Eur Spine J DOI 10.1007/s00586-013-3158-x

ORIGINAL ARTICLE

Surgical management of the fractures of axis body: indications and surgical strategy Yin-Shun Zhang • Jian-Xiang Zhang • Qing-Guo Yang Cai-Liang Shen • Wei Li • Zong-Sheng Yin



Received: 1 September 2013 / Revised: 23 December 2013 / Accepted: 24 December 2013 Ó Springer-Verlag Berlin Heidelberg 2014

Abstract Purpose The axis body fractures are relatively uncommon and have a variety of presentations. Surgical management to them has been only reported as case reports or included as a minor part of clinical management. The objective of this study is to summarize the indications for surgery and report the clinical outcome of surgical treatment based on different fracture patterns. Methods A retrospective analysis of 28 consecutive patients presenting with the axis body fractures was undertaken. The indications for surgical treatment were defined as: (1) fractures associated with instability of adjacent joints; (2) irreducible displaced superior articular facet fracture; (3) fractures resulting in spinal cord compression. The fractures were classified as sagittal, coronal, transverse and lateral mass fracture. One of the following surgical procedures was applied according to the fracture pattern: posterior C1–C2 pedicle screws fixation and fusion (I); posterior C1–C3 screws fixation and fusion (II); posterior osteosynthesis with C2 transpedicular half-thread lag screws (III). Results 13 patients were successfully managed operatively. Two transverse and two unilateral lateral mass fractures were treated with surgical procedure I, five sagittal fractures with II, four coronal fractures with III.

Y.-S. Zhang  J.-X. Zhang  Q.-G. Yang (&)  C.-L. Shen  W. Li  Z.-S. Yin (&) Department of Orthopaedics, The First Affiliated Hospital of AnHui Medical University, 218 Jixi Road, Shushan District, Hefei, Anhui 230022, China e-mail: [email protected] Z.-S. Yin e-mail: [email protected] Y.-S. Zhang e-mail: [email protected]

Complications of malposition of screws and neurologic deficit did not occur during operation. Satisfactory reduction and bony union were demonstrated on postoperative radiographics. Conclusions Conservative treatment is still advocated as primary management for most axis body fractures. But for patients with obvious adjacent joints instability or irreducible displaced superior articular facet fracture, surgical intervention based on the different fracture pattern is necessary. Keywords Axis fracture  Axis body  Lateral mass fracture  Surgical treatment  Atlanto-axial fusion

Introduction Unlike odontoid fractures and hangman’s fractures, fractures of the axis body are uncommon and have a variety of presentations. In 1993, Starr et al. [1] reported six atypical hangman’s fractures, which were actually fractures of the axis body. Benzel et al. [2] classified the axis body fractures into three types based on fracture orientation: coronal, sagittal and horizontal. Depending on the characteristic radiographic founding, Fujimura et al. [3] classified them into four types: avulsion, transverse, burst, and sagittal. Hahnle et al. [4] reported three variants of shear fractures through the axis body. Nonoperative treatment was suggested as primary therapy for fractures of the axis body in previous studies [3, 5– 9]. However, some axis body fractures are intrinsically unstable due to serious displacement or associated dislocation/subluxation of adjacent joints. Furthermore, a large percentage of these unfortunate cases cannot obtain or maintain a satisfactory reduction with conservative

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treatment [3, 4]. Although most of patients’ fractures can be healed with nonoperative management, sequelae of varying degrees of nuchal pain because of malalignment and osteoarthrosis of the atlanto-axial joint were common [3, 4, 10–12]. On the other hand, surgical management for fractures of the axis body has previously only been reported infrequently as case reports [13, 14] or included as a minor part of clinical management [3, 10]. This is a retrospective review of our 28 clinic case managements on fractures of the axis body over 6 years. We summarized the indications for surgery and gathered the clinical and radiographic results of surgical treatment on 13 of our 28 patients based on different types of fractures of the axis body. To the authors’ knowledge, this is the only case series report on surgical treatment of these kinds of fractures so far.

Materials and methods A retrospective analysis of 28 consecutive patients presenting with the axis body fractures treated in our institution between January 2006 and September 2012 was performed. Patients diagnosed with rheumatoid arthritis, congenital anomalies, or tumors of the upper cervical spine were excluded. Of the 28 patients, one died of the associated severe craniocerebral trauma 3 days after admission, 14 patients were treated with traditional conservative methods, and 13 patients were treated surgically. Of the 14 nonsurgically treated patients, 10 patients having no obvious adjacent joint instability and \3 mm fracture displacement were treated with a Philadelphia collar for 12 weeks. One patient with an undisplaced sagittal fracture was treated with 6 weeks of skull traction followed by 6 weeks of external immobilization with a Minerva Jacket because of an associated C1 Jefferson fracture. An additional three patients with more than 3-mm fracture displacement and without adjacent joint instability gained good reduction from skull traction alone and did not need surgery. They were further managed with a Minerva Jacket for 12 weeks. The 13 surgically treated patients were first treated with skull traction for 1–2 weeks with forces up to 10 kg for reduction followed by surgical intervention based on the following surgical indications: (1) fractures associated with instability of adjacent joints, such as atlanto-axial facet joint dislocation/subluxation, C2/3 subluxation and damage of the integrity of the C1–C2 and C2–C3 interspinal ligamentous system; (2) irreducible displaced lateral mass fractures impacting the superior articular facets of the axis; (3) fractures resulting in spinal cord compression. In our study, we categorized our axis body fracture cases into four subtypes that are slightly different from the

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previously mentioned classifications [2, 3]: sagittal, coronal (including the subgroup as Starr et al. [1] described), transverse and unilateral lateral mass fracture (when the fracture is only located in one lateral mass). One of the following surgical procedures was applied according to the fracture pattern: posterior C1–C2 pedicle screws fixation and fusion (I); posterior C1–C2 pedicle screws and C3 lateral mass screws fixation and fusion (II); posterior osteosynthesis with C2 transpedicular half-thread lag screws with/without laminar screws (III). Posterior elements of the fixed vertebrae were decorticated and autologous bone grafts from the posterior iliac crest were applied. The Philadelphia collar was worn by all patients for 6 weeks postoperatively. The fracture healing was confirmed when the fracture line was indistinct on the CT scans, and the bony union of fixed segments was considered to be present when a bone bridge was seen on the CT scans and there was no implant failure nor evidence of instability on follow-up image views. These surgically treated patients were also observed by their age, gender, injury cause, fracture pattern, associated injury, neurological function (Frankel grade) and surgical procedures. All of them underwent plain anteroposterior, lateral and open-mouth radiographs, CT scans and 3D reconstructions of the upper cervical spine, both preoperatively and postoperatively. MRI images of the cervical spine were also obtained for all patients preoperatively to exclude spinal cord compression and evaluate the integrity of the transverse ligament of atlas and C2–C3 intervertebral disk, and the integrity the posterior interspinal ligamentous system. Additional lateral flexion/extension X-rays and CT scans of the cervical spine were performed to evaluate the fracture healing and fusion at the 6th month postoperation follow-up.

Results Clinical information of the 13 patients is listed in Table 1. Their ages range from 19 to 59 years. Eight patients were injured in motor vehicle accidents, and five from falls. Three patients presenting with neurological deficit gained various degrees of improvement of neurological function postoperatively. All patients were associated with head injuries and, most of which were scalp contusion or laceration; additionally, two with the craniocerebral injury, two with the atlanto-axial facet joint dislocation, eleven with the atlanto-axial facet joint subluxation, ten with the fracture of superior articular facet of the axis, two with the subaxial spine injury, nine with the C2/3 subluxation, one with type II odontoid fracture, and three with the limb fractures. Sagittally oriented fractures Five patients. The fracture lines started from near the base of odontoid and extended

Eur Spine J Table 1 Clinical summary of 13 patients with axis body fractures treated operatively Patient no.

Age (years)

Gender

Injury cause

Fracture pattern

Associated injury

Surgical procedure

ASIA score Preo-Posto

1

48

M

Fall

Sagittal

A?C?D?F

II

2

32

F

MVA

Sagittal

B?D?F?H

II

3

37

M

MVA

Sagittal

B?C?D?F?G

II

4

19

M

MVA

Sagittal

B?C?D?F

II

5

49

M

MVA

Sagittal

B?D?F?H

II

6

46

F

Fall

Coronal

B?C?D?F

III

7 8

43 24

M M

Fall MVA

Coronal Coronal

B?C?D?F?N B?D?F

III III

D

E

9

33

M

MVA

Coronal

B?C?D?F?N

III

D

E

10

27

M

MVA

Transverse

A?C?F?H?N

I

B

D

11

59

M

Fall

Transverse

B?C?F

I

12

44

M

MVA

LMF

B?C?F?G

I

13

49

M

Fall

LMF

B?C?E?F

I

M male, F female, MVA motor vehicle accident, LMF lateral mass fracture, ASIA American Spinal Injury Association, Preo preoperative, Posto postoperative, A atlanto-axial facet joint dislocation, B atlanto-axial facet joint subluxation, C fracture of superior articular facet of axis, D C2– C3 subluxation, E type II odontoid fracture; F head injury, G subaxial spine injury, H limb fractures, N neurological deficit

a

b

c

d

Fig. 1 A 48-year-old patient fell from height. Lateral cervical radiograph after skull traction showed displaced fracture of the axis (a); CT on axial view and surface reconstruction demonstrated sagittally oriented fracture of the axis associated with unilateral

atlanto-axial facet joint dislocation and the C2/3 subluxation (b, c); Normal alignment of the upper cervical spine was recovered after operation (d)

backward to the posterior wall of the axis body with an associated lamina fracture. All patients had unilateral atlanto-axial facet joint dislocation/subluxation and the C2/3 subluxation. Posterior C1–C2 pedicle screws and C3 lateral mass screws fixation and fusion were undertaken. For unilateral atlanto-axial facet joint dislocation, the reduction was difficult to achieve without pulling the end of the C1 pedicle screw manually (Fig 1). Coronally oriented fractures Four patients. They were treated as type II hangman’s fractures with posterior axis transpedicular half-thread lag screws to preserve the movement of adjacent joints. Two of the four patients were variant with asymmetrical fractures involving the lateral posterior wall of the axis body and fracture lines running

from the unilateral lateral mass to the opposite laminar diagonally. Both patients were associated with mild muscle weakness of unilateral upper extremity. CT on sagittal view showed a coronal superior articular facet fracture with obvious displacement. For this variant, a laminar screw was added for the recovery of the C2 ring. Extreme care was taken to avoid injury of the C2/3 facet joint capsule during operation (Fig. 2). Transverse fractures Two patients. One patient was injured in a motor vehicle accident and associated with scalp contusion and laceration on his left tempus. Additional fractures were found on his left clavicle and femur shaft. He was also complicated with hemiplegia of his left extremities. MRI images showed obvious retropharyngeal

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a

b

c

Fig. 2 A 43-year-old male patient suffered a fall. The CT scans displayed a variant asymmetrical coronally oriented fracture of the axis body with fracture line running from unilateral lateral mass to the opposite laminar diagonally (a–c). The CT scans 6 months after

a

b

d

e

posterior osteosynthesis with the axis transpedicular and laminar halfthread lag screws demonstrated that the fracture was bony healed with perfect reduction (d, e)

c

d

Fig. 3 A 27-year-old male presented with a transverse avulsion fracture through the axis body (a). The MRI with STIR images revealed obvious retropharyngeal hematoma, damage of posterior atlanto-axial ligament and a spinal cord contusion (b). The lateral

radiograph of cervical spine under anesthesia demonstrated obvious axial fracture separation without the skull traction (c). The CT scans on a coronal view 6 months postoperation showed bony union with normal atlanto-axial alignment (d)

hematoma, damage of the posterior atlanto-axial interspinal ligament and a spinal cord contusion. CT showed a transverse fracture of the axis body with obvious instability of the atlanto-axial junction. The second patient presented with a serious displaced transverse fracture going through the body and left superior articular process of the axis. For both patients, operation with posterior atlanto-axial pedicle screws fixation and fusion was the treatment of choice (Figs. 3, 4). For the first patient, after skull traction with a force of 2 kg, he developed dizziness and increasing neck and shoulder pain with moderate dyspnea. Symptoms were improved immediately with oxygen supplementation and the decreasing of force of traction.

Unilateral lateral mass fractures of the axis Two patients. Both cases had the homolateral lateral mass of the atlas subluxed into the depressed or split superior articular process of axis with associated fixed rotatory subluxation of atlanto-axial facet joints. One case was also associated with a type II odontoid process fracture. The open-mouth radiograph of the atlanto-axial complex after more than 7 days of skull traction demonstrated unsatisfactory reduction with severe unevenness of the impinged superior articular facet and the asymmetrical atlanto-axial facet joints of two sides. Consequently, posterior atlanto-axial pedicle screws fixation and fusion were performed (Fig. 5).

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a

b

c

Fig. 4 A 59-year-old patient presented with a serious displaced transverse fracture through the body and the left superior articular process of the axis (a, b); intraoperative fluoroscopy showed satisfactory reduction and screws placement

Fig. 5 Posterior C1–C2 fusion was undertaken for a 49-year-old patient presented with a comminuted left lateral mass fracture of the axis with associated odontoid fracture

All operations were performed successfully with mean blood loss of 188 ml (ranging from 100 to 300 ml). The average operation time was 98 min (ranging from 60 to 160 min). All cases obtained satisfactory reduction of fractures and dislocation/subluxation without malposition of screws except one case of asymmetrical coronal fracture that had approximately a residual anterior displacement of 2 mm of C2 on C3. Three patients presenting with neurological deficits gained various degrees of improvement of neurological function postoperatively. None of the neurologically intact patients were complicated with neurological deficits postoperatively. No patients were complicated by wound infection. All patients were followed-up for a mean duration of 20.8 months (ranging from 6 to 45 months). The average

Visual Analogue Scale of 10 points for neck pain was 0.8 (ranging from 0 to 2) at the final follow-up. All patients with atlanto-axial fusion had restrictions of cervical rotation of different degrees at the final follow-up. Two patients complained of mild pain in the donor site with weather changes. Patients who were treated with only posterior axis transpedicular half-thread lag screws showed nearly normal range of cervical motion at the 6th month follow-up. All cases showed normal neurological function at the final follow-up except one who complained of numbness of his left extremities along with muscle weakness of his left upper extremity (grip strength was Grade 4/5). The fracture healing and the bony union of the fixed segments were revealed in all cases on CT and 3D reconstruction views. Implant failure and instability were not seen on lateral flexion/extension radiographs of the cervical spine.

Discussion Injury mechanisms of the axis body fractures have been reported in many studies [2–4, 6–9, 15, 16]. Both direct and indirect forces may cause fractures of the axis body, and fractures with similar imaging findings are often produced with different injury mechanisms [2]. Because of the anatomical peculiarity of the axis and the complexity of injury pathology, clinical management of the axis body fractures should often be individualized [5]. For patients without obvious adjacent joint instability, most axis body fractures have been treated with nonoperative management in the past [1, 3, 4, 6–9, 11, 12, 15, 16]. But the clinical results were not satisfactory in quite a few

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significant cases [3, 4, 10–12]. The reasons for the unsatisfactory clinical outcome are as follows. Firstly, the axis body fractures are relatively uncommon and often present with many variants. The management for them remains somewhat an enigma for many spine surgeons. Secondly, reduction was difficult for some cases with serious fracture displacement and adjacent joints dislocation using traditional atlanto-axial internal fixation technique such as posterior wiring fixation and bilateral transarticular screws fixation. Thirdly, the superior articular facets of the axis are often involved in many fractures. In recent years, many clinicians have recognized that reduced rotation of the C1– C2 per se is not a concern for the patients, but the C2 fractures affecting the lateral mass have higher incidence of the atlanto-axial degeneration and osteoarthritis, and patients with increased severity of the C2 malunion and new onset of the atlanto-axial arthritis have worse clinical outcomes and significantly reduced rotation of the C1–C2 [11, 12]. However, with the advancement of imaging technique, especially the application of three-dimensional multi-spiral slice CT and MRI, many complex or rare axis body fractures have been able to be depicted and identified accurately. Moreover, the C1 pedical screws [17–21] (which are actually the C1 lateral mass screws with the placement of screws via posterior arch into lateral mass), when combined with the C2 pedical screws, work as a thoracolumbar spine pedical screws fixation system and have shown obvious superiority in reduction. Many cases of axis body fractures, which previously could only be treated with nonoperative management or with surgical management with combined anterior and posterior approaches, are now able to obtain better clinical results through operative management with a simple posterior approach. Therefore, for patients without significant fracture displacement or evidence of adjacent joints instability, nonoperative management is appropriate. But for patients who fit into one of the above-mentioned three surgical indications as shown by our cases, operative management is valuable for better clinical outcomes. The optimal surgical choice is based on the type of fracture pattern: Sagittal fractures are mainly caused by axial load from the head [2]. Cases without significant fracture displacement are often caused by simple axial load and can get good result with nonoperative treatment [7]. However, if a rotational and lateral bending force vector is applied, the axis vertebra is often split into two parts, one of which usually displaces anteriorly with atlas causing fracture, dislocation/subluxation of the atlanto-axial facet joints, and the C2/3 subluxation. For patients with this fracture configuration, it is difficult to obtain satisfactory reduction with skull traction [3]. Fortunately, the atlas and pedicles of the axis are intact in most cases. Thus, the posterior screw-

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rod construct with the C1–C2 pedicle screws and the C3 lateral mass screws is the best choice to obtain and maintain reduction, which is similar to the posterior reduction process of the lumbar spondylolisthesis. A typical coronally oriented axis vertical body fracture is described as a vertical coronal fracture through the posterior aspect of the axis body [2]. A variant of that is the diagonal fracture of the axis vertebra with the fracture line running from one lateral mass to the opposite laminar. Starr et al. [1] highlighted that this variant was an atypical hangman’s fracture and associated with a higher incidence of neurologic compromise than a standard hangman’s fracture. Both of the two cases of this variant in this study also had mild neurological deficits. Some authors [14, 22, 23] define coronally oriented fractures as an atypical traumatic spondylolisthesis or unusual type of hangman’s fracture. Benzel et al. [2] emphasized that this fracture was characterized by a dorsally positioned vertical C2 body fracture, and described the injury mechanism of it in detail. But they were not able to give any recommendation on clinical management. No matter how people name this fracture, it is similar to the traumatic spondylolisthesis in terms of clinical management. Except for Marotta et al. [14] and Rainov et al. [13] reported two cases in total with operative treatment, nonoperative treatment was preferred in most studies [1, 7, 16, 24] in the past. In Levine et al. [25] series, 65 % reduction was achieved by traction for type II hangman’s fracture, but the final residual deformity reached to 60 % of the initial translation, and 40 % of the initial angulation due to the loss of reduction in the halo vest. Therefore, many authors applied the posterior transpedicular screw fixation for type II hangman’s fracture to obtain and maintain reduction sparing the motion of adjacent joints given its safety, low cost and technical feasibility [26–28]. Inspired by that, the cases of coronal vertical body fracture in this study were managed with transpedicular half-thread lag screws and, occasionally, laminar screws. It should be pointed out that the displaced fracture of superior articular process of the axis impacting superior articular facet could be reduced well by the compression effect of lag screws, because most of this kind of fractures are not comminuted (Fig. 2). As a result, the motion of the atlanto-axial joint was preserved. However, the atlanto-axial fusion should be considered if the lateral mass fracture is comminuted. The transverse fractures of the axis body are rare and considered to be produced by hyperextension or combined hyperflexion and distraction forces, which are similar to the thoracolumbar chance-type fractures with neurologically intact [6, 8, 9]. Nonoperative treatment has resulted in fracture healing and long-term stability even though they are unstable injury [3, 6, 8, 9]. Different from cases reported in previous studies, one of the current cases was

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caused by a lateral shear and distraction force and was a type III odontoid fracture [29] accompanied by the spinal cord impingement and serious vertical and transverse instability of the atlanto-axial joint due to the disruption of the posterior atlanto-axial interspinal ligament and the facet joint capsule. Surgical intervention is necessary to restore normal alignment and stability of the atlanto-axial complex. With regard to surgical procedure, anterior odontoid screw fixation is an alternative technique in the management of type III odontoid fractures because of its superiority of sparing much of the axial rotation at the C1–C2 joint [11]. For cases with serious vertical instability, however, placement of an anterior odontoid screw would be a potential risk of stretching spinal cord and could not provide sufficient stability of the C1–C2 articulation. The other case was a transverse fracture of the axis body involving left superior articular facet with significant displacement; hence, posterior atlanto-axial pedicle screws fixation and fusion was suggested. It is recommended that skull traction initiated with lightweight and special attention paid to complications, in particular to the possibility of vertical atlanto-axial instability. Unilateral lateral mass fractures of the axis are the result of a lateral flexion and compression injury often occurring with a rotated position of the atlas on the axis and are frequently associated with an odontoid fracture [4, 10]. Conservative treatment with appropriate cervical spine immobilization could achieve satisfactory clinical results with the preservation of the C1–C2 rotation for patients without fracture displacement or with a reducible fracture. However, chronic neck pain because of osteoarthrosis of the atlanto-axial joint has been reported in many cases with irreducible lateral mass fractures when treated with nonoperative methods [4, 11, 12]. Therefore, posterior atlantoaxial fusion was suggested for these patients.

Conclusions The axis body fractures should be treated with individualized clinical management. Conservative remedies with external immobilization is still advocated as primary management for most cases. But for cases with adjacent joints instability or irreducible displaced superior articular facet fracture, surgical intervention is necessary. The optimal surgical choice should be based on the type of fracture pattern. There are only 13 patients treated surgically with relative short-term follow-up in this study and because of the rarity and complexity of the axis body fractures, prospective multicentre studies with longterm follow-up are expected. Acknowledgments No funds were received in support of this article. No benefits in any form have been or will be received from a

commercial party related directly or indirectly to the subject of this manuscript. Conflict of interest

None.

Ethical standards This study was approved by the Institutional Review Board and the Ethics Committee of our institution.

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Surgical management of the fractures of axis body: indications and surgical strategy.

The axis body fractures are relatively uncommon and have a variety of presentations. Surgical management to them has been only reported as case report...
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