Predictors of Acute Kidney Injury in Older Adults With Extracapsular Hip Fractures

Abstract

Objective

Postoperative acute kidney injury (AKI) is a common and serious complication following hip fracture surgery in older adults. This study aimed to identify predictors of postoperative AKI and evaluate its association with short-term complications after extracapsular hip fracture surgery.

Methods

A retrospective cohort study was conducted using TriNetX Analytics, a federated electronic health record network of 109 United States healthcare organizations (2015-2025). Adults aged ≥ 65 years undergoing extracapsular hip fracture surgery (CPT 27244/27245) were included; those with prior AKI (ICD-10-CM N17) were excluded. Propensity score matching was performed 1:1. Predictors were assessed using Cox proportional hazards modeling and postoperative complications were compared using risk ratios, odds ratios, and Kaplan-Meier survival analysis.

Results

Among 46,287 eligible patients, 1,413 matched pairs (n=2,826) were analyzed. Predictors of postoperative AKI included Black race (HR=1.64), White race (HR=1.21), elevated preoperative serum chloride (HR=1.04), bicarbonate (HR=1.03), creatinine (HR=1.18), and decreased serum protein (HR=1.11). Protective factors included Hispanic/Latino ethnicity (HR=0.70), preoperative opioid use (HR=0.58), elevated serum sodium (HR=0.97), and Tdap vaccination (HR=0.82). Postoperative AKI was associated with increased 30-day risk of myocardial infarction (RR=8.01), sepsis (RR=5.99), respiratory failure (RR=5.30), arrhythmia (RR=2.22), deep vein thrombosis (RR=1.98), transfusion (RR=1.92), and mortality (RR=2.22).

Conclusions

Postoperative AKI was independently associated with increased short-term morbidity and mortality following extracapsular hip fracture surgery in older adults. Recognition of perioperative risk factors may support earlier identification and targeted strategies to reduce AKI incidence and improve postoperative outcomes.

Keywords

hip fracture femur fracture acute kidney injury postoperative complications risk stratification geriatric trauma metabolic bone disorders fragility fractures

Introduction

Acute kidney injury (AKI) is a common and serious complication defined by the Kidney Disease: Improving Global Outcomes (KDIGO) criteria as a rapid decline in kidney function, marked by a rise in serum creatinine (SCr) or a reduction in urine output.¹ This complication occurs in approximately 22% of hospitalized patients and is associated with significant adverse outcomes, including increased mortality, prolonged hospital stays, higher healthcare costs, and a greater risk of developing chronic kidney disease (CKD) and cardiovascular events.^2-4

Surgical patients are particularly vulnerable to AKI due to perioperative hemodynamic instability, fluid shifts, blood loss, rhabdomyolysis, and exposure to nephrotoxic agents.⁵

Postoperative AKI is defined as occurring when KDIGO criteria for AKI are met within seven days of surgery, is most prevalent in cardiac and emergency procedures, and is associated with higher rates of morbidity, mortality, and re-hospitalization.⁶ Identified risk factors include male sex, preoperative hypertension (HTN), CKD, diabetes, anemia, and intraoperative hypotension.^7,8

In orthopaedic surgery, AKI occurs in 3.7-11% of patients undergoing elective lower limb arthroplasty and in up to 21% of patients undergoing hip fracture surgery, with affected individuals experiencing increased risk of postoperative stroke, pneumonia, sepsis, venous thromboembolism, and respiratory failure.^9-12 Risk factors in this population include elevated body mass index (BMI), diabetes, CKD, and low preoperative hemoglobin levels.¹³

Hip fractures are a particularly common and costly clinical issue. In 1990, the global incidence of hip fractures was 1.3 million, and due to population aging, it is projected to rise to 7 to 21 million by 2050.¹⁴ Extracapsular femur fractures, specifically intertrochanteric, peritrochanteric, and subtrochanteric types, account for over 40% of all hip fractures, 44% of the annual direct medical costs associated with hip fractures in the United States (U.S.) ($2.63 billion out of $5.96 billion) and are associated with higher surgical complexity and bleeding risk.^15,16 Despite this, limited data exists on postoperative AKI specifically in the extracapsular fracture population, with existing studies often restricted by small sample sizes and single-center designs.^17,18

The primary aim of this study is to identify predictors of postoperative AKI in hospitalized patients aged ≥ 65 years undergoing surgery for extracapsular hip fractures. Secondary aims include comparing short-term postoperative outcomes between patients who develop postoperative AKI and those who do not, with the goal of improving clinical risk stratification and outcomes in this high-risk population, as well as increasing awareness of possible complications in patients with AKI.

Methods

A retrospective cohort study was conducted using the TriNetX analytics platform (Cambridge, Massachusetts), a federated electronic health record (EHR) network that aggregates de-identified patient data from 109 healthcare organizations (HCOs) across the U.S. This analysis accessed data from 52 HCOs on July 30, 2025. Because the data are de-identified, this study was exempt from Institutional Review Board (IRB) approval and was conducted in accordance with the Health Insurance Portability and Accountability Act (HIPAA).

Patients aged ≥ 65 years who underwent surgical treatment of extracapsular hip fractures, specifically intertrochanteric, peritrochanteric, and subtrochanteric femur fractures, between January 1, 2015 and July 30, 2025 were included. This timeframe was selected to ensure diagnostic consistency following the adoption of the International Classification of Disease, 10^th Revision, Clinical Modification (ICD-10-CM) in the U.S. Surgical patients were identified using Current Procedural Terminology (CPT) codes 27244 and 27245. Patients were excluded if they had a diagnosis of AKI (ICD-10-CM N17) at least one day prior to the date of surgery.

Two cohorts were created: the AKI cohort included patients diagnosed with AKI within seven days following hip fracture surgery, and the non-AKI cohort included patients without an AKI diagnosis within this postoperative window. The index event was defined as the date of hip fracture surgery to ensure the AKI was related to the fracture.

Data extracted included demographics, comorbid diagnoses, laboratory values, vital signs, medications, and procedures, and diagnoses identified using ICD-10-CM codes. Laboratory values and vital signs were grouped using TriNetX-curated codes, medications were classified using the Anatomical Therapeutic Chemical (ATC), Veterans Affairs (VA), and RxNorm coding systems, and procedures were identified using CPT codes (Supplemental Material 1).

To reduce confounding, 1:1 nearest-neighbor propensity score matching (PSM) without replacement was performed using the Compare Outcomes tool. Matching variables included components of the Charlson Comorbidity Index (CCI) (Supplemental Material 2). All covariates were time-restricted to data collected up to one day before surgery. Balance between matched cohorts was evaluated using density plots and standardized mean differences (SMDs).

Preoperative characteristics were compared before and after matching using the Baseline Comparison tool. Variables were selected, time-restricted, and binned according to clinically relevant cutoffs. Results were reported as means ± standard deviations (SD), counts, percentages, p values, and SMDs.

A Cox proportional hazards model was used to identify independent predictors of postoperative AKI. Covariates were categorized as binary or continuous and were selected and time-restricted in the same manner as the baseline comparison (Supplemental Material 1). The outcome was postoperative AKI (ICD-10-CM N17) occurring from the date of surgery to 30 days postoperatively. Model outputs included hazard ratios (HR) with 95% confidence intervals (CI), standard errors (SE), and p values.

Postoperative complications occurring within 0-30 days of surgery were assessed using the Explore Outcomes tool. Events were selected for clinical relevance (Supplemental Material 3) and analyzed individually using two statistical methods: Measures of Association, which reported risk ratios (RR), risk differences (RD), and odds ratios (OR) with 95% CIs, and Kaplan-Meier Analysis, which reported survival probabilities, HRs, log-rank test results, p values, and proportionality tests results. Patients with pre-existing outcomes were excluded from analyses.

Results

A total of 46,287 patients met inclusion criteria. Prior to matching, 1,414 patients in the AKI cohort and 28,732 patients in the non-AKI cohort had complete data available for analysis. After 1:1 PSM, 1,413 matched pairs (2,826 total patients) were included in the final analysis. After matching, baseline covariates were well-balanced with minor residual imbalances noted in age, ethnicity, BMI, and select preoperative laboratory values (Table 1 and Supplemental Material 4).

Table 1.

Baseline Characteristics of the Acute Kidney Injury and Non-Acute Kidney Injury Cohort Before and After Propensity Score Matching

Before matching					After matching
Variable	AKI (n = 1,414)	Non-AKI(n = 28,732)	p value	SMD	Variable	AKI (n = 1,413)	Non-AKI(n = 1,413)	p value	SMD
Demographics					Demographics
Age at index, years (mean ± SD)	81.74 ± 8.09	79.14 ± 8.84	< 0.01	0.31	Age at index, years (mean ± SD)	81.74 ± 8.10	79.01 ± 8.94	< 0.01	0.32
Female, % (n)	62.31% (881)	69.84% (20,067)	< 0.01	0.16	Female, % (n)	62.35% (881)	67.09% (948)	0.01	0.10
Male	33.10% (468)	28.23% (8,111)	< 0.01	0.11	Male	33.05% (467)	30.86% (436)	0.21	0.05
Hispanic or Latino	4.17% (59)	4.48% (1,286)	0.59	0.01	Hispanic or Latino	4.18% (59)	5.31% (75)	0.16	0.05
Not Hispanic or Latino	51.06% (722)	70.26% (20,187)	< 0.01	0.41	Not Hispanic or Latino	51.10% (722)	68.01% (961)	< 0.01	0.35
White	82.53% (1,167)	84.73% (24,344)	0.03	0.06	White	82.52% (1,166)	85.35% (1,206)	0.04	0.08
Black or African American	5.52% (78)	4.24% (1,218)	0.02	0.06	Black or African American	5.52% (78)	4.18% (59)	0.10	0.06
Asian	2.62% (37)	4.42% (1,271)	< 0.01	0.10	Asian	2.62% (37)	3.68% (52)	0.11	0.06
BMI (kg/m²)	26.05 ± 5.93	24.87 ± 5.53	< 0.01	0.21	BMI (kg/m²)	26.05 ± 5.93	24.90 ± 5.25	< 0.01	0.21
< 18.5	5.66% (80)	8.80% (2,527)	< 0.01	0.12	< 18.5	5.66% (80)	7.43% (105)	0.06	0.07
18.5-25	29.92% (423)	33.10% (9,511)	0.01	0.07	18.5-25	29.94% (423)	31.78% (449)	0.29	0.04
25-30	30.34% (429)	27.62% (7,936)	0.03	0.06	25-30	30.29% (428)	27.88% (394)	0.16	0.05
≥ 30	20.79% (294)	16.07% (4,617)	< 0.01	0.12	≥ 30	20.81% (294)	14.37% (203)	< 0.01	0.17
Medications					Medications
Diuretics	36.35% (514)	32.11% (9,225)	< 0.01	0.09	Diuretics	36.31% (513)	29.65% (419)	< 0.01	0.14
ACE inhibitors	24.54% (347)	22.11% (6,352)	0.03	0.06	ACE inhibitors	24.49% (346)	20.88% (295)	0.02	0.09
Beta blockers	41.94% (593)	41.76% (11,999)	0.90	0.00	Beta blockers	41.90% (592)	39.14% (553)	0.14	0.06
CCBs	27.09% (383)	27.88% (8,009)	0.52	0.02	CCBs	27.04% (382)	26.33% (372)	0.67	0.02
ARBs	14.64% (207)	15.18% (4,362)	0.58	0.02	ARBs	14.65% (207)	15.57% (220)	0.49	0.03
Anticoagulants	43.07% (609)	52.27%.(15,017)	< 0.01	0.18	Anticoagulants	43.03% (608)	47.98% (678)	0.01	0.10
Immunosuppressants	1.56% (22)	2.26% (648)	0.08	0.05	Immunosuppressants	1.56% (22)	2.12% (30)	0.26	0.04
Glucocorticoids	43.28% (612)	43.26% (12,429)	0.99	0.00	Glucocorticoids	43.24% (611)	38.64% (546)	0.01	0.09
Corticosteroids	37.06% (524)	38.26% (10,994)	0.36	0.02	Corticosteroids	37.01% (523)	34.04% (481)	0.10	0.06
Opioids	55.94% (791)	78.63% (22,593)	< 0.01	0.50	Opioids	55.91% (790)	73.67% (1,041)	< 0.01	0.38
NSAIDs	8.77% (124)	13.49% (3,875)	< 0.01	0.15	NSAIDs	8.78% (124)	11.04% (156)	0.04	0.08
Aminoglycosides	8.42% (119)	8.80% (2,527)	0.62	0.01	Aminoglycosides	8.42% (119)	7.43% (105)	0.33	0.04
Vancomycin	7.92% (112)	9.53% (2,739)	0.04	0.06	Vancomycin	7.93% (112)	8.56% (121)	0.54	0.02
Antineoplastics	6.93% (98)	8.18% (2,351)	0.09	0.05	Antineoplastics	6.94% (98)	6.09% (86)	0.36	0.03
Tdap vaccine	11.17% (158)	15.16% (4,355)	< 0.01	0.12	Tdap vaccine	11.18% (158)	12.95% (183)	0.15	0.05
COVID vaccine	7.99% (113)	11.30% (3,246)	< 0.01	0.11	COVID vaccine	8.00% (113)	9.41% (133)	0.18	0.05
Laboratory Values/Vital Signs					Laboratory Values/Vital Signs
Sodium (mmol/L)	138.22 ± 3.70	137.90 ± 3.95	0.01	0.08	Sodium (mmol/L)	138.21 ± 3.70	137.85 ± 3.75	0.03	0.10
< 135	26.59% (376)	29.88% (8,586)	0.01	0.07	< 135	26.61% (376)	27.53% (389)	0.58	0.02
135-145	67.68% (957)	79.28% (22,779)	< 0.01	0.27	135-145	67.66% (956)	76.15% (1,076)	< 0.01	0.19
≥ 145	10.96% (155)	10.88% (3,126)	0.92	0.00	≥ 145	10.97% (155)	8.49% (120)	0.03	0.08
Chloride (mmol/L)	103.47 ± 4.65	102.67 ± 4.56	< 0.01	0.17	Chloride (mmol/L)	103.47 ± 4.65	102.72 ± 4.45	< 0.01	0.17
< 96	14.00% (198)	16.23% (4,662)	0.03	0.06	< 96	13.94% (197)	14.01% (198)	0.96	0.00
96-106	62.02% (877)	70.50% (20,256)	< 0.01	0.18	96-106	62.00% (876)	66.38% (938)	0.01	0.09
≥ 106	46.61% (659)	44.52% (12,791)	0.12	0.04	≥ 106	46.57% (658)	39.99% (565)	< 0.01	0.13
Calcium (mg/dL)	8.98 ± 0.70	9.04 ± 0.63	< 0.01	0.09	Calcium (mg/dL)	8.98 ± 0.70	9.04 ± 0.62	0.04	0.09
< 8.5	32.82% (464)	31.50% (9,050)	0.30	0.03	< 8.5	32.77% (463)	27.39% (387)	< 0.01	0.12
8.5-10.2	65.35% (924)	77.84% (22,365)	< 0.01	0.28	8.5-10.2	65.32% (923)	74.45% (1,052)	< 0.01	0.20
≥ 10.2	13.65% (193)	14.17% (4,070)	0.59	0.01	≥ 10.2	13.66% (193)	11.96% (169)	0.18	0.05
Glucose (mg/dL)	127.63 ± 54.23	126.8- ± 42.27	0.56	0.02	Glucose (mg/dL)	127.67 ± 54.24	129.77 ± 44.89	0.33	0.04
< 72	10.11% (143)	10.06% (2,891)	0.95	0.00	< 72	10.12% (143)	9.91% (140)	0.85	0.01
72-108	52.05% (736)	60.07% (17,258)	< 0.01	0.16	72-108	52.02% (735)	54.00% (763)	0.29	0.04
≥ 108	59.55% (842)	73.08% (20,998)	< 0.01	0.29	≥ 108	59.52% (841)	69.92% (988)	< 0.01	0.22
Total cholesterol (mg/dL)	161.56 ± 45.41	168.19 ± 45.70	< 0.01	0.15	Total cholesterol (mg/dL)	161.59 ± 45.44	166.28 ± 44.65	0.09	0.10
< 200	35.93% (508)	33.09% (9,507)	0.03	0.06	< 200	35.88% (507)	31.49% (445)	0.01	0.09
200-240	13.79% (195)	14.45% (4,153)	0.49	0.02	200-240	13.80% (195)	12.88% (182)	0.47	0.03
≥ 240	6.37% (90)	6.49% (1,864)	0.85	0.01	≥ 240	6.37% (90)	5.59% (79)	0.38	0.03
Phosphate (mg/dL)	3.43 ± 0.79	3.28 ± 0.75	< 0.01	0.19	Phosphate (mg/dL)	3.43 ± 0.79	3.29 ± 0.71	0.01	0.18
< 2.5	7.92% (112)	10.59% (3,043)	< 0.01	0.09	< 2.5	7.93% (112)	9.48% (134)	0.14	0.06
2.5-4.5	24.68% (349)	29.10% (8,362)	< 0.01	0.10	2.5-4.5	24.70% (349)	26.47% (374)	0.28	0.04
≥ 4.5	5.30% (75)	4.67% (1,343)	0.27	0.03	≥ 4.5	5.31% (75)	4.18% (59)	0.16	0.05
Bicarbonate (mmol/L)	25.26 ± 3.85	25.41 ± 3.36	0.17	0.04	Bicarbonate (mmol/L)	25.26 ± 3.85	25.20 ± 3.18	0.69	0.02
< 22	26.59% (376)	24.00% (6,896)	0.03	0.06	< 22	26.61% (376)	22.79% (322)	0.02	0.09
22-29	65.56% (927)	76.71% (22,041)	< 0.01	0.25	22-29	65.53% (926)	73.53% (1,039)	< 0.01	0.17
≥ 29	35.57% (503)	41.55% (11,939)	< 0.01	0.12	≥ 29	35.53% (502)	36.80% (520)	0.48	0.03
SCr (mg/dL)	1.21 ± 0.56	0.93 ± 0.65	< 0.01	0.46	SCr (mg/dL)	1.21 ± 0.56	0.98 ± 0.75	< 0.01	0.36
< 0.6	12.09% (171)	26.68% (7,666)	< 0.01	0.38	< 0.6	12.10% (171)	23.43% (331)	< 0.01	0.30
0.6-1.3	60.33% (853)	76.06% (21,852)	< 0.01	0.34	0.6-1.3	60.30% (852)	72.47% (1,024)	< 0.01	0.26
≥ 1.3	35.22% (498)	14.93% (4,289)	< 0.01	0.48	≥ 1.3	35.17% (497)	16.63% (235)	< 0.01	0.43
BUN (mg/dL)	24.99 ± 12.90	19.09 ± 8.67	< 0.01	0.54	BUN (mg/dL)	24.99 ± 12.91	19.49 ± 9.35	< 0.01	0.49
< 6	3.82% (54)	8.05% (2,312)	< 0.01	0.18	< 6	3.82% (54)	6.58% (93)	< 0.01	0.12
6-24	56.37% (797)	70.89% (20,368)	< 0.01	0.31	6-24	56.33% (796)	64.90% (917)	< 0.01	0.18
≥ 24	47.24% (668)	33.17% (9,531)	< 0.01	0.29	≥ 24	47.21% (667)	32.13% (454)	< 0.01	0.31
Hemoglobin (g/dL)	11.25 ± 2.26	11.95 ± 1.99	< 0.01	0.33	Hemoglobin (g/dL)	11.24 ± 2.26	11.91 ± 2.01	< 0.01	0.31
< 12	51.27% (725)	52.17% (14,989)	0.51	0.02	< 12	51.31% (725)	49.33% (697)	0.29	0.04
12-17.5	53.11% (751)	67.44% (19,376)	< 0.01	0.30	12-17.5	53.08% (750)	63.27% (894)	< 0.01	0.21
≥ 17.5	0.78% (11)	0.83% (239)	0.83	0.01	≥ 17.5	0.78% (11)	0.71% (10)	0.83	0.01
Serum albumin (g/dL)	3.68 ± 0.56	3.76 ± 0.53	< 0.01	0.14	Serum albumin (g/dL)	3.68 ± 0.56	3.76 ± 0.53	< 0.01	0.15
< 3.5	34.30% (485)	33.71% (9,686)	0.65	0.01	< 3.5	34.32% (485)	29.72% (420)	0.01	0.10
3.5-5.5	53.04% (750)	62.85% (18,058)	< 0.01	0.20	3.5-5.5	53.01% (749)	59.09% (835)	< 0.01	0.12
≥ 5.5	1.13% (16)	0.55% (158)	< 0.01	0.06	≥ 5.5	1.13% (16)	0.71% (10)	0.24	0.04
Serum protein (g/dL)	6.72 ± 0.83	6.75 ± 0.76	0.29	0.04	Serum protein (g/dL)	6.72 ± 0.82	6.79 ± 0.73	0.07	0.09
< 6	17.75% (251)	18.83% (5,411)	0.31	0.03	< 6	17.76% (251)	16.99% (240)	0.58	0.02
6-8.3	51.84% (733)	61.24% (17,596)	< 0.01	0.19	6-8.3	51.81% (732)	57.47% (812)	< 0.01	0.11
≥ 8.3	4.17% (59)	4.29% (1,233)	0.83	0.01	≥ 8.3	4.11% (58)	4.32% (61)	0.78	0.01
Iron (mg/dL)	60.82 ± 45.06	64.03 ± 42.38	0.26	0.07	Iron (mg/dL)	60.82 ± 45.06	62.78 ± 39.42	0.64	0.05
< 50	9.48% (134)	8.31% (2,388)	0.12	0.04	< 50	9.48% (134)	7.93% (112)	0.14	0.06
50-175	10.61% (150)	9.94% (2,856)	0.41	0.02	50-175	10.62% (150)	8.21% (116)	0.03	0.08
≥ 175	0.71% (10)	0.59% (169)	0.57	0.01	≥ 175	0.71% (10)	0.71% (10)	1.00	0.00
Erythrocytes (million/mL)	3.64 ± 0.95	3.69 ± 1.17	0.17	0.05	Erythrocytes (million/mL)	3.64 ± 0.95	3.73 ± 1.13	0.04	0.09
< 4.2	56.93% (805)	64.91% (18,651)	< 0.01	0.16	< 4.2	56.97% (805)	61.22% (865)	0.02	0.09
4.2-6.1	44.77% (633)	53.08% (15,250)	< 0.01	0.17	4.2-6.1	44.73% (632)	48.27% (682)	0.06	0.07
≥ 6.1	0.71% (10)	0.59% (169)	0.57	0.01	≥ 6.1	0.71% (10)	0.71% (10)	1.00	0.00
PT (s)	12.79 ± 4.80	12.85 ± 4.46	0.77	0.01	PT (s)	12.79 ± 4.80	12.84 ± 4.70	0.84	0.01
< 11	14.43% (204)	18.66% (5,361)	< 0.01	0.11	< 11	14.44% (204)	18.47% (261)	< 0.01	0.11
11-13.5	20.86% (295)	33.32% (9,573)	< 0.01	0.28	11-13.5	20.88% (295)	31.56% (446)	< 0.01	0.24
≥ 13.5	14.85% (210)	20.29% (5,829)	< 0.01	0.14	≥ 13.5	14.79% (209)	18.40% (260)	< 0.01	0.10
ESR (mm/h)	26.14 ± 22.84	25.19 ± 23.25	0.56	0.04	ESR (mm/h)	26.14 ± 22.84	27.28 ± 24.99	0.63	0.05
< 20	9.05% (128)	9.77% (2,806)	0.38	0.02	< 20	9.06% (128)	8.63% (122)	0.69	0.01
20-30	3.40% (48)	4.06% (1,166)	0.22	0.04	20-30	3.40% (48)	3.82% (54)	0.55	0.02
≥ 30	6.44% (91)	6.21% (1,785)	0.73	0.01	≥ 30	6.44% (91)	6.65% (94)	0.82	0.01
CRP (mg/L)	25.85 ± 45.57	27.26 ± 49.31	0.71	0.03	CRP (mg/L)	25.85 ± 45.57	26.98 ± 46.42	0.82	0.02
< 3	4.60% (65)	5.24% (1,506)	0.29	0.03	< 3	4.60% (65)	4.81% (68)	0.79	0.01
3-10	5.73% (81)	5.25% (1,507)	0.43	0.02	3-10	5.73% (81)	4.88% (69)	0.31	0.04
10-100	5.45% (77)	6.24% (1,792)	0.23	0.03	10-100	5.45% (77)	5.17% (73)	0.74	0.01
≥ 100	2.33% (33)	1.88% (541)	0.23	0.03	≥ 100	2.34% (33)	1.77% (25)	0.29	0.04
PTH (pg/mL)	82.21 ± 63.31	77.64 ± 124.16	0.7	0.05	PTH (pg/mL)	82.21 ± 63.31	68.74 ± 55.15	0.11	0.23
< 10	0.71% (10)	0.11% (32)	< 0.01	0.09	< 10	0.71% (10)	0.71% (10)	1.00	0.00
10-65	4.88% (69)	5.67% (1,628)	0.21	0.04	10-65	4.88% (69)	4.67% (66)	0.79	0.01
≥ 65	4.10% (58)	3.76% (1,081)	0.51	0.02	≥ 65	4.11% (58)	3.26% (46)	0.23	0.05
Systolic BP (mmHg)	127.00 ± 25.66	126.21 ± 22.47	0.31	0.03	Systolic BP (mmHg)	126.99 ± 25.67	125.96 ± 21.80	0.36	0.04
< 120	46.11% (652)	52.68% (15,136)	< 0.01	0.13	< 120	46.07% (651)	48.27% (682)	0.24	0.04
120-130	48.16% (681)	53.55% (15,387)	< 0.01	0.11	120-130	48.13% (680)	48.48% (685)	0.85	0.01
≥ 130	56.79% (803)	65.49% (18,816)	< 0.01	0.18	≥ 130	56.76% (802)	60.01% (848)	0.08	0.07
Diastolic BP (mmHg)	67.33 ± 14.79	66.49 ± 12.99	0.06	0.06	Diastolic BP (mmHg)	67.31 ± 14.80	66.45 ± 12.49	0.18	0.06
< 80	59.19% (837)	68.25% (19,609)	< 0.01	0.19	< 80	59.17% (836)	63.06% (891)	0.03	0.08
80-90	46.61% (659)	52.52% (15,089)	< 0.01	0.12	80-90	46.57% (658)	46.85% (662)	0.88	0.01
≥ 90	32.46% (459)	38.68% (11,113)	< 0.01	0.13	≥ 90	32.41% (458)	33.05% (467)	0.72	0.01
Body temperature (°F)	97.50 ± 3.56	97.42 ± 4.66	0.68	0.02	Body temperature (°F)	97.50 ± 3.56	97.67 ± 2.52	0.28	0.06
< 97	17.26% (244)	21.99% (6,319)	< 0.01	0.12	< 97	17.27% (244)	19.89% (281)	0.07	0.07
97-99	42.01% (594)	53.35% (15,328)	< 0.01	0.23	97-99	41.97% (593)	50.39% (712)	< 0.01	0.17
≥ 99	21.85% (309)	24.43% (7,018)	0.03	0.06	≥ 99	21.87% (309)	21.73% (307)	0.93	0.00
RR (breaths/min)	16.85 ± 2.65	16.82 ± 2.59	0.82	0.01	RR (breaths/min)	16.85 ± 2.65	16.89 ± 2.40	0.79	0.02
< 12	3.40% (48)	3.58% (1,029)	0.71	0.01	< 12	3.40% (48)	4.11% (58)	0.32	0.04
12-20	33.45% (473)	40.28% (11,572)	< 0.01	0.14	12-20	33.40% (472)	39.99% (565)	< 0.01	0.14
≥ 20	20.72% (293)	23.71% (6,813)	0.01	0.07	≥ 20	20.67% (292)	22.79% (322)	0.17	0.05
LVEF (%)	57.93 ± 13.79	59.86 ± 12.12	0.17	0.15	LVEF (%)	57.93 ± 13.79	59.83 ±15.33	0.42	0.13
< 55	1.98% (28)	1.72% (493)	0.46	0.02	< 55	1.98% (28)	0.99% (14)	0.03	0.08
55-70	3.61% (51)	4.85% (1,394)	0.03	0.06	55-70	3.61% (51)	4.39% (62)	0.29	0.04
≥ 70	1.56% (22)	1.66% (476)	0.77	0.01	≥ 70	1.56% (22)	1.56% (22)	1.00	0.00
Diagnoses					Diagnoses
Primary hypertension	60.89% (861)	64.23% (18,453)	0.01	0.07	Primary hypertension	60.86% (860)	59.94% (847)	0.62	0.02
Diabetes	26.03% (368)	23.32% (6,700)	0.02	0.06	Diabetes	26.04% (368)	25.83% (365)	0.90	0.00
MI	6.37% (90)	6.11% (1,754)	0.69	0.01	MI	6.37% (90)	6.23% (88)	0.88	0.01
Ischemic heart disease	27.51% (389)	27.49% (7,899)	0.99	0.00	Ischemic heart disease	27.46% (388)	26.89% (380)	0.74	0.01
Heart failure	18.60% (263)	16.17% (4,646)	0.02	0.06	Heart failure	18.54% (262)	17.34% (245)	0.40	0.03
Rheumatic heart disease	6.37% (90)	7.62% (2,190)	0.08	0.05	Rheumatic heart disease	6.37% (90)	6.51% (92)	0.88	0.01
Pulmonary hypertension	5.45% (77)	5.44% (1,563)	0.99	0.00	Pulmonary hypertension	5.45% (77)	4.88% (69)	0.50	0.03
Peripheral vascular disease	8.06% (114)	8.09% (2,325)	0.97	0.00	Peripheral vascular disease	8.07% (114)	8.21% (116)	0.89	0.01
CKD	23.90% (338)	14.01% (4,025)	< 0.01	0.25	CKD	23.92% (338)	15.07% (213)	< 0.01	0.22
UTI	19.59% (277)	22.17% (6,371)	0.02	0.06	UTI	19.60% (277)	18.05% (255)	0.29	0.04
Kidney stone	4.10% (58)	3.68% (1,057)	0.41	0.02	Kidney stone	4.11% (58)	2.90% (41)	0.08	0.07
Anemia	23.98% (339)	26.80% (7,701)	0.02	0.07	Anemia	23.99% (339)	26.12% (369)	0.19	0.05
COPD	11.53% (163)	16.51 (4,743)	< 0.01	0.14	COPD	11.54% (163)	11.04% (156)	0.68	0.02
Pulmonary fibrosis	2.76% (39)	2.11% (605)	0.10	0.04	Pulmonary fibrosis	2.76% (39)	1.49% (21)	0.02	0.09
Asthma	5.73% (81)	7.54% (2,166)	0.01	0.07	Asthma	5.73% (81)	5.38% (76)	0.68	0.02
Sleep apnea	6.65% (94)	6.83% (1,962)	0.79	0.01	Sleep apnea	6.65% (94)	6.02% (85)	0.49	0.03
Hepatic fibrosis	0.85% (12)	0.49% (142)	0.07	0.04	Hepatic fibrosis	0.85% (12)	0.71% (10)	0.67	0.02
Liver disease	6.01% (85)	5.96% (1,713)	0.94	0.00	Liver disease	6.02% (85)	5.31% (75)	0.42	0.03
Rheumatoid arthritis	3.04% (43)	3.45% (991)	0.41	0.02	Rheumatoid arthritis	3.04% (43)	2.62% (37)	0.50	0.03
SLE	0.71% (10)	0.48% (138)	0.23	0.03	SLE	0.71% (10)	0.71% (10)	1.00	0.00
Sarcoidosis	0.71% (10)	0.26% (74)	< 0.01	0.06	Sarcoidosis	0.71% (10)	0.71% (10)	1.00	0.00
Amyloidosis	0.71% (10)	0.32% (93)	0.02	0.05	Amyloidosis	0.71% (10)	0.71% (10)	1.00	0.00
Peptic ulcer disease	1.34% (19)	1.14% (326)	0.47	0.02	Peptic ulcer disease	1.35% (19)	1.13% (16)	0.61	0.02
Dementia	13.51% (191)	16.99% (4,882)	< 0.01	0.10	Dementia	13.52% (191)	13.66% (193)	0.91	0.00
Tobacco use	9.90% (140)	14.40% (4,138)	< 0.01	0.14	Tobacco use	9.91% (140)	12.95% (183)	0.01	0.10
Alcohol related disorders	2.41% (34)	6.13% (1,761)	< 0.01	0.19	Alcohol related disorder	2.41% (34)	5.24% (74)	< 0.01	0.15
Opioid related disorders	1.34%(19)	1.69% (485)	0.32	0.03	Opioid related disorder	1.35% (19)	1.35% (19)	1.00	0.00
Procedures					Procedures
Blood transfusion	5.23% (74)	4.51% (1,296)	0.20	0.03	Blood transfusion	5.24% (74)	3.61% (51)	0.04	0.08
Chemotherapy	1.84% (26)	2.54% (729)	0.10	0.05	Chemotherapy	1.84% (26)	1.56% (22)	0.56	0.02
Foley catheterization	3.54% (50)	6.53% (1,875)	< 0.01	0.14	Foley catheterization	3.54% (50)	5.45% (77)	0.01	0.09

Abbreviations: AKI, acute kidney injury; SMD, standardized mean difference; SD, standard deviation; BMI, body mass index; ACE, angiotensin converting enzyme; CCBs, calcium channel blockers; ARBs, angiotensin II receptor blockers; NSAIDs, non-steroidal anti-inflammatory drugs; Tdap, tetanus diphtheria acellular pertussis; SCr, serum creatinine; BUN, blood urea nitrogen; PT, prothrombin time; ESR, erythrocyte sedimentation rate; CRP, C-reactive protein; PTH, parathyroid hormone; BP, blood pressure; RR, respiratory rate; LVEF, left ventricular ejection fraction; MI, myocardial infarction; CKD, chronic kidney disease; UTI, urinary tract infection; COPD, chronic obstructive pulmonary disease; SLE, systemic lupus erythematosus.

Cox proportional hazards modeling identified several independent predictors of postoperative AKI (Table 2 and Figure 1). Black or African American race (HR = 1.64; CI = 1.30-2.07) and White race (HR = 1.21; CI = 1.06-1.39) were associated with increased risk of AKI, while Hispanic or Latino ethnicity (HR = 0.70; CI = 0.55-0.88) was identified protective. Higher preoperative chloride (HR = 1.04; CI = 1.02-1.05), bicarbonate (HR = 1.03; CI = 1.01-1.05), SCr (HR = 1.18; CI = 1.07-1.31), and decreased serum protein levels (HR = 1.11; CI = 1.01-1.21) were identified as predictors. Conversely, higher sodium levels (HR = 0.97; CI = 0.95-0.99), preoperative opioid use (HR = 0.58; CI = 0.52-0.65), Tdap vaccination (HR = 0.82; CI = 0.72-0.94), and primary HTN (HR = 0.88; CI = 0.79-0.99) were protective factors.

Table 2.

Cox Proportional Hazards Analysis of Matched Cohorts

Covariate	HR	Coefficient	SE	Z score	p value	95% CI
Black or African American	1.64	0.50	0.12	4.18	< 0.01	(1.30, 2.07)
White	1.21	0.19	0.07	2.77	0.01	(1.06, 1.39)
SCr	1.18	0.17	0.05	3.37	< 0.01	(1.07, 1.31)
Serum protein	1.11	0.10	0.05	2.27	0.02	(1.01, 1.21)
Chloride	1.04	0.04	0.01	4.25	< 0.01	(1.02, 1.05)
Bicarbonate	1.03	0.03	0.01	3.54	< 0.01	(1.01, 1.05)
PT	1.01	0.01	0.01	2.31	0.02	(1.00, 1.03)
Diastolic BP	1.01	0.01	0.00	2.62	0.01	(1.00, 1.01)
Sodium	0.97	-0.03	0.01	-3.29	< 0.01	(0.95, 0.99)
Hispanic or Latino	0.70	-0.36	0.12	-2.98	< 0.01	(0.55, 0.88)
Opioids	0.58	-0.55	0.06	-9.46	< 0.01	(0.52, 0.65)
Primary HTN	0.88	-0.13	0.06	-2.20	0.03	(0.79, 0.99)
Sarcoidosis	1.74	0.55	0.35	1.57	0.12	(0.87, 3.46)
Amyloidosis	1.38	0.32	0.46	0.71	0.48	(0.56, 3.38)
OUD	1.32	0.28	0.21	1.31	0.19	(0.87, 2.00)
COPD	1.29	0.25	0.20	1.23	0.22	(0.86, 1.92)
Immunosuppressants	1.20	0.18	0.18	0.99	0.32	(0.84, 1.70)
Pulmonary fibrosis	1.17	0.16	0.15	1.02	0.31	(0.87, 1.58)
Antineoplastics	1.15	0.14	0.10	1.46	0.15	(0.95, 1.38)
SLE	1.15	0.14	0.33	0.42	0.67	(0.60, 2.19)
Pulmonary HTN	1.14	0.13	0.10	1.29	0.20	(0.93, 1.39)
PVD	1.14	0.13	0.24	0.53	0.60	(0.71, 1.82)
Serum albumin	1.10	0.10	0.06	1.59	0.11	(0.98, 1.25)
Anemia	1.09	0.09	0.06	1.44	0.15	(0.97, 1.22)
Calcium	1.07	0.07	0.04	1.54	0.12	(0.98, 1.16)
Tobacco use	1.07	0.06	0.09	0.72	0.47	(0.90, 1.27)
MI	1.07	0.06	0.09	0.69	0.49	(0.89, 1.27)
Asthma	1.06	0.06	0.10	0.59	0.55	(0.87, 1.29)
Anticoagulants	1.06	0.06	0.06	0.98	0.33	(0.95, 1.18)
Chemotherapy	1.06	0.06	0.20	0.29	0.78	(0.72, 1.55)
Blood transfusion	1.05	0.05	0.15	0.32	0.75	(0.79, 1.40)
Rheumatic HD	1.04	0.04	0.08	0.52	0.61	(0.89, 1.21)
Asian	1.04	0.04	0.15	0.26	0.79	(0.78, 1.38)
Hemoglobin	1.03	0.03	0.02	1.69	0.09	(1.00, 1.07)
Diuretics	1.03	0.03	0.06	0.57	0.57	(0.92, 1.15)
Corticosteroids	1.03	0.03	0.07	0.42	0.68	(0.89, 1.19)
Glucocorticoids	1.03	0.03	0.07	0.40	0.69	(0.90, 1.18)
Beta blockers	1.02	0.02	0.06	0.35	0.72	(0.91, 1.14)
ACE inhibitors	1.02	0.02	0.06	0.42	0.68	(0.92, 1.14)
RA	1.02	0.02	0.15	0.14	0.89	(0.77, 1.35)
Dementia	1.02	0.02	0.06	0.31	0.76	(0.90, 1.16)
Peptic ulcers	1.01	0.01	0.19	0.07	0.94	(0.70, 1.47)
LVEF	1.01	0.01	0.01	1.70	0.09	(1.00, 1.02)
Kidney stone	1.01	0.01	0.12	0.08	0.94	(0.80, 1.27)
Vancomycin	1.01	0.01	0.09	0.06	0.95	(0.84, 1.20)
Phosphate	1.01	0.01	0.05	0.11	0.92	(0.91, 1.12)
Male	1.00	0.00	0.05	0.07	0.94	(0.91, 1.11)
RR	1.00	0.00	0.01	0.42	0.68	(0.98, 1.03)
Aminoglycosides	1.00	0.00	0.08	0.03	0.98	(0.86, 1.18)
Iron	1.00	0.00	0.00	0.99	0.32	(1.00, 1.00)
Glucose	1.00	0.00	0.00	0.03	0.98	(1.00, 1.00)
Total cholesterol	1.00	0.00	0.00	-1.26	0.21	(1.00, 1.00)
PTH	1.00	0.00	0.00	-1.41	0.16	(1.00, 1.00)
ESR	1.00	0.00	0.00	-0.64	0.52	(0.99, 1.00)
Systolic BP	1.00	0.00	0.00	-1.12	0.26	(1.00, 1.00)
CRP	1.00	0.00	0.00	-1.25	0.21	(1.00, 1.00)
Age at index	1.00	0.00	0.00	-1.12	0.26	(0.99, 1.00)
BUN	1.00	0.00	0.00	-1.12	0.26	(0.99, 1.00)
Foley catheterization	1.00	0.00	0.13	-0.03	0.98	(0.77, 1.28)
UTI	1.00	-0.01	0.06	-0.08	0.94	(0.89, 1.12)
Body temperature	0.99	-0.01	0.01	-2.26	0.02	(0.98, 1.00)
HF	0.99	-0.01	0.08	-0.15	0.88	(0.84, 1.16)
Erythrocytes	0.98	-0.02	0.04	-0.41	0.68	(0.90, 1.07)
Sleep apnea	0.98	-0.02	0.09	-0.25	0.80	(0.82, 1.16)
ARBs	0.98	-0.03	0.06	-0.39	0.70	(0.86, 1.11)
Hepatic fibrosis	0.97	-0.03	0.25	-0.11	0.91	(0.59, 1.60)
Ischemic HD	0.97	-0.03	0.06	-0.52	0.60	(0.86, 1.09)
CCBs	0.95	-0.05	0.06	-0.94	0.35	(0.85, 1.06)
COVID vaccine	0.94	-0.07	0.08	-0.79	0.43	(0.79, 1.10)
Diabetes mellitus	0.90	-0.10	0.46	-0.23	0.82	(0.37, 2.20)
CKD	0.89	-0.11	0.06	-1.94	0.05	(0.80, 1.00)
Liver disease	0.87	-0.14	0.10	-1.37	0.17	(0.72, 1.06)
NSAIDs	0.87	-0.14	0.08	-1.83	0.07	(0.74, 1.01)
Tdap vaccine	0.82	-0.20	0.07	-2.87	< 0.01	(0.72, 0.94)
Alcohol disorders	0.76	-0.28	0.15	-1.87	0.06	(0.57, 1.01)

Abbreviations: HR, hazard ratio; SE, standard error; CI, confidence interval; SCr, serum creatinine; PT, prothrombin time; BP, blood pressure; HTN, hypertension; OUD, opioid use disorder; COPD, chronic obstructive pulmonary disorder; SLE, systemic lupus erythematosus; PVD, peripheral vascular disease; MI, myocardial infarction; HD, heart disease; ACE, angiotensin converting enzyme; RA, rheumatoid arthritis; LVEF, left ventricular ejection fraction; RR, respiratory rate; PTH, parathyroid hormone; ESR, erythrocyte sedimentation rate; CRP, C-reactive protein; BUN, blood urea nitrogen; UTI, urinary tract infection; HF, heart failure; ARBs, angiotensin II receptor blockers; CCBs, calcium channel blockers; CKD, chronic kidney disease; NSAIDs, non-steroidal anti-inflammatory drugs; Tdap, tetanus diphtheria acellular pertussis.

Figure 1.

Forest plots of hazard ratios from cox proportional hazards model

Measures of Association analysis revealed that AKI was significantly associated with increased 30-day risk of multiple adverse outcomes (Table 3 and Figure 2). Patients in the AKI cohort had a higher risk of developing myocardial infarction (MI) (RR = 8.01; CI = 4.17-15.39), sepsis (RR = 5.99; CI = 3.54-10.12), respiratory failure (RR = 5.30; CI = 3.76-7.46), stroke (RR = 2.58; CI = 1.65-4.03), arrhythmia (RR = 2.22; CI = 1.63-3.02), deep vein thrombosis (DVT) (RR = 1.98; CI = 1.15-3.42), transfusion (RR = 1.92; CI = 1.65-2.24), and mortality (RR = 2.22; CI = 1.63-3.02).

Table 3.

Measures of Association Analysis of Matched Cohorts

Outcome	Risk (% AKI vs. % Non-AKIcohort)	RD			RR (95% CI)	OR (95% CI)
Outcome	Risk (% AKI vs. % Non-AKIcohort)	RD (95% CI)	Z score	p value	RR (95% CI)	OR (95% CI)
MI	6.05% vs. 0.76%	5.29% (3.93%,6.66%)	7.52	< 0.01	8.01 (4.17,15.39)	8.46 (4.37,16.41)
Sepsis	6.99% vs. 1.17%	5.82% (4.35%,7.30%)	7.70	< 0.01	5.99 (3.54,10.12)	6.36 (3.73,10.87)
Respiratory failure	15.12% vs. 2.86%	12.27% (10.12%,14.42%)	10.90	< 0.01	5.30 (3.76,7.46)	6.06 (4.23,8.70)
Stroke	4.74% vs. 1.84%	2.90% (1.59%,4.21%)	4.32	< 0.01	2.58 (1.65,4.03)	2.66 (1.68,4.20)
Arrhythmia	3.65% vs. 1.65%	2.01% (0.78%,3.23%)	3.22	< 0.01	2.22 (1.35,3.65)	2.27 (1.36,3.77)
Mortality	8.68% vs. 3.92%	4.76% (2.97%,6.55%)	5.19	< 0.01	2.22 (1.63,3.02)	2.33 (1.68,3.23)
DVT	2.75% vs. 1.39%	1.36% (0.30%,2.42%)	2.51	0.01	1.98 (1.15,3.42)	2.01 (1.15,3.50)
Blood transfusion	28.53% vs. 14.83%	13.70% (10.63%,16.77%)	8.65	< 0.01	1.92 (1.65,2.24)	2.29 (1.89,2.77)
PE	1.23% vs. 0.73%	0.50% (-0.23%,1.23%)	1.34	0.18	1.69 (0.78,3.67)	1.70 (0.77,3.72)
Dialysis	0.99% vs. 0.71%	0.28% (-0.40%,0.96%)	0.81	0.42	1.40 (0.62,3.13)	1.40 (0.62,3.16)
Surgical site infection	0.93% vs. 0.78%	0.15% (-0.54%,0.83%)	0.42	0.68	1.19 (0.53,2.64)	1.19 (0.53,2.66)

Abbreviations: AKI, acute kidney injury; RD, risk difference; CI, confidence interval; RR, risk ratio; OR, odds ratio; MI, myocardial infarction; DVT, deep vein thrombosis; PE, pulmonary embolism.

Figure 2.

Forest plot of risk ratios from measures of association analysis dashed line at HR = 1. Solid markers indicate statistical significance. Abbreviations: MI, myocardial infarction; DVT, deep vein thrombosis; PE, pulmonary embolism

Kaplan-Meier analyses showed lower 30-day survival probabilities in the AKI cohort for MI (93.92% vs. 99.23%), sepsis (92.75% vs. 98.77%), respiratory failure (84.66% vs. 97.04%), stroke (95.13% vs. 98.12%), arrhythmia (96.23% vs. 98.34%), and transfusion (71.27% vs. 85.08%) (all p < 0.01). Corresponding HRs for these outcomes ranged from 2.06 to 8.20, with AKI also associated with increased mortality (HR = 2.33; CI = 1.69-3.20).

Discussion

This large, multi-center cohort study of adults aged ≥ 65 years undergoing surgical treatment of extracapsular hip fractures found postoperative AKI to be a common complication associated with significantly increased risks of short-term adverse outcomes. Matched analyses identified nonmodifiable predictors of postoperative AKI to be Black or African American and White race and modifiable predictors to be elevated preoperative chloride, bicarbonate, SCr, and decreased preoperative serum protein levels. Conversely, Hispanic or Latino ethnicity, preoperative Tdap vaccination, preoperative opioid use, and elevated preoperative serum sodium levels were protective, though these associations warrant further investigation. Patients who developed postoperative AKI experienced significantly higher 30-day risks of MI, sepsis, respiratory failure, stroke, arrhythmia, DVT, blood transfusion, and mortality.

Prior studies have identified an association between preoperative electrolyte abnormalities and postoperative AKI within the orthopaedic population.^9,19 Additionally, a relationship between impaired baseline renal function, including increased preoperative SCr and bicarbonate levels, has been established by prior research in both general surgical and orthopaedic populations.^5,7,11,13,19 The present study supports these findings, highlighting the importance of electrolyte balance and renal stabilization prior to hip fracture surgery in this high-risk population. Notably, this study found increased preoperative serum sodium to be a protective factor against postoperative AKI. This finding warrants future investigation given the identification of electrolyte abnormalities and baseline renal function as risk factors for postoperative AKI.

The association between preoperative anemia, hypoalbuminemia, and hypoproteinemia has been established previously.^6,7,20 This study found reduced preoperative serum protein levels to be an independent risk factor for postoperative AKI, reflecting the importance of hemodynamic stabilization.

Prior studies have found hip fracture patients who developed postoperative AKI to have higher morbidity rates and comorbidity burden, specifically cardiovascular complications, thromboembolism, and respiratory failure.¹² The present study also found postoperative AKI patients had higher rates of similar complications. These findings reflect the necessity of adequate screening protocols for AKI in this high-risk population, as well as the need for preventative measures prior to hip fracture surgery.

Of note, the current study identified Hispanic or Latino ethnicity, preoperative opioid use, and Tdap vaccination as predictors of postoperative AKI. These findings should be interpreted with caution and are best considered hypothesis-generating. Current literature does not strongly support these associations, and they may reflect unmeasured confounders or proxies for other factors such as healthcare access, baseline medical optimization, or differences in perioperative monitoring. Further investigation is necessary to determine whether these associations represent true protective effects or residual confounding.

These findings have important clinical implications for perioperative risk stratification in older adults undergoing hip fracture surgery. Several of the identified predictors of AKI, including electrolyte abnormalities and decreased serum protein levels, represent potentially modifiable preoperative factors. Optimization of fluid status, correction of electrolyte imbalances, and attention to nutritional status prior to surgery may help reduce the risk of postoperative AKI in this high-risk population. Because many of these laboratory markers are routinely obtained during preoperative evaluation, they may serve as practical indicators to guide perioperative optimization strategies to help mitigate the risk of postoperative AKI.

This study had several limitations. First, the use of ICD-10-CM codes to define AKI may under detect subclinical AKI and does not differentiate between AKI stages or severity. Second, the retrospective design precludes causal inference, and residual confounding may persist despite PSM. Third, key intraoperative variables could not be accessed by the TriNetX platform. Finally, coding variations and site-level differences may cause residual bias. Despite these weaknesses, this study identified several predictors and outcomes of postoperative AKI that strengthen prior studies, as well as various possibly novel variables that warrant further investigation.

Conclusion

Postoperative AKI is a frequent and clinically significant complication among older adults undergoing extracapsular hip fracture surgery. This study identified several independent predictors, including preoperative serum markers, race, and comorbid conditions, and highlighted a substantially increased risk of short-term complications and mortality in patients who developed AKI. A future meta-analysis that affirms all predictors induced in this study as well as previous studies that these findings highlight would also be particularly useful. These findings underscore the need for improved preoperative risk stratification and tailored interventions aimed at reducing the incidence and downstream consequences of postoperative AKI in this high-risk population.

Supplemental Material

Supplemental Material - Predictors of Acute Kidney Injury in Older Adults With Extracapsular Hip Fractures

Supplemental Material for Predictors of Acute Kidney Injury in Older Adults With Extracapsular Hip Fractures by Elizabeth Nocera, Dilan Prasad, Monica DiFiori and Saqib Rehman in Geriatric Orthopaedic Surgery & Rehabilitation.

Supplemental Material

Supplemental Material - Predictors of Acute Kidney Injury in Older Adults With Extracapsular Hip Fractures

Footnotes

Acknowledgements

The authors thank the Lewis Katz School of Medicine and Temple University Hospital Department of Orthopaedic Surgery & Sports Medicine for institutional support. The authors have no additional acknowledgements to declare.

ORCID iDs

Elizabeth Nocera

Dilan Prasad

Monica DiFiori

Ethical Considerations

Due to the retrospective and anonymized nature of the data for this non-interventional study, ethical approval and consent to participate were waived.

Author Contributions

• Elizabeth Nocera, BS: conceptualization, data curation, formal analysis, methodology, visualization, drafting of the manuscript

• Dilan Prasad, BS: data curation, methodology, results verification, manuscript review and editing

• Monica DiFiori, MD: clinical guidance, interpretation of the findings, critical manuscript revision

• Saqib Rehman, MD, MBA: study supervision, clinical expertise, methodology input, critical manuscript revision, senior authorship.

Funding

Publication of this article was funded in part by the Temple University Libraries Open Access Publishing Fund.

Declaration of Conflicting Interests

Dr. Saqib Rehman reports receiving royalties and consulting fees from Globus Medical and is a member of the editorial board of SurgiColl. All other authors declare no conflicts of interest.

Supplemental Material

Supplemental material for this article is available online.

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