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Histologic analysis of fetal ulnar variance
Histologic Analysis of Fetal Ulnar Variance Paul R. Kim, MD, A. Alan Giachino, MD, Hans K. Uhthoff, MD, Ottawa, Ontario, Canada
Twenty-eight fetal wrists aged 5 to 21 weeks gestation were examined histologically to assess ulnar variance. There was a trend from ulna negative to ulna neutral among this population. Of 10 wrists in group I (5-8 weeks gestation), 8 were ulna negative and 2 were ulna neutral. Of nine wrists in group II (11-13 weeks gestation), three were ulna negative and six were ulna neutral. Of nine wrists in group III (18-21 weeks gestation), two were ulna negative and seven were ulna neutral. Overall, 13 embryos demonstrated an ulna negative variance; the remainder had ulna neutral variance. These results are significantly different than the incidence of ulnar variance in adults. With growth, factors must occur that change this fetal relationship of radius to ulna. (J Hand Surg 1995;21A:114-116.)
Ulnar variance has been studied extensively in the adult, 1-5 but little has been written in the literature with regard to fetal ulnar variance. Kauer made the observation that one always finds a distal radioulnar joint with an ulna minus geometry in the early fetal stages, and he felt this tended to remain so during later fetal growth6; however, he gave no figures in support of this statement. We were unable to locate any other publications dealing with fetal ulnar variance. This study examines the incidence of ulnar variance during fetal growth and compares these results to those recorded in the literature on adults.
Materials and Methods Twenty-eight wrists from spontaneously aborted embryos and fetuses (aged 5-21 weeks gestation) From the Division of Orthopaedics,Universityof Ottawa, Ottawa, Ontario,Canada. Receivedfor publicationJuly 6, 1994; acceptedin revisedform May 24, 1995. No benefits in any form have been received or will be received from any commercialparty relateddirectlyor indirectlyto the subject of this article. Reprint requests: A. Alan Giachino, MD, FRCS(C), Suite 206, 1929 RussellRoad,Ottawa,Ontario,CanadaK1G4G3. 114
The Journal of Hand Surgery
were selected for study. Each specimen was noted to be free of any visible anatomic defects. There were 10 specimens in group I (aged 5-8 weeks gestation), 9 specimens in group II (aged 11-13 weeks gestation), and 9 specimens in group III (aged 18-21 weeks gestation). Gestational age was calculated using the crown-rump length of the intact specimen. The forearm rotation of each intact embryo and fetus was recorded prior to sectioning. Each wrist specimen was then sectioned at mid-forearm level and subsequently decalcified in ethylenediaminetetraacetic acid. Following this, the specimen was embedded in paraffin and serially sectioned in the frontal plane. Slides were stained alternately with Azan Heidenhain and Goldner Trichrome stains. Each slide was examined under light microscopy to determine ulnar variance. Ulnar variance was calculated by observing the relative relationship of the articular surface of the ulna to the articular surface of the radius at the level of the distal radioulnar joint. Ulnar variance was then classified as being either negative, neutral, or positive. Using a standardized grid (Integrationsplatte IV, Carl Zeiss, Oberkochen, Germany) an actual measurement of ulnar variance for each specimen was also completed.
The Journal of Hand Surgery / Vol. 21A No. 1 January 1996
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Results Forearm rotation recorded prior to sectioning showed 20 specimens in neutral rotation, 5 in supination (range, 10~176 and 3 in pronation (range, 10~176 Of 10 group I specimens, there were 8 ulna-negative (Fig. 1) and 2 ulna-neutral specimens. Of nine group II specimens, there were three ulna-negative and six ulna-neutral specimens (Fig. 2). Of nine group III specimens, there were two ulna-negative (Fig. 3) and seven ulna-neutral specimens. There were no ulna-positive specimens in the study group. Measurement of ulnar variance using the standardized grid was made by a single observer. The same grid and specimen magnification (40x) were used to assess the variance of the distal radioulnar joint in all specimens. The variance is expressed in millimeters. In the eight ulna-negative specimens in group I, variance measured -0.21 mm in one specimen, -0.18 mm in two specimens, - 0 . 1 4 mm in three specimens, and - 0 . 0 7 mm in two specimens. The other two specimens in group I had a neutral ulnar variance. The three ulna-negative specimens in group II measured -0.21 mm, -0.18 mm, and - 0 . 0 4 mm. The six other specimens in group II were ulna neutral. In group III, the oldest specimens studied, the variance of the two ulna-negative specimens measured -0.79 mm and -0.71 mm. The seven remaining specimens in group III were ulna neutral.
Figure 2. An 11-week-old specimen demonstrating ulna neutral variance. (Azan Heidenhain stain; original magnification xl6)
Ulnar variance has been studied in the adult by various authors. 1-5 Hulten, in 1928, examined wrist
x-ray films of 400 Swedes in order to determine the incidence of ulnar variance. His observations revealed a 22.8% incidence of ulna-negative variance, a 60.7% incidence of ulna-neutral variance, and a 16.2% incidence of ulna-positive variance.1 Chan and Huang in 1971 studied 400 wrists in a Chinese population. Their findings showed a 10% incidence of ulna-negative variance, a 41.8% incidence of ulnaneutral variance, and a 48.2% incidence of ulna-positive variance in this study population. 2 Gelberman and co-workers in 1975 reviewed wrist x-ray films of 419 black and 476 white persons and found a 21% incidence of ulna-negative, 26.2% incidence of ulnaneutral, and a 52.8% incidence of ulna-positive variance in the black population and a 29.2% incidence of ulna-negative, 31% incidence of ulna-neutral, and
Figure 1. A 6-week-old specimen demonstrating ulnanegative variance. (Azan Heidenhain stain; original magnification •
Figure 3. A 20-week-old specimen demonstrating ulnanegative variance. (Azan Heidenhain stain; original magnification •
Discussion
116
Kim etal./Fetal Ulnar Variance
39.8% incidence of ulna-positive variance in the white population. 3 The drawback in the studies by Hulten I and Chan and Huang 2 was that the examination technique had been poody described. In Hulten's study in particular, post-traumatic cases and cases with severe deformities were included, which may have affected the results. In a 1986 study, Tornvall and colleagues examined 50 wrists with no previous history or signs of trauma and found a 32% incidence of ulna-negative, 28% incidence of ulna neutral, and 40% incidence of ulna-positive variance. 4 Our study showed an overall incidence of 46% ulna-negative and 54% ulna-neutral variance. There were no ulna-positive specimens. Using chi-square analysis, these figures are significantly different than the incidence in the reported literature on adults (p = .00001). Group I had an 80% incidence of ulnanegative variance compared to groups II and III (33% and 22%, respectively). The difference in variance between group I and groups II and III was also significant using chi-square analysis (p = .012). During fetal growth between 5 and 20 weeks of gestation, a change in the incidence of ulnar variance occurs, from ulna-negative to a more ulna-neutral variance. We postulate that this trend continues during further fetal growth, as the incidence of ulnar variance in the adult includes fewer ulna-negative and more ulna-positive wrists than our fetal study group. We are not aware of any published studies of ulnar variance during later fetal life or childhood. This data would be required to determine at which time ulnar variance moves toward positive from neutral. For ulnar variance to change incidence during early fetal growth, we postulate that a differential growth rate between radius and ulna must occur. As all speci-
mens were in neutral or near neutral forearm rotation, in keeping with current standard radiographic analysis, we believe this should not account for the observed difference. 7 Since all specimens were spontaneously aborted, there may have been developmental, hormonal, or biochemical reasons for the high incidence of ulna-negative variance in our fetal study group that were not identified. Even with these limitations, we believe this is a fairly accurate representation of ulnar variance up to 20 weeks of fetal life. These findings are in contradiction to prior observations made by Kauer.6 One does not always find a fetal distal radioulnar joint with an ulna-minus configuration, as he stated. We have shown there is a high incidence of ulna-minus geometry in the early fetal stages, which soon changes to a more ulna-neutral configuration as fetal growth continues.
References 1. Hulten O. Uber anatomische Variationen der Handgelenkknochen. Acta Radiol 1928;9:155-72. 2. Chan KP, Huang P. Anatomic variations in radial and ulnar lengths in the wrists of Chinese. Clin Orthop 1971;80: 18-20. 3. Gelberman RH, Salamon PB, Jurist JM, Posch JL. The effect of ulnar variance on the incidence of Kienbrck's disease. J Bone Joint Surg 1975;57A:674--6. 4. Tomvall AH, af Ekenstam F, Hagert CG, kstam L. Radiologic examination and measurement of the wrist and distal radio-ulnar joint. Acta Radiol Diag 1986;27:581-8. 5. Forstner H. Zur Morphologie des distalen Radioulnargelenkes. Chirurgisch-orthopadische Konsequenzen. Handchir Mikrochir Plast Chir 1990;22:296-303. 6. Kauer JAG. The distal radioulnar joint: anatomical and functional considerations. Clin Orthop 1992;275:37-45. 7. Epner RA, Bowers WH, Guilford WB. Ulnar variance: the effect of wrist positioning and roentgen filming technique. J Hand Surg 1982;7:298-305.
Twenty-eight fetal wrists aged 5 to 21 weeks gestation were examined histologically to assess ulnar variance. There was a trend from ulna negative to ulna neutral among this population. Of 10 wrists in group I (5-8 weeks gestation), 8 were ulna negative and 2 were ulna neutral. Of nine wrists in group II (11-13 weeks gestation), three were ulna negative and six were ulna neutral. Of nine wrists in group III (18-21 weeks gestation), two were ulna negative and seven were ulna neutral. Overall, 13 embryos demonstrated an ulna negative variance; the remainder had ulna neutral variance. These results are significantly different than the incidence of ulnar variance in adults. With growth, factors must occur that change this fetal relationship of radius to ulna. (J Hand Surg 1995;21A:114-116.)
Ulnar variance has been studied extensively in the adult, 1-5 but little has been written in the literature with regard to fetal ulnar variance. Kauer made the observation that one always finds a distal radioulnar joint with an ulna minus geometry in the early fetal stages, and he felt this tended to remain so during later fetal growth6; however, he gave no figures in support of this statement. We were unable to locate any other publications dealing with fetal ulnar variance. This study examines the incidence of ulnar variance during fetal growth and compares these results to those recorded in the literature on adults.
Materials and Methods Twenty-eight wrists from spontaneously aborted embryos and fetuses (aged 5-21 weeks gestation) From the Division of Orthopaedics,Universityof Ottawa, Ottawa, Ontario,Canada. Receivedfor publicationJuly 6, 1994; acceptedin revisedform May 24, 1995. No benefits in any form have been received or will be received from any commercialparty relateddirectlyor indirectlyto the subject of this article. Reprint requests: A. Alan Giachino, MD, FRCS(C), Suite 206, 1929 RussellRoad,Ottawa,Ontario,CanadaK1G4G3. 114
The Journal of Hand Surgery
were selected for study. Each specimen was noted to be free of any visible anatomic defects. There were 10 specimens in group I (aged 5-8 weeks gestation), 9 specimens in group II (aged 11-13 weeks gestation), and 9 specimens in group III (aged 18-21 weeks gestation). Gestational age was calculated using the crown-rump length of the intact specimen. The forearm rotation of each intact embryo and fetus was recorded prior to sectioning. Each wrist specimen was then sectioned at mid-forearm level and subsequently decalcified in ethylenediaminetetraacetic acid. Following this, the specimen was embedded in paraffin and serially sectioned in the frontal plane. Slides were stained alternately with Azan Heidenhain and Goldner Trichrome stains. Each slide was examined under light microscopy to determine ulnar variance. Ulnar variance was calculated by observing the relative relationship of the articular surface of the ulna to the articular surface of the radius at the level of the distal radioulnar joint. Ulnar variance was then classified as being either negative, neutral, or positive. Using a standardized grid (Integrationsplatte IV, Carl Zeiss, Oberkochen, Germany) an actual measurement of ulnar variance for each specimen was also completed.
The Journal of Hand Surgery / Vol. 21A No. 1 January 1996
115
Results Forearm rotation recorded prior to sectioning showed 20 specimens in neutral rotation, 5 in supination (range, 10~176 and 3 in pronation (range, 10~176 Of 10 group I specimens, there were 8 ulna-negative (Fig. 1) and 2 ulna-neutral specimens. Of nine group II specimens, there were three ulna-negative and six ulna-neutral specimens (Fig. 2). Of nine group III specimens, there were two ulna-negative (Fig. 3) and seven ulna-neutral specimens. There were no ulna-positive specimens in the study group. Measurement of ulnar variance using the standardized grid was made by a single observer. The same grid and specimen magnification (40x) were used to assess the variance of the distal radioulnar joint in all specimens. The variance is expressed in millimeters. In the eight ulna-negative specimens in group I, variance measured -0.21 mm in one specimen, -0.18 mm in two specimens, - 0 . 1 4 mm in three specimens, and - 0 . 0 7 mm in two specimens. The other two specimens in group I had a neutral ulnar variance. The three ulna-negative specimens in group II measured -0.21 mm, -0.18 mm, and - 0 . 0 4 mm. The six other specimens in group II were ulna neutral. In group III, the oldest specimens studied, the variance of the two ulna-negative specimens measured -0.79 mm and -0.71 mm. The seven remaining specimens in group III were ulna neutral.
Figure 2. An 11-week-old specimen demonstrating ulna neutral variance. (Azan Heidenhain stain; original magnification xl6)
Ulnar variance has been studied in the adult by various authors. 1-5 Hulten, in 1928, examined wrist
x-ray films of 400 Swedes in order to determine the incidence of ulnar variance. His observations revealed a 22.8% incidence of ulna-negative variance, a 60.7% incidence of ulna-neutral variance, and a 16.2% incidence of ulna-positive variance.1 Chan and Huang in 1971 studied 400 wrists in a Chinese population. Their findings showed a 10% incidence of ulna-negative variance, a 41.8% incidence of ulnaneutral variance, and a 48.2% incidence of ulna-positive variance in this study population. 2 Gelberman and co-workers in 1975 reviewed wrist x-ray films of 419 black and 476 white persons and found a 21% incidence of ulna-negative, 26.2% incidence of ulnaneutral, and a 52.8% incidence of ulna-positive variance in the black population and a 29.2% incidence of ulna-negative, 31% incidence of ulna-neutral, and
Figure 1. A 6-week-old specimen demonstrating ulnanegative variance. (Azan Heidenhain stain; original magnification •
Figure 3. A 20-week-old specimen demonstrating ulnanegative variance. (Azan Heidenhain stain; original magnification •
Discussion
116
Kim etal./Fetal Ulnar Variance
39.8% incidence of ulna-positive variance in the white population. 3 The drawback in the studies by Hulten I and Chan and Huang 2 was that the examination technique had been poody described. In Hulten's study in particular, post-traumatic cases and cases with severe deformities were included, which may have affected the results. In a 1986 study, Tornvall and colleagues examined 50 wrists with no previous history or signs of trauma and found a 32% incidence of ulna-negative, 28% incidence of ulna neutral, and 40% incidence of ulna-positive variance. 4 Our study showed an overall incidence of 46% ulna-negative and 54% ulna-neutral variance. There were no ulna-positive specimens. Using chi-square analysis, these figures are significantly different than the incidence in the reported literature on adults (p = .00001). Group I had an 80% incidence of ulnanegative variance compared to groups II and III (33% and 22%, respectively). The difference in variance between group I and groups II and III was also significant using chi-square analysis (p = .012). During fetal growth between 5 and 20 weeks of gestation, a change in the incidence of ulnar variance occurs, from ulna-negative to a more ulna-neutral variance. We postulate that this trend continues during further fetal growth, as the incidence of ulnar variance in the adult includes fewer ulna-negative and more ulna-positive wrists than our fetal study group. We are not aware of any published studies of ulnar variance during later fetal life or childhood. This data would be required to determine at which time ulnar variance moves toward positive from neutral. For ulnar variance to change incidence during early fetal growth, we postulate that a differential growth rate between radius and ulna must occur. As all speci-
mens were in neutral or near neutral forearm rotation, in keeping with current standard radiographic analysis, we believe this should not account for the observed difference. 7 Since all specimens were spontaneously aborted, there may have been developmental, hormonal, or biochemical reasons for the high incidence of ulna-negative variance in our fetal study group that were not identified. Even with these limitations, we believe this is a fairly accurate representation of ulnar variance up to 20 weeks of fetal life. These findings are in contradiction to prior observations made by Kauer.6 One does not always find a fetal distal radioulnar joint with an ulna-minus configuration, as he stated. We have shown there is a high incidence of ulna-minus geometry in the early fetal stages, which soon changes to a more ulna-neutral configuration as fetal growth continues.
References 1. Hulten O. Uber anatomische Variationen der Handgelenkknochen. Acta Radiol 1928;9:155-72. 2. Chan KP, Huang P. Anatomic variations in radial and ulnar lengths in the wrists of Chinese. Clin Orthop 1971;80: 18-20. 3. Gelberman RH, Salamon PB, Jurist JM, Posch JL. The effect of ulnar variance on the incidence of Kienbrck's disease. J Bone Joint Surg 1975;57A:674--6. 4. Tomvall AH, af Ekenstam F, Hagert CG, kstam L. Radiologic examination and measurement of the wrist and distal radio-ulnar joint. Acta Radiol Diag 1986;27:581-8. 5. Forstner H. Zur Morphologie des distalen Radioulnargelenkes. Chirurgisch-orthopadische Konsequenzen. Handchir Mikrochir Plast Chir 1990;22:296-303. 6. Kauer JAG. The distal radioulnar joint: anatomical and functional considerations. Clin Orthop 1992;275:37-45. 7. Epner RA, Bowers WH, Guilford WB. Ulnar variance: the effect of wrist positioning and roentgen filming technique. J Hand Surg 1982;7:298-305.