French university study cautions surgeons to beware of impingement in
patients with high range of motion.
An observational study of the frequency and severity of
prosthetic impingement in
total hip arthroplasty found that impingement occurs in nearly
60% of hip replacements, one-third of which were rated as having severe
Impingement is a frequent phenomenon in cup
retrievals that is underestimated, Henri Migaud, MD, told
Orthopedics Today. It is a devastating complication for hard
bearings that may explain the high failure rate with some of these components.
Impingement after soft bearing use is usually clinically silent, but should be
considered as a major cause of failure in conventional hip replacement. The
improvement in wear resistance has a limited effect to reduce the consequences
Factors for removal
In the study, presented at the
12th EFORT Congress 2011, researchers at the Lille University
in France analyzed 311 cups retrieved from total hip arthroplasties (THAs)
performed by a single surgeon between 1989 and 2004. Of the 416 cups retrieved,
105 were either a combination of bipolar resurfacing cups or severely damaged
and unfit to be analyzed. Two researchers analyzed the notching at the cup rim
for each retrieval using optic magnification. The risk factors and severity of
impingement were studied using X-rays and clinical files.
Double impingement on ceramic-on-polyethylene marked with green
spots (anterior impingement) and red spots (posterior impingement).
Severe impingement on a metal-on-polyethylene with a posterior
elevated rim is shown. Polyethylene rim breakage is identified by red spots.
Ceramic-on-ceramic bearing with posterior
impingement diagnosed on preoperative CT scan (right, four red spots) confirmed
on retrievals with metal deposit on ceramic rim from the titanium femoral neck
(left, red spots).
Images: Migaud H
Main factors that necessitated removal of the cups
included loosening in 131 cases, infection in 43 cases, instability in 56
cases, osteolysis in 28 cases and unexplained pain in 48 cases. Prosthetic
impingement was deemed necessary for removal of the cup in five cases (1.6%),
which only had bearings, meaning that impingement was not expected in 98.4% of
cases, the authors wrote.
The results also showed that impingement was more
frequent when the sum of hip motion exceeded 200°. A younger age at the
time of surgery, use of skirted heads, liners with an elevated rim and a
head-neck ratio below two were determined to be additional risk factors for
impingement. Traditional factors such as cup inclination, duration of time
before retrieval and indication for primary prosthetic replacement were not
found to correlate with impingement, according to the study.
One severe impingement on a metal-on-metal skirted THA
(impingement between skirt red spots and liner green
Pictured is the cold flow deformity at the rim of a metal on
polyethylene THA (identified by red spots).
Steps to avoid impingement
The problem is how to manage those hips at risk of
impingement because of [the] normal-subnormal range of motion, Migaud
said in the presentation. One should increase the head-neck ratio using
large diameter heads or cups. We should avoid elevated rims and skirted heads
in these indications and use with caution hard bearings that are very sensitive
Migaud also stated that the use of computer-assisted
surgery, which could help orient the cups according to the patients range
of motion, would also reduce impingement and prevent dislocation. by
- Migaud H, Marchetti E, Bocquet D, et al. Rate and risk factors of
prosthetic impingement after THA: Observation of 311 cup retrievals. Paper
#786. Presented at the 12th EFORT Congress 2011. June 1-4. Copenhagen, Denmark.
- Marchetti E, Krantz N, Berton C, et al. Component impingement in
total hip arthroplasty: Frequency and risk factors. A continuous retrieval
analysis series of 416 cups. Orthop Traumatol Surg Res.
- Henri Migaud, MD, can be reached at the Centre Hospitalier
Régional Universitaire de Lille, 2 Avenue Oscar Lambret, 59037 Lille
Cedex, France; 03-20-44-68-28; email: firstname.lastname@example.org.
- Disclosure: Migaud has no relevant financial disclosures.