Evaluation of trochlear dysplasia in dogs with medial patellar luxation: comparative studies

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.

Algunas consideraciones sobre la trocleoplastia del fémur / Some considerations on the trochleoplasty of distal femur

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.

Clinics in diagnostic imaging (185)

A 20-year-old National Serviceman presented with left knee pain and swelling after training for his physical fitness test. Lateral knee radiography and magnetic resonance (MR) imaging showed patellar tendon-lateral femoral condyle friction syndrome (PT-LFCFS), on a background of patella alta and patellar malalignment. The patient was treated non-operatively with a course of physiotherapy and given advice on rest and activity modification. PT-LFCFS is a less well-recognised but important cause of anterior knee pain and represents an entity in a spectrum of disorders related to patellofemoral instability. We herein discuss the MR imaging findings specific to and associated with this condition, as well as briefly describing treatment options. In addition, we showcase a range of commonly encountered abnormalities that affect the infrapatellar fat pad and briefly discuss their specific MR imaging findings.

Measurement and evaluation of anatomic risk factors for recurrent patellar instability by MRI / 实用放射学杂志

Objective To identify related anatomical parameters and the strongest risk predictor leading to patients with recurrent patellar instability.Methods 52 young patients with recurrent patellar instability that failed of conservative treatment were retrospec-tively evaluated by MRI.Measurements included parameters of patellar tracking,which was characterized by bisect offset index (BSO),trochlear congruence angle (CA)and patellar lateral tilt (PTA),and anatomical parameters of patellofemoral joint,which were characterized by the sulcus angle (SA),lateral trochlear inclination (LTI),trochlear facet asymmetry,trochlear depth,Insall-Salvati Ratio (ISR),Caton-Deschamps index (C-D)and tibial tuberosity-trochlear groove (TT-TG)distance.The collection data were analyzed including the Pearson's correlation and multiple stepwise regression analysis.Results The patellofemoral joint ma-lalignment was significantly correlated with LTI,TT-TG distance and ISR,but not or partly with the trochlear depth,SA,trochlear facet asymmetry and C-D.Linear regression models including LTI,TT-TG distance and ISR explained 0.58,0.47 and 0.43 of the va-riance in BSO,CA and PTA,respectively (P<0.001).And the standardized beta coefficient was largest for LTI,then were TT-TG distance and ISR.Conclusion At full extension of the knee,anatomical related factors measured on MRI explain some degree of re-current lateral patella shift and tilt,the strongest predictor among anatomical related factors that could lead to maltracking is LTI, and then are TT-TG distance and ISR.

The Evaluation of Femoral Trochlear Dysplasia Using Imaging Analysis System Based on Three-Dimension Computed Tomography / 中国运动医学杂志

Objective To evaluate the application of imaging analysis system based on three-dimension computed tomography (3D-CT)for the diagnosis of femoral trochlear dysplasia.Methods Between May 2013 and January 2014,30 patients were diagnosed as recurrent patella dislocation and received surgical treatment.All the patients received 3D-CT diagnosis of the knee joints preoperatively,and the data of 3D-CT were transferred to imaging analysis system with MIMICS software that would be used to get the trochlear dysplasia index.The patients were also received knee fluoroscopic detection.A true lateral view was also used for evaluation of the trochlear dysplasia as the classic method.The difference between the two methods was compared.And the sensitivity,specificity,positive and negative predictive value of the imaging analysis system were analyzed.Results The mean trochlear dysplasia index was 5.3 ± 1.8 mm (3.2 to 8.4 mm)using the classic fluoroscopic method,showing no significant difference from the result according to the imaging analysis system,5.2 ± 1.5 mm (3.5 to 8.1 mm).When the fluoroscopic method was set as the golden standard,the sensitivity,specificity,positive and negative predictive value of the imaging analysis system were 89.5％,81.8％,89.4％ and 82.0％ respectively.Conclusion The imaging analysis system based on 3D-CT of knee joints could provide acceptable results without good sensitivity and specificity,without significant differences from the classic fluoroscopic method.So it is a more safer and easier approach worthy of clinical implication.

Clinics in diagnostic imaging (163). Transient lateral patellar dislocation with trochlear dysplasia

A 14-year-old girl presented with left knee pain and swelling after an injury. Magnetic resonance (MR) imaging showed a transient lateral patellar dislocation with patellar osteochondral fracture, medial patellofemoral ligament tear and underlying femoral trochlear dysplasia. Open reduction and internal fixation of the osteochondral fracture, plication of the medial patellar retinaculum and lateral release were performed. As lateral patellar dislocation is often clinically unsuspected, an understanding of its characteristic imaging features is important in making the diagnosis. Knowledge of the various predisposing factors for patellar instability may also influence the choice of surgical management. We also discuss signs of acute injury and chronic instability observed on MR imaging, and the imaging features of anatomical variants that predispose an individual to lateral patellar dislocation. Treatment options and postsurgical imaging appearances are also briefly described.

Estudio de imágenes de articulación patelofemoral: ¿en qué estamos?: [revisión] / Imaging studies of the patellofemoral joint: current reality: [review]

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.