Avulsion fractures of the scaphoid and triquetrum in a 15 year- old male

Abstract

Avulsion fractures of the perilunate ligaments occur in isolation, and multiple fractures are typically not seen in the same carpus. We present a case of a 15-year-old male who injured his wrist during football practice. He presented without wrist dislocation or deformity. Radiographs demonstrated avulsion fractures to the proximal pole of the scaphoid and proximal radial aspect of the triquetrum. The patient was immobilized with an upper extremity thumb spica cast; however, there was persistent non-union of both fractured segments. Magnetic resonance imaging confirmed avulsions at the site of the scapholunate and lunotriquetral ligaments, with both ligaments relatively intact. At the last follow-up, one year after the initial injury, the patient had a normal clinical exam, with no pain and full wrist range of motion despite fracture non-union at both locations. This is a unique injury with an unclear mechanism and complicated management.

1. Introduction

Avulsion fractures of the carpal bones are not uncommon.^1,2 The most common fractures diagnosed in the wrist involve the proximal carpal row, specifically the scaphoid bone (Fig. 1).¹ Although isolated avulsion fractures of a single carpal bone have been described in literature, there has yet to be a documented case of multiple avulsion fractures in the same carpus, in particular with involvement of the perilunate ligaments. Combined injuries to the scaphoid and triquetrum have been described in high-energy dorsiflexion accidents resulting in palmar lunate dislocation,³ but they have not been reported as two separate avulsion fractures. We report a case that involves a high school athlete with an avulsion fracture of the triquetrum at the site of the lunotriquetral ligament (LTL) attachment and an avulsion fracture involving the proximal pole of the scaphoid bone at the scapholunate ligament (SLL) attachment (Fig. 1).

Fig. 1.

Cartoon of Carpal bones and ligaments.

2. Case report

A 15-year-old, right-hand dominant male sustained an injury during football practice when another player fell on him, causing hyperextension of his left wrist. He presented 16 days after the date of injury with pain in his left wrist. Physical examination revealed tenderness to palpation over the anatomic snuffbox of the left hand and pain with flexion and extension of his wrist. Range of motion was restricted to approximately 45° of wrist flexion and extension. Otherwise, the neurovascular and motor exams were normal. Plain radiographs of the left hand demonstrated fractures of the proximal scaphoid and inferior triquetrum without dislocation or angulation (Fig. 2). The patient was placed in a left upper extremity thumb spica cast.

Fig. 2.

PA Radiograph at initial presentation, 2 weeks after the date of injury. Arrows indicate inferior triquetrum fracture with displaced proximal pole scaphoid fracture.

The patient was followed in clinic for several visits after placement of the cast. Radiographs obtained in clinic failed to demonstrate union of either fracture at 6 weeks and 12 weeks after injury. During this 12-week period, the patient had full resolution of his pain, with improved range of motion to 80° of wrist flexion and 70° of wrist extension.

Computer tomography (CT) was obtained 3 months after the date of injury to evaluate for non-union of both fractures. Imaging demonstrated avulsion of the proximal aspect of the triquetrum with slight volar displacement, as well as a comminuted avulsion fracture of the proximal pole of the scaphoid bone with 3 mm of displacement.

Further evaluation with magnetic resonance imaging (MRI) was obtained 9 months after injury. MRI demonstrated fracture non-union and mild heterogeneity of both the SLL and LTL reflecting mild sprain, without full-thickness tear (Fig. 3). Mild heterogeneity and hyperintensity of the dorsal extrinsic ligaments were also noted, suggesting sprain without discrete tear. Radiographs obtained again verified non-union of both fractures. The scapholunate and lunotriquetral intervals were not widened, and there was no evidence of intercalated segmental instability or proximal migration of the capitate. The patient was counseled that these avulsed fragments would not heal, and that surgical intervention was not a reasonable option. The patient has remained asymptomatic and continues to be followed in clinic.

Fig. 3.

Magnetic Resonance Imaging (MRI) of the wrist obtained 9 months after injury. (A) Coronal gradient echo image demonstrates an intact lunotriquetral ligament attached to the avulsed triquetral fracture fragment. (B) Coronal gradient echo image demonstrates an intact scapholunate ligament attached to the avulsed proximal pole scaphoid fracture fragment.

3. Discussion

Fractures of the scaphoid and triquetrum are the first and third most common carpal fractures, respectively, and avulsion fractures of these bones are not uncommon.¹ In contrast, multiple carpal avulsion fractures involving the perilunate ligaments are rare and have not been reported in the literature. This case presents a unique combination of avulsion fractures, involving both the scaphoid and triquetrum in the same carpus.

Avulsion fractures occur when there is a sudden application of tensile force through the insertion site of a tendon or ligament, which causes the bone to fracture. This force is often generated by sudden contraction of surrounding muscles in attempt to decelerate body mass during an injury.⁴ In the pediatric patient, avulsion fractures occur more frequently than fractures across the body of the bone because particularly in adolescence muscle insertions are mechanically weak.⁵

The scaphoid fracture in our case represented a proximal pole fracture associated with avulsion of the SLL. One study reviewing 108 pediatric scaphoid fracture presentations determined that avulsion fractures comprised 42.5% of all cases; however, the majority of these occurred at the distal pole and there was only one incident reported at the proximal pole.⁵ In that specific case, the authors reported complete fracture union after a splint was worn for 3 weeks; unfortunately, MRI was not obtained to assess for any ligamentous compromise. It is also important to note that proximal pole fractures in particular are prone to non-union and osteonecrosis. Gelberman and Menon originally described the entire arterial supply to the proximal pole arising from branches of the radial artery, entering just distal to the waist of the scaphoid.⁶ In effect, delayed diagnosis and management of a fracture through this site may prevent fracture union and precipitate avascular necrosis in the bone.

The second fracture in our case was an inferior triquetrum fracture secondary to avulsion of the LTL. The majority of avulsion fractures of the triquetrum are classified as chip fractures involving the dorsal cortex.⁷ Volar avulsion fractures have only been detailed in one case series of five patients.⁸ The authors described all five fractures occurring in young men (ages 20- 28) after sustaining a sports injury. Arthrography and MRI obtained in four of the cases revealed tears of the LTL, with three cases also involving the SLL. Two patients were treated operatively with arthroscopic debridement and three were treated non-operatively with a splint; however, persistent instability and pain were noted one year after injury with only one patient returning to sports. The authors emphasized that instability series radiographs may be necessary to initially evaluate these fractures, as they were all missed with initial radiographic evaluation.

Our case is a combination of two rare fracture patterns whose presentations have suggested a poor prognosis in previous reports. At presentation, initial clinical assessment and radiographic analysis were consistent with small, minimally displaced fractures of the triquetrum and the scaphoid. Due to the relative stability of each fracture pattern, the patient was initially treated non-operatively. Following continued radiograph-confirmed evidence of non-union, CT and MRI were obtained to further elucidate the etiology of the injury, confirming the diagnosis of avulsion fractures about the perilunate ligaments. Interestingly, there was only mild heterogeneity in the SLL and LTL reflecting sprain, without discrete tear. Though previous biomechanical studies have established that co-occurring SLL and LTL disruptions commonly result in perilunate dislocations, based on this presentation, simply spraining these ligaments do not contribute to additional instability.⁹ However, the mechanism of how both ligaments may be involved has not yet been elucidated. In order to involve both the triquetrum and the scaphoid, we suspect that the injury most likely involved a component of wrist hyperextension in ulnar deviation as well as radial deviation. Given the MRI finding of dorsal extrinsic ligament sprain, it is likely that this patient had a post-traumatic perilunate dislocation that had spontaneously reduced, without ligamentous tear.

Cases of persistent fracture non-union in the carpal bones are typically treated with surgical fixation of the fractured segment, and results have been reassuring in cases involving the scaphoid and the triquetrum in particular.^10,11 In our case, this was not a realistic option for several reasons. Primarily, the scaphoid would most likely not tolerate screw fixation given the comminution and small size of the displaced proximal pole fragment. The fractured triquetrum segment similarly was too small for operative fixation. Moreover, the patient had full clinical resolution of symptoms with return to activity despite non-union of the fractures and sprain of both the LTL and STL. As such, surgery was forgone, though the risks of carpal instability, osteonecrosis, and precipitated wrist osteoarthritis were disclosed to the patient.

When presented with a case such as this one, it is therefore important to consider multiple factors prior to determining appropriate management for the patient. When a traumatic injury occurs, a clinician should consider ordering instability series radiographs to evaluate fractures that may seem benign at onset in order to monitor healing due to the injury mechanism. It is also important to consider further diagnostic imaging such as CT or MRI when non-union continues to remain before twelve weeks despite improving or resolution of symptoms, as waiting an extended period of time may reduce a window of opportunity to consider operative management. For example, despite the difficulty due to size K-wires may have been used to at least secure the scaphoid fragments. In this case, though we followed institutional policy regarding patient follow-up, by the time avulsion fractures were diagnosed, there was little point in offering surgical management when the patient was asymptomatic, yet leaving unrepaired avulsed fragments may cause instability, pain, or rapid development of degenerative osteoarthritis of the joint in the future.

The reported case is a rare wrist injury that has not been previously described in the literature. Further investigation is required to understand the exact mechanism of injury and appropriate management for this unique fracture pattern.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Declaration of competing interest

The authors declare they have no conflict of interest.