TY - JOUR AU - Parker, S L; McGirt, M J; Farber, S H TI - Accuracy of free-hand pedicle screws in the thoracic and lumbar spine: analysis of 6816 consecutive screws JO - Neurosurgery IS - 01 VL - 68 PY - 2011 DO - 10.1227/NEU.0b013e3181fdfaf4 L3 - PubMed-ID: 21150762 SP - 170 EP - 178 N1 - , discussion 178 ER -