Effect of superior and superolateral relocations of the hip center on hip joint forces. An experimental and analytical analysis

Minimum 10-Year Survivorship of Uncemented Acetabular Reconstruction With Bulk Femoral Head Autografting in Crowe Type IV Developmental Hip Dysplasia

BACKGROUND

In total hip arthroplasty (THA) for severe dislocations such as Crowe type IV developmental dysplasia of the hip (DDH), sufficient bone volume for stable fixation of the acetabular component can be achieved by placing a reinforcing bone graft prepared from the resected femoral head into the deficient acetabulum. The purpose of the current study was to examine the long-term survivorship of uncemented THA in conjunction with a bulk femoral head autograft in patients who have Crowe type IV DDH.

METHODS

A total of 35 patients (42 hips) who have Crowe type IV DDH and underwent THA using uncemented cup fixation with bulk femoral head autografting were followed up for a mean period of 15.0 years (range, 10.0 to 20.0) postoperatively. Anteroposterior pelvic radiographs were used for measurements such as the horizontal coverage of the grafted bone and the center-edge angle. Kaplan-Meier survivorship analyses were performed with revision of the acetabular component as the endpoint.

RESULTS

The Kaplan-Meier analysis indicated 15-year survival rates of 90.4%. The mean horizontal coverage of grafted bone was 46.1% (range, 23.7 to 66.0), and there were 16 cases with horizontal coverage of ≥ 50%. There was no difference in the appearance of a thin (< 1 mm) radiolucency line around the cup between cases with < 50% versus ≥ 50% of the horizontal coverage of grafted bone (4 versus 2 hips; P = .446). Trabecular bridging and remodeling were seen in all cases after mean periods of 4.1 and 9.0 months postoperatively, respectively. Trabecular reorientation was seen in 41 of 42 hips (97.6%) at a mean follow-up of 19.9 months.

CONCLUSIONS

Acetabular reconstruction with femoral bulk bone grafting for Crowe type IV DDH resulted in high survival rates and was a good method to restore bone stock and obtain long-term fixation.

Impact of acetabular roof's angle on precision of cup center of rotation reproduction and placement in total hip arthroplasty

Introduction

Total hip arthroplasty (THA) is nowadays considered as the most effective treatment option for end-stage hip osteoarthritis (OA) and one of the most successful orthopedic procedures. Precise reproduction of the center of rotation (COR) is among the most important aspects of recreating native hip biomechanics after THA as it is strictly related to muscle tension and force distribution within the hip joint. Both vertical and horizontal shift in cup positioning and COR restoration are commonly observed radiological signs corresponding with lesser functional outcome. The aim of this study was to assess whether the superior border of the native acetabulum morphology has an impact on cup positioning and COR restoration in patients undergoing THA as treatment of primary OA of the hip.

Material and methods

A cohort of 150 consecutive patients with diagnosis of end-stage primary hip OA who underwent THA via an anterolateral approach with the same implant in 2021 was analyzed retrospectively. Standard standing pelvic X-rays were performed pre- and postoperatively and appropriate measurements were taken. Several radiological parameters on obtained X-rays were assessed. Statistical analysis of all the measurements was performed.

Results

There was a statistically significant positive weak correlation between cup offset and acetabular roof angle (rs = 0.25, p = 0.002). There were statistically insignificant positive correlations between acetabular roof angle and COR restoration (rs = 0.14, p = 0.097), acetabular roof angle and total offset (rs = 0.087, p = 0.29) and a negative correlation between acetabular roof angle and femoral offset (rs = 0.071, p = 0.39).

Conclusions

The present study revealed that preoperative acetabular roof angle influences the positioning of the prosthetic cup in the transverse axis. There also seems to be a correlation between the acetabular roof angle and COR restoration, but its significance needs further evaluation. Surgeons could use this knowledge to preoperatively assess the risk of cup malposition and adjust their technique during the THA procedure with probable improvement of hip function.

Medial Protrusio Technique Versus Structural Autologous Bone-Grafting Technique in Total Hip Arthroplasty for Crowe Type II to III Hip Dysplasia

BACKGROUND

It is unclear whether acetabular reconstruction techniques have any impact on clinical outcomes. This study aimed to determine (1) whether acetabular reconstruction techniques influenced the position of the acetabular cup and (2) whether clinical outcomes based on the acetabular reconstruction techniques differ in patients undergoing total hip arthroplasty (THA) with Crowe II to III developmental dysplasia of the hip.

METHODS

This was a retrospective analysis of prospectively collected data from 69 patients (74 hips) who were treated with cementless THA using medial protrusio technique (MPT) or structural autologous bone-grafting technique (SABT). There were 39 patients (41 hips) included in the MPT group and 30 patients (33 hips) in the SABT group. Clinical and radiographic outcomes were evaluated.

RESULTS

All patients were followed up for at least 3 years. There were similar results between the 2 groups in terms of blood loss, Harris hip score, leg length discrepancy, cup inclination, cup anteversion, and proportion of cup coverage (P > .05). The operative time was significantly longer in the SABT group compared with the MPT group (P < .001). The postoperative vertical center of rotation was significantly higher in the MPT group compared with the SABT group (P = .001), and postoperative horizontal center of rotation was significantly shallower in the SABT group compared with the MPT group (P < .001).

CONCLUSION

The MPT and SABT provide similar clinical and radiographic outcomes in the management of Crowe II to III developmental dysplasia of the hip by cementless THA. However, the MPT has the advantage of a shorter operative time, whereas the SABT is more conducive to placing the acetabular cup in an anatomic position.

LEVEL OF EVIDENCE

Level III, Therapeutic, Case-Control Study.

Clinical effects of different center of rotation reconstructions in total hip arthroplasty after femoral neck fractures: a cohort study including a follow-up analysis on patient's mobility and daily living ability

BACKGROUND

The aim of this study is a clinical evaluation of the center of rotation (COR) placement towards a patient's recovery with respect to daily living ability and mobility. In past experiments based on three-dimensional (3D) models, medialization of the COR in total hip arthroplasty (THA) showed a negative influence on muscle strength of the abductors and reaction force of the hip joint. This contradicts paradigms, where reduced hip loading forces are claimed to increase functional outcomes.

METHODS

The plain X-rays of 110 patients who underwent THA after a femoral neck fracture between January 2019 and January 2021 were retrospectively evaluated. A Barthel Index on discharge was obtained in 69 cases. 47 patients were available for a follow-up interview concerning the Barthel Index, Parker mobility score (PMS), and pain levels (NRS) 6 and 12 months after surgery.

RESULTS

Medialization of the COR had a significantly negative effect on the need for care (Barthel Index) at patient discharge (Spearman correlation 0.357, p = 0.013). The effect on the PMS is still existent at 6 and 12 months (Spearman correlation 0.471, p = 0.009 at 6 months; 0.472, p = 0.008 at 12 months). Mann-Whitney U tests showed that the groups with medialized COR performed significantly worse than the lateralized groups. This was seen for the Barthel Index at discharge and at 6 months after surgery and for the PMS at 6 and 12 months. The accurately reconstructed CORs showed no significant differences from the lateralized rotation centers in need of care and mobility. The superior COR placement group showed significantly reduced mobility at 12 months in contrast to the inferior COR placement group (p = 0.008), and the group of accurately reconstructed rotation centers showed significantly less pain than the inferior COR placement group (p = 0.007 after 6 months, p = 0.026 after 12 months). Especially the combination of both (superomedialization) leads to reduced mobility (Spearman correlation 0.67, p =  < 0.001).

CONCLUSIONS

COR superior displacement, COR medialization, and the combination of both (superomedialization, Spearman p =  < 0.001) lead to reduced mobility while inferior displacement showed increased pain. According to our results, we recommend an exact vertical COR restoration, while horizontal medial displacement needs to be avoided.

LEVEL OF EVIDENCE

III.

Downsizing and minimising medialisation of the acetabular component: Novel technique to preserve bone in THA

Standard practice for acetabular component placement in total hip arthroplasty (THA) is to medialise the acetabular component. Bone preservation techniques during primary THA are beneficial for possible future revisions. The goal of this study is to examine the effect of downsizing and minimising medialisation of the acetabular component on bone resection volume. The volume of bone resected during acetabular preparation for different sizes of components was calculated and the volume of bone preserved by downsizing the cup was determined. Minimising medialisation of the acetabular component by 1-3 mm from the true floor was calculated. Absolute values and percentage of bone volume preserved when acetabular components are downsized or less medialised is presented. Downsizing the acetabular component by one size (2 mm) preserves between 2.6 cm³ (size 40 vs 42) and 8.4 cm³ (size 72 vs 74) of bone volume and consistently reduces resected bone volume by at least 35% (range 35.2%-37.5%). Similarly, reducing medialisation of a 56 mm acetabular cup (as an example of a commonly implanted component) by 3 mm reduces bone loss by 5.9 cm³- 44% less bone volume resection. Downsizing and minimising medialisation of the cup in THA substantially preserves bone which may benefit future revision surgeries. Surgeons could consider implanting the smallest acceptable acetabular shell to preserve bone without compromising on head size.

Femoral Head Autograft to Manage Acetabular Bone Loss Defects in THA for Crowe III Hips by DAA: Retrospective Study and Surgical Technique

Introduction: The pathologic anatomy of Crowe III is characterized by the erosion of the superior rim of acetabulum, with a typical bone defect in its supero-lateral portion. The performance of a total hip arthroplasty requires the management of the acetabular bone defect, and femoral head autograft can be a valid option to optimize implant coverage. Material and Methods: In all, eight Crowe III patients (nine hips), seven of which having unilateral hip affected, and one with bilateral involvement by secondary osteoarthritis in DDH; maximum limb length discrepancy (LLD) of 3.5 cm in unilateral patients. All were operated on by direct anterior approach. Patients were evaluated in terms of clinical, surgical, and radiological (center-edge, horizontal coverage, cup inclination) parameters. Results: Cup placement was implanted with a mean of 39.5 ± 7.5°. Stem alignment showed average 1.5 ± 2.3° in valgus. LLD showed an overall average preoperative of -29.5 ± 10.5 mm at the affected side, with a significant improvement to -2.5 ± 6.4 mm (p = 0.023). The mean initial coverage evaluated like a percentage of the horizontal bone host was 52.1 ± 7.1%, while the mean final coverage at the last post-operative X-ray from femoral autograft bone was 97.0 ± 4.5% with an average improvement of 44.5%. Average CE improved from -9.5 ± 5.2° (CE I) to the immediate post-operative (CE II) of 40.6 ± 8.2°. At the final follow up, CE III showed a mean of 38.6 ± 6.2°, with an average decrease of 2.0°. Discussion: Acetabular bone defect in Crowe III DDH patients undergoing THA by DAA, can be efficiently managed by massive autograft femoral head, which allowed an adequate and long-lasting coverage of the implant, with cup positioning at the native acetabulum.

Mid- to Long-term Follow-up of Severe Acetabular Bone Defect after Revision Total Hip Arthroplasty Using Impaction Bone Grafting and Metal Mesh

OBJECTIVE

In revision total hip arthroplasty (THA), reconstruction of severe acetabular bone defect continues to be problematic for orthopedic surgeons. This study reports the mid- to long-term survivorship, radiological outcomes, and complications of impaction bone grafting (IBG) and metal mesh with a cemented acetabular component in the reconstruction of severe acetabular bone defects in revision THA.

METHODS

This retrospective consecutive study included 26 patients (29 hips: type II B, four; type II C, three; type III A, 10; and type III B, 12) who underwent revision THA, which was performed using IBG and metal mesh, between 2007 and 2014 in our institution. All patients were followed up regularly for clinical and radiographical assessments. Migration and loosening of prosthesis graft integration and complications were observed and analyzed. Survival analysis was performed using a Kaplan-Meier survival analysis.

RESULTS

At the time of revision, 75.9% of the hips (22 hips) were classified as type III bone defects. The average follow-up period was 9.4 ± 2.8 (range, 2.4-14.0) years. Of the 29 hips, four hips (13.8%) were assessed as clinical failures; at the last follow-up, two had undergone re-revision THA, and two had not been scheduled for re-revision THA despite radiological failure of the acetabular component. Among them, three clinical failures (10.3%) were due to aseptic loosening, and one (3.4%) was due to infection. Radiographic evaluation showed bone graft integration in all hips during the follow-up. The Kaplan-Meier survivorship analysis revealed an acetabular reconstruction survival rate of 86.5% (95% confidence interval, 61.4%-95.7%) at 10 years.

CONCLUSION

IBG and metal mesh with a cemented acetabular component for revision THA is an effective technique for treating severe acetabular bone defects, with effective mid- to long-term outcomes due to the solid reconstruction of the acetabular bone defect and restoration of the hip rotation center.

Supine versus lateral position for total hip replacement: accuracy of biomechanical reconstruction

BACKGROUND

Restoration of normal hip anatomy and biomechanics is a key surgical goal for success in total hip arthroplasty. The aim of this study was to evaluate the influence, if any, that patient positioning in the supine and lateral decubitus positions has in achieving this goal.

MATERIALS AND METHODS

A single center multi-surgeon case-matched series from a tertiary level referral center of patients undergoing primary unilateral THA for osteoarthritis between April 2018 and December 2019 was retrospectively analyzed. Patients (n = 200) were divided into two matched groups: supine (anterior approach, n = 100) and lateral decubitus (direct lateral or posterior/SuperPATH™ approaches, n = 100). Post-operative anteroposterior pelvic radiographs were analyzed using a previously validated software (SurgiMap, Nemaris Inc., USA) for parameters of reconstruction of the hip in the coronal plane; leg length discrepancy, vertical and horizontal displacement of the center of rotation, femoral offset, and total offset.

RESULTS

Mean absolute leg length discrepancy in the supine group was 0.6 ± 3.3 mm (95% [CI] - 0.1 to 1.2 mm) versus 2.4 ± 3.8 mm (95% [CI] 1.6 to 3.1) in the lateral decubitus position (p < 0.001). The center of rotation was displaced medially by a mean of 3.2 ± 2.7 mm in the supine group versus 1.3 ± 4.0 mm in the lateral decubitus group (p < 0.001). For a surgical target of reconstructing both leg length and total offset within 5 mm of native anatomy, the supine group was more than twice as likely to achieve these goals with fewer outliers (OR 2.631, 95% [CI] 1.901-3.643) (76% v 30%, p < 0.001).

CONCLUSION

Total hip arthroplasty through the anterior approach in the supine position is more consistent and accurate for the restoration of leg length and total offset. Further study is required to assess how this translates with outcome.

LEVEL OF EVIDENCE

III-retrospective cohort study.

Instability After Total Hip Arthroplasty and the Role of Advanced and Robotic Technology

Instability remains the leading cause of reoperation following total hip arthroplasty (THA). In this article, the risk factors for instability after THA are reviewed, including patient-related characteristics, surgical techniques, positioning of implants, and the role of advanced technology and robotics as a platform that may reduce the incidence of instability.

High Hip Center Technique in Total Hip Arthroplasty for Crowe Type II-III Developmental Dysplasia: Results of Midterm Follow-up

Objectives

We aimed to show the utility of high hip center technique used in patients with Crowe II–III developmental dysplasia of the hip at the midterm follow‐up and evaluated the clinical and radiographic results between different heights of hip center.

Methods

From December 2003 to November 2013, we retrospectively evaluated 69 patients (85 hips) with Crowe II–III dysplasia who underwent a high hip center cementless total hip arthroplasty. The patients were divided into two groups according to the height of hip center, respectively group A (≥ 22 mm and < 28 mm) and group B (≥28 mm). The survivorship outcomes and radiographic and clinical results, including the vertical and horizontal distances of hip center, femoral offset, abductor lever arm, cup inclination, leg length discrepancy, Trendelenburg sign, and limp were evaluated.

Results

The mean follow‐up time was 8.9 ± 1.8 years. The mean location of the hip center from the inter‐teardrop was 25.1 ± 1.6 mm vertically and 30.0 ± 3.8 mm horizontally in group A, and 33.1 ± 4.8 mm vertically and 31.4 ± 6.1 mm horizontally in group B. Eleven hips of group B showed a lateralization over 10 mm, and the same was shown in one hip in group A (P = 0.012). There were no statistically significant differences between two groups in postoperative femoral offset, abductor lever arm, leg length discrepancy and cup inclination. At the final follow up, the mean WOMAC and Harris hip score were significantly improved in both groups. Of the 85 hips, four hips in group A and three hips in group B showed a positive Trendelenburg sign. Additionally, four patients in group A and two patients in group B presented with a limp. No significant differences were shown regarding the Harris hip score, WOMAC score, Trendelenburg sign, and limp between two groups. One hip of group A was revised by reason of dislocation at 8.3 years after surgery. One hip of group B was diagnosed with osteolysis and underwent a revision at 8.1 years after surgery. The Kaplan–Meier implants survivorship rates at the final follow‐up for all‐causes revisions in group A and group B were similar (96.7% [95% confidence interval, 90.5%–100%] and 96.2% [95% confidence interval, 89.0%–100%], respectively).

Conclusions

The high hip center technique is a valuable alternative to achieve excellent midterm results for Crowe II–III developmental dysplasia of the hip. Further, between the groups with differing degrees of HHC, there were no significant differences in outcomes or survivorship in our study.

Pre-operative planning in THA. Part III: do implant size prediction and offset restoration influence functional outcomes after THA?

INTRODUCTION

Few studies evaluated clinical benefits of pre-operative templating in total hip arthroplasty (THA). We investigated whether mismatch between planned and real implant sizes and medio-lateral offsets compromises THA outcomes.

MATERIALS AND METHODS

We reviewed records of 184 primary THAs with pre-operative CT scans used for templating. Acetabular offset (AO), femoral offset (FO) and global offset (GO) were measured on pre-operative CT scans, during acetate templating, and post-operative antero-posterior radiographs. Multivariable analyses were performed to determine if Forgotten Joint Score (FJS) and Oxford Hip Score (OHS) at > 2 years were associated with differences between post-operative and planned parameters.

RESULTS

The FJS and OHS were not influenced by mismatch of component sizes nor of FO and GO. The FJS was better when the post-operative AO was greater than planned (p = 0.050). The FJS differed among arthritic types (p = 0.015). Multivariable analyses confirmed that older patients had better OHS (beta - 0.16; p = 0.033) and FJS (beta 0.74; p = 0.002), medialized hips had worse FJS (beta - 20.1; p = 0.041) and hips with greater AO than planned had better FJS (beta 1.71; p = 0.024) CONCLUSIONS: Implanting a component of different size than planned did not compromise THA outcomes, but medialized hips had worse scores, and conservative acetabular reaming improved scores.

Bilateral High Hip Center Provides Gait Parameters Similar to Anatomical Reconstruction: A Gait Analysis Study in Hip Replacement Patients With Bilateral Developmental Dysplasia

BACKGROUND

Total hip arthroplasty in severe dysplasia is challenging due to diminished periacetabular bone stock and the highly placed femoral head. Although anatomical reconstruction of the hip, with required interventions such as subtrochanteric osteotomy and graft usage, is the main aim of the procedure, good long-term clinical outcomes of the high hip center technique have also been reported. Information regarding the effect of hip center placement on gait characteristics is limited; therefore, the aim of this study is to analyze the differences in gait parameters between the high hip center technique and anatomical reconstruction of the hip.

METHODS

Twenty patients (40 hips) with bilateral Crowe type III-IV developmental dysplasia of the hip who underwent bilateral total hip arthroplasty and completed at least 2 years of follow-up were included. Group 1 comprised 10 patients (20 hips) who underwent anatomical hip center reconstruction, while group 2 comprised 10 patients (20 hips) who underwent high hip center reconstruction. The gait characteristics of patients were examined through markers placed in certain anatomical regions, the cameras placed around, and the force plates embedded in the walking platform.

RESULTS

There was no significant difference in the gait characteristics according to the location of the hip rotation center. The mean temporospatial, kinematic, and kinetic values were similar between the groups. The most prominent difference was in the peak dynamic hip extension, which was lower in group 2 (-9.71° ± 7.46°) compared to group 1 (-6.80° ± 11.44°), although it was not statistically significant (P = .09).

CONCLUSION

The bilateral high hip center technique can provide similar gait characteristics as anatomical reconstruction and may be preferred in particularly difficult cases based on the surgeon's decision.

Effect of placement of acetabular prosthesis on hip joint function after THA

The good recovery of hip function after THA depends on reconstruction of acetabular prosthesis accurately. So we investigated the effect of acetabular prosthesis placement on hip joint function after THA and analyzed the clinical data of 432 patients with unilateral THA retrospectively . The patients were followed-up to evaluate the Harris score and hip range of motion (ROM). The hip ROM, the Harris score and the good rate of Harris score were compared between different groups. Comparison of the good rate of Harris score showed that 85%∼100% group of the rotation center horizontal position ratio was higher than >100% group; 80%∼120% group of the rotation center vertical position ratio was higher than >160% group; and the 90%∼110% group and 110%∼130% group of femoral offset ratio were higher than 90% and >130% groups. Comparison of Harris score showed that 85%∼100% and 70%∼85% groups of rotation center horizontal position ratio were higher than 70% and >100% groups; 80%∼120% group of rotation center vertical position ratio was the highest; and 90%∼110% group and 110%∼130% group of femoral offset ratio were higher than >130% and 90% groups. Comparison of hip ROM showed that 85%∼100% and 70%∼85% groups of the rotation center horizontal position ratio were higher than 70% and >100% groups; 80%∼120% group of the rotation center vertical position ratio was the highest; and hip ROM from high to low are 90%∼110%, 110%∼130%, >130% and 90% groups of femoral offset ratio. These findings indicated that during the early follow-up period of THA, if the horizontal position of femoral head rotation center was reconstructed in 0.85 to 1 times of healthy side when compared with reconstruction >1 times of the healthy side and if the vertical position of femoral head rotation center was reconstructed in 0.8 to 1.2 times of the healthy side when compared with reconstruction in >1.6 times of the healthy side, better hip function recovery and optimal hip ROM were obtained. The optimal reconstruction range of femoral offset is 0.9 to 1.3 times of the healthy side.

High Hip Center Reduces the Dynamic Hip Range of Motion and Increases the Hip Load: A Gait Analysis Study in Hip Arthroplasty Patients With Unilateral Developmental Dysplasia

BACKGROUND

Long-term favorable clinical outcomes of anatomical or high hip center techniques in total hip arthroplasty (THA) are reported in patients with developmental dysplasia of the hip (DDH). However, there is little information about the effect of the hip center location on gait characteristics. The purpose of this study was to compare these surgical techniques with gait analysis, analyze the effect of the hip rotation center location on gait parameters, and discuss the possible problems that may arise.

METHODS

A total of 40 patients who underwent THA due to unilateral coxarthrosis secondary to Crowe type III-IV DDH and completed 5 years of follow-up were included in the study. Group 1 included 20 patients who underwent anatomical hip center reconstruction, while group 2 included 20 patients who underwent high hip center reconstruction. Gait analysis was performed, and the groups were compared according to the gait characteristics.

RESULTS

The mean temporospatial values were similar between the groups. The extension of the operated side was significantly lower in group 2 (-9.11 ± 8.92) than in group 1 (-1.87 ± 11.51) (P = .04). The mean longitudinal hip joint force was found to be significantly higher in group 2 (8.92 N/kg ± 0.54) than in group 1 (8.16 N/kg ± 0.66) (P = .04). The high hip center technique has been shown to increase the load on the hip and restrict the dynamic range of motion.

CONCLUSION

The high hip center technique can decrease the survival of the implant and increase the fall risk as it increases the load on the hip and reduces the dynamic range of motion. The hip center should be reconstructed anatomically when possible in DDH patients who undergo unilateral THA.

Impact of acetabular reaming depth on reconstruction of rotation center in primary total hip arthroplasty

PURPOSE

To study the impact of acetabular reaming depth on reconstruction of rotation center (RC) in unilateral primary total hip arthroplasty (UPTHA) and guide individualized preoperative design.

METHODS

200 postoperative standard bilateral hip anteroposterior radiographs after UPTHA were included, which were collected from January, 2013 to June, 2017 in our hospital. Osteonecrosis of femoral head was the only diagnosis in this cohort. The parameters were measured on the anteropoterior radiographs by using RadiAnt DICOM viewer.

RESULTS

The average of the thickness of the teardrop is about 6.13 ± 1.42 mm. The parameter a (the difference value of the distance of bilateral RC and midline) was positively correlated with the parameter e (the acetabular reaming depth), and the Pearson correlation coefficient was 0.49 when P = 0.05. Furthermore, the value of parameter (e) was 8.25 mm when a2 (the distance from the center of the prosthesis femoral head to the vertical line across the midpoint of pubic symphysis) equaled a1 (the distance from RC of the healthy femoral head to the vertical line across the midpoint of pubic symphysis).

CONCLUSIONS

The reaming depth of the acetabulum could influence the reconstruction of RC during UPTHA. When the medial margin of the cup was placed about 2 mm to the lateral border of the ipsilateral teardrop (the bottom of the ovum), the rotation center would be accurately restored.

Minimum 10-Year Outcome of One-Stage Total Hip Arthroplasty Without Subtrochanteric Osteotomy Using a Cementless Custom Stem for Crowe III and IV Hip Dislocation

BACKGROUND

Options for total hip arthroplasty (THA) in high dislocated hips include subtrochanteric osteotomy (STO), high hip center positioning, and 2-stage surgery with progressive lowering using an external fixator before THA. We described the long-term results of 1-stage THA performed without STO, using a cementless customized stem associated if necessary with sequential tenotomies and/or greater trochanteric osteotomy.

METHODS

Ninety-eight consecutive THA without STO were performed using this technique. Of those 98 hips, 26 hips with high dislocation (12 class III and 14 class IV according to the Crowe classification) were evaluated at an average follow-up of 16 (10-22) years.

RESULTS

At the time of last follow-up, the mean Harris Hip Score was 86 points (37-100). The mean leg-length discrepancy was 7 ± 5 mm (0-17). Two transient (7.7%) nerve palsies (1 sciatic and 1 femoral) were notified. A revision was required for 6 hips (23.1%). Kaplan-Meier survivorship analysis at 15 years regarding aseptic loosening of the femoral component was 87.5% (95% confidence interval, 76.5-99.1). During the same period, acetabular implant survivorship free from revision for aseptic loosening was 96.1% (95% confidence interval, 92.7-99.9).

CONCLUSION

The combination of intramedullary fit and extramedullary adaptation for offset and anteversion provided by the custom stem can avoid additional procedures associated to THA in high developmental dysplasia of the hip. The clinical function and long-term survival reported in this series is encouraging for THA performed in case of high hip dislocation.

Acetabular Cup Revision Arthroplasty Using Morselized Impaction Allograft

The rate of acetabular cup revision arthroplasty is gradually rising along with an increased risk of osteolysis and prosthesis loosening over time and an increase in life expectancy. The goals of revision total hip arthroplasty are: i) implant stability through reconstruction of large bone defects, ii) restoration of range of motion and biomechanics of the hip joint, and iii) normalization of uneven limb lengths. In acetabular cup revision arthroplasty, stable fixation of acetabular components is difficult in the presence of severe bone loss (e.g., evidence suggests that it is challenging to achieve satisfactory results in cases of Paprosky type 3 or higher bone defects using conventional techniques). The author of this study performed acetabular revision to manage patients with large areas of defective bones by filling in with morselized impaction allografts. These allografts were irradiated frozen-stored femoral heads acquired from a tissue bank, and were applied to areas of an acetabular bone defect followed by insertion of a cementless cup. When this procedure was insufficient to obtain primary fixation, a tri-cortical or structural allograft using a femoral head was carried out. Structural stability and bone incorporation were confirmed via long-term follow-up. This study aims to review conventional surgical techniques and verify the utility of surgical procedures by analyzing the author's surgical methods and discussing case reports.

The Acetabular Fossa May Not Be Located at the True Center of the Acetabulum: A Detailed Analysis Using Preoperative CT Images

BACKGROUND

The acetabular fossa is thought to be located in the center of the acetabulum, and acetabular reaming in total hip arthroplasty is conventionally performed in the center of the fossa. However, the actual location of the fossa and the influence that hypoplasia or deformity may have on the position of the fossa are unknown. We hypothesized that the fossa is located in the center of the acetabulum, regardless of hypoplasia or deformity.

METHODS

Fifty patients with normal hips (normal hip group), 50 patients with dysplasia who underwent rotational acetabular osteotomy (dysplastic hip group), and 46 patients with osteoarthritis who underwent total hip arthroplasty (osteoarthritic hip group) were evaluated by computed tomography (CT) imaging. On the horizontal plane that passes through the center of the femoral head, the center line of the acetabulum was defined as the perpendicular bisector of the anterior and posterior rims of the acetabulum. The angle and distance of the center of the acetabular fossa in relation to the center line of the acetabulum were evaluated; furthermore, the center position of the fossa from the anterior margin of the acetabulum was calculated as a ratio relative to acetabular size. A 1-way analysis of variance was performed to compare measurements among the 3 groups.

RESULTS

The center of the acetabular fossa was positioned anteriorly to the center line of the acetabulum in all 3 groups. The mean center angle of the acetabular fossa was 14.0° ± 3.8°, 15.2° ± 5.6°, and 14.9° ± 5.5° in the normal, dysplastic, and osteoarthritic hip groups, respectively (p = 0.33). The mean center distance of the acetabular fossa was 5.6 ± 1.8, 5.8 ± 2.3, and 6.1 ± 2.2 mm, respectively (p = 0.55). The mean center position of the acetabular fossa was 38.8% ± 3.3%, 38.5% ± 4.2%, and 38.3% ± 3.9%, respectively (p = 0.71).

CONCLUSIONS

The center of the acetabular fossa is positioned anteriorly to the center of the acetabulum, and the positioning is affected by neither dysplasia nor osteoarthritis. The preconception that the center of the acetabulum corresponds to the center of the acetabular fossa may risk eccentric reaming, possibly damaging the anterior wall.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Shortening subtrochanteric osteotomy and cup placement at true acetabulum in total hip arthroplasty of Crowe III-IV developmental dysplasia: results of midterm follow-up

Introduction

The anatomic abnormalities in developmental dysplasia of hip (DDH) often make total hip replacement (THR) inevitable at a younger age. However, there is no universal gold standard technique of THR for high dislocated dysplastic hips.

Materials and methods

Here we present the outcomes of midterm follow-up after THR in patients diagnosed with DDH Crowe type III and IV hospitalized in a tertiary center in Iran for whom placement of a cup in true acetabulum and selective transverse subtrochanteric osteotomy was performed. Pre- and postoperative Harris Hip Score, leg length discrepancy and postoperative complications were evaluated.

Results

A total of 48 patients with DDH Crowe type III and IV (uni- or bilateral which made 52 hips) were studied. Mean age of patients was 41 years with minimum follow-up ranging from 12 months to 3 years. Mean Harris Hip Score significantly improved from 41.70 preoperatively to 88.1 at last follow-up postoperatively. Leg length discrepancy of less than 2 cm was observed which was well tolerated using shoe lifts. Regarding postoperative complications, two patients had transient peroneal nerve palsy in early postoperative period which recovered within 2 months. No other major complication was encountered.

Conclusion

THR in patients with DDH (Crowe III and IV) with a cup positioned in true acetabulum and transverse subtrochanteric osteotomy is a safe successful procedure.

Electronic supplementary material

The online version of this article (10.1007/s00590-017-2076-8) contains supplementary material, which is available to authorized users.

The mechanical effects of cup inclination and anteversion angle on the bearing surface

BACKGROUND

Regarding the cup setting in total hip arthroplasty, range of motion and prevention of dislocation are important. From past reports, the wear of the bearing surface may affect long-term results. This study evaluated the stress applied to the bearing surface by the combined use of the three-dimensional rigid spring model and the finite-element analysis.

METHODS

For contact pressure distribution of the bearing surface, interference analysis was performed using a three-dimensional rigid body spring model. Furthermore, stress was applied to the inner surface of the cup installed in the bone so that the same stress distribution obtained from the interference analysis was achieved. The finite-element analysis was then performed at each condition, which changed the inclination and anteversion angles of the cup to examine the relationship of maximum equivalent stress.

RESULTS AND DISCUSSION

The maximum equivalent stresses on the bearing surface under the condition with fixation of an anteversion angle of 0° were 0.78, 0.85, and 1.15 MPa at inclination angles of 25°, 40°, and 55°, respectively. The stress value at 55° was approximately 1.5 times greater than that at 25°. The maximum equivalent stresses on the bearing surface under the condition with fixation of an inclination angle of 40° were 0.85, 0.9, and 1.02 MPa at anteversion angles of 0°, 15°, and 30°, respectively. The stress value at 30° was approximately 1.2 times greater than that at 0°. This study suggests that large inclination and anteversion angles may enhance the stress on the bearing surface and affect long-term results.

Restoration of the centre of rotation in primary total hip arthroplasty: the influence of acetabular floor depth and reaming technique

AIMS

One goal of total hip arthroplasty is to restore normal hip anatomy. The aim of this study was to compare displacement of the centre of rotation (COR) using a standard reaming technique with a technique in which the acetabulum was reamed immediately peripherally and referenced off the rim.

PATIENTS AND METHODS

In the first cohort the acetabulum was reamed to the floor followed by sequentially larger reamers. In the second cohort the acetabulum was only reamed peripherally, starting with a reamer the same size as the native femoral head. Anteroposterior pelvic radiographs were analysed for acetabular floor depth and vertical and horizontal position of the COR.

RESULTS

Horizontally, the mean medial displacement of the COR was 0.8 mm (standard deviation (sd) 1.4) in the peripheral remaing group and 5.0 mm (sd 3.30) in the standard reaming group (p < 0.001). Vertically, the mean superior displacement of the COR was 0.7 mm (sd 1.3) in the peripheral reaming group and 3.7 mm (sd 2.6) in the standard reaming group (p < 0.001). In the standard reaming group, there was a strong correlation between the pre-operative acetabular floor depth and displacement of the COR (p < 0.001).

CONCLUSION

Reaming the acetabulum to the floor can lead to significant displacement of the COR medially and superiorly. This displacement is related to the pre-operative acetabular floor depth and cannot always be compensated by using a high offset stem. Cite this article: Bone Joint J 2016;98-B:1597-603.

The necessity to restore the anatomic hip centre in congenital hip disease

Total hip replacement (THR) is the treatment of choice for the patient suffering from end-stage hip osteoarthritis. In the presence of deformities due to congenital hip disease (CHD), THR is, in most of the cases, a difficult task, since the technique of performing such an operation is demanding and the results could vary. We present our experience and preferred strategies focusing on challenges and surgical techniques associated with reconstructing the dysplastic hip.

Does High Hip Center Decrease Range of Motion in Total Hip Arthroplasty? A Computer Simulation Study

BACKGROUND

High placement of a cementless acetabular cup is often required to have sufficient bone coverage in hip dysplasia. We examined whether a high hip center decreases the postoperative range of motion (ROM) in total hip arthroplasty.

METHODS

Using a computer software, ROM and bone coverage were examined in 32 patients with unilateral osteoarthritis of the hip with Crowe type II or III hip dysplasia. The cup was placed at the anatomic hip center and moved vertically in 5-mm increments. Vertical center of rotation (V-COR) was defined as the distance from the head center to the interteardrop line. The required ROM was defined as flexion  ≥110°, internal rotation (IR) at 90° flexion ≥30°, extension ≥30°, and external rotation ≥30°. We determined the V-COR to satisfy the required ROM and cup center-edge angle (Cup-CE) ≥0°.

RESULTS

Only 40.6% of the patients satisfied Cup-CE ≥0° at the anatomic hip center. Bone coverage increased with the peak at 30, 35 mm of V-COR (90.6% satisfied Cup-CE ≥0°) and decreased at ≥40 mm. Higher V-COR resulted in lower range of flexion and IR, but increased the range of extension and external rotation. The cutoff value from the receiver-operating characteristic curve for both flexion and IR was a V-COR of 35 mm.

CONCLUSION

The higher hip center gained more bone coverage but decreased the range of hip flexion and IR. Acceptable V-COR in hip dysplasia was around 35 mm, about 20 mm above the true hip center, in terms of ROM.

A radiological study of the true anatomical position of the acetabulum in Japanese women

There is sometimes uncertainty concerning the correct socket position prior to total hip arthroplasty (THA). We conducted a study to determine the hip centre in Japanese women in order to define the true anatomical position of the acetabulum. The study involved 200 consecutive female patients in whom the contralateral hip joint was normal or was prearthritic and who underwent unilateral THA. The 'normal' group comprised 100 hip joints with no acetabular hip dysplasia, and the prearthritis group comprised 100 hip joints with Crowe type I dysplasia. The length of a perpendicular line drawn under the teardrop (interteardrop line) connecting both inferior edges of the teardrop with the centre of the femoral head was recorded as the vertical distance, and the distance from the intersection of the perpendicular line and interteardrop line up to the teardrop was recorded as the horizontal distance. We measured these distances on the femoral head of the side that did not undergo THA. The mean vertical distances in the 'normal' and prearthritis groups were 14.6 ± 2.8 mm and 16.8 ± 2.7 mm, respectively, and the mean horizontal distances were 30.2 ± 2.8 mm and 32.5 ± 2.7 mm, respectively. We therefore determined the mean centre of the hips to lie at a vertical distance of 11 to 22 mm and a horizontal distance of 27 to 38 mm. These values can serve as a useful index for socket positioning in THA.

Cementless Total Hip Arthroplasty With a High Hip Center for Hartofilakidis Type B Developmental Dysplasia of the Hip: Results of Midterm Follow-Up

BACKGROUND

Acetabular reconstruction in adults with Hartofilakidis type B developmental dysplasia of the hip is a major technical challenge. The purpose of this retrospective study was to evaluate hip function and radiographic outcomes regarding high hip center at midterm follow-up.

METHODS

From January 1, 2007 to December 31, 2009, 37 patients who had Hartofilakidis type B developmental dysplasia of the hip underwent a primary total hip arthroplasty using a high hip center technique. Functional, radiographic, and survivorship outcomes were evaluated.

RESULTS

Of the 37 patients, 31 patients (83.8%) were available for the mean follow-up of 6.1 years (range, 1.5-7.6 years). Thirty-one cementless cups were located at an average vertical distance of 38.1 ± 3.3 mm and at a mean horizontal distance of 35.5 ± 3.4 mm. The mean ratio of the height of the hip center was 2.4% (range, 2.0%-2.9%). The Harris Hip Scores were improved from 50.3 points (range, 38-63 points) preoperatively to 92.3 points (range, 85-100 points) at the final follow-up (P < .001). Four patients continued to present with Trendelenburg gait pattern at the last follow-up. With use of revision for any reason and aseptic loosening as the end point, the 5-year survival rates were 90.3% (95% CI, 79.9%-100%) and 93.3% (95% CI, 84.3%-100%), respectively.

CONCLUSIONS

The high hip center technique in conjunction with a cementless acetabular component seems to be a valuable alternative to achieve satisfactory midterm outcomes for Hartofilakidis type B developmental dysplasia of the hip.

Importance of maintaining the basic stress pathway above the acetabular dome during acetabular reconstruction

The basic stress pathway above the acetabular dome is important for the maintenance of implant stability in press-fit acetabular reconstruction of total hip arthroplasty. However, information on the basic stress pathway and its impact factors remains unclear. The objective of this study was to investigate the effects of the orientations and positions of the acetabular component on the basic stress pathway. The basic stress pathway above the acetabular dome was defined as two parts: 3D basic trabecular bone stress distribution and quantified basic cortical bone stress level, using two subject-specific finite element normal hip models. The effects were then analysed by generating 32 reconstructed acetabular cases with different cup abduction and anteversion angles within a range of 35-50° and 10-25°, respectively, and 12 cases with different hip centre heights within a range of 0-15 mm above the acetabular dome. The 3D trabecular stress distribution decreased remarkably in all cases, while the 80% of the basic cortical bone stress level was maintained in cases when the acetabular component was positioned at 10° or 15° anteversion and 40° or 45° abduction angles. The basic stress pathway above the acetabular dome was disturbed when the superior displacement of the hip centre exceeded 5 mm above the anatomical hip centre. Positioning the acetabular component correctly contributes to maintain the stress balance between the acetabular cup and the bone during acetabular reconstruction, thus helping restore the normal hip biomechanics and preserve the stability of the implants.

Reliability of measures used in radiographic evaluation of the adult hip

OBJECTIVE

The reliability of radiographic measurements has been studied in pediatric hips, but less has been published on the adult hip, and none have examined the reliability of measurements for the location of the center of rotation (COR) of the hip joint. We have investigated the reliability of various radiographic variables with a focus on the COR.

MATERIALS AND METHODS

The study was carried out on a standardized format for anterior-posterior radiographs of the pelvis. The measured variables were; (A) the distance from a sagittal reference line to the COR, (B) the distance from the sagittal reference line to the proximal end of the lateral cortical line of the femur, (C) the distance from the sagittal reference line to the medial rim of the acetabulum, (D) the distance from the horizontal reference line to the roof of the acetabulum, and (E) the distance from the horizontal reference line to the COR. One observer (JAB) conducted the measurements twice separated by a time interval of 45-60 days to assess intra-observer reliability, and the first measurements of JAB were compared to those performed by another observer (OR) to assess inter-observer reliability.

RESULTS

Intraclass correlation coefficients were above 0.98 for all measurements, and the minimum and maximum values that statistically include 95% of the observer differences were all within -3 to +3 mm.

CONCLUSIONS

These measurements proved to have high reliability and agreement of both within the same observer and between two observers. They should therefore be reproducible in a clinical setting.

The accuracy of positioning of a custom-made implant within a large acetabular defect at revision arthroplasty of the hip

We evaluated the accuracy with which a custom-made acetabular component could be positioned at revision arthroplasty of the hip in patients with a Paprosky type 3 acetabular defect.

A total of 16 patients with a Paprosky type 3 defect underwent revision surgery using a custom-made trabecular titanium implant. There were four men and 12 women with a median age of 67 years (48 to 79). The planned inclination (INCL), anteversion (AV), rotation and centre of rotation (COR) of the implant were compared with the post-operative position using CT scans.

A total of seven implants were malpositioned in one or more parameters: one with respect to INCL, three with respect to AV, four with respect to rotation and five with respect to the COR.

To the best of our knowledge, this is the first study in which CT data acquired for the pre-operative planning of a custom-made revision acetabular implant have been compared with CT data on the post-operative position. The results are encouraging.

Cite this article: Bone Joint J 2015; 97-B:780–5.

Mid-term clinical and radiographic outcomes of porous tantalum modular acetabular components for hip dysplasia

It is still challenging to perform successful cementless cup fixation during total hip arthroplasty for hip dysplasia. In this multicenter study we evaluated the clinical results of porous tantalum modular acetabular cups (TM cups) in 45 dysplastic hips with a mean follow-up period of 9.8 years. The mean Japanese Orthopaedic Association hip score improved from 48.2 preoperatively to 92.1 at the most recent follow-up. All of the cups were radiographically stable with no evidence of progressive radiolucencies or osteolysis regardless of bone grafting. Sixteen hips with bone grafts showed the integration of grafted bone without any radiolucencies. There were no revisions of TM cups. The use of TM cups for dysplastic hips provided satisfactory 10-year clinical and radiographic results.

Does rotational acetabular osteotomy affect subsequent total hip arthroplasty?

INTRODUCTION

Rotational acetabular osteotomy (RAO) has been used successfully in patients with developmental dysplasia of the hip (DDH). However, some patients are forced to undergo total hip arthroplasty (THA) because of the progression of osteoarthritis. We evaluated the effect of previous RAO on the outcome of THA performed for degenerative arthritis secondary to DDH, comparing outcomes for patients with THA and prior RAO versus outcomes for patients with THA and no prior RAO.

MATERIALS AND METHODS

At an average follow-up point of 8.2 years (range 7-11 years), we compared outcomes in dysplastic hips for 22 hips (group R) in patients who underwent THA after successful RAO with outcomes for a well-matched control group of 30 hips in patients who underwent primary THA (group C) during the same period.

RESULTS

Both groups had similar midterm results. No acetabular or femoral components exhibited loosening or revision in either group. Harris hip scores (HHSs) at the most recent follow-up had not been compromised by RAO, and there were no significant differences in intraoperative blood loss and operative time between the two groups. Although there was a tendency toward superolateral placement of the acetabular component in group R, there were no significant differences in the mean steady-state linear and volumetric wear rates between the two groups. There were no infections, dislocations, intraoperative fractures, damaged nerves, or deep vein thromboses in either group.

CONCLUSIONS

Our midterm results demonstrated that RAO does not lead to higher revision rates, compromised HHSs, or shortened survivorship in eventual THA for DDH.

Total hip arthroplasty after rotational acetabular osteotomy

In this study, we aimed to determine whether the outcomes of total hip arthroplasty (THA) after rotational acetabular osteotomy (RAO) are equal to those of primary THA, and to elucidate the characteristics of THA after RAO. The clinical and radiographic findings of THA after RAO (44 hips), with minimum 24 months of follow-up, were compared with a matched control group of 58 hips without prior RAO. We found that the outcomes in terms of functional scores and complication rates did not differ between THA after RAO and THA without previous pelvic osteotomy, indicating that the results of THA after RAO are equivalent to those of primary THA. Although THA after RAO requires technical considerations, similar clinical outcomes to primary THA can be expected.

Radiographic analysis of the restoration of hip joint center following open reduction and internal fixation of acetabular fractures: a retrospective cohort study

BACKGROUND

Unfavorable reduction is considered one of the key factors leading to joint degeneration and compromised clinical outcome in acetabular fracture patients. Besides the columns, walls, and superior dome, the postoperative position of hip joint center (HJC), which is reported to affect hip biomechanics, should be considered during the assessment of quality of reduction. We aimed to evaluate the radiographic restoration of HJC in acetabular fractures treated with open reduction and internal fixation.

METHODS

Patients with a displaced acetabular fracture that received open reduction and internal fixation in the authors' institution during the past five years were identified from the trauma database. The horizontal and vertical shifts of HJC were measured in the standard anteroposterior view radiographs taken postoperatively. The radiographic quality of fracture reduction was graded according to Matta's criteria. The relationships between the shift of HJC and the other variables were evaluated.

RESULTS

Totally 127 patients with 56 elementary and 71 associated-type acetabular fractures were included, wherein the majority showed a medial (89.0%) and proximal (93.7%) shift of HJC postoperatively. An average of 2.8 mm horizontal and 2.2 mm vertical shift of HJC were observed, which correlated significantly with the quality of fracture reduction (P < 0.001 for both). The horizontal shift of HJC correlated with the fracture type (P = 0.022).

CONCLUSIONS

The restoration of HJC correlates with the quality of reduction in acetabular fractures following open reduction and internal fixation. Further studies are required to address the effects of HJC shift on the biomechanical changes and clinical outcomes of hip joint, especially in poorly reduced acetabular fractures.

Effect of high hip center on stress for dysplastic hip

High hip center reconstruction has been advocated in treating deficient acetabulum. However, there is no consensus on the clinical outcome of this technique. In addition, it remains unclear to what extend this technique restores the normal hip biomechanics. The goal of this study was to investigate stress above the acetabular dome in response to a range of high hip center positioning for Crowe type I and II hip dysplasia. This study consisted of 2 main parts, radiologic and biomechanical. Pelvic radiographs of 18 patients were studied to determine the amount of displacement of the hip center in the superior direction compared with the normal side. Second, qualitative and quantitative changes in stress on cortical and trabecular bone in the region of the acetabular dome as a result of superior displacement of the hip center were analyzed with subject-specific finite element models. The results showed that the range of the hip center position in the superior direction for Crowe type I and II hip dysplasia was 0 to 15 mm above the contralateral femoral head center. When superior displacement of the hip center exceeded 5 mm above the anatomic hip center, cortical bone mass on the 2 thickest cross-sections above the acetabular dome decreased quickly and the stress value on posterolateral cortical bone was obviously lower than the normal level. This study showed that to restore the normal load above the acetabular dome, there is a limit of 5 mm above the anatomic hip center for high hip center acetabular reconstruction for Crowe type I and II hip dysplasia.

Does total hip arthroplasty restore native hip anatomy? three-dimensional reconstruction analysis

PURPOSE

Component orientations and positions in total hip arthroplasty (THA) are important parameters in restoring hip function. However, measurements using plain radiographs and 2D computed tomography (CT) slices are affected by patient position during imaging. This study used 3D CT to determine whether contemporary THA restores native hip geometry.

METHODS

Fourteen patients with unilateral THA underwent CT scan for 3D hip reconstruction. Hip models of the nonoperated side were mirrored with the implanted side to quantify the differences in hip geometry between sides.

RESULTS

The study demonstrated that combined hip anteversion (sum of acetabular and femoral anteversion) and vertical hip offset significantly increased by 25.3° ± 29.3° (range, -25.7° to 55.9°, p = 0.003) and 4.1 ± 4.7 mm (range, -7.1 to 9.8 mm, p = 0.009) in THAs.

CONCLUSIONS

These data suggest that hip anatomy is not fully restored following THA compared with the contralateral native hip.

How far above the true anatomic position can the acetabular cup be placed in total hip arthroplasty?

INTRODUCTION

There is controversy about which is more suitable for determining correct socket position in patients with severe bone deficiency of the acetabular roof because of developmental dysplasia of the hip (DDH): the anatomic centre of hip rotation or a high centre. 


METHOD

We evaluated the relationship, in 200 hips, between the centre of rotation and presence of the Trendelenburg sign to determine the upper limit of cup position from the standpoint of hip-abductor strength. 


RESULTS

Of the 200 hips, 20 (10%) showed a positive Trendelenburg sign. There were no statistically significant differences between parameters (the centre of rotation, femoral offset, abductor lever arm) regarding the presence of the Trendelenburg sign except for age at surgery. Patients with a positive Trendelenburg sign were significantly older (64.1 ± 9.4 years) than those with a negative Trendelenburg sign (58.8 ± 7.7 years) (P = 0.01).


CONCLUSIONS

Our findings indicate that a high centre of hip rotation of up to approximately 30 mm from the inter-teardrop line is a feasible option for patients with DDH from the standpoint of hip-abductor strength if stems are used that allow the restoration of femoral offset and the abductor lever arm.

Does hip implant positioning affect the peak external adduction moments of the healthy knees of subjects with total hip replacements?

After unilateral total hip replacement (THR) for hip osteoarthritis (OA), knee OA incidence or progression is common. The contralateral knee is at particular risk, and some have speculated that abnormal THR-hip biomechanics contributes to this asymmetry. We investigated the relationships between operated-hip joint geometry or gait variables and the peak external knee adduction moments-an indicator of knee OA risk-in 21 subjects with unilateral THRs. We found that the peak adduction moment was 14% higher on the contralateral versus the ipsilateral knee (p = 0.131). The best predictors of ipsilateral knee adduction moments were superior-inferior joint center position and operated-hip peak adduction moment (adj R(2)  = 0.291, p = 0.017). The sole predictor of the contralateral knee adduction moment was the medial-lateral hip center position (adj R(2)  = 0.266, p = 0.010). A postoperative medial shift of the hip center was significantly correlated with a lower postoperative contralateral/ipsilateral knee adduction moment ratio (R = 0.462, p = 0.035). Based on these relationships, we concluded that implant positioning could influence the biomechanical risk of knee OA progression after THR. Although implant positioning decisions are necessarily driven by other factors, it may be appropriate to assess individual THR candidate's knee OA risk and adjust perioperative management accordingly.

Displacement of the hip center of rotation after arthroplasty of Crowe III and IV dysplasia: a radiological and biomechanical study

To study the direction and biomechanical consequences of hip center of rotation (HCOR) migration in Crowe type III and VI hips after total hip arthroplasty, post-operative radiographs and CT scans of several unilaterally affected hips were evaluated. Using a three-dimensional model of the human hip, the HCOR was moved in all directions, and joint reaction force (JRF) and abductor muscle force (AMF) were calculated for single-leg stance configuration. Comparing to the normal side, HCOR had displaced medially and inferiorly by an average of 23.4% and 20.8%, respectively, of the normal femoral head diameter. Significant decreases in JRF (13%) and AMF (46.13%) were observed in a presumptive case with that amount of displacement. Isolated inferior displacement had a small, increasing effect on these forces. In Crowe type III and IV hips, the HCOR migrates inferiorly and medially after THA, resulting in a decrease in JRF, AMF, and abductor muscle contraction force.

Primary total hip arthroplasty with a spongy metal surface acetabular component for hip dysplasia

We evaluated the clinical and radiographic results of primary total hip arthroplasty for 81 dysplastic hips (71 patients) using cementless Spongiosa Metal II cups (ESKA Implants, Lübeck, Germany). The mean follow-up period was 6.4 years (minimum 5 years), and the preoperative mean Japanese Orthopaedic Association hip score had improved from 45.2 to 87.4 points at the latest follow-up. The radiographic outcome was no aseptic loosening in all 81 hips. The hip center was located significantly more superior than in the contralateral normal hip in 45 patients, but the difference was less than 10 mm; however, there was no significant difference in the lateral position of the hip center. The use of a Spongiosa Metal II cup for dysplastic hips provided satisfactory 5- to 10-year clinical and radiographic results.

Cross-sectional anatomy of the ilium: implications for acetabular component placement in total hip arthroplasty

BACKGROUND

High hip center reconstructions, used in revision and complex primary THAs, rely on pelvic bone stock at least 35 mm above the anatomic teardrop. However, the technique does not restore normal hip biomechanics and controversy exists regarding acetabular implant survival. Previous reports document a wide range of implant positioning above the teardrop. There is no anatomic guidance in the literature regarding the amount of bone stock available for initial implant stability in this area of the ilium.

QUESTIONS/PURPOSES

We therefore determined the thickness of the human ilium and related it to acetabulum cup coverage in high hip center reconstructions.

METHODS

We sectioned 16 cadaveric hips from the anterior superior iliac spine to the anatomic teardrop in 5-mm increments, then measured the thickness of the ilium for each cross section.

RESULTS

The maximum thickness of 42 ± 9 mm occurred at the dome of the acetabulum 35 ± 3 mm above the teardrop. At a distance of 1 cm above the dome, the ilium was reduced by 24%, to 32 ± 6 mm. At 2 cm above the dome, the ilium thickness was 22 ± 4 mm, a 48% reduction from its maximum.

CONCLUSION

There are substantial anatomic limitations to high hip reconstructions 2 cm above the acetabular dome.

Total hip arthroplasty for adult hip dysplasia

Preoperative planning is essential to define anatomy, clarify the operative approach and exposure, and ensure that suitable implants are available.Concerns exist regarding the long-term effectiveness and safety of hip resurfacing arthroplasty for the young dysplastic hip.In light of current evidence, concerns exist regarding the use of metal-on-metal articulations for hip arthroplasty in the young dysplastic hip.The ideal bearing surface is not known, although the longest data available support the use of metal-on-polyethylene.

Investigation into three dimensional hip anatomy in anterior dislocation after THA. Influence of the position of the hip rotation centre

BACKGROUND

The components position is a major factor under the surgeon's control in determining the risk of dislocation post total hip arthroplasty. The aim of this study was to investigate the proper three-dimensional components position including the centre of rotation in the case of anterior dislocation.

METHODS

Among 1764 consecutive patients who underwent total hip arthroplasty using a direct anterior approach, 27 experienced anterior dislocation. The three-dimensional hip anatomy was investigated in 12 patients who were paired with 12 patients from the same initial cohort who did not experience dislocation and also with 36 control patients with osteoarthritis. A pelvic Cartesian referential was defined to perform the acetabular analysis. The coordinates were expressed as percentages of the pelvic width, height and depth. The anteversion angles were measured.

FINDINGS

The hip centre of rotation was significantly shifted medially and posteriorly in the dislocation group when compared to the non-dislocation group and also to the control group. There was no significant difference in component angular position between the dislocation-group and the non-dislocation group. However, the stem anteversion in the dislocation group was increased in comparison to the mean natural femoral anteversion of the control group.

INTERPRETATION

A medial and posterior displacement of the hip rotation centre was found to correlate to anterior dislocation post total hip arthoplasty. These results suggest the importance of an accurate restoration of the centre of rotation, whilst avoiding an excessive acetabular reaming which may induce a medial and a posterior displacement.

LEVEL OF EVIDENCE

III comparative non randomised.

Fixation method does not affect restoration of rotation center in hip replacements: a single-site retrospective study

BACKGROUND

Aseptic loosening is one of the greatest problems in hip replacement surgery. The rotation center of the hip is believed to influence the longevity of fixation. The aim of this study was to compare the influence of cemented and cementless cup fixation techniques on the position of the center of rotation because cemented cup fixation requires the removal of more bone for solid fixation than the cementless technique.

METHODS

We retrospectively compared pre- and post-operative positions of the hip rotation center in 25 and 68 patients who underwent artificial hip replacements in our department in 2007 using cemented or cementless cup fixation, respectively, with digital radiographic image analysis.

RESULTS

The mean horizontal and vertical distances between the rotation center and the acetabular teardrop were compared in radiographic images taken pre- and post-operatively. The mean horizontal difference was -2.63 mm (range: -11.00 mm to 10.46 mm, standard deviation 4.23 mm) for patients who underwent cementless fixation, and -2.84 mm (range: -10.87 to 5.30 mm, standard deviation 4.59 mm) for patients who underwent cemented fixation. The mean vertical difference was 0.60 mm (range: -20.15 mm to 10.00 mm, standard deviation 3.93 mm) and 0.41 mm (range: -9.26 mm to 6.54 mm, standard deviation 3.58 mm) for the cementless and cemented fixation groups, respectively. The two fixation techniques had no significant difference on the position of the hip rotation center in the 93 patients in this study.

CONCLUSIONS

The hip rotation center was similarly restored using either the cemented or cementless fixation techniques in this patient cohort, indicating that the fixation technique itself does not interfere with the position of the center of rotation. To completely answer this question further studies with more patients are needed.

The results of a press-fit-only technique for acetabular fixation in hip dysplasia

The purpose of the present study was to evaluate the 6- to 11-year follow-up results of hemispherical porous-coated cups implanted into dysplastic hips using press-fit technique without screws focusing on the amount of host bone coverage. There were 87 patients who underwent 98 primary total hip arthroplasties. Bony coverage was measured as the angle between the vertical line and the line drawn from the cup center to the lateral edge of the acetabulum, which was named the cup center-edge angle (cup-CE angle). All 98 cups were judged to be bone ingrown. The minimum cup-CE angle was 8.4° (mean, 26.3°). Bone-cup contact of more than 8.4° of the cup-CE angle was large enough for press-fit cups to resist superior directed loads during this follow-up period.

The use of fibre-based demineralised bone matrix in major acetabular reconstruction: surgical technique and preliminary results

Acetabular osteolysis associated with socket loosening is one of the main long-term complications of total hip arthroplasty. In case of major bone loss, where <50% host bone coverage can be obtained with a porous-coated cementless cup, it is generally agreed that a metal ring or cage in association with a cemented component and allograft bone should be used. In order to promote allograft bone consolidation and incorporation, we have associated demineralised bone matrix (DBM, Grafton® A Flex) to the construct ion. Here we describe the technical details of major acetabular reconstruction using the Kerboull acetabular reinforcement device with allograft bone and DBM. This device has a hook that must be placed under the teardrop of the acetabulum and a plate for iliac fixation. The main advantages of this device are help in restoring the normal centre of hip rotation, guiding the reconstruction and partially unloading the graft. The Kerboull acetabular reinforcement device has provided a 92% survival rate free of loosening at 13-year follow-up in a consecutive series of 60 type III and IV deficiencies. Our preliminary results using DBM indicate faster allograft consolidation and remodelling.

High hip center technique using a biconical threaded Zweymüller cup in osteoarthritis secondary to congenital hip disease

BACKGROUND

The high hip center technique used for a deficient acetabulum is reconstruction of the hip at a high center of rotation. In the literature, there is no consensus regarding the value of this technique.

QUESTIONS/PURPOSES

We investigated whether the new-generation biconical threaded Zweymüller cup fixed in a high nonanatomic position in patients with arthritis secondary to congenital hip disease experienced different rates of polyethylene wear and long-term survivorship when compared with anatomically positioned cups.

PATIENTS AND METHODS

We studied the polyethylene wear rate and Kaplan-Meier survivorship of 104 titanium threaded Zweymüller cups in 88 patients (81 females), placed in 70 hips at near-normal hip center and in 34 hips at a high hip center position at a distance of 31.1 to 60 mm (mean, 39.7 mm) from the interteardrop line. Minimum followup was 2 years (mean +/- SD, 8.6 +/- 3.5 years; range, 2-15 years).

RESULTS

The mean linear polyethylene wear rates in the near-normal and high hip center groups were not different (0.110 +/- 0.050 mm and 0.113 +/- 0.057 mm, respectively). The Kaplan-Meier 15-year cup survivorship rates with revision for any reason as an event of interest in the near-normal and high hip center groups also were not different (97.2% [95% confidence interval, 88.5%-99.3%] and 97.1% [95% confidence interval, 73.8%-99.3%], respectively).

CONCLUSIONS

The high hip center technique using a biconical threaded Zweymüller cup in patients with arthritis secondary to congenital hip disease results in a polyethylene wear rate and long-term cup survivorship comparable to those observed in anatomically positioned cups.

LEVEL OF EVIDENCE

Level III, therapeutic study. See the Guidelines for Authors for a complete description of level of evidence.

Factors affecting bony impingement in hip arthroplasty

Computer modeling of 10 patients' computed tomographic scans was used to study the variables affecting hip arthroplasty range of motion before bony impingement (ROMBI) including acetabular offset and height, femoral offset, height and anteversion, and osteophyte removal. The ROMBI was compared with the ROM before component impingement and the native hip ROM. The ROMBI decreased with decreased total offset and limb shortening. Acetabular offset and height had a greater effect on ROMBI than femoral offset and height. The ROMBI lost with decreased acetabular offset was not fully recoverable with an increase in femoral offset or osteophyte removal. Bony impingement increased and component impingement decreased with decreased acetabular offset and increased head diameter.

Relative importance of gait vs. joint positioning on hip contact forces after total hip replacement

Implant loosening is a common indication for total hip replacement (THR) revision. High contact forces and implant twisting moments are thought to be associated with implant loosening. Relationships between joint positioning and hip forces, or outcomes, have been investigated through in vivo and in vitro modalities. Relationships between hip forces and gait are less understood, despite repeated findings that gait following a THR does not fully return to normal. We tested the hypothesis that gait parameters would be better predictors of implant force (peak contact forces and peak twisting moment during walking) than joint positioning parameters. Subjects underwent gait analysis, hip force modeling, and measurement of clinical radiographs 1 year after successful THR surgery. Gait parameters were consistently more influential in determining hip forces. Alone, gait explained as much as 67% of the variation in force, compared to a maximum of 33% by joint geometry. Combinations of gait and joint positioning parameters together explained up to 86% of the variation in hip force parameters. Results suggest that gait may provide a valuable postoperatively modifiable target to improve hip loads and potentially reduce the risk for implant loosening.

The effect of elbow joint centre displacement on force generation and neural excitation

Joint centre displacement may occur following total elbow replacement due to aseptic loosening or surgical misalignment, and has been linked to implant failure. In this study, the effects of joint centre displacement were examined using a neuromusculoskeletal model of the elbow joint. Isometric contractions were simulated at a range of joint angles during elbow flexion and extension. Displacement of the joint centre affected the force-generating capacity about the joint, due to changes in both muscle lengths and moment arms. The magnitude and direction of the maximum joint reaction force were also altered, potentially contributing to aseptic loosening and compromising joint stability. The relationship between force generated and the level of neural excitation to the elbow flexor and extensor muscles was also affected, suggesting that altered neural control patterns could be required following joint centre displacement.