Validation of a Novel Method of Measuring Cup Orientation Using BiPlanar Simultaneous Radiographic Images.

BACKGROUND: Accurate acetabular component positioning is paramount to the success of total hip arthroplasty (THA). Two-dimensional imaging alone remains a popular tool for implant position assessment despite known limitations. We investigated the accuracy of a novel method for assessing acetabular component position based upon orthogonal simultaneous biplanar X-ray images. METHODS: There were forty consecutive patients who had a preexisting THA on the contralateral side who underwent both computed tomography (CT) and simultaneous orthogonal biplanar radiographic scans for preoperative planning of THA. The operative inclination (OI) and operative anteversion (OA) of the acetabular cup were calculated by a new measurement method using the biplanar simultaneous scans. Those measurements were compared to measurement of the cup orientation on CT. The measurements were made by 2 independent observers. Interobserver correlation coefficients were calculated between the 2 observers to measure reliability. RESULTS: The mean error in OA measurement of the acetabular cup between simultaneous orthogonal biplanar radiographic and CT imaging was 0.5° (SD: 1.9°, minimum -4.0°, maximum 5.0°), the mean error in OI was 0.0° (SD: 1.7°, minimum -5.0°, maximum 4.0°). The average absolute error was 1.5° for OA and 1.2° for OI. Interobserver correlation coefficient was 0.83 for OA and 0.93 for OI. CONCLUSION: The novel method of measuring cup orientation using simultaneous biplanar radiographic scans utilized in this study was accurate and reproducible between observers compared to CT measurements.

Effect of pelvic tilt and rotation on cup orientation in standing anteroposterior radiographs.

BACKGROUND: Individual pelvic tilt and rotation have wide variability that can affect the measurement of cup orientation in anteroposterior (AP) radiographs. The purpose of this study was to analyse the effect of pelvic tilt and rotation on radiographic measurements of cup orientation. METHODS: A total of 53 patients (63 hips) were included in this study. The patients underwent a computed tomography study with standing AP pelvis radiographs taken both preoperatively and approximately 3 months postoperatively. We used 2-dimensional/3-dimensional matching to measure the pelvic tilt and rotation, and the non-standardised and standardised cup orientation. RESULTS: There was no difference in the pelvic tilt and rotation between the preoperative and postoperative radiographs. The distribution of the differences between the non-standardised and standardised cup anteversion exhibited a change within 5° in only 34/63 (54%) hips. The pelvic tilt correlated with the difference between the non-standardised and standardised cup anteversion, but the pelvic rotation did not. When all 63 hips were separated into the right and left sides, the pelvic rotation inversely correlated with the pelvic tilt-adjusted difference between the non-standardised and standardised cup anteversion of the right side but directly correlated with that of the left side. CONCLUSIONS: The current study demonstrated that the measurement of cup anteversion in standing AP radiographs is significantly affected by both the pelvic tilt and pelvic rotation. An improved understanding of the pelvic orientation may eventually allow for desired cup positioning on a patient-specific basis to potentially reduce complications associated with the malposition of the cup.

Alternating operating theatre utilization is not associated with differences in clinical or economic outcome measures in primary elective knee arthroplasty.

AIMS: The practice of alternating operating theatres has long been used to reduce surgeon idle time between cases. However, concerns have been raised as to the safety of this practice. We assessed the payments and outcomes of total knee arthroplasty (TKA) performed during overlapping and nonoverlapping days, also comparing the total number of the surgeon's cases and the total time spent in the operating theatre per day. MATERIALS AND METHODS: A retrospective analysis was performed on the Centers for Medicare & Medicaid Services (CMS) Limited Data Set (LDS) on all primary elective TKAs performed at the New England Baptist Hospital between January 2013 and June 2016. Using theatre records, episodes were categorized into days where a surgeon performed overlapping and nonoverlapping lists. Clinical outcomes, economic outcomes, and demographic factors were calculated. A regression model controlling for the patient-specific factors was used to compare groups. Total orthopaedic cases and aggregate time spent operating (time between skin incision and closure) were also compared. RESULTS: A total of 3633 TKAs were performed (1782 on nonoverlapping days; 1851 on overlapping days). There were no differences between the two groups for length of inpatient stay, payments, mortality, emergency room visits, or readmission during the 90-day postoperative period. The overlapping group had 0.74 fewer skilled nursing days (95% confidence interval (CI) -0.26 to -1.22; p < 0.01), and 0.66 more home health visits (95% CI 0.14 to 1.18; p = 0.01) than the nonoverlapping group. On overlapping days, surgeons performed more cases per day (5.01 vs 3.76; p < 0.001) and spent more time operating (484.55 minutes vs 357.17 minutes; p < 0.001) than on nonoverlapping days. CONCLUSION: The study shows that the practice of alternating operating theatres for TKA has no adverse effect on the clinical outcome or economic utilization variables measured. Furthermore, there is opportunity to increase productivity with alternating theatres as surgeons with overlapping cases perform more cases and spend more time operating per day. Cite this article: Bone Joint J 2019;101-B:1081-1086.

Early results of displaced femoral neck fragility fractures treated with supercapsular percutaneous-assisted total hip arthroplasty.

BACKGROUND: Total hip arthroplasty (THA) is the preferred treatment for displaced femoral neck fractures in select patients, although dislocation remains a concern. In some studies, the supercapsular percutaneously assisted (SuperPATH) approach has demonstrated early mobilization, short hospital stay, and low dislocation rates in primary THA, but there are little data on its use for fractures. This study describes the perioperative outcomes and early dislocation rate of SuperPATH THA for displaced femoral neck fragility fractures. METHODS: A retrospective review was performed of previous ambulatory patients with a displaced femoral neck fragility fracture treated with THA using the SuperPATH approach. Demographic data, time to ambulation, length of stay, and in-hospital complications during the hospital stay and follow-up period were recorded. Phone interviews were conducted to check for dislocations 1 year after surgery. RESULTS: Thirty-seven consecutive patients were included with an average age of 75.0 years. Hospital stay averaged 5.5 days, and patients were discharged on average postoperative day 3.6. About 83.8% of patients were ambulatory by postoperative day 1, and 94.6% ambulatory before discharge. Twenty-seven percent of patients were discharged home, 46% to inpatient rehabilitation, 24% to skilled nursing facility, and 1 patient to hospice. At follow-up, there was no symptomatic heterotopic ossification and no infections. Thirty-two patients were available for telephone interviews at 1 year, with no dislocations reported. CONCLUSIONS: In this small cohort, the SuperPATH approach for THA appears to be safe and effective for use in femoral neck fragility fractures, resulting in early ambulation and a low dislocation rate.

Higher Volume Surgeons Have Lower Medicare Payments, Readmissions, and Mortality After THA.

BACKGROUND: The advent of value-based care, in which surgeons and hospitals accept more responsibility for clinical and financial results, has increased the focus on surgeon- and hospital-specific outcomes. However, methods to identify high-quality, low-cost surgeons are not well developed. QUESTIONS/PURPOSES: (1) Is there an association between surgeon THA volume and 90-day Centers for Medicare & Medicaid Services (CMS) Part A payments, readmissions, or mortality? (2) What proportion of THAs in the United States is performed by low- and high-volume surgeons? METHODS: We performed a retrospective analysis of the CMS Limited Data Set on all primary elective THAs performed in the United States (except Maryland) between January 2013 and June 2016 on patients insured by Medicare. This represented 409,844 THAs totaling more than USD 7.7 billion in direct CMS expenditures. Surgeons were divided into five groups based on annualized volume of CMS elective THAs over the study period. Using linear and logistic regression, we calculated and compared 90-day CMS Part A payments, readmissions, and mortality among the groups. For each episode, demographic information (age, sex, and race), geographic location, and Elixhauser comorbidities were calculated to control for major confounding factors in the regression. RESULTS: When compared with the highest volume group, each lower volume group had increased payments, increased readmission rates, and increased mortality rates in a stepwise fashion when controlling for patient-specific variables including Elixhauser comorbidity index, demographic information, region, and background trend. The lowest volume group resulted in 27.2% more CMS payments per case (p < 0.001; 95% confidence interval [CI], 26.6%-27.8%), had an increased readmission odds ratio (OR) of 1.8 (p < 0.001; 95% CI, 1.7-1.9), and an increased mortality OR of 4.7 (p < 0.001; 95% CI, 4.0-5.5) when compared with the highest volume group. There was also variation within volume groups: some lower volume surgeons had lower payments, readmissions, and mortality than some higher volume surgeons despite the general trend. In terms of CMS volume, surgeons who were at least moderate volume (11+ annual cases) performed 78% of THAs and represented 26% of operating surgeons. The low- and lowest volume surgeons (10 or fewer annual cases) performed only 22% of THAs in the United States while representing 74% of unique operating surgeons. CONCLUSIONS: There is a strong association between a surgeon's Medicare volume and lower CMS payments, readmissions, and mortality. Furthermore, the majority of Medicare THAs in the United States are performed by surgeons who perform > 10 CMS operations annually. Compared with previous work, these results suggest a trend toward higher volume surgeons in the Medicare population. The results also suggest a benefit to the shift toward higher volume surgeons in reducing payments, readmissions, and mortality for elective THA in the United States. However, given that payments, readmission, and mortality of surgeons varied widely, it is important to note that available individual CMS data can be used to directly evaluate each individual surgeon based on their actual results well as through association with volume. LEVEL OF EVIDENCE: Level III, therapeutic study.

2018 John Charnley Award: Analysis of US Hip Replacement Bundled Payments: Physician-initiated Episodes Outperform Hospital-initiated Episodes.

BACKGROUND: The Centers for Medicare & Medicaid Services (CMS) launched the Bundled Payment for Care Improvement (BPCI) initiative in 2013 to create incentives to improve outcomes and reduce costs in various clinical settings, including total hip arthroplasty (THA). This study seeks to quantify BPCI initiative outcomes for THA and to determine the optimal party (for example, hospital versus physician group practice [PGP]) to manage the program. QUESTIONS/PURPOSES: (1) Is BPCI associated with lower 90-day payments, readmissions, or mortality for elective THA? (2) Is there a difference in 90-day payments, readmissions, or mortality between episodes initiated by PGPs and episodes initiated by hospitals for elective THA? (3) Is BPCI associated with reduced total Elixhauser comorbidity index or age for elective THA? METHODS: We performed a retrospective analysis on the CMS Limited Data Set on all Medicare primary elective THAs without a major comorbidity performed in the United States (except Maryland) between January 2013 and March 2016, totaling more than USD 7.1 billion in expenditures. Episodes were grouped into hospital-run BPCI (n = 42,922), PGP-run BPCI (n = 44,662), and THA performed outside of BPCI (n = 284,002). All Medicare Part A payments were calculated over a 90-day period after surgery and adjusted for inflation and regional variation. For each episode, age, sex, race, geographic location, background trend, and Elixhauser comorbidities were determined to control for major confounding variables. Total payments, readmissions, and mortality were compared among the groups with logistic regression. RESULTS: When controlling for demographics, background trend, geographic variation, and total Elixhauser comorbidities in elective Diagnosis-Related Group 470 THA episodes, BPCI was associated with a 4.44% (95% confidence interval [CI], -4.58% to -4.30%; p < 0.001) payment decrease for all participants (USD 1244 decrease from a baseline of USD 18,802); additionally, odds ratios (ORs) for 90-day mortality and readmissions were unchanged. PGP groups showed a 4.81% decrease in payments (95% CI, -5.01% to -4.61%; p < 0.001) after enrolling in BPCI (USD 1335 decrease from a baseline of USD 17,841). Hospital groups showed a 4.04% decrease in payments (95% CI, -4.24% to 3.84%; p < 0.01) after enrolling in BPCI (USD 1138 decrease from a baseline of USD 19,799). The decrease in payments of PGP-run episodes was greater compared with hospital-run episodes. ORs for 90-day mortality and readmission remained unchanged after BPCI for PGP- and hospital-run BPCI programs. Patient age and mean Elixhauser comorbidity index did not change after BPCI for PGP-run, hospital-run, or overall BPCI episodes. CONCLUSIONS: Even when controlling for decreasing costs in traditional fee-for-service care, BPCI is associated with payment reduction with no change in adverse events, and this is not because of the selection of younger patients or those with fewer comorbidities. Furthermore, physician group practices were associated with greater payment reduction than hospital programs with no difference in readmission or mortality from baseline for either. Physicians may be a more logical group than hospitals to manage payment reduction in future healthcare reform. LEVEL OF EVIDENCE: Level II, economic and decision analysis.

Cost Savings in a Surgeon-Directed BPCI Program for Total Joint Arthroplasty.

BACKGROUND: There are few studies available on the savings generated and strategies employed for cost reduction in total joint arthroplasty. In this study, our organization-a group of private practices partnering with a consultant-aimed to analyze the impact of a preoperative protocol on overall cost savings. MATERIALS AND METHODS: Using administrative data from the Medicare Bundled Payments for Care Improvement (BPCI) initiative, 771 consecutive total joint arthroplasty patients from 2009-2014 were compared with 408 consecutive BPCI patients from 2014-2017. The 30-day episode and Medicare part B total cost of care was analyzed. This included inpatient and post-discharge expenditure, laboratory and imaging costs, physician and ER visits, and readmission. RESULTS: Average total episode cost declined by $3,174 or 13% from $23,925 to $20,752 (p<0.001) in the BPCI period. Readmission rate was unchanged (p=0.20), and there was a 48% reduction in the percent of patients presenting to the emergency room (p=.03). There was a decline of $2,647 (78%) in skilled nursing cost per case, which represented the majority of savings. Post-discharge imaging, laboratory test claims, postoperative emergency room visits, primary care physician (PCP) visits, and cost per episode all decreased. The decrease in PCP utilization did not result in increased medical complications or readmissions. CONCLUSION: Our preoperative patient-education protocol has decreased non-home discharge, unnecessary postoperative physician visits, and diagnostic testing resulting in an episode cost savings of 13%. With Advanced BPCI on the horizon, orthopedic surgeon control as the awardee of the bundle, combined with an increasing focus on patient education, will continue to lower costs and improve patient care.

The Safe Zone Range for Cup Anteversion Is Narrower Than for Inclination in THA.

BACKGROUND: Cup malposition is a common cause of impingement, limitation of ROM, acceleration of bearing wear, liner fracture, and instability in THA. Previous studies of the safe zone based on plain radiographs have limitations inherent to measuring angles from two-dimensional projections. The current study uses CT to measure component position in stable and unstable hips to assess the presence of a safe zone for cup position in THA. QUESTIONS/PURPOSES: (1) Does acetabular component orientation, when measured on CT, differ in stable components and those revised for recurrent instability? (2) Do CT data support historic safe zone definitions for component orientation in THA? METHODS: We identified 34 hips that had undergone revision of the acetabulum for recurrent instability that also had a CT scan of the pelvis between August 2003 and February 2017. We also identified 175 patients with stable hip replacements who also had a CT study for preoperative planning and intraoperative navigation of the contralateral side. For each CT study, one observer analyzed major factors including acetabular orientation, femoral anteversion, combined anteversion (the sum of femoral and anatomic anteversion), pelvic tilt, total offset difference, head diameter, age, sex, and body mass index. These measures were then compared among stable hips, hips with cup revision for anterior instability, and hips with cup revision for posterior instability. We used a clinically relevant measurement of operative anteversion and inclination as opposed to the historic use of radiographic anteversion and inclination. The percentage of unstable hips in the historic Lewinnek safe zone was calculated, and a new safe zone was proposed based on an area with no unstable hips. RESULTS: Anteriorly unstable hips compared with stable hips had higher operative anteversion of the cup (44° ± 12° versus 31° ± 11°, respectively; mean difference, 13°; 95% confidence interval [CI], 5°-21°; p = 0.003), tilt-adjusted operative anteversion of the cup (40° ± 6° versus 26° ± 10°, respectively; mean difference, 14°; 95% CI, 10°-18°; p < 0.001), and combined tilt-adjusted anteversion of the cup (64° ± 10° versus 54° ± 19°, respectively; mean difference, 10°; 95% CI, 1°-19°; p = 0.028). Posteriorly unstable hips compared with stable hips had lower operative anteversion of the cup (19° ± 15° versus 31° ± 11°, respectively; mean difference, -12°; 95% CI, -5° to -18°; p = 0.001), tilt-adjusted operative anteversion of the cup (19° ± 13° versus 26° ± 10°, respectively; mean difference, -8°; 95% CI, -14° to -2°; p = 0.014), pelvic tilt (0° ± 6° versus 4° ± 6°, respectively; mean difference, -4°; 95% CI, -7° to -1°; p = 0.007), and anatomic cup anteversion (25° ± 18° versus 34° ± 12°, respectively; mean difference, -9°; 95% CI, -1° to -17°; p = 0.033). Thirty-two percent of the unstable hips were located in the Lewinnek safe zone (11 of 34; 10 posterior dislocations, one anterior dislocation). In addition, a safe zone with no unstable hips was identified within 43° ± 12° of operative inclination and 31° ± 8° of tilt-adjusted operative anteversion. CONCLUSIONS: The current study supports the notion of a safe zone for acetabular component orientation based on CT. However, the results demonstrate that the historic Lewinnek safe zone is not a reliable predictor of future stability. Analysis of tilt-adjusted operative anteversion and operative inclination demonstrates a new safe zone where no hips were revised for recurrent instability that is narrower for tilt-adjusted operative anteversion than for operative inclination. Tilt-adjusted operative anteversion is significantly different between stable and unstable hips, and surgeons should therefore prioritize assessment of preoperative pelvic tilt and accurate placement in operative anteversion. With improvements in patient-specific cup orientation goals and acetabular component placement, further refinement of a safe zone with CT data may reduce the incidence of cup malposition and its associated complications. LEVEL OF EVIDENCE: Level III, diagnostic study.

Effect of Pelvic Tilt and Rotation on Cup Orientation in Both Supine and Standing Positions.

BACKGROUND: The purpose of this study is to analyze the effect of pelvic tilt and rotation on radiographic measurement of cup orientation. METHODS: A total of 68 patients (79 hips) were included in this study. The patients had a computed tomography study and approximately 3 months of postoperative standing anteroposterior pelvic radiographs in both supine and standing positions. We used 2-dimensional (2D)/3-dimensional (3D) matching to measure pelvic tilt and rotation, and cup orientation. RESULTS: There was a wide range of pelvic tilt between individuals in both supine and standing positions. Supine pelvic tilt was different from standing pelvic tilt (P < .05). There were differences in cup anteversion before and after 2D/3D matching in both supine and standing positions (P < .05). Supine and standing pelvic tilt correlated with differences in cup anteversion before and after 2D/3D matching. When all 79 hips were separated into right and left side, pelvic rotation inversely correlated with the pelvic tilt-adjusted difference in anteversion before and after 2D/3D matching of the right side but directly correlated with that of the left side in both supine and standing positions. CONCLUSION: This study demonstrated that the measurement of cup anteversion on anteroposterior radiographs is significantly affected by both pelvic tilt and pelvic rotation (depending on the side). Improved understanding of pelvic orientation and improved ability to measure pelvic orientation may eventually allow for desired cup positioning to potentially protect against complications associated with malposition of the cup.

The Physician as the Provider at Risk: Rolling the Dice.

BACKGROUND: There is significant need for physician innovation and leadership in health care as we adapt to bundled payment models of health care delivery. METHODS: We engaged a collective of 16 different private company orthopedic physician groups to apply to become episode initiators under BPCI models 2 and 3. The application process itself provided historical cost data, enabling each group to independently decide whether or not to proceed with the BPCI initiative. RESULTS: Ultimately, 7 of the private orthopedic groups decided to continue with the BPCI initiative. At the first quarter reconciliation, savings ranged from 9% to 17% across the participating groups. CONCLUSION: The more leadership surgeons provide in value base care provision, the more our patients and health care system will benefit from optimization of care delivery.

A multidisciplinary total hip arthroplasty protocol with accelerated postoperative rehabilitation: does the patient benefit?

Since its debut over 10 years ago, minimally invasive total hip arthroplasty (THA) has often been associated with accelerated postoperative rehabilitation when compared with THA performed with a traditional surgical approach. The objective of this study was to investigate the effect of accelerated postoperative rehabilitation and early mobilization on length of stay and hospital readmissions in patients undergoing THA at one institution. We retrospectively reviewed a consecutive series of 590 patients who underwent THA between January 31, 2011 and April 30, 2011. Six arthroplasty surgeons using varying surgical techniques participated. One hundred ninety patients received accelerated rehabilitation and were mobilized on the day of surgery. The remaining 400 patients were mobilized on postoperative day one (POD1). Length of stay for the accelerated rehabilitation group was 2.06 days and 3.38 days for the standard group. One patient was readmitted to the hospital within 30 days (.52%) in the accelerated group compared to 19 re-hospitalizations (4.72%) in the POD1 group. Ninety-six percent of the accelerated group were discharged home versus 62% in POD1 group. Our results support the use of an accelerated rehabilitation protocol at one institution following total hip replacement surgery.

Total hip arthroplasty using the superior capsulotomy technique.

Dislocation of the native hip during total hip arthroplasty has traditionally been an integral part of all surgical exposures. However, dislocation of the native hip may require greater soft-tissue release than surgical excision of the femoral head during total hip arthroplasty. The superior capsulotomy technique allows preparation of the femur in situ, with excision of the femoral head after femoral component preparation has been completed. The advantages of this technique include preservation of the hip joint capsule and less tissue dissection during surgery; special traction equipment or fluoroscopy is not needed. This technique allows immediate mobilization of patients without motion or weight-bearing precautions, little parental narcotic use, and discharge home within 24 hours of surgery for most patients.

Pelvic tilt is minimally changed by total hip arthroplasty.

BACKGROUND: While surgical navigation offers the opportunity to accurately place an acetabular component, questions remain as to the best goal for acetabular component positioning in individual patients. Overall functional orientation of the pelvis after surgery is one of the most important variables for the surgeon to consider when determining the proper goal for acetabular component orientation. QUESTIONS/PURPOSES: We measured the variation in pelvic tilt in 30 patients before THA and the effect of THA on pelvic tilt in the same patients more than a year after THA. METHODS: Each patient had a CT study for CT-based surgical navigation and standing and supine radiographs before and after surgery. Pelvic tilt was calculated for each of the radiographs using a novel and validated two-dimensional/three-dimensional matching technique. RESULTS: Mean supine pelvic tilt changed less than 2°, from 4.4° ± 6.4° (range, -7.7° to 20.8°) before THA to 6.3° ± 6.6° (range, -5.7° to 19.6°) after THA. Mean standing pelvic tilt changed less than 1°, from 1.5° ± 7.2° (range, -13.1° to 12.8°) before THA to 2.0° ± 8.3° (range, -12.3° to 16.8°) after THA. Preoperative pelvic tilt correlated with postoperative tilt in both the supine (r(2) = 0.75) and standing (r(2) = 0.87) positions. CONCLUSIONS: In this population, pelvic tilt had a small and predictable change after surgery. However, intersubject variability of pelvic tilt was high, suggesting preoperative pelvic tilt should be considered when determining desired acetabular component positioning on a patient-specific basis.

LCPD: reduced range of motion resulting from extra- and intraarticular impingement.

BACKGROUND: Legg-Calvé-Perthes disease (LCPD) often results in a deformity that can be considered as a complex form of femoroacetabular impingement (FAI). Improved preoperative characterization of the FAI problem based on a noninvasive three-dimensional computer analysis may help to plan the appropriate operative treatment. QUESTIONS/PURPOSES: We asked whether the location of impingement zones, the presence of additional extraarticular impingement, and the resulting ROM differ between hips with LCPD and normal hips or hips with FAI. METHODS: We used a CT-based virtual dynamic motion analysis based on a motion algorithm to simulate the individual motion for 13 hips with LCPD, 22 hips with FAI, and 27 normal hips. We then determined the motion and impingement pattern of each hip for the anterior (flexion, adduction, internal rotation) and the posterior impingement tests (extension, adduction, external rotation). RESULTS: The location of impingement zones in hips with LCPD differed compared with the FAI/normal groups. Intra- and extraarticular impingement was more frequent in LCPD (79% and 86%, respectively) compared with normal (15%, 15%) and FAI hips (36%, 14%). Hips with LCPD had decreased amplitude for all hip motions (flexion, extension, abduction, adduction, internal and external rotation) compared with FAI or normal. CONCLUSIONS: Hips with LCPD show a decreased ROM as a result of a higher prevalence of intra- and extraarticular FAI. Noninvasive assessment of impingement characteristics in hips with LCPD may be helpful in the future for establishment of a surgical plan.

Implementation of an accelerated mobilization protocol following primary total hip arthroplasty: impact on length of stay and disposition.

With improvements in surgical techniques, implant design, and patient caremaps, surgeons have sought to accelerate early rehabilitation after total hip arthroplasty. Many authors have reported results of fundamentally similar protocols to achieve this end. These protocols focus on multi-modal pain management, early therapy, tissue-preserving surgical technique, and careful blood management. We present the implementation and results of such a protocol involving a different surgical approach, and highlight the published literature on this topic.

Factors affecting bony impingement in hip arthroplasty.

Computer modeling of 10 patients' computed tomographic scans was used to study the variables affecting hip arthroplasty range of motion before bony impingement (ROMBI) including acetabular offset and height, femoral offset, height and anteversion, and osteophyte removal. The ROMBI was compared with the ROM before component impingement and the native hip ROM. The ROMBI decreased with decreased total offset and limb shortening. Acetabular offset and height had a greater effect on ROMBI than femoral offset and height. The ROMBI lost with decreased acetabular offset was not fully recoverable with an increase in femoral offset or osteophyte removal. Bony impingement increased and component impingement decreased with decreased acetabular offset and increased head diameter.

Validation of a new method for determination of cup orientation in THA.

Our goal was to validate accuracy, consistency, and reproducibility/reliability of a new method for determining cup orientation in total hip arthroplasty (THA). This method allows matching the 3D-model from CT images or slices with the projected pelvis on an anteroposterior pelvic radiograph using a fully automated registration procedure. Cup orientation (inclination and anteversion) is calculated relative to the anterior pelvic plane, corrected for individual malposition of the pelvis during radiograph acquisition. Measurements on blinded and randomized radiographs of 80 cadaver and 327 patient hips were investigated. The method showed a mean accuracy of 0.7 +/- 1.7 degrees (-3.7 degrees to 4.0 degrees) for inclination and 1.2 +/- 2.4 degrees (-5.3 degrees to 5.6 degrees) for anteversion in the cadaver trials and 1.7 +/- 1.7 degrees (-4.6 degrees to 5.5 degrees) for inclination and 0.9 +/- 2.8 degrees (-5.2 degrees to 5.7 degrees) for anteversion in the clinical data when compared to CT-based measurements. No systematic errors in accuracy were detected with the Bland-Altman analysis. The software consistency and the reproducibility/reliability were very good. This software is an accurate, consistent, reliable, and reproducible method to measure cup orientation in THA using a sophisticated 2D/3D-matching technique. Its robust and accurate matching algorithm can be expanded to statistical models.

HipMatch: an object-oriented cross-platform program for accurate determination of cup orientation using 2D-3D registration of single standard X-ray radiograph and a CT volume.

The widely used procedure of evaluation of cup orientation following total hip arthroplasty using single standard anteroposterior (AP) radiograph is known inaccurate, largely due to the wide variability in individual pelvic orientation relative to X-ray plate. 2D-3D image registration methods have been introduced for an accurate determination of the post-operative cup alignment with respect to an anatomical reference extracted from the CT data. Although encouraging results have been reported, their extensive usage in clinical routine is still limited. This may be explained by their requirement of a CAD model of the prosthesis, which is often difficult to be organized from the manufacturer due to the proprietary issue, and by their requirement of either multiple radiographs or a radiograph-specific calibration, both of which are not available for most retrospective studies. To address these issues, we developed and validated an object-oriented cross-platform program called "HipMatch" where a hybrid 2D-3D registration scheme combining an iterative landmark-to-ray registration with a 2D-3D intensity-based registration was implemented to estimate a rigid transformation between a pre-operative CT volume and the post-operative X-ray radiograph for a precise estimation of cup alignment. No CAD model of the prosthesis is required. Quantitative and qualitative results evaluated on cadaveric and clinical datasets are given, which indicate the robustness and the accuracy of the program. HipMatch is written in object-oriented programming language C++ using cross-platform software Qt (TrollTech, Oslo, Norway), VTK, and Coin3D and is transportable to any platform.

Second-generation uncemented stems: excellent 5-13-year results.

INTRODUCTION: The purpose of this study was to prospectively evaluate the 5-13-year results of a cementless total hip arthroplasty with a special focus on the survivorship,occurrence of osteolysis, incidence of intraoperative femoral fractures, thigh pain, and cortical hypertrophy of the femoral stem. The femoral component used in this study was titanium fluted, slotted, symmetrical component that was prepared with intraoperative machining. The proximal third of the stem had hydroxyl-apatite coating and horizontal steps. METHODS: The clinical and radiographical results of a consecutive series of 157 total hip arthroplasties (124 patients)with this stem were investigated. Minimum follow-up was 5 years. The average age of the patients at the time of surgery was 47 years. Three patients died and ten patients were lost to follow-up, leaving 142 hips for evaluation. The clinical result was evaluated on the basis of the Merled'Aubigné score, complications and thigh pain. A detailed radiographic analysis was performed at each follow-up visit. Kaplan­Meier survivorship analysis was performed to evaluate stem, cup, and bearing survivorship. RESULTS: The mean follow-up was 8.5 years (range 5-13 years). The average Merle d'Aubigné score improved from 10.5 points preoperatively to 17.4 points postoperatively.The cumulative 10-year survival rate was 99% for the femoral component, 99% for the acetabular component,and 69% for the bearing. Thigh pain was identified in three patients (2%). There was no distal femoral osteolysis.Seventy-nine percent of all the hips had endosteal spot welds around the coated, proximal one-third of the prosthesis.51% had radio dense lines around the distal tip of the prosthesis,and 3% had cortical hypertrophy. One undersized stem and one cup were revised for aseptic loosening, and 25 bearings were exchanged. CONCLUSIONS: Uncemented, machined, fluted titanium canal-filling femoral components achieve reliable fixation in this young patient population. They have a decreased incidence of activity-related thigh pain, lower rate of intraoperative femur fractures and cortical hypertrophy with comparable bone-ingrowth in comparison to other second generation uncemented femoral components described in literature. Bearing wear and the need for bearing exchange was the only limitation of these constructs.