TO THE EDITOR:
We read with interest "Complications of Limb-Lengthening in Children Who Have an Underlying Bone Disorder" (80-A: 18—24, Jan. 1998), by Naudie et al.
We fully agree with the finding that patients who have an underlying bone disorder have more complications than patients who have a posttraumatic or postinfective bone disorder. We have already noted the high prevalence of complications associated with lengthening in patients who have a congenital limb-length discrepancy. We reviewed the results of limb-lengthening in a group of seventeen patients who were an average of 10.8 years old at the beginning of lengthening. The discrepancies ranged from 4.5 to 12.0 centimeters for the lower limbs and from 24.0 to 30.0 millimeters for the forearms3,4. Although we achieved correction of the limb-length discrepancy in all but one patient, all of the patients had some type of complication, including fracture, the need for exchange of the fixator, and the need for additional operations3,4.
More recently, we used dual-energy x-ray absorptiometry to study the accretion of bone-mineral content during lengthening in eleven young patients, five to seventeen years old, who had callotasis lengthening for the treatment of congenital, posttraumatic, or postinfective conditions involving the lower limb5. We were able to show that our patients exhibited one of three rates of new-bone formation. Analysis of the time graphs revealed a definite relationship between early bone formation and subsequent accretion of bone-mineral content. The different rates of bone accretion were not related to the type of fixator that was used or to the bone that was lengthened but appeared to be dependent on the underlying pathology. In patients who have intrinsically normal bone, such as those who have postinfective and posttraumatic conditions, bone-mineral content increases at a fast or moderate rate. In contrast, in patients who have congenital conditions, moderate bone accretion is the best that can be expected at the usual rate of distraction of 0.25 millimeter four times a day.
We fully agree that larger studies are needed in order to assess any statistical differences in the rates of complications in patients who have limb-lengthening for the treatment of congenital, posttraumatic, or postinfective conditions. We recently undertook such a study and conducted a retrospective review of data that had been prospectively collected at three centers in two European countries6. More specifically, we reviewed the charts and radiographs of 240 patients (281 lower limbs) who had been managed with limb-lengthening for the treatment of a congenital, posttraumatic, or postinfective condition from 1984 to 1992. We studied the age of the patients at the time of the operation, the bone segment lengthened, whether a corticotomy or an osteotomy had been performed, the amount of lengthening planned and achieved, the level or levels of corticotomy or osteotomy, the type of external fixator used, and the complications encountered. Two-way analysis of variance showed that the healing index associated with posttraumatic and postinfective conditions was significantly lower than that associated with congenital conditions; there were no significant differences between the index associated with posttraumatic shortening and that associated with postinfective shortening. We also found that there were no significant differences between the use of a circular fixator and the use of a unilateral fixator for lengthenings of less than 20 per cent. However, the Ilizarov and the Monticelli-Spinelli apparatuses were associated with significantly fewer complications when used for lengthenings of more than 20 per cent (p = 0.021).
In the end, we were quite surprised that our previous work on this subject was not cited even though it was published in high-quality, peer-reviewed, international journals.
Nicola Maffulli, M.D., M.S., Ph.D., F.R.C.S.(Orth): Department of Orthopaedic Surgery, University of Aberdeen School of Medicine, Polwarth Building, Foresterhill, Aberdeen AB25 2ZD, Scotland
John Fixsen, M.Ch., F.R.C.S.: Department of Orthopaedic Surgery, Great Ormond Street Hospital for Sick Children, Great Ormond Street, London WC1N 3JH, England
Dr. Naudie, Dr. Hamdy, Dr. Fassier, and Dr. Duhaime reply:
We thank Dr. Maffulli and Mr. Fixsen for their interesting comments regarding our paper.
First, we completely agree with everything that Dr. Maffulli and Mr. Fixsen mention concerning limb-lengthening in patients who have a congenital limb-length discrepancy. We also found that lengthening in these patients is associated with a higher prevalence of complications than lengthening in patients who have a posttraumatic or postinfective discrepancy. Furthermore, we agree that dual-energy x-ray absorptiometry may be valuable in the monitoring of patients who are managed with limb-lengthening. Our own experimental work with dual-energy x-ray absorptiometry confirmed these findings1,2.
However, we are afraid that Dr. Maffulli and Mr. Fixsen may have misunderstood the message of our paper. We studied patients who had a specific underlying bone disorder. In the Materials and Methods section, we explained that we excluded patients who had a congenital limb-length discrepancy, as we believe that such patients do not have structural abnormalities in the bone itself. To the best of our knowledge, there have been no published reports stating that patients who have a congenital limb-length discrepancy, such as a congenitally short femur or fibular hemimelia, have histological osseous abnormalities. We agree that these patients might have abnormalities of the soft tissues, ligaments, or muscles, or discrepancies in the shape and number of bones, but we think that the bones themselves have normal histological characteristics. For these reasons, we believe that congenital limb-length discrepancies and discrepancies secondary to pathological bone disorders are two different entities, and we included only the latter in our study for comparison.
Finally, we were fully aware of the papers by Maffulli et al.4-6. They are indeed very important studies with a large number of patients and compelling results. We did not cite them in our study, however, because they describe the experience with lengthening in patients who have congenital limb-length discrepancies and not in patients who have specific underlying disorders of bone.
Douglas Naudie, M.D.; Reggie C. Hamdy, M.D.; François Fassier, M.D.; Morris Duhaime, M.D.: Shriners Hospital for Crippled Children, 1529 Cedar Avenue, Montreal, Quebec H3G 1A6, Canada