Biomechanical effect of different lumbar interspinous implants on flexibility and intradiscal pressure

Interspinous implants are used to treat lumbar spinal stenosis or facet joint arthritis. The aims of implanting interspinous devices are to unload the facet joints, restore foraminal height and provide stability especially in extension but still allow motion. The aim of this in vitro study was to compare four different interspinous implants––Colfex, Wallis, Diam and X-Stop––in terms of their three-dimensional flexibility and the intradiscal pressure. Twenty-four human lumbar spine specimens were divided into four equal groups and tested with pure moments in flexion/extension, lateral bending and axial rotation: (1) intact, (2) defect, (3) after implantation. Range of motion and the intradiscal pressure were determined.In each implant-group the defect caused an increase in range of motion by about 8% in lateral bending to 18% in axial rotation. Implantation had similar effects with all four implants. In extension, Coflex, Wallis, Diam, and X-Stop all overcompensated the instability caused by the defect and allowed about 50% of the range of motion of the intact state. In contrast, in flexion, lateral bending and axial rotation the values of the range of motion stayed about the values of the defect state. Similarly the intradiscal pressure after implantation was similar to that of the intact specimens in flexion, lateral bending and axial rotation but much smaller during extension. All tested interspinous implants had a similar effect on the flexibility: they strongly stabilized and reduced the intradiscal pressure in extension, but had almost no effect in flexion, lateral bending and axial rotation

Estudo prospectivo comparativo entre pseudoartrose e fusão óssea na estenose de canal lombar Prospective-comparative study between pseudarthrosis and bone fusion in lumbar stenosis

OBJETIVO: Estudo prospectivo comparativo entre pseudoartrose e fusão óssea na estenose de canal lombar MÉTODO: 38 pacientes operados de estenose de canal lombar e submetidos à artrodese avaliados por meio de questionários (escala visual analógica - VAS e questionário de incapacidade Rolland Morris). Foram solicitadas radiografias para avaliação da fusão lombar. RESULTADOS: Foi observada uma efetiva melhora entre o momento pré-operatório e após um ano em relação ao VAS, tanto no grupo que obteve fusão óssea como no grupo com pseudartrose. Em relação ao questionário Rolland Morris houve uma tendência de melhora no grupo com fusão óssea e uma significante melhora no grupo com pseudoartrose. CONCLUSÃO: Não houve diferença entre os grupos (fusão óssea e pseudoartrose) em relação à dor e incapacidade. Nível de Evidência: Nível II, estudo prospectivo longitudinal.<br>OBJECTIVE: Prospective-comparative study between pseudarthrosis and bone fusion in lumbar stenosis METHODS: 38 patients operated on for lumbar spinal stenosis and submitted to arthrodesis were evaluated by the Visual Analogue Scale (VAS) and Roland Morris Disability Questionnaire. Radiographs were requested to evaluate spinal fusion. RESULTS: An effective improvement was observed between the preoperative period and one year after the operation, in relation to VAS, both in the group that received a bone fusion and in the group with pseudarthrosis. With regard to the Roland Morris questionnaire, there was a tendency towards an improvement in the bone fusion group and a significant improvement in the pseudarthrosis group. CONCLUSION: There was no difference between the groups (bone fusion and pseudarthrosis) in relation to pain and disability. . Level of Evidence: Level II, longitudinal prospective study