A Semispinalis Cervicis–Sparing Intermuscular Approach for C2-3 Posterior Fixation

Abstract

BACKGROUND AND IMPORTANCE:

Preservation of the semispinalis cervicis insertion at the C2 spinous process is important for maintaining cervical extensor function and postoperative alignment. However, muscle-preserving approaches for posterior fixation at the C2-3 level remain technically challenging.

CLINICAL PRESENTATION:

A 66-year-old man with a traumatic hangman's fracture underwent posterior C2-3 fixation using a semispinalis cervicis–sparing intermuscular approach. A natural connective tissue plane between the semispinalis capitis and semispinalis cervicis was developed, allowing exposure of C2 and C3 without detaching the semispinalis cervicis insertion. Instrumentation was successfully performed under intraoperative computed tomography–based navigation. Postoperative pain was minimal, and stable fixation was achieved without complications.

CONCLUSION:

This case demonstrates that the semispinalis cervicis–sparing intermuscular approach provides a feasible muscle-preserving corridor for C2-3 fixation and may represent a useful alternative in selected patients.

ABBREVIATIONS:

SSC

semispinalis cervicis

SSIA

semispinalis cervicis–sparing intermuscular approach.

Preservation of posterior cervical musculature has been increasingly recognized as an important factor in reducing postoperative axial symptoms and maintaining cervical alignment.^1-3 In particular, the semispinalis cervicis (SSC) insertion at the C2 spinous process plays a key role in cervical extensor function and the posterior tension band.^1-3

The spinous process–splitting approach described by Shiraishi preserves muscular attachment to C2 and remains a landmark concept in muscle-preserving posterior cervical surgery.^4,5 However, posterior fixation involving the C2-3 segment presents a different technical challenge as rigid instrumentation is required and reconstruction of a split spinous process may be less desirable.^4,5

Although several muscle-preserving posterior fusion techniques have been reported,^5,6 a reproducible intermuscular corridor allowing direct access to the C2-3 posterior elements while preserving the SSC insertion has not been clearly established.

Here, we report a case of posterior C2-3 fixation using a semispinalis cervicis–sparing intermuscular approach (SSIA) and describe its technical considerations.

CLINICAL PRESENTATION

A 66-year-old man presented with a traumatic hangman's fracture associated with C2-3 instability (Figure 1A) and cervical spondylosis. Surgical stabilization was indicated. Preoperative computed tomography angiography was performed to evaluate vertebral artery anatomy and confirm the feasibility of C2 pedicle screw placement. Postoperative radiographic evaluation confirmed stable fixation without mechanical complications (Figure 1B-1D).

FIGURE 1.

Preoperative and postoperative radiographic assessment. A, Preoperative lateral cervical radiograph demonstrating C2-3 instability associated with a hangman's fracture. B, Postoperative lateral cervical radiograph demonstrating C2-3 posterior fixation. C, Postoperative axial computed tomography image at the C2 level demonstrating appropriate bilateral C2 pedicle screw placement. D, Intraoperative axial computed tomography image obtained immediately after C3 pedicle screw placement. Asterisks indicate the bilateral semispinalis cervicis–sparing intermuscular approach corridors, and triangles indicate preservation of the semispinalis cervicis insertion at the C2 spinous process.

The patient was positioned prone with the head secured in a radiolucent head fixation system (DORO Radiolucent headrest system, Pro Med Instruments GmbH). A posterior midline incision was made, and the nuchal ligament was divided in the midline. The semispinalis capitis was gently retracted laterally, revealing a loose connective tissue plane between the semispinalis capitis and SSC (Figure 2A).

FIGURE 2.

Intraoperative findings of the semispinalis cervicis–sparing intermuscular approach. A, The connective tissue plane between the semispinalis capitis and semispinalis cervicis muscles is identified. The dashed line indicates the intended dissection plane along the intermuscular corridor. B, Exposure through the semispinalis cervicis–sparing intermuscular approach corridor provides access to the C3 pedicle screw entry point while preserving the semispinalis cervicis insertion at the C2 spinous process. A navigation pointer is shown to confirm the screw trajectory and anatomic orientation. C, Final intraoperative view after instrumentation demonstrating preservation of the semispinalis cervicis insertion at C2.

Sharp dissection along this plane allowed development of the SSIA corridor while preserving the SSC insertion at the C2 spinous process. Through this corridor, the lateral aspects of C2 and C3 were sufficiently exposed for instrumentation (Figure 2B).

C2 and C3 pedicle screws were inserted under intraoperative computed tomography–based navigation (StealthStation S8, Medtronic) integrated with cone beam computed tomography imaging (ARTIS pheno, Siemens Healthineers), followed by rod fixation using an Infinity occipitocervical and upper cervical posterior fixation system (Medtronic). Preservation of the SSC insertion was confirmed after instrumentation (Figure 2C). Although cross-link placement was limited by preserved musculature, stable fixation was achieved.

The operative time was 196 minutes, and the estimated blood loss was 30 mL. Postoperative pain was minimal, with movement-related neck pain improving from a numerical rating scale score of 8 preoperatively to 2 to 3 in the early postoperative period and eventually resolving to 0.

Institutional review board approval was waived for this single case report in accordance with local regulations, and written informed consent for publication was obtained from the patient.

DISCUSSION

This case demonstrates the technical feasibility of a SSIA for posterior fixation at the C2-3 level.

Preservation of the SSC insertion is important for maintaining cervical extensor function and postoperative alignment.^1-3 Conventional posterior approaches often involve detachment of paraspinal musculature, which may lead to muscle atrophy and postoperative axial symptoms.^1-3

By contrast, the SSIA uses a natural intermuscular plane between the semispinalis capitis and SSC, minimizing muscle disruption while maintaining adequate exposure for instrumentation. This concept is consistent with previously described intermuscular approaches and anatomic descriptions of the posterior cervical musculature.^5,7

Preservation of the SSC insertion to the C2 spinous process has been emphasized in posterior cervical surgery because of its important role in maintaining postoperative cervical alignment and extensor muscle function. Previous muscle-preserving posterior cervical techniques, including selective preservation of the SSC insertion during laminoplasty and spinous process–splitting approaches, have demonstrated the clinical importance of minimizing injury to the posterior cervical musculature.^1-5 In particular, Takeuchi et al reported favorable postoperative functional outcomes associated with preservation or reattachment of the SSC during cervical laminoplasty.^2,3

However, these previously described techniques were primarily developed for decompression procedures and were not specifically intended to provide a direct surgical corridor for C2-3 posterior fixation or pedicle screw placement. More recently, Takeuchi et al⁶ described a posterior decompression and fusion technique preserving 3 muscles inserted at C2 during multilevel cervical reconstruction using C2 pedicle screws. However, that technique was intended for long-segment posterior decompression and fusion and did not specifically address direct fixation across the C2-3 segment. The present SSIA, by contrast, was developed as a focused intermuscular approach specifically optimized for isolated C2-3 posterior fixation while preserving the SSC insertion.

This approach uses the natural plane between the semispinalis capitis and SSC muscles to access the C2-3 posterior elements while preserving the SSC insertion. This characteristic may be particularly advantageous in unstable hangman fractures requiring posterior fixation at the C2-3 level.

A key technical advantage is that preservation of the SSC does not interfere with C2 pedicle screw placement as the entry point and trajectory remain lateral. Furthermore, sufficient exposure for C3 instrumentation can be achieved through the same corridor, representing an important extension of muscle-preserving strategies to direct fixation across the C2-3 segment.

The surgical concept of the SSIA is illustrated in Figure 3.

FIGURE 3.

Schematic illustration of the SSIA. The SSIA uses the natural intermuscular plane between the semispinalis capitis and semispinalis cervicis muscles to access the C2-3 posterior elements while preserving the semispinalis cervicis insertion at the C2 spinous process. The arrow indicates the SSIA corridor. SSIA, semispinalis cervicis–sparing intermuscular approach.

The extent of caudal exposure may influence surgical ergonomics. A longer caudal incision may provide a more favorable working angle for distal screw placement while preserving muscle attachments.

Although this report describes a single case, this approach may be applicable to selected upper cervical fixation procedures.

Limitations include the single-case design and the technical difficulty associated with a narrow operative corridor. Further studies are needed to evaluate clinical outcomes and generalizability.

CONCLUSION

The SSIA provides a feasible and reproducible corridor for posterior C2-3 fixation while preserving the SSC insertion at C2. This technique may serve as a useful muscle-preserving alternative in selected patients.

Funding

This study did not receive any funding or financial support.

Disclosures

The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.

COMMENTS

Hangman's fractures—or fractures of the C2 pars interarticularis—comprise nearly one fourth of all C2 vertebral fractures. In addition to the pars fracture itself, the degree of disruption to the discoligamentous complex is indicated by the extent of C2/C3 angulation or translation, as seen in Type II fractures. Posterior transpedicular fixation of these unstable fractures can fail in approximately 10% of patients. Preserving the semispinalis cervicis muscle contributes significantly to the success of posterior C2/C3 fixation. The authors of this submission present a unique surgical technique that introduces a corridor between semispinalis cervicis and semispinalis capitis through which a transpedicular screw can be inserted using CT navigation without jeopardizing the muscular attachments. The technique is clearly described, and the figures effectively illustrate the procedure. A recent systematic review by Mahmoud et al¹ may provide additional value to readers of this article.

Bizhan Aarabi

Baltimore, Maryland, USA