Imaging the scaphoid problem : a diagnostic strategy for suspected scaphoid fractures
Beeres, F.J.P.
Citation
Beeres, F. J. P. (2008, May 14). Imaging the scaphoid problem : a diagnostic strategy for suspected scaphoid fractures. Retrieved from https://hdl.handle.net/1887/12857
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Chapter
2
F.J.P. Beeres1 S.J. Rhemrev1 M. Hogervorst2 S. Le Cessie3 K.A. Bartlema4 J.F. Hamming4
1Department of Surgery, Medical Centre Haaglanden, The Hague, the Netherlands
2Department of Surgery, Gelre Hospitals, Apeldoorn, the Netherlands
3Department of Medical Statistics and Bioinformatics, Leiden University Medical Centre, Leiden, the Netherlands
4Department of Surgery, Leiden University Medical Centre, Leiden, the Netherlands
Measurement of the function of the wrist and strength improve the diagnostic strategy
of suspected scaphoid fractures
Submitted
Abstract
The diagnostic strategy of suspected scaphoid fractures is surrounded by controversy.
Currently, clinical decision tools are being investigated for the diagnosis of suspected scaphoid fractures. The objective of the present study was to evaluate the function of the wrist and strength measurements as useful diagnostic tools in suspected scaphoid fractures.
Methods: Seventy-eight consecutive patients with a suspected scaphoid fracture, but no evidence of a fracture on scaphoid radiographs, were included. The anatomic snuffbox was examined for the presence of a haematoma or a swelling. Afterwards, flexion and extension of the wrist were measured. Supination strength and pronation strength were calculated, as was the maximal grip strength. All measurements were performed on both the suspected and contra-lateral side according to a standard protocol. Magnetic Resonance imaging, bone scintigraphy and clinical follow-up were used to define a final diagnosis.
Clinically feasible cut off points were chosen and the corresponding sensitivity and specificity were calculated comparing scaphoid fractures with no scaphoid fractures.
Results: Seventeen percent (13/78) of the suspected scaphoid fractures were diagnosed as a definite scaphoid fracture. A haematoma in the anatomic snuffbox was present in 6/13 (46%) patients with a scaphoid fracture and in 24/65 (37%) of the patients without a scaphoid fracture. A swelling in the anatomic snuffbox was present in 10/13 (77%) patients with a scaphoid fracture and in 41/65 (63%) of the patients without a scaphoid fracture. Using a cut-off value of 76% of the contra- lateral side for flexion and a cut-off value of 68% for extension, there was a sensitivity of 100% (no undetected fractures). The specificity, using these cut-off values was in both instances 28%.
Cut off values for supination strength, pronation strength and grip strength, corresponding to a sensitivity of 100% are respectively 34, 40 and 34% of the contralateral side, with a specificity of respectively 28%, 23% and 25%.
Conclusion: Impaired flexion and extension of the wrist and strength measurements improve the diagnostic strategy of suspected scaphoid fractures and are of use to decide if further diagnostics are required. The presence of a haematoma or swelling of the anatomic snuffbox does not always imply a scaphoid fracture.
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Materials and methods
Study population
Seventy-eight consecutive patients visiting the Emergency Department with a suspected scaphoid fracture were included in this study between April 2004 and January 2007.
Patients with a suspected scaphoid fracture (tender anatomic snuffbox and pain in the anatomic snuffbox when applying axial pressure on the first or second digit), a recent trauma (within 48 hours) and no evidence of a fracture on scaphoid radiographs were eligible for inclusion. Poly-trauma patients, patients aged under 18 years and patients with a bi-laterally suspected scaphoid fracture were excluded. This prospective study was performed in accordance with the standards of the regional Ethical Committee and all patients gave written informed consent for study inclusion.
Study protocol
At the Emergency Department a number of clinical tests were performed. In addition, a MR scan of the wrist was carried out within 24 hours after the initial presentation and a bone scintigraphy of the wrist was performed between 3 and 5 days after trauma.
Clinical tests
Experienced physicians, according to a predefined and standardised method on both the suspected and contra-lateral side, performed all clinical tests. The following clinical tests were performed:
1) Inspection of the anatomic snuffbox for the presence of a haematoma and or for the presence of swelling in comparison with the contra-lateral side (Figure 2.1).
2) Flexion and extension of the wrist were assessed using goniometry.
Figure 2.1
Anatomic snuffbox is shown with arrow. There is no evidence of a haematoma or swelling.
Anatomic snuffbox
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Chapter 2Function and strength measurement
3) Supination and pronation strength were measured with the use of a sup-pro meter (Leiden, the Netherlands) showing the maximum achieved strength (Figure 2.2).
4) Grip strength was calculated using a Saehan Hydraulic Hand Dynamometer (Masan, Korea) showing the maximum achieved strength (Figure 2.3).
For each measurement, the percentage of the injured side compared to the contra-lateral side was calculated.
Final diagnosis
Based on the outcome of MR imaging, bone scintigraphy and clinical follow-up, a final diagnosis was made after final discharge according to a standardised algorithm. If:
•
MR imaging and bone scintigraphy both showed a fracture, the final diagnosis was a fracture;•
MR imaging and bone scintigraphy both showed no fracture, the final diagnosis was no fracture;•
There was discrepancy between MR imaging and bone scintigraphy, the physical examination during follow-up was used to make a final diagnosis. If after 2 weeks there were remaining clinical signs consistent with a fracture, the final diagnosis was a fracture. However, if there were no more clinical signs after 2 weeks the final diagnosis was no fracture.Figure 2.2
Sup-pro meter to measure the supination and pronation strength. The achieved strength is displayed (arrow).
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Figure 2.3
Hydraulic Hand Dynamometer showing the maximum grip strength (arrow).
Statistical analysis
For the strength measurements box plots were made. Clinically feasible cut off points (75, 50, 25, 10% of the contra-lateral side) were chosen and the corresponding sensitivity and specificity were calculated comparing scaphoid fractures with no scaphoid fracture (no fracture or other fractures). Receiver operating characteristic (ROC) curves for the different strength measures were made, and corresponding areas under the curves were calculated.
Finally the cut-off points, corresponding to a sensitivity of 100%, implying that all fractures are detected, were determined for all strength measures and the corresponding specificity was calculated.
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Chapter 2Function and strength measurement
Results
Patient characteristics
Baseline characteristics are displayed in Table 2.1. All patients had a clinically suspected scaphoid fracture but initial scaphoid radiographs revealed no evidence of a scaphoid fracture.
Results of MR imaging and bone scintigraphy
MR imaging showed in 10/78 (13%) patients a scaphoid fracture and in 19/78 (24%) patients another fracture. There was no fracture detected in the remaining 49/78 (63%) patients.
Bone scintigraphy revealed in 20/78 (26%) patients a scaphoid fracture, in 36/78 (46%) patients another fracture and in 22/78 (28%) patients no fracture.
According to the final diagnosis, a scaphoid fracture was present in 13/78 (17%) patients.
In 27/78 (35%) patients another fracture was present and there was no fracture in the remaining 38/78 (49%) patients.
Clinical tests
As illustrated in Table 2.2a, a haematoma in the anatomic snuffbox was present in 6/13 (46%) patients with a scaphoid fracture. A haematoma was also present in 15/65 (23%) patients with no scaphoid fracture.
A swelling in the anatomic snuffbox was present in 10/13 (77%) patients with a scaphoid fracture, as displayed in Table 2.2b. However, a swelling in the anatomic snuffbox was also present in 41/65 (63%) patients with no scaphoid fracture.
Figure 2.4a displays that the degree of flexion in patients with a scaphoid fracture is slightly less compared to the contra-lateral side. Figure 2.4b shows that the degree of extension in patients with a scaphoid fracture is reduced in comparison with the contra-lateral side. Figure 2.4c, 2.4d and 2.4e illustrate that supination strength, pronation strength and grip strength are more than 50% impaired in patients with a scaphoid fracture in comparison with the contra-lateral side.
Table 2.1
Baseline characteristics.
Patient characteristics Number Percentage
Male 40 51 %
Age (years) 41(SD 16)
Dominant hand 43 55 %
Previous fracture 7 9 %
Suspected side 3 4 %
Contra-lateral side 4 5 %
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Different cut off values for the sensitivity and specificity to predict the presence of a scaphoid fracture are shown in Table 2.3. For flexion the sensitivity is 92% at a cut off value of 75%. The sensitivity of extension drops to 69% at a cut off value of 50%. On the contrary, the sensitivity for supination strength, pronation strength and grip strength
Table 2.2
a. Displays the presence of a haematoma in the anatomic snuffbox in accordance to the final diagnosis.
Snuffbox Final diagnosis
Haematoma Scaphoid fracture Other No Total
fracture fracture
Yes 6 6 9 21
No 7 21 29 57
Total 13 27 38 78
b. Displays the presence of a swelling in the anatomic snuffbox in accordance to the final diagnosis.
Snuffbox Final diagnosis
Swelling Scaphoid fracture Other No Total
fracture fracture
Yes 10 19 22 51
No 3 8 16 27
Total 13 27 38 78
Table 2.3
Sensitivity and specificity for the different cut off values for each clinical test, as a percentage of the contra-lateral side, below which a scaphoid fracture is assumed to be present.
Clinical test Cut off value
<75% <50% <25% <10%
Flexion sens 92 46 8 8
spec 29 68 88 97
Extension sens 100 69 54 54
spec 26 57 91 94
Supination strength sens 100 100 92 77
spec 6 22 40 79
Pronation strength sens 100 100 92 69
spec 9 22 39 68
Grip strength sens 100 100 85 77
spec 8 17 34 62
Chapter 2Function and strength measurement
sens = sensitivity; spec = specificity
Figure 2.4
The simple box plots for flexion (a), extension (b), grip strength (c), pronation strength (d) and supination strength (e) are shown. Every figure shows 3 box plots: scaphoid fracture, other fracture and no fracture.
100
a b
75
50
25
0 0
25 50 75 100
100
75
50
25
0 0
25 50 75 100 Scaphoid
fracture
Flexion %Supination strength %Grip strength % Pronation strength %Extension %
Other fracture
No fracture
Scaphoid fracture
Other fracture
No fracture
c
e
d
Scaphoid fracture
Other fracture
No fracture
Scaphoid fracture
Other fracture
No fracture
100
75
50
25
0
Scaphoid fracture
Other fracture
No fracture
97.5 percentile 75 percentile
median 25 percentile
2.5 percentile
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Figure 2.5
ROC curves for the different strength measures.
1
0,8
0,6
0,4
0,2
0
0 0,2 0,4 0,6 0,8 1
1 - Specificity
Sensitivity
Supination Flexion Grip
Pronation Extension
remains 100% for a cut off value of 75 and 50%. The sensitivity starts to drop if a cut off value of 25% of the contra-lateral side is used. Figure 2.5 shows the ROC curves for the different strength measures. The area under the curve was highest for supination strength (0.80), followed by extension (0.76), grip (0.76) and pronation (0.74). Flexion had the lowest area under the curve (0.60). The sum of the sensitivity and specificity was the highest for supination strength if a cut off value of 10% is chosen.
The cut off value for each independent clinical test for which all scaphoid fractures are detected (sensitivity 100%) is displayed in Table 2.4. For flexion and extension the cut off value is respectively 76 and 68% of the contra-lateral side (specificity 28% for both
Table 2.4
Cut off value and specificity for each clinical test, as a percentage of the contra-lateral side, corresponding to sensitivity of 100% (all fractures are detected).
Clinical test Cut off value Sensitivity Specificity
Flexion < 76 100% 28%
Extension < 68 100% 28%
Supination strength < 34 100% 28%
Pronation strength < 40 100% 23%
Grip strength < 34 100% 25%
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Chapter 2Function and strength measurement
measurements). The cut off values for supination strength, pronation strength and grip strength are respectively 34, 40 and 34% of the contra-lateral side, with specificities between 23 and 28%.
Discussion
I
n line with previous reports, the results of the current study emphasise that the diagnosis of a scaphoid fracture is complex. In fact, MR imaging and bone scintigraphy revealed a scaphoid fracture in 17% of the patients with no evidence of a scaphoid fracture on the initial scaphoid radiographs. However, the routine use of MR imaging and bone scintigraphy in the clinical setting is hampered by the long scanning time, low availability and high costs. Therefore, it is desirable to develop novel diagnostic modalities to accurately confirm or rule out a suspected scaphoid fracture in daily practice.In the present study it was established that the presence of a haematoma or swelling of the anatomic snuffbox is not necessarily associated with a scaphoid fracture. Impaired flexion and or extension of the wrist together with strength measurements are a helpful tool in the diagnostic management of patients with a suspected scaphoid fracture.
Anatomic snuffbox tenderness, anatomic snuffbox swelling, tubercle tenderness and pain with longitudinal compression of the thumb are commonly used clinical tools for suspected scaphoid fractures. Diminished grip strength as presumptive evidence of a scaphoid fracture has also been described.53-54The literature has also described that grip strength will “average 50% of the uninjured wrist”.30These results are promising, but no clear cut off value has been suggested. To date, no cut off value for either flexion or extension has been reported. In addition, no data regarding the value of supination strength and pronation strength has been published. In the clinical setting, it would be useful to define a clear cut off value in order to confirm or rule out a suspected scaphoid fracture.
The present study is the first to describe a systematical assessment of clinical tests. The results concerning the clinical value of supination strength, pronation strength and grip strength are especially novel and useful in daily practice. In addition, cut off values with a corresponding sensitivity and specificity are described to confirm or rule out a suspected scaphoid fracture. All clinical tests have been performed on both the suspected and contra-lateral side according to a standardised protocol. Therefore, the results presented are reliable and valid. Finally, the proposed strength measurements are fast, cost-effective and therefore easily implemented in daily practice.
Clinically the main point is to detect all scaphoid fractures. Consequently, the sensitivity of a clinical test to confirm a scaphoid fracture is more important than the specificity. The
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Chapter 2Function and strength measurement
most essential result of this study is, that when using a cut off value corresponding to 100%
sensitivity, patients can be identified who will not have a scaphoid fracture (Table 2.4).
Flexion and extension have a cut off value of respectively 76 and 68% above which a scaphoid fracture is not present. The cut off values for supination strength, pronation strength and grip strength are respectively 34, 40 and 34% of the contra-lateral side.
These results imply for daily practice that if any of these cut off values is used no scaphoid fracture will remain undetected. With these cut off values approximately 25% of patients without a scaphoid fracture, need no further investigation and can be functionally treated.
As a result, the use of the function of the wrist and strength measurements leads to a reduction of costs which should be further investigated in future cost-effectiveness studies.
If the function of the wrist or the strength measurement is below the cut off value, a scaphoid fracture can be present and further investigation (such as bone scintigraphy, MR imaging or CT) is required. Finally, the amount of other fractures scored is considerable.
The clinical tests are less useful to detect other fractures than scaphoid fractures. The aim of this article was to evaluate the role of clinical tests for suspected scaphoid fractures.
Therefore, no conclusions regarding other fractures are made.
In conclusion, the presence of a haematoma or swelling of the anatomic snuffbox is not necessarily associated with a scaphoid fracture. Impaired flexion and extension of the wrist and strength measurements both improve the diagnostic strategy of suspected scaphoid fractures and are of use to decide if further diagnostics are required. Measurement of the function of the wrist and strength improve the diagnostic strategy of suspected scaphoid fractures.
