Spine Deformity 3 (2015) 52e56www.spine-deformity.org

National Trends in Spinal Fusion Surgery For Scheuermann KyphosisAmit Jain, MD, Paul D. Sponseller, MD, Khaled M. Kebaish, MD, Addisu Mesfin, MD*

Department of Orthopaedic Surgery, The Johns Hopkins University, 601 N. Caroline Street, Baltimore, MD 21287, USA

Received 11 March 2014; revised 12 May 2014; accepted 18 June 2014

Abstract

Study Design: Analysis of a national database.Objective: To analyze national trends in spinal fusion surgery for Scheuermann kyphosis (SK) and to compare surgical approaches used intreatment.Summary of Background Data: The preferred surgical approach for treating SK is not well established. Recent studies support the use ofposterior spinal fusion (PSF) instead of anterior-posterior spinal fusion (APSF).Methods: Using the Nationwide Inpatient Sample database, we identified 2,796 patients (mean age, 24.9 years; 66% men) from 2000 to2008 who had spinal fusion surgery for SK. We compared the two approaches with respect to patient demographics, institutional char-acteristics, in-hospital complications, and hospitalization lengths and costs. Significance was set at a value of p less than .05.Results: The number of spinal fusion surgeries performed in patients with SK increased significantly (p 5 .03). The proportion of patientsundergoing surgery as adults also increased significantly (p ! .05). The number of PSF surgeries performed in patients with SK increased2.9-fold (34% to 78%) (p ! .01); APSF use declined by 7% per year. There was no significant association among surgical approach andpatient age, sex, hospital capacity, or teaching status. Compared with patients undergoing PSF, patients undergoing APSF had 2.1-fold morein-hospital complications (p ! .01), 3.8-fold more pulmonary complications (p ! .01), 2.7-fold more renal complications (p ! .01), andsignificantly longer hospitalizations (mean, 8.5 days vs. 5.9 days, respectively; p ! .01). There was no significant difference in mean totalhospital charges: $117,921 for APSF and $119,322 for PSF.Conclusion: There have been significant increases in the number of spinal fusion surgeries for SK, and in the proportion of patients withSK who are choosing surgery as adults. Surgical treatment has shifted predominantly toward an all-posterior approach. PSF is associatedwith lower complication rates (especially pulmonary complications) and shorter hospitalizations.� 2015 Scoliosis Research Society.

Keywords: Scheuermann kyphosis; Spinal fusion; Pediatric deformity; Posterior fusion; Complications

Introduction

Scheuermann kyphosis (SK) is a structural deformitycharacterized by anterior vertebral angulation or‘‘wedging’’ in the thoracic spine of three adjacent vertebraeby at least 5�. It most commonly develops in earlyadolescence and has been reported to occur in 0.4% to 8%of the population, without predominance in either sex [1,2].In contrast, idiopathic hyperkyphosis is a clinical entity thatdescribes a pattern of kyphosis over many segments.

Author disclosures: none.

*Corresponding author. c/o Elaine P. Henze, BJ, ELS, Medical Editor

and Director, Editorial Services, Department of Orthopaedic Surgery, The

Johns Hopkins University/Johns Hopkins Bayview Medical Center, 601 N.

Caroline Street, Baltimore, MD 21287, USA. Tel.: (410) 550-5400; fax:

(410) 550-2899.

E-mail address: ehenze1@jhmi.edu (A. Mesfin).

2212-134X/$ - see front matter � 2015 Scoliosis Research Society.

http://dx.doi.org/10.1016/j.jspd.2014.06.009

Together, SK and idiopathic hyperkyphosis account formost patients with thoracic hyperkyphosis. Although pa-tients with less severe deformities are usually treated withnonoperative methods, some patients require surgicalintervention. Although there is no consensus on the abso-lute indications for surgical treatment, the literaturegenerally supports surgery for patients with severe pro-gressive deformities larger than 70�, especially in thepresence of refractory pain, neurologic deficit, reduction infunction, or development of severe disability as a result ofthe deformity [3].

When performing spinal fusion surgery, the decisionregarding whether to perform a posterior spinal fusion(PSF) or an anterior-posterior spinal fusion (APSF) hasbeen a topic of debate. In the older literature, some groupsrecommended using APSF as the treatment of choice [4,5]because of concern of loss of correction without the

53A. Jain et al. / Spine Deformity 3 (2015) 52e56

additional anterior fusion. However, others stated that un-less the deformity is rigid and in need of anterior releases,PSF is adequate in most cases [6-10].

In a recent study of 27 patients, Johnston et al. [11]concluded that anterior release and fusion procedures areno longer necessary when posterior column-shorteningprocedures and modern rod instrumentation techniquesare used. In addition, Lee et al. [12] showed that APSF wasassociated with longer operating times, higher intra-operative blood losses, and more complications. However,both of those studies, along with most of the SK literature,focused on clinical outcomes from individual institutionsand did not provide a national perspective on the surgicaltreatment of SK.

The aim of our study was to analyze the national trendsin the use of spinal fusion surgery for SK and to comparesurgical approaches used in treatment.

Patients and Methods

Data source

The Nationwide Inpatient Sample (NIS) database,maintained by the Agency for Healthcare Research andQuality (Rockville, MD), was used for data collection. TheNIS is the largest inpatient database in the United Statesand contains approximately 20% sample of inpatient ad-missions to adult and pediatric hospitals in the UnitedStates. General and specialty hospitals such as thosefocusing exclusively on pediatrics are included in the NISsampling. Because this database is publicly available, ourstudy was exempt from institutional review board approval.

Data extraction

We queried the database from 2000 through 2008 toidentify all patients who underwent spinal fusion surgery(using primary procedural clinical classification softwarecode 158).

The International Classification of Diseases, NinthRevision, Clinical Modification (ICD-9-CM [13]), diag-nostic code ‘‘732.0: juvenile osteochondrosis of spine,excluding adolescent postural kyphosis’’ was used toidentify all patients with a diagnosis of SK. In this manner,2,796 patients were identified who presumptively had adiagnosis of SK and had received spinal fusion surgeryduring the study period.

For these patients, the database was used to query for thefollowing variables: patient demographics (patient’s sex,race, and age at surgery), institutional characteristics(hospital teaching status, bed capacity, and location in theUnited States), length of stay, and total hospitalizationcosts. Patients were divided by age into two groups: thosewho received surgery as adolescents (younger than age 18years) and those who received surgery as adults (aged 18years or older). The NIS database classifies hospitals as‘‘large’’ or ‘‘small/medium’’ based on bed capacity. The

NIS database also labels hospitals as ‘‘teaching’’ or‘‘nonteaching’’ based on their status.

Complications data

The ICD-9-CM codes were also used to query for majorin-hospital complications using previously describedmethodology [14]. Major complications were defined asthose that required a return to the operating room or thatcould have potentially long-term sequelae.

We collected data on the following complications.Neurologic complications were defined as perioperative ce-rebrovascular infarction or hemorrhage, and nervous systemcomplications from surgery or a surgically implanted devicesuch as sensory or motor changes after surgery. Cervical-spine-related complications were defined as injury to bloodvessels of head and neck (carotid artery, internal jugular vein,external jugular vein, etc), injury to the cervical sympa-thetics, paralysis of the vocal cords or larynx, hoarseness oraphonia, and dysphagia. Pulmonary complications weredefined as postoperative pulmonary insufficiency, acuterespiratory distress or failure, pneumonia, and iatrogenicpneumothorax. Cardiac complications were defined as car-diac arrest or insufficiency, heart failure, acute myocardialinfarction, and postoperative shock. Thromboembolic com-plications were defined as deep venous thrombosis and pul-monary embolism. Renal complications were defined aspostoperative acute renal failure or insufficiency, and post-operative tubular necrosis. Gastrointestinal complicationswere defined as acute vascular intestinal insufficiency,including bowel infarction and mesenteric ischemia. Infec-tious complications were defined as postoperative deepwound infection, sepsis, and bacteremia.

We excluded transient complications such as atelectasis,ileus, oliguria, seroma, hematoma, and urinary tract infec-tion from the complications analysis.

Statistical methods

For each variable, national estimates were created usingthe stratified samplings weights provided with the NISdatabase. In designing the NIS, the United States Agencyfor Healthcare Research and Quality use a stratified prob-ability sampling scheme in which hospitals sampled arerepresentative of the type of hospitals in each stratum, thusallowing for creating of national estimates with high fi-delity. Linear regression models were used to analyzetrends over time. The chi-square test was used to analyzethe associations among surgical approach and patient sexand hospital teaching status. Analysis of variance methodwas used to analyze association among surgical approachand hospital bed capacity and hospital location. The Stu-dent t test was used to compare length of stay and totalhospitalization costs between the two groups. The Z-test ofproportion was used to compare complication rates be-tween the two groups. Statistical significance was set at a pvalue less than .05 for all analyses.

54 A. Jain et al. / Spine Deformity 3 (2015) 52e56

Results

Population demographics

Overall, the mean age at surgery was 24.9 � 13.8 years;47% of patients were younger than age 18 years and 53%were aged 18 years or older when they underwent surgicaltreatment. Most (66%) patients who had surgery were men;34% were women. Distribution by race was as follows:88%, white; 7%, Hispanic; 1%, African American; 0.6%,Asian; 3.4%, not classified.

Trends in spinal fusion

Fig. 2. Over the study period, the percentage of patients who underwent

surgery as adults increased significantly.

During the study period, there was a significant increasein the number of patients with SK who underwent spinalfusion surgery (p 5 .03) (Fig. 1).

There was a modest but statistically significant increasein the percentage of patients who underwent surgery asadults (p ! .05) (Fig. 2). In 2000, 55% of the patientsunderwent surgery as adolescents; however, by 2008, 60%of patients had surgery as adults. In the group of patientsyounger than age 18 years, 95% were aged 15 to 16 years.In the group of patients aged 18 years or older, 95% wereaged 25 to 33 years.

Trends in use of specific approaches

During the study period, the number of PSF surgeriesperformed in patients with SK increased 2.9-fold;they accounted for 34% of the spinal fusion surgeriesin 2000 and 78% of the surgeries in 2008(p ! .01) (Fig. 3).

The rate of decline in APSF during the study period was7% per year. Although initially less common, PSF becamemore common than APSF in 2004. The most significantdecline in use of APSF was between the years 2005 and2006, when there was more than a 50% drop in APSFsurgeries performed nationally.

Fig. 1. From 2000 to 2008, there was a significant increase in the number

of patients undergoing spinal fusion surgery.

Patient demographics and approach

There was no significant difference in the mean age ofpatients by surgical approach (p 5 .61): 23.9 � 14.0 yearsfor the PSF group and 24.5 � 12.5 years for theAPSF group.

There was also no significant association between pa-tient sex and surgical approach (p 5 .07).

Institutional characteristics and approach

There was no significant association between hospitalcapacity and the surgical approach (p 5 .08): 58.6% of thePSF surgeries and 58.4% of the APSF surgeries were per-formed in hospitals classified as ‘‘large’’ bed capacity in theNIS database.

There was also no significant association betweenthe hospital’s teaching status and the surgical approach

Fig. 3. National trends in surgical approach for Scheuermann kyphosis

treatment, 2000 to 2008. APSF, anterior-posterior spinal fusion. PSF, pos-

terior spinal fusion.

Table

Complication rate by surgical approach after spinal fusion surgery for

Scheuermann kyphosis.

Category APSF (%) PSF (%) p value

Neurologic 0.43 0.86 .17

Cervical-spine-related 0 0.31 .06

Pulmonary 13 3.44 !.01*

Cardiac 0.85 1.23 .34

Thromboembolic 0.43 0.62 .50

Renal 2.31 0.86 !.01*

Gastrointestinal 0 0 e

Infectious/wound 0.77 1.23 .24

APSF, anterior-posterior spinal fusion; PSF, posterior spinal fusion.* The difference is statistically significant.

55A. Jain et al. / Spine Deformity 3 (2015) 52e56

(p 5 .13): 85% of the PSF surgeries and 83% of the APSFsurgeries were performed at teaching institutions.

Approach and complications

The rate of in-hospital major complications after spinalfusion surgery was 2.0-fold higher in patients undergoingAPSF than in patients undergoing PSF (17.8% vs. 8.5%,respectively; p ! .01) (Table). Patients undergoing APSFhad a 3.8-fold higher rate of pulmonary complications (p!.01) and a 2.7-fold higher rate of renal complications (p !.01) than did patients undergoing PSF.

The overall rate of complications decreased over thecourse of the study period, from 22.6% in 2000 to 15.5% in2008 (p 5 .03).

Approach and length of stay/total hospitalizationcosts

The mean length of hospitalization was significantlylonger for patients undergoing APSF surgery than for pa-tients undergoing PSF surgery (8.5 days vs. 5.9 days,respectively; p ! .01).

There was no significant difference in the mean totalhospital charges by approach (p 5 .8): $117,921 for APSFsurgery and $119,322 for PSF surgery.

Discussion

The surgical treatment of SK has been evolving over thelast few decades with the introduction of newer instru-mentation. Some of the earlier investigations of spinalfusion in patients with SK were conducted by Bradfordet al. in the 1970s [15] and 1980s [4]. In 1975, their groupreported on the use of PSF with Harrington instrumentationin 22 patients; they found substantial loss of correction withhigh rates of nonunion in most patients [15]. In hopes of‘‘improving the correction and preventing deteriorationafter correction,’’ they began using the APSF technique forsuch patients [4]. They found that they could achieve, onaverage, improved correction and a lower incidence ofpseudarthrosis using the APSF method with Harringtoninstrumentation.

As segmental instrumentation became popular in spinesurgery, the literature on surgical treatment of SK started tofavor the use of anterior releases followed by posteriorsegmental instrumentation [16]. In a study of 32 patients withkyphosis larger than 75�, Lowe and Kasten [16] reported anaverage correction at final follow-up of 43� after an APSFapproach involving Cotrel-Dubousset instrumentation. Inanother study in patients with SK where segmentalcompression instrumentation was used, Papagelopoulouset al. [8] reported that PSF and segmental compressioninstrumentation was effective for correcting and stabilizingkyphotic deformity in most patients; they recommendedAPSF in conjunction with segmental instrumentation for therigid and severely kyphotic deformities.

Over the last decade, as modern instrumentation becamemore popular, the literature on SK surgical treatmentcontinued to evolve. In a study of 23 patients with SK whounderwent spinal fusion using current-generation segmentalinstrumentation, Lim et al. [17] showed that correction ofdeformity in patients with SK could be achieved safely andeffectively using the modern instrumentation. In their study,87% of patients underwent combined APSF, and there wasa 60% rate of major and minor complications.

As pedicle screw constructs started to gain widespreadpopularity, the utility of the anterior release and fusionprocedures for patients with SK came into question. In astudy of 27 patients at the Texas Scottish Rite Hospitalundergoing correction of adolescent hyperkyphosis withposterior threaded rods, Johnston et al. [11] concluded thatthe traditional APSF technique provides no additionalimprovement in radiographic outcome compared withposterior-only surgery when modern instrumentation andposterior column-shortening procedures are used. In a studyof 18 patients with SK, Lee et al. [12] showed that all-posterior pedicle screw instrumentation led to less oper-ating time and intraoperative blood loss compared with theAPSF approach.

In the current study, we have reported the nationaltrends over the last decade in the surgical treatment of SK,documenting a significant increase in the total number ofspinal fusions performed for the treatment of SK and asignificant increase in patients choosing to have surgery asadults. We have also shown that although the APSFapproach was used in most SK operations in 2000, the useof anterior-posterior approaches in patients with SK haddropped markedly by 2008, and PSF became the predom-inant treatment option. We conjecture that the total numberof SK surgeries increased from 2000 through 2008 prob-ably because the posterior-only approach was moreappealing to patients and surgeons.

Although we did not find a relationship among surgicalapproach used and patient factors (age and sex) or institu-tional factors (hospital capacity or teaching status), we didfind that patients undergoing PSF had significantly lowerpulmonary (3.4% vs. 13%) and overall (8.5% vs. 17.8%)complication rates. These findings are consistent with those

56 A. Jain et al. / Spine Deformity 3 (2015) 52e56

of Lonner et al. [18]; in that study of 78 patients with SK,major complications developed in 24% of patients in theAPSF group and in only 6% of the patients in the PSF group.

Although we found that patients undergoing PSF hadsignificantly shorter hospital stays than those undergoingAPSF (5.9 vs. 8.5 days, respectively), we were surprised bythe lack of difference in hospital charges between the twosurgical approaches. We hypothesize that pedicle screwdensity is lower in the APSF group than in the PSF group;however, this hypothesis warrants further investigation.

Our study has several limitations. First, the NIS capturesonly data included in the patient discharge information anddoes not track the patient’s clinical course in a longitudinalfashion. As a result, we could not analyze the perioperativeand long-term complications that might have developedafter the patient was discharged from the hospital. Thispoint is quite important when comparing surgical ap-proaches because each approach may be associated with adifferent set of long-term sequelae and complications.Second, using the NIS, we could not identify the severity ofthe deformity, the specific indications for surgery, the typeof instrumentation used, the use of posterior column-shortening osteotomies, or the number of spinal levelsfused. Therefore, we were not able to control for thesepotential confounders when analyzing the complication andlength of hospitalization data. Third, we were not able todistinguish between patients with SK and those with idio-pathic hyperkyphosis. There is no separate ICD-9-CM codefor the latter, and we suspect that many patients with thatcondition might be coded as SK. Finally, the NIS databasedoes not contain clinical, radiographic, or functionaloutcome data, which would be ultimately needed tocompare treatment choices. However, despite these limita-tions, this study is the largest series focusing on patientswith SK, and it provides insight into recent treatment trendsand complications.

Conclusions

We found that a significant number of patients with SKare choosing surgery as adults and that over the last decadethe surgical treatment of SK has shifted predominantlytoward an all-posterior approach. There was no differencein the two approaches with respect to patient demographicsor institutional characteristics. However, patients with SKundergoing PSF had significantly lower complication rates(especially pulmonary complications) and shorter hospitalstays than did patients undergoing APSF.

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