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Background: The purpose of this study was to investigate variations in radiographic metacarpal anatomy as it relates to intramedullary (IM) fixation of metacarpal fractures and to compare this anatomy with available headless screw dimensions. Methods: We radiographically analyzed posteroanterior and lateral (LAT) radiographs of 120 metacarpals across 30 patients without structural abnormalities. Primary outcomes included IM isthmus diameter, isthmus location, metacarpal cascade, and head entry point collinear with IM canal. Measurements were compared with a list of commercially available headless screws used for IM fixation. Results: The average largest isthmus diameter was in the small metacarpal (3.4 mm), followed by the index (2.8 mm), long (2.7 mm), and ring (2.7 mm) metacarpals. The average cascade angle between long and index, long and ring, and long and small metacarpals was 0°, 24°, and 27°, respectively. The appropriate head entry point ranged between 25% and 35% from the dorsal surface of the metacarpal head on a LAT view. The retrograde isthmus location of the index and long finger was 39.2 and 38.1 mm, respectively. Twenty-five screws from 7 manufacturers were analyzed with sizes ranging from 1.7 to 4.5 mm. Only 8 of 17 screws between 2.3 and 3.5 mm had a length range above 35 mm. Conclusions: Metacarpal head entry point and cascade angle can help identify the appropriate reduction with the guide pin starting point in the dorsal 25% to 35% of the metacarpal head. Surgeons should be mindful to choose the appropriate fixation system in light of the variations between metacarpal isthmus size, isthmus location, and available screw lengths.

Background: Ulnar styloid fractures (USFs) are common concomitant injuries associated with distal radius fractures (DRFs). Recent studies have found conflicting evidence on whether these fractures treated or untreated effect pain and functional outcomes. The purpose of this study was to prospectively evaluate pain and function outcomes of consecutively untreated USFs in surgically repaired DRFs. The study hypothesis was that there would be no difference in outcomes whether an USF is present or not, with all cases left untreated. Methods: A prospective study at a single institution of consecutive DRF treated surgically with volar locked plating was undertaken. No patients underwent fixation of an USF if present. There were no treated USF that were excluded. Patients with associated ulnar neck and shaft fractures were excluded. Functional outcome measures were analyzed using the Quick Disabilities of the Arm, Shoulder, and Hand score (QDASH) and the Patient-Rated Wrist Evaluation (PRWE) scores. Outcome measures were collected at 3 months and 1 year postoperatively. Results: There was an incidence of 52.2% (n = 70/134) USF associated with surgically treated DRF. By location, there were 52.9% (n = 37/70) ulnar styloid tip fractures and 46.1% (33/70) ulnar styloid base. There were 75.7% of USF (53/70) still not healed by 1-year follow-up. When comparing patients with a DRF without an USF versus DRF with an associated USF at 12 months, there was no statistical difference in the QDASH score (6.7 vs 8.4, P = .47) or the PRWE total score (4.8 vs 7.5, P = .24). Similarly, subgroup analysis showed no statistical difference in QDASH or PRWE scores at final follow-up in united USF versus nonunited USF subjects (QDASH 14.2 vs 6.8, P = .112; PRWE 14.8 vs 5.4, P = .185). Conclusions: USFs are a common concomitant injury occurring in nearly half of DRFs treated surgically. Our prospective cohort analysis showed that neither the presence, type, nor bony union status of a concomitant USF has any significant effect on patient outcomes or reoperations at 1-year postoperatively. Our study confirms our hypothesis that USF of the tip and base should be left untreated.