Sushanta K. Sahoo

Technique for direct posterior reduction in irreducible atlantoaxial dislocation: Multi-planar realignment of C1-2

OBJECTIVE Apart from the commonly seen antero-posterior subluxation of C1 over C2, the dislocation may occur in vertical, lateral or rotational plane. Desired C1-2 realignment can be achieved by corrrecting its dislocation in all planes. We describe a technique for the same. MATERIAL AND METHODS The clinical and radiological features of 16 patients (4 – traumatic and 12 – congenital) with irreducible atlantoaxial dislocation (AAD) admitted in the last 1.5 years were studied. Specific attention was paid to vertical dislocation with lateral and rotational components, apart from anterior-posterior subluxation. They were operated through direct posterior approach. The technique using a long rod holder as lever and screw head (tulip) as fulcrum was employed to achieve C1-2 realignment in all planes. The postoperative clinical and radiological data was analyzed and compared with preoperative data. RESULTS Patients presented with progressive myelopathy and/or progressive worsening of neck pain. Vertical dislocation was seen in 11 patients with congenital AAD in addition to the antero-posterior subluxation seen in all. Three patients with traumatic AAD and 8 with congenital AAD had additional lateral dislocation or lateral tilt. Three patients with traumatic AAD and 7 with congenital AAD showed rotational component. Postoperatively, all patients showed clinical improvement. CONCLUSIONS The antero-posterior and vertical realignment could be achieved in all except one. Similarly, rotational and lateral components could be completely corrected in 8 out of 10 patients. The technique appears to realign the C1-2 in all planes and provides good anatomical restoration.

Comprehensive drilling of the C1–2 facets to achieve direct posterior reduction in irreducible atlantoaxial dislocation

OBJECT The cause of irreducibility in irreducible atlantoaxial dislocation (AAD) appears to be the orientation of the C1-2 facets. The current management strategies for irreducible AAD are directed at removing the cause of irreducibility followed by fusion, rather than transoral decompression and posterior fusion. The technique described in this paper addresses C1-2 facet mobilization by facetectomies to aid intraoperative manipulation. METHODS Using this technique, reduction was achieved in 19 patients with congenital irreducible AAD treated between January 2011 and December 2013. The C1-2 joints were studied preoperatively, and particular attention was paid to the facet orientation. Intraoperatively, oblique C1-2 joints were opened widely, and extensive drilling of the facets was performed to make them close to flat and parallel to each other, converting an irreducible AAD to a reducible one. Anomalous vertebral arteries (VAs) were addressed appropriately. Further reduction was then achieved after vertical distraction and joint manipulation. RESULTS Adequate facet drilling was achieved in all but 2 patients, due to VA injury in 1 patient and an acute sagittal angle operated on 2 years previously in the other patient. Complete reduction could be achieved in 17 patients and partial in the remaining 2. All patients showed clinical improvement. Two patients showed partial redislocation due to graft subsidence. The fusion rates were excellent. CONCLUSIONS Comprehensive drilling of the C1-2 facets appears to be a logical and effective technique for achieving direct posterior reduction in irreducible AAD. The extensive drilling makes large surfaces raw, increasing fusion rates.

‘Atlas shrugged’: congenital lateral angular irreducible atlantoaxial dislocation: a case series of complex variant and its management

PurposeThe commonly described congenital atlanto-axial dislocation and Basilar-Invagination is antero-posterior or rotational or vertical plane. However, congenital dislocation in lateral plane has received scant attention. The purpose of this manuscript is to describe this unusual entity and discuss its management.Materials and methodsThe clinic-radiological feature of seven patients with congenital lateral angular AAD (CLAAAD) were studied and managed. The unilateral C1 facet had subluxed lateral to C2–3 complex. The C1 and C2 facets were drilled comprehensively and repositioned with distraction, placement of metallic spacers and facet manipulation after insertion of screws. The post operative outcome was studied.ResultsThe presentation is usually with neck tilt (progressive in 3) and/or progressive spastic quadriparesis. The mean C1–2 tilt was 25.2°. C1 was bifid in six patients. C1 lateral mass was assimilated with occipital condyle on dislocated side in and the other side was normal (6 patients). The dislocated C1–2 joint was abnormally oblique as compared to contralateral side. The relationship of occiput and C1 was normal. Correction of dislocation and lateral tilt was achieved in all patients with subsequent correction of neck tilt and deficits. One patient required reoperation.ConclusionsThe acute angulation of joint on one side and near normal on other side leads to differential vertical movement, further accentuated by splaying of bifid C1. The entity is seen in young patients and often present with neck tilt and spastic quadriparesis. Management requires reshaping the joints and facet manipulation. If the reshaping is inappropriate, the joint is likely to redislocate before fusion occurs.

Focusing on the delayed complications of fusing occipital squama to cervical spine for stabilization of congenital atlantoaxial dislocation and basilar invagination

OBJECTIVES Occipito-cervical(OC) fusion is often practiced for congenital atlanto-axial dislocation (CAAD) and basilar invagination (BI) with claims of good long term outcome. Little has been discussed about the delayed complications following fusing occipital squama to cervical spine (OC fusion). We have described and analyzed delayed complications with OC fusion in our patients that helps us understand the underlying dynamics and biomechanics. PATIENTS AND METHODS Twenty seven patients of CAAD and BI underwent OC fusion (between 2008 and 11) after transoral odontoidectomy or direct posterior reduction with OC distraction. OC fusion was achieved using either sublaminar wiring or with precurved rods and screws or contoured loop. One patient was referred after OC fusion with contoured loop and wires with additional C1 laminectomy. The outcome (>12months) and delayed complications in these patients were analyzed. RESULTS Five types of delayed complications were noticed in 6 of the 28 patients who underwent OC fusion. Five of 6 patients were adults. Vertical redislocation with posterior midline fusion (n=2), adjacent level angular listhesis (n=1) and swan neck deformity (n=1) was seen in cases of OC fusion with sublaminar wires alone. Progressive C1 dislocation was seen in the lone patient who was referred after OC fusion with loop and wires. Vertical and angular dislocation was seen in 1 patient of OC fusion with precurved rod and screws. CONCLUSION Progressive redislocation and adjacent level dislocation are delayed complications seen after OC2 fusion. These complications are more often seen in adults, especially with sublaminar wiring/semi rigid OC fixation.

Bilateral inverted vertebral arteries (V3 segment) in a case of congenital atlantoaxial dislocation: Distinct entity or a lateral variant of persistent first intersegmental artery?

Background: Anomalous vertebral arteries (VAs), commonly involving the persistent first intersegmental artery (FIA), are often seen with congenital atlantoaxial dislocations (AAD). Here we describe an unusual variant consisting of bilateral VAs with normal loops but passing below the C1 (inverted VA) arch, distinctly different from the FIA. Case Description: A 9-year-old boy presented with a spastic quadriparesis. Preoperative radiographic studies showed an irreducible AAD with an occipitalized CO-C1 and C2-3 fusion. Although both VAs exhibited proximal and distal loops like normal VA, the distal loops did not pass through the C1 transverse foramina and coursed inferior to the C1 arch instead. With this critical preoperative information, both VAs could be better safeguarded during dissection of the C1-2 facets. Conclusion: In the case presented, although the course of the inverted VAs is similar, the norm, they coursed inferior to both C1 arches. Careful evaluation of the preoperative radiological studies allowed for careful dissection of the inverted VA (horizontal loop) while opening the C1-2 joint for subsequent alignment (e.g. reduction) and bony fusion. This information also facilitates safer insertion of lateral mass screws (e.g. choosing the appropriate C1 screw length to gain adequate bony purchase without compromising anomalous VA).

Revisiting the differences between irreducible and reducible atlantoaxial dislocation in the era of direct posterior approach and C1–2 joint manipulation

OBJECTIVE The current management of atlantoaxial dislocation (AAD) focuses on the C1-2 joints, commonly approached through a posterior route. The distinction between reducible AAD (RAAD) and irreducible AAD (IrAAD) seems to be less important in modern times. The roles of preoperative traction and dynamic radiographs are questionable. This study evaluated whether differentiating between the 2 groups is important in todays era. METHODS Ninety-six consecutive patients with congenital AAD (33 RAAD and 63 IrAAD), who underwent surgery through a posterior approach alone, were studied. The preoperative and follow-up clinical statuses for both groups were studied and compared using Japanese Orthopaedic Association (JOA) scores. The radiological findings of the 2 groups were compared, and the intraoperative challenges described. RESULTS A poor preoperative JOA score (clinical status) was seen in one-fifth of patients with IrAAD, although the mean JOA score was nearly similar in the RAAD and IrAAD groups. There was significant improvement in follow-up JOA score in both groups. However, segmentation defects (such as an assimilated arch of the atlas and C2-3 fusion) and anomalous vertebral arteries were found significantly more often in cases of IrAAD compared with those of RAAD. Os odontoideum was commonly seen in the RAAD group. The C1-2 joints were acute in IrAAD compared with RAAD. Preoperative traction in IrAAD resulted in vertical distraction and improvement in clinical and respiratory status. Surgery for IrAAD required much more drilling and manipulation of the C1-2 joints while safeguarding the anomalous vertebral artery. CONCLUSIONS Bony and vascular anomalies were much more common in patients with IrAAD, which made surgery more challenging than it was in RAAD despite similar approaches. An irreducible dislocation seen on preoperative radiographs made surgeons aware of difficulties that were likely to be encountered and helped them to better plan the surgery. Distraction achieved through preoperative traction reaffirmed the feasibility of intraoperative reduction. This made the differentiation between the 2 groups and the use of preoperative traction equally important.

Are C2 pars-pedicle screws alone for type II Hangman's fracture overrated?

BACKGROUND/OBJECT The recent trend for treatment of certain cases of type II Hangmans fracture has been towards motion preserving surgery. This is claimed to be achieved with placement of pedicle screws across the fracture fragments. However, the long term outcome in clinical scenario is not yet clear, neither are the factors determining suitability of such a technique. MATERIALS AND METHODS We have retrospectively analyzed the results of 11 patients of type II Hangmans fracture, according to the extent of translation. Nine patients underwent stabilization of fracture with C2 pedicle screws and 2 were managed with halo immobilization. The conservative management failed in one and this patient underwent internal fixation using pars-pedicle screw as well. The long term clinical and radiological (CT and dynamic X-rays) outcome was analyzed. RESULTS All patients including the one with halo immobilization, showed solid fusion across the fracture fragments. With the exception of one patient none had any clinical symptoms. This lone patient complained of restricted neck movements. Three different types of radiological results were observed. Two patients with translation >8mm showed C2-3 body fusion. Three of 6 patients with minimal translational (3-4mm) showed facet fusion. Three patients with moderate translational dislocation (4.5-5.5mm) showed persisting C2-3 angular instability. CONCLUSIONS The C2 pedicle screw is a good technique for osteosynthesis. However, the claimed long term advantage of motion segment preservation with this technique remains doubtful. It may be suitable for those fractures with minimal translation (<4mm), where the superiority of surgery, itself, over external immobilization is questionable. C2-3 fusion is preferable for those fractures with translation >4mm as these are unstable and C2 pedicle screws alone are likely to have less desirable results.

Redefining Congenital Atlantoaxial Dislocation: Objective Assessment in Each Plane Before and After Operation.

BACKGROUND The C1-C2 joint has multiple degrees of freedom of movement and C1-C2 dislocation (AAD) is often multiplanar. The existing methodology to assess the dislocation is limited to few planes. The object of this study is to redefine and objectively assess congenital AAD in each possible plane, before and after the operation. METHODS This study consisted of 95 patients of irreducible congenital AAD operated on with the posterior approach alone. Preoperative and postoperative computed tomography imaging was studied in the axial, coronal, and sagittal planes. The relationship of C1-C2 along with the C1-C2 joint inclination was studied in each plane. The extent and type of dislocation was objectively assessed in each plane (newer indices) and compared with follow-up imaging for correction. The preoperative and postoperative Japenese orthopaedics association scores were compared. RESULTS The commonest variety (61 patients) was a combination of anteroposterior (AP) and vertical C1-C2 dislocation. Five patients had predominant APnteroposterior, 6 vertical, 4 axial rotational, 9 lateral angular tilt, and 3 had lateral transalational. Seven patients had a combination of dislocation in AP, vertical, and rotational planes. AP dislocation was seen with sagittal inclination of C1-C2 joints and vertical dislocation with coronal inclination. Asymmetry in the joints sagittal inclination added to a rotational component, whereas asymmetry in the coronal angulation caused lateral angular tilt. Pure rotational or lateral translation dislocation had near-normal C1-C2 orientation. Preoperative Japenese orthopaedics association score was worst in the lateral tilt and the lateral translation. Correction in all planes was achieved in all patients. CONCLUSIONS The objective assessment of C1-C2 dislocation and joints in each plane was to determine its management and help in achieving multiplanar correction.

Congenital C1-2 Lateral Translational Dislocation: Case Illustration with Pre- and Postoperative Imaging

Background: Congenital atlantoaxial dislocation has been commonly described in the antero-posterior or vertical plane (basilar invagination). However, dislocation in the lateral translational plane due to congenital deformity is rare. Case Report: We present a case of a young male who presented with os odontoideum with C1-2 dislocation in the lateral plane along with antero-posterior dislocation. He was operated on through a midline posterior incision, and the C1-2 facet was manipulated so as to correct the dislocation in all planes. Conclusion: With os odontoideum, the C1-2 joints can exhibit movements that are out of the ordinary, even in the lateral translational plane. It suggests that the ligaments and joint capsule may weaken with time. Careful radiological evaluation helps in diagnosing this rare condition. An understanding of 3D facetal anatomy is important to achieve complete correction.

A typical radiological presentation in a case of choroid plexus carcinoma.

Dear Sir, Choroid plexus carcinomas are uncommon intracranial neoplasms accounting for 15-20% of choroid plexus tumors. About 80% of these are found in childhood.[3] The radiology usually shows a brilliantly enhancing heterogenous intraventricular mass invading the ependyma with edema.[9] However, the imaging may be atypical at times.[6] We describe here a case of choroid plexus carcinoma in an infant with atypical radiological features. A 1-year-old male child presented with ataxia and intracranial hypertension since 2 months. The noncontrast computerized tomography (CT) scan showed a heterogenously hyperdense lesion in right posterior fossa region with gross hydrocephalus. The magnetic resonance imaging (MRI) revealed a posterior fossa lesion with the epicenter being located in the 4th ventricle, the presence of a solid and cystic component with extension into the right cerebellar hemisphere. The cystic component was uniformly hyperintense on MRIT1 and T2 sequences, and the fluid attenuation inversion recovery (FLAIR) sequence. The solid component appeared isointense on T1, T2 sequences and had a heterogeneous contrast enhancement [Figure 1]. Although diffusion weighted imaging (DWI) would provide us with added information, this was not available as the patient was referred to us with imaging. With the above image findings, we considered the cyst contents being high in protein or fat contents, and one of the differential diagnoses we kept in mind was an atypical teratoid tumor among other, which include ependymoma with cyst or bleed, ectopic cranipharyngioma, and infected dermoid. At surgery, the cyst had machine oil like fluid, usually characteristic of craniopharyngioma cysts.[1] The solid component of the tumor was soft, friable, and vascular with a clear margin separating the tumor from the brain stem with an absent interface and vermian infiltration at places. We achieved a gross total resection (GTR) and histopathology revealed a choroid plexus carcinoma [Figure 2]. Figure 1 Noncontrast CT scan (First Row) showing heterogenously hypeerdense mass lesion in the posterior fossa compressing the fourth ventricle causing hydrocephalus. MRI showing posterior fossa lesion with cystic component hyperintense on T1, T2, and FLAIR (Second ... Figure 2 Micro-photograph shows solid as well as papillary architecture with nuclear atypia and many atypical mitosis. (H and E, ×20) The radiological imaging in our patient was unique in that the T1 and T2 sequences revealed a hyperintense signal suggestive of methemoglobin, high protein, or fat contents. However, in the absence of a fluid level we ruled out a prior hemorrhagic cyst. Furthermore, the CT scan images showed a slight hyperdensity within the lesion enabling us to rule out a high lipid containing lesion. The overall picture suggested a cystic solid lesion with high protein content. The differential in such cases would be craniopharyngiomas or atypical teratoid tumor and ependymoma with cyst.[1] Rare cases of ectopic fourth ventricular have been reported.[5] Craniopharyngiomas often appear isointense on T1, hyperintense on T2 with ring enhancement on contrast MRIs and, DWI shows no restriction.[1] Atypical teratoid tumor or teratomaand, ependymomas with a cystic component may share features with choroid plexus carcinoma. Atypical teratoid tumors are heterogeneously hypo-to isointense on T1, iso-to hyperintense on T2 with heterogenous contrast enhancement on MRI and shows mild to moderate diffusion restriction on DWI.[4] Ependymoma are heterogeneously hypointense on T1, hyperintense on T2 and FLAIR with homogenous contrast enhancement on MRI. DWI shows no restriction.[4] Our case turned out to be a choroid plexus carcinoma. Tumors arising from the choroid plexus account for 0.4-0.6% of all intracranial tumors. Among these, 20-40% are choroid plexus carcinoma and 70% of them occur in younger than 2 years of age.[3] These lesions on MRI usually appear as contrast enhancing heterogenous large intraventricular mass that invades the ependyma or surrounding parenchyma with vasogenic edema. Usually they are isointense on T1 with areas of increased signal intensity due to hemorrhage, heterogenous hyperintense on T2 and homogenously enhancing on contrast MRI. On FLAIR sequence, they appear heterogenous with surrounding edema. DWI show no restriction.[4] Heterogeneity is likely to be due to cysts, hemorrhage, necrosis, and calcification.[6,9] Horska et al. studied MR Spectroscopy of childhood intraventricular lesions.[2] Both Choroid plexus carcinoma and papilloma was characterized by high levels of choline-containing compounds and a complete absence of creatine and the neuronal/axonal marker N-acetyl aspartate. However, the Choroid plexus carcinoma showed higher levels of choline compared with the choroid plexus papilloma, and it also had elevated lactate.[2] MRS was not performed in our patient. MRS may provide additional diagnostic information but is neither sensitive nor specific in these cases. Treatment strategies include surgical resection followed by radiotherapy and/or chemotherapy depending on the extent of resection achieved. GTR of choroid plexus carcinoma increases the overall survival as well as progression free survival and is recommended if it can be safely performed. Five-year survivals are 58.1 ± 6.1% and 20.9 ± 5.1% for GTR and STR, respectively.[7] The role of adjuvant chemotherapy and/or radiotherapy in choroid plexus carcinoma is controversial, but increasing evidence suggests that combined radiation and chemotherapy should be given after subtotal resection.[8] Radiation is recommended following GTR in adults but not in children. Neoadjuvant chemotherapy (ifosfamide, carboplatin, and etoposide or ICE) regimen in choroid plexus carcinoma has shown to reduce vascularity, thereby increasing the chances of complete resection.[3] In case of subtotal resection, a reexploration to achieve a GTR may be attempted after completion of chemotherapy. This combined approach increases the survival rate.