Direct impact to the front of the knee from a fall or other blow is a common cause of tears. {"url":"/signup-modal-props.json?lang=us"}, Shetty A, Saber M, Rasuli B, et al. government site. A tight lateral retinaculum can tilt the patella leading to increased pressure on the lateral facet causing pain (Ficat). The convex articular surface of the patella places it at risk for chondral injury in either the dislocation or the reduction phases of injury. It has been shown that there is an association between edema at the superolateral aspect of Hoffas fat pad and a number of patellar maltracking parameters [30, 54, 55]. Patients with patella alta may also benefit from tibial tuberosity advancement. Am J Sports Med 45:10121017, Pedersen ME, DaCambra MP, Jibri Z, Dhillon S, Jen H, Jomha NM (2015) Acute osteochondral fractures in the lower extremities - approach to identification and treatment. Oper Tech Sports Med 6:247258, Dejour H, Walch G, Nove-Josserand L, Guier C (1994) Factors of patellar instability: an anatomic radiographic study. Because the diagnosis of lateral patellar dislocation is often unsuspected, MR provides valuable diagnostic information in such cases. The axial proton density-weighted image reveals a large osteochondral shearing injury involving the mid to medial patella (arrowheads). 7,14 While plain radiography is an important tool to diagnose APD, magnetic resonance imaging (MRI . When the knee moves slightly out of place or becomes tilted in the joint, it can cause tension and pain in the lateral retinaculum. volume10, Articlenumber:65 (2019) Although you may feel that being asked to make the specific diagnosis of lateral patellar dislocation from a single image is unrealistic, the coronal view in fact reveals a classic and highly characteristic appearance, allowing the diagnosis to be made with confidence. 3). At 0 extension, the patellar may lie completely above the level of the trochlea, without direct apposition between the two articular surfaces. Figure 1: ligaments (Gray's illustrations), View Pereshin Moodaley's current disclosures, see full revision history and disclosures, posterior suprapatellar (prefemoral or supratrochlear) fat pad, anterior suprapatellar (quadriceps) fat pad, accessory anterior inferior tibiofibular ligament, superficial posterior tibiotalar ligament, superficial posterior compartment of the leg (calf), accessory extensor digiti secundus muscle, descending branch of the lateral circumflex. This injury has been described in conjunction with numerous sports activities, particularly snow skiing. Division of Sports Trauma, Department of Orthopaedics, Aarhus University Hospital, Aarhus, Denmark. Injury. Of course, if medial soft tissue restraints are disrupted at the first dislocation, the loss of such restraints makes future dislocations more likely. Medial retinacular complex injury in acute patellar dislocation: MR findings and surgical implications. Would you like email updates of new search results? Surgical management procedures can broadly be categorized as soft tissue procedures (lateral release, medial imbrication, and MPFL repair or reconstruction) and bony procedures (tibial tubercle transfer procedures and trochleoplasty). Concave impaction deformity of the inferomedial patella is a specific sign of prior LPD. PubMedGoogle Scholar. A trochlear depth of < 3mm indicates dysplasia. The conditions are presented anatomicallyanterior, lateral, medial, or posteriorwith common etiologies, history and physical exam findings, and diagnosis and treatment options for each (see Table, page 28). A typical bone bruise is seen within the anterolateral aspect of the lateral femoral condyle (asterisk). Pedersen ME, DaCambra MP, Jibri Z, Dhillon S, Jen H, Jomha NM. AJR Am J Roentgenol 167:339341, Caton JH, Dejour D (2010) Tibial tubercle osteotomy in patello-femoral instability and in patellar height abnormality. The patella articulates with the trochlear groove of the anterior femur, which has corresponding lateral and medial patellar articular surfaces [6]. Migliorini F, Marsilio E, Cuozzo F, Oliva F, Eschweiler J, Hildebrand F, Maffulli N. Life (Basel). These parameters can be evaluated using dynamic MRI [29]. Surgical management of patellar instability should be guided on an individual patient basis depending on history, physical examination, and radiologic findings as outlined above. Guidelines and Gamuts in Musculoskeletal Ultrasound. Acute traumatic instability most commonly occurs in young athletes in their second and third decade at an incidence rate of 29 per 100,000. (1a) A single fat-suppressed proton density-weighted coronal image. 7). The most accepted indication for surgical management of patellar instability is the presence of a large displaced osteochondral fracture or loose body. The vastus medialis oblique (VMO) provides active stability of the patella. CAS Chronic fat impingement can result in chronic inflammation and fat pad hypertrophy. Radiology 187:205212, Jibri Z, Martin D, Mansour R, Kamath S (2012) The association of infrapatellar fat pad oedema with patellar maltracking: a case-control study. The TT-TG index is the TTTG/TT-TE ratio [44]. Both knees are scanned simultaneously. 2010 Aug;36(4):353-60. doi: 10.1007/s00068-010-9165-2. Excessive lateralization of the tibial tuberosity allows the patella to be pulled laterally in flexion and is considered to be a risk factor for instability. Falls. Patellar maltracking: an update on the diagnosis and treatment strategies. Complete disruption and avulsion are seen as discontinuity of ligament fibers with associated edema [50]. Skeletal Radiol 48:387393, Schoettle PB, Zanetti M, Seifert B, Pfirrmann CW, Fucentese SF, Romero J (2006) The tibial tuberosity-trochlear groove distance; a comparative study between CT and MRI scanning. Am J Sports Med. Google Scholar, Pfirrmann CW, Zanetti M, Romero J, Hodler J (2000) Femoral trochlear dysplasia: MR findings. The natural history. 5 a-d). Isacsson A, Olsson O, Englund M, Frobell RB. Various parameters can be used in assessing and predicting the presence of patellar maltracking. 5 Carrillon Y, Abidi H, Dejour D, et al. 1993;161(1):109-13. The anatomic relationship between the resultant force from the quadriceps and the line of pull of the patellar tendon is termed the Q angle and is normally 1015 of valgus [11]. Additionally, return to sport can be as low as 45%, leaving many patients searching for further management options [12]. Methods: We compared 361 treated cases of aneurysm occlusion after subarachnoid hemorrhage from 1997 to 2003 with 281 cases from 2006 to 2014. MRI plays a crucial role in quantification and characterization of these predisposing anatomic variations which are key to addressing the patient?s patellar instability operatively. The injuries involved the medial retinacular ligament in 16 of 17 patients and the medial and lateral retinacular ligament in one patient. This can provide a road map of developing a treatment strategy that would be primarily aimed at stabilizing the patellofemoral joint and halt the progression of cartilage loss. Operative lateral retinaculum release is indicated in refractory cases. A ratio equal or more than 1.2 indicates patella alta [35] (Fig. Abnormalities of the medial retinaculum and MPFL are seen in 82-100% of MRI examinations following patellar dislocation. Federal government websites often end in .gov or .mil. Subjective: Pain and tenderness on structure (lateral side of patella) (Juhn). et al. (7a) A coronal T1-weighted image at the level of the patella demonstrates blending of fibers of the VMO with the MPFL superiorly. Structures such as the iliotibial band, fibular collateral ligament, and biceps femoris tendon are readily apparent on MRI and are easy to identify. Most, however, agree regarding the importance of the MPFL and its role as the strongest restraint to lateral patellar displacement. Bookshelf Infrapatellar (Hoffas) fat pad impingement is recognized as a cause of anterior knee pain. (21a) A corresponding anterior coronal slice reveals the large displaced osteochondral fragment (arrow) that occurred as a result of this injury. Correspondingly, the patella must shift slightly medially during early flexion to engage the trochlear groove. A commonly used one is the InsallSalvati ratio of patellar tendon length: patellar length. Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. 2023 Apr;47(4):973-981. doi: 10.1007/s00264-023-05707-y. Osteochondral fractures are common in acute or recurrent transient lateral patellar dislocation, seen in up to 70% of cases. Acute lateral patellar dislocation at MR imaging: injury patterns of medial patellar soft-tissue restraints and osteochondral injuries of the inferomedial patella Injury to the medial retinaculum, MPFL, and VMO may be identified at MR imaging after acute LPD. The marrow edema and medial patellofemoral ligament (MPFL) injury pattern above are virtually pathognomonic of a transient lateral patellar dislocation, as little else will cause such an appearance. The above video demonstrates the mechanism of injury in patellar dislocation. Risk factors for recurrent instability include female sex, family history of patellar instability, and various anatomic risk factors such as patella alta, increased femoral anteversion, external tibial rotation, genu valgum, trochlear dysplasia, increased tibial tubercletrochlear groove (TT-TG) distance, and patellar tilt [13, 21,22,23]. The two features are associated with patellar maltracking. 3.1 ). For first-time dislocators without intra-articular loose bodies or chondral injury, a trial of nonoperative therapy is indicated. In effect all three medial layers of the knee thus comprise the medial retinaculum, which is by itself not a discrete, single structure. Both MRI and ultrasound are accurate imaging modalities in the detection of MPFL injuries [5, 50, 51]. The medial patellofemoral ligament (MPFL) is a condensation of the medial capsule of the knee joint. (12a) At an axial image 3 cm proximal to the femoral-tibial joint space, the lengths of the medial and lateral trochlear facets are obtained. To provide the highest quality clinical and technology services to customers and patients, in the spirit of continuous improvement and innovation. Eur J Trauma Emerg Surg. PubMed Central The anatomy of the medial patellofemoral ligament. The most common trochleoplasty procedure described is a combination of lateral trochlear osteotomy and bone graft to heighten the lateral trochlea. TT-TG assessment has its own limitations. As with the anatomy, there is considerable variability in both the surgical and radiology literature regarding the location of soft tissue injuries in patients following patellar dislocation. Less common predisposing factors to be aware of include laterally tilted patella, VMO dysplasia and generalized joint laxity. {"url":"/signup-modal-props.json?lang=us"}, Moodaley P, Hng J, Hacking C, et al. 2002 Dec;225(3):736-43. doi: 10.1148/radiol.2253011578. The deep layer of the lateral retinaculum contains thickenings that form ligaments providing stabilizing support to the patella. Knee Surg Sports Traumatol Arthrosc 14:707712, Ahmad M, Janardhan S, Amerasekera S, Nightingale P, Ashraf T, Choudhary S (2019) Reliability of patellotrochlear index in patellar height assessment on MRI-correction for variation due to change in knee flexion. Cite this article. High resolution magnetic resonance imaging of the patellar retinaculum: normal anatomy, common injury patterns . Predisposing factors to patellofemoral dislocation include patella alta, excessive lateral distance between the tibial tubercle and trochlear groove and a congenitally shallow trochlear groove5, any of which significantly increase a patients likelihood for dislocation. On the other hand, frank patellar dislocation is a significant risk factor in the development of patellofemoral osteoarthritis with an incidence of 49% at 25years after the patellar dislocation incident in comparison with 8% in a control group without a dislocation history [60]. AJR Am J Roentgenol 161:109113, Lance E, Deutsch AL, Mink JH (1993) Prior lateral patellar dislocation: MR imaging findings.
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