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Quantification of error in measurement of radial inclination angle and radial-carpal distance
Quantification inclination Posteroanterior
of error in measurement
angle and radial-carpal
wrist radiographs
inclination angle and radial-carpal
distance were measured by use of a standardized
The standard deviation for radial inclination radial-carpal
distance is 1 degree and 1 mm, respectively, SURG
Radial
technique.
angle was 2 degrees. The standard deviation for
distance was 1 mm. The measured rotational (J HAND
distance
of eight patients were evaluated by eight orthopedists.
radial-carpal and pronation.
of radial
variation of radial inclination
and
through a lo-degree arc of supination
1991;16A:399-400.)
Michael R. DiBenedetto, MD, Lawrence M. Lubbers, MD, Michael E. Ruff, MD, James F. Nappi, MD, and Carl R. Coleman, MD, Columbus, Ohio
T
he use of precise measurements from radiographs has allowed physicians to establish subtle angulations and abnormal bone or joint relationships. Unfortunately, these measurements have inherent errors from differences in radiographic technique, and from imperfections in constructing and measuring angles. This study quantifies the potential error from interobserver measurement and radiographic technique of the radial inclination angle and radial-carpal distance.
Methods Eight posteroanterior wrist radiographs were chosen randomly from teaching files. Eight orthopedists measured each radiograph for radial inclination angle and radial-carpal distance by use of a standardized technique” 2 (Fig. 1). The difference between each measured value and the average value of radial inclination angle and radial-carpal distance for each radiograph was determined. Since each radiograph had 8 measurements of radial inclination angle and radiocarpal distance, and 8 separate radiographs were evaluated, 64 total measurements were analyzed. One standard deviation for the radial inclination angle was 2 degrees and 1 mm for radial-carpal distance (Tables I and II).
From The Hand and Microsurgery pital, The Ohio State University Columbus, Ohio. Received for publication Feb. 23, 1990.
Center, Riverside Methodist HosOrthopedic Teaching Program,
Dec. 19, 1989; accepted
in revised form
No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Reprint requests: Lawrence M. Lubbers, River Rd., Columbus, OH 43214. 3/l/21043
MD, 3600B
Olentangy
Fig. 1. The radial-carpal distance (LJ is measured between
the proximal capitate (rotational center of the wrist) and a line bisecting the distal radial shaft, 4 and 8 cm proximal to the radial-carpal joint. Radial inclination angle (A) is formed between a perpendicular to the radial bisection line and a line formed between the radial styloid and distal sigmoid notch.
Posteroanterior radiographs of a phantom forearm (skeleton embedded in a plastic matrix used to teach radiographic technique) were obtained at known degrees of supination and pronation. The radial-carpal distance and radial inclination angle was measured for each radiograph (Table III). The radial inclination angle was within 1 degree through 11 degrees of supination and pronation, and the radial-carpal distance remained within 1 mm of the average through 11 degrees of supination and pronation.
THEJOURNALOFHANDSURGERY
399
400
DiBenedetto
The Journal of HAND SURGERY
et al.
Table I. Radial inclination Deviation from the average (“) 0
Table II. Radial-carpal
angle
Deviation from the average (mm)
Number
0
19 26 10 8
1 2 3 6
distance
33 28 2
1 2 3
1
Standard deviation.
Number
I
1 mm
Standard deviation, 2’.
Table III. Technique
error
Radiographic position
14”pronation 11” pronation 8“ pronation 4” pronation neutral 4” supination 8” supination
I 1” supination 14” supination
Radial inclination angle (“j
Radial-carpal
distance (mm)
21 22 22 22 22 22 23 23 24
Discussion The quantification of error in radiographic measurements has been poorly documented.3-8 Error can arise from radiographic positioning, inaccurately constructed and measured angles, and limits to the precision to which angles can be measured. The use of a radiographic phantom allowed accurate measurements of the radial inclination angle and radial-carpal distance through 14 degrees of forearm rotation. Ten degrees of supination or pronation changed the measurement of radial inclination angle plus or minus 1 degree, and radial-carpal distance plus or minus 1 mm. No additional measurement above 14 degrees was obtained because even at 11 degrees of supination or pronation, the forearm was noticeably rotated, and perceptively the position was inadequate as an posteroanterior radiograph. The interobserver error of the eight wrist radiographs was 2 degrees for radial inclination angle (Table I) and 1 mm for radial-carnal distance (Table II). The standard deviation for radial inclination angle would have been less than 1.5 degrees if the one erroneus 6 degree measurement were to be removed. Conclusion The error in measurement of radial inclination angle and radial-carnal distance is minimal. These measure-
ments can be used with confidence in the description of radiographic findings between physicians.
REFERENCES 1. DiBenedetto MR, Lubbers LM, Coleman CR. A standardized measurement of ulnar carpal translocation
J HAND SURG (In press.) 2. Jupiter JB, Masem M. Reconstruction of post-traumatic deformity of the distal radius and ulna. Hand Clinics 1988;4:377-90. 3. Garcia-Elias M, Kai-Nan A, Amadio PC, Cooney WP, Linscheid RL. Reliability of carpal angle determinations. J HAND SURG 1989;14A:1017-21. 4. Bohrer SP, Daniels SG. Error introduced by patient rotation in lateral pelvmetry. Br J Radio1 1969;42:753-6. 5. Adams P, Davies GT, Sweetnam PM. Observer error and measurements of the metacarpal. Br J Radio1 1969; 42:192-7. 6. Friberg S, Lundstrom B. Radiographic measurements on the radio-carpal joint in distal radial fractures. Acta Radio1 1976;17:869-76. 7. Benson DR, Schultz AB, Dewald RL. Roentgenographic evaluation of vertebral rotation. J Bone Joint Surg 1976; 58A: 1125-9. 8. Naor E, DiSengi V, Robin G, Makin M, Menczel J. Intraobserver variability in the determination of the metacarpal cortical index. Br J Radio1 1972:45:213-17.
of error in measurement
angle and radial-carpal
wrist radiographs
inclination angle and radial-carpal
distance were measured by use of a standardized
The standard deviation for radial inclination radial-carpal
distance is 1 degree and 1 mm, respectively, SURG
Radial
technique.
angle was 2 degrees. The standard deviation for
distance was 1 mm. The measured rotational (J HAND
distance
of eight patients were evaluated by eight orthopedists.
radial-carpal and pronation.
of radial
variation of radial inclination
and
through a lo-degree arc of supination
1991;16A:399-400.)
Michael R. DiBenedetto, MD, Lawrence M. Lubbers, MD, Michael E. Ruff, MD, James F. Nappi, MD, and Carl R. Coleman, MD, Columbus, Ohio
T
he use of precise measurements from radiographs has allowed physicians to establish subtle angulations and abnormal bone or joint relationships. Unfortunately, these measurements have inherent errors from differences in radiographic technique, and from imperfections in constructing and measuring angles. This study quantifies the potential error from interobserver measurement and radiographic technique of the radial inclination angle and radial-carpal distance.
Methods Eight posteroanterior wrist radiographs were chosen randomly from teaching files. Eight orthopedists measured each radiograph for radial inclination angle and radial-carpal distance by use of a standardized technique” 2 (Fig. 1). The difference between each measured value and the average value of radial inclination angle and radial-carpal distance for each radiograph was determined. Since each radiograph had 8 measurements of radial inclination angle and radiocarpal distance, and 8 separate radiographs were evaluated, 64 total measurements were analyzed. One standard deviation for the radial inclination angle was 2 degrees and 1 mm for radial-carpal distance (Tables I and II).
From The Hand and Microsurgery pital, The Ohio State University Columbus, Ohio. Received for publication Feb. 23, 1990.
Center, Riverside Methodist HosOrthopedic Teaching Program,
Dec. 19, 1989; accepted
in revised form
No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Reprint requests: Lawrence M. Lubbers, River Rd., Columbus, OH 43214. 3/l/21043
MD, 3600B
Olentangy
Fig. 1. The radial-carpal distance (LJ is measured between
the proximal capitate (rotational center of the wrist) and a line bisecting the distal radial shaft, 4 and 8 cm proximal to the radial-carpal joint. Radial inclination angle (A) is formed between a perpendicular to the radial bisection line and a line formed between the radial styloid and distal sigmoid notch.
Posteroanterior radiographs of a phantom forearm (skeleton embedded in a plastic matrix used to teach radiographic technique) were obtained at known degrees of supination and pronation. The radial-carpal distance and radial inclination angle was measured for each radiograph (Table III). The radial inclination angle was within 1 degree through 11 degrees of supination and pronation, and the radial-carpal distance remained within 1 mm of the average through 11 degrees of supination and pronation.
THEJOURNALOFHANDSURGERY
399
400
DiBenedetto
The Journal of HAND SURGERY
et al.
Table I. Radial inclination Deviation from the average (“) 0
Table II. Radial-carpal
angle
Deviation from the average (mm)
Number
0
19 26 10 8
1 2 3 6
distance
33 28 2
1 2 3
1
Standard deviation.
Number
I
1 mm
Standard deviation, 2’.
Table III. Technique
error
Radiographic position
14”pronation 11” pronation 8“ pronation 4” pronation neutral 4” supination 8” supination
I 1” supination 14” supination
Radial inclination angle (“j
Radial-carpal
distance (mm)
21 22 22 22 22 22 23 23 24
Discussion The quantification of error in radiographic measurements has been poorly documented.3-8 Error can arise from radiographic positioning, inaccurately constructed and measured angles, and limits to the precision to which angles can be measured. The use of a radiographic phantom allowed accurate measurements of the radial inclination angle and radial-carpal distance through 14 degrees of forearm rotation. Ten degrees of supination or pronation changed the measurement of radial inclination angle plus or minus 1 degree, and radial-carpal distance plus or minus 1 mm. No additional measurement above 14 degrees was obtained because even at 11 degrees of supination or pronation, the forearm was noticeably rotated, and perceptively the position was inadequate as an posteroanterior radiograph. The interobserver error of the eight wrist radiographs was 2 degrees for radial inclination angle (Table I) and 1 mm for radial-carnal distance (Table II). The standard deviation for radial inclination angle would have been less than 1.5 degrees if the one erroneus 6 degree measurement were to be removed. Conclusion The error in measurement of radial inclination angle and radial-carnal distance is minimal. These measure-
ments can be used with confidence in the description of radiographic findings between physicians.
REFERENCES 1. DiBenedetto MR, Lubbers LM, Coleman CR. A standardized measurement of ulnar carpal translocation
J HAND SURG (In press.) 2. Jupiter JB, Masem M. Reconstruction of post-traumatic deformity of the distal radius and ulna. Hand Clinics 1988;4:377-90. 3. Garcia-Elias M, Kai-Nan A, Amadio PC, Cooney WP, Linscheid RL. Reliability of carpal angle determinations. J HAND SURG 1989;14A:1017-21. 4. Bohrer SP, Daniels SG. Error introduced by patient rotation in lateral pelvmetry. Br J Radio1 1969;42:753-6. 5. Adams P, Davies GT, Sweetnam PM. Observer error and measurements of the metacarpal. Br J Radio1 1969; 42:192-7. 6. Friberg S, Lundstrom B. Radiographic measurements on the radio-carpal joint in distal radial fractures. Acta Radio1 1976;17:869-76. 7. Benson DR, Schultz AB, Dewald RL. Roentgenographic evaluation of vertebral rotation. J Bone Joint Surg 1976; 58A: 1125-9. 8. Naor E, DiSengi V, Robin G, Makin M, Menczel J. Intraobserver variability in the determination of the metacarpal cortical index. Br J Radio1 1972:45:213-17.