Scaphoid Implant Malplacement

73 Scaphoid Implant Malplacement

Wesley N. Sivak and Joseph E. Imbriglia

73.1 Patient History Leading to the Specific Problem

A 29-year-old right-hand-dominant woman presented 6 months after a fall on an outstretched right arm from which she sustained a scaphoid fracture. Her referring physician initially treated her with immobilization in a thumb spica cast for 12 weeks, but the fracture did not heal. An MRI demonstrated a scaphoid waist fracture and a nonunion. She had developed a mild humpback deformity across her nonunion (▶Fig. 73.1a, b). Of note, she was an active smoker and was chronically disabled secondary to bipolar disorder. She then underwent repair of her right scaphoid waist fracture nonunion by means of open reduction and internal fixation (ORIF) augmented with distal radius cancellous bone autograft. Her surgery was uneventful. Fixation of her fracture (by report) was obtained with a 20-mm Acutrak mini-screw with bone graft across the nonunion site. Intraoperative fluoroscopy was utilized to confirm hardware placement across the fracture site (▶Fig. 73.1c, d). She presented to us with point tenderness in the right anatomic snuffbox. No crepitus was appreciated with active or passive ranging of the wrist, although motion was both painful and limited secondary to her prolonged period of immobilization.

73.2 Anatomic Description of the Patient’s Current Status

The scaphoid receives its blood supply from the radial artery via the superficial palmar arch and the dorsal carpal branch. The dorsal carpal branch enters the scaphoid through foramina along its nonarticulating dorsal ridge and supplies the vast majority of the bone; branches from the superficial palmar arch supply only the distal third (or pole) after entering through the distal tubercle. While these branches provide ample blood supply to middle and distal thirds, the proximal pole receives no direct branches and relies solely on retrograde flow through the bone. Thus, when fractures occur across the middle third of the scaphoid, blood supply to the proximal pole is limited.

Fractures across the scaphoid become increasingly more difficult to heal as the fracture line moves proximal, resulting in greater degrees of disrupted blood supply to the bony fragment. Indications for ORIF of scaphoid fractures include unstable fractures, proximal pole fractures, displacement greater than 1 mm, greater than 15 degrees of scaphoid humpback deformity, radiolunate angle greater than 15 degrees (dorsal intercalated segment instability [DISI]), scaphoid fractures associated with perilunate dislocation, comminuted fractures, unstable vertical, or oblique fractures. Our patient met the criteria for ORIF at the time of presentation given her humpback and DISI deformities and degree of displacement. Unfortunately, the mini-screw was placed too volar in the scaphoid. X-rays from her first follow-up visit at 2 weeks confirm the problems, which can also be seen on the intraoperative fluoroscopy (▶Fig. 73.2a, b). Further complicating things, the mini-screw appeared too long and rested within the scaphoid facet of the distal radius. The patient continued to have persistent wrist pain, prompting a CT scan of the right wrist at 3 months post-op (▶Fig. 73.2c, d). CT scan confirmed a chronic nonunion of the scaphoid with a significant degree of comminution and demonstrated volar malplacement of the hardware.

Fig. 73.1 (a, b) MRI demonstrated a scaphoid waist fracture and a nonunion. She had developed a mild humpback deformity across her nonunion. (c, d) Intraoperative fluoroscopy was utilized to confirm hardware placement across the fracture site. A 20-mm Acutrak mini-screw with bone graft across the nonunion site.

Fig. 73.2 (a, b) X-rays from her first follow-up visit at 2 weeks confirm the problems. (c, d) CT scan of the right wrist at 3 months post-op. Nonunion is observed.