In 1998, Di Lorenzo et al. proposed a less invasive direct procedure by utilizing a translaminar approach (TLA) through a fenestration of the pars interarticularis, thus circumventing facetectomy or hemilaminectomy in many cases. The increasing availability of high-definition imaging modalities (MRI, CT) has contributed to the growing popularity of the TLA, since identifying the exact location and extent of the spinal lesion is crucial for surgical planning to limit unnecessary biomechanical damage and prevent intraoperative conversion to conventional approaches.
Several studies have demonstrated the feasibility, safety and efficacy of this technique to successfully treat disc herniations affecting the foraminal and preforaminal regions 1).
The translaminar approach is the only “tissue-sparing” technique viable in cases of cranially migrated lumbar disc herniation encroaching on the exiting nerve root in the preforaminal zones, for the levels above L2-L3, and in the preforaminal and foraminal zones, for the levels below L3-L4 (L5-S1 included, if a total microdiscectomy is unnecessary). This approach is more effective than the standard one, because it resolves the symptoms; it is associated with less postoperative pain and faster recovery times without the risk of iatrogenic instability, and it can also be used in cases with previous signs of radiographic instability. The possibility to spare the flavum ligament is one of the main advantages of this technique. For these reasons, the translaminar approach is a valid technique in terms of safety and efficacy. Vanni et al., extensively analyzed and highlighted the tips and tricks 2).
A consecutive series of 32 patients were divided, pre- and post-operatively, into 5 classes based on Oswestry Disability Index (ODI). Class 1: ODI 0-20% (minimal disability); class 2: 20-40 % (moderate disability); calss 3: 40-60% (severe disability); 60-80% (crippled); 80-100% (bed bound or exaggerating symptoms).
In terms of ODI, 4 (12.5%) patients upgraded of 1 class after the operation; 6 (18.7%) patients of 2 classes, 8 (25%) patients of 3 classes, 11 (34.4%) patients of 4 classes. Three (9.4%) patients did not modify their ODI score after the operation. After surgery, 7(21.9%) patients developed a mild low back pain. Mean follow-up was 25 months.
When performed by dedicated spinal neurosurgeons, the translaminar approach confirmed to be safe and effective in long-term follow-up. Moreover, the majority of patients showed an improvement of their ODI. Major pitfalls were related with surgical selection and the narrow working space 3).
Between May 2000 and July 2004, 104 patients (59 men)-presenting with upper lumbar root compression in 74% of the cases -underwent a translaminar approach. The mean age was 57 years (range, 27-80 yr). The lamina was approached either through the conventional subperiosteal route or via a muscle splitting access. Mostly intraforaminal disc fragments were removed through a translaminar hole 10 mm in diameter, and the disc space was cleared in cases of evident perforation of the annulus. Follow-up examinations were performed by an independent observer at 1 and 6 weeks; 3, 6, and 12 months; and once yearly thereafter (mean follow-up period, 32 mo).
Extruded (61%) or subligamentous (39%) disc fragments were found intra-operatively. Laminae L4 (44%) and L5 (26%) were mostly involved. In eight cases, the translaminar hole was enlarged to a conventional laminotomy. In 13 patients, the disc space was cleared. The outcomes according to the Macnab criteria were excellent (67%), good (27%), fair (5%), and poor (1%). The incidence of recurrent disc herniations was 7%. Functional radiography performed in the first 20 patients 6 months after surgery and an additional 12 patients complaining of postsurgical back pain excluded any instability.
The translaminar approach is recommended in disc herniations encroaching the exiting root, as an alternative to the conventional interlaminar route4).
Fifteen patients with far cranio-laterally extruded disc herniations underwent neurosurgical intervention using a translaminar approach. The paraspinal muscles were spread with a dilatator after performing a 1.5 cm skin incision. A 16 mm METRx tubular retractor system (Medtronic Sofamor Danek, Memphis, TN) was directly placed on the upper lamina. The next steps were performed through this channel using the surgical microscope. A small ovoid fenestration (10×5 mm) was performed using a high speed drill and the disc prolapse was removed in a standard manner. Follow-ups were routinely carried out 3 weeks postoperatively and reassessment was subsequently carried out by telephone inquiry 10 to 44 months (median 23 months) after treatment. These results were rated according to the modified MacNab criteria.
Five of the fifteen affected discs were at the level L3/4, eight at L4/5 and two at L5/S1. The average surgical time was 55 minutes. No complications occurred. In all patients sciatic pain disappeared immediately after the operation. One patient underwent fusion of the affected level one year later because of progression of a pre-existent pseudospondylolisthesis. Long-term follow-up demonstrated excellent results in six, good results in seven, a fair result in one and a poor result in one patient according to the modified MacNab criteria.
The translaminar approach in conjunction with a tubular retractor system seems to be an effective and safe alternative technique for treating the small entity of far cranio- laterally or foraminally extruded lumbar disc herniations. It combines the advantages of a blunt muscle-spreading approach that produces little damage to the soft tissues, and the avoidance of large bone removal that may jeopardize vertebral stability. Since this approach does not permit sufficient exploration of the intervertebral disc space of origin, it should be limited to patients without significant bulging of the disc itself 5).
Twenty-four patients with preforaminal and foraminal disc herniation underwent surgical treatment via a translaminar microsurgical approach. Excellent results were obtained in all patients in terms of pain relief, and all had improvement in motor strength except for 1 patient. No spinal instability was seen at the latest follow-up.
A classic interlaminar interspace approach combined with a very limited translaminar fenestration seem to be an acceptable surgical method for accessing a preforaminal disc herniation, and this technique has proven to be safe and did not cause any instability at the latest follow-up 6).
30 patients using the translaminar fenestration were analysed by a postoperative follow-up of 6 weeks and one year. The mean-age was 57.2 years. For resection of the disc herniation, a small round or oval fenestration (6-8 mm) in the hemilamina, craniomedially to the facet joint, was performed. No patient received a partial or total facetectomy.
RESULTS: The majority of affected discs were at the L4-L5 level (53%). An extruded fragment was found in 28 patients (93%). In 5 patients bleeding from epidural veins complicated the intra-operative course. In 50% the nerve root was visually exposed. 15 patients (50%) had an intervertebral discectomy additional to the fragment excision. One patient was re-operated on after 10 days because of persisting radicular pain by using the same translaminar approach. 28 patients showed complete or nearly complete relief of radicular pain. Using this approach we have seen no major complication or clinical instability during a follow-up of at least one year.
CONCLUSIONS: The translaminar approach is an effective and minimally invasive technique in both canalicular and cranio-dorsolateral disc herniations. It gives an additional possibility to avoid partial removal of the facet joints, can be performed in all lumbar segments and preserves structures important for segmental spinal stability. The approach allows access to the extruded disc fragment and intervertebral disc space comparable to classical approaches and is a frequently used operative technique in our department 7).