Distal Radioulnar Joint Kinematics Evaluated Using Ultrasonography During Handstanding in Female Gymnasts

Abstract

Background:

Wrist pain prevalence is significantly higher in female gymnasts than in male gymnasts, and the pathological site varies depending on patient age. However, the differences between age groups have not been elucidated with a focus on changes in the kinematics of the distal radioulnar joint (DRUJ).

Purpose:

To analyze the effect of wrist weightbearing during a handstand on the kinematics of the DRUJ using ultrasonography in female elementary school (ES), junior high school (JH), and high school (HS) gymnasts, and to determine whether wrist pain affects the kinematic measurements in female gymnasts.

Study Design:

Descriptive laboratory study.

Methods:

A total of 66 wrist joints in 33 female gymnasts (5 ES, 9 JH, and 19 HS students) were included. Ultrasound examinations were performed in neutral extension, nonweightbearing (NENWB); full extension, nonweightbearing; and full extension, weightbearing (FEWB). The radioulnar joint kinematics were evaluated by measuring the radioulnar separation and dorsivolar shift. The change in distance in the FEWB condition was determined as a reference for those in the NENWB condition and for comparison between the 3 school groups. Also, the change in distance was compared between the gymnasts with and without wrist pain.

Results:

The radioulnar separation increased from the NENWB to the FEWB condition in all 3 groups, and a significantly larger change in distance was observed in HS students compared with ES students (P = .008). The dorsivolar shift decreased from the NENWB to the FEWB condition in ES and JH students; it was almost unchanged in HS students. There was a significant difference in change in dorsivolar shift from the NENWB to the FEWB condition between ES and JH students (P = .023). There were 2 ES, 2 JH, and 10 HS students with wrist pain. The change in radioulnar separation was significantly greater separation in gymnasts with wrist pain compared with those without wrist pain (P < .001).

Conclusion:

The radioulnar joint kinematics during the FEWB condition varied with school age in female gymnasts. The larger increase in the radioulnar separation from the NENWB condition to the FEWB condition might be associated with a biomechanical mechanism of wrist pain in female gymnasts.

Clinical Relevance:

Repetitive tensile loads put female gymnasts at risk of wrist pain and overuse injury.

Artistic gymnastics is characterized by more frequent opportunities to load the upper limbs with body weightbearing than other sports. Furthermore, the load on the wrist joint is twice the body weight during a handspring. ⁶ As a result, 88% of artistic gymnasts experience wrist pain, ³ and wrist pain is the most common symptom in gymnasts, leading to its characterization as “gymnast’s wrist.” The prevalence thereof is also significantly greater in female gymnasts than in male gymnasts, with 87.5% of female gymnasts experiencing wrist pain compared with 50% of male gymnasts. ²

Load-bearing with wrist extension while performing floor exercises and the vault is one of the major causes of wrist pain. The cartwheel and round-off in floor exercises make up 30% of wrist injuries related to gymnastics. ¹⁰ Soft tissue impingement, scaphoid impaction, triangular fibrocartilage complex (TFCC) injuries, and distal radial physeal injuries have been reported as the mechanisms of wrist pain. ¹

The prevalent site of wrist pain injury varies depending on the patient's age. TFCC injuries tend to occur after growth spurts, whereas radial physeal injuries are more common in junior athletes aged 10 to 12 years. The mechanism leading to wrist pain with load-bearing has been reported in previous studies.^1,3 However, the mechanism in each age group is expected to differ from that of others and has not been elucidated with a focus on the kinematics of the distal radioulnar joint (DRUJ).

We therefore aimed to analyze the effect of wrist weightbearing with handstanding on the kinematics of the DRUJ using ultrasonography in female elementary school (ES), junior high school (JH), and high school (HS) student gymnasts, and to compare the kinematic measurements between the 3 school age groups. In addition, we investigated the association of kinematic measurements with the presence of wrist pain in female gymnasts.

Methods

A total of 66 wrists in 33 female gymnasts, 5 ES, 9 JH, and 19 HS students were involved in this study. The mean age of the participants was 14.6 ± 2.5 years. Table 1 presents the demographic data of the 3 school age groups. The study protocol was approved by the Clinical Research Ethics Board of our institution. Written informed consent was obtained from all participants and their guardians.

Table 1.

Demographic Data of Participants ^a

	Elementary School Students	Junior High School Students	High School Students
Age, y	10.4 ± 1.0	13.2 ± 0.9	16.4 ± 1.0
Height, cm	138.5 ± 11.9 b	152.2 ± 4.5	154.1 ± 3.3
Body weight, kg	31.3 ± 8.3 b	42.9 ± 4.6	48.3 ± 3.3
Age at start of competition, y	7.2 ± 0.7	6.6 ± 2.5	6.2 ± 3
Training hours per day	2.2 ± 0.4	3.1 ± 0.7	3.8 ± 0.4
Training days per week	4.8 ± 1.6	5.8 ± 0.6	6
Years of competition	3.6 ± 1.4	6.8 ± 2.3	10.4 ± 2.4

^aData are presented as mean ± SD.

^bn = 4.

Two ultrasound scanners (SONIMAGE613 KONICA, MINOLTA; ARIETTA Prologue, HITACHI) with a high-resolution linear array transducer with frequency ranges of 3 to 8 MHz and 5 to 12 MHz, respectively, were used by an experienced hand therapist (S.N). Ultrasound examinations were performed in 3 wrist conditions: neutral extension, nonweightbearing (NENWB); full extension, nonweightbearing (FENWB); and full extension, weightbearing (FEWB). In the NENWB condition, the elbow was flexed at 90° and the forearm was pronated at 90°, and the wrist was in dorsivolar and radioulnar flexion at 0°. In the FENWB condition, the elbow was extended to 0°, the forearm was pronated to 90°, and the wrist was in maximum dorsiflexion with 0° of radioulnar flexion. In the FEWB condition, the participants performed handstanding supported by a wall with 0° of elbow flexion, 90° of forearm pronation, maximum dorsiflexion, and 0° of radioulnar flexion of the wrist (Figure 1). An ultrasound transducer was placed at the dorsal DRUJ (Figure 2).

Figure 1.

Ultrasound examinations in 3 wrist conditions. (A) Wrist, neutral extension, nonweightbearing. (B) Wrist, full extension, nonweightbearing. (C) Wrist, full extension, weightbearing.

Figure 2.

Placement of the ultrasound transducer on the dorsal side of the distal radioulnar joint.

The acquired images were used to quantitatively evaluate the relative conditions of the radius and ulna. First, the dorsal tubercle of the distal radius and the dorsal vertex of the ulnar head were identified as reference points. Passing through each reference point, 2 lines were drawn parallel to the baseline, which corresponded with the position of the boundary surface between the skin and the ultrasound probe, on the ultrasound window. The distance between the 2 parallel lines was measured as the dorsivolar shift. Two additional lines were drawn perpendicular to the first 2 lines and passed through the reference points. The distance between the 2 parallel lines was measured as the dorsivolar shift (Figure 3), indicated with a plus sign when the dorsal vertex of the ulnar head was on the volar side of radial tubercle and a minus sign when it was on the dorsal side.

Figure 3.

Measurement of radioulnar separation (a) and dorsivolar shift (b). The dorsivolar shift is indicated with a plus sign when the dorsal vertex of the ulnar head was on the volar side of the radial tubercle and a minus sign when it was on the dorsal side.

Because the measurement of DRUJ geometry using an ultrasound image had been rarely utilized in previous reports, we conducted a preliminary study to assess intrarater reliability. The radioulnar separation and dorsivolar shift were measured twice with a time interval of 1 week in each school age group. The preliminary study included 8 images obtained in 2 ES students, 12 images obtained in 3 JH students, and 16 images obtained in 4 HS students. The single examiner (S.N.) who is a hand therapist with 15 years of experience measured the ultrasound image.

Statistical Analysis

The changes in the radioulnar separation and dorsivolar shift in the FEWB condition were determined with reference to those in the NENWB condition, and compared between the ES, JH, and HS groups. In addition, the participants were divided into 2 groups based on the presence of wrist pain, and the changes in radioulnar separation and dorsivolar shift were compared between the 2 groups.

Statistical analysis was performed using 1-way analysis of variance to compare the 3 school age groups. Post hoc comparisons were performed using the Tukey and Games-Howell tests. The radioulnar separation and dorsivolar shift between the 2 groups, with and without wrist pain, were compared using a 2-sample t test.

IBM SPSS Version 26 Statistics Premium Grad Pack (IBM) was used, and a P value <.05 was considered statistically significant.

Results

The intraclass correlation coefficient (1, 1) values of the radioulnar separation in the ES, JH, and HS groups were 0.971, 0.991, and 0.976 (all P < .001), respectively, and those of the dorsivolar shift in the 3 groups were 0.997, 0.993, and 0.981 (all P < .001), respectively.

The radioulnar separations in the NENWB, FENWB, and FEWB conditions were 22.8 ± 2.3 mm, 23.1 ± 2.0 mm, and 24.3 ± 2.9 mm in the ES group, 23.9 ± 2.1 mm, 24.6 ± 2.1 mm, and 27.2 ± 3.6 mm in the JH group, and 23.7 ± 2.3 mm, 24.3 ± 2.0 mm, and 28.4 ± 2.5 mm in the HS group, respectively (Table 2). In the FEWB condition compared with the NENWB condition, the radioulnar separation increased 1.5 ± 2.0 mm in the ES group, 3.4 ± 3.1 mm in the JH group, and 4.7 ± 2.8 mm in the HS group (Figure 4). There was a statistically significant difference in the change in radioulnar separation between the ES and HS groups (P = .008).

Table 2.

Radioulnar Separation (mm) of Each Wrist Condition in Elementary, Junior High, and High School Students ^a

Wrist Condition	Elementary School Students	Junior High School Students	High School Students
Neutral extension, nonweightbearing	22.8 ± 2.3	23.9 ± 2.1	23.7 ± 2.3
Full extension, nonweightbearing	23.1 ± 2.0	24.6 ± 2.1	24.3 ± 2.0
Full extension, weightbearing	24.3 ± 2.9	27.2 ± 3.6	28.4 ± 2.5

^aData are presented as mean ± SD.

Figure 4.

Comparison of change in radioulnar separation between elementary, junior high, and high school students.

The dorsivolar shifts in the NENWB, FENWB, and FEWB conditions were 1.4 ± 1.5 mm, 1.2 ± 2.4 mm, and −0.7 ± 2.3 mm in the ES group, 1.3 ± 1.7 mm, 0.9 ± 1.1 mm, and 0.3 ± 2.1 mm in the JH group, and 1.4 ± 1.6 mm, 1.8 ± 1.4 mm, and 1.4 ± 1.5 mm in the HS group, respectively (Table 3). In the FEWB condition, the dorsivolar shift decreased 2.0 ± 2.0 mm in the ES group and 1.0 ± 1.8 mm in the JH group, and increased 0.1 ± 2.3 mm in the HS group (Figure 5). There was a significant difference in the change in dorsivolar shift between the ES and HS groups (P = .023).

Table 3.

Dorsivolar Shift (mm) of Each Wrist Condition in Elementary, Junior High, and High School Students ^a

Wrist Condition	Elementary School Students	Junior High School Students	High School Students
Neutral extension, nonweightbearing	1.4 ± 1.5	1.3 ± 1.7	1.4 ± 1.6
Full extension, nonweightbearing	1.2 ± 2.4	0.9 ± 1.1	1.8 ± 1.4
Full extension, weightbearing	−0.7 ± 2.3	0.3 ± 2.1	1.4 ± 1.5

^aData are presented as mean ± SD. The dorsivolar shift is indicated with a plus sign when the dorsal vertex of the ulnar head was on the volar side of the radial tubercle and a minus sign when it was on the dorsal side.

Figure 5.

Comparison of change in dorsivolar shift between elementary, junior high, and high school students.

The weightbearing load caused a –2.0mm dorsal shift of the ulna from the wrist neutral condition in ES students, while the load caused a volar shift by 0.1 mm in HS students.

Fourteen gymnasts (42.4%) had wrist pain, including 2 ES, 2 JH, and 10 HS students. The increase in radioulnar separation from the NENWB to the FEWB condition was 6.0 ± 3.2 mm in gymnasts with wrist pain and 3.0 ± 2.5 mm in those without wrist pain, indicating a significant difference (P < .001). The change in dorsivolar shift from the NENWB to the FEWB condition was −0.8 ± 2.7 mm in gymnasts with wrist pain and −0.4 ± 2.1 mm in gymnasts without wrist pain, showing no significant difference (P = .603) (Table 4). In addition, using the data obtained from only HS students, the change in radioulnar separation and dorsivolar shift from the NENWB to the FEWB condition was compared between the students with and without wrist pain. As a result, the change in the radioulnar separation was 6.2 ± 3.0 mm in HS gymnasts with wrist pain and 3.9 ± 2.3 mm in those without wrist pain, indicating a significant difference (P = .018). In contrast, the change in the dorsivolar shift was 0.2 ± 2.2 mm in HS gymnasts with wrist pain and 0.0 ± 2.3 mm in those without wrist pain, showing no significant difference (P = .964).

Table 4.

Change in Radioulnar Separation and Dorsivolar Shift in Gymnasts With or Without Wrist Pain ^a

	With Wrist Pain	Without Wrist Pain	P Value
Radioulnar separation, mm	6.0 ± 3.2	3.0 ± 2.5	<.001
Dorsivolar shift, mm	−0.8 ± 2.7	−0.4 ± 2.1	.603

^aData are presented as mean ± SD.

Discussion

In the current study, the change in DRUJ geometry by setting the wrist joint from the NENWB to the FEWB condition was quantitatively assessed using ultrasonography in female gymnasts. A larger increase in radioulnar separation was observed in HS students compared with ES students, showing statistical significance. The dorsivolar shift decreased from the NENWB to the FEWB condition in ES and JH students, whereas it was almost unchanged in HS students. There was a statistically significant difference in the change in dorsivolar shift between the ES and HS students. In addition, 42.4% of the participants had wrist pain, and there was a statistically significant difference in the change in radioulnar separation between gymnasts with and without wrist pain. This study is the first to reveal that DRUJ kinematics during handstanding in female gymnasts varies with school age. Furthermore, an increased separation of the DRUJ during handstanding is associated with wrist pain.

The bony part of the DRUJ consists of the ulnar head and the sigmoid notch of the distal radius. Several soft tissues, such as the TFCC, distal radioulnar ligament, interosseous membrane, extensor carpi ulnaris tendon, and pronator quadratus, work to stabilize the DRUJ. The TFCC and distal radioulnar ligament directly connect the distal radius to the distal ulna. Xing et al ¹¹ used a computed tomography (CT) scanner to measure wrist joint kinematics in healthy adults, showing that the center of contact of the ulnar head on the sigmoid notch of the distal radius moved 4% in the volar plane and 9% distally by wrist extension with maximum forearm pronation compared with the neutral wrist condition. Hojo et al ⁵ measured the kinematics of the wrist joint in healthy adults using a CT loading device. The distal ulna moved 0.6 mm in the volar plane when an axial compression load of 7 kg was applied in forearm pronation and wrist dorsiflexion, compared with the unloaded state. In the current study, the wrist joint was loaded by handstanding, a basic posture that is frequently performed in gymnastics. The ultrasound scanner enabled measurement of the kinematics of the DRUJ in a condition reproducing mechanical loading in gymnastic performance without radiation exposure. As a result, the ulnar head moved away from the distal radius, indicated by the increased radioulnar separation in the FEWB condition, compared with the NENWB condition in all age groups. This supports the findings of a previous study. ⁵

In an experiment using a cadaveric study, Palmar and Werner ⁸ reported that a traction force of 44.5 N was applied in the direction of DRUJ separation, resulting in 3-mm widening of the joint space. In this study, the radioulnar separation in the handstand condition increased by >3 mm, on average, with reference to the NENWB condition in JH and HS students. Therefore, it was supposed that the DRUJ was subjected to a traction force equivalent to 44.5 N or more during handstanding.

Exposing the wrist joint to weightbearing, 80% of the axial load to the wrist joint is distributed to the radius and only 20% to the ulna in adults. ⁷ The ulna has a negative variance compared with the radius in children with an open physis, and the axial load might be more concentrated on the radius. ⁴ The reduced load on the ulna decreases a force component in the direction of the DRUJ separation, and thus the change in radioulnar separation from the NENWB to the FEWB condition is smaller in ES students.

As for the dorsivolar shift, the change was only 0.1 mm, on average, when the wrist joint changed from the NENWB to the FEWB condition in HS students, and was <0.6 mm as reported by Hojo et al. ⁵ During handstanding, both the dorsal and palmar radioulnar ligaments are taut at the DRUJ separation with full weightbearing, and thus the ulna was not allowed to move in the dorsivolar direction. In contrast, in the ES and JH students, the ulna moved dorsally in the FEWB condition. The smaller separation of the DRUJ left laxity in the dorsivolar direction, and forearm pronation provided much more tension to the dorsal radioulnar ligament than the palmar radioulnar ligament, ⁹ moving the ulna dorsally.

There was a statistically significant difference in the change in the radioulnar separation from the NENWB to the FEWB condition between gymnasts with and without wrist pain, but not in the change in dorsivolar shift. The group with wrist pain showed a larger increase in radioulnar separation than the group without wrist pain. It was suggested that soft tissue constructs, such as the TFCC and distal radioulnar ligament, were exposed to repetitive tensile loads and were consequently at risk of overuse injury and wrist pain.

This study had several limitations. First, a control group including healthy students who did not participate in artistic gymnastics was not available. It is difficult to determine whether the amount of change in the DRUJ kinematics is within the normal range or pathological. Second, wrist pain was not assessed in detail in terms of location, intensity, frequency, or duration from onset. Third, the participants were divided according to their school age. As growth speed varies considerably among adolescent female athletes, this should be based on biological age, such as in skeletal maturation. Because of the small number of participants, we could not conduct statistical analysis of the relationship of wrist pain with the change in DRUJ kinematics in either the ES or JH group. Fourth, this was a cross-sectional study, which is not suitable for research on the cause-and-effect relationship between a larger DRUJ separation and wrist pain; a longitudinal study should be conducted in the future. Finally, with respect to intrarater reliability testing, it was not the same as repeating the positioning and repositioning of the participants, and there was a risk in acquiring completely independent images on separate occasions. It is possible that the methodology underestimates variability in measurements.

Conclusion

The DRUJ kinematics during handstanding vary with school age in female gymnasts. From the NENWB condition to the handstand condition, a significantly larger increase in DRUJ separation was observed in HS students than in ES students. In contrast, ES students showed greater dorsal movement of the ulnar head than HS students. Furthermore, the larger increase in the DRUJ separation may be associated with the biomechanical mechanism of wrist pain in female gymnasts.