A 28-year-old patient with a painful and deformed wrist after a fall from a ladder presented for a wrist CT examination.
Fig. 1 Normal anatomy of the wrist.
Fig. 1A PA x-ray view shows:
Carpal bones are: Scaphoid (SCA), Lunate (LUN), Triquetrum (TRI),
Pisiform (PIS), Trapezium (TRM), Trapezoid (TPD), Capitate (CAP) and
Hamate (HAM).
The three carpal (Gilula’s) arcs are : The first (blue) one outlines the
proximal convexities of the scaphoid, the lunate and the triquetrum;
the second (red) one follows the distal concave surface of the same bones
while the third arc (black) traces the proximal curvature of the
capitate and hamate.
Fig. 1B and Fig. 1C show normal alignment of the distal radius, the
lunate, the capitate and 3rd metacarpal on lateral x-rays and
sagittal CT views.
Fig. 2A (sagittal), 2B (sagittal), 2C (axial), 2D (coronal) and 2E (VR
image) CT show fracture dislocation of the lunate, triquetrum and
scaphoid bones in a 28-year-old male. There is disruption of
the first and second carpal arcs and anterosuperior displacement of
both the lunate and triquetrum bones.
The wrist is composed of the distal radius and ulna, eight carpal bones aligned in two rows and several ligaments.
Carpal dislocation most often occurs after a severe trauma on an outstretched hand.
Lunate and perilunate dislocations constitute a potentially serious injury involving ligaments that may cause nerve or vascular disorder and long-term wrist disfunction. Lunate dislocation must be differentiated from the perilunate dislocation in which the lunate remains in normal alignment with the distal radius [6, 7].
Clinically the wrist is greatly enlarged and deformed. Oedema and haematoma are often present and palpation is very painful.
Imaging plays an important role in the diagnosis, by demonstrating the alignment of the carpal bones.
Conventional x-ray can show disruption of carpal arcs (Gilula's arcs), abnormal overlapping of lunate with other carpal bones, widening of radiolunate space and allows measurement of scapholunate angle (normal if 30-60°) and capitolunate angle (normal if < 30°) to look for a carpal instability [1, 8, 11]. The lateral wrist film will look for misalignment of the radius, lunate, and capitate. However, plain radiograph may miss carpal occult fractures and underestimate displacements which can alter treatment planning [2, 6].
CT acquisition and reformatted images (MPR, 3D, VR) makes it easier to detect bone misalignment and allows in addition to detect occult fractures [2, 3].
Mayfield et al. classified carpal instability in four stages [5, 6]. Radiographic findings are:
Stage I: Scaphoid rotation and scapholunate dissociation.
Stage II: Capitate dislocation.
Stage III: Perilunate dislocation: Malrotated triquetrum and scaphoid, triquetrolunate diastasis, dislocated triquetrum.
stage IV: Lunate dislocation.
Lunate dislocation is the last stage of perilunate injuries. These are rare and serious, involving ligaments with risk of nerve and vascular damage, requiring early diagnosis and treatment. The standard treatment in the acute phase, which consists of surgical reduction of dislocation, stabilisation of the fracture, and repairing any ligament damage [4, 9]. Long-term complications are not uncommon despite the correct treatment, including carpal instability, osteoarthritis, decrease of motion and grip strength [1, 9].
Imaging plays a major role in identifying lunate and other carpal dislocations.
Dislocations of the wrist should be diagnosed on conventional x-ray.
Displacements and misalignment are however best evaluated with CT which in addition allows to detect occult fractures giving a better assessment of lesions prior to definitive treatment [2, 7, 10].
Fracture dislocation of the lunate, triquetrum and scaphoid bones
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Based on the provided posteroanterior (PA) and lateral X-ray images of the wrist, as well as CT scans, the following key features are observed:
1. On the PA view, the normal continuous arcs of the radius, lunate, and other carpal bones (Gilula’s arcs) are interrupted, suggesting abnormal carpal alignment.
2. The lateral view shows displacement of the lunate, which is no longer vertically aligned with the radius and the capitate; the lunate is significantly angulated or displaced in the volar (palmar) direction.
3. The 3D CT reconstruction clearly demonstrates the anatomical malalignment of the lunate relative to the surrounding carpal bones (especially the capitate), and also helps to rule out other potential occult fractures or articular surface injuries.
4. The soft tissue window may indicate local edema or hemorrhage (although CT has limited resolution for soft tissue).
Combining the information about a young male patient with a fall from height, a high-energy trauma mechanism, and the radiological findings, the main differential diagnoses include:
Taking into account the high-impact fall (fall from a ladder), severe wrist deformity, pain, and the radiological findings, the most likely diagnosis is: Lunate Dislocation.
This diagnosis corresponds to Stage IV carpal instability in the Mayfield classification. Although rare, it is a serious ligamentous and bony injury of the wrist that requires prompt intervention to reduce the risk of long-term complications.
This report is intended as a reference medical analysis based on the current imaging and clinical information and does not replace a physician’s in-person diagnosis or treatment recommendations. If you have any concerns or changes in your condition, please consult a qualified orthopedic or specialized physician in a timely manner.
Fracture dislocation of the lunate, triquetrum and scaphoid bones
