Epidemiology
Enchondroma is a common benign bone tumor which is quite specific to phalange10. Spinal enchondroma is rare, accounting for approximately 2% of the all enchondroma4. In present study, the morbidity of spinal enchondroma is 3.05%(11/366), which is slightly higher compared with the previous study.Additionally, all age stages are susceptible to this disease with no gender dominance.
Clinical features
Mordard M et al revealed that thoracic vertebrae are more susceptible to be invased than other spinal regions11. This view was confirmed by Jing Guo et al in their case report5.However, we found that lumbar and thoracic region are both susceptible to enchondroma. The tumor can invaded any column of the vertebra,including vertebral body, pedicles and spinous process. A case report involving three cervical chondromas by Gaetani P showed posterior elements were commonly affected. In present study, there were six lesions affecting posterior elements,accounting for 54.4% of all cases. Thus, enchondroma can attack the the total spine but mainly the lumbar and thoracic vertebra, and the posterior elements of the vertebra were commonly involved.
Local pain is the chief clinical manifestation. Some authors hold that there was a well demarcation between tumor and adjacent structures. Additionally, enchondroma was characterized by slow growth. So they suggested that neurological symptoms were rarely occurred in spinal enchondroma4,12. However,there were 6 patients complaining for their numbness and weakness, which accounts for the majority in our cases series. The cause of this divergence should be attributed to the different location of the lesions. The tumor reported by previous study mainly involved the vertebral body and spinous process, while our 6 lesions are all involved in pedicles, foramen intervertebrale and spinal cord. In fact, whether neurological symptoms occur or not is mainly due to the involved scope of tumors, but not to their integrity and growth rate.
X-ray is of little value in diagnosis of enchondroma. However, some indications including radiolucent lesion, ambiguous vertebral pedicle and pathological fracture of vertebra suggest that a toumor lesion may exist. In CT scan, the lesion is characterized by expansive and osteolytic destruction.In a few cases, scattered calcification can be observed. MR images revealed well-circumscribed mass with hypointense on T1-weighted images and hyperintense on T2-weighted images. Classically, the cortices is always intact and the soft-tissue is rarely invased in CT scan and MRI4. However, the continuity of the cortex was interrupted and the soft-tissue developed in our two cases of recurrence.
Diagnosis and differential diagnosis
It is difficult for physician to diagnose spinal enchondroma initially for the rarity of this lesion. Additionly, there are no characteristic changes in radiology. In case reports presented by Willis BK and S.H. Apurva, the lesion was under suspicion as aneurysmal bone cyst or a giant cell tumor4,8.The same misdiagnosis was established in our two cases. Fortunately, this error has not result in any undesirable outcomes for the consistent treatment of those two disease. One patient was misdiagnosed as spinal tuberculosis.Although the lesion of this patient was eventually removed and the right diagnose was confirmed via histopathology after operation, it is important to differentiate spinal enchondroma and tuberculosis to avoid pateint to received their unnecessary anti-tuberculosis drugs treatment. In fact, to distinguish those two diseases is also difficult when the enchondroma located in vertebra for the similar radiological appearances. So, the preoperative biopsy should be performed.
Treatment
This spinal lesion should be removed decidely in following situations:when the diagnose of enchondroma is suspected for its possibility of sarcomatous degeneration;when signs of nerve root or spinal cord compression were existed11. As suggested by other author, the purpose of surgery were to establish a accurate diagnosis, prevent malignant transformation, and preserve neurologic function8,13. The treatment method of enchondroma include excision and curettage. Curettage has been demonstrated effective to the enchondroma located in phalanges. However, the chioce of treatment of spinal enchondroma is excision since the curettage may increase the risk of local recuurence7,14. This conclusion could be further confirmed in our data. There was one case who was performed via curettage developed into recurrence ultimately, while the other 9 cases treated by excision gained the good prognosis.
An appropriate approach play a key role in achieving complete resection15. Jing Guo et al. used posterior approach and observed a good results in their case report5. In present study, anterior approach was performed in 3cases, posterior aproach in 6 cases and posterior combined with anterior approach in 2 cases. We believe that the approach was decided by the location of the lesion. Posterior approach was typically used for the lesions located in middle and posterior columns, while the anterior approache were required when the tumor was growth arising from anterior colum. Although the antero-posterior approach is difficult to perform,it is still adopted to the lumbosacral tumors where anterior reconstruction was inadequate to provide spinal stability.
Prognosis
After reviewing of the previous literature, we found that most of the cases achieved an ideal outcome with no pain, no neurological symptoms and improvement of numbness and motor weakness5,8,9. Similar outcome was also observed in our follow-up. So it is seems that this benign tumor is so mild that we can cure them easily.However, the following two cases have sounded alarms for us. Case 9 suffered from recurrence after 6 mouths postoperatively with a recurrence rate of 10%(1/10,the patient send from other hospital for her recurrence was excluded), which was consistent of the privious study7. The reason of recurrence can be attribute to the inadequate resection. Although there was no recurrence after a second surgery, the lower extremity paralysis had no improvement for the invasion by the recurrent tumor.Case 2 was send to our hospital for the recurrence of the sacral enchondroma. Preoprative radiological examination showed that the tumor was very large and closed to the iliac vessels. We explained the surgical risk in detail,but the patient still required surgical treatment for the killing pain.After abundant preoperative plan, internal iliac artery ligation was performed via anterior approach and tumor removed via posterior approach. Unfortunately, the iliac artery was ruptured and the patient died from hemorrhagic shock.