Reduced dislocation rates and excellent functional outcomes with large-diameter femoral heads

Fibromyalgia Increases Post-Operative Healthcare Utilization Following Total Hip Arthroplasty

INTRODUCTION

Pre-operative factors can complicate the post-operative course and increase healthcare utilization following total hip arthroplasty (THA). Fibromyalgia is not generally recognized as a modifiable risk factor prior to THA. The aim of this investigation was to assess the effect of fibromyalgia on post-operative healthcare utilization following THA.

METHODS

Patients who underwent primary THA from 2018 to 2019 were identified from a large national database using Current Procedural Terminology (CPT) and International Classification of Diseases, tenth revision (ICD-10) codes. Patient demographics, age, sex, and pre-operative opioid use were collected. Analysis compared patients who did and did not have fibromyalgia for post-operative healthcare utilization metrics; lengths of stay (LOS), 90-day post-operative opioid usages, dislocations, and emergency room visits. Independent t-testings were used to compare LOS, and rates of ongoing opioid use. Logistic regression analyses with adjusted Odds Ratios (aORs) evaluated the risk of dislocation and emergency room visit after adjusting for demographic characteristics and comorbidities.

RESULTS

Compared to those who did not have fibromyalgia, patients who had fibromyalgia experienced longer LOS (P<0.0001), increased odds of opioid use 90-days post-operatively (P<0.0001), as well as increased odds of hip dislocation (P<0.0001) and presentation to the emergency room (P<0.0001). Patients who had fibromyalgia were also more likely to be "frequent flyers" with >5 emergency room visits after THA (P<0.0001).

CONCLUSIONS

Fibromyalgia can complicate post-operative care following THA with increased LOS, higher rates of opioid use, and increased odds of dislocation and emergency room visits. As focus shifts to pre-operative optimization and risk stratification, more attention should be placed on fibromyalgia prior to THA.

Metal-on-Metal Hips: Ten-Year Clinical and Radiographic Outcomes of the ADEPT Metal-on-Metal Hip Resurfacing and Modular Total Hip Arthroplasty

BACKGROUND

The aim of this study is to update the 10-year follow-up survivorship and metal ions levels of a cohort of metal-on-metal (MoM) hip resurfacing (HR) and large-diameter-head (LDH) total hip arthroplasty (THA).

METHODS

The study is a retrospective analysis of prospectively collected data that compared the outcomes of 24 MoM HR (21 patients) and 15 (11 patients) modular LHD MoM THA at >10 years follow-up. Baseline characteristics as well as intraoperative and postoperative information were collected, including complications, revisions, clinical and radiographic outcomes, and serum metal ions level (Cobalt, Chromium). Metal ion levels were compared using a two-tailed unpaired t-test and Wilcoxon signed-rank test (jamovi v2.3.3.0, Sydney, NSW, AU).

RESULTS

No significant differences were detected in gender, BMI, and ASA score between the two groups. Patients in the modular THA group were significantly older (57 years vs. 46 years; p < 0.05). The HR overall survivorship was 91.7% (22 of 24 hips) with survivorship from implant failure and/or aseptic loosening and/or metal debris related 100% of problems. The modular THA overall survivorship was 86.7% (13 of 15 hips) with survivorship from implant aseptic loosening and metal ions complications of 93.4% (14 of 15 hips). No significant difference was noted when comparing clinical outcomes. Metal ions were significantly lower in the HR group (Co 25.8 nmol/L vs. 89 nmol/L; p < 0.001-Cr 33.5 nmol/L vs. 55.2 nmol/L; p = 0.026).

CONCLUSION

Both implants reported excellent and comparable clinical outcomes at >10 years follow-up. The Adept HR reported remarkable survivorship, in line with the registry data, proving once again its reliability in young active males. The modular LDH THA, despite being discontinued, presented higher reliability and a lower failure rate when compared with similar withdrawn MoM implants. Trunnionosis did not appear to be a significant problem in this particular modular design.

Incidence, Timing, and Predictors of Hip Dislocation After Primary Total Hip Arthroplasty for Osteoarthritis

INTRODUCTION

Total hip arthroplasty (THA) may be complicated by dislocation. The incidence of and risk factors for dislocation are incompletely understood. This study aimed to determine the incidence and predictors of hip dislocation within 2 years of primary THA.

METHODS

The 2010 to 2020 PearlDiver MHip database was used to identify patients undergoing primary THA for osteoarthritis with a minimum of 2 years of postoperative data. Dislocation was identified by associated codes. Age, sex, body mass index, Elixhauser Comorbidity Index, fixation method, and bearing surface were compared for patients with dislocation versus control subjects by multivariate regression. Timing and cumulative incidence of dislocation were assessed.

RESULTS

Among 155,185 primary THAs, dislocation occurred within 2 years in 3,630 (2.3%). By multivariate analysis, dislocation was associated with younger age (<65 years), female sex, body mass index < 20, higher Elixhauser Comorbidity Index, cemented prosthesis, and use of metal-on-poly or metal-on-metal implants ( P< 0.05 for each). Among patients who experienced at least one dislocation, 52% of first-time dislocations occurred in the first 3 months; 57% had more than one and 11% experienced >5 postoperative dislocation events. Revision surgery was done within 2 years of index THA for 45.6% of those experiencing dislocation versus 1.8% of those who did not ( P < 0.001).

CONCLUSION

This study found that 2.3% of a large cohort of primary THA patients experienced dislocation within 2 years, identified risk factors for dislocation, and demonstrated that most patients experiencing dislocation had recurrent episodes of instability and were more likely to require revision surgery.

Influence of Accelerated Aging on the Wear Behavior of Cross-Linked Polyethylene Liners—A Hip Simulator Study

Sequential cross-linked and annealed ultra-high-molecular-weight polyethylene (SX-PE) is known as a low-wear articulating partner, especially for total hip endoprostheses. Aging of polymeric materials, irrespective of if induced by shelf or in vivo life, can degrade their tribological and mechanical properties. However, changes in wear behavior of aged SX-PE liners have not been not quantified so far. An accelerated aging procedure, to simulate shelf and in vivo aging, was performed on thin SX-PE liners after five million load cycles using a simulator (“worn-aged”) as well as on new SX-PE liners (“new-aged”). A subsequent hip simulator test was performed with both thin SX-PE liner sets in combination with large-diameter ceramic femoral head, representing a combination known as advantageous for treatment after revision because of dislocation. Oxidation indices were measured on the liners after each step of the procedure. SX-PE liners after accelerated aging show bedding-in phases during simulator test, which was a characteristic only known from clinical investigations. Hence, the wear rates of the “new-aged” ((1.71 ± 0.49) mg/million cycles) and of the “worn-aged” ((9.32 ± 0.09) mg/million cycles) SX-PE were increased in the first period compared to new unaged SX-PE liners. Subsequently, the wear rates decreased for “new-aged” and “worn-aged” inserts to (0.44 ± 0.48) mg/million cycles and (2.72 ± 0.05) mg/million cycles, respectively. In conclusion, the results show promising effects of accelerated aging on SX-PE liners in simulator testing and for potential long-term use in clinical applications.

To what extent could the acetabular liner thickness be reduced yet remaining tribologically acceptable in metal-on-vitamin E-diffused crosslinked polyethylene hip arthroplasty?

The aim of the present study was to evaluate how much reduction in acetabular liner thickness could be tribologically acceptable in metal-on-vitamin-E diffused highly crosslinked ultra-high molecular weight polyethylene (Vit-E XLPE) bearings for total hip arthroplasty. We tested thick- (10.3 mm), moderate- (6.3 mm), and thin- (4.3 mm) Vit-E XLPE liners coupled with 28-mm cobalt-chromium femoral heads on a hip simulator to 5 million cycles, and peak contact stress was predicted based on mathematical modeling. Wear damage was also evaluated in terms of surface topology and morphology. Wear simulation demonstrated that the 2-4 mm thickness reduction (6.3 → 4.3 mm and 10.3 → 6.3 mm) did not significantly affect the wear rate for Vit-E XLPE liner, whereas 6-mm reduction (10.3 → 4.3 mm) significantly increased liner wear (by 309%) and head roughness (by 415%). This effect was attributed to a contact stress increase (by 24-41%). However, the wear rates for all thicknesses tested were much lower than those previously reported for thicker non-crosslinked materials. The original crystalline morphology was maintained in all liners after wear. Our results suggest that the 2-4 mm thickness reduction may be tribologically acceptable in Vit-E XLPE liners. However, more severe and longer term simulations are necessary to determine a minimum acceptable thickness.

A conservative approach to dislocation following total hip arthroplasty: a review of 8606 hips

PATIENTS AND METHODS

We present the data on 8606 total hip arthroplasty (THA) procedures carried out in 7818 patients through a posterior approach between 1998 and 2017.

RESULTS

218 hips (2.5%) suffered at least 1 dislocation with dislocation rates declining from 6.2% from 1998 to 2002 to 1.5% from 2003 to 2017. Overall, 92 hips (1.06%) required revision surgery but of these, only 5 (0.06%) had a full revision of both components with the remaining 87 requiring intervention only on the acetabular side. None have had a pseudo-arthrosis; none were left dislocated and all remain stable to date.

CONCLUSIONS

In patients who have a second dislocation within 3 months of their primary surgery we recommend a spica or long leg cylinder cast to reduce the need for revision surgery. We propose an algorithm to manage instability with less aggressive operative treatment in this often-elderly patient population with the potential for less physiological insult and significant cost savings.

Direct Anterior Approach for Primary Total Hip Arthroplasty Lowers the Risk of Dislocation Compared to the Posterior Approach: A Single Institution Experience

BACKGROUND

One purported benefit of the direct anterior approach (DAA) for total hip arthroplasty (THA) is a lower rate of postoperative dislocation.

METHODS

An institutional database was used to identify 8840 primary THAs performed from 2003 to 2020 including 5065 (57%) performed using the DAA and 3775 (43%) performed via the posterior approach (PA). Direction and mechanism of dislocation were determined from chart review. Outcomes were compared using Kaplan-Meier survivorship with dislocation as the endpoint and a Cox multivariate regression was used to investigate factors associated with dislocation. The mean follow-up was 1.7 ± 2.0 years for the DAA and 3.1 ± 3.3 years for the PA.

RESULTS

The 0.5% (26/5065) incidence of dislocation among DAA hips was significantly less than the 3.3% (126/3775) among PA cases (P < .001). The majority of dislocations were posterior (DAA 57%, PA 79%) and occurred during activities of daily living (DAA 82%, PA 77%). Five-year survivorship was significantly higher for the DAA group compared to the PA group (99.1% vs 95.4%, P < .001). Dislocation risk was 4.9 times higher for the PA compared to the DAA (hazard ratio = 4.9, 95% confidence interval = 3.2-7.5, P < .001). Increasing head diameter reduced the risk (hazard ratio = 0.70, 95% confidence interval = 0.57-0.86, P < .001). The 0.2% incidence (10/5065) of revision for instability among the DAA group was significantly lower than the 1.1% (43/3775) rate for the PA group (P < .001).

CONCLUSION

Compared to primary THAs performed with the PA, DAA cases had a lower risk of dislocation, higher survivorship with dislocation as an endpoint, and a lower risk of revision for instability in this single institution cohort.

Effect of intraoperative treatment options on hip joint stability following total hip arthroplasty

Dislocation remains the leading indication for revision of total hip arthroplasty (THA). The objective of this study was to use a computational model to compare the overall resistance to both anterior and posterior dislocation for the available THA constructs commonly considered by surgeons attempting to produce a stable joint. Patient-specific musculoskeletal models of THA patients performing activities consistent with anterior and posterior dislocation were developed to calculate joint contact forces and joint positions used for simulations of dislocation in a finite element model of the implanted hip that included an experimentally calibrated hip capsule representation. Dislocations were then performed with consideration of offset using +5 and +9 offset, iteratively with three lipped liner variations in jump distance (10°, 15°, and 20° lips), a size 40 head, and a dual-mobility construct. Dislocation resistance was quantified as the moment required to dislocate the hip and the integral of the moment-flexion angle (dislocation energy). Increasing head diameter increased resistive moment on average for anterior and posterior dislocation by 22% relative to a neutral configuration. A lipped liner resulted in increases in the resistive moment to posterior dislocation of 9%, 19%, and 47% for 10°, 15°, and 20° lips, a sensitivity of approximately 2.8 Nm/mm of additional jump distance. A dual-mobility acetabular design resulted in an average 38% increase in resistive moment and 92% increase in dislocation energy for anterior and posterior dislocation. A quantitative understanding of tradeoffs in the dislocation risk inherent to THA construct options is valuable in supporting surgical decision making.

Impingement in total hip arthroplasty: A geometric model

Total Hip Arthroplasty (THA) is one of the most common and successful surgical interventions. The survivorship at 10 years for the most commonly used systems is over 95%. However, the incidence of revision is usually much higher in the 0-1 year time period following the intervention. The most common reason for revision in this early time period is dislocation and subluxation, which may be defined as complete or permanent, and partial or temporary loss of contact between the bearing surfaces respectively. This study comprises the development of a geometric model of bone and an in situ total hip replacement, to predict the occurrence and location of bone and component impingement for a wide range of acetabular cup positions and for a series of frequently practiced activities of daily living. The model developed predicts that anterior-superior component impingement is associated with activities that result in posterior dislocation. The incidence may be reduced by increased cup anteversion and inclination. Posterior-inferior component impingement is associated with anterior dislocation activities. Its incidence may be reduced by decreased cup anteversion and inclination. A component impingement-free range was identified, running from when the cup was positioned with 45° inclination and 25° anteversion to 70° inclination and 15°-20° anteversion.

Patient-reported outcome after dislocation of primary total hip arthroplasties: a cross-sectional study derived from the Danish Hip Arthroplasty Register

Background and purpose - Knowledge regarding patient-reported outcomes (PROs) after dislocation and closed reduction is lacking. We report health- and hip-related quality of life (QoL) after dislocation, following primary total hip arthroplasty (THA). Patients and methods - We conducted a crosssectional study with patients registered in the Danish Hip Arthroplasty Register from 2010 to 2014. Dislocations were captured based on diagnosis/procedure codes and patient file reviews. Patients with dislocation were matched 1:2, according to age, sex, date, and hospital of primary surgery, to patients without dislocation. 2 PRO questionnaires were applied (EQ-5D, HOOS). Results - We identified 1,010 living patients with dislocation. Mean follow-up was 7.2 years from index surgery and 4.9 years (range 0.6-9.7) from the latest dislocation. Patients without dislocation reported a higher EQ VAS score of 76 (95% CI 75-77) compared with 68 (CI 66-70) for the dislocation group. The EQ-5D-5L mean index score was 0.89 (CI 0.88-0.90) for the control group, compared with 0.78 (CI 0.76-0.80) for the cases with dislocation without revision. Patients with dislocation reported a lower HOOSQoL domain score of 63 (CI 60-65), compared with 83 (CI 82-84) for the control group. Even 5 years after the latest dislocation, the HOOS-QoL score remained low, at 66 (CI 62-69). The other HOOS domains were consistently 8-10 points worse after dislocation. Interpretation - Both health- and hip-related QoL were markedly and persistently reduced among dislocation patients compared with those in controls, for several years. Therefore, the avoidance of the initial dislocation episode is important because the THA does not appear to achieve the full relieving potential.

Monobloc Dual Mobility With a Minimum 5-Year Follow-Up: A Safe and Effective Solution in Primary Total Hip Arthroplasty

BACKGROUND

Instability constitutes over 20% of revisions after total hip arthroplasty (THA). Dual mobility (DM) designs were introduced as a solution to this problem. However, the few publications that have reported promising results for monobloc DM constructs have been limited by sample size or length of follow-up. The purpose of this study is to evaluate mid-term outcomes (minimum 5-year follow-up) of a single-surgeon series utilizing a monobloc DM acetabular component in patients with high risk for dislocation.

METHODS

This is a single-surgeon consecutive series of 207 primary THAs implanted with a monobloc DM component in patients who were considered at high risk for dislocation. Patient demographics and case-specific data were collected retrospectively. All patients had a minimum of 5-year follow-up. The Mann-Whitney U test was used to assess continuous variables, whereas categorical variables were analyzed using the chi-square test. Survival probability was calculated using the Kaplan-Meier method.

RESULTS

Radiographic analysis did not reveal acetabular radiolucency in any patients, and there were no revisions for aseptic loosening. In addition, there were no dislocations. Seven of 205 patients (3.4%) were revised, 5 on the femoral side due to periprosthetic fracture and the remaining two for infection. Survivorship of the acetabular component from revision was 99%. The mean Veteran RAND (VR-12) physical score improved from 7 (standard deviation [SD]: 13.7) preoperatively to 9.5 (SD: 17.6) at the final follow-up. Similarly, the hip disability osteoarthritis score improved from 8 (SD: 17.9) preoperatively to 21.2 (SD: 37).

CONCLUSION

Monobloc DM components reliably prevent dislocation after primary THA in high-risk patients. At mid-term follow-up, this DM monobloc component demonstrates excellent implant survivorship, radiographic fixation, and improved functional outcomes.

Despite higher revision rate, MoM large-head THA offers better clinical scores than HR: 14-year results from a randomized controlled trial involving 48 patients

BACKGROUND

The high failure rates of metal on metal (MoM) large diameter head total hip arthroplasty (LDH THA) and hip resurfacing (HR) prevented their long-term comparisons with regards to clinical outcome. Such knowledge would be important as ceramic LDH bearing is now available. With long-term follow-up, we investigated the difference in 1) patient-reported outcome measures (PROMs); 2) revision and adverse events rates, and 3) metal ion levels between MoM LDH THA and HR.

METHODS

Forty-eight patients were randomized for LDH THA (24) or HR (24) with the same MoM articulation. At a mean follow-up of 14 years, we compared between groups different PROMs, the number of revisions and adverse events, whole blood Cobalt (Co) and Chromium (Cr) ion levels, and radiographic signs of implant dysfunction.

RESULTS

LDH THA (all cases: revised and well-functioning) had significantly better WOMAC (94 versus 85, p = 0.04), and more frequently reported having no limitation (p = 0.04). LDH THA revision rate was 20.8% (5/24) versus 8.3% (2/24) for HR (p = 0.4). Mean Co and Cr ion levels were higher in LDH THA compared to the HR (Co: 3.8 μg/L vs 1.7 μg/L; p = 0.04 and Cr: 1.9 μg/L vs 1.4 μg/L, p = 0.1). On radiographic analyses, 2 LDH THAs showed signs of adverse reaction to metal debris, whereas 1 loose femoral HR component was documented.

CONCLUSION

In the long-term, MoM LDH THA had a high trunnion related revision rate but nonetheless showed better PROMs compared to HR. Provided with a well-functioning modular junction, non-MoM LDH THA would offer an appealing option.

TRIAL REGISTRATION

ClinicalTrials.gov ( NCT04516239 ), August 18, 2020. Retrospectively registered.

"True" Cumulative Incidence of and Risk Factors for Hip Dislocation within 2 Years After Primary Total Hip Arthroplasty Due to Osteoarthritis: A Nationwide Population-Based Study from the Danish Hip Arthroplasty Register

BACKGROUND

Hip dislocation is one of the leading indications for revision of total hip arthroplasty (THA) implants, and the extent of this complication is often measured by the number of revisions. The exact incidence of dislocation can be difficult to establish as closed reductions may not be captured in available registers. The purpose of this study was to identify the "true" cumulative incidence of hip dislocation (revisions and closed reductions) after primary THA, and the secondary aim was to identify risk factors for dislocation.

METHODS

From the Danish Hip Arthroplasty Register, we identified 31,105 primary THAs indicated by primary osteoarthritis that had been performed from 2010 to 2014 and had 2 years of follow-up. Dislocations were identified through extraction from the Danish National Patient Register. Matching diagnosis and procedure codes were deemed correct while non-matching codes were reviewed through a comprehensive, nationwide review of patient files. Risk factors were analyzed with multiple logistic regression analysis and presented as odds ratios (ORs) with 95% confidence intervals (CIs).

RESULTS

Our review of patient files identified 1,861 dislocations in 1,079 THAs, which corresponds to a 2-year cumulative incidence of 3.5% (CI = 3.3% to 3.7%). This was a 50% increase compared with the correctly coded dislocations captured by administrative register data only. Patients who were <65 years of age had a lower dislocation risk (OR = 0.70; CI = 0.59 to 0.83) and those who were >75 years of age had a higher risk (OR = 1.32; CI = 1.14 to 1.52) compared with those who were 65 to 75. Male sex (OR = 0.86; CI = 0.75 to 0.98), cemented fixation (OR = 0.71; CI = 0.58 to 0.87), and lateral approach (OR = 0.28; CI = 0.16 to 0.49) were all associated with a lower risk. A head size of 32 mm was associated with a higher risk of dislocation (OR = 1.27; CI = 1.10 to 1.46) than 36-mm heads, whereas dual-mobility cups had a reduced risk (OR = 0.13; CI = 0.05 to 0.36).

CONCLUSIONS

We found the "true" cumulative incidence of dislocations within 2 years after primary THAs performed between 2010 and 2014 in Denmark to be 3.5%. Age, sex, American Society of Anesthesiologists (ASA) score, head size and type, fixation method, and surgical approach were independent significant factors for dislocation. Comprehensive search algorithms are needed in order to identify all dislocations so that this complication can be accurately reported in national registers.

Outcome of Dual Mobility Constructs for Adverse Local Tissue Reaction Associated Abductor Deficiency in Revision Total Hip Arthroplasty

BACKGROUND

Treatment of adverse local tissue reaction (ALTR) is challenging owing to high complications and poor outcomes after a revision surgery. As dislocation is the most common cause of reoperation, it is often necessary to use advanced articulations such as dual mobility. This study aims to evaluate the outcome and complication rates after revision surgery with dual mobility constructs, compared to constrained and conventional articulations in the setting of significant abductor deficiency due to ALTR.

METHODS

Out of a total of 338 revision total hip arthroplasties for ALTR, 234 patients with a significant tissue necrosis and abductor muscle insufficiency (grade 3) were evaluated. The complication rates after revisions were compared between 42 hips with dual mobility implants, 24 hips with constrained liners, 104 hips with large diameter heads (36-40 mm), and 64 hips with small diameter heads (≤32 mm).

RESULTS

After an average of 4 years of follow-up (2.8-8.6), the dual mobility articulation had no dislocation, compared to 4.1% and 15.5% for constrained liner and conventional articulations, respectively (P < .001). Utilization of dual mobility and constrained liner cup also did not increase the risk of nondislocation complications, including periprosthetic joint infection and periprosthetic fracture (P = .18 and .52).

CONCLUSIONS

This study demonstrates significantly lower dislocation rates for dual mobility when compared to conventional articulations and comparable to constrained liners in cases of severe abductor deficiency due to ALTR, suggesting that dual mobility implants are viable surgical treatment alternatives to constrained liners to minimize dislocation during revision total hip arthroplasty in the setting of significant abductor deficiency due to ALTR.

Large Diameter Head in Primary Total Hip Arthroplasty: A Systematic Review

INTRODUCTION

The literature around use of Large Diameter Heads (LDH) is abundantly available for revision Total Hip Arthroplasty (THA) but is lacking for primary uncomplicated THA. This systematic review was undertaken to synthesize data around primary THA involving LDH and analyze the associated complications (dislocation, volumetric wear, implant survivorship and functional score) along with reported effects on range of motion (ROM), patient reported outcomes and impingement rate/groin pain.

METHODS

A PRISMA compliant systematic review was done using extensive search in PubMed database, along with offline search looking for the literature published in English language between 2008 and 2018. The articles providing data on the use of large diameter heads (LDH) (36 mm or larger) on various bearing surfaces were collected. This included robust national joint registries of different countries. Narrative approach to data synthesis was used.

RESULTS

A total of 23 papers met our inclusion criteria, including six national joint registries. It was observed that LDH had significantly low dislocation rates, excellent implant survival rate as per Kaplan-Meier survivorship (> 90% at five years). Surgical approaches, except Minimally Invasive Surgery (MIS), did not increase any risk of dislocation as long as it was meticulously repaired. There was no significant improvement in any functional scores or improved ROM.

CONCLUSIONS

LDH of 32-36 mm are now commonly used in primary THA and is accepted as a popular size. The beneficial effects of a large head size are negated beyond 38 mm. The most favored size for LDH THA, therefore, is 36 mm contrary to the older literature favoring 28 mm.

A Protocol of Pose Avoidance in Place of Hip Precautions After Posterior-Approach Total Hip Arthroplasty May Not Increase Risk of Post-operative Dislocation

BACKGROUND

Post-operative rehabilitation after posterior-approach total hip arthroplasty (P-THA) includes the use of standard hip precautions, defined as no hip flexion beyond 90°, hip adduction, or hip internal rotation for 6 to 12 weeks after surgery (sometimes for life). Since they were first implemented in the 1970s, subsequent advances may have made standard hip precautions no longer necessary, although little evidence supports that hypothesis. A modified set of precautions, a "pose avoidance protocol," could be effective in enhancing recovery, but its effectiveness on early dislocation and post-surgical outcomes is not known.

QUESTIONS/PURPOSES

We sought to determine the functional recovery of patients on a pose avoidance protocol after P-THA according to levels of pain and patient satisfaction, rates of dislocation, the use of assistive devices, and a return to driving.

METHODS

We conducted a retrospective, descriptive study of data from a consecutive case series of 164 patients treated by a single surgeon between January 2014 and December 2015. Patients who had undergone a primary uncemented P-THA were prescribed a pose avoidance protocol and followed for a minimum of 6 weeks. Exclusion criteria were patients with congenital hip dysplasia, revision THA, femoral neck fracture, rheumatoid arthritis, or neuromuscular disease. Changes to the rehabilitation protocol included elimination of the requirements to use elevated chairs, raised toilet seats, and abduction pillows for sleeping. Patients could resume driving at 2 and 3 weeks for left and right P-THA, respectively. The only motion restriction was avoiding the combination of hip flexion past 90°, hip adduction, and hip internal rotation. Patients could perform all other movements and to bear weight and stop using walking aids as tolerated. Patients completed a biweekly questionnaire to assess their functional recovery, opioid use, and pain levels.

RESULTS

At 2 weeks after surgery, 80% of patients reported no pain, 86% did not require walking aids, and 92% were satisfied with their recovery. At 6 weeks after surgery, 89% of patients reported no pain. Patients returned to driving at a mean of 2.7 weeks after surgery. No patients had experienced a dislocation at 6 weeks of follow-up.

CONCLUSION

A pose avoidance rehabilitation protocol in this P-THA population was found to be safe and was associated with accelerated functional recovery and high patient satisfaction without increased risk of early post-operative dislocation.

Effect of Femoral Head Size, Subject Weight, and Activity Level on Acetabular Cement Mantle Stress Following Total Hip Arthroplasty

In cases where cemented components are used in total hip arthroplasty, damage, or disruption of the cement mantle can lead to aseptic loosening and joint failure. Currently, the relationship between subject activity level, obesity, and prosthetic femoral head size and the risk of aseptic loosening of the acetabular component in cemented total hip arthroplasty is not well understood. This study aims to provide an insight into this. Finite element models, validated with experimental data, were developed to investigate stresses in the acetabular cement mantle and pelvic bone resulting from the use of three prosthetic femoral head sizes, during a variety of daily activities and one high impact activity (stumbling) for a range of subject body weights. We found that stresses in the superior quadrants of the cortical bone-cement interface increased with prosthetic head size, patient weight, and activity level. In stumbling, average von Mises stresses (22.4 MPa) exceeded the bone cement yield strength for an obese subject (143 kg) indicating that the cement mantle would fail. Our results support the view that obesity and activity level are potential risk factors for aseptic loosening of the acetabular component and provide insight into the increased risk of joint failure associated with larger prosthetic femoral heads. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1771-1783, 2019.

Causes of and treatment options for dislocation following total hip arthroplasty

The second most common complication following total hip arthroplasty (THA) is dislocation. The majority of dislocations occur early in the post-operative period and are due to either patient-associated or surgical factors. The patient-associated factors that have been implicated as causes of post-operative dislocation include previous surgery, lumbar spine fusion surgery and/or neurological impairment. The surgical factors include surgical approach, component orientation and prosthetic and/or bony impingement. In order to delineate the cause of the hip instability a thorough history and physical and a radiographic assessment (possibly including advanced imaging) needs to be performed. Approximately two thirds of cases are successfully treated; one third of cases will require surgical treatment (e.g., revision arthroplasty (including constrained liners, the use of elevated rim liners and dual mobility implants or trochanteric advancement). In this review, we discuss the causes leading to dislocation following THA and evaluate the different treatment options available.

The Role of Crosslinked Polyethylene in Reducing Aggregated Costs of Total Hip Arthroplasty in the United States

BACKGROUND

Widespread adoption of crosslinked polyethylene for the acetabular articular surface for total hip arthroplasty has substantially reduced revision rates and dislocation rates. We aim to provide estimates of the resulting magnitude of the annual reduction in aggregated costs of total hip arthroplasty surgery in the United States.

METHODS

After we obtained, from the literature, the contrasting mid-term rates of revisions and dislocations of total hip arthroplasty using conventional polyethylene vs those using crosslinked polyethylene, specifically from only registry studies and prospective, randomized controlled studies, we multiplied these incidence figures by the cost estimates of these failures to generate approximations of the cost savings in the United States from the use of crosslinked polyethylene.

RESULTS

The estimates suggest that in the United States these savings might be one billion dollars per annual cohort over a 15-year duration.

CONCLUSION

The use of crosslinked polyethylene has reduced substantially the overall costs of total hip arthroplasty surgery in the United States.

Plain radiography findings to predict dislocation after total hip arthroplasty

Background

With the improvements of modern surgical techniques and hip prosthesis, the causes for dislocation after total hip arthroplasty (THA) have changed. The aim of this retrospective analysis was to identify new plain radiography findings to predict dislocation after THA.

Methods

Five thousand five hundred thirteen consecutive primary THAs performed between January 2000 and December 2014 were reviewed through a nested case–control study design. Among them, 38 patients with 39 hip dislocations (dislocation group) were selected and matched to 78 hips in 78 patients without dislocation (control group). The factors that might influence the prosthetic stability were identified by univariate analyses, and a multivariate logistic regression analysis was performed to determine the odds ratio of each factor.

Results

The difference of the cup position was not statistically significant. The newly identified risk factors were the following: preoperative hip adduction deformity combined with limb lengthening of 2 cm postoperatively; a knee valgus combined with pelvic obliquity deformity and bilateral pathological hips.

Conclusions

Patients with soft tissue imbalance, across joint deformity around hips and bilateral pathological hips seem more predisposed to suffer from dislocation after THA. Appropriate surgical intervention strategies along with meticulously postoperative management may help preventing dislocation after THA.

The translational potential of this article

A better understanding of the probable causes of dislocation after THA proposed a new clinical application of plain radiography. This radiography-related clinical research may reveal the novel mechanism of dislocation after THA and new preventive measures.

Unexpected dislocation following accurate total hip arthroplasty caused by excessive hip joint laxity during myasthenic crisis: a case report

BACKGROUND

Dislocation following total hip arthroplasty is mainly caused by malposition. However, the coexistence of neuromuscular disorders is also considered a risk for dislocation due to excessive hip joint laxity. To minimize risk of dislocation, preoperative planning using combined anteversion has been widely used. The recommended combined anteversion angle (the total of cup and stem anteversion angles) is 50 ± 10°.

CASE PRESENTATION

A 33-year-old Japanese woman underwent elective total hip arthroplasty due to osteonecrosis of the femoral head associated with corticosteroid pulse therapy for myasthenia gravis. Intraoperatively, no tendency of dislocation was found when simulating an evoking position under general anesthesia. In postoperative X-ray and computed tomography scans, cup inclination, cup anteversion, and stem anteversion angles were 37°, 13°, and 35° respectively. The resulting combined anteversion was 48°, which was set as the target along with accurate placement. Her postoperative course was normal and she was discharged without adverse events. Three months postoperatively, due to worsening of myasthenic weakness in her lower extremities while resting, she tended to raise her left limb up using both hands for sitting up. An anterior dislocation occurred when her legs were in a figure-of-four position. She was brought to an emergency department, and reduction of dislocation was performed. It was inferred that myasthenic crisis in the affected limb enabled excessive passive motion due to joint hyperlaxity. At the end of 2016, elective total hip arthroplasty on the contralateral side was performed. Cup anteversion, stem anteversion, and the combined anteversion angles were 27°, 24°, and 51° respectively. We instructed her to exercise care during passive leg movement, which may worsen her myasthenic condition. She returned to a normal life and was able to walk long distances without a cane. No recurrence of dislocation was seen at final follow-up.

CONCLUSIONS

Even if accurate component orientation is attained in total hip arthroplasty, patients with neuromuscular disorders such as myasthenia gravis have a potential risk of muscle weakness in the affected limb. Therefore, physicians' instructions and patients' careful attention are required to prevent dislocation due to excessive hip joint laxity under conditions of motor weakness.

Cement interface and bone stress in total hip arthroplasty: Relationship to head size

The use of larger prosthetic femoral heads in total hip arthroplasty (THA) has increased considerably in recent years in response to the need to improve joint stability and reduce risk of dislocation. However, data suggests larger femoral heads are associated with higher joint failure rates. For cemented implants, ensuring the continued integrity of the cement mantle is key to long term fixation. This paper describes an investigation into the effect of variation in femoral head size on stresses in the acetabular cement mantle and pelvic bone. Three commonly used femoral head sizes: 28, 32, and 36 mm diameter were investigated. The study was undertaken using a finite element model validated using surface strains obtained from Digital Image Correlation (DIC) during experimentation on a composite hemipelvis implanted with a cemented all-polyethylene acetabular cup. Following validation, the models were used to investigate stresses in the pelvic bone and acetabular cement mantle resulting from two loading scenarios; an average weight subject (700 N) and an overweight subject (1,000 N) undertaking a single leg stand. We found that the highest peak stresses occurred in the anterosuperior and posterosuperior regions of the bone-cement interface, in the line of action of the load, where debonding usually initiates. Stress on the cortical bone-cement interface increased with femoral head diameter by up to 9% whilst stresses in the trabecular bone remained relatively invariant. Our findings may help to explain higher joint failure rates associated with larger femoral heads. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2966-2977, 2018.

Excellent results of large-diameter ceramic-on-ceramic bearings in total hip arthroplasty

Aims

This study reports the mid-term results of total hip arthroplasty (THA) performed using a monoblock acetabular component with a large-diameter head (LDH) ceramic-on-ceramic (CoC) bearing.

Patients and Methods

Of the 276 hips (246 patients) included in this study, 264 (96%) were reviewed at a mean of 67 months (48 to 79) postoperatively. Procedures were performed with a mini posterior approach. Clinical and radiological outcomes were recorded at regular intervals. A noise assessment questionnaire was completed at last follow-up.

Results

There were four re-operations (1%) including one early revision for insufficient primary fixation (0.4%). No hip dislocation was reported. The mean University of California, Los Angeles (UCLA) activity score, 12-Item Short-Form Health Survey (SF-12) Mental Component Summary (MCS) score, SF-12 Physical Component Summary (PCS) score, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score, and Forgotten Joint Score (FJS) were 6.6 (2 to 10), 52.8 (25.5 to 65.7), 53.0 (27.2 to 66.5), 7.7 (0 to 63), and 88.5 (23 to 100), respectively. No signs of loosening or osteolysis were observed on radiological review. The incidence of squeaking was 23% (n = 51/225). Squeaking was significantly associated with larger head diameter (p < 0.001), younger age (p < 0.001), higher SF-12 PCS (p < 0.001), and UCLA scores (p < 0.001). Squeaking did not affect patient satisfaction, with 100% of the squeaking hips satisfied with the surgery.

Conclusion

LDH CoC THAs have demonstrated excellent functional outcomes at medium-term follow-up, with very low revision rate and no dislocations. The high incidence of squeaking did not affect patient satisfaction or function. LDH CoC with a monoblock acetabular component has the potential to provide long term implant survivorship with unrestricted activity, while avoiding implant impingement, liner fracture at insertion, and hip instability. Cite this article: Bone Joint J 2018;100-B:1434–41.

A Survey of the Prevalence of and Techniques to Prevent Trunnionosis

Trunnionosis of total hip arthroplasty (THA) components has been an increasingly reported complication. Consensus is lacking regarding preventive practices and the overall incidence of trunnionosis. In this study, fellowship-trained adult reconstruction orthopedic surgeons were surveyed to identify expert opinions. A 25-question, web-based survey regarding trunnionosis incidence, prevention, and biomaterials was sent to 345 fellowship-trained adult reconstruction orthopedic surgeons in North America. The survey yielded 151 (43.8%) responses from surgeons with a mean of 11.97±9.49 years of experience. These surgeons believe that the material composite of the head-neck junction is the most important contributor to trunnionosis. They often choose a ceramic head with a metal alloy stem to reduce trunnionosis. They more commonly impact the femoral head 3 times than once. Fifty-one percent believe that trunnionosis leads to THA failure for between 0% and 2% of all THA revisions, whereas 48.3% believe that the failure rate is greater than 2%. More than half (53.6%) of these surgeons recommend a revision THA if a patient's serum cobalt level is greater than 10 µg/L, regardless of symptom presence. The incidence of trunnionosis appears to be increasing due to changes in implants and/or an increased awareness of the problem, with 48.3% of these surgeons believing that trunnionosis is the primary cause of THA failure for more than 1 in 50 patients. Some suggested preventive measures include cleaning and drying the trunnion, using ceramic femoral heads, matching THA components, and adding titanium sleeves on well-fixed stems that are retained during revision surgery. [Orthopedics. 2018; 41(4):e557-e562.].

Mid-Term Outcomes of Dual Mobility Acetabular Cups for Revision Total Hip Arthroplasty

BACKGROUND

This study evaluated (1) survivorship, (2) clinical outcomes, (3) complications, and (4) radiographic outcomes of dual mobility (DM) systems when compared to fixed-bearing prostheses in revision total hip arthroplasty (THA).

METHODS

A cohort of 85 patients who underwent revision THA using DM implants were compared to a prior matching cohort of 170 patients who received fixed-bearing implants. Mean follow-up time was 4 years in the DM cohort and 10 years in the fixed-bearing cohort. Kaplan-Meier analysis was performed to assess survivorships. Clinical outcomes were evaluated using the Harris Hip Score (HHS). Complications and radiographs were evaluated and reported at the final follow-up.

RESULTS

Overall aseptic and all-cause survivorships of the DM cohort were 96.5% and 95.3% compared to 94.7% and 93.5% in fixed-bearing cohort (P = .01 for aseptic and all-cause survivorships). The DM cohort had statistically significant higher survivorship when compared at equivalent follow-up interval in the fixed-bearing cohort. There were 3 aseptic (one due to dislocation) and 1 septic revision in the DM cohort compared to 9 aseptic (6 due to dislocation) and 2 septic revisions in the fixed-bearing cohort. Postoperative HHS scores were 88 and 86 points in the DM and fixed-bearing cohorts. However, the difference in mean improvement in HHS scores from preoperative to postoperative (ΔHHS) was not statistically significant (35 vs 34, P = .533). Except for the aforementioned revisions, there were no progressive radiolucencies or osteolysis on radiographic evaluation in both cohorts.

CONCLUSION

DM articulations demonstrated superior survivorship at equal follow-up intervals when compared to fixed-bearing implants and showed a trend toward lower dislocation rates.

Short-term Outcomes of Ceramic Coated Metal-on-Metal Large Head in Total Hip Replacement Arthroplasty

Purpose

This study characterizes the short-term outcomes of ceramic coated metal-on-metal (MoM) large head total hip arthroplasty (THA) in prospectively selected patients aged 70 to 75 years.

Materials and Methods

Eighteen patients (18 hips) between the ages of 70 and 75-years old with THA using ceramic-coated MoM large heads between June 2014 and December 2014 were evaluated. We prospectively selected patients younger than 70 years for bipolar hemiarthroplasty and older than 75 years for conventional THA. There were one case of osteoarthritis, 8 cases of femur neck fracture, and 9 cases of intertrochanteric fracture. All patients underwent clinical and radiological follow-up at 6 weeks, 6 and 12 months, and every year postoperatively. The mean duration of follow-up was 24.2 months (range, 18–34 months).

Results

The average Harris hip score at the final follow-up was 81.0, except one case which was ultimately converted to conventional THA due to acetabular cup loosening. Radiographically, mean acetabular cup inclination was 45.8°(range, 38–56°) and anteversion was 20.1° (range, 11–25°). The average femoral head size was 48.7 mm. All stems were neutral-positioned except 1 varus-positioned stem. There was 1 case of a soft tissue infection, 3 patients complained of persistent groin pain, and no dislocations occurred.

Conclusion

Ceramic coated large MOM articulation (ACCIS) have many complications: cup loosening, groin pain, which can lead to fatal outcomes in the elderly patients. Especially in patients with communicated intertrochanter fracture (AO 31-A22, 23), careful attention should be paid to the choice of surgical option.

High Risk of Readmission in Octogenarians Undergoing Primary Hip Arthroplasty

BACKGROUND

As life expectancy increases, more elderly patients with end-stage hip arthritis are electing to undergo primary THA. Octogenarians undergoing THA have more comorbidities than younger patients, but this is not reflected in risk adjustment models for bundled care programs. The burden of care associated with THA in octogenarians has not been well characterized, and doing so may help these value-based programs make adjustments so that this vulnerable patient population does not risk losing access under accountable care models.

QUESTIONS/PURPOSES

The purpose of this study was to describe care use, comorbidities, and complications among octogenarians undergoing primary THA.

METHODS

Five percent of the Medicare national administrative claims data was queried to identify patients diagnosed with hip osteoarthritis between January 1, 1998, and December 31, 2013. Patients who underwent primary THA were identified and followed longitudinally during the study period using their unique, encrypted Medicare beneficiary identifiers. We compared risk factors and complications between the octogenarian group versus those aged 65 to 69 years. Multivariate Cox regression was used to evaluate the effect of patient/hospital factors on risk of revision, periprosthetic joint infection, dislocation, venous thromboembolism (VTE), and mortality. Patient factors in the model included age, sex, race, region, socioeconomic status, and health status based on Charlson comorbidity score 12 months before replacement surgery.

RESULTS

There were 11,960 THAs in the octogenarians in 1998, which increased to 21,620 in 2013, an 81% increase during this study period. Octogenarians were more likely to have a Charlson score of 3 or higher than those patients aged 65 to 69 years (30% versus 17%, odds ratio [OR] 2.07 [1.98-2.20]; p < 0.001), and they were more likely to have coronary artery disease or congestive heart failure (47% versus 29%, OR 2.16 [2.06-2.26]; p < 0.001). The octogenarian group had a greater risk of dislocation (+12%, p = 0.01), VTE (+14%, p < 0.001), and mortality (+150%, p < 0.001) compared with the younger age cohort. A total of 21% of the octogenarians were readmitted after surgery compared with 12% for patients in the younger group (OR=1.64, 95% confidence interval 1.54-1.75; p < 0.001).

CONCLUSIONS

Because octogenarians are at increased risk of dislocation, VTE, medical complications, and mortality after THA, value-based care models that penalize hospitals for readmissions and complications may inadvertently result in loss of access to care for this group of patients as a result of the financial makeup of these bundled care models. Value-based care models were developed to improve care and decrease healthcare costs but may have unintended consequences in the octogenarian with higher complication and readmission risks. Financial losses may lead to institutions from withdrawing from the Bundled Payments for Care Improvement program. To try to prevent this from happening to this vulnerable patient population, bundled care programs should evolve and be modified to allow for risk stratification in the overall payment formula to account for increased age and comorbid conditions to ensure continued successful participation in the program among all the stakeholders.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Trends in total hip arthroplasty in young patients - results from a regional register

INTRODUCTION

In the United Kingdom, over 83,000 primary total hip arthroplasties (THAs) were performed last year, of which 20% are in patients under the age of 60 years. These patients generally have a longer life expectancy and a higher activity level than an older cohort, which may potentially translate to higher revision rates.

METHODS

We reviewed our Trent regional arthroplasty register to assess current surgical practice in younger patients undergoing total hip arthroplasty. The results were compared to a previous study published in 2005.

RESULTS

Between 2010 and 2012, 1,097 primary THAs were performed on patients aged 54 or less. There was an equal cohort of males to females with a mean age of 46 years of patients undergoing THA. Osteoarthritis was the commonest aetiology for patients having surgery. Reviewing the components used there were 32 different femoral and 30 different acetabular types along with 70 different combinations of components. There were 608 uncemented THAs, 313 hybrid THRs, 98 cemented THAs, 67 resurfacing arthroplasties and 11 reverse hybrid THAs.

DISCUSSION

The majority of implants were uncemented in both femur and acetabulum with consultants performing most of the procedures. There is a clear preference for uncemented femoral and acetabular fixation in the younger patient, and the trend towards uncemented components has increased over the last 10 years amongst the same surgeons. There continues to be a wide variety of cup and stem usage along with many different combinations of components, with no consensus on the ideal combination.

Effect of femoral head size and surgical approach on risk of revision for dislocation after total hip arthroplasty

Background and purpose - Recurrent dislocation is the commonest cause of early revision of a total hip arthropasty (THA). We examined the effect of femoral head size and surgical approach on revision rate for dislocation, and for other reasons, after total hip arthroplasty (THA). Patients and methods - We analyzed data on 166,231 primary THAs and 3,754 subsequent revision THAs performed between 2007 and 2015, registered in the Dutch Arthroplasty Register (LROI). Revision rate for dislocation, and for all other causes, were calculated by competing-risk analysis at 6-year follow-up. Multivariable Cox proportional hazard regression ratios (HRs) were used for comparisons. Results - Posterolateral approach was associated with higher dislocation revision risk (HR =1) than straight lateral, anterolateral, and anterior approaches (HR =0.5-0.6). However, the risk of revision for all other reasons (especially stem loosening) was higher with anterior and anterolateral approaches (HR =1.2) and lowest with posterolateral approach (HR =1). For all approaches, 32-mm heads reduced the risk of revision for dislocation compared to 22- to 28-mm heads (HR =1 and 1.6, respectively), while the risk of revision for other causes remained unchanged. 36-mm heads increasingly reduced the risk of revision for dislocation but only with the posterolateral approach (HR =0.6), while the risk of revision for other reasons was unchanged. With the anterior approach, 36-mm heads increased the risk of revision for other reasons (HR =1.5). Interpretation - Compared to the posterolateral approach, direct anterior and anterolateral approaches reduce the risk of revision for dislocation, but at the cost of more stem revisions and other revisions. For all approaches, there is benefit in using 32-mm heads instead of 22- to 28-mm heads. For the posterolateral approach, 36-mm heads can safely further reduce the risk of revision for dislocation.

Constrained liners, dual mobility or large diameter heads to avoid dislocation in THA

Dislocation remains a common cause of failure after total hip arthroplasty. The limitations of existing approaches to address instability have led to the development of powerfull options: constrained liners, dual mobility and large heads. These implant-related options have proven to be very efficient, but have raised concerns.With constrained liners, restricted range of motion (ROM) is responsible for impingement leading to high likelihood of failure, depending on the design, with various failure modes.Improvements of the bearing materials have addressed some of the concerns about increased volumetric wear of conventional polyethylene and offer an option to reduce instability: large diameter heads have the advantage of increased ROM before impingement, increased head-neck ratio, and jump distance. Highly cross-linked polyethylene helps address the risk for increased wear, and also large heads provide improved stability without the risk of mechanical failures observed with constrained liners. However, the increase of the head size remains limited as reducing the thickness of the liner may lead to fractures. In addition, the jump distance decreases as the cup abduction increases.The dual mobility concept simultaneously attempts to address head-neck ratio, constraint, and jump distance. Despite the need for longer follow-up, concerns raised about potential increased wear and intra-prosthetic dislocation with first generation implants have been addressed with modern designs.With a dramatic increase of the head-neck ratio whilst reducing the risk of mechanical failure or excessive wear, dual mobility THA outperforms large diameter heads and constrained liners at 10 years follow-up. For these reasons, dual mobility continues to gain interest worldwide and is becoming the most popular option to manage instability. Cite this article: Guyen O. Constrained liners, dual mobility or large diameter heads to avoid dislocation in THA. EFORT Open Rev 2016;1:197-204. DOI: 10.1302/2058-5241.1.000054.

Alumina Delta-on-Alumina Delta Bearing in Cementless Total Hip Arthroplasty in Patients Aged <50 Years

BACKGROUND

There are limited studies to evaluate long-term clinical and radiographic outcomes of alumina delta ceramic-on-ceramic bearings in cementless total hip arthroplasty (THA). The purpose of this study was to evaluate the clinical and radiographic results, prevalence of osteolysis, squeaking, and fracture of ceramic material associated with the use of the alumina delta ceramic-on-alumina delta ceramic bearing in cementless THA in patients aged <50 years.

METHODS

We reviewed the cases of 277 patients (334 hips) who underwent a cementless THA using alumina delta ceramic-on-alumina delta ceramic when they were 50 years or younger at the time of surgery. Demographic data; Harris Hip Score; Western Ontario McMaster Universities Osteoarthritis Index; and University of California, Los Angeles activity score were recorded. Radiographic and computerized tomographic evaluations were used to evaluate implant fixation and osteolysis. Squeaking sound and ceramic fracture were documented. The mean follow-up was 7.8 years (range, 6-9).

RESULTS

The mean postoperative Harris Hip Score, Western Ontario and McMaster Universities Osteoarthritis Index score, University of California, Los Angeles activity score were 93 points, 15 points, and 8.6 points, respectively. Two patients had thigh pain (grade 7 points). All acetabular components and all but 2 femoral components were well fixed. Thirty-three hips (10%) exhibited clicking sound, and 2 hips (0.6%) exhibited squeaking sound. No hip had osteolysis or ceramic head or liner fracture.

CONCLUSION

Our minimum 6-year follow-up results with the use of alumina delta ceramic-on-alumina delta ceramic bearings in patients aged <50 years suggest that cementless THA provides a high rate of survivorship without evidence of osteolysis or fracture of ceramic material.

Is there any range-of-motion advantage to using bearings larger than 36mm in primary hip arthroplasty: A case-control study comparing 36-mm and large-diameter heads

BACKGROUND

Large-diameter (>36mm) total hip arthroplasty (THA) has developed rapidly since the advent of ceramic-on-ceramic (CoC) bearings and highly cross-linked polyethylene. Theoretically, the increase in diameter reduces the risk of instability, although the advantage of calibers beyond 36mm has not been demonstrated in terms of range-of-motion recovery. We conducted a comparative study with a single prosthesis model to determine whether increasing the caliber beyond 36mm provides: (1) better recovery of range-of-motion, (2) a higher functional score, and (3) reduction of the dislocation rate.

HYPOTHESIS

Increasing the range-of-motion by increasing the caliber beyond 36mm provides better range-of-motion.

MATERIAL AND METHODS

We analyzed two consecutive, single-operator cementless THA series performed via the mini posterior approach, which differed only in the bearing system (51 metal-on-metal [MoM] with a mean caliber of 45mm±3.3 [range, 40-54] and 61 CoC with a 36-mm caliber). Both series were comparable preoperatively in terms of age, diagnosis, functional scores, preoperative range-of-motion, body mass index, UCLA activity level, and Charnley score. We compared the joint range of movement at follow-up and the gains in range of movement, onset of dislocation, and functional scores (Oxford, Postel-Merle d'Aubigné [PMA]).

RESULTS

The mean overall joint range-of-motion was 254°±39° (range, 150-310°) for an 81°±44° (range, -50 to 180°) gain in the MoM group and 256°±23° (range, 200-280°) for an 84°±40° (range, 0-160°) gain in the CoC group (NS). The MoM group presented the following results: Oxford=13.71±3.66 (range, 12-33) for a gain of 24.82 points±7.9 (range, -1 to 40), PMA=17.75±1.06 (range, 11-18) for a gain of 7.78 points±4.01 (range, 2-15). The CoC group had: Oxford=14.98±4.42 (range, 12-36) for a gain of 24.75 points±6.55 (range, 12-40), PMA 17.66±0.7 (range, 14-18) for a gain of 8 points±3.77 (range, 1-15). None of the gains and scores at follow-up differed significantly between the two groups. No episode of dislocation was identified.

DISCUSSION

The current trend of increasing femoral head diameters beyond 36mm to improve the gains in joint range-of-motion and function is not warranted. The potential side effects of increasing the caliber call for even greater caution in the use of large-diameter heads because our hypothesis has not been confirmed.

LEVEL OF EVIDENCE

Case-control study, level III.

Alumina Delta-on-Alumina Delta Bearing in Cementless Total Hip Arthroplasty in Patients Aged <50 Years

BACKGROUND

There are limited studies to evaluate long-term clinical and radiographic outcomes of alumina delta ceramic-on-ceramic bearings in cementless total hip arthroplasty (THA). The purpose of this study was to evaluate the clinical and radiographic results, prevalence of osteolysis, squeaking, and fracture of ceramic material associated with the use of the alumina delta ceramic-on-alumina delta ceramic bearing in cementless THA in patients aged <50 years.

METHODS

We reviewed the cases of 277 patients (334 hips) who underwent a cementless THA using alumina delta ceramic-on-alumina delta ceramic when they were 50 years or younger at the time of surgery. Demographic data; Harris Hip Score; Western Ontario McMaster Universities Osteoarthritis Index; and University of California, Los Angeles activity score were recorded. Radiographic and computerized tomographic evaluations were used to evaluate implant fixation and osteolysis. Squeaking sound and ceramic fracture were documented. The mean follow-up was 13.1 years (range, 10-14).

RESULTS

The mean postoperative Harris Hip Score, Western Ontario and McMaster Universities Osteoarthritis Index score, University of California, Los Angeles activity score were 93 points, 15 points, and 8.6 points, respectively. Two patients had thigh pain (grade 7 points). All acetabular components and all but 2 femoral components were well fixed. Thirty-three hips (10%) exhibited clicking sound, and 2 hips (0.6%) exhibited squeaking sound. No hip had osteolysis or ceramic head or liner fracture.

CONCLUSION

Our minimum 10-year follow-up results with the use of alumina delta ceramic-on-alumina delta ceramic bearings in patients aged <50 years suggest that cementless THA provides a high rate of survivorship without evidence of osteolysis or fracture of ceramic material.

[Larger heads compensate for an increased risk of THA dislocation in high-risk patients]

BACKGROUND

Dislocation is a devastating complication after total hip arthroplasty (THA) and occurs in 2-5% of primary THA cases and 5-10% of revision THA cases. Assuming correct implantation, dislocation risk can be reduced primarily by capsular repair and the use of larger prosthetic heads. However, larger heads are also associated with risks like accelerated wear or implant loosening, which is why heads with a maximum diameter of 36 mm are currently standard in primary THA. In cases with high dislocation risk, the use of 40 mm and 44 mm heads should be considered.

OBJECTIVES

This study aimed to quantify THA dislocation risk and retrospectively analyze the course of disease in high-risk patients treated with 40 mm or 44 mm femoral heads after primary or revision THA, concerning dislocation and other complications suffered.

MATERIALS AND METHODS

All patients with increased THA dislocation risk, treated from 2009-2014, were evaluated regarding dislocations. The cases with installation of 40 mm or 44 mm prosthetic heads were classified using a self-developed 5-level risk score and retrospectively analyzed.

RESULTS

During the observation period, 288 THA interventions with increased dislocation risk were performed. In 278 cases with ball diameters ≤ 36 mm the dislocation rate was 15.1% (n=42). In 10 high dislocation-risk cases (3A to 4B according to recommended scoring system), 40 mm and 44 mm heads were used. After a 22.8 month mean follow-up, no THA dislocations were reported.

CONCLUSION

Our results with 40 and 44 mm heads and the existing literature confirm much higher joint stability and, thus, significantly reduced dislocation risk with larger prosthetic heads in THA. Their use is, therefore, justified in high-risk patients and should be considered in future THA.

Is There a Benefit to Head Size Greater Than 36 mm in Total Hip Arthroplasty?

This study compares the rate of dislocation and revision for instability between 36-mm and anatomic femoral heads (large diameter metal-on-metal THA, dual-mobility bearings, and hip resurfacing arthroplasty) in patients at high risk for dislocation. A total of 501 high-risk patients, over a 10-year period, were identified (282 36-mm THA, 24 dual-mobility bearings, 83 metal-on-metal arthroplasty, and 112 hip resurfacing arthroplasty). There were 13 dislocations in the 36-mm group compared to 1 in the anatomic group (4.6% vs 0.5%; P = .005). Four patients dislocated more than once in the 36-mm group (1.4% vs 0%; P = .04), and 2 patients in the 36-mm group required a revision for instability (0.7% vs 0%; P = .11). These results suggest that anatomic head sizes significantly lower the risk of dislocation in high-risk patients.

Anterior and Anterolateral Approaches for THA Are Associated With Lower Dislocation Risk Without Higher Revision Risk

BACKGROUND

Lack of consensus continues regarding the benefit of anteriorly based surgical approaches for primary total hip arthroplasty (THA). The purpose of this study was to evaluate the risk of aseptic revision, septic revision, and dislocations for various approaches used in primary THAs from a community-based healthcare organization.

QUESTIONS/PURPOSES

(1) What is the incidence of aseptic revision, septic revision, and dislocation for primary THA in a large community-based healthcare organization? (2) Does the risk of aseptic revision, septic revision, and dislocation vary by THA surgical approach?

METHODS

The Kaiser Permanente Total Joint Replacement Registry was used to identify primary THAs performed between April 1, 2001 and December 31, 2011. Endpoints were septic revisions, aseptic revisions, and dislocations. The exposure of interest was surgical approach (posterior, anterolateral, direct lateral, direct anterior). Patient, implant, surgeon, and hospital factors were evaluated as possible confounders. Survival analysis was performed with marginal multivariate Cox models. Hazard ratios (HRs) and 95% confidence intervals (CIs) are reported. A total of 42,438 primary THAs were available for analysis of revision outcomes and 22,237 for dislocation. Median followup was 3 years (interquartile range, 1-5 years). The registry's voluntary participation is 95%. The most commonly used approach was posterior (75%, N = 31,747) followed by anterolateral (10%, N = 4226), direct anterior (4%, N = 1851), and direct lateral (2%, N = 667).

RESULTS

During the study period 785 hips (2%) were revised for aseptic reasons, 213 (0.5%) for septic reasons, and 276 (1%) experienced a dislocation. The revision rate per 100 years of observation was 0.54 for aseptic revisions, 0.15 for septic revisions, and 0.58 for dislocations. There were no differences in adjusted risk of revision (either septic or aseptic) across the different THA approaches. However, the anterolateral approach (adjusted HR, 0.29; 95% CI, 0.13-0.63, p = 0.002) and direct anterior approach (adjusted HR, 0.44; 95% CI, 0.22-0.87, p = 0.017) had a lower risk of dislocation relative to the posterior approach. There were no differences in any of the outcomes when comparing the direct anterior approach with the anterolateral approach.

CONCLUSIONS

Anterior and anterolateral surgical approaches had the advantage of a lower risk of dislocation without increasing the risk of early revision.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Dislocation following total hip replacement

BACKGROUND

Hip replacement ranks among the more successful operations on the musculoskeletal system, but it can have serious complications. A common one is dislocation of the total hip endoprosthesis, an event that arises in about 2% of patients within 1 year of the operation. Physicians should be aware of how this problem can be prevented and, if necessary, treated, so that the degree of trauma due to hip dislocation after hip replacement surgery can be kept to a minimum.

METHODS

The authors searched Medline selectively for pertinent publications and analyzed the annual reports of international endoprosthesis registries.

RESULTS

The rate of dislocation of primary hip replacements ranges from 0.2% to 10% per year, while that of artificial hip joints that have already been surgically revised can be as high as 28%, depending on the patient population, the follow-up interval, and the type of prosthesis. Patient-specific risk factors for displacement of a hip endoprosthesis include advanced age, accompanying neurologic disease, and impaired compliance. Patients should scrupulously avoid hip movements such as bending far forward from a standing position, or internal rotation of the flexed hip. Operation-specific risk factors include suboptimal implant position, insufficient soft-tissue tension, and inadequate experience of the surgeon. Conservative treatment is justified the first time dislocation occurs without any identifiable cause. If a mechanical cause of instability is found, then operative revision should be performed as recommended in a standardized treatment algorithm, because, otherwise, dislocation is likely to recur.

CONCLUSION

The dislocation of a total hip endoprosthesis is an emotionally traumatizing event that should be prevented if possible. Preoperative risk assessment should be performed and the operation should be performed with optimal technique, including the best possible physical configuration of implant components, soft-tissue balance, and an adequately experienced orthopedic surgeon.

Midterm Results of Delta Ceramic-on-Ceramic Total Hip Arthroplasty

This study reports mid-term results of Delta ceramic on ceramic (COC) in total hip arthroplasty (THA). Subjects received Delta COC THA in a prospective multi-center study with either 28 mm (n=177) or 36 mm (n=168) articulations. Annual clinical and radiographic evaluations were performed, and patients were asked about hip noises. At mean 5.3-year follow-up there were 3 (0.9%) post-operative liner fractures. Nine revisions were performed (2 liner fracture, 4 stem loosening, 3 deep infection). Kaplan-Meier survivorship at 6 years was 96.9% (94.0-98.4). Twenty-six (7.5%) subjects reported squeaking, of whom none were revised. One (0.3%) subject could reproduce a sound in clinic. More patients reported squeaking with a 36 mm bearing (28 mm: 7/177, 36 mm: 19/168, P=0.013).

Clinical and radiological outcomes with the Durom™ acetabular cup for large-diameter total hip arthroplasty: 177 implants after a mean of 80 months

BACKGROUND

Large-diameter metal-on-metal hip prostheses are no longer used, but their outcomes after more than 5 years are unknown. We conducted a retrospective study with a 6.8-year mean follow-up to assess clinical outcomes after Durom™ cup implantation, including the dislocation rate, comparatively to the reference metal-on-polyethylene bearing. We determined the rate of failure ascribable to Durom™ cup use. We also looked for a sharp drop in the implant survival curve during the follow-up period and for factors associated with adverse reactions to metal debris (ARMDs).

HYPOTHESIS

We hypothesised that clinical outcomes after Durom™ cup implantation were similar to those seen with a metal-on-polyethylene bearing, except for a lower rate of dislocation.

PATIENTS AND METHODS

We included 177 consecutive THA procedures that were performed between 2005 and 2008 in 165 patients with a mean age of 57.6 ± 9.4 years (range, 31-76 years) and involved the implantation of a Durom™ cup, a femoral head greater than 36mm in diameter, and a PF(®) femoral stem (Zimmer, Etupes, France). The mini-posterior approach was used, with 2mm of acetabular overreaming in 82% of cases, a short femoral neck in 75% of cases, and a mean cup inclination of 34 ± 5° (range, 21-50°).

RESULTS

Outcomes were assessed for 156 THA procedures in 146 patients after a mean follow-up of 6 years 8 months. The mean Postel-Merle d'Aubigné score improved from 9.7 ± 2.7 (range, 4-14) to 17.4 ± 1.7 (range, 15-18) and the mean Harris hip score from 45.2 ± 15.3 (range, 9-83) to 96.3 ± 7 (75-100). No episodes of dislocation were recorded. We identified 7 failures ascribable to the Durom™ cup including 6 due to ARMD and 1 to aseptic loosening. Implant survival after a mean of 80months was 95.5% (95% CI, 93.1-99.2), with no sharp drop in the survival curve.

CONCLUSION

The Durom™ cup eliminates the risk of hip dislocation and produces similar functional outcomes to those seen with metal-on-polyethylene bearings after a mean follow-up of 80 months. Nevertheless, given the difficulty in predicting ARMD and hypersensitivity reactions, the Durom™ cup has been discarded and patients carrying it are monitored closely.

No functional benefit of larger femoral heads and alternative bearings at 6 months following primary hip replacement

BACKGROUND AND PURPOSE

There has been a recent trend towards the use of greater femoral head sizes in an attempt to improve function and enhance stability after primary hip replacement. This has been associated with the use of alternative bearings, theoretically to reduce wear and improve implant longevity.

METHODS

We examined the influence of these variables on patient-reported outcome measures (PROMs) for a consecutive series of primary hip replacements using National Joint Registry (NJR) and PROMs-linked data. To minimize the confounding influence of implant design factors, the single most commonly used brand in England and Wales (DePuy Corail Pinnacle) was examined. Improvement in patient hip-specific outcomes (Oxford hip score, OHS), general health outcomes (Euroqol, EQ-5D), and rates of self-reported complications (bleeding, wound problems, re-admission, and reoperation) were compared for different head sizes (28-mm, 32-mm, and 36-mm) and bearings (metal-on-polyethylene (MoP), ceramic-on-polyethylene (CoP), and ceramic-on-ceramic (CoC)), adjusting for differences in case mix.

RESULTS

At a mean follow-up of 7 months, improvements in OHS and EQ5D index were similar for 28-mm and 36-mm heads. A 32-mm head was associated with poorer function (OHS: 20, 99% CI: 19-21, p = 0.002; EQ5D index: 0.39, 99% CI: 0.36-0.42, p = 0.004), although these small differences may not be of clinical importance. There were no statistically significant benefits of either CoP or CoC bearings compared to a MoP bearing. Complication rates were similar within comparisons of head sizes or bearings.

INTERPRETATION

In this short-term study, we did not find any functional benefits of larger head sizes or alternative bearings, after adjusting for other influences. We question their use in routine primary hip replacement given the lack of evidence of improved long-term survival in the literature.

Does dual-mobility cup geometry affect posterior horizontal dislocation distance?

BACKGROUND

Dual-mobility acetabular cups have been marketed with the purported advantages of reduced dislocation rates and improvements in ROM; however, the relative efficacies of these designs in terms of changing joint stability via ROM and dislocation distance have not been thoroughly evaluated.

QUESTIONS/PURPOSES

In custom computer simulation studies, we addressed the following questions: (1) Do variations in component geometry across dual-mobility designs (anatomic, modular, and subhemispheric) affect the posterior horizontal dislocation distances? (2) How do these compare with the measurements obtained with standard hemispheric fixed bearings? (3) What is the effect of head size on posterior horizontal dislocation distances for dual-mobility and standard hemispheric fixed bearings? (4) What are the comparative differences in prosthetic impingement-free ROM between three modern dual-mobility components (anatomic, modular, and subhemispheric), and standard hemispheric fixed bearings?

METHODS

CT scans of an adult pelvis were imported into computer-aided design software to generate a dynamic three-dimensional model of the pelvis. Using this software, computer-aided design models of three dual-mobility designs (anatomic, modular, and subhemispheric) and standard hemispheric fixed bearings were implanted in the pelvic model and the posterior horizontal dislocation distances measured. Hip ROM simulator software was used to compare the prosthetic impingement-free ROMs of dual-mobility bearings with standard hemispheric fixed-bearing designs.

RESULTS

Variations in component design had greater effect on posterior horizontal dislocation distance values than increases in head size in a specific design (p < 0.001). Anatomic and modular dual-mobility designs were found to have greater posterior horizontal dislocation distances than the subhemispheric dual-mobility and standard hemispheric fixed-bearing designs (p < 0.001). Increasing head sizes increased posterior horizontal dislocation distances across all designs (p < 0.001). The subhemispheric dual-mobility implant was found to have the greatest prosthetic impingement-free ROM among all prosthetic designs (p < 0.001; R(2) = 0.86).

CONCLUSIONS

The posterior horizontal dislocation distances differ with the individual component geometries of dual-mobility designs, with the anatomic and modular designs showing higher posterior horizontal dislocation distances compared with subhemispheric dual-mobility and standard hemispheric fixed-bearing designs.

CLINICAL RELEVANCE

Static, three-dimensional computerized simulation studies suggest differences that may influence the risk of dislocation among components with varying geometries, favoring anatomic and modular dual-mobility designs. Clinical studies are needed to confirm these observations.

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.

Dual mobility cup: dislocation rate and survivorship at ten years of follow-up

PURPOSE

The dual mobility cup introduced in France by Gilles Bousquet has been used in total hip replacement in high-risk patients. This device acts as a large ball implant and significantly reduces the risk of dislocation following hip arthroplasty. Published French literature has focused on low rates of dislocation and long-term follow-up similar to the low-friction arthroplasty.

METHODS

We retrospectively reviewed a continuous series of 105 cases of dual mobility cup Quattro (Groupe Lépine, Genay, France) implanted from 2000 to 2002. Selection of the patients requiring a primary hip replacement depended on risk criteria such as age, hip disease and activity score. The dual mobility cup was associated with a modular cemented femoral component and a 22.2-mm stainless steel head.

RESULTS

One dislocation occurred one month after the index surgery requiring no revision surgery. According to the Kaplan-Meier method, survival probability was 95.0% (95% confidence interval 81.5-98.8) at ten years of follow-up.

CONCLUSIONS

Based on clinical outcome and patient assessment we conclude that the dual mobility cup is a reliable option to decrease dislocation risk without increasing polyethylene wear.