Clin Orthop Surg.  2016 Jun;8(2):175-180. 10.4055/cios.2016.8.2.175.

The Role of Lunate Morphology on Scapholunate Instability and Fracture Location in Patients Treated for Scaphoid Nonunion

• Kim BJ
• Kovacevic
• Lee YM
• Seol JH
• Kim MS

• KMID: 2412343
• DOI: http://doi.org/10.4055/cios.2016.8.2.175

Abstract

BACKGROUND
To determine the association between lunate morphology and the scapholunate instability using radiographic images, and investigate the association between lunate morphology and scaphoid fracture location.
METHODS
Between January 2003 and December 2011, we retrospectively evaluated the plain radiographs and computed tomography (CT) images of 70 patients who underwent surgical intervention for a scaphoid nonunion, in order to determine the association between lunate type (I or II) and scapholunate instability or scaphoid fracture location. We determined the scaphoid fracture location using the fragment ratio and measured the radiolunate angle and capitate-triquetrum (C-T) distance.
RESULTS
A type II lunate was present in 68.6% (48 of 70 cases). Mean fragment ratio of fracture location was 50.6% in the type II lunate group and 56.2% in the type I lunate group (p = 0.032). Sixteen of the 70 patients had dorsal intercalated segmental instability (DISI) deformities. Nine of 22 cases showed DISI deformity in type I lunate and 7 of 48 cases showed DISI deformity in type II lunate (p = 0.029). However, there were no significant differences between the presence of DISI deformity and fracture location (p = 0.15). Morphologic comparisons by both plain radiography and CT indicated a mean C-T distance in the type I lunate group (22 cases) of 2.3 mm and 5.0 mm in the type II lunate group (48 cases). The C-T distances were significantly correlated with lunate morphology (p = 0.001).
CONCLUSIONS
A type II lunate was associated with low incidence of DISI deformity and proximal location of fracture in patients presenting with a scaphoid nonunion.

Keyword

Lunate morphology; Scaphoid nonunion; Dorsal intercalated segmental instability

MeSH Terms

Adolescent
Adult
Female
*Fractures, Bone/diagnostic imaging/physiopathology
Humans
Joint Instability/diagnostic imaging/physiopathology
*Lunate Bone/anatomy & histology/diagnostic imaging/physiopathology
Male
Middle Aged
Retrospective Studies
*Scaphoid Bone/diagnostic imaging/injuries/physiopathology
Tomography, X-Ray Computed
*Wrist Injuries/diagnostic imaging/physiopathology
Young Adult

Figure

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  Fig. 1 Type I lunate with a single midcarpal articulating facet with the capitate (A, B) and type II lunate with two midcarpal articulating facets, one with the capitate and the other with the hamate (C, D).

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  Fig. 2 (A) Fragment ratio. Horizontal lines were drawn to define the extent of the fragment. (B) The middle of the fragment was identified and a midline was drawn connecting the two horizontal lines. (C) The lengths of these lines (P: proximal fragment, D: distal fragment) were measured to determine the fragment size. Fragment ratio = P / (P + D).

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