33 The Translaminar Approach
L. Papavero
33.1
Terminology
The anatomical unit of the lumbar spine is a vertebral body and the disc below. According to McCulloch [2]
we can imagine a three-storied anatomical house: the first storey is the disc level, the second storey is the fo- raminal level, and the third storey is the pedicle level.
Without any exception the second storey, i.e., between the upper rim of the disc space and the lower border of the cephalic pedicle, is covered by the lamina (Fig.
33.1).
33.2
Surgical Principle
If we compare a disc fragment extruded underneath the lamina of the second storey to a fish on the bottom of a frozen lake, there are two methods to get it hooked.
The first one is to cross the surface with an icebreak- er and to start to angle . . . This is similar to the standard interlaminar exposure with flavectomy and partial re- section of the facet joint and/or of the lamina which al- lows for targeting a cranially extruded disc herniation.
However, the potential consequences of extensive re-
Fig. 33.1. Lumbar disc herniations (LDHs) which extrude ceph- alad into the second storey are the best indication for the trans- laminar approach. An example at the L5/S1 level is shown (black arrows)
section of bone and yellow ligament are segmental in- stability and more or less extensive scar tissue. After surgery both can result in increased axial-loading back pain.
The second option would be to cut a small hole in the frozen surface exactly targeted on the fish and to cast the line. If the disc fragment is extruded cephalad into the spinal canal or especially into the root canal en- croaching the exiting root, the translaminar approach (TLA) sparing partial facet joint resection and conven- tional flavectomy corresponds to this latter method of fishing.
33.3 History
There are only a few papers dealing with the topic of the TLA. Di Lorenzo et al. [1] proposed the approach in 1998. The comments of the reviewer were quite skepti- cal: the (suspected) technical difficulty of the proce- dure, the (assumed) inability to clear the disc space, and the risk of early or late fracture of the pars interar- ticularis were seen as important limitations of the tech- nique. In 2002, Soldner et al. [3] published their posi- tive experience with 30 patients. Although this time the description of the surgical technique was appreciated by the reviewers, the issue of long-term stability was questioned thoroughly.
33.4 Advantages
Facet joint and yellow ligament are mostly pre- served
Bypassing of the scar tissue when dealing with a cephalad recurrent herniation in a case operated previously via an interlaminar route (Fig. 33.2) Integrity of the yellow ligament when dealing with a first-storey recurrent disc herniation in a case previously approached via the TLA
Fig. 33.2. Left First-storey LDH successfully approached via a microsurgical interlaminar approach L4/L5. Right Three years later a huge recurrent herniation was completely removed via a TLA to L4
33.5
Disadvantages
MRI desirable for surgical planning
Keyhole target area requires microsurgical skills Bayoneted microinstruments (optional)
Fig. 33.3. Left About 22 % of LDHs migrate cranially en- croaching the exiting root.
Center Sagittal T1-weighted image shows at the L4/L5 level a “typical” disc frag- ment suitable for the TLA.
Right Axial T2-weighted slice: the intraforaminal compression of the exiting root L4 (gray arrow) by the extruded disc fragment (white arrow) is evident
Fig. 33.4. Left Caudally ex- truded disc fragments (white arrows), so called third-sto- rey LDHs, can also be ap- proached via the TLA.
Center Sagittal T1-weighted image shows an exemplary finding. Right Axial T1- weighted slice confirms the encroachment of the L5 root.
Remark: the MRI axial slice shows the cross-section of the pedicle in the third-sto- rey LDH where does it not in the second storey!
33.6 Indications
The best indication for the TLA is a second-storey ex- truded disc fragment, ideally when it pushes the exiting root upward against the lower border of the pedicle (Fig. 33.3). Some huge and caudally dislocated, so called “mid-vertebral body” fragments can also be ap- proached (Fig. 33.4). When previous disc surgery has been performed via an interlaminar access, then a sec- ond-storey recurrence may be treated with TLA.
33.7
Contraindications
Severe spinal canal stenosis is a contraindication for TLA because of the lack of an adequate lamina. The same holds true for malformations, such as spina bifi- da.
In the case of a foraminal disc herniation, the bulk of the fragment should be between two lines marking the medial and lateral borders of the superior facet. Disc material located more laterally should be approached through a paraspinal approach.
33.8
Patient’s Informed Consent
The patient should be informed that in case of necessity the TLA could be widened to a laminotomy with partial facet joint resection corresponding to the conventional interlaminar approach. There are no specific complica- tions related to the TLA.
33.9
Surgical Technique
When planning the TLA, the following anatomical de- tails should be kept in mind: the width and the overlap- ping of the lamina in relation to the disc space increase in the caudal-cephalic direction, whereas the width of the isthmus decreases. This means that the translami- nar hole will be more medially and more oval-shaped in the cranial direction (Fig. 33.5).
33.9.1 Anesthesia
The same anesthetic set-up as for any other surgery of lumbar disc herniation would be appropriate.
33.9.2 Positioning
It is up to the surgeon to choose between genupectoral, kneeling, or prone frame-supported position. Anato-
Fig. 33.6. Care should be tak- en to reduce the natural oblique inclination of the laminae in the caudal-ce- phalic direction (red line) by tilting the table “head-up- wards” in order to get an ap- proximately horizontal “lam- inar plane” (black line)
mical remark: the lumbar laminae are oblique in the sagittal plane, i.e., they “dive” in the caudal-cephalic di- rection. Attention should be paid to compensate for this fact, at least partially, by tilting the operating room table in a “head upwards” direction. The advantages of a horizontal target lamina are twofold: the placement of the retractor blade and the drilling of the hole become easier (Fig. 33.6).
Fig. 33.5. The height of the lamina and its overlapping onto the disc space in- creases (white num- bers in mm) in the caudal-cephalic direction whereas the width of the isthmus decreases (black numbers)
33.9.3
Radiographic Labeling
Since the surgical corridor to the target area is limited, the location of the skin incision has to be determined very accurately. Two skin marks are recommended in lateral fluoroscopy:
1. The equator or the upper border of the disc space 2. The upper rim of the extruded disc fragment as
shown by the MRI or as calculated on the axial CT scans
The distance between the two marks is usually up to 12 mm. Care should be taken to insert the needle exact- ly perpendicular to the horizontal spine. Once the sur- face of the lamina has been approached, looking at the twin skin drawings will enable the hole to be drilled ex- actly centered on the region of interest (Fig. 33.7).
33.9.4 Approach
The skin incision should be about 15 mm off the mid- line and centered on the twin marks. Provided the ra- diographic labeling is correct, a strictly vertical ap- proach will lead to the lamina.
Fig. 33.7. The fluoroscopic marking of the disc space (1) and of the cephalad extruded disc fragment (2) should be drawn on the skin. Once the lamina has been exposed the skin marks should be projected onto the lamina itself
Fig. 33.8. Left The outer cor- tical and the spongy bone can be drilled off with the cutting burr. Center The in- ner cortical bone is removed with the diamond burr.
Right Usually a 10-mm-di- ameter hole provides an ade- quate exposure of the lateral thecal sac and of the axilla of the exiting root. In our series at least 3 mm of the border of the pars interarticularis was spared. No fracture of this bony structure occurred Two options are given:
1. The subperiosteal route along the lateral surface of the spinous process requiring the incision of some of the tendinous insertions of the multifidus mus- cle. A Caspar- or Williams-type retractor is then inserted.
2. The transmuscular route by bluntly splitting the multifidus muscle with the index finger. A tubular retractor (15 mm diameter) is inserted and fixed with a holder arm.
Irrespective of the kind of speculum used, the lateral border of the lamina should be visible underneath the retractor valve. At the beginning of the learning curve it is useful to duplicate the skin marks onto the lamina prior to insert the retractor.
33.9.5
Microscopic Decompression
At this point the lamina should have been tilted parallel to the floor, so that the cutting burr can be held more easily perpendicular to the lamina. With slow circular movements a round (L5) or oval-shaped (L4 and cepha- lad) hole of about 10 mm in diameter is made. Three layers, “white” (= outer cortical bone), “red” (= spongy bone), and “white” (= inner cortical bone), will be drilled off. For the sake of safety the inner cortical bone should be drilled with a diamond burr (Fig. 33.8). Re- marks:
1. At least 3 mm of the lateral border should be spared in order to avoid a fracture of the pars in- terarticularis (Fig. 33.9).
2. Usually the translaminar hole is located just cepha- lad to the cranial insertion of the yellow ligament.
So, after removal of the thin shell of inner cortical bone with small punches epidural fat will appear.
The epidural exploration starts with the up and down dissection of the fat along the lateral border of the the- cal sac. That should be continued cephalad up to the ax- illa of the exiting root. Usually at this stage extruded or
Fig. 33.9. The three- dimensional CT shows how the shape of the hole becomes more oval at the L2 lamina compared with the more caudal L5 (Fig. 33.8)
subligamentous disc fragment(s) can be mobilized. Af- ter decompression the root slips caudally into the visi- ble field (Fig. 33.10). The root canal is probed with a double-angled hook.
If an extensive annular perforation is detected the disc space should be cleared. In our experience that was required in only 20 % of cases. The rate of recurrence was 4 %.
33.9.6 Wound Closure
The wound closure is quite straightforward. Gelfoam soaked with long-acting steroid to fill in the hole is op- tional, but should be avoided if the disc space has been cleared.
33.10
Postoperative Care and Complications
The patient can be mobilized the day of surgery. In the series of the first 30 patients, plain X-ray films were per- formed routinely 6 and 12 months after surgery in or-
Fig. 33.10. Top T1-weighted axial images show a second- storey disc fragment migrat- ed cephalad and impinging severely the root L3 into the canal. Bottom left The dis- sector (white asterisk) moves along the lateral border of the thecal sac (yellow) and uncovers the huge fragment (black asterisk) which is lo- cated in the axilla of the root L3 and pushes it cranially against the pedicle. Bottom center The “capsule” has been opened. Bottom right After removal of the herniat- ed disc material the root L3 relaxes back in its normal lo- cation
der to reveal segmental instability caused by a fracture of the pars interarticularis. The findings were negative without exception. Nowadays radiological investiga- tions are only performed in symptomatic patients.
Based on our experience with 63 patients treated by the TLA the following complications have been listed:
1. Wrong level surgery (2): This occurred at the be- ginning of the learning curve and was corrected intraoperatively. After introduction of the “twin marks” labeling access to the wrong level was no longer a problem. Tilting of the operating room ta- ble in order to direct the lamina absolutely parallel to the floor further minimizes this risk.
2. Dura tears (4): The particularly thin axillary dura should be handled very carefully during dissection of adherent disc fragments. Due to the narrow access gluing a patch on durotomy is the best working solution.
3. Enlarging the hole to conventional laminotomy (4):
Although not exactly a complication, this change of strategy becomes necessary whenever a significant annular perforation is detected on the caudal half of the disc space, especially at the L5/S1 level.
4. Recurrent disc herniation (2): The low incidence is more than acceptable, considering that in only 20 % of the patients the disc space has been clea- red.
33.11 Results
Sixty-three patients (37 men, mean age 54 years) most- ly presenting an exiting root syndrome underwent the TLA. The lamina at L4 (27) and L3 (19) was frequently involved. At surgery extruded (61 %) and subligamen-
tous (39 %) disc fragments were found. In 4 cases the translaminar hole was enlarged to a laminotomy and in 12 patients the disc space was cleared.
An independent observer performed follow-up ex- aminations at 1 and 6 weeks, 3, 6, and 12 months, and once yearly thereafter (mean follow-up 22 months).
The outcome was excellent (complete relief of symp- toms) in 59 %, good (mild discomfort not requiring medications) in 33 %, fair (better than preoperative, but functional limitations requiring medication or bracing) in 6 %, and poor (no better than preoperative) in 2 %.
The unsatisfactory results were related to the post- operative persisting back pain, as in patients complain- ing about a facet joint syndrome. In these cases the MRI showed a black disc with a significant spontaneous or postsurgical reduction of the height of the interverte- bral space. Facet block injection relieved the symptoms in most of the patients.
33.11.1 Special Case 1
A 65-year-old woman underwent an instrumented fu- sion at L4/L5 in 1999 because of severe load-depending back pain. The postoperative course was satisfactory until 3 years later. A sudden right-sided L3 syndrome with motor deficits prompted an MRI which showed a second-storey disc herniation at L3/L4. The TLA al- lowed for removal of the fragment skipping the scar tis- sue. Recovery was excellent, and 6 months after surgery plain X-Ray films showed a partial bony closure of the translaminar hole (Fig. 33.11).
33.11.2 Special Case 2
A 70-year-old man became unable to walk because of a severe weakness of the right thigh. The roots L3 and L4
Fig. 33.11. Left The plain film shows a regular instrument- ed fusion. Center The sagit- tal MRI picture shows a second-storey LDH L3/L4 (white arrow) impinging the exiting root L3. Top right TLA hole after surgery (white arrow). Bottom right Partial concentric bony closure of the hole (black arrow)
were both affected. The sagittal MRI image showed a combined impingement of these roots due to simulta- neous second-storey lumbar disc herniations L3/L4 and L4/L5. After removal of the extruded disc frag- ments via a two-level TLA the patient recovered par- tially and could walk with the help of a cane (Fig.
33.12).
33.11.3 Special Case 3
In a 72-year-old man affected by Parkinson disease the muscular dysbalance and the scoliotic deformity re- quired the preservation of the right facet joint L2/L3.
The huge cranially extruded disc fragment causing a severe palsy of the iliopsoas muscle was removed via a TLA (Fig. 33.13).
33.12
Critical Evaluations
Is it useful to perform a TLA if a cephalad migrated disc fragment encroaching the exiting root can be ap- proached via the conventional microsurgical interlami- nar route? In this context we could also ask if microsur- gery in itself is necessary at all, taking the point that a satisfactory decompression of the root can also be ob- tained by conventional disc surgery. It is the author’s firm belief that the combination of correct indication for (micro)surgery along with the least access trauma leads to rewarding clinical results. It is important to no- tice that less invasive surgical techniques are character- ized by a more “straightforward” approach to the target area, bypassing the exposition of anatomical structures merely seen as landmarks. The transmuscular inser- tion of pedicle screws gives an idea of this philosophy.
The TLA fulfils both requirements and can be rec- ommended as the route of choice for the specific sub-
Fig. 33.12. Left T1-weighted sagittal image shows adja- cent second-storey LDHs.
Right Plain film after surgery
Fig. 33.13. Left Coronal T1- weighted image depicting the kyphotic angulation L2/L3 and the severe degen- eration of the disc. Center The same finding on lateral slice. Top right Axial T1- weighted image showing the root impingement. Bottom right After surgery CT con- firms that the facet joint L2/L3 has been spared also on the right side
group of cranially extruded disc fragments. However, keyhole surgery should not be an end in itself, therefore switch to conventional laminotomy whenever prob- lems should arise!
Acknowledgements. Ralph Kothe M.D. is acknowl- edged for his help in revising the manuscript.
References
1. Di Lorenzo N, Porta F, Onnis G, Arbau G, Maleci A (1998) Pars interarticularis fenestration in the treatment of foram- inal lumbar disc herniation: a further surgical approach.
Neurosurgery 42:87 – 90
2. McCulloch JA (1998) Foraminal and extraforaminal lumbar disc herniations. In: McCulloch JA, Young PH (eds) Essen- tials of spinal microsurgery. Lippincott-Raven, Philadel- phia, pp 385 – 387
3. Soldner F, Helper BM, Wallenfang TH, Behr R (2002) The translaminar approach to canalicular and cranio-dorsolat- eral lumbar disc herniations. Acta Neurochir (Wien) 144:
315 – 320
