Ultrasound-Driven Diagnosis of Hamate Hook Stress Fracture in Athlete: A Case Report

Introduction

Stress fracture of the hook of the hamate can occur by impact from a hitting or swinging motion, such as with a bat in baseball or a club in golf [1]. There are several treatments for this fracture. Conservative treatment and osteosynthesis have been reported for preserving the hook of the hamate [2,3]. However, for an early return to sports, most surgeons recommend resection of the hook of the hamate [4–6]. Although satisfactory treatment methods exist for returning to sports as quickly as possible, early diagnosis of this stress fracture remains challenging. A previous study reported that computed tomography (CT) is effective for diagnosing stress fracture of the hook of the hamate, as it is considered difficult using plain X-ray alone [7,8]. It is very important clinically to address whether CT should be recommended for the prompt diagnosis of suspected stress fracture of the hook of the hamate.

In recent years, ultrasonography has become an essential tool for diagnosis of musculoskeletal disorders. It has the advantage of real-time and dynamic evaluation in an outpatient clinic setting for patients with tendon and nerve injuries [9,10]. Several researchers have applied ultrasonography to diagnose fractures. Jain et al reported that ultrasonography is more accurate and reliable than X-ray for the early diagnosis of scaphoid fractures [11]. Moreover, Kodama et al reported that ultrasonography can be useful for confirming the reduction position of distal radius fractures [12]. Therefore, we hypothesized that ultrasonography is useful in the early diagnosis of stress fracture of the hook of the hamate, for which early diagnostic accuracy is a concern. Herein, we present a case in which the diagnosis of stress fracture of the hook of the hamate in a professional baseball player was confirmed on the day of injury by ultrasound imaging. The patient was able to return to sports following early intervention.

Case Report

The patient was a 22-year-old male professional baseball player (outfielder, right-handed pitcher, left-handed hitter) for the Japan Professional Baseball Organization. During spring training camp, he reported having pain in his right palm during hitting practice and was examined by the team physician. On the practice field, tenderness around the hook of the hamate was noted. Ultrasonography revealed disruption of the bony cortical continuity of the ulnar aspect of the hook of the hamate and a hematoma around this lesion (Figure 1A, 1B). Stress fracture of the hook of the hamate was confirmed by CT (Figure 2).

After discussions among the patient, team, and attending physician, it was decided to perform resection of the hook of the hamate on the third day after the injury at the attending physician’s hospital, to facilitate a return to playing baseball as soon as possible. The surgery was performed under locoregional anesthesia. A 3-cm skin incision was made, avoiding the callus formed around the hook of the hamate, due to batting. The ulnar nerve and artery were identified, the soft tissues around the hook of the hamate were dissected, and the bone fragment of the hook of the hamate was resected (Figure 3A, 3B). Although some fibrillation was observed in the flexor tendon of the little finger, it was determined that repair of the flexor tendon was not necessary. Postoperatively, the wrist joint was immobilized for 2 weeks. Mobility training of the wrist joint was allowed, depending on pain.

One month after surgery, the range of motion of the wrist joint was 80° of flexion, 80° of extension, 90° of pronation, and 90° of supination. Grip strength relative to the healthy side was 59% (right 30 kg, left 51 kg). Batting was allowed 1 month after surgery, and the patient was allowed to return to playing baseball 3 months after surgery. Six months after surgery, the patient still had right palmar pain during playing baseball. Magnetic resonance imaging (MRI) showed that a bone bruise of the hook of the hamate remained. Since no disruption of the bone cortex was noted and 6 months had passed since the surgery, pain management and treatment using a low-intensity pulsed ultrasound unit were initiated. At 9 months after surgery, the pain in the palmar region had improved and no longer interfered with playing baseball. The range of motion of the wrist joint remained at 80° of flexion, 80° of extension, 90° of pronation, and 90° of supination. Grip strength relative to the healthy side improved to 92% (right 48 kg, left 52 kg). The visual analog scale score was 0/10, and the Q-DASH score was 0/100.

Discussion

In the case of stress fracture of the hook of the hamate in athletes, the time required for diagnosis and surgical treatment have a significant influence on the early return to competition. To return to competition earlier, resection of the hook of the hamate is performed as surgical treatment. The period from surgery to return to competition can be predicted, based on previous studies [4,5]. According to Kimura et al, patients who underwent resection of the hook of the hamate were able to return to their sports activities within 27±13 days [4]. Similarly, Engler et al reported that patients could resume live batting within 6 weeks after the resection of the hook of the hamate [5]. On the other hand, in stress fracture of the hook of the hamate, the time required for diagnosis greatly affects the time to return to competition. Engler et al reported a median time of 2 weeks from symptom onset to surgery; however, some patients underwent surgery 20 weeks or more after symptom onset [5]. These findings highlight the challenges associated with early diagnosis of stress fractures of the hook of the hamate. In the present case, a diagnosis of a stress fracture of the hook of the hamate in a professional baseball player was confirmed on the day of injury using ultrasonography. Early surgical treatment enabled the player to return to competition soon after surgery.

When a scaphoid fracture is missed, it can lead to a scaphoid nonunion, which can progress to a scaphoid nonunion advanced collapse wrist and wrist joint dysfunction [13]. To avoid this problem, MRI can be used to attempt an accurate diagnosis early after the injury [14]. However, MRI has the disadvantages of being expensive and taking a long time to obtain an image. Thus, alternative tests are necessary. Ultrasonography has been used as a fracture diagnosis tool in recent years. Vassalou et al reported that the detection rate of rib fractures by ultrasonography had a sensitivity of 100% and specificity of 89.7%, in contrast with that of X-ray, with sensitivity of 40% and specificity of 30.9%; furthermore, the accuracy of ultrasonography in detecting individual rib fractures was 94.9%, whereas that of X-ray examination was 35.4% [15]. These findings suggest that ultrasonography is effective in diagnosing stress fracture of the hook of the hamate, which is a sports injury that is difficult to diagnose, and that it is possible to diagnose it at the sports activity site immediately after the injury.

It is important to monitor sports injuries in athletes. Matsuura et al reported the use of ultrasonography for screening for baseball elbow [16]. In elementary school baseball players, osteochondritis dissecans of the capitellum does not necessarily cause pain on the outside of the elbow joint. In elementary school baseball players that experienced pain, the prevalence of osteochondritis dissecans of the capitellum was 0.5%. Moreover, osteochondritis dissecans of the capitellum detected by ultrasonography was 1.8%. Therefore, ultrasonography can be more useful than physical findings in screening for osteochondritis dissecans of the capitellum [16]. In the case of Jones fracture, a stress fracture in sports, efforts have been made to prevent its onset. Using X-ray, Fujitaka et al reported that the proximal bone length of the fifth metatarsal bone and the high medial longitudinal arch are risks for onset; thus, preventive measures are necessary [17]. However, patients must visit a medical institution to obtain an X-ray, and the complexity of measuring bone length and arch is an issue. Silva et al reported the usefulness of ultrasound for early diagnosis of stress fractures [18]. Considering the early diagnosis reported in this study, there are previous findings that ultrasound is a useful tool for fracture diagnosis [19] and a potential diagnostic tool for stress fractures [18]. Although there have been no reports of ultrasonography being used to diagnose stress fractures of the hook of the hamate, the present case suggests that ultrasonography can become a new screening tool for stress fractures of the hook of the hamate.

Although ultrasonography offers several advantages, its limited depth penetration and restricted field of view necessitate caution in specific clinical contexts [20]. These limitations are particularly evident in the evaluation of joints and intra-articular fractures, in which reflection of ultrasound waves at bony surfaces significantly impairs image clarity [20]. Furthermore, the diagnostic accuracy of ultrasonography is highly operator-dependent, underscoring the importance of standardized training protocols, to ensure consistent and reliable outcomes across various clinical environments [20].

Conclusions

Diagnosing a stress fracture of the hook of the hamate is challenging with plain X-rays alone. However, it is necessary to determine the appropriate treatment method to allow athletes to return to sports as soon as possible. This case report suggests that ultrasound can be a useful diagnostic tool for early diagnosis of a stress fracture of the hook of the hamate.