Abstract
Scaphoid fractures are a common injury accounting for more than 58% of all carpal bone fractures(1,2). Biomechanical studies have suggested that scaphoid mal-union may lead to altered carpal contact mechanics causing decreased motion, pain and arthritis(1,2). The severity of mal-union required to cause deleterious effects has yet to be established. This limits the ability to define surgical indications or impacts on prevention of posttraumatic arthritis. Computed tomography has been shown to be a useful in determining the 3D implications of altered bony alignment on the joint contact mechanics of surrounding joints. The objective of this study was to report mid-term follow-up image-based outcomes of patients with scaphoid mal-unions to determine the extent to which arthritic changes and decreased joint space is present after a minimum of 4 years following fracture.
Participants (n=14) who had previously presented with a mal-united scaphoid fracture (indicated by a Height:Length Ratio >0.6) between November 2005 and November 2013 were identified and contacted. A short-arm thumb spica case was used to treat X patients and X required surgical management. Baseline and follow-up CT images, were performed with the wrist in radial deviation and positioned such that the long axis of the scaphoid was perpendicular to the axis of the scanner. Three-dimensional inter-bone distance (joint space), a measure of joint congruency and 3D alignment, was quantified from reconstructed CT bone models of the distal radius, scaphoid, lunate, capitate, trapezium and trapezoid from both the baseline and follow-up scans(3). Repeated measures ANOVA was used to detect differences in contact area (mm2) between baseline and follow-up CT's for the radioscaphoid, scaphocapitate and scaphotrapezium-trapezoid joint.
The average age of participants was 43.1 years (16–64 years old). There was significant loss of joint space, indicated by a greater joint contact area 3–4 years post fracture, between baseline and follow-up reconstruction models, at the scaphocapitate (mean difference: 21.5±146mm2, p=0.007) and scaphotrapezoid joints (mean difference: 18.4 ±28.6mm2, 0.042). Significant differences in the measured contact area was not found for the radioscaphoid (0.153) and scaphotrapezium joints (0.72). Additionally, the scaphoid, qualitatively, appears to track in the vorsal direction in the majority of patients following fracture.
Increased joint contact area in the scaphocapitate and scaphotrapezoid joint 3–4 years following fracture results from decreased 3D joint space and overall narrowing. Joint space narrowing, while not significantly different for all joints examined, was reduced for all joints surrounding the scaphoid. Decreased joint space and increased contact area detectable within this short interval might be suggestive of a trajectory for developing arthritis in the longer term, and illustrates the potential value of these measures for early detection. Longer term follow-up and correlation to clinical outcomes are needed to determine the importance of early joint space narrowing, and to identify those most at risk.
