ABJS 62nd Annual Meeting Christian Veillette(5/7/10 7:49 PM)
Washington, DC - April 7 - 11, 2010
[Abstracts|ABJS 2010 Abstracts]
If noted, the author indicates something of value received. The codes are identified as: a\- research or institutional support; b\- miscellaneous funding; c\- royalties; d\- stock options; e\- consultant or employee; n\- no conflicts disclosed; * disclosure not available at the time of printing.(Rating: 0.0)
Most recent posters:
Fri Jul 30 09:36:27 PDT 2010
Novel Method for Assessment of Hill-Sachs Defect Size_Utility in Surgical Planning – Preliminary Study Alex Brooks-Hill(7/28/10 8:55 AM)
1. Purpose :*
Currently there is no standard quantitative methodology for the description of Hill-Sachs defects (HSD), the size of which is important in planning surgical treatment for patients with anterior shoulder instability. The main purpose was to develop a simple imaging measurement to improve communication regarding HSD’s. The secondary goal was to determine, using this new measurement, whether there was a significant difference in the size of HSD’s in patients who underwent a Weber osteotomy (more invasive surgical intervention for those failing Bankart repair) compared with patients who underwent clinically successful arthroscopic Bankart repairs (the first surgical intervention for anterior shoulder instability).
2. Method :*
HSD volume was calculated with newly developed methodology using computed tomography in ten patients who required eleven Weber osteotomies and using magnetic resonance imaging in twenty-two patients who had clinically successful arthroscopic Bankart repairs.
Within the Weber cohort, regression analysis was performed to determine correlation between HSD volume and each of height, maximum depth, and width. Student’s T-test analysis was used to compare HSD volume between the Weber and Bankart cohorts.
3. Results :*
In the Weber cohort, there is a statistically significant correlation between the HSD Volume Ratio and the HSD Maximum Depth Ratio (R2=0.83).
T-test comparison of mean HSD Volumes showed statistically significant (p<0.0015) larger HSD’s in the Weber cohort than the Bankart cohort.
4. Conclusion :*
HSD depth is a radiological indicator for HSD volume. This simple measurement may facilitate orthopedic pre-operative planning for patients with severe recurrent anterior shoulder instability. In this preliminary study, this new methodology for evaluation of HSD volume confirmed that patients who had Weber osteotomies after failed Bankart repairs had statistically significantly larger HSD’s than patients with clinically successful Bankart repair(Rating: 0.0)
The Effect of Femoral Neck Notching with the Birmingham Mid-Head Resection Michael Olsen(7/10/10 3:51 PM)
The Birmingham Mid-Head Resection (BMHR) is a short-stem alternative to hip resurfacing for patients with unsuitable femoral head anatomy. It is not known if femoral neck fracture risks associated with hip resurfacing pose the same hazard to mid-head resection arthroplasty, therefore the current study investigated the effect of superior femoral neck notching with the BMHR.
Twenty-four composite femurs were implanted with the BMHR prosthesis using imageless navigation and tested in axial compression. Six specimens each were prepared with notches in the superior cortex of the femoral neck, one approximating a sub-cortical thickness notch (2 mm) and one with a full-cortical thickness notch (5 mm). These groups were compared to a control group prepared without a superior neck notch. All components were positioned in neutral coronal alignment. To investigate the effect of valgus alignment, six specimens were then prepared and tested with a 5 mm superior neck notch with the implant aligned in an additional 10 degrees of valgus alignment (5 mm + 10 Valgus).
The mean load-to-failure for the intact group was 5002.0 N (SD 641.3 N), for the 2 mm notch group was 4367.3 N (SD 291.3 N), for the 5 mm notch group was 4060.3 N (SD 604.6 N), and for the 5 mm + 10 Valgus group was 4469.0 N (SD 614.7N). Introduction of a 2 mm notch resulted in a reduction in proximal femoral strength of approximately 13% (p=0.152) compared to femurs prepared without a femoral neck notch while a 5 mm notch resulted in a significant reduction of almost 19% (p=0.027) compared to controls. Additional valgus alignment had a protective effect on a 5 mm superior neck notch and this was not significantly different from the control no-notch group (p=0.405).
Mid-head resection arthroplasty is an alternative to hip resurfacing for patients presenting with unsuitable femoral head anatomy such as the case with avascular necrosis. Previous work has demonstrated that superior femoral neck notching with hip resurfacing significantly reduces the load bearing strength of the proximal femur with as little as a 2 mm notch. In such cases, it may be prudent to abort a hip resurfacing for a standard total hip arthroplasty. This study appears to provide biomechanical evidence that preparation of the femoral head for a BMHR may be more forgiving to minor preparatory errors such as a 2 mm superior femoral neck notch, however, a full cortical thickness notch resulted in a significant reduction in the load bearing capacity of the proximal femur. Relative valgus alignment of the metaphyseal stem may have a protective effect if superior neck notching occurs. The Birmingham Mid-head Resection may be more forgiving to minor preparatory errors than a typical hip resurfacing arthroplasty.(Rating: 0.0)
The Effect of Femoral Component Alignment with the Birmingham Mid-Head Resection Michael Olsen(6/28/10 3:52 AM)
The BMHR is a bone-conserving, short-stem femoral prosthesis designed for patients with compromised femoral head anatomy unsuitable for a hip resurfacing arthroplasty. Similar to hip resurfacing, the BMHR preserves the femoral neck and does not violate the femoral medullary canal; however, it is not known if the femoral neck fracture risks associated with hip resurfacing pose the same risk to a mid-head resection arthroplasty. The aim of the current investigation was to examine the effect of coronal implant alignment on proximal femoral strength with the BMHR.
Sixteen pairs of fresh-frozen cadaveric femurs were divided into two equal alignment groups. Individual pairs were divided into control and experimental specimens. The first alignment group prepared experimental specimens in 10 degrees of relative valgus alignment while the second group prepared experimental femurs in 10 degrees of relative varus. Control specimens were prepared with the implant aligned with the native neck-shaft angle of the femur. Femurs were tested in axial compression in single-leg stance.
Failure testing revealed no significant differences in peak failure loads between matched paired femurs prepared in relative varus (mean 4324 N, SD 2207) and controls (Mean 4114, SD 2153, p=0.996) or femurs aligned in valgus (mean 4623, SD 1608) compared to controls (Mean 4761, SD 1290, p=0.999). Femurs were well matched for BMD and anatomical parameters. Multivariate regression analysis including pre-operative geometric parameters and Neck BMD, showed that Neck BMD and neck width together explained 81% (adjusted R2, R=0.908, p<0.001) of the variance in failure load.
This biomechanical investigation appears to be the first to investigate the risk of femoral neck fracture associated with the Birmingham Mid-head Resection. The findings of the current study are in contrast to previous studies investigating implant alignment in hip resurfacing. Clinically relevant variations of stem alignment did not appear to impact proximal femoral strength with a BMHR in place. A valgus aligned implant did not appear to strengthen, nor a varus implant weaken, proximal femoral strength compared to a neutrally aligned implant. Failure of the proximal femur implanted with a BMHR appears less sensitive to variations in implant alignment than a typical hip resurfacing.(Rating: 0.0)
Failure of a Modular Neck of a Total Hip Replacement Component David Wilson(6/16/10 10:30 PM)
AIM: The purpose of this study was to investigate the early catastrophic failure of a modular total hip arthroplasty component.
INTRODUCTION: The Profemur-Z modular total hip replacement (Wright Medical Technology, Inc., Arlington, TN) is a primary total hip replacement system that offers surgeons the ability to alter the length and version of the femoral neck after the femoral stem has been implanted. The versatility is achieved through a double Morse taper modular neck component used to bridge the femoral stem and femoral head.
METHODS: The fractured neck and the stem were inspected visually, with light microscopy then with scanning electron microscopy (SEM). Energy dispersive X-ray spectroscopy (EDS) was performed to analyze the chemical composition of the modular neck around the fracture. The findings from the investigations were used in conjunction with finite element analysis (FEA) to develop an analytical model of the fractured component to assess the likelihood of reoccurrence.
RESULTS: The results of the investigations revealed a damage pattern consistent with fatigue failure. There was substantial surface damage in the area where the failure originated. The most likely source of this surface damage was interfacial contact during engagement of the Morse taper. The stress in a long retroverted neck component during normal patient ambulation was found with the FEA to be 270MPa. The stress in the component was compared with the known maximum fatigue stresses in Ti6Al4V alloy (the material the Profemur-Z is made from). The fatigue stress limit for Ti6Al4V alloy is 510MPa undamaged and 240MPa with surface damage. The stress in the component was found to exceed the materials fatigue strength when the surface had undergone damaged.
CONCLUSIONS: The findings of this study demonstrate that this design of modular neck total hip arthroplasty component is at a relatively high risk of early catastrophic failure. It is likely that other components of this design in similar patients will also fail prematurely.
(Rating: 0.0)
Characterization of Three-dimensional Pathological Patterns in Frontal Plane Alignment during Computer Navigated Total Knee Arthroplasty Michael Dunbar(6/16/10 10:24 PM)
Purpose.
Alignment in conventional TKA is planned using 2-D radiographs, however, TKA is a 3-D operation. While computer
assisted TKA has been shown to reduce outliers in frontal plane alignment (FPA) with the knee in extension, little
data is collected to assess the alignment through range of motion. Registration of the skeletal landmarks before
resections allows for real time analysis of FPA through range of motion in 3 dimensions. Magnitude and consistency
of pathological 3-D alignment can be assessed. Resection levels of medial and lateral proximal tibial, distal and
posterior femoral cuts is also recorded and are surrogates to the morphology of the femur and tibia. The purpose of
this study was to characterize 3-D FPA patterns through range of motion and correlate them to resection levels and
ability to afford a neutral alignment.
Methods.
Data on 60 consecutive navigated TKA?s was recorded and included FPA (varus/valgus) through range of motion
prior to bony cuts, after insertion of trial components, and after implantation of definitive components using the
Stryker KneeNav version 4.0 software. All cases were completed by a single fellowship trained arthroplasty surgeon.
There were no exclusion criteria in the study. A posterior stabilized, constant radius femoral component was used in all cases and all patellas were resurfaced. FPA was assessed and divided into patterns using visual inspection and
a thresholding algorithm. Reliability testing was performed on assessment of curve type using the Intraclass
Correlation Co-efficient (ICC). Once curve types were defined, the ratios of the medial and lateral posterior femoral
resection were correlated to the ratios of the medial and lateral distal femoral resection. A line of best fit was plotted
for a scatter plot of the resection ratios. The final 3-D FPA after insertion of the definitive TKA was recorded and
degree of correction to a neutral alignment through range of motion was assessed.
Results.
Four distinct 3-D patterns emerged prior to making the bony cuts. Thresholding algorithms demonstrated consistency
in the patterns and the ICC values were high, suggesting that the discrimination of curve types was valid and
reproducible. Plotting the line of best fit for the resection ratios by curve type demonstrated very strong relationships
(r-squared = 0.98). A progression of the magnitude of the ratios by curve type is suggestive of a continuum of
pathology within patients. Some curve types were more likely to result in a correction to neutral alignment through
range of motion.
Conclusion.
Distinct patterns in 3-D FPA exist in knees undergoing TKA. These patterns strongly correlate to bony resection
levels therefore is appears that curve type is related to combinations of femoral and tibial morphology and a
continuum of pathology within. Frontal plane alignment curves may be useful in developing a patient specific
customized implantation strategy for TKA.(Rating: 0.0)
Bead placement protocol for follow-up of thoracic spinal fusion using radiosteriometric analysis (RSA) Antony Francis(6/16/10 10:18 PM)
Objective: Develop a standardized radiostereometric analysis (RSA) bead placement protocol for studying thoracic spinal fusion in adolescent idiopathic scoliosis (AIS) patients.
Methods: The bead placement protocol was performed via a computer simulation, which aimed to electronically mimic an RSA exam following the thoracic spinal fusion of AIS. The accuracy and precision of the developed RSA system were determined to obtain an objective view of the performance of the system.
Results: The condition numbers for the marker models were all well below the recommended value of 100. All the beads of the marker models were matched between simulations with rigid body errors below 0.35 mm. Based on complete computer simulation, the average translational accuracy is 0.21, 0.1 and 0.55 mm along the x, y and z-axes, respectively, and the average translational precision is 0.012, 0.0021 and 0.067 mm along the x, y and z-axes, respectively. The average rotational accuracy is 0.93, 0.19 and 0.27 degrees about the x, y and z-axes, respectively, and the average rotational precision is 0.004, 0.003 and 0.006 degrees about the x, y and z-axes, respectively.
Conclusions: The computer simulation is a powerful tool than can be used to facilitate the development of an RSA system. Future work will include a physical validation of accuracy and precision to ensure that all sources of error in RSA are taken into account prior to the clinical introduction of this system.
(Rating: 0.0)
Audit of Arthroscopic Microfracture Treatment for Osteochondral Lesions of the Knee Zafar Ahmad(6/16/10 8:32 PM)
We assessed the functional outcomes of 41 patients treated with arthroscopic Microfracture of knee performed by a single surgeon for osteochondral lesions.
Between 2005 and 2009, a total of 41 patients aged between 16 and 73 years (mean: 44years) were treated for symptomatic Osteochondral lesions. Lysholm scores improved from an average of 57 preoperatively to 69 postoperatively Lysholm – 1 to 100). We assessed improvement in final outcome using Tegner, IKDC and SF 36. At the time final follow up average IKDC score was 58, the average Tegner score had improved from 2 preoperatively to 4 postoperatively (Tegner 1 to 4).
We analysed the response to early vs late surgery, relationship with age, high BMI, size & location of the lesions.
Two patients who had arthritic disease did not benefit from the procedure and underwent joint arthroplasty within one year of the index procedure.
(Rating: 0.0)
Imaging evaluation of Hill-Sachs lesions - a web-based survey of subspecialty radiologists and orthopaedic surgeons Cole Beavis(6/16/10 8:21 PM)
Introduction:
Little consensus exists regarding the radiologic evaluation and description of humeral head defects occurring in association with shoulder dislocation. Hill-Sachs lesions have been described according to size, depth, location and orientation and little is known about the accuracy of these descriptions. Management algorithms often differentiate treatment recommendations according to specific defect sizes which underscores the importance of accurate, reproducible and common descriptors. The purpose of our study was to determine the preferences and tendencies of subspecialty orthopaedic surgeons and radiologists in evaluating and describing Hill-Sachs lesions. Our hypothesis was that wide discrepancy would exist between and within the groups of participants.
Methods:
This descriptive study involved a web-based survey emailed to Canadian radiologists with subspecialty training or clinical interest in musculoskeletal radiology and Canadian orthopaedic surgeons with upper extremity or sports medicine fellowship training. The invitation list was based upon involvement in specialty societies, fellowship training programs or known subspecialty interest. The survey consisted of text questions examining terminology, preferences and confidence with imaging assessment followed by 2 cases with plain X-ray and MRI images. Non-responders were reminded by 2 additional invitations. Results were tabulated as a percentage of respondents and comparison performed between groups.
Results:
A total of 103 survey invitations were sent out and the response rate was for radiology was 50% (27/54) and 71% (35/49) for orthopaedics. No significant difference was found between radiologists and surgeons in self-reported ability to identify Hill-Sachs lesions on X-ray and MRI. Radiology respondents were significantly more confident in their ability to determine the size of Hill-Sachs lesions and presence of “engaging” lesions on both X-ray and MRI. Surgeons were more likely to categorize lesions as small, medium or large while radiologists were more likely to characterize size as a percentage of humeral head circumference. Radiologists were more likely to report the orientation or presence of “engaging” lesions than surgeons. When given the same cases, radiologists consistently characterized lesions as larger than surgeons.
Conclusions:
While radiologists and surgeons report a similar ability to detect Hill-Sachs lesions, significant differences exist in the terminology and description of them. Radiologists consistently described lesions as larger than surgeons. Substantial variation exists in the imaging description and characterization of Hill-Sachs lesions and this should be considered when basing treatment upon reported lesion size or orientation.
(Rating: 0.0)
Retrospective Audit of the Use of the Posterior Lip Augmentation Device for Recurrent Hip Dislocation in Patients with Previous Charnley Hip Arthroplasty Chinyelu Menakaya(6/16/10 2:39 PM)
Introduction:
In patients who have recurrent hip instability following total hip arthroplasty (THA) with a Charnley prosthesis, the posterior lip augmentation device (PLAD) is a minimally invasive surgical treatment option. Minimal data exists regarding the long-term outcome after PLAD application and variable success rates reported. This study aimed to further evaluate the role of PLAD application for recurrent hip instability following THA and its long-term outcomes.
Methods:
Patients undergoing PLAD application at Fairfield General Hospital (Bury, UK) for hip instability after THA were identified using hospital records coding data. Radiological and clinical data were analysed retrospectively using the patient’s hospital case-notes and electronic PACS system.
Results:
Data was available for 15 PLAD applications in 15 patients with an average age of 75.1 years. The mean follow-up period was 21.9 months. PLAD application prevented further dislocation in 73% (11/15) of patients. Girdlestone procedure was performed in 2 patients who experienced further hip dislocation. Long-term follow-up of patients with PLAD remaining in-situ demonstrated that 100% of patients were independently mobile at 2-4 years postoperatively, and all patients were pain-free during long-term follow-up after 1-year. Sub-group analysis of risk factors identified only a significantly higher ASA grade to be associated with further episodes of dislocation in patients undergoing PLAD application.
Discussion:
Our study provides further evidence supporting the role of PLAD as a safe minimally-invasive procedure for elderly patients with recurrent hip instability after Charnley THA in whom prosthetic components are well-positioned and well-fixed. Our results demonstrate that the majority of patients undergoing PLAD application return to independent mobility with no long-term hip pain. PLAD application should be used with caution in patients with an ASA grade of 3 or greater.
(Rating: 0.0)
Choose an association/society category to the left and locate the appropriate meeting. Select Add New Poster and complete the form and upload the requested documents.
By clicking "Add New Poster", you are representing that the posters do not violate Orthopaedia's Terms of Use and that you or your affiliated association/society own all copyrights for the poster or have authorization to upload them.
. Orthopaedia Meetings - Home. In: Orthopaedia - Collaborative Orthopaedic Knowledgebase. Created Oct 17, 2008 20:59 by Christian Veillette, Last modified Jun 14, 2010 14:07 ver.21. Retrieved 2010-07-30, from http://www.orthopaedia.com/x/GQDN.
Fri Jul 30 09:36:25 PDT 2010
