The use of constrained components in total hip arthroplasty

The use of a constrained component may be appropriate for the surgical treatment of recurrent dislocation due to soft-tissue insufficiency following a total hip arthroplasty. Constrained components usually include a locking mechanism incorporated into the polyethylene acetabular liner to keep the prosthetic femoral head in place. Two different prosthetic designs are available and have been approved by the U.S. Food and Drug Administration. The S-ROM constrained component uses additional polyethylene in the rim, which deforms to more fully capture the femoral head and then is held in place by a metal locking ring. The Howmedica Osteonics constrained component is a tripolar device; its bipolar component articulates with another polyethylene liner. These constrained components transfer hip forces that would otherwise lead to dislocation to the locking mechanism, the liner-shell interface, or the bone-prosthesis interface. These forces may eventually contribute to failure of the component due to loosening, dissociation, breakage, or recurrent dislocation. Studies of these components show a failure rate of 4% to 29% at relatively short-term follow-up.     

Prevention and treatment of dislocation after total hip replacement using large diameter balls

The purpose of this study was to review safety and efficacy of total hip arthroplasty using large-diameter femoral heads in treatment and prevention of dislocation. One hundred forty hips in 135 patients were replaced using femoral heads at least 36 mm in diameter. The average age of the patients was 61.6 years. The patients were grouped into three categories depending on their diagnoses: recurrent dislocations from previous total hip replacements (Group 1; 29 hips); revision surgeries not including revisions for dislocations (Group 2; 54 hips); and primary surgeries (Group 3; 57 hips). The average followup was 5.5 years (range, 1-17 years). A total of 16 hips were revised: six for instability, four for fracture or disassociation of a conventional polyethylene liner, three for aseptic loosening of the socket, and three for sepsis. One hip from Group 1 dislocated at 12.5 years postoperatively, was treated with closed reduction, and since has been nonrecurring. UCLA hip scores all improved significantly. The prevalence of dislocation varied among the three groups, with 13.7% for Group 1, 1.8% for Group 2, and 3.5% for Group 3. The failure in the six cases that required revision for instability was attributable to poor socket orientation. All the hips became stable after revision without the use of a constrained acetabular liner. Large-diameter femoral heads provide additional stability not only for patients with recurrent dislocations, but also for patients having revision. The new, more wear-resistant bearings now enable the surgeon to extend the use of big femoral heads to primary total hip arthroplasty. Metal-on-metal seems to be the material of choice for a bone-conserving reconstruction with large femoral heads.     

Are abductor muscle quality and previous revision surgery predictors of constrained liner failure in hip arthroplasty?

Dislocation is one of the most common complications of total hip arthroplasty. The use of constrained liners is an option for the management of chronic hip instability, typically used after other methods have failed. The purposes of this study were to evaluate the overall clinical outcomes and failure rates of a tripolar constrained liner design, to assess the radiographic outcomes of its use, and to examine whether various factors such as abductor mechanism quality and history of previous revision surgeries were associated with an increased risk of failure. Forty-three hips in 39 patients who had a mean follow-up of 51 months (range, 24–110 months) were reviewed. Ninety-one percent of the hips (39 of 43 hips) did not need any revisions over the study period. A new liner was implanted in all four failed hips with concurrent revision of the acetabular cup in three cases. No further dislocations occurred in this group. The mean hip score for surviving hips was 82 points (range, 38–100 points) at final follow-up. Radiographic evaluation revealed stable, well-fixed acetabular components in all surviving hips without progressive radiolucencies. No association was found between abductor muscle quality and the incidence of failure, but patients who experienced a constrained liner failure were more likely to have undergone at least one previous hip revision operation. Tripolar constrained acetabular liners can provide successful outcomes in patients with hip instability, although it is important not to rely on the use of a constrained liner alone in an attempt to compensate for other correctable factors such as component positioning.     

Prevention of dislocation after hip arthroplasty: lessons from long-term followup.

Regarding dislocation after total hip arthroplasty, prevention is worth an ounce of cure. The current authors evaluated dislocation after total hip arthroplasty during the 26-year practice of one surgeon to identify potential variables that can contribute to the prevention of dislocation. Between 1970 and 1996, dislocation after total hip replacement occurred after 7.2% of primary hip arthroplasty procedures (298 of 4164 primary hip replacements) and 11.2% of revision hip arthroplasty procedures (90 of 803 revision hip replacements). Significant findings included an increase in dislocation when 22-mm modular femoral heads were used and a decrease in dislocation after revision for dislocation when constrained liners were used. An additional finding was that 26% of first time dislocations occurred more than 2 years after surgery. Concerning prevention of dislocation, small head modular femoral components should be used cautiously, and constrained liners should be considered in complex revision cases. Patients should be counseled concerning the potential for dislocation many years after their arthroplasty.     

The use of a constrained acetabular component for recurrent dislocation

The poor results of surgical treatment of chronic instability after total hip arthroplasty (THA) led to the development of a constrained acetabular component. In this study, 87 constrained THAs implanted for recurrent instability were reviewed retrospectively. Eighty-five hips were available for follow-up evaluation, with an average follow-up period of 58 months. These 85 hips were evaluated at a minimum of 3 years. Two recurrent dislocations were seen, caused by dissociation of the liner from the shell. Four acetabular components and 1 femoral component were revised. Overall, a 2.4% dislocation rate and an 8.2% revision rate were seen. The recurrent dislocation rate of 2.4% represents a significant improvement over other methods reported. Repeat dislocation was only seen in dissociation of cemented liners into well-fixed shells. We do not recommend this mode of fixation.     

Effectiveness of Constrained Liner Use During Harrington Hip Reconstruction in Oncology Patient

Background

Patients with destructive acetabular lesions are at high risk for morbidity. Harrington described reinforcing acetabular diseased bone with methylmethacrylate, supplemented by metal fixation, to allow total hip reconstruction. However, all published studies using this technique report dislocations. We believe that initial use of constrained liners would help alleviate dislocation risk, without increasing component loosening or polyethylene wear.

Risk Factors for Dislocation and Re-revision After First-Time Revision Total Hip Arthroplasty due to Recurrent Dislocation – A Study From the Danish Hip Arthroplasty Register

BackgroundPersistent instability after hip revision is a serious problem. Our aim was to analyze surgical and patient-related risk factors for both a new dislocation and re-revision after first-time hip revision due to dislocation.MethodsWe included patients with a primary THA due to osteoarthritis and a first-time revision due to dislocation registered in the Danish Hip Arthroplasty Register (DHR) from 1996 to 2016. We identified dislocations in the Danish National Patient Register and re-revisions in the DHR. Risk factors were analyzed by a multivariable regression analysis adjusting for the competing risk of death. Results are presented as subdistribution hazard ratios (sHR).ResultsWe identified 1678 first-time revisions due to dislocation. Of these, 22.4% had a new dislocation. 19.8% were re-revised for any reason. With new dislocations treated by closed reduction as the endpoint, the sHR was 0.36 (95% CI, 0.27-0.48) for those who had a constrained liner (CL) during revision and 0.21 (0.08-0.58) for dual mobility cups (DMC), thereby lowering the risk of dislocation compared to regular liners. Changing only the head/liner increased the risk of dislocation (sHR = 2.65; 2.05-3.42) compared to full cup revisions. The protective effect of CLs and DMCs on dislocations vanished when re-revisions became the endpoint. The head/liner exchange was still found inferior compared to cup revision (sHR = 1.73; 1.34-2.23).ConclusionPatients revised with DMCs and CLs were associated with a lower risk of dislocation after a first-time revision but not re-revision, whereas only changing the head/liner was associated with a higher risk of dislocation and re-revision of any cause compared to cup revision.     

Salvage of a recurrently dislocating total hip prosthesis with use of a constrained acetabular component. A concise follow-up of a previous report

We previously reported the results at a mean of five years following the use of a tripolar constrained acetabular component to treat recurrently dislocating total hip prostheses. In this study, we report the results after longer follow-up, with emphasis on the prevalence of implant loosening, osteolysis, and later recurrent instability. Fifty-five patients treated with a total of fifty-six constrained acetabular components because of recurrent dislocations of a total hip prosthesis (average, six dislocations; range, two to twenty dislocations) were followed for an average of 10.2 years (range, 7.0 to 13.2 years) or until death. Four (7%) of the fifty-six hips had a subsequent dislocation or failure of the device. Three femoral components (5%) and two acetabular components (4%) were revised because of aseptic loosening. One hip was revised because of osteolysis. We concluded that this constrained acetabular component provides durable protection against additional dislocations without substantial deleterious effects on component fixation. We use this device to treat recurrent dislocation when other modalities are unlikely to be effective.     

Modular femoral head and liner exchange for the unstable total hip arthroplasty

Outcomes of femoral head and nonconstrained liner exchange in treating hip instability were evaluated. Forty-eight modular component exchanges performed in 45 patients for recurrent hip dislocations were retrospectively reviewed. Mean follow-up was 4.7 years. Overall success rate was 73% (35/48 hips). Thirty-two (67%) of 48 hips experienced no further dislocations. Three patients had 1 dislocation each with no subsequent dislocations. Ten patients (13 hips) had additional surgery to stabilize their hips (27% failure rate). Demographic, clinical, and implant variables were not associated with outcome. Isolated modular component exchange can be successful in treating recurrent hip dislocations; however, a significant failure rate, not easily predicted, exists. This represents the largest series of modular head and nonconstrained liner exchange for hip dislocation (122/125).     

Dissociation of the S-ROM metal-backed polyethylene acetabular liner--a case report and literature review

The authors report a case of early failure of a total hip arthroplasty with dissociation of the polyethylene liner of an S-ROM Oblong Cup*, which presented as a dislocation. Initial closed reduction of the dislocation was not possible. Open exploration of the hip revealed that the modular Poly Dial* polyethylene acetabular liner had become dislodged from the acetabular cup. The liner was revised and a stable reduction of the hip was achieved. To our knowledge, no previous case of dissociation of the polyethylene liner from the S-ROM Oblong acetabular component has been reported. A review of the literature with other relevant cases is presented.     

Dislocation after polyethylene liner exchange in total hip arthroplasty

Little has been published on the outcomes of polyethylene liner exchanges for wear or osteolysis. We assessed 24 patients from our clinic who had an isolated polyethylene liner exchange for wear or osteolysis with retention of the acetabular shell and femoral stem. At a mean 56-month follow-up time, 6 hips (25%) had dislocated. Of these, 2 underwent repeat surgery for recurrent dislocation; 1 had 3 dislocations; 1 had 2 dislocations; and 2 had single dislocations. Seventeen of the remaining patients answered our questionnaire: 13 recovered faster from the polyethylene liner exchange than from the primary arthroplasty; 4 believed that their hips were not as stable, 4 believed the hip did not function as well; and 1 underwent revision for cup loosening. We conclude that polyethylene liner exchanges, with or without femoral head exchange for wear or osteolysis, are associated with a high risk of dislocation and possible decrease in function.     

人工全髋关节置换术后假体脱位的治疗

目的探讨人工全髋关节置换术后假体脱位的治疗方法。方法1997年7月～2004年10月，共收治人工全髋关节置换术后假体脱位23例，男9例，女14例；年龄53～79岁。行CT及X线片检查，了解假体松动情况及假体位置，并分析脱位原因。无假体松动者，麻醉下手法复位、行稳定性试验。手法复位成功且稳定者，胫骨结节牵引4～6周。手法复位失败或不稳定者，原入路切开，根据术前及术中情况，调整offset值及部分假体组件。稳定者，关节囊修补，胫骨结节牵引4～6周。仍不稳定或松动者采用翻修手术。结果23例患者，1例松动者采用全髋关节翻修；10例手法复位治疗成功；12例手法复位后不稳定或失败患者中，5例行切开复位关节囊修补，2例采用加长股骨头增加offset值，2例改用防脱位髋臼内衬，1例采用加长股骨头并调整异常髋臼内衬位置，2例仍不稳定者采用全髋关节翻修。患者均获随访1～5年，平均1．9年。均未出现再脱位。术后1年Harris评分72～94分，平均87分。结论人工全髋关节置换术后假体脱位，应根据脱位原因和术中稳定情况选择不同的治疗方法。     

Gait instability may indicate liner failure in patients with total hip arthroplasty. A report of three cases

Total hip arthroplasty is one of the most common and successful orthopaedic procedures performed worldwide. Uncemented modular acetabular components and highly cross-linked polyethylene liners are the implants of choice for most arthroplasty surgeons. However, despite their well-known benefits, highly cross-linked polyethylene liners are not without complications, such as rim fracture, rupture and dissociation. We report three patients with gait instability and radiographic subluxation due to highly cross-linked polyethylene liner failures evidenced during stage one revision surgery. The three patients were symptoms free, with no new instability episodes, and the radiographs showed no evidence of implant loosening at the most recent follow-up. Although it is a rare complication, these three cases highlight the importance of suspecting and evaluating highly cross-linked polyethylene liner failures in patients referred for gait instability with no history of previous trauma.     

Failure Mechanisms and Closed Reduction of a Constrained Tripolar Acetabular Liner

Unlike traditional bipolar constrained liners, the Osteonics Omnifit constrained acetabular insert is a tripolar device, consisting of an inner bipolar bearing articulating within an outer, true liner. Every reported failure of the Omnifit tripolar implant has been by failure at the shell-bone interface (Type I failure), failure at the shell-liner interface (Type II failure), or failure of the locking mechanism resulting in dislocation of the bipolar-liner interface (Type III failure). In this report we present two cases of failure of the Omnifit tripolar at the bipolar-femoral head interface. To our knowledge, these are the first reported cases of failure at the bipolar-femoral head interface (Type IV failure). In addition, we described the first successful closed reduction of a Type IV failure.     

Polyethylene liner dislocation in Harris Galante acetabular components

AIM: Dislocation and subsequent dissociation of the polyethylene liner as a result of failure of the acetabular locking mechanism is a potential source of failure in the Harris-Galante acetabular component. The purposes of this study are to present seven cases with a liner dislocation due to failure of the liner locking mechanism. METHOD: Between March 1997 and December 2001, seven patients who had had a total hip arthroplasty presented with clinical and radiologic signs of liner dislocation and signs of polyethylene wear of the liner from a Harris Galante acetabular shell. In all cases the intraoperative findings showed evidence of failure of the liner locking mechanism and subsequent dislocation. The medical records, radiographs, operative notes and explanted retrieved components were reviewed. RESULTS: The components had been in situ for an average of 5.3 years (range 1-9 years). Two components were first generation, five were second generation. The symptoms developed spontaneously in five patients, the other two patients described a minor trauma. Radiographs showed eccentric position of the head in all cases. All acetabular components showed an excellent stability intraoperatively, nevertheless we had to remove the well fixed acetabular shell due to complete destruction of the liner locking mechanism in two cases. Treatment consisted of revision of the shell in two patients and exchange of the liner in five patients. All retrieved liners showed severe deformation and/or fracture of the rim. CONCLUSION: Harris Galante modular acetabular components have been used widely for primary and revision arthroplasty. The survival of this implant has been well documented in the literature. Failure of the liner locking mechanism and following dislocation or fracture of the polyethylene liner is a potential cause of failure which may possibly occur more often than the literature to date has documented. We report seven cases of liner dislocation, in which two acetabular components had to be removed completely due to destruction of the liner locking mechanism. In the other five cases exchange of the liner was possible thanks to well timed revision. We believe that, as the liner wears and becomes loose due to an inefficient locking mechanism, the load increases on the polyethylene rim until it deforms or fractures. As a consequence of the prosthetic design at that stage nothing can prevent the liner from rotating out of the shell.     

The dual mobility poly liner: A worthwhile articulation choice?

Dual mobility liners represent an alternative to large heads to prevent dislocation. We used dual mobility in primary total hip arthroplasty in 2 patients (3 hips) with cerebral palsy; there were no dislocations or revisions at a mean follow-up of 2.3 years. In 22 patients (22 hips) revised to dual mobility, the most prevalent indication was adverse reaction to metal debris. There were 3 re-revisions at 1.8 years: 1 recurrent dislocation precipitated by traumatic injury, 1 deep infection and 1 unexplained pain. For abductor deficiency, a constrained liner may be indicated.     

The role of constrained liners in total hip arthroplasty

Recurrent instability after total hip replacement is a complex problem with extensive literature detailing multiple etiologies and solutions. It has been shown that the success of surgical treatment depends on the identification of the cause. Unfortunately, in certain situations, there may not be an optimal solution for dealing with the cause, or the cause may remain unidentified. In these cases, the success rate of surgical treatment of the unstable total hip replacement is only 40% to 50%. Constrained acetabular liners were developed to address the problem of recurrent instability by holding the femoral head captive within the socket. Before the use of constrained liners, there were no reliable solutions to dislocation arising from inadequate soft tissues, a deficient abductor mechanism, or neuromuscular disorders. We have used a constrained liner for these situations, with poor patient compliance and instability without a clear cause as relative indications for its use. Our experience with attaining joint stability using one type of constrained liner has resulted in a 97.6% success rate (83 of 85 hips) at 4.8 years, surpassing the outcomes achieved by other means. The intermediate followup after implantation of a constrained liner has not shown significant rates of component wear or loosening.     

Closed reduction of a dislocation of a constrained acetabular component

A constrained acetabular liner occasionally is used in management of chronic instability after total hip arthroplasty. If dislocation occurs out of a constrained liner, open reduction is indicated. A case is presented of closed reduction of a femoral component into a constrained liner.     

Midterm radiographic comparison of cementless acetabular shells containing lateralized and nonlateralized liners

This retrospective study assessed the effect of lateralized acetabular inserts on polyethylene wear rates, radiographic loosening, and hip stability. Fifty-six 4-mm lateralized liners and 39 neutral liners were compared at a mean follow-up of 7.1 years. Multivariate regression analysis demonstrated a significant increase of 0.04 mm/y in polyethylene wear rate with use of lateralized liners. However, predictable cementless fixation was obtained without screws in both liner groups with no migration or radiographic signs of loosening observed for any cup. The dislocation rate for hips with lateralized liners (3.6%) was less than that for hip with neutral liners (10.3%), although the difference was not significant with the numbers available. Despite the increase in wear rate, hips with lateralized liners performed as well as those with neutral liners with regard to loosening and stability.