No abstract

As the volume of primary total knee arthroplasties continues to rise, so will the volume of revision arthroplasties. Bone loss is commonly encountered in revision surgery and must be managed appropriately to optimize outcomes. The concept of zonal fixation highlights the importance of attaining secure fixation within each of the three major osseous zones: the epiphysis, the metaphysis, and the diaphysis. While each zone is important, the metaphysis carries particular significance. The development of new implants such as metaphyseal cones and sleeves has greatly expanded the orthopedic surgeon's armamentarium to allow for solid metaphyseal fixation in virtually every case.

Level III.

Background: We investigated impact of vertebral axial rotation on neurovascular anatomy in adult spinal deformity (ASD) patients and provided recommendations on the approach based on degree of axial rotation. In order to isolate vertebral rotation (VR) impact from the superimposed degenerative cascade observed in adulthood, adolescent idiopathic scoliosis (AIS) patients were analyzed.Methods: Magnetic resonance imaging (MRI) scans (L1-S1) from 50 right-convex thoracic (left-convex lumbar) AIS patients were analyzed. At each intervertebral level, VR, lumbar plexus depth (LPD), and vascular structure depth (VSD) were evaluated. Paired t test analyses were used to describe anatomic differences between the concave and convex aspect of our patients' curves. Correlation analysis was used to investigate relationships with soft tissue modifications and VR.Results: Fifty AIS patients (17M, 33F) with mean thoracic Cobb of 50.68 6 17.08 and mean lumbar Cobb of 41.98 6 13.08 were included. Mean VR at each level was L1-2 ¼À6.68, L2-3 ¼À7.78, L3-4 ¼À6.58, L4-5 ¼À4.78, L5-S1 ¼À2.68 (negative value denotes clockwise rotation). We found significant differences (P , .05) between concave-convex (rightleft) LPD at each level (L1-2 ¼ 3.7 mm, L2-3 ¼ 5.1 mm, L3-4 ¼ 4.2 mm, L4-5 ¼ 2.2 mm, L5-S1 ¼ 2.2 mm). Vascular structure depth was significantly different at L1-L2 (3.2 mm) and L5-S1 (3 mm). Significant correlation was found between increasing VR and concave-convex LPD difference (r ¼ 0.68, P , .001).Conclusions: This study demonstrates that displacement of the lumbar plexus is tied to the magnitude of VR in patients with AIS. When approaching the lumbar spine, this displacement widens the safe surgical corridor on the convex side and narrows the corridor on the concave side.Level of Evidence: IV Clinical Relevance: Preoperative review of MRI scans should occur to assess the patient's safe surgical corridor for lateral lumbar interbody fusion (LLIF). Adult spinal deformity surgeons who approach a degenerated spine in patients with progressive AIS in adulthood must carefully plan for patient positioning, neurovascular anatomy, and realignment objectives prior to the day of surgical intervention.