What Is the Survival of the Telescope Allograft Technique to Augment a Short Proximal Femur Segment in Children After Resection and Distal Femur Endoprosthesis Reconstruction for a Bone Sarcoma?

Abstract

Background Large, malignant bone tumors and revision limb salvage procedures often result in the resection of extensive lengths of the involved bone segment, leaving a residual segment of bone that may be too short to support a standard intramedullary stem for endoprosthetic reconstruction. Telescope allografting, in which an allograft is used to augment the remaining bone segment by telescoping it into the residual bone segment, was described for situations in which residual bone stock is insufficient after tumor resection or prosthetic revision. Apart from one study that first described the procedure [15], there are no other studies reporting the outcome of this telescopic concept for restoring bone stock. Questions/purposes For patients younger than 18 years who underwent the telescopic allograft technique to augment a short segment of the proximal femur after resection of bone sarcomas who also underwent endoprosthesis reconstruction of the distal femur, we asked: (1) What is the survivorship free from removal of the telescopic allograft and the endoprosthetic stem at 7 years after surgery? (2) What proportion of these reconstructions will heal to the host bone without delayed union or nonunion? (3) What is the functional outcome based on the Musculoskeletal Tumor Society (MSTS) score? Methods We retrospectively studied our institutional database and identified 127 patients younger than 18 years who underwent surgery for a primary malignant bone tumor of the distal femur between December 2008 and October 2018. After excluding 16 patients undergoing amputation and rotationplasty and 57 patients undergoing recycled autograft/allograft reconstruction, 54 patients who underwent primary or revision distal femur endoprosthesis reconstruction were identified. Among these patients, we considered 15 patients who underwent telescopic allograft augmentation of the femur for analysis. One patient was lost to follow-up before 2 years but was not known to have died, leaving 14 for analysis at a median (range) 49 months (24 to 136 months) of follow-up. The indications for telescopic allograft augmentation of the femur in our institution were a proximal femur length of less than 120 mm after resection or resection of more than two-thirds of the total length of the femur. Ten of 14 patients underwent telescopic allograft augmentation as a revision procedure (distal femur resorption in five patients, endoprosthesis stem loosening in three patients, implant fracture in one patient, and infection in one patient), and the remaining four patients underwent telescopic allograft augmentation as a primary limb salvage procedure for large malignant bone tumors of the distal femur. The histologic diagnosis in all patients was osteosarcoma. At the time of telescopic allograft augmentation and reconstruction, the median age of the patients was 14 years (7 to 18 years). The size and the type of bone allograft to be used (femoral shaft or proximal femur) was planned before surgery, with consideration of the extent of resection, level of osteotomy, diameter of the host bone at the osteotomy site, and approximate diameter of the endoprosthesis stem to be used. The segment of the cylindrical allograft used for telescoping was thoroughly washed, prepared, and impacted onto the native femur to achieve telescoping and overlap. Serial digital radiographs were performed once a month for the first 6 months after the procedure, every 2 months until 1 year, and then every 6 months thereafter. Two surgeons in the department (at least one of which was involved in the surgery) retrieved and reviewed clinical notes and radiographs to determine the status of the telescopic allograft and endoprosthesis stem. We defined delayed union as radiological union at the osteotomy site more than 6 months after the procedure without additional surgery; we defined nonunion as no radiological evidence of callus formation at the osteotomy site 9 months after the procedure, necessitating additional surgery. The reviewers did not disagree about the definition of healing time. None of the patients missed radiographic follow-up. Kaplan-Meier survivorship free from removal of telescopic allograft and the endoprosthesis stem at 7 years after surgery was estimated. Patient function was assessed using the 1993 version of the MSTS [9], as determined by chart review of the institutional database performed by one of the surgeons from the department. Results The survivorship free from removal of the telescopic allograft and endoprosthesis stem at 7 years after surgery was 80% (95% confidence interval 22% to 96%). The allograft united with the host bone in 100% (14 of 14) of the patients. Though 21% (3 of 14) had delayed union, no nonunions were seen. The median (range) MSTS score at the final follow-up interval was 27 (22 to 30). Conclusion Although this is a small group of patients, we believe that allograft segments help augment short bone stock of the proximal femur after long-segment resections, and the telescopic technique seems to be associated with a low proportion of nonunion or delayed union, which is one of the most common complications of allografts. Maintaining an adequate length of the proximal femur is important in preserving the hip, and this technique may be especially useful for young individuals who may undergo repeated revision procedures. Level of Evidence Level IV, therapeutic study.

Classification and Reconstruction of Femoral Bone Defect in the Revision of Aseptic Loosening of Distal Femoral Endoprostheses: A 10-year Multicenter Retrospective Analysis

“…[48,49] With telescope technology, the grafted bone and the host bone are overlapped to maximize the surface contact between the host bone and the allogeneic bone to realize a stable xation of the distal end of the prosthesis. [45] Hindiskere et al [47] con rmed the effectiveness of telescope technology. In 14 patients with endoscopic bone allograft, the bone healing rate was 100%, and the MSTS score was 27 at the nal follow-up.…”

“…The revision of type loosening presents a challenge; thus, a good implantation environment is necessary for the prosthesis. Currently, the commonly used methods reported in the literature are the telescope tube-like allograft prosthesis [45][46][47] and the Compress® Compliant Pre-stress (CPS) prosthesis [50][51][52]. The telescope technology was rst proposed by Healey et al [45] and succeeded allogeneic bone grafts used in reconstruction and revision.…”

Intercalary reconstruction of long bones by massive allograft: Comparison of construct stability ensured by three different host-graft junctions and two types of fixations in a synthetic femur model

“…Tapering the host bone and graft ends provides an increase in contact surface by approximately 220 and 480% compared with that found in modified step-cut and end-to-end shapes, respectively. A greater contact area between the graft and viable host bone tissue should also facilitate cell colonisation of the graft, as suggested by early clinical results achieved with different intercalary reconstructions or telescope allograft techniques ( 22 , 52 , 56 , 57 ).…”

A comparison of cemented and cementless intra-neck curved stem use during hip-preserving reconstruction following massive femoral malignant tumor removal

“…This approach, however, is contraindicated in cases where the cortical thickness at the bone-implant surface is <2.5 mm ( 26 ). In children or patients who have undergone prior reconstructive procedures, the residual cortical thickness may be insufficient for this compression-based approach ( 27 ). Compression fixation has also been linked to various types of failure in cases of pathologic skeletal or extraskeletal conditions in which patients exhibit osteopenia and altered bone metabolism.…”

“…The complication rates associated with the use of stems with cross-fixation pins have been reported to be relatively low ( 29 ). However, this approach is associated with a need for more time to plan the procedure and manufacture the necessary customized systems, potentially making this approach infeasible for individuals undergoing neoadjuvant chemotherapy due to time constraints ( 27 ). Short-stemmed endoprostheses are theoretically susceptible to higher rates of aseptic loosening and implant failure ( 30 ), leading some to employ extra-cortical plants as a means of minimizing the risk of aseptic loosening through supplemental fixation.…”