Despite considerable efforts to develop cellular, molecular, and structural repair strategies and restore intervertebral disk function after injury, the basic biology underlying intervertebral disk healing remains poorly understood. Remarkably, little is known about the origins of cell populations residing within the annulus fibrosus, or their phenotypes, heterogeneity, and roles during healing. This review focuses on recent literature highlighting the intrinsic and extrinsic cell types of the annulus fibrosus in the context of the injury and healing environment. Spatial, morphological, functional, and transcriptional signatures of annulus fibrosus cells are reviewed, including inner and outer annulus fibrosus cells, which we propose to be referred to as annulocytes. The annulus also contains peripheral cells, interlamellar cells, and potential resident stem/progenitor cells, as well as macrophages, T lymphocytes, and mast cells following injury. Phases of annulus fibrosus healing include inflammation and recruitment of immune cells, cell proliferation, granulation tissue formation, and matrix remodeling. However, annulus fibrosus healing commonly involves limited remodeling, with granulation tissues remaining, and the development of chronic inflammatory states. Identifying annulus fibrosus cell phenotypes during health, injury, and degeneration will inform reparative regeneration strategies aimed at improving annulus fibrosus healing.

Highlights There is no standard procedure for periacetabular reconstruction following pelvic resections. High complication rates are associated with the use of massive implants/grafts. Deep infection is generally the most common cause for reconstruction failure. Functional outcomes decline with the occurrence of severe complications. Further efforts to avoid complications are crucial for improving outcomes.

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Should post-operative radiation for long bone metastases cover part or all of the orthopaedic hardware? Results of a large retrospective analysis,

Background and Objectives: Digital papillary adenocarcinoma (DPA) is a rare, aggressive neoplasm of sweat gland origin. It can recur at local, regional, or distant sites. There is limited knowledge about the role of sentinel lymph node biopsy (SLNB) in predicting recurrence in these patients. We present our experience with this uncommon tumor to evaluate the role of SLNB in predicting outcome. Methods: Medical records of all patients who underwent surgical treatment for biopsy-proven upper extremity DPA at the study institution were reviewed. Descriptive statistics and Fisher's exact test were used to analyze data. Results: Twenty-one patients were identified. Most patients were male (71%), and the median age was 51 years. SLNB was performed in 18 patients; three were positive for nodal metastatic disease (17%). At a median follow-up of 53 months, there were no local recurrences and two cases of systemic recurrence. No patient with a negative sentinel lymph node has evidence of metastasis or recurrence. Fisher's exact test demonstrated a significant association between a positive SLNB and recurrence (P = .02). Conclusion: SLNB revealed metastatic disease in 17% of patients with DPA and appears to predict systemic recurrence in this small series.