General
- CSD Patients are Intrinsically More Frail: CSD patients are generally more frail than those with thoracolumbar deformity and tend to have a higher number of medical comorbidities, which likely contributes to their higher postoperative complication rates.
Pathology of CK
- Any disruption of this balance can lead to a sagittal abnormality, most commonly a kyphotic deformity.
- Kyphosis begets kyphosis: CK shifts the load axis anteriorly → increasing the axial load on the anterior column → can cause wedge deformation of VBs and discs → leading to the progression of kyphosis
- Flexible vs. Fixed Kyphosis:
- CK is defined as fixed kyphosis if dynamic flexion-extension radiographs show less than 50% deformity reduction and CT scans show segmental ankylosis.
Aetiology
- Advanced degenerative disease
- Trauma
- Neoplastic disease
- Infection
- Systemic arthritides (e.g., ankylosing spondylitis, rheumatoid arthritis), and iatrogenic processes, which are the most common.
- Idiopathic
- Iatrogenic
- Postlaminectomy Kyphosis (PLK):
- Most common post-surgical deformity
- Incidence as high as 21% after laminectomy for cervical spondylotic myelopathy.
- PLK results from the disruption of posterior cervical stabilising structures, such as the tension band formed by interspinous ligaments, ligamenta flava, laminae, and facet joint complexes.
- Laminectomy of C2 and/or C7, multilevel removal of laminae, and significant facet joint removal may increase risk.
- Prevention of PLK:
- Posterior instrumentation and spinal fusion may be recommended in patients with predisposition to instability.
- Laminoplasty is also a prophylactic option, though a high rate of deformities has been reported even after laminoplasty.
- Failed Anterior Surgery:
- Pseudarthrosis OR
- Failure to restore normal cervical lordosis during anterior cervical surgery.
- Radiotherapy:
- Particularly in children, radiotherapy can impair bone growth, leading to kyphosis.
Mechanism
- Deformity
- Progressive cervical kyphosis leads to myelopath
- Kyphosis forces the spinal cord against vertebral bodies →
- Increasing longitudinal cord tension on the cord (since cord is tethered to the dentate ligaments and the cervical nerve roots) → Anterior cord pathology → Neuronal loss + demyelination
- Flattening small blood vessels → Reduced blood supply to the cord → Neuronal loss + demyelination
- Zhang 2011
- cervical cord is significantly longer in flexion than in the neutral or extension positions.
- cord available space: greatest > neutral position > flexion > extension
- cord impingement more likely on extension than flexion
- Primary cervical malalignment:
- in which flexion/kyphosis is the predominant position of the spine → myelopathy due to cord lengthening, flattening, and vascular compromise.
- The posterior neural arch is responsible for the majority of the load transmission through the cervical spine:
- Naturally the C spine is lordotic → allows posterior neural arch to distribute most of the load posteriorly.
- Removal of C spine arch → loss of stability (might not be destabilized initially) → Over time, the added there is a shift in load bearing from the posterior column to the anterior column → causes the discs and vertebral bodies become wedged with greater sagittal malalignment during the course of months to years → cervical kyphosis → draping of the cord → myelopathy
Risk Factors for Post Laminectomy Kyphosis
- Age (paediatric patients and young adults are more prone due to ongoing spinal growth, ligament laxity, and incomplete ossification of VBs)
- Preoperative lordosis loss
- Spinal instability
- Presence of intramedullary tumours
- Extent/number/location of laminectomies and facetectomies
Clinical Presentation:
- Neck pain
- Partly due to the cervical musculature being at a biomechanical disadvantage, requiring constant contraction.
- Neurological deficits
- Types
- Myelopathy
- Radiculopathy
- Quadriparesis
- Quadriplegia
- Due to
- Stenosis of the central canal and/or neuroforamina.
- The spinal cord can be "draped" over the dorsal aspect of the VBs at the kyphosis apex (the "bowstring effect"), leading to increased mechanical stress, microvascular compression, ischemia, myelomalacia, and spinal cord atrophy. Repetitive trauma to the cord during normal cervical flexion/extension can also contribute.
Tetreault 2017 mJOA
Severity | mJOA |
Mild | 15-17 |
Moderate | 12-14 |
Severe | 0-11 |
Nurick Grade For Myelopathy
Grade | Signs and Symptoms |
0 | Root symptoms only or normal |
1 | Signs of cord compression; normal gait |
2 | Gait difficulties but fully employed |
3 | Gait difficulties prevent employment; walks unassisted |
4 | Unable to walk without assistance |
5 | Wheelchair or bed-bound |
- Severe kyphosis → chin settling onto the chest.
- Can cause significant disability:
- Impaired forward vision
- Dysphagia (difficulty swallowing)
- Dyspnoea (difficulty breathing)
- Compensatory lumbar hyperlordosis may also develop, leading to low back pain.
Radiological Evaluation:
- Plain X-rays:
- Anteroposterior (AP) and lateral views,
- Kyphosis is measured locally or regionally (C2-C7) and globally
- Dynamic flexion-extension radiographs
- to assess flexibility and occult instability
- Standing long-cassette views
- for overall sagittal balance
- CT Scans:
- Used to identify segmental ankylosis in the anterior column and/or posterior facet joints
- Assess implant placement accuracy
- Detect fusion or pseudarthrosis.
- CTA: Vertebral artery anatomy
- MRI Scans:
- Evaluate spinal cord and nerve root compression.
- If CSF is present dorsal to VBs on T2-weighted sagittal MRI can indicate VBs suitable for anterior implant fixation during anterior construction
- A ratio of anteroposterior diameter between the spinal cord at the apex and the medullopontine junction below 0.3 on MRI is a risk factor for cervical myelopathy progression.
Surgical Treatment
Surgical algorithm for cervical deformity
- Hann algorithmn
- Hann paper has very good examples
Approach | Mean Correction (Cobb angle) |
ventral release & fusion | 11°–32° |
dorsal PSO | 23°–54°; 35°–52° in CBVA |
combined | 24°–61.4° |
- Kim algorithmn
- Williamson 2023
- A hierarchical approach prioritizing
- Correcting C2 slope to < 10 degrees
- Ensure lower instrumented vertebral (LIV) inclination between 0 and 40 degrees
- Correct cSVA to < 3.5 cm
Indicated for
- Neurological compromise
- Severe mechanical pain
- Progressive deformity
- Progressive disability (e.g., dysphagia, difficulty with forward gaze).
Goals of surgery
- Neural decompression
- Deformity correction
- Preoperative traction may be used to assess kyphosis reducibility.
- Spinal stabilisation with fusion.
Pre op considerations
- Left vs Right approach
- A left-sided approach is generally preferred in patients with normal vocal cord function due to the longer course of the recurrent laryngeal nerve.
- In cases of significant coronal deformity, approaching from the convex side is often easier.
- Neuro-monitoring
- Intraoperative neuro-monitoring baseline readings taken before any head/neck manipulation.
- Blood Pressure:
- For patients with spinal cord compression, MAP > 80 mmHg throughout the operation.
- Patient Positioning:
- Gardner-Wells tongs with approximately 15 lbs of traction are used to maintain proper rotational and coronal alignment.
- For rigid deformities, folded sheets are placed under the upper thoracic region to suspend the patient's head.
- The surgeon must anticipate the need to push the head back after the osteotomy.
- After completing the anterior osteotomy, the surgeon will ask the anesthesiologist to remove the sheets one at a time from under the head while the surgeon pushes on the forehead of the patient thru the sterile drapes → Osteoclasis (intentional breaking of the bone) of the posterior fusion mass in a controlled manner → After the deformity has been corrected, the head will be resting on the operating table
- The greater the magnitude of the desired correction, the higher the head must be off of the table.
Surgical approaches
Posterior approach:
- Indication:
- Flexible kyphosis
- Kyphosis due to ankylosing spondylitis.
- Techniques:
- Cervical pedicle screw fixation
- Indication
- Used for flexible degenerative kyphosis
- Used in evere deformity,
- osteoporosis
- performing revision surgeries after previous lateral mass screw placement.
- Enhanced Fixation Strength:
- Biomechanically, pedicle screws provide stronger fixation compared to traditional lateral mass screws.
- Improved Safety with Navigation:
- Advances in neuronavigation have enabled their safe and accurate placement, addressing previous concerns regarding neurovascular injuries with freehand techniques.
- Additional Proximal Fixation:
- They can be utilised for additional proximal fixation in constructs, which can be advantageous in procedures like pedicle subtraction osteotomy (PSO) to leverage strong proximal fixation for correction.
- Lateral mass screw fixation
- Less morbidity
- Posterior cervical extension osteotomy:
- See Cervical spine osteotomy
- For cases like ankylosing spondylitis, involving extensive laminectomy and facet joint removal, followed by head extension and internal fixation or halo vest.
- Associated with a high incidence of morbidity.
- Multirod Constructs:
- Increased Stability: When 3-column osteotomies (3CO) are necessary for correction, multirod constructs are considered for added stability.
- Reduced Mechanical Complications:
- In thoracolumbar deformity, the use of multiple rods across the lumbosacral junction has been associated with lower rates of
- Pseudarthrosis,
- Rod fracture,
- Need for reoperation.
- This suggests similar benefits for cervical constructs.
- Reinforcement of Osteotomy Sites: A third rod can be placed across an osteotomy site, such as a T2 pedicle subtraction osteotomy, for added stability.
Anterior approach:
- Pros
- Preferred by surgeons due to familiarity
- Ability to perform ventral decompression (where spinal cord compression usually occurs)
- Direct correction of deformity
- It is associated with lower rates of morbidity and mortality compared to the combined approach.
- Anterior cervical plating systems significantly improved stability by resisting flexion, extension, rotation, and lateral forces.
- Anterior corpectomies and arthrodesis without internal fixation.
- Lead to complications like graft dislodgement, loss of correction, and pseudarthrosis despite halo vest immobilisation.
- Hybrid decompression (corpectomy at compressed levels, discectomy at others) combined with multilevel instrumented fusions
- A more modern approach
- Pros
- Good clinical and neurological improvements
- Effective CK correction
- Decreased graft-related complications.
- Outcomes Comparison (vs. combined):
- Achieves a smaller reduction of CK (mean correction angle 23.0°).
- Lower rates of postoperative neurological deterioration (1.72%), complications (33.7%), revision surgery (11.9%), and mortality (4.2%). This may be due to familiarity with the procedure and fewer instances of neural injury.
- Higher rate of non-union (5.2%). Most complications are reconstruction-related, and revision surgeries are often for salvage after reconstruction failure.
- Surgical procedure
Combined Anterior and Posterior Strategy:
- Indications:
- Dorsal spinal cord compression and/or facet joint ankylosis is present
- When anterior approach alone is insufficient for correction.
- Patents with
- Significant instability factors (e.g., three-level corpectomies with laminectomy)
- Poor bone quality.
- Pros:
- Allows both ventral and dorsal osteotomies and release
- Thoroughly decompresses the spinal cord
- Effectively corrects kyphosis by lengthening the anterior column and shortening the posterior column
- Results in a greater degree of correction (mean correction angle 30.0°) and is more likely to achieve cervical lordosis.
- Provides strong dual fixation (dorsal and ventral)
- This dual fixation helps resist spinal translation/torsion, reduces graft-related complications, and increases fusion rates
- Cons
- Higher rate of postoperative
- Neurological deterioration (6.6%)
- Complications (48.9%)
- The higher rate of complications (e.g., gastrostomy/tracheostomy due to airway/swallowing dysfunction) may be linked to the stretching of contracted oesophagus and other neck structures during larger kyphosis correction.
- Revision surgery (12.5%)
- Mortality (6.3%)
- Lower rate of non-union (1.92%) due to combined anterior and posterior stabilization.
- Surgical sequence of Combined Procedures: Deformity correction can be achieved during either the anterior or posterior stage.
- Anterior-Posterior (AP):
- Most common sequence
- Anterior discectomies/osteotomies and grafting → by posterior instrumentation/osteotomies/correction.
- This is considered optimal when correction is achieved in the anterior stage.
- Posterior-Anterior-Posterior (PAP):
- Used for very severe kyphosis where anterior approach is initially difficult.
- Posterior release of ankylosis → anterior decompression/correction/reconstruction → posterior instrumentation/fusion.
- Anterior-Posterior-Anterior (APA):
- May be optimal to prevent anterior grafts from loosening/migrating during posterior correction
- May increase airway/swallowing complications.
- Posterior-Anterior (PA):
- Used when there is no anterior column ankylosis, with the anterior procedure reconstructing load-bearing capacity after posterior correction.
Surgical technique
Extent of Instrumentation and Fusion
- Determined by the etiology, location of deformity, bone quality, and extent of prior surgery.
- Generally, instrumented vertebrae include the most rostral and caudal involved in the deformity curve, often extending one to two levels into normal vertebrae to enhance correction and maintenance.
- In severe cases, fixation can extend from C2 to the upper thoracic spine.
Instrumentation and Grafts
- Instrumentation:
- Anteriorly, rigid or dynamic cervical plating systems are used.
- Posteriorly,
- Screw-rod systems (evolving from lateral mass screw-plate systems) facilitate transition from cervical to thoracic instrumentation.
- Cervical pedicle screws are also used.
- Grafts:
- Autografts (iliac crest, fibula), allografts, titanium structural grafts, and PEEK cages are employed.
- Local autograft
- Autografts are optimal for previous pseudarthrosis.
- rh-BMP often fills allografts/cages.
Postoperative Immobilisation
- Most patients are immobilised with a hard cervical collar for 2-3 months.
- More rigid support like a Philadelphia collar or cervicothoracic orthosis, or even a halo vest, may be used for occipitocervical/cervicothoracic fixations, osteoporosis, or prior fusion failure.
Surgical complications
- Complication:
- Overall rate
- Cervical kyphosis corrections
- 34% Perioperative complications (26/76)
- Traumatic fractures
- AS 51.1%
- DISH 32.7%
- By types of complications:
- Deep vein thrombosis (10.5%)
- Deep wound infection (7.9%)
- Pneumonia (5.2%)
- Pulmonary embolism (3.9%)
- Postoperative hematoma (3.9%)
- Non-transient dysphagia (>1 month) requiring a feeding tube (2.6%)
- Neurological Injury: 13.5%
- Most seen in patient who has undergone dorsal osteotomy at the cervicothoracic junction.
- Traumatic AS fractures 67.2%
- Traumatic DISH fracture 40.0%
- C5 root palsies may result from nerve root traction during kyphosis correction.
- Pseudarthrosis (3.8%)
- By surgical approach: (By Han et al)
- Gastrostomy/tracheostomy (12.0%)
- Deaths (7.6%)
- Progression of adjacent segment deformity (4.3%)
- Radicular symptoms (4.3%)
- Wound dehiscences (n=4)
- Hardware failures (n=3)
- Durotomy (n=3)
- Wound infections (n=2)
- Pseudoarthrosis (n=2)
- Quadriparesis (n=1)
- Quadriplegia (n=1)
- Construct failure (n=1)
- Dysphonia (n=1)
- Transient dysphagia (n=1)
- Airway and swallowing problems are particularly noted after multilevel anterior procedures.
- Graft dislodgments (4.2%)
- Pseudoarthrosis (1.1%)
- Screw loosening (3.2%)
- Vocal cord paresis (5.3%)
- Deaths (n=4)
- Pneumonia (n=4)
- Dysphagia (n=3)
- Neurological deterioration (n=2)
- Infection (n=2)
- Dural tear (n=1)
- Deep venous thrombosis (n=1)
- Reintubation (n=1)
- Wound dehiscence (n=1)
- Graft-related complications: 5 patients (5.3%).
- Implant-related complications: 3 patients (3.2%)
- Dorsal Approach (27%)
- Serious Immediate Perioperative Complications associated with surgical correction of cervicothoracic junction (CTJ) kyphosis include
- Massive hemorrhage
- Aortic dissections
- Strokes
- Vertebral artery injury.
- There was a greater risk of complications with the degree of kyphosis correction.
Combined approach (40%)
Ventral approach (33.7%)
- Mortality Rates:
- Cervical kyphosis 3.1% to 6.7%.
- AS 6.4%
- DISH 7.3%
Outcomes
- For Ankylosing diseases
- Patients who did not achieve the goal for kyphosis correction and had persistent kyphosis postoperatively experienced worse long-term Quality of Life (QOL) scores (as measured by modified Japanese Orthopedic Association scores) compared to those who gained cervical lordosis (CL) on follow-up.
- Conservative vs surgery outcome
- While serious immediate perioperative complications occurred with surgery, long-term complications such as pneumonia, respiratory insufficiency, nonunion, and further neurological deficits were much more prevalent in the conservative (non-surgical) management group.
- For Anterior vs combined procedures: (Han et al)
Surgical strategy | Neurological deterioration rate (%) | Correction degree | Postoperative kyphosis | Non-union rate (%) | Comp. rate (%) | Revision rate (%) | Mortality (%) |
Anterior | 1.72 | 23.0° | 3.5° | 5.20 | 33.7 | 11.90 | 4.20 |
Combined | 6.60 | 30.0° | −3.5° | 1.92 | 48.9 | 12.50 | 6.30 |
Total | 4.20 | 23.8° | 2.4° | 3.40 | 40.7 | 12.20 | 4.80 |
- Durable Improvement in Health-Related Quality of Life (HQROLs):
- Over 50% of CSD patients experience durable improvements in HQROLs over 1 to 3 years post-operative follow-up.
- Studies show that between 19-44% of patients met the minimum clinically important difference (MCID) for improvement in measures such as mJOA, NDI, or EQ-5D at 1-year follow-up.
- More than 50% of patients met MCID for
- EQ-5D (56.6%),
- neck pain Numeric Rating Scale (61.8%),
- NDI (55.6%)
- Sustained improvements in HQROLs have been reported at 2-year and even mean 3.4-year follow-up timepoints, with 37.3-62.3% of patients meeting MCID across various metrics.
- Challenges in Achieving Radiographic Alignment Targets:
- Achieving proposed radiographic alignment goals remains a significant challenge.
- While most patients show SOME improvement in C2-7 sagittal vertical alignment (cSVA) (96.3%),
- Only 1/3 to 1/2 improve in other key parameters like T1 slope-cervical lordosis (TS-CL) or horizontal gaze.
- Surgeons often fall short of their initial alignment goals, particularly in cases with greater baseline deformity, for example, by
- 17.2 mm for cSVA
- 15.6 degrees for TS-CL,
- Improvements in radiographic alignment do not always correlate with improvements in patient-reported outcome measures (HQROLs).
- This highlights a need for further refinement in both radiographic targets and HQROLs to better capture successful outcomes.
- Persistently High Complication Rates:
- Overall complication rate from CSD surgery to be 43.6%–56%, with a mortality rate of 9.2% at a mean 1.1-year follow-up.
- Common complications include
- Dysphagia
- Respiratory failure,
- New neurological deficit,
- Wound infection,
- Distal junctional kyphosis (DJK) or failure (DJF).
- While some later cohorts have shown lower overall and neurological complication rates (e.g., 23% vs. 38% overall, 2% vs. 16% neurological), DJK and DJF rates have remained consistently high.
- Long-term mortality rates are also significant, with one study reporting 18.2% of patients having died at 10-year follow-up.
- The persistently high complication rates might be partly explained by technical advances allowing more frail, medically complex patients to undergo CSD correction.
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