ORIGINAL PAPER

Skeletal analysis and comparison of bog bodiesfrom Northern European peat bogs

Jan M. Pestka & Florian Barvencik & Frank T. Beil & Robert P. Marshall & Eilin Jopp &

Arndt F. Schilling & Andreas Bauerochse & Mamoun Fansa & Klaus Püschel &Michael Amling

Received: 3 November 2009 /Revised: 25 January 2010 /Accepted: 27 January 2010 /Published online: 25 February 2010# Springer-Verlag 2010

Abstract Although numerous bodies were deposited inWestern European bogs in the past centuries, few werefound and underwent archeological analysis. No studiescomparing skeletal structure and mineralization of bogbodies from different ages have been performed to this day.Therefore, the aim of this study was to analyze andcompare skeletal features and specifics of the humanremains of three bog bodies from the Iron and MiddleAges found in Northern European peat bogs. Demineral-ization due to the acidic environment in peat bogs wascomparably pronounced in all three bodies. Still, themacroscopic state of skeletal preservation was excellent.In addition to contact radiography, we used peripheral

quantitative computed tomography to measure cortical bonemineral density. The conservation of skeletal three-dimensional microstructural elements was assessed byhigh-resolution microcomputed tomography analysis.These techniques revealed severe differences in bonemineral density and enabled us to determine handednessin all three bodies. Additionally, unique skeletal featureslike intravital bone lesions, immobilization osteoporosis,and Harris lines were found. A deformity of the left femoralhead was observed which had the typical appearance of anadvanced stage of Legg–Calve–Perthes disease. This studygives detailed insight into the skeletal microstructure andmicroarchitecture of 800- to 2,700-year-old bog bodies.Skeletal analysis enables us to draw conclusions not onlyconcerning changes in the acidic environment of the bog,but also serves as a diagnostic tool to unravel life circum-stances and diseases suffered by humans in the Iron andMiddle Ages.

Keywords Bog body . Bone mineral density . Radiography .

Immobilization osteoporosis . Bone

Introduction

Bog bodies are human remains found in peat bogs. Bogbody discoveries have been documented from differentlocations in Europe (Stead et al. 1986; Van der Sanden1996). Peat used to be a major source of energy in NorthernEurope during the late nineteenth and early twentiethcentury. The high turnover and intensive work in peat bogseventually lead to the discovery of several bodies duringthis time. Not all bodies could be conserved and some wereeven reburied in local churchyards. Fortunately, some well-preserved samples found their way into Northern European

Jan M. Pestka and Florian Barvencik contributed equally to this study.

J. M. Pestka : F. Barvencik : F. T. Beil : R. P. Marshall :M. Amling (*)Department for Osteology and Biomechanics,University Medical Centre Hamburg-Eppendorf,Martinistr. 52,20246 Hamburg, Germanye-mail: amling@uke.uni-hamburg.de

E. Jopp :K. PüschelInstitute for Forensic Medicine,University Medical Centre Hamburg-Eppendorf,Hamburg, Germany

A. F. SchillingTechnical University Hamburg-Harburg,Hamburg, Germany

A. BauerochseLower Saxony State Service for Cultural Heritage,Hannover, Germany

M. FansaOldenburg Nature and Folk Museum,Oldenburg, Germany

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museums, but only a small number became available forscientific analysis.

Initial analysis provided information that the state ofpreservation of the bodies mainly depends on the con-ditions in the bog. Polysaccharides such as sphagnan andtannic acids in the peat contribute to the good preservationof soft tissue, even after several thousand years in the bog(Pyatt et al. 1991). Tannic acids, on the other hand, lead tosevere demineralization of all skeletal elements. Usually,neither cellular structures nor DNA in bone are preserved(Pyatt et al. 1991; Hughes et al. 1986). Interestingly, it hasbeen reported that brain cell structures of 8,000-year-oldhuman remains found in peat bogs in Florida, USA werewell-preserved and dermal collagen could still be detectedin the skin of a 2,000-year-old bog body (Lawlor et al.1991; Doran et al. 1986; Stücker et al. 2001). All pH valueswere neutral in these bogs, which surely contributed to theexcellent state of preservation described here. Like mostNorthern European peat bogs, the bogs analyzed in thepresent study are all raised bogs. Here, acidic values (pH 3–4.8) were found, which can lead to severe demineralizationin bones, putting the preservation of organic tissue atjeopardy.

Nevertheless, our group was recently able to report that acomplete skeletal evaluation of a 2,700-year-old bog bodyrevealed interesting findings (Schilling et al. 2007).Quantitative and qualitative methods were used to analyzethe human remains of the bog body “Moora,” a femaleskeleton from the Iron Age. The bones were dated to ∼650B.C. by 14C radiocarbon analysis (Van der Pflicht et al.2004).The body was found in the year 2000 in a NorthernGerman peat bog near Uchte, Germany (52°30′0″ N, 8°55′0″ E) (Pueschel et al. 2005; Bauerochse et al. 2005;Schilling et al. 2007). Nondestructive qualitative evaluationof the bone was possible with the help of contactradiography. Using contact radiography, two-dimensionalimages of the bones in question were produced withoutfurther magnification. In addition, peripheral quantitativecomputed tomography (pQCT) and microcomputed tomog-raphy (µCT) were used to give a more detailed picture ofthe skeletal status of the bog bodies. pQCT represents anondestructive method for the assessment of bone mineraldensity (BMD). It uses multiple cross-sectional X-rays toreconstruct a volumetric model of the bone densitydistribution (in milligrams per cubic centimeter). In contrastto this method, µCT images give insight into the three-dimensional composition of bone and, therefore, reflectskeletal microarchitecture. It analyzes skeletal structuressimilar to histological methods without harming the bodyand, therefore, enabled us to evaluate the skeletal structurefrom the inside by virtually cutting through the bone.

pQCT revealed a loss of 92.7% of cortical bone mineraldensity (cBMD) in the radius due to 2,700 years in the

acidic environment of the bog (Table 1; Schilling et al.2007). Harris lines were found in the distal tibiae. Theyrepresent radiodense lines found perpendicular to thelongitudinal axis of long bones and result from temporaryslowing or cessation of longitudinal growth in periods ofdietary restriction, infection, or childhood stress (Hugheset al. 1996; Jopp et al. 2006). pQCT analysis showed ahigher BMD of the left upper extremity, leading to theconclusion that this young woman must have been left-handed. Furthermore, µCT analysis revealed the first three-dimensional data on trabecular microstructure of a bogbody from the Iron Age.

Information regarding the skeletal status of bog bodiesfrom different locations or different centuries is elusive.The aim of this study was, therefore, to study (1) the effectsof different time periods in the bog on bone and the effectson the grade of mineralization, (2) to determine thestructural integrity of skeletal elements after ∼800 years inthe bog by µCT analysis, and (3) to gather informationconcerning life circumstances and pathological conditionsof the individual bodies with the help of skeletal analysis.Taken together, with the help of these methods, this studyhas the potential to make a valuable contribution inunderstanding the evolving field of archeological preserva-tion of human remains in bog environments.

Materials and methods

The bog body analyzed by our institute in the spring of2009 (“BB 2009”) was found in the Sedelsberg peat nearEsterwegen, Germany (52°59′31″ N, 7° 38′1″ E). Thislocation is close to the peat near Uchte, Germany (52 30′0″N, 8°55′0″ E) where the second bog body analyzed by ourinstitute in 2005 (“BB 2005”) was discovered in the year2000. The human remains of a third body analyzed in 2007(“BB 2007”) were discovered approximately 500 milessouth from the peat bogs mentioned above in Peiting,Germany (52°59′31″ N, 7°38′1″ E; Table 1).

The skeletal remains of “BB 2009” were initiallydiscovered in February 1939 and preserved at the Old-enburg Nature and Folk museum. A total of 48 bones wereavailable for detailed osteological analysis (Fig. 1a). Softtissue was not present. Femora, humeri, and fibulae werefound in pairs. Additional paired long bones of the humanskeleton were either found solitarily (e.g., left ulna, righttibia) or were missing.

“BB 2007” was discovered in 1957 and made availableto our institute in 2007. The body had been buried in awooden coffin. Initially, 14C analysis of the coffin’s woodwas initiated in order to indirectly estimate the body’s agefollowed by 14C analysis of “BB 2007” itself (Haas-Gebhard and Pueschel 2009; Schlabow 1983). During the

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excavation, clothing and a pair of apparently unused leatherboots worn by the body were recovered. The body was inan excellent state of preservation and all skeletal elementswere preserved (Fig. 1b). Shortly after recovery, an autopsywas performed and numerous inner organs were removed,the skull was opened, and the intact brain was removed.Seventy years later, these organ’s whereabouts remainunknown. In comparison to the rest of the body’s softtissue, the skull, forearms, and hands were not continuouslycovered by bog and, therefore, soft tissue was not preservedin these locations.

For fine-grained contact radiographic analysis of the bogbodies, images of the bones were projected on mammography

films using a Faxitron X-ray cabinet (Faxitron X-ray,Wheeling, IL). For the estimation of cBMD, the shaft of eachlong bone was assessed by a pQCT (XCT-2000, StratecMedizintechnik, Pforzheim, Germany) according to ourstandardized protocols (Schilling et al. 2007). cBMD wasdetermined with the CORTBD software module using athreshold of 0 mg/cm3. For three-dimensional visualizationand analysis of the bone microstructure, bones were scanned(45 kV/88 µA) in a µCT40 (Scanco, Bassersdorf, Switzerland)with a voxel size of 30 and 37 µm, respectively. The raw datawere manually segmented and analyzed with the µCTEvaluation Software V4.4A (Scanco Medical, Brüttisellen,Switzerland). The thresholding parameters for these measure-

Table 1 Characteristics of the three individual bog bodies

“BB 2009” “BB 2007” “BB 2005”

Place of discovery Esterwegen, Germany(52°59′31″ N, 7°38′1″ E)

Peiting, Germany(47°48′0″ N, 10°56′0″ E)

Uchte, Germany(52°30′0″ N, 8°55′0″ E)

Date of discovery February 27, 1939 July 23, 1957 Sept. 6, 2000

Sex Unknown Female Female

Approximate age (years) 8–12 20–25 19

Approximate years in bog 800 700 2,700

Loss of cBMD (%) 78.2 (ulna) 83.4 (radius) 92.7 (radius)

Handedness Right-handed Left-handed Left-handed

Skeletal abnormalities Bone lesion, LCPD None Harris lines

Place and date of discovery can be found next to sex and approximate age at death. Approximate time spent in the bog was estimated using 14 C analysis(Van der Pflicht et al. 2004). cBMD was measured in the ulna and radius and loss of cBMD was calculated using reference data from the literature(Nikander et al. 2006; Neu et al. 2001). Handedness, as well as skeletal abnormalities, was determined for all bog bodies analyzed in this study

LCPD Legg–Calve–Perthes disease

Fig. 1 Schematic skeleton im-age of bones available forskeletal analysis. Three bogbodies from the Middle and IronAges were analyzed. Bonesavailable for skeletal analysisare highlighted in red. A total of48 bones were available for theanalysis of “BB 2009” (a),complete skeleton of “BB 2007”was available for osteologicalanalysis (b), and the skeletalremains of “BB 2005”consisted of 90 bones (c)

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ments were calculated from the results of the pQCT measure-ments. The segmented data sets were imported and visualizedusing µCT Ray V3.0 (Scanco Medical, Brüttisellen, Switzer-land) and Amira V3.1 (Mercury Computer Systems Europe,Merignac, France).

Results

Radiological assessment of three bog bodies

Due to approximately 800 to 2,700 years in the acidicenvironment of the bog, the bodies from the Middle andIron Ages showed severe signs of demineralization in allbones. Still, the skeletal elements of all three bodies wereintact and well-preserved. Contact radiography was per-formed and pronounced radiolucency due to severe loss ofBMD was observed. Figure 2 shows the state of preserva-tion for selected and particularly well-preserved skeletalelements. Here, the skull, iliac and sciatic bone, and avertebral body of “BB 2009” are displayed. Despite someexcavation artifacts at the ischium, the femoral bone, andsome other locations, no further pathological postmortalchanges were observed. The image of the skull displayspartly closed sutures. The mandible is missing and, in theupper jaw, the remains of a single tooth can be seen(Fig. 2a).

The bog body’s bones from the Middle Ages (“BB2007”), presumably the bones of a woman at 20 to 25 yearsof age, were equally well-preserved. Radiographic imagesof the skeleton’s skull, the left lower arm, and the firstvertebral body showed high radiolucency of all bonesassessed with intact cortices and, despite some excavationartifacts, no obvious pathological changes were visible(Fig. 2d–f). The skull was opened in 1957 in order to gainaccess to the brain. Eventually, it was removed; itswhereabouts are unknown. The skull was closed with metalpins. The synostosis sphenooccipitalis shows signs ofbeginning ossification. An ossification between the styloidprocessus and the temporal bone that physiologicallyoccurs after the age of 25 had not taken place (Fig. 2d).These findings support the estimation of an age between 15and 25 years (Schlabow 1983). In contrast to most otherbog bodies discovered in peats in Northern Europe, “BB2007” was found lying in a coffin. Parts of the coffin wereused to estimate the body’s age with the help of 14C datingin order to perform destruction-free analysis of the skeletalelements. 14C dating revealed an approximate age of800 years, concluding that the young woman presumablydied at around 1,200 A.D. (Schlabow 1983). Additionally,14C dating was performed at AMS Laboratory (Universityof Erlangen-Nürnberg, Germany), leading to a newlyapproximated time of death that was set between 1,290

and 1,370 A.D. and between 1,380 and 1,440 A.D. with aprobability of 95% (Haas-Gebhard and Pueschel 2009).

Images of the iliac and sacral bone and the left distaltibia of “BB 2005” were produced with fine-grained contactradiography (Fig. 2g–i). An interesting finding was made asHarris lines were found at the distal tibia. Harris lines areradiodense lines that can be found perpendicular to thelongitudinal axis of long bones (Jopp et al. 2006; Hughes etal. 1996). Radiolucency was elevated in all bones,including the third metacarpal bone shown here. This bonedid not show any pathological changes. Closed epiphysealgrowth plates of all long bones were observed macroscopi-cally and radiologically, correlating with an estimated ageof approximately 19 years.

µCT analysis reveals intact three-dimensional architecture

The three-dimensional inner microstructure of human bonescan be studied destruction-free using high-resolution µCTimaging (Fig. 3). Due to the small size of the metacarpaland metatarsal bones in comparison to other long bones ofthe body, these bones ideally fit into this technique.Analysis of inner trabecular architecture revealed excellentpreservation with intact three-dimensional structures in allthree specimens. Interestingly, ∼2,000 additional years inthe bog did not appear to have had a significant influenceon the inner trabecular microarchitecture of the metacarpalbone of the body from the Iron Age when compared to thebones from the bodies from the Middle Ages (Fig. 3c).

Bone mineral density assessment via pQCT revealshandedness

cBMD measurements of the upper extremity wereperformed with the help of pQCT. Previous studiesdemonstrated that the use of pQCT allows determinationof the dominant upper extremity and, therefore, allowsthe identification of handedness (Schilling et al. 2007;Gumustekin et al. 2004). Here, analysis of humeri of “BB2009” revealed a loss of 78.2% cBMD. Both humeri wereused to determine handedness via pQCT measurements.The right humerus presented with a 2.6% higher cBMDwhen compared to the left side (cBMD right humerus=66.4 mg/cm3 vs. cBMD left humerus=64.7 mg/cm3),indicating right-handedness (Fig. 4a).

Left-handedness could be presumed for both “BB 2007”and “BB 2005” where pairs of radii were present for bothbodies. A loss of cBMD of 83.4% was observed for thebody from the Middle Ages. The ∼2,700-year-old bog bodyfrom the Iron Age presented with a cBMD loss of 92.7%(Schilling et al. 2007). A comparison of cBMD of bothradii was carried out for both bodies, revealing a 9.1%higher cBMD of the left radius for “BB 2007” (cBMD right

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radius=130.4 mg/cm3 vs. cBMD left radius=143.0 mg/cm3) and a 2.1% higher cBMD of the left radius of “BB2005” (cBMD right radius=87.5 mg/cm3 vs. cBMD leftradius=89.3 mg/cm3; Fig. 4b, c).

A bone lesion leading to immobilization osteoporosis

An overview image of all skeletal elements available for“BB 2009” was taken (Fig. 5a). Here, during the macro-scopic analysis of these preserved skeletal elements, aninteresting finding could be made. Despite the sharp and

angled excavation and postmortal defects, a remarkablebone lesion was found in one long bone (Fig. 5b). Thelesion was located at the right anterior distal tibia andmeasured 2.8×0.5 cm, penetrating the cortex and occurredto have an intravital origin. Microscopically, smooth defectborders were observed. High-resolution contact radiogra-phy revealed distinct sclerosis of the defect’s margins whichtakes place during times of intense bone remodeling (e.g.,bone healing; Fig. 5c). Therefore, the lesion apparentlydeveloped during lifetime and does not appear to be anexcavation artifact.

Fig. 2 Radiological images of three bog bodies from the Middle andIron Ages. Image of “BB 2009” showing the skull with cranial sutures(arrows) not closed which indicates adolescence. The mandible wasmissing and remains of a single tooth were found in the upper jaw (a).The pelvis was preserved in parts with the sciatic bone showing asharp excavation artifact (arrow, b). High-resolution contact radiog-raphy highlights the radially oriented trabecular structure of a well-preserved cervical vertebral body (c). High-grained radiologicalimages of “BB 2007” showing the skull where ossification betweenthe styloid process (arrow) and the temporal bone is not fullycompleted. This finding indicates an age below 25 years (d). At the

left forearm, the interosseus membrane was preserved. Artifacts can beobserved where the radius and ulna were fixed together with wire(arrow) for exposition purposes (e). Due to high radiolucency, lowBMD can be estimated for the first vertebral body (f). Contactradiography of “BB 2005” with pelvic bones including the sacrum (g).Harris lines (arrows) were detected in the left distal tibia. They resultfrom temporary slowing or cessation of longitudinal growth in periodsof dietary restriction, infection, or childhood stress (h). The thirdmetacarpal bone of “BB 2005” showed no excavation artifacts orpathological changes and was hence used for µCT analysis (i)

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The bones of the lower extremity were analyzed withpQCT, which revealed a significant loss of cBMD in theright femur and fibula. The right femur showed a cBMD of60.5 mg/cm3, whereas a cBMD of 68.1 mg/cm3 was foundon the right side (∆cBMD=11.2%; Fig. 5d). For bothfibulae, differences in cBMD were even more pronounced.Here, cBMD in the right tibia measured 45.0 mg/cm3 andthe left fibula measured 59.9 mg/cm3 (∆cBMD=24.9%;Fig. 5e).

Examination of the lower right extremity showedexcavation artifacts of both femora. They were accidentallycut into halves by the sharp edges of the spades used to digin the peat (Fig. 5f).

A coxa vara was observed for the left femur with areduction of the center column diaphysis (CCD) angle to123° measured in the frontal plane (Fig. 5g). Healthyage-matched individuals have been reported to presentwith CCD angles between 130° and 140° (Glogowski1962).

Moreover, macroscopic changes of the left proximalfemur epiphysis and femoral head were present. The leftfemoral head had a condensed and flattened appearancewith a ruffled surface, whereas the apparently healthy rightside presented physiologically round with a smooth surface(Fig. 5h)

Discussion

In this study, we analyzed and compared a unique set ofbog bodies from Northern European peat bogs. Despitesevere demineralization, which had taken place in all

skeletal elements, we were able to obtain quantitative andqualitative data by using contact radiography, pQCT, andµCT.

Establishing the age of bog bodies was first described forthe Grauballe Man in 1956 by the radiocarbon method(Tauber 1956). This method required a substantial amountof tissue. In the 1980s, AMS dating was developed, whichonly requires few milligrams of tissue. Controversy aboutthe reliability of 14C dating elucidates that bog bodies arenot the most ideal subjects for this method. Due to theuniqueness of the human skeletal remains analyzed in thisstudy, we defined our superior goal to perform destruction-free analyses. Direct age determination with the 14C methodwas, therefore, initially performed for “BB 2005” and “BB2009” (Van der Pflicht et al. 2004). Since “BB 2007” wasburied and discovered in a wooden coffin, wood sampleswere obtained and 14C dating was administered. Anapproximate age of 800 years was estimated for the woodanalyzed. This can be used as an indirect indicator for theperson’s age without having to use tissue samples. Still, thismethod only indicates an approximate age since severalfactors can influence the results obtained here. Dependingon the type of tree used to build the coffin “BB 2007” wasburied in, its age might have been overestimated if a long-living tree (e.g., oak, conifer) was used where heartwoodmay differ significantly in age from the outer tree’ssapwood. Additionally, in large trees, sapwood may beinferior in hardness, strength, and toughness to heartwood,which can also have influences on the estimated age.However, after completion of our skeletal “BB 2007”analyses, 14C dating was performed on the individual’sbody at the AMS Laboratory (University of Erlangen-

Fig. 3 µCT analysis of meta-carpal and metatarsal bones. Thecaput of the metatarsal bone of“BB 2009” was detached fromthe corpus due to a non-ossifiedgrowth plate and remainsmissing. µCT analysis shows apreserved dense trabecularnetwork on the base of the bone(a). The second right metacarpalbone of “BB 2007” (b) and thethird left metacarpal bone of“BB 2005” (c) were availablefor µCT analysis, giving insightinto the three-dimensionalarchitecture of these bones. Aradially oriented trabecular net-work in the subchondral area ofthe bone with intact caput andapparently closed growthplates can be observed inboth images

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Nürnberg, Germany). Here, approximate times of deathbetween 1,290 and 1,370 A.D. or between 1,380 and 1,440A.D. were estimated with a 95% probability (Haas-Gebhardand Pueschel 2009). The newly calculated age of “BB2007” slightly differs from the age initially estimated, but ithighlights the accuracy of the indirect method appliedpreviously which led to similar results. With a moredetailed estimation of the bog body’s age, further analysesof the bog body and the coffin’s wood should provide newand interesting data and might contribute to a betterunderstanding of life during the Middle Ages.

A previous study carried out by members of our groupdemonstrated that destruction-free osteological analysis ofskeletal elements is possible with the help of the methodsdescribed above (Schilling et al. 2007). This study reportedthat, despite numerous decades in the acidic environment ofthe peat bog, pQCT measurements still allowed to assesscBMD of most skeletal elements. With the help of thisquantitative method, we were able to determine thedominant upper extremity in all three bog bodies. Accord-

ing to the pQCT results, “BB 2005” presented with a higherBMD of her left radius in comparison to the right side. Theleft radius of “BB 2007” had a higher BMD whencompared to its opposite side. These findings led to theconclusion that both women used their left arm as theirdominant extremity and apparently must have been left-handed. For “BB 2005,” this conclusion was also supportedby a higher BMD of her lower right extremity (Schilling etal. 2007). This conclusion is supported by the findings ofGumustekin who demonstrated that, in men and women,cBMD is generally higher in the dominant arm and in thecontralateral leg (Gumustekin et al. 2004).

During the excavation of “BB 2009,” no radii werefound. Therefore, cBMD measurements of the upperextremity were performed on both humeri. A difference incBMD of 2.6% in favor of the right side was observed. Thisled to the conclusion that this bog body from the MiddleAges must have been right-handed.

When the BMD values described above were comparedto reference data from the literature of age-matchedindividuals, a strong demineralization of 78.2–92.7% wasobserved for the skeletal elements analyzed (Nikander et al.2006; Ward et al. 2005). The longer the bones remained inthe bog, the stronger the demineralization appeared to be.When discussing the wide range of estimated demineral-ization given above, it needs to be kept in mind that, at thetime of death, “BB 2007” was fully dressed and buried in awooden coffin. This obviously had a positive impact onpreservation since, at the time of discovery, all inner organsand most of the woman’s skin were intact. Even thoughthese are fortunate circumstances for researchers fromvarious fields, it makes meaningful comparisons with directdeposit in the bog difficult until studies of larger numbersof individuals, either buried in a coffin or directlydeposited, have been carried out. It was particularlydifficult to estimate a mean cBMD loss for “BB 2009”since no reference data can be found in the literature foradolescent humeri. The fact that both femora showedpathological changes both in BMD and morphologycontributed to this difficulty.

Macroscopically, a large lesion of the right distal tibia,measuring 2.5×0.5 cm, became apparent upon first look.Previous studies demonstrated that the extent to which thebog environment has effects on bone cannot always beidentified with absolute certainty (Lynnerup 2007, 2009).Artificial bone lesions due to diagenesis (softening of thebone due to loss of mineralization) might, therefore, appearas genuine lesions. During the analysis of “BB 2009,” wemicroscopically observed smooth borders at this lesion’sedge, excluding the possibility of an excavation artifactwhere sharp edges would be expected. Contact radiographywas performed, revealing signs of sclerosis at the defect’sedges (Fig. 5c). Since sclerosis indicates bone remodeling,

Fig. 4 Comparative analysis of cBMD in the upper extremity wasused to determine handedness. cBMD in the left and right upper arm(humerus) of “BB 2009” were analyzed and compared. A 2.6%greater cBMD was observed for the right arm, indicating right-handedness (a). For “BB 2007” (b) and “BB 2005” (c) (Schilling et al.2007), higher cBMD (“BB 2007”=9.1% and “BB 2005”=2.1%) wasobserved for the left radius in both cases, leading to the conclusion ofleft-handedness

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which only takes place during lifetime, this injury musthave an intravital origin. The incidence leading to theformation of this lesion remains unknown and should,therefore, be discussed. It can be assumed that an initialpenetrating trauma lead to the destruction of the corticalbone. This could have resulted in a painful and hinderingdefect of the right lower extremity. Another possibleexplanation could be an inflammatory process (e.g.,osteitis). Nevertheless, this seems unlikely since infectionswith such severity rarely affect children at this age and,especially during the Middle Ages, it would have beenhighly unusual for a child to survive this disease longenough to allow bone remodeling in the defect area(Jansson et al. 2009). A third possibility is a cartilaginousexostosis or osteochondroma. These benign tumors couldhave developed over an extended period of time and mighthave been lost from its origin during the centuries in thebog or during the process of excavation. This, however, weconsider to be unlikely as well since these juvenile tumorsvery rarely result in a severe and hindering disability of theaffected extremity (Erler et al. 2003; Chin et al. 2000).

The observation that the right lower extremity revealedan approximately 17.9% lower cBMD when compared tothe left side led us to the conclusion of a disabling defect ofthe lower right extremity. This lesion could have con-strained the child in its use of the lower right extremity,leading to an immobilization of the right leg and aconsecutive loss of cBMD. The result could have been animmobilization osteoporosis which we were able todocument using pQCT measurements. It can further bespeculated that, consecutively, the child might have appliedhigher load on the lower left extremity, leading to theobserved changes of the femoral head and a subsequentdeformity of the proximal femur. The changes observedhere resemble macroscopical and radiological changestypically found in Legg–Calve–Perthes disease (LCPD;Fig. 5h; Kemp and Boldero 1966). Recent studies demon-strated a correlation between mechanical stress on thefemoral head and the development of LCPD whichsupports our hypothesis (Kandzierski 2004; Kandzierskiet al. 2006; Mihara and Hirano 1998; Suehiro et al. 2005).This aseptic necrosis of the femoral head usually affects

Fig. 5 Skeletal analysis of “BB2009” reveals pathologicchanges of the right and leftlower extremity. Overviewimage of all bones discovered(a total of 48 bones) and madeavailable for osteological analy-sis (a). Gross image of the rightshinbone (tibia) with a highermagnification of the defect areameasuring 2.5×0.5 cm (b).Contact radiography of the rightdistal tibia revealing scleroticchanges in the defect area (c).pQCT analysis of the lowerextremity where a decreasedcBMD was observed in theright femoral bone (∆cBMD=11.2%; d) and the right fibula(∆cBMD=24.9%; e). Grossimage (f) and radiological image(g) of the left and right femoralbone showing excavation arti-facts and coxa vara deformityof the left femur with a patho-logical CCD angle of 123°(arrow). Gross image andcontact radiography of the leftand right femoral head showingmacroscopic and radiologicalchanges typical for LCPD of theleft femoral head (arrows, h)

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boys between 3 and 12 years of age. We, therefore,concluded that higher mechanical stress on the left femoralhead due to an immobilizing defect of the right lowerextremity might have lead to the development of LCPD.Additionally, we observed a deformation of the left femur(coxa vara) with pathological changes of the CCD angle of123° (Fig. 5g). Healthy age-matched individuals have beenreported to present with CCD angles of >130° (Glogowski1962). This deformity has been described as a typicaldeformity following LCPD (Kim and Wenger 1997). Eventhough the initial event leading to the accumulation of thepathological changes observed here remains unclear, itmight be the reason for the child’s deposition in the bog. Asdescribed by Van der Sanden (1996), in the time ofquestion, disabled and ill individuals often died violentdeaths in bogs. Since the child described here mostprobably suffered from severely disabling bone pathologies,it is possible that this condition contributed to its death,even though the exact cause of death remains unclear.

Taken together, this study presents the first comparativeanalysis of the skeletal state of three bog bodies and,therefore, highlights that, despite 800–2,700 years in theacidic environment of a peat bog, detailed analyses of theskeletal status of bog bodies from the Middle and Iron Agesare possible. µCT analysis showed intact three-dimensionaltrabecular structures in metacarpal and metatarsal bones andcBMD was assessed using high-resolution radiological andbone density measurement methods. This allowed determi-nation of handedness. For the first time, unique orthopedicdiseases such as LCPD and immobilization osteoporosiscould carefully be documented in a bog body from theMiddle Ages. These observations contribute to a betterunderstanding of life circumstances, social rituals, andcommon diseases in the Middle and Iron Ages whichmight be appreciated by scientists from various fields.

Acknowledgements We would like to express our gratitude to themuseums and their curators who provided the bog bodies for ourresearch. We would also like to thank S. Kappelhoff for her assistanceduring the radiological analysis of “BB 2009.”

Ethical standards The experiments performed in this study complywith current German laws.

Conflict of interest The authors declare that they have no conflict ofinterest.

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