J Korean Orthop Assoc.  2017 Feb;52(1):83-91. 10.4055/jkoa.2017.52.1.83.

The Effect of Distal Hooks in Thoracolumbar Fusion Using a Pedicle Screw in Elderly Patients

• Lee DH
• Kim SS
• Kim JH
• Lim DJ
• Choi BW
• Kim JH
• Kim JH
• Park BO

• KMID: 2369575
• DOI: http://doi.org/10.4055/jkoa.2017.52.1.83

Abstract

PURPOSE
To investigate the clinical outcomes of distal hook augmentation using a pedicle screw in thoracolumbar fusion in elderly patients.
MATERIALS AND METHODS
This retrospective multicenter study recruited 20 patients aged 65 years or older, who underwent anterior support and long level posterior fusion in the thoracolumbar junction with a follow-up of one year. To assess the effect of distal hook augmentation, the patients were divided into two groups; the pedicle screw with hook group (PH group, n=10) and the pedicle screw alone group (PA group, n=10).
RESULTS
The average age was 72.4 years (65-83 years). The average fusion segment was 4.6 segments (3-6 segments). There were no significant differences in age, sex, causative diseases, bone mineral density of lumbar and proximal femur, number of patients with osteoporosis, and number of fused segments between the two groups (p≥0.05). At 1 year follow-up after surgery, parameters related with distal screw pullout were significantly worse in the PA group. No patients in the PH group had distal screw pullout. However, six patients (60%, 6/10) in the PA group had distal screw pullout. There were no significant differences in the progression of distal junctional kyphosis between the two groups.
CONCLUSION
Distal hook augmentation is an effective procedure in protecting distal pedicle screws against the pullout when long level thoracolumbar fusion was performed in elderly patients aged 65 years or older.

Keyword

osteoporosis; spinal fusion; pedicle screws

MeSH Terms

Aged*
Bone Diseases
Femur
Follow-Up Studies
Humans
Hydrogen-Ion Concentration
Kyphosis
Miners
Osteoporosis
Pedicle Screws*
Retrospective Studies
Spinal Fusion

Figure

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  Figure 1 Radiographic parameters. (A) The halo around the distal screw was checked by a radiolucent width from the screw thread end (arrow). (B) The insertion angle of the distal screw was measured by a Cobb angle between the upper endplate of the lowest instrumented vertebrae and its screw. (C) The insertion distance of the distal screw was measured by the distance from the midpoint of anterior cortex of the lowest instrumented vertebrae to its screw tip. (D) Distal junctional lordosis was measured by a Cobb angle between the upper end plate of the lowest instrumented vertebrae and the low end plate of the distal adjacent vertebrae.

• 

  Figure 2 A 77-year-old female patient with distal hook augmentation. She had had back pain and paresthesia on the lower extremities for four months and underwent vertebroplasty for L1 compression fracture at a local clinic two months ago. However, her symptoms were not relieved. She was finally diagnosed with tuberculosis spondylodiscitis. (A) Initial lateral radiography showed bone cement at L1. (B) She was treated by an anterior support using an autoiliac strut bone graft and posterior fusion from T10 to L3 using a pedicle screw with distal laminar hooks. (C) At the 1-year follow-up, there was no pullout of the distal screw.

• 

  Figure 3 A 70-year-old female patient treated without distal hook augmentation. She had severe back pain and paresthesia on both lower extremities after L1 kyphoplasty at a local clinic six months ago. (A) The cement mass was separated and migrated anteriorly with increasing kyphotic deformity. (B) She was treated by an anterior support using expandable cage and posterior fusion from T10 to L3 using a pedicle screw without distal hook. (C) At the 1-year follow-up, the distal screw was pulled out.

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