Bone transport nails for reconstruction of lower limb diaphyseal defects in patients with bone sarcomas

An 18-year-old male patient with Ewing’s sarcoma of the right tibial diaphysis underwent wide resection with clear surgical margins following 9 cycles of neoadjuvant CTX. A temporary spacer was implanted in the bony defect measuring 14.1 cm until completion of 5 adjuvant CTX cycles (Fig. 1a, b). Thereafter, a two-level tibial osteotomy was performed and a BTN 11.5/360 mm implanted. To shorten the transport period, a combined proximal and distal bone transport via a pulley mechanism was constructed (Fig. 1c). For this purpose, a wire was fixed to the proximal fragment, rerouted over a screw secured with a mini-plate in the proximal healthy bone, and again fixed at the distal fragment (Fig. 1c). By redirecting the force emerging from transport of the proximal fragment downwards, the distal fragment is pushed upwards. Following surgery, the patient was allowed 40 kg partial weight bearing. The pulley mechanism for retrograde transport of the distal segment failed 1.5 months after surgery, necessitating revision surgery (Fig. 1d). During this procedure, the simultaneous double osteotomy system was abandoned, aiming at enabling completion of proximal bone segment transport via the screw. In a second procedure 1.5 months later due to screw loosening (Fig. 1e), the proximal segment was fixed with a plate and a retrograde bone segment transport reinitiated via renewed osteotomy of the distal segment and a cable-wire pulley mechanism. Bone segment transport was completed after 10.3 months (Fig. 1f–h). Subsequently, the BTN was exchanged with a conventional tibial nail (Expert Tibial Nail, DePuy Synthes, Johnson&Johnson Medical Products GmbH, Vienna, Austria) and the proximal docking site was prepared with curettage and plate fixation due to the lack of complete consolidation (Fig. 1i). Thereafter, the patient was allowed full weight bearing. At latest follow-up 19.5 months after the start of bone transport, complete and partial bony consolidations (confirmed by CT scan) were present at the distal and proximal segments, respectively (Fig. 1j). The patient was fully weight bearing without any pain and had no evidence of disease.

Following histological verification of a periosteal osteosarcoma G2 of the left femoral shaft via open biopsy, a 30-year-old female patient underwent surgical resection of the femoral diaphysis (14.4 cm) and temporary implantation of a cement spacer (Fig. 2a, b). After clear margins had been confirmed, reconstructive surgery with distal femoral osteotomy and implantation of a BTN 11.5/360 mm for retrograde transport were performed (Fig. 2c). The patient was allowed 40 kg partial weight bearing until docking (Fig. 2d). Recharging of the BTN was carried out 2.8 months after implantation. The patient developed a peri-implant infection 3 weeks later, necessitating revision surgery with debridement, lavage and antibiotic treatment (initially i.v., later p.o.; Fig. 2e). After the infection had resolved, another recharging was carried out 2 months later (Fig. 2f). At that time point, the patient was allowed partial weight bearing with half body weight. Bone segment transport was completed 9.1 months after BTN implantation and bony consolidation was achieved soon thereafter (Fig. 2g–i), which was confirmed by CT scan. Surgery to exchange the BTN for a conventional femoral nail was carried out 19 months following surgery. Sonication of the explanted nail to rule out the presence of a low-grade implant-associated infection was inconspicuous. Despite a valgus deformity secondary to bone transport of the femur, the patient was free of complaints, fully weight bearing, with no signs of tumor recurrence or infection (Fig. 2j).

A 28-year-old female patient was diagnosed with an epithelioid MPNST originating from the right proximal tibial metaphysis. The diagnosis was ultimately reached in the multidisciplinary team meeting owing to 100% positivity for S100 and SRY-Box Transcription Factor 10 (SOX10) as well as loss of SWI/SNF Related BAF Chromatin Remodeling Complex Subunit B1 (SMARCB1/INI1) expression on immunohistochemistry. Molecular pathological investigations (Archer FUSIONPlex Sarcoma Panel v2; Integrated DNA Technologies, Boulder, CO, USA) revealed no specific genetic fusions. Prior to adjuvant CTX, the patient underwent a wide joint-sparing resection (resulting bone defect 8.5 cm) and implantation of a cement spacer (Fig. 3a, b). Notably, due to the close vicinity of the tumor to the joint, only a small fragment of the tibial epimetaphysis could be preserved. The patient received a full-leg Scotchcast bandage (3M™ Scotchcast, 3M Austria GmbH, 1120 Vienna, Austria) and weight bearing was not allowed (Fig. 3c). Following completion of 6 CTX cycles, the spacer was removed and a BTN 10/300 mm together with a supporting plate implanted (i.e. PABST technique) with retrograde transport of a distal tibial segment (Fig. 3d). Due to prolonged non-weight bearing throughout adjuvant CTX, an occult nondisplaced fracture occurred at the right distal femur (Fig. 3d). The fracture was treated conservatively in a full-leg brace and 15 kg partial weight bearing. Subsequent bone densitometry revealed osteopenia, for which the patient was prescribed vitamin K and calcium after counselling with an endocrinologist. Bone transport was initiated as planned on the 8th postoperative day (Fig. 3e, f). The BTN recharging was performed 3.2 months after initial surgery and the patient was allowed 15 kg partial weight bearing (Fig. 3g). Transport was finished 5.2 months after BTN implantation. To enhance healing, the two distal screws were subsequently removed (Fig. 3k) and 12 months after BTN implantation and 18 months after tumor surgery, partial bony consolidation had taken place (confirmed by CT scan), with progredient callus formation visible at the proximal docking site (Fig. 3i, j). To enhance healing and address the remaining ipsilateral limb length discrepancy as well as varus/flexion deformity of the distal femur, revision surgery with distal femoral osteotomy and implantation of an intramedullary growing nail was carried out 14 months after BTN implantation (Fig. 3k). During the same procedure, autologous cancellous bone grafting at the proximal tibial docking site was carried out. Currently, the distal femoral lengthening procedure is ongoing, the patient is fully weight bearing without complaints and there is no evidence of recurrent disease.