Distal Femoral Reconstruction Research Articles

Biomechanical analysis of patient specific cone vs conventional stem in revision total knee arthroplasty

BackgroundIn revision total knee arthroplasty, addressing significant bone loss often involves the use of cemented or press-fit stems to ensure implant stability and long-term fixation. A possible alternative to stem was recently introduced utilizing custom-made porous metaphyseal cones, designed to reconstruct the missing tibial and femoral geometries. Early clinical and radiological assessments have shown promising results. The objective of this research was to biomechanically evaluate the performances of these custom-made cones.MethodsThe biomechanical study was conducted using a validated finite element model. The bone geometries of a patient (selected for their history of four knee revisions due to infection and periprosthetic fractures, followed by a successful treatment with custom-made 3D-printed metaphyseal cones) were employed for the study. On these bone models, different revision scenarios were simulated and examined biomechanically: (A) custom-made cementless metaphyseal cones; (B) cemented stems; (C) press-fit stems; (D) distal femoral reconstruction with press-fit stem. All the models were analyzed at 0 °and 90 °of flexion, under physiological load conditions simulating daily activities; stress distribution, average Von-Mises stresses and risk of fracture were then analyzed and compared among configurations.ResultsThe use of custom-made 3D-printed cones exhibited the most favorable stress distribution in both femoral and tibial bones. Tibial bone stress was evenly distributed in custom-made cone configurations, while stress concentration was observed in distal regions for the other scenarios. Additionally, custom-made cones displayed overall homogeneity and lower stress levels, potentially contributing to limit pain. Symmetrical stress distribution was observed between the lateral and medial proximal tibia in custom-made cone models, whereas other scenarios exhibited uneven stress, particularly in the anterior tibial bone.ConclusionsThe biomechanical analysis of porous custom-made metaphyseal cones in re-revision arthroplasties is in agreement with the positive clinical and radiological outcomes. These findings provide valuable insights into the potential benefits of using custom-made cones, which offer more uniform stress distribution and may contribute to improve patient outcomes in revision TKA procedures. Further studies in this direction are warranted to validate these biomechanical findings.

The Patient Acceptable Symptom State (PASS) after proximal and distal femoral replacement

IntroductionFemoral megaprostheses are used for bone reconstruction surgery in patients with local tumors or who require multiple revisions. Patient reported outcome measures (PROMs) provide a subjective result and, like patient satisfaction, have become an integral part of the outcomes in orthopedics. However, the threshold of satisfaction (PASS: Patient Acceptable Symptom State) has not yet been defined in a French population after this type of arthroplasty. This led us to carry out a retrospective study on a population of patients who received a femoral reconstruction megaprosthesis in order to 1) define the PASS for the Harris Hip Score (HHS), Knee Society Score (KSS) and the Musculoskeletal Tumor Society score (MSTS), 2) study the complications. HypothesisThe PASS threshold for proximal femur and distal femur reconstruction prothesis for the HHS and the KSS, respectively, will be lower than the threshold for these same scores for primary arthroplasty. Materials and methodsForty-four patients who were operated on between 2009 and 2020 were included: 23 received a proximal femur prosthesis and 21 received a distal femur prosthesis. The PASS threshold was defined using an anchoring strategy by analyzing ROC curves for the HSS for the proximal femur, KSS for the distal femur and the MSTS for all the prostheses. Complications were classified according to Henderson. ResultsThe mean follow-up was 4.5 ± 3.6 (1–12.5) years. The PASS threshold was 47.5 (area under curve (AUC) 0.71 (0.45–0.97)) for the HHS, 69.5 (AUC 0.97 (0.92–1.0)) for the KSS knee and 62.5 (AUC 0.81 (0.61–0.99)) for the KSS function. Thirteen patients (29%) had complications, nine of whom required another surgery (20%). The most frequent were Henderson type 1 (soft tissue lesions, n = 5/44 [11%]) and type 2 (loosening, n = 5/44 [11%]) There was no relationship between satisfaction and postoperative complications (p = 0.071). DiscussionMost of the patients who undergo femoral resection and reconstruction (59%) are satisfied with their function, albeit reduced, despite a high complication rate (29%). Our hypothesis is confirmed for the PASS threshold for the HHS (47.5 versus 93) and the KSS knee and function (69.5 and 62.5 versus 85.5 and 72.5). Level of evidenceIV; retrospective observational single-center study.

Outcomes of distal femoral replacement versus internal fixation for metastatic bone diseases of the distal femur

BackgroundIn clinical practice, internal fixation (IF) is a commonly utilized technique for metastatic bone disease (MBD) to the distal femur. Additionally, distal femoral reconstruction (DFR) has shown to be an effective surgical technique for primary tumors and MBD in the distal femur. The existing body of research comparing these methods has not focused on MBD or pathological fractures and thus does not guide surgical approach in the case of distal femoral MBD. MethodsA multi-institutional retrospective review of musculoskeletal oncology patients treated surgically with IF (n = 29) or DFR (n = 34) for distal femoral MBD between 2005 and 2023. Overall survival, revision risk, and functional status were assessed. Results5-year patient overall survival was 47.9 % (CI, 29.5–77.6 %) and 46.6 % (CI, 31.5–68.8 %), for DFR and IF, respectively (p = 0.91). After competing risk analysis, the 5-year risk of implant revision for DFR was 18 % (95 % CI: 5.1–37 %) and 11 % for IF (95 % CI: 2.4–28 %) (p = 0.3). DFR had longer operative times (p = 0.002), higher blood loss (p < 0.001), and greater postoperative (p = 0.006) complications than IF. In addition, patients undergoing DFR had more distal lesions than patients who received IF (p = 0.003). ConclusionDespite similar overall survival and revision rates, IF may be preferable for patients due to its shorter operative time and lower rates of complication than DFR. However, specific anatomic location in the distal femur must be considered prior to deciding which procedure is optimal.

Mechanical failure of distal femur mega prosthesis due to polyaryl-ether-ether-ketone (PEEK) hinge component

BackgroundPolyaryl-ether-ether-ketone (PEEK) has gained popularity as a substrate for orthopaedic hardware due to its desirable properties such as heat and deformation resistance, low weight, and ease of manufacturing. However, we observed a relatively high failure rate of PEEK-based hinges in a distal femur reconstruction system. In this study, we aimed to evaluate the proportion of patients who experienced implant failure, analyse the mechanism of failure, and document the associated clinical findings.MethodsWe conducted a retrospective cohort study, reviewing the medical charts of 56 patients who underwent distal femur resection and reconstruction with a PEEK Optima hinge-based prosthesis between 2004 and 2018. Concurrently, we performed a clinical and biomechanical failure analysis.ResultsPEEK component failure occurred in 21 out of 56 patients (37.5%), with a mean time to failure of 63.2 months (range: 13–144 months, SD: 37.9). The survival distributions of PEEK hinges for males and females were significantly different (chi-square test, p-value = 0.005). Patient weight was also significantly associated with the hazard of failure (Wald’s test statistic, p-value = 0.031).DiscussionOur findings suggest that PEEK hinge failure in a distal femur reconstruction system is correlated with patient weight and male gender. Retrieval analysis revealed that failure was related to fretting and microscopic fractures due to cyclic loading, leading to instability and mechanical failure of the PEEK component in full extension. Further assessment of PEEK-based weight bearing articulating components against metal is warranted.

Optimizing implant lattice design for large distal femur defects: Stimulating interface bone growth to enhance osseointegration

Large bone defects in the distal femur present a significant challenge due to the lack of inherent self-healing capabilities. Traditional approaches, such as utilizing polymethyl methacrylate (PMMA) in conjunction with a plate for distal femur reconstruction, have shown unsatisfactory osseointegration outcome, which leads to complications. To address this challenge, this study focuses on developing a lattice-structured implant for reconstructing distal femoral bone defects. The lattice geometry is based on the cuboctahedron lattice, with its design optimized through the adjustment of pillar diameter and arrangement angle. The lattice structure is designed to stimulate the surrounding bone, ultimately enhancing osseointegration in distal femur reconstruction. Finite element analysis revealed that for promoting bone ingrowth toward the implant, setting the optimal lattice structure parameters, i.e., a 45&amp;deg; arrangement angle and a 0.8 mm pillar diameter, is required. Fabricated using state-of-the-art metal three-dimensional printing, the implant underwent rigorous validation through biomechanical testing, in vitro biological assays, and animal experiments. The comprehensive results affirmed the bioactivity of the lattice-structured implant, underscoring its capability to improve osseointegration in distal femoral defect reconstruction.

Long-lasting Limb Salvage After Malignant Femoral-Bone Tumor Resection Reconstructed With a Thin-mantle Titanium Stem Fixated With Cement.

The purpose of the present study was to review and report clinical outcomes of the Kyocera Modular Limb Salvage System (KMLS) using a thin-mantle titanium stem fixated with cement, for reconstruction after resection of malignant femoral-bone tumors. Twenty consecutive patients who had undergone reconstruction using the KMLS with cemented thin-mantle titanium stem fixation between July 2010 and December 2019 at Ryukyu University Hospital were included. We retrospectively collected the following data: age, sex, follow-up period, tumor location, histological diagnosis, stem size, overall implant survival, radiolucency, postoperative complications, overall survival, and oncological survival. The median follow-up period was 63 months (range=10.7-261 months). The bone tumors were in the proximal part of the femur in 9 patients and in the distal part of the femur in 11 patients. The 5-year overall implant survival rate was 90.9% among surviving patients. A revision surgery was required for only one patient (5%), due to infection. Radiolucency, due to an instability of the implant, was observed in 7 out of 20 patients: 6 patients with distal femoral reconstruction, and 1 patient with proximal femoral reconstruction. However, none of the patients complained of any symptoms or required revision surgeries at the last follow-up. The 5-year overall patient-survival rate was 67.6%. The KMLS with cemented thin-mantle titanium stem fixation for femoral bone reconstruction after resection for bone malignancy resulted in long-term patient benefit.

Cementless curved endoprosthesis stem for distal femoral reconstruction in a Chinese population: a combined anatomical & biomechanical study

BackgroundThe endoprosthetic knee reconstruction using a current universal femoral stem might not be suitable for local population due to the anatomical difference between Chinese and Western populations. We measured the anatomical parameters of Chinese femurs as reference for stem design, and proposed a cementless, curved, short endoprosthesis stem for the reconstruction of distal femur. This study analyzed the biomechanical performance of the newly designed stem aimed at the identification of better operative strategy.MethodsThe CT–scanning data of femurs derived from 96 healthy Chinese volunteers were imported into the Mimics software, and a segmental measurement strategy was applied to evaluate the radius of curvature (ROC) of the femoral medullary cavity. Then, 4 kinds of endoprosthetic replacement models were created based on the measurement results. Model A: the distal tumor resected femora + straight stem A; Model B: the distal tumor resected femora + curved stem B; Model C: the distal tumor resected femora + curved stem C; Model D: the distal tumor resected femora + curved stem D. Finally, the mechanical difference among these models were compared by finite element analysis.ResultsThe mean femoral ROC of Segment1, 2, 3, 4, 5 measured in the present study was 724.5 mm, 747.5 mm, 1016.5 mm, 1286.5 mm, and 1128 mm, respectively. Based on the femoral ROC of Segment2, the stem ROC of the curved stem B, C, and D was designed as 475 mm, 700 mm, and 1300 mm, respectively. Generally, all endoprosthetic replacement models showed a normal–like stress distribution on the femurs. However, compared to the straight stem, the biomimetic curved stem showed better biomechanical performance both in terms of reducing the extent of the stress shielding of the femur and in terms of minimizing the stress distribution of the implant.ConclusionsThe uncemented, curved, short stem with suitable ROC can perfectly match the Chinese femoral canal morphology which has better mechanical properties than the conventional femoral stem. Thus, this newly designed femoral stem might be an optimized method for treatment of malignant femoral tumours in the Chinese populations in the case that the numerical results are supported by future experimental studies.

Resurfaced allograft-prosthetic composite for distal femur reconstruction in children with bone tumor.

Reconstruction of the distal femur in children following resection of bone sarcoma is challenging. The main problem in children is the small size of bone and a possible limb-length discrepancy at the end of skeletal growth secondary to the loss of the physes. We reported the results of a new surgical technique for distal femur reconstruction after bone tumor resection in children. We analyzed 5 patients with distal femoral sarcomas who underwent intra-articular resection and reconstruction with resurfaced allograft-prosthetic composite at a mean follow-up of 70 months. There were 2 males and 3 females, with a mean age of 10 years (range 8-12) at the time of the diagnosis. All patients were affected by high-grade osteosarcoma. The patients' medical records were reviewed for clinical and functional outcomes as well as post-operative complications. The functional evaluation of the patients was done at the end of the follow-up using Musculoskeletal Tumor Society scoring system. The minimal follow-up was 24 months. At the last follow-up, 4 patients were continuously disease-free. We excluded one patient who died of disease secondary to lung metastases 16 months after the surgery. Complications occurred in 2 of 4 patients at 17 months and 24 months, respectively. One patient developed deep infection who required the removal of the original reconstruction and, once the infection was treated, the patient underwent reconstruction with an expandable prosthesis. An allograft fracture occurred in another of the 4 patients at 24 months after the first surgery, thus the original reconstruction was removed and the patient underwent reconstruction with modular prosthesis. In the two patients who retained the original reconstruction at the time of their latest follow-up, the mean implant survival time was 70 months. These patients had an excellent MSTS score (29.5 points) and walked without support or limitations with an active knee range of motion of > 90° and complete active extension of the knee. No degenerative changes of the articular surface of the proximal tibia and the patella were observed at the time of the last follow-up. Growth of the physis of the proximal tibia was observed in all the patients during follow-up and no angular deformity of the joint was observed. The limb discrepancy was 4 cm and 2 cm, respectively. Resurfaced allograft-prosthetic composite may represent an alternative surgical technique for distal femur reconstruction in children with bone sarcomas. Although its success is limited by high risk of complications, resurfaced allograft-prosthetic composite seems to be a viable option to preserve the bone stock and the physis of the proximal tibia in selected young patients, minimizing a potential limb-length discrepancy at the end of the skeletal growth.

Clinically Important Reductions in Physical Function and Quality of Life in Adults with Tumor Prostheses in the Hip and Knee: A Cross-sectional Study.

Clinically Important Reductions in Physical Function and Quality of Life in Adults with Tumor Prostheses in the Hip and Knee: A Cross-sectional Study.

CORR Insights®: Compliant Compression Reconstruction of the Proximal Femur Is Durable Despite Minimal Bone Formation in the Compression Segment.

CORR Insights®: Compliant Compression Reconstruction of the Proximal Femur Is Durable Despite Minimal Bone Formation in the Compression Segment.

Revision TKA with a distal femoral replacement is at high risk of reinfection after two-stage exchange for periprosthetic knee joint infection

PurposeMegaprosthetic distal femoral reconstruction (DFR) is a limb-salvage procedure to address bone loss following two-stage revision for periprosthetic knee joint infection (PJI). The purpose of this study was to analyze the survival of DFR compared to hinged total knee arthroplasty (TKA). It was hypothesized that DFR was associated with a poorer survival.MethodsIn this retrospective single-center study, 97 subjects who underwent two-stage revision of chronic knee PJI were included. Among these, 41 were DFR. The diagnosis of PJI was established using the Musculoskeletal Infection Society (MSIS) criteria. Implant survival was calculated using Kaplan–Meier method and compared with the log-rank test as well as multivariate Cox regression at a minimum follow-up period of 24 months.ResultsThe median follow-up period was 59 (interquartile range (IQR) 45–78) months. Overall, 24% (23/97) of patients required revision surgery for infection. The infection-free survival of rotating hinge revision TKA was 93% (95% Confidence Interval (CI) 86–100%) at five years compared to 50% (95% CI 34–66%) for DFR. In multivariate analysis, the risk factors for reinfection were DFR reconstruction (HR 4.7 (95% CI 1–22), p = 0.048), length of megaprosthesis (HR 1.006 (95% CI 1.001–1.012), p = 0.032) and higher BMI (HR 1.066, 95% CI 1.018–1.116), p = 0.007). 10% (4/41) of patients undergoing DFR underwent amputation to treat recurrent infection.ConclusionMegaprosthetic DFR as part of a two-stage exchange for PJI is a salvage treatment that has a high risk for reinfection compared to non-megaprosthetic TKA. Patients must therefore be counseled accordingly.Level of evidenceRetrospective observational study, Level IV.

What Is the 10-year Survivorship of Cemented Distal Femoral Endoprostheses for Tumor Reconstructions and What Radiographic Features Are Associated with Survival?

Aseptic loosening is one of the most common causes of revision of distal femoral endoprostheses and is considered a mid- to long-term complication. There are not many reports of 10-year survivorship free from aseptic loosening and all-cause survivorship in cemented stems. To our knowledge, there are no reports on radiographic features that are associated with aseptic loosening of these implants. (1) What is the 5- and 10-year survivorship free from aseptic loosening in patients undergoing reconstruction with a cemented distal femoral endoprosthesis after a tumor resection? (2) What is the all-cause 5- and 10-year survivorship at in these patients? (3) What radiographic features are associated with aseptic loosening at long-term follow-up? We performed a multicenter retrospective study reviewing aseptic loosening in cemented prostheses to determine radiographic features associated with long-term implant survivorship. Patients who underwent a cemented distal femoral reconstruction with a modular endoprosthesis after resection of a musculoskeletal tumor between 1997 and 2017 were reviewed. A total of 246 patients were identified from five institutions and met initial inclusion criteria. Of those, 21% (51) were lost to follow-up before 2 years, leaving 195 patients available for us to evaluate and analyze the survivorship and radiologic features associated with long-term implant survival. The mean (range) follow-up was 78 months (22 to 257). At the time of this analysis, 69% (135 of 195) of the patients were alive. Osteosarcoma was the most common diagnosis in 43% of patients (83 of 195), followed by metastatic carcinoma 13% (25 of 195). Fifty-six percent (110 of 195) of patients received chemotherapy; 15% (30 of 195) had radiation therapy. Aseptic loosening was diagnosed radiographically and was defined as a circumferential radiolucent line on all views, or subsidence around the stem in the absence of infection. We present 5- and 10-year Kaplan-Meier survivorship free from aseptic loosening, 5- and 10-year all-cause survivorship, and a qualitative assessment of radiographic features potentially associated with aseptic loosening (including the junctional radiolucent area, and cortical expansion remodeling). The junctional radiolucent area was defined as a radiolucent area of the bone starting at the bone-endoprosthesis junction to the tip of the femoral stem, and cortical expansion remodeling was defined as an increased cortical thickness at the stem tip. Although we wished to statistically analyze radiographic factors potentially associated with aseptic loosening, we did not have enough clinical material to do so (only nine patients developed loosening). Instead, we will report a few preliminary qualitative observations, which necessarily are preliminary, and which will need to be confirmed or refuted by future studies. We urge caution in interpreting these findings because of the very small numbers involved. Kaplan-Meier survivorship free from aseptic loosening of the femoral component at 5 and 10 years were 95% (95% CI 89 to 98) and 93% (95% CI 86 to 97), respectively. Kaplan-Meier survivorship free from revision for any cause at 5 and 10 years were 74% (95% CI 65 to 79) and 64% (95% CI 49 to 70), respectively. Although the numbers were too small to analyze statistically, all patients with aseptic loosening had a junctional radiolucent area more than 20% of the total length of the stem without cortical expansion remodeling at the stem tip. No aseptic loosening was observed if there was cortical ex remodeling, a junctional radiolucent area less than 20%, or curved stems that were 13 mm or greater in diameter. The numbers of patients with aseptic loosening in this series were too small to analyze statistically. Cemented distal femoral endoprostheses have a relatively low rate of aseptic loosening and acceptable projected first-decade survivorship. The presence of a radiolucent area more than 20% without cortical expansion remodeling at the stem tip may lead to aseptic loosening in patients with these implants. Close radiographic surveillance and revision surgery may be considered for progressive lucencies and clinical symptoms of pain. If revision is contemplated, we recommend using larger diameter curved cemented stems. These are preliminary and provisional observations based on a low number of patients with aseptic loosening; future studies with greater numbers of patients are needed to validate or refute these findings. Level III, therapeutic study.

Virtual Geometric Reconstruction of Australopithecine Femora: A Methodological Evaluation

The fragmentary nature of fossils, and the need to extract as much information from them as possible, mandates that broken portions be reconstructed. Virtual reconstruction using geometric morphometric techniques based on the thin plate spline (TPS) function can be used to locate landmarks that represent missing portions of fossil specimens. Here we evaluate the accuracy of TPS‐based reconstruction in artificially damaged australopithecine distal femora.Surface models of modern human (n=35) and chimpanzee (n=37) distal femora, as well as those of two australopiths (casts of A.L. 129‐1a and A.L. 333‐4), were created using a structured light scanner. Articular surfaces were trimmed from the rest of the surface model. 1007 sliding semilandmarks were distributed across the articular surface, and semilandmarks were then slid to minimize the bending energy of the TPS function relative to an updated Procrustes average. Fossils were then virtually destroyed by removing semilandmarks to mimic the type of destruction observed in other fossil specimens. Removed portions increased from a small, central hole in the middle of each condyle to removal of the entire condyle. Average chimpanzee and human femora were used as references to create two separate reconstructions using geometric reconstruction based on the TPS function. Procrustes distances (PD) between each reconstruction and the original fossil were calculated to evaluate reconstruction accuracy.Reconstructions based on both human and chimpanzee averages deviated further from the original fossils as the level of artificial damage increased. When the entire medial condyle was reconstructed, the original morphology of both australopithecine fossils was intermediate between the human‐based and chimpanzee‐based reconstructions. For these reconstructions, Procrustes distances indicate that both A.L. 129‐1a and A.L. 333‐4 are most similar to the human‐based reconstruction (A.L. 129‐1a: PD = 0.001 vs. 0.002; A.L. 333‐4: PD = 0.002 vs. 0.003). When the entire lateral condyle was reconstructed, the fossils fell outside the possible morphologies bounded by the human‐based and chimpanzee‐based reconstructions. Procrustes distances indicate that both fossils are more similar to the human‐based reconstructions than those based on the average chimpanzee (A.L. 129‐1a: PD = 0.004 vs. 0.005; A.L. 333‐4: PD = 0.005 vs. 0.009). These results suggest that while the australopithecine medial femoral condyle may be considered an interpolation between chimpanzee and human morphology, the lateral condyle does not follow the same trend. For australopithecine distal femur reconstructions to be accurate, medial and lateral condyles should be considered separately.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Modular tumor prostheses: are current stem designs suitable for distal femoral reconstruction? A biomechanical implant stability analysis in Sawbones.

High loosening rates after distal femoral replacement may be due to implant design not adapted to specific anatomic and biomechanical conditions. A modular tumor system (MUTARS®, Implantcast GmbH) was implanted with either a curved hexagonal or a straight tapered stems in eight Sawbones® in two consecutively generated bone defect (10cm and 20cm proximal to knee joint level). Implant-bone-interface micromotions were measured to analyze main fixation areas and to characterize the fixation pattern. Although areas of highest relative micromotions were measured distally in all groups, areas and lengths of main fixation differed with respect to stem design and bone defect size. Regardless of these changes, overall micromotions could only be reduced with extending bone defects in case of tapered stems. The tapered design may be favorable in larger defectswhereas the hexagonal may be advantageous in defects located more distally.

A 2-stage Distal Femur Reconstruction with Expandable Endoprosthesis in a Pediatric Patient Presenting with a Pathologic Fracture through an Osteosarcoma

Osteosarcoma in pediatric patients has traditionally been treated with amputation, especially if there is a pathologic fracture through the tumor.We report the case of a 12-year-old boy who sustained a pathologic fracture through distal femoral osteosarcoma. After neoadjuvant chemotherapy, he underwent limb saving surgery: wide excision of the osteosarcoma followed by a second-stage reconstruction with an expandable tumor endoprosthesis. He has a functional score of 93% and is free of disease 8 years since diagnosis and 2 years since the end of lengthening.This is the first reported case in Philippine medical literature of limb saving surgery in osteosarcoma reconstructed with an expandable endoprosthesis.

Distal femoral reconstruction following failed total knee arthroplasty is accompanied with risk for complication and reduced joint function

BackgroundSubstantial bone loss following failed total knee arthroplasty (TKA) represents a major challenge in revision arthroplasty, that can require distal femoral reconstruction (DFR). In this study, we aimed to assess the clinical outcome and the complication frequencies of individuals who underwent DFR with modular megaprostheses. Additionally, we aimed to compare functional outcome measures after DFR in these sophisticated cases to an age-matched control group of total knee prostheses to quantify the potential loss of function.MethodsA retrospective chart review of 30 consecutive patients after DFR from 1997 to 2017 with a mean age of 74.38 years (± 10.1) was performed. Complications were classified according to the Henderson classification. Knee Society Score (KSS) was calculated and range of motion (ROM) was assessed.ResultsThirteen (43.3%) patients had at least one complication requiring revision surgery. Revision-free survival was 74.8% at one year, 62.5% at three and 40.9% at 10 years post-op. Soft-tissue failure complications were found in three (10.0%) patients, aseptic loosening in four (13.3%) patients, structural failure in one (3.3%) patient and infection in eight (26.6%) patients. Of those with infection, five (16.6%) experienced ongoing prosthetic joint infection and three (10.0%) developed new infection after distal femur reconstruction. Patients with DFR achieved 69.3% of KSS pain score, 23.1% KSS function score and 76.2% of ROM compared to patients with primary TKA.ConclusionsDFR after failed TKA represents a treatment procedure with high risk for complication in this particular group. Despite the prospect of rapid postoperative mobilization, reduced functionality, range of motion and mobilization have to be considered when choosing this treatment option.

Chemotherapy Curtails Bone Formation From Compliant Compression Fixation of Distal Femoral Endoprostheses.

Modulated compliant compressive forces may contribute to durable fixation of implant stems in patients with cancer who undergo endoprosthetic reconstruction after tumor resection. Chemotherapy effects on bone hypertrophy and osteointegration have rarely been studied, and no accepted radiologic method exists to evaluate compression-associated hypertrophy. (1) What was the effect of chemotherapy on the newly formed bone geometry (area) at 1 year and the presumed osteointegration? (2) What clinical factors were associated with the degree of hypertrophy? (3) Did the amount of bone formation correlate with implant fixation durability? (4) Was the amount of new bone generation or chemotherapy administration correlated with Musculoskeletal Tumor Society (MSTS) score? Between 1999 and 2013, we performed 245 distal femoral reconstructions for primary or revision oncologic indications. We evaluated 105 patients who received this implant. Ten were excluded because they lacked 2 years of followup and two were lost to followup, leaving 93 patients for review. All underwent distal femur reconstruction with the compliant compressive fixation prosthesis; 49 received postoperative chemotherapy and 44 did not. During this period, the implant was used for oncology patients < 60 years of age without metastases and with > 8 cm of intact, nonirradiated bone distal to the lesser trochanter and ≥ 2.5 mm of cortex. Our cohort included patients with painful loosening of cemented or uncemented stemmed femoral megaprostheses when revision with the compliant compressive device was feasible. Patients with high-grade sarcomas all received chemotherapy, per active Children's Oncology Group protocols, for their tumor diagnosis. At each imaging time point (3, 6, 9, 12, 18, 24 months), we measured the radiographic area of the bone under compression using National Institutes of Health open-access software, any shortening of the spindle-anchor plug segment distance as reflected by the exposed traction bar length, and prosthesis survivorship. Clinical and functional status and MSTS scores were recorded at each followup visit. Duration of prosthesis retention without aseptic loosening or mechanical failure was evaluated using Kaplan-Meier analysis, censoring patients at last followup. Chemotherapy was associated with the amount of overall bone formation in a time-dependent fashion. In the 12 months after surgery there was more bone formation in patients who did not receive postoperative chemotherapy than those who did (60.2 mm, confidence interval [CI] 49.3-71.1 versus 39.1, CI 33.3-44.9; p = 0.001). Chemotherapy was not associated with prosthesis survival. Ten-year implant survival was 85% with chemotherapy and 88% without chemotherapy (p = 0.74). With the number of patients we had, we did not identify any clinical factors that were associated with the amount (area) of hypertrophy. The hypertrophied area was not associated with the durability of implant fixation. MSTS scores were lower in patients treated with chemotherapy (25 versus 28; p = 0.023), but were not correlated with new bone formation. The relationships among chemotherapy, bone formation, and prosthetic survivorship are complex. Because bone formation is less in the first year when the patient is being treated with chemotherapy, it is not clear if the rehabilitation schedule should be different for those patients receiving chemotherapy compared with those who do not. The relationship between early bone formation and the timing of weightbearing rehabilitation should be evaluated in a multicenter study. Level III, therapeutic study.

Uncemented, curved, short endoprosthesis stem for distal femoral reconstruction: early follow-up outcomes

BackgroundUncemented endoprosthetic knee replacement has become a mainstream treatment for malignant tumours of the distal femur. Most femoral stems, however, are straight and therefore poorly fit the anteriorly bowed curvature of the femur. To address this issue, we used a short, curved, uncemented press-fit femoral stem and evaluated its short-term outcomes after reconstruction of the distal femur.MethodsForty-two patients underwent distal femur replacement using curved press-fit stem. To assess the interface, we measured the axial length of the press-fit area and the perpendicular distance of the radiolucent area between the stem and bone on digital images obtained using tomosynthesis with Shimadzu Metal Artefact Reduction Technology (T-SMART). Postoperative complications and oncological outcomes were monitored at each follow-up visit.ResultsOf the 42 patients enrolled in the study, two had cancer-related deaths and one had local tumour recurrence. The minimum follow-up time of the surviving patients was 24 months, with no incidence of aseptic loosening or mechanical failure of the prosthesis. The average effective contact length between the press-fit stem and bone was 74.0 mm, with nearly undetectable radiolucent gaps between the implant and the bone on medial-lateral and anteroposterior views.ConclusionsOver the short term, uncemented, curved, short stem provides a stable bone-prosthesis interface without any aseptic loosening.

Stacked sparse autoencoder networks and statistical shape models for automatic staging of distal femur trochlear dysplasia.

The quantitative morphological analysis of the trochlear region in the distal femur and the precise staging of the potential dysplastic condition constitute a key point for the use of personalized treatment options for the patella-femoral joint. In this paper, we integrated statistical shape models (SSM), able to represent the individual morphology of the trochlea by means of a set of parameters and stacked sparse autoencoder (SSPA) networks, which exploit the parameters to discriminate among different levels of abnormalities. Two datasets of distal femur reconstructions were obtained from CT scans, including pathologic and physiologic shapes. Both of them were processed to compute SSM of healthy and dysplastic trochlear regions. The parameters obtained by the 3D-3D reconstruction of a femur shape were fed into a trained SSPA classifier to automatically establish the membership to one of three clinical conditions, namely, healthy, mild dysplasia, and severe dysplasia of the trochlea. The validation was performed on a subset of the shapes not used in the construction of the SSM, by verifying the occurrence of a correct classification. A major finding of the work is that SSM are able to represent anomalies of the trochlear geometry by means of specific eigenmodes of variation and to model the interplay between morphologic features related to dysplasia. Exploiting the patient-specific morphing parameters of SSM, computed by means of a 3D-3D reconstruction, SSPA is demonstrated to outperform traditional discriminant analysis in classifying healthy, mild, and severe trochlear dysplasia providing 99%, 97%, and 98% accuracy for each of the three classes, respectively (discriminant analysis accuracy: 85%, 89%, and 77%). From a clinical point of view, this paper contributes to support the increasing role of SSM, integrated with deep learning techniques, in diagnostics and therapy definition as quantitative and advanced visualization tools.

Growth of epiphysis after epiphyseal-preservation surgery for childhood osteosarcoma around the knee joint

BackgroundEpiphyseal-preservation surgery for osteosarcoma is an alternative method which has been indicated carefully to selected patients. The tumor-devitalised autograft treated with liquid nitrogen procedure is one of the biological reconstruction method to reconstruct the defect after tumor excision. The limb length discrepancy is usually appeared in children with their growth after limb-sparing surgery. This study was aimed to investigated the growth of residual epiphysis following epiphyseal-preservation surgery for childhood osteosarcoma around the knee joint.MethodsWe retrospectively reviewed 12 patients with osteosarcoma who underwent epiphysis preserving tumor excision (8 in distal femur and 4 in proximal tibia) and reconstructed by using tumor-devitalized autograft treated with liquid nitrogen. The mean patient age was 11 (range, 6 to 14) years. The mean follow-up period were 63 (range, 41 to 90) months. Epiphysis transverse growth rate, epiphysis-width discrepancy (EWD) and collapse of epiphysis were evaluated by using pre- and post-operative whole standing leg radiographs. A retrospective chart review was performed to investigate functional outcome, complications and oncological status.ResultsThe mean growth of epiphysis rate was 12.6% (range, 3.3 to 28.0%) of affected side and 12.7% (range, 3.8 to 28.9%) of contralateral side, mean EWD was 0.1 mm (range, − 1.0 to 1.7 mm), mean LLD was + 26.1 mm (range, + 1 to + 48 mm) and two patients with distal femoral reconstruction underwent limb lengthening of tibia. There was no collapse of the residual epiphysis. The mean MSTS score was 27.7 (range, 18 to 30).ConclusionsEpiphysis transverse growth was not diminished, and there was absence of epiphyseal collapse even after epiphyseal-preservation surgery in this small series of childhood osteosarcoma around the knee. With careful assessment for epiphyseal tumor involvement, epiphyseal-preservation surgery shall be possible, and could be an alternative method worth considering.