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The Risks of Pedicle Wall Breech with Larger Screws After Untapping

Scientific Paper

Chin KR1, Gibson B.

Interested medical professionals can read the full paper, published also in the Spine Journal, here.


A linear relation exists between the insertional torque when placing a screw and the ultimate screw pullout strength; therefore, undertapping of the pedicle followed by insertion of a larger screw may enhance the pullout strength of the screw.


To report the risk of pedicle wall breech with placement of 6.2-mm pedicle screws after undertapping with a 5.2-mm tap and to evaluate the effectiveness of direct visualization to identify these breeches. STUDY DESIGN/SETTINGS: Prospective evaluation of risks of pedicle wall breech with undertapping for a larger screw and the utility of directly visualizing pedicle walls during access and placement of pedicle screws for evidence of breech.


Sixty-five consecutive patients.


Intraoperative direct visualization of pedicle wall breech. Postoperative radicular leg symptoms.


We prospectively analyzed placement of pedicle screws in sixty-five consecutive patients during lumbar-instrumented fusions after laminectomies performed by a single spine surgeon. Forty-four patients were primary fusions, and 21 were revisions. Twenty-seven were male, and 38 were female, with a mean age of 54.7 years (range, 15-85 years). Four hundred twenty-eight total pedicle screws were placed for an average of 6.6 screws per patient (range, 2-12 screws).


The incidence of pedicle wall breech during access was 0.7% (3/428) and 1.6% (7/428) after screw placement. 71% (5/7) of the screw breeches were noted with direct inspection of the pedicles intraoperatively, and 29% (2/7) were identified on postoperative X-ray films as lateral breakthroughs that were missed on intraoperative fluoroscopy and direct visualization. Therefore, 100% of misplaced screws potentially harmful to nerve roots were identified on direct visualization. Eighty percent occurred from L2-4.


This study provides evidence that undertapping of pedicles followed by placement of a larger diameter pedicle screw may breech the pedicle cortices. Although the risk is low, the authors recommend direct visualization of the pedicle walls during screw placement to identify caudad, medial, and cephalad breeches. This technique is for open laminectomies and should be added to the armamentarium of other techniques and not as a replacement.


Dr. Kingsley R. Chin, Founder of philosophy and practice of The LES Society and The LESS Institute

Dr. Kingsley R. Chin is a board certified Harvard-trained orthopedic spine surgeon and professor with copious business and information technology exposure. He sees a niche opportunity where medicine, business and info. tech meet – and is uniquely educated at the intersection of these three professions. He has experience as Professor of Clinical Biomedical Sciences & Admissions Committee Member at the Charles E. Schmidt College of Medicine at Florida Atlantic University, Professor of Clinical Orthopedic Surgery at the Herbert Wertheim College of Medicine at Florida International University, Assistant Professor of Orthopaedics at the University of Pennsylvania Medical School, Visiting Spine Surgeon & Professor at the University of the West Indies, Mona, and Adjunct Professor of Clinical Biomedical Studies at the University of Technology, Jamaica.

Learn more about Dr. Chin here and connect via LinkedIn.


Less Exposure Surgery (LES) is based on a new philosophy of performing surgery, leading the charge to prove through bench and clinical outcomes research that LES treatment options are the best solutions – to lowering the cost of healthcare, improving outcomes and increasing patient satisfaction. Learn more at LESSociety.org.

The LES Society philosophy: “Tailor treatment to the individual aiding in the quickest recovery and return to a pain-free lifestyle, using LES® techniques that lessen exposure, preserve unoffending anatomy and utilize new technologies which are safe, easy to adopt and reproducible. These LES®techniques lessen blood loss, surgical time and exposure to radiation and can be safely performed in an outpatient center. Less is more.” – Kingsley R. Chin, MD


The LESS Institute is the world leader center of excellence in Less Exposure Surgery. Our safe, effective outpatient treatments help patients recover quickly, avoid expensive hospital stays and return home to their family the same day. Watch our patient stories, follow us on Facebook and visit TheLESSInstitute.com to learn more.


The above study utilized LES Technology from SpineFrontier – leading provider of LES Technologies and instruments – offering surgeons and patients superior technology and services.



Chin KR1, Gibson B.

Author information

  1. Spine Surgery Service, Department of Orthopaedic Surgery, University of Pennsylvania Medical School, 2 Silverstein, 3400 Spruce Street, Philadelphia, PA 19104, USA. [email protected]

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