Scheuermann kyphosis (SK) is a thoracic or thoracolumbar kyphosis defined by anterior wedging of 5° or more in at least 3 contiguous vertebrae.61,62,64 It is the most common cause of hyperkyphosis in adolescents, with a prevalence between 1% and 8% in the population.41 While its exact etiology remains unknown, genetic, hormonal, and mechanical influences have been implicated.12,41,63 Although patients frequently remain asymptomatic,40 many experience progression of their deformity and sequelae including axial pain, body image dissatisfaction, restrictive lung disease, hamstring tightness, and in rare cases, neural impairment.48,53 However, the natural history and impact of untreated SK are scarcely reported and controversial. Murray et al. concluded that patients generally tend to adapt well to SK with relatively minor interference in their lives, while other studies note impairment with activities of daily living and poor quality of life.48,59 The threshold for intervention is considered in light of the natural history and risks of intervention and dependent on the individual patient and surgeon. The goals of treatment are reduction or stabilization of the deformity, pain alleviation, and improved cosmesis.15
Both operative and nonoperative treatment approaches have been reported for SK, with the relative merits of each having been the subject of significant debate. The most robust data for nonoperative management come from studies employing the Milwaukee brace, first used for SK by Bradford and colleagues in 1974.6 Other braces and nonoperative interventions have also been reported, including physical therapy.3,18 Results from these studies have led some authors to advocate bracing for all but the most severe curves, such as those greater than 65°.48
Operative management has similarly been shown to provide satisfactory results. The first report of operative management for SK was published in 1965 by Moe, who described posterior instrumentation and fusion in adolescents.46 From 1975 to 1980, Bradford and colleagues reported their experiences with both the posterior-only approach and a staged approach combining anterior apical release and fusion with posterior instrumentation and fusion.5,7 This combined anterior-posterior approach gained early popularity in part due to failures of early distraction instrumentation used in posterior-only surgery. Later advances in instrumentation and operative technique, including segmental instrumentation and Ponte osteotomies, enabled surgeons to obtain desired correction with minimal loss of correction via posterior-only approaches.55,66,67 The importance of the anterior ligamentous release was subsequently called into question,29 as the posterior-only approach avoids the morbidity associated with anterior mediastinal dissection.15,29,36
To date, no high-quality studies have been performed comparing operative and nonoperative management of SK. Consequently, no consensus has been established to discern operative versus nonoperative patients and in choosing the optimal operative approach. To address this, in this study we report the results of a systematic review of the SK literature. To focus our review, we sought to answer four questions: 1) What are the indications for treatment of SK? 2) What degree of correction and loss of correction are provided by each treatment modality? 3) What are the complications of operative treatment of SK? 4) How have treatment approaches for SK changed over time?
To our knowledge, in addition to being the largest review on SK to date, this is the first to compare operative approaches with nonoperative approaches on a large scale. We also present a cross-sectional analysis with studies stratified by decade of treatment to provide historical perspective and insight into changing practice patterns over the last 50 years.
Methods
Electronic Literature Search
Following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, we conducted a systematic review of the English-language peer-reviewed literature using PubMed, Embase, CINAHL, Web of Science, and the Cochrane Library for all reports of operative or nonoperative management of SK with full-text availability published between January 1, 1950, and November 21, 2017. Databases were queried using the search strings listed in the Appendix. We additionally queried the bibliographies of included articles to identify further reports for review. Articles were evaluated using the four questions above to guide our search. Inclusion criteria involved fully published, peer-reviewed, retrospective or prospective studies of the primary medical literature, including randomized controlled trials, nonrandomized trials, cohort studies, case-control studies, and case series. Studies were excluded if they did not provide clinical outcomes and statistics specific to SK, did not address the four main questions, described fewer than 2 patients, or discussed results in nonhuman models.
Study Eligibility
All eligible studies underwent title and abstract screening by two independent reviewers (S.H., J.E.) guided by the predetermined inclusion and exclusion criteria. A third reviewer (A.K.A.) reviewed decisions and resolved any discrepancies. Articles deemed eligible by the title and abstract screen underwent full-text review by 3 authors (S.H., J.E., E.C.) and were subjected to the following exclusion criteria: failure to report pre- and posttreatment kyphosis, failure to distinguish between the outcomes of patients undergoing treatment with different modalities, and inclusion of patients with pathologies other than SK. In cases in which 2 or more studies described partially shared cohorts, the largest study was selected for inclusion. Reasons for exclusion during full-text review are provided in Fig. 1.
PRISMA flow diagram detailing the results of our systematic review of the medical literature. Of 659 unique articles identified, 197 were screened on full-text review, and 45 were included in the final review. Template obtained from Moher et al: Preferred Reporting Items for Systematic Reviews and Meta-Analyses: the PRISMA statement. PLoS Med 6(6):e1000097, 2009.
Data Extraction
Articles that passed full-text review underwent data extraction by 3 authors (S.H., J.E., E.C.). Extracted data included age; sex; treatment indications; treatment methodology (i.e., operative vs nonoperative management); complications; maximal thoracic kyphosis on pretreatment, immediate posttreatment, and final standing films; and loss of sagittal correction. Patients were classified as having undergone operative (posterior, anterior-posterior, or anterior approach) or nonoperative (Milwaukee brace, antigravity brace, or plaster cast jacket/plastic brace) management. Studies were assigned a level of evidence based on North American Spine Society (NASS) guidelines.
Data Analysis
Extracted data from each patient cohort were included in a database organized by treatment methodology. Within each treatment methodology, cohorts were further stratified by the decade in which treatment was performed. In instances in which treatment spanned the transition between two decades, the assigned decade was that which encompassed the median of the reported range (e.g., treatment performed between 1988 and 1993 was classified as “1990s”).
Mean values for extracted kyphosis variables were calculated for each cohort as the weighted mean of the values reported in each article. Weighted mean values among and between different treatment modalities were compared using 2-tailed, Mann-Whitney U-tests performed on GraphPad Prism (version 8.0, GraphPad).
Due to limited granularity and heterogeneous reporting of complication data, classes and average rates of major complications were recorded at the cohort level when available. Complication data are presented as low, mean, median, and high percentages from included study cohorts within each treatment modality.
Results
Demographics and Indications for Treatment
The literature search identified 659 unique citations, of which 197 met the criteria for full-text review (Fig. 1). Common reasons for exclusion were failure to report sagittal correction following treatment (n = 31) and lack of full-text availability (n = 25). Thirty-three sources were eliminated for being abstracts alone. Forty-five articles describing 58 unique cohorts and 1829 total patients were ultimately included in our analysis (Tables 1 and 2).2–7,10,13,15–19,21–23,25,27,28,31,33–36,38,39,42,44,45,47,49–52,54,56,58,60,65–68,70,73,75 Sex and age information were available for 1439 and 1726 patients, respectively: 61.8% of the cohort was male, and the average reported age was 18.3 years. Operatively treated patients were on average older (20.2 vs 13.1 years) and more likely to be male (65.5% vs 47.0%) than braced patients (Table 2). The most commonly reported indications for treatment included pain (n = 32 studies), progressive deformity (n = 34 studies), failing nonoperative treatment (n = 14 studies), and neural impairment (n = 3 studies). The mean follow-up was 40.3 months (Table 2). Included studies comprised level II–IV evidence according to NASS guidelines.
Studies included in systematic review
| Kyphosis (°) | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Authors & Year | Study Type | Mean Age (yrs) | No. of Pts | Approach | Indications | Complications | Pre-Tx | Post-Tx | FU |
| Arun et al., 2006 | Retro comp | 20 | 15 | A-P | — | Instrumentation failure, DJK, wound infection | 86 | 42 | 42 |
| Aulisa et al., 2016 | CS | 14.2 | 90 | B | — | — | 57.8 | — | 41.3 |
| Behrbalk et al., 2014 | Retro comp | 21 | 21 | P | Deformity, pain, failed nonoperative Tx | Instrumentation failure, PJK, wound infection, repeat Tx | 75 | 43 | 44 |
| Bradford et al., 1980 | CS | 21 | 24 | A-P | Deformity, pain, failed nonoperative Tx, neural impairment | Wound infection, pulmonary, cardiovascular, repeat Tx | 77 | 41 | 47 |
| Bradford et al., 1974 | CS | 14.3 | 75 | B | Deformity, pain | — | 58.9 | 34.9 | 35.9 |
| Bradford et al., 1975 | CS | 18.6 | 22 | P | Deformity, pain, failed nonoperative Tx, neural impairment | Instrumentation failure, wound infection, repeat Tx | 72 | 31 | 47 |
| Cobden et al., 2017 | CS | 19 | 20 | P | Deformity, pain, failed nonoperative Tx | Instrumentation failure, PJK, DJK, repeat Tx | 79.8 | 44.6 | 44.9 |
| De Jonge et al., 2001 | Retro comp | 18.3 | 6 | P | Deformity, pain, failed nonoperative Tx | Instrumentation failure, wound infection, repeat Tx | 82.2 | 42.2 | 46.3 |
| 19.5 | 2 | A-P | 97.5 | 47.5 | 53.5 | ||||
| Etemadifar et al., 2016 | Pro comp | 19.3 | 14 | P | Deformity, pain | PJK | 81.9 | 40.1 | 43.2 |
| 20.9 | 16 | A-P | PJK, DJK, pulmonary, wound infection, instrumentation failure | 83.6 | 41.4 | 43 | |||
| Etemadifar et al., 2017 | CS | 12 | 110 | B | Deformity, pain | Bursa and skin irritation | 63.2 | — | 38.1 |
| Faldini et al., 2015 | Retro comp | 19.6 | 20 | P | Deformity, pain | PJK, wound infection, repeat Tx | 78.6 | — | 45.8 |
| Farsetti et al., 1991 | Retro comp | 14.5 | 12 | B | — | — | 54.1 | 38.9 | 59 |
| Geck et al., 2007 | CS | 16.4 | 17 | P | Deformity, pain, failed nonoperative Tx | PJK, DJK, wound infection | 75 | 38 | 38 |
| Ghasemi et al., 2017 | Retro comp | 19.3 | 40 | P | Deformity, pain, failed nonoperative Tx | DJK | 81.1 | 47 | 48.7 |
| Graat et al., 2016 | Retro comp | — | 13 | P | — | Instrumentation failure, PJK | 78.8 | 51.9 | 57.7 |
| — | 15 | A-P | — | Instrumentation failure, PJK | 85.9 | 49.3 | 58.3 | ||
| Guler et al., 2017 | Retro comp | 17.1 | 32 | P | — | — | 76.3 | — | 40.9 |
| Herrera-Soto et al., 2005 | CS | 17.4 | 19 | A-P | Deformity, failed nonoperative Tx | Pulmonary, wound infection repeat Tx | 84.8 | 43.7 | 45.3 |
| Hosman et al., 2002 | Retro comp | 24.2 | 16 | P | Deformity, pain | Wound infection | 76.6 | 52.4 | 55.8 |
| 26 | 17 | A-P | Deformity, pain | PJK, wound infection, repeat Tx | 80.8 | 51.1 | 52.6 | ||
| Jansen et al., 2006 | Retro comp | 28 | 30 | A-P | — | — | 80 | — | 47 |
| Kim et al., 2017 | Retro comp | 18.9 | 44 | P | — | PJK, DJK, repeat Tx | 81.7 | — | 48.0 |
| Koller et al., 2014 | CS | 23.6 | 111 | A-P | Deformity, pain | Instrumentation failure, DJK, wound infection, repeat Tx | 68 | 40.5 | 39.5 |
| Koller et al., 2015 | Retro comp | 19.8 | 76 | P | Deformity, pain | — | 84.1 | 49.5 | 49.5 |
| 23.2 | 90 | A-P | — | 69 | 38.5 | 40.2 | |||
| Kostuik, 1990 | CS | 27.5 | 36 | A | Deformity, pain, failed nonoperative Tx, neural impairment | Instrumentation failure, repeat Tx | 75.5 | 56 | 60 |
| Lee et al., 2006 | Retro comp | 17.3 | 18 | P | — | — | 84.4 | 38.2 | 40.4 |
| 18 | 21 | A-P | — | Instrumentation failure, PJK, DJK, wound infection, repeat Tx, neural impairment | 89.1 | 51.9 | 54.4 | ||
| Lim et al., 2004 | CS | 27.7 | 3 | P | Deformity, pain | — | 77.3 | 43 | 49 |
| 19 | 20 | A-P | Instrumentation failure, neural impairment, pulmonary, repeat Tx | 83.6 | 47 | 51.3 | |||
| Lonner et al., 2007 | Retro comp | 16.9 | 36 | P | — | PJK, DJK, repeat Tx | 74.4 | 39.8 | 46.2 |
| 16.4 | 42 | A-P | — | Instrumentation failure, PJK, DJK, wound infection, repeat Tx, neural impairment, pulmonary | 82.6 | 52.5 | 55.8 | ||
| Lundine et al., 2012 | Retro comp | 18 | 16 | A-P | Deformity | Instrumentation failure, DJK, repeat Tx | 85 | — | 59 |
| Mikhaylovskiy et al., 2015 | Retro comp | 19 | 36 | A-P | — | DJK, PJK | 79.3 | 40.6 | 45.5 |
| Mirzashahi et al., 2018 | CS | 22.4 | 18 | P | Deformity, pain | — | 87.2 | 47.4 | — |
| Montgomery & Erwin, 1981 | Retro comp | 14.3 | 62 | B | Deformity, pain | — | 62 | 41 | 54 |
| Nasto et al., 2016 | Retro comp | 18.8 | 37 | P | Deformity, pain, failed nonoperative Tx | PJK, repeat Tx | 81.3 | 47.4 | 48.6 |
| Nasto et al., 2017 | Retro comp | 18.5 | 64 | P | Deformity, pain | — | 81.9 | 48.7 | 50.2 |
| Nerubay & Katznelson, 1986 | CS | 21 | 14 | A-P | Deformity, pain | Repeat Tx, neural impairment | 76.4 | — | 49.8 |
| Otsuka et al., 1990 | CS | 18.4 | 10 | P | Deformity, pain | — | 71.4 | 32 | 39.3 |
| Papagelopoulos et al., 2001 | Retro comp | 20.8 | 13 | P | Deformity, pain | PJK, DJK | 68.5 | 34.3 | 40 |
| 26.6 | 7 | A-P | — | 86.3 | 42 | 46.4 | |||
| Poolman et al., 2002 | Retro comp | 23 | 22 | A-P | Deformity, pain, failed nonoperative Tx | Instrumentation failure, PJK, cardiovascular | 70 | 39 | 55 |
| Reinhardt & Bassett, 1990 | Retro comp | 17.3 | 8 | P | Deformity, pain, failed nonoperative Tx | PJK, DJK | 68 | 41.4 | 48.9 |
| 16.3 | 6 | A-P | DJK | 75.3 | 42 | 49.8 | |||
| Sachs et al., 1987 | Retro comp | 11.9 | 110 | B | Deformity, pain | — | 60.1 | 39.7 | 51.1 |
| Speck & Chopin, 1986 | Retro comp | — | 53 | P | Deformity, pain | — | 75.7 | 35.7 | 39.0 |
| — | 6 | A-P | — | 82 | 44 | 45 | |||
| Sturm et al., 1993 | CS | 19 | 30 | P | Deformity, pain, failed nonoperative Tx | Instrumentation failure, wound infection, repeat Tx | 71.5 | 32.7 | 37.7 |
| Taylor et al., 1979 | CS | 16.7 | 20 | P | Deformity, pain | Instrumentation failure | 73.6 | 41.9 | 47.4 |
| Temponi et al., 2015 | Retro comp | 27.3 | 9 | P | Deformity, pain, failed nonoperative Tx | Repeat Tx | 72.9 | — | 44.3 |
| 19 | 19 | A-P | Instrumentation failure, wound infection, repeat Tx | 77.6 | — | 35.8 | |||
| Tsutsui et al., 2011 | Retro comp | 14.8 | 11 | P | Deformity, pain | — | 82.7 | — | 47.9 |
| 15.1 | 11 | A-P | — | 84.9 | — | 48.6 | |||
| Yanik et al., 2015 | Retro comp | 18.3 | 60 | P | — | PJK | 73.6 | — | 40.3 |
| Zhu et al., 2018 | Retro comp | 18.9 | 44 | P | — | PJK, DJK, wound infection | 72.2 | 35.4 | 37.1 |
A-P = anterior-posterior surgery; B = bracing; comp = comparative; CS = case series; FU = follow-up; P = posterior-only surgery; Pro = prospective; Pts = patients; Retro = retrospective; Tx = treatment.
Treatment modality breakdown by demographic information and time frame of treatment
| Demographics | Decade of Tx (no. of pts) | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Surgical Management | Cohorts | Pts | Males | Females | M:F Ratio | Mean Age, yrs | Mean FU, mos | 1960–1969 | 1970–1979 | 1980–1989 | 1990–1999 | 2000–2009 | 2010–Present |
| Posterior approach | 29 | 775 | 433 | 232 | 1.9 (n = 665) | 18.8 (n = 693) | 36.2 (n = 640) | 22 | 73 | 61 | 38 | 385 | 196 |
| Anterior-posterior approach | 22 | 559 | 322 | 165 | 2.0 (n = 487) | 21.4 (n = 538) | 45.9 (n = 317) | 0 | 44 | 13 | 161 | 341 | 0 |
| Anterior approach | 1 | 36 | 0 | 0 | — | 27.5 (n = 36) | — | 0 | 0 | 36 | 0 | 0 | 0 |
| Total | 52 | 1370 | 755 | 397 | 1.9 (n = 1152) | 20.2 (n = 1267) | 39.4 (n = 957) | 22 | 117 | 110 | 199 | 726 | 196 |
| Conservative management | |||||||||||||
| Milwaukee brace | 4 | 357 | 67 | 118 | 0.6 (n = 185) | 12.8 (n = 357) | 39.0 (n = 357) | 185 | 62 | 0 | 0 | 110 | 0 |
| Antigravity brace | 1 | 90 | 59 | 31 | 1.9 (n = 90) | 14.2 (n = 90) | 30.0 (n = 90) | 0 | 0 | 0 | 0 | 90 | 0 |
| Plaster cast jacket/plastic brace | 1 | 12 | 9 | 3 | 3.0 (n = 12) | 14.5 (n = 12) | 228.0 (n = 12) | 12 | 0 | 0 | 0 | 0 | 0 |
| Total | 6 | 459 | 135 | 152 | 0.9 (n = 287) | 13.1 (n = 459) | 42.2 (n = 459) | 197 | 62 | 0 | 0 | 200 | 0 |
| Pooled cohort | |||||||||||||
| Total | 58 | 1829 | 890 | 549 | 1.6 (n = 1439) | 18.3 (n = 1726) | 40.3 (n = 1416) | 219 | 179 | 110 | 199 | 926 | 196 |
Treatment Modality Overview and Breakdown by Decade
We identified 52 patient cohorts treated operatively (n = 29 posterior-only, n = 22 anterior-posterior, n = 1 anterior-only) and 6 cohorts treated nonoperatively (Table 2). The mean patient age was grossly similar in both the posterior-only and anterior-posterior approaches, with a mean of 18.8 (n = 693) and 21.4 (n = 538) years, respectively. Only 1 study reported the use of an anterior-only approach, with a total of 36 patients and mean age of 27.5 years.
Examining studies by decade of treatment, the greatest number of both posterior-only and anterior-posterior surgeries reported in the literature occurred between 2000 and 2009. The greatest proportion of reported cases performed by the anterior-posterior approach in a given decade occurred in the 1990s; years later, the posterior-only approach comprised the greatest proportion of reported cases from 2010 onward (Table 2, Fig. 2). The only study describing an anterior-only approach reported results for a cohort treated in the 1980s. A graphical depiction of the number and proportion of patients treated by each modality is illustrated in Fig. 2.
Proportion of cases treated by each modality by decade.
Kyphosis and Correction
Average pretreatment kyphosis was greater in the posterior-only group (77.9°, 95% confidence interval [CI] 77.5°–78.2°) than the anterior-posterior (76.7°, 95% CI 76.1°–77.3°) and bracing (60.3°, 95% CI 59.8°–60.8°) groups (Table 3, Fig. 3). Correction immediately following treatment was greater in both operative groups than the bracing group (21.4°, 95% CI 20.8°–21.9°). Among the operative groups, greater correction was noted postoperatively in the posterior-only group (35.5°, 95% CI 35.2°–35.9°) than the anterior-posterior group (33.1°, 95% CI 32.6°–33.6°). Similarly, correction at final follow-up was greater in posterior-only surgery (32.7°, 95% CI 32.3°–33.0°) than either the anterior-posterior (30.5°, 95% CI 30.0°–31.1°) or bracing (16.1°, 95% CI 15.4°–16.9°) groups. Notably, loss of correction was not significantly different between posterior-only (3.0°, 95% CI 2.7°–3.3°) and anterior-posterior (3.0°, 95% CI 2.6°–3.4°) surgery, although both operative approaches lost less correction than bracing (9.2°, 95% CI 8.5°–9.9°).
Changes in maximum kyphosis following treatment with each modality
| Maximum Kyphosis | |||||||
|---|---|---|---|---|---|---|---|
| Approach | Pre-Tx Kyphosis | Post-Tx Kyphosis | FU Kyphosis | Post-Tx Correction | FU Correction | Loss of Correction | FU (mos) |
| Posterior | 36 | ||||||
| Mean ± SD (°) | 77.9 ± 4.8 | 42.6 ± 6.5 | 45.1 ± 5.5 | 35.5 ± 4.4 | 32.7± 4.7 | 3.0 ± 3.5 | |
| 95% CI (°) | 77.5–78.2 | 42.1–43.2 | 44.7–45.4 | 35.2–35.9 | 32.3–33.0 | 2.7–3.3 | |
| No. of pts | 775 | 589 | 747 | 589 | 747 | 571 | |
| Anterior-posterior | 46 | ||||||
| Mean ± SD (°) | 76.7± 7.3 | 42.9 ± 4.8 | 46.0 ± 6.6 | 33.1 ± 5.3 | 30.5 ± 6.3 | 3.0 ± 4.6 | |
| 95% CI (°) | 76.1–77.3 | 42.5–43.4 | 45.5–46.6 | 32.6–33.6 | 30.0–31.1 | 2.6–3.4 | |
| No. of pts | 559 | 469 | 559 | 469 | 559 | 469 | |
| Bracing | 42 | ||||||
| Mean ± SD (°) | 60.3 ± 5.3 | 38.6 ± 3.7 | 44.2 ± 7.7 | 21.4 ± 4.2 | 16.1 ± 8.1 | 9.2 ± 5.7 | |
| 95% CI (°) | 59.8–60.8 | 38.1–39.0 | 43.5–44.9 | 20.8–21.9 | 15.4–16.9 | 8.5–9.9 | |
| No. of pts | 459 | 259 | 459 | 259 | 459 | 259 | |
Comparison by treatment modality of pretreatment sagittal deformity (A), improvement in sagittal deformity relative to baseline immediately following treatment (B), improvement in sagittal deformity relative to baseline at last follow-up (C), and loss of correction from first to last follow-up (D). Values are shown as mean ± SD. ns = not significant; **p < 0.005; ****p < 0.0001.
Correction Trends by Decade
Temporal trends in mean pretreatment kyphosis, immediate posttreatment correction, and correction at final follow-up are plotted by decade in Fig. 4. From the 1960s to the present, there is a small but notable increase in the severity of pretreatment kyphosis within the posterior-only surgery group. The proportion of operative cases using a posterior-only approach steadily increases, peaking in the most recent decade (Figs. 2 and 4). Use of the anterior-posterior approach peaked in the 1990s and 2000s, with no included reports of surgery performed in the current decade. The pretreatment kyphosis of the anterior-posterior group rose slightly from the 1970s to 1990s before falling in the 2000s. For the bracing cohort, the pretreatment kyphosis was grossly similar across the examined time frame.
Cross-sectional analysis by treatment modality (posterior surgery, anterior-posterior surgery, or bracing) and decade of intervention. Depicted are pretreatment sagittal deformity (A), improvement in sagittal deformity relative to baseline immediately following treatment (B), improvement in sagittal deformity relative to baseline at last follow-up (C), and loss of correction from first to last follow-up (D).
Immediate postoperative correction trended downward in both the posterior-only and the anterior-posterior surgery groups over time. By contrast, correction at latest follow-up trended upward in the posterior-only group, whereas it remained relatively constant in the anterior-posterior group. In the bracing group, correction at latest follow-up reached a nadir in the 1970s before increasing in the 2000s, although it must be noted that only 6 publications were used to support this curve.
Loss of correction decreased across time in both the posterior-only and anterior-posterior groups. The trend was greater among the posterior-only group, in which the loss of correction remained below 2° in studies from 2000 onward. By contrast, loss of correction increased from the 1960s to the 1970s for the bracing group, although analysis in this subgroup was limited by relatively sparse data (n = 259 total patients).
Complications
The most commonly reported complications for the posterior-only approach were hardware failure (25%, n = 6 cohorts), proximal junctional kyphosis (PJK; 14%, n = 15 cohorts), and distal junctional kyphosis (DJK; 14%, n = 10 cohorts) (Table 4). Additionally, 10% of patients required surgical revision (n = 10 cohorts). The most commonly reported complications for the anterior-posterior approach were pulmonary (i.e., pulmonary embolism, pleural effusion, pneumothorax, hemothorax, atelectasis, acute respiratory failure; 21%, n = 5 cohorts), DJK (20%, n = 9 cohorts), hardware failure (22%, n = 11 cohorts), PJK (26%, n = 7 cohorts), neural injury (8%, n = 5 cohorts), and cardiovascular (damaged aorta, pericardial effusion; 6%, n = 2 cohorts) complications. Eleven percent of patients required surgical revisions for their symptoms (n = 11 cohorts). While complication rates could not be directly compared between treatment approaches due to limited granularity of available data, we note a greater variety of documented complications from anterior-posterior surgery compared to posterior-only surgery.
Major complications when reported by operative approach
| Posterior Approach | Anterior-Posterior Approach | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| % Pts Affected | % Pts Affected | |||||||||
| Complication | No. of Cohorts | Low | High | Mean ± SD | Median | No. of Cohorts | Low | High | Mean ± SD | Median |
| Instrumentation failure | 6 | 5 | 85 | 25 ± 30 | 14 | 11 | 2 | 60 | 22 ± 20 | 15 |
| Repeat Tx | 10 | 4 | 23 | 10 ± 7 | 9 | 11 | 5 | 19 | 11 ± 6 | 10 |
| PJK | 15 | 3 | 46 | 14 ± 12 | 8 | 7 | 2 | 86 | 26 ± 33 | 10 |
| DJK | 10 | 3 | 50 | 14 ± 14 | 8 | 9 | 2 | 71 | 20 ± 26 | 6 |
| Neural impairment | — | — | — | — | — | 5 | 5 | 17 | 8 ± 5 | 5 |
| Pulmonary complications | — | — | — | — | — | 5 | 7 | 40 | 21 ± 13 | 21 |
| Cardiovascular complications | — | — | — | — | — | 2 | 5 | 8 | 6 ± 3 | 6 |
Rates reported as averages of cohorts within each modality.
Discussion
SK is a common deformity of the thoracic or thoracolumbar spine causing significant pain, cosmetic concern, and sometimes neural impairment. Since the first description of Scheuermann disease by Holger Scheuermann in 1920, both nonoperative and operative management strategies have been advocated. Nonoperative management largely employs bracing, most commonly with the Milwaukee brace, while operative management involves a combined anterior-posterior fusion or posterior-only fusion. The predominance of evidence for SK has been sourced from single-institution cohort studies, and to date there remains no consensus on optimal management strategies. To address this, we report the results of the largest systematic review on SK and the first to compare outcomes between patients undergoing operative and nonoperative management. We augmented this investigation through historical cross-sectional analysis depicting the evolution of SK management over time.
We included 45 studies describing 1829 unique patients, of whom 75% underwent surgery (56.6% posterior-only, 40.8% anterior-posterior, and 2.6% anterior-only). Of the studies reporting demographic information, 61.8% of patients were male and the average age at treatment was 18.3. Operatively managed patients were on average older, more likely to be male, and had more severe deformity preoperatively. This preoperative deformity was greater in the posterior-only surgery group than the anterior-posterior surgery group. While not a large difference clinically, this trend could potentially reflect shifts in surgeon preferences or changing thresholds for treatment over time. Across treatment groups, surgery offered greater correction at final follow-up than bracing; this was associated with lower loss of correction among both operatively managed groups compared to bracing. Within the operative group, patients treated with posterior-only surgery had greater correction at both immediate and final follow-up. Notably, loss of correction was not different between these groups. The posterior-only approach was also associated with a narrower spectrum of potential complications. Temporal analysis noted that selection of the anterior-posterior approach peaked in popularity during the 1990s and 2000s, after which point the posterior-only approach began to predominate. Lastly, temporal analysis showed a decrease in loss of correction seen at last follow-up in both operative groups.
As demonstrated by the data reviewed above, the treatment algorithm for SK can be coarsely broken into three key decisions: 1) determination of whether the patient’s clinical picture warrants intervention, 2) determination of whether they require operative or nonoperative management, and 3) selection of treatment approach. Our analysis focuses on surgery and bracing given their central role in SK management and standardized reporting of radiographic outcomes (e.g., Cobb angle). Other treatment approaches, such as physiotherapy, have also been reported,72 although this literature is not as robust and lacks consistent reporting of the radiographic outcomes included in our analysis. Among the studies reported here, the most common complaints were pain, progressive deformity, and body image dissatisfaction. Neural dysfunction was a rarely reported indication, suggesting that treatment need not proceed on an emergent basis.
Although our data were not granular enough to segment indication by patient age, prior literature suggests that there may be an interaction between the two. Chronic pain is the most common presenting complaint for adults.69 By comparison, among adolescents, cosmetic concerns (clinical deformity) are given disproportionate weighting, perhaps due to heightened social pressure and the desire to “fit in.”69 These same social pressures may additionally impact the treatment of adolescent patients by dissuading them from pursuing bracing and creating problems with adherence. We speculate that these adherence issues may in part contribute to curve progression and greater loss of correction among braced patients.57
Our data suggest that other indications for operative management include deformity severity and patient age. Patients with greater deformity require greater correction to see relief of their presenting complaints. Correcting these large deformities with bracing alone may not be feasible due to limitations in the ability of external compressive forces to be transferred to the spine. Patient age may additionally indicate operative intervention for several reasons. In the context of progressive deformity, older patients are likely to have more severe curvature amenable only to operative correction. Older patients are also likely to have less flexible curves43,71 that cannot be corrected with external pressure alone but rather require the osteotomy work afforded by operative intervention. Lastly, older adolescents and young adults are skeletally mature as compared to younger adolescents.26 While skeletal maturity may not necessarily be a contraindication to bracing,6 it is generally thought that skeletally mature patients are poorer candidates for bracing and more appropriately treated with surgery.1 On the contrary, it should be noted that operative intervention in younger patients with remaining growth potential may fail to adequately address kyphotic deformity given skeletal immaturity.20
Even in patients best managed operatively, surgery is not without risk, and our data suggest that postoperative complications are relatively common. The most common complications are mechanical in nature, with 14%–26% of patients experiencing deformity at the proximal or distal instrumented vertebra and 22%–25% experiencing hardware failure. Given the heterogeneity of the included results, we were unable to perform inferential statistics to evaluate complication risks. However, they appear to suggest that patients undergoing posterior-only operations are more likely to suffer hardware failure, whereas patients undergoing anterior-posterior procedures are more likely to experience junctional breakdown and pulmonary complications. Our results suggest similar rates of PJK and DJK, although the granularity of this data is limited. Others note that PJK may be a more common sequela than DJK in patients with SK,21 but patients with DJK may be more likely to require surgical revision.21
The reasons for the development of PJK and DJK are not well understood. Kim et al. recently published a meta-analysis identifying older age, higher sagittal vertical axis (SVA), lower lumbar lordosis (LL), greater correction of SVA and LL, and higher number of levels fused, among others, as factors contributing to junctional kyphosis in adult spinal deformity.32 To avoid junctional pathology, it is generally accepted that the fusion construct must include the proximal end vertebrae in the measured kyphosis.8,9,14,54 Selection of the distal end of the fusion construct is more controversial but typically includes at least the first lordotic level.40 Cho and colleagues noted the presence of DJK despite following this rule and subsequently recommended that the distal end of instrumentation should include the sagittal stable vertebra, the most proximal vertebra touched by the posterior sacral vertical line.8 Further contributors to junctional pathology may include overcorrection of preoperative kyphosis, particularly beyond 50%, as unfused spinal segments cannot adjust for global postoperative changes.9,40,54 Ultimately, this literature is still evolving; treatment goals should be tailored toward individual patient biomechanics and focused on restoring spinopelvic and spinal balance.14,33
We note that the apparent advantage of the posterior-only approach is relatively new and certainly not definitive. While support for the anterior-posterior approach was stronger before the 2000s, many investigators continued to advocate this combined approach;39 in fact, one of the largest series using the anterior-posterior approach, reported by Koller and colleagues, discussed surgeries performed in the 2000s.33 We also note a study by Coe and colleagues using cases between 2001 and 2004 from the Scoliosis Research Society morbidity and mortality database, which found no difference in complication rates between anterior-posterior and posterior-only approaches for SK.11 However, our results do largely align with more recent studies discussing the potential advantages of posterior-only surgery. Many of these studies call into question the utility of the anterior apical release,29 including a recent meta-analysis by Yun and Shen supporting the notion that correction loss is grossly similar between anterior-posterior and posterior-only surgery.74 We provide stronger evidence through a more expansive literature search including nearly twice as many studies, along with a detailed temporal analysis of pretreatment kyphosis, correction, and loss of correction trended over time. We also uniquely compare this operative management to bracing, which has remained a mainstay of treatment for SK, particularly before skeletal maturity and for less severe curves. While bracing has been shown to slow or halt curve progression, our analysis suggests that it ultimately provides less correction and may be less durable than surgery.
We speculate that reasons for shifting preferences in operative approach are largely derived from advances in instrumentation and operative techniques. The anterior-posterior approach was initially favored due to limitations of early distraction instrumentation systems used in posterior-only operations and lack of posterior osteotomy techniques. Early instrumentation of the thoracolumbar spine depended upon a combination of rods and laminar hooks, which have substantially decreased pullout strength relative to modern instrumentation systems.37 In 1970, Roy-Camille set the foundation for these modern systems when he described his experience correcting lumbosacral spondylolisthesis using a combination of cobalt chrome plates and stainless steel pedicle screws.30 Then, in 1986, Krag published testing of the Vermont Spinal Fixator, the direct precursor to modern screw-rod systems. Contemporaneously, the Wiltse pedicle screw system was brought to market, followed shortly by the Texas Scottish Rite System, the latter of which is essentially indistinguishable from modern systems.30 Ultimately, the development of segmental pedicle screws in the thoracic spine, combined with increasing awareness and routine use of Ponte osteotomies, likely played the most important role in shifting surgeon preferences toward a posterior-only approach following the 1990s.24,29 We note that it was after this time that postoperative correction and maintenance of correction in the posterior-only cohort began to improve relative to the anterior-posterior cohort. In addition to this correlation with improved instrumentation, other factors may also contribute to these differences, including improved preoperative planning and optimization for surgery. However, investigation of these factors is beyond the granularity of our data.
While the anterior-posterior procedure has been shown for years to provide good correction and maintenance of correction, these advances in the posterior-only procedure and narrower complication profile—borne out in our data and in increasing reports in recent years—warrant further discussion about the value of subjecting patients to the relative morbidity of the anterior-posterior procedure.
Although our study significantly strengthens the SK literature and provides insight into underlying discrepancies throughout the history of SK management, it is not without its limitations. We were limited by a lack of level I and II evidence. The level III and IV evidence used has high risk for selection, publication, reporting, and other biases that limit the strength of our analysis. Because results were largely reported as means of a given study cohort, rather than individual patient data, overall weighted means were constructed, reducing the granularity of the data. Similarly, we are wholly dependent upon the radiographic measurements provided by the authors and as a result are incapable of evaluating the influence of spinopelvic parameters (e.g., pelvic tilt, LL–pelvic incidence mismatch) on maintenance of correction. All of these factors are key determinants of postoperative outcomes in the field of spinal deformity, and although the literature is sparse, it is likely that these factors also contribute to radiological outcomes in SK. Additionally, our temporal analyses are based on the distribution of cases reported in the peer-reviewed literature; this distribution may not reliably reflect the distribution of all surgeries actually performed by the spine community. We were unable to include some potentially relevant studies on SK due to failure to meet prespecified inclusion and exclusion criteria. Additionally, our assessment of clinical outcomes is focused on radiographic correction rather than other clinical parameters such as pain, patient satisfaction, and functional capacity due to lack of standardized, widespread reporting of these outcomes. Our results should therefore be interpreted in the context of curve correction and not overall clinical outcome. Other limitations include those intrinsic to all systematic reviews, such as heterogeneity of studies and in variables such as age, curve flexibility, follow-up time, and goals of correction. Despite the limitations of this study, it is the first and most comprehensive systematic review assessing the operative and nonoperative management of SK.
Conclusions
The ideal management strategy for patients with SK is a notable outstanding question in the field of spine surgery. Here, we report the results of the largest systematic review of the extant literature describing historical changes in management strategy as well as radiological outcomes in both operatively and nonoperatively managed patients. We find that the best overall correction and maintenance of correction are afforded by operative intervention. Of operative patients, there has been a recent trend toward increased use of a posterior-only versus combined anterior-posterior approach. The results of our analysis largely align with modern studies suggesting that the posterior-only approach provides similar or superior correction compared to the anterior-posterior approach, along with a milder complication profile and identical maintenance of correction.
Acknowledgments
We would like to thank Carrie Price, MLS, for technical assistance with literature search criteria.
Disclosures
Dr. Sciubba reports being a consultant for DePuy-Synthes, NuVasive, Orthofix, Globus, K2M, Medtronic, Stryker, and Baxter.
Author Contributions
Conception and design: Sciubba, Huq, Ahmed. Acquisition of data: Huq, Ehresman, Cottrill. Analysis and interpretation of data: all authors. Drafting the article: all authors. Critically revising the article: all authors. Reviewed submitted version of manuscript: all authors. Approved the final version of the manuscript on behalf of all authors: Sciubba. Statistical analysis: Huq, Ahmed. Study supervision: Sciubba, Westbroek.
Supplemental Information
Online-Only Content
Supplemental material is available with the online version of the article.
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