16 detector multislice CT versus skeletal scintigraphy in the diagnosis of wrist fractures: value of quantification of⁹⁹Tc^m-MDP uptake

Abstract

To compare the measured uptake of 99Tcm-methylene diphosphonate (99Tcm-MDP) in those scaphoid fractures seen on both 16 detector multislice CT and scintigraphy, with those seen only on scintigraphy. Over a 12 month period a total of 51 patients with suspected fracture underwent both conventional 99Tcm-MDP scintigraphy and 16 detector multislice CT on the same day. The 99Tcm-MDP uptake was then quantified in patients with identified fracture. This was measured by placing a region of interest (ROI) over the fracture site and the mean and maximum number of counts were compared with those in a similar size ROI placed over background bone activity. A total of 23 fractures were identified on scintigraphy of which 16 were also detected on CT (concordant). In seven cases the fracture was not seen on CT, even in retrospect (discordant). In the discordant cases, follow-up radiographs and MRI (where available) also failed to demonstrate a fracture. The mean fracture count to background bone activity ratio averaged 7.7 (range 3.2-18.5) for concordant fractures and 3.8 (range 1.7-5.3) for discordant fractures (t-test p=0.04). The maximum fracture count to background bone activity ratio averaged 12.7 (range 4.3-27.7) for concordant fractures and 6.3 (range 2.6-9.5) for discordant fractures (t-test p=0.03). It is speculated whether these discordant fractures with less 99Tcm-MDP uptake may represent a less severe injury such as bone bruise.

Diagnosing Suspected Scaphoid Fractures: A Systematic Review and Meta-analysis

“…It has been recognized increased 99m Tc-methylene diphosphonate (MDP) uptake is sensitive to metabolic change; however, it is not specific regarding the underlying causes, such as fracture, bone bruise, soft tissue injury, and inflammation at adjacent joints [23]. Our analysis also showed the heterogeneity in specificity for bone scintigraphy among studies was substantial and the period between injury and the test was associated with the variation: longer period was associated with higher specificity and reduced heterogeneity.…”

Cost-Effectiveness of Diagnostic Strategies for Suspected Scaphoid Fractures

“…The prevalence of true fracture among suspected scaphoid fracture was derived from studies that prospectively or consecutively recruited at least 50 patients with suspected scaphoid fractures and confirmed scaphoid fracture with MRI or radiographs with follow-up of at least 6 weeks. 4,6,[14][15][16][17][18][19][20][21][22] The weighted mean (the numbers of patients with a clinical condition reported in different studies were summed and then divided by the sum of the total number of patients in each study) was used as the baseline value, and the range obtained from these studies was used for the sensitivity analysis. One prospective study provided the probability of positive clinical signs of patients with suspected scaphoid fracture at 2 weeks after injury.…”

Large series vindicates early MRI for the diagnosis of wrist pain following trauma

“…Skeletal scintigraphy has also been compared with CTand MRI. 8 The exact role of scintigraphy is yet to be defined because in the injured wrist scaphoids sometimes will show uptake in the absence of CT or MRI changes. CT however has been used in planning the type of surgery in established scaphoid fractures as also to develop a classification system.…”