Ga. Hack et al., LONG-TERM STABILITY AND PREDICTION OF SOFT-TISSUE CHANGES AFTER LEFORT-I SURGERY, American journal of orthodontics and dentofacial orthopedics, 104(6), 1993, pp. 544-555
Many evaluations of soft tissue changes after orthognathic surgery hav
e been undertaken, and many correlations of soft tissue to hard tissue
movements have been established. These studies have not, however, spe
cifically discussed the long-term stability or characteristics of the
soft tissue changes. The objectives of this study were (1) to determin
e the long term stability of soft tissue changes 5 years after LeFort
I osteotomy, (2) to determine reliable correlations, if any, of soft t
issue changes to bony movements effected in surgery, and (3) to determ
ine the predictability of soft tissue changes as an aid to orthodontic
treatment planning. Cephalometric data from 25 patients who were trea
ted with LeFort I osteotomy with or without a concurrent mandibular pr
ocedure were analyzed retrospectively. Cases were selected from the pa
tient records of the Department of Oral Surgery of the Vrije Universit
eit in Amsterdam, the Netherlands. These patients were followed up at
four time points, the last being a mean of 6.1 years after surgery. An
alysis of stability data revealed that most horizontal and vertical so
ft tissue change after LeFort I surgery occurred in the first year aft
er surgery. Significant (>10%) change continued to occur for subnasale
, labrale inferius, upper lip protrusion, lower lip protrusion, and so
ft tissue convexity during the subsequent 5 years. Hard tissue to soft
tissue correlations were calculated and ratios of soft tissue to hard
tissue movement were determined for appropriate hard and soft tissue
landmarks at four time intervals. Reliable correlations of hard tissue
change at surgery to 5-year soft tissue change could be made for 10 v
ariables, which was considerably less frequently than for 1-year soft
tissue change. The relatively low reliability of long-term prediction
correlations suggests that soft tissue movements may be more independe
nt of hard tissue over time. One-year prediction values were similar t
o 5-year values and thus could be used for prediction purposes in orth
odontic treatment planning. Most short-term hard to soft tissue correl
ations found in the present study were in the range of those establish
ed by previous authors. Long-term hard tissue to soft tissue correlati
ons gave higher ratios of soft tissue movement secondary to maxillary
surgery, approaching ratios of 1.0:1.0 for some variables. This findin
g, as well as the long-term stability data, suggest that soft tissue s
ettling or equilibrium after surgery may take several years to complet
e.