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Abstract

Background:

Metabolic syndrome (MetSy) is a global pandemic characterized by a cluster of interrelated abnormalities and risk factors. The prevalence of MetSy increases with advancing age. It is unknown whether increased age at the time of anterior cruciate ligament reconstruction (ACLR) is associated with an increased prevalence of MetSy.

Purpose:

To identify the association of age at ACLR with MetSy.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

Patients aged ≥18 years who underwent ACLR, with available blood pressure, blood lipids, hemoglobin A1c (HbA1c), and basic descriptive data, were included. All data were extracted from the medical records at a single academic institution. MetSy was defined as meeting any 3 of the following 5 criteria: (1) body mass index (BMI) ≥30 kg/m²; (2) triglycerides ≥150 mg/dL; (3) high-density lipoprotein (HDL) <40 mg/dL in men and <50 mg/dL in women; (4) systolic blood pressure of ≥130 mmHg or diastolic blood pressure of ≥85 mmHg; or (5) fasting (estimated) glucose of ≥100 mg/dL. Patients were also separated into groups based on age at the time of ACLR: (1) 18-29, (2) 30-39, (3) 40-49, and (4) ≥50 years.

Results:

The final analysis consisted of 493 patients (age, 18-29 years [n = 139]; 30-39 years [n = 158]; 40-49 years [n = 135]; and ≥50 years [n = 61]). Based on the criteria, 190 (38.5%) patients who underwent ACLR displayed MetSy. The prevalence of MetSy was not significantly different between age groups (P = .70). The proportion of patients meeting the individual BMI (P = .41), triglyceride (P = .05), HDL (P = .41), and blood pressure (P = .82) criteria of MetSy was not significantly different between age groups. In contrast, approximately 59% (n = 82) of patients in the 18-29 years age group compared with 88.5% (n = 54) in the ≥50 years age group had an estimated fasting glucose of ≥100 mg/dL (P < .01). HbA1c% was also significantly increased in the ≥50 years age group compared with the younger age groups (P < .01).

Conclusion:

Increased age at ACLR was not associated with MetSy but may be associated with an elevated HbA1c and estimated fasting glucose.

Keywords

anterior cruciate ligament anterior cruciate ligament reconstruction glucose hemoglobin A1c metabolic syndrome

Metabolic syndrome (MetSy) is a combination of metabolic abnormalities associated with an increased risk for developing chronic diseases, such as cardiovascular diseases and type 2 diabetes mellitus. These metabolic abnormalities are associated with obesity, insulin resistance, hypertension, and dyslipidemia.²⁸ The National Cholesterol Education Program Adult Treatment Panel III (NCEP-ATP III) defined MetSy as a patient either being diagnosed with or treated for ≥3 of the 5 criteria used in the characterization of this complex.¹² Traditionally, MetSy has been recognized as being more prevalent with advancing age or in older adults,¹¹ and a pooled analysis provided interesting evidence, showing the presence of MetSy in apparently healthy, free of disease, young adults (18-30 years).²³ In addition, data from the National Health and Nutrition Examination Survey (NHANES) demonstrate that the prevalence of MetSy has increased significantly in adults aged between 20 and 39 years.¹¹

Epidemiology and population characteristics of patients who have an anterior cruciate ligament (ACL) injury vary widely. Sanders et al²⁹ found that most ACL injuries occur in younger populations, with a mean age of ~29 years and a majority of patients being men.²⁹ Many of these patients experience injury in sports or other high-impact settings,¹ thereby illustrating a physically active lifestyle. Although the incidence of ACL injuries is increasing,¹³ it is surprisingly unknown whether an increased age at the time of ACL reconstruction (ACLR) associates with MetSy.

This study aimed to examine the association of age at ACLR with MetSy and its components. We hypothesized that increased age at the time of ACLR is associated with a greater prevalence of MetSy. Identifying MetSy after ACLR and while patients are receiving clinical care could provide an opportunity to implement early preventative strategies and increase the awareness of the lifelong burden of chronic diseases associated with this complex syndrome.

Methods

This study consisted of a retrospective, case series study design. Electronic medical records were queried for patients >18 years who underwent arthroscopic ACLR between November 2009 and April 2023 at a single academic institution (The Ohio State University, Wexner Medical Center, Columbus, Ohio, USA). The last date of data review and extraction from the electronic medical records was June 1, 2023. This study complies with the Declaration of Helsinki and was approved with a consent waiver by the Biomedical Institutional Review Board at The Ohio State University.

Patients were initially identified using the Current Procedural Terminology (CPT) codes. Patients who underwent ACLR (CPT code: 29888; n = 3521) were identified and further screened for study inclusion. The inclusion criteria were refined to include patients with blood lipids (ie, triglycerides and high-density lipoprotein [HDL]) and hemoglobin A1c (HbA1c) data obtained after ACLR and blood pressure data obtained within 30 days of ACLR. Based on this criterion, 3028 patients who underwent ACLR were excluded because they had no post-ACLR lipid or HbA1c data (n = 2988) or because they had no blood pressure data obtained outside the predetermined window of assessment (n = 40). These criteria identified 493 patients meeting the inclusion criteria and were subsequently separated into 5 groups based on age at ACLR: (1) 18-29 years, (2) 30-39 years, (3) 40-49 years, and (4) ≥50 years.

Descriptive data, blood chemistries, and corresponding dates were collected from patients meeting the inclusion criteria. All data were identified and extracted from electronic medical records and aligned with the date of ACLR. Blood chemistries were performed at our institution's central laboratory and conducted as a standard of care procedure separate from ACLR—the first available blood lipid and HbA1c after ACLR were used for this study.

Blood pressure data were preferably obtained on the day of, or within 30 days of ACLR, and were used in this study. Most patients (n = 456 [92.5%]) had multiple blood pressure assessments (median, 9 [interquartile range, IQR, 4]) on the day of surgery. For those patients, we compared the first with the mean systolic and diastolic blood pressures. The first and the mean systolic blood pressures (median, 132 [IQR, 25] vs 131 [22] mmHg, respectively; P = .47) were not significantly different. Likewise, the first and mean diastolic blood pressures (mean, 76 [IQR, 16] vs 75 [12] mmHg; P = .92; respectively) were not significantly different. The first and the mean systolic blood pressures (r = 0.80; P < .01; n = 456) and diastolic blood pressures (r = 0.73; P < .01; n = 456) were significantly correlated for those participants who had multiple blood pressure assessments recorded on the day of ACLR. Based on these findings, we decided to use the mean systolic and diastolic blood pressure data in the statistical analysis for those patients with multiple assessments on the day of ACLR.

MetSy components were determined based on the NCEP-ATP III, except for waist circumference.¹² Waist circumference was not collected as a standard of care procedure and subsequently substituted with body mass index (BMI). BMI is correlated with and has been previously substituted for waist circumference in other MetSy studies^7,18 and is more commonly used clinically. MetSy was defined as meeting any 3 of the 5 following criteria: (1) BMI ≥ 30 kg/m²; (2) triglycerides ≥150 mg/dL; (3) HDL <40 mg/dL in men and <50 mg/dL in women; (4) systolic blood pressure of ≥130 mmHg or diastolic blood pressure of ≥85 mmHg; or (5) estimated fasting glucose of ≥100 mg/dL. Fasting glucose was estimated with the following equation²²:

Estimated fasting glucose (mg/dL) = 28.7 × A1c% – 46.7.

Concomitant procedures performed on the meniscus (CPT codes: 29880, 29881, 29882, and 29883), articular cartilage (CPT code: 29877), other ligaments (CPT code: 27427), patella (CPT codes: 27520, 27524, and 27562), and proximal tibia (CPT code: 27530) at ACLR were identified in the electronic medical records database and recorded for each participant.

Statistical Analysis

Data were checked for normality with a Shapiro-Wilk test before statistical analysis. Group differences were assessed with separate 1-way analysis of variance (ANOVA) tests followed by a Bonferroni correction on multiple pairwise comparisons or with a Kruskal-Wallis 1-way ANOVA followed by a Dwass-Steel-Chritchlow-Fligner test for pairwise comparisons when appropriate. Separate Fisher Exact or chi-Square tests were performed to analyze the associations between categorical variables. Significance was set at P < .05. All statistical analyses were performed with SYSTAT Version 13.1 (Grafiti).

Results

Patient Characteristics

The final analysis consisted of 493 (women, n = 247 [50%]) patients who underwent ACLR with a median follow-up of ~6.83 years (Table 1). Based on the BMI, 43.8% of the patients were considered obese or severely obese. Most patients had blood pressure obtained on the day of ACLR, but all patients had blood pressure data obtained within 30 days of ACLR. Also, <5% of the patients displayed an HbA1c% of >6.4%.

Table 1

Patient Characteristics ^a

N (F/M)	493 (247/246)
Age, years	36.4 (14.7)
Height, m	1.73 (0.15)
Body mass, kg	86.2 (29.5)
BMI, kg/m²	28.7 (8.8)
Underweight, ≤18.5 kg/m²	2 (0.4)
Healthy weight, 18.5-24.9 kg/m²	117 (23.7)
Overweight, 25-29.9 kg/m²	158 (32)
Obese, 30-39.9 kg/m²	169 (34.3)
Severe obesity, ≥40 kg/m²	47 (9.5)
Follow-up, years	6.83 (5.76)
Systolic blood pressure, mmHg	131 (22)
Diastolic blood pressure, mmHg	75 (12)
Cholesterol, mg/dL	183 (46)
Triglycerides, mg/dL	103 (95)
HDL, mg/dL	50.0 (19.0)
LDL, mg/dL	103 (47)
Cholesterol/HDL-C ratio	3.60 (1.50)
Non-HDLC, mg/dL	128 (53)
HbA1c, %	5.30 (0.43)
HbA1c% classification
Normal, <5.7%	401 (81.3)
Prediabetic, 5.7%-6.4%	71 (14.4)
Diabetic, >6.4%	21 (4.3)
Estimated fasting glucose, mg/dL	105 (12)

Data presented as median (IQR) and n (%) unless noted otherwise. BMI, body mass index; F, female; HbA1c, hemoglobin A1c; HDL-C, high-density lipoprotein cholesterol; IQR, interquartile range; LDL, low-density lipoprotein; M, male.

Of the MetSy components, an estimated fasting glucose of ≥100 mg/dL was the most common (65.1%), followed by the blood pressure (55.8%) and BMI (43.8%) criteria components (Table 2). The HDL (29.8%) and triglyceride (29.4%) criteria were the least common MetSy components found in patients who underwent ACLR. The median HDL and triglycerides were within the normal range for this population. Few (9.5%) patients had no MetSy components, while the presence of 1 (25.8%) or 2 (26.2%) components of MetSy was the most common. There was a progressive decrease in the number of patients with 3 (16.4%), 4 (14%), or 5 (8.1%) components of MetSy. Overall, 190 (38.5%) patients who underwent ACLR displayed evidence (ie, ≥3 criteria components) of MetSy.

Table 2

MetSy Criteria and Components ^a

BMI ≥30 kg/m²	216 (43.8)
Triglycerides ≥150 mg/dL	145 (29.4)
HDL ^b	147 (29.8)
Blood pressure ^c	275 (55.8)
Estimated fasting glucose ≥100 mg/dL	321 (65.1)
No. of MetSy components
0	47 (9.5)
1	127 (25.8)
2	129 (26.2)
3	81 (16.4)
4	69 (14.0)
5	40 (8.1)
MetSy	190 (38.5)

Data are presented as n (%). BMI, body mass index; HDL, high-density lipoprotein. MetSy, metabolic syndrome.

Men <40 or women <50 mg/dL.

Systolic blood pressure of ≥130 or diastolic blood pressure of ≥85 mmHg.

Age Groups

Patient sex, height, BMI (ie, kg/m² and classification), systolic and diastolic blood pressures, and concomitant procedures at ACLR were not significantly different between age groups (Table 3). The body mass was significantly different in the ≥50 years group compared with the younger age groups (ie, 18-29, 30-39, and 40-49 years age groups) and in the 30-39 years age group compared with the 18-29 and 40-49 years age groups. The follow-up interval significantly decreased with increasing age groups.

Table 3

Patient Characteristics Based on Age Groups ^a

	18-29 Years	30-39 Years	40-49 Years	≥50 Years	P
N (F/M)	139 (74/65)	158 (76/82)	135 (65/70)	61 (32/29)	.77 ^e
Age, years	25.4 (5.0)	34.3 (5.0)	43.6 (4.6)	56.2 (5.3)	NA
Height, m	1.73 (0.15)	1.73 (0.15)	1.70 (0.15)	1.68 (0.16)	.11
Body mass, kg	81.6 (33.4)	90.7 (25.8) ^b	87.1 (28.9) ^c	81.6 (29.7) ^{b , c , d}	.03
BMI, kg/m²	27.1 (9.5)	29.5 (9.1)	29.3 (8.4)	27.9 (6.8)	.16
BMI classification					.06
Underweight, ≤18.5 kg/m²	1 (0.7)	0 (0)	0 (0)	1 (1.6)
Healthy weight, 18.5-24.9 kg/m²	47 (33.8)	29 (18.4)	28 (20.7)	13 (21.3)
Overweight, 25-29.9 kg/m²	38 (27.3)	55 (34.8)	44 (32.6)	21 (34.4)
Obese, 30-39.9 kg/m²	37 (26.6)	56 (35.4)	53 (39.3)	23 (37.7)
Severe obesity, ≥40 kg/m²	16 (11.5%)	18 (11.4)	10 (7.4)	3 (4.9)
Additional procedures at ACLR	110	113	102	51	.22
Follow-up, years	7.29 (5.83)	6.98 (5.29) ^b	6.25 (5.79) ^{b , c}	5.91 (12.3) ^{b , c , d}	.03
Systolic blood pressure, mmHg	131 (25)	132 (21)	134 (27)	130 (22.3)	.70
Diastolic blood pressure, mmHg	75 (11)	76 (11)	76 (16)	73 (13)	.15
Cholesterol, mg/dL	171 (43)	184 (45) ^b	194 (43) ^b	185 (52) ^{b , c , d}	<.01
Triglycerides, mg/dL	86 (86)	105 (92) ^b	116 (116) ^c	101 (80) ^{b , c , d}	<.01
HDL, mg/dL	51 (18)	49 (19) ^a	49 (18) ^c	55 (22) ^{b , c , d}	.03
LDL, mg/dL	97 (37)	103 (48) ^b	116 (50)	104 (54) ^{b , c , d}	<.01
Cholesterol/HDL-C ratio	3.20 (1.50)	3.70 (1.60) ^b	3.80 (1.70) ^c	3.20 (1.20) ^{b , c , d}	<.01
Non-HDLC, mg/dL	121 (46)	127 (52) ^b	143 (52) ^b	123 (56) ^{b , c , d}	<.01
HbA1c, %	5.20 (0.40)	5.20 (0.60)	5.30 (0.50)	5.50 (0.50) ^{b , c , d}	<.01
HbA1c classification					<.01
Normal, <5.7%	128 (92.1)	131 (82.9)	102 (75.6)	40 (65.6)
Prediabetic, 5.7%-6.4%	10 (7.2)	23 (14.6)	23 (17)	15 (24.6)
Diabetic, >6.4%	1 (0.7)	4 (2.5)	10 (7.4)	6 (9.8)
Estimated fasting glucose, mg/dL	103 (12)	103 (17) ^b	105 (14) ^b	111 (14) ^{b , c , d}	<.01

Data are presented as median (IQR) or n (%) unless otherwise indicated. ACLR, anterior cruciate ligament reconstruction; BMI, body mass index; F, female; HDL-C, high-density lipoprotein cholesterol; IQR, interquartile range; LDL, low-density lipoprotein; M, male.

P < .05 vs 18-29 years.

P <0.05 vs 30-39 years.

P < .05 vs 40-49 years.

Sex comparison P value.

Cholesterol (C) and non-HDLC were significantly different in the ≥50 years age group compared with the younger age groups (ie, 18-29, 30-39, and 40-49 years age groups) and in the 30-39 and 40-49 years age groups compared with the 18-29 years age group. Triglycerides, HDL, and cholesterol/HDL-C were significantly different in the ≥50 years age group compared with the younger age groups (ie, 18-29, 30-39, and 40-49 years age groups) and in the 30-39 years age group compared with the 18-29 and 40-49 years age groups. Low-density lipoprotein (LDL) was significantly different in the ≥50 years age group compared with the younger age groups (ie, 18-29, 30-39, and 40-49 years age group) and in the 30-39 years age group compared with the 18-29 years age group.

Most patients displayed an HbA1c within the normal range. However, the relative proportion of patients with a normal HbA1c classification progressively decreased (ie, 92.8%, 82.9%, 75.6%, and 65.6%) from the youngest to the oldest age group (ie, 18-29, 30-39, 40-49, and ≥50 years age groups, respectively). HbA1c was significantly increased in the ≥50 years age group compared with the younger age groups. The estimated fasting glucose was significantly elevated in the ≥50 years age group compared with the younger age groups (ie, 18-29, 30-39, and 40-49 years age groups) and in the 30-39 and 40-49 years age groups compared with the 18-29 years age group.

The number of patients meeting the BMI, HDL, and blood pressure criteria of the MetSy was not significantly different between age groups (Table 4). In contrast, the number of patients meeting the estimated fasting glucose criteria for MetSy was significantly different between age groups. For instance, approximately 59% of patients aged 18-29 years, compared with 88.5% of those aged ≥50 years, had an estimated fasting glucose of ≥100 mg/dL. There was also a trend (ie, P = .05) for more patients (38.5%) in the 40-49 age group to meet the triglyceride criteria of MetSy than the other groups (18-29 years, 25.2%; 30-39 years, 27.2%; and ≥50 years, 24.6%). MetSy (ie, ≥3 criteria components) was not significantly different between age groups.

Table 4

MetSy Criteria and Components Based on Age Groups ^a

	18-29 Years	30-39 Years	40-49 Years	≥ 50 Years	P
BMI ≥30 kg/m²	53 (38.1)	74 (46.8)	63 (46.7)	26 (42.6)	.41
Triglycerides ≥150 mg/dL	35 (25.2)	43 (27.2)	52 (38.5)	15 (24.6)	.05
HDL, mg/dL ^b	41 (29.5)	52 (32.9)	41 (30.4)	13 (21.3)	.41
Blood Pressure, mmHg ^c	80 (57.6)	90 (57)	74 (54.8)	31 (50.8)	.82
Estimated fasting glucose ≥100 mg/dL	82 (59.0)	87 (55.1)	98 (72.6)	54 (88.5)	<.01
Components of MetSy					.15
0	12 (8.6)	23 (14.6)	10 (7.4)	2 (3.3)
1	40 (28.8)	34 (21.5)	35 (25.9)	18 (13.3)
2	38 (27.3)	40 (25.3)	33 (24.4)	18 (13.3)
3	26 (18.7)	28 (17.7)	17 (12.6)	12 (8.9)
4	18 (12.9)	19 (12)	24 (17.8)	6 (9.8)
5	5 (3.6)	14 (8.9)	16 (11.9)	5 (8.2)
MetSy	49 (35.3)	61 (38.6)	57 (42.2)	23 (37.7)	.70

Data are presented as n (%). BMI, body mass index; HDL, high-density lipoprotein; MetSy, metabolic syndrome.

Men <40 mg/dL or women <50 mg/dL.

Systolic blood pressure of ≥130 mmHg or diastolic blood pressure of ≥85 mmHg.

Discussion

This study provides data suggesting that increased age at ACLR was not associated with an increased prevalence of MetSy. However, increased age at ACLR was associated with an elevated fasting glucose. In addition, HbA1c was found to be elevated, and more patients possessed a HbA1c percentage within the diabetic range with increased age at ACLR. These data suggest that despite the lack of association with MetSy, increased age at ACLR was associated with an elevated HbA1c, potentially impacting diabetic classification and estimated fasting glucose.

A significant finding of the present investigation was the elevated HbA1c with increased age. Upon further separation of HbA1c into normal (<5.7%), prediabetic (5.7%-6.4%), and diabetic (>6.4%) groups, it was also found that the ≥50 years age group had the highest percentage of patients with prediabetes and diabetes compared with the other age groups. The observation of increased HbA1c and increased estimated fasting glucose in those aged ≥50 years at the time of ACLR is consistent with trends in the general population.³⁰ Compelling evidence demonstrates that an elevated HbA1c or a history of diabetes could affect outcomes from ACLR.

In a retrospective review of diabetic patients who underwent ACLR, Lavoie-Gagne et al¹⁶ found that patients with a preoperative HbA1c of ≥6.7% were more likely to experience postoperative complications and develop arthrofibrosis independent of age and other factors. Data from the Multicenter Orthopaedic Outcomes Network (MOON) demonstrated that a history of diabetes is a significant risk factor for infection after ACLR compared with patients without a history of diabetes.² Likewise, results from revision ACLR also demonstrated a history of diabetes as a significant risk factor for postoperative infection.²⁶ Although HbA1c percentages or classifications were not linked to a diabetes diagnosis or postoperative outcomes, the present study extends those previously by indicating that an age of ≥50 years at the time of ACLR is associated with an increased HbA1c percentage and a classification characterized as diabetic without overtly impacting the prevalence of MetSy. Future research exploring the role of diet, physical activity, and other regulators (eg, medication) of HbA1c and glucose after ACLR is desired, especially with increased age.

In contrast to our hypothesis, the presence of MetSy was not significantly increased with increased age at the time of ACLR. This finding varies from the prevalence of MetSy in the general population, in which there is a significant increase in prevalence with increasing age.¹¹ One reason for this could be that patients who experience an ACL tear are, on average, more active than the general population. Most ACL injuries occur in the setting of a sport or other high-impact environment.¹ This suggests that most people who experience an ACL injury are engaged in some level of physical activity, which, in theory, can decrease their risk of developing MetSy.²⁷ A second explanation for this unexpected finding is that there is an overrepresentation of participants with comorbidities or risks factors of illness or disease in the younger age groups (eg, 18-29 and 30-39 years age groups) that prompted an attending physician to order lipid and HbA1c blood chemistries to assist in the clinical decision-making process of patient care independent from an ACL tear or reconstruction. This limitation could inherently constrain the study to potential participants with data available in their medical records and possibly result in selection bias based on non-uniform practices of health care providers. In addition, it is feasible that the current analysis is focused on patients who underwent ACLR with a subsequent physician-ordered or guided blood chemistry analysis due to an underlying or suspected condition, and thus, may limit the generalizability of the findings and partially explain the lack of difference in MetSy between age groups.

For this study, the overall presence of MetSy was 38.5%. Data from NHANES indicate that the prevalence of MetSy in the United States was approximately 41.8% in 2017-2018 using the NCEP-ATP III definition.¹⁷ In Canada, the prevalence of MetSy among adults was estimated at nearly 42% in 2009 and approximately 28.9% and 44.5% for men and women, respectively, in Mexico.^5,25 Although data are comparable to earlier ones, it is plausible that the prevalence of MetSy in the present study is overestimated, and caution is recommended if extrapolating the findings herein to a general and younger ACLR population. Future research exploring the prevalence of MetSy in patients post-ACLR would benefit from the inclusion of non-ACLR patients or patients who underwent ACLR with blood chemistries performed in the absence of any suspected or known underlying conditions, illnesses, or diseases as controls.

Another opportunity for future research includes investigating outcomes in patients who had ACLR with and without MetSy. For example, it is unknown whether the presence of MetSy associates with post-ACLR complications, return to preinjury activity level or sport, and posttraumatic knee osteoarthritis. Future efforts should consider the mechanism of ACL injury, time from injury to surgery, concomitant procedures performed at ACLR, surgeon and/or surgical factors, implementation and compliance with a standardized rehabilitation program, among others.

Of the 5 components of MetSy, the estimated fasting glucose was the most commonly met criteria in the 18-29, 40-49, and ≥50 years age groups, and the second most widely met criteria in the 30-39 years group after the blood pressure (ie, systolic and/or diastolic) criteria. Among other reasons, this finding could be due to the dietary habits of patients with an ACL injury. The effect of diet on insulin resistance and diabetes has been well studied.^15,19,20 It has also been shown that weight loss, whether through diet or exercise, can mitigate the risk of diabetes and elevated blood glucose.¹⁴ While patients who had ACLR may be more physically active at baseline than the general population, the diet of these patients may be contributing to the high prevalence of an elevated (estimated) fasting glucose across all age groups. Considering that the estimated fasting glucose was determined postoperatively, it is also plausible that physical activity patterns changed after surgery.

In addition to the estimated fasting glucose criteria, no other components of MetSy were significantly different between age groups. In this study, trends in obesity, which is defined as a BMI of ≥30 kg/m², are consistent with obesity trends in the general population, indicating that no significant difference exists between multiple age groups.¹⁰ Also, strong associations exist between obesity and dyslipidemia and obesity and hypertension.^6,21,24 These associations may help explain the lack of significant differences across age groups regarding the BMI, triglyceride, HDL, and blood pressure components of MetSy. While the association between obesity and diabetes is well studied, limited literature exists regarding the relationship between obesity and fasting blood glucose in patients who underwent ACLR.

Complementary to the MetSy and its component data, results herein illustrate an increase in cholesterol, triglycerides, HDL, LDL, HDLC, and non-HDLC with increased age. Similar to blood glucose levels, cholesterol and triglyceride levels are regulated in part by insulin. Thus, this patient population appears to have increased insulin resistance with age, as shown by the significant increase in HbA1c and estimated fasting glucose with age. The increased insulin resistance also helps explain the increasing dyslipidemia with age in patients who underwent ACLR. Despite these differences in lipid levels, the prevalence of patients who met the MetSy criteria of triglycerides ≥150 mg/dL and HDL was not significantly different between age groups. This could be due to a wide variance in data, as IQRs were quite large for triglyceride and HDL data. Another contributing factor for HDL data could be the difference in HDL levels needed to meet MetSy criteria between men and women.

Limitations

In addition to those mentioned above, there are other limitations to this study worth discussing. Clinical chemistries were documented at different times after ACLR. Blood chemistry, circulating lipids, and blood pressure data can vary greatly depending on a variety of factors, including but not limited to surgery, postoperative inflammation, diet, physical activity, illness, disease, and medication. Thus, the metabolic state for the patients included may have been temporally variable and not identified due to the lack of a temporally rigid, prospective protocol with serial assessments. With that said, HbA1c is much more resistant to change and less impacted by this limitation. Another limitation is the modification of the MetSy criteria by supplementing BMI with waist circumference. BMI and waist circumference are correlated, and BMI has been used in previous MetSy studies. Although BMI associates with cardiovascular disease risk factors, the long-term risk of type 2 diabetes and cardiovascular disease, and may function similarly to waist circumference assessments of central adiposity, future research utilizing BMI and waist circumference assessments for MetSy after ACLR is encouraged.^3,4,8,9 Finally, MetSy and its components were not linked to patient outcomes, such as pain, and it is unknown whether patients were diagnosed with and treated for MetSy. Future prospective research is encouraged to longitudinally explore the relationship of MetSy with outcomes after ACLR, and to compare outcomes and treatments (ie, medication) between patients clinically diagnosed with MetSy with those without a diagnosis but meeting the criteria-based evidence of MetSy.

Conclusion

MetSy is associated with an increased risk of developing chronic diseases and is traditionally recognized as being more prevalent with advancing age. Evidence is beginning to illustrate an increased prevalence of MetSy in apparently healthy young adults, and the presence of a single component of MetSy is predictive of developing this complex syndrome later in life. Here, we demonstrate that increased age at the time of ACLR did not associate with MetSy but did associate with increased HbA1c, which was implemented in the determination of the estimated fasting glucose criterion for MetSy. Assessing HbA1c in patients who have had ACLR and are receiving clinical care could provide an opportunity to implement early preventative strategies against postoperative impairments (eg, infection and arthrofibrosis) and increase the awareness of the lifelong burden of chronic diseases associated with an elevated HbA1c.

Footnotes

Final revision submitted May 14, 2025; accepted June 16, 2025.

One or more of the authors has declared the following potential conflict of interest or source of funding: This study was funded in part by the Heit Family Fund (Columbus, Ohio, USA). C.C.K. has received consulting fees from Arthrex and Bioventus; support for education from CDC Medical; and research support from DJO. R.A.M. has received research funding from Smith & Nephew, Vericel, and Moximed. D.C.F. has received consulting fees from DePuy Synthes, Linvatec, Medical Device Business Services, Smith & Nephew, Vericel, Bioventus, Zimmer Biomet Holdings, and Ceterix Orthopaedics; nonconsulting fees from Smith & Nephew, Vericel, Karl Storz Endoscopy, Linvatec, Pacira Pharmaceuticals, and Trice Medical; and honoraria from Vericel. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.

Ethical approval for this study was waived by the Biomedical Institutional Review Board at The Ohio State University.

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Association between Increased Age at Anterior Cruciate Ligament Reconstruction and Metabolic Syndrome

Abstract

Background:

Purpose:

Study Design:

Methods:

Results:

Conclusion:

Keywords

Methods

Statistical Analysis

Results

Patient Characteristics

Age Groups

Discussion

Limitations

Conclusion

Footnotes

References