Achondroplasia (ACH) is a common form of chondrodysplasia. The pathogenesis is closely related to point mutations in the transmembrane region of the fibroblast growth factor receptor 3 (FGFR3) gene, and 80% to 90% of cases are disseminated and are de novo mutations. The incidence is low, about 1/15,000 to 1/40,000, and the resulting spinal deformity is often thoracolumbar kyphosis with lumbar spinal stenosis. It can lead to intermittent claudication, dysraphism and, in severe cases, paraplegia. There are few cases of surgical treatment reported in the literature, and similar reports have not been seen in China.
From August 2006 to June 2009, six patients with thoracolumbar kyphosis with lumbar spinal stenosis due to ACH underwent posterior osteotomy and orthopedic decompression in our department. The results of the surgical treatment of this disease will be evaluated as follows.
1. clinical data.
There were 6 patients with spinal deformity due to ACH. Among them, 3 were male and 3 were female; age ranged from 12 to 36 years old, with an average age of 18.5 years. Preoperatively, 4 patients presented with lower limb weakness and hypoesthesia, and 3 patients had combined urinary difficulty symptoms. All patients had preoperative standing full spine X-ray, posterior convex Fulcrum X-ray, CT three-dimensional reconstruction, myelography or MRI to make a clear diagnosis, determine the position of the parietal vertebrae, the status of the parietal wedge and its relationship with the adjacent vertebrae, the segment of spinal stenosis, the severity, and exclude concomitant spinal cord abnormalities. The posterior convex Fulcrum line is used to evaluate the flexibility of the posterior convexity of the spine.
2.Treatment methods.
(a) Surgical method: general anesthesia with tracheal intubation and the patient in prone position. A posterior median incision is made in the back, and the posterior structures are exposed according to the preoperative fusion range and the pedicle nail is placed. After confirming the vertebral body of the parietal vertebra, the spinous process of the parietal vertebra, the vertebral plate, part of the vertebral plate and transverse processes of the upper and lower vertebrae are removed, and the thoracic vertebrae need to be excised from the posterior corner of the ribs to the small head of the ribs, the wedge-shaped change of the vertebral body is excised, and the normal bony endplates of the upper and lower to adjacent vertebrae are temporarily fixed, and a titanium cage filled with autologous cancellous bone is placed in the osteotomy gap. The laminectomy and decompression of the stenotic segment were performed, and in one patient with mild stenosis, a subcutaneous decompression of the L1-L3 lamina was performed. The dura should be observed at any time during the compression process to see if there are obvious folds, and the compression should be stopped when folds are produced, and the laminectomy should be further expanded to prevent spinal cord injury. Monitor the spinal motor evoked potential (MEP) throughout the operation, and perform arousal test when the monitoring signal is abnormal.
(B) Postoperative management: The spinal cord can be removed from bed on the second to fifth postoperative day. Wear Boston brace for 6 months.
3. Efficacy evaluation.
During the follow-up period, all patients had standing full spine X-rays taken and the Cobb angle of thoracolumbar segment kyphosis was recorded; patients were asked about the recovery of symptoms; and the recovery of the nervous system was assessed by the JOA [6] scale (out of 11 points).
4, Results.
All cases were followed up for 5-24 months, with a mean of 10.2 months. The operative time ranged from 160 to 460 min, with a mean of 320 min. intraoperative bleeding ranged from 400 to 3000 ml, with a mean of 1300 ml. fixed fusion segments ranged from 5 to 10 segments, with a mean of 8 segments. The sagittal Cobb angle was corrected from a mean of 53.3° to 13.3° before surgery, with a correction rate of 75.0%, and there was no significant loss at follow-up; all four patients with combined neurological injury showed varying degrees of improvement at follow-up, with the most obvious relief of intermittent claudication and urinary difficulty. The average preoperative JOA score was 4.5, and the average score at follow-up was 8.5, with an improvement rate of 88.9%.
Complications included: one case of intraoperative arch cut during compression, which was a longitudinal cut of the left side of the T9 arch and was replaced by compression and fixation after hugging the arch hook and transverse process hook together, and no neurological symptoms were found after surgery. Postoperatively, one patient developed tingling symptoms in the lower extremities, which were treated with hormone and nutritional nerve therapy, and the symptoms were relieved after one week.
5. Discussion.
The basic pathological change of ACH occurs in the chondrogenic process, and the disorder of the chondrogenic process causes the longitudinal growth of long bones to be blocked, while the intramembranous process of osteogenesis is not affected, so the diameter of the backbone develops normally. The clinical manifestation is characteristic of short-limbed dwarfism, in which the patient has a giant head, short stature, short limbs and a relatively normal trunk; the developmental abnormality of the spine is manifested by a decrease in vertebral body height and a short arch root and narrow arch root spacing of the lumbar vertebrae, an anterior convexity of the lumbar vertebrae but a mild posterior convexity of the thoracolumbar segment, and a wedge-shaped change of the vertebral body at the apex of the posterior convexity. This results in thoracolumbar lumbar kyphosis and spinal stenosis. Based on the typical clinical presentation and the characteristics of the spinal deformity, the diagnosis of ACH can be clarified.
The incidence of kyphosis is 87% in patients between 1 and 2 years of age and decreases to 39% between 2 and 5 years of age; without therapeutic intervention, permanent kyphosis of the thoracolumbar segment occurs in approximately 11% of patients. Pauli et al. devised a prevention and treatment plan that included prohibiting early sitting up and using a brace to make the upper body curvature less than 60 degrees when the child sat up. None of the 66 patients with ACH treated as described above developed permanent thoracolumbar kyphosis. Therefore, it is noted that the occurrence of kyphosis can be completely avoided if this protocol is strictly followed.
In the case of kyphosis of the thoracolumbar segment of the spine due to ACH. Tolo points out that when the thoracolumbar kyphosis is greater than 30 or the thoracic kyphosis is greater than 50, surgical orthopedic treatment should be considered even in the absence of any symptoms. Due to the small number of cases, there is no uniformity in the surgical treatment of this deformity. Ain et al. reported 4 cases of ACH patients aged 4-8 years who underwent anterior-posterior staged combination with internal fixation and fusion for posterior convexity, with good postoperative results and posterior convexity correction rates of 23.0% to 31.25% without neurological complications. Root nail fixation was performed. Xin et al. reported four patients with ACH aged 15-60 years who underwent posterior osteotomy orthopedic treatment. In two cases, the vertebral cuneiformity at the vertex with vertebral hypoplasia was treated with titanium cage anterior column support and internal fusion after removing the vertebral body at the vertex and the intervertebral discs of the adjacent vertebral bodies above and below. The average rate of posterior convexity correction was 43.6%, and there were no neurological complications. In our group of six patients, all of whom underwent posterior parietal laminectomy and spinal canal decompression, the sagittal Cobb angle was corrected from a mean of 53.3° to 13.3° preoperatively, with a correction rate of 75.0%; this was higher than the correction rate reported in the literature, and the reason for this was considered to be that parietal laminectomy, as the apex of the orthosis, provides better orthopedic results after titanium cage implantation and prevents spinal cord crepitus.
The literature reports that 20 to 50% of patients with ACH can develop symptoms of spinal stenosis, mostly neurogenic claudication, sensory abnormalities, and neurogenic pain. The onset of symptoms is mostly in patients aged 30 to 40 years. The majority of the stenosis is in the lumbar spine. Schkrohowsky et al. performed extensive decompression with multisegmental laminectomy of T12-L5 in 22 patients with spinal stenosis due to ACH and achieved significant symptomatic relief after surgery. In recent years, Thomeer et al. performed myelography in 36 patients with lumbar spinal stenosis and found 97% stenosis at L2 and 3, 61% stenosis at L3 and 4, and 58% stenosis at L1 and 2, with very little involvement of other segments; moreover, due to the compensatory effect of the posterior margin depression of the vertebral body, typical stenosis was not at the level of the vertebral plate, so sublaminar decompression was performed at L1-L3. Selective enlargement of the internal diameter of the lamina without laminectomy resulted in symptomatic relief in 71. 4% of patients after surgery. Of the six patients with ACH in this group, four had preoperative neurological symptoms. In the other 2 cases, preoperative MRI showed varying degrees of spinal stenosis. At the same time of thoracolumbar lordosis correction, laminectomy and decompression of the stenotic segment was performed in 5 patients with severe lumbar spinal stenosis. One patient with mild stenosis underwent sublaminar decompression of L1-L3. The postoperative results were good, with no neurological complications and satisfactory relief of the patient’s symptoms.
In 2009, Borkhuu et al. performed a retrospective analysis of 48 patients with ACH and noted that the range of thoracolumbar kyphosis in newborn patients was T8-L4, with the parietal vertebrae located at T12-L2. when the patient started to sit up and walk, the range of kyphosis became T10/T11-L3. when selecting the fusion segment for spinal deformity due to ACH, we believe that firstly, all the vertebrae within the range of kyphosis should be fused. In the selection of fusion segments for ACH, we believe that all vertebrae within the range of kyphosis should be fused first, and second, the vertebrae within the range of decompression should be fused in conjunction with MRI. In our case, the fusion range was T9-T11 at the upper end and L3-L5 at the lower end in combination with the stenosis, and the physiological curvature of the spine was well restored after surgery.
It is worth noting that: 1) ACH patients have significant vertebral deformities and short pedicles, and Kumar et al [12] pointed out after imaging 302 thoracolumbar pedicles in 11 ACH patients aged 16-45 years that the length of the upper thoracic screws should be less than 3.0 cm and the length of T7-L5 screws should be less than 3.5 Therefore, intraoperative pedicle screw implantation should be combined with imaging to select the type of pedicle screw in order to avoid damage to the spinal cord from screws that are too long. (2) The site and degree of spinal stenosis revealed by myelography or MRI should be combined with the choice of laminectomy for extensive decompression or sublaminar submarine decompression before surgery. (③The spinal deformity of ACH patients is mainly posterior convexity, and the extraction force of screws after orthopedic treatment is larger. The characteristics of the pedicle dictate the use of shorter screws. To avoid screw extraction, patients should wear a strict postoperative brace until implant fusion.
In conclusion, the spinal deformity due to ACH should be an overall change. The kyphosis of the thoracolumbar segment at the parietal vertebrae can directly compress the spinal cord, causing a decrease in blood supply to the spinal cord and leading to impaired neurological function; at the same time, it can cause a compensatory increase in lumbar anterior convexity, leading to an increase in lumbar spinal stenosis. The interconnectedness of thoracolumbar kyphosis and lumbar spinal stenosis determines that a surgical plan should be formulated in the treatment of deformities caused by ACH in combination with X-ray, CT, MRI, etc. When thoracolumbar kyphosis is found to be combined with lumbar spinal stenosis, posterior paravertebral resection and spinal decompression can achieve good treatment results.