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Purpose: The purpose of this study was to report results of elbow hemiarthroplasty for comminuted, intra-articular distal humerus fractures in low-demand elderly female patients. Methods: This is a retrospective case series of eight patients who underwent elbow hemiarthroplasty for comminuted, intra-articular distal humerus fractures between 2015 and 2019. Patients were considered for the procedure if the humeral fractures were deemed nonreconstructable by open reduction internal fixation. Patients were excluded if the extensor mechanism was not intact, evidence of significant ulnohumeral osteoarthritis, or a fracture to the proximal radius or ulna. A "triceps-on" approach was used in all cases. Appropriate sizing of the spool and length of the implant were determined by intraoperative fluoroscopy. Both ulnar collateral ligament and the lateral ulnar collateral ligaments were repaired through the central spool after final placement of the implant. Postoperative radiographs, clinical data, and the Mayo Elbow Performance Score were used to assess elbow pain and function. Results: Seven patients were included in final analysis. One patient was excluded from final analysis after sustaining a ground-level elbow dislocation at 13 weeks postoperatively, which subsequently revised to total elbow arthroplasty. The average age at the final follow-up was 72.1 years and duration of follow-up was 29.9 months (range 11.4-58.8 months). Average elbow range of motion was 21° ± 15° extension, 135° ± 9° flexion, 87° ± 5° pronation and 84° ± 8° supination. The average Mayo Elbow Performance Score was 88.3 (range 85-95; or "good" to "excellent") at the final follow-up. Postoperative ulnar neuropathy was reported by one patient at the first postoperative visit. This was followed up clinically and evaluation at 24 months revealed mild residual sensory deficits and adequate strength and motor function. Conclusion: Elbow hemiarthroplasty using the humeral component of the total elbow arthroplasty is an option for treatment of isolated, comminuted distal humerus fractures in select patient populations. The ideal candidates are elderly, low-demand, and able to adhere to postoperative activity and weight-bearing restrictions. Overall patient satisfaction with off-label use of humeral component of commercially available total elbow implants in the United States is promising, yet development of a more anatomic spool is warranted to further optimize outcomes intraoperatively. Some advantages of elbow hemiarthroplasty are a less-demanding operation and avoids complications associated with linked design including polyethylene wear, periprosthetic fracture, or implant loosening. Limitations of this study include small sample size and retrospective nature of the study.
RESUMO
RATIONALE: Mitochondria interact via actions of outer and inner membrane fusion proteins. The role of mitochondrial fusion in functioning of the heart, where mitochondria comprise ≈30% of cardiomyocyte volume and their intermyofilament spatial arrangement with other mitochondria is highly ordered, is unknown. OBJECTIVE: Model and analyze mitochondrial fusion defects in Drosophila melanogaster heart tubes with tincΔ4Gal4-directed expression of RNA interference (RNAi) for mitochondrial assembly regulatory factor (MARF) and optic atrophy (Opa)1. METHODS AND RESULTS: Live imaging analysis revealed that heart tube-specific knockdown of MARF or Opa1 increases mitochondrial morphometric heterogeneity and induces heart tube dilation with profound contractile impairment. Sarcoplasmic reticular structure was unaffected. Cardiomyocyte expression of human mitofusin (mfn)1 or -2 rescued MARF RNAi cardiomyopathy, demonstrating functional homology between Drosophila MARF and human mitofusins. Suppressing mitochondrial fusion increased compensatory expression of nuclear-encoded mitochondrial genes, indicating mitochondrial biogenesis. The MARF RNAi cardiomyopathy was prevented by transgenic expression of superoxide dismutase 1. CONCLUSIONS: Mitochondrial fusion is essential to cardiomyocyte mitochondrial function and regeneration. Reactive oxygen species are key mediators of cardiomyopathy in mitochondrial fusion-defective cardiomyocytes. Postulated mitochondrial-endoplasmic reticulum interactions mediated uniquely by mfn2 appear dispensable to functioning of the fly heart.