Minimally Invasive Intermuscular Approaches Versus Conventional Approaches in Total Hip Arthroplasty: A Systematic Review and Meta-Analysis.

BACKGROUND: To date, the literature has not yet revealed superiority of Minimally Invasive (MI) approaches over conventional techniques. We performed a systematic review to determine whether minimally invasive approaches are superior to conventional approaches in total hip arthroplasty for clinical and functional outcomes. We performed a meta-analysis of level 1 evidence to determine whether minimally invasive approaches are superior to conventional approaches for clinical outcomes. METHODS: All studies comparing MI approaches to conventional approaches were eligible for analysis. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were adhered to throughout this study. Registries were searched using the following MeSH terms: 'minimally invasive', 'muscle-sparing', 'THA', 'THR', 'hip arthroplasty' and 'hip replacement'. Locations searched included PubMed, the Cochrane Library, ClinicalTrials.gov, the European Union (EU) clinical trials register and the International Clinical Trials Registry Platform (World Health Organisation). RESULTS: Twenty studies were identified. There were 1,282 MI total hip arthroplasty (THAs) and 1,351 conventional THAs performed. There was no difference between MI and conventional approaches for all clinical outcomes of relevance including all-cause revision (P = .959), aseptic revision (P = .894), instability (P = .894), infection (P = .669) and periprosthetic fracture (P = .940). There was also no difference in functional outcome at early or intermediate follow-up between the two groups (P = .38). In level I studies exclusively, random-effects meta-analysis demonstrated no difference in aseptic revision (P = .461) and all other outcomes between both groups. CONCLUSION: Intermuscular MI approaches are equivalent to conventional THA approaches when considering all-cause revision, aseptic revision, infection, dislocation, fracture rates and functional outcomes. Meta-analysis of level 1 evidence supports this claim.

Frank Stinchfield Award: Identification of the At-risk Genotype for Development of Pseudotumors Around Metal-on-metal THAs.

BACKGROUND: Once touted as the future of hip arthroplasty, metal-on-metal (MoM) bearing surfaces have fallen sharply from favor with the emergence of a strong body of evidence demonstrating unacceptably high premature implant failure rates. The previously unpredictable development of adverse local tissue reactions (ALTRs) has been a substantive contributor to this. Although the underlying pathophysiology of these so-called "pseudotumors" is now well understood, the fundamental predisposing patient risk factors have remained elusive. QUESTIONS/PURPOSES: The aim of this research, as a clinical-genotype correlation analysis, was to identify specific alleles (genes) associated with the development of ALTRs in patients with in situ MoM THAs. METHODS: A case-control study of patients who received a large-head, primary MoM THA between 2005 and 2008 was performed with a minimum followup of 5 years. Twenty-six patients who had undergone revision of a primary MoM THA secondary to symptomatic ALTRs were recruited. The mean timeframe from primary MoM THA to symptomatic revision was 5.5 years (range, 1-10 years). Twenty-eight control subjects were randomly selected asymptomatic patients with no evidence of ALTRs on protocol-specific screening. Baseline demographics and high-resolution genotype (human leukocyte antigen [HLA] Class II) were collected for all patients. Cohorts were similar with respect to age at the time of primary MoM THA (mean, 54.8 versus 54.9 years, p = 0.95) and serum cobalt (mean, 5.5 versus 8.5 µg/L, p = 0.09) and chromium concentrations (mean, 2.9 versus 4.2 µg/L, p = 0.27). The association between genotype and revision surgery secondary to ALTRs was determined with gender as a covariate. RESULTS: The prevalence of the risk genotype was 30% (16 of 54) among the entire cohort. Adjusting for sex, the odds of revision were 6.1 times greater among patients with the risk genotype present than among patients without (95% confidence interval [CI], 1.5-25.4; p = 0.01). Among females, the specificity of the risk genotype was 1.0 (95% CIexact, 0.5-1.0; pexact = 0.03), and for males, it was 0.8 (95% CIexact, 0.6-0.9; pexact < 0.01). CONCLUSIONS: The findings of this study suggest that, among patients with a primary MoM THA, allelic variation within the HLA Class II loci may be a strong, independent risk factor associated with the need for subsequent revision surgery secondary to pseudotumor formation. CLINICAL RELEVANCE: Given the hypothesis-generating nature of this novel undertaking, confirmatory prospective clinical studies are required to further elucidate this correlation and to explore the clinical utility of targeted genetic screening in this specific population. This research may, however, represent a key missing piece in the puzzle that is metal ion-induced pseudotumor formation.

An Early Report of the Use of a Modular Dual Mobility Articulation in Revision Acetabular Reconstruction.

BACKGROUND: Instability remains one of the main problems after revision hip surgery. The aim of this study was to review the clinical, radiological, and patient-reported outcomes with the use of modular dual-mobility articulation for revision acetabular reconstruction and investigate the risk of fretting corrosion by measuring serum trace metal ion levels. METHODS: Sixty consecutive patients with a minimum of 24-month follow-up after the insertion of a modular dual-mobility (Stryker, Mahwah, NJ) cup at the time of revision hip surgery were identified. Follow-up included clinical and radiological patient review and functional outcome measures, and a subset of patients had their metal ion (cobalt and chromium) levels checked. RESULTS: At the most recent follow-up, 5 patients had died, 3 patients have been revised because of ongoing instability, and 3 patients have had revision surgery due to infection. Overall functional outcome (mean Western Ontario and McMaster Universities Osteoarthritis Indexfunction 76, University of California, Los Angeles 5.6, mean Oxford 74.7, Short Form-12 physical 41.6/mental 53.3) and overall pain relief (mean Western Ontario and McMaster Universities Osteoarthritis Index pain score 78.3) scores were good. The mean satisfaction score was 78 of 100. The median serum trace metal chromium and cobalt levels at the most recent follow-up were 0.4 µg/L (range 0.1-6.1 µg/L) and 0.42 µg/L (range 0.21-9.42 µg/L), respectively. The survival with revision as the end point was 90%. CONCLUSIONS: Dual-mobility cups with modularity represent an excellent option for the patient having revision hip surgery at high risk of instability. This series presents good patient-reported outcome measures and a low complication and revision rate.

What Is the Natural History of Asymptomatic Pseudotumors in Metal-on-metal THAs at Mid-term Followup?

BACKGROUND: The risk of early revision because of pseudotumors in patients who have undergone large-head metal-on-metal (MoM) total hip arthroplasty (THA) is well documented. However, the natural history of asymptomatic pseudotumors or of MoM articulations without pseudotumors is less well understood. The aim of our study was to investigate the natural history of primary MoM THA at mid-term followup. QUESTIONS/PURPOSES: The purposes of this study were: (1) Did previously detected pseudotumors persist or worsen in asymptomatic patients at mid-term followup; and if so, did any of them require revision THA? (2) Did new pseudotumors form in asymptomatic patients at mid-term followup? (3) What happened to serum trace metal ions at mid-term followup? (4) Were postoperative patient-reported outcome measures (PROMs) maintained at mid-term followup? METHODS: Seventy-one patients who underwent a MoM THA using a Metasul LDH implant with a Durom acetabular cup and an M/L Taper stem between September 2005 and October 2008 were reviewed. All patients for this study were part of two previously published studies from our early followup. Data from the previous studies were used for comparison only. Two of the 71 patients (2.8%) were lost to followup. The mean age at operation was 56 years (range, 34-68 years). There were 24 female patients. All patients had serum trace metal ions testing, ultrasound imaging, and PROMs at a mean 3.5 years (early followup) after the index operation (range, 3-5 years) and delayed followup at a mean 7 years (range, 6.5-9 years). The indication to undertake revision THA was based on clinical evaluation and not solely on the investigation results. RESULTS: Twenty-three of 71 patients (32%) had a positive ultrasound scan for pseudotumor at early followup. Of these, eight patients underwent revision THA (11% of MoM THA or 35% of patients with an early positive ultrasound scan). The mean time between positive ultrasound scan and revision surgery was 13 months (range, 5-22 months). Of the remaining 15 patients with pseudotumor noted on early ultrasound, 12 had persistent pseudotumor, two resolved, and one was lost to followup. Six patients (13%) with a normal ultrasound scan at early followup showed new ultrasound findings at delayed followup. Of these, four (8%) were conclusively diagnosed as pseudotumor and one was revised. Serum trace metal ion increased at mid-term followup in the seven cases that showed an increase in volume of pseudotumor. Of the five patients in whom the volume of pseudotumor decreased on ultrasound at mid-term followup, three showed a decrease in serum trace ions levels, whereas two showed an increase. New-onset pseudotumors at mid-term followup was associated with an increase in serum trace metal ions at mid-term followup only in two of six cases. PROMs at mid-term followup of patients in this study remain high. CONCLUSIONS: At mid-term followup, approximately 35% of patients who develop an early pseudotumor undergo revision arthroplasty, whereas the remaining are asymptomatic. The incidence of new-onset ultrasound findings suggestive of pseudotumors at mid- to long-term followup is approximately 8% and these require continued surveillance. LEVEL OF EVIDENCE: Level II, prognostic study.

Nonmodular Tapered Fluted Titanium Stems Osseointegrate Reliably at Short Term in Revision THAs.

BACKGROUND: The ideal femoral component for revision THA is undecided. Cylindrical nonmodular stems have been associated with stress shielding, whereas junctional fractures have been reported with tapered fluted modular titanium stems. We have used a tapered fluted nonmodular titanium femoral component (Wagner Self-locking [SL] femoral stem) to mitigate this risk. This component has been used extensively in Europe by its designer surgeons, but to our knowledge, it has not been studied in North America. Added to this, the design of the component has changed since early reports. QUESTIONS/PURPOSES: We asked: (1) Does the Wagner SL stem have low rates of rerevision and other complications at a minimum 2 years after surgery? (2) Is the Wagner SL stem associated with high levels of patient function and pain relief at a minimum 2 years after surgery? (3) Does the Wagner SL stem have low rates of subsidence at a minimum 2 years after surgery? (4) Is the Wagner SL stem associated with proximal femoral bone remodeling at a minimum 2 years after surgery? METHOD: Between May 2011 and December 2012, we performed 198 femoral revisions, of which 104 (53%) were performed using the Wagner SL femoral stem; during that period, our institution gradually shifted toward increasing use of these stems for all but the most severe revisions, in which modular fluted stems and proximal femoral replacements still are used on an occasional basis. Median followup in this retrospective study was 32 months (range, 24-46 months), and one patient was lost to followup before the 2-year minimum. The femoral deformities in this series were Paprosky Type I (10 hips), Paprosky Type II (26), Paprosky Type IIIA (52), Paprosky Type IIIB (nine), and Paprosky Type IV (two). Functional assessment was performed using the Oxford Hip Score (OHS), WOMAC, SF-12, and the University of California Los Angeles (UCLA) activity score. All complications and cases of revision were documented. All patients had radiographs performed within 1 year of the latest followup. These were assessed by two surgeons for signs of proximal femoral bone remodeling and subsidence. RESULTS: Complete preoperative scores were available for 98 patients (98 of 104; 94%). The mean OHS preoperatively and at final followup were 39 (SD, 15) and 87 (SD, 19), respectively (p < 0.001; mean difference, 48; 95% CI, 43-53). Average WOMAC scores were 44 (SD, 15) and 87 (SD, 20), respectively (p < 0.001; mean difference, 43; 95% CI, 38-48). At final followup, signs of restoration of proximal femoral bone stock was noted in 45 of 103 hips (44%). Six (six of 104; 6%) patients had subsidence of 10 mm to 15 mm. In the remainder (98 of 104; 94%), the mean subsidence was 2 mm (range, 0-9 mm). One revision was performed for loosening associated with infection. CONCLUSIONS: The Wagner SL stem is a viable option for patients with Paprosky Types II and III defects undergoing revision THA. This component provides high levels of patient function with low revision rates and low rates of subsidence during the early postoperative phase. They provide a viable alternative to modular components for treatment of Types II and III defects without the risk of junctional fractures. They can be used for very selected Type IV defects, however this extent of bone loss is most easily addressed with other techniques such as a proximal femoral replacement. LEVEL OF EVIDENCE: Level IV, therapeutic study.

The Outcomes Following Revision of Monoblock Metal on Metal Acetabular Components for Painful Micromotion in the Absence of Adverse Local Tissue Reaction to Metal.

BACKGROUND: Revision hip arthroplasty for metal-on-metal arthroplasty (MOMA) in the presence of an adverse local tissue reaction (ALTR) has been associated with compromised outcomes. We hypothesized that revision of MOMA for painful micromotion of the cup, in the absence of ALTR, would have a more favorable outcome. METHODS: We reviewed our database for Durom acetabular shell revision with minimum 24 months (24 months to 8 years) follow-up. Patients with a diagnosis of painful micromotion in the absence of pseudotumor was identified. RESULTS: At mid-term follow-up, 71 patients had undergone revision of a Durom MOMA. Twenty-seven of these (38%) were for painful micromotion (9 total hip arthroplasty, 18 hip resurfacing) of the cup alone. Following revision surgery, all patients reported resolution of the preoperative pain, as well as satisfactory outcome measures (mean scores: The Western Ontario and McMaster Universities Arthritis Index [WOMAC] 84.6, oxford hip score 84.7, Short Form Health Survey (SF-16) 51, University of California, Los Angeles (UCLA) 7.3). Radiologically, all cases demonstrated osseointegration of the revision shells; 1 case had zone-3 radiolucency that was nonprogressive. One patient had a dislocation treated by closed reduction at 10 weeks. CONCLUSION: Revision MOMA for painful micromotion of the shell in the absence of ALTR is not similar to revision for ALTR and is associated with predictable improvement in pain and quality of life.

The Wagner Cone Stem for the Management of the Challenging Femur in Primary Hip Arthroplasty.

BACKGROUND: Splined conical stems offer design features that facilitate their use in the misshapen, dysplastic proximal femur. METHODS: This study assessed the survivorship of a conical prosthesis when applied to secondary coxarthrosis because of a range of pathologies. Fifty-one prostheses were implanted in 50 patients with a mean age of 50 (range, 15-80) and a median follow-up of 34 months (range, 24-73 months). Indications for the stem included developmental (36), neuromuscular (7), post-traumatic or surgical (7), and inflammatory conditions (1). Survivorship, functional outcome (WOMAC [Western Ontaria and McMaster University Osteoarthrits Index], Oxford Hip Score, and UCLA [University of California Los Angeles]), health status (short form-12 [SF-12]), satisfaction, and osseointegration were determined. RESULTS: Survivorship for aseptic loosening was 100% at 2 years and 98.04% for septic revision. Eight patients required reoperation, 4 for instability, and 1 each for infection, impingement, adverse reaction to metal debris, and pelvic insufficiency fracture. The mean WOMAC score was 85 (standard deviation [SD], 18), the mean Oxford Hip Score 84 (SD, 18), the mean physical SF-12 score was 48.3 (SD, 8.6), and the mean mental SF-12 was 53.7 (SD, 9.2), the mean satisfaction score was 91.5 (SD, 3.9), and the mean UCLA was 6 (SD, 1.6). All femoral components demonstrated osseointegration. CONCLUSION: The cone femoral prosthesis demonstrates excellent early survival and osseointegration when applied to the challenging femur. Because of these encouraging results, we recommend this prosthesis be considered for the small, abnormal femur in primary hip arthroplasty.

Acute Kidney Injury With Tobramycin-Impregnated Bone Cement Spacers in Prosthetic Joint Infections.

BACKGROUND: Antibiotic-impregnated bone cement spacer (ACS) with tobramycin ± vancomycin is commonly used in a 2-stage replacement of infected prosthetic joints. This procedure has been associated with development of acute kidney injury (AKI). OBJECTIVE: To determine the incidence and risk factors for AKI after implantation of tobramycin-impregnated ACS. METHODS: This prospective, observational study evaluated 50 consecutive patients who received tobramycin ACS for first-stage revision of an infected hip or knee arthroplasty from August 2011 to February 2013. AKI was defined as 50% or greater rise in serum creatinine (SCr) from baseline within the first 7 postoperative days (PODs). RESULTS: The incidence of AKI was 20%, with median onset occurring at POD 2 (interquartile range [IQR] = 1-3); patients with AKI had a longer median duration of hospital stay (16 days, IQR = 12-17, vs 10 days, IQR = 8-10; P = 0.03). Serum tobramycin concentrations were significantly higher in the AKI group, peaking on POD 1 (median 1.9 vs 0.9 µg/mL, P = 0.01). Risk factors for nephrotoxicity identified by multivariate analysis were use of bone cement premanufactured with gentamicin (OR = 8.2; 95% CI = 1.1-60; P = 0.04), administration of blood transfusions intraoperatively (OR = 32.5; 95% CI = 2.3-454.3; P = 0.01) and nonsteroidal anti-inflammatory drugs postoperatively (OR = 23.0; 95% CI = 1.3-397.7; P = 0.03). CONCLUSIONS: Tobramycin ACS is associated with a high risk of AKI. Measures to minimize AKI risk in the perioperative period include early detection through close monitoring of SCr, avoiding use of premanufactured bone cement containing gentamicin, and avoiding potential nephrotoxins within the first 72 hours postoperatively.

Continued good results with modular trabecular metal augments for acetabular defects in hip arthroplasty at 7 to 11 years.

BACKGROUND: Reconstruction of large acetabular defects remains a substantial challenge in hip arthroplasty. There remains a paucity of data on the long-term results of acetabular trabecular metal augments. QUESTIONS/PURPOSES: The purpose of this study was to assess the survivorship, clinical outcomes, restoration of center of rotation of the hip, and radiological signs of component fixation of trabecular metal augments in the context of reconstruction of acetabular defects. METHODS: Between 2002 and 2005, we performed 56 revision (n=53) and primary (n=3) THAs using trabecular metal augments in combination with a trabecular metal acetabular component. Of the 56 patients, 16 (29%) died during followup. Of the 40 surviving patients, 37 (93%) had complete radiological followup, 23 (58%) had complete outcome questionnaire followup, and 17 (42%) provided partial questionnaire responses in the clinic or over the telephone. Median followup was 110 months (range, 88-128 months). During that period, we used these implants when preoperative templating indicated that an augment would be required to achieve acetabular implant stability with restoration of the hip center of rotation. We also chose during surgery to use an augment when we could not achieve a stable acetabular trial component without one. The combination of trabecular metal augments and trabecular metal shells was used in 18% (53 of 292) of our acetabular revisions during that time. Survivorship, functional outcome (WOMAC and Oxford hip score), health status (SF-12), and osseointegration according to the criteria of Moore and presence of radiolucencies were determined. RESULTS: Survivorship of the augments at 10 years was 92% (95% confidence interval, 81%-97%). Four patients underwent cup revision, one for infection and three for loosening. The mean WOMAC global score was 79 (SD 17), the mean Oxford hip score 76 (SD 18), the mean physical component SF-12 score was 39 (SD 11), and the mean mental component SF-12 score was 52 (SD 9). The center of rotation was corrected from more than 35 mm above the inter-teardrop line in 48 of 56 patients preoperatively to only five of 46 postoperatively. One patient had radiographic findings suggestive of loosening, but this patient was asymptomatic. CONCLUSIONS: The results of the acetabular trabecular metal augments continue to be encouraging in the medium to long term with low rates of revision or loosening in this complex group of patients. We continue to recommend the use of these augments in the reconstruction of complex acetabular defects. LEVEL OF EVIDENCE: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

The Role of Dual-mobility Cups in Total Hip Arthroplasty.

It is often challenging to address instability risks when dealing with complex primary total hip arthroplasty and revision hip surgery. The implant-related options available to surgeons to deal with the risks of instability include femoral head size, femoral neck length/offset, component orientation, and the use of constrained articulations. Dual-mobility articulations have long been used in Europe in the setting of a potential or proven unstable hip; this type of articulation is now available in North America after regulatory approval. However, a dual-mobility articulation has its own unique advantages and disadvantages. Before choosing this implant option, the arthroplasty surgeon needs to be fully informed of the design concept, the surgical technique, the advantages, the disadvantages, and the literature surrounding the use of a dual-mobility articulation.

Tapered, fluted titanium stems in revision total hip arthroplasty: role and results in contemporary practice.

The burden of revision total hip arthroplasty (THA) is rising. As increasingly younger patients are treated with THA procedures, it is likely that this trend will continue. The results of revision THA are greatly influenced by the quantity and the quality of available femoral bone stock available for reconstruction. Modular and nonmodular tapered fluted titanium stems are increasingly used in revision THA. It is helpful to be familiar with the use of these components in revision THA.

Arthroscopy as a diagnostic tool for painful trunnion corrosion after hip arthroplasty.

PURPOSE: Adverse local soft tissue reactions can occur in response to wear debris or corrosion products released from total hip arthroplasty (THA). Hip arthroscopy is a useful diagnostic adjunct in the investigation of painful THA. METHODS: A patient with a painful primary metal-on-highly cross-linked polyethylene THA underwent hip arthroscopy to confirm the diagnosis of trunnion corrosion. RESULTS: The prosthetic implants were well fixed and aligned with no indication of infection. Hip arthroscopy was used to confirm the presence of corrosion on the trunnion of a titanium stem at its junction with a cobalt-chrome head. Due to persistent symptoms, the patient subsequently underwent arthrotomy, which confirmed the diagnosis, and revision hip arthroplasty to a titanium adapter sleeve, ceramic head and liner exchange, with relief of his symptoms. CONCLUSION: Hip arthroscopy may prove a useful additional diagnostic tool in the investigation of this emerging clinical entity.

Tapered fluted titanium stems in the management of Vancouver B2 and B3 periprosthetic femoral fractures.

BACKGROUND: Surgeons have several implant choices when managing Vancouver B2 and B3 periprosthetic fractures about the hip. Few long-term studies have reported outcomes for tapered fluted titanium stems. QUESTIONS/PURPOSES: We determined (1) survival, with femoral revision as the end point, of distal taper stems in the treatment of Vancouver B2 and B3 periprosthetic fractures at our institution, (2) radiographic outcomes, and (3) quality of life and hip function after revision. METHODS: Of the 200 patients with Vancouver B2 or B3 periprosthetic fractures treated with femoral revision between February 2000 and February 2010, 55 (38 B2, 17 B3) were treated with modular tapered titanium stems. Of the surviving 47 patients, one was lost to followup, leaving 46 (30 B2, 16 B3) available for review at a mean of 54 months (range, 24-143 months). Initial indications for using these implants were treatment of periprosthetic fractures where less than 4 cm of diaphyseal fit was available, but this evolved during the study period to all fractures unless no diaphysis remained, in which case complex revision techniques were used. Radiographs were assessed to establish fracture healing, stem subsidence, and bone stock restoration. Quality of life and hip function were assessed using WOMAC, Oxford, SF-12, UCLA activity level, and satisfaction scores. RESULTS: Two femoral stems were revised: one subsided and was revised at 12 months; the other had deep infection and underwent two-stage revision at 49 months. Radiographic review showed one nonunion, with maintenance or improvement of bone stock in 89% of patients. Subsidence occurred in 24%. Mean Oxford score was 76 of 100, WOMAC function and pain scores were 75 and 82 of 100, satisfaction score was 91 of 100, and SF-12 mental and physical scores were 53 and 40 of 100. CONCLUSIONS: We report encouraging short-term results in terms of survival of distal taper stems in the treatment of B2 and B3 periprosthetic fractures. Although subsidence was frequent, most migrated less than 3 mm without correlation to poor pain and functional scores.

High complication rate after revision of large-head metal-on-metal total hip arthroplasty.

BACKGROUND: Previous studies have indicated poor outcomes in patients having revision of hip resurfacing resulting from adverse local tissue reaction and pseudotumor. QUESTIONS/PURPOSES: We reviewed all patients at our institution who had revision of failed large-head metal-on-metal total hip arthroplasty to determine (1) complications including reoperations; (2) radiologic outcomes; and (3) changes in serum ions after removal of the metal bearing. METHODS: From our research database, we identified 32 hips in 30 patients. Revisions were performed through a posterior approach; 17 were performed with a titanium fiber-metal shell and 15 with a porous tantalum shell, and 29 of the 32 revisions were performed with large (36- or 40-mm) femoral heads. Clinical records were reviewed and interviews conducted in the clinic or by telephone. Nineteen hips had a pre- or intraoperative diagnosis of adverse local tissue reaction, three had deep infection, and 10 had loosening of the acetabular component. RESULTS: Major complications occurred in 12 (38%) of the 32 revisions. Nine of 32 hips (28%) sustained dislocations. Four of 17 fiber-metal acetabular components failed to ingrow; none of the porous tantalum cups failed to ingrow. Seven repeat revisions were performed in six patients: three for acetabular loosening, three for recurrent dislocation, and one for recurrent adverse local tissue reaction. The mean WOMAC pain score was 78 of 100 and the function score was 83 of 100. Metal ion levels decreased after revision in most patients. CONCLUSIONS: As a result of the high rate of failure of the fiber metal cups, we have elected to use an enhanced fixation surface with a high-porosity cup for revision of these cases. We observed a high rate of dislocation despite the use of 36-mm and 40-mm heads.

The John Charnley Award: Diagnostic accuracy of MRI versus ultrasound for detecting pseudotumors in asymptomatic metal-on-metal THA.

BACKGROUND: The prevalence of pseudotumors in patients with large-head metal-on-metal (MOM) THA has been the subject of implant recalls and warnings from various regulatory agencies. To date, there is no consensus on whether ultrasound or MRI is superior for the detection of pseudotumors. QUESTIONS/PURPOSES: We prospectively compared ultrasound to MRI for pseudotumor detection in an asymptomatic cohort of patients with MOM THAs. We also compared ultrasound to MRI for assessment of pseudotumor growth and progressive soft tissue involvement at a 6-month interval. METHODS: We enrolled 40 patients with large-head MOM THAs in the study. The mean age was 54 years (range, 34-76 years). The mean time from surgery was 54 months (range, 40-81 months). There were 28 men and 12 women. All patients underwent ultrasound and MRI using slice encoding for metal artifact correction. The gold standard was defined as follows: if both ultrasound and MRI agreed, this was interpreted as concordant and the result was considered accurate. RESULTS: Ultrasound and MRI agreed in 37 of 40 patients (93%). The prevalence of pseudotumors was 31% (12 of 39) in our cohort. Twenty-three of 39 patients (59%) had completely normal tests and four (10%) had simple fluid collections. Ultrasound had a sensitivity of 100% and specificity of 96% while MRI had a sensitivity of 92% and specificity of 100%. CONCLUSIONS: A negative ultrasound rules out pseudotumor in asymptomatic patients as this test is 100% sensitive. Given its lower cost, we recommend ultrasound as the initial screening tool for pseudotumors.

Acetabular liner with focal constraint to prevent dislocation after THA.

BACKGROUND: Dislocation continues to commonly cause failure after primary and revision total hip arthroplasty (THA). Fully constrained liners intended to prevent dislocation are nonetheless associated with a substantial incidence of failure by redislocation, mechanical failure, aseptic loosening, or a combination. Constrained liners with cutouts of the elevated rims can theoretically increase range of movement and therefore decrease the risk dislocation, but it is unclear if they do so in practice and whether they are associated with early wear or loosening. QUESTIONS/PURPOSES: We therefore determined (1) occurrence or recurrence of dislocation and (2) rate of complications associated with constrained implants with cutouts; and (3) assessed for early cup loosening. METHODS: We retrospectively reviewed the records of 81 patients at high risk for dislocation who had 82 constrained liners inserted for primary (n = 10) or revision (n = 72) THA between 2008 and 2010. From the records we extracted demographic and implant data and instances of recurrent dislocation, implant failure, osteolysis, loosening, or construct failure. The minimum followup was 24 months (mean, 34 months; range, 24-49 months). RESULTS: Three liners failed as a result of further dislocation (3%). Three deep infections occurred. One patient had progressive loosening at the shell-bone interface. CONCLUSIONS: Our observations suggest this liner is associated with a relatively low risk of dislocation in patients at high risk for dislocation and those with recurrent dislocation.

High survival of modular tapered stems for proximal femoral bone defects at 5 to 10 years followup.

BACKGROUND: Currently, the two most commonly used options for the revision of femoral components in North America are: cylindrical, nonmodular, cobalt-chromium stems and tapered, fluted, modular, titanium (TFMT) stems. Previous reports have cited high failure rates with cylindrical cobalt chrome stems in large femoral defects but the longer term survival of the fluted stems is unknown. QUESTIONS/PURPOSES: We examined the 5- to 10-year survival of TFMT stems implanted for severe femoral defects. METHODS: We reviewed all 65 patients with severe proximal bone defects revised with the TMFT stem between January 2000 and 2006. Ten were lost to followup and seven were dead, leaving 48 patients for followup at 5 to 10 years (mean, 84 months; range, 60-120 months). All patients completed five quality-of-life (QOL) questionnaires. Radiographs were evaluated for loosening, subsidence, and preservation of proximal host bone stock. RESULTS: Implant survivorship was 90%. No patient underwent revision for either subsidence or loosening. Subsidence occurred in seven patients (average, 12.3 mm) but all achieved secondary stability. Five patients underwent revision as a result of fracture of the stem and all had the original standard stem design, which has since been modified. All five implant fractures occurred at the modular stem junction. Mean QOL outcomes were: WOMAC = 81 (pain), Oxford = 75, SF-12 = 54 (mental) and 38 (physical), UCLA Activity = 4, and satisfaction overall = 73. CONCLUSIONS: Midterm survivorship of modular titanium stems in large femoral defects is high; however, ongoing surveillance of stem junctional fatigue life is required. LEVEL OF EVIDENCE: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

The natural history of inflammatory pseudotumors in asymptomatic patients after metal-on-metal hip arthroplasty.

BACKGROUND: Although pseudotumors have been reported in 32% of asymptomatic metal-on-metal hips, the natural history of asymptomatic pseudotumors is unknown. QUESTIONS/PURPOSES: The purpose of this study was to assess changes over time in asymptomatic pseudotumors and the effect of revision on pseudotumor mass. METHODS: Followup ultrasound was performed a mean of 25.8 months (range, 21-31 months) after the detection of 15 pseudotumors and five isolated fluid collections in a cohort of 20 asymptomatic patients (13 metal-on-metal, three metal-on-polyethylene, and four hip resurfacings) [42]. Changes in pseudotumors and fluid collections size and nature, and serum ion levels were determined. RESULTS: Among the 15 nonrevised patients, pseudotumors increased in size in six (four solid and two cystic) of 10 patients, three of which had clinically important increases (13-148 cm(3); 28-74 cm(3); 47-104 cm(3)). Three pseudotumors (one solid and two cystic) disappeared completely (the largest measured 31 cm(3)). One solid pseudotumor decreased in size (24 to 18 cm(3)). In five revised patients, pseudotumors completely disappeared in four patients. The fifth patient had two masses that decreased from 437 cm(3) to 262 cm(3) and 43 cm(3) to 25 cm(3). All revision patients had a reduction of chromium (40.42 µ/L to 2.69 µ/L) and cobalt ions (54.19 µ/L to 0.64 µ/L). Of five isolated fluid collections, four completely disappeared (two metal-on-metal and two metal-on-polyethylene) and one (metal-on-metal) increased from 26 cm(3) to 136 cm(3). CONCLUSIONS: Our observations suggest pseudotumors frequently increase in size in asymptomatic patients with occasional remission of small masses. Revision resulted in remission of pseudotumors.

Outcomes of minimally invasive anterolateral THA are not superior to those of minimally invasive direct lateral and posterolateral THA.

BACKGROUND: There has been considerable interest in minimally invasive surgical (MIS) THA in recent years. The MIS anterolateral approach, or the MIS Watson-Jones approach, is a novel intermuscular abductor-sparing technique. Early reports from case series suggest the potential for superior function and reduced complications; however, the available information from clinical reports is inadequate to suggest surgeons should change from their accepted standard approach. QUESTIONS/PURPOSES: We examined the potential superiority of this anterolateral approach, as judged by quality-of-life (QoL) measures, radiographic parameters, and complications, compared to limited-incision MIS direct lateral and MIS posterolateral approaches. METHODS: We performed a prospective randomized controlled trial involving five surgeons at three centers, recruiting 156 patients undergoing primary THA to receive either the MIS anterolateral or the surgeon's preferred approach (direct lateral or posterolateral). For the 135 patients we report, we collected patient-reported WOMAC, SF-36, Paper Adaptive Test in 5 Domains of Quality of Life in Arthritis Questionnaire [PAT5D], and patient satisfaction scores. We recorded complications and evaluated radiographs for prosthetic component position, subsidence, and fracture. Minimum followup was 24 months (mean, 30 months; range, 24-42 months). RESULTS: QoL and patient-reported satisfaction were similar between groups. Radiographic evaluation demonstrated no differences in acetabular component positioning; however, mean stem subsidence was 4.6 mm for the MIS anterolateral group and 4.1 mm for the alternate group, with differences observed among the three centers for stem subsidence and fracture. One center had increased rate of fracture requiring treatment and need for revision in the MIS anterolateral group. CONCLUSIONS: We found no superiority of the MIS anterolateral approach but observed intersite differences in painful stem subsidence and fracture. We have returned to the standard surgical approaches in use before the trial. LEVEL OF EVIDENCE: Level I, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.

Patients report improvement in quality of life and satisfaction after hip resurfacing arthroplasty.

BACKGROUND: A number of reconstructive procedures are available for the management of hip osteoarthritis. Hip resurfacing arthroplasty is now an accepted procedure, with implant survivorship comparable to THA at up to 10 years' followup in certain series. Most reports focus on implant survivorship, surgeon-derived results, or complications. Fewer data pertain to patient-reported results, including validated measures of quality of life (QoL) and satisfaction and baseline measures from which to determine magnitude of improvement. Validated patient-reported results are essential to guide patients and surgeons in the current era of informed and shared decision making. QUESTIONS/PURPOSES: We determined whether patients reported improvement in disease-specific, joint-specific, and generic QoL after hip resurfacing arthroplasty; whether patients were satisfied with the results of the procedure; and latest activity level and return to sport. METHODS: We retrospectively reviewed 127 patients (100 men, 27 women) who underwent 143 hip resurfacing procedures between 2002 and 2006. Mean patient age was 52 years. Patients completed the WOMAC, Oxford Hip Score, and SF-12 at baseline and again at minimum 2-year followup (mean, 2.5 years; range, 2-6 years). At latest followup, patients completed a validated satisfaction questionnaire and UCLA activity score. RESULTS: All QoL scores improved (normalized to a 0-100 scale, where 100 = best health state). WOMAC improved from 46 to 95, Oxford Hip Score from 42 to 95, SF-12 (physical) from 34 to 54, and SF-12 (mental) from 46 to 56. Patient satisfaction score was 96. UCLA activity score was 8. CONCLUSIONS: The majority of patients reported improvement in QoL, were very satisfied with their outcome, and returned to a high level of activity after hip resurfacing arthroplasty. LEVEL OF EVIDENCE: Level IV, therapeutic study. See the Instructions for Authors for a complete description of levels of evidence.