L&K Biomed Co., Ltd. made various approach procedure with a single implant into the disc space through a PLIF approach, TLIF approach, DLIF approach ALIF or anywhere in between, for both open or less invasive procedures.
The LnK Lumbar Interbody Fusion Cage System’s implants are interbody fusion devices intended for use as an aid in spinal fixation. These hollow, rectangular implants are offered in a variety of widths, lengths, heights and lordotic angles designed to adapt to a variety of patient anatomies. They have serrations on the superior and inferior surfaces designed for fixation, ergonomically shaped anterior edges and flat posterior edges. Radiopaque markers have been embedded within the implants, which are designed to allow for visualization in radiographic images.
Posterior & Anterior Interbody Fusion with the L&K Biomed LnK Lumbar Interbody Fusion Cage System
Posterior interbody fusion techniques are increasingly recommended by spine surgeons. Improved surgical techniques and improved interbody implants are among the reasons interest in these techniques is increasing. Posterior interbody procedures provide both posterior and anterior stabilization through a single incision. Posterior interbody fusion represents a spectrum of techniques. These procedures can be performed as a PLIF through a paramedian annulotomy. Alternatively, TLIF utilizes a farther lateral annulotomy, colinear with the pedicle and ALIF through anterior approach. In reality, any point between the paramedian, far lateral and anterior approach can be selected. What one surgeon may call a TLIF might be termed a PLIF by another.
These procedures can be done through traditional open approaches, or they can be performed through tubular retractors in a nearly percutaneous manner, or virtually every point in between.
The posterior interbody fusion surgeon has a number of other choices as well. A variety of Cage materials and geometries are available for single or paired implantation. Typically, adjunctive stabilization is sought with transpedicular instrumentation. The graft material employed will also vary from iliac crest autograft to local bone.
Rationale of Posterior & Anterior Interbody Surgery
Appropriate Cage selection requires an understanding of the rationale and biomechanics of interbody procedures. Interbody techniques place the fusion mass under compression as this region has better vascularity than does the posterolateral, inter-transverse space. These techniques afford the surgeon every access to the motion segment without a separate, anterior approach. The disadvantages of these procedures need to be considered as well. For PLIFprocedures, the surgeon must be careful to avoid excessive nerve root retraction in order to avoid postoperative epidural fibrosis. In TLIF procedures, the sensitive dorsal root ganglion must be protected. Both procedures require segmental destabilization from facet removal. In ALIF procedures, large veins must be protected.
Goals & Contraindications
Regardless of the exact method selected, the goals of posterior interbody surgeries are to achieve a solid, stable arthrodesis of the spinal segment while maintaining proper disc height and restoring sagittal plane alignment. Interbody fusions are also added to longer posterior lateral fusions when additional anterior column stability is required. For example, in patients with marginal sagittal balance a TLIF/PLIF/ALIF may prevent post-operative flat- back. Posterior interbody procedures are not appropriate in every clinical situation, however. A number of relative contraindications must be considered when recommending a specific surgical strategy. Similarly, while osteoporotic patients are often more fragile overall, if interbody implants are required, the larger footprint of an ALIF Cage is less likely to subside than a posterior Cage. Alternatively, a bilateral approach may be considered in patients with borderline bone quality. Finally, both PLIF and TLIF procedures must be undertaken with great care in patients with extensive epidural scarring. In those cases, safe dural retraction required for PLIF may be difficult.
In TLIF cases, extensive epidural scarring limits the extent to which safe interbody distraction can be achieved. These devices must be used with supplemental fixation
LnK Lumbar Interbody Fusion Cage System is indicated for intervertebral body fusion procedures in skeletally mature patients with degenerative disc disease (DDD) at one or two contiguous levels from L2-S1. DDD is defined as discogenic back pain with degeneration of the disc confirmed by patient history and radiographic studies. These DDD patients may also have up to Grade 1 spondylolisthesis or retrolisthesis at the involved level(s).This device is to be used with autogenous bone graft. LnK Lumbar Interbody Fusion Cage System is to be used with supplemental fixation. Patients should have at least six (6) months of non-operative treatment prior to treatment with an intervertebral cage.
This device is not intended for cervical spine use.
Contraindications include, but are not limited to:
- Infection, local to the operative site
- Signs of local inflammation,
- Fever or leukocytosis,
- Morbid obesity,
- Mental illness,
- Any other condition which would preclude the potential benefit of spinal implant surgery, such as the presence of tumors or congenital abnormalities, fracture local to the operating site, elevation of segmentation rate unexplained by other diseases, elevation of white blood count (WBC), or a marked left shift in the WBC differential count.
- Suspected or documented allergy or intolerance to composite materials,
- Any case not needing a fusion,
- Any case not described in the indications,
- Any patient unwilling to cooperate with postoperative instructions.
- Patients with a known hereditary or acquired bone friability or calcification problem should not be considered for this type of surgery.
- These devices must not be used for pediatric cases, nor where the patient still has general skeletal growth.
- Spondylolisthesis unable to be reduced to Grade 1.
- Any case where the implant components selected for use would be too large or too small to achieve a successful result.
- Any case that requires the mixing of metals from two different components or systems.
- Any patient having inadequate tissue coverage over the operative site or inadequate bone stock or quality.
- Any patient in which implant utilization would interfere with anatomical structures or expected physiological performance.
- Prior fusion at the level to be treated.
Although not absolute contraindications, conditions to be considered as potential factors for not using this device include:
- Severe bone resorption.
- Severe osteoporosis
Surgeons planning posterior interbody fusions have a number of options in their approach to fit the pathology to be addressed. For example, the relative location of the dorsal root ganglion at the operative level may affect the medial- lateral approach angle to the disc space. Similarly, the width of the lateral pars and thepelvis may render PLIF or TLIF more appropriate in a given patient. In males with a narrow pelvis, the L5-S1 disc space may be more easily accessed through a paramedian (PLIF) approach. In the upper lumbar spine (L3-4 and above), the narrow pars and smaller canal to dural diameter ratio makes TLIF the preferred approach in most cases. Interbody fusion Cages can be mechanically compatible with the surrounding bone. That is, the stiffness or modulus of elasticity approximates the host bone. The Cage must be biologically compatible with little Cage/host reactivity or rejection. Finally, an interbody Cage can be radiographically compatible. Metallic Cages are often quite strong and are typically designed to resist compression failure, but are markedly stiffer than the surrounding bone. Today, PEEK (Poly-Ether-Ether- Ketone) Cages are designed to offer better compression resistance while approximating the modulus of elasticity of the hostbone. Moreover, PEEK is radiolucent allowing easier post-operative assessment of fusion.
Posterior interbody fusion Cages come in a number of shapes. Among the earliest Cages were threaded cylinders. These promote high stability once implanted because of a strong bone implant junction, but also may confer the highest risk of nerve injury during insertion because of their shape. Given the frequency of concomitant pedicle screw instrumentation, these large Cages are not mechanically necessary. Vertical cylinders were recommended by Harms for TLIF procedures, but their endplate contact areas are limited thereby limiting maintenance of height and segmental lordosis.
Today, most typically rectangular Cages are employed because they are designed to offer the greatest flexibility in insertion. They can be placed unilaterally or bilaterally and from a variety of angles. Geometrically, they are designed to confer outstanding endplate coverage while requiring little nerve root retraction for insertion.
Regardless of the approach, open vs. MIS, TLIF vs. PLIF. DLIF vs. ALIF, a number of technique tips apply in every interbody fusion procedure. First, even when open technique is employed, careful attention to soft tissue handling can help improve posterior rmuscular function and may decrease pain. Of course, the most important soft tissues are the nerves. Safer posterior lumbar interbody fusion techniques require identification of the exiting and traversing nerves. In TLIF, the exiting root and dorsal root ganglion are identified. In both cases, careful control of local, epidural bleeders through bipolar electro cautery, thrombin soaked gelfoam, or other means will help to allow improved visualization through the critical steps of disc space preparation and Cage insertion.
Second, even when an MIS approach is used, an adequate job must be performed mechanically. That is, Cages must be sized to fit the inter space and screws must be sized to fit the pedicle. If, in a given case, full disc space debridement cannot be performed through a less invasive approach, the incision should be opened to ensure that that annular tension is restored and the optimal Cage is implanted. Often, resection of surrounding endplate osteophytes will improve visualization into the disc space to confirm debridement and, subsequently, Cage sizing. Some surgeons prefer to apply bone wax to bleeding bone surfaces in the canal after the Cage has been inserted.
Third, a wide near total discectomy must be performed. The disc space around the Cage(s) should be packed with graft material.
Fourth, while removal of the endplate cartilage is critical, it is important to protect the bony endplates. Focal disruption of the endplate should result in selection of a new Cage trajectory. Placement of the Cage over a disrupted endplate may lead to early subsidence and a higher risk of Cage migration.
Fifth, ideal placement of the Cage(s) in the inter space may vary depending on the patient’s needs. For example, if the goal is to maximize segmental lordosis, Anterior Cage placement may be preferred. On the other hand, posterior placement may allow for improved foraminal decompression.
The L&K Biomed LnK Lumbar Interbody Fusion Cage System portfolio is designed to afford the surgeon an excellent tool for stabilization of the anterior column from a posterior approach.
This stabilization may be helpful in off-loading posterior instrumentation, increasing foraminal height, or improving spinal alignment. After proper disc space preparation, the LnK Lumbar Interbody Fusion Cage System helps to provide a proper geometry for safe insertion while maintaining excellent endplate coverage. Constructed from PEEK, the Cage closely matches the local bone mechanically and allows for visualization during postoperative imaging.
Exposure and Preparation of Facet Joints with PLIF & TLIF & DLIF cage
Step 1 – Exposure
A Lumbar Interbody Fusion procedure can be performed using a standard open or minimally
invasive approach, from the patient’s left or right side. Typically, cage insertion is performed from the symptomatic side in patients with radiculopathy. This technique describes a left-sided approach at L4-L5.
The incision is made over the spinous process of L3 and extends to L5. (Fig.1) Sharp para spinal dissection is performed exposing the L3-L4 and L4-L5 facets. Care must be taken to avoid damage to the L3-L4 facet capsules. Unless the surgeon intends to perform Concomitant inter transverse fusion, the transverse processes need not be exposed.
Minimally Invasive Approach
The LnK Lumbar Interbody Fusion Cage System lends itself to minimally invasive approaches as well. MIS systems rely on proprietary retractor systems and specialized tools, the use of which are best depicted in their individual technique guides. A minimally invasive system which can be used is the L&K Biomed System. You must refer to the surgical technique for additional information on minimally invasive exposure.(In case of DLIF, the patient is place on a bendable surgical table in a direct lateral decubitus(90°) position so that the iliac crest is directly over the table break.)
NOTE: The remaining steps in the surgical technique are similar in both open and minimally invasive surgical approaches. All images in this technique, however, depict an open approach for image clarity. You must refer to the Luxor surgical technique for additional information on minimally invasive approaches and detailed images.
Step 2 – Preparation of facet joints
Both L4-L5 facet capsules should be removed circumferentially. This is typically accomplished using a cautery device. Bipolar cautery may be useful in achieving hemostasis lateral to the facet joints. The right L4-L5 facet is prepared for fusion by removing the articular cartilage from the facet joint with a burr or other appropriate instrument. (Fig. 2)
Step 3 – Lumbar Interbody Fusion Site Preparation
The Lumbar Interbody Fusion site preparation is on the left side. An osteotome may be used to remove the left inferior articular process of L4 with two cuts, a vertical cut just medial to the facet extending superiorly to the superior border of the facet and a horizontal cut directed laterally towards the foramen. Once the two cuts are made, the inferior articulating process of L4 may be removed with a kerrison. (Fig. 3) The left lateral edge of the ligamentum flavum is then visualized. A curette may be used to release (but not resect)the ligamentum flavum from the superior lamina of L5, allowing for distraction. The ligamentum flavum should be preserved when possible, but resection of redundant flavum may be necessary in patients with neurologic compression.
Step 4 – Distraction
Effective distraction aids in removal of the superior articular process of L5,decompression of the neuroforamen, preparation of the disc space and insertion of the LnK Lumbar Interbody Fusion Cage System.
This may be accomplished through several techniques: pedicle screw distraction, distraction between boney elements, and/or distraction with a positioning device.
- If pedicle screw distraction is chosen, the screws should be positioned at this time, using standard technique. Apply distraction between pedicle screws placed at L4 and L5. (Fig. 4&5)
- Particularly in patients with less than ideal bone quality, it might be useful to size the interspace with paddle distractors, reamer distractors, or trials before locking the distraction down through the pedicle screws. Interspace distraction helps to give an excellent sense of restoration of annular tension and helps to avoids pedicle screw preloading (which may cause post-operative loosening).
- Choices for a supplemental spinal fixation system include, but are not limited to, L&K Biomed pedicle screw and rod or plate systems. Pleaserefer to the surgical techniques ofthe above mentioned L&K Biomed fixation systems for additional information on implantation.
- In an open procedure, apply direct distraction between the boney elements of L4 and L5, such as the spinous processes or laminae.
- The patient’s lordosis can be adjusted with a positioning device,such as a Wilson frame (open and minimally invasive procedures).
With sufficient distraction, the L4-L5 foramen will be opened and the entire superior articular process of L5 will be visualized. A small probe may be used to palpate the superior margin of the left L5 pedicle. The superior articular process of L5 should be resected exposing the L4-L5 disc in the L4-L5foramen. This may be accomplished with an osteotome, rongeur, orother appropriate instrument. Since a consistent leash of veins traverse the foramen over the disc space, the surgeon should be prepared to control bleeding from these veins with bipolarcautery. Hemostasis may be enhanced with topical hemostatic agents and cottonoid pledgets. The exiting L4nerve root is rostral at this point, under the pars interarticular is, and in many instances is not visible.
(In case of DLIF, restro peritoneal approach and then direct lateral approach)
Step 5 – Disectomy and Endplate Preparation
Access to the disc space is achieved through an annulotomy, made lateral to the posterior longitudinal ligament. Using a scalpel, vertical cuts should be made parallel to the dura and laterally in the foramen from the endplate of L4to the endplate of L5. Additional cuts extend horizontally along the end plates of L4 and L5, connecting the vertical units. The annulus and any accessible disc material are removed with a pituitary rongeur. (Fig. 6)
Commonly, a large osteophyte will protrude inferiorly off the end plate of L4, and sometimes superiorly off the endplate of L5. Sharp excision of these osteophytes with an osteotome or kerrison punch will help to provide alarger entry portal if desired.
Throughout the remainder of the procedure, care must be taken to not damage the remaining lateral, anterior or posterior annulus.
A curette or narrow cobb elevator is used to elevate disc material from the endplates of L4 and L5 on the
left lateral side. Next, angled curettesare used to elevate the disc from the endplates of L4 and L5centrally and on the right side. (Fig. 7) An easily missed portion of the disc lies posteriorly and centrally within the disc space, just ventral to the spinal canal. Special effort should be directed toward removing disc in this zone to provide optimal surface area for interbody fusion. Straight and up biting pituitary rongeurs should be used to remove the disc. Additionally, multiple passes with straight and angled curettes may be necessary to ensure adequate discectomy. Fluoroscopy may help in ensuring clearance of the disc space while limiting the risk of perforating the ventral, lateral or posteromedial annulus.
Step 6 – Sizing the Disc Space
The disc space height is then sized using a series of paddle distractors, reamer distractors, or trials (Fig. 8). The paddle distractor, reamer-distractor, or trial size is serially increased until the appropriate fit within the disc space is achieved. The paddle distractor, reamer-distractor, or trial should fit snugly within the disc space with distraction released, but care must be taken to not oversize the implant. Under sizing may contribute to a loss of lordosis and inadequate stability for fusion, while over sizing may result in difficult insertion of the implant and disruption of the vertebral boney endplate along with possible graft subsidence.
NOTE: The Trial footprint is available in all height and width offerings. A ridge exists on the post of the trial at 28mm and32mm, and is designed to assist the surgeon in determining which implant length is appropriate from radiographic images.(Fig. 9)
Step 7 – LnK Interbody Lumbar Cage System Preparation
Select the appropriately sized LnK Lumbar Interbody Fusion Cage System implant and assemble it to the appropriate PEEK Cage Inserter. (Fig. 10)
- All The LnK Lumbar Interbody Fusion Cage System implants which are 25 -32mm in length, 7mm-15mm in height should be assembled.
- All 11mm wide The LnK Lumbar Interbody Fusion Cage System.
Place the LnK Cage implants in the Graft Block and pack it with autogenous graft using the Graft Compactor. The compacted graft should be flush with the upper and lower surfaces of the implant, to later be in contact with the endplates.
NOTE: The LnK Lumbar Interbody Fusion Cage System is indicated for use with autogenous bone graft only.
Step 8 – LnK Intervertebral Lumbar Cage System Cage Insertion
Carefully insert the LnK Lumbar Interbody Fusion Cage System implant gently and progressively into the disc space. (Fig. 11) Optimal positioning maybe facilitated by directing the implant obliquely until it contacts the ventral annulus. Maintain posterior distraction until the implant clears the posterior annulus. If difficulty is encountered, it most likely represents a mechanical block to passage of the implant. Check for adequacy of the discectomy and be sure distraction is maintained. Then, reposition the implant as needed. The distraction may be released slightly to facilitate final positioning.
NOTE: Difficulty inserting the implant may be related to an inadequate distraction, an undersized annulotomy or oversized implant. Difficulty positioning the implant anteriorly in its oblique orientation and centrally within the disc space may be related to inadequate discectomy or an over sized implant.
Based on surgeon preference, the PL Impactor may be used to gently tamp the implant to its final position. (Fig. 12) Fluoroscopy may be useful in determining the appropriate trajectory for insertion and appropriate final positioning.
NOTE: To visually confirm the lordosis is restored in the desired plane, the implant must be inserted with the black circular marker towards the lateral aspects in an oblique insertion
Placement of Autogenous Bone Graft
There are two titanium alloy markers, oriented perpendicular to each other, embedded within the PEEK material of the LnK Lumbar Interbody Fusion Cage System implants, which are designed to help visually confirm the implant’s position under fluoroscopy. One marker is positioned horizontally at the anterior end and the other marker is positioned vertically at the posterior end of the implant.
In LnK Lumbar Interbody Fusion Cage System implants, the vertical posterior marker and anterior horizontal marker will appear as depicted, on a radiographic image of an implant centered from left-to-right within the disc space. (Fig. 14 & 15)
Step 9 – Placement of Autogenous Bone Graft
Autogenous bone graft may be placed lateral, ventral and/or dorsal to the implanted LnK Lumbar Interbody Fusion Cage System implant. (Fig. 16)
The PEEK Cage Inserter can help to rescue the implant if deemed medically necessary. Align the outer chamfered shaft with the contours of the implant, thread the internal shaft into the implant and remove it. The internal shaft alone or a blunt nerve hook may also be used.
Step 10 – Posterior Fusion
Since the interbody portion of the procedure is complete, distraction canbe released. If pedicle screws were not inserted earlier in the procedure they may now be inserted. Vertical rods connect the screws together and gentle compression should be applied betweenthe L4 and L5 screws bilaterally. This facilitates restoration of segmental lordosis and compression of the LnK Lumbar Interbody Fusion Cage System implant and bone graft. Apply appropriate final torque tightening to all screws. The remaining autogenous bone graft may be placed in the decorticated right L4-L5 facet to help promote posteriolateral fusion. Intraoperative radiographs should be performed to confirm satisfactory position of the LnK Lumbar Interbody Fusion Cage System implant, pedicle screws, and graft.
For the Cage Removal procedure (need to be removed)
The incision is made over the op- incision site. When the exposed site, place the Cage Holder to the Cage hole. And reverse hit the cage holder with the slotted hammer for the cage extraction. And make sure that the cage has been removed completely.
Step 11 –Remove Instrument
Once the cage is in the correct position, distractor Handle is loosened and the distraction released.
The Distractor is gently removed while the Cage is held in position by the Implant inserter.
Additional hammer blows will ensure a secure fit. The Implant inserter is then released from the Cage. The Cage graft holder may be used once the distractor has been removed
For the Cage Removal procedure (need to be removed)
The incision is made over the op-incision site. When the exposed site, place the Cage Holder to the Cage hole. And reverse hit the cage holder with the slotted hammer for the cage extraction. And make sure that the cage has been removed completely.
Procedure of ALIF
Skin Incision and Exposure of Disc Space
For anterior insertion, expose the inter vertebral disc, so that there is clear space on either side of the vertebral midline equal to one-half the width of the LnK ALIF Cage.
Create a window by cutting the anterior longitudinal ligament and annulus fibrosus in a rectangular shape with its width equal to that of the LnK ALIF Cage. A Trial Cage may be used to determine the width of the window.
Disc Space Preparation
Through the window in the anterior longitudinal ligament and annulus fibrosus, the disc material is resected and the superficial layers of the cartilaginous endplates are prepared until endplate bleeding is attained. Adequate cleaning of the endplates is important for vascular supply to the bone graft; however, preparation cleaning may disrupt the endplate due to removal of the dense bony layer of the endplate. The endplate should be prepared to match the shape of the curvature of the superior and inferior surfaces of the implant.
Distracting the Segment
Distraction of the segment is essential for restoration of disc height, opening of the neural foramina, and stability of the LnK ALIF Cage.
Cage Size Selection
To find the correct Cage size, begin with the Trial Cage that corresponds to the LnK ALIF Cage size determined during preoperative planning. Attach the Trial Cage to the Trial Cage Holder.
When the segment is fully distracted, the LnK ALIF Trial Cage must fit firmly with a tight press-fit between the endplates such that disc height is not lost when the Distractor is removed. Try smaller or larger Trial Cages as needed.
Once the Cage size has been determined, temporarily relax the distraction
Take the LnK ALIF Cage that corresponds to the selected Trial Cage and secure it to the LnK ALIF Cage Inserter. With the correct LnK ALIF Cage, it is held with the LnK ALIF Cage Inserter.
Packing the Cage with Bone Graft
To aid packing the graft, the LnK ALIF Cage with the Cage Inserter attached is set into the Bone Packing Block. Use the Bone chip inserter to firmly pack the graft material into the implant.
It is important to fill the Cage completely so that the graft protrudes from the holes in the LnK ALIF Cage, optimizing the blood supply to the graft.
Inserting the Cage
Insert the prepared LnK ALIF Cage into the disc space.
Check the position of the inserted LnK ALIF Cage.
Once the LnK ALIF Cage is placed in its correct position, remove the Cage Inserter.
Removing the Cage Holder
Once the cage is in the correct position, distractor Handle is loosened and the distraction released.
The Distractor is gently removed while the Cage is held in position by the Implant inserter.
Additional hammer blows will ensure a secure fit. The Implant inserter is then released from the Cage .The Cage graft holder may be used once the distractor has been removed
Verifying the Cage Placement
The optimal position for the LnK ALIF Cage is centered within the periphery of the vertebral endplates.
The location of the LnK ALIF Cage relative to the vertebral bodies in the AP direction should be verified using an image intensifier.
Check the left L4-L5 foramen and Lumbar Interbody Fusion site for any bone fragments or extraneous soft tissue. Once satisfactory decompression of the exiting and traversing nerve roots is confirmed the wound should be closed.