The Journal of Bone & Joint Surgery

The Journal of Bone & Joint Surgery, Volume 85, Issue 12

Scientific Articles | December 01, 2003

Harrington and Cotrel-Dubousset Instrumentation in Adolescent Idiopathic Scoliosis: Long-Term Functional and Radiographic Outcomes

Ilkka Helenius, MD, PhD¹; Ville Remes, MD, PhD²; Timo Yrjönen, MD, PhD²; Mauno Ylikoski, MD, PhD²; Dietrich Schlenzka, MD, PhD²; Miia Helenius, DDS, BM²; Mikko Poussa, MD, PhD²

¹ Hospital for Children and Adolescents, Helsinki University Central Hospital, P.O. Box 281, Helsinki FIN-00029 HUS, Finland. E-mail address: ilkka.helenius@helsinki.fi
² ORTON Orthopaedic Hospital, Invalid Foundation, Tenholantie 10, Helsinki FIN-00280, Finland

View Disclosures and Other Information

In support of their research or preparation of this manuscript, one or more of the authors received grants or outside funding from the Instrumentarium Scientific Foundation, Finnish Orthopaedic and Traumatology Foundation, Päivikki and Sakari Sohlberg Foundation, Emil Aaltonen Foundation, Juselius Foundation, The Foundation for Pediatric Research, and Sivia Kosti Foundation. None of the authors received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.

Investigation performed at ORTON Orthopaedic Hospital, Invalid Foundation, Helsinki, Finland

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J Bone Joint Surg Am, 2003 Dec 01;85(12):2303-2309

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Abstract

Background: Previous studies have shown that the long-term clinical outcome does not correlate with the radiographic outcome in patients treated with Harrington instrumentation for adolescent idiopathic scoliosis. Cotrel-Dubousset instrumentation has been reported to provide better correction radiographically, but it is unclear whether it provides better long-term clinical or functional outcomes. We are not aware of any long-term studies comparing Harrington and Cotrel-Dubousset instrumentation.

Methods: Seventy-eight patients in whom adolescent idiopathic scoliosis was treated with Harrington instrumentation and fifty-seven in whom it was treated with Cotrel-Dubousset instrumentation participated in this study. The mean duration of follow-up was 20.8 years for the Harrington instrumentation group and 13.0 years for the Cotrel-Dubousset instrumentation group. The mean age at the time of follow-up was thirty-six years and twenty-eight years, respectively. Radiographs were made preoperatively and at the two-year and final follow-up examinations. The Scoliosis Research Society questionnaire was completed, a physical examination was performed, and spinal mobility and non-dynamometric trunk strength were measured at the final follow-up visit.

Results: The mean preoperative Cobb angle of the thoracic curves was 53° in the Harrington instrumentation group and 55° in the Cotrel-Dubousset instrumentation group. The mean numbers of vertebrae included in the instrumentation were 10.7 and 9.9, respectively. At the two-year follow-up evaluation, the mean postoperative Cobb angles were 38° and 25°, respectively (p < 0.0001). At the final follow-up evaluation, the mean angles were 45° and 32° (p < 0.0001). No significant difference in thoracic kyphosis or lumbar lordosis was observed between the study groups at the final follow-up evaluation. The average score on the Scoliosis Research Society questionnaire was 97 points in both groups. Measurements of non-dynamometric trunk strength corresponded with age and sex-adjusted reference values, on the average, but patients with Cotrel-Dubousset instrumentation performed significantly better in the squatting test (p = 0.010). Abnormal lumbar extension and trunk side-bending were significantly more common in the Harrington instrumentation group (p = 0.050 and p = 0.0061, respectively). Complications were recorded for nine (12%) of the patients treated with Harrington instrumentation and fifteen (26%) of those treated with Cotrel-Dubousset instrumentation (p = 0.027).

Conclusions: Cotrel-Dubousset instrumentation yielded better long-term functional and radiographic outcomes in patients with adolescent idiopathic scoliosis than did Harrington instrumentation. However, complications were more common in the Cotrel-Dubousset instrumentation group.

Level of Evidence: Therapeutic study, Level III-2 (retrospective cohort study). See Instructions to Authors for a complete description of levels of evidence.

Figures in this Article

The goals of surgical treatment of adolescent idiopathic scoliosis are to obtain good correction, achieve a solid fusion, prevent curve progression, improve the cosmetic appearance, and prevent back pain and functional impairment in adulthood^1-8. Previous studies of the results of treatment with Harrington rod instrumentation and posterior spinal fusion have demonstrated that radiographic signs of correction in the coronal plane remain stable for five to twelve years postoperatively^2,5,7,9,10. Only a few studies^11,12 have shown substantial deterioration radiographically during the follow-up period. These patients have performed, on the average, as well as the normal population on tests measuring spinal mobility and trunk strength¹².

Cotrel-Dubousset instrumentation was designed to provide segmental spinal instrumentation with selective distraction and compression at different levels to improve alignment in the coronal, sagittal, and, possibly, axial planes¹³. Early and midterm results (at less than ten years) have shown that Cotrel-Dubousset instrumentation of thoracic curves provides slightly better correction in the coronal plane than does Harrington rod instrumentation^10,14-16. Cotrel-Dubousset instrumentation has a minimal effect on apical rotation^14,17, but it has improved thoracic and lumbar sagittal alignment^14,15. Coronal decompensation has been reported after use of Cotrel-Dubousset instrumentation, especially in patients with King type-II curves¹⁵.

We retrospectively compared two cohorts of patients more than ten years following surgical treatment of adolescent idiopathic scoliosis. Harrington rod instrumentation was used in one group and Cotrel-Dubousset instrumentation, in the other. Our study hypothesis was that the Cotrel-Dubousset instrumentation would be found to have provided better long-term radiographic results than the Harrington rod instrumentation and that this difference would be reflected by the patients' subjective assessment of the clinical results and by objective measurements of trunk strength and spinal mobility.

Materials and Methods

Materials and Methods | Results | Discussion | References

Patients

From January to November 1979, ninety-eight consecutive patients with adolescent idiopathic scoliosis were treated with Harrington rod instrumentation and posterior spinal fusion at our hospital by two senior orthopaedic surgeons. Between 1987 and 1990, seventy-one consecutive patients with the same diagnosis were treated with Cotrel-Dubousset instrumentation and posterior spinal fusion at the same hospital by three senior orthopaedic surgeons. All patients were invited to participate in the study, and seventy-eight patients (80%) treated with Harrington instrumentation and fifty-seven (80%) treated with Cotrel-Dubousset instrumentation agreed (Table I). Thirty-four patients did not participate for a variety of reasons, including lack of interest (nine); too long a traveling distance (five); pregnancy, recent delivery, or difficulties with child care (six); the patient's address was not known or he or she was abroad (seven); business commitments (five); or other disease (two). The mean age of the participants at the time of operation was 15.3 years (range, 10.8 to 22.5 years) in the Harrington instrumentation group and 15.4 years (range, 11.9 to 22.2 years) in the Cotrel-Dubousset instrumentation group. The mean duration of follow-up was 20.8 years (range, 19.1 to 22.4 years) and 13.0 years (range, 11.2 to 15.0 years), respectively. The results for the Harrington instrumentation group have been reported previously¹².

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TABLE I Comparison of Clinical and Radiographic Characteristics Between the Two Study Groups

Parameter	Harrington Instrumentation (N = 78)	Cotrel-Dubousset Instrumentation (N = 57)
Age^*(yr)
At time of surgery	15.3 ± 2.7	15.4 ± 2.2
At final follow-up evaluation	36.0 ± 2.8	28.3 ± 2.3
M/F	11/67	9/48
Duration of follow-up^*(yr)	20.8 ± 1.0	13.0 ± 0.9
King classification⁶ of scoliosis†
I	9 (12%)	2 (4%)
II	28 (36%)	24 (42%)
III	35 (45%)	26 (46%)
IV	4 (5%)	3 (5%)
V	2 (3%)	2 (4%)
Lowest fusion level†
T11	0 (0%)	2 (4%)
T12	4 (5%)	19 (33%)
L1	22 (28%)	13 (23%)
L2	28 (36%)	12 (21%)
L3	18 (23%)	11 (19%)
L4	6 (8%)	0 (0%)

The values are given as the mean and standard deviation. †The values are given as the number of patients, with the percentage in parentheses.

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TABLE I Comparison of Clinical and Radiographic Characteristics Between the Two Study Groups

Parameter	Harrington Instrumentation (N = 78)	Cotrel-Dubousset Instrumentation (N = 57)
Age^*(yr)
At time of surgery	15.3 ± 2.7	15.4 ± 2.2
At final follow-up evaluation	36.0 ± 2.8	28.3 ± 2.3
M/F	11/67	9/48
Duration of follow-up^*(yr)	20.8 ± 1.0	13.0 ± 0.9
King classification⁶ of scoliosis†
I	9 (12%)	2 (4%)
II	28 (36%)	24 (42%)
III	35 (45%)	26 (46%)
IV	4 (5%)	3 (5%)
V	2 (3%)	2 (4%)
Lowest fusion level†
T11	0 (0%)	2 (4%)
T12	4 (5%)	19 (33%)
L1	22 (28%)	13 (23%)
L2	28 (36%)	12 (21%)
L3	18 (23%)	11 (19%)
L4	6 (8%)	0 (0%)

The values are given as the mean and standard deviation. †The values are given as the number of patients, with the percentage in parentheses.

Study Design

The study design was a retrospective comparison of two cohorts. Preoperative and postoperative data were collected from the medical and hospital records. Follow-up physical examinations were performed by two independent observers. Standing posteroanterior radiographs of the whole spine were made preoperatively, two years postoperatively, and at the final follow-up visit. A lateral radiograph was made at the last follow-up visit. The Scoliosis Research Society questionnaire¹⁸ was mailed to the patients at the same time as the invitation to participate in the study. Previously validated spinal mobility and non-dynamometric trunk performance tests^19,20 were carried out at the follow-up visit.

Operative Technique and Postoperative Treatment

The details of our operative technique for application of Harrington rod instrumentation have been reported previously¹². Fifty (64%) of the seventy-eight patients treated with Harrington instrumentation underwent a two-stage procedure with a two-week interval between the operations. During the first operation, a Harrington distraction rod was inserted. During the second operation, posterior spinal fusion was performed with an osteoperiosteal tibial autograft and matchstick autografts from the spinous processes. The Harrington rod was routinely removed from those patients two years postoperatively, when fusion was evident radiographically. The remaining twenty-eight patients (36%) underwent a one-stage procedure involving application of a Harrington distraction rod and posterior spinal fusion with an osteoperiosteal tibial autograft (nine patients) or autologous iliac crest bone grafts (nineteen patients). These patients were allowed to walk one week postoperatively, and they wore a Milwaukee brace for six to nine months.

The Cotrel-Dubousset instrumentation was applied according to established guidelines²¹. The basic right thoracic hook pattern with concave rod rotation was used in forty-seven patients, and the modified hook pattern described by Shufflebarger and Clark²² was used in the remaining ten patients. Arthrodesis included decortication of the laminae, cleaning of the facet joints, and use of autograft from the posterior iliac crest. The patients treated with Cotrel-Dubousset instrumentation were allowed to walk on the second or third postoperative day, without restrictions and with no postoperative immobilization.

Neither group received prophylactic antibiotics preoperatively or intraoperatively.

Physical Examination

At the final follow-up evaluation, the patients underwent a systematic physical examination, including a complete neurological examination of the lower extremities. When the lower extremities were of unequal length, wooden blocks were placed beneath the short extremity for the clinical evaluation of spinal balance and the radiographic studies. Asymmetry of the waist was defined subjectively as being present or not present. The degree of rib hump was measured with a scoliometer²³.

Radiographic Evaluation

Standard standing posteroanterior and lateral radiographs of the entire spine were made. The thoracic and lumbar curves were measured with use of the Cobb technique²⁴. Spinal balance was determined on the basis of horizontal distance, in millimeters, of the C7 spinous process from the center sacral line. The curve patterns seen on the preoperative radiographs were classified according to the system of King et al.⁶. On the follow-up lateral radiographs, the thoracic kyphosis (between T4 and T12) and the lumbar lordosis (between L1 and L5) were measured²⁴. The status of the instrumentation was defined as in place and stable, loose, or removed. In addition, pseudarthrosis, degenerative changes (narrowing of the disc space and sclerosis of the facets), and vertebral subluxation (posterior, anterior, or lateral) were recorded.

Questionnaire

The Scoliosis Research Society questionnaire¹⁸ was translated into Finnish and was mailed to all patients before their follow-up visit. The questionnaire includes twenty-four questions, and the maximum possible score is 120 points, indicating that the patient is highly satisfied and asymptomatic. The questionnaire was completed by the patients at home and was returned at the follow-up visit. The answers were verified during the physical examination.

Spinal Mobility and Non-Dynamometric Trunk Performance Tests

Functional tests and measurements of spinal mobility and trunk muscle strength were carried out by the same physiotherapist. Spinal mobility was determined by measuring lumbar flexion and extension in degrees with a goniometer¹⁹. Trunk side-bending was defined by the distance, in centimeters, measured with a tape measure from the fingertips on the thigh to the knee joint¹⁹. An individual spinal mobility measurement was graded as abnormal when the value was below the mean age and sex-adjusted reference value by two standard deviations of that value¹⁹. Non-dynamometric trunk strength was evaluated by having the patient perform repetitive sit-up, arch-up, and squatting tests²⁰, with one repetition every two to three seconds for all tests. The movement was repeated as many times as possible at a comfortable but constant rate, with a maximum of fifty repetitions²⁰. The trunk strength results were scored from 1 (poor) to 5 (excellent). The result was considered to be poor when it was below the mean age and sex-adjusted normal population value by one standard deviation or more, and it was considered to be excellent when it exceeded the mean by one standard deviation or more²⁰.

Definitions

Subluxation of a lumbar vertebra was defined² as displacement of the vertebral body in the sagittal or coronal plane by >2 mm. Lower-extremity length discrepancy was recorded when it exceeded 5 mm. A disc space was considered to be narrowed when it was <50% of an adjacent, normal disc space²⁵. Spinal imbalance was recorded when the horizontal distance of the C7 spinous process from the center sacral line exceeded 20 mm.

Statistical Analysis

Statistical comparisons were performed with the chi-square test or the Mann-Whitney U test. Correlations were calculated with the Spearman rank correlation test. P values of =0.05 were considered to be significant.

Ethical Aspects

All participants provided informed consent. The authors obtained permission to perform this study from the ethics committee of the hospital where the study was conducted.

Results

Materials and Methods | Results | Discussion | References

Radiographic Results

The classifications according to the system described by King et al.⁶ and the lowest levels of the fusions are listed in Table I. Preoperatively, the mean Cobb angle of the thoracic curves was 53° (range, 37° to 79°) in the Harrington instrumentation group and 55° (range, 36° to 83°) in the Cotrel-Dubousset instrumentation group. The mean lumbar curve was 36° (range, 16° to 69°) and 34° (range, 10° to 64°), respectively. The mean number of vertebrae included in the instrumentation was 10.7 (range, eight to fourteen) and 9.9 (range, seven to twelve), respectively. There were more free lumbar intervertebral disc spaces in the Cotrel-Dubousset instrumentation group. Table II shows the magnitudes of the coronal plane deformities and the amounts of correction in both groups at the two-year and final follow-up visits. Significantly greater correction was achieved and maintained with use of Cotrel-Dubousset instrumentation.

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TABLE II Radiographic Degree and Correction of Coronal Plane Deformities

	Harrington Instrumentation^* (N = 78)	Cotrel-Dubousset Instrumentation^* (N = 57)	P Value†
Thoracic curve
Preoperative (deg)	53 ± 10	55 ± 10	NS
Two-year follow-up (deg)	38 ± 11	25 ± 12	<0.0001
Correction (%)	27 ± 18	55 ± 15	<0.0001
Final follow-up (deg)	45 ± 12	32 ± 11	<0.0001
Final correction (%)	14 ± 25	41 ± 19	<0.0001
Lumbar curve
Preoperative (deg)	36 ± 12	34 ± 11	NS
Two-year follow-up (deg)	27 ± 11	20 ± 15	0.0001
Correction (%)	29 ± 25	49 ± 39	<0.0001
Final follow-up (deg)	31 ± 13	23 ± 13	0.0012
Final correction (%)	15 ± 31	35 ± 33	0.0001

The values are given as the mean and standard deviation. †NS = not significant.

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TABLE II Radiographic Degree and Correction of Coronal Plane Deformities

	Harrington Instrumentation^* (N = 78)	Cotrel-Dubousset Instrumentation^* (N = 57)	P Value†
Thoracic curve
Preoperative (deg)	53 ± 10	55 ± 10	NS
Two-year follow-up (deg)	38 ± 11	25 ± 12	<0.0001
Correction (%)	27 ± 18	55 ± 15	<0.0001
Final follow-up (deg)	45 ± 12	32 ± 11	<0.0001
Final correction (%)	14 ± 25	41 ± 19	<0.0001
Lumbar curve
Preoperative (deg)	36 ± 12	34 ± 11	NS
Two-year follow-up (deg)	27 ± 11	20 ± 15	0.0001
Correction (%)	29 ± 25	49 ± 39	<0.0001
Final follow-up (deg)	31 ± 13	23 ± 13	0.0012
Final correction (%)	15 ± 31	35 ± 33	0.0001

The values are given as the mean and standard deviation. †NS = not significant.

The mean thoracic kyphosis at the time of final follow-up was 28° (range, 2° to 84°) in the Harrington instrumentation group. With the exclusion of one patient with a thoracic lordosis of 38°, the kyphosis averaged 33° (range, 8° to 70°) in the Cotrel-Dubousset instrumentation group. With the exclusion of one patient with a lumbar kyphosis of 8°, the mean lumbar lordosis at the final follow-up visit averaged 33° (range, 12° to 61°) in the Harrington instrumentation group. The mean lumbar lordosis averaged 40° (range, 5° to 72°) in the Cotrel-Dubousset instrumentation group. This difference was not significant. Lateral subluxation of the lumbar vertebrae was found in five patients treated with Harrington instrumentation but in none treated with Cotrel-Dubousset instrumentation (p = 0.051). Radiographic evidence of spinal imbalance (a horizontal distance of >20 mm) was found in nine patients (12%) treated with Harrington instrumentation and in four patients (7%) treated with Cotrel-Dubousset instrumentation. Narrowing of the lumbar disc spaces was observed in nineteen patients (24%) and degenerative lumbar spondylosis (sclerosis of facets, end-plate sclerosis, and osteophyte formation) was seen in seventeen patients (22%) treated with Harrington instrumentation. None of these changes was noted in the Cotrel-Dubousset instrumentation group (p < 0.001).

Clinical Results

At the final follow-up evaluation, fifty (64%) of the seventy-eight patients treated with Harrington instrumentation and twenty-nine (51%) of the fifty-seven treated with Cotrel-Dubousset instrumentation had waist asymmetry, whereas thirteen and eleven, respectively, had lower-extremity length discrepancy (mean, 10 mm; range, 5 to 20 mm). The mean magnitude of the thoracic rib hump, as measured with a scoliometer at the final follow-up evaluation, was similar in the two groups: 13° (range, 2° to 25°) and 11° (range, 1° to 21°), respectively. The neurological examination of the lower extremities revealed abnormal findings in one patient treated with Cotrel-Dubousset instrumentation (see Complications).

Subjective Patient Outcome as Assessed with the Scoliosis Research Society Questionnaire

The total score on the Scoliosis Research Society questionnaire averaged 97 points in both groups. Ten patients (13%) treated with Harrington instrumentation and six (11%) treated with Cotrel-Dubousset instrumentation reported that they felt back pain often or very often. Neither the magnitudes of the thoracic or lumbar curves or the corrections of those curves at the final follow-up visit correlated with the total score on the questionnaire. A significant inverse correlation was observed between the magnitude of the thoracic curve and the score for appearance in clothes (r_s = —0.29, p = 0.0029) at the final follow-up visit. No correlations were found between the scores for any of the other Scoliosis Research Society questions and the magnitude of the thoracic or lumbar curve. The magnitude of the rib hump as measured with a scoliometer had a significant inverse correlation with the appearance in clothes (r_s = —0.35, p = 0.0003) but did not correlate with the total score or the score for any other question on the Scoliosis Research Society questionnaire.

Trunk Strength and Spinal Mobility

The results of the trunk strength and spinal mobility measurements are shown in Table III. The mean score for squatting was significantly higher in the Cotrel-Dubousset instrumentation group than in the Harrington instrumentation group (p = 0.010). No correlations were observed between the magnitudes of the thoracic or lumbar curves and the trunk strength measurements. The numbers of patients with abnormal lumbar extension and trunk side-bending were significantly higher in the Harrington instrumentation group (p = 0.050 and p = 0.0061, respectively), and it remained higher in that group when patients with King Type-I curves were excluded from both groups (30% compared with 15% had abnormal lumbar extension [p = 0.039] and 56% compared with 36% had abnormal trunk side-bending [p = 0.026]). No correlations were observed between the magnitudes of the thoracic or lumbar curves and the spinal mobility measurements.

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TABLE III Trunk Strength and Spinal Mobility Measurements

Characteristic	Harrington Instrumentation^* (N = 78)	Cotrel-Dubousset Instrumentation^* (N = 57)	P Value†
Sit-up score^*(points)	3.0 ± 1.3	2.9 ± 1.3	NS
Arch-up score^*(points)	3.8 ± 1.3	4.2 ± 0.9	0.17
Squatting score^*(points)	3.6 ± 1.9	4.2 ± 1.2	0.010
Abnormal lumbar flexion‡	18 (23%)	9 (16%)	0.41
Abnormal lumbar extension‡	22 (28%)	8 (14%)	0.050
Abnormal trunk side-bending‡	46 (59%)	20 (35%)	0.0061

The values are given as the mean and standard deviation. †NS = not significant. ‡The values are given as the number of patients, with the percentage in parentheses. The value was considered abnormal when it was two standard deviations below the mean age and sex-adjusted normal population value¹⁹.

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TABLE III Trunk Strength and Spinal Mobility Measurements

Characteristic	Harrington Instrumentation^* (N = 78)	Cotrel-Dubousset Instrumentation^* (N = 57)	P Value†
Sit-up score^*(points)	3.0 ± 1.3	2.9 ± 1.3	NS
Arch-up score^*(points)	3.8 ± 1.3	4.2 ± 0.9	0.17
Squatting score^*(points)	3.6 ± 1.9	4.2 ± 1.2	0.010
Abnormal lumbar flexion‡	18 (23%)	9 (16%)	0.41
Abnormal lumbar extension‡	22 (28%)	8 (14%)	0.050
Abnormal trunk side-bending‡	46 (59%)	20 (35%)	0.0061

Complications

Nine patients (12%) in the Harrington instrumentation group and fifteen (26%) the Cotrel-Dubousset instrumentation group had a complication (p = 0.027). Four patients treated with Cotrel-Dubousset instrumentation sustained an intraoperative laminar fracture. One patient treated with Harrington instrumentation had a pseudarthrosis at the thoracolumbar junction. The caudad hook became dislodged during the follow-up period in eight patients treated with Harrington instrumentation and in six patients treated with Cotrel-Dubousset instrumentation. One early infection and three late deep infections developed in the Cotrel-Dubousset instrumentation group, but none developed in the Harrington instrumentation group (p = 0.018). The deep infections resolved after removal of hardware in all patients. A spastic paresis of the left lower extremity was observed immediately after the operation in one patient who had been treated with Cotrel-Dubousset instrumentation for a severe double curve. There was no mechanical compression, and overcorrection was assumed to be the reason for the neurological deficit. The Cotrel-Dubousset instrumentation was removed, and posterior instrumentation consisting of two Harrington rods and a device for transverse traction was applied with less correction. The paresis gradually resolved. At the final follow-up evaluation, hyperreflexia of the left lower extremity persisted.

Discussion

Materials and Methods | Results | Discussion | References

As seen radiographically, the long-term correction of adolescent idiopathic scoliosis with Cotrel-Dubousset instrumentation is significantly better than that seen after Harrington rod instrumentation. Both systems fail to correct rotational deformity, with the clinical appearance of the rib hump being equal after the two types of procedures. Cotrel-Dubousset instrumentation provided better restoration of both thoracic kyphosis and lumbar lordosis in our series. There were more free lumbar intervertebral disc spaces in the Cotrel-Dubousset instrumentation group, which produced significantly better spinal mobility in the long-term. The mean total scores on the Scoliosis Research Society questionnaire were the same in the two groups.

Validity of the Data

Owing to the nature of our study design, the mean follow-up time in the Harrington instrumentation group was almost eight years longer than that in the Cotrel-Dubousset instrumentation group. The participation rate was 80% in both groups. A similar methodology was applied in the two groups. Age and sex-adjusted reference values were used in the analysis of trunk strength and spinal mobility. The effect of age on Scoliosis Research Society questionnaire scores is not known. Degenerative changes in the lumbar spine, such as narrowing of the disc spaces, sclerosis of the facets, and vertebral subluxation, increased with age and were significantly more common in the Harrington instrumentation group than in the Cotrel-Dubousset instrumentation group. However, the prevalence of low-back pain was similar in the two groups.

Comparison with Previous Studies

Schlenzka et al.¹⁰ compared the radiographic results of Harrington-Wisconsin instrumentation with those of Cotrel-Dubousset instrumentation in a series of patients treated for adolescent idiopathic scoliosis. In contrast to our results, they found that the two systems provided similar amounts of correction of the thoracic curve. The less favorable long-term results observed in the Harrington instrumentation group in our study were partly due to loss of correction caused by removal of hardware and subsequent bending of the fusion mass¹². Moreover, unlike Harrington-Wisconsin instrumentation, the Harrington instrumentation included only one distraction rod. In accordance with our results, Schlenzka et al. could not find any difference between the two techniques with respect to postoperative apex rotation of the primary curves, as measured with the Pedriolle method. However, they did not assess the rib hump clinically. Willers et al.²⁶ showed, on computed tomography scans, that although Harrington rod instrumentation corrects coronal plane deformity, it does not decrease the rib hump, which is the major cosmetic deformity. In the present study, the mean rib-hump angles were similar in the two groups. This angle, measured with a scoliometer, correlated inversely with the score for appearance in clothes.

Dickson et al.⁹ did not find any correlation between back pain or fatigue and the type of curve, the degree of curvature on the preoperative or follow-up radiographs, the extent of fusion into the lumbar spine, or the presence of a broken rod. In contrast, Connolly et al.² found significant correlations between a low spine score on their own questionnaire and an increased Cobb angle of the secondary curve, increased kyphosis, and sclerosis of the facets. Lenke et al.¹⁵ observed that 38% (twenty-four) of sixty-three patients who had been treated with Cotrel-Du*bousset instrumentation reported low-back pain without evidence of lumbar disc degeneration. We found a substantially lower prevalence of low-back pain, as demonstrated by the responses on the Scoliosis Research Society questionnaire, in both of our groups, and the prevalence tended to be lower in the Cotrel-Dubousset instrumentation group than in the Harrington instrumentation group.

D'Andrea et al.²⁷ studied patient outcome with use of the Scoliosis Research Society questionnaire after anterior and posterior instrumentation in patients with adolescent idiopathic scoliosis. They did not find any correlation between the radiographic score or its improvement and the total score on the questionnaire. We did, however, note a significant correlation between the score for appearance in clothes and the magnitude of the primary curve.

Behensky et al.²⁸ studied spinal mobility in fifteen pairs of patients with adolescent idiopathic scoliosis, with one patient treated with Harrington instrumentation and the other treated with Cotrel-Dubousset instrumentation. Applying methods similar to those used in the present study, they did not find any difference in spinal mobility between the study groups after a minimum of four years. There were more free lumbar intervertebral disc spaces in the Cotrel-Dubousset instrumentation group, which produced substantially better spinal mobility in the long-term. Thus, the number of patients with abnormal lumbar extension or trunk side-bending was lower in the Cotrel-Dubousset group than in the Harrington instrumentation group.

To our knowledge, non-dynamometric trunk strength has not been measured previously in a long-term comparative study of treatment for adolescent idiopathic scoliosis. Although many of our patients had a long fusion from the upper thoracic spine to the middle of the lumbar spine, they performed, on the average, as well as the age and sex-adjusted reference population on the tests of trunk strength^19,20. Cotrel-Dubousset instrumentation preserved spinal mobility and sagittal balance somewhat better than Harrington instrumentation did, which may partially explain the better performance of these patients on the squatting test. In addition, improved spinal alignment may enable spinal and abdominal muscles to function more effectively.

Complications were significantly more common in the patients treated with the more complex Cotrel-Dubousset instrumentation than in those treated with the Harrington instrumentation. In particular, there was a higher prevalence of deep infections in the Cotrel-Dubousset instrumentation group. One possible explanation for this difference is that the operative time was significantly shorter for the Harrington rod instrumentation. The greater bulk and modularity of the Cotrel-Dubousset instrumentation also may be a contributing factor²⁹. Use of prophylactic antibiotics could have decreased the number of deep infections³⁰.

In conclusion, while the long-term radiographic outcome after the use of Cotrel-Dubousset instrumentation was significantly better than that after the use of Harrington rod instrumentation in the treatment of adolescent idiopathic scoliosis, clinical scores did not differ between the two groups. Long-term spinal mobility was better preserved in the Cotrel-Dubousset instrumentation group than in the Harrington instrumentation group, but the prevalence of low-back pain was similar in the two groups. The measurements of non-dynamometric trunk strength were, on the average, as good as those in the reference population, but they were better in the Cotrel-Dubousset instrumentation group than in the Harrington instrumentation group. The rib hump, which was the patients' main concern, was not corrected by either operation.

References

Materials and Methods | Results | Discussion | References

HarringtonPR. Treatment of scoliosis. Correction and internal fixation by spine instrumentation. J Bone Joint Surg Am.1962;44: 591-610.44591 1962

ConnollyBJ, Von Schroeder HP, Johnson GE, Kostuik JP. Adolescent idiopathic scoliosis. Long-term effect of instrumentation extending to the lumbar spine. J Bone Joint Surg Am.1995;77: 1210-6.771210 1995 [PubMed]

DicksonJH, Mirkovic S, Noble PC, Nalty T, Erwin WD. Results of operative treatment of idiopathic scoliosis in adults. J Bone Joint Surg Am.1995;77: 513-23.77513 1995 [PubMed]

GoldsteinLA. Treatment of idiopathic scoliosis by Harrington instrumentation and fusion with fresh autogenous iliac bone grafts. J Bone Joint Surg Am.1969;51: 209-22.51209 1969 [PubMed]

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Topics

scoliosis ; intervertebral mobility ; trunk structure ; adolescent idiopathic scoliosis ; posterior segmental spinal instrumentation ; harrington rod

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Ilkka Helenius, MD, PhD

Posted on December 30, 2003

Dr. Helenius and colleague respond

ORTON, Orthopaedic Hospital, Helsinki, Finland

We thank Dr Price for his interest in our retrospective comparative study between Harrington and Cotrel-Dubousset instrumentation in adolescent idiopathic scoliosis (JBJS Am 2003;85-A:2303-2309). Due to the historical nature of the study design, the studied groups were somewhat different, as the number of patients with King type I curves was three times (9/78 vs 2/57) more common in Harrington than in Cotrel-Dubousset instrumentation group. It is true that anterior instrumentation (Zielke) alone or along with Cotrel-Dubousset instrumentation was used for thoracolumbar or lumbar curves during the study period (between 1987 and 1990). However, those patients treated with anterior instrumentation were not included in the present study, which may have produced a small selection bias to this study. In the original manuscript we stated: "If patients with King type I curves were excluded from both groups, the number of patients with abnormal lumbar extension (30% vs. 15%) and trunk side bending (56% vs. 36%) was significantly higher in the Harrington rod instrumentation group (p = 0.039 and p = 0.026, respectively) (than in Cotrel-Dubousset instrumentation group). No correlations were observed between the magnitudes of the thoracic or lumbar curves and the spinal mobility measurements."

The large and significant difference in the radiographic correction does not disappear, if patients with King type I curves are excluded from both groups (Table 1), but instead becomes even more stronger.

Thus, based on our article and additional data represented here, we do not believe that improvements seen in this study would be due to patient selection or improvements in anteriorsurgery. Instead, we can conclude that Cotrel-Dubousset instrumentation yielded better long-term functional and radiographic outcomes in patients with adolescent idiopathic scoliosis than did Harrington instrumentation, even if patients with lumbar curves were excluded.

Ilkka Helenius, MD, PhD,Â Research Fellow
Mikko Poussa, MD, PhD, Chief Orthopedic Surgeon
ORTON, Orthopaedic Hospital, Helsinki, Finland

Table 1. Radiographic correction in coronal plane deformities if patients with King type I curve are excluded.

Â	Harrington Instrumentation (n=69)	Cotrel-Dubousset Instrumentation (n=55)	P value
Thoracic curve	Â	Â	Â
Â Â Â Preoperative	54Â±10Â°	55Â±10Â°	N. S.
Â Â Â Two-year follow-up	39Â±101Â°	25Â±12Â°	<0.0001
Â Â Â Correction	27Â±178%	55Â±15%	<0.0001
Â Â Â Final follow-up	45Â±12Â°	33Â±11Â°	<0.0001
Â Â Â Final correction	15Â±26%	40Â±19%	<0.0001
Lumbar curve	Â	Â	Â
Â Â Â Preoperative	35Â±11Â°	33Â±11Â°	N. S.
Â Â Â Two-year follow-up	26Â±11Â°	19Â±15Â°	0.0001
Â Â Â Correction	29Â±26%	50Â±39%	<0.0001
Â Â Â Final follow-up	29Â±13Â°	23Â±13Â°	0.001
Â Â Â Final correction	15Â±32%	35Â±32%	0.0001

Charles T. Price, M.D.

Posted on December 15, 2003

A Comparison of Harrington and Cotrel-Dubousset Instrumentation

Nemours Children's Clinic, 83 W. Columbia Ave., Orlando, FL 32806.

To the Editor:

The article by Helenius, et.al., "Harrington and Cotrel-Dubousset Instrumentation in Adolescent Idiopathic Scoliosis" (JBJS 85A:2303-9) is an excellent attempt to compare an older method to a newer method. Changes in techniques are often made for theoretical reasons without proven benefit. Then it becomes difficult to perform randomized contemporaneous studies of efficacy. The authors have indicated some of the limitations of this historical method of comparison.

However, it should be noted that there are more than four times the number of lumbar curves (King I) in the Harrington group than in the Cotrel-Dubousset group. Did this represent a change in selection of lumbar curves for anterior instrumentation during the time when Cotrel-Dubousset instrumentation was available? If so, the Harrington group may contain a disproportionate number of lumbar curves that underwent two-stage distraction with posterior instrumentation rather than anterior instrumentation. This small selection bias could affect the comparison due to elimination of patients from the Cotrel-Dubousset group who would no longer be candidates for posterior surgery. Thus the improvements seen in this study may reflect changes in patient selection and improvements in anterior surgery rather than a change in posterior instrumentation.

Charles T. Price, M. D. Chief of Pediatric Orthopedics Surgeon in Chief Nemours Children's Clinic 83 W. Columbia Ave. Orlando, FL 32806

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Ilkka Helenius, Ville Remes, Timo Yrjönen, Mauno Ylikoski, Dietrich Schlenzka, Miia Helenius, Mikko Poussa; Harrington and Cotrel-Dubousset Instrumentation in Adolescent Idiopathic ScoliosisLong-Term Functional and Radiographic Outcomes. The Journal of Bone & Joint Surgery. 2003 Dec;85(12):2303-2309.

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