Proximal junctional kyphosis and clinical outcomes in adult spinal deformity surgery with fusion from the thoracic spine to the sacrum: a comparison of proximal and distal upper instrumented vertebrae

Clinical article

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Object

Proximal junctional kyphosis (PJK) is a common and significant complication after corrective spinal deformity surgery. The object of this study was to compare—based on clinical outcomes, postoperative proximal junctional kyphosis rates, and prevalence of revision surgery—proximal thoracic (PT) and distal thoracic (DT) upper instrumented vertebra (UIV) in adults who underwent spine fusion to the sacrum for the treatment of spinal deformity.

Methods

In this retrospective study the authors evaluated clinical and radiographic data from consecutive adults (age > 21 years) with a deformity treated using long instrumented posterior spinal fusion to the sacrum in the period from 2007 to 2009. The PT group included patients in whom the UIV was between T-2 and T-5, whereas the DT group included patients in whom the UIV level was between T-9 and L-1. Perioperative surgical data were compared between the PT and DT groups. Additionally, segmental, regional, and global spinal alignments, as well as the sagittal Cobb angle at the proximal junction, were analyzed on preoperative, early postoperative, and final standing 36-in. radiographs. Patient-reported outcome measurements (visual analog scale, Scoliosis Research Society Patient Questionnaire-22, Oswestry Disability Index, and the 36-Item Short-Form Health Survey) were compared.

Results

Eighty-nine patients, 22 males and 67 females, had a minimum follow-up of 2 years, and thus were eligible for participation in this study. Sixty-seven patients were in the DT group and 22 were in the PT group. Operative time (p = 0.387) and estimated blood loss (p < 0.05) were slightly higher in the PT group. The overall rate of revision surgery was 48.0% and 54.5% in the DT and PT groups, respectively (p = 0.629). The prevalence of PJK according to radiological criteria was 34% in the DT group and 27% in the PT group (p = 0.609). The percent of patients with PJK that required surgical correction (surgical PJK) was 11.9% (8 of 67) in the DT group and 9.1% (2 of 22) in the PT group (p = 1.0). The onset of surgical PJK was significantly earlier than radiological PJK in the DT group (p < 0.01). The types of PJK were different in the PT and DT groups. Compression fracture at the UIV was more prevalent in the DT group, whereas subluxation was more prevalent in the PT group. Postoperatively, the PT group had less thoracic kyphosis (p = 0.02), less sagittal imbalance (p < 0.01), and less pelvic tilt (p = 0.04). In the DT group, early postoperative radiographs demonstrated that the proximal junctional angle of patients with surgical PJK was greater than in those without PJK and those with radiological PJK (p < 0.01). Clinical outcomes were significantly improved in both groups, and there was no significant difference between the groups.

Conclusions

Both PT and DT UIVs improve segmental and global sagittal plane alignment as well as patient-reported quality of life in those treated for adult spinal deformity. The prevalence of PJK was not different in the PT and DT groups. However, compression fracture was the mechanism more frequently observed with DT PJK, and subluxation was the mechanism more frequently observed in PT PJK. Strategies to avoid PJK may include vertebral augmentation to prevent fracture at the DT spine and mechanical means to prevent vertebral subluxation at the PT spine.

Abbreviations used in this paper:ASA = American Society of Anesthesiologists; DT = distal thoracic; ODI = Oswestry Disability Index; PJK = proximal junctional kyphosis; PT = proximal thoracic; R-PJK = radiographic PJK; S-PJK = surgical PJK; SF-36 = 36-Item Short-Form Health Survey; SRS-22 = Scoliosis Research Society Patient Questionnaire-22; SVA = sagittal vertical axis; UIV = upper instrumented vertebra; VAS = visual analog scale.

Article Information

Address correspondence to: Sigurd H. Berven, M.D., Department of Orthopedic Surgery, University of California, San Francisco, CA 94143-0112. email: BervenS@orthosurg.ucsf.edu.

Please include this information when citing this paper: published online July 12, 2013; DOI: 10.3171/2013.5.SPINE12737.

© AANS, except where prohibited by US copyright law.

Headings

Figures

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    Definition of proximal junctional angle: the caudal endplate of the uppermost instrumented vertebra to the cephalad endplate of 2 suprajacent vertebrae (UIV-2) above the UIV. The definition of PJK required the presence of both criteria: 1) proximal junction angle > 10°, and 2) proximal junction angle at least 10° greater than the preoperative measurement. A = proximal junctional angle.

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    Left: In the DT group, S-PJK developed significantly earlier than R-PJK. Most patients with S-PJK had revision surgery within 10 months after the index surgery. Right: In the PT group, there was no clear difference in onset time between S-PJK and R-PJK.

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    Comparison of preoperative, early postoperative, and last follow-up radiographic evaluations of proximal junctional angles in patients who had DT UIV or PT UIV. Left: DT UIV: In patients without PJK, the proximal junctional angle increased from 5.8° ± 1.3° preoperatively to 11.7° ± 1.1° early postoperatively and 11.7° ± 1.5° at the last follow-up. In patients with R-PJK, proximal junctional angle increased from 3.3° ± 1.2° preoperatively to 13.6° ± 1.4° at early postoperative and 22.0° ± 1.7° at last follow up. However, in patients with S-PJK, the proximal junctional angle increased from 8.7° ± 4.3° preoperatively to 29.6° ± 4.0° early postoperatively and 42.2° ± 3.0° at the last follow-up. Compared with the non-PJK patients, a significantly greater proximal junctional angle was observed in S-PJK (early postoperatively and at last follow-up) and R-PJK (last follow-up) patients. Right: PT UIV: In patients without PJK, the proximal junctional angle increased from 4.2° ± 1.0° preoperatively to 9.5° ± 1.4° early postoperatively and 10.3° ± 1.4° at the last follow-up. In PJK patients, the proximal junctional angle increased from 6.4° ± 2.3° preoperatively to 19.0° ± 4.4° early postoperatively and 27.2° ± 6.0° at the last follow-up. Compared with non-PJK patients, those with PJK had significantly greater proximal junctional angles on early postoperative and late follow-up radiographs. *p < 0.05 and **p < 0.01. n = number of patients; S.E. = standard error.

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    Case 1: Patient with DT UIV. This 59-year-old woman presented with kyphoscoliosis and previous L3–4 instrumented posterior spinal fusion. The sagittal C-7 plumb line on presentation was 239 mm, and she had 1° of thoracic kyphosis (T5–T12) and −1° of proximal junctional angle (T8–10). A: Preoperative radiograph. B: Immediately postoperative radiograph. The patient underwent a pedicle subtraction osteotomy at L-3 and posterior-only spinal instrumented fusion from T-10 to S-1 with local and autogenous iliac bone graft. C: At 9 months postsurgery, the patient returned with PJK. The sagittal C-7 plumb line was 180 mm. She had 54° of thoracic kyphosis (T5–T12) and 43° of proximal junctional angle (T8–10). We performed revision surgery with anterior corpectomy and cage insertion and then posterior instrumented fusion from T-3 to the pelvis. Arrow indicates PJK. D: Final radiograph. At 3 years after the index surgery, the patient's sagittal C-7 plumb line was 42 mm and she had 27° of thoracic kyphosis (T5–T12).

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    Case 2: Patient with PT UIV. This 69-year-old woman presented with PJK and flat-back deformity after an L1–4 posterior spinal fusion. A: Preoperative radiograph. She had 48° of thoracic kyphosis (T5–T12) and 6° of proximal junctional angle (T1–3). B: Immediately postoperative radiograph. She underwent an anterior interbody fusion at L4–5 and L5–S1 with a posterior instrumented fusion from T-3 to the pelvis. Additional anterior (L3–4) and lateral (T11–L2) interbody fusions were performed. C and D: Standing lateral radiograph and sagittal CT scan obtained at 3 years postsurgery. She had 38° of thoracic kyphosis (T5–T12) and 49° of proximal junctional angle (T1–3). The CT scan demonstrates UIV compression fracture with UIV-1 subluxation. She underwent an extension of posterior instrumentation and fusion from C-2 to T-3. Arrows indicate PJK. E: Final radiograph obtained immediately after the C2–pelvis fixation, showing restored sagittal alignment.

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