Role of obesity in orthopedic surgical outcomes and complications: A retrospective cohort study at King Fahad University Hospital

Abstract

BACKGROUND

Obesity is a global health problem, and its prevalence continues to increase significantly each year. It is also associated with many major chronic diseases, such as diabetes and hypertension. Some studies suggest that obesity has a major impact on postoperative complications, but this remains an area of ongoing investigation.

AIM

To evaluate the association between obesity and obesity-associated chronic diseases and the risk of post-orthopedic surgical complications, and to compare the surgical success rate, patient outcomes, and patient satisfaction between obese and non-obese patients.

METHODS

A retrospective cohort study was conducted comparing obese and non-obese patients who underwent elective or emergency orthopedic surgery at King Fahad University Hospital, Al-Khobar, Saudi Arabia, between January 1, 2020, and November 30, 2024. A body mass index cutoff of 30 kg/m² was used to classify obese patients, and all patients were aged 18 years or older.

RESULTS

After data collection and analysis, obese patients demonstrated a higher incidence of postsurgical complications and a lower success rate than non-obese patients. The complication rate was 26% (n = 48) in obese patients and 7% (n = 12) in non-obese patients. Obese patients had significantly higher complication rates than non-obese patients (odds ratio = 5.0; 95%CI: 2.5-9.8; P < 0.001). The success rate was 74% (n = 136) in obese patients, whereas it was 93% (n = 172) in non-obese patients. The success rate was significantly higher in non-obese patients than in obese patients (odds ratio = 5.0; 95%CI: 2.5-9.8; P < 0.001).

CONCLUSION

Obesity was significantly associated with higher postoperative complication rates and lower success rates. These findings highlight the importance of optimizing preoperative assessment in obese patients by incorporating preoperative weight management and enhanced follow-up care.

Key Words: Obesity; Orthopedic surgery; Postoperative complications; Surgical success rates; Body mass index; Preoperative optimization

Core Tip: Obesity significantly increases the risk of postoperative complications and reduces surgical success rates in orthopedic patients. In this retrospective cohort, obese individuals had markedly higher complication rates and poorer outcomes than non-obese patients. These findings highlight the importance of targeted preoperative optimization, including weight management and careful risk stratification, to improve surgical outcomes in this high-risk population.

INTRODUCTION

Obesity is defined as a body mass index (BMI) of 30 or higher[1]. In recent years, obesity has reached unprecedented levels, making it one of the most significant public health concerns worldwide. According to the World Health Organization, obesity affected one in eight people in 2022, representing a substantial increase across all age groups[1]. Obesity among adults has also more than doubled since 1990, indicating a rapidly worsening trend in the population[1].

In the surgical field, obesity is a modifiable risk factor that contributes to lifestyle-associated diseases such as degenerative joint disease[2]. In orthopedic surgery in particular, obesity greatly affects joint mobility, the complexity of perioperative management, and overall joint biomechanics. In Saudi Arabia, the marked rise in obesity prevalence parallels global trends and has been accompanied by increased demand for orthopedic surgical care[3]. However, the lack of local data assessing the influence of obesity on surgical outcomes within the Kingdom’s diverse population warrants further investigation. Understanding the relationship between obesity and orthopedic surgery outcomes is essential for improving surgical planning, risk assessment, patient counseling, and postoperative recovery strategies.

The purpose of this study is to evaluate how obesity affects surgical complications and recovery outcomes in patients undergoing orthopedic surgery by comparing obese and non-obese patients at King Fahad University Hospital. We hypothesize that obesity is associated with a higher risk of surgical complications and may adversely affect key recovery measures such as wound healing, length of hospital stay, and short-term functional outcomes.

MATERIALS AND METHODS

Study design and population

We conducted a retrospective cohort study comparing obese and non-obese patients who underwent elective or emergency orthopedic surgery at King Fahad University Hospital, Al-Khobar, Saudi Arabia, between January 1, 2020, and November 30, 2024. A BMI cutoff of 30 kg/m² was used to classify obese patients, and all patients were aged 18 years or older. Given the retrospective design, informed consent was waived, and prior approval was obtained from the Institutional Review Board of Imam Abdulrahman Bin Faisal University (No. IRB-2025-01-0285).

Participants

A sample of 368 patients was selected from an estimated population of 8300 eligible patients. Eligible cases were identified from all adult patients who underwent orthopedic surgery during the study period. Patients were then selected using simple random sampling generated through a computerized random number list. Obese and non-obese patients were sampled together from the same eligible population to ensure comparable representation between the two groups. The sample size calculation was based on a 95%CI, a 5% margin of error, and an assumed population proportion of 50%. All orthopedic surgeries were performed under the supervision of Saudi board-certified consultants. Patients were grouped into obese (≥ 30 kg/m²) and non-obese (< 30 kg/m²) categories, allowing comparison of postsurgical complications between the two groups. Obesity status was determined after sampling and was not used as a criterion for patient selection. Patients with severe chronic conditions known to affect surgical outcomes were excluded, including advanced cardiovascular disease, end-stage renal disease, chronic liver disease, active malignancy, and chronic immunosuppressive conditions.

Outcome variables

All relevant data, including BMI parameters, patient demographics (sex and age) comorbidities, admission notes, and operative details, were obtained from the electronic medical records of King Fahad University Hospital via the InterSystems TrakCare system. The primary outcome was postoperative complications, defined as the presence of one or more of the following: (1) Postsurgical infections; (2) Nerve injuries; (3) Prosthesis loosening; (4) Thromboembolism; and (5) Fracture malunion or non-union. Secondary outcomes included surgical success (defined as the absence of postoperative complications), postsurgical mobility scores, pain level recorded using the Visual Analog Scale, length of hospital stay, and reoperation. To minimize bias during data collection, all data were systematically extracted manually from patient charts by two independent reviewers, and a third reviewer resolved any discrepancies.

Statistical analysis

A sample of 368 patients was selected from a list of eligible orthopedic surgeries performed during the study period using simple random sampling. Descriptive statistics included means and standard deviations for continuous variables, including length of hospital stay and Visual Analog Scale score, and n (%) for categorical variables, including all remaining variables. All analyses were performed after dividing patients into obese and non-obese groups. The χ² test was used to compare categorical variables, whereas the independent t-test was used to compare continuous variables after normality was confirmed by the Shapiro-Wilk test. In addition, the χ² test was used to compare the composite primary outcome rate between the obese and non-obese groups, with the composite primary outcome defined as the occurrence of any postoperative complication. To minimize classification bias, multiple independent data extractors were involved, and a third party reviewed discrepancies. A P value < 0.05 was considered statistically significant for all analyses.

RESULTS

A total of 368 patients were included in the study, with equal representation of non-obese and obese participants (n = 184 in each group) (Figure 1). The overall mean age of the cohort was 45.7 ± 17.3 years, with obese patients being significantly older than non-obese patients (50.3 ± 17.1 years vs 41.0 ± 16.3 years, P < 0.001). Sex distribution differed significantly between the groups, with males constituting a higher proportion of the non-obese group (68.5%), whereas females were more prevalent in the obese group (58.2%) (P < 0.001). Diabetes mellitus was present in 73 patients (19.8%) overall and was more frequently observed in obese individuals (P = 0.013). Hypertension affected 88 patients (23.9%) and was significantly more common in the obese group (P < 0.001). Dyslipidemia was identified in 30 patients (8.2%) and hypothyroidism in 15 patients (4.1%), with both conditions showing a higher proportion in obese patients, although these differences did not reach statistical significance (P > 0.05). Smoking was reported by 33 patients (9.0%) and did not differ significantly according to obesity status (P = 0.144; Table 1).

Figure 1  Surgery outcomes based on obesity status.

Table 1 Baseline characteristics of study participants by obesity status, mean ± SD/n (%).

Variable		Non-obese (n = 184)	Obese (n = 184)	Total (n = 368)	P value
Age (years)		41.0 ± 16.3	50.3 ± 17.1	45.7 ± 17.3	< 0.001
Gender	Male	126 (68.5)	77 (41.8)	203 (100)	< 0.001
	Female	58 (31.5)	107 (58.2)	165 (100)
Diabetes mellitus	Yes	27 (37)	46 (63)	73 (100)	0.013
	No	157 (53.2)	138 (46.8)	295 (100)
Hypertension	Yes	27 (30.7)	61 (69.3)	88 (100)	< 0.001
	No	157 (56.1)	123 (43.9)	280 (100)
Dyslipidemia	Yes	10 (33.3)	20 (66.7)	30 (100)	0.057
	No	174 (51.5)	164 (48.5)	338 (100)
Hypothroidism	Yes	4 (26.7)	11 (73.3)	15 (100)	0.065
	No	180 (51)	173 (49)	353 (100)
Smoking status	Yes	12 (6.5)	21 (11.4)	33 (100)	0.144
	No	172 (93.5)	163 (88.6)	335 (100)

Post-orthopedic surgical outcomes and complications according to obesity status are presented in Table 2. Postoperative complications were significantly more frequent among obese patients, who accounted for 80.0% of all affected cases, compared with 20.0% among non-obese patients (P < 0.001). In contrast, successful surgical outcomes were more commonly observed in non-obese patients (55.8%) than in obese patients (44.2%). Obese patients also demonstrated a significantly higher proportion of thromboembolic events, accounting for 83.3% of cases compared with 16.7% among non-obese patients (P = 0.019). Similarly, prosthesis loosening or failure occurred predominantly in obese patients (88.9%), as did fracture non-union or malunion (90.0%), with both complications showing statistically significant associations with obesity (P < 0.05). Nerve injury was also markedly more common among obese patients, who represented 88.9% of affected cases (P = 0.001). Postsurgical infections were likewise observed more frequently in obese patients (73.9%) than in non-obese patients (26.1%), P = 0.018.

Table 2 Post-orthopedic surgical outcomes and complications by obesity status, n (%).

Outcome	Category	Non-obese	Obese	Total	P value
Surgical outcome	Complications	12 (20.0)	48 (80.0)	60 (100)	< 0.001
	Successful	172 (55.8)	136 (44.2)	308 (100)
Thromboembolism	No	182 (51.1)	174 (48.9)	356 (100)	0.019
	Yes	2 (16.7)	10 (83.3)	12 (100)
Prosthesis loosening/failure	No	183 (51.0)	176 (49.0)	359 (100)	0.018
	Yes	1 (11.1)	8 (88.9)	9 (100)
Fracture non-union/malunion	No	183 (51.1)	175 (48.9)	358 (100)	0.010
	Yes	1 (10.0)	9 (90.0)	10 (100)
Nerve injury	No	182 (52.0)	168 (48.0)	350 (100)	0.001
	Yes	2 (11.1)	16 (88.9)	18 (100)
Post-surgical infection	No	178 (51.6)	167 (48.4)	345 (100)	0.018
	Yes	6 (26.1)	17 (73.9)	23 (100)

Table 3 presents postoperative outcomes in obese and non-obese patients. Obese patients had a significantly longer hospital stay than non-obese patients (5.85 ± 9.03 vs 3.23 ± 2.94, P < 0.001). Postoperative pain scores were also significantly higher in obese patients than in non-obese patients (4.13 ± 2.27 vs 3.32 ± 2.62, P = 0.002). Regarding functional recovery, mobility status differed significantly by obesity status (P = 0.014). Obese patients were more likely to have limited postoperative mobility (63.3%), whereas non-obese patients were more likely to achieve moderate (53.1%) and normal mobility (55.3%). Reoperation was also significantly associated with obesity, with obese patients accounting for 70.6% of reoperation cases (P = 0.012).

Table 3 Postoperative outcomes by obesity status, mean ± SD/n (%).

Variables		Non-obese	Obese	P value
Length of hospital stay (days)		3.23 ± 2.94	5.85 ± 9.03	< 0.001
Pain score (VAS 0-10)		3.32 ± 2.62	4.13 ± 2.27	0.002
Mobility score (post-surgery)	Limited	33 (36.7)	57 (63.3)	0.014
	Moderate	68 (53.1)	60 (46.9)
	Normal	83 (55.3)	67 (44.7)
Reoperation	No	174 (52.1)	160 (47.9)	0.012
	Yes	10 (29.4)	24 (70.6)

VAS: Visual Analog Scale.

A multivariable logistic regression analysis was performed to identify predictors of successful surgical outcome (Table 4). Among the variables examined, non-obese patients had significantly higher odds of successful surgery than obese patients [odds ratio (OR) = 2.61; 95%CI: 1.29-4.72; P = 0.019]. In contrast, a longer hospital stay was associated with lower odds of success (OR = 0.87; 95%CI: 0.57-1.24; P = 0.032). Although patients older than 50 years had higher odds of successful outcomes (OR = 1.41; 95%CI: 1.05-1.89), this association did not reach statistical significance (P = 0.127). Similarly, sex, smoking status, diabetes mellitus, hypertension, and pain score were not significantly associated with surgical success (P > 0.05).

Table 4 Multivariable logistic regression for predictive factors for successful surgical outcome.

Dependent variable: Successful surgery (predictor)	Adjusted OR	95%CI for OR	P value
Age > 50 years	1.41	1.05-1.89	0.127
Gender (female vs male)	1.71	0.75-3.75	0.291
Obesity status (non-obese vs obese)	2.61	1.29-4.72	0.019
Length of hospital stay (days)	0.87	0.57-1.24	0.032
Smoking (no vs yes)	0.59	0.17-2.23	0.452
Diabetes mellitus (no vs yes)	1.08	0.28-4.15	0.926
Hypertension (no vs yes)	0.44	0.13-1.50	0.212
Thromboembolism (no vs yes)	-	-	-1
Post-surgical infection (no vs yes)	-	-	-1
Pain score (VAS 0-10)	1.12	0.81-1.98	0.271

¹Very low event count (unstable estimates).

OR: Odds ratio; VAS: Visual Analog Scale.

DISCUSSION

This study examined the relationship between obesity and orthopedic surgical complications at King Fahad University Hospital. Obese patients had higher rates of surgical complications than non-obese patients, including postsurgical infection, nerve injury, prosthesis failure, thromboembolic events, and malunion. Furthermore, obese individuals demonstrated delayed recovery of mobility, with the data showing lower mobility scores in obese participants. Obesity was also associated with a significantly longer hospital stay, which may reflect an increased need for postoperative care and a more challenging recovery course.

Multiple factors may explain the higher complication rates observed in obese participants in this study. First, the higher rates of postsurgical infection in obese patients could be linked to delayed wound healing, which may be associated with reduced tissue perfusion and oxygenation. Furthermore, because of the larger surgical incisions and greater surface area of exposed tissue, wound closure may be more difficult, potentially increasing susceptibility to infection. Second, excess adipose tissue can make surgical exposure and identification of anatomical landmarks more challenging, potentially increasing the risk of intraoperative nerve injury. Third, with respect to the mechanical and biomechanical stresses associated with obesity, prosthesis malfunction is a major concern. Higher loads on implants may increase the likelihood of implant failure.

Fourth, in addition to the prosthesis, higher forces may affect bone during its healing, leading to displacement before it fully heals. Fifth, regarding functional recovery, greater stress on the operated joint in obese patients may be associated with slower recovery and delayed mobility. Moreover, obese patients experienced greater difficulty performing physiotherapy exercises, which may have contributed to slower recovery and reduced mobility, potentially resulting in the longer hospital stay observed in our cohort. Finally, obese individuals may be at an increased risk of thromboembolic events due to a lack of movement. The longer time required before ambulation in this group could potentially contribute to this elevated risk. Many outcomes demonstrated statistically significant differences between obese and non-obese patients. However, statistical significance does not necessarily indicate clear clinical relevance. For example, postoperative pain showed only a small difference between the two groups and was unlikely to affect patient care.

The findings of this research align with the existing literature, which consistently reports higher rates of postoperative complications in obese patients than in non-obese patients. Previous studies have reported higher rates of postoperative infections in the obese population, showing an increased risk of superficial wound infections with increasing BMI[4]. These results are consistent with the findings of our cohort, in which postoperative infections were observed more frequently in obese patients. Additionally, higher rates of nerve injury have also been reported in previous literature, with increased risk in patients with higher BMI. This association is similarly reflected in our findings, with higher rates of nerve injury among study participants with higher BMI[5]. Moreover, prior research has indicated that individuals with higher BMI experience more frequent mechanical failures[4]. This trend is consistent with our data, as prosthesis failure was significantly more common in the obese group than in the non-obese group. In addition, previous literature has reported delayed fracture healing and higher rates of malunion/non-union among obese patients[6].

The results of our cohort show higher rates of malunion/non-union among participants with obesity, which align with data from previously published studies. In addition, previous reports have shown delayed ambulation and lower mobility scores in patients with higher BMI[7]. Our cohort demonstrated similar findings, with obese patients having lower scores than non-obese patients. In addition to reduced mobility, the high-BMI group reported greater postoperative pain than the low-BMI group. These findings are also consistent with the existing literature[7]. Participants in the obese group may be at an increased risk of thromboembolic events compared with the non-obese group, as shown in previously published data[8]. This is consistent with the results of our study, in which thromboembolic events were more frequent among obese participants than among non-obese participants. A systematic review reported that obesity is associated with an increased risk of complications and poorer outcomes in spine surgery. However, these findings do not suggest that obese patients should be excluded from surgical intervention. Instead, they highlight the need for further evaluation, careful patient selection, and enhanced perioperative care for this population[9]. Another study reported that obesity was associated with poorer outcomes following shoulder arthroplasty, including an unfavorable prognosis and delayed postoperative recovery[10].

A 2024 systematic review and meta-analysis examined the impact of obesity on functional outcomes and complications following arthroscopic rotator cuff repair and found that obesity is associated with a higher risk of readmission and reoperation[11].

This study has several strengths. First, it was conducted at King Fahad University Hospital, a tertiary care center, and evaluated the impact of obesity on orthopedic complications, a topic for which regional evidence remains limited. Second, the research was comprehensive, assessing both functional recovery and surgical outcomes, including a detailed analysis of postoperative infection, nerve injuries, and malunions/non-unions. Finally, the results have strong clinical relevance, highlighting the need for perioperative management and strategies to mitigate complications in the growing obese population in Saudi Arabia.

This study has several limitations. First, it was conducted at a single tertiary care center, which may limit the generalizability of the findings. Second, the study was a retrospective cohort study that primarily relied on electronic medical records. Inevitably, some patient data were missing from the records. The association observed between obesity and clinical outcomes could also have been influenced by the higher prevalence of comorbid conditions, such as type 2 diabetes or hypertension. These comorbidities are independent risk factors and may have acted as significant confounders, thereby limiting the ability to attribute the outcomes solely to obesity. Potential confounding factors, such as age and chronic conditions, may also have influenced the results. Furthermore, our research lacks a comprehensive description of fracture morphology and the specific injury patterns sustained by the patients.

In conclusion, obesity is associated with a higher risk of postoperative complications in orthopedic surgery, including nerve injury, postoperative infection, prosthesis failure, thromboembolism, higher pain scores, malunion/non-union and prolonged hospital stay. The findings of this study are consistent with the existing literature. These results highlight the importance of perioperative management to mitigate complications in the growing obese population. Further multicenter studies are recommended to validate these findings and assess their generalizability nationwide.

CONCLUSION

Obesity is a major global health issue and is strongly associated with chronic diseases. In this retrospective cohort study conducted at King Fahad University Hospital, we evaluated, compared, and assessed the relationship between obese and non-obese patients who underwent major orthopedic surgeries using specific inclusion and exclusion criteria. After analyzing the data using various statistical tests, the results demonstrated an association between obesity and postsurgical complications. Other variables, such as mobility score and length of stay, also showed significant associations with obesity. This study demonstrates a significant correlation between obesity and poorer surgical outcomes in major orthopedic surgeries.