Acute Lateral Patellar Dislocation Research Articles

Prevalence and Site of Concomitant Osteochondral Injuries in Patients With Acute Lateral Patellar Dislocation: A Systematic Review and Meta-analysis

Background: Osteochondral injuries (OCIs) are common in patients with acute lateral patellar dislocation, which can produce both short- and long-;term adverse effects. However, the pattern of these injuries warrants further analysis, especially in relation to patient age. Purpose: To determine the overall prevalence of concomitant OCIs as well as the prevalence differences based on location and age after acute lateral patellar dislocations. Study Design: Systematic review; Level of evidence, 4. Methods: A comprehensive search of PubMed, Embase, Web of Science, and Cochrane Library was completed from inception to July 20, 2022. All articles reporting the prevalence of OCI were included. The sample characteristics such as age, study design, magnetic resonance imaging diagnostic data, and the number of patients with OCI were extracted. The Methodological Index for Non-Randomized Studies (MINORS) was used for quality assessment. The overall and per-;site injury rates were calculated, and the prevalence was stratified by age-;group (≤16 and >16 years) and compared. Results: The systematic review included 39 studies involving 3354 patients. MINORS scores were 11.94 ± 1.98 and 16 ± 3.46 in the noncomparative and comparative studies, respectively. The overall prevalence of bone bruises and OCI was 89.6% (95% CI, 77.4%-97.7%) and 48.8% (95% CI, 39.0%-58.7%), respectively. In both overall and >16-year-old patients, the lateral femoral condyle (LFC) was the most common site of bone bruise (90.5% [95% CI, 84.0%-95.6%] and 91.5% [95% CI, 84.3%-96.9%], respectively); however, the medial patellar bruise was more common in patients ≤16 years (89.2% [95% CI, 82.9%-94.4%]). Among the pooled sites of OCI, the medial patella accounted for the largest proportion (36.9% [95% CI, 28.0%-46.3%]). OCIs were more common in patients >16 years (52.6% [95% CI, 39.4%-65.6%]) than in patients ≤16 years (46.6% [95% CI, 33.2%-60.3%]). Conclusion: Bone bruises on the LFC were most prevalent overall and in patients >16 years, whereas bone bruises on the medial patella were more prevalent in patients ≤16 years. OCIs were frequently seen in patients >16 years, with the most common site being the medial patella.

Acute patellar dislocation: how skeletal maturity affects patterns of injury.

The main objective of this study was to understand the role of skeletal maturity in the different patterns of osteochondral and ligamentous injuries after an acute lateral patellar dislocation. Two radiologists independently reviewed MRIs of 212 knees performed after an acute lateral patellar dislocation to evaluate the presence of high-grade patellar osteochondral injury, femoral osteochondral injury, and medial patellofemoral ligament injury. The association of skeletal maturity (indicated by a closed distal femoral physis), age, sex, and first-time versus recurrent dislocation with each of these various lesions was analyzed using Chi-square or T test, and multivariable logistic regression with estimation of odds ratios (OR). Skeletal maturity was significantly associated with high-grade patellar osteochondral injury [OR=2.72 (95% CI 1.00, 7.36); p=0.049] and femoral-side MPFL tear [OR=2.34 (95% CI 1.05, 5.25); p=0.039]. Skeletal immaturity was significantly associated with patellar-side MPFL tear [OR=0.35 (95% CI 0.14, 0.90); p=0.029]. Patterns of injury to the patella and medial patellofemoral ligament vary notably between the skeletally immature and mature, and these variations may be explained by the inherent weakness of the patellar secondary physis.

Differences of injury characteristics of medial patellofemoral ligament in acute lateral patellar dislocation and multiligament knee injuries.

The injury characteristics of medial patellofemoral ligament (MPFL) in multiligament knee injuries (MLKIs) and the differences of injury patterns of MPFL in MLKIs and acute lateral patellar dislocation (LPD) remain unclear. To explore the differences of injury characteristics of MPFL after acute LPD and MLKIs. Magnetic resonance images were prospectively analyzed in 219 patients after acute LPD or MLKIs. Statistical analyses of the injury patterns of MPFL were performed between LPD and MLKIs. The incidence of partial tear and complete MPFL tear in adolescent LPD and MLKIs were 40.3% and 48.4%, and 27.9% and 16.3%, respectively. Compared with LPD, MLKIs showed lower incidence rates of partial and complete MPFL tears (both P = 0). The MLKI subgroup showed lower incidence rates of MPFL tear at the patellar insertion (PAT), femoral attachment (FEM), and multiple-site of the MPFL (COM) (9.3%, 20.9%, and 14%) when compared with the LPD subgroup (45.2%, 24.2%, and 16.1%) (all P < 0.01). The incidence of partial tear and complete MPFL tear in adult LPD and MLKIs were 41.5% and 47.2%, and 24.6% and 16.4%, respectively. Compared with LPD, MLKIs showed lower incidence rates of partial and complete MPFL tears (both P = 0). The MLKI subgroup showed lower incidence rates of MPFL tear at PAT, FEM, and COM (8.2%, 18%, and 14.8%) when compared with the LPD subgroup (20.8%, 34%, and 30.2%) (all P = 0). Compared with LPD, MPFL tears are relatively uncommon in MLKIs. Even if MPFL tears occur, partial tears and femoral-sided tears are relatively more common.

Lateral Femoral Condyle CRATER sign of BRIK an Ancillary Sign of Lateral Patellar Dislocation

Introduction Acute lateral patellar dislocation is a common knee injury pattern. However, coincidental osseous defect may be present in normal knees. Purpose Evaluate the characteristics of osseous bone defect and describe a new ancillary sign associated with lateral patellar dislocation. Materials and Methods Magnetic resonance imaging (MRI) of 50 consecutive patients referred following a traumatic lateral patellar dislocation of the knee joint and 50 patients with knee pain without MR features of patellar dislocation were obtained for evaluation over a 7-year period. They were analyzed for location of bony defects in the periarticular region. Results Of the 50 patients who underwent MRI following a reduced traumatic lateral patellar dislocation, 3 patients had an osseous "crater" of more than 2 mm in depth on the non-articular surface of the lateral femoral condyle. None of control group of patients had an osseous defect measuring more than 2 mm in depth. Conclusion This associated finding of an osseous "crater" of more than 2 mm on the non-articular surface of the lateral femoral condyle following traumatic lateral patellar dislocation is a rare occurrence. We highlight this as an ancillary sign of lateral patellar dislocation necessitating careful evaluation (Crater sign of Bhamidipaty Rajesh Iyengar Kartik [BRIK]). The presence of lateral femoral condyle "CRATER" sign of BRIK on MRI undertaken for other reasons in the knee, in the absence of osseous edema may suggest a past episode of severe, reduced patellar dislocation.

Treatment of Knee Osteochondral Fractures.

Osteochondral lesions (OCLs) that are frequently encountered in skeletally immature and adult patients are more common than once thought, and their incidence rate is rising. These lesions can appear in many synovial joints of the body, such as the shoulder, elbow, hip, and ankle, occurring most often in the knee. The term osteochondral lesion includes a vast spectrum of pathologies such as osteochondritis dissecans, osteochondral defects, osteochondral fractures, and osteonecrosis of the subchondral bone. When considering this, the term osteochondral fracture is preserved only for an osteochondral defect that combines disruption of the articular cartilage and subchondral bone. These fractures commonly occur after sports practice and are associated with acute lateral patellar dislocations. Many of these lesions are initially diagnosed by plain radiographs; however, a computed tomography (CT) scan or magnetic resonance imaging (MRI) can add significant value to the diagnosis and treatment. Treatment methods may vary depending on the location and size of the fracture, fragment instability, and skeletal maturity. The paper reports a 14-year-old boy case with an osteochondral fracture due to sports trauma. The medical approach involved an arthrotomy of the knee, drainage of the hematoma, two Kirschner wires (K-wires) for temporary fixation to restructure anatomic alignment, and a titanium Herbert screw fixing the fracture permanently. The patient had a favorable postoperative outcome with no residual pain, adequate knee stability, and a normal range of motion. The mobility of the knee was fully recovered.

Factors associated with acute articular cartilage lesions of the patella and lateral femoral condyle in acute first-time lateral patellar dislocation: A prospective magnetic resonance imaging study

ObjectivesTo identify risk factors of acute articular cartilage lesions of the patella and lateral femoral condyle in acute first-time lateral patellar dislocation (LPD). MethodsMagnetic resonance images were prospectively analyzed in 115 patients in an acute first-time LPD. Factors included gender, skeletal maturity, trochlear dysplasia, patellar height, and tibial tuberosity–trochlear groove (TT-TG) distance. Binary logistic regression analysis was carried out to identify the independent risk factors for the incidence of acute articular cartilage lesions of the patella and lateral femoral condyle in acute first-time LPD. ResultsThe incidence of acute articular cartilage lesion of the patella and lateral femoral condyle were 46.1% and 27% in acute first-time LPD, respectively. Univariate analysis revealed significantly higher incidence rate of acute articular cartilage lesion of the patella in male (P = 0.027), skeletally mature (P = 0.035), normal TT-TG distance (P = 0.043) and normal femoral trochlea (P = 0.031). Risk factors for the incidence of acute articular cartilage lesion of the patella were skeletally mature (odds ratio (OR): 2.324), normal TT-TG distance (OR: 2.824) and normal femoral trochlea (OR: 3.835). Univariate analysis revealed significantly higher incidence rate of acute articular cartilage lesion of the lateral femoral condyle in skeletally mature (P = 0.027) and normal femoral trochlea (P = 0.031). Risk factor for the incidence of acute articular cartilage lesion of the lateral femoral condyle was normal femoral trochlea (OR: 3.347). ConclusionsFor patients in acute first-time LPD, compared with other parameters, the normal femoral trochlea, normal TT-TG distance and skeletally mature are independent risk factors for the incidence of acute articular cartilage lesion of the patella, and the normal femoral trochlea is an independent risk factor for the incidence of acute articular cartilage lesion of the lateral femoral condyle.

Diagnostic Performance of MRI Versus CT in the Evaluation of Intra-articular Osteochondral Fracture in Pediatric Patients With Acute Traumatic Lateral Patellar Dislocation.

Background:Evaluation of intra-articular osteochondral fractures in children with acute traumatic lateral patellar dislocation (LPD) is important for determining treatment options.Purpose:To (1) compare the diagnostic accuracy of computed tomography (CT) and magnetic resonance imaging (MRI) for evaluating intra-articular osteochondral fractures; (2) compare the interpretation of CT and MRI images between radiologists and pediatric orthopaedic surgeons (POS); and (3) investigate any clinical factors influencing the accuracy of CT and MRI evaluations.Study Design:Cohort study (diagnosis); Level of evidence, 2.Methods:We reviewed 35 knees in 35 patients (mean age, 12.2 ± 1.2 years; 12 boys and 23 girls) who were treated arthroscopically for acute traumatic LPD; 71% of the patients had patellar fractures, 54% had femoral fractures, and 60% had free osteochondral fracture fragments. All presurgical MRI and CT images were reviewed by POS who were blinded to both the reports of the radiologists and surgical records. We compared the accuracy of CT and MRI in diagnosing intra-articular osteochondral fractures against the arthroscopic findings and compared the interpretation of the images by the POS (MRI-O, CT-O) with those of the radiologists (MRI-R, CT-R).Results:There was no significant difference in diagnostic accuracy between CT and MRI for overall intra-articular osteochondral fractures by the POS or the radiologists; however, the CT-O images had a higher diagnostic specificity (84.2% vs 69.6%; P < .001) and sensitivity (88.1% vs 70.1%; P < .001) versus the MRI-R images. Regarding free fracture fragments, the CT-R images had a higher diagnostic accuracy than the MRI-R images (73.5% vs 47.1%; P = .026). When backed by clinical data, the MRI-O images had greater diagnostic accuracy (78.7% vs 60.3%; P = .001) and sensitivity (88.1% vs 30.7%; P = .021) but lower specificity compared with the MRI-R images, and the CT-O images had similar diagnostic accuracy but greater sensitivity than the CT-R images (70.1% vs 52.2%; P < .001). The diagnostic accuracy of MRI-O images was lower for children under 12 years versus children 12 years and over (67.5% vs 83.3%; P = .040).Conclusion:Compared with MRI, CT scans had better diagnostic performance in the evaluation of intra-articular osteochondral fractures in pediatric patients with acute traumatic LPD. Clinical data enhanced the diagnostic sensitivity of MRI and CT but decreased the specificity of MRI. MRI evaluations remain challenging for both POS and radiologists.

Patellofemoral Instability in Children: Imaging Findings and Therapeutic Approaches

Patellofemoral instability (PFI) is common in pediatric knee injuries. PFI results from loss of balance in the dynamic relationship of the patella in the femoral trochlear groove. Patellar lateral dislocation, which is at the extreme of the PFI, results from medial stabilizer injury and leads to the patella hitting the lateral femoral condyle. Multiple contributing factors to PFI have been described, including anatomical variants and altered biomechanics. Femoral condyle dysplasia is a major risk factor for PFI. Medial stabilizer injury contributes to PFI by creating an imbalance in dynamic vectors of the patella. Increased Q angle, femoral anteversion, and lateral insertion of the patellar tendon are additional contributing factors that affect dynamic vectors on the patella. An imbalance in the dynamics results in patellofemoral malalignment, which can be recognized by the presence of patella alta, patellar lateral tilt, and lateral subluxation. Dynamic cross-sectional images are useful for in vivo tracking of the patella in patients with PFI. Therapeutic approaches aim to restore normal patellofemoral dynamics and prevent persistent PFI. In this article, the imaging findings of PFI, including risk factors and characteristic findings of acute lateral patellar dislocation, are reviewed. Non-surgical and surgical approaches to PFI in pediatric patients are discussed.

Visualization of osteochondral fragments in the cavity of the knee joint in case of patellar dislocation in children

The objective was to assess the capabilities of MRI and CT in visualizing free bone and cartilage fragments in the knee cavity after lateral dislocation of the patella. Materials and methods. CT and MRI were performed in 220 patients, including 127 girls and 93 boys aged 12 to 18 years (mean age 14.5 years), with acute lateral patellar dislocation. Results. Lateral dislocation of the patella in 25% of cases led to the appearance of osteochondral fragments. CT scan revealed and confirmed osteochondral fragments surgery in 55 people (100%), MRI scan - in 50 people (90%). The sites of the detachment of the osteochondral fragments were: a medial facet of the patella in 22 (38.8%), the outer edge of femur lateral condyle in 33 (58.2%), t patella and lateral condyle of the femur in 2 patients (3%). Free cartilage fragments not detected by CT were detected by MRI in 2 patients. Conclusion. Patellar dislocation is an injury that is likely to require surgery. The volume of osteochondral and soft tissue lesions can be established with the maximum degree of probability by MRI while detecting small osteochondral fragments is most reliable with CT. Combining these two observation methods provides the complete possible information about the extent of damage, which allows timely resolution of treatment tactics.

Is an individually tailored programme of intense leg resistance and dynamic exercise acceptable to adults with an acute lateral patellar dislocation? A feasibility study

BackgroundLateral patellar dislocations mainly affect active teenagers and young adults. To help people recover, non-surgical exercise-based treatment is often recommended but the optimal exercise-based treatment is unknown. Currently, treatment outcomes after this injury are variable. Common problems include recurrent dislocation, reduced activity levels, and later surgery. A programme of intense leg resistance exercises, and dynamic exercises related to participants’ activity-related goals, has rationale, but has not been previously reported. In line with the Medical Research Council guidance, this study aimed to assess the acceptability of a novel evidence-based exercise programme for adults after acute lateral patellar dislocation and the feasibility of future research evaluating this treatment.MethodsA single-group prospective study was conducted at the John Radcliffe Hospital, Oxford, UK. Participants were 16 years or older with an acute first-time or recurrent lateral patellar dislocation. Participants received up to six face-to-face, one-to-one, physiotherapy sessions, over a maximum of 3 months, and performed intensive home exercises independently at least three times per week. Strategies to increase exercise adherence were used. Primary objectives were to determine the number of eligible patients, the recruitment rate (proportion of eligible patients that provided written informed consent), participant adherence to scheduled physiotherapy sessions and self-reported adherence to prescribed exercise, and intervention acceptability to participants measured by attrition and a study-specific questionnaire. Data were analysed using descriptive statistics.ResultsFifteen of 22 (68%) patients with a lateral patellar dislocation were eligible. All eligible (100%) were recruited. Two of 15 (13%) participants provided no outcome data, 2/15 (13%) provided partial outcome data, and 11/15 (73%) provided all outcome data. Questionnaire responses demonstrated high intervention acceptability to participants. Participants attended 56/66 (85%) physiotherapy sessions and 10/11 (91%) participants reported they ‘always’ or ‘often’ completed the prescribed exercise. One participant redislocated their patella; another experienced knee pain or swelling lasting more than one week after home exercise on three occasions.ConclusionThe intervention appeared acceptable to adults after acute lateral patellar dislocation, and a future randomised pilot trial is feasible. This future pilot trial should estimate attrition with increased precision over a longer duration and assess participants’ willingness to be randomised to different treatments across multiple centres.Trial registrationClinicalTrials.govNCT03798483, registered on January 10, 2019

First-Time Acute Lateral Patellar Dislocation in Children and Adolescents: What About Unaffected Knee Patellofemoral Joint Anatomic Abnormalities?

Background and Objectives: Acute lateral patellar dislocation (LPD) is the most common acute knee disorder in children and adolescents, and may lead to functional disability. The purpose of this study was to identify key differences and correlations of the patellofemoral joint (PFJ) morphology between intact and contralateral injured knees in a first-time traumatic LPD population aged under 18 years. Materials and Methods: The data were gathered prospectively from a cohort of 58 patients (35 girls and 23 boys). The prevalence and combined prevalence of patella alta (PA) and trochlear dysplasia (TD) in both knees of patients were evaluated using X-ray by two radiologists. Results: The PFJ of patients’ intact knees had a lower rate of TD (1.72% vs. 5.2%) and a less common combination of PA with shallow femoral sulcus (SFS) (22.4% vs. 44.8%) but more frequent PA (62.1% vs. 41.4%) compared with their injured knees. We noted statistically significant positive correlations (SSPCs) between the femoral sulcus angle (FSA) and PA in patients with intact (r = 0.37; p < 0.005) and contralateral injured knees (r = 0.33; p < 0.05). Conclusion: There were SSPCs between the FSA and PA in both gender and age groups of patients with intact and contralateral injured knees. The SSPCs between the FSA and PA of intact knees were higher in the patients with a more dysplastic PFJ anatomy (PA and TD) of the injured knees as compared to patients with only PA of the injured knees.

Prevalence and Site of Medial Patellofemoral Ligament Injuries in Patients With Acute Lateral Patellar Dislocations: A Systematic Review and Meta-analysis.

Background:Medial patellofemoral ligament (MPFL) injuries are common in patients with acute lateral patellar dislocations, but the pattern of MPFL injuries is unclear, especially with respect to patient age.Purpose:The primary aim was to determine the prevalence of MPFL injuries according to the site of injury in patients with acute lateral patellar dislocations. The secondary aim was to compare the site of MPFL injuries in patients aged ≤16 versus >16 years.Study Design:Systematic review; Level of evidence, 4.Methods:A systematic literature search was performed with PubMed, Embase, and CINAHL to identify articles published from January 1, 1999, to May 31, 2019, that examined the site of MPFL injuries in patients with acute patellar dislocations. The study design, sample size, age at injury, technique used for diagnosing MPFL injuries (magnetic resonance imaging, ultrasound, and/or surgery), and prevalence and site of MPFL injuries were extracted from each study. The pooled estimate of the proportion of MPFL injuries at each site was calculated (femur, patella, midsubstance, and combined sites of injury) as well as proportions stratified by age group (≤16 and >16 years).Results:The literature search yielded 420 unique articles, of which 52 were screened for eligibility; of these, 17 were excluded. Thus, a total of 35 articles (2558 patients) were included in the final analysis. The overall prevalence of MPFL injuries was 94.7% (95% CI, 91.2%-96.8%). Most MPFL injuries occurred at the patella (37.1% [95% CI, 30.8%-43.9%]), followed by the femur (36.8% [95% CI, 31.0%-43.0%]), combined sites (25.1% [95% CI, 20.7%-30.1%]), and the midsubstance (15.6% [95% CI, 13.2%-18.4%]). In patients aged ≤16 years, most MPFL injuries occurred at the patella (39.3% [95% CI, 27.9%-51.9%]), and in patients aged >16 years, most MPFL injuries occurred at the femur (47.2% [95% CI, 40.6%-54.0%]).Conclusion:The prevalence of MPFL injuries in patients with acute patellar dislocations varied by site of injury and by age. MPFL injuries at the patella were most prevalent overall and in children and adolescents, and MPFL injuries at the femur were more prevalent in adults.

Gender-related differences in concomitant articular injuries after acute lateral patellar dislocation.

To explore the gender differences in the concomitant articular injuries after acute lateral patellar dislocation (LPD). Magnetic resonance images were prospectively analyzed in 166 patients after an acute LPD. Concomitant articular injuries included bone contusion, medial patellofemoral ligament (MPFL) injury, articular cartilage lesion, and vastus medialis obliquus (VMO) lesion. Statistical analyses were performed between the patient's gender and the incidence of concomitant articular injuries in adolescent and adult subgroups. The incidence of partial and complete MPFL tear in adolescent males and females were (45%, 50%) and (63.2%, 29.8%), respectively. Compared with adolescent females, adolescent males showed higher incidence of complete MPFL tear (P=0.049). The incidence of articular cartilage lesion of patella in adolescent males and females were 40% and 21.1%, respectively. Compared with adolescent females, adolescent males showed higher incidence of articular cartilage lesion of the patella (P=0.043). No correlations were identified in other injuries in the adolescent group. The incidence of partial and complete MPFL tear in adult males and females were (34.4%, 65.6%) and (56.8%, 37.8%), respectively. Compared with adult females, adult males showed higher incidence of complete MPFL tear (P=0.036). The incidence of articular cartilage lesion of patella in adult males and females were 56.3% and 32.4%, respectively. Compared with adult females, adult males showed higher incidence of articular cartilage lesion of patella (P=0.047). The incidence of VMO injury in adult males and females were 59.4% and 35.1%, respectively. Compared with adult females, adult males showed higher incidence of VMO injury (P=0.044). No correlations were identified in other injuries in the adult group. Compared with females, males predispose to complete MPFL tear and articular cartilage lesion of patella after acute LPD. Compared with female adults, male adults predispose to VMO injury.

Knee Injury - Dancer

HISTORY: A 20 year old female dance instructor was performing split jump lunges when she developed acute onset of pain and swelling in the medial left knee while loading the leg in the posterior position. She reported feeling a tearing sensation and was unable to immediately weight bear. On presentation to the emergency room was partially weightbearing. Initial left knee radiographs were negative for acute fracture. She was given a soft knee sleeve, started ibuprofen 600mg TID, and initially used ice. She presented to outpatient sports medicine clinic 1 week later with persistent 7/10 pain and swelling in the medial knee. She denied locking or buckling of the knees. PHYSICAL EXAMINATION: Exam revealed mild-to-moderate effusion of the left knee and restricted range of motion due to pain (flexion to 100 degrees, extension to 10 degrees). There was tenderness to palpation over the medial joint line and pain with valgus stress testing. Anterior drawer with bilateral mild laxity but symmetric. McMurray’s was limited by guarding and restricted range of motion. Gait was antalgic with limited knee flexion on the left. Hip abduction strength 4-/5 bilaterally. DIFFERENTIAL DIAGNOSIS: 1. Medial meniscus tear 2. Medial collateral ligament injury 3. Anterior cruciate ligament injury 4. Patellar dislocation/subluxation 5. Osteochondral injury TESTS AND RESULTS: Left Knee X-ray: - No acute osseous findings - Suggestive of lateral patellar tilt and subluxation Left Knee MRI: - Sequela of prior transient lateral patellar dislocation and medial patellar retinaculum rupture - Osseous contusions of the medial patella and lateral femoral condyle - Shallow trochlear groove with minimal lateral patellar subluxation FINAL/WORKING DIAGNOSIS: Acute lateral patellar dislocation and medial patellar retinaculum rupture in setting of trochlear dysplasia TREATMENT AND OUTCOMES: 1. Left knee immobilizer started 1-week post-injury. 2. Isometric quadriceps strengthening exercises started 1-week post-injury. 3. Improved range of motion, swelling, and gait at 1 month follow up. 4. Started in physical therapy for knee range of motion, strengthening and stabilization exercises, hip abduction strengthening, and progression to return to dance/exercise. 5. Discussed orthopedic referral if no further improvement or recurrent dislocation.

Irreducible lateral patellar dislocation reduced using towel clip technique: A case report

Acute lateral patellar dislocation is relatively common in younger age group and most likely caused by indirect trauma which is a medical emergency. Lateral dislocation accounts for the vast majority of patellar dislocations and make up for approximately 3% of all knee injuries. We report a case of irreducible lateral patellar dislocation which was reduced using a towel clip under spinal anaesthesia. This case is reported for its rarity and reduction technique.

A new classification of injury patterns of the medial patellofemoral ligament after acute lateral patella dislocation detected using magnetic resonance imaging studies

IntroductionAcute lateral patellar dislocation is a very common condition in orthopedics, especially among adolescents and physically active patients. To evaluate distinct medial patellofemoral ligament (MPFL) injury patterns and the associated knee pathology after acute lateral patellar dislocation (ALPD) using magnetic resonance imaging (MRI) studies, which is essential for the development of treatment protocols. Materials and MethodsMRI images of 74 ALPD patients were taken between January 2015 to December 2016. Images were evaluated using standardized protocols. ResultsThe prevalence of MPFL injury following ALPD was 97.3% (72/74 patients). Among the 72 patients with MPFL, the prevalence of Type Ⅰ injury was 26.4% (19/72). Since only bone marrow edema and a partial tear were showed on MRI of these patients, conservative treatment was given. Tear of the MPFL occurred at the patellar attachment (Type Ⅱa) in 16 patients (16/72, 22.2%), at the middle area of the ligament (Type Ⅱb) in 5 patients (5/72, 6.9%), and at the femoral attachment (Type Ⅱc) in 27 patients (27/72, 37.5%). For Type Ⅱ injuries, all patients had the surgery to reconstruct the MPFL. The prevalence of Type Ⅲ MPFL injury was 6.9% (5/72) after the surgery. ConclusionMPFL injury of is a common sequel following ALPD. We assessed the distinct injury pattern and associated pathology of MPFL using MRI studies. A good understanding of the injury pattern and associated knee pathology of MPFL is essential in managing patients with ALPD, especially if surgical intervention is considered.

The Correlation between the Injury Patterns of the Medial Patellofemoral Ligament in an Acute First-Time Lateral Patellar Dislocation on MR Imaging and the Incidence of a Second-Time Lateral Patellar Dislocation.

ObjectiveTo evaluate the correlation between the injury patterns of the medial patellofemoral ligament (MPFL) on magnetic resonance imaging in an acute first-time lateral patellar dislocation (LPD) and incidence of a second-time LPD.Materials and MethodsMagnetic resonance images were prospectively analyzed in 147 patients after an acute first-time LPD with identical nonoperative management. The injury patterns of MPFL in acute first-time LPDs were grouped by location and severity for the analysis of the incidence of second-time LPD in a 5-year follow-up. Independent t tests, chi-square tests and Kruskal-Wallis tests were performed as appropriate.ResultsForty-six cases (46/147, 31.3%) of second-time LPD were present at the 5-year follow-up. Fourteen (14/62, 22.6%) and 31 cases (31/80, 38.8%) were present in the partial and complete MPFL tear subgroups, respectively. Twenty-five cases (25/65, 38.5%), 11 cases (11/26, 42.3%), and 8 cases (8/47, 17%) were present in the isolated femoral-side MPFL tear (FEM), combined MPFL tear (COM), and isolated patellar-side MPFL tear (PAT) subgroups, respectively. Compared with the partial MPFL tears, complete tears showed higher incidence of a second-time LPD (p = 0.04). The time interval between the two LPDs was shorter in the complete MPFL tear subgroup (24.2 months) than in the partial tear subgroup (36.9 months, p = 0.001). Compared with the PAT subgroup, the FEM and COM subgroups showed a higher incidence of a second-time LPD (p = 0.025). The time intervals between the two LPDs were shorter in the FEM and COM subgroups (20.8 months and 19.2 months) than in the PAT subgroup (32.5 months, p = 0.049).ConclusionA complete MPFL tear, isolated femoral-side tear and combined tear in a first-time LPD predispose a second-time LPD.

Correlation analysis between injury patterns of medial patellofemoral ligament and vastus medialis obliquus after acute first-time lateral patellar dislocation.

To evaluate the correlation between injury patterns of the medial patellofemoral ligament (MPFL) and vastus medialis obliquus (VMO) after acute first-time lateral patellar dislocation (LPD) in adults. Magnetic resonance imaging (MRI) was prospectively performed in 132 consecutive adults with acute first-time LPD. Images were acquired and evaluated using standardized protocols. Injury patterns of MPFL were grouped by location and severity for analysis of the prevalence of VMO injury. MRI demonstrated VMO injury in 63 (47.7%) patients. Twenty (38.5%) and 43 cases (56.6%) were present in partial and complete MPFL tear subgroups, respectively. Compared with partial MPFL tears, complete tears showed a higher prevalence of VMO injury (P=0.044). The mean coronal (28.5mm) and mean sagittal VMO elevations (20.7mm) were higher in the complete MPFL tear subgroup than in the partial tear subgroup (19.8mm, P=0.005; 11.9mm, P<0.001). No correlations were identified between the prevalence of VMO injury and location subgroups of MPFL injury (n.s.). Mean VMO elevations were higher in isolated femoral-side (FEM) and combined MPFL tear (COM) subgroups (mean coronal VMO elevation of 29mm and mean sagittal VMO elevation of 20.8mm in the FEM subgroup; mean coronal VMO elevation of 29.6mm and mean sagittal VMO elevation of 23.1mm in the COM subgroup) than in the isolated patellar-side MPFL tear (PAT) subgroup (P=0.022, P<0.001) (mean coronal VMO elevation of 20.7mm and mean sagittal VMO elevation of 10.6mm). Complete MPFL tear predisposes to VMO injury and has a higher elevation of torn VMO after acute first-time LPD in adults. Isolated femoral-side and combined MPFL tears predispose to higher elevation of torn VMO. IV.

Injury patterns of medial patellofemoral ligament after acute lateral patellar dislocation in children: Correlation analysis with anatomical variants and articular cartilage lesion of the patella.

To assess the relationship between injury patterns of medial patellofemoral ligament (MPFL) and anatomical variants and patellar cartilage lesions after acute lateral patellar dislocation (LPD) in children. MR images were obtained in 140 children with acute LPD. Images were acquired and evaluated using standardised protocols. Fifty-eight cases of partial MPFL tear and 75 cases of complete MPFL tear were identified. Injuries occurred at an isolated patellar insertion (PAT) in 52 cases, an isolated femoral attachment (FEM) in 42 cases and an isolated mid-substance (MID) in five cases. More than one site of injury was identified in 34 cases. Compared with Wiberg patellar type C, Wiberg patellar type B predisposed to complete MPFL tear (P = 0.042). No correlations were identified between injury patterns of MPFL and trochlear dysplasia, patellar height and tibial tuberosity-trochlear groove distance (P > 0.05). Compared with partial MPFL tear, complete MPFL tear predisposed to Grade-IV and Grade-V patellar chondral lesion (P = 0.02). There were no correlations between incidence of patellar cartilage lesion and injury locational-subgroups of MPFL (P = 0.543). MPFL is most easily injured at the PAT in children. Wiberg patellar type B predisposes to complete MPFL tear. Complete MPFL tear predisposes to a higher grade of patellar chondral lesion. • MPFL is most easily injured at its patellar insertion in children. • Wiberg patellar type B predisposes to complete MPFL tear. • No correlations between injury patterns of MPFL and other three anatomical variants. • Complete MPFL tear predisposes to higher grade patellar chondral lesion. • No correlations between injury locations of MPFL and patellar cartilage lesion.

Radiographic Assessment of Anatomic Risk Factors Associated with Acute, Lateral Patellar Dislocation in the Immature Knee.

Acute patellar dislocation remains a common injury in both adult and pediatric patients. Non-operative management has been advocated for patients without a history of recurrent instability. Although pathologic thresholds for consideration of operative management have previously been reported in adults, it is largely unknown in children. A retrospective review of all skeletally immature patients diagnosed with acute lateral patellar dislocation who had MRI imaging were included for analysis. An age-based control group was also identified. Six radiographic measurements were compared: lateral trochlear inclination (LTI), trochlear facet asymmetry (TFA), trochlear depth (TD), tibial tuberosity–trochlear groove (TT–TG), sulcus angle (SA) and patellar height ratio. A total of 178 patients were included for analysis (study: n = 108, control: n = 70). The mean age of patients in the study and control groups was 13.7 and 12.1 years respectively (p ≤ 0.001). Study group patients had significant differences in all radiographic measurements including a decreased LTI (p < 0.001), increased TFA (p < 0.001) and SA (p < 0.001). The mean trochlear depth was 3.4 mm and 5.6 mm for patients in the study and control groups respectively (p < 0.001). Study group patients had an increased patellar height ratio (p < 0.001) and TT–TG distance (p < 0.001). Morphologic abnormalities may predispose skeletally immature patients to an increased risk of acute lateral patellar instability.