Prolonged unilateral disuse osteopenia 14 years post external fixator removal: a case history and critical review.

Abstract

Disuse osteopenia is a complication of immobilisation, with reversal generally noted upon remobilisation. This case report focuses on a patient who was seen 18 years following a road traffic collision when multiple fractures were sustained. The patient had an external fixator fitted for a tibia and fibula fracture, which remained in situ for a period of 4 years. Following removal, the patient was mobilised but, still required a single crutch to aid walking. Fourteen years post removal of the fixator, the patient had a DXA scan which, demonstrated a T-score 2.5 SD lower on the affected hip. This places the patient at an increased risk of hip fracture on this side, which requires monitoring. There appear to be no current studies investigating prolonged disuse-osteopenia in patients following removal of long-term external fixators. Further research is required to quantify unilateral long-term effects to bone health and fracture risk in this population.

Full text

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Hindawi Publishing Corporation
Case Reports in Medicine
Volume 2010, Article ID 629020, 4 pages
doi:10.1155/2010/629020
Case Report
ProlongedUnilateral DisuseOsteopenia14 Years Post External
Fixator Removal: A Case History and CriticalReview
KarenM. Knapp,1AnnV.Rowlands,2JoanneR.Welsman,2andKennethM. MacLeod3
1College of Engineering, Mathematics and Physical Sciences, University of Exeter, Exeter, Devon EX4 4QL, UK
2School of Sport and Health Sciences, University of Exeter, EX1 2LU Devon, UK
3Peninsula Medical School, Peninsula College for Medicine and Dentistry, EX2 5AX Devon, UK
Correspondence should be addressed to Karen M. Knapp, k.m.knapp@exeter.ac.uk
Received 6 August 2009; Accepted 17 February 2010
Academic Editor: Thomas J. Zgonis
Copyright © 2010 Karen M. Knapp et al. This is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly
cited.
Disuse osteopenia is a complication of immobilisation, with reversal generally noted upon remobilisation. This case report focuses
on a patient who was seen 18 years following a road traffic collision when multiple fractures were sustained. The patient had
an external fixator fitted for a tibia and fibula fracture, which remained in situ for a period of 4 years. Following removal, the
patient was mobilised but, still required a single crutch to aid walking. Fourteen years post removal of the fixator, the patient had
a DXA scan which, demonstrated a T-score 2.5 SD lower on the affected hip. This places the patient at an increased risk of hip
fracture on this side, which requires monitoring. There appear to be no current studies investigating prolonged disuse-osteopenia
in patients following removal of long-term external fixators. Further research is required to quantify unilateral long-term effects
to bone health and fracture risk in this population.
1.Introduction
Disuse osteopenia or osteoporosis is a well-recognised
complication of immobilisation [1–4] and in the majority
of patients there is reversal of the disuse osteopenia upon
remobilisation [5]. However, stress fractures distal to the
acute fractures have been reported in a small minority of
patients post lower limb fracture upon mobilisation [6]. Low
trauma fractures have been reported in the lower-limb long-
bones of paraplegics [7, 8] and in nonambulatory children
with congenital conditions [9], demonstrating that disuse
osteopenia results in an increased fracture rate. However,
there appear to be no studies at present reporting the long-
term effects of prolonged immobilisation of patients placed
in external fixators following severe lower limb long-bone
fractures. This case report follows a patient who had a
dual energy X-ray absorptiometry (DXA) scan 14 years post
removal of her external fixator.
2. CasePresentation
Eighteen years prior to being seen (1989) the patient had
been involved in a major road traffic collision, when she sus-
tainedmultiplefracturesthroughouttheleftsideofherbody.
The patient was aged 19 years at the time of the accident.
The collision resulted in fractures of her left radius and ulna,
left femur and left tibia and fibula, with open reduction and
internal fixation being required for the radius and ulna and
femur fractures, with the femoral plate still remaining in-
situ. The fracture to the tibia and fibula was a particularly
severe compound fracture and an orthofix fixator (Orthofix,
TX, USA) was used initially for approximately six months
followedbyaSequoiaframe(ATS,Paris,France)externalfix-
atortoaidhealing.Suchcircularringfixatorscanbetolerated
forprolongedperiodswhencomparedtothreadeduniplanar
or multiplanar fixators and are therefore a viable option for
extended use [10]. The Sequoia ring fixator remained in situ
for an extended period of four years, to allow for sufficient
new bone growth to bridge the gap left by the fracture.
Mobilisation was intermittent during the 4 years over which
the patient wore the Sequoia frame external fixator and was
dependent upon the patient’s pain levels and her ability
to weight-bear. Weight-bearing commenced two days post
application of the Sequoia frame, with the assistance of
two walking sticks, which were changed to crutches since

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2Case Reports in Medicine
the patient found them too unsteady. Subsequent weight-
bearing was impeded intermittently as a result of pain due
to infected pin sites, frame adjustment and a corticotomy.
Day to day adjustment of the frame was undertaken by the
patient. A corticotomy was performed to allow the lower
leg to be compressed and new bone to form from the top
section of the tibia. A fibulectomy was also performed to
allow for free movement of the tibia within the frame, thus
allowing stimulation of bone growth to unite the fracture
site.Followingremovaloftheexternalfixator,thepatientwas
mobilised, although even now she uses the assistance of one
crutch when walking. The patient underwent extensive phys-
iotherapy, hyperbaric oxygen therapy and manual lymphatic
bandaging and massage post removal of the Sequoia frame.
Post rehabilitation, while there is no significant limb length
discrepancy, the patient suffers from a malunion deformity,
which is likely to result in the need for a stick or crutch.
The patient is however able to fully weight-bear on the
affected leg for short periods. During mobilisation, no insuf-
ficiency fractures were suffered by the patient. The patient,
now 37 years of age, has been without the external fixator
for 14 years and an osteoporosis risk factor questionnaire
indicated that she currently has none of the standard clinical
risk factors for osteoporosis. However, she did undergo
a hysterectomy for menorrhagia aged 35 and while still
premenopausal at the time of her visit, should premature
ovarian failure follow her hysterectomy, this is likely to have
a detrimental impact on her bones in the future. The patient
is otherwise fit and well, with no history of chronic disease.
3.ScansConducted andMethodology
A dual X-ray absorptiometry (DXA) scan (GE Lunar
Prodigy) was conducted of the patients lumbar spine (L1–
L4), bilateral proximal femora (Figure 1), and total body.
Manufacturers’ reference data were used for analysis of the
spine and total body results, whilst NHANES III reference
data were used for the proximal femora (Figure 2). The
results of these scans are shown in Table 1.
The difference in lean tissue was investigated for the left
andrightlegsusingthetotalbodyresults.Thesedemonstrate
similar lean tissue mass on both legs. Using a cohort of 37
normal control subjects, the agreement between the left and
right legs for BMD and lean tissue were calculated using
Bland-Altman analysis and a comparison made with this
case. The results of the Bland-Altman analysis are displayed
in Table 2, and demonstrate that this case falls within the
normal 95% limits for the difference in her lean tissue
mass between the left and right legs. However, the marked
reduction in BMD in her affected leg falls well outside the
expected 95% limits.
The hip remains anatomically normal and other reasons
for the marked osteopenia such as bone tumours have been
excluded.
4.Discussion
The disuse osteopenia in this patient is particularly marked.
This may be due to a number of factors. Firstly, the patient
Table 1: The results of the DXA scan are outlined below. Note the
2.5SDdifferencebetweentheleftandrighthipbasedontheT-score
difference (2.4 SD difference on the Z-score).
Site
Lumbar spine (L1–L4)
Left total hip
Right total hip
Total body
∗The Z-scores are weight adjusted.
BMD g/cm2
1.224
0.786
1.096
1.021
T-score
0.4
−1.8
0.7
1.0
Z-score∗
−0.8
−2.4
0.0
−0.6
Table 2: Bland-Altman agreement with 95% limits between the left
andrightlegsforBMDandleantissueinthecasereportsubjectand
the control population.
Subject
difference
Population
mean bias
95% Limits
BMD agreement
(g/cm2)
Lean tissue
agreement (g)
−0.317
−0.004
−0.065–0.057
−328.50
−73.41
−418.73–271.90
had an external fixator in situ for an extended period of four
years. Secondly, whilst the patient has been mobilised and
walks, a crutch is used for assistance, suggesting that the
affected leg is not fully weight-bearing at all times. Lastly,
the period of partial immobilisation was from age 19–23, an
important period for bone accrual and development of peak
bone mass [11].
There are few studies investigating disuse osteopenia in
single limbs. Tandon et al. [12] reported reduced disuse
osteopenia following external fixation of the tibia compared
to those placed in plaster of Paris, even though those
who underwent internal fixation had more severe fractures.
Marchetti et al. [13] reported disuse osteopenia following
shoulder surgery, which was partially reversed six weeks fol-
lowing remobilisation, whilst R¨ uegsegger et al. [14] reported
bone loss bilaterally post total hip replacement. One of the
most frequently studied groups suffering disuse osteoporosis
are astronauts following time spent in microgravity during
space missions. Lang [15] reported that up to 15% of bone
strength can be lost at the proximal femur over a flight of
6 months. Rapid and severe bone loss has been reported in
patients suffering stroke [16] and in volunteers on bed-rest
studies [17].
Studies of bed-rest volunteers and spinal cord injury
patients have consistently reported an increase in markers of
globalboneresorption[16]Ma¨ ımounetal.[18].However,in
most studies the markers of bone formation have remained
unchanged, suggesting that there is no decrease in bone
formation as a result of disuse osteopenia [17, 18]. Ma¨ ımoun
et al. studied the effects of disuse osteopenia on osteopro-
tegerin (OPG) and reported that OPG was stimulated in
spinal cord injury (SCI) patients, whilst nuclear factor κB
ligand (RANKL) was inhibited. These results led them to
hypothesise that OPG may provide a protective mechanism
in the body. Whilst the OPG was deemed to have a protective
role in this study, patients still lost bone and bone resorption

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Case Reports in Medicine3
Image not for diagnosisImage not for diagnosis
Figure1:LeftandrighthipdualenergyX-rayabsorptiometryscans
showing regions of interest used for analysis.
Reference: total
10090807060504030 20
Age (years)
0.38
0.50
0.63
0.76
0.88
1.01
1.13
1.26
1.39
1.51
BMD (g/cm2)
−5
−4
−3
−2
−1
0
1
2
3
4
YA T-score
Left
Right
Normal
Osteopenia
Osteoporosis
Figure 2: Plot of the BMD against NHANES III reference data
for the left and right hips, demonstrating the marked difference
between the two.
markers were elevated, suggesting that the stimulation of
OPG is insufficient to prevent osteoclastic proliferation
and bone resorption [18]. Studies of bed-rest volunteers
have also reported increased urinary and faecal excretion
of calcium coupled with increased serum calcium and
decreased intestinal calcium absorption. Increased serum
calcium results in low parathyroid hormone, a regulatory
response to the increased bone resorption, which results in a
decreased intestinal calcium absorption through the vitamin
D mediated pathway [17, 19–21].
Nutritional interventions have been reported to have a
small influence of addressing the negative calcium balance in
disuse osteopenia [22], and early remobilisation is the most
important factor for the prevention of disuse osteopenia
[7]. However, in patients where this is not possible, other
therapeutic interventions may be required. The bisphospho-
nate Tiludronate has been demonstrated to be an effective
treatment for disuse osteoporosis in paraplegic patients
[23], whilst aldendronate has been demonstrated to be well
tolerated and effective in non-ambulatory children [9]. In an
animal study, Ma et al. [24] reported increases in trabecular
bone in the tibiae of rats with continuously immobilised
hind legs treated with 1,38 human parathyroid hormone
(hPTH), suggesting this could be an effective treatment for
disuse osteopenia. It is possible that non-pharmacological
therapeutic interventions might improve disuse osteopenia
such as weight-bearing exercise, or vibrating plates, both of
which have been demonstrated to have positive effects on
bone density [25, 26].
In conclusion, the current research available on disuse
osteopenia, particularly long-term unilateral disuse osteope-
nia as seen in the patient discussed here is limited. Correct
diagnosis means this patient can be monitored and treated,
reducing her future fracture risk. Most research is focused
on SCI stroke patients, astronauts and bed-rest volunteers
and may not be directly comparable to the effects of immo-
bilisation of a single limb. Further research is required to
investigate long-term unilateral disuse osteopenia in a wider
population, including the fracture prevalence, and possible
therapeutic interventions to provide a reduction in their
long-term low trauma fracture risk. This is an important
consideration for all healthcare teams caring for patients
with long-term limb immobilisation or those with only
partial remobilisation. The long-term future fracture risk on
the affected side and appropriate therapeutic intervention
requires consideration.
Acknowledgments
The authors thank the patient for her time, assistance and
helpfulnessindraftingthiscasestudy.Theauthorswouldlike
to dedicate this paper to Dr. Kenneth MacLeod who sadly
passedawayin2009.Hewasaninspirationtoknowandwork
with.
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