Dual-mobility (DM) bearings are effective to mitigate dislocation in revision total hip arthroplasty (THA). However, data on its use for treating dislocation is scarce. Aim of this study was to compare DM bearings, standard bearings and constrained liner (CL) in revision THA for recurrent dislocation and to identify risk factors for re-dislocation. We reviewed 100 consecutive revision THAs performed for dislocation from 2012 and 2019. 45 hips (45%) received a DM construct, while 44 hips (44%) and 11 hips (11%) had a standard bearing and CL, respectively. Rates of re-dislocation, re-revision for dislocation and overall re-revision were compared. Radiographs were assessed for cup positioning, restoration of centre of rotation, leg length and offset. Risk factors for re-dislocation were determined by cox regression analysis. Modified Harris hip scores (mHHS) were calculated. Mean follow-up was 53 months (1 to 103). DM constructs were used more frequently in elderly patients (p=0.011) and hips with abductor deficiency (p< 0.001). The re-dislocation rate was 11.1% for DM bearings compared with 15.9% for standard bearings and 18.2% for CL (p=0.732). Revision-free survival for DM constructs was 83% (95% CI 0.77 – 0.90) compared to 75% (95% CI 0.68 – 0.82) for standard articulations and 71% (95% CI 0.56 – 0.85) for CL (p=0.455). Younger age (HR 0.91; p=0.020), lower comorbidity (HR 0.42; p=0.031), smaller heads (HR 0.80; p=0.041) and cup retention (HR 8.23; p=0.022) were associated with re-dislocation. Radiological analysis did not reveal a relationship between restoration of hip geometry and re-dislocation. mHHS significantly improved from 43.8 points to 65.7 points (p<0.001) with no differences among bearing types. Our findings suggest that DM bearings do not sufficiently prevent dislocation in revision THA for recurrent dislocation. Reconstruction of the abductor complex may play a key role to reduce the burden in these high-risk patients

Far too many cases of instability and recurrent dislocation occur after primary total hip replacement. The motivation for this paper came from yet another three cases of recurrent dislocation on our theatre list in a single month (March 2006). All three were recurrent dislocations after primary hip replacements. Since these were not three isolated cases we realised that there is an urgent need to improve the situation. In all three cases surgical or implant factors were responsible. We take a fresh look at the causes; which are implant, surgeon and patient related. Of these only patient related issues cannot always be corrected. The design of a stable implant is discussed and revolves around head size, head neck ratio and cup depth. The surgeons’ contribution can be equally important and controllable – it embodies correct peri-articular soft tissue tension, orientation of components and patient selection. Finally, patient factors are neuromuscular, anatomical and patient compliance. In this respect some unresolved factors should be identified pre-operatively. Especially for the occasional hip surgeon this is an extremely important issue. The recurrent dislocation results in extremely poor quality of life, often leading to revision surgery. These aged patients usually suffer multiple inherent risks and massive financial losses. Above all we believe that the great majority of these dislocations can be prevented by simply keeping to the clear and well proven principles of stability in total hip replacement

Background: Dislocation after total hip replacement (THR) is a significant concern with the increased number of THR carried out all over the world, although there has been a substantial lack of information regarding revision THR for instability in literature. Purpose: The purpose of this study was to evaluate the effectiveness of operative treatment for recurrent dislocation after THR. Material and methods: One hundred and eleven cases were treated operatively for recurrent dislocation after THR by a senior author (BMW). Group A; 104 cases were operated with change of either or both of components, a socket and a stem. Twenty-two mm head was used in 90 cases (A-1), 32 mm head in twelve (A-2), and 36 mm head in two (A-3). Group B; only modular head was changed in one case. Group C; augmentation device was applied on a cup in six cases. The average follow-up period was 6.2 years (range, 1 to 21 years). Results: Group A-1; twelve cases (13%) required further operations for instability (N=90). Group A-2; one case (8.3%) was converted to Girdle-Stone for recurrent dislocation (N=12). Group A-3; one of them was revised for periprosthetic fracture (N=2). Group B; the case survived at the follow-up of 3.3 years (N=1). Group C; two cases (33%) were revised for dislocation (N=6). Conclusion: We reported the largest series of revision THR for recurrent dislocation by a single surgeon with a considerable length of follow-up periods. Revision THR with change of components was an effective treatment for recurrent dislocation after THR

Background. Dislocation is one of the commonest complications of total hip arthroplasty (THA) with incidence of between 0.3 and 10% in primary, and from 15 % to 30% of revision cases. Despite this, little is known of the outcome of treatment strategies for dislocation. In this study, we evaluated clinical results in patient undergoing revision THA for recurrent dislocation. Materials and Methods. Twenty-four hips underwent revision THA for recurrent instability between 1998 and 2011 at our institution. Nine patients were male, and 15 were female. At the time of revision, the average age was 69.9 years (range, 45–83 years). Average follow-up was 29.8 months (range, 6–72 months). We recorded the number of times of dislocation, the direction of dislocation, the factor of dislocation and the operative strategy employed for each case. Demographic data and surgical treatment used were analyzed to determine risk factors for failure. We performed Mann-Whitney rank sum test, Student's t-test and Fisher exact test to evaluate the factors influencing failure. Significance was defined as a p value of <0.05 (Statistical Package for Social Sciences (SPSS) version 12.0 J for Windows (SPSS Inc., Chicago, IL, USA)). Results. Before revision surgery, dislocation was occurred more than three times in all cases. The anterior dislocation was only four cases. In the factor of dislocation, 5 were malposition of implant, 11 were soft tissue imbalance, 3 were highly posterior tilting of pelvic and 5 were multi-factorial. Revision treatment includedã��liner and ball exchange in 19 hips, cup exchange in 5 hips. There was eight substitution to constrain liner for sever soft tissue imbalance. Nine (37.5%) had further dislocation. Cup revision for implant malposition was a successful method in recurrent instability (P=0.04). Constrain liner exchange (P=0.03) was associated with higher failure rate. Conclusion. Recurrent dislocation has complex problems with multifaceted etiology that requires extensive preoperative planning of each dislocation factors and availability of multiple surgical options

This study reports the outcome of using the Posterior Lip Augmentation Device (PLAD) for recurrent dislocation of total hip replacement. Twenty-seven patients (16 in Inverness, 11 in Leeds) were treated with the device. The indication for its use was recurrent dislocation of the hip in a patient who had a well-orientated and well-fixed cemented acetabular component. The patients had had between 2 and 14 dislocations before using the PLAD. 24 of the 27 patients had satisfactory control of the dislocations after surgery. The operation was found to be straightforward in most cases with few complications, although one case in the Inverness series has a partial sciatic nerve palsy which is recovering. Of the three failures, two had recurrent dislocation after the use of the PLAD. In one of these, in whom the dislocation followed acetabular reconstruction with impaction grafting, the cup also pulled out due to the semi-captive state after use of the PLAD. Both of these cases were treated by a Girdlestone excision arthroplasty. There was one final failure in whom there has been no further dislocation but following an abduction injury some four months after surgery, progressive cup loosening developed and he awaits revision of the cup. One patient complains of an occasional click in the hip joint and a broken screw is visible on x-ray but there has been no loss of position of the device and no further evidence of dislocation. Overall, we have found that this device gives satisfactory control of recurrent dislocations of the hip but the failures have stressed the need to ensure that the cup fixation is sound before inserting the device

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

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-metal resurfacing, 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 cement Charnley acetabular components, use conventional polyethylene, autologous blood donation, or a drain; now constrained components join these obsolete techniques! In 2017, a dual mobility component, rather than a constrained liner, is the preferred solution in revision surgery to prevent and manage recurrent dislocation

Surgical treatment of recurrent dislocation after total hip arthroplasty (THA) is challenging with often disappointing results. The influence of the posterior hip capsule is important, and restoration of its function is a major goal of treatment. We describe our experience using an Achilles tendon allograft as a checkrein to limit hip internal rotation and to prevent posterior instability. Twenty unstable THAs were treated using this technique, eliminating instability in fifteen. At an average follow-up of 3.6 years, Achilles tendon allograft augmentation has proven a useful adjunct for the treatment of recurrent posterior dislocation after THA in selected patients. The purpose of this study is to review our results with a novel treatment for recurrent dislocation after total hip arthroplasty (THA) using an Achilles tendon allograft as a checkrein to prevent instability. Achilles tendon allograft augmentation has proved to be a useful adjunct for the treatment of recurrent posterior dislocation after THA in selected patients. Surgical treatment of recurrent dislocation after total hip arthroplasty (THA) is challenging with often disappointing results. Among possible causes of dislocation, the influence of the static soft tissue restraint provided by the hip capsule is important, and restoration of its integrity and function is a major goal of treatment. We describe a new technique in which an Achilles tendon allograft is employed as a checkrein to limit hip internal rotation and to prevent posterior instability. Twenty unstable THAs with recurrent instability were treated using this technique, eliminating instability in fifteen at an average follow-up of 3.6 (0.5 to 6.6) years. Prospective data was collected and reviewed on the first twenty patients with recurrent THA instability stabilized with an Achilles tendon allograft. Head and liner exchanges accompanied the allograft. Use of a constrained cup was considered a failure. Instability was successfully controlled in 75% of patients with use of the Achilles allograft. The technique is an important addition to the treatment arsenal of this difficult problem

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 head is snap-fit into the large polyethylene. New components have been released for use in North America over the past three years. In some European centers, these components are routinely used for primary total hip arthroplasty. However, their greatest utility may be to manage recurrent dislocation in the setting of revision total hip arthroplasty. Several small retrospective series have shown satisfactory results for this indication at short- to medium-term follow-up times. However, there are important concerns with polyethylene wear, late intra-prosthetic dislocation, and the lack of long-term follow-up data. These components are an important option in the treatment of recurrent dislocation in younger patients, revision of failed metal-metal resurfacing, and salvage of failed constrained liners. Until further long-term results are available, caution is advised in the routine use of dual mobility components in primary or revision total hip arthroplasty

Although the incidence of total hip dislocation has decreased, it still remains a major problem particularly if recurrent. The actual incidence is around 1–2% but it has been documented as the leading cause for hip revision in the United States. In patients with recurrent hip dislocation, technical issues of leg length inequality, incorrect offset, and poor implant position should be addressed surgically and the abnormality corrected. In patients with recurrent hip dislocation, the articulation is preferably converted to a more stable articulation, with constrained sockets and dual mobility being the choices. In my experience, dual mobility articulations remain an excellent option for recurrent hip dislocation and its use is increasing significantly. It provides improved hip stability and data have demonstrated good success with recurrent hip dislocation. However, with use of the modular variety of dual mobility which is needed for acetabular cup fixation with screw augmentation, dissimilar metals are placed in contact (titanium socket and cobalt chrome liner insert) which potentially can pose a fretting or corrosion problem in longer term outcomes. Constrained sockets of the tripolar configuration provide another option which is useful in those patients with severe abductor dysfunction or insufficiency. Constrained sockets can also be cemented into the existing shell in cases where there is a well-fixed cup and cup removal may lead to significant bone loss and need for complex acetabular reconstruction. It is important to remember that there are two types of constrained sockets, tripolar and focal constraint. Results with the tripolar constrained socket have been significantly better than the focal constraint variety which adds a polyethylene rim piece to the liner. In a mid-term follow up (2–9 years) of 116 constrained tripolar sockets, recurrent dislocation was only 3.3%. In papers reporting on focal constrained sockets, recurrent dislocation was in the 9–29% range. There continues to be a role for constrained sockets and selection of implant type has made a difference in ultimate outcome

Although the incidence of total hip dislocation has decreased, it still remains a major problem particularly if recurrent. The actual incidence is around 1–2% but it has been documented as the leading cause for hip revision in the United States. In patients with recurrent hip dislocation, technical issues of leg length inequality, incorrect offset, and poor implant position should be addressed surgically and the abnormality corrected. In patients with recurrent hip dislocation, the articulation is preferably converted to a more stable articulation, with constrained sockets and dual mobility being the choices. In my experience, dual mobility articulations remain an excellent option for recurrent hip dislocation and its use is increasing significantly. It provides improved hip stability and data have demonstrated good success with recurrent hip dislocation. However, with use of the modular variety of dual mobility which is needed for acetabular cup fixation with screw augmentation, dissimilar metals are placed in contact (titanium socket and cobalt chrome liner insert) which potentially can pose a fretting or corrosion problem in longer term outcomes. Constrained sockets of the tripolar configuration provide another option which is useful in those patients with severe abductor dysfunction or insufficiency. Constrained sockets can also be cemented into the existing shell in cases where there is a well-fixed cup and cup removal may lead to significant bone loss and a need for complex acetabular reconstruction. It is important to remember that there are two types of constrained sockets, tripolar and focal constraint. Results with the tripolar constrained socket have been significantly better than the focal constraint variety which adds a polyethylene rim piece to the liner. In a mid-term follow up (2–9 years) of 116 constrained tripolar sockets, recurrent dislocation was only 3.3%. In papers reporting on focal constrained sockets, recurrent dislocation was in the 9–29% range. There continues to be a role for constrained sockets and selection of implant type has made a difference in ultimate outcome

Recurrent dislocation of peroneal tendons is an uncommon presentation following ankle injuries. It usually follows an inversion injury to the ankle, most commonly seen in skiing, however it has also been described in many other sporting activities. X rays appear normal, and patients usually get treated as ankle sprain. The diagnosis, usually delayed is a clinical one, patients usually describe ankle instability and sudden painful snapping or popping of the subluxating peroneal tendons. This makes it difficult for them to participate in any sporting activities and is a source of continous discomfort while walking. Examination may show tender peroneal tendons and demonstration of subluxing tendons is facilitated by eversion against resistance or manually by thumb pressure. The common pathology is tear of the peroneal retinaculum and striping of periosteum from the anterior attachment to the lateral maleolus. We describe 11 cases of recurrent dislocation of peroneal tendons from February 1999 to October 2004. They all suffered trauma related dislocation of peroneal tendons, causing recurrent peroneal tendon dislocation. All procedures were performed by a single consultant. Procedure involves soft tissue anatomic reconstruction of the peroneal retinaculum. There were 9 males and 2 females, mean age was 30.1 years (range 15 to 58 years). All patients were treated initially with rest followed by period of physiotherapy to no benefit. All complained of ankle instability with pain associated with tendon dislocation even while walking. The mean duration from time of injury to surgery was 10 months (range 2 to 45 months). We performed clinical assessment, ankle scoring, SF 36 version2 scoring and assessed patient satisfaction with the procedure. At the latest follow up of 6 months to 6 years all patients were extremely satisfied with the procedure. There was no recurrence of dislocation. All patients were back to their normal daily activities and sports within 6 months of surgery. One patient complained of occasional mild pain over the tendon. One patient reported mild paraesthesiae in distribution of sural nerve, which recovered over 3 months. On clinical assessment the tendon was stable in all patients with full ROM and strength in the affected ankle when compared to normal side. The mean ankle score increased from 62 pre-op (range 22 to 89) to 96 post-operative (range 90 to 100). Mean SF 36 scores increased from PCS of 41 and MCS of 53 pre-op to a PCS of 57 and MCS of 60 post-op. In the past procedures have been described for treatment of recurrent dislocation of peroneal tendons. We report the results of a procedure previously described and published by the senior author ( ‘The Foot’: 2003 ). This is an anatomic procedure for repair of torn peroneal retinaculum and double breasting of redundant periosteum. Our latest follow up of 6 months to 6 years shows excellent results with no recurrence and no limitation of ankle movement or sporting activities

Introduction: Although a number of methods have been described to treat recurrent dislocation following total hip arthroplasty, this complication remains a challenging problem. The purpose of this retrospective study was to evaluate the minimum 2-year outcome in a consecutive series patients treated with a cemented tripolar unconstrained acetabular component for recurrent dislocation. Patients and Methods: Fifty-one patients presenting with recurrent dislocation following primary or revision total hip arthroplasty in the absence of an identifiable curable cause were treated with a cemented tripolar unconstrained acetabular component. There were thirty-nine females and twelve males with a mean age at the time of the index procedure of 71.3 years. A single acetabular component design was used consisting of a stainless steel outer shell with grooves for cement fixation with a highly polished inner surface. This shell articulated with a mobile intermediate component with an opening diameter smaller than the 22.2-mm femoral head. No locking ring or other mean of constraint was associated. Results: Of the fifty-one patients, forty-seven have had complete clinical and radiological evaluation data at a mean follow-up of 31.2 months (twenty-four to 56.3 months). The cemented unconstrained tripolar acetabular component restored complete stability of the hip in forty-nine patients (96%). The mean Merle d’Aubigné hip score was 15.8 ± 2.0 at the latest follow-up. Radiographic analysis revealed no or radiolucent lines less than 1 mm thick located in a single acetabular zone in forty-three of forty-seven hips (91.5%). The cumulative survival rate of the acetabular component at 36 months using revision for dislocation and/or mechanical failure as the end point was 93.3 ± 4.6% (95% confidence interval, 84.4% to 100%). Conclusion: A cemented tripolar unconstrained acetabular component was highly effective in the treatment of recurrent dislocation with none of the complications associated with constrained devices. However, because longer term follow-up is needed to warrant that dislocation and loosening rates will not increase, the use of such a device should be limited to strict indications

A review of total hip replacements (THR) performed in Palmerston North between 1991–2000 has identified a group of postoperative patients in whom recurrent dislocation has been previously deemed untreatable because of medical co-morbidity. From 1998 to 2001, 47 patients underwent THR utilizing a semi-constrained “Kasselt” cup to reduce the risk of dislocation. Indications for use of this cup were: Recurrent dislocation following primary or revision THR (3 or more dislocations) or perceived greater risk of recurrent dislocation eg. elderly, mental confusion, neurological compromise or fracture neck of femur. This paper presents the early results in these 47 patients (49 hips). Clinical records and radiographs of all hip replacement patients were retrospectively reviewed to identify the “Kasselt” group and telephone contact was made for permission to participate in the study. All living patients were sent a self-evaluation questionnaire and invitation to attend clinic for physical examination and radiographs of the hip joint. Twenty-one patients were recurrent dislocators and 24 were at risk patients. Out of 45 living patients 36 were physically examined between 6 and 36 months following surgery. All collected data was statistically analysed using StatWave software. Results: Forty-three of the 45 living patients (47 hips) had no dislocations following surgery. Two patients suffered further dislocation, both of whom were previously recurrent dislocators. One suffered a single dislocation postoperatively which was reduced closed and to date has not re-dislocated. The second continues to dislocate. The mean postoperative Harris Hip Score in the whole group is 79 (range 49–100). Early results reveal no dislocations in the “at risk” primary group

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

Introduction: Preliminary data suggest that immobilization in external rotation may be effective in lowering the incidence of recurrence after first traumatic shoulder dislocation, with a zero reoccurrence rate reported at 15 months follow-up. The purpose of the present study was to ascertain whether this method could lower the incidence of recurrent dislocation in a young, very physically active population. Methods: In an IRB approved prospective study, young males who sustained first traumatic shoulder dislocation were randomized to be treated for four weeks either using a traditional internal rotation brace or a new device which immobilizes the shoulder at 15 to 20 degrees of external rotation. Subjects were then treated according to a standard physical therapy protocol. Follow-up was done at five time points in the first year post dislocation. Subjects with clinically stable shoulders resumed full activity after three months. Differences in outcome were assessed by the chi square test. Results: Thirty nine subjects participated in the study. Thirty of them were soldiers. Twenty four subjects were treated with external rotation braces. At follow-up of between 4 to 28 months, a new dislocation was documented in 8 of the 24 subjects immobilized in external rotation (33%) and in 5 of the 15 subjects immobilized in internal rotation (33 %). No statistical difference (p=1.0) was found between the instability rates of the two treatment groups. Discussion: The present study indicates that even in a short-term follow-up the technique of immobilizing a first dislocation in external rotation was not effective in lowering the incidence of recurrent shoulder dislocations in a young, physically active population

Management of recurrent instability of the hip requires careful assessment to determine any identifiable causative factors. While plain radiographs can give a general impression, CT is the best methodology for objective measurement. Variables that can be measured include: prosthetic femoral anteversion, comparison to contralateral native femoral anteversion, total offset from the medial wall of the pelvis to the lateral side of the greater trochanter, comparison to total offset on the contralateral side, acetabular inclination, & acetabular anteversion.

Wera et al describe potential causes of instability. These are typed into I. Acetabular Component Malposition; II. Femoral Component Malposition; III. Abductor Deficiency; IV. Impingement; V. Late Wear; and VI. Unknown.

Acetabular component malposition is the most common cause of instability and so measurement of cup orientation is essential. It is well known that excessive or inadequate anteversion can lead to anterior and posterior dislocation respectively but horizontal components are also associated with posterior dislocation due to deficient posterior/inferior acetabular surface.

Similarly, excessive or inadequate femoral anteversion can be easily identified on CT as can insufficient total offset of the reconstructed joint compared to the contralateral side. This can be caused by medialization of the acetabular component.

Abductor deficiency can be a soft-tissue cause of instability, but it certainly isn't the only one. Knowledge of the prior surgical exposure can be instructive. Anterior exposures can be prone to deficient anterior capsule just as posterior exposures can be prone to deficient posterior capsule and short rotators, while anterolateral and lateral exposures can be associated with gluteus minimus and gluteus medius compromise.

Impingement, whether involving implants, bone, or soft tissue are primarily secondary to the above factors, if osteophytes were properly trimmed at the index procedure.

Correction of the incorrect variables is the primary goal of revision for instability and greatly preferable to using salvage options such as dual-mobility or constrained articulations which invoke additional concerns. Ultimately though, such salvage options are necessary if the cause of the instability cannot be determined or can be determined but not corrected. Bracing, while highly inconvenient and sometimes impractical for certain patients, still has a role in specific circumstances. Formal analysis of the unstable prosthetic reconstruction is the key to successful treatment.

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.

Dislocation after THA is the most common complication in modern THA, The reported failure rate of reoperation for recurrent instability is higher than any other indication for revision surgery.

Treatment of dislocation after THA

Non-operative treatment

The first episode of dislocation after THA is usually treated by close reduction with or without brace treatment. There is no agreement about the role and effectiveness of bracing. Generally, bracing is indicated in the following circumstances:

First dislocation

The main management issues are about managing recurrent instability. Treatment choice is often complex and management begins by identifying the cause of instability.

Causes to consider:

Component issue

Surgical Treatment

The decision to use operative treatment to stabilize the hip joint is complex and the surgeon must take into consideration:

How many times the hip dislocated

Treatment choices depends on the underlying mechanism of dislocation:

Correction of malposition

The most commonly used surgical techniques used to treat recurrent or habitual patellar dislocation in the child do not specifically address the patella alta, one of the major causes of patellar dislocation. Twelve knees in eight patients had a lowering of the patella by total tendon transfer, lateral release and vastus medialis obliquus advancement. At two years of follow-up, only one knee had redislocated. Radiographically, the patellar height was anatomically restored in all other knees. All patients were pain free. This surgical technique is a good treatment option in the immature patient with recurrent or habitual patellar dislocation.

Patella alta is one of the major causes known to predispose children to recurrent or habitual patellar dislocation. However, the surgical treatment of such a condition, before squeletal maturity, is rarely if ever mentioned in the literature.

Twelve knees in eight patients were treated with a surgical procedure designated to correct patella alta, the major predisposing factor causing recurrent patellar dislocation. The technique involves lowering of the patella by total tendon transfer, lateral release and vastus medialis obliquus advancement. All patients were complaining of recurrent or habitual dislocations leading to functional disability. Patellar height was assessed radiographically by the Koshimoto index (PT/FT) and Caton-Deschamps index (AT/AP). The average at surgery was 10.9 years and mean follow-up was 45.1 months.

Follow-up revealed redislocation in one knee. This patient required a second operation to achieve patellar stability. At the latest follow-up, all operated knees were functionally stable and pain free. The average preoperative ratios were 1.28 (PT/FT) and 1.53 (AT/AP) which improved to 0.97 (PT/FT) and 0.96 (AT/AP) at the time of follow-up. Few complications were noted.

This technique is a valid surgical alternative to treat the immature patient presenting with functional disability related to recurrent or habitual patellar dislocation associated with patella alta.