Dislocation is one of the most common complications in total hip arthroplasty (THA) and is primarily driven by bony or prosthetic impingement. The aim of this study was two-fold. First, to develop a simulation that incorporates the functional position of the femur and pelvis and instantaneously determines range of motion (ROM) limits. Second, to assess the number of patients for whom their functional bony alignment escalates impingement risk. 468 patients underwent a preoperative THA planning protocol that included functional x-rays and a lower limb CT scan. The CT scan was segmented and landmarked, and the x-rays were measured for pelvic tilt, femoral rotation, and preoperative leg length discrepancy (LLD). All patients received 3D templating with the same implant combination (Depuy; Corail/Pinnacle). Implants were positioned according to standardised criteria. Each patient was simulated in a novel ROM simulation that instantaneously calculates bony and prosthetic impingement limits in functional movements. Simulated motions included flexion and standing-external rotation (ER). Each patient's ROM was simulated with their bones oriented in both functional and neutral positions. 13% patients suffered a ROM impingement for functional but not neutral extension-ER. As a result, 48% patients who failed the functional-ER simulation would not be detected without consideration of the functional bony alignment. 16% patients suffered a ROM impingement for functional but not neutral flexion. As a result, 65% patients who failed the flexion simulation would not be detected without consideration of the functional bony alignment. We have developed a ROM simulation for use with preoperative planning for THA surgery that can solve bony and prosthetic impingement limits instantaneously. The advantage of our ROM simulation over previous simulations is instantaneous impingement detection, not requiring implant geometries to be analysed prior to use, and addressing the functional position of both the femur and pelvis.
Iliopsoas tendonitis occurs in up to 30% of patients after hip resurfacing arthroplasty (HRA) and is a common reason for revision. The primary purpose of this study was to validate our novel computational model for quantifying iliopsoas impingement in HRA patients using a case-controlled investigation. Secondary purpose was to compare these results with previously measured THA patients. We conducted a retrospective search in an experienced surgeon's database for HRA patients with iliopsoas tendonitis, confirmed via the active hip flexion test in supine, and control patients without iliopsoas tendonitis, resulting in two cohorts of 12 patients. The CT scans were segmented, landmarked, and used to simulate the iliopsoas impingement in supine and standing pelvic positions. Three discrete impingement values were output for each pelvic position, and the mean and maximum of these values were reported. Cup prominence was measured using a novel, nearest-neighbour algorithm. The mean cup prominence for the symptomatic cohort was 10.7mm and 5.1mm for the asymptomatic cohort (p << 0.01). The average standing mean impingement for the symptomatic cohort was 0.1mm and 0.0mm for the asymptomatic cohort (p << 0.01). The average standing maximum impingement for the symptomatic cohort was 0.2mm and 0.0mm for the asymptomatic cohort (p << 0.01). Impingement significantly predicted the probability of pain in logistic regression models and the simulation had a sensitivity of 92%, specificity of 91%, and an AUC ROC curve of 0.95. Using a case-controlled investigation, we demonstrated that our novel simulation could detect iliopsoas impingement and differentiate between the symptomatic and asymptomatic cohorts. Interestingly, the HRA patients demonstrated less impingement than the THA patients, despite greater cup prominence. In conclusion, this tool has the potential to be used preoperatively, to guide decisions about optimal cup placement, and postoperatively, to assist in the diagnosis of iliopsoas tendonitis.
Iliopsoas impingement occurs in between 5–30% of patients after hip arthroplasty and has been thought to only be caused by an oversized cup, cup malpositioning, or the depth of the psoas valley. However, no study has associated the relationship between preoperative measurements with the risk of impingement. This study sought to assess impingement between the iliopsoas and acetabular cup using a novel validated model to determine the risk factors for iliopsoas impingement. 413 patients received lower limb CT scans and lateral x-rays that were segmented, landmarked, and measured using a validated preoperative planning protocol. Implants were positioned according to the preference of ten experienced surgeons. The segmented bones were transformed to the standing reference frame and simulated with a novel computational model that detects impingement between the iliopsoas and acetabular cup. Definitions of patients at-risk and not at-risk of impingement were defined from a previous validation study of the simulation. At-risk patients were propensity score matched to not at-risk patients. 21% of patients were assessed as being at-risk of iliopsoas impingement. Significant differences between at-risk patients and not at-risk patients were observed in standing pelvic tilt (p << 0.01), standing femoral internal rotation (p << 0.01), medio-lateral centre-of-rotation (COR) change (p << 0.01), supine cup anteversion (p << 0.01), pre- to postoperative cup offset change (p << 0.001), postoperative gross offset (p = 0.009), and supero-inferior COR change (p = 0.02). Impingement between the iliopsoas and acetabular cup is under-studied and may be more common than is published in the literature. Previously it has been thought to only be related to cup size or positioning. However, we have observed significant differences between at-risk and not at-risk patients in additional measurements. This indicates that its occurrence is more complex than simply being related to cup position.
In 2021, Vigdorchik et al. published a large multicentre study validating their simple Hip-Spine Classification for determining patient-specific acetabular component positioning in total hip arthroplasty (THA). The purpose of our study was to apply this Hip-Spine Classification to a sample of Australian patients undergoing THA surgery to determine the local acetabular component positioning requirements. Additionally, we propose a modified algorithm for adjusting cup anteversion requirements. 790 patients who underwent THA surgery between January 2021 and June 2022 were assessed for anterior pelvic plane tilt (APPt) and sacral slope (SS) in standing and relaxed seated positions and categorized according to their spinal stiffness and flatback deformity. Spinal stiffness was measured using pelvic mobility (PM); the ΔSS between standing and relaxed seated. Flatback deformity was defined by APPt <-13° in standing. As in Vigdorchik et al., PM of <10° was considered a stiff spine. For our algorithm, PM of <20° indicated the need for increased cup anteversion. Using this approach, patient-specific cup anteversion is increased by 1° for every degree the patient's PM is <20°. According to the Vigdorchik simple Hip-Spine classification groups, we found: 73% Group 1A, 19% Group 1B, 5% Group 2A, and 3% Group 2B. Therefore, under this classification, 27% of Australian THA patients would have an elevated risk of dislocation due to spinal deformity and/or stiffness. Under our modified definition, 52% patients would require increased cup anteversion to address spinal stiffness. The Hip-Spine Classification is a simple algorithm that has been shown to indicate to surgeons when adjustments to acetabular cup anteversion are required to account for spinal stiffness or flatback deformity. We investigated this algorithm in an Australian population of patients undergoing THA and propose a modified approach: increasing cup anteversion by 1° for every degree the patient's PM is <20°.
Iliopsoas impingement occurs in 4% to 30% of patients after undergoing total hip arthroplasty (THA). Despite a relatively high incidence, there are few attempts at modelling impingement between the iliopsoas and acetabular component, and no attempts at modelling this in a representative cohort of subjects. The purpose of this study was to develop a novel computational model for quantifying the impingement between the iliopsoas and acetabular component and validate its utility in a case-controlled investigation. This was a retrospective cohort study of patients who underwent THA surgery that included 23 symptomatic patients diagnosed with iliopsoas tendonitis, and 23 patients not diagnosed with iliopsoas tendonitis. All patients received postoperative CT imaging, postoperative standing radiography, and had minimum six months’ follow-up. 3D models of each patient’s prosthetic and bony anatomy were generated, landmarked, and simulated in a novel iliopsoas impingement detection model in supine and standing pelvic positions. Logistic regression models were implemented to determine if the probability of pain could be significantly predicted. Receiver operating characteristic curves were generated to determine the model’s sensitivity, specificity, and area under the curve (AUC).Aims
Methods
Leg length discrepancy (LLD) is a common pre- and postoperative issue in total hip arthroplasty (THA) patients. The conventional technique for measuring LLD has historically been on a non-weightbearing anteroposterior pelvic radiograph; however, this does not capture many potential sources of LLD. The aim of this study was to determine if long-limb EOS radiology can provide a more reproducible and holistic measurement of LLD. In all, 93 patients who underwent a THA received a standardized preoperative EOS scan, anteroposterior (AP) radiograph, and clinical LLD assessment. Overall, 13 measurements were taken along both anatomical and functional axes and measured twice by an orthopaedic fellow and surgical planning engineer to calculate intraoperator reproducibility and correlations between measurements.Aims
Methods
Total hip arthroplasty (THA) continues moving to the outpatient arena, and may be feasible for some conversion and revision scenarios. Controversy surrounds appropriate patient selection. The purpose of this study is to report complications associated with outpatient revision and conversion THA, and to determine if comorbidities are associated with complications or overnight stay. From June 2013 through March 2018, 43 patients (44 hips) underwent conversion (n=12) or revision (n=32) THA at a free-standing ambulatory surgery center. Mean patient age was 58.4 years, and 52% of patients were male. Conversion procedures were for failed resurfacing in two, failed hemiarthroplasty in one, and failed fracture fixation with retained hardware in 9. Revision procedures involved head only in one, head and liner in 20, cup and head in 7, stem only in 2, and stem and liner in 2. Forty-four (93%) were discharged same day without incident, none required transfer to acute facility, and 3 required overnight stay with 2 of these for convenience and only one for a medical reason, urinary retention. Three patients with early superficial infection were successfully treated with oral antibiotics. There were no major complications, readmissions, or subsequent surgeries within 90 days. One or more major comorbidities were present in 17 patients (39%) including 1 valvular disease, 8 arrhythmia, 2 thromboembolism history, 3 obstructive sleep apnea, 6 chronic obstructive pulmonary disease, 2 asthma, 4 frequent urination, and 1 renal disease. The single patient who stayed overnight for a medical reason had no major medical comorbidities. Outpatient arthroplasty, including revision THA in some scenarios, is safe for many patients. Presence of medical comorbidities was not associated with risk of complications. The paradigm change of patient education, medical optimization, and a multimodal program to mitigate risk of blood loss and reduce need for narcotics facilitates performing arthroplasty safely in an outpatient setting.
The Intellijoint HIP system is a mini-optical navigation system designed to intraoperatively assist with cup orientation, leg length and offset in total hip replacement (THR). As with any imageless navigation system, acquiring the pelvic reference frame intraoperatively requires assumptions. The system does however have the ability to define the native acetabular orientation intra-operatively by registering 3-points along the bony rim. In conjunction with a pre-operative CT scan, the authors hypothesised that this native acetabular plane could be used as an intraoperative reference to achieve a planned patient-specific cup orientation. Thirty-eight THR patients received preoperative OPSTM dynamic planning (Optimized Ortho, Sydney). On the pre-operative 3D model of each patient's acetabulum, a 3-point plane was defined by selecting recognisable features on the bony rim. The difference in inclination and anteversion angles between this native 3-point reference plane and the desired optimal orientation was pre-operatively calculated, and reported to the surgeon as “adjustment angles”. Intraoperatively, the surgeon tried to register the same 3-points on the bony rim. Knowing the intraoperative native acetabular orientation, the surgeon applied the pre-calculated adjustment angles to achieve the planned patient specific cup orientation. All patients received a post-operative CT scan at one-week and the deviation between planned and achieved cup orientation was measured. Additionally, the cup orientation that would have been achieved if the standard Intellijoint pelvic acquisition was performed was retrospectively determined.Introduction
Method
Financial impact and patient satisfaction with four different anticoagulants for hip and knee arthroplasty in patients with a previous history of VTE- A prospective randomised trial New generation oral anticoagulants (dabigatran/rivaroxaban) have recently become available for the prevention of venous thromboembolism (VTE) following hip and knee arthroplasty. Traditional therapies (warfarin/low molecular weight heparins) are less costly, but have several limitations. The aim of this study was to evaluate the financial impact of substituting enoxaparin and warfarin with newer therapies dabigatran and rivaroxaban. A secondary objective was to investigate patient satisfaction with these treatments. A randomised prospective study was conducted over a 12 month period. Patients with a history of VTE undergoing hip or knee replacement were randomised to receive one of four anticoagulants for five weeks post surgery. Information was gathered during the hospital stay and then post discharge, by telephone, for five weeks(35 days)to determine costs. The costs included cost of drug, nursing time, blood monitoring and transport costs. The patients were also asked to complete the Duke Anticoagulation Satisfaction Scale (DASS). The DASS is a 26 item questionnaire which has 7 responses for each question.Introduction
Methods
CTEV is a difficult condition to treat with chances of recurrence, re-operation rate and over correction. Recent literature based on evidence is favourable with the Ponseti management. The aim of the study was to review our surgical results over a 5-year period using the Cincinnati approach. Children with failure of conservative serial stretching and casting for 6 months underwent open release. The records and radiographs were reviewed retrospectively from 1997–2002. 60 patients were identified with 92 feet undergoing primary sub radical releases using the Cincinnati approach in 40 male and 20 female children. The mean age at surgery was 10 months. 55 patients were idiopathic with 3 syndromal and 2 teratological. Consultants performed >
75% of operations, with k-wire stabilisation done in 46 patients and primary wound closure in 25; the majority of wounds were left open. The timing of plaster change varied, with the majority at 2 weeks. Wound problems occurred in 4 patients (significant in 2). All patients but one wore splints for an average length of 13 months. Complication rate was 20% comprising infection, over- correction and recurrence. Re-operation rate for early recurrence was 12%. Further surgery in the form of tibialis anterior transfer and derotation osteotomy was performed on 15% and 10% of feet respectively. 6 feet in 4 patients showed signs of significant over correction. Wound healing by secondary intention of the Cin-cinnati approach is safe. Results and complications are comparable to other series, but not to the Ponseti non-operative management. Practice is now changed to the latter based on evidence.
