According to the characteristics of knee joint motion and
extensor mechanism, the mechanism of Ni-Ti PC fixation
combined with suture cerclage is as follows: the transverse suture
cerclage converts the bilateral tension forces produced by the
patellofemoral and meniscopatellar ligament into compression
forces between bilateral fragments (Fig. 5a). The surrounding
suture cerclage converts surrounding tension forces into compression
forces among the fracture fragments (Fig. 5b). Ni-Ti PC
converts anterior tension forces produced by the extensor
mechanism into compression force at the transverse fracture
surface (Fig. 5c).
In our cohort, functional results were excellent or good in 75%
and 25% of patients. Because of the reliable fixation, functional
exercises were started as early as possible. Perhaps this is one of
the reasons that satisfactory results were noted. Skin irritation is
the main complication of the K-wire tension band [14]. Regarding
NT-PC fixation, the claws tightly attach to the patella, and are not
prominent at the patellar surface. The fragments were cerclaged
with Ethibond suture, avoiding the risk of skin irritation and
postoperative discomfort. Loosening of the implant is another
main complication [14]. In this study, loosening of NT-PC and
fragment displacement did not occur, because the size of NT-PC
was suitable and fixation was stable with the use of suture cerclage
to augment the Ni-Ti PC fixation.
According to our experience, the following points should be
noted when using this technique: (1) Ethibond suture passing
circumferentially around the patella should be in a purse-string
fashion, and closely along the cortical bone (Fig. 6). The transverse
suture should be in close contact with the bone surface to achieve
secure fixation and to avoid suture loosening after soft-tissue
atrophy. The knots should be buried in the lateral soft tissue to
reduce symptoms caused by them [1]. (2) The longitudinal
dimension of the Ni-Ti PC should be smaller than that of the
patella by 10–20%. Larger dimensions could cause the claws to not
be as tight, and smaller dimensions would result in an incomplete
shape recovery of the claws (3) Intraoperatively, the claw branch
should be uniformly stretched with the deformation not more than
8% of the primary shape; otherwise it would be impossible to
obtain complete shape memory function. (4) The temperature of
the saline should be between 40 and 45 8C, and kept for 3–5 min to
complete shape recovery.
Conclusions
Ni-Ti PC fixation with non-absorbable suture cerclage augmentation
is a feasible approach for comminuted patellar fractures.
Firm fixation with this technique allows for early functional
exercise, and has excellent clinical results. The limitations of our
study were its small sample size and the lack of a control group;
therefore, the results may be biased.
Conflict of interest
The authors state that there is no conflict of interest.