Minimally invasive techniques aimed at minimizing surgery-associated risk and morbidity of spinal surgery have increased in popularity in recent years. Their potential advantages include reduced length of hospital stay, blood loss, and requirement for post-operative analgesia and earlier return to work. One such minimally invasive technique is the use of percutaneous pedicle screw fixation, which is paramount for promoting rigid and stable constructs and fusion in the context of trauma, tumors, deformity and degenerative disease. Percutaneous pedicle screw insertion can be an intimidating prospect for surgeons who have only been trained in open techniques. One of the ongoing challenges of this percutaneous system is to provide the surgeon with adequate access to the pedicle entry anatomy and adequate tactile or visual feedback concerning the position and anatomy of the rod and set-screw construct. This review article discusses the history and evolution of percutaneous pedicle screw retractor technologies and outlines the advances over the last decade in the rapidly expanding field of minimal access surgery for posterior pedicle screw based spinal stabilization. As indications for percutaneous pedicle screw techniques expand, the nuances of the minimally invasive surgery techniques and associated technologies will also multiply. It is important that experienced surgeons have access to tools that can improve access with a greater degree of ease, simplicity and safety. We here discuss the technical challenges of percutaneous pedicle screw retractor technologies and a variety of systems with a focus on the pros and cons of various retractor systems.
Fig. 1 Advantages of percutaneous pedicle fixation. (A) Normal anatomy demonstrating the depth and angulation of the pedicle, (B) muscle retraction with traditional open surgery requires wide paraspinal muscle dissection and (C) because the approach angle matches the pedicle angle, tubular retractors with percutaneous pedicle screws require minimal paraspinal retraction.
Fig. 2 Medtronic Sextant-2 System. Percutaneous pedicle screw sleeves/towers with separate stab incision site for rod insertion (Medtronic). This fixation system provides pedicle screw fixation with small incisions and minimal soft tissue dissection. Each screw is placed through its own incision and a separate incision is required for placement of rods into the screws.
Fig. 3 Definitions of percutaneous retractor sleeve/tower and regional zones/spaces. The percutaneous retractor sleeve/tower attaches and provides direct access via a minimalist corridor from outside to the patient to the pedicle screw tulip. Following insertion of the percutaneous pedicle screw, the transition point is the skin, which divides the sleeve/tower into zones above and below the skin. The fixation point is the point of attachment of the retractor sleeve/tower to the tulip of the pedicle screw.
Fig. 4 The four types of retractors sleeves/towers: (A) standard: a simple tower that attaches to the pedicle tulip; (B) floppy/malleable: this has a soft and malleable sleeve/tower that provides the surgeon with an excellent view space; (C) flat: this presents nothing above the skin, both ends of the retractor being stuck/adherent to the skin and (D) reduction: this design incorporates an extended internal thread so that the set screw can capture the rod and gradually reduce a deformity.
Fig. 5 Evolution of retractors from complex to simple. (A) Percutaneous retractors were initially overly complicated, fiddly and technically demanding. Bulky retractor towers inhibited surgeon hand movement and caused significant retractor impact around the operative field. (Centennial Spine, Las Vegas, NV, USA). (B) Later designs have focused on simplicity and ease of use (Stryker). The arrow indicates a navigation reference tower for percutaneous screw placement that is attached midline to a spinous process.
Fig. 6 Potential issues with retractor sleeves/towers: L5S1 screw head proximity. Flexible retraction sleeves minimize the problem of screw head proximity because it is easy to deflect the retractors out of the way of percutaneous pedicle screw placement. It is common for the surgeon to require only a single incision at L5S1 because the retraction sleeves are immediately adjacent at the skin edge.
Fig. 7 Complex fracture management using a variety of percutaneous retractor sleeve/tower options. Retractor sleeves/towers will likely evolve towards the concept of “one system, many options” in response to surgeons’ demands for a flexible percutaneous pedicle screw system that provides multiple fixation and sleeve/tower options for managing complex pathologies. An example is shown of standard reduction pedicle screws spanning a fracture.
Fig. 8 Fracture management using percutaneous fixation with cement augmentation utilizing various retractor sleeves (ES-2 and MANTIS Systems; Stryker). In patients with pathological fractures associated with osteoporosis or metastatic disease, standard reduction pedicle screws can be used to span the fracture, with the option of cement augmentation at one or more levels.
Fig. 9 Flexible retraction sleeves that can be laid flat to reduce retractor impact and facilitate surgeon hand movement around the operative field. These types of malleable/bendable sleeves are potentially useful for cortical bone trajectory/MLST screws.
Fig. 10 Wings retractor concept. (A) A malleable retractor sleeve/tower provides the surgeon with ease of vision to the tulip rod/screw interface, (B) a benefit of malleable retractors is ease of packaging and storage and (C) issues of retractor collision, say at L5S1, are solved with malleable sleeves/towers.
References
Orthop Surg. 2016 Feb;8(1):3-10.
联系客服
