Abstract
Background Lunate morphology has been suggested to influence carpal kinematics.
Purpose We investigate a possible relation between presence of a medial lunate facet and
dorsal intercalated segment instability (DISI) of the wrist in patients with a scapholunate
(SL) dissociation.
Methods We retrospectively reviewed patients diagnosed with SL dissociation between 2000
and 2017. Lunate morphology was categorized based on radiographs and magnetic resonance
imaging (MRI), as type I or II according to Viegas and Galley. DISI was defined as
radiolunate angle > 15 degrees and SL instability as SL angle > 60 degrees. SL distance > 3 mm
was considered as widening and carpal height ratio < 0.5 was considered as carpal
collapse. We used descriptive statistics to report on SL instability and DISI in patients
with Viegas type I and type II lunates. We calculated kappa to determine agreement
between radiographs and MRI and to determine inter- and intraobserver agreement.
Results Of 119 patient files, 79 wrists met the inclusion criteria of which 25 were type
I lunates and 54 type II. Similar spreading of the data of both groups was found regarding
DISI, SL instability, and SL widening based on radiographic classification of the
lunate, even after adding MRI findings. In the presence of carpal collapse, capitate-to-triquetrum
distance was higher. We found a substantial inter- and intraobserver agreement for
lunate classification.
Conclusion Our results suggest a similar prevalence of DISI deformity or enlarged SL angle in
patients with type I or II lunate in presence of SL dissociation. The Viegas classification
is a reliable and reproducible classification system.
Level of evidence This is a Level III, cross-sectional study design.
Keywords
scapholunate instability - lunate morphology - wrist kinematics
