Is there any range-of-motion advantage to using bearings larger than 36mm in primary hip arthroplasty: A case-control study comparing 36-mm and large-diameter heads

Dislocation of primary total hip arthroplasty: Analysis of risk factors and preventive options

Total hip arthroplasty (THA) is one of the most successful elective operations in orthopedic surgery for improving pain and functional disability in patients with end-stage joint disease. However, dislocation continues to be a troublesome complication after THA, as it is a leading cause of revision and is associated with substantial social, health, and economic costs. It is a relatively rare, usually early occurrence that depends on both the patients' characteristics and the surgical aspects. The most recent and important finding is the special attention to be given preoperatively to spinopelvic mobility, which is closely related to the incidence of dislocation. Consequently, clinical and radiographic assessment of the lumbar spine is mandatory to identify an altered pelvic tilt that could suggest a different positioning of the cup. Lumbar spinal fusion is currently considered a risk factor for dislocation and revision regardless of whether it is performed prior to or after THA. Surgical options for its treatment and prevention include the use of prostheses with large diameter of femoral head size, dual mobility constructs, constrained liners, and modular neck stems.

Increasing femoral head size from 32 mm to 36 mm does not increase the revision risk for total hip replacement: a New Zealand joint registry study

BACKGROUND

The use of larger femoral heads in total hip replacement (THR) has increased over the last decade. While the relationship between increasing head size and increased stability is well known, the risk of revision with increasing head size remains poorly understood. The aim of this study was to compare the outcome of total hip joint replacement with 32-mm and 36-mm heads.

METHODS

We carried out a 20-year retrospective analysis of prospective data from the New Zealand Joint Registry (NZJR). All primary total hip replacements registered between January 1999 and December 2018 were included. We compared the rate of revision of 32-mm and 36-mm heads in THR. Sub-group analysis included comparisons of bearing type and all-cause revision.

RESULTS

60,051 primary THRs met our inclusion criteria. The revision rate per 100 component years was significantly higher with a 36-mm head than with a 32-mm head (0.649 vs. 0.534, p < 0.001). Subgroup analysis of bearing type showed no significant differences in revision rates for all combinations of 36-mm heads when compared to 32-mm (p = 0.074-0.92), with the exception of metal-on-metal (MoM); p = 0.038. When MoM was removed there was no significant difference in revision rates per 100 component years between 32-mm and 36-mm heads, 0.528 versus 0.578 (p = 0.099).

CONCLUSIONS

Increasing head size from 32 mm to 36 mm results in no significant increase in revision in all bearing combinations except MoM.

Cementless metal-on-metal versus ceramic-on-polyethylene hip arthroplasty in under-50 year-olds with 20 to 22 years' follow-up: Was it a good idea to abandon the small-diameter metal-on-metal bearing?

In 2005 and 2011, we reported results for a comparative study of two types of 28-mm bearing (metal-on-metal (MoM) and ceramic-on-polyethylene (CoP) in active patients with respectively 5 and 12 years' follow-up. The present report is an update at a mean 20 years' follow-up, addressing 2 issues: (1) implant survival at a mean 20 years; and (2) long-term complications with the metal-on-metal bearing. Twenty-eight millimeters MoM bearings show good survival at 20 years in young active subjects. Two groups of cementless hip prostheses were compared: Metasul™ 28mm MoM versus 28mm CoP. The MoM group comprised 30 patients (39 hips), with a mean age of 40±6.7 years [range, 22.6-49 years], and the CoP group comprised 32 patients (39 hips), with a mean age of 40.5±8.7 years [range, 15-50 years]. The groups were matched in 2005 for age, activity level and preoperative Harris score. At a mean 20±5.3 years' follow-up [range, 5-23 years], in the MoM group 2 hips (5%) showed limited non-progressive acetabular osteolysis, not requiring revision surgery; in the CoP group, there were 21 revision procedures (54%), including 15 for polyethylene wear. In the MoM group, the median total blood cobalt concentration was 1.03g/L [range, 0.3-3.5] and the median chromium concentration was 1.07g/L [range, 0.3-3.2]. Twenty-year all-cause survival was 100% in the MoM group, and 46% (95% CI, 37-59%) in the CoP group (p<0.0001). At long-term follow-up, MoM implants showed better survival than CoP implants in a young active population. Level of evidence: III, matched case series.

Analysis of biomechanical gait parameters in patients after total hip replacement operated via anterolateral approach depending on size of the femoral head implant: retrospective matched-cohort study

INTRODUCTION

Total hip replacement (THR) is considered one of the most effective medical procedures in treatment of osteoarthritis. Since its introduction, there has been a worldwide debate over proper implant selection in terms of size, bearing type and shape. Following study was designed to assess the importance of femoral head size in long-term follow-up.

MATERIALS AND METHODS

A cohort of 30 patients with primary end stage osteoarthritis who underwent total hip replacement was analysed retrospectively. A homogenous group was chosen with no major differences in BMI. Patients' gait parameters were measured in a biomechanics laboratory using the 3D BTS Smart system. WOMAC and VAS questionnaires were used to assess patient reported outcome.

RESULTS

The subgroup with larger implant head size had several outcomes significantly superior to the subgroup with standard head size and non-inferior to healthy hips. Following variables were measured during this study: time of support phase, time of swing phase, double support time, walking hip extension angle.

CONCLUSIONS

Use of larger sized femoral heads during THR gives better results in terms of gait pattern. Since restoring the gait pattern is one of the aspects of rehabilitation and returning to daily activities it seems to be an important observation.

Dislocation after total hip arthroplasty: does head size really matter?

INTRODUCTION

Recent advances in polyethylene and ceramic technologies has allowed us to use larger sized heads without compromising the wear properties of a total hip arthroplasty (THA). 1 benefit of this change has been proposed to be a lower incidence of dislocation.

METHODS

We retrospectively evaluated the dislocation rate in 913 THAs performed using the same standardised surgical technique employed by a single team of surgeons at our institution between 1995 and 2015. Patients were assigned to 2 groups: small (⩽28 mm), large diameter heads (⩾36 mm and larger). The cup position was measured and plotted to determine its status according to the Lewinnek's safe zone (15° ± 10° for anteversion, 40° ± 10° for inclination).

RESULTS

16 of the 472 small heads dislocated (3.4%) while 5 of the 441 in large head group (1.1%) (p = 0.04). In all of the large head patients that dislocated the cup position was in the safe range of Lewinnek. However, in the large head group only 64.5% of the cups were in the safe zone.

CONCLUSIONS

By changing the head size to 36 mm, we were able to decrease the dislocation rate significantly. Errors of cup positioning according to Lewinnek became oblivious when using large heads. In our opinion, using large heads in THA makes a difference in terms of dislocation.

Global diversity in bearings in primary THA

Choice of articulating materials, head size and the design of the articulation will become decisive for the long-term performance of a total hip arthroplasty (THA) and especially in terms of risk for dislocation and wear-related problems. Here we account for common alternatives based on available studies and the evidence that can be derived from them.Metal or ceramic femoral heads articulating against a liner or cup made of highly cross-linked polyethylene and ceramic-on-ceramic articulations have about similar risk for complications leading to revision, whereas the performance of metal-on-metal articulations, especially with use of big heads, is inferior. The clinical significance of problems related to ceramic-on-ceramic articulations such as squeaking remains unclear. With use of current technology ceramic fractures are rare.Large femoral heads have the potential to increase the range of hip movement before impingement occurs and are therefore expected to reduce dislocation rates. On the other hand, issues related to bearing wear, corrosion at the taper-trunnion junction and groin pain may arise with larger heads and jeopardize the longevity of THA. Based on current knowledge, 32-mm heads seem to be optimal for metal-on-polyethylene bearings. Patients with ceramic-on-ceramic bearings may benefit from even larger heads such as 36 or 40 mm, but so far there are no long-term reports that confirm the safety of bearings larger than 36 mm.Assessment of lipped liners is difficult because randomized studies are lacking, but retrospective clinical studies and registry data seem to indicate that this liner modification will reduce the rate of dislocation or revision due to dislocation without clear evidence of clinically obvious problems due to neck-liner impingement.The majority of studies support the view that constrained liners and dual mobility cups (DMC) will reduce the risk of revision due to dislocation both in primary and revision THA, the latter gaining increasing popularity in some countries. Both these devices suffer from implant-specific problems, which seem to be more common for the constrained liner designs. The majority of studies of these implants suffer from various methodological problems, not least selection bias, which calls for randomized studies preferably in a multi-centre setting to obtain sufficient power. In the 2020s, the orthopaedic profession should place more effort on such studies, as has already been achieved within other medical specialties, to improve the level of evidence in the choice of articulation when performing one of the most common in-hospital surgical procedures in Europe. Cite this article: EFORT Open Rev 2020;5:763-775. DOI: 10.1302/2058-5241.5.200002.

Personalized Cup Positioning Guides Improved Cup Positioning and Hip Ranges of Motion in Robotic Assisted Total Hip Arthroplasty

Objective

Precise hip cup positioning is essential for the prevention of component impingement and dislocation in robotic assisted total hip arthroplasty (THA). Currently, the robotic system uses a mechanical alignment guide (MAG) for cup placement, which is one-size-fits-all, and the optimal cup positioning is controversial. Robotic assisted THA has not used any personalized cup positioning guides. The goal of this study was to identify an optimal guide for cup placement in robotic assisted THA to improve prognosis and life quality after THA.

Materials and Methods

Pelvis and femoral CT data of 47 participants were retrospectively collected for preoperative planning of robotic THA. The universal MAG guide and three personalized guides, including acetabular rim labrum guide (ARLG), transverse acetabular ligament guide (TALG), and ischiatic-pubis line guide (IPLG), were used to pose cups in the acetabulum of each participant. The position of cups was evaluated by inclination and anteversion; the function of hip joints was evaluated by hip ranges of motion, including abduction, adduction, extension, flexion, internal rotation, and external rotation.

Results

In terms of cup positioning, ARLG provided a bigger cup inclination (p < 0.0001), while IPLG and TALG provided smaller cup inclination (p < 0.001) than MAG; the three personalized guides provided larger cup anteversion (p < 0.0001) than MAG. In terms of HROMs, compared with the use of MAG, the use of three personalized guides significantly decreased abduction (p < 0.0001), extension (p < 0.0001), and external rotation (p < 0.0001), but increased significantly flexion (p < 0.0001) and internal rotation (p < 0.0001); the use of ARLG significantly reduced adduction (p < 0.0001), but the use of IPLG and TALG increased adduction (p < 0.0001).

Conclusion

Compared with MAG, personalized guides provided greater flexion and internal rotation, which may reduce the risk of posterior dislocation. Among the three personalized guides, IPLG is the most reliable one for the preoperative planning of robotic assisted THA.

Large Diameter Head in Primary Total Hip Arthroplasty: A Systematic Review

INTRODUCTION

The literature around use of Large Diameter Heads (LDH) is abundantly available for revision Total Hip Arthroplasty (THA) but is lacking for primary uncomplicated THA. This systematic review was undertaken to synthesize data around primary THA involving LDH and analyze the associated complications (dislocation, volumetric wear, implant survivorship and functional score) along with reported effects on range of motion (ROM), patient reported outcomes and impingement rate/groin pain.

METHODS

A PRISMA compliant systematic review was done using extensive search in PubMed database, along with offline search looking for the literature published in English language between 2008 and 2018. The articles providing data on the use of large diameter heads (LDH) (36 mm or larger) on various bearing surfaces were collected. This included robust national joint registries of different countries. Narrative approach to data synthesis was used.

RESULTS

A total of 23 papers met our inclusion criteria, including six national joint registries. It was observed that LDH had significantly low dislocation rates, excellent implant survival rate as per Kaplan-Meier survivorship (> 90% at five years). Surgical approaches, except Minimally Invasive Surgery (MIS), did not increase any risk of dislocation as long as it was meticulously repaired. There was no significant improvement in any functional scores or improved ROM.

CONCLUSIONS

LDH of 32-36 mm are now commonly used in primary THA and is accepted as a popular size. The beneficial effects of a large head size are negated beyond 38 mm. The most favored size for LDH THA, therefore, is 36 mm contrary to the older literature favoring 28 mm.

Survival and outcomes of different head sizes in primary total hip arthroplasty

The femoral head size influences dislocation, range of motion (ROM), functional outcome, wear, and survival after total hip arthroplasty (THA). These aspects of different head sizes with contemporary bearings in primary THA have been reviewed. Based on the existing evidence, for highly-cross-linked polyethylene (HXLPE) bearings, a 32 mm cobalt chromium (CoCr) or ceramic head appears to be a suitable choice. If a 36 mm head with HXLPE is desired, a ceramic head may be preferable over CoCr due to reduced risk of fretting and corrosion with the former. For ceramic-on-ceramic (CoC) bearings, head sizes >36 mm do not appear to provide any significant benefit over 36 mm heads. Also, large ceramic heads may lead to increased risk of squeaking. If non-cross-linked PE bearing is considered for use, it would be prudent to opt for <32 mm head size.

[Total hip arthroplasty in young patients : Bearings and custom-made prostheses]

BACKGROUND

Carefully and correctly implanted components are the prerequisite for the lifespan of a prosthesis. Whether higher levels of activity lead to prior failure of total hip arthroplasty in young patients is controversially discussed. The right choice of bearings is still of great relevance.

BEARINGS

Ceramic-on-ceramic as well as polyethylene-on-ceramic bearings achieve comparable results, although ceramic-on-ceramic bearings should be avoided in patients with high demands on their range of motion. Polyethylene-on-metal bearings also show good clinical results, if corrosion between head and stem is absent. Metal-on-metal bearings lead to adverse systemic effects due to metal wear and should be implanted in individual cases only, e. g. as hip resurfacing. Alternative bearings have to give proof of effectivity first. Custom-made prostheses constitute an option for young patients with special conditions of hip anatomy. Planning and study results of these prostheses are elucidated in this review article.

Long-term comparative study of large-diameter metal-on-metal bearings: Resurfacing versus total arthroplasty with large-diameter Durom™ bearing

INTRODUCTION

Short-term results in total hip arthroplasty (THA) with large-diameter metal-on-metal (MoM) bearings were encouraging, but high failure rates have been reported in the long term, notably implicating corrosion due to modularity. Several studies compared resurfacing (to which modularity does not apply) versus large-diameter MoM THA; but, to our knowledge, none compared the same bearing in the two situations with more than 10 years' follow-up. We therefore conducted a retrospective case-control study, using a single cup model (Durom™, Zimmer, Warsaw, USA) for both resurfacing (R) and large-diameter THA, to determine the role of modularity in failure of large-diameter MoM bearings. The study compared (1) metallic ion levels, and (2) survival, functional scores and complications rates between R and THA.

HYPOTHESIS

Large-diameter MoM bearing failure implicates not bearing wear but head-neck junction modularity in larger-diameter MoM THA.

MATERIAL AND METHOD

Eighty-three THAs and 90 Rs were included between February 2004 and March 2006. All patients had clinical and radiologic follow-up with chromium (Cr) and cobalt (Co) ion blood assay.

RESULTS

In the THA group, 24 of the 83 patients (28.9%) underwent revision for adverse reaction to metal debris (ARMD), versus none in the R group. Ten-year all-cause survival was significantly better in R (97.7%; 95% CI, 96.2-99.2) than THA (67.1%; 95% CI, 60.9-73.3). Median blood ion level was higher in THA (with a difference between Co and Cr: 5.75μg/L (range, 3.82-19.2) versus 1.75μg/L (range, 1.34-2.94) respectively) than in R (no difference: 0.89μg/L (range, 0.67-2.89) and 1.07μg/L (range, 0.67-1.65) respectively). In the THA group, there were positive correlations between Co and Cr elevation and implant revision (both p<0.0001). Co/Cr ratio was significantly higher in THA (2.57) than R (0.88) (p<0.0001), and higher again in the 24 cases of THA revision (4.67). There was no significant difference in mean PMA score (THA: 17.08±1.82 (range, 7-18); R: 17.50±0.74 (range, 15-18)), whereas mean Oxford score was better in R (14.32±2.5 (range, 12-24)) than THA (18.17±8.05 (range, 12-42)) (p=0.02).

DISCUSSION

The present study confirmed the incontrovertible implication of modularity in failure of large-diameter MoM THA, by analyzing the same bearing in THA and in resurfacing. Trunnionosis was observed in the 24 cases of revision, with the THA adaptation ring inducing serious metallic ion release (with dissociated Co/Cr ratio), accounting for the high rate of revision.

LEVEL OF EVIDENCE

III, case-control study.

Does the direct anterior approach allow earlier recovery of walking following total hip arthroplasty? A randomized prospective trial using accelerometry

INTRODUCTION

In total hip arthroplasty (THA), the anterior approach is attractive, being intermuscular, with theoretic functional benefit. Such benefit has been frequently claimed, but there are few data from randomized comparative studies using more precise metrics than patient satisfaction. We therefore conducted a randomized trial comparing early functional results between anterior and posterior approaches on gait analysis and functional scores.

HYPOTHESIS

The study hypothesis was that there is no difference between the two approaches in terms of early recovery of walking.

MATERIALS AND METHOD

A single-center single-surgeon prospective randomized study was conducted between February 2017 and April 2018. Inclusion criteria comprised: age<85 years, body-mass index (BMI)<32, and hip osteoarthritis with indication for THA. Preoperatively, the 2 groups were comparable for age, gender, BMI, Charnley, Harris, Postel-Merle-d'Aubigné and Oxford-12 scores and locomotor parameters (triaxial acceleration, step regularity and walking power). Preoperative and 3-, 6- and 12-week assessment comprised triaxial acceleration in walking and Postel-Merle-d'Aubigné, Harris and Oxford SF-12 scores.

RESULTS

One hundred patients were randomized to the anterior approach (AA: n=50) and posterior approach (PA: n=50) groups. Hospital stay was comparable between groups: PA, 2.8±1.78 days [range, 2.29-3.31 days]; AA, 2.84±1.25 days [range, 2.48-3.2 days] (p=0.8). Operative time was significantly longer in AA: 70.1±11 minutes vs. 56.7±11.79 (p<0.0001). There were no significant differences in locomotor parameters (p 0.122 to 0.987) or functional scores (p 0.052 to 0.968) over the 3-month follow-up. There was no difference in cup inclination: PA, 39.6±6.87° [range, 37.65-41.55°] vs. AA, 37.74±4.2° [range, 36.55-38.93°] (p=0.09). There were 8/50 cases (16%) of neurapraxia of the lateral cutaneous nerve of the thigh in the AA group; rates for other complications did not differ between groups.

CONCLUSION

Early functional results and especially objective locomotor parameters following THA were comparable between anterior and posterior approaches at 3 to 12 weeks. The approach should be chosen according to the surgeon's experience.

LEVEL OF EVIDENCE

II, low-power prospective randomized study.

No Increase in Survival for 36-mm versus 32-mm Femoral Heads in Metal-on-polyethylene THA: A Registry Study

BACKGROUND

During the past decade, the 32-mm head has replaced the 28-mm head as the most common head size used in primary THA in many national registries, and the use of 36-mm heads has also increased. However, it is unclear whether 32-mm and 36-mm heads decrease the revision risk in metal-on-polyethylene (MoP) THA compared with 28-mm heads.

QUESTIONS/PURPOSES

(1) In the setting of the Nordic Arthroplasty Register Association database, does the revision risk for any reason differ among 28-, 32-, and 36-mm head sizes in patients undergoing surgery with MoP THA? (2) Does the revision risk resulting from dislocation decrease with increasing head diameter (28-36 mm) in patients undergoing surgery with MoP THA in the same registry?

METHODS

Data were derived from the Nordic Arthroplasty Register Association database, a collaboration among the national arthroplasty registries of Denmark, Finland, Norway, and Sweden. Patients with primary osteoarthritis who had undergone primary THA with a 28-, 32-, or 36-mm MoP bearing from 2003 to 2014 were included. Patients operated on with dual-mobility cups were excluded. In patients with bilateral THA, only the first operated hip was included. After applying the inclusion criteria, the number of patients and THAs with a complete data set was determined to be 186,231, which accounted for 51% of all hips (366,309) with primary osteoarthritis operated on with THA of any head size and bearing type during the study observation time. Of the included patients, 60% (111,046 of 186,231) were women, the mean age at surgery was 70 (± 10) years, and the median followup was 4.5 years (range, 0-14 years). A total of 101,094 patients had received a 28-mm, 57,853 a 32-mm, and 27,284 a 36-mm head with 32 mm used as the reference group. The revision of any component for any reason was the primary outcome and revision for dislocation was the secondary outcome. Very few patients are estimated to be lost to followup because emigration in the population of interest (older than 65-70 years) is rare. A Kaplan-Meier analysis was used to estimate THA survival for each group, whereas Cox regression models were fitted to calculate hazard ratios (HRs) with 95% confidence intervals (CIs) for THA revision comparing the 28- and 36-mm head diameters with the 32-mm head diameters adjusting for age, sex, year of surgery, type of cup and stem fixation, polyethylene type (crosslinked versus conventional), and surgical approach.

RESULTS

In the adjusted Cox regression model, there was no difference in the adjusted risk for revision for any reason between patients with 28-mm (HR, 1.06; 95% CI, 0.97-0.16) and 32-mm heads, whereas the risk of revision was higher for patients with 36-mm heads (HR, 1.14; 95% CI, 1.04-1.26) compared with patients with 32-mm heads. Patients with 28-mm heads had a higher risk of revision for dislocation (HR, 1.67; 95% CI, 1.38-1.98) compared with 32 mm, whereas there was no difference between patients with 36-mm (HR, 0.85; 95% CI, 0.70-1.02) and 32-mm heads.

CONCLUSIONS

After adjusting for relevant confounding variables, we found no benefits for 32-mm heads against 28 mm in terms of overall revision risk. However, when dislocation risk is considered, 32-mm heads would be a better option, because they had a lower risk of revision resulting from dislocation. There were no benefits with the use of 36-mm heads over 32 mm, because the transition from 32 to 36 mm was associated with a higher risk of revision for all reasons, which was not accompanied by a decrease in the risk of revision resulting from dislocation. The use of 32-mm heads appears to offer the best compromise between joint stability and other reasons for revision in MoP THA. Further studies with longer followup, especially of 36-mm heads, as well as better balance of confounders across head sizes and better control of patient-related risk factors for THA revision are needed.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Head size in primary total hip arthroplasty

The use of larger femoral head size in total hip arthroplasty (THA) has increased during the past decade; 32 mm and 36 mm are the most commonly used femoral head sizes, as reported by several arthroplasty registries.The use of large femoral heads seems to be a trade-off between increased stability and decreased THA survivorship.We reviewed the literature, mainly focussing on the past 5 years, identifying benefits and complications associated with the trend of using larger femoral heads in THA.We found that there is no benefit in hip range of movement or hip function when head sizes > 36 mm are used.The risk of revision due to dislocation is lower for 36 mm or larger bearings compared with 28 mm or smaller and probably even with 32 mm.Volumetric wear and frictional torque are increased in bearings bigger than 32 mm compared with 32 mm or smaller in metal-on-cross-linked polyethylene (MoXLPE) THA, but not in ceramic-on-XLPE (CoXLPE).Long-term THA survivorship is improved for 32 mm MoXLPE bearings compared with both larger and smaller ones.We recommend a 32 mm femoral head if MoXLPE bearings are used. In hips operated on with larger bearings the use of ceramic heads on XLPE appears to be safer. Cite this article: EFORT Open Rev 2018;3 DOI: 10.1302/2058-5241.3.170061.

The use of polycarbonate-urethane as an acetabular shell bearing surface: a 5-year prospective study

AIM

To evaluate the clinical performance of a polycarbonate-urethane liner as a bearing material inside a cobalt-chrome acetabular shell.

METHODS

Between December 2007 and July 2011, this material combination was used in 27 total hip replacement patients, most of whom had an indication of osteoarthritis. This report focuses on the first 5-year results of the clinical use of this material combination in the TriboFit® Hip System.

RESULTS

Mean Harris Hip Score showed significant improvement from 40 to 86 after 5 years, similar to studies in the literature. No adverse events - revisions or complications - or disadvantages that have been reported for other total hip materials were observed over the 5-year period. The radiographs showed no signs of wear, migration or loosening of the implants.

CONCLUSIONS

These early results indicate this new material combination offers promise as a safe and effective alternative bearing material for use in total hip systems. Further clinical trials are necessary to reconfirm these findings.

Is there a role for femoral offset restoration during total hip arthroplasty? A systematic review

Benefits of femoral offset restoration during total hip arthroplasty should be the reduction of bearing surfaces wear, implant loosening and dislocation rates. Modular neck stems ensure offset customization but fretting corrosion and catastrophic failures are well-documented complications. Since clinical evidences are needed to substantiate the effectiveness of femoral offset restoration and promote modular neck choice, we systematically reviewed the literature to ascertain whether femoral offset itself has a proven clinical influence: (1) on bearing surfaces wear, (2) implant loosening, (3) and dislocation rates. A systematic literature screening was conducted to find papers dealing with the influence of femoral offset on wear, dislocation and loosening, including articles with conventional radiographic femoral offset assessment and with comparative design. Observational studies, case reports, instructional course lectures, cadaveric and animal studies as well as biomechanical studies, letters to the editor, surgical techniques or technical notes were all excluded. No limits about publication date were supplied but only papers in English were taken into account. Data were extracted into an anonymous spreadsheet. Offset values, dislocation rates, wear rates, follow-up and surgical approaches were all detailed. Ten manuscripts were finally selected. A statistically significant correlation between femoral offset restoration and the reduction of conventional ultrahigh-molecular-weight polyethylene wear was found in two out of three papers investigating this issue, but no correlations were found between femoral offset and dislocation rates or implant loosening. Femoral offset modification influences ultrahigh-molecular-weight polyethylene liners wear, but no correlation was found with dislocation rates or implant loosening. Advantages on wear can be counterbalanced by the use of hard bearing surfaces or highly cross-linked polyethylene liners, besides the availability of larger femoral heads improving implant stability further reduces the importance of femoral offset restoration by means of modularity. We believe that efforts in restoring femoral offset during total hip arthroplasty do not translate into tangible clinical profits and consequently, we do not advise the routinely usage of modular neck stems in total hip arthroplasty.

LEVEL OF EVIDENCE

level III, systematic review of case-control studies.