Abstract Objective.
To investigate and analyze the causes of foot prolapse after MED surgery. METHODS: To retrospectively analyze the diagnosis and treatment process of 7 patients with foot drop after MED surgery. RESULTS: The lumbar and leg pain and sensory numbness in 7 patients were significantly reduced or disappeared, and the foot prolapse was restored after 3-6 months of nerve nutrition and functional exercises of the affected limbs. CONCLUSION: Intraoperative strain injury to the lumbar 5 nerve root during MED surgery and stimulation of the lumbar 5 nerve root by various factors are the key to foot ptosis.
Microendoscopic lumbar discectomy (MED surgery) system for the treatment of lumbar disc herniation has been carried out rapidly in recent years in China because of its many advantages such as less trauma, less bleeding, shorter bed rest and hospitalization time, and faster recovery. However, discoscopy has a smaller field of view and limited operating space than traditional open surgery, and once operated carelessly, it is prone to serious consequences such as nerve root and cauda equina injury leading to urinary and fecal dysfunction and sensory and motor impairment of the lower limbs. 7 patients with foot drop after MED were admitted from April 2006 to April 2011, and were analyzed and summarized.
Data and methods
General data: There were 7 patients in this group, including 4 males and 3 females; age ranged from 19 to 58 years old, with an average of 38.5 years old. The segments of the disc protruded, L4/5? protruded in 1 case, L5/S1 protruded in 1 case, and L4/5? and L5/S1 protruded in 5 cases. All patients in this group had typical clinical manifestations and signs of lumbar disc herniation, and all were confirmed by CT or MRI before surgery and had no foot prolapse before surgery. Two of them were treated preoperatively with non-surgical treatment such as massage, Chinese herbal scalding.
Surgical methods.
Preoperatively, based on the general anatomical landmark of the lumbar 4/5 spinous process gap by the iliac pterygoid line, a 12-gauge needle was used for initial localization and then a lumbar frontal and lateral radiograph was performed, requiring the localization needle to be on the opposite side of the surgical incision, and the radiograph to be dotted or nearly dotted in the frontal radiograph and perpendicular to the spine in the lateral radiograph for accurate localization. After successful epidural anesthesia, the patient is placed prone on the spinal operating table and routinely disinfected with a sheet. A small incision of 0.5 cm was made at the level of the lamina space on the corresponding side of the lesion, next to the midline, with a probe to the inferior edge of the superior lamina of the lesion, and a longitudinal incision of the skin, subcutaneous tissue and lumbar dorsal fascia, approximately 1.6 cm in length, was made with this center, separating the muscles to reach the surface of the lamina space. The expansion cannula and working channel tube are inserted sequentially, and the inspection channel is located at the inferior edge of the superior vertebral plate and the articular eminence does not exceed 1/2 of the channel, which is fixed with the free arm.
The residual soft tissue on the surface of the ligamentum flavum in the operative field is removed with pulpal forceps and an electric knife to reveal the inferior edge of the superior lamina and the ligamentum flavum of the intervertebral space, and the endoscope is installed and the focal length and field of view are adjusted. The ligamentum flavum is removed with a lance-like forceps, and the lateral saphenous fossa is enlarged to reveal the nerve roots if combined with lateral saphenous stenosis. The nerve roots and dural sac are detached and retracted with a hooked suction device to expose the intervertebral disc, dissect the annulus fibrosus, and remove the nucleus pulposus with a pelvic forceps. After confirming that the nerve root compression is completely released, the field is flushed, fibrinogen or sodium glacionate is injected to prevent nerve adhesions, the working channel tube is removed, and the incision is sutured.
Pre-operative and post-operative treatment: routine application of antibiotics 1 hour before surgery, antibiotics for 3-5 days after surgery, routine post-operative drops of 250 ml of mannitol combined with dexamethasone 5 mg for 3 days, early bed activity is not advocated, straight leg raising exercises in bed starting 6 hours after surgery, functional exercises for lumbar back muscles starting 3 days after surgery, and wearing a lumbar brace for bed activity after 5-7 days.
Prognosis
All seven patients with foot drop in our group had stage I healing of the surgical incision without intervertebral space infection, cerebrospinal fluid leakage, nerve root rupture and nucleus pulposus leakage. The postoperative follow-up ranged from 3 months to 2 years. 7 patients had significant reduction or disappearance of lumbar and leg pain and sensory numbness, and recovered after 3-6 months of nerve nutrition and functional exercises for the affected limbs.
Discussion
Foot drop is mainly due to paralysis of the anterior tibialis, peroneus longus, extensor hallucis longus and extensor digitorum longus muscles caused by injury to the lumbar 5 nerve root. The lumbar 5 nerve root originates from the level of the lumbar 4-5 intervertebral disc and its upper and lower margins, and exits the intervertebral foramen obliquely and inferiorly. It is adjacent to the posterior exterior of the intervertebral disc in the spinal canal and is susceptible to compression and injury. Normal nerve roots are round, 2-3 mm in diameter, and symmetrical on both sides [1]. Thus, intraoperative strain injury to the lumbar 5 nerve root during MED surgery and irritation of the lumbar 5 nerve root by various factors are key to causing foot drop.
Microendoscopic lumbar discectomy (MED) is done in a specific narrow working channel tube, and the operator has to change the previous direct vision surgery to spinal endoscopic surgery, and the confirmation of the microscopic orientation, the identification of tissue structures, and the reduction of the magnitude of the surgical operating space will affect the results of the surgery. Because of the limited scope of surgical exposure, it is relatively difficult to find the lesion, which requires the operator to have previous experience in routine open lumbar spine surgery and to carefully study the imaging data before surgery to determine the presence or absence of local anatomical changes and the characteristics and location of the lesion, and then to select the appropriate time for surgery in conjunction with the patient’s clinical symptoms and signs. Therefore, MED surgeons must have experience in open lumbar spine surgery and microsurgical skills.
For MED surgery, variations in the patient’s local anatomy will affect access to the spinal canal and surgical outcomes. Common conditions that affect access to the spinal canal include difficulty in accessing the spinal canal when the intervertebral tuberosity is developmental or hyperplastic coalescence, when the vertebral plate is too thick, when the herniated disc is close to the vertebral plate, and when the cross-section of the vertebral plate is tilted. At the same time, in a considerable number of patients, the spinous process is skewed to the side of the herniated disc, and the channel tube must be removed for most of the articular joints to enter vertically, otherwise the channel must be tilted by more than 30° to enter, and the nerve root canal becomes a blind area that cannot be probed and expanded, and the nerve root is easily stretched beyond the midline and injured.
Some patients with lumbar disc herniation have a long history of disease and are mostly treated preoperatively with various non-operative treatments, and there are varying degrees of adhesions between the herniation and the nerve root dura, and between the dura and the ligamentum flavum. Therefore, the operation after entering the spinal canal should be performed gently to avoid violence, and the intraoperative operation should try to avoid stretching and stimulation of the lumbar 5 nerve roots, near the spinous process into the spinal canal, and the operation in the spinal canal should always be centered on the nerve roots, with decompression of the nerve roots anteriorly, posteriorly, and laterally [2].
When removing part of the ligamentum flavum to expand the view, after cutting the vertebral plate, the lateral ligamentum flavum is removed while separating, paying attention to separating the nerve root that is compressed by the protruding disc and adhered to the ligamentum flavum; to expand the lateral root canal, the lateral dura is separated from head to tail, and the nerve tissue is pulled medially using a neuroprotective device and a cotton piece, and then the residual ligamentum flavum and the proliferating articular eminence are removed; attention is paid to the direction of nerve root retraction, avoiding too long retraction and The nerve roots should be pulled with intermittent relaxation so that the blood flow to the nerve roots is not blocked for too long during the pulling process.
The intravertebral canal is rich in veins, plus on the one hand the nucleus pulposus protrudes and compresses, and on the other hand the abdomen may be compressed in the prone position, so that the veins are often in an angry state, which can easily be damaged and bleeding during the operation. The nerve stripper is used to push away the dura and protect the nerve root. Bipolar electrocoagulation should not be used for continuous electrocoagulation, but “click” cautery, and saline flushing should be given quickly after electrocoagulation to avoid burning the nerve roots and making recovery difficult [4].
Postoperative blood accumulation cannot be diffused or absorbed through the soft tissues, and the dura and nerve roots are stimulated in the epidural cavity, resulting in extensive scarring and adhesions in the late spinal canal. In addition, in order to avoid scar adhesions in the spinal canal caused by postoperative blood accumulation, the traumatic cavity must be thoroughly hemostatic and flushed at the end of surgery, while a drainage tube can be placed for smooth drainage and early postoperative movement of the lower limbs. This shows that intraoperative bleeding, postoperative blood accumulation, and scar adhesions in MED surgery also tend to form compression and irritation of nerve roots.
Foot drop is a relatively rare complication of MED surgery, and its function can usually be fully restored if it is not caused by nerve root rupture. For foot ptosis caused by intraoperative nerve root pulling injury or stimulation of nerve root by bleeding and adhesions, we should pay great attention to it and actively provide nerve nutrition and guide the functional exercise of the affected limb to promote its functional recovery, because once it occurs, it will bring a lot of inconvenience to patients’ daily life and may lead to conflicts between doctors and patients.