Effect of Obesity on Clinical and Radiographic Outcomes Following Reconstruction of Stage II Adult Acquired Flatfoot Deformity

Abstract

Background:

Obesity is a known risk factor for the development of adult acquired flatfoot deformity (AAFD), but obesity’s effects on outcomes following AAFD reconstruction are unknown. We hypothesized that obesity would negatively impact outcomes following joint-preserving stage II AAFD reconstruction.

Methods:

This retrospective study compared the outcomes of normal-weight (18.5 kg/m² ≤ BMI < 25 kg/m²), overweight (25 kg/m² ≤ BMI < 30 kg/m²), and obese (BMI ≥ 30 kg/m²) patients after AAFD reconstruction. Clinical outcome measures included the Foot and Ankle Outcome Score (FAOS), Short-Form 12 (SF-12), and Numeric Rating Scale of Pain (NRS Pain) administered preoperatively and at least 1 year postoperatively. Anteroposterior and lateral radiographs were taken preoperatively and at least 6 months postoperatively. Pre- to postoperative changes in outcome measures were assessed within BMI classes. Preoperative, postoperative, and pre- to postoperative changes in outcomes were compared among BMI classes. There were 41 normal-weight patients, 39 overweight patients, and 44 obese patients with a mean age of 56 years, FAOS follow-up of 2.9 years, and radiographic follow-up of 2.1 years. Demographics and reconstructive procedures were comparable among the 3 BMI classes.

Results:

All outcomes significantly increased pre- to postoperatively in the 3 groups with the exception of the FAOS Symptoms subscale for normal-weight patients (P = .340) and SF-12 Mental Component score for all 3 BMI classes (P > .999). Preoperatively, obese patients had more symptoms than normal-weight patients, scoring 12 points lower on the FAOS Symptoms subscore (P = .008). Obese patients also scored 11 points lower preoperatively on the SF-12 Overall score (P = .028) and had 31% greater pain than normal-weight patients (P = .003). There were no differences among the 3 BMI classes in any postoperative outcomes assessed.

Conclusion:

Although obese patients had significantly worse symptoms, overall health, and NRS pain scores preoperatively, the short-term clinical and radiographic outcomes of stage II AAFD reconstruction were similar for normal-weight, overweight, and obese patients. We suggest that joint-preserving reconstruction remains a viable alternative to fusion of the triple joint complex for the treatment of overweight and obese stage II AAFD patients.

Level of Evidence:

Level III, retrospective cohort study.

Keywords

obesity adult acquired flatfoot deformity flatfoot reconstruction clinical outcomes radiographic outcomes

Introduction

The prevalence of worldwide obesity is on the rise, having more than doubled since 1980. In 2014, 39% of adults aged 18 years and older were overweight, and 13% were obese.³⁶ Being overweight or obese has adverse effects on bones and soft tissues both biomechanically and biochemically, with greater loads being placed on joints and increased fat-derived adipokines leading to chronic low-grade inflammation associated with perioperative wound complications and poor bone healing.⁴

Obesity is a known risk factor in the etiology of adult acquired flatfoot deformity (AAFD),^13,19 which is caused by dysfunction of the posterior tibialis tendon (PTT) and gradual failure of ligaments supporting the medial arch. This may lead to severe anatomic changes in the foot such as collapse of the medial arch, forefoot abduction through the talonavicular joint, and hindfoot valgus.⁹ AAFD may be classified by increasing severity from stage I to stage IV based on physical and radiologic findings, and operative treatment varies among these stages.²⁰ In stage II, elongation and degeneration of the tendon and ligaments results in a flexible deformity with hindfoot valgus, forefoot abduction, and collapse at the talonavicular joint.^9,25 Operative treatment of stage II AAFD includes a number of joint-preserving bony and soft tissue procedures including medializing calcaneal osteotomy (MCO), flexor digitorum longus (FDL) tendon transfer, lateral column lengthening (LCL), and spring ligament repair, which may be performed individually or in combination.

Obesity results in an increased load on the foot and ankle joint, which has been hypothesized to lead to a higher risk of deformity recurrence following joint-preserving procedures for stage II AAFD.¹⁶ Thus, it has been suggested that hindfoot arthrodesis may be more appropriate for these patients in order to maintain correction.^15,16 However, it is unclear whether this is truly the case, as there have been no previous studies assessing the outcomes of obese patients compared to overweight and normal-weight patients following joint-preserving reconstruction for stage II AAFD, particularly with osteotomy procedures. The objective of this study was to compare the clinical and radiographic outcomes of reconstruction for stage II AAFD in normal-weight, overweight, and obese patients. We hypothesized that obese patients would have worse outcomes than overweight and normal-weight patients after joint-preserving stage II AAFD reconstruction.

Methods

Study Cohort

Study approval was granted by the steering committee for the foot and ankle registry, an institutional review board–approved patient data registry at the investigators’ institution. A retrospective search of the foot and ankle registry using ICD-9 codes related to AAFD (726.72, 727.68, 727.69, or 734), with a concomitant CPT code for MCO (28300), was conducted to identify flatfoot patients who underwent operative reconstruction between January 1, 2006, and December 31, 2013, by 2 surgeons, fellowship trained in orthopedic foot and ankle surgery. Inclusion criteria were as follows: diagnosis of stage II AAFD, joint-preserving reconstruction of AAFD with an MCO because the 2 surgeons always perform an MCO as part of operative reconstruction, preoperative and minimum 1-year postoperative Foot and Ankle Outcome Score (FAOS) scores, and preoperative and minimum 6-month postoperative weight-bearing anteroposterior (AP) and lateral radiographs. A mimimum 1-year follow-up was chosen for clinical outcomes to ensure adequate sample size to determine short-term outcome differences among the 3 BMI classes. A minimum 6-month radiographic follow-up was chosen as patients had been fully weight bearing for at least 3 months by that time, and previous findings have suggested that radiographic measurements do not change after 6 months following flatfoot reconstruction.²⁶

Exclusion criteria were diagnosis other than stage II AAFD (8 stage III, 17 stage IV, 7 congenital), hindfoot fusion (7 subtalar, 6 triple arthrodesis), bilateral flatfoot reconstruction (39 patients), or unrelated procedures between initial reconstruction and follow-up (17 patients). Non–stage II AAFD patients were excluded as stage I rarely requires operative intervention, stage III requires hindfoot joint fusions, and stage IV includes ankle deformity, which was considered a confounding factor for outcomes of joint-preserving flatfoot reconstruction. Bilateral patients were excluded since the effect of a single foot on outcome measures could not be adequately isolated. A concomitant diagnosis of hallux valgus including hypermobility of the first ray was acceptable, as were concomitant minor soft tissue procedures for hallux valgus. Because hypermobility of the first ray also contributes to arch collapse, these procedures were routinely performed with flatfoot reconstruction and were considered not to have a confounding effect on the outcomes. The inclusion of LCL was also allowed as it is commonly used for the treatment of stage II AAFD at the investigator’s institution. A total of 124 eligible patients were identified from the 334 AAFD patients retrieved by the broad initial search (Figure 1).

Consistent with previous analyses in orthopedic literature on the effect of obesity on patient outcomes following hip,² knee,¹² and shoulder²³ surgery, the study population was subsequently divided into 3 groups according to the World Health Organization (WHO) BMI classification: normal (18.5 kg/m² ≤ BMI < 25 kg/m²), overweight (25 kg/m² ≤ BMI < 30 kg/m²), and obese (BMI ≥ 30 kg/m²).

The final cohort of 124 patients was 66% female and the mean age at the time of surgery was 56 (range, 25 to 81) years. Forty-one (33%) patients were normal weight, 39 (31%) were overweight, and 44 (35%) were obese. Reconstruction was performed on the right foot in 51 (41%) patients. Mean follow-up time was 2.9 (range, 1.0 to 6.9) years for the FAOS and 2.1 (range, 0.5 to 6.9) years for radiographic outcomes. No differences were found among the 3 BMI classes in age (P = .100), sex (P = .113), laterality of surgery (P = .917), FAOS follow-up time (P = .956), or radiographic follow-up time (P = .123) (Table 1). No differences were found among the BMI groups for history of smoking or any of the comorbidities assessed in this study (Table 1). Obese patients were found to have a greater total number of comorbidities (1.9 [1.5, 2.3]) than normal-weight patients (1.2 [0.9, 1.5]; P = .037).

Table 1.

Comparison of Demographic, Medical, Operative, and Hospital Stay–Related Variables.

	Normal-weight (n = 41)	Overweight (n = 39)	Obese (n = 44)	P value*
Demographic
Continuous^a
Age	56.4 [52.5, 60.3]	58.6 [56.0, 61.1]	53.7 [50.7, 56.7]	.100
FAOS follow-up time	2.9 [2.5, 3.4]	3.0 [2.5, 3.4]	3.0 [2.5, 3.4]	.956
Radiograph follow-up time	2.5 [2.0, 3.0]	1.8 [1.5, 2.0]	1.9 [1.5, 2.3]	.123
Categorical^b
Sex (female)	32 (78%)	22 (56%)	28 (64%)	.113
Laterality (right)	16 (39%)	17 (44%)	18 (41%)	.917
Medical history and comorbidities
Continuous^a
BMI (kg/m²)	22.9 [22.4, 23.4]	27.2 [26.8, 27.6]	34.9 [33.4, 36.4]	−
Comorbidities per patient	1.2 [0.9, 1.5]	1.4 [0.9, 1.8]	1.9 [1.5, 2.3]	.023
Categorical^b
Smoking	1 (2%)	0 (0%)	2 (5%)	.773
Hypertension	6 (15%)	7 (18%)	15 (34%)	.071
Hypercholesterolemia	9 (22%)	10 (26%)	10 (23%)	.930
Diabetes	2 (5%)	2 (5%)	6 (14%)	.345
Thyroid disease	4 (10%)	7 (18%)	9 (21%)	.401
Osteopenia/osteoporosis	3 (7%)	2 (5%)	3 (7%)	>.999
Cardiac	4 (10%)	3 (8%)	8 (18%)	.331
Asthma	8 (20%)	6 (15%)	8 (18%)	.880
Anxiety/depression	8 (20%)	6 (15%)	10 (23%)	.687
Cancer	4 (10%)	6 (15%)	5 (11%)	.785
Operative
Continuous^a
Amount of MCO	10.0 [9.3, 10.6] (30)	10.5 [9.5, 11.4] (28)	9.9 [9.1, 10.6] (32)	.695
Amount of LCL	7.1 [6.7, 7.6] (30)	7.8 [7.1, 8.4] (28)	7.9 [7.2, 8.6] (30)	.260
Amount of Cotton osteotomy	5.6 [5.2, 6.1] (11)	5.4 [5.0, 5.7] (15)	5.8 [5.1, 6.6] (13)	.512
Categorical^b
LCL	33 (81%)	32 (82%)	32 (73%)	.583
FDL transfer	37 (90%)	38 (97%)	43 (97%)	.382
Spring ligament repair	34 (83%)	34 (87%)	36 (82%)	.787
Spring ligament reconstruction	1 (2%)	7 (18%)	5 (11%)	.070
First TMT fusion	24 (59%)	20 (51%)	26 (59%)	.733
Cotton osteotomy	12 (29%)	16 (41%)	13 (30%)	.443
Gastrocnemius recession	39 (95%)	37 (95%)	42 (96%)	>.999
Modified McBride	9 (22%)	7 (18%)	9 (20%)	.960
Akin osteotomy	5 (12%)	7 (18%)	8 (18%)	.715
Hospital stay and postoperation
Continuous^a
Incision-to-closure time (min)	293 [265, 320] (40)	341 [308, 375] (36)	332 [301, 363] (40)	.077
Length of hospital stay (nights)	4.1 [3.7, 4.5] (39)	3.6 [3.4, 3.9] (38)	3.9 [3.5, 4.4] (42)	.154
Categorical^b
Complication (return to OR)	2 (5%)	4 (10%)	8 (18%)	.156
Revision (MCO and/or LCL)	5 (12%)	0 (0%)	3 (7%)	.085
Removal of hardware	22 (54%)	19 (49%)	22 (50%)	.899

Abbreviations: BMI, body mass index; FAOS, Foot and Ankle Outcome Score; FDL, flexor digitorum longus; LCL, lateral column lengthening; MCO, medializing calcaneal osteotomy; OR, operating room; TMT, tarsometatarsal.

P value of variation among the 3 BMI classes (significant P < .05).

Continuous variables reported as mean [95% confidence interval] (n), with n listed only when the mean is determined from a subset of the entire cohort.

Categorical variables reported as n (percentage).

Medical History and Operative Variables

Patient medical records were retrospectively reviewed for BMI, age, gender, laterality of AAFD reconstruction, comorbidities, smoking habits, and complications following surgery. Comorbidities assessed included vascular (hypertension), endocrine (hypercholesterolemia, diabetes, thyroid disease, osteopenia/osteoporosis), cardiac, respiratory (asthma), and psychiatric (anxiety/depression) pathologies, as well as cancer. Complications assessed included nonunions, stress fractures, and deep wound infections that required operative intervention. Subsequent removal of hardware and revision of MCO or LCL were also noted.

Operative notes were reviewed to determine the use of concomitant reconstructive procedures including LCL, FDL tendon transfer, spring ligament repair or reconstruction, first tarsometatarsal (1st TMT) fusion, medial cuneiform (Cotton) osteotomy, and gastrocnemius recession. Soft tissue procedures to correct hallux valgus were also assessed, and included the modified McBride and Akin osteotomy. The amounts of MCO, LCL, and Cotton osteotomy were recorded for patients who underwent those procedures as noted by the surgeon at the time of reconstruction. Hospital records were subsequently reviewed to determine the incision-to-closure time and length of hospital stay.

Postoperative Protocol

All patients were non-weight-bearing for 6 to 8 weeks postoperatively in a cast or removable boot. Patients subsequently progressed to full weight-bearing over a 4-week period in a CAM boot. Physical therapy started with the onset of weight bearing and continued until generally 6 months after surgery.

Outcome Measures

Scores for the 5 FAOS subscales (Pain, Symptoms, Activities of Daily Living [ADL], Quality of Life [QoL], and Sports/Recreation) were assessed to determine patient-reported outcomes and functionality following AAFD reconstruction. The 5 FAOS subscales are each given a score ranging from 0, representing the worst clinical outcome, to 100, representing the best clinical outcome. The FAOS has previously been validated for AAFD.²⁴ Short Form 12 (SF-12) Overall, Physical Component, and Mental Component scores were also collected to assess the effect of AAFD reconstruction in the context of overall health for each of the BMI classes. The SF-12 is an adaptation of the SF-36, which has been validated for general health outcomes and has been shown to be useful in assessing orthopedic outcome.^27,33 The Numeric Rating Scale of Pain (NRS Pain), in which respondents indicate their pain on a scale of integers from 0 to 10, with 0 representing the least and 10 the most pain, was also administered preoperatively and postoperatively. The NRS Pain has been shown to be a valid and reliable pain measurement.¹⁸ To ensure that 1 year was adequate follow-up time for clinical outcomes, the FAOS, SF-12, and NRS Pain scores at 1 year were compared with those from the most recent follow-up for the subset of 38 patients who had 2-year or greater follow-up times, which included 10 normal-weight, 14 overweight, and 14 obese patients.

Five radiographic measurements commonly used to assess flatfoot deformity were made using preoperative and postoperative AP, lateral, and hindfoot alignment radiographs of the foot which were taken with the patient full weightbearing. The following measurements used in this study have all been previously used for the assessment of AAFD: AP talonavicular coverage angle, lateral talar–first metatarsal (T-1MT) or Meary’s angle, calcaneal pitch, medial cuneiform–fifth metatarsal height, and hindfoot moment arm.^5,31,32,37

Statistical Analysis

An a priori power analysis was performed to determine the necessary sample size to detect the minimum detectable change (MDC) of 10 points on the FAOS subscale scores. This MDC was calculated using a previous study that validated the FAOS in a cohort of AAFD patients.²⁴ A minimum of 32 patients per group was required to provide 80% power at a level of significance of 0.05, conservatively assuming subscale standard deviations of 25.²⁴

The demographic, medical, operative, and hospital stay–related variables, as well as postoperative complications, were compared for differences among the 3 BMI classes using chi-squared or Fisher’s exact tests for categorical variables and single-factor analysis of variance, or the nonparametric equivalent (Kruskal Wallis) when non-normally distributed, for continuous variables. When significant, post hoc analyses were performed pairwise with Bonferroni correction for the multiple test error rate.

The differences between pre- and postoperative FAOS subscores, SF-12 component scores, and NRS Pain scores within each BMI class were assessed using Wilcoxon signed-rank tests. Differences between 1-year and most recent follow-up outcome scores in the entire subset of 38 patients with 2-year or greater follow-up times were assessed with Wilcoxon signed-rank tests. Differences among BMI classes in the preoperative, postoperative, and pre- to postoperative change in outcomes scores were assessed with single-factor analyses of variance or Kruskal Wallis tests. Analyses for radiographic alignment parameters parallelled those for outcomes scores. All statistical analyses were performed with SAS, version 9.3 (Cary, NC), with a level of significance of α = 0.05. Results are presented as frequencies and percentages for categorical variables and means and 95% confidence intervals for continuous variables.

Results

All stage II AAFD reconstructions performed by the 2 surgeons in this study included an MCO (n = 124). A subset of patients received additional concomitant reconstructive procedures, which included LCL in 97 (78%) patients, FDL transfer in 118 (95%), spring ligament repair in 104 (84%), spring ligament reconstruction in 13 (10%), first TMT fusion in 70 (56%), medial cuneiform (Cotton) osteotomy in 41 (33%), gastrocnemius recession in 118 (95%), modified McBride in 25 (20%), and Akin osteotomy in 20 (16%) patients. Patients who underwent MCO, LCL, and Cotton osteotomy received a mean of 10.1 [9.6, 10.5] mm of medial slide, 7.6 [7.3, 7.9] mm of lengthening, and 5.6 [5.3, 5.9] mm of opening wedge osteotomy, respectively. There were no significant differences in the use of any of the aforementioned concomitant procedures, amount of correction, incision-to-closure time, or length of hospital stay among the 3 BMI classes (Table 1). The overall complication rate (requiring operative intervention), as well as deep wound infection and nonunion rates, increased as BMI class increased (Table 2), but did not reach statistical significance. This study was not adequately powered to detect differences in complication rates.

Table 2.

Complications Requiring Operative Intervention.

Complication	Normal-weight (n = 41)	Overweight (n = 39)	Obese (n = 44)
Deep wound infection	1 (2%)	1 (3%)	3 (7%)
Nonunion	0 (0%)	2 (5%)	5 (11%)
Calcaneal stress fracture	0 (0%)	1 (3%)	0 (0%)
Fifth metatarsal stress fracture	1 (2%)	0 (0%)	0 (0%)
Total	2 (5%)	4 (10%)	8 (18%)

FAOS Outcomes

All 3 BMI groups showed improvements (P = .008) from pre- to postoperatively in Pain, ADL, Sports, and QoL subscores. In the Symptoms subscore, the obese and overweight groups showed improvement (P ≤ .001 for each), whereas the normal-weight group did not (P = .340). Preoperatively, the Symptoms subscore was worse in the obese group (61.2 [55.9, 66.5]) than in the normal-weight group (72.8 [67.9, 77.8]; P = .008). Postoperatively, there was no significant difference in the Symptoms subscore among the 3 BMI groups. The obese group had a greater pre- to postoperative improvement in Symptoms (14.1 [8.2, 20.0]) than the normal-weight group (5.0 [-0.7, 10.8]; P = .025). There were no significant differences in the preoperative, postoperative, or pre- to postoperative changes in Pain, ADL, Sports, or QoL subscores among the 3 BMI groups (Figure 2/Supplemental Table 1).

SF-12 and NRS Pain Outcomes

For all 3 BMI groups, there were improvements (P = .005) in SF-12 Overall and Physical Component scores, whereas Mental Component scores remained unchanged pre- to postoperation. Preoperatively, the SF-12 Overall score was worse in the obese group (53.2 [47.9, 58.6]) than in the normal-weight group (63.8 [58.6, 21.4]; P = .028). There was no significant difference in the postoperative SF-12 Overall score among the 3 BMI groups, nor was there a difference in the pre- to postoperative change in this score among the 3 groups. There were no significant differences in the preoperative, postoperative, or pre- to postoperative changes in SF-12 Physical Component and Mental Component scores among the 3 BMI groups (Figure 3/Supplemental Table 2).

The NRS Pain significantly decreased (P < .001) for all 3 BMI groups pre- to postoperatively. Preoperatively, the NRS Pain was worse in the obese group (6.7 [6.0, 7.3]) than in the normal-weight group (5.1 [4.4, 5.8]; P = .003) and in the overweight group (5.2 [4.5, 6.0]; P = .011). There was no significant difference in the postoperative NRS Pain among the three BMI groups, nor between the pre- to postoperative changes in this score among the 3 groups (Figure 4/Supplemental Table 2).

Clinical Outcome Follow-up Time

Mean follow-up time in the subset of 38 patients with greater than 1-year follow-up was 3.4 (range, 2.1 to 6.9) years. There were no significant differences found between the 1-year and most recent follow-up FAOS subscores with the numbers available except for in Symptoms, which increased by 6.6 points. However, this was below the MDC of 10 points that was considered clinically significant from a prior FAOS validation study in flatfoot patients.²⁴ There were no differences found in SF-12 or NRS Pain outcomes between the 1-year and most recent follow-up.

Radiographic Outcomes

There were significant pre- to postoperative decreases in AP talonavicular coverage angle, Meary’s angle, and hindfoot moment arm, and increases in calcaneal pitch and medial cuneiform–fifth metatarsal height for all 3 BMI groups. No significant differences were found among the 3 BMI groups in preoperative, postoperative, or pre- to postoperative changes in any of these radiographic measurements (Table 3).

Table 3.

Radiographic Measurement Variation Among BMI Groups.

Time Point	Normal-weight (n = 41)	Overweight (n = 39)	Obese (n = 44)	P Value of Interclass Variation
Talonavicular coverage angle^a (AP view, degrees)
Preoperative	30.9 [27.2, 34.7]	35.1 [30.0, 40.3]	33.8 [30.0, 37.7]	.578
Postoperative	14.5 [10.6, 18.3]	19.0 [13.9, 24.1]	20.1 [16.6, 23.7]	.153
Change	−16.5 [−21.0, −12.0]	−16.1 [−20.2, −12.0]	−13.7 [−17.9, −9.5]	.970
P value for change	<.001	<.001	<.001
Lateral talar–first metatarsal (Meary’s) angle^a (lateral view, degrees)
Preoperative	18.3 [14.5, 22.5]	20.3 [16.5, 24.1]	19.8 [16.4, 23.1]	.825
Postoperative	6.0 [2.6, 9.4]	7.5 [4.9, 10.1]	10.2 [7.0, 13.4]	.185
Change	−12.3 [−16.0, −8.7]	−12.8 [−16.4, −9.2]	−9.5 [−12.8, −6.2]	.807
P value for change	<.001	<.001	<.001
Calcaneal pitch^a (lateral view, degrees)
Preoperative	16.8 [15.5, 18.2]	16.2 [14.6, 17.7]	15.8 [14.3, 17.4]	.485
Postoperative	19.2 [17.8, 20.5]	18.9 [17.3, 20.4]	18.7 [17.2, 20.2]	.880
Change	2.3 [1.4, 3.3]	2.7 [1.6, 3.8]	2.9 [1.8, 3.9]	.811
P value for change	<.001	<.001	<.001
Medial cuneiform–fifth metatarsal height^a (lateral view, mm)
Preoperative	8.7 [6.4, 11.1]	8.2 [5.2, 11.1]	8.8 [6.8, 10.8]	.852
Postoperative	18.3 [16.9, 19.8]	17.4 [15.7, 19.0]	16.9 [15.5, 18.2]	.410
Change	9.6 [7.6, 11.6]	9.2 [6.6, 11.8]	8.1 [5.9, 10.2]	.733
P value for change	<.001	<.001	<.001
Hindfoot moment arm^a (hindfoot alignment view, mm)
Preoperative (23, 29, 27)^b	13.9 [10.8, 17.0]	14.0 [11.0, 17.0]	11.4 [8.4, 14.3]	.297
Postoperative (34, 35, 38)^b	−3.0 [−4.7, −1.2]	−1.4 [−3.9, 1.1]	−2.1 [−4.2, 0.0]	.646
Change (23, 28, 23)^b	−15.6 [−19.0, −12.1]	−15.7 [−19.3, −12.1]	−14.4 [−17.5, −11.3]	.858
P value for change	<.001	<.001	<.001

Radiographic measurements are reported as mean [95% confidence interval].

Values represent (n normal-weight, n overweight, n obese) for available data at the stated time point. All other radiographic measurements were composed of data from the entire study population (41, 39, 44).

Discussion

The goal of this study was to compare clinical and radiographic outcomes in normal-weight, overweight, and obese patients undergoing joint-preserving stage II AAFD reconstruction. Given expert opinion in the literature,^15,16 the authors of the present study hypothesized that obese patients would have significantly worse outcomes than normal-weight and overweight patients following joint-preserving stage II AAFD reconstruction. On the contrary, no significant differences in the postoperative outcomes or pre- to postoperative changes in clinical and radiographic outcomes were found among normal-weight, overweight, and obese patients, with the exception of the FAOS Symptoms subscale, which showed a significantly greater improvement for obese patients than for normal-weight patients. Furthermore, there was statistically significant pre- to postoperative improvement for all clinical and radiographic outcomes in each BMI group, except for normal-weight patients in the FAOS Symptoms subscale and all 3 BMI groups in the Mental Component of the SF-12.

There is no existing literature comparing the outcomes of AAFD procedures in obese versus nonobese patients. Such analysis may be useful for counseling overweight and obese patients on the expected benefits and associated risks of operative correction of AAFD in order to make an educated treatment decision. Although numerous studies in the hip,^2,3,11,14 knee,^6,11,21 and shoulder^22,23,34 literature have suggested that obesity negatively impacts outcomes following operations in those joints, studies on the effects of obesity on outcomes in orthopedic foot and ankle surgery have been more limited. One study examining complication rates following end-stage ankle arthritis operations, including total ankle arthroplasty and ankle arthrodesis, indicated a higher rate of complications in obese patients after both types of surgery.³⁵ This result correlates to similar findings on complication rates in the hip^8,17 and knee^1,21 arthroplasty literature.

The prevalence of each of the comorbidities assessed in this study was comparable for normal-weight, overweight, and obese patients, whereas the total number of comorbidities per patient was higher in obese patients than in normal-weight and overweight patients. Obese patients have been found to have a greater prevalence of numerous comorbidities, including hypertension, diabetes, hypercholesterolemia, and cardiac conditions, which also lead to increased complication rates.^29,35 In the present study, the complication rate increased as BMI class increased; however, this study was not adequately powered to detect statistically significant differences in complication rates among BMI classes.

A recent study on the outcomes of patients undergoing surgery for hallux valgus found no difference in postoperative patient-reported outcome scores between obese and non-obese patients using the American Orthopaedic Foot & Ankle Society Hallux Metatarsophalangeal-Interphalangeal Scale (AOFAS Hallux MTP-IP), Pain Visual Analog Scale, and SF-12 Mental and Physical Component scores, despite significantly worse preoperative AOFAS Hallux MTP-IP and SF-12 Physical Component scores in the obese group.⁴ Analogously, the present study found that the postoperative FAOS subscale scores were similar in all 3 BMI groups following joint-preserving AAFD reconstruction, suggesting that all 3 groups achieved a similar level of postoperative pain and symptom relief, daily activity and sports/recreation participation, and improvement in quality of life despite a significantly worse preoperative Symptoms subscale score in the obese group. Notably, this study is strengthened by the use of the FAOS, which is validated specifically for use in AAFD,²⁴ whereas the hallux valgus study is limited by the use of the AOFAS Hallux MTP-IP scale, which has been advised against by the AOFAS because of shortcomings in its validation.²⁸

The improvements in FAOS scores among the 3 BMI groups were supported by improvements in both NRS Pain scores and radiographic measurements. The minimum clinically important difference (MCID) in the NRS Pain has been suggested to be a 15% decrease in the initial NRS Pain score, whereas a 33% decrease has been shown to constitute “much better” improvement and a clinically important outcome for chronic musculoskeletal pain reduction.³⁰ By this standard, the observed decreases in the NRS Pain of 2.3 points (45%) in the normal-weight group, 2.9 points (52%) in the overweight group, and 3.4 (55%) points in the obese group surpassed the MCID and indicated a clinically important reduction in pain. These changes were comparable in all 3 BMI classes, despite a significantly worse preoperative NRS Pain score in the obese group. Similarly, the radiographic measurements in all groups clinically improved with a decline in the talonavicular coverage angle and lateral talar–first metatarsal (Meary’s) angle and an increase in the calcaneal pitch and medial cuneiform–fifth metatarsal height. The hindfoot moment arm was corrected from a radiographically valgus alignment to a mild varus alignment in all groups, which has been associated with the most favorable patient outcomes relative to a correction to moderate varus or valgus alignment in stage II AAFD reconstruction.⁷ The improvements in the NRS Pain and in radiographic measurements are in agreement with the patient-reported outcomes as assessed by the FAOS and corroborate the similarities in outcomes among all 3 BMI classes.

The outcomes assessed by the SF-12 contextualized the findings of the FAOS and NRS Pain in the overall health of the patient. The significant pre- to postoperative improvements observed in the SF-12 Overall and Physical Component scores and lack of changes in the Mental Component scores suggest that improvement in the overall health of the patient was primarily physical from AAFD reconstruction. These results also indicate that mental health likely had a negligible effect on the patient-reported outcomes observed in the FAOS subscale and NRS Pain scores. Furthermore, the SF-12 Overall score was significantly worse preoperatively for the obese group but, similarly to the FAOS Symptoms subscale and NRS Pain, had comparable postoperative scores across all 3 BMI classes. The combination of significantly worse preoperative FAOS Symptoms subscale, NRS Pain, and SF-12 Overall scores together suggest that obese patients start in a significantly worse clinical state preoperatively, yet achieve radiographic correction and clinical outcomes comparable to those in normal-weight and overweight patients. In addition, these results suggest that being overweight does not have a negative effect on such outcomes.

This study has a number of strengths, including a sample size with 80% power to detect a clinically significant difference in the FAOS, the use of multiple validated patient-reported outcomes, and assessment of radiographic outcomes in a single cohort of patients to allow for association of objective and subjective outcomes. Additionally, the lack of differences among the 3 BMI classes in age, gender, follow-up times, relevant comorbidities, and the use of all concomitant reconstructive procedures minimized confounding variables to allow for assessment of BMI effects on patient outcomes.

The study is also limited by several factors. These primarily include the limitations associated with all retrospective studies, such as a potentially nonrepresentative sample due to the single-institution nature of the study, the possibility of increased loss to follow-up for a certain portion of the population, such as those who had worse outcomes, and potential misclassification of or erroneous data in a patient’s medical record. Also, this study is a relatively short-term assessment of postoperative outcomes with varied follow-up times: the mean FAOS follow-up time was 2.9 years, ranging from 1 to 6.9 years, whereas the mean radiographic follow-up time was 2.1 years, ranging from 0.5 to 6.9 years. Although the minimum 6-month radiographic follow-up is a limitation, past literature has suggested that radiographic measurements do not change after 6 months²⁶ and most of our radiographs were obtained at 1 year or later. Further studies with greater than 5-year follow-up would allow for the more important assessment of mid- to long-term outcomes.

The tendency for greater mean pre- to postoperative improvements in all FAOS subscales in obese and overweight patients compared to normal-weight patients suggests that there may be clinically significant differences in these improvements among the 3 BMI classes, despite a lack of statistically significant differences. Although this study was powered to detect a conservatively estimated MCID of 10 points in the FAOS based upon the MDC calculated from a previous validation study of the FAOS for AAFD,²⁴ there is no existing literature to define what constitutes the MCID in FAOS subscales. Thus, an MCID of less than 10 points among BMI groups in the FAOS subscales may have gone undetected in this study.

Future studies should be conducted in order to compare the long-term outcomes and variation in outcomes over time among BMI classes, as well as to compare the differences in patient-reported outcomes between the treatments of triple arthrodesis and joint-preserving reconstruction for AAFD in obese patients. Previous literature indicates that outcomes worsen with increasing AAFD stage and suggests that this may be due to the use of hindfoot arthrodesis procedures to treat more severe AAFD, but the implications for the outcomes of obese patients undergoing fusion versus joint-preserving reconstruction are as of yet unknown.¹⁰ Additionally, analysis of patient-reported outcomes and complication rates in a prospective study and with a larger cohort would provide more conclusive evidence on the prevalence of comorbidities, rate of complications, and outcomes for obese and overweight patients following AAFD reconstruction.

In conclusion, we found that the short-term clinical and radiographic outcomes of stage II AAFD reconstruction were similar for normal-weight, overweight, and obese patients. Based on this study, joint-preserving reconstruction remains a viable alternative to fusion of the triple joint complex for the treatment of overweight and obese stage II AAFD patients, which is promising because of the limitations in motion and stress on adjacent joints imposed by the latter. Future long-term studies comparing the outcomes of joint-preserving reconstruction among BMI classes may provide additional evidence on the rates of deformity recurrence and changes in clinical improvement over time.

Footnotes

Supplemental Material

Supplemental material for this article is available on the Foot & Ankle International website at .

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

References

Belmont

Goodman

Waterman

Bader

Schoenfeld

AJ.

Thirty-day postoperative complications and mortality following total knee arthroplasty: incidence and risk factors among a national sample of 15,321 patients. J Bone Joint Surg Am. 2014;96:20-26. doi:10.2106/JBJS.M.00018.

Chan

Villar

RN.

Obesity and quality of life after primary hip arthroplasty. J Bone Joint Surg Br. 1996;78:78-81.

Chee

Teoh

Sabnis

Ballantyne

Brenkel

IJ.

Total hip replacement in morbidly obese patients with osteoarthritis: results of a prospectively matched study. J Bone Joint Surg Br. 2010;92:1066-1071. doi:10.1302/0301-620X.92B8.22764.

Chen

Lee

MJH

Rikhraj

. Effect of obesity on outcome of hallux valgus surgery. Foot Ankle Int. 2015;36(9):1078-1083. doi:10.1177/1071100715581449.

Chi

Toolan

Sangeorzan

Hansen

ST.

The lateral column lengthening and medial column stabilization procedures. Clin Orthop Relat Res. 1999;365:81-90.

Collins

Walmsley

Amin

Brenkel

Clayton

R a. E.

Does obesity influence clinical outcome at nine years following total knee replacement?

J Bone Joint Surg Br. 2012;94:1351-1355. doi:10.1302/0301-620X.94B10.28894.

Conti

Ellis

Chan

Deland

JT.

Optimal position of the heel following reconstruction of the stage II adult-acquired flatfoot deformity. Foot Ankle Int. 2015;36(8):919-927. doi:10.1177/1071100715576918.

Davis

Wood

Keenan

ACM

Brenkel

Ballantyne

JA.

Does body mass index affect clinical outcome post-operatively and at five years after primary unilateral total hip replacement performed for osteoarthritis? A multivariate analysis of prospective data. J Bone Joint Surg Br. 2011;93:1178-1182. doi:10.1302/0301-620X.93B9.26873.

Deland

JT.

Adult-acquired flatfoot deformity. J Am Acad Orthop Surg. 2008;16:399-406.

10.

Deland

Page

Sung

I-H

O’Malley

Inda

Choung

Posterior tibial tendon insufficiency results at different stages. HSS J. Musculoskelet. J Hosp Spec Surg. 2006;2:157-160. doi:10.1007/s11420-006-9017-0.

11.

Dowsey

Liew

Stoney

Choong

PFM.

The impact of obesity on weight change and outcomes at 12 months in patients undergoing total hip arthroplasty. Med J Aust. 2010;193:17-21.

12.

Foran

JRH

Mont

Etienne

Jones

Hungerford

DS.

The outcome of total knee arthroplasty in obese patients. J Bone Joint Surg Am. 2004;86-A:1609-1615.

13.

Fuhrmann

Trommer

Venbrocks

RA.

The acquired buckling-flatfoot. A foot deformity due to obesity? [in German]. Orthopade. 2005;34:682-689. doi:10.1007/s00132-005-0823-8.

14.

Gupta

Redmond

Hammarstedt

Stake

Domb

BG.

Does obesity affect outcomes in hip arthroscopy? A matched-pair controlled study with minimum 2-year follow-up. Am J Sports Med. 2015;43:965-971. doi:10.1177/0363546514565089.

15.

Haddad

Deland

. Pes Planus. In: Mann’s Surgery of the Foot and Ankle. Vol 2, 9th ed. Philadelphia, PA: Elsevier Saunders; 2014:1292-1360.

16.

Hatic

Philbin

TM.

Management of the recurrent deformity in a flexible foot following failure of tendon transfer: is arthrodesis necessary?

Foot Ankle Clin. 2012;17:299-307. doi:10.1016/j.fcl.2012.03.007.

17.

Haverkamp

Klinkenbijl

Somford

Albers

GHR

van der Vis

HM.

Obesity in total hip arthroplasty—does it really matter? A meta-analysis. Acta Orthop. 2011;82:417-422. doi:10.3109/17453674.2011.588859.

18.

Hawker

Mian

Kendzerska

French

Measures of adult pain: Visual Analog Scale for Pain (VAS Pain), Numeric Rating Scale for Pain (NRS Pain), McGill Pain Questionnaire (MPQ), Short-Form McGill Pain Questionnaire (SF-MPQ), Chronic Pain Grade Scale (CPGS), Short Form-36 Bodily Pain Scale (SF-36 BPS), and Measure of Intermittent and Constant Osteoarthritis Pain (ICOAP). Arthritis Care Res. 2011;63(suppl 11):S240-252. doi:10.1002/acr.20543.

19.

Holmes

Mann

RA.

Possible epidemiological factors associated with rupture of the posterior tibial tendon. Foot Ankle Int. 1992;13(2):70-79.

20.

Johnson

Strom

DE.

Tibialis posterior tendon dysfunction. Clin Orthop 1989;239:196-206.

21.

Kerkhoffs

GMMJ

Servien

Dunn

Dahm

Bramer

JAM

Haverkamp

The influence of obesity on the complication rate and outcome of total knee arthroplasty: a meta-analysis and systematic literature review. J Bone Joint Surg Am. 2012;94:1839-1844. doi:10.2106/JBJS.K.00820.

22.

Linberg

Sperling

Schleck

Cofield

RH.

Shoulder arthroplasty in morbidly obese patients. J Shoulder Elbow Surg. 2009;18:903-906. doi:10.1016/j.jse.2009.02.006.

23.

Williams

Nguyen

Craig

Warren

Gulotta

LV.

Functional outcomes after total shoulder arthroplasty in obese patients. J Bone Joint Surg Am. 2013;95:e160. doi:10.2106/JBJS.L.01145.

24.

Mani

Brown

Nair

. Validation of the Foot and Ankle Outcome Score in adult acquired flatfoot deformity. Foot Ankle Int. 2013;34(8):1140-1146. doi:10.1177/1071100713483117.

25.

Mann

Thompson

FM.

Rupture of the posterior tibial tendon causing flat foot. Surgical treatment. J Bone Joint Surg Am. 1985;67:556-561.

26.

Niki

Hirano

Okada

Beppu

Outcome of medial displacement calcaneal osteotomy for correction of adult-acquired flatfoot. Foot Ankle Int. 2012;33(11):940-946. doi:10.3113/FAI.2012.0940.

27.

Patel

Donegan

Albert

The 36-item short form. J Am Acad Orthop Surg. 2007;15:126-134.

28.

Pinsker

Daniels

TR.

AOFAS position statement regarding the future of the AOFAS clinical rating systems. Foot Ankle Int. 2011;32(9):841-842. doi:10.3113/FAI.2011.0841.

29.

Pi-Sunyer

The medical risks of obesity. Postgrad Med. 2009;121:21-33. doi:10.3810/pgm.2009.11.2074.

30.

Salaffi

Stancati

Silvestri

Ciapetti

Grassi

Minimal clinically important changes in chronic musculoskeletal pain intensity measured on a numerical rating scale. Eur J Pain Lond Engl. 2004;8:283-291. doi:10.1016/j.ejpain.2003.09.004.

31.

Saltzman

el-Khoury

GY.

The hindfoot alignment view. Foot Ankle Int. 1995;16(9):572-576.

32.

Sangeorzan

Mosca

Hansen

ST.

Effect of calcaneal lengthening on relationships among the hindfoot, midfoot, and forefoot. Foot Ankle Int. 1993;14(3):136-141.

33.

Ware

Kosinski

Keller

SD.

A 12-Item Short-Form Health Survey: construction of scales and preliminary tests of reliability and validity. Med Care. 1996;34:220-233.

34.

Warrender

Brown

Abboud

JA.

Outcomes of arthroscopic rotator cuff repairs in obese patients. J Shoulder Elbow Surg. 2011;20:961-967. doi:10.1016/j.jse.2010.11.006.

35.

Werner

Burrus

Looney

Park

Perumal

Cooper

MT.

Obesity is associated with increased complications after operative management of end-stage ankle arthritis. Foot Ankle Int. 2015;36(8):863-870. doi:10.1177/1071100715576569.

36.

WHO. Obesity and overweight. http://www.who.int/mediacentre/factsheets/fs311/en/. Accessed May 13, 2015.

37.

Younger

Sawatzky

Dryden

Radiographic assessment of adult flatfoot. Foot Ankle Int. 2005;26(10):820-825.

Supplementary Material

Please find the following supplemental material available below.

For Open Access articles published under a Creative Commons License, all supplemental material carries the same license as the article it is associated with.

For non-Open Access articles published, all supplemental material carries a non-exclusive license, and permission requests for re-use of supplemental material or any part of supplemental material shall be sent directly to the copyright owner as specified in the copyright notice associated with the article.

0.00 MB

0.07 MB