Acetabular Cup Position Research Articles

Impingement in total hip arthroplasty: A geometric model.

Total Hip Arthroplasty (THA) is one of the most common and successful surgical interventions. The survivorship at 10 years for the most commonly used systems is over 95%. However, the incidence of revision is usually much higher in the 0–1 year time period following the intervention. The most common reason for revision in this early time period is dislocation and subluxation, which may be defined as complete or permanent, and partial or temporary loss of contact between the bearing surfaces respectively. This study comprises the development of a geometric model of bone and an in situ total hip replacement, to predict the occurrence and location of bone and component impingement for a wide range of acetabular cup positions and for a series of frequently practiced activities of daily living. The model developed predicts that anterior-superior component impingement is associated with activities that result in posterior dislocation. The incidence may be reduced by increased cup anteversion and inclination. Posterior-inferior component impingement is associated with anterior dislocation activities. Its incidence may be reduced by decreased cup anteversion and inclination. A component impingement-free range was identified, running from when the cup was positioned with 45° inclination and 25° anteversion to 70° inclination and 15°–20° anteversion.

Comparison of Postoperative Instability and Acetabular Cup Positioning in Robotic-Assisted Versus Traditional Total Hip Arthroplasty

BackgroundRobotic-assisted total hip arthroplasty (R-THA) affords precision yet uncertain clinical benefits. This study compares dislocation rates and related revisions between R-THA and manual total hip arthroplasty (M-THA). Secondarily we evaluated cup position, patient-reported outcome measures (PROMs), and postoperative complications. MethodsA three-surgeon cohort study was conducted on 2247 consecutive patients (1724 M-THA and 523 R-THA) who received a primary THA between January 2014 and June 2020 at a single hospital. Demographics, PROMs, emergency department visits, readmissions, and 90-day complications were collected via the Michigan Arthroplasty Registry Collaborative Quality Initiative. Chart review yielded instability occurrence with an average follow-up of 4 years. Multivariate regression analysis was performed, and a sample of 368 radiographs, including all dislocations, were assessed. ResultsThere were significantly lower rates of dislocation in R-THA (0.6%) vs M-THA (2.5%; Multivariate odds ratio 3.74, P < .046). All cases of unstable R-THA were successfully treated conservatively, whereas 46% of unstable M-THA were revised for recurrent instability. Cup anteversion (25.6° ± 5.4° R-THA vs 20.6° ± 7.6° M-THA) was greater, and cup inclination (42.5° ± 5.3° R-THA vs 47.0° ± 6.7° M-THA) was lower in the R-THA group (P < .05). No significant differences were noted for demographics, PROMs, or other complications (P > .05). ConclusionR-THA resulted in less than one-fourth the dislocation rate compared to M-THA and no revision for instability. It was associated with no difference in PROMs or other early complications. The influence of R-THA on stability goes beyond simply cup positioning and deserves further study.

Effect of the acetabular cup positioning and leg length restoration after total hip arthroplasty using robotic-assisted surgery system

Objective: To assess the improvement of the robotic-assisted total hip arthroplasty (rTHA) regarding the acetabular cup positioning and the leg length restoration. Methods: Clinical data of 246 patients undergoing primary unilateral THA from September 2019 to June 2021 in Peking University Third Hospital were retrospectively reviewed, including patients treated with rTHA (n=113) and conventional THA (cTHA) (n=133). Thirty-seven male patients along with 76 females were enrolled into the rTHA group with a mean age of (62±9) years. In comparison, the average age of cTHA group was (60±12) years with 59 males and 74 females. The postoperative inclination and anteversion of the acetabular cup and the rate of acetabular cup within the Lewinnek and Callanan "safe zone" were documented and analyzed. For the patient with normal or surgically restored contralateral hip, the leg length discrepancy was also measured and compared between the two groups. Results: The overall mean postoperative inclination and anteversion was 39.0°±5.5° and 14.1°±5.1°, respectively. No statistically significant difference was found between the rTHA and cTHA group regarding postoperative inclination (39.3°±2.9° vs 38.7°±7.0°, P=0.383) and anteversion (13.4°±4.3° vs 14.7°±5.6°, P=0.054). In rTHA group, 97.3%(110/113) of the cups were implanted within the Lewinnek"safe zone"(75.9%(101/133) in cTHA group) and 94.7%(107/113) were within the Callanan"safe zone"(66.2%(88/133) in cTHA group), and those were both higher in rTHA group (both P<0.01). There was no significant difference in postoperative leg length discrepancy between the two groups (P=0.445). Meanwhile, 29(23.0%) cases of cTHA group had leg length discrepancy more than 5 mm, and it was 9.7%(9/93) in rTHA group. Conclusion: It indicated the benefit of rTHA in acetabular cup positioning as well as the leg length restoration.

Direct Anterior Approach for Total Hip Arthroplasty in the Elderly with Femoral Neck Fractures: Comparison with Conventional Posterolateral Approach.

BackgroundThe aim of this study was to determine if it was feasible and safe to perform total hip arthroplasty (THA) using the direct anterior approach (DAA) when compared with the conventional posterolateral approach (PA) in patients with femoral neck fractures. The time required to start walking was investigated to identify advantages of the muscle-sparing approach. Safety of the approach was judged based on the incidence and nature of all complications.MethodsWe retrospectively reviewed 67 THA cases due to femoral neck fractures from October 2015 to January 2019. The PA was used in 31 cases, and the DAA was used in 36 cases. The average operative time and amount of bleeding were evaluated. Cup inclination, anteversion, and leg length discrepancy (LLD) were also measured on radiographs. The time to start walking and complications (e.g., intraoperative fracture, infection, and dislocation) were recorded.ResultsThe mean operative time was 84.35 ± 13.95 minutes in PA group and 99.22 ± 20.33 minutes in DAA group (p = 0.010). But after experiencing 20 cases using the DAA, there was no statistically significant difference in the operative time between the groups. The mean volume of bleeding was 428.73 ± 207.26 mL in the PA group and 482.47 ± 150.14 mL in the DAA group. There was no difference in the acetabular cup position between two groups. Ambulation was started at 3.94 days after surgery on average in the PA group and 3.14 days in the DAA group, showing a statistically significant difference. Intraoperative fracture and infection were not observed in either group. The incidence of LLD was 1 in each group. The dislocation rate was 3.2% (1 case) in the PA group and 5.5% (2 cases) in the DAA group.ConclusionsAlthough the DAA for THA was similar to the PA in terms of operative time, volume of bleeding, and complications, the DAA showed a great advantage in early rehabilitation as a muscle-sparing procedure in the elderly with femoral neck fractures.

Improved accuracy and fewer outliers with a novel CT-free robotic THA system in matched-pair analysis with manual THA

Accurate component orientation and restoration of hip biomechanics remains a continuing challenge in total hip arthroplasty (THA). The goal of this study was to analyze the accuracy/reproducibility of a novel CT-free and pin-less robotic-assisted THA (RA-THA) platform compared to manual THA (mTHA). This matched-pair cadaveric study compared this RA-THA system to mTHA (n = 33/arm), both using the assistance of fluoroscopic imaging, in a group of 14 high-volume arthroplasty surgeons. In both groups, surgeons were asked to aim for 40°/15° for cup inclination/version, and 0 mm of leg length discrepancy (LLD). A validated and accurate method using radio-opaque markers measured cup inclination/version and LLD. The accuracy and reproducibility (fewer outliers) of cup inclination was significantly improved in the robotic group (1.8° ± 1.3° vs 6.4° ± 4.9°, respectively, robotic vs manual; p < 0.001), with no significant difference between groups for version. The reproducibility of LLD was significantly improved in the robotic group (p = 0.003). For all parameters studied, the robotic group had an improved accuracy and lower variance (fewer outliers). The percentage of cases within the more restrictive Callanan safe zone was 100% for RA-THA vs 73% for mTHA (p = 0.002). The CT-free RA-THA platform, using only fluoroscopic imaging, demonstrated more accurate acetabular cup positioning, when compared to the mTHA procedures performed by high-volume hip surgeons (naive to this RA-THA platform), with respect to cup inclination and placement within the Lewinnek/Callanan safe zones. Future study must incorporate economic factors, lower volume surgeons, clinical and patient-centric outcomes, and other radiographic parameters in controlled studies in large sample sizes.

Does obesity affect acetabular cup position, spinopelvic function and sagittal spinal alignment? A prospective investigation with standing and sitting assessment of primary hip arthroplasty patients

BackgroundTotal hip arthroplasty (THA) instability is influenced by acetabular component positioning, spinopelvic function and sagittal spinal alignment. Obesity is considered as a risk factor of THA instability, but the causal relationship remains unknown. This study aimed to investigate the influence of BMI on (1) spinopelvic function (lumbar flexibility, pelvic mobility and hip motion), (2) sagittal spinal alignment pre- and postoperatively and (3) acetabular cup position postoperatively in primary THA patients in a prospective setting.MethodsOne hundred ninety patients receiving primary total hip arthroplasty were enrolled in a prospective cohort study and retrospectively analysed. All patients received stereoradiography (EOS) in standing and relaxed sitting position pre-and postoperatively. C7-sagittal vertical axis (C7-SVA), lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT), anterior plane pelvic tilt (APPT), and pelvic femoral angle (PFA) were assessed. Key parameters of the spinopelvic function were defined as lumbar flexibility (∆ LL = LLstanding − LLsitting), pelvic mobility (∆ PT = PTstanding − PTsitting) and hip motion (∆ PFA = PFAstanding − PFAsitting). Pelvic mobility was further defined based on ∆ PT as stiff, normal and hypermobile (∆ PT < 10°; 10°–30°; > 30°). The patients were stratified to BMI according to WHO definition: normal BMI ≥ 18.5–24.9 kg/m2 (n = 68), overweight ≥ 25.0–29.9 kg/m2 (n = 81) and obese ≥ 30–39.9 kg/m2 (n = 41). Post-hoc analysis according to Hochberg's GT2 was applied to determine differences between BMI groups.ResultsStanding cup inclination was significant higher in the obese group compared to the normal BMI group (45.3° vs. 40.1°; p = 0.015) whereas standing cup anteversion was significantly decreased (22.0° vs. 25.3°; p = 0.011). There were no significant differences for spinopelvic function key parameter lumbar flexibility (∆ LL), pelvic mobility (∆ PT) and hip motion (∆ PFA) in relation to BMI stratified groups. The obese group demonstrated significant enhanced pelvic retroversion compared to the normal BMI group (APPT − 1.8° vs. 2.4°; p = 0.028). The preoperative proportion of stiff pelvic mobility was decreased in the obese group (12.2%) compared to normal (25.0%) and overweight (27.2%) groups. Spinal sagittal alignment in C7-SVA and PI-LL mismatch demonstrated significantly greater imbalance in the obese group compared to the normal BMI group (68.6 mm vs. 42.6 mm, p = 0.002 and 7.7° vs. 1.2°, p = 0.032, respectively) The proportion of patients with imbalanced C7-SVA was higher in the obese (58.5%) than in the normal BMI group (44.1%).ConclusionsThe significantly increased spinal sagittal imbalance with altered pelvic mechanics is a potential cause for the reported increased risk of THA dislocations in obese patients. Consequently, the increased spinal sagittal imbalance in combination with normal pelvic mobility need to be taken into account when performing THA in obese patients.

Application of Mako robot-assisted total hip arthroplasty in developmental dysplasia of the hip

To evaluate the early effectiveness and summarize the initial application experiences of Mako robot-assisted total hip arthroplasty (THA) for developmental dysplasia of the hip (DDH) in adults. Between August 2018 and January 2020, 55 cases of DDH (75 hips) were treated with Mako robot-assisted THA. There were 10 males and 45 females with an average age of 51 years (range, 30-73 years). There were 35 cases of unilateral hip and 20 cases of bilateral hips. The DDH was classified as Crowe type Ⅰin 29 hips, type Ⅱ in 20 hips, type Ⅲ in 6 hips, and type Ⅳ in 20 hips. The modified Harris score was 54.8±16.0, the hip joint range of motion was 90° (80°, 100°), and the leg length discrepancy (LLD) was 22.0 (10.5, 47.0) mm. The preoperative surgical plan was made in the robot system based on the CT data. The reaming and installation of the acetabular cup were completed with the assistance of the robot system. The distance between the rotation center of the hip joint and the teardrop (horizontal distance, vertical distance), inclination angle, and anteversion angle were measured on the pelvic X-ray film to evaluate the position of the acetabular prosthesis. The above indicators were compared with preoperative planning to evaluate the accuracy of robotic-assisted surgery. The modified Harris score, the range of motion, and the LLD were used to evaluate the early effectiveness. The 75 hips of THAs were completed with the assistance of Mako robots. There was no significant difference in the acetabular inclination angle, the horizontal distance and the vertical distance of the rotation center between the preoperative planning and the postoperative measurement values ( P>0.05); the acetabular anteversion angle was significantly smaller than the postoperative measurement value ( t=-2.482, P=0.015). Four hips located beyond the Lewinnek safety zone, and 71 hips located within the Lewinnek safety zone. All patients followed up 6-24 months (mean, 13 months). All incisions healed by first intention. At last follow-up, the modified Harris score was 85.5±11.2, the hip joint range of motion was 120° (110°, 120°), and the LLD was 3.8 (2.0, 8.1) mm; all improved significantly compared with preoperative ones ( P<0.05). Except for one nerve injury case, there was no other complication. Mako robot-assisted THA is a safe and effective method for adult DDH, which can optimize the acetabular cup positioning, hip function, and leg length, but the long-term effectiveness needs to be confirmed by further studies.

Acetabular cup position differs in spinopelvic mobility types: a prospective observational study of primary total hip arthroplasty patients

IntroductionSpinopelvic mobility was identified as a contributing factor for total hip arthroplasty (THA) instability. The influence of spinopelvic function on acetabular cup positioning has not yet been sufficiently investigated in a prospective setting. Therefore, our study aimed (1) to assess cup inclination and anteversion in standing and sitting based on spinopelvic mobility, (2) to identify correlations between cup position and spinopelvic function, (3) and to determine the influence of the individual spinal segments, spinal sagittal balance, and spinopelvic characteristics on the mobility groups.Materials and methodsA prospective study assessing 197 THA patients was conducted with stereoradiography in standing and sitting position postoperatively. Two independent investigators determined cup anteversion and inclination, C7-Sagittal vertical axis, cervical lordosis (CL), thoracic kyphosis (TK), lumbar lordosis (LL), sacral slope, pelvic tilt (PT), anteinclination (AI), and pelvic femoral angle (PFA). Spinopelvic mobility is defined based on ∆PT = PTstanding − PTsitting as ∆PT < 10° stiff, ∆PT ≥ 10–30° normal, and ∆PT > 30° hypermobile. Pearson coefficient represented correlations between the cup position and spinopelvic parameters.ResultsSignificant differences were demonstrated for cup anteversion (stiff/hypermobile 29.3°/40.1°; p < 0.000) and inclination (stiff/hypermobile 43.5°/60.2°; p < 0.000) in sitting, but not in standing position. ∆ (standing/sitting) of the cup anteversion (stiff/neutral/hypermobile 5.8°/12.4°/19.9°; p < 0.000) and inclination (stiff/neutral/hypermobile 2.3°/11.2°/18.8°; p < 0.000) revealed significant differences between the mobility groups. The acetabular cup position in sitting, was correlated with lumbar flexibility (∆LL) and spinopelvic mobility. Significant differences were detected between the mobility types and acetabular orientation (AI sit:stiff/hypermobile 47.6°/65.4°; p < 0.000) and hip motion (∆PFA:stiff/hypermobile 65.8°/37.3°; p < 0.000). Assessment of the spinal segments highlighted the role of lumbar flexibility (∆LL:stiff/hypermobile 9.9°/36.2°; p < 0.000) in the spinopelvic complex.ConclusionThe significantly different acetabular cup positions in sitting and in the ∆ between standing and sitting and the significantly altered spinopelvic characteristics in terms of stiff and hypermobile spinopelvic mobility underlined the consideration for preoperative functional radiological assessment. Identifying the patients with altered spinopelvic mechanics due to a standardized screening algorithm is necessary to provide safe acetabular cup positioning. The proximal spinal segments appeared not to be involved in the spinopelvic function.

CORR Insights®: A Modeling Study of a Patient-specific Safe Zone for THA: Calculation, Validation, and Key Factors Based on Standing and Sitting Sagittal Pelvic Tilt.

CORR Insights®: A Modeling Study of a Patient-specific Safe Zone for THA: Calculation, Validation, and Key Factors Based on Standing and Sitting Sagittal Pelvic Tilt.

A Modeling Study of a Patient-specific Safe Zone for THA: Calculation, Validation, and Key Factors Based on Standing and Sitting Sagittal Pelvic Tilt.

Lumbar-pelvic stiffness and sagittal imbalance have been reported to increase the risk of dislocation and wear after THA. One potential way to approach this concern is by identifying patient-specific safe zones for THA components based on the standing and sitting sagittal pelvic tilt. However, there is no algorithm to integrate the standing and sitting pelvic tilt into the surgical plan of component orientations. We established a new mathematical algorithm for determining a patient-specific safe zone for THA by integrating the impingement-free ROM requirements of standing and sitting while preventing edge loading while standing. We aimed to determine (1) the accuracy of this new method for predicting the impingement-free ROM for a given component orientation, (2) the sensitivity and specificity of detecting an impingement-free acetabular cup position for standing and sitting, and (3) the influences of key factors including pelvic tilt while standing and pelvic tilt while sitting and implant parameters on patient-specific safe zones. A strategy for calculating the intersection of standing and sitting impingement-free safe zones and the zone of a standing radiographic inclination of ≤ 45° was used to develop patient-specific safe zones. We conducted a computer simulation study including the pelvis and THA prosthesis to answer the three study questions. We enrolled 10 patients who underwent robot-assisted THA for avascular necrosis of the femoral head (mean age 49 ± 19 years; five were women) from October 2019 to December 2019. We used a prosthesis model with a conical stem neck and a non-hooded liner, with the femoral head diameter ranging between 28 mm and 40 mm, and the corresponding head-neck ratio ranging between 2.33 and 3.33. We tested 1680 movements for the accuracy of impingement-free ROM (Question 1), and 80 marginal points and 120 non-marginal points of the comprehensive impingement-free safe zone, which combines the standing and sitting postures (Question 2). For Question 3, we explored the influences of standing and sitting pelvic tilt, femoral head diameter, and ROM criteria on the size of the patient-specific safe zone. With the simulation method as a reference for detecting impingement, the mean absolute error (arithmetic mean of all the absolute errors) of the calculated impingement-free ROM was 1.4° ± 2.3°, and the limit of agreement of errors was between -3.6° and 3.7°. The sensitivity of detecting a safe cup orientation within the comprehensive impingement-free safe zone for a given ROM criterion was 98.9% (95% CI 93.6% to 99.9%), and specificity was 97.1% (95% CI 91.0% to 99.2%). There were no impingement-free safe zones for 29% (pelvic tilt combinations without an impingement-free safe zone and all tested combinations) and no patient-specific safe zones for 46% (pelvic tilt combinations without a patient-specific safe zone and all tested combinations) of the tested combinations of standing and sitting pelvic tilt. The patient-specific safe zone was sensitive to changes in standing and sitting pelvic tilt, femoral head diameter, stem version, and ROM criteria. Stem anteversions beyond 10° to 20° dramatically reduced the size of the patient-specific safe zone to 0 within a change of 10° to 20°. The patient-specific safe zone algorithm can be an accurate method for determining the optimal orientation for acetabular cups and femoral stems in THA. The patient-specific safe zone is sensitive to changes in standing and sitting pelvic tilt, stem version, ROM criteria, and the femoral head diameter. A narrow zone of 10° to 20° for stem anteversion is recommended to maximize the size of the patient-specific safe zone. This study suggests the potential of a mathematical algorithm to optimize the orientation of THA components and illustrates how key parameters affect the patient-specific safe zone.

Accuracy and reproducibility of visual estimation of the acetabular cup positioning in total hip arthroplasty on plain radiographs by orthopaedic surgeons.

To examine whether trauma and orthopaedic surgeons could visually assess the anteversion and inclination of a total hip replacement acetabular component from standard anteroposterior radiograph and anteversion on a standard lateral radiograph with accuracy or reproducibility.Main outcome measurement: The main outcome was accuracy of visual estimations of angles. The secondary outcome was whether these estimations were reproducible though intra-observer variability. Mean angles of anteversion on the anteroposterior, inclination on the anteroposterior and anteversion on the lateral on formal measurements were 15.2°, 45.4° and 19.9°; and the visual estimates were 17.5°, 45.9° and 18.2°, respectively. When comparing the visual estimates of surgeons and formal measurements, the results ranged from very poor to very good. Intra-observer reproducibility was moderate for all angles. The difference between the consultants and speciality registrars was not significant. This study illustrated that not all orthopaedic surgeons were able to visually estimate angles well. Although some of our participants were very accurate, there were some who statistically were very poor. This level of inaccuracy can lead to inconsistency and we strongly suggested specialist software is used to assess acetabular cup position on postoperative plane radiographs rather than relying on 'visual estimations'.

Computational modelling of hip resurfacing arthroplasty investigating the effect of femoral version on hip biomechanics.

How reduced femoral neck anteversion alters the distribution of pressure and contact area in Hip Resurfacing Arthroplasty (HRA) remains unclear. The purpose of this study was to quantitatively describe the biomechanical implication of different femoral neck version angles on HRA using a finite element analysis. A total of sixty models were constructed to assess the effect of different femoral neck version angles on three different functional loads: 0°of hip flexion, 45°of hip flexion, and 90° of hip flexion. Femoral version was varied between 30° of anteversion to 30° of retroversion. All models were tested with the acetabular cup in four different positions: (1) 40°/15° (inclination/version), (2) 40°/25°, (3) 50°/15°, and (4) 50°/25°. Differences in range of motion due to presence of impingement, joint contact pressure, and joint contact area with different femoral versions and acetabular cup positions were calculated. Impingement was found to be most significant with the femur in 30° of retroversion, regardless of acetabular cup position. Anterior hip impingement occurred earlier during hip flexion as the femur was progressively retroverted. Impingement was reduced in all models by increasing acetabular cup inclination and anteversion, yet this consequentially led to higher contact pressures. At 90° of hip flexion, contact pressures and contact areas were inversely related and showed most notable change with 30° of femoral retroversion. In this model, the contact area migrated towards the anterior implant-bone interface along the femoral neck. Femoral retroversion in HRA influences impingement and increases joint contact pressure most when the hip is loaded in flexion. Increasing acetabular inclination decreases the area of impingement but doing so causes a reciprocal increase in joint contact pressure. It may be advisable to study femoral neck version pre-operatively to better choose hip resurfacing arthroplasty candidates.

Significance of spinal sagittal balance for guiding acetabular prosthesis positioning

Since the concept of "safe area" put forward by Lewinnek, it has been widely recognized. While in recent years, many scholars have found that even if the acetabular prosthesis was placed on the "safe area", there were still many unexplained dislocation after total hip arthroplasty. And scholars began to question whether the "safe area" is really suitable for all patients. Spinal degeneration, deformity, lumbar fusion, etc. will lead to spine sagittal imbalance and changes in pelvic activity, which could lead to changes in acetabular orientation, and ultimately lead to edge loading, wear, impact, and even dislocation after total hip replacement. From the perspective of wear, impact and dislocation, it is determined by the functional positioning of the acetabular cup, not the anatomical positioning. The anatomical positioning and functional positioning of the neutral pelvic acetabular cup in the standing position can be considered equivalent. For pelvic rotation more than 20°, functional placement needs to be considered. In recent years, as the understanding of the internal relationship between the spine-pelvis-hip joint has become more and more profound, some scholars further classify the hip-spine relationship according to whether the spine is stiff or deformed, and propose corresponding acetabulums according to different types of hip-spine relationships The function of placement, so as to achieve a stable artificial hip joint. Therefore, it is of great significance to fully assess whether the patient's sagittal plane is balanced before surgery to guide artificial hip replacement surgery.

Comparison of the accuracy of the cup position and orientation in total hip arthroplasty for osteoarthritis secondary to developmental dysplasia of the hip between the Mako robotic arm-assisted system and computed tomography-based navigation.

We investigated the accuracy of the acetabular cup position and orientation in robotic-assisted total hip arthroplasty (rTHA) compared to navigated THA (nTHA) using computed tomography (CT) for patients with osteoarthritis secondary to developmental dysplasia of the hip (DDH). We studied 31 hips of 28 patients who underwent rTHA and 119 hips of 112 patients who underwent nTHA with the same target cup orientation. After propensity score matching, each group comprised 29 hips. Post-operative cup position and orientation were measured from the postoperative CT data. Errors from the target cup position and orientation were compared between the two groups. Post-operatively, the absolute error of the anteroposterior and superoinferior cup positions from the target position was significantly lower in the rTHA group than in the nTHA group. The change in the post-operative radiographic inclination from the target orientation was lower in the rTHA group than in the nTHA group. Screw fixation for cup implantation was required for three hips in the nTHA group but not in the rTHA group. rTHA achieved more precise cup implantation with reduced variation from the target orientation compared to nTHA in patients with osteoarthritis secondary to DDH.

Applying the Hip-Spine Relationship: What X-Rays and Measurements Are Important?

Understanding spinopelvic motion and the dynamic relationship of the hip, spine, and pelvis is essential in decreasing the risk of instability after total hip arthroplasty. The hip-spine relationship is complex, and a detailed analysis of each patient’s spinopelvic mobility is warranted to help guide safe acetabular component positioning. Through the use of a standing anteroposterior pelvis X-ray, lateral spinopelvic radiographs in the standing and seated position, and advanced functional imaging, key spinopelvic parameters can be obtained. A systematic preoperative workup can help to identify hip-spine pathology that predisposes patients to instability, and can help in planning and establishing a patient-specific “safe zone.” Based on the presence of concomitant hip-spine pathology, patients must be evaluated thoroughly with preoperative imaging to plan for the optimal target acetabular cup position. This paper guides readers through important parameters and imaging associated to spinopelvic motion as it relates to total hip arthroplasty stability.

Supercapsular percutaneously-assisted total hip (SuperPath) versus mini-incision posterolateral total hip arthroplasty for hip osteoarthritis: a prospective randomized controlled trial.

BackgroundSupercapsular percutaneously-assisted total hip (SuperPath) arthroplasty has been proposed to be minimally invasive and tissue sparing, with possible superior postoperative outcomes compared with conventional approaches for total hip arthroplasty (THA). However, previous studies have underlined the shortcomings of conventional THA approaches, including higher dislocation, more blood loss, longer incisions, more tissue damage, and delayed postoperative rehabilitation. In the present study, we compared the short-term outcomes of unilateral THA with those of SuperPath and the mini-incision posterolateral approach (PLA) for hip osteoarthritis (OA).MethodsPatients with unilateral hip OA were prospectively recruited and underwent either SuperPath (SuperPath group) or mini-incision PLA THA (PLA group). Perioperative status [operative time, incision length, intraoperative blood loss, soft tissue damage, and length of hospital stay (LOS)], and postoperative function outcomes, including range of motion (ROM), pain visual analog scale (VAS), and Harris Hip Score (HHS), were evaluated and compared between the groups at scheduled time points within 12 months postoperatively.ResultsCompared with the PLA group, the SuperPath group yielded a significantly shorter incision length (7.83 vs. 12.45 cm, P<0.001), longer operative time (102.72 vs. 66.22 min, P<0.001), more blood loss (1,007.38 vs. 844.55 mL, P=0.005), and more soft tissue damage (creatine kinase: 1,056.05 vs. 821.50 U/L, P=0.006) on postoperative day 3. The SuperPath group also showed deficient acetabular cup positioning (abduction angle: 36.94° vs. 42.66°, P=0.004) and a greater decrease in ROM (flexion: 107.66° vs. 114.44°, P=0.004; 109.83° vs. 116.11°, P=0.002; 111.66° vs. 118.88°, P<0.001) on postoperative days 1, 3, and 14, as well as severe early-term pain symptoms (pain VAS on postoperative day 3: 7.05 vs. 6.55, P=0.041). However, the LOS, C-reactive protein levels, erythrocyte sedimentation rate (within 2 weeks postoperatively), and HHS were comparable between the groups during the 12 months postoperatively.ConclusionsSuperPath may be a promising, minimally invasive technique for the treatment of OA in the future. Further investigation is necessary to evidence the possible superiority of SuperPath over other conventional mini-incision THA approaches.

Targeting the safe zones for cup position without fluoroscopic guidance in total hip arthroplasty: does the surgical approach affect the outcomes?

Proper acetabular cup positioning is crucial for achieving implant longevity and stability in total hip arthroplasty (THA). One of the elements that may affect the accuracy and precision of the positioning of the cup is the type of surgical approach used. This study compares the accuracy and the precision of conventional free-hand acetabular cup positioning relative to different "safe zones" in two groups of patients operated with THA using two different surgical approach. Retrospective radiological comparative matched-pair controlled study of two groups of patients operated with primary THA: the first group was operated in supine decubitus with a mini-invasive direct anterior approach (DA group), the second group was operated in lateral decubitus with a conventional posterolateral approach (PL group). Cup inclination and anteversion were assessed using the digital planning software TraumaCad. Cup position in the two groups were compared in terms of accuracy and precision. Forty four patients were enrolled for each group. The DA group showed a less inclined and less anteverted cup compared to the PL group (respectively 38.5 ± 5.2 vs. 49.6 ± 5.6 and 16.2 ± 3.6 vs. 22.9 ± 6.4; p < 0.01). The DA group showed a significantly higher percentage of cups within the "safe zone" in 4 out of 6 reference zones and a significantly lower variance in anteversion (12.96 vs. 40.96, p < .01). There was no difference in the variance for inclination. Our study found greater accuracy and precision in the positioning of the cup when surgery was performed through a direct anterior approach compared to the posterolateral approach due to the supine position of the patient which allows greater stability of the pelvis during surgery and makes it easier to target the desired angular references for cup positioning.

Total hip arthroplasty after periacetabular osteotomy versus primary total hip arthroplasty: a propensity-matched cohort study.

Controversy still exist regarding the outcomes of total hip arthroplasty (THA) after periacetabular osteotomy (PAO). The purpose of this study was to compare the clinical and radiologic outcomes of THA after PAO with primary THA based on balanced baseline characteristics with propensity score matching. Using propensity score matching, 1:2 matched cohort to facilitate comparison between patients who underwent primary cementless THA with or without previous PAO. Then, we compared the operative time, blood loss, complications, postoperative clinical score, cup size, position, and alignment of acetabular cup, and degree of bony coverage on cup between the two groups. Thirty-five patients with 37 hips who underwent THA after PAO were successfully matched to 70 patients with 74 hips who underwent primary THA. The operative time and blood loss in THA after PAO were significantly longer and larger than those in primary THA (P < 0.001 and = 0.0067, respectively). Clinical score showed no difference between the groups (P > 0.05). For THA after PAO, the cup size and bony coverage were larger (P = 0.0014 and < 0.001, respectively), and the hip center was significantly higher and laterally (P < 0.001 and < 0.001, respectively) comparing primary THA. This study demonstrated longer operative time and larger blood loss without difference in the postoperative clinical score or complications between THA after PAO and primary THA. Furthermore, THA after PAO provided larger cup size and superolaterally positioned cup center without difference in the cup inclination or anteversion comparing primary THA.

Unilateral total hip arthroplasty in bilateral ankylosed hips: A case-series of eight patients of ankylosing spondylitis

IntroductionIn approximately one-third to half of patients of ankylosing spondylitis (AS), involvement of the hips may occur with 50–90% of these presenting with bilateral hip involvement. Total hip arthroplasty (THA) in these patients provide mobile hip, which significantly improves their functional capability and lifestyle. Aim of our study was to assess the clinical outcome of unilateral THA in AS patients with bilaterally ankylosed hips in terms of pain, hip mobility, ability to perform functional activities like sitting and walking and radiological evaluation in terms of position of acetabular cup, heterotrophic ossification (HO) and any sign of osteolysis. MethodsEight male patients (8 hips), between 25 and 40 years with ankylosed hips and spine in which only unilateral cemented THA was done due to financial constraints, were studied with average follow-up of 18.25 months (Range- 12–30 months). Results were assessed by walking ability, Harris Hip Score (HHS) and radiological findings. ResultsMean pre-op HHS was 31.3. All these patients were more or less dependent on others for daily activities. None of the patient was able to sit on chair and all were able to walk indoor only. Mean HHS at final follow-up was 76.4. At final follow-up, all the patients could sit comfortably on a chair for more than 1 hour and were walking independently, although with a limp. Radiologically, acetabular cup inclination and anteversion was within Lewinnek’s safe zone in all the patients. ConclusionUnilateral cemented THA is a potential option in rehabilitation of patients of AS with bilaterally ankylosed hips, who cannot afford bilateral THA. But these young patients with rigid spine, who are very much dependent upon hip mobility, must be kept under observation to discover complications like loosening and for maintaining hip mobility.

Descripción del posicionamiento de una copa monobloque no cementada en el posoperatorio inmediato

BackgroundAppropriate positioning of the acetabular cup in total hip arthroplasty (THA) can improve hip function, reduce wear, impingement and dislocation. The position of the cup is described as the spatial relationship between the centre of rotation of the hip and the pelvis. The aim of this study is to describe the positioning of the uncemented monoblock cup in the immediate postoperative period in patients who underwent a primary THA. MethodsDescriptive observational study. The patients were operated by 4 joints arthroplasty surgeons in 8 different hospitals, from October 2015 to August 2018. The radiological measurements were taken from the AP Pelvis Xrays of the immediate postoperative. The inclination, anteversion, lateralization, percentage of cup uncovered and the space behind the acetabular cup. Results82.05% of the cups were in the range of inclination from 36 to 48 degrees; 85.71% had an anteversion between 5 to 15 degrees, 76.56% presented a lateralization of -2 to +2mm, 94.51% of the patients didnt have a uncover cup, and 92.67% of the cups had a space behind the cup from 0 to 3mm. DiscussionIn our study the highest percentage of cups were implanted with parameters agree to the safety areas reported by various authors. Adequate positioning of the uncemented monoblock acetabular cup can be achieved with a proper indication, a surgical approach that allows an ideal three-dimensional location and an acetabulum with a good peripheral rim that provides the required press-fit.Evidence Level: III