The Effect of Teriparatide on the Hip: A Literature Review / 대한고관절학회지

Teriparatide (TPTD) is a bone-forming agent used to treat postmenopausal osteoporosis. Since hip fractures are related to higher morbidity and mortality rates than other fractures, efficacious osteoporosis drugs for the hip are critical. We reviewed research articles reporting the efficacy of TPTD in terms of bone mineral density (BMD), fractures prevention, changes in the outer diameter, cortical thickness and porosity, post-operative periprosthetic BMD loss, and healing of typical and atypical fractures of the hip. Data meta-analyses indicated that TPTD not only increased the BMD of the proximal femur but also decreased the risk of hip fractures. Even though TPTD increases the cortical bone porosity of the proximal femur, the bone strength does not decrease as the majority of the porosity is located at the endocortex; further, it increases the outer diameter and thickens the cortical bone.TPTD stimulates bone remodeling and facilitates callus maturity and fracture healing. There have been many reports on improving the effect of TPTD on the healing of atypical fractures; therefore it is advisable to use TPTD considering the increase benefit compared to the risk.

Kinematically Aligned Total Knee Arthroplasty with Patient-Specific Instrument

Kinematically aligned total knee arthroplasty (TKA) is a new alignment technique. Kinematic alignment corrects arthritic deformity to the patient's constitutional alignment in order to position the femoral and tibial components, as well as to restore the knee's natural tibial-femoral articular surface, alignment, and natural laxity. Kinematic knee motion moves around a single flexion-extension axis of the distal femur, passing through the center of cylindrically shaped posterior femoral condyles. Since it can be difficult to locate cylindrical axis with conventional instrument, patient-specific instrument (PSI) is used to align the kinematic axes. PSI was recently introduced as a new technology with the goal of improving the accuracy of operative technique, avoiding practical issues related to the complexity of navigation and robotic system, such as the costs and higher number of personnel required. There are several limitations to implement the kinematically aligned TKA with the implant for mechanical alignment. Therefore, it is important to design an implant with the optimal shape for restoring natural knee kinematics that might improve patient-reported satisfaction and function.

Prevalence of Cam Deformity with Associated Femoroacetabular Impingement Syndrome in Hip Joint Computed Tomography of Asymptomatic Adults / 대한고관절학회지

PURPOSE: Femoroacetabular impingement (FAI) is considered an important cause of early degenerative arthritis development. Although three-dimensional (3D) imaging such as computed tomography (CT) and magnetic resonance imaging are considered precise imaging modalities for 3D morphology of FAI, they are associated with several limitations when used in out-patient clinics. The paucity of FAI morphologic data in Koreans makes it difficult to select the most effective radiographical method when screening for general orthopedic problems. We postulate that there might be an individual variation in the distribution of cam deformity in the asymptomatic Korean population. MATERIALS AND METHODS: From January 2011 to December 2015, CT images of the hips of 100 subjects without any history of hip joint ailments were evaluated. A computer program which generates 3D models from CT scans was used to provide sectional images which cross the central axis of the femoral head and neck. Alpha angles were measured in each sectional images. Alpha angles above 55° were regarded as cam deformity. RESULTS: The mean alpha angle was 43.5°, range 34.7–56.1°(3 o'clock); 51.24°, range 39.5–58.8°(2 o'clock); 52.45°, range 43.3–65.5°(1 o'clock); 44.09°, range 36.8–49.8°(12 o'clock); 40.71, range 33.5–45.8°(11 o'clock); and 39.21°, range 34.1–44.6°(10 o'clock). Alpha angle in 1 and 2 o'clock was significantly larger than other locations (P < 0.01). The prevalence of cam deformity was 18.0% and 19.0% in 1 and 2 o'clock, respectively. CONCLUSION: Cam deformity of FAI was observed in 31% of asymptomatic hips. The most common region of cam deformity was antero-superior area of femoral head-neck junction (1 and 2 o'clock).

Fracture Preventing Effects of Maxmarvil® Tablets (Alendronate 5 mg + Calcitriol 0.5 µg) in Patients with Osteoporosis

BACKGROUND: The purpose of this prospective, open-label, observational study was to assess the fracture preventing effect of Maxmarvil® tablets (alendronate 5 mg + calcitriol 0.5 µg) in patients with osteoporosis and to evaluate the change in bone mineral density (BMD) at the minimum 1-year follow-up. METHODS: In this multicenter observational study, 691 patients with osteoporosis (aged 50 years or older) were treated with alendronate 5 mg + calcitriol 0.5 µg/day during their normal course of care. Patients were assessed at baseline and at 6 and 12 months. Baseline characteristics (including age, gender, concomitant disease, and baseline fractures) were evaluated. RESULTS: From among the 848 participants, 149 individuals were lost to follow-up at the time of the study and 8 people had died. The 691 participants (54 men and 637 women) finished the follow-up study and completed the questionnaire. The mean age of the participants was 71.5 years (range, 50–92 years; mean age, 72.3 years for men and 71.4 years for women). Osteoporotic fracture occurred in 19 patients (2.7%). BMD of the lumbar spine and hip was improved by 5% and 1.5% at the latest follow-up. At the latest follow-up, 24 patients (3.5%) complained of drug-related complications such as dyspepsia, constipation, and nausea. CONCLUSIONS: This prospective observational study demonstrated that alendronate 5 mg + calcitriol 0.5 µg/day had a preventive effect on osteoporotic fracture and it increased the BMD of the lumbar spine by 5% at the latest follow-up.

The Efficacy of Low Molecular Weight Heparin for the Prevention of Venous Thromboembolism after Hip Fracture Surgery in Korean Patients

PURPOSE: The aim of this study was to investigate the efficacy of low-molecular-weight heparin (LMWH) for the prevention of venous thromboembolism in Korean patients who underwent hip fracture surgery (HFS). MATERIALS AND METHODS: Prospectively, a total 181 cases were classified into the LMWH user group (116 cases) and LMWH non-user group (65 cases). Each group was sub-classified according to fracture types as follows: 81 cases of intertrochanteric fracture (group A: 49, group B: 32) and 100 cases of neck fracture (group C: 67, group D: 33). We compared the incidence of deep vein thrombosis (DVT) and pulmonary embolism (PE) according to LMWH use. RESULTS: Of the 181 cases, four DVTs were found in the LMWH user groups (1 in group A, and 3 in group C). One case of PE was found in LMWH non-user group D. The incidences of DVT and PE showed no statistically significant differences between the LMWH user and non-user groups (p=0.298 and 0.359, respectively). In subgroup analysis, no statistically significant differences were found between groups A and B and between groups C and D. CONCLUSION: The administration of LMWH was not effective in the prevention of venous thromboembolism and PE in the Korean patients who underwent HFS.

Bone Mineral Density and Fatty Degeneration of Thigh Muscles Measured by Computed Tomography in Hip Fracture Patients

BACKGROUND: Recently, as an independent fracture factor from Bone mineral density (BMD), muscle weakness due to the fatty degeneration of thigh muscles have been attracting attentions as causes of hip fracture. The purpose of this study is to investigate the correlation between the body composition and BMD and fatty degeneration of thigh muscles of the female patients over 65 years old with osteoporotic hip fracture. METHODS: This study was conducted with 178 female osteoporotic hip fracture patients. Total hip BMD was measured using dual energy X-ray absorptiometry. Cross-sectional area (CSA), cross-sectional muscle area (CSmA), muscle attenuation coefficient (MAC), and intramuscular adipose tissue (IMAT) of gluteus maximus, hip abductors, quadriceps and hamstring muscle were measured with computed tomography. Normalized IMAT (nIMAT) was calculated by dividing the fat area in the muscle into the size of each muscle. The correlation between each measurement is examined then the differences between the intertrochanteric fracture group and the femoral neck fracture group were analyzed. RESULTS: CSmA and MAC of quadriceps were the largest and nIMAT was the lowest. CSA and CSmA of the four muscles showed a statistically significant positive correlation with weight, height, body mass index (BMI), and BMD. MAC of 2 gluteal muscles was positively correlated with weight, BMI and BMD. nIMAT of all four muscles was positively correlation with weight and BMI but nIMAT of 2 mid-thigh muscles was positively correlation with BMD. CONCLUSIONS: Muscle size and fatty degeneration in the thigh muscles were most positively correlated with the body weight. BMD was positively correlation with CSA and CSmA of all thigh muscles, and MAC of 2 gluteal muscles and fatty degeneration of 2 mid-thigh muscles. There was no statistically significant difference in the size of the femoral muscle and the degree of fatty degeneration between the two fracture groups.

Sarcopenia and Sarcopenic Obesity in Patients Undergoing Orthopedic Surgery

BACKGROUND: The purpose of this retrospective study was to determine the prevalence of sarcopenia and sarcopenic obesity among patients who underwent orthopedic surgery (OS). METHODS: A total of 222 patients were reviewed immediately after or prior to OS. In the control group, 364 patients from outpatient departments (OPDs) who did not have any OS were enrolled. Whole-body dual-energy X-ray absorptiometry was used to analyze body composition. Skeletal muscle mass was adjusted for height squared, total body weight, and height and fat mass (residuals). Obesity was defined as body mass index (BMI) > 25.0 kg/m2. RESULTS: The prevalence of sarcopenia in the OS group was 25.7%, 44.1%, and 26.6%, respectively, according to the 3 different criteria. The prevalence was significantly lower in the OPD group (6.0%, 33.1%, and 14.8%, respectively). The highest rates of sarcopenia with height-adjusted definition were seen in patients with a femoral neck fracture. In the multivariate analysis, factors associated with sarcopenia were male gender, older age, and lower BMI (odds ratio [OR]: 28.38, 1.03, and 1.83, respectively) when muscle mass was adjusted for height, whereas male gender, older age, and higher BMI were associated with sarcopenia (OR: 1.04, 2.57, and 1.83, respectively) when adjusted for weight. When residuals were used as a cutoff, decreased BMI and total hip bone mineral density (0.1 g/cm2) were independent risk factors associated with sarcopenia (OR: 1.09 and 1.05). The prevalence of sarcopenic obesity ranged from 1.8% to 21.2%. CONCLUSIONS: Our study demonstrated a high prevalence of sarcopenia among OS patients.

Sarcopenia and Sarcopenic Obesity in Patients Undergoing Orthopedic Surgery

BACKGROUND: The purpose of this retrospective study was to determine the prevalence of sarcopenia and sarcopenic obesity among patients who underwent orthopedic surgery (OS). METHODS: A total of 222 patients were reviewed immediately after or prior to OS. In the control group, 364 patients from outpatient departments (OPDs) who did not have any OS were enrolled. Whole-body dual-energy X-ray absorptiometry was used to analyze body composition. Skeletal muscle mass was adjusted for height squared, total body weight, and height and fat mass (residuals). Obesity was defined as body mass index (BMI) > 25.0 kg/m2. RESULTS: The prevalence of sarcopenia in the OS group was 25.7%, 44.1%, and 26.6%, respectively, according to the 3 different criteria. The prevalence was significantly lower in the OPD group (6.0%, 33.1%, and 14.8%, respectively). The highest rates of sarcopenia with height-adjusted definition were seen in patients with a femoral neck fracture. In the multivariate analysis, factors associated with sarcopenia were male gender, older age, and lower BMI (odds ratio [OR]: 28.38, 1.03, and 1.83, respectively) when muscle mass was adjusted for height, whereas male gender, older age, and higher BMI were associated with sarcopenia (OR: 1.04, 2.57, and 1.83, respectively) when adjusted for weight. When residuals were used as a cutoff, decreased BMI and total hip bone mineral density (0.1 g/cm2) were independent risk factors associated with sarcopenia (OR: 1.09 and 1.05). The prevalence of sarcopenic obesity ranged from 1.8% to 21.2%. CONCLUSIONS: Our study demonstrated a high prevalence of sarcopenia among OS patients.

Sarcopenia and Osteoporosis / 대한고관절학회지

Public health strategies designed to accomodate the ever-increasing human lifespan are urgently required. A good clinical understanding of frailty, as well as knowledge regarding how to prevent it, will therefore be required in order to overcome this challenge. Sarcopenia is an important component of the frailty syndrome, and its association with osteoporosis can lead to fractures and incident disability. Therefore, this review examined the literatuire pertaining to the association of sarcopenia with osteoporosis in order to assess preventive strategies.

Changes in Bone Mineral Density of Both Proximal Femurs after Total Knee Arthroplasty

BACKGROUND: This study investigated the effects of total knee arthroplasty (TKA) on bone mineral density (BMD) of the proximal femur in patients who underwent the procedure. METHODS: Forty-eight patients scheduled to undergo unilateral TKA because of primary knee osteoarthritis were included in this study, which was conducted at a medical center between October 2006 and October 2009. In these 48 patients, 96 hips were evaluated. Measurement of BMD was performed preoperatively and one month, three months, six months, and one year after unilateral TKA. Repeated measured analysis of variance and paired t-tests for comparison of two repeated samples were used to compare differences between time points (preoperation, one, three, six, and 12 months) and between the operative and nonoperative sides. RESULTS: Preoperatively, BMD of the femoral neck, trochanter, and total hip on the operative side were lower than on the nonoperative side; however, there was no statistical difference. BMD of both femoral neck areas was significantly lower than preoperative BMD at one month and three months after TKA. BMD of both trochanter areas was significantly lower than preoperative BMD at one month and three months after TKA. BMD of both total hips was significantly lower than preoperative BMD at three months after TKA. However, no statistical differences of changes in BMD were observed between the operative and nonoperative sides at each measurement time. CONCLUSIONS: According to our results, TKA was found to affect both proximal femurs during the acute period. However, TKA did not affect a change in BMD of the proximal femur during one year postoperative.

The Effects of Timing of Tourniquet Release on Blood Loss in Navigation Assisted Total Knee Arthroplasty / 대한정형외과학회잡지

PURPOSE: The aim of this study is to evaluate the effects of timing of tourniquet release on blood loss in navigation assisted total knee arthroplasty. MATERIALS AND METHODS: A total of 63 consecutive patients, who underwent navigation assisted total knee arthroplasty, were divided into two groups; 31 patients (31 knees, group I) were operated with tourniquet release after wound closure and applied compression dressing, and another 32 patients (32 knees, group II) were operated with tourniquet release and hemostasis before implantation of the polyethylene insert. We examined hemoglobin concentration and hematocrit at three points in time, preoperatively, 24 hours and 48 hours postoperatively. We compared the two groups of patients in terms of total blood loss, postoperative drained blood loss, hidden blood loss, visible blood loss and operation time. RESULTS: There were no significant differences between the two groups in the hemoglobin concentration at 24 hours and 48 hours postoperatively (p=0.371, p=0.247), and hematocrit at 24 hours and 48 hours postoperatively (p=0.428, p=0.125). No statistically significant differences between the two groups in the postoperative drained blood loss (p=0.381) and total blood loss (p=0.126) were found. We found statistically significant differences in the visible blood loss (p=0.023), hidden blood loss (p=0.045) and operation time (p=0.005). CONCLUSION: The releasing time of tourniquet have no effect on the actual total blood loss, and postoperative drained blood loss in navigation assisted total knee arthroplasty. We concluded that compared with intraoperative tourniquet release, postoperative tourniquet release are useful for making the broader operation field and less operation time.

Bone Mineral Density Changes after Total Knee Replacement in Women Over the Age of 65

BACKGROUND: There are few reports on bone mineral density (BMD) changes of axial bones after total knee replacement (TKR) due to severe osteoarthritis (OA) of the knee joint and its results are controversial. The purpose of our study was to measure the BMD changes of hip and spine in patients receiving TKR due to severe OA and to identify clinical factors relating BMD changes. METHODS: Among 66 female patients above 65 years old who underwent TKR due to severe OA and checked preoperative BMD, 52 patients who checked 1 year follow up BMD were enrolled. We investigated the association of the BMD changes with bilaterality of operation, obesity, preoperative knee functional scores, bisphosphonate medication, and diagnosis of osteoporosis. RESULTS: We found no correlation between BMD changes and bilaterality of operation, obesity, preoperative knee functional scores and diagnosis of osteoporosis. Spine BMD increased in non-treatment and bisphosphonate treatment group but total hip BMD significantly increased in bisphosphonate treatment group. CONCLUSIONS: Bisphosphonate treatment for 1 year prevents early reduction of hip BMD just after TKR regardless osteoporosis diagnosis. We considered that the bisphosphonate medication would be beneficial to prevention of later hip fracture in elderly patient receiving TKR due to severe OA of knee joints.

Comparison of the Radiologic Outcomes following the Kinds of Implants in Treating Unstable Osteoporotic Intertrochanteric Fracture / 대한골다공증학회지

OBJECTIVES: To determine whether kinds of implants would influence on the radiologic outcomes in the treatment of unstable osteoporotic intertrochanteric fractures. MATERIALS AND METHODS: In this retrospective study, radiologic outcomes of 151 patients with unstable osteoporotic intertrochanteric fractures undergoing surgical treatments were compared based on the types of fixation implants as follows : PFNA (53 cases, group I), gamma nail 3(31 cases, group II), CHS with TSP (43 cases, group III), and helical blade type LCP-DHS with TSP (24 cases, group IV). On the follow-up radiographs after operations, we assessed differences of bone union durations, neck-shaft ankle changes, lag screw or helical blade slippages, and varus alpha angle changes among the study groups. RESULTS: All the radiologic outcomes evaluated in this study were not significantly different among the study groups. The average bone union durations of the group I, II, III and IV were 17.7, 18.0, 18.2, and 17.8 weeks, respectively (P=0.429). The average variation of neck-shaft angle of the group I, II, III and IV were 3.6degrees, 3.1degrees, 3.7degrees and 2.9degrees, respectively (P=0.273). The average lag screw or blade slippage of the group I, II, III and IV were 5.1 mm, 3.3 mm, 3.6 mm and 2.7 mm, respectively (P=0.154). The average variation of varus alpha of the group I, II, III and IV were 5.3degrees, 4.7degrees, 4.1degrees and 4.6masculine, respectively (P=0.894). CONCLUSIONS: This study indicates that four typical types of fixation implants for treating unstable osteoporotic intertrochanteric fractures would not lead to differences in postoperative radiological outcomes.

Changes in the Microstructural and Mechanical Properties in the Medial Condyle of Human Distal Femur in Advanced Osteoarthritis / 대한골다공증학회지

OBJECTIVES: The purpose of this study is to analyze and compare the micro-structural and mechanical properties of subchondral trabecular bone of non-osteoarthritic and osteoarthritic distal femur using micro-images based on finite element analysis. MATERIALS AND METHODS: Twenty distal femurs were harvested from 10 cadavers. The subchondral trabeculae were obtained from the middle of the articular surface of the medial femoral condyle of distal femurs. A total of 20 specimens were scanned using the micro-CT system. Micro-CT images were converted to micro-finite element model using the mesh technique, and micro-finite element analysis was then performed for assessment of the mechanical properties. RESULTS: According to the results, trabecular bone of osteoarthritic distal femur showed a decrease in trabecular thickness, bone volume fraction, structure model index, and yield stress and an increase in trabecular separation and structure model index. CONCLUSIONS: Results of bone morphometry index and strength showed greater deterioration of microstructure and decreased mechanical strength in subchondral trabeculae of the osteoarthritic group.

Optimal Pelvic Inlet and Outlet Radiograph Angles in Korean Patients / 대한정형외과학회잡지

PURPOSE: Until now, pelvic injuries have been evaluated with 45degrees inlet and 45degrees outlet radiographs. Following these customary guidelines may not produce the best plane to evaluate pelvic injury due to variability of pelvic anatomy. Recent data based on the American population suggested 25degrees and 60degrees as the optimal angle for each inlet and outlet views, respectively. We hypothesized that inlet and outlet radiographic views to examine the clinically relevant landmarks vary from routine 45degrees inlet and outlet views and aimed to find optimal angles for Korean patients. MATERIALS AND METHODS: One hundred consecutive patients, aged between 30 to 60 years (50 male and 50 female patients), without pelvic ring disruption or fractures who had undergone routine axial pelvic computed tomography scans were retrospectively identified. The optimal inlet and outlet angles required to profile the clinically relevant pelvic anatomy were quantified for each patient. RESULTS: The optimal inlet angle to profile the anterior body of S1 and S2 required an average caudal tilt of 24.2degrees and 27.9degrees, respectively. The average outlet angle perpendicular to the body of S1 was 54.8degrees and perpendicular to S2 was 52.3degrees. The optimal angles were the same for male and female patients and were independent of patient age. CONCLUSION: Screening inlet and screening outlet radiographs made at 25degrees and 55degrees, respectively, are recommended for viewing clinically relevant osseous pelvic anatomy in Koreans.

Three Dimensional CT-based Virtual Patellar Resection in Female Patients Undergoing Total Knee Replacement: A Comparison between Tendon and Subchondral Method

BACKGROUND: Due to its small size, variable shape, and lack of distinct anatomical landmarks, osteoarthritic knees make a precise patellar resection extremely difficult. METHODS: We performed virtual patellar resection with digital software using three dimensional computed tomography scans of knees from 49 patients who underwent primary total knee replacement at our hospital. We compared 2 commonly used resection methods, the tendon method (TM) and the subchondral method, to determine an ideal resection plane with respect to the symmetry and thickness of the patellar remnant. RESULTS: The TM gave a thicker resected patella, and a less oval cut surface shape, which gives better coverage for a domed prosthesis. Both methods, however, gave a symmetric resection both superior-inferiorly, as well as mediolaterally. CONCLUSIONS: Although TM appears statistically better with respect to the thickness and cut surface shape, only further intraoperative studies with long-term clinical follow-up may provide us with the most appropriate patellar resection method.

Acute Gluteal Compartment Syndrome without Gluteal Hematoma: A Case Report / 대한고관절학회지

Acute gluteal compartment syndrome (AGCS) is a rare condition associated with trauma, drug abuse, alcohol intoxication, prolonged immobilization, hip arthroplasty and epidural anesthesia. We report the case of a 42-year-old woman presenting severe buttock pain following decreased lower extremity motor function after an incident whereby she rolled down a flight of stairs. We performed fasciotomy of the gluteal fascia in order to provide relief from acute gluteal compartment syndrome. At the 2 month follow up visit her sensory and motor function had improved. Acute gluteal compartment syndrome is a rare condition which can result in misdiagnosis or delayed diagnosis. Careful consideration is needed for patients suffering severe buttock pain.

Acute Gluteal Compartment Syndrome without Gluteal Hematoma: A Case Report / 대한고관절학회지

Acute gluteal compartment syndrome (AGCS) is a rare condition associated with trauma, drug abuse, alcohol intoxication, prolonged immobilization, hip arthroplasty and epidural anesthesia. We report the case of a 42-year-old woman presenting severe buttock pain following decreased lower extremity motor function after an incident whereby she rolled down a flight of stairs. We performed fasciotomy of the gluteal fascia in order to provide relief from acute gluteal compartment syndrome. At the 2 month follow up visit her sensory and motor function had improved. Acute gluteal compartment syndrome is a rare condition which can result in misdiagnosis or delayed diagnosis. Careful consideration is needed for patients suffering severe buttock pain.

Femoral Neck Anteversion Measured Using a 3D CT Scan Perpendicular to the Mechanical Axis of the Femur

PURPOSE: We wanted to measure the femoral neck anteversion (FNA) angles using a 3D CT scan that perpendicularly cut the mechanical axis of the femur and to assess the accuracy and reproducibility of different measuring methods. MATERIALS AND METHODS: We obtained 95 cases of 3D CT images of the cross-section perpendicular to the mechanical axis of the femur. The methods used to measure the FNA angles included a method using the CT image of the area where the femoral neck is confluent to the greater trochanter (method 1), a method using the CT image taken from the neck base immediately prior to the beginning of the area of the lesser trochanter (method 2) and a method by which measurements are made after putting 3D bone models on a horizontal plane in virtual space (method 3). The reference axes of the distal femur we used were the anatomical transepicondylar axis, the surgical transepicondylar axis and the real posterior condylar axis. RESULTS: The FNA angles measured by method 1 were 4.79+/-6.41degrees to the anatomical transepicondylar axis (ATEA), 6.09+/-6.58degrees to the surgical transepicondylar axis (STEA) and 7.96+/-6.81degrees to the real posterior condylar axis (rPCA). The FNA angles measured by method 2 were 16.01+/-8.31degrees to the ATEA, 19.52+/-8.38degrees to the STEA and 21.79+/-8.52degrees to the rPCA. The FNA angles measured by method 3 were 20.15+/-12.89degrees to the rPCA. CONCLUSION: The measurement of the FNA angle using a 3D CT scan perpendicular to the mechanical axis is reproducible. The measurement method on the neck base level is more reliable than the one on the proximal neck confluence, and more similar to the measurement method by classic definition.

Navigation-Assisted Total Knee Arthroplasty for the Knee Retaining Femoral Intramedullary Nail, and Distal Femoral Plate and Screws

Proper ligament balancing, restoration of the mechanical axis and component alignment are essential for the success and longevity of a prosthesis. In conventional total knee arthroplasty (TKA), an intramedullary guide is used to improve the alignment. An extramedullary guide can be used in cases of severe femoral bowing or intramedullary nailing but its use is more subjective and relies on the surgeon's experience. This paper reports two successful cases of navigation-assisted TKA for severe right knee osteoarthritis retaining a femoral intrameullary nail, and left knee osteoarthritis retaining a distal femoral plate.