2.1 Literature and database search

A systematic search of peer-reviewed studies published through October 17, 2024 was conducted using PubMed, Embase, and Cochrane databases, in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) criteria. The following terms were combined in the search strategy: primary cementless total hip arthroplasty (THA), grit-blasted femoral stems, and porous-coated femoral stems. Revision rates, surgical indications, implant characteristics, and reasons for revisions, such as periprosthetic fractures, stem loosening, dislocation, and infection were included as outcomes of interest. Details of the search are available in Table A.1, Table A.2, Table A.3, and Table A.4 of the Appendix. Queried studies were uploaded to the Covidence systematic review software for subsequent screening.

2.2 Eligibility criteria and study selection

Screening was conducted on Covidence by two independent reviewers, S.S. and R.C. Disagreements were resolved by a third reviewer, A.S. The first round of screening utilized titles and abstracts to identify studies in English that studied THA revision rates and specific indications for revision THA. Case series, prospective or retrospective cohort studies, and randomized controlled trials were also added to the inclusion criteria. Additionally, single-arm studies without direct comparisons of the two stem types were included. Non-English studies, cadaveric studies, in-vitro research, case reports, systematic reviews, technical papers, editorial commentary, and conference abstracts were excluded. We left out any studies that examined femoral stems with extra surface coatings, like hydroxyapatite (HA), during the abstract screen because a recent review has already compared HA-coated with uncoated stems.⁸ The second round of screening utilized the full text using the same inclusion and exclusion criteria. The complete flowchart from identification through screening can be seen in Fig. 1. Since the primary focus of this study was revision rates and surgical indications for revision, only studies reporting those metrics were included.

2.3 Bias assessment

JBI's Methodological Quality Assessment Tool for case series and cohort studies was used to assess risk of bias by two reviewers, with all discrepancies resolved by a third reviewer.

2.4 Data extraction

Data was extracted independently by one of two authors, S.S. and R.C. The opposite reviewer performed a second review and round of extraction. Only findings from patients available at the final follow-up time were included. Data points of interest included: study type, level of evidence, number of patients, sex, mean age, follow-up duration, surgical indication, Harris Hip score, revision rates, revision indication, and postoperative management.

2.5 Data analysis

Because of methodological and clinical heterogeneity, no meta-analysis was conducted. Rather, continuous variables were computed as means, while categorical variables were summated and displayed as counts or percent. Findings from individual research were reported by combining and tabulating additional outcomes of interest.

3.1 Literature screening and data extraction

Initial database searches yielded 2151 studies, but only 1188 underwent title and abstract screening due to the removal of duplicate studies. Of these studies, 61 were screened by the full text based on certain inclusion and exclusion criteria. Primary reasons for exclusion in this stage were wrong intervention and wrong patient population. This yielded 12 studies to be included in the review. Data extraction was performed on 3 Level II prospective cohort studies, 8 Level III retrospective cohort studies, and 1 Level IV case-series.

3.2 Quality assessment

Quality assessment was conducted by two authors (S.S. and R.C.) using the JBI Clinical Appraisal tool. The 3 prospective cohort studies analyzed had a mean score of 10.7/11. The 8 retrospective studies analyzed had a mean score of 10.9/11. The 1 case-series analyzed had a score of 10/10. All 12 studies were deemed eligible for data extraction.

3.3 Patient demographics

Across the 12 studies, a total of 1987 patients underwent primary cementless THA and were considered for the possibility for revision. The patients had a mean age of 57.3 years (13–96) and presented with a variety of indications for THA with the most common reason being osteoarthritis. The average follow-up duration across the 12 studies was 14.3 years with means ranging from 5.2 to 23.6 years in individual studies (Table 1).

3.4 Surgical indications

Surgical indications for primary THA among these studies were diverse with osteoarthritis being the most common. Other indications included avascular necrosis of the femoral head, rheumatoid arthritis, femoral neck fracture, congenital dysplasia, developmental dysplasia, Legg-Calve-Perthes disease, slipped capital femoral epiphysis, and other minor causes. Among the studies that reported surgical indication, 235 out of 562 hips had a reported indication for THA as osteoarthritis.^9–11

3.5 Postoperative management

Seven of the twelve studies reported postoperative management. Of the 7 studies, four studies added partial weight bearing for 6 weeks.^12–15 One study used NSAIDs for more than 2 weeks along with rehabilitation for 2 weeks.¹⁶ Two studies provided antibiotic prophylaxis for 48 h and thromboembolic prophylaxis for 1 month.^15,17 One study added mechanical compression via thrombo-embolic hose and sequential compression devices.¹⁷

3.6 Revision rates

For porous-coated stems, revision rates ranged from roughly 0 %–3.5 %. Anatomic Medullary Locking stems showed max revision rates at 1.90 % with Prodigy stems being slightly higher. On the other hand, grit-blasted stems had revision rates ranging from 4.80 % to 11.35 %, indicating a tendency for more revisions with this texture of femoral stem. All of these results can be seen in Table 2.

3.7 Complications for revision

Revision was indicated for a variety of reasons but six complications were shown to be the most common: stem loosening, periprosthetic femur fracture, dislocation, infection, intraoperative fracture, and progressive femoral osteolysis. Stem loosening was the most common reason for revision surgery totaling 38 cases in the 7 studies that reported this complication. The next most common reasons for revision were dislocation and infection at 29 and 24 cases respectively. Revision for periprosthetic femur fracture totaled 20 cases. Ten cases of intraoperative fractures were reported and there were 12 cases of progressive femoral osteolysis. Only one study reported progressive femoral osteolysis as a reason for revision (Table 3).

There were 123 total revisions for the grit-blasted stems (n = 1337) and 10 total revisions for the porous-coated stems (n = 650). There were no cases where a porous-coated femoral stem was used and infection, intraoperative fracture, or progressive femoral osteolysis was the indication for revision surgery.

3.8 Harris Hip Score

The Harris Hip Score (HHS) was only reported in 8 out of the 12 studies. Of those 8 studies, only 4 reported both preoperative and postoperative HHS scores with the other 4 studies only reporting postoperative scores. The means for the preoperative HHS ranged from 46 to 67.47. The means for the postoperative HHS ranged from 83.1 to 96.1 (Table 2).

Out of the 4 studies that reported both preoperative and postoperative HHS scores, only one used grit-blasted femoral stems¹⁸ while the other 3 used porous-coated femoral stems.^11,16,17 Comparing preoperative scores, the patients with grit-blasted femoral stems had preoperative scores of 55.3 ± 4.6 while the patients with porous-coated stems had mean preoperative scores of 46, 48.5, and 67.47. The mean postoperative HHS scores for the grit-blasted femoral stem studies were 83.1, 85.1, 86, and 90.8. The mean postoperative HHS scores for the porous-coated femoral stem studies were 83.64, 84, 87.3, and 96.1. Of the studies that reported both preoperative and postoperative HHS scores, the difference between the two scores for the grit-blasted femoral stem study was 35.5 points. For the 3 porous-coated femoral stem studies, the improvement in preoperative and postoperative HHS scores was 16.17, 38, and 47.6.

4.1 Summary of evidence

This systematic review demonstrates several encouraging outcomes regarding the use of both porous‐coated and grit‐blasted femoral stems in primary total hip arthroplasty. Many studies reported high rates of osseointegration with porous‐coated stems, which were associated with significant improvements in the Harris Hip Score (HHS) and a lower incidence of mechanical complications, such as aseptic loosening and periprosthetic fractures.^{11,16,17,19,20} The enhanced osseointegration appears to be attributable, in part, to the anatomical design of these implants. For example, porous‐coated stems that feature a more anatomically contoured design with medial cutouts or variable proximal geometries improve stress transfer to the femur and reduce stress shielding, thereby promoting more uniform load distribution and robust bone ingrowth.¹¹ In contrast, grit‐blasted stems rely solely on achieving an optimal press‐fit without anatomical customization, which makes them more susceptible to micromotion and subsequent mechanical failure when the patient's bone quality is suboptimal.^9,11,21

In addition to these mechanical advantages, both implant types yield generally acceptable long‐term outcomes with overall low revision rates. Notably, the porous‐coated stems consistently exhibit a more favorable complication profile, evidenced by lower revision rates for aseptic loosening and periprosthetic fractures.^12,16 The marked improvements in HHS observed in several studies not only indicate effective pain relief and enhanced mobility but also suggest an overall improvement in quality of life for these patients.^11,16 Furthermore, studies employing rigorous surgical techniques, such as aggressive reaming and standardized press‐fit protocols, demonstrated lower revision rates, underscoring the importance of precision and consistency in implant insertion.¹⁴ These positive findings highlight the clinical utility of advanced implant designs that effectively address the stiffness mismatch between implant and bone, thereby optimizing load transfer and facilitating successful osseointegration.

Differences in revision outcomes across studies may also be influenced by specific methodological factors. Several studies in our review differed in their surgical technique and postoperative protocols. For instance, studies that utilized more aggressive reaming or standardized press‐fit techniques often reported lower revision rates, suggesting that surgical precision and consistency are critical for long‐term success.^3,14 Conversely, studies with less strict control over these variables tended to show higher complication rates, suggesting that variability in technique can skew the comparative outcomes between porous‐coated and grit‐blasted stems.^18,19 Furthermore, the criteria used to define revision and the threshold for reoperation varied among studies, further complicating direct comparisons.

Patient selection also played an important role in influencing outcomes. Some studies included a broader age range, encompassing pediatric and adolescent patients, while others focused solely on older patients.^11,13,14,16 Revision rates may be impacted by the distinct stress distributions that younger patients encounter at the bone–implant interface due to their increased activity levels.¹¹ Although younger patients mostly demonstrate enhanced bone remodeling capacities, longer implant lifetimes often lead to higher likelihood of revision.^11,22 On the other hand, regardless of implant design, elderly individuals with diminished bone quality might be more vulnerable to mechanical issues.^4,18 In multiple instances, porous‐coated stems were used in patients with lower baseline functional scores or compromised bone quality, which may have led to more dramatic improvements in HHS postoperatively but also to different revision profiles compared with the more uniformly selected cohorts in grit‐blasted stem studies.¹¹

4.2 Limitations

Despite these positive findings, the review is limited by the heterogeneity of the included studies. Most of the included studies were single-arm case series, which means we couldn't perform a true head-to-head comparison between porous-coated and grit-blasted stems. Many of the studies were case series with limited sample sizes and varying follow-up durations, and the lack of randomized controlled trials reduces our ability to draw definitive conclusions. Additionally, adjunct coatings were not considered in this study which would likely influence outcomes when comparing stem types. Future well-controlled, long-term studies with standardized outcome measures and rigorous patient selection criteria are needed to more accurately assess the comparative performance of these femoral stem designs. Such studies would help isolate the effects of implant design from confounding variables such as surgical technique, rehabilitation protocols, and patient demographics, thereby yielding more precise revision and complication rates.