Accepted Manuscript

Percutaneous dorsal instrumentation for thoracolumbar extension-distraction fracturesin patients with ankylosing spinal disorders: a case series

Antonio Krüger, MD Michael Frink, MD, PhD Ludwig Oberkircher, MD Bilal Farouk El-Zayat, MD Steffen Ruchholtz, MD, PhD Philipp Lechler, Trauma, MD

PII: S1529-9430(14)00405-7

DOI: 10.1016/j.spinee.2014.04.018

Reference: SPINEE 55869

To appear in: The Spine Journal

Received Date: 11 December 2013

Revised Date: 10 March 2014

Accepted Date: 16 April 2014

Please cite this article as: Krüger A, Frink M, Oberkircher L, El-Zayat BF, Ruchholtz S, Lechler P,Percutaneous dorsal instrumentation for thoracolumbar extension-distraction fractures in patients withankylosing spinal disorders: a case series, The Spine Journal (2014), doi: 10.1016/j.spinee.2014.04.018.

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ACCEPTED MANUSCRIPTPercutaneous dorsal instrumentation for thoracolumbar extension-distraction fractures in patients with ankylosing spinal disorders: a case series

Short title: Spinal fractures in ankylosing disorders

Antonio Krüger, M.D., Department of Trauma, Hand and Reconstructive Surgery, University of Giessen and Marburg, Marburg, Email: akrüger@med.uni-marburg.de

Michael Frink, M.D., Ph.D., Department of Trauma, Hand and Reconstructive Surgery, University of Giessen and Marburg, Marburg, Email: frink@med.uni-marburg.de

Ludwig Oberkircher, M.D., Department of Trauma, Hand and Reconstructive Surgery, University of Giessen and Marburg, Marburg, Email: oberkirc@med.uni-marburg.de

Bilal Farouk El-Zayat, M.D., Department of Orthopaedics and Rheumatology, University of Giessen and Marburg, Marburg , Email: elzayat@med.uni-marburg.de

Steffen Ruchholtz, M.D., Ph.D., Department of Trauma, Hand and Reconstructive Surgery, University of Giessen and Marburg, Marburg, Email: ruchholt@med.uni-marburg.de

Philipp Lechler, Trauma, M.D., Department of Trauma, Hand and Reconstructive Surgery, University of Giessen and Marburg, Marburg, Email: lechler@med.uni-marburg.de

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Abstract 1

Background Context: Thoracolumbar extension-distraction fractures are rare injuries mainly restricted to patients suffering from ankylosing spinal 2

disorders. The most appropriate surgical treatment of these unstable spinal injuries remains to be clarified. 3

Purpose: To report on a cohort of 10 patients treated with closed reduction and percutaneous dorsal instrumentation. 4

Study design: Case series. 5

Patient sample: 10 consecutive patients with ankylosing spinal disorders and thoracolumbar extension-distraction fractures (type B3 according to 6

the AOSpine Thoracolumbar Spine Injury Classification System). 7

Outcome measures: Postoperative reduction, alignment, and implant position were analyzed by computed tomography. Loss of reduction was 8

assessed on lateral radiographs by using the Cobb-technique. Ambulation ability and pain were assessed at follow-up. 9

Methods: Minimally invasive dorsal percutaneous instrumentation was performed in 10 consecutive patients (3 male, 7 female) with a mean age of 10

81.5 years (range, 72–90 years) between May 2010 and December 2012. The mean postoperative follow-up time was 7.9 months (range, 4–28 11

months). The study was performed without internal or external sources of funding. The authors declare no study-specific conflict of interest. 12

Results: All 10 patients were treated with closed reduction and dorsal instrumentation; in no case was conversion to an open approach required. The 13

mean operation time was 60.2 minutes (range, 32–135 min). None of the patients presented neurologic deficits. Cement-augmented screws were 14

implanted in two cases. Sufficient radiographic correction was achieved in all patients, no case of loss of reduction was noted at final follow-up. In 15

one case, complete hardware removal was performed 9 months following the index operation because of persistent back pain at the level of the 16

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implant. One patient died of postoperative inferior vena cava obstruction. At discharge, all patients were able to ambulate without the need for 1

crutches or opioid analgesics. At final follow-up, all patients ambulated with full weight bearing; four patients reported persistent back pain. 2

Conclusions: In fragile patients with ankylosing spinal disorders and thoracolumbar extension-distraction fractures, closed reduction and 3

percutaneous dorsal instrumentation provides a satisfying mid-term functional outcome while minimizing perioperative risks compared with 4

conventional dorsoventral procedures. 5

Keywords: 6

spinal fracture, ankylosing disorders, diffuse idiopathic skeletal hyperostosis, ankylosing spondylitis; 7

8

Background 9

Thoracolumbar extension-distraction fractures are rare and represent less than 3% of the injuries to the thoracolumbar region.1 The mechanism 10

leading to these lesions involves spinal hyperextension with or without the occurrence of anteroposterior translational movements.2 Of note, until 11

the introduction of the AOSpine Thoracolumbar Spine Injury Classification System in November 2013 there was no fracture classification systems 12

which did sufficiently account for this entity of spinal injuries3. For example, in the Denis classification, the description of distraction injuries is 13

confined to lesions of the posterior ligament complex and the middle column, which are classified as flexion-distraction type or seat-belt type 14

injuries.4 The vast majority of the reported cases of thoracolumbar extension-distraction fractures are seen in patients suffering from ankylosing 15

disorders, i.e. diffuse idiopathic skeletal hyperostosis (DISH) and ankylosing spondylitis (AS).5-9 In this population, even simple falls may lead to 16

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devastating spinal fractures and concomitant neurologic deficits. In view of the substantial fragility of patients with ankylosing spinal disorders, a 1

number of historic reports have advocated nonoperative treatment strategies.10,11 However, poor clinical outcomes resulting from the biomechanical 2

instability at the affected segment directed a change toward operative stabilization of these injuries.4,12,13 To date, open surgical reduction with either 3

posterior or anteroposterior fixation represents the standard treatment of these injuries.14-16 4

To the best of our knowledge, the present study is the first case series of patients with thoracolumbar extension-distraction fractures treated solely 5

by closed reduction with percutaneous dorsal instrumentation. 6

7

Methods 8

We analyzed the characteristics of 10 patients admitted to a Level I trauma center (university hospital) between May 2010 and December 2012 who 9

were diagnosed with a thoracolumbar extension-distraction fracture (type B3 according to the AOSpine Thoracolumbar Spine Injury Classification 10

System3) following blunt spinal trauma. The cohort comprised three men and seven women with a mean age of 81.5 years (range, 72–90 y). All 11

suffered from an ankylosing spinal disorder, either AS (n = 1) or DISH (n = 9). To measure preexisting comorbidities the Charlson comorbidity 12

index (CCI) and the age-adjusted Charlson comorbidity index (ACCI) were calculated.17 The dominating preceding trauma was a low-energy fall (n 13

= 8), while high-energy impacts (i.e., road traffic accidents) were noted in two cases. Prehospital treatment included immediate immobilization of 14

the cervical spine by applying a cervical collar (Stifneck; Laerdal Medical, Stavanger, Norway) and inline immobilization on a spine board (Laerdal 15

Medical, Stavanger, Norway). In the emergency department, all patients were assessed and treated according to the Advanced Trauma Life Support 16

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guidelines. For initial spinal imaging, plain X-ray films (anteroposterior and lateral views) and computed tomography (CT) scans were acquired in 1

all patients (Figure 1A and B). Spinal magnetic resonance imaging (MRI) was available in three patients prior to surgery. In all patients, closed 2

reduction and percutaneous dorsal instrumentation (Sextant II, Medtronic, Minneapolis, MN (n = 7); and Longitude, Medtronic (n = 3)) were 3

performed by spine surgeons with trauma experience under general analgesia (Figure 2A – C). 4

Patients were positioned prone. In contrast to compression fractures were ligamentotaxis is used, a pillow was positioned exactly below the injury to 5

allow a maximum of anterior bending. The reposition was monitored using lateral fluoroscopy. The operative approach resembles the method as 6

used for percutaneous vertebroplasty, thus four guide-wires are placed transpedicularely. After fluoroscopic control of the guidewires, the 7

cannulated screws are implanted by a Seldinger technique. The decision making process in the selection of the number of instrumented 8

segments/levels was governed by the goal to make the instrumentation as short as possible to preserve the unaffected motion segments. In contrast 9

to compression injuries of the spine, the instrumentation is only performed to prevent translation and rotation, while it does not have to protect the 10

anterior column against compressive forces. Furthermore, bone quality as intraoperatively assessed by the surgeon determined the number of 11

instrumented levels. 12

The absence of neurologic symptoms was mandatory for a percutaneous approach. Postoperatively, all patients were monitored in the intensive care 13

unit for at least 12 hours and neurologic function was assessed regularly. Patients were mobilized within 48 hours by physiotherapists without the 14

use of an orthosis. In all cases, postoperative spinal CT scans were obtained within 24 hours. To investigate the achieved operative correction, pre- 15

and postoperative radiographs in the lateral plane were analyzed by measuring the Cobb angle according to the consensus statement of the Spine 16

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Trauma Study Group.18 In short, the Cobb angle is formed between a line drawn parallel to the superior endplate of one vertebra above the fracture 1

and a line drawn parallel to the inferior endplate of the vertebra one level below the fracture.18 Furthermore, lateral radiographs at final follow up 2

were obtained to detect a loss of the correction. The average follow-up time was 7.9 months (range, 4–28 months). At follow-up, the ability to 3

ambulate and the persistence of any back pain were noted. 4

5

Results 6

In the present series, thoracolumbar extension-distraction fractures (type B3 according to the AOSpine Thoracolumbar Spine Injury Classification 7

System) affected 1.8 % (n = 10) of all patients suffering from spinal fractures admitted to our hospital (n = 562). Concomitant injuries occurred in 8

five patients (for a detailed clinicopathologic characterization of the cohort, see Table 1). The mean preoperative American Society of 9

Anesthesiologists physical status score was 3 (range, 2–4), the mean age-adjusted Charlson comorbidity index score was 6.6 (range, 0-9) (see Table 10

2). In eight patients, a vertebral distraction fracture occurred, and in two, bone disruption occurred (vertebral disc interface was verifiable). At the 11

time of admission, none of the patients exhibited neurological deficiencies. The mean operation time was 60.2 minutes (range, 32–135 min). Single-12

Level and Two-Level instrumentation was performed in three and six patients, respectively. Only one patient was treated by multi-Level (n=3) 13

instrumentation. Cement-augmented screws were applied in two cases (n = 8 screws, 22.2%). The mean length of the postoperative intensive care 14

unit stay was 2.4 days (range, 1–6 d), and the mean inpatient stay was 16.6 days (range, 8–22 d). The mean difference between pre- and 15

postoperative hemoglobin concentration was 1.2 g/dl (range, 0 – 2.3). There was no case of postoperative spinal malalignment or instability. No 16

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operation-associated complications occurred (i.e., wound healing complications, cerebrospinal fluid leakage, hardware breakage, etc.). No cases of 1

screw malpositioning or cement embolism were noted. The mean difference between the pre- and postoperative Cobb-angle was 4.9°, and there was 2

no relevant loss of correction as detected by the Cobb technique at final follow up (1.5°) (see Table 3). Postoperatively, none of the patients showed 3

any form of neurological deficit. One female patient developed inferior vena cava obstruction and liver failure caused by Budd-Chiari syndrome and 4

died of acute liver failure on the first postoperative day. Overall, perioperative complications occurred in three patients (two cases of respiratory 5

insufficiency and one case of myocardial infarction); none of these events were implant-associated. At discharge, all surviving patients (n = 9) were 6

able to ambulate without crutches or the need for opioid analgesics. In one patient, complete hardware removal was performed 9 months following 7

the index operation because of persistent post-traumatic back pain related to the implants. No further revisions were performed. At final follow-up, 8

all patients were able to ambulate with full weight bearing. Four patients complained of persistent back pain, and all patients reported daily intake of 9

nonopioid analgesics for musculoskeletal discomfort. However, all patients had already been taking analgesics prior to the trauma. 10

11

Discussion 12

With an incidence of 3% to 4%, hyperextension fractures are rare injuries that usually affect abnormally rigid spines, as seen in patients with AS 13

and DISH.1 Despite their rarity, thoracolumbar extension-distraction fractures in patients with ankylosing spinal disorders represent a relevant 14

clinical challenge to the spine surgeon because these injuries differ significantly from thoracolumbar spine fractures in otherwise healthy 15

individuals5,19-21 and the post-traumatic and perioperative risks in this population are significantly increased.22 During hyperextension of the 16

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thoracolumbar spine, the adjacent ankylosed segments function as long lever arms, leading to enhanced stress at the apex of the bent spine.4 As seen 1

in the present cohort, the resulting fractures typically affect all three spinal columns. The impact of tensile loading on the anterior segment results 2

either in vertebral distraction fractures or disruption of the bone-vertebral disc interface. The high percentage of distraction fractures of the vertebral 3

body in the current study is in contrast to the case series reported by Burkus and Denis, who reported no osseous fractures in the anterior and middle 4

column following thoracolumbar hyperextension injuries in a cohort of four patients.5 In the absence of osseous lesions of the vertebral body, the 5

roentgenologic detection of these injuries requires a high level of suspicion (see Figure 1A), while spinal MRI provides a significantly increased 6

diagnostic sensitivity.23,24 Most fracture classifications are based on the biomechanical concept proposed by Whitesides,25 who defined spinal 7

stability as follows: “A stable spine has to withstand anterior compression forces on the vertebral body and disc, tension and rotational forces of the 8

posterior elements to keep the body upright, to prevent kyphosis and to protect the spinal cord.” However, in hyperextension-distraction injuries, 9

this concept of the weight-bearing vertebral body is not fully applicable, and from a biomechanical perspective, these injuries resemble highly 10

instable fractures best compared with slice fractures as described by Holdsworth et al.26 While a number of historic case series have reported on 11

nonoperative therapeutic approaches for treatment of these injuries in patients without neurologic deficits,6 conservative treatment led to poor 12

outcomes with relevant spinal malalignment and persistent instability resulting in pain and neurologic impairment.5 Current biomechanical studies 13

have demonstrated incomplete immobilization of thoracolumbar two-column fractures by the use of orthoses.27,28 Consequently, most previous 14

authors performed either one- or two-staged open dorsoventral reduction and instrumentation. Weiss et al. reported on isolated ventral single-level 15

fusion for the treatment of a thoracolumbar extension fracture in an otherwise healthy individual.1 Despite the advantage of direct visualization of 16

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the injured ventral column, the considerable operative trauma in consideration of the pre-existing frailty in the ankylosed population might outweigh 1

this benefit. Even when performed by spine surgeons with trauma experience, the incidence of complications of the ventral or combined 2

dorsoventral approach reaches 19%29 and might be even higher in the fragile ankylosed population with a high amount of comorbidities. We believe 3

that injury to the vertebral body or vertebral-disc-body interface does not lead to ventral instability in terms of axial forces. In fact, the involved 4

spinal segment is most vulnerable to shear or translational forces. Importantly, isolated dorsal instrumentation has been shown to effectively prevent 5

translational and rotational movement while allowing compressive forces on the ventral section of the injured spinal segment.30 A potential benefit 6

of semirigid dorsal instrumentation could also be reduced stress shielding of the vertebral body. While some authors stress the importance of 7

extensive multisegmental instrumentation for unstable spinal fractures, the lowest possible number of spinal segments was stabilized in the present 8

series of hyperextension fractures in patients with ankylosing spinal disorders. 9

To the best of our knowledge, the role of percutaneous instrumentation for spinal fractures in patients with ankylosing disorders has not yet been 10

systematically analyzed. Clearly characterized advantages of percutaneous approaches for the treatment of spinal fractures are a shorter operation 11

time, smaller operative trauma to the soft tissues, and reduced intraoperative blood loss.31 While minimally invasive spinal surgery is known to 12

require a higher level of surgical skill, a number of previous studies showed no significant differences in implant positioning or spinal reduction 13

when compared with open procedures.32 Of note, spinal decompression with existing neurologic deficits or as prophylactic intervention has been 14

reported for the treatment of these injuries.33 We believe that neurologic abnormalities are a clear contraindication to closed percutaneous 15

instrumentation of these injuries. Due to the high prevalence of severe comorbidities and the increasing number of elderly patients receiving oral 16

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anticoagulants, there should be a high suspicion for the development of epidural hematoma in the population with ankylosing spinal disorders and 1

thoracolumbar extension-distraction fractures. However, in the present series, no pre- or postoperative neurologic deficits or computer-tomographic 2

signs for the development of an epidural hematoma were noted, and spinal decompression was therefore unnecessary. 3

Cement-augmented screws were used in two cases in the present report. The decision to perform augmentation was based on the intraoperative 4

assessment of the quality of screw fixation by the individual surgeon. Considering the reduced bone density in the patients suffering from these 5

injuries, the frequency of the use of cement-augmented implants might even increase in future series.34,35,36 6

In the present cohort, one female patient died of perioperative inferior vena cava obstruction and associated Budd-Chiari syndrome. Although the 7

patient had multiple risk factors for the development of thrombosis, even the extensive pre- and postmortem examinations did not reveal a specific 8

underlying mechanism. There are a number of case reports describing inferior vena cava syndrome following the application of bone cement during 9

vertebroplasty and kyphoplasty37,38 or caused by compression of the vena cava by a retroperitoneal hematoma following lumbar disc surgery.39 10

Interestingly, Hwang et al. reported a case of entrapment of the inferior vena cava between two lumbar vertebrae following spinal trauma.40 11

Meticulous investigation of the cause of death in the present series revealed no surgery-related complication, but underlined the high-risk profile of 12

patients suffering from ankylosing spinal disorders. 13

The major shortcomings of the present study are its retrospective nature and lack of a control group. Still, when compared with previously published 14

reports, our series comprised a relatively large number of patients who received homogenous therapeutic measures and were followed-up 15

postoperatively. 16

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1

Conclusions 2

Thoracolumbar extension-distraction fractures are rare and mainly confined to patients suffering from spinal ankylosing conditions. The present 3

study is the first case series to report the minimally invasive management of these injuries. Percutaneous dorsal instrumentation led to anatomic 4

realignment and provided strong fixation with good to excellent overall patient outcomes. In view of the accompanying fragility of patients 5

suffering from ankylosing spinal disorders, minimally invasive therapeutic approaches with short operation times should be considered and must be 6

weighed against the high rate of complications in dorsoventral approaches. 7

8

Authors’ Contributions 9

AK – data collection, analysis, interpretation, writing 10

MF – data interpretation and writing 11

LO – data interpretation and writing 12

BFE – data collection and analysis 13

SR – critical revision and writing 14

PL – data analysis, interpretation and writing 15

16

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Abbreviations 1

ACCI - age-adjusted Charlson comorbidity index 2

AS - ankylosing spondylitis 3

ASA - American Society of Anesthesiologists 4

ATLS - advanced trauma life support 5

CCI - Charlson comorbidity index 6

CT – computer tomography 7

d - days 8

DISH - diffuse idiopathic skeletal hyperostosis 9

h - hours 10

MRI - magnetic resonance imaging 11

SCI – spinal cord injury 12

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Figure Legends 1

Figure 1 2

(A) Preoperative lateral plain x-ray film in a patient suffering from AS shows a thoracolumbar extension-distraction fracture at the 10th 3

thoracic segment. 4

(B) The MRT scan (sagittal plane) in the same patient reveals the involvement of all three vertebral columns and of the body of the 11th 5

thoracic vertebrae. 6

Figure 2 7

(A) The instability of the fracture is visualized by intraoperative image intensifier. 8

(B) Intraoperative image shows anatomic alignment following closed reduction and 9

percutaneous dorsal instrumentation. 10

(C) Postoperative antero-posterior and 11

(D) lateral x-ray films. 12

13

TABLE LEGENDS: 14

Table 1 15

Clinical characteristics of 10 patients with thoracolumbar extension-distraction fractures treated with percutaneous dorsal instrumentation. 16

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MI - myocardial infarction, UTI - urinary tract infection, RI - respiratory insufficiency, ICU – intensive care unit, m – male, f - female; 1

Table 2 2

ASA physical status classification and comorbidity measures of patients with thoracolumbar extension-distraction fractures treated with 3

percutaneous dorsal instrumentation. 4

ACCI - age-adjusted Charlson comorbidity index, ASA - American Society of Anesthesiologists physical status classification system, CCI - 5

Charlson comorbidity index, ∆ Hb (g/dl) – difference between pre- and postoperative serum hemoglobin levels, m – male, f - female; 6

Table 3 7

Cobb angle measured according to the consensus statement of the Spine Trauma Study Group of 10 patients with thoracolumbar extension-8

distraction fractures treated with percutaneous dorsal instrumentation. 9

m – male, f – female, angles are given in degrees; 10

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er

Ag

e (

ye

ars

)

An

ky

losi

ng

dis

ord

er

En

erg

y o

f tr

au

ma

Lev

el

of

spin

al

fra

ctu

re

Nu

mb

er

of

inst

rum

en

ted

se

gm

en

ts

Nu

mb

er

of

au

gm

en

ted

scr

ew

s

Op

era

tio

n t

ime

(m

inu

tes)

Co

nco

mit

an

t in

juri

es

Re

vis

ion

/re

op

era

tio

n

Pe

rio

pe

rati

ve

ad

ve

rse

ev

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ts

Len

gth

of

ICU

sta

y (

da

ys)

Len

gth

of

ho

spit

al

sta

y (

da

ys)

1 f 76 DISH low T 12 2 0 50 none none none 1 16

2 f 90 DISH low T11 2 0 56 none none none 2 19

3 m 88 DISH low L3 2 0 32 none none MI 1 22

4 m 78 DISH high T12 2 0 57 pelvis, clavicle, face, chest none none 4 21

5 f 83 DISH low L1 1 0 59 forearm, knee none none 1 8

6 m 72 DISH high L2 1 0 44 chest hardware removal RI 6 17

7 f 76 DISH low L2 2 4 60 none none RI 2 17

8 f 89 DISH low L2 2 0 74 hip none Budd-Chiari-syndrom,death 3 n/a

9 f 78 AS low T10 1 0 35 pelvis none MI 3 17

10 f 85 DISH low T12 3 4 135 none none none 1 12

mean 81,5 1,8 60,2 2,4 16,6

Table 1

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Patient Gender Age ASA CCI ACCI ∆ Hb

(g/dl)

1 f 76 3 2 5 1,1

2 f 90 3 4 9 0,2

3 m 88 4 5 9 1,6

4 m 78 3 4 7 2,3

5 f 83 3 2 6 1,2

6 m 72 2 0 0 0,8

7 f 76 3 6 9 1,4

8 f 89 4 5 9 1,3

9 f 78 2 3 6 0

10 f 85 3 2 6 1,2

mean 81,5 3,0 3,3 6,6 1,1

Table 2

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ACCEPTED

ACCEPTED MANUSCRIPTPatient Gender Age

Lev

el

of

spin

al

fra

ctu

re

Co

bb

an

gle

pre

op

era

tiv

e

Co

bb

an

gle

po

sto

pe

rati

ve

Co

bb

an

gle

fin

al

FU

1 f 76 T 12 0,4 -2,9 -3,9

2 f 90 T11 4,0 -2,7 -3,9

3 m 88 L3 20,2 10,5 8,9

4 m 78 T12 -18,6 -24,3 -26,1

5 f 83 L1 11,3 4,3 3,9

6 m 72 L2 8,5 4,6 3,5

7 f 76 L2 8,2 -2,8 -2,6

8 f 89 L2 3,9 4,5 n.a.

9 f 78 T10 6,9 -0,5 -1,1

10 f 85 T12 4,5 -2,1 -2,0

mean 81,5 4,9 -1,1 -2,6

Table 3

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T

ACCEPTED

ACCEPTED MANUSCRIPT

MANUSCRIP

T

ACCEPTED

ACCEPTED MANUSCRIPT