Chapter Clinical Summary
Academic synthesis, diagnostic methodology, and surgical recommendationsSpinal arthroplasty (total disc replacement, TDR) was engineered to maintain physiological segment motion, preserve native kinematics, and prevent adjacent segment degeneration (ASD) associated with traditional fusion procedures. In the cervical spine, Cervical Disc Arthroplasty (CDA) has achieved extensive clinical validation, demonstrating equivalent or superior functional outcomes and lower adjacent segment reoperation rates compared to anterior cervical discectomy and fusion (ACDF) in properly selected single- and two-level soft disc disease. In the lumbar spine, Lumbar Total Disc Arthroplasty (TDA) offers motion preservation for severe single-level discogenic low back pain in young, active patients without facet arthrosis or deformity. However, arthroplasty is not a universal substitute for arthrodesis: its clinical success relies strictly on precise patient selection, strict adherence to exclusion criteria (severe facet degeneration, osteoporosis, segmental instability, and spondylolisthesis), and flawless surgical technique with true midline positioning.
Detail the biomechanical principles, prostheses designs, indications, contraindications, surgical techniques, and clinical outcomes of cervical and lumbar spine arthroplasty. The reader will learn to select ideal candidates, position implants accurately along the true midline, manage heterotopic ossification, and prevent complications such as subsidence, migration, and facet overload.
Spinal fusion eliminates motion at the index level, increasing intradiscal pressures and shear stresses on adjacent mobile segments, accelerating adjacent segment disease. Disc arthroplasty restores disc height, maintains physiological range of motion (flexion, extension, lateral bending, and axial rotation), and normalizes load distribution across posterior facet joints.
CDA is indicated for symptomatic cervical radiculopathy or localized myelopathy due to single- or two-level soft disc herniations refractory to conservative care in patients with preserved motion. Contraindications include severe facet arthrosis, marked cervical kyphosis, gross instability, severe osteoporosis, and ossification of the posterior longitudinal ligament (OPLL). Randomized controlled trials confirm durable motion preservation and lower adjacent segment surgery rates compared to ACDF.
Lumbar TDA is indicated for severe discogenic low back pain (Modic changes, disc collapse) at L4-L5 or L5-S1 unresponsive to comprehensive conservative management in patients aged 18 to 60. Strict exclusion criteria must be enforced: facet joint osteoarthritis, isthmic or degenerative spondylolisthesis, lumbar scoliosis, spinal canal stenosis, and osteoporosis.
Prostheses are classified by mobility (constrained, semi-constrained, unconstrained) and bearing materials (metal-on-polyethylene, metal-on-metal, ceramic-on-ceramic, elastomeric). Mobile-core designs allow self-centering and reduce shear forces at the bone-implant interface, while semi-constrained designs provide intrinsic limits against excessive translational displacement.
Precise midline identification using biplanar fluoroscopy is critical; off-center prosthesis placement leads to asymmetric facet loading and early wear. Thorough decompression without excessive uncinate or facet resection is essential. Complications include heterotopic ossification (Park-McAfee classification), implant subsidence, migration, wear debris, and late facet joint arthrosis.
In clinical practice, candidate selection is the single most critical factor determining arthroplasty success. In the cervical spine, dynamic flexion-extension radiographs must demonstrate at least 3° to 4° of preserved baseline segmental motion and an absence of facet ankylosis. In the lumbar spine, facet joints must be evaluated by thin-slice CT to confirm pristine cartilage without hypertrophy or sclerosis. Intraoperatively, the true anatomical midline must be marked on the superior and inferior vertebral bodies under fluoroscopy prior to milling or rasping. The implant must match the footprint of the endplates perfectly to prevent subsidence while avoiding oversized heights that over-distract facet joints. Postoperative follow-up should monitor for heterotopic ossification, maintaining motion with appropriate anti-inflammatory protocols.