Constrained Liners Research Articles

Instability After Total Hip Arthroplasty: Treatment with Large Femoral Heads vs Constrained Liners

One of the most common complications after total hip arthroplasty is instability. This study reviewed the recent literature concerning the indications, contraindications, and results of recent studies using both constrained liners and large femoral heads to treat instability after total hip arthroplasty. We also report on the results of a series of 41 patients (52 hips) considered being at high risk for dislocation who were treated with large-diameter metal-on-metal bearings and who were compared with a matched group of hips treated with standard-size metal-on-polyethylene bearings. The large-diameter femoral head group had no dislocations at a minimum follow-up of 24 months, whereas the standard-size group had 2 dislocations. We support the use of large femoral heads to treat instability in a wide variety of patients because of the increased stability, decreased wear of modern metal-on-metal designs, increased range of motion, and variety of revision options.

Failure of Constrained Acetabular Liner Without Metal Ring Disruption

Constrained acetabular liners can fail leading to recurrent dislocation. Failure can occur at any of the five possible interfaces: bone-acetabular shell, acetabular shell-constrained liner insert, constrained liner insert-bipolar head, bipolar head- femoral head and femoral head-trunion. We report a patient who presented with dissociation of the cemented Osteonics acetabular constrained liner (Stryker-Howmedica-Osteonics, Rutherford, New Jersey). The failure interface was at the factory pre-assembled constrained liner insert-bipolar head without any locking ring failure; instead there was deformation of the constrained liner insert's polyethylene rim, which facilitated dissociation. To our knowledge, there are no previous reports of such a failure mode pertaining to this type of constrained liner. Constrained acetabular liners are indicated during primary or revision total hip arthroplasty for patients who are at high risk for dislocations or who have had recurrent dislocations. Failure rates (typically recurrent dislocation) range from 4% to 29% at mid-term follow-up. The first report on the Osteonics acetabular constrained liner was published in 1994. Failures have been reported previously to occur at surgically controllable interfaces, such as the acetabular shell from the bony surface and the constrained liner insert from the acetabular metal shell, and have been attributable to excessive constraint or improper technique. All dissociations pertaining to factory-preassembled component interfaces have been attributed to breakage of the locking ring. This article presents the first case of disengagement of the tripolar constrained liner without disruption of the locking ring.

A Unique Failure Mechanism of a Constrained Total Hip Arthroplasty: A Brief Review of the Literature

Constrained acetabular systems are successful in achieving stability in patients with recurrent dislocations, abductor deficiency, or where a source of instability cannot be determined. We report on one patient with 2 dissociations of a tripolar constrained acetabular liner caused by impingement when the patient exceeded the allowed range of motion. The inner liner dissociated from the outer liner, whereas the reinforcing ring remained intact and in place. Despite an extensive literature search, we were unable to find any other published reports concerning this specific mode of failure for this constrained liner. Surgeons should be aware that constrained liners are not infallible and have limitations to range of motion. Maximizing the size of the femoral head may reduce the risk of this mode of failure.

Caution on the Use of Combined Constrained Liners and Cages in Revision Total Hip Arthroplasty

Caution on the Use of Combined Constrained Liners and Cages in Revision Total Hip Arthroplasty

Constrained Liners for Recurrent Dislocations in Total Hip Arthroplasty

This study reports the results and complications from treating recurrent hip dislocations with a constrained liner (CL) after total hip arthroplasty (THA). Forty patients who had a CL inserted as a secondary prophylactic treatment were retrospectively reviewed after a median observation period of 27 months (range 7-77 months). During the observation period five patients had to be revised: one for deep infection and four on account of re-dislocations. Our results indicate that patients with recurrent THA dislocations can be treated with a CL and has a satisfactory low complication rate and a relatively low risk of re-dislocation.

Constrained liners for recurrent dislocations in total hip arthroplasty

This study reports the results and complications from treating recurrent hip dislocations with a constrained liner (CL) after total hip arthroplasty (THA). Forty patients who had a CL inserted as a secondary prophylactic treatment were retrospectively reviewed after a median observation period of 27 months (range 7-77 months). During the observation period five patients had to be revised: one for deep infection and four on account of re-dislocations. Our results indicate that patients with recurrent THA dislocations can be treated with a CL and has a satisfactory low complication rate and a relatively low risk of re-dislocation.

Constrained components for the unstable hip following total hip arthroplasty: a literature review

Patients with chronic instability or late dislocation following total hip arthroplasty often require operative management. Unfortunately, there is an increased risk of recurrent dislocation following revision in these patients. Over the past decade the use of constrained devices for patients with chronic instability has gained increased interest; however, there is a paucity of studies available in the literature regarding the use of these devices. The purpose of this study was to analyze the available literature over the past 15 years, focusing on larger, long-term studies, to obtain recommendations from the respective articles for indications and contraindications for the use of constrained devices. Our review of eight reports included 1,199 hips in 1,148 patients with a total mean follow-up of 51 months (range, 24 to 124 months). The mean rate of dislocation following revision with a constrained liner was 10% and the mean re-operation rate for reasons other than dislocation was 4%. We concluded that constrained liners are an option for patients who have failed management of instability with other implants, those with instability of unclear etiology, those with cognitive problems who are unable to follow dislocation precautions, those with deficient abductors, and elderly or low-demand individuals with well-positioned implants requiring revision.

Constrained Liners in Revision Total Hip Arthroplasty: An Overuse Syndrome: In the Affirmative

Instability after primary and revision total hip arthroplasty continues to be problematic for the surgeon. The use of constrained liners, which use a locking mechanism to capture the femoral head, has increased to help manage this problem. Constrained liners, however, present problems with acetabular component loosening, dissociation of the liner/shell interface, failure by breakage, and excessive polyethylene wear. Rather than resort to constrained liners, our approach has been to restore joint stability with large-diameter femoral heads. The advantages are increased range of motion due to more favorable head/neck ratio, increased resistance to dislocation due to increased jump distance, and the avoidance of skirted femoral heads. With the addition of cross-linked polyethylene, the volumetric wear associated with large heads is much decreased and makes this a viable option today.

Constrained Liners in Revision: Total Hip Arthroplasty An Overuse Syndrome: In Opposition

Use of constrained liners in revision total hip arthroplasty is frequently a necessary evil. Concomitant with the increasing complexity of the operative intervention is the deterioration of periarticular soft-tissue envelope integrity, causing increased risk of dislocation. Risk factors can be categorized as impingement independent or impingement related. Impingement-independent risk factors include those related to compromised soft-tissue tension, patient-specific issues, and surgical approach. Impingement-related risk factors include head-to-neck size and geometry, acetabular liner geometry, and surgical technique. Indications for constraint include recurrent hip instability after arthroplasty, intraoperative multidirectional hip instability, neuromuscular diseases that impair hip dynamics, neurologic diseases that impair the patient's ability to restrict activities, and proximal muscle weakness with or without deficiency of the protective muscular. Newer designs featuring large heads, improved range of motion, and reduced impingement hold the promise of improved results.

Use of a Constrained Tripolar Acetabular Liner to Treat Intraoperative Instability and Postoperative Dislocation After Total Hip Arthroplasty: A Review of Our Experience

Use of a Constrained Tripolar Acetabular Liner to Treat Intraoperative Instability and Postoperative Dislocation After Total Hip Arthroplasty: A Review of Our Experience

High Failure Rate of a Constrained Acetabular Liner in Revision Total Hip Arthroplasty

Fifty-five consecutive revision total hip arthroplasties (THAs) in 51 patients in which a constrained acetabular liner was used (Duraloc Constrained Liner, DePuy, Warsaw, Ind) were reviewed. In these revisions, 41 constrained liners were placed for recurrent instability and 14 for inadequate stability at the time of revision THA. The mean age of the cohort was 62 years, and 38 of the hips were in female patients (69%). At a minimum of 2 years, 9 of the 55 hips (16%) dislocated. Of these 9 dislocations, 8 occurred in patients who had undergone revision to a constrained liner for recurrent instability without femoral or acetabular component revision. Revision THA for recurrent instability by placing a constrained liner without optimizing other aspects of the reconstruction leads to a high rate of recurrent failure.

Instability after Total Hip Replacement

Instability after total hip replacement is a major cause of patient morbidity, second only to aseptic loosening of the components. Many factors, including surgical approach, implant design, soft tissue integrity, patient compliance, and experience of the surgeon, play an important role in the etiology of hip dislocation. An understanding of the timing, mechanism, and direction of the instability helps in formulating a treatment plan whether surgical or nonoperative. Radiographic evaluation, especially component orientation, restoration of offset, and leg length, can give valuable information about any abnormal biomechanics of the dislocated hip. Initial treatment of postoperative hip dislocation may not require surgery, but recurrent dislocation with an identifiable cause is best managed surgically. Revision hip surgery for recurrent instability can be a challenging problem. A better understanding of the etiology and the use of constrained liners at many centers have shown improved results with surgical management. Patients should be counseled regarding realistic expectations before revision surgery for recurrent dislocations. As a result of the greater emphasis paid to meticulous capsule repair, orientation of the components, and soft tissue tension, the incidence of instability after a primary hip arthroplasty is extremely low.

Design factors influencing performance of constrained acetabular liners: finite element characterization

Constrained acetabular liners are utilized to deal with the infrequent but devastating problem of recurrent dislocation. While an encouraging treatment of last resort, the clinical performance of contemporary constrained liners has been somewhat mixed. There are multiple factors contributing to this variability, one of which is the limited understanding of the intrinsic mechanical characteristics of these specialty devices. To address this issue, a three-dimensional, materially nonlinear, multi-surface contact finite element model of a representative constrained liner was created. The model was physically validated, and then used for parametric testing to explore the effects of individual design features. The model was exercised for both intra-operative assembly and lever-out dislocation. It was found that the coefficient of friction between the femoral head and the liner substantially affected both the force required to seat the femoral head into the liner during assembly, and the peak moment resisting dislocation (226% increase in assembly force for friction coefficients of 0.2 versus 0.0; 49% reduction in dislocation moment for friction coefficients of 0.013 versus 0.135). As expected, the cup opening radius also had a dominant effect on both maneuvers: decreasing the opening radius from 13.9 to 13.6 mm increased assembly force by 506 N and increased the dislocation moment by over 3.5 N-m, whereas the influence of other design parameters was much more modest.

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.

Modular constrained devices and reconstruction cages in the management of the unstable hip in major acetabular deficiency

We retrospectively reviewed 26 patients with 28 acetabular reconstructions using constrained liner and modular, metalbacked components cemented into a reconstruction cage. All deficiencies were Type IIIC. Overall, the reoperation rate was 39.3%, including 3 aseptic failures, each occurring with breakage and failure of superior, then inferior fixation, then superomedial migration; 2 dislocations despite the constraint; and 4 deep infections. Mean HHS improvement was 36.2 points. The use of allograft bone, different component and/or cage designs was not significant for revision or infection (p>0.05). This technique is effective for extensive bone loss with instability. Modularity allows for position fine-tuning and exchange if needed.

Early failure mechanisms of constrained tripolar acetabular sockets used in revision total hip arthroplasty

Fifty-eight patients received an Osteonics constrained acetabular implant for recurrent instability (46), girdlestone reimplant (8), correction of leg lengthening (3), and periprosthetic fracture (1). The constrained liner was inserted into a cementless shell (49), cemented into a pre-existing cementless shell (6), cemented into a cage (2), and cemented directly into the acetabular bone (1). Eight patients (13.8%) required reoperation for failure of the constrained implant. Type I failure (bone-prosthesis interface) occurred in 3 cases. Two cementless shells became loose, and in 1 patient, the constrained liner was cemented into an acetabular cage, which then failed by pivoting laterally about the superior fixation screws. Type II failure (liner locking mechanism) occurred in 2 cases. Type III failure (femoral head locking mechanism) occurred in 3 patients. Seven of the 8 failures occurred in patients with recurrent instability. Constrained liners are an effective method for treatment during revision total hip arthroplasty but should be used in select cases only.

Dislocation after total hip arthroplasty: A single surgeon's experience

The purpose of this article is to evaluate the dislocations that occurred in a single surgeon practice over a 26 year period. After extensive research, the authors concluded that dislocation continues to occur long after the initial arthroplasty procedure. Patients should be aware that more than a quarter of dislocations occur 2 years following surgery. Use of modular 22 millimeter components were associated with the highest dislocation rate. These components should be used very cautiously. Constrained liners have helped decrease the dislocation rate following revision for dislocation.