Use of Non-Specific Knee Diagnoses and Incidence of Obscure Knee Injuries in a Large Government Health System.

Purpose: Within a large government health system, to assess the practice of using non-specific diagnoses for knee disorders and determine how often they appear as the only diagnosis without more specificity. The secondary purpose was to identify the incidence of obscure knee disorders diagnosed: pes anserine bursitis, prepatellar bursitis, pigmented villonodular synovitis, and plica syndrome. Patients and Methods: Eligible beneficiaries of the Military Health System (MHS) seeking care for a knee disorder between 1 January 2009 and 31 December 2013 with at least 2-year follow-up. Data were sourced from the MHS Data Repository. The study outcomes were 1) utilization rate of non-specific knee diagnosis codes, 2) proportion of cases that never received a specific knee diagnosis, 3) incidence of obscure knee pathology in this cohort. Results: There were 127,570 beneficiaries seeking care for knee pain during this period. While the majority (99.7%) initially received a non-specific knee diagnosis, these occurred in isolation for only 16.5% of the cases (n=20,042) over two-year follow-up. The use of non-specific codes was similar between military and civilian clinic settings (45.3% and 47.0%, respectively, of all knee disorders diagnosed), which appears to reflect clinical practice in which diagnoses become more specified over time and diagnostic workup aims to exclude competing diagnoses. The incidence of obscure knee pathology was small (0.2% to 4.0%). Conclusion: Most of the cohort (99.7%) received a non-specific diagnosis at their initial visit, but only 15% did not eventually receive a more specific diagnostic code. These findings suggest that diagnoses may become more specific over time as condition-specific signs and symptoms become more evident, and diagnostic workup excludes competing diagnoses. A better understanding of diagnostic patterns and criteria for knee pain will improve the quality and interpretation from epidemiological studies.

Does Surgery for Concomitant Cruciate and Meniscus Injuries Increase or Decrease Subsequent Comorbidities at 2 Years?

Concomitant cruciate and meniscus injuries of the knee are generally associated with acute trauma and commonly treated with surgical intervention. Comorbidities (simultaneous presence of two or more medical conditions) may be acquired from changes in activity levels and lifestyle after an injury and/or treatment. This study aimed to compare differences in comorbidity proportions between surgical and nonsurgical approaches in Military Health System beneficiaries who had concurrent cruciate and meniscus injuries. The retrospective case control design included 36-month data that were analyzed to reflect 12 months prior to injury/surgery and 24 months after injury/surgery. A comparison of differences within and between groups in surgical and nonsurgical approaches was calculated and logistic regression was used to determine if surgery increased or decreased the odds of comorbidities at 24 months. In our sample of 2,438 individuals with concurrent meniscus and cruciate injury, 79.1% (n = 1,927) received surgical intervention and 20.9% (n = 511) elected for nonoperative management. All comorbidities demonstrated significant within-group differences from pre- to postsurgery for those with a surgical intervention; approximately, half the comorbidities increased (i.e., concussion or traumatic brain injury, insomnia, other sleep disorders, anxiety, posttraumatic stress disorder, and tobacco abuse disorder), whereas the other half decreased (i.e., chronic pain, apnea, cardiovascular disease, metabolic syndrome, mental health other, depression, and substance abuse disorders). The odds of acquiring a comorbid diagnosis after surgery reflected the bivariate comparisons with half increasing and half decreasing in odds. To our knowledge, this is the first study to explore comorbidity changes with a control group for individuals with concurrent meniscus and cruciate injuries.

Fungal osteomyelitis and septic arthritis in an immune competent man: The first report of invasive osteoarticular infection due to Scedosporium dehoogii.

Invasive osteoarticular infections (IOI) due to Scedosporium spp. are rare in the immune competent patient, but have been associated with direct inoculation from antecedent trauma. Here we describe a case of IOI due to Scedosporium dehoogii in a previously healthy man. The clinical presentation and the diagnosis and treatment is discussed. To our knowledge, this is the first reported case of IOI caused by S. dehoogii.

Generating the American Shoulder and Elbow Surgeons Score Using Multivariable Predictive Models and Computer Adaptive Testing to Reduce Survey Burden.

BACKGROUND: The preferred patient-reported outcome measure for the assessment of shoulder conditions continues to evolve. Previous studies correlating the Patient-Reported Outcomes Measurement Information System (PROMIS) computer adaptive tests (CATs) to the American Shoulder and Elbow Surgeons (ASES) score have focused on a singular domain (pain or physical function) but have not evaluated the combined domains of pain and physical function that compose the ASES score. Additionally, previous studies have not provided a multivariable prediction tool to convert PROMIS scores to more familiar legacy scores. PURPOSE: To establish a valid predictive model of ASES scores using a nonlinear combination of PROMIS domains for physical function and pain. STUDY DESIGN: Cohort study (Diagnosis); Level of evidence, 3. METHODS: The Military Orthopaedics Tracking Injuries and Outcomes Network (MOTION) database is a prospectively collected repository of patient-reported outcomes and intraoperative variables. Patients in MOTION research who underwent shoulder surgery and completed the ASES, PROMIS Physical Function, and PROMIS Pain Interference at varying time points were included in the present analysis. Nonlinear multivariable predictive models were created to establish an ASES index score and then validated using "leave 1 out" techniques and minimal clinically important difference /substantial clinical benefit (MCID/SCB) analysis. RESULTS: A total of 909 patients completed the ASES, PROMIS Physical Function, and PROMIS Pain Interference at presurgery, 6 weeks, 6 months, and 1 year after surgery, providing 1502 complete observations. The PROMIS CAT predictive model was strongly validated to predict the ASES (Pearson coefficient = 0.76-0.78; R2 = 0.57-0.62; root mean square error = 13.3-14.1). The MCID/SCB for the ASES was 21.7, and the best ASES index MCID/SCB was 19.4, suggesting that the derived ASES index is effective and can reliably re-create ASES scores. CONCLUSION: The PROMIS CAT predictive models are able to approximate the ASES score within 13 to 14 points, which is 7 points more accurate than the ASES MCID/SCB derived from the sample. Our ASES index algorithm, which is freely available online (https://osf.io/ctmnd/), has a lower MCID/SCB than the ASES itself. This algorithm can be used to decrease patient survey burden by 11 questions and provide a reliable ASES analog to clinicians.

What Is the Critical Tibial Resection Depth During Unicompartmental Knee Arthroplasty? A Biomechanical Study of Fracture Risk.

BACKGROUND: Fracture after medial unicompartmental knee arthroplasty (UKA) is a rare complication. Biomechanical studies evaluating association between depth of resection and maximum load to failure are lacking. The purpose of this study is to establish the relationship between depth of resection of the medial tibial plateau and mean maximum load to failure. METHODS: Medial tibial resections were performed from 2 to 10 mm in 25 standardized fourth-generation Sawbones composite tibias (Sawbones, Vashon Island, Washington). A metal-backed tibial component with a 9-mm polyethylene bearing was used (Stryker PKR). Tibias were mounted on a biomechanical testing apparatus (MTESTQuattro) and axially loaded cyclically 10 times per cycle and incrementally increased until failure occurred. RESULTS: Load to failure was recorded in 25 proximal tibia model samples after medial UKA using sequential resections from 2 to 10 mm. Analysis of variance testing identified significant differences in mean maximum load to failure between groups (P = .0003). Analysis of regression models revealed a statistically significant fit of a quadratic model (R2 = 0.59, P = .0001). The inflection point of this quadratic curve was identified at 5.82 mm, indicating that the maximum load to failure across experimental models in this study began to decline beyond a resection depth of 5.82 mm. CONCLUSION: In this biomechanical model, medial tibial resections beyond 5.82 mm produced a significantly lower mean load to failure using a quadratic curve model. Resections from 2 to 6 mm showed no significant differences in mean load to failure. Identification of the tibial resection depth at which the mean load to failure significantly decreases is clinically relevant as this depth may increase the risk of periprosthetic fracture after a medial UKA.

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.

Preoperative Management of Antithrombotics in Arthroplasty.

Antithrombotic therapy is common in the arthroplasty patient population; the preoperative management of chronic antithrombotic medications requires coordination among the medical team. It is estimated that approximately 250,000 or 10% of patients on chronic antithrombotic medication undergo treatment interruption for surgical procedures annually in North America. Although the description of postoperative anticoagulation management after arthroplasty is extensive, orthopaedic literature describing the preoperative management of antithrombotic therapy is lacking. The goal of this guideline is to provide practicing orthopaedic surgeons concise recommendations for the preoperative management of common contemporary antithrombotics in the setting of elective arthroplasty using evidence-based guidelines from other medical specialties. All arthroplasty procedures are considered high bleeding risk in accordance with collaborative AAOS and ACC guidelines. Orthopaedic surgeons should collaborate with their colleagues in cardiology, anesthesia, and other specialties when planning perioperative antithrombotic interruption, particularly in the case of medically complex patients such as those with known risk factors for bleeding and clotting disorders. Resumption of antithrombotic therapy after arthroplasty is beyond the scope of this discussion; this should be performed in accordance with cardiology and anesthesia recommendations.

Contact Dermatitis Reaction to 2-Octyl Cyanoacrylate Following 3 Orthopedic Procedures.

Two-octyl cyanoacrylate is a popular skin adhesive used for closing surgical incisions. Since Food and Drug Administration approval in 1998, the few reports of adverse reactions following its use have primarily been limited to the nonorthopedic literature. The authors present a case series of contact dermatitis associated with 2-octyl cyanoacrylate following orthopedic surgery and a review of the literature on the diagnosis and treatment of this complication. All 3 patients presented with blistering around their incisions within 2 weeks of surgery and responded to treatment involving removal of the offending agent and use of oral diphenhydramine and hydroxyzine and topical triamcinolone. One case was complicated by a draining hematoma, requiring irrigation and debridement. Complete resolution occurred in all cases. This case series is intended to increase awareness in the orthopedic community of allergic contact dermatitis to 2-octyl cyanoacrylate and its appropriate treatment. [Orthopedics. 2018; 41(2):e289-e291.].

Using a non-invasive secure skin closure following total knee arthroplasty leads to fewer wound complications and no patient home care visits compared to surgical staples.

BACKGROUND: Superficial wound complications occur in up to 10% of total knee arthroplasty (TKA) procedures and have been associated with periprosthetic joint infection. The ideal material for TKA closure should offer: 1) fast intraoperative application, 2) minimal wound complications and 3) removable by patients without assistance. We evaluated a novel, non-invasive, removable skin closure system for TKA to determine its effect on wound complications. METHODS: We prospectively evaluated 221 consecutive TKA patients who received skin closure using a non-invasive zipper-like system ('Zip'; Zip 16 Surgical Skin Closure System; Zipline Medical). All procedures were performed by a single surgeon using the mini-midvastus approach. Patients received two weeks of rivaroxaban postoperatively. Demographics, comorbidities, in-hospital complications and six-week wound evaluation were recorded. Data was compared to a cohort of 1001 patients from the same surgeon who received staples for closure and coumadin for thromboprophylaxis. RESULTS: Zip patients had a significantly higher BMI (p=0.001), incidence of diabetes (p=0.035) and smoking (p=0.005). Zip patients removed dressings themselves and did not report problems with dressing care. Rate of readmission for wound-related complications was significantly lower in the Zip closure group (p=0.045). Overall readmission rates were similar between groups. CONCLUSIONS: In our experience, the Zip 16 Surgical Skin Closure System is easy to apply, avoids home care and has produced fewer wound complications compared to staples. Results have been positive despite the study cohort having a higher number of diabetic patients and using an anticoagulant associated with a higher risk of wound complications.

The Cost-Effectiveness of Dual Mobility Implants for Primary Total Hip Arthroplasty: A Computer-Based Cost-Utility Model.

BACKGROUND: Dislocation remains a clinically important problem following primary total hip arthroplasty, and it is a common reason for revision total hip arthroplasty. Dual mobility (DM) implants decrease the risk of dislocation but can be more expensive than conventional implants and have idiosyncratic failure mechanisms. The purpose of this study was to investigate the cost-effectiveness of DM implants compared with conventional bearings for primary total hip arthroplasty. METHODS: Markov model analysis was conducted from the societal perspective with use of direct and indirect costs. Costs, expressed in 2013 U.S. dollars, were derived from the literature, the National Inpatient Sample, and the Centers for Medicare & Medicaid Services. Effectiveness was expressed in quality-adjusted life years (QALYs). The model was populated with health state utilities and state transition probabilities derived from previously published literature. The analysis was performed for a patient's lifetime, and costs and effectiveness were discounted at 3% annually. The principal outcome was the incremental cost-effectiveness ratio (ICER), with a willingness-to-pay threshold of $100,000/QALY. Sensitivity analyses were performed to explore relevant uncertainty. RESULTS: In the base case, DM total hip arthroplasty showed absolute dominance over conventional total hip arthroplasty, with lower accrued costs ($39,008 versus $40,031 U.S. dollars) and higher accrued utility (13.18 versus 13.13 QALYs) indicating cost-savings. DM total hip arthroplasty ceased being cost-saving when its implant costs exceeded those of conventional total hip arthroplasty by $1,023, and the cost-effectiveness threshold for DM implants was $5,287 greater than that for conventional implants. DM was not cost-effective when the annualized incremental probability of revision from any unforeseen failure mechanism or mechanisms exceeded 0.29%. The probability of intraprosthetic dislocation exerted the most influence on model results. CONCLUSIONS: This model determined that, compared with conventional bearings, DM implants can be cost-saving for routine primary total hip arthroplasty, from the societal perspective, if newer-generation DM implants meet specific economic and clinical benchmarks. The differences between these thresholds and the performance of other contemporary bearings were frequently quite narrow. The results have potential application to the postmarket surveillance of newer-generation DM components. LEVEL OF EVIDENCE: Economic and decision analysis Level III. See Instructions for Authors for a complete description of levels of evidence.

What Are Normal Metal Ion Levels After Total Hip Arthroplasty? A Serologic Analysis of Four Bearing Surfaces.

BACKGROUND: The recent experiences with adverse local tissue reactions have highlighted the need to establish what are normal serum levels of cobalt (Co), chromium (Cr), and titanium (Ti) after hip arthroplasty. METHODS: Serum Co, Cr, and Ti levels were measured in 80 nonconsecutive patients with well-functioning unilateral total hip arthroplasty and compared among 4 bearing surfaces: ceramic-on-ceramic (CoC); ceramic-on-polyethylene (CoP); metal-on-polyethylene (MoP), and dual mobility (DM). The preoperative and most recent University of California, Los Angeles (UCLA) and Western Ontario and McMaster Universities Arthritis Index (WOMAC) scores were compared among the different bearing surfaces. RESULTS: No significant difference was found among serum Co and Cr levels between the 4 bearing surface groups (P = .0609 and P = .1577). Secondary analysis comparing metal and ceramic femoral heads demonstrated that the metal group (MoP, modular dual mobility (Stryker Orthopedics, Mahwah, NJ) [metal]) had significant higher serum Co levels compared with the ceramic group (CoC, CoP, MDM [ceramic]) (1.05 mg/L ± 1.25 vs 0.59 mg/L ± 0.24; P = .0411). Spearman coefficient identified no correlation between metal ion levels and patient-reported outcome scores. CONCLUSION: No serum metal ion level differences were found among well-functioning total hip arthroplasty with modern bearing couples. Significantly higher serum Co levels were seen when comparing metal vs ceramic femoral heads in this study and warrants further investigation. Metal ion levels did not correlate with patient-reported outcome measures.

Incidence, indications, outcomes, and survivorship of stems in primary total knee arthroplasty.

PURPOSE: The indications, incidence, outcomes, and survivorship of stems in primary total knee arthroplasty (TKA) are lacking in the contemporary literature. Our hypothesis is stems in primary TKA would result in worse outcomes and survivorship. METHODS: All primary TKAs between 2007 and 2011 with 2-year follow-up were identified. Revision TKA or UKA conversion was excluded. Demographic information (age, sex, race, BMI, primary diagnosis, and Charlson-Deyo comorbidity index), outcome measures including KOOS and WOMAC, and any revisions were identified from the registry. A 2:1 matched cohort of non-stemmed/stemmed primary TKA patients was created to compare revision rates and outcomes at baseline and 2 years post-TKA. Subgroup analyses of long versus short stems, 1 versus 2 stems, and cemented versus hybrid stem fixation were completed. Two-sample t tests and Chi-square tests were used to compare conventional and stemmed TKA groups. RESULTS: The registry review included 13,507 conventional TKA and 318 stemmed TKA resulting in an incidence of 2.3 % in primary TKA. The mean follow-up was approximately 49 months in both groups. No difference was found in revision rates between stemmed TKA (2.5 %) and conventional TKA (2.2 %). Patients with post-traumatic arthritis had an odds ratio of 10.5 (95 % CI 1.2-15.3) of receiving stems. Stem length did not affect revision rates. Patients with two stems had worse KOOS and WOMAC scores at baseline which equalized to single-stem patients at 2 years. CONCLUSIONS: The use of stems may provide a survival benefit in complex primary TKA over the short term and no adverse effect on patient outcomes or satisfaction. LEVEL OF EVIDENCE: III.

Capsular Preservation Using Suture Suspension Technique in Hip Arthroscopy for Femoroacetabular Impingement.

This article describes the use of sutures to enhance visualization while protecting the capsule in both the central and peripheral compartments during hip arthroscopy. We describe first a technique to preserve the proximal capsule cuff while working in the central compartment and then an alternative to the T-capsulotomy while maintaining excellent visualization of the peripheral compartment during femoroplasty of cam-type femoroacetabular impingement. By use of suture suspension of the capsule, multiple goals are achieved: The integrity of the proximal capsule cuff is maintained while aiding in visualization of the central compartment; the iliofemoral ligament is spared, which plays a critical role in preventing microinstability; the necessary space is created to obtain adequate visualization of the peripheral compartment for complete femoroplasty; and operative time is reduced because creation and subsequent repair of the T-capsulotomy can be avoided.

Magnetic Resonance Imaging Predicts Adverse Local Tissue Reaction Histologic Severity in Modular Neck Total Hip Arthroplasty.

BACKGROUND: The association between advanced imaging, serum metal ion levels, and histologic adverse local tissue reaction (ALTR) severity has not been previously reported for Rejuvenate modular neck femoral stems. METHODS: A cohort of 90 patients with 98 Rejuvenate modular neck femoral stems was revised by a single surgeon from July 2011 to December 2014. Before revision, patients underwent multiacquisition variable resonance image combination sequence magnetic resonance imaging (MRI), and serum cobalt and chromium ion levels were measured. Histologic samples from the revision surgery were scored for synovial lining, inflammatory infiltrate, and tissue organization as proposed by Campbell. Regression based on the generalized estimating equations approach was used to assess the univariate association between each MRI, demographic, and metal ion measure and ALTR severity while accounting for the correlation between bilateral hips. Random forest analysis was then used to determine the relative importance of MRI characteristics, demographics, and metal ion levels in predicting ALTR severity. RESULTS: Synovial thickness as measured on MRI was found to be the strongest predictor of ALTR histologic severity in a recalled modular neck femoral stem. CONCLUSION: MRI can accurately describe ALTR in modular femoral neck total hip arthroplasty. MRI characteristics, particularly maximal synovial thickness and synovitis volume, predicted histologic severity. Serum metal ion levels do not correlate with histologic severity in Rejuvenate modular neck total hip arthroplasty.

Does Degenerative Lumbar Spine Disease Influence Femoroacetabular Flexion in Patients Undergoing Total Hip Arthroplasty?

BACKGROUND: Sitting pelvic tilt dictates the proximity of the rim of the acetabulum to the proximal femur and, therefore, the risk of impingement in patients undergoing total hip arthroplasty (THA). Sitting position is achieved through a combination of lumbar spine segmental motions and/or femoroacetabular articular motion in the lumbar-pelvic-femoral complex. Multilevel degenerative disc disease (DDD) may limit spine flexion and therefore increase femoroacetabular flexion in patients having THAs, but this has not been well characterized. Therefore, we measured standing and sitting lumbar-pelvic-femoral alignment in patients with radiographic signs of DDD and in patients with no radiographic signs of spine arthrosis. QUESTIONS/PURPOSES: We asked: (1) Is there a difference in standing and sitting lumbar-pelvic-femoral alignment before surgery among patients undergoing THA who have no radiographic signs of spine arthrosis compared with those with preexisting lumbar DDD? (2) Do patients with lumbar DDD experience less spine flexion moving from a standing to a sitting position and therefore compensate with more femoroacetabular flexion compared with patients who have no radiographic signs of arthrosis? METHODS: Three hundred twenty-five patients undergoing primary THA had preoperative low-dose EOS spine-to-ankle lateral radiographs in standing and sitting positions. Eighty-three patients were excluded from this study for scoliosis (39 patients), spondylolysis (15 patients), not having five lumbar vertebrae (7 patients), surgical or disease fusion (11 patients), or poor image quality attributable to high BMI (11 patients). In the remaining 242 of 325 patients (75%), two observers categorized the lumbar spine as either without radiographic arthrosis or having DDD based on defined radiographic criteria. Sacral slope, lumbar lordosis, and proximal femur angles were measured, and these angles were used to calculate lumbar spine flexion and femoroacetabular flexion in standing and sitting positions. Patients were aligned in a standardized sitting position so that their femurs were parallel to the floor to achieve approximately 90° of apparent hip flexion. RESULTS: After controlling for age, sex, and BMI, we found patients with DDD spines had a mean of 5° more posterior pelvic tilt (95% CI, -2° to -8° lower sacral slope angles; p < 0.01) and 7° less lumbar lordosis (95% CI, -10° to -3°; p < 0.01) in the standing position compared with patients without radiographic arthrosis. However, in the sitting position, patients with DDD spines had 4° less posterior pelvic tilt (95% CI, 1°-7° higher sacral slope angles; p = 0.02). From standing to sitting position, patients with DDD spines experienced 10° less spine flexion (95% CI, -14° to -7°; p < 0.01) and 10° more femoroacetabular flexion (95% CI, 6° to 14°; p < 0.01). CONCLUSIONS: Most patients undergoing THA sit in a similar range of pelvic tilt, with a small mean difference in pelvic tilt between patients with DDD spines and those without radiographic arthrosis. However, in general, the mechanism by which patients with DDD of the lumbar spine achieve sitting differs from those without spine arthrosis with less spine flexion and more femoroacetabular flexion. CLINICAL RELEVANCE: When planning THA, it may be important to consider which patients sit with less posterior pelvic tilt and those who rotate their pelvises forward to achieve a sitting position, as both mechanisms will limit or reduce the functional anteversion of the acetabular component in a patient with a THA. Our study provides some additional perspective on normal relationships between pelvic tilt and femoroacetabular flexion, but further research might better characterize this relationship in outliers and the possible implications for posterior instability after THA.

Outcomes of Custom Flange Acetabular Components in Revision Total Hip Arthroplasty and Predictors of Failure.

BACKGROUND: Custom triflange acetabular components (CTAC) have become more popular in the treatment of Paprosky type IIIB defects with an average survivorship of 80% at 4 years. Many studies report survivorship of CTAC, but radiographic parameters of CTAC success or failure have not been previously reported. The purpose of the study was to assess radiographic and patient factors predictive of failure in CTAC. METHODS: A retrospective review of 63 patients with >24 months of follow-up was completed. Continuous and categorical variables were compared between failed vs successful CTAC using Wilcoxon rank-sum test and Fisher exact test, respectively. RESULTS: The failure rate of the CTAC was 13.5% over an average follow-up of 4.32 years (±2.94). Patients had a mean of 2 revisions (range, 0-11) before CTAC implantation. Compared with the contralateral hip center of rotation, the failed CTAC group tended to lateralize the hip center by a mean of 18.29 mm (±11.90 mm) compared to a mean of 9.86 mm (±11.89) in the intact group, although this did not reach statistical significance (P = .1029). The Western Ontario and McMaster Universities Osteoarthritis Index function score improved from 38.94 (±14.23) to 71.35 (±21.96) at most recent follow-up (P = .0002). The Western Ontario and MacMaster Universities Osteoarthritis Index scores were not significantly different between intact and failed CTAC groups. CONCLUSIONS: CTAC tends to lateralize the hip center by approximately 1 cm, and there is a trend toward nearly 2 cm of lateralization in the small subset of failed CTAC. Future efforts should focus on medializing the hip center in CTAC to improve ingrowth and survivorship.