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Quantifying interdigital web morphology
QUANTIFYING
INTERDIGITAL
P. C. SHEWELL,
WEB
J. D. NANCARROW
MORPHOLOGY
and F. FATAH
From the West Midlands Regional Plastic and Jaw Surgery Unit, Wordsley Hospital, Stourbridge, West Midlands
A new method for the measurement of the interdigital webs of the hand is described and is shown to be reproducible. Measurements are taken from photographs and the method would be suitable for the comparison of post-operative appearances in the evaluation of “web creep” after surgery. Journal of Hand Surgery (British Volume, 1992) 17B: 198-200
of +/- two standard deviations from the mean for the dorsal web ratios allowed a spread of up to 7 mm. for distance B against the mean length of distance A. Therefore the reproducibility of dorsal web measurements was felt to be unacceptably poor and the method was abandoned.
In recent years much has been written and spoken on the subject of recurrent contractures following surgery to the web spaces of the hand, and in particular following corrective surgery for syndactyly. Depending upon the surgical technique employed, web recurrence, or “web creep”, has been reported in 2 to 24% of cases (Keret and Ger, 1987; Percival and Sykes, 1989). If the development of “web creep” is to be used to assess and compare differing surgical techniques we felt that it was necessary to define what comprises a normal web and to develop a reproducible method for its measurement. Methods previously applied to the first web include clinical measurements (Meyer et al., 1981; Comtet and Bemelmans, 1979; Boyes, 1970); radiological assessment of the angle between the first and second metacarpals; and stent mould angles (Bhattacharya et al., 1989). However, these are all functional measurements of adduction deformities, giving little information about the soft tissue morphology of the web.
Palmar web measurements
For palmar web measurements the dominant creases at the level of the DIP and PIP joints were marked where they crossed the edge of the finger (Fig. 2). In the event of two dominant creases, measurements were taken from the mid-point. The point at which the web was judged to meet the skin of the finger, or where it interesected the line of the edge of the finger skin, was also marked. Palmar web measurements were taken as a ratio between lengths A and B as shown in Figure 2 for both the ulnar and radial borders of each digital web. Again a single observer took ten sets of measurements of a single pair of hands over several weeks and the results were compared. Individual measurements were consistent to within 2 mm. A range of +/ - two standard deviations from the mean allowed a spread of no more than 2 mm. for distance B against the mean length of distance A. However, when ten separate observers were asked to mark and measure the same pair of hands, individual measurements ranged by up to 7 mm. and a range of
Method and results Examination of a hand quickly demonstrates that the appearance of the webs depends on the position of the fingers and on whether the hand is viewed from the dorsal or palmar aspect. For this reason two sets of measurements were chosen; from the dorsum of the hand with the hand clenched, and from the palmar aspect with the hand held flat and the fingers abducted by 10”. To standardise the position during measurement, the hand was lightly held against a glass plate and photographed through it. Measurements were taken from the photographs. Each photograph included a ruler so that any degree of magnification during development could be excluded. Standard deviations were calculated for each web, and +/ - two standard deviations from the mean were taken to contain 95% of a normal distribution. Dorsal web measurements
Dorsal web measurements (Fig. 1) were taken as a ratio between the height of the clenched fist (A) and the distance from the point at which the web starts to dip in, to the base of the fist (B). A single observer took ten sets of measurements of a single pair of adult hands over several weeks and the results were compared. While distance A was consistent to within 2 mm. in all measurements, distance B varied by up to 6 mm. A range
Fig. 1 198
Dorsal web measurements.
Third dorsal web ratio= A/B.
INTERDIGITAL
WEB MORPHOLOGY
199
most accurate and reproducible method, they were performed on 20 male and 20 female adult hands selected from hospital staff. Individuals were excluded if they exhibited clinical evidence of syndactyly, other congenital abnormalities or severe injury to their hands. None gave a family history of congenital hand abnormalities. Since a single observer appeared to be more consistent in measurements of a single pair of hands all the sample population hands were measured by one person. The means and standard deviations are given in Table 1 and shown diagrammatically for female and male hands in Figure 3. Discussion
Fig. 2
Palmar web measurements. ratio = A/B.
Third
radial
border
palmer
web
+ / - two standard deviations from the mean allowed a spread of up to 7 mm. for distance B against the mean length of distance A. Measurements of a sample population
Having established that the palmar web ratios gave the
The webs of the hand are highly complex and variable, making their quantification difficult. Previous attempts have concentrated on the functional assessment of first web space abduction. However, assessment of varying surgical approaches to the interdigital webs demands objective quantification. From our attempts it is clear that the dorsal web measurements are unacceptably inaccurate due to variation in localisation of the point at which the web starts to dip in, even when measured by the same observer on the same subject. Measurements of the palmar webs are reproducible, but only for a single observer. The use of a photographic record allows a series of hands to be conveniently measured at the same time. This could equally well be employed for the comparison
a Fig. 3
(a) Diagrammatic representation of interdigital webs in a control population of 20female hands. Stippled area represents + / - 2 standard deviations from the mean web (M). (b) Diagrammatic representation of interdigital webs in a control population of 20 mole hands. Stippled area represents + / - 2 standard deviations from the mean web (M).
200 Table l-Variation
THE JOURNAL
OF HAND SURGERY
VOL. 17B No. 2 APRIL 1992
of interdigital web ratios in male and female bands Second web space Rad. Uln.
Third web space Rad. ml.
Fourth web space Rad. ml.
Male hands Average web ratio Standard deviation 95% range
1.96 1.91 0.12 0.13 1.72-2.20 1.65-2.17
1.88 2.08 0.11 0.17 1.662.10 1.74-2.42
1.68 1.98 0.11 0.14 1.46-1.90 1.7Ck2.26
Female hands Average web ratio Standard deviation 95% range
1.86 1.88 0.12 0.08 1.62-2.10 1.72-2.04
1.85 2.0 0.08 0.13 1.69-2.01 1.74-2.26
1.88 1.98 0.09 0.15 1.7-2.06 1.69-2.27
of serial post-operative photographs by a single observer. It is also possible to enlarge photographs of childrens’ hands by a factor of two or three in order to reduce observer error when measuring small hands. The results of measurements for a sample population highlight the tremendous variation in hand size and shape. Using ratios of measurements taken from hands reduces the variation in absolute measurements. We are presently using the method to measure the interdigital web morphology in children of different ages and hope to report the collated information shortly. Conclusion
We have demonstrated a method which can be employed for the measurement of the morphology of palmar finger webs. These measurements can be taken from photographs allowing easy comparison of serial post-operative appearances. Although the measurements are subjective we have shown that they are reproducible only if marked and measured by a single observer. It is therefore doubtful if comparison of different published series is acceptable unless original photographs are available and reassessed
by a single observer. Measurements of a control population of male and female hands demonstrates a wide variation in normal web morphology which may, however, go some way towards the definition of a normal finger web. References BHAlTACHARYA, S., PANDEY, S. D., CHANDRA, R. and SINGH, G. K. (1989). Documentationof the first web space angle. Journalof Hand Surgery, 14B: 3: 298-300. BOYES, J. H. Bunnell’s Surgery of the Hand, 5th edn. Philadelphia, J. B. Lippincott, 1970. COMTET, J. J. and BEMELMANS, D. (1979). The palmar abduction-pronation osteotomy of the first metacarpal bone combined with tendon transfer for lateral thenar muscle paralysis. The Hand, 11: 2: 191-197. KERET, D. and GER, E. (1987). Evaluation of a uniform operative technique to treat syndactyly. Journal of Hand Surgery, 12A: 5(l): 727-729. MEYER, R. D., GOULD, J. S. and NICHOLSON, B. (1981). Revision of first web space, techniques and results. Southern Medical Journal, 74: 10: 1204 1208. PERCIVAL, N. J. and SYKES, P. J. (1989). Syndactyly: a review of the factors which influence surgical treatment. Journal of Hand Surgery, 14B: 2: 196 200.
Accepted:?5 June 1991 Mr P. C. Shewell,M.Sc., F.R.C.S., Hospital, 0
Department
Birmingham.
1992 The Brutish Society
for Surgery
of the Hand
of Orthopaedic
Surgery,
East Birmingham
INTERDIGITAL
P. C. SHEWELL,
WEB
J. D. NANCARROW
MORPHOLOGY
and F. FATAH
From the West Midlands Regional Plastic and Jaw Surgery Unit, Wordsley Hospital, Stourbridge, West Midlands
A new method for the measurement of the interdigital webs of the hand is described and is shown to be reproducible. Measurements are taken from photographs and the method would be suitable for the comparison of post-operative appearances in the evaluation of “web creep” after surgery. Journal of Hand Surgery (British Volume, 1992) 17B: 198-200
of +/- two standard deviations from the mean for the dorsal web ratios allowed a spread of up to 7 mm. for distance B against the mean length of distance A. Therefore the reproducibility of dorsal web measurements was felt to be unacceptably poor and the method was abandoned.
In recent years much has been written and spoken on the subject of recurrent contractures following surgery to the web spaces of the hand, and in particular following corrective surgery for syndactyly. Depending upon the surgical technique employed, web recurrence, or “web creep”, has been reported in 2 to 24% of cases (Keret and Ger, 1987; Percival and Sykes, 1989). If the development of “web creep” is to be used to assess and compare differing surgical techniques we felt that it was necessary to define what comprises a normal web and to develop a reproducible method for its measurement. Methods previously applied to the first web include clinical measurements (Meyer et al., 1981; Comtet and Bemelmans, 1979; Boyes, 1970); radiological assessment of the angle between the first and second metacarpals; and stent mould angles (Bhattacharya et al., 1989). However, these are all functional measurements of adduction deformities, giving little information about the soft tissue morphology of the web.
Palmar web measurements
For palmar web measurements the dominant creases at the level of the DIP and PIP joints were marked where they crossed the edge of the finger (Fig. 2). In the event of two dominant creases, measurements were taken from the mid-point. The point at which the web was judged to meet the skin of the finger, or where it interesected the line of the edge of the finger skin, was also marked. Palmar web measurements were taken as a ratio between lengths A and B as shown in Figure 2 for both the ulnar and radial borders of each digital web. Again a single observer took ten sets of measurements of a single pair of hands over several weeks and the results were compared. Individual measurements were consistent to within 2 mm. A range of +/ - two standard deviations from the mean allowed a spread of no more than 2 mm. for distance B against the mean length of distance A. However, when ten separate observers were asked to mark and measure the same pair of hands, individual measurements ranged by up to 7 mm. and a range of
Method and results Examination of a hand quickly demonstrates that the appearance of the webs depends on the position of the fingers and on whether the hand is viewed from the dorsal or palmar aspect. For this reason two sets of measurements were chosen; from the dorsum of the hand with the hand clenched, and from the palmar aspect with the hand held flat and the fingers abducted by 10”. To standardise the position during measurement, the hand was lightly held against a glass plate and photographed through it. Measurements were taken from the photographs. Each photograph included a ruler so that any degree of magnification during development could be excluded. Standard deviations were calculated for each web, and +/ - two standard deviations from the mean were taken to contain 95% of a normal distribution. Dorsal web measurements
Dorsal web measurements (Fig. 1) were taken as a ratio between the height of the clenched fist (A) and the distance from the point at which the web starts to dip in, to the base of the fist (B). A single observer took ten sets of measurements of a single pair of adult hands over several weeks and the results were compared. While distance A was consistent to within 2 mm. in all measurements, distance B varied by up to 6 mm. A range
Fig. 1 198
Dorsal web measurements.
Third dorsal web ratio= A/B.
INTERDIGITAL
WEB MORPHOLOGY
199
most accurate and reproducible method, they were performed on 20 male and 20 female adult hands selected from hospital staff. Individuals were excluded if they exhibited clinical evidence of syndactyly, other congenital abnormalities or severe injury to their hands. None gave a family history of congenital hand abnormalities. Since a single observer appeared to be more consistent in measurements of a single pair of hands all the sample population hands were measured by one person. The means and standard deviations are given in Table 1 and shown diagrammatically for female and male hands in Figure 3. Discussion
Fig. 2
Palmar web measurements. ratio = A/B.
Third
radial
border
palmer
web
+ / - two standard deviations from the mean allowed a spread of up to 7 mm. for distance B against the mean length of distance A. Measurements of a sample population
Having established that the palmar web ratios gave the
The webs of the hand are highly complex and variable, making their quantification difficult. Previous attempts have concentrated on the functional assessment of first web space abduction. However, assessment of varying surgical approaches to the interdigital webs demands objective quantification. From our attempts it is clear that the dorsal web measurements are unacceptably inaccurate due to variation in localisation of the point at which the web starts to dip in, even when measured by the same observer on the same subject. Measurements of the palmar webs are reproducible, but only for a single observer. The use of a photographic record allows a series of hands to be conveniently measured at the same time. This could equally well be employed for the comparison
a Fig. 3
(a) Diagrammatic representation of interdigital webs in a control population of 20female hands. Stippled area represents + / - 2 standard deviations from the mean web (M). (b) Diagrammatic representation of interdigital webs in a control population of 20 mole hands. Stippled area represents + / - 2 standard deviations from the mean web (M).
200 Table l-Variation
THE JOURNAL
OF HAND SURGERY
VOL. 17B No. 2 APRIL 1992
of interdigital web ratios in male and female bands Second web space Rad. Uln.
Third web space Rad. ml.
Fourth web space Rad. ml.
Male hands Average web ratio Standard deviation 95% range
1.96 1.91 0.12 0.13 1.72-2.20 1.65-2.17
1.88 2.08 0.11 0.17 1.662.10 1.74-2.42
1.68 1.98 0.11 0.14 1.46-1.90 1.7Ck2.26
Female hands Average web ratio Standard deviation 95% range
1.86 1.88 0.12 0.08 1.62-2.10 1.72-2.04
1.85 2.0 0.08 0.13 1.69-2.01 1.74-2.26
1.88 1.98 0.09 0.15 1.7-2.06 1.69-2.27
of serial post-operative photographs by a single observer. It is also possible to enlarge photographs of childrens’ hands by a factor of two or three in order to reduce observer error when measuring small hands. The results of measurements for a sample population highlight the tremendous variation in hand size and shape. Using ratios of measurements taken from hands reduces the variation in absolute measurements. We are presently using the method to measure the interdigital web morphology in children of different ages and hope to report the collated information shortly. Conclusion
We have demonstrated a method which can be employed for the measurement of the morphology of palmar finger webs. These measurements can be taken from photographs allowing easy comparison of serial post-operative appearances. Although the measurements are subjective we have shown that they are reproducible only if marked and measured by a single observer. It is therefore doubtful if comparison of different published series is acceptable unless original photographs are available and reassessed
by a single observer. Measurements of a control population of male and female hands demonstrates a wide variation in normal web morphology which may, however, go some way towards the definition of a normal finger web. References BHAlTACHARYA, S., PANDEY, S. D., CHANDRA, R. and SINGH, G. K. (1989). Documentationof the first web space angle. Journalof Hand Surgery, 14B: 3: 298-300. BOYES, J. H. Bunnell’s Surgery of the Hand, 5th edn. Philadelphia, J. B. Lippincott, 1970. COMTET, J. J. and BEMELMANS, D. (1979). The palmar abduction-pronation osteotomy of the first metacarpal bone combined with tendon transfer for lateral thenar muscle paralysis. The Hand, 11: 2: 191-197. KERET, D. and GER, E. (1987). Evaluation of a uniform operative technique to treat syndactyly. Journal of Hand Surgery, 12A: 5(l): 727-729. MEYER, R. D., GOULD, J. S. and NICHOLSON, B. (1981). Revision of first web space, techniques and results. Southern Medical Journal, 74: 10: 1204 1208. PERCIVAL, N. J. and SYKES, P. J. (1989). Syndactyly: a review of the factors which influence surgical treatment. Journal of Hand Surgery, 14B: 2: 196 200.
Accepted:?5 June 1991 Mr P. C. Shewell,M.Sc., F.R.C.S., Hospital, 0
Department
Birmingham.
1992 The Brutish Society
for Surgery
of the Hand
of Orthopaedic
Surgery,
East Birmingham