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Paper 218: Comparison of Mobile-bearing versus Fixed bearing in High - Flex Total Knee Arthroplasty
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ABSTRACTS
by 14.8°⫾7.2 relative to the TEA (females 15.6°⫾6.3, males 13.9°⫾8.1, p ⫽ 0.2440) The AP and ML dimensions, as well as the aspect ratio are almost identical when the reference axes are PTM or TEA (p ⫽ 0.6504): AP ⫽ 46.4⫾4 and 46.2⫾4; ML⫽73.7⫾6 and 73.7⫾6; ML/AP ⫽1.59⫾0,12 and 1.6 ⫾ 0,11. Measurements differ significantly when the reference axis is the ATT (p ⬍ 0.0001): AP⫽ 51⫾8; ML⫽71.9⫾5 and ML/AP⫽ 1.44⫾0.18. The AP and ML dimensions differ significantly according to gender but the aspect ratio remains unchanged, except when the reference axis is the ATT. This could be due to a slightly higher external rotation of the ATT in females than in males. The AP dimension of the lateral plateau is greater than or equal to that of the medial plateau in 15% of knees (PTM), or 17% (TEA) or 3% (ATT). Conclusion The dimensions that define the shape and asymmetry of the tibial plateaus are variable depending on reference axis used for measurement. The majority of prosthetic tibial components available are designed for alignment with the PTM. A different design would be necessary if we wish to align the implant with the ATT and to avoid prosthetic overhang or insufficient coverage. Paper 217: Posterior Stabilized TKA’s are Less Sensitive to Implantation Tightness than PCL-Retaining Designs: A Biomechanical Study ROCHELLE NICHOLLS, PHD, AUSTRALIA, PRESENTING AUTHOR BEN JEFFCOTE, MD, AUSTRALIA HILAIRE A.C. JAKOB, PHD, SWITZERLAND MARKUS KUSTER, MD, SWITZERLAND ANDREAS SCHIRM, MD, SWITZERLAND ABSTRACT Introduction: Restricted range of motion or excessive laxity are potential complications of total knee arthroplasty (TKA). In contrast patients demand more function for daily activities. To achieve a good function after TKA is important but the aim for all patients should be a better flexion to kneel, work and live without restrictions. Hence the present study was to investigate the effects of implantation tightness on soft tissue strain during passive range of motion. Method and Material: Fourteen fresh frozen cadaver knee joints mounted in a passive flexion rig. Passive flexion was applied to the tibia in 15 deg increments from 0 to 150 deg of flexion. Tibiofemoral force and ligament strain of the medial and lateral collateral ligaments were measured using a custom-built force plat-
form inserted beneath the polyethylene inlay. The standard implantation technique and two variations (2 mm tighter, 2 mm looser) were tested for four prosthesis types: fixed-bearing PCL-retaining (with and without PCL) (PFC), mobile-bearing PCL-sacrificing (LCS), posterior-stabilised (PS), posterior-stabilised with HiFlex femoral component (HF). Results: As expected all prostheses showed a significant increase in tibiofemoral force at full extension when implantation tightness was increased. By comparison in the midrange between 15-90 deg the tibiofemoral force dropped down and was independent of variation in implantation tightness in all designs. Beyond 90 deg the fixed bearing design (PFC) and in the LCS knee were sensitive on implantation tightness. In contrast the two posterior stabilised prosthesis types (PS and HF) showed a different pattern of tibiofemoral force during flexion, with low force throughout the range of motion. Conclusion: As a result in full extension and deep flexion both the PFC prosthesis and the LCS knee represent sensitive designs when considering implantation tightness. Whereas posterior stabilised knee implants are associated with lower tibiofemoral force during the range of motion and more forgiving designs in relation to implantation tightness. The data also suggest that soft tissue structures other than the collaterals tighten as the knee flexes and cause an increase in tibiofemoral compressive force.
Paper 218: Comparison of Mobile-bearing versus Fixed bearing in High - Flex Total Knee Arthroplasty CHURL HONG CHUN, MD, PHD, KOREA, PRESENTING AUTHOR JUNG WOO KIM, MD, KOREA SEOK HYUN KWEON, MD, KOREA JUNG HWAN YANG, MD, SOUTH KOREA CHUL MIN LIM, MD, SOUTH KOREA ABSTRACT Purpose: The purpose of this study was to compare the clinical and radiological results of a PFC flex mobile bearing design with those of a LPS flex fixed bearing design in high-flex total knee arthroplasty. Materials and Methods: From January 2005 to November 2006, Forty-six patients who received PFC flex mobile bearing prosthesis in one knee and LPS flex fixed bearing prosthesis in the contralateral knee followed up for a minimum 2 years were evaluated. Clinical results were assessed using the ROM, the Hospital for Special Surgery, the Knee rating systems of the knee society, WOMAC score and SF-36. Radiological results were evaluated tibio-femoral angle and loosening or osteolysis
ABSTRACTS of components. We subdivided preoperative less 90 degree and more 90 degree in each group. Results: Mean ROM range of last follow up was increased to 131.1 degree in LPS group and 130.1 degree in PFC group. But there was no significant difference between the two groups. HSS score, knee pain and function score, WOMAC score, SF-36 score didn’t differ significantly between two groups. But descending stairs, rising from sitting, bending to the floor more improved significantly in LPS group. Tibio-femoral angle was changed from preoperative 8.2 degree varus to a postoperative 4.8 valgus. No knee had aseptic loosening or osteolysis. Conclusion: Postoperative ROM was increase significantly in PFC flex mobile bearing groups and LPS flex fixed bearing groups. But we found no significant differences between the two groups with regard to clinical and radiological parameters excepts descending stairs, rising from sitting, bending to the floor in WOMAC score. There was no aseptic loosening or osteolysis but needed long term observation about these concerns. Key Words: Total knee arthroplasty, High-flex total knee arthroplasty Paper 219: Reproducibility and the Importance of Isokinetic Tibial Rotatory Strength Findings in Healthy Individuals VEDRAN HADŽIC, MD, SLOVENIA, PRESENTING AUTHOR EDVIN DERVIŠEVIC, ASSOCIATE PROF, SLOVENIA MATJAZ VESELKO, MD, SLOVENIA ABSTRACT Background: The importance of knee rotatory strength following the ACL injury and surgical reconstruction was highlighted in the past years. Several studies reported the significant decrease in internal tibial rotation strength, following the reconstruction using the semitendinosus-gracillis graft. Strength deficits were identified using the isokinetic testing of the knee rotatory strength. No data regarding the reproducibility of such testing exists in the literature. The aim of our study was to evaluate the reproducibility of those testing procedure. Study Design: Descriptive Laboratory Study (validation study). Methods: Twenty three healthy physical education students without previous knee injury were tested twice over a period of one week using an isokinetic dynamometer. The main outcome measure was isokinetic peak torque of tibial internal and external rotation. For the evaluation of the reproducibility we have used absolute reproducibility indices and repeated measures analysis using factors muscle, contraction type, velocity and set.
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Results: Test-retest agreements were relatively low (0.20-0.72) with systematic difference between two consecutive sets of testing. The SEM%, representing the smallest change that indicates a real improvement for a group of subjects, was relatively small (10-18%). On the other hand, SRD%, that represents the smalles change that indicates a real improvement for single subject ranged from 38-50% for internal tibial rotators and from 23-42% for external tibial rotators. Conclusion: Isokinetic testing of the tibial rotatory strength shows a strong learning effect that contributes to the test-retest differences and indicates the need for extremely good familiarization with the device and testing procedure prior to any clinical decisions based on single testing.
Paper 220: Hamstring Antagonist Moments in Females Compared to Males: Further Investigation of the ACL Gender-bias ADAM BRYANT, AUSTRALIA, PRESENTING AUTHOR ERIK HOHMANN, FRCS, MD, PHD, AUSTRALIA KAY CROSSLEY, PHD, AUSTRALIA MARK CREABY, PHD, AUSTRALIA ABSTRACT Introduction: Given their role in reducing anterior tibial translation (ATT), the recruitment patterns and viscoelastic properties of the hamstring muscles have been implicated as neuromuscular factors contributing to the anterior cruciate ligament (ACL) gender bias. Nevertheless, it is uncertain whether patterns of aberration displayed by the female neuromuscular system significantly alters the antagonist moments generated by the hamstrings during maximal effort knee extension. Therefore, the purpose of the current study was to examine the effect of gender on hamstring antagonist moments in order to explain the higher ACL injury rates in females. Methods: Eleven females (age 30.6 ⫾ 10.1 yr, mass 62.1 ⫾ 6.9 kg, height 165.9 ⫾ 4.6) and 11 males (age 29.0 ⫾ 8.2 yr, mass 78.6 ⫾ 14.4 kg, height 178.5 ⫾ 6.2) with no history of trauma or disease in either knee and no evidence of abnormality on clinical examination were recruited as subjects. Surface electrodes were placed over the semitendinosus (ST) and biceps femoris (BF) muscles of the dominant and non-dominant limbs. Each subject performed two sets of five maximal extension and flexion repetitions at 180o●s-1 on a Cybex? isokinetic dynamometer. Test order for the non-dominant and dominant limbs was randomised. EMG, isokinetic torque and knee displacement data were sampled at 1000Hz using an AMLAB? data acquisition system.
ABSTRACTS
by 14.8°⫾7.2 relative to the TEA (females 15.6°⫾6.3, males 13.9°⫾8.1, p ⫽ 0.2440) The AP and ML dimensions, as well as the aspect ratio are almost identical when the reference axes are PTM or TEA (p ⫽ 0.6504): AP ⫽ 46.4⫾4 and 46.2⫾4; ML⫽73.7⫾6 and 73.7⫾6; ML/AP ⫽1.59⫾0,12 and 1.6 ⫾ 0,11. Measurements differ significantly when the reference axis is the ATT (p ⬍ 0.0001): AP⫽ 51⫾8; ML⫽71.9⫾5 and ML/AP⫽ 1.44⫾0.18. The AP and ML dimensions differ significantly according to gender but the aspect ratio remains unchanged, except when the reference axis is the ATT. This could be due to a slightly higher external rotation of the ATT in females than in males. The AP dimension of the lateral plateau is greater than or equal to that of the medial plateau in 15% of knees (PTM), or 17% (TEA) or 3% (ATT). Conclusion The dimensions that define the shape and asymmetry of the tibial plateaus are variable depending on reference axis used for measurement. The majority of prosthetic tibial components available are designed for alignment with the PTM. A different design would be necessary if we wish to align the implant with the ATT and to avoid prosthetic overhang or insufficient coverage. Paper 217: Posterior Stabilized TKA’s are Less Sensitive to Implantation Tightness than PCL-Retaining Designs: A Biomechanical Study ROCHELLE NICHOLLS, PHD, AUSTRALIA, PRESENTING AUTHOR BEN JEFFCOTE, MD, AUSTRALIA HILAIRE A.C. JAKOB, PHD, SWITZERLAND MARKUS KUSTER, MD, SWITZERLAND ANDREAS SCHIRM, MD, SWITZERLAND ABSTRACT Introduction: Restricted range of motion or excessive laxity are potential complications of total knee arthroplasty (TKA). In contrast patients demand more function for daily activities. To achieve a good function after TKA is important but the aim for all patients should be a better flexion to kneel, work and live without restrictions. Hence the present study was to investigate the effects of implantation tightness on soft tissue strain during passive range of motion. Method and Material: Fourteen fresh frozen cadaver knee joints mounted in a passive flexion rig. Passive flexion was applied to the tibia in 15 deg increments from 0 to 150 deg of flexion. Tibiofemoral force and ligament strain of the medial and lateral collateral ligaments were measured using a custom-built force plat-
form inserted beneath the polyethylene inlay. The standard implantation technique and two variations (2 mm tighter, 2 mm looser) were tested for four prosthesis types: fixed-bearing PCL-retaining (with and without PCL) (PFC), mobile-bearing PCL-sacrificing (LCS), posterior-stabilised (PS), posterior-stabilised with HiFlex femoral component (HF). Results: As expected all prostheses showed a significant increase in tibiofemoral force at full extension when implantation tightness was increased. By comparison in the midrange between 15-90 deg the tibiofemoral force dropped down and was independent of variation in implantation tightness in all designs. Beyond 90 deg the fixed bearing design (PFC) and in the LCS knee were sensitive on implantation tightness. In contrast the two posterior stabilised prosthesis types (PS and HF) showed a different pattern of tibiofemoral force during flexion, with low force throughout the range of motion. Conclusion: As a result in full extension and deep flexion both the PFC prosthesis and the LCS knee represent sensitive designs when considering implantation tightness. Whereas posterior stabilised knee implants are associated with lower tibiofemoral force during the range of motion and more forgiving designs in relation to implantation tightness. The data also suggest that soft tissue structures other than the collaterals tighten as the knee flexes and cause an increase in tibiofemoral compressive force.
Paper 218: Comparison of Mobile-bearing versus Fixed bearing in High - Flex Total Knee Arthroplasty CHURL HONG CHUN, MD, PHD, KOREA, PRESENTING AUTHOR JUNG WOO KIM, MD, KOREA SEOK HYUN KWEON, MD, KOREA JUNG HWAN YANG, MD, SOUTH KOREA CHUL MIN LIM, MD, SOUTH KOREA ABSTRACT Purpose: The purpose of this study was to compare the clinical and radiological results of a PFC flex mobile bearing design with those of a LPS flex fixed bearing design in high-flex total knee arthroplasty. Materials and Methods: From January 2005 to November 2006, Forty-six patients who received PFC flex mobile bearing prosthesis in one knee and LPS flex fixed bearing prosthesis in the contralateral knee followed up for a minimum 2 years were evaluated. Clinical results were assessed using the ROM, the Hospital for Special Surgery, the Knee rating systems of the knee society, WOMAC score and SF-36. Radiological results were evaluated tibio-femoral angle and loosening or osteolysis
ABSTRACTS of components. We subdivided preoperative less 90 degree and more 90 degree in each group. Results: Mean ROM range of last follow up was increased to 131.1 degree in LPS group and 130.1 degree in PFC group. But there was no significant difference between the two groups. HSS score, knee pain and function score, WOMAC score, SF-36 score didn’t differ significantly between two groups. But descending stairs, rising from sitting, bending to the floor more improved significantly in LPS group. Tibio-femoral angle was changed from preoperative 8.2 degree varus to a postoperative 4.8 valgus. No knee had aseptic loosening or osteolysis. Conclusion: Postoperative ROM was increase significantly in PFC flex mobile bearing groups and LPS flex fixed bearing groups. But we found no significant differences between the two groups with regard to clinical and radiological parameters excepts descending stairs, rising from sitting, bending to the floor in WOMAC score. There was no aseptic loosening or osteolysis but needed long term observation about these concerns. Key Words: Total knee arthroplasty, High-flex total knee arthroplasty Paper 219: Reproducibility and the Importance of Isokinetic Tibial Rotatory Strength Findings in Healthy Individuals VEDRAN HADŽIC, MD, SLOVENIA, PRESENTING AUTHOR EDVIN DERVIŠEVIC, ASSOCIATE PROF, SLOVENIA MATJAZ VESELKO, MD, SLOVENIA ABSTRACT Background: The importance of knee rotatory strength following the ACL injury and surgical reconstruction was highlighted in the past years. Several studies reported the significant decrease in internal tibial rotation strength, following the reconstruction using the semitendinosus-gracillis graft. Strength deficits were identified using the isokinetic testing of the knee rotatory strength. No data regarding the reproducibility of such testing exists in the literature. The aim of our study was to evaluate the reproducibility of those testing procedure. Study Design: Descriptive Laboratory Study (validation study). Methods: Twenty three healthy physical education students without previous knee injury were tested twice over a period of one week using an isokinetic dynamometer. The main outcome measure was isokinetic peak torque of tibial internal and external rotation. For the evaluation of the reproducibility we have used absolute reproducibility indices and repeated measures analysis using factors muscle, contraction type, velocity and set.
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Results: Test-retest agreements were relatively low (0.20-0.72) with systematic difference between two consecutive sets of testing. The SEM%, representing the smallest change that indicates a real improvement for a group of subjects, was relatively small (10-18%). On the other hand, SRD%, that represents the smalles change that indicates a real improvement for single subject ranged from 38-50% for internal tibial rotators and from 23-42% for external tibial rotators. Conclusion: Isokinetic testing of the tibial rotatory strength shows a strong learning effect that contributes to the test-retest differences and indicates the need for extremely good familiarization with the device and testing procedure prior to any clinical decisions based on single testing.
Paper 220: Hamstring Antagonist Moments in Females Compared to Males: Further Investigation of the ACL Gender-bias ADAM BRYANT, AUSTRALIA, PRESENTING AUTHOR ERIK HOHMANN, FRCS, MD, PHD, AUSTRALIA KAY CROSSLEY, PHD, AUSTRALIA MARK CREABY, PHD, AUSTRALIA ABSTRACT Introduction: Given their role in reducing anterior tibial translation (ATT), the recruitment patterns and viscoelastic properties of the hamstring muscles have been implicated as neuromuscular factors contributing to the anterior cruciate ligament (ACL) gender bias. Nevertheless, it is uncertain whether patterns of aberration displayed by the female neuromuscular system significantly alters the antagonist moments generated by the hamstrings during maximal effort knee extension. Therefore, the purpose of the current study was to examine the effect of gender on hamstring antagonist moments in order to explain the higher ACL injury rates in females. Methods: Eleven females (age 30.6 ⫾ 10.1 yr, mass 62.1 ⫾ 6.9 kg, height 165.9 ⫾ 4.6) and 11 males (age 29.0 ⫾ 8.2 yr, mass 78.6 ⫾ 14.4 kg, height 178.5 ⫾ 6.2) with no history of trauma or disease in either knee and no evidence of abnormality on clinical examination were recruited as subjects. Surface electrodes were placed over the semitendinosus (ST) and biceps femoris (BF) muscles of the dominant and non-dominant limbs. Each subject performed two sets of five maximal extension and flexion repetitions at 180o●s-1 on a Cybex? isokinetic dynamometer. Test order for the non-dominant and dominant limbs was randomised. EMG, isokinetic torque and knee displacement data were sampled at 1000Hz using an AMLAB? data acquisition system.