Morphology of occult posterior malleolus fractures associated with tibial shaft fractures

Aims: Occult posterior malleolar fractures (PMFs) associated with tibial shaft fractures are thought to occur most commonly in spiral fracture types of the tibia. We hypothesize that tibial diaphyseal fracture patterns would be associated with certain PMFs, highlighting the pathomechanics of the in...

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Main Authors: Darren Myatt, Howard Stringer, James Chapman, Ben E. Fischer, Lyndon Mason
Format: Article
Language:English
Published: The British Editorial Society of Bone & Joint Surgery 2025-04-01
Series:Bone & Joint Open
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Online Access:https://online.boneandjoint.org.uk/doi/epdf/10.1302/2633-1462.64.BJO-2024-0132.R1
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author Darren Myatt
Howard Stringer
James Chapman
Ben E. Fischer
Lyndon Mason
author_facet Darren Myatt
Howard Stringer
James Chapman
Ben E. Fischer
Lyndon Mason
author_sort Darren Myatt
collection DOAJ
description Aims: Occult posterior malleolar fractures (PMFs) associated with tibial shaft fractures are thought to occur most commonly in spiral fracture types of the tibia. We hypothesize that tibial diaphyseal fracture patterns would be associated with certain PMFs, highlighting the pathomechanics of the injury. Methods: A retrospective review was performed on data collected between 1 January 2013 and 9 November 2020. The inclusion criteria were patients aged over 16 years with a diaphyseal tibial fracture who had undergone a CT of the affected lower limb. The Mason and Molloy posterior malleolar fracture classification system was used to describe the morphology of the PMFs. Results: There were 764 diaphyseal fractures identified. Of these, 442 met the inclusion criteria. A total of 107patients (24.21%) had PMF extensions. The classification of the PMFs according to Mason and Molloy revealed eight type 1 fractures (7.48%), 60 type 2A (56.07%), six type 2B (5.61%), and 33 type 3 fractures (30.84%). The most common PMF seen in this study was the minor rotational pilon (type 2A). PMFs generally occur in combination with spiral diaphyseal fractures (42A1, 42B1, 42C1, and 43A1). The majority of PMFs were undisplaced pre-surgical intervention. Only the 2B subtype (major rotational pilon) had a significant association with fracture displacement. Conclusion: This study highlighted an association between spiral tibial shaft fractures and type 2A posterior malleolus fractures. Unlike the PM fractures of the ankle, the majority of PM fractures associated with tibia fractures are undisplaced. We theorize that unlike the force transmission in ankle fractures, where the rotational force is in the axial plane in a distal-proximal direction, in the PM fractures related to tibia fractures, the rotational force in the axial plane progresses from proximal-distal. Therefore, the force transmission which exits posteriorly, finally dissipates the force and is thus unlikely to displace. Cite this article: Bone Jt Open 2025;6(4):446–453.
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spelling doaj-art-6750aeb25e8b43eda5e1c3e653bb0a002025-08-20T03:53:42ZengThe British Editorial Society of Bone & Joint SurgeryBone & Joint Open2633-14622025-04-016444645310.1302/2633-1462.64.BJO-2024-0132.R1Morphology of occult posterior malleolus fractures associated with tibial shaft fracturesDarren Myatt0Howard Stringer1James Chapman2Ben E. Fischer3Lyndon Mason4Trauma and Orthopaedic Department, Liverpool University Hospitals NHS Foundation Trust, Liverpool, UKTrauma and Orthopaedic Department, Liverpool University Hospitals NHS Foundation Trust, Liverpool, UKTrauma and Orthopaedic Department, Liverpool University Hospitals NHS Foundation Trust, Liverpool, UKTrauma and Orthopaedic Department, Liverpool University Hospitals NHS Foundation Trust, Liverpool, UKTrauma and Orthopaedic Department, Liverpool University Hospitals NHS Foundation Trust, Liverpool, UKAims: Occult posterior malleolar fractures (PMFs) associated with tibial shaft fractures are thought to occur most commonly in spiral fracture types of the tibia. We hypothesize that tibial diaphyseal fracture patterns would be associated with certain PMFs, highlighting the pathomechanics of the injury. Methods: A retrospective review was performed on data collected between 1 January 2013 and 9 November 2020. The inclusion criteria were patients aged over 16 years with a diaphyseal tibial fracture who had undergone a CT of the affected lower limb. The Mason and Molloy posterior malleolar fracture classification system was used to describe the morphology of the PMFs. Results: There were 764 diaphyseal fractures identified. Of these, 442 met the inclusion criteria. A total of 107patients (24.21%) had PMF extensions. The classification of the PMFs according to Mason and Molloy revealed eight type 1 fractures (7.48%), 60 type 2A (56.07%), six type 2B (5.61%), and 33 type 3 fractures (30.84%). The most common PMF seen in this study was the minor rotational pilon (type 2A). PMFs generally occur in combination with spiral diaphyseal fractures (42A1, 42B1, 42C1, and 43A1). The majority of PMFs were undisplaced pre-surgical intervention. Only the 2B subtype (major rotational pilon) had a significant association with fracture displacement. Conclusion: This study highlighted an association between spiral tibial shaft fractures and type 2A posterior malleolus fractures. Unlike the PM fractures of the ankle, the majority of PM fractures associated with tibia fractures are undisplaced. We theorize that unlike the force transmission in ankle fractures, where the rotational force is in the axial plane in a distal-proximal direction, in the PM fractures related to tibia fractures, the rotational force in the axial plane progresses from proximal-distal. Therefore, the force transmission which exits posteriorly, finally dissipates the force and is thus unlikely to displace. Cite this article: Bone Jt Open 2025;6(4):446–453.https://online.boneandjoint.org.uk/doi/epdf/10.1302/2633-1462.64.BJO-2024-0132.R1posterior malleolar fracturetibial shaft fracturemorphologyarticular extensionspiral fractureposterior malleolus fracturestibial shaft fracturestibial fracturesfractures of the ankleposterior malleolar fracturesdiaphyseal tibial fracturesdiaphyseal fracturestibiatibial diaphyseal fracturelower limb
spellingShingle Darren Myatt
Howard Stringer
James Chapman
Ben E. Fischer
Lyndon Mason
Morphology of occult posterior malleolus fractures associated with tibial shaft fractures
Bone & Joint Open
posterior malleolar fracture
tibial shaft fracture
morphology
articular extension
spiral fracture
posterior malleolus fractures
tibial shaft fractures
tibial fractures
fractures of the ankle
posterior malleolar fractures
diaphyseal tibial fractures
diaphyseal fractures
tibia
tibial diaphyseal fracture
lower limb
title Morphology of occult posterior malleolus fractures associated with tibial shaft fractures
title_full Morphology of occult posterior malleolus fractures associated with tibial shaft fractures
title_fullStr Morphology of occult posterior malleolus fractures associated with tibial shaft fractures
title_full_unstemmed Morphology of occult posterior malleolus fractures associated with tibial shaft fractures
title_short Morphology of occult posterior malleolus fractures associated with tibial shaft fractures
title_sort morphology of occult posterior malleolus fractures associated with tibial shaft fractures
topic posterior malleolar fracture
tibial shaft fracture
morphology
articular extension
spiral fracture
posterior malleolus fractures
tibial shaft fractures
tibial fractures
fractures of the ankle
posterior malleolar fractures
diaphyseal tibial fractures
diaphyseal fractures
tibia
tibial diaphyseal fracture
lower limb
url https://online.boneandjoint.org.uk/doi/epdf/10.1302/2633-1462.64.BJO-2024-0132.R1
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AT benefischer morphologyofoccultposteriormalleolusfracturesassociatedwithtibialshaftfractures
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