1 Introduction

Short tapered-wedge femoral stems have gained significant traction in primary total hip arthroplasty (THA) over the past decade, driven by their unique biomechanical advantages and utility in specific clinical contexts ^1–8.

Short tapered-wedge femoral stems have seen increasing adoption in primary total hip arthroplasty due to their favorable biomechanical profile and versatility across surgical approaches. The Taperloc Microplasty stem (Zimmer Biomet, Warsaw, IN) represents a shortened modification of the standard Taperloc design, reduced in length by 35 mm to facilitate minimally invasive techniques while maintaining the wedge-shaped titanium geometry and proximal porous plasma spray coating to achieve reliable metaphyseal fixation. These design features enable use through smaller incisions, including the direct anterior (DA) approach, and may be particularly advantageous in patients with Dorr A femoral morphology or pronounced metaphyseal–diaphyseal mismatch. In such cases, conventional longer stems may require more extensive canal preparation, prophylactic cerclage cabling, or even corrective osteotomy to achieve stability. Shorter stems also preserve distal bone stock, potentially simplifying future revision surgery—an important consideration in younger, active patients at higher risk of revision during their lifetime.^7,9

While short, taper-wedge femoral stems offer significant promise, their widespread adoption has been constrained by a lack of large-scale clinical studies with extended follow-up, particularly in the context of the DA approach. Concerns remain regarding fixation durability, especially in patients with capacious femoral canals or thin cortical bone, where the absence of diaphyseal engagement inherent to these designs may increase the risk of implant subsidence or periprosthetic fractures. Moreover, the DA approach, though increasingly popular, is characterized by a steep initial learning curve due to technical challenges in achieving adequate femoral exposure and canal preparation, with cortical perforations frequently observed during early adoption.^9,10 As the DA approach continues to gain traction, rigorous investigations are needed to validate the feasibility, safety, and long-term performance of short femoral stems within this specific surgical context.

The objective of this retrospective study was to evaluate clinical and radiographic outcomes at a minimum of 5-years postoperatively in a consecutive series of 128 patients undergoing primary THA with a short tapered-wedge femoral stem at a single, high-volume dedicated total joint replacement center. We hypothesized that the mid-term survivorship of short taper-wedge stems would be equivalent to or greater than that of traditional designs, with lower complication rates in Dorr A and B femora.

2 Methods

2.2

2.2 Surgical technique

All primary total hip arthroplasties (THAs) were performed using the DA approach on a Hana traction table (Mizuho OSI, Union City, CA). Preoperative planning was conducted using TraumaCad software (Brainlab, Munich, Germany), and intraoperative fluoroscopy, combined with Radlink GPS digital radiography alignment software (Radlink™ Inc., El Segundo, CA), ensured precise component alignment. Target acetabular component orientation was 15–20 degrees of anteversion and 40–45 degrees of inclination, with a combined version of the femoral and acetabular components aiming for 35°. Restoration of leg length and offset was also confirmed intraoperatively.

The DA approach was performed through a longitudinal skin incision with an L-shaped capsulotomy, which was meticulously repaired during wound closure. Implantation of a short, taper-wedge titanium alloy femoral stem (Taperloc Microplasty, Zimmer Biomet, Warsaw, IN; Fig. 1), featuring a proximally porous plasma spray coating, was achieved using a "broach-only" technique. Careful attention was directed toward achieving appropriate lateralization to facilitate a slightly valgus-biased stem position. A 36-mm ceramic femoral head was paired with a vitamin E-infused, highly crosslinked polyethylene liner unless spinopelvic rigidity was identified on preoperative lumbar radiographs, in which case a G7 dual mobility construct (Zimmer Biomet, Warsaw, IN) was selected to mitigate the risk of dislocation (see Fig. 2).

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Fig. 1 (A) 3-day postoperative image of a displaced spiral fracture of the proximal femur with displacement of the lesser trochanter and loosening of femoral implant. Required fixation of the fracture and femoral implant revision. (B) Short tapered-wedge stem revised to a modular, diaphyseal-engaging revision stem (C) Cortical thinning, subsidence and mechanical loosening of the femoral stem, requiring revision of the stem. (D) Short tapered-wedge stem revised to an Arcos modular hip revision system with a distal stem.

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Postoperatively, patients were made weight-bearing as tolerated (WBAT) with protected-gait for the first two weeks. Transition to unassisted ambulation was guided by the absence of a limp or thigh pain during alternating gait. Postoperative follow-up evaluations were scheduled at 2 weeks, 6 weeks, 3 months, 6 months, 1 year, 2 years, and 5 years per institutional protocol.

3 Results

4 Discussion

The adoption of short, metaphyseal-engaging tapered-wedge stems in primary, cementless THA has increased substantially over the past decade, largely due to their versatility and efficacy in addressing complex femoral anatomies.¹⁴ While concerns have been raised regarding the mid- and long-term rotational and axial stability of these stems due to their absence of diaphyseal engagement, our study demonstrated a revision-free survivorship rate of 92.9% at 5 years in a consecutive cohort of 128 consecutive patients undergoing primary THA with the Taperloc Microplasty short femoral stem via the DA approach (Fig. 2). To our knowledge, this represents the first evaluation of midterm clinical and radiographic outcomes for short femoral stems in the context of the DA approach, a technique recognized for its initially steep learning curve due to challenges in femoral exposure and canal preparation, with cortical perforations frequently reported during early adoption.^9,10

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Fig. 2 An illustrative case-example of a successful bilateral total hip arthroplasty performed under a single anesthetic session with Taperloc Microplasty stems. (a) Pre-operative radiology of a 64-year-old female patient depicting bilateral osteoarthritis. The patient was an ASA II patient with diabetes, asthma and hypertension. (b) 1-year post-operative follow-up. (c) Latest post-operative follow-up, May 2021 (6-year).

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A particular advantage of short femoral stems is that they are well-suited to address potentially challenging femoral morphologies such as Dorr A femurs, metaphyseal-diaphyseal mismatch, iliotrochanteric overhang, and significant abdominal pannus. These anatomies often complicate femoral exposure and stem placement via the DA approach. While comparative analysis of our results is challenging due to limited studies on short taper-wedge stems in this context, existing literature supports their utility. Saragaglia et al. reported 100% five-year survivorship of the Taperloc Microplasty stem in a series of 108 patients (mean age 58.8 years, SD 10 years) undergoing THA via a piriformis-sparing posterior approach. Nearly 50% of their cohort presented with Dorr A femurs, and no periprosthetic fractures or subsidence occurred, though 7.5% exhibited distal pedestal formation.⁶ Similarly, Lombardi et al. compared 389 primary THAs using conventional-length femoral stems and 269 THAs with the Taperloc Microplasty stem via a modified Hardinge approach, reporting a periprosthetic fracture rate of 3.1% for conventional stems versus 0.4% for shorter stems, with no significant differences in survivorship or PROMs at five years.¹⁴ Luger et al. also found a 1.5% reduction in periprosthetic fractures with short stems (Fitmore) compared to straight stems (Alloclassic SL/SLO; Zimmer Biomet) at one year postoperatively (p = 0.02) in a cohort of 1147 cementless primary THAs matched via propensity scores.¹⁵

In contrast, nine patients in our series (7.03%) required revision, including five cases of Vancouver B2 periprosthetic fractures occurring early (mean 14.8 days postoperatively). Age emerged as the sole significant predictor of complications, with patients experiencing fractures having a mean age of 77.8 years. Consistent with guidelines developed since the inception of this study, hybrid THA is now employed in our practice, with a cemented femoral stem and a cementless or press-fit acetabular component used in male patients over 75 years, female patients over 70 years, and in those with osteoporosis or a capacious (Dorr C) femoral canal ^16–22. Supporting these findings, Sershon et al. analyzed 2417 patients undergoing THA with a short, single-wedge taper stem and 3892 with a fit-and-fill stem, observing a 2.3-fold increased risk of periprosthetic fractures with the former, particularly in patients aged >65 years.²³ Bishop et al. also evaluated peak stress distribution in the proximal femur using four matched-pair cadaveric femora implanted with small taper-wedge and standard-length femoral stems. They reported stress increases of up to 35% when stems were placed in varus, a risk significantly mitigated by valgus stem positioning.²⁴ Hayama et al. further validated these findings in a cohort of 257 Asian patients with DDH undergoing THA via a posterior approach, reporting no cases of implant subsidence, periprosthetic fractures, or failure of bony ingrowth at a mean follow-up of four years.²⁵ Their findings emphasize the critical importance of avoiding varus positioning and achieving slight valgus alignment, as well as the adaptability of short stems for accommodating variations in femoral version. Our experience similarly underscores the necessity of achieving proper lateralization and valgus positioning to mitigate the risks of varus malposition or calcar compromise, an adjustment facilitated by the smaller profile of short stems.

The Taperloc Microplasty stem offers several advantages, including a shortened design that preserves distal bone stock, reduces stress shielding through proximal load transfer, and facilitates insertion through the DA approach. Its metaphyseal fixation provides stable engagement in narrow, funnel-shaped Dorr A femora. In this cohort, three fractures occurred in Dorr A femurs and two in Dorr B femurs, all within six weeks of surgery. All femoral stems in the study achieved bone-ingrowth. They were tightly fitted within the canal using fluoroscopic guidance, maximizing fit and fill of the stem in the canal. The surgical technique employed by the experienced surgeons was rarely associated with issues such as early subsidence or rotational instability (only two in this series). Given that minimal postoperative pain is often associated with the direct anterior approach,²⁶ patients often came off a protective gait too early. Therefore, careful adherence to standardized postoperative protocols remains critical, emphasizing good gait patterns and safety to optimize outcomes, particularly in the first six weeks. This highlights the importance of robust patient counseling to support recovery, especially for Dorr A patients, when using this stem.

Limitations of the stem include potential instability in patients with poor bone quality or capacious canals, reflected by subsidence and periprosthetic fractures in older individuals—consistent with reliance on metaphyseal fixation without diaphyseal support. In our series, two cases of subsidence (≤3 mm) were observed; both were clinically asymptomatic, showed no progressive radiolucent lines, and demonstrated complete osseointegration at latest follow-up. Subsidence of this degree is generally considered clinically acceptable. Gallart et al., in a series of 32 THAs using the Taperloc Complete Microplasty stem with mean 36.5-month follow-up, reported one case of 1 mm subsidence, which did not progress or result in radiolucent lines.²⁷ Similarly, a mid-term series of 119 stems reported no subsidence greater than 3 mm and radiolucent lines in only 2% of cases,⁶ affirming reliable osseointegration while acknowledging the potential for early subsidence in high-risk groups. Collectively, these findings support the clinical utility of the Microplasty stem in appropriately selected patients, while reinforcing the continued role of cemented fixation in elderly or osteoporotic individuals.

Strengths of this study include an adequate sample size, robust five-year clinical and radiographic follow-up, and the exclusive focus on assessing the feasibility and clinical outcomes of short femoral stem placement via the DA approach. However, a few important limitations warrant consideration. The retrospective design of the study inherently introduces selection bias, although this was largely mitigated through the use of a consecutive cohort and standardized protocols. Secondly, clinical outcomes were assessed using the Harris Hip Score (HHS), which provides valuable insight into pain, function, and range of motion but lacks the breadth of additional PROMs such as WOMAC or HOOS Jr., which were excluded due to incomplete data at five years for a substantial portion of the cohort (data availability <70%). Future analyses from our ongoing long-term follow-up will incorporate these metrics to provide a more comprehensive assessment of patient-centered outcomes. Finally, this study evaluated a single short, tapered-wedge stem design (Taperloc Microplasty, Zimmer Biomet, Warsaw, IN) and may not be directly applicable to other vendor designs of short femoral stems, which can exhibit considerable variability in geometry and porous coatings. Long-term follow-up at 10- and 15-years is ongoing and is anticipated to offer further insights into implant survivorship and clinical outcomes.

5 Conclusions

Short taper-wedge femoral stems have demonstrated reliability in primary DA-THA, with a revision-free survivorship of 92.7% at five-years postoperatively. These stems are particularly well-suited for addressing complex femoral anatomies, including Dorr-A femurs, metaphyseal-diaphyseal mismatch, and challenging scenarios such as wide iliotrochanteric overhang or abdominal pannus, where conventional femoral stems may present technical difficulties. The majority of complications in this series were early periprosthetic fractures, predominantly occurring in patients with a mean age of 77.8 years and poor bone quality. These findings have supported our adoption of cemented femoral fixation in such patients, aligning with national trends that have emerged since the inception of this study. Long-term data collection is ongoing to provide additional insights into the durability and versatility of short taper-wedge stems in primary DA-THA.

Ethical statement

Ethical approval for this study was obtained from the Texas Health Resources and UT Southwestern Medical Center Institutional Review Boards on August 6th, 2020; with the following determinations:

Waiver of Documentation of Consent § 46.117(c);

Waiver of Documentation of Consent Qualifications § 46.117(c).

Informed patient consent

The study was approved by the Texas Health Resources Institutional Review Board and the UT Southwestern Medical Center Institutional Review Board, under the revised Common Rule (45 CFR 46). The IRB approved a waiver of documentation of informed consent permitting verbal consent to be obtained. All participants provided verbal informed consent after being a read a detailed information script describing the study's purpose, procedures, risks, benefits, voluntariness and confidentiality protections. Verbal consent was documented in the study records by research coordinators.

Credit author statement

Shuvalaxmi D. Haselton: Patient follow-up, data collection, data analysis, writing – original draft.

Vivek P. Chadayammuri: Formal data analysis, writing – review and editing.

Roger H. Emerson: Conceptualization, patient contribution, investigation, writing – review and editing, supervision.

Funding statement

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.