1993;161(1):109-13. Other structures combine to form the region referred to as the medial retinaculum (MR) more anteriorly. Sports Med Arthrosc 15:6871, Longo UG, Rizzello G, Ciuffreda M et al (2016) Elmslie-Trillat, Maquet, Fulkerson, Roux Goldthwait, and other distal realignment procedures for the management of patellar dislocation: systematic review and quantitative synthesis of the literature. A study has found that the femoral groove tends to be shallower in osteoarthritis patients compared to those with normal cartilage, regardless of age. PFA of 0 or if it opens medially (negative value) is considered abnormal indicating lateral patellar tilt [27, 48]. (3a) Graphical depictions of the mechanism of patellar dislocation: With the knee in flexion, the patella dislocated laterally. There is a degree of variability in the literature about what is considered an abnormally high TT-TG. Femoral condylar chondral injuries occur during the dislocation phase due to impaction shearing forces of the patella upon the flexed femur, typically occurring at the weightbearing surface. The patellofemoral joint has two primary functions; firstly, it acts as an anatomic pulley to provide mechanical advantage for the extensor mechanism and, secondly, to reduce friction between the extensor mechanism and the femur. The knee is a complex synovial joint that can be affected by a range of pathologies: Please Note: You can also scroll through stacks with your mouse wheel or the keyboard arrow keys. A second line is drawn parallel to a line along the posterior femoral condyles. Lateral patellar compression syndrome is the improper tracking of the patella in the trochlear groove generally caused by a tight lateral retinaculum. It is the angle between a line tangential to the subchondral bone of the posterior aspect of the femoral condyles and a line along the lateral trochlear facet. government site. 1-31. An inclination angle of less than 11 indicates trochlear dysplasia [32]. In addition, symptomatic knees may demonstrate normal engagement between the patella and trochlea beyond 30 of flexion. (17a) An axial T2 fat-suppressed image in another patient reveals a fluid filled gap (short arrow) at the site of attachment of the medial retinaculum. This injury has been described in conjunction with numerous sports activities, particularly snow skiing. (6a) A more distal T1-weighted image reveals fibers of the oblique decussation of the MPFL which blend with the medial collateral ligament (MCL). Skeletal Radiol 41:925931, Wittstein JR, Bartlett EC, Easterbrook J, Byrd JC (2006) Magnetic resonance imaging evaluation of patellofemoral malalignment. For first-time dislocators without intra-articular loose bodies or chondral injury, a trial of nonoperative therapy is indicated. The posterior articulating surface of the patella is composed of two facets, a medial and lateral facet, separated by a vertical ridge, and in 30% of the population, there is a third facet, the odd facet, most medially. Transient medial patellar dislocation: injury patterns at US and MR Bethesda, MD 20894, Web Policies Various parameters can be used in assessing and predicting the presence of patellar maltracking. The angle between the two lines is the lateral trochlear inclination (LTI). The lateral patellar retinaculum is a fibrous expansion comprising of superficial and deep layers. Diagnosis is made clinically with pain with compression of the patella and moderate lateral facet tenderness and sunrise knee radiographs will often show patellar tilt in the lateral direction. J Bone Joint Surg Am 89:17491755, PubMed (8a) A more posterior coronal T1-weighted image also demonstrates the intimate relationship of the VMO and MPFL. 2021;50(7):1399-409. Jumping. In one MRI study, 76% of cases of prior lateral patellar dislocation showed medial retinacular injury at its patellar insertion and 30% at its midsubstance, and injury of the femoral origin of the MPFL was identified in 49% of the cases [49]. What is the diagnosis? A commonly used one is the InsallSalvati ratio of patellar tendon length: patellar length. The most accepted indication for surgical management of patellar instability is the presence of a large displaced osteochondral fracture or loose body. 7 Balcarek P, Jung K, Frosch KH, Sturmer KM. The transverse stabilizers include the medial and lateral retinaculum, the vastus medialis and lateralis muscles, the ilio-tibial band, and the medial patellofemoral ligament (MPFL). Arthroscopy 22:643649, Carrillon Y, Abidi H, Dejour D, Fantino O, Moyen B, Tran-Minh VA (2000) Patellar instability: assessment on MR images by measuring the lateral trochlear inclination-initial experience. At the time the article was last revised Mohamed Saber had Infrapatellar (Hoffas) fat pad impingement is recognized as a cause of anterior knee pain. Distally, it attaches to the tibial tubercle via the patellar tendon. A focused history of the mechanism, number, and circumstances of instability to date is essential. LTI < 11 degrees indicates dysplasia. Crossref, Medline, Google Scholar; 32 Starok M, Lenchikl L, Trudell D, Resnick D. Normal patellar retinaculum: MR and sonographic imaging with cadaveric correlation. Eur Radiol 10:10511055, Stefanik JJ, Zumwalt AC, Segal NA, Lynch JA, Powers CM (2013) Association between measures of patella height, morphologic features of the trochlea, and patellofemoral joint alignment: the MOST study. Medial patellofemoral ligament injury patterns and associated pathology Part of On the other hand, the PTI is significantly altered with knee flexion [37]. Medial retinacular complex injury in acute patellar dislocation: MR Sanders T, Paruchuri N, Zlatkin M. MRI of Osteochondral Defects of the Lateral Femoral Condyle: Incidence and Pattern of Injury After Transient Lateral Dislocation of the Patella. no financial relationships to ineligible companies to disclose. Romero J, Hodler J. Radiology. Medial patellar chondral injuries may occur during either the dislocation or reduction phases of injury. PTI of less than 12.5% suggests the presence of patella alta. Nonoperative treatment is generally recommended in first time dislocators unless there are MRI findings of severe predisposing dysplasia and the presence of a chondral or osteochondral body. 4. The technique has been refined, and a better understanding of the anatomical features of both the origin and insertion of the ligament onto the patella has made the operation more reproducible (Fig. The latter distinction is important to recognize among both radiologists and surgeons. Several osteotomies have been described including the medializing ElmslieTrillat procedure, the anteromedializing Fulkerson osteotomy, and distalization osteotomy [87]. In general realignment surgery such as tibial tubercle transfer should be strongly considered in patients with TT-TG > 15mm (borderline) and typically should be performed in patients with TT-TG > 20mm. High resolution magnetic resonance imaging of the patellar retinaculum: normal anatomy, common injury patterns, and pathologies. TTTG is the distance between the solid and the dashed lines in (b). 1835 31 - 40 27 30.0 41 - 50 22 24.4 50 + 4 4.4 Total 90 100.0 Age Distribution Number Percent Sex Female 19 21.1 Male 71 78.9 Knee 13:266273. California Privacy Statement, The injury typically occurs from a twisting event with the knee in mild flexion (less than 30). 1 Pain is often described as medial because of soft tissue injuries that occur to the medial retinaculum and/or MPFL. Clipboard, Search History, and several other advanced features are temporarily unavailable. 8). Patellar tendon lateral femoral condyle friction syndrome is one of several entities that result in anterior knee pain and in which abnormalities of the patellar fat pads are found on MR imaging. VMO dysplasia may play a role in patellofemoral instability. 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). 7). Trochlear depth of less than 3 mm on MRI has a sensitivity of 100% and a specificity of 96% for trochlear dysplasia.10. Trochleoplasty is rarely performed in this country and is reserved for significant dysplasias or when other surgical options have been insufficient in restoring patellofemoral stability. Google Scholar, Amis AA, Firer P, Mountney J, Senavongse W, Thomas NP (2003) Anatomy and biomechanics of the medial patellofemoral ligament. Skeletal Radiol 38:785790, Campagna R, Pessis E, Biau DJ et al (2012) Is superolateral Hoffa fat pad edema a consequence of impingement between lateral femoral condyle and patellar ligament? Deep lacerations are often associated with this type of injury. In full extension, the patella has little to no contact with the trochlear groove and, therefore, is in a position of higher risk for instability. Diederichs G, Issever A, Scheffler S. MR Imaging of Patellar Instability: Injury Patterns and Assessment of Risk Factors. In a series of 474 patients with anterior knee pain, patellar tilt or subluxation was present in 40% of the cases on axial MRI [46]. The adductor magnus tendon (AT) attaches to the adductor tubercle, which lies posterior and superior to the femoral attachment of the MPFL. A bone bruise of the lateral femoral condyle (asterisk) and an abnormally shallow trochlear groove (red line) are also indicated. A ratio > 1.3 indicates patella alta. Magnetic Resonance Imaging Characteristics of the Medial Patellofemoral Ligament Lesion in Acute Lateral Patellar Dislocations Considering Trochlear Dysplasia, Patella Alta, and Tibial Tuberosity-Trochlear Groove Distance Kirsch M, Fitzgerald S, Friedman H, Rogers L. Transient Lateral Patellar Dislocation: Diagnosis with MR Imaging. Curr Rev Musculoskelet Med 11:253260, Article At less than 30 of flexion, asymptomatic knees may demonstrate physiologic patellar tilt or subluxation. HHS Vulnerability Disclosure, Help lateral patellar retinaculum tear or invasion. There are several different techniques described in the literature to assess patella alta and many of these are reviewed in detail in the MRI Web Clinic, August 20106. All authors read and approved the final manuscript. et al. Patellar dislocation most commonly results from a twisting motion, with the knee in flexion and the femur rotating internally on a fixed foot (valgus-flexion-external rotation) 1. Knee Surg Sports Traumatol Arthrosc 13:522528, Farr J, Schepsis AA (2006) Reconstruction of the medial patellofemoral ligament for recurrent patellar instability. At 0 extension, the patellar may lie completely above the level of the trochlea, without direct apposition between the two articular surfaces. Discussion. Lateral Patellar Compression Syndrome - Knee & Sports - Orthobullets AJR Am J Roentgenol. MRI and CT are superior modalities in looking for predisposing factors associated with patellar maltracking [26,27,28]. AJR Am J Roentgenol 167:339341, Caton JH, Dejour D (2010) Tibial tubercle osteotomy in patello-femoral instability and in patellar height abnormality. (21a) A corresponding anterior coronal slice reveals the large displaced osteochondral fragment (arrow) that occurred as a result of this injury. To provide the highest quality clinical and technology services to customers and patients, in the spirit of continuous improvement and innovation. A bone bruise at the anterolateral aspect of the lateral femoral condyle is also apparent (arrowheads). A high Q angle or TT-TG would exert a lateral pressure on the patella during knee extension, and if this is not counteracted by vastus medialis muscle contraction, it can predispose to lateral patellar subluxation and instability [39, 40]. Trochlear depth assessment. Depends on how bad: Small tears are observed and heal. [Nov;2019 . The most important active stabilizer of the patella is the vastus medialis oblique (VMO). The knee then was flexed 30, 60, 90, and 120, and the transducer recorded changes in tension within the lateral patellofemoral . Before Background Lateral Patella dislocations are common injuries seen in the active and young adult populations. CAS Acta Orthop Belg 72:6571, Panagopoulos A, van Niekerk L, Triantafillopoulos IK (2008) MPFL reconstruction for recurrent patella dislocation: a new surgical technique and review of the literature. Lateral Retinacular Release - Surgery Information a Sagittal PD knee MRI showing the method of assessing the InsallSalvati index, calculated as the ratio of the patellar tendon length at its inner aspect (white dashed line) to the greatest diagonal length of the patella (white line). The authors declare that they have no competing interests. Less common predisposing factors to be aware of include laterally tilted patella, VMO dysplasia and generalized joint laxity. Retinaculum - Differential Diagnosis of the Knee 3 Dirim B, Haghighi P, Trudell D et al. Incidence and concomitant chondral injuries in a consecutive cohort of primary traumatic patellar dislocations examined with sub-acute MRI. The patellar dislocations were clinically unsuspected in the initial evaluation of eight of these nine patients. Advantages of CT over MRI include the reduced cost, larger gantry diameter allowing to fit larger patients, faster acquisition with less potential for claustrophobia, fewer absolute and relative contraindications related to implanted devices, and better cortical bone definition. AJR Am J Roentgenol 194:721727, Kalichman L, Zhang Y, Niu J et al (2007) The association between patellar alignment and patellofemoral joint osteoarthritis features--an MRI study. Note the edema in the superolateral aspect of Hoffas fat pad (arrow). Evaluation of both of these soft tissue structures is critical when one examines a MRI following lateral patellar dislocation, as the extent of soft-tissue injury influences the use of operative repair. The most common trochleoplasty procedure described is a combination of lateral trochlear osteotomy and bone graft to heighten the lateral trochlea. It acts as a powerful extensor of the knee. Google Scholar, Diederichs G, Issever AS, Scheffler S (2010) MR imaging of patellar instability: injury patterns and assessment of risk factors. Unauthorized use of these marks is strictly prohibited. A 2015 Cochrane Review concluded that there is no significant increase in functional scores between nonoperative and operative management; however, surgical management does result in a significantly lower risk of recurrent dislocation at the cost of surgical complications [19]. Some controversy exists regarding whether female gender is a definite risk factor for patellar instability with certain studies identifying a 33% increased likelihood of first-time dislocation as well as three times high re-dislocation rates than males, whereas others have found roughly equal rates [2, 12,13,14]. (2a) In this case, it is the bone bruise within the anterolateral aspect of the lateral femoral condyle (long arrow) and the edema adjacent to the medial femoral condyle (arrowhead) that are the key to the diagnosis. Chondral and Soft Tissue Injuries Associated to Acute Patellar Dislocation: A Systematic Review. The lateral retinaculum provides significant additive support to the medial stabilizers. (13a) A line is drawn between the cortex of the lateral trochlear facet on the most superior axial image showing cartilage. At the time the article was last revised Joel Hng had Surgical realignment procedures include medialization of the tibial tubercle particularly in patients with a TT-TG distance greater than 20mm. [Google Scholar] 6. 5). Dejour et al. AIM: To describe the sonographic appearances of the medial retinacular (MPFR) complex of the knee in patients with acute and recurrent patellar dislocation.MATERIALS AND METHODS: Thirty patients were scanned within 2-4 weeks of an acute episode of lateral patellar dislocation. Lateral patellar dislocation. Usually, young individuals, particularly women, suffer the consequences of this disorder [2]. This is the ratio between a line measured between the inferior margin of the patellar articular surface and the anterior aspect of the tibial plateau and the greatest length of the patellar articular surface. {"url":"/signup-modal-props.json?lang=us"}, Moodaley P, Hng J, Hacking C, et al. 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. Created for people with ongoing healthcare needs but benefits everyone. 2023 BioMed Central Ltd unless otherwise stated. In order for the patella to engage with the femoral trochlea, a higher degree of flexion than normal is needed. The TT-TG is evaluated by measuring the distance between the most anterior point of the tibial tuberosity and the deepest point of the trochlear groove using two lines drawn perpendicular to the tangent to the posterior borders of the femoral condyles [31] (Fig. Int Orthop 34:311316, Donell ST, Joseph G, Hing CB, Marshall TJ (2006) Modified Dejour trochleoplasty for severe dysplasia: operative technique and early clinical results. Less than 3-mm trochlear depth is indicative of trochlear dysplasia [24].