Systematic approach to identifying fourth and fifth carpometacarpal joint dislocations

Area of Science:

• Orthopedic Surgery
• Radiology
• Hand Surgery

Background:

• Carpometacarpal (CMC) joint dislocations are uncommon injuries.
• Radiographic findings can be subtle and easily missed.
• Accurate diagnosis is crucial for appropriate management.

Purpose of the Study:

• To develop a systematic approach for evaluating CMC joint dislocations.
• To analyze radiographic findings in 17 cases of fourth and fifth CMC joint dislocations.
• To improve the detection of these rare injuries on standard radiographs.

Main Methods:

• Analysis of radiographic findings in 17 patients with CMC dislocations.
• Development of evaluation principles: parallelism, symmetry, overlapping articular surfaces, indistinct cortical rim, and parallel M lines.
• Categorization of dislocations into combined fourth/fifth and solitary fifth CMC joint injuries.

Main Results:

• Most CMC dislocations are dorsal (71%).
• Combined dislocations show loss of parallelism/symmetry at the fourth CMC and overlap at the fifth.
• Solitary fifth dislocations present with ulnar offset, loss of parallelism/symmetry, and overlap.
• Associated fractures of the metacarpal base are common.

Conclusions:

• A systematic radiographic approach is essential for diagnosing CMC joint dislocations.
• Key radiographic signs include loss of parallelism, symmetry, and articular overlap.
• Early and accurate diagnosis from standard views can be achieved with this systematic evaluation.