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Favorable Results of a Short, Tapered, Highly Porous, Proximally Coated Cementless Femoral Stem at a Minimum 4-Year Follow-Up
Favourable Results of a Short, Tapered, Highly Porous, Proximally Coated Cementless Femoral Stem at a Minimum Four-Year Follow-up Anthony Albers MD, Ahmed Aoude MD, David Zukor MD, FRCSC, Olga Huk MD, FRCSC, John Antoniou MD, PhD, FRCSC, Michael Tanzer MD, FRCSC PII: DOI: Reference:
S0883-5403(15)00774-3 doi: 10.1016/j.arth.2015.08.020 YARTH 54672
To appear in:
Journal of Arthroplasty
Received date: Revised date: Accepted date:
18 June 2015 6 August 2015 13 August 2015
Please cite this article as: Albers Anthony, Aoude Ahmed, Zukor David, Huk Olga, Antoniou John, Tanzer Michael, Favourable Results of a Short, Tapered, Highly Porous, Proximally Coated Cementless Femoral Stem at a Minimum Four-Year Follow-up, Journal of Arthroplasty (2015), doi: 10.1016/j.arth.2015.08.020
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ACCEPTED MANUSCRIPT Favourable Results of a Short, Tapered, Highly Porous, Proximally Coated Cementless
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Femoral Stem at a Minimum Four-Year Follow-up.
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Authors
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MD, PhD, FRCSC, M Tanzer, MD, FRCSC
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A Albers, MD, A Aoude, MD, D Zukor, MD, FRCSC, O Huk, MD, FRCSC, J Antoniou,
Affiliations
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Division of Orthopaedic Surgery, McGill University, Montreal, Quebec, Canada
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Dr. John Antoniou
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Correspondence to be addressed to:
Jewish General Hospital, Room E-003
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3755 Côte-Sainte-Catherine Road Montreal, Quebec, Canada H3T 1E2
Email: [email protected] Tel: (514) 340-8222 x4615 Fax: (514) 340-7595
ACCEPTED MANUSCRIPT TITLE Favourable Results of a Short, Tapered, Highly Porous, Proximally Coated Cementless
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Femoral Stem at a Minimum Four-Year Follow-up.
ABSTRACT
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Background
Shorter femoral stems have many potential advantages in total hip arthroplasty (THA),
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and as such, their use has been increasing. However, there are very few clinical studies
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evaluating the outcomes of these stems and comparing them to their regular sized counterparts.
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Methods
We undertook a study to provide radiological and functional outcomes of the Tri-Lock
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Bone Preservation Stem, a short, tapered, highly porous, proximally coated cementless
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stem with minimum four-year follow-up. One hundred and thirty-one THAs were
Results
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evaluated and mean follow-up was five years (range, 4.1 - 5.5 years).
Stem related complications were low and only one stem required revision THA for aseptic loosening. Kaplan-Meier analysis indicated five-year stem survival to be 99.2% (95% CI: 94.7-100.0%), which is comparable to conventional length Tri-Lock stems (99.8% at 8.9 years). Conclusion This study demonstrates that this short femoral stem can provide reproducible and successful outcomes at five-year follow-up. Further studies are necessary to determine the long-term outcome of these implants and their results in patients with poor bone stock.
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Key Words:
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Primary, Total Hip Arthroplasty, Short Stem, Cementless, Taper
ACCEPTED MANUSCRIPT INTRODUCTION Uncemented total hip arthroplasty (THA) using standard length femoral prostheses has
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been performed for more than 40 years and has demonstrated clinical success and cost
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effectiveness in the treatment of degenerative joint disease of the hip [1-7]. More recently, the use of shorter bone preserving stems is becoming more widespread [8]. While the
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idea of short femoral stems is not new, their renewed popularity derives from certain
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potential advantages they present over their standard length counterparts [9]. Certain design features, such as a reduced lateral shoulder, a thin tapered geometry and a shorter
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overall length aim to conserve native bone stock, which is especially important in younger patients [10]. Smaller stems also facilitate insertion when using less invasive
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surgical techniques. Furthermore, metaphyseal as opposed to diaphyseal fitting stems
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have improved load transfer characteristics, they avoid problems caused by proximaldistal femoral diaphyseal mismatch, decrease rates of thigh pain and reduce stress
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shielding [3, 8, 11-15]. Notwithstanding these potential advantages, short femoral stems
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must demonstrate an equivalent outcome to that of regular length cementless stems in order to support their routine use in primary THA. To date, only short to midterm survivorship data is available on certain implant designs and questions remain regarding learning curve, stem positioning, subsidence and suitability for patients with poor bone stock [16, 17]. There are very few studies in the literature that directly compare short stems to their regular sized counterparts in a randomized fashion using validated measurement tools[18] . The goal of this study was to evaluate cementless primary THAs performed using the TriLock Bone Preservation Stem (Tri-Lock BPS, DePuy, Johnson & Johnson, Warsaw, IN,
ACCEPTED MANUSCRIPT USA). The Tri-Lock BPS is a short tapered-wedge, proximally porous-coated titanium femoral stem that is identical in geometry, but significantly shorter in length than its
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clinically successful conventional predecessor, the Tri-Lock stem (Figure 1 and Table 1).
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The proximal porous coating of these two stems is identical in length, but the Tri-Lock BPS has a highly porous and roughened coating (Gription), while the Tri-Lock stem has a
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conventional porous coating of smooth beads. We hypothesize that this short stem will
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provide comparable results to regular length cementless femoral stems used for primary
MATERIAL AND METHODS
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THA.
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For the current study we selected all patients who received a Tri-Lock BPS for a primary
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cementless THA between July 2009 and April 2010. All clinical data, obtained from our patient database, was acquired prospectively. Institutional review board approval was
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obtained prior to the onset of the study. Surgeries were performed by one of four In these
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attending orthopedic surgeons practicing in two independent institutions.
institutions, the Tri-Lock BPS is the primary femoral implant used for THA in patients judged to have adequate bone stock (Dorr type A or B femur) [19]. Exclusion criteria included revision THA, previous hemi-arthroplasty or surgical arthrodesis on the ipsilateral side, hips in which pre-operative templating demonstrated the femur could not accommodate a size 0 implant, hips with significant anteversion deformity such as in Crowe IV hips and Dorr C femora where templating demonstrated distal canal fill with marked undersizing of the proximal femur.
ACCEPTED MANUSCRIPT All patients were evaluated clinically pre-operatively then post-operatively at six weeks, one year and every second year thereafter. Clinical evaluation included the Harris Hip
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Score (HHS), University of California Los Angeles (UCLA) activity level and presence
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or absence of thigh pain [20, 21]. Any significant postoperative complications related to the femoral implant were documented.
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Antero-posterior (AP) radiographs of the pelvis with the legs internally rotated 15
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degrees and AP and lateral radiographs of the operated hip were obtained and evaluated for Dorr femur type [19], signs of bony ingrowth or signs of loosening and were
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classified as osseointegrated, fibrous stable or unstable [22]. Standard radiographic parameters where used to assess adequacy of the films such as symmetry of the obturator
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foramen, tip of coccyx in line and within 2-4 cm of symphysis pubis. Radiographs were
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repeated if deemed inadequate by the treating surgeon. Radiographic analysis was performed retrospectively by two authors (AA and AA) using
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OrthoView (OrthoView LLC, Jacksonville, FL, USA) software, which facilitated
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calculation of image magnification and allowed us to determine the amount of subsidence and varus/valgus positioning of the implant in the coronal plane. Subsidence was measured as the distance between the summit of the lesser trochanter and bottom edge of the stem at six weeks post-operatively in comparison to the latest follow up imaging (Figure 2). Coronal plane alignment was determined using stem templating software in OrthoView and comparing the stem axis to the anatomic axis of the femur (Figure 2). With the collected data, we compared subsidence and coronal plane alignment based on surgical approach and femur type. Varus or valgus inclination of the stem relative to the
ACCEPTED MANUSCRIPT canal of over 5 degrees was defined to be malpositioned and a progressive subsidence of more than 3 mm was determined to be a sign of possible loosening [23-26].
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Patient demographics were calculated with arithmetic mean and all errors are reported as
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standard deviations. Since all analyzed outcomes failed the Shapiro-Wilk test for normality, a non-parametric Mann Whitney U test was conducted to determine the
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significance between preoperative and the last postoperative HHS and UCLA activity
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scores and to compare mean difference in subsidence and coronal inclination with different surgical approaches or Dorr femur type. A non-parametric Spearman test was
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used to determine the correlations between stem subsidence, positioning, surgical approach or Dorr femur type. All other comparisons between different time-points and
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follow up groups were performed using a non-parametric Kruskal-Wallis test followed by
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a Dunn’s multiple comparisons. A p-value of less than 0.05 was considered to be statistically significant. Interobserver reliability was determined using weighted and
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unweighted Cohen’s Kappa analysis. Finally, the survival analysis was performed using
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the Kaplan-Meier method with corresponding 95% confidence interval (CI). The TriLock BPS survivorship was determined for stem failure with femoral revision or impending revision as an endpoint. The time between the index procedure and revision was a measurement of survival of the joint. Survival times for patients who had not undergone revision were recorded at the study census date (January 15, 2015). GraphPad Prism software (GraphPad Software, La Jolla, CA, USA) was used for all statistical analyses.
ACCEPTED MANUSCRIPT RESULTS Between July 2009 and April 2010, in both institutions, 124 patients (131 hips) had a
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primary THA using a Tri-Lock BPS femoral stem. Five patients were lost to follow-up
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(4%) leaving 119 patients (126 hips) for study. Of the patients lost to follow-up, two died within two years after surgery from causes unrelated to the index procedure and three
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patients could not be reached, two of which were over age 90 years old. The mean age of
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patients at the time of the surgery was 65 years (range, 34 – 89 years) and the mean follow-up was five years (range, 4.1 - 5.5 years). Preoperative diagnoses were:
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osteoarthritis (94%), avascular necrosis (4%), developmental dysplasia of the hip (1%) and rheumatoid arthritis (1%) (Table 2). The surgery was performed through a mini direct
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lateral approach in 25% of the cases and through a mini posterolateral approach in 75%
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of the cases. All patients, without complications, were allowed full weight bearing immediately post-operatively. Femoral implant sizes ranged from 0 to 8 in either
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Standard or High offset as determined by pre-operative templating and intra-operative
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evaluation. All patients received a cementless fully porous coated acetabular cup. The HHS and UCLA scores (85 ± 13 and 6 ± 2 respectively) at the last follow up significantly improved (p < 0.0001) from their pre-operative values (42 ± 15 and 4 ±2 respectively) (Table 3). Two patients (2 hips), both having received a posterior approach, had mild postoperative thigh pain that resolved after with three weeks of protected weight bearing with crutches and non-steroidal anti-inflammatories. Of the patients included in the study, 116 patients (123 hips) had complete radiological follow-up. The remaining three patients were reached by phone and reported they were very satisfied with their THA but they were either unable or refused to return for follow-
ACCEPTED MANUSCRIPT up. Subsidence occurred in 49 cases (39.8%) with an average of 1.04 ± 0.73 mm (range, 0.5 to 5 mm) for the subsided stems (Table 4). The mean stem subsidence for the entire
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cohort was 0.41 ± 0.69 mm. The only stem that showed subsidence exceeding 3 mm was
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a 60 year-old female with Behcets disease on immunosuppressive drug therapy. The patient developed aseptic loosening of both the stem and cup. The stem had subsided 5
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mm over the first 12 months postoperatively. She required revision THA using a standard
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length fully porous coated stem (Figure 3). All the remaining stems were found on the radiographs to be osseointegrated (Figure 4).
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Eighty-three stems (67.5%) were placed in varying degrees of valgus (range 0 to 7, mean 1.99 ± 1.13 degrees) and 11 (8.9%) in varus (range 0 to 3, mean 1.82 ± 0.87 degrees)
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(Table 4). The mean stem coronal plane position was 1.18 ± 1.58 degrees of valgus
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compared to the femoral axis. Only one stem in our series was outside the acceptable 5 degree range for coronal alignment. This stem was placed in 7 degrees of valgus
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alignment. This did not affect the patient’s outcome as the stem was osseointegrated and
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the HHS was 88 at 5.3 years follow-up. Intersobserver reliability for subsidence and coronal position measurements was κ = 0.7 and 0.8, respectively. There was no significant difference in stem subsidence or coronal positioning with different surgical approaches (posterolateral vs. direct lateral) or Dorr femur type (Table 5), and no significant correlations were observed between stem subsidence, positioning, surgical approach or Dorr femur type. Kaplan-Meier analysis indicated five-year stem survival to be 99.2% (95% CI: 94.7-100.0 %) (Figure 5). In terms of complications, two hips with Type A femora had an iatrogenic fracture of the greater trochanter during femoral broaching. They both healed uneventfully after being
ACCEPTED MANUSCRIPT treated with intra-operative wiring and six weeks protected weight bearing. Two patients had a postoperative dislocation; one was treated closed, the other required acetabular
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component revision for recurrent instability secondary to acetabular malposition. The
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femoral stem was stable at the time of surgery and did not require revision.
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DISCUSSION
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This study evaluated the Tri-Lock BPS femoral stem, a short single tapered wedge, proximally porous-coated titanium primary THA stem. At a mean follow-up of five years,
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the implant performed exceedingly well with an overall survivorship of 99.2%. Stem related complications were low and only one stem, which subsided 5 mm, required
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revision for aseptic loosening. Overall, the use of this short stem was associated with a
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significant improvement in the HHS and UCLA scores. Only two hips (1.6%) experienced mild, transient thigh pain following their THA.
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In this study, the short stem was very stable and exhibited a mean subsidence of only
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0.41± 0.69 mm. This is likely related to the design features and the roughened porous coating. Proximally, the taper design allows complete fill of the medial-lateral dimensions of the femoral metaphysis, thereby enhancing rotational stability. The tapered wedge design may allow a certain amount of migration in the cranio-caudal and mediallateral planes, however, the concept of rest-fit enhances stability [27-30]. It is unclear whether settling of the implant leads to increased stability and potential for ingrowth or whether it represents a risk factor for early loosening [16, 23, 31]. Early data suggested that settling of the prosthesis into a stable position was non-detrimental [16, 32, 33]. However, more recent studies have indicated that subsidence of 2 to 3 mm could be a
ACCEPTED MANUSCRIPT threshold for early failure. In accordance to these findings, implant undersizing could also be linked to instability and early failure [8, 23, 31, 32]. In our series, the average
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subsidence of 0.41± 0.69 mm was well below the previously stated threshold for
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loosening. Stems with subsidence between 0 and 3mm were all stable while a single stem, which subsided 5mm required revision. This may indicate that 3wmm is a threshold for
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stability. The amount of subsidence was unaffected by the geometry of the femur or
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surgical approach used. This is likely due to the versatility of the implant and its ease of insertion using a broach-only technique. It must also be noted that all of our cases were
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Dorr type A or B. While standard length tapered wedge stems and certain short stems have been used with success in Dorr C femurs, data remains limited [16, 34].
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Stem position has also been linked to implant survival. Learning curve and prosthesis
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design are known variables for proper prosthesis placement. Varus malalignment, especially in cemented implants, has been shown to impact negatively on implant
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survival [35]. However, many studies evaluating cementless implants have failed to show
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any difference [26, 36, 37]. In our series, most stems (67.5%) where placed in minimal valgus (1.99 ± 1.13 degrees) with only one stem inserted in more than 5 degrees from the anatomic axis of the femur. This position did not negatively affect function or survival at short-term follow-up. Coronal alignment did not correlate with femoral morphology or surgical approach. The relative valgus positioning of the stem in this study is thought to be due to the surgeon’s desire to avoid varus placement. As well, the absence of a lateral shoulder and a longer stem to engage the more distal femoral diaphysis makes it more difficult for the surgeon to feel if the stem is in neutral or slight valgus intraoperatively when the canal is being broached.
ACCEPTED MANUSCRIPT The single case of aseptic loosening of both stem and cup, in this study, occurred in a patient with Behcets disease who was on multiple immunosuppressive agents including
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Prednisone and Infliximab. An immunocompromised state and decreased capacity for
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osseointegration may preclude the use of a short, proximally porous coated femoral stem. A more extensively porous coated device is most likely indicated in these cases in order
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to increase the surface area for potential osseointegration.
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Our implant survival probability of 99.2% at five years compares favorably with conventional length Tri-Lock stems (99.8% at 8.9 years) [7, 27, 28]. The extent to which
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the highly porous and rough porous coating of the Tri-Lock BPS contributes to the survivorship remains unclear. The patients in our study had a low incidence of thigh pain
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(1.6%) compared to the reported incidence for standard length Tri-Lock stems (5.1%)
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[28]. Biomechanical and clinical research has correlated stem length, materials used and stem design with thigh pain [38]. Shorter metaphyseal fitting stems appear to be
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beneficial in reducing thigh pain [39]. One pitfall of the cementless metaphyseal-fitting
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tapered component is its broach-only technique, which has been described to increase the risk of iatrogenic femur fracture [40]. Nonetheless, compared to broach-only technique using diaphyseal-fitting stems, this risk is far diminished. The rate of iatrogenic femur fractures in our study (1.6%) is comparable to the rates found in the literature [11]. The limitations of our study are its non-randomized design and lack of a control group. Patient factors such as age, level of activity, individual anatomy and bone quality can impact the surgeon’s choice of implant leading to a selection bias that may have improved outcomes in our study, particularly in patients with poor bone stock, where a different type of implant would have been selected. Another limitation of this particular
ACCEPTED MANUSCRIPT stem, despite its reduced length and mostly metaphyseal fit is that the smallest available size is sometimes too large for some particularly small femora. When this is found during
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pre-operative templating another stem is selected. Finally, we were limited to using the
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available software in our institution for measurement of subsidence. While using OrthoView software aids in determining image magnification and implant position in the
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coronal plane, Radiostereometric Analysis (RSA) is the gold standard for measurement of
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stem migration [41, 42]. Nevertheless, using the threshold of our software makes our values clinically relevant, as RSA is not used in routine clinical practice. Ultimately, our
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study has a short follow-up period and the majority of femoral prostheses have excellent results at less than five-years. Although the mid-term results of the Trilock BPS are
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encouraging and similar to the traditional Trilock stem, it is not clear without further
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follow-up whether or not these results will be sustained at the 10-year follow-up time period. While long-term studies are warranted, our follow-up period is in keeping with
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most currently available studies evaluating the use of short femoral stems in THA. The
unclear.
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extent to which these results can be extrapolated to other short stem designs remains
CONCLUSION: This study demonstrates that a short, tapered, highly porous, proximally coated cementless femoral stem can provide reproducible and successful outcomes at a mean of five years following primary THA. Patient outcomes were independent of age, Dorr femur types A or B and surgical approach. Revision rates, intra-operative femur fractures as well as the incidence of thigh pain were equal or lower than those quoted in the
ACCEPTED MANUSCRIPT literature. At short to midterm follow up, these stems appear to perform as well as historical controls, thus justifying their use in THA. Further studies are necessary to
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determine the long-term outcome of these implants and their results in patients with poor
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bone stock.
ACCEPTED MANUSCRIPT REFERENCES
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1. Pivec R, Johnson AJ, Mears SC, Mont MA. Hip arthroplasty. The Lancet 380(9855): 1768, 2012 2. Kim YH. Long-term results of the cementless porous-coated anatomic total hip prosthesis. J Bone Joint Surg Br 87(5): 623, 2005 3. Hozack WJ, Rothman RH, Eng K, Mesa J. Primary cementless hip arthroplasty with a titanium plasma sprayed prosthesis. Clin Orthop Relat Res (333): 217, 1996 4. Lombardi AV, Berend KR, Mallory TH. Hydroxyapatite-coated titanium porous plasma spray tapered stem: experience at 15 to 18 years. Clin Orthop Relat Res 453: 81, 2006 5. Marshall AD, Mokris JG, Reitman RD, Dandar A, Mauerhan DR. Cementless titanium tapered-wedge femoral stem: 10- to 15-year follow-up. J Arthroplasty 19(5): 546, 2004 6. McLaughlin JR, Lee KR. Total hip arthroplasty with an uncemented tapered femoral component. J Bone Joint Surg Am 90(6): 1290, 2008 7. Burt CF, Garvin KL, Otterberg ET, Jardon OM. A femoral component inserted without cement in total hip arthroplasty. A study of the Tri-Lock component with an average tenyear duration of follow-up. J Bone Joint Surg Am 80(7): 952, 1998 8. Lombardi AV, Berend KR, Adams JB. A short stem solution: through small portals. Orthopedics 32(9), 2009 9. Morrey BF. Short-stemmed uncemented femoral component for primary hip arthroplasty. Clin Orthop Relat Res (249): 169, 1989 10. Huo MH, Parvizi J, Bal BS, Mont MA. What's new in total hip arthroplasty. The Journal of Bone & Joint Surgery 91(10): 2522, 2009 11. Molli RG, Lombardi AV, Berend KR, Adams JB, Sneller MA. A short tapered stem reduces intraoperative complications in primary total hip arthroplasty. Clin Orthop Relat Res 470(2): 450, 2012 12. Albanese CV, Santori FS, Pavan L, Learmonth ID, Passariello R. Periprosthetic DXA after total hip arthroplasty with short vs. ultra-short custom-made femoral stems: 37 patients followed for 3 years. Acta Orthop 80(3): 291, 2009 13. Bourne RB, Rorabeck CH, Ghazal ME, Lee MH. Pain in the thigh following total hip replacement with a porous-coated anatomic prosthesis for osteoarthrosis. A five-year follow-up study. J Bone Joint Surg Am 76(10): 1464, 1994 14. Chen HH, Morrey BF, An KN, Luo ZP. Bone remodeling characteristics of a shortstemmed total hip replacement. J Arthroplasty 24(6): 945, 2009 15. Stulberg SD, Dolan M. The short stem: a thinking man's alternative to surface replacement. Orthopedics 31(9): 885, 2008 16. Reitman RD, Emerson R, Higgins L, Head W. Thirteen year results of total hip arthroplasty using a tapered titanium femoral component inserted without cement in patients with type C bone. J Arthroplasty 18(7 Suppl 1): 116, 2003 17. van Oldenrijk J, Molleman J, Klaver M, Poolman RW, Haverkamp D. Revision rate after short-stem total hip arthroplasty: a systematic review of 49 studies. Acta Orthop 85(3): 250, 2014 18. McCalden RW, Korczak A, Somerville L, Yuan X, Naudie DD. A randomised trial comparing a short and a standard-length metaphyseal engaging cementless femoral stem using radiostereometric analysis. Bone Joint J 97-B(5): 595, 2015
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19. Dorr LD, Faugere MC, Mackel AM, Gruen TA, Bognar B, Malluche HH. Structural and cellular assessment of bone quality of proximal femur. Bone 14(3): 231, 1993 20. Harris WH. Traumatic arthritis of the hip after dislocation and acetabular fractures: treatment by mold arthroplasty. An end-result study using a new method of result evaluation. J Bone Joint Surg Am 51(4): 737, 1969 21. Amstutz HC, Thomas BJ, Jinnah R, Kim W, Grogan T, Yale C. Treatment of primary osteoarthritis of the hip. A comparison of total joint and surface replacement arthroplasty. J Bone Joint Surg Am 66(2): 228, 1984 22. Engh CA, Massin P, Suthers KE. Roentgenographic assessment of the biologic fixation of porous-surfaced femoral components. Clin Orthop Relat Res (257): 107, 1990 23. Kim YH, Kim JS, Joo JH, Park JW. A prospective short-term outcome study of a short metaphyseal fitting total hip arthroplasty. J Arthroplasty 27(1): 88, 2012 24. Kim YH, Kim JS, Oh SH, Kim JM. Comparison of porous-coated titanium femoral stems with and without hydroxyapatite coating. J Bone Joint Surg Am 85-A(9): 1682, 2003 25. Barreca S, Ciriaco L, Ferlazzo M, Rosa MA. Mechanical and biological results of short-stem hip implants: consideration on a series of 74 cases. Musculoskelet Surg 99(1): 55, 2015 26. Min BW, Song KS, Bae KC, Cho CH, Kang CH, Kim SY. The effect of stem alignment on results of total hip arthroplasty with a cementless tapered-wedge femoral component. J Arthroplasty 23(3): 418, 2008 27. Parvizi J, Keisu KS, Hozack WJ, Sharkey PF, Rothman RH. Primary total hip arthroplasty with an uncemented femoral component: a long-term study of the Taperloc stem. J Arthroplasty 19(2): 151, 2004 28. Healy WL, Tilzey JF, Iorio R, Specht LM, Sharma S. Prospective, randomized comparison of cobalt-chrome and titanium trilock femoral stems. J Arthroplasty 24(6): 831, 2009 29. Noble PC, Alexander JW, Lindahl LJ, Yew DT, Granberry WM, Tullos HS. The anatomic basis of femoral component design. Clin Orthop Relat Res (235): 148, 1988 30. Leali A, Fetto J, Insler H, Elfenbein D. The effect of a lateral flare feature on implant stability. International orthopaedics 26(3): 166, 2002 31. Kim YH, Kim VE. Early migration of uncemented porous coated anatomic femoral component related to aseptic loosening. Clin Orthop Relat Res (295): 146, 1993 32. Sakalkale DP, Eng K, Hozack WJ, Rothman RH. Minimum 10-year results of a tapered cementless hip replacement. Clin Orthop Relat Res (362): 138, 1999 33. Mulliken BD, Bourne RB, Rorabeck CH, Nayak N. A tapered titanium femoral stem inserted without cement in a total hip arthroplasty. Radiographic evaluation and stability. J Bone Joint Surg Am 78(8): 1214, 1996 34. Kim YH, Park JW, Kim JS. Is diaphyseal stem fixation necessary for primary total hip arthroplasty in patients with osteoporotic bone (Class C bone)? J Arthroplasty 28(1): 139, 2013 35. Kobayashi S, Takaoka K, Saito N, Hisa K. Factors affecting aseptic failure of fixation after primary Charnley total hip arthroplasty. Multivariate survival analysis. J Bone Joint Surg Am 79(11): 1618, 1997
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36. Berend KR, Mallory TH, Lombardi AV, Dodds KL, Adams JB. Tapered cementless femoral stem: difficult to place in varus but performs well in those rare cases. Orthopedics 30(4): 295, 2007 37. de Beer J, McKenzie S, Hubmann M, Petruccelli D, Winemaker M. Influence of cementless femoral stems inserted in varus on functional outcome in primary total hip arthroplasty. Can J Surg 49(6): 407, 2006 38. Campbell AC, Rorabeck CH, Bourne RB, Chess D, Nott L. Thigh pain after cementless hip arthroplasty. Annoyance or ill omen. J Bone Joint Surg Br 74(1): 63, 1992 39. Brown TE, Larson B, Shen F, Moskal JT. Thigh pain after cementless total hip arthroplasty: evaluation and management. J Am Acad Orthop Surg 10(6): 385, 2002 40. Fitzgerald RH, Brindley GW, Kavanagh BF. The uncemented total hip arthroplasty. Intraoperative femoral fractures. Clin Orthop Relat Res (235): 61, 1988 41. Malchau H, Karrholm J, Wang YX, Herberts P. Accuracy of migration analysis in hip arthroplasty. Digitized and conventional radiography, compared to radiostereometry in 51 patients. Acta Orthop Scand 66(5): 418, 1995 42. Nistor L, Blaha JD, Kjellstrom U, Selvik G. In vivo measurements of relative motion between an uncemented femoral total hip component and the femur by roentgen stereophotogrammetric analysis. Clin Orthop Relat Res (269): 220, 1991
ACCEPTED MANUSCRIPT TABLES Table 1: Trilock BPS vs. corresponding original Ti-Trilock stem lengths
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STD: Standard Offset
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Δ Length (mm)
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6.3 STD 7.5 STD 8.8 STD 10 STD 11.3 STD 12.5 STD 13.8 STD 15 STD 17.5 STD 20 STD 22.5 STD
Lateral Shoulder / Tip (mm) 134.0 137.0 140.0 142.0 145.0 147.0 150.0 152.0 157.0 162.0 167.0
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Old Ti TriLock Size
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0 STD 1 STD 2 STD 3 STD 4 STD 5 STD 6 STD 7 STD 8 STD 9 STD 10 STD 11 STD 12 STD -
Lateral Shoulder / Tip (mm) 114.5 116.5 118.5 122.0 124.0 126.0 128.0 130.0 132.0 134.0 136.0 138.0 140.0 -
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TriLock BPS Size
19.5 20.5 21.5 20.0 21.0 21.0 22.0 22.0 23.0 24.0 -
ACCEPTED MANUSCRIPT Table 2: Patient demographic data Characteristic
Finding
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No. patients/hips 64.6 (34-89) yrs.
Gender
55 male / 64 female
Follow-up*
5.0 (4.1-5.5) yrs.
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Age (range)*
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Surgical approach Direct Lateral
31 hips (25%) 95 hips (75%)
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Postero-Lateral
Osteoarthritis
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Congenital dysplasia
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Etiology
119 hips (94.4%) 1 hip (0.8%) 1 hip (0.8%)
Avascular necrosis
5 hips (4.0%)
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Rheumatoid arthritis
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* This value is reported as the mean in years.
ACCEPTED MANUSCRIPT Table 3: Clinical results Preoperative
Final Follow-Up
P-Value
Harris Hip Score*
41.9 (± 15.2)
84.5 (± 12.6)
< 0.0001
3.9 (± 2.1)
5.8 (± 2.0)
< 0.0001
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UCLA Activity Score*
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Clinical Parameters
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* The values are reported as the mean (± standard deviation).
Number stems (%) Subsidence 123 74 (60.2%) 49 (39.8%)
All Neutral Varus Valgus
123 29 (23.0%) 11 (8.9%) 83 (67.5%)
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All No subsidence Subsidence
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Table 4: Tilt and subsidence
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Tilt
Average ± SD (mm) 0.41 ± 0.69 − 1.04 ± 0.73 (degrees) 1.18 ± 1.58 − 1.82 ± 0.87 1.99 ± 1.13
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Table 5: Tilt (coronal inclination) and subsidence with different surgical approaches or Dorr femur type
Parameter
Tilt* (degree) Subsidence* (mm)
P-Value Dorr classification A B (79%) (21%) 1.50 (± 1.34) 1.54 (± 1.03) 0.40 (± 0.57) 0.46 (± 1.03)
0.5069 0.7254
Surgical approach Direct Lateral Postero-Lateral (25%) (75%) Tilt* (degree) 1.45 (± 1.32) 1.67 (± 1.12) 0.2613 Subsidence* (mm) 0.34 (± 0.53) 0.65 (± 1.02) 0.1111 The values are presented in mean (± standard deviation) of the absolute values
ACCEPTED MANUSCRIPT Acknowledgments The authors would like to thank Maricar Alminiana, Adrian Cartaleanu and Karen Smith
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assistance in data analysis and manuscript preparation.
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for their assistance in the collection and recording clinical data and to Laura Epure for her
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Figure 1. AP radiograph of the pelvis following bilateral THAs with a conventional Tri-
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lock stem in the right hip and the shorter Tri-lock BPS stem in the left hip.
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Figure 2. OrthoView template image showing subsidence calculation on the AP pelvis
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radiograph. Subsidence was calculated as the difference in the distance between the summit of the lesser trochanter and distal tip of the implant at six weeks and last follow-
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up.
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Figure 3: AP hip radiographs of a patient who developed aseptic loosening of the
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acetabular cup and femoral stem. Compared to the post-operative image (left) the oneyear follow-up image (right) shows acetabular cup migration and femoral stem
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subsidence of 5mm.
Figure 4. Pre-operative and post-operative images of a patient who underwent staged bilateral uncemented primary THA using the Tri-Lock BPS.
Figure 5: Kaplan-Meier survival curve at minimum four years for all patients with the Tri-Lock BPS stem with revision for stem failure. Kaplan-Meier survival analysis showed a 99.2% (95% CI: 94.7-100.0%) survival rate (circles = censored observations).
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Figure 5
S0883-5403(15)00774-3 doi: 10.1016/j.arth.2015.08.020 YARTH 54672
To appear in:
Journal of Arthroplasty
Received date: Revised date: Accepted date:
18 June 2015 6 August 2015 13 August 2015
Please cite this article as: Albers Anthony, Aoude Ahmed, Zukor David, Huk Olga, Antoniou John, Tanzer Michael, Favourable Results of a Short, Tapered, Highly Porous, Proximally Coated Cementless Femoral Stem at a Minimum Four-Year Follow-up, Journal of Arthroplasty (2015), doi: 10.1016/j.arth.2015.08.020
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT Favourable Results of a Short, Tapered, Highly Porous, Proximally Coated Cementless
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Femoral Stem at a Minimum Four-Year Follow-up.
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Authors
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MD, PhD, FRCSC, M Tanzer, MD, FRCSC
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A Albers, MD, A Aoude, MD, D Zukor, MD, FRCSC, O Huk, MD, FRCSC, J Antoniou,
Affiliations
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Division of Orthopaedic Surgery, McGill University, Montreal, Quebec, Canada
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Dr. John Antoniou
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Correspondence to be addressed to:
Jewish General Hospital, Room E-003
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3755 Côte-Sainte-Catherine Road Montreal, Quebec, Canada H3T 1E2
Email: [email protected] Tel: (514) 340-8222 x4615 Fax: (514) 340-7595
ACCEPTED MANUSCRIPT TITLE Favourable Results of a Short, Tapered, Highly Porous, Proximally Coated Cementless
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Femoral Stem at a Minimum Four-Year Follow-up.
ABSTRACT
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Background
Shorter femoral stems have many potential advantages in total hip arthroplasty (THA),
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and as such, their use has been increasing. However, there are very few clinical studies
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evaluating the outcomes of these stems and comparing them to their regular sized counterparts.
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Methods
We undertook a study to provide radiological and functional outcomes of the Tri-Lock
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Bone Preservation Stem, a short, tapered, highly porous, proximally coated cementless
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stem with minimum four-year follow-up. One hundred and thirty-one THAs were
Results
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evaluated and mean follow-up was five years (range, 4.1 - 5.5 years).
Stem related complications were low and only one stem required revision THA for aseptic loosening. Kaplan-Meier analysis indicated five-year stem survival to be 99.2% (95% CI: 94.7-100.0%), which is comparable to conventional length Tri-Lock stems (99.8% at 8.9 years). Conclusion This study demonstrates that this short femoral stem can provide reproducible and successful outcomes at five-year follow-up. Further studies are necessary to determine the long-term outcome of these implants and their results in patients with poor bone stock.
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Key Words:
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Primary, Total Hip Arthroplasty, Short Stem, Cementless, Taper
ACCEPTED MANUSCRIPT INTRODUCTION Uncemented total hip arthroplasty (THA) using standard length femoral prostheses has
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been performed for more than 40 years and has demonstrated clinical success and cost
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effectiveness in the treatment of degenerative joint disease of the hip [1-7]. More recently, the use of shorter bone preserving stems is becoming more widespread [8]. While the
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idea of short femoral stems is not new, their renewed popularity derives from certain
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potential advantages they present over their standard length counterparts [9]. Certain design features, such as a reduced lateral shoulder, a thin tapered geometry and a shorter
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overall length aim to conserve native bone stock, which is especially important in younger patients [10]. Smaller stems also facilitate insertion when using less invasive
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surgical techniques. Furthermore, metaphyseal as opposed to diaphyseal fitting stems
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have improved load transfer characteristics, they avoid problems caused by proximaldistal femoral diaphyseal mismatch, decrease rates of thigh pain and reduce stress
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shielding [3, 8, 11-15]. Notwithstanding these potential advantages, short femoral stems
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must demonstrate an equivalent outcome to that of regular length cementless stems in order to support their routine use in primary THA. To date, only short to midterm survivorship data is available on certain implant designs and questions remain regarding learning curve, stem positioning, subsidence and suitability for patients with poor bone stock [16, 17]. There are very few studies in the literature that directly compare short stems to their regular sized counterparts in a randomized fashion using validated measurement tools[18] . The goal of this study was to evaluate cementless primary THAs performed using the TriLock Bone Preservation Stem (Tri-Lock BPS, DePuy, Johnson & Johnson, Warsaw, IN,
ACCEPTED MANUSCRIPT USA). The Tri-Lock BPS is a short tapered-wedge, proximally porous-coated titanium femoral stem that is identical in geometry, but significantly shorter in length than its
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clinically successful conventional predecessor, the Tri-Lock stem (Figure 1 and Table 1).
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The proximal porous coating of these two stems is identical in length, but the Tri-Lock BPS has a highly porous and roughened coating (Gription), while the Tri-Lock stem has a
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conventional porous coating of smooth beads. We hypothesize that this short stem will
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provide comparable results to regular length cementless femoral stems used for primary
MATERIAL AND METHODS
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THA.
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For the current study we selected all patients who received a Tri-Lock BPS for a primary
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cementless THA between July 2009 and April 2010. All clinical data, obtained from our patient database, was acquired prospectively. Institutional review board approval was
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obtained prior to the onset of the study. Surgeries were performed by one of four In these
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attending orthopedic surgeons practicing in two independent institutions.
institutions, the Tri-Lock BPS is the primary femoral implant used for THA in patients judged to have adequate bone stock (Dorr type A or B femur) [19]. Exclusion criteria included revision THA, previous hemi-arthroplasty or surgical arthrodesis on the ipsilateral side, hips in which pre-operative templating demonstrated the femur could not accommodate a size 0 implant, hips with significant anteversion deformity such as in Crowe IV hips and Dorr C femora where templating demonstrated distal canal fill with marked undersizing of the proximal femur.
ACCEPTED MANUSCRIPT All patients were evaluated clinically pre-operatively then post-operatively at six weeks, one year and every second year thereafter. Clinical evaluation included the Harris Hip
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Score (HHS), University of California Los Angeles (UCLA) activity level and presence
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or absence of thigh pain [20, 21]. Any significant postoperative complications related to the femoral implant were documented.
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Antero-posterior (AP) radiographs of the pelvis with the legs internally rotated 15
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degrees and AP and lateral radiographs of the operated hip were obtained and evaluated for Dorr femur type [19], signs of bony ingrowth or signs of loosening and were
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classified as osseointegrated, fibrous stable or unstable [22]. Standard radiographic parameters where used to assess adequacy of the films such as symmetry of the obturator
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foramen, tip of coccyx in line and within 2-4 cm of symphysis pubis. Radiographs were
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repeated if deemed inadequate by the treating surgeon. Radiographic analysis was performed retrospectively by two authors (AA and AA) using
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OrthoView (OrthoView LLC, Jacksonville, FL, USA) software, which facilitated
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calculation of image magnification and allowed us to determine the amount of subsidence and varus/valgus positioning of the implant in the coronal plane. Subsidence was measured as the distance between the summit of the lesser trochanter and bottom edge of the stem at six weeks post-operatively in comparison to the latest follow up imaging (Figure 2). Coronal plane alignment was determined using stem templating software in OrthoView and comparing the stem axis to the anatomic axis of the femur (Figure 2). With the collected data, we compared subsidence and coronal plane alignment based on surgical approach and femur type. Varus or valgus inclination of the stem relative to the
ACCEPTED MANUSCRIPT canal of over 5 degrees was defined to be malpositioned and a progressive subsidence of more than 3 mm was determined to be a sign of possible loosening [23-26].
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Patient demographics were calculated with arithmetic mean and all errors are reported as
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standard deviations. Since all analyzed outcomes failed the Shapiro-Wilk test for normality, a non-parametric Mann Whitney U test was conducted to determine the
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significance between preoperative and the last postoperative HHS and UCLA activity
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scores and to compare mean difference in subsidence and coronal inclination with different surgical approaches or Dorr femur type. A non-parametric Spearman test was
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used to determine the correlations between stem subsidence, positioning, surgical approach or Dorr femur type. All other comparisons between different time-points and
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follow up groups were performed using a non-parametric Kruskal-Wallis test followed by
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a Dunn’s multiple comparisons. A p-value of less than 0.05 was considered to be statistically significant. Interobserver reliability was determined using weighted and
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unweighted Cohen’s Kappa analysis. Finally, the survival analysis was performed using
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the Kaplan-Meier method with corresponding 95% confidence interval (CI). The TriLock BPS survivorship was determined for stem failure with femoral revision or impending revision as an endpoint. The time between the index procedure and revision was a measurement of survival of the joint. Survival times for patients who had not undergone revision were recorded at the study census date (January 15, 2015). GraphPad Prism software (GraphPad Software, La Jolla, CA, USA) was used for all statistical analyses.
ACCEPTED MANUSCRIPT RESULTS Between July 2009 and April 2010, in both institutions, 124 patients (131 hips) had a
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primary THA using a Tri-Lock BPS femoral stem. Five patients were lost to follow-up
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(4%) leaving 119 patients (126 hips) for study. Of the patients lost to follow-up, two died within two years after surgery from causes unrelated to the index procedure and three
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patients could not be reached, two of which were over age 90 years old. The mean age of
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patients at the time of the surgery was 65 years (range, 34 – 89 years) and the mean follow-up was five years (range, 4.1 - 5.5 years). Preoperative diagnoses were:
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osteoarthritis (94%), avascular necrosis (4%), developmental dysplasia of the hip (1%) and rheumatoid arthritis (1%) (Table 2). The surgery was performed through a mini direct
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lateral approach in 25% of the cases and through a mini posterolateral approach in 75%
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of the cases. All patients, without complications, were allowed full weight bearing immediately post-operatively. Femoral implant sizes ranged from 0 to 8 in either
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Standard or High offset as determined by pre-operative templating and intra-operative
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evaluation. All patients received a cementless fully porous coated acetabular cup. The HHS and UCLA scores (85 ± 13 and 6 ± 2 respectively) at the last follow up significantly improved (p < 0.0001) from their pre-operative values (42 ± 15 and 4 ±2 respectively) (Table 3). Two patients (2 hips), both having received a posterior approach, had mild postoperative thigh pain that resolved after with three weeks of protected weight bearing with crutches and non-steroidal anti-inflammatories. Of the patients included in the study, 116 patients (123 hips) had complete radiological follow-up. The remaining three patients were reached by phone and reported they were very satisfied with their THA but they were either unable or refused to return for follow-
ACCEPTED MANUSCRIPT up. Subsidence occurred in 49 cases (39.8%) with an average of 1.04 ± 0.73 mm (range, 0.5 to 5 mm) for the subsided stems (Table 4). The mean stem subsidence for the entire
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cohort was 0.41 ± 0.69 mm. The only stem that showed subsidence exceeding 3 mm was
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a 60 year-old female with Behcets disease on immunosuppressive drug therapy. The patient developed aseptic loosening of both the stem and cup. The stem had subsided 5
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mm over the first 12 months postoperatively. She required revision THA using a standard
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length fully porous coated stem (Figure 3). All the remaining stems were found on the radiographs to be osseointegrated (Figure 4).
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Eighty-three stems (67.5%) were placed in varying degrees of valgus (range 0 to 7, mean 1.99 ± 1.13 degrees) and 11 (8.9%) in varus (range 0 to 3, mean 1.82 ± 0.87 degrees)
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(Table 4). The mean stem coronal plane position was 1.18 ± 1.58 degrees of valgus
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compared to the femoral axis. Only one stem in our series was outside the acceptable 5 degree range for coronal alignment. This stem was placed in 7 degrees of valgus
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alignment. This did not affect the patient’s outcome as the stem was osseointegrated and
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the HHS was 88 at 5.3 years follow-up. Intersobserver reliability for subsidence and coronal position measurements was κ = 0.7 and 0.8, respectively. There was no significant difference in stem subsidence or coronal positioning with different surgical approaches (posterolateral vs. direct lateral) or Dorr femur type (Table 5), and no significant correlations were observed between stem subsidence, positioning, surgical approach or Dorr femur type. Kaplan-Meier analysis indicated five-year stem survival to be 99.2% (95% CI: 94.7-100.0 %) (Figure 5). In terms of complications, two hips with Type A femora had an iatrogenic fracture of the greater trochanter during femoral broaching. They both healed uneventfully after being
ACCEPTED MANUSCRIPT treated with intra-operative wiring and six weeks protected weight bearing. Two patients had a postoperative dislocation; one was treated closed, the other required acetabular
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component revision for recurrent instability secondary to acetabular malposition. The
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femoral stem was stable at the time of surgery and did not require revision.
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DISCUSSION
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This study evaluated the Tri-Lock BPS femoral stem, a short single tapered wedge, proximally porous-coated titanium primary THA stem. At a mean follow-up of five years,
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the implant performed exceedingly well with an overall survivorship of 99.2%. Stem related complications were low and only one stem, which subsided 5 mm, required
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revision for aseptic loosening. Overall, the use of this short stem was associated with a
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significant improvement in the HHS and UCLA scores. Only two hips (1.6%) experienced mild, transient thigh pain following their THA.
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In this study, the short stem was very stable and exhibited a mean subsidence of only
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0.41± 0.69 mm. This is likely related to the design features and the roughened porous coating. Proximally, the taper design allows complete fill of the medial-lateral dimensions of the femoral metaphysis, thereby enhancing rotational stability. The tapered wedge design may allow a certain amount of migration in the cranio-caudal and mediallateral planes, however, the concept of rest-fit enhances stability [27-30]. It is unclear whether settling of the implant leads to increased stability and potential for ingrowth or whether it represents a risk factor for early loosening [16, 23, 31]. Early data suggested that settling of the prosthesis into a stable position was non-detrimental [16, 32, 33]. However, more recent studies have indicated that subsidence of 2 to 3 mm could be a
ACCEPTED MANUSCRIPT threshold for early failure. In accordance to these findings, implant undersizing could also be linked to instability and early failure [8, 23, 31, 32]. In our series, the average
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subsidence of 0.41± 0.69 mm was well below the previously stated threshold for
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loosening. Stems with subsidence between 0 and 3mm were all stable while a single stem, which subsided 5mm required revision. This may indicate that 3wmm is a threshold for
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stability. The amount of subsidence was unaffected by the geometry of the femur or
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surgical approach used. This is likely due to the versatility of the implant and its ease of insertion using a broach-only technique. It must also be noted that all of our cases were
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Dorr type A or B. While standard length tapered wedge stems and certain short stems have been used with success in Dorr C femurs, data remains limited [16, 34].
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design are known variables for proper prosthesis placement. Varus malalignment, especially in cemented implants, has been shown to impact negatively on implant
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survival [35]. However, many studies evaluating cementless implants have failed to show
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any difference [26, 36, 37]. In our series, most stems (67.5%) where placed in minimal valgus (1.99 ± 1.13 degrees) with only one stem inserted in more than 5 degrees from the anatomic axis of the femur. This position did not negatively affect function or survival at short-term follow-up. Coronal alignment did not correlate with femoral morphology or surgical approach. The relative valgus positioning of the stem in this study is thought to be due to the surgeon’s desire to avoid varus placement. As well, the absence of a lateral shoulder and a longer stem to engage the more distal femoral diaphysis makes it more difficult for the surgeon to feel if the stem is in neutral or slight valgus intraoperatively when the canal is being broached.
ACCEPTED MANUSCRIPT The single case of aseptic loosening of both stem and cup, in this study, occurred in a patient with Behcets disease who was on multiple immunosuppressive agents including
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Prednisone and Infliximab. An immunocompromised state and decreased capacity for
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osseointegration may preclude the use of a short, proximally porous coated femoral stem. A more extensively porous coated device is most likely indicated in these cases in order
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to increase the surface area for potential osseointegration.
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Our implant survival probability of 99.2% at five years compares favorably with conventional length Tri-Lock stems (99.8% at 8.9 years) [7, 27, 28]. The extent to which
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the highly porous and rough porous coating of the Tri-Lock BPS contributes to the survivorship remains unclear. The patients in our study had a low incidence of thigh pain
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(1.6%) compared to the reported incidence for standard length Tri-Lock stems (5.1%)
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[28]. Biomechanical and clinical research has correlated stem length, materials used and stem design with thigh pain [38]. Shorter metaphyseal fitting stems appear to be
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beneficial in reducing thigh pain [39]. One pitfall of the cementless metaphyseal-fitting
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tapered component is its broach-only technique, which has been described to increase the risk of iatrogenic femur fracture [40]. Nonetheless, compared to broach-only technique using diaphyseal-fitting stems, this risk is far diminished. The rate of iatrogenic femur fractures in our study (1.6%) is comparable to the rates found in the literature [11]. The limitations of our study are its non-randomized design and lack of a control group. Patient factors such as age, level of activity, individual anatomy and bone quality can impact the surgeon’s choice of implant leading to a selection bias that may have improved outcomes in our study, particularly in patients with poor bone stock, where a different type of implant would have been selected. Another limitation of this particular
ACCEPTED MANUSCRIPT stem, despite its reduced length and mostly metaphyseal fit is that the smallest available size is sometimes too large for some particularly small femora. When this is found during
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pre-operative templating another stem is selected. Finally, we were limited to using the
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available software in our institution for measurement of subsidence. While using OrthoView software aids in determining image magnification and implant position in the
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coronal plane, Radiostereometric Analysis (RSA) is the gold standard for measurement of
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stem migration [41, 42]. Nevertheless, using the threshold of our software makes our values clinically relevant, as RSA is not used in routine clinical practice. Ultimately, our
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study has a short follow-up period and the majority of femoral prostheses have excellent results at less than five-years. Although the mid-term results of the Trilock BPS are
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encouraging and similar to the traditional Trilock stem, it is not clear without further
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follow-up whether or not these results will be sustained at the 10-year follow-up time period. While long-term studies are warranted, our follow-up period is in keeping with
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most currently available studies evaluating the use of short femoral stems in THA. The
unclear.
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extent to which these results can be extrapolated to other short stem designs remains
CONCLUSION: This study demonstrates that a short, tapered, highly porous, proximally coated cementless femoral stem can provide reproducible and successful outcomes at a mean of five years following primary THA. Patient outcomes were independent of age, Dorr femur types A or B and surgical approach. Revision rates, intra-operative femur fractures as well as the incidence of thigh pain were equal or lower than those quoted in the
ACCEPTED MANUSCRIPT literature. At short to midterm follow up, these stems appear to perform as well as historical controls, thus justifying their use in THA. Further studies are necessary to
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determine the long-term outcome of these implants and their results in patients with poor
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bone stock.
ACCEPTED MANUSCRIPT REFERENCES
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1. Pivec R, Johnson AJ, Mears SC, Mont MA. Hip arthroplasty. The Lancet 380(9855): 1768, 2012 2. Kim YH. Long-term results of the cementless porous-coated anatomic total hip prosthesis. J Bone Joint Surg Br 87(5): 623, 2005 3. Hozack WJ, Rothman RH, Eng K, Mesa J. Primary cementless hip arthroplasty with a titanium plasma sprayed prosthesis. Clin Orthop Relat Res (333): 217, 1996 4. Lombardi AV, Berend KR, Mallory TH. Hydroxyapatite-coated titanium porous plasma spray tapered stem: experience at 15 to 18 years. Clin Orthop Relat Res 453: 81, 2006 5. Marshall AD, Mokris JG, Reitman RD, Dandar A, Mauerhan DR. Cementless titanium tapered-wedge femoral stem: 10- to 15-year follow-up. J Arthroplasty 19(5): 546, 2004 6. McLaughlin JR, Lee KR. Total hip arthroplasty with an uncemented tapered femoral component. J Bone Joint Surg Am 90(6): 1290, 2008 7. Burt CF, Garvin KL, Otterberg ET, Jardon OM. A femoral component inserted without cement in total hip arthroplasty. A study of the Tri-Lock component with an average tenyear duration of follow-up. J Bone Joint Surg Am 80(7): 952, 1998 8. Lombardi AV, Berend KR, Adams JB. A short stem solution: through small portals. Orthopedics 32(9), 2009 9. Morrey BF. Short-stemmed uncemented femoral component for primary hip arthroplasty. Clin Orthop Relat Res (249): 169, 1989 10. Huo MH, Parvizi J, Bal BS, Mont MA. What's new in total hip arthroplasty. The Journal of Bone & Joint Surgery 91(10): 2522, 2009 11. Molli RG, Lombardi AV, Berend KR, Adams JB, Sneller MA. A short tapered stem reduces intraoperative complications in primary total hip arthroplasty. Clin Orthop Relat Res 470(2): 450, 2012 12. Albanese CV, Santori FS, Pavan L, Learmonth ID, Passariello R. Periprosthetic DXA after total hip arthroplasty with short vs. ultra-short custom-made femoral stems: 37 patients followed for 3 years. Acta Orthop 80(3): 291, 2009 13. Bourne RB, Rorabeck CH, Ghazal ME, Lee MH. Pain in the thigh following total hip replacement with a porous-coated anatomic prosthesis for osteoarthrosis. A five-year follow-up study. J Bone Joint Surg Am 76(10): 1464, 1994 14. Chen HH, Morrey BF, An KN, Luo ZP. Bone remodeling characteristics of a shortstemmed total hip replacement. J Arthroplasty 24(6): 945, 2009 15. Stulberg SD, Dolan M. The short stem: a thinking man's alternative to surface replacement. Orthopedics 31(9): 885, 2008 16. Reitman RD, Emerson R, Higgins L, Head W. Thirteen year results of total hip arthroplasty using a tapered titanium femoral component inserted without cement in patients with type C bone. J Arthroplasty 18(7 Suppl 1): 116, 2003 17. van Oldenrijk J, Molleman J, Klaver M, Poolman RW, Haverkamp D. Revision rate after short-stem total hip arthroplasty: a systematic review of 49 studies. Acta Orthop 85(3): 250, 2014 18. McCalden RW, Korczak A, Somerville L, Yuan X, Naudie DD. A randomised trial comparing a short and a standard-length metaphyseal engaging cementless femoral stem using radiostereometric analysis. Bone Joint J 97-B(5): 595, 2015
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19. Dorr LD, Faugere MC, Mackel AM, Gruen TA, Bognar B, Malluche HH. Structural and cellular assessment of bone quality of proximal femur. Bone 14(3): 231, 1993 20. Harris WH. Traumatic arthritis of the hip after dislocation and acetabular fractures: treatment by mold arthroplasty. An end-result study using a new method of result evaluation. J Bone Joint Surg Am 51(4): 737, 1969 21. Amstutz HC, Thomas BJ, Jinnah R, Kim W, Grogan T, Yale C. Treatment of primary osteoarthritis of the hip. A comparison of total joint and surface replacement arthroplasty. J Bone Joint Surg Am 66(2): 228, 1984 22. Engh CA, Massin P, Suthers KE. Roentgenographic assessment of the biologic fixation of porous-surfaced femoral components. Clin Orthop Relat Res (257): 107, 1990 23. Kim YH, Kim JS, Joo JH, Park JW. A prospective short-term outcome study of a short metaphyseal fitting total hip arthroplasty. J Arthroplasty 27(1): 88, 2012 24. Kim YH, Kim JS, Oh SH, Kim JM. Comparison of porous-coated titanium femoral stems with and without hydroxyapatite coating. J Bone Joint Surg Am 85-A(9): 1682, 2003 25. Barreca S, Ciriaco L, Ferlazzo M, Rosa MA. Mechanical and biological results of short-stem hip implants: consideration on a series of 74 cases. Musculoskelet Surg 99(1): 55, 2015 26. Min BW, Song KS, Bae KC, Cho CH, Kang CH, Kim SY. The effect of stem alignment on results of total hip arthroplasty with a cementless tapered-wedge femoral component. J Arthroplasty 23(3): 418, 2008 27. Parvizi J, Keisu KS, Hozack WJ, Sharkey PF, Rothman RH. Primary total hip arthroplasty with an uncemented femoral component: a long-term study of the Taperloc stem. J Arthroplasty 19(2): 151, 2004 28. Healy WL, Tilzey JF, Iorio R, Specht LM, Sharma S. Prospective, randomized comparison of cobalt-chrome and titanium trilock femoral stems. J Arthroplasty 24(6): 831, 2009 29. Noble PC, Alexander JW, Lindahl LJ, Yew DT, Granberry WM, Tullos HS. The anatomic basis of femoral component design. Clin Orthop Relat Res (235): 148, 1988 30. Leali A, Fetto J, Insler H, Elfenbein D. The effect of a lateral flare feature on implant stability. International orthopaedics 26(3): 166, 2002 31. Kim YH, Kim VE. Early migration of uncemented porous coated anatomic femoral component related to aseptic loosening. Clin Orthop Relat Res (295): 146, 1993 32. Sakalkale DP, Eng K, Hozack WJ, Rothman RH. Minimum 10-year results of a tapered cementless hip replacement. Clin Orthop Relat Res (362): 138, 1999 33. Mulliken BD, Bourne RB, Rorabeck CH, Nayak N. A tapered titanium femoral stem inserted without cement in a total hip arthroplasty. Radiographic evaluation and stability. J Bone Joint Surg Am 78(8): 1214, 1996 34. Kim YH, Park JW, Kim JS. Is diaphyseal stem fixation necessary for primary total hip arthroplasty in patients with osteoporotic bone (Class C bone)? J Arthroplasty 28(1): 139, 2013 35. Kobayashi S, Takaoka K, Saito N, Hisa K. Factors affecting aseptic failure of fixation after primary Charnley total hip arthroplasty. Multivariate survival analysis. J Bone Joint Surg Am 79(11): 1618, 1997
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36. Berend KR, Mallory TH, Lombardi AV, Dodds KL, Adams JB. Tapered cementless femoral stem: difficult to place in varus but performs well in those rare cases. Orthopedics 30(4): 295, 2007 37. de Beer J, McKenzie S, Hubmann M, Petruccelli D, Winemaker M. Influence of cementless femoral stems inserted in varus on functional outcome in primary total hip arthroplasty. Can J Surg 49(6): 407, 2006 38. Campbell AC, Rorabeck CH, Bourne RB, Chess D, Nott L. Thigh pain after cementless hip arthroplasty. Annoyance or ill omen. J Bone Joint Surg Br 74(1): 63, 1992 39. Brown TE, Larson B, Shen F, Moskal JT. Thigh pain after cementless total hip arthroplasty: evaluation and management. J Am Acad Orthop Surg 10(6): 385, 2002 40. Fitzgerald RH, Brindley GW, Kavanagh BF. The uncemented total hip arthroplasty. Intraoperative femoral fractures. Clin Orthop Relat Res (235): 61, 1988 41. Malchau H, Karrholm J, Wang YX, Herberts P. Accuracy of migration analysis in hip arthroplasty. Digitized and conventional radiography, compared to radiostereometry in 51 patients. Acta Orthop Scand 66(5): 418, 1995 42. Nistor L, Blaha JD, Kjellstrom U, Selvik G. In vivo measurements of relative motion between an uncemented femoral total hip component and the femur by roentgen stereophotogrammetric analysis. Clin Orthop Relat Res (269): 220, 1991
ACCEPTED MANUSCRIPT TABLES Table 1: Trilock BPS vs. corresponding original Ti-Trilock stem lengths
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STD: Standard Offset
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Δ Length (mm)
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6.3 STD 7.5 STD 8.8 STD 10 STD 11.3 STD 12.5 STD 13.8 STD 15 STD 17.5 STD 20 STD 22.5 STD
Lateral Shoulder / Tip (mm) 134.0 137.0 140.0 142.0 145.0 147.0 150.0 152.0 157.0 162.0 167.0
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Old Ti TriLock Size
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0 STD 1 STD 2 STD 3 STD 4 STD 5 STD 6 STD 7 STD 8 STD 9 STD 10 STD 11 STD 12 STD -
Lateral Shoulder / Tip (mm) 114.5 116.5 118.5 122.0 124.0 126.0 128.0 130.0 132.0 134.0 136.0 138.0 140.0 -
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TriLock BPS Size
19.5 20.5 21.5 20.0 21.0 21.0 22.0 22.0 23.0 24.0 -
ACCEPTED MANUSCRIPT Table 2: Patient demographic data Characteristic
Finding
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No. patients/hips 64.6 (34-89) yrs.
Gender
55 male / 64 female
Follow-up*
5.0 (4.1-5.5) yrs.
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Age (range)*
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Surgical approach Direct Lateral
31 hips (25%) 95 hips (75%)
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Postero-Lateral
Osteoarthritis
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Congenital dysplasia
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Etiology
119 hips (94.4%) 1 hip (0.8%) 1 hip (0.8%)
Avascular necrosis
5 hips (4.0%)
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Rheumatoid arthritis
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* This value is reported as the mean in years.
ACCEPTED MANUSCRIPT Table 3: Clinical results Preoperative
Final Follow-Up
P-Value
Harris Hip Score*
41.9 (± 15.2)
84.5 (± 12.6)
< 0.0001
3.9 (± 2.1)
5.8 (± 2.0)
< 0.0001
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UCLA Activity Score*
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Clinical Parameters
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* The values are reported as the mean (± standard deviation).
Number stems (%) Subsidence 123 74 (60.2%) 49 (39.8%)
All Neutral Varus Valgus
123 29 (23.0%) 11 (8.9%) 83 (67.5%)
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All No subsidence Subsidence
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Table 4: Tilt and subsidence
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Tilt
Average ± SD (mm) 0.41 ± 0.69 − 1.04 ± 0.73 (degrees) 1.18 ± 1.58 − 1.82 ± 0.87 1.99 ± 1.13
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Table 5: Tilt (coronal inclination) and subsidence with different surgical approaches or Dorr femur type
Parameter
Tilt* (degree) Subsidence* (mm)
P-Value Dorr classification A B (79%) (21%) 1.50 (± 1.34) 1.54 (± 1.03) 0.40 (± 0.57) 0.46 (± 1.03)
0.5069 0.7254
Surgical approach Direct Lateral Postero-Lateral (25%) (75%) Tilt* (degree) 1.45 (± 1.32) 1.67 (± 1.12) 0.2613 Subsidence* (mm) 0.34 (± 0.53) 0.65 (± 1.02) 0.1111 The values are presented in mean (± standard deviation) of the absolute values
ACCEPTED MANUSCRIPT Acknowledgments The authors would like to thank Maricar Alminiana, Adrian Cartaleanu and Karen Smith
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assistance in data analysis and manuscript preparation.
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for their assistance in the collection and recording clinical data and to Laura Epure for her
ACCEPTED MANUSCRIPT FIGURES:
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Figure 1. AP radiograph of the pelvis following bilateral THAs with a conventional Tri-
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lock stem in the right hip and the shorter Tri-lock BPS stem in the left hip.
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Figure 2. OrthoView template image showing subsidence calculation on the AP pelvis
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radiograph. Subsidence was calculated as the difference in the distance between the summit of the lesser trochanter and distal tip of the implant at six weeks and last follow-
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up.
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Figure 3: AP hip radiographs of a patient who developed aseptic loosening of the
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acetabular cup and femoral stem. Compared to the post-operative image (left) the oneyear follow-up image (right) shows acetabular cup migration and femoral stem
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subsidence of 5mm.
Figure 4. Pre-operative and post-operative images of a patient who underwent staged bilateral uncemented primary THA using the Tri-Lock BPS.
Figure 5: Kaplan-Meier survival curve at minimum four years for all patients with the Tri-Lock BPS stem with revision for stem failure. Kaplan-Meier survival analysis showed a 99.2% (95% CI: 94.7-100.0%) survival rate (circles = censored observations).
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Figure 1
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Figure 2
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Figure 3
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Figure 4
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Figure 5