Some Offset Restoration Options Can Paradoxically Lead to Decreased Range of Motion in Primary Total Hip Arthroplasty: A 3-Dimensional Computer Simulation Study.

BACKGROUND: In total hip arthroplasty (THA), femoral offset restoration results in optimal biomechanics and range of motion (ROM) without bone-bone impingement. We hypothesized that differences in implant design features significantly affect bone-bone impingement risk in primary THA. METHODS: This retrospective computer simulation study included a cohort of 43 primary robotic arm-assisted THA. Considering sagittal pelvic tilt, we measured the maximum external rotation at 0° hip flexion and the maximum internal rotation at both 90° and 100° hip flexion before any bone-bone impingement occurred. To influence the offset, we included neutral or extended polyethylene liners, neutral or plus prosthetic heads, standard or high-offset stems, and stems with 132° or 127° neck angles. RESULTS: Extended polyethylene liner use resulted in decreased bone-bone impingement for both stems but also decreased prosthetic ROM in hip extension (mean -4.5 to 5°, range -10 to 0°) and hip flexion (mean -3 to 3.7°, range -10 to 0°) due to decreases in head diameter. Using a plus head or different stem offset/neck angle options resulted in either (1) no improvement in ROM (stem 1: 60%; stem 2: 28%) or (2) a paradoxical increase in bone-bone impingement (stem 1 with 127°: 19% and stem 2 with high offset option: 7%). CONCLUSION: Counterintuitively, a subset of patients experience a paradoxical increase in bone-bone impingement when transitioning from standard to high-offset or varus necks due to the pelvic and proximal femoral bone shape. For this group of patients, preoperative personalized 3-dimensional modeling may help guide implant choice for optimizing outcomes.

How Do Spinopelvic Characteristics Change Post-Total Hip Arthroplasty? A Longitudinal Assessment Raising Awareness of the Postoperative Period.

BACKGROUND: Spinopelvic characteristics, including sacral slope (SS), are commonly evaluated in different positions pre-total hip arthroplasty (THA). This study aimed to: 1) investigate the change in spinopelvic parameters at 7 days (early) and 1-year post-THA; and 2) identify patient characteristics associated with a change in SS of more than 7° post-THA. METHODS: We prospectively studied 250 patients who underwent unilateral THA [132 women, age 66 years (range, 32 to 88)] and underwent biplanar images preoperatively and at 7 days and 1-year post-THA. Parameters measured included pelvic incidence, standing lumbar lordosis, SS, and proximal femoral angle (PFA). A SS change ≥ 7° was considered the threshold as it would result in more than a 5° change in cup orientation. RESULTS: Early post-THA SSstanding remained within ± 6º from preoperative measurements in 75% of patients, reduced by ≥ 7° in 9%, and increased by ≥ 7° in 16%. Those that showed a reduction in SS had the lowest PFA and the highest SS pre-THA (P = .028, .107, and < 0.001, respectively). From 7 days until the 1-year mark, pelvic tilt increased, SS reduced (mean: -4º, range: -29 to 17º, P < .001), and patients stood with greater hip extension ΔPFAstanding (mean 7°, range: -34 to 37°, P < .001). At 1 year, SSseated had remained within ± 6º, relative to the pre-THA value, in 49% of patients. CONCLUSIONS: Standing spinopelvic characteristics, especially SSstanding, remain within ±6° in three-quarters of patients both early- and at 1-year post-THA. In the remaining cases, pelvic tilt changes significantly. In 9% of cases, SS reduces ≥ 7° early THA, probably due to the alleviation of fixed-flexion contractures. The SSseated changes by ≥ ± 7° in almost 50% of cases in this study, and its clinical value as a preoperative planning tool should be questioned. LEVEL OF EVIDENCE: Level II, diagnostic study.

Implementation of the New Medicare-Mandated Patient-Reported Outcomes After Joint Arthroplasty Performance Measure.

A new mandatory hospital-level, risk-standardized performance measure for elective total hip arthroplasty (THA) and total knee arthroplasty (TKA) based on patient-reported outcomes (THA/TKA PRO-PM) has been implemented by the Centers for Medicare & Medicaid Services (CMS). All THA and TKA in Medicare fee-for-service beneficiaries at inpatient facilities are included. The THA/TKA PRO-PM is the proportion of risk-standardized THA or TKA patients meeting or exceeding the substantial clinical benefit threshold between preoperative and postoperative outcomes measures (Hip dysfunction and Osteoarthritis Outcome Score for Joint Replacement, Knee injury and Osteoarthritis Outcome Score for Joint Replacement). This binary outcome (yes/no) is then divided by all eligible patients creating a percentage of patients reaching substantial clinical benefit. The percentile score among hospitals will be reported. Following 2 voluntary reporting periods, mandatory reporting will begin in 2025. The CMS requires 50% reporting rates; failure leads to annual payment reduction in fiscal year 2028. The CMS intends the THA/TKA PRO-PM to be a patient-centered, meaningful, and relatable measure of hospital performance reported to the public. For surgeons, this is an opportunity to collaborate with hospitals for developing and implementing a THA/TKA data collection system to avoid penalties for the hospital. Further implementation for outpatient surgery and in ambulatory surgery centers has been announced by CMS. Major resources will be needed to succeed in the expected capture rates.

The Current Proposed Total Hip Arthroplasty Surgical Planning Guidelines Based on Classification of Spine Stiffness May be Flawed Due to Incorrect Assumptions.

BACKGROUND: The available classifications and preoperative planning tools for total hip arthroplasty assume that: 1) there is no variation in the sagittal pelvic tilt (SPT) if the radiographs are repeated, and 2) there is no significant change in the postoperative SPT postoperatively. We hypothesized that there would be significant differences in postoperative SPT tilt as measured by the sacral slope, thus rendering the current classifications and tools flawed. METHODS: This study was a multicenter, retrospective analysis of preoperative and postoperative (1.5-6 months) full-body imaging of 237 primary total hip arthroplasty (standing and sitting positions). Patients were categorized as 1) stiff spine (standing sacral slope sitting sacral slope < 10°) and 2) normal spine (standing sacral slope-sitting sacral slope ≥ 10°). Results were compared using the paired t-test. The posthoc power analysis showed a power of 0.99. RESULTS: The difference in mean standing and sitting sacral slope between the preoperative and postoperative measurements was 1°. However, in standing position, this difference was more than 10° in 14.4% of patients. In the sitting position, this difference was more than 10° in 34.2% of patients and more than 20° in 9.8% of patients. Postoperatively, 32.5% of patients switched groups based on the classification, which rendered the preoperative planning suggested by the current classifications flawed. CONCLUSION: Current preoperative planning and classifications are based on a single acquisition of preoperative radiographs without the incorporation of possible postoperative changes in SPT. Validated classifications and planning tools should incorporate repeated measurements to determine the mean and variance in SPT and consider the significant postoperative changes in SPT.

Utilization Patterns, Efficacy, and Complications of Venous Thromboembolism Prophylaxis Strategies in Primary Hip and Knee Arthroplasty as Reported by American Board of Orthopedic Surgery Part II Candidates.

BACKGROUND: Many strategies for venous thromboembolism (VTE) prophylaxis following hip and knee arthroplasty exist, with extensive controversy regarding the optimum strategy to minimize risk of VTE and bleeding complications. Data from the American Board of Orthopedic Surgery Part II (oral) Examination case list database was analyzed to determine efficacy, complication rates, and prescribing patterns for different prophylactic strategies. METHODS: The American Board of Orthopedic Surgery case database was queried utilizing Current Procedural Terminology codes 27447 and 27130 for primary total knee and hip arthroplasty, respectively. Geographic region, patient age, gender, deep vein thrombosis prophylaxis strategy, and complications were obtained. Less aggressive prophylaxis patterns were considered if only aspirin and/or sequential compression devises were utilized. More aggressive VTE prophylaxis patterns were considered if any of low-molecular-weight heparin (enoxaparin), warfarin, rivaroxaban, fondaparinux, or other strategies was used. RESULTS: In total, 22,072 cases of primary joint arthroplasty were analyzed from 2014 to 2016. The national rate of less aggressive VTE prophylaxis strategies was 45.4%, while more aggressive strategies were used in 54.6% of patients. Significant regional differences in prophylactic strategy patterns exist between the 6 regions. The predominant less aggressive prophylaxis pattern was aspirin with sequential compression devises at 84.8% with 14.8% receiving aspirin alone. Use of less aggressive prophylaxis strategy was significantly associated with patients having no complications (95.5% vs 93.0%). Use of more aggressive prophylaxis patterns was associated with higher likelihood of mild thrombotic (0.9% vs 0.2%), mild bleeding (1.3% vs 0.4%), moderate thrombotic (1.2% vs 0.4%), moderate bleeding (2.7% vs 2.1%), severe thrombotic (0.1% vs 0.0%), severe bleeding events (1.2% vs 0.9%), infections (1.9% vs 1.3%), and death within 90 days (0.7% vs 0.3%). Similar results were found in subgroup analysis of total hip and knee arthroplasty patients. CONCLUSION: It was not possible to ascertain the individual rationale for use of more aggressive VTE prophylaxis strategies; however, more aggressive strategies were associated with higher rates of bleeding and thrombotic complications. Less aggressive strategies were not associated with a higher rate of thrombosis. LEVEL OF EVIDENCE: Therapeutic Level III. DISCLAIMER: All views expressed in the study are the sole views of the authors and do not represent the views of the American Board of Orthopedic Surgery.

Does Patients' Perception of Leg Length After Total Hip Arthroplasty Correlate With Anatomical Leg Length?

BACKGROUND: This study assessed the correlation among the patients' perception of the leg length discrepancy (LLD) after total hip arthroplasty (THA) and the anatomical and functional leg length, pelvic and knee alignments, and foot height. METHODS: Patients without significant spinal pathology or previous spine or lower extremity surgery who underwent primary THA (101 patients) were evaluated using EOS images obtained in standing position. All 3-dimensional measures were evaluated and compared for the repeatability and reproducibility and correlation with patients' perception of leg length. RESULTS: In our study, the anatomical femoral length (odds ratio [OR] 0.9, P = .732) did not correlate with patients' perception of the LLD, but other variables like the distance from the middle of the tibial plafond to ground (OR 14.3, P = .003), sagittal knee alignment (OR 1.07, P = .021), and pelvic obliquity (OR 1.05, P = .021) were correlated with the patients' perception of LLD. CONCLUSION: The LLD is a multifactorial complication. We found that the anatomical femoral length as the factor that can be modified with THA technique or choice of prosthesis is not the only important factor. We recommend comprehensive physical examination to investigate spinal deformities, pelvic obliquity, abductor muscle weakness, sagittal and coronal knee alignment, and foot deformity in patients who complain of LLD after THA.

Acetabular and Femoral Anteversions in Standing Position are Outside the Proposed Safe Zone After Total Hip Arthroplasty.

BACKGROUND: Although most hip dislocations occur in either standing or sitting position, the safe zone for implant position is defined for the supine position. Our goal was to determine preoperative and postoperative pelvis and hip orientations and whether the safe zone defined in supine position can be used to assess standing radiographs. METHODS: Preoperative and postoperative three-dimensional EOS images were assessed in 66 total hip arthroplasty patients. None of the patients had dislocation within the follow-up period (12-36 months). The acetabular anteversion (both anterior pelvic plane [APP] and patient functional plane) and the femoral anteversion were measured. The sacral slope, pelvic version, pelvic inclination, and pelvic incidence were also measured. RESULTS: Acetabular anteversion increased postoperatively in both APP and patient functional plane (P <.001). Femoral neck anteversion decreased postoperatively (P =.0942). Sacral slope was 42.4° (-25.9° to 24°) preoperatively compared with 40.3° (-4.1° to 64.2°) postoperatively (P =.013). Pelvic version changed from 15.2° (-10.4° to 43.8°) to 17.2° (-6° to 46.7°; P = 0.008). Pelvic inclination was 1.12° (-25.9° to 24°) before total hip arthroplasty and -1.2° (-40.7° to 23.4°) postoperatively (P =.005). CONCLUSION: The acetabular and femoral implant orientations in standing position reside out of the safe zone in most patients. The APP is not vertical in standing position in most patients due to anterior or posterior pelvic tilt. The proposed safe zone in supine position may not be a useful measure in the assessment of standing radiographs of patients with significant anterior or posterior pelvic tilt. LEVEL OF EVIDENCE: Level IV, therapeutic case series study.

What is the Impact of a Spinal Fusion on Acetabular Implant Orientation in Functional Standing and Sitting Positions?

BACKGROUND: This study used EOS imaging of primary total hip arthroplasty (THA) patients, with and without predating spinal fusion, to investigate (1) the impact of spinal fusion on acetabular implant anteversion and inclination, and (2) whether more extensive spinal fusion (fusion starting above the thoracolumbar junction or extension of fusion to the sacrum) affects acetabular implant orientation differently than lumbar only spinal fusion. METHODS: Ninety-three patients had spinal fusion (case group), and 150 patients were without spinal fusion (controls). None of the patients experienced dislocation. The change in sacral slope (SS) and cup orientation from standing to sitting was measured. RESULTS: Mean SS change from the standing to sitting positions was -7.9°in the fusion group vs -18.4°in controls (P = .0001). Mean change in cup inclination from the standing to sitting positions was 4.9°in the fusion group vs 10.2°in controls (P = .0001). Mean change in cup anteversion from standing to sitting positions was 7.1°in the fusion group vs 12.1°in controls (P = .0001). For each additional level of spinal fusion, the change in SS from standing to sitting positions decreased by 1.6(95% confidence interval [CI], 2.2073-1.0741), the change in cup inclination decreased by 0.8(95% CI, 0.380-1.203), and the change in cup anteversion decreased by 0.9(95% CI, 0.518-1.352; P < .001 in all cases). CONCLUSION: Patients with spinal fusion demonstrated less adaptability of the lumbosacral junction. Longer spinal fusion or inclusion of the pelvis in the fusion critically impacts hip-spine biomechanics and significantly affects the ability to compensate in the standing-to-sitting transition.

Simulating movements of daily living in robot-assisted total hip arthroplasty with 3D modelling.

Aims: Computer-assisted 3D preoperative planning software has the potential to improve postoperative stability in total hip arthroplasty (THA). Commonly, preoperative protocols simulate two functional positions (standing and relaxed sitting) but do not consider other common positions that may increase postoperative impingement and possible dislocation. This study investigates the feasibility of simulating commonly encountered positions, and positions with an increased risk of impingement, to lower postoperative impingement risk in a CT-based 3D model. Methods: A robotic arm-assisted arthroplasty planning platform was used to investigate 11 patient positions. Data from 43 primary THAs were used for simulation. Sacral slope was retrieved from patient preoperative imaging, while angles of hip flexion/extension, hip external/internal rotation, and hip abduction/adduction for tested positions were derived from literature or estimated with a biomechanical model. The hip was placed in the described positions, and if impingement was detected by the software, inspection of the impingement type was performed. Results: In flexion, an overall impingement rate of 2.3% was detected for flexed-seated, squatting, forward-bending, and criss-cross-sitting positions, and 4.7% for the ankle-over-knee position. In extension, most hips (60.5%) were found to impinge at or prior to 50° of external rotation (pivoting). Many of these impingement events were due to a prominent ischium. The mean maximum external rotation prior to impingement was 45.9° (15° to 80°) and 57.9° (20° to 90°) prior to prosthetic impingement. No impingement was found in standing, sitting, crossing ankles, seiza, and downward dog. Conclusion: This study demonstrated that positions of daily living tested in a CT-based 3D model show high rates of impingement. Simulating additional positions through 3D modelling is a low-cost method of potentially improving outcomes without compromising patient safety. By incorporating CT-based 3D modelling of positions of daily living into routine preoperative protocols for THA, there is the potential to lower the risk of postoperative impingement events.

Back pain and total hip arthroplasty: a prospective natural history study.

BACKGROUND: Many patients with degenerative joint disease of the hip have substantial degeneration of the lumbar spine. These patients may have back and lower extremity pain develop after THA and it may be difficult to determine whether the source of the pain is the hip or spine. QUESTIONS/PURPOSES: We therefore: (1) identified the incidence/prevalence of pain in the lower back in a group of patients with end-stage arthritis of the hip undergoing THA; (2) described the natural history of low back pain in this cohort undergoing THA; and (3) determined factors that were predictive of persistent low back pain after THA. METHODS: We administered a detailed questionnaire and a diagram of the human body on which the patients could draw the site of their pain, to 344 patients preoperatively, at 6 weeks, 6 months, and 1-year after THA. Before the THA, 170 patients (49.4%) reported pain localized to the lower lumbar region, whereas 174 patients did not have low back pain. RESULTS: Low back pain was variable in location. Postoperatively, the low back pain resolved in 113 (66.4%) of the 170 patients. Thirty-seven of the remaining 57 patients had known spine disorders. Thirty-five of the 174 patients (20%) without prior low back pain had low back pain develop within 1 year postoperatively. The low back pain improved in 17 of these 35 patients; 12 of the remaining 18 patients had preexistent spine disorders. Pain radiating below the knee was associated most closely with preexisting spine disorders. CONCLUSIONS: Hip and spine arthritis often coexist. Most patients who presented with hip arthritis and lower lumbar pain experienced resolution or improvement of their pain after THA. LEVEL OF EVIDENCE: Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.

Bioabsorbable screw fixation of the syndesmosis in unstable ankle injuries.

PURPOSE: The purpose of this study was to retrospectively evaluate the clinical and radiographic outcomes of the medium and long-term results of Bionx bioabsorbable screw fixation of the ankle syndesmosis in unstable ankle injuries. MATERIALS AND MATERIALS: Between May 2001 and July 2006, 75 patients underwent syndesmotic fixation with a bioabsorbable screw. All patients had closed primary ankle fractures or dislocations with syndesmotic instability. Open reduction and internal fixation of the ankle fracture was performed using current standard orthopaedic technique. Patients were followed clinically and radiographically from 12 to 74 months with the mean being 32.5 months. RESULTS: Seventy of 75 patients (93%) returned for the final evaluation. Mean AOFAS Ankle-Hindfoot score was 90 of 100 and mean VAS for pain was 1.8 out of 10 at the time of final followup. No patients in this population showed radiographic syndesmotic instability, loss of mortise congruency, or post-traumatic arthritis in the sigmoid notch area at final followup. No patients required revision surgical fixation of the syndesmosis. CONCLUSION: This study demonstrates that the use of bioabsorbable screw for syndesmotic fixation is associated with satisfactory restoration of ankle function and syndesmotic stability.