Evaluation of the hip center in total hip arthroplasty for old developmental dysplasia

Medium- to long-term clinical efficacy of total hip arthroplasty with structural bone grafting for dysplasia of the hip

BACKGROUND

Patients with dysplasia of the hip (DDH) have different degrees of bone defects above and outside the acetabulum, and anatomically reconstructing the acetabular centre of rotation is difficult in primary total hip arthroplasty (THA).

METHODS

From April 2012 to December 2022, 64 patients (64 hips) with DDH treated with THA with structural bone graft in the superolateral acetabulum were selected. The Oxford hip score(OHS), Barthel index (BI), leg length discrepancy, Wibegr central edge-angle(CE), gluteus medius muscle strength, vertical and horizontal distance of the hip rotation center, coverage rate of the bone graft and complications were used to evaluate the clinical effectiveness of the patients.

RESULTS

All patients were followed up for an average of 7.3±1.9 years. The OHS improved significantly after the operation (P<0.001). The postoperative BI was significantly greater than that before operation (P<0.001). The postoperative leg length discrepancy was significantly lower than that before the operation (P<0.001). Postoperative bedside photography revealed that the height and horizontal distance to the hip rotation center were significantly lower after surgery than before surgery (P<0.001). The postoperative CE was significantly greater than that before surgery (P<0.001). No acetabular component loosening or bone graft resorption was found during the postoperative imaging examination.

CONCLUSIONS

The use of biological acetabular cup combined with structural bone graft in the superolateral acetabulum in THA for DDH can obtain satisfactory medium and long-term clinical and radiological results.

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.

John Charnley Award: Deep Learning Prediction of Hip Joint Center on Standard Pelvis Radiographs

BACKGROUND

Accurate hip joint center (HJC) determination is critical for preoperative planning, intraoperative execution, clinical outcomes after total hip arthroplasty, and commonly used classification systems in primary and revision hip replacement. However, current methods of preoperative HJC estimation are prone to subjectivity and human error. The purpose of the study was to leverage deep learning (DL) to develop a rapid and objective HJC estimation tool on anteroposterior (AP) pelvis radiographs.

METHODS

Radiographs from 3,965 patients (7,930 hips) were included. A DL model workflow was created to detect bony landmarks and estimate HJC based on a pelvic height ratio method. The workflow was utilized to conduct a grid-search for optimal nonspecific, sex-specific, and patient-specific (using contralateral hip) pelvic height ratios on the training/validation cohort (6,344 hips). Algorithm performance was assessed on an independent testing cohort for HJC estimation comparison.

RESULTS

The algorithm estimated HJC for the testing cohort at a rate of 0.65 seconds/hip based on features in AP radiographs alone. The model predicted HJC within 5 mm of error for 80% of hips using nonspecific ratios, which increased to 83% with sex-specific and 91% with patient-specific pelvic height ratio models. Mean error decreased utilizing the patient-specific model (3.09 ± 1.69 mm, P < .001).

CONCLUSION

Using DL, we developed nonspecific, sex-specific, and patient-specific models capable of estimating native HJC on AP pelvis radiographs. This tool may provide clinical value when considering preoperative component position in patients planned to undergo THA and in reducing the subjective variability in HJC estimation.

LEVEL OF EVIDENCE

Diagnostic, level IV.

Risk factors of dislocation after total hip arthroplasty in patients with developmental dysplasia of the hip

PURPOSE

Dislocation following total hip arthroplasty (THA) is a well-known complication. However, there is little data on its rate and predictors in patients with developmental dysplasia of the hip (DDH). The current study is aimed to determine the rate and specific risk factors of dislocation following THA in DDH patients.

METHODS

All the medico-surgical records of primary THAs from January 2014 to January 2019 were retrospectively reviewed. They were categorized into three main groups: primary OA, DDH, and others. Pre-operative and post-operative radiographs, past medical and surgical history, and surgical notes were reviewed in DDH cases.

RESULTS

In a total of 171 patients with DDH, 21 suffered from dislocation after THA (12%) which was significantly more frequent than those with primary OA. In univariate analysis, higher grade of dysplasia, smaller head size, intra-operative fracture, Wagner Cone stem, failure of offset restoration, and implanting the cup outside the Lewinnek's safe zone were identified as predictors of dislocation. In multiple regression analysis, however, only higher Crowe grade, intra-operative fracture, and post-operative acetabular offset less than 16 mm were independent predictors of dislocation.

CONCLUSION

Dysplastic hips can be more prone to post-THA dislocation than those with primary OA. Higher grades of dysplasia, failure of offset restoration, and intra-operative fracture can increase the rate of dislocation in this group of patients.

The accuracy of digital templating in cementless total hip arthroplasty in dysplastic hips

Background

Total hip arthroplasty (THA) for developmental dysplasia of the hip (DDH) is a complex procedure due to associated anatomical abnormalities. We studied the extent to which preoperative digital templating is reliable when performing cementless THA in patients with DDH.

Methods

We templated and compared the pre- and postoperative sizes of the acetabular and femoral components and the center of rotation (COR), and analysed the postoperative cup coverage, leg length discrepancy (LLD), and stem alignment in 50 patients (56 hips) with DDH treated with THA.

Results

The implant size exactly matched the template size in 42.9% of cases for the acetabular component and in 38.2% of cases for the femoral component, whereas the templated ±1 size was used in 80.4 and 81.8% of cases for the acetabular and femoral components, respectively. There were no statistically significant differences between templated and used component sizes among different DDH severity levels (acetabular cup: p = 0.30 under the Crowe classification and p = 0.94 under the Hartofilakidis classification; femoral stem: p = 0.98 and p = 0.74, respectively). There were no statistically significant differences between the planned and postoperative COR (p = 0.14 horizontally and p = 0.52 vertically). The median postoperative LLD was 7 (range 0–37) mm.

Conclusion

Digital preoperative templating is reliable in the planning of cementless THA in patients with DDH.

Does Cup Position at the High Hip Center or Anatomic Hip Center in THA for Developmental Dysplasia of the Hip Result in Better Harris Hip Scores and Revision Incidence? A Systematic Review

BACKGROUND

One goal of THA is to restore the anatomic hip center, which can be achieved in hips with developmental dysplasia by placing cups at the level of the native acetabulum. However, this might require adjuvant procedures such as femoral shortening osteotomy. Another option is to place the cup at the high hip center, potentially reducing surgical complexity. Currently, no clear consensus exists regarding which of these cup positions might offer better functional outcomes or long-term survival.

QUESTION/PURPOSE

We performed a systematic review to determine whether (1) functional outcomes as measured by the Harris hip score, (2) revision incidence, and (3) complications that do not result in revision differ based on the position of the acetabular cup (high hip center versus anatomic hip center) in patients undergoing THA for developmental dysplasia of the hip (DDH).

METHODS

We performed a systematic review using Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guidelines, including studies comparing the functional outcomes, revision incidence, and complications of primary THA in dysplastic hips with acetabular cups placed at the high hip center versus those placed at the anatomic hip center, over any time frame. The review protocol was registered with PROSPERO (registration number CRD42020168183) before commencement. Of 238 records, eight comparative, retrospective nonrandomized studies of interventions were eligible for our systematic review, reporting on 207 hips with cups placed at the high hip center and 268 hips with cups at the anatomic hip center. Risk of bias within eligible studies was assessed using the Risk Of Bias In Non-randomized Studies of Interventions tool. Due to low comparability between studies, data could not be pooled, so these studies were assessed without summary effects.

RESULTS

Six studies compared Harris hip scores, two of which favored high hip center cup placement and three of which favored anatomic hip center cup placement, although none of the differences between cohorts met the minimum clinically important difference. Five studies reliably compared revision incidence, which ranged from 2% to 9% for high hip center at 7 to 15 years and 0% to 5.9% for anatomic hip center at 6 to 16 years. Five studies reported intra- and postoperative complications, with the high hip center being associated with higher incidence of dislocation and lower incidence of neurological complications. No clear difference was observed in intraoperative complications between the high hip center and anatomic hip center.

CONCLUSION

No obvious differences could be observed in Harris hip score or revision incidence after THA for osteoarthritis secondary to DDH between cups placed at the anatomic hip center and those placed at the high hip center. Placement of the acetabular cup in the high hip center may lead to higher risk of dislocation but lower risk of neurologic complications, although no difference in intraoperative complications was observed. Surgeons should be able to achieve satisfactory functional scores and revision incidence using either technique, although they should be aware of how their choice influences hip biomechanics and the need for adjunct procedures and associated risks and operative time. These recommendations should be considered with respect to the several limitations in the studies reviewed, including the presence of serious confounding factors and selection biases, inconsistent definitions of the high hip center, variations in dysplasia severity, small sample sizes, and follow-up periods. These weaknesses should be addressed in well-designed future studies.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Functional and radiographical results of asymmetrically reconstructed total hip arthroplasty in patients with bilateral dysplastic arthritic hips with one hip Crowe II-III and the other Crowe IV: a retrospective cohort study

Background

The study aimed to evaluate the functional and radiographical results of asymmetrically reconstructed total hip arthroplasty in patients with bilateral dysplastic arthritic hips with one hip Crowe II–III and the other hip Crowe IV.

Materials and methods

From April 2006 to April 2019, we evaluated 23 patients who had a reconstruction of one Crowe II–III hip with high hip center (HHC) and the other Crowe IV hip at the anatomical position (H group). The radiographic and clinical outcomes were compared with those of a control group of 19 patients with bilateral dysplasia who had one Crowe IV hip and the contralateral hip both reconstructed in the anatomical position (A group). Medical records and radiographs were reviewed, and a complete follow-up was conducted for all patients.

Results

The mean vertical center of rotation (V-COR) and horizontal center of rotation (H-COR) in the H group were 30.6 ± 5.8 mm and 30.0 ± 5.5 mm, respectively. In the A group, the corresponding values were 14.0 ± 4.3 mm and 23.0 ± 2.3 mm, respectively. A significant difference was found in terms of V-COR and H-COR between the two groups, and no significant difference was shown regarding the cup inclination, abductor lever arm (ALA), ALA ratio, and leg length discrepancy (LLD). Three patients of the H group and four patients of the A group exhibited LLD > 10 mm. All seven patients who had LLD > 10 mm underwent the shortening subtrochanteric osteotomy (SSTO) of the Crowe IV hip. Subgroup analysis based on the presence and absence of SSTO showed that the LLD of the SSTO group was greater than that of the non-SSTO group in both groups, but the difference was only statistically significant in the A group. At the last follow-up, the mean Harris Hip Scores significantly improved in the two groups, and there was no revision during the follow-up period. In the H group, four patients presented with a slight limp and three patients with a moderate limp, while it was six patients and one patient in the A group, respectively.

Conclusions

Asymmetrical reconstruction in patients with bilateral dysplastic arthritic hips with one hip Crowe II–III and the other Crowe IV is acceptable and comparable when compared with bilateral anatomical reconstruction.

Level of evidence

III, retrospective observational study.

Trial registration Chinese Clinical Trail Registry. ChiCTR2000033848

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.

Design of custom-made navigational template of femoral head and pilot research in total hip resurfacing arthroplasty

Background

To develop a novel custom-made navigational template for accurate prosthesis implantation in total hip resurfacing arthroplasty (THRA) by computer-aided technology.

Methods

The template was produced based on data preoperatively acquired from computed tomography (CT) scan. The position of the drill guide was obtained according to the anatomical axis of the femoral neck which was defined by the point of the femoral head center and another point of the femoral neck center. The final direction of the drill guide was confirmed by a valgus angle. The surface of the template was constructed based on the inverse of the femoral neck surface. Then the template was made of acrylate resin by using rapid prototyping (RP) technique. Finally, all the templates were verified in 17 cadavers arranged for THRA and postoperative medical images were employed to evaluate the accuracy and validity of the template.

Results

The templates had achieved a high fitting with the femoral neck surface, and there were no guide failures. Postoperative evaluation revealed that the Kirschner-wires pass through the center of the femoral head and femoral neck, presenting a relative expected and acceptable valgus angle to the central axis of the femoral neck. The lateral offset showed the relative valgus angle achieved as expected, the horizontal offset showed that no obvious antero-posterior deviation occured. The comparison between the preoperative Neck-shaft angle (NSA) and the postoperative Stem-shaft angle (SSA) showed there is no significant difference(P > 0.05).

Conclusion

The novel custom-made navigational template of femoral head can effectively assist surgeons for accurately implanting the femoral head components to the desired position in THRA.

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.

Cementless Total Hip Arthroplasty in Crowe III and IV Dysplasia: High Hip Center and Modular Necks

BACKGROUND

Total hip arthroplasty (THA) in severe developmental dysplasia of the hip (DDH) is a challenging procedure. The most used techniques involve anatomic cup positioning, augmentation femoral osteotomy. However, anatomic cup positioning is not always feasible in severe DDH and osteotomy nonunion may ensue. The purpose of the study was to assess the survivorship, the hip score results, the radiological parameters (fixation, loosening, component position) of a large cohort of patients with Crowe III and IV DDH, treated with high hip center and modular necks THAs.

METHODS

Eighty-four THAs in Crowe III and IV DDH were evaluated, achieving a final follow-up of 15.1 years. All the patients were treated with the same cementless implant (modular necks and ceramic-on-ceramic coupling) and the same approach (high cup placement with slight medialization). The patients were clinically evaluated (Harris Hip score and Merle d'Aubigne and Postel score). A radiographic evaluation was performed, analyzing the orientation of the cup.

RESULTS

Eighty patients were available at the last follow-up. The clinical scores were good at the final follow-up. Two sciatic lesions occurred: one patient fully recovered. The overall survivorship was 90.5% at 15 years: only 2 cases of aseptic loosening were reported. The mean center of rotation height was 33 ± 8 mm and the medialization was 30 ± 5 mm.

CONCLUSION

A high cup placement with slight medialization is a valid technique in DDH patients. A good restoration of the offset, ceramic-on-ceramic coupling and a porous socket may provide durable results, overcoming the effects of increasing joint reaction forces related to high cup placement.

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.

Patient-reported outcomes in patients who undergo total hip arthroplasty after periacetabular osteotomy

BACKGROUND

There has been constant discussion about whether the clinical outcome of THA after periacetabular osteotomy (PAO) is equivalent to that after primary total hip arthroplasty (THA). However, there have been few reports about patient-reported outcomes (PRO) for those who undergo THA after PAO. We compared the pre- and postoperative PRO of patients who underwent THA after PAO and those who underwent primary THA alone.

METHODS

We performed a case-control study. Twenty-seven patients (29 hips) underwent THA after PAO (osteotomy group); their mean age at surgery was 57.2 years, and they underwent postoperative follow-up for a mean period of 3.0 years. For the control group, after matching age, sex, and Crowe classification, we included 54 patients (58 joints) who underwent primary THA for hip dysplasia. Assessment performed preoperatively and at the last follow-up included the Harris hip score, the Short Form 36 (SF-36) for the Physical Component Summary (PCS), Mental Component Summary (MCS), and Role/Social Component Summary (RCS) domains, Japanese Orthopaedic Association Hip-Disease Evaluation Questionnaire (JHEQ) for pain, movement, and mental health, and the visual analog scale (VAS) score of hip pain and satisfaction.

RESULTS

The two groups demonstrated no significant difference in the preoperative Harris hip score, each domain of the SF-36, JHEQ, and the VAS score of hip pain and satisfaction. The osteotomy group demonstrated significantly poor Harris hip scores for gait and activity, and JHEQ for movement at the last follow-up. There was no significant difference in each domain of the SF-36 and the VAS score of hip pain and satisfaction at the last follow-up.

CONCLUSION

Previous PAO affects the quality of physical function in patients who undergo subsequent THA.

Computed Tomographic Evaluation of Bone Stock in Patients With Crowe Type III Developmental Dysplasia of the Hip: Implications for Guiding Acetabular Component Placement Using the High Hip Center Technique

BACKGROUND

We evaluated acetabular cup coverage (CC) and rim contact (RC) to evaluate the bone stock above the acetabulum for guiding acetabular component placement using the high hip center technique in patients with Crowe type III developmental dysplasia of the hip.

METHODS

Using hip computed tomography and image processing software, pelvises were reconstructed digitally in 20 hips with Crowe type III developmental dysplasia of the hip. Mimicked cup was placed with anteversion angles of 0° (group I), 5° (group II), and 10° (group III) respectively. In each group, the cup was placed at the anatomical hip center at first, and then the cup was moved up to 40 mm vertically about the native rotation center with an increment of 2.5 mm at each step. CC and RC were calculated and documented with each movement.

RESULTS

CC was 65.87%, 67.77%, and 68.98% for group I, group II, and group III at the native rotation center, and increased progressively to 86.45%, 85.85%, and 84.71% at 25 mm above. RC was 49.17%, 50.25%, and 51.92% for group I, group II, and group III at the native rotation center, and increased progressively to 86.87%, 86.39%, and 84.94% at 22.5 mm above. CC and RC were positively correlated, despite the different anteversion angles (r = 0.687 at 0°, 0.683 at 5°, and 0.645 at 10°; P < .001).

CONCLUSION

Computed tomography analysis and computer stimulation demonstrate that it is feasible to use high hip center technique in Crowe type III hips.

Cementless acetabular component with or without upward placement in dysplasia hip: Early results from a prospective, randomised study

BACKGROUND

Total hip arthroplasty (THA) in developmental dysplasia of hip (DDH) is difficult for the abnormal acetabulum. The purpose of this study was to evaluate the difference of anatomic and upward placement of acetabular component during early stage.

METHODS

From April 2014 through June 2015, forty DDH patients (Crowe I to III, 42 hips) were prospectively randomized to either anatomic or upward group. Patient recorded diaries were collected. Radiographs were reviewed. WOMAC and Harris scores were tabulated from pre-operation to 12 months after surgery.

RESULTS

The patients' characteristics including age and body mass index (BMI) had no significant difference (P > 0.05). There were no statistically differences between two groups for surgery time, intraoperative blood loss, hemoglobin (Hb), blood transfusion, albumin decrease, length of stay-day, but surgery time and blood loss in patients with structural bone graft was much higher in anatomic group. The postoperative limb-length discrepancy (LLD) was also no difference, but limb lengthening was better in anatomic group (P = 0.042). The total hospital costs in the anatomic group were higher, but no significant differences. With regard to Harris and WOMAC score, there were significant improved after surgery in both groups, and the anatomic group was better in the value, but these differences were no statistically significant.

CONCLUSIONS

Acetabular reconstruction for DDH subluxation should be reconstructed as close to the actual acetabular location as possible, but an appropriate (<20 mm) upward placement that can achieve at least 70% native bone coverage of the acetabular implant is a valuable technique for early faster recovery.

Preoperative planning of total hip arthroplasty on dysplastic acetabuli

BACKGROUND

When performing total hip arthroplasty (THA) on a dysplastic hip, proper positioning of the acetabular component may not allow for more than 70% coverage. Structural support in the form of an autograft or a high porosity metal augment may be necessary. The purpose of the study was to investigate the value of preoperative templating and deformity classification in predicting cup coverage and the need for structural support.

METHODS

65 cases of THA for DDH were retrospectively analysed. 2 observers independently classified each dysplastic hip according to Hartofilakidis and determined the extent of cup coverage via templating software on preoperative digital AP pelvic radiographs.

RESULTS

Weighted kappa interobserver agreement was 0.68 for cup coverage and 0.76 for Hartofilakidis type. Structural support was necessary in 10 hips. No structural support was necessary in Hartofilakidis type 1, dysplasia cases. However, 27-30% of cases with type 2 or type 3 dysplasia required structural support. All cases with templated cup coverage of 65% or less required structural support. Templated coverage within 65-75% and over 75% resulted in 20% and 10% of patients receiving structural augmentation, respectively.

CONCLUSIONS

Preoperative planning for THA in the setting of hip dysplasia is crucial and can provide valuable insight to the need for column augmentation. However, the 3-D severity of the deformity may be underestimated in the 2-D radiographs.

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.

Favorable Results of Primary Total Hip Arthroplasty With Acetabular Impaction Bone Grafting for Large Segmental Bone Defects in Dysplastic Hips

BACKGROUND

The aim of the present study was to assess midterm results after acetabular impaction bone grafting (IBG) in primary total hip arthroplasty (THA) for developmental dysplasia of the hip (DDH) with large acetabular segmental defect.

METHODS

Primary THA with IBG for DDH with large acetabular segmental defect was performed in 40 hips of 38 patients. The average age was 61.6 years (range: 33-82 years), and the average follow-up period was 7.5 years (range: 3-10.3 years). The Merle d'Aubigné and Postel hip score and complications were assessed. For radiological assessment, postoperative location of the hip rotation center, the socket inclination angle, and the socket center-edge angle were assessed. Kaplan-Meier survival analysis was performed with the end points of any type of reoperation and aseptic acetabular loosening.

RESULTS

The mean Merle d'Aubigné and Postel hip score improved from 10.4 points to 16.2 points at the final follow-up. Reoperation was performed in 1 case for acute infection without loosening. In 39 out of 40 hips (97.5%), the center of hip rotation was located beneath the "high hip center." The average socket inclination angle was 39.3° (range: 30°-54°), and the average socket center-edge angle was -11.8° (range: -23° to 9°). Survival rate of acetabular component at 8 years with the end point of any reoperation and of aseptic loosening was 96.6% (95% confidence interval: 89.9%-100%) and 100%, respectively.

CONCLUSION

Acetabular IBG represents one of the useful options for restoring a normal hip center and acetabular bone stock in primary THA for DDH with large acetabular defect.

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.

MODULUS Stem for Developmental Hip Dysplasia: Long-term Follow-up

Between October 2001 and December 2010, 143 patients with developmental dysplasia underwent hip arthroplasty surgery using a conical stem with modular necks (MODULUS system, Lima Corporate, Villanova di San Daniele del Friuli, Italy). Thirty (21.0%) patients had both hips replaced, for a total of 173 implants. The mean age at the time of surgery was 55 years (range: 22-81 years). The mean follow-up was 87 months (range: 36-146 months); average Harris Hip Score increased from 42 (range: 23-65) preoperatively to 92 (range: 76-100) at the last follow-up. Stem revision was required in two cases. The MODULUS stem showed good long-term clinical and radiographic results, with a Kaplan-Meier survivorship of 97.6% (95% CI: 94.8-100.0%) at 8 years.

Three-dimensional computerized preoperative planning of total hip arthroplasty with high-riding dislocation developmental dysplasia of the hip

OBJECTIVE

To assess whether computed tomography (CT)-based 3-dimensional (3D) computerized pre-operative planning is accurate and reliable in patients with high-riding dislocation developmental dysplasia of the hip (DDH) undergoing total hip arthroplasty (THA).

METHODS

Between September 2009 and February 2011, a prospective study with an inbuilt means of comparing predictive techniques in 20 patients (20 hips) with high-riding dislocation DDH was undertaken. All patients had pre- and post-operative CT scans, data from which were transferred digitally to Mimics software. 3D pre-operative planning to predict the acetabular component size, hip rotation center position and acetabular component coverage was performed using Mimics software. The results and post-operative course were compared with those of the traditional acetate templating technique.

RESULTS

Using 3D computerized planning, 14/20 components (70%) were predicted exactly and 6/20 (30%) within one size, whereas with the conventional acetate templating technique, 5/20 components (25%) were predicted exactly, 9/20 (45%) within one size and 6/20 (30%) within two or more sizes. There was a strong correlation between the 3D computerized planned acetabular component size, hip rotation center distance, acetabular component host coverage and that found postoperatively. Five patients were considered to need structural bone graft on the basis of 3D computerized planning; this was highly coincident with the intraoperative findings in all five cases.

CONCLUSION

CT-based 3D computerized pre-operative planning using Mimics software is an accurate and reliable technique for patients with high-riding dislocation DDH undergoing THA.

Porous titanium particles for acetabular reconstruction in total hip replacement show extensive bony armoring after 15 weeks. A loaded in vivo study in 10 goats

BACKGROUND AND PURPOSE

The bone impaction grafting technique restores bone defects in total hip replacement. Porous titanium particles (TiPs) are deformable, like bone particles, and offer better primary stability. We addressed the following questions in this animal study: are impacted TiPs osteoconductive under loaded conditions; do released micro-particles accelerate wear; and are systemic titanium blood levels elevated after implantation of TiPs?

ANIMALS AND METHODS

An AAOS type-III defect was created in the right acetabulum of 10 goats weighing 63 (SD 6) kg, and reconstructed with calcium phosphate-coated TiPs and a cemented polyethylene cup. A stem with a cobalt chrome head was cemented in the femur. The goats were killed after 15 weeks. Blood samples were taken pre- and postoperatively.

RESULTS

The TiP-graft layer measured 5.6 (SD 0.8) mm with a mean bone ingrowth distance of 2.8 (SD 0.8) mm. Cement penetrated 0.9 (0.3-1.9) mm into the TiPs. 1 reconstruction showed minimal cement penetration (0.3 mm) and failed at the cement-TiP interface. There were no signs of accelerated wear, metallic particle debris, or osteolysis. Median systemic titanium concentrations increased on a log-linear scale from 0.5 (0.3-1.1) parts per billion (ppb) to 0.9 (0.5-2.8) ppb (p=0.01).

INTERPRETATION

Adequate cement pressurization is advocated for impaction grafting with TiPs. After implantation, calcium phosphate-coated TiPs were osteoconductive under loaded conditions and caused an increase in systemic titanium concentrations. However, absolute levels remained low. There were no signs of accelerated wear. A clinical pilot study should be performed to prove that application in humans is safe in the long term.

Coxa recta, coxa profunda and abductor ratio: hip morphology variants compared in an arthroplasty and control population

Morphology variants of the hip such as coxa recta (aspherical femoral head and/or reduced head-neck concavity) or coxa profunda (overcoverage, or "deep" socket) are associated with cam and pincer impingement respectively, and may ultimately lead to coxarthrosis. Several population studies have documented the prevalence of hip morphotypes, but few studies have examined this prevalence in total hip arthroplasty (THA) patients, or persons without hip symptoms or signs.
We reviewed whether coxa recta and profunda morphotypes were more prevalent in THA patients compared to normal controls. Further, we explored differences in hip abductor mechanism related to hip morphology.
We examined 113 THA patients and 83 normal controls with anteroposterior pelvic and lateral hip 
radiographs. Coxa recta and profunda were classified with alpha and lateral CE-angle, respectively. The abductor ratio (AR) was measured on AP pelvic radiographs.
Both coxa recta and profunda were more prevalent in THA patients than normal controls (coxa recta: male 42% vs 8%, female 15% vs 5%, respectively and coxa profunda: male 20% vs 1%, female 19% vs 6% respectively). AR was higher in females than males, both in THA patients (1.66 vs 1.47) and normal controls (1.68 vs 1.57). Coxa profunda was associated with a lower AR (1.54 vs 1.61).
The higher prevalence of coxa recta and profunda in arthroplasty patients supports the theory of a role of these morphotypes in the development of coxarthrosis. The higher AR in females signifies the need for increased abductor work. Coxa profunda may be an adaptation to lower the AR.

Acetabular configuration and its impact on cup coverage of a subtype of Crowe type 4 DDH with bi-pseudoacetabulum

The purpose of this study was to explore the acetabular configuration of a special subtype of Crowe type 4 DDH and its impact on cup coverage, which was identified with a particular bi-pseudoacetabulum and an inter-pseudoacetabulum spine structure. The altered bone stock and anatomic structures were believed to be a result of lesser trochanter impingement on the pelvis as observed in all hips of this series, which was supported by the radiographic and intraoperative findings. Acetabular characteristics were depicted by means of radiographic assessment and direct observation during surgery. Preoperatively, the horizontal distance to the hip centre was 80.5 mm on average and 52.9 mm for femoral head height with a significant difference compared to the general series of DDH cases. Anterosuperior bony coverage was found 
to be more adequate with a thicker anterior wall. The postoperative hip centre was restored to the true acetabulum to within 23.4 mm vertically and 25.2 mm horizontally, and sufficient cup containment was achieved when the acetabular inclination angle was below 45°. A larger diameter cup (range 46-50 mm) was employed. No structural bone graft was required, and the medial protrusion technique was infrequently required. This subtype of DDH facilitated cup coverage during THA.

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.

Better primary stability with porous titanium particles than with bone particles in cemented impaction grafting: an in vitro study in synthetic acetabula

AIMS

Impaction bone grafting creates new bone stock after hip joint replacement. Utilizing a synthetic bone substitute instead of bone might increase primary stability and is not associated with graft shortage and pathogen transmission. This study compares the initial stability of a graft layer of porous titanium particles (TiP), cancellous bone particles, and a 1:2 bone-titanium mix in synthetic cemented acetabular reconstructions. Displacement was measured by radiostereometric analysis after cyclic loading (1 Hz, maximum stress 2.5 MPa). Shear stress resistance was quantified by a lever out test of the cup. Cement penetration was quantified from cross-sections.

FINDINGS

Titanium reconstructions showed less residual displacement (0.13 ± 0.13 mm) than pure bone particle reconstructions (0.57 ± 0.18 mm) (p < 0.01). Titanium reconstructions were also more resistant to shear stress (p < 0.001). The bone-titanium mix showed intermediate results. Cement penetrated deeper into the bone particle graft layers (4.8 ± 0.7) than into the titanium graft layers (3.8 ± 0.5 mm) (p < 0.02).

CONCLUSIONS

Cemented acetabular revision reconstructions with porous TiP show better initial stability despite less cement penetration than bone particle reconstructions. Realistic preclinical in vivo testing should explore the hypothesis that porous TiP offer a safe alternative to the current gold standard of bone grafts.

Accuracy of cup height and medialization in THA for dysplastic hip osteoarthritis using an imageless navigation system

In total hip arthroplasty (THA) for dysplastic hip osteoarthritis, bony deformity makes it difficult to identify the correct cup height and medialization. The authors developed a new technique for registration and navigation of cup position for dysplastic hips using an imageless navigation system. Eighty dysplastic hips (Crowe type I, n=58; type II, n=18; type III, n=4) underwent THA. Thirty-four hips were operated on while in the supine position and 46 hips were operated on while in the lateral position. Before capsulectomy, the anterior pelvic plane and the position of the femur were registered. After exposure of the acetabulum, the teardrop, posterior rim, and medial wall of the acetabulum were registered. Then the cup height, cup medialization, cup inclination, anteversion, and leg lengthening were navigated. The difference between the navigated and radiographic cup heights was 4.5 ± 4.0 mm, the difference in cup medialization was 3.0 ± 2.5 mm, the difference in cup inclination was 4.3° ± 3.1°, the difference in cup anteversion was 5.5° ± 3.8°, and the difference in leg lengthening was 3.7 ± 3.0 mm. Comparison of the first 20 cases with the last 20 cases showed that the accuracy of cup medialization was significantly improved. These differences were not affected by Crowe type or surgical position. Because the correct cup height and medialization are key issues in THA for dysplastic hip osteoarthritis, the accuracy of cup height and medialization in this imageless navigation system were acceptable for clinical application.

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.

Total hip replacement in developmental dysplasia using an oval-shaped cementless press-fit cup

PURPOSE

Acetabular roof deficiency due to subluxation of the femoral head (Hartofilakidis type II) increases the complexity of total hip arthroplasty. In these cases some form of support is usually required, to reach stable fixation of the acetabular component. Pursuing this aim, the oval-shaped cementless cranial socket could be an alternative to conventional treatment options.

METHODS

Between 1998 and 2008, 37 patients (40 hips) underwent primary total hip arthroplasty using the cranial socket (mean follow-up 5.6 years, range 26 to 133 months). In a retrospective study we compared these clinical and radiological results with the results of a matched control group consisting of 35 patients (40 hips) treated with a standard cementless hemispherical cup in combination with bulk femoral autografting (mean follow-up 6.9 years, range 30 to 151 months).

RESULTS

There were no statistically significant differences in the HHS (p=0.205) or the SF-36 (p=0.26) between both groups. There was no prosthesis failure due to septic or aseptic loosening. Time of surgery was significantly shorter in the cranial socket group (p<0.001). The acetabular component could be placed in the ideal rotational hip centre in 24 (60%) hips in the cranial socket group and 32 (80%) hips in the control group, respectively.

CONCLUSIONS

Our study indicates, that the cranial socket can be an alternative treatment option for the reconstruction of acetabular deficiency in osteoarthritis secondary to developmental dysplasia.

[Total hip replacement in developmental dysplasia: anatomical features and technical pitfalls]

Total hip arthroplasty is the procedure of choice for most patients with advanced, symptomatic osteoarthritis due to congenital dysplasia of the hip. However, the complexity of arthroplasty is significantly increased because of anatomic abnormalities associated with dysplasia of the hip. In addition the relatively young age of patients may affect survival of the implant. From a biomechanical standpoint the primary surgical objective is reconstruction of the anatomical center of rotation. Independent of the pelvic bone stock the socket should be located as near as possible to the anatomical acetabular location. There are various operative strategies to ascertain sufficient stability of the socket. The anterolateral deficiency of the acetabulum can be reconstructed by bulk femoral autografting or bone impaction grafting. Furthermore controlled perforation of the medial wall or implantation of reinforcement rings and oval sockets have been described. Cementless, biological socket fixation shows superior long-term results compared to cemented cups, especially in these young patients. The location of the reconstructed acetabulum and the desired leg length influence the type of femoral reconstruction and in some cases femoral shortening is required. In this article endoprosthetic reconstructive options for developmental dysplasia of the hip are discussed depending on the femoral and acetabular deformity.

Preliminary application of computer-assisted patient-specific acetabular navigational template for total hip arthroplasty in adult single development dysplasia of the hip

BACKGROUND

The considerable variation in anatomical abnormalities of hip joints associated with different types of developmental dysplasia of hip (DDH) makes reconstruction in total hip arthroplasty (THA) difficult. It is desirable to create patient-specific designs for THA procedures. In the cases of adult single DDH, an accuracy-improved method has been developed for acetabular cup prosthesis implantation of hip arthroplasty.

METHODS

From October 2007 to November 2008, 22 patients with single DDH (according to the Crowe standard, all dysplasia hips were classified as type I) were scanned with spiral CT pre-operatively. These patients scheduled for THA were randomly assigned to undergo either conventional THA (control group, n = 11) or navigation template implantation (NT group, n = 11). In the NT group, three-dimensional (3D) CT pelvis image data were transferred to a computer workstation and 3D models of the hip were reconstructed using the Mimics software. The 3D models were then processed by the Imageware software. In brief, a template that best fitted the location and shape of the acetabular cup was 'reversely' built from the 3D model, the rotation centre of the pathological hip determined by mirroring that of the healthy site, and a guiding hole in the template was then designed. The navigational templates were manufactured using a rapid prototyping machine. These navigation templates guide acetabular component placement.

RESULTS

Based on the predetermined abduction angle 45° and anteversion angle 18°, after 1 year follow-up, the NT group showed significantly smaller differences (1.6° ± 0.4°, 1.9° ± 1.1°) from the predetermined angles than those in the control group (5.8° ± 2.9°, 3.9° ± 2.5°) (P < 0.05).

CONCLUSIONS

The template designs facilitated accurate placement of acetabular components in dysplasia of acetabulum. The hip's center of rotation in DDH could be established using computer-aided design, which provides a useful method for the accurate location of prosthesis with a low cost-performance ratio without excessive technical workload on the surgical team.

Total hip replacement with an uncemented Wagner cone stem for patients with congenital hip dysplasia

PURPOSE

The purpose of this study was to review retrospectively the cases operated upon in our department in recent years with a Wagner stem and a small socket in cases of Crowe I or II dysplastic hips.

METHODS

We conducted a retrospective clinical radiological review of 30 hips diagnosed with hip dysplasia Crowe I or II treated in our centre between 2002 and 2008. All of them were treated with a Wagner cone stem and a small Trilogy acetabulum (Zimmer ®).

RESULTS

There were 15 men and 11 women with 13 left and 17 right femurs. Mean follow-up was 43.44 months (range 14-87). Eight patients were Crowe I type and 22 were Crowe II type. Merlé d'Aubigne score pre-operatively was 12.23 and at the last follow-up was 15.54. Mean leg length inequality was 1.79 and after surgery it was 0.69 cm. Complications included three infection and three dislocations (two of them in the same patient).

CONCLUSIONS

The use of a Wagner stem is a good option to correct the different deformities in the proximal femur in these cases. A small socket allows a correct relocation of the acetabulum in a dysplastic socket with good bone coverage.

Hip offset in total hip arthroplasty: quantitative measurement with navigation

BACKGROUND

Offset in THA correlates to abductor muscle function, wear, and impingement. Femoral offset after THA is not independent of the cup center of rotation (COR) so hip offset, a combination of femoral offset and change in hip COR, becomes the important measurement.

QUESTIONS/PURPOSES

We therefore asked whether hip offset in arthritic hips would correlate with cup COR; whether offset could always be balanced within 6 mm of contralateral normal hips; and whether hip length could also be kept within 6 mm.

METHODS

We compared hip offset of arthritic and contralateral normal hips on radiographs in 82 patients (82 hips) who had THA. We used computer navigation in all patients with the aim of reconstructing the hip offset and to compare hip offset change to the quantitative change of the hip COR.

RESULTS

The preoperative radiographic change to equalize the offset ranged from -12 to +21 mm (mean, 1.5); postoperatively the change was 1.4 ± 6.4 mm and was within ± 6 mm in 78 of 82 hips. As COR displaced superiorly from 3 to 6+ mm the offset had to be substantially increased. Only with COR 0-3 mm superior and 0-5 mm medial was offset always within 5 mm.

CONCLUSIONS

Hip offset reconstruction was directly related to the position of the hip COR, and navigation allowed quantitative control of offset and hip length.

Personalized image-based templates for precise acetabular prosthesis placement in total hip arthroplasty: a pilot study

OBJECTIVE

In order to achieve accurate implantation of the acetabular prosthesis in total hip arthroplasty (THA), we designed individual templates based on a three-dimensional (3D) model generated from computed tomography (CT) scans.

METHODS

Individual templates were designed for 12 patients who underwent THA. A physical template was designed to conform to the contours of the patient's acetabulum and to confirm the rotation of the acetabular center. This guided the acetabular component orientation.

RESULTS

The preoperative and postoperative X-ray and CT scans were obtained to assess the location with respect to the accuracy of the acetabular component. For all patients, the abduction angle of the acetabular component was 46.7 degrees to 54.3 degrees and the anteversion angle was 11.3 degrees to 18.5 degrees .

CONCLUSIONS

The assessment of postoperative CT scans demonstrated higher accuracy of the acetabular component bore when used with the individual template. Therefore, the individual template can be an alternative to the computer-assisted navigation systems, with a good cost-performance ratio.

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.

The utility of digital templating in Total Hip Arthroplasty with Crowe type II and III dysplastic hips

With the superiority of digital imaging, conventional preoperative acetate templating is gradually being replaced by digital templating in total hip arthroplasty (THA). The purpose of this study was to assess the utility of digital templating for patients with Crowe type II and III dysplastic hips. In this study, 41 THA patients with Crowe type II or III dysplastic hips and 48 THA patients with other primary diseases were retrospectively reviewed. All patients were fitted with cementless prostheses in 2008. For the THA patients with dysplastic hips, we attempted to restore their hip centres to the position of the true acetabulum. Digital templating was the method chosen to achieve hip centre restoration. The prosthesis prediction accuracy (within ± one size using digital templating) was 20 (48.8%) for the cup size and 30 (73.2%) for the stem size. Meanwhile, for patients with other primary diseases, the accuracy for the cup size within ± one size was 34 (70.8%) and for the stem size accuracy was within ± one size in 38 (79.2%). Between the two patient groups, there was a significant difference in the predicted cup size. In patients with dysplastic hips, the low accuracy of the predicted cup size may have resulted from difficulty in predicting the vertical location of the hip centre. Despite this limitation, preoperative planning using digital templating is a convenient technique for THA patients with Crowe type II and III dysplastic hips.