown by Increased Sulcus Angle Is Associated With Osteochondral Damage in Patients With Patellar Instability

The primary study objective was to describe the incidence of osteochondral damage (OD) in our cohort of patients with patellar instability (PI). The secondary objective was to assess for associations between patient demographic characteristics, duration of PI, and quantitative radiographic measurements of anatomic risk factors for PI and OD in this cohort. A retrospective chart review identified patients treated for PI at a tertiary referral center between 2013 and 2018. Patients were evaluated for osteochondral injury with either magnetic resonance imaging if treated nonoperatively or operative reports if treated surgically. The Caton-Deschamps ratio, proximal tibial tubercle-to-trochlear groove (pTT-TG) distance, distal tibial tubercle-to-trochlear groove (dTT-TG) distance, lateral trochlear inclination (LTI) angle, lateral patellar inclination (LPI) angle, and sulcus angle were calculated from magnetic resonance imaging scans. Trochlear dysplasia is an important risk factor for PI that can be reliability quantified by the pTT-TG distance, dTT-TG distance, LTI angle, sulcus angle, and LPI angle. Demographic data including age at first instability event, sex, body mass index, symptom duration, and number of dislocations were documented. A total of 125 knees in 118 patients (average age, 13.9 ± 3.4 years; 48% female patients) with PI were identified. Within this cohort, 67% were treated surgically and 53% had OD. No association was identified between osteochondral injury and age, sex, body mass index, symptom duration, LTI angle, LPI angle, dTT-TG distance, pTT-TG distance, or number of dislocations. An increased sulcus angle (more dysplasia) showed a statistically significant association with osteochondral pathology (P= .021), and higher sulcus angles were statistically significantly associated with acute osteochondral fracture compared with chondral injury (P= .001). Using quantitative analysis of trochlear dysplasia, this study identified a significant associationbetween trochlear dysplasia (sulcus angle) and the incidence of OD in our cohort of patients with PI. The frequency of dislocation or subluxation and patient demographic characteristics were not significantly associated with OD. Level III, retrospective prognostic study.

199 Use of A 3D Hand-Held Scanner to Capture Trochlear Groove Shape, A Proof-of-Concept Study

Abstract Introduction Trochleoplasty is a surgical procedure used to treat patellar instability through modifying the trochlear groove. Analysis of the groove with a hand-held scanner would enable accurate real time planning and facilitate tailor made correction. We aimed to measure trochlear depth, sulcus angle, trochlear facet ratio, trochlear angle and lateral trochlear inclination angle and establish inter- and intra-rater reliability for each knee model. Method The trochlear groove of the knee models was scanned by two investigators and 3D reference models created. These were surface matched and custom software along with Excel was utilised to determine the desired parameters. Intraclass correlation coefficient (ICC) was used for test-retest reliability and to determine which parameter results, for each model, showed the best reproducibility. Results There was good inter-observer reliability - trochlear depth (1.0 mm), sulcus angle (2.7°), trochlear angle (4.0°) and lateral trochlear inclination angle (4.0°), except in the trochlear facet ratio (32.0%) of one knee model. With outliers removed ICC was good-excellent in (46.7%) of measurements, with trochlear depth showing the best reproducibility. Conclusions This feasibility study showed that the hand-held scanner in conjunction with supporting software can measure trochlear parameters in a controlled environment and justifies extending research into its use in trochleoplasty.

The relationship between quadriceps fat pad syndrome and patellofemoral morphology: a case\u2013control study

BackgroundThe purpose of this prospective case–control study is to investigate the relationship between quadriceps fat pad syndrome (QFPS) and patellofemoral morphology.Materials and methodsTwenty-two patients with QFPS and 22 age- and gender-matched healthy volunteers were included. The diagnosis of QFPS was supported both clinically and radiologically. On magnetic resonance imaging (MRI), patellofemoral morphology was evaluated with 13 radiological measurements including trochlear sulcus angle, trochlear sulcus depth, trochlear facet asymmetry, trochlear condyle asymmetry, lateral trochlear inclination angle, patellar translation, tibial tubercle–trochlear groove (TT–TG) distance, Insall–Salvati ratio, patellotrochlear index, patellar tilt, the ratio between lateral and medial facet lengths, interfacet angle, and quadriceps tendon thickness. The mean of measurements was compared between groups using the Mann–Whitney U test.ResultsThere were 22 patients (12 male, 10 female) with mean age of 30.81 ± 1.41 (range 19–38) years in group I and 22 patients (12 male, 10 female) with mean age of 31.13 ± 1.31 (range 19–39) years in group II. The mean age and the gender distribution were statistically similar between groups (p = 0.845, p = 1, respectively). All measured values except for patellar tilt (p = 0.038) and TT–TG distance (p = 0.004) were similar (p > 0.05 for the other variables). However, all of the measured variables were within the normal range.ConclusionsQFPS may not be associated with anatomical variations of the patellofemoral joint. Further studies are required to understand the etiology and risk factors.Level of evidenceLevel III, prospective case–control study

Lateral Trochlear Inclination Angle: Measurement via a 2-Image Technique to Reliably Characterize and Quantify Trochlear Dysplasia.

Background:Trochlear dysplasia (TD) is a risk factor for patellar instability (PI). The Dejour classification categorizes TD but has suboptimal reliability. Lateral trochlear inclination (LTI) is a quantitative measurement of trochlear dysplasia on a single axial magnetic resonance imaging (MRI) scan.Hypothesis:A modified LTI measurement technique using 2 different axial MRI scans that reference the most proximal aspect of the trochlear cartilage on 1 image and the fully formed posterior condyles on the second image would be as reliable as and significantly different from the single-image measurement technique for LTI. Further, the 2-image LTI would adequately represent overall proximal trochlear morphologic characteristics.Study Design:Cohort study (diagnosis); Level of evidence, 2.Methods:Patients aged 9 to 18 years treated for PI between 2014 and 2017 were identified. The Dejour classification was radiographically determined. Single-image LTI was measured on a single axial MRI scan at the most proximal aspect of visible trochlear cartilage. A 2-image LTI was measured from 2 separate MRI scans: 1 at the most proximal aspect of trochlear cartilage and the second at the fully formed posterior condyles. This 2-image LTI was repeated at 3 subsequent levels (the first measurement is referred to as LTI-1; repeated measurements are LTI-2, LTI-3, and LTI-4, moving distally). In total, 65 patients met the inclusion criteria, and 30 were randomly selected for reliability analysis.Results:Inter- and intrarater reliability trended toward more variability for single-image LTI (intraclass correlation coefficient [ICC], 0.86 and 0.88, respectively) than for 2-image LTI (ICC, 0.97 and 0.96, respectively). The Dejour classification had lower intra- and interrater reliability (ICC, 0.31 and 0.73, respectively). Average single-image LTI (9.2° ± 12.6°) was greater than average 2-image LTI-1 (4.2° SD ± 11.9°) (P = .0125). Single-image LTI classified 60% of patients with PI as having TD, whereas the 2-image LTI classified 71% as having TD. The 2-image LTI was able to capture 91% of overall proximal trochlear morphologic characteristics.Conclusion:LTI has higher reliability when performed using a 2-image measurement technique compared with single-image LTI and Dejour classification. The strong correlation between 2-image LTI and average LTI shows that 91% of TD is represented on the most proximal axial image. Because the single-image measurement appears to underestimate dysplasia, previously described thresholds should be reexamined using this 2-image technique to appropriately characterize TD.

Relationship between patellar tendon–lateral femoral condyle friction syndrome and patellofemoral instability

Aim: The etiology of the patellar tendon–lateral femoral condyle friction syndrome (PTLFCFS) is not fully known and the number of studies on the diagnosis, treatment, and prognosis of PTLFCFS is limited. The aim of this study was to evaluate the relationship between PTLFCFS and patellofemoral instability in magnetic resonance imagingMaterial and Methods: Six morphological parameters were measured in magnetic resonance imaging (MRI) to evaluate patellofemoral stability in patients with PTLFCFS (study group n = 82) and patients without detection PTLFCFS (control group n = 204) in the knee MRI examination. These parameters include the Insall–Salvati ratio, ventral trochlear prominence, sulcus angle, lateral trochlear inclination angle, patellar inclination angle, and patellar lateralization measurement. In addition, the chondromalacia patella relationship was also evaluated.Results: The Insall–Salvati ratio, patellar inclination angle, patellar lateralization, sulcus angle, and ventral trochlear prominence were significantly higher and lateral trochlear inclination angle was significantly lower in the study group than in the control group. The incidence of chondromalacia patella was significantly higher in the study group. In the study group, there was a positive correlation between the chondromalacia patella and the ventral trochlear prominence. Conclusion: Among the factors causing PTLFCFS, patellofemoral instability was found to be effective. The measured parameters having high sensitivity and specificity suggest that these parameters can be used as risk factors and for the diagnosis.

Quantitative magnetic resonance imaging in patellar tendon-lateral femoral condyle friction syndrome: relationship with subtle patellofemoral instability.

To investigate the correlation of patellar tendon-lateral femoral condyle friction syndrome (PTLFCFS) with subtle patellofemoral instability to explore its pathogenesis. One hundred knees of 80 patients with PTLFCFS were analyzed retrospectively by retrieving magnetic resonance imaging (MRI) data over a 3-year period from our database. Seven quantitative parameters for evaluating patellofemoral stability were measured on MR images, including the Insall-Salvati ratio, tibial tuberosity-trochlear groove (TT-TG) distance, trochlear groove depth, medial trochlear/lateral trochlear length (MT/LT) ratio, medial trochlear/lateral trochlear height (MH/LH) ratio, lateral patellofemoral angle (LPA), and lateral trochlear inclination (LTI) angle. These patellofemoral parameters of the PTLFCFS group and the normal control group were compared (n = 88), and receiving-operator characteristic (ROC) curve analysis was conducted to determine the specificity and sensitivity of these parameters. The trochlear depth, MT/LT, LPA, and LTI angle were significantly lower (p < 0.001) and the Insall-Salvati ratio was significantly higher (p < 0.001) in the PTLFCFS group. However, the TT-TG distance and MH/LH ratio showed no significant difference (p = 0.231 and 0.073 respectively). The area under the ROC curve of the Insall-Salvati ratio, trochlear depth, MT/LT, LPA, and LTI angle were 0.925, 0.784, 0.8, 0.731, and 0.675 respectively. The efficiency of the Insall-Salvati ratio was the highest among those five parameters. This study verified the presence of subtle patellofemoral instability by measuring various patellofemoral parameters in patients with PTLFCFS. It confirmed that PTLFCFS is associated with subtle patellofemoral instability and could largely explain the pathogenesis of PTLFCFS.

Association between patellofemoral congruence and patellofemoral chondropathy in patients with anterior knee pain: A T2 mapping knee MRI study.

In this study, the T2 mapping magnetic resonance imaging technique was used to evaluate early cartilage changes associated with patellofemoral alignment and morphology. Fifty four patients (Study group: 38 females, 16 males) with anterior knee pain and a randomly selected and age-matched 50 controls (Control group; 37 females, 13 males) were compared by two blinded authors in terms of T2 values of the patella medial, lateral facet, and trochlea, Insall-Salvatti index, lateral trochlear inclination angle, patellar tilt angle, sulcus angle, and patella medial and lateral facet lengths. The inter- and intra-observer reliability tests were assessed. The T2 medial patellar facet value, T2 lateral patellar facet value, T2 trochlea value, Visual Analog Scale, tibial tubercle - greater trochanter distance, and patellar tilt angle measure were statistically significantly higher in the study group. Based on our study findings, the T2 mapping magnetic resonance imaging (MRI) technique was found to be reliable test that can be used to diagnose early cartilage damage in patients with anterior knee pain. In patients with anterior knee pain, especially with decreased Insall Salvatti index, low lateral trochlear inclination angle, and higher patellar tilt angle, adding a T2 mapping sequence to the standard knee MRI protocol is recommended to help detect early cartilage damage.

Patellofemoral instability: Quantitative evaluation of predisposing factors by MRI

Objective: To determine the contribution of MRI in evaluating patellofemoral instability (PFI) and to compare the underlying predisposing factors between the study and control groups. Materials and methods: We enrolled knee MRI scans of 38 patients with lateral patellar dislocation (LPD) and 38 control subjects. All MRI scans were examined for LPD and patellofemoral joint (PFJ) morphological abnormalities. The lateral trochlear inclination angle, sulcus angle and trochlear depth were the MR measures for trochlear dysplasia (TD), patellar height ratio was used for evaluation of patella alta, the patellar tilt angle, and the tibial tuberosity-trochlear groove (TT-TG) distance were also measured. Results: MRI confirmed PFI in 84.2% of study group and detected abnormal PFJ morphological factors in all cases. The prevalences and mean values of all MR parameters showed significant differences (p<0.001) between the study and control groups. MR parameters for TD had the highest sensitivity of 57.9%, while the TT-TG distance was the most specific 97.4% for PFI. The prevalence of combined PFJ abnormal morphological factors was 36.8% in the study group. Conclusion: MRI was useful in quantitative measuring of the predisposing factors contributing to PFI resulting in significant difference in all MR parameters between the study and control groups.

A Risk Prediction Model for Redislocation Following First Time Lateral Patellar Dislocation (LPD)

Objectives:There is not a formula that is regularly used to help predict the risk of redislocation for an individual patient following first time lateral patellar dislocation (LPD). Our objective was to develop a model to help predict the risk of redislocation that can be easily applied in a clinic visit following first time LPD.Methods:Between 2008-2012, patients were prospectively identified at 2 musculoskeletal outpatient clinics. Patients were included if they had a history, physical exam, & magnetic resonance imaging (MRI) consistent with LPD without other significant ligamentous injury. Multiple anatomic & injury variables were obtained from the MRI including tibial tubercle - trochlear groove distance, patellar tilt, trochlear depth, trochlear facet asymmetry, trochlear condyle asymmetry, lateral trochlear inclination angle, trochlear sulcus angle (SA), Insall-Salvati ratio (ISR), Caton-Deschamps index, patellotrochlear index, location & severity of chondral injury, location & severity of MPFL injury, location of bone bruising, & whether the patient had open or closed physes (GP). Demographic patient information was also collected to include age, sex, & whether the injury was contact or non-contact. Patients were contacted at a minimum of 2 years post injury to determine if they had experienced a redislocation injury. Demographic and MRI variables were compared between patients with and without patellar redislocation using two group t-tests for continuous variables and Fisher’s exact tests for categorical variables; the statistical analysis was completed by an independent professional statistician at our institution. Stepwise logistic regression models were used to identify potential predictors of redislocation. Initially, MRI variables that had continuous data were treated as continuous variables and then a second stepwise logistic regression model was run using binary indicator variables. A cutpoint for each variable was determined using an outcome-oriented approach; the cutpoint yielding the most significant association with the redislocation outcome in a simple logistic regression model was chosen. P-values less than 0.05 were considered statistically significant. A prediction model was then created using the statistically significant variables, and a receiver operating characteristic (ROC) curve was applied to the model to evaluate for diagnostic performance.Results:Inclusion criteria were met by 108 patients. Of all of the variables, the statistically significant variables were sex, GP, SA, and ISR. The cutpoints were SA ≥ 154 degrees and ISR ≥ 1.3. The predicted probability of redislocation (percent) was 6.4 for males and 2.3 for females if the patient had closed growth plates and normal SA and ISR. The predicted probability of redislocation (percent) was 89.9 for males and 75.7 for females if the patient had open growth plates and abnormal SA and ISR. If two of three variables (GP, SA, ISR) were positive, the risk was M70.4/F45.4 (GP, SA), M46.5/F23.3 (GP, ISR), and M72.5/F47.9 (SA, ISR). The area under the curve for the ROC curve was 0.81 indicating good diagnostic performance.Conclusion:Our model demonstrates high risk of redislocation with open growth plates and SA & ISR values above the cutpoints, whereas there are low rates of redislocation with the inverse findings. This model may serve as a clinically applicable means of predicting redislocation following first time LPD.