Study DesignRetrospective, longitudinal observational study.PurposeTo describe the natural history of anterior bone loss (ABL) in cervical disc arthroplasty (CDA) and introduce a classification system for its assessment.Overview of LiteratureABL has recently been recognized as a complication of CDA, but its cause and clinical effects remain unknown.MethodsPatients with non-keeled CDA (146) were retrospectively reviewed. X-rays were examined at 6 weeks, 3, 6, 9, 12, 18, and 24 months, and annually thereafter for a minimum of 5 years. These were compared with the initial postoperative X-rays to determine the ABL. Visual Analog Scale pain scores were recorded at 3 months and 5 years. Neck Disability Index was recorded at postoperative 5 years. The natural history was determined and a classification system was introduced.ResultsComplete radiological assessment was available for 114 patients with 156 cervical disc replacements (CDRs) and 309 endplates (average age, 45.3 years; minimum, 28 years; maximum, 65 years; 57% females). ABL occurred in 57.1% of CDRs (45.5% mild, 8.3% moderate, and 3.2% severe) and commenced within 3 months of the operation and followed a benign course, with improvement in the bone stock after initial bone resorption. There was no relationship between ABL degree and pain or functional outcome, and no implants were revised.ConclusionsABL is common (57.1%). It occurs at an early stage (within 3 months) and typically follows a non-progressive natural history with stable radiographic features after the first year. Most ABL cases are mild, but severe ABL occurs in approximately 3% of CDAs. ABL does not affect the patients’ clinical outcome or the requirement for revision surgery. Surgeons should thus treat patients undergoing CDA considering ABL.

Study Design. Retrospective hospital-registry study. Objective. To characterize the microbial epidemiology of surgical site infection (SSI) in spinal fusion surgery and the burden of resistance to standard surgical antibiotic prophylaxis. Summary of Background Data. SSI persists as a leading complication of spinal fusion surgery despite the growth of enhanced recovery programs and improvements in other measures of surgical quality. Improved understandings of SSI microbiology and common mechanisms of failure for current prevention strategies are required to inform the development of novel approaches to prevention relevant to modern surgical practice. Methods. Spinal fusion cases performed at a single referral center between January 2011 and June 2019 were reviewed and SSI cases meeting National Healthcare Safety Network criteria were identified. Using microbiologic and procedural data from each case, we analyzed the anatomic distribution of pathogens, their differential time to presentation, and correlation with methicillin-resistant Staphylococcus aureus screening results. Susceptibility of isolates cultured from each infection were compared with the spectrum of surgical antibiotic prophylaxis administered during the index procedure on a per-case basis. Susceptibility to alternate prophylactic agents was also modeled. Results. Among 6727 cases, 351 infections occurred within 90 days. An anatomic gradient in the microbiology of SSI was observed across the length of the back, transitioning from cutaneous (gram-positive) flora in the cervical spine to enteric (gram-negative/anaerobic) flora in the lumbosacral region (correlation coefficient 0.94, P < 0.001). The majority (57.5%) of infections were resistant to the prophylaxis administered during the procedure. Cephalosporin-resistant gram-negative infection was common at lumbosacral levels and undetected methicillin-resistance was common at cervical levels. Conclusion. Individualized infection prevention strategies tailored to operative level are needed in spine surgery. Endogenous wound contamination with enteric flora may be a common mechanism of infection in lumbosacral fusion. Novel approaches to prophylaxis and prevention should be prioritized in this population. Level of Evidence: 3

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Bisphosphonate therapy can be used as the definitive treatment of spinal ABCs, except in patients with instability or progressive neurology, where surgical intervention is required. Clinicians should expect a patients symptoms to rapidly improve, their bone oedema to resolve by 3 months and their lesion to partially or completely ossify by 6-12 months.

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