Bone anchors and related methods for their use are described. The inventive anchor is suitable for placement in bone and for use in orthopedic surgery and dentistry. The bone anchor can be made from a bone/polymer or bone substitute/polymer composite, and can provide a firm and secure base for attaching a fastening device. The bone anchor can be used in various orthopedic and dental procedures including spinal surgery, where normal, cancellous, cortical, diseased or osteoporotic bone is present. The bone anchor can be resorbed and/or replaced with native bone tissue over a period of time. In certain embodiments, the bone anchor is made malleable or flowable and formed in situ or in vivo.