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

Aims: Instability and dislocation of the hip is one of the most striking problems for children and young people with neuromuscular disorders. The purpose of this study was to find out pathomechanical risk factors relating to specific neuromuscular disorders. We compared our findings with literature and questioned if there is any impact on current screening and treatment principles. Methods: In a prospective long-term-study 2500 patients with neuromuscular disorders regularly underwent analysis of both muscular dysfunction and structural deformities by clinical examination and native radiographs. Walking patients had additional slow motion video-analysis and in the case of surgical intervention pre- and postoperative 3D-gait analysis. The vast majority of patients with the TBI-type of cerebral palsy had unstable hips. 66 severely subluxated or dislocated hip joints underwent 3D-CT-scan examinations prior to surgical reconstruction, soft tissue releases and muscle transfers. Conclusions: Developmental biological studies presume that a complex systemic network of both genetical determining factors and external biomechanical influences affect physiological growth and maturing of the juvenile hip joint. Under clinical condiions it may be possible to discover and analyse some of the most important factors. Primary, compensating and secundary functional disorders have to be differentiated by clinical examination, radiographs, and motion analysis. Increased or spastic and decreased or paretic muscular activity may cause different degrees of muscular imbalance. Together with additional compensating movements they form specific pathological motor patterns which occur typically related to specific neuromuscular diseases

There has been a marked increase in the number of hip arthroscopies performed over the past 16 years, primarily in the management of femoroacetabular impingement (FAI). Insights into the pathoanatomy of FAI, and high-level evidence supporting the clinical effectiveness of arthroscopy in the management of FAI, have fuelled this trend. Arthroscopic management of labral tears with repair may have superior results compared with debridement, and there is now emerging evidence to support reconstructive options where repair is not possible. In situations where an interportal capsulotomy is performed to facilitate access, data now support closure of the capsule in selective cases where there is an increased risk of postoperative instability. Preoperative planning is an integral component of bony corrective surgery in FAI, and this has evolved to include computer-planned resection. However, the benefit of this remains controversial. Hip instability is now widely accepted, and diagnostic criteria and treatment are becoming increasingly refined. Instability can also be present with FAI or develop as a result of FAI treatment. In this annotation, we outline major current controversies relating to decision-making in hip arthroscopy for FAI. Cite this article: Bone Joint J 2022;104-B(5):532–540

Aims. We aimed to determine hip-related quality of life and clinical findings following treatment for neonatal hip instability (NHI) compared with age- and sex-matched controls. We hypothesized that NHI would predispose to hip discomfort in long-term follow-up. Methods. We invited those born between 1995 and 2001 who were treated for NHI at our hospital to participate in this population-based study. We included those that had Von Rosen-like splinting treatment started before one month of age. A total of 96 patients treated for NHI (75.6 %) were enrolled. A further 94 age- and sex-matched controls were also recruited. The Copenhagen Hip and Groin Outcome Score (HAGOS) questionnaire was completed separately for both hips, and a physical examination was performed. Results. The mean follow-up was 18.2 years (14.6 to 22.0). The HAGOS scores between groups were similar and met statistical and clinical significance only in the Symptoms subscale (mean difference 3.80, 95% confidence interval (CI) 0.31 to 7.29; p = 0.033). Those patients who had undergone treatment for NHI had a higher frequency of positive flexion-adduction-internal rotation test (odds ratio (OR) 2.6, 95% CI 1.2 to 5.6; p = 0.014), resisted straight leg rise test (OR 4.5, 95% CI 1.4 to 14.9; p = 0.014), and also experienced more pain in the groin during passive end range hip flexion (OR 2.5, 95% CI 1.2 to 5.3; p = 0.015) than controls. Conclusion. NHI predisposes to hip discomfort in clinical tests, but no clinically relevant differences in experience of pain, physical function, and hip-related quality of life could be observed between the treated group and matched controls in 18 years of follow-up. Cite this article: Bone Joint J 2020;102-B(12):1767–1773

Aims. Adverse spinal motion or balance (spine mobility) and adverse pelvic mobility, in combination, are often referred to as adverse spinopelvic mobility (SPM). A stiff lumbar spine, large posterior standing pelvic tilt, and severe sagittal spinal deformity have been identified as risk factors for increased hip instability. Adverse SPM can create functional malposition of the acetabular components and hence is an instability risk. Adverse pelvic mobility is often, but not always, associated with abnormal spinal motion parameters. Dislocation rates for dual-mobility articulations (DMAs) have been reported to be between 0% and 1.1%. The aim of this study was to determine the early survivorship from the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) of patients with adverse SPM who received a DMA. Methods. A multicentre study was performed using data from 227 patients undergoing primary total hip arthroplasty (THA), enrolled consecutively. All the patients who had one or more adverse spine or pelvic mobility parameter had a DMA inserted at the time of their surgery. The mean age was 76 years (22 to 93) and 63% were female (n = 145). At a mean of 14 months (5 to 31) postoperatively, the AOANJRR was analyzed for follow-up information. Reasons for revision and types of revision were identified. Results. The AOANJRR reported two revisions: one due to infection, and the second due to femoral component loosening. No revisions for dislocation were reported. One patient died with the prosthesis in situ. Kaplan-Meier survival rate was 99.1% (95% confidence interval 98.3 to 100) at 14 months (number at risk 104). Conclusion. In our cohort of patients undergoing primary THA with one or more factor associated with adverse SPM, DM bearings conferred stability at two years’ follow-up. Cite this article: Bone Joint J 2022;104-B(7):820–825

Instability is the most common reason for revision after total hip arthroplasty (THA). Since THA requires arthrotomy of the hip and replacement with a femoral head that is smaller than the normal hip, instability following THA is always a potential concern. Many factors contribute to the development of instability after THA including: restoration of normal anatomy, implant design, component position, surgical approach and technique, and numerous patient related factors. Recently, the role of spinal mobility and deformity has been shown to have a significant effect on risk of dislocation after THA. The long held guidelines for component positioning or so called “safe zone” described by Lewinnek have also been questioned since most dislocations have been shown to occur in patients whose components are positioned within this “safe” range. In the early post-operative period, dislocation can occur prior to capsular and soft tissue healing if the patient exceeds their peri-operative range of motion limits. Closed reduction and abduction bracing for 6 weeks may allow for soft tissue healing and stabilization of the hip. It is important to try and identify the mechanism of dislocation since this can affect the technique of closed reduction, how the patient is braced following reduction and what may need to be addressed at the time of revision if dislocation recurs. Closed reduction and bracing may be effective in patients who have a previously well-functioning, stable THA who suffer a traumatic dislocation after the peri-operative period. Despite successful closed reduction, recurrent dislocation occurs in many patients and can be secondary to inadequate soft tissue healing, patient noncompliance or problems related to component positioning. Patients who incur more than 2 dislocations should be considered for revision surgery. Prior to revision surgery, an appropriate radiographic evaluation of the hip should be performed to identify any potential mechanical/kinematic issues that need to be addressed at the time of revision. Typically this involves plain radiographs, including a cross table lateral of the involved hip to assess acetabular version, but may also involve cross-sectional imaging to assess femoral version. Patients with soft tissue pseudotumors frequently have significant soft tissue deficiencies that are not amenable to component repositioning alone and require use of constrained or dual mobility components. In general, “limited revisions” consisting of modular head and liner exchange with insertion of a lipped liner and larger, longer femoral head rarely correct the problem of recurrent instability, since component malposition that frequently contributes to the instability is not addressed. Similarly, insertion of a constrained liner in a malpositioned cup is associated with a high rate of implant failure and recurrent dislocation since impingement contributing to the instability is not addressed. In patients who fail closed management and have a history of recurrent instability, we have found the treatment paradigm described by Wera, et al. to be very helpful in the management of the unstable THA. Several studies have shown that tripolar type constrained liners appear to perform considerably better than locking ring type constrained liners. As a result, dual mobility implants are becoming more widely utilised in patients with abductor and other soft tissue deficiencies, hip instability of uncertain etiology and patients with increased risk factors for instability undergoing primary THA. Early results with dual mobility components have been shown to have a low rate of failure in high instability risk revision THAs. These devices do have several unique potential complications and their use should be limited to patients with significantly increased risk of dislocation and instability

Introduction. Four parts inter trochanteric fracture of femur are commonest in elderly people. DHS fixation is gold standard treatment of such fractures. Various Complications of DHS implant are reported in the literature. However, Hip Instability: Subluxation and Dislocation is very rare. We report, five cases of Hip instability following DHS fixation surgery. Materials and Methods. This is a retrospective study conducted at ACPM Medical College, Dhule. We found only five cases that developed hip instability after DHS fixation since 1997. Available clinical notes and X-rays of these patients were studied to get the relevant information. Results and Observations. Three patients were male, two female, four had right sided fracture and one had left sided. Three had instability after six weeks and remaining two developed dislocation after eight months which were associated with infection. 1 patient refused further investigations & treatment, 2 other died with due course of time 1 lost to follow-up and one patient with deep infection underwent excision arthroplasty. We could only speculate cause for dislocation / subluxation on the basis of clinical examination, X-ray, Investigations and review of literature. In these cases it appeared that the factors responsible for instability could be mechanical factors and pyogenic infection. Review of literature and possible aetiological factors, investigations and various aspects of management of such cases are discussed. Conclusions. Mechanical factors such as intra-operative femoral head rotation, avulsion of greater trochanter, excessive medialisation, valgus reduction, excessive collapse, soft tissue injury, and infection are contributing factors for hip instability

Introduction: Hip instability is a complex and challenging problem. In experienced units, up to 4% of patients undergoing total hip arthroplasty will require revision surgery to treat hip instability, with only 60% of these treatments being successful. Many authors reporting results with various constrained systems available have described dislocation rates post implantation of the constrained component of 4% to 29%. Method: The thirteen patients who underwent placement of a constrained component as a revision procedure in our unit from 1989 to 2000 were reviewed. Results: The indications for revision surgery included recurrent dislocation in eight and intraoperative instability in five revision hip arthroplasties. No patients were lost to follow up. The average follow-up was 43 months(range 14 to 121). The average age at time of surgery was 73 years(range: 52 to 84 years). No component has been revised. The average hip score after revision surgery was 72(range: 52 to 89). There have been no episodes of dislocation of the constrained arthroplasty. In seven cases the constrained arthroplasty was implanted into a previously placed well fixed shell. Conclusion: Constrained acetabular components were a highly effective tool in the treatment of hip instability

1. The problem of paralytic hip instability has been studied in a series of twenty-one patients brought to a spina bifida clinic. 2. Thirty iliopsoas tendon transfers were done in an attempt to reduce deformity and improve hip stability. 3. At the time of review, ten of these hips were stable and twenty were unstable. Ten hips were improved by operation, and one hip was worse. The other nineteen remained the same. 4. All of the children except one were capable of walking with an orthotic device. 5. Some of the complexities of the problem of paralytic hip instability in the patient with myelomeningocele are discussed

Reported rates of dislocation after primary and revision total hip replacement (THR) vary widely, whereas subluxation after THR is not commonly reported. Importantly, it is now recognised that reported dislocation rates are likely to be an underestimate of the true dislocation rate. The primary aim of this study was to develop and validate a Patient Hip Instability Questionnaire and subsequently to use this questionnaire to determine the incidence of dislocation, subluxation and symptoms due to hip instability following primary and revision THR. In addition the associated costs, morbidity, disability and effects on health-related quality of life were examined. A retrospective review of dislocation rates from 1996 to 1998 identified problems in determining the true dislocation rate from standard hospital and database records. Therefore, a patient-completed Hip Instability Questionnaire was developed and validated to monitor dislocation and subluxation rates. This was then mailed to patients three and 12 months following primary or revision THR. All dislocations were then confirmed by telephone interview and radiographs. Telephone interviews and patient completion of the SF-36 questionnaire were used to assess morbidity, disability and quality of life. Costs of treating patients with hip dislocation were also determined. The response rate to the mailed questionnaire was greater than 95%. The questionnaire was shown to be a valid measure of the true rate of dislocation following THR and confirmed the inaccuracies in previous methods of determining dislocation rate based on hospital and database records. Using this questionnaire, the rate of subluxation was higher than previously reported and the significant morbidity and health care costs associated with with this complication were identified. The use of this questionnaire will allow better assessment of morbidity and costs due to complications following THR

Purpose of the study: An unstable hip prosthesis is a therapeutic challenge. The prevalence of revision is 5 to 26.6% in the literature. We evaluated the contribution of double-mobility implants for revisions of unstable hip implants. Material and methods: This series was composed of 45 patients who underwent revision between January 2000 and December 2003 for hip instability (44 dislocations, 1 subluxation). The same implant was used for all patients, either for the first-intention version (press-fit or cemented), or for the revision version (press-fit). For certain patients, the first-intention implant was cemented in an armature. The series included 28 females and 17 males, mean age 66.5 years (range 36–48 years). The initial diagnosis was osteoarthritis in 34 cases (76%), dysplasia in seven (16%), osteonecrosis in two (4%), Paget’s disease in one (2%) and rheumatoid disease in one (2%). The patients had had 2.8 dislocations on average (range 1 – 10). Time from first dislocation to the first-intention operation was 45.6 months (range 15 days – 20 years). Mean time from the first-intention operation to revision was 64.3 months (range 3 weeks – 20 years). Risk factors for instability were repeated hip surgery (> 3 operations) for 13 patients, wear for seven, nonunion of the greater trochanter for five, neurological and cognitive impairment in five, and malposition in three. Results: Mean follow-up was 25.2 months. None of the patients were lost to follow-up. Two patients died late after the operation. Among the complications observed, there were: two cases of recurrent dislocation, one case of subluxation, two cases of infection (one with favorable outcome after surgical cleaning and antibiotics the other followed by patient death), two cases of deep vein thrombosis, one case of popliteal paresia with favorable outcome, one case of delirium tremens. Surveillance was the therapeutic option for the patient with subluxation. For patients with dislocation, revision surgery was performed using the same implant. For one of these patients, the dislocation occurred following early loosening. Conclusion: Use of double-mobility implants for prosthetic revision undertaken because of prosthesis instability provides encouraging results, with a rate of dislocation (4%) close to that observed with first-intention implants

Instability following total hip arthroplasty (THA) is an unfortunately frequent and serious problem that requires thorough evaluation and preoperative planning before surgical intervention. Prevention through optimal index surgery is of great importance, as the management of an unstable THA is challenging even for an experienced joints surgeon. However, even after well-planned surgery, a significant incidence of recurrent instability still exists. Moreover leg-length discrepancy (LLD) after THA can pose a substantial problem for the orthopaedic surgeon. Such discrepancy has been associated with complications including nerve palsy, low back pain, and abnormal gait. Consequently we may use a big femoral head or increase femoral offset (FO) in unstable THA for avoiding LLD. However we do not know the relationship between FO and STT. The objective of this study is to assess hip instability of three different FOs in same patient undergoing THA during an operation. We performed 70 patients who had undergone unilateral THA using CT based navigation system at a single institution for advanced osteoarthoritis from May 2013 to May 2014. We used postero-lateral approach in all patients. After cup and stem implantation, we assessed soft tissue tensioning in THA during operation. Trial necks were categorized into one of three groups: standard femoral offset (sFO), high femoral offset (hFO, +4mm compared to sFO) and extensive high femoral offset (ehFO, +8 mm compared to sFO). We measured distance of lift-off about each of three femoral necks using CT based navigation system and a force gauge with hip flexed at 0 degrees and 30 degrees under a traction of lower extremity. Traction force was 40% of body weight. Forty patients had leg length restored to within +/− 3mm of the contralateral side by post-operative CT analysis. We examined these patients. Traction force was 214±41.1Nm. The distances of lift-off were 8.8±4.5mm (sFO), 7.4±4.1mm (eFO), 5.1±3.9mm (ehFO) with 0 degrees hip flexion and neutral abduction(Abd) / adduction(Add) and neutral internal rotation(IR)/ external rotation(ER). The distance of lift-off were 11.5±5.9mm (sFO),10.5±5.5mm (eFO),9.1±5.9mm (ehFO) with 30 degrees hip flexion and neutral Abd / Add and neutral IR/ER. Significant difference was observed between 0 degrees hip flexion and 30 degrees hip flexion on each FO (p<0.05). On changing the distance of lift-off, hFO to ehFO (2.2±1.6mm)was more stable than sFO to hFO (1.4±1.7mm)with 0degrees hip flexion.(p<0.05). On the other hands, hFO to ehFO (1.4±1.6mm) was more stable than sFO to hFO (1.0±1.3mm) with 30 degrees hip flexion. However, we did not find significant difference (p=0.18). Hip instability was found at 30 degrees hip flexion more than at 0 degrees hip flexion. We found that changing ehFO to sFO can lead to more stability improvement of soft tissue tensioning than sFO to eFO, especially at 0 degrees hip flexion. Whereas In a few cases, the distance of lift-off did not change with increasing femoral offset by 4mm. When you need more stability in THA without LLD, We recommend increasing FO by 8mm

This retrospective study was to investigate radiographic and clinical outcomes in treatment of hip instability in children and young adults undergoing periacetabular osteotomy (PAO) with or without femoral osteotomy. 19 patients (21 hips) with CP were treated with PAO with or without femoral osteotomy The mean age was 16.2 years old (7 to 28 years). Five patients (5 hips) received PAO, Six patients (7 hips) PAO with femoral derotation osteotomy, Eight patients (9 hips) PAO with varus derotational osteotomy (VDRO). Anteroposterior pelvic radiographs and CT were taken to assess the migration percentage (MP), lateral center-edge angle (LCEA), Sharp angle, femoral neck anteversion, neck-shaft angle. Gross Motor Function Classification System (GMFCS) was assessed pre- and post-surgery. Complications were recorded. The mean follow-up time was 41.2 months (range, 24 to 86 months). All hips but one were pain free at final visit. The GMFCS improved by one level in 10 of 19 patients. MP improved from a mean of 76.6% to 18.6% at the final follow-up(p<0.001). The mean pre-operative LCEA and Sharp angle were −33.5 ? and 35 ? respectively, improved to 21.5 ? and 11.8 ? at the final follow-up (p < 0.001). There were six patients (7 hips) had re-subluxation at latest follow-up. Nervus cutaneus femoris lateralis was impaired in four patients after surgery. There was no re-dislocation, AVN, or infections in this group. Satisfactory clinical and radiologic results can be obtained by PAO with or without femoral osteotomy minor complications

Purpose: To assess the performance of a constrained liner in an unstable hip prosthesis. Materials and methods: This is a retrospective study of 66 hip prostheses implanted in 66 patients by means of the same constrained cup (Lefevre, Lepine Group, France). The cup was implanted into 15 primary prostheses and 51 revision ones in order to treat recurrent dislocations (10 cases) or to prevent dislocations (56 cases with a deficit of the periarticular musculature or mental or neuromuscular disorders). The mean age was 76.7 years, 75.7% were female, 53% were operated in the right side and the mean follow up was 30.2 months. Results: By the time the last review was made, four patients died for reasons not related to their hip surgery. One patient showed a dissociation between the femoral head and the stem at the level of the Morse taper; the head was trapped in the retentive liner and an open reduction was needed to replace the existing prosthetic head by a new one with a long neck. Another patient had a prosthetic infection that was treated by means of a two-stage replacement. Radiolucent lines were observed in de DeLee’s zone 1 in 1.5% of patients, in 3% the lines were in zone II and in 3% they were in zone. However, according to Hodgkinson’s radiographic criteria, no cups were loose. Conclusions: Although retentive cups do address hip instability, the various cases of failure that have occurred, the appearance of radiolucencies and the concerns about their long-term fixation suggest that their use should be carefully weighted

Juvenile hip instability is associated with many conditions. Most of them belong to the group of neuromuscular diseases. Generally following categories can be enumerated: 1. Cerebral palsy, 2. Myelomeningocele, 3. Spinal cord injury, 4. Paraplegia following spine surgery, 5. Poliomyelitis, 6. Inflammatory hip disease, 7. Idiopathic instability, 8. Recurrent post-traumatic hip instability. In the groups 1–5 a chronic muscle imbalance is the reason of the displacement of the femoral head. Inflammatory joint disease produces displacement through cartilage and bone destruction and increased intra-articular pressure. Very rare idiopathic instability is usually associated with generalised hypermobility. For the early diagnosis a careful clinical examination is necessary involving range of motion, testing of the hip stability by the Palmén’s test in the same way like in new-borns. Routine x-ray screening at least once per year is mandatory. For the groups 1–5 a muscle imbalance has to be corrected first. Elimination of muscles contractures or muscles transfers respectively, showed a high efficiency if these surgical corrections were performed early. Femoral osteotomy alone does not provide reliable results. Any form of pelvic osteotomy is necessary to correct acetabular insufficiency. For the inflammatory hip disease early active surgical treatment is best prevention of displacement. Idiopathic hip instability has to be differentiated from common snapping hip. No treatment is necesary. Recurrent hip dislocation can be cured by a posterior capsulorrhaphy

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

Hip instability is one of the early complications following total hip arthroplasty. The aetiology of hip instability is often multi-factorial. The aim of this study was to assess the efficacy of prosthesis with dual mobility system in reducing hip instability in high risk cases at a short term follow up. A retrospective analysis was performed covering 25 total hip arthroplasties on 24 patients (5 males and 19 females) between January 2007 and August 2008. Patient medical records and imaging were reviewed, and the indications for surgery and surgical outcome were analysed. Among 25 procedures performed, 18 were revision procedure for dislocations, loosening, peri-prosthetic fractures. Seven patients have primary procedure, among which two were for acute hip fractures. One patient underwent conversion from previously failed screw fixation for hip fracture. The 25 patients were followed up for a mean period of 12 months (ranging from 4 to 24 months). At the last follow up, all patients were able to mobilise pain-free either independently, or with aids; no patients presented an episode of hip instability. The result of our study demonstrated good early stability of total hip arthroplasty with dual mobility system (POLARCUP)

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

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

Purpose of the study: Prenatal screening and search for risk factors has lead to early diagnosis of congenital hip dysplasia. The percent of excentration of the dysplastic hip can be quantified with ultrasonography. The purpose of this study was to evaluate the usefulness of ultrasound monitoring of confirmed hip dysplasia as a method for determining the appropriate time to discontinue treatment. Material and methods: We collected a series of patients presenting unstable hips one month after birth. Ultrasonographic examinations were performed to quantify the instability. Initial treatment was forced abduction. If the infant’s weight was greater than 5.6 kg, a Pavlik harness was used. Physical examination and control ultrasound examinations were performed at 4, 8 and 12 weeks. Forced abduction and ultrasound surveillance were discontinued when the percent of acetabular cover was greater than 50%. Long-term surveillance consisted in physical examination and plain ap view of the pelvis at four months and at onset of walking. Results: Ultrasound monitoring was instituted for 71 hips in 51 patients. Mean age at onset of the monitoring scheme was 37.7 days (range 38–74 days). Mean acetabular cover, as evaluated by ultrasound before treatment, was 35.5% (range 20–45%). After four weeks, mean cover for 42 hips was 54.7% (range 50–85%). For the other 29 hips, mean acetabular cover was 41.4% (range 36–47%) at four weeks. At eight weeks, 26 of these 29 hips had a mean cover of 60% (52–85%). Acetabular cover remained below 50% for three hips at twelve weeks. Mean HTE at four months was 20.7° (range 10–26°). At walking, all hips were centered and no irregularities were noted on the x-rays of the femoral nucleus. Discussion: The majority of infants with unstable hips diagnosed at birth achieve spontaneous cure without treatment. For others, cure can be achieved with forced abduction but with a risk of osteochondritis. In our study, ultrasound monitoring enabled a reliable assessment of the proper moment to interrupt treatment. Conclusion: Ultrasound examination of the hip joint is a satisfactory method for monitoring hip dysplasia in infants aged less than four months. It appears to be useful for determining the moment to interrupt treatment