Image-guided Intraarticular Hip Injections and Risk of Infection After Hip Arthroscopy (141)

Objectives: Intraarticular injections are fundamental in the diagnosis and treatment of many types of hip pathology. However, there are conflicting data about their safety ≤3 months prior to hip arthroscopy. One large database study demonstrated over a two-fold increase in infection risk (with infection rates far higher than what is typically seen clinically [>1-2%]), while a recent institutional study reported 0 infections in a series of 500 patients undergoing injection within 3 months of arthroscopy. An important difference between these works was the use of image-guidance, with the former not evaluating this factor and the latter including only ultrasound (US)-guided injections. In fact, despite the growing use of US-guided hip injections, no prior study has compared the risk of complications, including infection, between US and fluoroscopic (FL)- guided hip injections prior to hip surgery. Therefore, the purposes of this study were to assess the risk of infection associated with image-guided intraarticular injections prior to hip arthroscopy and compare that risk between US and FL- guidance. Methods: This was a retrospective cohort study of patients undergoing hip arthroscopy in a large commercial claims database (MarketScan) from 2007-2017. Patients were required to have 1-year of continuous enrollment prior to and 6-months after hip arthroscopy. Patient age, sex, geographic region, medical history, surgical details, and hip injections (including image- guidance, timing, and laterality) were collected. For both the US and FL cohort, patients who underwent injection ≤3 months preoperatively and >3-12 months preoperatively were compared to those who did not undergo preoperative injection. Patients with both types of injections, with an infection diagnosis at the time of index injection, or with missing laterality data were excluded. The primary outcome of this study was surgical site infection within 6 months of surgery. Chi-squared or Fisher’s exact tests and multivariable logistic regressions were used to assess the association between preoperative hip injection and infection. Finally, we performed sensitivity analyses that did not exclude patients with an infection at time of hip arthroscopy. Results: We identified 17,093 hip arthroscopy patients (mean [SD] age 37.2 [14.0] years; 14,685 [85.9%] no injection control patients and 2,408 [14.1%] patients who underwent hip arthroscopy within 12-months of image-guided hip injection) (Table 1). In the FL cohort (n=1,219 [50.7%]), 673 (55.2%) patients underwent hip arthroscopy ≤3 months after hip injection, while 546 (44.8%) patients underwent hip arthroscopy >3-12 months following hip injection. Similarly, for the US cohort, 673 (56.6%) patients underwent hip arthroscopy ≤3 months after their hip injection, while 516 (43.4%) patients underwent hip arthroscopy >3-12 months following hip injection. Patients undergoing FL-guided (0.55%) and US-guided (0.58%) hip injection >3-12 months prior to hip arthroscopy had similar infection rates as those who did not undergo intraarticular injection in the 12 months prior to hip arthroscopy (0.50%, p=0.76 and p=0.75, respectively) (Table 1). Similarly, the infection rates for patients undergoing US-guided (0.45%) and FL-guided (0.45%) injections in the 3-months prior to arthroscopy were not significantly different from control patients who did not undergo preoperative hip injection (0.50%, p=1 for both). Results held in adjusted analysis controlling for age, sex, geography, year, smoking, and comorbidities. In reference to the no injection cohort, the adjusted odds ratio (95% CI) of postoperative infection for patients undergoing FL-guided injection ≤3 months and >3-12 months prior to hip arthroscopy were 0.90 (0.28-2.94, p=0.87) and 1.17 (0.36-3.84, p=0.80), respectively. For US-guided injection, the adjusted odds ratios at ≤3 months and >3-12 months were 0.89 (0.28-2.87, p=0.84) and 1.11 (0.34-3.60, p=0.86), respectively. Notably, infection rates in the arthroscopy ≤3 months cohort were substantially higher when including patients with an infection at the time of hip arthroscopy (FL 1.18%, US 0.74%). Conclusions: Postoperative infection following intraarticular hip injection ≤3 months prior to hip arthroscopy is rare (<0.5%) and no more common than in patients who did not undergo preoperative injection. Moreover, there do not appear to be substantial differences in infection risk between imaging-modalities. Notably, postoperative infection rates were substantially higher in sensitivity analyses where we did not exclude patients who had an infection at the time of the hip injection/aspiration. As the common procedural code for hip injections also includes aspirations, the elevated rates seen in the prior large database study were likely due to the ‘injections’ being aspirations of infected joints that then underwent arthroscopy[VNH1] . In conclusion, in the largest ever sample of patients undergoing hip injections prior to hip arthroscopy, hip injection ≤3 months prior to hip arthroscopy was not associated with increased infection risk for either US- or FL-guided injections.

Image-Guided Intra-articular Hip Injections and Risk of Infection After Hip Arthroscopy

Background: Although intra-articular injections are important in the management of patients who may later undergo hip arthroscopy, conflicting data are available regarding the safety of such injections when administered within 3 months of surgery. Furthermore, despite the increasing use of image-guided intra-articular hip injections, it is unknown whether the type of imaging modality used is associated with infection after hip arthroscopy. Purpose: To assess the risk of infection associated with image-guided intra-articular injections before hip arthroscopy and, secondarily, compare that risk between ultrasound (US) and fluoroscopic (FL) guidance. Study Design: Cohort study; Level of evidence, 3. Methods: This was a retrospective cohort study of patients in a large national insurance database who underwent hip arthroscopy between 2007 and 2017. Patients were required to have continuous enrollment from at least 1 year before to 6 months after hip arthroscopy. Patient age, sex, geographic region, medical history, surgical details, and hip injections were collected. Patients who underwent injection ≤3 months preoperatively and >3 to ≤12 months preoperatively were compared with patients who did not undergo preoperative injection. Bivariate analyses and multivariable logistic regressions were used to assess the association between ipsilateral preoperative hip injection and surgical site infection within 6 months of surgery. Results: We identified 17,987 patients (36.3% female; mean ± SD age, 37.6 ± 14.0 years) undergoing hip arthroscopy, 2276 (12.7%) of whom had an image-guided hip injection in the year preceding surgery (53.0% FL). Patients who underwent intra-articular injection ≤3 months preoperatively had similar infection rates to patients who did not undergo preoperative injection in the year before surgery for both the FL (0.46% vs 0.46%; P≥ .995) and the US cohorts (0.50% vs 0.46%; P = .76). Results persisted in adjusted analysis (FL ≤3 months: OR, 1.04; 95% CI, 0.32-3.37; P = .94; US ≤3 months: OR, 1.19; 95% CI, 0.36-3.90; P = .78). Similar results were seen for patients undergoing injections >3 to ≤12 months preoperatively. Conclusion: Postoperative infection was rare in patients undergoing intra-articular hip injection ≤3 months before hip arthroscopy and was no more common than in patients not undergoing preoperative injection. Moreover, no differences were seen in infection risk between US and FL guidance. Although intra-articular hip injections should always be administered with careful consideration, these results do not suggest that these injections are uniformly contraindicated in the 3 months preceding hip arthroscopy.

The Clinical Outcomes of Ultrasound-Guided Hip Joint Injection in The Treatment of Persistent Pain After Hip Arthroscopy

Background: To evaluate the short-term and long-term clinical outcomes of ultrasound-guided hip joint injection in the treatment of persistent pain after hip arthroscopy.Methods: Patients who had persistent pain after hip arthroscopy and underwent ultrasound-guided hip injection for treatment between January 2016 and February 2019 were involved. Pre-injection patient-reported outcomes (PROs) and post-injection PROs 1 month after injection and at final follow-up were obtained, including visual analog scale (VAS), modified Harris Hip Score (mHHS), Hip Outcome Score – Sport Specific Subscale (HOS - SSS) and Hip Outcome Score - Activity of Daily Living (HOS – ADL). VAS 10 minutes after injection was also recorded. Patient satisfaction with outcome of injection (graded as excellent, good, fair or poor) was documented at the end of follow-up. Results: A total of 33 patients were involved in this study. The mean follow-up time after injection was 24.1 months. The mean time between surgery and injection was 10.7 months. The VAS, mHHS, HOS-SSS and HOS-ADL improved from 5.6 ± 1.4, 56.4 ± 10.7, 59.1 ± 8.5 and 44.2 ± 17.1 to 3.3 ± 2.1, 67.3 ± 12.7, 69.1 ± 14.7 and 57.2 ± 23.0, respectively at 1 month after injection and improved to 2.4 ± 2.2, 76.4 ± 11.7, 80.3 ± 14.3 and 69.6 ± 23.0 at final follow-up. All results demonstrated statistically significant difference between different time point (P < 0.05). Three (9.1%) patients thought the outcome of ultrasound-guided hip injection was excellent, 8 (24.2%) thought the outcome was good, 9 (27.3%) thought the outcome was fair, and 13 (39.4%) thought the effect of injection was poor.Conclusion: Ultrasound-guided hip joint injection would be a feasible treatment method of persistent pain after hip arthroscopy, especially in older patients, patients with higher BMI and patents who are sensitive to intra-articular injection.Level of Evidence IV.

Hip MRI findings and outcomes following imaging-guided hip injections

Objective: To determine if MRI findings prior to intra-articular corticosteroid hip infiltration are related to treatment outcomes. Methods: This prospective outcome study with retrospective MRI evaluation includes 100 consecutive patients with MRI within 6 months before a therapeutic intra-articular hip injection. Labrum, bone marrow, acetabular and femoral cartilage abnormalities were assessed by two radiologists blinded to patient outcomes: the proportion reporting "improvement" on the Patient’s Global Impression of Change (PGIC) scale at 1 day, 1 week and 1 month follow-up were compared based on MRI findings using χ2. The t-test was used to compare pain change scores with MRI abnormalities. Results: Patients with a normal labrum in the posterosuperior quadrant were more likely to report PGIC "improvement" at 1 week compared to labral degeneration (p = 0.048). Significant differences in pain change scores were found at all time points for the labral anteroinferior quadrant (p = 0.001, 1 day; p = 0.010, 1 week; p = 0.034, 1 month) with the highest reduction in patients with labral degeneration. Females were 2.80 times more likely to report clinically relevant "improvement" at 1 day (p = .049) and 2.90 times more likely to report clinically relevant "improvement" at 1 month (p = .045). Conclusion: Cartilage defects and marrow abnormalities were not associated with outcomes. Patients with a normal labrum in the posterosuperior quadrant had better outcomes at 1 week. Patients with labral degeneration of the anteroinferior quadrant had higher levels of pain reduction at all time points. Females were significantly more likely to report PGIC "improvement" Advances in knowledge: A significant treatment outcome was observed amongst gender, although there were no significant differences in the MRI findings.

P130 Qualitative findings from the Hip Injection Trial (HIT): experiences of living with hip osteoarthritis and receiving trial treatments

Background The HIT trial compared ultrasound-guided intra-articular hip injection (USGI) of triamcinolone acetonide and 1% lidocaine hydrochloride combined with best current treatment (BCT) with (i) BCT alone and (ii) an USGI of 1% lidocaine only combined with BCT (EudraCT: 2014-003412-37). BCT included verbal and written advice on exercise, weight loss and pain management. This nested qualitative study explored participants’ experiences of living with hip osteoarthritis (OA) and of the treatment they received. Methods Semi-structured interviews were completed with purposefully sampled trial participants after 2-month follow-up. Interviewers knew whether participants had received an injection within the trial, but not which injection. Thematic analysis was undertaken blind to the clinical trial results to facilitate an interpretive and inductive approach. Sampling ceased on inductive thematic saturation. Results 34 trial participants were interviewed across all arms (USGI of triamcinolone acetonide and lidocaine plus BCT = 13, BCT alone = 8, USGI of lidocaine plus BCT = 11). Interviewees were males (n = 13) and females, of varying ages (53 - 83 years), with varying self-reported improvement. Participants described how hip OA impacted on many aspects of their life. It caused pain and physical limitations, difficulties at work, lowered mood, and commonly disrupted sleep. Participants who received BCT alone reported receiving an examination, information/explanation and exercises. Despite this, most felt that they had not received ‘treatment’ and reported limited exercise adherence. They described little or no benefit from BCT, and thoughts about the future tended to focus on inevitable decline. In contrast, participants in both injection groups experienced marked improvements in pain and other aspects of life, including sleep. Participants described getting their “life back” and having “a new lease of life”. Perceived benefit appeared greater among those randomised to USGI of triamcinolone acetonide and lidocaine plus BCT, however length of benefit varied in both injection groups. Despite uncertainty about the longer-term benefits of injection and the possibility of having repeated injections, there was more hope and optimism about the future among participants who had received an injection in comparison to those who had received BCT alone. Conclusion Hip OA is burdensome, affecting many different aspects of life. Participants perceived little or no benefit from BCT alone but reported marked improvements when combined with an USGI of triamcinolone and lidocaine or lidocaine alone. This complements the clinical trial results which demonstrated superiority of USGI of triamcinolone and lidocaine plus BCT over 6 months compared with BCT alone, but no significant difference in hip pain intensity between the injection groups. Together these findings raise the possibility of a degree of placebo effect. Varying duration of response to injection between individuals and reported uncertainty regarding effectiveness and safety of future injections, suggest these areas as important for future research. Disclosures M. Holden None. A. Hawarden None. Z. Paskins None. E. Roddy None. C. Mallen None. C. Jinks None.

Application of Machine Learning for Predicting Clinically Meaningful Outcome After Arthroscopic Femoroacetabular Impingement Surgery

Background: Hip arthroscopy has become an important tool for surgical treatment of intra-articular hip pathology. Predictive models for clinically meaningful outcomes in patients undergoing hip arthroscopy for femoroacetabular impingement syndrome (FAIS) are unknown. Purpose: To apply a machine learning model to determine preoperative variables predictive for achieving the minimal clinically important difference (MCID) at 2 years after hip arthroscopy for FAIS. Study Design: Case-control study; Level of evidence, 3. Methods: Data were analyzed for patients who underwent hip arthroscopy for FAIS by a high-volume fellowship-trained surgeon between January 2012 and July 2016. The MCID cutoffs for the Hip Outcome Score–Activities of Daily Living (HOS-ADL), HOS–Sport Specific (HOS-SS), and modified Harris Hip Score (mHHS) were 9.8, 14.4, and 9.14, respectively. Predictive models for achieving the MCID with respect to each were built with the LASSO algorithm (least absolute shrinkage and selection operator) for feature selection, followed by logistic regression on the selected features. Study data were analyzed with PatientIQ, a cloud-based research and analytics platform for health care. Results: Of 1103 patients who met inclusion criteria, 898 (81.4%) had a minimum of 2-year reported outcomes and were entered into the modeling algorithm. A total of 74.0%, 73.5%, and 79.9% met the HOS-ADL, HOS-SS, and mHHS threshold scores for achieving the MCID. Predictors of not achieving the HOS-ADL MCID included anxiety/depression, symptom duration for >2 years before surgery, higher body mass index, high preoperative HOS-ADL score, and preoperative hip injection (all P < .05). Predictors of not achieving the HOS-SS MCID included anxiety/depression, preoperative symptom duration for >2 years, high preoperative HOS-SS score, and preoperative hip injection, while running at least at the recreational level was a predictor of achieving HOS-SS MCID (all P < .05). Predictors of not achieving the mHHS MCID included history of anxiety or depression, high preoperative mHHS score, and hip injections, while being female was predictive of achieving the MCID (all P < .05). Conclusion: This study identified predictive variables for achieving clinically meaningful outcome after hip arthroscopy for FAIS. Patient factors including anxiety/depression, symptom duration >2 years, preoperative intra-articular injection, and high preoperative outcome scores are most consistently predictive of inability to achieve clinically meaningful outcome. These findings have important implications for shared decision-making algorithms and management of preoperative expectations after hip arthroscopy for FAI.