Abstract
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.
Keywords: metacarpal dimensions, metacarpal anatomy, metacarpal implants, post-operative complications
Background
Fractures of the metacarpals are one of the most common hand fractures comprising 50% of hand fractures, with an annual incidence of 8.4 per 10,000 people in the United States.1,2 Typically, metacarpal fractures are secondary injuries, following a direct blow or falling directly on the hand.3 Metacarpal fractures predominately occur in males (82.3%) compared to females (16.8%).4 Injuries to the base of the first and neck of the fifth metacarpal are more common; however, in the elderly, diaphyseal and basal fractures are more common.4,5 Younger patients often acquire metacarpal fractures through athletic events, middle-aged patients through work-related injuries, and older adults following falls.3
Metacarpal fractures are often considered isolated injuries, which can be treated operatively or nonoperatively.2,6 Some fractures may not require immobilization.7 Literature suggests no superior methods of conservative management of metacarpals, with optimal recovery still being achieved.7 Indications for internal reduction include unstable or comminuted fractures, multiple fractures with associated soft tissue injury, history of unsuccessful closed reduction attempts, and markedly displaced shaft fractures.1 Fractures with malrotation, segmental bone loss, or polytraumatic fractures are good candidates for operative treatment.8 Successful treatment of metacarpal pathology such as fractures and malunions requires an understanding of normal metacarpal anatomy, which can aid in allowing early motion, an appropriate degree of fixation, and can lessen any soft tissue injury.9,10 Intermedullary nailing or plate and screw fixation comprise a few of the numerous surgical techniques that may be employed.2,11,12
Surgical management can unfortunately lead to postoperative complications. Complications postoperatively include tendon irritation and rupture, stiffness, and plate prominence.1 Stiffness has been cited almost universally as a complication. However, there is disagreement in the field about whether it is considered a minor or major complication, as well as the accuracy of self-reported degree of stiffness experienced by patients.13 Ridley and colleagues reported that exposed Kirschner wires (K-wire) present higher infection occurrence compared to patients with buried K-wires.14 Infection occurred commonly in patients exhibiting skeletal injury and soft tissue damage. However, the functional outcome of the infection was also associated with the type of the initial fracture.15 Recent literature has suggested that a smaller plate with screws reduces complications associated with intraoperative fixation.2 Despite technical advances in plate design and insertion, complications still occur due to issues with placement and plate fixation in metacarpal and phalangeal fractures.13,16
Few studies have assessed the anatomical measurements of metacarpals such as the length and width. Predominantly, children’s metacarpals have been examined, with few studies analyzing adult metacarpals.17-19 More research is needed to further our understanding of metacarpal anatomy to improve fixation techniques and reduce postoperative complications. Therefore, the purpose of this anatomic study was to evaluate the length, midshaft metaphyseal width, area of the articular surface of the head and base of metacarpals 1 to 5. Additionally, the effects of sex and age on these measures were further evaluated for possible anatomic variations. The results of this study may play a role in further development of optimal plate and screw design due to anatomic variations in metacarpal length, in efforts to reduce postoperative complications of metacarpal fracture.
Materials and Methods
This prospective study used 17 cadavers from 1 institution’s anatomy lab. Cadavers were dissected by 2 research study members for measurements of length, width, and area of the articular surfaces of the head (AH) and base (AB) of metacarpals 1 to 5 in both the right and left hand. Epidemiological data including sex and age at death were also collected. This study was deemed exempt from the institutional review board.
Dissection Technique
Dissections were performed posteriorly to anteriorly for ease of access to the metacarpals, bypassing the removal of the pad of the palm to avoid damaging the bone. A scalpel was used as the tool for dissection of the metacarpal bones. The metacarpals were removed from the carpal bones and phalanges. The cartilage at the head and base of each metacarpal was kept intact to measure the articular surface of each metacarpal. The metacarpals were not dried or cleaned, and any remaining fascia was removed. The metacarpal length was measured from the superior aspect of the cartilage in the head to the inferior aspect of the base. The length and width of each articular surface of the head and base of the metacarpal were measured to obtain the area, as described in previous literature with addition of the articular surface.20 Length was measured as the surface of the metacarpal from medial to lateral and the width from anterior to superior. The width was measured at midshaft. A certified, calibrated Mitutoyo caliper was used to measure the length and width of each metacarpal. The caliper was also used to measure the articular surface of the head and base of each metacarpal.
Statistical Analysis
For the purposes of this study, the length and width of the metacarpal head and base were multiplied to obtain the area of the head and base. The averages ± standard error of the mean (SEM) of each metacarpal’s length, width, AH, and AB were calculated from the data collected. Using SPSS v25, we analyzed the degree of correlation between the dimensions of the metacarpals (Pearson correlations), the effects of sex and age on these measures (multivariate analysis of variance [MANOVA]). Significance was determined at the level of P < .05.
Results
With the 17 cadavers used in this study, 29 hands were dissected for metacarpal anatomic measurements, for a total of 145 metacarpals. Of the cadavers, 60 metacarpals from 12 hands (7 right, 5 left) were from male cadavers, and 85 metacarpals from 17 hands (9 right, 8 left) were from females. The average age of the cadavers was 80.97 years old, with a standard deviation of 13.9 years (minimum: 36; maximum: 95). For all metacarpals, the averages ± SEM of the width, length, AH, and AB were calculated (Table 1) and divided by sex and placed into age groups of 30 to 59 years (men only), 60 to 79 years, and 80 to 99 years (Table 2, Figure 3, Supplemental Figures 1-4).
Table 1.
Averages (in mm) and Standard Error of the Mean (SEM) of Metacarpals 1 to 5.
| Metacarpal | Width average ± SEM | Length average ± SEM | Area of articular head surface average ± SEM | Area of articular base surface ± SEM |
|---|---|---|---|---|
| 1 | 8.57 ± 0.18 | 49.95 ± 0.62 | 183.41 ± 6.45 | 251.55 ± 15.24 |
| 2 | 8.94 ± 0.20 | 69.58 ± 0.74 | 172.00 ± 8.57 | 207.09 ± 10.78 |
| 3 | 9.11 ± 0.23 | 66.57 ± 0.75 | 173.49 ± 6.81 | 159.09 ± 9.51 |
| 4 | 6.97 ± 0.20 | 58.69 ± 1.00 | 139.05 ± 6.24 | 104.95 ± 5.56 |
| 5 | 6.71 ± 0.22 | 54.27 ± 0.66 | 119.75 ± 4.41 | 116.76 ± 5.44 |
Note. SEM = standard error of the mean.
Table 2.
Averages (in mm) and Standard Error of the Mean (SEM) of Metacarpals 1 to 5 in Men and Women.
| Metacarpal | Sex | Age (in years) | Width average ± SEM | Length average ± SEM | Area of articular head average ± SEM | Area of articular base ± SEM |
|---|---|---|---|---|---|---|
| 1 | M | 30-59 | 9.02 ± 0.27 | 50.07 ± 0.79 | 205.47 ± 8.29 | 209.52 ± 17.49 |
| 60-79 | 9.81 ± 0.18 | 50.51 ± 1.13 | 211.57 ± 9.33 | 312.75 ± 6.21 | ||
| 80-99 | 9.31 ± 0.29 | 49.34 ± 1.77 | 223.58 ± 23.42 | 334.59 ± 56.91 | ||
| F | 60-79 | 7.76 ± 0.25 | 47.21 ± 0.18 | 157.14 ± 3.94 | 151.43 ± 9.45 | |
| 80-99 | 8.02 ± 0.22 | 44.04 ± 0.35 | 163.22 ± 5.60 | 242.96 ± 18.50 | ||
| 2 | M | 30-59 | 9.24 ± 0.44 | 74.15 ± 2.56 | 172.36 ± 9.25 | 249.13 ± 31.70 |
| 60-79 | 10.09 ± 0.19 | 72.96 ± 2.10 | 204.19 ± 16.64 | 217.35 ± 14.60 | ||
| 80-99 | 10.15 ± 0.35 | 71.46 ± 1.51 | 217.38 ± 38.24 | 258.19 ± 27.18 | ||
| F | 60-79 | 8.66 ± 0.30 | 68.80 ± 1.32 | 161.09 ± 13.63 | 183.30 ± 17.68 | |
| 80-99 | 8.15 ± 0.19 | 66.86 ± 0.44 | 148.93 ± 9.15 | 185.04 ± 17.28 | ||
| 3 | M | 30-59 | 10.65 ± 0.73 | 67.87 ± 1.57 | 193.58 ± 25.45 | 161.07 ± 18.06 |
| 60-79 | 10.50 ± 0.42 | 71.28 ± 1.88 | 203.20 ± 8.88 | 174.27 ± 6.45 | ||
| 80-99 | 9.75 ± 0.27 | 69.21 ± 2.13 | 215.25 ± 18.37 | 188.74 ± 12.41 | ||
| F | 60-79 | 8.30 ± 0.17 | 65.64 ± 0.81 | 147.99 ± 13.47 | 121.21 ± 4.00 | |
| 80-99 | 8.28 ± 0.15 | 63.93 ± 0.65 | 152.43 ± 5.64 | 155.32 ± 19.27 | ||
| 4 | M | 30-59 | 6.66 ± 0.56 | 64.62 ± 6.04 | 159.59 ± 12.79 | 108.88 ± 9.67 |
| 60-79 | 8.05 ± 0.52 | 63.75 ± 1.64 | 173.43 ± 4.89 | 110.57 ± 4.14 | ||
| 80-99 | 8.04 ± 0.16 | 60.88 ± 2.05 | 172.08 ± 6.07 | 128.59 ± 18.80 | ||
| F | 60-79 | 6.59 ± 0.31 | 57.65 ± 0.83 | 112.50 ± 9.41 | 90.10 ± 1.14 | |
| 80-99 | 6.42 ± 0.21 | 55.02 ± 0.59 | 119.10 ± 7.64 | 99.17 ± 10.17 | ||
| 5 | M | 30-59 | 7.22 ± 0.40 | 57.98 ± 2.44 | 141.99 ± 8.88 | 115.97 ± 16.33 |
| 60-79 | 7.86 ± 0.61 | 57.31 ± 1.63 | 146.88 ± 1.08 | 134.82 ± 16.26 | ||
| 80-99 | 7.08 ± 0.29 | 56.56 ± 1.78 | 146.75 ± 4.41 | 153.95 ± 14.52 | ||
| F | 60-79 | 5.88 ± 0.17 | 54.33 ± 0.66 | 108.66 ± 2.24 | 108.40 ± 5.08 | |
| 80-99 | 6.29 ± 0.32 | 51.52 ± 0.34 | 99.28 ± 2.47 | 101.12 ± 4.83 |
Note. SEM = standard error of the mean.
Figure 3.
Full correlations of each metacarpal 1’s dimension and age. (a) Width of metacarpal 1 correlated by age. (b) Length of metacarpal 1 correlated by age. (c) AB of metacarpal 1 correlated by age. (d) AH of metacarpal 1 correlated by age.
Full and partial correlations of all metacarpal measurements as well as cadaver age are reported in Table 3. Full correlations revealed significant positive associations of the width of metacarpal 1 and length of metacarpal 3, width of metacarpal 1 and length of metacarpal 4, AB of metacarpal 1 and width of metacarpal 3, width of metacarpal 2 and width of metacarpal 4, width of metacarpal 3 and length of metacarpal 3, length of metacarpal 3 and length of metacarpal 4, and AH of metacarpal 3 and length of metacarpal 4 (Table 3, Figure 1 and 2). MANOVA revealed an effect of sex on the anatomic dimensions of metacarpals, with men consistently having greater dimensions than women, although there was no significant difference for the width of metacarpal 2, AB of metacarpal 2, AB of metacarpal 3, width of metacarpal 4, AH of metacarpal 4 (Tables 2 and 4). Additionally, there was an effect of age on anatomical dimensions, with dimensions decreasing in size as age increased, except for AH of metacarpal 1 (P = .02, F = 3.43) and 2 (P < .00, F = 5.73), and AB of metacarpal 1 (P < .00, F = 11.54), 4 (P = .01, F = 4.21), 5 (P = .04, F = 2.92), which increased (Tables 2 and 4). However, AH of metacarpal 2 and AB of metacarpal 5 was observed to decrease in women with increasing age, and increase in men with increasing age, with no significance (Table 4). There was no interactive effect of age and sex in metacarpal dimensions aside from length, AH and AB of metacarpal 1 (Table 4).
Table 3.
Correlations (and Full Correlations) of Anatomical Measurements of Metacarpals 1 to 5.
| Variable | Metacarpal 1 |
Metacarpal 2 |
Metacarpal 3 |
Metacarpal 4 |
Metacarpal 5 |
Age | ||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| W | L | AH | AB | W | L | AH | AB | W | L | AH | AB | W | L | AH | AB | W | L | AH | AB | |||
| Metacarpal 1 | W | 1 | 0.598*** (−0.479) | 0.740*** (0.344) | 0.509** (−0.659) | 0.762*** (0.028) | 0.525** (0.376) | 0.406* (−0.125) | 0.398* (−0.464) | 0.755*** (0.728) | 0.599*** (0.892)** | 0.648*** (0.439) | 0.418* (0.345) | 0.686*** (0.170) | 0.495** (−0.693)* | 0.722*** (−0.354) | 0.570*** (−0.030) | 0.776*** (0.219) | 0.463* (−0.733) | 0.804*** (0.518) | 0.565*** (−0.334) | −0.291 |
| L | — | 1 | 0.716*** (0.113) | 0.256 | 0.701*** (−0.423) | 0.635*** (0.034) | 0.477** (−0.211) | 0.285 | 0.742*** (0.234) | 0.686*** (0.567) | 0.594*** (0.308) | 0.046 | 0.553** (0.537) | 0.679*** (−0.486) | 0.589*** (−0.447) | 0.321 | 0.423* (0.102) | 0.697*** (−0.157) |
0.814*** (0.555) | 0.539** (0.066) | −0.550** (−0.565) | |
| AH | — | 1 | 0.567*** (0.350) | 0.694*** (−0.481) | 0.559** (−0.234) | 0.601*** (−0.441) | 0.411* (0.156) | 0.713*** (−0.310) | 0.659*** (−0.240) | 0.756*** (0.430) | 0.191 | 0.583*** (0.442) | 0.587*** (−0.042) | 0.778*** (0.496) | 0.542** (0.240) | 0.505** (0.128) | 0.605*** (0.490) | 0.813*** (0.309) | 0.610*** (0.479) | −0.300 | ||
| AB | — | 1 | 0.517** (0.103) | 0.299 | 0.410* (0.023) | 0.258 | 0.472** (0.773)* | 0.414* (0.705) | 0.529** (0.473) | 0.189 (0.140) | 0.467* (0.163) | 0.253 | 0.485** (−0.130) | 0.210 | 0.292 | 0.258 | 0.466* (0.254) | 0.389* (−0.449) | 0.256 | |||
| Metacarpal 2 | W | — | — | — | — | 1 | 0.486** (−0.154) | 0.521** (−0.374) | 0.312 | 0.749*** (−0.126) | 0.579** (0.134) | 0.692*** (0.438) | 0.221 | 0.763*** (0.786)* | 0.601*** (−0.315) | 0.613*** (0.104) | 0.431* (0.357) | 0.591*** (0.035) | 0.539** (0.294) | 0.814*** (0.241) | 0.580*** (0.312) | −0.258 |
| L | — | — | — | — | — | 1 | 0.536** (−0.150) | 0.412* (0.072) | 0.698*** (−0.339) | 0.839*** (−0.248) | 0.620*** (−0.191) | 0.182 | 0.230 | 0.715*** (0.243) | 0.570*** (−0.019) | 0.315 | 0.231 | 0.933*** (0.722) | 0.686*** (−0.133) | 0.500** (0.351) | −0.497** (−0.306) | |
| AH | — | — | — | — | — | — | 1 | 0.613*** (−0.005) | 0.489** (−0.065) | 0.624*** (0.159) | (0.751)*** (0.589) | 0.328 | 0.417* (0.528) | 0.574*** (−0.363) | 0.574*** (0.370) | 0.414* (0.119) | 0.172 | 0.625*** (0.264) | 0.598*** (0.010) | 0.623*** (0.341) | −0.174 | |
| AB | — | — | — | — | — | — | — | 1 | 0.415* (0.302) | 0.367* (0.550) | 0.539** (0.219) | 0.676*** (0.557) | 0.403* (0.452) | 0.342 | 0.310 | 0.331 | 0.244 | 0.383* (−0.263) | 0.446* (0.707) | 0.463* (−0.224) | −0.230 | |
| Metacarpal 3 | W | — | — | — | — | — | — | — | — | 1 | 0.649*** (−0.730)* | 0.674*** (−0.405) | 0.247 | 0.615*** (−0.023) | 0.728*** (0.648) | 0.675*** (0.217) | 0.342 | 0.563*** (−0.002) | 0.702*** (0.715) | 0.850*** (−0.265) | 0.568*** (0.479) | −0.474** (−0.100) |
| L | — | — | — | — | — | — | — | — | — | 1 | 0.634*** (−0.538) | 0.065 | 0.307 | 0.765*** (0.807)* | 0.661*** (0.407) | 0.380* (0.061) | 0.207 | 0.867*** (0.676) | 0.694*** (−0.546) | 0.541** (0.323) | −0.336 | |
| AH | — | — | — | — | — | — | — | — | — | — | 1 | 0.372* (0.355) | 0.571*** (−0.620) | 0.762*** (0.821)* | 0.625*** (−0.255) | 0.400* (0.008) | 0.377* (−0.278) | 0.666*** *(0.175) | 0.790*** (0.012) | 0.731*** (−0.100) | −0.244 | |
| AB | — | — | — | — | — | — | — | — | — | — | — | 1 | 0.492** (0.248) | 0.051 | 0.198 | 0.362 | 0.483*** (0.477) | 0.062 | 0.239 | 0.370* (0.554) | 0.022 | |
| Metacarpal 4 | W | — | — | — | — | — | — | — | — | — | — | — | — | 1 | 0.413* (0.543) | 0.476** (−0.079) | 0.399* (−0.285) | 0.704*** (0.096) | 0.242 | 0.653*** (−0.232) | 0.603*** (−0.134) | −0.061 |
| L | — | — | — | — | — | — | — | — | — | — | — | — | — | 1 | 0.550** (−0.083) | 0.192 | 0.235 | 0.783*** (−0.0398) | 0.700*** (0.275) | 0.588*** (−0.077) | −0.491** (−0.395) | |
| AH | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 1 | 0.523** (0.181) | 0.565*** (−0.005) | 0.611*** (−0.307) | 0.834*** (0.635) | 0.539** (−0.259) | −0.284 | |
| AB | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 1 | 0.557** (0.414) | 0.304 | 0.442* (−0.230) | 0.463* (0.169) | −0.104 | |
| Metacarpal 5 | W | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 1 | 0.185 | 0.609*** (0.324) | 0.279 | −0.195 |
| L | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 1 | 0.732*** (0.410) | 0.505** (−0.596) | −0.472 | |
| AH | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 1 | (0.382) | −0.419* (0.344) | |
| AB | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | — | 1 | −0.140 | |
p < 0.05. **p < 0.01. ***P < 0.001.
Figure 1.
Full correlations of metacarpals by sex and age.
Note. (a) Initial correlations and full correlations were performed on width of metacarpal 1 (M1) and length of metacarpal 3 (M3) revealing a significance of P < .01. (b) Initial and full correlations of width of M2 and width of M4 revealed a significance of P < .05. (c) Initial and Full correlations of width of M3 and AB of M1 revealed a significance of P < .05.
Figure 2.
Full correlations of metacarpals by sex and age.
Note. (a) Initial and full correlations of length of M3 and length of M4 revealed a significance of P < .05. (b) Initial and full correlations of width of M1 and length of metacarpal 4 (M4), revealing a significance of P < .05. (c) Initial and full correlations of AH of M3 and Length of M4 revealed a significance of P < .05.
Table 4.
Relationship of Cadaver Sex and Age on Metacarpal Anatomic Measurements.
| Metacarpals | Anatomic variables | Sex |
Age |
Sex × age |
|---|---|---|---|---|
| P-value (F-value) | P-value (F-value) | P-value (F-value) | ||
| Metacarpal 1 | W | 0.00 (37.10) | 0.00 (6.34) | 0.33 (1.03) |
| L | 0.00 (47.58) | 0.00 (5.10) | 0.00 (32.85) | |
| AH | 0.00 (37.52) | 0.02 (3.43) | 0.03 (5.81) | |
| AB | 0.00 (21.82) | 0.00 (11.54) | 0.05 (4.97) | |
| Metacarpal 2 | W | 0.07 (3.88) | 0.32 (1.31) | 0.91 (0.01) |
| L | 0.00 (17.71) | 0.04 (2.81) | 0.87 (0.03) | |
| AH | 0.01 (9.66) | 0.00 (5.73) | 0.91 (0.01) | |
| AB | 0.14 (2.55) | 0.37 (1.22) | 0.74 (0.12) | |
| Metacarpal 3 | W | 0.01 (11.77) | 0.15 (1.82) | 0.51 (0.47) |
| L | 0.00 (44.79) | 0.01 (4.13) | 0.28 (1.31) | |
| AH | 0.02 (8.01) | 0.55 (0.94) | 0.90 (0.02) | |
| AB | 0.30 (1.16) | 0.37 (1.22) | 0.62 (0.26) | |
| Metacarpal 4 | W | 0.19 (1.93) | 0.11 (2.07) | 0.61 (0.27) |
| L | 0.02 (7.89) | 0.34 (1.28) | 0.89 (0.02) | |
| AH | 0.06 (4.40) | 0.80 (0.63) | 0.82 (0.06) | |
| AB | 0.03 (5.80) | 0.01 (4.21) | 0.31 (1.14) | |
| Metacarpal 5 | W | 0.05 (4.87) | 0.00 (6.63) | 0.57 (0.34) |
| L | 0.00 (44.07) | 0.00 (7.29) | 0.52 (0.45) | |
| AH | 0.00 (42.73) | 0.18 (1.71) | 0.41 (0.73) | |
| AB | 0.03 (6.26) | 0.04 (2.92) | 0.86 (0.03) |
Note. W = Width; L = Length; AH = Area of the articular surface of the head of the metacarpal; AB = Area of the articular surface of the base of the metacarpal.
Discussion
The results of this study provide a foundation for examining the anatomical properties of metacarpals 1 to 5. One study has reported that the lengths of all metacarpals range between 44.53 and 65.42 mm.21 In our study, the length of the second metacarpal was longest at 69.58 mm, followed by metacarpals 3, 4, 5, and 1, which were 66.57, 58.69, 54.7, and 49.95 mm, respectively. The results were within ranges in the previous literature, aside from the length of metacarpal 1 which was 43.8 mm with a standard deviation of 3.5 mm in a study from Singla and colleagues, which could be attributed to potential differences in sex and age groups, with no documentation of these factors in their study.5,20 Wong and colleagues analyzed 50 total metacarpals (10 of each metacarpal) through computed tomographic analysis and observed the second metacarpal to be the largest of the metacarpals with a length of 62.7 mm, followed by metacarpal 3, 4, 5, and 1.22 In comparison, our average lengths for each metacarpal were greater, which could also be accounted by the difference in age and sex of the subjects from whom metacarpals were collected.22 Additionally, the difference in modalities, such as the use of computed tomographic analysis vs. cadaveric measurements may also account for the discrepancies in measurements.
Although literature has not evaluated midshaft width, a previous study evaluated metaphyseal width at the proximal and distal metacarpal through radiographic imaging, reporting an average range of 11.42 to 16.42 mm.21 To our knowledge, this is the first study to assess metaphyseal width through a cadaveric study.
We attempted to obtain a better understanding of the articular surface, given the undefined shape of the metacarpal. Our literature review revealed only 1 study has evaluated for AB and AH.20 The study revealed larger metacarpals at the AB and AH for metacarpals 1 to 5, aside from AB of metacarpal 1.20 However, the articular surface was kept intact in our study and was used to evaluate the AH and AB of the metacarpals. It is possible that the knowledge of the articular surface can be utilized to aid in surgical planning, serving as a fortifying structure in screw fixation, as well as playing a role in the development of joint replacement components.
To our knowledge, no studies have evaluated correlations between metacarpal anatomic dimensions. Thus, ours is the first to reveal significance for multiple dimensions between metacarpals (Table 3 and Figures 1-2). With the data revealing significant correlations, as shown in Table 3, the knowledge of metacarpal dimensions can be further utilized in successful massive bone loss reconstruction (gunshot wounds, infection, or tumor resection) due to a better understanding of proper anatomical relationships.9
Metacarpal fractures commonly occur in men (82.3% males and 16.8% females), particularly in the second decade of life.4 Our results reveal men have significantly greater anatomical measures in metacarpals, except for width of metacarpal 2, AB of metacarpal 2, AB of metacarpal 3, width of metacarpal 4, and AH of metacarpal 4, which revealed no significant difference when compared to women (Table 4). Increasing age was further associated with a decrease in metacarpal measurements aside from the AH of metacarpals 1 and 2, and AB of metacarpals 1, 4, and 5 (Figure 3, Supplemental Figures 1, 3, 4). Although not significant, further grouping of the measurements revealed the AH of metacarpal 2 and AB of metacarpal 5 was observed to decrease in women with increasing age and increase in men with increasing age (Table 4). This is likely due to the low sample size leading to no significance. Our finding of age- and sex-dependent differences in metacarpal measures varies from previous claims in literature indicating minimal variation between men and women.9 These differences can potentially lay the framework in utilizing different implant sizes that is both age and sex dependent.
The strengths of this study include the novelty of evaluating the anatomical dimensions of metaphyseal mid-shaft width, AH, and AB of metacarpals 1 to 5. Additionally, our study stratified results based on age and sex, revealing significant effects of both on our measures. Further studies can evaluate similar anatomical dimensions through radiographic imaging to compare and evaluate differences between cadaveric and radiographic measurements. Further information through radiographic analysis may be better applicable to everyday clinical practice in efforts to reduce postoperative complications.
Limitations
Our study is limited by a small cadaver population, allowing for a potentially skewed result, particularly with age stratification. However, the number of metacarpals measured were equal among groups. The complex morphological shape of the articular surface allowed for difficulty in accurately measuring the area. Therefore, the novelty of shape definition of the articular surface was used in attempt to quantify the area of both the head and base of the metacarpal. Additionally, with no knowledge of previous metacarpal pathology in our cadaver, we were unable to determine the impact of prior fracture on metacarpal dimensions.
Conclusion
Our data reveal further information regarding metacarpal dimensions of length, midshaft width, AH and AB. The significant correlations between measures may be useful when planning for surgical management. Additionally, to the best of our knowledge, this is the first study to evaluate the effects of sex and age on metacarpal dimensions. The results of the study allow for the potential foundation to further improve metacarpal implants, development of optimal plate and screw design, and development of techniques to better accommodate anatomical differences based on age and sex, to ultimately reduce postoperative complications and improve the standard of care.
Supplemental Material
Supplemental material, Supplemental_material for 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 by Andrew Sephien, Claire F. Bethel, Danielle Gulick, Christa Nairn, Felicia Ourn and Francisco A. Schwartz-Fernandes in HAND
Footnotes
Supplemental material is available in the online version of the article.
Authors’ Note: Andrew Sephien, Claire F. Bethel, and Christa Nairn are also affiliated to USF Health Morsani College of Medicine, Tampa, Fl, USA.
Ethical Approval: This study was deemed exempt by our institutional review board.
Statement of Human and Animal Rights: This article does not contain any studies with human or animal subjects.
Statement of Informed Consent: The study did not include human subjects, thus no informed consent was obtained.
Declaration of Conflicting Interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding: The author(s) received no financial support for the research, authorship, and/or publication of this article.
ORCID iD: Andrew Sephien 
https://orcid.org/0000-0002-9945-3549
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Supplementary Materials
Supplemental material, Supplemental_material for 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 by Andrew Sephien, Claire F. Bethel, Danielle Gulick, Christa Nairn, Felicia Ourn and Francisco A. Schwartz-Fernandes in HAND