The Journal of Bone and Joint Surgery, Vol 62, Issue 3 320-327, Copyright © 1980 by Journal of Bone and Joint Surgery, Inc
The spherocentric knee: a re-evaluation and modification
FR Convery, M Minteer-Convery and LL Malcom
The purpose of this study was to assess prospectively the initial results
of total knee replacement with the standard spherocentric component and to
identify retrospectively the pathogenesis of any unsatisfactory results. As
a consequence of this study, the femoral component was modified. Thirty-six
knees were reviewed twenty-two to fifty-two months after a standard
spherocentric total knee replacement, with a mean follow-up of thirty-five
months. Twenty-five (70 per cent) of the knees had significant relief of
pain and improved function. Eleven knees were not improved because of
confirmed loosening in five, supracondylar fracture in two, infection in
one, and suspected loosening in three. Ten of these eleven complications
became manifest within the first postoperative year. Alignment in the
coronal plane was not consistently precise and hyperextension was a
recurrent problem in twelve of the thirty-six knees. A modification in the
femoral component was made: the stem was lengthened to 10.0 centimeters and
the body was reoriented so that there was 5 degrees of valgus and 15 more
degrees of posterior rotation than the original design. This modified
prosthesis was used in twenty-five additional knees, with definite
improvement in alignment, but the follow-up was insufficient to ascertain
the effect of the modification on lossening and fracture.