Metaphyseal Engaging Short and Ultra-Short Anatomic Cementless Stems in Young and Active Patients

Successful reconstruction of natural femoral anteversion using a short femoral stem in total hip arthroplasty surgery

Objective

Total hip arthroplasty (THA) involves postoperative risks, such as thigh pain, periprosthetic fractures, and stress yielding. Short, anatomical, metaphyseal-fitting, cementless femoral stems were developed to reduce these postoperative risks. This study aimed to examine the “MiniMAX” prosthesis, which is a new generation, short, anatomical femoral stem made by Medacta.

Methods

Patients underwent a low-dose computed tomography scan. Femoral anteversion was measured. We assessed the position and anteversion of the femoral component and compared them with the unoperated side. We also assessed the patients’ satisfaction and functional levels at 6 months postsurgery using the Harris Hip Score (HHS) and the Oxford Hip Score (OHS).

Results

Nineteen individuals were recruited in this study. We found no significant difference in femoral anteversion between the operated hip and the native hip. Using the HHS and OHS questionnaires, we found clinical improvement in the 6-month postoperative scores compared with the preoperative scores.

Discussion

The new-generation, short, anatomical femoral stem made by Medacta is successful in reproducing natural femoral anteversion, while also improving patients’ functioning and lifestyle. Future large-scale, prospective comparison trials are required to further investigate this topic.

Amount and type of physical activity and sports from one year forward after hip or knee arthroplasty-A systematic review

INTRODUCTION

After rehabilitation following total hip or knee arthroplasty (THA/TKA), patients are advised to participate in physical activity (PA) and sports. However, profound insight into whether people adopt a physically active lifestyle is lacking. Aim is to gain insight into the performed amount and type of PA (including sports) and time spent sedentarily by persons after THA/TKA.

METHODS

A systematic review (PROSPERO: CRD42020178556). Pubmed, Cinahl, EMBASE and PsycInfo were systematically searched for articles reporting on amount of PA, and on the kind of activities performed between January 1995-January 2021. Quality of the articles was assessed with the adapted tool from Borghouts et al.

RESULTS

The search retrieved 5029 articles, leading to inclusion of 125 articles reporting data of 123 groups; 53 articles reported on subjects post-THA, 16 on post-hip-resurfacing arthroplasty, 40 on post-TKA, 15 on post-unicompartimental knee arthroplasty and 12 on a mix of arthroplasty types. With respect to quality assessment, 14 articles (11%) met three or fewer criteria, 29 (24%) met four, 32 (26%) met five, 42 (34%) met six, and 6 (5%) met seven out of the eight criteria. PA levels were comparable for THA and TKA, showing a low to moderately active population. Time spent was mostly of low intensity. Roughly 50% of -subjects met health-enhancing PA guidelines. They spent the largest part of their day sedentarily. Sports participation was relatively high (rates above 70%). Most participation was in low-impact sports at a recreational level. Roughly speaking, participants were engaged in sports 3 hours/week, consisting of about three 1-hour sessions.

CONCLUSION

Activity levels seem to be low; less than half of them seemed to perform the advised amount of PA following health-enhancing guidelines Sports participation levels were high. However, many articles were unclear about the definition of sports participation, which could have led to overestimation.

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

The migration pattern and initial stability of the Optimys short stem in total hip arthroplasty: a prospective 2-year follow-up study of 33 patients with RSA

BACKGROUND AND PURPOSE

The consensus that bone stock preservation and optimal restoration of offset and leg length is important in total hip arthroplasty is now widespread, especially for young and active patients. Short stems seem promising in this aspect, though implant stability is still of concern. This study looked at the migration pattern of the Optimys short stem through RSA analysis.

PATIENTS AND METHODS

40 patients were included. RSA images were made directly postoperatively (within 5 days), at 6 weeks and at 3, 6, 12 and 24 months. Double examinations were made for precision measurement. HOOS and pain scores were obtained preoperatively and at 2 years. 4 patients were excluded due to protocol violation and 1 patient was excluded for RSA analysis with a CN number >110. 2 patients were lost to follow-up after 3 and 6 months (n = 1 lost, n = 1 deep infection, respectively).

RESULTS

Mean age was 60 years with a mean BMI of 27. RSA analysis of 34 patients showed a significant initial median proximodistal translation (subsidence) of 0.21 mm (IQR 0.64-0.06) and anteversion-retroversion rotation of 0.59° (IQR 0.01-1.34) at 6 weeks, after which the stem stabilises and showed no further significant movement. Median migration in other directions was small. 4 patients had an initial subsidence of >2 mm, all showed secondary stabilisation. HOOS outcomes were satisfactory, with the domain symptoms and pain showing a median score of 95/100 at 2 years.

CONCLUSIONS

After initial migration the Optimys achieves secondary stabilisation, suggesting low risk on long-term aseptic loosening.

CLINICAL TRIALS REGISTRATION

NL47055.048.13.

Comparison of Tri-Lock Bone Preservation Stem and the Conventional Standard Corail Stem in Primary Total Hip Arthroplasty

Objective

To compare the clinical and radiographic outcomes between the Tri‐Lock Bone Preservation Stem (BPS) and the conventional standard Corail stem in primary total hip arthroplasty (THA).

Methods

From March 2012 to May 2014, we retrospectively reviewed 84 patients (104 hips) who received Tri‐Lock (BPS) and 84 patients (115 hips) who received conventional standard Corail stem in THA. Their mean ages were 53.12 ± 2.32 years and 52.00 ± 2.11 years, respectively. The clinical outcomes were assessed by Western Ontario and McMaster University Osteoarthritis Index (WOMAC), Pain Visual Analogue Scale (VAS) and Harris Hip Score (HHS). The radiological outcomes were evaluated by the radiological examination. Accordingly, Intraoperative and postoperative complications were observed as well.

Results

The mean follow‐up time was 48.23 ± 2.91 months in the Tri‐Lock (BPS) group and 49.11 ± 2.11 months in the Corail group, respectively. The bleeding volumes in two groups were comparable (169.22 ± 58.11 mL vs 179.30 ± 59.14 mL, P = 0.003), with more bleeding volume in Corail group patients, while no statistically significance with respect to operation time was observed (65.41 ± 6.24 min vs 63.99 ± 6.33 min, P = 0.567). The rates of intraoperative fracture was 8% for the Corail group while 1% for the Tri‐Lock (BPS) group (8% vs 1%, P = 0.030). At final follow‐up, no statistical differences in regard to HHS, WOMAC, and Pain VAS were revealed between the two groups (P > 0.05). The rate of thigh pain was higher in Corail group than in Tri‐lock (BPS) group (5% vs 0%, P = 0.043). However, incidence of stress shielding in grade 1 was higher in Tri‐Lock (BPS) than in the Corail group (76% vs 23%, P < 0.01), while those in grade 2 and 3 were lower compared to the Corail stem (15% vs 28%, P < 0.01; 9% vs 16%, P = 0.008, respectively). Intriguingly, other assessments in relation to radiographic outcomes and postoperative complications were not comparable between the two groups. The Kaplan–Meier survival rate (revision surgery performed for any reason was defined as the end point) was similar between the two groups (P = 0.57), with 98.8% (95% confidence interval, 92.3%–100%) in Tri‐lock (BPS) group and 97.6% (95% confidence interval, 94.6%–100%) in Corail group.

Conclusions

The Tri‐Lock (BPS) has similar clinic performances compared to the Corail stem. Furthermore, the Tri‐lock (BPS) stem has some advantages in achieving lower incidence of thigh pain, stress shielding and intra‐operative fracture. Therefore, we recommend the Tri‐lock (BPS) stem as a good alternative in primary total hip arthroplasty, especially taking into account patient factors, including bone deficiency and convenience of extraction of the stem in hip revision.

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.

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.

Age-related osseointegration of a short hip stem: a clinical and radiological 24 months follow-up

PURPOSE

The purpose of this study was to examine potential differences between patients under and over 60 years who underwent a total short hip stem arthroplasty in a 24-month follow-up in a clinical setting.

METHODS

Sixty seven patients were included in this prospective study and divided in two groups. In the younger cohort 39 patients ≤ 59 years and in the older cohort 28 patients ≥ 60 years were included. Clinical and radiological examinations of the patients took place preoperatively, postoperatively and after 3, 6, 12 and 24 months. The Harris Hip Score (HHS) was raised as clinical examination. Changes of bone mass density (BMD), stress shielding, reactive lines, spot welds and sclerosing were examined as radiological analysis.

RESULTS

The HHS improved from 53.6 ± 8.2 preoperative to 93.2 ± 9.6 in the younger cohort and for the older cohort from 57.6 ± 14.8 to 94.1 ± 7.6 after 24 months. BMD growth was detectable in regions of interest (ROI) 3 and 6 for both groups. Different results between the cohorts could only be detected in ROIs 4 and 5. The older cohort showed a loss of BMD of 5.95% in ROI 4 and 3.17% in ROI 5 after 24 months, whereas the younger cohort showed no loss of BMD in both ROIs.

CONCLUSIONS

No significant differences or any influences of osseointegration and clinical outcome of the short hip stem for both groups were detectable. Lower losses (ROIs 1 and 2) and higher growths (ROIs 3, 4, 5) were discovered in younger patients and the HHS improved in both groups. Reasons for this result could be age, sex or the level of activity of the patients, but in both groups the short hip stem shows comparable results in clinical as well as in radiological examination. We conclude that the short hip stem seems to be an adequate treatment also for older patients.

Short Stems Versus Conventional Stems in Cementless Total Hip Arthroplasty: A Long-Term Registry Study

BACKGROUND

Short stems in total hip arthroplasty (THA) have recently gained increasing popularity, allowing mini-invasive exposures and bone-sparing approaches. However, long-term studies and recommendations for the routine use are not available. The aim of this report was to compare the survival rates and the reasons for revision of short stems versus conventional stems in cementless THAs, in a registry-based population.

METHODS

The Registry of Prosthetic Orthopedic Implants (RIPO) was inquired about cementless THAs performed since 2000 to 2016. The stems were divided into short (<12 cm) and conventional ones, and then, classified according to the classification by Feyen and Shimmin: short stems with neck-retaining osteotomy (group A: 1684 hips), short stems with standard osteotomy (group B: 2727 THAs), and conventional stems (group C: 57,359 cases). Demographics, survivorships, and reasons for revision were investigated and compared.

RESULTS

Short stems were preferentially implanted in younger patients and normal morphologies. Short and conventional stems showed comparable survival rates at long-term follow-up (>90% at 15 years). The rates of stem aseptic loosening, intraoperative fractures, and periprosthetic fractures were similar in the 3 groups. Group B had higher rates of revisions due to primary instability (early dislocations and impingement-related events; P < .05). Revisions due to pain were nonsignificantly higher in group B.

CONCLUSION

Short stems are reliable implants at long-term follow-up. The comparison with conventional stems showed no additional risk of premature aseptic loosening and intraoperative and periprosthetic fractures. However, the high rate of revisions due to pain and, mostly, primary instability should be investigated in clinical trials.

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

A predictive radiological analysis of short stems versus both shortened and long stems in primary hip replacement: A case-control study of 100 cases of Metha versus ABG II and Omnifit HA at 2-8years' follow-up

INTRODUCTION

Short hip stems, intended to conserve bone stock and ensure a more physiological distribution of stress in the femur under loading, are meeting with renewed interest. Radiologic semiology is not known exactly, particularly in relation to conventional implants; we therefore conducted a case-control study of 3 types of implant differing only in stem length: short, shortened or long. The aim was: (1) to compare radiographic aspects, (2) to attempt to systematize medium-term radiologic status for the 3 types, and (3) to assess the impact of radiographic aspect on loosening and revision rates.

HYPOTHESIS

The short Metha stem is better adapted to the recipient bone than longer stems, without sacrificing stability.

MATERIAL AND METHODS

A prospective series comprising the first 100 selected cases of hip replacement using the short Metha stem was compared to two other series of 100 "long" (Omnifit HA) and 100 "shortened" (ABG II) stems at comparable follow-up: 4.05±1.44years (range: 2-8years) for Metha, 4.48±0.97years (range: 2-8years) for Omnifit, and 4.75±2.07years (range: 2-8years) for ABG II. Selection criteria in this initial phase were very strict: young age and/or high activity level, with good bone stock and femoral morphology suited to fitting a Metha stem (no "stovepipe" or "champagne-flute" femurs), for which 12.8% of primary hip replacements were selected. Matching was performed by sampling on criteria of age, gender, body-mass index and etiology. Radiographic parameters were compared between the short stem group and the two control groups and classified according to Engh-Massin score (10 points for fixation and 17 for stability).

RESULTS

The short Metha stem provided excellent fixation scores: 7.65/10, versus 7.16 (P=0.003) and 5.92 (P=0.0001) for ABG II and Omnifit, respectively. Likewise, stability was scored 14.23/17 for Metha, vs. 14.51 (NS) and 11.83 (P=0.0001) respectively, and the total score was higher for Metha (21.88/27) than ABG II (21.67; P=0.03) or, more particularly, Omnifit (17.83; P=0.0001). The Metha stem was never associated with thigh pain or periprosthetic fracture. 8-year survival was 100%, without significant difference with respect to ABG II (100%; NS) or Omnifit (98.8%; 95% CI: 0.964-1; NS).

DISCUSSION

The apparent radiologic superiority of the short Metha stem requires long-term confirmation in non-selected series. Meanwhile, Metha can be asserted to have demonstrated optimal compromise between lasting bone anchorage and respect of bone physiology under loading at medium term.

LEVEL OF EVIDENCE

III, case-control study.

Periprosthetic bone remodeling of short cementless femoral stems in primary total hip arthroplasty: A systematic review and meta-analysis of randomized-controlled trials

BACKGROUND

Short-stem total hip arthroplasty (SHA) has been increasingly used in the treatment of hip arthroplasty. However, it is unclear whether there is a superiority of SHA in periprosthetic bone remodeling over standard stem total hip arthroplasty (THA). This meta-analysis of randomized-controlled trials (RCTs) compared the periprosthetic bone remodeling after SHA and THA.

METHODS

PubMed and Embase were screened for relevant publications up to May 2017. RCTs that compared periprosthetic bone remodeling with bone mineral density (BMD) changes between SHA and THA were included. Meta-analysis was conducted to calculate weighted mean differences (WMDs) and 95% confidence intervals (CIs) using Stata version 12.0. Quality appraisal was performed by 2 independent reviewers using RevMan 5.3 software and Grades of Recommendation Assessment, Development, and Evaluation criteria.

RESULTS

Seven studies involving 910 patients and 5 SHA designs (Proxima, Fitmore, Microplasty short, Unique custom, and Omnifit-HA 1017) were included for meta-analysis. The pooled data showed no significant differences in the percentage BMD changes in all Gruen zones, with Gruen zone 1 [mean difference (MD) = 11.33, 95% CI, -1.67 to 24.33; P = .09] and Gruen zone 7 (MD = 8.46, 95% CI, -1.73 to 18.65; P = .10). Subgroup analysis of short SHA stems with lateral flare showed a significant less percentage BMD changes compared with standard THA in Gruen zone 1 (MD = 27.57, 95% CI, 18.03-37.12; P < .0001) and Gruen zone 7 (MD = 18.54, 95% CI, 8.27-28.81; P < .0001).

CONCLUSION

The study shows moderate-quality evidence that periprosthetic bone remodeling around the analyzed SHA stems was similar to standard THA stems. However, short SHA stems with lateral flare revealed a moderate- to low-quality evidence for superiority over the standard THA and highlighted the importance of the different SHA designs. Besides, it has to be noticed that despite a similar pattern of periprosthetic bone remodeling, the femoral length where periprosthetic bone remodeling occurs is clearly shorter in SHA. Due to the moderate- to low-quality evidence and the limited stem designs analyzed, the further large-scale multicenter RCTs including the most recent SHA designs are required. However, the current findings should be considered by surgeons for counseling patients regarding total hip replacement.

Better early functional outcome after short stem total hip arthroplasty? A prospective blinded randomised controlled multicentre trial comparing the Collum Femoris Preserving stem with a Zweymuller straight cementless stem total hip replacement for the treatment of primary osteoarthritis of the hip

OBJECTIVES

Primary aim was to compare the functional results at 3 months and 2 years between short and conventional cementless stem total hip arthroplasty (THA). Secondary aim was to determine the feasibility of a double-blind implant-related trial.

DESIGN

A prospective blinded randomised controlled multicentre trial in patients with osteoarthritis of the hip. All patients, research assistants, clinical assessors, investigators and data analysts were blinded to the type of prosthesis.

POPULATION

150 patients between 18 and 70 years with osteoarthritis of the hip, 75 in the short stem and 75 in the conventional stem group. Mean age: 60 years (SD 7).

INTERVENTIONS

the Collum Femoris Preserving short stem versus the Zweymuller Alloclassic conventional stem.

MAIN OUTCOME MEASURES

The Dutch version of the Hip Disability and Osteoarthritis Outcome Score (HOOS). Secondary outcomes measures: Harris Hip Score, the Physical Component Scale of the SF12, the Timed Up and Go test, Pain and the EQ-5D. Feasibility outcomes: continued blinding, protocol adherence and follow-up success rate.

RESULTS

No significant difference between the two groups. Mean HOOS total score in the short stem group increased 32.7 points from 36.6 (95% CI 32.9 to 40.2) preoperatively to 69.3 (95% CI 66.4 to 72.1) at 3 months follow-up. Mean HOOS total score in the conventional straight stem group increased 36.3 points from 37.1 (95% CI 33.9 to 40.3) preoperatively to 73.4 (95% CI 70.3 to 76.4) at 3 months follow-up. 91.2% of patients remained blinded at 2 years follow-up. Both protocol adherence and follow-up success rate were 98%.

CONCLUSIONS

Functional result at 3 months and 2 years after short stem THA is not superior to conventional cementless THA. There were more perioperative and postoperative complications in the short stem group. Direct comparison of two hip implants in a double-blinded randomised controlled trial is feasible.

TRIAL REGISTRATION NUMBER

NTR1560.

Low Short-Stem Revision Rates: 1-11 Year Results From 1888 Total Hip Arthroplasties

BACKGROUND

In total hip arthroplasty, short stems were developed as a bone-conserving alternative to traditional cementless stems. So far, there have been very few recorded medium to long-term results of these comparatively new implants. The aim of our retrospective study was to report on the survival of calcar-loading short stems.

METHODS

All Metha stem implantations from 2004 to 2014 were recorded from the operation protocols (n = 1888). Due to the chronological development of the stem, 3 different versions were implanted: modular titanium stems with neck adapters from titanium or cobalt-chrome and monoblock stems. Patients were questioned by post about revision, dislocation, and satisfaction.

RESULTS

Data were complete for 93% of the procedures (1090 monoblock stems, 314 modular stems with titanium neck, and 230 modular stems with cobalt chrome neck). Mean follow-up was 6 years (1-11 years). Fifteen modular titanium implants were affected by cone fractures (4%). Therefore, monoblock, modular cobalt chrome, and modular titanium implants were analyzed separately. The 7-year revision rate for monoblock stems was 1.5%; for modular cobalt-chrome stems it was 1.8%, and for modular titanium stems it was 5.3%.

CONCLUSION

Our data show the midterm survival of the monoblock and modular cobalt-chrome implants equivalent to the traditional cementless stems. These might, therefore, be considered as a bone-conserving alternative for young and active patients.

Ultrashort versus Conventional Anatomic Cementless Femoral Stems in the Same Patients Younger Than 55 Years

BACKGROUND

Because the clinical and radiographic performance of an ultrashort anatomic cementless stem has been investigated in only two randomized controlled studies, well-designed trials should aim for a thorough comparison of the outcomes of ultrashort anatomic cementless and conventional anatomic cementless stems.

QUESTIONS/PURPOSES

The purposes of this study were to compare (1) the clinical results, including Harris hip score, thigh pain, and WOMAC index score, (2) radiographic results, (3) bone mineral density; and (4) proportions of patients undergoing revision of a THA using an ultrashort anatomic cementless stem versus a conventional anatomic cementless stem in the same patients who underwent bilateral sequential THAs under the same anesthetic.

METHODS

Two hundred patients (mean age, 53 years; range, 26-54 years) who underwent bilateral sequential THAs received an ultrashort anatomic cementless stem in one hip and a conventional anatomic cementless stem in the contralateral hip. From January 2004 to December 2005, we performed 524 same-day bilateral short and conventional anatomic cementless THAs in 262 patients, of whom 212 (81%) participated in this study. Five patients were lost to followup before 2 years, five were lost between 2 to 10 years, and two were lost between 10 to 13 years, leaving 200 patients. Patients who had end-stage bilateral hip disease and were younger than 55 years were selected for inclusion. The predominant diagnoses were osteonecrosis (118 patients, 59%) and osteoarthritis (44 patients, 22%). One hundred thirty-eight were men and 62 were women. At the time of each followup, the patients were assessed clinically and radiographically. In addition, each patient completed the WOMAC and the University of California Los Angeles (UCLA) activity scores. The minimum followup was 10 years (mean, 11.8 years; range, 10-13 years). Followups were done in person, with all images and followup clinic notes. Based on the power analysis, we estimated a sample size of 178 hips was needed in each group to detect a 3-point difference in the Harris hip score with 80% power.

RESULTS

At the latest followup, there were no differences between the two groups regarding the mean Harris hip scores (94 versus 94 points; p = 0.189), mean WOMAC scores (17 versus 16 points; p = 0.191), or mean UCLA activity scores (9 versus 9 points; p = 0.381). Two patients in the ultrashort stem group and one patient in the conventional stem group had severe (9 points) thigh pain, and 30 patients (15%) in the conventional stem group had mild thigh pain (2 or 3 points) after vigorous exercise. Bone mineral density in the ultrashort and conventional stem groups, respectively, was greater in the ultrashort stem group than in the conventional stem group. Bone mineral density in Zone 1 at 12 years was 3.29 versus 1.88 g/cm(2) (p = 0.021), and 2.97 versus 0.91 g/m(2) in Zone 7 (p = 0.001). With the numbers available, there were no differences between the stem designs in terms of the proportion undergoing revision (one hip, 0.5%, in the short-stem group versus one hip, 0.5%, in the conventional group; p = 1.881).

CONCLUSIONS

At followup into the second decade, ultrashort stems showed no differences from conventional cementless stems in terms of validated outcomes scores or fixation, although less stress shielding was observed. Reduction of stress shielding may reduce the long-term risk of periprosthetic fracture, but this was not shown in our study.

LEVEL OF EVIDENCE

Level I, therapeutic study.