Development of Machine Learning Models for Predicting the 1-Year Risk of Reoperation After Lower Limb Oncological Resection and Endoprosthetic Reconstruction Based on Data From the PARITY Trial.

BACKGROUND: Oncological resection and reconstruction involving the lower extremities commonly lead to reoperations that impact patient outcomes and healthcare resources. This study aimed to develop a machine learning (ML) model to predict this reoperation risk. METHODS: This study was conducted according to TRIPOD + AI. Data from the PARITY trial was used to develop ML models to predict the 1-year reoperation risk following lower extremity oncological resection and reconstruction. Six ML algorithms were tuned and calibrated based on fivefold cross-validation. The best-performing model was identified using classification and calibration metrics. RESULTS: The polynomial support vector machine (SVM) model was chosen as the best-performing model. During internal validation, the SVM exhibited an AUC-ROC of 0.73 and a Brier score of 0.17. Using an optimal threshold that balances all quadrants of the confusion matrix, the SVM exhibited a sensitivity of 0.45 and a specificity of 0.81. Using a high-sensitivity threshold, the SVM exhibited a sensitivity of 0.68 and a specificity of 0.68. Total operative time was the most important feature for reoperation risk prediction. CONCLUSION: The models may facilitate reoperation risk stratification, allowing for better patient counseling and for physicians to implement measures that reduce surgical risks.

Larger stem to bone diameter ratio predicts lower cemented endoprosthesis failure.

BACKGROUND AND OBJECTIVES: With continued advances in treatment options, patients with endoprosthetic reconstruction are living longer and consequently relying upon their devices for a longer duration. Major causes of endoprosthesis failure include aseptic loosening and mechanical failure. In the setting of tumor resection, loss of bone stock and use of radiation therapy increase the risk for these complications. As such, considerations of remaining native bone and stem length and diameter may be increasingly important. We asked the following questions: (1) What was the overall rate of endoprosthesis failure at a minimum of 5-year follow-up? (2) Does resection length increase implant failure rates? (3) Does implant size and its ratio to cortical width of bone alter implant failure rates? METHODS: We retrospectively analyzed patient outcomes at a single institution between the years of 1999-2022 who underwent cemented endoprosthetic reconstruction at the hip or knee and identified 150 patients. Of these 150, 55 had a follow-up of greater than 5 years and were used for analysis. Radiographs of these patients at time of surgery were assessed and measured for resection length, bone diameter, stem diameter, and remaining bone length. Resection percentage, and stem to bone diameter ratios were then calculated and their relationship to endoprosthesis failure were analyzed. RESULTS: Patients in this cohort had a mean age of 55.8, and mean follow-up of 59.96 months. There were 78 distal femoral replacements (52%), 16 proximal femoral replacements (10.7%), and 56 proximal tibial replacements (37.3%). There were five patients who experienced aseptic loosening and six patients who experienced mechanical failure. Patients with implant failure had a smaller mean stem to bone diameter (36% vs. 44%; p = 0.002). A stem to bone diameter of 40% appeared to be a breaking point between success and failure in this series, with 90% of patients with implant failure having a stem: bone ratio less than 40%. Stem to bone ratio less than 40% increased risk for failure versus stems that were at least 40% the diameter of bone (6/19 [31.6%] vs. 0/36 [0%]; odds ratio 0.68; p < 0.001). Resection length did not appear to have an impact on the rates of aseptic loosening and mechanical failure in this series. CONCLUSIONS: Data from this series suggests a benefit to using stems with a larger diameter when implanting cemented endoprostheses at the hip or knee. Stems which were less than 40% the diameter of bone were substantially more likely to undergo implant failure.

Occlusive wound closure prevents prolonged wound discharge-A randomised controlled trial in patients undergoing tumour resection and endoprosthetic reconstruction of the proximal femur because of metastatic bone disease.

Prolonged wound discharge is a common postoperative complication of orthopaedic procedures and a risk factor for implant-related infection. Occlusive wound closure methods have previously been suggested to reduce or even prevent this complication. We performed a randomised controlled trial on 70 patients who underwent surgical treatment for metastatic bone disease involving the proximal femur at our centre between January 2017 and August 2018. At conclusion of the tumour resection and endoprosthetic reconstruction procedure, patients were randomised to either occlusive wound closure (n = 35), using the Dermabond Prineo-22 skin closure system, or routine wound closure with conventional skin staples (n = 35). Skin closure with occlusive wound closure resulted in a lesser degree (P < .0001) and shorter duration of postoperative wound discharge (HR 2.89 [95% CI 1.6-5.05], P < .0018). Compared with staples, surgical wounds were already dry after a mean of 3.5 days [95% CI 3.2-3.9] versus 6.1 days [95% CI 4.8-7.3] (P < .0001). Prolonged wound discharge for 7 days or more was observed in 23% of patients (n = 8) in the Staples-group but was entirely absent in the occlusive wound closure group (P < .003). This study provides strong evidence that occlusive wound closure reduces frequency, degree, and duration of wound discharge in a patient population at particularly high risk for this complication.

Tranexamic acid improves early postoperative mobilization in cancer patients undergoing endoprosthetic reconstruction.

BACKGROUND AND OBJECTIVES: Tranexamic acid (TXA) has been shown to decrease perioperative blood loss, transfusions, and cost in patients undergoing resection of aggressive bone tumors and endoprosthetic reconstruction. This study explored the effect of TXA administration on postoperative mobilization in these patients. METHODS: This study included 126 patients who underwent resection of an aggressive bone tumor and endoprosthetic reconstruction; 61 patients in the TXA cohort and 65 patients in the non-TXA cohort. Postoperative physical therapy (PT) and occupational therapy notes were reviewed; patient ambulation distance and duration of therapies were recorded. RESULTS: Patients in the TXA cohort ambulated further on all postoperative days, which was significant on postoperative Day 1 (POD1) (p = 0.002) and postoperative Day 2 (POD2) (p < 0.001). The TXA cohort ambulated 85% further per PT session 87.7 versus 47.4 ft (p < 0.001) and participated 14% longer, 36.1 versus 31.7 min (p < 0.001). Multivariate analysis identified a significant inverse association between postoperative hospitalization length and POD1, POD2, postoperative Day 3, and total ambulation (p < 0.001). Blood transfusion was independently associated with a 1.5 day increase in postoperative hospitalization (95% confidence interval: 0.64-2.5; p < 0.001). CONCLUSIONS: TXA administration was associated with increased postoperative ambulation and endurance. Increased postoperative ambulation was associated with decreased length of stay and increased likelihood to discharge home.

Reconstruction survival of segmental megaendoprostheses: a retrospective analysis of 28 patients treated for intercalary bone defects after musculoskeletal tumor resections.

INTRODUCTION: Intercalary endoprosthetic reconstructions have been reserved for patients with a limited life expectancy due to reports of high rates of early mechanical and reconstruction failure. MATERIALS AND METHODS: In this study, we retrospectively analyzed 28 patients who underwent intercalary endoprosthetic reconstruction of the femur (n = 17) or tibia (n = 11) regarding reconstruction survival and causes of complications and reconstruction failure. RESULTS: A total of 56 stems were implanted in this collective, 67.9% of which were implanted using cementation. Eight different stem designs were implanted. The mean patient age at the time of operation was 42.3 years. The mean bone defect needing reconstruction measured 18.5 cm. Resection margins were clear in 96.4% of patients. Of twenty-six complications, five were not implant-associated. We observed infection in 10.7% (n = 3) and traumatic periprosthetic fracture in 3.6% (n = 1) of cases. The most frequent complication was aseptic stem loosening (ASL) (53.8%; n = 14) occurring in eight patients (28.6%). The metaphyseal and meta-diaphyseal regions of femur and tibia were most susceptible to ASL with a rate of 39.1% and 31.3% respectively. No ASLs occurred in epiphyseal or diaphyseal location. Overall reconstruction survival was 43.9% and 64.3% including patients who died of disease with their implant intact. Overall limb survival was 72.7%. CONCLUSIONS: Proper planning of segmental reconstructions including stem design with regard to unique anatomical and biomechanical properties is mandatory to address the high rates of ASL in metaphyseal and metadiaphyseal stem sites. With continued efforts of improving stem design in these implantation sites and decreasing rates of mechanical failure, indications for segmental megaendoprostheses may also extend to younger patients with the localized disease for their advantages of early weight bearing and a lack of donor-site morbidity.

Reconstruction after periacetabular tumor resection with Lumic® endoprosthesis: What are the midterm results?

INTRODUCTION: This study aimed to analyze the midterm outcomes of LUMiC® endoprosthetic reconstruction following periacetabular resection of primary bone sarcomas and carcinoma metastases. PATIENTS AND METHODS: We retrospectively reviewed the charts of 21 patients (11 male [52.3%], 10 female [47.6%]; mean age 47 ± 16 years) for whom a LUMiC® endoprosthesis (Implantcast) was used to reconstruct a periacetabular defect after internal hemipelvectomy. The tumor was pathologically diagnosed as Ewing's sarcoma in six (28.5%), chondrosarcoma in 10 (47.6%), and bone metastasis from carcinoma in five (23.8%) patients. RESULTS: The median follow-up of patients was 57.8 months (95% confidence interval: 51.9-63.7). The implant survival rate at 1, 2, and 5 years were 95.2%, 85.7%, and 80.9%, respectively. The overall complication rate was 33.3% (n = 7). Four (19%) complications resulted in reconstruction failure. Total reoperation rate was 28.5% (n = 6). The complications were soft tissue failure/dislocation in two patients, aseptic loosening in one, infection in two, and local recurrence in two. At the time of study, seven patients were alive with no evidence of disease, seven were alive with disease, and seven died of disease. The 5-year overall survival rate and local recurrence-free survival rates were 67% and 76%, respectively. The median Musculoskeletal Tumor Society score at final follow-up was 70% (range: 50%-86.6%). CONCLUSION: We conclude that LUMiC® endoprosthesis provides good functional outcomes and a durable reconstruct. Even though this reconstruction method presents some complications, it provides a stable pelvis in the management of periacetabular malignant tumors.

Is osseous reattachment of the greater trochanter necessary compared to soft-tissue-only abductor repair in proximal femoral megaprosthesis reconstruction?

BACKGROUND: One of the challenges to surgical reconstruction following oncologic proximal femur resection is reliable re-establishment of the abductor mechanism. Surgical and functional outcomes following re-approximation of the abductor mechanism to a metallic endoprosthetic after tumor resection of the proximal femur have not been well established in the literature. METHODS: A retrospective review was performed, inclusive of patients who received a proximal femur replacement with a metallic endoprosthesis following tumor resection. Patients were divided into two groups: (1) those that received an abductor repair involving a trochanteric osteotomy and osseous fixation of the greater trochanter/abductor mechanism to the endoprosthesis, and (2) those that did not have a trochanteric osteotomy and therefore had an abductor repair consisting of only soft tissue reattachment to the endoprosthesis. The two groups were assessed for demographic characteristics, diagnosis, surgical outcomes including rates of complication and failure, radiographic evidence of trochanteric failure, and functional outcomes. Descriptive statistics, comparative statistics, and logistic regression analyses were performed to discern differences between the two study groups. RESULTS: Fifty-three patients were included in the analysis, 29 had abductor reconstructions involving reattachment of the greater trochanter to the metallic endoprosthesis and 24 had soft tissue reconstruction of the abductor mechanism without bony fixation. There were no differences between the two groups for demographic data, cancer diagnosis, follow up, or survivorship. Radiographic evidence of trochanteric dissociation from the endoprosthesis was observed in 45% of osteotomy cases. Only 10% of patients in the trochanter osteotomy group and 38% of the soft tissue only group were able to resume a normal, non-Trendelenburg gait at final postoperative visit (p = .024). Need for an assistive ambulatory device was seen in 83% and 67% of the osteotomy and soft-tissue-only patients, respectively (p = .21). CONCLUSION: Re-establishing the abductor mechanism following proximal femur oncologic resection remains a challenge to orthopedic oncologists. Even when possible, salvage of the greater trochanter for reattachment to the endoprosthesis did not lead to improved function in this series, when compared to a similar cohort that received a soft-tissue-only abductor repair. Abductor mechanism reconstruction with a greater trochanteric osteotomy and subsequent fixation to the proximal femur endoprosthesis had a high rate of radiographic failure. Additionally, reattachment of the greater trochanter to the proximal femur endoprosthesis demonstrated no improvement in Trendelenburg gait or reliance on an assistive ambulatory device when compared to a soft-tissue-only abductor repair.

[Enhancing Soft-tissue Reattachment with Artificial Mesh in Joint Endoprosthetic Reconstruction for Bone Tumors].

Objective: To investigate the operative method and clinical application of the BARD(®) Mesh in enhancing joint stability and function of endoprosthetic reconstruction for bone tumors. Methods: From Jan 2013 to Jun 2015, the clinical data of 51 patients aged (44.75±23.18) years underwent wide resection of tumor and endoprosthetic reconstruction using the BARD(®) Mesh were collected. Among them, 27 were male and 24 were female. The surgical treatments received by these patients included 5 shoulder arthroplasties, 12 elbow replacements, 12 hip replacements and 32 knee replacements (including 24 femoral tumors and 8 tibial tumors). According to the pathologic type, there were 12 metastatic tumors, 20 osteosarcomas, 7 chondrosarcomas, 5 malignant fibrous histiocytomas, 4 giant cell tumors of bone, 1 Ewing sarcoma, 1 leiomyosarcoma and 1 pigmented villonodular synovitis (pvns). These patients received extensive tumor resection, tumorous prosthesis replacement, preserved articular capsule and muscles repair with artificial mesh and endoprosthesis wrapping. The curative effect including joints range of motion and Musculoskeletal Tumour Society Scores (MSTS) were evaluated. Results: The median follow-up time was (19.75±8.17) months. The drainages were removed out on an average of 4 days after operation. The postoperative complications included 2 superficial incision infection, 1 deep incision infection and 1 osteofascial compartment syndrome, infection or dislocation of prosthesis wasn't observed. The mean active flexion of shoulder joint after replacement was (34.00±10.84)°, mean active abduction was (20.00±9.35)° and the mean MSTS was 19.80±9.54. The superior rate of shoulder flexion function was 0. The mean active flexion of elbow joint after replacement was (75.00±7.07)°, mean active abduction was (-5.00±7.07)° and the mean MSTS was 25.00±2.83. The superior rate of elbow flexion function was 50.0% (1/2). The mean active flexion of hip joint after replacement was (86.67±20.60)°, mean active abduction was (2.08±4.98)° and the mean MSTS was 25.42±1.78. The superior rate of hip flexion function was 83.3% (10/12). The mean active flexion of knee joint after replacement was (89.69±22.39)°, mean active abduction was (-0.63±1.68)° and the mean MSTS was 23.31±2.09. The superior rate of knee flexion function was 50.0%(16/32). Among them, the superior rate of femoral flexion function was 66.7% (16/24), the superior rate of tibial flexion function was 0. All of patients were satisfied with the curative effect of operation at the end of follow-up time. Conclusions: The BARD(®) Mesh may enhance the attachment of soft-tissue to endoprosthesis, improve the joint stability, decrease the endoprosthetic infection and dislocation, facilitate the attachment of tendon to endoprosthesis and recover the muscular motivation after endoprosthetic reconstruction. This plays an important role in joint stability and motivation reconstruction of soft-tissue impairment, effectively prevents surgical complications.

Limb Salvage and Pelvic Reconstruction With Endoprosthesis After Pelvic Tumor Resection: A Narrative Review.

Periacetabular defects following tumor resection present formidable challenges in reconstruction and continue to pose clinical difficulties. Historically, treatment approaches leaned towards hindquarter amputation; however, due to associated morbidities and functional limitations, limb-sparing procedures gained prominence in the 1980s. Nevertheless, the intricacies of pelvic anatomy and the imperative of achieving wide surgical margins while preserving essential structures make pelvic tumor resection and subsequent reconstruction inherently complex. Various reconstruction modalities have been explored, including non-vascularized fibular grafts and prosthetic implants. Among these options, the LUMiC® endoprosthesis stands out as a promising solution for pelvic reconstruction post-tumor resection. Characterized by a modular design featuring a hydroxyapatite-coated stem and acetabular cup, this device has shown favorable implant survival rates in studies, despite encountering complications primarily associated with soft tissue failure, dislocation, and infection. Notably, the incidence of complications varies across studies. The Henderson classification system delineates these complications, encompassing soft tissue issues, aseptic loosening, periprosthetic fractures, infections, and tumor recurrence. Despite the encouraging functional outcomes associated with the LUMiC® endoprosthesis, it is not immune to limitations. Concerns persist regarding complications such as dislocation and infection, underscoring the imperative for further research to evaluate the long-term durability and reliability of this reconstructive approach. Moreover, advancements in surgical techniques, perioperative management, and the advent of navigation-assisted procedures hold promise for enhancing outcomes and mitigating complication rates in pelvic reconstruction surgeries.

Finite element analysis of patient-specific additive-manufactured implants.

Introduction: Bone tumors, characterized by diverse locations and shapes, often necessitate surgical excision followed by custom implant placement to facilitate targeted bone reconstruction. Leveraging additive manufacturing, patient-specific implants can be precisely tailored with complex geometries and desired stiffness, enhancing their suitability for bone ingrowth. Methods: In this work, a finite element model is employed to assess patient-specific lattice implants in femur bones. Our model is validated using experimental data obtained from an animal study (n = 9). Results: The results demonstrate the accuracy of the proposed finite element model in predicting the implant mechanical behavior. The model was used to investigate the influence of reducing the elastic modulus of a solid Ti6Al4V implant by tenfold, revealing that such a reduction had no significant impact on bone behavior under maximum compression and torsion loading. This finding suggests a potential avenue for reducing the endoprosthesis modulus without compromising bone integrity. Discussion: Our research suggests that employing fully lattice implants not only facilitates bone ingrowth but also has the potential to reduce overall implant stiffness. This reduction is crucial in preventing significant bone remodeling associated with stress shielding, a challenge often associated with the high stiffness of fully solid implants. The study highlights the mechanical benefits of utilizing lattice structures in implant design for enhanced patient outcomes.

Postoperative Functional Assessment in Patients with Tumors Around the Knee Treated with Endoprosthetic Reconstruction: A Multicenter Retrospective Cohort Study.

OBJECTIVES: The restoration of as much normal function as possible has become an important goal following the endoprosthetic reconstruction. The objective of this study was to assess the functional outcome after endoprosthetic reconstruction for tumors around the knee and to explore prognostic factors of functional outcome. METHODS: We retrospectively collected data on patients who underwent tumor prosthetic replacements consecutively. Musculoskeletal Tumour Society score and Toronto Extremity Salvage Score were used to assess the functional outcome at 1, 3, 6, 12, and 24 months after surgery. The logistic model was used to select factors that had potential predictive value for postoperative function. Potential prognostic factors included age, gender, tumor site, type of tumor, length of bone resection, type of prosthesis, length of prosthetic stem, chemotherapy, pathological fracture, and body mass index. RESULTS: At the 24 months after surgery, the mean musculoskeletal tumor society (MSTS) score was 81.4% and the mean Toronto extremity salvage score (TESS) was 83.6%. At the last follow-up, 68% of patients and 73% of patients received perfect or good MSTS score and TESS score, respectively. The multivariate analysis according to ordered-logit model showed that age < 35 years, distal femoral prosthesis, and length of bone resection < 14 cm were independent prognostic factors of better functional outcome. CONCLUSIONS: Endoprosthetic reconstruction may provide good functional results for most patients. Younger patients with distal femoral prosthesis and shorter resection of bone (on the premise of complete resection of tumor) are more likely to obtain satisfactory functional results after surgery.

The Use of Proximal Femur Replacement for the Management of Oncologic Lesions in the Proximal Femur: A Review.

With improved chemotherapeutic treatment, patients with primary or metastatic bone tumor have improved prognoses and longer life expectancies; therefore, durable limb-salvage constructs are critical. For tumors of the proximal femur, endoprosthetic replacement is an option for treatment in primary and metastatic disease, with the goals being tumor and pain control, earlier mobilization, shorter recovery period, and, in primary tumors, cure. This study provides a summary of current concepts in the treatment of oncologic lesions in the proximal femur with endoprostheses. Discussion of the inherent complications of these constructs is presented as well as the risks and treatment of reconstruction failure.

Periprosthetic distal femur fractures around total knee replacements: A comprehensive review.

With a growing number of patients undergoing total knee replacements globally, coupled with an elderly population, the incidence of periprosthetic fractures around total knee replacements is increasing. As such, this is a highly topical subject that is gaining increasing interest within the orthopaedic community. This review provides a narrative synthesis of the most contemporary literature regarding distal femoral periprosthetic fractures. We review the related epidemiology, initial patient evaluation, the evolution and relevance of the classification systems and treatment options, particularly related to endoprosthetics and hybrid fixation constructs. The latest orthopaedic evidence related to this topic has been included.

Intravenous tranexamic acid decreases intraoperative transfusion requirements and does not increase incidence of symptomatic venous thromboembolic events in musculoskeletal sarcoma surgery.

BACKGROUND AND OBJECTIVES: Tranexamic acid (TXA) is poorly studied in patients with bone and musculoskeletal sarcoma due to perceived increased risk of venous thromboembolism (VTE). This study aims to assess the safety and efficacy of intravenous (IV) TXA for patients undergoing surgical resection of primary bone or soft-tissue sarcoma. METHODS: A retrospective, single center review of adult patients with pelvic or extremity sarcoma who underwent surgical resections between January 2005 and March 2020 was performed. Patients between 2005 and 2012 were included as a historical comparison prior to the routine use of IV TXA for all sarcoma resections at our institution. RESULTS: Thirty-nine non-TXA and 59 TXA resections were identified. Two non-TXA patients experienced symptomatic pulmonary embolism compared to zero VTEs amongst TXA patients. IV TXA administered at any dose significantly reduced the probability of intraoperative transfusion (p = 0.003) and the median units of blood transfused at the time of any perioperative transfusion (p = 0.007). Intraoperative times were significantly shorter for TXA patients (128 vs 190 min; p = 0.004). A subset of patients who underwent wide resection with endoprosthetic reconstruction and received TXA similarly showed decreased requirement for intraoperative transfusion (p = 0.014) and decreased procedure times (p = 0.009). CONCLUSIONS: During sarcoma resection, at least 1 g of IV TXA can safely decrease the need for any intraoperative transfusion and the median number of PRBCs transfused by 2 units when any perioperative transfusion is given.

Effect of implant length variations on stress shielding in proximal humeral replacement after tumor excision under torsion: Finite element study.

The proximal humerus is the most common site of occurrence of primary bone tumors in the upper limb. Endoprosthetic replacement is deemed as the preferred reconstructive option following primary resection of bone tumors. However, it has been also associated with complications such as stress shielding and aseptic loosening compromising prosthetic survival. Our objective was to conduct a finite element (FE) study to investigate the effect of varying endoprosthesis length on bone stresses as well as to quantify the extent of stress shielding across the bone length (BL) in a humerus-prosthesis assembly for proximal humeral replacement after tumor excision thereby allowing us to identify the optimal implant length with best biomechanical performance. FE models of the intact humerus and humerus-prosthesis assemblies were established where they were loaded at the elbow joint under torsion with the glenohumeral joint fixed to represent twisting. After dividing the bone into individual slices consisting of 5% BL, the maximum cortical and cancellous principal, von Mises and shear bone stresses were calculated. To measure the level of stress shielding, the percentage stress change from the intact state was evaluated across each slice. Similar stress patterns were observed between the intact state and shorter endoprosthesis compared to the longer endoprostheses. Our findings illustrated the possibility of stress shielding occurring under torsional forces with its effect increasing with implant lengthening. To conclude, we believe that using a shorter prosthesis may substantially diminish the risk of potential implant failure due to stress shielding.

Stress-shielding resistant design of custom pelvic prostheses using lattice-based topology optimization.

Endoprosthetic reconstruction of the pelvic bone using 3D-printed, custom-made implants has delivered early load-bearing ability and good functional outcomes in the short term to individuals with pelvic sarcoma. However, excessive stress-shielding and subsequent resorption of peri­prosthetic bone can imperil the long-term stability of such implants. To evaluate the stress-shielding performance of pelvic prostheses, we developed a sequential modeling scheme using subject-specific finite element models of the pelvic bone-implant complex and personalized neuromusculoskeletal models for pre- and post-surgery walking. A new topology optimization approach is introduced for the stress-shielding resistant (SSR) design of custom pelvic prostheses, which uses 3D-printable porous lattice structures. The SSR optimization was applied to a typical pelvic prosthesis to reconstruct a type II+III bone resection. The stress-shielding performance of the optimized implant based on the SSR approach was compared against the conventional optimization. The volume of the peri­prosthetic bone predicted to undergo resorption post-surgery decreased from 44 to 18%. This improvement in stress-shielding resistance was achieved without compromising the structural integrity of the prosthesis. The SSR design approach has the potential to improve the long-term stability of custom-made pelvic prostheses.

Implant survival and functional results of endoprosthetic reconstruction for proximal femoral metastases with pathological fractures.

BACKGROUND: This study aimed to evaluate the patient and implant survival, clinical and functional outcomes, and the rate of complications resulting in reconstruction failure following endoprosthetic reconstruction (EPR) of extensive proximal femoral metastases associated with actual or impending pathological fractures. METHODS: A total of 111 patients with actual or impending pathological fractures due to metastatic disease of the proximal femur were treated with EPR between 2003 and 2018. Staged surgery, bilateral EPR, was performed in 3 cases. The patients comprised 51 females and 60 males with a mean age of 52.1 ± 12.3 years. The patient and implant survival were recorded. Clinical and functional outcomes were assessed by using the visual analogue scale (VAS), Musculoskeletal Tumour Society (MSTS) functional scoring, and Karnofsky Performance Scale (KPS). The different types of abductor mechanism repair were evaluated by functional tests and existence of Trendelenburg gait at postoperative follow-ups. The complications resulting in reconstruction failure were investigated. RESULTS: The mean follow-up was 23.1 ± 17.9 months. The overall survival of patients after EPR was 89% at 6 months, 72% at 1 year and 10% at 5 years. The estimated 1- and 5-year overall implant survival was 100% and 97.3% (95% CI, 0.95-0.98), respectively, as the endpoint was defined as complete removal of the prosthesis. Median VAS score before endoprosthetic replacement was 8 and after 3 months 4. Before surgery, the median MSTS score was 40 (30-56.6%) and the median KPS score was 40 (30-50). Postoperative third month, the median MSTS score was 56.6 (53.3-86.6%) and the median KPS score was 60 (40-70). Functional scores were superior in trochanter major split osteotomized group compared to trochanter major removed group. Trendelenburg gait was seen in 20 (17.5%) patients postoperatively. There were 10 (8.7%) complications resulting in reconstruction failure. CONCLUSION: Endoprosthetic replacement can provide a durable fixation with high implant survival rate and good clinical and functional results in extensive proximal femoral metastases associated with a pathological fracture.

Novel axial compressive endoprosthesis ACE can enhance metaphyseal fixation and facilitate osseointegration: A biomechanical study.

Background: Metaphyseal fixation for endoprosthetic reconstruction after bone tumor resection is difficult due to the short residual bone length and reverse funnel shape of the metaphysis. In the current study, 3D-printed axial compressive endoprosthesis (ACE) with a short stem and intramedullary axial compressive mechanism is proposed to improve metaphyseal fixation. The rationales of ACE are that 1) intramedullary axial compress enhances the stability of endoprosthesis and facilitates bone ingrowth at the osteotomy site; 2) 3D printed porous metallic surface at osteotomy surface and stem allows bone ingrowth to achieve osseointegration. Methods: A biomechanical study was performed to explore the initial stability using Sawbones. A diaphysis and metaphyseal segmental defect were created and four fixation structures were simulated: 1) ACE; 2) ACE + lateral plate; 3) stem prosthesis + unilateral plate; 4) stem prosthesis + bilateral plates. Bending and torsional stiffness were determined with a material testing machine. The relationship between the torque of the compression nut and the axial compression force of the bone-implant surface was measured using a round gasket load sensor. Results: ACE + lateral plate was the stiffest in the bending test (sagittal 324.3 ± 110.8 N/mm, coronal 307.7 ± 8.7 N/mm). ACE + lateral plate and stem prosthesis + bilateral plates had the highest torsional stiffness (10.9 ± 1.3 Nm/° and 10.7 ± 0.2 Nm/° respectively). The bending stiffness of ACE was equivalent to stem prosthesis + bilateral plates (sagittal 196 ± 10 N/mm vs. 200 ± 7 N/mm, coronal 197 ± 14 N/mm vs. 209 ± 3 N/mm), but the torsional stiffness of ACE was inferior to stem prosthesis + bilateral plates (6.1 ± 1.3 Nm/° vs. 10.7 ± 0.2 Nm/°). Stem prosthesis + unilateral plate was the least stiff both in bending and torsion. The relationship between torque (T/Nm) and axial pressure (F/N) was F = 233.5T. Conclusion: The axial compressive design of ACE enhances primary stability and facilitates osseointegration, which provides an alternative option of metaphyseal fixation for endoprosthetic reconstruction.

Distal Femoral Replacement as a Salvage Treatment After Desmoplastic Fibroma Resection.

Desmoplastic fibroma is an extremely rare primary bone tumor that can mimic the presentation of other bone lesions. We describe the case of a middle-aged male with a mass on the left distal femur initially diagnosed as fibrous dysplasia that underwent a wide margin excision followed by a distal femoral replacement to restore anatomy and functionality. Histologic examination of the complete surgical specimen was consistent with a desmoplastic fibroma. This case is the first report of a successful application of endoprosthetic reconstruction after desmoplastic fibroma resection.

Tourniquet use in patients undergoing tumour resection and endoprosthetic reconstruction of the knee.

AIMS: The aim of this study was to determine the prevalence and impact of tourniquet use in patients undergoing limb salvage surgery with endoprosthetic reconstruction for a tumour around the knee. METHODS: We retrieved data from the Prophylactic Antibiotic Regimens in Tumor Surgery (PARITY) trial; specifically, differences in baseline characteristics, surgical details, and postoperative functional outcomes between patients who had undergone surgery under tourniquet and those who had not. A linear regression model was created to evaluate the impact of tourniquet use on postoperative Toronto Extremity Salvage Scores (TESSs) while controlling for confounding variables. A negative-binomial regression model was constructed to explore predictors of postoperative length of stay (LOS). RESULTS: Of the 604 patients enrolled in the PARITY trial, 421 had tumours around the knee joint, of whom 225 (53%) underwent surgery under tourniquet. The tourniquet group was younger (p = 0.014), more likely to undergo surgery for a tumour of the tibia, and had shorter operating times by a mean of 50 minutes (95% confidence interval 30 to 72; p < 0.001). The adjusted linear regression model found that the use of a tourniquet, a shorter operating time, and a higher baseline TESS independently predicted better function at both three- and six-month follow-up. The negative-binomial regression model showed that tourniquet use, shorter operating time, younger age, and intraoperative tranexamic acid administration independently predicted a shorter LOS in hospital. CONCLUSION: The results of this study show that in patients undergoing resection of a tumour around the knee and endoprosthetic reconstruction, the use of an intraoperative tourniquet is associated with a shorter operating time, a reduced length of stay in hospital, and a better early functional outcome.Cite this article: Bone Joint J 2022;104-B(10):1168-1173.