Medial patellar. Starok M, Lenchik L, Trudell D, Resnick D. Normal patellar retinaculum: MR and sonographic imaging with cadaveric correlation. Additionally, MRs ability to delineate the extent of injury and predisposing factors is important in patient care and surgical planning. In fact, most patellar maltracking occurs between extension and the first 30 of flexion. Am J Knee Surg 13:8388, Izadpanah K, Weitzel E, Vicari M et al (2014) Influence of knee flexion angle and weight bearing on the Tibial Tuberosity-Trochlear Groove (TTTG) distance for evaluation of patellofemoral alignment. Early diagnosis is essential, as chronic maltracking will lead to patellofemoral cartilage damage and osteoarthritis [3]. Curr Rev Musculoskelet Med 11:253260, Article Rethy Chhem, Etienne Cardinal. In acute patellar dislocation, CT may demonstrate osseous impaction or fractures of the medial margin of the patella (with or without involvement of the articular surface) and/or the lateral surface of the lateral femoral condyle and intraarticular fragments. The main morphological features associated with patellar maltracking are trochlear dysplasia, lateralization of the tibial tuberosity, patella alta, and lateral patellar tilt. The distance from the tibial tubercle to the trochlear groove (TT-TG) provides a quantitative evaluation of excessive lateralization of the tibial tuberosity.7, (10a) Axial image of the knee with superimposition of the tibial tubercle from another slice (yellow outline). The MCL is composed of the superficial layer (layer 2 of the medial supporting structures) and the deep layer (layer 3 of the medial . Radiographics 30:961981, Tscholl PM, Wanivenhaus F, Fucentese SF (2017) Conventional radiographs and magnetic resonance imaging for the analysis of trochlear dysplasia: the influence of selected levels on magnetic resonance imaging. 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. 2). Prevalence of Lateral Patellofemoral Maltracking and Associated Complications in Patients with Osgood Schlatter Disease. More recently, the TT-TG index was developed, which takes knee size into account by assessing the proximaldistal distance between the entrance of the chondral trochlear groove (TE) and the tibial tuberosity (TT). PTI of less than 12.5% suggests the presence of patella alta. 1). The purpose of this article is to discuss the evaluation of patellar maltracking providing an update on the imaging assessment and also a synopsis on the management options. A bone bruise at the anterolateral aspect of the lateral femoral condyle is also apparent (arrowheads). 4. California Privacy Statement, The patients are then J-braced for 3 to 6 months for all sports activities. Subluxation and dislocation: recurrent. LTI < 11 degrees indicates dysplasia. Adjunctive treatments such as knee aspiration and patellar stabilizing braces have been proposed to decrease swelling and enable early range of motion; however, there is no conclusive evidence for their use [71]. The medial patellar retinaculum is part of the anterior third of the medial joint capsule. 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 First, a line is drawn paralleling the posterior femoral condyles surfaces. As the knee progresses through greater flexion, the contact surface becomes more proximal on the patella. In addition, symptomatic knees may demonstrate normal engagement between the patella and trochlea beyond 30 of flexion. 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. The above video demonstrates the mechanism of injury in patellar dislocation. MRI has been found to be 85%-92% sensitive for diagnosing MPFL injury (Seeley, 2013). AJR Am J Roentgenol 1997; 168:1493-1499. Acta Orthop 76:699704, Nikku R, Nietosvaara Y, Kallio PE, Aalto K, Michelsson JE (1997) Operative versus closed treatment of primary dislocation of the patella. Bookshelf In the past two decades dissection studies have shown that it extends from the superomedial border of the patella to the femoral epicondyle, at or immediately above the adductor tubercle. Twenty-six pelvic limbs were used for gross dissection, and four stifle regions from two animals were used for radiography and magnetic resonance imaging (MRI). Eleven gave a history of recurrent patellar dislocation. provided a morphologic classification system for trochlear dysplasia describing four types [26,27,28]. Specialists of neuroradiology and vascular neurosurgery decided over the modality assignment. (20a) A fat-suppressed proton density-weighted sagittal image in a patient following patellar dislocation reveals an osteochondral injury with a chondral defect (arrows) at the lateral weightbearing surface of the lateral femoral condyle, a finding seen in only 5% of patients. 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. 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]. As is typical, a bone bruise extends anteriorly (arrowheads) from the site of the chondral defect. Traumatic lateral patellar dislocation is a common injury among young, athletic individuals and is generally transient in nature. Springer Nature. It can not only detect any underlying morphological risk factors but also look for structural damage associated with maltracking including patellofemoral articular cartilage loss, osteochondral defects, or damage to the medial patellar stabilizers [4, 5]. There is a degree of variability in the literature about what is considered an abnormally high TT-TG. 1 Pain is often described as medial because of soft tissue injuries that occur to the medial retinaculum and/or MPFL. Acute patellar dislocation (APD) is a common injury in children, accounting for up to 16% of acute knee hemarthroses. Osteochondral fractures are common in acute or recurrent transient lateral patellar dislocation, seen in up to 70% of cases. Knee Surg Sports Traumatol Arthrosc 22:26552661, Seitlinger G, Scheurecker G, Hgler R, Labey L, Innocenti B, Hofmann S (2012) Tibial tubercle-posterior cruciate ligament distance: a new measurement to define the position of the tibial tubercle in patients with patellar dislocation. Medial patellofemoral ligament injury following acute transient dislocation of the patella: MR findings with surgical correlation in 14 patients. Radiology 2000; 216: 582-585. . 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. Patellar maltracking: an update on the diagnosis and treatment strategies, https://doi.org/10.1186/s13244-019-0755-1, http://creativecommons.org/licenses/by/4.0/. One of the more common MPFL reconstruction procedures uses a single hamstring tendon graft passed through the medial intermuscular septum at the adductor magnus insertion fixed by an anchor in the femoral condyle and sutured or anchored to the superomedial pole of the patella11. Zaid Jibri. The radiograph can also be useful in detecting osseous morphologic features associated with patellar maltracking such as patella alta and trochlear dysplasia [24, 25]. It is a geometric abnormality of the trochlear groove that affects its shape and depth mainly at its superior part, which can result in abnormal tracking of the patella along the trochlea. In patients without osseous malalignment, MPFL reconstruction and plication of the medial restraints is reported to decrease re-dislocation rates to 5%. Patella alta is related to a long patellar tendon and is considered a major factor associated with reduced contact area at the patellofemoral joint and a major contributor to patellar instability [33]. James M. Provenzale, Rendon C. Nelson, Emily N. Vinson. The injury typically occurs from a twisting event with the knee in mild flexion (less than 30). PubMed Central 8600 Rockville Pike MRI and CT are superior modalities in looking for predisposing factors associated with patellar maltracking [26,27,28]. The injuries involved the medial retinacular ligament in 16 of 17 patients and the medial and lateral retinacular ligament in one patient. AJR Am J Roentgenol. However, subtle sprains are seen at the anterior medial retinaculum (arrowhead) and posterior MPFL (arrow) along with a large joint effusion. Patellar maltracking: an update on the diagnosis and treatment strategies. Patellar maltracking occurs as a result of an imbalance in the dynamic relationship between the patella and trochlea. The axial proton density-weighted image reveals a large osteochondral shearing injury involving the mid to medial patella (arrowheads). 1. Clin J Sport Med 15:6266, Colvin AC, West RV (2008) Patellar instability. At less than 30 of flexion, asymptomatic knees may demonstrate physiologic patellar tilt or subluxation. A perpendicular line is measured to the most posterior cortex of the central trochlea. b Trochlear dysplasia (9 inclination), Facet asymmetry assessment for trochlear dysplasia on axial MRI. The trochlear groove and patella may have abnormal morphology that predisposes to patellar dislocation. 30 Correctly diagnosing APD can be difficult as the displaced patella usually relocates spontaneously, with fewer than 10% of patients presenting with fixed lateral dislocation. 4 Sanders TG, Morrison WB, Singleton BA, Miller MD, Cornum KG. There are numerous techniques reported in literature and commonly used to reconstruct the medial sided soft tissue constraints. 2. The pages that follow contain general guidance on the diagnosis and treatment of chronic nontraumatic knee pain. Intervention: Taping the knee to promote medial glide . (21a) A corresponding anterior coronal slice reveals the large displaced osteochondral fragment (arrow) that occurred as a result of this injury. If the lateral retinaculum tendon is tight enough to pull the patella out of the trochlear groove, a lateral release procedure can loosen the tissue and correct the patellar malalignment. 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. Int Orthop 34:305309, Biedert RM, Albrecht S (2006) The patellotrochlear index: a new index for assessing patellar height. ADVERTISEMENT: Supporters see fewer/no ads. Rheumatology (Oxford) 46:13031308, Sanders TL, Pareek A, Johnson NR, Stuart MJ, Dahm DL, Krych AJ (2017) Patellofemoral arthritis after lateral patellar dislocation: a matched population-based analysis. 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]. Epub 2011 Nov 9. Of course, if medial soft tissue restraints are disrupted at the first dislocation, the loss of such restraints makes future dislocations more likely. Lateral patellar dislocation. Because as noted above, the femoral bone bruise occurs as the patella moves forward during reduction, bone bruises at the lateral femoral condyle always course anteriorly from the site of any femoral chondral injury that may be present. Fractures may be caused either by excessive force through the extensor mechanism or by a direct blow. 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. 5 Carrillon Y, Abidi H, Dejour D, et al. A patient with acute first-time transient patellar dislocation without osteochondral lesions and severe risk factors for redislocation is generally treated conservatively. AJR Am J Roentgenol. Acute lateral patellar dislocation at MR imaging: injury patterns of medial patellar soft-tissue restraints and osteochondral injuries of the inferomedial patella. In these patients, a triad of findings that included focal impaction injuries involving the lateral femoral condyle, osteochondral injuries of the medial patellar facet, and injuries of the medial retinacular ligament were seen. Normal = 0.8 to 1.2. Surgical repair is most commonly directed to MPFL reconstruction and to distal realignment in the subset of patients who have significant osseous malalignment. Areas of scarring and osteochondral lesions become more common as the frequency of patellar dislocation increases. Springer, New York, pp 1529, Cash JD, Hughston JC (1988) Treatment of acute patellar dislocation. 7 Balcarek P, Jung K, Frosch KH, Sturmer KM. A sliver of fluid undermines a moderately thickened and scarred MPFL at the medial femoral condyle attachment consistent with a chronic partial stripping tear (arrowheads). Knee Surg Sports Traumatol Arthrosc 14:264272, McNally EG, Ostlere SJ, Pal C, Phillips A, Reid H, Dodd C (2000) Assessment of patellar maltracking using combined static and dynamic MRI. Before The Medial Patellofemoral Ligament (MPFL) is an hour-glass shaped ligament made of bands of retinacular tissue. From this insertion, it extends posteriorly to blend with the lateral margin of the knee capsule and inferior surface of the lateral tibial condyle 1,2. High resolution magnetic resonance imaging of the patellar retinaculum: normal anatomy, common injury patterns . Objective: This prospective study is designed to detect changes in the treatment of ruptured intracranial aneurysms over a period of 17 years. Ellas et al. Flattening or developmental dysplasia of the trochlea leads to loss of normal patellar tracking and can predispose to lateral patellar dislocation with flexion. Patellar tilt can also be assessed using the patellofemoral angle (PFA). The VMO is active, not only in full extension but also at 30 degrees and up to 100 degrees of flexion. (13a) A line is drawn between the cortex of the lateral trochlear facet on the most superior axial image showing cartilage. Medial patellar chondral injuries may occur during either the dislocation or reduction phases of injury. Disadvantages of CT compared to MRI include the use of ionizing radiation, which reduced soft tissue contrast resulting in limited evaluation of the cartilage, tendons, ligaments, muscles, and internal structures of the knee [64]. 11 Lind M, Jakobsen B, Lund B, et al. 1995 Jan;164(1):135-9. doi: 10.2214/ajr.164.1.7998526. Crossref, Medline, Google Scholar; 32 Starok M, Lenchikl L, Trudell D, Resnick D. Normal patellar retinaculum: MR and sonographic imaging with cadaveric correlation. Distally, it attaches to the tibial tubercle via the patellar tendon. Despite the presence of numerous detailed anatomical dissection and MRI based studies of the anatomy2,3, there is much variability in the description of these structures within the literature. Although varied in presentation, successful management of all patients relies on thorough history taking, physical examination of the entire lower extremity, and appropriate imaging. An association has been demonstrated between patellofemoral cartilage damage and patellar maltracking. This is often secondary to an underlying structural abnormality. Axial PDFS left knee MR image, demonstrating the method used for the measurement of trochlear depth. Epidemiology Patellar dislocation accounts for ~3% of all knee injuries and is commonly seen in those individuals who participate in sports activities. 1997 Jan;168(1):117-22. doi: 10.2214/ajr.168.1.8976933. TTTG is the distance between the solid and the dashed lines in (b). The authors declare that they have no competing interests. In order for the patella to engage with the femoral trochlea, a higher degree of flexion than normal is needed. ity. 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. AJR Am J Roentgenol 169:211215, Buchner M, Baudendistel B, Sabo D, Schmitt H (2005) Acute traumatic primary patellar dislocation: long-term results comparing conservative and surgical treatment. Thus, imaging at positions both less than and greater than 30 can be used to avoid missing maltracking that might be captured at only certain degrees of flexion [64]. Eur J Trauma Emerg Surg. AJR Am J Roentgenol 187:13321337, White BJ, Sherman OH (2009) Patellofemoral instability. Lateral trochlear inclination is another quantitative method to diagnose trochlear dysplasia. A focused history of the mechanism, number, and circumstances of instability to date is essential. Knee 10:215220, Terry GC, Hughston JC, Norwood LA (1986) The anatomy of the iliopatellar band and iliotibial tract. The medial patellofemoral ligament is composed of a transverse (T) component arising between the adductor tubercle and medial epicondyle and an oblique decussation that originates from the medial collateral ligament (MCL). Understanding the biomechanics of these joints is essential to investigating and appropriately treating patellofemoral joint pathology. Trauma itself rarely causes patellofemoral dislocations without predisposing factors such as trochlear dysplasia, patella alta and lateralization of the tibial tuberosity. Patellar tracking refers to the dynamic relationship between the patella and trochlea during knee motion [1]. From the inside of the knee the lateral retinaculum is incised, from the inside, allowing the kneecap to untilit itself. a Normal trochlea. Both MRI and ultrasound are accurate imaging modalities in the detection of MPFL injuries [5, 50, 51]. Terms and Conditions, 5). Tears of the medial retinaculum and the MPFL are commonly present at both the patellar and femoral attachments, though tears of the transverse band of the MPFL are more likely at the femoral attachment.
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