The technique we applied for the cervical disc herniation is simple microdiscectomy, which has been constantly modified by the senior author since the 1990s [14,15]. If one makes a search about the simple microdiscectomy technique in the literature one will find a lot of publications with good results before generalization of the instrumented fusion techniques [1,16-18]. The senior author has supported doing simple microdiscectomy for many years, and has also made some modifications for avoiding conventional simple microdiscectomy technique’s limitations. In most medical literature, the recommended approach and incision site is on the right side of the neck except for the left handed surgeons [1,16,18]. Based on the left-handed surgeons permission in the classical literature, the senior author described the contralateral approach: the incision site is on the opposite side of the brachialgia consistent with extrusion site [14,15]. Considering that C7-T1 disc herniations are prone to lateral-foraminal localization, it is very important to provide a contralateral view. It provides resection by directly visualizing the pathology, by directly viewing the disc piece and foramen from the opposite direction.
The most important change is on the selection of the retractor system, which eliminates the bulky automated equipment, instead replaced with the Zenker hand-held retractor.10-12mm wide and different lengths, and replaced it with conventional Cloward’s hand held retractor, which was designed in the pre-microscope era. The Zenker retractor used by the assistant provides instant and intermittent retraction of oesophagus and trachea and does not cause blood supply problems like in constant retractors. When the assistant has tired, or when there is no need for retraction, the Zenker retractor is released and this helps the blood supply of oesophagus and trachea and prevents ischemia. This disadvantage can actually be an advantage for the patient’s less postoperative pain and swallowing difficulty, however. Another advantage of the Zenker retractor is the easy adjustment for the instant retraction needs of surgeon, which provides better exposure of the offending lesion. When it is needed, a second Zenker can be applied for further exposure from below or upper site of the surgical field. Other techniques require exposure of the T1 corpus to insert a screw or retractor during fusion. Undoubtedly, this is a disadvantage for the narrowed operation area, as it will increase convergence to the sternum. In our technique, it is sufficient to see the T1 corpus edge for level visualization.
The location of the incision is accustomed to a little bit lower in index level checked by C-arm and close to the mid-line. The incision site is located after tangential retraction of the trachea- oesophageal structure for avoiding lateral part retraction during surgery. This is crucial for contralateral technique, because of usage of one side Zenker retractor design. The incision length is 15-20 mm, and it does not let the surgeon use an additional retractor. The surgeon performs lateral part retraction with a suction tube.
The shape of the intervertebral cartilage is like convex roof, facing each other as a dome. Sparing the anterior borders of the vertebrae and staying at intradiscally with avoiding end plate violation prevents the postoperative collapse. It is not recommended to clean the lateral parts of this cupola unless there are mobile degenerated floating free fragments. Lateral parts of annulus fibrosus is relatively stays stable and behaves like a washer and with the aid of a dome shape of the intervertebral surface, it contributes the physiological alignment preservation of the spinal column. After achieving all of these during the operation the postoperative vertebral collapse and alignment problems, which can occur after conventional simple microdiscectomy surgery, could be avoided and this result made this technique really minimally invasive. Microforceps designed for endoscopic techniques are useful in our technique also, especially during removal of foraminal fragments.
In chronic cervical disc herniations, ostephytic changes occur frequently accompanying the soft protrusions. During decompression process surgeon should remove the osteophytes besides cleaning up the degenerated nucleus pulposus. Removal of osteophytes leaves behind open cancellous bone surfaces at the upper and lower vertebral corpus edges, which can promote bone healing and end up with spontaneous fusion. The idea of putting fat graft in disc space is for pseudoathrosis, and this leads motion segment preservation by preventing development of fusion between the corpus edges.
Preservation of the motion segment is the most important part of the cervical total disc replacement, in other words application techniques of cervical disc prosthesis. It has been become to have wide usages, but in long term it has risks of heterotopic ossification, that undermines its effectiveness [19,20].
A head down position for adjustment of the operation microscope light array is required. For being parallel to intervertebral surface is essential for avoiding end plate injury and better exposure of the mid-line of the intervertebral level. This important adjustment gives the surgeon a direct approach to the site of the protrusion in addition to gain lateral access.
Although there are difficulties in axial imaging parallel to the disc, MRI is still the gold standard for displaying disc at C7-T1 level. If the neurological examination findings strongly indicate this level, if the MRI does not help us, we try to make a second shot but contain thinner sections. Because of the distortion of axial images by most of the shoulders, computed tomographic imaging at the C7 – T1 level is difficult. Also it is hard to see the C7-T1 level in lateral X-rays. We do not use tomography and X-ray examinations routinely for C7-T1 disc herniation.
In the literature, the series of interventions applied to this level consist of either large cervical series or only the patient series belonging to this level, which in this article are presented. Ryu et al. [8] reported 36 patients with disc herniations at the cervicothorasic junction, anterior approach with Smith-Robinson technique and posterior foraminotomy with discectomy were performed in 21 and 15 patients respectively. This study is known to be the largest series in which they investigated the characteristics, symptom duration, clinical course and biomechanics of cervicothoracic junction disc herniation. In the series of Flavigna et al. [10] in which they evaluated the radiological diagnosis, clinical appearance, neurological outcomes and surgical planning of the anterior approach to disc herniations at the C7 – T1 level, 19 patients were operated with the anterior approach mostly from the side opposite to the herniation to optimize visualization and they concluded that a single cage was insufficient despite the discectomy and fusion, and recommended the use of an anterior cervical plate. Post et al. [3] performed anterior cervical discectomy and fusion in ten patients in which they reviewed their experience in operative management, especially in terms of clinical presentation, imaging, operative exposure problems, and neurological outcomes. They stated that they did not encounter any difficulties during anterior intervention. Ozer et al. [4] reported their experience in 8 patients with C7–T2 soft foraminal disc herniation. In their series in which they reviewed pre- and postoperative neurologic charts, surgical techniques, and clinical outcomes, they operated on their patients with anterior fusion and, at one level, partial minicorpectomy. Lee et al. [6] studied the clinical features of 13 patients with cervicothoracic junction disc herniation, and in 10 of them anterior intervention via standard supramanubrial Smith-Robinson approach was sufficient while manubriotomy-sternotomy was required in two patient and the wrong level was operated in one patient. Mostofi, et al [11] operated 21 patients of whom 13 patients underwent posterior simple discectomy whereas anterior discectomy with fusion was performed for 8 patients. All the reported series concerning anterior approach for C7-T1 disc herniation, bone fusion or cage replacement and/or anterior instrumentation have been used except for Takeuchi, et all’s study consisting of 5 patients [3-6,8,10,11]. They performed anterior keyhole foraminotomy without fusion via drilling C7 corpus, but in their method only the fragments of disc material or osteophytes compressing the nerve root were removed.
We see that the common belief in most series is that the anterior approach is sufficient, but the difficulties encountered during the anterior approach are emphasized [3-6,10]. At the C7 – T1 level, the vertebral bodies are deeply inclined away from the surgeon due to thoracic kyphosis. This situation is more of a problem in short and obese patients. The "narrowed operative space" due to bone occlusion by the vertebrae was the presence and difficulty of vital anatomical structures such as large blood vessels, oesophagus, trachea, and recurrent laryngeal nerve. In our series, in our technique, these risky anatomical formations did not pose a threat, and sternotomy was not required in any of our patients.
At the C7 – T1 level, the vertebral bodies are deeply inclined away from the surgeon due to thoracic kyphosis. This is a greater problem in short and obese patients. The way to deal with this is by placing the operating table upside down in Trendelenburg position and then raising it as we do at all levels so that the microscope is in the same plane as the distance. Frankly, we think like Post et al. [3], we did not have any difficulties in anterior route intervention. We made an incision in one of our short-necked-obese patient , in whom we could not show the level, using the C6-7 marking as a reference to the C6-7 distance, and we saw that we had difficulty because it remained above the level. We had to use a modified Zencker retractor. Again, it should be kept in mind that there may be individual variations in bone anatomy.
Some authors advice posterior approach to the CTJ because of the difficulty in accessing through anterior approach [2]. In the past series, there were series in which anterior fusion or posterior intervention with microforaminotomy was applied to patients [8,11], as well as series in which only posterior intervention was performed [2]. It was shared that posterior intervention is also appropriate because most herniations are foraminal. Posterior approaches allow limited surgical workspace as well as the possibility of entering the wrong level [2]. Excessive resection of more than 50% of the facet joint can cause instability that can result in hypermobility [21]. There is also the opinion that the protection of the facet joint is not indispensable due to the other biomechanical features of the sternum and cervicothoracic junction, which argues the opposite [11].