High Rate of Intramedullary Canal Culture Positivity in Total Knee Arthroplasty Resection for Prosthetic Joint Infection.

BACKGROUND: Periprosthetic infection is a devastating complication following total knee arthroplasty. A 2-stage protocol often includes an interim antibiotic spacer with intramedullary (IM) dowels. However, the necessity of IM dowels has recently been challenged. Specifically, the data supporting bacterial colonization of the IM canal are limited and controversial. The purpose of this study was to identify the rate of positive IM cultures during resection arthroplasty in periprosthetic knee infection. METHODS: A total of 66 IM diaphyseal cultures were taken during resection arthroplasty from 34 patients diagnosed with periprosthetic knee infection. These IM cultures were taken from the femoral and tibial canals using separate sterile instruments. All patients had infected primary total knee arthroplasty implants at the time of resection. RESULTS: Thirty one percent (n = 21) of IM canal cultures in this study were positive from either the tibial or the femoral diaphysis at the time of resection arthroplasty. There were 18 of 21 (86%) of the positive IM canal cultures with concordant intraoperative joint cultures where the IM cultures matched the intraarticular cultures. CONCLUSION: With a 31% positive IM canal culture rate, this study confirms the logic of using IM dowels with an antibiotic spacer to treat periprosthetic knee infection. Since the failure of a 2-stage reimplantation is catastrophic, any attempt to provide additional local antibiotic delivery seems warranted. Since nearly one-third of our patients had positive IM cultures, this simple addition to an antibiotic spacer has the potential to improve 2-stage results. Claims supporting the elimination of IM dowels during resection arthroplasty seem ill-advised.

Does Treatment at a Specialized Prosthetic Joint Infection Center Improve the Rate of Reimplantation.

BACKGROUND: Two-stage exchange arthroplasty is currently the preferred treatment method for periprosthetic joint infection (PJI). The effectiveness of this strategy in returning patients to premorbid function has recently been challenged. In a review of 18,535 PJI knee patients, 38% did not undergo reimplantation. In another review of 18,156 hip and knee PJI patients, 43% did not undergo reimplantation. These disturbing statistics led us to ask whether treatment at a specialized PJI center could improve the rate of reimplantation compared to the previously noted studies from large national administrative databases. METHODS: A retrospective review of our registry was performed to identify 390 patients who underwent a two-stage exchange after total knee arthroplasty and total hip arthroplasty who had a confirmed chronic bacterial PJI, defined by Musculoskeletal Infection Society criteria, from January 2010 through December 2019. Variables included number of joints resected, number reimplanted, and the number not reimplanted. RESULTS: Of the 390 patients undergoing 2-stage treatment, 386 of 390 (99%) were reimplanted and 4 of 390 (1%) were not reimplanted due to medical issues. CONCLUSION: We have shown that 2-stage treatment at a PJI center significantly improves the rate of reimplantation. A specialized PJI center with experienced revision surgeons doing high volume infection procedures complemented by infectious disease and medical consultants familiar with the special needs of PJI patients may be advantageous. A national network of such centers may have the ability to improve outcomes, standardize treatment protocols, and allow for collaborative research.

Radiologist Overreads of Intraoperative Radiographs-Value or Waste?

BACKGROUND: All aspects of the arthroplasty pathway must be scrutinized to maximize value and eliminate unnecessary cost. Radiology providers' contracts with hospitals often call for readings of all radiographs. This policy has little effect on patient care when intraoperative radiographs are taken and used to make real-time decisions. In order to determine the value of radiologist overreads, we asked 3 questions: what was the delay between the time an intraoperative radiograph was taken and time the report was generated, were the overreads accurate, and what is the associated cost? METHODS: Two hundred hip and knee radiograph reports generated over 6 months during 391 cases were reviewed. The time the report was dictated was compared to the time taken and time of surgery completion. To determine accuracy, each overread was rated as accurate or inaccurate. The cost of the overread was determined by multiplying the number of radiographs times the radiology fee less the technical fee. RESULTS: Median delay between taking the radiograph and filing the report was 45 minutes (range, 0-9778 minutes). Only 31.5% were filed before completion of the procedure. And 18.0% (36/200) were considered inaccurate despite lenient criteria. The reading fee for hip radiographs was $52.00, and for knee radiographs was $38.00, representing a total cost of $10,182 in our select series. This cost projects to $43,614 annually at our facility. CONCLUSION: Radiology overreads of intraoperative radiographs have no effect on real-time decision-making. In the era of value-based care, payors should stop paying for overreads and reimburse providers who actually read the films intraoperatively.

Debridement and Implant Retention for Acute Periprosthetic Knee Infection.

Periprosthetic joint infection (PJI) is a devastating complication of total joint arthroplasty. We reviewed the current data on DAIR procedures and two-stage exchange for periprosthetic knee infection. This case study illustrates successful treatment of an acute PJI using a debridement and implant retention (DAIR) technique with adjuvant intraosseous (IO) vancomycin. (Journal of Surgical Orthopaedic Advances 30(4):249-252, 2021).

One-Stage Periprosthetic Joint Infection Reimbursement-Is It Worth The Effort?

BACKGROUND: One-stage protocols for the management of periprosthetic infection take an extended period of time requiring two separate preps and sets of instruments to ensure optimal sterility. While intraoperative service time is one part of the reimbursement algorithm, reimbursement has lagged behind for single-stage treatment with respect to the time and resources necessary to perform these complex treatment regimens. If one-stage results are shown to be acceptable, but not reimbursed appropriately, surgeons will be discouraged from managing periprosthetic joint infection (PJI) in a one-stage fashion. METHODS: The reimbursement and operative time for 50 PJI procedures were compared with 250 primary total hips and 250 primary total knees by the same 4 surgeons. RESULTS: The average reimbursement for a one-stage knee procedure was $2,597.08, with an average intraoperative service time of 259 minutes ($601.60/h). The average reimbursement for a primary total knee was $2,435.00, with an average intraoperative service time of 100 minutes ($1,461/h). The average reimbursement for a one-stage hip procedure was $2,826.17, with an average intraoperative service time of 311 minutes ($545.24/h). The average reimbursement for a primary total hip was $2,754.71 with an average intraoperative service time of 104 minutes ($1,589.26/h). CONCLUSION: One-stage procedures for PJI are reimbursed at approximately 1/3 the hourly rate of a primary procedure, which may discourage surgeons from selecting this treatment alternative even if recent studies confirm efficacy. Payers should be encouraged to reimburse physicians commensurate with the intraoperative service time needed to perform a one-stage procedure as adoption will decrease morbidity and save the healthcare system financially.

Inferomedial Hip Center Decreases Failure Rates in Cementless Total Hip Arthroplasty for Crowe II and III Hip Dysplasia.

BACKGROUND: We sought to evaluate the outcomes of cementless acetabular components used in patients with Crowe II and III dysplasia, and to compare outcomes between cups placed within vs outside of an "anatomic" zone. Our specific aims were to (1) plot hip centers in these patients at our institution to characterize "anatomic" vs "nonanatomic" positions, (2) evaluate the association between hip center and radiographic loosening, (3) determine whether hip center was associated with acetabular component revision, and (4) compare patient-reported outcome scores between groups. METHODS: We retrospectively reviewed 88 primary cementless total hip arthroplasties at a mean follow-up of 10 years (range 2-26 years). Patients were 85% female, with a mean age of 44 years (range 28-61 years) and a body mass index of 27 kg/m2 (range 19-42 kg/m2). Medical records and radiographs were reviewed, and a survey was conducted for all patients. Anatomic hip center was defined using the 4-zone system, wherein centers are "anatomic" if they are <1 cm superior and <1 cm lateral to the approximate femoral head center. Cox proportional analyses were used to compare outcomes between groups. RESULTS: Seventy hips (80%) had an anatomic hip center. Anatomic hips had a lower incidence of radiographic acetabular loosening (0% vs 17%, P = .007) and cup revision (0% vs 28%, P = .0002). There were no differences in Hip Disability and Osteoarthritis Outcome and Joint Replacement Scores (96.2 ± 5 vs 91.9 ± 12, P = .7). CONCLUSION: The incidence of aseptic loosening and cup revision were lower when hip center was <1 cm superior and 1 cm lateral to the approximate femoral head center.

Should Depression Be Treated Before Lower Extremity Arthroplasty?

BACKGROUND: Patient optimization is becoming increasingly important before arthroplasty to ensure outcomes. It has been suggested that depression is a modifiable risk factor that should be corrected preoperatively. It remains to be determined whether psychological intervention before surgery will improve outcomes. We theorized that the use of preoperative depression scales to predict postoperative outcomes may be influenced by the pain and functional disability of arthritis. To determine whether depression is a modifiable risk factor that should be corrected preoperatively we asked the following questions: (1) What is the prevalence of depression in arthroplasty patients preoperatively? (2) Do depressive symptoms improve after surgery? (3) Is preoperative depression associated with outcome? METHODS: Patients scheduled for surgery completed a patient health questionnaire (PHQ-9) to assess the presence and severity of depression pre-operatively and one year post-operatively. RESULTS: Sixty-five of the 282 patients had a PHQ-9 score >10 indicating moderate depression and 57 (88%) improved to <10 postoperatively (P = .0012). Ten patients had a PHQ-9 score >20 indicating severe depression and 9 (90%) improved to <10 postoperatively (P = .10). Of the 65 patients who had a PHQ-9 score >10 preoperatively, the median postoperative Hip Disability and Osteoarthritis Outcome Score (N = 40) was 92.3, while the median postoperative Knee Injury and Osteoarthritis Outcome Score (N = 25) was 84.6. The median postoperative Hip Disability and Osteoarthritis Outcome Score and Knee Injury and Osteoarthritis Outcome Score in nondepressed patients were 96.2 and 84.6, respectively (P = .9041). CONCLUSION: By diminishing pain and improving function through arthroplasty, depression symptoms improve significantly. Patients with depressive symptoms preoperatively had similar postoperative outcome scores compared to non-depressed patients. Patients should not be denied surgical intervention through optimization programs that include a depression scale threshold. LEVEL OF EVIDENCE: III.

Radiographic Findings in Patients With Catastrophic Varus Collapse After Total Knee Arthroplasty.

BACKGROUND: Catastrophic varus collapse is an uncommon mechanism of failure in primary total knee arthroplasty (TKA). Varus collapse has been associated with obesity and smaller implant sizes. However, to our knowledge, preoperative radiographic characterization of this cohort has not been performed. Therefore, the following study evaluated preoperative alignment and how this correlates with the degree of eventual varus collapse identified in this patient population prior to revision. METHODS: Utilizing our institutional database, 1106 revision TKAs were performed from 2004 to 2017. Of these, 35 patients were revised secondary to tibial varus collapse. Twenty-seven patients had their primary TKA performed at our institution. Coronal alignment of the knee was recorded from anteroposterior knee radiographs. Medial tibial bone loss was recorded at final follow-up. RESULTS: The average body mass index was 38 kg/m2. Twenty-six of 27 patients had a preoperative varus deformity (4.2° varus) and all were corrected to a valgus coronal alignment immediately postoperatively (5.2° valgus, P = .0001). Twenty-four of 27 patients' coronal alignment after varus collapse was within 2° of their preoperative alignment (5.8° varus). Twenty-five of 27 patients had radiographic medial tibial bone loss prior to varus collapse. CONCLUSION: Tibial varus collapse in an uncommon cause of failure after primary TKA. Preoperative varus deformity, postoperative medial tibial bone loss, and obesity were common findings in this series of patients. Therefore, increased tibial stem lengths should be considered in patients with a preoperative varus deformity, small tibial implant size, and a body mass index ≥35 kg/m2 undergoing primary TKA.

Midterm Survivorship After Revision Total Hip Arthroplasty With a Custom Triflange Acetabular Component.

BACKGROUND: Custom triflange acetabular components are being increasingly used for the reconstruction of Paprosky type IIIB acetabular defects. However, midterm survivorship data are lacking. METHODS: We queried the prospective registries at 2 high-volume revision centers for patients who had undergone revision total hip arthroplasty using a custom triflange component between 2000 and 2011. We identified 73 patients with minimum 5-year follow-up. These patients' records were reviewed to determine incidence of revision or reoperation, clinical performance, and radiographic stability. The mean follow-up was 7.5 years (range 5-12 years). RESULTS: Fifteen of 73 triflange components (20.5%) were indicated for revision during the follow-up period, including 6 for instability (8%) and 8 for infection (11%). Twelve of 73 patients (16%) underwent reoperation for reasons other than failure of the triflange component. The median hip disability and osteoarthritis outcome score for joint replacement score at midterm follow-up was 85 (interquartile range 73-100). Only 1 of 73 implants was determined to be radiographically loose at midterm follow-up. CONCLUSION: Custom triflange reconstruction for severe acetabular deficiency is a viable option; however, complications are common and significant challenges remain for those that fail.

Efficacy of Revision Surgery for the Treatment of Stiffness After Total Knee Arthroplasty: A Systematic Review.

BACKGROUND: Knee stiffness following total knee arthroplasty (TKA) may cause pain and reduced functionality, contributing to unsatisfactory surgical outcomes. Revision surgery remains a possible treatment for refractory postoperative stiffness. However, the efficacy of the procedure has not been systematically evaluated. METHODS: A systematic review of the literature was performed to identify studies that reported on outcomes for patients who underwent revision surgery for postoperative stiffness after TKA. RESULTS: Ten studies (including 485 knees) were reviewed. The most common etiologies of stiffness requiring revision TKA were component malposition, malalignment, overstuffing, aseptic loosening, arthrofibrosis, patella baja, and heterotopic ossification. Of 9 studies reviewing range of motion outcomes after revision TKA, 7 studies documented significant improvement and 2 found trends toward improvement. Seven of 8 studies documenting Knee Society knee scores and 7 of 9 studies documenting functional scores found improvement after revision TKA. All studies reporting on pain found improvement at final follow-up after revision TKA. CONCLUSION: Revision TKA results in increased range of motion, improved functionality, and reduced pain in most patients who require surgery for stiffness. The present literature is inadequate to predict which patients will achieve adequate outcomes from revision TKA based on the specific etiology of their stiffness, although identification of the etiology may help in surgical planning. Surgeons performing revision TKA should counsel patients on the risks and benefits of undergoing revision surgery, with the understanding that outcomes for well-selected patients are generally favorable.

Variability of Pelvic Orientation in the Lateral Decubitus Position: Are External Alignment Guides Trustworthy?

BACKGROUND: The position of the acetabular component in total hip arthroplasty (THA) is critical for success. However, this remains the most variable aspect of the surgery. We hypothesized that there is wide variation in pelvic orientation in the lateral decubitus position. We sought to determine the variability in pelvic positioning and the frequency of pelvic malposition during THA in lateral decubitus with regard to pelvic tilt and pelvic rotation. METHODS: We analyzed preoperative standing and intraoperative anteroposterior pelvis X-rays in 248 consecutive THAs performed in lateral decubitus by one surgeon. Pelvic tilt and rotation were determined for preoperative and intraoperative X-rays. Proper intraoperative positioning was defined as less than 10° change in tilt or rotation between preoperative and intraoperative X-rays. RESULTS: With regard to pelvic tilt, the intraoperative position was proper in 188 (76%) cases. There was a pelvic tilt discrepancy of 10°-20° in 43 (17.5%) cases and greater than 20° in 16 (6.5%) patients. With regard to pelvic rotation, the intraoperative position was proper in 202 (81%) cases. There was a pelvic rotation discrepancy of 10°-20° in 38 (15.4%) cases and greater than 20° in 7 (2.8%) cases. In 248 cases, only 154 (62.1%) had intraoperative positioning within 10° of preoperative tilt and axial rotation. Pelvic malposition occurred in 38% of cases overall. CONCLUSION: There is wide variation in pelvic orientation in lateral decubitus and frequent discrepancy in pelvic tilt and rotation between preoperative and intraoperative anteroposterior X-rays. Anatomic landmarks should be used to guide acetabular component positioning. LEVEL OF EVIDENCE III: Diagnostic.

Fluoroscopically Assisted Radiographs Improve Sensitivity of Detecting Loose Tibial Implants in Revision Total Knee Arthroplasty.

BACKGROUND: Fluoroscopically assisted radiographs theoretically improve detection of total knee arthroplasty (TKA) implant loosening by providing a better evaluation of the true implant interface, but their utility has not been well studied. We sought to determine whether fluoroscopically guided radiographs improve the sensitivity, specificity, and interobserver reliability of determining TKA implant loosening compared to standard radiographs. METHODS: Standard anteroposterior and lateral and fluoroscopically assisted radiographs were retrospectively obtained from 60 patients within 6 months before revision TKA. Thirty knees were revised for aseptic loosening and 30 knees for other indications, most commonly instability. The radiographs were randomized. Four reviewers independently determined whether each tibial and femoral component was radiographically loose or stable. Intraoperative determination of implant stability was utilized as the gold standard. RESULTS: Fluoroscopically guided radiographs had a significantly higher sensitivity for detecting tibial component loosening compared to standard radiographs (85.3% vs 74.8%, P = .02). Sensitivity in detecting femoral component loosening was poor overall and not improved by fluoroscopic enhancement compared to standard radiographs (58.8% vs 66.5%, P = .33). Fluoroscopically guided radiographs did not improve the specificity of detecting well-fixed implants in either tibial or femoral components nor affect the mean interobserver reliability over standard radiographs (kappa = 0.58 vs kappa = 0.60, P = .6). CONCLUSION: Fluoroscopically assisted radiographs increased the sensitivity of detecting tibial component loosening over standard radiographs, but this clinical significance is unclear. Fluoroscopically guided radiographs may provide benefit in diagnosing aseptic loosening in select patients with painful TKAs.

Catastrophic Varus Collapse of the Tibia in Obese Total Knee Arthroplasty.

BACKGROUND: Mechanical complications have been underemphasized in reports on total knee arthroplasty (TKA) in obese patients. Noticing an increased prevalence of varus collapse of the tibia in obese total knee patients, we sought to determine if variability in proximal tibial cancellous bone strength played a role in failure. We attempted to define a cancellous threshold above which alternative methods of fixation should be used. METHODS: One thousand one hundred six revision TKAs from 2004-2014 identified 35 patients with varus collapse of the tibia, defined as a change in component position of >10°. Variables analyzed included weight, alignment, component size, and proximal tibial bone stress. Postoperative alignment was compared with prerevision alignment. To calculate tibial stress the following formula was used: mass (kg) × acceleration of gravity (9.8 m/s2)/tibial surface area (mm2) = pascals or N/M2. RESULTS: Twenty-nine of 35 patients weighed >200 lbs, whereas 17 of 35 patients weighed >250 lbs (range 130-354 lbs). Average body mass index was 40.5 kg/m2 (range 24-61 kg/m2). Twenty-seven of 35 failed tibial components were in the lower half of the manufacturer's tibial size offering. Postsurgical alignment averaged 4.9° valgus (range 2° varus-7° valgus) and collapsed an average of 14.9° (range 10°-22°) before revision. Proximal tibial bone stress averaged 334,324 Pascals (range 188,524-601,416). Twenty-five of 35 patients had proximal tibial bone stress >300,000 Pascals. CONCLUSION: Despite good initial primary TKA alignment, we report catastrophic varus collapse of tibial components in obese patients with small tibial components. When a cancellous threshold of 300,000 Pascals is exceeded, strong consideration should be given to either optimizing the patient's weight or using a longer tibial stem to dissipate forces on proximal tibia.

A Novel Percentage-Based System for Determining Aseptic Loosening of Total Knee Arthroplasty Tibial Components.

BACKGROUND: There are limited data on evaluating the significance of radiolucent lines and aseptic loosening in total knee arthroplasty (TKA). We sought to compare the sensitivity, specificity, and reliability of the Knee Society Total Knee Arthroplasty Roentgenographic Evaluation and Scoring System (KSRES) in detecting tibial component loosening compared to a novel percentage-based system (PBS). METHODS: We retrospectively reviewed radiographs obtained from 48 patients within 6 months prior to revision TKA. The radiographs were randomized and four reviewers independently used the KSRES to categorize tibial implants as nonconcerning, clinical follow-up for progression, or loose as described by KSRES. For the PBS, the percent involvement of the tibial implant interface of any radiolucency at the bone-cement or cement-implant interface was determined. The higher percentage from either the anteroposterior or the lateral image was the final score. Components were categorized as nonconcerning (≤10%), clinical follow-up for progression (11%-24%), or loose (≥25%). We compared the sensitivity, specificity, and interobserver reliability using intraoperative assessment of implant fixation as the gold standard. RESULTS: For the KSRES, the mean sensitivity for determining tibial loosening was 7.3% and mean specificity for determining a nonconcerning implant was 95.9%. The PBS significantly increased the sensitivity to 91.1% (P < .001) while maintaining a specificity of 87.9% (P = .2). Interobserver reliability significantly increased from a mean kappa of 0.26 to 0.75 (P < .001). CONCLUSION: The KSRES significantly underestimates implant loosening. The proposed percentage-based system demonstrated excellent sensitivity, specificity, and interobserver reliability in determining tibial implant loosening in this patient population.

Dissociation and Intrapelvic Entrapment of a Dual-mobility Polyethylene Component.

BACKGROUND: Dual-mobility bearings have gained popularity in recent years as a proposed method of reducing the risk of dislocation after primary and revision hip arthroplasties. Intraprosthetic dislocation, defined as dissociation of the smaller femoral head from the larger outer polyethylene head, is a known complication of these designs. Intraprosthetic dislocation typically requires reoperation and revision as closed reduction of intraprosthetic dislocations of these components is not effective. The small femoral head typically remains inside the large diameter acetabular component during intraprosthetic dislocation, thus the diagnosis may be missed if femoral head eccentricity is not identified on radiographs. Intraprosthetic dislocation leads to a free polyethylene bearing which typically stays in the joint space, however in theory, migration of the bearing is possible. CASE DESCRIPTION: We report a case of polyethylene bearing disengagement and intrapelvic entrapment after anterior dislocation of a hip with a modern dual-mobility bearing. The diagnosis of polyethylene component migration to an intrapelvic location was not made until surgery. Isolated acetabular revision of the dual-mobility bearing was performed to correct the instability in this patient. The entrapped polyethylene head was left in its intrapelvic position as retrieval was thought to be more morbid than retention of the component. LITERATURE REVIEW: Intraprosthetic dislocation, with disassociation of the polyethylene bearing from the femoral head, is a known complication of dual-mobility designs. Reports of intrapelvic entrapment of trial femoral heads of conventional hip arthroplasties have been described extensively in the literature. To our knowledge, intrapelvic migration and entrapment of a polyethylene bearing after dislocation of a hip with a dual-mobility implant has not been reported. CLINICAL RELEVANCE: We discuss an implant-specific complication that has not been reported, and surgeons should be aware that this unique complication can occur. Surgeons should recognize the eccentricity of the femoral head on postreduction radiographs so an intraprosthetic dislocation is not missed. Furthermore, surgeons should be aware that intraprosthetic dislocation carries a risk of intrapelvic migration of the polyethylene component which is not visible on plain radiographs.

Cystic Adverse Local Tissue Reactions in Asymptomatic Modular Metal-on-Metal Total Hips May Decrease Over Time.

BACKGROUND: The presence of pain as a harbinger of bearing-related problems has recently been challenged. Adverse local tissue reactions (ALTRs) have been noted on cross-sectional imaging even in asymptomatic patients. The purpose of this study was to determine the natural history of such lesions in asymptomatic patients. METHODS: Eighty-three asymptomatic patients with modular metal-on-metal total hip arthroplasties underwent metal ion reports and metal artifact reduction sequence magnetic resonance imaging (MARS MRI). MARS MRI images were reviewed and evaluated for the presence or absence of an ALTR lesion by a musculoskeletal radiologist and the senior author. We defined an ALTR lesion as abnormal fluid collections, solid or semisolid pseudotumors, or muscle or bone damage and was classified according to the MRI Classification System of Hart et al. In addition, serum cobalt and chromium levels were measured and analyzed at the time of MRI. RESULTS: Twenty-six of 83 (31%) asymptomatic patients had cystic lesions identified. All patients with positive MRIs were contacted to have repeat studies a year later. Nineteen of 26 were available for follow-up. Three patients who became symptomatic were revised. Most ALTRs in asymptomatic patients with modular metal-on-metal total hip arthroplasties that underwent repeat MARS MRI decreased in size (15 of 19 [79%]); 3 lesions increased, whereas 1 remained the same. All patients in the series had Co and Cr ion levels below the threshold of 7 ppb. CONCLUSION: Although most cystic lesions decreased in size, vigilance is still required as 3 patients became symptomatic requiring revision.

Preoperative Evaluation for Pelvic Discontinuity Using a New Reformatted Computed Tomography Scan Protocol.

BACKGROUND: The identification of suspected pelvic discontinuity is important for preoperative planning in revision hip arthroplasty. Computed tomography (CT) of the pelvis with reconstructions in the axial, sagittal, and coronal planes has been previously described for the identification of pelvic discontinuity but fails to show some discontinuities. The purpose of this study was to determine whether reformatted 45° oblique CT scans of the pelvis, similar in projection to Judet views on plain films, provide advantages in detecting pelvic discontinuity preoperatively over standard reconstruction CT scans. We describe a new technique of reformatting conventional CT scans to present 45° oblique views of the pelvis. METHODS: Using an institutional joint registry, we retrospectively identified 22 patients who had intraoperative findings of pelvic discontinuity and also had a preoperative CT scan of the pelvis. The criterion for diagnosis of pelvic discontinuity was a continuous visible fracture line involving the entire width of the anterior and posterior columns. RESULTS: In this study, standard reconstruction CT scans were 73% sensitive in identifying discontinuity based on these parameters and the addition of reformatted 45° oblique CT scans increased sensitivity to 91%. CONCLUSION: Unique reconstructive techniques in revision hip arthroplasty can be used, and the operative plan may be modified if pelvic discontinuity is identified preoperatively. CT scans of the pelvis with reconstructions at 45° iliac oblique and obturator oblique views in patients with suspected pelvic discontinuity provide a high level of sensitivity when the diagnosis cannot be firmly established from plain films.

Cobalt to Chromium Ratio is Not a Key Marker for Adverse Local Tissue Reaction (ALTR) in Metal on Metal Hips.

The diagnosis of adverse local tissue reaction (ALTR) after metal-on-metal total hip arthroplasty (MoMTHA) presents a significant challenge. No single biomarker is specific for ALTR. The purpose of this study was to determine if the ratio of cobalt to chromium ions is useful for diagnosing ALTR in MoMTHA. In 89 bearing-related revision THAs, preoperative cobalt and chromium ion levels were compared to an intraoperative soft tissue damage grading scale. The average cobalt to chromium ratio was 2.96 (0-20). There was no correlation between the tissue scale and the cobalt to chromium ratio (R=0.095; P=0.41). Many variables affecting ion production/excretion mitigate the use of the ion ratio. The cobalt to chromium ratio is not a predictive biomarker for ALTR in MoMTHA.

Initial stability of press-fit acetabular components under rotational forces.

The primary goal of this study was to determine the initial press-fit stability in acetabular components without screw fixation. Mechanical testing was performed with the implantation of press-fit acetabular components in cadaveric specimens. No significant difference was found in load to failure testing between 1 and 2 mm of under-reaming. However, there was significant variability in bending forces required to create 150 µm of micromotion ranging from 49.3 N to 214.4 N. This study shows that cups implanted in a press-fit fashion, which are felt to be clinically stable, have high degrees of variability in resisting load and may be at risk for loosening. There is a need for more objective intra-operative techniques to test cup stability.