siding technique for the manual phalanges

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International Journal of OsteoarchaeologyInt. J. Osteoarchaeol. 16: 338346 (2006)

Published online 11 April 2006 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/oa.826

New Siding Techniques for the

Manual Phalanges: A Blind TestD. T. CASE

a* AND J. HEILMAN

b

a Department of Sociology and Anthropology, North Carolina State University, Box 8107,

Raleigh, NC 27695-8107, USAb 1222 W. 1st Place, Mesa, AZ 85201, USA

ABSTRACT The purpose of this study was to conduct a blind test of siding techniques for the 14phalanges of the human hand. A list of possible siding techniques was initially developedusing four loosely articulated hand skeletons from an anatomical supply company, was laterrefined using ten skeletons with individually labelled hand bones from the Terry AnatomicalCollection, and then was field tested on protohistoric Arikara skeletons from South Dakota.

The most promising of these techniques were blind tested by the authors on a sample of 50Terry collection individuals. For each bone, the first author selected a specimen from eitherthe right or left side, and the second author determined the side to which it most likelybelonged, based on a written description of each technique and a rough sketch. Accuraciesfor the proximal phalanges (PP) were generally good, ranging from 100% for PP1 to 88% forPP5. Among the intermediate phalanges (IP), accuracies clustered between 96% and 98%except for IP4, which could only be correctly sided 78% of the time. Results for the distalphalanges (DP) were generally poor. Although DP1 was correctly sided 94% of the time,accuracies for the other distal phalanges ranged from a low of 52% to a high of 78%.Copyright 2006 John Wiley & Sons, Ltd.

Key words: proximal phalanges; intermediate phalanges; distal phalanges; side

Introduction

The first step in almost any study of the humanskeleton is identification and siding of the bonespresent. It is somewhat surprising, therefore, thatno standardised techniques for siding the handphalanges have been published. Osteology text-books typically treat the phalanges by type,focusing on distinguishing the proximal, inter-mediate and distal phalanges of the hand fromone another, and from the analogous bones of the

feet (Steele & Bramblett, 1988; Bass, 1995; White,2000). None provide techniques for sidingthe phalanges, and only Scheuer & Black (2000:31920) include relative length ratios as a guide

to placement of these bones into their correctrays.

Scheuer & Black (2000) correctly point outthat the lack of attention to individual identifica-tion of the phalanges is due to the fact thatcorrect assignment to the proper ray and siderelies primarily on subtle changes in bone mor-phology. Furthermore, siding of phalanges can-not be done without knowledge of their position,and attempts to position the phalanges in thecorrect ray are much more likely to succeed when

all of the phalangeal bones of a particular type arepresent. Such is rarely the case in archaeologicalsamples. Perhaps for this reason, bioarchaeolo-gists often treat the phalanges either as a group(e.g. Douglas et al., 1997; Kilgore et al., 1997)or by row (e.g. Oxenham et al., 2005) whenperforming skeletal analyses, counting the num-ber of phalanges and noting obvious abnormal-ities without attempting to identify the specific

Copyright# 2006 John Wiley & Sons, Ltd. Received 31 May 2004Revised 16 May 2005

Accepted 31 May 2005

* Correspondence to: Department of Sociology and Anthropology,

North Carolina State University, Box 8107, Raleigh, NC 27695-8107, USA.e-mail: [email protected]


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the labels on the phalanges used for this studyappear to be correct, and while the possibility ofpositioning error must be acknowledged, thenumber of errors is probably small.

The ten skeletons on which the siding techni-ques were initially evaluated included five

African-Americans and five Euro-Americans,with both sexes represented. Those featuresthat appeared to work at least 65% of the timewere used singly or in combination to assist in thesiding of hand phalanges among Arikara skele-tons from the Mobridge and Sully sites in SouthDakota (Case, 1996). A total of 165 skeletonswith one or more digital bones of the hands orfeet were examined, although hand phalangeswere not present for all individuals. Siding tech-niques were applied where appropriate, and par-ticular attention was paid to their utility insituations where the right and left sides couldbe confidently distinguished, such as cases inwhich only one of the two hands appeared tohave been recovered, or in which all of the bonesfrom one side were stained a different color thanthose from the other side. Features that appearedto distinguish one side from the other consis-tently among the Arikara sample were included inthe present study.

A total of 20 new siding techniques were blindtested by the second author (JH) on 50 skeletonsfrom the Terry Anatomical Collection (Figures 1& 2; Table 1). JH is a trained osteologist and hasconsiderable experience in working with skeletalmaterial, but no special expertise with the bonesof the hand. The sample included 27 African-Americans (17 male, 10 female) and 23 Euro-Americans (15 male, 8 female). Only skeletonswith phalanges individually labelled by ray andside were used. The hands of each skeleton werelaid out by ray, and the bones examined to verifythat all phalanges were present on both sides, andthat none exhibited trauma or disease that might

affect the test results. Skeletons with bone labelson the articular facets were replaced in somecases because the written labels could not beeffectively obscured without hampering some ofthe siding techniques.

The two authors were separated from eachother by a small barrier, so that neither couldsee what the other was writing. Beginning withPP1, a right or left phalanx of each bone type was

selected by DTC and handed to JH with allvisible labelling obscured by a small strip ofpaper. Most of the skeletons in the Terry collec-tion have a somewhat greasy external surface thatacted like a weak adhesive, so obscuring thelabels in this way was relatively simple. JH was

informed of the type of phalanx and its number.She then consulted the written techniques andsome rough sketches in order to determine a side.For each phalanx, DTC recorded the bone andside on one sheet of paper, while JH recorded herassessment on another sheet of paper. No infor-mation about the results was exchanged duringthe test. A side was assigned to a total of 50phalanges of each type using the 20 techniques.For bones with two different techniques avail-able, only one was tested during a given round.Once the first group of techniques had beenapplied to a particular skeleton, a second groupwas applied beginning again with PP1. The mostaccurate of the tested techniques for each bone ispresented in Figures 1 and 2.

Results and discussion

Accuracies for the various bone rows were gen-erally quite good. For the proximal phalanges,the ability to assign bones to the correct sideranged from 88100%, with a median accuracy of94%. The intermediate phalanges could also beaccurately sided in most cases. Although thetechnique for siding IP4 was only accurate 78%of the time, those for all the other intermediatephalanges were accurate for 9698% of thephalanges examined. The distal phalanges showedthe greatest variability in siding accuracy.Although the technique for DP1 worked 94%of the time, and that for DP5 78% of the time, thethree central distal phalanges were only accu-rately sided between 52% and 68% of the time.

All three of the techniques that produced thesepoor results for the central DPs required anevaluation of the relative size of the two lobesof the proximal facet (Figure 2). JH reported thatthe two lobes were very difficult to see on manyof the Terry collection skeletons because of abuild-up of semi-transparent bone grease com-monly found within the facet areas of the smallbones associated with these skeletons. The two

340 D. T. Case and J. Heilman

Copyright# 2006 John Wiley & Sons, Ltd. Int. J. Osteoarchaeol. 16: 338346 (2006)


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Figure 1. Most accurate siding techniques for the hand phalanges (PP1 to IP3). Any siding indicators described afterthe word additionally in the above descriptions were identified after the blind test was completed, and were notconsidered in determining technique accuracies.

Siding Techniques for the Manual Phalanges 341



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Figure 2. Most accurate siding techniques for the hand phalanges (IP4 to DP5). Any siding indicators described afterthe word additionally in the above descriptions were identified after the blind test was completed, and were notconsidered in determining technique accuracies.




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lobes may be easier to see in dry bones fromarchaeological contexts, and in anatomical ske-letons that are more intensively processed. Writ-ten descriptions and accuracies for the remainingtested techniques are provided in Table 1.

Another study of phalanx siding techniqueswas brought to the authors attention after the

blind test had been completed. The study waspart of a PhD dissertation by Ricklan (1988) fromthe University of Witwatersrand in South Africa.Ricklan initially used ten hands from five cadaverskeletons that were carefully prepared so thatnone of the bones would become mixed. Thesebones were used to identify features that

Table 1. Additional techniques from this study and Ricklan (1988)

Bone Accuracy Description of feature Source

PP1 96% Distal view: Place the bone on a flat surface on its palmar aspect, holdingthe proximal end down firmly. The distal end does not contact the flatsurface opposite the side the bone is from

This study

PP1 83% Distal view: With the palmar aspect down, the largest part of the distalarticular surface is on the side the bone is from Ricklan (1988)

PP2 94% Distal view: Place the bone on a flat surface on its palmar aspect, holdingthe proximal end down firmly. The distal end does not contact the flatsurface on the side the bone is from

This study

PP2 82% Distal view: With the palmar aspect down, the largest part of the distalarticular surface is opposite the side the bone is from

Ricklan (1988)

PP3 80% Distal view: With the palmar aspect down, the largest part of the distalarticular surface is opposite the side the bone is from

Ricklan (1988)

PP5 98% Palmar view: The most distal point on the bone is on the side the boneis from

Ricklan (1988)

PP5 82% Dorsal view: The mass of the proximal base is greater on the side thebone is from

This study

IP2 93% Proximal view: Looking at the proximal facet with the palmar aspectdown, the larger of the two facet areas is on the side the bone is from Ricklan (1988)

IP2 90% Proximal view: Lay the bone on a flat surface on its dorsal aspect. Theside of the proximal base highest above the flat surface is on the side thebone is from

This study

IP3 90% Proximal view: Lay the bone on a flat surface on its dorsal aspect. Theside of the proximal base highest above the flat surface is on the side thebone is from

This study

IP3 85% Proximal view: Looking at the proximal facet with the palmar aspectdown, the larger of the two facet areas is on the side the bone is from

Ricklan (1988)

IP5 96% Dorsal view: The degree of curvature of the shaft margin is greater on thelateral side, which is opposite the side the bone is from

This study

DP2* 91% Palmar view: A line tangent to the medial- and lateral-most edges of theproximal articular surface trends distally opposite the side the bone is

from (Figure 6)

Ricklan (1988)

DP3* 77% Palmar view: A line tangent to the medial- and lateral-most edges of theproximal articular surface trends distally opposite the side the bone isfrom (Figure 6)

Ricklan (1988)

DP4* 57% Palmar view: A line tangent to the medial- and lateral-most edges of theproximal articular surface trends distally on the side the bone is from(Figure 6)

Ricklan (1988)

DP5* 89% Palmar view: A line tangent to the medial- and lateral-most edges of theproximal articular surface trends distally on the side the bone is from(Figure 6)

Ricklan (1988)

*The tubercle on the palmar aspect of the distal phalangeal base (the insertion site for the flexor digitorum profundusmuscle) can also help with this technique. Imagine a best fit line drawn through the tubercle, and assess its trend in thesame way you would the tangent line described by Ricklan (1988). These lines are somewhat parallel, but the linethrough the tubercle may be easier to visualise.

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appeared to vary by side. Ricklan later added theleft and right hands of 45 individuals whose handbones had been kept separate by side, for a totalsample of 50 individuals and up to 100 specimensof each bone type.

Ricklans (1988) approach was to identify

features that tended to be asymmetrical in loca-tion or orientation on either side of the bonesmidline, and then to score these features on allthe bones of each row. Many of the features aresimilar or identical to those used in the presentstudy. Written summaries of some of the addi-tional features reported by Ricklan are includedin Table 1. It should be noted that the accuraciesreported are from Ricklans own analysis andwere not blind tested by the authors. Some ofRicklans descriptions have been rewritten tomatch more closely the format of descriptionsin the present study, and only features thatresulted in an 80% or greater accuracy for aparticular bone, or which outperformed thetechniques used in the present study, areincluded.

Among these additional techniques, thosewith the greatest potential to improve sidingaccuracy are the ones associated with DP2,DP3 and DP5. Ricklans technique for DP2 hasan accuracy of 91%, versus 52% for the techniquetested in the present study; his DP3 techniquehas an accuracy of 77%, versus 66% in thepresent study; and his DP5 technique has anaccuracy of 89% versus 78% in the present study.Ricklans techniques for DP4 only achieved 5758% accuracy. However, Ricklans more accuratedistal phalanx techniques for DP2DP4 aresomewhat difficult to apply. We have includedFigure 3, which is based on a figure in Ricklansdissertation, to assist in siding the distal pha-langes using his approach.

With practice, the accuracies presented herecan probably be treated as minimum estimates.

Within a given skeleton, the ability to side aphalanx correctly should improve if the samebones are present from both sides, because errorsseem to result mostly from trait ambiguity, andone of the sides is likely to show less ambiguitythan the other. Furthermore, Figures 1 and 2, andTable 1, present additional information to assistwith siding these bones which was not taken intoaccount during the blind test.

Positioning the phalanges

Application of the above techniques to museumor forensic skeletons requires first that eachphalanx be assigned to its proper ray. Withoutthe ability to determine the appropriate positionfor each phalanx, the siding techniques areuseless. As has been pointed out by previousresearchers (Susman, 1979; Scheuer & Black,2000), one way to position phalanges is to assesstheir lengths relative to the other bones of thesame row. Relative length ratios for the phalangesusually follow a distinct pattern (Susman, 1979;Ricklan, 1988):

Proximal phalanges: III> IV> II>V> IIntermediate phalanges: III IV> II>VDistal phalanges: I> III IV> II>V

Among the bones of the proximal row, PP2and PP4 are most likely to be similar in length.In such cases, these bones can usually be distin-guished by base robusticity: PP2 is normallywider mediolaterally than PP4 at the proximalend (Figure 4). Susman (1979) also noted thatPP2 has a more robust body and displays basalasymmetry because of an enlarged radial tuber-cle. In contrast, PP4 is less robust and does notdisplay basal asymmetry, but the flexor sheathridges are more distinct on PP4 than PP2. Amongthe intermediate phalanges, IP3 and IP4 are mostlikely to be similar in length. In most individuals,

Figure 3. Palmar view of distal phalanges depictingRicklans (1988) best siding techniques (see Table 1 fordescription). Drawing A represents DP2 & DP3 from theleft side, and DP4 & DP5 from the right side. Drawing Brepresents DP2 & DP3 from the right side, and DP4 &DP5 from the left side.




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References

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Case DT. 1996.Developmental Defects of the Hands and Feetin Paleopathology. Masters thesis, Department ofAnthropology, Arizona State University, Tempe,Arizona.

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siding technique for the manual phalanges

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