Effects of Hallux Valgus Surgery on Balance and Gait in Middle Aged and Older Adults

Abstract

Background:

Hallux valgus is associated with poorer balance, and has been implicated as an independent risk factor for falls in older adults. However, it is unknown what effect hallux valgus surgery has on static and dynamic (i.e., while walking) balance in older adults.

Methods:

We enrolled 13 middle-aged and older aged adults (mean age 54.3+/−12.7 yrs, range 47 to 70) who underwent isolated hallux valgus surgery and followed them for 12 months. Preoperative and postoperative gait and balance performance was assessed using non-invasive body worn sensors with standardized and validated testing protocols. Visual analog scale (VAS) for pain and radiographic angles were also assessed.

Results:

All subjects reported improvements in pain (VAS mean change −38.3+/−10.3 mm), and all subjects demonstrated improvements in their hallux valgus angles and 1^st/2^nd intermetatarsal angles (mean change 16.3+/−8.8°, and 5.5+/−3.0°, respectively). While standing in full tandem, center of mass (COM) sway was improved upon by 59% at 1 year postoperative (p<0.05, paired t-test). While most gait parameters demonstrated little change postoperatively, patients tended to spend less time in double support (p=0.08, paired t-test), while gait variability increased by 55% (p=0.03, paired t-test) and medial-lateral sway while walking increased by 43% (p=0.08, paired t-test) 12 months postoperatively.

Conclusion:

Balance improved after hallux valgus surgery in our population, particularly when subjects were forced to rely on their operative foot for support (e.g., full tandem). Patients also seemed to walk with greater variability in stride velocity and with greater medial-lateral sway postoperatively, suggesting perhaps increased ambulatory confidence after successful hallux valgus surgery.

Level of Clinical Evidence:

prospective case series, level 4

Introduction:

Hallux valgus is associated with poorer performance during balance and functional tests in older adults.^1,2 Patients with bunions, for example, demonstrate increased postural sway, decreased maximum balance range, increased time needed to perform alternate step test, increased time for sit-to-stand, and decreased walking speed compared to patients without bunions.^1,2 Hallux valgus may also contribute to less rhythmic movements of the upper body when walking on uneven ground.³

Recently, several studies have recognized foot impairment as an independent risk factor for falls among older adults.^4–7 In a prospective study of 100 men aged 65–85 years, Gabell and colleagues⁸ reported that “foot problems” were associated with a 4-fold increased risk of falling. Similarly, a study of musculoskeletal pain in 1002 older adult women found that the foot was the only pain site associated with an increased risk of falling.⁹ Moreover, hallux valgus deformity itself appears to be a particularly important risk factor for falling among older adults.^10–12 Tinetti et al.¹⁰, for example, found that the presence of a “serious foot problem” (which included a moderate to severe bunion deformity) doubled the risk of falling in 336 older adults. Similarly, a prospective study of 979 people older than 70 years in Finland found that hallux valgus specifically was associated with a 2-fold increased risk of falling.¹¹

While previous work has hypothesized that corrective bunion surgery may lead to improved walking and better balance control postoperatively,² there have been no prospective studies yet to examine balance before and after bunion surgery. In this study, we prospectively assessed the effects of hallux valgus surgery on balance and gait using a middle aged and older adult patient population attending a single foot/ankle specialty practice.

Materials & Methods:

Patients were prospectively recruited from the Weil Foot and Ankle Institute from January 15, 2016 to June 30, 2017. All patients signed an informed consent document and HIPAA authorization prior to enrollment. Inclusion criteria for the study were: age 45 years or older with a chief complaint of “bump pain” and a clinical diagnosis of hallux valgus. All patients must have previously failed attempts at non-surgical management for at least 6 months and have elected for unilateral hallux valgus surgery that required (as determined by the surgeon) a 1^st metatarsal osteotomy. Additionally, all subjects had to be independent community ambulators. Exclusion criteria for this study included patients using gait assistive devices (e.g., cane or walker), and patients requiring additional osseous surgery outside of hallux valgus correction (e.g., Weil osteotomy, tailor’s bunionectomy, hindfoot arthrodesis, etc.). We also excluded patients who were anticipating undergoing major orthopedic lower extremity surgery (e.g., total hip arthroplasty, total knee arthroplasty, etc.) during the 12 month postoperative follow up period.

Consecutive patients were approached and asked to participate during the enrollment period, and 13 patients agreed after having satisfied all of the inclusion criteria. All participants completed pre- and postoperative gait and balance testing using a validated and standardized testing protocol and portable body-wearable technology (LEGSys™ and BalanSens™, BioSensics LLC, Cambridge, MA, Figure).

Center of mass (COM) was assessed in the mediolateral and anteroposterior directions, and the area of sway was then calculated for each testing condition (see Balance & Gait protocol below). All of the values were recorded and reported as area of COM sway. In addition, postural coordination between the upper and lower body in the mediolateral and anteroposterior directions was also examined for each participant and was quantified using the reciprocal compensatory index (RCI). This index measures postural coordination between the upper and lower body (reciprocal coordination between hip and ankle motions, which, in turn, allows reducing center of mass sway).¹³ The closer the value is to zero, the better the coordination between distal joints (hip and ankle); a value of 1 signifies no coordination, and values greater than 1 indicate poor coordination.

Additionally, Visual Analog Scale (VAS) for pain and radiographic alignment were assessed preoperatively and 12 months postoperatively for all subjects. Any complications were documented and recorded.

Summary statistics for the study population were generated and reported as mean (sd). Individual gait and balance parameters were analyzed using ANOVA and paired t-tests to compare preoperative data and postoperative data within subjects. Additionally mean change in radiographic angles were also compared using paired t-tests. All tests of significance were two tailed. P values <0.05 were considered significant.

Balance & Gait Testing Protocol

The set up involved placing four small motion sensors on the participant’s lower extremities, one each on the front of the lower leg and thigh. The sensors were held in place with elastic Velcro straps, and a lightweight data logger is worn on the patient’s belt around their waist. An additional small sensor was then attached to the lumbar region which allows for measuring the range of motion of center of mass (COM)

Patients were asked to perform two walking trials while wearing their habitual footwear to assess gait postural control. In the first walking trial, patients were asked to walk a distance of at least 40 feet on a level surface at their habitual speed to a predetermined stopping point. In the second trial, patients were asked to then return to the starting point.¹³ Only the second trial was used in the analysis. Static balance and postural control were then evaluated by first asking patients to stand erect with hands by their sides and feet together (i.e., double support). We tested subjects under three different conditions: 1) double support (Romberg’s Test) eyes opened for 30 seconds, 2) double support eyes closed for 30 seconds, and 3) with feet in the full tandem position with eyes opened for 15 seconds. All full tandem testing was performed with the operative foot placed behind the non-operative foot. Each of these evaluations were performed preoperatively and 12 months postoperatively using the same footwear. The area of sway for COM was used to determine balance control.¹⁴

Results:

Mean (sd) patient age was 54.3 (12.7) years (range 47 to 70 years), and mean (sd) body mass index (BMI) was 27.2 (6.6) kg/m² (range 18.5 to 42.1 kg/m²). A full list of the descriptive characteristics of the study population are provided in Table 1. All patients (n=13) underwent Scarf/Akin osteotomies for their hallux valgus correction, and the hallux abductus angles and 1^st/2^nd intermetatarsal angles for all subjects were corrected to within normal ranges at the 12 month radiographic follow up assessment.¹⁵ The mean change for the study population in 1^st/2^nd intermetatarsal angle and hallux abductus angle were −16.3 +/− 8.8° and −5.5 +/− 3.0°, respectively. Similarly, all subjects reported improvements in their VAS pain at 12 months postoperatively (VAS mean change −38.3 +/− 10.3 mm, p<0.01).

Table 1.

Descriptive statistics of the study population (n=13).

	Age (years)	Height (cm)	Weight (kg)	BMI (kg/m2)	VAS Pre-op (mm)	VAS Post-op (mm)
Mean	54.3	165.30	74.3	27.2	48.2	9.9
Standard Deviation	12.7	8.96	16.3	6.6	31.1	20.8

VAS, visual analog scale for pain; BMI, body mass index

Changes in the performance of both static balance tasks and dynamic balance (while walking) were observed postoperatively. Most notably, COM sway was decreased by 59% (p=0.04) after bunion surgery when performing full tandem test which was designed to specifically challenge the operative foot (Table 2). No significant differences in COM sway were found during eyes open and eyes closed condition while participants were in double support static stance, although trivial increases were observed in RCI medial/lateral sway during both the eyes open and eyes closed conditions. While there were no significant changes in most gait parameters, including stride velocity, stride length, and cadence, patients tended to spend slightly less time in double support postoperatively (p=0.08), while gait variability increased on average by 55% postoperatively (p=0.02), and medial-lateral sway while walking showed a trend towards increasing by as much as 43% on average (p=0.08, Table 3).

Table 2.

Static balance assessment under various testing conditions, pre and postoperatively (n=13).

	FT COM (cm2)	FT RCIAP	FT RCIML
Pre-op (SD)	4.83 (2.96)	0.68 (0.23)	0.53 (0.24)
Post-op (SD)	1.98 (0.53)	0.56 (0.35)	0.49 (0.35)
p-value	0.04	0.23	0.41
	DSEO COM (cm2)	DSEO RCIAP	DSEO RCIML
Pre-op (SD)	0.24 (0.47)	0.68 (0.27)	0.61 (0.22)
Post-op (SD)	0.24 (0.24)	0.73 (0.18)	0.80 (0.12)
p-value	0.47	0.26	0.01
	DSEC COM (cm2)	DSEC RCIAP	DSEC RCIML
Pre-op (SD)	0.21 (0.37)	0.56 (0.13)	0.59 (0.27)
Post-op (SD)	0.39 (0.49)	0.72 (0.29)	0.80 (0.14)
p-value	0.11	0.07	0.01

All tests of significance were performed using paired t-test. All table values are displayed as mean (standard deviation).

SD, standard deviation; FT, full tandem; COM, center of mass sway; RCI, reciprocal compensatory index; AP, anteroposterior; ML, mediolateral; DS, double support; EO, eyes opened; EC, eyes closed

Table 3.

Gait assessment and dynamic balance assessment before and after hallux valgus corrective surgery (n=13).

	Gait Variability, SV (%)	Medial-Lateral Sway (deg.)	Double Support (%)
Pre-op (SD)	2.57 (0.58)	5.28 (0.91)	23.97 (1.49)
Post-op (SD)	3.76 (0.84)	7.45 (1.37)	23.06 (1.18)
p-value	0.02	0.08	0.08

All tests of significance were performed using paired t-test. All table values are displayed as mean (standard deviation).

SD, standard deviation; SV, stride velocity; deg., degrees

Discussion:

In this study we found that static balance was significantly improved upon when assessed 12 months after undergoing successful hallux valgus surgery. More specifically, we found that COM sway was improved by as much as 59% when challenging the operative foot (i.e., during full tandem testing) which is very similar to, and builds upon, the 63% improvement previously suggested by Sadra et al.² during early bunion surgery recovery. Our study is however a clear improvement on the cross-sectional study design performed by Sadra and colleagues², as we followed patients longitudinally, both pre and postoperatively, out to 12 months.

During the past several decades, the size of the elderly population has increased steadily across most of the western world.^16–18 In 2010, 40 million US residents (over 13% of the total population) were age 65 and above. ¹⁸ With baby boomers (those born between 1946 and 1964) beginning to turn 65 in 2011, the number of older adults is expected to more than double to 88.5 million by 2050 and will represent 20% of the total US population.¹⁹ Fall prevention (and avoidance) has quickly become a high priority public health concern given our rapidly growing elderly population. With 1 in 3 people aged 65 and over experiencing a fall each year, falls are the leading cause of injury among older adults in the US.¹⁰ The economic impact of falls is staggering. Fall-related injuries among older adults cost the US healthcare system more than $19 billion dollars annually.²⁰

The reduction in COM sway observed in the current study is therefore a very welcoming finding as COM sway has been shown to be directly correlated with increased fall risk among middle aged and older adults.²¹ Due to the detrimental effects of falls on the older population, as well as the financial burden associated with falls, it is critical that foot and ankle providers better understand the effects of the interventions which we provide to our older and elderly patients.

In this work we also observed a trend for decreased double support time during gait, which may suggest modest improvements in stability at 1 year postoperatively.^22,23 Similarly, while in static stance (double support) the increase in RCI seen postoperatively can be explained by the fact that patients were inherently more stable during this period and required less coordination between their ankle and hip to maintain stability which was confirmed with the decrease in COM sway seen during full tandem. Moreover, it is only relatively low levels of coordination that are needed between the ankle and hip in the medial-lateral direction, as little correction is required in this direction while standing in during double support. During the full tandem testing, which better challenges medial-lateral coordination within the operative foot, patients observed less COM sway postoperatively, while also maintaining low RCI values in both anteroposterior and medial-lateral directions. Finally, our subjects also demonstrated increased gait variability postoperatively which may suggest greater confidence while walking as patients more freely altered their walking pattern and stride velocity during initiation, steady state, and termination.

It is not unreasonable to expect that improvements in balance control might be observed after hallux valgus surgery. We would suggest that enhancements in balance may occur via several mechanisms. A corrected position of the great toe, for example, may allow for better proprioception or first metatarsophalangeal joint range of motion, processes that are known to deteriorate with the aging process.^24,25 Surgical realignment of hallux valgus deformity may also lead to improvements in tactile sensation in the plantar foot. This concept is supported by the fact that some authors have found that plantar pressures beneath the hallux become normalized after hallux valgus corrective surgery.²⁶ Improved tactile sensation coupled with better proprioceptive feedback and possibly better first metatarsophalangeal joint range of motion would be expected to enhance one’s ability to regulate the COM over the foot. Finally, enhancements in balance control might also be achieved through a reduction in foot pain which is frequently seen after bunion surgery and was observed in our sample.

This study’s conclusions should of course be interpreted within the context of its limitations. Although we report on the largest series of patients to date, assessed both pre and postoperatively, we were still likely underpowered to demonstrate with certainty several of the suspected changes/improvements observed in balance control postoperatively. Also the lack of a comparison group (i.e., those with hallux valgus deformities not undergoing corrective surgery) makes it difficult to draw any hard and fast conclusions at this time. Finally, we chose to study both older adults and elderly subjects (mean age 54.3 yrs); however, the greatest fall risk is clearly present in those patients with advanced age. Future studies may want to focus more specifically then on those patients who are 65 and older.

In conclusion, participants in the study exhibited better postural control as noted by decreased COM sway after successful bunion surgery. Patients also displayed greater variability in stride velocity and greater medial–lateral sway while walking postoperatively which, to the authors, suggests greater confidence while walking. While this study is limited by its relatively small number of patients, it certainly suggests that balance may be improved (and at the very least does not appear to be made worse) after bunion surgery in middle aged and older adults. Further work in this area is warranted.

Figure 1:

Illustration of sensor placement for gait assessment (N1-N4, LegSys™) and balance assessment (N5, BalanSens™)

Figure 2:

Results of full tandem (FT) center of mass (COM) sway area (in cm²), and anterior/posterior (AP) and medial/lateral (ML) reciprocal compensatory index (RCI) preoperatively and at 12 months postoperatively (n=13). RCI is a ratio of hip and ankle motion and provides insight into the postural coordination strategy for reducing COM sway. When RCI values are close to 0, this represents good ankle/hip coordination.