Sonography on injury of the medial patellofemoral ligament after acute traumatic lateral patellar dislocation: Injury patterns and correlation analysis with injury of articular cartilage of the inferomedial patella
Introduction
Acute lateral patellar dislocation is a common injury that typically occurs in young, active patients. The prevalence of acute lateral patellar dislocations may account for 2–3% of all knee injuries [1]. This injury may result in numerous lesions, including contusions or articular cartilage injuries of the lateral femoral condyle and medial patella, injuries of the medial patellofemoral ligament (MPFL) and vastus medialis obliquus (VMO), joint effusion and so on [2]. Although there is controversy on whether surgical treatment can improve clinical outcome after traumatic patellar dislocation, a complete ligament tear is still considered by many authors to be an indication for early surgery [3], [4], [5]. Sillanpää and Kang also found that different parts of MPFL injury play a significant role in the incidence of patellar instability after conservative treatment [6], [7]; hence, the localisation and extent of MPFL injury are important factors that should be taken into consideration in a decision on the treatment strategy. Although the applications of high-frequency ultrasonography (US) in musculoskeletal system are increasingly extensive, it has been rarely applied in acute traumatic lateral patellar dislocation compared with magnetic resonance imaging (MRI) [8], [9], [10], [11]. As the major static soft-tissue restraint to lateral patellar translation [12], [13], there still remain some conflicts about the tear locations of the MPFL with traumatic lateral patellar dislocations [2], [8], [9], [10], [11], [14], [15], [16], [17], [18], [19], [20], [21], [22]. Although there were some studies about the articular cartilage lesions of the inferomedial patella [2], [10], [14], [15], [16], [17], [18], there were no studies concentrating on the correlation between injuries of the MPFL and the articular cartilage of the inferomedial patella. We undertook this retrospective sonographic study to assess the injury pattern of MPFL, as well as the accuracy of US in the diagnosis of MPFL injury and the correlation between injuries of MPFL and articular cartilage of the inferomedial patella after acute traumatic lateral patellar dislocations based on the surgical results.
Section snippets
Clinical data
This is a retrospective analysis of data selected from the Department of Orthopaedic Surgery of Qianfoshan Hospital between January 2009 and June 2012.
The inclusion criteria were first-time traumatic patella dislocation, treated surgically as an urgent case, a mandatory preoperative US scan and the time interval between trauma and the US scan of less than 14 days.
The exclusion criteria were a history of previous patellar dislocations in the same knee, subluxation or other previous traumas,
MPFL injury
Twenty-one cases of partial MPFL tear and 28 cases of complete MPFL tear were identified in surgery. There were nine cases of partial MPFL tear at the femoral attachment (Fig. 2), eight cases at the patellar insertion (Fig. 3, Fig. 4) and one case at the midsubstance diagnosed by US, which were confirmed by following surgery. Fifteen cases of complete MPFL tear at the femoral attachment (Fig. 5, Fig. 6) and 11 cases at the patellar insertion (Fig. 7) diagnosed by US were confirmed by following
Discussion
As the MPFL is major ligamentous restraint against lateral patellar dislocation, MPFL injuries occur in up to 94–100% of lateral patellar dislocations [18], [25]. Injury to this ligament reduces passive stability by 50–60% and may predict subsequent instability with non-operative treatment; this has led to an increase in initial management by operative repair or reconstruction of the MPFL [4], [6], [19], [26], [27], [28], [29], [30], [31], [32], [33].
However, the injury patterns of MPFL,
Conflict of interest statement
The authors declared no conflict of interest. No external funding was received in the study.
Acknowledgements
The authors would like to thank Dr. Zheng-Wu Bai and Dr. Ming Zhang (Department of Orthopaedic Surgery, Qianfoshan Hospital of Shandong University) for help with clinical contributions and the valuable remarks given to improve this article.
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