#353 Does Minimally Invasive Surgical (MIS) Treatment of Adult Spinal Deformities Affect the Incidence of Proximal Junctional Kyphosis (PJK)?

General Session: Lateral Interbody Fusion

Presented by: N. Anand


N. Anand (1)
B. Khandehroo (1)
S. Kahwaty (1)
E.M. Baron (1)

(1) Cedars Sinai Medical Center, Spine Center, Los Angeles, CA, USA


Introduction: Proximal Junctional Kyphosis is one of the possible side effects of surgical treatment for adult spinal deformities. It is the result of the trunk self-adjustment after the interference of the surgery to achieve overall balance in the sagittal plane. Minimally Invasive Surgery (MIS) has previously been shown to achieve comparable deformity correction in both sagittal and coronal plane but lower morbidity and complications. This study assesses if MIS correction of adult spinal deformity affects the incidence of postoperative PJK.

Methods: A retrospective study of 176 patients underwent MIS correction for their thoracolumbar deformities identified 123 patients with 2 or more levels fusion for this study. Deformities included Degenerative Scoliosis (83), Idiopathic Scoliosis (27), Iatrogenic Scoliosis (11) and Kyphosis (2). All underwent all or a combination of 3 MIS techniques: Posterior instrumentation (119), DLIF (109) and AxiaLIF (53). Radiographic measurements were analyzed on preoperative, early postoperative and final follow-up on standing long cassette radiographs. PJK was defined as the sagittal Cobb angle between the lower endplate of the uppermost instrumented vertebra and the upper endplate of two vertebras supra-adjacent, which is more than 10o and at least 10o greater than the pre-op measurement.

Results: Mean follow-up was 37.5 months (range: 6-69 moths) with more than1 year in 116 patients. Mean age was 63 years (21-85 years). Mean operated levels were 4.7 levels (2-13 levels).The pre-op Cobb angle was 27o (5.9o-74.7o) and corrected to 10o (0.6o-41.2o). The pre-op Coronal balance was 30.7mm (0 to 142.9) and corrected to 12.8mm (0 to 30.4). The pre-op Sagittal balance was 51.9mm (-47 to160) and corrected to 11mm (-119 to113.9). The mean pre-op lumbar lordosis which was 43o, maintained at 41.7o by the last follow-up. The incidence of PJK in our study was 3.2% (4 of 123 patients) and only 3 patients needed revision surgery. In the first patient, the pre-op proximal junctional angle was 8.14o and increased to 28.9o at 5 months post-op. This patient underwent kyphoplasty with MIS extension of posterior instrumentation 3 levels cephalad. In the 2nd patient the angle increased from 0.62o to 17.83o at 15 months post-op secondary to a compression fracture of the supra-adjacent vertebra and it was corrected by kyphoplasty. Last follow-up shows both patients were asymptomatic. In the 3rd patient, the pre-op angle was 10o and increased to 26.54o at 24 months post-op. This patient has been scheduled for kypoplasty and posterior reinstrumentation. In the 4th patient the pre-op angle increased from 1.69o to 13.73o, at 28 months post-op. Although theoretically this patient was placed in PJK group, she has been asymptomatic and declined any revision.

Conclusions: A combination of 3 novel MIS techniques for correction of adult spinal deformity, offers excellent curve correction, maintains lumbar lordosis and appropriate kyphosis at thoracolumbar junction. The incidence of PJK in our study was 3.2%. This is considerably less than the 26-46% PJK rate quoted for surgical correction of adult spinal deformity.