Cementless Tapered Wedge Femoral Stems Decrease Subsidence in Obese Patients Compared to Traditional Fit-and-Fill Stems

Comparison of Short Curved Stems and Standard-length Single Wedged Stems for Cementless Total Hip Arthroplasty

Purpose

The purpose of this study was to compare the clinical and radiographic outcomes with use of short-curved stems versus standard-length single wedged stems over a minimum follow-up period of five years.

Materials and Methods

A retrospective study of primary total hip arthroplasties performed using the Fitmore® stem (127 hips, 122 patients) and the M/L taper® stem (195 hips, 187 patients) between October 2012 and June 2014 was conducted. The clinical and radiographic outcomes were obtained for evaluation over a minimum follow-up period of five years.

Results

In both the Fitmore® and M/L taper® groups, the mean Harris hip score improved from 52.4 and 48.9 preoperatively to 93.3 and 94.5 at the final follow-up, respectively (P=0.980). The mean Western Ontario and McMaster Universities Osteoarthritis Index scores also improved from 73.3 and 76.8 preoperatively to 22.9 and 25.6 at the final follow-up, respectively (P=0.465). Fifteen hips (Fitmore®: 14 hips; M/L taper®: one hip, P<0.001) developed intraoperative cracks and were treated simultaneously with cerclage wiring. Radiography showed a radiolucent line in 24 hips in the Fitmore® group and 12 hips in the M/L taper® group (P=0.125). Cortical hypertrophy was detected in 29 hips (Fitmore® group: 28 hips; M/L taper® group: one hip, P<0.001).

Conclusion

Similarly favorable clinical and radiographic outcomes were achieved with use of both short-curved stems and standard-length single wedged stems. However, higher cortical hypertrophy and a higher rate of femoral crack were observed with use of Fitmore® stems.

Incidence and Predictors of Subsidence Using Modular, Tapered, Fluted Titanium Femoral Stems in Aseptic Revision Total Hip Arthroplasty

BACKGROUND

Tapered, fluted titanium (TFT) femoral stems have become the gold standard in revision total hip arthroplasty (rTHA). However, there is a paucity of data on TFT stem subsidence rates following aseptic rTHA. Subsidence can lead to instability, mechanical failure, leg-length discrepancy, and may require revision surgery. This study evaluated the incidences and predictors of TFT subsidence in aseptic rTHA.

METHODS

A total of 102 TFT femoral stems of 4 designs were retrospectively reviewed. Stem subsidence was measured on digital radiographs taken immediately after surgery and at standard clinical follow-up. Patient characteristics, risk factors for subsidence, revision etiologies, and implant characteristics were recorded. Patient-reported outcome measures were also evaluated for a subset of cases.

RESULTS

Overall, 12% of stems subsided >1 cm, and subsidence was minimal (<3 mm) in ≥64% of cases. From immediate postoperative to 1-month radiographic follow-up, 79% of stems subsided a mean of 2.9 mm (range, 0.1 to 12 mm). Beyond 1 month, subsidence was minimal for ≥77% of cases. In multivariate analyses, women and less femoral implant canal fill were associated with greater subsidence (P ≤ .034). The TFT stem design was not associated with early subsidence (P = .816). There were no modular junction fractures. There were 2 fractures and 2 subsidence-related revisions for aseptic loosening that occurred postoperatively.

CONCLUSIONS

The amount of subsidence in TFT stems was low and was detectable in the early (less than 1 year) postoperative period. Maximizing TFT stem fill within the femoral canal appears to reduce the risk of subsidence without increasing femoral fracture rates and should be the goal with implantation of these devices.

LEVEL OF EVIDENCE

IV-Case Series, No Control Group.

Three Differing Methods of Treating Intraoperative Nondisplaced Calcar Fractures Demonstrate Similar Radiographic Stem Subsidence

BACKGROUND

Several management strategies have been described to treat intraoperative calcar fractures during total hip arthroplasty (THA), including retaining the primary implant and utilizing cerclage cables (CCs) or switching the implant to one that bypasses the fracture and achieves diaphyseal fixation. However, the radiographic and clinical outcomes of these differing strategies have never been described and compared.

METHODS

We retrospectively identified 50 patients who sustained an intraoperative calcar fracture out of 9,129 primary total hip arthroplasties (0.55%) performed by one of three surgeons between 2008 and 2022. Each of the three surgeons consistently employed a distinct strategy for the management of these fractures: retention of the primary metaphyseal-engaging implant and placement of CCs; exchange to a modular, tapered-fluted stem (MTF); or exchange to a fully-coated, diaphyseal-engaging stem (FC). Stem subsidence was then evaluated on standing anteroposterior pelvis radiographs at three months and one year postoperatively. Postoperative medical and surgical complication rates were evaluated.

RESULTS

A total of fifteen patients were treated with CC, 15 with MTF, and 20 with FC. At three-month follow-up, mean stem subsidence was 0.43 ± 0.08 mm, 1.47 ± 0.36 mm, and 0.68 ± 0.39 mm for CC, MTF, and FC cohorts, respectively (P = .323). At one-year, mean stem subsidence was 0.70 ± 0.08 mm, 1.74 ± 0.69 mm, and 1.88 ± 0.90 mm for the CC, MTF, and FC cohorts, respectively (P = .485). Medical complications included 2 venous thromboembolic events (4%) within 90 days of surgery. There were 6 reoperations (12%); 3 (6%) for acute periprosthetic joint infection (all within the FC cohort); 2 (4%) for postoperative periprosthetic fractures (one fracture distal to the stem in the FC cohort and one fracture at the level of the stem in the MTF cohort), and 1 (2%) closed reduction for instability (within the CC cohort).

CONCLUSIONS

The three described methods of managing intraoperative nondisplaced calcar fractures demonstrated little radiographic stem subsidence; however, the risk of reoperation was much higher than expected.

Durability of Primary Total Hip Arthroplasty With Cementless Stems Without a Collar in Elderly Patients Age 75 Years and Over

BACKGROUND

Cementless femoral fixation in total hip arthroplasty (THA) has increased in prevalence worldwide. However, cementless fixation in elderly patients is controversial due to the risks of periprosthetic fracture and aseptic loosening. This study evaluated outcomes in patients undergoing primary THA utilizing a cementless stem without a collar, comparing those less than 75 years to those older than 75 years.

METHODS

Between 2011 and 2021, there were 2,605 cementless THAs performed by 4 surgeons utilizing a highly porous metal fixation surface without a collar and consistent clinical protocols. There were 469 patients who had an age ≥ 75 years. Revision rates, intraoperative fractures, and 90-day mortality were compared between cohorts. In the ≥ 75 year age group, there were more women, more American Society of Anesthesiologists physical status classification III or IV, a lower body mass index, and more kidney disease, osteoporosis, and thyroid disease (P ≤ .002).

RESULTS

All-cause revision rates trended lower for the ≥75 year age group compared to < 75 year (1.9 versus 3.5%, P = .082) at 20-months of follow-up. Moreover, there was no difference in all-cause femoral component revisions comparing ≥ 75 to < 75 year age groups (1.5 versus 2.2%, P = .375), with only 3 of 10 femoral revisions due to aseptic loosening being in the ≥ 75 year age group. Intraoperative fracture (0.2 versus 0.5%, P = .701) and 90-day mortality (0.2 versus 0.1%, P = .460) did not differ between ≥ 75 and < 75 year age groups.

CONCLUSIONS

Older patients had comparable revision rates compared to younger patients using cementless femoral fixation without a collar. Furthermore, there was no difference in 90-day mortality or intraoperative fracture rates. Study findings provide evidence for the safety and durability of cementless THA using collarless femoral stems in elderly patients ≥ 75 years of age.

LEVEL OF EVIDENCE

III.

Retrospective clinical and X-ray-based outcome analysis of a short-stem hip arthroplasty taking into account the operative learning curve over 7 years in the 3-year control course

INTRODUCTION

Self-monitoring is crucial to work progressively with a high-quality standard. A retrospective analysis is a valuable tool for studying the postoperative outcome of a prosthesis and for evaluating the learning process for the surgeon.

MATERIALS AND METHODS

The learning process of one surgeon was analysed in 133 cases of hip arthroplasty. These were divided into seven groups representing the surgical years 2008-2014. Over the course of 3 postoperative years, a total of 655 radiographs were analysed at regarding three radiological quality parameters (centrum-collum-diaphyseal angle (CCD angle), intramedullary fit&fill ratio (FFR), and migration) and ancillary outcome parameters (Harris Hip Score (HHS), blood loss, operating time, and complications). This period was divided into five times: 1st-day post-op, 6 M, 12 M, 24 M, and 36 M. Bivariate Spearman's correlation analysis and pairwise comparisons were performed.

RESULTS

The total collective achieved a proximal FFR of over 0.8. The distal prosthesis tip migrated and was located on the lateral cortex within the first months. The CCD angle initially showed a variation with a subsequent constant course. The HHS showed a significant increase (p < 0.001) to over 90 points postoperatively. Over time, the operating time and blood loss decreased. Intraoperative complications existed only at the beginning of the learning phase. A learning curve effect can be determined for almost all parameters by comparing the subject groups.

CONCLUSIONS

Operative expertise was shown to gain through a learning curve, whereby postoperative results corresponded to the system philosophy of the short hip stem prosthesis. The distal FFR and the distal lateral distance could represent the principle of the prosthesis, which overall could be an interesting approach for verification of a new parameter.

The Use of a High Offset Fully Coated Collarless Cementless Stem Does Not Result in Early Failures in Total Hip Arthroplasty

INTRODUCTION

The Corail femoral stem has excellent long-term survivorship in total hip arthroplasty (THA). However, there remains a paucity of information on the specific performance of the high offset collarless stem in relation to subsidence, loosening, offset, and failure rates.

METHODS

Retrospective data were collected on all consecutive high offset collarless Corail stems implanted at a single centre in the UK. Data included patient demographics, femoral Dorr classification, radiographic analysis for radiolucent lines, and stem subsidence. The postoperative femoral offset was measured against the native offset of the contralateral hip. Any early failures, re-operations, or requirements for revision surgery were recorded.

RESULTS

We identified 162 stems for inclusion in the study. Ninety-five patients were male. The mean age was 60.5 (40 to 78) years, and the mean BMI was 29.8 (21 to 50) kg/m2. The mean length of follow-up was 84.5 (12-130) months. Subsidence was recorded on 113 (69.7%) stems. The mean amount of total stem subsidence in the whole cohort was 1.62mm (0 to 3.9mm). There was no correlation between the amount of subsidence and the preoperative Dorr classification, age, sex, BMI, or indication for surgery. Radiolucent lines were exclusively seen in stems paired with a large-diameter 36-mm femoral head. The high offset stem accurately reproduced native femoral offset; the mean difference in offset was -1.21mm (-24mm to +21mm). There were no early failures, re-operations, or revision surgeries.

CONCLUSION

The use of a high offset stem can accurately reproduce native femoral offset when chosen for THA. The high offset collarless Corail stem does not result in early failures in THA, and we support its use.

Mid-Term Migration Behavior of an Uncemented Proximally Anchored Straight Stem-A Retrospective EBRA Migration Analysis

BACKGROUND

Aseptic loosening is one of the most-common causes of the failure of cementless stems. Einzel Bild Röntgen Analyse-Femoral Component Analysis (EBRA-FCA) allows the diagnosis of stem migration, which can be considered a factor in predicting implant survival. The current study aimed to present the migration behavior of a tapered proximally anchored straight stem.

METHODS

This retrospective study reviewed all consecutive patients who received a cementless CBC straight stem (Mathys AG, Bettlach, Switzerland) between 2005 and 2019. We analyzed the migration pattern using the EBRA-FCA software and reviewed their medical histories. In addition, periprosthetic radiolucency was rated according to the Gruen zones and femoral configuration according to Dorr.

RESULTS

A total of 333 stems in 332 patients (female 191; male 141) met our inclusion criteria. The mean age at surgery was 63 (range 21-87) years. Migration analysis by EBRA-FCA showed a mean subsidence of 1.6 mm at final follow-up at 96 months with a maximum noted mean subsidence of 2.0 mm at 72 and 84 months. Dorr Type A showed a tendency of less subsidence than did Dorr Type B and was statistically significant at 6 (p = 0.0396) and 72 months (p = 0.0127). The body mass index (BMI) and increased subsidence were not found to correlate (p > 0.05). For this cohort, the overall femoral revision-free rate was 95.2% and the revision-free rate for aseptic loosening was 99.1%.

CONCLUSIONS

The results showed migration behavior in cementless stems with initial increased migration and subsequent secondary stabilization, suggesting an excellent long-term outcome. Stem migration of this tapered proximally anchored stem might be lower in Dorr Type A than in Dorr Type B femurs without being statistically significant at all time points.

Subsidence of a Single-Taper Femoral Stem in Primary Total Hip Arthroplasty: Characterization, Associated Factors, and Sequelae

BACKGROUND

We characterized subsidence of an uncemented single-taper femoral stem in primary total hip arthroplasty (THA), determined factors associated with subsidence, and evaluated the impact of subsidence on outcome.

METHODS

This retrospective study included 502 primary THAs performed using a single-taper stem in Dorr type A and B femora between 2014 and 2018. Subsidence was measured based on distance from the greater trochanter to stem shoulder on calibrated X-rays. Demographics, case-specific data, and outcomes were collected. Changes in subsidence and variables associated with subsidence were determined.

RESULTS

Stem subsidence was 1.5 ± 2.3 mm, 1.6 ± 2.0 mm, 2.0 ± 2.6 mm, 2.3 ± 2.3 mm, 2.6 ± 2.5 mm, and 2.7 ± 3.0 mm at 6 weeks, 3 months, 6 months, 1 year, 2 years, and ≥3 years from THA, respectively. Subsidence across all patients at final mean follow-up of 24 months (range, 1 to 101 months) was 2.2 ± 2.6 mm. Pairwise comparison demonstrated that subsidence occurred predominantly within the first 6 months. Significant subsidence (≥5 mm) occurred in 17.3% and was associated with a body mass index (BMI) ≥25 (P=0.04). Dorr type, age, sex, and American Society of Anesthesiologists class were not associated with subsidence. There were two patients (0.4%) who underwent a revision that could be attributed to subsidence. There was no association between subsidence and pain, limp, need for ambulatory aid, or analgesic use.

CONCLUSION

In primary THAs performed using a single-taper prosthesis, average subsidence was 2.2 mm and significant subsidence occurred in 17.3%. Patient BMI was associated with subsidence. Revision surgery related to subsidence was infrequent (0.4%).

Penalty for Switching Implants? Assessing the Learning Curve With a Collarless, Tapered Wedge Cementless Femoral Component

Background

Surgeon learning curve associated with a tapered wedge femoral implant as measured by early femoral component subsidence and 90-day risk of reoperation was evaluated.

Methods

The first 451 patients undergoing primary, cementless total hip arthroplasty by a single, fellowship-trained arthroplasty surgeon with a tapered wedge stem design were retrospectively reviewed. Early radiographic femoral component subsidence during the first 6 weeks postoperatively and 90-day reoperations was recorded.

Results

When stratified by approach, there was no association between date of surgery and femoral component subsidence in the posterior approach (P-value for linear trend over time = 0.44). In the direct anterior approach, there was a significant association between date of surgery and early femoral component subsidence (P-value for linear trend over time = 0.01). For both approaches, there was an increase in implanted stem size relative to templated stem size over time (P < .01 and P = .03, respectively). There was no association between the date of surgery and risk of 90-day reoperation (P = .45).

Conclusions

In a single surgeon's initial use of a tapered cementless wedge stem, early femoral component subsidence was not impacted by the surgeon's learning curve when the posterior approach was utilized. Although subsidence was associated with date of surgery in the direct anterior cohort, this was not associated with increased risk of 90-day reoperation. Should a surgeon adopt a new tapered-wedge stem, these findings suggest that the stem is forgiving both in relation to subsidence and 90-day reoperation risk when appropriate surgical technique is utilized.

A New Classification System for Cementless Femoral Stems in Total Hip Arthroplasty

BACKGROUND

The growing variety of total hip arthroplasty implants necessitates a standardized, simple, and brand-neutral language to precisely classify femoral components. Although previous classifications have been useful, they need updating to include stems that have current surface treatment technologies, modularity, collar features, and other geometric characteristics.

METHODS

To accomplish this, we propose a new classification system for stems based on 3 distinguishing stem features: (1) geometry, (2) location of modularity, and (3) length.

RESULTS

Our system allows for the easy classification of all currently used stem types.

CONCLUSIONS

One goal of this endeavor is to improve clinical record keeping to facilitate study comparisons as well as literature reviews.

Taper-wedge stem suitable for anterior approach total hip arthroplasty: Adequate biomechanical reconstruction parameters and excellent clinical outcome at mid-term follow-up

BACKGROUND

The direct anterior approach (DAA) for total hip arthroplasty (THA) is a less invasive and muscle-sparing approach that seems to improve early function and patient satisfaction. Several studies, however, have reported high complication and revision rates due to the technical difficulties related to the femoral preparation.

AIM

To evaluate the usefulness and safety of a new stem equipped with a morphometric design and a size-specific medial curvature in DAA for THA.

METHODS

This retrospective study was based on 130 patients that underwent mini-invasive DAA procedures for THA using the Accolade II stem. A total of 144 procedures were included in the assessment, which was based on postoperative complications, survival rates, functional parameters, and patient related outcomes.

RESULTS

Overall complications were recorded in 6 procedures (4.2%). There were no complications related to the stem implantation and no intraoperative fractures. Only one patient was revised for deep infection. On radiographs, biomechanical hip reconstruction was satisfactory and no stem showed any subsidence greater than 2 mm. Full osseointegration based on Engh scores was seen in all of the implanted stems. Median Harris hip score at final follow-up was 99 points (range 44-100 points), which resulted excellent in 91.3% of patients. The median values of the osteaorthritis outcome score ranged from 87.5 to 95.

CONCLUSION

The mid-term positive outcomes and low complication rate in our consecutive series of patients support the safety and suitability of this new stem design in DAA for THA.

Single Wedge Femoral Stem Designs are Associated With a Higher Risk for Revision After Cementless Primary Total Hip Arthroplasty

BACKGROUND

Cementless total hip arthroplasty (THA) femoral stems are the most commonly selected prostheses in the United States. Optimal stem geometry remains controversial with excellent survivorship reported for many designs. We compared cause-specific stem revision of single-wedge versus double-wedge designs from a multicenter US cohort.

METHODS

Data from an integrated healthcare network's total joint replacement registry were used to conduct a cohort study. Primary elective cementless THAs were identified (2001 to 2018). Implant exposure groups were classified by design geometry using the system proposed by Khanuja et al. Type 1 single-wedge (n = 11,082) and type 2 double-wedge (n = 32,380) designs were compared, and other design types were excluded; the final study cohort comprised 43,462 THAs. Cause-specific multivariable Cox regressions were used to evaluate risk for revision due to infection or aseptic reasons, including loosening, instability, periprosthetic fracture, or other reasons.

RESULTS

After adjustment for covariates, a higher aseptic revision risk was observed for type 1 when compared to type 2 designs (hazard ratio = 1.91, 95% confidence interval = 1.33-2.75). When looking at specific revision reasons, revision for aseptic loosening (hazard ratio = 3.46, 95% confidence interval = 2.24-5.34) was higher for type 1 versus type 2 designs. No differences were found for septic revision, instability, periprosthetic fracture, or revisions for other reasons.

CONCLUSIONS

Type 1 single-wedge designs were found to have a higher risk of revision due to aseptic loosening relative to type 2 double-wedge designs. Femoral stem geometry should be considered when selecting a cementless femoral implant.

LEVEL OF EVIDENCE

Level III.

Insufficient lateral stem contact is an influencing factor for significant subsidence in cementless short stem total hip arthroplasty

BACKGROUND

Subsidence is one of the concerning early complications in cementless femoral stem. Few publications have studied the influencing factors for subsidence in short cementless stems, due to their metaphyseal anchoring without diaphyseal invasion, they might demonstrate different subsidence patterns than with the conventional stems.

AIM

To analyze the factors associated with significant subsidence in short stems, including any radiographic parameters.

METHODS

The digitized radiographs of 274 consecutive short stem total hip arthroplasties were retrospectively reviewed. Subsidence, neck-filling ratio (NFR), seating height and lateral stem contact were evaluated after a minimum of two years follow-up. A threshold of subsidence > 3 mm was considered a clinically significant migration.

RESULTS

For the entire cohort, subsidence occurred in 75 cases (27.4%) with the mean stem subsidence of 0.5 mm. (0-12.7, 1.68). Twelve hips (4.4%) had significant subsidence (> 3 mm). The univariate regression analysis demonstrated that age, diagnosis, BMI, Dorr’s type B, NFR, and seating height had no significant influence on significant subsidence, whereas insufficient lateral stem contact (≥ 1 mm) did have a statistically significant influence [Odds ratio (OR) = 5.02; 95%CI: 1.3-18.9; P = 0.017]. The multivariate regression analysis also demonstrated that insufficient lateral stem contact was a statistically significant influencing factor (OR = 5.5; 95%CI: 1.4-21.4; P = 0.014). There was no femoral stem revision for aseptic loosening in our cohort.

CONCLUSION

This study demonstrated that insufficient lateral stem contact was a statistically significant influencing factor on significant subsidence. Therefore, it is a particularly important step to create proper lateral cortical contact when performing the short stem total hip arthroplasty.

Tapered wedge stems decrease early postoperative subsidence following cementless total hip arthroplasty in Dorr type C femurs compared to fit-and-fill stems

Background

To compare the degree of stem subsidence between two different femoral component designs and to determine the risk factors associated with stem subsidence after cementless total hip arthroplasty (THA) in Dorr type C femurs.

Methods

We retrospectively reviewed 104 consecutive hips in 100 patients with Dorr type C proximal femoral morphology who underwent primary cementless THA using a fit-and-fill stem or a tapered wedge femoral stem at our institution between January 2012 and June 2021. A fit-and-fill stem was used in 55 hips and a tapered wedge stem was used in 49 hips. Radiologically, the distance between the apex of the major trochanter and the stem shoulder were measured at three different time points (immediately [0W], one week [1W], and six weeks [6W] after surgery) and the degrees of stem subsidence were assessed by comparing the distance between 0 and 1W, 1W and 6W, and 0W and 6W, respectively.

Results

The mean degree of stem subsidence (0W vs. 1W) was 0.24 mm (standard deviation [SD] 0.36) in the fit-and-fill stem group, and 0.23 mm (SD 0.41) in the tapered wedge stem group. There was no significant difference between the two groups (P = 0.4862). However, the mean degrees of subsidence were significantly higher in the fit-and-fill stem group (1W vs. 6W, 0.38 mm [SD 0.68]; 0W vs. 6W, 0.65 mm [SD 0.87]) than in the tapered wedge stem group (1W vs. 6W, 0.16 mm [SD 0.32]; 0W vs. 6W, 0.24 mm [SD 0.38]) (P < 0.05 for both). In addition, the rates of > 3 mm subsidence (in which instability can be observed) were 18.2% (10 of 55 hips) and 2.0% (1 of 49 hips), respectively. There was also a significant difference between the two stems (P = 0.0091). Multivariate analysis demonstrated that fit-and-fill stem was a risk factor for > 3 mm subsidence after THA in Dorr type C femurs (P = 0.0050).

Conclusion

Our findings suggest that the tapered wedge stem is more suitable for Dorr type C femurs than the fit-and-fill stem to avoid early postoperative subsidence in cementless THA.

Pneumatic femoral broaching decreases post-operative subsidence of a cementless taper-wedge stem

PURPOSE

Stem subsidence is a known cause of early failure in cementless total hip arthroplasty (THA). The aim of this study was to determine the usefulness of pneumatic femoral broaching in preventing post-operative subsidence of a proximally porous-coated, taper-wedge stem.

METHODS

We reviewed 169 cases of primary THA with a single taper-wedge stem. Eighty THAs performed using pneumatic broaching were compared with 89 THAs performed using manual broaching in terms of postoperative canal fill ratio (CFR) at three levels, stem subsidence at one year post-operation, and stem fixation at latest follow-up (median, 24 months).

RESULTS

The median CFRs were higher in the pneumatic group than in the manual group at all levels (p < 0.05). The median stem subsidence at one year after THA was lower in the pneumatic group than in the manual group (0.2 mm vs. 0.6 mm, p = 0.007). A multivariate analysis determined a decreased CFR at 60 mm below the lesser trochanter and the manual broaching as independent factors affecting post-operative stem subsidence. At the latest follow-up, all stems showed stable fixation by bone ingrowth in both groups.

CONCLUSION

Our results showed that the pneumatic broaching device was useful in maximizing the mediolateral canal filling and initial stability and minimizing the subsidence of taper-wedge stems.

The fate of sagittal alignment in tapered uncemented femoral components in total hip arthroplasty: 889 hips followed for a minimum of 10 years

PURPOSE

Aseptic loosening is rare after primary total hip arthroplasty (THA) with mostly uncemented tapered stems; however, different factors can modify the results. We question whether 3 different current femoral components and/or the surgical technique affect the clinical and radiological outcome after a minimum follow-up of 10 years.

METHODS

889 uncemented tapered stems implanted from 1999 to 2007 were evaluated for a minimum follow-up of 10 years. Group 1 (273 hips) shared a conical shape and a porous-coated surface, group 2 (286 hips) a conical splined shape and group 3 (330 hips) a rectangular grit-blasted stem. Groups 1 and 2 were implanted through a posterolateral approach and group 3 using an anterolateral approach. Clinical outcomes and anteroposterior and sagittal radiographic analyses were compared.

RESULTS

No thigh pain was reported in unrevised patients. Mean Harris Hip score was lower for patients in group 3 for pain and function at all intervals. 14-year implant survival for aseptic loosening was 98.2% (95% confidence interval [CI] 96.2-100) in group 3. No revision for aseptic loosening was found with the other designs. A stem position outside neutral limits in the sagittal alignment (p = 0.001, hazard ratio: 6.17, 95% CI, 2.05-18.61) was associated with aseptic loosening in group 3.

CONCLUSIONS

Most current uncemented straight tapered femoral components can provide adequate bone fixation in primary THA after 10 years. Conical stems inserted through a posterolateral approach are more reliable than rectangular ones inserted through an anterolateral approach.

Volumetric Bone Mineral Density in Cementless Total Hip Arthroplasty in Postmenopausal Women: Effects on Primary Femoral Stem Stability and Clinical Recovery

BACKGROUND

In cementless total hip arthroplasty, femoral stems should preferably not migrate at all postoperatively. This goal is difficult to achieve in postmenopausal women with impaired bone quality. Here, we explored the clinical importance of initial stem migration, measured by radiostereometric analysis (RSA), in women who underwent quantitative computed tomography (CT) of the involved hip preoperatively.

METHODS

A prospective cohort of 65 postmenopausal women (mean age, 69 years) with hip osteoarthritis and Dorr type-A or B femoral anatomy underwent total hip arthroplasty with implantation of a tapered, single-wedge femoral stem. Volumetric bone mineral density (BMD) was measured using quantitative CT. Femoral stem translation and rotation were measured using model-based RSA within 3 days after the surgical procedure and were repeated at 3, 5, and 11 months. Postoperative recovery parameters included walking speed, walking activity, and patient-reported outcome measures. Subjects were categorized into 2 groups according to the magnitude of initial 5-month stem subsidence (<2 mm or ≥2 mm); RSA outliers (n = 7) were analyzed separately.

RESULTS

Subjects with stem subsidence of ≥2 mm (mean, 3.09 mm [95% confidence interval (CI), 2.70 to 3.47 mm]) had lower intertrochanteric volumetric BMD (p = 0.008). Subjects with subsidence of <2 mm (mean, 0.80 mm [95% CI, 0.51 to 1.09 mm]) had faster improvement of patient-reported outcome measures and exhibited faster walking speed (p = 0.007) and greater walking activity (p = 0.010) at 11 months as well as better Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores (p = 0.002) and RAND 36-Item Health Survey mental component scores (p = 0.006) at 2 years. All cohort stems were osseointegrated at 2 years.

CONCLUSIONS

Femoral stem stability and resistance to subsidence were sensitive to adequate intertrochanteric volumetric BMD. Low intertrochanteric volumetric BMD was associated with greater stem migration. With initial migration, clinical recovery was slower and patient-reported outcome measures were less satisfactory.

LEVEL OF EVIDENCE

Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Mid-Term Survivorship, Performance, and Predictors of Outcome in Primary Total Hip Arthroplasty With a Porous Tantalum Femoral Prosthesis

BACKGROUND

Femoral stem subsidence is a known cause of early implant failure, increasing the risk for aseptic loosening and periprosthetic fracture. Overall survivorship and subsidence in a novel porous tantalum-coated femoral prosthesis have not been well-studied.

METHODS

Consecutive patients undergoing primary total hip arthroplasty with a porous tantalum-coated femoral prosthesis between January 2008 and January 2015 with minimum 5-year follow-up were included. Clinical and radiographic data were obtained from hospital and office records. Multivariate logistic regression analyses were used to determine predictors of subsidence and clinical outcomes. Kaplan-Meier survivorship curves were performed to illustrate primary failure endpoints of (1) all-cause revision and (2) femoral prosthesis revision.

RESULTS

A total of 398 patients with a mean (±standard deviation) age of 61.0 ± 11.5 years, body mass index (BMI) 32.8 ± 8.0 kg/m², and follow-up of 6.9 (range 5.0-11.2 years) were included. Survivorship at 5 years was 94.9% for all-cause revision and 98.0% for femoral component revision. Average subsidence was 1.8 ± 1.3 mm (range 0-15.5), with 8.1% patients experiencing subsidence >5 mm. Statistically significant mean improvements were observed at latest follow-up in the Hip Disability and Osteoarthritis Outcome Score Joint Replacement (40.6 ± 11.5 vs 85.2 ± 10.1, P < .001), Harris Hip Score (38.0 ± 12.0 vs 79.5 ± 12.8, P < .001), and hip flexion (92.8° ± 15.3° vs 103.3° ± 10.3°, P < .001). Multivariate logistic regression analyses revealed that greater BMI (odds ratio [OR] 1.17, P < .001), non-white/Caucasian race (OR 2.0, P = .036), and female gender (OR 2.4; P = .005) conferred a higher likelihood of subsidence >3 mm. BMI was a statistically significant and independent predictor of subsidence >5 mm (OR 1.25, P < .001) and subsidence >7 mm (OR 1.25, P < .001).

CONCLUSION

The trabecular metal taper femoral prosthesis conferred excellent clinical outcome improvement and survivorship. Increasing BMI was independently associated with an increased risk of subsidence in these patients and caution is recommended in utilizing this implant in obese, morbidly obese, and super morbidly obese populations.

Contributing factors to the initial femoral stem migration in cementless total hip arthroplasty of postmenopausal women

In cementless total hip arthroplasty (THA), femoral stems rely on the initial press-fit fixation against cortical bone to achieve osseointegration. Decreased bone mineral density (BMD) in postmenopausal women poses natural difficulties in achieving axial and rotational femoral stem stability. The present study examined contributing demographic, surgery-related and postoperative factors in determining the magnitude of early stem migration prior to osseointegration. A prospective cohort of 65 postmenopausal women with hip osteoarthritis (Dorr type A or B femur anatomy) underwent THA with implantation of an uncemented parallel-sided femoral component. Postoperative femoral stem translation and rotation were measured using model-based radiostereometric analysis. Based on analysis of covariance, which controlled for outliers and randomized antiresorptive treatment with denosumab or placebo, none of the analyzed demographics (including BMI) and surgery-related variables (including the stem-to-canal fil ratio) was associated with stem subsidence. Stem subsidence (mean 1.8 mm, 95% CI 1.2 to 2.4) occurred even in women with normal hip BMD. Total hip BMD and postoperative walking activity (measured three months after surgery) were significantly associated with stem rotation, and height acted as a confounding factor. The effect of walking activity on stem rotation was significant at 5 months (p = 0.0083) and at 11 months (p = 0.0117). This observation confirms the previous results of instrumented hip prostheses on torsional moments affecting stems during daily activities. High-resolution imaging modalities of local bone quality are needed to explore reasons for RSA-measurable stem subsidence even in women with normal hip BMD.

Outcomes of Cerclage Cabling for Intraoperative Calcar Cracks in Cementless Total Hip Arthroplasty Using Broach-Only, Tapered Wedge Stems

BACKGROUND

Intraoperative femoral fractures are well-known but often overlooked complications in total hip arthroplasty (THA). We examined outcomes of cerclage cabling for intraoperative calcar cracks in THA with cementless tapered wedge stems.

METHODS

In total, 4928 primary THAs were performed using broach-only, tapered wedge stems between January 2007 and November 2017 in a single institution. Of these, we identified 71 intraoperative calcar cracks (69 patients) managed by 2-mm cerclage cables. Clinical outcomes, amount of stem subsidence, and implant survivorship of the calcar crack group (68 THAs) were compared with those of the matched control group (68 THAs) without intraoperative fractures. Multivariate analysis was performed to identify potential risk factors for stem subsidence >3 mm.

RESULTS

The mean stem subsidence was greater in the calcar crack group (2.0 vs 1.2 mm, P = .021), whereas revision-free survivorships of THA were similar between groups at 6 years (98.5% vs 98.4%; log-rank, P = .987). In the calcar crack group, a Dorr type C femur and the absence of cabling proximal to the lesser trochanter (LT) were identified as independent risk factors for stem subsidence >3 mm. For the subgroup with 42 calcar cracks managed by a single cable applied proximal to the LT, revision-free survivorship of THA was 100% at 6 years. There was no complete radiolucency to indicate aseptic stem loosening in either group.

CONCLUSION

The application of a single cable proximal to the LT of the femur for intraoperative calcar cracks demonstrated 100% revision-free survivorship with lower stem subsidence in THA with tapered wedge stems.

Inadequate Metadiaphyseal Fill of a Modern Taper-Wedge Stem Increases Subsidence and Risk of Aseptic Loosening: Technique and Distal Canal Fill Matter!

BACKGROUND

Adequate interference fit and mechanical stability through optimal surgical technique are essential to prevent subsidence and loosening in cementless total hip arthroplasty. The purpose of this study is to determine the effect of surgical technique on radiographic subsidence and subsequent stability of a modern taper-wedge cementless stem.

METHODS

A retrospective review of 250 consecutive cementless primary total hip arthroplasties performed by 2 surgeons was completed. Surgeon A vigorously broached, maximizing the mediolateral stem dimension and confirmed final broach stability with a torsional test, whereas Surgeon B did not. All patients received identical taper-wedge stems. Preoperative bone morphology (canal flare index), postoperative subsidence, and canal fill were radiographically assessed.

RESULTS

Canal flare index was not different between groups (P = .747). There was significantly less subsidence at 1 month for Surgeon A (0.3 vs 1.3 mm, P < .001). Additional subsidence at 1 year occurred in only 0.8% of Surgeon A (1/119) compared to 51.6% of Surgeon B stems (33/64, P < .001). Surgeon technique and canal fill measured at 60 mm below the lesser trochanter were the only variables predictive for subsidence, where Surgeon A and B had a mean canal fill of 95% and 86%, respectively. Surgeon B had 2 cases of aseptic loosening (2%) at 2 and 3 years postoperatively.

CONCLUSION

These observations support that maximizing mediolateral canal fill and avoiding under-sizing the femoral implant with meticulous broaching technique minimizes subsidence and optimizes stability of modern cementless taper-wedge stems. Failure to optimize canal fill with appropriate broaching and surgical technique may predispose femoral components to failure from aseptic loosening.

Bone Mineral Density and Cortical-Bone Thickness of the Distal Radius Predict Femoral Stem Subsidence in Postmenopausal Women

BACKGROUND

The distal radius is an optional site for evaluation of bone quality in postmenopausal women before cementless total hip arthroplasty. We hypothesized that dual-energy X-ray absorptiometry (DXA) and pulse-echo ultrasonometry of the distal radius may help discriminate subjects at high risk of femoral stem subsidence.

METHODS

A prospective cohort of postmenopausal women with primary hip osteoarthritis underwent total hip arthroplasty with implantation of a parallel-sided femoral stem. Postoperative stem migration was measured using radiostereometric analysis. Preoperatively, subjects had multisite DXA measurement of bone mineral density (BMD) and pulse-echo ultrasonometry of the cortical-bone thickness. The diagnostic abilities of these methods to discriminate <2 mm and ≥2 mm femoral stem subsidence were tested.

RESULTS

The accuracy of the distal radius BMD and cortical-bone thickness of the distal radius were moderate (area under the curve, 0.737 and 0.726, respectively) in discriminating between <2 mm and ≥2 mm stem subsidence. Women with low cortical-bone thickness of the radius were more likely (odds ratio = 6.7; P = .002) to develop stem subsidence ≥2 mm. These subjects had lower total hip BMD (P = .007) and reduced thickness of the medial cortex of the proximal femur (P = .048) with lower middle (P < .001) and distal (P = .004) stem-to-canal fill ratios.

CONCLUSION

Femoral stem stability and resistance to subsidence are sensitive to adequate bone stock and unaltered anatomy. DXA and pulse-echo ultrasonometry of the distal radius may help discriminate postmenopausal women at high risk of stem subsidence.

Predictors of Perioperative Vancouver B Periprosthetic Femoral Fractures Associated With the Direct Anterior Approach to Total Hip Arthroplasty

BACKGROUND

There is an association between intraoperative and postoperative femoral fractures and the direct anterior approach (DAA) to total hip arthroplasty (THA). The purpose of our study is to identify risk factors for Vancouver B fractures and to establish a predictable timeline for when these occur.

METHODS

We retrospectively identified patients with Vancouver B periprosthetic femoral fractures (n = 49) after 11,509 elective primary cementless THA procedures through the DAA between 2012 and 2018 at a single institution. Fracture patients were matched to nonfracture patients (n = 267) by date of surgery and surgeon. Clinical and radiographic factors were collected for multivariable analysis to identify predictors of fracture.

RESULTS

Periprosthetic Vancouver B femoral fracture incidence was 0.4%. 48 (98%) fractures were postoperative. Fractures occurred at an average of 44 days after surgery (range: 1 to 653 days) with >85% of fractures occurring in the first 6 weeks postoperatively. Significant variables predictive of fracture included >3 degrees valgus and >5 degrees varus coronal stem malalignment, Dorr B and C femoral geometry, lower canal flare index (2.75 vs 3.20), advanced age, increased comorbidities, greater stem canal fill, and right-sided procedures.

CONCLUSION

Despite an overall low rate of Vancouver B perioperative periprosthetic femoral fractures, it is a devastating complication that typically presents within the first 6 weeks after DAA THA surgery. The risk is increased in patients with unfavorable proximal femoral geometry, coronal stem malalignment, advanced age, increased comorbidities, and right-sided procedures.

An increase in the risk of excessive femoral anteversion for relatively younger age and types of femoral morphology in total hip arthroplasty with direct anterior approach

BACKGROUND

Direct anterior approach (DAA) is known to diminish a dislocation risk and widely used for total hip arthroplasty (THA). On the other hand, anterior dislocation due to increasing stem anteversion and cup anteversion is an important complication.

METHODS

A retrospective analysis of 140 (male/female: 10/130) consecutive patients with 149 hips who had undergone primary THA in the period between 2011 and 2015 was conducted. Factors including age, gender, body mass index (BMI), and primary diagnosis were examined. Radiographic parameters including the Dorr proximal femoral types, cortical thickness index (CTI), canal flare index (CFI), and canal to calcar index were measured. To investigate relationships of combined anteversion (CA) with other factors, a stepwise regression analysis was performed.

RESULTS

The mean age, BMI, and the follow-up period were 69.5 ± 10.3 years old, 23.4 ± 3.4 kg/m², and 48.2 ± 13.6 months, respectively. The proximal femurs of the 149 hips were categorized as Dorr type A ( n = 33), type B ( n = 110), and type C ( n = 6). The mean CTI, CFI, and canal to calcar index were 0.56 ± 0.08, 4.15 ± 0.83, and 0.46 ± 0.09, respectively. The mean stem varus angle, radiographic inclination, and radiographic anteversion of the cup were 0.19 ± 1.63, 40.9 ± 6.0°, and 12.7 ± 3.5°, respectively. Stem anteversion measured by computed tomography (CT) axial image was 17.7 ± 12.0°. The mean radiographic inclination, radiographic anteversion (CTRA), and anatomical anteversion analyzed by Kyocera 3-D template were 40.8 ± 7.2°, 19.8 ± 6.6°, and 28.8 ± 10.0°, respectively. Mean CA defined as the sum of stem anteversion and CTRA was 37.5 ± 14.5°. To investigate relationships of CA with other factors, a stepwise regression analysis was performed and resulted in a model with age ( p < 0.001). In the same way, stem anteversion and CTRA were analyzed; only for the stem anteversion, the stepwise selection process resulted in a model with age ( p < 0.001) and the Dorr types ( p = 0.047).

CONCLUSION

The risk of excessive femoral anteversion increases for relatively younger age and for types of femoral morphology according to the Dorr classification, moreover with an increase of CA in DAA-THA with cementless tapered-wedge stem.

Partial implant retention in two-stage exchange for chronic infected total hip arthroplasty

BACKGROUND

The efficacy of partial retention of well-fixed components during two-stage exchange for chronic total hip arthroplasty (THA) infection has remained unknown.

METHODS

A total of 14 patients with chronic infected THA were treated with damage control two-stage revision, including selective retention of the well-fixed femoral or acetabular component, aggressive debridement, antibiotic-laden cement spacer, antibiotic therapy, and delayed reimplantation. Indications for this treatment included chronic infected THAs with ingrown femoral or acetabular component and positive microbial growth with sensitive antibiotics. We excluded patients with acute infection; negative microbial growth; positive pathogen with high-virulence bacterial infections and multiple drug-resistant bacteria such as methicillin-resistant Staphylococcus aureus, fungi, and Mycobacterium tuberculosis; sinus formation; a prior failure for periprosthetic joint infection (PJI) treatment; and obvious bone resorption in both femoral and acetabulum side. During the study period, this represented 3.3% (14/425) of the patients treated for infected THA. Minimum follow-up was three  years. None of the 14 patients in this series were lost to follow-up. Successful treatment was defined according to a modified Delphi-based international multidisciplinary consensus.

RESULTS

No repeated debridement and recurrence of infection occurred during the study period; no patient need chronic antibiotic suppression. Successful treatment of chronic PJI was achieved in all patients. Despite the high peri-operative complication rate, no severe consequences were observed. The mean Harris Hip Score was 86 (range, 82-92; SD, 3.3).

CONCLUSIONS

The selective partial implant retention two-stage revision for chronic PJI may be a treatment option in properly selected patients with low virulence bugs.

Subsidence of Hydroxyapatite-Coated Femoral Stem in Dorr Type C Proximal Femoral Morphology

BACKGROUND

Good bone quality and proper proximal femoral morphology are thought to be necessary for tapered design, cementless femoral stems to resist subsidence. Using tapered, cementless stem for patients with stovepipe morphology or Dorr type C is controversial. The purpose of this study is to analyze (1) subsidence of the fully hydroxyapatite (HA)-coated, tapered, cementless stem in different morphology according to Dorr classification, (2) subsidence of the stem related to radiographic canal-fill ratio.

METHODS

The digitized radiographs of 311 consecutive cementless primary total hip arthroplasty with fully HA-coated, tapered stem were retrospectively reviewed. Subsidence and the canal-fill ratio at 4 locations were evaluated postoperatively after a minimum of 2 years of follow-up. The threshold of subsidence >3 mm was considered as a clinically significant migration.

RESULTS

A multivariate regression analysis of subsidence across Dorr type, controlling for age, gender, and intraoperative calcar fracture, demonstrated 0.40 mm (P = .28) and 0.18 mm (P = .51) greater subsidence in Dorr type C and B when compared to Dorr type A. Age, gender, and calcar fracture had no influence on subsidence, whereas greater canal-fill ratio at 2 cm below lesser trochanter resulted in significantly less subsidence (P = .02). Additionally, all variables did not affect the risk of having subsidence >3 mm.

CONCLUSION

The proximal femoral morphology has no statistically significant effect on the subsidence of fully HA-coated stem. Therefore, this stem type might be a viable option for Dorr type C. Increasing the canal-fill ratio at metadiaphyseal junction may ensure the stability of the stem.

The Use of Extended Trochanteric Osteotomy in 2-Stage Reconstruction of the Hip for Infection

BACKGROUND

The effect of extended trochanteric osteotomy (ETO) with immediate cerclage wire fixation on the scene of chronic periprosthetic joint infection on infection eradication and the osteotomy healing remains unclear.

METHODS

One hundred seventeen patients who underwent two-stage revision total hip arthroplasty for chronic periprosthetic joint infection were enrolled in the study. The minimum follow-up was 2 years. Of these, 48 patients had underwent ETO and immediate cerclage wire fixation during the first-stage surgery, while 69 did not undergo ETO or any other osteotomy. In addition, 18 patients had underwent ETO in the second-stage reimplantation surgery. Repeated debridement, curative rate of infection, and complications were compared between the 2 groups. Meanwhile, osteotomy healing between the first and second osteotomy were also compared.

RESULTS

The repeated debridement rate and curative rate of infection were 2.1% and 95.8% in the ETO group, compared with 13.0% and 82.6% in the non-ETO group; there were significant difference between the 2 groups in these parameters (P = .037 and .030, respectively). Meanwhile, osteotomy healing rate was 93.8% in first-stage surgery with infection scene and 100% in second-stage surgery without infection; no significant difference was detected in osteotomy healing rate and time to healing (P = .278 and .803, respectively). The rate of complication was similar in both groups.

CONCLUSIONS

ETO combined with immediate cerclage wire fixation does not appear to reduce the rate of infection eradication. There was no harmful effect on complication rate and osteotomy healing.

Femoral Stem Survivorship in Dorr Type A Femurs After Total Hip Arthroplasty Using a Cementless Tapered Wedge Stem: A Matched Comparative Study With Type B Femurs

BACKGROUND

There is a lack of understanding on relationship between the femoral geometry and outcomes of total hip arthroplasty (THA). We investigated clinical and radiographic outcomes of THA using a cementless tapered wedge stem in patients with Dorr type A proximal femoral morphology and compared with those of type B femurs at a minimum follow-up of 5 years.

METHODS

We analyzed 1089 hips (876 patients) that underwent THA using an identical cementless tapered wedge stem. We divided all femurs into 3 types (Dorr type A, B, and C). Type A and B femurs were statistically matched with age, gender, body mass index, and diagnosis by using propensity score matching. Clinical, radiographic results, and stem survivorship were compared between the matched 2 groups.

RESULTS

A total of 611 femurs (56%) were classified as type A, 427 (39%) as type B, and 51 (5%) as type C. More radiolucent lines around femoral stems were found in type A femurs (7.8%) than in type B femurs (2.5%) (P < .001). Patients with radiolucency showed worse Harris Hip Score (86.2 points) compared with those without radiolucency (93.0 points) (P < .001). The stem survivorship of type A femur (97.8%) was lower than that of type B femur (99.5%) (P = .041). The reasons for femoral revision in type A femurs were periprosthetic fracture (67%), aseptic loosening (22%), and deep infection (11%).

CONCLUSIONS

This study showed a higher rate of complications after THAs using a cementless tapered wedge stem in Dorr type A femurs than those performed in type B femurs.

The impact of canal flare index on leg length discrepancy after total hip arthroplasty

INTRODUCTION

The femoral stem should protrude from femur by an appropriate vertical distance to allow leg length equalization at hip arthroplasty; this distance depends on the size/shape of medullary canal and implant. The relationship between femoral morphology and achievability of leg length restoration is currently unclear. Our aim was to examine the impact of the femoral canal flare index (CFI) on the risk of leg length discrepancy (LLD) after total hip arthroplasty with different femoral stems.

MATERIALS AND METHODS

The study cohort included 126 patients with unilateral primary total hip arthroplasty due to idiopathic osteoarthritis and three different types of implanted femoral stems. The impact of CFI on postoperative LLD was assessed with separate logistic regression model for each implant and covariables of age, gender, body mass index and femoral neck resection level.

RESULTS

Higher CFI was an independent risk factor for postoperative LLD ≥ 5 mm with odds ratio 4.5 (p = 0.03) in 49 stems with cementless metaphyseal fixation Implantcast-EcoFit®, regardless of the femoral neck resection level. CFI had no significant impact on LLD in 30 stems with cementless diaphyseal fixation EndoPlus-Zweymüller® or 47 cemented collared stems Link-SPII®. No significant difference was observed between groups in pre/postoperative WOMAC scores, postoperative radiographic LLD, subjectively reported LLD, insole use or complications after mean 6.8 years of follow-up.

CONCLUSIONS

Higher CFI increases the risk of clinically detectable postoperative LLD in single-wedge femoral stems with cementless metaphyseal fixation. CFI has no significant impact on LLD in femoral stems with cementless diaphyseal fixation or cemented fixation.

Comparison of hip muscle volume between fit-and-fill stem and tapered-wedge stem after total hip arthroplasty using the anterolateral approach

BACKGROUND

In total hip arthroplasty (THA) surgery, hip muscle preservation is important in strengthening the stability of the hip and improving the activities of the patient. However, whether the type of femoral stem affects the recovery of the hip muscles remains unknown. The aim of this study was to compare the postoperative hip muscle recovery among femoral stem varieties after THA.

METHODS

The computed tomography (CT) images of 44 patients (44 hips) who underwent THA using an anterolateral approach were reviewed. Twenty-two patients received a fit-and-fill (FF) stem and 22 received the tapered-wedge (TW) stem. The volumes of the gluteus maximus (GMA), gluteus medius (GME), and obturator internus (OI) were measured on three-dimensional models reconstructed using preoperative and 6-month postoperative CT images. Relationships between muscle volume changes and factors including the femoral stem length were evaluated.

RESULTS

The GMA and GME volumes increased postoperatively by 8.2% and 8.3%, respectively, in the FF stem group and 7% and 6%, respectively, in the TW stem group, with no group differences. In contrast, the OI volume decreased postoperatively by 17.8% in the FF group and was preserved in TW group (p < 0.001). Moreover, OI volume was decreased in 19 patients (86%) in the FF group and in 11 patients (50%) in the TW group (p = 0.01). The normalized stem length was significantly associated with the postoperative change in OI volume (r = -0.45, p = 0.002).

CONCLUSIONS

The TW stem showed a significant advantage over the FF stem in terms of OI preservation. Surgeons should pay close attention during surgery to avoid OI injury when using different femoral stem types. We suggest that a short and reduced lateral shoulder femoral stem is a better choice for the preservation of external rotation muscles.