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Anales del Sistema Sanitario de Navarra

versión impresa ISSN 1137-6627

Anales Sis San Navarra vol.46 no.1 Pamplona ene./abr. 2023  Epub 10-Jul-2023 

Artículos Originales

Lower estimated glomerular filtration rate at admission is associated with a worse outcome in older patients with hip fracture who undergo surgical treatment

El filtrado glomerular bajo al ingreso se relaciona con un peor pronóstico en pacientes mayores con fractura de cadera tratados quirúrgicamente

Carmen Da Casa (orcid: 0000-0002-2290-126X)1  , Methodology, Data curation, Investigation, Writing - Original draft preparation, Writing -Reviewing and Editing; Marta Vidal-Terrancle (orcid: 0009-0006-0209-7223)2  , Investigation; María Agustina Hierro-Estévez (orcid: 0000-0001-5634-1179)1  , Investigation; Rocío Montoya-Saenz (orcid: 0000-0001-5938-9979)2  , Investigation; Helena Fidalgo (orcid: 0000-0002-3757-8434)1  , Methodology, Data curation, Writing -Reviewing and Editing; Alfonso González-Ramírez (orcid: 0000-0002-3223-0332)1  2  , Investigation; Carmen Pablos-Hernández (orcid: 0000-0001-5083-6971)1  2  , Investigation; Juan F Blanco (orcid: 0000-0001-7803-9149)1  2  , Conceptualization, Writing - Original draft preparation, Supervision, Writing -Reviewing and Editing

1Instituto de Investigación Biomédica de Salamanca (IBSAL). Salamanca. España

2Servicio de Cirugía Ortopédica y Traumatología. Hospital Universitario de Salamanca. Salamanca. España



We assessed the relationship of estimated glomerular filtration rate values at hospital admission on the outcome of surgically treated older adults who had suffered a hip fracture.


Prospective study that included patients > 65 years of age, surgically treated for primary hip fracture, with no pathologic or high-energy trauma aetiology admitted to a tertiary teaching hospital between 2018 and 2019. We stratified patients based on their estimated glomerular filtration rate at admission and examined its association to demographic and clinical variables, including 90-day post-discharge mortality.


The study included 942 hip fracture patients. Lowered estimated glomerular filtration rate was significantly associated to a worsening of the functional status, higher incidence of medical postoperative complications, higher postoperative renal dysfunction, and greater number of blood transfusions. Mortality displayed a staircase pattern, increasing with decreasing estimated glomerular filtration rate. Patients with estimated glomerular filtration rate <60 had significantly higher mortality at 90 days after discharge. In-hospital mortality rate was 10.7% in hip fracture patients with chronic kidney disease who experienced a significant variation in the estimated glomerular filtration rate (>5 mL/min/1.73m2) on admission in comparison to baseline values.


Older adult patients treated for hip fracture with lower glomerular filtration rate values have poorer functional status and worse prognosis. A significant clinical variation of estimated glomerular filtration rate upon hospital admission for hip fracture may be associated with increased in-hospital mortality of chronic kidney disease patients.

Keywords: eGFR; Hip fracture; Mortality; Outcome; Postoperative complications



Evaluar la influencia de los valores de filtrado glomerular estimado (eFG) al ingreso en el pronóstico de los pacientes mayores con fractura de cadera tratados quirúrgicamente.


Estudio prospectivo de pacientes >65 años, tratados quirúrgicamente por una fractura de cadera primaria, sin etiología tumoral o traumatismo de alta energía, en un hospital universitario terciario entre 2018 y 2019. Estratificamos a los pacientes según el FG al ingreso y estudiamos su asociación con distintas variables demográficas y clínicas, incluida la mortalidad hasta 90 días después del alta hospitalaria.


Se incluyeron 942 pacientes. La disminución del eFG se asoció significativamente a peor estado funcional, mayor incidencia de complicaciones médicas postoperatorias, mayor disfunción renal postoperatoria y mayor necesidad de transfusión sanguínea. La mortalidad mostró un patrón en escalera que aumentaba con la disminución del eFG. A los 90 días, la mortalidad fue significativamente mayor en pacientes con eFG <60. Los pacientes con enfermedad renal crónica que sufrían una fractura de cadera y experimentan al ingreso una variación significativa del eFG (>5 mL/min/1,73m2) respecto a los valores basales mostraron una tasa de mortalidad intrahospitalaria del 10,7%.


Los pacientes ancianos tratados quirúrgicamente por fractura de cadera con valores más bajos de tasa de eFG presentan peor estado funcional y peor pronóstico. Una variación clínica significativa del FG (>5) en el momento del ingreso hospitalario tras una fractura de cadera podría asociarse a un aumento de la mortalidad intrahospitalaria de los pacientes con insuficiencia renal crónica.

Palabras clave: eFG; Fractura de cadera; Mortalidad; Pronóstico; Complicaciones postoperatorias


The increase of chronic kidney disease (CKD) prevalence in patients with underlying lifestyle-related disorders (hypertension and diabetes mellitus) has become a a social and health problem1. well known, not without controversy. Changes in renal structure in older adults, a normal progressive and slow phenomenon according to some authors, have been linked with the decrease of glomerular filtration rate (GFR)2. Thus, lower GFR values in comparison to those of younger individuals does not necessarily imply the existence of a disease, but an expression of the aging process3.

CKD patients usually present osteoporosis and therefore high risk of suffering fractures4. Some authors have related low GFR values with increased risk of vertebral and hip fractures among older adults5,6. Renal function may be impaired in patients who suffer a hip fracture, and in turn, previous kidney disease may negatively affect treatment outcomes in aged patients who suffer a hip fracture7-10.

Incidence of hip fracture is high among older adults and the associated morbidity and mortality positions it as one of the most relevant age-related health problems11.

Renal function worsening in surgically treated older adults after hip fracture seems to be associated to a worse outcome12, which indicates the relevance of renal function in the internal homeostasis of this patients population. Moreover, as it is well known, renal dysfunction is frequently associated with osteoporosis and, therefore, with higher risk of fracture13-15. Renal function should be considered in the patient’s general clinical condition, it could be also demarcated by ranges of laboratory values. Hip fracture involves different degrees of bleeding or hydro-electrolytic disorders, among other possible alterations that may be detected through kidney-related laboratory tests.

The clinical situation of some older adults may be altered after a hip fracture, with the consequent worsening of their prognosis. Renal dysfunction affects patients’ internal homeostasis and the pharmacodynamics of their current medication, which may interfere with the management of the fracture. Early detection of altered laboratory values can help prevent complications should a patient suffer a hip fracture.

In this study, we aimed to determine the relationship between estimated GFR admission values (eGFR) and the outcomes after surgical treatment of hip fractures in a large cohort of older adults, paying special attention to patients with CKD.

Material and methods

Prospective study that included all patients >65 years of age who had suffered a hip fracture, had been surgically treated for primary hip fracture, with no pathologic or high-energy trauma aetiology, admitted to the Orthogeriatric Unit of Hospital Universitario de Salamanca (Salamanca, Spain) (a tertiary teaching hospital) between January 1, 2018 and December 31, 2019.

The following variables were recorded at admission:

  • - Demographic: sex (male, female), age (years and >80 years of age), place of residence (urban or rural considering < 13,000 inhabitants), previous living in an institution;

  • - Laboratory: haemoglobin (g/dL), lymphocyte count (x103/µL), albumin (g/dL), glucose (mg/dL), parathyroid hormone (PTH, pg/mL), vitamin D (ng/mL), creatinine (mg/ dL), urea (mg/ dL);

  • - Kidney damage and function: eGFR as a continuous variable (mL/min/1.73 m2) using the CDK-EPI equation16, as the single point-by-point variation may be highly dynamic, we also classified patients in five categories according to their eGFR ranges at admission:

    • eGFR ≥90: possible kidney damage with normal kidney function

      60 ≤ eGFR < 90: kidney damage with mild loss of kidney function

      30 ≤ eGFR < 60: mild to a severe loss of kidney function

      15 ≤ eGFR < 30: severe loss of kidney function

      eGFR <15: kidney failure

  • - Fracture-related: type of hip fracture (extracapsular, intracapsular) and surgical procedure (osteosynthesis, partial replacement, total replacement).

From the patient´s medical records we collected previous diagnosis of renal and cardiovascular risk comorbidities (CKD, any cardiovascular risk, hypertension, type I and II diabetes, chronic cardiac insufficiency, ischemic heart failure) and medications related to cardiovascular risk (anticoagulant and antiplatelet agents).

For CKD patients, we collected laboratory data at three moments: basal (from records up to 6 months before being admitted to the hospital for hip fracture), at hospital admission, and at discharge (after hip fracture surgery).

While in the hospital, the relatives of the patients were interviewed to find out about their previous functional situation (Comprehensive Geriatric Assessment, CGA). Data were analysed using different geriatric scores:

  • - The Katz index (KI) to evaluate independence of daily functions (bathing, dressing, toileting, transferring, continence, eating), from A (independent) to G (dependent for all the evaluated functions).

  • - The Barthel index (BI) to measure the performance in activities in daily living (feeding, bathing, grooming, dressing, bowels, bladder, toilet use, transfers, mobility, stairs), from 0 (total dependency) to 100 (totally independent) using a five-item scale. Score was categorized in < 20: total dependency, 20-35: severe dependency, 40-55: moderate dependency, 60-95 slight dependency; 100: independent).

  • - The Lawton-Brody index (LBI) to evaluate independent living skills (use of a telephone, shopping, food preparation, housekeeping, laundry, transportation, responsibility for own medications) from 0 (low function/dependent) to 8 (high function/independent). No discrimination by gender was found.

  • - The Physical Red Cross scale (PRCS) to evaluate the physical ambulatory ability from 0 (full capability without the need of assistance) to 5 (bed-ridden patients).

We also collected the following factors: waiting time to surgery, whole Length of Stay (LOS), incidence of post-surgical complications (any, seroma, wound bleeding), and medical postoperative complications (any, renal, digestive, cardiac, respiratory, neurologic complications, and need for transfusion).

Upon hospital discharge, in-hospital mortality rates, and 30- and 90-day mortality rates were recorded.

The study was conducted following the Declaration of Helsinki and approved by the Institutional Review Board of CEIm Hospital Universitario de Salamanca (ref. code: 2020 09 563). All participants (or their relatives) signed an informed consent before their inclusion in the study.

Statistical Analysis

Qualitative variables were presented as percentage and outlined by contingency tables; the Chi-square test was used to determine if there were any inter-variable statistical significant differences. Quantitative variables were presented as mean ± standard deviation and median and interquartile range (IQR). The Kolmogorov-Smirnov and Levene tests were used to assess normality and homogeneity. An ANOVA (followed by a post hoc Bonferroni test) was performed to compare inter-group variables. The Wilcoxon matched-pairs signed-rank test was used to compare quantitative variables between two paired groups from basal situation to hospital admission and hospital discharge.

Association between variables were addressed by odds ratio (OR) with its confidence interval at 95% (95%CI) from the binary logistic model (for binary dependent variables) and by β (95%CI) from the linear regression model (for quantitative dependent variables); for the multilevel dependent variables, the β (95%CI) for the most significant category is shown from a mixed-effects model.

All data were analysed with IBM SPSS Statistics version 23 and R version 3.6.2 (2019-12-12). In all cases, a p-value <0.05 was considered statistically significant. Patients with incomplete data records were excluded from statistical analysis.


Nine hundred and forty-five patients met the inclusion criteria. Three patients were transferred prior hospital discharge, thus, 942 patients were included in the study (attrition rate 0.003%); 72.8% of the patients were female and mean age was 86.2±6.8 years (range 65-103).

Mean eGFR at hospital admission was 58.2±20.2 mL/min/1.73m2 (median: 59; IQR: 42-76). Based on eGFR levels at admission, the 942 study patients were classified into five groups (Table 1); most study patients (84.7%) had eGFR values of 30-89 mL/min/1.73m2. Around half of the patients had an eGFR at admission >60 mL/min/1.73m2 (48%, n = 452), and 101 (10.7%) patients had values <30 mL/min/1.73m2.

Table 1. Biodemographic summary and frequency (%) of previous diagnosis of renal and cardiovascular risk comorbidity of older patients surgically treated for hip fracture based on the estimated glomerular fraction rate range. 

Admission eGFR ranges (mL/min/1,73m2) Total ≥90 89-60 59-30 29-15 <15 p-value
n (%) 942 43 (4.6) 409 (43.4) 389 (41.3) 92 (9.8) 9 (1.0)
Sex (women, %) 72.8 58.1 74.6 72.5 75.0 55.6 0.140
Age (years)
Mean ± SD 86.2±6.8 77.3±6.6 84.8±6.6 88.1±5.9 88.7±6.5 85.2±5.4 <0.001
≥80 (%) 83.9 30.2 80.4 91.5 92.4 77.8 <0.001
Place of residence (rural, %) 48.1 45.2 49.9 46.0 49.5 66.7 0.621
Institution-living (%)
At admission 32.4 34.9 29.6 34.8 34.8 22.2 0.512
At discharge 54.1 51.2 51.0 56.8 59.8 44.4 0.369
Extracapsular fracture (%) 57.2 58.1 53.3 59.1 64.1 77.8 0.164
Surgical procedure (%)
Osteosynthesis 55.7 55.8 53.3 56.6 60.9 77.8 0.175
Partial replacement 42.2 37.2 44.0 41.9 39.1 22.2
Total replacement 2.1 7.0 2.7 1.5 - -
Chronic kidney disease 15.2 2.3 3.2 17.2 57.6 100 <0.001
Cardiovascular risk (any) 87.2 69.8 81.4 92.5 96.7 100 <0.001
Hypertension 74.3 48.8 65.5 82.5 90.2 77.8 <0.001
Diabetes (type I and II) 26.8 32.6 21.8 27.8 39.1 55.6 0.002
Chronic cardiac insufficiency 9.5 7.0 10.0 14.7 25.0 22.2 0.002
Ischemic heart failure 12.8 11.6 8.8 15.9 19.6 0.0 0.006
Pharmacologic treatment
Antiplatelet 34.2 34.9 32.8 35.0 34.8 55.6 0.677
Oral Anticoagulant 20.7 2.3 19.3 21.9 31.5 11.1 0.002

eGFR: estimated glomerular filtration rate; SD: standard deviation; significant differences among eGFR ranges are marked in bold.

Table 1 summarizes the demographic characteristics of the study population. Patients with and eGFR ≥90 at admission were younger. We observed a decrease in eGFR values with increasing age (β = -0.967 mL/min/1.73m2 per year; 95%CI: -1.152 to -0.781; p < 0.001). As for the place of residence, no statistically significant differences were found; however, overall, individuals who lived in rural areas showed an eGFR <15 mL/min/1.73m2. In all eGFR groups, institutionalization increased ~ 20% at discharge.

The most frequent type fracture was extracapsular, which increased with decreasing eGFR ranges. Osteosynthesis was the most performed procedure, mostly in patients with eGFR <15 mL/min/1.73m2; total hip replacement was performed when eGFR ≥30 mL/min/1.73m2.

An increasingly higher number of patients with lower eGFR values (from 2.3 to 31.5%, p = 0.002; OR per mL/min/1.73m2 = 0.528; 95%CI: 0.296 to 0.760; p = 0.003) were under oral anticoagulant treatment. However, there were no statistically significant differences among patients taking any antiplatelet treatment.

As for laboratory tests at admission, besides the clear differences in creatinine and urea levels (both highly increased with decreasing eGFR), we found statistically significant differences in haemoglobin, glucose, and PTH serum levels (Table 2). With pairwise comparisons, we confirmed decreasing haemoglobin and increasing PTH with decreasing eGFR. Moreover, we determined differences in glucose levels at admission, mainly due to the differences between patients within the eGFR ranges 29-15 and 89-60 mL/min/1.73m2 (155±56 vs 134±33; p = 0.033).

Table 2. Biochemical values (mean±standard deviation) at admission of older patients who suffered hip fracture and were surgically treated based on the estimated glomerular fraction rate range. 

Admission eGFR ≥90 89-60 59-30 29-15 <15 p-value
(mL/min/1,73m2) (n=43) (n=409) (n=389) (n=92) (n=9)
Haemoglobin (g/dL) 12.5±2.2 13.0±1.6 12.5±1.7(388) 11.3±1.7 11.5±1.2 <0.001
Lymphocyte count (x103/µL) 1.3±0.7 1.3±1.1 1.3±0.7(388) 1.2±0.7 1.2±0.8 0.574
Albumin (g/dL) 3.9±0.5(35) 3.9±0.4(344) 3.9±0.4(336) 3.9±0.5(81) 3.6±0.7(7) 0.353
Glucose (mg/dL) 134±33 138±42 146±54(384) 155±56 144±34 0.031
PTH (pg/mL) 54.0±34.3(10) 58.4±32.0(127) 71.5±46.0(138) 120.8±82.7(41) 132.8±64.8(3) <0.001
VitaminD (ng/mL) 13.6±10.9(11) 11.5±8.5(121) 12.5±8.9(134) 12.6±9.9(41) 7.7±-(1) 0.785
Creatinine (mg/dL) 0.6±0.1 0.8±0.1 1.2±0.2 2.0±0.4 5.2±1.8 <0.001
Urea (mg/dL) 33.7±9.5 43.5±12.4(398) 61.3±19.0(387) 106.4±38.3 122.6±45.2 <0.001

(n): valid n for specified cell; PTH: paratohormone; significant differences are marked in bold.

We observed a statistically significant relationship between the eGFR and functional status of the patient (Table 3) based on different CGA variables: the lower the eGFR value the worse the functional status, which was manifested by the need of some type of support, measured using the Physical Red Cross scale.

Table 3. Description of the functional status of older patients who suffered hip fracture and were surgically treated based on the estimated glomerular fraction rate range. 

Admission eGFR (mL/min/1,73m2) ≥90 89-60 59-30 29-15 <15
Katz Index n=40 n=393 n=372 n=91 n=9
A 40.0% 37.2% 29.0% 17.6% 44.4%
B 10.0% 15.0% 17.2% 18.7% 11.1%
C 20.0% 16.0% 19.6% 26.4% 0.0%
D 2.5% 13.0% 12.6% 16.5% 11.1%
F 12.5% 7.4% 9.1% 11.0% 11.1%
G 2.5% 3.6% 6.2% 4.4% 11.1%
Barthel Index n=40 n=389 n=371 n=90 n=9
100 37.5% 22.1% 14.6% 10.0% 22.2%
60-95 37.5% 54.0% 59.8% 63.6% 44.4%
40-55 25.0% 15.9% 15.1% 18.9% 22.2%
20-35 0.0% 5.4% 8.4% 6.7% 0.0%
<20 0.0% 2.6% 2.2% 1.1% 11.1%
Lawton-Brody Index n=42 n=390 n=368 n=89 n=9
0 21.4% 19.5% 24.2% 21.3% 11.1%
1 19.0% 11.5% 14.7% 27.0% 22.2%
2 11.9% 19.0% 18.8% 18.0% 0.0%
3 14.3% 11.8% 10.3% 10.1% 33.3%
4 2.4% 5.9% 5.7% 5.6% 0.0%
5 7.1% 3.6% 4.1% 0.0% 22.2%
6 0.0% 4.6% 4.1% 2.2% 0.0%
7 9.5% 9.0% 8.7% 10.1% 11.1%
8 14.3% 15.1% 9.5% 5.6% 0.0%
Physical Red Cross Scale n=42 n=396 n=378 n=90 n=9
0 143% 5.3% 2.6% 0.0% 0.0%
1 38.1% 29.8% 29.4% 17.8% 22.2%
2 19.0% 34.6% 40.2% 40.0% 44.4%
3 28.6% 25.5% 23.5% 38.9% 22.2%
4 0.0% 4.5% 3.7% 3.3% 11.1%
5 0.0% 0.3% 0.5% 0.0% 0.0%

We observed longer mean length of hospital (LOS) stays of patients with low eGFR values (Table 4). This extended stay coupled with longer mean waiting times to surgery, significantly increased in patients with lower eGFR values. However, the number of patients operated within the first 24 hours or 48 hours was similar in all groups (confirmed by pair-wise comparisons).

Similar incidence of postoperative surgical complications were found in the five study groups, but patients with lower eGFR values showed higher incidence of medical postoperative complications.

Specifically, at lower eGFR at admission there was increased exacerbation of postoperative renal dysfunction, leading to increased incidence of hyperkalaemia (OR = 0.949; 95%CI: 0.925 to 0.972; p <0.001). Likewise, higher incidence of digestive complications was observed in patients with eGFR in the 29-15 mL/min/1.73m2 (p = 0.0048) range, as well as increased need for blood transfusion, particularly in patients with eGFR <60 mL/min/1.73m2 onwards. Incidence of cardiac and respiratory complications increased with decreasing eGFR ranges, although without statistical significance.

As for in-hospital mortality, no statistically significant differences were observed between eGFR ranges; however, a noticeable increase in the most underdiagnosed group of patients (eGFR 59-30 ml/min/1.73m2) was identified. The 30-day mortality rate showed a staircase pattern, increasing with decreasing eGFR. Ninety days after hospital discharge, we had all the data for 502 patients and found a statistically significant increase in the mortality rate with lowering eGFR values at the time of hospital admission (Table 4).

Table 4. Outcome measurements of surgically treated older patients with hip fracture on potential CKD stages based on the estimated glomerular fraction rate range. 

Admission eGFR ranges (mL/min/1,73m2) p-value
≥90 89-60 59-30 29-15 <15
(n=43) (n=409) (n=389) (n=92) (n=9)
Quantitative variables β (95%CI) mean ± standard deviation
Length of stay 0.014 8.7±4.5 8.4±4.1 8.7±4.1 9.8±3.9 9.7±2.2 0.002
(-0.031 to -0.004)
Time to surgery -0.011 2.4±2.5 2.8±2.7 2.9±2.5 3.5±2.4 3.0±1.8 0.024
(-0.019 to -0.003)
Qualitative variables OR (95%CI) % p-value
TTS <24h 1.011 (1.002 to 1.019) 20.9 21.8 16.7 13.0 11.1 0.203
p = 0.016
TTS <48h 1.010 (1.003 to 1.017) 39.5 39.4 35.7 26.1 11.1 0.074
p = 0.003
Surgical postoperative complications
Any 18.6 25.6 27.2 25.0 11.1 0.623
Seroma 14.0 19.2 22.8 19.6 11.1 0.498
Wound bleeding 4.7 3.7 3.6 5.4 0.0 0.887
Medical postoperative complications
Any 0.983 (0.974 to 0.991) 65.1 73.1 79.6 89.1 88.9 0.002
p <0.001
Renal 0.984 (0.977 to 0.991) 20.9 30.0 34.9 52.2 11.1 <0.001
Digestive 23.3 23.8 23.0 38.0 22.2 0.048
Cardiac 4.7 4.9 9.0 10.9 0.0 0.085
Respiratory 9.3 15.7 16.0 19.6 22.2 0.629
Neurologic 7.0 15.2 17.6 18.5 11.1 0.400
Transfusion 0.983 (0. 977 to 0.991) 34.9 32.8 42.6 56.5 77.8 <0.001
p <0.001
In-hospital 0.0 2.2 4.6 3.3 0.0 0.229
30-day 0.0982 (0.970 to 0.997) 0.0(39) 4.4(385) 7.6(369) 9.0(89) 11.1(9) 0.107
p = 0.016
90-day 0.0979 (0.969 to 0.990) 0.0%(22) 12.3(211) 22.7(211) 34.6(52) 16.7(6) <0.001
p < 0.001

OR: odds ratio (only significant values); 95%CI: 95% confidence interval; (n): valid n per cell; TTS: time to surgery; significant differences are marked in bold.

Six patients died before hospital discharge: one from lung cancer, two from heart diseases (ischemic heart disease and congestive heart failure), and three due to multiorgan failure associated to significant comorbidity.

Chronic Kidney Disease patients

Eleven (7.7%) from the 142 CKD older patients had been receiving dialysis before suffering a hip fracture. We determined significant differences between the basal situation and at hospital admission (n = 102) in lymphocyte count (p <0.001), calcium (p <0.001, n = 33), glucose (p 0.001), and phosphorus (p= 0.029, n = 30). Upon hospital discharge, there was a significant decrease in haemoglobin and albumin serum levels compared to hospital admission levels (p <0.001). The comparison between the basal situation and the discharge status (n = 88) revealed significant differences in lymphocyte count (p <0.001) and serum albumin (p <0.001) (Table 5).

Table 5. Basal, hospital admission, and discharge laboratory data (mean and standard deviation). 

Biochemical parameter (unit) Basal situation At admission At discharge
n x_±SD n x_±SD n x_±SD
eGFR (mL/min/1.73m2) 102 40.6±19.1 141 38.5±19.6 119 41.6±22.9
Creatinine (mg/dL) 101 1.7±1.3 142 1.8±1.1 121 1.7±1.1
Urea (mg/dL) 103 77.1±36.9 142 83.4±41.2 119 84.7±45.8
Haemoglobin (g/dL) - - 141 11.7±1.9 139 10.3±1.1
Lymphocyte count (x103/µl) 103 1.7±0.8 141 1.2±0.7 140 1.2±0.5
Albumin (g/dL) 6 3.8±0.9 115 3.8±0.4 3 3.0±0.5
Glucose (mg/dL) 102 110±38 141 146±47 - -
Calcium (mg/dL) † 8 9.1±0.7 1 8.5±0.7 - -
Phosphorus (mg/dL) † 3 3.3±0.6 6 3.7±.0 - -
Paratohormone (pg/mL) † 2 173.7±130.0 2 100.6±72.6 - -
Vitamin D (ng/mL) † 0 17.5±12.4 9 14.3±9.8 - -

Basal: from records up to 6 months before being admitted to the hospital for hip fracture; at discharge: after hip fracture surgery; ?: serum levels of calcium, phosphorus, paratohormone, and vitamin D were only recorded once during the hospital stay, either pre or post-surgically.

It is noteworthy that patients with clinically significant variations in admission eGFR (increases/decreases >5 mL/min/1.73m2) in comparison to baseline values (n = 56) showed higher in-hospital mortality rate than CKD patients without these admission eGFR variations (n = 46) (10.7 vs 2.2%, respectively). From another point of view, 85.7% of the CKD patients who died early after hip fracture surgery showed a clinically significant eGFR variations in comparison to baseline values.

From the 56 CKD hip fracture patients with clinically significant eGFR variations, 37 (66.1%) showed decreased eGFR values at admission in comparison to baseline values, with 45.9% presenting eGFR <30 mL/min/1.73m2. Three patients died before hospital discharge. eGFR for the remaining patients at discharge was significantly higher (p = 0.002), but without reaching baseline values (p = 0.024) (Fig. 1A). Conversely, 19 patients showed a clinically significant increase of the eGFR at admission compared to baseline levels; from these, three died before being discharged. This increased eGFR was maintained upon hospital discharge and did not reach baseline values (p = 0.003) (Fig. 1B).

Figure 1. Estimated glomerular filtration rate misbalance through the hip fracture process in chronic kidney disease patients. A. Patients with a significant decrease of the estimated glomerular filtration rate upon admission. B. Patients with a significant increase of the estimated glomerular filtration rate upon admission. 


In this study, we show that lower values of eGFR, a widely used parameter in early evaluations of older patients who suffer hip fracture, is a bad prognostic factor in terms of postoperative complications and mortality.

At admission, half of our study population (942 patients who suffered hip fracture) had an eGFR >60 and 101 patients <30 mL/min/1.73m2; 82.2% of the individuals with an eGFR between 60 and 30 at admission had no prior medical history of CKD, which may imply CKD underdiagnoses among the aged13.

Cardiovascular comorbidity of patients with eGFR <60 ml/min/1.73m2 is significantly higher than that of the patients with higher eGFR at admission. The relationship between the incidence of cardiovascular pathology and renal dysfunction, i.e., cardiorenal syndrome, has been previously described17 and may explain the worse prognosis of these patients.

Our results are in line with other studies that report a reduction of eGFR values with increasing age. Advanced age has also been associated with a higher rate of complications and mortality after a hip fracture10,18. We observe an increasing trend in the incidence of extracapsular hip fractures with decreasing eGFR, but without statistical significance. This type of trochanteric fractures have been traditionally associated with the frailest patients and we should bear in mind that the mean age of our study population was greater than that reported elsewhere10,12.

Moreover, we measured the functional status of the patients through the CGA and show that lower eGFR values at hospital admission relate to a worse functional status of the patient. Our results are in line with other works in which the authors defend that kidney-related diseases have a high impact on the functional ability and mortality rate of hip fracture patients19.

Renal dysfunction implies some impaired physiologic conditions, including metabolic homeostasis and anaemia12. Therefore, our results should point to lower haemoglobin and higher PTH at admission of patients with lowered eGFR values, as we show. The higher incidence of anaemia may be related to a greater number of postoperative blood transfusions. This does directly relate to a worse prognosis20, but it may reflect the higher incidence of fractures in CKD patients21,22. On the other hand, blood transfusions in patients with impaired renal function requires careful management due to possible volemia alterations.

The clinical situation of a patient with lower eGFR values must be optimized before surgical treatment, with the consequent delay of hip fracture treatment6. The pharmacodynamics (i.e., half-life) of medication may differ from the reference levels, and hereafter widens the clinical optimization of hip fracture patients before surgery. LOS and mean TTS significantly increase with decreasing eGFR at admission, which may indicate that the management of these patients is more complex. There is no significant relationship between eGFR value ranges and surgical postoperative complications. Contrarily, we show a significant increase in postoperative medical complications, which is in agreement with the observed increased LOS. The intensification of renal impairment is significantly more prevalent in patients with lower eGFR at admission, along with postoperative constipation. Although there are no statistically significant differences in the increase of incidence of cardiac and respiratory complications versus eGFR values, the trend should be studied further.

There is a pattern of increasing mortality, but without significance in early mortality and a noticeable increase in the in-hospital mortality rate of most underdiagnosed patients (eGFR 59-30 mL/min/1.73m2). As for the 90-day follow-up, the mortality increases with lower eGFR values. Some authors have pointed out excess mortality after hip fracture in haemodialysis patients7,23,24, emphasizing that hip fracture is a critical event for the survival of this group of patients. A higher mortality rate in patients with advanced CKD has been shown in femoral neck fracture patients14, and in all types of hip fractures in the longer term19.

In the diagnosed CKD patients in this work, we observe a deterioration of renal function related to the hip fracture, manifested by increased creatinine, urea, phosphorus, and glucose values, and decreased haemoglobin, lymphocyte count, and calcium values. These findings indicate the need of a multidisciplinary careful management of older CKD patients who suffer a hip fracture. Changes in laboratory values have been reported by other authors8,25, but no paired baseline data have been previously studied. To the best of our knowledge, our study examines for the first time the evolution of these laboratory values during a hip fracture care process, considering the baseline values of each patient. A relevant aspect of our study is the detection of patients whose eGFR varies by more than 5 mL/min/1.73m2 from baseline values and are associated with a worse prognosis. This occurs in cases with decreased or increases eGFR values and, for the time being, we have no clear explanation. This eGFR variation may indicate greater lability of these patients compared to those who present a more stable renal function; this early renal autoregulatory dysfunction may be a warning of CKD progression26.

There are some limitations to this study. Firstly, although the study population (942 patients) is large compared to other similar single-centre studies, the number of patients with eGFR values <15 mL/min/1.73m2 is still small. Secondly, the longer follow-up of patients, 90 days after hospital discharge, showed an attrition rate of 46.7%. Lastly, we could not establish baseline laboratory parameters before the admission of the patients for hip fracture.

We conclude that admission eGFR values provide information on the outcome of surgically treated older adults who suffer a hip fracture. Lower eGFR values implies a worse outcome, in terms of postoperative complications and mortality. We therefore suggest a protocol for the detection and follow-up of patients according to their renal function on hospital admission for hip surgery (Appendix I).

Initially, we noted a high incidence of older adults with hip fracture (without a prior diagnosis of CKD) with decreased eGFR levels at admission. On the other hand, significant eGFR variations upon hospital admission after a hip fracture may be associated with increased in-hospital mortality of CKD patients. We also report a significant relationship between lower eGFR value ranges with 90-day mortality rate after hip fracture surgery.

Our findings highlight the need of careful monitoring in patients with impaired renal function who are undergoing surgical treatment for hip fracture. To record and analyse eGFR values upon hospital admission of older adults who suffer a hip fracture may facilitate the assignment of resources throughout the process of hip management.


Authors would like to thank the whole team working for the Orthogeriatric Unit of the University Hospital of Salamanca.


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Appendix I.

Protocol for detection and follow-up of patients according to renal function on admission for hip surgery. 

eGFR Actions
89-60 - Monitoring of renal function every 72 hours
- Actions on cardiovascular risk factors
59-30 - Nephotoxic grug adjustement.
- Monitoring of drug levels (antibiotics, low molecular weight heparin, etc.).
- Monitoring of renal function every 24-28 hours (depending on factors such anemization rate, pre-surgical waiting time, compliance with intakes, fluid therapy, etc.).
- Therapeutic conciliation at discharge.
29-15 - Hygienic-dietary measures.
- Adjustment of nephrotoxic drugs.
- Monitoring of drug levels.
- Monitoring of renal function every 24 hours.
- Consultation with Nephrology.
<15 - Follow-up with Nephrology on a daily inter-consultation basis.
- Consensual assessment of the use of EPO and analogues.
- Recommendations, drug conciliation and consensus on discharge follow-up (Nephrology and Orthopedics).
Patients on dialysis - Notification of hospital admission from the Emergency Department to the Nephrology Department (management of dialysis sessions).
- Consensual scheduling of the time of surgery with the Nephrology Department (previous dialysis).
- Recommendations, pharmacological conciliation and follow-up at discharge (Nephrology and Orthopedics).

eGFR: estimated glomerular filtration rate (mL/min/1.73m2), determined by the CDK-EPI equation16.

Financial disclosureThe present work has been performed with no public or private funding.


Da Casa C, Vidal-Terrancle M, Hierro-Estévez MA, Montoya-Saenz R, Fidalgo H, González-Ramírez A, Pablos-Hernández C, Blanco JF. Lower estimated glomerular filtration rate at admission is associated with a worse outcome in older patients with hip fracture who undergo surgical treatment. An Sist Sanit Navar 2023; 46(1): e1036

Received: August 23, 2022; Revised: November 02, 2022; Accepted: March 03, 2023; pub: April 27, 2023

Corresponding author: Juan Francisco Blanco

Conflict of interest

All authors declare no conflicts of interest.

Author contributions

Conceptualization: JFB;

Methodology and Data curation: CdaC, HF;

Investigation: MVT, MAHE, RMS, AGR, CPH, CdaC;

Writing – Original draft preparation: JFB, CdaC;

Supervision: JFB;

Writing –Reviewing and Editing: CdaC, HF, JFB.

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