Taishi Sato

Femoral anteversion is correlated with acetabular version and coverage in Asian women with anterior and global deficient subgroups of hip dysplasia: a CT study.

ObjectiveMorphological correlation between the acetabulum and femur at the hip joint is still controversial. We tested the hypothesis that femoral anteversion correlates with acetabular version and coverage in patients with developmental dysplasia of the hip (DDH).Materials and methodsUsing pelvic computed tomography (CT) images of 79 hips in 49 Asian women with DDH and 49 normal hips, we measured femoral anteversion, the axial and vertical acetabular version and the acetabular sector angle (ASA) to demarcate femoral head coverage. Depending on the location of the acetabular bone defect, dysplastic hips were divided into three subgroups: the anterior, global and posterior deficiency groups. We performed a comparative analysis between dysplastic and normal hips using the Wilcoxon rank sum test, and a relative analysis between femoral anteversion and acetabular measurements in dysplastic hips using Pearson’s correlation coefficient.ResultsThe amount of femoral anteversion in dysplastic hips was greater and more variable than in normal hips (p < 0.0001, p = 0.0277 respectively). Femoral anteversion in dysplastic hips correlated significantly with acetabular anteversion in the groups with anterior and global deficiency subgroups (p < 0.05, r = 0.2990, p < 0.05, r = 0.451 respectively), but not with the posterior deficiency subgroup. Femoral anteversion also correlated with vertical acetabular version. When acetabular coverage was examined, significant correlations were noted between femoral anteversion and anterior and superior coverage, but not with posterior coverage. These correlations were not observed in normal hips.ConclusionsOur results showed significantly greater and more variable femoral anteversion in DDH, and a significant correlation between femoral anteversion and acetabular version and coverage in DDH with anterior and global acetabular bone deficiency.

Pelvic deformity influences acetabular version and coverage in hip dysplasia.

BackgroundAlthough a wide variety of acetabular deformities in developmental dysplasia of the hip (DDH) have been reported, the morphologic features of the entire pelvis in DDH are not well characterized and their correlation with acetabular deformity is unknown.Questions/purposesWe determined whether there was a rotational deformity of the entire innominate bone, and if so, whether it related to acetabular version and coverage.Patients and MethodsWe examined the morphologic features of the pelvis using CT for 50 patients with DDH (82 hips). Forty normal hips were used as controls. The innominate rotation angle was determined at three levels in the axial plane. The acetabular sector angle served as an indicator of acetabular coverage of the femoral head. We evaluated the association between innominate rotation angles and acetabular version and coverage.ResultsWe observed greater internal rotation of the innominate bone in patients with DDH than in the control subjects. Internal rotation of the innominate bone was associated with increased acetabular anteversion angle and acetabular inclination angle. In hips with acetabular retroversion (nine of 82 hips; 11.0 %), the entire innominate bone was externally rotated, compared with hips with acetabular anteversion. Internal rotation of the innominate bone also was associated with decreased anterior and superior acetabular coverage.ConclusionOur observations suggest structural abnormalities exist throughout the pelvis in DDH, and the morphologic abnormalities of the acetabulum are not caused solely by local dysplasia around the hip, but are influenced by the morphologic features of the entire pelvis.Level of EvidenceLevel IV, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.

Acetabular tilt correlates with acetabular version and coverage in hip dysplasia.

BackgroundThe rotational position of the acetabulum to the pelvis (acetabular tilt) may influence acetabular version and coverage of the femoral head. To date, the pathologic significance of acetabular tilt in hip dysplasia is unknown.Questions/PurposesWe determined whether acetabular tilt in hip dysplasia is different from that in normal hips and whether this correlates with acetabular version and coverage.MethodsWe measured the acetabular tilt angle on the lateral view of three-dimensional pelvic CT images of 40 patients (72 hips) with hip dysplasia. Forty normal hips from 40 patients were used as controls. The acetabular sector angle was measured as an index for acetabular coverage of the femoral head.ResultsThe mean acetabular tilt angle was increased in dysplastic hips compared with controls. In dysplastic hips, a posteriorly rotated acetabulum (increased acetabular tilt) was associated with increased acetabular anteversion and with decreased anterior and anterosuperior acetabular coverage. No correlation was found in controls. In dysplastic hips with a posterior acetabular deficiency, the acetabulum was rotated anteriorly (decreased acetabular tilt) compared with hips with anterior and lateral deficiencies.ConclusionsWe observed a correlation between the rotational position of the acetabulum in the pelvis with acetabular version and coverage in hip dysplasia. Our observations confirmed anterior rotation of the acetabular fragment during periacetabular osteotomies is an anatomically reasonable maneuver for hips with anterolateral acetabular deficiencies, while the maneuver can exacerbate posterior coverage and should be avoided in hips with a posterior acetabular deficiency.Level of EvidenceLevel IV, diagnostic study. See the Guidelines for Authors for a complete description of levels of evidence.

Wear resistant performance of highly cross-linked and annealed ultra-high molecular weight polyethylene against ceramic heads in total hip arthroplasty

The purpose of this study was to examine the effects of ceramic femoral head material, size, and implantation periods on the wear of annealed, cross‐linked ultra‐high molecular weight polyethylene (UHMWPE) (XLPE) in total hip arthroplasty compared to non‐cross‐linked conventional UHMWPE (CPE). XLPE was fabricated by cross‐linking with 60 kGy irradiation and annealing. Femoral heads made from zirconia and alumina ceramics and cobalt–chrome (CoCr) of 22 or 26 mm diameter were used. In this retrospective cohort study, the femoral head penetration into the cup was measured digitally on radiographs of 367 hips with XLPE and 64 hips with CPE. The average follow‐up periods were 6.3 and 11.9 years, respectively. Both XLPE creep and wear rates were significantly lower than those of CPE (0.19 mm vs. 0.44 mm, 0.0001 mm/year vs. 0.09 mm/year, respectively). Zirconia displayed increased wear rates compared to alumina in CPE; however, there was no difference among head materials in XLPE (0.0008, 0.00007, and −0.009 mm/year for zirconia, alumina, and CoCr, respectively). Neither head size or implantation period impacted XLPE wear. In contrast to CPE, XLPE displayed low wear rates surpassing the effects of varying femoral head material, size, implantation period, and patient demographics. Further follow‐up is required to determine the long‐term clinical performance of the annealed XLPE.

Modular Necks Improve the Range of Hip Motion in Cases with Excessively Anteverted or Retroverted Femurs in THA

BackgroundAnteversion of an acetabular component often is difficult to ascertain in patients with THA in whom excessively anteverted or retroverted femurs may result in limited ROM or risk of dislocation. Restriction of motion, however, is determined by the combination of version of both components.Questions/purposesWe therefore determined the combined anteversion values that provide adequate ROM. We varied acetabular version by differing implantations and varied femoral version with modular necks.MethodsROM was tested by changing cup anteversion after setting the femoral version to 20° or 60° anteversion or 20° retroversion. The angle of the modular neck was adjusted in 11 increments of 5° each. Range of internal rotation (IR) at 90° flexion, external rotation (ER) at 0° extension, and flexion (Flex) were measured when any impingement occurred before dislocation. We defined a required ROM as having 40° IR, 30° ER, and 110° Flex.ResultsAt 60° anteversion, ER was less than 10° even when the acetabular component was set at 10° retroversion because of posterior impingement. When a modular neck with 25° retroversion was used, ER improved to greater than 30°. At 20° retroversion, IR was 31° even when the acetabular component was opened to 35° anteversion. IR improved to 34° and 40° with 20° and 25° anteverted modular necks, respectively.Conclusions and Clinical RelevanceIn cases with excessive femoral anteversion or retroversion, the required ROM could not be achieved by simply changing the version of acetabular components. The adjustment of femoral versions using the modular necks allowed additional improvement of ROM.

Bone bonding strength of diamond-structured porous titanium-alloy implants manufactured using the electron beam-melting technique

The present study examined the bone bonding strength of diamond-structured porous titanium-alloy (Porous-Ti-alloy) manufactured using the electron beam-melting technique in comparison with fiber mesh-coated or rough-surfaced implants. Cylindrical implants with four different pore sizes (500, 640, 800, and 1000μm) of Porous-Ti-alloy, titanium fiber mesh (FM), and surfaces roughened by titanium arc spray (Ti-spray) were implanted into the distal femur of rabbits. Bone bonding strength and histological bone ingrowth were evaluated at 4 and 12weeks after implantation. The bone bonding strength of Porous-Ti-alloy implants (640μm pore size) increased over time from 541.4N at 4weeks to 704.6N at 12weeks and was comparable to that of FM and Ti-spray implants at both weeks. No breakage of the porous structure after mechanical testing was found with Porous-Ti-alloy implants. Histological bone ingrowth that increased with implantation time occurred along the inner structure of Porous-Ti-alloy implants. There was no difference in bone ingrowth in Porous-Ti-alloy implants with pore sizes among 500, 640, and 800μm; however, less bone ingrowth was observed with the 1000μm pore size. These results indicated Porous-Ti-alloy implants with pore size under 800μm provided biologically active and mechanically stable surface for implant fixation to bone, and had potential advantages for weight bearing orthopedic implants such as acetabular cups.

Effects of posterior pelvic tilt on anterior instability in total hip arthroplasty: A parametric experimental modeling evaluation

BACKGROUND Anterior dislocation is one of the concerns of patients with posterior pelvic tilt undergoing total hip arthroplasty. This study aimed to evaluate the magnitude of posterior pelvic tilt constituting a risk for anterior dislocation by measuring the range of motion until impingement and dislocation under various pelvic tilt. METHODS Using a jig mounted prosthetic hip model, the ranges of external rotation at extension and internal rotation at flexion until reaching dislocation were tested. The site of impingement prior to dislocation was also recorded. Posterior pelvic tilt and the cup version were changed with 10° increments from 0° to 40° and from 10° retroversion to 30° anteversion, respectively. Effects of increasing femoral offset were also tested. We defined a required range of motion as having 30° external rotation at extension and 40° internal rotation at 90° flexion. FINDINGS External rotation decreased in a posterior pelvic tilt-dependent manner. In the case with more than 20° posterior pelvic tilt, available external rotation extended beyond required range with the cup anteversion of 20°. Decreasing cup anteversion improved external rotation, however, internal rotation decreased simultaneously. In the case with posterior pelvic tilt more than 20°, only cup anteversion with 0° or 10° satisfied the required range of motion. A +4 mm horizontal offset improved external rotation by 10° with delaying bony impingement. INTERPRETATION More than 20° of posterior pelvic tilt may cause anterior instability and diminish the optimal range of cup version. Increasing the femoral offset improved external rotation without reducing internal rotation.

High prevalence of acetabular retroversion in both affected and unaffected hips after Legg-Calvé-Perthes disease

BackgroundAcetabular retroversion is observed in hips after various pediatric hip diseases. This study sought to examine the frequency of acetabular retroversion in both affected and unaffected hips after Legg-Calvé-Perthes disease and its correlation with the prominence of the ischial spine.MethodsWe retrospectively investigated the version and morphological features of the acetabulum using pelvic radiographs after Legg-Calvé-Perthes disease (107 affected hips treated non-operatively and 72 unaffected hips from the contralateral side). The diagnosis of acetabular retroversion was made based on the presence of a positive cross-over sign on anteroposterior pelvic radiographs. The correlation between the presence of a positive cross-over sign and modified Stulberg classes, the onset age of Legg-Calvé-Perthes disease, radiographic parameters for acetabular dysplasia and the prominence of the ischial spine were examined.ResultsThe prevalence of a positive cross-over sign was 49.5 % (45 of 91 hips) in affected hips and 45.8 % (33 of 72 hips) in unaffected hips. Hips with a positive cross-over sign were significantly coexistent bilaterally. The prevalence of prominence of the ischial spine in the positive cross-over sign group was 71.4 % in the affected side and 81.8 % in the unaffected side, indicating a significant correlation between the cross-over sign and the prominence of the ischial spine in both affected and unaffected hips. The positive cross-over sign did not have any correlation with the parameters for acetabular dysplasia and the onset age, however, had a significant correlation with the severity of the femoral head deformity.ConclusionsHigh prevalence of acetabular retroversion in both affected and unaffected hips after Legg-Calvé-Perthes disease was demonstrated. Symmetric acetabular deformity and the coexistence of prominence of the ischial spine suggested the effects of the Legg-Calvé-Perthes disease lesions on the skeletal development of the whole pelvis. Further follow-up is needed to clarify the pathological significance of acetabular retroversion after Legg-Calvé-Perthes disease.

The Absence of Hydroxyapatite Coating on Cementless Acetabular Components Does Not Affect Long-Term Survivorship in Total Hip Arthroplasty

BACKGROUND Hydroxyapatite (HA) has been applied to joint prostheses as a bioactive coating to prolong their durability. However, HA benefits for cup survival in total hip arthroplasty (THA) remain controversial. In this study, we compared the survival of cups with and without HA coating during a minimum follow-up of 18 years. METHODS In total, 183 THA cases in 163 patients were analyzed, including 73 cups with HA coating (HA(+) group) and 110 without HA coating (HA(-) group); otherwise, the cups had identical titanium-sprayed rough surfaces and were fixed with screws. In both groups, the same conventional polyethylene liners were applied. Zirconia and alumina ceramic heads were used in the HA(+) and HA(-) groups, respectively. We retrospectively analyzed cup survival based on cup revision for any reason or aseptic loosening as end points. RESULTS In total, 7 and 8 revisions were performed in the HA(-) and HA(+) groups with survival rates of 86.3% and 90.1%, respectively. Among them, 3 cups in the HA(-) group and 1 cup in the HA(+) group were revised for aseptic loosening in 20 years (survival rates 94.1% and 98.7%, respectively). No significant difference was detected in cup survival rates between the groups based on both end points. There were no stem revisions during the observation period. CONCLUSION The results suggested that HA coating did not have either beneficial or adverse effects on the long-term cup survival in primary cementless THA.

Comparison of polyethylene wear between highly crosslinked and annealed UHMWPE and conventional UHMWPE against ceramic heads in total hip arthroplasty

The purpose of this study was to examine the effects of ceramic femoral head material on the wear of annealed, crosslinked ultra-high molecular weight polyethylene (UHMWPE) (XLPE) in total hip arthroplasty compared to non-crosslinked conventional UHMWPE (CPE). XLPE was fabricated by crosslinking with 60 kGy irradiation and annealing. Femoral heads made from zirconia and alumina ceramics, and cobalt-chrome (CoCr) of 22 mm or 26 mm diameter were used. In this study, the femoral head penetration into the cup was measured digitally on radiographs of 70 hips with XLPE and 50 hips with CPE. The average follow-up periods were 6.1 and 12.7 years, respectively. The steady wear rate of XLPE was significantly lower than those of CPE (0.002 versus 0.08 mm/year, respectively). Zirconia displayed increased wear rates compared to alumina in CPE; however, there was no difference among head materials in XLPE (0.0028, 0.011 and 0.009 mm/year for zirconia, alumina and CoCr, respectively). Neither head size or implantation period impacted XLPE wear. In contrast to CPE, XLPE displayed low wear rates surpassing the effects of varying femoral head material, size, implantation period and patient demographics.