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The majority of patellar avulsion fractures in first-time acute patellar dislocations included the inferomedial patellar border that was different from the medial patellofemoral ligament attachment

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Accurate assessment of the locations of patellar avulsion fractures in acute patellar dislocations is clinically relevant for decision making for treatment. The study aim was to classify the locations of patellar avulsion fractures with a focus on the ligament attachments of medial stabilizing structures.


Out of 131 first-time acute traumatic patellar dislocations, 61 patients had patellar fractures. Subsequently, 10 patients with isolated osteochondral fractures of the articular surface in the patella were excluded. Finally, 51 patients (34 females and 17 males, average age: 18.5 years, 95% CI 16.1–20.9) were included in the study cohort. Based on the locations of the patellar attachment, the patients were divided into three groups: the superior group [medial patellofemoral ligament (MPFL) attachment], inferior group [medial patellotibial ligament (MPTL)/medial patellomeniscal ligament (MPML) attachment], and mixed group.


In the patellar avulsion group (51 patients), the superior group, mixed group, and inferior group contained 8/51 (16%), 12/51 (24%), and 31/51 (61%) patients, respectively.


This study showed that 84% of the patellar avulsion fractures were located in the inferomedial patellar border, which consisted of MPTL/MPML attachments that were clearly different from the true “MPFL” attachment at the superomedial patellar border. In terms of the clinical relevance, the acute surgical repair of MPTL/MPML attachments in the inferomedial patellar border may not sufficiently control the patella if optimal management of the MPFL is not performed.

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The authors would like to thank all doctors in Niigata University and the affiliated hospitals: Drs. Watanabe K, Yamamoto N, Omori G, Shiozaki H, Segawa H, Matsueda M, Yamagiwa H, Higano Y, Ariumi A, Mera H, Murayama T, Fujii T, Koga H, Takagi S, Muraoka O, Yamanaka K, Hokari S, Hosono Y, Otani K, Soeno T, Hijikata H, Sasage Y, Maeda K, Someya K, Fujita Y, Takagi Y, Shima T, and Koga Y.

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Correspondence to Tomoharu Mochizuki.

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All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

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Mochizuki, T., Tanifuji, O., Watanabe, S. et al. The majority of patellar avulsion fractures in first-time acute patellar dislocations included the inferomedial patellar border that was different from the medial patellofemoral ligament attachment. Knee Surg Sports Traumatol Arthrosc (2020). https://doi.org/10.1007/s00167-020-05853-5

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  • Acute patellar dislocation
  • Patellar avulsion facture
  • Medial patellofemoral ligament
  • Medial patellotibial ligament
  • Medial patellomeniscal ligament