Referencing the trochlear groove based on three-dimensional computed tomography imaging improves the reliability of the measurement of the tibial tuberosity-trochlear groove distance in patients with higher grades of trochlea dysplasia

Semiautomated Three-Dimensional Landmark Placement on Knee Models Is a Reliable Method to Describe Bone Shape and Alignment

Purpose

To assess the inter- and intrarater reliability of 21 anatomical landmarks initially placed with an artificial intelligence algorithm and then manually verified with human input.

Methods

Thirty computed tomography scans of the knees of participants from the Multicenter Osteoarthritis Study (MOST) ages 45 to 55 years were included. Approximately one-half experienced progression of patellofemoral osteoarthritis, defined as an increased cartilage score in the patellofemoral compartment on magnetic resonance imaging over 2 years. The algorithm automatically placed 19 anatomic landmarks on the femur, tibia, and patella. An additional 2 landmarks were added manually. Two landmark reviewers separately reviewed all 30 scans and verified all landmarks. After 2 weeks, one reviewer repeated the process for the same dataset. The mean Euclidean distance of manual landmark displacement, mean absolute disagreement between and within raters, and intraclass correlation coefficients for inter- and intrarater reliability were calculated.

Results

All landmarks had excellent inter-rater reliability. The tibial and femoral shaft centers had intraclass correlation coefficients (ICCs) of 1, indicating their positions did not differ. Seventeen landmarks had ICCs between 0.90 and 0.99 and the tibial tuberosity had an ICC of 0.87. Intrarater reliability scores were 1 for 16 landmarks and between 0.90 and 0.99 for the remaining 5.

Conclusions

There was excellent agreement on the locations of all 21 landmarks evaluated in this study.

Clinical Relevance

The potential role of artificial intelligence in medical imaging and orthopaedic research is a growing area of interest. The excellent reliability demonstrated across multiple landmarks in our study reveals the potential for semiautomated 3-dimensional methods to enhance precision of anatomical measurements of the knee over 2-dimensional methods.

Inconsistent repeatability of the Dejour classification of trochlear dysplasia due to the variability of imaging modalities: a systematic review

PURPOSE

The purpose of this systematic review was to critically assess the quality of papers that report on the intra- and inter-observer repeatability of the Dejour classification for trochlear dysplasia, and to identify the possible causes for poor repeatability.

METHODS

Two authors independently conducted an electronic search (four databases) on 8 February 2023 for studies (English or French) that assessed trochlear dysplasia classifications on imaging of skeletally mature participants. Exclusion criteria were reviews of clinical studies, conference proceedings, or editorials. After title, abstract, and full-text screening, characteristics of eligible studies were tabulated (author, year, journal, study design, cohort characteristics, and intra- and/or inter-observer agreement coefficients). The methodological quality of studies was assessed using the Joanna Briggs Institute (JBI) checklist for analytical cross-sectional studies. Authors analysed three components of the included studies: (1) classifications based on true lateral radiographs and slice imaging; (2) dysplasia graded into Type A vs B vs C vs D and 3) coefficients of intra- and/or inter-observer agreement.

RESULTS

The electronic search returned 3,178 references, and after removal of duplicates and irrelevant studies, ten were eligible for data extraction. A second search (31 July 2023) yielded one additional study. Eight studies did not include lateral radiographs, two studies did not explicitly state if radiographs were true lateral views, and one used true lateral radiographs in isolation. Classification of trochlear dysplasia into A vs B vs C vs D using different imaging modalities resulted in moderate to near-perfect intra-observer agreement, and slight to near-perfect inter-observer agreement. Studies distinguished between moderate and severe dysplasia using a variety of combinations: A vs B/C/D, A/B vs C/D and A/C vs B/D.

CONCLUSION

This systematic review revealed that the Dejour classification remains the most widely used to assess trochlear dysplasia and that the majority of studies that assessed the reliability of the Dejour classification, reported moderate to near-perfect inter-observer agreement; however, pooling of results for comparison among the included studies was inappropriate due to substantial variation in imaging protocols and non-standardised criteria to distinguish severe from moderate dysplasia.

LEVEL OF EVIDENCE

Level IV.

TRIAL REGISTRY

The PROSPERO registration number is CRD42023386731.

Tibial tubercle to trochlear groove distance versus tibial tubercle to posterior cruciate ligament distance for predicting patellar instability: a systematic review

PURPOSE

To determine the reliability and diagnostic accuracy of tibial tubercle-trochlear groove (TT-TG) distance versus tibial tubercle-posterior cruciate ligament (TT-PCL) distance, and to determine cutoff values of these measurements for pathological diagnosis in the context of patellar instability.

METHODS

Three databases MEDLINE, PubMed and EMBASE were searched from inception to October 5, 2022 for literature outlining comparisons between TT-TG and TT-PCL in patellar instability patients. The authors adhered to the PRISMA and R-AMSTAR guidelines as well as the Cochrane Handbook for Systematic Reviews of Interventions. Data on inter-rater and intra-rater reliability, receiver-operating characteristic (ROC) curve parameters such as area under the curve (AUC), sensitivity and specificity, as well as odds ratios, cutoff values for pathological diagnosis and correlations between TT-TG and TT-PCL were recorded. The MINORS score was used for all studies in order to perform a quality assessment of included studies.

RESULTS

A total of 23 studies comprising 2839 patients (2922 knees) were included in this review. Inter-rater reliability ranged from 0.71 to 0.98 and 0.55 to 0.99 for TT-TG and TT-PCL, respectively. Intra-rater reliability ranged from 0.74 to 0.99 and 0.88 to 0.98 for TT-TG and TT-PCL, respectively. AUC measuring diagnostic accuracy of patellar instability for TT-TG ranged from 0.80 to 0.84 and 0.58 to 0.76 for TT-PCL. Five studies found TT-TG to have more discriminatory power than TT-PCL at distinguishing patients with patellar instability from patients who do not. Sensitivity and specificity ranged from 21 to 85% and 62 to 100%, respectively, for TT-TG. Sensitivity and specificity ranged from 30 to 76% and 46 to 86%, respectively, for TT-PCL. Odds ratio values ranged from 1.06 to 14.02 for TT-TG and 0.98 to 6.47 for TT-PCL. Proposed cutoff TT-TG and TT-PCL values for predicting patellar instability ranged from 15.0 to 21.4 mm and 19.8 to 28.0 mm, respectively. Eight studies reported significant positive correlations between TT-TG and TT-PCL.

CONCLUSION

TT-TG resulted in overall similar reliability, sensitivity and specificity as TT-PCL; however, TT-TG has better diagnostic accuracy than TT-PCL in the context of patellar instability as per AUC and odds ratio values.

LEVEL OF EVIDENCE

Level IV.

Sulcus Angle, Trochlear Depth, and Dejour's Classification Can Be Reliably Applied To Evaluate Trochlear Dysplasia: A Systematic Review of Radiological Measurements

PURPOSE

To summarize data on the reliability of available imaging criteria for the assessment of trochlear dysplasia and to assess the methodological quality of the included studies.

METHODS

This systematic review was conducted following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guideline. Search was performed using major electronic databases from their inception to September 2021. All studies enrolling patients of any age who underwent a radiological exam to rule out features related to trochlear dysplasia were included. After the identification of available imaging criteria, reliability studies were analyzed. Descriptive statistics were used to summarize findings. Methodological quality was assessed using the Quality Appraisal of Reliability studies checklist.

RESULTS

A total of 2391 articles were identified, and 33 articles comprising 3036 patients with a mean age of 28.6 years were included. Thirty different measurements were extracted. Magnetic resonance imaging (MRI) was the most used imaging modalities (21 studies), followed by computed tomography (10 studies), conventional radiology (8 studies) and ultrasonography (US) (1 study). Sulcus angle, trochlear depth, and Dejour's classification were the most explored measurements. Overall, sulcus angle can be reliably assessed on radiography, CT and MRI, whereas trochlear depth can be reliably measured only with CT and MRI. Reliability of Dejour's classification ranged from poor or fair to very good for all imaging modalities. Methodological quality of included studies varied from 2 to 9 positive items out of 11 possible. Twenty-four studies (72.7%) were considered at high risk of bias.

CONCLUSION

Trochlear dysplasia can be reliably evaluated at least with 3 measurements: sulcus angle, trochlear depth and Dejour's classification. Methodological quality assessment showed high risk of bias in most included studies.

LEVEL OF EVIDENCE

Level III, systematic review of Level II-III studies.

Arthroscopic Anatomical Double-Bundle Medial Patellofemoral Complex Reconstruction Improves Clinical Outcomes in Treating Recurrent Patellar Dislocation Despite Trochlear Dysplasia, Elevated Tibial Tubercle-Trochlear Groove Distance, and Patellar Alta

PURPOSE

To evaluate the clinical outcomes of arthroscopically assisted double-bundle medial patellofemoral complex reconstruction (MPFC-R).

METHODS

A retrospective review was carried out among adult patients who experienced at least 2 patellar dislocations and underwent primary arthroscopically assisted MPFC-R between January 2014 and November 2019. Dejour classification, tibial tubercle-trochlear groove (TT-TG) distance, and patellar height (with Insall-Salvati index) were measured. Pre- and postoperative patellar tilt were compared. Information on outcome scores, ability to return to sports, postoperative recurrent dislocations, and complications was recorded.

RESULTS

A total of 42 MPFC-Rs in 39 patients were included. Mean age at surgery was 22.2 ± 7.6 years; 69.2% of patients were female. Mean follow-up was 47.3 ± 20.2 months. Seventy-four percent of cases had Dejour B (19.0%), C (33.3%), and D (21.4%) trochlear dysplasia; mean TT-TG distance was 19.6 ± 3.5 mm, and mean Insall-Salvati index was 1.21 ± 0.17. Mean patellar tilt decreased from 27.6 ± 11.6° to 9.4 ± 6.5° (P < .001). All patients had statistically significant (P < .001) improvement in mean International Knee Documentation Committee (IKDC) (44.9 ± 18.2 to 87.5 ± 6.9), Lysholm (61.4 ± 16.6 to 94.1 ± 6.4), Kujala (56.0 ± 16.8 to 92.9 ± 5.3), and Tegner score (2.7 ± 1.3 to 4.6 ± 1.4). The majority of patients (96.9%) returned to sports, with 90.3% returning to the same or greater level of activity. No postoperative dislocations or subluxations were reported.

CONCLUSIONS

Arthroscopically assisted double-bundle MPFC-R is a promising procedure to treat recurrent patellar instability at 2- to 7-year mid-term follow-up, despite the presence of trochlear dysplasia, elevated TT-TG distance and patellar alta. The improvement of IKDC score exceeded the minimal clinically important difference in 95.2% patients, and 66.7% surpassed the patient acceptable symptomatic state based on postoperative IKDC score with no redislocations being reported at latest follow-up.

LEVEL OF EVIDENCE

Level IV, case series, retrospective.

Assessment of the reliability and validity of imaging measurements for patellofemoral instability: an updated systematic review

OBJECTIVE

To provide an update on the reliability and validity of all radiological measures used to assess patients presenting with patellofemoral instability.

METHODS

A search of the CINHAL, EMBASE, MEDLINE, and SCOPUS databases and the Cochrane library was conducted. All studies assessing the validity, reliability, sensitivity, and specificity of radiological measures of the patellofemoral joints of patients with patellofemoral instability from 2010 onwards were considered for inclusion. Discrimination validity, inter- and intra-observer reliability, and the sensitivity and specificity of specific imaging measures were evaluated.

RESULTS

Seventy-three studies met the selection criteria and were included for analysis. We identified eight radiological measures in four categories with good reliability and validity: the tibial tubercle to trochlear groove distance, specific measures of patellar height (Blackburne-Peel index, Caton-Deschamps index and Insall-Salvati ratios), three measures of trochlear dysplasia (sulcus angle, trochlear depth, and lateral trochlear inclination), and the tibial tubercle to posterior cruciate ligament distance. No included studies examined the reliability and validity of patellofemoral instability ultrasound measures.

CONCLUSION

Our updated review demonstrated good inter- and intra-observer reliability and discrimination validity for the tibial tubercle-trochlear groove distance, specific patellar height, and trochlear dysplasia measures on MRI. The tibial tubercle to posterior cruciate ligament distance, an indirect measure of rotational asymmetry, was a valid and reliable measure on MRI. Due to a lack of assessments across more than one study, there are a variety of proposed measures with insufficient evidence to determine their validity, reliability, sensitivity, and specificity.

Reliability of the Tibial Tubercle-Roman Arch Distance for Evaluating Tibial Tubercle Malposition and Predicting Patellar Dislocation via Magnetic Resonance Imaging

Background:

The tibial tubercle (TT)–trochlear groove (TT-TG) distance has low reproducibility in patients with a dysplastic trochlea, whereas the clinical value of the TT–posterior cruciate ligament (TT-PCL) distance remains controversial.

Purposes:

To establish a method to assess the position of the TT on magnetic resonance imaging (MRI) scans using the TT–Roman arch (TT-RA) distance, compare this method with the TT-TG and TT-PCL distance, and provide the pathological threshold value of the TT-RA distance in patients with patellar dislocation.

Study Design:

Cross-sectional study; Level of evidence, 3.

Methods:

The TT-RA distance, TT-TG distance, and TT-PCL distance were measured on MRI scans in 70 patients with a history of patellar dislocation and 70 healthy individuals. Inter- and intraobserver reliability of each measurement parameter were evaluated. The discriminatory capacity and the interrelationship of the 3 measurement parameters were investigated using Pearson correlation and the receiver operating characteristic curve. The pathological threshold values of these measurements were calculated according to the data of healthy individuals. Finally, logistic regression analysis was performed using these values.

Results:

Patients with patellar dislocation had a greater TT-RA distance compared with healthy individuals (18.05 ± 4.16 vs 13.86 ± 2.90 mm; P < .001). The TT-RA distance had a stronger diagnostic capacity, with an area under the curve of 0.802 compared with 0.625 for TT-PCL distance. Excellent reproducibility was seen for TT-RA distance measurement at any degree of trochlear dysplasia (all intraclass correlation coefficients [ICCs] >0.90). The inter- and intraobserver ICCs of the TT-TG distance measurements were extremely low for Dejour type D dysplasia (ICC, 0.509 and 0.616, respectively). The pathological TT-RA distance threshold was calculated as 19.5 mm. Logistic regression showed that patients with a TT-RA distance >19.5 mm were 11.7 times more likely to sustain patellar dislocation than were those with TT-RA distance less than this value.

Conclusion:

The TT-RA distance was a more reliable parameter with which to evaluate TT position than was TT-TG distance in patients with trochlear dysplasia. The TT-PCL distance was the least reliable among the 3 parameters studied.

Tibial Tuberosity-Trochlear Groove Distance and Its Components in Patients with and without Episodic Patellar Dislocation: A Study of 781 Knees

BACKGROUND

The purposes of the present study were (1) to measure the tibial tuberosity-trochlear groove distance and its components with the knee in extension, (2) to determine their diagnostic performance in distinguishing between patients with and without episodic patellar dislocation, and (3) to investigate the relationship of each component to the total tibial tuberosity-trochlear groove distance.

METHODS

We retrospectively reviewed computed tomography (CT) images of the knee joint in a group of patients with episodic patellar dislocation and a group of control subjects who were treated for another type of knee disorder in our institution between 2015 and 2021. Tibial tuberosity-trochlear groove distance, tibial tubercle lateralization, trochlear groove medialization, and knee rotation were measured on axial images. Partial correlation analysis of the measured parameters was performed after adjusting for remaining variables. Receiver operating characteristic (ROC) curves and the areas under the ROC curves (AUCs) were assessed to assess the diagnostic accuracy. A subgroup analysis based on femoral trochlear dysplasia classification was also performed.

RESULTS

After screening of 653 patients (947 knees) in our hospital's patient registry, a total of 521 patients (781 knees) were analyzed, including 541 knees (69.3%) with episodic patellar dislocation and 240 knees (30.7%) without episodic patellar dislocation (control group). The tibial tuberosity-trochlear groove distance demonstrated the best diagnostic performance, with the AUC being significantly better than that for other parameters (p < 0.001). The tibial tuberosity-trochlear groove distance was moderately to strongly correlated with knee rotation and trochlear groove medialization in the control and episodic patellar dislocation groups (p < 0.001). However, tibial tubercle lateralization showed a weak correlation with the tibial tuberosity-trochlear groove distance in the control group and moderate correlation in the episodic patellar dislocation group (p < 0.001). Knees with a type-D femoral trochlea had a significantly greater tibial tuberosity-trochlear groove distance than those with a type-A, B, or C femoral trochlea (p ≤ 0.011).

CONCLUSIONS

Tibial tuberosity-trochlear groove distance, a reliable predictor of episodic patellar dislocation, was affected more by knee rotation and trochlear groove medialization and was less affected by tibial tubercle lateralization, and it increased with an increasing grade of femoral trochlear dysplasia. The correlation of the tibial tuberosity-trochlear groove distance and its components as noted in the current study will help to achieve a better understanding of the tibial tuberosity-trochlear groove distance.

LEVEL OF EVIDENCE

Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

The relationship between patellar volume and trochlear volume in patients with patellofemoral instability

AIM

To investigate a possible relationship between both the volume and morphology of the patella and the volume of the trochlea in trochlear dysplasia (TD).

MATERIALS AND METHODS

Eighteen patients with TD and 18 controls were evaluated retrospectively in two groups using computed tomography (CT). Patellar morphology was evaluated with the standard measurement methods described in the literature. Additionally trochlear sulcus volume (TV) and patellar volume (PV) were measured quantitatively using the three-dimensional volume-rendering method. The relationship between patella dimensions and volume and trochlea volume was evaluated.

RESULTS

The length of the medial patellar facet (lMP), patellar width (PW), TV and PV were significantly lower in the patient group. When compared according to Dejour types, PW was statistically significantly lower than the control group in those with high-grade and those with low-grade dysplasia. A positive correlation was found between the TV and PV in both groups (patient group: r=0.583 p=0.011; control group: r=0.485 p=0.042). CONCLUSİONS: PV and the TV are related. Therefore, PV can be used as a determining parameter in the evaluation of TD. This technique can also be used for prosthesis construction and more accurate surgical planning.

Current Concepts Regarding Patellofemoral Trochlear Dysplasia

Optimal treatment of patients with patellofemoral trochlear dysplasia and recurrent patellar instability requires in-depth understanding of this complex structural anomaly. An extensive review of the literature suggests that dysplasia occurs as a result of aberrant forces applied to the patellofemoral joint in the majority of cases. Evidence supports surgical stabilization that reconstructs the medial patellofemoral and/or medial quadriceps tendon-femoral ligament without added trochleoplasty in the majority of patients with trochlear dysplasia and recurrent patellar instability. Adding tibial tubercle transfer distally, medially, or anteromedially in those who need it to treat specific deficits in alignment or articular cartilage can be beneficial in selected patients with trochlear dysplasia and recurrent patellar instability. Trochleoplasty may be appropriate in those few cases in which permanent stable patellofemoral tracking cannot be restored otherwise, but the indications are not yet clear, particularly as trochleoplasty adds risk to the articular cartilage. Improved understanding of imaging techniques and 3-dimensional reproductions of dysplastic patellofemoral joints are useful in surgical planning for patients with recurrent patellar instability and trochlear dysplasia.

Validating the Role of Tibial Tubercle-Posterior Cruciate Ligament Distance and Tibial Tubercle-Trochlear Groove Distance Measured by Magnetic Resonance Imaging in Patients With Patellar Dislocation: A Diagnostic Study

PURPOSE

To (1) compare these parameters between patients with patellar dislocation and healthy individuals on magnetic resonance imaging measurements, (2) validate the diagnostic capacity of the tibial tubercle-posterior cruciate ligament (TT-PCL) distance and tibial tubercle-trochlear groove (TT-TG) distance, (3) define the pathologic threshold values of these parameters for tibial tubercle osteotomy indication, and (4) compare these values with those of previous studies.

METHODS

Seventy patients with patellar dislocation and 70 healthy volunteers were identified. The inter- and intraobserver reliability values were determined using Bland-Altman analysis and the intraclass correlation coefficient (ICC). The diagnostic capacity of the parameters was evaluated using receiver operating characteristic curves and the area under the receiver operating characteristic curve. The data of the control group were used to determine the pathologic threshold values of the measurements. Logistic regression analysis was performed with these pathologic threshold values.

RESULTS

Significant differences in the TT-PCL distance (P = .01) and TT-TG distance (P < .001) were found between the study group (21.48 ± 3.18 and 12.91 ± 3.80, respectively) and the control group (20.07 ± 2.99 and 8.46 ± 3.16, respectively). Both the TT-PCL distance and TT-TG distance had excellent inter- and intraobserver agreement, with inter-ICCs >0.915 and intra-ICCs >0.932, respectively. However, the TT-TG distance had a higher area under the receiver operating characteristic curve than did the TT-PCL distance (0.820 vs 0.627). The pathologic threshold value of the TT-PCL distance was 24.76 mm. The pathologic threshold value of the TT-TG distance was 13.64 mm. Subjects with a TT-TG distance of >13.64 mm had a greater risk for patellar dislocation, with an odds ratio of 14.02 (95% confidence interval 4.00-49.08, P < .001).

CONCLUSIONS

Both the TT-PCL distance and TT-TG distance can be measured reliably by magnetic resonance imaging; however, the TT-TG distance has a better diagnostic capacity than does the TT-PCL distance.

LEVEL OF EVIDENCE

Retrospective cohort study (diagnosis); Level of evidence, I.

Comparative study of the tibial tubercle-trochlear groove distance measured in two ways and tibial tubercle-posterior cruciate ligament distance in patients with patellofemoral instability

BACKGROUND

A comparative analysis of the strengths and weaknesses of three different methods for radiologic evaluation of patellofemoral instability (PFI).

METHODS

Computed tomography (CT) and magnetic resonance imaging (MRI) were performed in 47 patients with or without PFI. The tibial tubercle-trochlear groove (TT-TG) distance was measured by two observers through conventional CT and three-dimensional CT reconstruction (TDR-TT-TG) respectively and the tibial tubercle-posterior cruciate ligament (TT-PCL) distance with MRI. The intraclass correlation coefficient (ICC) was used to evaluate the interobserver reliability. In addition, the differences of three measurements between different patients were compared. The consistency of TT-TG and TDR-TT-TG was analyzed by the Bland-Altman method.

RESULTS

The ICCs of three measurements were high between two observers; the results were TT-TG (ICC = 0.852), TDR-TT-TG (ICC = 0.864), and TT-PCL (ICC = 0.758). The values of PFI patients were significantly higher than those of non-PFI patients, and the mean TT-TG, TDR-TT-TG, and TT-PCL distance in patients with PFI were 19.0 ± 3.8 mm, 19.0 ± 3.7 mm, and 25.1 ± 3.6 mm, respectively. There was no statistically significant difference between the TT-TG distance and the TDR-TT-TG distance, we found no significant difference. The Bland-Altman analysis showed that the TDR-TT-TG distance was in good agreement with the TT-TG distance.

CONCLUSION

All three methods can be used to assess PFI; the TDR-TT-TG measurement method has superior operability and better interobserver consistency. It may be an alternative method to the conventional TT-TG distance measurement.

Tibial Tubercle-Roman Arch Distance: A New Measurement of Patellar Dislocation and Indication of Tibial Tubercle Osteotomy

Background:

The surgical indication for tibial tubercle osteotomy (TTO) has been based on a tibial tubercle–trochlear groove (TT-TG) distance of 20 mm or greater in patients with patellar dislocation. However, the measurement of this parameter is less reliable in patients with trochlear dysplasia.

Hypothesis:

The novel measurement of tibial tubercle–Roman arch (TT-RA) distance would be a reliable parameter for identifying the relative position of the tibial tubercle in patients with patellar dislocation, especially those with trochlear dysplasia.

Study Design:

Cohort study (diagnosis); Level of evidence, 2.

Methods:

A total of 56 patients with a diagnosis of patellar dislocation and 60 volunteers (60 knee joints) without a history of lower extremity pain or injury were included in our study. The TT-RA distance, TT-TG distance, and some femoral anatomic parameters were assessed by use of computed tomography. The measurements were performed by a radiologist and an orthopaedic surgeon in a blinded and randomized fashion. The difference in each parameter between the study and control groups was analyzed through use of an unpaired t test. Receiver operating characteristic curve analysis was performed to evaluate the discriminatory capacity of the included parameters. The cutoff values of the included measurements with specificity and sensitivity were calculated. In addition, the TT-TG distance and TT-RA distance were analyzed using the Dejour classification to evaluate the intraclass correlation coefficient (ICC) of each parameter in different types of femoral trochlea.

Result:

A significant difference for TT-RA distance was found between the study group (23.24 ± 4.41 mm) and control group (19.15 ± 4.24 mm) (P < .001). The TT-RA distance had an area under the curve of 0.757. At a value greater than 23.74 mm, TT-RA distance had 53.57% sensitivity and 88.33% specificity for patellar dislocation. The ICCs of TT-RA distance measurements were excellent in all Dejour classifications (>0.939), whereas the ICCs of TT-TG distance measurements were relatively lower than the ICCs of TT-RA distance measurements. According to the data from included healthy individuals, the pathological TT-RA distance threshold was 26 mm.

Conclusion:

Compared with TT-TG distance, the TT-RA distance is a more reliable parameter for identifying the relative position of the tibial tubercle in patients with trochlear dysplasia. For patients with a TT-RA distance greater than 26 mm, surgery should be considered to correct the malposition of the tibial tubercle.