The over-the-arch (OTA) technique is a safe and feasible alternative for C1 screw fixation in patients in whom conventional techniques cannot be employed, according to a recent study published in the Journal of Neurosurgery: Spine by Hyung Rae Lee (Uijeongbu Eulji Medical Center, Uijeongbu Republic of Korea) and Dong-Ho Lee (Asan Medical Centre, Seoul, Republic of Korea) et al.
The aim of the study was to evaluate the feasibility and complications of the OTA technique for screw insertion into the C1 lateral mass in patients in whom conventional techniques such as posterior arch (PA) and inferior lateral mass [ILM]) are not feasible due to either a PA with a very small height (<3.5mm), a caudally tilted PA blocking the inferior part of the C1 lateral mass, or loss of height at the ILM (<3.5mm).
The medical records of 60 patients who underwent C1 screw fixation with the OTA technique (13 screws) and the PA/ILM technique (107 screws) between 2011 and 2019 were reviewed by the research team. Vertebral artery (VA) injuries, screw malposition, and bony union were radiologically assessed and clinical outcome measures—including Neck Disability Index (NDI), Japanese Orthopaedic Association (JOA) scale score, and occipital neuralgia—were recorded.
According to the researchers, a total of 13 OTA screws were successfully inserted without any major complications. In addition, NDI and JOA scale scores did not show significant differences between the two groups at final follow-up and no VA injuries were recognised during screw insertion.
There was also no evidence of ischaemic damage to the VA or bony erosion in the occiput or atlas. Medial wall violation was observed in one screw (7.7%); however, no C0–1, C1–2, or lateral wall violations were observed. No patients developed new-onset neuralgia postoperatively after C1 fixation with the OTA technique.
Speaking to Spinal News International, the researchers said: “Our present study is meaningful because it is the first to describe the feasibility of using superior lateral mass as an entry point in situations where current conventional screw insertion techniques for C1 fixation were unavailable. We referred to this situation as the risky triad of C1.
“We employed the OTA screw instead of extending surgical level to occipitocervical fixation. We evaluated feasibility and possible complications from this, including vertebral artery injury, occipital neuralgia, and screw malpositioning.”