Proximal junctional kyphosis above long spinal fusions.

Introduction: Spinal deformity in adults is a major public health problem. After failure of conservative treatment, correction and fusion surgery leads to clinical and radiological improvement. However, mechanical complications and more particularly - proximal junctional kyphosis (PJK) - are common with an incidence of 10%-40% depending on the studies.

Analysis: Several risk factors have been identified and can be grouped into three categories. Among the patient-related factors, advanced age, comorbidities, osteoporosis and sarcopenia play a determining role. Among the radiological factors, changes in sagittal alignment (cranial migration of thoracolumbar inflection point, over-correction of lumbar hyperlordosis, preoperative thoracolumbar kyphosis) play a key role. Finally, the fusion technique itself may increase the risk of PJK (use of screws instead of hooks) as a surgical factor.

Prevention: Prevention happens at each phase of treatment. A patient assessment is done preoperatively to identify those at risk of PJK. Treating osteoporosis is beneficial. The surgical strategy must also be adapted: the choice of transitional implants such as sublaminar links or hooks and the use of ligament reinforcement techniques can help minimize the risk of PJK. Finally, methodical clinical and radiological follow-up will help to detect early signs of PJK and allow a surgeon to reoperate right away.

Treatment: Not all PJK requires surgical revision. Radiological monitoring and functional treatment is sometimes sufficient. However, if the patient develops pain, neurological complications or instability detected by imaging (unstable fracture, spondylolisthesis, spinal cord compression), revision surgery is necessary. It may consist of proximal extension of the fusion combined with decompression of the stenosis levels at a minimum.

Conclusion: PJK is a major challenge for surgeons. The best treatment is prevention, with a thorough analysis of risk factors leading to a well-planned and personalized surgery. Regular postoperative follow-up is essential.

Level of evidence: Expert opinion.