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Clinical Outcome Assessments in Composite Endpoints for Orthopedics

Clinical Context

Lumbar disc herniation or rupture can occur as a result of gradual breakdown of the intervertebral disc during normal aging or as a result of overloading of the spine. In either case, a herniated disc occurs when the soft, cushion-like center (nucleus) of the spinal disc pushes out through a tear in the tougher, rubbery outer layer (anulus) of the disc. Radiculopathy caused by irritation or compression of nearby nerves can cause pain, numbness, or weakness.

Conservative treatments like rest, pain medications, physical therapy, and cortisone injections often resolve symptoms. However, if symptoms do not improve with conservative treatment, surgery may be considered. A limited discectomy to remove the portion of the herniated disc that is protruding can help resolve the irritation of surrounding nerves and lead to improvement in pain and function.

Device Description

The Barricaid Anular Closure Device (ACD) (Premarket Approval P160050) is a Class III reherniation reduction device that can be implanted at the time of discectomy to close the defect from removal of the protruding lumbar disc. This permanent implant consists of a flexible polymer component to fill the gap and an anchoring metal component. The Premarket Approval submission for the Barricaid ACD was approved in February 2019.

Indications for Use

The Barricaid ACD is indicated for reducing the incidence of reherniation and reoperation in skeletally mature patients with radiculopathy (with or without back pain) attributed to a posterior or posterolateral herniation, and confirmed by history, physical examination and imaging studies which demonstrate neural compression using MRI to treat a large anular defect (between 4-6 mm tall and between 6-10 mm wide) following a primary discectomy procedure (excision of herniated intervertebral disc) at a single level between L4 and S1; see Summary of Safety and Effectiveness Data (PDF).

Context of Clinical Outcome Assessment (COA) Use

A large, prospective, multi-center randomized controlled clinical investigation was conducted to evaluate the safety and effectiveness of the Barricaid ACD. During the clinical investigation, co-primary endpoints were prospectively defined to test for statistical superiority of the group implanted with the Barricaid ACD after discectomy over a non-implanted discectomy group.

For success, both co-primary endpoints were required to achieve statistical superiority independently. The first co-primary endpoint was reherniation at any time up to and including the 24-month follow up. The second co-primary endpoint was a composite endpoint which included 8 components to evaluate both safety and effectiveness. Two of these 8 components were patient-reported outcome (PRO) instruments (also used as part of the inclusion criteria for the investigation):

  • The Oswestry Disability Index (ODI), which measures a patient’s functional status and how it is impacted by low back pain.
  • A visual analog scale (VAS) for leg pain, which gauges the patient’s pain level in the affected leg.

Seven secondary endpoints were assessed, two of which were PRO instruments:

  • The VAS for back and contralateral leg pain
  • The Short Form (SF)-36 Health Survey mental and physical component summary scores.

In addition, post-approval studies which rely on collection of VAS and ODI data were required as a condition of approval to mitigate uncertainties regarding long-term device performance.

Lessons Learned

The Barricaid ACD submission used co-primary endpoints to provide a detailed description of device safety and effectiveness. The second co-primary endpoint was intentionally a composite to reflect the necessity of evaluating critical components of the safety and effectiveness of this device from various perspectives. The PRO instruments included assessed patient disability and pain, both items unable to be evaluated by other observers or clinical measures. The resulting combination of clinical assessments and PROs provided a more complete understanding of the clinical performance of the Barricaid ACD.

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