Spine

Is surgery needed in lumbar degenerative kyphosis?

Lumbar degenerative kyphosis (LDK) is affecting older adults with increasing frequency. Although it has always been a diagnosis that we’ve encountered in clinical practice, as the activities and expectations of older adults have risen exponentially over the past two decades we are now at a stage where treatment for symptomatic sagittal imbalance is increasingly sought. As with all spinal surgery, the key is establishing when to take the decision to operate. The evidence for surgical correction of LDK is poor, and so it is currently unknown whether surgery offers a better outcome than conservative management. Surgery generally requires a corrective osteotomy and, in some cases, still results in persisting symptoms. The decision to proceed to operation for these patients is difficult at the best of times. However, Goh et al,¹ who have conducted a cohort study of over 100 patients, have been able to show the relative successes of these two treatments. The authors from South Korea report a two-year prospective cohort study between January 2008 and December 2012, with 97 patients presenting to a unit in Busan, South Korea. Patients were allocated to either surgical or non-surgical treatment based on patient preference, after having both treatments impartially and objectively explained to them. Patients were excluded from the study if they showed compression fracture, tumour, hip pathology, spondylolisthesis or spondylosis, abnormal muscle activity, or ambulation. Patients were also discounted from the reporting and analysis if they had less than two years of follow-up. Patients were treated either with physiotherapy and analgesia, or with a posterior subtraction osteotomy (PSO) with or without a posterolateral fusion if spinal stenosis was present, using pedicle screw fixation and subsequent thoracolumbar spinal orthosis for three months. Outcomes were assessed with a Visual Analogue Scale (VAS) score for pain, the Oswestry Disability Index (ODI) score, a SF-36 score, and radiological measurement of sagittal balance. A total of 47 patients were treated with surgery, while 50 were conservatively managed. At 12 and 24 months, those who underwent surgery showed a lower ODI score and significantly less back pain. After six months, surgical patients also showed an improved SF-36 score. Similarly, the C7-sagittal vertical axis was improved when compared with conservatively treated patients after six months. There were 15 complications in surgical patients, and six in conservatively managed patients. Both treatments improved symptoms throughout the follow-up of the study; however, this improvement was found to be significantly greater in those surgically treated. Only surgery improved sagittal balance. These results should be tempered with the evident weaknesses of this study. Patient allocation leaves a fair amount to be desired, as a well-established principle shows that patients undergoing surgery are more likely to be well and active. Similarly, different pathologies that give rise to longstanding post-treatment back pain, which can cloud results, are not considered. The age-old argument of too few patients being included in the study rears its head and the role of population characteristics limits its generalisability. This is, in short, a useful study that starts to steer treatment of LDK towards surgery, but the question remains unanswered. I think more work is needed here.

Aspirin continuation in spinal surgery: a systematic review and meta-analysis

The efficacy of local autologous bone dust: a systematic review

A second tempting systematic review crossing the editorial desks at 360 this month comes from Auckland (New Zealand), where the authors have been exploring the use of bone dust taken from high-speed burrs as a source of viable bone grafting in spinal fusion.³ Bone grafting has a long-established role in spinal surgery when trying to achieve solid fusion, but its harvesting is fraught with painful, prolonged surgery and increased peri-operative bleeding. Despite a range of biologics (such as bone morphogenetic protein) and local bone graft being used, nonunion in cervical and lumbar spine fusions can reach 50%. Again, using a strategy compatible with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), and assessing the evidence using the Oxford Centre for Evidence-Based Medicine (CEBM) levels of evidence criteria, the authors conducted a systematic review. They searched for any preclinical and clinical studies that provide evidence of bone dust, collected during high-speed burring of the spine, being used as bone graft to stimulate fusion. A total of 14 studies were identified for inclusion in this review. Preclinical in vitro studies showed that burr ‘swarf’ is composed of 65% bone (the remainder being blood and fibrous tissue), which also contains osteoblasts that are able to proliferate when placed in an osteoconductive environment. These cells were, however, slower to grow and less likely to be successfully cultured than those found in bone chips. Interestingly, the authors note that these differences in proliferation seemed to be due to the nature of the tissue harvested, rather than due to the mechanical effects of the burr. Preclinical in vivo studies show that bone dust can form organised bone, but it forms incomplete bony structures when applied to defects in animal models. Three clinical studies were found in the search, two of which showed that bone dust led to ossification when applied to a surgical bed, and one of which showed a complete absence of osteogenic activity. Only one of these studies controlled for thermal injury using hand tools, which the authors suggest may be a sensible precaution in harvesting graft. Similarly, the paucity of relevant studies means that it is impossible to predict the impact of bone dust in the clinical setting. The conclusion of the review explains that the weight of evidence suggests that bone dust will most likely find its niche as a component of a graft strategy, rather than superseding traditional graft chips.

Late bedtime video games are bad for your back

Platelet-rich plasma enhances bone union in posterolateral lumbar fusion

Achieving a solid fusion depends on many factors, including surgical technique and choice of bone graft. In addition, biological agents with osteoinductive properties have the potential to stimulate and boost bone formation. Platelet-rich plasma (PRP) contains several osteoinductive growth factors, such as platelet-derived growth factor and transforming growth factor beta, and has been shown to promote bone formation in animal models. A group from Chiba (Japan) has now performed a prospective randomised controlled clinical trial comparing posterolateral fusion with local bone autograft, with and without PRP.⁵ Patients enrolled in the study were randomised to either simple fusion alone or fusion with PRP. The plasma was prepared by drawing 400 ml of blood from the patient immediately before surgery and this solution underwent several stages of centrifugation to prepare the PRP, which was applied as a gel and added to the autogenous local bone graft while the red blood cells were returned to the patients during surgery. Bone union was assessed by a benchmark final CT and regular radiographs, which were interpreted by three surgeons blinded to the treatments. The authors were able to successfully recruit 62 patients (31 in each arm) into the study, and outcome assessment, including bone fusion rate, the area of bone fusion mass, the duration of bone fusion, and the clinical score using the Visual Analogue Scale (VAS), were reported as the endpoints of this study. The findings suggested enhanced bone fusion with PRP. The bone union rate (defined as the presence of bone bridging the adjacent transverse processes) was significantly greater in the PRP group (94%) than in the control group (74%), as was the fusion mass area (572 mm²vs 367 mm²), and the time required for union was shorter (7.8 months vs 9.8 months). In terms of clinical outcomes, there was no significant difference in lower back pain, leg pain, or numbness in either group at any timepoint. The mean growth factor concentrations were 50 times greater than those measured in the blood. For the spine surgeon looking to improve fusion rates, this technique represents a lower-cost alternative to directly applying growth factors or bone morphogenetic proteins. Further studies are required to determine its safety (is heterotopic bone formation induced?), but this study does suggest that PRP is a useful adjunct to stimulate bone fusion.

Twenty years of scoliosis surgery: are things improving?

Surgery for adolescent idiopathic scoliosis (AIS) has changed significantly as instrumentation, intra-operative care, classification, indications for surgery, and the understanding of deformity have evolved over the past decades. The authors of this study from New York, New York (USA) have analysed their multicentre AIS registry database, which was established in 1995, to assess the changes that have occurred in aetiology over the more than 20 years of this study, and specifically to see whether there is a corresponding improvement in patient outcomes.⁶ The authors assessed a range of parameters, which included pre-operative sagittal and coronal radiological parameters, surgical approach, operative time, need for thoracoplasty, estimated blood loss, levels fused, anchor type, lowest instrumented vertebra (LIV), and length of stay. They also reported the Scoliosis Research Society-22r (SRS-22r) questionnaire as a quality-of-life measure. The study essentially describes a change such that patients are currently presenting with greater pre-operative Cobb angles, but, overall, a better correction was achieved. There have also been a number of changes in ‘surgical pattern’, with an increased number of levels fused, and the LIV became more distal in certain curve types (Lenke 1 and 2) over time. From a technical perspective, things have become markedly better over the past 20 years; operative times have fallen, there has been a decrease in blood loss, and, overall, post-operative days in hospital have also reduced. In terms of approaches, anterior spinal fusion (ASF) rates for Lenke 1 (main thoracic) curves in this series have fallen from 81% to 0%, whereas posterior spinal fusion (PSF) has increased consistently over the years with improvements in surgery and instrumentation to 99.6% for this curve type, essentially reflecting the increased power and effectiveness of posterior instrumentation for effecting and maintaining a curve. The incidence of thoracoplasty has fallen from 76% to 20.3%, as pedicle screw constructs now allow better vertebral body derotation that decreases the size of the rib hump. While other orthopaedic interventions, such as joint replacement surgery, have remained relatively unchanged for the past 30 years, spinal deformity surgery has rapidly evolved. This study provides a useful insight into this evolution, particularly for the more junior surgeon. The question is whether this pace of improvement can be maintained and whether current ‘novel’ innovations such as growing rods and tethering will stand the test of time.

Delayed dural leak following posterior spinal fusion for idiopathic scoliosis using all posterior pedicle screw technique

To further the knowledge on pedicle screw malposition and its consequences, this group of authors from Turku (Finland) provide some much-needed insight into delayed dural leak after posterior spinal fusion.⁷ The literature suggests that about 16% of pedicle screws are malpositioned, and, among these, those screws breaking the medial pedicle wall can produce a leak of cerebrospinal fluid through a tear in the dural sac. This is not always noted at operation, and hence a delayed dural leak can be seen. In this study of 322 patients, the authors identified just three in whom a delayed dural leak had developed (a rate of 0.9%), and the diagnosis was reached a mean five months after the initial surgery. The typical symptom of this condition is delayed positional headaches in patients who underwent posterior spinal fusion. If the headaches persist, this should prompt a diagnostic workup consisting of a CT myelogram that can show the leak very precisely, along with a brain/cervical spine MRI that can show a Chiari I malformation. It seems likely to us here at 360 that, given the imprecise nature of the presenting symptoms, many of these complications probably go unrecognised. The authors agree that treatment consists, for the most part, of simply removing the malpositioned screw and closing the dural defect, usually providing full resolution of symptoms.