Lower periprosthetic bone loss and good fixation of an ultra-short stem compared to a conventional stem in uncemented total hip arthroplasty

Periprosthetic bone mineral density, assessed using dual energy x-ray absorptiometry, following arthroplasty in patients with femoral neck fracture: 5-year outcomes of a randomized controlled trial

OBJECTIVE

The relationship between the surgical approach used for hemiarthroplasty and periprosthetic bone mineral density (BMD) is not well understood. We have previously described a decrease in BMD 1 year postoperatively. Here, we assessed the medium-term changes in periprosthetic BMD.

METHODS

We performed a follow-up study of patients with femoral neck fracture (FNF) who underwent uncemented hemiarthoplasty using a direct lateral or anterolateral approach. Dual-energy X-ray absorptiometry (DXA) was used to evaluate the changes in BMD in 23 patients over 5 years.

RESULTS

A mean 6% loss of total BMD occurred over 1 year, but between 1 and 5 years, BMD was restored to the baseline value. The mean total BMD in the anterolateral group had decreased by 2% after 3 months and 3% after 12 months, and increased by 2% after 5 years, vs. decreases of 7%, 8%, and 3% for the direct lateral group. Between 1 and 5 years, BMD increased in Gruen zones 2, 3, 4, 5, and 6 in both groups. There was a significantly larger increase in zone 4 in the lateral group (4%) than the anterolateral group.

CONCLUSION

The surgical approach affects periprosthetic BMD in patients with FNF. Furthermore, BMD is restored to the baseline value 5 years postoperatively.ClinicalTrials.gov registration number: NCT03753100.

Midterm Comparative Analysis of Short Femoral Stem Survivorship in Dorr Type A Femurs

Background

Proximal-distal mismatch has emerged as a prominent concern in Dorr type A femoral morphology, prompting the exploration of short stems as promising alternatives to conventional stems. This study aimed to evaluate clinical and radiographic outcomes of total hip arthroplasty (THA) using short femoral stems in Dorr type A proximal femoral morphology with a minimum follow-up of 5 years.

Methods

Patients with short femoral stems in Dorr type A between 2011 and 2017 were included. Patients with the Short Modular Femoral (SMF) stem and Metha stem were recruited and patients with a shortened tapered stem (Tri-Lock BPS) were matched by propensity score matching based on age, sex, body mass index, calcar to canal ratio, and diagnosis. Patient-reported outcomes and the presence of thigh pain were assessed at 5 years postoperatively. Revision rate, complication rate, and radiographic outcomes were also assessed and compared.

Results

Twenty-two cases (81%) in the SMF stem and 43 cases (65%) in the Metha stem had more than 5 years of follow-up data available. The SMF stem showed a higher failure rate than the other 2 groups, with 18% requiring revision surgery in the SMF stem compared to 4.6% in the Metha stem, and 2.3% in the Tri-Lock BPS. The SMF stem showed considerable complications such as stem position change and lateral cortical hypertrophy with inferior clinical outcomes than the other 2 stem groups. When the Metha stem and the Tri-Lock BPS groups were compared, more intraoperative fractures were observed in the Metha stem, whereas stress shielding and anterior thigh pain were significantly more prevalent in the Tri-Lock BPS.

Conclusions

The SMF stem might be less reliable than previously reported, showing a high failure rate and increased radiologic complications. Thus, its use for THA in Dorr Type A femurs needs caution. On the other hand, the Metha stem showed comparable outcomes to the shortened tapered Tri-Lock BPS.

Stable fixation of an ultra-short femoral neck-preserving hip prosthesis: a 5-year RSA, DXA, and clinical prospective outcome study of 48 patients

BACKGROUND AND PURPOSE

We previously showed promising primary stability and preservation of bone stock with the ultra-short neck-loading hip implant in total hip arthroplasty (THA). The aim of this study was to evaluate clinical outcome, implant stability, and bone mineral density (BMD).

METHODS

50 patients were treated with the ultra-short neck Primoris hip implant at baseline and 48 were available for evaluation at 5-year follow-up. 5 different patient-reported outcome measures (PROMs) including hip-specific scores, disease-specific and generic quality of life outcome measures, and an activity score were used. Furthermore, implant stability using radiostereometric analysis (RSA) and assessment of periprosthetic BMD using dual-energy X-ray absorptiometry (DXA) were applied.

RESULTS

By 1-year follow-up, all PROMs showed improvements and remained high at 5-year follow-up. After initial distal translation (subsidence) and negative rotation around the z-axis (varus tilt) the implant showed stable fixation at 5-year follow-up with no further migration beyond 12 months. In the regions of interest (ROI) 3 and 4, BMD remained stable. In ROI 2, further bone loss of 12% was found at 5-year follow-up.

CONCLUSION

Clinical outcome including PROMs was satisfying throughout the 5-year follow-up period. The hip implant remains stable with both bone preservation and loss 5 years after surgery.

Subsidence after calcar-guided short stem total hip arthroplasty: five-year results of a prospective multicentre study

PURPOSE

Calcar-guided short-stem total hip arthroplasty (THA) has shown excellent clinical outcomes. However, the migration pattern of such prostheses and its effect on clinical outcomes are less known. Therefore, we assessed the five-year subsidence after calcar-guided short-stem THA and its implications on clinical outcomes, patient-related factors, and complications.

METHODS

In this prospective multicentre study, we enrolled 213 patients (224 hips) who underwent calcar-guided short-stem THA mostly for degenerative hip diseases. We examined patients radiographically and clinically after six to 12 weeks, one year, two years, and five years. We evaluated subsidence using Einzel-Bild-Roentgen-Analyse femoral component analysis, assessed clinical outcomes, and systematically recorded all complications.

RESULTS

Overall, 131 patients (133 hips) were available for final follow-up at a median of 60 months (range, 2 to 72 months). We found a mean subsidence of 0.63 ± 1.22 mm at three months, 1.03 ± 1.60 mm at one year, 1.21 ± 1.91 mm at two years, and 1.54 ± 1.97 mm at five years. Patient-related factors (sex, age, weight, and BMI) did not significantly impact subsidence at five years (P > 0.05). Additionally, the Harris hip score, pain, and satisfaction improved significantly at five years compared to pre-operative values (P < 0.0001). Lastly, five patients underwent revision.

CONCLUSION

Calcar-guided short-stems revealed the highest subsidence rate within the first three months after THA and stabilisation after one year through the final follow-up examination. Moreover, patient-related factors had no influence on subsidence. Finally, clinical scores and patient satisfaction remained high at five years.

Rectangular tapered short stem excellently preserves proximal bone mineral density preservation than tapered wedge short stem

Fitmore stem is a rectangular, tapered, short, cementless stem. A characteristic feature of this stem is that it provides rotational stability due to the high medullary occupancy achieved by its rectangular cross-section and thick antero- posterior width. We aimed to investigate the differences in periprosthetic bone remodelling between a rectangular- tapered short stem and a short tapered-wedge stem. Eighty patients who underwent primary total hip arthroplasty using a rectangular-tapered short stem (Fitmore) or a short tapered-wedge stem (Tri-Lock BPS) were enrolled in this study. Bone mineral densities (BMDs) in the seven Gruen zones were evaluated using dual-energy X-ray absorptiometry at baseline, and at 6 and 24 months postoperatively. Peri-prosthetic BMD and clinical factors were assessed and compared. In addition, correlations between periprosthetic BMD changes and stem anteversion error were analyzed using Pearson's correlation coefficient in the two groups. A significantly better postoperative periprosthetic BMD change was found in zones 1 and 7 in the rectangular-tapered group. Additionally, no significant correlation was observed between stem anteversion error and periprosthetic BMD changes in the rectangular-tapered groups. However, in the tapered-wedge group, there were significant negative correlations between the stem anteversion error and BMD changes at 6 months and 24 months in zones 1 and 7. In the rectangular-tapered group, a significantly better postoperative periprosthetic BMD change was found particularly in the region proximal to the stem. Rectangular-tapered short stem can be more resistant to rotation due to higher medullary occupancy and may lead to better periprosthetic BMD than the tapered-wedge short stem, especially in the proximal region of the stem.

Migration Characteristics of a Proximally Coated Collarless Femoral Stem: A Prospective 2-Year Radiostereometric Analysis Study

Background

Collared femoral stems have been considered to reduce the risk of early subsidence over collarless stems. However, with advances in material technology, new surface treatments have been introduced into cementless stem design to enhance primary fixation and long-term stability. This study aims to analyze the early migration behaviors of a proximally coated collarless femoral stem and cementless acetabular component and compare the outcomes with commercially available cementless stems and acetabular cups.

Methods

A total of 24 patients (25 hips) undergoing total hip arthroplasty were recruited and followed up for 2 years. All patients received a Masterloc femoral stem (Medacta International SA, Castel San Pietro, Switzerland) and an Mpact acetabular component (Medacta International SA, Castel San Pietro, Switzerland) with tantalum beads embedded during the operation. Radiographs for radiostereometric analysis were taken immediately postsurgery, 6-months, 1-year, and 2-years postoperatively.

Results

The median condition number for this study was 59. The median stem subsidence was -0.08 mm (-2.47 to 0.40) at 2 years. The median cup subsidence was -0.03 mm (-0.38 to 0.57) at 2 years. The migration of the Masterloc stem was less than that of other cementless collarless, as well as collared stems, as reported in literature.

Conclusions

This study has demonstrated the high stability and fixation provided with the use of a collarless cementless stem. The subsidence seen in both this cementless femoral stem and acetabular cup at 2 years postoperative was below the range reported in literature for cementless collarless and collared stems.

Femoral Anteversion in Total Hip Arthroplasty: Retrospective Comparison of Short- and Straight-Stem Models Using CT Scans

Data on reconstruction of the femoral anteversion (FA) and the center of rotation after total hip arthroplasty (THA) are rare. We aimed to answer whether a short-stem fixation enables improved anatomical reconstruction of the FA compared to a straight-stem. Methods: One hundred and thirty patients who underwent short- (n = 89, group A, prospective) or straight-stem THA (n = 41, group B, retrospective) were included. CT scans of the hip, knee, and ankle were performed pre- and postoperatively in group A and in group B during the last follow-up. Femoral torsion was determined using three-dimensional models. Results: The mean preoperative FA was 22.4° ± 11.0°, and the mean postoperative FA was 23.4° ± 10.1°. The relative difference was −0.8° ± 8°, and the absolute difference was 6.4° ± 4.9°. Gender analysis revealed significant differences in preoperative FA between female (f) and male (m) patients (28.1° ± 11.2° (f) vs. 18.4° ± 8.3° (m); p > 0.001) as well as in postoperative FA (26.7° ± 23.5° (f) vs. 21.0° ± 9.7° (m); p < 0.007) in group A. Postoperative FA was higher in group A (mean 6.8°; 23.9° ± 10.1° (f) vs. 16.6° ± 8.6° (m); p < 0.001). Conclusions: The study’s findings suggest that short-stem THA leads to improved anatomical FA reconstruction; however, a substantial postoperative gender-related FA difference was detectable, which may warrant consideration by surgeons when determining the final stem anteversion. It should be noted that the impact of the postoperative gender-related FA difference on clinical outcomes is not entirely clear, and further research is warranted to elucidate this relationship.

Computational prediction of the long-term behavior of the femoral density after THR using the Silent Hip stem

Aseptic loosening due to the progressive periprosthetic bone resorption following total hip replacement is a crucial concern, that causes complications and failure of the arthroplasty surgery. The mismatch in stiffness between the hip implant and the surrounding femoral bone is one of the key factors leading to bone density resorption. This paper aimed to investigate the long-term response of the femoral bone after THR using the Silent Hip stem. For this purpose, a validated thermodynamic-based computational model was used to compute the change in bone density before and after THR. This model incorporated essential factors involved in bone remodeling process, such as mechanical loading, and biochemical affinities. The results of the numerical simulations using 3D finite element analysis were analyzed in five zones of interest qualitatively and quantitatively. Bone density predictions showed notable bone resorption in cervical areas, specifically in zone 1 and zone 5 of -18.7% and -14%, respectively. Conversely, bone formation was observed in the greater trochanter area (zone 2) of +25%. Stress shielding seemed to occur at cervical area due to the reduction in the mechanical loading in this region. Based on the quantitative analysis of the bone density distribution throughout the femoral bone, it appears that the Silent Hip stem achieved less bone resorption compared to conventional hip stem designs reported in the literature, which could be used for active patients.

Patient-specific femoral implant design using metamaterials for improving load transfer at proximal-lateral region of the femur

Loading configuration of hip joint creates resultant bending effect on femoral implants. So, the lateral side of femoral implant which is under tension retracts from peri‑implant bone due to positive Poisson's ratio. This retraction of implant leads to load shielding and gap opening in proximal-lateral region, thereby allowing entry of wear particle to implant-bone interface. Retraction of femoral implant can be avoided by introducing auxetic metamaterial to the retracting side. This allows the implant to push peri‑implant bone under tensile condition by virtue of their auxetic (negative Poisson's ratio) nature. To develop such implants, a patient-specific conventional solid implant was first designed based on computed-tomography scan of a patient's femur. Two types of metamaterials (2D: type-1) and (3D: type-2) were employed to design femoral meta-implants. Type-1 and type-2 meta-implants were fabricated using metallic 3D printing method and mechanical compression testing was conducted. Three finite element (FE) models of the femur implanted with solid implant, type-1 meta-implant and type-2 meta-implant were developed and analysed under compression loading. Significant correlation (R² = 0.9821 and R² = 0.9977) was found between the experimental and FE predicted strains of the two meta-implants. In proximal-lateral region of the femur, an increase of 7.1% and 44.1% von-Mises strain was observed when implanted with type-1 and type-2 meta-implant over the solid implant. In this region, bone remodelling analysis revealed 2.5% bone resorption in case of solid implant. While bone apposition of 0.5% and 7.7% was observed in case of type-1 and type-2 meta-implants, respectively. The results of this study indicates that concept of introduction of metamaterial to the lateral side of femoral implant can prove to provide higher osseointegration-friendly environment in the proximal-lateral region of femur.

Bionic reconstruction of tension trabeculae in short-stem hip arthroplasty: a finite element analysis

BACKGROUND

Short-stem hip arthroplasty (SHA) is characterized by metaphyseal load transfer that effectively preserves the bone stock, but still suffers from stress shielding in the proximal femur. We designed a tension screw to mimic tension trabeculae in the new bionic collum femoris preserving (BCFP) short stem for bionic reconstruction, aiming to restore the biomechanics of hip joint.

METHODS

Native femur finite element model was constructed to investigate the biomechanics of hip joint based on computed tomography (CT) data. The maximum absolute principal stress/strain cloud chart allowed the direction of stress/strain to be assessed. Six BCFP models with different screw angles (5°, 10°, 15°, 20°, 25°, and 30°) and the Corail model were created. The stress/strain distribution and overall stiffness were compared between each of the BCFP and Corail implanted models.

RESULTS

The native model visualized the transfer pathways of tensile and compressive stress. The BCFP stems showed significantly higher stress and strain distribution in the greater trochanteric region compared to conventional total hip arthroplasty (THA). In particular, the BCFP-5° stem demonstrated the highest average strain in both medial and lateral regions and the overall stiffness was closest to the intact femur.

CONCLUSIONS

Stress transfer pathways of trabecular architecture provide biomechanical insight that serves as the basis for bionic reconstruction. The tension screw improves load transfer pattern in the proximal femur and prevents stress reduction in the greater trochanteric region. The BCFP-5° stem minimizes the stress shielding effect and presents a more bionic mechanical performance.

Three-year migration analysis of a new metaphyseal anchoring short femoral stem in THA using EBRA-FCA

Cementless calcar-guided femoral short stems in total hip arthroplasty (THA) have become increasingly popular over the years. Early distal migration of femoral stems measured by Einzel-Bild-Roentgen Analyse, Femoral Component Analyse (EBRA-FCA) has been reported to be a risk factor for aseptic loosening. The aim of this study was to analyse axial migration behavior and subsidence of a new short stem (launched in 2015) over a follow-up period of 3 years. According to the study protocol, 100 hip osteoarthritis patients who consecutively received an unilateral cementless calcar-guided short stem (ANA.NOVA proxy) at a single department were prospectively included in this mid-term follow-up study. Thirteen patients were lost to follow-up, resulting in 87 patients with unilateral THA who fulfilled the criteria for migration analysis with EBRA-FCA. The cohort comprised 41 males (mean age: 60 ± 16.5; mean BMI (Body Mass Index): 30 ± 13) and 46 females (mean age: 61 ± 15.5; mean BMI: 27 ± 10). Seven standardized radiographs per patient were analyzed with EBRA-FCA. An average migration of 2.0 mm (0.95-3.35) was observed within the first 3 years. The median increase during the first year was higher than in the second and third year (1.2 mm [IQR: 0.5-2.15] vs. 0.3 mm [IQR: 0.1-0.6 mm] vs. 0.25 mm [IQR: 0.1-0.5 mm]. Detected migration did not lead to stem loosening, instability, dislocation, or revision surgery in any patient. A higher risk for subsidence was observed in male and heavyweight patients, whereas the female gender was associated with a lower risk. No correlation between migration and revision could be observed. Although moderate subsidence was detectable, the performance of the short stem ANA.NOVA proxy is encouraging. Yet, its use may be re-considered in overweight and male patients due to more pronounced subsidence.

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.

Do Cementless Short Tapered Stems Reduce the Incidence of Thigh Pain After Hip Arthroplasty? Systematic Review and Meta-Analysis

BACKGROUND

The purpose of this study was to determine whether short tapered stems reduce the rate of thigh pain through a systematic review and meta-analysis of comparative studies between short tapered stems and standard-length tapered stems.

METHODS

We conducted a meta-analysis of comparative studies: 1) retrospective studies and 2) randomized controlled trials (RCTs), on 2 stem designs: short tapered stem versus standard-length tapered stem. Studies were selected by means of the following criteria: 1) study design: retrospective comparative studies, prospective comparative studies, RCTs; 2) study population: patients with total hip arthroplasty or hemiarthroplasty for hip disease or hip fracture; 3) intervention: short tapered stem and standard tapered stem; and 4) outcomes; thigh pain, other clinical results.

RESULTS

Among the 250 articles that were identified at the initial search, 6 studies, 4 RCTs and 2 retrospective comparative studies, were included in this meta-analysis. In the analysis of retrospective studies, the short tapered stem reduced the risk of thigh pain compared to the standard tapered stem (risk ratio [RR] = 0.13; 95% confidence interval [CI], 0.02-0.09; Z = -2.07; P = 0.039). However, in the analysis of RCTs, the incidence of thigh pain was similar between the two stem designs (RR = 1.21; 95% CI, 0.76-1.93; Z = 0.82; P = 0.410). Overall meta-analysis including all studies showed that the short tapered stem did not reduce the incidence of thigh pain compared to the standard-length tapered stem (RR = 0.91; 95% CI, 0.59-1.40; Z = -0.44, P = 0.663).

CONCLUSIONS

We did not find a significant difference in the incidence of thigh pain between short tapered stem and standard tapered stem in hip arthroplasty.

TRIAL REGISTRATION

PROSPERO Identifier: CRD42021231240.

Continuous periprosthetic bone loss but preserved stability for a collum femoris-preserving stem: follow-up of a prospective cohort study of 21 patients with dualenergy X-ray absorptiometry and radiostereometric analysis with minimum 8 years of follow-up

Background and purpose - We previously described a decrease in bone mineral density (BMD) in the calcar region 2 years after insertion of the collum femoris-preserving (CFP) stem, but the implants were stable. Now we have examined the long-term changes in periprosthetic BMD and stability of the CFP stem. Patients and methods - We conducted a minimum 8-year follow-up of 21 patients from our original investigation. We examined periprosthetic BMD by dual-energy X-ray absorptiometry (DEXA) and implant stability by radiostereometric analysis (RSA). Results - Between 2 and 8 years 1 stem was revised due to aseptic loosening. Between 2 and 8 years we found a 14% (95% confidence interval [CI] 9-19) reduction in BMD in Gruen zone 6 and 17% (CI 6-28) in Gruen zone 7. From baseline the reduction in BMD was 30% (CI 23-36) in Gruen zone 6, 39% (CI 31-47) in Gruen zone 7, and 19% (CI 14-23) in Gruen zone 2. Between 2 and 8 years, RSA (n = 17) showed a mean translation along the stem axis of 0.02mm (CI -0.02 to 0.06) and a mean rotation around the stem axis of 0.08° (CI -0.26 to 0.41). From baseline mean subsidence was 0.07 mm (CI -0.16 to 0.03) and mean rotation around the stem axis was 0.23° (CI -0.23 to 0.68) at 8 years. Interpretation - There was continuous loss of proximomedial BMD at 8 years while the CFP stem remained stable. Proximal periprosthetic bone loss cannot be prevented by this stem.

Preserved periprosthetic bone stock at 5 years post-operatively with uncemented short hip stem in both collared and collarless version

INTRODUCTION

Previous bone density studies have generally shown bone resorption around both cemented and uncemented total hip arthroplasty (THA) stems. This is presumed to be due to stress shielding. Short stems have been introduced partly to preserve bone in the proximal femur by a more physiological loading of the bone. The purpose of this study was to evaluate bone remodeling around a short, fully hydroxyapatite-coated titanium stem that comes in a collared and collarless version.

PATIENTS AND METHODS

A prospective cohort of 50 patients included in a study evaluating the Furlong Evolution stem has been followed for 5 years. Examination was done with dual energy X-ray absorptiometry (DXA) postoperatively, at 1, 2 and 5 years. Clinical outcome was followed with radiography and both general and hip specific outcome measures.

RESULTS

The two versions of the stem behaved similarly regarding bone remodeling. After an initial decrease up to 1 year, bone mineral density (BMD) increased in all Gruen zones up to 2 years and at 5 years bone stock was still preserved compared with postoperatively (net BMD + 1.2% (95% CI - 0.4 to 2.8)). Increase in BMD occurred mainly in the greater trochanter and distally around the stem with a decrease in the calcar area. Both versions showed excellent clinical outcome up to 5 years.

CONCLUSION

This short stem seems to preserve proximal bone stock up to 5 years, exhibiting similar behaviour both with and without a collar.

TRIAL REGISTRATION NUMBER AND DATE OF REGISTRATION

ClinicalTrials.gov, (identifier: NCT01894854). July 10, 2013.

Short-term success of proximal bone stock preservation in short hip stems: a systematic review of the literature

Total hip arthroplasty is performed more frequently in younger patients nowadays, making long-term bone stock preservation an important topic. A mechanism for late implant failure is periprosthetic bone loss, caused by stress shielding around the hip stem due to different load distribution. Short stems are designed to keep the physical loading in the proximal part of the femur to reduce stress shielding. The aim of this review is to give more insight into how short and anatomic stems behave and whether they succeed in preservation of proximal bone stock.

A systematic literature search was performed to find all published studies on bone mineral density in short and anatomic hip stems. Results on periprosthetic femoral bone mineral density, measured with dual-energy X-ray absorptiometry (DEXA), were compiled and analysed per Gruen zone in percentual change.

A total of 29 studies were included. In short stems, Gruen 1 showed bone loss of 5% after one year (n = 855) and 5% after two years (n = 266). Gruen 7 showed bone loss of 10% after one year and –11% after two years. In anatomic stems, Gruen 1 showed bone loss of 8% after one year (n = 731) and 11% after two years (n = 227). Gruen 7 showed bone loss of 14% after one year and 15% after two years.

Short stems are capable of preserving proximal bone stock and have slightly less proximal bone loss in the first years, compared to anatomic stems.

Cite this article: EFORT Open Rev 2021;6:1040-1051. DOI: 10.1302/2058-5241.6.210030

Total hip arthroplasty with ultra-short uncemented stem in patients with osteonecrosis of the femoral head: mid-term results

BACKGROUND

Mid-term results (clinical and radiographic) of ultra-short anatomical cementless stem total hip arthroplasty (THA) in patients with osteonecrosis of the femoral head (ONFH) has not often been presented. The aim of this study is to evaluate THA using the Proxima stem in patients with ONFH in the mid-term.

METHODS

The study consists of 73 patients (97 THAs) with a Proxima stem implanted between 2006 and 2015. The mean age of patients was 47.4 years, with a mean follow-up 105.2 months. The clinical results include preoperative and postoperative Harris Hip Scores (HHSs). Radiological follow-up reports on stem migration, bony trabecular development and radiolucent lines. The complications and revisions were registered. Kaplan-Meier survival analysis was performed to determine the implant survival.

RESULTS

The average HHS improved significantly from 40.3 preoperatively to 98.0 at the final evaluation (p ˂ 0.0001). Stem migration (subsidence and "varisation") was observed in 11 hips (in 9 of them up to 6th postoperative month without any further progression, in 2 with progressive migration and radiological loosening). Bony trabecular development was detected in modified Gruen zones (1,2,4,6,7 for Proxima stem): in zone 1 (0%), 2 (67.0%), 4 (64.9%), 6 (64.9%), 7 (0%). Radiolucent lines were observed in 1 cup and 6 stems (2 were loose, 4 with fibrous stable fixation). Complications were found in 5 hips (5.1%): squeezing hip once, repeated dislocation in 1, 1 early deep infection, and 2 loose stems. 2 hips (2.1%) were revised (dislocation, infection). The implant survival was 98.9% and 97.9% clinically and radiologically, respectively.

CONCLUSIONS

Observations in the mid-term show that the clinical and radiological results of the Proxima stem in patients with ONFH are promising. The stem design preserves the proximal femoral bone stock. The bony trabecular appearance confirms physiological proximal femoral load transmission.

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.

Three-dimensional analysis of the cortical contact state of short and conventional stems in different stem positions in total hip arthroplasty

BACKGROUND

Despite the increasing use of short cementless stems in total hip arthroplasty, their potential benefits have yet to be confirmed. We evaluated the cortical contact state of short and conventional stems in different femoral canal types and stem positions using a CT-based 3-dimensional templating software.

METHODS

We reviewed 153 hips in 153 patients, grouped according to femoral canal type-normal (68), champagne-flute (41), and stove-pipe canal (44). We investigated the influence of stem position on the contact state by evaluating three situations of stem anteversion (original anteversion, +5°anteverted, and +5°retroverted), three stem positions, neutral +2°extended, and +2°flexed positions using Taperloc Complete Microplasty^Ⓡ stem.

FINDINGS

The contact values of all zones between both stems in all canal types exhibited no significant differences. The values in zones 1, 2, 6, and 7 of both stems in 5° retroverted and anteverted, 2° extended and flexed positions were not significantly different compared to those of the neutral position. However, the values in zones 3, 4, and 5 of both stems were significantly greater compared to those of the neutral position in 2° extended and flexed positions; these values were also significantly larger in all canal types for the conventional stem.

INTERPRETATION

We demonstrated that the short and conventional stems can achieve the same proximal cortical contact in any femoral canal, regardless of the stem position. However, extended and flexed stem positions increase the distal contact, especially in conventional stems. Furthermore, the distal contact increases for the retroverted stem insertions.

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.

Influence of Femoral Component Design on Proximal Femoral Bone Mass After Total Hip Replacement: A Randomized Controlled Trial

BACKGROUND

In this randomized controlled trial (RCT), we compared bone remodeling and bone turnover between 2 total hip arthroplasty implants-the short, proximally porous-coated Tri-Lock Bone-Preservation Stem and a conventional, fully-coated Corail prosthesis-over a 2-year postoperative period.

METHODS

Forty-six participants received the Tri-Lock prosthesis and 40 received the Corail prosthesis. At baseline, the 2 groups had similar demographics, proximal femoral bone mineral density (BMD), bone turnover markers, radiographic canal flare index, and patient-reported outcome measure (PROM) scores. Outcomes were measured at weeks 26, 52, and 104.

RESULTS

Loss of periprosthetic bone, measured by high-sensitivity dual x-ray absorptiometry region-free analysis (DXA-RFA), was identified at the calcar and proximal-lateral aspect of the femur in both prosthesis groups (p < 0.05). However, the conventional prosthesis was associated with a smaller reduction in BMD compared with the bone-preservation prosthesis (p < 0.001). This effect was most prominent in the region of the femoral calcar and greater trochanter. A small gain in BMD was also identified in some areas, and this gain was greater with the conventional than the bone-preservation prosthesis (p < 0.001). The 2 groups had similar changes in bone turnover markers and improvement in PROM scores over the study period (p > 0.05). The adverse-event rate was also similar between the groups (p > 0.05).

CONCLUSIONS

This RCT shows that prostheses intended to preserve proximal femoral bone do not necessarily perform better in this regard than conventional cementless designs. DXA-RFA is a sensitive tool for detecting spatially complex patterns of periprosthetic bone remodeling.

LEVEL OF EVIDENCE

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

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.

Neck-sparing short femoral stems: A meta-analysis

BACKGROUND

Neck sparing short femoral stems are supposed to ease restoration of the proximal femoral anatomy and physiological hip biomechanics. This stem design is of particular interest as they have the potential to generate prosthetic hips that have higher functional performance with an improved lifespan, and revise more easily. Unlike previously published meta-analysis, this meta-analysis was initiated to determine if neck sparing short femoral stems compared to conventional stems: (1) resulted in improved functional performance; (2) reduced risk of thigh pain; (3) reduced risk of reoperation/revision, and 4) reduced stress shielding related bone loss in the proximal femur.

MATERIAL AND METHODS

Literature databases were searched between 1st January 2005 and 30th March 2019. The primary search was conducted using the electronic databases MEDLINE, EMBASE, PubMed, Open Grey, Trip Pro, Evidence Search, and Cochrane. Eligible studies were assessed for homogeneity, with continuous outcomes expressed as standardized mean difference with 95% confidence interval and dichotomous data as odds-ratio with 95% confidence interval.

RESULTS

Ten randomised clinical trials were eligible; these trials included 1259 total hip arthroplasty procedures, inclusive of 616 neck sparing short stems and 643 conventional stems. We were not able to find a significant functional advantage of using neck sparing short stems based on Harris Hip scores (0.0850; 95% CI: -0.03 to 0.20 [p=0.40]) and WOMAC scores (-0.0605; 95% CI: -0.03 to 0.15 [p=0.87]). We found a trend in favour of neck sparing short stems to reduce the risk of thigh pain but this was non significant (odds ratio of 0.11; 95% CI: 0.03 to 0.43 [p=0.178]). Neck sparing short stems were associated with similar early- to mid-term dislocation and revision rates compared to conventional stems with odds ratio of 1.435 (95% CI: 0.545 to 3.780 [p=0.968]) and of 0.581 (95% CI: 0.220 to 1.532 [p=0.972]), respectively. Neck sparing short stems were found to have less bone loss in both Gruen zones 1 and 7 (3.324; 95% CI: -7.683 to 1.036 [p<0.001], and of -4.632; 95% CI: -9682 to 0.418 [p<0.001], respectively).

DISCUSSION/CONCLUSION

Neck sparing short femoral stems achieve excellent early to mid-term outcomes in both clinical and radiological outcome scores that are in keeping with conventional stems functionally. Hitherto, results from this meta-analysis suggest that neck-sparing stems may achieve better maintenance of bone mineral density than their conventional counterparts, in addition to fewer cases of thigh pain.

LEVEL OF EVIDENCE

I; meta-analysis.

Influence of different anteversion alignments of a cementless hip stem on primary stability and strain distribution

BACKGROUND

Stem anteversion in total hip arthroplasty is well known to have a high impact on dislocation, but empirical data regarding the clinical and biomechanical influence is lacking. Therefore, we evaluated the impact of different anteversion alignments on the primary stability and strain distribution of a cementless stem.

METHODS

The cementless CLS Spotorno stem was implanted in 3 different groups (each group n = 6, total n = 21) with different anteversion alignments: reference anteversion (8°), +15° torsion in anteversion (+23°), -15° torsion in retroversion (-7°) using composite femurs (Sawbones). Primary stability was determined by 3-dimensional micromotions using a dynamic loading procedure simulating walking on level ground. Additionally, surface strains were registered before and after stem insertion in the 3 different groups, using one composite femur for each group (total n = 3).

FINDINGS

The micromotion measurements did not show a significant difference between the 3 evaluated alignments. Moreover, determination of the strain distribution did also not reveal an obvious difference.

INTERPRETATION

This biomechanical study simulating walking on level ground indicates that there is no considerable influence of stem ante-/retroversion variation (±15°) on the initial stability and strain distribution when evaluating the cementless CLS Spotorno in composite femora.

Conversion from a failed proximal femoral nail anti-rotation to a cemented or uncemented total hip arthroplasty device: a retrospective review of 198 hips with previous intertrochanteric femur fractures

Background

At present, it is unclear which device (uncemented or cemented total hip arthroplasty [UTA or CTA, respectively]) is more suitable for the conversion of a failed proximal femoral nail anti-rotation (PFNA). The aim of this review was to assess the outcomes of failed PFNAs converted to a UTA or CTA device in elderly individuals with intertrochanteric femoral fractures (IFFs).

Methods

Two hundred fifty-eight elderly individuals (258 hips) with IFFs who underwent a conversion to a UTA or CTA device following failed PFNAs during 2007–2017 were retrospectively identified from the China Southern Medical Centre (CSMC) database. The primary endpoint was the Harris Hip Score (HHS); secondary endpoint was the key orthopaedic complication rate.

Results

The median follow-up was 65 months (60–69 months). Significant distinctions were observed (87.26 ± 16.62 for UTA vs. 89.32 ± 16.08 for CTA, p = 0.021; 86.61 ± 12.24 for symptomatic UTA vs. 88.68 ± 13.30 for symptomatic CTA, p = 0.026). A significant difference in the overall key orthopaedic complication rate was detected (40.8% [40/98] vs. 19.0% [19/100], p = 0.001). Apparent distinctions were detected in terms of the rate of revision, loosening, and periprosthetic fracture (11.2% for UTA vs 3.0% for CTA, p = 0.025; 13.2% for UTA vs 5.0% for CTA, p = 0.043; 10.2% for UTA vs 3.0% for CTA, p = 0.041, respectively).

Conclusion

For elderly individuals with IFFs who suffered a failed PFNA, CTA devices may have a noteworthy advantage in regard to the revision rate and the rate of key orthopaedic complications compared with UTA devices, and CTA revision should be performed as soon as possible, regardless of whether these individuals have symptoms.

Does radiopaque cement conceal periprosthetic bone loss around femoral stems?

BACKGROUND

Periprosthetic bone remodelling may increase fracture risk and deplete bone stock around hip implants. These changes are in part caused by implant design, advocating an early evaluation of bone remodelling properties of new implants. This can be done by repeated dual-energy x-ray absorptiometry (DXA) measurements. We know that radiopaque cement falsely elevates bone mineral density (BMD) in single measurements, however, its impact on repeated measurements, i.e. BMD changes is unexplored. We have therefore investigated whether the presence of radiopaque cement affect repeated BMD measurements.

METHODS

33 patients eligible for total hip replacement were randomly assigned to either radiopaque or radiolucent cement. BMD changes up to 12 months were measured by DXA, in addition to Harris Hip Score, plain radiographs and radiostereometric analysis (RSA).

RESULTS

Periprosthetic BMD declined during the first 3-6 months in all zones in both groups. The greatest reduction (14%) was seen in the proximal Gruen zones (1 and 7). We found a significant difference in Gruen zones 1 and 2, where the measured bone loss was higher in the radiolucent cement group.

CONCLUSIONS

The presence of radiopaque agents in bone cement may influence DXA measurements of bone remodelling.ClinicalTrials.gov identifier NCT00473421.

Metaphyseal anchoring short stem hip arthroplasty provides a more physiological load transfer: a comparative finite element analysis study

BACKGROUND

Short stem total hip arthroplasty (SHA) preserves femoral bone stock and is supposed to provide a more natural load transfer compared to standard stem total hip arthroplasty (THA). As comparative biomechanical reference data are rare we used a finite element analysis (FEA) approach to compare cortical load transfer after implantations of a metaphyseal anchoring short and standard stem in native biomechanical femora.

METHODS

The subject specific finite element models of biomechanical femora, one native and two with implanted metaphyseal anchoring SHA (Metha, B. Braun Aesculap) and standard THA (CLS, Zimmer-Biomet), were generated from computed tomography datasets. The loading configuration was performed with an axial force of 1400 N. Von Mises stress was used to investigate the change of cortical stress distribution.

RESULTS

Compared to the native femur, a considerable reduction of cortical stress was recorded after implantation of SHA and standard THA. The SHA showed less reduction proximally with a significant higher metaphyseal cortical stress compared to standard THA. Moreover, the highest peak stresses were observed metaphyseal for the SHA stem while for the standard THA high stress pattern was observed more distally.

CONCLUSIONS

Both, short and standard THA, cause unloading of the proximal femur. However, the metaphyseal anchoring SHA features a clearly favorable pattern in terms of a lower reduction proximally and improved metaphyseal loading, while standard THA shows a higher proximal unloading and more distal load transfer. These load patterns implicate a reduced stress shielding proximally for metaphyseal anchoring SHA stems and might be able to translate in a better bone preservation.

Blood loss in primary total hip arthroplasty with a short versus conventional cementless stem: a retrospective cohort study

INTRODUCTION

To evaluate the impact of short cementless stem on several clinical and radiographic outcomes, with particular focus on blood loss, in comparison with conventional cementless stem in total hip arthroplasty (THA).

MATERIALS AND METHODS

Patients undergoing THA with GTS short stem or CLS conventional stem were included. Clinical data were retrospectively collected including preoperative and postoperative day 1 value for haemoglobin (HB); rate of postoperative blood transfusions; intraoperative bone infractions; stem alignment; 5-year follow-up Harris Hip Score (HHS) and rate of stem revision at 5 years of follow-up of the short and conventional cementless stem.

RESULTS

GTS and CLS stem group included 374 and 321 patients, respectively. The mean difference between the preoperative and postoperative day 1 HB value was 3.98 g/dL (SD 1.12) and 3.67 g/dL (SD 1.19) in the GTS and CLS group, respectively, which correspond to a crude effect (β) of 0.32 (95% CI 0.15; 0.49) and adjusted effect of 0.11 (95% CI - 0.08; 0.3). GTS group reported a significantly higher number of patients with excellent results in terms of HHS (p = 0.001). The rate of intraoperative bone infractions was 1.6% and 0.3% in the GTS and CLS group, respectively (p = 0.013). At radiographic assessment, the rate of varus position of the stem was 14% in the GTS group and 6% in the CLS group (p < 0.0001). The rate of stem revision at 5 years of follow-up was 0.8% and 0.4% in the GTS and CLS group, respectively (p = 0.63).

CONCLUSIONS

GTS short stem was not associated with a clinically significant lower blood loss in the immediately postoperative period. Unadjusted exploratory analyses show that GTS stem provides the same results of CLS stem in terms of HHS and rate of stem revision at 5 years of follow-up.

Cemented versus uncemented total hip replacement for femoral neck fractures in elderly patients: a retrospective, multicentre study with a mean 5-year follow-up

Background

Cemented or uncemented total hip replacement (CTR or UTR) for femoral neck fractures (AO/OTA type 31B/C) is a relatively common procedure in elderly individuals. The recent literature is limited regarding long-term outcomes following CTR versus UTR in the Asian population.

Methods

Using our institutional database, we performed long-term outcome analysis on 268 patients with femoral neck fractures (AO/OTA type 31B/C) who had undergone a primary UTR or CTR (CTR: n = 132, mean age, 67.43 ± 6.51 years; UTR: n = 136, mean age, 67.65 ± 6.13 years) during 2007–2014, and these patients were followed until 2019. Follow-up occurred 1, 3, 6, and 12 months postoperatively and yearly thereafter. The primary endpoint was the Harris hip score (HHS); the secondary endpoint was the incidence of orthopaedic complications.

Results

The mean follow-up time was 62.5 months (range, 50.1–76.1 months). At the final follow-up, the HHS was 79.39 ± 16.92 vs 74.18 ± 17.55 (CTR vs UTR, respectively, p = 0.011). Between-group significant differences were observed regarding the incidence of prosthesis revision, prosthesis loosening, and periprosthetic fracture (7.6% [95% CI, 6.4–8.2] for CTR vs 16.9% [95% CI, 14.7–17.3] for UTR, p = 0.020; 9.8% [95% CI, 8.3–10.7] for CTR vs 19.9% [95% CI, 18.2–20.9] for UTR, p = 0.022; 5.3% [95% CI, 4.4–6.7] for CTR vs 13.2% [95% CI, 12.1–13.8] for UTR, p = 0.026, respectively).

Conclusion

CTR showed superiority to UTR by improving the HHS and decreasing the incidence of orthopaedic complications. Our findings need to be confirmed in a prospective, randomized controlled study to verify whether they can be applicable to a broader population.

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.

Prospective Short-Term and Return-to-Sports Results of a Novel Uncemented Short-Stem Hip Prosthesis with Metaphyseal Anchorage

Short-stem hip prostheses were developed to treat active patients requiring total hip arthroplasty (THA). This study provides short-term data about a short-stem total hip arthroplasty system. Functional and radiological outcomes as well as return to sports and activity level were assessed. A series of 55 patients was primarily included. Data were available for 47 patients at an average follow-up of 38 ± 4.6 months. The back-to-sports analysis showed a 98% return-to-sports rate (46/47 patients). The average time for return to sports was 13 weeks (± 8) postoperatively. Five patients (10.6%) were more active postoperatively. The Harris Hip Score (HHS) improved from 34.8 (±9.4) preoperatively to 94.7 (±8.4, p ≤ 0.001) and the University of California, Los Angeles (UCLA) score improved from 4.5 (±1.8) to 6.9 (±1.9) (p ≤ 0.001). The High Activity Arthroplasty Score (HAAS) was 12 (±3.6) at 3-year follow-up. Pre- and postoperative UCLA and postoperative HHS and HAAS scores had a positive influence on the return-to-sports rate (p ≤ 0.05). The collection of radiographic data during all postoperative follow-ups showed no signs of radiolucent lines or bone fissures. The complication rate was at 5%. Short-stem systems are equaling conventional prostheses and offer benefits regarding soft tissue and bone stock preservation. Fast recovery and return to sports can be achieved.

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.

Comparative Analysis between Short Stem and Conventional Femoral Stem in Patients with Osteonecrosis of Femoral Head: Metha Stem and Excia Stem

Objective

To compare the intraoperative, radiological, and clinical short‐term outcomes of cementless total hip arthroplasties (THA) using a short stem (SS) and a conventional femoral stem (CS) in a randomized prospective control study.

Methods

From June 2011 to October 2017, patients who underwent cementless THA for idiopathic osteonecrosis of the femoral head were recruited. Patients had a minimum 2 years of follow‐up after the operation. The patients were divided into two groups: those who underwent THA using an SS and those who underwent THA using a CS. SS were used in 34 patients (41 hips) and CS were used in 41 patients (45 hips). In both groups, the same cup was used in all cases, and the mean follow‐up periods were 63 (26–101) months in the SS and 64 (26–101) months in the CS groups. Intraoperative, clinical, and radiological evaluations were performed for the two groups.

Results

There was no difference in the demographics of the two groups. There was one patient with a proximal femoral crack in the SS group and one with a distal femoral crack in the CS group. Clinically, the mean Harris hip score was improved in both groups at 2‐year follow‐up. Radiographically endosteal osseointegrations were found in 40 of 41 cases in the SS group and in 44 of 45 cases in the CS group. There was one case of dislocation in each group. In the SS group, the acetabular cup was changed and repositioned 7 months after the initial operation. Stem loosening, infection, ceramic breakage, and varus/valgus change were not observed. There was a statistically significant lower stress shielding effect in the SS group. There were no differences in vertical/parallel offset and leg length discrepancy.

Conclusion

The intraoperative, radiological, and clinical evaluations in both groups showed good outcomes and there was no statistically significant difference between the two groups.

Comparison of Bone Preservation in Elderly Patients with Femoral Neck Fracture After Bipolar Hemiarthroplasty Using Shorter Femoral Stem and Standard Femoral Stem

BACKGROUND

This randomized control study was designed to compare the clinical and radiological outcomes, including periprosthetic bone mineral density (BMD) changes, between the short and standard stems after using cementless hemiarthroplasty in elderly patients with femur neck fractures.

MATERIALS AND METHODS

From January 2013 to May 2017, 151 patients (aged ≥ 65 years) underwent hemiarthroplasties due to femoral neck fractures. Patients were randomized into two groups; 77 patients in Group A implanting the short femoral stem and 74 patients in Group B implanting the standard femoral stem. Clinical and radiographic evaluations were performed in all patients.

RESULTS

75 patients (40 patients in Group A and 35 patients in Group B) completed routine follow-up for a minimum of 2 years. The clinical outcomes, including ambulatory functions and thigh pain, were similar in both groups. All the femoral stems acquired radiologic stability. At postoperative one year, BMD values in Gruen zone (G) seven on the standard stem side were significantly lower than those on the short stem side (P = 0.038). At the second year of follow-up, the BMD values of Group A in G1, G3, G4, and G7 were significantly greater than those of Group B (P = 0.007, 0.032, 0.026, and P < 0.000, respectively).

CONCLUSIONS

Both the clinical outcomes and radiologic stability in both group demonstrated similar results in elderly patients with femoral neck fracture at the latest follow-up. In addition, the periprosthetic BMD of the short femoral stems demonstrated better periprosthetic bone preservation at a minimum of 2 years of follow-up.

LEVEL OF EVIDENCES

Therapeutic Level II.

Calcar-Guided Short Stems in Total Hip Arthroplasty: A Two-Year Prospective Multicentre Study

Background:

Calcar-guided short-stem Total Hip Arthroplasty (THA) is increasingly being used to preserve proximal femoral bone stock for potential later revision surgery.

Objective:

In this study, we aimed to expand the clinical evidence on calcar-guided short-stem THA used in daily clinical practice, focusing on clinical outcomes as well as radiographic signs of stress shielding and femoral bone loss.

Methods:

In a prospective multicentre study, we enrolled 213 patients with a total of 224 THAs for mainly degenerative indications. The patients were examined clinically and radiographically 6 to 12 weeks, 12 months, and 24 months postoperatively.

Results:

All clinical outcomes improved significantly over the first 6 to 12 weeks compared to preoperative values (P < 0.001). At 24 months, the mean Harris hip score was 95.3 ± 6.7, and the mean visual analogue scale for pain was 1.0 ± 1.7 under load and 0.5 ± 1.3 at rest. We observed early distal stem migration in six patients and late migration in one patient. Additionally, we found 16 cases of radiographic signs indicative of stress shielding. Four patients required stem revision surgery: two for stem migration, one for periprosthetic fracture, and one for deep infection.

Conclusion:

Overall, calcar-guided short-stem THA resulted in excellent clinical outcomes after two years of follow-up, and the radiographs revealed few signs of stress shielding. We, therefore, regard calcar-guided short-stem THA as a safe and effective treatment alternative in daily clinical practice.

The DePuy Proxima™ short stem for total hip arthroplasty - Excellent outcome at a minimum of 7 years

PURPOSE

Metaphyseal, proximally anchored uncemented stems for total hip arthroplasty provide bone preservation and decrease the incidence of proximal stress shielding and thigh pain. Our study investigated the clinical and radiological outcome of the DePuy Proxima™ short stem at a minimum of 7 years.

METHODS

Eighty-one consecutive patients (86 procedures) under the age of 70 undergoing primary total hip replacement at two arthroplasty centres were enrolled. Follow-up was clinical (Harris Hip Score (HHS), thigh pain and satisfaction) and radiological (subsidence, malalignment and loosening) at 6 months and yearly thereafter.

RESULTS

Average age was 50 (range 32-65) with 79% (68 of 86) being male. Preoperative diagnosis included primary osteoarthritis (OA) 36%, avascular necrosis of femoral head 51%, dysplasia 9% and post-traumatic OA 4%. HHS improved 51 points at latest follow-up (from 40 to 91). We had 3.5% (3 of 86) periprosthetic fractures, one requiring revision. We had one dislocation, no infections and no thigh pain. Malalignment rate (≥5° off neutral) was 12% (10 of 86), not affecting clinical results.

CONCLUSION

Overall stem survival was over 97% at 7 years. The DePuy Proxima provides excellent clinical results at a minimum of 7 years post-operatively.

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.

Is early migration enough to explain late clinical loosening of hip prostheses?

Prosthetic loosening has been debated for decades, both in terms of the timing and nature of the triggering events. Multiple radiostereometric studies of hip prostheses have now shown that early migration poses a risk of future clinical failure, but is this enough to explain late clinical loosening?To answer this question, the progression of loosening from initiation to radiographic detection is described; and the need for explanations other than early prosthetic loosening is analysed, such as stress-shielding, particle disease, and metal sensitivity.Much evidence indicates that prosthetic loosening has already been initiated during or shortly after the surgery, and that the subsequent progression of loosening is affected by biomechanical factors, fluid pressure fluctuations and inflammatory responses to necrotic cells and cell fragments, i.e. the concept of late loosening appears to be a misinterpretation of late-detected loosening.Clinical implications: atraumatic surgery and initial prosthetic stability are crucial in ensuring low risk of prosthetic loosening. Cite this article: EFORT Open Rev 2020;5:113-117. DOI: 10.1302/2058-5241.5.190014.

Denosumab Prevents Early Periprosthetic Bone Loss After Uncemented Total Hip Arthroplasty: Results from a Randomized Placebo-Controlled Clinical Trial

Implant loosening is the most common indication for revision surgery after total hip arthroplasty (THA). Although bone resorption around the implants plays a pivotal role in the pathophysiology of loosening, it is unknown whether potent early inhibition of osteoclasts could mitigate this process and thus reduce the need for revision surgery. We performed a randomized, double-blind, placebo-controlled phase 2 trial in 64 patients aged 35 to 65 years with unilateral osteoarthritis of the hip. They underwent surgery with an uncemented THA and were randomized to either two subcutaneous doses of denosumab (n = 32) or placebo (n = 32) given 1 to 3 days and 6 months after surgery. Patients were followed for 24 months. Primary outcome was periprosthetic bone mineral density (BMD) of the hip at 12 months as measured by dual-energy X-ray absorptiometry (DXA). In addition, [¹⁸ F] sodium fluoride positron emission tomography/CT (F-PET) was performed in half of the patients for analysis of periprosthetic standardized uptake value (SUV). Analyses were made according to intention-to-treat principles. The trial was registered at ClinicalTrials.gov 2011-001481-18, NCT01630941. Denosumab potently inhibited early periprosthetic bone loss. After 12 months, BMD in the denosumab group was 32% (95% confidence interval [CI] 22-44) higher in Gruen zone 7 and 11% (95% CI 8-15) higher in zones 1 to 7. After 24 months, the difference in BMD between groups had decreased to 15% (95% CI 4-27) in zone 7 and 4% (95% CI 0-8) in zones 1 to 7. In both groups, SUV increased after surgery, but the increase was less pronounced in the denosumab group. Biochemical markers of bone metabolism decreased in the denosumab group in the first 12 months, but a rebound effect with marker concentrations above baseline was observed after 24 months. Denosumab potently prevents early periprosthetic bone loss after uncemented THA; however, the effect diminishes after discontinuation of treatment. Further research is needed to determine whether this bone loss will prove to be of clinical importance and, if so, whether the positive effect observed in this study could be preserved by either prolonged treatment with denosumab or additional antiresorptive treatment. © 2019 American Society for Bone and Mineral Research. © 2019 American Society for Bone and Mineral Research.

Femoral bone remodeling after short-stem total hip arthroplasty: a prospective densitometric study

PURPOSE

Due to improved prosthesis designs and surgical techniques, indications for total hip arthroplasty (THA) now include younger and more active patients. Preserving bone stock and soft tissue in these patients is paramount to allow for future revision. Designed for anatomical reconstruction, short femoral stems have the potential to reduce adaptive bone loss and stress shielding. To confirm this, we evaluated bone remodeling around a short femoral stem and the accuracy of hip joint reconstruction.

METHODS

This prospective observational study involved 46 patients with short-stem THA for clinical and radiographic analysis. We evaluated bone remodeling by Gruen zone using dual-energy X-ray absorptiometry in 45 patients and assessed the accuracy of hip joint reconstruction using caput-collum-diaphyseal angles. Additionally, we reported functional scores and pain.

RESULTS

Patients were followed for a mean of 24.1 (SD 2.2) months. Bone mineral density increased mainly in the lateral region (Gruen zones 2 and 3) and in the distal-medial region (Gruen zone 5), suggestive of lateral loading. Most caput-collum-diaphyseal angles remained stable after surgery, especially in patients with varus hips. Harris Hip Scores improved significantly, from 57.2 (SD 20.0) pre-operatively to 97.2 (SD 4.0) at 24 months post-operatively (P < 0.0001). Finally, we encountered one peri-operative dislocation but no post-operative complications.

CONCLUSION

Short femoral stems successfully limited stress shielding and minimized periprosthetic bone loss without compromising primary stability. We were able to accurately reconstruct anatomical relationships in most patients. Finally, excellent clinical outcomes and low complication rates confirmed the favourable results of short-stem THA.

TRIAL REGISTRATION

DRKS00017076.

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.

Effects of hip replacement combined with alendronate sodium on postoperative healing of osteoporotic femoral neck fracture and levels of CTX-1 and BALP in patients

This study aimed to explore the improvement of hip replacement combined with alendronate sodium on the condition of patients with osteoporotic femoral neck fracture and factors affecting the efficacy of patients. In total, 140 patients with femoral neck fracture from July 2015 to October 2017 in the Affiliated Xuzhou Hospital of Jiangsu University were collected. Of these, 61 patients were treated with hip replacement as the control group and 79 patients were treated with alendronate sodium as the observation group on the basis of the control group. ELISA was used to detect levels of carboxy-terminal opeptide of type I collagen (CTX–I) and bone alkaline phosphatase (BALP) in serum of patients before and after treatment. Harris score was used to compare the clinical efficacy of patients after treatment. Changes in the expression of CTX–I and BALP before and after treatment were compared between the two groups, and the correlation between CTX–I and BALP levels and Harris score was analyzed. According to the clinical efficacy of patients, the two groups were divided into the significant effect group and poor effect group. Risk factors affecting the efficacy of patients were analyzed, and the ROC of subjects with risk factors was drawn. After treatment, the expression of BALP in serum increased significantly compared with that before treatment, and the expression of CTX–I decreased significantly. After treatment, the expression of BALP in serum in the observation group was significantly higher than that in the control group (P<0.05). Multivariate analysis revealed that age, time of operation, CTX–I after treatment and BALP after treatment were independent risk factors affecting the efficacy of patients. In conclusion, hip replacement combined with alendronate sodium can effectively improve the clinical efficacy of patients, and age, time of operation, CTX–I after treatment and BALP after treatment are found to be independent risk factors affecting the postoperative efficacy of patients.

Independent assessment and outcomes of 196 short-tapered stems short-term follow-up and review of the literature

BACKGROUND:

Longer term outcome data are now becoming available for short-tapered femoral stems for cementless total hip arthroplasty. The shorter stem has a metaphyseal fit, loading the bone in this area, leading to physiological bone remodelling. It is also bone preserving, as it is 35 mm shorter. It may be easier to insert through a smaller incision and potentially reduce complication rates. We present a retrospective single surgeon case series of 196 patients (>53% follow-up over 5 years). All patients had the cementless 'Microplasty Taperloc' (Biomet). Primary outcome measures were femoral component revision rates. Secondary outcome measures included complications, patient-reported functional outcome scores (Oxford hip) and radiographic evidence of loosening.

METHODS:

Patients were identified using electronic software. All were routinely followed up and assessed in clinic since implant introduction in 2009. Oxford hip scores were routinely obtained. A surgeon who had not carried out the procedure independently assessed radiographs.

RESULTS:

One hundred ninety-six patients were identified. The revision rate was 0.5% due to an intraoperative peri-prosthetic fracture of the femur identified on post-operative radiograph. The complication rate was 2%, attributable to: subsidence of the prosthesis (one hip), post-operative dislocation (two hips), one of which required acetabular revision. Oxford hip scores increased on average from 21 to 45 (pre- to post-operatively). There were no signs of radiographic loosening.

CONCLUSION:

The results show that using the short-tapered stem is proving so far to be a reliable and safe alternative to its longer counterpart, with low complication rates in the short term.

Periprosthetic fracture morphology of a femoral neck prosthesis: An in vitro study

Femoral neck prostheses have been developed for the treatment of osteoarthritis in young and active patients. The concept combines a bone-conserving and minimal invasive technique with proximal load transferring by metaphyseal anchoring, which results in a more physiological loading pattern. However, little is known about the morphology of periprosthetic fractures. Thus, the aim of this study was to describe fracture patterns and to determine patient-specific factors favoring periprosthetic fracture. This study was performed as a biomechanical experimental study using 10 fresh frozen femora and 10 Silent-Hip femoral neck implants (DePuy International Ltd., Leeds, UK). In order to simulate physiological loading, a static muscle reconstruction (abductor muscles and iliotibial band) and a dynamic simulation of the gait cycle were applied. During biomechanical testing (50% and 100% of normal weight-bearing), three periprosthetic fractures with two different morphologies occurred. The first pattern corresponds to an abrupt breakaway. The second type was of spiral configuration extending to the diaphyseal region and emerging from an initial fissure. Specimen-specific factors favoring periprosthetic fracture were body mass index and varus angle of the implant. Periprosthetic fractures may extend to the subtrochanteric/diaphyseal region and may be of spiral configuration. According to the finding of this study, body mass index and varus/valgus position of the implant are important factors influencing the risk of periprosthetic fractures. Furthermore, partial weight-bearing as part of the postoperative regimen may be favorable.

Femoral neck prostheses: A systematic analysis of the literature

Primary total hip arthroplasty (THA) is one of the most successful surgical procedures. Considering the demographic change the use of new ultra-short femoral implants has gained importance especially when treating young patients. Main features are bone conservation, metaphyseal anchoring and thus reducing stress shielding by proximal load transferring. The objective of this study is to give an overview over the subject of femoral neck prostheses. A systematic review was conducted. A total number of 27 publications were taken into this systematic review. Over all, just a few follow-up, biomechanical and radiostereometric studies have been conducted in the past. Still no long-term results (>10 years of follow-up) are available. The available mid-term results indicate unsatisfactory survival rates. Aseptic loosening was the most common reason for revision. Valgus angle and good bone mineral density were considered to be crucial for primary stability of femoral neck prostheses. Register data report a very low percentage of femoral neck prostheses in THA with even more diminishing implantation rates. To conclude, further studies are necessary in order to provide evidence-based recommendations. Currently, due to the inhomogeneous and poor data a reasonable and legitimate recommendation cannot be given.

Is there a significant decrease in the femoral cortical bone around Furlong® stems after 18 years of follow-up?

INTRODUCTION

In the context of total hip arthroplasty (THA), there are several reasons that have motivated the development of short stems. It has been postulated that short stems allow a better conservation of the bone stock if compared to conventional stems. As far as we have knowledge, the quantitative loss of diaphyseal bone stock in patients with standard femoral stems has not been fully described. The aim of this study was to provide evidences about the thickness of the cortical bone at the diaphysis in patients who have undergone unilateral THA with Furlong^® stems with a minimum follow-up of 18 years.

PATIENTS AND METHODS

A retrospective study of patients who underwent THA in a single hospital was performed. The inclusion criteria were patients who had undergone a non-cemented elective THA with a Furlong^® stem, minimum follow-up of 18 years, and contralateral femur and hip without history of previous surgical procedures. The follow-up analysis was performed by means of radiological examinations performed at the last follow-up visit. Data related to the sex, age at surgery and adverse events registered during the follow-up were gathered. The cortical thickness index (CTI) and cortical thickness (CT) assessed at the last follow-up visit in anteroposterior pelvic X-rays were analyzed, both in the operated hip and in the non-operated hip (which was used as control). Calibration of the measurements was done by means of using the circumference of the head of the THA.

RESULTS

The total number of patients who met the inclusion criteria was 22. There were 14 women and eight men. There were 12 left hips. The mean age at the time of surgery was 59.32 ± 6.83 (range 50-70) years. The mean follow-up was 20.86 ± 1.90 (range 18-24) years. The CTI was found to be 11.93% greater in the non-operated hips. The CT measured at 3 cm and 6 cm from lesser trochanter, and at 9 cm from the greater trochanter, was found to be 21.64%, 15.33% and 18.73% greater in the non-operated hips, respectively.

CONCLUSION

After a minimum of 18 years from the implantation of a Furlong^® stem, the bone density that surrounds the implant seems to involve a cortical bone ten percent less thick than the cortical bone of the non-operated contralateral side. With this stem, the cortical zones with less CT seem to be the lateral cortex at 9 cm from the greater trochanter, and the medial cortex at 3 and 6 cm from the lesser trochanter.

LEVEL OF EVIDENCE

III, retrospective case-control study.

Similar clinical results and early subsidence between the Collum Femoris Preserving and the Corail stem: a randomized radiostereometric study of 77 hips with 2 years' follow-up

Background and purpose - Femoral neck preserving hip replacement has been suggested to improve clinical results and facilitate late revision. We compared the 2-year outcome and radiostereometric pattern of femoral head migration between the Collum Femoris Preserving (CFP) stem and the Corail stem. Patients and methods - 83 patients were randomized to either a CFP stem or a Corail stem. All patients received the same cup. At 2 years clinical outcomes were assessed using validated scoring systems and plain radiographs. 2-year migration was determined using radiostereometric analysis. Results - At 2 years the clinical outcomes (Oxford Hip Score, Harris Hip Score, SF-36, EQ5D-VAS, satisfaction VAS, and pain VAS) were similar between the 2 groups. The radiographic measurements showed that the femoral neck was resected around 1 cm more proximally with use of CFP stems (p < 0.001). The proximal-distal and medial-lateral migration of the femoral head center was similar. The Corail stem showed increased posterior displacement after 1 year, but no difference was found between the absolute translations in the anterior-posterior direction (p = 0.2). 2 CFP stems were revised due to loosening within the first 2 years. None of the Corail stems was revised. Interpretation - In the 2-year perspective clinical outcomes suggested no obvious advantages with use of the CFP stem. The magnitude of the early stem migration was similar, but the pattern of migration differed. The early revisions in the CFP are a cause of concern.