Plantar compartment block for hallux valgus surgery: a proof-of-concept anatomic and clinical study.

BACKGROUND: Hallux valgus surgery is associated with moderate to severe postoperative pain. We hypothesized that a plantar compartment block may be a good technique for postoperative analgesia. We describe an anatomic approach to ultrasound-guided plantar compartment block and assess the clinical efficacy of the block for outpatient surgery. METHODS: The anatomic study was aimed to describe the plantar compartment, using both dissection methods and imaging, and to define a volume of local anesthetic. Patients scheduled for hallux valgus surgery with a popliteal sciatic nerve block, and combined plantar compartment and peroneal blocks were included in the clinical study. Data on attaining the criteria for rapid exit from the outpatient center, duration of sensory and analgesic block, visual analog scale (VAS) values for postoperative pain at rest and during movement, and the consumption of morphine as rescue analgesia were recorded. RESULTS: Plane-by-plane dissections and cross-sections were done in five cadaveric lower limbs. The medial calcaneal nerve divides into medial plantar and lateral plantar nerves in the upper part of the plantar compartment. These nerves were surrounded by 5 mL of colored gelatin, and 10 mL of injectates dye spread to the medial calcaneal branches. Thirty patients (26 women) were included in the clinical study. There were no failures of surgical block. Ninety per cent of patients successfully passed functional testing for ambulatory exit from the center within 5 hours (25th-75th centiles, 3.8-5.5 hours). The median duration of plantar compartment sensory block was 17.3 hours (10.5-21.5 hours), and the first request for rescue analgesic was 11.75 hours (10.5-23 hours) after surgery. The median VAS score for maximum pain reported within the 48-hour period was 2 (1-6). Twelve patients received 2.5 mg (0-5 mg) of morphine on day 1. Patients were highly satisfied and no adverse events were noted. CONCLUSIONS: This anatomic description of the ultrasound-guided plantar compartment block reported the injection area to target the medial and lateral plantar nerves with 5 mL of local anesthetic. Normal walking without assistance is attained rapidly with this regional anesthesia technique, and the time to request postoperative analgesia after hallux valgus surgery is long. TRIAL REGISTRATION NUMBER: NCT03815422.

Finite element analysis in the optimization of posterior-stabilized total knee arthroplasty.

Posterior-stabilized total knee arthroplasty (PS-TKA) is associated with high rates of satisfaction and functional recovery. This is notably attributed to implant optimization in terms of design, choice of materials, positioning and understanding of biomechanics. Finite elements analysis (FEA) is an assessment technique that contributed to this optimization by ensuring mechanical results based on numerical simulation. By close teamwork between surgeons, researchers and engineers, FEA enabled testing of certain clinical impressions. However, the methodological features of the technique led to wide variations in the presentation and interpretation of results, requiring a certain understanding of numerical and biomechanical fields by the orthopedic community. The present study provides an up-to-date review, aiming to address the following questions: what are the principles of FEA? What is the role of FEA in studying PS design in TKA? What are the key elements in the literature for understanding the role of FEA in PS-TKA? What is the contribution of FEA for understanding of tibiofemoral and patellofemoral biomechanical behavior? What are the limitations and perspectives of digital simulation and FEA in routine practice, with a particular emphasis on the "digital twin" concept? LEVEL OF EVIDENCE: V, expert opinion.

Midfoot Tarsectomy in Cavovarus: Why PSI Makes a Difference?

The cavovarus foot is a complex deformity that can be treated using multiple surgical procedures, ranging from soft tissue surgery to triple arthrodesis. Among these options, anterior midfoot tarsectomy is a three-dimensional closed-wedge osteotomy, traditionally performed slowly and progressively in a blind fashion, and remaining a challenge for unexperimented surgeons with variable outcomes. As such, we investigated and discussed the use of patient-specific cutting guides (PSCGs) in computer-assisted anterior midfoot tarsectomy in terms of accuracy, reproducibility, and safety.

Contemporary mortality rate and outcomes in nonagenarians after aseptic revision hip and knee arthroplasty.

Aims: Nonagenarians (aged 90 to 99 years) have experienced the fastest percent decile population growth in the USA recently, with a consequent increase in the prevalence of nonagenarians living with joint arthroplasties. As such, the number of revision total hip arthroplasties (THAs) and total knee arthroplasties (TKAs) in nonagenarians is expected to increase. We aimed to determine the mortality rate, implant survivorship, and complications of nonagenarians undergoing aseptic revision THAs and revision TKAs. Methods: Our institutional total joint registry was used to identify 96 nonagenarians who underwent 97 aseptic revisions (78 hips and 19 knees) between 1997 and 2018. The most common indications were aseptic loosening and periprosthetic fracture for both revision THAs and revision TKAs. Mean age at revision was 92 years (90 to 98), mean BMI was 27 kg/m2 (16 to 47), and 67% (n = 65) were female. Mean time between primary and revision was 18 years (SD 9). Kaplan-Meier survival was used for patient mortality, and compared to age- and sex-matched control populations. Reoperation risk was assessed using cumulative incidence with death as a competing risk. Mean follow-up was five years. Results: Mortality rates were 9%, 18%, 26%, and 62% at 90 days, one year, two years, and five years, respectively, but similar to control populations. There were 43 surgical complications and five reoperations, resulting in a cumulative incidence of reoperation of 4% at five years. Medical complications were common, with a cumulative incidence of 65% at 90 days. Revisions for periprosthetic fractures were associated with higher mortality and higher 90-day risk of medical complications compared to revisions for aseptic loosening. Conclusion: Contemporary revision THAs and TKAs appeared to be relatively safe in selected nonagenarians managed with multidisciplinary teams. Cause of revision affected morbidity and mortality risks. While early medical and surgical complications were frequent, they seldom resulted in reoperation.

Extensively Porous-Coated Stems Demonstrate Excellent Long-Term Survivorship in Revision Total Hip Arthroplasty.

BACKGROUND: Extensively porous-coated cylindrical stems have demonstrated excellent results in revision total hip arthroplasties (THAs). However, most studies are midterm follow-ups and of modest cohort size. This study aimed to evaluate long-term outcomes of a large series of extensively porous-coated stems. METHODS: From 1992 to 2003, 925 extensively porous-coated stems were utilized in revision THAs at a single institution. The mean age was 65 years, and 57% of patients were males. Harris hip scores were calculated, and clinical outcomes were assessed. Radiographic assessment for stem fixation was categorized as either in-grown, fibrous stable, or loose according to Engh criteria. Risk analysis used Cox proportional hazard method. The mean follow-up was 13 years. RESULTS: Mean Harris hip scores improved from 56 to 80 at the last follow-up (P < .001). Fifty-three femoral stems (5%) were rerevised: 26 for aseptic loosening, 11 for stem fractures, 8 for infection, 5 for periprosthetic femoral fractures, and 3 for dislocation. Cumulative incidence of aseptic femoral loosening and femoral rerevision for any reason were 3% and 6.4% at 20 years, respectively. Nine of eleven stem fractures occurred with 10.5-13.5 mm diameters (mean 6 years). Radiographic review of unrevized stems demonstrated 94% bone-ingrown. Demographics, femoral bone loss, stem diameter, and length were not predictors of femoral rerevision. CONCLUSION: In this large series of revision THAs using a single extensively porous-coated stem design, the cumulative incidence of rerevision for aseptic femoral loosening was 3% at 20 years. These data confirm the durability of this stem in femoral revision, providing a long-term benchmark for newer uncemented revision stems. LEVEL OF EVIDENCE: Level IV, retrospective study.

Combined structural allograft and tantalum cone to manage segmental metaphyseal tibial bone defect in revision knee arthroplasty.

Tibial bone defect remains a challenge in revision knee arthroplasty. The present innovative technique combines structural allograft and tantalum metaphyseal cone for treatment of AORI stage 2A and 2B (uncontained peripheral metaphyseal) tibial defect. The aim is to reconstitute bone stock and enhance allograft osseointegration, while limiting stress to the allograft by implanting the metaphyseal cone through the allograft and the original bone. LEVEL OF EVIDENCE: V (expert opinion).

Knee immobilization reproduces key arthrofibrotic phenotypes in mice.

AIMS: As has been shown in larger animal models, knee immobilization can lead to arthrofibrotic phenotypes. Our study included 168 C57BL/6J female mice, with 24 serving as controls, and 144 undergoing a knee procedure to induce a contracture without osteoarthritis (OA). METHODS: Experimental knees were immobilized for either four weeks (72 mice) or eight weeks (72 mice), followed by a remobilization period of zero weeks (24 mice), two weeks (24 mice), or four weeks (24 mice) after suture removal. Half of the experimental knees also received an intra-articular injury. Biomechanical data were collected to measure passive extension angle (PEA). Histological data measuring area and thickness of posterior and anterior knee capsules were collected from knee sections. RESULTS: Experimental knees immobilized for four weeks demonstrated mean PEAs of 141°, 72°, and 79° after zero, two, and four weeks of remobilization (n = 6 per group), respectively. Experimental knees demonstrated reduced PEAs after two weeks (p < 0.001) and four weeks (p < 0.0001) of remobilization compared to controls. Following eight weeks of immobilization, experimental knees exhibited mean PEAs of 82°, 73°, and 72° after zero, two, and four weeks of remobilization, respectively. Histological analysis demonstrated no cartilage degeneration. Similar trends in biomechanical and histological properties were observed when intra-articular violation was introduced. CONCLUSION: This study established a novel mouse model of robust knee contracture without evidence of OA. This was appreciated consistently after eight weeks of immobilization and was irrespective of length of remobilization. As such, this arthrofibrotic model provides opportunities to investigate molecular pathways and therapeutic strategies.Cite this article: Bone Joint Res 2023;12(1):58-71.

Influence of kinematics of the lumbopelvic complex in hip arthroplasty dislocation: from assessment to recommendations.

INTRODUCTION: In total hip arthroplasty (THA), misplacement of the implant can provide instability. Adequate orientation of the acetabular cup is a challenge due to variations in inter-individual anatomy and kinematics of the pelvis in everyday life. The aim of this study was to characterize the kinematic factors influencing the risk of dislocation in order to give recommendations for optimal placement of the cup. We hypothesized that the lack of pelvic adaptation would influence the risk of prosthetic instability and motivate adapted. MATERIALS AND METHODS: Eighty patients with primary unilateral THA were included in a matched case-control study. Seventy-four patients were divided into two groups: group 1 (G1) consisting of patients with postoperative THA dislocation (37 patients) and group 2 (G2), without episodes of dislocation within two years postoperatively (37 patients). In both groups, spino-pelvic parameters and cup orientation were measured in standing and sitting positions with EOS® X-ray imaging and compared to each other between 12 and 24 months post-operatively. RESULTS: No significant difference between the two groups was found for static parameters. In a sitting position, a lack of pelvic retroversion with a significant lower variation in sacral slope was observed in group 1 (8.0° ± 9.3 for G1 versus 14.7° ± 6.2 for G2, p < 0.01). Twenty-two (59%) patients with THA instability had sacral slope variations of less than 10° versus eight (21% of patients) with stable THA (p < 0.01). Cup orientation in the Lewinnek safe zone was not significantly different (59% vs 67%, p = 0.62), and the spino-pelvic parameters and cup orientation measured did not change between the standing and sitting positions. However, only 14 (37%) cups in G1 were in the functional safe zone versus 24 (67%) in G2 (p = 0.03). CONCLUSION: Static parameters of the sagittal spinopelvic balance have a low predictive value for prosthetic instability. Dynamic analysis is essential. Kinematic parameters must be taken into account in determining the ideal position of the cup or stem. Stiffness with locked standing or sitting pelvis must be integrated in order to determine a personalized safe zone. LEVEL OF EVIDENCE: Level III (matched case-control study).

Validation of a novel finite-element model for evaluating patellofemoral forces and stress during squatting after posterior-stabilized total knee arthroplasty.

INTRODUCTION: Several studies have documented the relationship between patellofemoral pain and patient dissatisfaction after total knee arthroplasty (TKA). However, few computer simulations have been designed to evaluate the patellofemoral joint during flexion. The aim of this study was to validate a new computational simulation, driven by forces and moments, and to analyze patellofemoral reaction forces and stress under squat loading conditions after TKA implantation. HYPOTHESIS: This computational simulation of a squat using a model driven by forces and moments is comparable to in vitro and in silico data from the literature. MATERIAL AND METHODS: We developed a finite element model of the lower limb after implantation of a fixed-bearing posterior-stabilized TKA. To simulate squat loading conditions when standing on both legs, an initial load of 130N was applied to the center of the femoral head. Quadriceps force, patellofemoral contact force and Von Mises stress on the patellar implant, tibiofemoral contact forces and pressure on the tibial insert, and post-cam contact force were evaluated from 0° to 100° of knee flexion. RESULTS: Quadriceps force increased during flexion, up to 6 times the applied load. Von Mises stress on patellar implant increased up to 16MPa at 100° flexion. Tibiofemoral contact forces increased up to 415 N medially and 339 N laterally, with 64% distributed medially on the tibial insert. Post-cam contact started slightly before 70° of flexion. DISCUSSION: In this simulation, tibiofemoral, patellofemoral and post-cam contact forces, and pressure distribution on the tibial insert were consistent with various published studies. This agreement suggests that computational simulation driven by forces and moments can reproduce squat loading conditions during knee flexion after TKA, without experimental kinematic data used to drive the simulation. CONCLUSION: This study represents an initial step towards validating tibiofemoral and patellofemoral mechanical behavior under squat conditions, from this computational simulation driven by forces and moments. This model will help us better understand the influence of various implantation techniques on patellofemoral forces and stress during flexion. LEVEL OF EVIDENCE: IV, biomechanical computational study.

Three-dimensional biometrics using weight-bearing imaging shows relationship between knee and hindfoot axial alignment.

BACKGROUND: Existence of a relationship between knee and hindfoot alignments is commonly accepted, but not clearly proven. While studied in the coronal plane using 2D imaging, axial alignment has not been studied yet, likely requiring 3D measurements. We aimed to investigate how knee and hindfoot rotational alignments are related using 3D biometrics and modern 3D weight-bearing technologies. HYPOTHESIS: Hindfoot alignment is correlated with femoral and tibial torsions. PATIENTS AND METHODS: All patients who underwent both weight-bearing CT (WBCT) and low dose biplanar radiographs (LDBR) were selected in this retrospective observational study, resulting in a cohort of 157 lower limbs from 99 patients. Patients' pathologies were stratified in subgroups and those with a history of trauma or surgery affecting lower limb alignment were excluded. Foot Ankle Offset was calculated from WBCT; femoral and tibial torsions and coronal alignment were calculated from LDBR, respectively. RESULTS: Overall, mean Foot Ankle Offset was 1.56% (SD 7.4), mean femoral anteversion was 15.6° (SD 9.5), and mean external tibial torsion was 32.6° (SD 7.6). Moderate negative correlation between Tibial Torsion and Foot Ankle Offset was found in the whole series (rho=-0.23, p=0.003) and for non-pathologic patients (rho=-0.27, p=0.01). Linear models to estimate Tibial Torsion with Foot Ankle Offset and conversely were found, with a low adjusted R2 (3%

Procedural simulation training in orthopaedics and traumatology: Nationwide survey among surgeon educators and residents in France.

BACKGROUND: Simulation is among the tools used in France to train residents specialising in orthopaedic and trauma surgery (OTS). However, implementing simulation-based training (SBT) is complex and poorly reported. The objective of this study was to describe the use of simulation for OTS training in France. HYPOTHESIS: Nationwide, SBT is not used to its full capacity for teaching OTS in France, and differences in opinions about SBT may exist between surgeon educators and residents. STUDY DESIGN: Nationwide questionnaire survey in France. MATERIALS AND METHODS: We built two specific self-questionnaires then e-mailed them between December 2020 and February 2021 to the surgeon educators who were members of the national university council and to the residents specialising in OTS during the current academic year. The questions were about the 2018-2019 academic year, before the COVID-19 pandemic. Two classes of residents who were still medical students during this period were not included, leaving three classes for the analysis. RESULTS: The participation rates were 57% (67/117) for the educators and 24% (87/369) for the three classes of residents. Of the 67 educators, 47 (70%) reported being involved in SBT and identified the university (70%) and industry (53%) as the main funders of this teaching modality. The educators indicated that the mean number of SBT laboratories in their region was 1.4±0.9 (range, 0-4). The main types of simulators were saw bones (77%); cadavers (85%); and commercial simulators (74%), notably for the knee (87%) and shoulder (78%). The educators estimated that they had achieved a mean of 33%±23% (range, 0%-100%) of the teaching objectives set out in the OTS curriculum and that the main obstacles were insufficient funding (81%) and lack of time (67%). Only 21% of educators reported conducting SBT research. The residents reported that they accessed SBT via the OTS teaching module (28/87, 32%), local university degrees (23/87, 26%), their hospital department (17/87, 18%), or the industry (15/87, 17%); 25/87 (29%) had never received SBT. On a 0-10 scale (0, completely disagrees; 10, completely agrees), the mean score for SBT effectiveness was 8.6±2.1 for residents and 7.1±3.0 for educators (p<0.001); the corresponding values for the quality of SBT integration in the region were 1.5±1.8 and 3.8±2.6, respectively (p<0.001). CONCLUSION: SBT is not yet used to its full potential for teaching OTS in France. Insufficient funding and lack of time were identified by the educators as the main obstacles to greater use of SBT. Both the residents and the educators felt that SBT mightbe beneficial for training. LEVEL OF EVIDENCE: IV, nationwide survey.

Are modern knee outcomes scores appropriate for evaluating anterior knee pain and symptoms after total knee arthroplasty?

BACKGROUND: Up to 45% of patients who undergo primary total knee arthroplasty (TKA) with contemporary implants have residual anterior knee pain. While a specific evaluation of anterior knee symptoms is mandatory, little is known about the capability of patellofemoral scores to be used individually. This study aimed to assess the distribution of patellofemoral scores after TKA from a uniform cohort and to investigate their external validity and ability to detect anterior knee symptoms using floor and ceiling effects. HYPOTHESIS: Patellofemoral scores have high construct validity and fewer floor/ceiling effects than general knee scores. METHODS: We prospectively included 113 consecutive patients who underwent primary TKA for primary osteoarthritis at a single University Hospital. Clinical outcomes included patellofemoral scores (HSS Patella, Kujala and Lille scores) and general knee scores (KOOS and new KSS) at 1-year follow-up. The floor and ceiling effects were considered as significant when greater than 15%. These were determined for each score individually and for composite scores (combination of patellofemoral scores and new KSS). The construct validity of each score and their ability to detect anterior knee pain was evaluated. RESULTS: Patellofemoral scores showed no floor effect but a significant ceiling effect (from 25% to 65%). This ceiling effect decreased when composite scores were used. The convergent validity test showed strong correlation between patellofemoral scores (from 0.741 to 0.819, p<0.00001) and a better ability to discriminate anterior knee pain than the general knee scores. CONCLUSIONS: Patellofemoral scores showed no floor effect and a very good construct validity for anterior knee pain after TKA. However, studies aiming to monitor anterior knee symptoms after TKA should combine scoring systems to included patellofemoral-related items rather than use patellofemoral scores alone due their ceiling effects. LEVEL OF EVIDENCE: III; prospective study.

Influence of residual anterior laxity on functional outcomes after anterior cruciate ligament reconstruction.

INTRODUCTION: Residual laxity can persist after anterior cruciate ligament (ACL) reconstruction. This increased anterior translation can be measured with a knee arthrometer. Nevertheless, the measurement parameters and functional impact of this residual laxity are not well understood. The aims of this study were to (1) evaluate the effect of applying loads of 134N, 200N and 250N on the measured residual laxity after ACL reconstruction and (2) evaluate the prognostic ability of the various measurement parameters on the functional outcomes. HYPOTHESIS: After ACL reconstruction, the functional outcomes will be correlated to the postoperative residual laxity. METHODS: We did a prospective study of 61 recreational athletes who underwent surgical reconstruction of their ACL with the Kenneth-Jones technique between 2016 and 2019. The mean age of these patients was 27±7 years, and most were men (75%). The side-to-side difference in laxity was measured pre- and postoperatively using the GNRB® arthrometer at three load levels: 134N, 200N and 250N. The functional outcomes were determined based on the return to sports and the KOOS, IKDC and ARPEGE scores. The mean follow-up was 30±10 months. RESULTS: Half the patients had returned to sport at their pre-injury levels, while 25% had returned to a lower level and 25% had stopped doing any physical activity. At 134N, a 1-mm increase in side-to-side difference was associated with a 2-fold higher risk of not returning to sports (OR 2; 95% CI 1.22-3.23; p<0.01). At 200N, a 1-mm increase in side-to-side difference was associated with a 50% higher probability of having a poor/fair ARPEGE score (OR 1.5; 95% CI 1.05-2.02; p=0.02). At 200N, a 4-mm side-to-side difference was the prognostic threshold for failure to return to sports with a positive predictive value of 86% and specificity of 98%. CONCLUSIONS: This case series found a strong correlation between residual laxity and the functional outcomes after ACL reconstruction. A threshold of 4mm residual laxity evaluated on the GNRB® at 200N was predictive of adverse outcomes and failure to return to sports in our population of recreational athletes. LEVEL OF EVIDENCE: IV, retrospective study.

Survivorship of 4,748 Contemporary Total Ankle Replacements from the French Discharge Records Database.

BACKGROUND: Studies of survivorship of primary total ankle replacements (TARs) beyond 5 years have shown varying results among early and modern designs. National cohorts give valuable insights about TAR outcomes, revision risk factors, and specific designs. The purpose of this study was to investigate implant survivorship and risk factors for revision of contemporary TARs using our national database. METHODS: This observational study included patients identified in the national PMSI (Programme médicalisé des systèmes d'information) database as having undergone TAR from 2010 to 2019. Demographics, discharge data, concomitant procedures, and type of implant were extracted. Kaplan-Meier estimations were performed to determine time to revision using metal component revision for implant failure and revision for deep infection as end points. Weighted Cox models were used for risk factor analysis, including risks of early revision (within the first 2 years). The adjusted hazard ratios (HRadj) were reported with 95% confidence intervals. RESULTS: A cohort of 4,748 patients was extracted. The mean age at surgery was 63 years; 43% of the patients were female. The mean follow-up was 5 years (range, 1 to 10 years). Revisions were noted in 817 cases (17%), including 734 with metal component revision and 83 with revision due to deep infection. The 1-year, 2-year, 5-year, and 10-year survivorship free of metal component revision was 95%, 90%, 84%, and 78%, respectively. Younger age, implants derived from second-generation designs, and an institutional volume of ≤10 TARs per year were found to be independent predictors of revision for any cause. In addition to the above factors (except for implant generation), male sex and concomitant osteotomies and/or fusion were found to be significant predictors for any early revision. CONCLUSIONS: The 10-year survivorship free of metal component revision after TAR was 78%, which was consistent with other national registries. Revisions were associated with young age, associated arthritis or deformities requiring concomitant fusion or osteotomy, and implants derived from second-generation designs. Institutions where >10 procedures were performed per year were associated with better TAR survivorship. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Influence of dual-mobility acetabular implants on revision and survivorship of cup and Kerboull-type reinforcement ring constructs in aseptic acetabular loosening.

INTRODUCTION: Dual-mobility (DM) acetabular implants have been used in revision total hip arthroplasty (THA) to prevent postoperative instability, with excellent mid-term survivorship. However, few comparative studies assessed the long-term outcomes of DM implants used in Kerboull-type reinforcement ring constructs for acetabular revision. The present study aimed to compare long-term survivorship, dislocation rates and clinical outcome between DM acetabular implants and conventional single-bearing (SB) implants when cemented in a reinforcement ring. HYPOTHESIS: Dual-mobility implants are associated with equivalent survivorship and lower dislocation rates than SB implants. MATERIAL AND METHODS: A retrospective study included 60 revision THAs for aseptic loosening using a Kerboull-type reinforcement ring, and finally included 2 groups of 23 patients with either DM or SB cemented acetabular implants after matching for age, gender, BMI and preoperative Harris hip score. Mean follow-up was 10 years (range, 6-14 years). Acetabular implant survivorship, dislocation rate and radiographic failure incidence (>5mm migration, progressive radiolucency, graft non-integration, reinforcement ring breakage) were compared between the two groups. Clinical outcomes used the Harris hip score, the Postel-Merle d'Aubigné score and the Parker score. RESULTS: Survivorship free of aseptic acetabular re-revision was 89% at 10 years, with no significant difference between DM and SB (91% and 86%, respectively; p=0.54). Single-bearing implants showed a hazard ratio for dislocation of 6.7 (95% CI, 1.5-29.6; p=0.01) compared to DM implants. There were no significant differences in radiologic failure (10-year survivorship 72% and 64%, respectively; p=0.88) or functional scores. DISCUSSION: The present study confirmed the impact of dual-mobility implants in reducing long-term dislocation risk when used in Kerboull-type reinforcement ring constructs for acetabular aseptic revision, with no increased risk of re-revision compared to conventional single-bearing implants. LEVEL OF EVIDENCE: III, comparative retrospective study.

Biomechanical, histological, and molecular characterization of a new posttraumatic model of arthrofibrosis in rats.

Experimental analyses of posttraumatic knee arthrofibrosis utilize a rabbit model as a gold standard. However, a rodent model of arthrofibrosis offers many advantages including reduced cost and comparison with other models of organ fibrosis. This study aimed to characterize the biomechanical, histological, and molecular features of a novel posttraumatic model of arthrofibrosis in rats. Forty eight rats were divided into two equal groups. An immobilization procedure was performed on the right hind limbs of experimental rats. One group was immobilized for 4 weeks and the other for 8 weeks. Both groups were remobilized for 4 weeks. Limbs were studied biomechanically via assessment of torque versus degree of extension, histologically via whole knee specimen, and molecularly via gene expression of posterior capsular tissues. Significant differences were observed between experimental and control limbs at 4 N-cm of torque in the 4-week (knee extension: 115° ± 8° vs. 169° ± 17°, respectively; p = 0.007) and 8-week immobilization groups (knee extension: 99° ± 12° vs. 174° ± 9°, respectively; p = 0.008). Histologically, in each group experimental limbs demonstrated increased posterior capsular thickness and total area of tissue when compared to control limbs (p < 0.05). Gene expression values evaluated in each group were comparable. This study presents a novel rat model of arthrofibrosis with severe and persistent knee contractures demonstrated biomechanically and histologically. Statement of clinical significance: Arthrofibrosis is a common complication following contemporary total knee arthroplasties. The proposed model is reproducible, cost-effective, and can be employed for translational investigations studying the pathogenesis of arthrofibrosis and efficacy of neoadjuvant pharmacologic agents.

Contemporary Mortality Rate and Outcomes in Nonagenarians After Primary Total Knee Arthroplasty.

BACKGROUND: Nonagenarians (90-99 years) have experienced the fastest percent growth in primary total knee arthroplasty (TKA) utilization recently. However, there are limited data on the results of the procedure in this population. The goals of this study are to determine the mortality rate, implant survivorship, clinical outcomes, and complications of primary TKAs in nonagenarians. METHODS: Our institutional total joint registry was used to identify 105 nonagenarians who underwent 119 primary cemented TKAs for osteoarthritis between 1997 and 2017. Mean age was 92 years, with 58% being female. Mortality, revision, and reoperation were assessed using cumulative incidence with death as a competing risk and Cox regression methods. Clinical outcomes were assessed using Knee Society Scores. A posterior-stabilized design was used in 88%. Mean follow-up was 4 years. RESULTS: The mortality rates were 0%, 2%, 9%, and 47% at 90 days, 1 year, 2 years, and 5 years, respectively. The 5-year cumulative incidences of any revision and reoperation were 0% and 3%, respectively. The reoperations included 2 internal fixations for periprosthetic fracture and 1 hardware removal. The mean Knee Society Score improved significantly from 34 preoperatively to 80 at 5 years (P < .001). The 5-year cumulative incidence of any nonmortality complication was 66%. The most common complications were urinary tract infections and retention (8%) in the early postoperative period, and acquired idiopathic stiffness (10%) later. CONCLUSION: Nonagenarians undergoing primary TKA had low mortality rates at 90 days (0%) and 1 year (2%) with substantial functional improvements. The cumulative incidences of revision and reoperation were low at 5 years. LEVEL OF EVIDENCE: Level IV, retrospective cohort.

Renal Toxicity Associated With Resection and Spacer Insertion for Chronic Hip PJI.

BACKGROUND: Two-stage exchange arthroplasty with high-dose antibiotic-loaded bone cement spacer and intravenous (IV) antibiotics is the most common method of managing infected total hip arthroplasties. However, the contemporary incidence, risk factors, and outcomes of acute kidney injuries (AKIs) in this cohort are unknown. METHODS: We identified 227 patients treated with 256 antibiotic-loaded bone cement spacers after resection of an infected primary total hip arthroplasty between 2000 and 2017. Mean age was 65 years, mean body mass index was 30 mg/kg2, 55% were men, and 16% had pre-existing chronic kidney disease (CKD). Spacers were in situ for a mean of 15 weeks, concomitantly associated with IV or oral antibiotics for a mean of 6 weeks. AKI was defined as a creatinine ≥1.5X baseline or ≥0.3 mg/dL. Mean follow-up was 8 years. RESULTS: AKI occurred in 13 patients without pre-existing CKD (7%) vs 10 patients with CKD (28%; OR 5; P = .0001). None required acute dialysis. Postoperative fluid depletion (ß = 0.31; P = .0001), ICU requirement (ß = 0.40; P = .0001), and acute atrial fibrillation (ß = 0.43; P = .0001) were independent predictors for AKI in patients without pre-existing CKD. Duration of in situ spacer, mean antibiotic dose in cement, use of amphotericin B, and type of IV antibiotics were not significant risk factors. At last follow-up, 8 AKIs progressed to CKD, with one receiving dialysis 7 years later. CONCLUSION: AKIs occurred in 7% of patients with normal renal function, with 5-fold greater risk in those with CKD, and 4% did develop CKD. Importantly, causes of acute renal blood flow impairment were independent predictors for AKI. LEVEL OF EVIDENCE: Level III, comparative study.

Acute Kidney Injury When Treating Periprosthetic Joint Infections After Total Knee Arthroplasties with Antibiotic-Loaded Spacers: Incidence, Risks, and Outcomes.

BACKGROUND: Two-stage exchange arthroplasty with a high-dose antibiotic-loaded bone cement (ALBC) spacer and intravenous or oral antibiotics is the most common method of managing a periprosthetic joint infection (PJI) after a total knee arthroplasty (TKA). However, little is known about the contemporary incidence, the risk factors, and the outcomes of acute kidney injuries (AKIs) in this cohort. METHODS: We identified 424 patients who had been treated with 455 ALBC spacers after resection of a PJI following a primary TKA from 2000 to 2017. The mean age at resection was 67 years, the mean body mass index (BMI) was 33 kg/m2, 47% of the patients were women, and 15% had preexisting chronic kidney disease (CKD). The spacers (87% nonarticulating) contained a mean of 8 g of vancomycin and 9 g of an aminoglycoside per construct (in situ for a mean of 11 weeks). Eighty-six spacers also had amphotericin B (mean, 412 mg). All of the patients were concomitantly treated with systemic antibiotics for a mean of 6 weeks. An AKI was defined as a creatinine level of ≥1.5 times the baseline or an increase of ≥0.3 mg/dL within any 48-hour period. The mean follow-up was 6 years (range, 2 to 17 years). RESULTS: Fifty-four AKIs occurred in 52 (14%) of the 359 patients without preexisting CKD versus 32 AKIs in 29 (45%) of the 65 patients with CKD (odds ratio [OR], 5; p = 0.0001); none required acute dialysis. Overall, when the vancomycin concentration or aminoglycoside concentration was >3.6 g/batch of cement, the risk of AKI increased (OR, 1.9 and 1.8, respectively; p = 0.02 for both). Hypertension (ß = 0.17; p = 0.002), perioperative hypovolemia (ß = 0.28; p = 0.0001), and acute atrial fibrillation (ß = 0.13; p = 0.009) were independent predictors for AKI in patients without preexisting CKD. At the last follow-up, 8 patients who had sustained an AKI had progressed to CKD, 4 of whom received dialysis. CONCLUSIONS: In our study, the largest series to date that we are aware of regarding this issue, AKI occurred in 14% of patients with normal renal function at baseline, and 2% developed CKD after undergoing a 2-stage exchange arthroplasty for a PJI after TKA. However, the risk of AKI was fivefold greater in those with preexisting CKD. The causes of acute renal blood flow impairment were independent predictors for AKI. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.