| Abstract|| |
Background: Avulsion or fracture of posterior ring apophysis of lumbar vertebra is not a common clinical entity and is missed often. These fractures are mostly traumatic lesions typically seen in adolescents and young adults, because fusion in this area is not complete until the age of 18 to 25 years. These fractures are occult on plain radiographs and are frequently missed due to unfamiliarity with the entity. But, CT scanning and MR imaging shows characteristic picture.
Methods: We had 21 cases of fracture of posterior margin of a lumbar vertebral body from 1991 to 2002. Fracture in all patients were classified according to CT imaging, into the three types described by Takata et al. Out of these, 8 patients were of type I, 4 patients of type II and 9 patients of type III respectively. Focal deficit / muscle weakness was present in only three patients. No fractures of type IV (Epstein et al) was found. Twelve patients were treated conservatively and 9 patients were treated by posterior decompression with total laminectomy and removal of retropulsed fragment and discectomy.
Results: The mean follow-up period was of 42 months. Conventional radiography could locate the fracture in only 6 cases and CT scan was required in all cases for stamping the diagnosis and classification. Though it is uncommon, high index of suspicion is required to diagnose it, in especially adolescent patients. All the 21 patients had good outcome following the management.
Conclusion: Avulsion or fracture of posterior margin of lumbar vertebral body is not so rare entity. In children and young adults diagnosed as having lumbar disc herniation, this lesion may be the proper diagnosis. These fractures need to be accurately diagnosed because as compared to simple disc herniations these fractures require more extensive exposure and resection to relieve the nerve impingent.
Keywords: Ring apophysis; Vertebral limbus; Vertebral margin; End-plate; Lumbar fractures.
|How to cite this article:|
Krishnan A, Patel JG, Patel DA, Patel PR. Fracture of posterior margin of lumbar vertebral body. Indian J Orthop 2005;39:33-8
| Introduction|| |
Avulsion or fracture of posterior ring apophysis of lumbar vertebra is not a common lesion because of the unfamiliarity with the entity and difficulty in evaluating the three dimensional characteristics of the fracture by conventional radiography , . But with the excellent modalities of CT scanning and MR imaging, lumbar vertebral posterior apophyseal fractures are a well documented cause of lowback and leg pain ,,, . Vertebral apophyseal fractures occur at the margins of the superior or inferior vertebral end-plates. Although they have been recognized throughout the spine, but most commonly lumbar vertebral inferior end-plate is involved , . Takata et al have classified these fractures into three types on the basis of CT scan studies : Type I, a simple separation of the entire arcuate posterior margin of the vertebra ; Type II, an avulsion fracture of the posterior rim of the vertebral body, including the overlying cartilage of the annulus fibrosus, resulting in a thicker and larger fragment ; Type III, a more localized fracture involving a larger amount of the vertebral body such that the resulting fragment is larger than the vertebral rim. A round defect in the bone adjoining the fracture site is seen  . Epstein et al proposed an additional category: Type IV, a fracture of both the cephalad and caudad end plates and spans the full length of the posterior margin of vertebral body  .
This report is a retrospective study of the clinicoradiological features, management and its outcome of 21 patients with lumbar vertebral posterior apophyseal fractures.
| Material and methods|| |
At our institute, between October 1991 and August 2002, 21 patients with fracture of posterior margin of a lumbar vertebral body were seen [Table - 1]. Fifteen patients were male and 6 were female. Eight patients had history of sports activities, 7 patients had history of heavy weight lifting and 2 patients had history of trauma. Other 4 patients had no relevant history of trauma.
All patients were first subjected to plain radiography and only 6 patients showed bony fragment retropulsion. All the patients were put through CT scanning and it showed marginal vertebral fracture of apophysis in all the cases. CT myelography in 12 patients showed filling defect and varying compression interiorly. Eight patients were classified as Type I and were between 10 and 14 years at onset of symptoms [Fiugre 1]. Four patients were classified as Type II and were slightly older, between 14 and 18 years [Figure - 2]. Nine patients were classified as Type III , of these 4 were under 18 years and the other 5 were 21,24,35,37 and 42 years old respectively [Figure - 3]. No patient of Type IV, was seen in our series. L4 vertebra was involved in 9 patients. Caudal vertebral end plate was involved in all the cases except one in S 1 and one in L 4.
All the patients without any neurological deficit were given conservative treatment with rest for few weeks, analgesics, progressive physiotherapy and mobilization. Two patients with focal muscle weakness at presentation and seven patients who did not respond to conservative treatment were treated by posterior decompression with total laminectomy and removal of retropulsed fragment and discectomy. Operated patients were mobilized from 2nd postoperative day with restriction of sitting and avoidance of sports activities for three months. In all patients postoperative period was uneventful. All patients were followed up monthly for 3 months, then every 3 months for 1 year and then at final follow-up. The lowest follow-up was 28 months and the mean follow-up was 42 months.
| Results|| |
Out of 1000 cases of discogenic pain of lumbosacral origin between 1991-2002 at our institute, 21 patients had posterior apophyseal fracture of vertebra. Sixteen of these patients were below the age of 18 years. Out of 72 patients of discogenic pain younger than 18 years, 16 had a posterior lumbar apophyseal fracture. Seventeen patients had some history of sport activities, lifting of heavy weights or trauma. Positive straight leg raising was present in 20 patients. Muscle weakness was present in only two patients at initial presentation and one patient developed muscle weakness during conservative treatment.
Conventional radiography could locate the fracture in 6 cases only. CT scanning spotted the entity in rest of the cases and was needed for classification. All the 8, Type I fractures gave excellent result with conservative treatment. Three out of 4 patients with Type II fractures recovered completely with conservative treatment and one patient developed muscle weakness during treatment. He was managed surgically and recovered fully. Two patients of Type III fracture with focal defecit / muscle weakness at presentation were treated primarily by surgery. The other 7 patients of Type III were given conservative treatment. One of the patients responded favourably but rest of the 6 patients eventually needed surgery. All the operated patients required good surgical exposure for adequate decompression and removal of retropulsed fragment. These patients required little more exposure than usual disc prolapsed patients because there is gross amount of fibrosis around the retropulsed fragment ,,. All the 9 operated patients recovered satisfactorily without any complication. In one patient with absent ankle reflex, the reflex did not come back even at 32 months follow-up.
| Discussion|| |
The superior and inferior surfaces of a developing vertebra are covered by thin cartilaginous plate. These cartilaginous plates are thickened peripherally and are called ring apophyses. The ring apophysis is separated from the vertebral body by a thin layer of cartilage  . There is some dilemma in literature regarding whether the ring is always complete or is deficient posteriorly in some or all normal persons  . The calcification of the cartilaginous rim occurs at the age of 6 years, normally begins to ossify at about 13 years and fuses with the vertebral body by the end of skeletal growth, i.e. by the age of 18 to 25 years , . The development occurs at different rate in various spinal segments. The progress is relatively slower in lumbar area and like other body skeletons, maturation is faster in females than in males  . The ring apophyses do not participate in longitudinal growth of vertebra. It lays outside the epiphyseal plates and resembles traction apophyses corresponding to the attachments of longitudinal spinal ligaments and intervertebral Sharpey's fibers ,,,,.
Lumbar vertebral posterior apophyseal fractures are avulsion fractures of the posterior ring apophysis, that develops in children and adolescents commonly and are now well documented cause of back pain and leg pain ,,,,,,, . The intervertebral disc of the immature spine is fastened to the cartilaginous marginal ridge by the outermost fibers of the annulus fibrosus (Sharpey's fibers). As the vertebral rim ossifies, these fibers become embeded in the bone. So, there is relatively weak point between the ring apophysis and the vertebral body until osseous union is complete  . There are two possible mechanisms by which the fracture can occur. Firstly, the force transmitted to the Sharpey's fibers by the nucleus pulposus during herniation may cause disruption at the weak point of osteocartilaginous junction, thus resulting in an avulsion fracture  . Secondly, the migration of the nucleus pulposus through the weak point, similar to the mechanism which results in a limbus vertebra .
Ruptured lumbar discs are not common in patients under 20 years of age  . The incidence of surgically treated ruptured intervertebral disc in young age group is very less  . Epstein and Lavine reported an incidence of 3.2%  . Love at Mayo clinic reported that, only 2.1% of the operated prolapsed discs were between the ages of 10 and 19 years  . On reviewing other large series of surgically treated lumbar intervertebral disc herniations, it is apparent that children and adolescents constitute less than 2% of the reported cases .
Several case reports have reported ring apophyses fracture associated with disc herniation in young patients ,,,,,,,,,, . In upto 90% of patients with lumbar vertebral posterior apophyseal fractures, intervertebral disc herniation is associated ,,. Whether the disc herniation produces avulsion fracture or whether the fracture results in annular disruption is unclear  . Lowrey reported lumbar posterior apophyseal fracture in 3 patients out of his 14 patients operated for ruptured intervertebral disc in 18 years of age or younger  . Banerian et al reported a prevalence of 19% overall and 32% in the subgroup of patients 14 to 17 years old  . Some authors have reported rarity of the lesion ,,, .
Fractures of vertebral ring apophysis in lumbar spine are now a well documented cause of low back pain and leg pain. The injury is often not recognized due to the unfamiliarity with the entity and failure to recognize its three dimensional configuration by conventional radiographic methods ,,,,,,,,,,. Most of the authors have postulated that the pathogenesis of these fractures is trauma or strenuous physical activity ,,,,,,, . Takata et al attributed the fracture to fragility of end plate  . In our series 17 patients had history of trauma, sports activity or lifting of heavy weights.
Patients with lumbar vertebral apophyseal fractures present with back pain and leg pain, paraspinal spasm, mechanical findings of nerve entrapment and a relative paucity of focal neurological finding ,, . All our patients presented with discogenic back pain, 20 patients showed positive straight leg raising test at 40 0 or less. Only three patients had focal neurologic findings including the two patients with muscle weakness.
These fractures are often occult on plain radiographs and myelograms ,,,,,,,,. When the entity is identified on lateral view radiograph the findings seen include, mild disc space narrowing, irregularity of the posterior vertebral corner and irregular wedge shaped ossific defect displaced into the spinal canal  . In the series of Takata et al only 5 of the 31 patients had diagnostic picture on radiographs. In our series of 21 patients, only 6 patients could be diagnosed on plain radiography alone  . The lesion is frequently missed on a radiograph due to the very small size of the fragment and unfamiliarity with the entity ,,7] .
It is difficult to evaluate the three dimensional characteristics of the fracture on plain radiograph.On CT scan the osteocartilaginous fragment has a characteristic arcuate or semilunar configuration that parallels the border of the posterior vertebral body ,,,7] . The fragment may appear irregular rather than arcuate if it contains a large fragment of vertebral body  . Takata et al have classified it into three types on the basis of CT studies: Type I, is a simple separation of the posterior margin of the vertebra. An arcuate fragment lies in the spinal canal. The underlying vertebral body appears normal because very little bone is present in the fractured fragment. This type is found in children younger than 13 years, because the cartilage in younger patients is thicker, softer, and attached more weakly to the bone of the vertebral body than in older patients. Type II, is an avulsion fracture of the posterior rim of the vertebral body, including the overlying cartilage and annulus fibrosus. The shape of the fragment is not arcuate, rather irregular because there is some bone in the fragment. This occurs in older children and adolescents. Type III, is a more localized small fracture posterior to an irregularity in the cartilaginous end plate. This involved a larger amount of vertebral body such that the resulting fragment is larger than the vertebral rim. These fractures seem to be related to a weakness or an irregularity in the structure of the end plate and more frequent in people older than 18 years. Epstein et al proposed an additional category of type IV. In this, the fracture spanned the entire length of the vertebral body and involves the superior and inferior end plates. This is a rare pattern.
Takata et al reported 10 fractures of type I, 9 fractures of type II and 12 patients of type III, in his 29 case (31 fractures) series  . Epstein et al reported 4 fractures of type IV  . In our series, 8 patients were of type I and were between 10 and 14 years of age. Four patients were classified as type II and were adolescent between 13 and 18 years. Nine patients were classified as type III and 4 of these were under 18 years and rest of the 5 was above 18 years. No fractures of type IV were seen in our series.Thus there exists a correlation of the fracture type with the age.
Posterior vertebral apophyseal fractures have been recognized throughout the spine but more common in lumbar spine. In the Handel's series of 10 patients 8 fractures occurred at L 4 - L 5 level  . In Takata et al's series of 31 fractures, posterior cephalad margin of S 1 vertebra was involved in 17 cases  . In Epstein et al's series L 4 caudal margin was more commonly involved  . In our series of 21, 9 patients of caudad L 4 , 5 patients of caudad L 3 , 2 patients of cephalad L 3 , 2 patients of caudad L5, 1 patient of cephalad S 1 , 1 patient of caudad L 1 and 1 patient of caudad L 2 were noted.
On MR images the fragment is difficult to characterize because of the difficulty in distinguishing the osseous rim from the low signal intensity of the posterior longitudinal ligament .On axial MR images the fracture fragment appears as an area of low signal intensity protruding into the spinal canal with similar curvilinear configuration as that seen on CT scan images. On sagittal MR images the displaced fragment is seen as an area of low signal intensity in the "Y" or "7" shape, elevating an intact posterior longitudinal ligament. This appearance is thought to be representing the avulsed osseous fragment and the attached unruptured Sharpey's images also show the extent of impingement by the fragment and protruding disc on neural tissue  .
Further study will be necessary to establish the sensitivity and specificity of CT and MR imaging  . Myelograms show the varying degrees of block of the spinal canal or stenosis at the respective level of affection.
Treatment of the condition is not standardized. In all the cases reported earlier in literature, surgical treatment by posterior decompression was done with removal of the protruded vertebral margin and the disc ,,,,,. In most of these cases a confirmation of the entity was by peroperative findings, thus not accounting the conservatively managed patients. In Takata et al's series of 29 patients (31 fractures), 24 patients (83%) were managed surgically: 5 were treated by anterior decompression and interbody fussion, 19 had posterior discectomy and removal of fragment and one patient was treated by chemonucleosis. All the patients had good results  . In Epstein et al's series of 10 patients posterior decompression was done as surgical management in most of the patients with favourable results is all  . Banerian et al reported requirement of posterior surgical decompression in 67% (4 out of 6) of patients with vertebral end plate fracture treated at their institute  . In our series of 21 patients, 12 patients (57%) responded well to conservative treatment and 9 patients (43%) required surgery in form of total laminectony with discectony and removal of fragment. All the 8 type I fracture were managed conservatively. Three of the 4 type II fracture, responded to conservative treatment alone and only one required operative treatment, who developed muscle weakness during conservative regimen. Two of the 9 type III fractures with neurological defecit or muscle weakness at presentation were treated at the outset itself with surgery. Out of the 7 who were given conservative treatment, only one responded favourably. Rest of the 6 patients eventually needed surgery. All the 21 patients gave good results, with full recovery except one patient who did not show recovery of ankle reflex even after 32 months.
The fracture fragment is less pliable than the disc material, often requiring wider surgical exposure for excision of the fragment with disc ,, . In all the 9 patients in our series operated upon, partial laminectomy was inadequate and all needed total laminectomy for satisfactory excision of disc and fragment. All the cases confirmed the herniated disc and retropulsed osteocartilaginous fragment under an intact posterior longitudinal ligament.
The results suggest that type I occurs in children less than 14 years which respond to conservative regimen well. Type II fracture occurred in somewhat older children between 14 and 18 years and they also respond to conservative regimen with some potentiality for operative treatment. Type III fractures occur in older children and younger adults and frequently require surgical treatment. These fractures need to be recognized preoperatively because in patients requiring surgery, removal of disc alone may not be sufficient enough to relieve nerve impingement as the osteocartilaginous fragment has a space occupying effect which contemplates its removal The patients in whom the entity goes unrecognized or untreated, the fracture could heal with residual bony spinal stenosis, which could be labelled as congenital in origin due to unawareness  .
Finally, in conclusion we noted that lumbar vertebral posterior apophyseal fractures are not rare. In children and young adults diagnosed as having lumbar disc herniation, this lesion may be the proper diagnosis. These fractures are occult on plain radiographs and myelograms and are frequently missed due to unfamiliarity with the entity and occult nature of the fracture. CT scan can diagnose and satisfactorily classify these images are also characteristic. These fractures need to be accurately diagnosed because as compared to simple disc herniations these fractures need more extensive surgical exposure and resection to relieve the nerve impingement.
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Source of Support: None, Conflict of Interest: None
[Figure - 1], [Figure - 2], [Figure - 3]
[Table - 1]