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Received: 25 January 2000Revision requested: 22 May 2000Revision received: 15 September 2000

Accepted: 4 January 2001

Abstract Objective. To report theimaging findings in nine patientswho developed pelvic instability af-

ter bone graft harvest from the poste-rior aspect of the iliac crest.

Design and patients. A retrospectivestudy was performed of the imagingstudies of nine patients who devel-oped pelvic pain after autologousbone graft was harvested from theposterior aspect of the ilium for spi-nal arthrodesis. Plain films, bonescans, and CT and MR examinationsof the pelvis were reviewed. Perti-nent aspects of the clinical history ofthese patients were noted, including

age, gender and clinical symptoms.Results. The age of the patientsranged from 52 to 77 years (average69 years) and all were women. Thebone graft had been derived from theposterior aspect of the iliac crestabout the sacroiliac joint. All pa-tients subsequently developed sub-

luxation of the pubic symphysis.Eight patients had additional insuffi-ciency fractures of the iliac crest ad-

jacent to the bone graft donor site,and five patients also revealed sub-luxation of the sacroiliac joint. Twohad insufficiency fractures of thesacrum and one had an additionalfracture of the pubic ramus.Conclusions. Pelvic instability is apotential complication of bone graftharvesting from the posterior aspectof the iliac crest. The pelvic instabil-ity is manifested by insufficiencyfractures of the ilium and sublux-ation of the sacroiliac joints and pu-

bic symphysis.

Keywords Pelvis Lumbar spine Fusion Insufficiency Fracture

Skeletal Radiol (2001) 30:278281 Int Skeletal Soc (ISS) 2001 A R T I C L E

Karence ChanDonald ResnickMini PathriaJon Jacobson

Pelvic instability after bone graft harvesting

from posterior iliac crest:

report of nine patients

Introduction

The posterior portion of the ilium is a common harvest

site for autologous bone graft used for various surgicalapplications such as spinal arthrodesis and reconstructivesurgery [1]. This site is popular because of its large quan-tity of cancellous or corticocancellous bone [2]. However,there are a few complications that have been associatedwith such harvesting, including infection, hematoma,neurologic and vascular injury, acute fracture at the har-vest site, and muscle or bowel herniation through this site[3]. Some of these complications are readily recognizedand are treated accordingly, but others are overlooked [4].

In 1972, Coventry and Tapper reported six cases of pel-vic instability after bone graft had been harvested from theiliac bone [5]. Since then, this complication of harvesting

has not been addressed and is unknown to many physicians.When this instability develops, patients symptoms very of-ten are nonspecific and can be indistinguishable from thoseof many spinal disorders [5]. Therefore, vague lower backpain, resulting from pelvic instability, is often attributed to apre-existing back problem, and is not recognized or treated.

In this study, we report nine patients with such a com-plication, i.e., pelvic instability after harvesting of bonefrom the posterior aspect of the iliac crest, causing per-sistent disability after lumbar or lumbosacral fusion.

Supported by VA Grant number SA-360

K. Chan M. Pathria J. JacobsonDepartment of Radiology,School of Medicine, University of California,San Diego Medical Center, San Diego,CA 92103-1990, USA

D. Resnick ()Department of Radiology (114),Veterans Affairs Medical Center,San Diego, CA 92161, USA

Present addresses:K. Chan, Department of Radiology,One Hoag Drive, Newport Beach,CA 92663, USA

J. Jacobson, Department of Radiology,University of Michigan Medical Center,Taubman Center 9210 G,1500 East Medical Center Drive,Ann Arbor, Michigan 48109-0326, USA

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Materials and methods

We retrospectively reviewed the imaging studies in nine patientsseen during a 2-year period who developed pelvic pain after autol-ogous bone graft had been harvested from the posterior aspect ofthe ilium for spinal fusion. Conventional radiographs of the pelviswere evaluated. Patients with subluxation of the pubic symphysis

or sacroiliac joints, or both, and/or sclerosis of the ilium were se-lected. Pertinent clinical histories, information regarding the typeof surgery that had been performed, the site of bone graft, and theinterval from the times of surgery to the first radiographic exami-nation demonstrating pelvic instability were studied. Availablebone scans and CT and MR imaging studies were also reviewed.

MR imaging was obtained on Signa 1.5-T superconductingunit magnet (General Electric Medical Systems, Milwaukee,Wis.). The following pulse sequences were used: sagittal T1-weighted (TR/TE, 550/160) and T2-weighted (TR/TE, 3900/96)with field of view 2727, slice thickness 4 mm and 4 NEX; andaxial proton density (TR/TE, 3150/17) and T2-weighted (TR/TE,3150/102) with field of view 2020, slice thickness 6 mm and 2NEX. T1-weighted (TR/TE, 550/16) images obtained with fat sat-uration following intravenous administration of a gadolinium-con-taining compound were also available in one patient; the matrix

was 256192. CT scanning (General Electric, High Speed Advan-tage, Milwaukee, Wis.) was performed with contiguous axial sec-tion of 5 mm thickness through the pelvis.

Results

All patients were women. Their age range was 52 to 77years (average 69 years). None of the patients had bonedensitometry performed prior to the surgery and none ofthe patients had metabolic or metastatic bone disorder.All had bone graft removed from the ilium for lumbarspine fusion, a procedure that was performed by several

different spine surgeons. Five patients had graft takenfrom the posterior aspect of the right ilium, three fromthe left, and one from both sites. Three patients under-went repeated bone graft harvesting from the same site.After surgery, all developed vague pelvic pain, whichwas different from the type of back pain they had experi-enced prior to surgery. Six patients developed pain with-in months of the surgery. Information regarding the tem-poral relationship of the pain and the time of surgery wasincomplete in the other three patients (Table 1).

Soon after the onset of pelvic pain, conventional ra-diographs were obtained as summarized in Table 1. Allpatients developed incongruity at the pubic symphysis(Fig. 1). Eight patients also had an additional fracture ofthe ilium at the site of harvesting (Fig. 2), and two had apositive bone scan (Fig. 3) at these sites as well as ab-

normal radionuclide accumulation in the sacroiliac jointsand pubic symphysis. Five patients had subluxation ofone or both sacroiliac joints. One patient had sclerosis ofboth iliac crests but no further study was obtained.Moreover, two patients had additional fractures of thesacrum, and one had a fracture of the pubic rami.

One patient had additional CT and MR studies (Fig.4). Both studies demonstrated a fracture of the ilium atthe harvest site. Both sacroiliac joints were widened andsubluxed. Fracture fragments were noted around the sac-roiliac joints. MR images showed edema in the sacrumand ilium and about the sacroiliac joints.

Discussion

The most common site used for bone graft harvesting isthe posterior aspect of the ilium, just posterior to the sac-roiliac joint and extending to the posterior rim of the ili-ac crest. Occasionally, the harvest site also is extended tothe sacroiliac joint when large amounts of cancellousbone are needed for surgery, but the harvesting proce-dure should not violate the sacroiliac joint itself [2]. Al-though violation of the pelvic ring is known to cause pel-vic instability, this is not reported as a complication ofthis type of surgery, probably because proper respect is

given to the important posterior stabilizing structures ofthe pelvis at the time of surgery. However, in our pa-tients, pelvic instability developed within a few monthsafter the harvesting procedure, suggesting that the insta-bility was a complication of the procedure itself. By thesurgical removal of a significant amount of bone, thestrength of the posterior pelvic ring clearly weakens. Thedistribution of mechanical forces applied to the pelvicframe changes, and the risk of deformation of the pelvicbones increases substantially [6]. Three of nine patients

Table 1 Patient analysis(+, positive; , negative) Patient no. Interval from time Symphysis pubis Harvest site Sacroiliac

of surgery to positive subluxation/ fracture jointimaging findings dislocation subluxation

1 3 months + + 2 3 months + + +3 2 months + + 4 Unknown + + +

5 7 months + + +6 ? 7 years + 7 Unknown + + 8 1 month + + +9 4 months + + +

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Fig. 1 A 52-year-old woman had bone graft harvested from theright iliac crest. Two months later, she developed pelvic pain. Pel-vic film shows subluxation and bone sclerosis at the pubic sym-physis (arrow)

Fig. 2 A 72-year-old woman with bone graft removed from rightiliac crest. Three months later, her pelvic film shows subluxationat the pubic symphysis and fracture (arrow) of right iliac bone, atthe graft harvest site

Fig. 3AC A 68-year-old woman with pelvic insufficiency frac-ture. A Initial radiograph of the pelvis reveals the bone graft har-vesting from the left iliac crest. The pubic symphysis is normal.

B Bone scan obtained 2 years later shows intense uptake in poste-rior portion of both ilii, sacrum, about both sacroiliac joints, andpubic symphysis. C Pelvic radiograph obtained 7 months later re-veals dislocation of the pubic symphysis (arrows) with the pubicbones overlapping on top of each other. Both iliac crests showedincreased sclerosis, consistent with insufficiency fractures

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in our study underwent repetitive bone graft harvesting,with material derived from the same site, further sup-porting the hypothesis that excessive and aggressive re-moval of bone from the posterior aspect of the pelvis in-creases the risk of pelvic fracture. Lichtblau [7] andCoventry and Tapper [5] emphasized that the major liga-mentous support of the sacroiliac joint is posterosuperiorin location. Removal of bone graft from the posterior as-pect of the ilium potentially can destroy some of the lig-aments, leading to pelvic instability as well.

Although none of the patients had bone density evalu-ation prior to the bone graft harvesting, the fact that all

the patients were women and elderly suggests pre-exist-ing osteopenia or osteoporosis may also predispose suchpatients to insufficiency fractures when the distribution offorce around the pelvis has been altered and the posteriorsupporting ligaments have been weakened. Perioperativeimmobilization causes further disuse osteopenia, also pre-disposing to pelvic instability. Perhaps, in elderly women,evaluation of bone density should be performed beforeconsidering autologous bone graft harvesting. If a patient

has pre-existing osteopenia, alternative sources for graftmaterial, such as cadaveric bone, should be considered.

In our series, the most common initial imaging mani-festation of pelvic instability was subluxation or disloca-tion of the pubic symphysis. All patients had suchchanges. The second most common radiographic mani-festation in our patients was diffuse sclerosis just inferior

to the harvest site. A fracture line also may be apparent.Diastasis of the sacroiliac joint adjacent to the harvestsite also was a common finding in our series. Insufficien-cy fractures also involved the sacrum. Therefore, whenevaluating a radiograph of the pelvis following such har-vesting procedure, the symphysis pubis, sacroiliac joint,sacrum, and harvest site should be assessed.

There are a number of limitations to our study. First, aswe did not review all patients undergoing such harvestingprocedures, we do no know the frequency of this complica-tion. Second, as we also did not review all such postopera-tive patients with persistent or new back pain, we do notknow the frequency of this complication in symptomatic

patients. Third, although several different surgeons hadperformed the procedures in our patients, it is not clearwhether some specific aspect of the surgery was instru-mental with regard to subsequent pelvic instability. Allwere experienced spine surgeons, however. Fourth, thenumber of patients reported here is small and our observa-tions are restricted to those undergoing lumbar arthrodesis.It is possible that fusion of the lumbar spine, as comparedwith the thoracic or cervical spine, alters the distribution offorces applied to the pelvis. Obviously, analysis of a largerseries of patients undergoing various surgical proceduresof the spine requiring harvesting of bone from the pelvisneeds to be accomplished. Finally, our purpose was to re-

port this complication and to review the associated imag-ing findings; we are unable to document the diagnostic ad-vantages of one imaging method compared with the others.

In conclusion, pelvic instability is a potential compli-cation of harvesting of bone from the posterior aspect ofthe iliac crest. Such instability is manifested by insuffi-ciency fractures of the ilium or sacrum, or both, sublux-ation of the sacroiliac joint, and fracture or dislocation ofor about the pubic symphysis.

Fig. 4 A 52-year-old woman had multiple spinal fusions. Bonegraft was repeatedly obtained from both iliac crests. One month af-ter the final bone graft harvesting, she developed severe lower backpain. CT scan of the sacrum shows fractures of both iliac crests andsacrum with subluxation of both sacroiliac joints (arrows)

References

1. Hall MB, Vallerand WP, Thompson D,Hartley G. Comparative anatomic studyof anterior and posterior iliac crests asdonor sites. J Oral Maxillofac Surg1991; 49:560563.

2. Xu R, Ebraheim NA, Yeasting RA,Jackson WT. Anatomic considerationsfor posterior iliac bone harvesting. Spine1996; 21:10171020.

3. Hu RW, Bohlman HH. Fracture at the il-iac bone graft harvest site after fusion ofthe spine. Clin Orthop 1994; 208213.

4. Kurz LT, Garfin SR, Booth RE Jr.Harvesting autogenous iliac bone grafts:a review of complications and tech-niques. Spine 1989; 14:13241331.

5. Coventry MB, Tapper EM. Pelvic insta-bility: a consequence of removing iliacbone for grafting. J Bone Joint Surg Am1972; 54:83101.

6. Varga E, Hu R, Hearn TC, et al. Biome-chanical analysis of hemipelvic defor-mation after corticospongious bone graftharvest from the posterior iliac crest.Spine 1996; 21:14941499.

7. Lichtblau S. Dislocation of the sacro-ili-ac joint: a complication of bone-graft-ing. J Bone Joint Surg Am 1962;44:193198.

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