Dr. Edwin Su Overview of 3rd Advanced Resurfacing Course Ghent, Belgium June 2009
by Dr. Edwin Su
My overview of the 3rd annual “Advanced Resurfacing Course in Ghent Belgium”
Overall, I was extremely impressed with the course. It was a thrill to be part of this faculty, since the lecturers were all long-time resurfacing experts who had a collective experience of more than 35,000 resurfacings! The faculty included experts from around the world – from the US, Germany, UK, Australia, France, and of course, Belgium.
There were about 80 attendees, all surgeons who had done more than 20 resurfacings. Thus, it was an interested congress that made for a sophisticated discussion. The program was organized into specific mini-topics, all of which I found extremely interesting. Fortunately, I can say that while nothing was that new in concept to me, it solidified beliefs and ideas that I have had about resurfacing. Also, I was able to share some of my own observations and experiences.
Below is a detailed account of the course topics. But to summarize, I would say that there was a lot of attention given to the recent reports of metal hypersensitivity, pseudotumor, and results in women. Overall, the consensus was that these can be problems, but in a very small percentage (particularly hypersensitivity). Pseudotumor seems to be related to accurate positioning of the implant, so once again, experience is key!! As for female patients, results seem to be more related to component size rather than gender itself. Despite our recognition that these issues can cause problems, the majority of the attendees remained dedicated resurfacing surgeons and would still continue to perform this life-changing operation.
Fractures and Retrievals (
Fractures are certainly multifactorial, there are definitely “too much, too soon” fractures. She showed a case of a young male who went back to break dancing at 3 weeks postop and fractured his femoral neck.
A rare cause is wear-induced osteolysis, meaning weakening of the bone from the reaction to wear debris.
Overall, femoral neck fractures as an inability to withstand mechanical forces in an environment that is affected as a result of injury from implantation, surgical factors, and bone quality.
Fractures in Resurfacing (Peter McLardy Smith, Oxford)
842 posterior approach resurfacings performed at Oxford and Coventry
1.8% fracture rate overall
14 patients had bilateral simultaneous resurfacings, and 3 fractured
Thus, 11% of those hips fractured, which led them to believe that this is a risky procedure.
They examined the fracture group and found no patient related factors such as gender, age, weight. They found no surgical factors such as implant position, lengthening of the neck, or notching. When comparing the fracture group to a control group that did not fracture, there were no differences in these variables.
Thus, femoral neck fracture remains multifactorial without a single identifiable cause.
Impingement (John O’Hara)
Believes internal head diameter should be 4 mm > neck diameter in males, and 6mm > in females.
He admits that this will result in the removal of more acetabular bone, but he doesn’t think this is a problem because of the durability of the acetabular component.
METAL IONS
Metal ions in different designs (David Langton)
594 unilateral patients, all under care of highly experienced surgeons
312 BHR, 145 ASR, 127 C+
Looked at cup anteversion and inclination
Trend toward lower metal ion levels with increasing size
There were implant specific findings:
Cup inclination: ASR between 40-45 degrees okay, but ions go up if steeper than 45
BHR and C+ were more tolerant
Between 45-50 degrees had the lowest ions, surprisingly (since one would believe lower angles would have even lower ions)
Same was true of anteversion, related to the ASR and other devices
Why the difference?
Explained by contact patch to rim (CPR) distance. Average patient has a force vector 14 degrees medial to the upright. CPR is the distance from this force vector to the edge of cup.
ASR has coverage angle of 146 – 156 degrees
BHR is 158-164
C+ is 170
Metal ions as a diagnostic tool (Richie Gill, Oxford, UK)
Tried to relate a patient’s clinical outcome to metal ion levels. This was the most controversial talk, because there are many patients who are outliers. There were 25% of patients with ion levels below their proposed upper limit, who had problems. Therefore, the metal ion test will have poor specificity for problems.
Pseudotumor (David Murray, Oxford,UK)
Defined it as a soft tissue mass that can be solid or cystic.
Admitted that it may not have been the best term, but they didn’t know what else to call it.
They found a spectrum of symptoms in patients with pseudotumor. Generally, the fluid was grey/yellow and was locally destructive. There was dead tissue with lymphocytes and macrophages.
He reported a 1.8% revision rate for pseudotumor. There was a predicted 4% revision for pseudotumor at 8 years survival curve.
Was higher rate in women, smaller size components, and <40yo
Outcomes of revision for pseudotumor were poorer than revision for other reasons; 50% had major complications. 3x higher dislocation, increase risk of nerve injury
There was also a higher rate of wear in the retrieved specimens, so he does believe it is related to wear.
Furthermore, there was a higher variability of cup inclination and anteversion in the pseudotumor patients.
Within the ideal 40 inclination and 20 anteversion, there was a lower incidence of pseudotumor, but there were still cases.
Retreival findings of pseudotumor (Pat Campbell)
Believes there are 2 causes of pseudotumor; one is wear related and the other is hypersensitivity related.
Has an ALVAL score, with a maximum of 12. Scores features such as lymphocytes and size of aggregates.
If higher, is suggestive of sensitivity, but there can be ALVAL features even in wear cases.
31 revisions with “big bursal tissue” as described by the referring surgeon
20 with high wear findings, macrophages, predominantly B cells, macrophages with metal; avg ALVAL score was 3.3
11 with metal allergy (clinically), with avg ALVAL of 8.7: predom lymphocytes, a mix of B/T cells and lymphocytes in aggregates.
CUP ANGLE AND PLACEMENT
What can we do as a surgeon (Edwin Su)
This section emphasized the importance of cup placement. I had the opportunity on giving the lecture about what we can do as surgeons to get it right. My major points are: education and training of surgeons starting with the procedure, but also conferences such as this one to discuss the continuing results. Surgically, it is important to obtain a good exposure, so "mini-inicisions" are not conducive to good positioning. Finally, the instrumentation must be helpful, so a curved impactor is helpful in avoiding steep cup position.
In THR, we are led to believe a certain position is ideal for every patient, but in resurfacing, the cup should be less inclined and possibly less anteverted. One of the engineers stated that "35 degrees is the new 45 degrees", which was a particularly catchy phrase, though not borne out with data yet.
ILIOPSITIS/GROIN PAIN
This section outlined the frequency of groin pain after resurfacing. This has many potential causes such as iliopsoas tendonitis, loose socket, impingement, and metal sensitivity.
Dr. Paul Beaule compared resurfacing done through an anterior approach vs. posterior approach and did not find any difference in the frequency of groin pain.
Dr. Thomas Gross cautioned that a loose cup may be a cause of groin pain.
Dr. David Young spoke about the role of arthroscopy in these problem cases, both for diagnositic and therapeutic reasons. He has released the psoas tendon in some cases with good results.
Neck thinning (Andrew Shimmin, Melbourne, Australia)
Defined as thinning of the neck > 10 percent. It does occur, but is usually benign.
Poor prognosis if progressive beyond 3 years.
Incidence in 77% of patients, average of 2.1 mm
But only 20% had >10% thinning
Has not been associated with any adverse clinical events
But, if progressive, need to follow yearly
Liliakis reported 27% of >10% narrowing with a cementless implant.
Possible causes
altered bone loading/stress shielding
vascularity/local AVN at neck
pressure phenomenon
impingement
Has not found it to lead to fracture
FRIDAY, JUNE 19, 2009
Anterior approach (Beaule)
Uses orthopedic table to achieve hyperextension
25% incidence of lateral femoral cutaneous nerve palsy, even with going into TFL sheath
Oxygenation studies (Murray)
found a modified posterior approach, with soft tissue cuff left around neck, the oxygen tension did not drop significantly after the approach. Couldn't complete the study of measuring oxygenation after the preparation of bone and cementation because of the use of the lesser trochanter suction.
Anterolateral approach found oxygenation incrased with the approach, went down with implantation, then recovers to normal.
Troch flip found oxygen tension remained static with approach, then went down with implantation, and recovered to normal.
Dresden experience (Christoph Witzleb)
Had a 5% revision rate at 7 years, in first 100 resurfacings. Average age 51
Canadian Registry (Antoniou)
This is a voluntary registry, with only 70% participation
From 4/1/03 to 4/08, found resurfacing to be 3.5% of all THR in 2007-8
48% of these were BHR, 28% were Zimmer Durom
approx 1300 resurfacing/yr
Australian Registry
Began in 1999, same year as resurfacing came to Australia
98% participation, from 294 hospitals
Correlates with industry records, has about 10000+ resurfacing
As of 2007, resurfacings were 7.8% of primary THR
BHR> Mitch (Stryker) > ASR
Cumulative revision rate at 7 years, in males<55 years old, hip resurfacing was 2.4%; THR was 2.8%
excludes ORIF, dislocations
BHR was 2.5% revision rate at 3 years
ASR was 6% revision rate at 3 years
Durom was 5% revision rate at 3 years
Also looked results compared with volume of hospital
64% resurfacings done at only 16 hospitals; better results associated with higher volume centers
Pseudotumor (McClardy-Smith)
Revision rate in males at 8 years due to pseudotumor was 0.5%
in women > 40 yo - 6%
in women < 40 yo - 25% !!!!!!!!!!!
If you find a large lesion on MRI or U/S, consider early revision. Outcomes of late revision are poor.
Revisions of hip resurfacing (DeSmet)
87 revisions, 57 for cup malposition
23 were for high metal ions
Found 39% had evidence of impingement intraop
METAL ALLERGY
Overview (Campbell)
lymphocytes in tissues does not necessarily mean allergy
metal allergy vs metal response
necrosis necrosis
lymphocytes macrophages
mix of T/B cells mostly B cells
higher ALVAL score lower ALVAL score
Reference Rau (Orthopade Feb 2008) - no consequence of a positive metal sensitivity test preop, thus would not recommend routine screening.