We performed a retrospective case-matched comparison of patients who underwent LAP and those who underwent classic lengthening. From 2006 to 2009, we treated 25 patients (27 extremities) with the LAP technique. Proximal tibia lengthening was performed in 21 cases and distal femoral lengthening in six. In general, we perform LON for femoral lengthening and LATN for tibial lengthening. Indications for the LAP procedure were deformity about the knee requiring a metaphyseal osteotomy and any other problems precluding the use of an intramedullary nail, including, for example, a tight intramedullary canal. Contraindications were a history of osteomyelitis at the osteotomy site and poor skin condition at the proposed plate insertion site. From 2000 to 2010, we treated 87 patients with a classic approach. As controls, we identified 26 of these 87 patients (27 extremities) and matched them for etiology (Table ), age, amount of lengthening (cm), mechanical axis deviation (MAD), and tibia/femur distribution (Table ). The minimum followup was 28 months (mean, 45 months; range, 28–63 months) for the LAP group and 25 months (mean, 80 months; range, 25–140 months) for the classic group. No patients were lost to followup. No patients were recalled specifically for this study; all data were obtained from medical records and radiographs.
The gender distribution in the two groups was similar (p = 0.1): 17 male patients in the classic group and 10 in the LAP group versus nine female patients in the classic group and 15 in the LAP group. The relative proportions of the sides also were similar (p = 0.4): 12 left sides in the classic group and 15 left sides in the LAP group.
We used a Taylor Spatial FrameTM
(Smith and Nephew, Memphis, TN, USA) (FDA-approved) in all patients. Our typical external fixator application consisted of the following steps. We used a “rings first” [25
] method for mounting the external fixator. We began with a fibular osteotomy. We used a lateral approach to the middle 1/3 of the fibula using the interval between the lateral and posterior compartments. Multiple drill holes were made, and the osteotomy was completed using an osteotome. The proximal tibia 2/3 (open) ring then was applied. This was our reference ring. We rotated the ring such that the open section was facing laterally, simplifying future lateral plate placement (Fig. ). Bone fixation of the proximal ring consisted of three tapered, 6-mm hydroxyapatite-coated half-pins (Biomet, Warsaw, IN, USA). All pins were placed from the medial side to prevent contact with the area of future plate placement (Fig. ). We used a medial half-pin to stabilize the proximal tibiofibular using a cannulated technique described by Green [11
]. We fixed the distal tibiofibula syndesmosis at the ankle with one 4.5-mm quadricortical screw or a tensioned tibiofibular wire. Mounting parameters were obtained for the proximal ring [9
] for later use with the Taylor Spatial FrameTM
web-based software [28
]. The distal ring then was attached at the midtibia level. This was done using a 1.8-mm medial face wire going anterolateral to posteromedial and two anteromedial half-pins. The six Taylor Spatial FrameTM
struts were attached and their lengths were recorded. The struts then were detached from the proximal ring, and the tibial osteotomy was performed. This was done using a percutaneous technique under C-arm fluoroscopy. The Taylor Spatial FrameTM
struts were reattached providing an anatomic reduction of the osteotomy. Next, mounting parameters were obtained intraoperatively using the C-arm as described previously [9
Fig. 1A–D (A) Anteroposterior, (B) lateral, and (C) axial views of a plastic bone model of the external fixator configuration and lateral plate placement for proximal tibia lengthening are shown. (D) An intraoperative photograph shows a plate provisionally fixed (more ...)
The osteotomy and external fixator application were similar for patients in the classic group. The proximal tibia 2/3 ring in this group was applied in traditional fashion with the opening on the back for uninhibited knee flexion.
Postoperatively the patients were allowed to bear weight as tolerated on the affected extremity using crutches or a walker. A Taylor Spatial FrameTM
strut adjustment schedule (using the total residual mode) was generated using the web-based software. The patients started their own adjustments on postoperative Day 7 at a rate of 1 mm/day. Postoperatively, the patients in both groups followed a routine protocol as described previously [27
]. Knee and ankle ROM exercises were encouraged with supervision of a physical therapist three times per week for 1 hour. Patients also were given a daily 1-hour home therapy program. Patients with bilateral deformities had staged correction with surgery on the second-side typically at 6 to 8 weeks after the first side. ROM exercises of the knee and ankle were encouraged. A daily shower, including washing the pin sites with antibacterial soap, was encouraged. This was followed by daily pin care with half-strength hydrogen peroxide and then coverage of pin sites with a dry sterile gauze wrap. Patients were seen in the clinic every 10 to 14 days by the senior author (SRR) during the distraction phase. During each office visit the patients in both groups were examined clinically including inspection of the external fixator, pin sites, and ROM in adjacent joints. Neurovascular status also was assessed routinely to detect any neuropathy related to the distraction and deformity correction process. Anteroposterior and lateral radiographs were obtained at each visit and long leg radiographs were obtained on completion of the adjustment schedule.
The distraction phase was completed when the necessary length and desired alignment were achieved. We then performed the locking plate insertion and removal of the external fixator. A proximal tibia locking plate (Smith and Nephew) (FDA-approved) was used. The external fixator was prepared in the field, all of the pin sites were covered with Betadine® (Purdue Pharma LP, Stamford, CT, USA) -soaked gauze, and the external fixator was covered with sterile blue towels (Fig. ). It was necessary to insert the plate with the external fixator still in place. The newly formed regenerate bone was not mature or rigid enough to maintain length at the time of plate insertion. The external fixator also served to maintain the bone in an ideal alignment during plate insertion. We inserted the in situ submuscular plate using a 4-cm lateral incision over the proximal tibia. The distal locking screws were inserted using an external targeting jig using small stab skin incisions and blunt dissection down to the plate. Contact between internal and external fixation was avoided. The external fixator was removed only after the plate stabilized the bone. Autologous bone marrow aspirate concentrate (BMACTM; Harvest Technologies, Plymouth, MA, USA) was injected into the regenerate in 15 extremities at the time of plating.
Postoperatively the patients remained toe-touch weightbearing for approximately 6 weeks until three of four cortices of bridging callus of the regenerate were observed. During this time the patients continued supervised physical therapy to maintain ROM in adjacent joints. The patients were seen in the clinic first 2 weeks after the surgery and every 4 to 6 weeks afterward. During each visit, all surgical wounds were inspected, neurovascular status was assessed, gross extremity alignment was noted, and adjacent joint ROM was documented. Anteroposterior, lateral, and long leg radiographs were obtained (Fig. ). When deemed appropriate, gradual transition to full weightbearing was allowed during a period of 4 weeks.
Fig. 2A–E (A) AP and (B) lateral radiographs of the left ankle of a 49-year-old man with advanced left ankle arthritis and varus deformity are shown. The patient was treated with ankle fusion and simultaneous proximal tibia lengthening. (C) AP and (D) lateral radiographs (more ...)
Information regarding time wearing the frame, knee and ankle ROM, alignment, and complications were extracted from the medical records. We used the classification described by Paley [23
] to define complications. According to that classification, true complications are all intraoperative injuries and all problems during lengthening that are not resolved by the end of the treatment. Even though pin-tract infection and cellulitis were not considered true complications according to this classification, they still were included in the analysis as we thought they could be relevant when comparing the LAP and classic groups.
All radiographs were evaluated by one observer (SRR). We used serial radiographs to determine the BHI. Bony union was determined by radiographs showing three of four cortices of bridging callus. Alignment was assessed by measuring the MAD on a 51-inch bipedal standing radiograph. MAD was considered normal within the range of 6 mm lateral to 17 mm medial. The same radiographs were used to assess leg length discrepancy. There were no missing radiographs. We computed BHI and EFI. BHI was defined as the time until bony union in months divided by the amount of lengthening in centimeters. EFI was defined as the time wearing the external fixator in months divided by the amount of lengthening in centimeters. Before taking radiographs, the leg length discrepancy was estimated clinically and appropriate height blocks were used under the foot of the short leg to level the patient’s pelvis and improve reliability of measurement of the discrepancy.
Using the classic group results, we examined data distribution for the EFI data. The mean was 2 months/cm and the median was 1.7 months/cm. Assuming a Mann-Whitney test, our power would be greater than 70% to detect a difference greater than 0.6 (18 days/cm difference between the two groups) with 27 extremities per group. This seemed to be an important clinical difference.
The Shapiro-Wilk test was used to check if outcome variables could be considered normally distributed. They could not. Therefore, Mann-Whitney analysis was used to determine outcome differences between the classic and LAP groups (EFI, BHI, and ROM). Considering the limited sample size, Fisher’s exact test was used to determine differences in the incidence of malalignment and complications. We used StatXact 8 (Cytel Inc, Cambridge, MA, USA) SYSTAT 12 and SYSTAT 13 (SYSTAT Software Inc, Chicago, IL, USA) and PASS (NCSS, Kaysville, UT, USA) for all analyses.