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Vertebral deformities and vertebroplasty

Correspondence: Dr. K.H. Mak, Kwong Wah Hospital, Hong Kong.

Hong Kong Journal of Orthopaedic Surgery2002;6(2):117-128.

© 2002 Hong Kong Orthopaedic Association & Hong Kong College of Orthopaedic Surgeons.

MINI-SYMPOSIUM ON OSTEOPOROSIS

Vertebral deformities in the osteoporotic spine and early

experience in vertebroplasty

Mak KH, Kwok TK, Wong KKKwong Wah Hospital, Hong Kong.

ABSTRACT

Of the 360 patients aged 65 and above admitted consecutively within a period of 3 years to a regional hospitalbecause of genuine back pain, 288 of them were found to have osteoporotic spinal deformities. The radiologicalfeatures of these vertebral deformities were reviewed by the author and grouped according to the classificationdetailed by the European Vertebral Osteoporosis Study Group. Three major types were identified: the wedge,biconcave, and the crushed. The wedge and crushed types can be further defined according to their fracturepatterns, their distribution on different curvatures of the spinal column, and their likelihood of complications.Wedge deformity of the thoracolumbar junction was the most common. It affected either a single level (D12 orL1), or two levels (D11 and L1), with a spared level in between. The present study in the pattern of osteoporoticdeformities has helped in selecting the vertebrae for vertebroplasty, a procedure aimed at alleviating back pain inrelation to osteoporotic spinal deformities.

Key Words: Bone cement; Deformity; Fracture; Osteoporosis; Spine

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sis is an endemic pathology in all developed countries.Ageing leaves both men and women exposed to ahigher risk of osteoporotic fracture; because womenlive longer, the lifetime risk of a vertebral fracture fromage 50 years onward is 16% in white women and only5% in white men. Vertebral fractures affect approxi-mately 25% to 30% of postmenopausal women.6 Unlikeother osteoporotic fractures, spinal fractures have re-

INTRODUCTIONWith the advance in health care and the provision ofsocial security benefits, longevity is no longer unusual.People tend to live and remain active for more yearsthan in the past. The invention of machinery and elec-tronics spares people from exerting their musculoskel-etal appendages. Our bone and muscle are no requiredto work as hard in labour and daily activities. Osteoporo-

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ceived little attention, probably because they are quitecommon and tend to heal within a few weeks or monthswithout significant morbidity. In addition, neurologicalcomplications from these osteoporotic compressionfractures are uncommon. This study aimed at lookinginto the magnitude of osteoporotic back pain amonglocal women who were otherwise active, at identifyingpatterns of vertebral deformities in their spinal columns,at considering their chances of neurologicalcomplications, as well as at reviewing our early experi-ence in vertebroplasty, a procedure aimed at relievingback pain related to osteoporotic vertebral collapse.

METHODSThere were 360 women aged 65 years and over whowere admitted consecutively from April 1998 to March2001 to a local hospital through the Emergency Depart-ment because of back pain and paraesthesia in theirlower limbs. The thoracolumbar vertebrae in theseolder women were examined radiologically for any os-teoporotic vertebral deformities. Presence of pain andtenderness at levels corresponding to radiologicaldeformities, vertebral fractures, or fracture progressionwere taken as genuine symptoms related to the verte-bral deformity. Those subsequently found to have ma-lignancies and infections were excluded from this study.Various patterns of osteoporotic vertebral deformitieswere identified in 288 patients. The age of the patientsranged from 65 to 99 years with an average of 78.6 years.Patients who presented with acute cauda equina com-plications were noted and managed accordingly.

Management

Unlike wrist and hip fractures, persistent pain due toosteoporotic spinal fracture has not been receivingmuch attention. Many orthopaedists seem to believethat most of these fractures will heal up and that backpain can be controlled eventually, but some of thesefractures have caused persistent symptoms. There hasbeen increased morbidity associated with decreasedmobility or decreased chest expansion. Some cases mayhave developed into pseudoarthrosis. Other factorsassociated with persistent symptoms were newfractures, either in the affected levels or in new levels.Studies in a cohort group of 65-year-old patients haveshown a 15% to 30 % increase in the mortality rate ofpatients with osteoporotic spinal fractures after ageadjustment.5

For those with persistent back pain after 2 to 4 weeks,particularly on change of posture while lying in bed,

vertebroplasty, injection of bone cement into the bodyof a deformed vertebra through the pedicle, wasconsidered. It was performed in 10 patients. Indicationsof the procedure and their progress in 1 year’s follow-up are reported.

Vertebroplasty

Percutaneous bone cement injection to the painful, de-formed vertebra was tried to stabilise the endplate andthus relieve pain and improve mobility in a group ofpatients with persistent and disabling back pain. Basedon our understanding of the pattern of osteoporoticvertebral fractures and their evolution, we have identi-fied five criteria for injection: (1) new vertebral frac-tures responsible for back pain and not responsive toconservative management for more than 2 to 4 weeks;(2) back pain due to a newly involved level in the pres-ence of previously documented old fracture levels; (3)no more than two levels of old vertebral deformity; (4)the collapse patterns confined to wedge-shaped or bi-concave types; and (5) no radiological evidence ofpseudoarthrosis or vacuum sign in the level to beinjected.

We did not use magnetic resonance imaging to definethe chronicity of the fracture nor to select vertebraefor injection.

Methods in transpedicular

vertebroplasty

With the patient in prone position under C arm, thelevels to be injected were marked and 2% lignocainewas infiltrated. Local anaesthesia was used and the en-try point was taken from the superolateral cortex of thepedicle. Craig’s spinal biopsy needle was initially useduntil the Vertebroplasty needle (Stryker HowmedicaOsteonics, Mahwah, NJ, US) became available.

Insertion of the trocar and the sheath was performedmanually under fluoroscopy. The medial and the infe-rior cortices had to be avoided until the needle was to-tally inside the vertebral bodies. Injection can begin onlywhen the needle has advanced to the center of a body.

Half of the preparation of Simplex P bone cement(Stryker Howmedica Osteonics) is used together withhalf of the polymerisation agent. The bone cementshould be chilled overnight in order to prolong theworking time. About 10 g of sterilised barium sulphateis mixed with the Simplex P powder before that is mixed

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with the polymer catalyst. The cement is backfilled tofour 1-mL and one 5-mL syringes when it is in fluid state.

Injection with the 5-mL syringe was made initially, fol-lowed by injections with two to three 1-mL syringes.With adequate pressurisation, cement should fill up theanterior body, crossing the midline to the other side,and then to the posterior part of the body.

Occasionally, some cement that leaked outside the lat-eral cortex or that had gone through the superiorendplates was observed. This usually occurred in thosepatients who suffered from superior endplate fracture.These leaks were of no major clinical consequence.When cement starts to fill the body behind the needle,it is time to stop pushing bone cement in. The syringewith the needle is then turned two to three times toallow breakage of the cement column, before it is pulledout.

Unless the filling of the body is not satisfactory, onlyone pedicle is usually used for injection. The needleshould aim at the anterior third of the vertebral body.

Venogram

In our early cases, vertebral venogram with contrastwas performed before cement injection in order to de-tect any communication with a major vein. We did notfind leakage to be a common phenomenon, and becausethe retention in the vertebral body can interfere withthe visualisation of the injection, we abandoned thispractice. Vasconcelos and Murphy had not found veno-gram necessary in their evaluation of 205 consecutiveprocedures.7

RESULTS

Radiological features of vertebral

bodies

There were 570 osteoporotic vertebral deformities iden-tified on the plain radiographs of 288 patients. Levelsaffected spanned from the fourth thoracic to the fifthlumbar spine. The vertebral bodies of the D11, D12,L1, and L2 were most frequently affected. On theaverage, each patient had two vertebral bodies affected.

Different patterns of deformities were found in the spi-nal columns. Levels affected clustered around the tho-racolumbar junction. According to the classificationdescribed by European Vertebral Osteoporosis StudyGroup,4 three different patterns of osteoporotic verte-

bral deformities can be identified: wedge, biconcave,and crushed. Their radiological features can representdifferent stages of the fracture, or a reflection of thestress taken up by the affected vertebral bodies locally.

Type A: wedge-shaped fracture

Wedge compression of the vertebral body (Fig. 1) wasthe first and the most common fracture developed inthe osteoporotic spines, especially for the levels aroundthe thoracolumbar junction, where the center of grav-ity is anterior to the vertebral body (Fig. 2) and createsa relatively greater load on the anterior column. Theosteoporotic vertebral body effectively gives in to thelocal stress at the thoracolumbar junct ion.Compression, collapse, and shortening of the anteriorcolumn (A1) or fracture and sinking of the superiorendplate into the vertebral body (A2) can effect wedg-ing of a vertebra. The fractured endplate is driven intothe vertebral body (Fig. 3) through a mechanism simi-lar to those in Schmorl’s nodes. Wedge compression(A1) was more common than fracture of the superior

Figure 1 Type A wedge collapse of L3 in a 74-year-old womanwith back pain. The L1 osteoporotic fracture (vertebral planus typeC) was old.

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endplate (A2), which was commonly found in lumbarlevels that are related to axial loading (Fig. 4).

Type B: biconcave deformity

Typically found in lumbar levels where the loading isaxial, biconcave deformities were seen when the cen-tral vertebral body appeared shortened with relativelypreserved anterior and posterior vertebral cortices(Fig. 5). In early osteoporosis, the cortical bone is af-fected to a lesser extent than the trabecular bone in-

Figure 3 An 81-year-old man was admitted because of acuteretention of urine. The findings were type A2 fracture of superiorendplate of L3; lumbar spine in kyphosis; and old collapse frac-tures of L1 and L4 (type C). Magnetic resonance imaging showedno cord compression on all lumbar levels.

Figure 2 The vertical axis of the spine is anterior to the vertebralbody at the thoraco-lumbar junction and through the vertebral bodyin lumbar lordosis. It is responsible for anterior wedge loading andthe axial loading stress producing the respective wedge and bi-concave deformities.

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side the body and the relative turgidity and complianceof the lumbar intervertebral discs distended into thecentre of the endplates. The incidence of biconcave de-formities was higher in the lumbar than the thoracicspine, and it did not decrease at lower lumbar levels(Fig. 6).

Typically, several contiguous segments were affected,appearing as intervertebral discs bulging between fish-tailed vertebral bodies (Fig. 7).

Figure 4 Distribution of wedge deformities in the vertebral column.(A) Wedged anterior body. (B) Fractured superior endplate.

Figure 5 Type B deformities of L4 and L5. Ballooned interverte-bral discs and Type C deformity of L2

Figure 6 Distribution of type B deformities in the vertebral column.

Figure 7 Osteoporotic lumbar spine with distended intervertebraldisc. All lumbar segments were affected (type B). They representednumerous micro-fractures in multiple lumbar vertebral bodies.

A

B

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Early compression fracture in the centrum of the lum-bar vertebral bodies can be easily missed, but thesefractures may represent repeated episodes of micro-fractures and recurrent attacks of low back pain in theseosteoporotic women (Fig. 8).

The upper lumbar levels that first present with a type Bfracture pattern invariably progress to type C fracturebecause of the stress locally and the decreased mobil-ity in the thoracolumbar junction.

Type C: crush

Crushed vertebral bodies represented the final defor-mity that osteoporotic vertebrae can adopt (Fig. 1). Theentire vertebral body is collapsed. Fortunately, the pos-terior vertebral cortex is usually intact and seldom pro-trudes into the spinal canal. There is a localisedkyphosis. Neurological complications in osteoporoticspinal fracture are only seen occasionally. In our 3-yearseries, we have seen and managed eight patients.

C1: vertebral planus

Vertebral planus was the most common deformity clus-tered around the thoracolumbar junction (Fig. 9), wherethe vertebral bodies became thin slices of bone (Fig.10). There was a localised kyphos that had evolved fromthe wedge compression. Very often, the intact poste-rior walls could still be identified.

C2: crushed body and displaced anterior

column

Crushed vertebral body and displaced anterior columnwas occasionally seen in the lumbar levels. It was theprogression of either the wedge fracture with fracturedsuperior endplate, or the biconcave deformities. The

Figure 8 An 88-year-old woman with low back pain. X-ray showedtype B fracture of L2 and L4.

Figure 9 Distribution of type C deformities in the vertebral column.

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Figure 10 C1, vertebral planus in D11. The 79-year-old womanpresented with back pain and some weakness of left lower limb:Vertebral planus also present in mid-dorsal spine with exagger-ated lumbar lordosis and type B fracture in the L2 vertebra.

Figure 11 Type C2 deformities. A woman aged 88 years withback pain. Type C2 deformity of L1with anterior displacement ofanterior body was present. Type B deformity was present at D9.

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anterior column of the vertebral body was extruded andbulged anteriorly (Fig. 11).

C3: burst fracture with retropulsion

In this study, it was least frequent to see that the middlecolumn had burst into the spinal canal and caused me-chanical compression to the dural content or the emit-ting nerve roots. The posterior cortex seldomretropulsed into the spinal canal (Fig. 12). This condi-tion was found only in the thoracolumbar junction, T11,T12, L1, and very occasionally L2 and was related tothe mobility of the junction and the local stress.

Single-level lesions

Nearly half (46.5%) of our patients had only one spinallevel affected, and the most common single-level de-formity was seen at L1 (40%), the second-most com-

Figure 12 Type C3. An 82-year-old woman was admitted initiallybecause of back pain and girdle type of chest pain. X-ray showedcrushed fracture of D12. She experienced urinary retention andlower limb weakness in 2 weeks. Magnetic resonance imagingshowed retropulsed posterior body of D12.

Figure 13 A 98-year-old woman had a L2 superior endplate frac-ture after a fall. Her persistent back pain improved after injectionof bone cement.

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mon at D12 (20%). These were predominantly wedgecompression with collapse and shortening of the ante-rior column. The remaining first osteoporotic fractureinvolved the other lumbar levels indiscriminately. Theywere mainly type B deformities with ballooning of theintervertebral discs.

Double-level lesions

Seventy-one (24.6%) of our patients had two spinal lev-els affected. There were different combinations of typeA1 and A2 fractures. Deformities affecting consecutivesegments were uncommon in the thoracolumbarjunction. Collapse of a level in the thoracolumbar junc-tion may have relieved the stress on its adjacent levels.For example, if D11 were in a wedge shape, then D12integrity could usually be preserved, and the first lum-bar level would be collapsed instead. In our study,wedge fracture of the D11 and L1 was the most com-mon association (Table 1).

In the lower lumbar segments, biconcave collapses(type B) in adjacent levels were common. The mostfrequently involved level was L3. It had collapsed witheither L1 or L2. The vertical loading on this vertebra inlordosis may have contributed to this pattern of thedeformity.

Multiple-level lesions

Multiple-level lesions were found in patients with re-peated episodes of back pain, at times related to a fall.There were new fractures among some deformities thathad evolved from previous collapse patterns. Vertebral

planus (type C1) fracture patterns were invariably foundin the thoracolumbar junctions among some lumbarlevels affected by ballooned discs (type B).

Neurological complications

Of the 288 patients who presented with back pain andosteoporotic spinal deformities, eight (2.8%) of themwere complicated with neurological deficits, mainlycauda equina syndrome due to dural sac compressionby the retropulsion of the collapsed posterior cortex atthe thoracolumbar junction. Anterior decompressionand stabilisation of the osteoporotic spinal column wasoften fraught with complications. Position andstabilisation of the implant and graft were difficult tomaintain in osteoporotic bone. Limited posterior lami-nectomy offered relief in some patients.

Our experience with vertebroplasty

Pain relief

All patients had good relieve of pain after injection.There were often significant improvements with changeof resting posture. Most researchers have reported sig-nificant pain relief with stabilisation of the fracture andinternal support of the vertebral cortices, almost im-mediately after the injection. With control of pain, thepatient’s chest expansion, respiratory function, andmobility were improved (Fig. 13).

Recurrence of pain

We did not see further collapse of the levels afterinjection. Three out of the 10 injected patients had re-currence of back pain within 1 year after injection,

Table 1 Commonest combinations in two levels deformities were D11/L1, L1/L3 and L2/L3. The lumbar combinations were usually TypeB deformities.

D7 D8 D9 D10 D11 D12 L1 L2 L3 L4 L5

D4D5D6D7 1 2D8 2D9 1 1 2 1D10 1 2 1D11 9 2 1 2D12 3 4 3 1 3L1 5 9 2 1L2 9 2L3 1L4L5

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Figure 14 An 80-year-old man presented with back pain for 3 months in February 2001. (A) X-ray showed only a wedge fracture of D12.(B) The back pain recurred 5 months later. There was a type B collapse of L3. (C), (D) Back pain improved after injection of bone cement.(E) One year later, there was recurrence of back pain and X-ray demonstrated a new superior endplate fracture affecting the level aboveand below L2 and L4.

A

B

C

D

E

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however. Recurrence of pain was due to recruitment ofnew levels, especially of the adjacent levels or the sand-wiched levels (Fig. 14). Collapse of an adjacent levelwas especially common at the thoracolumbar junctions(Fig. 15). Follow-up studies also revealed a slight butsignificant increased risk of vertebral fracture in thevicinity of a cemented vertebra.3

DISCUSSION

Choice of level for injection

Until a more biocompatible bone-filling substrate isavailable, vertebroplasty cannot be taken as a standardtreatment modality. Most osteoporotic fractures do healwithout complications and the associated back painusually improves with conservative treatment. Wheninjection becomes necessary, either because of chronicor recurrent presentation, selecting the correct levelfor injection becomes a clinical dilemma. Douglas etal2 reported that new fractures suitable for injectionwere those with bone marrow oedema seen in mag-netic resonance imaging, hypointensity or isointensityon the T1-weighted images, and a linear hyperintensityzone underlying the depressed endplate on short TIinversion recovery sequence.

We used local tenderness and reproduction of pain onchange of posture as indications of which levels were

Figure 15 A 73-year-old woman was admitted repeatedly because of back pain. X-ray follow-up showed progressive collapse of L2 fromfish-tail deformity (type B) to vertebral planus (type C1) with pseudoarthrosis and vacuum sign. There was also D12 wedge fracture (typeA1). Bone cement injection to the D12 and L2 helped to control the intractable back pain. However, the sandwiched level L1 collapsedwithin one month after injection. High chance of extravasation of injected cement in type C fractures.

responsible for symptoms. Any appearance of new de-formities when compared with previous plain radio-graph and those correlated with the duration of symp-toms would be a reliable indicator of levels suitable forinjection.

Leakage of cement

Leakage of cement was common, especially for spinallevels with marked compression collapse of the body.Cotton et al1 found an incidence as high as 75%. Theyreported 15 epidural leaks, eight intra-discal leaks, andtwo venous leaks out of 40 treated levels. Only one outof the 15 paravertebral leaks produced transient femo-ral nerve palsy. Surgical intervention was necessary intwo nerve root compressions out of the eight foraminalleaks. When we restricted injection to type A and typeB fracture, leakage became uncommon. Occasionally,cement did leak into the intervertebral disc throughthe fractured superior endplate, but this was not foundto be problematic. In other sites, although leakage hadnot been found to have major consequences, it couldhave definitely undermined the success of the proce-dure through the loss of filling material.

In order to minimise uncontrollable cement leakage,we excluded levels with pseudoarthrosis and those withvacuum sign on plain radiograph from injection. We do

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not recommended vertebroplasty for deformities likevertebral planus and burst fractures (all type Cfractures).

The future

For patients who are susceptible to osteoporoticfractures, multiple level injections may be the treatmentthat will strengthen the whole vertebral column andprevent compression collapse, especially at the thora-columbar junction. The physical properties of bonecement, however, prevent its more liberal use in other-wise intact vertebral bodies. Development of abiocompatible calcium phosphate bone cement that isinjectable, that can be resorbed and remodeled, andthat preferably replicates osteo-inductive properties isessential before this procedure can be routinely rec-ommended for the painful osteoporotic spine. Thereare further questions the need to be answered: howdoes injection of a collapsed level affect the distribu-tion of stress to the adjacent levels? Will the reconstitu-tion of a stable and strong vertebral body protect theadjacent levels from compression fracture? Or, since itis not uncommon to find an intact body in between col-lapsed levels at the thoracolumbar junction, does a col-lapsed segment at the thoracolumbar junction relievethe stress on the anterior bodies of the neighbouringlevels? All these questions need to be answered beforethe role of vertebroplasty and the merits of kyphoplastycan be defined.

REFERENCES1. Cotten A, Dewatre F, Cortet B, Assaker R, Leblond D,

Duquesnoy B, Chastanet P, Clarisse J. Percutaneousvertebroplasty for osteolytic metastases and myeloma: Effectsof the percentage of lesion filling and the leakage ofmethymethacrylate at clinical follow-up. Radiology 1996;200:525-30.

2. Douglas A, Linville II. Vertebroplasty and kyphoplasty. SouthMed J 2002;95:583-7.

3. Grados F, Depriester C, Cayrolle G, Hardy N, Deramond H,Fardellone P. Long-term observations of vertebral os-teoporotic fractures treated by percutaneous vertebroplasty.Rheumatology 2000;39:1410-4.

4. Ismail AA, Cooper C, Felsenberg D, Varlow J, Kanis JA,Silman AJ, O’Neill TW and the European Vertebral Os-teoporosis Study Group. Number and type of vertebraldeformities: epidemiological characteristics and relation toback pain and height loss. Osteoporosis International 1999;9:206-13.

5. Kado DM, Browner WS, Palermo L, Nevitt MC, Genant HK,Cummings SR. Vertebral fractures and mortality in olderwomen: a prospective study. Study of Osteoporotic FracturesResearch Group. Arch Intern Med 1999;159:1215-20.

6. Melton LJ III. Epidemiology of spinal osteoporosis. Spine1997;22(suppl 24):S2-11.

7. Vasconcelos C, Gailloud P, Beauchamp NJ, Heck DV,Murphy KJ. Is percutaneous vertebroplasty without pretreat-ment venography safe? Evaluation of 205 consecutiveprocedures. Am J Neuroradiology 2002;23:913-7.

The AuthorMak Kan-Hing, FHKCOS, FHKAM, Consultant, Kwong Wah

Hospital, Hong Kong.Kwok TK, FHKCOS, FHKAM, Senior Medical Officer, Kwong

Wah Hospital, Hong Kong.Wong KK, MBChB, MRCS(Edin), Medical Officer, Kwong

Wah Hospital, Hong Kong.