Funcion Pulmnar en Escoliosis

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Pulmonary Function Following Early ThoracicFusion in Non-Neuromuscular Scoliosis

By Lori A. Karol, MD, Charles Johnston, MD, Kiril Mladenov, MD, Peter Schochet, MD,Patricia Walters, RRT-NPS, and Richard H. Browne, PhD

Investigation performed at the Department of Orthopaedic Surgery, Texas Scottish Rite Hospital for Children, Dallas,

and the Department of Pulmonology, Children’s Medical Center of Dallas, Dallas, Texas

Background: While early spinal fusion may halt progressive deformity in young children with scoliosis, it does not facilitate

lunggrowth and,in certainchildren,it canresultin thoracic insufficiency syndrome. Thepurpose of thisstudywas to determine

pulmonary function at intermediate-term follow-up in patients with scoliosis who underwent thoracic fusion before the age of

nine years.

Methods: Patients who had thoracic spine fusions before the age of nine years with a minimum five-year follow-up under-went pulmonary function testing. Forced vital capacity, forced expiratory volume in one second, and maximum inspira-

tory pressure were measured and compared with age-matched normal values. Patients with neuromuscular disease,

skeletal dysplasias, or preexisting pulmonary disease were excluded, while those with rib malformations were included.

The relationships between forced vital capacity and age at the time of surgery, length of follow-up, extent of the fusion,

proximal level of the fusion, and revision surgery were studied.

Results: Twenty-eight patients underwent evaluation. Twenty patients had congenital scoliosis, three had idiopathic

scoliosis, three had scoliosis associated with neurofibromatosis, one had congenital kyphosis, and one had syndromic

scoliosis. Seventeen patients had one spinal surgery, while eleven had additional procedures. The average age of the

patients was 3.3 years at the time of surgery and 14.6 years at the time of follow-up. The average extent of the thoracic

spine fused was 58.7%. The average forced vital capacity was 57.8% of age-matched normal values, and the average

forced expiratory volume in one second was 54.7%. The forced vital capacity was <50% of normal in twelve of the twenty-

eight patients, and two required respiratory support, implying that substantial restrictive lung disease was present. With

the numbers studied, no significant correlation could be detected between the age at the time of fusion or the lengthof follow-up and pulmonary function. The extent of the spine fused correlated with the forced vital capacity (p = 0.01,

r =20.46). Fusions in the proximal aspect of the spine were found to be associated with diminished pulmonary function

as eight of twelve patients with a proximal fusion level of T1 or T2 had a forced vital capacity of <50%, but only four of six-

teen patients with a fusion beginning caudad to T2 had a forced vital capacity of <50% (p = 0.0004, r = 0.62).

Conclusions: Patients with proximal thoracic deformity who require fusion of more than four segments, especially those

with rib anomalies, are at the highest risk for the development of restrictive pulmonary disease. Pulmonary function tests

should be performed for all patients who have an early fusion. The pursuit of alternative procedures to treat early spinal

deformity is merited.

Level of Evidence: Therapeutic Level IV. See Instructions to Authors for a complete description of levels of evidence.

Scoliosis in children who are less than nine years old is mostfrequently due to congenital vertebral malformations.These very young patients also are likely to have thoracic

and rib abnormalities, which may further restrict the ability of

the pulmonary system to develop and grow. Spinal deformity inthis group of patients is often relentlessly progressive and his-torically has been treated by anterior and posterior spinal fu-sion at a young age with posterior spinal instrumentation when

Disclosure: The authors did not receive any outside funding or grants in support of their research for or preparation of this work. Neither they nor a

member of their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercial

entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, division, center, clinical practice,

or other charitable or nonprofit organization with which the authors, or a member of their immediate families, are affiliated or associated.

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COPYRIGHT Ó 2008 BY THE JOURNAL OF BONE AND JOINT SURGERY, INCORPORATED

J Bone Joint Surg Am. 2008;90:1272-81 d doi:10.2106/JBJS.G.00184



possible1,2. This treatment was undertaken with the belief that aspine that was short and straight would be better in the long term than one with further curve progression3,4.

A recent study by Campbell et al. led to a change of phi-losophy in the treatment of young patients with congenitalspinal deformity 5. The description of thoracic insufficiency syndrome, defined as ‘‘the inability of the thorax to supportnormal respiration or lung growth,’’ as a result of the lack of pulmonary development associated with congenital scoliosis,rib fusions, and chest wall anomalies, has led to a resurrectionof interest in growing-rod technology and chest wall expan-

sion. Yet little is known about which patients are most at risk for the development of thoracic insufficiency syndrome. Whilethe infant with multiple thoracic vertebral malformations andassociated fused or missing ribs appears most likely to havepremature pulmonary failure develop following fusion, there isuncertainty regarding patients with lesser involvement whomay not be candidates for thoracic expansion surgery by to-day’s guidelines.

The purpose of this study was to assess the pulmonary function of patients who had undergone spinal fusions beforethe age of nine years. We set out to establish which patients

Fig. 1

The percentage of the thoracic spine fused at the index procedure plotted against the

percentage of predicted forced vital capacity (FVC) for twenty-eight patients. More extensive

thoracic fusions were associated with diminished forced vital capacity at the time of follow-

up (r =2

0.46, p = 0.01).

Fig. 2

The average percentage of predicted forced vital capacity (FVC) plotted against the most proximal thoracic vertebra fused in the index

procedure (r = 0.62, p = 0.0004). The patients whose fusions included T1 and T2 had the greatest pulmonary compromise.

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T H E J O U R N A L O F B O N E & J O I N T S U R G E R Y d J B J S . O RG

VO L U M E 9 0 - A d N U M B E R 6 d J U NE 2 0 0 8

P U L M O N A R Y F U N C T I O N F O L L O W I N G EA R L Y T H O R A C I C

F U S I O N I N N ON - N E U R O M U S C U L A R S C O L I O S I S



were at the highest risk for pulmonary compromise and todefine a threshold of the magnitude of thoracic fusion and ageat the time of surgery that were most likely to lead to thoracicinsufficiency syndrome.

Materials and Methods

A ll patients who were less than nine years old when they had fusion of some portion of the thoracic spine, between

1983 and 1998, were identified for this study. A minimum of five years of postoperative follow-up was required. Patients with

primary pulmonary disease, such as diaphragmatic hernias,were excluded. Likewise, patients with neuromuscular diseasewho were likely to have weakness, such as those with congenitalmuscular dystrophy and spinal muscular atrophy, were ex-cluded. Finally, patients with skeletal dysplasias, such as chon-drodysplasia punctata and diastrophic dysplasia, whichinterfere with growth potential, were not included in the study.The study was approved by the university institutional review board, and consent was obtained from adult patients and legalguardians of minors.

Medical records were reviewed for diagnosis, pulmonary comorbidities, age at the time of surgery, and the extent of thesurgical fusion. Records were also reviewed for occurrences of

pneumonia,the need for oxygen supplementation, and the needfor nighttime ventilatory support. Additional spinal surgicalprocedures were recorded.

Radiographs were reviewed for sagittal and coronal planedeformity at the time of surgery and at the time of follow-up.The presence or absence of rib abnormalities, such as rib fu-sions or absent ribs, was noted. Final radiographs were re-viewed, and the thoracic height from T1 to T12 was measuredand compared with normal values as reported by Dimeglio andBonnel6.

All patients were asked to report for standard pulmonary function testing, during which spirometric volumes and flows

were measured. Values were normalized with use of Polgar ref-erence values rather than solely by age7. The regression curvesfor these reference values factor in height and age, and thereare separate curves for females and males. Forced vital capacity and forced expiratory volume in one second were selected foranalysis. Maximum inspiratory pressure was measured, with<80 mm Hg representing abnormally decreased pressure.

Statistical AnalysisPearson r correlation coefficients and 95% confidence limits

were calculated to determine whether there were linear ornearly linear relationships between pulmonary function valuesand the percentage of the thoracic spine that had been fused,the proximal level of the fusion, the age at the time of surgery,and the length of follow-up. Correlation coefficients of <0.50 inabsolute value are considered to be weak correlations and toosmall to be of clinical importance. Correlations between 0.50and 0.80 show a noticeable, but modest, relationship betweentwo variables. A correlation of ‡0.80 is considered a strong cor-relation and would be quite evident if the variables were plotted.With a sample size of twenty-eight subjects, it is unlikely thatweak correlations would yield a significant Pearson r value. If the true correlation is ‡0.51, there is at least an 80% chance of

achieving a significant correlation with twenty-eight subjects.Therefore, a sample size of twenty-eight subjects provides an80% probability of achieving a significant result if the true cor-relation is at least modest in size. The relationship between theforced vital capacity and the occurrence of revision surgery wassubjected to a two-sample t test.

Results

Forty-four patients were identified through a computerizedsearch of surgical patients who were less than nine years

old at the end of 1998. All patients were alive, to our knowl-edge, at the time of writing.

Fig. 3

The thoracic height at the time of follow-up versus the percentage of predicted forced vital capacity

(FVC). Patients with the shortest thoracic spinal height (measured from T1 to T12) had the greatestrestriction of pulmonary volume (r = 0.73, p < 0.001).

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Twenty-eight patients participated in the pulmonary func-

tion study (see Appendix). The average age at the time of sur-gery for the twenty-eight patients was 3.3 years (range, fourmonths to 8.4 years). The average age at the time of follow-upwas 14.6 years (range, 7.3 to 22.8 years). Therefore, the lengthof follow-up was an average of 11.2 years (range, 6.4 to 20.8

years). The average age at the time of surgery for the sixteenpatients who did not return for pulmonary function testing was 3.9 years (range, 1.4 to 7.0 years).

The most common diagnosis was congenital scoliosis,occurring in twenty of the twenty-eight study subjects. Threepatients had scoliosis associated with neurofibromatosis, threehad idiopathic scoliosis, one had syndromic scoliosis, and one

had congenital kyphosis. The diagnoses in the sixteen patients

who did not return were similar, with congenital scoliosis ineleven patients, scoliosis associated with neurofibromatosis intwo, congenital kyphosis in two, and scoliosis associated with achromosomal deletion in one patient.

Twenty-six of the twenty-eight patients had anterior andposterior surgery as the primary initial surgery, while one hadan isolated posterior spinal fusion and one had an isolatedanterior spinal fusion. Twenty-six anterior surgical procedureswere done by open thoracotomy, and one was performed en-doscopically. The average extent of the thoracic spinal fusionwas 58.7%. At the time of this review, eleven of the twenty-eight patients had undergone revision spinal surgery. For all of

Fig. 4-A

Figs. 4-A, 4-B, and 4-C An 11.3-year-old boy with infantile scoliosis and congenital

toxoplasmosis whohad fusioninitiallyat theage of 1.9years, withsubsequentrevision

fusion and instrumentation. Figs. 4-A and 4-B Anteroposterior and lateral radiographs

of the spine made when the patient was 11.6 years old.

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these patients, pulmonary function testing for this study wasdone more than two years after their revision surgery.

Pulmonary Function Test ResultsForced vital capacity averaged 57.8% (range, 27% to 99%) of normal predicted values. Forced vital capacity was <50% intwelve of the twenty-eight patients, implying that clinically im-

portantrestrictivelung disease waspresent in 43%of thepatients.The average forced expiratory volume in one second was 54.7%(range, 23%to 91%) of predicted values for the entire group andwas <50% in twelve (43%) of the twenty-eight patients.

Maximum inspiratory pressure was documented intwenty-five patients. A maximum inspiratory pressure of <80mm Hg indicates some element of respiratory muscle weakness.For eleven (44%) of the twenty-five patients in whom themaximum inspiratory pressure was measured, the pressuregenerated was <80 mm Hg.

Obstructive pulmonary disease, most commonly asthma,occurs when the ratio of forced vital capacity to forced expira-

tory volume in one second is <85%. This value may also reflectan inability to empty the lungs secondary to respiratory muscleweakness or chest wall stiffness. Ten (36%) of twenty-eightpatients had a ratio of <85%.

With the numbers studied, statistical analysis failed toshow a correlationbetween age at thetime of surgery and forcedvital capacity at the time of follow-up (r= 0.28 [95% confidence

interval, –0.10 to 0.59]; p= 0.15). The results are consistent withthe proposition that the youngest patients at the time of spinalfusion are not automatically those with the poorest pulmonary function, but it is possible that a larger sample size could show acorrelation between these variables. Likewise, the percentage of predicted forced vital capacity did not correlate with the lengthof follow-up (r = 0.09 [95% confidence interval, –0.29 to 0.45];p = 0.65). Since the confidence interval values are all <0.50,patients who had the longest duration of follow-up were notmore likely to have greater compromisein pulmonary function.Because patients underwent pulmonary function testing on asingle occasion for this study, the relationship between pro-

Fig. 4-B

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gressive pulmonary restrictive disease documented by serialpulmonary function tests and length of follow-up is unknown.

The percentageof forced vital capacity did,however, have asignificant inverse correlation with the extent of the thoracicspine that was fused at the index procedure (r = 20.46 [95%confidence interval, –0.71 to –0.11]; p = 0.01), with more ex-tensive fusions resulting in poorer pulmonary function at thetime of follow-up (Fig. 1). All patients with forced vital ca-pacity of <50% had more than four thoracic vertebrae fused.The relationship between the most proximal level fused anddiminished pulmonary function was also significant (r = 0.62[95% confidence interval, 0.32 to 0.81]; p = 0.0004) (Fig. 2).Eight of the twelve patients in whom the proximal level of the

fusion began at T1 or T2 had a forced vital capacity of <50% of predicted normal values, while only four of the sixteen patientswith fusions at or caudad to T3 had a forced vital capacity of <50%. None of the seven patients with a proximal level of fusion at T6 or caudad had a forced vital capacity of <50% atthe time of follow-up. There was also a significant inverse cor-relation between the proximal level fused and the extent of thefusion of the thoracic spine, with proximal fusions tending tobe more extensive (r = 20.57 [95% confidence interval, –0.78to –0.25]; p = 0.0016).

With the small numberof patients in the study, the patientswho had revision spinal surgery did not show a significantly

greater degree of pulmonary compromise than did those whohad one operation. A two-sample t test evaluating the effect of revisionsurgery on forcedvital capacity yielded a p value of 0.15(95% confidence interval, –53.7% to –27.3%), so that the effectof revision surgery on forced vital capacity cannot be deter-mined from this study.

Radiographs were measured to assess the height of thethoracic spine, represented as the vertical distance between T1and T12. Thevalues fornormal thoracic height were taken fromthe work by Dimeglio and Bonnel6. They found that normalthoracic height is 11 cm in the newborn, 18 cm at the age of five years, 22 cm at the age of ten years, and 26.5 and 28 cm inthe female and male adult, respectively. Sixteen of the twenty-

eight patients in this series had a thoracic height of <18 cm atthe time of follow-up, indicating that the thoracic height wasless than normal for a five-year-old child, although the age of these sixteen patients ranged from 7.3 to 17.8 years at the timeof testing. The average predicted forced vital capacity for thisgroup was 48.2% (range, 27% to 86%), and ten of the sixteenpatients had severe restrictive lung disease as evidenced by aforced vital capacity of <50%. Eight patients (who ranged from12.4 to 22.8 years old) had a thoracic height measuring between18 and 22 cm. The average predicted forced vital capacity of theeight patients was 63% (range, 42% to 99%), and two of themhad a forced vital capacity of <50%. Finally, four patients had a

Fig. 4-C

Computed tomography scan of the chest, made when the patient was 12.8 years old,

reveals severe vertebral rotation and reduced right lung volume.

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thoracic height measuring between 22 and 28 cm, which wasnormal for their ages, which ranged from 13.6 to 19.1 years. Inthis group, the average forced vital capacity was 85.2% (range,80% to 91%), and none of these patients had a forced vitalcapacity of <50%. Clearly, the shorter the thoracic spine, thesmaller the forced vital capacity and the greater the likelihoodof pulmonary restrictive disease (r = 0.73 [95% confidenceinterval, 0.49 to 0.87]; p < 0.001) (Fig. 3). The confidenceinterval values confirm a positive correlation.

Two patients had pulmonary symptoms at the time of follow-up. The first (Case 18) was an 11.3-year-old boy withcongenital toxoplasmosis who underwenta 92% thoracic fusion(T2 to L1) at the age of 1.9 years. He had revision anterior andposteriorfusion with osteotomies and halo traction at the age of eight years. Atthe timeof testing, he was 11.3 years old and usedbilevel positive airway pressure nightly for respiratory assistancewith supplemental oxygen during the day when short of breath.The forced vital capacity was 33% of predicted, and the forced

expiratory volume in one second was only 31% of normalvalues. When he was eleven years old, the thoracic spine mea-sured 16.9 cm, whichwas less than thenormal thoracic height of a five-year-old child (Figs. 4-A, 4-B, and 4-C).

The second patient (Case 1) was a twelve-year-old girlwho underwent a 58% thoracic fusion (T1 to T7) for congenitalscoliosis with extensive abnormalities of the left ribs when shewas3.9 yearsold. Shewas found to have 27%of predictedforcedvital capacity and a severely diminished maximum inspiratory pressure, indicating severe restrictive disease and chest weak-ness. Subsequently, blood gas testing and a sleep study revealedhypercarbia. She subsequently was placed on bilevel positive air-way pressurenightly. Thethoracicspine measured 14.1 cm, which

again was less than the normal value for a five-year-old child.

Discussion

Severe spinal deformity in veryyoung childrenis an extremely difficult surgical management problem. While the progres-

sion of spinal deformity requires treatment, spinal fusion limitsthe capability of the thoracic spine and the thoracic cage togrow normally. If the chest cannot elongate with growth, in-sufficient space is available for pulmonary alveolar growth, withresultant intrinsic restrictive lung disease8. While the most rapidperiod of alveolar growth occurs prior to the age of two years9,continued growth of the lungs occurs until mid-adolescence innormal individuals10. Dimeglio showed that normal thoracic

spinal growth occurs at a rate of 1.4 cm per year from birth tothe age of five years, 0.6 cm per year between the ages of fiveand ten years, and 1.2 cm per year in adolescence11. With use of these growth rates, a boy with a complete thoracic fusion at theage of three would lose 13 cm of thoracic spine growth. Theassociation with pulmonary function is clearly demonstrated inthe comparison of thoracic height at the time of follow-up withthe percentage of forced vital capacity in our patients.

We chose to includepatients who had spinal fusions priorto the age of nine years on the basis of the knowledge that lung growth by alveolar multiplication occurs up until that age12.Children undergoing fusion prior to nine years of age should

be most at risk for the development of thoracic insufficiency syndrome. While we did find a substantial number of childrenwith clinically important restrictive lung disease, the rela-tionship between the age at the time of fusion and the pul-monary function values was weak. It should be noted that mostof the children in this study were quite young, with twenty patients who were less than four years old at the time of fusion,and only eight patients who were between the ages of four andeight years at the time of fusion. Perhaps because of the smallsample size, we did not find that those with a younger age atthe time of fusion had a reliably greater diminution of forcedvital capacity or forced expiratory volume at one second thanthose who had a fusion closer to nine years of age.

Also, there was variability in the nature of the deformity among the subjects in the study group, as some had markedthoracic deformityon the basis of fused ribs or missingribs, whileothers had relatively normal rib anatomy. We hypothesized thatthe children who are undergoing spinal fusion at earlier ages and

whohave a preexisting thoracicdeformitywould be most likelytodevelop thoracic insufficiency syndrome, as has been stated by Campbell et al5. When the data on all twenty-eight patients arecombined, any effect of age at the time of surgery on pulmonary function in this group of children who all had a fusion beforethe age of nine years is no more than modest and may be of noclinical importance.

A major limitation of this study is that pretreatment dataon pulmonary function are unavailable. Preoperative data werenot collected because the children were very young at the time of surgery, with ages ranging from four months to 8.4 years. Stan-dard pulmonary function tests may be impossible to performprior to the age of five years13. On the basis of the results of this

study and on those in the study by Campbell et al.5, we arecurrently prospectively collecting infant pulmonary functiontests in young children with scoliosis and hope to use thesedata to direct treatment of not only the spinal deformity butalso the thoracic deformity.

Additionally, the effect of spinal fusion on pulmonary function compared with the effect of the spinal deformity aloneon pulmonary function cannot be easily separated. It is acceptedthat congenital spinal malformations resulting in scoliosis arelikely to lead to diminished vital capacity, presumably because of the decreased growth potential of the malformed vertebrae andthe resultant spinal and chest wall deformity 14. Additionally,it is known that an increased number of involved vertebrae in

patients with congenital scoliosis is linked to worsening pul-monary function15. There was no control group of untreatedpatients with similar spinal deformities in this study. The naturalhistory of pulmonary function in untreated spinal deformity associated with thoracic malformations is unknown, and itvery well may be more dismal than the data in the presentstudy. Nonetheless, we documented clinically important re-strictive lung disease in 43% of the tested patients, leading tothe conclusion that early anterior and posterior spinal fusionin children of less than six years of age is not associated witha satisfactory pulmonary outcome. Three patients in the groupunderwent spinal fusion between the ages of seven and nine

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years, and all of these patients had nearly normal pulmonary function at the time of evaluation. The age at the time of surgery for the children with a forced vital capacity of <50%,representing substantial restrictive pulmonary disease, rangedfrom four months to 5.8 years.

We did find an association between poor pulmonary function and the proximal level of the thoracic fusion. This ispartially due to the fact that the patients who had fusions be-ginning at T1 or T2 tended to have a more extensive fusion of the thoracic spine. The correlation between the proximal levelof fusion and the decreased percentage of forced vital capacity was significant (p = 0.0004, r = 0.62). The correlation betweenthe percentage of thoracic vertebrae fused and pulmonary com-promise was also significant (p = 0.01, r =20.46). It is impos-sible to know with statistical certainty whether the diminishedpulmonary function measured in patients in this study resultedmore from the proximal extent of the fusion or from the extentof the thoracic spine fused. Both of these factors correlated with

decreased forced vital capacity at the time of follow-up and areadmittedly confounding variables.

The study group in the present report was not composedof patients with a single diagnosis. Twenty of the twenty-eightpatients had congenital scoliosis, while eight had other condi-tions associated with the spinal deformity. Although it mightseem logical that pulmonary compromise would occur mostlikely in patients with congenital spine and chest wall malfor-mations, restrictive lung disease was found in patients withcongenital scoliosis, neurofibromatosis, and infantile scoliosis.Because of the small number of patients with diagnoses otherthan congenital scoliosis, no conclusions can be drawn fromthis study with regard to the effect of diagnosis on respiratory

function postoperatively. Goldberg et al., in a report on twenty-three patients with infantile scoliosis, noted that the meanforced vital capacity was 41% (range, 12% to 67%) of normalat maturity in eleven patients who had fusion prior to the ageof ten years, compared with 68% (range, 48% to 88%) in thosewho had a fusionat anolderage16. There is growing support forthe idea that young patients who undergo early fusion are mostat risk for thoracic insufficiency syndrome.

Kim et al. recently reported the results of a comparison of postoperative pulmonary function and preoperative values forpatients with adolescent idiopathic scoliosis17. In a small group of twelve patients who underwent combined anterior and posteriorspinal fusion at a mean age of 13.7 years, the mean forced vital

capacity showed no significant change at the five-year follow-upevaluation, but the normalized percentage of predicted forcedvital capacity significantly decreased from 81% to 70% (p =

0.02). It can be assumed that the younger children in that study must have had growth remaining at the time of surgery since it isknown that forced vital capacity increases in absolute value untilthe age of eighteen years (more so in males than in females).Since a significant decline in pulmonary function following definitive fusion in adolescents was documented in the study by Kim et al. (p < 0.05), it lends further support to the con-cerns that the same surgery performed in much younger chil-dren could result in even greater impairment of lung function.

We chose 50% of predicted forced vital capacity as theindicator of substantial restrictive disease on the basis of thecommon criteria applied by pediatric pulmonologists. Pehrssonet al. reported that when vital capacity is <43%, eventual re-spiratory failure may occur in adults with scoliosis18-20. Eight of our twenty-eight patients had a forced vital capacity of <43%at the time of evaluation and therefore remained at risk. Anadditional expected gradual decline in pulmonary functionmeasurements during adulthood was documented by Burrowset al.21. Furthermore, a decrease in vital capacity of 700 mL canbe expected by the age of sixty in the normal adult male22.Three of our twenty-eight patients were less than ten years oldat the time of the last evaluation, and only two were over theage of twenty years. In light of the pulmonary function testing re-sults in our study, if the patients who had undergone spinal fusionsin early childhood experience such decline throughout their lives,the long-term outcome for their survival is questionable.

Alternative methods of treatment, including growing-rod

instrumentation and expansion thoracoplasty, should continueto be pursued and studied. While these methods are unprovento date, it is hoped that by promoting thoracic growth, pul-monary function at maturity might be better than that docu-mented in this study. Campbell and Hell-Vocke showed thatspinal growth can be measured following sequential lengthen-ings of the vertical expandable prosthetic titanium rib devicein patients with congenital scoliosis who had not had a priorarthrodesis23. Early interim studies of pulmonary function insixteen patients with congenital scoliosis treated by Campbellwith the expansion thoracoplasty protocol found that theforced vital capacity increased over time, while the percentageof predicted normal value for forced vital capacity remained

stable. This would indicate that the lung is able to ‘‘keep up’’with growth following expansion thoracoplasty and the use of the vertical expandable prosthetic titanium rib, as pulmonary function does not ‘‘fall off’’ the growth curve. Emans et al.24

and Motoyama et al.25 documented similar findings in theirpatients with congenital scoliosis treated by expansion thora-coplasty. Emans et al. additionally documented by computedtomography that the three-dimensional volume of the lungsincreases with expansion of the vertical expandable prosthetictitanium rib device24. It remains to be proven that pulmonary growth will continue in longer-term follow-up in this group of patients who have had documented spinal growth23-25.

Theaveragepredicted forced vital capacity forthe twenty-

eight patients in the present study was 58%. This comparesfavorably with the patients treated by Campbell and Hell-Vockewith vertical expandable prosthetic titanium rib devices andexpansion thoracostomy 23. This does not imply that expansionthoracoplasty has created greater pulmonary compromise thanthe traditional anterior-posterior spinal fusion. An explanationfor the variation between the two studies is that all of thepatients in the study by Campbell and Hell-Vocke had morethan three rib abnormalities, and many children were onventilatory support preoperatively, whereas none of the chil-dren in our study were dependent on oxygen or a ventilatorbefore surgery. Additionally, Goldberg et al. reported an av-

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erage forced vital capacity of 42% in their patients who un-derwent fusion at less than ten years of age for treatment of infantile scoliosis compared with the average forced vital ca-pacity of 58% in the present study 16. A critical difference be-tween the studies is that all of the patients in the Goldberg series were mature at the time of follow-up, whereas fifteenpatients in our series were less than fourteen years of age at thetime of the latest evaluation. Since arm span is used to nor-malize pulmonary values in patients with scoliosis, and sincesome of the younger tested patients will continue to grow priorto skeletal maturity while their pulmonary volume cannot in-crease because of the spinal fusion, it is logical but unfortunatethat their predicted pulmonary function values will continueto decrease.

The documentation of obstructive pulmonary disease inten of the twenty-eight patients who were tested was surprising.Many of these patients were unaware that they had obstructivedisease. As bronchodilator treatment can improve pulmonary

function in these patients, we advise pulmonary function test-ing on all patients who have had early spinal fusions, as im-provement in their pulmonary status by medical managementof obstructive disease mightprove helpful to their overall health.

In conclusion, clinically importantrestrictive lung diseasewas found in twelve of the twenty-eight patients who had un-dergone spinal fusion for scoliosis before the age of nine. Poorpulmonary function was linked with extensive thoracic fusionand with fusions with the proximal level beginning at T1 or T2.With the numbers studied, pulmonary function was not foundto be related to length of follow-up nor were we able to identify an age at the time of surgery at which patients would inevitably have pulmonary compromise develop. Obstructive disease was

diagnosed in ten of the twenty-eight patients. On the basis of this information, we recommend routine pulmonary functiontesting in all patients who have undergone spinal fusion prior to

the age of nine years. Young children who require surgicaltreatmentof spinaldeformity that involves a large portion of thethoracic spine and those with proximal thoracic involvementare most at risk for thoracic insufficiency syndrome, and al-ternative treatments should be considered for these children.

Appendix

A table showing data on all twenty-eight study subjects isavailable with the electronic versions of this article, on

our web site at jbjs.org (go to the article citation and click on‘‘Supplementary Material’’) and on our quarterly CD-ROM(call our subscription department, at 781-449-9780, to orderthe CD-ROM). n

Lori A. Karol, MDCharles Johnston, MDRichard H. Browne, PhDDepartment of Orthopaedic Surgery, Texas Scottish Rite Hospital,2222 Welborn Street, Dallas, TX 75219.E-mail address for L.A. Karol: [email protected]

Kiril Mladenov, MDAltonaer Children’s Hospital, Bleickenallee 38,22763 Hamburg, Germany

Peter Schochet, MDDepartment of Pulmonology,Children’s Medical Center of Dallas,1935 Motor Street, Dallas, TX 75235

Patricia Walters, RRT-NPS6422 East Lake Sammamish Parkway, NE#308,Redmond, WA 98052

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Funcion Pulmnar en Escoliosis

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