SHORT COMMUNICATON
Nagoya J. Med. Sci. 85. 333–342, 2023
doi:10.18999/nagjms.85.2.333

Changes in medical costs for adolescent idiopathic scoliosis
over the past 15 years
Kazuyoshi Kobayashi1, Koji Sato1, Toshihiro Ando1 and Shiro Imagama2
Department of Orthopaedic Surgery, Japan Red Cross Aichi Medical Center Nagoya Daini Hospital,
Nagoya, Japan
Department of Orthopaedic Surgery, Nagoya University Graduate School of Medicine, Nagoya, Japan1
2

ABSTRACTUse of instrumentation has become widespread in spinal surgery due to intraoperative spinal cordmonitoring, navigation, and improvement and development of implant materials. However, recent advancesin spine surgery may have also led to an increase in medical costs. The purpose of this study is toinvestigate the trends of operative resource utilization and the costs of surgery for adolescent idiopathic
scoliosis (AIS) over 15 years. Surgery for AIS was performed for 118 patients from January 2004 to
December 2019 at national University Hospital. Trends were examined through retrospective calculationof the costs for outpatient, inpatient, and surgical services, and changes over time and the characteristics
of fees were examined. Differences between groups were analyzed by Mann-Whitney U test and Student
t-test. During the 15-year period, the length of hospital stay decreased, but costs for scoliosis surgery
increased by 1.6 times and the total cost increased by 1.3 times. The fee for intensive care per day perperson increased by 1.5 times. There were slight increases in MRI and CT fees, but no changes in fees
for radiography, rehabilitation, subsequent visits, and prescriptions. New charges for medical supervision,
medical clerk support, medical safety measures, and prevention of infection were added at different times
during the 15-year period. Itemized costs related to surgery have increased with technological advances.
Although these results only show changes in costs for AIS surgery, the findings indicate the challenges
faced by the healthcare economy and the need for spine surgeons to understand medical costs.
Keywords: medical costs, trends, spine surgery, adolescent idiopathic scoliosis, spinal instrumentation
Abbreviations:
AIS: adolescent idiopathic scoliosis
MHLW: Ministry of Health, Labour and WelfareThis is an Open Access article distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
License. To view the details of this license, please visit (http://creativecommons.org/licenses/by-nc-nd/4.0/).

INTRODUCTION
Cost for medical care in Japan have increased from $353.9 billion in 2000 to more than $453.0
billion in 20171 and these costs are a major economic concern for healthcare sustainability. The
Received: April 14, 2022; accepted: July 26, 2022
Corresponding Author: Kazuyoshi Kobayashi, MD, PhD
Department of Orthopeadic Surgery, Japan Red Cross Aichi Medical Center Nagoya Daini Hospital, 2-9
Myoken-cho, Showa-ku, Nagoya 466-8650, Japan
TEL: +81-52-832-1121, Fax: +81-52-832-1130, E-mail: kobak@nagoya2.jrc.or.jp333Kazuyoshi Kobayashi et also-called “bundle payment”, an all-inclusive payment system, was introduced in certain hospitals
in Japan in 2003, and national hospitals, social insurance hospitals, and other centers have used
this system since 2005. An all-inclusive payment for daily administrative fees, examinations,drugs, and imaging, and itemized payments covering surgery and rehabilitation are used forthe costs of hospitalization, with these costs mostly determined officially by the government on
a two-yearly basis. Cost containment and defining healthcare value for patients are now focal
points in Japanese healthcare policy.2-5
Adolescent idiopathic scoliosis (AIS) is a deformity of the spine that causes physical impairment that may lead to back pain and psychosocial difficulties that include lowered self-image
and self-esteem.6-8 Surgery for AIS is performed to correct or prevent progression of curvature of
the spine, and to achieve spinal balance in the coronal and sagittal planes. Surgical treatment for
AIS has evolved and expanded, and currently posterior fixation with a pedicle screw is commonlyused because this procedure reduces revision surgeries and improves radiographic and clinicaloutcomes.9 In recent years, use of instrumentation in spinal surgery has become widespread withadvances in intraoperative spinal cord monitoring, navigation, and implant materials, with similar
trends observed worldwide.
These recent advances in surgery have led to a corresponding increase in medical costs. Manyspine surgeries have been found to be cost-effective, but the surgical costs themselves havereceived less attention.10,11 Therefore, we examined resource utilization in surgery and treatment
costs for AIS, with the goal of defining the value of operative management.
Hospitalization costs in Japan generally include an all-inclusive payment (hospital administration fees per day, medical examination, medication, injection, diagnostic imaging) and an itemized
payment (surgery, rehabilitation), with most costs determined by the government as official medical prices every two years. In the current study, a series of reimbursement prices for spine surgery
were calculated for outpatient, inpatient, and surgical services, and the changes over time and thecharacteristics of the reimbursement were examined. The details of all costs related to treatment
and the costs for examination, surgery and hospitalization were then calculated individually.

MATERIALS AND METHODS
Surgery for AIS was performed for 118 patients, of whom 110 were females, in the period
January 2004 to December 2019 at national University Hospital. A one-stage posterior only approach was used with a pedicle screw and the patient in a prone position. Cases that underwent
anterior surgery, a combination of anterior and posterior surgery, and surgery for syndromic
or congenital scoliosis were excluded. Motor status before surgery and comorbidities were notevaluated as exclusion criteria. Normally, MRI and CT scans were recorded only once before
surgery and once after surgery. A team-based treatment approach was used and there were no
major changes in the treatment policy during the study period. The study was approved by theinstitutional ethical committee.
Demographic, radiographic, and surgical data were reviewed for each case. The Cobb method
was used to determine pre- and postoperative scoliosis, with curves classified using the Lenke
system.12 Spinal cord monitoring using intraoperative brain-evoked muscle-action potentials (Br(E)MsEPs) was performed in all cases. Insertion of pedicle screws with simultaneous passing ofpolyethylene tape under the lamina was performed for all vertebrae. Following local bone graft,rods bent into a good sagittal alignment were positioned on the concave side and rotation was
performed to achieve correction. Ponte osteotomy was used if required. Distraction was applied
to the pedicle screws for correction of the concave side of the curve. For the convex side, theNagoya J. Med. Sci. 85. 333–342, 2023

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Medical costs for AIS

rods were located in situ following local bone graft, and compression between the screws wasused for correction.13,14
The surgeries for AIS were evaluated retrospectively based on the fusion range, number ofscrews, screw density, operative time, estimated blood loss (EBL), and cost of hospitalization andsurgical treatment of AIS for 15 years. Trends were examined for the costs of scoliosis surgery,local bone grafting, hospital administrative fees (intensive care, acute hospitalization) per day,fee for first visit per day, rehabilitation fee per day, subsequent visit fee per day, prescription
fee per day, fee associated with imaging tests (MRI, CT, roentgenography) per person, andnew charges associated with spine surgery care per person. In Japan, an all-inclusive payment
system, a so-called “bundle payment”, was introduced in hospitals with specific functions in
2003. Since 2005, this method has been used in national hospitals, social insurance hospitals, andother centers. Hospitalization costs in Japan generally include an all-inclusive payment (hospitaladministration fees per day, medical examination, medication, injection, diagnostic imaging) andan itemized payment (surgery, rehabilitation), with most costs determined by the government as
official medical prices. Cost containment and definition of the value of healthcare provided topatients has become a focal point in Japanese health care policy. All fees are determined by
the government every two years.
Statistical analysis was performed to evaluate changes in the characteristics of AIS surgery
over the study period. Differences between two groups were analyzed by Mann-Whitney U test
and Student t-test, using SPSS ver. 22 for Windows (IBM, Chicago, IL). P<0.05 was considered
to be significant in all analyses.

RESULTS
The preoperative characteristics of the patients are shown in Table 1. The mean age of the 118
patients at the time of surgery was 14.9 years (range 10–19 years). Surgery was performed in 10
cases in 2004–2005, 12 in 2006–2007, 22 in 2008–2009, 10 in 2010–2011, 19 in 2012–2013, 13
in 2014–2015, 19 in 2016–2017, and 13 in 2018–2019. The pre- and postoperative mean Cobb
angles were 54.9° (range 43°–96°) and 10.8° (1°–41°), respectively, and the correction rate was
80.3% (45.0%–97.6%) (Table 1). The number of patients, fusion range, number of screws, andscrew density for each year are shown in Table 2. Over 15 years, the mean fusion range was
9.9 levels, and 15.3 screws were used per patient at a density of 1.54 screws per fusion range,
with little variation from year to year. Preoperative autologous blood donation and postoperative
blood transfusion were performed in all cases. There were no postoperative neurological deficits.
Regarding costs defined by the Ministry of Health, Labour and Welfare (MHLW) during the
15-year period, fees for scoliosis surgery and for local bone graft both increased steadily. Costs
for scoliosis surgery increased from $3283 to $5278 (about 1.6 times) and those for local bone
grafting increased from $783 to $1588 (about 2.0 times) in 15 years (Figure 1).
There was a slight increase in first visit fees and the fee for acute hospitalization, and thefee for intensive care per day per person increased by 1.5 times (Figure 2). There was a slightincrease in MRI and CT fees, but radiography fees remained the same (Figure 3). There were no
increases in the fees for rehabilitation, subsequent visits, and prescriptions (Figure 4). However,a charge for medical supervision was added, followed by charges for a medical clerk in 2006,
for medical safety measures in 2008, and for prevention of infection in 2012 (Figure 5). There
were decreases in costs of surgical instruments such as screws (Figure 6). The proportion ofsurgical costs among the total costs also increased over time (Figure 7) and showed a significant
increase in 2018–2019 compared to 2004-2005 (p<0.05).
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Kazuyoshi Kobayashi et al

Table 1

Demographic and operative data (n=118)

PeriodTotal(n=118)

Factor2004-2008(n=32)

2009-2013(n=41)

2014-2019(n=45)

14.1±2.4

14.9±2.6

15.4±2.3

Demographic data
Age (years)

14.9±2.5

Female (n)110 (93%)29 (91%)39 (94%)42 (93%)Height (cm)155.4±8.2

153.5±8.0156.2±8.3

156.0±8.4

Body weight (kg)47.5±8.946.1±8.548.2±8.947.8±9.0

35 (30%)10 (29%)11 (31%)14 (40%)

Lenke classification (n)Type 1
Type 221 (18%)5 (24%)

7 (33%)

9 (43%)

Type 313 (11%)

3 (23%)

6 (46%)

4 (31%)

Type 46 (5%)

2 (33%)

1 (17%)

3 (50%)

Type 529 (25%)8 (28%)

11 (38%)10 (34%)

Type 614 (12%)4 (29%)

5 (35%)

5 (36%)

54.9±14.1

52.2±13.955.1±14.0

56.4±14.4

Operative time (min)297±82289±80299±83301±85

Estimated blood loss (mL)

763±547748±526776±551762±547

Postoperative Cobb angle (°)

10.8±7.1

10.1±6.3

12.2±6.8

10.0±7.2

Preoperative Cobb angle (major curve) (°)
Procedural variables

OutcomeCorrection rate (%)

80.3±11.7

80.9±12.6

78.3±11.4

81.7±12.3

Average length of stay (days)

20.6±9.822.4±9.4

20.9±10.1

19.0±9.7

Postoperative surgical site infection

2 (1.6%)

1 (1.6%)

1 (1.6%)0 (0%)

Data are shown as the mean ± standard deviation or a number.

Table 2Year

Trends in fusion range, number of screws, and screw density over time for 15 years

Patients (n)Fusion range

Number of screws

Screw density*

2004–2005

10

9.5

15.2

1.60

2006–2007

12

10.2

15.9

1.56

2008–2009

22

9.8

14.7

1.50

2010–2011

10

10.0

15.1

1.51

2012–2013

19

9.6

14.1

1.47

2014–2015

13

10.3

15.3

1.49

2016–2017

19

10.4

16.1

1.59

2018–2019

13

9.7

15.9

1.64

Total

83

9.9

15.3

1.54

Screw density is reported per vertebral level.

*

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Medical costs for AIS

Fig. 1 Trends in fees for scoliosis surgery and local bone graft per person,
as defined by the Ministry of Health, Labour and Welfare

Fig. 2 Trends in individual reimbursement fees for intensive care, acute hospitalization,and first visit per person per day over time

Fig. 3 Trends in fees associated with imaging tests (MRI, CT, roentgenography) over time
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Kazuyoshi Kobayashi et al

Fig. 4 Trends in fees for rehabilitation, subsequent visits, and prescriptions per person over time

Fig. 5 Trends in new charges associated with spine surgery care (medical clerk, prevention of infection,
medical safety measures) per person

Fig. 6
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Medical costs for AIS

Fig. 7 Total costs and proportion due to surgical costs (per person)*p<0.05 for 2004–2005 vs 2018–2019

DISCUSSION
The Diagnosis Procedure Combination (DPC) for “bundle payment” of medical expenses wasintroduced in Japan in 2003.15,16 and by 2015 this system was used for about 55% of general
hospital beds.17 Using the DPC, an all-inclusive payment is calculated based on the classified“diagnosed disease”. This approach is distinct from that using an “itemized payment” for thecost of each medical procedure. The diagnosed disease determined by the MHLW is used toestablish a total cost, which is calculated from the all-inclusive (drugs, treatment, examination,
imaging, hospital fees, etc) and itemized (surgery, anesthesia, rehabilitation, etc) payments. Thus,
the all-inclusive payment is unchanged, regardless of the usage level of drugs and imaging,whereas surgery and rehabilitation expenses are itemized.
Evaluation of the costs of AIS surgery is particularly important because most patients who
undergo this surgery are younger (10 to 20 years old) than those treated for other diseases,
and most have no serious medical history. Therefore, the postoperative course until discharge isnormally very good and there are few postoperative complications. There have also been few
reports focusing on this surgery to date. In a retrospective review, Kamerlink et al18 found hospitalcosts of $29,955 to $60,754 for surgery for AIS, with implants, intensive care unit (ICU) costs,
time in the operating room, and bone grafts being the most important elements. Reimbursement
for primary surgical treatment of AIS is more closely linked to surgery costs, rather than generalcosts.18 Increased spending on implants per level fused has been found to be positively related
to the % Cobb angle correction.19 However, the details over time of government-determined
medical costs, such as surgical costs and hospital administration fees, have not been examined.
Orthopedic surgery is a specialty that is implant-intensive, and this is a major contributor to thetotal cost of care. This is especially true of spine surgery, and surgeons improve operative carethrough adaptations in techniques or implants. Competitive group pricing is a common strategy
used in Europe and the United States to reduce the cost per implant.20-22 In contrast, Japan has
used public health insurance since 1961, through which all people receive equal treatment, andcost reimbursements are calculated by the MHLW every two years. The cost of surgery, including
implant surgery, does not vary widely among hospitals and manufacturers in Japan, and there isno difference among hospitals in the total costs charged to patients. The self-payment amountis low because universal insurance is available for the whole population.
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In this study, the fees for hospitalization, first visit, and rehabilitation barely increased overtime, and thus, the trends reflect recent government policies aimed at control of medical costs.
These results may be due to these aspects of treatment not being directly involved in thesurgical procedure. Over the past 15 years, costs for outpatient consultations, prescriptions,and imaging tests have generally remained unchanged. In addition, the price of the screw was
found to have decreased over the years, and the delivery price has also decreased. There was
essentially no change in the indications in the surgical plan over the last 15 years. However,the MHLW-defined costs for scoliosis surgery have increased by about 1.6 times over 15 years,
and fees for intensive care have increased by 1.5 times in 15 years. The total medical expenses
for this surgery also increased, despite the decrease in the length of the hospital stay. Surgicalprocedure and ICU management fees have increased, and additional costs for medical safetymeasures and physician administrative support systems have been added. These changes reflect
fees for surgeries and postoperative management requiring a high level of expertise, ensuring
medical safety, and reducing the workload of physicians. An understanding of these issues isvery important to the surgeon. The changes may reflect the value the MHLW places on advanced
surgery with good outcomes, under current economic conditions. An understanding of the trendsof costs for surgical spinal intervention is useful for assessment of the treatment benefit and islikely to have an influence on healthcare costs.
This study has several limitations. First, the number of cases was limited because the facility
is a national university hospital and we focused on AIS treated with a posterior approach overa relatively short 15-year period. Second, the costs examined were mainly those for hospitalization, during which a pediatric patient pays only bed and meal fees due to preferential treatmentof these patients in Japan. The cost to the patient was mainly examined in this study, and thedetails of other indirect costs (ie, round-trip costs to medical institutions, and time and costrequired of the family to allow the patient to receive medical care) were not examined. Third,
among spinal surgeries, the number of AIS surgeries is relatively small and there is no evidence
that AIS itself has led to an increase in medical costs. We did not investigate trends in spinal
surgeries other than for AIS. However, despite the lack of details of medical care, this is thefirst report of Japanese medical costs in AIS and may reflect the current medical economy inJapan, as the most rapidly aging society worldwide. We also note that a longitudinal study
in one hospital has an advantage of low variation of confounding factors, including operating
room protocols, surgical and anesthetic methods, pain regimens after surgery, and rehabilitation
protocols. Therefore, the results of this study provide a unique understanding of the costs andclinical approach to management of AIS.

CONCLUSION
The results of this study show that itemized costs related to surgery have increased withtechnological advances. The increase in intensive care fees and the establishment of additionalcharges for medical safety measures and for physician support systems reflect the desire forsurgical procedures and postoperative management that require a high level of expertise, as
well as ensuring medical safety and reducing the workload of physicians. This examination of
medical costs in AIS surgery revealed trends that reflect problems in medical economics. These
trends are a challenge for the healthcare economy and show the importance of spine surgeons
understanding medical and surgical costs.

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Medical costs for AISDISCLOSURE STATEMENT
Financial support was from institutional sources only. None of the authors have a conflict ofinterest to declare.

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