Safety and Efficacy of Posterior Isola Instrumentation and Arthrodesis for Idiopathic Scoliosis: 2 to 12 year Follow-up

• (c, d - Isola Implants, Inc.)

Purpose: This is an observational retrospective case series to survey the safety and efficacy of this integrated wire, hook and pedicle screw anchor system utilizing torsional-counter torsional correction loads.

Methods: From January 1989 through December 2000 one hundred eighty-five (156F, 29M) consecutive, index case included, patients age 10 through 20 years, mean 14.7 years ±3.3, were operated. Ninety nine had thoracic, 61 combined, 17 thoracolumbar/lumbar, and 8 triple curves. Seventeen had preliminary open anterior diskectomy and non instrumented arthrodesis, 15 sequential and 2 staged. Safety was determined by complications and re-operations; effectiveness by deformity correction and health related quality of life questionnaire responses. A minimum two year follow up was available radiographically for 174 patients (94%) at an average of 4.9 years (± 6 years) and for outcome for 179 patients(97%) at an average of 6.0 years, (±3.1 years) post operative.

Results: There were no deaths, cord or spinal nerve complications, or acute post operative posterior wound infections. Three patients (1.6%) (3/185) required peri-operative reoperation, one for empyema and two for incision separation reclosure. Later reoperations were required in 14 patients (8%) (14/179); delayed deep wound infection 2 (1.1%), pseudarthrosis/malunion 3 (1.7%), implant prominence 1 (0.6%), late operative site pain 7 (3.9%), and peri adjacent spondylolisthesis 1 (0.6%). The largest Cobb was 62º (±13º) pre operative, 19º (±10º) (69% correction) post operative, and 21 º (±11º) (66% correction) at follow up. The largest angle of trunk inclination (ATI) was 16.5 pre operative and 9.6 (42% correction) at follow up, p<0 .001. The mean SRS/HRQoL questionnaire scores (5 best, 1 worst) were function 4.16 (±0.71), pain 4.05(± 0.91), self image 4.19 (± 0.71), mental health 4.08 (±0.76), satisfaction with management 4.55 0.70), and total (±0.63). Better results (total SRS score> 3.5) were achieved after transverse connector redesign than before, 77/83 (93%) versus 77/96 (80%), p=0.018. One hundred fifty seven (88%) (157/179) were satisfied or very satisfied with management (SRS score 4 to 5).

Discussion: The principal problem encountered was late operative site pain (LOSP) which presents significantly later than delayed deep wound infection . LOSP appears to have been successfully addressed with development of a mechanically stronger, lower profile, connector. The low delayed deep wound infection rate is attributed to technical considerations of secure sterile field, periodic intraoperative irrigation, dissection considerations including dorsal primary rami and spinous process sparing exposure, and secure hemostatic closure. Even though this series includes both a technology and technique "learning curve", results appear to be at least as good as and in some instances better than comparable reported series.

Conclusion: This integrated wire, hook and pedicle screw instrumentation system and the torsional-counter torsional corrective loads recommended can be used safely and effectively for surgical treatment of idiopathic scoliosis.Precis: No deaths, spinal cord or nerve root complications, or acute posterior wound infections occurred in 185 consecutive, index included, patients. Later reoperations were required in 14 (8%) (14/178). Largest Cobb averaged 62º pre operative, 19º post operative and 21º at follow up. SRS/HRQoL total score averaged 4.18 and satisfaction/dissatisfaction score averaged 4.55 (scale 5 best-1 lowest) at latest follow up.

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