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Extracellular vesicle (EV) secretion is an important mechanism used by cells to release biomolecules. A common necroptosis effector—mixed lineage kinase domain like (MLKL)—was recently found to participate in the biogenesis of small and large EVs independent of its function in necroptosis. The objective of the current study is to gain mechanistic insights into EV biogenesis during necroptosis. Assessing EV number by nanoparticle tracking analysis revealed an increased number of EVs released during necroptosis. To evaluate the nature of such vesicles, we performed a newly adapted, highly sensitive mass spectrometry‐based proteomics on EVs released by healthy or necroptotic cells. Compared to EVs released by healthy cells, EVs released during necroptosis contained a markedly higher number of unique proteins. Receptor interacting protein kinase‐3 (RIPK3) and MLKL were among the proteins enriched in EVs released during necroptosis. Further, mouse embryonic fibroblasts (MEFs) derived from mice deficient of Rab27a and Rab27b showed diminished basal EV release but responded to necroptosis with enhanced EV biogenesis as the wildtype MEFs. In contrast, necroptosis‐associated EVs were sensitive to Ca2+ depletion or lysosomal disruption. Neither treatment affected the RIPK3‐mediated MLKL phosphorylation. An unbiased screen using RIPK3 immunoprecipitation‐mass spectrometry on necroptotic EVs led to the identification of Rab11b in RIPK3 immune‐complexes. Our data suggests that necroptosis switches EV biogenesis from a Rab27a/b dependent mechanism to a lysosomal mediated mechanism.

Abstract Aneurysmal bone cysts (ABCs) in the periacetabular region can be challenging to treat because they create unique problems, given their proximity to articular cartilage and a significant weight bearing surface. This case series details the assessment and treatment of four periacetabular ABCs with a review of pertinent current literature. Treatment approaches used include curettage with 6% phenol chemical adjuvant, type III hemipelvectomy, serial image-guided sclerotherapy injections, and in one case, an exostotic lesion was treated with hip arthroscopy.

Abstract Background: Nonunions of an osteotomy site are the most reported surgical complication following periacetabular osteotomy (PAO) for the treatment of symptomatic acetabular dysplasia. Identification of patient-specific risk factors for nonunion remains an ongoing area of research. Objective: To identify patient-specific risk factors associated with nonunion after PAO for symptomatic hip dysplasia at approximately one year postoperatively. Methods: We retrospectively identified 103 hips (94 patients) that underwent Bernese PAO at our institution between December 2017 and May 2023. We collected patient demographics, Beighton score, lateral center-edge angle, anterior center-edge angle, femoral version, and preoperative vitamin D status. We also obtained comprehensive HU measurements at the femoral neck, as described by Christensen et al. (2019), from preoperative low-dose radiation CT scans. Nonunion was defined as noncontiguous osseous healing across any osteotomy site on 12-month postoperative radiographs. 12 hips were exluded due to insufficient postoperative radiographs. We used logistic regression to assess the relationships between odds of nonunion and potential demographic and radiographic predictor variables in univariate analyses. Results: Final analysis included 91 hips (83 patients). 84.4% of patients were female, average age was 29.20 ± 9.59 years, and average BMI was 25.35 ± 4.27 kg/m2. The nonunion rate was 14.3%. Age (27.15 ± 9.28 years healed versus 37.07 ± 7.75 years nonunion; OR 1.14; 95% CI, 1.03-1.25; p=0.02) and BMI (24.64 ± 4.02 kg/m2 healed versus 28.39 ± 4.00 kg/m2; OR 1.24; 95% CI, 1.03-1.48; p=0.02) were significantly higher in the nonunion group. Comprehensive HU measurement at the femoral neck was significantly lower in the nonunion group (218.26 ± 75.10 HU healed versus 156.41 ± 43.01 HU nonunion; OR 0.981; 95% CI, 0.96-0.99; p=0.03). Beighton score (p=0.31), lateral center-edge angle (p=0.62), anterior center-edge angle (p=0.22), femoral version (p=0.28) and preoperative vitamin D level (p=0.21) were not significantly different between the healed and nonunion groups. Conclusions: Decreased bone attenuation on low-dose radiation CT scan, increased age, and high BMI can independently predict nonunion after PAO for acetabular dysplasia. Surgeons should consider these factors and assess bone health using preoperative CT to better inform patients about the risk of nonunion.

Abstract Background: Hip dysplasia is characterized by joint instability and progression to osteoarthritis. The lateral center-edge angle (LCEA) is a radiographic measure of acetabular coverage where <18 degrees is diagnostic of dysplasia and 18-25 degrees indicates borderline dysplasia. Borderline hip dysplasia is a difficult diagnosis for hip preservation surgeons because some patients have hip instability that requires periacetabular osteotomy (PAO) for treatment, whereas other patients have hip impingement that can be treated with arthroscopy alone. No single standard exists to determine whether borderline dysplastic patients should undergo arthroscopy or the more invasive PAO. Objective: To describe new measures of acetabular wall intersection with the sorcil – anterior (WiSA) and – posterior (WiSP) and identify whether these measures predicted surgical management of patients with borderline dysplasia upon retrospective review of prospectively collected registry data. Methods: This retrospective study consisted of 256 hips (n=241 arthroscopy, n=15 PAO) with borderline dysplasia that were surgically treated between October 2017 and June 2022. LCEA, acetabular wall intersection with the sorcil – anterior (WiSA) and – posterior (WiSP) were measured on preoperative AP pelvis radiographs. Univariate logistic regressions estimated the predictive power of the measures for surgical management using odds ratios and ROC curves. Results: Compared to arthroscopy patients, average LCEA, WiSA, and WiSP were lower in the PAO cohort (p<0.0001; p=0.0004; p=0.0131). A 1 degree increase in WiSA on preoperative radiographs decreased the odds of PAO by 17% (OR=0.83; 95% CI, 0.75-0.93). A 1 degree increase in WiSP on preoperative radiographs decreased the odds of PAO by 10% (OR=0.90; 95% CI, 0.82-0.98). LCEA and WiSA were strong discriminators between the arthroscopy and PAO cohorts (AUC=0.851 and 0.789 respectively). Conclusions: WiSA and WiSP measured retrospectively on preoperative radiographs predicted surgical management of borderline hip dysplasia patients and correlated with whether the patient ultimately had a hip arthroscopy alone or periacetabular osteotomy. As hip preservation continues evolving, WiSA and WiSP are novel measurements that can further delineate the gray area of borderline dysplasia and help determine whether an arthroscopy or PAO is the preferred treatment.

Abstract Background: Pericapsular scarring is one etiology of pain after hip arthroscopy for the treatment offemoroacetabular impingement (FAI). Hip manipulation under anesthesia (MUA) has been proposed as a potential treatment. Hip MUA is a quick, outpatient procedure where the patient is sedated, and the hip is manipulated through various movements to break up pericapsular adhesions. The aim of this study was to determine the efficacy of hip MUA in patients with pericapsular scarring post-hip arthroscopy for FAI in improving hip range of motion (ROM), symptoms, and function. Methods: Patients who underwent hip MUA from June 2020 to July 2023 were prospectively enrolled (n = 41) into this retrospective cohort study. ROM (flexion, internal rotation at 90°, and external rotation at 90°) and various patient-reported outcomes (PROs; International Hip Outcome Tool-12 [iHOT-12], Modified Harris Hip Score [mHHS], Hip Outcome Score [HOS], Single Assessment Numeric Evaluation [SANE], and Patient-Reported Outcome Measurement Information System [PROMIS]) were assessed pre-operatively (prior to the initial hip arthroscopy) and at 3, 6, 9, and 12 months post-operatively. Wilcoxon signed-rank tests were used to evaluate for change in post-MUA ROM and PROs. Mixed modeling was also used to look at repeated ROM measures on a continuous scale with time and MUA as predictor. LSmeans estimates were compared between MUA groups at each time point. Results: Immediately after the hip manipulation under anesthesia, patients had significant gains in all 3 ROM assessments (p ≤ 0.001), and mixed modeling demonstrated that these gains were sustained 9+ months post-MUA (p < 0.0175). Twenty-eight patients had sufficient data for PRO analysis. Post-MUA, patients had statistically significant improvements in mHHS (p = 0.0475), iHOT-12 (p = 0.0036), SANE-ADL (p = 0.0103), and HOS-Sport (p = 0.0386). Conclusions: Hip MUA is an effective, non-invasive treatment for patients with pericapsular scarring post-hip arthroscopy for FAI. The improvements in ROM and PROs suggest that hip MUA can alleviate patients’ pain while improving their hip range of motion, sports performance and ability to execute activities of daily living.

Abstract Background: Hip arthroscopy is a rapidly expanding practice in orthopaedic surgery that is most used to treat femoroacetabular impingement syndrome (FAIS) with associated labral tears. Studies of knee arthroscopy and total knee arthroplasty demonstrate the effectiveness of neuraxial anesthesia with an additional advantage of decreased postoperative pain scores. The first direct comparison of neuraxial and general anesthesia for hip arthroscopy studied the immediate postoperative period and identified improved pain control without major adverse effects in the neuraxial anesthesia group. Objective: To compare the short-term (3-months to 3 years) clinical and patient reported outcomes in patients who received neuraxial anesthesia versus general anesthesia for hip arthroscopy to treat FAIS. Methods: Patients undergoing isolated hip arthroscopy to address FAIS from October 2017 to July 2020 with available two year postoperative patient reported outcome data were retrospectively reviewed. Patient reported outcomes were obtained from an IRB approved hip preservation registry. Primary outcomes included surgical complications, revision surgery, and postoperative patient reported outcomes including the International Hip Outcome Tool-12 (iHOT-12), Modified Harris Hip Score (mHHS), Hip Outcome Score Activities of Daily Living (HOS-ADL) and Sport Specific (HOS-SS) subset scores. Demographics and outcome variables were analyzed using t tests or fixed effects modeling where appropriate. Data are currently being collected for hip arthroscopies performed through March 2022. Results: 58 patients met inclusion criteria consisting of 40 females (69%) and 18 males (31%). 34 patients (59%) had neuraxial anesthesia and 24 patients (41%) underwent general anesthesia. Almost all reported complications were perineal (n=4) or lateral femoral cutaneous nerve (n=7) paresthesias. 4 patients underwent revision hip arthroscopy, 2 underwent subsequent periacetabular osteotomy, and 2 converted to total hip arthroplasty. Anesthesia type had no effect on whether a complication was reported (P=0.938) or a subsequent ipsilateral hip surgery was performed (P=0.688). Patient reported outcome scores increased for all scales over the postoperative period for both anesthesia groups without a significant difference between them at any postoperative interval (P > 0.161). Conclusions: Patients undergoing neuraxial anesthesia for hip arthroscopy to treat FAIS have similar postoperative clinical and patient reported outcomes to those who undergo general anesthesia for the procedure.