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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.

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The aim of this study was to present a novel surgical method for correction of medial patellar luxation in small-breed dogs with trochlear dysplasia and marked hypoplasia of the medial femoral condyle. The "Watermelon" approach was applied together with trochlear wedge recession or trochlear block recession and consisted in increasing the height of the medial condyle with an osteochondral autograft resembling a watermelon slice, placed into an additional slot in the medial femoral condyle to prevent the postoperative reluxation of the patella. The study cohort included 19 dogs (25 joints) from small breeds (Pinscher, Pomeranian, and Chihuahua) with second-grade medial patellar luxation. Fourteen joints were submitted to wedge recession surgery combined with "Watermelon" grafting, and 11 joints: to block recession surgery with "Watermelon" grafting. The sulcus-deepening trochleoplasty combined with "Watermelon" grafting was clinically successful and with low percentage of minor postoperative complications. The mean duration of anesthesia was significantly longer for block recession combined with "Watermelon" (P<0.001), but the recovery period was shorter (P<0.05).

O objetivo deste estudo foi apresentar um novo método cirúrgico para correção da luxação patelar medial em cães de raça pequena com displasia troquelar e hipoplasia marcada do côndilo femoral medial. A abordagem "Melancia" foi aplicada juntamente com a recessão da cunha trocolear ou recessão do bloco trocolear e consistiu em aumentar a altura do côndilo medial com um auto-enxerto osteocondral parecido com uma fatia de melancia, colocado em uma fenda adicional no côndilo femoral medial para evitar o relaxamento pós-operatório da patela. A coorte do estudo incluiu 19 cães (25 juntas) de raças pequenas (Pinscher, Pomeranian, e Chihuahua) com luxação patelar medial de segundo grau. Catorze juntas foram submetidas à cirurgia de recessão em cunha combinada com enxerto de "melancia", e 11 juntas: para bloquear a cirurgia de recessão com enxerto de "melancia". A trocleoplastia de "melancia" combinada com o enxerto de "melancia" foi clinicamente bem sucedida e com baixo percentual de pequenas complicações pós-operatórias. A duração média da anestesia foi significativamente maior para a recessão em bloco combinada com "Melancia" (P<0,001), mas o período de recuperação foi mais curto (P<0,05).

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BACKGROUND: Lateral patellar dislocation can become a recurrent problem after the first episode. Identifying those patients who are at increased risk of redislocation is important for the treatment decision-making process. PURPOSE: To identify clinical and radiologic risk factors for recurrence of patellar dislocation after a first episode. STUDY DESIGN: Case-control study; Level of evidence, 3. METHODS: The study included patients with lateral patellar dislocation and a 1-year minimum follow-up who were seen between 2011 and 2018. Patients aged 10 to 65 years were included. Patient characteristics, physical examination (patellar apprehension, J sign), and radiographs were reviewed. The Caton-Deschamps and Insall-Salvati ratios were used to evaluate patella alta. High-grade trochlear dysplasia was defined as Dejour types B, C, and D. RESULTS: A total of 130 patients (139 knees) with primary lateral patellar dislocation were included. Recurrent dislocation was seen in 83 knees (59.71%). Stepwise logistic regression analysis demonstrated that Caton-Deschamps ratio ≥1.15 (OR, 2.39; 95% CI, 1.09-5.22; P = .029), age <21 years (OR, 2.53; 95% CI, 1.11-5.77; P = .027), and high-grade trochlear dysplasia (OR, 4.17; 95% CI, 1.90-9.17; P < .001) were significantly associated with patellar redislocation. Based on the presence of these factors, the probability of dislocation after a first lateral patellar dislocation was 31.2% with no factors present, 36.6% with any 1 factor present, 71.7% with any 2 factors present, and 86.2% if all 3 conditions were present. CONCLUSION: The results of this study indicated that patella alta, high-grade trochlear dysplasia, and age <21 years were independent risk factors for patellar redislocation after a first episode, with an additive effect when they were present together. This may help to guide the type of treatment for these patients.

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Medial patellar luxation (MPL) is one of the commonest orthopaedic diseases in small dog breeds. Although the bone deformities associated with canine medial patellar luxation are described in numerous studies, the pathogenesis of the condition is still disputable. What is more, there is no categorical evidence that luxation of the patella is associated to a shallow trochlear groove as no objective method for determination of trochlear depth and shape has been proposed. The aim of the present study was to evaluate the depth and shape of femoral trochlear groove on radiographs obtained from healthy dogs and dogs affected with grade II and grade III MPL. A total of 45 dogs (33 with MPL and 12 healthy) from 4 small breeds (Mini-Pinscher, Pomeranian, Chihuahua and Yorkshire terrier) were included in the study. After deep sedation, stifle radiographs were obtained in tangential projection (skyline view). The dogs were positioned in ventral recumbency, the examined stifle bent as much as possible, and the central beam focused on the patella between femoral condyles. Six morphometric parameters associated with the onset of trochlear dysplasia similar to those used in human medicine were measured: trochlear sulcus angle (SA), lateral and medial trochlear inclination angles (LTI; MTI), trochlear groove depth (TD), patellar thickness (PaT) and the ratio between trochlear depth and patellar thickness (PaT/TD). The non-parametric Mann-Whitney test was used for evaluation of differences between healthy joints and those affected with grade II and III MPL. The association between measured variables was evaluated via the Spearman's rank-order correlation. TD was greater in healthy joints as compared to those affected with MPL grade II and III (P < 0.001). In healthy stifles, PaT value exceeded significantly (P < 0.01) that in joints with grade III MPL. The TD/PaT ratio was significantly greater in healthy joints vs both those with grade II (P < 0.01) and grade III MPL (P < 0.001). In healthy joints, there was a significant negative relationship (rho­0.508; P = 0.0113) between SA and TD: smaller sulcus angles corresponded to deeper trochleas. This correlation was even stronger in joints with patellar luxation (rho ­0.723; P < 0.0001). The LTI and MTI showed a very strong positive correlation in healthy joints (rho 0.854; P < 0.0001) and at the same time, lack of significant association in joints affected with MPL (rho -0.163; P = 0.327 for grade II MPL and rho 0.175; P = 0.448 for grade III MPL) was demonstrated. The altered trochlear shape and depth were more pronounced in joints with grade III MPL. As MPL grade increased, the SA became statistically significantly greater. In grade III MPL it was accompanied with considerably reduced trochlear depth, medial trochlear inclination angle and trochlear depth/patellar thickness ratio. Five of the measured morphometric parameters for radiographic detection of trochlear dysplasia in dogs were found to be important in the evaluation of trochlear morphology in dogs. The obtained results indicated the presence of trochlear dysplasia in dogs with MPL. A 3-stage classification system for assessment of abnormal trochlear development in small dog breeds: mild; moderate and severe trochlear dysplasia, was proposed. The occurrence of shallow trochlear groove and medial femoral condyle's hypoplasia could be accepted as signs of mild and moderate trochlear dysplasia. The pre-operative measurements of these parameters could improve surgical planning and decisions-making.

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La mala alineación patelofemoral tiene múltiples causas anatómicas y una de ellas es la displasia de la tróclea del fémur distal, por lo cual su tratamiento depende de varios factores. Para profundizar en los elementos esenciales de la técnica de trocleoplastia, se realizó una revisión bibliográfica exhaustiva donde se analizaron algunos aspectos de interés, a saber: clasificación más empleada para las displasias de la tróclea, elementos imagenológicos más importantes, indicaciones de la técnica quirúrgica, contraindicaciones, principales modalidades de trocleoplastia y vías de acceso quirúrgico. Se concluyó que este es un proceder con indicaciones muy específicas y puede realizarse mediante cirugía abierta o por vía artroscópica.

The poor patellofemoral alignment has multiple anatomical causes and one of them is the dysplasia of the distal femur trochlea, reason why its treatment depends on several factors. To deepen in the essential elements of the trochleoplasty technique, an exhaustive literature review was carried out where some aspects of interest were analyzed, that is: most used classification for the trochlear dysplasias, most important imagenologic elements, indications of the surgical technique, contraindications, main modalities of trochleoplasty and surgical approaches. It was concluded that this is a procedure with very specific indications and can be carried out by means of open surgery or arthroscopic way.

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PURPOSE: The purpose of the study was to investigate the theoretical isometric point based of the curve of the femoral groove and relating it to the origin of the MPFL femoral tunnel on lateral radiograph by comparing a patellar instability cohort with a control cohort. METHODS: From a Patellar Instability database the radiographs of 40 consecutive patients were analysed to define Schöttle's point, and the arc of the circle of the trochlear groove. A comparison population of 20 radiographs from comparable patients with tibiofemoral joint disorders was used as a control. The distance from Schöttle's point to the most anterior part of the groove (extension) was also compared to the distance to the distal end of the roof of the notch (flexion). RESULTS: The trochlea was circular in the controls but not the Patellofemoral Instability cohort where trochlear dysplasia is usually present. The difference between the extension and flexion length was a mean of - 2.0 ± 0.5 mm in the controls and + 6.0 ± 0.5 mm in the patellofemoral cohort. In neither cohort did the centre of the circle correspond to Schöttle's point. The extension distance correlated with the boss height. CONCLUSIONS: The dysplastic trochlea is not circular and the centre of the best matched circle was different to the control trochleae which were circular. The circle centres did not correlate with Schöttle's point for either cohort, and was more proximal in the Patellofemoral Instability cohort. CLINICAL RELEVANCE: For the MPFL to have equal tension throughout flexion within the groove, the length should not change. In normal knees the MPFL does not behave isometrically. The change in length, as measured from Schöttle's point to the trochlea, was greater for patellofemoral instability patients explaining why an isolated MPFL reconstruction in the presence of severe trochlear dysplasia risks poor outcomes. Level of evidence III.

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La disfunción patelofemoral (DPF) es causa frecuente de consulta clínica y se refiere, a grandes rasgos, a una patología en la cual la patela falla en la correcta entrada en la tróclea. Es un tema en el que la terminología suele ser ambigua y confusa, debido entre otras cosas a la discrepancia entre la clínica y la imaginología. Además, la etiología de la DPF es multifactorial, incluyendo factores anatómicos locales, rotacionales y dinámicos, no existiendo tampoco claridad acerca de su real influencia. Desde el punto de vista imaginológico, existen innumerables publicaciones, con diferentes clasificaciones y mediciones descritas para las distintas técnicas, sin embargo, no hay un consenso amplio en relación a cuáles son las alteraciones anatómicas o los valores normales que el reporte imaginológico debiera incluir. Se realiza una revisión de la literatura existente y se propone para los pacientes con DPF, un estudio radiológico que considera los factores etiológicos anatómicos y un estudio tomográfico de segunda línea, que incluye estudio rotacional de extremidades inferiores, sistematizando las mediciones y puntos relevantes en una plantilla de informe.

Patellofemoral dysfunction (PFD) is a common cause for medical consultation and in a broad sense it refers to a condition in which the patella fails to engage securely in the trochlear groove. This is a topic in which terminology is often ambiguous and confusing due, inter alia, to the discrepancy between symptomatology, imaging findings and physical examination. In addition, PFD has a multifactorial etiology that includes local anatomical, rotational and dynamic factors, with no certainty about its real influence. From the imaging point of view, there are countless publications proposing different classifications and measurements obtained trough different imaging techniques; however, there is no consensus regarding what are the anatomical alterations or the normal values that imaging reports should include. A review of the existing literature is performed and we propose that patients with PFD should undergo both a radiological study comprising etiologic and anatomic factors and a second-line tomographic exploration including lower extremity rotational profiles. From the radiological and clinical viewpoints, relevant issues to be considered as well as assessments performed should be systematized and recorded in a report sheet.

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