MITLIF Operative Nuances- Step by Step
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.329566
Source of Support: None, Conflict of Interest: None
Keywords: Minimally Invasive Transforaminal Interbody Fusion (MITLIF), Indications, Technical nuances
MITLIF has been receiving increasing attention among the posterior approaches for lumbar interbody fusion to treat various degenerative spinal conditions. This is due to its inherent advantages of reduced blood loss, wound infections and CSF leak while ensuring lesser normal damage in comparison to open TLIF.,, Though open and MITLIF have similar long-term outcomes, MITLIF patients have been noted to have lesser adjacent segment degeneration. The current literature on Endoscopic TLIF is limited to case series and technical notes. This operative video of MITLIF and the noted technical nuances will elaborate appropriate surgical anatomy regarding pedicle screw placement and facetectomy for successful execution of the surgical procedure.
Description of the technical nuances of MITLIF along with an operative video in a case of L4-L5 grade 1 spondylolisthesis.
This 42-year-old female patient with no comorbidities presented with complaints of back pain for 6 months which radiated to the right lower limb and along the lateral aspect of the foot. Complaints were aggravated while climbing up stairs and on standing up from sitting position, and were relieved on lying down. Severity of the complaints have increased over the last 2 months and there was associated paraesthesia in the same dermatomal distribution. The symptoms did not respond to a trial of conservative management. On examination, straight leg raising test (SLRT) was positive on the right side, there was a sensory deficit in L5.
On dynamic X-rays of Lumbosacral spine, a reducible grade-1 L4-L5 listhesis was noted. On supine CT Lumbosacral spine, normal sagittal alignment with bilateral facetal hypertrophy at L4-5 level was noted. Magnetic Resonance Imaging revealed mild disc bulges at L3-4 and L4-5 with foraminal stenoses as L4-5 as well as enlarged facet fluid space at the same level. This last finding is an indicator of dynamic instability. Other presurgical routine workup was unremarkable. DEXA scan was suggestive of normal bone density. With the diagnosis of grade 1 dynamic spondylolisthesis of L4-L5, MITLIF was planned.
Positioning of the patient, C arm and Incision Marking
Video link: https://youtu.be/vR61103zs24
Video Timeline for the manuscript
(0.47-0.59 minutes) - Patient is positioned prone with bolsters under the upper chest and the hips. Table alignment is manipulated to minimize the slip in cases of reducible subluxations (0.47-0.59 minutes).
(1.01-1.06 minutes) - C arm is used to confirm the level in both lateral and AP views. Care must be taken to avoid misjudging the surgical level particularly in cases of sacralisation of L5 or lumbarisation of the S1 vertebra. C arm positioning is vital. In the AP view, the spinous process must be visible in the midline, the endplates of the vertebrae must be parallel and entire pedicle boundaries must be clearly visible. In the lateral view, the endplates should be parallel and any rotation must be avoided.
(1.15-1.30 minutes) - In cases of mild scoliosis of the spine, the C arm position needs to be adjusted for each vertebral level. In each case, the disc space and lateral pedicle line are marked on AP and confirmed on lateral view X rays on the C arm [Figure 1]B. Paramedian incisions of 2.5 to 3cm length are made on either side, about 3 to 3.5 cm lateral to the midline and half a centimetre lateral to the lateral margin of the pedicle.
The centre point of the incision should correspond to a transverse line drawn across the disc space.
Skin is incised and the incision is extended deeper into the facia. The fascial incision is extended both cranially and caudally beyond the skin incision by about 5mm to achieve easy manoeuvrability of instruments.
(1.38-2.00 minutes) - Pedicle tapping
Muscle is split from the cranial pedicle entry point to the caudal pedicle entry point using blunt dissection with a finger. The transverse process and superior facet junction is palpated and Jamshidi needles are parked lateral to the lateral border of the pedicles at the junction of their upper 1/3 and lower 2/3 as visualised on AP view of C-arm. Subsequently, tapping is done. The general rule to be followed while tapping is that advancement of approximately 20-25mm of needle tip on lateral x-ray translates to reaching the pedicle-body junction. At this point, the needle tip should be at the centre of the pedicle on AP view.
(2.14-2.34 minutes) - Beyond the pedicle-body junction, a more medially directed trajectory is adopted with supero-inferior angulation guided by lateral view X rays. Guide wires are now inserted via the Jamshidi needles in all pedicles and their distal ends are bent and anchored to the surgical drapes.
Steps, thus far are illustrated in [Figure 1].
(4.47-4.59 minutes) - Facetectomy and Decompression
Serial dilators are positioned over the facets at the pathological level under C arm guidance and finally the tubular retractor system (MARS 3V, GLOBUS medical, Philadelphia, USA) is inserted and fixed in place.
(5.05-5.30 minutes) - Under microscopic vision, facets are visualized after clearing the overlying muscle using monopolar cautery. Facetal bone is excised using a chisel and hammer. For excision of the inferior/medial facet, two cuts, one at the lamino-facetal junction and one at the pars, are required followed by ligamentous disconnection using Kerrison rongeurs.
(5.35-5.44 minutes) - Superior 1/3rd of lateral/superior facet is also excised for complete visualization of the Kambin's triangle.
(6.23-7.12 minutes) - Disc Space Preparation and Cage insertion
The disc space is accessed in between the exiting and the traversing nerve root. Annulus is cut with a no. 15 knife. Disc curette, disc punch/forceps, disc shaver and box curette (REVOLVE system, GLOBUS medical, Philadelphia, USA) are used for completing the discectomy and preparing the end plates.
(7.14-7.30 minutes) - Bone graft obtained from the excised facets is packed in the ventral portion of the disc space following which a cage filled with bone chips is inserted under C-arm guidance
(7.50-8.12 minutes) - Screw placement and wound closure
Screws are inserted over the guide wires and subsequently rods are inserted in to screw heads. Compression is done to snugly hold the Interbody cage in situ. These steps are illustrated in [Figure 2] and [Figure 3].
Technique pertaining to Spondylodiscitis
In Spondylodiscitis cases, if the involved vertebrae have healthy pedicles and only partial destruction of the body, screws are placed in the pathological vertebrae. Otherwise, the adjacent healthy vertebrae are chosen for placement of screws. Facetectomy in lumbar spine and transpedicular approach in thoracic spine are taken to access the disc space. Complete debridement of necrotic disc material is done and tissue is sent for histopathological examination, culture and GeneXpert for tuberculosis (TB). In cases of suspected and proven TB, antituberculosis treatment (ATT) is started immediately and the drugs are continued for 18 months.
Pearls and pitfalls
MITLIF has ensured its place in the armamentarium of today's spinal surgeon. Attention to the technical notes described above will aid smoothen and shorten the learning curve for this procedure.
[Figure 1], [Figure 2], [Figure 3]