Measurement of the radiographic anatomy of the small and ring metacarpals using computerized tomographic scans

Morphological Analysis of Metacarpal Shafts With Respect to Retrograde Intramedullary Headless Screw Fixation

Background: The use of retrograde intramedullary headless compression screw fixation for metacarpal neck and shaft fractures has been described in the literature. The purpose of this study was to perform a computed tomography (CT)-based morphological analysis of metacarpal size to help surgeons anticipate expected hardware needs. Methods: In all, 108 consecutive hand CT scans were evaluated for the medullary diameter in the volar-dorsal and radial-ulnar planes at the narrowest point of the canal, as well as for the distance from the articular surface to this point. Results were then analyzed by finger and by sex. Results: The ring finger had the smallest average medullary canal diameter for both men and women (2.7 and 2.6 mm, respectively); the small finger had the largest average diameter (3.9 mm) for men and the middle finger (3.6 mm) for women. Radial-ulnar was the rate-limiting dimension in the index, middle, and ring fingers, whereas volar-dorsal was the smallest dimension in the small finger, regardless of sex. Medullary diameter tended to be larger in patients aged more than 50 years. More than 50% of fingers have diameters >3.0 mm, and at least 40% of index, middle, and small fingers have diameters >3.5 mm, which are common diameters of commercially available headless compression screws. Conclusions: When preparing to perform open reduction internal fixation of a metacarpal using retrograde intramedullary headless compression screws, the surgeon needs to be prepared with screws of larger diameters to optimize fixation. Screws of larger diameters are needed to achieve endosteal purchase, regardless of sex.

The inter-and intra-observer reliability of volar angulation measurements in a fifth metacarpal neck fracture

INTRODUCTION

The fifth metacarpal neck fracture is the most common metacarpal fracture. The palmar angulation from the fracture displacement is critical for determining treatment, yet there is no consensus regarding the angulation measurement method or the surgical cut-off value. This study aimed to identify a reliable measurement method for assessing palmar angulation. We evaluated inter-observer and intra-observer validation of measuring palmar angulation in oblique plain X-ray and computed tomography (CT) sagittal cuts.

MATERIALS AND METHODS

We identified surgically treated patients for acute isolated fifth metacarpal neck fracture between January 1, 2008, and December 31, 2020, and obtained preoperative, opposite hand, and final follow-up oblique X-rays and sagittal computed tomography (CT) radiograms. The oblique radiograph was taken with a 45° posteroanterior pronation. The metacarpal neck palmar angulation was measured in the radiograms using the metacarpal neck-shaft center (MNSC) angle and the shaft articular surface (SAS) angle methods by three orthopedic surgeons in two sessions. For the CT radiograms, each measurer selected the sagittal slot at their discretion to measure the angle. The final palmar angulation was the average of six measurements (two sessions, three measurers per session).

RESULTS

The study included 51 patients; the average age was 32.5 (range 18-73) years, with 46 men and 5 women. The MNSC angle inter-observer reliability was better than the SAS angle. The MNSC angle inter-observer reliability was better than that of SAS angle. Intraclass coefficients (ICCs) for the MNSC angle demonstrated an excellent inter-observer agreement among the three measurers in the first (0.93) and second (0.88) session compared to ICCs for the SAS angle in the first (0.81) and second (0.87) session. The MNSC angle intra-observer reliability was also better than the SAS angle, with higher ICCs. Preoperative CT radiograms were available for 42 patients. Using CT scans for measurements, in the two sessions, the MNSC angle inter-observer reliability was higher than that of the SAS angle [MNSC: 0.83; SAS: 0.35], second [MSNC: 0.85; SAS: 0.81]. The intra-observer reliability was also better in the MNSC angle. When comparing average value among obtained radiograms, the physiologic angulation of the opposite hand oblique X-ray had the smallest average value, followed by preoperative CT and preoperative oblique radiography. Overall, the SAS angle measurement had a slightly larger angle than the MNSC method in the fractured and non-fractured hand measurements. Finally, a serial comparison of the oblique X-rays (pre-and postoperative, final follow-up, and the opposite hand with closed reduction and internal fixation) indicated that the angulation significantly decreased, and the post-operative values did not differ from the final follow-up X-ray for either method.

CONCLUSIONS

The palmar angulation measurement in 45° pronated oblique X-ray using the MNSC angle method had good-to-excellent reliability, with superior results to sagittal CT radiograms. Although the angle is likely overestimated, the MNSC method is reliable for judging the fracture degree and reduction adequacy after surgery compared to the non-fractured hand physiologic angulation.

Inter-relationships of Metacarpals 1 to 5, Regarding Their Length, Metaphyseal Midshaft Width, Articular Surface Area of Head and Base, Age, and Sex: A Cadaveric Study

Background: Metacarpal factures are common, comprising up to 50% of hand fractures. More work is needed to further our understanding of metacarpal anatomy to improve fixation techniques and reduce postoperative complications following surgical implants. The purpose of this anatomic study was to evaluate the length, midshaft metaphyseal width, and area of the articular surface of the head (AH) and base (AB) of metacarpals 1 to 5. Methods: This prospective study assessed measures from 17 cadavers at 1 institution's anatomy lab. The anatomic dimensions of the metacarpals in both the right and left hands were measured. Epidemiological data including sex and age at death were also collected. Results: In all, 29 hands were dissected for metacarpal anatomic measurements, for a total of 145 metacarpals. The second metacarpal was longest, at 69.58 mm. Multivariate analysis of variance revealed a significant effect of sex overall, with greater metacarpal dimensions in men. Increasing age was associated with decreasing dimensions, except for AH of metacarpal 1 (F = 3.43, P = .02) and AB of metacarpal 1 (F = 11.54, P < .001) and 4 (F = 4.21, P = .01). Multiple metacarpal dimensions were also significantly correlated with each other. Conclusion: Our data reveal further information regarding metacarpal dimensions of length, midshaft width, and AH and AB. The results allow for potential to improve surgical management through improving metacarpal implants, developing an optimal plate and screw design, techniques to better accommodate anatomical differences based on age and sex, reducing postoperative complications and improving the standard of care.

Morphometric analysis of the second through fifth metacarpal through posteroanterior X-Rays

Over the past 10 years, metacarpal fractures have had an annual incidence of 13.6 per 10,000 individuals. Literature has not reviewed anatomical variations through radiographic imaging, which may play a role in reducing postoperative complications. The purpose of this study was to use radiographic imaging to provide a detailed anatomy of the second through fifth metacarpals. This retrospective study measured length, neck width, narrowest body width, and narrowest medullary canal width of the second through fifth metacarpals through the use of posteroanterior X-rays. Patients who were ≥18 years and received hand radiographs from January 2015 to July 2019 were included in this study. Those with acute injury or fracture of the metacarpal were excluded. Five hundred and seventy-two metacarpals were included in this study, with 143 metacarpals measured each for the second through fifth metacarpal. The second metacarpal had the largest measured length, neck width, and narrowest body width at 68.72, 12.34, and 8.74 mm, respectively. The fifth metacarpal had the greatest average medullary canal width at 4.15 mm. This is the largest study in literature to comprehensively examine the anatomical variation of the second through fifth metacarpals. The second metacarpal had greatest dimensions except for canal width, which was the fifth metacarpal. Men almost consistently had greater metacarpal size when compared to women, and age was associated with second and third metacarpal canal width. The increased knowledge of metacarpal anatomy may potentially lay the foundation of further improvement of metacarpal implants and potentially reduce postoperative complications. Clin. Anat., 33:1014-1018, 2020. © 2019 Wiley Periodicals, Inc.

Bony anatomy of the third metacarpal and relationship with the capitate: a computed tomography study

PURPOSE

The purpose of this study was to accurately establish the anatomical variability of the third metacarpal, its medullary canal, and the relationship with the capitate in the context of high rates of component loosening still seen in total wrist arthroplasty.

METHODS

CT scans of a 100 hands (age: 41 ± 14 years (range: 16-71 years); male/female ratio: 53/47) were studied to establish the detailed anatomy of the third metacarpal and the capitate.

RESULTS

Although the shape of the third metacarpal and the angles formed with the capitate were highly variable, the third metacarpal length was longer in males (p < 0.001), the proximal cortical bone was thicker (p < 0.001) and the sagittal metacarpal-capitate axis offset was greater (p = 0.01). A relationship was found between the total length of the metacarpal and the distance to the isthmus from the base (r = 0.63; p < 0.0001) which was unaffected by gender. No age-related relationships were significant.

CONCLUSION

The anatomy of the third metacarpal and capitate varies considerably more than has been alluded to in current wrist arthroplasty literature. Differences between males and females can likely be attributed to hand size. The distance of the isthmus from the base can be predicted from the total length of the metacarpal with a standard error of 1.9 mm.