Metal ion release after hip resurfacing arthroplasty and knee arthroplasty: a retrospective study of one hundred ninety-five cases

PURPOSE

Hip arthroplasty with metal-on-metal bearings like hip resurfacing results in the release of metallic ions. In parallel, like every metallic implant, knee arthroplasty implants undergo passive corrosion. We analyzed blood levels of cobalt and chromium ions in patients who have a hip resurfacing arthroplasty and compared them to patients who have undergone knee arthroplasty at a minimum follow-up of one year. The hypothesis was that there is no difference in the ion release between hip resurfacing and knee arthroplasty.

METHODS

Sixty-three patients who underwent knee arthroplasty were compared to a cohort of 132 patients who underwent hip resurfacing. The blood levels of cobalt and chromium ions were determined preoperatively and at six and 12 months postoperatively and then compared between groups. We analyzed the relationship between ion release and the change in clinical outcome scores (Harris Hip score, Oxford Hip score, Merle D'Aubigné Postel score, Oxford Knee score, International Knee Society score), the BMI, sex, physical activity, implant size and inclination of the acetabular implant (hip resurfacing patients only). Mixed linear models were used to assess the changes in ion blood levels over time.

RESULTS

The cobalt blood levels were higher in the first 6 months in the resurfacing group (0.87 ug/L vs 0.67 ug/L; p = 0.011), while it was higher in the knee arthroplasty group at 12 months (1.20 ug/L vs 1.41 ug/L; p = 0.0008). There were no significant differences in chromium levels during the follow-up period.

CONCLUSION

The increase in metal ion release after knee arthroplasty is as high as after hip resurfacing at the one year follow-up. The monitoring of this parameter probably should not be recommended in case of good clinicals outcomes.

[Asthma and scuba diving: Creation and evaluation of a website (For doctors, asthmatics and diving instructors)]

INTRODUCTION

Scuba diving has long been strictly contraindicated for asthmatics; this contraindication has been questioned in recent years. Our objective was to provide a website, evaluated by its users, for doctors, diving instructors and asthmatics.

MATERIALS AND METHODS

Creation of the site Asthme-Plongee.com based on a peer-reviewed literature review, then distribution of a questionnaire in summer 2018 to diving clubs, general practitioner groups, pulmonologists and FFESSM federal offices, and via social networks.

RESULTS

Our sample consisted of 413 assessors, including 264 health professionals (63.9%), 74 asthmatics (17.9%) and 92 diving instructors (22.3%), spread over the entire territory of France. The structure of the website, the clarity of the information written and its relevance were generally appreciated by the entire population with a median score of 8/10. The site was found useful: 72.9% of respondents thought they would visit it later.

CONCLUSION

Faced with a growing number of amateur divers, it seems essential to raise awareness of current recommendations and good diving practices.

Hip survival after plain core decompression alone versus bone morphogenetic protein and/or bone marrow reinjection with core decompression for avascular osteonecrosis of the femoral head: a retrospective case control study in ninety two patients

INTRODUCTION

Injecting bone marrow or bone morphogenetic protein 7 (BMP) during core decompression for avascular osteonecrosis (AVN) may improve survival. We hypothesized that adding a complementary technique (injection of BMP and/or non-concentrated bone marrow) to core decompression would reduce the number of patients requiring a subsequent total hip arthroplasty (THA).

METHODS

We retrospectively reviewed 92 cases from 2003 to 2018 with a minimum of 2 years of follow-up and an average follow-up of 64 months (24-204). Twenty-four patients had a core decompression (CD) (26.1% (24/92)), 25 had a CD associated with reinjection of bone marrow and BMP (rhBMP7) (27.2% (25/92)), and 43 patients had a CD with bone marrow reinjection (46.7% (43/92)).

RESULTS

Hip survival after CD was 66.3% (61/92) at two years and 59.8% (55/92) at 10 years. CD with bone marrow and BMP reinjection had a better hip survival at ten years (HR: 0.492 (CI95%: 0.254-0.952) p = 0.035). A volume of necrosis greater than 30% (HR = 12.97 (CI95 [3.88-43.3] (p < 0.001))) and a Kerboul angle greater than 60° (HR: 12.5 (CI95 [2.84-54.6] (p < 0.001))) were risk factors for a subsequent THA.

CONCLUSIONS

CD is an interesting non-invasive technique to preserve the native hip after AVN of the femoral head. Reinjection of bone marrow and/or BMP improved CD hip survival.

Fusion of Factor IX to Factor XIII-B Sub-Unit Improves the Pharmacokinetic Profile of Factor IX

Prophylaxis is currently considered the optimal care for severe haemophilia. For patients and their families one of the major difficulties with prophylaxis is the need for frequent venipunctures. The half-life of standard factor IX (FIX) concentrates is approximately 18 hours, which requires 2 or 3 intravenous infusions per week to achieve bleeding prevention in patients with severe haemophilia B. Prolonging the half-life of FIX can therefore reduce the frequency of infusions. Recently, extended half-life recombinant FIX (rFIX) concentrates have been developed. We designed a new rFIX molecule fused to coagulation FXIII-B sub-unit. This sub-unit is responsible for the long half-life of the FXIII molecule (10–12 days). The rFIX-LXa-FXIIIB fusion protein contains a short linker sequence cleavable by activated FX (FXa), to separate rFIX from the carrier protein as soon as traces of FXa are generated, leaving rFIX free to perform its enzymatic role in the tenase complex. The rFIX-LXa-FXIIIB fusion protein was expressed in human hepatic Huh-7 cells and Chinese hamster ovary cells, and both wild-type rFIX (rFIX-WT) and rFIX-LXa-FXIIIB showed similar clotting activity and thrombin generation capacity in vivo after injection in haemophilia B mice compared with rFIX-WT. The half-life of the rFIX-LXa-FXIIIB molecule in WT mice and rats was 3.9- and 2.2-fold longer, respectively, compared with rFIX-WT. A potential advantage of this new molecule is its capacity to bind to fibrinogen via FXIII-B, which might accelerate fibrin clot formation and thus improve haemostatic capacity of the molecule.

Diagnostic accuracy of the alpha defensin lateral flow device (Synovasure) for periprosthetic infections in microbiologically complex situations: A study of 42 cases in a French referral centre

BACKGROUND

Joint aspiration is currently the reference standard test for diagnosing periprosthetic joint infection (PJI) despite the high rate of false-negative results, of which a major cause is the fastidious nature of some microorganisms. A rapid diagnostic test that detects alpha defensin (Synovasure™, Zimmer, Warsaw, IN, USA) in joint fluid can provide the diagnosis of PJI within a few minutes across the full spectrum of causative organisms (including mycobacteria and yeasts). Its performance in detecting bacterial infections is unaltered by concomitant antibiotic therapy. Few studies of Synovasure™ have been conducted by groups that were involved in designing the test, which has not been validated in France. Assessments in referral centres where complex microbiological situations are common hold considerable interest. The objective of this prospective study was to determine the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and causes of error of Synovasure™ used to diagnose periprosthetic infection in complex microbiological situations.

HYPOTHESIS

The rapid diagnostic test Synovasure™ has greater than 90% NPV for detecting periprosthetic infections in complex microbiological infections.

MATERIAL AND METHODS

Synovasure™ was used 42 times in 39 patients between October 2015 and October 2017 in challenging microbiological situations [discordant joint aspiration results (n=20), negative cultures with clinical or laboratory evidence of infection, (n=21), and concomitant antibiotic therapy (n=1)]. Of the 39 patients, 23 had total knee prostheses, 13 total hip prostheses, and 3 total femoral prostheses. The reference standard to which the Synovasure™ results were compared was the PJI criteria set developed by the Musculoskeletal Infection Society (MSIS).

RESULTS

Synovasure™ was negative in 30 cases with negative joint fluid cultures (30/42, 71.4%). Of the 12 (28.6%) cases with positive Synovasure™ results, only 7 (7/12, 58.3%) had positive joint fluid cultures. According to the MSIS criteria 9 cases were infected, including 8 with positive and 1 with negative Synovasure™ results. Of the 33 cases that were not infected according to MSIS criteria, 29 had negative and 3 positive Synovasure™ results; the remaining case had a positive Synovasure™ result but was excluded when metallosis was found intra-operatively. NPV was 96.7%, PPV 72.7%, sensitivity 88.9%, and specificity 90.6%.

DISCUSSION

The high NPV of Synovasure™ suggests a role for this test in microbiologically complex situations as a new tool for ruling in and, most importantly, ruling out infection in doubtful cases.

LEVEL OF EVIDENCE

III, prospective study of diagnostic accuracy.

Course of dislocated posterior hip arthroplasty: A continuous 232-patient series at a mean 10 years' follow up (range, 1-22 years)

BACKGROUND

Dislocation rates in posterior total hip arthroplasty (THA) range between 2% and 5%, but long-term course (recurrence of dislocation or revision surgery) is not known, most series having short follow-up or small populations. We therefore conducted a retrospective study on a large series, to determine long-term rates of recurrence and surgical revision and recurrence risk factors.

HYPOTHESIS

Long-term follow-up of a large cohort of THA dislocations enables recurrence rate and factors to be determined.

MATERIAL AND METHOD

Five hundred and nine cases of THA dislocation were admitted to our center between 1994 and 2008. A hundred and twenty seven incomplete files and 150 patients who had received their THA elsewhere were excluded, leaving 232 patients: 150 female, 82 male. Mean age at THA (163 primary, 69 revision) was 63 years (range, 15-90 years), and 65 years (range 20-90 years) at first dislocation, with a mean interval to dislocation of 25 months. Minimum follow-up was 8 years up to 2016, or 1 year taking account of deaths (111 deaths). There were 46 anterior, 185 posterior and 1 multidirectional dislocations. The following potential recurrence factors were assessed: gander, age, body-mass index (BMI), etiology, surgical history, bearing diameter and type, component fixation means, dislocation direction, and time to dislocation.

RESULTS

A hundred and thirty three of the 232 patients (57%) showed at least 1 recurrence, at a mean 38 months (range, 0.5-252 months); 78 experienced a second and 32 a third recurrence. Ninety-nine (43%) had only 1 dislocation, without recurrence, but 17 of these (17%) underwent reoperation for other causes. The reoperation rate was 17/232 (7%) excluding recurrent instability, and 84/232 (36%) for instability. Fourty-eight months after the first dislocation, 84/133 cases of recurrence (63%) had been reoperated on: 16 complete replacements, 18 bearing replacements, 42 dual mobility cups, one large diameter cup, seven Lefèvre retentive cups. The rate of revision surgery for instability was high, at 84/232 (36%), and higher again in relation to recurrence (84/133: 63%). Only posterior dislocation emerged as a factor for recurrence (HR=1.774, 95% CI [1.020-3.083]), the other tested factors showing no correlation.14 of the 84 revision surgeries for instability (16.6%) were followed by recurrence, without identifiable risk factors.

CONCLUSION/DISCUSSION

The recurrence rate was 57%, with posterior dislocation as the only risk factor. The rate of revision surgery for recurrence was 84/232 (36%), with 14/84 revision procedures (16.6%) followed by further recurrence.

LEVEL OF EVIDENCE

IV, retrospective, without control group.

Hip resurfacing before 50years of age: A prospective study of 979 hips with a mean follow-up of 5.1years

BACKGROUND

Hip resurfacing arthroplasty (HRA) is an alternative to total hip arthroplasty (THA) for the treatment of hip osteoarthritis in patients younger than 50 years. Data on revision rates after HRA are conflicting. The National Institute for Health and Care Excellence (NICE) recommends performing only those hip arthroplasty procedures associated with 10-year revision rates no greater than 5% (0.5% per year). Follow-up studies can rapidly determine whether this criterion is met. The uncertainties surrounding revision rates after HRA prompted us to design a study of prospectively enrolled patients aiming (1) to determine the revision rate after HRA performed before 50years of age and (2) to assess the functional, radiological, and biological outcomes of HRA.

HYPOTHESIS

The revision rate after HRA performed before 50years of age meets the NICE criterion.

MATERIAL AND METHODS

Consecutive patients undergoing HRA before 50years of age were enrolled prospectively. The same implant was used in all patients. Functional outcomes were assessed based on the Harris Hip Score (HHS), Postel-Merle d'Aubigné (PMA) score, 12-item Oxford Hip Score (OHS), and UCLA activity score. Radiographic outcomes were assessed, and blood levels of chromium and cobalt were assayed.

RESULTS

The study included 936 patients (979 HRAs) with a mean age of 42.7years (16.4-50.0years) at surgery and a mean follow-up of 5.1years (range: 3.1-9.0 years). All four mean functional scores were significantly improved at last follow-up vs. baseline: HHS, 95.9 (39.0-100) vs. 44.3 (18.0-83.0); PMA score, 17.6 (6.0-18.0) vs. 11.7 (3.0-16.0); OHS, 14.3 (12.0-37.0) vs. 40.6 (25.0-60.0); and UCLA activity score, 7.8 (2.0-10.0) vs. 5.6 (1.0-10.0) (p<0.0001). Mean cup inclination in the coronal plane was 42.1° (25.0°-68.0°). Mean blood cobalt level was significantly higher at last follow-up than at baseline (1.36μg/L [0.05-8.2μg/L] vs. 0.61μg/L [0.01-3.6]) (p<0.001). No patient experienced dislocation. Revision was required for 17 hips and involved changing the implant in 12 (1.2%). The 10-year survival rate with implant change, as the endpoint was 98.7% (95%CI, 97.6%-99.3%), indicating that the NICE criterion was easily met.

DISCUSSION

The NICE criterion allows the rapid identification of prostheses with insufficient survival. HRA is theoretically associated with a high risk of aseptic mechanical loosening, as it is performed in young patients who have a high level of physical activity. Nevertheless, our study showed that implant survival after HRA was better than required by the NICE criterion. Thus, HRA is a valid alterative to THA in patients younger than 50years.

LEVEL OF EVIDENCE

IV, prospective study with no control group.

Characterization by Scanning Precession Electron Diffraction of an Aggregate of Bridgmanite and Ferropericlase Deformed at HP-HT

Scanning precession electron diffraction is an emerging promising technique for mapping phases and crystal orientations with short acquisition times (10-20 ms/pixel) in a transmission electron microscope similarly to the Electron Backscattered Diffraction (EBSD) or Transmission Kikuchi Diffraction (TKD) techniques in a scanning electron microscope. In this study, we apply this technique to the characterization of deformation microstructures in an aggregate of bridgmanite and ferropericlase deformed at 27 GPa and 2,130 K. Such a sample is challenging for microstructural characterization for two reasons: (i) the bridgmanite is very unstable under electron irradiation, (ii) under high stress conditions, the dislocation density is so large that standard characterization by diffraction contrast are limited, or impossible. Here we show that detailed analysis of intracrystalline misorientations sheds some light on the deformation mechanisms of both phases. In bridgmanite, deformation is accommodated by localized, amorphous, shear deformation lamellae whereas ferropericlase undergoes large strains leading to grain elongation in response to intense dislocation activity with no evidence for recrystallization. Plastic strain in ferropericlase can be semiquantitatively assessed by following kernel average misorientation distributions.

High-impact sport after hip resurfacing: The Ironman triathlon

BACKGROUND

Returning to high-impact sport is an increasingly frequent functional demand following hip replacement. The literature, however, is sparse on the subject and nonexistent regarding triathlon. We therefore conducted a retrospective study of hip resurfacing in triathlon players, to determine: (1) whether it is possible to return to this kind of sport; (2) if so, whether it is possible to return to the same level; and (3) how a resurfaced hip behaves under these conditions.

HYPOTHESIS

Hip resurfacing allows return to competition level in long-distance triathlon.

MATERIAL AND METHODS

A single-center single-operator retrospective study included patients undergoing hip resurfacing with the Conserve Plus implant inserted through a posterolateral approach, who had ceased long-distance triathlon practice due to osteoarthritis of the hip. Fifty-one of the 1688 patients undergoing resurfacing during the inclusion period were long-distance triathlon players.

RESULTS

The series comprised 48 patients: 51 implants; 43 male, 5 female; mean age, 44.8 years (range, 28.2-58.9 years). At a mean 4.7 years' follow-up (range, 2.2-7.6 years), all clinical scores showed significant improvement; Merle d'Aubigné and Harris scores rose respectively from 12.3 (5-16) and 42 (37-56) preoperatively to 17.5 (13-18) and 93.2 (73-100) (P<0.001). There were no cases of dislocation or implant revision. Forty-five patients returned to sport (94%). Rates of return to swimming, cycling and running were respectively 38/48 (79%), 41/48 (85%) and 33/48 (69%). Preoperatively, all patients had taken part in at least 1 competition: 29 with distance=70.3km and 19 with distance=140.6km. At follow-up, 28 patients had taken part in an Ironman competition: 21 with distance=70.3km and 7 with distance=140.6km. Mean competition performance did not differ between pre and postoperative periods.

DISCUSSION

Return-to-sport rates were good following hip resurfacing. Non-impact sports (swimming, cycling) predominated postoperatively, whereas the rate of impact sport (running) diminished. Return to competition-level sport (extreme triathlon) was possible for 28/48 patients (58%). Implant survival seemed unaffected by this high-impact sports activity at a mean 4.7 years' follow-up.

LEVEL OF EVIDENCE

IV, retrospective, non-controlled.

Epidemiology of patients with MSSA versus MRSA infections of orthopedic implants: Retrospective study of 115 patients

Factors that predict the occurrence of a surgical site infection due to methicillin-resistant Staphylococcus aureus (MRSA) are not well known; however this information could be used to modify the recommended antimicrobial prophylaxis. We carried out a retrospective study of S. aureus infections on orthopedic implants to determine: (1) whether epidemiological factors can be identified that predict a MRSA infection, (2) the impact of these factors as evidenced by the odds ratio (OR).

HYPOTHESIS

Risk factors for a MRSA infection can be identified from a cohort of patients with S. aureus infections.

MATERIALS AND METHODS

We identified 244 patients who experienced a S. aureus surgical site infection (SSI) in 2011-2012 documented by intraoperative sample collection. Of these 244 patients, those who had a previous SSI (n=44), those with a SSI but no orthopedic implant (n=80) or those who had the infection more than 1-year after the initial surgery (n=5) were excluded. This resulted in 115 patients (53 arthroplasty, 62 bone fixation) being analyzed for this study. There were 24 MRSA infections and 91 MSSA infections. The following factors were evaluated in bivariate and multifactorial analysis: age, sex, type of device (prosthesis/bone fixation), predisposition (diabetes, obesity, kidney failure), and environmental factors (hospitalization in intensive care unit within past 5 years, nursing home stay).

RESULTS

Two factors were correlated with the occurrence of MRSA infections. (1) Nursing home patients had a higher rate of MRSA infections (67% vs. 18%, P=0.017) with an OR of 8.42 (95% CI: 1.06-66.43). (2) Patients who had undergone bone fixation had a lower rate of MRSA infections than patients who had undergone arthroplasty (13% vs. 30%, P=0.023), OR 0.11 (95% CI: 0.02-0.56). Although the sample size was too small to be statistically significant, all of the patients with kidney failure (n=4) had a MRSA infection.

DISCUSSION

Since these MRSA infection risk factors are easy to identify, the antimicrobial prophylaxis could be adapted in these specific patient groups.

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.

Technique to treat iliopsoas irritation after total hip replacement: Thickening of articular hip capsule through an abridged direct anterior approach

Iliopsoas irritation due to acetabular cup component impingement following total hip arthroplasty (THA) is usually treated by infiltration or by distal iliopsoas tenotomy in case of recurrence; however, this can result in an active flexion deficit of the thigh. To prevent this complication, we developed an original technique that we performed between 2012 and 2014 in patients with recurrent impingement following extraarticular corticosteroid injections. This included 5 patients (mean age: 64 [53-75] years old) in whom we performed an ambulatory bursectomy by the Hueter approach and placed a polyglactin 910 (Vicryl™) mesh plate on the entire anterior hip capsule. After a mean follow-up of 12months (9-29months), anterior pain had decreased in all patients with improvement and an increase in the Oxford-12 (mean: 15 points [10-19]), Merle d'Aubigné (mean: 2.5 points [1-5]) and Harris (mean: 18 points [10-29]) scores. No flexion deficits were observed. An infected postoperative hematoma had to be drained but was cured at follow-up. This simple procedure provides satisfactory results and preserves THA function. It does not jeopardize future procedures and is an alternative option in case of unsuccessful conservative treatment.

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.

Computed tomography evaluation of hip geometry restoration after total hip resurfacing

BACKGROUND

Anatomic reconstruction of the hip is among the main requirements for hip arthroplasty to be successful. Resurfacing arthroplasty may improve replication of the native joint geometry but has been evaluated only using standard radiographs. We therefore performed a computed tomography (CT) study to assess restoration of hip geometry after total hip resurfacing (HR), comparatively with the non-operated side.

HYPOTHESIS

HR does not change native extra-medullary hip geometry by more than 5mm and/or 5°.

PATIENTS AND METHODS

CT was used to evaluate unilateral HR in 75 patients with a mean age of 52.2years (range, 22-67years). The normal non-operated side served as the control in each patient. Mean follow-up was 2.5years (range, 1.9-3.1years). The primary evaluation criteria were femoral offset (FO) and femoral neck anteversion (FNA) and the secondary criteria were cup inclination angle, cup anteversion angle, and lower-limb length.

RESULTS

FO showed a non-significant decrease (mean, -2.2mm; range, -4.5 to +3.7mm). FNA was preserved, with a difference of less than 2° at last follow-up versus the preoperative value. Cup measurements showed a mean anteversion angle of 24.8° (0.9-48.6) and mean inclination angle of 44.1° (32.1-56.3); corresponding values for the native acetabulum were 38.9° (20.5-54.8) and 24.8° (4.8-33.6). The residual lower-limb length discrepancy was less than 1mm (mean, -0.04mm [-1.2 to +1.6mm]). The mean angle between the femoral implant and the femoral neck axis was 5.4° of valgus.

DISCUSSION

Our results show that HR accurately restored the native extra-medullary hip geometry.

LEVEL OF EVIDENCE

III, prospective diagnostic case-control study.

In vivo efficacy of human recombinant factor IX produced by the human hepatoma cell line HuH-7

INTRODUCTION

Post-translational modifications of the CHO-cell-derived-recombinant human factor IX (FIX) currently used for the treatment of hemophilia B (HB) are different from plasma derived FIX. Our previous studies described a rFIX (HIX) having better profile of post-translational modifications than rFIX produced by CHO cells. The aim of the study consisted to verify the improved post-translational modifications effect of HIX on in vivo recovery.

MATERIALS AND METHODS

HIX has been produced in a bioreactor and then purified from supernatants. In vitro activation and activity were evaluated measured by thrombin generation tests (TGT) and compared to commercial molecules, Benefix(®) , Mononine(®) . The three molecules were then administrated (i.v.) to FIX-knockout mice and two minutes after injection, blood samples were collected and subjected to human FIX-specific-ELISA and TGT.

RESULTS

The clotting function of HIX, activation courses of HIX by FXIa and FVIIa-TF complex appear normal as did activation of Benefix(®) , Mononine(®) and TG constants of each FIX were equivalent. After injection to HB mice, circulating HIX did not present any significant difference in term of antigen value with Benefix(®) . Intriguingly, TGT were clearly exhibiting a better velocity for HIX than Benefix(®) and Mononine(®) . These data suggested that HIX may improve in vivo coagulant efficacy in comparison with the two commercial FIX injected at the same dose.

CONCLUSION

The study shows that HuH-7-derived-rFIX has better in vivo haemostatic activity in hemophilia B mice compared to the reference rFIX molecule despite similar in vivo recovery rates, suggesting that HuH-7 cells could represent an effective cellular system for production of rFIX.

Femoral lengthening during hip resurfacing arthroplasty: a new surgical procedure

Correction of leg length discrepancy during hip arthroplasty is a technical challenge. Although resurfacing proposed to young subjects presents a number of advantages (stability, bone stock, etc.), it does not correct leg length discrepancy. We propose an original femoral lengthening technique concomitant to resurfacing performed through the same approach, consisting in a Z-shaped subtrochanteric osteotomy. Resurfacing was performed first and the femoral and acetabular reaming material was used for autografting. The series comprised five cases followed for a mean 42.2 months (range, 33-64 months). The mean surgical time was 100 min (range, 76-124 min). Weightbearing was authorized in all cases at the 8th week. The mean lengthening was 32 mm (range, 25-40 mm). Healing was observed in all cases. This surgical technique, reserved for very young subjects who accept an 8-week postoperative period without weightbearing, can be proposed in cases with substantial preoperative leg length discrepancy.

Expression and characterization of a novel human recombinant factor IX molecule with enhanced in vitro and in vivo clotting activity

INTRODUCTION

Hemophilia B is an inherited X-linked recessive bleeding disorder, due to a defect in human factor IX (FIX). The main treatment for hemophilia B is replacement therapy using FIX concentrates. Prophylactic treatment in severe hemophilia B is very effective but is limited by cost issues. Production of a recombinant FIX (rFIX) with enhanced clotting activity, offering the possibility of fewer infusions and fewer costs with similar efficacy, is one of the current challenges for hemophilia B treatment. The present study focused on an important amino acid sequence known to be involved in the interaction of activated FIX (FIXa) with its cofactor, activated factor VIII (FVIIIa).

MATERIALS AND METHODS

Using site-directed mutagenesis of glutamate E410 (c240, chymotrypsin numbering), four recombinant FIX-E410 (E410H, A, L and N) mutants were developed and produced by the human hepatoma cell line Huh-7.

RESULTS

The in-vitro clotting activity of mutant FIX molecules was 3 to 5-fold higher than wild-type recombinant FIX (FIX-WT). FIX-E410H compound showed the highest in-vitro procoagulant activity. Enhanced specific activity was confirmed using thrombin generation assay. FIX-E410H induced 5.2-fold higher thrombin generation than FIX-WT. In hemophilia B mice, we observed significantly higher in-vivo clotting activity and thrombin generating capacity with FIX-E410H compared to FIX-WT. We demonstrated that increased procoagulant activity of FIX-E410H was mainly explained by 2.5- fold enhanced affinity of the mutant for human FVIIIa.

CONCLUSION

We have engineered and characterized four improved FIX proteins with enhanced in-vitro and in-vivo activity. Future studies are required to evaluate the immunogenicity of FIX-E410.

Structured illumination fluorescence microscopy with distorted excitations using a filtered blind-SIM algorithm

Structured illumination microscopy (SIM) is a powerful technique for obtaining super-resolved fluorescence maps of samples, but it is very sensitive to aberrations or misalignments affecting the excitation patterns. Here, we present a reconstruction algorithm that is able to process SIM data even if the illuminations are strongly distorted. The approach is an extension of the recent blind-SIM technique, which reconstructs simultaneously the sample and the excitation patterns without a priori information on the latter. Our algorithm was checked on synthetic and experimental data using distorted and nondistorted illuminations. The reconstructions were similar to that obtained by up-to-date SIM methods when the illuminations were periodic and remained artifact-free when the illuminations were strongly distorted.

Incidental discovery of an undisplaced ceramic liner fracture at total hip arthroplasty revision for squeaking

Squeaking has been reported after ceramic-on-ceramic total hip arthroplasty (THA), but its pathomechanics is not fully understood. Impaired lubrication is suspected to be the main reason. The management of patients impacted by this phenomenon is not well defined and, as it is not considered to be cause for alarm, revision is not strongly recommended. Here, we describe a ceramic insert fracture discovered during revision surgery performed to correct severe squeaking. Preoperative investigation (plain X-rays, ultrasound and computed tomography) did not reveal ceramic fracture or definite component malposition. To date, there are no other published cases of incidental discovery of a bearing component fracture during revision of ceramic-on-ceramic hip replacement due to squeaking. We believe that squeaking is not a trivial phenomenon and recommend careful management of patients suffering with this symptom.

Durom hip resurfacing system: retrospective study of 644 cases with an average follow-up of 34 months

INTRODUCTION

The performance of second-generation metal-on-metal bearings has led to the reintroduction of hip resurfacing. The goal of this multicentre study was to evaluate the short-term radiological and clinical outcomes with the Durom hip resurfacing system.

HYPOTHESIS

The Durom hip-resurfacing system will have similar results to other hip resurfacing systems and traditional hip arthroplasty implants.

MATERIALS AND METHODS

In the four participating centers, 580 patients (406 men, 174 women) and 644 hips were included. The average patient age was 48 years (range 16-77). A posterolateral surgical approach was used in 357 cases; a Hardinge-type approach was used in 182 cases and a Rottinger-type approach in 105.

RESULTS

After an average follow-up of 34 months, 31 hips (4.8%) had been revised. The reasons for revision were the following: 10 (1.6%) neck fracture (seven with Rottinger operative approach, one with Hardinge approach and one with posterolateral approach); 12 (1.9%) femoral loosening (four with lateral approach and eight with posterolateral approach); four (0.6%) acetabular cup migration; three (0.5%) unexplained pain; one (0.2%) adverse reaction to metal debris; one (0.2%) infection. Four hips (0.6%) dislocated but without recurrence - all were operated using the Hardinge approach. The 613 hips that were not operated on again had satisfactory clinical results; the Merle d'Aubigné score was 17.2 (range 12-18) and the WOMAC score was 91 (range 20-100). The five-year survival rate was 91% (95% CI: 87-94%). Based on radiographs, the average cup inclination was 44.4° (range 30 to 70°). The femoral offset was reduced by an average of 2.4mm (-31 to 23 mm) and the leg length had increased by an average of 0.8mm (-15 to 19 mm) relative to the other side, which was prosthesis-free. None of the non-revised implants showed any signs of loosening.

DISCUSSION

This multicentre evaluation revealed that the Durom revision rate was slightly higher than the rate with other hip resurfacing systems and traditional total hip arthroplasty. Although the Durom system displayed excellent tribological performance, the differences relative to other implants may be attributed to the challenges associated with impaction, related to the geometry and design of the cup, and to precarious primary fixation. The choice of surgical exposure and implantation technique was an important factor in the survival of the implant.

LEVEL OF PROOF

Level IV - Retrospective study.

Abstract 3774: Regulation of the pro-invasive properties of neuroblastoma-stem cells by membrane type-1 matrix metalloproteinase

Neuroblastoma (NB) is an aggressive childhood cancer that represents the leading cause of cancer deaths in children. Despite aggressive therapy, more than half of the children with advanced NB usually die because of uncontrolled metastatic disease. In order to develop new therapeutic strategies to limit NB's metastatic potential, it is crucial to identify key molecular targets governing the invasive process. The study of Cancer stem cells (CSCs) may be of interest in this regard because after chemotherapy, CSCs persist in tumors and cause relapse and metastasis. We had recently demonstrated that CD133 allowed to detect CSCs in NB. Membrane type-1 matrix metalloproteinase (MT1-MMP) is important in the metastatic process and its expression was correlated with unfavourable outcome in NBs. Our preliminary data had indicated that MT1-MMP was highly expressed in CD133high NB.

The purpose of this study is to characterize the interaction between CD133 and MT1-MMP in NB and determinate the role of MT1-MMP in pro-invasive properties of CSCs. We constructed paraffin-embedded blocks of tissue microarrays (TMA) from 235 patients. In vitro experiments were performed on four established NB cell lines (SK-N-DZ, SK-N-FI and SK-N-SH and SJNB-10). We performed immunohistochemical studies on paraffin-embedded TMA sections with two antibodies (CD133, MT1-MMP). To verify correlation of expression of MT1-MMP and CD133, we realized western blot and immunofluorescence (IF) of both proteins in non treated versus treated NB cell lines. CD133high NB cells were isolated by flow cytometry. CD133high and CD133low NB cells were grown within a 3D collagen matrix and the cell migration assay was tested in collagen-coated transwells. All experiments were performed with or without an anti-MT1-MMP neutralizing antibody or GM6001, a broad-spectrum MMP inhibitor.

To assess the interaction between CD133 and MT1-MMP, lysates were subjected to immunoprecipitation (IP) using an anti-CD133 antibody, followed by immunodetection with an anti-MT1-MMP antibody. Finally, we determined which domain of MT1-MMP is involved in its interaction with CD133. Different dominant negative mutants of MT1-MMP (catalytically inactive E240A, cytoplasmic domain-deleted CΔ20 and non-phosphorylatable Y573F) were transfected into NB cells followed by an IP.

There is a correlation between MT1-MMP and CD133 expressions in tumors of patients and in cell lines. Cells selected after chemotherapy express both CD133 and MT1-MMP. CD133high cells presented higher migration and invasion properties than CD133low which were MT1-MMP dependent. IF and IP showed a colocalization and interaction between CD133 and MT1-MMP. The cytoplasmic domain of MT1-MMP seems to be responsible for the interaction with CD133.

These results contribute to a better understanding CSCs properties in NB and may be of great interest to improve new therapeutic strategies.

Citation Format: Assila Belounis, Carine Nyalendo, Sonia Cournoyer, Sarah Hadj-Mimoune, Alexandre Benoit, Elliot Lasalle, Jonathan Girard, Mona Beaunoyer, Pierre Teira, Hervé Sartelet. Regulation of the pro-invasive properties of neuroblastoma-stem cells by membrane type-1 matrix metalloproteinase. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3774. doi:10.1158/1538-7445.AM2013-3774

Hip prosthesis infection related to an unchecked intrauterine contraceptive device: a case report

Intrauterine devices (IUD) used for contraception can be the source of local infections or can migrate, which justifies regular checking recommendations and limitations around the implantation period. To our knowledge, bone and joint infections related to an infected IUD have not been described in the scientific literature. This paper reports on a case of the repeated infection of a total hip prosthesis related to an infected IUD that had been forgotten after being implanted 34years previously. The arthroplasty infection revealed itself through dislocation of a dual mobility cup. Commensal bacteria that colonize the female genital tract (Streptococcus agalactiae) were identified at the site of hip arthroplasty. This led to the discovery of the IUD that was infected by the same bacterium. Despite lavage of the non-loosened arthroplasty, removal of the IUD and 2months of antibiotic treatment, the dislocation recurred and the prosthesis was again infected with the same microorganism 4months later. This recurrence of the infection, with persistence of a uterine abscess containing the same bacterium, was treated with repeated lavage of the joint, total hysterectomy and antibiotics treatment. The infection had resolved when followed-up 3years later. The occurrence of a bone and joint infection with this type of bacterium should trigger the evaluation of a possible IUD infection.

Far-field optical control of a movable subdiffraction light grid

We demonstrate experimentally a subdiffraction light pattern, with a period down to 150 nm, at the surface of an optimized silicon nanostructured thin film. We show, using near-field and far-field characterization, that this subdiffraction pattern can be translated and rotated just by changing the illumination angle. The movable high frequency light pattern paves the way for subdiffraction resolution surface imaging microscopy without scanning near-field probes.

Foraging habitat and diet of Song Sparrows (Melospiza melodia) nesting in farmland: a stable isotope approach

Agricultural intensification has been linked to declines in farmland and grassland bird populations in Europe and in North America. One factor thought to be behind these declines is reduced invertebrate food abundance in the breeding season, leading to reduced reproductive success. However, little is known about foraging habitat or diet of farmland birds in North America. We used stable isotopes to study foraging habitat and diet of Song Sparrows ( Melospiza melodia (A. Wilson, 1810)), a common hedgerow-breeding bird, by collecting claw clippings of Song Sparrow nestlings from farms in eastern Ontario, Canada. Mean values of δ13C and δ15N were compared between claws and invertebrate food sources from adjacent land-cover types, using a Bayesian mixing model. The portion of nestling diet that came from seminatural and forage habitats was higher than expected, based on the proportion of seminatural and forage cover at the nest. This was particularly evident at nests with low seminatural cover, where hedgerows were the only noncrop habitat. The most important food sources for Song Sparrow nestlings were hoppers (Auchenorrhyncha) and caterpillars (Lepidoptera). Management actions to increase invertebrate abundance in hedgerows may benefit Song Sparrows and other farmland birds with minimal impact on crop yield.

Joint perception after hip or knee replacement surgery

INTRODUCTION

Knee and hip arthroplasties are recognized as being effective. However, subjects with a prosthetic joint rarely report returned sensation comparable to their native joint.

HYPOTHESIS

Joint perception by patients following hip joint replacement is better than following knee replacement and in both cases this perception is directly related to the clinical results measured with currently validated scores.

PATIENTS AND METHODS

Patient joint perception in prosthetic reconstruction was evaluated in 347 patients, 46 who underwent unicompartmental knee arthroplasty (UKA), 119 tricompartmental knee arthroplasty (TKA), 93 hip resurfacing (HR), and 89 total hip arthroplasty (THA). The subjects' joint perception, their satisfaction, and the WOMAC clinical score were recorded and compared.

RESULTS

Joint perception was significantly worse for knee arthroplasties (TKA and UKA) compared to hip arthroplasties (THA or HR) (P<0.001). The WOMAC score was also significantly less favorable for knee arthroplasties than for hip arthroplasties (P<0.0001). However, there was no significant difference for the clinical scores between TKA and UKA as well as between HR and THA. Joint perception was strongly correlated with the WOMAC score for all groups (R(2)=0.951).

DISCUSSION

No difference was found after more conservative surgeries such as HR or UKA compared to traditional arthroplasty procedures (THA or TKA). Demonstrating inferior results in comparison to the hip, knee arthroplasties deserve particular attention and can still be improved. The assessment of joint perception used in this study can be considered a valuable clinical tool that is strongly correlated to validated, but more complex to apply, clinical scores.

De-escalation exchange of loosened locked revision stems to a primary stem design: complications, stem fixation and bone reconstruction in 15 cases

INTRODUCTION

Femoral stem revision with a locked stem after total hip arthroplasties treats severe bone defects by favoring spontaneous bone reconstruction. Initially, once reconstruction was obtained, the temporary implant was to be replaced by a standard primary component. The use of locked stems has increased, but repeat revision with a short stem which is also called "de-escalation" has not been extensively studied.

HYPOTHESIS

Repeat revision of a locked stem with a short stem is not associated with any specific morbidity and does not affect the quality of reconstruction obtained, or fixation of the subsequent standard length primary design stem.

PATIENTS AND METHODS

Fifteen patients whose locked femoral stem was exchanged due to thigh pain and/or radiographic images showing failed osteointegration were analyzed. These 15 patients were all followed-up and evaluated by the Postel Merle d'Aubigné score. Progression of bone defects was evaluated using the Hofmann cortical index.

RESULTS

There were no difficulties extracting the locked stem and a standard length primary stem was inserted with no associated procedures or bone complications in any of the cases. At a mean follow-up of 55 months (36-84months), thigh pain had disappeared and the Postel Merle d'Aubigné score had increased from 12.6±2.9 (7-16) to 16.5±0.9 (15-18) (P=0.0001). The use of a locked femoral stem resulted in bone reconstruction in all cases, the Hofmann index increased from 30.5%±17.9% (12-71%) before insertion of the locked stem to 43.6%±25.6% (19-90%) at exchange (P<0.05). Bone reconstruction was durable after the exchange with a stable Hofmann index 43.7%±26.2% (17-92%) at the final follow-up (P=0.9). No recurrent loosening occurred.

DISCUSSION

Revision of a loosened locked femoral stem with a standard design primary stem does not result in any specific increased morbidity, or modify bone reconstruction obtained with the locked stem and results in stable fixation of a new standard length stem.

LEVEL OF EVIDENCE

IV: retrospective or historical series.

Severe corrosion after malpositioning of a metallic head over the Morse taper of a cementless hip arthroplasty. A case report

Morse tapers are frequently used in total hip replacement to achieve precise adjustment of lengths and femoral offset. Mechanically, they do not raise any specific problems so long as strict positioning requirements are observed and elements from different manufacturers are not mixed together. We report a case in which the implant induced unexplained pain at 2 years, in relation to a defective fit between the metallic head and the Morse taper. Asymmetric partial fit of the head onto the taper was detected on control X-ray and was implicated as causing metallosis due to excessive release of metal debris from the Morse taper. Revision required femoral stem exchange because of the damage to the Morse taper as well as replacing the cup with new metal-metal bearings. Evolution was favorable at 3 years' follow-up. Most hip replacements include a Morse taper; the present clinical case is a reminder that strict positioning rules are to be respected, without which corrosion and wear may lead to mechanical failure.

Femoral head to neck offset after hip resurfacing is critical for range of motion

BACKGROUND

Range of motion after hip arthroplasty may be limited by soft tissues around the hip, extra-articular contact and femoral stem-neck contact with the acetabular articular surface. Femoral head-neck diameter ratio is recognized as a major factor influencing hip range of motion. In hip resurfacing, range of motion is constrained by "cup component to femoral neck" contact. To avoid cup-to-bone contact or to increase the degree of flexion at which it occurs, anterior translation of the femoral component relative to the central femoral neck axis may improve anterior head-neck offset and hip flexion. We questioned whether low or high anterior femoral head to neck offset, cup inclination, stem anteversion, and component size influenced postoperative range of motion and hip flexion in patients who had undergone hip resurfacing.

METHODS

We prospectively followed 66 patients (68 hips) who underwent hip resurfacing at a mean age at operation of 46.4 years (range, 19-60 years). Mean follow-up was 37.5 months (range, 33-41 months). No patient was lost to follow-up. All patients were evaluated clinically and range of motion was precised. Radiological measurement evaluated the anterior femoral head-neck offset.

FINDINGS

Mean anterior neck-head offset was 7.5mm (range, 5-12 mm). We found significant linear regression correlation between anterior offset and flexion (R=0.66) and between anterior offset and global range of motion (R=0.51). One millimeter of anterior offset increased hip range of motion by 5° in flexion. No significant correlations were found between global range of motion or flexion arc of motion and component size, stem anteversion, cup inclination, gender ratio, preoperative arc of flexion or global range of motion.

INTERPRETATION

Restoring or improving deficient anterior femoral head-neck offset appears important for restoring postoperative range of motion and specifically hip flexion.

Component impingement in total hip arthroplasty: frequency and risk factors. A continuous retrieval analysis series of 416 cup

INTRODUCTION

Impingement is a factor of failure in total hip replacement (THR), causing instability and early wear. Its true frequency is not known; cup-retrieval series reported rates varying from 27 to 84%.

HYPOTHESIS

The hypothesis was that a large continuous series of THR cup removals would help determine the frequency of component impingement.

OBJECTIVES

The hypothesis was tested on a continuous retrospective series of cups removed in a single center, with a secondary objective of identifying risk factors.

MATERIAL AND METHODS

[corrected] Macroscopic examination looked for component impingement signs in 416 cups retrieved by a single operator between 1989 and 2004. Risk factors were investigated by uni- and multivariate analyses in the 311 cases for which there were complete demographic data. In these 311 cases, removal was for aseptic loosening (131 cases), infection (43 cases), instability (56 cases), osteolysis (28 cases) or unexplained pain (48 cases); impingement was explicitly implicated in only five cases (1.6%), always with hard-on-hard bearing components.

RESULTS

Impingement was found in 214 of the 416 cups (51.4%) and was severe (notch>1mm) in 130 (31.3%). In the subpopulation of 311 cups, impingement was found in 184 cases (59.2%) and was severe in 109 (35%). Neither duration of implant use nor cup diameter or frontal orientation emerged as risk factors. On univariate analysis, impingement was more frequently associated with revision for instability, young patient age at THR, global hip range of motion >200° or use of an extended femoral head flange (or of an elevated antidislocation rim liner), and was more severe in case of head/neck ratio<2. On multivariate analysis, only use of an extended head flange (RR 3.2) and revision for instability (RR 4.2) remained as independent risk factors for impingement.

DISCUSSION

Component impingement is frequently observed in cups after removal, but is rarely found as a direct indication for revision, except in case of hard-on-hard friction couples (polyethylene being the most impingement-tolerant material). Systematic use of extended head flanges and elevated antidislocation rims is not to be recommended, especially in case of excessive ROM. A good head/neck ratio should be sought, notably by increasing the head diameter in less impingement-tolerant hard-on-hard friction couples. Although not identified as a risk factor in the present study, implant orientation should be checked; computer-assisted surgery can be useful in this regard, for adaptation to the patient's individual range-of-motion cone.

Stem subsidence after total hip revision: 183 cases at 5.9 years follow-up

INTRODUCTION

Secondary subsidence of a revision femoral stem is often a negative predictive sign for successful osseointegration and perfect long-term stability.

MATERIALS AND METHODS

We performed a retrospective study in a series of 183 revision total hip replacements between 1996 and 2000 to evaluate the importance and risk factors of secondary subsidence with a cementless press-fit design femoral stem as well as this subsidence's consequences to osseointegration.

RESULTS

Secondary subsidence did not occur in 80 cases (53%), was between 0 and 4mm in 41 cases (27%); between 5 and 10mm in 17 cases (12%) and was greater than 10mm in 12 cases (8%). Mean subsidence of all patients was 3mm (0-30). There was a statistically significant negative correlation between subsidence and the quality of osseointegration (P=0.03). There was no significant relationship between component diameter and stem subsidence (P=0.9). The presence of preoperative bone deficiencies did not increase the risk of secondary subsidence (P=0.2).

CONCLUSION

In the case of revision with press-fit stems, the importance of secondary subsidence should not be overestimated, because it usually does not negatively affect satisfactory osseointegration.

Anterior hip subluxation following fixation of a T-shaped acetabular fracture through an extended iliofemoral approach

We report the case of a 34-year-old female patient who, six week following her acetabular fracture ORIF through an extended iliofemoral approach, presented with anterolateral incomplete dislocation of the femoral head. In the absence of joint incongruence as demonstrated on radiographs and CT images, a capsular tightening was performed via the anterior Hueter approach. This capsular plasty stabilized the hip for 2 years, but gradual osteoarthritis deterioration resulted in the need for arthroplasty. At the 2-year follow-up, this secondary arthroplasty showed satisfactory result. The substantial muscle exposure of the lateral aspect of the acetabulum and the circumferential capsulotomy related to the use of the iliofemoral approach were retained as factors promoting this complication. In case early postoperative mobilization is impossible, temporarily maintaining the limb in abduction and flexion can be recommended after an extended iliofemoral approach with circumferential capsulotomy.

Radiographic preoperative templating of extra-offset cemented THA implants: how reliable is it and how does it affect survival?

INTRODUCTION

Securing femoral offset should in theory improve hip stability and abductor muscles moment arms. As problems arise mainly in case of originally increased offset (>40 mm), a range of extra-offset stems is available; the exact impact in terms of fixation, however, is not known.

HYPOTHESIS

Extra-offset stems should more reliably reestablish original femoral offsets exceeding 40 mm than standard femoral components, limiting instability risk without possible adverse effect on fixation.

OBJECTIVE

To compare the ability of five commonly available femoral stem designs to restitute offset exceeding 40 mm, and to assess function and cement fixation at a minimum 6 years' follow-up in a stem conceived to reproduce such offset.

PATIENTS AND METHODS

A continuous series of 74 total hip replacements (THR) in hips with increased (>40 mm) femoral offset was studied. All underwent preoperative X-ray templating on Imagika™ software to assess offset reproduction by five models of stem: four standard, and one Lubinus SP2™ extra-offset stem. A retrospective clinical and X-ray study was conducted with a minimum 6 years' follow-up on the Lubinus SP2™ 117° stems used to try to reproduce offset in the 74 THRs.

RESULTS

Apart from the increased (>40 mm) offset, the cervicodiaphyseal angle was consistently <135°, <130° in 60 femurs (81%) and <125° in 45 (60%). Planning showed the four standard stems to induce (>5mm femoral offset reduction in 50-83% of cases, versus only 25% with the Lubinus SP2™ 117°). All 74 hips received Lubinus SP2™ 117° stems: at a mean 78 months FU (range, 70-94 mo), their mean Postel-Merle d'Aubigné score was 17±1.8 (range, 13-18). Five of the 74 THRs underwent surgical revision: three cases of loosening, in which the stem was replaced, and two of instability, without change of stem. Loosening was not related to offset reproduction quality; two of the three cases were due to initial cementing defect, and the third occurred in a femur with previous history of two osteotomies. There were four cases of dislocation (5.4%: two primary, which were not operated on, and two recurrent, managed by acetabular revision), despite good reproduction of the preoperative offset in three of the four cases. Mean 7-year implant survivorship was 95.1% (±4.8).

DISCUSSION AND CONCLUSION

The anatomic form of the Lubinus™ SP2 117° should in theory provide a uniform cement mantle. Survivorship, however, is less good than for regular offset versions (126° or 135°). On the other hand, it does reproduce anatomy in case of >40mm offset, providing extra offset of more than 51mm. The slightly shorter survivorship requires more long-term surveillance.

LEVEL OF EVIDENCE

Level IV, retrospective study.

Shelf arthroplasties long-term outcome: influence of labral tears. A prospective study at a minimal 16 years' follows up

INTRODUCTION

Osteoarthritis lesions extent and dysplasia severity (negative vertical center edge [CE] angle) are recognized as unfavorable criteria for the survival of shelf arthroplasties performed for correcting hip dysplasia. Labral tears have recently been described on dysplastic hips, indicating beginning osteoarthritis and worsening the risk of instability.

HYPOTHESIS

The labral tears identified in the course of shelf arthroplasty procedures for correction of hip dysplasia carry a predictive value for the survival of this operation.

OBJECTIVES

Evaluate this hypothesis at the intermediate term in a long-term prospective observational study.

PATIENT AND METHODS

Eighteen adult patients (18 dysplastic hips) having undergone shelf arthroplasty were included consecutively in a continuous prospective study. At the time the shelf arthroplasty was performed, a hip arthroscopic exam was carried out to search for and resect a labral tear if necessary. Fifteen patients were reviewed with a minimum follow-up of 16 years. Two patients died and one patient was lost to follow-up.

RESULTS

During arthroscopic exploration, 10 hips presented labral tears (55.6%). At a mean follow-up of 16.3 years (range, 16-18 years), eight hips underwent hip arthroplasty. Of these hips, only one did not present a labral tear. The seven other hips had a tear of the labrum (p<0.001). The overall survival rate was 41.3%; it was 83.3% for hips with no labral tear and 15.2% for hips with a lesion of the labrum (p=0.048).

DISCUSSION AND CONCLUSION

Labral tears had a negative impact on the outcome of shelf arthroplasty for hip dysplasia. This lesion therefore warrants being sought using appropriate exploration techniques (MRI or CT-arthrography) before shelf arthroplasty surgery. The existence of a preoperative labral tear does not seem to cast doubt on shelf arthroplasty itself. However, it should be identified so as to set objectives and expectations: long-term survival is significantly lower in the presence of a labral tear. It seems preferable to repair this type of lesion with arthroscopic guidance during shelf arthroplasty to prevent a potential source of residual pain, keeping in mind that secondary resection will be more difficult after covering the lesion.

LEVEL OF EVIDENCE

Level 3 prospective observational prognostic study.

Proximal tibial derotation osteotomy for torsional tibial deformities generating patello-femoral disorders

INTRODUCTION

Torsional abnormalities of the leg may cause instability and pain in the patellofemoral joint. Although derotation osteotomies seem logical to address these conditions, there are very few surgical results reported in the literature.

HYPOTHESIS

Isolated tibial derotation osteotomies relieve patellofemoral pain and instability even in the event of combined femoral and tibial torsion abnormalities.

AIM

Test this hypothesis in a retrospective and continuous series of thirty-six tibial derotation osteotomies and define the factors of success and failure.

PATIENTS AND METHODS

Thirty-six derotation osteotomies of the proximal tibial metaphysis were performed between 1995 and 2006 in 29 patients (five men and 24 women, an average of 26.5 years old±7.4 (18-44)) followed-up for a mean 4.7 years. There was confirmed patellar instability in five knees, and patellofemoral pain without instability in 31. A proximal metaphyseal osteotomy was performed to correct excessive external tibial rotation as well as to recenter the tibial tubercle after anterior tibial cortex elevation. All patients were followed-up and the clinical data were analysed according to criteria from the Lille score [specifically designed for patellofemoral joints (100 point score)] and the IKS score. All patients had a preoperative radiological evaluation [(including measurement of torsion abnormalities in 32 cases by computed tomodensitometry (CT scan))]. The mean preoperative external tibial torsion measured on CT scan was 36.2°±9.48 (26-51°) and the mean femoral anteversion was 19.4°±9.5 (8-36°).

RESULTS

Twenty-seven patients (94%) were satisfied or very satisfied. The Lille score increased from 54.8±16.9 (30-92) preoperatively to 85.2±14.2 (36-100) at follow-up. The mean IKS knee scores and function increased from 56±14.8 (45-94) to 94±12.1 (60-100) and from 71±18.4 (30-100)-96±11.9 (50-100). Patellofemoral dislocations did not occur in any of the five cases with instability. Mean derotation was 25° measured with a mean tibial torsion measured clinically at follow-up 8.6°±7.2 (0-30). Two reoperations were necessary, (one knee manipulation under general anesthesia, and in another the fibular fibrous arch had to be released). One case of regressive palsy of the common fibular nerve was observed. Union of the osteotomy was obtained in all patients.

DISCUSSION

This series is one of the largest series published to date. Isolated medialization of the anterior tibial tubercle only partially corrects these morphological abnormalities. In cases of associated excessive femoral anteversion we recommend surgery to the tibia alone because results were comparable in groups with and without excessive anteversion of the femoral neck.

LEVEL OF EVIDENCE

level IV. Retrospective study.

The Durom large diameter head acetabular component: early results with a large-diameter metal-on-metal bearing

Implantation of a large-diameter femoral head prosthesis with a metal-on-metal bearing surface reduces the risk of dislocation, increases the range of movement, minimises the risk of impingement and, in theory, results in little wear. Between February 2004 and March 2007 we implanted 100 consecutive total hip replacements with a metal-on-metal bearing and a large femoral head into 92 patients. There were 51 men and 41 women with a mean age of 50 years (18 to 70) at the time of surgery. Outcome was assessed using the Western Ontario McMaster University osteoarthritis index and the Harris hip score as well as the Devane activity score. These all improved significantly (p < 0.0001). At the last follow-up there were no cases of dislocation, no impingement, a good range of movement and no osteolysis, but seven revisions, two for infection and five for aseptic loosening. The probability of groin pain increased if the other acetabular component inclination exceeded 50 degrees (p = 0.0007). At 4.8 years of follow-up, the projected survival of the Durom acetabular component, with revision for any reason, was 92.4% (sd 2.8) (95% confidence interval 89.6 to 95.2). The design of the component made it difficult both to orientate and seat, which when combined with a poor porous coating, produced unpredictable fixation and a low survival at five years.

Metal ions levels measurments for early total hip replacement malfunction diagnosis with "plasma-sprayed ceramic" bearings couple

Diagnosis of total hip arthroplasty malfunction is usually based on clinical and radiographic findings, while metal ion blood levels monitoring is generally recommended for metal-on-metal bearings hip replacements. However, these measurements may be very useful in detecting anomalies in other bearing surfaces such as plasma sprayed ceramic bearings. We report on the case of a patient with a painful cementless ceramic-on-ceramic total hip prosthesis (Plasmaceram) for which metal ions blood levels suggested revision surgery in the absence of any demonstrable radiographic anomaly. The high Cobalt and moderate Chromium ion levels in blood suggested a mechanical dysfunction of the bearing couple which revealed to be a severe cam effect requiring revision surgery of both components. Measurement of metal ion blood levels may play a substantial role in the assessment of a total hip prosthesis mechanism when using another bearing surface than metal-on-metal for which this measurement is usually recommended.

Metal ion release from bearing wear and corrosion with 28 mm and large-diameter metal-on-metal bearing articulations: a follow-up study

We have updated our previous randomised controlled trial comparing release of chromium (Cr) and cobalt (Co) ions and included levels of titanium (Ti) ions. We have compared the findings from 28 mm metal-on-metal total hip replacement, performed using titanium CLS/Spotorno femoral components and titanium AlloFit acetabular components with Metasul bearings, with Durom hip resurfacing using a Metasul articulation or bearing and a titanium plasma-sprayed coating for fixation of the acetabular component. Although significantly higher blood ion levels of Cr and Co were observed at three months in the resurfaced group than in total hip replacement, no significant difference was found at two years post-operatively for Cr, 1.58 microg/L and 1.62 microg/L respectively (p = 0.819) and for Co, 0.67 microg/L and 0.94 microg/L respectively (p = 0.207). A steady state was reached at one year in the resurfaced group and after three months in the total hip replacement group. Interestingly, Ti, which is not part of the bearing surfaces with its release resulting from metal corrosion, had significantly elevated ion levels after implantation in both groups. The hip resurfacing group had significantly higher Ti levels than the total hip replacement group for all periods of follow-up. At two years the mean blood levels of Ti ions were 1.87 microg/L in hip resurfacing and and 1.30 microg/L in total hip replacement (p = 0.001). The study confirms even with different bearing diameters and clearances, hip replacement and 28 mm metal-on-metal total hip replacement produced similar Cr and Co metal ion levels in this randomised controlled trial study design, but apart from wear on bearing surfaces, passive corrosion of exposed metallic surfaces is a factor which influences ion concentrations. Ti plasma spray coating the acetabular components for hip resurfacing produces significantly higher release of Ti than Ti grit-blasted surfaces in total hip replacement.

Bilateral simultaneous metal inlay dissociation from the polyethylene liner of a metal-on-metal hip replacement

INTRODUCTION

Hard-on-hard bearings for total hip replacement may require a modular acetabular inlay for which polyethylene is often used in a sandwich-type configuration. However, differences in the elastic modulus of the materials make fixation of this metal insert uncertain. The aim of this study is to report a case of bilateral separation of the metal insert from the polyethylene sandwich in a metal-on-metal bearings prosthesis.

MATERIALS AND METHODS

A bilateral total hip arthroplasty was performed in two operations, four months apart, in a 53-year-old woman following a corticosteroid-induced osteonecrosis. The total hip replacement system included a cementless stem, and a press-fit hemispheric cup containing a polyethylene sandwich with a metallic insert (Sikomet).

RESULTS

Three years later, the patient consulted because of abnormal noise in her right hip which appeared normal on conventional X-ray. Three months later she consulted again for persistent noise. Separation of the metal insert from the polyethylene sandwich was diagnosed and an acetabular revision was performed selecting a metal-on-polyethylene articulation system. The postoperative course, for this revision, was uneventful, but the patient returned with the similar symptoms in her left hip four months later, resulting in the same type of revision. During the revisions, osteolysis secondary to metallosis was diagnosed, requiring synovectomy and acetabular reconstruction with morcelized allograft impaction. The left side postoperative course included three dislocations in nine months which were conservatively treated and have not since recurred.

DISCUSSION AND CONCLUSION

This is the first reported case recording an almost simultaneous bilateral dissociation of a hard-on-hard inlay from its polyethylene sandwich. This bilateral case suggests that the fixation of the metal insert inside the polyethylene was probably defective. This case is also a reminder that mechanical complications (separation, implant fracture) should be searched for in presence of any abnormal noise occurring after hard-on-hard bearings prosthetic implantation. This confirms the necessity of periodical follow-up of hip arthroplasties and the importance of knowing their radiological features. The low carbon content of the Sikomet bearing may have been the cause of this failure by increasing frictional torque on the bearing surface, causing metallosis which has already been described in the literature in this type of hip replacement system.

Total knee arthroplasty in valgus knees: predictive preoperative parameters influencing a constrained design selection

INTRODUCTION

In valgus knees, ligament balance might remain a challenge at total knee prostheses implantation; this leads some authors to systematically propose the use of constrained devices (constrained condylar knee or hinge types...). It is possible to adapt the selected level of constraints, by reserving higher constraints to cases where it is not possible to obtain final satisfactory balance: less than 5 degrees of residual frontal laxity in extension in each compartment, and a tibiofemoral gap difference not in excess to 3 mm between flexion and extension.

HYPOTHESIS

It is possible to establish preoperative criteria that can predict a constrained design prosthetic implantation at surgery.

MATERIALS AND METHODS

A consecutive series of 93 total knee prostheses, implanted to treat a valgus deformity of more than 5 degrees was retrospectively analysed. Preoperatively, full weight bearing long axis AP views A-P were performed: hip knee angle (HKA) averaged 195 degrees (186 degrees to 226 degrees), 36 knees had more than 15 degrees of valgus, and 19 others more than 20 degrees of valgus. Laxity was measured by stress radiographies with a Telos system at 100 N. Fifty-two knees had preoperative laxity in the coronal plane of more than 10 degrees. Fourteen knees had more than 5 degrees laxity on the convex (medial) side, 21 knees had more than 10 degrees laxity on the concave (lateral) side. Statistical assessment, using univariate analysis, identified the factors that led, at surgery, to an elevated constraint selection level; these factors of independence were tested by multivariate analysis. Logistical regression permitted the classification of the said factors by their odds ratios (OR).

RESULTS

High-constraints prostheses (CCK type) numbered 26 out of 93 implantations; the other total knee prostheses were regular posterostabilized (PS) prostheses. Statistically, the preoperative factors that led to the choice of a constrained prosthesis were: (1) valgus severity as measured by HKA (PS=193 degrees, CCK=198 degrees), (2) increased posterior tibial slope (PS=4.8 degrees, CCK=6.5 degrees), (3) low patellar height (using Blackburne and Peel index PS=0.89, CCK=0.77), (4) severity of laxity in valgus (PS=2.3 degrees, CCK=4.3 degrees). Among all these factors, the only independent one was laxity in valgus (convex side laxity) (p=0.0008). OR analysis showed a two-fold increased probability of implanting an elevated constraints prosthesis for each one degree increment of laxity in valgus.

DISCUSSION

This study demonstrated that it was not the valgus angle severity but rather the convex medial side laxity that increased the frequency of constrained prostheses implantation. Other factors, as a low patellar height or an elevated posterior tibial slope, when associated, potentiate this possible prosthetic switch (to higher constraints) and should make surgeons aware, in these situations, of encountering difficulties when establishing ligament balance.

LEVEL OF EVIDENCE IV

Therapeutic retrospective study.

The role of the lipogenic pathway in the development of hepatic steatosis

Non-alcoholic fatty liver disease (NAFLD) represents a wide spectrum of diseases, ranging from simple fatty liver (hepatic steatosis) through steatosis with inflammation and necrosis to cirrhosis. NAFLD, which is strongly associated with obesity, insulin resistance and type 2 diabetes, is now well recognized as being part of the metabolic syndrome. The metabolic pathways leading to the development of hepatic steatosis are multiple, including enhanced non-esterified fatty acid release from adipose tissue (lipolysis), increased de novo fatty acids (lipogenesis) and decreased beta-oxidation. Recently, several mouse models have helped to clarify the molecular mechanisms leading to the development of hepatic steatosis in the pathogenesis of NAFLD. This review describes the models that have provided evidence implicating lipogenesis in the development and/or prevention of hepatic steatosis.