Orthopedics

Feature Articles 

Assessing Rotational Deformity of the Little Finger

Philip J. Lahey, MD; Archit Patel, MD; Kevin K. Kang, MD; Mihir R. Patel, MS; Jack Choueka, MD

Abstract

Excessive scissoring or overlap of fingers can cause discomfort, weaken grip strength, and affect cosmesis. The treatment of little finger fractures is guided by the degree of scissoring or rotational deformity perceived in the digit. The purpose of this study is to assess the variation of little finger scissoring or overlap in the normal population using standard clinical examination. We evaluated 80 uninjured little fingers in 40 normal patients. The digital images of photographed hands, taken in both extension and flexion, were used to evaluate the overlap percentage of the adjacent fingernail as a proxy for rotation of the digits. Paired t tests were used for statistical analysis. The average fingernail overlap was 25%±20%, ranging from 0% to 71%. The average overlap on the left hand was significantly less at 21%±18% as compared to 30%±21% on the right ( P<.01). The average variation between hands in individuals was 16%±13%.

This study confirms that overlap or scissoring of the little finger varies between the hands of a given individual. Our results question the usefulness of assessing rotational deformity of the little finger by checking for overlap and comparing with the contralateral side. This has implications not only in assessing patients for possible surgery, but also in planning and performing surgical reductions of acute fractures and for correction of malunions.

Drs Lahey, Patel (Archit), Kang, and Choueka, and Mr Patel (Mihir) are from the Department of Orthopedic Surgery, Maimonides Medical Center, Brooklyn, New York.

Drs Lahey, Patel (Archit), Kang, and Choueka and Mr Patel (Mihir) have no relevant financial relationships to disclose.

Scissoring or overlap of fingers can lead to patient reports of discomfort, decreased grip strength, and cosmetic deformity. Scissoring of the digits on flexion has long been described as an accurate clinical tool to predict functional impairment on healing. 1,2 As a result, the basis of acceptable treatment is influenced by the degree of scissoring, or rotational deformity perceived in the digit. It is commonly accepted that the tip of a finger in the flexed position should touch adjacent fingers as they approach the base of the thenar eminence, but should not overlap. 3 Degree of rotation and function is determined by comparison to the unaffected hand. Tan et al 4 demonstrated in a recent article that 90% of normal patients had overlap of at least 1 finger using a specialized device to standardize hand position. These findings, while important, are not always clinically applicable. In the office, surgeons are left with clinical examination to assess for rotational deformities without the use of specialized instruments. We therefore sought to assess the reproducibility and degree of overlap and asymmetry in a standard clinical examination.

Study patients were healthy volunteers. Any individual with a history of finger or hand trauma, arthritis of the hands, or any other known deformity of the nails or fingers was excluded. To ensure clinical reproducibility, a digital camera with a Canon (5.8–17.4mm lens; Lake Success, New York) was mounted on a tripod and set at a distance comparable to the eye level of a practitioner (45 cm). Photographs of each individual’s hands were taken with the fingers in extension to measure the nail width of the little finger (Figure ). A second photograph was obtained with the metacarpophalangeal and proximal interphalangeal joints in flexion (Figure ). To observe the fingers in extension, the patients placed their hands in approximately 90° of pronation with their palms resting on a flat surface. For analysis in flexion, hands were placed in 90° of supination with the dorsal aspect of the hand resting on the same flat surface. The digital images…

Abstract

Excessive scissoring or overlap of fingers can cause discomfort, weaken grip strength, and affect cosmesis. The treatment of little finger fractures is guided by the degree of scissoring or rotational deformity perceived in the digit. The purpose of this study is to assess the variation of little finger scissoring or overlap in the normal population using standard clinical examination. We evaluated 80 uninjured little fingers in 40 normal patients. The digital images of photographed hands, taken in both extension and flexion, were used to evaluate the overlap percentage of the adjacent fingernail as a proxy for rotation of the digits. Paired t tests were used for statistical analysis. The average fingernail overlap was 25%±20%, ranging from 0% to 71%. The average overlap on the left hand was significantly less at 21%±18% as compared to 30%±21% on the right ( P<.01). The average variation between hands in individuals was 16%±13%.

This study confirms that overlap or scissoring of the little finger varies between the hands of a given individual. Our results question the usefulness of assessing rotational deformity of the little finger by checking for overlap and comparing with the contralateral side. This has implications not only in assessing patients for possible surgery, but also in planning and performing surgical reductions of acute fractures and for correction of malunions.

Drs Lahey, Patel (Archit), Kang, and Choueka, and Mr Patel (Mihir) are from the Department of Orthopedic Surgery, Maimonides Medical Center, Brooklyn, New York.

Drs Lahey, Patel (Archit), Kang, and Choueka and Mr Patel (Mihir) have no relevant financial relationships to disclose.

Correspondence should be addressed to: Archit Patel, MD, Department of Orthopedic Surgery, 927 49th St, Brooklyn, NY 11219 (apatel2@maimonidesmed.org).
Posted Online: July 07, 2011

Scissoring or overlap of fingers can lead to patient reports of discomfort, decreased grip strength, and cosmetic deformity. Scissoring of the digits on flexion has long been described as an accurate clinical tool to predict functional impairment on healing. 1,2 As a result, the basis of acceptable treatment is influenced by the degree of scissoring, or rotational deformity perceived in the digit. It is commonly accepted that the tip of a finger in the flexed position should touch adjacent fingers as they approach the base of the thenar eminence, but should not overlap. 3 Degree of rotation and function is determined by comparison to the unaffected hand. Tan et al 4 demonstrated in a recent article that 90% of normal patients had overlap of at least 1 finger using a specialized device to standardize hand position. These findings, while important, are not always clinically applicable. In the office, surgeons are left with clinical examination to assess for rotational deformities without the use of specialized instruments. We therefore sought to assess the reproducibility and degree of overlap and asymmetry in a standard clinical examination.

Materials and Methods

Study patients were healthy volunteers. Any individual with a history of finger or hand trauma, arthritis of the hands, or any other known deformity of the nails or fingers was excluded. To ensure clinical reproducibility, a digital camera with a Canon (5.8–17.4mm lens; Lake Success, New York) was mounted on a tripod and set at a distance comparable to the eye level of a practitioner (45 cm). Photographs of each individual’s hands were taken with the fingers in extension to measure the nail width of the little finger (Figure ). A second photograph was obtained with the metacarpophalangeal and proximal interphalangeal joints in flexion (Figure ). To observe the fingers in extension, the patients placed their hands in approximately 90° of pronation with their palms resting on a flat surface. For analysis in flexion, hands were placed in 90° of supination with the dorsal aspect of the hand resting on the same flat surface. The digital images were uploaded to a computer and analyzed by 2 independent observers (P.J.L., M.R.P.) using ImageJ (NIH, Bethesda, Maryland) software to measure both the width of the little fingernail in extension and the degree of overlap in flexion. The degree of overlap was quantified by the percentage of nail obscured by the adjacent finger.

Fingers in extension.

Figure 1:. Fingers in extension.

Fingers in flexion.

Figure 2:. Fingers in flexion.

The mean and standard deviation were calculated for percentage of overlap and chi-square analysis was used to test for significance between groups. The average difference between left and right hands in each individual was also analyzed. A P value of <.05 was considered significant. The Kappa coefficient was calculated to measure interobserver reliability between the 2 authors.

Results

Forty patients met inclusion criteria and had measurements made of both hands. The 23 men and 17 women had an average age of 35.9 years (range, 22–69 years). Seven patients were left-hand dominant. Seventy of 80 hands had at least partial overlap of the little finger, and 37 of 40 patients showed asymmetric overlap between left and right hands. The average variation between hands in individuals was 16%±13%. The average little finger fingernail overlap was 25%±20%, ranging from 0% to 71%. The average overlap on the left was 20%±18% as compared to 30%±21% for right hands. This difference was statistically significant ( P<.01). The Kappa coefficient calculated was 0.82, reflecting substantial agreement between the 2 authors performing measurements.

Discussion

Malrotation of the little finger is an indication for surgery for metacarpal and phalangeal fractures since it can lead to overlap and impaired function. A number of different methods have been described to assess malrotation. Scissoring or overlap at the fingertip with the metacarpophalangeal and proximal interphalangeal joints flexed, particularly when compared to the contralateral hand, is a well-known technique. 1

While testing with the distal interphalangeal in flexion may offer additional functional information, it would be impossible to assess fingernail overlap in this position. As a result, testing was done with the distal interphalangeal joint in extension to reproduce this common and accepted clinical examination. However, it can be painful for a patient to make a fist with a fracture.

Tan et al 4 showed that end-on examination of the fingernails in extension or flexion is somewhat problematic. Their study showed that in normal patients, fingernails are neither horizontal nor parallel to each other and the little finger is the most supinated in both extension and flexion with a range of 30° (-5° to 25°). In addition to substantial variation in the alignment of the fingernails within a hand, significant asymmetry of nail inclination between the 2 hands also exists. In another study evaluating nail inclination, 20% of fingernails did not match within 5°, and nearly 5% did not match within 10°. 5

We challenge the traditional thinking that normal individuals have no overlap when testing for scissoring. In this study, we found that scissoring is not only common, but actually the norm, with 70 of 80 hands exhibiting some degree of little finger overlap. The large variability of overlap and the frequent asymmetry in these normal patients demonstrate that scissoring, even when compared to the contralateral hand, may not reliably demonstrate malrotation. We found the average difference in overlap of the little finger to vary significantly. This has implications not only in assessing patients for possible surgery, but also in planning and performing surgical reductions of acute fractures and for correction of malunions.

This study is somewhat limited by the fact that small variations in the position of the hand under the camera could have affected the amount of overlap recorded. Efforts were made to standardize hand positions while attempting to mimic a clinical examination. Functional tests were also not performed to determine if any of our normal patients had any functional deficit from their overlapped little fingers. While it is possible the variation between left and right hands found during data analysis may be attributed to hand dominance, that analysis goes beyond the scope of our study.

The practitioner must be aware of the variation among the population as well as the individual when determining the treatment for a patient with little finger pathology.

References

  1. 1. Jupiter JB, Axelrod TS, Belsky MR. Fractures and dislocations of the hand. In: Browner BB, ed. Skeletal Trauma. 4th ed. Philadelphia, PA: Saunders; 2003:1221–1341.
  2. 2. Rosenwasser MP, Quitkin HM. Malunion and other posttraumatic complications in the hand. In: Berger RA, Weiss AC, eds. Hand Surgery. Philadelphia, PA: Lippincott, Williams & Wilkins; 2004:207–232.
  3. 3. Weckesser EC. Rotational osteotomy of the metacarpal for overlapping fingers. J Bone Joint Surg Am. 1965; (47):751–756.
  4. 4. Tan V, Kinchelow T, Beredjiklian PK. Variation in digital rotation and alignment in normal subjects. J Hand Surg Am. 2008; 33(6):873–878. doi: 10.1016/j.jhsa.2008.02.006 [CrossRef]
  5. 5. Bansal R, Craigen MA. Rotational alignment of the finger nails in a normal population. J Hand Surg Eur. 2007; 32(1):80–84. doi: 10.1016/j.jhsb.2006.09.011 [CrossRef]

10.3928/01477447-20110526-12

Sign up to receive

Journal E-contents
click me