Femoral head diameter considerations for primary total hip arthroplasty

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.

Lower Revision Rates and Improved Stability With a Monoblock Ceramic Acetabular Cup

BACKGROUND

Monoblock ceramic cups are designed to accommodate large-diameter femoral heads. This has the potential to offer the advantages of an increased range of motion and enhanced joint stability. These features could benefit younger and high-demand patients in need of total hip arthroplasty. The aim of this study was to assess the survival rate and the reasons for revision of the DeltaMotion cup.

METHODS

Data from the AOANJRR were analyzed for all patients who had undergone a primary conventional THA performed between January 1, 2001 and December 31, 2021. Only prostheses with ceramic/ceramic, ceramic/XLPE, metal/XLPE, or CM/XLPE bearing surfaces were included. The primary outcome measure was the cumulative percent revision for all causes. Secondary outcome measures were revision for dislocation/instability, ceramic breakage, or noise. A subanalysis for cup size was also performed.

RESULTS

There were 486,946 primary conventional THA procedures undertaken for any reason. Of these, 4,033 used the DeltaMotion cup and 482,913 were modular designs. The DeltaMotion cup had the lowest CPR for all diagnoses compared to the modular bearings at all time points, had a significantly lower revision rate for prosthesis dislocation and no revisions for squeaking compared to other modular bearings. There were 175 ceramic breakages recorded in the modular bearing group and 1 ceramic breakage in the DeltaMotion group.

CONCLUSIONS

The DeltaMotion cup had a low rate of all-cause revision, and for dislocation, ceramic breakage, and noise. Although this cup is no longer manufactured, ongoing follow-up of newer monoblock ceramic cups will determine their suitability for younger and more active patients.

A novel primary stability test method for artificial acetabular shells considering vertical load during level walking and shell position

Uncemented acetabular shell primary stability is essential for optimal clinical outcomes. Push-out testing, rotation testing, and lever-out testing are major evaluation methods of primary stability between the shell and bone. However, these test methods do not consider shell loads during daily activity and shell installation angle. This study proposes a novel evaluation method of acetabular shell primary stability considering load during level walking and acetabular installation angles such as inclination and anteversion. To achieve this, a novel primary stability test apparatus was designed with a shell position of 40° acetabular inclination and 20° anteversion. The vertical load, corresponding to walking load, was set to 3 kN according to ISO 14242-1, which is the wear test standard for artificial hip joints. The vertical load was applied by an air cylinder controlled by a pressure-type electro-pneumatic proportional valve, with the vertical load value monitored by a load cell. Torque was measured when angular displacement was applied in the direction of extension during the application of vertical load. For comparison, we also measured torque using the traditional lever-out test. The novel primary stability test yielded significantly higher primary stabilities; 5.4 times greater than the lever-out test results. The novel primary stability test failure mode was more similar to the clinical failure than the traditional lever-out test. It is suggested that this novel primary stability test method, applying physiological walking loads and extension motions to the acetabular shell, better reflects in vivo primary stability than the traditional lever-out test.

In vivo creep and wear performance of vitamin-E-diffused highly crosslinked polyethylene in total hip arthroplasty

INTRODUCTION

An acetabular liner thickness of around 6 mm remains the "gold standard" in total hip arthroplasty. Some surgeons have been recommending the use of the thickest possible liner because contact stress and strain in articulating surfaces decrease with increasing the wall thickness. The purpose of this study was to determine whether in vivo creep and wear performance could be enhanced using a thicker liner over the standard thickness in vitamin-E-diffused highly crosslinked polyethylene (HXLPE).

MATERIALS AND METHODS

One hundred and twenty-two hips were allocated to age-matched, sex-matched, and body mass index-matched two subgroups implanted either with a 6.8- or 8.9-mm-thick vitamin-E-diffused HXLPE liner against 28-mm cobalt-chrome femoral head, and followed-up for 7 years. Linear and volumetric penetration of femoral head into the liners attributed to creep and wear were analyzed for each group.

RESULTS

Compressive creep strain generated at the initial 6 months was significantly larger in the 6.8-mm group (2.6%) than in the 8.9-mm group (2.2%). The linear steady-state wear observed after 2 years was 0.0019 and 0.0015 mm/year, whereas the volumetric steady-state wear was 0.54 and 0.45 mm3/years in the 6.8- and 8.9-mm-thick groups, respectively. Although less strain in the thicker group resulted in a slightly less wear, it did not reach significant differences in the steady-state wear rates between the groups.

CONCLUSION

No clinical significance for using a thicker liner over the standard thickness (6.8 mm → 8.9 mm) was confirmed in the vitamin-E-diffused HXLPE according to the 7-year follow-up. The wear rates for both thicknesses were very low enough to prevent osteolysis, and no mechanical failure was observed at any follow-up interval. Nevertheless, since the significantly higher strain was seen in the thinner liner, further follow-up is needed to compare the longer term wear and the incidence of osteolysis and component fracture.

Morphometric Analysis of the Proximal Femur With Its Clinical Correlation in Eastern Uttar Pradesh Region

The anthropometry of the proximal femur holds great clinical significance in designing implants and prostheses for proximal femoral fractures and hip joint arthroplasties. Surgical fixation with a properly matched prosthesis plays a crucial role in improving long-term treatment outcomes and preventing post-operative complications such as osteolysis with aseptic loosening and increased load. The femur is also one of the most commonest used bones for stature estimation. Often during forensic investigations, only fragmented remains of femur are found available from which femoral length is estimated by application of linear regression equations. The estimated femoral length thus obtained is used for stature estimation of the unidentified individual. This study has measured nine bony parameters from the proximal femur in a total of 96 dry femora. These measurements include the vertical head diameter, neck diameter, neck thickness, neck length, neck shaft angle, the transverse diameter of the fovea, longitudinal diameter of the fovea, foveal depth, and the intertrochanteric line length. In addition, the total length of the femur was also measured. The results were tabulated and statistically analyzed using SPSS software, version 25. The mean femoral head diameter was observed to be 41.59±3.25 mm, mean foveal depth was found to be 2.95±0.75 mm, mean foveal transverse and longitudinal diameters were observed to be 11.38±2.35 mm and 15.94±3.37 mm, respectively. The mean neck diameter was 29.45±3.33 mm. Mean neck length and neck thickness were observed to be 36.06±4.94 mm and 27.61±2.71 mm, respectively. Neck shaft angle was noted to range from 109° to 128°, with a mean of 119.08°±5.18°. The mean length of the inter-trochanteric line was measured to be 41.92±3.9 mm. The mean femoral length was observed to be 42.11±2.91 cm. Significant positive correlations were found between the various measured proximal morphometric parameters of the femur. The length of the femur showed a maximum positive correlation with the vertical head diameter, followed by the neck diameter, thickness, and foveal depth. The findings of this study can throw further light on the existing data. They can serve as a guideline for designing better-matched prostheses and implants for hip surgeries in the eastern Uttar Pradesh population.

Influence of Accelerated Aging on the Wear Behavior of Cross-Linked Polyethylene Liners—A Hip Simulator Study

Sequential cross-linked and annealed ultra-high-molecular-weight polyethylene (SX-PE) is known as a low-wear articulating partner, especially for total hip endoprostheses. Aging of polymeric materials, irrespective of if induced by shelf or in vivo life, can degrade their tribological and mechanical properties. However, changes in wear behavior of aged SX-PE liners have not been not quantified so far. An accelerated aging procedure, to simulate shelf and in vivo aging, was performed on thin SX-PE liners after five million load cycles using a simulator (“worn-aged”) as well as on new SX-PE liners (“new-aged”). A subsequent hip simulator test was performed with both thin SX-PE liner sets in combination with large-diameter ceramic femoral head, representing a combination known as advantageous for treatment after revision because of dislocation. Oxidation indices were measured on the liners after each step of the procedure. SX-PE liners after accelerated aging show bedding-in phases during simulator test, which was a characteristic only known from clinical investigations. Hence, the wear rates of the “new-aged” ((1.71 ± 0.49) mg/million cycles) and of the “worn-aged” ((9.32 ± 0.09) mg/million cycles) SX-PE were increased in the first period compared to new unaged SX-PE liners. Subsequently, the wear rates decreased for “new-aged” and “worn-aged” inserts to (0.44 ± 0.48) mg/million cycles and (2.72 ± 0.05) mg/million cycles, respectively. In conclusion, the results show promising effects of accelerated aging on SX-PE liners in simulator testing and for potential long-term use in clinical applications.

The Effect of Femoral Head Size on Groin Pain in Total Hip Arthroplasty

BACKGROUND

Although increased femoral head size reduces the risk of instability in total hip arthroplasty (THA), it may lead to iliopsoas irritation and increased anterior groin pain. The purpose of this study is to compare outcomes between non-modular dual-mobility (NDM) implants and small (≤32 mm) and large (≥36 mm) fixed-bearing (FB) constructs.

METHODS

A retrospective review of all primary total hip arthroplasties from 2011 to 2021 was conducted at a single, urban academic institution. Patients were separated into 3 cohorts: NDM implant ≤32 mm and FB implant ≥36 mm. Demographics and outcomes such as length of stay, dislocation, and anterior groin pain were assessed. Patients were deemed as having groin pain if they received an iliopsoas injection or had extended physical therapy ordered beyond 3 months postoperatively.

RESULTS

There were 178 NDM implants, 936 ≤32-mm FB, and 2,454 ≥36-mm FB implants included. Length of stay significantly differed between the groups (48.4 ± 43.3 vs 63.2 ± 40.6 vs 57.2 ± 38.1 hours; P = .001). Although not statistically significant, the ≥36-mm FB cohort had the highest rate of dislocations (0.6% vs 0.7% vs 0.9%; P = .84). Although no patients with an NDM implant received an iliopsoas injection, 9 patients (0.9%) with a ≤32-mm FB implant and 9 patients (0.4%) with a ≥36-mm implant received an injection (P = .06). However, 18 (10.1%) patients with an NDM implant, 304 (32.5%) patients with a ≤32-mm FB implant, and 355 (14.5%) patients with a ≥36-mm FB implant received extended physical therapy 3 months after surgery (P < .001).

CONCLUSION

NDM implants, as well as FB implants with both small and large head sizes are effective at preventing dislocation. NDM implants did not result in an increase in anterior groin pain compared to ≤32-mm and ≥36-mm FB constructs.

LEVEL III EVIDENCE

Retrospective cohort study.

Long-term survival of the Lefèvre retentive cup: 12-year follow-up analysis of 466 consecutive cases

INTRODUCTION

The Lefèvre retentive cup is a salvage solution for total hip replacement at high risk of dislocation. Only a few studies have reported the medium or long-term survival; most often, only a small number of patients were included in these studies. This led us to conduct a retrospective analysis of a large population to determine: 1) the 10-year survival rate after primary or revision arthroplasty, 2) the complication rate.

HYPOTHESIS

The dislocation rate is<5% for revision arthroplasty and<2% for primary arthroplasty.

MATERIAL AND METHODS

This single-center retrospective study included 466 consecutive total hip replacements performed with the Lefèvre retentive cup with a 12-year theoretical minimum follow-up (1/1/1998 to 31/8/2006). There were 257 indications for primary arthroplasty and 209 for revision arthroplasty. The cohort had 316 women and the mean age at surgery was 72.9years (30.2-89.9). The mean follow-up was 10.2±5 years (0.1-19.3). A statistical analysis was done based on the Kaplan-Meier survival curves in two subsets of patients: primary and revision surgery.

RESULTS

At the final review, 264 patients had died because of reasons unrelated to the procedures (mean 7.8±4.7years after the procedure), 48 were lost to follow-up (mean 3.0±3.3years after the procedure), and 39 patients (8%) had undergone acetabular revision of which 12 were for infection (2.5%), 25 were for loosening (5.4%) (5 femoral loosening only) and 2 were for dislocation (0.4%). In all, there were 10/466 dislocations (2.1%) of which 5/257 (1.9%) were in the primary group and 5/209 (2.4%) were in the revision group: 2 had a cup exchange and 8 were reduced by closed procedures. The probability of survival free of mechanical complications at 10years was estimated at 94.8%±1.6% (95% CI: 91.6%-98.0%) for the primary group and 87.8%±2.7% (95% CI: 82.4%-93.2%) for the revision groups (p=0.0017). There were 39 re-operations in the overall cohort: 1/257 (0.4%) for dislocation, 7/257 (2.7%) for aseptic loosening and 3/257 (1.2%) for infection in the primary group, while in the revision group, 1/209 (0.5%) was for dislocation, 18/209 (8.6%) for aseptic loosening and 9/209 (4.3%) for infection.

CONCLUSION

The Lefèvre retentive cup has good long-term survival with a low mechanical complication rate, both in primary and revision surgery. To us, this implant appears to be a reliable salvage procedure for total hip replacement in patients at high risk for dislocation.

LEVEL OF EVIDENCE

IV; retrospective study without control group.

Implant factors that might influence components' survival in primary total hip arthroplasty

Primary total hip arthroplasty (THA) is an invaluable surgical procedure that has revolutionised the treatment of various end-stage hip pathologies. Aseptic loosening of either acetabular cup and/or femoral stem as well as components' dislocation are well-known post-operative complications due to so many factors: environmental, surgeon, patient related, disease related or implant design. The aim of this literature review is to look at some relevant implant designs that might influence acetabular and femoral components' survival for primary cementless THA using revision for aseptic loosening and dislocation as criteria for failure. This may also assist the surgeon in making an informed choice of using appropriate implants to match the demographic and disease-specific need of the patients undergoing the surgical procedure. This review article was performed using an online literature search on relevant publications.

The Diagnosis and Treatment of Acetabular Bone Loss in Revision Hip Arthroplasty: An International Consensus Symposium

Despite growing evidence supporting the evaluation, classification, and treatment of acetabular bone loss in revision hip replacement, advancements have not been systematically incorporated into a single document, and therefore, a comprehensive review of the treatment of severe acetabular bone loss is needed. The Stavros Niarchos Foundation Complex Joint Reconstruction Center at Hospital for Special Surgery held an Acetabular Bone Loss Symposium on June 21, 2019, to answer the following questions: What are the trends, emerging technologies, and areas of future research related to the evaluation and management of acetabular bone loss in revision hip replacement? What constitutes the optimal workup and management strategies for acetabular bone loss? The 36 international experts convened were divided into groups, each assigned to discuss 1 of 4 topics: (1) preoperative planning and postoperative assessment; (2) implant selection, management of osteolysis, and management of massive bone loss; (3) the treatment challenges of pelvic discontinuity, periprosthetic joint infection, instability, and poor bone biology; and (4) the principles of reconstruction and classification of acetabular bone loss. Each group came to consensus, when possible, based on an extensive literature review. This document provides an overview of these 4 areas, the consensus each group arrived at, and directions for future research.

Trends of Femoral Neck Fracture Treatment Using Total Hip Arthroplasty: Reported From the American Joint Replacement Registry

INTRODUCTION

Total hip arthroplasty (THA) rather than hemiarthroplasty for displaced femoral neck fracture (FNF) is often chosen for younger patients who are more active and/or have underlying hip osteoarthritis. However, instability remains the primary concern of doing THA. Dual mobility (DM) has been shown to decrease this risk through a larger effective head size and greater head-to-neck ratio compared with conventional THA. The purpose of this study was to identify femoral head size and DM usage patterns for the treatment of FNF with THA in the United States using the American Joint Replacement Registry.

METHODS

A retrospective cohort study was conducted, including all primary THAs done for FNF from 2012 to 2019. THA and FNF were defined using Current Procedural Terminology or International Classification of Diseases-9 or -10 diagnosis and procedure codes. Analysis was based on patient demographics, femoral head size, and DM usage. Descriptive statistics were used using a Pearson chi-square test. All analyses were conducted using SAS version 9.4, and statistical significance was set at P < 0.05.

RESULTS

There were 18,752 THAs done by 3,242 surgeons at 789 institutions during the 8-year study period. The overall population was 66% female, and the mean age was 72.3 ± 11.8 years. The most commonly used femoral head size was 36 mm (48.5%) followed by 32 mm (24.5%), ≤28 mm (10.7%), DM (10.8%), and ≥40 mm (5.7%). A trend was observed toward decreased use of ≤28, 32, and ≥40-mm heads starting in 2016 across the years and increased use of 36-mm heads (P < 0.0001). A significant increase was observed in the usage of DM over time from 6.4% in 2012 to 16.2% in 2019 (P < 0.0001).

DISCUSSION

Most of the femoral heads used were ≥36 mm, and the use of DM increased during the study period. Additional analysis is warranted to understand how these trends will affect overall outcomes and postoperative dislocation rates.

Dissociation of Acetabular Polyethylene Liners With a Morse Taper Design

BACKGROUND

Polyethylene liner dissociation is an uncommon complication of hip replacement. Dissociation has been associated with particular acetabular component designs. This study reviewed acetabular liner dissociations in a specific modular cup with a Morse taper locking mechanism that has not been previously reported.

METHODS

The senior author performed 655 primary total hip arthroplasties with one particular design of acetabular component using Class A polyethylene liners and metal head articulation. Cases with revision surgery performed for acetabular liner dissociation were reviewed.

RESULTS

Seven of 655 patients with this cup underwent revision surgery for a dissociated liner. Liner dissociation occurred at a mean of 73 months postoperatively. Patients presented with new-onset hip pain or squeaking, 4 of which developed symptoms acutely. Two patients treated with polyethylene liner exchange into the same cup required a second revision surgery for recurrent dissociation.

CONCLUSION

Polyethylene liner dissociation is an infrequent but possible complication associated with modular acetabular components using a Morse taper locking. Providers should be vigilant with long-term follow-up of patients with this acetabular system for patient complaints of catching or squeaking. Patients treated for liner dissociation should not have a new liner placed into the same acetabular shell given the risk for further dissociation.

Dual Mobility Total Hip Arthroplasty Is Not Associated with a Greater Incidence of Groin Pain in Comparison with Conventional Total Hip Arthroplasty and Hip Resurfacing:A Retrospective Comparative Study

BACKGROUND

Groin pain is a common long-term complication of total hip arthroplasty (THA). Femoral head size has been proposed as one of the primary causes. The implants used in dual mobility (DM) THA have large outer-bearing articulations, which could increase the risk of post-operative groin pain. Hip resurfacing (HR), too, has been shown to be associated with a risk of groin pain.

QUESTIONS/PURPOSES

The goals of this study were to compare the incidence of groin pain at 1 year after hip arthroplasty in patients with different femoral head diameters and in patients undergoing conventional THA, DM THA, and HR.

METHODS

After combing an institutional registry for all patients who had undergone THA or HR for primary hip osteoarthritis, we included 3193 patients in the analysis; 2008 underwent conventional THA, 416 underwent DM THA, and 769 underwent HR. We used logistic regression modeling to analyze the relation of groin pain at 1 year after surgery to patient demographics and clinical characteristics, including age, sex, body mass index (BMI), University of California at Los Angeles activity score at 1 year after surgery, bearing couple, and the ratio of acetabular diameter to femoral head diameter. We also measured cup inclination and anteversion in a subset of patients with and without groin pain at 1 year to assess whether pain could be related to implant position.

RESULTS

Overall, 8.7% of patients reported groin pain at 1 year. Patients with groin pain were younger and had lower BMIs. There were increased odds of groin pain with a greater cup-to-head ratio, although DM implants, interestingly, were not significantly associated with groin pain; this may be attributable to so much of their movement taking place inside the implant. Subgroup analysis measuring cup inclination and anteversion showed no difference in cup position between patients with and without pain.

CONCLUSION

In this population of hip arthroplasty patients, the incidence of groin pain 1 year after surgery did not differ among patients undergoing DM and conventional THA; DM THA in particular was not associated with a higher risk of groin pain, despite its comparatively larger femoral head sizes. HR, on the other hand, was associated with a higher risk of pain. Appropriate implant sizing and bearing couple choice may optimize the functional benefit of THA.

Hip Arthroplasty Instability After Implantation of a Spinal Cord Stimulator

A 46-year-old man with a left hip resurfacing that had been stable for over 5 years sustained a hip dislocation immediately after the implantation of a spinal cord stimulator (SCS). He continued to experience multiple episodes of instability after this initial event, requiring several revision hip arthroplasty surgeries with variable degrees of constraint. It was not until after SCS removal and prolonged hip spica casting that the patient returned to pain-free, independent ambulation. SCS implantation may affect spino-pelvic stability and alter the biomechanics of the hip after hip arthroplasty procedures. We present the unique case of a patient with a well-fixed hip resurfacing with no previous episodes of instability who experienced dislocation immediately after SCS implantation.

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.

A discrete element model to predict anatomy of the psoas muscle and path of the tendon: Design implications for total hip arthroplasty

BACKGROUND

The accurate estimation of a muscle's line of action is a fundamental requirement in computational modelling. We present a novel anatomical muscle wrapping technique and demonstrate its clinical use on the evaluation of the Psoas muscle mechanics in hip arthroplasty.

METHODS

A volume preserving, spring model to parameterize muscle anatomy changes during motion is presented. Validation was performed by a CT scan of a cadaver model in multiple positions. The predicted psoas musculotendinous path was compared with the actual imaging findings. In a second stage, psoas kinetics were compared between a conventional versus a resurfacing hip arthroplasty during gait.

FINDINGS

Anatomy prediction error was found to be 2.12 mm on average (SD 1.34 mm). When applied to psoas mechanics during walking, the muscle was found to wrap predominantly around the femoral head providing a biomechanically efficient and nearly constant moment arm for flexion during the entire gait cycle. However, this advantage was found to be lost in small diameter hip arthroplasty designs resulting in an important mechanical disadvantage. The moment arm for flexion, was on average 36% (SD 0.03%) lower in the small diameter conventional hip arthroplasty as compared to the large diameter head of the hip resurfacing and this difference was highly significant. (p < 0.001).

INTERPRETATION

Despite the shortcomings of an "in silico" and cadaveric study, our findings are in accordance with previous clinical and gait studies. Furthermore, the findings are strongly in favour of large diameter implant designs, warranting their further development and optimisation.

Effects of total hip arthroplasty for primary hip osteoarthritis on postural balance: A systematic review

BACKGROUND

Hip osteoarthritis is one of the major causes of disability worldwide, and although total hip arthroplasty is considered effective in the management of this condition, its effects on postural balance remain unclear.

RESEARCH QUESTION

What are the effects of total hip arthroplasty for primary hip osteoarthritis on the postural balance compared to preoperative status and/or to healthy controls?.

METHOD

A systematic review was conducted, and the Embase, Latin American and Caribbean Health Sciences (LILACS), PubMed, Scopus, The Cochrane Library, and Web of Science databases were searched. Randomized and non-randomized studies were considered eligible for inclusion. The risk of bias of included studies was assessed using the Joanna Briggs Institute critical appraisal tools.

RESULTS

Among the 41 potentially eligible studies, 13 studies were included for qualitative synthesis-8 studies had low risk of bias and 5 had moderate risk of bias. Ten studies compared the effects of total hip arthroplasty on the postural balance in healthy controls. Meanwhile, the remaining 3 studies compared such effects to the preoperative status only. Comparable results on the postural balance between the intervention and control groups were observed in 5 studies, whereas 3 studies showed better scores among healthy controls. The other 2 studies reported that postural balance could still be impaired at 6 months to 3 years postoperatively. All 3 studies with no healthy controls reported an improvement in the postural balance compared to the preoperative status.

CONCLUSIONS

Major post-surgical improvements were consistently observed compared to preoperative status, although postural balance impairment was still noted compared to healthy controls.

SIGNIFICANCE

The results of this study might be a useful guide for clinicians on the extent of the therapeutic effects of hip arthroplasty on postural balance. Furthermore, the standardization of balance assessment tools could strengthen the certainty of cumulative evidence in future studies.

The risk of revision after total hip arthroplasty in young patients depends on surgical approach, femoral head size and bearing type; an analysis of 19,682 operations in the Dutch arthroplasty register

Background

Total hip arthroplasty (THA) is used increasingly in younger patients. There is little knowledge about the effect of THA characteristics on risk of revision, especially in young patients. Therefore, we studied the influence of both patient-related and surgical factors on the risk of revision using data from the Dutch Arthroplasty Registry (LROI).

Methods

All patients younger than 55 years with a primary THA implanted in the Netherlands between 2007 and 2017 were selected (n = 19,682). The covariates age, sex, primary diagnosis, ASA-classification, surgical approach, fixation method, bearing type, head size and year of surgery were entered into Cox proportional hazards models to calculate hazard ratios for the risk of revision.

Results

The overall 5-year survival of primary THA was 95.3% (95% CI, 94.9–95.6). Use of the anterior approach resulted in a lower risk of revision than the use of the posterolateral approach (HR: 0.66, 95% CI: 0.47–0.92). THAs with a head diameter ≥ 38 mm had a higher risk of revision (HR: 1.90, 95% CI: 1.33–2.72) than THAs with 32 mm heads. Use of MoM bearings resulted in an increased risk when compared to C-PE (HR: 1.76, 95% CI: 1.27–2.43).

Conclusion

The risk of revision in patients younger than 55 years depends on surgical approach, head size and bearing type. The anterior approach resulted in a decreased risk of revision, whereas use of ≥38 mm heads and MoM bearings resulted in an increased risk of revision for any reason.

Effect of Femoral Head Size, Subject Weight, and Activity Level on Acetabular Cement Mantle Stress Following Total Hip Arthroplasty

In cases where cemented components are used in total hip arthroplasty, damage, or disruption of the cement mantle can lead to aseptic loosening and joint failure. Currently, the relationship between subject activity level, obesity, and prosthetic femoral head size and the risk of aseptic loosening of the acetabular component in cemented total hip arthroplasty is not well understood. This study aims to provide an insight into this. Finite element models, validated with experimental data, were developed to investigate stresses in the acetabular cement mantle and pelvic bone resulting from the use of three prosthetic femoral head sizes, during a variety of daily activities and one high impact activity (stumbling) for a range of subject body weights. We found that stresses in the superior quadrants of the cortical bone-cement interface increased with prosthetic head size, patient weight, and activity level. In stumbling, average von Mises stresses (22.4 MPa) exceeded the bone cement yield strength for an obese subject (143 kg) indicating that the cement mantle would fail. Our results support the view that obesity and activity level are potential risk factors for aseptic loosening of the acetabular component and provide insight into the increased risk of joint failure associated with larger prosthetic femoral heads. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1771-1783, 2019.

S, Shenoy B. S, R. Kini C. Static structural analysis of different stem designs used in total hip arthroplasty using finite element method

BACKGROUND

The Hip joint is the primary joint which gives stability to the human body. The wear and tear associated with age and other factors, require these joints to be replaced by implants using hip arthroplasty surgeries. Cobalt chromium alloy (CoCr), titanium alloy, stainless steel are some of the most common hip joint materials used for hip implants. The design requirement for hip joint implants are very stringent to avoid revision joint surgeries due to aseptic loosening. There are various choices in shapes and materials used for stem and acetabular designs. This makes it more difficult to make an informed decision on the type of design and material that can be used for hip implants.

METHODS

Circular, Oval, ellipse and trapezoidal designs with three individual cross sections (defined as profile 1, profile 2 and profile 3) are considered for the study. All models are modeled using CATIA V-6. Static structural analysis is performed using ANSYS R-19 to arrive at the best possible design and material combination for stem and acetabular cup.

RESULTS

It was found that, profile 2 of all the four designs has the lowest possible deformation and von Mises stress when compared to profile 1 and profile 2. In general, profile 2 with trapezoidal stem has best outcomes in terms of its mechanical properties. Besides, stem designed with material CoCr and its associated acetabular cup with CoC (ceramic on ceramic) material can produce an implant having better properties and longer durability.

CONCLUSIONS

CoCr was found to be the preferred choice of material for stem design. It was also observed that, irrespective of material considered for the analysis profile 2 with trapezoidal stem showcased lesser deformation and von Mises stress over the other eleven models. For analysis involving acetabular cups, CoC implants exhibited better mechanical properties over the conventional CoPE (Ceramic on polyethylene) materials such as Ultra-high molecular weight polyethylene (UHMWPE). It is inferred from the findings of this study that, the profile 2 with trapezoidal stem design made of CoCr material and acetabular cup made of CoC material is best suited for hip joint implants.

Arthroscopic techniques for treating ilio-psoas tendinopathy after hip arthroplasty

Impingement of hip arthroplasty components on soft tissues may adversely affect outcomes. An example is impingement of the cup on the ilio-psoas tendon, which has been reported in 0.4% to 8.3% of patients. Contributors to ilio-psoas tendon impingement (IPTI) can be categorised as anatomic (hypoplastic anterior wall), technical (inadequate anteversion and/or lower inclination, oversized cup, cement in contact with the tendon, and intra-muscular screw), and prosthetic (e.g., aggressive cup design, large-diameter head, resurfacing, and collared femoral prosthesis). IPTI manifests as groin pain, raising diagnostic challenges since this symptom lacks specificity. Physical findings of value for the diagnosis include pain exacerbation during active hip flexion, groin pain upon straight-leg raise to 30°, and/or snapping hip syndrome. Confirmation is then provided by ultrasonography and, most importantly, computed tomography. Once the diagnosis is confirmed, non-operative treatment combining physical therapy and local corticosteroid injections is prescribed. When these measures fail, endoscopic or arthroscopic surgery is generally effective. In patients with major cup malposition, revision of the cup is the preferred option, despite the higher complication rate. When cup position is adequate, ilio-psoas tenotomy can be performed either extra-articularly at the lesser trochanter (by endoscopy) or intra-articularly (by arthroscopy). The arthroscopic technique is more demanding but useful when the diagnosis is in doubt, as it allows examination of the prosthetic bearing surfaces. Both techniques and the risks inherent in each are discussed in detail. Tenotomy, whether performed endoscopically or arthroscopically, promptly provides good outcomes in over 85% of patients, usually with full recovery of hip flexor strength over time. These minimally invasive techniques, while as effective as conventional surgery, are associated with lower morbidity rates.

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.

Total hip arthroplasty: Survival and modes of failure

Total hip arthroplasty (THA) is a very satisfactory surgical procedure for end-stage hip disorders.

Implant modifications, such as large femoral heads to improve stability, porous metals to enhance fixation and alternative bearings to improve wear, have been introduced over the last decade in order to decrease the rate of early and late failures.

There is a changing pattern of THA failure modes.

The relationship between failure modes and patient-related factors, and the time and type of revision are important for understanding and preventing short and late failure of implants.

The early adoption of innovations in either technique or implant design may lead to an increased risk of early failure.

Cite this article: EFORT Open Rev 2018;3 DOI: 10.1302/2058-5241.3.170068

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.

Third-generation pure alumina and alumina matrix composites in total hip arthroplasty: What is the evidence?

Wear, corrosion and periprosthetic osteolysis are important causes of failure in joint arthroplasty, especially in young patients.

Ceramic bearings, developed 40 years ago, are an increasingly popular choice in hip arthroplasty. New manufacturing procedures have increased the strength and reliability of ceramic materials and reduced the risk of complications.

In recent decades, ceramics made of pure alumina have continuously improved, resulting in a surgical-grade material that fulfills clinical requirements.

Despite the track record of safety and long-term results, third-generation pure alumina ceramics are being replaced in clinical practice by alumina matrix composites, which are composed of alumina and zirconium.

In this review, the characteristics of both materials are discussed, and the long-term results with third-generation alumina-on-alumina bearings and the associated complications are compared with those of other available ceramics.

Cite this article: EFORT Open Rev 2018;3:7-14. DOI: 10.1302/2058-5241.3.170034

Adventure sports and sexual freedom hip replacement: the tripolar hip

Certain athletic activities and lifestyles require a completely stable and very mobile hip. Total hip replacement with a natural femoral head size and two mobile-bearing surfaces (i.e., a "tripolar" prosthesis) is the most stable prosthesis. Elegant design and wear-resistant bearing surfaces are the keys to long-term implant survivorship. The hypothesis is that a ceramic-coated tripolar prosthesis using highly cross-linked polyethylene can provide full function and complete stability with low wear. This study sought to determine: (1) patient-reported outcomes, (2) functional outcomes, (3) implant survivorship and complications, and (4) postoperative sexual limitations. Between 1998 and 2011, the author performed 160 primary total hip replacements using tripolar prostheses in patients participating in adventure sports and other physically demanding activities. The institutional review board approved this study. The inclusion criteria were patients who needed unrestricted activity and who were not candidates for or did not choose hip resurfacing. Patients were followed every second year and assessed with radiographs, Harris Hip Score, WOMAC, SF-12, and UCLA functional outcome scores. Patients were asked about symptoms of instability and satisfaction with their hip replacement. Patients were asked both preoperatively and 2 years postoperatively four questions about their sexual activity. Mean follow-up was 11 years. At 2 years' postoperatively, 98% of patients reported their satisfaction as excellent or good and 99% were not limited for sexual activity following surgery. Seventy-four percent of patients reported they were recovered within 6 weeks of surgery. There were no dislocations. There were three revision procedures for implant loosening, infection, and periprosthetic fracture, but there were no failures of the tripolar articulation. The mean postoperative UCLA score was the highly athletic score of 8. There were no signs of osteolysis, wear, or metal sensitivity reactions. The range of motion achieved, sexual, and functional outcomes were higher than with other types of total hip replacement. This ceramic-coated tripolar prosthesis using highly cross-linked polyethylene provides full function, complete stability, and low wear to younger, active patients, thus confirming the hypothesis and clinical relevance.

Complications after surgical treatment of femoral neck fractures in men with alcohol dependence syndrome: retrospective register analysis of 154 cases

PURPOSE

One-third of hip fractures occur in men. The causes underlying hip fractures in men differ from those in women and include alcohol abuse. This retrospective register study evaluated the trends and results associated with different surgical treatment methods for nondisplaced and displaced femoral neck fractures in male patients with alcohol dependence syndrome.

METHODS

Men with hip fractures were identified from a local district hospital database. Alcohol dependence syndrome was identified as a diagnosis in medical records.

RESULTS

For displaced fractures, implant survival after total hip arthroplasty was significantly lower compared to hemiarthroplasty. For nondisplaced fractures, implant survival of cannulated screws was significantly lower compared to sliding hip screws. Overall patient survival for males with alcohol dependence syndrome with hip fracture was 62% at 1 year and 49% at 2 years. Patient survival in this population did not differ between displaced and nondisplaced fractures or among different surgical methods.

CONCLUSION

Patients with alcoholism who had documented evidence of alcohol dependence syndrome represented nearly half of patients <70 years old with low-energy hip fracture. In patients with nondisplaced femoral neck fractures, stability of the internal fixation appeared to play a major role in implant survival; sliding hip screws should be considered over multiple cannulated screws. In patients with displaced fracture, total hip arthroplasty was associated with a significantly higher risk of complications leading to revision compared to hemiarthoplasty.

LEVEL OF EVIDENCE

Prognostic Level III.

Total hip arthroplasty survival in femoral head avascular necrosis versus primary hip osteoarthritis: Case-control study with a mean 10-year follow-up after anatomical cementless metal-on-metal 28-mm replacement

BACKGROUND

Total hip arthroplasty is the most widely used procedure to treat avascular necrosis (AVN) of the femoral head. Few studies have compared the outcomes of THA in femoral head AVN and primary hip osteoarthritis. Therefore we performed a case-control study to compare THA for femoral head AVN vs. primary hip osteoarthritis in terms of: (1) prosthesis survival, (2) complication rates, (3) functional outcomes and radiographic outcomes, (4) and to determine whether specific risk factors for THA failure exist in femoral head AVN.

HYPOTHESIS

THA survival is similar in femoral head AVN and primary hip osteoarthritis.

MATERIAL AND METHODS

We compared two prospective cohorts of patients who underwent THA before 65 years of age, one composed of cases with femoral head AVN and the other of controls with primary hip osteoarthritis. In both cohorts, a cementless metal-on-metal prosthesis with a 28-mm cup and an anatomical stem was used. Exclusion criteria were THA with other types of prosthesis, posttraumatic AVN, and secondary osteoarthritis. With α set at 5%, to obtain 80% power, 246 patients were required in all. Prosthesis survival was assessed based on time to major revision (defined as replacement of at least one implant fixed to bone) and time to aseptic loosening. The other evaluation criteria were complications, Postel-Merle d'Aubigné (PMA) score, and the Engh and Agora Radiographic Assessment (ARA) scores for implant osseointegration.

RESULTS

The study included 282 patients, 149 with AVN and 133 with osteoarthritis. Mean age was 47.8±10.2 years (range, 18.5-65) and mean follow-up was 11.4±2.8 years (range, 4.5-18.3 years). The 10-year survival rates were similar in the two groups: for major revision, AVN group, 92.5% (95% confidence interval [95% CI], 90.2-94.8) and osteoarthritis group, 95.3% (95% CI, 92.9-97.7); for aseptic loosening, AVN group, 98.6% (95% CI, 97.6-98.6) and osteoarthritis, 99.2% (95% CI, 98.4-100). The AVN group had higher numbers of revision for any reason (19 vs. 6, P=0.018) and for dislocation (8 vs. 1, P=0.031). Mean PMA scores at last follow-up were comparable in the AVN group (17.65±1.27 [range, 10-18]) and osteoarthritis group (17.59±1.32 [range, 14-18]) (P=0.139). Osseointegration was also similar in the two groups: global Engh score, 26.51±1.81 (range, 14-27) for AVN and 26.84±0.91 (range, 19.5-27) for osteoarthritis (P=0.065); femoral ARA score, 5.83±0.46 (range, 3-6) for AVN and 5.90±0.42 (range, 3-6) for osteoarthritis (P=0.064); and cup ARA score, 5.74±0.67 (range, 3-6) for AVN and 5.78±0.66 (range, 3-6) for osteoarthritis (P=0.344).

DISCUSSION

Survival in this study was good and consistent with recent data on AVN, with no difference between AVN and osteoarthritis. Revisions for any cause or for dislocation were more common after THA for AVN. Functional outcomes were similar in the AVN and osteoarthritis groups. An anatomical cementless prosthesis combined with metal-on-metal 28-mm bearing provides durable good outcomes.

LEVEL OF EVIDENCE

III, non-randomized comparison of two prospective cohorts.

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

BACKGROUND

Large-diameter (>36mm) total hip arthroplasty (THA) has developed rapidly since the advent of ceramic-on-ceramic (CoC) bearings and highly cross-linked polyethylene. Theoretically, the increase in diameter reduces the risk of instability, although the advantage of calibers beyond 36mm has not been demonstrated in terms of range-of-motion recovery. We conducted a comparative study with a single prosthesis model to determine whether increasing the caliber beyond 36mm provides: (1) better recovery of range-of-motion, (2) a higher functional score, and (3) reduction of the dislocation rate.

HYPOTHESIS

Increasing the range-of-motion by increasing the caliber beyond 36mm provides better range-of-motion.

MATERIAL AND METHODS

We analyzed two consecutive, single-operator cementless THA series performed via the mini posterior approach, which differed only in the bearing system (51 metal-on-metal [MoM] with a mean caliber of 45mm±3.3 [range, 40-54] and 61 CoC with a 36-mm caliber). Both series were comparable preoperatively in terms of age, diagnosis, functional scores, preoperative range-of-motion, body mass index, UCLA activity level, and Charnley score. We compared the joint range of movement at follow-up and the gains in range of movement, onset of dislocation, and functional scores (Oxford, Postel-Merle d'Aubigné [PMA]).

RESULTS

The mean overall joint range-of-motion was 254°±39° (range, 150-310°) for an 81°±44° (range, -50 to 180°) gain in the MoM group and 256°±23° (range, 200-280°) for an 84°±40° (range, 0-160°) gain in the CoC group (NS). The MoM group presented the following results: Oxford=13.71±3.66 (range, 12-33) for a gain of 24.82 points±7.9 (range, -1 to 40), PMA=17.75±1.06 (range, 11-18) for a gain of 7.78 points±4.01 (range, 2-15). The CoC group had: Oxford=14.98±4.42 (range, 12-36) for a gain of 24.75 points±6.55 (range, 12-40), PMA 17.66±0.7 (range, 14-18) for a gain of 8 points±3.77 (range, 1-15). None of the gains and scores at follow-up differed significantly between the two groups. No episode of dislocation was identified.

DISCUSSION

The current trend of increasing femoral head diameters beyond 36mm to improve the gains in joint range-of-motion and function is not warranted. The potential side effects of increasing the caliber call for even greater caution in the use of large-diameter heads because our hypothesis has not been confirmed.

LEVEL OF EVIDENCE

Case-control study, level III.

High serum ion levels in Conserve Plus big femoral head cemented total hip arthroplasty

AIM

We report the short-term clinical, radiographic and ion level data of the Conserve Plus metal-on-metal (MoM) big femoral head (BFH) total hip arthroplasty (THA), used with a cemented cobalt-chrome (Co-Cr) Profemur Xm stem and a titanium (Ti) modular neck.

RESULTS

In a consecutive series of 40 hips, survivorship at 3 years was 92.5% with revision for any reason. Average Harris Hip Score was 91.3. There were no implant loosenings. No osteolysis was observed. 5 patients had signs of adverse local tissue reaction (ALTR); their clinical scores were not different from the whole cohort. All but 1 patient had their Co serum ion levels measured. The average Co level was 14,1 µg/l (range 0.9-29.0; median 13.0 µg/l). Clinical scores did not correlate with ion level data. A comparative group of 42 hip resurfacing arthroplasties from the same manufacturer had significantly lower serum Co levels: 1.51 µg/l (range 0.9-4.0; median 0.9 µg/l).

CONCLUSIONS

All patients with the MoM BFH THA design should be followed regularly and should have ion level testing.

Excellent short-term results of hip resurfacing in a selected population of young patients

BACKGROUND

Hip resurfacing (HR) is an alternative option to total hip arthroplasty (THA) in a population of selected patients (young and/or active).

HYPOTHESIS

The short-term survivorship rate is as least as good as that for THA with no abnormal increase in serum metal ion levels.

MATERIALS AND METHODS

A continuous prospective series of 502 hip resurfacings in 481 patients mean age 48.7 years old (±10.3; 18-68) (Conserve Plus, Wright Medical Technology) was analyzed clinically, radiologically and biologically (total blood chrome, cobalt and titanium metal ion levels). Mean follow up was 4.1 years (1.9-4.9).

RESULTS

There were no dislocations. There were 5 cases of revision surgery with component replacement (including 2 infections). Implant survivorship using implant removal as the criteria (excluding infection) was 99.4% at 4 years (CI 95%: 98.1-99.8). The evaluation of metal ion levels showed a significant increase in cobalt from a preoperative level of 0.24 μg/L (0.01-3.6) to 0.86 μg/L (0.01-5.7) at the final follow-up (P<0.001). Chrome and titanium levels went from 0.68 μg/L (0.01-4.4) and 2.36 μg/L (0.39-7) to 1.28 μg/L (0.1-5.5) and 4.49 μg/L (1.29-8.21) respectively (P<0.001). All clinical scores had significantly improved at the final follow-up. Mean frontal plane cup inclination was 42.7° (35-62).

DISCUSSION

In a selected population of young and/or active patients, the short-term results of hip resurfacing are excellent. At the postoperative 4-year follow-up the rate of complications (in particular the absence of dislocations) was less than that for THA in young and/or active patients. Certain conditions must be respected to obtain these results; frontal plane cup inclination of between 40 and 45°, a femoral head diameter of at least 48 mm and good quality femoral bone.

LEVEL OF EVIDENCE

IV.