Spinal instrumentation hardware

Spinal instrumentation hardware refers to various types of implants used for fixation in spinal surgery. They can be used in various combinations and include wires, clamps, screws, different plate-screw and rod-screw interfaces, intervertebral prostheses and disk replacements.

Cervical spine instrumentation hardware

Wires and cables

Wires and cables are used in several posterior cervical fusion and occipitocervical fusion techniques such as the Gallie or modified Gallie technique, Brooks technique, wire-bone-graft, wire-plate, rod-wire, pin-wire strategies or complex fusion procedures ^1-3:

• regular wires

• Songer cables (braided titanium or stainless steel – more pliable)

• interspinous wiring

• facet wiring

• sublaminar wiring

Screws

Screws can be used as standalone hardware in various anterior and posterior transarticular screw fixation or odontoid screw fixation procedures or in conjunction with plate-screw and rod-screw interfaces ¹:

• cortical screws (unicortical, bicortical screws)

• cancellous screws (threaded, partially-threaded, double threaded)

• cannulated (hollow) screws

• lateral mass screws

• pars screws

• laminar screws

• pedicle screws

• odontoid screws

• transarticular screws

• occipital screws

Clamps and hooks

Clamps and hooks have been as a posterior cervical fusion technique in atlantoaxial fixation or conjunction with a pre-contoured rod-screw system for occipitocervical fusion.

• inverted-hook occipital clamp system

• Halifax clamps

Plates

Plates are used in conjunction with screws and selected cases with rod-screw interfaces. They are more commonly used in anterior fusion procedures such as anterior cervical discectomy and fusion ¹.

• anterior cervical plate

  • restricted backout plate (screws affixed to the plate allowing for unicortical screws)

  • constrained (rigid) plate

  • semi-constrained plate-screw interface

• odontoid plate

• posterior cervical plates

  • malleable reconstruction plates

  • Haid plate

  • tubular plates

  • hook plate

• occipital plate

Rods

Rods are usually seen as rod-screw constructs in different posterior cervical fusion procedures including prebent and preshaped rod-systems such as rod-screw-plate, rod-screw-clamp, rod-screw-cable, or inverted-hook-rod-screw interfaces for occipitocervical fusion strategies ^1,2.

• conventional connecting rods

• malleable cervical rods

• pre-contoured occipitocervical rods

  • Ohio Medical Instruments Loop

  • Hartshill-Ransford contoured loop

Cages

Interbody fusion cages are used in the anterior fusion discectomy and fusion procedure in conjunction with an anterior cervical plate ². Some devices come feature interlocking devices, some are bevelled.

• synthetic cages (PEEK)

• carbon composite cages (e.g. PLDLLA)

• metallic cages (titanium, stainless steel, tantalum)

• cylindrical implants

• mesh cages

Artificial cervical discs

Artificial cervical discs are used in cervical disc arthroplasty typically in single-level disease and offer some maintenance of mobility at that level. Diverse titanium and cobalt-chrome implants with or without polyethylene lining exist ².

Thoracolumbar spine instrumentation hardware

Wires and cables

Nowadays wires and cables are not commonly used for instrumentation of the thoracic lumbar spine. They have been used in conjunction with other implants (e.g. Hartshill rectangles).

Screws

In the thoracolumbar spine, screws are commonly used in conjunction with other implants such as interconnecting rods, interbody cages, or screw-plate interfaces ².

• pedicle screws

• translaminar or facet screws

• spinopelvic screws

• interlocking screws

Plates

Similar to rods plates are used as connecting elements more often in spinal surgeries with a fusion of fewer levels and with an anterior, oblique or lateral approach.

Rods

Rods are used as connecting elements for posterolateral thoracic, lumbar, lumbosacral and spinopelvic fusion procedures (e.g. PLIF and TLIF) and for scoliosis surgery ².

• connecting rods

• threaded rods

• rod-screw constructs with or without tandem connector

• growing rods

  • traditional growing rods

  • magnetically controlled growing rods

• Harrington rod (lengthenable rods hooked to the laminar surface of the concave side of scoliosis, used in the 1960s-1990s)

• Luque rod (posterior thoracolumbar stabilization with sublaminar wires, not used anymore)

Interbody spacers and vertebral body replacements

Interbody spacers and vertebral body replacements include cages and solid tapered constructs. Various implants exist including rigid, expandable and stackable devices, which might be combined with rod-screw or plate-screw constructs ^2,4. Some of them feature integral interlocking or fixation mechanisms ⁶.

• rigid mesh cages

• expandable cages

• stackable cages with or without interconnecting rods

• cylindrical implants

• tapered implants

Artificial discs

Artificial discs are used in lumbar disc replacements with symptomatic degenerative disk disease but with the absence of significant facet joint arthritis, spondylolisthesis or instability ². Semiconstrained ball-and-socket devices and unconstrained devices exist. Some of them have a metal-on-metal interface others come with metal endplates and a polyethene liner ⁷.

Dynamic stabilization devices

Dynamic stabilization devices pose an alternative to rigid fusion devices in patients with low back pain due to chronic degenerative changes ⁴ and come in a few forms ⁸: 

• hybrid stabilization devices

• artificial ligament systems

• posterior element or facet replacement systems

• interspinous devices

Interspinous devices

Interspinous devices are used to prevent spinal extension and thus decrease the load on the facet joints and alleviate symptoms from spinal canal stenosis ⁵:

• X-Stop (two parallel wings connected by a spacer)

• Wallis (interspinous PEEK spacer fixed with Dacron bands)

• Coflex (U-shaped titanium implant with vertical wings)