Non-cemented Cup Research Articles

Short- and mid-term effectiveness of impaction bone allograft with acetabular components in treatment of severe acetabular defects

To investigate the short- and mid-term effectiveness of revision hip arthroplasty by using impaction bone allograft and acetabular components in treatment of severe acetabular defects. A clinical data of 42 patients (44 hips) with severe acetabular defects between February 2011 and May 2018 were retrospectively analyzed. All patients underwent revision hip arthroplasty by using impaction bone allograft and acetabular components. Cemented cup (24 cases, 24 hips) and non-cemented cup (18 cases, 20 hips) were used in the revision surgery. There were 17 males and 25 females with an average age of 62.8 years (range, 22-84 years). The interval between the first total hip arthroplasty and revision was 2.5-12.0 years (mean, 8.3 years). The patients were accepted revision surgery for prosthesis aseptic loosening in 32 hips (31 cases) and the periprosthetic infection in 12 hips (11 cases). Twenty-nine hips (28 cases) were Paprosky type ⅢA and 15 hips (14 cases) were type ⅢB. The preoperative Harris score was 22.25±10.31 and the height of hip rotation center was (3.67±0.63) cm and the length difference of lower limbs was (3.41±0.64) cm. The operation time was 130-245 minutes (mean, 186 minutes) and the intraoperative blood loss was 600-2 400 mL (mean, 840 mL). The postoperative drainage volume was 250-1 450 mL (mean, 556 mL). Superficial infection of the incision occurred in 1 case, and the incisions healed by first intention in the other patients. All patients were followed up 6-87 months, with an average of 48.6 months. At last follow-up, the Harris score was 85.85±9.31, which was significantly different from the preoperative score ( t=18.563, P=0.000). Imaging examination revealed that the allogeneic bone gradually fused with the host bone, and no obvious bone resorption was observed. At last follow-up, the height of the hip rotation center was (1.01±0.21) cm, which was significantly different from the preoperative level ( t=17.549, P=0.000); the length difference of lower limbs was (0.62±0.51) cm, which was significantly different from the preoperative level ( t=14.211, P=0.000). The Harris score in the cemented group and non-cemented group increased significantly at last follow-up. The height of the hip rotation center decreased, and the hip rotation centers of both groups were within the Ranawat triangle zone. The length difference of the lower limbs also decreased, and the differences in all indexes were significant between pre- and post-operation ( P<0.05). There was significant difference in the height of the hip rotation center between groups ( t=2.095, P=0.042), but there was no significant difference in the Harris score and the length difference of lower limbs between groups ( P>0.05). For severe acetabular defect (Paprosky type Ⅲ), the hip can be reconstructed with the impaction bone allograft and cemented or non-cemented components in revision hip arthroplsty. The short- and mid-term effectiveness are satisfactory.

Model-based roentgen stereophotogrammetric analysis using elementary geometrical shape models: 10\xa0years results of an uncemented acetabular cup component

BackgroundNon-cemented acetabular cup components demonstrated different clinical performance depending on their surface texture or bearing couple. However, clinical osseointegration needs to be proved for each total joint arthroplasty (TJA) design. Aim of this study was to detect the in vivo migration pattern of a non-cemented cup design, using model-based roentgen stereophotogrammetric analysis with elementary geometrical shape models (EGS-RSA) to calculate early cup migration.MethodsInterchangeable applicability of the model-based EGS-RSA method next to gold standard marker-based RSA method was assessed by clinical radiographs. Afterwards, in vivo acetabular cup migration for 39 patients in a maximum follow up of 120 months (10 years) was calculated using model-based EGS-RSA.ResultsFor the axes with the best predictive capability for acetabular cup loosening, mean (±SD) values were calculated for migration and rotation of the cup. The cup migrated 0.16 (±0.22) mm along the cranio-caudal axis after 24 months and 0.36 (±0.72) mm after 120 months, respectively. It rotated − 0.61 (±0.57) deg. about the medio-lateral axis after 24 months and − 0.53 (±0.67) deg. after 120 months, respectively.ConclusionsInterchangeable applicability of model-based EGS-RSA next to gold standard marker-based RSA method could be shown. Model-based EGS-RSA enables an in vivo migration measurement without the necessity of TJA specific surface models. Migration of the investigated acetabular cup component indicates significant migration values along all the three axes. However, migration values after the second postoperative year were within the thresholds reported in literature, indicating no risk for later aseptic component loosening of this TJA design.

Long-term Results of Primary Hip Arthroplasty with Cup Inclination Angle Bigger than Fifty Degrees

BackgroundMost of studies suggest the cup inclination angle is controversial. All of the studies previous have not control the prosthesis type and head diameter, it is difficult to determine relative or synergistic effects of cup angle. MethodsWe retrospectively reviewed 54 patients (61 hips) with primary total hip arthroplasties which cup inclination angle bigger than 500 after a mean 11.8 years follow-up. All the prosthesis are noncemented cup with a 28mm metal head(Trilogy Acetabular Shell, Zimmer). The cup inclination was divided into three groups, 50–550 in 26 hips, 55–600 in 21 hips, and bigger than 600 in 14 hips. An immediate postoperative radiograph was compared with a follow-up radiograph. The polyethylene wear rates and abduction of the acetabular cups was measured in all of the patients. ResultsThe preoperative mean Harris hip score improved from 47.36 to 94.3 points at 10 years. The survivorship of the cup was 100% at 10 years. The mean rate of liner wear was 0.144±0.031mm/y (0.105–0.178mm/y) in cup inclination angle between 500–550, and 0.260±0.043mm/y (0.215–0.394mm/y) in angle between 550–600, 0. 403±0.016mm/y (0.378–0.423mm/y) in angle bigger than 600. The different cup inclination groups are different with liner and volumetric wear. ConclusionFor the metal-on-polyethylene prostheses, the liner wear obvious correlate with cup inclination after angle bigger than 500. It can be concluded that the ideal abduction angle for metal-on-polyethylene prostheses should be less than 55° in hip total replacement.

Safety of total hip arthroplasty for femoral neck fractures using the direct anterior approach: a retrospective observational study in 86 elderly patients.

BackgroundThe femoral neck fracture is one of the most common fractures in the elderly. A variety of methods and approaches are used to treat it. Total hip arthroplasty is a preferred approach in independent, mobile, elderly patients, given its more favorable long-term outcome.Our hypothesis is that the direct anterior approach in geriatric trauma patients has a lower dislocation-rate with the advantage of early recovery due to a muscle sparing approach and therefore early possible full weight-bearing.MethodsPatients were retrospectively sought who suffered a femoral neck fracture from 2008 to 2013. All patients were treated through a direct anterior approach and using the same brand of implants. Medical history, standardized physical exam, conventional pelvic plain and axial hip x-rays, Harris Hip Score, Merle D'Aubigné and Postel and SF-36 were assessed.ResultsEighty-six patients were included in the study with a mean age of seventy-five years. The mortality rate was 16.7 %. Complications were encountered in nineteen patients (22.0 %) who needed operative revision and one postoperative complication (1.2 %) which could be handled conservatively. There were five intraoperative complications (5.8 %), two dislocations (2.3 %), one aseptic loosening in a non-cemented stem (1.2 %), six periprosthetic fractures in non-cemented stems (6.9 %), one displacement of a non-cemented cup (1.2 %), two early infections (2.3 %) and three hematomas (3.5 %) recorded.ConclusionsAlthough the direct anterior approach is associated with a rather long learning curve we have found it to preserve the soft-tissues with no injury to abductors. It therefore shows an early advantage in elderly patients in terms of early recovery and therefore early possible full weight-bearing. Fracture treatment with dual mobility cups might lead to lower dislocation rates, but are associated with higher costs. Due to higher complication rates in non-cemented versus cemented shafts, we have changed our practice towards favoring cemented femoral stems in patients with suspected or manifest osteoporosis.

Treatment algorithm of acetabular periprosthetic fractures.

Periprosthetic fractures of the acetabulum represent a rare incident in primary and revision total hip arthroplasty. The management of these fractures can be challenging. At present, there are no reliable guidelines for the treatment of periprosthetic acetabular fractures. Periprosthetic acetabular fractures can occur intra-operatively, in particular during insertion of non-cemented cups or in the context of revision surgery. Post-operative causes for periprosthetic acetabular fractures are traumatic events or, more commonly, pelvic discontinuity due to severe bone loss related to osteolysis. Despite their aetiology, the main objective of surgery is to achieve a stable acetabular component and fracture. While stable fractures and implants could be treated non-operatively, unstable fractures require surgery to achieve component stability and allow appropriate biological fixation of the revision cup. Assessment of the stability plays a crucial role before determining the treatment strategy. There is a large variety of surgical techniques available for the management of these fractures. This review article outlines the epidemiology, aetiology and current classification systems, and provides a distinct diagnostic and therapeutic algorithm for the treatment of periprosthetic acetabular fractures.

Prospective cohort study of six hundred and sixty four revisions of loose failed acetabular implants.

The purpose of the study was to determine the optimal technique of revision surgery according to the deficiency of acetabular bone to ensure maximum survival of the implant and reduce the risk of complications. From January 1992 through May 2012, 664 revisions of failed acetabular total hip components were performed in the joint replacement department of the Moscow Central Scientific and Research Institute (CITO). The patients were divided into three major groups based on the type of the revision implant: group I--cemented polyethylene cups only, group II--acetabular cages and rings, and group III--non-cemented metal cups. In each of these groups, further subdivisions were made based on the Paprosky Classification of the acetabular defects. Failures were classified as early mechanical instability, chronic pain, and deep wound infection. The most satisfactory results--91% were obtained in patients of groups I and III with relatively minor bony acetabular defects (Paprosky classification types 1, 2A and 2B). The most unsatisfactory results--25% were in the cases with greater bone loss (Paprosky classification type 3B in group I and type 2C in group III)-of the unsatisfactory results. Infection was a significant problem in all the groups, but was the highest (8%) in group II. The study showed that the success of acetabular revisions was directly related to the severity of the bony defects at the time of the operation and to the reconstruction technique applied.

Changes of Load Distribution on Cup-Bone Interface at the Different Positions of Non-Cemented Acetabular Cup

Objective To explore the relationship between acetabular cup position and the load distribution within the acetabulum and to confirm an optimal range of cup position, thereby providing a theoretical criterion from a biomechanical aspect for proper cup implantation in clinical work. Methods A male adult cadaveric pelvic was scanned with spiral CT, and then the two-dimensional images were evaluated using GE medical systems software and the outline of the pelvis was identified by the edge detective estimation. Pelvic coordinate data were put into the computer to build up a three-dimensional (3D) finite element model of the pelvic using Solidworks software . A φ48 non-cemented cup from Tianjin Huabei Medical Instrument Factory was used, and the 3D measurement of the cup was carried out by CLY single-arm 3D measurement apparatus, which was made in Testing Technology Institute of China. The measurement data were transferred into computer. Through the CAD Sliod Works 2010 software, the 3D model of the cup was automatically reconstructed. After wards, one-foot standing position was simulated to conduct the loading and constraint of the model, the Mises and shear force distributing of the cup were analyzed, forecasting the mechanical risk of prosthetic failure. Results In the 3D finite element model of human pelvis, the number of total nodes was 103043 and the number of total elements was 69271. Abduction angle did not affect the Mises and shear force distributions between the range of 40°-50°(P&gt;0.05). However, significant affects appeared in Mises and shear force once the abduction angle was &lt; 35° or &gt; 50°. The change of the cup anteversion within5°-30°would not affect the Mises and shear forces in the acetabulum (P &gt; 0.05). Conclusion A uniform load distribution on the cup-bone interface can be obtained when the cup abduction angle is from 40°to 50°. The change of the cup anteversion angle can not affect the load distribution in the acetabulum, therefore the cup abduction range of 40°-50°can be confirmed as the safe range for cup implantation.

Cementless cups do not increase osteolysis risk in metal-on-metal total hip arthroplasty

Metal-on-metal bearings in total hip arthroplasty (THA) were introduced to reduce the production of wear debris and debris-induced periprosthetic osteolysis. Analysis of various series according to the type of selected acetabular fixation highlights different evolutions: favourable results with uncemented cups contrasting with loosening and radiolucent lines (RLL) evolution for cemented cups. Combining metal-on-metal bearings to uncemented cups does not increase the osteolysis risk at a minimum 5 years' follow-up. From January 1999 to December 2002, 106 Metasul THAs were implanted in 95 patients using a Hardinge anterolateral approach (40 women and 55 men with an average age of 59.2 years). The cups were of cementless, hydroxyapatite-coated Cedior type (Zimmer) housing a Metasul insert in a polyethylene sandwich. The femoral stem used was the cemented Acora, then the Exafit (Zimmer) type with Metasul 28-mm head mounted on a 8/10 Morse taper. Patients were evaluated clinically using the Postel-Merle-d'Aubigné (PMA) scoring system and radiologically using various markers: cup inclination angle, eventual RLL presence, appearance of osteolysis images, ectopic ossifications and finally, eventual implant migration. In the eventuality of suspected RLL evolution or osteolysis, advanced imaging was performed; joint aspiration liquid and cobalt serum level were studied. We reviewed 94 prostheses (85 patients) with an average follow-up of 6.4 years (4.3 to 9.3 years, median of 6.3 years). The rate of patient loss from follow-up and death was 12.1%. The PMA score of non-revised patients increased from 11.4+/-1.5 to 17.6+/-0.2 at follow-up. We numbered ten re-operations not attributable to the type of bearings used. Three revisions were directly related to the metal-on-metal bearing: two metallosis due to impingement and one case of hypersensitivity. Cup inclination angle was 45.7+/-5.49 degrees . No implant migration was noted during the follow-up duration. Only one cup undergoing revision presented a substantial osteolysis. On the femoral side, with non-revised implants, we observed 13 cement/bone RLL images around nine femoral stems and six calcar resorptions. The survival rate at more than 6 years was 95.8% (91.8-99.8) for the cups and 94.8% (90.3-99.2) for the femoral stems (95% confidence interval). The present study confirms our hypothesis: with Metasul bearings equipped cementless cups, the rates of aseptic loosening, RLL or acetabular osteolysis are low and remain stable over time, unlike the results observed for Metasul series with polyethylene directly cemented on bone. Specific complications, such as metallosis due to impingement and hypersensitivity, can rarely be encountered. These results encourage us to continue employing metal-on-metal bearings with non-cemented cups in active patients. Level IV: Therapeutic study.

2 Year RSA Evaluation of Femoral Head Penetration in a Challenge Population of Young THR Patients

Methods: After informed consent, 45 patients enrolled in an IRB approved, prospective, randomized study to receive either a crosslinked or a conventional UHMWPE liner in a noncemented hemispheric cup (Trilogy). Both liners are prepared from compression-molded GUR 1050 resin; calcium-stearate free. Highly crosslinked liners undergo further e-beam irradiation and heat-annealing. A 28mm femoral head was used in all cases. 1.0mm tantalum markers were implanted in the liner periphery. RSA film pairs were obtained at 10 days, 6 months, 1 year, and 2 years post-op. Harris Hip, UCLA, SF-12, PCS, MCS, and WOMAC scores were obtained.

Modes of periacetabular load transfer to cortical and cancellous bone after cemented versus uncemented total hip arthroplasty: A prospective study using computed tomography‐assisted osteodensitometry

Stress-shielding and periprosthetic bone loss after total hip arthroplasty (THA) may be clinically relevant for high-demand patients. Analysis of cortical and cancellous bone density (BD) changes in vivo after THA is of interest to basic science researchers and joint reconstruction surgeons. An insufficient periprosthetic bone stock may predispose to migration, early mechanical failure, and major problems in revision surgery. We used computed tomography (CT)-assisted osteodensitometry in two prospectively analyzed cohorts after cemented (n = 21) versus noncemented (n = 23) cup fixation. Periacetabular BD (mgCaHa/mL) was determined in five CT scans cranial and five CT scans at the level of the cup 10 days and 26 months postoperatively. For press-fit cups BD decreased significantly in all CT cans except in four out of the five scans of cortical bone cranial to the cup. The decrease was highest for cancellous bone ventral to the cup (-45 to -53%). After cemented cup fixation, significant cortical BD decrease was seen ventral to the cup (-11 to -20%). Cancellous BD decrased only ventral (-21 to -31%) and in two scans cranial (-11 and -12%) to the cup. The modes of load transfer between cemented and uncemented cups differ fundamentally. Cemented cups especially prevent the loss of cancellous bone of the acetabulum while also cortical BD loss was significantly lower in most CT scans surrounding the cemented cup compared to the press-fit component. Long-term results are required to prove whether third-generation cementing technique protects periprosthetic BD and thereby improve implant survival.

Étude prospective comparant la voie postérieure minimale invasive versus voie postérieure standard sur prothèse totale de hanche de première intention

Purpose of the study There have been few prospective studies comparing minimally invasive approaches for total hip replacement. We wanted to ascertain the contribution of the minimally invasive posterior approach in comparison with the standard posterolateral approach in terms of early outcome. Materials and methods This was prospective comparative consecutive series of patients. Patients with major architectural problems or undergoing revision arthroplasty were excluded. One hundred ten patients (116 hips) were divided into two groups which were comparable for number of patients, gender, age, body mass index, indication for surgery, and preoperative function scores. The preoperative ASA score was lower in the minimally invasive group (p = 0.04). The patients were in the lateral reclining position for the two approaches and classical instrumentation using the same implants (stems and cemented or non-cemented cups) were used. We noted operative time and blood loss (using the Brecher method based on the hematocrit at day 1 and 5 and the number of blood transfusions), postoperative pain, and implant position. Functional outcome was assessed with the modified Harris score and the WOMAC index (at 6 weeks and 3 and 6 months). Statview ® was used to search for statistical significance considering p < 0.05 as significant. Results Mean length of incision was 8.5 cm versus 15.1 cm. Mean blood loss was significantly less in the minimally invasive group (p = 0.027) as was the level of postoperative pain as confirmed by the lesser consumption of morphine analgesics (p = 0.006). Other operative variables as well as implant position were comparable. There were no major complications in the minimally invasive group. In the standard group, there was one case of common peroneal nerve palsy, two dislocations, and two fractures related to falls after prosthesis implantation. The WOMAC index was better after the minimally invasive approach at six weeks and at three months (p < 0.05). The modified Harris score was better only at six weeks. Functional outcome and pain became comparable thereafter. Discussion and conclusion The minimally invasive posterior approach does not require an orthopedic table nor specific instrumentation. A minute procedure is required with ligature of the posteromedial circumflex artery of the thigh to improve exposure and limit intraoperative bleeding. It enables satisfactory reproducible implant positioning. Conversion to an open posterolateral approach is possible if needed. The minimally invasive posterior approach enables a reduction in intraoperative bleeding and in postoperative pain while allowing earlier more rapid rehabilitation. Early clinical outcome is better but beyond six weeks, the functional results are comparable for the two approaches. The minimally invasive posterior approach is a reliable reproducible approach with a progressive learning curve.

Evolution of surgical techniques for the treatment of angular and torsional deviation in DDH: 20 years experience

The anatomical abnormalities associated with developmental dysplasia of the hip (DDH) increase the complexity of hip arthroplasty. In addition, previous femoral osteotomy can deform the proximal femur. Noncemented cups and stems are specifically designed for dysplasia to recover the true acetabular region in Crowe grade IV and sometimes Crowe grade III; additional surgical procedures are required. The purpose of the study was to analyse the surgical procedure and then the reconstructive options in DDH. From 1984 until now, total arthroplasty has been performed, on dysplastic hips, in 2,101 patients for 2,308 hips (207 patients bilateral 9% rate). All the procedures were performed by the senior authors (LS, GG) at the same hospital specialised in elective hip surgery. More than 80% of patients came from Northern Italy. The average age was 51 (range 32-83), 565 cases had involved a previous femoral osteotomy. Out of these 2,308 cases, 128 cases needed treatment for corrections of femoral side deformity; 64 cases were subjected to a greater trochanter osteotomy. In 12 cases, proximal femur shortening was involved. In 9 cases, rotational abnormality and shortening were controlled with a distal femur osteotomy. Fifty-five cases were treated by a shortening subtrochanteric osteotomy that allows corrections of any deformity. Only noncemented stems were used. Long-term results in these patients are consistently inferior (70% survival rate at 15 years) compared to those in the non-DDH population (97.7% survival at 15 years). On the femoral side, early failures are the reflection of a learning curve and are due to insufficient fixation of the osteotomy. The more promising outcomes are those involving a shortening subtrochanteric osteotomy.

Evolution of Surgical Techniques for the Treatment of Angular and Torsional Deviation in DDH: 20 Years Experience

The anatomical abnormalities associated with developmental dysplasia of the hip (DDH) increase the complexity of hip arthroplasty In addition, previous femoral osteotomy can deform the proximal femur. Noncemented cups and stems are specifically designed for dysplasia to recover the true acetabular region in Crowe grade IV and sometimes Crowe grade III; additional surgical procedures are required. The purpose of the study was to analyse the surgical procedure and then the reconstructive options in DDH. From 1984 until now, total arthroplasty has been performed, on dysplastic hips, in 2,101 patients for 2,308 hips (207 patients bilateral 9% rate). All the procedures were perfomed by the senior authors (LS, GG) at the same hospital specialised in elective hip surgery. More than 80% of patients came from Northern Italy. The average age was 51 (range 32–83), 565 cases had involved a previous femoral osteotomy. Out of these 2,308 cases, 128 cases needed treatment for corrections of femoral side deformity; 64 cases were subjected to a greater trochanter osteotomy. In 12 cases, proximal femur shortening was involved. In 9 cases, rotational abnormality and shortening were controlled with a distal femur osteotomy. Fifty-five cases were treated by a shortening subtrochanteric osteotomy that allows corrections of any deformity. Only noncemented stems were used. Long-term results in these patients are consistently inferior (70% survival rate at 15 years) compared to those in the non-DDH population (97.7% survival at 15 years). On the femoral side, early failures are the reflection of a learning curve and are due to insufficient fixation of the osteotomy. The more promising outcomes are those involving a shortening subtrochanteric osteotomy.

Tiges fémorales sur mesure non cimentées pour séquelle de dysplasie et luxation congénitale de hanche

Purpose of the study Arthroplasty in developmental dysplasia of the hip joint raises technical problems related to the anatomy and age of the young patient. The purpose of this work was to report results obtained with a custom-designed cementless stem. Material and methods This study included 257 hips reviewed at mean 82 months (range 43-162 months). Mean patient age was 55 years (17-78), mean weight 67 kg (42-118), and mean height 164 cm (147-190). A standard imaging protocol was performed for all patients: AP pelvis in reclining position, AP and lateral views of healthy and pathological hip, AP view of entire lower limb in standing position, computed tomography of lower limb. La position of the greater trochanter and the lengthening necessary was determined from the preoperative films. Stem integration and migration as well as osteolysis were studied postoperatively. Femoral anteversion and the anteroposterior diameter of the paleoacetabulum were measured on the superposed computed tomographic images. Surgery was performed via a Watson-Jones approach to insert a noncemented cup hooked in the obturator foramen and implanted in the paleoacetabulum. The femur endomedullary cavity was prepared with a ream having the form of the definitive stem and the prosthetic neck was custom fit to match the desired lever arm and anteversion. Results The series included 174 cases of dysplasia and 83 dislocations, 39% stage 1, 30% stage 2, 14% stage 3 and 17% stage 4. Mean lengthening was 39 mm. The mean helitorsion was 28 ± 16̊ and the mean anteroposterior diameter of the acetabulum was 51 mm. On average, the alpha correction in the prosthetic neck was -13.4̊ (-71̊to +37̊). The Postel-Merle-d’Aubigné score improved from 10.4 points preoperatively to 16.7 points at last follow-up. Postoperative x-rays showed signs of osteointegration in 88% of cases, osteolysis in 5% and one case of stem impaction. Ten hips (3.9%) required revision for replacement (7 for an aseptic problem and 3 for sepsis). Survival was 94.7% at 13 years. Discussion This study confirmed the anatomic modifications observed in patients with developmental hip dysplasia and the surgical problems they cause. There was no correlation between the degree of dislocation and the degree of helitorsion which is difficult to assess without a preoperative computed tomography. The survival rate at 13 years is encouraging in this population. The intramedullary portion of the cementless stem must be adapted to the dimensions of the femoral canal which decrease with increasing dislocation.

A Case of Periprosthetic Fracture of Acetabulum Associated with Osteolysis

Periprosthetic acetabular fracture after total hip arthroplasty is relatively uncommon but can occur in high-energy trauma or in patients with bone loss secondary to osteolysis. We encountered a periprosthetic acetabular fracture after minor trauma. The fracture was minimally displaced, and was treated conservatively. After eight-weeks non-weight-bearing, the fracture was healed but the acetabular cup had migrated. Acetabular revision was performed with morcellized allograft and non-cemented acetabular cup. At the one-year follow-up, the injured hip showed good range of motion with a stable acetabular component.

Secondary stability of cemented and non-cemented acetabular implants ex-vivo under dynamic load

To measure the bone-prosthetic implant interface micromovement during the application of physiological load by using a material testing system (MTS). The cadaveric hip specimens were used to simulate a single leg stance and the joint in the neutral position. Micromovement was recorded via a 3-dimensional transducer in the acetabula of postmortem specimens, which had been preserved in formalin. The study data of the cemented and uncemented prosthsis refereed to the lone-term clinical process and the radiological status and experimental results. Cemented cups showed higher transverse relative motion up to 90 microm, whereas the maximum transverse movement of the non-cemented cup was 60 microm. Orthogonal motion perpendicular to the implant surface showed compression for all cups at all sites. The results indicate that there are large differences in survival time between 2 groups. That could not be compared statistically in secondary stability. Nevertheless, according to the results, the amount of micromotion of press-fit cup is relatively less than that of cemented polyethylene cup, which is instrumental in bone ingrowth and secondary stability.

Load transfer and fixation mode of press-fit acetabular sockets

Adequate initial fixation is a prerequisite for osseointegration and secondary stability of noncemented cups. Physiologic force transmission between the cup and acetabulum guarantees the best long-term fixation. To study load transfer within the natural hip joint and in the bone–implant interface of 2 different hemispherical noncemented press-fit cups, 10 hips were investigated in an experimental setup simulating single-leg stance. Load distribution and contact area were measured using prescale pressure-sensitive films and digital image analysis. Three dominant locations near the periphery of the acetabulum could be identified. Main load transfer occurs in the cranial region of the acetabulum, where it is buttressed by the iliac bone; the second location is at the posterior-inferior region at the ischial facet, and the third location is at the anterior region, where support is provided by the pubic bone. Peripheral rim contact was present in both cups but not completely circumferential. It showed marked loading at the same 3 locations similar to the natural hip joint. The ilioischial diagonal axis produced the highest press-fit. Peak local forces were found at the ischial and iliac facets. Local forces can be grouped into an iliac, an ischial, and a pubic group contributing 55%, 25%, and 20% to the total hip joint force. Pole contact was not present in the natural hip and with the biradial press-fit cup with flattened pole area but was observed with the pure hemispherical cup. Hence, stable fixation of an acetabular cup is achieved best by a 3-point-like bony support at the iliac, ischial, and pubic bone. The acetabular fovea does not provide functional support of the femoral head or endoprosthetic socket. In revision surgery, remaining peripheral bone stock at the iliac, ischial, and pubic locations allows stable implanation of primary cups. Copyright 2002, Elsevier Science (USA). All rights reserved.

Interface Stability on Insufficient Coverage of Non-cemented Acetabular Cup with Screw Fixations

Purpose : To analyze the effects of various amount of peripheral defect of the acetabulum in terms of the stability of the acetabular cup with screw fixation. Materials and Methods : The porous coated acetabular cup of Trilogy was press-fitted with 3 screw fixations after 2 mm undersized reaming into the distal part of 100 bovine femurs, but with insufficient peripheral coverage of 0%, 5%, 10%, 15% and 20% respectively. The micromotions of the acetabular cups were measured under the axial loads of 50, 100, 150, 200, 250, and 300 Kp, and torques were measured at of cup rotation under applied rotational force in 10 specimens in each of five groups. Results : The micromotion between the cup and bone interface increased proportionally with peripheral coverage insufficiency and the torque values in the five groups increased in proportion to the rotation degree and were inversely proportinal peripheral coverage insufficiency. Conclusion : 15% or less coverage insufficiency of the acetabular cup may be acceptable as the average micromotion is less than and compatible with biologic fixations.

Early Failure of Acetabular Component after Total Hip Arthroplasty in Irradiated Hip

Purpose : The treatment of the osteonecrosis in the acetabulum and femoral head after irradiation has not been well estabilished. The early failure of acetabular component after total hip arthroplasty (THA) is the main concern in osteonecrosis after irradiation. Materials and Methods : Our study included 18 patients with post-radiation osteonecrosis of 26 hips who had a THA, mean age 54.2 years. Average irradiation dosage was 4611 cGy and interval between irradiation and primary total hip replacement was 64.3 months. The cementless acetabular components were used in 16 hips (group one) and acetabular reinforcement rings were used in 10 hips (group two: Muller cup 6 cases, Ganz cup 4 cases). Results : Acetabular loosenings were occurred at 8 of 16 hips (Group 1: 50%) during the mean follow-up 46 months. The cases of M ller cup (Group 2: 33%) was failed in 2 of 6 hips at postoperative 12 months and 22 months. Conclusion : Although follow up duration is short and cases are small, the use of cemented cup with acetabular reinforcement ring was better than non-cemented cup for THA in irradiated hip in terms of preventive of early failure of acetabular component.

Three-dimensional secondary stability of cemented and non-cemented acetabular implants ex-vivo under dynamic load

INTRODUCTION: Aseptic loosening is still the most important cause for long-term failure of total hip joint arthroplasty. Therefore, the objective of our investigation is to test the stability of retrieved cemented and noncemented endoprosthetic acetabular cups by measuring the relative motion between the bone and the implant surface at various sites of the interface under physiological dynamic loading conditions. MATERIAL AND hfETHODSz A special device to hold the specimen and to simulate the motion of the hip joint during the stance phase of the gait cycle was constructed (Fig. 1). The gait data, i.e. the angles of flexionextension, abduction-adduction, internal and external rotation and the step frequency, were derived from a gait analysis of a normal person recorded in the gait laboratory. Combined joint movements were carried out between 25” of flexion and 5’ of extension, 5” of abduction and 3” of adduction and 3’ of internal and 5” of external rotation while applying the hip joint force at an angle of 23” to the femoral axis. The force is controlled with reference to telemetric data of Bergmann et al. (1993). Relative motion is measured by a micromechanical 3D-sensor at different locations of the bone-implant-interface. Specimens with a cemented Mueller polyethylene cup and a non-cemented Press-Fit Cup with titanium mesh coating had been tested. The complete set-up is mounted into the load frame of a biaxial material testing machine, where the joint is moved by the rotational actuator and the hip force is produced by the linear actuator. RESULT% In plane relative motions , i.e. transverse movements in the bone-implant interface, were site-dependent for both the cemented and the non-cemented cups. Cemented cups showed higher transverse relative motion up to 90 pm, whereas the maximum transverse movement of the non-cemented cup was 60 pm. Orthogonal motion perpendicular to the implant surface showed compression for all cups at ah sites. Bone and implant approached up to 40 pm when cemented cups were implanted and up to 20 pm for non-cemented cups. The results differed highly from specimen to specimen indicating different degrees of stability. CONCLUSION: Non-cemented acetabular press-fit cups with titanium mesh coating show better secondary stability than cemented polyethylene cups. But more retrieved specimens with comparable history should be tested.