Anterior cervical discectomy with fusion is a common surgical procedure for patients experiencing pain and/or neurological deficits due to cervical spondylosis. Although iliac crest bone graft remains the gold standard today, the associated morbidity has inspired the search for alternatives, including allograft, synthetic and factor/cell-based grafts; and has further led to a focus on cage fusion technology. Compared to their graft counterparts, cage interbody implants have enhanced biomechanical properties, with designs constantly improving to maximise biocompatibility and osseointegration. We present a systematic review examining the historical progress of implant designs and performance, as well as an update on the currently available designs, and the potential future of cervical interbody implants. We performed a systematic review using the keywords “cervical fusion implant design”, with no limits on year of publication. Databases used were PubMed, Medline, Embase and Cochrane. In addition, the search was extended to the reference lists of selected articles. 180 articles were reviewed and 64 articles were eligible for inclusion. Exclusion criteria were based around study design, implant information and patient cohorts. The evolution of cage implant design has been shaped by improved understanding of ideal anatomy, progress in materials research and continuing experimentation of structural design. Originally, designs varied primarily in their choice of structure, however long-term studies have displayed the overall advantages of non-threaded, wedge shaped cages in complementing healthy anatomical profiles, and thus focus has shifted to refining material utilisation and streamlining anterior fixation. Evolution of design has been dramatic over the past decades; however an ideal cage design has yet to be realised. Current research is focusing on the promotion of osseointegration through bioactiviation of surface materials, as well as streamlining anterior fixation with the introduction of integrated screws and zero profile designs. Future designs will benefit from a combination of these advances in order to achieve ideal disc heights, cervical alignments and fusions.

Background: Rats are a widely accepted preclinical model for evaluating intervertebral disc (IVD) degeneration and regeneration. IVD morphology is commonly assessed using histology, which forms the foundation for quantifying the state of IVD degeneration. IVD degeneration severity is evaluated using different grading systems that focus on distinct degenerative features. A standard grading system would facilitate more accurate comparison across laboratories and more robust comparisons of different models and interventions.Aims: This study aimed to develop a histology grading system to quantify IVD degeneration for different rat models.Materials & Methods: This study involved a literature review, a survey of experts in the field, and a validation study using 25 slides that were scored by 15 graders from different international institutes to determine inter‐ and intra‐rater reliability.Results: A new IVD degeneration grading system was established and it consists of eight significant degenerative features, including nucleus pulposus (NP) shape, NP area, NP cell number, NP cell morphology, annulus fibrosus (AF) lamellar organization, AF tears/fissures/disruptions, NP‐AF border appearance, as well as endplate disruptions/microfractures and osteophyte/ossification. The validation study indicated this system was easily adopted, and able to discern different severities of degenerative changes from different rat IVD degeneration models with high reproducibility for both experienced and inexperienced graders. In addition, a widely‐accepted protocol for histological preparation of rat IVD samples based on the survey findings include paraffin embedding, sagittal orientation, section thickness < 10 μm, and staining using H&E and/or SO/FG to facilitate comparison across laboratories.Conclusion: The proposed histological preparation protocol and grading system provide a platform for more precise comparisons and more robust evaluation of rat IVD degeneration models and interventions across laboratories.

Background: The field of orthopaedics is a constantly evolving discipline. Despite the historical success of plates, pins and screws in fracture reduction and stabilisation, there is a continuing search for more efficient and improved methods of fracture fixation. The aim of this study was to evaluate shape‐memory staples and to compare them to a currently used implant for internal fracture fixation. Multi‐plane bending stability and interfragmentary compression were assessed across a simulated osteotomy using single and double‐staple fixation and compared to a bridging plate.Methods: Transverse osteotomies were made in polyurethane blocks (20 × 20 × 120 mm) and repairs were performed with one (n = 6), or two (n = 6) 20 mm nitinol staples, or an eight‐hole 2.7 mm quarter‐tubular plate (n = 6). A pressure film was placed between fragments to determine contact area and compressive forces before and after loading. Loading consisted of multi‐planar four‐point bending with an actuator displacement of 3 mm. Gapping between segments was recorded to determine loads corresponding to a 2 mm gap and residual post‐load gap.Results: Staple fixations showed statistically significant higher mean compressive loads and contact areas across the osteotomy compared to plate fixations. Double‐staple constructs were superior to single‐staple constructs for both parameters (p < 0.001). Double‐staple constructs were significantly stiffer and endured significantly larger loads before 2 mm gap formation compared to other constructs in the dorsoventral plane (p < 0.001). However, both staple constructs were significantly less stiff and tolerated considerably lower loads before 2 mm gap formation when compared to plate constructs in the ventrodorsal and right‐to‐left lateral loading planes. Loading of staple constructs showed significantly reduced permanent gap formation in all planes except ventrodorsally when compared to plate constructs.Conclusions: Although staple fixations were not as stable as plate fixations in particular loading planes, double‐staple constructs demonstrated the most consistent bending stiffness in all planes. Placing two perpendicular staples is suggested instead of single‐staples whenever possible, with at least one staple applied on the compression side of the anticipated loading to improve construct stability.