MIS-LTLIF: large-footprint cage in lumbar fusion
BY DRS AYUSH SHARMA, SHUBHAM KADAM, AJIT RAMPURE, AND NANDAN MARATHE
Combining direct posterior decompression with a large-footprint cage through a tubular approach
"Enter through a narrow corridor; finish with a broad footprint."
A reverse-orthogonal maneuver allows a large-footprint cage to enter through a familiar posterior tubular corridor and finish in a near-transverse position across the disc space. The opportunity is broader endplate coverage; the obligation is meticulous preparation and disciplined positioning.
A large-footprint cage can be placed through a posterior minimally invasive tubular corridor and rotated into a near-transverse position across the disc space. That is the central finding from our first prospective series of minimally invasive large-footprint transforaminal lumbar interbody fusion, or MIS-LTLIF. It may sound like an implant story. In practice, it is a corridor, preparation and positioning story.
The most important message is not that every transforaminal lumbar interbody fusion should use a larger cage. It is that one familiar compromise can be reconsidered. Conventional MIS-TLIF offers direct decompression, posterior familiarity and limited muscle disruption, but its narrow working corridor often dictates a small, bullet-shaped cage. Anterior and lateral approaches permit larger cages and broader endplate coverage, but they use different anatomical corridors and carry their own approach-specific considerations. MIS-LTLIF was developed to explore whether selected patients could receive both direct posterior decompression and a broad interbody footprint through one minimally invasive posterior route.
- MIS-LTLIF combines a posterior tubular approach and direct neural decompression with placement of a large-footprint cage.
- Its defining feature is the final cage position: the cage enters obliquely, crosses the midline and is rotated into a near-transverse orientation using a reverse-orthogonal maneuver.
- Our prospective technical series of 30 patients and 39 levels established early feasibility, but it was small, single-surgeon and short-term; one cage migration required reoperation and realignment.
- A separate revision case illustrates how MIS-LTLIF can be used after posterior cage back-out, but one case cannot prove that footprint alone prevents migration or subsidence.
The tradeoff that started the idea
For years, I accepted a familiar tradeoff in lumbar fusion. When I chose MIS-TLIF, I gained a muscle-sparing posterior corridor, direct access to the neural elements and a technique that could be combined naturally with percutaneous pedicle screw fixation. But the same corridor limited the cage that could pass through it. The implant was usually narrow enough to enter safely, yet its footprint and graft volume were modest once it reached the disc space.
When I wanted a cage that extended across more of the endplate, the usual answer was an anterior or lateral approach such as ALIF, OLIF or XLIF. These are powerful procedures and remain the best choice in many clinical situations. They provide access to the broad anterior disc space and can support substantial disc-height and alignment correction. They may also depend on indirect decompression and require navigation of vascular, visceral, sympathetic or psoas-related anatomy.
The question behind MIS-LTLIF was therefore simple: Could a cage be narrow in its entry pathway but broad in its final working position? The solution was not to force a large implant through a small opening. It was to change the opening, prepare the disc more completely and separate the insertion trajectory from the final cage orientation.
What is unique about MIS-LTLIF?
MIS-LTLIF is a modification of MIS-TLIF, not a lateral interbody procedure and not simply a conventional TLIF with a longer cage. Through an approximately 2-centimeter incision, an expandable tubular retractor is docked over the facet. A complete facetectomy and adequate laminotomy expose the exiting and traversing nerve roots and create a broad working window that combines the transforaminal and trans-Kambin corridors. The surgeon can perform direct decompression and preserve the removed bone for autograft.
The dedicated cage is long and tapered and uses two attachments: a straight inserter for entry and a rotational inserter for final positioning. In our published series, cage lengths ranged from 35 to 50 mm, with a maximum central width of 15 mm and heights from 9 to 14 mm. The average implanted cage measured approximately 40 by 15 by 10 mm.
The final position is the distinguishing feature. A conventional bullet cage generally advances along an oblique posterior-to-anterior trajectory and remains broadly aligned with that path. In MIS-LTLIF, the cage enters from lateral to medial, advances until it has crossed the midline on the anteroposterior view and then rotates around its far end. The reverse-orthogonal maneuver brings the cage into a near-horizontal or transverse orientation across the disc space. The implant's insertion profile and its final footprint are therefore different.
The core idea: Enter through a controlled posterior corridor, then rotate the cage so that its final footprint is broader than its insertion pathway.
The operation succeeds or fails before the cage rotates
A larger cage is not automatically a safer cage. In fact, a long cage introduced through an inadequate window or an incompletely prepared disc space may be more difficult to control. The technical sequence matters more than the acronym.
- Create the window, do not improvise it. Complete facetectomy and appropriate laminotomy should allow direct identification of both the exiting and traversing roots. The expandable tube must provide enough working freedom for insertion and rotation.
- Prepare beyond the visible ipsilateral disc. Contralateral and hidden-zone disc material must be removed so the cage can advance and rotate without being forced. Endplates should be prepared across a broad area while preserving subchondral bone.
- Protect the neural elements throughout insertion. A dissector can shield the traversing and exiting roots, while the cage is advanced under direct vision with minimal root retraction.
- Use fluoroscopy as a positional checkpoint. Before rotation, the cage should have crossed the midline on the anteroposterior view; on the lateral view, approximately one-third remains posterior within the disc space. The straight inserter is then exchanged for the rotational attachment.
- Rotate under control, not by force. The far end becomes the fulcrum as the cage is turned into its final orientation. Resistance should prompt reassessment of disc clearance, trajectory or implant size, rather than greater impaction.
These steps explain why MIS-LTLIF is better understood as a surgical approach and positioning strategy than as an implant substitution. The cage cannot compensate for poor visualization, incomplete disc preparation, endplate violation, excessive height selection or unstable fixation.
Why footprint and final position may matter
A broader cage-endplate interface should distribute axial load over a larger surface and reduce focal stress. It also creates more space for graft and may extend support toward stronger peripheral endplate bone. These are reasonable biomechanical goals, especially when compared with a small cage concentrated over a limited central region.
Position, however, matters as much as length. A long cage that remains excessively oblique may not deliver the intended coverage. By rotating toward a transverse orientation, MIS-LTLIF aims to use more of the available endplate width and achieve a stable final seat. The same maneuver can contribute to restoration of disc height and reduction of listhesis when combined with decompression, release and posterior instrumentation.
These advantages should be described as potential mechanisms, not established superiority. Bone quality, cage height, endplate integrity, graft biology, fixation, alignment goals and patient factors all influence subsidence and fusion. A large footprint cannot neutralize poor technique or unfavorable biology.
What our early series shows—and what it does not
Our prospective technical-feasibility study included 30 patients undergoing MIS-LTLIF at 39 levels for symptomatic degenerative lumbar disease that had not responded to conservative care. The mean age was approximately 61 years. L4-L5 and L5-S1 were the most frequently treated levels. Mean operative time was 115 minutes per level, mean blood loss was approximately 130 mL and the large-footprint cage was implanted successfully at every intended level.
Back-pain visual analog scale scores improved from 8.0 to 4.22, leg-pain scores from 8.22 to 1.67 and Oswestry Disability Index scores from 59.78 to 21.22 at the early postoperative assessment. One patient developed unilateral radicular pain that resolved with medication within two weeks. There were no reported new neurological deficits, durotomies, infections or wound complications. One cage migrated at three weeks and required reoperation; it was realigned using the same technical sequence. Mean follow-up was only about 25 weeks.
The correct conclusion is feasibility, not superiority. The series came from one surgeon and one center, had no control group and was not designed to quantify fusion, long-term subsidence or sagittal correction. Early improvement in pain and disability follows the entire operation—decompression, stabilization and fusion—and cannot be attributed to cage footprint alone. The migration event is equally important: innovation should report its failure modes, not edit them out.
What a revision case taught us
Our second publication described a 45-year-old man who developed posterior cage migration after L4-L5 MIS-TLIF performed at another hospital. A 9 by 22 mm cage backed into the canal on the fifth postoperative day, producing bilateral leg weakness, urinary retention and bowel disturbance. This was cauda equina syndrome and required emergency revision.
The migrated cage was removed. A contralateral complete facetectomy provided a fresh corridor, and the disc was cleared bilaterally with careful endplate preparation. A 10 by 40 mm large-footprint cage was inserted through the posterior MIS corridor and rotated into position using the reverse-orthogonal maneuver, followed by pedicle screw stabilization. Imaging confirmed the final position and restored disc height. The patient recovered bowel and bladder function over six weeks and remained clinically stable during the reported follow-up.
The case demonstrates that MIS-LTLIF can be used as a revision strategy after dangerous posterior cage back-out. It does not prove that a larger cage alone prevents migration. Disc preparation, cage size and height, endplate contact, final position and fixation were all addressed during revision. The lesson is therefore broader: cage stability is a system outcome. Footprint matters, but it matters within a technically sound construct.
Where MIS-LTLIF fits—and where it may not
I see MIS-LTLIF as an additional option between conventional posterior fusion and anterior or lateral large-footprint strategies. It may be particularly useful when direct neural decompression is required, a posterior approach is preferred and the surgeon wants greater endplate coverage without creating a second access corridor.
It is not a replacement for ALIF, OLIF or XLIF. Those approaches may provide more powerful anterior release, indirect decompression and alignment correction in appropriately selected patients. MIS-LTLIF also differs from facet-sparing percutaneous trans-Kambin large-cage techniques: it deliberately uses complete facetectomy and direct visualization of the neural elements to create a broad insertional window.
Patient selection remains essential. Severe osteoporosis was excluded from our early series. Constrained anatomy, poor bone quality, deformity requiring major correction, inadequate access for safe root protection or an inability to complete bilateral disc preparation should lower the threshold for choosing another strategy. The most minimally invasive operation is not the one with the smallest incision; it is the one that achieves the surgical objective safely, reproducibly and with the least necessary tissue disruption.
The next evidence question
The first study asked whether a large-footprint cage could be placed safely through a tubular MIS-TLIF corridor. The next studies must ask whether the technique produces durable benefits. That requires comparative cohorts or randomized trials, standardized definitions of subsidence, computed tomography-based fusion assessment, cage-to-endplate coverage measurements, quantitative disc-height and segmental-lordosis analysis, patient-reported outcomes and implant-related reoperation rates.
It will also be important to separate the effects of cage size, final position, bone quality, endplate preparation and fixation. Without that analysis, a good result may be credited too easily to the implant, while the surgical work that enabled it remains invisible.
Beyond the bullet cage
The most useful idea in MIS-LTLIF is not simply "use a bigger cage." It is to separate the size of the entry pathway from the footprint of the final construct: enter through a controlled posterior corridor, cross the midline and rotate into a broad final position.
Our two publications show that this is technically feasible in a prospective early series and adaptable in a demanding revision case. They also define the limits of what can currently be claimed. MIS-LTLIF may bridge part of the gap between posterior direct decompression and anterior or lateral footprint, but its long-term value must be established through comparative evidence. That is how surgical innovation should progress—from a clinical problem, to a reproducible technique, to transparent early results, and finally to rigorous validation.
References and further reading
- Sharma A, Kadam S, Marathe N, Rangala A, Das SL, Rampure A. Technical Feasibility and Early Outcomes of Minimally Invasive Transforaminal Lumbar Interbody Fusion with Large-Footprint Cage via Tubular Approach: A Novel Surgical Technique. Asian Journal of Neurosurgery. 2026. doi:10.1055/s-0046-1825548.
- Sharma A, Marathe N, Kadam S, Rampure A, Jawale NS. Cauda Equina Syndrome Following Posterior Interbody Cage Migration after TLIF: A Rare Case Report. Journal of Orthopaedic Case Reports. 2026;16(6):447-451. doi:10.13107/jocr.2026.v16.i06.7502.
Declaration
Conflict-of-interest disclosure to finalize before submission. Dr. Ayush Sharma conceived the MIS-LTLIF technique and participated in development of the dedicated cage design.
About the authors
Dr Ayush Sharma
Dr Ayush Sharma is a Mumbai-based orthopedic spine surgeon and Head of Spine Surgery at Dr. B. R. Ambedkar Memorial Hospital. His clinical and research interests include endoscopic surgery, MIS-TLIF, OLIF, navigation and lumbar reconstruction. He leads an NBE-recognized spine training center. He serves as Director-at-Large (India) for SMISS Asia Pacific. His MIS-LTLIF research explores how posterior direct decompression can be combined safely with broad cage-endplate coverage.
Dr Shubham Kadam
Dr Shubham Kadam, MBBS, MS Orthopaedics, is a Mumbai-based orthopedic spine surgeon with clinical and research interests in minimally invasive and endoscopic spine surgery and advanced interbody fusion techniques. He has undertaken long-term minimally invasive and endoscopic spine training under Dr. Ayush Sharma. He was selected as a SMISS-AP Fellow in Australia, where he gained clinical exposure under Dr. John Choi to advanced UBE, robotic-assisted, lateral, and anterior spine procedures. His clinical interests include MIS-LTLIF, OLIF, endoscopic spine surgery, cervical spine surgery, and complex lumbar reconstruction. His research focuses on novel minimally invasive techniques, with a particular interest in large-footprint interbody cage design and novel posterior approaches for its insertion.
Dr Ajit Rampure
Dr Ajit Rampure, MBBS, MS Orthopaedics, DNB Orthopaedics, FNB Spine Fellow working under the mentorship of Dr. Ayush Sharma in Mumbai. His clinical interests include minimally invasive spine surgery, MIS-TLIF, tubular decompression, spinal navigation, and lumbar interbody fusion techniques. His academic and research interests focus on minimally invasive surgical techniques, interbody cage technology, and clinical and radiological outcomes following lumbar fusion. He is involved in research exploring MIS-LTLIF and large-footprint interbody cage techniques.
Dr Nandan Marathe
Dr Nandan Marathe, MS Orthopaedics, is a spine surgeon at Synapse Hospital, Mumbai. His clinical interests include minimally invasive spine surgery, lumbar interbody fusion, and contemporary techniques in spinal reconstruction. His academic and research interests include minimally invasive surgical techniques, interbody cage technology, and clinical and radiological outcomes following lumbar fusion. He is involved in research exploring MIS-LTLIF and large-footprint interbody cage techniques.