Threshold for anterior acetabular component overhang correlated with symptomatic iliopsoas impingement after total hip arthroplasty.

Aims: Mechanical impingement of the iliopsoas (IP) tendon accounts for 2% to 6% of persistent postoperative pain after total hip arthroplasty (THA). The most common initiator is anterior acetabular component protrusion, where the anterior margin is not covered by anterior acetabular wall. A CT scan can be used to identify and measure this overhang; however, no threshold exists for determining symptomatic anterior IP impingement due to overhang. A case-control study was conducted in which CT scan measurements were used to define a threshold that differentiates patients with IP impingement from asymptomatic patients after THA. Methods: We analyzed the CT scans of 622 patients (758 THAs) between May 2011 and May 2020. From this population, we identified 136 patients with symptoms suggestive of IP impingement. Among them, six were subsequently excluded: three because the diagnosis was refuted intraoperatively, and three because they had another obvious cause of impingement, leaving 130 hips (130 patients) in the study (impingement) group. They were matched to a control group of 138 asymptomatic hips (138 patients) after THA. The anterior acetabular component overhang was measured on an axial CT slice based on anatomical landmarks (orthogonal to the pelvic axis). Results: The impingement group had a median overhang of 8 mm (interquartile range (IQR) 5 to 11) versus 0 mm (IQR 0 to 4) for the control group (p < 0.001). Using receiver operating characteristic curves, an overhang threshold of 4 mm was best correlated with a diagnosis of impingement (sensitivity 79%, specificity 85%; positive predictive value 75%, negative predictive value 85%). Conclusion: Pain after THA related to IP impingement can be reasonably linked to acetabular overhang if it exceeds 4 mm on a CT scan. Below this threshold, it seems logical to look for another cause of IP irritation or another reason for the pain after THA before concluding that impingement is present.

What role for short stems in 2023?

Current trends in total hip replacement aim at soft tissue and bone stock conservation. At the same time, mean patient age has been decreasing from decade to decade, raising the issue of iterative revision. Short stems seek to resolve the problem on the femoral side. Hopefully, revision of a short stem will be easier and bone stock depletion will be less than with a standard stem. Short stems also seem to have other advantages: automatically personalized biomechanical reconstruction, easier minimally invasive strategies, very low rate of hip pain, more harmonious distribution of bone stress, etc. Despite these advantages, however, use of short stems since their introduction in the late 1980s has varied from country to country, and is not widespread in France. The present study addressed several questions concerning these implants. Firstly, what is a "short" stem? Then, what are the indications and contraindications? Shortened standard stems do not come under the concept of short stem and will not be dealt with here. Furthermore, the learning curve and specificities of short stems need to be acquired. Implantation technique differs greatly from standard stems, and short stem implantation requires particular rigor. Results also need to be assessed, and especially the rate of complications as compared to standard stems. And lastly, it needs to be determined whether the advantages are real or only theoretical: this will determine their usefulness and role in the armamentarium, in which short stems are a new paradigm. LEVEL OF EVIDENCE: Expert opinion.

Long-term results (after a mean 11.3years, and up to 22years, of follow-up) of the Legacy Constrained Condylar Knee (LCCK™) in primary total knee arthroplasty.

INTRODUCTION: The use of a sliding prosthesis in total knee arthroplasty (TKA) with increased stress is an intermediate solution in primary surgery, between posteriorly stabilized prostheses and hinged prostheses, in cases of ligamentous laxity and/or loss of bone substance. Favorable results have been reported in the medium term but to our knowledge, this type of prosthesis has not been evaluated in Europe beyond 10 years of follow-up. We therefore conducted a retrospective study in order to carry out: 1) the study of the survival of the Legacy Constrained Condylar Knee (LCCK™) prosthesis in primary surgery, 2) the analysis of complications, functional scores and radiographic data, 3) the analysis of the link between the diaphyseal filling rate and prosthetic loosening. HYPOTHESIS: The LCCK™ sliding prosthesis with increased constraint has equivalent long-term survival and clinical results to standard posteriorly stabilized TKA and superior to hinged TKA. MATERIAL AND METHOD: A retrospective series of 141 LCCK™ implanted in 134 patients between 1997 and 2010 was analyzed. Survival was assessed with censoring through an evaluation of partial or total revision of the implants. The functional results were evaluated using the IKS and Oxford 12 scores. Data regarding the Canal Fill Ratio (CFR) and the presence of pathological periprosthetic lines were also collected. RESULTS: The average follow-up was 11.3±5.3years with a maximum follow-up of 22.7years. Survival at 20years was 90.8% [95% CI: 83.7-95.7]. The rate of early complications was 13.5% (19/141), predominantly comprised of venous thrombosis (6/141), hematomas (3/141 including two requiring surgical drainage), stiffness (3/141) and early infections (3/141). The rate of late complications was 17% (24/141), led by stiffness (4.4%; 6/141), infections (2.9%; 4/141) and hardware failure (2. 2%; 3/141). Ten of the 141 patients (7.1%) had LCCK failure, including 3 (2.1%) for stiffness, 3 (2.1%) for hardware failure, 2 (1.4%) for infection, 1 (0.7%) for laxity and 1 (0.7%) for a periprosthetic fracture. No aseptic loosening was found. The total IKS score went from 65 [0-116] to 143 [79-200] at follow-up, the IKS knee score went from 30 [0-66] to 85 [44-100], and the IKS function score went from 35 [0-70] to 57 [0-100]. The Oxford score went from 14 [2-25] to 34 [15-48] at follow-up. Only two patients (1.4%) presented with a partial periprosthetic line. The tibial CFR was 0.81 and the femoral CFR was 0.76. The influence of the CFR could not be analyzed due to the absence of loosening. DISCUSSION: The LCCK™ prosthesis in primary surgery has good medium-term survival, a significant improvement in functional scores and a complication rate comparable to posteriorly stabilized prostheses. The complication rate is lower than that of hinged prostheses. LEVEL OF EVIDENCE: IV; single-center retrospective study.

What happens in the medium-term to capsule-thickening plasties for iliopsoas impingement after total hip arthroplasty? Evaluation of 14 procedures at 4years' follow-up.

INTRODUCTION: In 2015, we described a capsule-thickening technique via an anterior approach for iliopsoas cup impingement. To our knowledge, medium-term results have not been reported. We therefore retrospectively analyzed all cases in the initial series and those since 2015, to assess this original technique over a longer follow-up: (1) to analyze complications, and (2) to assess functional outcome. HYPOTHESIS: The study hypothesis was that this surgical solution has a success rate sufficient for it to be included in the therapeutic armamentarium for iliopsoas impingement. MATERIAL AND METHOD: Fourteen patients were included. Nine plasties were in first line, 3 after tenotomy, and 2 after cup exchange. The anterior Hueter approach was used, visualizing anterior cup overhang, sometimes associated with penetration of the anterior capsule, and enabling capsule-thickening by a folded Vicryl™ mesh. Functional results were analyzed. RESULTS: At a median 4years' follow-up (IQR: 2-5; range: 1-9), change over baseline in Oxford score was 7 points (p=0.004), median Medical Research Council thigh flexion strength score was 5 (IQR: 5-5), and 50% of patients (7/14) were satisfied or very satisfied. The major complications rate was 7% (1/14), for 1 irrigation of infected hematoma, cured without recurrence; there was also 1 minor case of injury to the lateral cutaneous nerve of the thigh. Forty-three percent of patients (6/14) exhibited a minimal clinically important difference (MCID) and 64% (9/14) a patient-acceptable symptom state (PASS). Median anatomic overhang on anatomic CT transverse slice was 7mm (IQR: 3-8; range: 0-13). Four patients underwent secondary acetabular component exchange; their median overhang was 7.5mm (IQR: 7-8) compared to 5mm (IQR: 2-8) for the other patients (p-value non-calculable). CONCLUSION: This surgical option seems interesting when acetabular overhang is not too great, especially as it does not affect flexion strength. LEVEL OF EVIDENCE: IV.

Should microbiological samples be taken routinely when performing revision surgery for post-surgical hematoma after hip or knee replacement? Retrospective study of 78 cases of surgically drained hematoma with a minimum follow-up of 2 years.

INTRODUCTION: The relationship between the occurrence of a periprosthetic hip or knee joint infection, a post-surgical hematoma and the time to surgical revision, along with the need to take samples for microbiology analysis has not been clearly defined. This led us to perform a retrospective study to: 1) define the rate of infected hematoma and subsequent infection after surgical revision for hematoma and 2) analyze in which time frame the hematoma was likely to be infected. HYPOTHESIS: The more time elapsed before the postoperative hematoma is drained surgically after hip or knee replacement, the higher the hematoma infection rate and the late infection rate. PATIENTS AND METHODS: Between 2013 and 2021, 78 patients (48 hip and 30 knee replacements) who had a postoperative hematoma without signs of infection upon draining were included in the study. Surgeons decided whether samples for microbiology were collected (33/78 patients (42%)). The data compiled consisted of the patient's demographics, the risk factors for infection, number of infected hematomas, number of subsequent infections at a minimum follow-up of 2 years, and the time to revision surgery (lavage). RESULTS: Of the 27 samples collected from the hematoma during the first lavage, 12/27 (44%) were infected. Of the 51 that did not have samples collected initially, 6/51 (12%) had them collected during the second lavage; 5 were infected and 1 was sterile. Overall, 17/78 (22%) of the hematomas were infected. Conversely, there were no late infections at a mean follow-up of 3.8 years (min 2, max 8) after the hematoma was drained in any of the 78 patients. The median time to revision was 4 days (Q1=2, Q3=14) for non-infected hematomas that were drained surgically versus 15 days (Q1=9, Q3=20) for hematomas that were found to be infected (p=0.005). No hematoma was infected when it was drained surgically within 72hours post-arthroplasty (0/19 (0%)). The infection rate went up to 2/16 (12.5%) when it was drained 3 to 5 days later and 15/43 (35%) when it was drained after more than 5 days (p=0.005). We believe this justifies collecting microbiology samples immediately when the hematoma is drained more than 72hours after the joint replacement procedure. Diabetes was more prevalent in patients who had an infected hematoma (8/17 [47%] versus 7/61 [11.5%], p=0.005). The infection was due to a single bacterium in 65% of cases (11/17); S. epidermidis was found in 59% (10/17) of infections. CONCLUSION: The occurrence of a hematoma after hip or knee replacement that requires surgical revision is associated with increased risk of infection, since the hematoma infection rate was 22%. Since hematomas drained within 72hours are less likely to be infected, samples do not need to be collected for microbiology at that time. Conversely, any hematomas being drained surgically beyond this time point should be considered as infected, thus microbiology samples should be collected, and empirical postoperative antibiotic therapy initiated. Early revision may prevent the occurrence of late infections. The standard treatment of infected hematomas appears to resolve the infection at a minimum follow-up of 2 years. LEVEL OF EVIDENCE: Level IV Retrospective study.

Are CPR (Contact Patch to Rim) distance anomalies associated with the occurrence of abnormal noises from ceramic-on-ceramic THA?

INTRODUCTION: The ceramic-on-ceramic couple in total hip arthroplasties (THA) has the advantage of excellent wear resistance and the bioinert nature of its debris. Noise occurring from this friction torque is a common complication, the contributing factors of which are debated. The noise is caused by a lack of lubrication, due in most part to the positioning of the acetabular cup. The study of metal-on-metal couples identified that the calculation of the Contact Patch to Rim (CPR) distance provides information on lubrication defects and also that it is correlated with the wear of metal-on-metal implants. This CPR distance is not recognized to be correlated with the occurrence of noise for the ceramic-on-ceramic couple at a caliber ≤ 36mm. We therefore conducted a retrospective case-control study to assess: 1) The influence of the CPR distance on noise occurrence; 2) Whether other factors associated to noise occurrence exist? HYPOTHESIS: Our hypothesis was that a low CPR distance was correlated with noise occurrence. METHOD: This was a case-control study with 3 controls for each case, analyzing 21 THAs (21 patients) with noise compared to 63 THAs without noise (63 patients) matched for age, sex and body mass index. These patients were taken from a continuous retrospective series of 96 patients for 104 total hip arthroplasties (THA) with a single operator and 4th generation Biolox Delta ceramic-on-ceramic single implant, performed between 2007 and 2012. The calculation of the CPR distance was then performed for both groups using measurements of inclination angles, anteversion angles, and implant data regarding the head/insert contact angle, head/insert diameter and clearance. RESULTS: At the mean follow-up of 7.1 years±1.2 [5 to 9.6], the mean CPR distance was lower in the noise group 10mm±3.3 [3.8 to 16.4] than in the control group 14.8mm±4.3 [7.3 to 24.4] (p=0.0007). The mean inclination angle was higher in the noise group 45.1°±7.8 [31 to 62] than in the control group 41.2°±7.2 [26 to 56] (p=0.04). The occurrence of noise was independent of anteversion, head caliber, cup diameter, neck length and stem size, and stem type (standard or lateralized). CONCLUSION: A low CPR distance was correlated with the occurrence of noises, similarly a steep inclination was correlated with the occurrence of noises. LEVEL OF EVIDENCE: III; Retrospective case-control study.

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

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

Hip resurfacing for small-sized osteonecrosis: 73 cases at a median 8years' follow-up.

INTRODUCTION: Total hip resurfacing arthroplasty (THRA) is an alternative to conventional total hip replacement (THR) in young patients with osteonecrosis of the femoral head. Series have been small, without criteria regarding extent of necrosis, thus vitiating results. We therefore conducted a retrospective assessment of THRA for small necrosis, to determine (1) implant survival, (2) functional scores, and (3) systemic chromium, cobalt and titanium ion concentrations. HYPOTHESIS: The study hypothesis was that the revision rate is low, meeting the National Institute for Health and Care Excellence (NICE) criterion of<0.5% revision per year. MATERIAL AND METHOD: A single-center single-surgeon retrospective study included 62 patients, for 73 RTHAs, with a mean age of 45.6years (range: 23-68years) presenting Ficat stage 3 or 4 osteonecrosis of the femoral head with<330° total Kerboul angle (frontal+lateral angles) on simple preoperative X-ray. Study data comprised implant survival and preoperative and last follow-up functional scores (Postel-Merle-d'Aubigné, Oxford-12, Harris, and Devane) and titanium, chromium and cobalt blood concentrations. Necrosis size was assessed on preoperative Kerboul angle. RESULTS: At a median 8years' follow-up (IQR: 5.9-9.3years), implant survival was 98.6% (95% CI: 97.22-99.98%). Only 1 implant was exchanged, for femoral loosening. Three other patients underwent revision surgery: 2 cases of lavage for infection, and 1 muscle hernia repair. Postel-Merle-d'Aubigné, Oxford-12 and Harris functional scores and Devane activity scores were significantly improved at follow-up, by a median +5 (IQR: 5 to 7), -26 (IQR: -29 to -23), +55 (IQR: 49 to 61) and +1 (IQR: 1 to 2), respectively (all p<0.001). Ion concentrations at last follow-up for titanium, chromium and cobalt were respectively 4.0µg/L (range: 3.6-4.1), 1.1µg/L (range: 0.8-1.9) and 1.1µg/L (range: 0.6-1.8). CONCLUSION: THRA is a useful option in the long-term for young patients with osteonecrosis with Kerboul angle<330°. LEVEL OF EVIDENCE: IV, retrospective study.

Tibiofemoral lift-off and resulting laxity following total knee arthroplasty: Frequency in a series of 906 continuous cases and functional consequences at 4 years' follow-up in a case-control study.

BACKGROUND: Tibiofemoral instability is one reason for early revision of total knee arthroplasty. It can be the consequence of tibiofemoral laxity, especially in the coronal plane with tibiofemoral lift-off. But does femoral condyle lift-off on conventional postoperative radiographs suggest the presence of laxity or potential instability? To our knowledge, this question has not yet been answered. This led us to conduct a retrospective study to evaluate (1) the frequency of lift-off on postoperative radiographs, (2) the relationship between lift-off and laxity in the short term and (3) the functional consequences of lift-off. HYPOTHESIS: Postoperative lift-off is a rare event that is predictive of laxity. METHODS: We carried out a single-center retrospective study using postoperative radiographs from patients who underwent primary total knee arthroplasty between 2014 and 2016. The sample consisted of 906 patients. Lift-off was defined as a tibiofemoral angle of 3° or more on immediate postoperative radiographs (day 0) that were non-weightbearing and had no stress applied. The functional outcomes were determined in the 17 patients identified as having lift-off who had been operated in the first year (2014) to ensure the follow-up was long enough. These patients were compared to 34 matched control patients who were operated the same year and chosen randomly among patients not having lift-off. The matching ratio was 2 controls to 1 case. Preoperative and surgical data were compiled from each patient's electronic medical record. Patients were evaluated at 4 years postoperatively using the subjective Oxford-48, objective HSS score, IKS score, overall patient satisfaction and stress radiographs of the knee. The cases of lift-off observed in 2014 (n=17) were paired with a control group of patients selected randomly during 2014. RESULTS: The frequency of the lift-off event was 63/906 or 7%. The frequency was consistent over the three years studied: 7.1% in 2014 (19/269), 6.2% in 2015 (22/354) and 7.8% in 2016 (22/283). There was no significant difference between the two groups (17 with lift-off and 34 without) in the sex, age, body mass index and coronal plane deformity (preoperative HKA angle). At a mean follow-up of 4 years (range 12-49 months), the knees with postoperative lift-off had more laxity (p=0.002), particularly laxity when varus stress was applied (p=0.009). There were no other significant differences in the outcomes. DISCUSSION: Immediate postoperative lift-off after total knee arthroplasty is not a rare event, with a 7% frequency in our study. While it reveals that laxity is present in the particular compartment, there is no evidence of functional consequences at 4 years' follow-up; however, a long-term assessment is required to verify this finding. LEVEL OF EVIDENCE: III - case-control study.

Debridement, antibiotics and implant retention for prosthetic joint infection: comparison of outcomes between total hip arthroplasty and hip resurfacing.

INTRODUCTION: The management of prosthetic joint infection (PJI) has been widely studied in the context of total hip arthroplasty (THA). However, the outcomes of debridement, antibiotics and implant retention (DAIR) for PJI have never been compared between hip resurfacing arthroplasty (HRA) and THA. This led us to carry out a retrospective case-control study comparing the surgical treatment of post-operative infections between HRA and THA to determine the infection remission rate and the medium-term functional outcomes. METHODS: This single-centre case-control study analysed 3056 HRA cases of which 13 patients had a PJI treated by DAIR. These patients were age-matched with 15 infected THA hips treated by DAIR and modular component exchange (controls). Their survival (no recurrence of the infection) was compared and factors that could affect the success of the DAIR were explored: sex, body mass index, age at surgery, presence of haematoma, type of bacteria present and antibiotic therapy. RESULTS: At a mean follow-up of five years (2-7), the infection control rate was significantly higher in the HRA group (100% [13/13]) than in the THA group (67% [10/15]) (p = 0.044). More patients in the THA group had undergone early DAIR (< 30 days) (73% [11/15]) than in the HRA group (54% [7/13]). There was no significant difference between the two groups in the ASA score, presence of comorbidities, body mass index and duration of the initial arthroplasty procedure. At the review, the Oxford-12 score of 17/60 (12-28) was better in the HRA group than the score of 25/60 (12-40) in the THA group (p = 0.004). CONCLUSION: DAIR, no matter the time frame, is a viable therapeutic option for infection control after HRA.

Influence of shelf acetabuloplasty on the outcomes of total hip arthroplasty in hips with dysplasia: a case-control study.

INTRODUCTION: Total hip arthroplasty (THA) in young adults, especially in those with hip dysplasia, is affected by wear and acetabular fixation problems. Shelf acetabuloplasty is performed to delay THA in patients with acetabular dysplasia. Thus, we conducted a retrospective, continuous case-control study at a single healthcare facility to analyze (1) the influence of prior shelf acetabuloplasty on the survival of a subsequent THA and (2) the functional outcomes. MATERIALS AND METHODS: We evaluated 105 patients (124 THA) who underwent THA due to hip dysplasia: 54 patients (61 THA) were included in the THA post-shelf acetabuloplasty group (case group) and 51 patients (63 THA) in the THA for dysplasia group (control group). RESULTS: At 15 years' follow-up, 89% of patients (95% CI: 84-91%) in the shelf group and 83% (95% CI: 81-90%) in the dysplasia group had not undergone surgical revision. This difference between groups was not statistically significant (p = 0.566). The functional outcomes were satisfactory in both groups; however, they were significantly better in the dysplasia group than in the shelf group based on the Merle d'Aubigne and Postel score (16.9 vs 16.0 min-max: 14-18 vs 3-18) (p = 0.01), Harris Hip score (90.0 vs 84.7, min-max: 62-100 vs 22-100) (p = 0.017), and the Oxford-12 (18/60 vs 21/60, min-max: 45-12 vs 51-12) (p = 0.04). CONCLUSION: Shelf acetabuloplasty before THA does not negatively affect THA survivorship. The functional outcomes appear to be better in the hips that did not undergo shelf acetabuloplasty, although the results were good in both groups.

French hip resurfacing registry: A study of 1650 cases.

BACKGROUND: Hip resurfacing has been the focus of many evaluations based on international registries but, to date, no prospective studies have evaluated this procedure in France. In 2015, the French Society for Orthopaedics and Traumatology (SoFCOT) and the French Hip and Knee Society concluded an agreement with the French Medicines Agency (ANSM) and French National Health Authority (HAS) to establish an exhaustive observational hip resurfacing registry. The primary objective of this study was to evaluate the hip resurfacing survival rate since the creation of the registry 5 years ago. The secondary objectives were to evaluate the clinical, functional, and radiological outcomes of hip resurfacing and to check the absence of specific complications related to this implant. HYPOTHESIS: The hypothesis was that the registry survival rate was below 0.5% per year. METHODS: Since 2015, data from all patients undergoing hip resurfacing were collected into a monitored database using the software suite OrthoWave. The following were collected for each patient: demographics, anthropometric characteristics, clinical parameters (Postel Merle d'Aubigné score, Harris Hip Score, Oxford Hip Score, and UCLA Activity Score), and radiological findings. Completeness of data collection was checked once a year. RESULTS: In total, 1650 hip resurfacings in 1506 patients (1409 males and 97 females) with a mean age of 50.7 years (range, 17-70 years) were included. Mean follow-up was 3.8 years (range, 2-4.8 years). Mean completeness of data recording was 98.2%. All clinical scores improved significantly. Hip revision was required for 7 (0.4%) complications including 4 femoral neck fractures, 1 aseptic lymphocyte-dominant vasculitis-associated lesion with a large joint effusion, 1 femoral component loosening, and 1 delayed sepsis requiring bipolar removal. At 5 years, the survival rate without hip revision for any cause was 99.6% (95% confidence interval, 99.3-100%). DISCUSSION: The short-term outcomes of patients in the French registry are encouraging in terms of complication and surgical revision rates. The near absence of complications related to metal-on-metal bearing surfaces demonstrates that the criteria used in France (at least 48mm head diameter, use of implants for which long-term data are available, and specific training of surgeons) ensure successful long-term outcomes. LEVEL OF EVIDENCE: II.

French Hip & Knee Society classification of short-stem hip prostheses: Inter- and intra-observer reproducibility.

INTRODUCTION: In total hip replacement (THR), a short stem theoretically provides more physiological force transfer to the proximal femur, conserves bone stock and facilitates minimally invasive surgery. On the other hand, such implants involve a learning curve and incur risk of malpositioning or fracture and of secondary mobilization. There are several types of short stem, and classification is needed. Classifications exist, but are based more on implant length than on anchorage zone, and most have not been tested for reproducibility. The French Hip & Knee Society (SFHG) developed a short-stem classification based on anchorage zone inside the femur. The objectives of the present study were: (1) to present the classification, (2) to apply it to the short-stem models available in France and those widely used worldwide, and (3) to assess reproducibility. HYPOTHESIS: The SFHG short-stem classification enables reproducible comparison. MATERIAL AND METHOD: A short-stem classification according to anchorage zone was drawn up by an expert group. The stems and the classification were presented to 12 surgeons performing THR, who classified the stems according to the classification; a retest was performed 2 months later. RESULTS: The classification is based on femoral stem anchorage site, in 5 types: type 1, cephalic; type 2, isolated cervical; type 3, Calcar femorale; type 4, metaphyseal; and type 5, conventional metaphyseal-diaphyseal, with shortened stems. Inter-observer reproducibility was 92.7% [95%CI: 91.7%-93.6%], with kappa 0.785 [95%CI: 0.755-0.814], and Lin test-rest concordance correlation coefficient 0.852 [95%CI: 0.836-0.869]. Intra-observer reproducibility was 94.0% [95%CI: 91.9%-96.1%], with kappa 0.820 [95%CI: 0.759-0.882], and Lin test-retest concordance correlation coefficient 0.820 [95%CI: 0.792-0.849]. DISCUSSION: This new classification enables femoral implants to be reproducibly compared according to anchorage zone. LEVEL OF EVIDENCE: IV; retrospective study without control group.

Mapping and Crosswalk of the Oxford Hip Score and Different Versions of the Hip Disability and Osteoarthritis Outcome Score.

BACKGROUND: Patient-reported outcome measures such as the Oxford-12 Hip Score and Hip Disability and Osteoarthritis Outcome Score (HOOS) are used in daily orthopaedic practice to evaluate patients. Because different studies use different scores, it would be important to build conversion tables between scores (crosswalk) to compare the results of one study with those of another study. Various mapping methods can be used to develop crosswalk tables that convert Oxford-12 scores to the HOOS (and its derivatives, including the HOOS physical function short form, HOOS joint replacement, and HOOS-12) and vice versa. Although prior studies have investigated this issue, they are limited to short forms of the HOOS score. Consequently, they cannot be applied to hip preservation surgery and do not include quality-of-life items, whereas the Oxford-12 Hip Score is used for all hip evaluations. QUESTIONS/PURPOSES: We prospectively studied the Oxford-12 and HOOS and its derivatives to (1) determine which version of the HOOS has the best mapping with the Oxford-12, (2) define the most-appropriate mapping method using selected indicators, and (3) generate crosswalk tables between these two patient-reported outcome measures. METHODS: The study enrolled 500 adult patients before primary THA (59% men [294 of 500 patients]) with hip osteoarthritis or avascular necrosis of the femoral head who completed the HOOS and Oxford-12. Patients were recruited from January 2018 to September 2019 in a tertiary-care university hospital, and we included all primary THAs in patients older than 18 years with a BMI lower than 35 kg/m2 and greater than 18 kg/m2. After a minimum of 6 months of follow-up, 39% (195 of 500) of the patients were assessed using the same tools. To determine which version of the HOOS mapped best to the Oxford-12 and what the most-appropriate mapping method was, we used preoperative data from all 500 patients. Because there is no consensus on the method to establish crosswalk, various mapping methods (linear regression, tobit regression, and quantile regression) and equating methods (linear equating and equipercentile method) were applied along with cross-validation to determine which method was the most suitable and which form of the HOOS provided the best result according to different criteria (mean absolute error, r2, and Kolmogorov-Smirnov distance).To generate crosswalk tables, we created a conversion table (between the Oxford-12 and the HOOS form that was chosen after answering our first research question and the method chosen after answering our second question) using preoperative and postoperative data (n = 695). This table was meant to be simple to use and allows easy conversions from one scoring system to another. RESULTS: The Oxford-12 and HOOS were strongly correlated (Pearson correlation coefficient range 0.586-0.842) for the HOOS subcategories and HOOS physical function, HOOS joint replacement, and HOOS-12. The correlation between the HOOS-12 and Oxford-12 was the strongest (r = 0.825). According to the three different criteria and five methods, the HOOS-12 was the best suited for mapping. The goal was to minimize the mean absolute error (perfect model = 0), have a Kolmogorov-Smirnov distance as close as possible to 0, and have the r2 as close as possible to 1. Regarding the most-suitable method for the crosswalk mapping (research question 2), the five methods generated similar results for the r2 (range 0.63-0.67) and mean absolute error (range 6-6.2). For the Kolmogorov-Smirnov distance, the equipercentile method was the best (Kolmogorov-Smirnov distance 0.04), with distance reduced by 43% relative to the regression methods (Kolmogorov-Smirnov distance 0.07). A graphical comparison of the predicted and observed scores showed that the equipercentile method provided perfect superposition of predicted and observed values after mapping. Finally, crosswalk tables were produced between the HOOS-12 and Oxford-12. CONCLUSION: The HOOS-12 is the most complete and suitable form of the HOOS for mapping with the Oxford-12, while the equipercentile method is the most suitable for predicting values after mapping. This study provides clinicians with a reliable tool to crosswalk between these scores not only for joint arthroplasty but also for all types of hip surgeries while also assessing quality of life. Our findings should be confirmed in additional studies. CLINICAL RELEVANCE: The resulting crosswalk tables can be used in meta-analyses, systematic reviews, or clinical practice to compare clinical studies that did not include both outcome scores. In addition, with these tools, the clinician can collect only one score while still being able to compare his or her results with those obtained in other databases and registries, and to add his or her results to other databases and joint registries.

Does the alpha-defensin lateral flow test conserve its diagnostic properties in a larger population of chronic complex periprosthetic infections? Enlargement to 112 tests, from 42 tests in a preliminary study, in a reference center.

BACKGROUND: Diagnosis of periprosthetic infection (PPI) is crucial for management of bone and joint infection. The preoperative gold-standard is joint aspiration, providing results after 2-14 days' culture, with non-negligible false negative rates due to the fragility of certain micro-organisms and/or prior antibiotic treatment. The Synovasure™ alpha-defensin lateral flow test (Zimmer, Warsaw, IN, USA) contributes within minutes to joint fluid diagnosis of almost all infectious agents, including in case of concomitant antibiotic therapy. Validity remains controversial, notably in complex microbiological situations: multi-operated patients, diagnostic doubt despite iterative sterile culture, long-course antibiotic therapy. We extended a prospective study reported in 2018, to determine whether the test maintained diagnostic value in a larger population, assessing 1) negative (NPV) and positive (PPV) predictive value, and 2) sensitivity and specificity. HYPOTHESIS: Synovasure™ maintains NPV above 95% in a broader population of microbiologically complex suspected PPI. MATERIAL AND METHODS: Synovasure™'s performance was assessed between October 2015 and October 2019 in 106 patients (112 tests) in complex diagnostic situations: 37 discordant cultures (discordant findings between 2 samples), 65 cases with clinically or biologically suspected infection but iterative sterile culture, 10 emergencies (requiring surgery, precluding antibiotic window, or mechanical failure in suspected infection), including 5 with ongoing antibiotic therapy for infection in another organ. Six tests were repeated in the same patient and same joint at >6 months' interval for strong clinical suspicion of infection. The main endpoint was the MSIS score (MusculoSkeletal Infection Society, 2018). RESULTS: NPV was 98.8%, PPV 72.4%, sensitivity 95.5% and specificity 91%. Prevalence of infection was 19.6%. Only 1 of the 22 infected patients had negative Synovasure™ tests, compared to 81 of the 84 non-infected patients. CONCLUSION: Synovasure™ is a reliable novel diagnostic test, contributing mainly to ruling out infection thanks to its strong NPV. The cost imposes sparing use, but medico-economic assessment would be worthwhile. LEVEL OF EVIDENCE: III; prospective of diagnostic performance.

Can the minimal clinically important difference be determined in a French-speaking population with primary hip replacement using one PROM item and the Anchor strategy?

BACKGROUND: The impact of surgery on the patient is classically assessed on pre- and post-treatment scores. However, it is increasingly recommended to rank these results according to the minimal clinically important difference (MCID), using either the data distribution method or the anchor method, latter consisting in an extra question specifically targeting the patient's improvement. MCIDs vary between populations and, to the best of our knowledge; there have been no investigations in France regarding this in the context of total hip replacement (THR). Therefore, we conducted a prospective study in a population with THR to determine: 1) whether MCID scores in France were comparable to those reported in the data from the international literature; 2) whether a general item taken from a different score could serve as an anchor; and 3) whether an item from the actual questionnaire itself could serve as an anchor. HYPOTHESIS: When pre- and post-treatment scores are available, an item from the questionnaire itself can serve as an anchor for MCID. MATERIAL AND METHODS: In a prospective observational study, 123 primary THR patients (69 male, 54 female), out of 150 initially included, completed the 5 domains of the HOOS hip disability and osteoarthritis outcome score and the Oxford-12 questionnaire, preoperatively and at 6-12 months. The MCID was calculated via the distribution-based and the anchor-based methods. Two Oxford items (questions 1 and 2) and 2 HOOS items (questions S1 and Q4) were used as anchors, as well as a supplementary question on improvement and the Forgotten Joint Score (FJS). RESULTS: At a mean 10.12±1.2 months' follow-up [range, 6.5-11.9 months], the Oxford-12 score increased from 19±8 [3-35] to 40±10 [8-48] (p<0.001), all HOOS components demonstrated improvement, and the FJS at the final follow-up was 71±29 [0-100]. The general items (Oxford question 1 and HOOS question Q4) were more discriminating than the joint-specific items (Oxford question 2 and HOOS question S1). Based on results from the 3 anchors (improvement rated 1 to 5, Oxford question 1 and HOOS question Q4), 3 to 5 patients showed deterioration, 5 to 6 were unchanged, 30 to 40 were slightly improved, and 73 to 80 were improved by THR. The mean MCID on both distribution and anchor methods was 9 [5.5-12] for Oxford-12, 20 [12-27] for HOOS symptoms, 26 [10-36] for HOOS pain, 22 [11.5-28] for HOOS function, 26 [13-34] for HOOS sport and 22 [14-28] for HOOS quality of life. DISCUSSION: The MCID for the Oxford-12 and HOOS scores in a French population was comparable to data from the past literature. Using a score item as an anchor to define improvement is possible, but only if a general item is used. LEVEL OF EVIDENCE: IV; prospective study without control group. CLINICAL TRIALS REGISTRATION: NCT04057651.

Does change in language change the properties of a shortened score previously validated in its complete version? Validation of the French versions of the HOOS-12 and KOOS-12 scores in primary knee and hip arthroplasties.

BACKGROUND: The HOOS and KOOS scoring questionnaires comprise respectively 40 and 42 items; a shorter 12-item version was recently developed, but remains to be validated in a French-speaking population. We therefore conducted a prospective study: 1) to determine whether the new 12-item versions in French are equivalent to the longer HOOS and KOOS versions, and 2) to validate the French-language HOOS-12 and KOOS-12 patient-reported outcome measures in a population of primary total hip and knee arthroplasty: validity, reliability, and responsiveness. HYPOTHESIS: The change in language in a score already validated in its long version does not alter its properties in the short version. MATERIAL AND METHODS: One hundred patients (59 males, 41 females) undergoing primary total hip arthroplasty and 100 patients (43 males, 57 females) undergoing primary total knee arthroplasty were prospectively included. They filled out the original HOOS or KOOS questionnaires, their simplified versions (PS: Physical function Short form; JR: Joint Replacement) and the short HOOS-12 and KOOS-12 versions, and also the Oxford-12 score assessing the affected joint, preoperatively, then at 6-12 months. RESULTS: The 100% response rate confirmed ease of use. There were no redundant items. There were strong correlations between the 12-item and longer versions (>0.9). The HOOS-12 and KOOS-12 scores were reliable and valid: 1) there were no ceiling or floor effects for pre- or postoperative KOOS-12 scores, although a ceiling effect was found for HOOS-12 postoperatively (20% of patients having maximum scores of 100); 2) internal consistency was confirmed, with Cronbach alpha>0.8; 3) external consistency between Oxford-12 and HOOS-12/KOOS-12 was excellent, with Pearson correlation coefficient>0.8. Sensitivity to pre-/postoperative change was confirmed, with effect size>0.8. DISCUSSION: The present study confirmed the usefulness of this new 12-item form for HOOS and KOOS. Properties were identical between the French- and English-language versions, authorising everyday use of these simpler versions. LEVEL OF EVIDENCE: IV; prospective study without control group.

Hip arthroscopy in France: An epidemiological study of postoperative care and outcomes involving 3699 patients.

BACKGROUND: Hip arthroscopy is a surgical procedure that is becoming more and more prevalent in France. Even though indications are now well-established little is still known about patient outcomes. Therefore, the purpose of our retrospective study was to: (1) describe the circumstances in which hip arthroscopies are being performed; (2) study arthroscopy and arthroplasty reoperation rates; (3) assess the incidence of readmissions for complications. HYPOTHESIS: Hip arthroscopy in France produced similar results to those observed in other countries. MATERIALS AND METHODS: We conducted a cohort study from January 2008 to December 2014 in the French population using the national hospital discharge database called "Programme de médicalisation des systèmes d'information (PMSI)." We included all admissions that had a hip arthroscopy code and analyzed readmissions for conversion to hip arthroplasty, revision hip arthroscopy and complications (without being able to provide detailed descriptions). Risk factors associated with conversion, revision and readmission for complications were studied after performing a population analysis. RESULTS: A total of 3,699 patients were included over a period of seven years. The mean age was 40 years, with women being significantly older (mean age of 43 years) than men (38 years) (p<0.05). The number of procedures increased from 240 in 2008 to 702 in 2014. Synovectomies (67.9%; 2514/3699) and surgical bone procedures (acetabuloplasty or femoroplasty) (47.3%; 1751/3699) were the main procedures performed during the primary arthroscopy. In total, 410 patients underwent a conversion to arthroplasty, 231 patients had a revision arthroscopy, and 126 patients suffered a complication. Five years after the index procedure, the conversion rate was 16.3%, revision rate was 8.2%, and readmission rate for a postoperative complication was 5%. The main risk factor associated with conversions was [Hazard ratio (HR) and 95% Confidence Index (CI)] an age between 40 and 79 years during the first arthroscopy [3.04 (2.40; 3.87) compared with the reference class of 25-39 years]. Patients between ages 16 to 24 years during the first arthroscopy (0.35 [0.20; 0.61] compared with the reference class of 25-39 years) had a decreased risk of conversion (HR and 95% CI). The main risk factors associated with revisions were: synovectomies [1.90 (1.34; 2.70)] and surgical bone procedures on the femoral neck and/or the acetabulum [1.82 (1.36; 2.4)]. The risk factor associated with complication-related readmissions was an age greater than 40 years [2.23 (1.43; 3.49)]. CONCLUSION: Unlike the international literature, our study population was largely male. The rates of revision (8.2% after five years) and conversion to arthroplasty (16.3% after five years) were relatively low and comparable to the different international studies. This procedure, which is not widely performed, is growing in popularity, has low morbidity and remains an interesting approach given the revision and conversion rates after five years. The implementation of specific coding for arthroscopic hip procedures and the pathologies to be treated seems warranted. LEVEL OF EVIDENCE: IV; descriptive epidemiological study.