Trochlear Depth Research Articles

CT-based measurement and analysis of distal humerus morphology in healthy adults from Northern China

BackgroundThis study aims to investigate the morphological characteristics of the distal humerus in healthy adults from northern China using computed tomography and three-dimensional reconstruction techniques and compared whether there were diferences in morphology among populations from diferent geographical regions.MethodsThe CT data of 80 patients were imported into Mimics software for three-dimensional reconstruction and measurement. The differences in distal humeral morphological parameters between different genders and sides were compared, and the correlation between the parameters was explored. The distal humeral morphological parameters between Western and Chinese populations based on current and previous pooled results were compared.ResultsThirty-one morphological parameters were measured and analyzed in this study. The average (and standard deviation) of capitellum depth, capitellum width, capitellum height, distal humerus width, epitrochlea width, and humeral metaphyseal width was 10.83 ± 1.18 mm, 17.60 ± 2.06 mm, 21.10 ± 2.03 mm, 44.38 ± 4.07 mm, 12.02 ± 1.90 mm and 58.95 ± 4.86 mm, these parameters were significantly higher (P < 0.001*) in males than females. The capitellum width (r = -0.300, P = 0.007*), anterior lateral trochlear depth (r =-0.227, P = 0.043*), medial crest coronal tangential angle (r = 0.307, P = 0.006*), olecranon fossa volume (r = -0.408, P < 0.001*), olecranon fossa surface area (r = -0.345, P = 0.002*) and coronoid fossa surface area (r = -0.279, P = 0.012*) were significantly correlated with the age of the subjects. In the comparison of people from different regions, the capitellum height, lateral trochlear high, trochlear groove high, trochlear depth and medial trochlear high of the Western population were 23.25 ± 2.56 m, 21.6 ± 2.20 mm, 17.8 ± 2.00 mm, 17.80 ± 2.00 mm, 29.9 ± 4.10 mm, are significantly higher than those in the Chinese population. while capitellum width (15.55 ± 2.68 mm) and capitellum depth (9.00 ± 1.00 mm) were slightly lower.ConclusionThe findings provide a basis for the design of distal humeral orthopaedic implants, ensuring greater alignment with the anatomical structure of the distal humerus and improved surgical outcomes. Furthermore, the study provides a reference point for the diagnosis and classification of distal humeral diseases, as well as guidance for patient rehabilitation.

Trochleoplasty and à-la-carte procedures for patellar instability in young and active patients: Clinical outcomes at minimum 2 Years follow-up

IntroductionPatellar instability is a common condition affecting approximately 6 individuals per 100,000, but among adolescents, this incidence is notably higher. Trochlear dysplasia has been recognized as the pathoanatomic risk factor exerting the most significant biomechanical influence. Over time, various surgical techniques have been developed to address trochlear dysplasia. The purpose of this study is to evaluate the clinical outcomes, return to sport, as well as complications and re-operation rate of sulcus deepening trochleoplasty performed in a cohort of young and active patients using the Bereiter technique. Materials and methodsBetween January 2019 and February 2022, 11 cases of recurrent patellar dislocations underwent trochleoplasty. Preoperative radiological assessment included X-rays, CT scans following the Lyons and MRI. Inclusion criteria for the study and trochleoplasty indications included patients aged 10–25 with recurrent patellar dislocations unresponsive to nonoperative treatment and minimum type B trochlear dysplasia. Clinical follow-up occurred at 1-3-6 months and annually, with control X-rays at these intervals. Patient-reported outcome scores included the Knee Society Score, Kujala score, and Karnofsky performance status scale. ResultsBetween January 2019 and February 2022, 11 patients underwent trochleoplasty and were included in this study. Preoperative radiological measurements indicated mean values: sulcus angle (152.5°), trochlear depth (3.4 mm), Caton-Deschamps index (1.2), tibial tuberosity to trochlear groove (TT-TG) distance (17.5 mm), external patellar tilt angle (6.8°), femoral anteversion (11.5°), and tibial torsion (32°). All patients were followed up for at least 2 years, with an average of 43 months. Concurrent surgeries included tibial tuberosity transposition (100 %), MPFL reconstruction in 9 cases (81.8 %) and 2 patients also underwent division of the external alar ligament (18,2 %). PROMs at final follow-up showed mean values: Knee Society Score (KSS) (80.5), Kujala score (88.3), and Karnofsky performance status scale (88.8). Return to sport was reported by all active patients. Three cases required secondary surgical intervention for removal of the screws. ConclusionTrochleoplasty, especially with the Bereiter "thin flap" approach, improves patellofemoral congruency. Combining trochleoplasty with tibial tuberosity transposition addresses mal-tracking related to severe dysplasia and other à-la-carte procedures like medial patellofemoral ligament (MPFL) reconstruction enhance stability. In young and active patients, it resolves instability issues and reduces the likelihood of further dislocations with high return to sport rates.

Computed Tomographic Measurement Method for Morphoanatomical Comparison of Femur, Tibia, and Patella in Cats with and without Medial Patellar Luxation.

The aims of this study are to describe a computed tomographic (CT) measurement method of feline femoral, tibial, and patellar conformation, and to compare these measurements between a cat population diagnosed with medial patellar luxation (MPL) and cats without MPL. Eleven measurements were performed by two observers, including anatomical lateral distal femoral angle (aLDFA), femoral trochlear width (FTW) and femoral trochlear depth (FTD), anteversion angle of the femoral neck, patellar length, patellar width, patellar height, patellar volume, mechanical medial proximal tibial angle, tibial torsion angle, and tibial tuberosity displacement. Mean and standard deviation differences between the groups were statistically assessed. Intraobserver and interobserver interclass correlation coefficients (ICCs) were calculated. The aLDFA was significantly higher in the MPL II compared with the control and MPL III. The FTW was significantly larger in the MPL III than in the control or the MPL II group. The FTD in the control group was significantly larger than in the MPL II and III groups. The TTA of the control group was significantly smaller than the MPL II and III. The intraobserver ICC was high at 64%, and the interobserver ICC was high at 36% of the measurements. This study identified shallower FTD and increased TTA in cats diagnosed with MPL. The TTA difference was less than 5 degrees and FTD was less than 1 mm. The findings provide information on feline pelvic limb morphology. However, the differences between the two populations are small.

Isolated Medial Patellofemoral Ligament Reconstruction for Recurrent Patellar Instability Regardless of Tibial Tubercle–Trochlear Groove Distance and Patellar Height: Minimum 5-Year Outcomes

Background: It remains unclear which subset of patients with recurrent patellofemoral instability would benefit from a concomitant bony realignment procedure in addition to a medial patellofemoral ligament (MPFL) reconstruction. Purpose: To provide midterm results for patients who underwent an isolated MPFL reconstruction as part of an ongoing prospective trial. Study Design: Case series; Level of evidence, 4. Methods: Patients with recurrent patellar instability were prospectively enrolled in an institutional registry beginning in March 2014. Exclusion criteria included history of a previous surgery for patellar instability, an off-loadable (inferior/lateral) chondral defect, anterior knee pain ≥50% of their chief complaint, and a “jumping J” sign. All patients underwent primary, unilateral, isolated MPFL reconstruction regardless of their bony anatomic characteristics. Patient-reported outcome measures (PROMs), episodes of recurrent instability, and ability to return to sport were obtained annually. Radiographic measurements of baseline radiographs and MRI were obtained at baseline. Results: A total of 138 patients underwent isolated MPFL reconstruction between March 2014 and December 2019. The mean radiographic measurements were tibial tubercle–trochlear groove, 15.1 ± 4.9 mm; Caton-Deschamps index, 1.14 ± 0.16; patellar trochlear index, 46.9% ± 15.1%; trochlear depth index, 2.5 ± 1.2 mm; tibial tubercle to lateral trochlear ridge, −8.4 ± 5.7 mm; and patellar tendon to lateral trochlear ridge, 5.7 ± 6.2 mm. Trochlear dysplasia, defined as a trochlear depth index <3 mm, was present in 79/125 (63%) patients. A total of 50 patients reached ≥5 years, of whom 40 (80%) completed follow-up PROMs. A total of 119 patients reached ≥2 years, of whom 89 (75%) completed follow-up PROMs. Six patients (5%) reported recurrent instability with a mean time of 2.97 years after surgery. All PROMs improved over time except for the Pediatric Functional Activity Brief Scale (Pedi-FABS), which had no change. At 2 years, the mean changes from baseline for Knee injury and Osteoarthritis Outcome Score (KOOS) Quality of Life subscale (QOL), Pedi-FABS, International Knee Documentation Committee (IKDC) score, KOOS Physical Function Short Form (PS), and Kujala score were 42.1, 0.6, 35.1, –23.5, and 32.3, respectively. All changes had P values <.001 except for Pedi-FABS, which showed no change and had P > .999. At 5 years, the mean changes from baseline for KOOS-QOL, Pedi-FABS, IKDC, KOOS-PS, and Kujala score were 42.6, –2.8, 32.6, –21.5, and 31.6, respectively. All changes had P values <.001 except for Pedi-FABS, which showed no change and had P > .453. In total, 89% of patients returned to sport with a mean of 9.1 months. Conclusion: Midterm outcomes for patients who underwent isolated MPFL reconstruction were favorable and were maintained at 5 years. Outcomes for the expanded cohort of patients with a minimum 2-year follow-up support previously published results.

Trochlea Dysplasia as the Major Anatomic Risk Factors for Patellofemoral Joint Instability: An Infographic as a Visual Learning Tool.

Patellofemoral instability (PFI) is a common condition in children and adolescents, ranging from mild discomfort and mal-tracking to lateral patellar dislocation [1]. A number of anatomical risk factors have been described in the literature, such as trochlear dysplasia, patella alta, excessive tibial tuberosity to trochlear groove (TT-TG) distance, patellar tilt and soft tissue alterations [2]. Among them, TD has been identified as the main anatomical risk factor with the strongest association with PFI [1, 2]. In the study by Dejour et al. [2] radiographically observed TD was identified in 96% of patients with a history of patellofemoral dislocation [1, 2]. Patients with Dejour Type D dysplasia are characterized by a prominent and convex lateral facet with a vertical connection to a hypoplastic medial facet (Figure 1), which provides inadequate tracking of the patella in the trochlea during flexion leading to patella subluxation [2]. Non-operative treatment of lateral patellar dislocation presents a rate of re-dislocation up to 70% within 24 months of the first episode [3]. Sulcus deepening trochleoplasty is indicated for Type B and D dysplasia, in order to improve patella tracking, reduce the rate of re-dislocation and achieve good functional outcomes [2, 4]. Trochlea dysplasia is defined as a shallow or flattened groove with decreased resistance to lateral patellar translation. TD can be assessed on computed tomography (CT) and magnetic resonance imaging (MRI) with the use of overlapping axial images and are able to show perfectly the global shape of the femoral trochlea [2]. The thresholds for identifying trochlear dysplasia are established based on the sulcus angle ≥ 145°, medial/lateral trochlea facet asymmetry < 40%, trochlear depth < 3 mm and lateral trochlear inclination ≤ 11° and therefore it can be used in young adolescents [4, 5]. A deep knowledge of anatomic variations and abnormalities of the patellofemoral joint, which may predispose to PFI, is crucial in order to choose the appropriate treatment for each patient.

Patellar osteochondritis dissecans:maturation-dependent patellofemoral joint characteristics.

The likelihood of healing of osteochondritis dissecans decreases with skeletal maturity and there are theories that abnormal biomechanical forces contribute to the development and progression of these lesions. To characterize, according to regional skeletal maturity, the morphology and alignment indices of the patellofemoral joint on MRI in patients with patellar osteochondritis dissecans. MRI examinations of patients with patellar osteochondritis dissecans obtained between January 2008 and May 2023 were retrospectively reviewed to determine regional skeletal maturity, osteochondritis dissecans lesion size and location, patellar and trochlear morphology (Wiberg/Dejour classifications), and to calculate trochlear sulcus angles, trochlear depth index, lateral trochlear inclination, Insall-Salvati index, Caton-Deschamps index, patellar tendon-lateral trochlear ridge, and tibial tubercle-trochlear groove distances. Values were compared between skeletally immature and mature groups. Sixty-eight children (22 girls, 46 boys, age: 14.0 ± 1.7 years) yielded 74 knees with patellar osteochondritis dissecans lesions, 14 (19%) of which were skeletally mature. The most common anatomic location was over the central patella [median ridge (34/74 - 46%) on the axial images and over the middle third (45/74 - 61%) on the sagittal images]. Overall, mean trochlear sulcus angle (high, 151 ± 11°), trochlear depth index (low, 2.8 ± 1.4mm), and Insall-Salvati index (borderline, 1.3 ± 0.1) were abnormal for the entire sample. Skeletally mature knees were significantly more likely to have higher (more dysplastic) Dejour types whencompared to skeletally immature knees (p < 0.01). Knees in the mature group, compared to immature, had significantly more abnormal mean lateral trochlear inclination (15 ± 8° vs. 19 ± 6°, p = 0.03) and patellar tendon-lateral trochlear ridge distance (5.55 ± 4.31mm vs. 2.89 ± 4.69mm, p = 0.04). Half of the knees had ≥ 4 abnormal features that predispose to patellofemoral maltracking; mature knees weresignificantly (p = 0.02) more likely to have a higher number of abnormal features (> 6 features, 7/14, 50.0%) versus immature knees (0-3 features, 33/60, 55.0%). In children with patellar osteochondritis dissecans, abnormal patellofemoral morphology and alignment indices were common in all patients and more severe in mature knees.

Three-Dimensional Imaging of the Patellofemoral Joint Improves Understanding of Trochlear Anatomy and Pathology and Planning of Realignment

Three-dimensional (3D) modeling using digital or printed models provides a unique perspective that caters to cognitive spatial ability in a way that can add to our understanding and mental representations of human anatomy. This is particularly useful in the setting of trochlear dysplasia, where the morphology of the groove can exhibit substantial variability and complexity. Using 3D reformatted images and models, a pragmatic understanding of how morphology influences patellofemoral pathology can be gleaned. Further, this perspective facilitates cognition of what patellar tracking may look like after realignment procedures. Using 3D modeling, concepts such as patella alta, trochlear depth, lateralization of the patellar entry point, trochlear curvature, and the presence of a proximal trochlear spur can help afford a better understanding of how trochlear anatomy may influence tracking while also providing insight as to the ideal tracking path. The use of 3D has recently emerged as a useful tool in multiple surgical subspecialties, particularly in situations involving surgical planning or complex anatomy. Given the complexity and variation in trochlear morphology in patients with trochlear dysplasia who develop either patellar instability or focal overloading, 3D modeling is well-suited to provide a perspective that can add to our understanding of trochlear dysplasia, and potentially even how we diagnose and treat it. Level of EvidenceLevel V, expert opinion.

Superolateral Hoffa fat pad edema in adolescent competitive alpine skiers: temporal evolution over 4 years and risk factors

ObjectivesTo longitudinally assess and correlate the prevalence of superolateral Hoffa fat pad (SHFP) edema with changes in features of the knee extensor mechanism in adolescent competitive alpine skiers over 48 months.MethodsCompetitive alpine skiers were prospectively enrolled in 2018 and underwent bilateral knee MRI at baseline and after 48 months. MRI was assessed for the prevalence of SHFP edema. Features of the knee extensor mechanism were assessed by measuring the trochlear sulcus angle and depth, lateral and medial trochlear inclination, trochlear angle, patella tilt, Insall‒Salvati ratio (ISR), and patellar ligament to lateral trochlear facet (PL-T) distance. Separate logistic regression models were used to calculate the odds ratios between each measurement and the presence of SHFP edema at both time points.ResultsSixty-three athletes were included in the study (mean age 15.3 ± 1.3 years, 25 women). At baseline, 23 knees had SHFP edema, increasing to 34 knees at the 48-month follow-up. At baseline, knees with measurements in the highest quartile for ISR and lowest quartile for trochlear depth and PL-T were 9.3, 5.1, and 7.7 times more likely to show SHFP edema, respectively. At follow-up, these correlations were confirmed and additionally, knees with measurements in the highest quartile for trochlear sulcus angle and the lowest quartile for lateral trochlear inclination were 4.1 and 3.4 times more likely to show SHFP edema.ConclusionAn increased prevalence of SHFP edema in competitive alpine skiers during adolescence was associated with persistent high-riding patella, reduced patellar ligament to trochlear distance, and flattened lateral trochlear facet.Critical relevance statementIn clinical routine, assessment of the mechanical properties of the knee extensor mechanism, together with anatomical developments during adolescence, may improve the understanding and management of patellofemoral instability.Key points• Superolateral Hoffa fat pad (SHFP) edema is a frequent cause of anterolateral knee pain but the role of predisposing factors is still debated.• A higher prevalence of SHFP edema was associated with high-riding patella, reduced patellar ligament to trochlear distance, and flattened lateral trochlear facet.• Understanding of the mechanical interaction and the anatomical development of the knee during adolescence provides further insight into the development of SHFP edema.Graphical

Ultrasound evaluation of the femoral trochlea in newborns: incidence of trochlear dysplasia and associated risk factors.

This study aimed to describe the femoral groove morphology using ultrasound in children under 6 months, estimate the incidence of trochlear dysplasia, and evaluate associated risk factors. A prospective study included 298 patients who underwent universal ultrasound screening for hip dysplasia [developmental dysplasia of the hip (DDH)] and knee ultrasound. Measurements of sulcus angle (SA), trochlear depth (TD), and trochlear facet asymmetry (TFA) were analyzed. Trochlear dysplasia was considered present if the ASO was ≥159°. Reproducibility was assessed using the intraclass correlation coefficient (ICC) in 60 knees. Logistic regression adjusted for confounders, presenting odds ratios (OR) and 95% confidence intervals (CI). Significance was set at P < 0.05. Analysis included 596 knees (298 patients). Females accounted for 51% of patients, with 7% having breech presentation, 4.4% DDH, 6.4% family history of DDH, and 5% family history of patellofemoral instability. ICC showed excellent agreement for SA and TD, but poor for TFA. Trochlear dysplasia incidence was 3% (9/298; 67% bilateral). Median (IQR) values were 147.5 (144.0-150.5) for SA, 2.4 (2.2-2.8) for TD, and 1.1 (1.0, 1.1) for TFA. Breech presentation (OR, 9.68; 95% CI 1.92-48.71, P = 0.006) and concomitant DDH (OR 6.29, 95% CI 1.04-37.78, P = 0.044) were associated with trochlear dysplasia. Ultrasound effectively evaluates femoral groove morphology and diagnoses trochlear dysplasia in newborns. Trochlear dysplasia incidence was 3%, with a 10-fold higher risk in breech presentation and 6-fold higher risk in concomitant DDH. Standardized screening and timely treatment protocols should be further investigated. Level of evidence: Diagnostic Level II.

Association of Hip Dysplasia With Trochlear Dysplasia in Skeletally Mature Patients.

Developmental dysplasia of the hip (DDH) and trochlear dysplasia (TD) are distinct pathologies with several important features in common. In addition to shared risk factors, both forms of dysplasia cause abnormal joint kinematics and force transmission, predisposing patients to pain, injuries to cartilage and soft tissue stabilizers, and ultimately arthritis. To evaluate for an association between hip dysplasia and TD in skeletally mature patients with symptomatic hip dysplasia. Cross-sectional study; Level of evidence, 3. A total of 48 patients with DDH who underwent periacetabular osteotomy were compared with 48 sex-matched patients who underwent hip arthroscopy for femoroacetabular impingement (FAI) between July 2014 and February 2021. All patients were skeletally mature. The Tönnis angle and lateral center-edge angle were measured on preoperative pelvis radiographs. Femoral version, trochlear depth, lateral trochlear inclination (LTI), tibial tubercle-trochlear groove distance (TTTG-d), and posterior lateral condylar angle (PLCA) were measured on preoperative magnetic resonance imaging scans of the symptomatic hip and ipsilateral knee. Continuous variables were compared between the patient groups using 2-sample t tests. Interobserver reliability was measured using the intraclass correlation coefficient. Patients with DDH demonstrated a reduced trochlear depth compared with patients with FAI (3.6 vs 4.6 mm; P < .001). There were no differences between groups in femoral anteversion, LTI, TTTG-d, or PLCA. Two (4.2%) patients with FAI and 17 (35.4%) patients with DDH had a trochlear depth <3 mm (P < .001). One (2.1%) patient with FAI and 7 (14.6%) patients with DDH had an LTI <11° (P = .027). There was no difference between groups in frequency of a convex proximal trochlea, patient-reported ipsilateral knee pain, or ipsilateral knee procedures. Patients with DDH had reduced trochlear depth compared with patients with FAI, demonstrating a higher incidence of dysplastic trochlear features that may predispose patients to patellofemoral joint disease. Further research is needed to determine whether screening at-risk patients and treating TD will help to prevent symptomatic patellofemoral disease.

Diagnostic value of patellofemoral parameters in small breed dogs with medial patellar luxation: a tangential X-ray study

Knowing the diagnostic value of radiological patellofemoral parameters is important for evaluating the status of small-breed dogs with medial patellar luxation (MPL). This retrospective survey was conducted in four small dog breeds (Mini Pinscher, Pomeranian, Chihuahua, and Yorkshire terrier) on 46 healthy stifle joints and 72 joints with grade II and III MPL. The following morphometric parameters were measured on tangential radiographs: trochlear sulcus angle, lateral and medial trochlear inclination angles, trochlear depth, horizontal and vertical patellar diameters, length of the lateral and medial patellar facets, lateral and medial facet angles, Wiberg angle, congruence angle, and axial linear patellar displacement. Receiver operating characteristic (ROC) analysis was performed to evaluate the cut-off values, sensitivity, and specificity of the parameters associated with MPL. The trochlear sulcus angle and trochlear depth were capable of consistently identifying the MPL-affected joints (AUCs &gt; 0.9). The parameters describing the position of the patella within the trochlear groove (congruence angle and axial linear patellar displacement) were found to be the most accurate, with an AUC of over 0.990 and a sensitivity/specificity of over 94%. The patellar morphology parameters had no diagnostic value in distinguishing between healthy and MPL stifles.

Patients with bilateral patellar instability have multiple and symmetric risk factors in each knee.

Bilateral involvement is common in patients with patellar instability. The management of bilateral patellar instability is associated with increased complication rate. The higher complication rate in this cohort may be related to the presence of underlying anatomic risk factors. The purpose of the study was to evaluate the presence and side-to-side differences in risk factors between knees in bilateral patellar instability. In a retrospective study (2008-2017), demographic information, characteristics of patellar dislocation and anatomic risk factors on MRI (trochlear dysplasia, patellar height, tibial tubercle lateralization, patellar tilt, sulcus angle, bump height) were evaluated in both knees of all patients (n = 32, 15 males and 17 females) with bilateral patellar instability. The risk factors were analyzed based on established cut off values and were compared between gender, laterality and more symptomatic (index) knee. Knee symmetry and absolute differences between risk factors for both knees were analyzed. The mean age of 32 patients was 14.6 ± 2.3years. Of the 4 major anatomic risk factors, the most common were trochlear dysplasia in 59/64 (92.1%) knees and patella alta in 51/64 (79.7%) knees. Tibial tubercle lateralization was the least common risk factor being present in 8/64 (12.5%) knees. Of 64 knees, 55 (85.9%) had 2 or more risk factors and 30 (46.8%) had 3 or all 4 risk factors present. There were no significant differences in risk factors based on gender, laterality or index knee. There was symmetry between paired knees for 31/32 (96.8%) patients for trochlear depth, 29/32 (90.6%) for patellar tilt, 27/32 (84.3%) for TT-TG distance and 25/32 (78.1%) for patellar height. There were no significant differences in absolute measurements between knees for any of the risk factors. Patients with bilateral instability had multiple risk factors, with trochlear dysplasia being the most common and increased TT-TG distance being the least common. Majority of patients had 2 or more risk factors and about half had 3 or 4 risk factors in each knee. There was symmetry between paired knees for each risk factorwithout any significant differences between the index knee compared to the contralateral knee. Level III.

Characterization of the CT-based risk factors for concomitant patellofemoral instability in patients with anterior cruciate ligament injury.

Underestimation of concomitant patellofemoral instability in patients with anterior cruciate ligament (ACL) injury has aroused extensive attention. However, the characteristics of the combined injury is not well recognized. Hence, we aimed to characterize the features of the combined injury, and determine the radiographic risk factors. Fifteen radiological parameters were identified after discussion and pilot-tested. Radiographic measurements were compared using the analysis of variance model with Tukey post hoc analysis. A stepwise binomial logistic regression was performed and a nomogram model combining the significant risk factors was created. The model performance was validated by C-index, calibration plot, and decision curve. A total of 204 patients (mean [SD] age, 25.1 [6.7] years; 108 [52.9%] male) were included. The final model was updated through regression analysis using 4 parameters as significant risk factors: lateral femoral condyle ratio (OR (95% CI), 1.194 (1.023 to 1.409)), medial anterior tibial subluxation (mATS) (OR (95% CI), 1.234 (1.065 to 1.446)), medial posterior plateau tibial angle (mPPTA) (OR (95% CI), 1.266 (1.088 to 1.500)), and trochlear depth (OR (95% CI), 0.569 (0.397 to 0.784)). C-index for the nomogram was 0.802 (95% CI, 0.731 to 0.873) and was confirmed to be 0.784 through bootstrapping validation. Calibration plot established a good agreement between prediction and observation. Decision curve analysis showed that if threshold probability was over 10%, using the nomogram adds more benefit than either all or none scheme. Lateral femoral condyle ratio, mATS, mPPTA, and trochlear depth are strong adverse predictors of patellofemoral instability in patients with ACL injury. This study characterizes the radiological features of the combined injury. Patellofemoral instability should be noted when treating ACL injuries. • The radiological characteristics of the combined ACL injury and patellofemoral instability is not well recognized. • Lateral femoral condyle ratio, mATS, mPPTA, and trochlear depth are predominant risk factors for patellofemoral instability in patients with ACL injury. • Patellofemoral instability should be noted when treating ACL injuries.

Poster 263: MRI Evaluation of Pediatric Knee Morphology

Objectives: Abnormal patellar femoral morphology is a central risk factor for patellar instability. While this relationship has been well studied in the adult population, less is known about the relationship during skeletal development. Prior studies have demonstrated that the morphology of the knee changes as a child develops. We predict that a significant difference in the morphological development of children with instability compared to children without instability. Our objective is to compare the progression of morphological parameters in patients with patellar instability to patients without patellar instability. Methods: An IRB approved retrospective chart review was performed measuring TT-TG, trochlear depth, and patellar height (Caton Deschamps Index) in skeletally immature patients between the ages of 5 and 16 who underwent an MRI of their knee. Patients with patellar instability were MRI age matched in a 1 to 2 ratio to patients without patellar instability. Exclusion criteria included osteoarthritis, prior knee surgery, and unreadable MRIs. Morphological measurements were then compared between the two group. Statistical analysis was performed using paired sample t-tests with p≤ 0.05 considered significant. Morphological measurements were then plotted overtime at each age group to determine changes in morphology as a patient develops. Results: A total of 180 patients were included in our analysis. Sixty patients with patellar instability were compared to 120 patients without patellar instability. There was a significant difference in all measurements between the patients with patellar instability and patients without (TT-TG 10.50mm versus 15.72mm, p&lt;0.01; trochlear depth 5.55 mm versus 3.77mm, p&lt;0.01; Caton Deschamps Index 1.07 versus 1.19, p&lt;0.01). TT-TG for patients with prior instability was greater at all ages when compared patients without patellar instability. As patients aged, trochlear depth increased in patients without patellar instability, while it remained relatively stable in patients with patellar instability. Caton Deschamps Index was greater in patients with patellar instability compared to patients without patellar instability at most ages, however they were mostly within normal limit (0.6-1.3). Conclusions: Our data demonstrates that trochlear depth continues to increase in skeletally immature patients without patellar instability as they aged, while patients with patellar instability remained relatively stable. Future studies can be aimed at determining if intervening at a younger age and reducing the patella in these unstable patients can result in increased trochlear depth as they develop.

Poster 276: Assessment of Trochlear Cartilage Thickness and Volume Using Sagittal Magnetic Resonance Images to Quantify Trochlear Dysplasia: A Matched-Cohort Study

Objectives: Trochlear dysplasia is considered a major contributing factor for patellar instability. More recently, trochleoplasty procedures have become popularized to address this morphological abnormality. Both thick and thin flap trochleoplasty techniques exist, with the goal to deepen the trochlea while avoiding perforation of the trochlear cartilage during the procedure. However, the relative cartilage thickness in the dysplastic trochlea has not been well described. This study aimed to assess trochlear cartilage thickness and volume in knees with and without patellar instability and the relationship to measurements of trochlear dysplasia. Methods: 25 knees with symptomatic patellar instability were compared with 25 gender-matched knees. Retrospective chart review was performed to obtain demographic data. On sagittal images, trochlear cartilage thickness (TCT) and trochlear cartilage volume (TCV) were analyzed at the center, medial border, and lateral border of the trochlea. TCT was defined as the cartilage thickness halfway along the trochlear length at its maximum dimension. TCV was defined by total area of cartilage proximal to the plane of the intercondylar midpoint. Symptomatic and control values were compared using paired sample t-test. Stepwise multivariate linear regression was performed to assess for associations with standard radiographic parameters of trochlear dysplasia. Results: TCT was significantly different between the medial, central and lateral trochlea in both the symptomatic and control groups (p&lt;0.001). Only lateral TCT demonstrated a significant difference between groups, which was 20.3% (p=0.035) thicker in the symptomatic cohort compared to controls. No significant differences existed in TCV between symptomatic and control groups. In females, central TCT was 28.3% thicker in the symptomatic cohort (p=0.024), while medial TCV was 2.3x greater (p = 0.019). Males failed to demonstrate gender specific differences. Regression analysis demonstrated that patient height showed a significant relationship with all measurements except for medial TCV. Central TCT demonstrated a significant, independent relationship with trochlear depth (Coefficient 0.38, p = 0.011), while central TCV demonstrated a significant, independent relationship with trochlear depth (Coefficient 9.9, p &lt;0.001), sulcus angle (Coefficient 1.1, p &lt;0.001), and lateral trochlear inclination (Coefficient -1.1, p &lt;0.001). Conclusions: While trochlear dysplasia typically refers to abnormal bony morphology, this study demonstrates the role of differential contributions of chondral thickness and volume between knees with and without patellar instability, and that these measurements correlated with severity of dysplasia. Future studies should further investigate the relationship between TCT and TCV with other dysplasia parameters to better inform the surgical considerations of performing trochleoplasty in the treatment of patellar instability. [Table: see text]

Poster 269: 4-in-1 Quadricepsplasty for Habitual and Fixed Lateral Patellar Dislocation in Children

Poster 269: 4-in-1 Quadricepsplasty for Habitual and Fixed Lateral Patellar Dislocation in Children

Comparison of Habitual Versus Recurrent Patellar Dislocation in Children and Adolescents: Differences in Radiological Features.

Recurrent patellar dislocation (RPD) and habitual patellar dislocation (HPD) in flexion are frequently encountered in children and adolescents. To compare the radiological features of RPD and HPD in children and adolescents. Cross-sectional study; Level of evidence, 3. Imaging data were collected from patients aged 9 to 15 years who received surgical treatment for HPD or RPD at a single institution between June 2015 and September 2020. The prevalence of trochlear dysplasia, tibial tubercle lateralization, and lower limb rotational deformity was assessed through hip/knee/ankle computed tomography (CT) using the following quantitative indicators: trochlear depth index, lateral trochlear inclination, sulcus angle, tibial tubercle-trochlear groove (TT-TG) distance, ratio of TT-TG distance to femoral width, TT-TG angle, femoral anteversion angle, and tibial external rotation angle. The morphology of trochlea and patella were graded on knee CT using the Dejour and Wiberg classification. The Insall-Salvati index and Caton-Deschamps index were used to evaluate the height of the patella on lateral view radiographs. To evaluate lower limbs malalignment, the mechanical lateral distal femoral angle and medial proximal tibial angle were measured on weightbearing full-length radiographs. The collected data were analyzed and compared between the HPD and RPD groups. Enrolled were 15 patients (21 knees) diagnosed with HPD and 18 patients (22 knees) diagnosed with RPD. The age of first dislocation was significantly younger in the HPD group (7.6 ± 3.4 vs 11.2 ± 1.4 years; P = 0.003). Knees in the HPD group had a significantly higher proportion of Dejour type C dysplasia (57.1% vs 4.5%; P < .005) and Wiberg type 3 patella (66.7% vs 9.1%; P < .001). There were statistically significant differences between the groups in the trochlear depth index (HPD vs RPD: 1.1 ± 1.7 vs 2.2 ± 1.5 mm; P = .039), sulcus angle (170.3° ± 13.7° vs 157.3° ± 16.0°; P = .007), Insall-Salvati index (1.1 ± 0.2 vs 1.3 ± 0.2; P = .034), and tibial external rotation angle (31.3° ± 7.8° vs 38.4° ± 8.5°; P = .009). Patients in the HPD group presented with poorer trochlear and patellar development, lower patellar height, and less tibial external rotation compared with patients in the RPG group.

Patellofemoral joint geometry and osteoarthritis features 3-10 years after knee injury compared with uninjured knees.

In this cross-sectional study, we compared patellofemoral geometry in individuals with a youth-sport-related intra-articular knee injury to uninjured individuals, and the association between patellofemoral geometry and magnetic resonance imaging (MRI)-defined osteoarthritis (OA) features. In the Youth Prevention of Early OA (PrE-OA) cohort, we assessed 10 patellofemoral geometry measures in individuals 3-10 years following injury compared with uninjured individuals of similar age, sex, and sport, using mixed effects linear regression. We also dichotomized geometry to identify extreme (>1.96 standard deviations) features and assessed likelihood of having extreme values using Poisson regression. Finally, we evaluated the associations between patellofemoral geometry with MRI-defined OA features using restricted cubic spline regression. Mean patellofemoral geometry did not differ substantially between groups. However, compared with uninjured individuals, injured individuals were more likely to have extremely large sulcus angle (prevalence ratio [PR] 3.9 [95% confidence interval, CI: 2.3, 6.6]), and shallow lateral trochlear inclination (PR 4.3 (1.1, 17.9)) and trochlear depth (PR 5.3 (1.6, 17.4)). In both groups, high bisect offset (PR 1.7 [1.3, 2.1]) and sulcus angle (PR 4.0 [2.3, 7.0]) were associated with cartilage lesion, and most geometry measures were associated with at least one structural feature, especially cartilage lesions and osteophytes. We observed no interaction between geometry and injury. Certain patellofemoral geometry features are correlated with higher prevalence of structural lesions compared with injury alone, 3-10 years following knee injury. Hypotheses generated in this study, once further evaluated, could contribute to identifying higher-risk individuals who may benefit from targeted treatment aimed at preventing posttraumatic OA.

Association of Trochlear Length on Sagittal MRI to Trochlear Dysplasia in Knees With Patellar Instability.

Trochlear dysplasia is a primary risk factor for patellar instability and leads to loss of the osteochondral constraint of the patella. Trochleoplasty techniques include the Peterson grooveplasty, which alters the length of the trochlea; however, a radiographic measurement of trochlear length to support this has not been described. To describe measurements to quantify trochlear length on sagittal magnetic resonance imaging in patients with and without patellar instability and to correlate trochlear length with measurements of trochlear dysplasia. Cross-sectional study; Level of evidence, 3. A total of 66 age- and sex-matched knees (36 female and 30 male; mean age, 20.8 ± 4.8 years) were included in this study, of which 33 had patellar instability. Trochlear extension length (TEL) and trochlear alpha angle (TAA) were measured on 3 sagittal magnetic resonance imaging scans (center of the knee, center of the medial condyle, and center of the lateral condyle), and measurements were compared between symptomatic and control knees. Receiver operating characteristic curve analysis was performed, and the area under the curve (AUC) was calculated to describe the accuracy of each measurement to distinguish between knees with and without patellar instability. Linear and multivariate regression analyses were performed to assess the relationship between sagittal measurements and axial measurements of trochlear dysplasia, including lateral trochlear inclination, sulcus angle, and trochlear depth, as well as patient size reflected by the epicondylar distance. In symptomatic knees, the central trochlea extended more proximally than in control knees, as determined by the TEL (14.0 ± 3.0 vs 11.5 ± 2.3 mm, respectively; P < .001) and TAA (68.4° ± 3.8° vs 70.5° ± 3.4°, respectively; P = .017). AUC calculations showed that a TEL ≥11 mm at the central trochlea was predictive of patellar instability in both male and female knees (AUC = 0.83 and 0.77, respectively), as was a TAA ≤67° in female knees (AUC = 0.72). An independent association between the central TEL and sulcus angle was found. The central TEL showed a weak correlation with patient size, as measured by the epicondylar distance, while the TAA did not. In knees with symptomatic patellar instability, the central trochlea was found to extend 2.5 mm more proximally than in control knees, and this increase in length correlated with severity of trochlear dysplasia. As radiographic examinations of the trochlea and grooveplasty procedures are often based on the proximal extent of the cartilaginous trochlea, further studies are needed to identify the role of trochlear length in the assessment and treatment of trochlear dysplasia in the setting of patellar instability.

Morphometrics of Facies Patellaris Femoris in Dry Bones.

The aim of this study was to investigate the morphological features of the distal femur, with a specific focus on the facies patellaris femoris. A total of 45 dry femurs from adult individuals (24 right, 21 left) were used for the study. Measurements were taken using a calibrated digital vernier caliper and a contour gauge. Anteroposterior (AP) measurements were taken for the medial and lateral condyles of the femur, as well as the articular surfaces of the facies patellaris, sulcus height (51.186±3.81mm), trochlear depth (7.436±1.19mm), and trochlear index (2.295±0.06mm). The results showed that the width of the facies patellaris had a significant positive correlation with the trochlear depth and trochlear index. The length of the facies patellaris was positively correlated with the AP length of the medial condyle and sulcus height, although it was not statistically significant. Additionally, there was a statistically significant positive correlation between the length, width, and medial and lateral articular surfaces of the facies patellaris (p<0.005). Understanding the relationship between the morphometry of the medial and lateral condyles of the distal femur and the morphometry of the facies patellaris, sulcus height, trochlear depth, and trochlear indexand examining the anatomy of the distal femur and patella in individualsare crucial factors for determining appropriate medical treatment and implant selection and compatibility. The findings of this study are expected to contribute to clinicians' interventions in this region (total knee arthroplasty/replacement operation etc.). These data can also be used byimplant designersand forensic experts during investigations.