Research progress in biomechanics of deep squat / 医用生物力学

High flexion squat is extremely common in the daily activities of Asian countries and certain occupations. In this paper, different types of deep squats and their motion characteristics were summarized, and recent research progress of squat biomechanics was reviewed. Different research methods on squats such as in vitro experiment, in vivo test and computer simulation were also classified and represented. Biomechanical studies on deep squat of the knee can benefit establishment of reasonable rehabilitation training, prevention of sports risks as well as provide some references for optimization of knee prosthesis design.

Research progress in biomechanics of deep squat / 医用生物力学

High flexion squat is extremely common in the daily activities of Asian countries and certain occupations.In this paper,different types of deep squats and their motion characteristics were summarized,and recent research progress of squat biomechanics was reviewed.Different research methods on squats such as in vitro experiment,in vivo test and computer simulation were also classified and represented.Biomechanical studies on deep squat of the knee can benefit establishment of reasonable rehabilitation training,prevention of sports risks as well as provide some references for optimization of knee prosthesis design.

Rango de movilidad y resultados funcionales en tres disenos diferentes de artroplastia de rodilla primaria. estudio comparativo / Range of motion and functional results in three different designs of total knee arthroplasty. comparative study

Introducción: El objetivo de este trabajo fue analizar los resultados funcionales y el rango de movilidad entre tres grupos de pacientes con artroplastia total de rodilla: dos con prótesis de alta flexión y otro con un diseño convencional. Materiales y Métodos: Sesenta y cuatro pacientes fueron operados con una prótesis total de rodilla Zimmer® NexGen® y 34, con una Optetrack® de alta flexión. Luego de la exclusión de pacientes, 22 (grupo A) fueron tratados con un diseño Zimmer® de alta flexión; 21 (grupo B), con una prótesis Zimmer® convencional y 25 (grupo C), con una prótesis Optetrack ® PS. La evaluación funcional se realizó con el Knee Society Score, el Western Ontario and McMaster Universities Osteoarthritis index y la escala analógica visual. Resultados: En el posoperatorio, el promedio de flexión máxima subió de 99° a 113º en el grupo A, con un aumento promedio de 14º; de 106° a 118º en el grupo B, con una ganancia promedio de 12º y de 110° a 111° en el grupo C, con una ganancia de 1°. Los resultados funcionales evaluados con los dos puntajes mejoraron en los tres grupos. Conclusiones: Las evaluaciones clínicas funcionales son favorables en los tres diseños evaluados. Este estudio muestra que no hay diferencias significativas en la flexión final lograda y los resultados funcionales entre los dos primeros diseños; sin embargo, estos son significativamente superiores al diseño del tercer grupo luego de un año de seguimiento.

Introduction: The purpose of this comparative study was to analyze functional results and the range of motion of the knee among three groups of patients with total knee arthroplasty using high-flex prosthesis (in two groups) and a conventional design (one group). Methods: Sixty-four patients were surgically treated with total knee arthroplasty using a Zimmer® NexGen® prosthesis, and 34 patients received a high-flex Optetrack® design. After exclusion of patients, 22 patients (group A) were treated with a high-flex Zimmer® NexGen® design, 21 patients (group B) were treated with a conventional implant, and 25 patients (group C) received a high-flex PS Optetrack® prosthesis. Functional evaluation was performed with the Knee Society Score, the Western Ontario and McMaster Universities Osteoarthritis index, and a visual analogue scale. Results: Mean post-surgical maximum flexion increased from 99° to 113º in group A, with an average increase of 14º, from 106° to 118º in group B, with an average gain of 12º, and from 110 to 111° in group C, with an average increase of 1°. Functional results assessed with both scores showed improvements in all three groups. Conclusions: The functional and radiographic outcomes were favorable in the three designs. This study suggests that there are no significant differences in the final flexion and functional outcomes between the first two designs; however together they are significantly superior to the third group after one year of follow-up.

Analysis of Impingement between Patella Bone and Bearing Post in Cruciate-Substituting High-Flexion Total Knee Arthroplasty

BACKGROUND: We investigated the causes of impingement between the patella bone and the bearing post during high flexion in cruciate-substituting total knee arthroplasty and proposed a treatment strategy. METHODS: This prospective cohort study included 218 cases that had undergone cruciate-substituting total knee arthroplasty from February 2014 to January 2015; a single surgeon performed the operation using the same method without patellar resurfacing in all patients. RESULTS: In these patients, the occurrence of impingement was determined by performing more than 120° high knee flexion after inserting a bearing perioperatively. The incidence of impingement was significantly associated with bearing design, femoral implant size, patella bone length, and patella inferior pole angle (p < 0.05). The impingement was resolved by resection of the lower articular side of the patella bone. CONCLUSIONS: In the cruciate-substituting high-flexion total knee arthroplasty, impingement between the patella bone and bearing post was more common in patients with mobile bearing, small-size femoral component, and a long patella or a large inferior pole angle. In cases of intraoperative impingement between the patella bone and the bearing post, resection in the lower portion of the patella prevented impingement of the bearing with soft tissue or the patella by widening the space between the patella and the bearing post, which in turn prevented postoperative reduction in range of motion.

Analysis of Impingement between Patella Bone and Bearing Post in Cruciate-Substituting High-Flexion Total Knee Arthroplasty

BACKGROUND: We investigated the causes of impingement between the patella bone and the bearing post during high flexion in cruciate-substituting total knee arthroplasty and proposed a treatment strategy. METHODS: This prospective cohort study included 218 cases that had undergone cruciate-substituting total knee arthroplasty from February 2014 to January 2015; a single surgeon performed the operation using the same method without patellar resurfacing in all patients. RESULTS: In these patients, the occurrence of impingement was determined by performing more than 120° high knee flexion after inserting a bearing perioperatively. The incidence of impingement was significantly associated with bearing design, femoral implant size, patella bone length, and patella inferior pole angle (p < 0.05). The impingement was resolved by resection of the lower articular side of the patella bone. CONCLUSIONS: In the cruciate-substituting high-flexion total knee arthroplasty, impingement between the patella bone and bearing post was more common in patients with mobile bearing, small-size femoral component, and a long patella or a large inferior pole angle. In cases of intraoperative impingement between the patella bone and the bearing post, resection in the lower portion of the patella prevented impingement of the bearing with soft tissue or the patella by widening the space between the patella and the bearing post, which in turn prevented postoperative reduction in range of motion.

Results of High-Flex Total Knee Arthroplasty: Minimum 3-Year Follow-Up Result / 대한정형외과학회잡지

PURPOSE: The purpose of this study was to evaluate the results of high-flexion total knee arthroplasty. MATERIALS AND METHODS: We evaluated 355 patients (372 cases) who underwent total knee arthroplasty using high-flexion implants from January 2005 to December 2011. The patients included 36 men and 336 women with a mean age of 70.6 (52-88 years) years. Average follow-up duration was 59 months (36-77 months) months. Three types of high flexion implants were used in this study. We performed preoperative assessment and last follow-up clinical evaluation was performed using range of motion (ROM), knee score and function score according to the knee society clinical rating system and complications. Radiologic evaluation was performed using plain radiographs to evaluate loosening or osteolysis. RESULTS: The mean ROM increased from 114.9° preoperatively to 127.0° at the final follow-up. The average knee score improved from 60.5 points preoperatively to 90.9 points at final follow-up and knee function score improved from 49.0 to 84.4 points. The clinical results were improved in each type of implants. A radiolucent line was detected in 2 cases in the Sigma rotating platform flexion group and patellar tendon rupture occurred in 1 case in the NexGex legacy posterior-stabilized-flex group. Infection occurred in 2 cases after 2 and 5 years postoperatively in the Scorpio non-restrictive geometry group and were treated with revision arthroplasty. No significant loosening was observed. CONCLUSION: This study obtained good results after total knee arthroplasty using high-flexion implants, and no loosening was observed. There were no differences in the type of implants in regard to the ROM and clinical variables.

Usefulness of the Korean Knee Score for Evaluation of the Results of Total Knee Arthroplasty

PURPOSE: The Korean Knee score (KKS) was designed to reflect the floor-sitting lifestyle that necessitates high knee flexion. The purpose of this study is to assess whether the KKS reflects the floor-sitting lifestyle more accurately than the previously developed Knee Society clinical rating system. In addition, the presence of ceiling effects was compared between the two rating systems. MATERIALS AND METHODS: Eighty-one consecutive patients (120 knees) who were assessed regularly after total knee arthroplasty (TKA) on an outpatient basis between January 2012 and December 2012 were enrolled. All patients were asked to complete a questionnaire to assess the Knee Society Knee score (KSKS), Knee Society Function score (KSFS), and KKS. RESULTS: At the final follow-up, the mean KSKS, KSFS, and KKS were 91.2, 86.0, and 70.1, respectively, and the scores were similar between the > or =125degrees maximum flexion group and 125degrees maximum flexion group (15.13 vs. 11.24, p=0.001). The number of cases with the highest possible score was 24 (20%) for the KSKS and 47 (39%) for the KSFS, whereas none of the cases obtained the highest possible KKS. According to the standard deviation method, more substantial ceiling effects were present in the KSKS (83 cases, 69.1%) and KSFS (67 cases, 55.8%) than in the KKS (23 cases, 19.2%). CONCLUSIONS: Although, the KKS was effective in reducing the ceiling effect, it demonstrated limited improvement in assessing the ability to perform high knee flexion after TKA. However, the 'floor life' subdomain of KSS appeared to be valid for evaluating high flexion of the knee.

Comparison of Two Year Follow-Up Results in High Flexion Total Knee Arthroplasty with Lospa and Scorpio NRG / 대한정형외과학회잡지

PURPOSE: The purpose of this study is to evaluate the clinical and radiologic results after high flexion Lospa (Corentec Inc.) and Scorpio NRG (Stryker Inc.) total knee arthroplasty. MATERIALS AND METHODS: We prospectively compared 205 knees in 128 patients who underwent arthroplasty using Lospa (group A) and 164 knees in 102 patients who underwent arthroplasty using Scorpio NRG (group B) from September 2010 to March 2012 at Department of Orthopaedic Surgery, Sun General Hospital (Daejeon, Korea). Mean follow-up period was 23 months in group A and 24 months in group B. The radiologic analysis included the change of mechanical axis deviation and femoro-tibial angle, implant position (alpha, beta, gamma, delta), and patellar tilt. The clinical results were evaluated according to hospital for special surgery (HSS), knee society score (KSS), and range of motion. RESULTS: Mechanical axis deviations were change in varus from 34.8 mm to 2.6 mm (p=0.02) in group A, and change in varus from 34.3 mm to 3.1 mm (p=0.04) in group B; no statistically significant difference was observed between them (p=0.13). Femoro-tibial angles were varus 4.3degrees to valgus 6.6degrees (p=0.02) in group A, and varus 4.4degrees to valgus 6.5degrees (p=0.03) in group B; no significant difference was observed between them (p=0.25). No significant difference in implant position was observed between the two groups (p=0.25 in alpha, p=0.17 in beta, p=0.12 in gamma, p=0.17 in delta). Mean HSS improved from 48.5 to 93.6 (p=0.02) in group A, and from 41.4 to 94.4 (p=0.01) in group B. CONCLUSION: Lospa total knee arthroplasty showed excellent early radiologic, clinical results and no statistically significant difference in the results was observed between Lospa and Scorpio NRG.

Advance in biomechanics researches of major knee ligaments at high flexion angles / 医用生物力学

High flexion of the knee is very common for some specifically occupations and daily activities in many Asian and Mid-East countries. The major ligaments, including anterior cruciate ligament, posterior cruciate ligament, medial collateral ligament, lateral collateral ligament and joint capsule, are the most important static structures with function to maintain stability of the knee. Therefore, a thorough understanding on biomechanics and kinematics of the major knee ligaments at high flexion angles is significant in treatment of soft tissue release during total knee arthroplasty, anatomical cruciate ligament reconstruction and rehabilitation of knee disorders. In this paper, the research methods on knee biomechanics in recent years, and the biomechanical properties of the static knee structure from stretching to high flexion are reviewed. The further aim of the research direction in soft tissue balance during total knee arthroplasty, repair and reconstruction of knee ligaments, postoperative rehabilitation after knee injuries in the future are predicted.

High-Flexion Posterior-Stabilized Total Knee Prosthesis: Is It Worth the Hype?

High-flexion knee prosthesis was introduced with the aim of obtaining higher degree of flexion and good survivorship in patients with high functional demands or those requiring squatting, kneeling, etc., which is more common in Asians. Based on all the research and experience with this prosthesis, it was concluded that high flexion designs meet the need of deeper degrees of flexion in selected sets of patients only. Results were equal and comparable to the traditional standard posterior-stabilized total knee arthroplasty design and superior to it in terms of gaining more flexion and fulfilling activities, such as squatting, kneeling, and sitting cross-legged.

Mid-term Results of Total Knee Arthroplasty Using PFC Sigma RP-F

PURPOSE: We compared the mid-term results after total knee arthroplasty (TKA) using PFC Sigma RP-F mobile model with PFC Sigma PS fixed model. MATERIALS AND METHODS: We analyzed 45 knees that underwent TKA with PFC Sigma RP-Fn (study group) and 45 knees with PFC Sigma PS (control group). The mean follow-up period was 65 months (range, 60-69 months). The evaluation system of the American knee society was used for clinical and radiological assessment. Also, the maximal knee flexion angle was assessed. RESULTS: The mean maximum flexion angle in the study group (135degrees) was greater than that in the control group (125degrees) at the early post-operation & final follow-up period (p=0.033). The range of motion (ROM) in the study group was recovered earlier at the postoperative 6 months, and ROM gain was improved to a greater extent at the final follow-up period (p=0.039). The knee score and function score and radiographic evaluation were no difference between the two groups (p>0.05) at the final follow-up. The two cases of radiolucency in posterior condyle and medial tibial plateau and one case of patellar elongation were seen in the study group. CONCLUSIONS: The PFC Sigma RP-F mobile system appears to facilitate greater maximum flexion angle and ROM gain with two cases of radiolucent line.

Comparison of Mobile-Bearing and Fixed-Bearing Designs in High Flexion Total Knee Arthroplasty: Using a Navigation System

PURPOSE: We compared and analyzed the short term results of high flexion total knee arthroplasty (TKA) with mobile-bearing and fixed bearing designs. MATERIALS AND METHODS: We studied 32 patients that had undergone TKA with LPS-Flex Mobile and 34 patients with LPS-Flex Fixed using an electromagnetic navigation system between January 2010 and June 2010, and were followed up for at least 1 year. RESULTS: Knee Society Functional Score (KSFS) and Knee Society Knee Score (KSKS) of the mobile-bearing group were 94.5 and 93.8 points, respectively, and were 48.2 and 45.3 points preoperatively, whereas those of the fixed-bearing group were 95.1 and 94.2 points, respectively, and were 49.5 and 46.9 points preoperatively. Postoperative mechanical axis deviation and implant position of the femoral and tibial component both on the coronal and sigittal planes showed no significant differences between the two groups. Range of motion (ROM) and maximal flexion angle (MFA) of the knee joint also showed no significant differences between the two groups. The possibility of crossed-legged sitting and kneeling position also showed no significant differences between the two groups. CONCLUSIONS: Clinical and radiologic parameters, ROM and MFA of knee joints showed no significant differences in both the groups, but long term follow-up results may be necessary, including survival rate.

The Mid-Term Results of High-Flex Total Knee Arthroplasty: Minimum 5-Year Follow-Up Results / 대한정형외과학회잡지

PURPOSE: The purpose of this study was to evaluate the mid-term results of high-flexion total knee arthroplasty. MATERIALS AND METHODS: We retrospectively reviewed 77 patients who underwent 119 total knee arthroplastys using high-flexion implants (LPS-flex(R) , Zimmer, Warsaw, IN, USA) from November 2004 to June 2006. The mean age was 67.3 years (range, 54-83 years), and the average follow-up duration was 71.1 months. We assessed preoperative and last follow-up functional outcomes with ranges of motion (ROM) and the Hospital for Special Surgery (HSS) score and investigated their ability to squat, sit cross-legged knee, kneel, or stand up from the floor or a chair at the final follow-up. The Knee Society Radiographic evaluation and scoring system was used for radiologic evaluation. RESULTS: The mean ROM increased from 104.7degrees preoperatively to 129.8degrees postoperatively at the final follow-up. The average HSS score improved from 42.7 points preoperatively to 93.5 points postoperatively. At the final follow-up, 33 patients (42.8%) were able to squat; 75 patients (97.4%) were able to sit cross-legged; 27 patients (35.0%) were able to kneel; 45 patients (58.4%) were able to stand up from the floor and 73 patients (94.8%) were able to stand up from a chair. Six cases encountered stiff knees as a complications, and were treated with manipulation procedures. 1 mm radiolucent lines were detected in 5 cases, but none of them were progressive. CONCLUSION: We believe that the hyperflexion implant itself is not a cause of early loosening. Research on reasons regarding early loosening and long-term follow-ups will be needed.

Comparison of the Clinical Outcomes after Total Knee Arthroplasty with the LCS Rotating Platform Mobile Bearing Knee System and the PFC Sigma RP-F Mobile Bearing Knee System

BACKGROUND: We compared clinical outcomes after total knee arthroplasty with the Low Contact Stress (LCS) rotating platform mobile bearing knee system and the Press Fit Condylar Sigma rotating platform high flexion (PFC Sigma RP-F) mobile bearing knee system. METHODS: Fifty cases of total knee arthroplasty were performed with the PFC Sigma RP-F mobile bearing knee system and sixty-one cases were performed with the LCS mobile bearing total knee arthroplasty. The average duration of follow-up was 2.9 years. RESULTS: The mean Hospital for Special Surgery (HSS) knee score was 62.1 (range, 52 to 75) in the LCS group and 61.9 (range, 50 to 74) in the Sigma RP-F group preoperatively, and 90.1 (range, 84 to 100) in the LCS group and 89.8 (range, 83 to 100) in the Sigma RP-F group at the final follow-up. The mean preoperative flexion contracture was 6.7degrees (range, 0degrees to 10degrees) in the LCS group and 9.3degrees (range, 0degrees to 15degrees) in the Sigma RP-F group preoperatively. The mean range of motion was 124.6degrees (range, 105degrees to 150degrees) in the LCS group and 126.1degrees (range, 104degrees to 145degrees) in the Sigma RP-F group at the final follow-up. CONCLUSIONS: After a minimum duration of follow-up of two years, we found no significant differences between the two groups with regard to the range of knee motion or the clinical or radiographic results.

Evaluation of Postoperative Range of Motion and Functional Outcomes after Cruciate-Retaining and Posterior-Stabilized High-Flexion Total Knee Arthroplasty

PURPOSE: The purpose of this study was to compare postoperative range of motion and functional outcomes among patients who received high-flexion total knee arthroplasty using cruciate-retaining (CR-Flex) and posterior-stabilized (PS-Flex) type prostheses. MATERIALS AND METHODS: Among 127 patients (186 knees) who underwent high-flexion total knee arthroplasty between 2005 and 2007, 92 knees were placed in the CR-Flex group, and 94 knees were placed in the PS-Flex group. After two years of postoperative follow-up, clinical and radiographic data were reviewed. Postoperative non-weight-bearing range of knee motion, angle of flexion contracture and functional outcomes based on the Western Ontario and McMaster Universities Osteoarthritis (WOMAC) functional sub-scale were assessed and compared between the two groups. RESULTS: After the 2-year postoperative period, the mean range of motion was 131degrees in the CR-Flex group and 133degrees in the PS-Flex group. There were no significant differences in postoperative range of motion between the two groups. Only age at operation and preoperative range of motion were significantly associated with postoperative range of motion after high-flexion total knee arthroplasty. Postoperative functional outcomes based on the WOMAC functional sub-scale were slightly better in the CR-Flex group (9.2+/-9.1 points) than in the PS-Flex group (11.9+/-9.6 points); however, this difference was not statistically significant (p=non-significant). CONCLUSION: The retention or substitution of the posterior cruciate ligament does not affect postoperative range of motion (ROM) or functional outcomes, according to 2 years of postoperative follow-up of high-flexion total knee arthroplasty.

Comparison of the Mobile-bearing and Fixed-bearing Designs for High Flexion Total Knee Arthroplasty

PURPOSE: We compared and analyzed the follow-up results of high flexion total knee arthroplasty (TKA) with using the mobile-bearing and fixed-bearing designs. MATERIALS AND METHODS: We studied 130 patients who had undergone high-flexion TKA from December 2003 to December 2007 and who were followed up for at least 2 years. Of all the 130 patients, 65 patients had undergone TKA using a mobile-bearing design, and the other 65 patients had undergone TKA using the fixed-bearing design. RESULTS: The post-operative Knee Society Knee Score (KSKS) and Knee Society Functional Score (KSFS) of the mobile-bearing group were 95.6 and 96.1 points, which were 53.2 and 49.7 points, respectively, preoperatively, and the post-operative KSKS and KSFS of the fixed-bearing group were 94.5 and 95.1 points, which were 54.1 and 50.9 points, respectively, preoperatively. The range of motion (ROM) and maximal flexion angle (MFA) of the knee joints of the mobile-bearing group were 129.1degrees and 131.4degrees, which were 122.3degrees and 125.8degrees, respectively, preoperatively, and those of the fixed-bearing group were 128.3degrees and 129.3degrees, which were 122.2degrees and 123.9degrees, respectively, preoperatively. There were no significant differences between the two groups. Crossed-legged sitting and attaining a kneeling position also showed no significant differences between the two groups, but the mobile-bearing group could easily take a crossed-legged sitting position. CONCLUSION: The clinical parameters and the ROM and MFA of the knee joint showed no significant differences between both groups, but the mobile-bearing group felt more comfortable in the crossed-legged sitting position.

Comparative Study of the Postoperative Maximal Flexion Angle in PCL-substituting TKAs: Conventional PS vs. High-flex PS / 대한정형외과학회잡지

PURPOSE: This study was performed to compare the postoperative maximal flexion angle (MFA) of standard PCL-substituting (PS) prosthesis with that of high-flexion PS prosthesis after total knee arthroplasty (TKA). MATERIALS AND METHODS: A total of 81 patients (133 knees) were enrolled in this study. Sixty-eight primary bilateral TKAs were performed in 34 consecutive patients. The bilateral TKAs were performed in a staged sequential manner, with a standard PS prosthesis in one knee and a high-flexion PS prosthesis in the contralateral knee. We also analyzed the results of another 47 patients as several control groups, and this consisted of standard or high-flexion PS total knee prostheses in the bilateral TKAs, and standard or high-flexion PS total knee prostheses in the unilateral TKAs. The patients were clinically assessed with the Knee Society scoring system and the MFA was measured with a goniometer. RESULTS: At the last follow up, the mean postoperative MFA of the 34 patients operated with the combination of different prostheses was 131.6+/-10.4degrees for high-flexion prosthesis side and 131.6+/-9.5degrees for standard prosthesis side respectively. There was no statistically significant difference. On comparing with the results of the 47 patients in the control group, no statistically significant difference in the mean postoperative MFA was found between the groups. CONCLUSION: We found no significant differences between the high-flexion PS prosthesis and the standard PS prosthesis in the postoperative MFA.

High Flex Knee Arthroplasty and Range of Motion / 대한정형외과학회잡지

PURPOSE: The aim of this prospective study was to determine which factors are predictive of the post operative range of motion and to evaluate the short-term clinical results after total knee arthroplasty using The Nexgen Legacy Knee LPS-Flex fixed bearing knee system replacement. MATERIALS AND METHODS: A total of 67 patients (101 knees) were enrolled in this study. 101 knees were operated on using the LPS-Flex fixed bearing knee system replacement. The same surgeon performed the surgery between December 2001 and March 2002. The patients' ages ranged from 52 to 77 years, with an average of 68.4 years. Preoperatively the factors considered were the age of the patient, gender, the body mass index, the flexion contracture and further flexion possible. The factors considered postoperatively were patellar tilting and displacement, the postoperative knee and functional score, and a varus deformity. The patients were followed up once every 3 month for up to 2 years. RESULTS: At the latest follow-up, the average flexion in this series was 130.8degrees (range, 90degrees-150degrees). Thirty knees could attain more than 140degrees flexion. Twenty patients could comfortably kneel down. The 53 patients could sit cross-legged. The eleven knees could attain less than 120degrees of flexion at the final follow-up. There was a significant improvement in flexion at each successive review 12 months after surgery. The most important factor that influenced the range of motion after an arthroplasty was the preoperative range of flexion. The average Knee Society knee score was 90 points (range, 80-100), and the function score was 91 points (range, 45-100). CONCLUSION: A total knee arthroplasty with LPS-flex showed an excellent range of motion and satisfactory early clinical results. The most important factor that influences the range of motion after an arthroplasty is the preoperative range of flexion.