Minimally Invasive Posterior Cervical Arthrodesis and Fixation

Pars interarticularis screws for posterior cervical fusion - investigating a new trajectory using a CT-based multiplanar reconstruction: Part I

BACKGROUND

Lateral mass screw fixation is the standard for posterior cervical fusion between C3 and C6. Traditional trajectories stabilize but carry risks, including nerve root and vertebral artery injuries. Minimally invasive spine surgery (MISS) is gaining popularity, but trajectories present anatomical challenges.

RESEARCH QUESTION

This study proposes a novel pars interarticularis screw trajectory to address these issues and enhance in-line instrumentation with cervical pedicle screws.

MATERIALS AND METHODS

A retrospective analysis of reformatted cervical CT scans included 10 patients. Measurements of the pars interarticularis morphology were performed on 80 segments (C3-C6). Two pars interarticularis screw trajectories were evaluated: Trajectory A (upper outer quadrant entry, horizontal trajectory) and Trajectory B (lower outer quadrant entry, cranially pointed trajectory). These were compared to standard lateral mass and cervical pedicle screw trajectories, assessing screw lengths, angles, and potential risks to the spinal canal and transverse foramen.

RESULTS

Trajectory B showed significantly longer pars lengths (15.69 ± 0.65 mm) compared to Trajectory A (12.51 ± 0.24 mm; p < 0.01). Lateral mass screw lengths were comparable to pars interarticularis screw lengths using Trajectory B. Both trajectories provided safe angular ranges, minimizing the risk to delicate structures.

DISCUSSION

and Conclusion. Pars interarticularis screws offer a viable alternative to lateral mass screws for posterior cervical fusion, especially in MISS contexts. Trajectory B, in particular, presents a feasible and safe alternative, reducing the risk of vertebral artery and spinal cord injury. Preoperative assessment and intraoperative technologies are essential for successful implementation. Biomechanical validation is needed before clinical application.

Minimally Invasive Instrumentation of the Cervical Spine: Past, Present, and Future

Posterior cervical instrumentation and fusion procedures are becoming more and more common with the aging population and rising numbers of multisegmental and revision procedures. The instrumentation of the cervical spine has so far been performed almost exclusively via open approaches. Over the past two decades, minimally invasive surgery (MIS) techniques have gained increasing popularity. To date, only a few attempts to instrument the cervical spine in a minimally invasive fashion have been reported. The following article, after a detailed review of the currently available literature, overviews MIS in dorsal cervical instrumentation and past, present and future techniques, and it discusses the current limitations. Nevertheless, and because of the multiple advantages of MIS instrumentation, a lot of work remains to be carried out to fully establish MIS procedures for posterior cervical instrumentation.

Less exposure surgery for multilevel anterior cervical fusion using 2 transverse incisions

Multilevel anterior cervical fusion often necessitates a large extensile incision for exposure and substantial retraction of the esophagus for placing long plates, potentially predisposing patients to complications such as dysphagia, dysphonia, and neurovascular injury. To the authors' knowledge, the use of 2 incisions as an option has not been published, and so it is not intuitive to young surgeons or widely practiced. In this report, the authors discuss the advantages and raise awareness of using 2 incisions for multilevel anterior cervical fusion, and they document a safe skin bridge length. They also describe the advantages of using 2 incisions for performing multilevel anterior cervical fusion either at contiguous or noncontiguous levels as in adjacent-segment disease. By using the 2-incision technique, the authors made the surgery technically easier and diminished the amount of esophageal retraction otherwise needed through 1 long transverse or longitudinal incision. A skin bridge of 3 cm was safe.

Minimally Invasive Atlantoaxial Fusion

BACKGROUND

C1–C2 fusion has significantly advanced from predominantly wiring/cable modalities to more biomechanically stable screw-rod techniques. Minimally invasive surgical techniques represents the most recent modification of atlantoaxial fixation. The indications, rationale, and surgical technique of this novel procedure are described.

METHODS

Six patients requiring C1–C2 fusion (5 type II odontoid fractures and 1 os odontoideum) underwent minimally invasive C1–C2 fusion over a 2-year period. The cohort consisted of 5 men and 1 woman with a mean age of 51 years (age range, 39–64 y). All 6 patients underwent bilateral segmental atlantoaxial fixation using an expandable tubular retractor.

RESULTS

The mean follow-up time was 32 months (age range, 24–46 mo) There were no intraoperative complications, and the mean estimated blood loss was 100 mL. Solid fusion was achieved in all 6 patients, without pathological motion on dynamic studies. Postoperative computed tomographic images showed no hardware malposition in the scanned patients (4 of the 6 patients).

CONCLUSIONS

Placement of C1 and C2 instrumentation using minimally invasive techniques is technically feasible. Because the instrumentation and the means of obtaining arthrodesis do not differ substantively from the standard approach, we would not anticipate long-term results to be different from those of an open procedure, apart from the approach-related morbidity.