**1. Introduction**

Cervical degenerative disc disease is one of the most common diagnoses for patients suffering from neck and back pain. These symptoms may present with various conditions, such as radiculopathy or myelopathy, involving compression of the nerve root and spinal cord, respectively [1]. Patients may suffer from pain, lack of function, immobility and sensory loss. Initial treatments often include anti-inflammatory medicine, immobilization, and physical therapy [1]. However, when conservative treatment options fail, a surgical approach such as anterior cervical discectomy and fusion (ADCF) may be warranted. This anterior approach involves excising the affected disc(s), removing osteophytes, and decompressing the nerve root or spinal cord. Following disc removal, the residual vertebral space is typically implanted with a bone or synthetic graft, with or without the additional support of plates and screws.

Robinson and Smith described this technique in 1955 [2]. Their approach involved implantation of a horseshoe-shaped bone graft harvested from iliac crest, followed by immobilization. Patients treated with this technique demonstrated promising clinical outcomes [2]. In 1958, Cloward described a similar technique, however, it included decompression of the neural structures and implantation of a bone dowel in the interbody space [3]. Regardless of the approach, a graft was used as a spacer to restore disc height, provide stability, and help promote bone fusion. Autograft, generally taken from the iliac crest, is often considered to be the gold standard for interbody fusion [4]. The use of autograft has led to high fusion rates and clinical success, although there are several disadvantages, such as extended operating time, donor site pain, limited supply, and variable quality depending upon the patient's health [5–8]. In an effort to avoid the complications seen with autografts, there has been a decades-old shift towards the use of alternative interbody spacers for treatment of degenerative disc disease [9, 10]. Two of the most common choices have been structural allograft bone or synthetic cages manufactured using polyetheretherketone (PEEK) [10]. Here, a comparison of the material properties and clinical performance of structural allografts and conventional PEEK cages is provided.
