Page 3 - Methodology Continued

In the femur, these drill holes were always made before reaming to act as venting holes, thereby reducing the risk of fat embolism, as well as to ensure that the reamings would extrude out the holes to “autograft” the osteotomy site. In the tibia, 1 anterior hole and 1 medial hole are drilled to avoid extrusion of reamings into the anterior or deep posterior compartments. Such extrusion can lead to compartment syndrome. Although percutaneous prophylactic fasciotomy of the anterior compartment can be performed to reduce the risk of compartment syndrome, it leaves the patients with bulging muscles anteriorly, which is unacceptable cosmetically. Therefore, it is best to avoid any extrusion into the compartments by not creating lateral or posterior cortical holes. Posterior and lateral cortical holes are drilled after the reaming in order to notch the tibia and make completion of the osteotomy easier. The canal is reamed 2mm over the nail diameter for both femur and tibia. For the femur, the noncannulated PRECICE nail is advanced up to the osteotomy site. An extension moment is applied while the bone is osteotomized with an osteotome from the lateral side. The nail is then advanced down the bone after the osteotomy is completed. In the tibia, the bone is osteotomized without the nail in place but after the reaming and drilling are completed. The nail is then inserted and advanced down the tibia. The location of the nail magnet is marked on the skin using fluoroscopy. The ERC is then placed sterilely on the area and activated for 7 minutes to lengthen 1 mm, which is confirmed on comparative images. For the tibia, a mid-diaphyseal fibular osteotomy is performed through a small posterolateral incision, usually before the reaming of the tibia. The author’s (D.P.) fibular osteotomy technique is to make multiple drill holes with a 1.8mm Ilizarov bayonet wire, followed by completion of the osteotomy using a small diameter osteotome (3 mm). The fibula is also first fixed distally using a 4.5mm screw between the fibula and tibia. The orientation of this screw, which is referred to as a “temporary arthrodesis screw of the tibiofibular joint” is proximal on the tibia and distal on the fibula. The author (D.P.) prefers the head of the screw to be on the tibial side. The proximal tibiofibular joint is also fixed with a screw. Whenever possible this is done using one of the proximal locking screws. This requires targeting the fibula at the time of insertion of the anteromedial to posterolateral screw in the nail. As this screw is at a different level for the right or left legs, the nail has to be advanced more on the left side to match the trajectory of the screw hole with the head of the fibula. If the targeting misses the proximal fibula, a second 4.5mm temporary arthrodesis screw should be inserted by first inserting a wire followed by a cannulated drill hole followed by the solid screw. The authors do not use a cannulated screw because it is too weak and may bend or break. The lengthening rate for the tibia is usually 0.75 mm/d and for femurs 1 mm/d (each broken into 0.25-mm intervals). The distraction starts on postoperative day 1, for patients under 30 years, and day 7 for those 30 years or older for femur lengthening and for all tibial lengthening. After surgery the patient is usually in the hospital for 3 to 4 nights. They are anticoagulated with XARELTOs (rivaroxaban) from the second or third day after surgery until they are fully ambulatory without crutches after completing the consolidation phase.

Coincidentally, there were equal numbers of limb segments (femur, tibia) lengthened in the P1 and P2 groups (P1—25 patients and 58 limb segments and P2—26 patients and 58 limb segments), which made for simplified statistical analysis (Table 1). In the P1 group, there were 6 nails for bilateral tibia lengthening (3 patients), 16 nails for 4 segment bilateral femur and tibia lengthening (4 patients), and 36 nails for bilateral femur lengthening (18 patients). In the P2 group, there were 2 nails for bilateral tibia lengthening (1 patient), 12 nails for 4 segments (3 patients), and 44 nails for bilateral femur lengthening (22 patients). Two femoral nails in each group (total of 4 nails) were inserted through trochanteric starting points and the remainder of the femoral nails by piriformis starting points. Overall our cohort consisted of 44 males and 6 females with a mean age of 27.8 years (range, 15 to 51 y). The mean preoperative height in patients was 164.7 cm (range, 150 to 180 cm) [64.8 inches (range, 59 to 70.9 inches)]. Patients were followed every 2 weeks during the distraction phase and once a month during the consolidation phase until anteroposterior and lateral radiographs demonstrated 3 of 4 cortices were solid. Radiographic alignment parameters were measured digitally as previously described,16 and done using PACS (Picture Archiving and Communications System) (OnePacs LLC, New York, NY).

The statistical analysis was carried out using the statistical software, SAS 9.2 (SAS Institute Inc., Cary, NC). All variables were analyzed as continuous, categorical, or ordinal, as deemed appropriate. Given the nature of data, a paired Student t test was used to analyze differences between matched data sets. Descriptive statistics were used when suitable. No power analysis was done prior, as this is a retrospective series. IRB approval for a retrospective study was obtained.