summary Base of Thumb metacarpal fractures can be extra-articular fractures, Bennett fractures (partial intra-articular), or Rolando fractures (complete intra-articular). Diagnosis can be made by orthogonal radiographs of the thumb. Treatment ranges from splint immobilization for certain extra-articular fractures to surgical fixation for displaced Bennett or Rolando fractures. Epidemiology Incidence 80% of thumb fractures involve the metacarpal base the most common pattern is extraarticular epibasal fracture Etiology Pathophysiology mechanism of injury most Bennett and Rolando are fractures caused by axial force applied to the thumb in flexion pathoanatomy imperfect reductions and above forces lead to increased joint contact pressures and subsequent predisposition to early arthritis excessive angulation may lead to MCP joint hyperextension deformity Anatomy Osteology CMC joint is a saddle-shaped joint composed of the trapezium and the base of the thumb (1st) metacarpal flexion-extension motion abduction-adduction motion Muscles three muscles provide deforming forces at the base of the thumb abductor pollicis longus (PIN) login to view 1 more bullet extensor pollicis longus (PIN) login to view 1 more bullet adductor pollicis (Ulnar n.) login to view 1 more bullet Ligament volar beak ligament spans the tuberosity of the trapezium to the volar edge of the 1st metacarpal keeps trapezium connected to the volar-ulnar base fragment dorsoradial ligament spans the dorsoradial tubercle of the trapezium to the dorsal base of the 1st metacarpal Biomechanics very limited axial rotation average flexion-extension of 53 degrees average abduction-adduction of 42 degrees Classification Classification of fractures of the first metacarpal Extra-articular oblique Oblique fracture line not involving the articular surface Extra-articular transverse Pure transverse fracture line not involving the articular surface Intra-articular Bennett Intra-articular fracture with a palmar ulnar fragment Intra-articular Rolando Y or T shaped complete intra-articular fracture Intra-articular comminuted Severely comminuted complete intra-articular fracture Presentation Symptoms acute pain at the base of thumb with Physical exam inspection swelling and ecchymosis tenderness to palpation at CMC joint motion pain with range of motion Imaging Radiographs recommended views true AP of thumb (Robert's View) login to view 1 more bullet true lateral of thumb login to view 1 more bullet oblique optional imaging traction view may be obtained to better understand the fracture pattern in Rolando and severely comminuted fractures findings bennett fractures login to view 1 more bullet rolando fractures login to view 2 more bullets criteria dictating treatment extra-articular fracture login to view 1 more bullet Bennett's fracture login to view 1 more bullet Rolando login to view 1 more bullet sensitivity and specificity a 30-degree pronated view provides the best view CT indications complex fracture patterns for assessment of fracture fragment detail Diagnosis Radiographic diagnosis confirmed by history, physical exam, and radiographs Treatment Nonoperative closed reduction and thumb spica casting indications login to view 2 more bullets modalities login to view 1 more bullet thumb spica casting indications login to view 1 more bullet Operative closed reduction and percutaneous k-wire fixation indications login to view 4 more bullets open reduction internal fixation indications login to view 1 more bullet distraction and external fixation indications login to view 3 more bullets Techniques Closed reduction and percutaneous k-wire fixation instrumentation a transverse extra-articular fracture can be treated with transarticular k-wire fixation oblique extra-articular fractures can be treated with intermetacarpal k-wire fixation complication specific to this treatment loss of reduction Open reduction internal fixation approach volar approach of Gedda and Moberg soft tissue thenar muscles are reflected volarly and a longitudinal capsulotomy is made bone work fracture is clamped in a volar-dorsal plane instrumentation fracture provisionally reduced with k-wire and fixed with screws or T-plate depending on fracture pattern complication specific to this treatment injury to the superficial branch of the radial nerve wound healing complications if significant edema is present outcomes adequacy of anatomic reduction predicts development of radiographic arthritis but does not predict symptomatic arthritis Distraction and external fixation instrumentation two 3mm are placed in the dorsoradial aspect of the distal shaft of the metacarpal two 3mm are placed in the dorsoradial aspect of the radius pins may be placed into the second metacarpal shaft to control deforming forces complications specific to this treatment pin site infection Complications Posttraumatic arthirtis incidence the exact incidence is unclear risk factors highly comminuted intra-articular fracture major step off multiple small fragments Malunion Prognosis Malreductions may lead to early short-term stiffness or instability and long-term radiographic arthritis Prognostic variables favorable acute intervention extra-articular fracture negative Bennett fracture Rolando fracture severely comminute fracture delayed intervention