Preoperative radiographs to predict component malposition in direct anterior approach total hip arthroplasty

Introduction: There is conflicting evidence as to whether or not patients undergoing total hip arthroplasty (THA) via the direct anterior approach (DAA) have increased risk of component malposition. The aim of this study was to investigate whether specific preoperative radiographic features were predictive of postoperative component malposition in DAA THA. Patients and methods: We examined 204 THA operations performed for osteoarthritis via the DAA at a single institution. Preoperative radiographs were analysed with numerous pre-specified measurements and classifications being recorded. Postoperative radiographs were analysed to determine if any of these preoperative radiographic factors correlated with component malposition in regard to cup inclination, cup version, femoral stem coronal alignment, leg-length discrepancy (LLD) and femoral offset discrepancy. Results: Numerous preoperative factors were associated with component malposition. Coxa profunda was found to be a significant predictor of cup anteversion being outside of the target range ( p = 0.0089) and an increased centre-edge angle was a significant predictor for a postoperative LLD ( p = 0.0134). A decreased neck-shaft angle ( p = 0.0007) and a lower preoperative LLD ( p = 0.0019) were both predictive of femoral stem coronal malalignment. Conclusions: Preoperative radiographs can be a valuable tool for surgeons in predicting patients at risk of component malposition in DAA THA.

The Agility Total Ankle Arthroplasty: A Concise Follow-up at a Minimum of 20 Years

Background: Between 1984 and 1994, a single surgeon performed 132 primary cementless total ankle replacements using the Agility total arthroplasty system. The purpose of this study was to report on the 20-year follow-up, which we believe is the first study with this length of follow-up. Methods: Living patients were contacted and interviewed to determine the status of their implant (revised or unrevised) and to answer a simple questionnaire concerning overall satisfaction, pain, and functional improvement, as in a previous study. Thirty-three (26.2%) patients with 33 (25%) ankles of the original series were alive at a minimum of 20 years postoperatively, with a median follow-up of 22 years. They were asked to return to the office for standing anteroposterior and lateral ankle and foot radiographs or to send these radiographs if performed elsewhere. Radiographs were evaluated for radiolucencies around the components and subsidence (talar component) or migration (tibial component) of components. Results: Seventeen (13.5%) ankles of the 126 available for follow-up, including 5 (15.2%) ankles in living patients, had undergone revision ( n = 10) or arthrodesis ( n = 7) for loosening. One additional ankle was revised for infection and 1 for talar component malposition; thus, 19 (15.1%) ankles were revised. Conclusion: These results should provide a 20-year benchmark for newer total ankle arthroplasty designs when a similar length of follow-up becomes available. Level of Evidence: Level III, retrospective cohort study.

The impact of extreme genu varum and genu valgum on postoperative outcomes using mini-subvastus approach in TKA

Increasing interest in using minimally invasive approaches in TKA has led to the question: how much deformity is accepted for using MIS in TKA? A single surgeon performed 87 consecutive TKAs with mini-subvastus approach, using unconstrained prosthesis in 84 knees and constrained prosthesis in 3 knees. We conducted a prospective study in which patients were divided into two groups according to preoperative tibiofemoral axes (TFM), one group with 160°<TFM<195° and the second group with 160°≥TFM≥195°. Clinical and radiographic outcomes were compared. Postoperative ROM and knee score were improved in both groups, with similar results (p<0.01). Postoperative radiographic analyses showed that TFM was improved in both groups (p<0.01) with the coronal alignment inferior in 160°≥TFM≥195° group than the 160°<TFM<195° group. The results of this study suggest that mini-subvastus approach is a proper technique to use in primary TKA in patients with a TFM angle less than 160° and more than 195° with similar results with TFM angle between 160° and 195°, and for the use of constrained prosthesis designs with promising results. Preoperative TFM angle less than 160° and greater than 195° increases the risk of component malposition in coronal plane.

Influence of Implant Acetabular Component Orientation on Hip Stability

Introduction.Acetabular component malposition at total hip arthroplasty is a common situation that may affect the frequency of dislocation and the rate of implant friction unit wear. The purpose of the study was to determine the influence of different factors on the variability of acetabular component orientation and evaluate the role of orientation in dislocation development.Patients and methods.Total number of patients made up 1408. Out of them 695 patients were operated on at RSRITO named after R.R. Vreden using standard approaches (group 1), 184 - using low invasive approach (group 2) and 55 patients were admitted with implant head dislocation (group 4). At City St. Petersburg hospitals 474 patients (group 3) were operated on. Orientation of acetabular component (inclination and anteversion angles) was evaluated on digital pelvis and plain hip roentgenograms. Dispersion unifactorial analysis was used to evaluate the dependence of the precision of acetabular component positioning upon the surgeon’s experience, patient’s body mass index, type of surgical approach and the use of guide for acetabular component implantation.Results.Within the first postoperative year the rate of femoral component dislocation in group 1 made up 0.9%. Within the Lewinnek safe zone 76.6% of acetabular components were implanted with the use of a guide and 71.8% without. The rate of dislocation in group 2 made up 71.8% and 63.4% of components were implanted within the safe zone. In group 3 the intra-hospitalization dislocation developed in 1.9% of patients and satisfactory positioning relative to Lewinnek safe zone was achieved in 68.2% of cases. The risk factors for acetabular component malposition included high body mass indices, use of low invasive approach and insufficient experience of the operating surgeon. No direct influence of acetabular component orientation upon the femoral component dislocation was detected.Conclusion. Further studies directed to the more detailed analysis of additional factors that either directly or indirectly affect the implant function and to the optimization of surgical technique that would enable the reproducibility of total hip arthroplasty results are required.

Influence of Implant Acetabular Component Orientation on Hip Stability

Introduction. Acetabular component malposition at total hip arthroplasty is a common situation that may affect the frequency of dislocation and the rate of implant friction unit wear. The purpose of the study was to determine the influence of different factors on the variability of acetabular component orientation and evaluate the role of orientation in dislocation development. Patients and methods. Total number of patients made up 1408. Out of them 695 patients were operated on at RSRITO named after R.R. Vreden using standard approaches (group 1), 184 - using low invasive approach (group 2) and 55 patients were admitted with implant head dislocation (group 4). At City St. Petersburg hospitals 474 patients (group 3) were operated on. Orientation of acetabular component (inclination and anteversion angles) was evaluated on digital pelvis and plain hip roentgenograms. Dispersion unifactorial analysis was used to evaluate the dependence of the precision of acetabular component positioning upon the surgeon’s experience, patient’s body mass index, type of surgical approach and the use of guide for acetabular component implantation. Results. Within the first postoperative year the rate of femoral component dislocation in group 1 made up 0.9%. Within the Lewinnek safe zone 76.6% of acetabular components were implanted with the use of a guide and 71.8% without. The rate of dislocation in group 2 made up 71.8% and 63.4% of components were implanted within the safe zone. In group 3 the intra-hospitalization dislocation developed in 1.9% of patients and satisfactory positioning relative to Lewinnek safe zone was achieved in 68.2% of cases. The risk factors for acetabular component malposition included high body mass indices, use of low invasive approach and insufficient experience of the operating surgeon. No direct influence of acetabular component orientation upon the femoral component dislocation was detected. Conclusion. Further studies directed to the more detailed analysis of additional factors that either directly or indirectly affect the implant function and to the optimization of surgical technique that would enable the reproducibility of total hip arthroplasty results are required.

Pedobarographic Analysis in Total Knee Arthroplasty

Pedobarographic gait analysis is a useful tool for the determination of loading distributions and alterations on the lower extremity and their reflection on the foot sole after many orthopaedic surgical applications. To date, there have been no studies evaluating the relationship between component alignment and changes of pedobarographic gait analysis in total knee arthroplasty (TKA). We aimed to investigate the effects of TKA and prosthetic alignment on the distribution of pedobarographic parameters. Quantitative gait patterns of 47 patients were prospectively evaluated by using pedobarography 1 week before surgery and at the seventh month, on average, postoperatively. Component positions were assessed, and all applications were divided into three groups according to tibial component position as varus, neutral, and valgus. Pedobarographic results were compared between pre- and postoperative values for all applications and compared among the groups. Mean postoperative tibiofemoral angle was 5.4 degrees in valgus, and preoperative knee scores were markedly improved postoperatively. The range of tibial component alignment changed between 1 and 4 degrees in the varus and valgus groups. Plantar loading parameters (force and pressure) were significantly decreased in all operated knees, especially in forefoot and midfoot. In varus tibial components, plantar loading values decreased in midfoot and hindfoot. However, in the neutral and valgus groups, similar alterations of plantar loadings were obtained, which included decreasing in forefoot and midfoot with significant increase in hindfoot. Plantar loading distribution changed statistically significantly after TKA despite good clinical and radiographic results. Tibial component alignment was also responsible for plantar loading distribution. Tibial components in varus position create different foot loading characteristics compared with neutral and valgus aligned components. Pedobarographic evaluation in TKA allows clinicians to obtain a proper understanding of abnormal gait caused by component malposition.