Yongjung J. Kim

Comparative analysis of pedicle screw versus hook instrumentation in posterior spinal fusion of adolescent idiopathic scoliosis.

Study Design. A retrospective matched cohort study. Objective. To comprehensively compare the 2-year postoperative results of posterior correction and fusion with segmental pedicle screw instrumentation versus with hybrid (proximal hooks and distal pedicle screws) constructs in adolescent idiopathic scoliosis (AIS) treated at a single institution. Summary of Background Data. Despite the reports of satisfactory correction and maintenance of scoliotic curves by pedicle screw instrumentation, there have been no reports on the comprehensive comparison of AIS treatment after segmental pedicle screw instrumentation versus hybrid instrumentation. Materials and Methods. A total of 58 AIS patients that underwent posterior fusion with hybrid instrumentation (29) or pedicle screw (29) instrumentation at a single institution were sorted and matched according to four criteria: similar patient age, fusion levels, identical Lenke curve type, and identical operative methods. Patients were compared at 2-year follow-up according to radiographic changes, operative time, intraoperative blood loss, pulmonary function tests, and SRS-24 outcome scores. Results. The two cohorts were well matched. The preoperative major Cobb angle averaged 62° in the screw group and 60° in the hybrid group. Average major curve correction was 70% in the screw group and 56% in the hybrid group (P = 0.001). At 2-year follow-up, major curve correction was 65% and 46%, respectively (P < 0.001). At 2-year follow-up, thoracic sagittal Cobb angle changes between T5 and T12 were 9.0° decrease in the screw group and 2.4° decrease in the hybrid group compared with preoperative (P = 0.024). There were no differences in the lowest instrumented vertebra below the lower end vertebra (P = 0.56), operative time (P = 0.14), and average estimated blood loss (P = 0.54). Two years following surgery, the screw group demonstrated improved percent predicted pulmonary function values compared with that of the hybrid group (FVC; 81% → 81% in screw group vs. 85% → 79% in hybrid group P = 0.08, FEV1; 73% → 79% in screw group vs. 79% → 75% in hybrid group, P = 0.006). Postoperative total SRS-24 scores were similar in both groups (hybrid group: 99 vs. screw group: 95) (P = 0.19). There were no neurologic complications related to hybrid or pedicle screw instrumentation. Conclusion. Pedicle screw instrumentation offers a significantly better major curve correction and postoperative pulmonary function values without neurologic problems compared with hybrid constructs. Both instrumentation methods offer similar junctional change, lowest instrumented vertebra, operative time, and postoperative SRS-24 outcome scores in the operative treatment of AIS.

Proximal junctional kyphosis in adult spinal deformity following long instrumented posterior spinal fusion : Incidence, outcomes, and risk factor analysis

Study Design. To analyze patient outcomes and risk factors associated with proximal junctional kyphosis (PJK) in adults undergoing long posterior spinal fusion. Objectives. To determine the incidence of PJK and its effect on patient outcomes and to identify any risk factors associated with developing PJK. Summary of Background Data. The incidence of PJK and its affect on outcomes in adult deformity patients is unknown. No study has concentrated on outcomes of patients with PJK. Risk factors for developing PJK are unknown. Methods. Radiographic data on 81 consecutive adult deformity patients with minimum 2-year follow-up (average 5.3 years, range 2–16 years) treated with long instrumented segmental posterior spinal fusion was collected. Preoperative diagnosis was adult scoliosis, sagittal imbalance or both. Radiographic measurements analyzed included the sagittal Cobb angle at the proximal junction on preoperative, early postoperative, and final follow-up standing long cassette radiographs. Additional measurements used for analysis included the C7-Sacrum sagittal plumb and the T5–T12 sagittal Cobb. Postoperative SRS-24 scores were available on 73 patients. Results. Incidence of PJK as defined was 26%. Patients with PJK did not have lower outcomes scores. PJK did not produce a more positive sagittal C7 plumb. PJK was more common at T3 in the upper thoracic spine. Conclusions. Incidence of proximal junctional kyphosis was high, but SRS-24 scores were not significantly affected in patients with PJK. The sagittal C7 plumb was not significantly more positive in PJK patients. No patient, radiographic, or instrumentation variables were identified as risk factors for developing PJK.

Results of lumbar pedicle subtraction osteotomies for fixed sagittal imbalance: a minimum 5-year follow-up study.

Study Design. Retrospective study. Objective. To report results at a minimum 5 years after pedicle subtraction osteotomy for fixed sagittal imbalance. Summary of Background Data. No one has reported results of pedicle subtraction osteotomies with a 5- to 8-year follow-up. Method. Thirty-five consecutive patients with sagittal imbalance (29 females/6 males, average age at surgery, 53.1 years) treated with lumbar pedicle subtraction osteotomies (1 at L1, 13 at L2, 20 at L3, and 1 at L4) at 1 institution were analyzed (average follow-up, 5.8 years; range, 5–7.6 years). Radiographic and clinical outcomes analysis was performed. Results. There were no significant regional radiographic changes between 2 years postoperative and the ultimate follow-up (proximal junctional change, P = 0.30; thoracic kyphosis, P = 0.38; and lumbar lordosis, P = 0.84), although many patients did demonstrate an increasingly anterior C7 sagittal plumb with time. Ten pseudarthroses (29%) occurred in 8 patients and were revised between 2 and 5 years postoperative. There were no pseudarthroses at the osteotomy level (9 at the thoracolumbar junction, 1 at the LS junction), but at the levels added to the previous fusions. There was no degradation in Oswestry and Scoliosis Research Society (SRS) outcome scores between 2 years postoperative and ultimate follow-up (P = 0.23 and 0.90, respectively). Patients reported very good satisfaction (87%), good self-image (76%), good function (69%), and fair pain subscales (66%) at ultimate follow-up. Sagittal vertical axis <8 cm at ultimate follow-up was significant for better SRS outcomes scores (P = 0.038). Eight patients with revised pseudarthroses did not demonstrate poorer SRS outcomes scores (P = 0.52). Those 8 patients were queried after their pseudarthrosis revision surgery. Conclusion. Pedicle subtraction osteotomy can provide satisfactory clinical and radiographic outcomes for patients with a minimum 5-year follow-up despite needing pseudarthrosis revision and some component of increasingly positive sagittal vertical axis between 2 years and 5 to 8 years of follow-up. The level of patient satisfaction and self-image subscales were high after more than 5 years of follow-up. Restoration and maintenance of sagittal vertical axis <8 cm were important to the ultimate sagittal reconstruction.

Pseudarthrosis in long adult spinal deformity instrumentation and fusion to the sacrum: prevalence and risk factor analysis of 144 cases.

Study Design. Retrospective study. Objective. To analyze the incidence of and risk factors for pseudarthrosis in long adult spinal instrumentation and fusion to S1. Summary of Background Data. Few studies on pseudarthrosis in long adult spinal instrumentation and fusion to S1 exist. Methods. A clinical and radiographic assessment of 144 adult patients with spinal deformity (average age 52.0 years; range 21.1–77.6) who underwent long (5–17 vertebrae, average 11.9) spinal instrumentation and fusion to the sacrum at a single institution between 1985 and 2002, with a minimum 2-year follow-up (average 3.9; range 2–14) was performed. Results. Of 144 patients, 34 (24%) had pseudarthroses. There were 17 patients who had pseudarthroses at T10–L2 and 15 at L5–S1. A total of 24 patients (71%) presented with multiple levels involved (2–6). Pseudarthrosis was most commonly detected within 4 years postoperatively (31 patients; 94%). Factors that statistically increased the risk of pseudarthrosis were: thoracolumbar kyphosis (T10–L2 ≥20° vs. <20°, P < 0.0001); osteoarthritis of the hip joint (P = 0.002); thoracoabdominal approach (vs. paramedian approach, P = 0.009); positive sagittal balance ≥5 cm at 8 weeks postoperatively (vs. ≤5 cm, P = 0.012); age at surgery older than 55 years (vs. 55 years or younger, P = 0.019); and incomplete sacropelvic fixation (vs. complete sacropelvic fixation, P = 0.020). Fusion from upper thoracic spine (T2–T5) did not statistically increase the pseudarthrosis rate compared to lower thoracic spine (T9–T12) (P = 0.20). Patients with pseudarthrosis had significantly lower Scoliosis Research Society 24 outcome scores (average score 71/120) than those without (average score 90/120; P < 0.0001) at ultimate follow-up. Conclusion. The overall prevalence of pseudarthrosis following long adult spinal deformity instrumentation and fusion to S1 was 24%. Thoracolumbar kyphosis, osteoarthritis of the hip joint, thoracoabdominal approach (vs. paramedian approach), positive sagittal balance ≥5 cm at 8 weeks postoperatively, older age at surgery (older than 55 years), and incomplete sacropelvic fixation significantly increased the risks of pseudarthrosis to an ex-tent that was statistically significant. Scoliosis Research Society 24 outcomes scores at ultimate follow-up were adversely affected when pseudarthrosis developed.

Proximal junctional kyphosis in adult spinal deformity after segmental posterior spinal instrumentation and fusion: minimum five-year follow-up.

Study Design. A retrospective study. Objective. To analyze time-dependent change of, prevalence of, and risk factors for proximal junctional kyphosis (PJK) in adult spinal deformity after long (≥5 vertebrae) segmental posterior spinal instrumented fusion with a minimum 5-year postoperative follow-up. Summary of Background Data. No study has focused on time-dependent long-term proximal junctional change in adult spinal deformity after segmental posterior spinal instrumented fusion with minimum 5-year follow-up. Methods. Clinical and radiographic data of 161 (140 women/21 men) adult spinal deformity patients with minimum 5-year follow-up (average 7.8 years, range 5–19.8 years) treated with long posterior spinal instrumentation and fusion were analyzed. Radiographic measurements included sagittal Cobb angle at the proximal junction on preoperative, 8-weeks postoperation, 2-year postoperation, and ultimate follow-up (≥5 years). Postoperative SRS outcome scores were also evaluated. Results. The prevalence of PJK at 7.8 years postoperation was 39% (62/161 patients). The PJK group (n = 62) demonstrated a significant increase in proximal junctional angle at 8 weeks (59%), between 2 years postoperation and ultimate postoperation (35%), and in thoracic kyphosis (T5–T12) at ultimate follow-up (P = 0.001). However, the sagittal vertical axis change at ultimate follow-up did not correlate with PJK (P = 0.53). Older age at surgery >55 years (vs. ≤55 years) and combined anterior and posterior spinal fusion (vs. posterior only) demonstrated significantly higher PJK prevalence (P = 0.001, 0.041, respectively). The SRS outcome scores did not demonstrate significant differences with the exception of the self-image domain when PJK exceeded 20°. Conclusion. The prevalence of PJK at 7.8 years postoperation was 39%. PJK progressed significantly within 8 weeks postoperation (59%) and between 2 years postoperation and ultimate follow-up (35%). Older age at surgery (>55 years) and combined anterior and posterior spinal fusion were identified as risk factors for developing PJK. The SRS outcome instrument was not adversely affected by PJK, except when PJK exceeded 20°.

Selective Posterior Thoracic Fusions for Adolescent Idiopathic Scoliosis: Comparison of Hooks versus Pedicle Screws

Study Design. A retrospective review of adolescent idiopathic scoliosis (AIS) patients with major thoracic-compensatory lumbar C modifier curves treated with a selective posterior fusion using an all-hook construct versus pedicle screw construct. Objectives. To compare the clinical and radiographic results of selective posterior thoracic fusion using hooks versus pedicle screws in patients with major thoracic-compensatory lumbar C modifier AIS curves. Summary of Background Data. Although spontaneous lumbar curve correction often occurs following a selective thoracic spinal fusion, there are few reports that focus on selective posterior thoracic spinal fusion in the presence of a lumbar C modifier curve. Methods. Sixty-six consecutive patients with major thoracic-compensatory lumbar C modifier AIS curves underwent selective posterior thoracic fusion to T12 or L1 at a single institution (1987–2001). Hooks were used for instrumentation in 32 patients and pedicle screws were used in 34 patients. Patients were evaluated at a minimum 2-year follow-up. To test for differences between groups analysis of covariance (ANCOVA) was used. Results. There was no statistical difference between the preoperative thoracic and lumbar Cobb values for the hook group versus the pedicle screw group. The amount of correction obtained surgically of the thoracic Cobb and the amount of spontaneous lumbar Cobb correction were significantly greater in the pedicle screw group (P < 0.001). The incidence of postoperative coronal decompensation, with a greater than 20 mm shift to the left of the C7 plumbline, was higher in the hook group (13 patients) as compared with the pedicle screw Group 4 patients (P < 0.005). There were no complications or reoperations in either group. Conclusion. Selective thoracic fusion of main thoracic-compensatory lumbar C modifier AIS curves with pedicle screws allowed for better thoracic correction and less postoperative coronal decompensation than seen with hooks.

Proximal junctional kyphosis in adolescent idiopathic scoliosis after 3 different types of posterior segmental spinal instrumentation and fusions: incidence and risk factor analysis of 410 cases.

Study Design. Retrospective study. Objective. Determine proximal junctional kyphosis (PJK) prevalence and analyze risk factors associated with PJK in adolescent idiopathic scoliosis (AIS) patients following 3 different posterior segmental spinal instrumentation and fusion surgeries. Summary of Background Data. No comparison study exists on proximal junctional AIS changes following 3 different segmental posterior spinal instrumentation and fusion surgeries at 2 years postoperative. Methods. A clinical/radiographic assessment was conducted in 410 consecutive AIS patients (average age = 14.7, range = 10.6–20) (men/women = 73/337) treated with instrumented segmental posterior spinal fusion with 2-year follow-up. Revision and anterior cases were not included. Standing long-cassette radiographic measurements were analyzed including various sagittal/coronal parameters for preoperative, early postoperative, and 2-year follow-up. Abnormal PJK was defined by proximal junction sagittal Cobb angles between the lower endplate of the uppermost instrumented vertebra and the upper endplate of 2 supradjacent vertebrae ≥+10° and at least 10° greater than the preoperative measurement at 2 years postoperative. Results. PJK prevalence defined at 2 years postoperative was 27% (111 of 410 patients). Statistically significant factors: larger preoperative thoracic kyphosis angle (T5–T12 >40° vs. T5–T12 10°–40° vs. T5–T12 <10°; P < 0.0001), greater immediate postoperative thoracic kyphosis angle decrease (decrease >5° vs. 5° decrease-5° increase vs. increase >5°; P < 0.0001), thoracoplasty versus no thoracoplasty (P = 0.001), and men versus women (P = 0.007). Instrumentation types (hook-only vs. proximal hook, distal pedicle screw vs. pedicle screw P = 0.058), number of fused vertebrae >12 versus 12≥ (P = 0.12), the uppermost instrumented vertebra among T2, T3, T4, T5 (P = 0.75). There were no significant differences in Scoliosis Research Society Patient Questionnaire-24 outcome-scores (PJK total score = 97.0, self-image subscales = 21.3 vs. non-PJK group = 95.3, 21.0) (P = 0.34 total score, P = 0.54 self-image subscale). Conclusion. Two-year postoperative PJK prevalence in AIS following 3 different posterior segmental spinal instrumentation and fusion surgeries was 27%. A larger preoperative thoracic kyphosis angle, greater immediate postoperative thoracic kyphosis angle decrease, thoracoplasty, and male sex correlated significantly with PJK. There were no significant differences in Scoliosis Research Society Patient Questionnaire-24 outcome-scores between the PJK and non-PJK group.

Proximal junctional kyphosis in adolescent idiopathic scoliosis following segmental posterior spinal instrumentation and fusion: minimum 5-year follow-up.

Study Design. A retrospective study. Objective. To analyze the long-term proximal junctional change in adolescent idiopathic scoliosis (AIS) following segmental posterior spinal instrumentation and fusion 5 years or more after surgery. Summary of Background Data. No study has concentrated on time-dependent long-term proximal junctional change in AIS following segmental posterior spinal instrumentation and fusion after 5 years postoperation. Risk factors for developing proximal junctional kyphosis (PJK) are unknown. Methods. A total of 193 consecutive AIS patients with a minimum 5-year follow-up (average, 7.3 years; range, 5–16.7 years) treated with segmental posterior spinal instrumentation and fusion were evaluated. Radiographic measurements analyzed included sagittal Cobb angle at the proximal junction on preoperative, early postoperation, 2-year postoperation, and final follow-up (≥5 years) by standing long cassette radiographs. Postoperative Scoliosis Research Society (SRS)-24 outcome scores were also evaluated. Abnormal PJK was defined as the final proximal junctional sagittal Cobb angle between the lower endplate of the uppermost instrumented vertebra and the upper endplate of two vertebrae supra-adjacent, which was > 10° and at least 10° greater than the preoperative measurement. Results. The incidence of PJK at 7.3 years postoperation was 26% (50 of 193 patients). The average proximal junctional angle increased 15.2° until 2 years postoperation and then increased 1.7° until final follow-up in the PJK group (n = 50). Factors that were statistically significant for PJK development were as follows: a thoracoplasty procedure (P = 0.001), preoperative hyperkyphotic thoracic alignment (T5–T12 > 40°) (P = 0.015), and hybrid instrumentation (proximal hooks and distal pedicle screws) compared with the hooks only group (P = 0.029). The number of fused vertebrae more than 11 was also related with PJK (P = 0.08). The level of the uppermost instrumented vertebra did not affect the PJK incidence. SRS-24 outcome scores did not demonstrate any significant differences (P = 0.54 for total score and P = 0.49 for self-image subscale) between the PJK and non-PJK groups. Conclusion. The incidence of proximal junctional kyphosis at 7.3 years postoperation was 26% and did not progress significantly after 2 years postoperation. Risk factors for developing PJK were an associated thoracoplasty, hybrid instrumentation (proximal hooks and distal pedicle screws), and a preoperative larger sagittal thoracic Cobb angle (T5–T12 > 40°). The SRS-24 outcome instrument was not affected by PJK.

Thoracic Adolescent Idiopathic Scoliosis Curves Between 70° and 100°: Is Anterior Release Necessary?

Study Design. A retrospective review of adolescents with main thoracic scoliotic curves surgically treated with either anterior release and posterior fusion or posterior fusion only. Objectives. To compare the radiographic and clinical outcomes of two surgical treatments: anterior-posterior spinal fusion (APSF) versus posterior spinal fusion (PSF) alone in patients with large 70° to 100° thoracic adolescent idiopathic scoliosis (AIS) curves. Summary of Background Data. Surgical treatment of thoracic AIS curves between 70° and 100° often consists of anterior and posterior fusion to improve the coronal correction and fusion rate, with the anterior release and fusion performed through either an open thoracotomy or by video-assisted thoracoscopy. Methods. All patients (n = 84) with main thoracic major AIS curves between 70° and 100° who underwent spinal fusion (APSF or PSF) at one center between 1987 and 2001 were included for analysis. The minimum follow-up was 2 years after surgery (mean, 4.5 years; range, 2.0–10.2 years). The mean age of patients was 13.8 years (range, 10.7–18.2 years), with 66 females and 18 males. Multiple radiographic measures were assessed. The primary and secondary statistical analyses performed were nonparametric analyses, using the Wilcoxon-Mann-Whitney tests for the primary analysis of APSF and PSF groups. The PSF subgroup analysis was performed with the Kruskal-Wallis test. Results. There were 22 patients in the APSF (open ASF in 18, and video-assisted thoracoscopy in 4) group and 62 patients in the PSF group. There were no statistically significant differences between the groups for gender, age, number of levels fused, Cobb measurement of preoperative coronal or sagittal thoracic curve magnitude, or coronal curve flexibility. The APSF group, when compared with the PSF group, had greater intraoperative correction of the coronal curve (48.3° vs. 38.7°, P = 0.0087) as well as final overall correction (47.2° vs. 34.2°, P = 0.0008). There were no significant differences seen in the sagittal alignment from T5–T12 (P = 0.3150) or the SRS outcomes data between the APSF and PSF only groups. Subanalysis of the PSF only group identified three distinct groups based on implants: hook-only constructs (n = 36), hybrid constructs of proximal hooks and distal pedicle screws (n = 15), and pedicle screw-only constructs (n = 11). Pedicle screw-only constructs corrected the coronal Cobb measurements more than the other two groups (47.5° vs. hooks 37.7° vs. hybrid 34.4°, P = 0.0110), and to a similar extent as to the APSF group with no statistically significant difference in coronal correction (PSF, 47.5°; APSF 48.3°; P = 0.9014), nor any other parameter except for sagittal T5–T12 changes. There were no reoperations for implant failure/pseudarthroses in any of the patients. Conclusion. APSF of large thoracic curves allows greater coronal correction of thoracic curves between 70° and 100°, when compared with PSF alone using thoracic hook constructs, but not with the use of thoracic pedicle screw constructs. Scoliosis surgeons not using pedicle screw constructs need to decide if the modest improvement in coronal correction with a combined approach justifies its routine use in this patient population.

Pulmonary function in adolescent idiopathic scoliosis relative to the surgical procedure

BACKGROUND The long-term pulmonary function of patients with adolescent idiopathic scoliosis undergoing surgical correction is uncertain. To our knowledge, no report has demonstrated the changes in pulmonary function five years or more following spinal arthrodesis with use of modern segmental spinal instrumentation techniques for the treatment of all types of adolescent idiopathic scoliosis in a similar adolescent population. METHODS One hundred and eighteen patients with adolescent idiopathic scoliosis undergoing surgical treatment at a single institution were evaluated with pulmonary function tests to assess the absolute and percent-predicted value of forced vital capacity and forced expiratory volume in one second at the preoperative examination and at regular intervals postoperatively. The patients were divided into four groups depending upon the surgical procedure: Group 1 comprised forty-nine patients who had posterior spinal arthrodesis with iliac crest bone graft; Group 2, forty-one patients who had posterior spinal arthrodesis with thoracoplasty; Group 3, sixteen patients who had open anterior spinal arthrodesis with a rib resection thoracotomy; and Group 4, twelve patients who had combined anterior and posterior spinal arthrodesis with a rib resection thoracotomy and iliac crest bone graft, respectively. RESULTS A comparison of absolute pulmonary function values from the preoperative and final follow-up evaluations demonstrated a significant (p < 0.0001) increase in both the forced vital capacity and the forced expiratory volume in one second for Group 1, whereas no change was seen in those values for Groups 2, 3, and 4. A comparison of the changes in the percent-predicted pulmonary function values demonstrated significant (p < 0.05) decreases in forced vital capacity and forced expiratory volume in one second for Groups 2, 3, and 4, except for the latter value for Group 4, whereas Group 1 had no change. CONCLUSIONS Patients who have had any type of chest cage disruption during the surgical treatment of adolescent idiopathic scoliosis demonstrate no change in the absolute value and a significant decline in the percent-predicted value of pulmonary functions at five years following surgery. Chest cage preservation is recommended to maximize both absolute and percent-predicted pulmonary function values after surgical treatment of adolescent idiopathic scoliosis.