A randomised trial comparing a short and a standard-length metaphyseal engaging cementless femoral stem using radiostereometric analysis

Validation for the effect of intra-exposure patient motion on the assessment of radiostereometric implant migration in a tibial component phantom study

BACKGROUND

An increasing number of radiostereometry (RSA) research studies have long-term follow-up implant migration outcomes, which show ascending curves of implant migration with occasionally decreasing migration. After scrutinizing images and RSA scenes related to the alternating curves, we suppose that intra-exposure patient motion may contribute to that. The main purposes of this in vitro study were 1) to identify whether the patient motion in different directions could result in the inaccurate assessment of implant migration, and 2) to figure out which direction(s) accounted for the alternating curves.

HYPOTHESIS

It was hypothesized that the assessments of implant migration would be less precise and accurate than they could be when patient motion occurred, and such motion would contribute to the alternating curves of radiostereometric implant migration.

MATERIALS AND METHODS

A customized phantom, assembled with a tibial component, was designed for simulating intra-exposure patient motion during follow-up RSA examinations. Two different Roentgen tubes were used as the current standard of radiology departments. Radiographs were acquired in a uniplanar technical arrangement. Two defined protocols were conducted: one is to simulate implant migration outcomes at post-op, the early stage (6months), and the later stage (2 to 10years) ; during the later stage, the other is to mimic patient motion by phantom motion in the medial-lateral (x), distal-proximal (y), and anterior-posterior (z) axes.

RESULTS

Phantom motion could result in the inaccurate assessment of implant migration, and translations along the medial-lateral (x) axis were the most influenced by patient motion. Motion along the medial-lateral (x) axis could account for the curves with decreasing migration.

DISCUSSION

Our assessments of implant migration may be less precise and accurate than they could be when intra-exposure patient motion occurs. We probably neglect the importance of 100% simultaneous exposures, and the influence of patient motion on RSA accuracy and data reliability, due to the difficulty in detecting patient (micro)motion. Electronically synchronized exposures of two paired Roentgen tubes are 100% simultaneous for image acquisition, and they are thus highly recommended for the assessment of implant migration in RSA.

TYPE OF STUDY AND LEVEL OF PROOF

not applicable.

Very early migration of a calcar-guided short stem: a randomized study of early mobilization and the influence of a calcium phosphate coating with 60 patients

This study analyzed the migration of a calcar-guided short stem to determine the course of very early migration, as well as evaluated the effect of an additional calcium phosphate (CP) coating on a titanium plasma spray (TPS) coating, which has not been analyzed previously. Sixty patients were enrolled in this study and were treated with the A2 calcar-guided short stem. The implant coating was randomized with either the TPS or an additional CP coating, and radiostereometric analysis was performed with the baseline measurement before initial weight-bearing, along with follow-up examinations at 1 week, 6 weeks, 3 months, and 6 months. Implant migrations were 0.27 mm (standard deviation [SD], 0.13 mm) and 0.74 mm (SD, 1.11 mm) at 1 week and 6 months post-surgery, respectively, and 65% and 87% of the implants reached their final position 1 week and 6 weeks after surgery, respectively. After 6 weeks, 3 months, and 6 months, a significant increase was noted in the migration of the CP coating group vs. that of the TPS coating group. Upon the final observation at 6 months, the groups displayed on average a 0.74-mm migration. Most of the analyzed implants ceased migration within the first week post-surgery, but the CP coating demonstrated a higher and more prolonged migration compared to the TPS coating.

Stress shielding effect after total hip arthroplasty varies between combinations of stem design and stiffness-a comparing biomechanical finite element analysis

PURPOSE

Total hip arthroplasty (THA) has become a highly frequent orthopaedic procedure. Multiple approaches have been made to design the femoral component for THA with a mechanical behaviour as close as possible to a natural femur. The aim of this study was to compare different combinations of design and biomechanical properties of THA prostheses and their impact on stress shielding of the periprosthetic bone.

METHODS

Virtual implantation of different stem designs (straight standard stem, straight short stem, anatomical short stem) by finite element analysis based on in vivo data from computer tomography was performed. For each stem, three grades of stiffness were generated, followed by a strain analysis.

RESULTS

Reduction of stem stiffness led to less stress shielding. Implantation of an anatomical short-stem prosthesis with low stiffness provided the most physiological strain-loading effect (p < 0.001).

CONCLUSION

A combination of a short and an anatomically designed stem with a low stiffness might provide a more physiological strain transfer during THA. Biomechanical properties of the femoral component for THA should be considered as a multifactorial function of dimensions, design, and stiffness.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Diagnosis and Detection of Subtle Aseptic Loosening in Total Hip Arthroplasty

Aseptic loosening is a common cause of revision total hip arthroplasty (rTHA), and with the rising number of primary THAs, revisions for aseptic loosening represent a significant burden for arthroplasty surgeons. Aseptic loosening remains a diagnostic and management challenge. Loosening can occur as a result of inadequate initial fixation, mechanical loss of fixation over time, or a biological loss of fixation over time. However, in most cases, etiology is multifactorial, involving all 3 factors. The diagnosis of aseptic loosening involves a careful history, focused clinical exam, and thorough evaluation of imaging using several diagnostic modalities. The careful evaluation of serial radiographs remains the cornerstone of diagnosis with additional input from advanced imaging modalities such as FDG-PET, DEXA, MRI, and several others, each offering unique advantages and disadvantages. In certain patients, history and physical exam might be the only initial obvious signs of loosening, and thus, unexplained continuous pain augmented by imaging findings serves as an indication for revision surgery.

Short neck-preserving femoral stem for total hip arthroplasty: medium-term results of a 68-case series

INTRODUCTION

Short stems seem to be a good alternative for young patients as they offer promising results, rapid recovery and preservation of metaphyseal bone stock. This is one of the few studies in the literature to report medium-term clinical-radiological results for short hip stems.

MATERIALS AND METHODS

This prospective study evaluated 68 short femoral stems in 63 patients treated with total hip replacement. Clinical, functional and quality-of-life outcomes were measured at 6 and 12 months, and annually thereafter until the end of follow-up. The radiological analysis included measurements of potential leg length discrepancies, stem alignment and signs compatible with stress shielding.

RESULTS

Fifty-four males (59 hips) and nine females (9 hips) of an average age of 44.3 years (range, 25-68) were studied. The most common diagnosis was osteoarthritis (51.5%). Mean overall follow-up was 7.8 years (range, 5.8-9.8). The overall survival rate was 97.1% (95% CI 88.7-99.7%). Surgery resulted in an increase of 42.3 ± 1.1 points in the modified Harris Hip Score and 21.9 ± 0.6 points in the Oxford Hip Score (p < 0.001, respectively). Moreover, the pain score as measured on a numerical rating scale (NRS) improved from 95.8 to 36.3. As regards function, an improvement was observed from 3.2 ± 0.8 points to 6.8 ± 1.14 points on the University of California at Los Angeles activity score (p < 0.001, respectively). The radiological analysis showed an absence of radiolucencies or stress-shielding throughout the series. The complications rate at the end of follow-up was 5.7%.

CONCLUSIONS

The use of ultra-short cylindrical stems with complete anchorage in the femoral neck was shown to offer promising medium-term results. Such stems appear to be a good option for young patients, who are likely to require several revisions over their lifetime.

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

Background

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

Methods

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

Results

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

Conclusion

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

Are short press-fit stems comparable to standard-length cemented stems in reverse shoulder arthroplasty? A prospective, randomized clinical trial

BACKGROUND

The literature comparing humeral implants in reverse shoulder arthroplasty is sparse. With minimal supporting literature, there has been a trend away from standard-length cemented humeral implants to press-fit stems and, recently, to shorter-stem implants. It is known that early implant migration, within the first 2 years postoperatively, is predictive of later implant loosening and possible revision surgery. Therefore, the purpose of this study was to compare clinical outcomes and implant migration between cemented standard-length humeral stems and press-fit short stems using model-based radiostereometric analysis.

METHODS

After a power analysis, 41 shoulders were prospectively randomized to receive either a cemented standard-length or press-fit short humeral stem for primary reverse shoulder arthroplasty between July 2017 and June 2019. Following surgery, participants were imaged with stereo radiographs acquired at 6 weeks (baseline), 3 months, 6 months, 1 year, and 2 years. Migration of the humeral stem at each time point was compared with baseline, with differences in migration between cohorts assessed using a mixed-effects model with the Bonferroni test for multiple comparisons. Patient-reported outcome measures (Subjective Shoulder Value; American Shoulder and Elbow Surgeons shoulder score; Simple Shoulder Test score; Disabilities of the Arm, Shoulder and Hand score; and Constant score) were also compared.

RESULTS

At 6 months (P = .025), 1 year (P = .004), and 2 years (P = .001) postoperatively, press-fit short stems migrated significantly more than cemented stems along the superior-inferior translation axis; in addition, they showed greater total translation at 2 years (P = .003). Mean total translation (± standard deviation) at 2 years was 0.4 ± 0.2 mm and 1.0 ± 1.1 mm for the cemented and press-fit cohorts, respectively. Mean migration between the 1- and 2-year time points was minimal for both stem fixation groups along all axes (<0.1 mm and 0.6°). There was no difference in active range of motion, pain, or validated outcome measures between the cohorts at 2 years (P ≥ .170).

CONCLUSION

This randomized clinical trial shows that press-fit short humeral stems subside substantially more than standard-length cemented stems but ultimately achieve stability from 1 year through 2 years. Conversely, no significant differences were observed in clinical outcomes between cohorts.

Ultra-Short Bone Conserving Cementless Femoral Stem

Excellent long-term results have been reported with conventional length cementless femoral stems in total hip arthroplasty; however, proximal stress shielding and thigh pain are still a concern. Metaphyseal engaging bone conserving short stems provide theoretical benefits compared with conventional length cementless stems, including avoiding proximal-distal mismatch, decreasing proximal stress shielding, and limiting perioperative fractures. The purpose of the ultra-short bone conserving cementless stem was to reproduce natural load transfer with an ultra-short stem obtaining optimal stability using the morphology of the proximal femur. Loss of stability of the stem and failure of osseous ingrowth is a potential concern with the use of ultra-short proximal loading cementless femoral stems. Ultra-short, metaphyseal-fitting anatomic or non-anatomic cementless femoral stems provided stable fixation without relying on diaphyseal fixation in young and elderly patients, suggesting that metaphyseal-fitting alone is sufficient in young and elderly patients who have good bone quality.

A Prospective, Randomized Comparison of the Long-Term Clinical and Radiographic Results of an Ultra-Short vs a Conventional Length Cementless Anatomic Femoral Stem

BACKGROUND

The purpose of this study is to compare the long-term clinical and radiographic results, survival rates, and complication rates of an ultra-short vs a conventional length cementless anatomic femoral stem.

METHODS

We reviewed 759 patients (858 hips) (mean age, 56.3 ± 12.9 y) who had an ultra-short cementless anatomic stem and 759 patients (858 hips) (mean age, 54.8 ± 12.3 y) who had a conventional length cementless anatomic stem. The mean follow-up was 16.5 years (range 14-17) in the ultra-short stem group and 17.5 years (range 17-20) in the conventional stem group.

RESULTS

At the latest follow-up, there were no significant differences between the 2 groups in terms of the Harris Hip Scores (92 ± 6 vs 91 ± 7 points, P = .173), Western Ontario and McMaster Universities Osteoarthritis scores (12 ± 8 vs 13 ± 7 points, P = .972), University of California Los Angeles activity scores (7.6 vs 7.8 points, P = .841), patient satisfaction scores (7.7 ± 2.3 vs 7.5 ± 2.5 points, P = .981), and survival rates (97.6% vs 96.6%). However, incidence of thigh pain (P = .031) and stress shielding (P = .001) was significantly higher in the conventional length stem group than in the ultra-short anatomic stem group. Complication rates were similar (1.8% vs 2.7%) between the 2 groups.

CONCLUSION

Although an ultra-short cementless anatomic femoral stem confers equivalent clinical and radiographic outcomes, survival rates, and complication rates to conventional length cementless anatomic stem, the incidence of thigh pain and stress shielding was significantly lower in the ultra-short cementless anatomic stem.

LEVEL OF EVIDENCE

Therapeutic Level I.

Effect of stem position and length on bone-stem constructs after cementless hip arthroplasty

Aims

There are concerns regarding initial stability and early periprosthetic fractures in cementless hip arthroplasty using short stems. This study aimed to investigate stress on the cortical bone around the stem and micromotions between the stem and cortical bone according to femoral stem length and positioning.

Methods

In total, 12 femoral finite element models (FEMs) were constructed and tested in walking and stair-climbing. Femoral stems of three different lengths and two different positions were simulated, assuming press-fit fixation within each FEM. Stress on the cortical bone and micromotions between the stem and bone were measured in each condition.

Results

Stress concentration was observed on the medial and lateral interfaces between the cortical bone and stem. With neutral stem insertion, mean stress over a region of interest was greater at the medial than lateral interface regardless of stem length, which increased as the stem shortened. Mean stress increased in the varus-inserted stems compared to the stems inserted neutrally, especially at the lateral interface in contact with the stem tip. The maximum stress was observed at the lateral interface in a varus-inserted short stem. All mean stresses were greater in stair-climbing condition than walking. Each micromotion was also greater in shorter stems and varus-inserted stems, and in stair-climbing condition.

Conclusion

The stem should be inserted neutrally and stair-climbing movement should be avoided in the early postoperative period, in order to preserve early stability and reduce the possibility of thigh pain, especially when using a shorter stem.

Cite this article: Bone Joint Res 2021;10(4):250–258.

Complex Primary Total Hip Arthroplasty: Small Stems for Big Challenges

Total hip arthroplasty is one of the most successful operations in all of medicine. Femoral deformities from malunion, prior osteotomy, and retained surgical implants all present unique challenges. Corrective osteotomy and hardware removal add significant morbidity to an operation that typically has a fast recovery. Short stems can be used in these cases to spare patients' increased morbidity. We present a case-based illustration and surgical technique for the use of short stems in complex primary total hip arthroplasty with femoral deformity and retained hardware. We discuss how these implants can spare significant morbidity, show radiographic examples of their use, and present short-term outcomes.

Abductor Muscle Force after Straight-Stem Compared to Short-Stem Total Hip Arthroplasty through a Modified Direct Lateral Approach: Functional Assessment of 70 Consecutive Patients of a Randomized Controlled Clinical Trial

Because of preservation of proximal femoral bone stock and minimized soft tissue trauma, short-stem implants are becoming increasingly important in total hip arthroplasty (THA). The postulated advantage regarding the functional outcome has not been verified. We hypothesized an increased abductor muscle strength by the use of a short-stem design. Seventy consecutive patients of a randomized clinical trial were included. Of these, 67 patients met the inclusion criteria after 12 months. Thirty-five patients received a standard straight stem and 32 patients a short-stem femoral component. All surgeries were performed by a modified direct lateral approach. Isometric muscle strength of the hip abductors was evaluated preoperatively 3 and 12 months after surgery. Harris hip score (HHS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores were evaluated. After three months, there were no differences between the two groups; the abductor force was comparable to the preoperative initial values. After 12 months, a significant increase in muscle strength for the short stem patient group compared to preoperative baseline values was measured (straight-stem THA, 0.09 Nm/kg ± 0.4, p = 0.32; short-stem THA, 0.2 Nm/kg ± 0.3, p = 0.004). Comparison of the 12-month postoperative total HHS and WOMAC revealed no significant differences between both groups. A significant increase in hip abductor muscle strength 12 months after short-stem THA compared to conventional-stem THA was observed.

A comparison of short-stem prostheses and conventional stem prostheses in primary total hip arthroplasty: a systematic review and meta-analysis of randomized controlled trials

Background

In total hip arthroplasty (THA), short-stem prostheses (SS) were designed to achieve better preservation of proximal femoral bone stock and stability than conventional stem prostheses (CS), however these effects are controversial. We aimed perform a systematic review and meta-analysis to evaluate the effectiveness of SS and CS in primary THA.

Methods

Relevant randomized controlled trials (RCTs) involving the comparison of SS and CS in primary THA were screened using the electronic databases PubMed, Embase and Web of Science. Data were analyzed with the RevMan 5.3 software program and evaluated with mean difference (MD), risk ratio (RR) and 95% confidence intervals (CIs) by random or fixed-effect models.

Results

Sixteen RCTs involving 1,233 patients (1,486 hips) were included. Compared with CS, the incidence of thigh pain was significantly reduced with Proxima SS (RR 0.13, 95% CI, 0.03–0.51; P=0.004). Bone mineral density (BMD) with femoral neck-preserved SS [SS (I)] showed less decrease in Gruen zone 1 (MD 14.60, 95% CI, 10.67–18.54; P<0.00001) and Gruen zone 7 (MD 9.72, 95% CI, 5.21–14.23; P<0.0001) than CS. However, the changes of BMD were not significantly different between the SS without femoral neck preservation group [SS (II)] and the CS group. In addition, no significant differences were found in the revision rate, Harris Hip Score (HHS), or maximum total point motion (MTPM) between the SS and CS groups.

Conclusions

The results of this study showed that compared with CS, Proxima SS decreased the incidence of thigh pain and that SS (I) provided better proximal bone remodeling than CS. But the revision rates, HHS, and MTPM between SS and CS were similar. However, the findings of this meta-analysis require further verification in high-quality RCTs.

Malalignment and distal contact of short tapered stems could be associated with postoperative thigh pain in primary total hip arthroplasty

PURPOSE

Short tapered stem placement has been extensively employed in total hip arthroplasty (THA). Suboptimal fixation tends to cause postoperative complications, such as thigh pain. However, it remains unclear whether poor seating/alignment of short tapered stems contributes to thigh pain. In this study, we retrospectively examined the factors that might be associated with thigh pain.

METHODS

Medical records of 230 patients who had undergone THAs at our hospital were reviewed retrospectively. All patients received the same mediolateral (ML) short tapered femoral stems. The association between thigh pain and patients' demographics, radiographic findings, or the type of fitting of the femoral stems was investigated.

RESULTS

In our cohort, 68 patients (27.8%) presented with thigh pain. Among 203 type I fit patients, 62 (30.5%) developed thigh pain, while only 6 out of 43 (12.2%) type II fit patients had thigh pain, with the differences being statistically significant (x² = 6.706, p = 0.01). In addition, hip anteroposterior radiographs exhibited that the stem angulation (mean 2.52°), the variation in angulation (mean 1.32°), and the extent of femoral stem subsidence (mean 0.29 cm) were greater in patients with thigh pain than in their counterparts without thigh pain (all p < 0.05).

CONCLUSION

Malalignment and improper seating of short tapered stems could be at least one of the reasons for post-THA thigh pain. The distal contact between the stem tip and the medial femoral cortex might result in thigh pain. Our study suggested that distal implant contact should be avoided, and stem alignment should be meticulously performed in the placement of ML short tapered femoral stems for THA.

Mid-term subsidence and periprosthetic radiolucency of the AMIStem: a 5-year EBRA-FCA analysis

Background

There has been an evolution in cementless total hip arthroplasty (THA) with newer short stem designs aimed to preserve metaphyseal bone stock and facilitate implantation through minimally invasive approaches. While early subsidence has been correlated to aseptic loosening in conventional stems, there is a paucity of data regarding short stems. The current study aims to report on stem subsidence and mid-term clinical outcomes of a cementless, metaphyseal-anchored short femoral stem, specifically designed for the direct anterior approach (DAA).

Methods

Ninety-four consecutive patients (100 hips) with a minimum follow-up of 5 years following cementless THA were included in this single-center retrospective study. Subsidence was evaluated using the “Ein-Bild-Roentgen-Analyse” (EBRA). Periprosthetic radiolucency allocated to the zones of Charnley and Gruen was assessed. Additionally, demographic and implant-related factors potentially associated with increased subsidence and clinical outcomes were evaluated.

Results

At the last follow-up, the average stem subsidence was 1.98 ± 1.20 mm, with 48% of the implants demonstrating subsidence of > 2 mm. Periprosthetic radiolucency of > 2 mm was found in 26% of the implants in zone 1 and in 9% in zone 7, respectively. Neither the amount of subsidence nor proximal periprosthetic radiolucency was associated with aseptic loosening or worse clinical outcomes.

Conclusions

Comparable to other proximally fixed short stem designs, the highest subsidence was observed within the first 3 months following implantation. No demographic or implant-related factors were found to have a statistically significant influence on stem subsidence. Periprosthetic radiolucency and subsidence of the AMISstem is not correlated with worse clinical outcomes at 5-year follow-up.

Mid-term results of total hip arthroplasty using a novel uncemented short femoral stem with metaphyso-diaphyseal fixation

PURPOSE

Short stems were developed with the promise of providing easier implantation, facilitating revision, reducing thigh pain and proximal stress shielding. The aim of this study is to present the mid-term clinical results of a titanium short stem with modular neck.

METHODS

This is a prospective case series of 144 THAs performed on a series of 131 patients using the PROFEMUR Preserve Femoral Stem (MicroPort Orthopedics, Arlington, TN, USA). 2 surgeons, operated on the patients using a mini-posterior approach. The primary outcomes evaluated were stem revision for aseptic loosening and all-cause stem revision. Clinical and radiographic outcomes were also assessed.

RESULTS

Of the 144 THAs, there were 43 males and 101 females, with an average age of 61 (range 22-92) years at surgery. After a mean of 78 (range 53-87) months follow-up, there were 2 (1.5%) femoral implant revisions; 1 for early femoral periprosthetic fracture and 1 for fatigue failure of the modular femoral neck. There were no cases of stem aseptic loosening and radiographic analysis demonstrated no cases of stem migration. The mean UCLA activity, WOMAC and Fogotten Joint scores were respectively 6.1, 10.7 and 86.6. 70% of prosthetic hips were observed as having no restriction and 99.2% of patients were satisfied with their THA.

CONCLUSIONS

This short modular stem produced satisfactory clinical and radiological results at mid-term, with 98.5% implant survival for any cause of stem revision and no revisions for aseptic loosening. Long-term results are required to further evaluate the stem's promising early results.

The effect of femoral stem collar on implant migration and clinical outcomes following direct anterior approach total hip arthroplasty

AIMS

The direct anterior (DA) approach has been associated with rapid patient recovery after total hip arthroplasty (THA) but may be associated with more frequent femoral complications including implant loosening. The objective of this study was to determine whether the addition of a collar to the femoral stem affects implant migration, patient activity, and patient function following primary THA using the DA approach.

METHODS

Patients were randomized to either a collared (n = 23) or collarless (n = 26) cementless femoral stem implanted using the DA approach. Canal fill ratio (CFR) was measured on the first postoperative radiographs. Patients underwent a supine radiostereometric analysis (RSA) exam postoperatively on the day of surgery and at two, four, six, 12, 26, and 52 weeks postoperatively. Patient-reported outcome measures (Western Ontario and McMaster Universities Osteoarthritis (WOMAC) Index, the 12-item Short Form Health Survey Mental and Physical Score, and University of California, Los Angeles (UCLA) Activity Score) were measured preoperatively and at each post-surgery clinic visit. Activity and function were also measured as the weekly average step count recorded by an activity tracker, and an instrumented timed up-and-go (TUG) test in clinic, respectively.

RESULTS

Comparing the RSA between the day of surgery baseline exam to two weeks postoperatively, subsidence was significantly lower (mean difference 2.23 mm (SD 0.71), p = 0.023) with collared stems, though these patients had a greater CFR (p = 0.048). There was no difference (p = 0.426) in subsidence between stems from a two-week baseline through to one year postoperatively. There were no clinically relevant differences in PROMs; and there was no difference in the change in activity (p = 0.078) or the change in functional capacity (p = 0.664) between the collared stem group and the collarless stem group at any timepoint.

CONCLUSION

Presence of a collar on the femoral stem resulted in reduced subsidence during the first two postoperative weeks following primary THA using the DA approach. However, the clinical implications are unclear, and larger studies examining patient activity and outcomes are required. Cite this article: Bone Joint J 2020;102-B(12):1654-1661.

Mid-term migration pattern of a calcar-guided short stem: A five-year EBRA-FCA-study

BACKGROUND

Short-term results of several short-stem designs have indicated early axial migration. Mid- and long-term results for most designs are lacking. The objective of this study was to evaluate the mid-term migration pattern of a calcar-guided short stem five years postoperative.

METHODS

Implant migration of 191 calcar-guided short stems was assessed by Ein-Bild-Roentgen-Analysis Femoral-Component- Analysis (EBRA-FCA) 5 years after surgery. Migration pattern of the whole group was analyzed and compared to the migration pattern of implants potentially being "at hazard" with a subsidence of more than 1.5 mm at 2 years postoperatively. Influence of preoperative Dorr types (A vs. B vs. C), age (<70 vs. >70 years), gender (female vs. male), weight (<90 kg vs. >90 kg), BMI (<30 vs. >30) and uni-vs. bilateral procedures on mid-term migration pattern was analyzed. Additionally outcome of varus- and valgus stem alignment was assessed.

RESULTS

Mean axial subsidence was 1.5 mm (SD 1.48 mm) at final follow-up. Two years after surgery 73 short stems were classified "at hazard". Of these stems, 69 cases showed secondary stabilisation in the following period, whereas 4 cases presented unstable with more than 1 mm of further subsidence. Stem revision was not required neither in the group of implants with early stabilisation nor the group with pronounced early onset migration. Male gender and heavy-weight patients had a significant higher risk for axial migration, as well as extensive valgus stem alignment, whereas for Dorr type B, compared to A, no statistical difference could be observed.

CONCLUSIONS

In most cases, even in the group of stems being "at hazard", settling could be documented. While different Dorr types did not show a statistically significant impact on axial migration, particularly in male and heavy-weight patients the risk of continuous subsidence is increased. In those 4 cases with further migration, undersizing of the stem could be recognized. At present, clinical consequences are still uncertain.

Role of a bone conserving short stem femoral component in revision total hip arthroplasty: A case report

Choice of the implant during revision total hip arthroplasty (THA) is crucial in younger patients due to the impaired quality of bone and deficient bone stock. The short femoral stem provides an appealing unorthodox alternative implant in young patients undergoing primary total hip arthroplasty. A classic revision total hip arthroplasty predominantly describes the use of conventional or long stem for revision of the femoral component. However, little is known about the use of short femoral stem in revision THA. This case report discusses the revision of cemented conventional femoral stem using a bone-conserving short-stem femoral implant with circumferential metaphyseal fixation, which is seldom reported in the literature. Associated benefits are less aggressive surgery with a reduction in blood loss, magnitude and duration of surgery by avoiding the removal of distal cement in the femur canal, thus making the femoral component revision easier. Moreover, it facilitates postoperative rehabilitation and recovery as well. Also, it preserves the femoral bone stock and offers a long term solution especially in young patients retaining the choice of using a conventional or long stem femoral implant should a second revision becomes imperative.

A comparison of patient-reported outcome measures (PROMs) between short and conventional stem hip replacements: a systematic review and meta-analysis

INTRODUCTION

Short stem hip replacements may allow preservation of proximal bone stock and minimise soft tissue disruption, easing future revision surgery. However patient satisfaction with these implants must be determined before widespread use. We aimed to compare patient reported outcome measures (PROMs) between short and conventional stem hip replacements.

METHODS

A systematic review was conducted according to PRISMA guidelines for studies comparing short and conventional stem hip replacements with validated PROMs. Meta-analyses were performed for studies reporting Harris Hip and WOMAC scores. Study bias was assessed with the Cochrane Risk of Bias tool and Newcastle-Ottawa Scale.

RESULTS

24 studies, incorporating 2593 total hip replacements were included for qualitative analysis. 17 studies were included in the meta-analyses. Of the 7 excluded, 1 study reported the Japanese Orthopaedic Association score and 2 others reported the Oxford Hip score. All three showed no difference between the stems. A meta-analysis of 17 studies reporting Harris hip scores showed no statistically significant difference between short and conventional stems (standard mean difference (SMD) -0.06, 95% CI -0.20-0.07, p = 0.35). 6 studies reported WOMAC scores with higher scores indicating worse outcome. No difference was seen between the two groups (SMD 0.21, 95%CI, -0.01-0.42, p = 0.06). 4 studies reported higher WOMAC scores as better. Once again, a meta-analysis showed no statistically significant difference between the stems (SMD 0.28, 95% CI -0.07-0.63, p = 0.12).

CONCLUSIONS

Our systematic review showed no difference in PROMs between short and conventional stem total hip replacements. This is in keeping with previous evidence but is a more comprehensive analysis. Short stems may have an important role in younger individuals as they allow preservation of proximal femoral bone, minimal access surgery and are amenable to abnormal anatomy. The current literature is hindered by non-uniform methodologies and outcome assessments across studies. Further, standardised, high quality evidence is required before widespread changes in practice.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Fixation of the short global tissue-sparing hip stem

AIMS

Short, bone-conserving femoral components are increasingly used in total hip arthroplasty (THA). They are expected to allow tissue-conserving implantation and to render future revision surgery more straightforward but the long-term data on such components is limited. One such component is the global tissue-sparing (GTS) stem. Following the model for stepwise introduction of new orthopaedic implants, we evaluated early implant fixation and clinical outcome of this novel short-stem THA and compared it to that of a component with established good long-term clinical outcome.

METHODS

In total, 50 consecutive patients ≤ 70 years old with end-stage symptomatic osteo-arthritis were randomized to receive THA with the GTS stem or the conventional Taperloc stem using the anterior supine intermuscular approach by two experienced hip surgeons in two hospitals in the Netherlands. Primary outcome was implant migration. Patients were followed using routine clinical examination, patient reported outcome using Harris Hip Score (HHS), Hip Disability And Osteoarthritis Outcome Score (HOOS), EuroQol five-dimension questionnaire (EQ5D), and Roentgen Stereophotogrammetric Analysis (RSA) at three, six, 12, and 24 months. This study evaluated the two-year follow-up results.

RESULTS

In addition to the initial migration pattern of distal migration (subsidence, Y-translation) and retroversion (Y-rotation) also exhibited by the Taperloc stem, the GTS stem showed an initial migration pattern of varization (X-translation combined with Z-rotation) and posterior translation (Z-translation). However, all components stabilized aside from one Taperloc stem which became loose secondary to malposition and was later revised. Clinical outcomes and complications were not statistically significantly different with the numbers available.

CONCLUSION

A substantially different and more extensive initial migration pattern was seen for the GTS stem compared to the Taperloc stem. Although implant stabilization was achieved, excellent long-term survival similar to that of the Taperloc stem should not be inferred. Especially in the absence of clinically proven relevant improvement, widespread usage should be postponed until long-term safety has been established. Cite this article: Bone Joint J 2020;102-B(6):699-708.

Greater early migration of a short-stem total hip arthroplasty is not associated with an increased risk of osseointegration failure: 5th-year results from a prospective RSA study with 39 patients, a follow-up study

Background and purpose - Short-stem hip arthroplasty has been a viable alternative to standard stems for the treatment of hip osteoarthritis for over 10 years. This study assessed whether a correlation existed between a greater initial increase in implant migration and inferior clinical outcomes at 5 years postoperatively. Results on these patients after 2 years have been published previously.Patients and methods - Radiostereometry and clinical scoring were undertaken after surgery and at 3, 6, 12, and 24 months, and 5 years postoperatively. The migration and the clinical outcomes data from the patients with initial migrations at 3 months above the 75th percentile (≥ 75% group) were compared with those with migrations at 3 months of less than the 75th percentile (< 75% group).Results - Between 3 months and 5 years after surgery, the mean resultant implant migrations were 0.40 mm (SD 0.32) in the ≥ 75% group and 0.39 mm (SD 0.25) in the < 75% group. The mean Harris Hip Scores and SF-36 physical scores at 5 years postoperatively were 100 (SD 0.4) and 44 (SD 12), respectively, for the ≥ 75% group and 99 (SD 2) and 50 (SD 10), respectively, for the < 75% group. The differences between the patient groups were not statistically significant.Interpretation - There was no correlation between a greater initial migration and inferior clinical outcomes at 5 years postoperatively. Despite a greater initial migration, there were no risks of early aseptic loosening and inferior midterm clinical outcomes associated with a short-stem implant with a primary metaphyseal anchorage.

Short stems for total hip replacement among middle-aged patients

INTRODUCTION

The purpose of the present study was to investigate the role of short stem implants for primary total hip arthroplasty in middle-aged patients. For this purpose, a meta-analysis of the current literature was conducted. The focus was on clinical outcomes,radiological parameters, and further complications of both components.

MATERIAL AND METHODS

The study was performed according to the PRISMA guidelines. All randomized and non-randomized clinical trials comparing short stem versus standard stem prostheses for THA were considered for inclusion. Only studies reporting data concerning uncemented stems for primary total hip arthroplasty were included. Only studies reporting data concerning patients with a mean age of 45 to 69 were included.

RESULTS

A total of 2197 procedures in 2116 patients were analysed. The mean follow-up was 30.2 months. The short stem group showed a statistically significant higher WOMAC score and a reduced total estimated blood loss compared with the standard stem group. The short stem group showed a reduced rate of femoral fractures, dislocations, and revision, but without statistical significance.

CONCLUSIONS

According to the main findings of this meta-analysis and current evidence, we encourage the use of the uncemented short stems during primary total hip arthroplasty in middle-aged patients.

New Implant Introduction in Total Hip Arthroplasty Using Radiostereometric Analysis: A Cautionary Note

BACKGROUND

It has been proposed that the introduction of new hip implant technology in orthopedic surgery be conducted in a more controlled manner in order to properly ensure patient safety and the likelihood of favorable outcomes. This stepwise introduction would first require a prospective randomized study in a small cohort of patients, using radiostereometric analysis (RSA). The aim of this study is to determine if the recent literature supports the use of RSA as an early screening tool to accurately predict the long-term outcomes of cementless femoral stems.

METHODS

A review of the recent published literature identified 11 studies that used RSA to predict the long-term stability of a cementless femoral component. These RSA predictive data were compared to the 10-year revision rate reported in the Australian Registry or in the published literature to determine its reliability.

RESULTS

RSA data did not universally predict long-term stem fixation. In 2 of the 11 cases (18%), the RSA study incorrectly predicted the ability of the cementless stem to reliably osseointegrate. Of the 9 stems considered stable in the RSA studies, the 10 year registry and literature data confirmed that 6 implants had a low revision rate and were well performing. One stem has not performed well clinically and has been listed as having a higher than anticipated rate of revision in the registry. Two stems do not have sufficient follow-up. Of the 2 stems RSA predicted to do poorly, 1 is well performing at 10 years, and 1 has a high revision rate at 8 years.

CONCLUSION

In the stepwise introduction of new hip implants, RSA should be best considered as an adjunct tool in deciding whether or not an implant should be evaluated in a larger multicenter clinical studies, rather than the sole criterion.

An Ultra-Short Femoral Neck-Preserving Hip Prosthesis: A 2-Year Follow-up Study with Radiostereometric Analysis and Dual X-Ray Absorptiometry in a Stepwise Introduction

BACKGROUND

Total hip arthroplasty (THA) with a diaphyseal stem may risk bone loss. In order to save proximal bone stock in young patients with a high activity level and a long life expectancy, the interest in short stems has evolved. The purpose of this prospective observational cohort study was to evaluate the fixation of, and bone remodeling around, the Primoris femoral neck-preserving hip implant.

METHODS

Fifty younger patients with end-stage osteoarthritis were managed with the Primoris hip implant. We evaluated bone mineral density (BMD) using dual x-ray absorptiometry (DXA) and implant migration using radiostereometric analysis (RSA). A region-of-interest (ROI) protocol for 4 ROIs was applied to assess BMD. The association between BMD and migration was evaluated to determine the fixation of the Primoris implant and bone remodeling in the proximal part of the femur. Follow-up evaluation was performed at regular intervals from day 1 (baseline) until 24 months after surgery.

RESULTS

The major stem migrations were subsidence (Y axis; mean, 0.38 mm) at 6 weeks and varus tilt (rotation) (Z axis; mean, 0.93°) at 6 to 12 months. In ROI4 (the calcar area), a significant gain in bone was found with a mean difference of 4.1% (95% confidence interval [CI], 0.8% to 7.4%; p < 0.02) at 24 months postoperatively. Significant bone loss was found in ROI1 and ROI2, with a mean difference of -4.9% (95% CI, -7.4% to -2.4%; p = 0.0003) and -8.9% (95% CI, -11.5% to -6.2%; p = 0.0001), respectively. Linear regression and multivariate regression analysis showed a significant negative association between maximal total point motion and BMD (p = 0.02, R = 15%; and p < 0.05, R = 26%, respectively).

CONCLUSIONS

The Primoris component showed satisfactory primary stability with promising results at the 24-month follow-up. DXA scans showed limited stress-shielding with the proximal loading pattern of the Primoris. Better bone quality was associated with less implant migration.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Migration analysis of a metaphyseal-anchored short femoral stem in cementless THA and factors affecting the stem subsidence

Background

Early femoral stem subsidence following a cementless THA is correlated with aseptic loosening of the femoral component. The short femoral stems allow bone sparing and implantation through a minimally invasive approach; however, due to their metaphyseal anchoring, they might demonstrate different subsidence pattern than the conventional stems.

Methods

In this prospective single-center study, a total of 68 consecutive patients with an average age of 63 years, and a minimum follow-up of 5 years following a cementless THA with a metaphyseal-anchored short femoral stem were included. The femoral stem subsidence was evaluated using “Ein Bild Roentgen Analyse” (EBRA).

Results

Average stem migration was 0.96 +/− 0.76 mm at 3 months, 1.71 +/− 1.26 mm at 24 months, and 2.04+/− 1.42 mm at last follow-up 60 months postoperative. The only factor that affected migration was a stem size of 6 or more (r² = 5.74; p = 0.039). Subdivision analysis revealed, that only in females migration appeared to be affected by stem size irrespective of weight but not in men (female stem size of 6 or more vs. less (Difference = − 1.48 mm, R² = 37.5; p = 0.001). Migration did not have an impact on clinical outcome measures.

Conclusions

The examined metaphyseal-anchored short femoral stem showed the highest subsidence within the first 3 months postoperative, the implant began to stabilize at about 24 months but continued to slowly migrate with average total subsidence of 2.04 mm at 5 years following the THA. The amount of stem subsidence was not associated with worse clinical outcomes such as HHS, patient satisfaction, or pain.

A systematic review of short metaphyseal loading cementless stems in hip arthroplasty

AIMS

Short-stemmed femoral implants have been used for total hip arthroplasty (THA) in young and active patients to conserve bone, provide physiological loading, and reduce the incidence of thigh pain. Only short- to mid-term results have been presented and there have been concerns regarding component malalignment, incorrect sizing, and subsidence. This systematic review reports clinical and radiological outcomes, complications, revision rates, and implant survival in THA using short-stemmed femoral components.

MATERIALS AND METHODS

A literature review was performed using the EMBASE, Medline, and Cochrane databases. Strict inclusion and exclusion criteria were used to identify studies reporting clinical and radiological follow-up for short-stemmed hip arthroplasties.

RESULTS

A total of 28 studies were eligible for inclusion. This included 5322 hips in 4657 patients with a mean age of 59 years (13 to 94). The mean follow-up was 6.1 years (0.5 to 20). The mean Harris Hip Score improved from 46 (0 to 100) to 92 (39 to 100). The mean Oxford Hip Score improved from 25 (2 to 42.5) to 35 (12.4 to 48). The mean Western Ontario & McMaster Universities Osteoarthritis Index improved from 54 (2 to 95) to 22 (0 to 98). Components were aligned in a neutral coronal alignment in up to 90.9% of cases. A total of 15 studies reported component survivorship, which was 98.6% (92% to 100%) at a mean follow-up of 12.1 years.

CONCLUSION

Short-stemmed femoral implants show similar improvement in clinical and radiological outcomes compared with conventional length implants. Only mid-term survivorship, however, is known. An abundance of short components have been developed and used commercially without staged clinical trials. Long-term survival is still unknown for many of these components. There remains tension between innovation and the moral duty to ensure that the introduction of new implants is controlled until safety and patient benefit are demonstrated. Implant innovation and subsequent use should be driven by proven clinical outcomes, rather than market and financial forces, and ethical practice must be ensured. Cite this article: Bone Joint J 2019;101-B:502-511.

Outcome of short versus conventional stem for total hip arthroplasty in the femur with a high cortical index: a five year follow-up prospective multicentre comparative study

BACKGROUND

The uncemented total hip arthroplasty (THA) has become the choice for many hip surgeons. Although conventional uncemented femoral components have a proven track record, there remain concerns about the rate of thigh pain, proximal stress shielding, and consequent loss of bone stock at revision surgery.

METHODS

Inclusion criteria were the following: patients between 50 and 85 years old undergoing primary THA with implant of short (group 1) or conventional (group 2) femoral stem and with femoral shape type A, according to Dorr classification. Clinical follow-up was registered using OHS, HHS, and Womac scores. The radiographic scans were evaluated in order to compare component positioning and bone remodeling at five year follow-up.

RESULTS

We included in the analysis 60 subjects in group 1 and 67 in group 2. No differences were registered between the groups comparing demographic and operative data. One case in group 1 (1.7%) and three cases in group 2 (4.5%) reported an intra-operative fracture. There was a significant improvement in the functional scores in both groups with no significant difference at final follow-up. The incidence of reported thigh pain at follow-up was 14.9% in group 2 and 3.3% in group 1 (p = 0.033). Radiographic analysis documented a difference in terms of stress shielding and thinning of medial and lateral cortex in favour of group 1. Moreover, patients of group 1 showed a higher varus angle at six month follow-up.

CONCLUSION

In patients with high cortical index, a short stem shows better clinical and radiological outcomes at five year follow-up.

Short stems in total hip replacement: evidence on primary stability according to the stem type

BACKGROUND:

As the prevalence of total hip replacement is increasing in younger patients, less invasive implants (short stems) are becoming more favourable. However, despite the advantages of these stems, clinical results with a follow-up of more than 10 years are limited to a very few stem designs. There has been an increase in publications recently - mechanical and clinical studies - concerning the primary stability of short stems. Primary stem stability is an important factor as it reflects final stem stabilisation and is related to the clinical results of the prosthesis.

METHOD:

We conducted a systematic review of the literature to retrieve evidence concerning primary implant stability in short stems - as expressed by implant micromotion and stem subsidence - according to our previously proposed short-stem classification.

RESULTS:

Mechanical in vitro studies on stem micromotion are very few and limited to type 2 "partial collum" short stems. The results are comparable to those of stems with a known long-term excellent clinical course. Clinical results concerning stem migration patterns are also limited to some of the commercially available short stems. Although comparative studies are very few, the results for most of the short stems are similar to those of standard stems.

CONCLUSION:

There are promising results concerning biomechanical studies of the initial micromotion of short stems, as well as clinical results of stem migration patterns. Long-term clinical studies are needed in order to confirm these findings. The existing literature concerns very few of the many commercially available implants.

Mid-term migration analysis of a femoral short-stem prosthesis: a five-year EBRA-FCA-study

INTRODUCTION:

The objective of this study was to evaluate the mid-term migration pattern of a femoral short stem.

METHODS:

Implant migration of 73 femoral short-stems was assessed by Ein-Bild-Roentgen-Analysis Femoral-Component-Analysis (EBRA-FCA) 5 years after surgery. Migration pattern of the whole group was analysed and compared to the migration pattern of implants "at risk" with a subsidence of more than 1.5 mm 2 years postoperative.

RESULTS:

Mean axial subsidence was 1.1 mm (-5.0 mm to 1.5 mm) after 60 months. There was a statistical significant axial migration until 2 years postoperative with settling thereafter. 2 years after surgery 18 of 73 Implants were classified "at risk." Nevertheless, all stems showed secondary stabilisation in the following period with no implant failure neither in the group of implants with early stabilisation nor the group with extensive early onset migration.

CONCLUSION:

In summary, even in the group of stems with more pronounced early subsidence, delayed settling occurred in all cases. The determination of a threshold of critical early femoral short stem subsidence is necessary because of the differing migration pattern described in this study with delayed settling of the Fitmore stem 2 years postoperatively compared to early settling within the first postoperative year described for conventional stems.

Periprosthetic Bone Mineral Density Changes After Implantation of a Curved Bone Preserving Hip Stem Compared to a Standard Length Straight Stem: 5-Yr Results of a Prospective, Randomized DXA-Analysis

INTRODUCTION

The objective of this prospective, randomized study was to evaluate differences in periprosthetic bone mineral density changes in the proximal femur after implantation of a cementless bone preserving stem (Fitmore) compared to a cementless straight stem (CLS Spotorno).

METHODOLOGY

Periprosthetic bone mineral density was measured in 140 patients (aged 33-74 yr) before surgery, 7 d, 3, 12, and 60 mo postoperatively, using dual energy X-ray absorptiometry. The 1-yr results have already been published. The results of the first postoperative measurement served as the baseline value. Because of the different length of the 2 implants we used adapted Gruen zones to divide the periprosthetic bone in seven regions of interest with comparable length. Clinical results were recorded using the Western Ontario and McMaster Universities Arthritis Index and the Harris hip score.

RESULTS

Clinical findings showed comparable results in both groups at all follow-ups (p > 0.05). A total of 5 yr after surgery, the comparison of periprosthetic bone mineral density changes showed significant differences in regions of interests 3 (CLS -3.9% vs Fitmore -0.2%, p < 0.001) and 5 (CLS -3.6% vs Fitmore -1.3%, p = 0.0028) between both implants.

CONCLUSION

Despite the fact that no exclusive proximal load distribution could be observed, proximal periprosthetic bone loss in the proximal femur was less pronounced after implantation of the bone preserving stem than with the straight stem.

Are short-stem prostheses superior to conventional stem prostheses in primary total hip arthroplasty? A systematic review and meta-analysis of randomised controlled trials

OBJECTIVE

Cementless total hip arthroplasty (THA) is associated with reliable clinical results and high patient satisfaction. Short-stem prostheses (SS) were designed to achieve superior preservation of proximal bone stock and stability compared with those of conventional-stem prostheses (CS). This meta-analysis was conducted to determine the proximal bone remodelling, revision rate, Harris Hip Score, radiolucent line and maximum total point motion values of both SS and CS for primary THA.

METHOD

Relevant randomised controlled trials (RCTs) involving SS and CS in primary THA were identified from electronic databases, such as EMBASE, PubMed and the Cochrane Library.

RESULT

Ultimately, 12 RCTs involving 1130 patients (1387 hips) were included. The results showed that compared with CS, SS resulted in less bone mineral density (BMD) changes in Gruen zone 7 at 1 year and 2 years postoperatively (mean difference (MD)=5.11; 95% CI, 1.61, 8.61; P=0.30; and MD=4.90; 95% CI, 1.01, 8.79; P=0.17, respectively). No difference in BMD changes was found for Gruen zone 1 (MD=2.66; 95% CI, -3.31, 8.64; P<0.00001), and no differences were observed for the revision rate (relative risk (RR)=1.52; 95% CI, 0.71, 3.26; P=0.94), Harris Hip Score (MD=-0.38; 95% CI, -1.02, 0.26; P=0.89) or stem migration (MD=0.02; 95% CI, -0.07, 0.11; P=0.04).

CONCLUSION

Our results suggest that compared with CS, SS may provide superior bone remodelling and similar survival rates and clinical outcomes. However, the short-term follow-up of the included studies was inadequate to determine the long-term performance of SS.

Additively manufactured implant components for imaging validation studies

Radiographic imaging is the current standard for evaluating postoperative joint replacements. Prior to application, such imaging methods need to be validated to determine the lower limits of performance under ideal conditions, using either a phantom or cadaver setup. Conventionally manufactured orthopedic implants for use in such studies are not always accessible and may be cost-prohibitive to purchase. We propose the use of additively manufactured implants as a cheaper, more accessible alternative for use in radiographic imaging validation studies. Bias and repeatability were compared between conventionally manufactured and additively manufactured reverse total shoulder implant sets under a standard model-based radiostereometric analysis phantom study environment. Measurements were compared using the humeral stem or glenosphere model relative to reference bone beads, and the humeral stem relative to the glenosphere model to measure implant relative displacement. Compared to the conventionally manufactured implants, the additively manufactured implants had less bias along the internal-external rotation axis (p < 0.001), but greater bias along the abduction-adduction and flexion-extension rotation axes (p = 0.005, 0.011). Additively manufactured implants had greater repeatability along the internal-external rotation axis (p < 0.001), but worse repeatability along the medial-lateral translation axis (p = 0.001) and the abduction-adduction rotation axis (p < 0.001). Differences were on the orders of 0.01 mm and 0.5°. For the purpose of validating two-dimensional-three-dimensional radiographic imaging techniques of orthopedic implants, additively manufactured implants can be used in place of conventionally manufactured implants, assuming they are fabricated to the manufacturer's specifications. Observed differences were within the errors of the measurement technique and not clinically meaningful.

Uncemented short stems in primary total hip arthroplasty: The state of the art

Over the last two decades, several conservative femoral prostheses have been designed. The goals of conservative stems include: the spearing of the trochanteric bone stock; a more physiological loading in the proximal femur reducing the risk of stress shielding; and to avoid a long stem into the diaphysis preventing impingement with the femoral cortex and thigh pain.

All stems designed to be less invasive than conventional uncemented stems are commonly named ‘short stems’. However, this term is misleading because it refers to a heterogeneous group of stems deeply different in terms of design, biomechanics and bearing. In the short-term follow-up, all conservative stems provided excellent survivorship. However, variable rates of complications were reported, including stem malalignment, incorrect stem sizing and intra-operative fracture.

Radiostereometric analysis (RSA) studies demonstrated that some conservative stems were affected by an early slight migration and rotation within the first months after surgery, followed by a secondary stable fixation. Dual-energy x-ray absorptiometry (DEXA) studies demonstrated an implant-specific pattern of bone remodelling.

Although the vast majority of stems demonstrated a good osseointegration, some prostheses transferred loads particularly to the lateral and distal-medial regions, favouring proximal stress shielding and bone atrophy in the great trochanter and calcar regions.

Cite this article: EFORT Open Rev 2018;3:149-159. DOI: 10.1302/2058-5241.3.170052

Periprosthetic femoral fracture as cause of early revision after short stem hip arthroplasty-a multicentric analysis

BACKGROUND

The objective of this study was to analyze the prevalence and causes of early re-operation after hip replacement surgery using short bone-preserving stems in a large multicentre series. Specifically, we evaluated the clinical features of periprosthetic fractures occurring around short stems.

METHODS

A total of 897 patients (1089 hips) who underwent primary total hip arthroplasty or bipolar hemiarthroplasty from January 2011 to February 2015 using short bone-preserving femoral stems were recruited. Mean patient age was 57.4 years (range, 18-97 years), with a male ratio of 49.7% (541/1089). Re-operation for any reason within two years was used as an endpoint. The incidence and clinical characteristics of the periprosthetic femoral fractures were also recorded. Mean follow-up period was 5.1 years (range, 2-7.9 years).

RESULTS

Early re-operation for any reason was identified in 16 (1.5%) of 1089 hips. The main reason for re-operation was periprosthetic femoral fracture, which accounted for eight (50%) of the 16 re-operations. The overall incidence of periprosthetic femoral fracture at two years was 1.1% (12/1089). According to the Vancouver classification, two fractures were AG type and the other ten were B1 type. Advanced age, higher American Society of Anesthesiologist grade, femur morphology of Dorr type C, and the use of a calcar-loading stem increased the risk for periprosthetic femoral fracture.

CONCLUSION

Periprosthetic femoral fracture was the major reason for re-operation after hip replacement surgery using short bone-preserving stems accounting for 50% (8/16) of re-operations two years post-operatively, but did not seem to deteriorate survivorship of implanted prostheses.

Short-Term Results of Ultra-Short Anatomic vs Ultra-Short Non-Anatomic Proximal Loading Uncemented Femoral Stems

BACKGROUND

Question arises as to whether rigid fixation of ultra-short anatomic or ultra-short non-anatomic proximal loading uncemented femoral stem can be obtained without diaphyseal stem fixation. The purpose of this study is to compare the short-term clinical results, radiographic results, revision and survival rates, and complication rates of ultra-short anatomic versus ultra-short non-anatomic uncemented femoral stems.

METHODS

This study consisted of 50 patients (56 hips) in the ultra-short anatomic uncemented stem group (mean age 61.4 ± 14.7 years) and 50 patients (56 hips) in the ultra-short non-anatomic uncemented stem group (mean age 59.5 ± 15.2 years). The mean follow-up was 3.4 years (range 3-4) in the ultra-short anatomic stem group and 3.5 years (range 3-4) in the ultra-short non-anatomic stem group.

RESULTS

At the final follow-up, the mean Harris hip scores (92 vs 93 points), Western Ontario and McMaster Universities Osteoarthritis scores (16 vs 15 points), University of California at Los Angeles activity scores (6.5 vs 6.8 points), the incidence of thigh pain (0% vs 4%), revision rates (0% vs 4%), aseptic loosening rate (0% vs 2%), and complication rates (2% vs 4%) were not significantly different between 2 groups.

CONCLUSION

Both ultra-short anatomic and ultra-short non-anatomic proximal loading uncemented femoral stems obtained rigid fixation without diaphyseal stem fixation in the short-term follow-up. This finding suggests that an ultra-short anatomic uncemented femoral stem can be replaced with an ultra-short non-anatomic uncemented stem to reduce inventory of the femoral stems, and consequently reduce manufacturing and delivery cost of these femoral stems.

Bone preserving level of osteotomy in short-stem total hip arthroplasty does not influence stress shielding dimensions - a comparing finite elements analysis

Background

The main objective of every new development in total hip arthroplasty (THA) is the longest possible survival of the implant. Periprosthetic stress shielding is a scientifically proven phenomenon which leads to inadvertent bone loss. So far, many studies have analysed whether implanting different hip stem prostheses result in significant preservation of bone stock. The aim of this preclinical study was to investigate design-depended differences of the stress shielding effect after implantation of a selection of short-stem THA-prostheses that are currently available.

Methods

Based on computerised tomography (CT), a finite elements (FE) model was generated and a virtual THA was performed with different stem designs of the implant. Stems were chosen by osteotomy level at the femoral neck (collum, partial collum, trochanter sparing, trochanter harming). Analyses were performed with previously validated FE models to identify changes in the strain energy density (SED).

Results

In the trochanteric region, only the collum-type stem demonstrated a biomechanical behaviour similar to the native femur. In contrast, no difference in biomechanical behaviour was found between partial collum, trochanter harming and trochanter sparing models. All of the short stem-prostheses showed lower stress-shielding than a standard stem.

Conclusion

Based on the results of this study, we cannot confirm that the design of current short stem THA-implants leads to a different stress shielding effect with regard to the level of osteotomy. Somehow unexpected, we found a bone stock protection in metadiaphyseal bone by simulating a more distal approach for osteotomy. Further clinical and biomechanical research including long-term results is needed to understand the influence of short-stem THA on bone remodelling and to find the optimal stem-design for a reduction of the stress shielding effect.

Electronic supplementary material

The online version of this article (doi:10.1186/s12891-017-1702-2) contains supplementary material, which is available to authorized users.

Stable migration pattern of an ultra-short anatomical uncemented hip stem: a prospective study with 2 years radiostereometric analysis follow-up

INTRODUCTION

Shorter, anatomically shaped and proximally loading stems have been developed to achieve better stress distribution and be more bone preserving. The purpose of this prospective study was to evaluate the migration pattern of the Proxima™ ultra-short uncemented stem using radiostereometric analysis (RSA), and to review the literature regarding the migration of short stemmed hip arthroplasty.

METHODS

25 patients (28 hips) with hip osteoarthritis received a Proxima stem during total hip arthroplasty (THA). To measure stem migration, repeated RSA examinations were done during a 2 year follow up period. The patients were evaluated with the hip specific (HOOS) and the generic health (EQ5D) scores up to 1 year, and clinically for 6 years postoperatively.

RESULTS

Almost all migration occurred within the first 3 months, with mean subsidence of 0.22 mm and varus rotation of 1.04°, being the primary effect variables. After the third postoperative month and up to the 2 year RSA follow up no further significant migration occurred. The outcome scores showed substantial improvement after 1 year. No revisions were performed or indicated for any stem after a mean clinical follow up of 72.1 months.

CONCLUSIONS

Like many other uncemented stems, the Proxima showed early migration up to 3 months hereafter osseointegration seems to have occurred. The achieved stability and clinical outcomes indicate favorable early results for this stem in younger patients who have good bone quality and average BMI. We found, however, the surgical technique to be slightly more demanding compared to conventional stems owing to the unique implant design that necessitates specific adjusted femoral cutting and broaching procedures.

Early performance-based and patient-reported outcomes of a contemporary taper fit bone-conserving short stem femoral component in total hip arthroplasty

Aims

The aim of this study was to compare early functional and health related quality of life outcomes (HRQoL) in patients who have undergone total hip arthroplasty (THA) using a bone conserving short stem femoral component and those in whom a conventional length uncemented component was used. Outcome was assessed using a validated performance based outcome instrument as well as patient reported outcome measures (PROMs).

Patients and Methods

We prospectively analysed 33 patients whose THA involved a contemporary proximally porous coated tapered short stem femoral component and 53 patients with a standard conventional femoral component, at a minimum follow-up of two years. The mean follow-up was 31.4 months (24 to 39). Patients with poor proximal femoral bone quality were excluded. The mean age of the patients was 66.6 years (59 to 77) and the mean body mass index was 30.2 kg/m2 (24.1 to 41.0). Outcome was assessed using the Oxford Hip Score (OHS) and the University College Hospital (UCH) hip score which is a validated performance based instrument. HRQoL was assessed using the EuroQol 5D (EQ-5D).

Results

There were no major peri-operative complications. There was no difference in the mean post-operative OHS, EQ-5D or function subscale of the UCH hip scores between the two groups. The mean pre-operative OHS and EQ-5D scores improved significantly (all p <  0.001). The mean functional component of the UCH hip score at final follow-up was 42.5 and 40.6 in the short stem and conventional stem groups, respectively. There was no statistically significant difference between the groups (p = 0.42). A total of seven patients (21.2%) in the short stem group and nine (16.98%) in the conventional group achieved a ceiling effect using the OHS; none did using the function subscale of the UCH hip score.

Conclusion

The proximally porous coated tapered short stem femoral component achieves comparable short-term functional outcomes when compared with a conventional longer stem uncemented femoral component when THA is undertaken in patients with good bone quality. Cite this article: Bone Joint J 2017;99-B(4 Supple B):49–55.

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

BACKGROUND

Femoral component stability and resistance to subsidence is critical for osseointegration and clinical success in cementless total hip arthroplasty. The purpose of this study was to radiographically evaluate the anatomic fit and subsidence of 2 different proximally tapered, porous-coated modern cementless femoral component designs.

METHODS

A retrospective cohort study of 126 consecutive cementless total hip arthroplasties was performed. Traditional fit-and-fill stems were implanted in the first 61 hips with the remaining 65 receiving morphometric tapered wedge stems. Preoperative bone morphology was radiographically assessed by the canal flare index. Canal fill in the coronal plane, subsidence, and the sagittal alignment of stems was measured digitally on immediate and 1-month postoperative radiographs.

RESULTS

Demographics and canal flare indices were similar between groups. The percentage of femoral canal fill was greater in the tapered wedge compared to the fit-and-fill stem (P = .001). There was significantly less subsidence in the tapered wedge design (0.3 mm) compared to the fit-and-fill design (1.1 mm) (P = .001). Subsidence significantly increased as body mass index (BMI) increased in the fit-and-fill stems, a finding not observed in the tapered wedge design (P = .013).

CONCLUSION

An anatomically designed morphometric tapered wedge femoral stem demonstrated greater axial stability and decreased subsidence with increasing BMI than a traditional fit-and-fill stem. The resistance to subsidence, irrespective of BMI, is likely due to the inherent axial stability of a tapered wedge design and may be the optimal stem design for obese patients.

Short-stem prostheses in primary total hip arthroplasty: A meta-analysis of randomized controlled trials

BACKGROUND

Short-stem (SS) prostheses require less resection of the femoral neck, produce a more physiological load pattern in the proximal femur, reduce stress shielding, and aid bone conservation and are, therefore, beneficial for young patients. Conventional cementless implants in total hip arthroplasty (THA) have shown excellent clinical results; however, it is unclear whether SS prostheses can obtain the same clinical and radiological outcomes. We conducted a meta-analysis of randomized controlled trials (RCTs) to evaluate whether SS prostheses are superior to conventional implants after primary THA.

METHODS

We reviewed the literature published up to June 2016 from PubMed, Web of Science, and the Cochrane Library to find relevant RCTs comparing SSs and conventional stems in primary THA. Quality assessment was performed by 2 independent reviewers. The RevMan 5.3 software program of the Cochrane Collaboration was used to analyze the data. Random- or fixed-effect models were used to calculate standardized mean differences (SMDs) and 95% confidence intervals (CIs) for each comparison.

RESULTS

Six RCTs involving 552 patients with 572 hips were identified. Strong evidence indicated that SS prostheses were more effective for reducing thigh pain than conventional implants (I = 46%, P = 0.002; risk ratio [RR], 95% CI 0.15, 0.04-0.49). However, there were no significant differences between the 2 groups in Harris Hip Scores (I = 0%, P = 0.84; SMD, 95% CI 0.02, -0.15-0.18), Western Ontario and McMaster Universities Osteoarthritis Index Scores (I = 0%, P = 0.35; SMD, 95% CI 0.09, -0.10-0.27), femoral offset of stem (I = 0%, P = 0.57; SMD, 95% CI 0.06, -0.16-0.29), and leg-length discrepancy (I = 79%, P = 0.88; SMD, 95% CI 0.04, -0.44-0.51).

CONCLUSION

SS prostheses achieve the same clinical and radiological outcomes as conventional implants, and were superior in terms of reducing thigh pain. But whether the postoperative thigh pain applied in 2nd-generation cementless prosthesis still needs further large-scale multicenter studies with longer follow-up to confirm.