Biomechanical considerations of the posterior surgical approach to the lumbar spine

The biomechanical consequence of posterior interventions at the thoracolumbar spine on the passively stabilized flexed posture

In the flexed end-of-range position (e.g., during slumped sitting), the trunk is passively stabilized. Little is known about the biomechanical consequence of posterior approaches on passive stabilization. The aim of this study is to investigate the effect of posterior surgical interventions on local and distant spinal regions. While being fixed at the pelvis, five human torsos were passively flexed. The change in spinal angulation at Th4, Th12, L4 and S1 was measured after level-wise longitudinal incisions of the thoracolumbar fascia, the paraspinal muscles, horizontal incisions of the inter- & supraspinous ligaments (ISL/SSL) and horizontal incision of the thoracolumbar fascia and the paraspinal muscles. Lumbar angulation (Th12-S1) was increased by 0.3° for fascia, 0.5° for muscle and 0.8° for ISL/SSL-incisions per lumbar level. The effect of level-wise incisions at the lumbar spine was 1.4, 3.5 and 2.6 times greater compared to thoracic interventions for fascia, muscle and ISL/SSL respectively. The combined midline interventions at the lumbar spine were associated with 2.2° extension of the thoracic spine. Horizontal incision of the fascia increased spinal angulation by 0.3°, while horizontal muscle incision resulted in a collapse of 4/5 specimens. The thoracolumbar fascia, the paraspinal muscle and the ISL/SSL are important passive stabilizers for the trunk in the flexed end-of-range position. Lumbar interventions needed for approaches to the spine have a larger effect on spinal posture than thoracic interventions and the increase of spinal angulation at the level of the intervention is partially compensated at the neighboring spinal regions.

Variability in wound closure technique in midline posterior lumbar fusion surgery. International survey and standardized closure technique proposal

Background:

Surgical wound complications represent an important risk factor, particularly in multilevel lumbar fusions. However, the literature regarding optimal wound closure techniques for these procedures is limited.

Methods:

We performed an online survey of 61 spinal surgeons from 11 countries, involving 25 different hospitals. The study included 26 neurosurgeons, 21 orthopedists, and 14 residents (Neurosurgery – 6 and orthopedics 8). The survey contained 17 questions on demographic information, closure techniques, and the use of drainage in posterior lumbar fusion surgery. We then developed a “consensus technique.”

Results:

The proposed standardized closure techniques included: (1) using subfascial gravity drainage (i.e., without suction) with drain removal for <50 ml/day or a maximum duration of 48 h, (2) paraspinal muscle, fascia, and supraspinous ligament closure using interrupted-X stitches 0 or 1 Vicryl or other longer-lasting resorbable suture (i.e., polydioxanone suture), (3) closure of subcutaneous tissue with interrupted inverted Vicryl 2-0 sutures in two planes for subcutaneous tissue greater >25 mm in depth, and (4) skin closure with simple interrupted nylon 3-0 sutures.

Conclusion:

There is great variability between closure techniques utilized for multilevel posterior lumbar fusion surgery. Here, we have described various standardized/evidence-based proven techniques for the closure of these wounds.