Clinical and radiographic results after implant removal in idiopathic scoliosis

Abstract

Study design: Prospective radiographic and clinical analysis of patients with idiopathic scoliosis who had complete implant removal following posterior spinal fusion (PSF) at least 2 years previously.

Objective: To evaluate the clinical and radiographic effect of implant removal after PSF for idiopathic scoliosis.

Summary of background data: Occasionally, implants must be removed following instrumented PSF. Indications for removal include infection and late operative site pain. Previously, it has been thought that there was little morbidity associated with implant removal in the presence of a solid fusion. However, recent studies have reported loss of coronal correction after implant removal in patients who had a PSF for adolescent idiopathic scoliosis. Few long-term studies have assessed the clinical or radiographic results of complete implant removal after PSF.

Methods: We identified 56 patients who had undergone PSF for idiopathic scoliosis and subsequently had complete removal of all instrumentation. None of these patients had a pseudarthrosis at the time of implant removal. After IRB approval, 43 of 56 (77%) patients returned for new standing posteroanterior and lateral spine radiographs and completion of an SRS-22 questionnaire.

Results: For the 43 patients who had new radiographs and completed an SRS-22, the time from the original PSF to complete implant removal averaged 2.9 years (range, 7 months to 7.25 years). Twenty-two patients had implants removed because of infection, and 21 patients had implants removed secondary to pain. The average time from implant removal to completion of the most recent radiographs and SRS-22 questionnaire was 9.5 years (range, 3.2-17.9 years). Patients were considered to have had progression of deformity after implant removal if their Cobb angle measurements increased by more than 10 degrees . Two patients had 11 degrees to 20 degrees of coronal plane progression of their main thoracic curve. No patient had more than 10 degrees of coronal plane progression of a lumbar curve. Sagittal curve progression was identified more frequently. Nineteen patients had between an 11 degrees and 20 degrees increase in thoracic kyphosis, and 5 patients had >20 degrees of thoracic kyphosis progression. Patients with >20 degrees of thoracic kyphosis progression after implant removal had greater thoracic kyphosis before surgery and larger main thoracic and lumbar coronal curves at the time of implant removal. Progressive kyphosis did not correlate with: reason for implant removal, length of follow-up, or time from fusion to implant removal. Although total SRS-22 scores correlated inversely with increased thoracic kyphosis, this trend did not reach statistical significance.

Conclusion: Implant removal after PSF for idiopathic scoliosis may be complicated by progression of deformity. Patients requiring implant removal should be appropriately counseled and monitored.