INTRODUCTION
Active loading of the affected lower limb from the early postoperative period has recently been recommended for the rehabilitation of patients with hip fracture. However, these patients exhibit load asymmetry in standing, sit-to-stand (STS), and walking, wherein the amount of load on the affected limb decreases while that on the unaffected limb predominates (Houck et al., 2011; Pfeufer et al., 2019). The load asymmetry is particularly pronounced in STS than in standing and walking (Talis et al., 2008). In addition, STS without upper limb assistance promotes the load predominantly on the unaffected side (Kneiss et al., 2012). Load asymmetry in the lower limbs during STS is a frequent clinical problem in patients with hip fracture.
Load asymmetry during STS is associated with decreased walking ability, impaired balance, and an increased risk of falling (Briggs et al., 2018a; Kneiss et al., 2015). This asymmetry may result from factors, such as pain in the affected limb, muscle weakness, and differences in leg length (Kneiss et al., 2012). Furthermore, load asymmetry may be related to motor learning, with a predominance of the unaffected limb resulting from postoperative pain-avoidance behavior (Zablotny et al., 2020). Notably, the condition can persist even after postoperative pain has subsided (Houck et al., 2011). Therefore, load asymmetry during STS is one of the issues that must be addressed in rehabilitation to improve the performance of activities of daily living in patients with hip fracture.
In a review of interventions to improve motor function in patients with hip fracture, resistance, balance, lower limb function, gait, and endurance training were reported (Fairhall et al., 2022). Among these, the training content aimed at improving load asymmetry includes single-leg standing, standing steps, symmetry-aware walking, and STS (Briggs et al., 2018b; Sherrington et al., 2004). These reports have examined the effects of a compound exercise program; however, it remains unclear which exercises are effective for addressing asymmetry in loading (Briggs et al., 2018b; Sherrington et al., 2004). The STS movements included in the compound exercise programs in previous studies were performed using the conventional method of same position on the affected and unaffected feet (Briggs et al., 2018b; Sherrington et al., 2004). However, few studies have directly compared different STS conditions with respect to their immediate and training effects on lower limb loading in patients with hip fractures.
Given the persistent challenges in addressing load asymmetry with conventional STS methods, alternative approaches warrant investigation. For instance, an STS movement in which the paretic foot is positioned posteriorly has been devised for patients with hemiplegic stroke to improve load distribution (Roy et al., 2006). This modification has also demonstrated effectiveness in healthy young participants, increasing the load on the posterior limb (Jeon et al., 2019). Furthermore, in patients with hip fracture, pain limits the amount of load on the affected limb and reduces the hip flexion angle during STS (Walheim et al., 1990). Notably, STS movements with a high seat height reduce the hip flexion angle, which may increase the amount of load on the affected limb in these patients (Burdett et al., 1985). Therefore, changes in foot position and seat height during STS movements can be effective ways to immediately increase the load on the affected lower limbs in patients with hip fracture. However, few studies have directly compared these modified STS techniques with conventional methods to determine their effectiveness in improving lower limb loading and functional gait outcomes through repeated training.
This study aimed to determine whether modified STS training increases the amount of load on the affected limb during STS and whether it increases the amount of load on the affected limb during walking for patients with hip fracture, thereby contributing to improved gait ability. We hypothesized that modified STS training would promote weight bearing on the affected limb more than aligned STS and improve load asymmetry during STS and gait in patients with hip fracture.
MATERIALS AND METHODS
Participants
Seventy-two patients with hip fracture admitted to a rehabilitation unit or community comprehensive care unit between September 2023 and December 2024 participated in the study. Patients who could perform STS without upper limb support from a seat height of 130% of their lower leg length and walk with or without a cane were included. The exclusion criteria comprised orthopedic, central nervous system, neuromuscular, and internal disorders that significantly affected STS and walking. The purpose, content, and ethical requirements of this study were fully explained to the participants orally and in writing. Written informed consent was obtained from all the participants. This study was approved by the Research Ethics Committee of Seijoh University (approval number: 2022C009) and the Ethics Committee of Ichinomiya City Kisogawa Municipal Hospital (approval number: R4-1).
The effect size f for the repeated measures analysis of variance in the F test family was set at a moderate value of 0.25, with power at 0.80, resulting in a total sample size of 34. Sample size was calculated using the G*Power software version 3.1 (Franz Faul, Heinrich Heine University Düsseldorf, Germany). Overall, 33 participants were included, excluding those who declined consent or had measurement difficulties due to cognitive decline. The participants were stratified by age and randomized into groups: 17 and 16 in the modified and normal STS groups, respectively (Fig. 1). Furthermore, participants who can measure their right and left lower limb loads during walking were selected, which comprised 12 in the modified STS group and 10 in the normal STS group. Basic attributes, such as age, sex, diagnosis, surgical form, postoperative days, cognitive function, and level of walking independence, as determined by the mobility item of the functional independence measure, were obtained from medical records at the time of admission.
Interventional methods
In the modified STS group, the affected limb was positioned one-half posterior to the unaffected limb. In the normal STS group, the participants stood from the same position on the affected and unaffected limbs (Fig. 2). Both groups stood at a seat height of 140% of the participant’s lower leg length. The number of STS repetitions was set to 10 times per set, and the number of sets was defined as the number of sets the participant felt “a little tight” in terms of lower limb fatigue. The number of sets was reset weekly, and the number of sets performed was recorded for each patient. The daily STS training time for the study intervention was approximately 15 min for both groups. The training was conducted under one-on-one supervision, and any deviations in foot position were corrected. The training was supervised by physical therapists with 1 to 30 years of postgraduate experience. The training period was 2 weeks, 7 days a week, and a total of 14 interventions were performed. The participants were blinded and were not informed of the training task. Physical therapy other than the intervention consisted mainly of range-of-motion training, muscle strengthening training, and gait training, which were similar in both groups. Each item was measured before and after the intervention. The measurement items included the amount of load on the affected and unaffected limbs during STS, amount of load on the affected and unaffected limbs during walking, stance time on the affected and unaffected limbs, 10-m gait speed, maximum isometric muscle strength of the affected limb, balance function (Berg Balance Scale score, BBS score), and degree of pain in the affected limb (visual analogue scale score, VAS score).
Amount of lower limb load during STS
The load on the lower limbs during STS was measured using a stabilometer GP-6000 (ANIMA Co., Japan) (Fig. 3). Unlike the training protocol, the seat height was set at 130% of the lower leg length, at which all participants could perform STS. The starting posture for the measurement was with both upper limbs crossed in front of the chest and the participant’s feet grounded in the same position on the left and right plates of the stabilometer. The participants were instructed to perform STS using a verbal cue from the examiner, which was performed thrice. The STS speed was controlled using an electronic metronome, and the time from start to finish of the STS was 3 sec. The STS movements were captured from the sagittal plane of the affected side using a video camera. The reflective markers were placed on the acromion, greater trochanter, lateral femoral epicondyle, and lateral malleolus. Image analysis software Image J version 1.53 (NIH Co., USA) was used to determine the lower limb joint angles at the start and end of the STS. Standing was defined as the point at which the hip flexion angle increased; bottom-off was defined as the point at which the self-actuated light switch was turned off; and the completion of STS was defined as the point at which the hip extension angle reached its maximum. The amount of lower limb load for each affected and unaffected side was the average value of the interval from the bottom-off to the completion of STS, and the average value of the three trials was adopted.
Amount of lower limb load and stance time during walking
Lower limb load and stance time were measured using a shoe-type load meter Sokumaru (DUPLODEC Co., Japan) during walking (Fig. 3). Shoe-type load meters were attached to the left and right feet, and measurements were obtained while walking for 15 m at an optimum speed. Participants who had difficulty walking unaided were allowed to use a walking aid, such as a cane, which did not differ before and after intervention. Changes in the load on the right and left lower limbs during the measurement were captured using a personal computer with a sampling frequency of 8–12 Hz. The onset and end of loading were defined as the onset and end of loading, respectively, when the load increased from and returned to the baseline value. The time from the start of the loading to the start of the next loading was defined as one gait cycle. In one gait cycle, the loading and swing times were determined for the affected and unaffected limbs, and the stance time was calculated by excluding the double support time. Thereafter, a 10-step gait cycle was added and averaged. The peak of the mean load waveform divided by the participant’s body weight (%BW) was used as the load on the affected and unaffected limbs.
Maximum isometric muscle strength, BBS score, and VAS score
The maximum isometric muscle strength was measured during hip flexion, extension, abduction, and knee extension of the affected limb using a handheld dynamometer μTas F-1 (ANIMA Co., Japan). Hip flexor strength was measured in the sitting position with the hip flexors fixed at 80° with a belt and a sensor placed on the distal anterior thigh. Hip extension was measured in the single-leg standing posture with both upper limbs supported by a belt fixed at 30° of hip flexion and a sensor placed on the distal posterior femur. Hip abduction was measured in the supine position, with both hip joints fixed with a belt at 0° abduction and a sensor placed on the distal outer femur. Knee extension was measured in the sitting position with a belt fixed at 80° of knee joint flexion and a sensor placed on the distal front of the lower leg (Fig. 4). Three measurements were performed, and the average value of each measurement was calculated.
BBS is an evaluation of balance function using activity of daily living and consists of 14 items (Berg et al., 1989) scored on a 5-point scale, with a total score of 56 points. Higher scores indicate better balance. The participants performed the actions under the verbal instructions of the examiner and were scored based on their ability or inability to perform the actions.
The VAS for pain at the surgical site was measured by drawing a 10-cm-long line on a sheet of paper with the left end as “no pain” and the right end as “the strongest pain in life.” The participants were instructed to indicate the degree of pain in the affected limb at rest on the line, and the distance from the left end was recorded.
Statistical analysis
Basic attributes were compared between the modified and normal STS groups using the chi-square test, unpaired t-test, and Mann–Whitney U-test, depending on the data scale. Two-way analysis of variance was performed for two factors, time and group, amount of load during STS, amount of load during walking, maximum isometric muscle strength, and BBS score. Bonferroni multiple comparison test was used to determine the interaction effects. For subanalysis, the Pearson correlation coefficient or Spearman rank correlation coefficient was used to examine the relationship between pre- and postintervention changes in each measurement item. Statistical analyses were performed using BellCurve for Excel Statistics (Social Survey Research Information Co., Japan), with statistical significance set at 5%.
RESULTS
Participant flow
Thirty-three participants were included the intervention; however, one participant in the normal STS group was discharged early due to a deterioration of his general condition. After excluding those for whom measuring the load on the left and right lower limbs during walking was impossible, 12 and 10 participants remained in the modified and normal STS group, respectively (Fig. 1). None of the participants in the modified STS group dropped out during the intervention period, and no adverse events, such as lower limb overload, were observed. All 17 participants completed the 2-week modified STS training program. The number of STS attempts per day in each group was 35.00±5.00 in the modified STS group and 34.50±8.29 in the normal STS group (mean± standard deviation), with no significant difference between the two groups (P=0.698).
Baseline data
The baseline values of both groups are shown in Table 1. In terms of sex, a difference in the proportion of male and female participants was observed between the modified and normal STS groups (P<0.05). No significant differences were noted in age, diagnosis, surgical form, postoperative days, cognitive function, degree of pain in the affected limb, and degree of walking independence between the two groups.
Amount of lower limb load during STS
Table 2 shows the load during the STS test before and after the intervention in both groups. An interaction was observed for the load amount on the affected limb (P<0.05). Post hoc test results showed that the modified STS group showed a significant increase after the intervention compared with pre-intervention (P<0.05), whereas the normal STS group showed no significant difference between pre- and post-interventions (P=0.185). After the intervention, the modified STS group showed a significantly higher load on the affected limb than that in the normal STS group (P<0.05). No main or interaction effects were observed for the amount of load on the unaffected limb or load symmetry.
Amount of lower limb load during walking, stance time, and 10-m gait speed
Table 3 shows the load, stance time, and 10-m gait speed before and after the intervention in both groups. No main effect or interaction was observed for the amount of load on the affected limb and the ratio of the load on the affected limb to that on the unaffected limb. An interaction effect exists for the stance time of the affected limb (P<0.05). Post hoc test results showed a significant increase in the modified STS group after the intervention compared with that before the intervention (P<0.05), and no significant difference was observed in the normal STS group before and after the intervention (P=0.276). Additionally, no significant difference was observed between the two groups after the intervention (P=0.211). Notably, an interaction exists between the symmetry of the stance time of the affected and unaffected limbs (P< 0.05). Post hoc test results showed that the modified STS group was significantly greater after the intervention than before (P<0.05), whereas the normal STS group was not significantly different before and after the intervention (P=0.225). No significant difference was observed between the two groups after the intervention (P=0.472). The 10-m gait speed showed a main effect of time and was significantly higher in both groups after the intervention (P<0.05).
Maximum isometric muscle strength and BBS scores before and after the intervention in both groups
The maximum isometric muscle strength and BBS scores before and after the intervention in both groups are shown in Table 4. Hip flexion and extension showed a main effect for the intervention period and significantly increased after the intervention in both groups (P<0.05). Hip abduction exhibited no main or interaction effects. The knee extensors showed an interaction (P<0.05). Post hoc test results showed a significant increase in the modified STS group after the intervention compared with that before the intervention (P<0.05), and no significant difference was observed in the normal STS group before and after the intervention (P=0.177).
BBS exhibited an interaction effect (P<0.05). Post hoc test results showed that both the modified and normal STS groups increased significantly after the intervention compared with before (P<0.05 for both groups), with markedly greater change in the modified than in the normal STS group (5.3 vs. 3.3 respectively).
DISCUSSION
All 17 patients completed the 2-week modified STS training program without any adverse events. No differences were observed between the modified and normal STS groups regarding the daily number of STS attempts; therefore, the modified STS training was considered safe and practical in terms of clinical application. In the modified STS group, the load on the affected limb during STS, stance time of the affected limb, symmetry of stance time during walking, knee extensor strength, and BBS score significantly improved after the intervention (Tables 2Table 3–4). The normal STS group trained using a conventional foot placement (feet aligned) and the same seat height as the modified STS, reflecting typical post-hip fracture rehabilitation practice (Briggs et al., 2018b; Sherrington et al., 2004). This approach facilitated a realistic comparison for evaluating the benefits of the modified STS technique.
STS with one foot positioned posteriorly is thought to reduce the trunk flexion angle and facilitate the placement of the center of mass on the posteriorly positioned foot, thereby increasing the load on the posterior limb (Jeon et al., 2019). An STS posture with an elevated seat decreases the hip flexion angle at the bottom-off, which may have reduced compensatory movements to the unaffected limb and efficiently facilitated loading to the affected limb (Burdett et al., 1985). Therefore, the modified STS training with a high seat height and the affected foot positioned posteriorly further promoted loading on the affected limb and may have increased the amount of loading on the affected limb while standing with feet together after the intervention (Table 2).
The fact that the amount of load on the affected limb during walking did not change after modified STS training may be due to the influence of the variation in the amount of load on the affected limb during the stance phase while walking. This concept is supported by the finding that patients with hip fracture exhibit greater variability in step velocity and length in the affected limb than in the unaffected limb (Thingstad et al., 2015). Another potential reason is that more participants in the modified STS group used walking aids to reduce the amount of loading on the affected side (seven and three participants in the modified and normal STS groups, respectively). The use of walking aids while ambulation may have negated the benefit of the modified STS training in increasing load on the affected side during the stance phase. In contrast, the stance time during walking significantly increased after the intervention only in the modified STS group. Furthermore, a correlation analysis performed as a subanalysis revealed that the rate of increase in the load on the affected limb during the STS movement influenced the extension of stance time for the affected limb during walking. As those who showed asymmetry in lower limb muscle strength similarly showed asymmetry in stance time during walking (Laroche et al., 2012), the improvement in muscle strength of the affected limb may have contributed to the increase in the stance time of the affected limb. The gait of patients with hip fracture is characterized by antalgic gait patterns, such as shortened stance time, decreased walking speed of the affected limb, and decreased step length of the affected limb compared with those of the unaffected limb (Thingstad et al., 2015). The increase in the stance time of the affected limb in the modified STS group in this study may have led to an improvement in antalgic gait and contributed to an improvement in walking ability.
In the modified STS group, only knee extension muscle strength was higher after the intervention than before the intervention (Table 4). The hip joint extension moment decreases during STS movements in which the seat is elevated because the hip flexion angle decreases (Burdett et al., 1985). Furthermore, STS with one foot placed behind the other increases the hip and knee extension moments in the trailing leg (Liu et al., 2016). The modified STS, which involved a high seat height and backward positioning of the affected leg, was considered a manipulation that suppressed the increase in the hip extension moment and increased only the knee extension moment. In this study, the BBS scores were significantly higher in the modified STS group after the intervention than before the intervention (Table 4). Balance in patients with hip fracture is often limited by changing direction and stepping onto steps that require support from the affected limbs (Radosavljevic et al., 2013). Because strength training of the affected limb improves balance in patients with hip fracture (Sylliaas et al., 2011), enhanced knee extensor strength may have led to improved balance among the participants of our study.
Our study has some limitations. Many participants resolved pain involving the affected limb, and the small sample size resulted in sex-specific group differences. As pain in the affected limb in patients with hip fracture is influenced by the amount of load and walking ability, it remains unclear whether the results of this study are generalizable to patients with hip fracture experiencing pain (Walheim et al., 1990). In addition, participants were recruited from rehabilitation and community comprehensive care units, which may introduce selection bias. These individuals may have had better access to continued care and relatively higher functional status, limiting the generalizability of the findings to patients in acute care settings or those who do not receive ongoing rehabilitation. This was a pilot study with a small sample size; therefore, the effect of the modified STS training on improving lower limb load symmetry was unclear. Moreover, this may have weakened the power of some indicators, such as the symmetry of lower limb loading (P=0.078). However, this study provides initial insights into the effectiveness of new STS methods in patients with hip fracture and serves as a basis for large-scale studies. Future studies should verify whether modified STS training is effective for patients with hip fracture experiencing pain in the affected limb and for improving load symmetry. If modified STS training is found to be effective in patients with hip fracture experiencing pain in the affected limb, more patients with hip fracture may be expected to improve their activities of daily living abilities.
In conclusion, 2 weeks of modified STS training with a high seat height and the affected foot positioned backward increases the load on the affected limb during standard STS with both feet aligned in patients with hip fracture. The increase in weight loading on the affected limb during STS contributes to the enhancement of knee extensor strength, extending the stance time of the affected limb during walking and improving balance function. The modified STS is a useful functional training tool for patients with hip fracture, as it promotes increased weight loading on the affected lower limb in a relatively short period.
PDF Links
PubReader
ePub Link
XML Download
Full text via DOI
Download Citation 
Print 
