Orthopedics

Feature Article 

Secondary Surgery Rates After Primary Fusion for Adolescent Idiopathic Scoliosis

Joseph H. Dannenbaum, MD; Bryan J. Tompkins, MD; William B. Bronson, MD; Mark L. McMulkin, PhD; Paul M. Caskey, MD

Abstract

Instrumented spinal fusion is the gold standard treatment for surgical magnitude adolescent idiopathic scoliosis (AIS), with the goal being stable fusion without the need for additional procedures. The purpose of this study was to define the surgical return rates of AIS at a single center with respect to various instrumentation constructs used during initial spinal fusion. A retrospective chart review was performed of all patients with AIS who underwent instrumented fusion with a minimum of 2-year follow-up. Demographic information, implant type, and surgical approach for the primary surgery and all subsequent secondary operations were recorded. Four hundred eleven patients who underwent instrumented fusion for AIS during the study period met inclusion criteria. Sixty-six secondary operations were performed in 50 patients (12.2%). Symptomatic hardware, pseudarthrosis, and infection were the most common indications for secondary surgery. Posterior pedicle screw constructs had a lower secondary surgery rate (5.8%) compared with hybrid and combined fusions (P<.05). The all hook, hybrid, anterior only, and combined fusions had secondary surgery rates of 13.0%, 18.5%, 10.0%, and 20.8%, respectively, which were not statistically different. When specifically comparing pedicle screw with hook constructs, there was a statistically lower pseudarthrosis rate (P=.03) favoring pedicle screw instrumentation. Patients undergoing instrumented fusion for AIS are at some risk for subsequent surgery. To lessen that risk, pedicle screw constructs should be considered, as they have shown an overall lower secondary surgery rate and in particular a lower rate of pseudarthrosis. [Orthopedics. 2019; 42(4):235–239.]

Abstract

Instrumented spinal fusion is the gold standard treatment for surgical magnitude adolescent idiopathic scoliosis (AIS), with the goal being stable fusion without the need for additional procedures. The purpose of this study was to define the surgical return rates of AIS at a single center with respect to various instrumentation constructs used during initial spinal fusion. A retrospective chart review was performed of all patients with AIS who underwent instrumented fusion with a minimum of 2-year follow-up. Demographic information, implant type, and surgical approach for the primary surgery and all subsequent secondary operations were recorded. Four hundred eleven patients who underwent instrumented fusion for AIS during the study period met inclusion criteria. Sixty-six secondary operations were performed in 50 patients (12.2%). Symptomatic hardware, pseudarthrosis, and infection were the most common indications for secondary surgery. Posterior pedicle screw constructs had a lower secondary surgery rate (5.8%) compared with hybrid and combined fusions (P<.05). The all hook, hybrid, anterior only, and combined fusions had secondary surgery rates of 13.0%, 18.5%, 10.0%, and 20.8%, respectively, which were not statistically different. When specifically comparing pedicle screw with hook constructs, there was a statistically lower pseudarthrosis rate (P=.03) favoring pedicle screw instrumentation. Patients undergoing instrumented fusion for AIS are at some risk for subsequent surgery. To lessen that risk, pedicle screw constructs should be considered, as they have shown an overall lower secondary surgery rate and in particular a lower rate of pseudarthrosis. [Orthopedics. 2019; 42(4):235–239.]

Instrumented fusion has become the gold standard for the definitive management of surgical magnitude adolescent idiopathic scoliosis (AIS). In large adolescent population studies, the overall incidence of scoliosis is 4.5%, with higher magnitude curves being more prevalent in females.1 The incidence of surgical magnitude curves ranges from 0.1% to 0.3% in the adolescent population, with higher rates of curve progression.2–4

The goals of surgical treatment for AIS are to obtain a stable fusion during the initial surgery without the need for additional future procedures. In a large review of the Scoliosis Research Society Morbidity and Mortality database, the complication rate for AIS surgery was reported to be 6.3%.5 However, this rate was based on operative and perioperative complications occurring up to 30 days after surgery and not necessarily a reoperation rate for concerns such as pseudarthrosis or symptomatic hardware. Historical literature has shown that reoperation rates range from 3.9% to 19%.6–13 The purpose of this study was to define the secondary surgery rates in AIS following primary fusion at a single referral-based pediatric center and to compare the secondary rates among various instrumentation constructs used during the definitive instrumented spinal fusion.

Materials and Methods

Institutional review board approval was obtained prior to conducting this study. This was a retrospective review of all spine procedures performed at a single pediatric orthopedic surgical hospital. Patients older than 10 years but younger than 19 years with AIS who underwent definitive instrumented fusion at the authors' institution during a 21-year period (January 1, 1990, through December 31, 2011) were included. Patients were excluded if they had a diagnosis of congenital, infantile, juvenile, or neuromuscular scoliosis or if the primary fusion procedure had been performed at another institution.

Surgical logs were reviewed for all spine surgeries performed at the hospital during the study period. At least 2-year follow-up from the definitive instrumented fusion was required. Patient demographics, date of surgery, age at surgery, diagnosis, surgical approach, instrumentation construct, subsequent reoperations, and the primary indication for reoperation surgery were recorded. For the purpose of this study, reoperation was defined as any unintended surgical procedure performed after the index definitive operation. Reoperations for infection often required serial irrigation and debridement during the hospitalization, which, for this review, were considered a single surgical reoperation. Symptomatic hardware was defined as pain overlying a symptomatic implant or pain in the region of the hardware not explained by evidence of pseudarthrosis or infection.

Statistical analysis was performed using the 2-tailed Student's t test to compare proportions. P<.05 was considered statistically significant.

Results

A total of 829 patients underwent spine surgery during the 21-year study period (40 spine surgeries per year). Of these, 418 patients were excluded: 202 with a neuromuscular diagnosis, 87 with kyphosis or another concern, 80 with congenital scoliosis, 17 who were older than 19 years, and 32 for whom charts could not be located. The remaining 411 patients with AIS underwent instrumented spinal fusion and were included in the study. The mean age at the time of the index procedure was 14.8±1.9 years (range, 10.2–18.9 years). The procedures were performed by 6 pediatric spine surgeons; however, during the study period with staff turnover, only 3 surgeons each year performed surgeries (approximately 13 total spine surgeries per year per surgeon, approximately 7 per year per surgeon included in the study).

Of the 411 included patients, 50 patients (12.2%) underwent a least 1 secondary procedure. There were a total of 66 secondary procedures during the study period: 37 patients underwent 1 secondary surgery, 11 patients underwent 2 secondary procedures, 1 patient underwent 3 secondary surgeries, and 1 patient underwent 4 secondary surgeries. Overall, multiple additional surgeries occurred in 13 (26%) of the current 50 patients who underwent secondary surgeries. Of the 66 secondary surgical interventions performed in the 50 patients, the most common indications at the time of reoperation were symptomatic hardware, pseudarthrosis, and infection (Table 1).

Indications for Secondary Surgery

Table 1:

Indications for Secondary Surgery

Symptomatic hardware requiring secondary surgery was the most common indication for additional surgeries. This occurred in 5.8% of the patient population (26 reoperations in 24 of 411 patients). The most common site of prominence was inter-rod cross-links. Pseudarthrosis occurred in 4.1% of patients who underwent reoperations (18 secondary surgery cases in 17 patients). Pseudarthrosis was confirmed at the time of secondary surgery. One patient developed a pseudarthrosis secondary to metallic allergy. This was complicated by an infection and required a later staged removal of implants and subsequent revision instrumented fusion with titanium implants. The patient went on to definitive fusion without further complications. Twelve of the reoperations were due to infection at the time of the additional surgery, and 2 additional cases of deep infection were diagnosed at subsequent secondary surgeries. These 14 reoperations occurred in 13 patients. Based on this analysis, the historical infection rate for this cohort was 3.2% after definitive fusion for idiopathic scoliosis.

Regarding surgical approach, there were no statistically significant differences among overall posterior, anterior, and combined approaches (Table 2). There was a trend toward a lower secondary surgery rate in the posterior approach group (11.1%) compared with the combined posterior and anterior approach group (20.8%; P=.056). There was no statistical difference in age between these various subgroups.

Comparison of the 3 Approachesa

Table 2:

Comparison of the 3 Approaches

The secondary surgery rates for the different types of specific constructs were compared (Table 3). Only 3 patients had wire only constructs—too few for comparison with other groups. The posterior pedicle screw construct had a lower secondary surgical rate (5.8%) compared with the posterior hybrid construct (18.5%) and with the combined anterior and posterior fusion approach (20.8%) (Table 3). There was also a trend toward lower secondary surgery rates in the pedicle screw group compared with the posterior hook only construct group (13.0%; P=.054).

Comparison of Reoperation Rates by Constructsa

Table 3:

Comparison of Reoperation Rates by Constructs

On comparison of the 3 most common secondary surgery complications between the posterior pedicle screw and the hook constructs, there was no pseudarthrosis in the posterior pedicle screw constructs compared with 9 cases in the hook constructs, which was statistically significant (Table 4). However, no significant differences in secondary surgical rates for symptomatic hardware or infection were seen between pedicle screw and hook constructs.

Comparison of Types of Complications by Posterior Surgical Constructs

Table 4:

Comparison of Types of Complications by Posterior Surgical Constructs

Discussion

Surgical magnitude curves are routinely managed with a single definitive spinal fusion with instrumentation. Complications including risks of infection, neurologic injuries, pseudarthrosis, and the need for further surgeries are common concerns among patients, their families, and surgeons. These complications have a negative effect on outcomes and frequently result in additional health care cost. The overall secondary surgical rate was found to be 12.2%. However, the posterior pedicle screw construct was found to have a lower secondary surgical rate (5.8%) than the posterior hybrid (18.5%) and the combined anterior and posterior (20.8%) constructs.

Previous studies have evaluated the complication rates during the past several decades. Lenke et al8 reported a reoperation rate of 5.2% for their 95 patients using Cotrel-Dubousset instrumentation. Bago et al12 and Cook et al9 reported higher reoperation rates of 17.3% for 133 patients and 19% for 182 patients, respectively. The most common complications in these studies included infection, hardware failure, and local pain. The current study found similar patterns of complications, with symptomatic hardware being the most common etiology of otherwise undefinable pain. More recently, Richards et al6 reported an overall secondary surgery rate of 12.9% for 1046 patients during a 15-year period. Again, the 3 most common diagnoses for secondary surgery were pseudarthrosis, infection, and symptomatic hardware. Although Luhmann et al7 reported a lower reoperation rate of 3.9%, they began using pedicle screws in the late 1990s and had significantly more pedicle screw constructs in their cohort. The study by Richards et al6 evaluated primarily Texas Scottish Rite Hospital implants, finding a statistically higher rate of reoperation of 14% for posterior approaches.

In the current study, the posterior approaches were analyzed by the type of construct as well as compared with anterior and combined approaches to assess if any difference may exist between implants. On comparison of posterior pedicle screw constructs with all other constructs, there was a statistical difference favoring lower reoperation rates in the pedicle screw construct, in particular when compared with posterior hooks and combined constructs. When all posterior approaches vs anterior surgeries were compared, there was no statistical difference in secondary surgery rates (P=.85).

Infection rates, another important concern to patients, families, and surgeons, have been previously evaluated. Clark and Shufflebarger10 reported a 2.2% infection and prominent hardware rate, which required repeat intervention. Additionally, acute and late infections have been reported at rates of 2.2% and 7.5%, respectively.12 A large review of the Scoliosis Research Society Morbidity and Mortality database revealed 0.5% and 0.8% superficial and deep infection rates, respectively, in idiopathic scoliosis.5 Richards et al6 reported 45 patients with infection among their 1046 patients, for an infection rate of 4.3%. In the current study, the reoperation rate for infection was 3.2%, which is similar to previously reported reoperation rates.

In the current study, the most common indication for additional surgery was symptomatic hardware—5.8% of patients and 39.4% of total complications. Richards et al6 reported an overall additional surgery rate for symptomatic hardware of 3.7% for their 1046 patients, representing 22.7% of the total reoperation rate. Luhmann et al7 reported that the reoperation rate for symptomatic hardware was 0.7% for 1057 patients, 15% of their total reoperations. The current authors' overall symptomatic hardware rate was comparable to the rates reported by Richards et al.6 Pseudarthrosis as a percentage of total complications—27.3%—was likewise similar to the previously published literature. Luhmann et al7 reported that 43% of their reoperations were secondary to pseudarthrosis. The patient population of Richards et al6 had a pseudarthrosis rate of 17.4%. The larger disparity between rates may be related to the more difficult nature of diagnosing pseudarthrosis vs symptomatic hardware.

A unique aspect of the current study was the analysis of the different posterior constructs. Two previous studies primarily evaluated either all Texas Scottish Rite Hospital implantation6 or Cotrel-Dubousset implants.7 The current study specifically evaluated pedicle screw constructs, hybrid constructs, and hook only constructs through a posterior approach. A lower rate of reoperation was found in the posterior pedicle screw instrumented fusion compared with the hybrid constructs. Additionally, there was a trend toward overall lower reoperation rates in pedicle screw constructs compared with hook constructs (P=.054). Those patients who underwent combined anterior and posterior fusions had a significantly higher rate of reoperations than those who underwent posterior pedicle screw constructs.

Regarding specific causes of secondary surgery, there was a statistically lower rate of pseudarthrosis for the pedicle screw construct compared with the hook construct. This complication is a clinically relevant concern in the goal of single-procedure definitive fusion, as up to 43% of cases of reoperation have been reported to be due to pseudarthrosis.7 In the current study, pedicle screw constructs reduced this complication and lowered overall secondary surgical rates.

The limitations of this study were those typically due to the nature of a retrospective study. First, patients were not randomized into instrumentation construct groups. The choice of constructs was related to time period and surgeon preference. The lack of a standard surgical protocol with surgeon choice and time frame was a weakness of the study. Second, because pedicle screw constructs are strong, a pseudarthrosis may not present as early as it would with a broken rod or may never present because of more rigidity than a hook construct. Not all of the pedicle screw constructs were explored nor were computed tomography scans obtained to help document the lack of pseudarthrosis. Re-exploration or the radiation from a computed tomography scan when a patient has no broken hardware and no continued curve progression would not be reasonable. Patients with localized pain secondary to suspected pseudarthrosis would have a computed tomography scan in an attempt to document pseudarthrosis before exploration. Third, due to the nature of the authors' pediatric institution, patients were typically not followed after the age of 21 years; thus, secondary surgeries that might have occurred in adulthood could not be captured.

Conclusion

Patients undergoing instrumented fusion for AIS are at some risk of requiring subsequent surgery after their initial procedure. This reoperation rate was found to be 12.2% in this study. To lessen this risk, pedicle screw constructs should be considered, as they showed an overall lower reoperation rate compared with other constructs and a lower rate specifically regarding pseudarthrosis compared with posterior hook only constructs.

References

  1. Rogala EJ, Drummond DS, Gurr J. Scoliosis: incidence and natural history. A prospective epidemiological study. J Bone Joint Surg Am. 1978;60(2):173–176. doi:10.2106/00004623-197860020-00005 [CrossRef]
  2. Weinstein SL, Ponseti IV. Curve progression in idiopathic scoliosis. J Bone Joint Surg Am. 1983;65(4):447–455. doi:10.2106/00004623-198365040-00004 [CrossRef]
  3. Weinstein SL, Zavala DC, Ponseti IV. Idiopathic scoliosis: long-term follow-up and prognosis in untreated patients. J Bone Joint Surg Am. 1981;63(5):702–712. doi:10.2106/00004623-198163050-00003 [CrossRef]
  4. Weinstein SL, Dolan LA, Spratt KF, Peterson KK, Spoonamore MJ, Ponseti IV. Health and function of patients with untreated idiopathic scoliosis: a 50-year natural history study. JAMA. 2003;289(5):559–567. doi:10.1001/jama.289.5.559 [CrossRef]
  5. Reames DL, Smith JS, Fu KM, et al. Scoliosis Research Society Morbidity and Mortality Committee. Complications in the surgical treatment of 19,360 cases of pediatric scoliosis: a review of the Scoliosis Research Society Morbidity and Mortality database. Spine (Phila Pa 1976). 2011;36(18):1484–1491. doi:10.1097/BRS.0b013e3181f3a326 [CrossRef]
  6. Richards BS, Hasley BP, Casey VF. Repeat surgical interventions following “definitive” instrumentation and fusion for idiopathic scoliosis. Spine (Phila Pa 1976). 2006;31(26):3018–3026. doi:10.1097/01.brs.0000249553.22138.58 [CrossRef]
  7. Luhmann SJ, Lenke LG, Bridwell KH, Schootman M. Revision surgery after primary spine fusion for idiopathic scoliosis. Spine (Phila Pa 1976). 2009;34(20):2191–2197. doi:10.1097/BRS.0b013e3181b3515a [CrossRef]
  8. Lenke LG, Bridwell KH, Baldus C, Blanke K, Schoenecker PL. Cotrel-Dubousset instrumentation for adolescent idiopathic scoliosis. J Bone Joint Surg Am. 1992;74(7):1056–1067. doi:10.2106/00004623-199274070-00013 [CrossRef]
  9. Cook S, Asher M, Lai SM, Shobe J. Reoperation after primary posterior instrumentation and fusion for idiopathic scoliosis: toward defining late operative site pain of unknown cause. Spine (Phila Pa 1976). 2000;25(4):463–468. doi:10.1097/00007632-200002150-00012 [CrossRef]
  10. Clark CE, Shufflebarger HL. Late-developing infection in instrumented idiopathic scoliosis. Spine (Phila Pa 1976). 1999;24(18):1909–1912. doi:10.1097/00007632-199909150-00008 [CrossRef]
  11. Campos M, Dolan L, Weinstein S. Unanticipated revision surgery in adolescent idiopathic scoliosis. Spine (Phila Pa 1976). 2012;37(12):1048–1053. doi:10.1097/BRS.0b013e31823ced6f [CrossRef]
  12. Bago J, Ramirez M, Pellise F, Villanueva C. Survivorship analysis of Cotrel-Dubousset instrumentation in idiopathic scoliosis. Eur Spine J. 2003;12(4):435–439. doi:10.1007/s00586-001-0374-6 [CrossRef]
  13. Asher M, Lai SM, Burton D, Manna B, Cooper A. Safety and efficacy of Isola instrumentation and arthrodesis for adolescent idiopathic scoliosis: two- to 12-year follow-up. Spine (Phila Pa 1976). 2004;29(18):2013–2023. doi:10.1097/01.brs.0000138275.49220.81 [CrossRef]

Indications for Secondary Surgery

IndicationNo. (%)
Symptomatic hardware26 (39.4)
Pseudarthrosis18 (27.3)
Infection14 (21.2)
Curve progression4 (6.1)
Wound complications2 (3.0)
Rib prominence1 (1.5)
Chylothorax1 (1.5)
Total reoperation66 (100)

Comparison of the 3 Approachesa

ApproachNo. of PatientsNo. (%) of Patients Undergoing ReoperationsNo. of ReoperationsMean Age, y
Posterior33337 (11.1)4814.6
Anterior303 (10.0)415.7
Combined4810 (20.8)1414.8
Total41150 (12.2)14.8

Comparison of Reoperation Rates by Constructsa

ConstructNo. of PatientsNo. (%) of Patients Undergoing Reoperations
Posterior pedicle1036 (5.8)
Posterior hook20026 (13.0)
Posterior hybrid275 (18.5)
Posterior wire30 (0)
Anterior only303 (10.0)
Combined4810 (20.8)
Total41150 (12.2)

Comparison of Types of Complications by Posterior Surgical Constructs

ComplicationPosterior Pedicle (n=103)Posterior Hook (n=200)P


No.%No.%
Symptomatic hardware21.9115.5.148
Pseudarthrosis0094.5.029a
Infection32.931.5.403
Authors

The authors are from the Department of Surgery (JHD), Orthopaedic Surgery Service, Blanchfield Army Community Hospital, Fort Campbell, Kentucky; Shriners Hospitals for Children (BJT, WBB, MLM), Spokane, Washington; and the University of Wisconsin Madison (PMC), School of Medicine and Public Health, Madison, Wisconsin.

The authors have no relevant financial relationships to disclose.

The views expressed in this manuscript are those of the authors and do not reflect the official policy of the Department of the Army, Department of Defense, or US Government. Dr Dannenbaum is an employee of the US Government. This work was prepared as part of his official duties and as such, there is no copyright to be transferred.

Correspondence should be addressed to: Mark L. McMulkin, PhD, Shriners Hospitals for Children, 911 W 5th, Spokane, WA 99204 ( mmcmulkin@shrinenet.org).

Received: January 10, 2019
Accepted: April 16, 2019
Posted Online: May 28, 2019

10.3928/01477447-20190523-02

Sign up to receive

Journal E-contents