Relationship between patellofemoral joint morphology and chondromalacia patella.

BACKGROUND: For the normal functioning of the patellofemoral joint (PF), the relationship between the patella and the trochlear groove must be compatible. PURPOSE: To investigate the relationship between patellofemoral joint morphology (PFM) and patellar chondromalacia. MATERIAL AND METHODS: Overall, 136 knees of patients aged 20-55 years examined between March 2020 and March 2021 were included in this study. In all patients, trochlear sulcus angle, trochlear sulcus depth, trochlear facet asymmetry, patella alta (Insall-Salvati [IS] index), and patellar facet asymmetry were measured. Of these cases, 66 knees with an abnormality detected in any of the measurements for PFM were included in the case group. Moreover, 70 knees with demonstrating normal PFM measurements were included in the control group. RESULTS: The incidence and grade of chondromalacia was higher in the case group than in the control group (P < 0.001). Between the patients with and without chondromalacia trochlear sulcus angle (mean = 138.25° ± 10.02° vs. 132.58° ± 7.24°; P = 0.001), IS index (mean = 1.25 ± 0.21 vs. 1.16 ± 0.15; P = 0.014), patellar facet asymmetry (mean = 0.77 ± 0.09 vs. 0.73 ± 0.12; P = 0.039), trochlear sulcus depth (mean = 5.39 ± 1.42 mm vs. 6.27 ± 1.04 mm; P < 0.001), and trochlear facet asymmetry (mean = 0.67 ± 0.11 vs. 0.71 ± 0.09; P = 0.023) measurements, there was a significant difference. CONCLUSION: The presence of at least one of the measures indicating pathology in PFM is associated with the presence and severity of chondromalacia.

Prevalence of trochlear dysplasia in an 1162 retrospective cohort study using CT scans.

HYPOTHESIS/PURPOSE: The prevalence of trochlear dysplasia is common in different populations. BACKGROUND: The prevalence of trochlear dysplasia in the general population, categorised by sex, race, age, and body mass index, has been sparse. This study aimed to define the prevalence of trochlear dysplasia based on the latter categories. STUDY DESIGN: Cohort retrospective study. METHODS: 1162 skeletal mature healthy femora were obtained from a CT-scan-based modelling system (SOMA). Thin slice CT scans were acquired exclusively for medical indications such as polytrauma (20%), CT angiography (70%) and other reasons (i.e. Total Joint Replacement) (10%). Trochlear dysplasia was measured using Pfirmann's method. Patient demographics such as age, race and sex were recorded. RESULTS: The overall prevalence of trochlear dysplasia is 4.5% and is far more common in Asian female patients compared to Caucasian, African and Middle Eastern knees. CONCLUSION: Overall, the prevalence of dysplasia in the general population was determined to be 4.5%, with female patients being more likely to suffer from the condition. Patients of Asian and Caucasian race were more likely to have trochlear dysplasia, while Middle Eastern male patients displayed more dysplastic values than their female counterparts.

A novel adapted MRI-based scheme for Dejour classification of trochlear dysplasia.

PURPOSE: To elaborate an optimized scheme for the Dejour classification of trochlear dysplasia based on axial and sagittal MR images and to evaluate its intra- and inter-reader reliability. MATERIAL AND METHODS: Over a period of 20 months patients with a knee MRI and the diagnosis of trochlear dysplasia were retrospectively included. Exclusion criteria were incomplete examination, qualitatively non-diagnostic examination, post trochlear surgery, missing informed consent for research purposes. Three independent evaluations were performed by two radiologists: first using an established description of the Dejour classification (types A-D) and then two evaluations using a new adapted scheme (types A-D). The adapted scheme includes a shallow trochlea, in type A no spur/no cliff, in type B with spur/no cliff, in type C no spur/with cliff, and in type D with spur/with cliff. RESULTS: One hundred seventy-one knee MRIs (female:65.5%; left side:52.6%) were included with a median age of 34.3 years (range:11.3-79.2). Inter-reader reliability using the established description was fair for the four-type-classification (kappa(k) = 0.23; 95%CI:0.11-0.34), fair for differentiation low-grade versus high-grade dysplasia (k = 0.28;0.13-0.43), slight for differentiation spur versus no-spur types (k = 0.20;0.05-0.34). Inter-reader reliability using the adapted scheme was substantial (k = 0.79;0.75-0.83) for the four-type-classification, substantial for differentiation low-grade versus high-grade dysplasia (k = 0.80;0.75-0.85), substantial for differentiation spur versus no-spur presence (k = 0.76;0.71-0.81). Intra-reader reliability was almost perfect for the adapted scheme (k-values: 0.88-0.95; 95%CIs: 0.84-0.98). CONCLUSION: The novel adapted scheme for Dejour classification shows an almost perfect intra-reader reliability and a substantially higher inter-reader reliability. It may become a helpful tool in the daily diagnostic work of radiologists.

No significant difference in thick versus thin osteochondral flap trochleoplasty in the treatment of trochlear dysplasia: A systematic review.

PURPOSE: Trochleoplasty has become increasingly utilised to address patellar instability in the setting of severe trochlear dysplasia. There remains a paucity of literature on the outcomes of 'thick'- versus 'thin'-osteochondral flap trochleoplasty. The purpose of this study is to compare clinical and radiographic outcomes between patients with patellar instability with symptomatic trochlear dysplasia treated using a 'thick' versus 'thin' osteochondral flap trochleoplasty. METHODS: A systematic review and meta-analysis were conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines using a PRISMA checklist. Quality assessment of final articles was conducted by two blinded reviewers. Articles were separated based on the use of a 'thick' versus 'thin' flap trochleoplasty. Data collection consisted of recording the following variables: patient demographics, indications for trochleoplasty, mean follow-up time, additional procedures performed during trochleoplasty, patient-reported outcome measures (PROMs), radiographic outcomes (tibial tubercle-trochlear groove [TT-TG] distance, Caton-Deschamps Index [CDI] and sulcus angle [SA]) and the incidence of any postoperative complications and patellar redislocation rates. RESULTS: A total of 24 studies, consisting of 927 patients, were identified as meeting inclusion criteria. A total of five papers described a 'thick' flap technique, while 19 papers described the use of a 'thin' flap technique. No significant difference in the mean improvement of Kujala scores was appreciated when comparing 'thick' versus 'thin' techniques (p > 0.05). Improvements in mean radiographic outcomes based on TT-TG, CDI and SA were observed in both 'thick' and 'thin' flap trochleoplasty groups. The overall redislocation rate was 0.35%. CONCLUSION: No significant difference in Kujala scores was observed in patients undergoing trochleoplasty utilising 'thick' versus 'thin' technique, while improvements in mean TT-TG, CDI and SA were noted in both technique groups, with an overall redislocation rate of 0.35%. LEVEL OF EVIDENCE: Level IV.

The Dejour classification for trochlear dysplasia shows slight interobserver and substantial intraobserver reliability.

PURPOSE: Trochlear dysplasia is one of the main risk factors for recurrent patellar dislocation. The Dejour classification identifies four categories that can be used to classify trochlear dysplasia. The purpose of this study is to evaluate the inter- and intraobserver reliability of the Dejour classification for trochlear dysplasia. The hypothesis was that both intra- and interobserver reliability would be at least moderate. METHODS: This is a cross-sectional, reliability study. Twenty-eight examiners from the International Patellofemoral Study Group 2022 meeting evaluated lateral radiographs of the knee and axial magnetic resonance images from 15 cases of patellofemoral instability with trochlear dysplasia. They classified each case according to Dejour's classification for trochlear dysplasia (A-D). There were three rounds: one with only computed radiograph (CR), one with only magnetic resonance imaging (MRI) and one with both. Inter- and intraobserver reliability were calculated using κ coefficient (0-1). RESULTS: The mean age of patients was: 14.6 years; 60% were female and 53% had open physis. The interobserver reliability κ probabilities were 0.2 (CR), 0.13 (MRI) and 0.12 (CR and MRI). The intraobserver reliability κ probabilities were 0.45 (CR), 0.44 (MRI) and 0.65 (CR and MRI). CONCLUSION: The Dejour classification for trochlear dysplasia has slight interobserver reliability and substantial intraobserver reliability. LEVEL OF EVIDENCE: Level I.

The role of the most cranial trochlear orientation in patellar maltracking to better characterise trochlear morphology.

PURPOSE: The purpose of our study is to describe a magnetic resonance imaging quantitative parameter to assess the morphology of the trochlea that could be measurable from normal to high-grade trochlear dysplasia while evaluating the most proximal slice with trochlear cartilage. METHODS: Two groups of patients have been compared: patients with no patellofemoral pain, no previous trauma and undergoing surgery for a suspected isolated meniscal tears (group A) and patients with objective patellar instability (group B). The cranial trochlear orientation (CTO) angle is defined as the angle between the posterior bicondylar line and the most lateral and most medial points on the subchondral bone covered by cartilage digitised on the first and most cranial image with the trochlear cartilage clearly visible. RESULTS: The final cohort included 253 patients (109 in group A and 144 in group B). CTO was significantly higher in group B (-2.5 ± 8.4 vs. -10.8 ± 5,1; p < .001). Moreover, 75% of knees in group B had a CTO > -7°, while 75% of knees in group A had a CTO < -7°. CTO was measurable in all 253 knees, whereas the lateral trochlear inclination and the sulcus angle were measurable in only 202 knees. The entire cohort was also divided into knees with CTO ≤ 0° and CTO > 0°. All knees with a CTO > 0 were in group B, and 49% of knees with CTO < 0 were in group B. CTO was positively correlated with lateral patellar tilt. CONCLUSIONS: CTO is the only parameter that can be measured on the most cranial slice, in every patient, even in high-grade trochlear dysplasia. According to this new system, the axial trochlear shape may be divided into two types: a positive CTO and a negative CTO, with the trochlea serving, respectively, as a medial and lateral barrier. LEVEL OF EVIDENCE: Level III.

Adolescents with prior patellar dislocation report affected quality of life and function, as measured using the Banff Patella Instability Instrument, Kujala and EQ-5D-5L index scores.

PURPOSE: We aimed to establish patient-reported outcome measure (PROM) reference data for a cohort of patients with prior patellar dislocation without previous knee surgery. METHODS: All inhabitants of the Faroe Islands aged 15-19 years were sent an online survey via secure email to establish a national cohort. They were asked to answer questions regarding demographics, whether they had prior patellar dislocation and to complete the PROMs: the Banff Patella Instability Instrument (BPII), Kujala, Marx activity and EQ-5D-5L questionnaires. Participants who had undergone knee surgery were excluded. Participants who had prior patellar dislocation underwent radiographic examinations to diagnose trochlear dysplasia. The study included three cohorts: the general population, prior patellar dislocation and prior patellar dislocation and trochlear dysplasia cohorts. RESULTS: Of the 3749 individuals contacted, 1119 completed the survey and responded to at least one PROM. Of these, 102 reported a history of patellar dislocation and 57 of them had trochlear dysplasia. All PROMs, except the Marx score, reflected a worse quality of life and function after patellar dislocation than in the general population cohort; this was most pronounced in the BPII. The percentage of people experiencing problems in EQ-5D-5L dimensions was higher in the patellar dislocation and trochlear dysplasia cohorts than in the general population cohort in all EQ-5D-5L domains, except anxiety/depression. CONCLUSION: Adolescents who had patellar dislocation reported reduced quality of life and function according to the BPII, Kujala and EQ-5D-5L index values, as well as all EQ-5D-5L domains, except for anxiety/depression. However, their activity levels remained high. LEVEL OF EVIDENCE: Level III.

Shallow trochlear groove and narrow medial trochlear width at the proximal trochlea in patients with trochlear dysplasia: A three-dimensional computed tomography analysis.

PURPOSE: Although the Dejour classification is the primary classification system for evaluating trochlear dysplasia, concerns have been raised about its reliability owing to its qualitative criteria and challenges associated with obtaining accurate radiographs. This study aimed to quantify trochlear dysplasia using three-dimensional (3D) computed tomography (CT) reconstruction with novel parameters related to the transepicondylar axis (TEA). METHODS: Sixty patients were enrolled, including 20 with trochlear dysplasia and 40 healthy controls. The 3D CT model was generated using the Materialise Interactive Medical Image Control System software. The following six parameters were measured in eight consecutive planes at 15° intervals (planes 0-105): the distance from the TEA to the most cortical point of the lateral condyle ('LP-TEA', where LP stands for lateral peak), medial condyle ('MP-TEA', MP for medial peak) and deepest point of the trochlea ('TG-TEA', TG for trochlear groove). The distances from the medial epicondyle (MEC) to the corresponding TEA points were measured ('LP-MEC', 'MP-MEC' and 'TG-MEC'). RESULTS: In the dysplasia group, TG-TEA (planes 0, 15 and 30) and MP-MEC (planes 0, 15 and 30) were significantly greater than those in the control group (all p < 0.05 for planes of TG-TEA and MP-MEC). For type A dysplasia, LP-MEC (plane 0) was greater than that in the control group. For type B dysplasia, the MP-MEC (planes 0 and 15) and TG-TEA (planes 0 and 15) were greater than those of the control group. For type D dysplasia, MP-MEC (planes 0, 15 and 30) and TG-TEA (planes 0 and 15) were elevated. CONCLUSION: The 3D CT reconstruction analysis established a reproducible method for quantifying osseous trochlear morphology. Patients with trochlear dysplasia had a shallow TG and narrow medial trochlear width at tracking angles of 0°-30°. This finding corroborates the clinical manifestations of recurrent patellar instability that occur during early flexion. LEVEL OF EVIDENCE: Level III.

Medial orientation of the trochlear groove is a strong indicator of high-grade trochlear dysplasia.

PURPOSE: The objective is to evaluate the orientation of the trochlear groove in patients with objective patellar instability (OPI) compared to a control group. The hypothesis is that the trochlear groove angle (TGA) is correlated with the severity of the trochlear dysplasia. METHODS: From 2019 to 2023, magnetic resonance imaging of 82 knees with OPI were compared with 82 control knees. TGA quantified the angle between the femoral anatomical axis and the trochlear groove. The intraclass correlation coefficient for TGA was evaluated. Central spur in the sagittal plane (CSSP) and cranial trochlear orientation (CTO) angle were also measured. TGA, CSSP and CTO were compared between the two groups. A TGA subgroup analysis separating the OPI group into low-grade (CSSP < 5 mm or negative CTO) and high-grade dysplasia (CSSP ≥ 5 mm or positive CTO) was also performed. RESULTS: A significant difference (p < 0.001) was found between the TGA of the OPI group (mean [SD], 11.3 [3.7]°) and the control group (4.2 [2.5]°). TGA for patients with high-grade dysplasia (11.9 [3.8]°) was significantly higher than patients with low-grade dysplasia (9.6 [3.9]°). CONCLUSION: Patients with OPI have a TGA of 11°, compared to the control group, which exhibits a TGA of 4°. The femoral mechanical axis can be considered an appropriate threshold for separating these two groups. Furthermore, TGA is correlated with the severity of dysplasia. STUDY DESIGN: Case-control study. LEVEL OF EVIDENCE: Level III.

Prevalence and a correlation analysis of discoid meniscus and femoral trochlear dysplasia.

BACKGROUND: Discoid meniscus (DM) and femoral trochlear dysplasia (FTD) are common knee disorders. Both as congenital malformation, whether there is a connection between them is unclear and the research on their prevalence in the general population is inadequate. This study aimed to investigate the prevalence of FTD and DM in the general population through a large sample size, and to explore the relationship between them. STUDY DESIGN: Retrospective study. METHODS: Patients undergoing knee magnetic resonance imaging (MRI) examinations at our outpatient clinic were screened and 1003 patients were enrolled in DM group with 989 patients in non-DM (NDM) group. The type of DM and FTD was classified with Watanabe classification and Dejour's classification, respectively. The prevalence of FTD and DM in the general population and the relationship between them were evaluated. RESULTS: The prevalence of DM and FTD was 10.0% and 14.5%, respectively. The overall percentage of FTD was higher in DM group (P < 0.001). The DM group has a higher percentage of all types of FTD except type D (P < 0.05), and a higher percentage of both low- and high-grade FTD (P < 0.001). There were 633 cases of type I DM and 370 cases of type II DM. The overall percentage of FTD was not significantly different between the two types (P = 0.106). No significant difference was detected for all types of FTD except type B (P < 0.05). The Type I DM group has a significant higher percentage of high-grade FTD than Type II group (P < 0.05). CONCLUSION: Patients with a DM are more likely to have FTD regardless of the type of DM, while those with a type I DM are more prone to have a high grade FTD.

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.

Patients with trochlear dysplasia have dysplastic medial femoral epiphyseal plates.

PURPOSE: To investigate the growth of the epiphyseal plate in patients with trochlea dysplasia using a 3D computed tomography (CT)-based reconstruction of the bony structure of the distal femur. The epiphysis plate was divided into a medial part and a lateral part to compare their differences in patients with trochlear dysplasia. METHODS: This retrospective study included 50 patients with trochlea dysplasia in the study group and 50 age- and sex-matched patients in the control group. Based on the CT images, MIMICS was used to reconstruct the bony structure of the distal femur. Measurements included the surface area and volume of the growth plate (both medial and lateral), the surface area and capacity of the proximal trochlea, trochlea-physis distance (TPD) (both medial and lateral), and height of the medial and lateral condyle. RESULTS: The surface area of the medial epiphyseal plate (1339.8 ± 202.4 mm2 vs. 1596.6 ± 171.8 mm2), medial TPD (4.9 ± 2.8 mm vs. 10.6 ± 3.0 mm), height of the medial condyle (1.1 ± 2.5 mm vs. 4.9 ± 1.3 mm), and capacity of the proximal trochlear groove (821.7 ± 230.9 mm3 vs. 1520.0 ± 498.0 mm3) was significantly smaller in the study group than in the control group. A significant positive correlation was found among the area of the medial epiphyseal plate, the medial TPD, the height of the medial condyle and the capacity of the proximal trochlear groove (r = 0.502-0.638). CONCLUSION: The medial epiphyseal plate was dysplastic in patients with trochlea dysplasia. There is a significant positive correlation between the surface area of the medial epiphyseal plate, medial TPD, height of the medial condyle and capacity of the proximal trochlear groove, which can be used to evaluate the developmental stage of the trochlea in clinical practice and to guide targeted treatment of trochlear dysplasia. LEVEL OF EVIDENCE: III.

Lateral trochlear inclination measured by the transepicondylar axis holds potential for evaluating trochlear dysplasia in patients with lateral patellar dislocation.

PURPOSE: To verify that lateral trochlear inclination (LTI) measured by the transepicondylar axis can reliably be used to evaluate trochlear dysplasia (TD) on MRI and can serve as an objective indication of trochleoplasty for patients with lateral patellar dislocation (LPD). METHODS: Eighty patients with recurrent LPD and eighty healthy subjects were included. TD, posterior condylar angle (PCA), and LTI measured by the posterior condylar reference line (LTIp), surgical transepicondylar axis (LTIs), and anatomical transepicondylar axis (LTIa) were assessed on MRI. The intraclass correlation coefficient (ICC) and Bland-Altman analysis were performed, the correlations and differences amongst the parameters were identified, and a binary logistic regression model was established. RESULTS: Each measurement had excellent inter- and intra-observer agreement. The LTIp, LTIs and LTIa were smaller in the study group than in the control group, with mean differences of 9.0°, 7.2° and 7.0°, respectively (P < 0.001). The PCA was larger in patients with LPD than in the control group (P < 0.001). LTIp was associated with PCA in the study group (r = - 0.41, P < 0.001). The pathological values of LTIp, LTIs and LTIa were 11.7°, 15.3° and 17.4°, respectively. LTIs and LTIa were independent risk factors for LPD, with ORs of 7.33 (95% CI [1.06-52.90], P = 0.048) and 10.29 (95% CI [1.38-76.96], P = 0.023), respectively. CONCLUSION: The LTI can be reliably measured by MRI, but LTIp could potentially decrease the recorded value from the actual inclination angle. LTIs and LTIa are more appropriate to serve as trochleoplasty indications for patients with LPD, which could help orthopedists with surgical decision-making. LEVEL OF EVIDENCE: Level III.

Distal femoral torsion is correlated with higher-grade trochlear dysplasia and shorter anterior condyles in patients with patellar dislocation and increased femoral torsion.

PURPOSE: To describe the characteristics of femoral torsion in patients with different segmental torsion types and to evaluate the correlations between segmental torsion and the morphology of the femoral condyles and trochlea in patients with patellar dislocation and increased femoral torsion. METHODS: Between January 2021 and March 2023, 69 patients were included and classified into two groups according to the femoral segment contributing the most to total torsion: 32 patients in Group A (femoral neck and shaft torsion) and 37 patients in Group B (distal torsion). Trochlear dysplasia was evaluated using Dejour's classification and sulcus angle. The morphology of the femoral condyles was evaluated using the lengths and ratios of the medial and lateral condyles. Correlations between femoral torsion and morphology were evaluated. RESULTS: Total torsion was significantly correlated with femoral neck and shaft torsion (r = 0.882, P < 0.001) and distal torsion (r = 0.262, P = 0.030). Femoral neck and shaft torsion was significantly increased with increasing total torsion. The trochlear sulcus was flatter and more dysplastic, and the anterior condyles were shorter in Group B. Distal torsion was significantly correlated with the lengths of the medial and lateral anterior condyles (r = - 0.567, P < 0.001; r = -0.701, P < 0.001), sulcus angle (r = 0.611, P < 0.001) and Dejour trochlea type (r = 0.512, P = 0.001), while femoral neck and shaft torsion showed no correlations. CONCLUSION: Femoral torsion is a complex of femoral neck and shaft torsion and distal torsion, especially femoral neck and shaft torsion. Distal torsion was significantly correlated with a flatter trochlear sulcus, higher-grade trochlear dysplasia, and shorter anterior condyles. The new findings highlighted the importance of the segmental evaluation of femoral torsion, which would facilitate understanding of the anatomical characteristics of femoral torsion in patients with patellar dislocation and increased femoral torsion and may lead to improvement in the surgical options regarding femoral torsion. LEVEL OF EVIDENCE: Level III.

Two-type classification system for femoral trochlear dysplasia in recurrent patellar instability based on three-dimensional morphology.

PURPOSE: Radiographic and two-dimensional (2D) CT/MRI analysis of femoral trochlear dysplasia play a significant role in surgical decision-making for recurrent patellar instability. However, the three-dimensional morphology of dysplastic trochlea is rarely studied due to the limitations of conventional imaging modalities. This study aimed to (1) develop a 3D morphological classification for trochlear dysplasia based on the concavity of the trochlear groove and (2) analyze the interrater reliability of the classification system. METHODS: The 3D trochleae of 132 knees with trochlear dysplasia and recurrent patellar instability were reconstructed using CT scan data and classified using the innovative classification criteria between January 2016 and June 2020. A concave trochlear sulcus with sloped medial and lateral trochlear facets was classified as Type I trochlea. The trochlear groove with no concavity is classified as Type II. Furthermore, in Type II, the trochlea with the elevated trochlear floor at the proximal part was identified as IIa and the trochlea with the hypoplastic trochlear facets as IIb. The intra- and inter-rater reliability was examined using kappa (κ) statistics. RESULTS: The 3D classification system showed substantial intra-rater agreement and moderate interrater agreement (0.581 ~ 0.772). The intra- and interrater agreement of Dejour's four-grade classification was fair-to-moderate (0.332 ~ 0.633). Eighty-one trochleae with concave trochlear sulcus were classified as Type I, and fifty-one without concavity as Type II. Twenty-five non-concave trochleae were classified as type IIa due to the elevated trochlear floor and 26 trochleae into IIb with the hypoplasia of trochlear facets. CONCLUSION: This study developed a 3D classification system to classify trochlear dysplasia according to trochlear concavity and morphology of the trochlear facets. On CT/MRI scans or 3D reconstructions, the interpretation of features of dysplastic trochleae may vary, especially for the flat and convex trochleae. The novel system provides morphological evidence for when to consider trochleoplasty according to the different types of trochlear sulcus.

Derotational distal femur osteotomy combined with medial patellofemoral ligament reconstruction yields satisfactory results in recurrent patellar dislocation with excessive femoral anteversion angle and trochlear dysplasia.

PURPOSE: The purpose of this study was to evaluate the clinical outcomes of medial patellofemoral ligament (MPFL) reconstruction combined with derotational distal femur osteotomy in patients with recurrent patellar dislocation who had excessive femoral anteversion angle and trochlear dysplasia. METHODS: Between 2015 and 2020, 64 patients (64 knees) with recurrent patellar dislocation, who had excessive femoral anteversion angle (≥ 25°) and trochlear dysplasia and were surgically treated using derotational distal femur osteotomy and MPFL reconstruction, were eligible for this retrospective study. These patients were assigned to two groups according to the grade of trochlear dysplasia. Group A (type A trochlear dysplasia, n = 33) and Group B (type B, C, D trochlear dysplasia, n = 31). Preoperative and postoperative patellar tilt angle (PTA), Caton-Deschamps index (CD-I), tibial tubercle-trochlear groove (TT-TG) distance and femoral anteversion angle were evaluated. Patient outcomes were assessed using the preoperative and postoperative International Knee Documentation Committee (IKDC) score, Kujala score, Lysholm score, Tegner score, and visual analog scale (VAS) score. RESULTS: A total of 64 patients (64 knees) were evaluated in this study, with a mean follow-up period of 28.4 ± 3.6 months. There were no cases of wound infection, osteotomy site fractures, deep venous thrombosis of the lower extremities, or re-dislocation in the two groups during the postoperative follow-up period. All patients returned to full extension and flexion. The postoperative Tegner score, Lysholm score, Kujala score, IKDC score, VAS score, PTA, CD-I, TT-TG distance, and femoral anteversion angle were significantly improved compared with the preoperative status (P < 0.05). There was no significant difference between the two groups (n.s.). CONCLUSION: MPFL reconstruction combined with derotational distal femur osteotomy showed satisfactory clinical outcomes during follow-up in patients with recurrent patellar dislocation who had excessive femoral anteversion angle and trochlear dysplasia. Even patients with high-grade trochlear dysplasia showed satisfactory results. For those patients, additional surgery is not necessary. LEVEL OF EVIDENCE: Level III.

Functional outcomes after Medial Patellofemoral Ligament Reconstruction show inverted J-shaped relation with Body Mass Index.

PURPOSE: Medial patellofemoral ligament reconstruction (MPFL-R) is a recognised surgical procedure for the treatment of recurrent patellofemoral instability with excellent outcomes reported. The aim of this study is to determine if body mass index can influence these outcomes. METHODS: This is a single-centre retrospective analysis of a longitudinal patellofemoral database. Patients with recurrent patellar instability, without patellar alta or severe trochlear dysplasia were treated using a MPFL-R between 2015 and 2019 at The Robert Jones & Agnes Hunt Orthopaedic Hospital. The clinical efficacy following surgery was assessed by Kujula, International Knee Documentation Committee Score (IKDC), and EuroQol-5 score (EQ-5D) at baseline and up to 26 months post-operatively; their safety assessed by complication rate and requirement for further surgery. The effect of Body Mass Index (BMI) on clinical outcome was analysed using linear, curvilinear, and segmented models following propensity score weighting. RESULTS: A total of 97 patients (97 Knees, mean age 25y) were analysed. Of these, 61 patients had a BMI < 30 kg/m2 (mean age 23y, mean BMI 24) of which 7 patients (12.3%) required additional surgery. A further 36 patients had a BMI > 30 kg/m2 (mean age 27y, mean BMI 36) of which 2 patients (5.6%) required additional surgery. The re-dislocation rate was 0% in each BMI group. Both groups had a significantly improved mean outcome following surgery, with improvements in mean IKDC above the minimum clinical important differences (MCID) of 20.5. BMI had an inverted J-shaped association with functional outcome, showing peak outcomes at BMI of 20.5 (95% CI 18.5 to 22.4; IKDC and Kujala) or BMI of 28 (EQ-5D index). No evidence for an association between BMI and complication risk was found. CONCLUSION: BMI influences the functional outcomes in MPFL-R with an inverted J-shaped relation, without evidence it affected the complication or re-dislocation rate. In the absence of patella alta and severe trochlear dysplasia, an isolated MPFL reconstruction is a safe and effective procedure to treat patellar instability, with the best functional outcome in patients with a BMI around 20 to 21. LEVEL OF EVIDENCE: Level III.

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

PURPOSE: 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. METHODS: 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. RESULTS: The mean age of 32 patients was 14.6 ± 2.3 years. 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. CONCLUSION: 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 factor without any significant differences between the index knee compared to the contralateral knee. LEVEL OF EVIDENCE: Level III.

Low re-dislocation rate following Bereiter trochleoplasty for recurrent patellar instability with severe trochlear dysplasia.

PURPOSE: Trochlear dysplasia is an independent risk factor for recurrent patellar instability with evidence demonstrating its presence in up to 85% of patients with patellar instability. Severe trochlear dysplasia can be treated with trochleoplasty to improve engagement of the patella in the trochlear groove and prevent future dislocations. The aim of this study was to determine the clinical outcome of Bereiter trochleoplasty in patients with recurrent patellar instability and severe trochlear dysplasia. METHODS: This was a retrospective case series of all trochleoplasties performed in our institution from 2008-2019. All clinical records and pre-operative MRI scans were reviewed to assess for trochlear dysplasia, tibial tuberosity to trochlear groove distance (TTTG) and patella height using patella trochlear index (PTI). Trochlear dysplasia was classified using Dejour classification. Incidence of re-dislocation, infection, arthrofibrosis, chondral necrosis and re-operation were recorded. All patients were invited to complete a post-operative visual analog score for pain (VAS-P) and Banff Patella Instability Instrument (BPII). RESULTS: Fifty-eight trochleoplasties were performed in fifty patients during this period. All trochleoplasties were combined with additional procedures. 93% had concomitant medial patellofemoral ligament (MPFL) reconstructions and 47% had tibial tuberosity transfer. The mean follow-up period was 36.8 months. The rate of dislocation and arthrofibrosis were 5% each. There were no chondral necrosis or nonunion. The mean post-operative BPII was 58.4 and VAS-P was 30.4. CONCLUSIONS: Bereiter trochleoplasty, often combined with MPFL reconstruction and/or tibial tuberosity transfer results in low re-dislocation and complication rate. LEVEL OF EVIDENCE: IV.

What is the relationship between the breech presentation and femoral trochlear dysplasia? An experimental study of the breech presentation model in neonatal rats.

BACKGROUND: The relationship between breech presentation and trochlear dysplasia has been confirmed. However, the pathological process of breech-related trochlear dysplasia remains unclear. This study aimed to establish an animal model to simulate breech presentation and to analyze the pathological process of the femoral trochlea. MATERIALS AND METHODS: One hundred and twenty neonatal rats were randomly assigned into a control group and two experimental groups that were swaddled (using surgical tape) to keep the hip flexed and knees extended to simulate human breech presentation for the 5 days (short Swaddling) and the 10 days (prolonged Swaddling) of life. Gross and cross-sectional observation, histological staining measurement in two experimental time points (5 and 10 days after birth) were conducted to evaluate the morphological changes of the femoral trochlea. RESULTS: The incidence of trochlear dysplasia increased with the Swaddling time. Rats in the prolonged Swaddling group had the high prevalence of trochlea dysplasia (52 of 60), followed by short Swaddling group (42 of 60). Gross and cross-sectional observation showed a shallower trochlea groove in two experimental groups. Histologicalstaining measurement indicated that the trochlear sulcus angle and trochlear sulcus depth were significantly different between the experimental group and the control group since day 5 and day 10. CONCLUSION: In this model, breech presentation had an adverse effect on neonatal knees and could induce trochlear dysplasia. In addition, this study also showed that the more time in breech presentation, the more incidence of trochlear dysplasia.