The natural history of a posteriorly dislocated total hip replacement

Laceration of the Sciatic Nerve After Closed Reduction of a Dislocated Total Hip Arthroplasty

Sciatic nerve injury after closed reduction of a dislocated total hip arthroplasty (THA) is an exceedingly rare but tremendously devastating complication. Closed reduction is the standard of care and is typically associated with a low complication rate. There have only been seven sciatic nerve injuries after closed reduction of a dislocated THA reported in the literature, and none were secondary to nerve laceration. We report a case of sciatic nerve laceration after attempted closed reduction of a dislocated THA. This resulted in complete loss of sensory and motor sciatic nerve function. This case highlights the importance of a detailed neurologic examination before and after closed reduction of a dislocated total hip, the importance of using careful reduction maneuvers, and transitioning to open reduction when necessary.

Does Surgical Approach Influence the Natural History of the Unstable Total Hip Arthroplasty?

BACKGROUND

Dislocation following total hip arthroplasty (THA) is a significant complication that occurs in 0.3%-10% of cases with 13%-42% of patients requiring revision surgery. The literature has primarily focused on the dislocation risk associated with different surgical approaches. However, little is known about the natural history of the dislocated hip and whether surgical approach of the index THA is associated with further instability and revision surgery.

METHODS

This is a retrospective, single-center, multi-surgeon consecutive case series of all patients who experienced THA dislocation from 2002 to 2020. Patients were excluded if the initial dislocation was secondary to infection or fracture. The natural history of the cohort as per approach was determined. Outcome measurements of interest were the number of dislocations; the treatment surrounding each dislocation; the necessity and type of revision; and the complications encountered.

RESULTS

Of the 75 patients, 58 (77%) dislocated within 6 months following primary THA. The anterior group had greater odds of dislocation within 2 weeks post-THA compared to the lateral and posterior groups (P = .04). The mean number of dislocations per patient was significantly lower in the anterior (1.5 ± 0.7) compared to the lateral (2.4 ± 1.2) and posterior (2.1 ± 1.0) groups (P = .02). Revision surgery was needed in 30% (6/20) of patients in the anterior, 69% (25/36) of the posterior, and 68% (13/19) of the lateral groups (P = .01).

CONCLUSION

This study illustrates that while primary THA dislocations happen earlier with the anterior approach, they are typically less complicated and have a lower risk of recurrent instability and revision surgery.

Outcome of revision surgery in recurrent dislocation of primary total hip arthroplasty

BACKGROUND

The cause of recurrent dislocation following primary total hip arthroplasty (THA) is multifactorial. A re-dislocation rate of up-to 34% following revision is reported. The aim of this study was to determine the re-dislocation rates following revision for recurrent THR dislocation.

METHODOLOGY

Patients who underwent revision for recurrent dislocation between January 2008 and January 2015 were identified. We identified the date and type of primary implant, overall number and reasons for dislocation, revision implant details and complication data.

RESULTS

Over an 8-year period, 24 patients underwent revision. The median age was 77 (68-85) years, median time to first dislocation was 78 (23-160) months and median number of dislocations was 3 (2-4) with a mean follow-up of 18 months. Socket Mal-Orientation (10) and Abductor deficiency (5) were the main causes of recurrent dislocation. 21 patients (88%) underwent revision of both components, 1 patient underwent isolated cup revision and 2 patients had revision of acetabular component with insertion of a BioBall. There were no dislocations within 90 days of revision surgery. 4 patients had late dislocations (3 recurrent, 1 isolated). There was no significant increase risk of dislocation after revision surgery in the neck of femur group (p = 0.467).

CONCLUSIONS

We report favourable outcomes for revision of both components for recurrent dislocation with no dislocations within 90 days. The overall late dislocation rate was 16.7%, however, these patients have settled following closed reduction. Due to its multifactorial aetiology, both component revision can be considered in this patient population.

Gait Analysis Reveals that Total Hip Arthroplasty Increases Power Production in the Hip During Level Walking and Stair Climbing

BACKGROUND

total hip arthroplasty (THA) is associated with decreased pain and improved function, including increased walking speed, but it does not always improve overall joint mechanics during activities of daily living such as level walking and stair climbing. The hip's ability to generate power to move and allow for smooth and efficient forward motion is critical to success after surgery. Although osteoarthritis (OA) of the hip limits the power of the affected joint, it is not known whether other joints in the affected limb or in the contralateral limb need to produce more power to compensate. Additionally, it is not known whether alterations in the production of power before and after surgery are gender-specific.

QUESTIONS/PURPOSES

(1) Is there a change in the power production of the bilateral ankles, knees, and hips during level walking before and after patients undergo unilateral THA, and are there important gender-specific differences in these findings? (2) How do these findings differ for stair climbing?

METHODS

Three-dimensional motion and ground reaction force data were collected for 13 men and 13 women who underwent primary, unilateral THA. This was a secondary analysis of previously collected data on gait mechanics from 60 patients who underwent THA. In the initial study, patients were included if they were scheduled to undergo a primary, unilateral THA within 4 weeks of the study and were able to walk without an assistive device. Patients were recruited from the practices of four surgeons at a single institution from 2008 to 2011. Patients were included in the current study if they were enrolled in the previous study, attended all three assessment visits (preoperative and 6 weeks and 1 year postoperative), and, during the preoperative visit, were able to walk without using an assistive device and climb stairs without using a handrail. Patients walked and ascended stairs at a self-selected speed at the three assessment visits. The power of each ankle, knee, or hip was calculated in Visual 3D using kinematic and kinetic data collected using motion capture. Power for each joint was normalized to the total power of the bilateral lower limbs by dividing the individual joint power by the total lower-extremity joint power. A mixed-model repeated-measures ANOVA was used to determine differences in normalized joint power for the ankle, knee, and hip, based on gender, limb (surgical-side versus nonsurgical-side) and timepoint (preoperative and 6 weeks and 1 year postoperative).

RESULTS

Surgical-side absolute (preoperative: -0.2 ± 0.2 [CI, -0.3 to -0.2], 1 year postoperative: -0.5 ± 0.3 [CI, -0.6 to - 0.5]; p < 0.001) and normalized (preoperative: 0.05 ± 0.04 [CI, 0.03-0.06], 1 year postoperative: 0.08 ± 0.04 [CI, 0.06-0.09]; p = 0.020) hip power production increased during walking. Surgical-side absolute (preoperative: 1.1 ± 0.3 [CI, 1.0-1.3], 1 year postoperative: 1.6 ± 0.2 [CI, 1.3-2.0]; p = 0.005) and normalized (preoperative: 0.16 ± 0.04 [CI, 0.14-0.18], 1 year postoperative: 0.21 ± 0.06 [CI, 0.18-0.24]; p = 0.008) hip power production increased during stair climbing, while nonsurgical ankle absolute (preoperative: 0.9 ± 0.5 [CI, 0.6 - 1.2], 1 year postoperative: 0.6 ± 0.3 [CI, 0.4-0.8]; p = 0.064) and normalized (preoperative: 0.13 ± 0.06 [CI, 0.10-0.16], 1 year postoperative: 0.08 ± 0.04 [CI, 0.06-0.10]; p = 0.015) power decreased during stair climbing after THA. No consistent effect of gender was observed.

CONCLUSIONS

In this gait-analysis study, power was improved in hip joints that were operated on, and power production in the ipsilateral and contralateral ankles and ipsilateral hips was reduced during level walking and stair climbing. The success of surgical intervention must be based on restoring reasonable balance of forces in the lower limb. Patients with OA of the hip lose power production in this joint and must compensate for the loss by producing power in other joints, which then may become arthritic. To determine future interventions, an understanding of whether changes in forces or joint angle affect the change in joint power is needed. Based on these results, THA appeared to effectively increase hip power and reduce the need for compensatory power production in other joints for both men and women in this patient cohort.

LEVEL OF EVIDENCE

Level I, prognostic study.

Lack of consensus on optimal acetabular cup orientation because of variation in assessment methods in total hip arthroplasty: a systematic review

INTRODUCTION:

Dislocation is 1 of the main reasons for revision of total hip arthroplasty but dislocation rates have not changed in the past decades, compromising patients' well-being. Acetabular cup orientation plays a key role in implant stability and has been widely studied. This article investigates whether there is a consensus on optimal cup orientation, which is necessary when using a navigation system.

METHODS:

A systematic search of the literature in the PubMed, Embase and Cochrane databases was performed (March 2017) to identify articles that investigated the direct relationship between cup orientation and dislocation, including a thorough evaluation of postoperative cup orientation assessment methods.

RESULTS:

28 relevant articles evaluating a direct relation between dislocation and cup orientation could not come to a consensus. The key reason is a lack of uniformity in the assessment of cup orientation. Cup orientation is assessed with different imaging modalities, different methodologies, different definitions for inclination and anteversion, several reference planes and distinct patient positions.

CONCLUSIONS:

All available studies lack uniformity in cup orientation assessment; therefore it is impossible to reach consensus on optimal cup orientation. Using navigation systems for placement of the cup is inevitably flawed when using different definitions in the preoperative planning, peroperative placement and postoperative evaluation. Further methodological development is required to assess cup orientation. Consequently, the postoperative assessment should be uniform, thus differentiating between anterior and posterior dislocation, use the same definitions for inclination and anteversion with the same reference plane and with the patient in the same position.

Course of dislocated posterior hip arthroplasty: A continuous 232-patient series at a mean 10 years' follow up (range, 1-22 years)

BACKGROUND

Dislocation rates in posterior total hip arthroplasty (THA) range between 2% and 5%, but long-term course (recurrence of dislocation or revision surgery) is not known, most series having short follow-up or small populations. We therefore conducted a retrospective study on a large series, to determine long-term rates of recurrence and surgical revision and recurrence risk factors.

HYPOTHESIS

Long-term follow-up of a large cohort of THA dislocations enables recurrence rate and factors to be determined.

MATERIAL AND METHOD

Five hundred and nine cases of THA dislocation were admitted to our center between 1994 and 2008. A hundred and twenty seven incomplete files and 150 patients who had received their THA elsewhere were excluded, leaving 232 patients: 150 female, 82 male. Mean age at THA (163 primary, 69 revision) was 63 years (range, 15-90 years), and 65 years (range 20-90 years) at first dislocation, with a mean interval to dislocation of 25 months. Minimum follow-up was 8 years up to 2016, or 1 year taking account of deaths (111 deaths). There were 46 anterior, 185 posterior and 1 multidirectional dislocations. The following potential recurrence factors were assessed: gander, age, body-mass index (BMI), etiology, surgical history, bearing diameter and type, component fixation means, dislocation direction, and time to dislocation.

RESULTS

A hundred and thirty three of the 232 patients (57%) showed at least 1 recurrence, at a mean 38 months (range, 0.5-252 months); 78 experienced a second and 32 a third recurrence. Ninety-nine (43%) had only 1 dislocation, without recurrence, but 17 of these (17%) underwent reoperation for other causes. The reoperation rate was 17/232 (7%) excluding recurrent instability, and 84/232 (36%) for instability. Fourty-eight months after the first dislocation, 84/133 cases of recurrence (63%) had been reoperated on: 16 complete replacements, 18 bearing replacements, 42 dual mobility cups, one large diameter cup, seven Lefèvre retentive cups. The rate of revision surgery for instability was high, at 84/232 (36%), and higher again in relation to recurrence (84/133: 63%). Only posterior dislocation emerged as a factor for recurrence (HR=1.774, 95% CI [1.020-3.083]), the other tested factors showing no correlation.14 of the 84 revision surgeries for instability (16.6%) were followed by recurrence, without identifiable risk factors.

CONCLUSION/DISCUSSION

The recurrence rate was 57%, with posterior dislocation as the only risk factor. The rate of revision surgery for recurrence was 84/232 (36%), with 14/84 revision procedures (16.6%) followed by further recurrence.

LEVEL OF EVIDENCE

IV, retrospective, without control group.

Comparison of outcome measures and complication rates following three different approaches for primary total hip arthroplasty: a pragmatic randomised controlled trial

BACKGROUND

Total hip arthroplasty is one of the most commonly performed surgical procedures worldwide. There are a number of surgical approaches for total hip arthroplasty and no high-level evidence supporting one approach over the other. Each approach has its unique benefits and drawbacks. This trial aims to directly compare the three most common surgical approaches for total hip arthroplasty.

METHODS/DESIGN

This is a single-centre study conducted at Western Health, Melbourne, Australia; a large metropolitan centre. It is a pragmatic, parallel three-arm, randomised controlled trial. Sample size will be 243 participants (81 in each group). Randomisation will be secure, web-based and managed by an independent statistician. Patients and research team will be blinded pre-operatively, but not post-operatively. Intervention will be either direct anterior, lateral or posterior approach for total hip arthroplasty, and the three arms will be directly compared. Participants will be aged over 18 years, able to provide informed consent and recruited from our outpatients. Patients who are having revision surgery or have indications for hip replacement other than osteoarthritis (i.e., fracture, malignancy, development dysplasia) will be excluded from the trial. The Oxford Hip Score will be determined for patients pre-operatively and 6 weeks, 6, 12 and 24 months post-operatively. The Oxford Hip Score at 24 months will be the primary outcome measure. Secondary outcome measures will be dislocation, infection, intraoperative and peri-prosthetic fracture rate, length of hospital stay and pain level, reported using a visual analogue scale.

DISCUSSION

Many studies have evaluated approaches for total hip arthroplasty and arthroplasty registries worldwide are now collecting this data. However no study to date has compared these three common approaches directly in a randomised fashion. No trial has used patient-reported outcome measures to evaluate success. This pragmatic study aims to identify differences in patient perception of total hip arthroplasty depending on surgical approach.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry, ACTRN12617000272392 . Registered on 22 February 2017.

A multimodal approach prevents instability after total hip arthroplasty: A 1 year follow-up prospective study

INTRODUCTION

Joint dislocation is one of the most frequent complications after hip arthroplasty. Multiple strategies have demonstrated ability to prevent instability when used in isolation, but the effect when more than one intervention is implemented has not been measured. The purpose of this study is to assess the rate of dislocation after implementation of a protocol of combined strategies for prevention of instability.

MATERIALS AND METHODS

Consecutive patients undergoing primary total hip replacement for hip osteoarthritis between February 2012 and June 2014 were included. A multimodal protocol including patient education, use of large femoral heads, posterior soft-tissue repair, and intraoperative adjustment of limb length and hip offset was applied. Dislocation episodes were documented trough medical records review and a telephonic follow-up at 3 and 12 months after surgery.

RESULTS

During the period of study 331 patients were included, mean age was 66 years and 68.8% were females. Only 0.91% of patients were lost to follow-up. Eighty-nine percent of patients received all interventions. Cumulative dislocation rate at 3 months was 0.60% and 0.90% at 12 months.

CONCLUSIONS

The implementation of a multimodal protocol for prevention of prosthesis instability produces a low rate of dislocation, which compares favorably with benchmarks. We recommend the use of a combination of multiple interventions to prevent this complication.

Acetabular cup position and risk of dislocation in primary total hip arthroplasty

Background and purpose - Hip dislocation is one of the most common complications following total hip arthroplasty (THA). Several factors that affect dislocation have been identified, including acetabular cup positioning. Optimal values for cup inclination and anteversion are debatable. We performed a systematic review to describe the different methods for measuring cup placement, target zones for cup positioning, and the association between cup positioning and dislocation following primary THA. Methods - A systematic search of literature in the PubMed database was performed (January and February 2016) to identify articles that compared acetabular cup positioning and the risk of dislocation. Surgical approach and methods for measurement of cup angles were also considered. Results - 28 articles were determined to be relevant to our research question. Some articles demonstrated that cup positioning influenced postoperative dislocation whereas others did not. The majority of articles could not identify a statistically significant difference between dislocating and non-dislocating THA with regard to mean angles of cup anteversion and inclination. Most of the articles that assessed cup placement within the Lewinnek safe zone did not show a statistically significant reduction in dislocation rate. Alternative target ranges have been proposed by several authors. Interpretation - The Lewinnek safe zone could not be justified. It is difficult to draw broad conclusions regarding a definitive target zone for cup positioning in THA, due to variability between studies and the likely multifactorial nature of THA dislocation. Future studies comparing cup positioning and dislocation rate should investigate surgical approach separately. Standardized tools for measurement of cup positioning should be implemented to allow comparison between studies.

Comparison of Gait Motion Including Postoperative Trunk Deflection Between Direct Lateral and Anterolateral Approaches in Supine Total Hip Arthroplasty

BACKGROUND

A prospective study was conducted to compare the effect of an anterolateral approach in the supine position (ALS) with that of a direct lateral (DL) approach on gait motion, including trunk deflection, in walking after total hip arthroplasty. We hypothesized that trunk deflection in walking after ALS would be significantly improved in comparison with use of the DL approach.

METHODS

The subjects were 15 patients, with 7 in the ALS group and 8 in the DL group. Walking before and 9 and 28 weeks after surgery was analyzed using 3-dimensional motion analysis.

RESULTS

Walking velocity, stride length, hip joint range of motion in the sagittal plane in walking, and locomotion range of trunk inclination were significantly improved 28 weeks after surgery in both groups. In gait analysis, there were no significant differences between the 2 groups.

CONCLUSION

This study was conducted to compare the effect of ALS with that of a DL approach on locomotion in walking after total hip arthroplasty. Hip pain at 9 weeks after surgery was significantly improved using ALS compared to the DL approach, but there were no significant differences in gait function at 28 weeks after surgery using ALS or DL approach. Further long-term studies are required to examine differences between these procedures.

Birmingham hip resurfacing in patients who are seventy years of age or older

There is no published literature to support mid to long term results of hip resurfacing (HR) arthroplasty in patients over the age of 70 years. The purpose of our study was to evaluate the function HR in this age group (70 or older at the time of surgery) at medium to long term follow-up. Between July 1997 and November 2002, the Oswestry Outcome Centre independently and prospectively collected data on 5000 Birmingham Hip Resurfacings (BHRs). 106 had been implanted in elderly patients who were 70 years of age or older. The post-operative Harris and Merle D'Aubigné and Postel (MDP) hip scores and causes for revision were used to ascertain function and implant survival. Hip scores for the older BHR patients were compared with those from younger patients. The average age at surgery of the elderly BHR cohort was 73.2 years (range, 70.0 to 87.9 years) with a mean follow-up of 7.1 years (range, 0.5 to 10.9 years). Four patients had a femoral neck fracture and required conversion to a conventional total hip replacement. There were no patients lost to follow-up and no dislocations in this series. The median Harris hip score (HHS) was significantly better in the younger BHR group compared with the elderly BHR group, (96 vs. 94 p=0.008). There was no significant difference in recovery rates after surgery. There was a significantly higher rate of revision in women than men among the elderly patients (male= 1 of 65 (1.5%); women = 3 of 19 (15.8%), p=0.03). At latest follow-up the elderly patients continued to function well when compared with the younger BHR patients. There was a high mid to long term success rate after HR in patients who were 70 years of age or older, without the failure burden possibly anticipated. Elderly patients had a poorer functional outcome, but a difference in HHS of two points may be of only minor clinical significance.

Unipedal balance is affected by lower extremity joint arthroplasty procedure 1 year following surgery

Lower Extremity Joint Arthroplasty (LEJA) surgery is an effective way to alleviate painful osteoarthritis. Unfortunately, these surgeries do not normalize the loading asymmetry during the single leg stance phase of gait. Therefore, we examined single leg balance in 234 TJA patients (75 hips, 65 knees, 94 ankles) approximately 12 months following surgery. Patients passed if they maintained single leg balance for 10s with their eyes open. Patients one year following total hip arthroplasty (THA-63%) and total knee arthroplasty (TKA-69%) had similar pass rates compared to a total ankle arthroplasty (TAA-9%). Patients following THA and TKA exhibit better unilateral balance in comparison with TAA patients. It may be beneficial to include a rigorous proprioception and balance training program in TAA patients to optimize functional outcomes.

Efficacy of revision surgery for the dislocating total hip arthroplasty: report from a large community registry

BACKGROUND

Historically, achieving stability for the unstable total hip arthroplasty (THA) with revision surgery has been achieved inconsistently. Most of what we know about this topic comes from reports of high-volume surgeons' results; the degree to which these results are achieved in the community is largely unknown, but insofar as most joint replacements are done by community surgeons, the issue is important.

QUESTIONS/PURPOSES

We used a community joint registry to determine: (1) the frequency of repeat revision after surgery to treat the unstable THA; (2) what surgical approaches to this problem are in common use in the community now; (3) are there differences in repeat revision frequency that vary by approach used; and (4) has the frequency of repeat revision decreased over time as surgical technique and implant options have evolved?

METHODS

We reviewed 6801 primary THAs performed in our community joint registry over the last 20 years. One hundred eighteen patients (1.7%) with a mean age of 67 years were revised within the registry for instability/dislocation. Failure was defined as a return to the operating room for rerevision surgery for instability. Minimum followup was 2 years (average, 9.4 years; range, 2-20 years) with six patients having incomplete followup. The frequency of rerevisions was calculated and compared using Pearson's chi-square test. Cumulative rerevision rates were calculated using the Kaplan-Meier method and types of revision procedures were compared using the log-rank test.

RESULTS

The initial revision procedure was successful in 108 patients (92%); 10 patients underwent repeat surgery for recurrent dislocation after their initial revision surgery. The most frequently performed procedure was revision of the head and liner only (35 of 118 [30%]); constrained devices were used in 19% (22 of 118) of the procedures. There was no difference in the cumulative rerevision rates for instability or dislocation by type of revision procedure performed. Six of 22 constrained liners were rerevised for varying indications. There was no difference in frequency of repeat revision for instability between those patients revised for THAs performed before 2003 and those managed more recently.

CONCLUSIONS

Revision surgery for unstable THA is successfully managed in the community with a variety of surgical interventions. Identifying the reason for dislocation and addressing the source remain paramount. Constrained liners should be used with caution; although typically used in the most problematic settings, rerevision for a variety of failure modes remains troublesome.

LEVEL OF EVIDENCE

Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Does surgical approach during total hip arthroplasty alter gait recovery during the first year following surgery?

Multiple surgical approaches exist for total hip arthroplasty (THA). Each approach has risks and benefits in regard to complications and changes in postoperative gait. This study examined the effect of three surgical approaches on postoperative gait mechanics. Thirty patients completed a self-selected speed level walking gait assessment preoperatively, 6 weeks, and 1 year after surgery. We found no difference between approaches 1 year following surgery for any study variable. Several differences existed between time points independent of surgical approach. Significant improvement was found in sagittal and frontal plane hip ROM, peak hip extension and adduction angle and moment, the functional measures, walking speed, and the Harris Hip Score. This study suggests that postoperative gait changes are similar for the three analyzed surgical approaches.

Management of hip instability with a cemented, constrained acetabular component

We evaluated the use of a cemented constrained acetabular component to treat recurrent or potential instability after hip replacement. Over a seven year period, 109 patients who had undergone 110 operations were identified from hospital records. Patients were reviewed based on clinical and radiological follow-up. Post-operative function and quality of life was assessed using the Oxford Hip Score (OHS) and SF-12. From an original cohort of 109 patients, 9 patients were lost to follow up. Of the remaining 100 patients, the mean follow up was 2.9 years (SD±2 years). There were 4 failures, requiring 3 further revisions. The mean post-operative OHS was 33, SF-12 PCS 34 and SF12 MCS 52. 5-year survivorship was 90%. Cementing a constrained acetabular component provides satisfactory mid term results in patients at high risk of hip dislocation.

Constrained cups appear incapable of meeting the demands of revision THA

BACKGROUND

Failure rates of constrained cups for treating recurrent dislocation in revision THA range from 40% to 100%. Although constrained liners are intended to stabilize the hip by mechanically preventing dislocation, the resulting loss of range of motion may lead to impingement and, ultimately, implant failure.

QUESTIONS/PURPOSES

We therefore documented the mechanisms of failure of constrained acetabular cups in revision THA and determined the type and severity of damage (wear, fracture, and impingement) that occurs in situ.

METHODS

We retrieved 57 constrained components of four different designs at revision THA and examined for the presence of rim impingement, oxidation, cracks within the liner, backside wear, pitting, scratching, abrasion, burnishing, and the presence of embedded particles. Articular wear was calculated from the volume of the concave articular bearing surface, which was measured using the fluid displacement method.

RESULTS

Failure of the locking ring was responsible for 51% of failures, whereas 28% of revisions were the result of acetabular cup loosening, 6% backside wear, and 22% infection. Impingement damage of the rim of the polyethylene liner was seen in all retrievals with moderate or severe damage in 54%. The average volumetric wear rate of the articular surface was 95 mm(3)/year.

CONCLUSIONS

Failure of the locking liner ring and loosening of the acetabular cup are the primary causes of mechanical failure with constrained liners; polyethylene is an inadequate material for restricting motion of the hip to prevent instability. The durability of these devices is unlikely to improve unless the mechanical demands are modified through increased range of motion leading to less frequent rim impingement.

The effect of total hip arthroplasty surgical approach on postoperative gait mechanics

Surgical approach for total hip arthroplasty (THA) is determined by clinician preference from limited prospective data. This study aimed to examine the effect of surgical approach (direct lateral, posterior, and anterolateral) on 6-week postoperative gait mechanics. Thirty-five patients (direct lateral, 8; posterior, 12; anterolateral, 15) were tested preoperatively and 6 weeks after THA. Patients underwent a gait analysis at a self-selected walking speed. A 2-way analysis of variance was used for analysis. Stride length, step length, peak hip extension, and walking speed increased after THA. The 3 surgical approach variables were not significantly different for any of the study variables after THA. All patients showed some increase in selected variables after THA regardless of surgical approach. In this study, surgical approach did not appear to significantly influence the early postoperative gait mechanics that were quantified.

Achilles allograft reconstruction for recurrent dislocation in total hip arthroplasty

Recurrent dislocation secondary to posterior soft tissue deficiency is a challenging complication of total hip arthroplasty. We describe the use of an Achilles allograft sling to improve hip stability. Eight patients treated with the sling were followed an average of 5 years. Seven patients had no recurrent instability and good postoperative range of motion. One graft failed in a patient with a neuropathic hip. Cadaveric biomechanical testing was also performed to investigate the stiffness and torque to failure of the sling in 6 specimens. Allograft slings can be used to improve hip stability. The technique is relatively easy to perform and does not limit postoperative range of motion. The graft decreases joint stiffness and has a greater torque to failure than the intact capsule.

Unipolar versus bipolar Exeter hip hemiarthroplasty: a prospective cohort study on 830 consecutive hips in patients with femoral neck fractures

BACKGROUND

Hip replacement using a hemiarthroplasty (HA) is a common surgical procedure in elderly patients with fractures of the femoral neck. Data from the Swedish Hip Arthroplasty Register suggest that there is a higher risk for revision surgery with the bipolar HA compared with the unipolar HA.

PURPOSE

In this study we analysed the reoperation and the dislocation rates for Exeter HAs in patients with a displaced femoral neck fracture, comparing the unipolar and bipolar prosthetic designs. Additionally, we compared the outcome for HAs performed as a primary intervention with those performed secondary to failed internal fixation.

METHODS

We studied 830 consecutive Exeter HAs (427 unipolar and 403 bipolar) performed either as a primary operation for a displaced fracture of the femoral neck or as a secondary procedure after failed internal fixation of a fracture of the femoral neck. Cox regression analyses were performed to evaluate factors associated with reoperation and prosthetic dislocation. Age, gender, the surgeon's experience, indication for surgery (primary or secondary) and type of HA (unipolar or bipolar) were tested as independent variables in the model.

RESULTS

The prosthetic design (uni- or bipolar) had no influence on the risk for reoperation or dislocation, nor had the age, gender or the surgeon's experience. The secondary HAs were associated with a significantly increased risk for reoperation (HR 2.6, CI 1.5-4.5) or dislocation (HR 3.3, CI 1.4-7.3) compared to the primary HAs. We found no difference in the risk for reoperation or dislocation when comparing Exeter unipolar and bipolar HAs, but special attention is called for to reduce the risk of prosthesis dislocation and reoperation after a secondary HA.

Lower rates of dislocation with increased femoral head size after primary total hip replacement

Increased femoral head size may reduce dislocation rates following total hip replacement. The National Joint Registry for England and Wales has highlighted a statistically significant increase in the use of femoral heads ≥ 36 mm in diameter from 5% in 2005 to 26% in 2009, together with an increase in the use of the posterior approach. The aim of this study was to determine whether rates of dislocation have fallen over the same period. National data for England for 247 546 procedures were analysed in order to determine trends in the rate of dislocation at three, six, 12 and 18 months after operation during this time. The 18-month revision rates were also examined.

Between 2005 and 2009 there were significant decreases in cumulative dislocations at three months (1.12% to 0.86%), six months (1.25% to 0.96%) and 12 months (1.42% to 1.11%) (all p < 0.001), and at 18 months (1.56% to 1.31%) for the period 2005 to 2008 (p < 0.001). The 18-month revision rates did not significantly change during the study period (1.26% to 1.39%, odds ratio 1.10 (95% confidence interval 0.98 to 1.24), p = 0.118). There was no evidence of changes in the coding of dislocations during this time.

These data have revealed a significant reduction in dislocations associated with the use of large femoral head sizes, with no change in the 18-month revision rate.

Ceramic-on-ceramic bearing surface and risk of revision due to dislocation after primary total hip replacement

Dislocation is a common reason for revision following total hip replacement. This study investigated the relationship between the bearing surface and the risk of revision due to dislocation. It was based on 110 239 primary total hip replacements with a diagnosis of osteoarthritis collected by the Australian Orthopaedic Association National Joint Replacement Registry between September 1999 and December 2007. A total of 862 (0.78%) were revised because of dislocation. Ceramic-on-ceramic bearing surfaces had a lower risk of requiring revision due to dislocation than did metal-on-polyethylene and ceramic-on-polyethylene surfaces, with a follow-up of up to seven years. However, ceramic-on-ceramic implants were more likely to have larger prosthetic heads and to have been implanted in younger patients. The size of the head of the femoral component and age are known to be independent predictors of dislocation. Therefore, the outcomes were stratified by the size of the head and age. There is a significantly higher rate of revision for dislocation in ceramic-on-ceramic bearing surfaces than in metal-on-polyethylene implants when smaller sizes (< or = 28 mm) of the head were used in younger patients (< 65 years) (hazard ratio = 1.53, p = 0.041) and also with larger (> 28 mm) and in older patients (> or = 65 years) (hazard ratio = 1.73, p = 0.016).

Influence of patient-, design-, and surgery-related factors on rate of dislocation after primary cementless total hip arthroplasty

We performed clinical, radiographic, and computed tomography examinations on a consecutive series of 1268 patients (1648 hips) to determine the prevalence of and factors contributing to dislocation after using a primary cementless total hip system. The prevalence of posterior dislocation was 3.6% (60 hips). Significant risk factors (Fisher exact test or chi(2) test, P < .05) were female sex, advanced age, high American Society of Anesthesiologists score (3 or 4), fracture of the femoral neck, nonrepair of the posterior soft-tissue sleeve, low or high cup anteversion, low or high stem anteversion, and low height of hip rotation center.

Short-term outcome after posterior versus lateral surgical approach for total hip arthroplasty - A randomized clinical trial

Purpose

Currently, total hip replacement (THR) is most commonly performed via a posterior or a direct lateral approach, but the impact of the latter on the invention's outcome has yet not been quantified.

Methods

We compared the short-term outcome of cementless THR using the both approaches in a prospective, randomized controlled trial. 60 patients with unilateral osteoarthritis were included. Outcome assessment was performed one day before surgery and one week, four weeks, six weeks and 12 weeks after surgery, respectively, using the Harris Hip score as primary objective.

Results

We found no significant difference in the intraindividual Harris Hip Score improvement at the pre-and three months post-operative assessments between both treatment groups (p = 0.115). However, Harris Hip scores and most functional and psychometric secondary endpoints showed a consistent tendency of a slightly better three months result in patients implanted via the posterior approach. In contrast a significant shorter operating time of the direct lateral approach was recorded (67 minutes versus 76 minutes, p < 0.001).

Conclusion

In our opinion this slightly better short-term functional outcome after posterior approach is not clinical relevant. However, to make definitive conclusions all clinical relevant factors (i.e. mid- to long-term function, satisfaction, complication rates and long-term survival) have to be taken into account. Level of evidence: I - therapeutic

Modular femoral head and liner exchange for the unstable total hip arthroplasty

Outcomes of femoral head and nonconstrained liner exchange in treating hip instability were evaluated. Forty-eight modular component exchanges performed in 45 patients for recurrent hip dislocations were retrospectively reviewed. Mean follow-up was 4.7 years. Overall success rate was 73% (35/48 hips). Thirty-two (67%) of 48 hips experienced no further dislocations. Three patients had 1 dislocation each with no subsequent dislocations. Ten patients (13 hips) had additional surgery to stabilize their hips (27% failure rate). Demographic, clinical, and implant variables were not associated with outcome. Isolated modular component exchange can be successful in treating recurrent hip dislocations; however, a significant failure rate, not easily predicted, exists. This represents the largest series of modular head and nonconstrained liner exchange for hip dislocation (122/125).

Outcome of treatment for dislocation after primary total hip replacement

We have studied the natural history of a first episode of dislocation after primary total hip replacement (THR) to clarify the incidence of recurrent dislocation, the need for subsequent revision and the quality of life of these patients.

Over a six-year period, 99 patients (101 hips) presented with a first dislocation of a primary THR. A total of 61 hips (60.4%) had dislocated more than once. After a minimum follow-up of one year, seven patients had died. Of the remaining 94 hips (92 patients), 47 underwent a revision for instability and one awaits operation (51% in total). Of these, seven re-dislocated and four needed further surgery. The quality of life of the patients was studied using the Oxford Hip Score and the EuroQol-5 Dimension (EQ-5D) questionnaire. A control group of patients who had not dislocated was also studied. At a mean follow-up of 4.5 years (1 to 20), the mean Oxford Hip Score was 26.7 (15 to 47) after one episode of dislocation, 27.2 (12 to 45) after recurrent dislocation, 34.5 (12 to 54) after successful revision surgery, 42 (29 to 55) after failed revision surgery and 17.4 (12 to 32) in the control group. The EuroQol-5 dimension questionnaire revealed more health problems in patients undergoing revision surgery.

Dislocation rate after conversion from hip hemiarthroplasty to total hip arthroplasty

BACKGROUND

Revision hip arthroplasty is associated with a dislocation rate that is three to five times greater than the rate following primary hip replacement. Conversion of a hip hemiarthroplasty to a total hip replacement is a revision arthroplasty, but it differs from revisions of total hip arthroplasties because a native acetabulum is replaced and the subsequent prosthetic femoral head is smaller. It was our purpose to determine whether the risk of dislocation following conversion surgery is the same as or greater than that following revision total hip replacement.

METHODS

From 1994 to 2005, eighty-nine hemiarthroplasties were converted to a total hip arthroplasty in seventy-seven patients, and the results were compared with those of 115 first-time revision total hip replacements following a primary total hip replacement in 111 patients. A retrospective chart review was performed, and radiographic measurements were obtained. The patient demographics were similar between the two groups. The percentages of patients who had undergone revision of only the acetabular component as compared with both components as well as the percentages of those who had received a modular femoral stem as compared with a nonmodular stem were also similar between the two groups.

RESULTS

Postoperatively, the femoral head size and the positioning of the acetabular component were similar between the two groups. The acetabular components were significantly larger (p < 0.001) in the group in which a total hip arthroplasty had been revised because they required additional acetabular reaming for placement of a new component. There were significantly more dislocations after the conversion procedures (22%) than after the revisions of the total hip arthroplasties (10%) (p < 0.018). Within both groups, the size of the acetabular component, the intraoperative range of motion, and the positioning of the acetabular component were similar between the hips that dislocated and those that did not. However, smaller femoral head components were at greater risk for dislocation after conversion surgery than after revision of a total hip arthroplasty.

CONCLUSIONS

A substantial reduction of the size of the prosthetic femoral head is unique to conversion arthroplasty and appears to play a role in instability after the revision surgery. While the smallest heads dislocated in the conversion group, a larger femoral head did not ensure stability. The increased dislocation risk with conversion surgery requires emphasis on soft-tissue balance and avoidance of excessive downsizing of the femoral head in an attempt to maximize hip stability.

Association between dislocation, impingement, and articular geometry in retrieved acetabular polyethylene cups

We used a novel analysis technique and retrieved acetabular polyethylene liners to investigate relationships between impingement damage, dislocation history, and polyethylene liner geometry. Forty-eight polyethylene liners with neutral rim elevation were visually assessed for peripheral rim damage consistent with impingement between the liner rim and femoral component. Liner articular geometry was measured using a digital stylus, and the geometric relationships between the liner rim and center of the femoral head were characterized by lip height, head center inset, and head penetration into the polyethylene liner. Thirteen (27%) retrieved liners had rim impingement damage and 12 (25%) had a history of dislocation. The proportion of liners with impingement was not significantly different among dislocated and stable liners. Lip height, head center inset, and head penetration were not significantly different between liners with and without impingement damage. Dislocated liners had a significantly shorter head center inset, with significantly less head penetration because of shorter functional duration. Designing polyethylene liners with a sufficiently deep articular surface that exceeds 0.95 mm may prove beneficial for decreasing the prevalence of early dislocation, independent of impingement damage.

Posterior versus lateral surgical approach for total hip arthroplasty in adults with osteoarthritis

BACKGROUND

Osteoarthritis (OA) of the hip is a progressive condition that has no cure and often requires a total hip arthroplasty (THA). The principal methods for THA are the posterior and direct lateral approaches. The posterior approach is considered to be easy to perform, however, increased rates of dislocation have been reported. The direct lateral approach facilitates cup positioning which may decrease rates of hip dislocation and diminishes the risk of injury to the sciatic nerve. However, there is an increased risk of limp. Dislocation of a hip prosthesis is a clinically important complication after THA, in terms of morbidity implications and costs.

OBJECTIVES

To determine the risks of prosthesis dislocation, postoperative Trendelenburg gait and sciatic nerve palsy after a posterior approach, compared to a direct lateral approach, for adult patients undergoing THA for primary OA and to update the previous review made in 2003.

SEARCH STRATEGY

MEDLINE, EMBASE, CINAHL and Cochrane databases were searched and updated, from the previous search of 2002, to Oct 13, 2005. No language restrictions were applied.

SELECTION CRITERIA

Published trials comparing posterior and direct lateral surgical approaches to THA in participants 18 years and older with a diagnosis of primary hip OA.

DATA COLLECTION AND ANALYSIS

Retrieved articles were assessed independently by the two reviewers for their methodological quality.

MAIN RESULTS

Four prospective cohort studies involving 241 participants met the inclusion criteria. The primary outcome, dislocation, was reported in two studies. No significant difference between posterior and direct lateral surgical approach was found [1/77 (1.3%) versus 3/72 (4.2%); relative risk (RR) 0.35; 95% confidence intervals (CI) 0.04 to 3.22]. The presence of postoperative Trendelenburg gait was not significantly different between these surgical approaches. The risk of nerve palsy or injury (all nerves taken together) was significantly higher among the direct lateral approaches [1/43 (2%) versus 10/49 (20%); RR 0.16, 95% CI 0.03 to 0.83]. However, there were no significant differences when comparing this risk nerve by nerve for both approaches, in particular for the sciatic nerve. Of the other outcomes considered only the average range of internal rotation in extension of the hip was significantly higher (weighted mean difference 16 degrees, 95% CI 8 to 23) in the posterior approach group (mean 35 degrees , standard deviation 13 degrees ) compared to the direct lateral approach (mean 19 degrees , standard deviation 13 degrees ).

AUTHORS' CONCLUSIONS

The quality and quantity of information extracted from the trials performed to date are insufficient to make any firm conclusion on the optimum choice of surgical approach in adult patients undergoing primary THA for OA.

Constrained liners in revision: total hip arthroplasty an overuse syndrome: in opposition

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

A constrained device with increased range of motion prevents early dislocation

Constrained components can treat or prevent instability after total hip arthroplasty. Some previous designs have shown a high rate of early dislocation. These early dislocations appear to be secondary to component impingement and levering out of the femoral head. We report the early rate of dislocation in 81 consecutive patients undergoing constrained total hip arthroplasty using a novel constrained device that allows substantially more range of motion and a higher lever out strength. One hip redislocated at 6 months followup, for a success rate of 98.8%. The success rate was 93% for patients for whom a constrained device was placed during revision for recurrent instability. This device allows a higher range of motion before prosthetic impingement and maintains a higher levering out strength when impingement occurs. These changes should provide long lasting hip stability in these difficult cases.

Large diameter femoral heads on highly cross-linked polyethylene: minimum 3-year results

Contemporary highly cross-linked polyethylenes have become the most widely used alternative bearing surfaces in total hip replacement and may be paired with large diameter femoral heads (> 32 mm) in patients considered to be at high risk for dislocation. We report on a prospective series of 42 patients (45 hips) who had total hip replacement using large diameter cobalt-chrome femoral heads articulating with a highly cross linked polyethylene after a minimum of 3 years followup (mean 3.3 years). At final followup, the final patient cohort showed excellent clinical results with no radiographic failures or episodes of loosening. There was no evidence of pelvic or femoral osteolysis. One patient sustained a dislocation due to a grossly malpositioned acetabular component necessitating early isolated acetabular revision. The average yearly steady state wear rate was -0.06 +/- 0.41 mm/year. The results of our short-term prospective series indicated total hip replacement with large femoral heads articulating with a highly cross linked polyethylene showed excellent wear characteristics and clinical results and could be considered in patients at increased risk for dislocation.

The cemented all-polyethylene acetabular cup: factors affecting survival with emphasis on the integrated polyethylene spacer: an analysis of the effect of cement spacers, cement mantle thickness, and acetabular angle on the survival of total hip arthroplasty

Four hundred seven primary total hip arthroplasties were performed using a cemented, direct compression molded all-polyethylene acetabular component. Based on a double-blinded randomization schedule, one group received acetabular cups with cement spacers made from polyethylene integrated into the cup, whereas the other group received the same acetabular cups with the polyethylene spacers removed. Patients were followed up for an average of 6.5 years. During this follow-up period, there were 3 revisions for acetabular cup loosening and 40 acetabular cups that had a global radiolucent line at least 1 mm wide. Acetabular cups with polyethylene spacers were found to have a significantly higher initial rate of failure (P < .0380) when compared with cups without cement spacers. Yet, polyethylene spacers resulted in a significantly thicker and more uniform cement mantle in zones 1, 2, and 3 (P < .0001). Cups initially placed at an angle of 45.0 degrees to 50.5 degrees had the highest survival rate compared with all possible angle ranges (P < .0158).

Closed reduction of prosthetic hip dislocation by emergency physicians

OBJECTIVE

The purpose of this study was to determine the frequency of successful closed reduction (CR) of dislocated prosthetic hips performed by emergency physicians (EPs) as well as the incidence of acute complications.

METHODS

The study design was an explicit chart review set at an academic ED with an annual census of 55,000. The study was performed on March 1, 1999 to February 28, 2004. Patients were identified using coded ED diagnoses, and data were obtained by a trained abstractor.

RESULTS

One hundred twelve dislocations in 66 patients had attempted CR in the ED. Eighty-one had CR attempted solely by an EP with 91% success. Twenty-eight of the remaining 31 (90%) had successful CR performed by either an orthopedic surgeon or both an EP and an orthopedic surgeon. Overall, 10 patients (9%) failed ED CR. No postreduction complications were identified in any patient.

CONCLUSIONS

EPs can safely and successfully perform CR on patients with dislocated total hip arthroplasties.

Study of hip joint dislocation after total hip arthroplasty

The present study was undertaken to identify the factors responsible for hip joint dislocation after total hip arthroplasty, laying emphasis on analysis of the background variables of the patients. Of the 317 hips included in the study, ten (3.2%) dislocated. Only the anteversion angle of the cup differed significantly between the dislocation group and the dislocation-free group. The safe zone of the anteversion angle seems to be between 20 and 30 degrees. but it is also essential to set the antetorsion angle of the stem to match the shape of individual bones to create a more stable hip joint. This safe zone may be expanded by the additive effect of antetorsion angle of the stem.

The long-term outcome of 755 consecutive constrained acetabular components in total hip arthroplasty examining the successes and failures

Constrained acetabular components can treat or prevent instability after total hip arthroplasty (THA). We examine long-term results of 755 consecutive constrained THA in 720 patients (1986-1993; 62 primary, 59 conversion, 565 revision, 60 reimplantation, and 9 total femur). Eighty-three patients (88 THAs) were lost before 10-year follow-up, leaving 639 patients (667 THAs) available for study. Dislocation occurred in 117 hips (17.5%), in 37 (28.9%) of 128 constrained for recurrent dislocation, and 46 (28.2%) of 163 with dislocation history. Other reoperations were for aseptic loosening (51, 7.6% acetabular; 28, 4.2% stem; 16, 2.4% combined), infection (40, 6.0%), periprosthetic fracture (19, 2.8%), stem breakage (2, 0.3%), cup malposition (1, 0.1%), dissociated insert (1, 0.1%), dissociated femoral head (1, 0.1%), and impingement of 1 broken (0.1%) and 4 (0.6%) dissociated constraining rings. Although constrained acetabular components prevented recurrent dislocation in 71.1%, they should be used cautiously, with a 42.1% long-term failure rate observed in this series. Dislocation was common despite constraint with previous history as a significant risk.

Range of motion and stability in total hip arthroplasty with 28-, 32-, 38-, and 44-mm femoral head sizes

The purpose of this study was to evaluate, via experimental models, the effect of larger head sizes for total hip arthroplasty on the type of impingement, range of motion (ROM), and joint stability. Testing was conducted using an anatomic full-size hip model (anatomic goniometer) and a novel anatomic dislocation simulator with 28-, 32-, 38-, and 44-mm diameter femoral heads within a 61-mm acetabular shell. Femoral heads >32-mm provided greater ROM and virtually complete elimination of component-to-component impingement. A significant increase in both flexion before dislocation and displacement between the femoral head and acetabulum to produce dislocation occurred with femoral heads >32-mm in diameter. These data indicate that larger femoral heads offer potential in providing greater hip ROM and joint stability.

Mini-incision anterior approach does not increase dislocation rate: a study of 1037 total hip replacements

Correct positioning of the prosthetic components in total hip replacements is important to prevent dislocations. Correct positioning is made easier by extensive approaches, but it also is possible using the mini-incision approach. The mini-incision used to facilitate early rehabilitation should not produce a higher dislocation rate than that of the more conventional approaches. The anterior surgical approach we describe allows for good exposure, despite the reduced size of the skin incision. Its length is 5-10 cm and usually 6-8 cm for patients with normal corpulence. Our mini-incision anterior approach using intermuscular planes allows a surgical approach to the hip and implantation of a total prosthesis with no muscle, tendon, or trochanteric section, even partially. This is not possible with any other surgical approach. A series of 1037 primary total hip replacements done between June 1993 and June 2000 was studied retrospectively. The dislocation rate was 0.96% (10 of 1037 hips). The mini-incision approach allows for adequate positioning of the two prosthetic components. Preserving the muscular potential also may contribute to dynamic stabilization of the hip.

A novel system of four-dimensional motion analysis after total hip arthroplasty

We have developed a novel system of four-dimensional motion analysis after total hip arthroplasty (THA) that can aid in preventing dislocation by assessing safe range of motion for patients in several daily activities. This system uses skeletal structure data from CT and motion capture data from an infrared position sensor. A 3-D model reconstructed from CT data is combined with the motion capture data. Using this system, we analyzed hip motion when getting up from and sitting down in a chair or picking up an object while sitting in a chair in 17 patients (26 hips) who underwent THA. To assess the accuracy of this system's measurements, open MRI was used to evaluate positions of skin markers against bones in five healthy volunteers in various postures. No impingement between bones and/or implants was found in any subjects during any activities. However, mean angle at the point of maximum hip flexion was different for each patient. The open MRI results indicated that average error in hip angle of the present system was within 5 degrees for each static posture. The functional position of the pelvis during daily activities must be taken into account when assessing the real risk of dislocation. The present system enables dynamic analysis involving not only alignment of components and bones of each patient, but also individual differences in characteristics of daily motions. Further investigation using this system can help determine safe ranges of motion for preventing hip dislocation, improving the accuracy of individualized guidance for patients regarding postoperative activities.

Influence of component positions on dislocation: computed tomographic evaluations in a consecutive series of total hip arthroplasty

Component positions in a consecutive series of total hip arthroplasty through a posterolateral approach without capsular and external rotator repair, using the same prosthesis type, head size, and liner, were evaluated using computed tomography, and correlation with occurrence of postoperative dislocation was assessed. The 9 hips with posterior dislocation had significantly lower cup anteversion than the 181 hips without dislocation. Seven (78%) of the 9 hips with posterior dislocation had cup anteversion <20 degrees, irrespective of stem anteversion. These findings suggest that among variables of component positions, cup anteversion is one of the important factors for risk of dislocation, and that intentionally placing the cup at low anteversion to compensate for high femoral neck anteversion may predisposes the hip to postoperative dislocation.

Posterior versus lateral surgical approach for total hip arthroplasty in adults with osteoarthritis

BACKGROUND

Osteoarthritis (OA) of the hip is a progressive condition that has no cure and often requires a total hip arthroplasty (THA). The principal methods for THA are the posterior and direct lateral approaches. The posterior approach is considered to be easy to perform, however, increased rates of dislocation have been reported. The direct lateral approach facilitates cup positioning which may decrease rates of hip dislocation and diminishes the risk of injury to the sciatic nerve. However, there is an increased risk of limp. Dislocation of a hip prosthesis is a clinically important complication after THA, in terms of morbidity implications and costs.

OBJECTIVES

To determine the risks of prosthesis dislocation, postoperative Trendelenburg gait and sciatic nerve palsy after a posterior approach, compared to a direct lateral approach, for adult patients undergoing THA for primary OA.

SEARCH STRATEGY

MEDLINE, EMBASE, CINHAL and Cochrane databases were searched until 2002. No language restrictions were applied.

SELECTION CRITERIA

Published trials comparing posterior and direct lateral surgical approaches to THA in participants 18 years and older with a diagnosis of primary hip OA.

DATA COLLECTION AND ANALYSIS

Retrieved articles were assessed independently by the two reviewers for their methodological quality.

MAIN RESULTS

Four prospective cohort studies involving 241 participants met the inclusion criteria. The primary outcome, dislocation, was reported in two studies. No significant difference between posterior and direct lateral surgical approach was found [1/77 (1.3%) versus 3/72 (4.2%); relative risk (RR) 0.35; 95% confidence intervals (CI) 0.04 to 3.22]. The presence of postoperative Trendelenburg gait was not significantly different between these surgical approaches. The risk of nerve palsy or injury was significantly higher among the direct lateral approaches [1/43 (2%) versus 10/49 (20%); RR 0.16, 95% CI 0.03 to 0.83]. However, there were no significant differences when comparing this risk nerve by nerve for both approaches, in particular for the sciatic nerve. Of the other outcomes considered only the average range of internal rotation in extension of the hip was significantly higher (weighted mean difference 16 degrees, 95% CI 8 to 23) in the posterior approach group (mean 35 degrees, standard deviation 13 degrees ) compared to the direct lateral approach (mean 19 degrees, standard deviation 13 degrees ).

REVIEWER'S CONCLUSIONS

The quality and quantity of information extracted from the trials performed to date are insufficient to make any firm conclusion on the optimum choice of surgical approach in adult patients undergoing primary THA for OA.

Using cost-effectiveness analysis to compare Hospital at Home and in-patient interventions. Part 1

An economic analysis was conducted as an integral part of a comparison of the effectiveness and suitability of Hospital at Home (HaH) and in-patient interventions. The sample comprised of 109 adult primary total joint replacement patients and 21 of their coresident informal carers. The paper is presented in two parts. Part 1 includes the background and rationale for the study and the findings from the comparison of the effectiveness of the two interventions using multiple data collection sources. Data were collected using questionnaires, audit and semi-structured interviews. Hospital at Home was found to be significantly more effective in terms of patient satisfaction and reduced joint stiffness and as least as effective as in-patient care in relation to levels of joint pain, joint disability and incidence of postoperative complications. In addition informal carers reported 107 positive comments compared with 36 negative comments related to HaH care and all except one of the 21 carers would choose HaH again in preference to in-patient care.

Femoral head sizes larger than 32 mm against highly cross-linked polyethylene

The advent of highly cross-linked ultrahigh molecular weight polyethylene, which shows extremely low wear independent of head size in vitro, allows for the reevaluation of the use of femoral heads larger than 32 mm. The current authors discuss information that supports this hypothesis. The supporting information includes in vitro wear testing and in vitro anatomic studies, and prior clinical studies in which large femoral heads were used.

Posterior transosseous capsulotendinous repair in total hip arthroplasty : a cadaver study

BACKGROUND

While recent clinical articles have reported a dramatic reduction in rates of total hip dislocation after posterior transosseous repair, we are not aware of any published biomechanical data to support this finding. The objectives of this study were to investigate the functional anatomy of the posterior transosseous repair and its effect on stability after total hip replacement.

METHODS

Six total hip prostheses were implanted into three fresh cadavera. Three different repair situations (no repair, soft-tissue repair, and transosseous fixation) were then consecutively tested on each hip. Values for torque resistance and the angular range of motion at dislocation were recorded. Each repair was tested twice, yielding a total of thirty-six torque values and thirty-six angles of rotation.

RESULTS

The transosseous repair was superior with regard to both torsion strength (four times stronger than that after no repair [p = 0.0002] and more than twice as strong as that after soft-tissue repair [p = 0.002]) and the magnitude of the angle of rotation observed prior to dislocation (an increase of 83% in comparison with that after no repair [p = 0.0005] and an increase of 46% in comparison with that after soft-tissue repair [p = 0.004]).

CONCLUSIONS

In a cadaver model, posterior transosseous repair provides superior stability of a total hip replacement. Optimal surgical technique with a slightly modified approach allows greater retention of capsule and tendon length and a more anatomical reinsertion of the soft tissues.

Acetabular revision for recurrent dislocations: results in 14 cases after 3 years of follow-up

17 acetabular revisions (16 patients) were performed for recurrent dislocations. 14 patients were examined clinically and radiographically after mean 3 (1-8) years. We found malpositions of components in 12 of 17 cases. 8 of 17 had redislocations and 2 were rerevised. Harris hip scores improved from 57 to 70. 10 of 14 patients were satisfied with the surgical result. Recurrent dislocations have several causes. In our patients, lack of cup anteversion was the commonest indication for revision surgery. We noted a high rate of redislocations and poor clinical results, despite correction of the preoperative component malposition in the 14 cases with follow-up.

Factors predisposing to dislocation after primary total hip arthroplasty: a multivariate analysis

We conducted this study to determine the relative influence of various mechanical and patient-related factors on the incidence of dislocation after primary total hip asthroplasty (THA). Of 2,023 THAs, 21 patients who had at least 1 dislocation were compared with a control group of 21 patients without dislocation, matched for age, gender, pathology, and year of surgery. Implant positioning, seniority of the surgeon, American Society of Anesthesiologists (ASA) score, and diminished motor coordination were recorded. Data analysis included univariate and multivariate methods. The dislocation risk was 6.9 times higher if total anteversion was not between 40 degrees and 60 degrees and 10 times higher in patients with high ASA scores. Surgeons should pay attention to total anteversion (cup and stem) of THA. The ASA score should be part of the preoperative assessment of the dislocation risk.

Instability in primary total hip arthroplasty with the direct lateral approach

Instability after a total hip arthroplasty is a serious complication. Dislocation rates as much as 6.5% after posterior approaches have been reported within the past decade. For this reason, the authors use the direct lateral approach for primary and revision total hip arthroplasties. A review of the arthroplasty database yielded 1515 primary total hip arthroplasties done via a direct lateral approach in 1333 patients. These arthroplasties were done within a 10-year period and patients with followup data less than 12 months were excluded. At the most recent examination, 11.6% of the patients had a moderate or severe limp and 2.5% had severe heterotopic ossification. Only six hips (0.4%) had a dislocation or episode of instability. Three patients had more than one dislocation and required revision surgery. The results of the current study show that dislocation after primary total hip arthroplasty almost can be eliminated using the direct lateral approach. The associated risks of heterotopic ossification or limp are acceptable.

Survey of patient-oriented total hip replacement information on the World Wide Web

The author conducted an informal survey of materials relating to diseases of the hip and total hip replacement as they appeared on the World Wide Web. The results varied depending on the key words used: hip and replacement yielded 1,818 matches; total hip replacement yielded 1,740 matches; hip replacement yielded 4,565 sites; and hip surgery yielded 1,073 sites. The number of sites for total hip replacement was observed to increase with time, having found an additional 30 sites from an identical search performed only 6 weeks earlier. The nature and quality of these sites varied from well-organized and informative, to personal testaments, to obvious commercial endeavors. Overall, this survey found an abundance of material regarding the hip and hip replacements on the World Wide Web, but orthopaedic societies need to take a more active role in constructing, maintaining, and monitoring these sites to best serve the needs of their patients and their members.