An expandable implant for augmenting a damaged or otherwise torn posterior annulus fibrosus. The implant is deployable into an evacuated posterior disc space following a subtotal nuclectomy. The implant includes an inflatable balloon which is fixed to the annulus fibrosus to protect against migration. When inflated with a curable polymer, the posterior wall of the implant is intimately disposed along the inner surface of the annulus fibrosus to provide a substantially fluid-tight seal of the annular tear or defect and reinforce the weakened posterior annulus. The anterior wall of the implant sequesters the nuclear remnant to guard against disc remnant herniation. The implant can restore intradiscal pressure and disc height. An integrated posterior reinforcement band creates a strong, yet flexible and resilient structure, resistant to penetration of the implant through the annular tear or defect.