Introduction. Computer navigation systems are quite sophisticated intra-operative support systems for the precise placement of acetabular or femoral components in THA. However, few studies have addressed the clinical benefits derived from using a navigation system to achieve precise placement of the implants. The purpose of this study is to investigate the early dislocation rate of navigation-assisted primary THA through a posterior approach in order to clarify the short-term benefit of using a computer navigation system. Methods. We retrospectively reviewed the early dislocation rate (within 12 months after surgery) of 475 consecutive primary cementless or hybrid THAs with femoral head sizes ≦32mm performed via posterior approach. There were 85 men and 390 women, with a mean age of 60 years (17 to 88) at operation. Preoperative diagnoses included osteoarthritis in 384 hips, osteonecrosis in 45 hips, and others in 46 hips (ex. RA, trauma, infection, congenital disease). All THAs were planned using a 3D templating system based on the combined anteversion theory, performed by single surgeon through a posterior approach with repair of the posterior capsule, assisted by a CT-based surface matching type computer navigation system for cup implantation. All patients were directly followed up at least 1 year after surgery. We classified all 475 joints into four groups: normal or mildly deformed hips (Group A; 308 joints, ex. primary OA, Crowe group 1, osteonecrosis), moderately deformed hips (Group B; 97 joints, ex. Crowe group 2, protrusio acetabuli, Perthes like deformity), severely deformed hips (Group C; 53 joints, ex. Crowe group 3 or 4, ankylosis, fused hip), and neuromuscular and cognitive disorders (Group D; 17 joints), and examined the dislocation rate for each group. Results. We had eleven early dislocations, for an overall dislocation rate of 2.3% (11/475). All dislocations occurred posteriorly within 6 weeks after surgery. Three joints were Crowe group 4 dislocated hips, three were Charcot joints, two were Girdlestone hips after pyogenic arthritis, two was a Crowe group 1 hip, and one was osteonecrosis. All 11 cups were implanted within 5 degree of error from the preoperative planning, and all were placed within the Lewinnek safe zone. The dislocation rates according to group were 0.6% for group A (2/308), 0% for B (0/97), 9.4% for C (5/53), and 23.5% for D (4/17). Discussion. The use of computer navigation system in patients undergoing THA improves the precision of acetabular cup placement by decreasing the number of outliers, which may result in reducing the risk of dislocation. In this series, most dislocations occurred in the highly risky or rare condition cases in groups C or D. In such cases, precise and appropriate cup implantation assisted by the navigation system could not completely prevent dislocation because of the patients' specific special backgrounds. On the other hand, early dislocation was prevented for the normal/mild to moderately deformed joints such as those in groups A or B. Computer navigation system was effective for prevent early dislocation in the normal or mild to moderately deformed joints

To establish the incidence of early dislocation following primary total hip arthroplasty performed through a direct lateral approach when no post-operative restrictions on patient positioning or mobilization were imposed. 499 primary total hip arthroplasties performed in 483 patients between October 1997 and July 2000 were studied prospectively. Surgery was performed through a direct lateral (Hardinge) approach with the patient in a supine or lateral position according to surgeon preference. An Exeter femoral stem with a 26mm head (Howmedica) and an Ogee socket (Depuy) were both cemented. Post-operatively abduction pillows were not used. Patients were specifically advised both pre- and post-operatively by their surgeon, nurses and physiotherapist that no restrictions were placed on their mobilization. They were encouraged to move in any way that they found comfortable and adopt any position they chose. They were allowed to sleep in their usual position and bathe or shower normally. Mean patient age was 72 (range 35–95). 304 patients (61%) were female. The grade of operating surgeon was consultant in 326 (65%) cases, staff grade in 122 (25%) and specialist registrar in 51 (10%). 284 (57%) operations were performed with the patient placed in the lateral position. No patients were lost to follow-up. There were three dislocations within six weeks of surgery (defined as ‘early’), a rate of 0. 6%. All were reduced closed and managed conservatively. One hip dislocated for a second time eleven days later but every patient subsequently achieved stability without further intervention. There were no late dislocations. Our results suggest that a very low early dislocation rate can be achieved when performing primary hip arthroplasty through a direct lateral approach without the need to impose restrictions on post-operative mobilization which patients often find intrusive

Introduction and Objectives: Posterior or posterolateral approaches to the hip joint have classically been associated with higher rates of dislocation. The goal of this study is to investigate the effect of reconstructive procedures of the posterior joint capsule and external rotator muscles in the short term on incidence of luxation and to compare these procedures with anterior or anterolateral approaches in which such procedures were not performed. Materials and Methods: This is a prospective study of 605 total primary hip arthroplasties based on 2 models that have been widely used in our centre. The cases included 431 biological fixation prostheses coated with hydroxyapatite with 28mm heads and 174 low-friction cemented prostheses with 22.25 mm heads. These surgeries were performed consecutively in our centre, with a minimum follow-up of 6 months. Each patient was assigned to one of two groups based on the individual preference of the surgeon performing the operation: anterior or posterior. Only in the latter group was reconstruction of the capsule and external rotator musculature performed. Cases in which previous surgery had been performed on the hip were not included in this study in order to avoid skewing results, as previous surgery is the factor known to have the greatest impact on dislocation rate. Results: A procedure involving reconstruction of both the posterior capsule and external rotator musculature significantly reduced the rate of early dislocation in primary total hip arthroplasties done using a posterior approach. Incidence of dislocation in these cases was lower than in cases with anterior approaches where a wider capsulectomy was performed without reconstruction. Conclusion: The idea that the dislocation rate in total hip arthroplasties is higher with a posterior approach should be reconsidered

Purpose: Dislocation is one of the most common complications following total hip arthroplasty (THA), with rates reported between 1% and 3%, but as high as 6% using a posterior approach with metal on polyethylene bearing surfaces. The purpose of this study was to assess the dislocation rates in ceramic-on-ceramic THAs.

Method: Primary ceramic-on-ceramic (Stryker Orthopaedics) THAs performed at 9 institutions from October 1996 through July 2005 were included in the study (1635 hips in 1485 patients). Sixty-one percent were male. The average age was 52 years (range 15–83). Osteoarthritis was the leading reason for surgical intervention (86%). A posterior approach and 32 mm or 36 mm femoral head was used in the majority of patients (90%). Patients returned for routine clinical examination or were contacted by telephone to assess for dislocations at a minimum of one year (average three years) after surgery.

Results: Of the 1635 ceramic-on-ceramic THAs performed, there were 18 dislocations (1.1%). Of these, 15 were 32 mm femoral heads; 3 were 28 mm; none were 36 mm. The majority of dislocations occurred within 3 months after surgery (72%). Closed reduction was successful in 17 hips with one requiring a revision.

Conclusion: A low rate of dislocations in ceramic-on-ceramic THAs occurred in this study (1.1%). Compared with reported metal-on-polyethylene bearing surfaces, the ceramic-on-ceramic articulation design appears to have fewer dislocations. Other factors associated with this low dislocation rate may be decreased femoral neck diameters and/or larger average femoral head size in patients receiving the ceramic-on-ceramic design. These results will need to be compared with contemporary THA using different articular surfaces.

Introduction

Multiple factors contributing to an elevated risk for dislocation after total hip arthroplasty (THA) have been identified. Patient-related risk factors that have been identified are prior hip surgery, old age and female gender. However, there have been no prospective reports whether inflammatory arthritis (IA) is an independent risk factor.

Material and methods

From January 1996 to December 1999 427 primary total hip arthroplasties were carried out using one type of uncemented prosthesis: a hydroxyapatite coated EPF-PLUS^® cup and a SL-PLUS^® stem (PLUS Endoprothetik AG, Rotkreuz-CH). A 28 mm. ball head was used in every hip. To evaluate whether IA is a risk factor for dislocation the incidence and cause of early (< 2 year post-surgery) dislocation in IA hips was compared with those carried out for osteoarthrosis (OA). There were 341 THAs in 311 patients with OA and 69 THAs in 59 patients with IA (mainly rheumatoid arthritis) included in this study. The remaining 17 THAs were for various other reasons and excluded from this study.

Statistical analysis of the dichotomous variables was carried out by the chi-square test and the Fisher’s exact test, Student’s t-test was used for the analysis of continuous variables.

Results and discussion

Both groups were comparable with respect to the following risk factors: gender, approach (either straight-lateral or anterolateral), position of the acetabular component and experience of the surgeon. Mean age was lower in the IA group than in the OA group: 61. 0 vs 68. 1 years. Furthermore, the incidence of prior hip surgery was higher in the OA group.

The incidence of dislocation was 7 out of 69 (10. 1%) in IA hips and 10 out of 341 (2. 9%) in OA hips (p=0. 006). All dislocations in IA where posterior, in OA 5 were posterior and 4 were anterior (1 unknown). No other mechanical factors leading to an increased instability of the hip in IA, such as trochanteric fractures, could be identified. Due to the relatively small numbers a statistical difference in the direction of dislocation could be identified (p= 0. 088).

So, IA has to be considered as an independent risk factor for dislocation after THA. Both the polyarticular impairments and the lower quality of the soft tissues in IA could explain this elevated risk. To reduce the incidence of dislocation in IA it therefore seems advisable to pay detailed attention the soft tissues and the position of the prosthetic components in IA at the time of surgery. Also, consideration should be given to the use of an acetabular component with an elevated rim.

Aims: Patient-related risk factors of dislocation after total hip arthroplasty (THA) that have been identified are previous hip surgery, old age and female gender. However, there have been no prospective reports whether inflammatory arthritis (IA) is an independent risk factor. Methods: Prospective evaluation of the incidence of early (< 2 year post-surgery) dislocation in a consecutive series of primary THA. From January 1996 to December 1999 341 THAs in 311 patients with osteoarthrosis (OA) and 69 THAs in 59 patients with IA (mainly rheumatoid arthritis) were included in this study. One type of prosthesis having a 28 mm. ball head was implanted in every hip through an anterior appoach. Results: Both groups were comparable with respect to the following risk factors: gender, position of the acetabular component and experience of the surgeon. Average age was lower in the IA group than in the OA group: 61.0 vs 68.1 years. Furthermore, the incidence of previous hip surgery was higher in the OA group. Despite the presence of these risk factors in the OA group, the incidence of dislocation was higher in IA than in OA: 10.1% vs. 2.9% (p=0.006). All dislocations in IA where posterior, in OA 5 were posterior and 4 were anterior (1 unknown). No other mechanical factors leading to an increased instability of the hip in IA, such as trochanteric fractures, could be identified. Conclusions: Inflammatory arthritis is an independent risk factor of dislocation after THA. Both the polyarticular impairments and the lower quality of the soft tissues in IA could explain this increased risk.

Background: Our multi-centre international randomized controlled trial compared the one-year incidence of dislocation between a 36 mm and 28 mm metal on highly cross-linked polyethylene articulation in primary and revision total hip replacement (THR).

Patients: 644 patients were entered into the study. Surgical approach was posterior in primary THR and posterior, transfemoral or transtrochanteric in revision THR. Patients were stratified according to a number of factors which may influence dislocation risk and polyethylene wear. Patients were randomized intra-operatively to either a 28 or 36 mm articulation.

Results: The 12-month incidence of dislocation was statistically significantly lower in patients undergoing THR with a 36 mm articulation than in those with a 28 mm articulation (1.3% vs 5.4%, p=.004). When primary and revision THR were examined separately, the 12-month incidence of dislocation was statistically significantly lower in patients undergoing primary THR with a 36 mm articulation than in those with a 28 mm articulation (0.8% vs 4.4%, p=.007). Of the 12 primary THR patients with a 28 mm articulation who dislocated within one year, four experienced recurrent dislocation and two were revised for dislocation. Two patients with a 36 mm articulation dislocated, one of whom experienced recurrent dislocation and was revised. The incidence of dislocation after revision THR with a 36 mm articulation was 4.9%, compared to 12.2% with a 28 mm articulation. Three of the five patients who dislocated following revision THR with a 28 mm articulation experienced recurrent dislocation and were revised within one year of surgery. Two patients dislocated following revision THR with a 36 mm articulation but neither experienced recurrent dislocation or further revision.

This large randomized study unequivocally shows for the first time that, compared to a 28 mm articulation, a 36 mm articulation in THR is efficacious in reducing the incidence of dislocation in the first year following THR.

Large articulations using cross-linked polyethylene and other alternate bearings are increasingly being used to reduce the incidence of dislocation, the most common early complication following total hip replacement. While indirect evidence has suggested the potential benefits of a large articulation in reducing dislocation risk, this has not been proven in a well-controlled clinical trial. The primary objective of our multi-centre international randomized controlled trial was to compare the one-year incidence of dislocation between a 36 mm and 28 mm metal on highly cross-linked polyethylene articulation in primary and revision total hip replacement.

644 patients were entered into the study. Patients were stratified according to a number of factors which may influence dislocation risk, including primary or revision total hip replacement, age, sex, Charnley grade, diagnosis and stem type. Patients were randomized intra-operatively to either a 28 or 36 mm articulation.

The 12-month incidence of dislocation was statistically significantly lower in patients undergoing total hip replacement with a 36 mm articulation than in those with a 28 mm articulation (1.3% vs 5.2%, p< .05). A total of 6 dislocations occurred in the 4 patients who dislocated with a 36 mm articulation, compared to a total of 36 dislocations in the 17 patients who dislocated with a 28 mm articulation. When primary and revision THR were examined separately, the 12-month incidence of dislocation was statistically significantly lower in patients undergoing primary total hip replacement with a 36 mm articulation than in those with a 28 mm articulation (0.7% vs 4.2%, p< .05). A total of 4 dislocations occurred in two patients with a 36 mm articulation, compared to a total of 19 dislocations in 12 patients with a 28 mm articulation. The incidence of dislocation after revision total hip replacement with a 36 mm articulation was 4.8%, compared to 11.1% with a 28 mm articulation.

This large randomized study unequivocally shows for the first time that, compared to a 28 mm articulation, a 36 mm articulation in total hip replacement is efficacious in reducing the incidence of dislocation in the first year following hip replacement.

Purpose: Postoperative dislocation after revision total hip arthroplasty (rTHA) is a frequent complication. Certain risk factors have been well identified (greater trochanter non-union, history of repeated dislocation or infection, multiple operations), but the role of spinal morphology is not well known. The purpose of this prospective study was to determine the role of spinal morphology on postoperative dislocation.

Material and methods: Between September 2000 and March 2002, 49 patients underwent rTHA. The prospective analysis included a preoperative radiographic evaluation of the spinal morphology for lumbopelvic assessment using the Legave and Duval Beaupère criteria. A standard information card was used pre- intra- and postoperatively to record usual patient- and material-related risk factors of dislocation. Five patients experienced postoperative dislocation despite any apparent defect in implant position.

Results: Mean sacral slope was significantly different (p=0.006) between patients with and without dislocation. This difference remained significant (p=0.017) when limiting the study to the 33 patients who had no associated risk factor postoperatively (history of recurrent dislocation or infection, multiple operations, tight non-union of the greater trochanter).

Discussion: Our study demonstrated the role of lumbar morphology on the risk of postoperative dislocation. Spinal morphology modifies the pelvic orientation and thus landmarks habitually used for implantation. It also affects the amplitude of pelvic movement when moving from the sitting to standing position, requiring hip compensation, particularly extension.

Adverse spinopelvic characteristics (ASC) have been associated with increased dislocation risk following primary total hip arthroplasty (THA). A stiff lumbar spine, a large posterior standing tilt when standing and severe sagittal spinal deformity have been identified as key risk factors for instability. It has been reported that the rate of dislocation in patients with such ASC may be increased and some authors have recommended the use of dual mobility bearings or robotics to reduce instability to within acceptable rates (<2%). The aims of the prospective study were to 1: Describe the true incidence of ASC in patients presenting for a THA 2. Assess whether such characteristics are associated with greater symptoms pre-THA due to the concomitant dual pathology of hip and spine and 3. Describe the early term dislocation rate with the use of ≤36mm bearings. This is an IRB-approved, two-center, multi-surgeon, prospective, consecutive, cohort study of 220 patients undergoing THA through anterolateral- (n=103; 46.8%), direct anterior- (n=104; 27.3%) or posterior- approaches (n=13; 5.9%). The mean age was 63.8±12.0 years (range: 27.7-89.0 years) and the mean BMI 28.0±5.0 kg/m. 2. (range: 19.4-44.4 kg/m. 2. ). There were 44 males (47.8%) and 48 females (52.2%). The mean follow-up was 1.6±0.5 years. Overall, 54% of femoral heads was 32 mm, and 46% was 36mm. All participants underwent lateral spinopelvic radiographs in the standing and deep-flexed seated positions were taken to determine lumbar lordosis (LL), sacral slope (SS), pelvic tilt (PT), pelvic-femoral angle (PFA) and pelvic incidence (PI) in both positions. Spinal stiffness was defined as lumbar flexion <20° when transitioning between the standing and deep-seated position; adverse standing PT was defined as >19° and adverse sagittal lumbar balance was defined as mismatch between standing PI and LL >10°. Pre-operative patient reported outcomes was measured using the Oxford Hip Score (OHS) and EuroQol Five-Dimension questionnaire (EQ-5D). Dislocation rates were prospectively recorded. Non-parametric tests were used, significance was set at p<0.05. The prevalence of PI-LL mismatch was 22.1% (43/195) and 30.4% had increased standing PT (59/194). The prevalence of lumbar stiffness was 3.5% (5/142) and these patients had all three adverse spinopelvic characteristics (5/142; 3.5%). There was no significant difference in the pre-operative OHS between patients with (20.7±7.6) and patients without adverse spinopelvic characteristics (21.6±8.7; p=0.721), nor was there for pre-operative EQ5D (0.651±0.081 vs. 0.563±0.190; p=0.295). Two patients sustained a dislocation (0.9%): One in the lateral (no ASC) and one in the posterior approaches, who also exhibited ASC pre-operatively. Sagittal lumbar imbalance, increased standing spinal tilt and spinal stiffness are not uncommon among patients undergoing THA. The presence of such characteristics is not associated with inferior pre-operative PROMs. However, when all characteristics are present, the risk of instability is increased. Patients with ASC treated with posterior approach THA may benefit from the use of advanced technology due to a high risk of dislocation. The use of such technology with the anterior or lateral approach to improve instability is to date unjustified as the rate of instability is low even amongst patients with ASCs

BACKGROUND. Early dislocation is a foremost complication of total hip arthroplasty through a postero-lateral approach. The extra-articular impingement of the anterior part of the great trochanter with ileum bone, with or without soft tissue interposition is a well recognized but underestimated etiopathogenetic cause reported in literature. In this retrospective study through the assessment of clinical and radiographic follow-up at a minimum of six months, the effectiveness of an antero- longitudinal osteotomy of the great trochanter for early dislocation prevention is evaluated. MATERIALS AND METHODS. 209 patients (48.3% males and 51,7% females) underwent a total hip arthroplasty from June 2011 to September 2015, with surgery being performed by the same surgeon. A modified posterolateral approach was used according to the tissue-sparing criteria, in all the cases an anterior longitudinal osteotomy of the great trochanter has been performed at 90° to the antiversion angle of the implant and aligned posteriorly with the prosthesis. All the patients underwent a clinical and radiological follow up at one, three, and six months. RESULTS. In this study, only one patient reported dislocation of THA. One patient suffered from a wound infection which was subsequently treated with antibiotics and had complete remission. All patients demonstrated a fast recovery of ROM and walking, starting from pre-op Harris Hip Score 42.24pts and obtaining a score of 81.52pts at three months, and 92.03 at six months post-op. After surgery and during the follow up period, there were no trochanteric fractures detected. DISCUSSION. The correct positioning of the implants, the head diameter, offset, soft tissues repair, absence of impingement, and patients compliance are all elements that define the prosthetic stability. Literature shows and incidence of primary total hip arthroplasty dislocation between 0.80% to 10%. The incidence of dislocation reported in a preliminary study in our Institute is 0.48%, demonstrating the effectiveness of the trochanteric osteotomy. CONCLUSIONS. The osteotomy of the great trochanter is an effective surgical technique used to decrease the anterior impingement and early dislocation incidence. It is particularly effective on patients with good compliance and correctly implanted prosthetic components

Aims

Radiostereometric analysis (RSA) is the most accurate radiological method to measure in vivo wear of highly cross-linked polyethylene (XLPE) acetabular components. We have previously reported very low wear rates for a sequentially irradiated and annealed X3 XLPE liner (Stryker Orthopaedics, USA) when used in conjunction with a 32 mm femoral heads at ten-year follow-up. Only two studies have reported the long-term wear rate of X3 liners used in conjunction with larger heads using plain radiographs which have poor sensitivity. The aim of this study was to measure the ten-year wear of thin X3 XLPE liners against larger 36 or 40 mm articulations with RSA.

Aims

For rare cases when a tumour infiltrates into the hip joint, extra-articular resection is required to obtain a safe margin. Endoprosthetic reconstruction following tumour resection can effectively ensure local control and improve postoperative function. However, maximizing bone preservation without compromising surgical margin remains a challenge for surgeons due to the complexity of the procedure. The purpose of the current study was to report clinical outcomes of patients who underwent extra-articular resection of the hip joint using a custom-made osteotomy guide and 3D-printed endoprosthesis.

Aims

Machine learning (ML) holds significant promise in optimizing various aspects of total shoulder arthroplasty (TSA), potentially improving patient outcomes and enhancing surgical decision-making. The aim of this systematic review was to identify ML algorithms and evaluate their effectiveness, including those for predicting clinical outcomes and those used in image analysis.

Introduction: Dislocation rates with THA vary from 3% to 15%. One specialist centre reported a 6.4% early dislocation rate with a 28mm ceramic on polyethylene THA in young patients (mean age 56 years) in a single surgeon series. Although young patients have the advantage of better soft tissues, their greater mobility demands increase dislocation risk. Dislocation rates in large headed metal-on-metal resurfacings are extremely low. However, many patients are unsuitable for resurfacing and need a replacement. In such cases, it is attractive to transfer the large-headed metal-metal bearing advantage to replacement arthroplasty in order to reduce wear and dislocation rates. Does large diameter metal-metal total hip replacement really reduce the early dislocation rate?. Methods: 206 consecutive primary metal-metal THRs (189 patients) were included. The device consists of an uncemented cup, a matching modular cobalt chrome head (head diameter ranged 38 – 58mm) fixed on a stem through a 12/14 cone. Cemented stems were used in 107 procedures and 99 were proximal-porous uncemented stems. Age at operation ranged from 37 to 83 years. Thirty patients were 55 years or under, eighty one were 56 – 65 years and ninety five were over 65 years. There were 122 females and 67 males. Posterior approach was used in all. Results: There were no dislocations in these 206 consecutive procedures. Discussion: Metal-metal hips have lower dislocation rates than hips containing polyethylene (0.9% against 6.4% in a matched series). This is attributed to the suction-fit effect of metal-metal bearings. Large diameter bearings have the additional benefit of having to translate a greater jump distance before a dislocation. This dual advantage leading to extremely low dislocation rates was first noted in metal-metal resurfacings. In large headed metal-metal THRs, the head-neck ratio is even more favourable and these devices appear to eliminate early dislocation as a major complication

Surgeons often target the Lewinnek zone (40°±10° of inclination; 15°±10° of anteversion) for acetabular orientation during total hip arthroplasty (THA). However, matching native anteversion (20°-25°) may achieve optimal stability. The purpose of this study was to (1) determine incidence of early dislocation with increased target acetabular anteversion, and (2) report the accuracy of imageless navigation for achieving target acetabular position in a large, single-surgeon cohort. A posterolateral approach with soft tissue repair was performed in the 553 THA meeting the inclusion criteria. The same imageless navigation system was used for acetabular component placement in all THA. Target acetabular orientation was 40° ± 10° of inclination and 25° ± 10° of anteversion. Computer software was used to measure acetabular positioning on 6-week postoperative anteroposterior pelvic radiographs. Incidence of dislocation within 6 months of surgery was determined. Repeated measures multiple regression using the Generalised Estimating Equations approach was used to identify baseline patient characteristics (age, gender, BMI, primary diagnosis, and laterality) associated with component positioning outside of the targeted ranges for inclination and anteversion. Fisher exact tests were used to examine the relationship between dislocation and component placement in either the Lewinnek safe zone or the targeted zone. All tests were two-sided with a significance level of 0.05. Mean inclination was 42.2° ± 4.9°, and mean anteversion was 23.9° ± 6.5°. 82.3% of cups were placed within the target zone. Variation in anteversion accounted for 67.3% of outliers. Only body mass index was associated with inclination outside the target range (p = 0.017), and only female gender was associated with anteversion outside the target range (p = 0.030). Six THA (1.1%) experienced early dislocation, and 3 THA (0.54%) were revised for multiple dislocations. There was no relationship between dislocation and component placement in either the Lewinnek zone (p = 0.224) or the target zone (p = 0.287). This study demonstrates that increasing target acetabular anteversion using the posterolateral approach does not increase the incidence of early THA dislocation. However, the long-term effects on bearing surface wear and stability must be elucidated. The occurrence of instability even in patients within our target zone emphasises the importance of developing patient-specific targets for THA component alignment

Component malposition in total hip arthroplasty (THA) contributes to wear, dislocation, and leg length discrepancy (LLD). Robotic assisted total hip arthroplasty (rTHA) utilises computer-assisted haptically guided bone preparation and implant insertion to improve accuracy. The goal of this study is to compare accuracy and clinical outcome with manual THA (mTHA) and rTHA at minimum 1 year follow-up interval. Consecutive primary THA performed by one fellowship trained surgeon included: the first 100 mTHAs in his clinical practice (Group1- year 2000), the last 100 mTHAs before rTHA use (Group2- year 2010), and the first 100 rTHA (Group3- year 2011). All THAs utilised cementless implants, cross-linked polyethylene, and a posterior approach. Comparisons included age, sex, diagnosis, implant head size, blood loss (EBL), operative time, LLD, early dislocation and infection. Acetabular abduction (AAB), anteversion (AAV), and LLD were measured using validated software (Martell Hip Analysis Suite). The Lewinnek safe zone defined accuracy (AAB- 30°-50°, AAV- 5°-25°). Statistical analysis included ANOVA, Chi squared, and Fisher tests. Power analysis demonstrated adequate sample sizes. No differences were noted regarding group demographics. Average operative times varied: Group 1, 2, and 3- (160, 129, and 143 minutes, respectively). No deep infections occurred in any group. LLD greater than 1.5 cm varied: Groups 1, 2, and 3 (9%, 1%, 1%, respectively). Dislocation rates varied: Groups 1, 2, and 3- (5%, 3%, and 0%, respectively). EBL was less with rTHA than mTHA (Groups 1, 2, 3: 533cc, 437cc, 357cc, respectively). Average implant head size increased comparing Groups 1, 2, and 3 (31mm, 34.6mm, and 35.2mm, respectively). AAB accuracy varied: Groups 1, 2, and 3 (66%, 91%, and 98%, respectively). AAB greater than 55 degrees varied: Groups 1, 2, and 3 (15%, 1%, and 0%, respectively). There was a 3% fractured acetabular liner rate in Group 1, all cases occurred with AAB > 55 degrees, and AAB greater than 55 degrees correlated with increased acetabular liner fracture rate (20% vs. 0%, P < 0.05). No cases of fractured acetabular liners occurred in Group 2 or 3. rTHA improved AAV accuracy compared with mTHA (Group 2- 48%, Group 3- 75%; p<0.0001). Improved acetabular component accuracy with rTHA correlated with lower dislocation rates compared with mTHA (p<0.001). Total hip arthroplasty performed with traditional manual techniques has demonstrated excellent clinical outcomes in the majority of patients with many THA designs if components are placed accurately. Limitations in mTHA remain that alter results if accurate component placement is not achieved. In our study, clinical experience over 10 years improved AAB accuracy with mTHA, but AAV remained problematic. rTHA improved AAB and AAV accuracy compared with mTHA and demonstrated reduced early dislocation rates, improved rate of LLD, and reduced acetabular liner fracture risk compared with mTHA (p<0.05). Average rTHA operative times were 14 minutes longer than mTHA (Group 2), but this was not associated with increased EBL or infection rates. Further study is needed to evaluate whether the short term clinical and radiographic advantages noted with rTHA compared with mTHA will be maintained at longer follow up intervals

Introduction: A critical determinant of early dislocation following total hip arthroplasty (THA) is correct positioning of the acetabular component. This challenging aspect of THA has not been lessened by the introduction of more minimally invasive techniques. In this paper we introduce a simple and reproducible technique, which uses the transverse acetabular ligament (TAL) to determine cup orientation. We have used this technique as the sole method of cup orientation in our last 1000 consecutive primary total hips. Methods: One thousand consecutive patients were studied in order to determine the prevalence of early dislocation (within 3 months) following acetabular component placement determined by reference to the transverse ace-tabular ligament. All patients underwent primary total hip arthroplasty via a posterolateral approach with a posterior repair. Results: At a minimum follow-up of 9 months (range 9–39 months) 6 of the 1000 hips (0.6%) had dislocated. Conclusion: Although multiple factors are known to contribute to this rate correct placement of the acetabular component is critical. As our results compare favourably with other published series where a posterior repair has been performed by extrapolation we feel that that the TAL does provide an acceptable method of determining cup orientation. The fact that it is independent of patient position on the table and is easy to locate with a minimally invasive approach makes it an attractive method

Objectives: Dislocation is one of the common complications of total hip Arthroplasty. Posterolateral approach and small femoral heads have been shown to be high-risk factors for dislocation of the implanted total hip prosthesis. The use of a posterior capsulorraphy has also shown to decrease the rate of dislocation with a posterolateral approach. The objective of this study was to evaluate the early dislocation rate using size 22 mm head and a Posterolateral approach augmented with a posterior capsulorraphy. Methods: Questionnaire and case notes review of 148 patients operated at one institution by 3 different senior surgeons from Aug’03 to Jan’05. A posterior capsulorraphy was performed in all the patients. The primary outcome measure was the dislocation of the prosthetic hip within the first year of surgery. Results: 4 of the 148 patients (2.7%) had an episode of dislocation during the first year of surgery. 3 patients were treated conservatively and 1 required operative intervention in the form of PLAD. Radiographic analysis of this patient showed excessive anteversion of the socket(28. 0). . Conclusions: Studies have consistently shown an increased rate of dislocation with a Posterolateral approach and use of a size 22mm head. A recently published study by Berry et.al has shown a 12.1% dislocation rate with the use of this approach and size 22mm head. However posterior capsulorraphy was not performed in patients in this study group. Our study shows that performing a posterior capsulorraphy can reduce early dislocation rates using Posterolateral approach and size 22 mm head. The dislocation rate (2.7%) is comparable to any other approach and the use of a larger head size. These patients continue to be monitored to evaluate long term outcomes with this approach. (301 words)

The current, most popular recommendation for cup orientation, namely the Lewinnek box, dates back to the 70's, that is to say at the stone age of hip arthroplasty. Although Lewinnek's recommendations have been associated with a reduction of dislocation, some complications, either impingement or edge loading related, have not been eliminated. Early dislocations are becoming very rare and most of them probably occur in “outlier” patients with atypical pelvic/hip kinematics. Because singular problems usually need singular treatments, those patients need a more specific personalised planning of the treatment rather than a basic systematic application of Lewinnek recommendations. We aim in this review to define the potential impacts that the spine-hip relations (SHRs) have on hip arthroplasty. We highlight how recent improvements in hip implants technology and knowledge about SHRs can substantially modify the planning of a THR, and make the «Lewinnek recommendations» not relevant anymore. We propose a new classification of the SHRs with specific treatment recommendations for hip arthroplasty whose goal is to help at establishing a personalized planning of a THR. This new classification (figures 1 and 2) gives a rationale to optimize the short and long-term patient's outcomes by improving stability and reducing edge loading. We believe this new concept could be beneficial for clinical and research purposes