Association of Lunate Morphology With Carpal Instability in Scapholunate Ligament Injury

Relationship Between Carpal Bone Morphology and Distal Radius Fracture Pattern

Abstract Background: In this study, we examined whether carpal bones (lunate, hamate, capitate) morphologies and fourth metecarp-capitate articulation have an effect on the distal radius fracture pattern. Methods: 206 patients who applied to the emergency department with distal radius fracture between 2016-2020 were included in the study. Preoperative and pre-reduction x-ray films of the patients were examined. Lunate, hamate, capitate morphologies and 4.metacarp articulation analyzed and classified. Distal radius fracture types were classified according to AO and Fernandez. The relationship between carpal bone morphology and distal radius fracture type was analyzed. Results: This study consisted of 101 men and 103 women. AO fracture types and carpal bone morphologies (lunate joint type according to Viegas, lunate type according to Zapico, capitate morphology, hamate morphology and capitate-4 metacarpal joint morphology) did not differ significantly (p > 0.05). Fernandez fracture types and carpal bone morphologies (lunate joint type according to Viegas, lunate type according to Zapico, capitate morphology, hamatum morphology and capitate-4.metacarp joint morphology) were compared, there was no significant difference (p > 0.05). Conclusion: As a result, no clear relationship could be demonstrated between carpal bone morphology and distal radius fracture pattern.

Is DISI Deformity Related to Presence of a Medial Lunate Facet in Patients with Scapholunate Dissociation?

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.

Radiocarpal Contact Pressures Are Not Altered after Scapholunate Ligament Tears

Background  The scapholunate interosseous ligament (SLIL) couples the scaphoid and lunate, preventing motion and instability. Prior studies suggest that damage to the SLIL may significantly alter contact pressures of the radiocarpal joint. Questions/Purposes  The purpose of this study was to investigate the contact pressure and contact area in the scaphoid and lunate fossae of the radius prior to and after sectioning the SLIL. Methods  Ten cadaveric forearms were dissected distal to 1-cm proximal to the radiocarpal joint and a Tekscan sensor was placed in the radiocarpal joint. The potted specimen was mounted and an axial load of 200 N was applied over 60 seconds. Results  Sectioning of the SLIL did neither significantly alter mean contact pressure at the lunate fossa ( p  = 0.842) nor scaphoid fossa ( p  = 0.760). Peak pressures were similar between both states at the lunate and scaphoid fossae ( p  = 0.301-0.959). Contact areas were similar at the lunate fossa ( p  = 0.508) but trended toward an increase in the SLIL sectioned state in the scaphoid fossa ( p  = 0.055). No significant differences in the distribution of contact pressure ( p  = 0.799), peak pressure ( p  = 0.445), and contact area ( p  = 0.203) between the scaphoid and lunate fossae after sectioning were observed. Conclusion  Complete sectioning of the SLIL in isolation may not be sufficient to alter the contact pressures of the wrist. Clinical Relevance  Injury to the secondary stabilizers of the SL joint, in addition to complete sectioning of the SLIL, may be needed to induce altered biomechanics and ultimately degenerative changes of the radiocarpal joint.

Association of Lunate Morphology With Progression to Scaphoid Fracture Nonunion

Background: The purpose of our study was to review a series of patients with scaphoid fractures to determine whether there was an association between lunate morphology and progression to delayed union or nonunion when treated operatively or nonoperatively. Secondary aims included evaluation of the relationship between lunate morphology and scaphoid fracture location. Methods: A retrospective review of all patients with a diagnosis of scaphoid fracture was performed at our institution between 2014 and 2017. Medical records and radiographs were evaluated to determine lunate morphology, scaphoid fracture location, treatment, and time to union. Differences between groups were determined using χ² analysis with significance set at P <.05. Multiple logistic regression analyses were used to evaluate scaphoid union in the setting of lunate morphology when controlling for confounders. Results: A total of 169 patients were included; 45.0% (n = 76) of patients had type I lunate morphology, and 55.0% (n = 93) had type II. In all, 64.5% (n = 49) of patients with type I lunate and 68.8% (n = 64) with type II lunate had a fracture at the scaphoid waist. Among all patients with a scaphoid fracture, type II lunates were more likely than type I lunates to progress to nonunion when treated both operatively and nonoperatively (18.3% vs 4.0%, P = .0042). Lunate facet size was not shown to be a significant risk factor for nonunion among patients with a type II lunate (P = .4221). Conclusions: Patients with a scaphoid fracture and type II lunate morphology were more likely to progress to nonunion than patients with a type I lunate.

Imaging evaluation of traumatic carpal instability

PURPOSE

To review the epidemiology, pertinent wrist anatomy, classification system, and emergent imaging evaluation of carpal instability with a focus on radiographic assessment of instability.

METHODS

A review of current literature on carpal instability was performed with summary presentation of carpal instability epidemiology, carpal anatomy, imaging evaluation, and classification with imaging evaluation focused on diagnosis in the emergency setting.

RESULTS

Carpal instability is a common pathology in falls on outstretched hand and is likely underdiagnosed due to instability being occult or demonstrating subtle malalignment on static imaging of the wrist. While there is a complex network of intrinsic and extrinsic ligaments contributing to carpal instability, a detailed knowledge of these ligaments is not necessary for radiologists to make an accurate diagnosis in the emergency setting, as identification and classification of carpal instability is based on identification of carpal malalignment patterns on radiography as opposed to identification of specific ligament injuries on advanced imaging. The Mayo classification is the most widely used classification system, which divides carpal instability into four categories: dissociative, non-dissociative, complex, and adaptive. Understanding this classification system allows radiologists to successfully classify almost all carpal instability injuries they will encounter, even in the setting of unusual or rare instability patterns.

CONCLUSION

In working with the treating clinician, it is essential that the emergency radiologist is comfortable with identifying and classifying carpal instability. This will ensure prompt treatment of seemingly benign injuries and those that require intervention, surgical or otherwise, improving the likelihood of a good outcome.