Spinal Surgery Flashcards
Degenerative cervical spinal disease
A broad term encompassing a number of pathologies resulting in structural changes in the joints i.e. the intervertebral disc, facet joints and the uncovertebral joints which can potentially lead to compression of neural structures, deformity, pain and disability.
Factors affecting the rate of degenerative change
Load and intensity of use over time
Smoking, genetics, localised trauma, infection.
Pathophysiology of degenerative cervical spinal changes
Intervertebral discs bear the load of the head and neck.
Axial loading through the nucleus pulposus of the disc is converted to hoop stresses acting on the annulus fibrosus and the vertebral endplates.
This alters the cellular composition of the nucleus pulposus with reduction in hydrophilic proteoglycans and increased collagen.
The mechanical properties of the disc change with the loss of intervertebral height and cracks and fissures appearing predisposing to the pulposus herniation.
Consequences of altered mechanical stresses in degenerative cervical spinal disease
Transferred to the facet joints leading to segmental hypermobility with osteophytic spurs deposited in an adaptive remodelling process meant to confer increased stability.
Ligamentous hypertrophy also occurs
Commonest levels affected by degenerative cervical spinal disease
C5/6
C6/7
Cause of neural compression in the cervical spine of patients <55
Tends to be soft disc prolapse encroaching into the spinal canal or the neural exit foramina causing myelopathy or radiculopathy
Cause of neural compression in the cervical spine of patients >55?
Osteophytes and thickened annulus
Morphology of the degenerated cervical spine
Alters normal cervical lordosis leading to straightening or the adoption of kyphotic, hyperlordotic or scoliotic curvatures
At what degree of stenosis of the spinal canal does myelopathy result?
Reduction in the cross-sectional area >30%
Normal cervical canal diameter
18mm
Normal cervical cord diameter
10mm
Pathophysiological mechanisms contributing to cord injury in degenerative cervical myelopathy
Static compression results in direct trauma and chronic cord ischaemia
Dynamic compression results from excessive translational movements.
Neuroinflammatory response triggers a cascade of cellular events causing demyelination of the corticospinal tract, central grey matter degeneration with loss of interneurons, anterior horn cell atrophy and gliosis.
Symmetrical involvement of motor and sensory tracts
Bilateral weakness below the affected level
Paraesthesia, numbness, tingling and sensory loss with a discrete sensory level
?Cervical myelopathy
Examination findings in DCM
Increased tone
Brisk and pathological reflexes
Symptoms of difficulty with sphincter control
Symptom progression in DCM
Insidious onset with steady deterioration in hand control, progressive clumsiness, gait unsteadiness, falls.
What is the most common clinical presentation of degenerative cervical disease?
Radiculopathy from compression of a nerve root
Motor and sensory deficits with reduced deep tendon reflexes in the distribution of the affected nerve root
Pain with associated reduced movements radiating into the arm as brachalgia
Positive root compression tests can reproduce pain
?Cervical radiculopathy
Ix in diagnosis of degenerative cervical disease
MRI
Dynamic cervical spine radiographs can assist in operative planning
CT may be useful for assessing the degree of osteophytosis and the extent of foraminal stenosis
Myelography has excellent sensitivity for detecting SC compression
Surgical decompression in DCM
Indicated in most patients because the majority deteriorate over time.
Timing of intervention in DCM
Earlier intervention in symptomatic cervical myelopathy is associated with improved outcomes.
Chronic neurological deficit is unlikely to improve.
Conservative vs surgical Mx of cervical radiculopathy
RCTs have shown that surgery rapidly improves symptoms but in the long term PT and Sx are equally effective
Aim of surgical decompression in DCM?
Halt disease progression
Outcomes in DCM decompression
60-70% of patients improve
30% have stable disease
10% continue to progress
Outcomes in surgical treatment of cervical radiculopathy?
90% have improvement in arm symptoms
OPLL
Ossification of posterior longitudinal ligament
OLF
Ossification of ligamentum flavum
Pathophysiology of OPLL and OLF
NIDDM, IGT, excessive weight gain, hypoPTHism and hypophosphataemic rickets all implicated.
More common in Japan.
Ectopic bone forms within the ligaments, with ossification, ligamentous hyperplasia, cell proliferation and vascular ingrowth seen.
Classification of OPLL
Based on CT findings
Hirbayashi
Hirayabashi classification of OPLL
a) Continuous type
b) Segmental
c) Circumferential (confined to disc space)
d) Mixed type
Impact of OPLL on surgery
Complicates anterior surgical decompression and dramatically increases the risk of intraoperative durotomy.
When ossification bridges the disc spaces, segmental mobility is reduced and the PLL fuses with thecal sac.
Posterior approach is inidcated
Pathology of RA
Involves novel antigenic expression by synovial cells, leading to persistent cellular activation and immune complex production (RF- IgM).
Cytokine mediated chronic inflammation is initiated (IL-1, 6, TNF-alpha)
Results in granulation deposition within the synovium (rheumatoid pannus) which produces proteolytic enzymes capable of destroying adjacent cartilage, ligaments, tendons and bone.
Consequence of RA in the cervical spine
Destructive synovitis leads to ligamentous laxity and bony erosions with subsequent instability and subluxation.
Compression of neural structures can result from instability or from direct pannus compression.
Why are the upper cervical articulations primarily affected in rheumatoid cervical spinal disease?
Occiput/C1 and C1/2 because the normal ligamentous structures surrounding the occipito-atlantoaxial region conferring its significant strength and stability are degraded as part of the disease process.
What are the most common cervical spine pathologies in RA
C1/2 instability (65%)
Basilar invagination (20%)
Subaxial subluxation
Cause of C1-2 instability (atlantoaxial subluxation)
Results from the destruction of the transverse, apical and alar ligaments e.g. from rheumatoid pannus.
Also occurs in AS, achondroplasia, Down’s syndrome, Morquio’s syndrome and secondary to trauma.
Radiographic features of atlantoaxial subluxation
Plain XR
In a non-traumatic setting flexion and extension views may be performed. The expected distance between anterior arch of C1 and the dens in the fully flexed position should be <3 mm in an adult (~5 mm in a child).
In a vertical subluxation, the dens is often above the McGregor line by over 8 mm in men and 9.7 mm in women.
Atlantoaxial subluxation
Normal ADI in adults should be <3mm
Atlantoaxial subluxation
On CT, C1 is not orientated in line with the head. The head may be pointed anteriorly, C1 is turned. If this is a fixed defect, C2 is rotated in conjunction with C1.
Indications for surgical stabilisation of atlantoaxial subluxation
Asymptomatic with ADI >8mm
All patients with cervical myelopathy.
Normal posterior atlanto-dental interval?
>14mm
Basilar erosion
Occurs from erosion of occiput/C1 and C1/2 joints such that the dens migrates into the foramen magnum
May present with HCP, syringomyelia, progressive myelopathy
Chamberlain’s line
Extends from the hard palate to the opisithion (back of the foramen magnum)
The dens should be <3mm above this line
McGregor’s line
Extends from the hard palate to the most caudal point of the occipital curve
The dental tip should be <4.5mm above this line
McRae’s line
Drawn from the basion (front of the foramen magnum) to the opisthion (back of the foramen magnum)
The odontoid tip should not be above this line, is normally 5mm below.
Additional use of McRae’s line
Used to diagnose Chiari 1 malforamations where the cerebellar tonsils are seen to descend more than 3mm in children or 5mm in adults, below this line.
What is the difference between basilar impression and basilar invagination
The basilar impression is caused by softening of the bones of the skull base rather than migration of the dens upwards due to ligamentous instability
There can be brainstem compression as a result of the basi-occiput and condylar segment of the occipital bone leading to infolding of the foramen magnum.
Causes of basilar invagination
Most common is RA
Klippel-Feil
Osteogenesis imperfecta
Achondroplasia
Chiari malformations
Cleidocranial dysostosis
Schwartz-Jaempl Syndrome 2
Morquio’s syndrome
HyperPTH
Osteomalacia
Paget’s
Morquio’s syndrome
Morquio syndrome, also known as Mucopolysaccharidosis Type IV (MPS IV), is a rare metabolic disorder in which the body cannot process certain types of sugar molecules called glycosaminoglycans (AKA GAGs, or mucopolysaccharides). In Morquio syndrome, the specific GAG which builds up in the body is called keratan sulfate. This birth defect, which is autosomal recessive, is a type of lysosomal storage disorder. The buildup of GAGs in different parts of the body causes symptoms in many different organ systems.[2]:544 In the US, the incidence rate for Morquio is estimated at between 1 in 200,000 and 1 in 300,000 live births.
Klippel Feil syndrome
Klippel Feil syndrome (KFS) is a congenital, musculoskeletal condition characterized by the fusion of at least two vertebrae of the neck. Common symptoms include a short neck, low hairline at the back of the head, and restricted mobility of the upper spine.
Cleidocranial Dysostosis
Cleidocranial Dysplasia (cleido = collar bone, + cranial = head, + dysplasia = abnormal forming), also known as Cleidocranial Dysostosis and Marie-Sainton Disease, is a condition characterized by defective development of the cranial bones and by the complete or partial absence of the collar bones (clavicles).
Schwartz-Jampel syndrome
Schwartz–Jampel syndrome (SJS) is a rare genetic disease caused by a mutation in the perlecan gene (HSPG2)[1] which causes osteochondrodysplasia associated with myotonia.[2] Most people with Schwartz–Jampel syndrome have a nearly normal life expectancy
Options for surgical treatment of basilar invagination?
Traction
Anterior decompression
Craniocervical fusion with or without foramen magnum decompression
Basilar invagination with no cranial nerve palsies
Posterior fusion is usually adequate.
Preoperative traction may help to predict whether adequate reduction can be achieved intra-operatively.
Basilar invagination with cranial nerve palsies
Anterior transnasal or transoral resection of the odontoid peg.
Def: Platybasia
Flattening of the skull base
Usually asymptomatic unless associated with other abnormalities.
Skull base angle is formed by a line joining the nasion with the centre of the pituitary fossa and a line joining the anterior border of the foramen magnum with the centre of the pituitary fossa
Platybasia is present if this angle is >143
Basilar kyphosis angle
If the angle from lines drawn from nasion to pituitary fossa and then to the anterior border of the foramen magnum is <125 degrees
Associations of platybasia
Basilar invagination
Achondroplasia
Down’s Syndrome
Chiari malformations
Craniocleidodysostosis
Craniofacial anomalies
Osteogenesis imperfecta
Paget’s
Osteomalacia
Ricket’s
Fibrous dysplasia
HypoPTH
Types of seronegative spondyloarthropathies
PEARU
P: psoriatic arthritis
E: enteropathic arthritis (i.e. extraintestinal manifestation of IBD)
A: ankylosing spondylitis
R: reactive arthritis (Reiter syndrome)
U: undifferentiated spondyloarthritis
Associations of AS
HLA-B27 genotype seen in 80-98% of affected pateints
Cervical spine manifestations of AS
Stiffness from joint and ligament ossification and kyphosis.
Leading to chin on chest deformity.
When should surgical correction of AS kyphotic spine be considered?
Only if concomitant thoracolumbar and hip/knee joint abnormalities excluded.
AS also leads to bony osteopenia which influences planning of instrumentation
Forestier Disease
Diffuse idiopathic skeletal hyperostosis
Presence of non-marginal syndesmophytes at three successive levels involving four contiguous vertebrae
Appears radiologically as flowing anterior ossification of the ALL with disc space preservation.
There is an absence of facet joint ankylosis, SI erosion, sclerosis and intra-articular osseous fusion
Indications for surgical management of DISH
Treated if canal stenosis becomes symptomatic
With large anterior syndesmophytes, dysphagia, stridor and hoarseness of voice may also be rare indications for intervention
General principles of anterior cervical approaches
Techniques for decompression include discectomy and corpectomy
Following decompression, decision . is made to either fuse the joint (arthrodesis) or to preserve motion (arthroplasty)
In fusion, autograft, allograft or synthetic graft may be used. This may be supplemented with anterior cervical plating.
Corpectomy
Involves removing some or all of the vertebral body
Indications for anterior cervical approach
Anterior compression of neural elements
Correction of cervical kyphosis
Contraindications to anterior cervical approach
Posterior compression
OPLL
Previous anterior cervical surgery and/or neck RTx with or without VC dysfunction should be considered relative contraindications
Asympatomic RLN palsy is common after anterior surgery so redo surgery should be on the same side unless laryngoscopy has proved that both vocal cords are working.
Patients reliant on voice should be counselled about the risk of VC injury.
Technical considerations in anterior cervical surgery:
Extensive osteophytes with OPLL
May require a corpectomy for more complete decompression
Technical considerations in anteiror cervical surgery:
Fusion rates
Fusion rates for single level surgery approach 100% but decrease with multilevel discecotmies.
Plating may thus confer a biomechanical advantage
Smoking and NSAIDs may impair fusion
Technical considerations in anteiror cervical surgery:
Multilevel corpectomy
Associated with a higher rate of implant dislodgement and failure.
Many surgeons thus prefer multilevel discectomies or augment the anterior construct with posterior instrumented fusion to improve biomechanics
Technical considerations in anterior cervical approahces
Single level discectomy
There is no difference in outcome with decompression alone and decompression with graft.
Not using a graft reduces cost and operative time as well as harvest site pain.
What is an advantage of synthetic grafts
Morbidity of donor site including pain, infection, haematoma, peripheral nerve injury or irritation.
Issues with supplemental anterior plating
Adds stability and strength in extension.
Strongest possible anterior surgical construct
Increases incidence of dysphagia
Conclusions regarding anterior cervical appraoches
No superior in anterior cervical discectomy alone or with cage over ACFG with fusion or corpectomy with fusion.
Approach to anterior cervical discectomy
Supine
Head ring, with jellyroll under shoulders.
Held tilt can help reduce venous pressure.
Skin incision over the pathological level with radiographic confirmation.
Transverse incision
Platysma divided and undermined.
Superficial cervical fascia and the bloodless avascular plane between SCM and carotid sheath laterally and the trachea and oesophagus medially are used to access the prevertebral fascias.
Important to palpate, identify and protect the carotid sheath.
Prevertebral fascia incised exposing the vertebral bodies, discs and longus colli muscles.
Medial border of longus colli is undermined and elevated.
Confirmation of disc level
Disc space incised and distracted.
Osteophytes removed.
Discectomy is completed with a combination of curettes, rongeurs and a drill.
PLL identified and removed. Dorsal osteophytes must be undercut in myelopathic patients. Neural exit foramina undercut in radiculopathy.
Graft can be used after discectomy.
Closure with dissolvable sutures
Wound drain.
Surface landmarks:
C3/4 level
Caudal to hyoid bone
Surface landmarks:
C4/5
Thyroid cartilage
Surface landmarks:
C5/6
Cricothyorid membrane
Surface landmarks:
C6/7
Cricoid cartilage
Factors determining which side to approach for ACDF?
Right RLN takes a less predictable course
On the left the thoracic duct is at risk, especially with low approaches near the cervicothoracic junction.
What is the bloodless plane sought during anterior cervical approaches?
Between the caroitd and SCM laterally and the trachea and oesophagus laterally.
What is this muscle?
What is its innervation?
Longus colli
Anterior rami of C2-6
What structure should be protected during the retraction of longus colli?
The sympathetic chain which is found superficially and 1cm lateral to its medial border
What helps identify the PLL
Its cranio-caudal orientation
Approach to anterior cervical corpectomy
As for discectomy
Discectomies are performed at the rostral and caudal level with a central channel of bone removed from the interventing vertebra
A width of 15-18mm is sufficient in most patients for decompression.
A rigid or expandable cage filled with bone graft can be used to reconstruct and restore aloignement
Preservation of cervical arthroplasty
To preserve segmental kinematics.
What are the main complications associated with anterior cervical approach?
Hoarsenss
Dysphagia
Haemorrhage
Dural tear
Oesopgageal injury
Paralysis worsening myelopathy
Horner’s syndrome
Infection
Adjacent segment disease
Rare:
Extrusion of graft
Vascular injury (vertebral or carotid artery, jugular vein)
Thoracic duct injury
Death
What is the risk of death in anterior cervical approach?
0.1%
Complications of anterior cervical approach
Incidnece:
Hoarseness of voice
4%
Complications of anterior cervical approach
Incidence:
Dyphagia
10%
Complications of anterior cervical approach
Incidence:
Haemorrhage
2-3%
Complications of anterior cervical approach
Incidence:
Dural tear
0.5%
Complications of anterior cervical approach
Incidence:
Oesophageal injury
<1%
Complications of anterior cervical approach
Incidence:
Paralysis worsening myelopathy
0.5% up to 5%
Complications of anterior cervical approach
Incidence:
Horner’s syndrome
<1%
Complications of anterior cervical approach
Incidence:
Infection
1%
Complications of anterior cervical approach
Incidence:
Adjacent segment disease
2.9% per annum
Anterior cervical approach complication features:
Voice hoarseness
Usually, 2o to RLN injury
Compression is thought to occur between retractors and the ETT cuff as the nerve runs in the tracheo-oesophageal groove underneath the inferior constrictor
Deflating and reinflating the ETT after positioning the retractor may reduce this complication.
Anterior cervical approach complication features:
Dysphagia
Risk factors include multi-level surgery
Older age
High profile plates
Lower levels
Must exclude implant migration
Anterior cervical approach complication features:
Haemorrhage
Risk factors include:
Absence of post-op drain, inadequate haemostasis
Can precipitate airway obstruction and post-op swelling.
Anterior cervical approach complication features:
Dural tear
More common in patients with OPLL (up to 25%)
Should be repaired intraoperatively with stitches, clips and fibrin sealant
Anterior cervical approach complication features:
Oesophageal injury
Risk factors include scarring from previous surgery
Early ENT or UGI involvement
Anterior cervical approach complication features:
Paralysis worsening myelopathy
Careful positioning and avoid overextension
Avoid over-distraction
Early post-op MRI to exclude haematoma.
Anterior cervical approach complication features:
Horner’s syndrome
Caused by excessive dissection of longus colli too laterally
Usually resolves
Anterior cervical approach complication features:
Infection
Risk factors include:
Immunosuppression and oesophageal perforation
Treat with Abx, implants may need removal
Anterior cervical approach complication features:
Adjacent segment disease
Symptomatic disease requiring treatment is about 2.9% per annum following fusion (1/4 of patients in 10y)
When should cervical arthroplasty be considered?
Younger patients with predominantly soft disc herniations
Contraindications to cervical arthroplasty
Inflammatory arthropathy
Infectious arthropathy
OPLL
DISH
Significant osteophytosis
Cervical instability
Radiological Ix ahead of cervical arthroplaty
Pre-operative CT and dynamic XR in all patients
Technical considerations for cervical arthoplasty
Identical approach to exposure as anterior cervical discectomy.
Care should be taken to avoid excessive decompression of the uncovertebral joints.
This may cause hypermobility of the treated segment and potential instability and implant failure.
What is an issue with excessive bone dust in arthroplasty
May increase the risk of post-op osteophyte formation or heterotopic calcification.
Types of posterior cervical approach
Laminectomy or laminoplasty for foraminotomy
Posterior cervical discecotmy for radiculopathy
Indications for posterior cervical approach
Hypertrophic ligamentum flavum and facets
Multilevel disease
OPLL
Congenital multilevel canal stenosis
Foraminal decompression
What are the benefits of posterior approaches
Avoid the risk of hoarse voice, dysphagia and adjacent segment disease.
Maybe preferable in elderly who are more likely to have multilevel disease with posterior cervical instability of less concern.
Supplemental fusion should be considered if there is instability or kyphosis
Approach to cervical laminectomy
Pone, flexed in a head clamp
Midline exposure through the nuchal ligament
Subperiosteal muscle elevation.
Radiological confirmation of the level
Laminectomy can be performed en bloc by drilling through bilaterally at the lamina-lateral mass junctions.
The ligamentum flavum can be dissected away from the theca to achieve decompression.
Piecemeal removal is another approach.
What may result with excessive posterior cervical muscle stripping and adjacent facet joint exposure?
Instability and progressive deformity (post-laminectomy kyphosis and swan-neck deformity)
What is the lateral limit for cervical laminectomy
Medial border of the lateral masses
What can cause cervical nerve root compression without myelopathy?
Facet joint spondylosis
Uncovertebral osteophytes
Foraminal disc herniation
What are some modified posterior cervical exposures
Skip laminectomy- alternate standard laminectomies at selected levels allow partial preservation of midline structures
Cervical laminoplasty- spinal canal diameter is augmented by repositioning the laminae and removing the ligamentum flavum
Approach to cervical foramintoomy
Prone, Mayfield, flexed.
Exposure can involve either ipsilateral muscle stripping or slitting.
The cranial and caudal laminae and the facet overlying the exiting nerve root are exposure.
Radiological confirmation
Fenestration achieved by removing bone from the cranial and caudal lamina and undercutting of the medial facet to decompress the exiting nerve root.
What is the limit on facet removal in cervical formainotomy
Removal of more than half of the facet compromise the shear strength of the spine
Complications of posterior cervical approach
Persistent neck pain
Kyphotic deformity
Intraoperative fusion can be considered if concern about instability.
Post-op neurological deficit (commonly C5 palsy)
What are the two main techniques for C1/2 stabilisation
Magerl’s C1/2 transarticular screw fixation
or
Harms-Goel technique of posterior C1 lateral mass screws with C2 pars/pedicle screws
Approach to Margerl’s C1/2 stabilisation
A single screw on each side is placed through the pars interarticularis of C2 passing through the C1/2 joint directed at the lateral mass of C1
It provides the most stable and rigid fixation biomechanically of the C1/2 joint with almost complete obliteration of rotation.
Contraindication to Magerl’s C1/2 fixation
Anomalous high riding vertebral artery
Technical considerations of Magerls’s C1/2 transarticular screws
Technically demanding with increased risk of vascular injury.
Care must be taken to avoid anterior perforation of the 1 lateral mass which could result in an injury to the pharynx, ICA and or lower cranial nerves.
Pre-op Ix for Magerls’
CTA
Approach to Magerl’s transarticular screws
Prone, skull clamp, flexed.
C1 posteiror arch and lateral masses, C2 laminae, C2 pars and C2/3 facet joints are exposed.
Caudal stab incisions may be required to obtain screw trajectory (usually 1-2cm lateral to the C7/T1 spinous process).
C1/2 joint capsule can be opened to denude the articular surface.
Drilling is fluoroscopic guided.
A bone graft can be sited on exposed surfaces to supplement the fusion
Fixation often supplemented with a Dickmann=Sonntag posterior sublaminar wire.
