Volar Wedge Bone Grafting and Internal Fixation of Scaphoid Nonunions



Volar Wedge Bone Grafting and Internal Fixation of Scaphoid Nonunions


Evan D. Collins





ANATOMY



  • Nearly 80% of the scaphoid’s surface is covered by articular cartilage.6


  • Through ligamentous connections, the scaphoid serves as the bridge or link between the proximal and distal rows (FIG 1). Due to these strong tethers proximally and distally, it is highly susceptible to an acute fracture after a fall on an outstretched hand.18


  • Other key factors that influence scaphoid fracture healing are its tenuous vascular supply and its unique bony architecture.



    • The vulnerable vascularity of the scaphoid, especially the proximal pole, is well described in the literature.8,14,15,16,20 This is the result of the scaphoid’s retrograde blood supply, with approximately 70% of the vascular supply provided through the dorsal ridge vessel and 30% through branches to the scaphoid tubercle (at the level of the radiocarpal joint via superficial palmar branch perforators off the radial artery).






      FIG 1 • Anatomy of the wrist joint. The scaphoid bridges the proximal and distal carpal rows and is largely covered by articular cartilage.


    • The complex geometry of the bone makes it difficult to anatomically reduce the bone fragments.


PATHOGENESIS



  • Although there may be a variety of reasons for the development of a scaphoid nonunion, a fractured scaphoid usually fails to heal for three primary reasons:



    • The fracture is either undetected or untreated within the first 4 weeks after the injury.


    • The location of the fracture is proximal, resulting in poor vascularity of the most proximal fragment.


    • The fracture is displaced more than 1 mm.


NATURAL HISTORY



  • Scaphoid nonunion advanced collapse (SNAC), described in the literature, is a predictable sequence of changes that occurs as a result of scaphoid nonunion leading to wrist arthrosis, often associated with pain and limitation of motion.4,5


  • In studying patients with painful wrists over a 15-year period to determine who will develop symptoms, it is evident that the incidence of symptomatic wrist pathology requiring reconstruction is significantly higher for scaphoid nonunions that have gone untreated.1


  • Techniques used to detect an acute scaphoid fracture and its susceptibility to nonunion, wrist pain, and corresponding arthrosis have been discussed in great detail in the literature.14,15,20


PATIENT HISTORY AND PHYSICAL FINDINGS



  • The patient who presents with a scaphoid nonunion is usually a man between the ages of 18 and 35 years.


  • Unrecognized injuries in adolescence may present with pain related to early SNAC wrist arthrosis in the middle-aged adult.


  • Patients generally complain of wrist pain that limits range of motion or hinders activities such as push-ups, weightlifting, or simple daily tasks such as opening a door. Moderate to heavy pinch and grip pain have also been described.


  • A specific event resulting in the original scaphoid fracture years before is rarely cited by the patient on presentation.


  • Consistent physical examination findings include subtle tenderness in the region of the scaphoid tubercle or the anatomic snuffbox, limited wrist extension compared to the contralateral side, and localized pain on the radial side along the radiostyloid or scaphoid with loaded wrist extension. If arthrosis has developed, soft tissue swelling may be noted over the dorsal and radial wrist.



IMAGING AND OTHER DIAGNOSTIC STUDIES



  • Standard radiographs include posteroanterior (PA), lateral, and scaphoid oblique 45- and 60-degree pronated views (FIG 2). Such views



    • Confirm the diagnosis


    • Provide information regarding displacement, angulation, shortening, and the presence of a “humpback deformity”


    • Reveal compensatory carpal instability, dorsal intercalated segment instability (DISI)


  • As part of a treatment algorithm, dividing scaphoid fracture nonunions into either proximal, middle, or distal is very helpful.


  • Other factors considered in diagnostic assessment include previous wrist fracture or sprain later becoming symptomatic; tenderness on the scaphoid tubercle or in the anatomic snuffbox; localized pain to the radial side of the wrist along the radiostyloid or scaphoid itself, with a loaded dorsiflexed wrist; and pinching and heavy grip pain.


  • Once the scaphoid nonunion is diagnosed, a computed tomography (CT) scan performed in the plane of the scaphoid helps define bony architecture. Sagittal and coronal images are particularly helpful in characterizing the nonunion site and its orientation, displacement, and degree of bone loss.



    • Scaphoid collapse (or humpback deformity) is most clearly determined by measuring the lateral intrascaphoid angle on the sagittal CT views.


  • Magnetic resonance imaging (MRI), especially when combined with intravenous gadolinium, is helpful in defining the presence or absence of osteonecrosis and any associated ligamentous or cartilaginous injuries. If osteonecrosis of the proximal fragment is seen, the surgeon should consider a vascularized bone graft10 (see Chap. 38) rather than the nonvascularized grafting procedure described in this chapter.




NONOPERATIVE MANAGEMENT



  • Surgery is generally indicated for established scaphoid nonunions that are displaced and symptomatic because of the strong likelihood that radiocarpal arthrosis may develop with this type of persistent nonunion.18,20


  • Nonoperative management may be appropriate for minimally symptomatic scaphoid nonunions. All factors should be taken into consideration when determining the most appropriate treatment: Scaphoid nonunion alone is not an absolute reason for surgery.12


SURGICAL MANAGEMENT

Jul 22, 2016 | Posted by in ORTHOPEDIC | Comments Off on Volar Wedge Bone Grafting and Internal Fixation of Scaphoid Nonunions
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