Scaphoid Nonunion: Surgical Fixation with Local Nonvascularized Bone Graft (Open)

Fig. 9.1

Preoperative imaging. a The scaphoid nonunion is clearly noted on the standard PA wrist radiograph. b The scaphoid waist view reveals cystic changes consistent with nonunion. c Sagittal CT imaging of the humpback deformity. This image shows the classic humpback deformity as angulation of opposing poles of the scaphoid in the presence of a mid-waist nonunion. (Published with kind permission of © Sidney M. Jacoby and Justin D. Stull, 2015. All rights reserved)

Diagnosis

Scaphoid waist nonunion with humpback deformity

Management Options

Management options for scaphoid nonunion are based on a number of factors including the location of the fracture, vascularity, the degree of carpal instability, and a critical analysis of early degenerative changes. In this case, the patient is a healthy college athlete with a mid-waist scaphoid nonunion showing early signs of a humpback deformity. We consider numerous variables in formulating a treatment plan including: (1) timing of intervention, (2) choice of procedure, (3) surgical approach, (4) graft donor location, and (5) method of fixation.

In the setting of scaphoid nonunion with humpback deformity , surgical intervention is necessary both to correct scaphoid geometry and to promote healing via internal fixation. If left untreated, collapse of the scaphoid waist due to deterioration of the lesion’s opposing ends can further deteriorate into dorsal intercalated segment instability (DISI) [1–3]. Eventually, failure to achieve union will result in a predictable pattern of scaphoid nonunion advanced collapse (SNAC) with additional long-term sequelae. While nonoperative treatment may be utilized for acute nondisplaced scaphoid fractures , in the setting of a known scaphoid nonunion, particularly those with carpal collapse, nonoperative treatment is considered suboptimal [4].

Selection of operative technique should be based primarily on the location of the scaphoid fracture and the vascular integrity of the proximal pole. While a dorsal approach is typically utilized for proximal pole fractures , in the setting of a scaphoid nonunion at the waist or distal pole, a volar approach spares the dorsal blood supply. This blood supply is received at the dorsal ridge of the scaphoid and provides arterial inflow to 70–80 % of the bone, including the proximal pole [3, 5, 6]. Additionally, as is the case in this particular patient’s fracture pattern, humpback deformities necessitate volar access to facilitate secure fixation of the graft and the internal fixation device [5, 7].

A critical consideration in scaphoid nonunion surgery is the potential need for a vascularized bone graft to address scaphoid avascular necrosis (AVN). In the setting of AVN, both the osseous nonunion and the vascular status can be addressed with a vascularized bone graft and internal fixation [8, 9]. However, in the absence of AVN, there is a diminished indication for a vascularized bone graft, and nonvascularized bone graft is acceptable [1, 10].

With the decision to utilize an avascular graft, various donor graft sites are considered, including the distal radius, iliac crest , medial proximal tibia, and olecranon [11]. The iliac crest is distinguished for both its strength and pluripotent stem cells [12], while distal radius bone grafting offers the advantage of proximity to the implantation site, thus potentially reducing surgical morbidity associated with choosing a donor site ectopic to the scaphoid incision [13, 14]. In a comparison between iliac bone grafts and those derived from the distal radius, it has been reported that the source of graft donor site does not have a significant impact on the healing and incorporation of the graft [3, 14, 15].

Preference for a wedge graft over cancellous autograft bone is indicated to properly correct scaphoid collapse associated with a humpback deformity [7, 16]. The wedge graft utilizes a corticocancellous graft with additional cancellous bone to augment the recipient site [17].

Management Chosen

The patient presented in this report was a healthy young male, with radiographic evidence of scaphoid nonunion with humpback deformity and no radiographic evidence of AVN. The decision was made to proceed with a wedge-shaped nonvascularized distal radial bone graft to correct the scaphoid nonunion and associated humpback deformity. Fixation with a cannulated, continuous headless compression screw via a volar approach was also utilized.

Operative Technique

Following routine prep and drape as well as administration of IV antibiotics, the limb was elevated, and tourniquet inflated. A modified Russe approach was utilized extending from the distal volar radial forearm, paralleling the thenar web space [18, 19]. The flexor carpi radialis tendon was incised along its ulnar margin and the subsheath was identified and released. Blunt dissection was performed in order to mobilize the forearm flexors, and the thenar musculature was gently elevated in order to gain access to the distal pole of the scaphoid. In a capsular sparing approach popularized by Garcia-Elias [20], a “U-shaped” incision was made directly over the scaphoid and extended proximally along the radial aspect of the radial metaphysis (Fig. 9.2) . The distal pole and the body of the scaphoid were identified with the use of intraoperative fluoroscopic imaging and an 18-gauge needle. Intraoperatively, the scaphoid nonunion demonstrated a humpback deformity that had previously been visualized on CT imaging. K-wires were then placed in the proximal and distal scaphoid poles in a position that would later allow for optimal positioning of a guidewire for the fixation screw. A small bone distractor was positioned around the K-wires and utilized to maintain distraction during this portion of the procedure (Fig. 9.3).

Fig. 9.2

Volar capsular ligament splitting approach to the scaphoid. This approach minimizes trauma to the capsule, while allowing for appropriate visualization of the scaphoid and distal radius. D distal, P proximal, R radial, U ulnar. (Published with kind permission of © Sidney M. Jacoby and Justin D. Stull, 2015. All rights reserved)

Fig. 9.3

Intraoperative visualization of the scaphoid nonunion. a Placement of K-wires for the small bone distractor. Note that the distractor is placed in a location that will not interfere with later guidewire placement for scaphoid screw . b Pre-graft distraction of nonunion site and debridement of nonunion in preparation for cancellous and cortico-cancellous graft. c Post-wedge graft placement in the mid-waist of the scaphoid nonunion , providing correction of the humpback deformity. Note that the distractor is no longer utilized to provide a distraction force and will be removed prior to scaphoid screw insertion. (Published with kind permission of © Sidney M. Jacoby and Justin D. Stull, 2015. All rights reserved)

It should be noted that the distractor was later removed during screw fixation. If desired, a compressor bone clamp can be applied in its place during screw insertion to maintain compression.

The fracture site was identified and all fibrous debris within the nonunion site was carefully debrided with a combination of small curettes and a small burr. Throughout this delicate process, irrigation was utilized to minimize the risk of heat necrosis to the scaphoid. Importantly, the proximal pole of the scaphoid was noted to have punctate bleeding when the tourniquet was released indicating adequate vascularity. Direct measurement revealed an 8-mm gap at the nonunion site. The fracture fragments were mobilized with the previously placed K-wires and an appropriately sized graft harvested from the volar distal radius.

To access the volar distal radius, the pronator quadratus was gently elevated, and a 1-cm² graft was chosen. A K-wire was utilized to mark the borders of the distal radius bone graft. To obtain a rectangular-shaped corticocancellous bone graft, an osteotome and mallet were utilized. Cancellous bone was also harvested from the volar distal radius donor site.

Attention was directed back to the scaphoid nonunion site, where a small amount of harvested cancellous graft was packed into the void created by the scaphoid nonunion. At this stage, the volar distal radius corticocancellous graft was sculpted and wedged into the scaphoid nonunion site with gentle distraction provided by the previously placed small bone clamp distractor in order to recreate the normal intra-scaphoid angle.

Intraoperative fluoroscopy revealed correction of the humpback deformity with placement of an appropriately sized graft into the scaphoid nonunion site. A guidewire was placed down the central axis of the scaphoid to stabilize the graft. Upon measurement, a 24-mm scaphoid screw was deemed to be the appropriate size. To minimize migration of the graft, as well as to minimize heat necrosis to the scaphoid, reaming for the screw was performed by hand. At this point, a 24-mm, headless Acutrak II (Acumed, Hillsboro, OR) screw was inserted in a retrograde fashion. There was an excellent fixation noted with compression across the scaphoid nonunion site. Intraoperative fluoroscopy demonstrated appropriate placement of the screw in multiple planes. Crushed cancellous bone allograft was then placed into the void at the donor site at the volar distal radius and the pronator quadratus was gently repaired over the volar distal radius. The volar capsule and subcutaneous tissue were repaired with 3-0 Vicryl with 4-0 Nylon used to close the skin. Sterile dressings were applied, including a short-arm thumb spica splint.

Clinical Course and Outcome

The patient presented back to the clinic 6 days postoperatively for the first evaluation. Radiographic imaging demonstrated a well-positioned bone graft and fixation of the scaphoid waist fracture with the surgical screw in a near center–center position on multiple views. There was evidence of an improved intra-scaphoid angle indicative of correction of the previous humpback deformity.

At 1 month postoperatively, the patient had well-healed surgical incisions, marked improvement in swelling, and less pain in the anatomic snuffbox with deep palpation. Range of motion revealed 30° extension and 30° flexion with full digital range of motion. Radiographic imaging showed evidence of scaphoid healing, indicating a well-incorporated bone graft and fixation of the scaphoid waist fracture with the compression screw still in unchanged position on multiple views. A scaphoid mobilization splint was provided, allowing for gentle range of motion, including “dart throwers” motion. The scaphoid mobilization splint is a dynamic splint that offers limited wrist motion, but at the same time allows for direction-specific range of motion. In this case, radial and ulnar deviation with limited flexion and extension was allowed. The scaphoid mobilization splint provides the ability to mildly stretch the soft tissues of the wrist including the joint capsule, potentially minimizing postoperative contractures. A certified hand therapist provided instruction and guidance throughout the postoperative therapy.

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