C1 translaminar screw as a salvage technique for a failed lateral mass screw: A case report and literature review

Abstract

The placement of C1 lateral mass screws is a common procedure in posterior atlantoaxial fixation, but variations in local anatomy, including the C1 lateral mass and vertebral artery, can complicate screw placement, increasing the risk of complications. This case report presents the use of a C1 translaminar screw as a salvage technique following the failure of a C1 lateral mass screw during the treatment of a type II odontoid fracture. A 16-year-old male involved in a motor vehicle accident was scheduled for posterior atlantoaxial fixation with C1 lateral mass screws and C2 pedicle screws. However, intraoperative failure of one C1 lateral mass screw necessitated the insertion of a C1 translaminar screw. Postoperative recovery was without complications, with fracture healing confirmed by computed tomography imaging at 3 months after the operation, showing no signs of implant loosening or delayed union. This case highlights the effectiveness of the C1 translaminar screw as a reliable salvage technique in complex situations where conventional screw placement is compromised. It provides a viable alternative for ensuring stable fixation and achieving favorable outcomes in patients with challenging anatomical variations.

Background

Traditional posterior fixation techniques for C1 include wire fixation, transarticular screws, and lateral mass screws (LMSs), with C1 LMS fixation currently being the most widely adopted technique.^1,2 Numerous clinical and biomechanical studies have demonstrated that C1 LMSs provide immediate postoperative biomechanical stability and a high rate of fusion.^{3 –5} However, the placement of C1 LMSs is highly dependent on local anatomy, and anatomical variations of the C1 lateral mass and vertebral artery may pose challenges and risks during screw placement. ⁶ Additionally, intraoperative screw placement failure and trajectory breach using conventional methods may necessitate alternative C1 fixation techniques, such as the translaminar screw (TLS). Compared to LMSs, the C1 TLS is infrequently used in clinical practice, with most reports being individual case studies.^{7 –17} It is predominantly indicated in cases involving vertebral artery anomalies or tumor-induced destruction of the C1 lateral mass, which preclude the use of conventional LMSs. To the best of our knowledge, no literature reports have described the use of a C1 TLS as a salvage technique for a failed LMS. This case report presents a C1–C2 fixation for the treatment of a type II odontoid fracture, where LMS placement on one side of C1 failed, and a C1 TLS was successfully used as a salvage technique.

Case presentation

A 16-year-old man was injured in a car accident, sustaining a type II odontoid fracture with significant displacement and angulation. An atlantoaxial fixation was scheduled. The patient was placed in the prone position under general anesthesia, and neuromonitoring was performed. A standard atlantoaxial posterior midline approach was utilized to expose the posterior structures of the C1–C2 vertebrae. A unilateral C1 LMS and bilateral C2 pedicle screws were initially inserted using the Harms and Melcher technique under fluoroscopic guidance. ¹ Due to the manual insertion of a C1 pedicle screw during surgery, an optimal screw trajectory could not be achieved. Several screw placement attempts resulted in inadequate cortical engagement. However, after repeated failure of LMS placement on one side of C1, a unilateral C1 TLS was inserted as a salvage technique (Figure 1).

Figure 1.

Preoperative and postoperative pictures of this case: (a) preoperative sagittal CT scans showed a type II odontoid fracture with significant displacement or angulation, (b) intraoperative fluoroscopy displayed the failed placement of the C1 LMS, (c) intraoperative images demonstrated bilateral C2 pedicle screws, a right C1 LMS, and a left C1 TLS utilized as a salvage option for the failed C1 LMS, (d) a postoperative sagittal CT scan confirmed a successful reduction of the odontoid fracture, (e) axial CT scan showed the correct position of unilateral C1 TLSs, and (f) postoperative cervical spine radiograph showed all screws in position.

Preoperative sagittal computed tomography (CT) scans demonstrated that the height of the midpoint of the posterior arch of C1 was ~6.86 mm, and the width was ~4.20 mm. The screw trajectory for C1 posterior arch screws could extend up to 27.47 mm, which influenced the decision to employ posterior TLSs as a corrective fixation method during surgery (Figure 2). A 3.0-mm high-speed bur was used to create an entry point at the posterior tubercle of the C1 posterior arch. The hand drill was gradually inserted freehand through the bony canal, advancing to the contralateral posterior arch. A 3.5-mm diameter, 28-mm length polyaxial screw was inserted into the C1 posterior arch. On one side, a rod was connected to the C1 LMS and the C2 pedicle screw, while on the contralateral side, the rod was connected to the C1 TLS and the C2 pedicle screw.

Figure 2.

Preoperative CT measurements of the C1 posterior arch: (a) a preoperative sagittal CT scan revealed the height of the midpoint of the right C1 posterior arch to be ~6.86 mm, (b) a preoperative axial CT scan revealed the width of the midpoint of the right C1 posterior arch to be ~4.20 mm, (c) a preoperative axial CT scan showed that the screw trajectory length in the right C1 posterior arch could reach 27.47 mm, and (d) the preoperative 3D CT reconstruction did not show any significant vertebral artery anomalies.

The patient was allowed to ambulate with a neck brace on postoperative day 3 and was instructed to continue wearing the brace for the subsequent 3 months. CT scans were performed ~3 months after the operation to confirm successful fracture union (Figure 3). Twelve months postoperatively, the patient underwent hardware removal.

Figure 3.

Postoperative 1-year follow-up imaging of the case: (a, b) postoperative CT scans demonstrated complete bony healing of the odontoid fracture, with resolution of the fracture line and continuous bone trabecular growth and (c, d) postoperative CT scans confirmed the correct positioning of the unilateral C1 TLS, with the screw trajectory length reaching 27.82 mm.

Discussion

The clinical application of C1 TLSs is rarely reported in the literature, despite their potential utility in complex cases. They are typically employed in situations where conventional LMS placement is anatomically contraindicated or fails, such as in the presence of vertebral artery anatomical variations or destruction of the lateral mass bone, which pose significant risks during screw placement (Table 1).^{7 –17} Donnellan et al. ⁸ reported two cases where C1 TLSs were used as an alternative technique due to the inability to insert C1 LMSs, attributed to anomalous vertebral artery locations and erosion of the C1 lateral masses. Tsuji et al. ¹¹ and Ono et al. ¹³ each reported a case where C1 TLS was employed as an alternative option due to variations in vertebral artery anatomy. Kirubakaran et al. ¹⁴ utilized C1 TLSs and C2 TLSs in three patients who faced difficulties due to vertebral artery anomalies, high-riding vertebral arteries, or unilateral atlantoaxial joint fractures, thereby reinforcing ipsilateral TLS fixation. Baaj and Vrionis ⁹ reported a case in which C1 TLSs were used as a salvage procedure due to an osteolytic lesion of the lateral mass. In contrast to the cases in the aforementioned literature, where no failures of routine intraoperative C1 pedicle screw placement were reported, this case demonstrates the use of unilateral C1 TLS fixation as a salvage technique. In this case, TLS was not planned as a primary strategy but was used as an intraoperative salvage solution. Cadena et al. ¹² used cross-C1 TLS combined with bilateral C2 pars screws as a salvage option due to significant venous bleeding encountered during C1 lateral mass exposure. The minimum thickness of the C1 posterior arch required for screw placement is ~4 mm. ¹⁷ Previous studies predominantly used standard 3.5 mm diameter screws inserted directly into the cervical cortical bone, except Floyd and Grob, ⁷ who utilized 2.7-mm diameter screws. In the present case, a 3.5 mm × 28 mm C1 TLS was successfully employed as a salvage technique in this patient following the intraoperative failure of LMS insertion.

Table 1.

Literature review of clinical studies for C1 TLSs.

No.	Study	Type of study	No. of cases	Diagnosis	Anatomical characteristics	C1 TLSs	Size of screws
1	Floyd and Grob 7	Clinical	5	Atlantoaxial instability	Deficiency of the arch of C1	Bilateral	2.7 mm × 10–15 mm
2	Donnellan et al. 8	Clinical	3	Osteoarthritis	Erosion of C1 lateral mass	Bilateral	3.5 mm × 12–14 mm
				Osteoarthritis	Erosion of C1 lateral mass
				Unstable C1–C2 complex	Bifid of C1 posterior arch
3	Baaj and Vrionis 9	Clinical	1	Metastatic tumor	Tumor invasion to C1 lateral mass	Unilateral	3.5 mm × 14 mm
4	Yew et al. 10	Clinical	1	Odontoid fracture	Anomalous vertebral artery	Bilateral	–
5	Tsuji et al. 11	Clinical	2	Os odontoideum with C1–C2 instability	Anomalous vertebral artery	Unilateral	3.5 mm in diameter
				Traumatic atlantoaxial rotatory fixation	vertebral artery occlusion
6	Cadena et al. 12	Clinical	1	Odontoid fracture	Excessive bleeding during surgery	Bilateral	3.5 mm × 12 mm
7	Ono et al. 13	Clinical	1	Odontoid fracture	High-riding vertebral artery	Unilateral	3.5 mm × 18 mm
8	Kirubakaran et al. 14	Clinical	3	Odontoid fracture	Vertebral artery anomaly	Unilateral	–
				Odontoid fracture	Odontoid fracture
				Odontoid fracture	Atlantoaxial joint fracture
9	Tanaka et al. 15	Clinical	1	Bowhunter’s syndrome	Vertebral artery anomaly	Unilateral	3.5 mm in diameter
10	Carelli et al. 16	Clinical	1	Tumor	Tumor invasion to C1 lateral mass	unilateral PAS	–
11	Liu et al. 17	Clinical	4	Odontoid fracture	Ankylosing spondylitis	Bilateral	3.5 mm × 14–20 mm
				Traumatic atlantoaxial rotatory fixation	–	Unilateral
				Aneurysmal bone cyst of C1	Osteolytic lesion of the C1 lateral mass	Unilateral
				Odontoid fracture	Osteoporosis	Unilateral

TLS: translaminar screw.

Several biomechanical studies have investigated the use of TLS fixation (Table 2).^{18 –23} The combination of a unilateral C1 TLS with a contralateral LMS fixation has demonstrated good biomechanical stability, further supporting its clinical application. Jin et al. ¹⁸ indicated that both C1 LMSs and TLS fixation significantly reduce flexibility compared to the intact position, suggesting that C1 TLS fixation may serve as an effective alternative for posterior atlantoaxial fixation, especially in salvage scenarios. Cadena et al. ¹² reported a biomechanical analysis demonstrating equivalent stability between the C1 TLS/C2 pars screw construct and the conventional C1 lateral mass/C2 pars screw construct, further supporting the role of C1 TLSs in upper cervical spine fixation. Additionally, Zarro et al. ¹⁹ demonstrated that TLSs exhibit superior resistance to pullout under C1 loading conditions compared to LMSs, underscoring the viability of TLSs as a salvage option for C1 stabilization. A biomechanical analysis shows that unilateral C1 TLS and C2 TLS combined with unilateral C1 pedicle screws provided equivalent acute stability to that of the pedicle screw, with no statistically significant difference in acute stability between the two fixation techniques. This suggests that C1 TLS fixation could serve as an alternative method for posterior atlantoaxial fixation. ²⁰ In the present case, the C1 TLS fixation technique demonstrated favorable clinical outcomes, characterized by an absence of implant loosening and fusion failure, reinforcing its biomechanical efficacy as a salvage technique for upper cervical spine fixation.

Table 2.

Literature review of biomechanical studies for C1 TLSs.

No.	Study	Type of study	Observational indicators	Fixation methods	Comparative protocols	Results	Size of screws
1	Jin et al. 18	Cadavers	Three-dimensional angular motion	C1 TLS/C2 pedicle screw	C1 pedicle screw/C2 pedicle screw	No statistically significant difference	–
3	Zarro et al. 19	Cadavers	Pullout strength	C1 TLS	C1 LMS	Greater pullout strength	3.5-mm diameter
4	Jin et al. 20	Cadavers	Stability	Ipsilateral C1 TLS/C2 TLS	C1 pedicle screw/C2 pedicle screw	No statistically significant difference	3.5 mm × 22 mm
5	Shen et al. 21	Cadavers	Range of motion	Ipsilateral C1 TLS/C2 TLS	C1 pedicle screw/C2 pedicle screw	Better stability	3.6 mm × 22 mm
6	Cadena et al. 12	Cadavers	Stability	C1 TLS/C2 pars screw	C1 LMS/C2 pars screw	No statistically significant difference	3.5 mm × 16 mm
7	Liu et al. 22	Finite element	Range of motion	C1 TLSs/C2 pedicle screw	C1 pedicle screw/C2 lamina screw	Better stability in lateral bending and axial rotation	3.5 × 24 mm
8	Fernandes et al. 23	Cadavers	Range of motion	C1 TLS/C2 TLS	C1 pedicle screw/C2 pedicle screw	Similar biomechanical stability	3.5 mm × 20 mm

LMS: lateral mass screw; TLS: translaminar screw.

This study has several limitations. First, it is a case report. However, using C1 TLSs as a salvage option for failed C1 LMSs in upper cervical spine fixation is infrequently performed, making it difficult to study large cohorts of patients undergoing this procedure. Furthermore, this was a retrospective study with short-term follow-up; therefore, a long-term prospective study is necessary to adequately evaluate the efficacy of C1 TLSs as a salvage method in this surgical context and to assess potential complications. Additional investigation into the biomechanical effects of C1 TLSs as a salvage measure for upper cervical spine fixation is warranted. As a single case report, the findings may not be generalizable to broader populations, though they provide insight for similar clinical scenarios.

Conclusions

The C1 TLS is an effective salvage technique for failed LMSs in atlantoaxial fixation, as demonstrated in this case. It offers a viable option for patients with anatomical variations, ensuring stability and fusion.