Factors influencing patient-reported outcomes following periacetabular osteotomy and open osteochondroplasty in the setting of borderline hip dysplasia

Aims

This study reports mid-term outcomes after periacetabular osteotomy (PAO) exclusively in a borderline hip dysplasia (BHD) population to provide a contrast to published outcomes for arthroscopic surgery of the hip in BHD.

Methods

We identified 42 hips in 40 patients treated between January 2009 and January 2016 with BHD defined as a lateral centre-edge angle (LCEA) of ≥ 18° but < 25°. A minimum five-year follow-up was available. Patient-reported outcomes (PROMs) including Tegner score, subjective hip value (SHV), modified Harris Hip Score (mHHS), and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) were assessed. The following morphological parameters were evaluated: LCEA, acetabular index (AI), α angle, Tönnis staging, acetabular retroversion, femoral version, femoroepiphyseal acetabular roof index (FEAR), iliocapsularis to rectus femoris ratio (IC/RF), and labral and ligamentum teres (LT) pathology.

Results

The mean follow-up was 96 months (67 to 139). The SHV, mHHS, WOMAC, and Tegner scores significantly improved (p < 0.001) at last follow-up. According to SHV and mHHS, there were three hips (7%) with poor results (SHV < 70), three (7%) with a fair score (70 to 79), eight (19%) with good results (80 to 89), and 28 (67%) who scored excellent (> 90) at the last follow-up. There were 11 subsequent operations: nine implant removals due to local irritation, one resection of postoperative heterotopic ossification, and one hip arthroscopy for intra-articular adhesions. No hips were converted to total hip arthroplasty at last follow-up. The presence of preoperative labral lesions or LT lesions did not influence any PROMs at last follow-up. From the three hips that had poor PROMs, two have developed severe osteoarthritis (> Tönnis II), presumably due to surgical overcorrection (postoperative AI < -10°).

Conclusion

PAO is reliable in treating BHD with favourable mid-term outcomes. Concomitant LT and labral lesions did not negatively influence outcomes in our cohort. Technical accuracy with avoidance of overcorrection is essential in achieving successful outcomes.

Accuracy of ZedView, the Software for Three-Dimensional Measurement and Preoperative Planning: A Basic Study

Background and Objectives: In the field of orthopedic surgery, novel techniques of three-dimensional shape modeling using two-dimensional tomographic images are used for bone-shape measurements, preoperative planning in joint-replacement surgery, and postoperative evaluation. ZedView^® (three-dimensional measurement instrument and preoperative-planning software) had previously been developed. Our group is also using ZedView^® for preoperative planning and postoperative evaluation for more accurate implant placement and osteotomy. This study aimed to evaluate the measurement error in this software in comparison to a three-dimensional measuring instrument (3DMI) using human bones. Materials and Methods: The study was conducted using three bones from cadavers: the pelvic bone, femur, and tibia. Three markers were attached to each bone. Study 1: The bones with markers were fixed on the 3DMI. For each bone, the coordinates of the center point of the markers were measured, and the distances and angles between these three points were calculated and defined as "true values." Study 2: The posterior surface of the femur was placed face down on the 3DMI, and the distances from the table to the center of each marker were measured and defined as "true values." In each study, the same bone was imaged using computed tomography, measured with this software, and the measurement error from the corresponding "true values" was calculated. Results: Study 1: The mean diameter of the same marker using the 3DMI was 23.951 ± 0.055 mm. Comparisons between measurements using the 3DMI and this software revealed that the mean error in length was <0.3 mm, and the error in angle was <0.25°. Study 2: In the bones adjusted to the retrocondylar plane with the 3DMI and this software, the average error in the distance from the planes to each marker was 0.43 (0.32-0.58) mm. Conclusion: This surgical planning software could measure the distance and angle between the centers of the markers with high accuracy; therefore, this is very useful for pre- and postoperative evaluation.

How Relevant Is the Parallax Effect on Low Centered Pelvic Radiographs in Total Hip Arthroplasty

The correct cup position in total hip arthroplasty (THA) is usually assessed on anteroposterior low centered pelvic radiographs, harboring the risk of misinterpretation due to projection of a three-dimensional geometry on a two-dimensional plane. In the current study, we evaluate the effect of this parallax effect on the cup inclination and anteversion in THA. In the course of a prospective clinical trial, 116 standardized low centered pelvic radiographs, as routinely obtained after THA, were evaluated regarding the impact of central beam deviation on the cup inclination and anteversion angles. Measurements of the horizontal and vertical beam offset with two different methods of parallax correction were compared with each other. Furthermore, the effect of parallax correction on the accuracy ofmeasuring the cup position was investigated. The mean difference between the two parallax correction methods was 0.2° ± 0.1° (from 0° to 0.4°) for the cup inclination and 0.1° ± 0.1° (from -0.1° to 0.2°) for the anteversion. For a typically intended cup position of a 45° inclination and 15° anteversion, the parallax effect led to a mean error of -1.5° ± 0.3° for the inclination and 0.6° ± 1.0° for the anteversion. Central beam deviation resulted in a projected higher cup inclination up to 3.7°, and this effect was more prominent in cups with higher anteversion. In contrast, the projected inclination decreased due to the parallax effect up to 3.2°, especially in cups with high inclination. The parallax effect on routinely obtained low centered pelvic radiographs is low and not clinically relevant due to the compensating effect of simultaneous medial and caudal central beam deviation.

Effect of Total Hip Arthroplasty on Ipsilateral Lower Limb Alignment and Knee Joint Space Width: Minimum 5-Year Follow-up

BACKGROUND

This study aimed to 1) assess the effect of total hip arthroplasty (THA) on coronal limb alignment, namely, the hip-knee-ankle angle (HKA), 2) identify factors that determine changes in the HKA, and 3) determine whether alignment changes influence the knee joint space width.

METHODS

We retrospectively evaluated 266 limbs of patients who underwent THA. Three types of prostheses with neck shaft angles (NSAs) of 132°, 135°, and 138° were used. Several radiographic parameters were measured in the preoperative and final radiographs (at least 5 years after THA). A paired t-test was used to confirm the effect of THA on HKA change. Multiple regression analysis was performed to identify radiographic parameters related to HKA changes following THA and changes in knee joint space width. Subgroup analyses were performed to reveal the effect of NSA change on the HKA change, and the proportion of total knee arthroplasty usage and changes in radiographic parameters between maintained joint space and narrowed joint space groups were compared.

RESULTS

The preoperative mean HKA was 1.4° varus and increased to 2.7° varus after THA. This change was related to changes in the NSA, lateral distal femoral angle, and femoral bowing angle. In particular, in the group with a decrease in NSA of > 5°, the preoperative mean HKA was largely changed from 1.4° varus to 4.6° varus after THA. The prostheses with NSA of 132° and 135° also led to greater varus HKA changes than those with an NSA of 138°. Narrowing of the medial knee joint space was related to changes in the varus direction of the HKA, decrease in NSA, increase in femoral offset.

CONCLUSION

A large reduction in NSA can lead to considerable varus limb alignment after THA, which can have adverse effects on the medial compartment of the ipsilateral knee.

Measurement of the normal contralateral hip flexion angle and posterior pelvic tilt angle using a pelvic guide pin in total hip arthroplasty

BACKGROUND

We aimed to measure the posterior pelvic tilt angle at maximum hip flexion and hip flexion range of motion at the femoroacetabular joint using a pelvic guide pin and to examine the difference in flexion range of motion when determined by a physical therapist and under anesthesia.

METHODS

Data of 83 consecutive patients undergoing primary unilateral total hip arthroplasty were assessed. Using a pin inserted into the iliac crest to define the cup placement angle under anesthesia before and after total hip arthroplasty, the posterior pelvic tilt angle was determined as the change in pin tilt from the supine position to maximum hip flexion. Flexion range of motion under anesthesia was calculated as the difference in the angle between the trunk and thigh at maximum flexion and the posterior pelvic tilt angle. Flexion range of motion with a fixed pelvis measured preoperatively by a physical therapist was compared to that under anesthesia. A goniometer was used for all measurements and the number of measurements was one.

FINDINGS

Mean posterior pelvic tilt angle of the pin inserted into the pelvis under anesthesia was 15.8° ± 5.3° (3°-26°) preoperatively and 12.1° ± 4.9° (3°-26°) postoperatively. Mean flexion range of motion under anesthesia was 109.4° ± 6.9° (88°-126°) and that measured by a physical therapist was 101.1° ± 8.2° (80°-120°); the difference was significant (9.7°; p < 0.01).

INTERPRETATION

These results highlight the difficulty in accurately determining hip flexion angles without the use of special devices and may help surgeons and physical therapists recognize and address this issue.

A Simple Preoperative Score Predicting Failure Following Decompression Surgery for Degenerative Lumbar Spinal Stenosis

BACKGROUND CONTEXT

Proper patient selection is crucial for the outcome of surgically treated degenerative lumbar spinal stenosis (DLSS). Nevertheless, there is still not a clear consensus regarding the optimal treatment option for patients with DLSS.

PURPOSE

To investigate the treatment failure rate and introduce a simple, preoperative score to aid surgical decision-making.

STUDY DESIGN/SETTING

Retrospective observational study.

PATIENT SAMPLE

Four hundred forty-five patients who underwent surgical decompression for DLSS.

OUTCOME MEASURES

Treatment failure (defined as conversion to a fusion of a previously decompressed level) of lumbar decompression.

MATERIALS AND METHODS

Several risk factors associated with worse outcomes and treatment failures, such as age, body mass index, smoking status, previous surgery, low back pain (LBP), facet joint effusion, disk degeneration, fatty infiltration of the paraspinal muscles, the presence of degenerative spondylolisthesis and the facet angulation, were investigated.

RESULTS

At a mean follow-up of 44±31 months, 6.5% (29/445) of the patients underwent revision surgery with spinal fusion at an average of 3±9 months following the lumbar decompression due to low back or leg pain. The baseline LBP (≥7) [odds ratio (OR)=5.4, P <0.001], the presence of facet joint effusion (>2 mm) in magnetic resonance imaging (OR=4.2, P <0.001), and disk degeneration (Pfirrmann >4) (OR=3.2, P =0.03) were associated with an increased risk for treatment failure following decompression for DLSS. The receiver operating characteristic curve analysis demonstrated that a score≥6 points yielded a sensitivity of 90% and specificity of 64% for predicting a treatment failure following lumbar decompression for DLSS in the present cohort.

CONCLUSIONS

The newly introduced score quantifying amounts of LBP, facet effusions, and disk degeneration, could predict treatment failure and the need for revision surgery for DLSS patients undergoing lumbar decompression without fusion. Patients with scores >6 have a high chance of needing fusion following decompression surgery.

LEVEL OF EVIDENCE

Retrospective observational study, Level III.

Validation of a Novel Method of Measuring Cup Orientation using BiPlanar Simultaneous Radiographic Images

BACKGROUND

Accurate acetabular component positioning is paramount to the success of total hip arthroplasty. Two-dimensional imaging alone remains a popular tool for implant position assessment despite known limitations. We investigated the accuracy of a novel method for assessing acetabular component position based upon orthogonal simultaneous biplanar Xray images.

METHODS

There were forty consecutive patients who had a pre-existing total hip arthroplasty (THA) on the contralateral side who underwent both computed tomography (CT) and simultaneous orthogonal biplanar radiographic scans for pre-operative planning of THA. The operative inclination (OI) and operative anteversion (OA) of the acetabular cup were calculated by a new measurement method using the biplanar simultaneous scans. Those measurements were compared to measurement of the cup orientation on CT. The measurements were made by two independent observers. Interobserver correlation coefficients were calculated between the two observers to measure reliability.

RESULTS

The mean error in OA measurement of the acetabular cup between simultaneous orthogonal biplanar radiographic and CT imaging was 0.5° (Standard Deviation (SD): 1.9°, minimum -4.0°, maximum 5.0°), the mean error in OI was 0.0° (SD: 1.7°, minimum -5.0°, maximum 4.0°). The average absolute error was 1.5° for OA, and 1.2° for OI. Interobserver correlation coefficient was 0.83 for OA and 0.93 for OI.

CONCLUSION

The novel method of measuring cup orientation using simultaneous biplanar radiographic scans utilized in this study was accurate and reproducible between observers compared to CT measurements.

Application of transverse acetabular ligament in total hip arthroplasty: a systematic review

INTRODUCTION

In total hip arthroplasty (THA), the correct position of the acetabular component directly determines the outcome of the surgery, or the success of the surgery. Therefore, how to accurately locate the position of the acetabular component has become a very critical step in THA. As an important anatomical structure of the hip joint, the transverse acetabular ligament (TAL) is helpful for acetabular component orientation in THA. The aim of this systematic review was to investigate application of TAL in THA.

MATERIALS AND METHODS

A systematic literature search of PUBMED, EMBASE, and Cochrane Library was performed (January and February 2023) using keywords "total hip arthroplasty," "total hip replacement," "total hip replacements," "total hip arthroplasties," "total hip prosthesis," and "transverse acetabular ligament" in all possible combinations. Reference lists of included articles were reviewed. Study design, surgical approach, patient demographics, TAL identification rate, appearance of the TAL, anteversion and inclination angle and rate of dislocations were recorded.

RESULTS

In total, 19 studies met the screening criteria. Study designs were prospective cohorts (42%), retrospective cohorts (32%), Case series (21%), and randomized controlled trial (5%). Twelve of the 19 (63.2%) studies investigated the application of TAL as an anatomical landmark for locating acetabular component position in THA. Analysis revealed that TAL is a reliable anatomical landmark for acetabular component orientation within the safe zone in THA.

CONCLUSIONS

TAL can reliably be used to align the acetabular component in the safe zone for anteversion and inclination in THA. However, TAL has individual variation influenced by some risk factors. More randomized controlled studies with larger numbers of patients are needed to investigate the precision and accuracy of TAL as an intraoperative landmark in THA.

LEVEL OF EVIDENCE

IV.

Ten to 13-Year Results of Delta Ceramic-on-Ceramic Total Hip Arthroplasty in Patients Less Than 30 Years Old

BACKGROUND

We previously reported mid-term results of total hip arthroplasty (THA) using Delta ceramic-on-ceramic (CoC) bearings in 72 patients (86 hips) who were <30 years old. Noise was noted in 8 (9.3%) of the hips, no osteolysis or loosening was detected, and no patient required reoperation. The purpose of this study was to assess clinical and radiographic outcomes, complications, and survivorship at >10 years after THA using Delta CoC bearings in patients who were <30 years old.

METHODS

Cementless THA with a Delta CoC bearing was performed between March 2008 and January 2012 in 91 hips of 76 patients who were <30 years old. Eighty-five hips in 71 patients (44 men and 27 women) with a mean age of 25.9 years (range, 16 to 29 years) at surgery were followed for a mean of 10.9 years (range, 10 to 13 years).

RESULTS

No ceramic bearings fractured. The incidence of squeaking increased to 5.9% (5 of 85), but the squeaking was not reproducible within individual patients. Periprosthetic osteolysis developed in 3 hips (3 patients): around the stem in 2 and around the metal shell in 1. The stem in 1 hip underwent revision because of a Vancouver type-B2 periprosthetic femoral fracture. One patient with systemic lupus erythematosus underwent irrigation and debridement for periprosthetic joint infection. Survivorship free of reoperation for any reason was 92.4% (95% confidence interval, 82.4% to 100%) at 13 years.

CONCLUSIONS

The long-term results and survivorship of Delta CoC THA in patients <30 years old were favorable.

LEVEL OF EVIDENCE

Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.

A comparison of accuracy and safety between stem-first and cup-first total hip arthroplasty: a prospective randomised controlled trial

BACKGROUND

The combined anteversion theory to prevent impingement in total hip arthroplasty (THA) has been proposed. However, because stem-anteversion is influenced by the native femoral anteversion and the stem flexion/extension angle, it is often difficult to adjust stem anteversion during surgery. Therefore, the stem-first (combined anteversion) technique may be useful to adjust and achieve appropriate cup anteversion during surgery with respect to the implanted stem anteversion angle. However, the technique may adversely affect cup or stem angle accuracy and result in intra-operative bleeding, post-operative adverse events, and prolonged operative time. It is inconclusive whether either the stem-first or cup-first technique is safe or accurate. Therefore, this study assessed the accuracy and safety of stem-first THA compared to those of cup-first THA.

MATERIALS AND METHODS

This prospective randomised controlled trial analysed 114 patients who were randomly divided into 2 groups (stem-first group: n = 57, cup-first group (control group): n = 57). Primary outcomes included cup and stem angle, the discrepancies from the targeted angle and combined anteversion (evaluated via CT at 3 months postoperatively). Secondary outcomes included intraoperative blood loss, operative time, WOMAC, and adverse events.

RESULTS

There were no significant differences in age, gender, BMI or in the primary and secondary outcomes between the 2 groups.

CONCLUSIONS

Performing stem-first in THA did not adversely affect cup and stem angle accuracy, or result in intraoperative bleeding, prolongation of operative time, or postoperative adverse events. Thus, performing stem-first may be advantageous for achieving combined anteversion theory.

TRIAL REGISTRATION

University Hospital Medical Information Network (UMIN) registration number UMIN000025189.

Accuracy of cup placement using computed tomography-based navigation system in total hip arthroplasty through the direct anterior approach

BACKGROUND

This study aimed to elucidate the accuracy of cup placement with the computed tomography (CT)-based navigation system (CTN) in the direct anterior approach (DAA)-total hip arthroplasty (THA) in the supine position compared with the mechanical cup alignment guide (MG) or the fluoroscopy (FS).

METHODS

A total of 171 hips of 156 patients undergone primary THA were classified into the following three groups (the MG group: 63 hips, the FS group: 58 hips, the CTN group: 50 hips). Comparing the preoperative planning with postoperative CT measurement by three-dimensional templating software, the accuracy of cup placement was investigated in the three groups.

RESULTS

There were significant differences in the mean absolute error of radiographic inclination (RI) between the MG group (4.4° ± 3.2°) and the CTN group (2.8° ± 2.5°) (p = 0.01). The mean absolute error of radiographic anteversion (RA) also showed significant differences between the CTN group (2.8° ± 1.9°) and the MG group (5.8° ± 4.7°) (p = 0.0001) or the FS group (4.8° ± 4.1°) (p = 0.02). Regarding the cup center position, the mean absolute error of vertical position from preoperative planning was the smallest in the CTN group (1.8 ± 1.4 mm) compared with those in other groups (MG: 3.3 ± 3.2 mm, p = 0.007, FS: 3.2 ± 3.0 mm, p = 0.017).

CONCLUSION

The CTN guarantees accurate cup placement in the DAA-THA in the supine position compared with the MG and FS groups.

The effect of range of motion simulated with a patient-specific three-dimensional simulation analysis on dislocation after total hip arthroplasty

BACKGROUND

Dislocation continues to be a common complication following total hip arthroplasty (THA). Although previous studies of computed simulation analysis investigated the range of motion (ROM), it is unclear whether the ROM before impingement simulated using computed tomography-based 3-dimensional simulation analysis (simulated ROM) is related to dislocation after THA. It is also unclear what angles are required in computed simulation analyses for stable hips after THA. In this study, we compared the simulated ROM in patients with and without dislocation.

METHODS

16 patients with posterior dislocation were compared with 48 matched patients without dislocation. Risk factors including preoperative bone morphology of the hip, implant position, change of femoral offset, change of leg length, anterior aspect of the greater trochanter (GTa) length, and anterior inferior iliac spine length were also compared.

RESULTS

The mean flexion angle, internal-rotation at 90° flexion (IR) angle, cup anteversion based on the anterior pelvic plane (APP), tilt-adjusted cup anteversion and GTa length were significantly different between patients with dislocation and patients without dislocation (p = 0.033, 0.002, 0.010, 0.047, 0.046). A receiver-operating characteristic curve analysis suggested cutoff points for flexion angle, IR angle, cup anteversion based on the APP, tilt-adjusted cup anteversion and GTa length, of 114.5°, 45.5°, 19.5°, 12.0° and 15.3 mm.

CONCLUSIONS

This study suggests that preoperative planning to achieve a larger simulated ROM, flexion angle and IR angle, may reduce the risk of posterior dislocation. This study also suggests that fine-tuning of cup anteversion and/or trimming of the overhanging GTa during preoperative planning may reduce the risk of posterior dislocation.

Effects of changes in whole-body alignment on ipsilateral knee pain after total hip arthroplasty

BACKGROUND

Total hip arthroplasty decreases hip pain and often reduces knee pain in patients with hip osteoarthritis. Whole-body alignment may be associated with knee pain, but to our knowledge this relationship has not been previously investigated. The purpose of this study was to investigate the effect of changes in whole-body alignment on ipsilateral knee pain in patients after total hip arthroplasty.

METHODS

In total, 94 patients with unilateral hip osteoarthritis who underwent total hip arthroplasty were enrolled in this study. A visual analog scale (VAS) was used to investigate perioperative knee pain. An EOS 2D/3D X-ray system was used to quantify the whole-body alignment of the spine, pelvis, and lower extremities in the standing position. The relationship between perioperative changes in knee pain and whole-body alignment was investigated.

RESULTS

Among 61 patients who had preoperative ipsilateral knee pain, pain resolved in 30 (50%) and persisted in 31 (50%) after surgery. In these patients, average ipsilateral knee pain decreased significantly after surgery, from 41 mm to 14 mm on the VAS (P < 0.01). Preoperative knee pain was correlated with femorotibial rotation, and postoperative knee pain was correlated with K-L grade, preoperative knee pain visualized analog scale, and preoperative sagittal vertical axis. Multiple linear regression identified preoperative sagittal vertical axis as significantly associated with residual postoperative ipsilateral knee pain.

CONCLUSIONS

Ipsilateral knee pain decreased in half of patients after total hip arthroplasty. Patients with a considerable forward-bent posture may have residual ipsilateral knee pain after total hip arthroplasty.

The effectiveness of virtual reality, augmented reality, and mixed reality training in total hip arthroplasty: a systematic review and meta-analysis

BACKGROUND

Extended reality (XR), including virtual reality (VR), augmented reality (AR), and mixed reality (MR), has been used in the training of total hip arthroplasty (THA). This study aims to examine the effectiveness of XR training in THA.

METHODS

In this systematic review and meta-analysis, we searched PubMed (MEDLINE), EMBASE (OVID), Cochrane Central Register of Controlled Trials (CENTRAL), Web of Science, and clinicaltrials.gov from inception to September 2022 for eligible studies. The Review Manager 5.4 software was applied to compare accuracy of inclination and anteversion, and surgical duration between XR training and conventional methods.

RESULTS

We identified 213 articles, of which 4 randomized clinical trials and 1 prospective controlled study including 106 participants met inclusion criteria. The pooled data indicated the XR training had better accuracy of inclination and shorter surgical duration than conventional methods (MD = -2.07, 95% CI [- 4.02 to -0.11], P = 0.04; SMD = -1.30, 95% CI [- 2.01 to -0.60], P = 0.0003), but the accuracy of anteversion was similar in the two groups.

CONCLUSIONS

This systematic review and meta-analysis found XR training had better accuracy of inclination and shorter surgical duration than conventional methods in THA, but the accuracy of anteversion was similar. Based on the pooled results, we suggested that XR training can better improve trainees' surgical skills than conventional methods in THA.

Prospective randomized controlled trial on the accuracy of prosthesis positioning in total hip arthroplasty assisted by a newly designed whole-process robotic arm

INTRODUCTION

The purpose of this article is to study whether the newly designed whole-process total hip arthroplasty (THA) robotic arm can improve the accuracy of prosthesis placement in THA.

METHOD

In this study, 72 patients undergoing THA were prospectively included and randomly divided into two groups. The experimental group was treated with THA assisted by a newly designed robotic arm. The control group received THA with conventional surgical methods. The imaging data were compared after operation.

RESULT

Compared with the conventional operation, the whole-process robotic arm can more accurately place the acetabular prosthesis in the anteversion safe zone of 5 ~ 25°, but in terms of the inclination angle, whether the reference is the safe zone of 30 ~ 50° or 30 ~ 45°, there is no statistical difference between the two groups. The average lower limb length discrepancy (LLLD) in the experimental group was 3.77 ± 8.31 mm longer than contralateral side, while the counterpart in the control group was 8.39 ± 9.11 mm, with significant difference (P = 0.029). The femoral prosthesis was fixed in neutral position in 35 (100%) cases in the experimental group and only 30 (83.3%) in the control group (P = 0.036). There was no significant difference in the recovery of hip offset, femoral anteversion, and canal fill ratio (CFR) between the two groups.

CONCLUSION

Robotic arm can improve the accuracy of anteversion of acetabular cup, restore the consistency of the length of lower limbs, and more accurately implant the femoral prosthesis to the neutral position in the coronal position.

CLINICAL TRIAL REGISTRATION NUMBER

ChiCTR2100044124 (date of registration: 2021-3-11).

Achieving Precise Cup Positioning in Direct Anterior Total Hip Arthroplasty: A Narrative Review

Malpositioned implants in total hip arthroplasty are associated with impingement, increased wear, and dislocations, thus precise cup positioning is crucial. However, significant deviations between targeted and actually achieved cup positions have been found even in patients operated by experienced surgeons. When aiming for higher accuracy, various methods based on freehand positioning lead by anatomic landmarks, C-arm fluoroscopy, imageless navigation, or robotic-assisted-surgery have been described. There is a constant development of new products aiming to simplify and improve intraoperative guidance. Both the literature and expert opinions on this topic are often quite controversial. This article aims to give an overview of the different methods and systems with their specific advantages and potential pitfalls while also taking a look into the future of cup positioning in anterior hip replacements.

The association of postoperative global femoral offset with total hip arthroplasty outcomes

Global femoral offset (GFO) and femoral offset (FO) reportedly affect outcomes following total hip arthroplasty (THA). However, FO assessed using plain radiography is affected by internal and external rotations of the hip joint. We investigated the relationship between leg length discrepancy and Harris hip score (HHS), and their influence on acetabular offset (AO), FO, GFO, anterior femoral offset, and outcomes after THA. We retrospectively evaluated 140 patients with hip osteoarthritis who underwent THA. A three-dimensional (3D) pelvis and femur model created from computed tomography (data using ZedHip software was used to investigate these parameters. The modified (m)HHS scores were significantly improved from 49.0 to 88.8 in total mHHS, 20.0-44.5 in pain, and 28.9-44.4 points in function. Significant correlations were found between the differences in AO, FO, GFO, and pain score in binominal, with maximum values of - 1.24, + 1.54, and + 0.90 mm/100 cm body height, respectively. The maximum value of GFO and mHHS in binominal was + 1.17 mm/100 cm body height (BH). The optimal range of difference of GFO was - 1.75 to 4.09 mm/100 cm BH. This is the first report using a 3D method for assessing FO. Preoperative planning using the system could improve postoperative function.

Effect of Total Hip Arthroplasty with Ceramic Acetabular Component on Clinical, Radiographic and Functional Parameters in Older Patients with Hip Osteoarthritis: Two-Year Follow-Up

Background: Total hip arthroplasty (THA) is a widely used surgical procedure to reduce pain and improve function and quality of life in patients with hip disorders. The most common condition that leads to THA is osteoarthritis, with most surgeries being performed to treat severe osteoarthritis with pain and functional limitations. Despite the evident success of THA, the search for its improvement and better results, especially in the long term, continues, especially in older patients, for which there is still little scientific evidence. Objective: To evaluate the clinical, radiological, and functional aspects preoperatively and two years after THA with a ceramic acetabular component device in older patients with hip osteoarthritis. Methods: A retrospective cohort study was conducted to evaluate 65 older individuals who underwent THA of the hip with an acetabular component (MD® ceramic head with a ceramic acetabular insert) associated with the MD6® Phenom® femoral rod type, in Hospital of the Luz, São Paulo/SP, between 2018 and 2019. Anthropometric and clinical information about the operative procedure and two years follow-up were collected from the patients’ medical records. For the clinical-functional evaluation, the Harris Hip Score (HHS) questionnaire and hip movement goniometry were applied. For the radiographic parameters, the following were evaluated: the positioning of the acetabular component, the Zone of DeLee and the offset of the femoroacetabular component. Results: There was a higher prevalence of performing THA in males (53.8%). Preoperative and two-year postoperative radiographic parameters of surgical treatment for THA showed maintenance of the acetabular (p = 0.083) and femoral (p = 0.102) positioning angles and increased functionality (p < 0.001) and joint mobility of the hip (p = 0.001) with reduced pain after two years of THA. Complications related to dislocation, loosening, infection, and inadequate positioning of the implant were low, ranging from 1.5 to 3%. Conclusion: Older people who underwent cementless THA with an ceramic acetabular component device, in a two-year follow-up, showed effectiveness in improved clinical, radiological, and functional aspects.

Achieving Target Cemented Femoral Stem Anteversion Using a 3-Dimensional Model

Background

Total hip arthroplasty aims to provide patients with a pain-free and stable hip joint through optimization of biomechanics such as femoral anteversion. There are studies evaluating the limits of cementless stem version, however, none assessing the range of version achieved by a cemented collarless stem. A computed tomography (CT)-based study was performed, utilizing a contemporary robotic planning platform to assess the amount of rotation afforded by a cemented collarless stem, whilst maintaining native biomechanics.

Methods

The study utilized 36 cadaveric hips. All had CT scans of the pelvis and hip joints. The CT scans were then loaded into a contemporary robotic planning platform. A stem that restored the patients native femoral offset was selected and positioned in the virtual femur. The stem was rotated while checking for cortical contact at the level of the neck cut. Cortical contact was regarded as the rotation limit, assessed in both anteversion and retroversion. Target range for stem anteversion was 10°-20°. Failure to achieve target version triggered a sequence of adjustments to simulate surgical decisions.

Results

Native femoral offset and target version range was obtained in 29 of 36 (80.5%) cases. Following an adjustment sequence, 4 further stems achieved target anteversion with a compromise in offset of 2.3 mm. Overall 33 of 36 (91.7%) stems achieved the target anteversion range of 10°-20°.

Conclusions

Target femoral stem anteversion can be achieved using a cemented, collarless stem in a CT-based 3-dimensional model in 80.5% of hips. With a small compromise in offset (mean 2.3 mm), this can be increased to 91.7%.

Effectiveness and Accuracy of a Patient-Specific Instrumentation System for Total Hip Arthroplasty

OBJECTIVE

Traditional total hip arthroplasty (THA) is often performed by visual inspection due to the lack of reliable reference, which results in inappropriate position of prosthesis and poor outcomes. This study attempts to introduce a novel patient-specific instrumentation (PSI) system and assess its effectiveness and accuracy compared with freehand operation and robot system through bone model experiments.

METHODS

Equally divide 30 sawbone models into the freehand group, PSI group, and robot group. Ten sets of prosthesis parameters were randomly generated as planning, and the three groups underwent simulated THA depending on these parameters. After the placement of the femoral prosthesis, the acetabular anteversion plan was adjusted in the PSI and robot groups so that the combined anteversion was maintained before and after adjustment. After the surgery, the actual prosthesis parameters of all bone models were measured and analyzed statistically.

RESULTS

No statistically significant difference was found in femoral anteversion error among the three groups (p = 0.951). The errors of acetabular cup anteversion, acetabular cup abduction, and combined anteversion in PSI group were 3.92° (2.94°, 4.62°), 5.65° (4.63°, 6.70°), and 3.93° (2.94°, 4.62°), respectively, which were significantly smaller than those in the freehand group [11.84° (9.92°, 13.87°), 13.54° (9.81°, 15.21°), 16.04° (8.18°, 19.25°), respectively, p < 0.05], but significantly larger than those in the robot group [1.34° (0.98°, 1.70°), 1.80° (1°, 2.02°), 1.34° (0.98°, 1.70°), respectively, p < 0.05].

CONCLUSION

Compared with the traditional freehand operation, the patient-specific instrumentation system is feasible in total hip arthroplasty because it improves the accuracy of prosthesis placement. In addition, the rapid measurement of intraoperative femoral prosthesis parameters can help surgeons optimize preoperative planning.

A 10- to 12-year follow-up study of delta ceramic-on-ceramic total hip arthroplasty

BACKGROUND

We previously reported five-to-seven-year results of total hip arthroplasty (THA) with the use of delta ceramic-on-ceramic (CoC) bearing. We conducted an extension study with a CT scan at a minimum of 10 years after surgery.

METHODS

From March 2009 to March 2011, 273 patients (310 hips) received cementless THA with delta CoC bearing, porous-coated cup and hydroxyapatite-coated stem. In this extended study, 252 patients (144 men and 108 women) (288 hips) with a mean age of 49.7 years (16-83) at surgery were followed for a mean of 10.4 years (10-12) with CT scans in 133 hips (46.2%, 133/288). Clinical and radiographic evaluations were made at each follow-up and Kaplan-Meier survival analysis was performed with revision and reoperation as endpoints.

RESULTS

There were no more ceramic fractures. Compared to mid-term results, the incidence of squeaking and RLLs increased to 3.1% (9/288) and 19.4% (56/288), respectively. The RLL progressed to focal osteolysis in 3 hips (5.4%, 3/56). No hip had detectable wear or prosthetic loosening. Two hips were reoperated due to periprosthetic joint infection and periprosthetic femoral fracture in each. The survivorship decreased to 98.3% (96.7-99.9%) at 12 years.

CONCLUSION

During the extended follow-up, no additional ceramic fracture occurred, and the incidence of squeak increased by 0.7%. The long-term survivorship of Delta CoC THA was encouraging. However, focal osteolysis occurred around the hydroxyapatite-coated stem in 1% (3/288).

LEVEL OF EVIDENCE

II (Prospective cohort study).

Cup positioning and its effect on polyethylene wear of vitamin E- and non-vitamin E-supplemented liners in total hip arthroplasty: radiographic outcome at 5-year follow-up

BACKGROUND

Aseptic loosening remains a challenging problem after total hip arthroplasty. Accurate cup placement and supplementation of antioxidants in acetabular liners might reduce material failure rates. The aim of this study is to assess the effect of the cup position on the wear behaviour of UHMWPE-XE and UHMWPE-X liners in vivo using virtual radiographs.

METHODS

We conducted a prospective, randomized, controlled, multicenter trial. Clinical data of 372 probands were analyzed. Anteroposterior pelvic X-rays of 324 patients immediately postoperatively and after 1 and 5 years were evaluated by the RayMatch® analysis software regarding cup position and wear behaviour.

RESULTS

Mean cup anteversion was 20.3° (± 7.4) and inclination was 41.9° (± 7.0) postoperatively. 62.3% of all patients had an anteversion and inclination within the Lewinnek safe zone. Anterior and anterolateral approaches led to significantly higher cup anteversion compared to lateral approaches (27.3° ± 5.5; 20.9° ± 7.2; 17.5° ± 6.6; p < 0.001 and p = 0.001, respectively). Mean anteversion increased to 24.6° (± 8.0) after 1 year (p < 0.001). Only one revision occurred because of implant dislocation. Wear rates from UHMWPE-X and UHMWPE-XE did not differ significantly. Anteversion angles ≥ 25° correlated to increased polyethylene wear (23.7 µm/year ± 12.8 vs. 31.1 µm/year ± 22.8, p = 0.012) and this was amplified when inclination angles were ≥ 50° (23.6 µm/year ± 12.8 vs. 38.0 µm/year ± 22.7, p = 0.062).

CONCLUSION

Anterior approaches lead to the highest inaccuracy of cup placement, but cup positioning outside the Lewinnek safe zone does not necessarily cause higher dislocation rates. Moreover, mean anteversion increased by approximately four degrees within the first year after operation, which is expected to be functional due to a regularization of pelvic tilt after intervention. Mid-term wear rates of UHMWPE-X and UHMWPE-XE liners are comparable, but steep cup positions lead to significantly increased polyethylene wear. In summary, a re-evaluation of target zones for intraoperative cup positioning might be considered. In the long-term reduced oxidative embrittlement could lead to superior wear behaviour of vitamin E-blended liners.

How does corrective fusion surgery for adult spinal deformities affect pelvic inclination in the supine position as the reference plane for THA?

PURPOSE

To determine the changes in pelvic inclination in the supine and standing positions after spinal corrective surgery, and to identify the most predictive factor for changes in pelvic inclination with the supine position as the reference plane for total hip arthroplasty.

METHODS

We retrospectively analysed the data of 124 patients who underwent spinal corrective fusion surgery for adult spinal deformity between 2012 and 2016 at our institution. Spinal parameters were assessed preoperatively and postoperatively using whole spine radiographs in the standing position. The sacral slope (SS) was measured using spine and pelvis computed tomography. Differences between the preoperative and postoperative SS values in each position were calculated as Δsupine SS_{pre post} and Δstanding SS_{pre post}, respectively. We statistically analysed the correlations between Δsupine SS _{pre post} and preoperative spinal parameters to determine the most useful predictor of Δ supine SS_{pre post}.

RESULTS

The mean Δsupine SS_{pre post} of 10.5°(-13°-50°) was significantly smaller than the mean Δstanding SS_{pre post} of 13.2° (-19°-44°) (p = 0.02). Moreover, 21 patients (17%) had Δsupine SS_{pre post} > 20°. The Δsupine SS _{pre post} was correlated with preoperative LL (r = -0.34 p < 0.01), PT (r = 0.42 p < 0.01), and SVA (r = 0.37 p < 0.01). Preoperative supine SS (r = -0.54, p < 0.01) had the highest correlation with Δsupine SS_{pre post}, whereas preoperative standing SS showed no correlation (r = -0.14 p = 0.12).

CONCLUSION

Preoperative supine SS is the most useful predictive factor for changes in supine pelvic inclination, and low preoperative values should be noted. This information should be considered for the management of patients with hip-spine syndrome.

Validating the accuracy of a novel virtual reality platform for determining implant orientation in simulated primary total hip replacement

Introduction

Accurate acetabular cup and femoral stem component orientation are critical for optimising patient outcomes, reducing complications and increasing component longevity following total hip replacement (THR). This study aimed to determine the accuracy of a novel virtual reality (VR) platform in assessing component orientation in a simulated THR model.

Methods

The VR platform (HTC Vive Pro® system hardware) was compared against the validated Vicon® optical motion capture (MoCap) system. An acetabular cup and femoral stem were manually implanted across a range of orientations into pelvic and femur sawbones, respectively. Simultaneous readings of the acetabular cup operative anteversion (OA) and inclination (OI) and femoral stem alignment (FSA) and neck anteversion (FNA) were obtained from the VR and MoCap systems. Statistical analysis was performed using Pearson product-moment correlation coefficient (PPMCC) (Pearson’s r) and linear regression (R²).

Results

A total of 55 readings were obtained for the acetabular cup and 68 for the femoral stem model. The mean average differences in OA, OI, FSA and FNA between the systems were 3.44°, −0.01°, 0.01° and −0.04°, respectively. Strong positive correlations were demonstrated between both systems in OA, OI, FSA and FNA, with Pearson’s r = 0.92, 0.94, 0.99 and 0.99, and adjusted R² = 0.82, 0.9, 0.98 and 0.98, respectively.

Conclusion

The novel VR platform is highly accurate and reliable in determining both acetabular cup and femoral stem component orientations in simulated THR models. This adaptable and cost-effective digital tracking platform may be modified for use in a range of simulated surgical training and educational purposes, particularly in orthopaedic surgery.

Localization of the ilioischial line on axial computed tomography images for preoperative planning of total hip arthroplasty

BACKGROUND

If the bony region indicating the ilioischial line is established on the preoperative axial computed tomography (CT) image, the distance between the simulated cup and the ilioischial line can be measured on this image so that the surgeon can use these data to define a more accurate preoperative two-dimensional (2D) template of total hip arthroplasty (THA). This study aimed to verify the hypothesis that on the CT axial image, the cortical bone area, indicated by the superimposition of a line (line α) with a perspective projection angle to the ilioischial line on radiography and tangent to the medial acetabular wall, is the cortical bone that represents the ilioischial line on radiography.

METHODS

Study 1: If the two measured distances (distance A' and distance B) are sufficiently equal, then the hypothesis can be supported. Distance A' was calculated by multiplying the distance A, between the ilioischial line and the medial margin of the metal cup after THA measured at the level of the hip joint center on the pelvic radiograph, by 0.91 to correct for radiographic magnification. Distance B was defined as the distance between the medial margin of the metal cup and line α on the axial CT image at the level of the hip joint center. These two distances were measured for all 51 hip joints included in the study. Study 2: The difference between distance A and distance A^# (distance A on the 2D template) was compared between the group containing 59 primary THAs in which distance B' was measured (distance B in the simulation) and the control group containing 59 primary THAs.

RESULTS

Study 1: The average distance for A' was 4.5 ± 2 mm, and the average distance for B was 4.7 ± 2.1 mm. The difference between distances A and B was 0.2 ± 0.2 mm. Study 2: The mean difference between distance A and distance A^# for the measurement and control groups was 1.8 ± 1.3 mm and 3.7 ± 2.4 mm, respectively (P < 0.001).

CONCLUSIONS

The ilioischial line is located in the bony region where line α intersects the medial acetabular wall with a maximum overlap on axial CT images.

Efficacy of bed exercise in elderly patients after total hip arthroplasty: A retrospective study of 539 patients

The purpose of this study was to observe the necessity of bed exercise therapy in the rehabilitation of elderly patients after hip replacement and to analyze whether bed exercise therapy has an impact on patients' psychological scores, hip function and postoperative complications. From January 2018 to January 2021, a total of 539 patients with end-stage femoral head necrosis or hip osteoarthritis were retrospectively analyzed. According to the method of postoperative rehabilitation exercise, patients were divided into 2 groups: Group A (routine gait) and Group B (bed exercise). There was no significant difference in general information between the 2 groups. There was no significant difference in baseline pain scores between patients in Group A and Group B (25.2 ± 9.6 vs 24.8 ± 10.4, P = .429). However, at 5 weeks post-operatively, the pain scores of patients in Group A were significantly higher than those in Group B (38.6 ± 7.7 vs 34.1 ± 8.1, P = .016). At 17 weeks post-operatively, the difference between Group A and Group B remained (40.9 ± 6.9 vs 37.5 ± 7.5, P = .041). Similar to the pain score, the hip function score compared between the 2 groups was significantly different at 5 weeks (39.7 ± 8.4 in Group A, 45.9 ± 9.2 in Group B, P < .001) and 17 weeks post-operatively (41.5 ± 7.6 in Group A, 47.2 ± 8.8 in Group B, P < .001). At 17 weeks post-operatively, between the 2 groups, only the range of motion (ROM) of abduction showed no significant difference. Patients in Group B exhibited a better ROM in any other movement posture. The results showed that compared with Group A, bed exercise rehabilitation training could reduce the incidence of deep venous thrombosis. This study demonstrates that bed exercise can improve the hip function and quality of life of elderly patients with total hip arthroplasty (THA) at an early postoperative stage. It can reduce the incidence of deep venous thrombosis of the lower limbs after surgery. For these patients, systematic bed exercise rehabilitation training is recommended in the early postoperative period.

A new accelerometer-based portable navigation system provides high accuracy of acetabular cup placement in total hip arthroplasty in both the lateral decubitus and supine positions

INTRODUCTION

No studies have compared the accuracy of acetabular cup placement in total hip arthroplasty (THA) in the supine and lateral decubitus positions using the same portable navigation system. Thus, this study aimed to compare the accuracy of acetabular cup placement using a new accelerometer-based portable navigation system combined with an infrared stereo camera and inertial measurement unit between the supine and lateral decubitus positions.

MATERIALS AND METHODS

This retrospective study compared 45 THAs performed in the supine position (supine group) and 44 THAs performed in the lateral decubitus position (lateral group) using the same portable navigation system. The primary outcome was the absolute errors of cup placement angles, defined as the absolute values of the differences between cup radiographic inclination and anteversion angles displayed on the navigation system and those measured on postoperative computed tomography images.

RESULTS

No significant difference in the median absolute error of the cup inclination angle (supine group 1.7° [interquartile range 0.8°-3.1°] vs. lateral group 2.1° [interquartile range 1.0°-3.7°]; p = 0.07) was found between the two groups. Similarly, no significant difference in the median absolute error of the anteversion angle (supine group 1.9° [interquartile range 0.8°-3.4°] vs. lateral group 2.1° [interquartile range 0.9°-3.1°]; p = 0.42) was found.

CONCLUSION

This new accelerometer-based portable navigation system may provide high accuracy of the cup placement in THA in the lateral decubitus and supine positions.

Implications of the uncertainty of postoperative functional parameters for the preoperative planning of total hip arthroplasty

The functional parameters pelvic tilt (PT) and hip joint force (HJF) are required to calculate patient-specific target zones based on the range of motion (ROM) and implant loading for preoperative planning of total hip arthroplasty (THA). Both functional parameters may change after THA. The preoperative prediction of the postoperative PT and HJF is associated with a specific amount of uncertainty. The prediction uncertainty has to be considered in the preoperative planning process to avoid a suboptimal implantation. So far, very little attention has been paid to the necessary reduction of patient-specific target zones by the prediction uncertainties of postoperative functional parameters. Prediction models for the postoperative PT in standing position and for the HJF during one-leg stance as a surrogate for the peak force phase during level walking were used to quantify the reduction of the ROM- and load-based target zones of 196 Japanese THA patients. The prediction uncertainty was about 14° for the postoperative standing PT and ranged from 17% body weight to 37% body weight for the components of the HJF. On average, the prosthetic ROM-based target zone had to be significantly reduced by 43% and the load-based target zone by 39%. This led to a median reduction of the combined prosthetic ROM- and load-based target zone of 96%. The study sharpens the awareness for the substantial reduction of ROM- and load-based target zones by prediction uncertainties of the postoperative PT and HJF and highlights the importance of further research to improve prediction models for both functional parameters.

Functional Femoral Anteversion: Axial Rotation of the Femur and its Implications for Stem Version Targets in Total Hip Arthroplasty

Background

Acetabular and femoral component positioning are important considerations in reducing adverse outcomes after total hip arthroplasty (THA). Previous assessments of femoral anteversion examined anatomic femoral anteversion (AFA) referenced to anatomic landmarks. However, this does not provide a functional understanding of the femur's relationship to the hip. We investigate a new measurement, functional femoral anteversion (FFA), and sought to measure its variability across a large sample of patients undergoing THA.

Methods

A total of 1008 consecutive patients underwent THA surgery between September 2019 and July 2021. All patients were measured for supine and standing functional femoral rotation (FFR), AFA, and FFA.

Results

The mean standing FFA was 13.2° ± 12.2° (-27.8° to 52.3°). The mean change in FFR from supine to standing was -2.2° ± 11.8° (-43.0° to 41.9°). Of all, 161 (16%) patients had standing FFA version greater than 25°. Four hundred sixty (46%) patients had standing FFR (internal or external) greater than 10°. One hundred twenty-three (12%) patients exhibited an increase in external rotation from supine to standing of greater than 10°. A moderate, negative linear relationship was observed between AFA and standing external femoral rotation (P <<.001, R = -0.46), indicating people may externally rotate their femur as AFA decreases with age.

Conclusions

Functional alignment of the femur in patients requiring THA is understudied. It is now understood that the femur, like the pelvis, can rotate substantially between functional positions. Enhancing our understanding of FFA and FFR may improve both acetabular and femoral component positioning.

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.

Abnormal Spinopelvic Motion and Spine Deformity are Associated With Native Femoral Retroversion in the Setting of Total Hip Arthroplasty

Background

The effect of spinopelvic pathology on femoral version is unclear. This study investigated variability in native femoral anteversion in patients undergoing total hip arthroplasty (THA) and its relationship to the patient’s underlying spinopelvic pattern.

Methods

A retrospective chart review was performed to include in the study all patients undergoing robot-assisted THA over a 3-year period. Native femoral version was measured for each patient using a preoperative computed tomography scan and categorized as excessive, normal, or retroverted. Additionally, a subset analysis was performed for all patients with sit-to-stand dynamic pelvic radiographs available, and cases were classified by spinopelvic pattern.

Results

A total of 119 patients were included in the study with a mean age of 68.6 years; 61 (51%) were female. The median femoral anteversion for the entire study group was 6.0° (−32° to 40°, interquartile range 13.5°). Eleven patients (9.2%) had excessive femoral anteversion, 54 of the 119 (45.4%) had normal femoral version, and 54 of the 119 (45.4%) had native retroversion. Forty-two patients (35.3%) had sit-to-stand radiographs available and were subclassified by femoral version type and spinopelvic parameters. Welch’s analysis of variance demonstrated a significant difference in femoral version among spinopelvic patterns (F = 7.826, P = .003), with Games-Howell post hoc analysis showing increased retroversion in deformity-stiff patients compared to deformity-normal mobility patients (P = .003).

Conclusions

This study demonstrates that native femoral retroversion is present in a significant number of patients undergoing THA and is more common in patients with stiff spine deformities. Based on this observation, currently available spinopelvic classification systems should be modified to account for native femoral version.

Handheld Navigation Improves Accuracy in Direct Anterior Total Hip Replacement

Background

This study sought to determine the accuracy in placing the acetabular component, estimation of leg length, offset, radiation time and dose, and operative time using a handheld navigation device compared to conventional anterior total hip arthroplasty (THA). It also examined the learning curve of the handheld navigation device.

Methods

Data were prospectively collected for a consecutive series of 159 THAs; 99 THAs with handheld navigation and 60 conventional THAs. Thresholds of <5°, ≥5° to <10°, and ≥10° for acetabular inclination and version and thresholds of <5 mm, ≥5 mm to <10 mm, and ≥10 mm for leg-length and combined offset discrepancy were used to assess accuracy. Fluoroscopy time and exposure, operative time, and complications were compared. Learning curve was determined using operative time. Statistical analysis was performed for the different accuracy thresholds with P values set a <0.05 for significance.

Results

The handheld navigation device demonstrated a mean accuracy of 3.2° and 1.8° for version and inclination, respectively. The handheld navigation group had significantly fewer outliers in version (P < .001), inclination (P < .001), leg-length discrepancy (P < .001), and offset discrepancy (P < .001). Fluoroscopic dose and time (P < .001) were lower in the handheld navigation cohort. The learning curve for handheld navigation was 31-35 cases. The mean operative time after the learning curve was similar to that in the conventional fluoroscopy group (P = .113).

Conclusions

Handheld navigation technology provided more accurate results while mitigating radiation exposure to the surgeon and patient. There were fewer outliers in the handheld navigation group. After the learning curve, all metrics improved in accuracy, and operative time was similar to that of the conventional technique.

Comparing the accuracy of three-dimensional mini-optical portable navigation and accelerometer-based portable navigation system for acetabular cup placement during total hip arthroplasty

INTRODUCTION

This study compared the accuracy of three dimensional (3D) mini-optical navigation and accelerometer-based portable navigation systems for cup positioning during a total hip arthroplasty (THA) in the supine position.

MATERIALS AND METHODS

This retrospective cohort study assessed data for 77 hips using 3D mini-optical navigation (n = 37) and accelerometer-based portable navigation (n = 40). The patients underwent THA through the mini-anterolateral approach in the supine position using a portable navigation system. We assessed the preoperative target angles, recorded intraoperative cup angles, postoperative CT imaging angles, cup angle measurement errors, and other clinical parameters.

RESULTS

The mean absolute differences in radiographic inclination were similar between 3D mini-optical navigation and accelerometer-based portable navigation systems during THA in the supine position (2.8° ± 1.7° vs 2.8° ± 1.9°, p = 0.637). The mean absolute differences in radiographic anteversion were also similar (2.6° ± 2.3° vs 2.5° ± 1.9°, p = 0.737). Cup malalignment (absolute difference of inclination or anteversion between postoperative CT and preoperative target angle of > 5°) was significantly associated with body mass index (BMI) in accelerometer-based portable navigation but not in 3D mini-optical navigation.

CONCLUSIONS

This is the first study to compare the accuracy of cup positioning between 3D mini-optical and accelerometer-based navigations in THA in the supine position. Both portable navigation systems accurately identified the orientation of cup placement. The accuracy of 3D mini-optical navigation is not affected by high BMI and may be preferred over other options in such patients.

Accuracy of Acetabular Cup Placement During Total Hip Arthroplasty in Supine Position Using a Pelvic Rotation Correction Device

Background

Accurate cup placement during total hip arthroplasty (THA) is difficult because the intraoperative pelvic position changes even in supine patient position. We developed a device known as HipPointer; it corrects pelvic rotation and creates a functional pelvic plane as a reference. The aim of this study was to determine the device placement accuracy and investigate causes of error.

Material and methods

HipPointer was used for cup placement in 353 hips of 308 patients who underwent direct-anterior-approach THA in supine position. The mean age at surgery and body mass index were 63.9 (17-90) years and 24.9 (16.6-42.0) kg/m², respectively. The mean observation period was 40.5 (12-73) months. To investigate the accuracy of HipPointer, preoperative planning and postoperative cup placement angles relative to the functional pelvic plane were evaluated using a three-dimensional analysis software, and absolute errors were determined.

Results

The means ± standard deviations of radiographic inclination (RI) and radiographic anteversion (RA) were 40.2 ± 3.0° and 15.8 ± 3.6°, respectively. The absolute errors of RI and RA were 2.2 ± 2.0° and 2.7 ± 2.3°, respectively. The ratio of the cup placement angle for which both RI and RA are ≤10° in the target zone was 99% (350/353 hips), and the ratio of the absolute errors for which both RI and RA are ≤5° was 80.4% (284/353 hips).

Conclusions

HipPointer is simple in structure, easy to use, and useful for direct-anterior-approach THA in supine position. It provides good cup placement accuracy.

Revision Total Hip Arthroplasty with Severe Acetabular Defect: A Preliminary Exploration and Attempt of Robotic-Assisted Technology

Background

Robotic‐assisted technology may be useful in hip revision cases with acetabular defects. However, data on the use of robotic‐assisted technology for such complex diseases is lacking.

Case Presentation

This case study described the adoption of MAKO robotic‐assisted treatment of revision total hip arthroplasty (THA) combined with severe acetabular defect (Paprosky type IIIB). Robotic‐assisted technology accurately achieved preoperative planning; the acetabular component and augment were placed in the original position and angle as planned. Robotic‐assisted acetabular reaming was successful in a single pass, preserving the remaining acetabular bone mass very well with no procedure‐related complications. The Harris Hip Score (HHS) at 6 months postoperatively was 84 and the Western Ontario and McMaster Universities (WOMAC) Osteoarthritis Index was 24.

Conclusion

Robotic‐assisted technology can help in the accurate reconstruction of acetabular defect in complex hip revision surgery.

Development of bony range of motion (B-ROM) boundary for total hip replacement planning

BACKGROUND AND OBJECTIVE

Pre-operative surgical planning using computer simulation is increasingly standard practice before Total Hip Arthroplasty (THA), in order to determine the optimal implant positions, and thereby minimise post-operative complications such as dislocation, wear and leg length discrepancy. One of the limitations of current methods, however, is the lack of information on the subject-specific reference range of motion (ROM) that could be used as targets for surgical planning. Only a limited number of hip motions are considered, which are neither subject-specific, nor representative of all the hip motions associated with all the activities of daily livings (ADLs). In this paper, therefore, a method was developed to calculate subject-specific representative bony range of motion (B-ROM) that would cover all the possible joint motions and presented in terms of pure joint motions.

METHODS

Only 3D bone geometries of femur and pelvis, constructed from personalised CT scan, were used as inputs for healthy hip joint whereas implant geometries and their positions on native bone geometries were required for planned treatment side or replaced side. Hip joint motion simulation was carried out using six different Tait-Bryan intrinsic rotation sequences of three pure joint motions - flexion-extension, abduction-adduction and internal-external rotation, and B-ROM was then identified for any of these six different sequences which caused earliest feasible impingement. The B-ROM could be used as a list of ROM data points or visualised as multiple 2D surface plots or a 3D envelop. Using the developed method, the B-ROM of a contralateral healthy hip joint of a patient can be used to define the subject-specific target ROM values to inform the surgical planning of the arthritic hip side so that the patient's natural ROM could be restored as closely as possible by the planned implant placements. This was demonstrated with a clinical verification study using 'non-dislocating' and 'dislocating' THA patients.

RESULTS

The results supported the study hypothesis that the percentage of intersected volume of the healthy and replaced side B-ROM was higher for the 'Non-Dislocator' patient (95%) compared to 'Dislocator' (78%). Also, the results showed that the only one sequence (first flexion-extension, then abduction-adduction and finally internal-external rotation) was not adequate to identify all the possible limiting B-ROM, and therefore, all the six rotation sequences should be considered.

CONCLUSIONS

The method encompasses every potential ADL, and as a result, more comprehensive surgical planning is possible, as the implant positions can be optimised in order to maximise impingement-free ROM, and consequently minimise clinical complications.

Associations between implant alignment or position and patient-reported outcomes after total hip arthroplasty

BACKGROUND

We aimed to evaluate the associations between implant alignment/position and patient-reported outcomes following total hip arthroplasty using CT-based simulation software.

METHODS

We reviewed hips of 137 patients (27 males, 110 females, mean age: 67.3 years old) who underwent total hip arthroplasty. Radiographic evaluations were based on the software for evaluation of the parameters related to implant alignment/position and femoral/3-dimensional offset using post-operative CT data. Pre-operative and one-year post-operative patient-reported outcomes using Japanese Orthopaedic Association Hip Disease Evaluation Questionnaire scores were evaluated.

FINDINGS

The total and movement scores of normal combined anteversion and stem anteversion angle groups were significantly higher than those of lower and higher groups. The pain and movement scores of decreased femoral offset group were significantly lower than those of restored and increased femoral offset group. There were no significant differences in all scores in cup inclination and anteversion angle, stem coronal alignment, and 3-dimensional femoral offset among groups. Moreover, investigation of the associations between combined anteversion angle/stem anteversion/femoral offset and movement scores revealed that combined anteversion angle and stem anteversion were significantly associated with the movement that needs deep hip flexion and occasionally deep abduction, and high femoral offset was also associated with the movement that needs deep hip flexion.

INTERPRETATION

Surgeons should consider the stem anteversion, stem sagittal alignment, and combined anteversion, in addition to the femoral offset to achieve patient's post-operative satisfaction, although the surgeon may have a relatively larger choice for the implant positioning, especially on the cup side.

A neck-preserving short stem better reconstructs the centre of rotation than straight stems: a computed tomography-based cadaver study

INTRODUCTION

Short femoral hip stems with a metaphyseal anchoring concept have been designed to treat younger patients with good bone quality. The aim of this study was to reconstruct the centre of rotation and soft tissue balancing and preserve bone in the long-term perspective.

MATERIALS AND METHODS

Eighteen human femurs were randomised into three groups: (1) metaphyseal anchoring short stem, (2) shortened straight stem, (3) straight stem). Prior to the implantation of the hip stems, a computed tomography (CT) of the bones was performed and the femoral ante-torsion and ante-tilt was measured and compared to the results of the post-implantation CT. This could be calculated based on the 3D coordinates taken from the pre- and post-op CT scans, which were transformed into the same coordinate systems.

RESULTS

The mean preoperative caput-collum-diaphyseal (CCD) angle for the three groups was 126.87° ± 3.50° (Group 3: 129.64° ± 3.53°, Group 1: 123.76° ± 5.56°, Group 2: 127.53° ± 1.42°) and was consistent with published reports. The postoperative CCD angles with 126.85° ± 3.43° were within a very good reconstruction range for all three groups. The anterior offset comparison among these three groups showed significant difference in reconstruction. The smallest difference between the anatomical (preoperative) and postoperative condition was seen in Group 1 (1.47° ± 0.60°), followed by Group 2 (3.60° ± 0.23°) and Group 3 (8.00° ± 0.70°) groups. The horizontal offset showed no significant difference among the groups and was within the window of ± 5 mm.

CONCLUSION

In this cadaver study, we found that the metaphyseal anchoring, partially neck-preserving short hip stem best reconstructs the ante-torsion and the ante-tilt of the femoral neck. Therefore, it can be a useful stem in younger or active middle-aged patients.

Relationship between the Accuracy of the Acetabular Cup Angle and BMI in Posterolateral Total Hip Arthroplasty with CT-Based Navigation

Background and Objectives: Precise acetabular cup placement is essential for successful total hip arthroplasty (THA). In obese patients, its accuracy is often difficult to achieve because of the thickness of the soft tissues. This study aimed to determine the relationship between the accuracy of acetabular cup angle and body mass index (BMI) in posterolateral THA using the computed tomography-based navigation (CT-navi) system. Materials and Methods: We retrospectively reviewed 145 consecutive primary THAs using the CT-navi system between January 2015 and January 2018. All surgeries were performed using cementless cups employing the posterolateral approach with the patient in the decubitus position. We compared the radiographic inclination and anteversion obtained intraoperatively from the CT-navi with those measured by postoperative CT using three-dimensional templating software. We evaluated the relationship between the extent of errors and correlation with BMI. Results: In non-overweight patients (BMI < 25, 88 hips), the mean navigation errors for inclination were 2.8 ± 2.2° and for anteversion were 2.6 ± 2.3°. Meanwhile, in overweight patients (BMI ≥ 25, 57 hips), the mean navigation errors were 2.6 ± 2.4° for inclination and 2.4 ± 2.4° for anteversion. We found no significant difference between overweight and non-overweight patients in both inclination and anteversion. There was no correlation between the extent of errors and BMI. Conclusions: In posterolateral THA, CT-navi can aid the precise placement of the acetabular cup irrespective of a patient’s BMI.

Model-Based Acetabular Cup Orientation Optimization Based On Minimizing the Risk of Edge-Loading and Implant Impingement Following Total Hip Arthroplasty

In this paper, a computationally-efficient model-based method for determining patient-specific optimal acetabular cup alignment for total hip arthroplasty (THA) is presented. The proposed algorithm minimizes the risk of implant impingement and edge-loading, which are reported as the major causes of hip dislocation following THA. First, by using motion capture data recorded from the patient performing different daily activities, the hip contact force and the relative orientation of the femur and pelvis are calculated by a musculoskeletal model. Then, by defining two quantitative indices i.e., angular impingement distance and angular edge-loading distance, the risk of impingement and edge-loading are assessed for a wide range of cup alignments. And finally, three optimization criteria are introduced to estimate the optimal cup alignment with a tradeoff between the risk of impingement and edge-loading. The results show that patient-specific characteristics such as pelvic tilt could significantly change the optimal cup alignment, especially the value of cup anteversion. Therefore, in some cases, the well-known Lewinnek safe zone may not be optimal, or even safe. Unlike other dynamic model-based methods, in this work, the need for force plate measurements is eliminated by estimating the ground reaction forces and moments, which makes this method more practical and cost-efficient. Furthermore, the low computational complexity due to analytical formulas makes this method suitable for both preoperative and intra-operative planning.

The role of the femoral component orientation on dislocations in THA: a systematic review

INTRODUCTION

Dislocation remains a major complication in total hip arthroplasty (THA), in which femoral component orientation is considered a key parameter. New imaging modalities and definitions on femoral component orientation have been introduced, describing orientation in different planes. This study aims to systematically review the relevance of the different orientation parameters on implant stability.

METHODS

A systematic review was performed according to the PRISMA guidelines to identify articles in the PubMed and EMBASE databases that study the relation between any femoral component orientation parameters and implant stability in primary THA.

RESULTS

After screening for inclusion and exclusion criteria and quality assessment, nine articles were included. Definitions to describe the femoral component orientation and methodologies to assess its relevance for implant stability differed greatly, with lack of consensus. Seven retrospective case-control studies reported on the relevance of the transversal plane orientation: Low femoral- or low combined femoral and acetabular anteversion was statistical significantly related with more posterior dislocations, and high femoral- or combined femoral and acetabular anteversion with anterior dislocations in two studies. There were insufficient data on sagittal and coronal component orientation in relation to implant stability.

CONCLUSION

Because of incomparable definitions, limited quality and heterogeneity in methodology of the included studies, there is only weak evidence that the degree of transverse component version is related with implant stability in primary THA. Recommendations about the optimal orientation of the femoral component in all three anatomical planes cannot be provided. Future studies should uniformly define the three-dimensional orientation of the femoral component and systematically describe implant stability.

Which Safe Zone Is Safe in Total Hip Arthroplasty? The Effect of Bony Impingement

“Safe zones” for cup position are currently being investigated in total hip arthroplasty (THA). This study aimed to evaluate the impact of bony impingement on the safe zone and provide recommendations for cup position in THA. CT scans were performed on 123 patients who underwent a cementless THA. Using the implant data and bone morphology from the CT scans, an impingement detection algorithm simulating range of motion (ROM) determined the presence of prosthetic and/or bony impingement. An impingement-free zone of motion was determined for each patient. These zones were then compared across all patients to establish an optimized impingement-free “safe zone”. Bony impingement reduced the impingement-free zone of motion in 49.6% (61/123) of patients. A mean reduction of 23.4% in safe zone size was observed in relation to periprosthetic impingement. The superposition of the safe zones showed the highest probability of impingement-free ROM with cup position angles within 40–50° of inclination and 20–30° of anteversion in relation to the applied cup and stem design of this study. Virtual ROM simulations identified bony impingement at the anterosuperior acetabular rim for internal rotation at 90° of flexion and at the posteroinferior rim for adduction as the main reasons for bony impingement.

Accurate cup placement using a portable navigation system during total hip arthroplasty based on pelvic orientation in the lateral decubitus position

BACKGROUND

We previously proposed an accurate cup placement procedure using a portable navigation system (PNS) for total hip arthroplasty (THA) in the lateral decubitus position; however, as the accuracy of our proposed procedure has not been shown, the aim of this study was to demonstrate the accuracy.

METHODS

We prospectively analyzed 79 hips treated with primary THA; 40 hips treated until June 2020 were included in the conventional procedure (CP) group, and 39 hips treated from July 2020 were included in the modified procedure (MP) group. In the MP, pelvic orientation is considered to the set coordinate axes in addition to the CP using the PNS. The accuracy was based on the difference between the navigation record (NR) and postoperative computed tomography measurement.

RESULTS

The radiographic inclination (RI) and anteversion (RA) accuracies were 1.55° and 2.14°, respectively, in the MP group and 3.03° and 6.20°, respectively, in the CP group (p < 0.001). The error was within 5° of the NR for both the RI and RA in 34 in the MP group (87.2%) and 14 in the CP group (35.0%) (p < 0.001). The error was within 5° of the target angle (RI 40°, RA 15°) for both the RI and RA in 29 hips in the MP group (74.7%) and 12 in the CP group (30.0%) (p < 0.001).

CONCLUSIONS

Our procedure with the consideration of pelvic orientation achieved dramatically improved the accuracy of PNS and was suitable to facilitate accurate cup placement.

A method combining the use of a mobile application and a dedicated pelvic positioner for acetabular cup insertion

Background

We developed a mobile device application and dedicated pelvic positioner with the aim of improving the acetabular cup placement accuracy in patients undergoing total hip arthroplasty (THA). The function of the application was to display the intra-operative cup angle. The accuracy and clinical usefulness of this combined method were verified through comparison with the conventional alignment guide method.

Methods

In total, 60 patients who underwent cementless THA were included in this study. We compared the cup alignment when using this combined method with that when using the conventional alignment guide method. The absolute value error between the intra- and post-operative angles of inclination and anteversion of the cup was calculated.

Results

The absolute value error of inclination was 2.4° ± 2.1° in the study group and 4.0° ± 3.3° in the control group (P = 0.107). The absolute value error of anteversion was 2.8° ± 2.6° in the study group and 7.4° ± 5.3° in the control group (P < 0.001).

Conclusion

Using the application and pelvic positioner is simple and can be introduced at a low cost. The more accurate measurement of the intra-operative cup angle using this combined method has improved the cup insertion accuracy compared with that of the conventional alignment guide method.

Patient-specific 3D-printed shelf implant for the treatment of hip dysplasia: Anatomical and biomechanical outcomes in a canine model

A solution for challenging hip dysplasia surgery could be a patient-specific 3D-printed shelf implant that is positioned extra-articular and restores the dysplastic acetabular rim to normal anatomical dimensions. The anatomical correction and biomechanical stability of this concept were tested in a canine model that, like humans, also suffers from hip dysplasia. Using 3D reconstructed computed tomography images the 3D shelf implant was designed to restore the radiological dysplastic hip parameters to healthy parameters. It was tested ex vivo on three dog cadavers (six hips) with hip dysplasia. Each hip was subjected to a biomechanical subluxation test, first without and then with the 3D shelf implant in place. Subsequently, an implant failure test was performed to test the primary implant fixation. At baseline, the dysplastic hips had an average Norberg angle of 88 ± 3° and acetabular coverage of 47 ± 2% and subluxated at an average of 83 ± 2° of femoral adduction. After adding the patient-specific shelf implants the dysplastic hips had an average Norberg angle of 122 ± 2° and acetabular coverage of 67 ± 3% and subluxated at an average of 117 ± 2° of femoral adduction. Implant failure after primary implant fixation occurred at an average of 1330 ± 320 Newton. This showed that the patient-specific shelf implants significantly improved the coverage and stability of dysplastic hips in a canine model with naturally occurring hip dysplasia. The 3D shelf is a promising concept for treating residual hip dysplasia with a straightforward technology-driven approach; however, the clinical safety needs to be further investigated in an experimental proof-of-concept animal study.

Measurement of safe acetabular medial wall defect size in revision hip arthroplasty with a porous cup

INTRODUCTION

The majority of acetabular revisions can be performed with an uncemented, porous acetabular component with or without bone grafting. These are contained acetabular defects, with an intact acetabular rim (Paprosky type I and II). As defects of the medial wall of the acetabulum are a challenge situation revision surgery, we performed this biomechanical study on a pig pelvis model with contained acetabular defects to determine the size of medial wall defect at which the acetabular cup will have sufficient primary stability.

MATERIALS AND METHODS

In 24 pig pelvis models, different diameter of medial wall defects were created, followed by acetabular component placement. The acetabulum externally loaded, and the force at a level in which the acetabular component remains stable for each diameter of defect, or at which point the acetabular cup moves into the pelvis for >2 mm.

RESULTS

In the models with acetabular medial wall defects of 10 and 20 mm, 2 mm acetabular displacement occurred under a force between 1000 and 1500 N. In those with a medial wall defect of 25 mm, the force that caused acetabular instability was between 700 and 1000 N. In the models with 30 mm of medial wall defect all acetabular components were unstable under a force of 700 N.

CONCLUSIONS

According to our results, acetabular component should be stable if the defect of the medial wall of the acetabulum is less than 68% of the diameter of the acetabular component or if the uncovered surface area of the acetabular component is not greater than 27%, and the force <700 N. For a load of 1000 N, the medial wall defect should not exceed 45% of acetabular component diameter or 18% of uncovered acetabular component surface.

Optimal combined anteversion range for obtaining a wider range of motion without prosthetic impingement after total hip arthroplasty: a three-dimensional analysis study

Background

Obtaining a larger theoretical range of motion (ROM) is crucial to avoid prosthetic impingement after total hip arthroplasty (THA); however, no reports have examined the permissible range values of combined anteversion (CA) satisfying targeted ROM without prosthetic impingement. This retrospective study aimed to evaluate the possible postoperative CA extent that would allow meeting target ROM criteria according to Yoshimine’s theory using computed tomography (CT)-based three-dimensional motion analysis after THA.

Methods

This study included 114 patients (133 hips) who underwent cementless primary THA using a CT-based navigation system and implants (oscillation angle ≥ 135°). Implant positions were determined using Yoshimine's CA formula. Postoperative evaluation was conducted using a three-dimensional templating software for CT data. The postoperative Yoshimine’s and Widmer’s CA was calculated, and the difference between the target and postoperative values was defined as the error of Yoshimine’s CA and Widmer’s CA. Prosthetic ROM was assessed by Yoshimine’s stringent criteria for activities of daily living. Based on fulfilling these criteria, all patients were divided into the ROM (+) and ROM (−) groups. Evaluation items were compared between the two groups.

Results

There were 111 and 22 hips in the ROM (+) and ROM (−) groups, respectively. A significant difference was noted in the absolute error of Yoshimine’s and Widmer’s CA between the two groups. Using receiver operating characteristic analysis, threshold values of 6.0 (higher values indicate greater disability; sensitivity 90.9%, specificity 72.1%) for the absolute Yoshimine’s CA difference (area under the curve [AUC] 0.87, P < 0.01) and 6.9 (higher values indicate greater disability; sensitivity 68.2%, specificity 88.3%) for the absolute Widmer’s CA difference (AUC 0.83, P < 0.01) were predictors in the ROM (−) group.

Conclusions

The target range of Yoshimine’s CA (90.8° ± 6.0°) and Widmer’s CA values (37.3° ± 6.9°) was crucial in implant orientation for obtaining theoretical ROM without prosthetic impingement after THA.

Computer simulation of optimal lipped polyethylene liner orientation against prosthetic impingement

Background

Lipped or elevated acetabular liners are to improve posterior stability and are widely used in hip arthroplasty. However, concerns of increasing impingement exist when using such liners and optimal orientation of the elevated rim remains unknown. We aimed to identify the impact of lipped liner on the range of motion (ROM) before impingement and propose its optimal orientation.

Methods

An isochoric three-dimensional model of a general hip-replacement prosthesis was generated, and flex-extension, add-abduction and axial rotation were simulated on a computer. The maximum ROM of the hip was measured before the neck impinged on the liner. Different combinations of acetabular anteversion angles ranging from 5 to 30 degrees, and lipped liner orientations from posterior to anterior were tested.

Results

When acetabular anteversion was 10 or 15 degrees, placing the lip of the liner in the posterosuperior of the acetabulum allowed satisfactory ROM in all directions. When acetabular anteversion was 20 degrees, extension and external rotation were restricted. Adjusting the lip to the superior restored satisfactory ROM. When acetabular anteversion was 25 degrees, only placing the lip into the anterosuperior could increase extension and external rotation to maintain satisfactory ROM.

Conclusions

This study showed that optimal lipped liner orientation should depend on acetabular anteversion. When acetabular anteversion was smaller than 20 degrees, placing lip in the posterior allowed an optimally ROM. When acetabular anteversion was greater than 20 degrees, adjusting lip to the anterior allowed a comprehensive larger ROM to avoid early impingement.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-022-03093-6.

Postoperative Hip Center Position Associated With the Range of Internal Rotation and Extension During Gait in Hip Dysplasia Patients After Total Hip Arthroplasty

Background: Total hip arthroplasty (THA) for hip dysplasia patients is sometimes complex and compromises pathomorphological changes in these patients. However, it remains unclear whether it is preoperative deformities or postoperative structures or anatomic changes during THA that have the most remarkable correlation with the hip dynamic function during gait. The purpose of this study was to investigate this relationship and propose insights into the surgical reconstruction strategy in patients with developmental dysplasia of the hip.

Methods: A total of 21 unilateral hip dysplasia patients received computed tomography scans for the creation of 3D hip models before surgery and at the last follow-up. Acetabular and femoral orientations, hip center positions, and femoral length were measured before and after THA. Hip kinematics of the operated side during gait was quantified using a dual fluoroscopic imaging technique. Pearson correlation and multiple linear regression were performed to evaluate the relationship between hip maximum range of motion in six directions and demographics characters and above hip anatomic parameters before and after THA and their changes in surgery.

Results: Pearson correlation analysis found significant correlations with the gait range of motion mainly in postoperative structures, including postoperative hip center positions and acetabulum and combined anteversion. Further multiple linear regression indicated that a laterally placed hip center was significantly correlated with an increased internal rotation (R2 = 0.25, p = 0.021), which together with increased postoperative acetabulum anteversion explained 45% of external rotation decreasing (p = 0.004). A proximally placed hip center was correlated with more extension (R2 = 0.30, p = 0.010). No significant demographic characters or preoperative deformities or surgical changes were included into other multiple regression models.

Conclusion: Strong correlations between postoperative structures, especially hip center positions and gait range of motion in unilateral hip dysplasia patients after THA were found. It indicated that postoperative prosthesis structures, particularly hip center positions had significant impact on the hip gait motion range and should be treated with particular caution in surgery.

Impingement in total hip arthroplasty: A geometric model

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