It is important to ensure a hip replacement that has no complications and lasts for a
reasonable length of time especially in young active patients. The ideal articulation
should have good lubrication with minimal wear, should be hard enough to resist
fractures, and should be highly biocompatible and available in different head sizes.
The use of ceramics as bearing surfaces has had a long and successful history.
Ceramic-on-ceramic (C.o.C) is a very wear-resistant, versatile articulation with
different neck lengths and head diameters (28–32mm, with large ceramic heads
with a diameter of 36–40mm now available).
Aim
The aim of the study was to investigate a possible effect of different ceramic head
sizes on early clinical results in patients treated with C.o.C total hip replacement
(THR), with special concern on postoperative hip range of motion (ROM) and
stability.
Patients and methods
This study included 40 cases in 35 patients with end-stage arthritis. All cases were
treated with C.o.C THR. Cases were divided into three groups according to the size
of the ceramic head. Group I included 13 cases with 28-mm heads. Group II
included 12 cases with 32-mm heads. Group III included 15 cases with 36-mm
heads. Results were assessed according to the Harris Hip Score (HHS).
Results
There was significant improvement in the HHS at 6 weeks postoperatively in all the
three groups compared with the preoperative HHS; this improvement became
much more significant at 6 months postoperatively. At 6 weeks postoperatively,
there was a statistically nonsignificant difference in the mean postoperative hip
ROM scores between group I and group II cases and also between group II and
group III cases, whereas there was a statistically significant difference in the mean
postoperative hip ROM scores only between group I and group III cases. At 6
months postoperatively, the difference in mean postoperative hip ROM scores
between all the three groups of cases became statistically nonsignificant. Although
dislocation occurred in only one case (representing 2.5% of all the studied cases)
with a 28-mm head, no sharp correlation between the head size and dislocation was
detected.
Conclusion
Increasing the head size can safely improve the ROM especially in the early
postoperative period but the term ‘large head’ could be a relative or a
nonspecific term when considering the clinical (true) but not the technical
(theoretically possible) ROM or if the relation between the head diameter to the
size of the ceramic liner/cup construct and the head/neck ratio are not considered.
The head size is critical for stability in THR but dislocation is multifactorial. Although
C.o.C articulation is a marvelous bearing surface for young active patients,
especially women in the child-bearing period, the 36-mm heads could not be
used in most female cases (being restricted by the size of the native bony
acetabulum), and therefore male patients have a better scope of being treated
with 36-mm heads |
