SPECIAL ISSUE - ORIGINAL ARTICLE

Cranial translation of the humeral head on radiographs in rotatorcuff tear patients: the modified active abduction view

J. F. Henseler • P. B. de Witte • J. H. de Groot •

E. W. van Zwet • R. G. H. H. Nelissen •

J. Nagels

Received: 16 November 2012 / Accepted: 5 March 2013

� International Federation for Medical and Biological Engineering 2013

Abstract Cranial translation of the humeral head is rela-

ted to massive rotator cuff tears; however, it may be

unapparent in early-stage tears. The goal of this study was

to investigate whether active abduction leads to increased

active cranial humeral translation in early-stage tears. We

assessed 20 consecutive patients (9 full-thickness supra-

spinatus tears, 11 posterosuperior tears) using the newly

introduced modified active abduction view: acromiohu-

meral (AH) distance was measured on radiographs acquired

during rest and active isometric abduction and adduction

tasks with the arm alongside the body. Rest AH was 7.5 mm

(SD = 1.53); during abduction and adduction, it decreased

to 2.1 mm (95 % CI 1.28–3.01, p \ 0.001) and 1.1 mm

(95 % CI 0.46–1.65, p = 0.001), respectively. Cranial

translation during abduction was more severe in shoulders

with posterosuperior cuff tears (DAH = 3 mm, SD = 1.5)

compared to supraspinatus tears (DAH = 1 mm,

SD = 1.6), with a mean difference of 2 mm (95 % CI

0.64–3.58, p = 0.007). Both active isometric abduction

and adduction leads to active cranial translation in cuff tear

patients. Cranial translation is largest during active abduc-

tion. Furthermore, there is significant more cranial transla-

tion in posterosuperior cuff tear patients compared to

supraspinatus cuff tear patients. Possibly, radiographs

combined with active tasks offer new possibilities in diag-

nosing early-stage rotator cuff tears.

Keywords Rotator cuff � Shoulder pain � Radiography �Tear � Active abduction � Proximal migration

1 Introduction

Rotator cuff degeneration is responsible for a substantial

part of all shoulder complaints [14, 18]. It mainly affects a

population in the fifth to seventh decade of life, ranging

from subacromial impingement to full-thickness supraspi-

natus or posterosuperior (i.e., supraspinatus and infraspi-

natus) rotator cuff tears. Imaging studies demonstrated that

the prevalence of asymptomatic rotator cuff tears ranges up

to 54 % in the general population over 60 years-old [20].

Differentiation between symptomatic and asymptomatic

cuff rotator tears it difficult, even more since no causal

relation exists between shoulder symptoms and an observed

rotator cuff tear.

‘‘Fixed’’ proximal migration, which is synonymous to

passive cranial translation of the humeral head, with

respect to the glenoid leads to narrowing of the subacro-

mial space. It can be observed on standard radiographs and

is indicative for chronic massive rotator cuff tears [2, 10,

12, 13, 21, 27, 28]. Due to the lost supraspinatus and

infraspinatus function and degeneration of subacromial

tissues, the humeral head migrates cranially slowly over

time, sometimes even leading to actual contact between the

J. F. Henseler (&) � P. B. de Witte � R. G.

H. H. Nelissen � J. Nagels

Department of Orthopaedics, Leiden University Medical Center,

Postzone J11-R, Postbus 9600, 2300 RC Leiden,

The Netherlands

e-mail: j.f.henseler@lumc.nl

J. F. Henseler � P. B. de Witte � J. H. de Groot

Laboratory for Kinematics and Neuromechanics,

Leiden University Medical Center, Leiden, The Netherlands

J. H. de Groot

Department of Rehabilitation, Leiden University

Medical Center, Leiden, The Netherlands

E. W. van Zwet

Department of Medical Statistics and BioInformatics,

Leiden University Medical Center, Leiden, The Netherlands

123

Med Biol Eng Comput

DOI 10.1007/s11517-013-1057-2

humerus and the acromion. However, imminent cranial

translation may be unapparent in early-stage rotator cuff

tears [1]. It has been reported that active abduction, through

prime deltoid activation, can lead to increased ‘‘dynamic’’

cranial translation in rotator cuff tear patients, which is

especially pronounced in the case of infraspinatus weak-

ness. Bloom applied this phenomenon as a clinical tool: the

active abduction view (AAV) [1]. With this method, the

acromiohumeral distance is measured on radiographs

acquired with the subjects’ arm in 90� of active abduction

or, if not capable of keeping the arm at 90�, with maximal

abduction. The AAV might have potential as an easily

available and inexpensive measure to quantify rotator cuff

dysfunction and diagnose early-stage rotator cuff tears [1,

26]. However, differences in abduction position, rotation

and scapular position can lead to large projection and

magnification errors when comparing AAV measurements

within and between subjects [16, 19].

In this experimental study, we propose to modify the

AAV method with active isometric arm abduction, with the

subjects’ arms alongside the body, to measure active cra-

nial translations of the humeral head while eliminating

some of the methodological problems of the AAV. Our first

hypothesis was that active isometric abduction will result

in active cranial translation in symptomatic rotator cuff

patients, resulting in a smaller subacromial space during

isometric abduction as compared to a position in rest. In

contrast, isometric adduction will result in caudal transla-

tion, due to the caudally directed muscle lines of action of

the adductor muscles. Our second hypothesis was that

posterosuperior tear patients show more active cranial

translation compared to supraspinatus tear patients. We

further hypothesized that there is a strong positive relation

between active cranial translation of the humeral head and

shoulder pain.

2 Methods

In this experimental study, twenty consecutive patients

with a full-thickness supraspinatus or posterosuperior

rotator cuff tear were included by two experienced shoul-

der surgeons (JN and RN) at the outpatient clinic of the

Orthopaedic department at the Leiden University Medical

Center (LUMC) between April 2011 and February 2012.

Inclusion criteria were: shoulder symptoms C6 months,

aged [50 years, diffuse unilateral shoulder pain, pain at

night or incapable of lying on the shoulder and pain during

activities with arm abduction, elevation and/or internal

rotation (e.g., overhead activities). With clinical examina-

tion, patients had to have the following findings: a positive

Hawkins test, clinically observed scapulohumeral dyski-

nesia characterized by increased and/or decreased scapular

lateral rotations, a classic painful arc at abduction and a

positive empty can test. The diagnosis was confirmed with

magnetic resonance imaging with arthrography (MRA)

and/or ultrasound. All patients had a full-thickness tear of

the supraspinatus and 11 patients (55 %) also had a tear of

the infraspinatus (i.e., posterosuperior tear) (Table 1).

There were 11 (55 %) males and 9 (45 %) females and the

mean age was of the total group was 65 (SD = 9.8).

Patients were excluded if one or more of the following

criteria were found on the concerning shoulder: prior

shoulder dislocations or positive apprehension test or sul-

cus sign (shoulder instability), previous surgery, subscap-

ularis tendon tear, osseous pathology, history of fracture,

osteoarthritis or rheumatoid arthritis of the glenohumeral or

acromioclavicular joint, capsulitis adhesiva (frozen shoul-

der syndrome), or a subacromial injection with anesthetics

and/or corticosteroids \6 weeks before intake. Further-

more, patients were excluded in case of cervical radicu-

lopathy, neuromuscular pathologies, or insufficient Dutch

language skills.

49 patients were considered for inclusion. Ten patients

declined informed consent and nineteen patients did not

fulfill the eligibility criteria: seven had a full-thickness

subscapularis tear, four patients had previous shoulder

surgery, four patients had a symptomatic acromioclavicular

osteoartritis, two patients had rheumatoid arthritis, one

Table 1 Patient characteristics

Supraspinatus

tear (n = 9)

Posterosuperior

tear (n = 11)

Total group

(n = 20)

Mean age (SD) 65 (9.5) 65 (10) 65 (9.8)

Sex, n (%)

Male 2 (22) 9 (82) 11 (55)

Female 7 (78) 2 (18) 9 (45)

Dominant arm affected, n (%)

Yes 5 (55) 7 (64) 18 (90)

No 4 (44) 4 (36) 2 (10)

Duration of symptoms, mo

Median (range) 36 (9–300) 24 (6–300) 30 (6–300)

CS (SD) 62 (17) 63 (15) 62 (15)

IPQ (SD) 47 (15) 41 (12) 44 (13)

WORC (SD) 58 (21) 57 (24) 57 (22)

Abduction

strength, N (SD)

90 (39) 73 (41) 81 (40)

Pain, VAS (SD)

VAS in rest 3.1 (2.3) 3.9 (2.8) 3.5 (2.5)

VAS during ADL 4.5 (3.4) 4.0 (2.3) 4.2 (2.7)

SD standard deviation, n number, mo months, CS constant score, IPQillness perception questionnaire, WORC Western Ontario Rotator

Cuff index, N Newton, VAS visual analog scale, ADL activities of

daily living

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123

patient had Parkinson’s disease and one patient had prior

shoulder dislocations.

The institutional review board approved all stages of the

study. All subjects received oral and written information

about the study and signed informed consent. A sample

size of 20 participants was estimated with a power of 90 %

and two times the maximum previously reported SD of

1.14 mm for the acromiohumeral distance applied as the

standardized difference [16].

Prior to the radiograph series, a maximum voluntary

force (MVF) was measured for abduction and adduction.

For each subject, a series of three radiographs was acquired

to compare the position of the humeral head with respect to

the scapula in a subsequent order at rest and during iso-

metric abduction and adduction, respectively at 60 ±

3.75 % of the lowest absolute value of abduction and

adduction MVF. The target force for the abduction and

adduction tasks (Fmax) was equal in both directions. The

subjects performed at least one full practice trial before

imaging. Before these dynamic radiographs were made, the

constant score (CS), Western Ontario Rotator Cuff index

(WORC) and illness perception questionnaire (IPQ) were

acquired. VAS scores for pain at rest and during daily

activities in the last 2 weeks were obtained using a 10 cm

line, with 0 cm indicating no pain and 10 cm indicating

severe incapacitating pain. In addition, after each radio-

graph and task, a similar VAS score for shoulder pain was

recorded.

2.1 Radiography

For the modified active abduction view (MAAV), subjects

were positioned for true anteroposterior (AP) shoulder

radiographs (Fig. 1): the upper body was turned 30� from

the frontal plane toward the Rontgen focus beam, with the

affected arm in external rotation alongside the subjects’

body and the hand in the frontal plane with the palm facing

forward. The arm was attached to a 1-dimensional force

transducer at the wrist using a circular brace to prevent

movement in the shoulder [5]. First, a radiograph was

acquired in rest position, with a film focus distance of

roughly 120 cm and a 15� craniocaudal tilt with respect to

the patient, to project the caudal surface of the acromion

perpendicular to the X-ray, creating a true anterior-pos-

terior radiograph of 90� perpendicular with respect to the

glenohumeral joint. Next, subjects were asked to deliver a

MVF against the force transducer in adduction and

abduction, respectively. Next, patients performed a 2-s

isometric equal abduction and adduction task, during which

additional shoulder radiographs were obtained.

Radiograph quality was controlled by the coordinating

investigator (JF) during each session using the following

criteria: (1) visible projection of the scapular spine with at

least 2/3 of the scapula on the image [16]; (2) The base of

the coracoid visible just above the scapular spine, opposite

of the glenoid rim [16]; (3) Overlap of the humeral head

with the glenoid in the form of an ellipse, with the anterior

margin of the glenoid projecting cranial to the humeral

head and posterior through the humeral head [7]; (4) The

greater tuberosity is seen in profile [7]; (5) Clearly defined

AH space, bordered cranially by the acromion and distally

by the humeral head. Any images not fulfilling these cri-

teria were re-acquired.

There is no ‘‘golden standard’’ for subacromial space

measurements and a wide variety of cranial translation

measurements have been described. Therefore, we used

three reported measuring methods for the subacromial

space (Fig. 2a): (1) The acromiohumeral distance (AH) is

the distance between the most cranial articular cortex of the

Fig. 1 Experimental setup for the modified active abduction view

(MAAV). Subjects were positioned for true anteroposterior shoulder

radiographs: the upper body was turned 30� from the frontal plane

toward the Rontgen focus beam (R) with the arm in external rotation

alongside the subjects’ body (dotted arrow). The arm was attached to

a 1-dimensional force transducer sensor (S) at the wrist using a brace

to prevent movement in the shoulder and to enable isometric

abduction (FAB) and adduction (FAD) tasks in the frontal plane.

Radiographs were acquired with a film focus distance of roughly

120 cm and a 15� craniocaudal tilt

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humeral head and the caudal cortex marking of the caudal

surface of the acromion [9, 13, 29]. (2) The upper migra-

tion index (UMI) is the quotient of the distance from the

center of the humeral head to the caudal cortex of the

acromion and the radius of the humeral head [10, 27, 28].

(3) The scapular spine-humeral head center method (SHC)

is defined as the perpendicular distance between a line

running through the linear part of the supraspinatus fossa

floor and the geometric center of the humeral head [16].

The AH method is still the most commonly used cranial

translation measurement, although it is prone to projection

and magnification errors [16]. The magnification error of

AP shoulder radiographs is reduced when using the upper

migration index, making direct intra- and intersubject

comparisons of the measurements during different tasks

more reliable [16, 27]. The SHC method is reported least

sensitive to projection errors because the scapular spine lies

roughly in the same coronal and axial planes as the center

of the humeral head [16]. The SHC method has not been

validated in vivo, but is reported to be least susceptible to

changes to the anatomic measurement landmarks in an

in vitro study [16]. All subacromial space measurements

were reported in mm, except for the upper migration index,

which is a relative measure. Humeral head translation

during active abduction and adduction translations were

measured with respect to the position at rest, thus mea-

suring active cranialization or active caudalization. These

relative translations were expressed as DAH, DUMI, and

DSHC. One observer (JF) conducted all of the subacromial

space measurements, blinded for the specific task. When

the necessary anatomic landmarks could not be identified,

the measurement was not performed and was reported as

missing.

2.2 Statistical analyses

The mean differences in subacromial space, expressed in

AH, UMI, and SHC, between rest and isometric abduction

and adduction radiographs were assessed by means of

paired students’ t tests to determine active cranial transla-

tion. The independent students’ t test was used for subgroup

analyses, comparing the differences in active cranial

translation (DAH, DUMI and DSHC) between rest and

abduction in patients with superior and posterosuperior

rotator cuff tears. The relation between AH and VAS pain

(dependant variable) was assessed using linear mixed model

analyses, accounting for the performed task (abduction,

adduction, and rest). The linear mixed model included a

random effect for repeated measures in each subject.

p values of B0.05 (two-sided) were considered statisti-

cally significant. Statistical analysis was done using PASW

statistics 17 (IBM Inc., USA).

3 Results

The results of the subacromial space measurements during

the rest, abduction, and adduction tasks are presented in

Table 2. In one instance, the scapular spine could not be

unambiguously ascertained and this measurement was

excluded from further analyses. On average, there was

significant active cranial translation of the humeral head

during both active abduction and adduction compared to

rest. In rest, the mean AH was 7.5 mm (SD = 1.53), and,

during active isometric abduction, it decreased to 5.4 mm

(SD = 2.60), resulting in a mean AH difference of 2.1 mm

(95 % CI [1.28, 3.01], p \ 0.001). During active isometric

adduction the AH decreased to 6.4 mm (SD = 2.30),

resulting in a mean difference of 1.1 mm (95 % CI [0.46,

1.65], p = 0.001) compared to rest. Similar results were

observed for the UMI and SHC measurements (Table 2).

Fig. 2 a Subacromial space measuring methods example of suba-

cromial space measurement techniques used during a rest task. AHacromiohumeral distance method; UMI upper migration index; SHCscapular spine-humeral head center method; Cor base of the coracoid;

R radius of the humeral head; C center of the humeral head; », parallel

lines; :, right 90� angle. b Example of subacromial space measure-

ment techniques used during active isometric abduction, demonstrat-

ing active cranial translation compared to the rest measurements (a).

AH acromiohumeral distance method, UMI upper migration index;

SHC scapular spine-humeral head center method; Cor base of the

coracoid; R radius of the humeral head; C center of the humeral head;

», parallel lines; :, Right 90� angle

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In patients with a posterosuperior rotator cuff tear, there

was significantly more cranial translation during abduction

(DAH = 3.1 mm, SD = 1.53) in comparison with cranial

translation for supraspinatus rotator cuff tear patients

(DAH = 1.0 mm, SD = 1.59), leading to a mean DAH

difference of 2.1 mm (95 % CI [0.64, 3.58], p = 0.007)

between groups (Table 3).

Mean VAS score for shoulder pain at rest was 1.6 cm

(SD = 2.36). VAS pain increased to a mean of 5.6 cm

(SD = 2.65) for active isometric abduction tasks, giving a

mean difference of 4.0 cm (95 % CI 2.49–5.45, p \ 0.001)

compared to rest. For active isometric adduction tasks, the

mean VAS pain increased to 4.1 cm (SD = 2.68), com-

pared to rest, giving a mean difference of 2.5 (95 % CI

[1.15, 3.68], p = 0.001).

In mixed model analyses, accounting for task and AH,

abduction tasks coincided with increased VAS pain (effect:

3.4 cm, 95 % CI [1.97, 4.91], p \ 0.001) compared to rest.

Adduction tasks also coincided with more pain (effect:

2.1 cm, 95 % CI [0.85, 3.46], p = 0.002). An increase in

VAS pain of 1 cm coincided with an effect of -2.4 mm on

the AH, indicating more cranial translation is associated

with more pain. However, this effect was not statistically

significant (95 % CI [-6.17, 1.25], p = 0.19).

4 Discussion

The modified active abduction view (MAAV) of the

shoulder is the first radiographic method evaluating cranial

translation of the humeral head as an indicator of rotator

cuff tears in a standardized fashion. In this study, all three

applied radiographic subacromial space measurement

methods showed cranial translation of the humeral head

during isometric abduction tasks compared to a position of

the humeral head at rest. There was significant more cranial

translation in posterosuperior tear patients compared to

supraspinatus tear patients.

Table 2 Subacromial space measurements in rest, during active abduction and adduction

Measurement Task Mean (SD) Mean difference (SD) 95 % CI p value

AH (mm) Rest 7.5 (1.53)

Abduction 5.4 (2.60) 2.1 (1.86) 1.28–3.01 \0.001

Adduction 6.4 (2.30) 1.1 (1.27) 0.46–1.65 0.001

UMI Rest 1.27 (0.06)

Abduction 1.20 (0.09) 0.07 (0.07) 0.04–0.11 \0.001

Adduction 1.23 (0.09) 0.03 (0.05) 0.02–0.06 0.003

SHC (mm) Rest 3.7 (7.28)

Abduction 6.2 (8.40) 2.5 (3.07) 1.06–3.93 0.002

Adduction 5.7 (7.42) 2.0 (2.36) 0.84–3.05 0.002

r (mm) Rest 28.1 (3.13)

Abduction 28.0 (3.18) 0.1 (0.79) -0.26 to 0.48 0.556

Adduction 28.2 (3.09) 0.1 (1.07) -0.55 to 0.46 0.853

Paired t tests were used to identify the differences in subacromial space between rest and abduction and rest and adduction, respectively. The

subacromial space measurements were reported in mm, except for the upper migration index, which is a relative measure. All applied methods

showed similar results: significant active cranial translation during active tasks, predominantly during active abduction

AH acromiohumeral distance method, UMI upper migration index, SHC scapular spine-humeral head center method, mm millimeter, SD standard

deviation, 95 % CI 95 % confidence interval

Table 3 Difference in cranial translation during abduction between supraspinatus cuff tears and posterosuperior cuff tears

Measurement Mean difference supraspinatus (SD) Mean difference posterosuperior (SD) 95 % CI difference p value

AH 1.0 (1.59) 3.1 (1.53) 0.64–3.58 0.007

UMI 0.04 (0.05) 0.11 (0.05) 0.01–0.11 0.021

SHC 0.7 (2.58) 4.0 (2.70) 0.77–5.77 0.013

Unpaired student’s t tests were applied to compare difference in humeral head translations in rest and during abduction between supraspinatus

and posterosuperior cuff tears

AH acromiohumeral distance method, UMI upper migration index, SHC scapular spine-humeral head center method, SD standard deviation,

95 % CI 95 % confidence interval

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Cranial translation of the humeral head during active

abduction has been reported in earlier studies. Both Deu-

tsch et al. [6] and Bloom [1] found significant cranial

translation on AP radiographs at different elevation angles

during active abduction in patients with rotator cuff

pathology. Graichen et al. [8] found similar results at dif-

ferent abduction angles using open MRI to measure the

subacromial space during active arm abduction tasks. We

found a similar magnitude of humeral head translations

compared to studies measuring translation in elevated arm

positions using radiographs, ultrasound, and open MRI [1,

6, 8]. However, these measurements are not directly

comparable with the current series, as we specifically did

not assess cranial translation at different abduction angles,

but with shoulder radiographs in a standardized arm posi-

tion during simultaneous isometric force tasks. Further-

more, we used regular radiographs in a standardized setup.

The current study is the first to measure active cranial

translation of the humeral head in full-thickness rotator

cuff tear patients in similar arm positioning during active

isometric tasks.

Active cranial translation of the humeral head is con-

sidered to be elicited by activity of the deltoid [8, 15]. In

rotator cuff tear patients, there is increased deltoid activity,

as the deltoid compensates for lost rotator cuff abduction

moment, while generating a destabilizing cranial force [23,

24]. The combination of the increased superiorly directed

forces of the deltoid during abduction and the impaired

stabilizing function of the torn rotator cuff lead to exces-

sive cranial translation and thereby narrowing of the sub-

acromial space [8, 22–24]. Surprisingly, we also found

cranial translation during isometric adduction tasks, albeit

to a lesser extent. In biomechanical and electromyograph-

ical studies, adductor co-activation has been reported in

rotator cuff tear patients during abduction tasks [22, 25]. In

theory, adductor activation leads to caudally directed for-

ces on the humerus [22, 25]. Obviously, the cranially

directed forces of the deltoid on the humerus exceed the

caudally directed forces during both abduction and

adduction, respectively. In the absence of supraspinatus

and infraspinatus force, the only remaining muscles for

glenohumeral stabilization are the deltoid and potentially

the superior part of the subscapularis [15, 23].

We found significantly more cranial translation in

patients with a posterosuperior rotator cuff tear than in the

supraspinatus tear group on radiographs acquired during

isometric active abduction (modified AAV). The present

findings support the idea that the infraspinatus plays an

important role in the mechanical force and torque balance

centering the humeral head onto the glenoid [11]. Loss of

infraspinatus abduction torque requires additional deltoid

forces resulting in a nett increase of the cranial force

component and subsequent additional cranial translation

[22]. In the only non-designer AAV study, Umans et al.

[26] were unable to detect any differences in the subacro-

mial space during active abduction compared to rest in

partial and full-thickness supraspinatus rotator cuff tear

patients. However, they did not use isometric abduction

tasks and did not include posterosuperior tear patients,

where both the supraspinatus and infraspinatus functions

are impaired.

We did not find a strong relation between increased

active cranial translation and shoulder pain. Our results

suggest that, if present, mechanical osseous impingement

due to narrowing of the subacromial space seems only for a

minor part responsible for reported pain in rotator cuff tear

patients. Our results are consistent with previous studies

[11, 17, 23]. Individual pain perception is subjective and is

considered difficult to measure directly. Tolerance to pain

varies considerably among patients and may affect the

relation between cranial translation and shoulder pain, so

the interpretations of the current results must be drawn with

caution. However, these measurements are repeated after

each task and tolerance to pain is considered intraobserver

reliable [4]. The underlying causes of symptomatic rotator

cuff tears have traditionally been identified as either

intrinsic degeneration of the rotator cuff, altering the nor-

mal biomechanics of the glenohumeral joint or extrinsic

mechanisms impinging the rotator cuff under the coraco-

acromial arch, e.g., cranial translation of the humeral head

and acromion shape. Although Neer’s [17] theory is widely

accepted and focuses on the extrinsic mechanism, we found

only a minor effect of osseous impingement. The spectrum

of causality of symptoms in rotator cuff tears as both partly

intrinsic and partly extrinsic possibly explains the great

clinical variability observed in these patients.

In previous studies, differences in abduction position,

arm rotation and glenohumeral configuration could have

lead to large projection and magnification errors with over-

estimation of the observed effect [16, 19]. This makes it

difficult to compare cranial translations of the humeral head

within and between subjects with previously reported

methods. With the proposed modified AAV, the abduction

position and glenohumeral configuration is kept constant.

The experimental setup was easy to use for both rest and

active abduction radiographs. However, although this pro-

vided a uniform method for MAAV radiographs, we still

observed a great intra- and inter-individual variation in

projection of the acromion and scapular spine between the

radiographs, resulting in relative large dispersions of the

SHC measurements [16]. However, there were no clear

systematic differences between rest, abduction and adduc-

tion tasks. Furthermore, our observations fall between -10�and ?10� spinal tilt, which were previously estimated with

3D scapular position measurements in 0� abduction [3]. The

three measuring methods for cranial translation supported

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123

each other, displaying similar results. Each measurement

has its own advantages and shortcomings [16]. More

research is needed to assess which radiographic measure-

ment method is most reliable and responsive for active

cranial translation.

There are several issues concerning the collection and

interpretation of the data. First, we are unable to ascertain

whether the observed effect is group specific as we did not

measure e.g., healthy individuals or asymptomatic rotator

cuff tear patients. However, earlier reports indicate that the

caudal translations of the humeral head in healthy indi-

viduals are less than 1 mm during arm abduction from 0� to

120� [6]. Second, it might be difficult to differentiate

between symptomatic and asymptomatic cuff rotator tears.

It is possible that some patients in our study had shoulder

symptoms which were not derived from the diagnosed cuff

tear. However, inclusion was performed by two experi-

enced orthopedic shoulder surgeons, using extensive

imaging techniques and strict eligibility criteria based on

current knowledge to have as homogeneous a study group

as possible. Lastly, systematic measurement errors are

common for shoulder radiographs. Patient positioning

might greatly influence the projection of the glenoid and

subacromial space on an AP radiographs. When using this

experimental setup, care must be taken to keep patient

positioning constant. All cranial translation measurements

were performed by one observer and we did not control for

intraobserver variance. However, earlier reports state that

the applied measurements on AP radiographs are highly

reproducible within and between investigators [16, 27].

In conclusion, active isometric abduction leads to active

cranial translation of the humeral head in symptomatic

rotator cuff tear patients using the MAAV method for

radiographs. The MAAV can be used to quantify cranial

translation of the humeral head in rotator cuff tear patients.

More research is needed to determine if the MAAV can

differentiate between healthy subjects, asymptomatic and

symptomatic cuff tear patients. Possibly, combining

radiographs with active tasks offers new possibilities in

diagnosing and detecting massive rotator cuff tears

functionally.

Acknowledgments We gratefully acknowledge the work of H.

Fraterman for building the experimental setup. The institution of the

authors has received funding from Dutch Arthritis Association (grant

number 09-1-303).

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