Acetabular Cup Position Research Articles

Total Hip Arthroplasty in the Spinal Deformity Population: Does Degree of Sagittal Deformity Affect Rates of Safe Zone Placement, Instability, or Revision?

BackgroundChanges in spinal alignment and pelvic tilt alter acetabular orientation in predictable ways, which may have implications on stability of total hip arthroplasty (THA). Patients with sagittal spinal deformity represent a subset of patients who may be at particularly high risk of THA instability because of postural compensation for abnormal spinal alignment. MethodsUsing standing stereoradiography, we evaluated the spinopelvic parameters, acetabular cup anteversion, and inclination of 139 THAs in 107 patients with sagittal spinal deformity. Standing images were compared with supine pelvic radiographs to evaluate dynamic changes in acetabular cup position. Dislocation and revision rates were procured through retrospective chart review. The spinal parameters and acetabular cup positions among dislocators were compared with those who did not dislocate. ResultsThe rate of THA dislocation in this cohort was 8.0%, with a revision rate of 5.8% for instability. Patients who sustained dislocations had significantly higher spinopelvic tilt, T1-pelvic angle, and mismatch of lumbar lordosis and pelvic incidence. Among all patients, 78% had safe anteversion while supine, which decreased significantly to 58% when standing due to increases in spinopelvic tilt. Among dislocating THA, 80% had safe anteversion, 80% had safe inclination, and 60% had both parameters within the safe zone. ConclusionIn this cohort, patients with THA and concomitant spinal deformity have a particularly high rate of THA instability despite having an acetabular cup position traditionally thought of as within acceptable alignment. This dislocation risk may be driven by the degree of spinal deformity and by spinopelvic compensation. Surgeons should anticipate potential instability after hip arthroplasty and adjust their surgical plan accordingly.

Rigid Patient Positioning is Unreliable in Total Hip Arthroplasty

BackgroundTo our knowledge, no study has assessed the ability of rigid patient positioning devices to afford arthroplasty surgeons with ideal acetabular orientation throughout surgery. The purpose of this study is to use robotic arm–assisted computer navigation to assess the reliability of pelvic position in total hip arthroplasty performed on patients positioned with rigid positioning devices. MethodsA prospective cohort of 100 hips (94 patients) underwent robotic-guided total hip arthroplasty in the lateral decubitus position from the posterior approach, 77 stabilized by universal lateral positioner, and 23 by peg board. Before reaming, computed tomography–templated computer software generated true values of pelvic anteversion and inclination based on the position of the robot arm registered to the patient’s preoperative pelvic computed tomography. ResultsMean alteration in anteversion and inclination values was 1.7° (absolute value, 5.3°; range, −20° to 20°) and 1.6° (absolute value, 2.6°; range, −8° to 10°), respectively. And 22% of anteversion values were altered by >10° and 41% by >5°. There was no difference between hip positioners used (P = .36). Anteversion variability was correlated with body mass index (P = .02). ConclusionDespite the use of rigid patient positioning devices—a lateral hip positioner or peg board—this study reveals clinically important malposition of the pelvis in many cases, especially with regard to anteversion. These results show a clear need to pay particular attention to anatomic landmarks or computer-assisted techniques to assure accurate acetabular cup positioning. Patient positioning should not be solely trusted.

Application of jumbo cup in acetabular revisions for patients with massive acetabular bone deficiency

Objective To investigate the effects of the jumbo cup in acetabular revision for patients with massive acetabular bone deficiency. Methods We retrospectively studies 48 patients (49 hips) who underwent jumbo cup revisions between 2006 and 2015 (19 men and 29 women; average age: 62±12 years). The acetabular bone defects were classified according to Paprosky classification (Paprosky II 27 hips, Paprosky IIIA 18 hips, Paprosky IIIB 4 hips). Radiological assessments were conduced to evaluate the acetabular prosthesis loosening, dislocation and infection. The reasons for revisions were mechanical loosening in 41 cases, and infections in another 8 cases with cement spacer putted by last surgery. Results The operation duration and blood loss was 110 min (85-160 min) and 315 ml (270-455 ml) respectively. After an average follow-up of 6.8 years (1-11 years), Harris hip score was increased from 47.6 ± 7.1 preoperatively to 82.4 ± 6.2 postoperatively. Osseointegration occurred in the acetabular components at 6 months postoperatively. Radiograph analysis showed satisfied position of acetabular cup without complications such as damages of vessels or nerves. The successful rate of jumbo cup revisions was 89.8%±4.4%. However, two in Paprosky IIIA failures for periprosthetic infection occurred and two in Paprosky IIIA, one in Paprosky IIIA and the other in Paprosky IIIB for acetabular component loosening. One patient in Paprosky IIIB had weight-bearing pain and relieve slightly after conservative treatment. The radiologic study showed that there was no relationship between failure rate and acetabular abduction angle (r=0.06, P= 0.53), rotation center migration in vertical direction (r=0.11, P=0.14) and horizontal direction (r=0.04, P=0.89). Conclusion The mid-term results show that using jumbo cup in revising acetabular failure with massive bone deficiency are optimal, which can be achieved by simplified operation procedures, reduction in the need of bone graft and promotion in acetabulum osseointegration. However, higher failure rate may occur in Paprosky IIIB patients. Key words: Arthroplasty, replacement, hip; Reoperation; Acetabulum; Osteolysis; Prosthesis failure

Acetabular cup position and risk of dislocation in primary total hip arthroplasty

Background and purpose — Hip dislocation is one of the most common complications following total hip arthroplasty (THA). Several factors that affect dislocation have been identified, including acetabular cup positioning. Optimal values for cup inclination and anteversion are debatable. We performed a systematic review to describe the different methods for measuring cup placement, target zones for cup positioning, and the association between cup positioning and dislocation following primary THA.Methods — A systematic search of literature in the PubMed database was performed (January and February 2016) to identify articles that compared acetabular cup positioning and the risk of dislocation. Surgical approach and methods for measurement of cup angles were also considered.Results — 28 articles were determined to be relevant to our research question. Some articles demonstrated that cup positioning influenced postoperative dislocation whereas others did not. The majority of articles could not identify a statistically significant difference between dislocating and non-dislocating THA with regard to mean angles of cup anteversion and inclination. Most of the articles that assessed cup placement within the Lewinnek safe zone did not show a statistically significant reduction in dislocation rate. Alternative target ranges have been proposed by several authors.Interpretation — The Lewinnek safe zone could not be justified. It is difficult to draw broad conclusions regarding a definitive target zone for cup positioning in THA, due to variability between studies and the likely multifactorial nature of THA dislocation. Future studies comparing cup positioning and dislocation rate should investigate surgical approach separately. Standardized tools for measurement of cup positioning should be implemented to allow comparison between studies.

IMAGING ANALYSIS OF ACETABULAR CUP POSITIONS IN TOTAL HIP ARTHROPLASTY FOR ADULTS WITH ACETABULAR DYSPLASIA

To investigate the influence of the degree of acetabular deformity and the learning-curve on the acetabular cup positions in total hip arthroplasty (THA) for adults with developmental dysplasia of hip (DDH). Between January 2008 and December 2015, 130 patients (144 hips) with DDH underwent primary THA, and the clinical data were analyzed retrospectively. Fifty-three patients (59 hips) were admitted before 2012, and 77 patients (85 hips) were treated after 2012. There were 32 males and 98 females, aged from 31 to 83 years (mean, 61). Unilateral replacement was performed in 116 cases and bilateral replacement in 14 cases. Of 144 hips, 48 hips were rated as Crowe type I, 57 hips as type II, and 39 hips as type of III/IV. The standard pelvic radiograph was taken within 1 week after operation. The mediCAD software was adopted to measure the angle of anteversion and abduction, bony coverage, and the distance between true rotating center and optimal rotating center to the connection of teardrops and the horizontal distance between two centers to evaluate the qualified rate of acetabular cup positions. Compared with the patients with the same type in 2013-2015 group, the anteversion angle and qualified rate of acetabular cup position significantly decreased in patients with Crowe I (P<0.05); the horizontal distance significantly increased and qualified rate of acetabular cup position significantly decreased in patients with Crowe II (P<0.05); and the anteversion angle significantly decreased and the horizontal distance significantly increased in patients with Crowe III/IV (P<0.05) in 2008-2012 group. But no significant difference was shown in the other indexes (P>0.05). In all Crowe types, the vertical distance between the true rotating center and the optimal rotating center increased with the degree of acetabular deformity in both 2008-2012 group and 2013-2015 group, showing significant difference (P<0.05), but no significant difference was found in the other indexes (P>0.05). For adults with acetabular dysplasia, there are high potential risks for unsatisfactory acetabular cup positions during primary THA. So it is necessary to evaluate acetabular deformities and to sum up operative experience so as to improve the accuracy of cups installation.

Total hip arthroplasty for post-traumatic hip fusion ankylosis secondary to operation in acetabular combined with femoral head fracture

Objective To investigate the technique and clinical results of total hip arthroplasty in treating post-traumatic hip fusion ankylosis secondary to operation in acetabular combined with femoral head fracture. Methods From October 2009 to January 2015, 7 patients (7 hips) with post-traumatic hip fusion ankylosis underwent total hip arthroplasty. There were 6 males and 1 female with an average age of 38 years (range, 25-51 years). There were 4 hips on the left side, 3 hips on the right side. Open reduction and internal fixation were performed on all patients. One patient had a postoperative deep infection and 6 patients under-went implant removal. The hip bony fusion ankylosis was developed secondary to post-traumatic arthritis after the surgery of ipsilateral acetabular combined with femoral head facture. The interval between internal fixation and total hip arthroplasty was 37.6 months on average (range, 21-67 months). The hip bony fusion ankylosis was relieved by wedge shape osteotomy at femoral neck level. The cementless prostheses were implanted in suitable places based on the accuracy position of acetabular center. One infection case was treated via surgical debridement, removal of all the screws, and antibiotic-loaded cement spacer implantation in the first stage. The cementless prostheses were implanted in the second stage. Results The average operation time and blood loss was 108 min (90-150 min) and 320 ml (280-450 ml) respectively. The internal fixation devices were explanted completely, including plate and screw in 5 cases, only screw in 1 case, intramedullary nail and screw in 1 case. The mean fallow-up period was 32.5 months (range, 15-48 months). The average Harris hip score improved from 48.8±6.5 points preoperatively to 92.6±5.1 points post-operatively (t=22.82, P=0.001). Osseointegration was developed in all of the acetabular and femoral components at 3 months post-operatively. Radiograph analysis showed satisfied position of acetabular cup and no evidence of implant migration or center of rotation change. Stem subsidence (<1.0 mm) occurred in 2 cases and heterotopic ossification in 2 cases (Brooker typeⅠ and typeⅡin 1 case, respectively) at one year postoperatively. No complication occurred, such as damages of vessels and nerve, dislocation, component loosening or infection. Conclusion The wedge shape osteotomy of femoral neck is a safe and reliable method in treating hip fusion ankylosis. Total hip arthroplasty can be achieved by reconstruction of acetabular center, suitable components implanted in anatomical position and ideal reconstruction of soft tissue around hip. Key words: Acetabulum; Femur head; Fractures, bone; Ankylosis; Arthroplasty, replacement, hip

Research progress on positioning accuracy of acetabulum prosthesis

In order to prevent the dislocation of total hip arthroplasty (THA) and reduce the wear rate, the position of the acetabular component in THA is very important. However, due to the influence of many potential factors, the accurate implantation of the acetabular component in the operation is still a challenge. Lewinnek safety zone positioning the cup anteversion angle (15±10)°, abduction (40±10)°, has been regarded as acetabular prosthesis installation standards, in an attempt to reduce the risk of instability, but there are still reported a dislocation. Based on the Lewinnek safety zone, Ha proposed the use of acetabular anatomical landmarks. According to patient specific shape positioning the position of the acetabular component methods are used to determine the specificity of the target area, thereby reducing the impact of hip replacement, and to maintain a lower liner wear rate. Image navigation system can improve the positioning of acetabular cup, but it is affected by many factors, such as high cost, difficult operation and so on.

Results of Primary Total Hip Arthroplasty Using 36 mm Femoral Heads on 1st Generation Highly Cross Linked Polyethylene in Patients 50 Years and Less with Minimum Five Year Follow-up.

PurposeWe evaluated the clinical and radiographic midterm results of primary total hip arthroplasty (THA) using a 36 mm diameter femoral head on 1st generation highly cross-linked polyethylene (HXLPE) in patients 50 years and less with minimum five year follow-up.Materials and MethodsWe retrospectively reviewed 31 patients (41 hips) aged 50 years and less underwent primary THA with a 36 mm diameter femoral head on HXLPE between 2004 and 2010. Clinical follow-ups included specific measurements like modified Harris hip scores (HHS) and Merle d'Aubigne and Postel score. For radiologic evaluations, together with position of acetabular cup at six weeks later of postoperation, we separately calculated the penentrations of femoral head into polyethylene liners during postoperation and one year later check-ups, and during one year later check-ups and final check-ups.ResultsThere were no major complications except for one case of dislocation. Average modified HHS at final follow-up was 88 (81-98), and Merle d'Aubigne and Postel scores were more than 15. Mean acetabular cup inclination and anteversion were 45.81°(36.33°-54.91°) and 13.26°(6.72°-27.71°), respectively. Average femoral head penetration of steady-state wear rate determined using radiographs taken at one-year postoperatively and at latest follow-up was 0.042±0.001 mm/year.ConclusionBased on minimum 5 years clinical results, we think 36 mm metal head coupling with HXLPE as the good alternate articulation surface when planning THA for patients aged 50 years and less.

A Kirschner wire as a transverse-axis guide to improve acetabular cup positioning.

To compare cup-positioning accuracy in total hip arthroplasty (THA) with or without use of a Kirschner wire as a transverse-axis guide for pelvic alignment. Records of 18 men and 73 women (mean age, 60 years) who underwent primary THA with (n=49) or without (n=42) use of a Kirschner wire as a transverse-axis guide for pelvic alignment were reviewed. A 2.4-mm Kirschner wire as a transversea-xis guide was inserted to the anterior superior iliac spine and was parallel to a line linking the left and right anterior superior iliac spine. The safe zone for cup positioning was defined as 30º to 50° abduction and 10º to 30º anteversion. Of the 5 operative surgeons, 2 were classified as experienced (total surgical volume >300) and 3 as inexperienced (total surgical volume of <50). The proportion of patients with the cup in the safe zone was compared in patients with or without use of the transverse-axis guide and in experienced and inexperienced surgeons. For inexperienced surgeons, the use of the transverse-axis guide significantly improved the proportion of patients with the cup in the safe zone from 90% to 100% for abduction, from 50% to 82.4% for anteversion, and from 40% to 82.4% for both. Patients with the cup inside or outside the safe zone were comparable in terms of body height, weight, BMI, subcutaneous fat thickness, incision length, and acetabular cup size. The use of the transverse-axis guide improved the accuracy of cup positioning by inexperienced surgeons.

Total hip arthroplasty via the anterior approach: tips and tricks for primary and revision surgery.

Described for the first time in the 1950s, the direct anterior approach to the hip has been gaining in popularity over the last decade following the trend of minimally invasive surgery. This paper provides an overview of the approach and its indications and various uses and focuses on its utility in the revision setting. A detailed overview of the technique including tips and tricks as well as an explanation of common errors are included. Graphic and clinical study of the approach, indications and feasibility. The reported benefits of the direct anterior technique include enhanced post-operative recovery and respect for all the innervation and vascularization territories. It has been shown to be safe and effective in revision settings, to decrease the occurrence of heterotopic ossification, to enhance the accuracy of acetabular cup positioning, and to improve post-operative rehabilitation while having comparable outcomes in terms of loosening or component failure. Additionally, thromboembolic events have been shown to be decreased compared to other approaches. The most common reported complications in the revision setting is intra-operative fracture. The decision of a surgeon to transition to this approach, however, comes with a learning curve and potentially detrimental complications if done improperly. In addition to its appeal in the primary setting, the approach could possibly be a solution to decrease the morbidity associated with revision surgery through its use of a fresh tissue plane not previously traumatized with the primary approach.

The Prevalence of Positive Findings on Metal Artifact Reduction Sequence Magnetic Resonance Imaging in Metal-on-Metal Total Hip Arthroplasty

BackgroundWe sought to assess the prevalence of soft tissue changes seen on magnetic resonance imaging (MRI) after metal-on-metal (MOM) total hip arthroplasty (THA) and determine if the presence of pseudotumors was associated with metal ion levels, acetabular cup position, outcomes scores, and femoral head size. MethodsAfter receiving an institutional review board exemption for secondary data analysis, we performed a cross-sectional study identifying 55 patients (55 hips) that underwent primary THA with a MOM articulation and had subsequent MRI imaging between February 2013 and February 2014 at a single academic medical center. ResultsTwenty-four patients (44%) had no evidence of pseudotumors, 27 (49%) had type I pseudotumors, and 4 (7%) were classified as having type II pseudotumors. The presence and severity of pseudotumors were associated with higher serum chromium levels (P = .043). Neither acetabular inclination nor acetabular version was associated with the presence of pseudotumors, the severity of pseudotumors, or elevated serum metal ion levels (all P > .05). Increased metal ion levels were associated with lower Harris Hip Score and higher Harris Hip Score pain subscores (all P < .05). ConclusionIn conclusion, pseudotumors on metal artifact reduction sequencing MRI may be present in both symptomatic and asymptomatic MOM THAs. Surgeons should therefore exercise caution in placing too much emphasis on isolated studies such as cross-sectional imaging. Instead, a structured approach to evaluation of MOM arthroplasty should be followed.

Influence of hip replacement on sagittal alignment of the lumbar spine: An EOS study.

Changes in pelvic position can influence the sagittal alignment of the lumbar spine. The restoration of hip kinematics by hip replacement thus appears to offer the possibility of correcting sagittal alignment. This preliminary retrospective study used EOS imaging to investigate the influence of total hip arthroplasty on pelvic parameters in patients with normal preoperative pelvic parameters. Twenty patients with hip osteoarthritis undergoing total hip arthroplasty (THA) between 2011 and 2012 received unilateral THA. To evaluate the preoperative and postoperative changes of the pelvic parameters, we analyzed EOS imaging of the patients to determine pelvic incidence, sacral slope, sacral tilt, pelvic tilt, anterior pelvic plane inclination and pelvic axial rotation. Additionally, anteversion and inclination of the acetabular cup position were determined. No statistically significant difference was found between the preoperative and postoperative measurements of pelvic parameters, although the change in pelvic tilt approached significance. Postoperatively, respective average values of 42.6° and 22.7° were measured for inclination and anteversion of the acetabular cup position. THA did not influence pelvic position and sagittal alignment in patients with normal preoperative pelvic parameters. A subsequent study will investigate whether corrections of pelvic parameters outside the norm in patients with OA are possible with THA.

Does Robotic-Assisted Computer Navigation Affect Acetabular Cup Positioning in Total Hip Arthroplasty in the Obese Patient? A Comparison Study

Obese populations present challenges for acetabular cup placement during total hip arthroplasty (THA). This study examines the accuracy of acetabular cup inclination and version in the obese patient with robotic-assisted computer navigation. A total of 105 patients underwent robotic-assisted computer navigation THA with a posterior approach. Groups were divided on body mass index (BMI, kg/m2) of <30, 30–35, and >35. There was no statistical difference between the BMI <30 (n=59), BMI 30–35 (n=34) and BMI >35 (n=12) groups for acetabular inclination (P=0.43) or version (P=0.95). Robotic-assisted computer navigation provided accurate and reproducible placement of the acetabular cup within safe zones for inclination and version in the obese patient.

Does component alignment affect gait symmetry in unilateral total hip arthroplasty patients?

BackgroundComponent malposition in total hip arthroplasty patients has been associated with adverse clinical outcomes. However, whether the component alignment influences hip dynamic performance following total hip arthroplasty remains unclear. The purpose of this study was to investigate the relationship between the component alignment and in vivo hip kinematics during gait. MethodsNineteen unilateral total hip arthroplasty patients received CT scan for creation of 3D hip models. The component alignment between the non-implanted and implanted hips were measured and compared. Three-dimensional hip kinematics for both hips of the total hip arthroplasty patients during gait was quantified using a dual fluoroscopic imaging technique. The differences between the implanted and non-implanted hip kinematics during gait were calculated. A forward stepwise multiple linear regression was performed to evaluate the relationships between the changes in implanted hip kinematics and the differences in component alignment with respect to the non-implanted hips. FindingsAn average 5.1° (SD 6.5°; range −11.1° to 18.3°) increase in internal rotation was observed in the implanted hip than the contralateral non-implanted hip and significantly correlated with a linear combination of the increase of cup anteversion, cup medial translation and leg lengthening (R=0.81). InterpretationResults suggested that the total hip arthroplasty patients compensated the changes in hip geometry by altering the dynamic movement during gait. Restoration of the native hip geometry, including acetabular cup anteversion, position and leg length could be one of the factors that influence the hip kinematics symmetry in total hip arthroplasty patients during gait.

Acetabuloplasty with bone grafting in uncemented hip replacement for protrusion.

This retrospective study investigated midterm outcomes of uncemented total hip replacement with acetabuloplasty using impacted bone grafts in acetabular protrusion or primary hip arthritis with an inadequate thickness of the medial acetabular wall. The medial acetabular wall was augmented by impaction bone grafting, and an uncemented cup was implanted in all cases. Hip centre of rotation, medial acetabular wall thickness and cup positioning were evaluated radiologically, with the Harris Hip Score determined at each follow-up. A total of 32 patients (39 hips) were followed for a mean of 4.5 years, with significant improvement of the Harris Hip Score at the last follow-up. Hip centre of rotation was restored close to the optimal position. Medial acetabular wall thickness and cup position obtained immediately postoperatively were maintained up to the last follow-up, without statistically significant differences. Bone graft integration was observed in all cases by one or two years postoperatively, with no signs of loosening or cup migration at the last follow-up. Heterotopic ossification was identified in 15.4% of cases, without clinical evidence of hip mobility impairment or pain. Impaction bone grafting for acetabuloplasty, associated with the implantation of an uncemented cup, yields good midterm results in patients with acetabular protrusion and with primary hip arthrosis with a thinned medial acetabular wall. The restored bone stock and medial acetabular wall thickness enable the placement of the hip centre of rotation close to the optimal location, which could offer further long-term benefits.

The Divergence of Wear Propagation and Stress at Steep Acetabular Cup Positions Using Ceramic Heads and Sequentially Cross-Linked Polyethylene Liners

The aim of the present wear simulator study was to assess the effect of steep acetabular cup positions on the wear propagation of highly cross-linked-PE (HX-PE) liners. Furthermore, a finite element analysis (FEA) was performed in order to calculate the stress within the HX-PE material in case of steep cup positions under physiological loadings. The higher stress in the HX-PE at a steep acetabular cup position did not result in increased wear in the present wear simulator study. The gravimetrical wear rates at normal (45°) and steep cup inclinations (75°) showed wear amounts of 3.15±0.27mg and 2.18±0.31mg per million cycles (p=0.028), respectively. However, FEA revealed clear increase in stress at the HX-PE liners with respect to steep cup positions.

Adverse condition testing with hip simulators

Recent clinical failures and abnormal sounds observed in certain prosthetic hip designs have directed attention to adverse condition hip simulator testing. In the present study, hip simulator wear and friction tests were made with a macroscopic separation of the bearing surfaces in the swing phase, steep acetabular cup position, increased load, poor or lacking lubrication, roughened bearing surfaces including titanium third bodies, and with combinations of these. The only conditions that resulted in squeaking were dry sliding with alumina-on-alumina and metal-on-metal, and an extreme peak load of 4kN with serum lubricated metal-on-metal. The wear rate of metal-on-metal increased by an order of magnitude when the cup position was steep, 64°, compared with the optimal position of 48°. The increase of the peak load from 2kN to 3kN with the cup position of 48° increased the running-in wear of metal-on-metal, but the steady state wear rates were equally low, of the order of 1mg per one million cycles. Crosslinked polyethylene was the superior cup material under adverse conditions, including dry sliding and roughened femoral head.

A 42-year-old patient presenting with femoral head migration after hemiarthroplasty performed 22 years earlier: a case report.

IntroductionTreatment of femoral neck fractures in young adults may require total hip arthroplasty or hip hemiarthroplasty using a bipolar cup. The latter can, however, result in migration of the femoral head and poor long-term results.Case presentationWe report a case of femoral head migration after hemiarthroplasty performed for femoral neck fracture that had occurred 22 years earlier, when the patient (a Japanese man) was 20 years old. He experienced peri-prosthetic fracture of the femur, subsequent migration of the prosthesis, and a massive bone defect of the pelvic side acetabular roof. After bone union of the femoral shaft fracture, the patient was referred to our hospital for reconstruction of the acetabular roof. Intra-operatively, we placed two alloimplants of bone from around the transplanted femoral head into the weight-bearing region of the acetabular roof using an impaction bone graft method. We then implanted an acetabular roof reinforcement plate and a cemented polyethylene cup in the position of the original acetabular cup. Eighteen months post-operatively, X-rays showed union of the transplanted bone.ConclusionsTreatment of femoral neck fractures in young adults is usually accomplished by osteosynthesis, but it may be complicated by femoral head avascular necrosis or by infection or osteomyelitis. In such cases, once an infection has subsided, either hip hemiarthroplasty using a bipolar cup or total hip arthroplasty may be required. However, if the acetabular side articular cartilage is damaged, a bipolar cup should not be used. Total hip arthroplasty should be performed to prevent migration of the implant.

Predictive value of robotic-assisted total hip arthroplasty.

Acetabular cup positioning, leg-length discrepancy, and global offset are important parameters associated with outcomes following total hip arthroplasty (THA). Deviation from an accepted range of values can lead to significant complications, including dislocation, leg-length discrepancy, impingement, accelerated bearing surface wear, and revisions. The purpose of this study was to assess whether robotic-assisted THA was reliable in predicting radiographic measurements of cup inclination and anteversion, leg-length change, and global offset change. All 61 robotic-assisted THAs that met the inclusion and exclusion criteria were performed by a single surgeon through a mini-posterior approach. Data provided by the robot were collected prospectively, and radiographic data were collected retrospectively by 2 blinded independent reviewers. The cohort in this study consisted of 27 male and 34 female patients, with an average age of 60.5 years. A strong inter- and intraobserver correlation was found for the radiographic measurements of cup inclination, cup anteversion, leg-length discrepancy, and global offset (r>0.8 with P<.001 for all). Ninety-six point seven percent of robotic-measured inclination angles and 98.4% of robotic-measured anteversion angles were within 10° of radiographic measurements. One hundred percent of robotic-measured leg-length change and 91.8% of robotic-measured global offset change were within 10 mm of radiographic measurements. Robotic-assisted THA showed good predictive value for cup inclination and anteversion angles and measurements of leg-length change and global offset change done postoperatively on plain radiographs. Further refinement of the robotic system would make it more accurate in predicting the postoperative parameters mentioned.

Results of Primary Total Hip Arthroplasty with 36-mm Femoral Heads on Highly Cross-linked Polyethylene-Minimum Seven-years Follow-up.

PurposeWe evaluate the clinical and radiographic midterm results of primary total hip arthroplasty (THA) using a 36 mm diameter femoral head on highly cross-linked polyethylene (minimum 7-year follow-up).Materials and MethodsWe retrospectively reviewed 73 patients (74 hips) that underwent primary THA with a 36 mm diameter femoral head on highly cross-linked polyethylene between July 2004 and February 2007. Clinical follow-ups included specific measurements like modified Harris hip scores (HHS) and Merle d'Aubigne and Postel score. For radiologic evaluations, together with position of acetabular cup at 6 weeks later of post-operation, we separately calculated the penentrations of femoral heads into polyethylene liners during post-operation and one year later check-ups, and during one year later check-ups and final check-ups.ResultsThere were no complications except for one case of dislocation. Average modified HHS at final follow-up was 88±7.5 (range, 81-96), and Merle d'Aubigne and Postel scores were more than 15 (range, 15-18). Mean acetabular cup inclination and anteversion were 50.1°(range, 35°-58°) and 23.6°(range, 5°-38°), respectively. Average femoral head penetration during the first postoperative year was 0.071±0.034 mm/year, and steady-state wear rate determined using radiographs taken at one-year postoperatively and at latest follow-up was 0.051±0.022 mm/year. Average femoral head penetration during entire follow-ups was 0.058±0.013 mm/year.ConclusionPrimary THA with a large diameter femoral head on highly cross-linked polyethylene was found to produce the results comparable to previous in vitro laboratory hip simulation studies. And we also find out good scores in terms of patient's functionality.