Does the relative density of periarticular bone influence the failure pattern of intra-articular fractures?
BACKGROUND
The architecture of joints almost certainly influences the nature of intra-articular fractures, and the concavity is much more likely to fail than the associated convexity. However, local differences in periarticular bone density potentially also plays a critical role. The purpose of this study was to investigate if there was any difference in periarticular bone density in intra-articular fractures between the two opposing joint surfaces, comparing the convexity to the concavity.


METHODS
We retrospectively identified a series of 1003 intra-articular fractures of the hip, knee, and ankle; 129 of these patients had previously undergone CT scanning during their routine clinical assessment. Periarticular bone density was assessed using Hounsfield Units (HU) as a measure of the composite density of the adjacent bone. Bone density was compared between the opposite sides of each joint, to determine if a relationship exists between local bone density and the risk of articular surface fracture.


RESULTS
There was a statistically significant difference in density between the two opposing surfaces, with the convexity 19% more dense than the concavity (p=0.0001). The knee exhibited the largest difference (55%), followed by the hip (18%); in the ankle, an inverse relationship was observed, and the concave surface was paradoxically denser (5%). There was no significant difference between those cases where the concavity failed in isolation compared to those where the convexity also failed (p=0.28).


CONCLUSIONS
When the results were pooled for all three joints, there was a statistically significant higher local bone density demonstrated on the convex side of an intra-articular fracture. However, while this relationship was clearly exhibited in the knee, this was less evident in the other two joints; in the ankle the reverse was true, and the local bone adjacent to the concavity was found to have greater density. This suggests local bone density plays only a minor role in determining the nature of intra-articular fractures.
Department of Orthopaedic Surgery, The Royal Brisbane and Women's Hospital, Brisbane, Australia; University of Queensland, School of Medicine, Brisbane, Australia.
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Tetsworth
Department of Orthopaedic Surgery, The Royal Brisbane and Women's Hospital, Brisbane, Australia; University of Queensland, School of Medicine, Brisbane, Australia.
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Borshch
Department of Trauma, General Hospital of Vienna, Medical University of Vienna, Austria.
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Dlaska
Musculoskeletal Research Unit, Central Queensland University, Rockhampton, Australia; University of Queensland, School of Medicine, Brisbane, Australia. Electronic address: ehohmann@optusnet.com.au.
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Hohmann
D000328:Adult; D064386:Ankle Fractures / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D001696:Biomechanical Phenomena; D015519:Bone Density / Q000502:physiology; D005260:Female; D006620:Hip Fractures / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D006801:Humans; D057072:Intra-Articular Fractures / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D007718:Knee Injuries / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D010329:Patella / Q000000981:diagnostic imaging / Q000473:pathology*; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed
Biomechanics; Bone density; Intra-articular fractures; Trauma