Abstract
We present two coronal fractures of the proximal scaphoid which were both missed in the acute stage as interpretation of initial radiographs was difficult. In both cases, recognition of the so-called “Proximal Ring Sign” on the PA ulnar deviation radiographs may have helped diagnosis. CT scans were necessary to fully demonstrate the fractures. Open reduction and internal fixation, performed 2 and 4 months after the injury, resulted in union in both cases.
Keywords
CASE 1
A 33-year-old truck driver fell from a height and hyperextended his dominant right wrist. His initial pain was minimal and he did not seek any advice or treatment. One month later he sustained a direct injury on the dorsal aspect of his right wrist resulting in local pain and oedema. Poor quality PA, lateral and semi-pronated X-rays of his right wrist were then performed and interpreted as normal, and a below-elbow cast was applied for pain relief. The patient was referred to our institution 2 weeks later with his initial X-rays. As a fracture of the proximal scaphoid was suspected on the semi-pronated view, scaphoid series X-rays and a CT scan were performed. Standard PA and lateral radiographs appeared normal but the PA ulnar deviated view (Fig 1) showed a possible curved fracture line in the proximal scaphoid which overlapped its cortices (“proximal ring-shaped overlap”). Long axis coronal CT slices of the scaphoid showed a very proximal fracture but did not fully delineate the fracture line. However, long axis sagittal CT slices clearly showed a displaced coronal fracture of the proximal scaphoid (Fig 2). The concave fracture line began on the dorsum of the proximal scaphoid, and ended at its dorsal ridge. There was no lunate malalignment. The fracture was treated surgically 2 months after injury through a limited dorsal “Z” approach. The dorsal part of the proximal scaphoid, including its dorsal ridge, had fractured off the rest of the bone, and there was a 2 mm cartilage step-off. The scapholunate ligament was intact, but its dorsal part was attached to the displaced scaphoid fragment. The fracture fragment was anatomically reduced and fixed with two (1.5 and 2.0) miniscrews inserted in the sagittal plane. A short-arm cast was applied for 2 months, followed by gentle rehabilitation and the patient returned to his original job 3 months after the operation. The wrist was painfree 9 years after this injury, when the active range of flexion–extension was 80° (50° of extension) and grip strength was 55 kg (compared with 45 kg for the left). Wrist function was unrestricted and the patient worked in heavy manual labour. Plain radiographs only demonstrated slight narrowing of the radio-carpal joint at the very tip of the radial styloid (Fig 3).
CASE 2
A 25-year-old industrial painter injured his dominant right wrist when hitting a punch bag. Plain X-rays obtained 6 days after the injury (PA ulnar deviation view and poor quality lateral view) were interpreted as normal. The patient was referred to our institution 3.5 months later and a standard scaphoid series of X rays was performed. The PA and lateral views showed no abnormality but the ulnar deviation PA view demonstrated an atypical displaced fracture of the proximal scaphoid. Again, there was a curved fracture line in the proximal scaphoid which overlapped its cortices (“proximal scaphoid ring-shaped overlap”) (Fig 4). This was confirmed by a CT scan which demonstrated the fracture and its displacement in both the sagittal and transverse planes (Fig 5). The patient was operated on 4 months after his injury through a dorsal “Z” approach. The dorsal part and the proximal scaphoid, including its dorsal ridge, was found to be significantly displaced, but the dorsal and proximal parts of the scapholunate ligament were intact, and still attached to the displaced scaphoid fragment. There was a partial rupture of the anterior part of the scapholunate ligament. The fragment was reduced and fixed with two Kirschner wires (no bone graft was necessary), and the tear of the the anterior part of the scapholunate ligament was left untreated. A short-arm cast was applied for 3 months, after which the Kirschner wires were removed. The patient returned to his original job 5 months after the operation and was reviewed 9 years later, when the right wrist was painfree and had an active range of flexion–extension of 145° (70° of extension). Right hand grip strength was 55 kg compared with 50 kg for the left. PA and ulnar deviation PA radiographs showed slight osteolysis of the very proximal scaphoid without collapse. The lateral view demonstrated thickening of the dorsal ridge of the scaphoid. The alignment of the carpal bones was satisfactory.
DISCUSSION
Missed or delayed diagnosis of scaphoid fractures may result in nonunion, malunion and ultimately incapacitating degenerative changes. In the past 20 years, marked improvements have occurred in the radiological diagnosis of scaphoid fractures and their associated carpal bone and ligament injuries. Numerous classification systems have been developed based on fracture pattern and stability. Trojan and de Mourgues (1959) and Russe (1960) divided the scaphoid into three proximal, middle and distal thirds to describe fracture location. Fractures of the middle third were further divided into transverse, horizontal or vertical oblique ones according to the orientation of the fracture line with respect to the long axis of the scaphoid. Cooney (1980) defined two groups of scaphoid fractures based on their anatomic alignment: unstable, displaced fractures and stable, undisplaced fractures. In a series of 221 acute scaphoid fractures, Schernberg et al. (1984) identified six basic types of fracture and Herbert (1990) has classified acute scaphoid fractures into stable (tubercle and incomplete fractures through the waist) and unstable (distal oblique, complete fractures of the waist, proximal pole, and trans-scaphoid perilunate fracture-dislocations) types. More recently, Compson et al. (1997) drew attention to the need to understand the three-dimensional anatomy of the scaphoid bone in order to diagnose fractures. In a series of 91 acute fractures, they found three basic patterns: transverse through the waist; oblique in the plane of the dorsal sulcus and; through the proximal pole. There was some variation and comminution in these patterns (Compson, 1998). Despite these numerous attempts to classify scaphoid fractures, their radiological diagnosis remains challenging and delayed or missed diagnosis continues to occur. Moreover there are reports in the literature of occult (Kukla et al., 1997), and unusual acute fractures of the scaphoid. Atypical dorsal avulsion fractures (Compson et al., 1993), unusual displacement of the proximal pole (Shestak and Ruby, 1983), or simultaneous fractures of the waist and tuberosity (Fritsche et al., 1997) have been described, and comminution or fractures with a large middle third “intermediate” fragment have been reported in scaphoid fractures associated with perilunate dislocations (Herzberg et al., 1993). To the best of our knowledge, coronal fracture of the proximal scaphoid has not been previously reported. Difficulty with the interpretation of the initial films and incomplete scaphoid views series caused the delayed diagnoses in our two cases. This emphasizes the importance of adequate scaphoid series radiographs whenever one suspects a scaphoid fracture. We believe that in addition to standard PA and lateral views, an ulnar-deviated PA “clenched fist” view and semi-pronated and semi-supinated oblique views are necessary. We propose the term “proximal scaphoid ring sign” to describe the ring-shaped overlap of this coronal fracture that is visible on PA ulnar deviation views. Due to the socio-economical importance of early diagnosis and treatment of scaphoid fractures in young adults, scaphoid CT scan should be performed more frequently in cases of uncertainty. In our two cases, a limited dorsal “Z” approach (Herzberg, 2000) demonstrated the full extent of the fractures and allowed their fixation.