Hammering the Hamate Bone

Recently, my favorite professional baseball player, Mike Trout of the Anaheim Angels, had to leave an at bat early due to left wrist pain after foul tipping a ball off. Diagnostic testing later revealed he had suffered a fracture of the hamate bone (www.espn.com). Let’s hammer down the main points regarding the hamate bone and its relationship to sports injuries.

The hamate bone, aka the unciform bone, is one of eight carpal bones that form the wrist joint. The word hamate comes from the latin word hamulus, which means “little hook”. This bone is aptly named because it is a small wedge shaped bone with a hook like process on the medial side of the wrist (see Figure 1). The hamate bone connects to the 4th metacarpal (ring finger) and 5th metacarpal (little finger) via muscles and tendons. It is important to note that the ulnar nerve and artery run very close to the hamate bone and consequently can be injured with a hamate fracture.

As a baseball player, this bone is of special interest as it is the most commonly involved bone in hand and wrist injuries requiring surgery in professional baseball players (Rhee PC, Camp CL, D'Angelo J, et al. Epidemiology and Impact of Hand and Wrist Injuries in Major and Minor League Baseball. Hand (N Y) 2021; 16:498.)

There are generally 2 types of hamate bone fractures: Type 1 involving the hook of the hamate and Type 2 involving the body of the hamate. Type 1 are more common than Type 2 fractures.

Common sports that can be associated with a hamate hook fracture are baseball, hockey, golf and tennis. These sports require a firm grip which can place pressure on the hook of hamate and cause it to break over time. Additionally, repeated impact like a bat hitting a baseball exerts direct force against the hamate bone (healthjade.net). The timing of Mike Trout’s pain right after fouling the ball off suggests this is what led to his hamate bone fracture.

Type 2 fractures are usually a result of high energy trauma to the wrist or a direct blow over the hyperthenar eminence. For example, punching a wall with a closed fist could result in a hamate body fracture.

Symptoms of a hamate bone fracture includes wrist pain but can be otherwise vague and nonspecific. There can be pain in palm area on the side of the pinky finger. Weakened grip strength is also a common finding. Other symptoms include swelling, tenderness and numbness in that area as well. (medicalnewstoday.com)

Aside from a thorough medical history, a pull test can be performed which actively flexes the distal interpharangeal joints of the ring and small finger which may cause pain (healthjade.net) Diagnosis is usually made through imaging. Radiographs of the wrist area can find the fracture. However, x-rays have a high rate of false negatives with 70% sensitivity (Suh et al, J Hand Surg Am. 2014 Apr 39(4) 785-91.) CT scan with 100% sensitivity is very often required to make the diagnosis of a hamate bone fracture (Andersen et al. Invest Radiol. 1999 Jan; 34(1) 46-50). MRI is only necessary for chronic disease state.

Treatment typically depends on if the fracture is non displaced or displaced. Non displaced fractures may heal with immobilization using an ulnar gutter cast for 6 weeks. However, there is debate whether early surgical correction would be better for athletes to return sooner from injury. Displaced fractures typically require surgery. Surgery can involve removing the bony fragment (the hook) or using an open reduction and internal fixation with screws or wires. At the time of this posting, no announcement has been made if Mike Trout would be undergoing surgery or not.

In general, hamate fractures have a good prognosis. On average recovery takes about 2 months with early surgery patients returning back to full activity sooner than non surgical/casting patients. As with other sports injuries, recovery also depends on the full extent of damage and effort in recovery and physical therapy.