Dislocation and Fracture-Dislocation Patterns of the 4th and 5th Carpometacarpal Joints: A five year retrospective analysis
Adnan Prsic, MD; William K Snapp, MD; Geoffrey Hogan, BS; Nicholas Nissen, BS; Jonathan Bass, MD; Reena Bhatt, MD; Scott Schmidt, MD; Jin Bo Tang, MD
Alpert Medical School of Brown University, Providence, RI
Introduction Carpometacarpal (CMC) dislocations and fracture-dislocations are rare injuries caused by high energy trauma and commonly missed on radiographs. [1, 2] The most commonly affected carpometacarpal joints are the 4th and 5th.  There is a paucity of large prospective or retrospective studies that report the incidence, distribution, mechanism of injury and treatment of the various injury patterns of 4th and 5th CMC dislocations and fracture-dislocations.  The goal of our study was to delineate the incidence, distribution, mechanism of injury and the effects of dislocation and fracture-dislocation patterns on the management of such injuries.
Methods A retrospective chart review was performed of 35 patients with 4th and 5th carpometacarpal dislocations and fracture-dislocations treated between years 2011 and 2016. Patients were stratified into eight groups based on the metacarpal involved and the presence of an associated dislocation, fracture-dislocation or a combination. Patient demographics, mechanism of injury, presence of hamate fracture, and treatment were compared across groups. Data was analyzed using Fischer's exact test.
Results Punching (62%) followed by fall (31%) were the most frequent mechanisms of injury. Mechanism of injury did not confer significance for operative intervention (p>0.05). 4th CMC fracture-dislocation with concurrent 5th CMC dislocation was the most common injury pattern (25%), followed by combined 4th and 5th CMC dislocations without fracture (22%). Isolated injuries of the 4th CMC were the least common injury (2%). There was a significant difference in the number of concurrent hamate fractures in patients with a 4th CMC injury (42%) relative to isolated 5th CMC injuries (9%). Presence of a hamate fracture for any injury pattern conferred significance for operative intervention (p<0.05). Presence of both 4th and 5th fracture-dislocation resulted in operative treatment for 80% of patients (p<0.05) with 60% having an associated hamate fracture. Only the combined 4th and 5th CMC fracture dislocation group had a significant difference in need for operative management compared to all others (p<0.05).
Conclusion Our study successfully identifies injury patterns of the 4th and 5th CMC joint. Concurrently, it identifies common mechanisms to be high energy trauma such as punching and fall. Of clinical interest is the significantly statistical relationship of associated hamate fracture and operative intervention as well as the combined fracture dislocation of the 4th and 5th CMC joint. The findings of this study will assist in improved diagnostic ability based on fracture patterns, in clinical decision making and improved patient counseling.
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