Biomedical Engineering Reference
In-Depth Information
4.5.2.3 Clinical Outcomes of Second Generation Total Ankle Arthroplasty
a) B-P Mark I (LCS) Total Ankle System (Shallow Sulcus)
The B-P Mark I ankle first implanted in 1978 was more successful than the typical
semi-constrained devices. Unfortunately it suffered from a problem, which although
unrelated to constraint, caused the device to be abandoned and redesigned. Below are
summarized six mobile bearing clinical studies associated with this early mobile
bearing design. These studies represent Mark I clinical performance over a twenty-year
time span. The four studies are summarized as follows:
Buechel FF, Buechel FF Jr., and Pappas MJ: Twenty Year Evaluation of
Cementless Mobile-Bearing Total Ankle Replacements.
Clinical Orthop.
424:19-26, 2004.
There were 38 patients implanted with 40 Mark I (shallow sulcus) ankles
over an eighteen-year time span. Mean age was 55 years. Using a strict
ankle scoring system, twenty-eight (70%) patients reported
good/excellent results. One patient developed a fracture of the loading
plate. Two patients had tibial components revised as a result of excessive
wear. No tibial components were noted as clinically loose, all revised
tibial components were stable at time of revision. Bearing subluxation
problems occurred in 10% of cases. Talar subsidence occurred in 15% of
cases. Both were rectified by a revised design (see 5. The prototype: B-P
TAR, deep sulcus). Cumulative survivorship using an endpoint of
revision of any component was 74.2% at eighteen years.
The authors concluded that the mobile bearing greatly improved the
ability of surgeons to replace ankles while minimizing wear and
loosening problems. Design improvements, such as the deepening the
sulcus while maintaining bispherical congruity of the bearing surface,
have enhanced the longevity of the device [25].
Buechel FF and Pappas MJ et al.: New Jersey Low-Contact Stress Ankle
Replacement: Biochemical Rationale and Review of 23 Cementless
Cases:
Foot and Ankle
Vol. 8, No. 8,
1988, 279-290.
There were 21 patients implanted with 23 ankles. The mean age was 56
years. The follow-up period ranged from 24 months to 64 months with a
mean of 35.3 months. The pre-operative ROM arc was 15 to 24 degrees.
Post-operatively mean arc was 25 to 34 degrees. Postoperatively, 87% of
ankles had no pain or, at most, mild pain and all had an improvement on
their preoperative condition.
