[Comparative functional outcome of reverse shoulder prostheses implanted on degenerative and oncological indications]. / Degeneratív és onkológiai indikációk alapján beültetett reverz vállprotézisek funkcionális kimenetelének összehasonlítása.

INTRODUCTION: Several methods (bone graft, endoprosthesis) are used to reconstruct proximal humerus resections due to primary and metastatic tumours. One of the new procedures is the replacement of the joint surfaces and the removed proximal humerus end with reverse shoulder prosthesis, optionally supplemented with bone implantation (composite procedure) in the hope of achieving better shoulder function. AIM: The aim of this study was to compare the shoulder function of the patient group operated by the above procedure with reverse prosthesis to a patient group operated by indication of degenerative shoulder disease (rotator cuff arthropathy). METHOD: The study involved 23 patients (13 men, 10 women) who were operated between 2012 and 2016 in our institution. Among them, 15 had rotator cuff arthropathy indication of reverse prosthesis, while in 8 cases, resection of the humerus and prosthesis implantation were performed due to tumour lesions. The average age of our patients was 62.5 years (17-82) and the average follow-up was 23.5 months (5-57). We performed physical examination, X-ray pictures on their operated arm, and data were recorded and analysed based on functional score systems. RESULTS: The level of postoperative pain was almost the same in the two groups, but only the rotator cuff arthropathy group needed pain medications. In line with our expectations, we received slightly lower values by each of the three scoring systems in case of tumorous patients. The tumorous patients were satisfied with the results achieved. CONCLUSIONS: Following proximal humerus resections, reversed prosthesis implantation with occasional bone allografts is a reliable method of reconstruction, which approaches available functions and reliability as compared to non-tumour-indicating patients. Orv Hetil. 2018; 159(45): 1838-1843.

[Survival of pediatric patients with Ewing sarcoma treated at Semmelweis University]. / A Semmelweis Egyetemen kezelt Ewing-szarkómás gyermekek kezelési eredményeinek vizsgálata.

The survival of children treated with Ewing sarcoma at Semmelweis University were investigated. Pediatric patients with Ewing sarcoma treated at Semmelweis University from 2001 through 2013 were analyzed in terms of overall survival and clinical factors (age, primary localization and extent of the tumor, time interval from primary complaints to diagnosis). For statistical analysis Kaplan-Meier estimated survival and log rank test were applied. Mean age and follow-up time of the 78 patients were 11.16 and 6.29 years, respectively. In 57% of patients time interval from primary symptoms to diagnosis was less than half year. In 53.8% of the patients the disease was metastatic at primary diagnosis (pulmonary only: 29.5%, any other: 24.3%). 5- and 10-year overall survival of patients were 68.1% and 60.4%, respectively. Among the analyzed factors, the presence of metastasis impaired 5-year overall survival significantly (88.5% for localized disease, 63.5% for pulmonary only and 40.9% for any other metastasis). The survival rate of pediatric patients with Ewing sarcoma treated at Semmelweis University is similar to the result in Western European countries.

Epigenetic regulation of SMARCB1 By miR-206, -381 and -671-5p is evident in a variety of SMARCB1 immunonegative soft tissue sarcomas, while miR-765 appears specific for epithelioid sarcoma. A miRNA study of 223 soft tissue sarcomas.

Complete/partial loss of SMARCB1 nuclear-immunopositivity is characteristic of a certain subset of soft tissue sarcomas (STSs). Our previous work showed that oncomiRs-206,-381, and 671-5p could silence the SMARCB1 mRNA and protein expression and that they display significant overexpression in epithelioid sarcomas (ESs). MiR-765 was overexpressed too, but functionally was inactive in the silencing. In the current work, using quantitative PCR, we conducted a miRNA study of 51 ESs, 20 rhabdoid tumors (RTs), 20 synovial sarcomas (SSs), 15 malignant peripheral nerve sheath tumors (MPNSTs), 11 myoepithelial carcinomas (MECs), and 10 extraskeletal myxoid chondrosarcomas (EMCSs) with complete/partial loss of SMARCB1 nuclear immunostain, in contrast to controls (SMARCB1-immunopositive) of 96 STSs, 13 melanomas and 10 sarcomatoid carcinomas. The SMARCB1 genetic status of ESs was determined by MLPA and FISH. A subset of ESs (5/51) showed biallelic deletion of SMARCB1 with no overexpression of any miRNA, suggesting these tumors could be the counterpart of pediatric RT, at least genetically. Another subset (5/51) was genetically either intact or monoallelic deleted with at least threefold overexpression of one of miR-206,-381,-671-5p, suggesting epigenetic regulation only. 39/51 ESs had a biallelic deletion (>20% by FISH and/or by MLPA) but with overexpressed miR-206,-381, and 671-5p, suggesting intratumoral heterogeneity, i.e., both genetic and epigenetic regulation. At least threefold overexpression of one of miR-206,-381, and 671-5p was detected in all MPNSTs, EMCSs, SSs and 7 MCs. Except for ESs, four SSs and one MPNST, there was no event above threefold overexpression of miR-765 among all 195 tested tumors. Our results suggest a general role of miR-206,-381, and 671-5p in SMARCB1 gene silencing of ES, MC, EMCS, MPNST and SS. In the future, miR-765 could possibly be a diagnostic tool for ES because of its 97% specificity and 80% sensitivity. © 2016 Wiley Periodicals, Inc.

[Change of paradigm in the surgical treatment of metastatic diseases of bone. Part I. Bony metastases of the extremities and pelvis]. / Paradigmaváltás a csontmetasztázisok sebészetében. I. Végtagi és medencelokalizációjú áttétek.

According to the statistical data of tumor registries the incidence of cancer has increased in the last decade, however the mortality shows only a slight change due to the new and effective multimodal treatments. The aim of our overview article is to present the changes in the survival of the metastatic patients, and to demonstrate which factors influence their prognosis. The improvement of survival resulted in a more active surgical role both in metastases of the bone of the extremities and the pelvis. We present a diagnostic flow chart and current options for the reconstruction of the different regions of the bone and skeleton, and we will discuss their potential advantages, disadvantages and complications. It is evident that apart from the impending and pathological fracture surgery it is not the first choice of treatment but rather a palliative measure. The aim of surgery is to alleviate pain, to regain mobility and improve quality of life. If possible minimal invasive techniques are performed, as they are less demanding and allow fast rehabilitation for the patient, and they are solutions that last for a lifetime. In optimal conditions radical curative surgery can be performed in about 10 to 15 per cent of the cases, and better survival is encouraging. Orv Hetil. 2017; 158(40): 1563-1569.

[Epidemiology of soft tissue sarcomas in a university center in Hungary]. / A lágyrészszarkóma epidemiológiája egy hazai egyetemi centrumban.

Our aim was to investigate the rare malignant soft tissue sarcomas responsible for 1.5% of all malignant tumors, to compare our epidemiological data from the patient population of the Department of Orthopaedics, Semmelweis University, to data described in the international literature for soft tissue tumors. We reviewed 595 cases of primary soft tissue sarcomas treated between 1994 and 2014 and compared results to international data from the literature. Our results were similar to those found in the international literature: mean age, mild male predominance, the most common sarcoma subgroups, the superficial and deep sarcoma ratio, low and high grade sarcoma ratio, the ratio of patients with a primary lung metastasis. Compared to other European data we found significantly longer patient referral to centers (3.6 months in case of superficial sarcomas, 8 months in case of deep localization) which surprisingly had no substantial effect on average tumor size (superficial: 5 cm, deep: 10.5 cm). This corresponds with data from the literature. The long delay period in patients' request of medical service draws attention to difficulties in differential diagnosis in this rare type of tumor, delays in referring patients to a center, and the lack of consultation. We recommend that the required investigations be performed in a musculoskeletal oncology center where this type of cancer is treated.

[Is suction drainage necessary in elective total hip arthroplasty?]. / Szükség van szívódrénre elektív csípoprotézis-mutétek során?

INTRODUCTION: Several studies have been published which questioned the use of suction drain during elective hip arthroplasty. AIM: In this prospective study the authors examined how the use of suction drainage affected complications related to perioperative blood loss and hemorrhage in patients undergoing elective hip arthroplasty. METHOD: Eighty-six patients undergoing elective hip arthroplasty were divided into two groups. In 54 patients ("drain" group) suction drains were used during operation, whereas in 32 patients no suction drain was applied. Perioperative blood loss, use of tranexamic acid, method of thrombosis prophylaxis, transfusion requirement, incidental postoperative hemorrhage, septic complications, and all other postoperative complications were recorded. RESULTS: Perioperative blood loss was affected with the use of tranexamic acid but not with the use of drainage (p = 0.94). Patients without the use of drain showed a tendency of lower transfusion requirement (p = 0.08). There was no correlation between any complications and the use of drainage. CONCLUSION: In accordance with published results the authors conclude that the routine use of suction drainage during elective hip arthroplasty is not definitely necessary. Orv. Hetil., 2016, 157(29), 1171-1176.

Improved survival in osteosarcoma patients with atypical low vascularization.

BACKGROUND: Osteosarcoma is considered a highly vascularized bone tumor with early metastatic dissemination through intratumoral blood vessels mostly into the lung. Novel targets for therapy such as tumor vascularization are highly warranted since little progress has been achieved in the last 30 years. However, proof of relevance for vascularization as a major prognostic parameter has been hampered by tumor heterogeneity, difficulty in detecting microvessels by immunohistochemistry, and small study cohorts. Most recently, we demonstrated that highly standardized whole-slide imaging could overcome these limitations (Kunz et al., PloS One 9(3):e90727, 2014). In this study, we applied this method to a multicenter cohort of 131 osteosarcoma patients to test osteosarcoma vascularization as a prognostic determinant. METHODS: Computer-assisted whole-slide analysis, together with enzymatic epitope retrieval, was used for CD31-based microvessel quantification in 131 pretreatment formalin-fixed and paraffin-embedded biopsies from three bone tumor centers. Kaplan-Meier-estimated survival and chemoresponse were determined and multivariate analysis was performed. Conventional hot-spot-based microvessel density (MVD) determination was compared with whole-slide imaging. RESULTS: We detected high estimated overall (p ≤ 0.008) and relapse-free (p ≤ 0.004) survival in 25 % of osteosarcoma patients with low osteosarcoma vascularization in contrast to other patient groups. Furthermore, all patients with low osteosarcoma vascularization showed a good response to neoadjuvant chemotherapy. Comparison of conventional MVD determination with whole-slide imaging suggests false high quantification or even exclusion of samples with low osteosarcoma vascularization due to difficult CD31 detection in previous studies. CONCLUSION: Low intratumoral vascularization at the time of diagnosis is a strong predictor for prolonged survival and good response to neoadjuvant chemotherapy in osteosarcoma.

SMARCB1 expression in epithelioid sarcoma is regulated by miR-206, miR-381, and miR-671-5p on Both mRNA and protein levels.

Proximal type epithelioid sarcoma shares similarities with malignant rhabdoid tumor, including the lack of nuclear immunoreactivity of SMARCB1. Biallelic mutation of SMARCB1 has been convincingly established as the cause of loss of protein expression in rhabdoid tumor, but the cause in epithelioid sarcoma remains unknown. In our previous work, we demonstrated that DNA hypermethylation and post-translational modification mechanisms were not involved. In this current work, we explored the hypothesis that miRNAs regulate SMARCB1 gene expression in epithelioid sarcomas. In silico target prediction analysis revealed eight candidate miRNAs, and quantitative PCR-in 32 formalin-fixed, paraffin-embedded tumor samples comprising 30 epithelioid sarcomas and two malignant rhabdoid tumors-demonstrated significant (P < 0.001) overexpression of four miRNAs in epithelioid sarcomas: miR-206, miR-381, miR-671-5p, and miR-765. Two human tumors (fibrosarcoma and colon adenocarcinoma) and a normal cell line (human dermal fibroblast) with retained SMARCB1 expression were cultured for miRNA transient transfection (electroporation) experiments. SMARCB1 mRNA expression was analyzed by quantitative real-time PCR and immunostaining of SMARCB1 was performed to examine the effect of miRNAs transfections on both RNA and protein levels. Only three of the overexpressed miRNAs (miR-206, miR-381, and miR-671-5p) could silence the SMARCB1 mRNA expression in cell cultures; most effectively miR-206. Transfection of miR-206, miR-381, miR-671-5p, and some combination of them also eliminated SMARCB1 nuclear staining, demonstrating a strong effect on not only mRNA but also protein levels. Our results suggest loss of SMARCB1 protein expression in epithelioid sarcoma is due to the epigenetic mechanism of gene silencing by oncomiRs.

Variability of gait in the early postoperative period of total knee arthroplasty with different surgical technique.

PURPOSE: The purpose of this study was to work out an objective and sensitive method for the early postoperative period following total knee arthroplasty (TKA) in which analysis of the gait parameters is possible and also to investigate the influence of different surgical approaches for TKA on the gait during stepping in the first three months of the postoperative period. METHODS: Three groups of patients: age-matched healthy elderly patients as a control group, patients operated upon by the conventional technique and finally by the minimally invasive technique combined with computer-assisted navigation. All three groups included ten patients. The motions of knee, shoulder and pelvis were measured by ZEBRIS ultrasound-based system preoperatively plus six and 12 weeks postoperatively. From the joint motion, the variability of cadence, and the variability of knee joint motion and that of pelvis and shoulder girdle was determined. RESULTS: Osteoarthritis (OA) of the knee joint and TKA using both operation techniques significantly influenced the variability of stepping parameters compared to the controls. In the early postoperative period a significant difference was detected between the two groups of the operated patients in all parameters. CONCLUSION: Our data prove that our method seems appropriate to provide objective measurement of the gait in the early postoperative period. The variability of motion of the patient groups approaches that of the healthy control group steadily, but does not reach them.

[Contemporary management of bone tumors at Semmelweis University]. / Csonttumorellátás a Semmelweis Egyetem Ortopédiai Klinikáján.

The incidence of bone tumors is low therefore it is highly recommended to treat patients in specialized centers. In the late 70ies a bone tumor registry was initiated at the Department of Orthopedics of the Semmelweis University followed by the development of a specialized diagnostic unit and a bone cancer center. Several novel surgical procedures have been introduced, including the extremity-sparing surgery, leading to a significant improvement of the patients survival. This is fully supported by a specialized bone cancer oncoteam of experts. The 6000-sized registry and biobank now allows the development of translational research in this orphan tumor type.

[Resection and reconstruction in cases of musculosceletal soft tissue sarcomas]. / Sebészi radikalitás és rekonstrukciós lehetõségek végtagi lágyrészsarcomáknál.

Soft tissue sarcomas are rare, reaching some 1.5% of all malignant tumors. While formerly the surgical management of sarcomas almost exclusively consisted of amputation, in the recent years limb saving surgery has become the first choice of therapy. Negative factors affecting the survival rate are: histologically high-grade tumor, size and localization of the tumor, vascular invasion, extensive tumor necrosis, certain subgroups, local recurrence and oncologically positive surgical margin at the resection. Many modern reconstruction possibilities are essential for the safe limb saving surgery with wide surgical margins, such as bone allograft implantation, tumor endoprostheses reconstruction, vascular grafting and plastic surgery. There should always be an attempt to perform limb saving surgery, however life quality, life expectancy and survival are more important considerations influencing essentially the surgical method of choice. In our follow-up study no significant difference in recurrence rate was found between the group of patients with sarcomas requiring a complex reconstruction procedure and the group of those treated by only resection methods (32% versus 47%).

[Limb saving surgery in cases of bone sarcomas]. / Végtagmegtartó mûtétek csontsarcomáknál.

At the Orthopedic Department of Semmelweis University we operate an internationally recognized bone and soft tissue tumor center. Our specialty is the treatment of benign and malignant bone tumors, tumor-like lesions and surgery of soft tissue tumors. Our main aim, taking into account the appropriate oncologic radicality, is to create the conditions for the development of limb saving surgery. Limb saving surgery is an interdisciplinary activity both in diagnosis and in treatment. We have proper pathology, radiology and interventional radiology background for the fast and advanced pathomorphological and radiomorphological diagnosis of different tumors. Using modern chemotherapy, radiotherapy and other advanced cancer treatment protocols rapid access to oncology background is provided for children and adults as well, both primary and secondary bone tumors and soft tissue sarcoma cases of the extremities. The limb saving surgery after removal of the tumor is essentially a reconstructive surgery. Reconstructive surgery in childhood and younger ages mean mainly the biological solutions (vascularized autologus bone grafts and/or homologous bone graft), otherwise in elderly ages implantation of tumor endoprostheses has a greater significance. Furthermore, the final tumor surgery requires experienced abdominal surgeon, vascular surgeon and plastic surgeon to ensure the background as well. The professional background of our clinical practice is based on participating in international conferences and spending several months abroad in different big tumor centers. Over the past 15 years, several international cancer congresses were organized in Hungary by our Department.

Epiphysis preserving resection of malignant proximal tibial tumours.

PURPOSE: The purpose of the study was to evaluate the treatment of five patients with proximal tibial epiphysis preserving resection for malignant tumours of the tibia. METHOD: Three patients suffered from Ewing sarcoma, two had osteosarcoma. The proximal level of the resection was in the line of the growth plate in four patients, and 2 cm below of the growth plate in one patient. The distal resection level was in the diaphysis, depending on the tumour border. The resected part of the tibia was substituted by both the ipsilateral and contralateral fibulas. The two fibulas were proximally built into the epiphysis, the contralateral, freely transplanted fibula was placed distally into the tibial diaphysis. The leg was fixed in an Ilizarov frame. RESULTS: The follow-up period was 4.9 years on average (range, 3.5-8 years). Neither local recurrence nor metastasis was noticed in patients with tibia tumour resection during the observation time. Proper fixation of the transplanted fibula with all of the patients, both proximal to the tibia epiphysis and distal to diaphysis, was experienced. The range of motion of the knee was 122° on the average. Two patients can walk without support and three can walk with an orthosis fully weight bearing. The limb shortening of the affected side was 2.6 cm on average (range,1.5-4.5 cm). In three patients the transplanted opposite side fibula has broken. In one patient, chronic osteomyelitis developed at the distal part of the transplanted fibula. CONCLUSIONS: The difficulties of intercalary segment supplementation were present to a greater extent because of the small size of proximal epiphysis, but the preserved knee joint can produce better function for the patient in this limb-saving surgery.

Serum albumin enhances bone healing in a nonunion femoral defect model in rats: a computer tomography micromorphometry study.

PURPOSE: Blood-derived proliferative factors such as platelet rich plasma or activated plasma are promising adjuvants for bone grafts. Our earlier studies showed that serum albumin itself can markedly enhance the proliferation of stem cells on bone allograft and postulated that albumin coating alone may improve bone graft integration in vivo. METHODS: Two femoral defect models were performed in adult male Wistar rats. In the critical size model a six millimetre gap was created in the midshaft of the femur and fixed with plate and screws, while a nonunion model was established by the interposition of a spacer in the osteotomy for four weeks which resulted in compromised healing and nonunion. Albumin coated and uncoated grafts were placed into the defects. Bone healing and morphometry were evaluated by µCT and histology four weeks after implantation of the grafts. RESULTS: In the critical size model none of the bone grafts were able to bridge the defect, and graft resorption was the typical outcome. In the nonunion model regular uncoated grafts had a low union rate (two out of six), which increased markedly when albumin coating was applied (six out of eight). Trabecular thickness and pattern factor improved significantly in the albumin coated group versus uncoated or empty controls. CONCLUSIONS: Our results showed that serum albumin coating of bone grafts can enhance the remodelling and efficacy of treatment in a nonunion model.

[Simplified, low-cost gene expression profiling for the prediction of outcome in breast cancer based on routine histologic specimens]. / Egyszerusített, alacsony költségu génexpressziós teszt az emlodaganatos betegségek kimenetelének elorejelzésére rutin patológiai blokkok felhasználásával.

BACKGROUND: Grade 2 breast carcinomas do not form a uniform prognostic group. AIM: To extend the number of patients and the investigated genes of a previously identified prognostic signature described by the authors that reflect chromosomal instability in order to refine characterization of grade 2 breast cancers and identify driver genes. METHODS: Using publicly available databases, the authors selected 9 target and 3 housekeeping genes that are capable to divide grade 2 breast carcinomas into prognostic groups. Gene expression was investigated by polymerase chain reaction in 249 formalin-fixed, paraffin-embedded breast tumors. The results were correlated with relapse-free survival. RESULTS: Histologically grade 2 carcinomas were split into good and a poor prognosis groups. Centroid-based ranking showed that 3 genes, FOXM1, TOP2A and CLDN4 were able to separate the good and poor prognostic groups of grade 2 breast carcinomas. CONCLUSION: Using appropriately selected control genes, a limited set of genes is able to split prognostic groups of breast carcinomas independently from their grade.

Histomorphometric Analysis of 38 Giant Cell Tumors of Bone after Recurrence as Compared to Changes Following Denosumab Treatment.

Giant cell tumor of bone (GCTB) is an osteolytic tumor driven by an H3F3A-mutated mononuclear cell with the accumulation of osteoclastic giant cells. We analyzed tissue from 13 patients with recurrence and 25 patients with denosumab therapy, including two cases of malignant transformation. We found a decrease in the total number of cells (p = 0.03), but not in the individual cell populations when comparing primary and recurrence. The patients treated with denosumab showed induction of osteoid formation increasing during therapy. The total number of cells was reduced (p < 0.0001) and the number of H3F3A-mutated tumor cells decreased (p = 0.0001), while the H3F3A wild-type population remained stable. The KI-67 proliferation rate dropped from 10% to 1% and Runx2- and SATB2-positive cells were reduced. The two cases of malignant transformation revealed a loss of the H3F3A-mutated cells, while the KI-67 rate increased. Changes in RUNX2 and SATB2 expression were higher in one sarcoma, while in the other RUNX2 was decreased and SATB2-positive cells were completely lost. We conclude that denosumab has a strong impact on the morphology of GCTB. KI-67, RUNX2 and SATB2 expression differed depending on the benign or malignant course of the tumor under denosumab therapy.

Poorly differentiated synovial sarcoma is associated with high expression of enhancer of zeste homologue 2 (EZH2).

BACKGROUND: Enhancer of zeste homologue 2 (EZH2) is a polycomb group (PcG) family protein. Acting as a histone methyltransferase it plays crucial roles in maintaining epigenetic stem cell signature, while its deregulation leads to tumor development. EZH2 overexpression is commonly associated with poor prognosis in a variety of tumor types including carcinomas, lymphomas and soft tissue sarcomas. However, although the synovial sarcoma fusion proteins SYT-SSX1/2/4 are known to interact with PcG members, the diagnostic and prognostic significance of EZH2 expression in synovial sarcoma has not yet been investigated. Also, literature data are equivocal on the correlation between EZH2 expression and the abundance of trimethylated histone 3 lysine 27 (H3K27me3) motifs in tumors. METHODS: Immunohistochemical stains of EZH2, H3K27me3, and Ki-67 were performed on tissue microarrays containing cores from 6 poorly differentiated, 39 monophasic and 10 biphasic synovial sarcomas, and evaluated by pre-established scoring criteria. Results of the three immunostainings were compared, and differences were sought between the histological subtypes as well as patient groups defined by gender, age, tumor location, the presence of distant metastasis, and the type of fusion gene. The relationship between EZH2 expression and survival was plotted on a Kaplan-Meier curve. RESULTS: High expression of EZH2 mRNA and protein was specifically detected in the poorly differentiated subtype. EZH2 scores were found to correlate with those of Ki-67 and H3K27me3. Cases with high EZH2 score were characterized by larger tumor size (≥ 5cm), distant metastasis, and poor prognosis. Even in the monophasic and biphasic subtypes, higher expression of EZH2 was associated with higher proliferation rate, larger tumor size, and the risk of developing distant metastasis. In these histological groups, EZH2 was superior to Ki-67 in predicting metastatic disease. CONCLUSIONS: High expression of EZH2 helps to distinguish poorly differentiated synovial sarcoma from the monophasic and biphasic subtypes, and it is associated with unfavorable clinical outcome. Importantly, high EZH2 expression is predictive of developing distant metastasis even in the better-differentiated subtypes. EZH2 overexpression in synovial sarcoma is correlated with high H3K27 trimethylation. Thus, along with other epigenetic regulators, EZH2 may be a future therapeutic target.

Variability of gait parameters in patients with total knee arthroplasty.

PURPOSE: Gait analysis has provided important information about the variability of gait for patients prior to and after total knee arthroplasty (TKA). The objective of this research was to clarify how the different surgical techniques influence gait variability. METHODS: Gait analysis was performed at 0.8, 1.0, and 1.2 m/s in three groups of patients (operated on using the conventional technique, conventional technique combined with computer-assisted navigation, and the minimally invasive technique combined with computer-assisted navigation; n = 15 each) and a control group (n = 15; healthy, age, body mass, and body height matched). Gait analysis was performed preoperatively and 6 and 12 months after the surgery. Gait parameter variability was characterized by the coefficient of variance of spatio-temporal parameters and by the mean coefficient of variance of angular parameters. RESULTS: One year after surgery, the variability of spatio-temporal parameters recovered to normal in patients operated on using the conventional technique; however, the variability of articular motion of the affected side decreased and the variability of articular motion of the non-affected side and pelvis increased compared to the control group. In patients operated on using the minimally invasive technique, the variability of spatio-temporal and angular parameters was similar to that of the control group. CONCLUSION: The type of surgical technique significantly influences the variability and stability of gait. Difference in the variability of angular parameters predicts gait instability and increased risk of falling after TKA with the conventional surgical technique. The minimally invasive technique ensures a recovery of gait variability and stability. Thus, particular attention must be paid to improving gait stability during postoperative rehabilitation. LEVEL OF EVIDENCE: II.