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Background: Little is known about patients' postoperative week-by-week progress after undergoing posterior approach total hip arthroplasty (THA) with regard to pain, function, return to work, and driving. Purpose: We sought to evaluate a large cohort of patients undergoing posterior approach THA with modified posterior hip precautions to better understand the trajectory of recovery. Methods: Patients at a single institution undergoing primary posterior approach THA by fellowship-trained arthroplasty surgeons were prospectively enrolled. Patient functional status and early rehabilitation recovery milestones were evaluated preoperatively and each week postoperatively for 6 weeks. Results: Of 312 patients who responded to weekly questionnaires, there were varying response rates per question. At 1 week after surgery, 15% (39/256) of respondents had returned to work, increasing to 57% (129/225) at week 6. At 6 weeks, 77% of patients (174/225) had returned to driving; 25% (56/225) were taking pain medication (including prescription opioids or nonsteroidal anti-inflammatory drugs); and 15% (34/225) were using assistive devices (down from 91%, 78%, 56%, 35%, and 27% at weeks 1, 2, 3, 4, and 5, respectively). Average postoperative Hip dysfunction and Osteoarthritis Outcome Score for Joint Replacement and Lower Extremity Functional Scale scores were significantly higher than preoperative scores. Respondents reported significantly less pain at each week postoperatively than the previous week. Conclusion: These findings suggest that there may be an expected pathway for recovery after posterior THA using perioperative pain protocols, modified postoperative precautions, and physical therapy protocols to improve patient outcomes after THA, with most patients returning to normal at 4 weeks. Defining the expected recovery timeline may help surgeons in counseling patients preoperatively and guiding their recovery.

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¼ Perioperative corticosteroids are strongly recommended for reducing the incidence and severity of postoperative nausea and vomiting following elective total hip or total knee arthroplasty.¼ Corticosteroids may reduce postoperative pain and opioid requirements. Similarly, corticosteroids appear to have a neutral-to-positive effect on length of stay, venous thromboembolism, mobility, delirium, acute kidney injury, and bone cement implantation syndrome (i.e., decreased length of stay).¼ Perioperative corticosteroids may induce hyperglycemia among both diabetic and nondiabetic patients; however, there is no strong evidence indicating that these transient corticosteroid-induced glycemic derangements may increase the risk of postoperative infectious complications.¼ The dosage and frequency of perioperative corticosteroid administration play a critical role in optimizing postoperative outcomes, with higher doses showing promise in reducing opioid consumption, postoperative pain, and length of stay.¼ The optimal dosage and frequency of corticosteroids remain unclear; however, the perioperative administration of 8 to 16 mg dexamethasone, or equivalent steroid, appears reasonable and safe in most cases.

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INTRODUCTION: Arthrofibrosis is a common postoperative total knee arthroplasty (TKA) complication that results in limited range of motion (ROM). There is limited literature on outcomes after revision TKA (rTKA) for arthrofibrosis based on preoperative ROM restriction. The aims of this study were to: (1) examine ROM trajectory after rTKA for arthrofibrosis patients who have severe versus non-severe limitations; (2) compare ROM gains and final arc of motion (AOM) between severe and non-severe cohorts; (2a) compare ROM gain in a severe cohort treated with a rotating hinge (RH) versus a non-rotating hinge (non-RH) construct; and (3) assess the impact of arthrofibrosis severity on patient-reported outcome measures (PROMs). METHODS: Patients were divided into 2 groups: Group A had preoperative ROM < 70o (severe), and Group B had preoperative ROM > 70o (non-severe). Patients were assessed clinically using AOM gain, absolute ROM, Knee injury and Osteoarthritis Outcomes Score for Joint Replacement (KOOS, JR), Lower Extremity Activity Scale (LEAS), and pain scores. Postoperative gains in AOM were compared between both groups. RESULTS: A total of 56 rTKAs (Group A (severe): n = 36, Group B (non-severe): n = 20) were performed for patients who have postoperative fibrosis. Group B had better ROM at the one-year timepoint (Group B: 95.9 ± 22.5 versus Group A: 83.2 ± 25.7). Group A had significantly better improvement in absolute AOM than Group B (31.1 ± 20.9 versus 11.4 ± 25.0, P < 0.01). The RH group demonstrated significantly better absolute AOM gain than the non-RH group (41.3 ± 19.4 versus 18.3 ± 15.2, P < 0.001). However, there were no significant differences in PROMs between Groups A and B or between RH and NRH groups at the final follow-up. DISCUSSION: Final ROM achieved between severe and non-severe arthrofibrosis groups were similar, and patients who have severe arthrofibrosis can expect greater absolute ROM gains and similar functional outcomes than non-severe arthrofibrosis patients. The RH rTKAs provided greater AOM gains for patients who have severe arthrofibrosis, with equivalent functional outcomes to non-RH implants. For severe arthrofibrosis patients, RH designs provided twice the overall ROM gain, however, longer follow-up is necessary to determine whether RH designs have inferior overall implant survivorship.

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BACKGROUND: The purpose of this study was to determine implant survivorship and functional outcomes for revision total knee arthroplasty (rTKA) with contemporary rotating-hinge knee implants. METHODS: A retrospective review identified 115 rTKAs using contemporary rotating-hinge implants from 2014 to 2018 for the treatment of instability (34, 30%), reimplantation after periprosthetic joint infection (PJI) (33, 29%), aseptic loosening (25, 22%), arthrofibrosis (14, 12%), periprosthetic fracture (4, 3%), osteolysis (4, 3%), and femoral component fracture (1, 1%). There were 70 women (61%), and the mean age was 67 years (range, 27 to 94). The mean follow-up was 3 years (range, 2 to 6). Kaplan-Meier analysis and Cox proportional hazard models estimated survivorship. RESULTS: The re-revision rate was 20% (23 of 115) at an average of 18 months postoperatively. Re-revision indications included PJI (n = 14), aseptic loosening (n = 4), arthrofibrosis (n = 2), instability/malalignment (n = 1), femoral stem fracture (n = 1), and hinge mechanism disruption (n = 1). At 2 and 5 years, survivorship free from all-cause re-revision was 86% and 64%, and survivorship free from re-revision for aseptic loosening was 100% and 87%, respectively. Use of a rotating-hinge implant in reimplantation after PJI was a risk factor for subsequent re-revision (hazard ratio = 2.4, P = 0.046). On a radiographic review of unrevised rotating-hinges, there were major radiolucent lines around 2 femoral and 5 tibial components. The mean Knee Osteoarthritis Outcomes Score for Joint Replacement (KOOS JR) increased from 43 preoperatively to 60 at 1 year (P < 0.001). CONCLUSION: In patients treated with a rotating-hinge implant for rTKA, there were relatively poor 2-year (86%) and 5-year (64%) survivorship free from all-cause re-revision, most commonly due to PJI. Mid-term survivorship free from re-revision for aseptic loosening was modest (87%). There should be a goal to mitigate complications in complex rTKAs with rotating-hinge implants, namely PJI.

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Background: Robotic-assisted total knee arthroplasty (RA-TKA) allows surgeons to perform intraoperative soft tissue laxity assessments prior to bone resections and is used to alter resections to achieve gap balance. This study compared 2 techniques for flexion gap laxity assessment during RA-TKA. Methods: A prospective study of 50 primary RA-TKAs performed by a single surgeon was conducted between February and October 2023. Following full exposure, anterior tibial dislocation, and osteophyte removal, maximal medial and lateral compartment flexion laxity was quantified to the nearest 0.5 mm by the robotic system using a dynamic, surgeon-applied stress (SURGEON). This data was used to plan a balanced flexion gap by adjusting the femoral component size, rotation, and anterior-posterior translation. Flexion laxity was quantified again after distal femoral and proximal tibial resections using a ligament tensor instrument (TENSOR). These new data were used to plan for the same desired flexion gap using the same variables. Paired-samples t-tests and a simple linear regression were used for analysis. Results: Both methods produced near-identical recommendations for femoral component sizing (mean deviation 0.06 sizes, range -1 to +1 size; P = .569), rotation (deviation mean 1.0°, range -3.0° to +3.0°; P = .741), and anterior-posterior translation (deviation mean 0.13 mm, range -0.5 to +0.5 mm, P = .785). SURGEON femoral component rotation predicted TENSOR rotation (R2 = 0.157; 95% confidence interval = 0.124, 0.633; P = .004). Conclusions: Assessing flexion laxity with a surgeon-applied stress vs a ligament tensor produced near-identical laxity data in RA-TKA, suggesting surgeons may comfortably choose either technique as a reliable method. Level of Evidence: Level III.

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Background: Perioperative practices have been introduced over the last decade to decrease the risk of periprosthetic joint infection (PJI). We sought to determine whether rates of revision total knee arthroplasty (TKA) for PJI decreased during the period 2006-2016. Methods: This observational cohort study used data from the New York Statewide Planning and Research Cooperative System to identify patients undergoing TKA in 2006-2016. Data through 2017 were used to determine if patients underwent revision TKA for PJI (including debridement, antibiotics and implant retention) within 1 year of the primary surgery. A generalized estimating equation model, clustered by hospital, was used to examine the impact of time on likelihood of revision TKA for PJI. Results: In 2006-2016, 233,165 primary TKAs performed were included. Mean age was 66.1 (standard deviation 10.3) years, and 65% were women. Overall, 0.5% of the patients underwent revision TKA for PJI within 1 year of surgery. The generalized estimating equation model showed that for primary TKA performed in 2006-2013, year of surgery did not impact the likelihood of revision TKA for PJI (odds ratio 1.00, 95% confidence interval 0.97-1.03, P = .9221), but that for primary TKA performed in 2014-2016, the likelihood decreased by year (odds ratio 0.76, 95% confidence interval 0.66-0.88, P = .0002). Conclusions: The likelihood of revision TKA for PJI was stable from 2006 to 2013 but declined during the period 2014-2016 across patient and hospital categories. This decline could be due to infection mitigation strategies or other unmeasured factors.

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Background: The outcomes of revision total hip arthroplasty (rTHA) have become increasingly important as their volume increases. Computer navigation, a reliable method to improve component positioning during primary total hip arthroplasty (THA), is not well studied in the rTHA setting. Given that dislocation rates following rTHA are significantly higher than those of primary THA, component positioning becomes paramount in these cases. Methods: Here, we present two case reports and surgical techniques, one of a 77-year-old man undergoing rTHA for recurrent hip instability following primary THA, and one of a 61-year-old woman undergoing rTHA for severe iliopsoas bursitis who was at increased risk for instability and dislocation given her history of large segment spinal fusion. Results: Both patients achieved optimal acetabular component positioning after rTHA with imageless computer navigation. Conclusions: The use of imageless computer navigation in rTHA provides accurate and reproducible component positioning during acetabular rTHA.

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Background: Hip dysplasia is considered one of the leading etiologies contributing to hip degeneration and the eventual need for total hip arthroplasty (THA). We validated a deep learning (DL) algorithm to measure angles relevant to hip dysplasia and applied this algorithm to determine the prevalence of dysplasia in a large population based on incremental radiographic cutoffs. Methods: Patients from the Osteoarthritis Initiative with anteroposterior pelvis radiographs and without previous THAs were included. A DL algorithm automated 3 angles associated with hip dysplasia: modified lateral center-edge angle (LCEA), Tönnis angle, and modified Sharp angle. The algorithm was validated against manual measurements, and all angles were measured in a cohort of 3869 patients (61.2 ± 9.2 years, 57.1% female). The percentile distributions and prevalence of dysplastic hips were analyzed using each angle. Results: The algorithm had no significant difference (P > .05) in measurements (paired difference: 0.3°-0.7°) against readers and had excellent agreement for dysplasia classification (kappa = 0.78-0.88). In 140 minutes, 23,214 measurements were automated for 3869 patients. LCEA and Sharp angles were higher and the Tönnis angle was lower (P < .01) in females. The dysplastic hip prevalence varied from 2.5% to 20% utilizing the following cutoffs: 17.3°-25.5° (LCEA), 9.4°-15.6° (Tönnis), and 41.3°-45.9° (Sharp). Conclusions: A DL algorithm was developed to measure and classify hips with mild hip dysplasia. The reported prevalence of dysplasia in a large patient cohort was dependent on both the measurement and threshold, with 12.4% of patients having dysplasia radiographic indices indicative of higher THA risk.

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BACKGROUND: Modular metaphyseal engaging (MME) femoral components in total hip arthroplasty (THA) allow optimized femoral length, offset, and anteversion and are useful in patients with unusual proximal femoral anatomy. Fretting, corrosion, and stem fractures above the modular sleeve are complications associated with these implants. The purpose of this study was to identify failure mechanisms of retrieved MME femoral components at our institution, identify all broken stem cases, and evaluate how often an extended trochanteric osteotomy (ETO) was required for removal. METHODS: All consecutively retrieved MME femoral components from September 2002 to May 2023 were reviewed. Patient demographics, procedure information, component specifications, indications for removal, and requirements for further revision surgery were reviewed. Descriptive statistics were calculated for variables of interest. RESULTS: There were 131 retrieved MME components. The mean age at surgery was 59 years (range, 28 to 75), 49% were women, mean body mass index was 29.4 (range, 20.7 to 33.3), and mean American Society of Anesthesiologists score was 2.4 ± 0.5. There were 102 (78%) stems of 1 design (stem A), and 29 (22%) stems of a different design (stem B). Of 131 components, 10 (7.6%) failed secondary to stem fracture proximal to the modular sleeve. Four of 102 (4%) of stem A and 6 of 29 (21% of stem B) fractured. All broken stems required additional intervention for removal during revision THA, using an ETO (N = 9) or cortical window (N = 1) in which an intraoperative proximal femoral fracture occurred. CONCLUSIONS: Broken MME stems present a challenge for orthopaedic surgeons during revision THA. When a stem fracture occurs above the ingrown sleeve, the distal splines may have osseous interdigitation into the clothespin. Thus, when revising a broken MME stem, an ETO should be performed, and the segment should be long enough to allow distal access.

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Extensor mechanism (EM) disruption is a rare but severe complication of total knee arthroplasty (TKA) that can greatly impair function. Treatment options for chronic patella tendon ruptures include primary repair, autograft augmentation, and reconstruction with allograft or synthetic material. Despite various techniques, failures can occur, and options for reconstruction after a failed allograft or mesh are limited, especially if the tibial component is well-fixed and cannot be easily removed, and if there is proximal tibial deficiency from a previous failed EM allograft. This case report presents a novel solution for revision EM reconstruction in a 72y.o. female patient with a history of multiple EM failures using an off-label Trabecular Metal Cone-Mesh-Cone (TM CMC) clamshell construct. The surgical procedure involved the removal of a non-viable allograft from the knee joint and the creation of a custom trabecular metal (TM) clamshell construct with a Marlex mesh graft in between the two TM implants. The customized TM cone was designed to cover the deficient anterior tibia and wrap around the ingrown TM cone. The Marlex mesh was cemented between the existing implant and the customized TM cone, and the construct was secured in place with two cancellous screws. The mesh was tunneled between soft tissue to prevent contact with the implant and rotated scar tissue was interposed to prevent abrasion of the mesh on the implant surfaces. The patient tolerated the procedure well and no complications were noted postoperatively. At a follow-up 12 months after the operation the patient remains satisfied with the result.

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BACKGROUND: Knee instability in midflexion may contribute to patient dissatisfaction following total knee arthroplasty (TKA). Midflexion instability involves abnormal motions and tissue loading in multiple planes. Therefore, we quantified and compared the tensions carried by the medial and lateral collateral ligaments (MCL and LCL) following posterior-stabilized (PS) TKA through knee flexion, and then compared these tensions with those carried by the native knee. Finally, we examined the relationships between collateral ligament tensions and anterior tibial translation (ATT). METHODS: Eight cadaveric knees (from 5 male and 3 female donors with a mean age of 62.6 years and standard deviation of 10.9 years) underwent PS TKA. Each specimen was mounted to a robotic manipulator and flexed to 90°. ATT was quantified by applying 30 N of anterior force to the tibia. Tensions carried by the collateral ligaments were determined via serial sectioning. Robotic testing was also conducted on a cohort of 15 healthy native cadaveric knees (from 9 male and 6 female donors with a mean age of 36 years and standard deviation of 11 years). Relationships between collateral ligament tensions during passive flexion and ATT were assessed via linear and nonlinear regressions. RESULTS: MCL tensions were greater following PS TKA than in the native knee at 15° and 30° of passive flexion, by a median of ≥27 N (p = 0.002), while the LCL tensions did not differ. Median tensions following PS TKA were greater in the MCL than in the LCL at 15°, 30°, and 90° of flexion, by ≥4 N (p ≤ 0.02). Median tensions in the MCL of the native knee were small (≤11 N) and did not exceed those in the LCL (p ≥ 0.25). A logarithmic relationship was identified between MCL tension and ATT following TKA. CONCLUSIONS: MCL tensions were greater following PS TKA with this typical nonconforming PS implant than in the native knee. Anterior laxity at 30° of flexion was highly sensitive to MCL tension during passive flexion following PS TKA but not in the native knee. CLINICAL RELEVANCE: Surgeons face competing objectives when performing PS TKA: they can either impart supraphysiological MCL tension to reduce anterior-posterior laxity or maintain native MCL tensions that lead to heightened anterior-posterior laxity, as shown in this study.

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BACKGROUND: Research on hip instability has focused on establishing "safe" ranges of combined component position in supine posture or functional placement of the acetabular component based on the hip-spine relationship. A new angle, the polar axis angle (PAA), of the total hip arthroplasty (THA) components describes the concentricity of both components and can be evaluated in functional positions that confer a greater risk of instability (ie, sitting). The goal of this study was to compare the PAA in functional positions between patients who experienced a postoperative dislocation and a matched control group who did not have a dislocation. METHODS: An institutional database was searched for patients experiencing a dislocation after primary THA. Patients who had postoperative full-length standing and lateral-seatedradiographs were included in the dislocator group. A control group of nondislocator patients was matched 2:1 by age, body mass index, sex, and hip-spine classification. Radiographic measurements of the neck angle, acetabular ante-inclination, and PAA were performed by 2 separate blinded, trained reviewers. RESULTS: The lateral-seated neck angle and lateral-seated PAA measurements were significantly lower in the dislocator groups (n = 37) than the control group (n = 74) (23 versus 33 degrees, P < .001; 74 versus 83 degrees, P = .012, respectively). Significant differences were also observed in changes in the polar axes and neck angles between standing and seated positions (P < .001 and P < .001, respectively). When comparing patients who have mobile spines versus stiff spines within the dislocator group, there were no differences in the acetabular, neck, or PAAs. The effect of neck angle on the PAA showed a linear trend across cohorts. CONCLUSIONS: Patients who experience postoperative instability have a significantly lower PAA on lateral-seated radiographs when matched for age, sex, body mass index, and hip-spine classification. In addition, the lower seated PAA is driven more strongly by decreased functional femoral anteversion, which emphasizes the role of functional femoral version on stability in THA.

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BACKGROUND: Research has suggested that glucagon-like peptide-1 receptor agonists (GLP-1-RAs) may have therapeutic effects on osteoarthritis of the hip and knee, in addition to managing diabetes and obesity. However, there is a lack of understanding regarding the association between GLP-1-RA use and the diagnosis of osteoarthritis (OA) of the hip and knee. METHODS: A collaborative network analytics platform was queried for obese diabetic (n = 1,094,198), obese nondiabetic (n = 916,235), and nonobese diabetic (n = 157,305) patients who had an index visit between 2015 and 2017. Patients who had pre-existing hip and/or knee OA were excluded. A 1:1 propensity score matching was used to balance GLP-1-RA use in stratified cohorts for age, sex, race, body mass index, and hemoglobin A1c. The primary outcomes were rates of progression to hip OA, knee OA, major joint injections, total hip arthroplasty, and total knee arthroplasty. Cox proportional hazards models determined hazard ratios (HRs) between cohorts prescribed and not prescribed GLP-1-RAs. RESULTS: All patients had a five-year follow-up. Rates of progression to hip and knee OA were higher among the GLP-1-RA users in both obese diabetic (hip HR: 1.63, 95% confidence interval [CI]: 1.46 to 1.82; knee HR: 1.52, CI: 1.41 to 1.64) and nonobese diabetic (hip HR: 1.78, CI: 1.50 to 2.10; knee HR: 1.58, CI: 1.39 to 1.80) cohorts. These diabetic cohorts received higher rates of major joint injections, though there was no difference in rates of total hip arthroplasty or total knee arthroplasty. No differences in five-year outcomes were seen when comparing obese, nondiabetic patients who were prescribed GLP-1-RAs with obese, nondiabetic patients not exposed to GLP-1-RAs. CONCLUSIONS: This five-year analysis found a greater risk of progression to hip and knee OA among obese and non-obese diabetic GLP-1-RA users. Further studies should explore GLP-1-RA effects upon glucose management, weight loss, and lower extremity arthritis development. LEVEL OF EVIDENCE: III, retrospective cohort study.

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BACKGROUND: In revision total knee arthroplasty (TKA), there is little information on the magnitude of potential limb lengthening, risk factors for lengthening, or its impact on patient-reported outcome measures. We aimed to quantify limb length alteration during revision TKA and assess risk factors for lengthening. METHODS: We identified 150 patients over a 3-year period who underwent revision TKA and had preoperative and postoperative EOS hip-to-ankle standing radiographs. The average patient age was 64 years, 51% were women; 68% had a preoperative varus deformity and 21% had a preoperative valgus deformity. Outcomes assessed included change in functional and anatomic limb length, risk factors for lengthening, and clinical outcome scores, including the Knee Osteoarthritis Outcome Score Joint Replacement, and the Veterans RAND 12-item Physical and Mental Scores. RESULTS: There were 124 patients (83%) who had functional limb lengthening, and 108 patients (72%) had anatomic limb lengthening. Patients had an average functional limb lengthening of 7 mm (range, -22 to 35) and an average anatomic limb lengthening of 5 mm (range, -16 to 31). Patients undergoing revision for instability experienced significantly greater anatomic lengthening (7.6 versus 4.6, P = .047). Patients who had ≥ 10° of deformity were more likely to be functionally lengthened (91 versus 79%) and had significantly greater average functional lengthening (12 versus 6 mm; P = .003). There was no significant change in clinical outcome scores at 6 weeks and 1 year for patients lengthened ≥ 5 or 10 mm compared to those not lengthened as substantially. CONCLUSIONS: There is major potential for functional and anatomic limb lengthening following revision TKA, with greater preoperative deformity and revision for instability being risk factors for lengthening.

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BACKGROUND: Interprosthetic femur fractures (IPFFs) are a rare, but devastating complication following total joint arthroplasty. There is limited evidence to help guide their management. The purpose of this study was to describe the features, treatment, and outcomes of surgically managed IPFFs. METHODS: We retrospectively identified 75 patients who had 76 IPFFs. The mean age at the time of IPFF was 75 years (range, 29 to 94), and 78% were women. The mean body mass index was 30 (range, 19 to 51), and the mean follow-up was 3 years (range, 0 to 14). There were 16 Vancouver B1 fractures, 28 Vancouver B2 fractures, 2 Vancouver B3 fractures, and 30 Vancouver C fractures. All B1 fractures underwent open reduction internal fixation (ORIF). All Vancouver B2 and B3 fractures underwent revision arthroplasty, including 1 proximal femur replacement and 1 total femur replacement. Vancouver C fractures were treated with ORIF (n = 20), distal femoral replacement (n = 9), and in 1 case, total femur replacement (n = 1). Kaplan-Meier survivorship was used to calculate 2-year survival free from all-cause reoperation and periprosthetic joint infection (PJI). RESULTS: The 2-year survivorship-free rate from reoperation was 71%. There were 18 reoperations following initial surgical management of the IPFF, including 9 for infection, 3 for refracture, 3 for nonunion, 2 for hardware failure, and 1 for instability. An initial IPFF involving a stemmed femoral total knee arthroplasty component was associated with increased risk for reoperation (P = .007) and PJI (P = .044). There was no difference in survivorship free of reoperation between IPFFs managed with ORIF or revision arthroplasty (P = .72). CONCLUSIONS: An IPFF is a devastating complication following total joint arthroplasty with high reoperation rates, most commonly secondary to PJI. Those IPFFs that occurred between 2 stemmed components were at the highest risk for reoperation.

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BACKGROUND: The impact of a preoperative self-reported nickel allergy in patients undergoing primary total knee arthroplasty (TKA) remains unclear. The aim of this study was to compare the revision rates and outcomes of patients who have a self-reported nickel allergy undergoing primary TKA to patients who do not have a self-reported nickel allergy. METHODS: Over 5 years, a total of 284 TKAs in patients who have and 17,735 in patients who do not have a self-reported nickel allergy were performed. Revision rates and differences in preoperative and postoperative patient-reported outcome measures, including Knee Osteoarthritis Outcome Score Joint Replacement (KOOS JR), Visual Analog Scale, Lower Extremity Activity Scale, and the Patient-Reported Outcomes Measurement Information System Mental and Physical Scores, were compared. RESULTS: Survivorship free of all-cause revision at 1 year was similar for patients who have and do not have a self-reported nickel allergy (99.5% [95% CI (confidence interval): 98.6 to 100.0] versus 99.3% [95% CI: 99.1 to 99.4]), P = .49). Patients who have a self-reported nickel allergy undergoing primary TKA had no difference in KOOS JR, Visual Analog Scale, or Lower Extremity Activity Scale scores at 6 weeks and 1 year and slightly worse Patient-Reported Outcomes Measurement Information System mental and physical scores at 6 weeks compared to patients who did not have an allergy. Matched analysis revealed no difference in 6-week or 1-year KOOS, JR scores between patients who did and did not have a self-reported nickel allergy when stratified by implant class (nickel-free versus standard cobalt-chromium) (P = .113 and P = .415, respectively). CONCLUSIONS: Patients who have a self-reported nickel allergy can be advised that, on average, their clinical outcome scores will improve similarly to patients who do not have a self-reported nickel allergy, and revision rates will be similar.

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Patient-specific flanged acetabular components are utilized to treat failed total hip arthroplasties with large acetabular defects. Previous clinical studies from our institution showed that these implants tend to lateralize the acetabular center of rotation. However, the clinical impact of lateralization on implant survivorship is debated. Our goal was to develop a finite element model to quantify how lateralization of the native hip center affects periprosthetic strain and implant-bone micromotion distributions in a static level gait loading condition. To build the model, we computationally created a superomedial acetabular defect in a computed tomography 3D reconstruction of a native pelvis and designed a flanged acetabular implant to address this simulated bone defect. We modeled two implants, one with ~1 cm and a second with ~2 cm of hip center lateralization. We applied the maximum hip contact force and corresponding abductor force observed during level gait. The resulting strains were compared to bone fatigue strength (0.3% strain) and the micromotions were compared to the threshold for bone ingrowth (20 µm). Overall, the model demonstrated that the additional lateralization only slightly increased the area of bone at risk of failure and decreased the areas compatible with bone ingrowth. This computational study of patient-specific acetabular implants establishes the utility of our modeling approach. Further refinement will yield a model that can explore a multitude of variables and could be used to develop a biomechanically-based acetabular bone loss classification system to guide the development of patient-specific implants in the treatment of large acetabular bone defects.

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Aims: Obtaining solid implant fixation is crucial in revision total knee arthroplasty (rTKA) to avoid aseptic loosening, a major reason for re-revision. This study aims to validate a novel grading system that quantifies implant fixation across three anatomical zones (epiphysis, metaphysis, diaphysis). Methods: Based on pre-, intra-, and postoperative assessments, the novel grading system allocates a quantitative score (0, 0.5, or 1 point) for the quality of fixation achieved in each anatomical zone. The criteria used by the algorithm to assign the score include the bone quality, the size of the bone defect, and the type of fixation used. A consecutive cohort of 245 patients undergoing rTKA from 2012 to 2018 were evaluated using the current novel scoring system and followed prospectively. In addition, 100 first-time revision cases were assessed radiologically from the original cohort and graded by three observers to evaluate the intra- and inter-rater reliability of the novel radiological grading system. Results: At a mean follow-up of 90 months (64 to 130), only two out of 245 cases failed due to aseptic loosening. Intraoperative grading yielded mean scores of 1.87 (95% confidence interval (CI) 1.82 to 1.92) for the femur and 1.96 (95% CI 1.92 to 2.0) for the tibia. Only 3.7% of femoral and 1.7% of tibial reconstructions fell below the 1.5-point threshold, which included the two cases of aseptic loosening. Interobserver reliability for postoperative radiological grading was 0.97 for the femur and 0.85 for the tibia. Conclusion: A minimum score of 1.5 points for each skeletal segment appears to be a reasonable cut-off to define sufficient fixation in rTKA. There were no revisions for aseptic loosening at mid-term follow-up when this fixation threshold was achieved or exceeded. When assessing first-time revisions, this novel grading system has shown excellent intra- and interobserver reliability.

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BACKGROUND: Partial or total release of the posterior cruciate ligament (PCL) is often performed intraoperatively in cruciate-retaining total knee arthroplasty (CR-TKA) to alleviate excessive femoral rollback. However, the effect of the release of selected fibers of the PCL on femoral rollback in CR-TKA is not well understood. Therefore, we used a computational model to quantify the effect of selective PCL fiber releases on femoral rollback in CR-TKA. METHODS: Computational models of 9 cadaveric knees (age: 63 years, range 47 to 79) were virtually implanted with a CR-TKA. Passive flexion was simulated with the PCL retained and after serially releasing each individual fiber of the PCL, starting with the one located most anteriorly and laterally on the femoral notch and finishing with the one located most posteriorly on the medial femoral condyle. The experiment was repeated after releasing only the central PCL fiber. The femoral rollback of each condyle was defined as the anterior-posterior distance between tibiofemoral contact points at 0° and 90° of flexion. RESULTS: Release of the central PCL fiber in combination with the anterolateral (AL) fibers, reduced femoral rollback a median of 1.5 [0.8, 2.1] mm (P = .01) medially and by 2.0 [1.2, 2.5] mm (P = .04) laterally. Releasing the central fiber alone reduced the rollback by 0.7 [0.4, 1.1] mm (P < .01) medially and by 1.0 [0.5, 1.1] mm (P < .01) laterally, accounting for 47 and 50% of the reduction when released in combination with the AL fibers. CONCLUSIONS: Releasing the central fibers of the PCL had the largest impact on reducing femoral rollback, either alone or in combination with the release of the entire AL bundle. Thus, our findings provide clinical guidance regarding the regions of the PCL that surgeons should target to reduce femoral rollback in CR-TKA.

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INTRODUCTION: Options for soft tissue coverage in revision total knee arthroplasty (rTKA) range from primary wound closure to complex muscle flap reconstructions. The purpose of this study was to investigate the institutional experience of wound coverage options for complex soft tissue defects in rTKA. MATERIALS AND METHODS: 77 patients undergoing rTKA with complex wound closure by a single plastic surgeon were retrospectively reviewed. The average follow-up was 30.1 months. In 18 (23.4%) patients, an intraoperative decision for primary closure was made. Fifty-nine patients (76.6%) received either a local fasciocutaneous (N = 18), a medial gastrocnemius (N = 37), a free latissimus dorsi (N = 3) or a lateral gastrocnemius flap (N = 1). Revision-free survival and complication rates were assessed and risk factors were analyzed with Cox-regression analysis. RESULTS: Medial gastrocnemius flaps had significant lower cumulative revision-free survival rates than local fasciocutaneous flaps (P = 0.021) and primary closures (P < 0.001) (42.5% vs. 71.5% vs. 100%,respectively). Comparing the most common complex closure procedures medial gastrocnemius flaps had the highest rate of prolonged wound healing (29.7%) and infection/reinfection (40.5%). Infection-associated flap procedures had significant lower cumulative revision-free survival rates (30.5%) than non-infection associated flap procedures (62.8%,P = 0.047). A history of more than two prior surgeries (HR = 6.11,P < 0.001) and an age ≥ 65 years (HR = 0.30,P = 0.018) significantly increased the risk of revision. CONCLUSIONS: The results of this study indicate that primary closure -if possible- should be preferred to early proactive muscle flap coverage. Even in the hands of an experienced plastic surgeon muscle flaps have high revision and complication rates. The study highlights the need to clarify flap indications and to investigate alternative approaches.