Clinical validation of a universal deformity correction strategy using direct incremental segmental translation (DIST)

2011

SUMMARY

Clinical and radiographic analysis of 487 consecutive spinal deformity patients (idiopathic scoliosis-100, degenerative scoliosis-84, kyphosis-50, spondylolisthesis-253) surgically corrected using the same 3 step strategy of direct incremental segmental translation (DIST):1-free the spine, 2-bend rods to desired contour, 3-pull spine to rods. At 5 years follow-up, significant clinical improvement, deformity correction, and expected complications were noted. The same universal translational correction strategy applies to mild and severe deformity of all types. Corrections are consistent with computer modeling predictions.

INTRODUCTION

Biomechanical computer modeling shows that excellent coronal, sagittal, and rotational deformity correction can be achieved with primarily translational forces. A common deformity reduction strategy using direct incremental segmental translation (DIST) was tested for correcting scoliosis (SC), kyphosis (KY), and spondylolisthesis (SP).

METHODS

Analysis of prospective data on 487 consecutive deformity patients(195 degenerative SP, 58 isthmic SP, 75 adult idiopathic SC, 25 adolescent idiopathic SC, 84 degenerative SC, 21 Scheuermann's KY, 29 other KY), age 58 years (12-90 years); prior surgery-52, smokers-56. All underwent posterior fusion and instrumented deformity correction (except grade 1 SP) with DIST using 3 universal steps: 1-release the spine to move, 2-bend the rods to desired spinal contour, 3-pull the spine to contoured rods in a gradual, incremental, low-stress fashion. Releasing the spine to move occasionally required 3-column osteotomy (n=24). Anterior release/fusion was performed in 113 (avg 4.8 levels); TLIF (avg 1.7 levels) in 294. Clinical and radiographic data collected pre-op, 1 year, 2 years, latest follow-up.

RESULTS

At 5 years follow-up (24-108 months), complications: nonunion-17, adjacent degeneration-115 (31 in degenerative scoli, 50 in degenerative spondy), adjacent fracture-31 (14 in degenerative scoli), infection-20, footdrop-9; 60 underwent revision surgery. Two osteoporotic patients had single screw loosening during reduction both without consequence. Oswestry improved: SC pre-41, 4 year-23; KY pre-57, 3 years-32; SP pre-47, 3 year-26 (P<0.01). VAS improved: SC pre-5.7, 4 year-2.7; KY pre-7.7, 3 year-2.4; SP pre-6.3, 2 year-2.9 (P<0.01). Degenerative scoliosis (84) corrected from 31° pre to 11°, idiopathic scoliosis (100) corrected from 57° pre to 19° at 2 years. KY and SP were corrected in the sagittal plane using cantilever (KY) or direct translation.

CONCLUSIONS

The same universal translational correction strategy applies to mild and severe deformity of all types. Corrections are consistent with computer modeling predictions.

SIGNIFICANCE

Translational forces are effective in reducing all types of coronal, sagittal, and rotational deformity.