Mean 5-year clinical and radiographic outcomes of cementless total hip arthroplasty in patients under the age of 30. Biomed Res Int. 2013;2013:649506. [PMID: 23865060 PMCID: PMC3707213 DOI: 10.1155/2013/649506]

Dysplastic Hips That Are Too Late for Periacetabular Osteotomy Are Not Too Early for Total Hip Arthroplasty

BACKGROUND

Total hip arthroplasty (THA) is often performed in symptomatic patients who have hip dysplasia and do not qualify for periacetabular osteotomy. The impact of osteoarthritis (OA) severity on postoperative outcomes in dysplasia patients who undergo THA is not well described. We hypothesized that dysplasia patients who have mild OA have slower initial recovery postoperatively but similar one-year patient-reported outcome measures (PROMs) compared to dysplasia patients who have severe OA.

METHODS

We performed a retrospective review at a single academic institution over a 6-year period of patients who have dysplasia who underwent THA compared to patients who have primary OA who underwent THA. There were 263 patients who had dysplasia, compared to 1,225 THA patients who did not have dysplasia. Within the dysplasia cohort, we compared PROMs stratified by dysplasia and OA severity. The diagnosis of dysplasia was verified using the radiographic lateral center edge angle. A minimum one-year follow-up was required. The PROMs were collected through one year postoperatively. Logistic and linear regression models were used, adjusting for age, sex, body mass index, and Charlson comorbidity index.

RESULTS

No significant differences were found in postoperative PROMs or revision rates (P = .58). When stratified by dysplasia severity, patients who had lower lateral center edge angle had more improvement in physical function scores from preoperative to 2 weeks (P < .01) and higher physical function scores at 2 weeks (P = .03). When stratified by OA severity, patients who had a worse Tönnis score had more improvement in physical function scores from preoperative to 2 weeks (P < .01). Recovery curves in dysplasia patients based on dysplasia and OA severity were not significantly different at 6 weeks, 1 year, and 2 years postoperative.

CONCLUSIONS

Patients who had hip dysplasia and mild OA had similar recovery curves compared to those who had severe OA or who did not have dysplasia. We believe that THA is a reasonable surgical intervention for symptomatic dysplasia patients who have mild arthritis and do not qualify for periacetabular osteotomy.

Characteristics of Very Young Patients Undergoing Total Hip Arthroplasty: A Contemporary Assessment

Background

This study aims to compare indications, patient characteristics, hospital factors, and complication rates between total hip arthroplasty (THA) patients aged 30 years or younger and those older than 30 years using a large national database.

Methods

The Premier Healthcare Database was utilized to identify primary THA patients from 2015 to 2021 who were aged ≤30 or >30 years. Patient demographics, hospital factors, and primary indications were compared for each cohort. Rates of complications and readmissions were assessed for each cohort by primary indication. Differences were assessed through univariate analysis.

Results

Overall, 539,173 primary THA patients were identified (age ≤30: 1849; >30: 537,234). Compared to the >30 cohort, the ≤30 cohort was more likely to be male (56.5% vs 44.9%, P < .001) and non-White (34.0% vs 14.2%, P < .001). The most common indications for THA in the ≤30 cohort were osteonecrosis (49.3%), osteoarthritis (17.8%), and congenital hip deformities (16.0%), and in the >30 cohort, they were osteoarthritis (77.0%), other arthritis (11.3%), and osteonecrosis (5.4%). Patients aged ≤30 years had lower rates of respiratory failure (0.16% vs 0.57%, P < .001), acute renal failure (0.32% vs 1.72%, P < .001), and urinary tract infection (0.38% vs 1.11%, P = .003) than those aged >30 years, but higher rates of wound dehiscence (0.59% vs 0.29%, P = .015) and transfusion (3.68% vs 2.21%, P < .001). There were no differences in 90-day readmission rates (P = .811) or 90-day in-hospital death (P = .173) between cohorts.

Conclusions

Younger patients undergoing THA differed significantly in indication, patient characteristics, and hospital factors compared to the older population on univariate analysis. Despite differences in indications, the cohorts did not differ markedly with regard to complication rates in this study.

Evolution of Natural Product Scaffolds as Potential Proteasome Inhibitors in Developing Cancer Therapeutics

Homeostasis between protein synthesis and degradation is a critical biological function involving a lot of precise and intricate regulatory systems. The ubiquitin-proteasome pathway (UPP) is a large, multi-protease complex that degrades most intracellular proteins and accounts for about 80% of cellular protein degradation. The proteasome, a massive multi-catalytic proteinase complex that plays a substantial role in protein processing, has been shown to have a wide range of catalytic activity and is at the center of this eukaryotic protein breakdown mechanism. As cancer cells overexpress proteins that induce cell proliferation, while blocking cell death pathways, UPP inhibition has been used as an anticancer therapy to change the balance between protein production and degradation towards cell death. Natural products have a long history of being used to prevent and treat various illnesses. Modern research has shown that the pharmacological actions of several natural products are involved in the engagement of UPP. Over the past few years, numerous natural compounds have been found that target the UPP pathway. These molecules could lead to the clinical development of novel and potent anticancer medications to combat the onslaught of adverse effects and resistance mechanisms caused by already approved proteasome inhibitors. In this review, we report the importance of UPP in anticancer therapy and the regulatory effects of diverse natural metabolites, their semi-synthetic analogs, and SAR studies on proteasome components, which may aid in discovering a new proteasome regulator for drug development and clinical applications.

Evolution of total hip arthroplasty in patients younger than 30 years of age: A systematic review and meta-analysis

INTRODUCTION

While surgical technique and implant technology for total hip arthroplasty (THA) has improved over the years, it is unclear whether recent progress has translated to improved clinical outcomes for young patients. The goal of this study is to determine trends in (1) indications, (2) surgical technique (3) clinical and radiographic outcomes, and (4) survivorship for THA in patients younger than 30 years of age.

METHODS

MedLine, Cochrane, EMBASE, and Google Scholar were searched using several key phrases for articles focusing on THA performed on patients younger than 30 years of age between 1971 and 2020. A total of 34 qualifying articles were identified and stratified into three groups according to operative years and compared to one another on the basis of (1) indications; (2) fixation technique; (3) implant design; (4) clinical and radiographic outcomes; and (7) survivorship.

RESULTS

The mean patient age at index THA were 20.5 (9-30), 22.1 (11-30) and 21.5 (10-30) years, respectively, for each study group. Over time, patients underwent fewer THAs for JRA (Juvenile Rheumatoid Arthritis) (p < 0.001) but more for post-treatment and iatrogenic avascular necrosis (p < 0.001; p < 0.001). Early THAs primarily used metal on UHMWPE (Ultra high molecular weight polyethylene) (71.7%, p < 0.001), modern THA predominantly use ceramic on HXLPE (Highly cross-linked polyethylene) (42.5%, p < 0.001). Early fixation methods used cement (60.4%, p < 0.001), and modern fixation primarily use press fit technology (95.9%, p < 0.001). Prevalence of radiographic loosening decreased significantly (p < 0.001) over time. There was no significant difference in clinical improvement on HHS. Lastly, fewer patients required THA revision in recent decades (p < 0.001).

CONCLUSIONS

Advances in surgical technique and technology have served to improve implant longevity. Surprisingly, subjective clinical scores showed no significant improvement over time, suggesting that early iterations of THA were extremely successful.

Anti-diabetic potential of Urtica Dioica: current knowledge and future direction

Aim

This review summarizes studies on the anti-diabetic effect of Urtica Dioica (UD) in Type-2-diabetes.

Materials and methods

We studied worldwide traditional medicines, old texts, and published literature for anti-diabetic effect of UD. Electronic databases comprising PubMed, Web of Science, Science Direct, Scopus and Google Scholar were searched to collect articles published between 1990 and 2021 years.

Results

Our literature investigation suggests UD as a glucose lowering, blood lipid regulating, anti-inflammatory and anti-oxidation plant.

Conclusions

UD's anti-diabetic properties make it potential traditional therapeutics for lowering the clinical manifestations of T2DM through affecting hyperglycemia and therefore suggest it as a proper medication with no or limited side effects.

Management of femoral neck fracture non union with modified Pauwels' osteotomy

Modified Pauwels' intertrochanteric osteotomy is a promising procedure to heal a non union of the femoral neck fracture, with a success rate of 80-90%. Caxa vara correction and limb length equalization can be achieved simultaneously with this procedure. Two stage surgical procedure has the advantage of keeping blood loss and bone exposure to minimise the risk of infection. We herewith present some tips and tricks and the details of doing this osteotomy.

Revision rate of THA in patients younger than 40 years depends on primary diagnosis - a retrospective analysis with a minimum follow-up of 10 years

Background

Treating osteoarthritis in elderly patients with THA is very successful. However, surgeons hesitate to recommend THA in younger patients. The spectrum of etiologies for end stage hip disease in the younger population is diverse and therefore different courses may be assumed. Our objective was to evaluate THA revision rate within a minimum follow-up period of 10 years in young patients and to analyze the difference between different primary diagnoses.

Methods

We included 144 consecutive hips in 127 patients younger than 40 years, who received a primary THA from 01/1996 to 12/2007. Operative reports, clinical and radiographic documentation were reviewed to determine primary diagnosis, prior hip surgery, component specifications and revision surgery. 111 hips in 97 patients were available for outcome analysis with a minimum follow-up of 10 years.

Results

The mean age was 33 years (range 15–40 years) at the time of the index THA, 68 patients were female and 59 were male. Ten years revision rate on the prosthetic components was 13%. The most common primary diagnosis was DDH. DDH was associated with a risk of 17% for requiring a reoperation on the prosthetic components because of mechanical fatigue and therefore, significantly higher than for any other primary diagnosis (p = 0.005).

Conclusion

THA in young patients is associated with a high revision rate of 13% in 10 years. 17% of patients with DDH required revision surgery for mechanical fatigue within 10 years, which was significantly higher than for any other primary diagnosis (1.2%, OR 16.8).

Prediction of adolescent pelvis development using femoral head and acetabulum growth in a longitudinal radiographic study

INTRODUCTION

Adolescent total hip arthroplasty (THA) is guarded partially due unclarity as to when pediatric hip joints reach full development. This study sought to identify when maximum acetabular and femoral head diameters are achieved with relation to chronological and skeletal age.

MATERIALS AND METHODS

Consecutive femoral head and acetabular diameters were measured in a random sample of 54 female and 78 male subjects, which were queried from a historical collection of annual radiographs of children. Femoral head and triradiate physeal plates were scored according to Oxford bone parameters.

RESULTS

At 14 years females had femoral diameters of 4.16 +/- 0.23 cm and acetabular diameters of 5.15 +/- 0.30 cm. At 16 years males had femoral diameters of 4.85 +/- 0.30 cm and acetabular diameters of 5.90 +/- 0.35 cm. In the year following maximal femoral Oxford scores, no significant change was seen in femur and acetabulum diameters in females and in femur diameters in males. In the year following maximal acetabular Oxford scores, there was a significant increase in both femur and acetabulum diameters in both females and males.

CONCLUSIONS

Females on average reach maximum pelvis maturity at 14 years and males reach maximum pelvis maturity at 16 years. A closed femoral head was found to be a good marker of full hip growth, while a closed triradiate was not. This study provides anatomical data for surgeons to consider in assessing risk factors of THA failure in adolescents.

Time-dependent Viscoelastic Response of Acetabular Bone and Implant Seating during Dynamic Implantation of Press-fit Cups

Deformation of an acetabular cup implant during cementless implantation is indicative of the radial compressive forces, and such of the initial implant fixation strength. Stress relaxation in the surrounding bone tissue following implantation could reduce the deformation of the cup and thus primary implant fixation. The aim of this study was therefore to determine the early shape change of the implanted cup immediately after implantation with different press-fit levels and whether recording the force during cup impaction can be used to estimate initial cup fixation. Cup implantations into porcine acetabulae (n=10) were performed using a drop tower. The force induced by the drop weight and cup seating after each impact was recorded. Deformation of the implanted cup was determined with strain gauges over a period of 10min. Lever-out torques were measured to assess the initial fixation strength. Stress relaxation in the bone caused a reduction in cup deformation of 13.52±4.06% after 1min and 29.34±5.11% after 10min. The fixation strength increased with a higher force magnitude during impaction (R_s²=0.810, p=0.037). Reduction of the radial compressive forces due to stress relaxation of the surrounding bone should be considered during press-fit cup implantation in order to compensate for the reduced fixation strength over time. In addition, recording the implantation force could help to estimate initial fixation strength.

Total Hip Arthroplasty for the Sequelae of Femoral Neck Fractures in the Pediatric Patient

Although rare, total hip arthroplasty (THA) may be indicated in pediatric patients with degenerative changes of the hip joint after previous trauma. To illustrate management principles in this patient population, this study describes the case of a 15-year-old female who sustained bilateral femoral neck fractures after a generalized tonic-clonic seizure, an atypical, low-energy mechanism for this injury. These fractures were not diagnosed until 14 weeks after the seizure episode, at which point they had progressed to nonunion on the left side, malunion on the right side, and degenerative hip joint changes were developing bilaterally. Bilateral THA was ultimately performed, and the patient had favorable outcomes at 1 year postoperatively. In determining the optimal management strategy for such patients, a multidisciplinary approach should be used, with input from the patient’s family, pediatrician, pediatric endocrinologist, pediatric orthopaedic surgeon, and adult reconstruction surgeon. From a surgical standpoint, this report highlights the importance of selecting the appropriate bearing surfaces, broaching technique, mode of implant fixation, and implant features when performing THA in the active pediatric patient.

Uncemented Total Hip Arthroplasty Through the Direct Anterior Approach: Analysis of a Consecutive Series of 275 Hips With a Minimum Follow-Up of 10 Years

BACKGROUND

The purpose of this study was to document complications, outcomes, and 10-year survivorship of primary total hip arthroplasty (THA) using a direct anterior approach with an uncemented, straight, hydroxyapatite-coated stem and an uncemented cup.

METHODS

A retrospective, consecutive series of 275 primary THAs through a direct anterior approach with traction table using Medacta Versafit cup and Quadra-H stem with a minimum of 10-year follow-up was identified. The cumulative 10-year survival of the implants was estimated using Kaplan-Meier estimator. All complications, reoperations, and failures were analyzed. Subjective and clinical outcomes (Subjective Hip Value, Western Ontario and McMaster Universities Osteoarthritis Index, and Harris Hip Score) were measured.

RESULTS

Of 256 patients (275 hips, 143 men and 113 women) with a mean age of 63 (range, 24-85) years, 48 (19%) patients (52 hips) deceased not related to the surgery after a mean time 49 months (range, 3-118) postoperatively. At >10-year follow-up, 9 THAs were revised. The overall implant survival rate was 96.8% (95% confidence interval, 94.4-98.7) at 10 years. One cup and 1 stem were revised because of aseptic loosening. At the last follow-up, the median Subjective Hip Value was 90% (range, 20-100), the Western Ontario and McMaster Universities Osteoarthritis Index score reached a median of 0.2 points (range, 0-6.3), and the median Harris Hip Score points was 99 (range, 29-100).

CONCLUSION

Primary THA through an anterior minimal invasive approach with the mentioned implants showed low revision rates and good to excellent clinical outcome after at least 10 years.

The influence of cavity preparation and press-fit cup implantation on restoring the hip rotation center

BACKGROUND

Reaming of the acetabular cavity and cup implantation directly influence the hip rotation center and contact area between implant and bone. Previous studies have reported on an altered rotation center after total hip arthroplasty, but have not studied the influence of reaming and cup implantation separately. Aim of this study was therefore to analyze the individual influence of acetabular reaming and subsequent cup implantation on the rotation center and how this influences the contact conditions at the bone-implant interface.

METHODS

Acetabular press-fit cups were implanted into the left and right hips of three full cadavers (n = 6). CT scans were performed to calculate the change in hip rotation center after reaming and prior to liner insertion. 3D models of the cups were used to determine the polar gap, the contact conditions and the effective press-fit.

FINDINGS

Reaming the acetabular cavity shifted the rotation center medially (median 5.8 mm, range 4.8-9.1), superiorly (5.3 mm, 3.0-7.0) and posteriorly (2.9 mm, 1.0-5.3). With cup implantation, the rotation center shifted back towards the native position, but no full restoration was observed. The degree of shift increased with the size of polar gap (r_s = 0.829, P = .042), which inversely reduced the contact area (r_s = 0.886, P = .019).

INTERPRETATION

This study reveals that the dominant factor in hip rotation center restoration is the reaming process, while the cup implantation for a given nominal press-fit has only a small influence. Increasing the press-fit would improve the restoration but bares the danger of insufficient bone coverage and periprosthetic fractures due to the high forces needed.

Competitive Running After Total Hip Arthroplasty: The World's Fastest Total Hip: A Case Report

CASE

We report the case of a young man who underwent total hip arthroplasty (THA) for osteonecrosis at the age of 20 years, and subsequently competed in collegiate long-distance running. The pinnacle of his career was setting the school record time of 3:47.64 (min:sec) in the 1,500-m "metric mile" run (equivalent to 4:05.09 for the "English" mile). This is the fastest known time for any patient who has undergone THA. Excellent clinical and radiographic outcomes had been maintained at 6 years postoperatively.

CONCLUSION

Patients who undergo arthroplasty procedures may be capable of remarkable physical accomplishments, but pursuing such feats is not advised.

Ten-year survivorship of primary total hip arthroplasty in patients 30 years of age or younger

Aims

For this retrospective cohort study, patients aged ≤ 30 years (very young) who underwent total hip arthroplasty (THA) were compared with patients aged ≥ 60 years (elderly) to evaluate the rate of revision arthroplasty, implant survival, the indications for revision, the complications, and the patient-reported outcomes.

Patients and Methods

We retrospectively reviewed all patients who underwent primary THA between January 2000 and May 2015 from our institutional database. A total of 145 very young and 1359 elderly patients were reviewed. The mean follow-up was 5.3 years (1 to 18). Logistic generalized estimating equations were used to compare characteristics and the revision rate. Survival was evaluated using Kaplan-Meier curves and hazard rates were created using Cox regression.

Results

The overall revision rate was 11% (16/145) in the very young and 3.83% (52/1359) in the elderly groups (odds ratio (OR) 2.58, 95% confidence interval (CI) 1.43 to 4.63). After adjusting for the American Society of Anesthesiologists (ASA) score, gender, and a history of previous surgery in a time-to-event model, the risk of revision remained greater in the very young (adjusted hazard ratio (HR) 2.48, 95% CI 1.34 to 4.58). Survival at ten years was 82% (95% CI, 71 to 89) in the very young and 96% (95% CI, 94 to 97) in the elderly group (p < 0.001). The very young had a higher rate of revision for complications related to metal-on-metal (MoM) bearing surfaces (p < 0.001). At last follow-up, the very young group had higher levels of physical function (p = 0.002), lower levels of mental health (p = 0.001), and similar levels of pain (p = 0.670) compared with their elderly counterparts.

Conclusion

The overall revision rate was greater in very young THA patients. This was largely explained by the use of MoM bearings. Young patients with non-MoM bearings had high survivorship with similar complication profiles to patients aged ≥ 60 years. Cite this article: Bone Joint J 2018;100-B:867-74.

Outcomes of Unilateral Total Hip Arthroplasty in Patients Aged Under 35 Years in Iranian Population: A Preliminary Study

Background:

The purpose of this study is to report outcomes of total hip arthroplasty (THA) in patients under the age of 35 years regarding pain and joint function.

Materials and Methods:

This preliminary analytic-descriptive study was performed in prospective consecutive series of forty-three patients younger than 35 years old who had undergone unilateral THA during a 36-month period. As the primary outcome, the severity of pain using visual analog scale (VAS) of 1–10, and as the secondary outcomes, joint range of motion (ROM) and the Harris Hip Score (HHS) were assessed in the preoperative visit, 1, 6, and 18 months after operation for each patient. Complications were recorded at 6 months and 18 months after surgery.

Results:

The data of VAS showed the mean severity of pain was significant between preoperation measurements and postoperative assessments (P < 0.001). The means of HHS and hip ROM were also statistically significant before the operation in comparison with postoperative assessments (P < 0.001 for both means). A total of 19 patients had postoperative complications including periprosthetic fracture in two patients, infection in two patients, cup loosening in three patients, limb length discrepancy in 10 patients, and heterotopic ossification in two patients. Seven patients had been readmitted.

Conclusion:

We believe THA using uncemented prosthesis has a high survivorship with low rate osteolysis in young patients with good bone stock. It is necessary to have longer follow-up to have a better evaluation on outcomes.

Challenges in Total Hip Arthroplasty in the Setting of Developmental Dysplasia of the Hip

BACKGROUND

Developmental dysplasia of the hip (DDH) is a recognized cause of secondary arthritis, which may eventually lead to total hip arthroplasty (THA). An understanding of the common acetabular and femoral morphologic abnormalities will aid the surgeon in preparing for the complexity of the surgical case.

METHODS

We present the challenges associated with acetabular and femoral morphologies that may be present in the dysplastic hip and discuss surgical options to consider when performing THA. In addition, common complications associated with this population are reviewed.

RESULTS

The complexity of THA in the DDH patient is due to a broad range of pathomorphologic changes of the acetabulum and femur, as well as the diverse and often younger age of these patients. As such, THA in the DDH patient may offer a typical primary hip arthroplasty or be a highly complex reconstruction. It is important to be familiar with all the subtleties associated with DDH in the THA population. The surgeon must be prepared for bone deficiency when reconstructing the acetabulum and should place the component low and medial (at the anatomic hip center), and avoid oversizing the acetabular component. Femoral dysplasia is also complex and variable, and the surgeon must be prepared for different stem choices that allow for decoupling of the metaphyseal stem fit from the implanted stem version. In Crowe III and IV dysplasia, femoral derotation/shortening osteotomy may be required. Many complications associated with THA in the DDH patient may be mitigated with careful planning and surgical technique.

CONCLUSION

Performed correctly, THA can yield excellent results in this complex patient population.

Influence of trabecular bone quality and implantation direction on press-fit mechanics

Achieving primary stability of uncemented press-fit prostheses in patients with poor quality bone can involve axial implantation forces large enough to cause bone fracture. Radial implantation eliminates intraoperative impaction forces and could prevent this damage. Platens of two commercial implant surfaces ("Beaded" and "Flaked") were implanted onto trabecular bone specimens of varying quality in a press-fit simulator. Samples were implanted with varying interference, either axially (shear) or radially (normal). Push-in and pull-out forces were measured to assess stability. Microstructural changes in the bone were determined from μCT analysis. For force-defined implantation analysis, push-in and pull-out forces both increased proportionally with increasing radial force, independent of implantation direction, bone quality or implant surface. For position-defined implantation analysis, pull-out forces were generally found to increase with interference and to be greater for radial than axial implantation direction, and to be lower for poor quality bone. Bone density increased locally at the tested interface due to implantation, in particular for the Beaded surface under axial implantation. If a safe radial stress can be determined for cortical bone in a particular patient, the associated implantation force, and pull-out force which represents primary stability, can be directly derived, regardless of implantation direction, bone quality or implant surface. Radial implantation delivers primary stability that is no worse than that for axial implantation and may eliminate potentially damaging impaction forces. Development of implant designs based on this principal might improve implant fixation. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:224-233, 2017.

Valgus osteotomy for nonunion and neglected neck of femur fractures

Nonunion neck of femur can be a difficult problem to treat, particularly in the young, and is associated with high complication rates of avascular necrosis due to the precarious blood supply and poor biomechanics. The various treatment options that have been described can be broadly divided according to the aim of improving either biology or biomechanics. Surgeries aimed at improving the biology, such as vascularized fibula grafting, have good success rates but require high levels of expertise and substantial resources. A popular surgical treatment aimed at improving the biomechanics-valgus intertrochanteric osteotomy-optimizes conditions for fracture healing by converting shear forces across the fracture site into compressive forces. Numerous variations of this surgical procedure have been developed and successfully applied in clinical practice. As a result, the proximal femoral orientation for obtaining a good functional outcome has evolved over the years, and the present concept of altering the proximal femoral anatomy as little as possible has arisen. This technical objective supports attaining union as well as a good functional outcome, since excessive valgus can lead to increased joint reaction forces. This review summarizes the historical and current literature on valgus intertrochanteric osteotomy treatment of nonunion neck of femur, with a focus on factors predictive of good functional outcome and potential pitfalls to be avoided as well as controversies surrounding this procedure.

Friction coefficient and effective interference at the implant-bone interface

Although the contact pressure increases during implantation of a wedge-shaped implant, friction coefficients tend to be measured under constant contact pressure, as endorsed in standard procedures. Abrasion and plastic deformation of the bone during implantation are rarely reported, although they define the effective interference, by reducing the nominal interference between implant and bone cavity. In this study radial forces were analysed during simulated implantation and explantation of angled porous and polished implant surfaces against trabecular bone specimens, to determine the corresponding friction coefficients. Permanent deformation was also analysed to determine the effective interference after implantation. For the most porous surface tested, the friction coefficient initially increased with increasing normal contact stress during implantation and then decreased at higher contact stresses. For a less porous surface, the friction coefficient increased continually with normal contact stress during implantation but did not reach the peak magnitude measured for the rougher surface. Friction coefficients for the polished surface were independent of normal contact stress and much lower than for the porous surfaces. Friction coefficients were slightly lower for pull-out than for push-in for the porous surfaces but not for the polished surface. The effective interference was as little as 30% of the nominal interference for the porous surfaces. The determined variation in friction coefficient with radial contact force, as well as the loss of interference during implantation will enable a more accurate representation of implant press-fitting for simulations.

Mild to Moderate Hip OA: Joint Preservation or Total Hip Arthroplasty?

Treatment of structural hip disease such as FAI and acetabular dysplasia has increased dramatically over the past decade with the goal of preservation of the native hip joint. A number of patient and disease specific parameters including the amount of underlying hip osteoarthrosis can help predict success with joint preservation surgery. Total hip arthroplasty remains a very good option in young patients who are not ideal candidates for joint preservation surgery. Future developments will help to better identify ideal surgical candidates and improve understanding of the disease processes.

A new automated way to measure polyethylene wear in THA using a high resolution CT scanner: method and analysis

As the most advantageous total hip arthroplasty (THA) operation is the first, timely replacement of only the liner is socially and economically important because the utilization of THA is increasing as younger and more active patients are receiving implants and they are living longer. Automatic algorithms were developed to infer liner wear by estimating the separation between the acetabular cup and femoral component head given a computed tomography (CT) volume. Two series of CT volumes of a hip phantom were acquired with the femoral component head placed at 14 different positions relative to the acetabular cup. The mean and standard deviation (SD) of the diameter of the acetabular cup and femoral component head, in addition to the range of error in the expected wear values and the repeatability of all the measurements, were calculated. The algorithms resulted in a mean (± SD) for the diameter of the acetabular cup of 54.21 (± 0.011) mm and for the femoral component head of 22.09 (± 0.02) mm. The wear error was ± 0.1 mm and the repeatability was 0.077 mm. This approach is applicable clinically as it utilizes readily available computed tomography imaging systems and requires only five minutes of human interaction.