Faculty Bibliography

Accurate and reproducible acetabular component positioning is among the most important technical factors affecting outcomes of total hip arthroplasty. Although several studies have investigated the influence of pelvic tilt and obliquity on functional acetabular anteversion, the effect of pelvic axial rotation has not yet been established. We analyzed a generic simulated pelvis created using preoperative full-body standing and sitting radiographs. A virtual acetabulum was placed in 144 different scenarios of acetabular anteversion and abduction angles. In each scenario, the effects of pelvic tilt and pelvic axial rotation on different combinations of acetabular orientations were assessed. The change in acetabular anteversion was 0.75° for each 1° of pelvic tilt and was most linear in abduction angles of 40°±45°. The change in acetabular anteversion was 0.8° for each 1° of pelvic axial rotation. Surgeons may consider adjusting acetabular anteversion in fixed axial pelvic deformities when the degree of deformity affects functional acetabular positioning, assessed from preoperative standing and sitting weight-bearing radiographs. [Orthopedics. 2023;46(1):e27-e30.].

BACKGROUND:Supervised machine learning techniques have been increasingly applied to predict patient outcomes after hip and knee arthroplasty procedures. The purpose of this study was to systematically review the applications of supervised machine learning techniques to predict patient outcomes after primary total hip and knee arthroplasty. METHODS:A comprehensive literature search using the electronic databases MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, and Cochrane Database of Systematic Reviews was conducted in July of 2021. The inclusion criteria were studies that utilized supervised machine learning techniques to predict patient outcomes after primary total hip or knee arthroplasty. RESULTS:Search criteria yielded n = 30 relevant studies. Topics of study included patient complications (n = 6), readmissions (n = 1), revision (n = 2), patient-reported outcome measures (n = 4), patient satisfaction (n = 4), inpatient status and length of stay (LOS) (n = 9), opioid usage (n = 3), and patient function (n = 1). Studies involved TKA (n = 12), THA (n = 11), or a combination (n = 7). Less than 35% of predictive outcomes had an area under the receiver operating characteristic curve (AUC) in the excellent or outstanding range. Additionally, only 9 of the studies found improvement over logistic regression, and only 9 studies were externally validated. CONCLUSION/CONCLUSIONS:Supervised machine learning algorithms are powerful tools that have been increasingly applied to predict patient outcomes after total hip and knee arthroplasty. However, these algorithms should be evaluated in the context of prognostic accuracy, comparison to traditional statistical techniques for outcome prediction, and application to populations outside the training set. While machine learning algorithms have been received with considerable interest, they should be critically assessed and validated prior to clinical adoption.

AIM/OBJECTIVE:Posterior stabilized (PS) and varus valgus constrained (VVC) knee polyethylene liners have been shown to confer excellent long-term functional results following revision total knee arthroplasty (rTKA). The purpose of this study was to compare outcomes of patients who underwent rTKA using either a PS or VVC liner. METHODS:A retrospective comparative study of 314 rTKA with either PS or VVC liner and a minimum follow-up time of two years was conducted. Patient demographics, complications, readmissions, and re-revision etiology and rates were compared between groups. Kaplan-Meier survivorship analysis was performed to estimate freedom from all-cause revision. RESULTS:Hospital LOS (3.41 ± 2.49 vs. 3.34 ± 1.93 days, p = 0.793) and discharge disposition (p = 0.418) did not significantly differ between groups. At a mean follow-up of 3.55 ± 1.60 years, the proportion of patients undergoing re-revision did not significantly differ (19.1% vs. 18.7%, p = 0.929). In subgroup analysis of re-revision causes, the VVC cohort had superior survival from re-revision due to instability compared to the PS cohort (97.8% vs. 89.4%, p = 0.003). Freedom from re-revision due to aseptic loosening did not significantly differ between groups (85.2% vs. 78.8%, p = 0.436). Improvements in range of motion (ROM) from preoperative to latest follow-up were similar as well. CONCLUSIONS:PS and VVC liners confer similar survivorship, complication rates, and overall knee ROM in rTKA. VVC liners were not associated with increased postoperative aseptic loosening and demonstrated superior freedom from re-revision due to instability. Future studies with longer follow-up are warranted to better determine significant differences in clinical outcomes between the two bearing options. LEVEL III EVIDENCE/METHODS:Retrospective Cohort Study.

INTRODUCTION/BACKGROUND:Despite the excellent outcomes associated with primary total hip arthroplasty (THA), implant failure and revision continue to burden the healthcare system. The use of computer-assisted navigation (CAN) offers the potential for more accurate placement of hip components during surgery. While intraoperative CAN systems have been shown to improve outcomes in primary THA, their use in the context of revision total hip arthroplasty (rTHA) has not been elucidated. We sought to investigate the validity of using CAN during rTHA. METHODS:A retrospective analysis was performed at an academic medical institution identifying all patients who underwent rTHA using CAN from 2016-2019. Patients were 1:1 matched with patients undergoing rTHA without CAN (control) based on demographic data. Cup anteversion, inclination, change in leg length discrepancy (ΔLLD) and change in femoral offset between pre- and post-operative plain weight-bearing radiographic images were measured and compared between both groups. A safety target zone of 15-25° for anteversion and 30-50° for inclination was used as a reference for precision analysis of cup position. RESULTS:Eighty-four patients were included: 42 CAN cases and 42 control cases. CAN cases displayed a lower ΔLLD (5.74 ± 7.0 mm vs 9.13 ± 7.9 mm, p = 0.04) and greater anteversion (23.4 ± 8.53° vs 19.76 ± 8.36°, p = 0.0468). There was no statistical difference between the proportion of CAN or control cases that fell within the target safe zone (40% vs 20.9%, p =  0.06). Femoral offset was similar in CAN and control cases (7.63 ± 5.84 mm vs 7.14 ± 4.8 mm, p = 0.68). CONCLUSION/CONCLUSIONS:Our findings suggest that the use of CAN may improve accuracy in cup placement compared to conventional methodology, but our numbers are underpowered to show a statistical difference. However, with a ΔLLD of ~ 3.4 mm, CAN may be useful in facilitating the successful restoration of pre-operative leg length following rTHA. Therefore, CAN may be a helpful tool for orthopedic surgeons to assist in cup placement and LLD during complex revision cases.

PURPOSE/OBJECTIVE:Aseptic loosening is a common cause of implant failure following total knee arthroplasty (TKA). Cement penetration depth is a known factor that determines an implant's "strength" and plays an important role in preventing aseptic loosening. Tourniquet use is thought to facilitate cement penetration, but its use has mixed reviews. The aim of this study was to compare cement penetration depth between tourniquet and tourniquet-less TKA patients. METHODS:A multicenter retrospective review was conducted. Patients were randomized preoperatively to undergo TKA with or without the use of an intraoperative tourniquet. The variables collected were cement penetration measurements in millimeters (mm) within a 1-month post-operative period, length of stay (LOS), and baseline demographics. Measurements were taken by two independent raters and made in accordance to the zones described by the Knee Society Radiographic Evaluation System and methodology used in previous studies. RESULTS:A total of 357 TKA patients were studied. No demographic differences were found between tourniquet (n = 189) and tourniquet-less (n = 168) cohorts. However, the tourniquet cohort had statistically, but not clinically, greater average cement penetration depth [2.4 ± 0.6 mm (range 1.2-4.1 mm) vs. 2.2 ± 0.5 mm (range 1.0-4.3 mm, p = 0.01)]. Moreover, the tourniquet cohort had a significantly greater proportion of patients with an average penetration depth within the accepted zone of 2 mm or greater (78.9% vs. 67.3%, p = 0.02). CONCLUSION/CONCLUSIONS:Tourniquet use does not affect average penetration depth but increases the likelihood of achieving optimal cement penetration depth. Further study is warranted to determine whether this increased likelihood of optimal cement penetration depth yields lower revision rates.

The use of intraoperative technology (IT), such as computer-assisted navigation (CAN) and robot-assisted surgery (RA), in total knee arthroplasty (TKA) is increasingly popular due to its ability to enhance surgical precision and reduce radiographic outliers. There is disputing evidence as to whether IT leads to better clinical outcomes and reduced postoperative pain. The purpose of this study was to determine if use of CAN or RA in TKA improves pain outcomes. This is a retrospective review of a multicenter randomized control trial of 327 primary TKAs. Demographics, surgical time, IT use (CAN/RA), length of stay (LOS), and opioid consumption (in morphine milligram equivalents) were collected. Analysis was done by comparing IT (n = 110) to a conventional TKA cohort (n = 217). When accounting for demographic differences and the use of a tourniquet, the IT cohort had shorter surgical time (88.77 ± 18.57 vs. 98.12 ± 22.53 minutes; p = 0.005). While postoperative day 1 pain scores were similar (p = 0.316), the IT cohort has less opioid consumption at 2 weeks (p = 0.006) and 1 month (p = 0.005) postoperatively, but not at 3 months (p = 0.058). When comparing different types of IT, CAN, and RA, we found that they had similar surgical times (p = 0.610) and pain scores (p = 0.813). Both cohorts had similar opioid consumption at 2 weeks (p = 0.092), 1 month (p = 0.058), and 3 months (p = 0.064) postoperatively. The use of IT in TKA does not yield a clinically significant reduction in pain outcomes. There was also no difference in pain or perioperative outcomes between CAN and RA technology used in TKA.

The Risk Assessment Prediction Tool (RAPT) predicts discharge disposition after total joint arthroplasty with only 75% accuracy. The goal of this study was to evaluate whether higher accuracy can be achieved with basic electronic health record (EHR) data combined with machine learning (ML) algorithms. Three ML analysis models were developed: model 1 (M1) evaluated the accuracy of predicted discharge disposition in concordance with the RAPT; model 2 (M2) used the RAPT questionnaire to develop an ML algorithm to predict the likelihood of discharge to home vs facility; and model 3 (M3) was developed with non-RAPT data (age, surgeon, and discharge preference) with the same ML training process as M2. Evaluation metrics included accuracy for home discharge (HD), positive predictive value for HD (PPV-HD), negative predictive value for HD (NPV-HD), sensitivity, specificity, and area under the receiver operating curve (AUROC). A total of 1405 patients were included. With M1, the overall accuracy for HD was 83.5%, PPVHD was 92.1%, NPV-HD was 45%, sensitivity was 0.88, and specificity was 0.56. With M2, the overall accuracy for HD decreased to 82.8%, PPV-HD was 91.7%, NPV-HD was 43.1%, sensitivity was 0.87, specificity was 0.53, and mean AUROC was 0.87±0.03. With M3, overall accuracy for HD increased to 90.3%, PPV-HD was 95.2%, NPV-HD was 68.6%, sensitivity was 0.93, specificity was 0.76, and AUROC was 0.91±0.02. The use of basic EHR data combined with ML can exceed the accuracy of the RAPT. Applying big data on an individual level for this purpose may allow for safer and more appropriate discharge planning. [Orthopedics. 2022;45(4):e211-e215.].

BACKGROUND:Isolated head and liner exchange is an appealing alternative to a more extensive revision total hip arthroplasty in patients who have well-fixed components. Despite efforts to increase femoral offset and restore soft tissue tensioning, limited component revision may be associated with higher rates of postoperative instability. METHODS:(range, 18.2-46.7). The most common indications for surgery included acetabular liner wear in 86 hips (41%), instability in 40 hips (19%), and infection in 36 hips (17%). RESULTS:increase, 95% CI 0.80-0.99, P = .046). CONCLUSION/CONCLUSIONS:In a large cohort of patients who had isolated head and liner exchange, patients who had prior instability had 7-fold elevated odds of postoperative dislocation. This risk remains significant after controlling for cup positioning outside the Lewinnek safe zone, liner type, head size, neck length, soft tissue compromise, neuromuscular disease, and dual mobility constructs. LEVEL OF EVIDENCE/METHODS:III, retrospective cohort study.

INTRODUCTION/BACKGROUND:The purpose of this study was to identify common complications and the rates of readmission and revision in total knee arthroplasty (TKA) patients younger than 65 years. METHODS:Using the American Joint Replacement Registry, we conducted a retrospective review of all TKAs done in patients aged 18 to 65 years from 2012 to 2020. Demographic factors such as age, sex, Charlson Comorbidity Index (CCI), and preoperative Veterans RAND 12-Item Health Survey Physical Component Summary (VR-12 PCS) scores were collected. We excluded patients older than 65 years and revision, oncologic, and nonelective cases. Primary outcomes included cumulative revision rate, 90-day readmission rate, and reason for revision. Univariate analysis and the Kaplan-Meier method were used. RESULTS:Six thousand one hundred seventy-nine patients were included. The average age was 58.8 years (SD 5.5 years), 61% were female, 82% were White, and 88% had a CCI of 0 (1 = 8% and ≥2 = 4%). The mean follow-up was 42.51 months. Seventy-four patients (1.2%) underwent revision. Sixty-nine patients (1.1%) were readmitted within 90 days. No factors assessed increased revision rates. Revision-free survivorship was 98.7% (95% CI 98.4 to 99.0) and 98.6% (95% CI 98.2 to 99.0) at 5 and 8 years, respectively. Infection (15%), aseptic loosening (14%), and instability (12%) were the most common indications for revision. CONCLUSION/CONCLUSIONS:TKA done in young and presumed active patients has excellent survivorship. Long-term follow-up is needed to assess survival trends in this growing population.

INTRODUCTION/UNASSIGNED:Isolated head and liner exchange in aseptic revision total hip arthroplasty (rTHA) is an appealing option rather than full acetabular component revision; however, early outcome reports suggest high rates of complications requiring re-revision. This study seeks to compare the outcomes of these procedures. METHODS/UNASSIGNED:This retrospective study assessed 124 head and liner exchanges and 59 full acetabular cup revisions conducted at a single center between 2011 and 2019 with at least 2 years of follow-up. Baseline demographics did not vary by group. Mean follow-up was 3.7 (range 2.0-8.6) years. RESULTS/UNASSIGNED:0.22) were associated with failure within 2 years. CONCLUSIONS/UNASSIGNED:In this analysis, 2-year outcomes for isolated head and liner exchange were non-inferior to full acetabular component revision. A future randomised prospective study should be conducted to better assess the optimal approach to revision in an aseptic failed hip arthroplasty.