Department of Archaeology
Click to edit Master title style Determining a Contracted Pelvis from Fragmented Remains Candace McGovern
Introduction With only a few published cases, the high frequency of females found in archaeological populations is often attributed to an obstetric dilemma, such as a contracted pelvis.¹ A contracted pelvis occurs when the size of the pelvis is too small for the neonate to pass through. Aside from skeletal development it can be caused by morphological changes to the pelvis as the result of metabolic diseases or trauma. By using measurements from the pelvic inlet of fragmented, non-articulated pelves in conjunction with modern clinical measurements, it may be possible to provide evidence of contracted pelves.
A birth is considered “high risk” due to a contracted pelvis when the inlet conjugate measurement is between 9.5-12cm, the transverse 9.5-12.8cm, and the resulting brim area is 78-120.6cm². When the conjugate or transverse is below 9.5cm or the brim area is below 78cm² a successful birth would be theoretically impossible based on full-term neonate measurements.³ The shape of the pelvis (Figure 2), determines the location of the transverse measurement.⁴
Steps to measuring a fragment pelvis • Measure either the complete side or each individual fragments making up the pelvic brim along the accurate line. • This measurement will provide the circumference of the pelvic brim which can be used to determine the brim area.
There are 3 sets of measurements which can be used to determine if a woman has a contracted pelvis (Figure 1).
• Use the formula 𝐴 =
• Outlet – the transverse measurement is determined by the distance between the ischial tuberosities. There is no conjugate measurement.
Figure 2. The four main pelvis typologies as determined by Cadwell and Moloy ( 1938).⁴
Methods used in living populations: A doctor uses two fingers, inserted via the vaginal opening to measure the pelvic inlet based on the distance from the base of the doctor’s thumb to the tip of the forefinger. Using callipers a series of external measurements are taken at the hips.² These types of measurements, which rely on soft tissue to maintain the shape of the pelvis, are designed for clinical use and not easily transferred to archaeological populations. Previous methods used in archaeological populations: There have been limited studies done on female pelvic measurements and all have relied upon complete pelves, which are frequently limited. Held in place by bands or straps, researchers take three measurements of the articulated pelvis (the inlet, mid-plane, and outlet). The aims of these studies often focus on pelvis typologies (Figure 2), bipedalism or providing evidence of death in childbirth for a specific set of remains.
Figure 1. Measurements taken from the female pelvis in order to determine if the pelvis is contracted.²
𝐶2 , 4π
where 𝐴= brim area, and 𝐶=
circumference.
• Pelvic inlet (brim area) – the conjugate is the shortest
• Mid-plane –the conjugate is taken from the distal edge of the pubic symphysis to the distal edge of the last sacral segment (S5). The transverse or lateral measurement is the distance between the ischial spines.
The fragment pelvis method measures the pelvic inlet and does not necessitate a complete or articulated pelvis. It requires an S1 with a complete right or left ilium extending to the pubis or all fragments of the accurate line. In order to determine the accuracy of the fragmented method, measurements were taken first with the fragment method and then compared against those taken using the traditional articulated method.
Discussion
Background
distance between the pubic symphysis and the sacral promontory. The transverse is taken from the area with the widest diameter at the brim based on shape.
Methods
The fragmented method underestimated measurements on gynaecoid shape pelves (n=3) and had the lowest error range (-3.24-0.96mm). Measurements on Android shaped pelves (n=2) were overestimated and had the highest error range (2.0-5.2mm). The single platypelloid pelvis examined had an error of 1.43mm. There was no correlation between age or typology and pelvic size. Additionally, this method allowed for a 51.2% (n=16) increase in the number of useable remains within the larger study.
The results show that within Poundbury Camp, Dorset of these six pelves two sets of remains, PC 794A (aged 30-34, android shape) and PC616 (aged 20-24, gynaecoid shape) are considered “high risk”. This method will be applied to a larger research project covering puberty and childbirth in Roman Britain in order to determine the effects of pelvis shape and size as a possible contributing factor to female deaths.
• When necessary the brim area can be used to determine a contracted pelvis when no other measurements are available.
Summary
• If the sacrum (S1) is complete and the ilium is intact at the widest part, take the transverse or conjugate measurements if possible.
• Fragmented pelvis method successfully determined brim area, transverse and conjugate measurements of pelvic inlet.
• Use the formula 𝐴 =
π𝑎𝑏 , where 𝐴= brim area, 𝑎= transverse 4
and 𝑏= conjugate.
• Can be used to determine obstetric dilemmas, primarily a contracted pelvis, in archaeological populations.
• This will provide the brim area and possibly the missing transverse or conjugate, which can be used to determine the presence of a contracted pelvis.
References 1. Wells, C, ‘Ancient obstetric hazards and female mortality’, Journal of Urban Health, 1975 Dec, pp 1235-1249 2. Moore, et al. Clinically Oriented Anatomy, 6th ed. , Lippincott Williams & Wilkins, 2010 3. Bull, HC., ‘Pelvimetry in obstetrics’, Postgraduate Medical Journal, 1949 Jul, pp 310-8
Results A sample study (n=6) of females aged 20-45 at death with varying pelvis typologies from the Romano-British Poundbury Camp, Dorset collection show that brim area calculated from fragmentary pieces of the pelvic inlet can accurately be determined to within 0.17mm. With a mean difference of 0.52mm or less than 2% between the fragmented method and the articulated method there is no significant difference between the results.
4. Caldwell, WE and Moloy HC, ‘Anatomical variations in the female pelvis: their classification and obstetrical significance’, Journal of the Royal Society of Medicine, 1938 Nov, pp 1-30
Acknowledgements • Advisor, Dr Mary Lewis, Associate Professor, University of Reading. • Advisor, Dr Hella Eckardt, Associate Professor, University of Reading. • Robert Kruszynski, Curator, Natural History Museum London.
Contact information •
Department of Archaeology, University of Reading, Whiteknights, RG6 6AH
•
Email:
[email protected]
