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A Randomized Study Comparing Uncemented and Hybrid Hip Replacements in Young Patients with Osteonecrosis Femoral Head
* Corresponding author: Dr Rahul Bhargava, Prof and HOD, Departmrent of Ophthalmology, GS Medical College, Pilkhuwa, Uttar Pradesh, India. brahul2371@gmail.com
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Received: ,
Accepted: ,
How to cite this article: Dwivedi A, Avishkar, Mittal S, Singh A, Bhargava R. A Randomized Study Comparing Uncemented and Hybrid Hip Replacements in Young Patients with Osteonecrosis Femoral Head. Int J Recent Surg Med Sci. 2025:11(e012). doi: 10.25259/IJRSMS_53_2025
Abstract
Objectives
There is a scarcity of data comparing cemented and hybrid implants for total hip arthroplasty in relatively younger patients. The aim was to evaluate the clinical outcomes of uncemented and hybrid implants in patients who undergo total hip arthroplasty for avascular necrosis (AVN) of the hip.
Material and Methods
A prospective, interventional, randomized study included patients aged 30-55 with grade 3 or 4 AVN as per the modified Ficat and Arlet classification.
Results
The mean age of patients for hybrid total hip arthroplasty (THA) (Group 1) was 43.1±6.2 years, and for uncemented total hip arthroplasty (Group 2) was 42.4±4.3 years. The age difference between the groups was not statistically significant (Independent t-test, P=0.744). Both treatment groups demonstrated a significant improvement (P<0.05) in Harris hip score (HHS) at 1, 3, and 6 months after THA. Patients in Group 1 had significantly higher (P<0.05) HHSs than those in Group 2. The length of hospital stay for patients with hybrid implants (11.5±1.6 days) was significantly longer than for those with uncemented implants (10.8±0.9 days, independent t-test, P=0.040). The quantity of blood transfusion units administered was comparable between the two groups (P=0.123). There was no statistically significant difference observed in the incidence of deep infections, prosthetic fractures, or implant dislocations between the two groups (P>0.05). Group 2 exhibited a higher rate of superficial infections, whereas intraoperative complications were more common in Group 1.
Conclusion
For young patients with osteonecrosis, both uncemented and hybrid hip replacements represent viable surgical options. Recent advancements in implant design and bearing surfaces have contributed to the growing preference for uncemented prostheses. Nevertheless, our study demonstrated that the HHS at 6 months postoperatively was higher in the hybrid implant group, indicating superior functional outcomes. It is noteworthy, however, that patients receiving THA had a longer mean hospital stay (11.5 ± 1.6 vs. 10.8 ± 0.9 days, P=0.040) compared to those with uncemented arthroplasty. Additionally, the uncemented group exhibited a higher incidence of superficial infections, while the rates of other complications were comparable between the two cohorts.
Keywords
Avascular necrosis hip
Hybrid implant
Total hip arthroplasty
Uncemented implant
INTRODUCTION
Osteonecrosis refers to the disruption of blood supply to the femoral head, which leads to the collapse of the articular surface and eventually results in osteoarthritis. Since Mankin’s 1962 report of cases with osteonecrosis of the femoral head (ONFH) (n=27), shows steady growth.[1] It is uncertain whether this represents an actual increase or is a result of increased awareness and advancements in diagnostic techniques.
ONFH is a severe condition that commonly results in osteoarthritis of the hip joint, particularly affecting relatively young adults. There is a lack of data on the epidemiological profile of ONFH in the Indian population. In the United States, it is estimated that between 10,000 and 20,000 new cases of ONFH are diagnosed annually; approximately 5-18% of the 500,000 hip arthroplasties performed annually are estimated to treat ONFH.[2-4]
Treatment options for ONFH include medications, biophysical therapies, and surgeries. Surgeries are divided into Femoral Head Sparing Procedures (FHSP) for pre-collapse stages and (FHRP) for post-collapse stages. Total hip arthroplasty (THA) has been the preferred treatment for symptomatic advanced-stage femoral head collapse, especially when secondary acetabular changes are observed.
Although revision rates for THA have decreased due to improvements in surgical methods and implant technology, younger patients continue to experience higher failure rates compared to older patients.[5]
Uncemented implants are frequently used in young patients. Recent studies have shown that both cemented, and hybrid THAs have good survival rates in this subset.[6] However, there is a lack of comparative studies on this topic in the literature. Currently, the selection of implants is primarily influenced by surgeon preference and marketing. This study aims to compare the survival and outcomes of the most commonly used uncemented and hybrid implants in a sample of young patients from the North Indian population, to guide implant selection for THA.[7-8]
MATERIAL AND METHODS
Study design
A prospective, interventional, randomized study was conducted in the Orthopedics department at a north Indian tertiary care teaching hospital from June 2022 to December 2023. Approved by the institutional ethics committee (SUIEC/2022/071), written consent was obtained from all patients as per the Declaration of Helsinki.
Inclusion criteria
Patients clinically suspected and radiologically confirmed to have avascular necrosis (AVN) of the hip were included in this study. The diagnosis was determined through clinical examination, radiological assessment (X-ray of the pelvis in an anteroposterior view), and magnetic resonance imaging (MRI) of the pelvis. Only patients with AVN classified as grade 3 or grade 4 according to the modified Ficat and Arlet classification were considered. Additionally, eligible participants were required to be between 30 and 65 years of age.
Exclusion criteria
Patients over 65 years of age and those with coxa vara, coxa valga, developmental dysplasia of the hip, tubercular hip, or traumatic AVN were excluded.
Sample size calculation
Formula for sample size calculation.
In this formula, N=Sample size in each group, µ1=mean change in group 1or mean score at baseline, µ2=mean change in group 2 or mean score after intervention, µ1-µ2=clinically significant difference, SD=standard deviation, Zα/2=This depends on the level of significance (for 5%=1.96), Zβ =This depends on power (for 80%=0.84).
Sample size calculation was based on the principle of ‘Inference for Means: Comparing means of two independent samples.’ Sample size calculation was done using the web-based calculator of the University of British Columbia (UBC). This calculator can be accessed using the link [https://www.stat.ubc.ca/∼rollin/stats/ssize/n2.html]. The sample size can also be calculated manually using the above-mentioned formula.
To calculate the sample size and to compare the mean change in Harris hip score (HHS) between patients receiving an uncemented implant (Group 1) and patients receiving a hybrid implant (Group 2), a pilot study was first done on 6 subjects. The mean postoperative improvement in the HHS Group 1 was 55 and in Group 2 was 50, respectively. The standard deviation was 9.8. Assuming 1:1 randomization, 80% power (α= 0.05), and a precision error of 5% to detect a difference of 20% or more in HHS between the two groups, the estimated sample size was calculated to be 60.
Randomization and masking
Sixty patients with avascular necrosis were randomly assigned to two groups of 30 via parallel assignment. The allocation codes were computer-generated and concealed in green envelopes, which were opened by non-health care staff.
Group 1 patients underwent total hip replacement with a hybrid implant (uncemented acetabular component and cemented femoral stem), while Group 2 received entirely uncemented implants. Patients did not know their implant type. The same team performed all surgeries using a standard posterolateral approach under spinal anesthesia. The hybrid THR group got an uncemented acetabular component with a cross-linked polyethylene liner and a cemented femoral stem with restrictors. The uncemented THR group received a porous-coated acetabular component with a cross-linked polyethylene liner and a proximally coated, distally polished femoral stem. Independent investigators, not involved in the surgery, were blinded to both the surgeon’s identity and procedure type.
The data collected for all patients included age, sex, body mass index (BMI), cause of osteonecrosis, occupation, and duration of symptoms.
Preoperative evaluation
Preoperative evaluation included routine blood investigations, radiographs, MRI findings, and functional assessment using the HHS. Intraoperative parameters such as surgical time, blood loss, and any technical difficulties encountered were documented.
Postoperative care, follow up and rehabilitation
Both groups received standardized postoperative care, including antibiotics, thromboprophylaxis, and a physiotherapy-guided rehabilitation program. Patients were followed up at 2 weeks, 6 weeks, 3 months, and 6 months postoperatively. At each visit, clinical assessments recorded pain visual analogue scalr (VAS), range of motion, grip strength, and any complications like infection, dislocation, limb length discrepancy, or pain. Radiological evaluation at 1 and 3 months checked position, alignment, pin loosening, or heterotopic ossification.
Outcome measures
The primary outcome measure was the HHS at 12 weeks, assessing pain, function, absence of deformity, and range of motion. Secondary outcome measures included time to recovery, postoperative pain scores, rehabilitation milestones (time to independent walking, stair climbing), and incidence of complications.
Participants were informed about the study’s nature, purpose, risks, and benefits. They were aware of the standard risks of hip replacement surgery, including bleeding, infection, implant failure, fracture, and neurovascular damage. Patients could withdraw from the study anytime without affecting their treatment at Santosh Hospital. Patient confidentiality was maintained, and published data did not include personal information. Investigators’ contact details were provided for any queries or concerns during the study.
Statistics
Statistical analysis was performed using IBM statistical software, SPSS Statistics version 29 (IBM Inc.). Data was checked for normality using the Shapiro-Wilk test. Outliers were identified by visual inspection of boxplots. Normally distributed data was reported as mean with standard deviation (SD). Frequencies and percentages were calculated for all categorical variables. Median (interquartile range) was reported for data not normally distributed. The independent-samples t-test or Mann-Whitney U test was used to determine if a difference exists between the means of two independent groups on a continuous dependent variable. The association between two categorical variables was evaluated using the Chi-square test. A one-way ANOVA was run to determine whether there are any statistically significant differences between the means of two or more independent groups. A P value less than 0.05 was considered statistically significant.
RESULTS
The mean age of patients for hybrid THA (Group 1) was 45.3±8.5 years (range: 34-58), and for uncemented total hip arthroplasty (Group 2) was 46±8.8 years (range: 34-60). The age difference between the groups was not statistically significant (Independent t-test, P=0.744). Group 1 consisted of 23 males, resulting in a male-to-female ratio of 3.3:1, while Group 2 had 21 males, with a male-to-female ratio of 2.3:1. The difference in sex distribution between the two groups was not statistically significant (Fischer’s exact test, P=0.771).
Table 1 and Figure 1 compare the Harris Hip score (preoperative, 1 month, 3 months, and 6 months after total hip arthroplasty between the two groups.
| *Harris hip score | Study group 1 | Study group 2 | **P value |
|---|---|---|---|
| Preoperative | 36.1±1.9 | 35.8±1.8 | 0.721 |
| 1 month | 78±5.3 | 76±3.1 | 0.041 |
| 3 months | 87±2.3 | 83.3±3.1 | <0.001 |
| 6 months | 91.4±2.8 | 85.8±3.4 | <0.001 |
- Line diagram comparing Harris Hip score (preoperative, 1 month, 3 months, and 6 months after total hip arthroplasty between the two groups).
At 1, 3, and 6 months, HHS were significantly higher (P<0.05) in patients who had hybrid THA compared to those with uncemented THA.
Table 2 compares the mean follow-up, length of stay (LOS) in hospital, and blood transfusion (units) between the two study groups.
| *Parameter | Study group 1 | Study group 2 | **P value |
|---|---|---|---|
| Follow up (months) | 7.1±0.9 | 7.2±1.2 | 0.721 |
| Length of stay in hospital (days) | 11.5±1.6 | 10.8±0.9 | 0.040 |
| Blood transfusion (units) | 1.9±0.2 | 1.8±0.3 | 0.398 |
Follow-up did not differ significantly between the two groups (P=0.721). Group 1, with hybrid THA [Figures 2a and 2b], had a significantly longer hospital stay (11.5±1.6 vs. 10.8±0.9 days, P=0.040) compared to Group 2 with uncemented THA [Figures 3a and 3b]. Blood transfusion units were similar for both groups.
- (a)Preoperative pelvis radiograph (AP view) of a 65-year-old female with right ONFH. (b) Postoperative X-ray of the same patient after THA with a hybrid implant. ONFH: Osteonecrosis femoral head, THA: Total hip arthroplasty.
- (a) Preoperative pelvis radiograph (AP view) of a 38-year-old male with left ONFH. (b) Postoperative X-ray of the same patient after THA with an uncemented implant. ONFH: Osteonecrosis femoral head, THA: Total hip arthroplasty.
Table 3 compares postoperative complication between the two groups.
| *Complication | Study group 1 | Study group 2 | **P value |
|---|---|---|---|
| Superficial infection | 1(3.3) | 3(10) | 0.040 |
| Deep infection | 1(3.3) | 1(3.3) | 0.876 |
| Prosthetic fracture | 1(3.3) | 1(3.3) | 0.992 |
| Dislocation of implant | 1(3.3) | 1(3.3) | 0.986 |
| Intraoperative complications | 3(10) | 2(6.7) | 0.123 |
There were no significant differences (P>0.05) in deep infections, prosthetic fractures, or implant dislocations between the two groups. However, Group 2 had more superficial infections, and Group 1 had more intraoperative complications.
Postoperative outcome
Table 4 compares the postoperative outcomes between the two groups.
| *Outcome | Study group 1 | Study group 2 | **P value |
|---|---|---|---|
| Excellent | 2(6.7) | 0 | 0.021 |
| Good | 23(76.7) | 16(53.4) | |
| Fair | 2(6.7) | 1(3.3) | |
| Poor | 3(10) | 7(23.3) | |
| Total | 30(100) | 30(100) |
DISCUSSION
This study examined the outcomes of hybrid versus uncemented implants in patients undergoing total hip replacement surgery (THA) for osteonecrosis of the hip. The results indicated that both treatment arms showed a significant improvement in the HHS at 1, 3, and 6 months after THA. Patients with hybrid implants (Group 1) had higher HHS than those with uncemented implants (Group 2).
Patients with hybrid implants stayed longer in the hospital (11.5±1.6 days) compared to those with uncemented implants (10.8±0.9 days, P=0.040). The quantity of blood transfusion units administered was equivalent between the two groups.
There was no statistically significant difference in the incidence of deep infections, prosthetic fractures, or implant dislocations between the two groups (P>0.05). Group 2 experienced a higher rate of superficial infections, while intraoperative complications occurred more frequently in Group 1.
THA for hip joint disorders has tangentially increased. In 2022, India performed around 74,860 total hip replacement surgeries, highlighting a rising trend in these procedures.[9]
Maloney and Harris conducted a retrospective comparison of uncemented (n=25) total hip replacements with hybrid (n=25) replacements, which included uncemented acetabular components and cemented femoral components. The mean postoperative hip score was 96 for patients with hybrid implants and 84 for those with cementless implants (P < 0.02) at a 2-year follow-up. The occurrence of thigh pain, limping, femoral component migration, and reoperation was higher in the cementless group. Overall, patients who received the hybrid replacement experienced better outcomes compared to those with an uncemented femoral component.[10] These outcomes were similar to ours, but our follow-up was much shorter (6 months compared to 24 months).
Kim et al.[11] evaluated 98 consecutive patients with an average follow-up period of 9.3 years. Fifty patients underwent bilateral THA, receiving hybrid fixation in one hip and uncemented fixation in the other. Forty-eight patients underwent unilateral uncemented THA. The HHS at the final follow-up was comparable between the two groups. No evidence of aseptic loosening was found in either the hybrid or uncemented group. Our study reported the results of hybrid THA in patients with osteonecrosis of the femoral head. The average preoperative HHS of 36 ± 1.9 points rose to 91.4 ± 2.8 points at final follow-up.[11]
Wixon and colleagues conducted a clinical and radiographic comparison of total hip replacement using cemented, uncemented, and hybrid prostheses. A cemented or hybrid prosthesis was utilized for males over 70 years of age, females over 60 years of age, and younger patients where initial fixation without cement was inadequate. Uncemented, porous-surfaced implants were employed for all other patients. The average Harris scores for cemented, hybrid, and uncemented prostheses were 91, 90, and 95, respectively. The corresponding pain scores for these prostheses were 42, 43, and 43, respectively. The incidence of component migration and the formation of radiolucent lines was more prevalent in acetabula with cemented components compared to those with cups designed to promote bone ingrowth.[12] The clinical outcomes based on HHS for hybrid and uncemented prosthesis in this study were comparable to our study
Managing osteonecrosis of the femoral head is difficult. Early treatment focuses on preserving the femoral head, while late-stage treatment remains debated. In advanced stages (Ficat and Arlet stage IV or Steinberg stages V and VI), THA effectively relieves pain and restores function. Studies have shown a higher failure rate in patients with osteonecrosis compared to those with osteoarthritis.[13,14]
Ahmad et al.[15] compared outcomes of uncemented (n=76) and hybrid (n=67) THA in elderly patients (80-89 years). The follow-up period was a minimum of 5 years. Radiological assessment of preoperative and postoperative radiographs was performed to evaluate bone quality, implant fixation, and any loosening that occurred afterward. The uncemented group had fewer intraoperative complications (P=0.017) and a lower transfusion rate (P=0.002). Hospital stay duration was similar (P=0.27). Two patients in each group required revision surgery.[15] In contrast, all patients in our study were under 65. The uncemented group had a higher rate of superficial infections, but other complications and hospital stays were similar between the groups.
Cebesoy et al.[16] assessed the midterm outcomes of THA for femoral neck osteonecrosis, comparing uncemented implants with hybrid implants. Osteonecrosis was due to femoral neck fractures in 11 hips (15.3%), steroid use in 23 hips (31.9%), and idiopathic in 38 hips (52.8%). The average follow-up was 4.1 years (range: 2 to 7 years). Although there was no statistically significant difference between cementless and hybrid systems (p>0.05), the mean hip score was notably higher with press-fit acetabular systems in comparison to expansion cups (p<0.001). Intraoperative complications included fissures in five patients and isolated trochanteric fractures in another five, all occurring in cementless THA. Both cementless and hybrid systems yield satisfactory results in hip osteonecrosis, regardless of cause.
Our study had several limitations and strengths. The sample size (n=30 in each group) was relatively small, which could potentially lead to type II errors and consequently, overestimation. Patient satisfaction levels following THR were not assessed in this study. Additionally, the follow-up period was relatively short (6 months). Long-term follow-up is necessary for patients undergoing THR.
For young patients with osteonecrosis, both uncemented and hybrid hip replacements represent viable surgical options. Recent advancements in implant design and bearing surfaces have contributed to the growing preference for uncemented prostheses. Nevertheless, our study demonstrated that the HHS at 6 months postoperatively was higher in the hybrid implant group, indicating superior functional outcomes. It is noteworthy, however, that patients receiving hybrid THA had a longer mean hospital stay (11.5 ± 1.6 vs. 10.8 ± 0.9 days, P=0.040) compared to those with uncemented arthroplasty. Additionally, the uncemented group exhibited a higher incidence of superficial infections, while the rates of other complications were comparable between the two cohorts.
CONCLUSION
In summary, both uncemented and hybrid hip replacements are effective options for young osteonecrosis patients. Hybrid implants may afford better early functional outcomes, albeit with slightly longer hospitalization, while the overall complication profile remains comparable between the two approaches.
Ethical approval
The research/study approved by the Institutional Review Board at Santosh Medical College, Ghaziabad, number SUIEC/2022/071, dated 10th April, 2022.
Declaration patient consent
The authors certify that they have obtained all appropriate patient consent.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
Use of artificial intelligence (AI)-assisted technology for manuscript preparation
The authors confirm that there was no use of artificial intelligence (AI)-assisted technology for assisting in the writing or editing of the manuscript and no images were manipulated using AI.
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