Spinal fusion

Crosslinks Unhelpful in Spinal Fusion for Scoliosis

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Crosslinks didn’t improve outcomes, but added bulk and cost.

  • In posterior spinal fusion for adolescent idiopathic scoliosis, crosslink use in conjunction with pedicle screw constructs did not improve outcomes, researchers reported here.

A multicenter analysis revealed no obvious improvement for young patients who had crosslinks compared with patients who didn’t, and discontinuation of crosslink use could save roughly $1,000 per surgery, according to Cameron R. Niswander, BA, of the University of Colorado, and colleagues.

“Traditional constructs utilizing pedicle posts and wires suffer from a lack of rotational stability. Crosslinks are traditionally utilized as a way to reduce that motion,” Niswander said in a presentation at the annual meeting of the American Academy of Orthopaedic Surgeons. “However, with the implementation of more modern systems such as the pedicle screws it’s unclear whether crosslinks still need to be utilized.”

“We found no differences in radiographic outcomes, clinical outcomes, or complication rates between groups. Therefore, crosslinks are no longer utilized in adolescent idiopathic scoliosis surgery with pedicle screw constructs at our institution,” he added. “This has resulted in a cost reduction of about $1,000” per patient.

For the study, Niswander and colleagues — who included Sumeet Garg, MD, and Mark Erickson, MD, of Children’s Hospital of Colorado in Aurora — searched a multicenter database for patients who underwent posterior spinal fusion for adolescent idiopathic scoliosis both with and without the use of crosslinks.

Inclusion criteria required pedicle screw fixation with more than 90% fixation points, no three-column osteotomy, no sacrum/pelvic fixation, and a minimum follow-up period of 2 years.

In a final sample of 500 patients, 377 with crosslinks and 123 without crosslinks, the researchers matched patients between groups based on age, BMI, and gender, as well as Lenke classification (P=0.6743), riser sign (P=0.2599), and preoperative radiographic measurements.

Implant density was 1.67 in in the crosslink group, and 1.70 in the non-crosslink group (P=0.3611).

At the 2-year follow-up, the crosslink group had a slightly decreased lumbar Cobb angle of 2.7 degrees compared with the non-crosslink group, but no other radiographic measures differed between groups in coronal balance, shoulder height, trunk shift, or sagittal balance.

Complications were reported in 21 patients in the crosslink group, and nine patients in the no-crosslink group (P=0.478). One infection was reported in the crosslink group, but none were reported in the no-crosslink group.

Reoperations were necessary for four patients, all of whom had crosslinks, and three of those surgeries were to remove implants at the patient’s own request.

Scores on the Scoliosis Research Society-22r questionnaire from pre- and postsurgery were similar between groups (P=0.4634). However, self-image scores were slightly improved for non-crosslink patients, and function scores were slightly higher in the crosslink group.

 The only difference that reached statistical significance was the improvement in mental health scores in the crosslink group (P<0.05).

Spinal Appearance Questionnaire scores were also similar for appearance (P=0.2125), expectations (P=0.5007), and improvement in appearance (P=0.1651) and expectation (P=0.1133).

“Since both groups were around that same 1.7 mark, it’s hard to know whether more pedicle screws were used, if they were using fewer crosslinks, or no crosslinks for that matter. From our data, we can’t say, if we use fewer pedicle screws, can we get away with fewer crosslinks,” Niswander said.

The authors reported that the list price for crosslinks used at their institution ranged from $1,000-$2,000 per unit, depending on the specific type.

Reporting of industry funded study outcome data: comparison of confidential and published data on the safety and effectiveness of rhBMP-2 for spinal fusion.

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Abstract

Objective To investigate whether published results of industry funded trials of recombinant human bone morphogenetic protein 2 (rhBMP-2) in spinal fusion match underlying trial data by comparing three different data sources: individual participant data, internal industry reports, and publicly available journal publications and conference abstracts.

Data collection and synthesis The manufacturer of rhBMP-2 products (Medtronic; Minneapolis, MN) provided complete individual participant data and internal reports for all its studies of rhMBP-2 in spinal fusion. We identified publications and conference abstracts through comprehensive literature searches. We compared outcomes provided in the individual participant data against outcomes reported in publications. For effectiveness outcomes, we compared meta-analyses of randomised controlled trials based on each of the three data sources. For adverse events, meta-analysis of the published aggregate data was not possible and we compared the number and type of adverse events reported between data sources.

Results 32 publications reported outcomes from 11 of the 17 existing manufacturer sponsored studies. For individual randomised controlled trials, 56% (9/16) to 88% (15/17) of effectiveness outcomes known to have been collected were reported in the published literature. Meta-analyses of effectiveness data were almost identical for pain outcomes and similar for fusion across the three data sources. A minority of adverse event data known to have been collected were reported in the published literature. Several journal articles reported only “serious,” “related,” or “unanticipated” adverse events, without defining these terms. Others reported a small proportion of the collected adverse event categories. Around 23% (533/2302) of the total adverse events collected in published randomised controlled trials have been reported in the literature, with randomised controlled trials evaluating the licensed preparation (Infuse) reporting around 11% (122/1108) of collected adverse events.

Conclusions The published literature only partially represents the total data known to have been collected on the effects of rhBMP-2. This did not lead to substantially different results for meta-analysis of effectiveness outcomes. In contrast, reporting of adverse event data in trial publications was inadequate and inconsistent to the extent that any systematic review based solely on the publicly available data would not be able to properly evaluate the safety of rhBMP-2. Analysis of individual participant data enabled the most complete, detailed, and in-depth analysis and was not more resource intensive than extracting, collating, and analysing aggregate data from multiple trial publications and conference abstracts. Confidential internal reports presented considerably more adverse event data than publications, and in the absence of individual participant data access to these reports would support more accurate and reliable investigation, with less time and effort than relying on incomplete published data.

Discussion

Controversy around use of recombinant human bone morphogenetic protein 2 (rhBMP-2) in spinal fusion began with suggestions that inadequate peer review and editorial oversight were responsible for an apparent absence of adverse events from early peer reviewed publications of industry sponsored studies. A subsequent investigation led by the editor in chief of The Spine Journal14 found fewer reported adverse events in academic publications of industry sponsored studies than in related study data available in FDA summaries and public meeting documents. The FDA materials available for that investigation appear to be partial outcome data from a subset of industry funded studies evaluating Infuse/LT-CAGE, Infuse/MASTERGRAFT, and AMPLIFY rhBMP-2 matrix preparations. Our investigation was able to explore this issue in greater depth having individual participant data on all recorded effectiveness and safety outcomes as well as internal reports provided for all Medtronic funded studies of rhBMP-2 for spinal fusion. Given their previous confidentiality, high degree of detail, and availability for all known studies, we consider the combination of individual participant data and internal reports to be the most comprehensive and trustworthy source of Medtronic trial evidence available to date.

Source: BMJ