Page 10 - The Outcome Question Continued

Nail breakage is a previously reported complication with ILN.8,12,13,16,43–46 This was also seen in our P1 cohort. These patients did not comply with the weight-bearing restrictions. All the P1 nails broke at the welds of the nail. Schiedel et al47 also reported breakage with the P1 nail. In comparison, in the same number of patients treated for the same indication, we saw only 1 nail breakage in the P2 nail with its 1-piece outer tube (no welds), despite allowing patients to bear 50% more weight than we did for P1 nails (75 vs. 50 lb for the 12.5mm nail). The 1 breakage was again associated with a weightbearing restriction noncompliant patient, who began walking without crutches prematurely. Two other contributing factors were identified that may have played a role. The length of the large diameter part of the nail remaining engaged in the distal cortical segment was 1 cm at the end of the distraction. This places a lot of stress on the telescopic junction of the nail. The authors recommend that there be at least 3 cm of overlap at the end of distraction to ensure that the stress distribution is not concentrated at this junction. Secondly, the end of the larger diameter of the nail is slotted at 4 places and mated and welded to a crown that has 4 ridges to provide antirotation stability to the telescopic nail. The fins between the slots are a site of fragmentation of the end of the nail tube. Breakages of the crown and fins have been identified in some cases including this patient (Fig. 9). To strengthen the nail and avoid crown failures, Ellipse Technologies released the P2.1 in December 2014, which has a modified keying feature without “thru-slots” or tack welds (Fig. 9).

Failure of the distraction mechanism has been reported with the P1 in 4% to 8% of cases,16,17 which is similar to the 3% we found in our series. This issue was addressed in the P2 redesign. In the P1, the problem lay with the connection between the gears and the drive shaft. There was no clutch mechanism. Therefore, if the nail met a high resistance, such as from a thick callus or large muscle mass, the powerful rotation of the magnet could fracture the connection to the drive shaft. In the P2, a clutch mechanism, in combination with a stronger junction to the drive shaft to prevent fracture and also increase the obtainable distraction force minimizes the risk of premature consolidation. We found no distraction failures in our P2 series.

Our P1 group had 3 patients with delayed union; 2 of these were tibial, which generally take longer to consolidate. In these patients we took advantage of the bidirectional nature of the nail and asked them to cyclic load the regenerate by alternating between elongating and shortening, 0.25 to 0.5mm at a time at least 4 times a day. This “accordion” maneuver seemed to work well as these patients went on to heal without requiring bone grafting. Of importance, we had no patients with nonunion of the femur or tibia and no secondary procedures were required to achieve union. This is in marked contrast to the high nonunion rate experienced by the senior author in his 2 reports on femur and tibia stature lengthening with the ISKD.39,40,44

An important consideration with cosmetic limb lengthening is the long-term effect on the body and particularly the joints. Femoral lengthening along the anatomic axis versus the mechanical axis, theoretically leads to valgus deformity at the knee.47 With 94 femurs to analyze in our series, the mLDFA did not significantly change despite the theoretical expectation that it would. One explanation is that a very mild varus bowing of the titanium nail occurs in many cases of femoral lengthening with the PRECICE. This mild varus may compensate for the tendency of the anatomic axis to go into valgus. This predicted valgus failed to be seen in another study as well.47

More surprising was the valgus deviation seen with tibial lengthening with the PRECICE. The 22 tibial cases demonstrated a significant change (P < 0.01) of the MPTA from 86.5 degrees (± 1.7 degrees) preoperative to 90.0 degrees (± 3.2 degrees) after lengthening. This may support the recent recommendation by Rozbruch and colleagues that blocking screws be used for tibial lengthening due to the wider canal at the level of the osteotomy site of the tibia.11,50–53

SSL by external fixation has been reported by several authors.6,7 Catagni et al6 (Lecco, Italy), reported on 54 patients undergoing the procedure using Ilizarov external fixators. At 6.25 years (range, 1 to 16 y) follow-up, the overall patient satisfaction was excellent (90.7%) or good (9.3%). They achieved an average 7 cm (range, 5 to 11 cm) of increased height for their patients. External fixation time was a mean of 9.5 months (range, 7 to 18 mo) with further casting 48% or bracing 51.85% into a brace after fixator removal. Other complications included: 35.2% equinus contracture requiring Achilles tendon lengthening, 48.2% pin site infection, 2 patients requiring bone grafting, and 3 patients with fracture collapse of the regenerate after frame removal. Overall 25 (46.3%) patients had to return to the operating room for further intervention. These cases were all tibial with double osteotomy sites, which may have increased complication rates.