Harrington-Luque and Cotrel-Dubousset instrumentation for idiopathic thoracic scoliosis. A postoperative comparison using segmental radiologic analysis

Prediction of Scoliosis Curve Correction Using Pedicle Screw Constructs in AIS: A Comparison of Fulcrum Bend Radiographs and Traction Radiographs Under General Anesthesia

STUDY DESIGN

Retrospective radiographic review.

OBJECTIVES

Our objectives were to (1) compare the ability of fulcrum bend radiographs and traction radiographs under general anesthesia to predict correction of adolescent idiopathic scoliosis (AIS) using pedicle screw only constructs and (2) compare the fulcrum bend correction index (FBCI) with a new measurement: the traction correction index (TCI).

METHODS

This is a retrospective radiographic review of 80 AIS patients (62 female and 18 male), who underwent scoliosis correction with pedicle screw only constructs. The mean age at surgery was 14 years (range 9-20 years). Radiographic analysis was carried out on the preoperative and immediate postoperative posteroanterior standing radiographs and the preoperative fulcrum bend radiographs and traction radiographs under general anesthesia. FBCI is calculated by dividing the correction rate by the fulcrum flexibility and TCI is calculated by dividing the correction rate by the traction flexibility.

RESULTS

Preoperative mean Cobb angle of 63.9° was corrected to 25.8° postoperatively. The mean fulcrum bending Cobb angle was 37.6° and traction Cobb angle was 26.6°. The mean fulcrum flexibility was 41.1%, traction flexibility 58.4%, and correction rate 59.6%. The median FBCI was 137% and TCI was 104.3%.

CONCLUSIONS

When comparing fulcrum bend and traction radiographs, we found the traction radiographs to be more predictive of curve correction in AIS using pedicle screw constructs. TCI takes into account the curve flexibility better than FBCI.

Comparison of harrington rod and cotrel-dubousset devices in surgical correction of adolescent idiopathic scoliosis

Background

Since the time of Paul Harrington numerous implants have been introduced for correction of scoliosis, but none are ideal. Newer devices are very expensive, and in our country some patients cannot afford them.

Objectives

The aim of this study was to compare the results of the Harrington rod (HR) device and the newer Cotrel-Dubousset (CD) device in treatment of adolescent idiopathic scoliosis (AIS).

Materials and Methods

A retrospective review assessed patients with AIS admitted for spinal curve correction treated with HR (n = 120) and CD devices (n = 138) between October 1988 to April 2001 at the Shafa Yahyaeian Hospital, Tehran, Iran. We extracted information from the patient’s file and radiographs before, after and two years post-operation.

Results

The mean age of patients was 16.7 ± 2.5 years. There was no statistically significant difference between the two groups regarding gender, age, curve before surgery, and percentage of flexibility. The mean curvature was 70 ± 20.7 in the HR and 64.81 ± 19.4 in the CD group before surgery (P = 0.09); and the mean curvature was 40 ± 16.3 and 26.58 ± 15.37 in HR and CD groups respectively after surgery (P = 0.156). The mean curvature was 47.2 ± 15.9 in HR and 31.2 ± 15.4 in CD groups at two years follow-up (P = 0.156).

Conclusions

Results of many studies have shown no significant impairment in long-term quality of life and function in patients treated with Harrington rods. According to previously performed studies and the current study, surgical correction with Harrington rods seem to be comparable with the newer more expensive CD device. Although there is no doubt that the preference is to use newer devices in view of some disadvantages of HR, but this does not preclude using it for patients that cannot afford the newer devices.

Vertebral derotation in adolescent idiopathic scoliosis causes hypokyphosis of the thoracic spine

BACKGROUND

The purpose of this study was to test the hypothesis that direct vertebral derotation by pedicle screws (PS) causes hypokyphosis of the thoracic spine in adolescent idiopathic scoliosis (AIS) patients, using computer simulation.

METHODS

Twenty AIS patients with Lenke type 1 or 2 who underwent posterior correction surgeries using PS were included in this study. Simulated corrections of each patient's scoliosis, as determined by the preoperative CT scan data, were performed on segmented 3D models of the whole spine. Two types of simulated extreme correction were performed: 1) complete coronal correction only (C method) and 2) complete coronal correction with complete derotation of vertebral bodies (C + D method). The kyphosis angle (T5-T12) and vertebral rotation angle at the apex were measured before and after the simulated corrections.

RESULTS

The mean kyphosis angle after the C + D method was significantly smaller than that after the C method (2.7 ± 10.0° vs. 15.0 ± 7.1°, p < 0.01). The mean preoperative apical rotation angle of 15.2 ± 5.5° was completely corrected after the C + D method (0°) and was unchanged after the C method (17.6 ± 4.2°).

CONCLUSIONS

In the 3D simulation study, kyphosis was reduced after complete correction of the coronal and rotational deformity, but it was maintained after the coronal-only correction. These results proved the hypothesis that the vertebral derotation obtained by PS causes hypokyphosis of the thoracic spine.

Fixation points within the main thoracic curve: does more instrumentation produce greater curve correction and improved results?

STUDY DESIGN

Prospective consecutive multicenter case series.

OBJECTIVE

To compare fixation type and amount to curve correction controlled for curve flexibility.

SUMMARY OF BACKGROUND DATA

The enhanced spinal purchase from segmental fixation should increase the force implants can exert without failure. This study evaluates whether this translates into correction beyond that expected from preoperative bending radiographs in thoracic curves where maximum correction was feasible (1A, 1B, and nonselective 1C fusions).

METHODS

One hundred seventy-one Lenke type 1 curves (118 1A, 36 1B, 23 1C) with 2-year follow-up were evaluated for the number and type of fixation points within the main curves compared to the correction obtained on preoperative bend films. SRS scores were compared to the amount of correction.

RESULTS

The number of fixation points both within the curve (P = 0.01) and for each vertebral body (P = 0.002) was larger for curves with greater correction compared to the bend films than those with less correction. Overall absolute correction was best for all screw and screw and wire constructs, followed by hook and screw, and least with hooks. However, compared to the bend films, these differences were not significant (P = 0.132). For all groups, the SRS scores significantly improved (P < 0.001), and was slightly more notable for the all screw constructs than other instrumentation patterns (P = 0.023). However, there were no significant difference in this improvement between those correcting more and those correcting less than the bend films (P = 0.578).

CONCLUSION

Absolute curve correction improved most with all pedicle screw and screw and wire constructs, but, when compared to bending films, the number of fixation points is more important than fixation type for curve correction. Although SRS scores improved the most in those with all screw constructs, the significance of this improvement is uncertain, and the SRS scores did not relate to whether curve correction was more or less than the bend films.

The "X-Factor" index: a new parameter for the assessment of adolescent idiopathic scoliosis correction

The correction rate (CR) and fulcrum bending correction index (FBCI) based on the fulcrum bending radiograph (FBR) were parameters introduced to measure the curve correcting ability; however, such parameters do not account for contributions by various, potential extraneous "X-Factors" (e.g. surgical technique, type and power of the instrumentation, anesthetic technique, etc.) involved in curve correction. As such, the purpose of the following study was to propose the concept of the "X-Factor Index" (XFI) as a new parameter for the assessment of the correcting ability of adolescent idiopathic scoliosis (AIS). A historical cohort radiographic analysis of the FBR in the setting of hook systems in AIS patients (Luk et al. in Spine 23:2303-2307, 1998) was performed to illustrate the concept of XFI. Thirty-five patients with AIS of the thoracic spine undergoing surgical correction were involved in the analysis. Plain posteroanterior (PA) plain radiographs were utilized and Cobb angles were obtained for each patient. Pre- and postoperative PA angles on standing radiograph and preoperative fulcrum bending angles were obtained for each patient. The fulcrum flexibility, curve CR, and FBCI were determined for all patients. The difference between the preoperative fulcrum bending angle and postoperative PA angle was defined as Angle(XF), which accounted for the correction contributed by "X-Factors". The XFI, designed to measure the curve correcting ability, was calculated by dividing Angle(XF) by the fulcrum flexibility. The XFI was compared with the curve CR and FBCI by re-evaluating the original data in the original paper (Luk et al. in Spine 23:2303-2307, 1998). The mean standing PA and FBR alignments of the main thoracic curve were 58.3° and 24.5°, respectively. The mean fulcrum flexibility was 58.8%. The mean postoperative standing PA alignment was 24.7°. The mean curve CR was 58.0% and the mean FBCI was 101.1%. The mean XFI was noted as 1.03%. The CR was significantly positively correlated to curve flexibility (r = 0.66; p < 0.01).The FBCI (r = -0.47; p = 0.005) and the XFI (r = -0.45; p = 0.007) were significantly negatively correlated to curve flexibility. The CR was not correlated to Angle(XF) (r = 0.29; p = 0.089).The FBCI (r = 0.97; p < 0.01) and the XFI (r = 0.961; p < 0.01) were significantly positively correlated to Angle(XF). Variation in XFI was noted in some cases originally presenting with same FBCI values. The XFI attempts to quantify the curve correcting ability as contributed by "X-Factors" in the treatment of thoracic AIS. This index may be a valued added parameter to accompany the FBCI for comparing curve correction ability among different series of patients, instrumentation, and surgeons. It is recommended that the XFI should be used to document curve correction, compare between different techniques, and used to improve curve correction for the patient.

Surgical correction of scoliosis by in situ contouring: a detorsion analysis

STUDY DESIGN

A detorsion analysis of the scoliosis surgical correction by means of in situ contouring technique (ISC).

OBJECTIVE

To describe the technique of ISC. To measure the vertebral and intervertebral axial rotation in thoracic and lumbar curves and their correction obtained by ISC.

SUMMARY AND BACKGROUND DATA

The vertebral and intervertebral axial rotation allows to evaluate the severity of the curves. However, the intervertebral axial rotation is barely studied and the vertebral axial rotation is a controversial point of the surgical correction.

METHODS

Twenty patients with thoracic and lumbar scoliosis were operated on with ISC. Vertebral axial rotation at the apex and the sum of intervertebral axial rotations all along the curve were computed before and after surgery from the three-dimensional stereoradiographic reconstruction of the spine and the pelvis. All the measurements were made in the standing position.

RESULTS

Correction of the axial rotation was obtained at the apex of both thoracic and lumbar curves of idiopathic and degenerative scoliosis. The mean values of correction (in terms of axial rotation) were 8 degrees to 19 degrees (62%-67%). The percentage of correction of the sum of intervertebral axial rotations all along the curve, proposed as a "detorsion index" (preoperative - postoperative/preoperative), was found at 57% to 92%. No significant differences were found for the correction (in terms of axial rotation and detorsion) between idiopathic and degenerative curves.

CONCLUSIONS

The axial rotation was measured in clinics on standing patients with scoliosis from three-dimensional stereoradiographic reconstruction and demonstrated a reliable detorsion obtained by ISC.

Three-dimensional quantitative segmental analysis of scoliosis corrected by the in situ contouring technique

STUDY DESIGN

A three-dimensional analysis of right thoracic scoliosis before and after surgical correction was performed.

OBJECTIVE

To compare the orientations of the vertebrae in apical and junctional zones before and after surgery.

SUMMARY AND BACKGROUND DATA

Three-dimensional segmental analysis considering the lateral, sagittal, and axial (vertebral and intervertebral) rotations that can define apical and junctional zones has been described previously. Modern surgical techniques have been designed to correct scoliosis three-dimensionally. Therefore, the effect of the surgery must be evaluated in three dimensions.

METHODS

The three-dimensional reconstruction of the spine and pelvis of 10 patients with right thoracic scoliosis was obtained by a stereoradiographic method before and after surgery. The orientations of all vertebrae were computed, and the apical and junctional zones were defined. The correction of these characteristic vertebrae obtained by the in situ contouring technique was evaluated.

RESULTS

The mean three-dimensional pattern for the 10 patients was 20 degrees of vertebral axial rotation with 6 degrees of intervertebral extension in the thoracic apex and 30 degrees of vertebral lateral rotation with 10 degrees of intervertebral axial rotation in the junctional zones of the thoracic curve. The correction obtained by in situ contouring was 52% to 79% for all these three-dimensional vertebral orientations.

CONCLUSIONS

Three-dimensional reconstruction of the spine allows quantitative segmental analysis of the deformity. This could be used as a reliable tool to evaluate both the severity of the scoliosis and the effects of the surgical correction.

Patient and parental perception of adolescent idiopathic scoliosis before and after surgery in comparison with surface and radiographic measurements

STUDY DESIGN

This prospective 2-year follow-up study evaluated patients treated surgically for adolescent idiopathic scoliosis (AIS).

OBJECTIVE

To report parents' perception, patients' perception, and pain and disability before and after surgery and to examine their relationship to anthropometric, back surface, and radiographic measurements.

SUMMARY OF BACKGROUND DATA

No longitudinal studies have examined these factors and their interrelationships.

METHODS

Between 1995 and 1999, 39 AIS patients treated by anterior or posterior USS (Universal Spine System, Stratec, Oberdorf, Switzerland) instrumentation had complete prospective questionnaire, back surface, and radiographic appraisal.

RESULTS

The preoperative Visual Analogue Score (VAS) for pain-predominantly mild backache-was 24 mm (range, 0-78 mm), and the Oswestry Disability Index (ODI) score was 9.2% (0-44.4%). Patients and parents wanted surgery to correct spinal curvature, stop curve progression, and correct the rib-hump (thoracic) and hip and waist asymmetry (thoracolumbar curves). The maximum angle of trunk inclination correlated with VAS and with short-form McGill Pain Questionnaire scores for thoracic curves (P = 0.005, Spearman rank correlation coefficient). Apical vertebral translation correlated with short-form McGill scores and ODI for thoracolumbar curves (P < 0.006, Spearman rank correlation coefficient). Parents rated scoliosis problems more severely than did their children (P < 0.0001, repeated measures of multivariate analysis of variants). There was no change in body image, VAS, ODI, or short-form McGill scores by 2 years' follow-up. Parents and patients perceived scoliosis problems to be less by 2 years' follow-up (P < 0.0005, Wilcoxon matched-pairs signed ranks test). The preoperative surface asymmetry score correlated with the patients' grading of their rib-hump (P = 0.007).

CONCLUSIONS

Back pain incidence was higher than reported for healthy adolescents. Oswestry Disability Index was within normal adult limits. Pain varied by curve type, related to the maximum angle of trunk inclination and the maximum apical vertebral translation. After surgery, back pain and ODI were unchanged, but concerns regarding scoliosis were reduced.

A comparison of single-rod instrumentation with double-rod instrumentation in adolescent idiopathic scoliosis

STUDY DESIGN

A consecutive series of patients with idiopathic scoliosis treated with single-rod instrumentation was followed prospectively. Outcomes were compared with results obtained from a retrospective review of a consecutive series of patients treated with double-rod instrumentation.

OBJECTIVE

To compare single-rod instrumentation with segmental fixation with double-rod instrumentation for the treatment of adolescent idiopathic scoliosis.

SUMMARY OF BACKGROUND DATA

Mechanical testing of single-rod instrumentation with segmental fixation at every level showed it to be as resistant to torsion as a double-rod construct. A clinical trial was initiated to document the clinical outcome in single-rod patients.

METHODS

A total of 43 of 51 consecutive patients underwent spinal fusion with a single rod. Outcome was evaluated at a minimum of 2 years after surgery. The control group comprised 103 patients who had standard double-rod instrumentation at the same institution.

RESULTS

The single- and double-rod groups were similar with respect to age, sex, curve type, length of follow-up, curve magnitude, and best bend. For King III-V curves undergoing posterior spinal fusion, there was significantly less blood loss in the single-rod group (703 mL vs 1011 mL), less cell saver collection (189 mL vs 367 mL), and less operating time (220 minutes vs 260 minutes). Blood loss and operating time were not different for patients with King I and King II curves. There were eight patients (19%) requiring reoperation because of hardware-related problems in the single-rod group compared with four (4%) in the double-rod group. There were nine patients (21%) with broken rods in the single-rod group, six of whom were symptomatic and five of whom required reoperation. Two patients required multiple operations because of pseudarthrosis in the single-rod group. There were no broken rods in the double-rod group. The single-rod group had 2 early postoperative infections and no late infections compared with 10 late infections in the double-rod group. There was a statistically significant relationship between hardware problems and fusion below L1 in the single-rod group.

CONCLUSION

Because of rod failure, single-rod instrumentation should be considered only in curves that can be instrumented to L1 and higher.

Proximal kyphosis after posterior spinal fusion in patients with idiopathic scoliosis

STUDY DESIGN

For this retrospective study, preoperative and postoperative radiographs of posterior spinal fusions for idiopathic scoliosis were reviewed.

OBJECTIVES

To determine the prevalence and possible causes of proximal kyphosis after posterior spinal fusion for idiopathic scoliosis.

SUMMARY OF BACKGROUND DATA

Proximal kyphosis has been anecdotally noted after the insertion of Harrington rods and after use of the new posterior multisegmented hook/rod systems. In this study no attempt was made to determine whether this condition is painful or an adverse outcome for the patient or just a radiographic abnormality; however, it is suspected that this may be a problem in the long term, and it may be worthwhile to try to avoid it if predictive values can be ascertained.

METHODS

Patients with adolescent idiopathic scoliosis who had undergone posterior spinal fusion not extending above T3 with good-quality radiographs of the proximal thoracic spine and a minimum 2-year follow-up were studied. Of the 106 patients who underwent posterior spinal fusion from 1990 through 1994, 69 met the inclusion criteria. Abnormal kyphosis from T2 to the proximal level of the instrumented fusion was defined as kyphosis of more than 5 degrees above the summed normal angular segments.

RESULTS

Of 69 patients, 37 (54%) had normal proximal kyphosis, and 32 (46%) of the 69 were defined as having abnormal proximal kyphosis. In the 32 patients with abnormal proximal kyphosis, the measurement from T2 to the fusion was 10.3 degrees before surgery and 21.2 degrees after surgery. The normal group had kyphosis measuring 2.7 degrees from T2 to fusion before surgery and 5.3 degrees after surgery (P < 0.00001). Junctional kyphosis in the kyphosis group measured 6.5 degrees before surgery and 12.6 degrees after surgery, compared with normal kyphosis of 1.7 degrees and 2.6 degrees, respectively (P < 0.00001). When analyzing who would develop proximal kyphosis, preoperative one-level junctional kyphosis of more than 5 degrees above the proposed proximal instrumented vertebrae was shown to have the highest sensitivity (78%) and specificity (84%).

CONCLUSIONS

In this study, 32 (46%) of 69 patients had abnormal proximal kyphosis after undergoing posterior spinal fusion. A preoperative junctional kyphosis of more than 5 degrees above the proposed proximal instrumented vertebrae indicates that extending the fusion to a higher level in the thoracic spine would be beneficial in avoiding this problem.

Assessment of scoliosis correction in relation to flexibility using the fulcrum bending correction index

STUDY DESIGN

A prospective study on adolescent idiopathic scoliosis to assess a new method of describing frontal plane correction.

OBJECTIVE

To assess the difference between using the correction rate and using the new fulcrum bending correction index when describing scoliosis correction.

SUMMARY OF BACKGROUND DATA

A description of the outcome of scoliosis surgery based on the correction rate does not take into account the curve's flexibility.

METHODS

The fulcrum bending correction index is calculated by dividing the correction rate by the fulcrum flexibility (based on the fulcrum bending radiograph) and is expressed as a percentage. The fulcrum bending correction index was compared with the correction rate in 35 patients with adolescent idiopathic scoliosis undergoing surgical correction. These patients were divided into a stiff and a flexible group based on a fulcrum flexibility of 50% to show the advantage of the fulcrum bending correction index over the correction rate.

RESULTS

The difference in correction rate between the flexible (66%) and the stiff group (45%) was significant (P < 0.05). The difference in the fulcrum bending correction index between the flexible (96%) and the stiff group (107%) was not significant (P = 0.2).

CONCLUSIONS

The fulcrum bending correction index takes into account the curve flexibility and is therefore better than the correction rate for comparing curve correction and use of instrumentation systems between different series of patients. A fulcrum bending correction index of close to 100% suggests that the instrumentation has taken up all the flexibility revealed by the fulcrum bending radiograph. It is recommended that the fulcrum bending correction index be used in the future as part of the postoperative assessment of frontal plane correction in cases of thoracic scoliosis.

Eighteen-level analysis of vertebral rotation following Harrington-Luque instrumentation in idiopathic scoliosis

We used the Perdriolle method to measure the rotation of each vertebra from the seventh cervical to the fifth lumbar level, before and after posterior spinal arthrodesis and Harrington-Luque instrumentation in fifteen patients who had idiopathic scoliosis. The primary curve was corrected an average of 50 per cent and the secondary curve, an average of 73 per cent. Following the operation, the average number of vertebrae involved in the primary curve increased from seven (range, five to ten) to nine (range, seven to fifteen). The rotation of the apical vertebra of the primary curve increased 10 degrees in four patients and 5 degrees in two patients and decreased 5 degrees in one patient. The rotation of the apical vertebra of the secondary curve increased 10 degrees in three patients and 5 degrees in one patient and decreased 5 degrees in four patients. In seven patients, correction of the curve was associated with unexpected counter-rotation, beyond the levels of instrumentation, of three or more vertebral segments that had been in neutral position before the operation.