Leg length and offset differences above 5mm after total hip arthroplasty are associated with altered gait kinematics

Determination of rotation center and diameter of femoral heads using off-the-shelf augmented reality hardware for navigation

In total hip arthroplasty (THA), determining the center of rotation (COR) and diameter of the hip joint (acetabulum and femoral head) is essential to restore patient biomechanics. This study investigates on-the-fly determination of hip COR and size, using off-the-shelf augmented reality (AR) hardware. An AR head-mounted device (HMD) was configured with inside-out infrared tracking enabling the determination of surface coordinates using a handheld stylus. Two investigators examined 10 prosthetic femoral heads and cups, and 10 human femurs. The HMD calculated the diameter and COR through sphere fitting. Results were compared to data obtained from either verified prosthetic geometry or post-hoc CT analysis. Repeated single-observer measurements showed a mean diameter error of 0.63 mm ± 0.48 mm for the prosthetic heads and 0.54 mm ± 0.39 mm for the cups. Inter-observer comparison yielded mean diameter errors of 0.28 mm ± 0.71 mm and 1.82 mm ± 1.42 mm for the heads and cups, respectively. Cadaver testing found a mean COR error of 3.09 mm ± 1.18 mm and a diameter error of 1.10 mm ± 0.90 mm. Intra- and inter-observer reliability averaged below 2 mm. AR-based surface mapping using HMD proved accurate and reliable in determining the diameter of THA components with promise in identifying COR and diameter of osteoarthritic femoral heads.

[An update on clinical gait analysis : Current developments and applications]

The objective acquisition and assessment of joint movements and loads using instrumented gait analysis has become an established tool in clinical diagnostics. In particular, marker-based 3D gait analyses make use of an increasingly comprehensive database for the assessment of orthopaedic or neurological questions. Based on this data and medical-scientific experience, increasingly reliable approaches and evaluation strategies are emerging, which also draw on methods from artificial intelligence and musculoskeletal modelling. This article focusses on marker-based gait analyses of the lower extremity (hip, knee, foot) and how these can be used in a clinically relevant way using current methods, e.g. for determining indications or optimization of surgical planning. Finally, current developments and applications by using alternative methods from sensor technology and optical motion capture will be briefly discussed.

Impact of Offset and Leg Length on Functional Outcomes Post-Total Hip Arthroplasty: How Accurate Should Coronal Reconstruction Be?

BACKGROUND

Accurate hip reconstruction is associated with improved biomechanical behavior following total hip arthroplasty (THA). However, whether this is associated with improved patient-reported outcomes (PROs) is unknown.

HYPOTHESIS/PURPOSE

This study aimed to: 1) describe the ability to reconstruct coronal geometry during THA without advanced technology; 2) assess whether restoration of global offset (GO) and leg length (LL) is associated with improved PROs; and 3) investigate whether increased femoral offset (FO) to compensate for reduced acetabular offset (AO) influences PROs.

METHOD

This was a prospective, multicenter, consecutive cohort study of 500 patients treated with primary THA without robotics or navigation. The Oxford Hip score (OHS) was obtained preoperatively and at 1-year follow-up. Supine anteroposterior pelvic radiographs were analyzed to determine AO, FO, GO, and LL relative to the native contralateral side. Contour plots for ΔOHS based on ΔLL and ΔGO were created, and ΔOHS was calculated within and outside various ranges (±2.5, ±5, or ±10 mm).

RESULTS

In the operated hip, mean FO increased by 3 ± 6 mm (range, -16 to 27), while AO decreased by 2 ± 4 mm (range, -17 to 10). The contour graph for ±2.5 mm zones showed the best outcomes (ΔOHS >25) with GO and LL centered on 0 ± 2.5 mm (P < .01). However, only 10% achieved such reconstruction. When GO and LL differences were within ±10 mm, ΔOHS was superior when both AO and FO were within ±5 mm (mean: 24 ± 10; range, -5 to 40) compared with when FO was above 5 mm to compensate for a reduction in AO (mean: 22 ± 11; range, -10 to 46; P = .040).

CONCLUSIONS

The PROs were associated with biomechanical reconstruction, and the best clinical improvement can be expected when GO and LL differences are both within 2.5 mm. Maintenance of AO is important, as compensation by increasing FO is associated with inferior OHS.

The learning curve of a novel seven-axis robot-assisted total hip arthroplasty system: a randomized controlled trial

BACGROUND

The aim of this study was to assess the learning curve of a novel seven-axis robot-assisted total hip arthroplasty (RaTHA) system.

METHODS

A total of 59 patients who underwent unilateral total hip arthroplasty at our institution from June 2022 to September 2022 were prospectively included in the study. In this randomized controlled clinical trial, robot-assisted THA (RaTHA) and Conventional THA (CoTHA) were performed using cumulative sum (CUSUM) analysis to evaluate the learning curve of the RaTHA system. The demographic data, preopera1tive clinical data, duration of operation, postoperative Harris Hip Score (HHS), postoperative Western Ontario and McMaster Universities Arthritis Index (WOMAC) score, and duration of operation between the learning stage and the proficiency stage of the RaTHA group were compared between the two groups.

RESULTS

The average duration of operation of the RaTHA group was increased by 34.73 min compared with the CoTHA group (104.26 ± 19.33 vs. 69.53 ± 18.38 min, p < 0.01). The learning curve of the RaTHA system can be divided into learning stage and proficiency stage, and the former consists of the first 13 cases by CUSUM analysis. In the RaTHA group, the duration of operation decreased by 29.75 min in the proficiency stage compared to the learning stage (121.12 ± 12.84 vs.91.37 ± 12.92, p < 0.01).

CONCLUSIONS

This study demonstrated that the surgical team required a learning curve of 13 cases to become proficient using the RaTHA system. The duration of operation, total blood loss, and drainage gradually shortened (decreased) with the learning curve stage, and the differences were statistically significant.

TRIAL REGISTRATION

Number: ChiCTR2200061630, Date: 29/06/2022.

The Value of Computed Tomography Scan in Three-dimensional Planning and Intraoperative Navigation in Primary Total Hip Arthroplasty

Total hip arthroplasty (THA) is a frequently performed procedure; the objective is restoration of native hip biomechanics and achieving functional range of motion (ROM) through precise positioning of the prosthetic components. Advanced three-dimensional (3D) imaging and computed tomography (CT)-based navigation are valuable tools in both the preoperative planning and intraoperative execution. The aim of this study is to provide a thorough overview on the applications of CT scans in both the preoperative and intraoperative settings of primary THA. Preoperative planning using CT-based 3D imaging enables greater accuracy in prediction of implant sizes, leading to enhancement of surgical workflow with optimization of implant inventory. Surgeons can perform a more thorough assessment of posterior and anterior acetabular wall coverage, acetabular osteophytes, anatomical landmarks, and thus achieve more functional implant positioning. Intraoperative CT-based navigation can facilitate precise execution of the preoperative plan, to attain optimal positioning of the prosthetic components to avoid impingement. Medial reaming can be minimized preserving native bone stock, which can enable restoration of femoral, acetabular, and combined offsets. In addition, it is associated with greater accuracy in leg length adjustment, a critical factor in patients' postoperative satisfaction. Despite the higher costs and radiation exposure, which currently limits its widespread adoption, it offers many benefits, and the increasing interest in robotic surgery has facilitated its integration into routine practice. Conducting additional research on ultra-low-dose CT scans and examining the potential for translation of 3D imaging into improved clinical outcomes will be necessary to warrant its expanded application.

Gender differences in cementless short stem total hip arthroplasty: significantly higher femoral lengthening in female patients

Modern cementless short stems in total hip arthroplasty (THA) enable a precise reconstruction of the native pre-arthritic hip geometry. While gender differences have been reported for older generation straight hip stems, there are hardly reports regarding modern cementless short hip stems. Therefore, we aimed to evaluate the influence of gender differences in hip anatomy in cementless short stem THA. A total of 207 patients (109 females, 98 males) with unilateral THA and absence of contralateral joint space narrowing (Kellgren-Lawrence grade ≤ 2) were included. Acetabular height and offset as well as femoral height and offset were measured on pre- and 3-months-postoperative anteroposterior X-rays of the pelvis and compared to the contralateral hip. Additionally, implant position was evaluated on the postoperative radiograph. In male patients, the loss of acetabular offset was significantly greater than in females (p = 0.012), leading to a compensatory increase in femoral offset (p = 0.041). Femoral height discrepancy was significantly higher in females (p < 0.001), accounting for an increased global hip height discrepancy (p < 0.001). The mean acetabular anteversion was significantly greater in female patients (p < 0.001). Female patients are at higher risk of femoral lengthening in THA with a cementless short stem potentially caused by a further proximally conducted femoral neck osteotomy and show significantly higher cup anteversion angles. Therefore, surgeons should take special care to the level of neck resection and implant positioning in female patients.

Imageless navigation system (Naviswiss) provides accurate component position in total hip arthroplasty with lateral decubitus position for end-stage hip osteoarthritis: a prospective cohort study with CT-validation

AIMS

The Naviswiss system (Naviswiss AG, Brugg, Switzerland) is a handheld imageless navigation device used to improve the accuracy of implant positioning in total hip arthroplasty (THA). However, clinical data for leg length discrepancy and femoral offset is lacking, and the validity of the system has not been reported for patients undergoing THA in the lateral decubitus position. This study aimed to report the accuracy of the device in this patient population.

METHODS

Patients underwent THA in the lateral decubitus position performed by a single surgeon. Component position measured by the device intraoperatively was compared to postoperative measurements on computed tomography (CT) scans. Agreement between the navigation system and postoperative measurements was reported for acetabular cup inclination, acetabular cup version, femoral offset, and leg length discrepancy.

RESULTS

Thirty-three patients were included in the analysis. The mean difference between intraoperative and postoperative CT measurements was within 2° for angular measurements and 2 mm for leg length. Absolute differences in the two indices were up to 4° and 3 mm. The mean bias was 1°-2° overestimation for cup orientation and up to 2 mm overestimation for leg length change. However, 95% limits of agreement did not exceed absolute thresholds of 10° and 10 mm, especially after correction for bias. One case (3%) was declared intraoperatively for issues with fixation on the greater trochanter.

CONCLUSIONS

The accuracy of the Naviswiss system falls within clinically acceptable recommendations for acetabular cup placement, femoral offset, and leg length for total hip arthroplasty with a anterolateral approach in lateral decubitus position. The system could be further improved with regression-based bias correction.

Less groin pain with dual-mobility bearings versus fixed bearings in total hip arthroplasty

INTRODUCTION

The relationship between implant type, dual mobility (DM) or fixed bearing (FB), and postoperative groin pain remains unexplored. We examined the incidence of groin pain in DM implants and compare this to a cohort of FB THA patients.

METHODS

From 2006 to 2018, a single surgeon performed 875 DM THA and 856 FB THA procedures with 2.8-year and 3.1-year follow-up, respectively. Each patient received a questionnaire postoperatively and was asked if they had any groin pain (yes/no). Secondary measurements were implant characteristics such as head size, head offset, cup size, and cup-to-head ratio. Additional PROMs that were collected included: Veterans RAND 12 (VR-12), University of California Los Angeles (UCLA) activity score, Pain visual analogue scale (Pain VAS), and range of motion (ROM).

RESULTS

The incidence of groin pain was 2.3% in the DM THA cohort and 6.3% in the FB THA group (p < 0.001). Also, low head offset (⩽0 mm) had a significant odds ratio (1.61) for groin pain in both cohorts. There was no significant difference in terms of revision rate between the cohorts (2.5% vs. 3.3%, p = 0.39) at the latest follow up.

CONCLUSIONS

This study demonstrated a lower incidence of groin pain (2.3%) in patients with a DM bearing compared to a FB (6.3%) and a greater risk of groin pain with low head offset (<0 mm). As such, surgeons should try to recreate offset of the hip compared to the contralateral side to avoid groin pain.

Quantification of soft tissue artifacts using CT registration and subject-specific multibody modeling

The potential use of gait analysis for quantitative preoperative planning in total hip arthroplasty (THA) has previously been demonstrated. However, the joint kinematic data measured through this process tend to be unreliable for surgical planning due to distortions caused by soft tissue artifacts (STAs). In this study, we developed a novel motion capture framework by combining computed tomography (CT)-based postural calibration and subject-specific multibody dynamics modeling to prevent the effect of STAs in measuring hip kinematics. Three subjects with femoroacetabular impingement syndrome were recruited, and CT data for each patient were collected by attaching marker clusters near the hip. A subject-specific multibody hip joint model was developed based on reconstructed CT data. Spring-dashpot network calculations were performed to minimize the distance between the anatomical landmark and its corresponding infrared reflective marker. The STAs of the thigh was described as six degrees of freedom viscoelastic bushing elements, and their parameter values were identified via smooth orthogonal decomposition. Least squares optimization was used to modify the pelvic rotations to compensate for the rigid components of STAs. The results showed that CT-assisted motion tracking enabled the successful identification of STA influences in gait and squat positions. Furthermore, STA effects were found to alter maximal pelvis tilt and hip rotations during a squat. Compared to other techniques, such as dual fluoroscopic imaging, the adopted framework does not require additional medical imaging for patients undergoing robot-assisted THA surgery and is thus a practical way of evaluating hip joint kinematics for preoperative surgical planning.

Arthroplasty for femoral neck fractures is at risk for under restoration of lateral femoral offset

PURPOSE

The aim of the study was to determine the restoration of hip biomechanics through lateral offset, leg length, and acetabular component position when comparing non-arthroplasty surgeons (NAS) to elective arthroplasty surgeons (EAS).

METHODS

131 patients, with a femoral neck fracture treated with a THA by 7 EAS and 20 NAS, were retrospectively reviewed. 2 blinded observers measured leg-length discrepancy, femoral offset, and acetabular component position. Multivariate logistic regression models examined the association between the surgeon groups and restoration of lateral femoral, acetabular offset, leg length discrepancy, acetabular anteversion, acetabular position, and component size, while adjusting for surgical approach and spinal pathology.

RESULTS

NAS under-restored 4.8 mm of lateral femoral offset (43.9 ± 8.7 mm) after THA when compared to the uninjured side (48.7 ± 7.1 mm, p = 0.044). NAS were at risk for under-restoring lateral femoral offset when compared to EAS (p = 0.040). There was no association between lateral acetabular offset, leg length, acetabular position, or component size and surgeon type.

CONCLUSIONS

Lateral femoral offset is at risk for under-restoration after THA for femoral neck fractures, when performed by surgeons that do not regularly perform elective THA. This indicates that lateral femoral offset is an under-appreciated contributor to hip instability when performing THA for a femoral neck fracture. Lateral femoral offset deserves as much attention and awareness as acetabular component position since a secondary analysis of our data reveal that preoperative templating and intraoperative imaging did not prevent under-restoration.

Minimal pre-operative leg length discrepancy as a risk factor of post-operative leg length discrepancy after total hip arthroplasty: a retrospective study of patients with non-traumatic osteonecrosis of the femoral head

BACKGROUND

Leg length discrepancy (LLD) is one of the troublesome complications of total hip arthroplasty (THA). Previously, several risk factors have been suggested, but they were subjected to their inherent limitations. By controlling confounding variables, we hypothesized that known risk factors be re-evaluated and novel ones be discovered. This study aimed to analyze the independent risk factors for LLD after primary THA in patients with non-traumatic osteonecrosis of the femoral head (ONFH).

METHODS

We retrospectively reviewed patients with non-traumatic ONFH who underwent unilateral THA between 2014 and 2021. All patients were operated by one senior surgeon using a single implant. Demographic data, surgical parameters, and radiological findings (pre-operative LLD, Dorr classification, and femoral neck resection) were analyzed to identify the risk factors of ≥ 5 mm post-operative LLD based on radiological measurement and to calculate odds ratios by logistic regression analysis. Post hoc power analysis demonstrated that the number of analyzed patients was sufficient with 80% power.

RESULTS

One hundred and eighty-six patients were analyzed, including 96 females, with a mean age of 58.8 years at the time of initial THA. The average post-operative LLD was 1.2 ± 2.9 mm in the control group and 9.7 ± 3.2 mm in the LLD group, respectively. The LLD group tended to have minimal pre-operative LLD than the control group (-3.2 ± 5.1 mm vs. -7.9 ± 5.8 mm p = 2.38 × 10- 8). No significant difference was found between the groups in age, gender, body mass index, femoral cortical index, and implant size.

CONCLUSION

Mild pre-operative LLD is associated with an increased risk of post-operative LLD after primary THA in patients with ONFH. Thus, surgeons should recognize pre-operative LLD to achieve an optimal outcome and must inform patients about the risk of developing LLD.

CT validation of intraoperative imageless navigation (Naviswiss) for component positioning accuracy in primary total hip arthroplasty in supine patient position: a prospective observational cohort study in a single-surgeon practice

BACKGROUND

The aim of this study was to report on the validity of the Naviswiss handheld image-free navigation device for accurate intraoperative measurement of THA component positioning, in comparison with the three-dimensional (3D) reconstruction of computed tomography (CT) images as the gold standard.

METHODS

A series of patients presenting to a single-surgeon clinic with end-stage hip osteoarthritis received primary hip arthroplasty with the anterolateral muscle-sparing surgical approach in the supine position. Imageless navigation was applied during the procedure with bone-mounted trackers applied to the greater trochanter and ASIS. Patients underwent routine CT scans before and after surgery and these were analyzed by using three-dimensional reconstruction to generate cup orientation, offset and leg length changes, which were compared to the intraoperative measurements provided by the navigation system. Estimates of agreement between the intraoperative and image-derived measurements were assessed with and without correction for bias and declared cases with potential measurement issues.

RESULTS

The mean difference between intraoperative and postoperative CT measurements was within 2° for angular measurements and 2 mm for leg length. Absolute differences for the two indices were between 5° and 4 mm. Mean bias was 1.9°-3.6° underestimation for cup orientation and up to 2 mm overestimation for leg length change, but absolute thresholds of 10° and 10 mm were not exceeded by 95% limits of agreement (LOA), especially after correction for bias. Four cases (12%) were declared intraoperatively for issues with fixation on the greater trochanter. Inclusion of these cases generated acceptable accuracy overall and their omission failed to improve between-case variability in accuracy or LOA for both offset and leg length.

CONCLUSIONS

The accuracy of the Naviswiss system applied during primary THA in a supine position and anterolateral surgical approach falls within clinically acceptable recommendations for acetabular cup placement, femoral offset, and length. With refinements to surgical technique to adapt to the navigation hardware, the system could be further improved with regression-based bias correction.

TRIAL REGISTRATION

Registered with the Australian New Zealand Clinical Trials Registry (ACTRN12618000317291).

Fluoroscopy-guided direct anterior approach total hip arthroplasty provides more accurate component positions in the supine position than in the lateral position

PURPOSE

The position of the acetabular and femoral components is critical for stability and wear resistance. The aim of this study is to investigate whether the fluoroscopy-guided direct anterior approach in the supine position (S-DAA) is more helpful in improving the position of acetabular and femoral components than the fluoroscopy-guided direct anterior approach in the lateral decubitus position (L-DAA).

METHODS

A retrospective analysis of 76 cases of fluoroscopy-guided direct anterior approach total hip arthroplasty (38 cases in the S-DAA and 38 cases in the L-DAA group) was performed in one hospital from 2019 to 2021. The differences in inclination, anteversion, femoral offset (FO), global offset (GO), and leg length discrepancy (LLD) measurements during and after surgery were analyzed. The postoperative femoral offset (FO), global offset (GO), leg length discrepancy (LLD), and preoperative and postoperative Harris hip score were compared between the two groups.

RESULTS

In the S-DAA group, there were no significant differences in the mean intraoperative inclination angle anteversion angle, FO, GO, and LLD compared to the postoperative values, whereas in the L-DAA group, there were significant differences between the intraoperative and postoperative measurements (P < 0.001, P = 0.009, P＜0.001, P＜0.001 and P = 0.008, respectively). Additionally, there were significant differences in the accuracy of LLD, FO, and GO between the two groups (P < 0.001). Compared with the L-DAA group, the average differences of inclination, anteversion, LLD, FO, and GO during and after operation in the S-DAA group were smaller, and the consistency was higher. There was a significant difference in Harris hip score between the two groups at 1 week after surgery (P = 0.033). There was no significant difference in Harris hip score between 1 month and 3 months after surgery (P = 0.482 and P = 0.797, respectively).

CONCLUSIONS

In the supine group, the direct anterior approach (DAA) provides more accurate positioning of the acetabular and femoral components. However, there was no significant difference in hip joint function and activity between the two groups at follow-up.

The Anterior Position of the Hip Center of Rotation Is Related to Anterior Cup Protrusion Length and Symptomatic Iliopsoas Impingement in Primary Total Hip Arthroplasty

BACKGROUND

Iliopsoas impingement (IPI) is an important complication after total hip arthroplasty (THA), and anterior cup protrusion is believed to be its main cause; however, the relationship between the hip center of rotation (COR) and symptomatic IPI or cup protrusion remains poorly understood. Therefore, the present study investigated these relationships.

METHODS

The medical records of 138 patients who underwent unilateral primary THA were retrospectively reviewed. There were 8 patients (5.8%) who had symptomatic IPI. The COR and cup protrusion length measured with 2 methods were assessed on computed tomography. Risk factors for symptomatic IPI and the relationship between the COR and protrusion length were evaluated.

RESULTS

Logistic regression analyses showed that anteroposterior position of the COR, sagittal cup protrusion length (SCPL) at the COR, and both axial and SCPLs at the most anterior margin of the cup were related to symptomatic IPI. Multivariable regression analyses showed that acetabular offset was related to axial protrusion length at the COR, and anteroposterior position of the COR was related to both axial and sagittal protrusion lengths at the most anterior margin of the cup.

CONCLUSION

Anterior position of the cup was related to symptomatic IPI and both axial and sagittal protrusion lengths at the most anterior margin of the cup. Anterior reaming and cup protrusion should be avoided as much as possible to prevent symptomatic IPI.

Stricter correction of leg length discrepancy is required during total hip arthroplasty in patients with ankylosing spondylitis

BACKGROUND

Patients with ankylosing spondylitis often have fusions in the spine and sacroiliac joints, such that it is difficult to compensate for leg length discrepancy (LLD).

METHODS

We retrospectively measured the LLD after total hip arthroplasty (THA) in 89 patients with ankylosing spondylitis from June 2004 to February 2021 at our institute. Patients were divided into two groups based on an LLD of 5 mm. Clinical outcomes were investigated using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and Harris Hip Score (HHS). In addition, these points are investigated: patient satisfaction with the operation; whether there was a current difference in leg length; and whether there was a limping gait.

RESULTS

The group with an LLD of 5-10 mm rather than < 5 mm had significantly worse WOMAC pain and stiffness. The survey revealed statistically significant differences in patient satisfaction with the operation, limping gait, and whether back pain had improved.

CONCLUSION

For patients with ankylosing spondylitis, reducing the LLD to < 5 mm, which is more accurate than the current standard of < 10 mm, may produce greater improvement in clinical outcomes after hip arthroplasty.

Functional and Radiological Outcomes Following Simultaneous Bilateral Total Hip Arthroplasty: Analysis of a Retrospective Series

Introduction The prevalence of bilateral hip arthritis continues to rise. With the dramatic change in the practice of modern-day arthroplasty with standard operating protocols and guidelines in place to reduce the incidence of surgical site infection and peri-operative thromboembolic events, simultaneous bilateral total hip replacement (THR) has been considered a viable option to reduce morbidity. The efficacy of simultaneous bilateral THR with regard to patient outcomes and complications has been debated. The aim of this study was to assess and compare the functional outcomes, radiological outcomes, and complications following bilateral simultaneous THR with the existing literature. Methods We conducted a retrospective study of 28 patients who underwent simultaneous bilateral THR by a single surgeon at a district general hospital in the United Kingdom between 2010 and 2019. All the patients in the study were operated on via the posterior approach to the hip and received uncemented implants. Data on blood loss and hospital stay were collected from the hospital records. The radiological outcomes were studied from the post-operative radiographs. The patient-reported outcomes were measured via a telephone session at an average follow-up of 7.8 years. Results Our results noted a statistically significant drop in haemoglobin after the procedure from a mean of 13.5 g/dl to 9.05 g/dl (t: -15.84, p < 0.00001). The average blood loss was 643 ml +/- 330 ml (200-1850 ml). Nine patients (32.1%) required blood transfusions and a total of 21 units were transfused. The mean duration of stay in the hospital was 6.7 days (three to 20 days). There were no intra-operative/immediate/early post-operative complications. The revision rate was 1.7%, as one patient had a revision of the femoral component following a peri-prosthetic fracture. The mean visual analogue scale pain score was 1.51 +/- 0.58 (1-3). The mean Oxford Hip Score improved from 19.5 (12-28) pre-operatively to 44.3 (37-48) post-operatively at the time of the study (t: -21.88945; p < 0.00001), with the difference being statistically significant using a paired t-test. From the series, 14 (50%) patients were found to have limb length discrepancies. The mean limb length discrepancy was found to be 2.3 mm (0-16 mm). In 13 of the 28 patients (46.4%), the global hip offset was equal on both sides. In two patients, the difference in the global hip offset was more than 10 mm. Conclusion We reported good patient-reported functional outcomes with simultaneous bilateral THR with a low complication rate. Despite the lack of opportunity to template the second hip, the limb length and global hip offset can be restored after a simultaneous bilateral THR.

Hip offset and leg-length restoration in revision hip arthroplasty with a monoblock, hydroxyapatite-coated stem

AIMS

Restoration of normal hip biomechanics in arthroplasty surgery is important in order to achieve good muscle function and joint stability.

METHODS

In this retrospective cohort study, we examined the postoperative radiographs of 131 femoral revision arthroplasty procedures using a monoblock, fully hydroxyapatite (HA)-coated titanium stem. Femoral offset, modified-global offset and leg length were measured of the operated and contralateral hips.

RESULTS

Femoral offset was restored to ±10 mm in 108 cases (82%), modified-global offset was restored ±10 mm in 93 cases (71%) and leg length was restored to ±10 mm in 102 cases (81%). There were 4 dislocations with a mean follow-up period of 38 months.

CONCLUSIONS

Restoration of hip biomechanics is achievable with a monoblock stem and thus is a viable option in revision hip arthroplasty.

Peripheral Nerve Blockade in Total Hip Arthroplasty: A Retrospective Study with Propensity Score Matching

The effect of peripheral nerve block (PNB) according to leg lengthening following total hip arthroplasty (THA) has not been studied yet. The purpose of this study was to investigate the effect of PNB according to the change in leg length after THA. From January 2016 to August 2021, 353 patients who underwent unilateral THA for osteonecrosis of the femoral head or osteoarthritis of the hip joint were retrospectively reviewed. The patients were divided into two groups for comparison: 217 patients who controlled postoperative pain using only intravenous venous patient-controlled analgesia (IV PCA) (PCA group) and 136 patients who controlled postoperative pain using PNB and IV PCA (PCA + PNB group). We further divided the patients into two groups (leg lengthening after surgery < 10 mm and >10 mm) and compared them. After propensity score matching, the PCA and PCA + PNB groups, with 134 patients each, were compared and analyzed. The pain intensity at rest was significantly lower in the PCA + PNB group compared with that in the PCA group at postoperative 6, 24, and 48 h (p = 0.0001, 0.0009, and <0.0001, respectively). In the subgroup analysis, for patients whose limb lengthening was less than 10 mm after THA, the pain intensity at rest was significantly lower in the PCA + PNB group compared with that in the PCA group at postoperative 24 and 48 h (p = 0.0165 and 0.0015, respectively). However, in patients whose limb lengthening was more than 10 mm after THA, there was no significant difference between the pain intensity at activity and rest in the two groups at postoperative 6, 24, and 48 h (p > 0.05). PNB did not show superiority in terms of pain reduction in patients whose limb lengthening was more than 10 mm after THA. Further investigations on methods for reducing pain in patients whose leg length is increased by more than 10 mm are needed.

METAL ION RELEASE ACCORDING TO LEG LENGTH DISCREPANCY IN CERAMIC-ON-METAL HIP ARTHROPLASTY

Objective

The ceramic-on-metal (CoM) bearing has the theoretical advantages over ceramic-on-ceramic (CoC) and metal-on-metal bearings. This study aimed to analyze factors affecting the metal ion release of CoM bearings and compare clinical performance with CoC bearings.

Methods

The 147 patients were divided into 96 patients in group 1 (CoM group) and 51 patients in group 2 (CoC group). Additionally, within group1, 48 patients and 30 patients were sub-categorized into group 1-A with leg length discrepancy (LLD) less than 1cm and group 1-B greater than 1 cm. The level of serum metal ions, functional scores and plain radiographs were obtained for the analysis.

Results

The level of cobalt (Co) 2-years after surgery and chromium (Cr) 1-year after surgery showed significantly higher in the group1 than the group2. LLD indicated statistically significant positive correlation between serum metal ion levels among CoM bearing THAs. In comparison of the average metal ions level changes, group 1-B showed higher level of metal ion than group 1-A.

Conclusion

In patients underwent THA with CoM bearings, large LLD have a higher risk of complications associated to metal ions. Therefore, it is critical to reduce the LLD to 1 cm or less in using CoM bearing. Level of Evidence III; Case Control Study.

Digital Templating of THA Using PACS and an iPhone or iPad is as Accurate as Commercial Digital Templating Software

BACKGROUND

Digital templating is a standard preoperative planning method in THA. Unfortunately, many hospitals cannot afford the software or have accessibility barriers owing to a limited number of installed computer workstations. We created a templating method using a picture archiving and communication system and the Keynote program on a mobile phone. The method's accuracy and reliability have not been compared with those of commercial digital templating software.

QUESTIONS/PURPOSES

(1) How accurate is this novel method on iPhone and iPad mobile devices compared with a commercially available digital templating software program? (2) Is the method reproducible among users with different levels of experience? (3) Are the results similar for different types of femoral prostheses?

METHODS

Between January 2017 and May 2020, we treated 209 patients for hip disease or trauma with primary cementless THA. We considered patients with a normal contralateral hip as potentially eligible for this retrospective study. Thus, 91% (191 of 209 hips) were eligible; a further 13% (27 hips) were excluded because of postoperative leg length discrepancy > 5 mm, femoral offset discrepancy > 5 mm (9% [18 hips]), intraoperative periprosthetic fracture (4% [eight hips]), and proximal femoral deformity (0.5% [one hip]), leaving 78% (164 hips) for analysis here. Their preoperative radiographs were evaluated by three independent assessors, including one senior orthopaedic surgeon, one senior resident, and one junior resident, using three methods. The first was digital templating using OrthoView software, which is a commercially available digital templating software program used worldwide and known to possess high accuracy. The other two methods were technically similar to one another, with the only difference being the interface: iPhone versus iPad. In both of those approaches, using the picture archiving and communication system measurement tool, we drew a circle on an acetabular radiograph to depict the cup. We took a photograph of the computer display and imported the photograph into slides of the Keynote program, a presentation software application for Mac computers, on both devices. It was then underlaid on transparent digital templates of the femoral stem, which were scanned from plastic templates and positioned at the center of each slide. We scaled the image to the template by adjusting the image size until a 15-cm straight line on the hip photograph was equal to the 15-cm scale markers of the template. All templating results were compared with the actual implanted cementless THA components to assess accuracy. All assessors were blinded to the information about the actual implants, and they were not involved in performing the surgical procedures. The intrarater and interrater reliabilities were analyzed using intraclass correlation coefficients and kappa values. The accuracy for predicting stem size for each type of the four stem designs was compared among the three methods.

RESULTS

We were able to predict the acetabular cup size within one size in 92% of hips (151 of 164) using OrthoView and in 92% (150 of 164) using the novel method (p > 0.99). The accuracies of the three methods were comparable for predicting a femoral stem size within one size (OrthoView: 90% [148 hips], iPhone: 93% [152 hips], and iPad: 91% [149 hips]; p = 0.78), and neck length (OrthoView: 96% [157 hips], iPhone: 96% [158 hips], and iPad: 97% [159 hips]; p = 0.95). Using OrthoView, the neck offset was correctly predicted in 80% (132 hips), compared to 85% (139 hips) when using the iPhone and 82% (134 hips) when using the iPad (p = 0.57). All methods showed substantial or excellent agreement regarding intrarater and interrater reliability. There was no difference in accuracy regarding any of the four femoral stem designs we evaluated (Avenir, Excia, ML taper, and Metha).

CONCLUSION

The digital templating technique for THA using an iPhone or iPad combined with a picture archiving and communication system demonstrated high accuracy, comparable to that of commercial digital templating software. This technique is reliable and reproducible for predicting a cementless prosthesis size, neck length, and offset in different types of femoral stems. It may be useful as an alternative in resource-constrained centers where commercial software programs are too expensive to be used in practice.

LEVEL OF EVIDENCE

Level IV, diagnostic study.

Forgotten joint score is worse when the affected leg perceived longer than shorter after total hip arthroplasty

BACKGROUND

One of the causes of patient dissatisfaction after total hip arthroplasty (THA) is leg length discrepancy (LLD). Even when radiographic LLD (R-LLD) is within 5 mm, some people perceive the affected side to be longer, while others perceive it is shorter. The purpose of this study was to investigate the relationship between perceived LLD (P-LLD), R-LLD, and Forgotten Joint Score (FJS-12) after THA.

METHODS

A retrospective study of 164 patients with unilateral hip disease was conducted. Based on P-LLD after THA, they were classified into three categories: perceived short (PS 21 patients), no LLD (PN 121 patients), and perceived long (PL 22 patients). On the other hand, based on R-LLD after THA, they were divided into <  - 5 mm (RS 36 patients), - 5 mm ≤ x < 5 mm (RN 99 patients), and 5 mm ≥ (RL 29 patients), respectively. The proportion of P-LLD in the RN group was also evaluated. In each group, the relationship between P-LLD, R-LLD and FJS-12 was investigated.

RESULTS

After THA, the PL group had significantly worse FJS-12 (PS: 68.3 ± 26.2, PN: 75.0 ± 20.9, PL: 47.3 ± 25.2, P < .0001). In the R-LLD evaluation, there was no difference in FJS-12 among the three groups (RS: 73.7 ± 21.1, RN: 70.0 ± 24.5, RL: 67.7 ± 25.4, P < .53). The RN group perceived leg length to be longer (RN-PL) in 12.1% of cases, and the RN-PL groups had significantly worse FJS-12 (RN-PS: 65.4 ± 24.8, RN-PN: 73.8 ± 23.1, RN-PL: 41.8 ± 27.6, P < .0001).

CONCLUSION

One year after THA, patients with longer P-LLD had worse FJS-12, even if the R-LLD was less than 5 mm.

How is hip anatomy reconstruction and inlay wear associated up to 10 years after primary THA using ceramic on highly crosslinked polyethylene bearings?

INTRODUCTION

Conventional polyethylene (PE) wear has been reported to be associated with femoral offset reconstruction and cup orientation after THA. Thus, the present study aimed (1) to determine the polyethylene wear rate of 32 mm ceramic heads with highly cross-linked polyethylene (HXLPE) inlays up to 10 years postoperatively and (2) to identify patient and surgery-related factors affecting the wear rate.

METHODS

A prospective cohort study was performed, investigating 101 patients with 101 cementless THAs and ceramic (32 mm) on HXLPE bearings after 6-24 months, 2-5 years and 5-10 years postoperatively. The linear wear rate was determined using a validated software (PolyWare®, Rev 8, Draftware Inc, North Webster, IN, USA) by two reviewers, blinded to each other. A linear regression model was used to identify patient and surgery-related factors on HXLPE -wear.

RESULTS

After an initial bedding-in phase of 1 year after surgery, the mean linear wear rate was 0.059 ± 0.031 mm/y at ten years (mean 7.7 years; SD 0.6 years, range 6-10), being below the osteolysis relevant threshold of 0.1 mm/year. The regression analysis demonstrated that age at surgery, BMI, cup inclination or anteversion and the UCLA score were not associated with the linear HXLPE-wear rate. Only increased femoral offset showed a significant correlation with an increased HXLPE-wear rate (correlation coefficient of 0.303; p = 0.003) with a moderate clinical effect size (Cohen's f²=0.11).

CONCLUSION

In contrast to conventional PE inlays, hip arthroplasty surgeons may be less concerned about osteolysis-related wear of the HXLPE if the femoral offset is slightly increased. This allows focusing on joint anatomy reconstruction, hip stability and leg length.

Precise acetabular positioning, discrepancy in leg length, and hip offset using a new seven-axis robot-assisted total hip arthroplasty system requires no learning curve: a retrospective study

Objective

The purpose of the present study was to determine the learning curve for a novel seven-axis robot-assisted total hip arthroplasty (RA-THA) system, and to explore whether it was able to provide greater accuracy in acetabular cup positioning, superior leg length discrepancy (LLD), and hip offset than conventional methods.

Methods

A total of 160 patients in which unilateral THA was performed in the second affiliated Hospital of Xi'an Jiaotong University from July 2021 to September 2022 were studied. The first 80 patients underwent robot-assisted THA, while conventional THA was performed on the subsequent 80 by the same team of experienced surgeons. The learning curve for the RA-THA system was evaluated using cumulative sum (CUSUM) analysis. The demographic data, preoperative clinical data, duration of surgery, postoperative Harris hip score (HHS) and postoperative radiographic data from patients that had conventional THA were compared.

Results

The 80 patients who underwent primary unilateral RA-THA comprised 42 males and 38 females and were followed up for 12 weeks. Using analysis by CUSUM, the learning curve of the RA-THA system could be divided into learning and proficiency phases, the former of which consisted of the first 17 cases. There was no significant difference between the learning and proficiency phases in terms of LLD, hip offset, or accuracy of acetabular prosthesis position in the RA-THA groups. The proportion of acetabular prostheses located in the Lewinnek safe zone was 90.5% in the proficiency group and 77.5% in the conventional group, respectively, a difference that was statistically significant (P < 0.05). The absolute error between target angle and postoperative measured angle of anteversion was statistically significant in the proficiency group and the conventional group((P < 0.05). Postoperative acetabular anteversion and LLD were 19.96 ± 5.68° and 6.00 (5.00) mm in the proficiency group, respectively, and 17.84 ± 6.81° and 8.09 (4.33) mm using conventional surgery, respectively (anteversion: P = 0.049; LLD: P < 0.001).

Conclusions

The surgical team required a learning curve of 17 cases using the RA-THA system to become proficient. There was no learning curve for other parameters, namely LLD, hip offset, or accuracy of acetabular prosthesis positioning. During the proficiency phase, the RA system was superior to conventional THA for control of leg length and accuracy of acetabular cup placement.

Reduction in Offset Is Associated With Worse Functional Outcomes Following Total Hip Arthroplasty

BACKGROUND

Conflicting reports exist about the effect of offset variation on functional outcomes following total hip arthroplasty. Reproducing native hip offset is thought to optimize function by restoring biomechanics and appropriately tensioning the hip abductor muscles. The aim of this study is to assess the effect of failing to restore global hip offset in comparison to the native contralateral hip.

METHODS

A retrospective analysis of a prospective patient cohort was performed on patients undergoing an elective primary total hip arthroplasty. A total of 414 patients who had a minimum of 12 months of follow-up were included. Postoperative plain radiographs were analyzed for offset and compared to the contralateral native hip. Western Ontario and McMaster Universities Arthritis Index (WOMAC) and Veterans RAND 12 (VR-12) scores were assessed preoperatively and at 12 months postoperatively.

RESULTS

Regression analyses indicated that a reduction in offset of >20 mm resulted in worse WOMAC pain (P = .005) and motion (P = .015) scores compared to those with maintained offset. WOMAC function (P = .063), global (P = .025), and VR-12 scores were not affected (physical P = .656; mental P = .815). Reduction in offset up to 20 mm and increased offset were not significantly associated with patient-reported outcome measures (P-values ranged from .102 to .995).

CONCLUSION

This study demonstrated an association between reduction in offset by >20 mm and worse WOMAC pain and motion scores following total hip arthroplasty. Surgeons should avoid decreases in offset >20 mm in order to optimize functional outcomes.

Assessing Leg Length and Offset in Anterior Total Hip Arthroplasty: Overlay Versus AP Pelvis Intraoperative Radiographic Techniques: A Retrospective Cohort Study

INTRODUCTION

Two intraoperative radiographic techniques to determine leg length and offset during anterior total hip arthroplasty (THA) are the AP pelvis and overlay techniques. The AP pelvis method measures LLDs and offset using AP fluoroscopic images, whereas the overlay method uses printed images of the native and replaced hips. The purpose of this study was to compare these techniques regarding clinical and radiographic LLD and offset discrepancies.

METHODS

Patients of a single surgeon at two hospitals from September 2017 to January 2021 were retrospectively reviewed. Clinically detectable LLD was recorded. Radiographic measurements were obtained from preoperative and postoperative radiographs. LLD was determined based on the vertical distance between the lesser trochanters and the ischial tuberosities. Total offset was measured using a combination of femoral and medial offset. The Student t-test, Fisher exact test, and Wilcoxon rank sum tests were used for statistical analysis.

RESULTS

Seventy-one procedures were done using the overlay technique and 61 used for the AP pelvis technique. No significant differences were observed in mean postoperative LLD (2.66 versus 2.88 mm, P = 0.66) and mean postoperative offset discrepancy (5.37 versus 4.21 mm, P = 0.143) between the overlay versus AP pelvis groups. The mean preoperative to postoperative absolute difference in offset was less than 5 mm in both groups. Clinically detectable LLD was noted in six of 71 patients in the overlay group and one of 61 in the AP pelvis group (P = 0.123).

CONCLUSION

No notable differences were observed in intraoperative leg length and offset discrepancies during direct anterior THA between the AP pelvis and overlay techniques, suggesting they are equally effective in determining LLD and offset intraoperatively. The choice of technique to use anterior THA should be based primarily on the surgeon's preference, comfort, and available resources.

Intraoperative method of femoral head central measurement to prevent leg length discrepancy following hemiarthroplasty

Purpose

This study aimed to introduce and investigate the safety and efficiency of the intraoperative central measurement method of the femoral head (IM-CMFH) to prevent leg length discrepancies (LLD) after hemiarthroplasty.

Methods

Overall, 79 patients aged 75 to 85 years with femoral neck fractures who underwent hemiarthroplasty were divided into two groups: the Control group (n = 46) and the IM-CMFH group (n = 33). The two groups were compared for postoperative LLD and the proportions of patients with greater than 10 mm, 6-10 mm, and within 5 mm, postoperative femoral offset (FO) difference and the proportions of patients within 5 mm, incremental greater than 5 mm and reduction greater than 5 mm. Next, the vertical distance from the center of the femoral head to the tip of the greater trochanter on the anatomical axis of the femur (VD-CFH-TGTAAF), leg length, and FO on the operative and non-operative sides within the IM-CMFH group. Finally, operative time, hemoglobin loss, Harris scores 3 months after surgery, and postoperative complications were analyzed.

Results

Compared with the control group, the postoperative LLD and FO differences were significantly lower in the IM-CMFH group (P = 0.031; P = 0.012), and the proportion of patients with postoperative LLD greater than 10 mm decreased significantly (P = 0.041), while the proportion of patients with FO difference of within 5 mm increased (P = 0.009). In addition, there was no significant difference in the operative time, hemoglobin loss, and Harris score at 3 months postoperatively and postoperative complications between the two groups (P > 0.05). There was no significant difference in FO, leg-length, and VD-CFH-TGTAAF between the operative and non-operative sides within the IM-CMFH group (P > 0.05).

Conclusion

Satisfactory results can be achieved by using the IM-CMFH to prevent LLD following hemiarthroplasty, and there is no increase in operative time, hemoglobin loss, or postoperative complications. This technique is efficient for hemiarthroplasties and is both simple and convenient.

The effectiveness and influencing factors of the "Y" line technique in reducing the leg length discrepancy after total hip arthroplasty

Objective

To introduce a surgical technique (the "Y" line technique) that will control leg length discrepancy (LLD) after total hip arthroplasty and to observe its effectiveness and influencing factors.

Methods

According to the inclusion and exclusion criteria, a total of 350 patients were selected in this study; 134 patients in whom used the "Y" line technique was used to control lower limb length were included in Group A and 166 patients treated with freehand methods to control lower limb length were included in Group B. A total of 50 patients in whom the standard anteroposterior x-ray of bilateral hips was taken preoperatively and in whom the "Y" line technique was used during the operation were included in Group C.

Results

The postoperative LLD of Group A was 4.74 mm (3.93), that of Group B was 5.85 mm (4.60), and that of Group C was 2 mm (1.00)-the difference was statistically significant (p < 0.001). There were significant statistical differences when comparisons were made between any two groups (p < 0.01). The distribution of postoperative LLD in Group A was better than that in Group B, and this factor was better in Group C than in Group A-the difference was statistically significant (p < 0.001). Severe unequal length rates of the lower extremities (LLD > 10 mm) were 5.97% (8/134) in Group A, 14.3% (24/166) in Group B, and 0% (0/50) in Group C-the difference was statistically significant (p < 0.001). There were significant differences between Group A and Group B and between Group B and Group C (p < 0.05), but there was no significant difference between Group A and Group C (p = 0.078).

Conclusion

The "Y" line technique, which does not increase the operating time and patient cost, can effectively reduce postoperative LLD. Insufficient internal rotation of the healthy lower extremity and the low projection position in the preoperative anteroposterior x-ray of the bilateral hips were important factors affecting the accuracy of the "Y" line technique.

The Importance of Monitoring and Factors That May Influence Leg Length Difference in Developmental Dysplasia of the Hip

In unilateral Developmental Dysplasia of the Hip (DDH), avascular necrosis (AVN), femoral or pelvic osteotomy, and residual dysplasia causing subluxation of the proximal femur may influence Leg Length Discrepancy (LLD). This can lead to gait compensation, pelvic obliquity, and spinal curvature. The aim of this study is to determine the prevalence of LLD, establish which limb segment contributes to the discrepancy, describe how AVN influences LLD, and ascertain variables that may influence the need for LLD corrective procedures.

METHODOLOGY

This study assessed long-leg radiographs at skeletal maturity. Radiographs were assessed for the articulo-trochanteric distance (ATD) and femoral and tibial length. AVN was classified according to Kalamchi-MacEwen.

RESULTS

109 patients were included. The affected/DDH leg was longer in 72/109 (66%) patients. The length difference was mainly in the subtrochanteric segment of the femur. AVN negatively influenced leg length. Older (≥three years) patients with multiple procedures were more likely to have AVN. LLD interventions were performed in 30 (27.5%) patients. AVN grade or type of DDH surgery did not influence the odds of needing a procedure to correct LLD.

CONCLUSIONS

Procedures to correct LLD were performed irrespective of previous DDH surgery or AVN grades. In most patients, the affected/DDH leg was longer, mainly in the subtrochanteric segment of the femur, largely influenced by femoral osteotomy in patients with multiple operative procedures for DDH. We recommend careful monitoring of LLD in DDH.

A smaller femoral stem is needed for asian females

BACKGROUND

Current femoral implants are manufactured based on Western anatomical structures and may be too large for smaller physiques, such as those of Asian females. This study reviewed the femoral stem size distribution used in a high-volume total hip arthroplasty (THA) practice and evaluated malalignment in patients receiving a size one implant.

MATERIALS AND METHODS

A consecutive cohort of female patients self-reported as Asian (257 patients, 331 hips) or Caucasian (158 patients and 190 hips) were retrospectively evaluated. A single femoral stem type was used in all cases, performed by a single surgeon. Global hip offset (GHO) and leg length difference (LLD) were measured before and 6 weeks following THA. Differences between races were evaluated through Mann-Whitney U tests and chi-squared tests for continuous and categorical variables, respectively.

RESULTS

The proportion of size one implants was higher amongst Asian patients (20.5%) than Caucasian patients (2.6%) (p < 0.001). A LLD greater than 6 mm was noted in 24.6% of size one patients and 11.4% of all other sizes (p = 0.010). Varus malalignment occurred in 47.9% of size one patients and 22.1% of all other sizes (p < 0.001). No fractures occurred in size one patients, and nine fractures (one intraoperative and eight post-operative) occurred in all other sizes (p = 0.258).

CONCLUSION

The high proportion of size one stems required in Asian females and the higher incidence of LLD > 6 mm and varus malalignment suggest a distinct need for smaller femoral implants, especially for Asian females.

Radiologic restoration inaccuracy increases postoperative dislocation in primary total hip arthroplasty: a retrospective study with propensity score matching

BACKGROUND

Dislocation is a complicated process and associated with multivariate etiology and risk factors. The purpose of this study was to verify if radiologic restoration inaccuracy increases postoperative dislocation in primary total hip arthroplasty (THA) individually or synergistically.

METHODS

From 2017 to 2020, we identified 76 (1.9%) patients who suffered postoperative dislocations from 3926 THAs in our institution. After excluded patients with previously proven patient-related and implant-related risk factors, the remaining patients were used to match a 1:1 control patients who were without dislocation. The cup position (inclination and anteversion angles), hip offset (HO), leg length discrepancy (LLD), and abductor lever arm (ALA) were analyzed by univariate analyses and multivariate logistic regressions.

RESULTS

Measurements on radiographs showed excellent interobserver agreement (intraclass correlation coefficient (ICC) 0.922-0.952) and intraobserver agreements (ICC 0.933-0.967). HO restoration inaccuracy (without ± 5 mm) was associated with higher dislocation risk (OR 4.241 95% CI 1.440-12.492, P = 0.009). The restoration inaccuracy of the cup position, LLD, or ALA could not increase the dislocation risk individually. When combining the radiologic restoration inaccuracy factors, the HO + LLD restoration inaccuracy and HO + ALA restoration inaccuracy increased the odds of postoperative dislocation (OR 12.056, 95% CI 1.409-103.127, P = 0.023; OR 4.770, 95% CI 1.336-17.028, P = 0.016, respectively). Combining the four risk factors of cup safe zone, HO, LLD, and ALA, patients with 3 or 4 radiologic restoration inaccuracy factors showed a higher risk of dislocation (OR 13.500, 95% CI 1.340-135.983, P = 0.027).

CONCLUSION

Hip offset (HO) restoration inaccuracy increased the risk of dislocation following primary THA. Multivariate radiologic restoration accuracy is critical for the prevention of dislocation and needs to be valued by surgeons.

Accuracy of a Three-Dimensional (3D)-Printed Patient-Specific (PS) Femoral Osteotomy Guide: A Computed Tomography (CT) Study

Femoral neck osteotomy creates a critical anatomical landmark for surgeons performing primary Total Hip Arthroplasty (THA); it affects the final height and position of the femoral component. Patient Specific Instrumentation (PSI) has been developed to guide the osteotomy. We aimed to assess the accuracy of a patient-specific (PS) femoral osteotomy guide in primary THA using three-dimensional (3D) computed tomography (CT) analysis. We included pre- and post-operative CT data of 103 THAs. All patients underwent 3D planning to define the optimal femoral neck osteotomy level. Our primary objective was to quantify the discrepancy between the achieved and planned osteotomy level; our secondary objective was to evaluate the clinical outcome. The median (Interquartile Range—IQR) discrepancy between the achieved and planned osteotomy level was 0.3 mm (−1 mm to 2 mm). We found a strong positive correlation between the planned and achieved osteotomy level (R2 = 0.9, p < 0.001). A satisfactory clinical outcome was recorded. Our findings suggest that surgeons can use 3D-printed PS guides to achieve a femoral neck osteotomy with a high level of accuracy to the plan.

Gait Analysis in Orthopaedic Surgery: History, Limitations, and Future Directions

Gait analysis has expanding indications in orthopaedic surgery, both for clinical and research applications. Early work has been particularly helpful for understanding pathologic gait deviations in neuromuscular disorders and biomechanical imbalances that contribute to injury. Notable advances in image acquisition, health-related wearable devices, and computational capabilities for big data sets have led to a rapid expansion of gait analysis tools, enabling novel research in all orthopaedic subspecialties. Given the lower cost and increased accessibility, new gait analysis tools will surely affect the next generation of objective patient outcome data. This article reviews the basic principles of gait analysis, modern tools available to the common surgeon, and future directions in this space.

A novel method of manual positioning based on anatomical mark (shoulder-to-shoulder) to prevent postoperative leg-length discrepancy for femoral neck fractures in hip arthroplasty

OBJECTIVE

To determine whether the two lower extremities are of equal length after hip arthroplasty for femoral neck fractures, we developed a novel method of manual positioning based on anatomical mark (shoulder-to-shoulder) in hip arthroplasty.

METHODS

Patients with femoral neck fractures requiring hip arthroplasty from July 2020 to March 2022 in the orthopedic department of Jinjiang Municipal Hospital, Fujian Province, China were recruited. Hip arthroplasty was performed using the proposed "shoulder-to-shoulder" method of manual positioning based on anatomical mark in 52 patients with femoral neck fractures who met the inclusion criteria. "Shoulder-to-shoulder" was achieved by alignment of the marked femoral "shoulder" and the "shoulder" of prosthesis stem. There were 16 male and 36 female patients, with 27 undergoing total hip arthroplasty (THA) and 25 undergoing hip hemiarthroplasty (HA). The fractures were categorized according to the Garden classification: type II, type III, and type IV in 5, 11, and 36 patients, respectively. The vertical distance from the apex of the medial margin of the femoral trochanter to the tear drop line on both sides which was regarded as the length of both limbs were compared via postoperative imaging, and the apex-shoulder distance on the ipsilateral side measured via postoperative imaging was compared with those measured intraoperatively.

RESULTS

All patients completed the surgery successfully. The measurement results for the lower extremities after THA were as follows: contralateral group, 43.87 ± 5.59 mm; ipsilateral group, 44.64 ± 5.43 mm. The measurement results for the lower extremities after HA were as follows: contralateral group, 45.18 ± 7.82 mm; ipsilateral group, 45.16 ± 6.43 mm. The measurement results for the lower extremities after all arthroplasties were as follows: contralateral group, 44.50 ± 6.72 mm; ipsilateral group, 44.89 ± 5.90 mm. The results for the apex-shoulder distance were as follows: postoperative imaging, 19.44 ± 3.54 mm; intraoperative apex-shoulder distance, 27.28 ± 2.84 mm. Statistical analysis results indicated no statistically significant difference in the postoperative bilateral lower extremity length after hip arthroplasty (P = 0.75), while a statistically significant difference was found between the intraoperative and postoperative imaging measurements of the apex-shoulder distance (P < 0.01).

CONCLUSION

The novel method of manual positioning based on anatomical mark (shoulder-to-shoulder) for femoral neck fractures in hip arthroplasty is simple and accurate, making it effective for preventing postoperative bilateral leg length discrepancy.

Utilizing Three-Dimensional Head-Lesser Trochanter Distance Could Further Reduce Leg Length Inequality in Primary Bipolar Hemiarthroplasty

Background: The aim of this study was to investigate whether the use of three-dimensional (3-D) computed tomography (CT)-based head-lesser trochanter distance (HLD) could reduce leg length discrepancy (LLD) more than the use of a two-dimensional (2-D) plain film method in primary bipolar hemiarthroplasty. Methods: Propensity score matching (PSM) analysis was used to adjust the confounding factors. A retrospective comparative analysis of 128 patients was performed. In the control group, the leg length was equalized using the 2-D, plain film-based HLD. In the study group, primary bipolar hemiarthroplasty was performed using the 3-D CT-based HLD method. Postoperative LLDs were compared between the two groups using the method of Ranawat. In addition, the Harris hip score (HHS) was evaluated and compared at one year after surgery. Results: A significant difference was observed in mean postoperative LLD between the 2-D HLD group and the 3-D CT HLD group: 1.6 ± 1.2 mm (range, 0.1−6.0 mm) and 1.1 ± 1.2 mm (range, 0.1−5.1 mm), respectively (p < 0.05). Additionally, a higher percentage of patients in the 3-D CT HLD group had an LLD of less than 2 mm. The mean HHS at one year after surgery showed no significant difference between the two groups. Conclusions: To minimize the occurrence of LLD, HLD measurement from a CT scanner may be more accurate than an X-ray. The 2-D and 3-D HLD differences in the 3-D CT HLD group were statistically significant. Using a 3-D, CT-based HLD method might decrease the possibility of an LLD over 2 mm.

Spinopelvic Relationship and Its Impact on Total Hip Arthroplasty

The dynamic, complex interaction among the spine, pelvis, and hip is often underappreciated, yet understanding it is vital for both arthroplasty and spinal surgeons. There is an increasing incidence of degenerative hip and spinal pathologies as a result of the ageing population. Furthermore, hip pathology can cause spine pathology and vice versa through “hip-spine” and “spine-hip syndrome.” Consequently, total hip arthroplasty (THA) and spinal fusion surgery, which both affect spinopelvic mobility, are also on the rise. Alteration in spinopelvic motion can affect the orientation of the acetabulum and, therefore, implant positioning in THA, leading to complications such as dislocation, impingement, aseptic loosening, and wear of components. This makes it imperative to assess spinopelvic motion and pelvic tilt prior to patients undergoing THA. In this paper, we explore how the surgeon should proceed to reduce risk of component malalignment, as well as the role of navigation systems in acetabular cup positioning.

Quantitative gait analysis after total hip arthroplasty through a minimally invasive direct anterior approach: A case control study

INTRODUCTION

Total Hip Arthroplasty (THA) leads to excellent clinical and functional results. The Minimally Invasive Anterior Approach (MIAA) theoretically allows rapid recovery and a reduction in the need for rehabilitation, but alterations in muscle and static balance have previously been demonstrated. Kinetic, kinematic and muscular alterations have been shown to persist up to 1year postoperatively but data beyond 1year postoperatively is lacking. Thus, the objective of this study was to compare the data from Quantitative Gait Analysis (QGA) coupled with electromyography (EMG), of patients one year postoperatively with THA through MIAA, compared to an asymptomatic control group.

HYPOTHESIS

We hypothesized that QGA and EMG parameters would not normalize beyond one year postoperatively.

PATIENTS AND METHODS

Twenty-seven patients were recruited, including 15 subjects (64.6±6.6years) operated on by MIAA, who at 15.9±3.1months postoperatively, along with 12 asymptomatic control subjects (68.9±9.7years), who underwent QGA and maximal isometric muscle strength tests, coupled with EMG on the gluteus medius and maximus, Tensor Fascia Lata (TFL) and Sartorius muscles. The spatiotemporal parameters of walking (step length, walking speed, cadence, single leg support time), kinetics (vertical ground reaction forces, hip moments in the 3 planes) and kinematics (coxofemoral and pelvic amplitudes) were analyzed.

RESULTS

The walking speed was lower on the non-operated side of the experimental subjects (0.96ms^-1 compared to 1.13ms^-1 for asymptomatic [p=0.018]), as was the step length on the operated side (0.53m compared to 0.60m for asymptomatic [p=0.042]). Maximal isometric muscle strength was lower in subjects operated on for the gluteus maximus and medius (p=0.004), compared to asymptomatic subjects. Moments were lower in the subjects operated on in extension (0.72Nm on the operated side, 0.75Nm on the non-operated side compared to 1.06Nm for asymptomatic [p=0.007 and p=0.024]) and lateral rotation (0.09Nm on the operated side, 0.05Nm on the non-operated side compared to 0.16Nm for asymptomatic subjects [p=0.009 and p=0.0005]). Hip adduction amplitudes were lower on the operated side compared to asymptomatic subjects (3.93° versus 9.14° for asymptomatic [p=0.005]). Pelvic amplitudes in the frontal plane were lower amongst operated subjects (0.44° against 1.97° for asymptomatic [p=0.041]). Pelvic amplitudes in the sagittal plane were higher in the operated subjects (15.74° on the operated side, 15.43° on the non-operated side compared to 9.65° for asymptomatic [p=0.041 and p=0.032]).

DISCUSSION

Our initial hypothesis was validated, since walking deficits persisted beyond one year postoperatively after THA through MIAA. A decrease in maximal isometric muscle strength of the gluteus medius and gluteus maximus was observed, as well as an alteration of kinetic and kinematic parameters in the sagittal and frontal planes. The results were in agreement with the literature and reflected the establishment of compensatory mechanisms to overcome alterations in joint strength and range more than one year postoperatively. These results would allow rehabilitation programs to be more specific and would justify a study on the other approaches for THA.

LEVEL OF EVIDENCE

III; non-randomized control trial.

Improved hip symmetry with an adjustable fluoroscopic grid during total hip arthroplasty

BACKGROUND

The use of intraoperative fluoroscopy (IF) is common with direct anterior total hip arthroplasty (THA), however image distortion in IF may limit its usefulness. The supplementation of IF with an adjustable grid (AG) may provide consistently better accuracy in component placement. Therefore, the purpose of this study was to compare the accuracy, consistency, and surgical efficiency between IF only and AG supplementation.

METHODS

2 cohorts were retrospectively evaluated, including 573 IF only patients and 211 AG patients having undergone unilateral THA between 2011 and 2018. Post-THA radiographic assessment was performed to evaluate the accuracy of component placement, with target placements for global hip offset (GHO) and leg-length differences (LLD) <10 mm and acetabular cup abduction of 45° (±10°). Accuracy and surgical efficiency were evaluated between groups and over time.

RESULTS

The AG group had a significant greater percentage of components placed within the target zone compared to IF only for GHO (99.5%, 92.7%, p < 0.001), LLD (99.1%, 96.5%, p = 0.039) and abduction (99.5%, 96.3%, p = 0.009), with no difference in fluoroscopic time (p = 0.973). Over time, accuracy was significantly different in IF group for GHO (p = 0.008) and abduction (p = 0.002) and trended toward significance for LLD (p = 0.055). There were no significant differences over time for the AG group.

CONCLUSIONS

The addition of an AG to IF significantly increased the accuracy of component placement during direct anterior THA. These results were consistent over 2 years of use and did not decrease surgical efficiency.

Imaging in Hip Arthroplasty Management-Part 1: Templating: Past, Present and Future

Hip arthroplasty is a frequently used procedure with high success rates. Its main indications are primary or secondary advanced osteoarthritis, due to acute fracture, osteonecrosis of the femoral head, and hip dysplasia. The goals of HA are to reduce pain and restore normal hip biomechanics, allowing a return to the patient’s normal activities. To reach those goals, the size of implants must suit, and their positioning must meet, quality criteria, which can be determined by preoperative imaging. Moreover, mechanical complications can be influenced by implant size and position, and could be avoided by precise preoperative templating. Templating used to rely on standard radiographs, but recently the use of EOS^® imaging and CT has been growing, given the 3D approach provided by these methods. However, there is no consensus on the optimal imaging work-up, which may have an impact on the outcomes of the procedure. This article reviews the current principles of templating, the various imaging techniques used for it, as well as their advantages and drawbacks, and their expected results.

Imaging in Hip Arthroplasty Management Part 2: Postoperative Diagnostic Imaging Strategy

Hip arthroplasty (HA) is a frequently used procedure with high success rates, but 7% to 27% of the patients complain of persistent postsurgical pain 1 to 4 years post-operation. HA complications depend on the post-operative delay, the type of material used, the patient’s characteristics, and the surgical approach. Radiographs are still the first imaging modality used for routine follow-up, in asymptomatic and painful cases. CT and MRI used to suffer from metallic artifacts but are nowadays central in HA complications diagnosis, both having their advantages and drawbacks. Additionally, there is no consensus on the optimal imaging workup for HA complication diagnosis, which may have an impact on patient management. After a brief reminder about the different types of prostheses, this article reviews their normal and pathologic appearance, according to each imaging modality, keeping in mind that few abnormalities might be present, not anyone requiring treatment, depending on the clinical scenario. A diagnostic imaging workup is also discussed, to aid the therapist in his imaging studies prescription and the radiologist in their practical aspects.

Three-Dimensional Functional Impingement in Total Hip Arthroplasty: A Biomechanical Analysis

BACKGROUND

Although component offset can affect impingement after total hip arthroplasty, the exact impact is unclear. Evaluation of offset on an anterior-posterior pelvic radiograph is different than evaluation in functional positions of impingement, namely flexion/internal rotation and extension/external rotation. We quantified the effect of acetabular (cup/liner) vs femoral (head/stem) offsets on changes in range of motion to extra-prosthetic impingement in these 2 impingement-prone functional positions.

METHODS

We retrospectively identified 16 total hip arthroplasty patients (age 61.5 ± 12.1 years, body mass index 28.3 ± 4.9 kg/m²) with preoperative and postoperative computerized tomography scans. To eliminate metal artifact, femoral and pelvic 3-dimensional models were created using preoperative scans aligned with postoperative scans, and 3-dimensional scanned implant models were used to reproduce clinical implantation. We tested ±5 mm acetabular cup, acetabular liner, femoral stem, and femoral head offsets. Maximum range of motion (ROM) to bone-bone impingement was calculated for internal rotation at 90° flexion and external rotation at 10° extension.

RESULTS

In all cases, increased offset increased ROM to impingement, and vice versa. During internal rotation at 90° flexion, ±5 mm liner offset had the greatest impact on ROM (+9°/-10°), followed by cup (+8°/-9°), head (+5°/-7°), and stem (+3°/-5°) offset. During external rotation at 10° extension, ±5 mm cup offset had the greatest impact on ROM (+10°/-10°), followed by liner (+9°/-9°), head (+7°/-8°), and stem (+4°/-4°) offset. However, no statistically significant differences were found in the changes to ROM in flexion obtained through cup and liner offsets, the changes to ROM in extension obtained through liner and head offsets, and the changes to ROM in extension obtained through increasing stem and head offsets.

CONCLUSION

Increasing offset by any method reduces impingement. Center-of-rotation offset changes via acetabular cup or liner have the greatest impact on extra-prosthetic impingement.

Learning Curve of Total Hip Arthroplasty in Direct Anterior Approach without Requiring Corrective Osteotomy for Hip Dysplasia

OBJECTIVE

To explore the learning curve of total hip arthroplasty in direct anterior approach (DA-THA) without requiring corrective osteotomy for patients with unilateral developmental dysplasia of the hip (DDH) through the evaluation of clinical and radiographic results.

METHOD

From December 2015 to January 2021, we retrospectively evaluated a surgeon's first 100 patients with unilateral hip dysplasia (Crowe I-III) who underwent DA-THA. All procedures were performed by a fellowship-trained joint surgeon. Cementless hemispheric porous-coated acetabular cups and tapered cementless stems were used in all hips. The radiographic data, including leg length, the height of the center of rotation, femoral head offset, the cup anteversion and inclination angle, were measured. The cumulative sum analysis (CUSUM) and risk-adjusted cumulative sum analysis (RA-CUSUM) were used to determine the learning curve of DA-THA for each patient's operation time. By analyzing the operation time, complication rate, postoperative length of hospitalization and creatine kinase (before surgery and the third day after surgery), estimated blood loss, Harris score, radiographic data were compared between the different stages of the learning curve.

RESULTS

The mean follow-up time was 35.45 ± 16.82 months. The CUSUM method obtained the maximum turning point of the curve at 43 cases, which divided the learning curve into Learning Period and Mastery Period. The CUSUM learning curve was best modeled as a cubic curve with the equation: CUSUM (min) = 0.001x³  - 0.495x²  + 33.60x - 10.00, which had a higher R² value of 0.967. The pre-operative data, creatine kinase, estimated blood loss and postoperative Harris scores of the two stages were not statistically significant (P > 0.05). The mean operation time was 118 min in the Learning Period and 87 min in the Mastery Period. Statistically significant differences were detected in the operation time (P < 0.001), postoperative length of hospitalization(P = 0.024), and postoperative leg length discrepancy (P = 0.012) between the two stages. The overall complication rates were 27.9% in the Learning Period and 12.3% in the Mastery Period (p = 0.049). The overall outliers of radiographic data were 34 cases in the Learning Period and 31 cases in the Mastery Period (79.07% vs 54.39%, P = 0.010).

CONCLUSIONS

The DA-THA is a valuable alternative to achieve satisfactory clinical results for mild-to-moderate DDH patients. Furthermore, accurate analysis of the learning curve of DA-THA for hip dysplasia by the CUSUM method showed that the surgeons need to finish about 43 cases to master the technique.

Acetabular Revision Arthroplasty Based on 3-Dimensional Reconstruction Technology Using Jumbo Cups

Background: This study was aimed at evaluating the changes in cup coverage (CC) and hip center of rotation (HCOR) in acetabular defects of various severities treated with acetabular revision using jumbo cups.

Methods: A total of 86 hips were included. The American Academy of Orthopedic Surgeons (AAOS) classification of these patients was as follows: 16 patients, AAOS I; 16 patients, AAOS II; and 16 patients, AAOS III. A three-dimensional (3D) implant simulation technique was used to visualize the placement of jumbo cups during revision arthroplasty. The acetabular anteversion, inclination, CC, and the HCOR were measured.

Results: The inclination and anteversion of simulated acetabular cups in AAOS I–III groups were consistent with the normal acetabular anatomy. Compared with the controls, in AAOS I–III groups, the HCOR was significantly increased and CC was significantly decreased. The HCOR elevation was significantly higher in AAOS III patients than in AAOS I (p = 0.001) and AAOS II patients (p < 0.001). The use of the jumbo cup technology for acetabular revision would decrease the CC in AAOS I–III patients to 86.47, 84.78, and 74.51%, respectively.

Conclusion: Our study demonstrated that in patients with acetabular defects, acetabular revision arthroplasty using jumbo cups will lead to decreased CC and HCOR upshift. Upon classifying these patients according to the AAOS classification, CC decreased with the severity of acetabular defects, and the elevation of the HCOR in AAOS III patients exceeded 10 mm and was significantly higher than in other patients.

Kinematic pelvic tilt during gait alters functional cup position in total hip arthroplasty

Static pelvic tilt impacts functional cup position in total hip arthroplasty (THA). In the current study we investigated the effect of kinematic pelvic changes on cup position. In the course of a prospective controlled trial postoperative 3D-computed tomography (CT) and gait analysis before and 6 and 12 months after THA were obtained in 60 patients. Kinematic pelvic motion during gait was measured using Anybody Modeling System. By fusion with 3D-CT, the impact of kinematic pelvic tilt alterations on cup anteversion and inclination was calculated. Furthermore, risk factors correlating with high pelvic mobility were evaluated. During gait a high pelvic range of motion up to 15.6° exceeding 5° in 61.7% (37/60) of patients before THA was found. After surgery, the pelvis tilted posteriorly by a mean of 4.0 ± 6.6° (p < .001). The pelvic anteflexion led to a mean decrease of -1.9 ± 2.2° (p < .001) for cup inclination and -15.1 ± 6.1° (p < .001) for anteversion in relation to the anterior pelvic plane (APP). Kinematic pelvic changes resulted in a further change up to 2.3° for inclination and up to 12.3° for anteversion. In relation to the preoperative situation differences in postoperative cup position ranged from -4.4 to 4.6° for inclination and from -7.8 to 17.9° for anteversion, respectively. Female sex (p < .001) and normal body weight (p < .001) correlated with high alterations in pelvic tilt. Kinematic pelvic changes highly impact cup anteversion in THA. Surgeons using the APP as reference should aim for a higher anteversion of about 15° due to the functional anteflexion of the pelvis during gait.

Femoroacetabular offset restoration in total hip arthroplasty; Digital templating a short stem vs a conventional stem

BACKGROUND

Failure in restoring individual anatomy could be a reason for persistent functional limitations post total hip arthroplasty. Femoroacetabular offset (FAO) plays an important role in anatomic restoration, as loss of offset ≥ 5 mm is associated with altered gait and decreased functional outcome. Preoperative assessment by use of digital templating has shown to be a reliable method for sizing the components in total hip arthroplasty, and can show if anatomic restoration is achieved. In recent years, short stems are growing in popularity as it could allow better restoration due to more variety in placement.

AIM

To assess whether restoration of the FAO differs between a short or a conventional stem by use of digital templating. Additionally, association of the preoperative offset and caput-colllum-diaphyseal angle (CCD-angle) within restoration of both stems was investigated, and the reliability of measurements was assessed.

METHODS

A total of 100 standardized hip radiographs were used for digital templating. Restoration of FAO was classified into “restored” or “not restored”, when a < 5 mm or ≥ 5 mm difference from baseline value presented, respectively. Differences between the two stems concerning proportions of correct restoration of the FAO were analyzed by use of McNemar tests. To assess association between CCD-angle and preoperative FAO with absolute FAO restoration, multi-level analysis was performed by use of a linear mixed model to account for paired measurements. Through determination of the optimal point under the curve in operating curve-analysis, bootstrapping of thousand sets was performed to determine the optimal cutoff point of the preoperative FAO for restoration within the limits of 5 mm. Three observers participated for inter-observer reliability, with two observers measuring the radiographs twice for intra-observer reliability.

RESULTS

The mean preoperative FAO was 79.7 mm (range 62.5-113 mm), with a mean CCD-angle of 128.6° (range 114.5°-145°). The conventional stem could only restore the FAO in 72 of the cases, whereas the short stem restored the FAO in all cases. CCD-angle was not a predictor, but the preoperative FAO was. A cut-off point of 81.25 mm (95% confidence interval of 80.75-84.75 mm) in preoperative FAO was found where the conventional stem was unable to restore the FAO. Reliability of measurements was excellent, with an intra-observer reliability of 0.99 and inter-observer reliability in baseline measurements higher than 0.9 between the three observers.

CONCLUSION

In preoperative planning of FAO restoration in total hip arthroplasty, digital templating shows that short stems with a curve following the medial calcar are potentially better at restoring the FAO compared to conventional stems if the preoperative offset is ≥ 80.0 mm.

Effectiveness of an accelerometer-based portable navigation for intraoperative adjustment of leg length discrepancy in total hip arthroplasty in the supine position

BACKGROUND

This study aimed to examine the accuracy of the HipAlign® accelerometer-based portable navigation system by measuring the intraoperative leg length change of patients who underwent total hip arthroplasty (THA) and comparing the measured leg length discrepancy (LLD) determined by the navigation system and a freehand technique.

METHODS

A total of 61 patients who underwent THA using the anterolateral approach in the supine position were included in this study and divided into two groups: those who underwent THA with navigation (Group N; N = 31) and with the freehand technique (Group F; N = 30). Statistical analyses were performed to compare the intraoperative leg length change, pre- and post-LLD, absolute values of post-LLD, and the number of patients with the postoperative LLD within 10 mm and 5 mm between the two groups. Additionally, we examined the correlation between the leg length change obtained through intraoperative navigation and measured from the radiographs. Moreover, to evaluate the navigation accuracy, we examined the correlation between the absolute error of leg length change and cup orientation.

RESULTS

The postoperative LLD was significantly lower and the number of patients with the postoperative LLD within 5 mm was significantly higher in Group N, compared with Group F. Additionally, the amount of leg length change measured intraoperatively by the navigation system was strongly correlated with the values obtained by the postoperative radiographic measurement with a small absolute error and minimal wasted time. Moreover, a significant positive correlation was found between the absolute error of the leg length change and that of the cup inclination.

CONCLUSIONS

Our study demonstrates that the accelerometer-based portable navigation system is useful for the intraoperative adjustment of leg length discrepancy during THA for patients in the supine position, as it provides good accuracy and minimizes required time for use.

Restoration of Hip Biomechanics after a Hemiarthroplasty for a Femoral Neck Fracture—Who Does It Better?

Introduction: The restoration of the preoperative biomechanics of the hip, in particular leg length and femoral offset, are critical in restoring normal function and diminishing the risk of dislocation following hip arthroplasty. This study compares the consistency of arthroplasty and non-arthroplasty orthopedic surgeons in restoring the normal biomechanics of the hip when performing a hemiarthroplasty for the treatment of a femoral neck fracture. Methods: We retrospectively reviewed the preoperative and postoperative digital radiographs of 175 hips that had a modular hemiarthroplasty for the treatment of a displaced femoral neck fracture at a Level 1 academic hospital. Fifty-two hips were treated by one of the three fellowship-trained arthroplasty surgeons (Group A), and 123 were treated by one of the nine non-arthroplasty fellowship-trained orthopedic surgeons (Group B). Results: Patients in Group A were more likely to have their femoral offset restored to normal than patients in Group B, both with respect to under correcting the offset (p = 0.031) and overcorrecting the offset (p = 0.010). Overall, there was no difference in restoration of leg lengths between the two groups (p = 0.869). Conclusions: Following a hemiarthroplasty for a displaced femoral neck fracture, the normal biomechanics of the hip are more likely to be restored by an arthroplasty-trained surgeon than by a non-arthroplasty-trained surgeon. Identifying the inconsistency of non-arthroplasty surgeons and, to a lesser degree, arthroplasty surgeons in restoring hip biomechanics is important for sensitizing surgeons to rectify this in the future with appropriate templating and femoral implant selection.

The morphology of the proximal femur in cementless short-stem total hip arthroplasty: No negative effect on offset reconstruction, leg length difference and implant positioning

Background

Correct reconstruction of hip offset (HO) and leg length are important for clinical–functional outcome and patient satisfaction in total hip arthroplasty (THA). The morphology of the proximal femur can pose a risk for increased leg length difference (LLD) in cementless straight-stem THA. We therefore wanted to evaluate, if this is also applicable in THA with a cementless meta-diaphyseal short stem.

Methods

In a retrospective study, 106 patients (index surgery 2014–2019) with unilateral THA and a morphologically healthy hip as a reference (Kellgren–Lawrence ≤ 1) were included. The same cementless short stem with meta-diaphyseal fixation and cementless press-fit cup was implanted. The proximal femur was rated by Dorr’s classification, and subgroups were formed afterward. Measurements were carried out on preoperative and 3 months postoperative anterior–posterior radiographs of the pelvis. Kruskal–Wallis test, Fisher’s exact test and binary logistic regression were performed to evaluate the influence of the anatomical shape on postoperative leg length difference and offset reconstruction.

Results

The Dorr type did not show any significance influence on LLD (p = 0.532), or postoperative difference in femoral offset (p = 0.243), acetabular offset (p = 0.106) and hip offset (p = 0.698). Stem alignment (p = 0.705) and canal fill indices (CFI I: p = 0.321; CFI II: p = 0.411; CFI III: p = 0.478) were also without significant differences. Logistic regression did not show any significant increased risk for a LLD ≥ 5 mm or ≥ 10 mm as well as HO ≥ 5 mm or ≥ 10 mm.

Conclusion

Reconstruction of hip offset and postoperative leg length difference is not negatively influenced by Dorr type, canal flare index, cortical index and canal-to-calcar ratio in cementless short-stem THA. Implant positioning and canal fill are also not negatively affected by the anatomical shape of the proximal femur.

Level of evidence: Level IV.

Comparing Postoperative Leg Length Discrepancy and Femoral Offset Using Two Different Surgical Approaches for Hemiarthroplasty of the Hip

INTRODUCTION

The direct anterior approach (DAA) and anterolateral approach (ALA) may be used for hip hemiarthroplasty (HHA) as a treatment for femoral neck fractures. The DAA often utilizes intraoperative fluoroscopy to determine leg length and offset, while the ALA traditionally utilizes an intraoperative clinical exam to determine offset and leg length. This study will evaluate two techniques: the "grid fluoroscopy [GF] technique" and the "intraoperative exam [IE] technique," each performed by one of two separate surgeons, and compare each technique's accuracy to restore leg length and femoral offset in a patient population that underwent HHA.

METHODS

Two investigators retrospectively reviewed charts of 208 randomly selected patients who had an HHA from either a DAA or ALA performed by two different surgeons for the treatment of femoral neck fractures. Postoperative AP pelvis radiographs were measured to determine offset and leg length compared with the non-operative extremity. Non-normal continuous variables were provided by median and interquartile range. Data were analyzed with the Mann-Whitney U test and Student's t-test.

RESULTS

After inclusion and exclusion criteria, data were reviewed on 173 hemiarthroplasties. The mean age was 80.3 years (± 11.2 years). Of the surgical patients, 65.9% were female, and 70.9% identified their ethnicity as white. The DAA was used in 93 patients and ALA in 80 patients. Analysis comparing the two techniques demonstrated no statistically significant differences in median leg length between GF technique (1.02 IQR -0.1, 2.0 mm) and IE technique (1.25 IQR -2.4, 1.3 mm,) (p=0.67). There was also no statistically significant difference in offset between GF technique (1.3 IQR 0.2, 2.1 mm) and IE technique (0.6 IQR -2.7 mm, 3.2 mm) (p=0.13). However, a difference was found in mean length of surgery that was statistically significant. We found that the mean length of surgery for the IE technique was 74.8 ± 24.7 minutes versus the GF technique, which was 95.1 ± 23.0 minutes, (p<0.0001).

DISCUSSION

There was no significant difference between leg length and offset with the use of intraoperative fluoroscopy with DAA compared to no intraoperative imaging with ALA. Our study suggests that DAA and ALA are equally effective approaches for re-establishing symmetric leg length and offset in HHA for femoral neck fractures. In this study, the ALA had a shorter surgical time compared to DAA, potentially due to the utilization of intraoperative fluoroscopy for this particular technique during the DAA.

The External Obturator Footprint Is a Usable, Accurate, and Reliable Landmark for Stem Depth in Direct Anterior THA

BACKGROUND

Previous CT and cadaver studies have suggested that the external obturator footprint might be used as a landmark for stem depth in direct anterior THA. Instructions on where to template this structure with small variability in height have been developed but have not been tested in daily clinical practice.

QUESTIONS/PURPOSES

In this study we sought to investigate the (1) usability, (2) accuracy, and (3) reliability of the external obturator footprint as a landmark for stem depth in direct anterior THA.

METHODS

The distance between the superior border of the external obturator tendon and the shoulder of the stem was measured intraoperatively in all patients (n = 135) who underwent primary THA via a direct anterior approach performed by the senior author between November 2019 and October 2020. The landmark was considered useful when two of thre`e evaluators agreed that the intersection of the vertical line comprised of the lateral wall of the trochanteric fossa and the oblique line formed by the intertrochanteric crest was clearly visible on the preoperative planning radiograph, and when the landmark was furthermore identified with certainty during surgery. Accuracy was defined as the degree of agreement (categorical for thresholds of 2 and 5 mm, the latter representing the threshold for developing unphysiological gait parameters) between the intraoperative distance and radiographic distance as measured on intraoperative fluoroscopy images or postoperative radiographs, which were calibrated based on femoral head sizes in a software program commonly used for templating. Intrarater reliability was defined as the degree of agreement (categorical for thresholds of 1 mm, which we considered an acceptable measurement error) between the ratings of one observer, who measured the radiographic distance on two different occasions separated by a washout period of at least 2 weeks. Interrater reliability was defined as the degree of agreement (categorical for thresholds of 1 mm, which we considered an acceptable measurement error) between the ratings of three observers with varying levels of experience (a fellowship-trained hip surgeon, a hip surgery fellow, and a medical student).

RESULTS

The landmark was considered useful in 77% (104 of 135) of patients who underwent direct anterior THA based on the observations that the trochanteric fossa was clearly visible on the planning radiograph in 117 patients and that the tendon was identified with certainty during surgery in 118 patients. There was good-to-excellent accuracy (intraclass correlation coefficient 0.75-087), and intrarater reliability (ICC 0.99) and interrater reliability (ICC 0.99) were both excellent.

CONCLUSION

This clinical study showed that the external obturator footprint is a useful, accurate, and reliable landmark for stem depth in direct anterior THA.

CLINICAL RELEVANCE

The external obturator landmark allows the surgeon to position the stem within a range of the templated depth that is beneath the threshold for the development of unphysiological gait parameters. Although strictly speaking it was found useful in 77% of patients in this study, we found that this percentage of usability can easily be improved to around 90% by providing the radiology lab technician with instructions to correct external rotation of the foot during the taking of the planning radiograph. Future studies could compare the established (in)equality in leg length in patients using the external obturator landmark with computer-assisted surgery.

A Workflow Change in Anterior Approach Total Hip Arthroplasty Leads to Improved Accuracy of Biomechanical Reconstruction Without Increased Risk of Complications

Background

During anterior approach total hip arthroplasty (THA), the femur may be an impediment for acetabular access, pushing reamers proximally and consequently altering the hip center. In an effort to address this, the senior author changed the surgical workflow from acetabulum first (AF) to femur first (FF). The objective of this study was to compare the precision of biomechanical hip reconstruction and clinical outcomes between the FF and AF techniques.

Methods

This is a retrospective, case-control study of 267 anterior THAs (132 AF and 135 FF). A normal, contralateral hip was used to determine the native biomechanical parameters. Using a calibrated software program, radiographic measurements were performed to calculate the hip center position, femoral offset, global offset, and leg length of the operative and native hips using 2-week postoperative anteroposterior pelvis radiographs. Demographics, operative information, hemoglobin change, and complication data were obtained. Functional outcomes were assessed with the Hip Dysfunction and Osteoarthritis Outcome Score for Joint Replacement survey at 1 year postoperatively.

Results

The groups exhibited similar demographic characteristics. The FF group demonstrated significantly more accurate and more precise reconstruction of horizontal and vertical hip centers, femoral offset, and leg length. There was no significant difference in operative time, hemoglobin change, complication rate, or Hip Disability and Osteoarthritis Outcome Score, Joint Replacement scores between groups.

Conclusions

The FF technique allowed for more accurate and precise reconstruction of the hip center, leg length, and offset in THA than the AF workflow. Furthermore, the FF approach demonstrated no significant differences in complication rate or blood loss, nor in clinical outcomes.

Level of Evidence

Therapeutic Study Level III.