Surgical technique of lateral unicompartmental knee arthroplasty and discussion of the maximum correction value in the treatment of knee valgus deformity / 中国修复重建外科杂志

OBJECTIVE@#To investigate the surgical technique and the short-term effectivenss of lateral unicompartmental knee arthroplasty (LUKA) through lateral approach in the treatment of valgus knee and to calculate the maximum value of the theoretical correction of knee valgus deformity.@*METHODS@#A retrospective analysis was performed on 16 patients (20 knees) who underwent LUKA and met the selection criteria between April 2021 and July 2022. There were 2 males and 14 females, aged 57-85 years (mean, 71.5 years). The disease duration ranged from 1 to 18 years, with an average of 11.9 years. Knee valgus was staged according to Ranawat classification, there were 6 knees of type Ⅰ, 13 knees of type Ⅱ, and 1 knee of type Ⅲ. All patients were assigned the expected correction value of genu valgus deformity by preoperative planning, including the correction value of lateral approach, intra-articular correction value, and residual knee valgus deformity value. The actual postoperative corrected values of the above indicators were recorded and the theoretical maximum correctable knee valgus deformity values were extrapolated. The operation time, intraoperative blood loss, incision length, hospital stay, hip-knee-ankle angle (HKA), mechanical lateral distal femoral angle (mLDFA), mechanical medial proximal tibia angle (mMPTA), joint line convergence angle (JLCA), posterior tibial slope (PTS), range of motion (ROM), Hospital for Special Surgery (HSS) score, and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score were also recorded for effectiveness evaluation.@*RESULTS@#The patients' incision length averaged 13.83 cm, operation time averaged 85.8 minutes, intraoperative blood loss averaged 74.9 mL, and hospital stay averaged 6.7 days. None of the patients suffered any significant intraoperative neurological or vascular injuries. All patients were followed up 10-27 months, with a mean of 17.9 months. One patient with bilateral knee valgus deformities had intra-articular infection in the left knee at 1 month after operation and the remaining patients had no complication such as prosthesis loosening, dislocation, and infection. The ROM, HSS score, and WOMAC score of knee joint significantly improved at each time point after operation when compared to those before operation, and the indicators further improved with time after operation, the differences were all significant ( P<0.05). Imaging measurement showed that HKA, mLDFA, JLCA, and PTS significantly improved at 3 days after operation ( P<0.05) except for mMPTA ( P>0.05). Postoperative evaluation of the knee valgus deformity correction values showed that the actual intra-articular correction values ranged from 0.54° to 10.97°, with a mean of 3.84°. The postoperative residual knee valgus deformity values ranged from 0.42° to 5.30°, with a mean of 3.59°. The actual correction values of lateral approach ranged from 0.21° to 12.73°, with a mean of 4.26°.@*CONCLUSION@#LUKA through lateral approach for knee valgus deformity can achieve good early effectiveness. Preoperative planning can help surgeons rationally allocate the correction value of knee valgus deformity, provide corresponding treatment strategies, and the maximum theoretical correction value of knee valgus deformity can reach 25°.

Effect of prosthetic joint line installation height errors on insert wear in unicompartmental knee arthroplasty / 生物医学工程学杂志

The clinical performance and failure issues are significantly influenced by prosthetic malposition in unicompartmental knee arthroplasty (UKA). Uncertainty exists about the impact of the prosthetic joint line height in UKA on tibial insert wear. In this study, we combined the UKA musculoskeletal multibody dynamics model, finite element model and wear model to investigate the effects of seven joint line height cases of fixed UKA implant on postoperative insert contact mechanics, cumulative sliding distance, linear wear depth and volumetric wear. As the elevation of the joint line height in UKA, the medial contact force and the joint anterior-posterior translation during swing phase were increased, and further the maximum von Mises stress, contact stress, linear wear depth, cumulative sliding distance, and the volumetric wear also were increased. Furthermore, the wear area of the insert gradually shifted from the middle region to the rear. Compared to 0 mm joint line height, the maximum linear wear depth and volumetric wear were decreased by 7.9% and 6.8% at -2 mm joint line height, and by 23.7% and 20.6% at -6 mm joint line height, the maximum linear wear depth and volumetric wear increased by 10.7% and 5.9% at +2 mm joint line height, and by 24.1% and 35.7% at +6 mm joint line height, respectively. UKA prosthetic joint line installation errors can significantly affect the wear life of the polyethylene inserted articular surfaces. Therefore, it is conservatively recommended that clinicians limit intraoperative UKA joint line height errors to -2-+2 mm.

Long-Term Mechanical Property Prediction of the Proximal Tibia after Knee Arthroplasty / 医用生物力学

Objective To study the short-term variation patterns of graft viscosity after anterior cruciate ligament reconstruction (ACLR) surgery. Methods Six male New Zealand rabbits were selected. The ACLR animal model of unilateral knee was made with Achilles tendon as the graft. The experimental rabbits were euthanized 15 days after ACLR surgery, with removal of the graft, healthy anterior cruciate ligament (ACL) and Achilles tendon. The cross-sectional area and viscosity coefficient of the graft were measured, and the creep experiments were carried out under equilibrium conditions of 0.1 MPa and 1 MPa, respectively. The viscosity coefficent was calculated. Variation patterns of graft viscosity were summarize. The grafts were compared with healthy ACL. Results The cross-sectional area of the graft increased slowly within 15 days after ACLR surgery. The viscosity of ACL and graft changed nonlinearly. The viscosity coefficient was quite different under different stresses. The viscosity coefficient of the graft decreased with the time after ACLR surgery, which was more obviously under the condition of low stress. Conclusions The results are helpful to guide the implementation of early postoperative rehabilitation plan after ACLR surgery .

The influence of UKA Installation Error of Joint Line on Contact Mechanics and Kinematics of Knee Joint / 医用生物力学

Objective Aiming at the medial prosthetic loosening failure and lateral cartilage degeneration after unicompartmental knee arthroplasty ( UKA), the effects of prosthetic installation errors of joint line in UKA on knee contact mechanics and kinematics during different physiologic activities were studied using musculoskeletal multi-body dynamic method. Methods Taking the medial natural joint line as 0 mm error, six installation errors ofjoint line including ±2 mm, ±4 mm and ±6 mm were considered respectively, and seven musculoskeletal multi body dynamic models of medial UKA were established, to comparatively study the variations in knee contact mechanics and kinematics during walking and squatting. Results At 70% of walking gait cycle, compared with 0 mm error, the medial prosthetic contact force was increased by 127. 3% and the contact force of the lateral cartilage was decreased by 12. 0% under 2 mm elevation in joint line, the medial prosthetic contact force was close to 0 N, but the lateral cartilage contact forces were increased by 10. 1% under 4 mm reduction in joint line. The tibiofemoral total contact forces were increased by 19. 7% and decreased by 14. 2% under 2 mm elevation and 2 mm reduction in joint line, respectively. At the 100°knee flexion during squatting, compared with 0 mm error, the medial prosthetic contact force and the tibiofemoral total contact force increased by 31. 6% and 11. 1% under 2 mm elevation in joint line, and decreased by 24. 5% and 8. 5% under 2 mm reduction in joint line, respectively. The change in the lateral cartilage contact force was not marked. Moreover, at 70% of walking gait cycle, the varus angle decreased, the internal rotation and the anterior translation increased along with the elevation of joint line in UKA, while it was just the opposite along with the reduction of joint line in UKA. The trends of the varus valgus movement and anterior-posterior translation during squatting were consistent with those during swing phase of walking, but the trend of the internal-external rotation was opposite. Conclusions In order to reduce the risk of medial prosthetic loosening failure and lateral cartilage degeneration, it is recommended that the installation error of joint line in UKA should be controlled in the range of -2 mm to +2 mm. This study provides theoretical basis for UKA clinical failure caused by changes in joint line

Effect of Pin Holes Location of Unicompartmental Knee Arthroplasty on Postoperative Tibial Plateau Mechanical Properties / 中国医疗器械杂志

OBJECTIVE@#The purpose of this study is to explore the biomechanical characteristics of the tibia after unicompartmental knee arthroplasty with different distributions of two-pin holes, and to optimize the two-pin holes scheme to reduce the risk of tibial fractures after unicompartmental knee arthroplasty.@*METHODS@#Lower limbs model is segmented and reconstructed from computed tomography images. Four combinations of two pin holes created for tibial cutting guide placement are simulated with finite element analysis.@*RESULTS@#In the third mode, the positioning hole at the proximal medial edge of the tibial plateau has the highest stress value, and the position of the positioning hole near the medial edge of the proximal tibial plateau appears stress concentration.@*CONCLUSIONS@#The present study revealed that placing tibial cutting guide holding pins centrally would lower the risks of periprosthetic fracture of the medial tibial plateau.

Effect of motor imagery on knee function after unicompartmental knee arthroplasty / 中国康复理论与实践

ObjectiveTo explore the effect of motor imagery (MI) on knee function after unicompartmental knee arthroplasty (UKA). MethodsFrom January to September, 2022, 32 patients underwent UKA for the first time in Xuanwu Hospital were randomly divided into control group (n = 16) and experimental group (n = 16). All the patients accepted routine rehabilitation, and the experimental group accepted MI in addition, until four weeks after discharge. They were assessed with Oxford Knee Score (OKS), Visual Analogue Scale for pain (VAS), range of motion (ROM) of knee, and Timed Up and Go Test (TUGT) before and after treatment. ResultsAll the indexes improved after treatment (|t| > 2.517, P < 0.05), except ROM in the control group; and they improved more in the experimental group than in the control group (F > 7.999, P < 0.01), except the VAS score. ConclusionMI can further improve the knee function after UKA, but do less for pain.

Research of early outcomes of cementless Oxford unicompartmental knee arthroplasty / 中华骨科杂志

Objective:To assess the early clinical outcomes of Oxford cementless unicompartmental knee arthroplasty (UKA) in the management of anteromedial osteoarthritis of the anterior medial knee (AMOA).Methods:A retrospective review was conducted on a cohort of 90 patients who underwent primary UKA for AMOA at the Fuzhou Second Hospital between January 2020 and June 2021. The patients were divided into two groups based on the type of prosthesis used: the cementless UKA group and the cemented UKA group. The cementless UKA group included 45 patients (22 males and 23 females), with a mean age of 65.6±7.0 years (ranging from 52 to 81 years). The cemented UKA group consisted of 45 patients, including 21 males and 24 females, with a mean age of 67.9±6.1 years (ranging from 55 to 79 years). The study compared various parameters between the two groups, including the duration of surgery, amount of blood loss, length of hospitalization, pain visual analogue scale (VAS) scores, Hospital for Special Surgery (HSS) scores, and forgotten joint score (FJS). Additionally, radiolucency around the prosthesis, medial proximal tibial angle (MPTA), and mechanical axis deviation (MAD) were observed and measured before and after surgery to assess prosthesis stability, improvement of knee deformity, and knee joint mobility, respectively.Results:Both groups were followed up for a minimum of 18 months. No statistically significant differences were found in demographic data such as gender, age, and body mass index between the two groups. The cementless UKA group demonstrated superior results in terms of shorter duration of surgery (97.8±21.1 min) and less blood loss (70.8±37.6 ml) compared to the cemented UKA group ( P<0.05). However, no significant difference in length of stay was observed between the groups. Postoperative VAS scores, HSS scores, MPTA, and MAD were significantly improved compared to preoperative values in both groups ( P<0.05). The median VAS scores for the cementless UKA group at 6, 12, and 18 months postoperatively were 4.0(3.0, 5.0), 2.0(2.0, 3.0), and 2.0(1.0, 3.0) respectively. The corresponding median HSS scores for the cemented UKA group were 78(75, 82), 85 (80, 89), and 86(82, 90) preoperatively and at 6, 12, and 18 months postoperatively, respectively. The median FJS scores for the cementless UKA group were 73.0(70.5, 76.0), 76.0(74.0, 78.0), and 66.0(63.0, 68.0) preoperatively and at 6, 12, and 18 months postoperatively, respectively. There was no statistically significant relationship between preoperative VAS scores and preoperative FJS scores ( P>0.05). However, there was a significant difference in VAS scores between the two groups at 6 months postoperatively ( P<0.05). The cementless UKA group consistently exhibited better VAS scores and HSS scores compared to the cemented UKA group at 6, 12, and 18 months postoperatively ( P<0.05). The median MPTA values for the cementless UKA group were 85.41°(84.22°, 86.54°), 85.80°(84.74°, 87.41°), 86.51°(85.47°, 88.14°), and 86.80°(86.09°, 88.27°) preoperatively and at 6, 12, and 18 months postoperatively, respectively. The median MAD values for the cementless UKA group were 2.29(1.79, 2.65) cm, 1.11(0.69, 1.75) cm, 1.02(0.65, 1.66) cm, and 0.91(0.61, 1.63) cm preoperatively and at 6, 12, and 18 months postoperatively, respectively. There were no significant differences in MPTA and MAD between the two groups at all time points, except for the preoperative MPTA and postoperative MAD at 6 and 12 months. The incidence of physiological radiolucency around the prosthesis was significantly lower in the cementless UKA group 3 than in the cemented UKA group 28 ( P<0.05). However, no complete radiolucency was observed in either group. Conclusion:Oxford cementless UKA is a highly effective treatment for relieving joint pain and correcting knee deformity in patients with knee AMOA. It offers the advantages of shorter surgical duration, reduced blood loss, and improved subjective outcomes for patients after the operation.

Comparison of outcomes of mixed unicompartmental knee arthroplasty and total knee arthroplasty in the treatment of medial osteoarthritis of the knee / 中国骨伤

OBJECTIVE@#To evaluate outcomes of mixed unicompartmental knee arthroplasty(UKA) and total knee arthroplasty(TKA) in the treatment of medial osteoarthritis(OA) of the knee.@*METHODS@#Retrospective analysis of 156 patients, 44 males and 112 females, aged from 50 to 75 years old with an average of(58.76±4.97) years old, who underwent knee arthroplasty from October 2017 to October 2019. The patients were divided into two groups:81 cases(81 knees) underwent TKA, including 23 males and 58 females, aged from 51 to 75 years old with an average of (58.60±5.01) years old, and 75 case (75 knees) underwent UKA with mixed phase 3 Oxford, including 21 males and 54 females, aged from 50 to 72 years old with an average of (58.92±4.95) years old. The two groups were compared regarding to the clinical outcomes, assessed using surgical information and complications, American Knee Society score(AKSS) clinical score and functional score. Radiographs were assessed using hip-knee-ankle angle(HKA), tibial component valgus/varus angle(TCVA), tibial component posterior slope angle(TCPSA), femoral component valgus/varus angle(FCVA), femoral component posterior slope angle(FCPSA), looking for bearing dislocation, prosthesis loosening, progression of OA in lateral compartment.@*RESULTS@#Intraoperative bleeding, operative time and hospital days were significantly better in the UKA group than in the TKA group (P<0.05), and there were no postoperative complications in either group. Patients in both groups were enrolled with an average follow-up time of (38.01±8.90) months, ranged from 24 to 54 months. AKSS functional, AKSS clinical, HKA in both groups significantly improved at the final follow-up compared with those before operation. At the final follow-up, the UKA group was significantly better than the TKA group in AKSS functional and AKSS clinical, whereas HKA in the TKA group was better. At the final follow-up. TCVA and FCVA between the two groups were not significantly different, while TCPSA and FCPSA in the UKA group were significantly greater than the TKA group. No signs of progression of OA to the lateral compartment were observed.@*CONCLUSION@#Mixed phase 3 Oxford UKA in medial unicompartmental knee osteoarthritis was considerably better than TKA for less blood loss, shorter operation time, shorter hospital stay, rapid postoperative recovery, helping achieve satisfactory function, provided satisfactory outcome.

Short- and mid-term effectiveness of unicompartmental knee arthroplasty for post-traumatic arthritis of knee / 中国修复重建外科杂志

OBJECTIVE@#To investigate the short- and mid-term effectiveness of unicompartmental knee arthroplasty (UKA) for post-traumatic arthritis (PTA) of knee.@*METHODS@#The clinical data of 30 patients with PTA of unilateral knee between March 2014 and September 2021 was retrospectively analyzed. There were 14 males and 16 females with an average of 64.5 years (range, 33-81 years). The average body mass index was 26.7 kg/m 2 (range, 19.8-35.6 kg/m 2). The types of injuries that caused PTA included intra-articular fracture in 16 cases, extra-articular fracture in 8 cases, and soft tissue injury in 6 cases. The initial injuries were treated by conservative therapy in 12 cases and by surgical therapy in 18 cases. Ten cases were medial compartment osteoarthritis and 20 cases were lateral compartment osteoarthritis. According to Kellgren-Lawrence staging, there were 19 cases of grade Ⅲ and 11 cases of grade Ⅳ. The operative time, the length of hospital stay, complications, and subjective satisfaction were recorded. The Oxford Knee Function Score (OKS), Hospital for Special Surgery (HSS) score, and knee range of motion (ROM) were used to evaluate knee function. Weight-bearing X-ray films were taken to measure the femoro-tibial angle (FTA) and to assess alignment correction of the lower limb.@*RESULTS@#The operative time ranged from 50 to 95 minutes (mean, 63.7 minutes), the length of hospital stay ranged from 3 to 8 days (mean, 6.9 days). Superficial infection occurred in 2 patients, while the remaining incisions healed by first intention. There was no deep vein thrombosis or neurovascular injury. All patients were followed up 17-109 months (median, 70 months). At last follow-up, OKS score, HSS score, and ROM in 30 cases significantly improved when compared with those before operation (P<0.05). Lower limb alignment was significantly corrected and there was significant difference in FTA of the varus and valgus knees between pre- and post-operation ( P<0.05). The patient satisfaction rate was 86.7% (26/30). Two cases developed contralateral osteoarthritis progression during follow-up. No bearing dislocation, prosthesis loosening or sinking occurred and none required further revision.@*CONCLUSION@#For patients with PTA of knee, UKA can obtain definite short- and mid-term effectiveness with high patient satisfaction.

Musculoskeletal multibody dynamics investigation for the different medial-lateral installation position of the femoral component in unicompartmental knee arthroplasty / 生物医学工程学杂志

The surgical installation accuracy of the components in unicompartmental knee arthroplasty (UKA) is an important factor affecting the joint function and the implant life. Taking the ratio of the medial-lateral position of the femoral component relative to the tibial insert (a/A) as a parameter, and considering nine installation conditions of the femoral component, this study established the musculoskeletal multibody dynamics models of UKA to simulate the patients' walking gait, and investigated the influences of the medial-lateral installation positions of the femoral component in UKA on the contact force, joint motion and ligament force of the knee joint. The results showed that, with the increase of a/A ratio, the medial contact force of the UKA implant was decreased and the lateral contact force of the cartilage was increased; the varus rotation, external rotation and posterior translation of the knee joint were increased; and the anterior cruciate ligament force, posterior cruciate ligament force and medial collateral ligament force were decreased. The medial-lateral installation positions of the femoral component in UKA had little effect on knee flexion-extension movement and lateral collateral ligament force. When the a/A ratio was less than or equalled to 0.375, the femoral component collided with the tibia. In order to prevent the overload on the medial implant and lateral cartilage, the excessive ligament force, and the collision between the femoral component and the tibia, it is suggested that the a/A ratio should be controlled within the range of 0.427-0.688 when the femoral component is installed in UKA. This study provides a reference for the accurate installation of the femoral component in UKA.

Cohorte histórica de artroplastia unicompartimental de rodilla en un hospital universitario chileno / Historical cohort of unicompartmental knee arthroplasty in a Chilean university hospital

OBJETIVO Describir el resultado funcional informado por el paciente de una cohorte de pacientes sometidos a artroplastia unicompartimental de rodilla (AUR) en un hospital universitario chileno. MÉTODOS Se diseñó un estudio de cohorte histórica. Se incluyeron todos los pacientes que se sometieron a AUR de platillo fijo entre 2003 y 2019. Un evaluador independiente se puso en contacto con los pacientes en junio de 2020. Se utilizó el índice de artritis de las universidades de Western Ontario y McMaster (WOMAC) para comparar los procedimientos de AUR (medial o lateral), la edad (mayor o menor de 70 años), y el seguimiento (más o menos de 5 años). RESULTADOS Se incluyeron 78 pacientes, en un total de 94 AURs. La mediana de edad fue de 64 años (rango: 43 a 85 años). Hubo 72 (76,6%) casos de AUR medial. Un paciente necesitó revisión para artroplastia total de rodilla (ATR). Un total de 60 pacientes (76,9%), correspondientes a 72 AURs (76,7%), fueron contactados con éxito por teléfono para el seguimiento final. La mediana del puntaje en los dominios del WOMAC fue: dolor ­ 1 (rango: 0 a 12); rigidez ­ 0 (rango: 0 a 4); y función física ­ 2 (rango: 0 a 29). La mediana del puntaje total en el WOMAC fue de 4 (rango: 0 a 44). Los pacientes sometidos a AUR lateral lograron mejores puntuaciones funcionales (p » 0,0432), y el puntaje total en el WOMAC fue similar en pacientes mayores o menores de 70 años (p » 0,3706). CONCLUSIONES La AUR es un tratamiento eficaz y reproducible para pacientes con artrosis de rodilla unicompartimental. La edad parece no afectar los resultados funcionales, y la AUR es un tratamiento eficaz en pacientes mayores de 70 años. Estos resultados deberían animar a los cirujanos de rodilla a aprender esta técnica y a los responsables de las políticas de salud pública a considerar la AUR para la osteoartritis de rodilla.

PURPOSE To describe the patient-reported functional outcome of a cohort of patients undergoing unicompartmental knee arthroplasty (UKA) in a Chilean university hospital. METHODS A historical cohort study was designed. All patients who underwent fixedbearing UKA between 2003 and 2019 were included. An independent evaluator contacted the patients in June 2020. The Western Ontario and McMaster Universities Arthritis Index (WOMAC) was used to compare UKA procedures (medial or lateral), age (over or under 70 years), and follow up (longer or shorter than 5 years). RESULTS A total of 78 patients, corresponding to 94 UKAs, were included. The median age was 64 years (range: 43 to 85 years). There were 72 (76.6%) cases of medial UKA. One patient needed revision to total knee arthoplasty (TKA). A total of 60 patients (76.9%), corresponding to 72 UKAs, were successfully contacted by phone for the final follow-up. The median scores on the WOMAC domains were: pain ­ 1 (range: 0 to 12); stiffness ­0 (range: 0 to 4); and physical function ­ 2 (range: 0 to 29). The median total score on the WOMAC was 4 (range: 0 to 44). Patients submitted to lateral UKA had better functional scores (p » 0.0432), and the total WOMAC score was similar among patients older or younger than 70 years of age (p » 0.3706). CONCLUSIONS For patients with unicompartmental knee osteoarthritis, UKA is an effective and reproducible treatment. Age does not seem to affect the functional results, and UKA is an effective treatment in patients over 70 years old. These results should encourage knee surgeons to learn this technique and those responsible for public health policies to consider UKA for knee osteoarthritis

Progress of lateral unicompartmental knee arthroplasty for lateral compartment osteoarthritis of the knee / 国际外科学杂志

With the development of the knee-preservation concept and surgical techniques, lateral unicompartmental knee arthroplasty (UKA) has become an effective method for the lateral compartment osteoarthritis of the knee.The incidence of knee osteoarthritis is low in the lateral compartment, which is different from the medial compartment in anatomical and kinematic characteristics. These two factors increase the challenge of lateral UKA, so the clinical efficacy of lateral UKA has been controversial. With the improvement and renewal of treatment concepts, surgical techniques and prosthesis design, the clinical effect of lateral UKA and the survival rate of the prosthesis have been continuously optimized. This article aims to summarize the characteristics of lateral compartment knee osteoarthritis, clinical efficacy, prosthesis selection, reasons for revision, future application and prospects, combined with relevant literature in recent years, to review the current progress of lateral UKA.

Failure Analysis on Interface Stress in Unicompartmental Knee Arthroplasty / 医用生物力学

Objective To analyze interface stress of cemented tibial prosthesis platform and determine the interface stress damage area, so as to provide references for stress failure of tibial platform in clinical single condylar replacement. Methods The full cycle gait was simulated by human dynamics software to obtain the load-bearing condition of knee joint. A complete model of the knee joint was established by medical imaging and three-dimensional (3D) reconstruction software, and unicompartmental replacement was performed. The distribution of interfacial stress of tibial prosthesis platform after single condylar replacement was analyzed by finite element method. ResultsIn gait, force and angle of the knee joint changed periodically with time, a cycle lasted 1.3 s, and the peak of knee joint resultant force was 760 N. The maximum shear stress of the interface was 11.82 MPa and the maximum tensile stress was 6.849 MPa, both occurred at inner front end of the corner of prosthesis cement interface. The maximum interface stress of titanium alloy prosthesis was lower than that of stainless steel prosthesis. Conclusions The decrease in elastic modulus of prosthesis can reduce the maximum principal stress at the interface. Considering the interface stress, titanium alloy prosthesis is better than stainless steel prosthesis. The area of tibial prosthetic platform interface damage is mainly at the medial anterior and posterior corners and lateral middle ends,so improving the ability of prosthesis cement bonding in this area can prevent the loosening of tibial prosthesis of unicompartmental knee joint.The findings have practical implications for the prevention of tibial prosthetic platform loosening after unicompartmental knee arthroplasty in clinic.

Biomechanical Analysis of the Knee after Unicompartmental Knee Arthroplasty during Stair Ascent / 医用生物力学

Objective To investigate the effect of medial unicompartmental knee arthroplasty (UKA) surgery on knee biomechanics during stair ascent. Methods Nine osteoarthritis patients who received fixed-bearing medial UKA participated in this study. All patients completed pre-surgical (3 weeks before UKA surgery) and post-surgical ［(7±2) months after UKA surgery］ test. Their synchronized biplane radiographs during stair ascent were collected. Motion of the femur, tibia, and implants were tracked using an automated volumetric model-based tracking process that matched subject-specific 3D models of the bones and prostheses to the biplane radiographs with sub-millimeter accuracy. Anatomic coordinate systems were created within the femur and tibia and used to calculate tibiofemoral kinematics. Additional outcome measures included the center of contact in the medial and lateral compartments, and the lateral compartment dynamic joint space. Results The UKA knee was in 4.8° varus compared with the pre-surgical contralateral knee. The post-surgical UKA knee was in 3.1°valgus compared with the pre-surgical knee. The post-surgical UKA knee was 4.4° externally rotated compared with the pre-surgical contralateral knee. However, the medial tibia contact center of the UKA knee moved posteriorly 2.5 mm compared with that of the contralateral knee (P0.05). Conclusions UKA can effectively improve varus of the knee joint and restore biomechanical characteristics of UKA knee rotation, without affecting lateral compartment joint space. However, changes are found in contact center of the medial tibia compartment of the UKA knee after surgery.

Effects of Different Posterior Tibial Slopes in Unicompartmental Knee Arthroplasty on the Wear and Function of Prosthesis / 医用生物力学

Objective To establish the three-dimensional (3D) finite element model of unicompartmental knee arthroplasty (UKA) with 3° and 7° posterior tibial slope at different knee flexion angles, and to study biomechanical properties and prosthetic wear of the knee joints with two types of posterior tibia slope and their effects on knee function. Methods Combining CT and MRI images of human knee joints with the 3rd-generation Oxford prosthesis, the finite element UKA model with 3° and 7° posterior tibia slope were established. The 1 kN load was applied to center point of the medial and lateral condyles of the femur to simulate the standing load of human body. The maximum stresses and distributions of the prosthesis and articular cartilage at different knee flexion angles were analyzed. ResultsThe maximum stress of the meniscus liner with 3° posterior tibia slope at 0°, 30°, 60°, 90°, 120° knee flexion angles increased by 28.06%, 68.99%, 19.45%, 21.06% and 53.38%, the distribution area was concentrated from the side of the meniscus liner to the central area, and the stress concentration was obvious at 120° knee flexion. The maximum stress of prosthesis with 3° posterior tibia slope was greater than that with 7 ° posterior tibia slope. The expansion of stress concentration area would cause wear and loosening of the prosthesis, contact stress and concentration area of the articular cartilage would subsequently increase with posterior tibia slope increasing, and stress concentration would be more obvious at high knee flexion angles. Conclusions Tibial prosthesis has the higher stress and greater wear under the condition of 3° posterior tibia slope than 7° posterior tibia slope. The research findings provide theoretical basis for the UKA design in clinic.

Effect of posterior tibial slope on the short-term outcome in mobile-bearing unicompartmental knee arthroplasty / 北京大学学报(医学版)

OBJECTIVE@#To evaluate the relationship between postoperative knee function and the sagittal position of tibial component in unicompartmental knee arthroplasty (UKA).@*METHODS@#We retrospectively enrolled the patients who underwent UKA from January 2016 to May 2020. They were assigned into 2 groups according to postoperative posterior tibial slope (PTS): the normal PTS group (PTS≥3° and PTS < 8°) and the abnormal PTS group (PTS < 3° or ≥8°). The patients were followed up for at least 12 months. The postoperative Knee Society Clinical Score (KSS-C), Knee Society Functional Score (KSS-F) and knee range of motion (ROM) were compared between the two groups.@*RESULTS@#A total of 72 patients (82 knees) were included with 51 patients (58 knees) in PTS normal group and 21 patients (24 knees) in PTS abnormal group. All the patients were followed up with median of 23.6 months. There was no significant difference in the general data [gender, age, body mass index (BMI)], pre-operative knee range of motion, preoperative KSS-C score and KSS-F score (P > 0.01). The KSS-C score, KSS-F score, and knee range of motion significantly improved after surgery (P < 0.01) for all the patients. The postoperative KSS-C score in normal PTS group (88.76±2.79) was significantly higher than the KSS-C score in abnormal PTS group (84.42±3.35, P < 0.01), but no significant difference between the 2 groups was observed in postoperative KSS-F score and knee range of motion (P > 0.01). In addition, there was no correlation between the change of PTS and postoperative KSS-C score (r=-0.034, 95%CI: -0.247 to 0.186, P = 0.759), KSS-F score (r = -0.014, 95%CI: -0.238 to 0.198, P = 0.901) and knee range of motion (r= 0.045, 95%CI: -0.214 to 0.302, P = 0.686).@*CONCLUSION@#The posterior tibial slope between 3° and < 8° can be recommended to improve knee joint function in mobile UKA, and excessive or insufficient PTS should be avoided.

Multivariate analysis of varus after Oxford unicompartmental knee arthroplasty / 北京大学学报(医学版)

OBJECTIVE@#To analyze the preoperative influencing factors of varus after Oxford unicompartmental knee arthroplasty.@*METHODS@#A total of 660 patients (767 knees) undergoing Oxford unicompartmental knee arthroplasty in adult joint reconstruction surgery department of Beijing Jishuitan Hospital from January 2018 to December 2019 were retrospectively analyzed. Inclusive criteria: diagnosis was osteoarthritis, single compartment lesions in the medial side of the knee; preoperative flexion deformity was less than 10°, active range of motion was greater than 90°; preoperative X-ray full-length images of both lower limbs showed less than 15° varus (Noyes method); anterior cruciate ligament was well functioned, The cartilage of lateral compartment of knee joint was intact.@*EXCLUSION CRITERIA@#combined with other inflammatory arthropathy; combined with extraarticular deformity; previous knee surgery history. The average age of the patients was (64.4±8.1) years, including 153 males and 497 females. The degree of post-operative varus was measured with Noyes method. The total patients were divided into varus group (Noyes≥3 °) and normal group (Noyes < 3 °). Gender, age, body mass index (BMI), range of motion (ROM), preoperative flexion deformity (FD), American Knee Society pain score (AKS) and American Knee Society function score (AKS function) were recorded. The standard anteroposterior and lateral X-ray films of knee joint and full-length lower extremity kinematic line films were taken by Sonialvision Safine Ⅱ (Shimadzu, Japan) multi-function digital tomography system. The image was measured by picture archiving and communication system (PACS). The following angles were measured preoperative Noyes angle, lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA) and joint line converge angle (JLCA) were measured and analyzed.@*RESULTS@#Gender(P=0.346), operative side (P=0.619), age (P=0.746), BMI (P=0.142), preoperative ROM (P=0.102), preoperative knee pain score (P=0.131) and functional score (P=0.098) were not risk factors for postoperative varus. The influencing factors of postoperative varus were preoperative MPTA < 84 ° (P= 0.018, OR= 3.712, 95%CI: 1.250-11.027), preoperative Noyes > 5°(P=0.000, OR= 3.105, 95%CI: 1.835-5.254), preoperative FD > 5° (P= 0.001, OR=1.976, 95%CI: 1.326-3.234). Pre-operative LDFA (P=0.146) and preoperative JLCA (P= 0.709) had no significant effect on postoperative kinematic line.@*CONCLUSION@#Patients with severe preoperative varus, especially those with varus deformity mainly from the tibial side, and those with preoperative flexion deformity are more prone to get varus lower extremity kinematic line after Oxford unicompartmental knee arthroplasty.

Comparison of total knee arthroplasty and unicompartmental knee arthroplasty in treatment of traumatic osteoarthritis / 中国组织工程研究

BACKGROUND: The incidence of traumatic osteoarthritis is increasing in recent years. At present, total knee arthroplasty and unicondylar arthroplasty are commonly used in clinical treatment, and their therapeutic effects still need to be verified. OBJECTIVE: To compare effects between total knee arthroplasty and unicompartmental knee arthroplasty on the patients with traumatic knee osteoarthritiss. METHODS: A total of 102 patients with bilateral traumatic osteoarthritis were treated in the Affiliated Hospital of Qingdao University between January 2016 and June 2018. The patients were divided into total knee arthroplasty group and unicompartmental knee arthroplasty group (n=51 for each group). Operation indexes (operation time, intraoperative blood loss, decrease of hemoglobin 48 hours after operation, proportion of patients receiving blood transfusion during perioperative period, total length of stay and hospitalization cost) were compared between the two groups. Visual analogue scale score, American knee society knee score, and The Western Ontario and McMaster Universities osteoarthritis index were compared before surgery and 2 weeks, 3 and 6 months after surgery. The postoperative complications and subjective satisfaction after 6 months of follow-up were compared between the two groups. RESULTS AND CONCLUSION: (1) Operation time, intraoperative blood loss and decrease in hemoglobin at 48 hours after surgery were significantly lower in the unicompartmental knee arthroplasty group than those in the total knee arthroplasty group. The proportion of blood transfusion during perioperative period was significantly lower in the unicompartmental knee arthroplasty group than that in the total knee arthroplasty group. Total length of stay and hospitalization cost were significantly less in the unicompartmental knee arthroplasty group than those in the total knee arthroplasty group (P 0.05). Compared with those before surgery, visual analogue scale score and American knee society knee score were significantly lower; and The Western Ontario and McMaster Universities osteoarthritis index was significantly higher in both groups at 2 weeks, 3 and 6 months after surgery (P < 0.05). Visual analogue scale score, American knee society knee score, and The Western Ontario and McMaster Universities osteoarthritis index were significantly better in the unicompartmental knee arthroplasty group than those in the total knee arthroplasty group at various time points after surgery (P < 0.05). (3) During the 6-month follow-up, subjective satisfaction was significantly higher in the unicompartmental knee arthroplasty group than that in the total knee arthroplasty group (P < 0.05). (4) Complications: In the total knee arthroplasty group, there were 3 cases of postoperative infection and 2 cases of deep vein thrombosis, and the total incidence of postoperative complications was 10%. In the unicompartmental knee arthroplasty group, there was 1 case of postoperative infection, and the total incidence of postoperative complications was 2%. The incidence of postoperative complications in unicompartmental knee arthroplasty group was lower than that in total knee arthroplasty group, but the difference was not statistically significant (P < 0.05). (5) Unicompartmental knee arthroplasty in treatment of traumatic knee osteoarthritis has obvious advantages, can reduce length of stay and hospitalization cost, and patients have high satisfaction after operation. Unicompartmental knee arthroplasty is beneficial to the postoperative recovery of patients, and can be used as the first choice for clinical treatment of traumatic osteoarthritis.

Finite Element Analysis on Biomechanical Properties of Unicompartmental Knee Arthroplasty in ACL Fracture of the Knee Joint / 医用生物力学

Department of Orthopedics, Yang Pu Hospital Affiliated to Tongji University,

Research progress in unicompartmental knee arthroplasty / 中国修复重建外科杂志

Objective: To summarize the clinical application and research progress in unicompartmental knee arthroplasty (UKA). Methods: The literature related to UKA in recent years was reviewed and the emerging indications, implant options, comparisons between other surgical techniques, and recent advances were summarized. Results: Clinical studies show that UKA has many advantages, such as less trauma, faster recovery, and fewer postoperative complications. At present, the operative indication has been expanded. The body mass index more than 25 kg/m 2, less than 60 years old, patellofemoral arthritis, and anterior cruciate ligament dysfunction are no longer considered as contraindications. The prosthesis type in UKA should be selected according to the patient's condition. In recent years, the robot-assisted UKA can effectively improve the effectiveness, improve patient satisfaction, and reduce postoperative complications. Conclusion: With the development of surgical techniques, designs of prosthesis, and the robotic technology, UKA would be further applicated. As more long-term data on UKA become available, it will further guide clinicians in counseling patients on whether UKA should be performed.