Fifth Metacarpal Neck Fractures: Outcome-influencing Factors

Abstract

Introduction Fifth metacarpal neck fractures are extremely common, but there is still no consensus regarding the ideal course of treatment.

Volar angulation and shortening are decisive factors; however, there is still controversy about the cut-off values that translate into worse clinical results.

The present study aims to answer these questions in order to provide additional data to aid in the clinical practice and decision making.

Materials and Methods A retrospective study evaluated patients with fifth metacarpal fractures treated between 2013 and 2018. A total of 133 patients were included, with an average follow-up of 2 months. Surgery was performed in 21 patients, and 112 were treated conservatively. The radiological assessment of volar anguation and shortening was based in the first and last radiographs of the follow-up. The patients were contacted and submited to a questionnaire that included the Quick Disabilities of the Arm, Shoulder and Hand (QuickDASH) score and subjective evaluations of pain (Visual Analogue Scale, VAS), hand strength, stiffness and finger mobility, and cosmetic result.

Results Surgery was more successful in reducing angulation than the conservative treatment, achieving more anatomic final values for angulation and shortening (p < 0.05). On the other hand, surgery seems to be associated with a higher notion of limited finger mobility (p = 0.02).

Among patients treated conservatively, inicial angulations > 60° and final angulations > 50° were associated with worse cosmetic results (p = 0,039). Final shortening > 4 mm translated into a higher notion of stiffness and limited finger mobility (p = 0.034).

More advanced age showed a correlation with higher scores on the VAS (p = 0.023) and QuickDASH (p < 0,001). Female patients (p = 0.02) were also associated with higher VAS scores. The overall satisfaction rate was of 97%.

Conclusion Although globally the functional outcome of these fractures is very good, the present study reports several factors that should be considered when treating fifth metacarpal neck fractures.

Keywords

fifth metacarpal neck fractures - volar angulation - shortening

Introduction

Fractures of the neck of the fifth metacarpal are extremely common, comprising up to 20% of all hand fractures[1] [2]

They are commonly known as “boxer's fracture”, due to the fact that the mechanism of injury is often punching solid objects with clenched fists.

Most of these fractures are isolated and stable, which are ususally accepted for conservative treatment, with good functional results. Other fracture sequelae commonly observed in other parts of the skeletal system, like non-union and secondary arthritis in the adjacent joints, are rare after metacarpal fractures. However, there are a few situations in which the surgical treatment is recommended, like any degree of rotational deformity and “significant” volar angulation and shortening.

Many authors[3] [4] believe that the functional impairment of the hand is minimal even after mal-union in a fracture angulated up to 70°. Meanwhile, the recommendions found in the literature for the acceptable values of volar angulation vary between 20° and 70°.

Even though volar angulation and shortening are important factors to consider when choosing the treatment, there is still much controversy around the cut-off values above which patients report worse functional outcomes or residual symptoms when treated conservatively, and no treatment guidelines have been established yet.

For the conservative treatment, the traditional type of immobilization is made with Plaster-of Paris, and it includes the ray of the affected finger and of its neighbouring finger, which extends proximally to the upper forearm.[2] [5] [6] [7]

Another aspect for which there is no consensus is the duration of immobilization in the conservative treatment. The recomendations are also extremely variable, with a few studies reporting only one week, followed by progressive functional rehabilitation, while other studies[2] report longer periods.

When the surgical treatment is indicated, the fracture is usually fixed with intramedullary (IM) mininails/ Kirschner wires (K-wires).[8] [9] Other surgical options can be used, such as K-wires placed as crossed pins at the fracture site,[10] transverse pins to the neighbouring metacarpal[11] or open reduction and internal fixation (ORIF) with screws and plates. Compared to IM K-wire fixation, these carry the risk of increased stiffness and significant reduced range of motion of the finger.[12]

With the present study, we aim to tackle some of the aforementioned controversial topics, as a way of providing additional evidence to aid clinicians in their decision making when faced with fifth metacarpal neck fractures.

Methods

Patients presenting in the emergency room with fifth metacarpal neck fractures between 2013 and 2018 were identified, and their demographic data, admission and follow-up radiographs, and clinical records were retrospectively reviewed.

Subjects were excluded if they were under 18 years old, had multiple metacarpal or open fractures, incomplete medical records, or inadequate radiographic images. Subjects were also excluded if their follow-up was conducted at a different institution (such as insurance companies).

A total of 133 patients were included. Their mean age was of 34 years, and 92% of them were male. Patients were followed up in the outpatient clinic until fracture consolidation. The mean follow-up time was of two months.

Surgery was performed in 21 patients (17 with IM K-wires, and 4 with a mini-plate), and 112 were treated conservatively. The immobilization time varied between 1 and 7 weeks, with an average of 3.7 weeks. ([Table 1])

Table 1

Gender	Male	122
	Female	11
Mean age (in years)		34
Mean follow-up (in months)		2
Treatment	Conservative	112
	Surgery	21
Surgical procedure	Intramedullary Kirschner wire	17
	Mini-plate	4
Mean immobilization time (in weeks)		3.8

The records of the follow-up appointments were extensively reviewed, and data regarding complications such as malunion, non-union, rotational deformity, iatrogenic fractures, or hardware-related complications were collected.

The radiographic measurements of the volar angulation were performed using a 30° oblique view, according to method medullary canal-oblique (MC-30).[13] The shortening measurements were performed using the anteroposterior (AP) view. These measurements were performed in the initial X-rays and at the end of the follow-up.

At least two years after the fracture, the included patients were contacted by telephone, and they answered a questionnaire about the impact of the facture on their daily activities and work, which included the Quick Disabilities of the Arm, Shoulder and Hand (QuickDASH) score and a subjective evaluation of pain through the Visual Analogue Scale (VAS), loss of hand strenght and finger mobility, and cometic result. Out of the 133 patients included, only 71 were available to answer the questionnaire.

The data were organized, and the statistical analysis was performed using the Statistical Package for the Social Sciences (IBM SPSS Statistics for Windows, IBM Corp., Armonk, NY, US) software, version 26.0.

The parametric Student t-test was used to compare quantitative values, and non-parametric tests were used when the variables did not meet the criteria. We used the Chi-squared test to compare qualitative values ≥ 5. The Fisher test was used for lower values, and the Pearson correlation coefficient was used to determine the association between two continuous variables. Values of p < 0.05 were deemed statistically significant.

Results

The average initial fracture angulation for all patients was of 43,75° (range: 16°–84°), and the final angulation averaged 37.8° (range: 13°–63°). The mean variation between these two measurements was of -5.9°.

The average initial and final shortenings were of 2.86mm (range: 0–8.7 mm) and 2.84 mm (range: 0–8.9 mm) respectively. The mean variation between these measurements was of 0.04 mm.

A total of ten complications were reported, three in patients treated surgically and seven in the group treated conservatively. No statistically significant differences were found between them regarding the rate of complications ([Table 2]).

Table 2

	Conservative (N = 112)	Surgery (N = 21)		p*
		Intramedullary Kirschner wires (N = 17)	Mini-plate (N = 4)
TOTAL	7	3	0	0.35
Refracture	4	0	0	1
Loss of fixation	0	1	0	0.15
Iatrogenic fracture	0	1	0	0.15
Malunion	2	1	0	0.40
Rotational deformity	1	0	0	1

The surgical group had a significantly higher initial volar angulation (50° versus 43°; p = 0.008), a greater difference in angulation was achieved with surgery (-23° versus -3°; p < 0.001), and the final volar angulation was, therefore, significantly lower in the surgical group (27° versus 40°; p < 0.001) when compared to the conservative treatment group.

The surgical group had a significantly higher mean initial shortening (4.02 mm versus 2.63 mm; p = 0.001), but no statistically significant difference was found regarding the shortening variation or the final values. ([Table 3])

Table 3

		Conservative	Surgery	p*
Angulation (°)	Initial	43	50	0.008
	Final	40	27	< 0.001
	Variation	(-) 3	(-) 23	< 0.001
Shortening (mm)	Initial	2.63	4.02	0.001
	Final	2.8	2.9	0.734
	Variation	(+) 0.3	(-) 1.1	0.078

The mean score on the QuickDASH (0-100) was of 5.46 (range: 0 to 68.2); the VAS score (0-10) averaged 1.24 (range: 0 to 9), and the cosmetic result (0-5) averaged 1.17.

Most patients (83%) did not report any limitation in finger mobility or stiffness, 14% reported mild limitation, and only 3% reported severe limitation in finger mobility and stiffness, with an impact on their daily activities.

Morevoer, most patients (73%) did not report any notion of diminished hand strength, 21% had mild loss, and only 6% noted severe loss of hand strength.

Overall, 97% of the patients claimed to be satisfied with their treatment ([Table 4]).

Table 4

		Mean	Count	%
QuickDASH (0-100)		5.46
Visual Analog Scale (0-10)		1.24
Cosmetic score (0-5)		1.17
Finger mobility limitation	None		59	83
	Mild		10	14
	Severe		2	3
Loss of strength	None		52	73
	Mild		15	21
	Severe		4	6
Patient satisfaction	Yes		69	97
	No		2	3

Patients who underwent surgery reported a significantly higher notion of limitation in finger mobility and stiffness than the ones treated conservatively (p = 0.02). No other statistically significant differences were found between the surgical and conservative treatment groups regarding the clinical outcomes.

Among the patients treated conservatively, higher values of volar angulation were significantly associated to a worse cosmetic result. The cut-off values that yielded worse cosmetic results were initial angulations higher than 60° (p = 0.039) and final angulations higher than 50° (p = 0.039). Among the large range of volar angulations, there were no other significant differences regarding the functional results, pain, stiffness, or hand strength.

When considering shortening, patients with final values higher than 4 mm reported more limited finger mobility (p = 0.034). The shortening values had no significant influence on the other outcomes.

Advanced age was positively correlated with higher VAS (p = 0.023) and QuickDASH (p < 0.001) scores at the end of the follow-up. The female gender (p = 0.02) was also associated with higher VAS scores ([Table 5]).

Table 5

	QuickDASH (0-100)		p	VAS (0-10)	p	Cosmetic score (0-5)	p	Stiffness/limitation in finger mobility			p	Loss of strength			p	Patient satisfaction		p
								None	Mild	Severe		None	Mild	Severe		Yes	No
Gender	Male	4		1	p = 0.02 [*]	1		52	9	1		47	13	2		61	1
	Female	15.7		3		1		7	1	1		5	2	2		8	1
Mean age (in years)			p < 0.001		p = 0.023			36	37	61		35	36	60		36	61
Mean Follow-up time (in months)								2	3.1	2		2	2.1	4.8		2.2	2
Treatment	Conservative	4.8		1		1		51	4	1	p = 0.02	42	12	2		55	1
	Surgery	7.9		1		1		8	6	1		10	3	2		14	1
Surgical procedure	Kirschner wire	2.9		0		1		7	4	0		8	3	0	p = 0.03	11	0
	Mini-plate	21.6		1		1		1	2	1		2	0	2		3	1
Immobilization time (in weeks)								3.6	3.5	3		3.7	3.4	3.5		3.6	3
Angulation (°)	Initial (a)						p = 0.039 (a)	43	47	41		45	42	39		44	41
	Final (b)						p = 0.039 (b)	39	32	35		39	36	28		38	35
	Variation							(-) 5	(-) 15	(-) 6		(-) 6	(-) 6	(-) 11		(-) 6	(-) 6
Shortening (mm)	Initial							2.67	3.09	3.15		2.79	2.6	2.7		2.74	3.15
	Final (c)							2.3	3.9	4.1	p = 0.034 (c)	2.5	3	2.8		2.5	4.1
	Variation							(-) 0.3	(+) 0.9	(+) 1		(-) 0.3	(+) 0.4	(+) 1		(-) 0.1	(+) 1

Discussion

The age and sex distribution of the sample of the present study is typical for this fracture.

The only difference found in the present study between the two main treatment approaches was a higher notion of stiffness and limitation in finger mobility among the patients submitted to surgery. This was consistent with reports found in the literature;[12] [14] however, we have found no differences regarding the complication rate and the two types of surgical treatment (IM K-wires and plates).

The worse cosmetic result reported by patients with higher initial volar angulation values could be used as an argument for the operative treatment in such patients; however, no relationship was found between the angulation values and the worse functional results or pain scores; in fact, there were only incidental complaints among the paients with worse cosmetic deformity. At the end of the follow-up, 97% of the patients were satisfied with the overall result, irrespective of the cosmetic result.

The good results of the conservative treatment may be due to the great mobility of the fifth ray of the hand, which makes it more forgiving regarding the permanent changes in the skeletal anatomy than the fixed second and third rays.

In the literature, the optimal management of these fractures is still highly variable. Studies support the conservative treatment for fractures with up to 70° of residual angulation,[3] [4] and other studies support more a aggressive management of these injuries.[1] [15]

The present is a retrospective study, and the use of clinical records as a source of data may introduce some bias.

Due to the coronavirus disease 2019 (COVID-19) contingency, the assessment of the functional outcomes was based on a questionnaire applied by telephone, which may lead to more subjective results regarding some of the outcomes, such as stiffness/finger mobility or strength.

Another potential limitation was the use of oblique radiographs for the measurements of the volar angulation. Although there is less superimposition of the metacarpals, which is one of the reasons we chose this view, there have been reports that this incidence is associated not only with higher fracture angles (by approximately 10°) when compared with the lateral view, but also with more rotational variability, which may influence the measurement of the angle.[16] [17]

Conclusion

The functional outcome of these fracture is overall very good. The surgical treatment appears to yield more anatomical values of angulation and shortening than the conservative treatment; however, these differences do not seem to result in better functional or clinical results. In fact, surgically-treated patients reported a higher notion of stiffness and limited finger mobility, as did patients with final shortening values higher than 4 mm.

Initial and final angulations higher than 50° and 60° respectively were associated with worse cosmetic results, without any influence on the other outcomes.

Conflict of Interests

The authors have no conflcit of interests to declare.

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Publication History

Received: 26 February 2021

Accepted: 09 August 2021

Article published online:
13 December 2021