Acute Primary Patellar Dislocation Research Articles

High Rates of Damage to the Medial Patellofemoral Ligament, Lateral Trochlea, and Patellar Crest After Acute Patellar Dislocation: Magnetic Resonance Imaging Analysis

The primary outcome of interest of this study was to determine the frequency, location, and extent of chondral injuries and medial patellofemoral ligament (MPFL) tears, along with the rate of loose bodies, in the knee after acute primary patellar dislocation. The secondary outcome of interest was to conduct a multivariate analysis to investigate whether the presence of pathoanatomic abnormalities, including structural differences in the knees of the patients, is associated with the features of the lesions. Patients who underwent magnetic resonance imaging after primary acute patellar dislocation were identified from our institutional databases. We analyzed a total of 175 magnetic resonance imaging scans of patients aged between 14 and 25 years who were eligible for inclusion. Chondral damage to the medial facet of the patella was present in 36 patients; patellar crest, 78 patients; and lateral patellar facet, 28 patients. One patient presented with chondral defects in the medial trochlear facet, whereas 118 patients showed chondral defects in the lateral trochlear facet. Loose bodies were present in 142 patients. A total of 161 patients (92%) showed MPFL damage. The patellar portion was affected in 119 patients. Of the patients, 28 showed a partially damaged MPFL (<50%), 42 showed MPFL damage greater than 50%, and 49 presented with a complete tear of the MPFL. MPFL lesions were observed on the femoral side in 42 patients. Fourteen patients presented with an avulsion fracture on the patellar side; 28 patients, on the femoral side. The MPFL was injured in 92% of 175 patients after a first-time acute patellar dislocation. Chondral damage was most frequent at the patellar crest, followed by the lateral femoral epicondyle. No association was found between patella alta, the sulcus angle, the Q angle, the tibial tubercle-trochlear groove distance, trochlear and patellar dysplasia, and soft-tissue damage. Level IV, retrospective cohort study.

Magnetic Resonance Imaging of Patellofemoral Morphometry Reveals Age and Gender Variations in the Knees of Children and Adolescents.

Background: The morphology and alignment of the patellofemoral joint are crucial risk factors for patellar instability, and the incidence of acute primary patellar dislocation is the highest in women in their second decade of life. The purpose of the study was to analyze age and gender variations of the patellofemoral joint using magnetic resonance imaging (MRI). Methods: A total of 852 patients aged between 4 and 18 years with a history of knee MRI examinations were screened for eligibility and 663 patients (470 males, 193 females) were included. Patients were divided into groups according to age and sex. The age group was divided into five groups (Group 1, 4–6 years; Group 2, 7–9 years; Group 3, 10–12 years; Group 4, 13–15 years; and Group 5, 16–18 years). Three orthopaedic surgeons measured MRI parameters reflecting the patellofemoral morphology (sulcus angle, lateral trochlear inclination, trochlear facet symmetry, and femoral depth) and alignment (tibial tuberosity–trochlear groove distance, percent sulcus location, and percent tibia tuberosity location). Results: Parameters including tibial tuberosity–trochlear groove distance, sulcus angle, percent tibial tuberosity location, trochlear facet symmetry, and femoral depth showed significant differences between the age groups (p < 0.05). The sulcus angle decreased fin Group 2, and the femoral depth showed an increasing trend with aging in male patients. However, the sulcus angle in females decreased first and then increased in Group 3 as the inflection point. The femoral depth showed an opposite pattern. Conclusions: Patellofemoral morphometry showed age and gender variation. Notably, the sulcus angle and femoral depth were significantly different between males and females and changed according to the development. These findings may reflect the sex difference and peak incidence of the patellar instability risk. Understanding the morphological changes and differences of the patellofemoral joint may facilitate the diagnosis of patellofemoral pathologies.

Medial Patellofemoral Complex Advancement for Recurrent Lateral Patellar Instability and Selective Acute Primary Patellar Dislocations

Medial patellofemoral complex (MPFC) is considered as the primary medial patellar restraint and has a static, as well as dynamic, component. MPFL reconstruction (MPFL-R) restores only the static component of MPFC, is associated with multiple technical concerns, and has a steep learning curve. Need for physeal sparing techniques and relatively high rates of complications including patella fracture are some other concerns with MPFL-R. We propose a simple procedure for advancement of MPFC onto patella, which is indicated in most of the recurrent lateral instabilities (with a positive lateral glide test result and an intact MPFL on magnetic resonance imaging). The procedure is also indicated in selective acute primary dislocations—those with associated chondral lesions and magnetic resonance imaging–documented isolated patellar side avulsion/injury. MPFC advancement is a more anatomical procedure that also restores dynamic medial checkrein of patella and can be performed even by a novice surgeon. MPFC advancement is devoid of the multiple technicalities of MPFL-R, does not require intraoperative imaging or any postoperative immobilization, and renders complications like donor graft-site morbidity and patella fractures irrelevant. It requires no modifications in patients with open physes and can be performed in isolation or with other procedures as per à la carte principle.

Surgical medial patellofemoral ligament reconstruction versus non-surgical treatment of acute primary patellar dislocation: a prospective controlled trial.

The acute primary (first-time) lateral patellar dislocation is associated with a high rate of functional disability. There is no consensus as to the choice of surgical or non-surgical treatment for these patients. The aim of this study is to compare the clinical results between the surgical (reconstruction of the medial patellofemoral ligament [MPFL]) and non-surgical treatments for acute primary patellar dislocations. Sixty-nine skeletally mature patients (69 knees) were included in this prospective non-randomized controlled trial. At least one predisposing factor for patellar dislocation (including patella alta, high lateral patellar tilt, trochlear dysplasia, and increased TT-TG distance) was identified in the included patients. Thirty patients were treated surgically with MPFL reconstruction, and the other 39 patients were treated non-surgically. The main outcome variable was patellar redislocation within a two year follow-up period. The Kujala questionnaire was applied for analyzing the pain and the quality of life. The additional surgeries due to patellofemoral problems were also recorded. Patellar redislocation occurred in eight patients in the non-surgical group, while no redislocation occurred in the surgical group (P < 0.05). Four patients in non-surgical group underwent further surgery due to patellar redislocation and poor function during the follow-up period. The Kujala score and the percentage of "good/excellent" results on the Kujala score of the surgical group were significantly better than that of the non-surgical group (P < 0.05). The surgical MPFL reconstruction achieved better clinical outcomes compared with non-surgical treatment for the acute primary patellar dislocation in the skeletally mature patients with the presence of abnormal patellofemoral anatomy. Surgery should be considered as the better choice for these specific patients.

Surgical versus Nonsurgical Treatments of Acute Primary Patellar Dislocation with Special Emphasis on the MPFL Injury Patterns.

The objective of the present study was to compare the clinical results of the surgical versus nonsurgical treatments of acute primary patellar dislocations with a medial patellofemoral ligament (MPFL) injury in the nonoverlap region with the vastus medialis oblique. In this study, 62 patients with an acute patellar dislocation and a concurrent MPFL injury in the nonoverlap region were randomly divided into two groups based on their birth years (even vs. odd years) and received either surgical or nonsurgical treatment. Of the 62 eligible patients, 30 were in the nonsurgical treatment group (Group 1) and 32 were in the surgical group (Group 2). Patellar stability tests and the Kujala knee questionnaire were performed, and radiographs were evaluated for patellar tilt and the lateral shift ratio by two blinded investigators. An osteochondral injury was noted in six (23.1%) patients from Group 1 and five (16.7%) patients from Group 2, with no statistical difference between the two groups. The mean Kujala score was 80.19 ± 5.07 and 93.57 ± 4.03 (p < 0.001) between the surgical and nonsurgical groups, respectively. The mean patellar tilt was 8.96 ± 1.64 and 6.83 ± 1.44 degrees (p < 0.001) and the lateral shift ratio was 11.08 ± 1.99 and 9.23 ± 1.96 (p = 0.001) between the surgical and nonsurgical groups, respectively. This study showed that the surgical treatment of MPFL injuries in the nonoverlap region achieved better clinical outcomes and improved subjective knee function compared with conservative therapy. Surgery should therefore be considered as the treatment of choice for these specific injuries.

Long-term follow-up of nonoperatively and operatively treated acute primary patellar dislocation in skeletally immature patients.

Purpose. The present study reports a long-term follow-up of acute primary patellar dislocation in patients with open physes. The purpose of the study was to evaluate knee function and recurrence rates after surgical and nonsurgical treatment of patellar dislocation. Methods. A total of 51 patients, including 29 girls and 22 boys, who were 9–14 years of age at the time of injury, were retrospectively evaluated. The minimum follow-up time was 5 years. Thigh muscle torque, range of motion, the squat test, the knee injury and osteoarthritis outcome score (KOOS), the Kujala score, and the recurrence rate were registered. Radiological predisposing factors at the time of injury were determined. Results. Quality of life and sports/recreation were the most affected subscales, according to KOOS, and a reduced Kujala score was also observed in all treatment groups. The surgically treated patients had a significantly lower recurrence rate. Those patients also exhibited reduced muscle performance, with a hamstring to quadriceps ratio (H/Q) of 1.03. The recurrence rate was not correlated with knee function. Conclusions. Patellar dislocation in children influences subjective knee function in the long term. Surgery appears to reduce the recurrence rate, but subjective knee function was not restored.

Vastus Medialis Obliquus Muscle Morphology in Primary and Recurrent Lateral Patellar Instability

The morphology of the vastus medialis obliquus (VMO) muscle in the anatomical setting of an unstable patella has not been described. Therefore, the purpose of this study was to investigate the morphological parameters of the VMO muscle that delineate its importance in the maintenance of patellofemoral joint stability. Eighty-two consecutive subjects were prospectively enrolled in this study. The groups were composed of thirty patients with an acute primary patellar dislocation, thirty patients with recurrent patellar dislocation, and twenty-two controls. Groups were adjusted according to sex, age, body mass index, and physical activity. Magnetic resonance imaging was used to measure the VMO cross-sectional area, muscle-fiber angulation, and the craniocaudal extent of the muscle in relation to the patella. No significant difference was found with respect to all measured VMO parameters between primary dislocation, recurrent dislocation, and control subjects with a trend noted for only the VMO cross-sectional area and the VMO muscle-fiber angulation. This finding is notable in that atrophy of the VMO has often been suggested to play an important role in the pathophysiology of an unstable patellofemoral joint.

Incidence and Risk Factors of Acute Traumatic Primary Patellar Dislocation

The purpose of this study was to investigate incidence, nature, and risk factors of primary traumatic patellar dislocations. We identified acute first-time traumatic patellar dislocations from a national hospital discharge register. Patients with previous patellar dislocations, subluxations, or knee traumas were excluded. The sample consisted of 128,714 Finnish male conscripts (median age 20). Background risk factor data were obtained from a Finnish conscript service database. The dislocators were observed during their service period for a short-term outcome. From the 128,714 male conscripts, 278 had patellar dislocations, and 72 were classified as having sustained first-time traumatic patellar dislocations. The 128,436 nondislocators served as a control group. The incidence of acute traumatic primary patellar dislocations among male conscripts was 77.4 (95% CI: 61.1-96.8) per 100,000 persons per year. The male patients with traumatic primary patellar dislocations were taller (P = 0.03) and weighed more (P = 0.02) than the controls. Hemarthrosis was present in all patients, and when MRI or open surgery was performed, medial retinacular disruption and medial patellofemoral ligament (MPFL) injury were identified. Patients' return to military service was unrelated to the choice of treatment. Primary patellar dislocation is not a negligible cause of morbidity among young male adults. It can be concluded that hemarthrosis and MPFL rupture are the definite signs of an acute traumatic primary patellar dislocation. Height and weight were significant risk factors, whereas poor physical performance was not associated with primary patellar dislocation.

Medial marginal fracture of the patella following patellar dislocation

Among patients with patellar dislocation, a small fragment is occasionally found along the medial border of the patella. However, the detailed pathology of this fracture has not been clearly described, especially in relation to the medial patellofemoral ligament (MPFL). The purpose of this study was to describe the pathology of this fracture in relation to the MPFL. The subjects were seven patients with an acute primary patellar dislocation showing a medial marginal fracture of the patella. An open exploration was performed to confirm the relationship between the fragment and the MPFL. The MPFL was repaired by re-attachment to the patella with anchors. The patellar fracture site was determined by the location of anchors in the post-operative plain radiograph. The fragments were continuous with the thick and taut MPFL in all cases. Re-attachment of the MPFL stabilized the patella against lateral shift by manual force improving the tracking. All patients returned to their pre-injury activity level without any episodes of recurrent dislocation or subluxation at the final follow up (av. 31 months). Medial marginal fracture of the patella was an avulsion fracture of the MPFL that occurred at the middle one-third of the patella.

An Algorithm Guiding the Evaluation and Treatment of Acute Primary Patellar Dislocations

Primary patellar dislocation continues to be a common problem facing clinicians today. These injuries are associated with significant morbidity and a substantial recurrence rate. A myriad of operative and nonoperative options have been described to treat these injuries though the evidence-based literature is sparse. As a result, much controversy exists regarding the ideal management of the primary patellar dislocation. This article reviews the literature on this topic, from the initial examination and management to definitive treatment. Furthermore, an algorithm is presented to help the clinician approach and treat these patients.

Acute Traumatic Primary Patellar Dislocation

This report evaluates the subjective, clinical, and functional long-term results comparing surgical and conservative treatment in patients with a primary traumatic patellar dislocation. This retrospective clinical study focuses on patients with primary acute traumatic patellar dislocation. Patients with radiologic signs indicative of a predisposition for recurrent patellar instability were excluded from this study. A total of 126 patients were examined a mean of 8.1 years after initial treatment of their primary patellar dislocation. Patients were retrospectively divided into groups with conservative therapy (n = 63), diagnostic arthroscopy only (n = 20), immediate surgical reconstruction of the parapatellar ligament complex (n = 37), and refixation of osteochondral fragments (n = 6). Redislocation and resurgery rate, activity level, and subjective, clinical, and functional results were evaluated in these patients, and the outcomes in these groups were compared. In the long term, functional results (as expressed in the Lysholm score) were excellent or good in 85% of the patients, and good subjective results were reported by 71%, but follow-up revealed a recurrence rate of 26% in the total study population. The high activity level before the initial trauma could not be completely regained after treatment. There was no significant difference between the surgically and conservatively treated groups in the redislocation and reoperation rates, level of activity, or functional and subjective outcomes. Even with a focus on acute traumatic etiology and when factors predisposing to recurrent instability are largely excluded, the redislocation rate after treatment of acute patellar dislocation is still high, despite good clinical and subjective results. Conservative management seems to be the treatment of choice in patients with acute patellar dislocation, provided that the generally accepted indications for surgery, such as evidence of osteochondral fragments and major defects of the parapatellar ligament complex, are given due consideration.

Characteristics of patients with primary acute lateral patellar dislocation and their recovery within the first 6 months of injury.

We prospectively studied the characteristics and early recovery of an unselected population of patients who had acute first-time lateral patellar dislocation. The recovery program used standardized rehabilitation, emphasizing range of motion, muscle strength, and return of function. Patients returned to stressful activities including sports as tolerated when they regained full passive range of motion, had no effusion, and when quadriceps muscle strength was at least 80% compared with the noninjured limb. Seventy-four patients met the enrollment criteria; 37 men and 37 women. The average age was 19.9 years, and preinjury sports participation was similar to that of ligament-injury patients. Four percent of patients (N = 3) had a history of birth complications, 3% (N = 2) had a history of lower extremity problems as an infant or child, and 9% (N = 7) had a family history of patellar dislocation. Radiographs revealed a 50% incidence (N = 37) of patella alta; all patients demonstrated lateral patellar overhang. Patients regained range of motion (mean, 0 degrees to 132 degrees) by 6 weeks. Sports participation remained significantly reduced throughout the first 6 months after injury, with the greatest limitations in kneeling and squatting. At 6 months, 58% of patients (N = 43) noted limitation in strenuous activities. The patients who had acute primary patellar dislocation were young and active. Most injuries occurred during sports, and few patients had abnormal physical features, contradicting any stereotype of an overweight, sedentary, adolescent girl whose patella dislocates with little or no trauma.

Patellofemoral osteoarthritis after patellar dislocation.

Clinical and radiographic studies were done for 85 patients treated conservatively for acute primary patellar dislocation occurring an average 13 years (range, 6-26 years) previously. Osteoarthritic changes in the patellofemoral joint were evaluated with special reference to the primary conservative treatment and treatment of redislocations (operative or conservative) or treatment for other subsequent problems such as pain and/or subluxations (late surgery). The patients were divided into two groups on the basis of findings in the unaffected knee and other joints. There were 56 patients (66%) with predisposing factors such as an abnormal quadriceps angle, positive apprehension test, quadriceps muscle atrophy, or generalized joint laxity common to all patients. Patients with or without predisposing factors did not differ from each other in terms of arthritic changes. Patellofemoral joint degeneration was found in the affected knee in 19 patients (22%) and in the unaffected knee in nine (11%). Conservative treatment without subsequent redislocations resulted in osteoarthritic changes in 29% of the cases and in 13% of cases with occasional redislocations. Osteoarthritic changes were found in 17% of patients treated operatively and in 12% of patients treated conservatively for redislocations. Of the patients who underwent late surgery for patellofemoral pain or subluxations, 35% showed osteoarthritic changes. In general, there were more degenerative changes in patients with stable patellae (no redislocations) than in those with occasional recurrences, especially in older and heavier patients.

Acute dislocation of the patella

We report a prospective study of 55 patients with acute primary patellar dislocation, all treated by operation and followed up for at least two years. Diagnosis was based on the history of a lateral displacement, with medial tenderness and a positive apprehension test; redislocations were excluded. Before operation, the difference in lateral shift on skyline views of the injured and control patellae was highly significant. At operation, rupture of the medial retinaculum of the patella was seen in all but one case. There were medial marginal fractures of the patella in 23 cases. Subjective results of the operation were excellent or good in 44 of the 55 at two years with a redislocation rate of only 9%. Most patients were able to return to the same level of sporting activity as before the injury.

Acute dislocation of the patella. A prospective review of operative treatment

We report a prospective study of 55 patients with acute primary patellar dislocation, all treated by operation and followed up for at least two years. Diagnosis was based on the history of a lateral displacement, with medial tenderness and a positive apprehension test; redislocations were excluded. Before operation, the difference in lateral shift on skyline views of the injured and control patellae was highly significant. At operation, rupture of the medial retinaculum of the patella was seen in all but one case. There were medial marginal fractures of the patella in 23 cases. Subjective results of the operation were excellent or good in 44 of the 55 at two years with a redislocation rate of only 9%. Most patients were able to return to the same level of sporting activity as before the injury.