Effect of acetabular modularity on polyethylene wear and osteolysis in total hip arthroplasty.

BACKGROUND: Debris from polyethylene wear causes osteolysis. In this study, we examined the effect of acetabular liner modularity on polyethylene wear and osteolysis. METHODS: We compared forty-one hips (thirty-nine patients) treated with a nonmodular, porous-coated acetabular component with a matched group of forty-one hips (forty patients) treated with a modular acetabular component. The groups were matched by patient gender and age, type of polyethylene material, method of polyethylene sterilization, femoral head size and manufacturer, and stem manufacturer. The mean follow-up period was 5.3 years (range, 3.8 to 6.8 years) for the nonmodular group and 5.5 years (range, 3.8 to 8.0 years) for the modular group. Using serial radiographs and a computer-assisted method, we measured two-dimensional head penetration into the polyethylene liner. Temporal head-penetration data and linear regression analysis were used to calculate the true wear rates. RESULTS: The nonmodular acetabular components demonstrated a lower, but not a significantly lower, mean true wear rate than did the modular components (0.11 compared with 0.16 mm/yr, p = 0.22), and they were associated with a significantly lower rate of osteolysis (2% compared with 22%, p = 0.01). In addition, the true wear rates of the nonmodular components were less variable than those of the modular components. The 95% confidence interval for the wear rates of the nonmodular components (0.08 to 0.13 mm/yr) was nearly half that of the modular group (0.11 to 0.20 mm/yr). CONCLUSIONS: The lower and more consistent true wear rates of the nonmodular components could be attributed to the fact that these cups were designed to have greater liner-shell conformity, greater liner thickness, and less liner-shell micromotion than modular components. These design factors could have favorably altered the stress distribution throughout the liner and could have thereby decreased wear. Although nonmodular components may present a partial solution to the problems of wear and osteolysis, they pose a disadvantage when a failed liner in a bone-ingrown acetabular component needs to be revised.     

Complete acetabular cup revision versus isolated liner exchange for polyethylene wear and osteolysis without loosening in cementless total hip arthroplasty

Introduction  

Revision surgery in patients showing polyethylene wear and acetabular osteolysis without visible acetabular cup loosening involves the difficult decision of whether to revise only the liner or both the cup and the liner. The purpose of this study is to compare the outcomes of complete acetabular revision and isolated liner exchange in patients showing wear and osteolysis without loosening.     

Aseptic loosening in total hip arthroplasty secondary to osteolysis induced by wear debris from titanium-alloy modular femoral heads

Since 1984, we have used components made of titanium alloy for total joint arthroplasty. Recently, two patients needed revision hip arthroplasty, approximately three years after the initial procedure, because of aseptic loosening secondary to severe osteolysis that had been induced by metallic debris. Although implants made of titanium alloy have many favorable qualities--most importantly, superb biocompatibility--the alloy is more susceptible to wear by particles of acrylic cement and tends to generate more polyethylene wear than do components made of stainless steel or chromium-cobalt. A new process of implanting ions has reportedly improved resistance to wear as well as fatigue properties and has enhanced the resistance to corrosion of the implants. Although, to our knowledge, only in vitro studies of this process have been reported to date, we recommend avoiding the use of components made of titanium alloy in which ions have not been implanted. We suggest considering the possibility of osteolysis secondary to appreciable metallic debris in patients who have aseptic loosening of titanium-alloy components that were not implanted with ions.     

Iliopsoas bursal distension caused by acetabular loosening after total hip arthroplasty. A rare complication of total hip arthroplasty.

In a 58-year-old woman, a cystic mass at the ileocecal region communicated with the loosened hip prosthesis 20 years after total hip arthroplasty (THA). The preoperative arthrogram of the hip and the intraoperative cystogram suggested a one-way communication from the hip to the cystic mass. The mass was diagnosed as an iliopsoas bursitis distended by the influx of the synovial fluid from the loosened THA.     

Review Article: Polyethylene wear and osteolysis in total hip arthroplasty

Polyethylene wear has been accepted as a major cause of osteolysis in total hip arthroplasty. Submicron particles, which are secondary to abrasive wear, migrate into the effective joint space and stimulate a foreign-body response resulting in bone loss which is mainly mediated by macrophages. Diagnosis depends on serial radiographic evaluation and frequent follow-up. Polyethylene wear and osteolysis can be prevented by reducing the wear such as using a small femoral head, adaptive polyethylene thickness, suitable surgical techniques, non-polyethylene articulation, etc. The presence of cement or circumferential coatings may also retard the distal migration of particles. Medicines such as NSAIDs and bisphosphonate appear to inhibit the progress of osteolysis. As far as treatment, revision surgery is able to reconstruct the joint by replacing partial or total prosthesis and repair the defect by bone grafting according to intraoperative assessment.     

Premature wear and osteolysis in an HA-coated, uncemented total hip arthroplasty

The ABG I cementless hip prosthesis has demonstrated unacceptably high rates of wear and osteolysis in our patients. We performed a retrospective study of 97 hips implanted between 1992 and 1998. Radiographic analysis revealed high rates of wear of the polyethylene liner with marked peri-acetabular osteolysis. Clinical examination indicated that many of these patients were initially asymptomatic. Wear-related problems have required ten hips to be revised and a furher 13 are awaiting revision. This gives a failure rate of 24% at a mean follow-up of 69 months. Contributing factors are likely to include poor wear characteristics of the polyethylene liners which were gamma irradiated in air, and increased wear debris caused by a poor fit of the polyethylene liner within the shell. We believe that all ABG I implants should be immediately reviewed and remain under careful, long-term follow-up.     

H/G非骨水泥人工全髋关节置换术后聚乙烯内杯磨损临床研究

目的 对H/G非骨水泥人工全髋关节置换术后聚乙烯内杯的磨损及髋臼周围骨溶解的情况进行总结.方法 我院1991至1995年共进行58例(65髋)H/G非骨水泥人工全髋关节置换,其中35例(40髋)获得10年以上随访.对这35例(40髋)患者获得随访的病例,采用计算机数字化方法测量髋臼聚乙烯内杯的二维线性磨损.结果 35例40髋均有不同程度的磨损,磨损范围2～8 mm,平均磨损为(0.32±0.31)mm/年.10髋聚乙烯磨损超过6 mm,髋臼假体周围的骨溶解严重,并伴有金属假体的移位,其中5髋聚乙烯内杯完伞磨透,金属股骨头与金属髋臼相接触;5髋聚乙烯内杯磨损严重伴明显骨溶解,内杯松动.2髋聚乙烯内杯脱位.共实施翻修手术12例,包括更换聚乙烯内杯和金属股骨头2例、金属闩杯翻修2例、全髋翻修8例.28髋在髋臼侧发现骨溶解,其中14髋股骨侧亦有骨溶解发生.结论 本组病例所观测到的H/G髋臼聚乙烯内杯的磨损程度超过文献所报道,而且由于磨损产生的大量磨屑,导致假体周围出现明显骨溶解,直接影响到假体的稳定.关节置换术后应定期随访,避免出现严重骨溶解后增加翻修手术的困难.     

Polyethylene debris-induced osteolysis and loosening in uncemented total hip arthroplasty. A cause of late failure.

Uncemented total hip arthroplasty has proven to be an acceptable alternative to cemented total hip arthroplasty with good short-term results. With the elimination of the use of polymethyl methacrylate for component fixation, failure at the bone-cement interface, with resultant osteolysis and progressive loosening, was thought to be preventable. Unfortunately the ultra-high-molecular-weight polyethylene acetabular insert can wear and produce particulate debris. This debris can stimulate an osteolytic reaction and lead to late aseptic loosening in a cementless total hip arthroplasty.     

Radiographic versus clinical loosening of the acetabular component in noninfected total hip arthroplasty

In a series of 100 total hip arthroplasties revised due to various noninfectious causes, intraoperative determinations of the stability of the socket were compared with conventional preoperative radiographs. All seven hips without radiolucency around the cemented socket were found to be stable. Loosening was demonstrated in 6%-31% of the hips with radiolucency, depending on the classification system. Significantly, 35% of sockets with radiographic signs of migration were found to be stable. Radiographic evaluations of socket stability are difficult and require serial images obtained in precisely defined positions.     

Polyethylene wear, osteolysis and acetabular loosening with an HA-coated hip prosthesis. A follow-up of 94 consecutive arthroplasties.

We have followed up for a period of seven to nine years 100 consecutive arthroplasties of the hip in which an entirely HA-coated implant had been used. The clinical results were excellent and bony incorporation was extensive in all components. No stem became loose or subsided but five cups were revised because of loosening after 3.8 to 5.5 years, having functioned painlessly and shown radiological ingrowth. Revision procedures because of excessive polyethylene wear have been performed on 18 hips and are planned for six more. Two eroded metal backings with worn-through polyethylene were exchanged; six hips showed metallosis without polyethylene wear-through. There were two cases of granulomatous cysts in the groin and 66 hips had osteolysis located periarticularly, in the greater trochanter or in the acetabulum.     

Management of osteolysis around total hip arthroplasty.

The indications for treatment of osteolysis are based on osteolysis severity and progression. At present, there is a trend toward selective retention of well-fixed, undamaged components of satisfactory design, but long-term results of limited procedures with component retention for osteolysis are lacking. An algorithm for treatment of osteolysis around THA can be constructed. Such algorithms can help guide treatment, although it is important to note that judgment is still needed about the optimal treatment for each individual case. Regular follow-up of joint arthroplasty patients-especially those who are young and active and those with problematic implant designs--is important to identify osteolysis early and facilitate more limited intervention. There is increased understanding that osteolysis is a progressive process in the great majority of cases, and thus, most surgeons tend to consider intervention earlier than once was the case. Plain radiographs frequently underestimate the severity of osteolysis, particularly in the pelvis and greater trochanter, and metallic implants can obscure bone loss on routine radiographs. Therefore, when operative treatment is undertaken, the surgeon must be prepared for more severe bone loss than is visible on plain radiographs.     

The influence of acetabular component position on wear in total hip arthroplasty

Our experience has implicated cup inclination as an important factor in wear, whereas others have suggested that the hip center of rotation (COR) must be closely reestablished to reduce wear. We conducted a retrospective study to determine the relative importance of these 2 factors. One hundred thirty-nine total hip arthroplasties were studied after a mean follow-up of 9.2 years (range, 6-3 years). Forty-nine of 139 operated hips had a contralateral normal hip, which allowed the most accurate measurement of the influence of change in the COR. Wear was related to the inclination of the cup but not to a change in the COR. Secondarily, wear was less with a ceramic-polyethylene polyarticular surface than with metal-polyethylene. The importance of this data is related to cup implantation techniques. The hip COR can be moved superiorly and/or medially to permit cup inclination below 45 degrees with correct cup coverage.     

Effects of acetabular abduction on cup wear rates in total hip arthroplasty

This study was designed to determine the effect of acetabular abduction on the polyethylene wear rates of the acetabular component. The hypothesis of this study is that acetabular placement, in particular abduction, effects contact forces and therefore polyethylene wear. A total of 364 total hip arthroplasties that were performed between 1974 and 1976 were included in this study. The cemented all-polyethylene acetabular components were the same for each case and came from a single supplier. The polyethylene wear rates were calculated by measuring the shortest radius from the center of the prosthetic femoral head to a point on the outer surface of the acetabular cup. An immediate postoperative radiograph was compared with a follow-up radiograph at least 9.5 years later. A standardized radiograph was used to prevent differences due to magnification. The abduction or inclination of the acetabular cups was measured in all of the patients. The amount of acetabular cup abduction was measured relative to the ischial tuberosity line. The mean abduction was 44.1° with a standard deviation of 9.2° and a median of 44°. The range of abduction was from 0° to 85°. This analysis failed to show a correlation between the amount of acetabular abduction and polyethylene wear rates (Pearson's correlation coefficient = 0.0679; P = .20). With a sample size of 364, there is over a 95% change (statistical power) of detecting an underlying true correlation between wear and abduction that is greater than or equal to 0.20. We were unable to demonstrate a difference in wear that would correlate with the differing degrees of abduction of the acetabular socket. We felt that the radiographic measurements of wear were quite accurate. This method of determining acetabular abduction has also been documented and supported in previous literature and has allowed us to accurately determine acetabular abduction. The results of our study demonstrate that within the normal ranges described by our study, polyethylene wear did not significantly increase with increased abduction of the acetabular component.     

Femoral component loosening after total hip arthroplasty.

To determine the long-term durability of total hip arthroplasty and to identify factors responsible for femoral component loosening, 106 total hip arthroplasties were reviewed in patients with a minimum postoperative period of 3 years. Seventy-four had Charnley-Müller prostheses and 32 had Charnley prostheses. Femoral component loosening occurred in 16 of 106 hips. Not all loose components were symptomatic. The femoral component at risk was the femoral Charnley-Müller type that had been inserted in varus position in a functioning active heavy patient who previously had had a femoral head prosthesis.     

Risk factors for accelerated polyethylene wear and osteolysis in ABG I total hip arthroplasty

We analysed data from 155 revisions of identical cementless hip prostheses to determine the influence of patient-, implant- and surgery-related factors on the polyethylene wear rate and size of periprosthetic osteolysis (OL). This was calculated by logistic regression analysis. Factors associated with an increased/decreased wear rate included position of the cup relative to Kohler’s line, increase in abduction angle of the cup, traumatic and inflammatory arthritis as a primary diagnosis, and patient height. Severe acetabular bone defects were predicted by an increased wear rate (odds ratio, OR = 5.782 for wear rate above 200 mm³/y), and increased height of the patient (OR = 0.905 per each centimetre). Predictors of severe bone defects in the femur were the increased wear rate (OR = 3.479 for wear rate above 200 mm³/y) and placement of the cup outside of the true acetabulum (OR = 3.292). Variables related to surgical technique were the most predictive of polyethylene wear rate.