There are several clinical scenarios to consider cementing an acetabular liner into a secure cementless shell including cases of: 1) inadequate capturing mechanism, 2) damaged locking mechanisms, 3) unavailability of the mating polyethylene liner, 4) instability following debridement for wear, 5) instability at the time of femoral side revision, and 6) recurrent dislocation. The last two situations are common scenarios for cementing a constrained liner into a secure shell. Technique includes: 1) scoring the shell in cases with no screw holes or polished inner shells, 2) scoring the acetabular liner in a “spider web” pattern, 3) pressurizing cement into the shell, and 4) inserting a liner that allows 2mm of cement mantle. Results of Cementing Constrained Liner Into Secure Cementless Shell: Callaghan et al. JBJS 2004. Thirty-one hips at 2–10 year follow-up. Two of 31 failed. Technical considerations: do not cement proud and do not cement into a malpositioned shell; Haft et al. J Arthroplasty 2002. Seventeen hips with minimum 1 year follow-up. One of 17 failed. Technical considerations: do not cement proud. Results of Cementing Non-Constrained Liners Into Secure Cementless Shell: Beaule et al. JBJS 2004. Thirty-two hips at mean 5.1 year avg f/u. Four components revised for loosening; Callaghan et al. CORR 2012. Thirty-one hips at mean 5.3 year f/u. No revisions

Introduction: Recurrent dislocation can be a significant problem after total hip replacement. The use of a constrained tripolar liner is an option in the surgical treatment of dislocation or instability. Methods: A retrospective review was carried out of patients identified from a prospective database. All patients had a constrained liner cemented onto a satisfactory pre-existing cement mantle, cemented into a reconstruction ring, or cemented into a well fixed cementless shell. The Osteonics Tripolar Liner was used in all cases; the outer aspect of the liner was prepared with a burr to create grooves and thus improve cement interlock. Data collected included demographics, reason for revision, re-revision rate, outcome and survival. Results: There were 58 cases identified where a cemented constrained liner was inserted at revision hip surgery. Average age at time of surgery was 77years (range 40–94). There were 9 patients who died with less than 2 years follow-up; they were excluded, leaving a study group of 49 cases. No cases were lost to follow-up. Average duration of follow-up was 46months (range 24–76). There have been 4 infections, one of which required removal of prostheses and a 2-stage revision. There was one case of fall post-operatively and fracture of the contra-lateral femoral neck. There have been 4 implant failures requiring re-revision. All failures were due to disarticulation of the liner, 2 of which occurred in the same patient on separate occasions. There have been no revisions for loosening, and there have been no cases of failure at the bone-cement interface or at the cement-cement interface with the cement-in-cement technique. Overall survival of the cemented constrained liner was 90% at average 3.8years. Conclusion: This study demonstrates that cementing a constrained liner into the acetabulum is a viable option in revision hip surgery, particularly in the management of instability

Introduction: Recurrent dislocation is a significant problem after total hip replacement. Aetiology is multifactorial and treatment should address the reason for dislocation. The use of a constrained tripolar liner is an option in the surgical treatment of dislocation. Methods: A retrospective review was carried out of patients who have undergone revision hip surgery and had a constrained liner cemented into the acetabulum. Patients were identified from a computer database. All patients had a constrained liner cemented onto a satisfactory pre-existing cement mantle, cemented into a reconstruction ring, or cemented into a well fixed cementless shell. The Osteonics Tripolar Liner was used in all cases and the outer aspect of the tripolar liner was prepared with a burr to create grooves and thus improve cement interlock. Data collected included demographics, reason for revision, components used, re-revision rate, outcome and survival. Results: There were 58 cases identified where a cemented constrained liner was inserted at revision hip surgery. Average age at time of surgery was 77years (range 40–94). Reason for use of a constrained liner was recurrent dislocation in over 95% of cases. There were 9 patients who died with less than 2 years follow-up; they were excluded, leaving a study group of 49 cases. Average duration of follow-up was 46months (range 24–76). There have been 4 infections, one of which required removal of prostheses and 2 stage revision. There was one case of fall post-operatively and fracture of the contra-lateral femoral neck. There have been 3 implant failures requiring re-revision. All failures were due to disarticulation of the liner, 2 of which occurred in the same patient on separate occasions. There have been no revisions for loosening, and there have been no cases of failure at the bone-cement interface or at the cement-cement interface with the cement-in-cement technique. Overall survival of the cemented constrained liner was 91.8% at average 3.8years. Conclusion: This study demonstrates that a cemented constrained tripolar liner is a viable option in revision hip surgery, particularly in the treatment of recurrent dislocation

There remains concern with the use of constrained liners (CL) implanted at the time of acetabular cup revision in revision total hip replacement (rTHA). The aim of this study was to determine the implant survival in rTHA when a CL was implanted at the same time as acetabular cup revision. We reviewed our institutional database to identify all consecutive rTHAs where a CL was implanted simultaneously at the time acetabular cup revision from 2001 to 2021. One-hundred and seventy-four revisions (173 patients) were included in the study. Mean follow-up of 8.7 years (range two – 21.7). The most common indications for rTHA were instability (35%), second-stage periprosthetic joint infection (26.4%), and aseptic loosening (17.2%). Kaplan Meier Analysis was used to determine survival with all-cause re-revision and revision for cup aseptic loosening (fixation failure) as the endpoints. A total of 32 (18.3%) patients underwent re-revision at a mean time of 2.9 years (range 0.1 – 14.1). The most common reasons for re-revision were instability (14), periprosthetic joint infection (seven), and loosening of the femoral component (four). Three (1.7%) required re-revision due to aseptic loosening of the acetabular component (fixation failure) at a mean of two years (0.1 – 5.1). Acetabular component survival free from re-revision due to aseptic loosening was 98.9% (95% CI 97.3 – 100) at five-years and 98.1% (95% CI 95.8 – 100) at 10-years. There were no acetabular component fixation failures in modern highly porous shells. CLs implanted at the time acetabular cup revision in rTHA have a 98.1% 10-year survival free from acetabular cup aseptic loosening (fixation failure). There were no cup fixation failures in modern highly porous shells. Thus, when necessary, implanting a CL during revision of an acetabular component with stable screw fixation is safe with an extremely low risk of cup fixation failure

Aims. The liner design is a key determinant of the constraint of a reverse total shoulder arthroplasty (rTSA). The aim of this study was to compare the degree of constraint of rTSA liners between different implant systems. Methods. An implant company’s independent 3D shoulder arthroplasty planning software (mediCAD 3D shoulder v. 7.0, module v. 2.1.84.173.43) was used to determine the jump height of standard and constrained liners of different sizes (radius of curvature) of all available companies. The obtained parameters were used to calculate the stability ratio (degree of constraint) and angle of coverage (degree of glenosphere coverage by liner) of the different systems. Measurements were independently performed by two raters, and intraclass correlation coefficients were calculated to perform a reliability analysis. Additionally, measurements were compared with parameters provided by the companies themselves, when available, to ensure validity of the software-derived measurements. Results. There were variations in jump height between rTSA systems at a given size, resulting in large differences in stability ratio between systems. Standard liners exhibited a stability ratio range from 126% to 214% (mean 158% (SD 23%)) and constrained liners a range from 151% to 479% (mean 245% (SD 76%)). The angle of coverage showed a range from 103° to 130° (mean 115° (SD 7°)) for standard and a range from 113° to 156° (mean 133° (SD 11°)) for constrained liners. Four arthroplasty systems kept the stability ratio of standard liners constant (within 5%) across different sizes, while one system showed slight inconsistencies (within 10%), and ten arthroplasty systems showed large inconsistencies (range 11% to 28%). The stability ratio of constrained liners was consistent across different sizes in two arthroplasty systems and inconsistent in seven systems (range 18% to 106%). Conclusion. Large differences in jump height and resulting degree of constraint of rTSA liners were observed between different implant systems, and in many cases even within the same implant systems. While the immediate clinical effect remains unclear, in theory the degree of constraint of the liner plays an important role for the dislocation and notching risk of a rTSA system. Cite this article: Bone Jt Open 2024;5(10):818–824

Hip instability is one of the most common complications after total hip arthroplasty (THA). Among the possible techniques to treat and prevent hip dislocation, the use of constrained liners is a well-established option. However, there is concern regarding the longevity of these devices due to higher mechanical stress caused by limited hip motion. The primary aim of this paper is to analyze the failure rate of a specific constrained liner in a series of consecutive cases. This study is a retrospective consecutive case series of THA and revision hip arthroplasty (RHA), in which a constrained polyethylene insert was used to treat or prevent hip instability. Patients were divided in 3 different groups (THA for hip fracture, THA for osteoarthrosis, and RHA). Survival analysis was performed for failure, defined as at least one episode of hip dislocation or radiographical signs of acetabular loosening. Logistical regression was used to investigate risk factors for failure. A total of 103 patients were included in the study. Fourteen patients (13,6%) were THA for osteoarthrosis, 60 (58,3%) were THA for hip fracture, and 29(28,2%) were RHA. The median follow-up was 28 months (ranging 12 − 173 months). Failure occurred in 4 cases (3,9%) comprehending 2 dislocations (1,9%) and 2 early acetabular loosening (1,9%). Amongst the groups, there were no cases of failures in the THA due to osteoarthrosis, in the THA for hip fracture there were 3 cases (5%) and in the RHA one case (3,4%). Failure-free survival was not statistically different between groups. There were no risk factors statistically related to failure. The use of constrained acetabular insert to prevent or treat instability achieved an adequate survival time with a low rate of complications. Further studies are necessary to corroborate our findings

Dual mobility (DM) components are increasingly used to prevent and treat dislocation after total hip arthroplasty (THA). Intraprosthetic dissociation (IPD) is a known rare complication of these implants and has reportedly decreased with modern implants. The purpose of this paper is to report the diagnosis and treatment of modern DM IPD. 1453 DM components were implanted between 2010 and 2021. 695 in primary and 758 in revision THA. 49 hips sustained a dislocation of the large head and 5 sustained an IPD at presentation. 6 additional IPD occurred at the time of reduction of large head. The average age was 64, 54% were female and the mean follow-up was three years. Of the 11 IPD, 8 had a history of instability, 5 had abductor insufficiency, 4 had prior lumbar fusion, and 3 were conversions from fracture. The overall IPD incidence was 0.76%. Ten of the 11 DM IPD were missed at initial presentation or at the time of reduction, and all were discharged with presumed reduction. The mean time from IPD to surgical treatment was 3 weeks. One patient died with an IPD at 5 months. A DM head was reimplanted in six, two underwent revision of the acetabular component with exchange of DM head, and four were revised to a constrained liner. The re-revision rate was 55% at a mean 1.8 years. None of the patients who underwent cup revision required subsequent re-revision while half of the constrained liners and exchange of DM heads required re-revision. The overall rate of DM dislocation or IPD is low. It is critical to identify an IPD on radiographs as it was almost universally missed at presentation or when it occurred iatrogenically. For patients presenting with IPD, the surgeon should consider acetabular revision and conversion to a constrained liner or a larger DM, with special attention to removing impinging structures that could increase the risk of re-dislocation

Fully constrained liners are used to treat recurrent dislocations or patients at high risk after total hip replacements. However, they can cause significant morbidities including recurrent dislocations, infections, aseptic loosening and fractures. We examine long term results of 111 patients with tripolar constrained components to assess their redislocation and failure rate. The purpose of this study was to assess survivorship, complications and functional outcomes at a minimum 10 years after the constrained tripolar liners used in our institute. We retrospectively identified 111 patients who had 113 revision tripolar constrained liners between 1998 and 2008. Eighty-nine were revised due to recurrent dislocations, 11 for pseudotumor with dysfunctional abductors, and 13 for periprosthetic infection with loss of soft tissue stabilizers. All patients had revision hip arthroplasty before the constrained liner was used: 13 after the first revision, 17 after the second, 38 after the third, and 45 had more than 3 revisions. We extracted demographics, implant data, rate of dislocations and incidence of other complications. Kaplan Meier curves were used to assess dislocation and failure for any reason. WOMAC was used to assess quality of life. At 10 years, the survival free of dislocation was 95.6% (95%CI 90- 98), and at 20 years to 90.6% (95% CI 81- 95.5). Eight patients (7.1%) had dislocations of their constrained liners: 1 patient had simultaneous periprosthetic infection identified at the time of open reduction, and 1 patient sustained stem fracture 3 months prior to the liner dislocation. At 10 years, the survival to any further surgery was 89.4% (95% CI 82–93.8), and at 20 years, this was 82.5 (95% CI 71.9–89.3). Five patients (4.4%) had deep infection: 4 of these had excision arthroplasty due to failure to control infection, while 1 patient was treated successfully with debridement, exchange of mobile components and intravenous antibiotics. Two patients (1.8%) had dissociated rings that required change of liner, ring and head. Two patients (1.8%) had periprosthetic femoral fractures that were treated by revision stems and exchange of constrained liners. The mean WOMAC functional and pain scores were 66.2 and 75.9 of 100, respectively. Constrained tripolar liners in our institute provided favourable results in the long term for recurrent dislocation hip arthroplasty with dysfunctional hip stabilizers. Infection in these patients can prove to be difficult to treat due to their poor soft tissue conditions from repeated surgeries. Comparing long terms results from other types of constrained liners is essential to evaluate these salvage liners

Aims. Pelvic discontinuity is a rare but increasingly common complication of total hip arthroplasty (THA). This single-centre study evaluated the performance of custom-made triflange acetabular components in acetabular reconstruction with pelvic discontinuity by determining: 1) revision and overall implant survival rates; 2) discontinuity healing rate; and 3) Harris Hip Score (HHS). Methods. Retrospectively collected data of 38 patients (39 hips) with pelvic discontinuity treated with revision THA using a custom-made triflange acetabular component were analyzed. Minimum follow-up was two years (mean 5.1 years (2 to 11)). Results. There were eight subsequent surgical interventions. Two failures (5%) of the triflange acetabular components were both revised because of deep infection. There were seven (18%) patients with dislocation, and five (13%) of these were treated with a constraint liner. One patient had a debridement, antibiotics, and implant retention (DAIR) procedure. In 34 (92%) hips the custom-made triflange component was considered stable, with a healed pelvic discontinuity with no aseptic loosening at midterm follow-up. Mean HHS was 80.5 (48 to 96). Conclusion. The performance of the custom triflange implant in this study is encouraging, with high rates of discontinuity healing and osteointegration of the acetabular implant with no aseptic loosening at midterm follow-up. However, complications are not uncommon, particularly instability which we successfully addressed with constrained liners. Cite this article: Bone Jt Open 2022;3(11):867–876

Background. Fully constrained liners are used to treat recurrent dislocations or patients at high risk after total hip replacements. However, they can cause significant morbidities including recurrent dislocations, infections, aseptic loosening and fractures. We examine long term results of 111 patients with tripolar constrained components to assess their redislocation and failure rate. Questions/purposes. The purpose of this study was to assess survivorship, complications and functional outcomes at a minimum 10 years after the constrained tripolar liners used in our institute. Methods. We retrospectively identified 111 patients who had 113 revision tripolar constrained liners between 1998 and 2008. Eighty-nine were revised due to recurrent dislocations, 11 for pseudotumor with deficient abductors, and 13 for periprosthetic infection with loss of soft tissue stabilizers. All patients had revision hip arthroplasty before the constrained liner was used: 13 after the first revision, 17 after the second, 38 after the third, and 45 had more than 3 revisions. We extracted demographics, implant data, rate of dislocations and incidence of other complications. Kaplan Meier curves were used to assess dislocation and failure for anything reason. WOMAC was used to assess quality of life. Results. At 10 years, the survival free of dislocation was 95.6% (95%CI 90– 98), and at 20 years to 90.6% (95% CI 81.0– 95.5). Eight patients (7.1%) had dislocations of their constrained liners: 1 patient had simultaneous periprosthetic infection identified at the time of open reduction, and 1 patient sustained stem fracture 3 months prior to the liner dislocation. At 10 years, the survival to any further surgery was 89.4% (95% CI 82–93.8), and at 20 years, this was 82.5 (95% CI 71.9–89.3). Five patients (4.4%) had deep infection: 4 of these had excision arthroplasty due to failure to control infection, while 1 patient was treated successfully with debridement, exchange of mobile components and intravenous antibiotics. Two patients (1.8%) had dissociated rings that required change of liner, ring and head. Two patients (1.8%) had periprosthetic femoral fractures that were treated by revision stems and exchange of constrained liners. The mean WOMAC functional and pain scores were 66.2 and 75.9 of 100, respectively. Conclusions. Constrained tripolar liners in our institute provided favourable results in the long term for recurrent dislocation hip arthroplasty with dysfunctional hip stabilizers. Infection in these patients can prove to be difficult to treat due to their poor soft tissue conditions from repeated surgeries. Comparing long term results from other types of constrained liners is essential to evaluate these salvage liners

Introduction. Many surgeons are reluctant to use a constrained liner at the time of acetabular component revision given concerns this might result in early acetabular component loosening. We hypothesized that with appropriate initial implant stabilization of highly porous acetabular components with supplemental screw fixation, constrained liners could be safely used at the time of acetabular revision. Methods. We retrospectively identified 148 revision total hip arthroplasties (THAs) where a constrained liner of one design was cemented into a newly placed highly porous acetabular component fixed with supplemental screws (mean 5 screws). Mean age at revision THA was 69 years, with 68% being female. The most common indications for revision were two-stage re-implantation (33%), recurrent dislocation (30%), and aseptic loosening (22% acetabular; 9% acetabular/femoral component). Mean follow-up was 8 years. Results. There were no failures at the bone-implant interface, and there were no revisions for aseptic loosening of the acetabular component. Furthermore, all acetabular components were bone ingrown on radiographic analysis. The 10-year survivorships free from any acetabular revision and free from any reoperation were 75% and 67%, respectively. Overall, 33 hips (22%) required revision or reoperation for infection/wound complications (n=12), dislocation (n=11), periprosthetic femur fracture (n=4), femoral loosening (n=3), and other (n=3). The 10-year survivorship free from dislocation was 84% overall, which was similar to the 85% 10-year survivorship free from dislocation for those specifically revised for instability (p=0.9). Conclusions. Implanting a constrained liner at the time of acetabular revision in high-risk patients resulted in no cases of aseptic acetabular component loosening in this large series. This is likely related to the fact that a highly porous acetabular component was utilized with a large number of supplemental screws in each case. Such information is valuable as these data favor a paradigm shift when compared to some traditionally-held tenets. For any tables or figures, please contact the authors directly

Dislocation remains among the most common complications of, and reasons for, revision of both primary and revision total hip arthroplasties in the United States. We have advocated identifying the primary cause of instability to plan appropriate treatment (Wera, Della Valle, et al., JOA 2012). Once implant position, leg length, and offset have been optimised and sources of impingement have been removed, the surgeon can opt for a large femoral head, a dual mobility articulation or a constrained liner. Given the limitations of constrained liners, we have looked to dual mobility articulations as an alternative, including its use in patients with abductor deficiency. We retrospectively compared a consecutive series of revision THA that were at high risk for instability and treated with either a constrained liner or a dual mobility articulation. At a minimum of two years, there were ten dislocations in the constrained group (10/43 or 23.3%) compared to three in the dual-mobility group (3/36 or 8.3%; p = 0.06). With repeat revision for instability as an endpoint, the failure rate was 23% for the constrained group and 5.5% for the dual mobility group (p = 0.03). We have also performed a systematic review of the published literature on the use of dual mobility in revision THA. Of the 3,088 hips reviewed, the dislocation rate was 2.2%, the risk of intraprosthetic dislocation was 0.3% and overall survivorship was 96.6% at 5 years. Dual mobility articulations offer anatomic sized femoral heads that greatly increase jump distance, without many of the negatives of a constrained liner. While dual mobility is associated with its own concerns and problems (including intraprosthetic dislocation and wear) our initial results suggest that they are a viable alternative to a constrained liner, even in the most challenging situations

In the revision situation in general and for recurrent dislocation specifically, it is important to have all options available including tripolar constrained liners in order to optimise the potential for hip stability as well as function. Even with the newer options available, dislocation rates of higher than 5% have been reported in the first two years following revision surgery at institutions where high volumes of revision surgery are performed (Wera et al). Because of the deficient abductors, other soft tissue laxity and the requirement for large diameter cups, revision cases will always have more potential for dislocation. In these situations, in the lower demand patient, tripolar constrained liners provided excellent success in terms of preventing dislocation and maintaining implant construct fixation to bone at intermediate term follow-up. Hence in these situations, tripolar with constraint remains the option we utilise in many cases. We are also confident in using this device in cases with instability or laxity where there is a secure well positioned acetabular shell. We cement a tripolar constrained liner in these situations using the technique described below. Present indication for tripolar constrained liners: low demand patient, abductor muscle deficiency or soft tissue laxity, large outer diameter cups, multiple operations for instability, instability with well-fixed shells that are adequately positioned. Technique of cementing liner into shell: score acetabular shell if no holes, score liner in spider web configuration, all one or two millimeters of cement mantle. Results: Constrained Tripolar Liner - For Dislocation: 56 Hips; 10 year average f/u; 7% failure of device, 5% femoral loosening, 4% acetabular loosening. Constrained Tripolar Liner - For Difficult Revisions: 101 hips; 10 year average f/u; 6% failure of device, 4% femoral loosening, 4% acetabular loosening. Cementing Liner into Shell: 31 hips; 3.6 year average f/u (2–10 years); 2 of 31 failures. We, like others, are trying to define cases where dual mobility will be as successful or more successful than tripolar constrained liners

Constrained liners are a tantalizing solution to both prevent and treat instability, as they markedly increase the force needed for a dislocation to occur. They have, however, several important negatives that the surgeon must consider before entertaining their use including: Increased stresses at the implant bone interface which can increase the risk of loosening or cause catastrophic failure in the early post-operative period; Decreased range of motion with a greater risk of impingement; and Usually require an open reduction if they dislocate or otherwise fail. Given the limitations of constrained liners, we have looked to dual mobility articulations as an alternative to constrained liners in the past five years in our practice, including patients with abductor deficiency. We retrospectively compared a consecutive series of revision THA that were at high risk for instability and treated with either a constrained liner or a dual mobility articulation. Indications for both groups included abductor insufficiency, revision for instability, or inadequate intra-operative stability when trialing. Forty-three hips were reviewed in the constrained group (mean follow-up 3.4 years) and thirty-six in the dual-mobility group (mean follow-up 2.4 years). The rate of failure was compared using a Fisher's exact test with a p-value of < 0.05 considered significant. At a minimum of two years, there were 10 dislocations in the constrained group (10/43 or 23.3%) compared to 3 in the dual-mobility group (3/36 or 8.3%; p = 0.06). There were 15 repeat revisions in the constrained group (10 for instability, 4 for infection, and 1 broken locking mechanism) compared to 4 in the dual mobility group (2 mechanical failures of cemented dual mobility liners with dislocation and 2 for infection); 34.9% vs. 11.1% (p = 0.01). With repeat revision for instability as an endpoint, the failure rate was 23% for the constrained group and 5.5% for the dual mobility group (p = 0.03). Mean Harris Hip Score (HHS) improved from 45 to 76 points in the constrained liner group, and from 46 to 89 points in the dual-mobility group. Dual mobility articulations offer anatomic sized femoral heads that greatly increase jump distance, without many of the negatives of a constrained liner. While dual mobility is associated with its own concerns and problems (including intra-prosthetic dislocation and wear) our initial results suggest that they are a viable alternative to a constrained liner, even in the most challenging situations

Recurrent dislocation following total hip arthroplasty (THA) is a complex, multifactorial problem that has been shown to be the most common indication for revision THA. At our center, we have tried to approach the unstable hip by identifying the primary cause of instability and correcting that at the time of revision surgery. Type 1:. Malposition of the acetabular component treated with revision of the acetabular component and upsizing the femoral head. Type 2:. Malposition of the femoral component treated with revision of the femur and upsizing the femoral head. Type 3:. Abductor deficiency treated with a constrained liner or dual mobility bearing. Type 4:. Soft tissue or bony impingement treated with removal of impingement sources and upsizing the femoral head. Type 5:. Late wear of the bearing treated with bearing surface exchange and upsizing the femoral head. Type 6:. Unclear etiology treated with a constrained liner or dual mobility articulation. These may be patients with abnormal spino-pelvic motion. The most common etiologies of instability in our experience include cup malposition (Type 1) and abductor deficiency (Type 3). We reviewed 75 hips revised for instability and at a mean 35.3 months 11 re-dislocations occurred (14.6%). Acetabular revisions were protective against re-dislocation (p<0.02). The number of previous operations (p=0.04) and previously failed constrained liners (p<0.02) were risk factors for failure. The highest risk of failure was in patients with abductor insufficiency with revisions for other etiologies having a success rate of 90%. Although instability can be multifactorial, by identifying the primary cause of instability, a rational approach to treatment can be formulated. In general the poorest results were seen in patients with abductor deficiency. Given the high rate of failure of constrained liners (9 of the 11 failures were constrained), we currently are exploring alternatives such as dual mobility articulations. Our early experience with dual mobility suggests improved results when compared to constrained liners

In primary total hip replacements there are numerous options available for providing hip stability in difficult situations (i.e. Down's syndrome, Parkinson's disease). We have considered constrained liners in some of these cases. However, in the revision situation in general and in revision for recurrent dislocation situation specifically it is important to have all options available including tripolar constrained liners in order to optimise the potential for hip stability as well as function of the arthroplasty. Even with the newer options available dislocation rates of higher than 10–15% have been reported following revision surgery at institutions where high volumes of revision surgery are performed. Because of the deficient abductors, other soft tissue laxity and the requirement for large diameter cups revision cases will always have more potential for dislocation. In these situations in the lower demand patient, constraint has provided excellent success in terms of preventing dislocation and maintaining implant construct fixation to bone at intermediate- term follow-up. Hence in these situations tripolar constrained liners remains the option we utilise. We are also confident in using this device in cases with instability or laxity where there is a secure well- positioned acetabular shell. We cement a dual mobility constrained liner in these situations using the technique described below. Present indication for tripolar constrained liners: low demand patient, large outer diameter cups, instability with well-fixed shells that are adequately positioned, abductor muscle deficiency or soft tissue laxity, multiple operations for instability. Technique of cementing liner into shell: score acetabular shell if no holes, score liner in spider web configuration, all one or two millimeters of cement mantle. Results. Constrained Dual Mobility Liner. For Dislocation: 56 Hips, 10 yr average f/u, 7% failure of device, 5% femoral loosening, 4% acetabular loosening. For Difficult Revisions:101 hips, 10 yr average f/u, 6% failure of device, 4% femoral loosening, 4% acetabular loosening. Cementing Liner into Shell: 31 hips, 3.6 yr average f/u (2–10 years), 2 of 31 failures

Recurrent dislocation following total hip arthroplasty (THA) is a complex, multifactorial problem that has been shown to be the most common indication for revision THA. At our center, we have tried to approach the unstable hip by identifying the primary cause of instability and correcting that at the time of revision surgery. Type 1: Malposition of the acetabular component treated with revision of the acetabular component and upsizing the femoral head. Type 2: Malposition of the femoral component treated with revision of the femur and upsizing the femoral head. Type 3: Abductor deficiency treated with a constrained liner or dual mobility bearing. Type 4: Soft tissue or bony impingement treated with removal of impingement sources and upsizing the femoral head. Type 5: Late wear of the bearing treated with bearing surface exchange and upsizing the femoral head. Type 6: Unclear etiology treated with a constrained liner or dual mobility articulation. The most common etiologies of instability in our experience include cup malposition (Type 1) and abductor deficiency (Type 3). We reviewed 75 hips revised for instability and at a mean 35.3 months, 11 re-dislocations occurred (14.6%). Acetabular revisions were protective against re-dislocation (p<0.02). The number of previous operations (p=0.04) and previously failed constrained liners (p<0.02) were risk factors for failure. The highest risk of failure was in patients with abductor insufficiency with revisions for other etiologies having a success rate of 90%. Although instability can be multifactorial, by identifying the primary cause of instability, a rational approach to treatment can be formulated. In general, the poorest results were seen in patients with abductor deficiency. Given the high rate of failure of constrained liners (9 of the 11 failures were constrained), we currently are exploring alternatives such as dual mobility articulations. Our early experience with dual mobility suggests improved results when compared to constrained liners

Dual mobility components for total hip arthroplasty provide for an additional articular surface, with the goals of improving range of motion, jump distance, and overall stability of the prosthetic hip joint. A large polyethylene head articulates with a polished metal acetabular component, and an additional smaller metal or ceramic head is snap-fit into the large polyethylene. In some European centers, these components are routinely used for primary total hip arthroplasty. However, their greatest utility will be to prevent and manage recurrent dislocation in the setting of revision total hip arthroplasty. Several retrospective series have shown satisfactory results for this indication at medium-term follow-up times. The author has used dual mobility components on two occasions to salvage a failed constrained liner. At least one center reports that dual mobility outperforms 40mm femoral heads in revision arthroplasty. Modular dual mobility components, with screw fixation, are the author's first choice for the treatment of recurrent dislocation, revision of failed metal-on-metal resurfacing or total hips, unipolar arthroplasties, and salvage of failed constrained liners. There are concerns of elevated metal levels with one design, and acute early intra-prosthetic dissociation following attempted closed reduction. Total hip surgeons no longer use conventional polyethylene, autologous blood donation, or a hemovac drain; now constrained components join these obsolete techniques! In 2018, a dual mobility component, rather than a constrained liner, is the preferred solution in revision surgery to prevent and manage recurrent dislocation

Total hip arthroplasty (THA) has been efficacious for treating hip fractures. However, in these patients with fractures a widely variable prevalence of dislocation has been reported, partly because of varying durations of follow-up for this specific end-point. The purpose of the present study was to determine the risk of dislocation as a function of time after total hip arthroplasty in these patients with fractures and to investigate if constrained liners influence the cumulative risk of dislocation. Between 2000 and 2005, 425 patients with neck fracture underwent primary THA using a constrained acetabular liner (Cemented retentive cup, Groupe lépine, Genay, France). The results of these 425 constrained acetabular liners were compared with 380 THA without constrained liners performed for neck fractures between 1994 and 1999 in the same hospital. All patients were followed for a minimum of 5 years for radiographic evidence of implant failure. The patients were followed at routine intervals and were specifically queried about dislocation. The cumulative risk of dislocation was calculated with use of the Kaplan-Meier method. Results. For patients without constrained liners, the cumulative risk of a first-time dislocation was 5% at one month and 12% at one year and then rose at a constant rate of approximately 2% every five years to 17% at five years, 19% at ten years, 21% at 15 years for patients who were alive and had not had a revision by that time. For patients with constrained liners, the cumulative risk of a first-time dislocation was 1% at one month, 2% at one year and then did not changed at 5 years and at 10 years for patients who were alive and had not had a revision by that time. Multivariate analysis revealed that the relative risk of dislocation for female patients (as compared with male patients) was 2.1 and that the relative risk for patients who were 80 years old or more (as compared with those who were less than 80 years old) was 1.5. Two underlying diagnoses - cognitively impaired patients or neurologic desease—were also associated with a significantly greater risk of dislocation. At minimum 7 year follow up (range 5 10 yrs), there were 8 radiographic failures (dislocations) of the 425 constrained liners (2%), and no loosenings were noted. Conclusions. The cumulative long-term risk of dislocation for patients with hip fractures is considerably greater than has been reported in short-term studies. The incidence of dislocation is highest in the first year after arthroplasty and then continues at a relatively constant rate for the life of the arthroplasty. Patients at highest risk are old female patients and those with a diagnosis of neurologic desease. Constrained liners in these patients is an efffective technique to prevent post operative hip dislocation

Recurrent dislocation following total hip arthroplasty (THA) is a complex, multifactorial problem that has been shown to be the most common indication for revision THA. At our center, we have tried to approach the unstable hip by identifying the primary cause of instability and correcting that at the time of revision surgery. Type 1: Malposition of the acetabular component treated with revision of the acetabular component and upsizing the femoral head. Type 2: Malposition of the femoral component treated with revision of the femur and upsizing the femoral head. Type 3: Abductor deficiency treated with a constrained liner or dual mobility bearing. Type 4: Soft tissue or bony impingement treated with removal of impingement sources and upsizing the femoral head. Type 5: Late wear of the bearing treated with bearing surface exchange and upsizing the femoral head. Type 6: Unclear etiology treated with a constrained liner or dual mobility articulation. The most common etiologies of instability in our experience include cup malposition (Type 1) and abductor deficiency (Type 3). We reviewed 75 hips revised for instability and at a mean 35.3 months 11 re-dislocations occurred (14.6%). Acetabular revisions were protective against re-dislocation (p<0.015). The number of previous operations (p=0.0379) and previously failed constrained liners (p<0.02) were risk factors for failure. The highest risk of failure was in patients with abductor insufficiency with revisions for other etiologies having a success rate of 90%. Although instability can be multifactorial, by identifying the primary cause of instability, a rational approach to treatment can be formulated. In general the poorest results were seen in patients with abductor deficiency. Given the high rate of failure of constrained liners (9 of the 11 failures were constrained), we currently are exploring alternatives such as dual mobility articulations