Background: Cemented endoprosthetic reconstruction after resection of primary bone sarcomas has been in common use for decades. Although multiple studies have reported the survivorship of primary endoprostheses, implant survivorship after revision surgery is less well established. Given that earlier advances in systemic therapy improved survival of patients with sarcoma, the usage of revision endoprostheses can be expected to increase and, as such, understanding revision implant survivorship will help to inform patient and surgeon expectations. Additionally, as new implants are developed that allow alternative reconstruction options, a normative dataset establishing accurate expectations for revision cemented endoprostheses is a critical benchmark by which to measure progress. Questions/purposes: (1) What is the implant survivorship free of all-cause revision for primary and revision cemented distal femoral replacements (DFRs) used in the treatment of malignant or benign tumors? (2) What are the most common indications for revision of primary and revision DFRs in an oncology population with mean follow-up of more than 10 years? (3) How does the indication for revision of a primary DFR affect the subsequent risk for and type of revision DFR complication? (4) What patient, tumor, or implant characteristics are associated with improved survivorship free of revision in cemented DFRs used in patients treated initially for primary malignant or benign tumors? Methods: This was a retrospective, comparative study using our institution’s longitudinally-maintained database of 806 cemented endoprostheses starting in 1980 and assessed through December 31, 2018. In all, 365 DFRs were inserted during this time, but 14% (51 of 365) were placed for nonprimary bone tumors and 1% (5 of 365) were cementless reconstructions, leaving 309 cemented DFRs. Seventy-one percent (218 of 309) were primary implants and 29 percent (91 of 309) were revision implants (used to revise a prior DFR in all patients). During this time period, our strong bias was to use cemented stems and, thus, nearly all of our patients had cemented stems. Six percent (13 of 218) of primary DFRs were implanted more than 2 years before the study end; however, they lacked 2 years of follow-up data and, thus, were considered lost to follow-up, leaving 205 implants in the primary DFR analysis group. Only the first revision after primary DFR revision surgery was included in the revision cohort analysis. Thirty-two percent (29 of 91) of revision DFRs were second or more revision patients and were excluded, leaving 62 implants in the revision analysis group. Most patients in both groups were men (57% [117 of 205] for primary and 71% [44 of 62] for revision) who had been diagnosed with osteosarcoma (75% [153 of 205] and 73% [45 of 62] for primary and revision, respectively). The primary cohort had mean age of 26 ± 16 years with a mean follow-up of 136 ± 122 months, and the revision cohort had mean age of 31 ± 13 years (p = 0.02) with 141 ± 101 months of follow-up. Study endpoints included all-cause implant revision and cause-specific revision for soft tissue complications, aseptic loosening, structural complications (defined as periprosthetic or implant fracture), infection, or tumor progression. Planned surgery for implant lengthening procedures was excluded. Implant survivorship free from all-cause revision was calculated using a competing risk (cumulative incidence) estimator with death as a competing risk. A log-rank test using chi-square analysis was used to evaluate the differences in implant survivorship between primary DFRs and first revisions. The cause-specific incidences of implant revision were tabulated for primary and revision DFRs. Cox regression analysis investigated the odds of subsequent all-cause revision surgery for revision cemented DFRs based on the primary implant complication. A binary logistic regression analysis using age, gender, indication for revision, tumor type, infection, perioperative chemotherapy, and radiation was performed to identify factors associated with a second DFR reoperation. Relative effect sizes are reported as ORs. Results: The revision DFR cohort had a shorter mean survival to all-cause revision than the primary cohort (mean 10 years [95% CI 7 to 12] versus 18 years [95% CI 15 to 20]; p < 0.001). The most common complications necessitating revision for revision implants were periprosthetic or implant fracture in 37% (23 of 62) and aseptic loosening in 15% (9 of 62), and the type of primary implant complication was not associated with risk of subsequent all-cause revision surgery for revision implants. Stem diameter less than 15 mm was associated with repeat all-cause revision in cemented revision DFRs after controlling for resection length, stem length, implant fabrication (custom or modular), and presence of a porous collar (OR 4 [95% CI 1 to 17]; p = 0.03). No other parameters that we explored, including patient age, gender, chemoradiation history, or primary tumor diagnosis, were associated with repeat revision surgery. Conclusion: Understanding modifiable factors that can improve revision DFR survival is critical to achieving long-term limb salvage for patients with tumors around the knee. Our data suggest that utilizing implants with the largest possible stems—or at a minimum increasing the stem size over the primary implant—is important to revision cemented DFR survivorship and is an important part of our revision practice. Improving revision implants’ resistance to aseptic loosening through designs that resist torsion (a common mode of cemented fixation failure)—such as with the use of custom cross-pin fabrication—may be one method to improve survivorship. Another will be improved implant metallurgy that is resistant to fatigue fracture. Next steps may include understanding the optimal ratio of femoral diaphyseal width to implant...

Background: Although pediatric lower extremity sarcoma once was routinely treated with amputation, multiagent chemotherapy as well as the evolution of tumor resection and reconstruction techniques have enabled the wide adoption of limb salvage surgery (LSS). Even though infection and tumor recurrence are established risk factors for early amputation (< 5 years) after LSS, the frequency of and factors associated with late amputation (≥ 5 years from diagnosis) in children with sarcomas are not known. Additionally, the resulting psychosocial and physical outcomes of these patients compared with those treated with primary amputation or LSS that was not complicated by subsequent amputation are not well studied. Studying these outcomes is critical to enhancing the quality of life of patients with sarcomas. Questions/purposes: (1) How have treatments changed over time in patients with lower extremity sarcoma who are included in the Childhood Cancer Survivor Study (CCSS), and did primary treatment with amputation or LSS affect overall survival at 25 years among patients who had survived at least 5 years from diagnosis? (2) What is the cumulative incidence of amputation after LSS for patients diagnosed with pediatric lower extremity sarcomas 25 years after diagnosis? (3) What are the factors associated with time to late amputation (≥ 5 years after diagnosis) in patients initially treated with LSS for lower extremity sarcomas in the CCSS? (4) What are the comparative social, physical, and emotional health-related quality of life (HRQOL) outcomes among patients with sarcoma treated with primary amputation, LSS without amputation, or LSS complicated by late amputation, as assessed by CCSS follow-up questionnaires, the SF-36, and the Brief Symptom Inventory-18 at 20 years after cancer diagnosis? Methods: The CCSS is a long-term follow-up study that began in 1994 and is coordinated through St. Jude Children’s Research Hospital. It is a retrospective study with longitudinal follow-up of more than 38,000 participants treated for childhood cancer when younger than 21 years at one of 31 collaborating institutions between 1970 and 1999 in the United States and Canada. Participants were eligible for enrollment in the CCSS after they had survived 5 years from diagnosis. Within the CCSS cohort, we included participants who had a diagnosis of lower extremity sarcoma treated with primary amputation (547 patients with a mean age at diagnosis of 13 ± 4 years) or primary LSS (510 patients with a mean age 14 ± 4 years). The LSS cohort was subdivided into LSS without amputation, defined as primary LSS without amputation at the time of latest follow-up; LSS with early amputation, defined as LSS complicated by amputation occurring less than 5 years from diagnosis; or LSS with late amputation, defined as primary LSS in study patients who subsequently underwent amputation 5 years or more from cancer diagnosis. The cumulative incidence of late amputation after primary LSS was estimated. Cox proportional hazards regression with time-varying covariates identified factors associated with late amputation. Modified Poisson regression models were used to compare psychosocial, physical, and HRQOL outcomes among patients treated with primary amputation, LSS without amputation, or LSS complicated by late amputation using validated surveys. Results: More study participants were treated with LSS than with primary amputation in more recent decades. The overall survival at 25 years in this population who survived 5 years from diagnosis was not different between those treated with primary amputation (87% [95% confidence interval [CI] 82% to 91%]) compared with LSS (88% [95% CI 85% to 91%]; p = 0.31). The cumulative incidence of amputation at 25 years after cancer diagnosis and primary LSS was 18% (95% CI 14% to 21%). With the numbers available, the cumulative incidence of late amputation was not different among study patients treated in the 1970s (27% [95% CI 15% to 38%]) versus the 1980s and 1990s (19% [95% CI 13% to 25%] and 15% [95% CI 10% to 19%], respectively; p = 0.15). After controlling for gender, medical and surgical treatment variables, cancer recurrence, and chronic health conditions, gender (hazard ratio [HR] 2.02 [95% CI 1.07 to 3.82]; p = 0.03) and history of prosthetic joint reconstruction (HR 2.58 [95% CI 1.37 to 4.84]; p = 0.003) were associated with an increased likelihood of late amputation. Study patients treated with a primary amputation (relative risk [RR] 2.04 [95% CI 1.15 to 3.64]) and LSS complicated by late amputation (relative risk [RR] 3.85 [95% CI 1.66 to 8.92]) were more likely to be unemployed or unable to attend school than patients treated with LSS without amputation to date. The CCSS cohort treated with primary amputation and those with LSS complicated by late amputation reported worse physical health scores than those without amputation to date, although mental and emotional health outcomes did not differ between the groups. Conclusion: There is a substantial risk of late amputation after LSS, and both primary and late amputation status are associated with decreased physical HRQOL outcomes. Children treated for sarcoma who survive into adulthood after primary amputation and those who undergo late amputation after LSS may benefit from interventions focused on improving physical function and reaching educational and employment milestones. Efforts to improve the physical function of people who have undergone amputation either through prosthetic design or integration into the residuum should be supported. Understanding factors associated with late amputation in the setting of more modern surgical approaches and implants will help surgeons more effectively manage patient expectations and adjust practice to mitigate these risks over the life of the patient. Level of Evidence: Level III, therapeutic study.

Background and Objectives: Diffuse‐tenosynovial giant cell tumor (D‐TGCT) is a rare, locally aggressive, typically benign neoplasm affecting mainly large joints, representing a wide clinical spectrum. We provide a picture of the treatment journey of D‐TGCT patients as a 2‐year observational follow‐up. Methods: The TGCT Observational Platform Project registry was a multinational, multicenter, prospective observational study at tertiary sarcoma centers spanning seven European countries and two US sites. Histologically confirmed D‐TGCT patients were categorized as either those who remained on initial treatment strategy (determined at baseline visit) or those who changed treatment strategy with specific changes documented (e.g., systemic treatment to surgery) at the 1‐year and/or 2‐year follow‐up visits. Results: A total of 176 patients were assessed, mean diagnosis age was 38.4 ( SD ± 14.6) years; most patients had a knee tumor (120/176, 68.2%). For the 2‐year observation period, most patients (75.5%) remained on the baseline treatment strategy throughout, 54/79 patients (68.4%) remained no treatment, 30/45 patients (66.7%) remained systemic treatment, 39/39 patients (100%) remained surgery. Those who changed treatment strategy utilized multimodal treatment options. Conclusions: This is the first prospectively collected analysis to describe D‐TGCT patient treatments over an extended follow‐up and demonstrates the need for multidisciplinary teams to determine an optimal treatment strategy.

Summary: Critical-sized bone defects in the tibia can arise as sequelae of trauma, infection, tumor, or the treatment of congenital limb deficiencies. Treatment of these defects often requires bone transport, which has traditionally been accomplished using circular external fixators. The development of a bone transport nail facilitated tibia reconstruction through distraction osteogenesis using an all-internal device, thus avoiding the complications associated with chronic external fixation. Given the rarity of these cases, few studies have been published on the reconstruction outcomes using this implant. We sought to investigate the bone healing indices (including regenerate consolidation and time to docking site union) associated with the use of a magnetically controlled all-internal bone transport nail for the reconstruction of 4 patients treated for posttraumatic tibial bone loss. Perioperative and device-related complications are also reported.

Background: Transtibial amputation (TTA) reconstruction via press-fit osseointegration permits direct skeletal connection between a patient’s residual limb and the prosthetic leg. Osseointegration reconstruction has predominantly been utilized in transfemoral amputation (TFA), resulting in overwhelmingly positive functional and quality-of-life improvements compared with traditional socket prostheses ^1–3 . The adoption of this technology has been slower in TTA, likely because patients undergoing TTA have superior mobility compared with those undergoing TFA, leading some clinicians to believe that their mobility cannot be further improved. However, patients undergoing TTA are still plagued by a degree of socket-related issues and decreased quality of life that is similar to those undergoing TFA ⁴ . With the safety of osseointegration demonstrated in the literature ^5–7 and the high prevalence of TTAs in the general population ⁸ , it is important that osseointegration be utilized in the rehabilitation and reconstruction offered to patients undergoing TTA. Description: Planning starts with anteroposterior and lateral radiographs as well as computed tomography to optimally size the implant. The surgical procedure begins with exposure of the residual tibia, revising the bone cut if needed, and taking routine deep cultures. Reaming is performed over a centrally placed intramedullary guidewire, followed by sequential broaching up to the implant size under fluoroscopic guidance. The implant is then impacted into place. The muscles are closed in a purse-string fashion, followed by skin closure and the creation of a stoma. The external components are then attached to the implant. Alternatives: Traditional prostheses are attached to the residual limb via suction sockets. Patients who have undergone an amputation and are dissatisfied with the resulting quality of life or mobility can undergo attempted modification of their socket or liner components by a prosthetist. Alternatively, these patients can modify or limit their activities and forgo prosthetic limb support entirely. Other surgical options that may improve socket fit include revision amputation, residual bone lengthening, or soft-tissue contouring. Additional osseointegration implant designs also exist ⁹ . Rationale: Suction sockets are known to cause multiple issues for patients who have undergone an amputation, including skin ulceration, sweating, poor fit, residual limb pain, physical disability, and impaired quality of life ^10,11 . TTA patients can be affected as substantially as TFA patients ^4,12 . The poor functionality of the socket is exacerbated in patients whose residual soft-tissue envelope is either in excess or fails to provide proper cushioning against the circumferential squeezing of a socket. Osseointegration bypasses these issues by linking patient and prosthesis via direct skeletal connection. Of the different design options available, press-fit osseointegration is the most commonly utilized and simplifies the implantation process into a single stage, in contrast with alternative 2-stage designs ⁹ . Press-fit osseointegration has been successfully performed in patients having had an amputation for a variety of etiologies ^13–15 . Expected Outcomes: Outcome studies consistently showed improvements in patient physical function, prosthesis wear time, overall satisfaction, and quality of life following conversion to osseointegration from traditional socket prostheses ^5,16 . We recently reported on 31 consecutive osseointegration patients (13 TTA and 18 TFA) with a follow-up of 18 months ¹⁵ . Overall and functional outcome domains of the Patient-Reported Outcomes Measurement Information System (PROMIS) and Questionnaire for Persons with a Transfemoral Amputation (Q-TFA) improved significantly, as did performance on physical function tests. The most common complications following prosthetic osseointegration—which have been better documented in studies of femoral osseointegration—are superficial soft-tissue infections responsive to oral antibiotics ^15,17 and, much less commonly, periprosthetic fractures that are treatable with implant retention and standard internal-fixation techniques ¹⁸ . Important Tips: Template an implant that matches the inner diameter of the diaphyseal bone. Do not cement press-fit osseointegration implants for any reason ¹⁹ . In cases of a short residuum with a greater proportion of proximal tibial metaphyseal bone, favor broaching after under-reaming to impact cancellous bone. Distal stress fractures with implantation do not typically affect implant stability. Perform tight, circumferential muscle closure around the bone-implant interface with absorbable sutures, creating a biologic purse string. Excise excess subscarpal fat and skin from the anterior and/or posterior flaps prior to closure ²⁰ . Graduated, partial weightbearing typically begins around week 4 and progresses to full weightbearing by week 10 to 12. Acronyms & Abbreviations: LLD = limb length discrepancy CT = computed tomography TMR = targeted muscle reinnervation OI = osseointegration MRI = magnetic resonance imaging AP = anteroposterior EQ-5D = EuroQol 5 Dimensions LD-SRS = Limb Deformity – Scoliosis Research Society I&D = irrigation and debridement