Held in Los Angeles on October 24 & 25, 2008
By Dr. John Rogerson

Vicky,

Here is my summary of the Second Annual U.S. Comprehensive Course on Total Hip Resurfacing Arthroplasty, October 24-25, 2008, Los Angeles, California.

Hope it is helpful,
John

• The Australian Registry as reported by Andrew Shimmin shows the best results in males with osteoarthritis and poorer results with females with smaller component size.
• Vertical cup position, varus head position, femoral head cysts greater than 1 cm, greater than 65 years old and AVN were also associated with less success as reported be Tom Schmalzried.
• Vertical socket position (greater than 55 degrees of abduction) is associated with rim contact and higher wear and pseudotumors and can be evaluated by following blood ion levels as discussed by Koen DeSmet and John Fisher.
• Allergic reactions are very rare and are affected by the amount of metal wear and one observes foreign body response in the surrounding tissues. No reliable pre-op tests are available at this time.
• John Fisher emphasized that volumetric simulator wear is similar for all the devices presently on the market but has not looked at particle size with the as cast vs heat treated metals.
• Paul Beaule studied the circulation affects of the trochanteric flip lateral approach and found the oxygen levels stayed higher with this approach but had an 8% trochanteric delayed or malunion and an 18% bursitis that had to be operated and corrected. He no longer uses this approach routinely and uses the straight anterior approach.
• David Murray analyzed their neck fracture patients and found that AVN may be more important than mechanical factors as an etiology.
• Pat Campbell found on retrieval specimens a higher percentage of failures in females with most of the fractures occurring through healing bone of the femur. Socket loosening seems to occur at around 20 months. “Pseudotumors” are “fluid hernias” secondary to high wear usually secondary to socket malposition. Metal sensitivity is usually associated with early pain in well done joints and is associated with T-cell accumulations. Most cases of unexplained pain are more likely wear related.
• Schmalzried discussed cementing technique and cement mantles and stressed the importance of femoral suction and dry interface on the head.
• Lavigne performed a double blind controlled study comparing functional outcomes with large head metal on metal versus resurfacing replacement and found them to be equal at all time periods. Therefore, the major advantage of resurfacing appears to be bone conservation if survivorship ultimately equals that of total hip replacement.
• DeSmet, Shimmin, Antoniou, Amstutz and Lavigne all discussed technical points of importance with resurfacing with avoiding vertical cup placement being the most important with neck varus and notching and patient selection being critical also.
• Isaac and DeSmet stressed cup inclinations greater than 55 degrees are associated with increased metal ion levels and may require revision.
• Murray reported on a series of “pseudotumors” collected in the UK. These were all in females. Presentation was generally pain with also dislocation, nerve palsy, swelling and rash occasionally. The histologic picture was of extensive necrosis and lymphocytic infiltration. 13 of 20 have been revised with several others pending. Cause is unknown but postulated to be related to increased metal wear vs hypersensitivity. Obviously, further observation and study is warranted.
• Jacobs reported on adverse tissue reactions to metal and felt that ALVAL reactions were rare and involved both allergic and metal load factors mthat influenced the degree of reaction.
• Campbell reported on retrieved femoral head specimens and noted remodeling of the head and neck for up to 2 years post op. Early fractures of the neck occurred through healing new bone. Pseudoarthrosis occurred some painful hips and secondary fatigue fractures occurred in some midterm neck fractures.

Overall, the conference again emphasized the importance of

1) patient selection,

2) exposure and importance of maintaining as much blood supply to the head as possible with any approach and

3) the meticulous technique of the procedure especially as regards to cup position. Vertical cup, varus head, excess anteversion in dysplasia and notching are to be avoided.

Enthusiasm for minimally invasive approaches for resurfacing was negligible at this meeting because of the importance of cup positioning.

Direct anterior approach has potential advantages to the blood supply if the posterior capsule is released at the socket but requires significant equipment investment and it’s own learning curve ahich may not outweigh the improvement noted in head oxygenation with the modified posterior approach.

Barrack noted a definite learning curve with resurfacing and some tendency to vertical cups even after the initial learning curve was accomplished. Several aids to cup position including computer navigation and laser aiming devices were presented.

Thanks to all of the participants,
John S. Rogerson, MD