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ACL Deficient Patients With Passive Knee Joint Instability Overcompensate During Active Movements
2013 ISAKOS ABSTRACTS
implantation. Stage 1 involved ipsilateral knee arthroscopic chondral biopsy. Stage 2 involved arthroscopic debridement of the talar lesion with implantation of the cultured chondrocytes 4-6 weeks following stage 1. This latest generation of ACI (Chondron, Regenerative Medical Systems) is delivered to the lesion site as an injectable mixture of chondrocytes and fibrin that solidifies within 4 minutes of implantation. The step of cell implantation was performed as a dry arthroscopy with the use of a CO2 insufflator. Group C (n¼8) underwent two-stage open autologous chondrocyte implantation and included patients with depth of lesion > 8 mm on MRI or arthroscopy, or posterior talar lesions not amenable to arthroscopic implantation. Stage 2 implantation using either a medial malleolar osteotomy or anterolateral arthrotomy often involved bone grafting for lesions with depth > 8 mm. Patients from all groups underwent a similar postoperative rehabilitation program that included 6 weeks of non-weight bearing. Each patient was evaluated preoperatively and postoperatively with the American Orthopaedic Foot and Ankle Society ankle & hindfoot score (AOFAS), radiographs, and by magnetic resonance imaging (MOCART score). T2-mapping cartilage scans were performed at a minimum 1 year follow-up. The mean followup was 31 months (range 12 to 63 months). Results: All 3 groups had a similar distribution of cases with respect to patient age, lesion chronicity, defect location, and defect size. The mean preoperative AOFAS scores were group A 44 +/- 16 points, group B 41 +/- 8 points, group C 37 +/- 11 points. The mean postoperative AOFAS scores were group A 85 +/- 6 points, group B 89 +/- 11 points, group C 84 +/- 10 points. There was significant improvement from preoperative to postoperative AOFAS scores (P < .001) in all groups. There was no statistically significant difference in results between the groups. No patient in either group had any complications related to surgery, no patient in groups B/C had any knee complaints related to chondral biopsy, and no patient required any additional surgical procedures to the ankle joint besides implant removal in group C. The mean MOCART scores were group A ¼ 71, group B ¼ 87, group C ¼ 82. Restoration of the articular surface with a remodeled articular topography was commonly noted in groups B and C, whereas 38% of group A had incomplete defect repair with incongruent restoration of the articular topography. Most group A patients with poor MOCART scores had lesion size exceeding 200 mm2 and lesion depth > 5 mm. On MRI T2mapping at minimum 1 year follow-up 31% of group A and 65% of groups B/C revealed regenerated cartilage that was similar to surrounding healthy hyaline cartilage. Conclusion: Although the short-term clinical outcomes of arthroscopic BMS are comparable with arthroscopic / open ACI for symptomatic primary focal osteochondral defects of the talus, the radiological results (MOCART and T2 mapping) of ACI are significantly better than BMS. Both techniques are effective and safe as demonstrated by the significant and similar clinical improvements with no complications at a minimum 1-year follow-up. Although arthroscopic BMS is attractive in that it is a cost-effective single stage surgery, arthroscopic ACI has better radiological repair and the theoretical advantage of a more durable
e181
hyaline-rich cartilage repair. Further investigation is necessary to determine if this superior radiological repair results in improved structural and biomechanical properties, and whether this translates into better long-term outcomes. Paper #247: ACL Deficient Patients With Passive Knee Joint Instability Overcompensate During Active Movements TOBIAS MAXIMILIAN JUNG, MD, GERMANY PRESENTING AUTHOR MARKUS O. HELLER, PHD, GERMANY SEBASTIAN KOPF, MD, GERMANY RALF DOYSCHER, MD, GERMANY SVEN U. SCHEFFLER, MD, PHD, GERMANY GEORG DUDA, PHD, GERMANY WILLIAM TAYLOR, PHD, GERMANY HEIDE BOETH, MSC DIPL ING, GERMANY $ Julius Wolff Institute, Charité, Berlin, Berlin, Germany
SUMMARY By developing a novel technique to allow assessment of tibio-femoral kinematics, this study aimed to define the role of passive joint stability on active tibio-femoral kinematics during walking. ABSTRACT DATA Introduction: It is well known that rupture of the ACL does not only modify movement patterns of the lower limb, but also influences muscle activation, and hence results in a movement strategy that is thought to compensate for pain and joint instability by actively contracting and co-contracting local muscles during dynamic activities. The amount of additional joint stability provided by muscle activation remains unclear, but the additional muscular forces are thought to raise joint loading in a process that could play a key role in the subsequent clinically observed degenerative changes to the joint, including osteoarthritis (OA). By developing a novel technique to allow assessment of tibio-femoral kinematics, this study aimed to define the role of passive joint stability on active tibio-femoral kinematics during walking. Methods: Using motion capture, together with combinations of advanced techniques for assessing skeletal kinematics (SARA [1], SCoRE [2], OCST [3]), a novel noninvasive approach to evaluate dynamic tibio-femoral motion was tested in 8 healthy subjects. Here, the coefficient of variation (CV) was used in order to test the variability in A-P translation between multiple repetitions of walking trials. The intra-class correlation was calculated using ICC(3,1), to assess the intra-subject repeatability of A-P translation as well as the range of tibio-femoral A-P translation (difference between the minimum and maximum A-P movement over an entire gait cycle) between repetitions. The passive (KT1000) and active tibiofemoral joint stability was then examined in 13 patients with ACL rupture and compared to their healthy contralateral limbs. After verification using multi-factorial ANOVA analyses that ACL deficiency has an effect on A-P translation, a post-hoc test was applied to determine the magnitude of the difference in A-P translation between ACL ruptured and healthy (contralateral) knees.
2013 ISAKOS ABSTRACTS
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Results: The mean CV across all 16 healthy knees showed 5.2% variation (SD 1.2%) in A-P translation, demonstrating the high repeatability of the novel approach for assessing tibio-femoral kinematics between trials. Furthermore, excellent reliabilities were observed for both A-P translation over an entire gait cycle (mean ICC(3,1) ¼ 0.92) as well as the range of A-P translation (mean ICC(3,1) ¼ 0.98) between repetitions in individuals. The femora of the ACL ruptured knees generally remained more posterior relative to the tibia over the walking cycles compared to the healthy contralateral limbs. Surprisingly, the mean active range of tibio-femoral anterior-posterior translation over an entire gait cycle was significantly lower in ACL ruptured knees than in healthy joints (p<0.05). However, the passive tibial anterior translation was significantly greater in the ACL ruptured knees than in the healthy controls. A positive correlation was detected for both the ACL ruptured (R 2¼0.34) and the healthy contralateral knee joints (R 2¼0.47) between active and passive instability, but with a consistent offset of approximately 4mm between the healthy and ACL deficient knees. Discussion: Joints with pathological knee instability displayed reduced tibio-femoral A-P translation during active movements compared to healthy, passively stable knees. These results indicate that active stabilization of tibiofemoral kinematics appears to not only compensate for any passive joint instability, but actually overcompensate, and produce a situation that is kinematically more stable than in knees that are physiologically stable. One key finding of this study was that a positive relationship between passive and active instability exists for both physiologically healthy as well as for unstable knees. Additional stabilization of the joint in unstable knees, presumably through muscular co-contraction, led to a significant and almost constant 4-mm reduction of anterior motion of the tibia compared to healthy joints during the same activity. It seems that stabilization of the kinematics of the joint beyond these levels may either not be required or not be feasible, possibly since the anatomical lines of action of the stabilizing muscles are limited in their ability to restrain anterior tibial motion. An additional important observation was that the femora of the ACL ruptured knees were consistently located more posteriorly relative to the tibia during active movements. This phenomenon is unlikely to be an artifact of the assessment approach since the relative tibio-femoral motion was determined in a global manner (the approach imposes no artificial reference or “zero” position on the bones). It therefore seems reasonable that the additional femoral posterior translation occurred due to ACL deficiency [4]. The consequence of such altered kinematics would be joint loading in regions that may not be adapted to such loading conditions and therefore an increased risk for possible early joint degeneration [5]. Significance: Subjects after ACL rupture appear to overcompensate for passive knee joint instability by actively reducing tibio-femoral A-P translation, suggesting overloading of the joint, and thereby providing a plausible mechanism for explaining post-traumatic degeneration of cartilage in the joint.
REFERENCES 1. Ehrig RM, Taylor WR, Duda GN, Heller MO. A survey of formal methods for determining functional joint axes. J Biomech. 2007;40(10):2150-2157. 2. Ehrig RM, Taylor WR, Duda GN, Heller MO. A survey of formal methods for determining the centre of rotation of ball joints. J Biomech. 2006;39(15):27982809 3. Taylor WR, Ehrig RM, Duda GN, Schell H, Seebeck P, Heller MO. On the influence of soft tissue coverage in the determination of bone kinematics using skin markers. J Orthop Res. 2005;23(4):726-734. 4. Li G, Moses JM, Papannagari R, Pathare NP, DeFrate LE, Gill TJ. Anterior cruciate ligament deficiency alters the in vivo motion of the tibiofemoral cartilage contact points in both the anteroposterior and mediolateral directions. J Bone Joint Surg Am. 2006;88(8):1826-1834. 5. Lohmander LS, Ostenberg A, Englund M, Roos H. High prevalence of knee osteoarthritis, pain, and functional limitations in female soccer players twelve years after anterior cruciate ligament injury. Arthritis Rheum. 2004;50(10):3145-3152. Paper #248: Does Preoperative Exercise Influence the Outcome of ACL Reconstruction? RAJKUMAR SUKIRTH AMARAVATI, MBBS, DNB, MNAMS, INDIA PRESENTING AUTHOR PADMANABAN SEKARAN, MSC PT, INDIA $ St. John’s Medical College and Hospital, Bangalore, Karnataka, India
SUMMARY Does preoperative exercise influence the outcome of ACL reconstruction? ABSTRACT DATA Background and Purpose: Although volumes of literature have been generated every year relating to the rehabilitation parameters and protocols to be followed postoperatively, very few studies have addressed the pre operative period of an individual selected to undergo ACL reconstruction. We hypothesized that a structured preoperative exercise program would enhance postoperative functional outcomes following ACL reconstruction. The objective of the present study was to investigate the effectiveness of a structured pre operative exercise program. Methods: A single blind, prospective, randomized controlled study was undertaken. A total of 63 subjects were allocated into two groups. One group performed a structured pre-operative exercise program for 3 weeks (pre-op exercise group, n¼32), and the second group did not perform any exercise pre-operatively (No pre-op exercise group, n¼31). Both groups underwent an identical postoperative exercise regimen. A range of outcome measures were documented by a blinded assessor postoperatively at 6 weeks, 3 months, 6 months and one year.
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implantation. Stage 1 involved ipsilateral knee arthroscopic chondral biopsy. Stage 2 involved arthroscopic debridement of the talar lesion with implantation of the cultured chondrocytes 4-6 weeks following stage 1. This latest generation of ACI (Chondron, Regenerative Medical Systems) is delivered to the lesion site as an injectable mixture of chondrocytes and fibrin that solidifies within 4 minutes of implantation. The step of cell implantation was performed as a dry arthroscopy with the use of a CO2 insufflator. Group C (n¼8) underwent two-stage open autologous chondrocyte implantation and included patients with depth of lesion > 8 mm on MRI or arthroscopy, or posterior talar lesions not amenable to arthroscopic implantation. Stage 2 implantation using either a medial malleolar osteotomy or anterolateral arthrotomy often involved bone grafting for lesions with depth > 8 mm. Patients from all groups underwent a similar postoperative rehabilitation program that included 6 weeks of non-weight bearing. Each patient was evaluated preoperatively and postoperatively with the American Orthopaedic Foot and Ankle Society ankle & hindfoot score (AOFAS), radiographs, and by magnetic resonance imaging (MOCART score). T2-mapping cartilage scans were performed at a minimum 1 year follow-up. The mean followup was 31 months (range 12 to 63 months). Results: All 3 groups had a similar distribution of cases with respect to patient age, lesion chronicity, defect location, and defect size. The mean preoperative AOFAS scores were group A 44 +/- 16 points, group B 41 +/- 8 points, group C 37 +/- 11 points. The mean postoperative AOFAS scores were group A 85 +/- 6 points, group B 89 +/- 11 points, group C 84 +/- 10 points. There was significant improvement from preoperative to postoperative AOFAS scores (P < .001) in all groups. There was no statistically significant difference in results between the groups. No patient in either group had any complications related to surgery, no patient in groups B/C had any knee complaints related to chondral biopsy, and no patient required any additional surgical procedures to the ankle joint besides implant removal in group C. The mean MOCART scores were group A ¼ 71, group B ¼ 87, group C ¼ 82. Restoration of the articular surface with a remodeled articular topography was commonly noted in groups B and C, whereas 38% of group A had incomplete defect repair with incongruent restoration of the articular topography. Most group A patients with poor MOCART scores had lesion size exceeding 200 mm2 and lesion depth > 5 mm. On MRI T2mapping at minimum 1 year follow-up 31% of group A and 65% of groups B/C revealed regenerated cartilage that was similar to surrounding healthy hyaline cartilage. Conclusion: Although the short-term clinical outcomes of arthroscopic BMS are comparable with arthroscopic / open ACI for symptomatic primary focal osteochondral defects of the talus, the radiological results (MOCART and T2 mapping) of ACI are significantly better than BMS. Both techniques are effective and safe as demonstrated by the significant and similar clinical improvements with no complications at a minimum 1-year follow-up. Although arthroscopic BMS is attractive in that it is a cost-effective single stage surgery, arthroscopic ACI has better radiological repair and the theoretical advantage of a more durable
e181
hyaline-rich cartilage repair. Further investigation is necessary to determine if this superior radiological repair results in improved structural and biomechanical properties, and whether this translates into better long-term outcomes. Paper #247: ACL Deficient Patients With Passive Knee Joint Instability Overcompensate During Active Movements TOBIAS MAXIMILIAN JUNG, MD, GERMANY PRESENTING AUTHOR MARKUS O. HELLER, PHD, GERMANY SEBASTIAN KOPF, MD, GERMANY RALF DOYSCHER, MD, GERMANY SVEN U. SCHEFFLER, MD, PHD, GERMANY GEORG DUDA, PHD, GERMANY WILLIAM TAYLOR, PHD, GERMANY HEIDE BOETH, MSC DIPL ING, GERMANY $ Julius Wolff Institute, Charité, Berlin, Berlin, Germany
SUMMARY By developing a novel technique to allow assessment of tibio-femoral kinematics, this study aimed to define the role of passive joint stability on active tibio-femoral kinematics during walking. ABSTRACT DATA Introduction: It is well known that rupture of the ACL does not only modify movement patterns of the lower limb, but also influences muscle activation, and hence results in a movement strategy that is thought to compensate for pain and joint instability by actively contracting and co-contracting local muscles during dynamic activities. The amount of additional joint stability provided by muscle activation remains unclear, but the additional muscular forces are thought to raise joint loading in a process that could play a key role in the subsequent clinically observed degenerative changes to the joint, including osteoarthritis (OA). By developing a novel technique to allow assessment of tibio-femoral kinematics, this study aimed to define the role of passive joint stability on active tibio-femoral kinematics during walking. Methods: Using motion capture, together with combinations of advanced techniques for assessing skeletal kinematics (SARA [1], SCoRE [2], OCST [3]), a novel noninvasive approach to evaluate dynamic tibio-femoral motion was tested in 8 healthy subjects. Here, the coefficient of variation (CV) was used in order to test the variability in A-P translation between multiple repetitions of walking trials. The intra-class correlation was calculated using ICC(3,1), to assess the intra-subject repeatability of A-P translation as well as the range of tibio-femoral A-P translation (difference between the minimum and maximum A-P movement over an entire gait cycle) between repetitions. The passive (KT1000) and active tibiofemoral joint stability was then examined in 13 patients with ACL rupture and compared to their healthy contralateral limbs. After verification using multi-factorial ANOVA analyses that ACL deficiency has an effect on A-P translation, a post-hoc test was applied to determine the magnitude of the difference in A-P translation between ACL ruptured and healthy (contralateral) knees.
2013 ISAKOS ABSTRACTS
e182
Results: The mean CV across all 16 healthy knees showed 5.2% variation (SD 1.2%) in A-P translation, demonstrating the high repeatability of the novel approach for assessing tibio-femoral kinematics between trials. Furthermore, excellent reliabilities were observed for both A-P translation over an entire gait cycle (mean ICC(3,1) ¼ 0.92) as well as the range of A-P translation (mean ICC(3,1) ¼ 0.98) between repetitions in individuals. The femora of the ACL ruptured knees generally remained more posterior relative to the tibia over the walking cycles compared to the healthy contralateral limbs. Surprisingly, the mean active range of tibio-femoral anterior-posterior translation over an entire gait cycle was significantly lower in ACL ruptured knees than in healthy joints (p<0.05). However, the passive tibial anterior translation was significantly greater in the ACL ruptured knees than in the healthy controls. A positive correlation was detected for both the ACL ruptured (R 2¼0.34) and the healthy contralateral knee joints (R 2¼0.47) between active and passive instability, but with a consistent offset of approximately 4mm between the healthy and ACL deficient knees. Discussion: Joints with pathological knee instability displayed reduced tibio-femoral A-P translation during active movements compared to healthy, passively stable knees. These results indicate that active stabilization of tibiofemoral kinematics appears to not only compensate for any passive joint instability, but actually overcompensate, and produce a situation that is kinematically more stable than in knees that are physiologically stable. One key finding of this study was that a positive relationship between passive and active instability exists for both physiologically healthy as well as for unstable knees. Additional stabilization of the joint in unstable knees, presumably through muscular co-contraction, led to a significant and almost constant 4-mm reduction of anterior motion of the tibia compared to healthy joints during the same activity. It seems that stabilization of the kinematics of the joint beyond these levels may either not be required or not be feasible, possibly since the anatomical lines of action of the stabilizing muscles are limited in their ability to restrain anterior tibial motion. An additional important observation was that the femora of the ACL ruptured knees were consistently located more posteriorly relative to the tibia during active movements. This phenomenon is unlikely to be an artifact of the assessment approach since the relative tibio-femoral motion was determined in a global manner (the approach imposes no artificial reference or “zero” position on the bones). It therefore seems reasonable that the additional femoral posterior translation occurred due to ACL deficiency [4]. The consequence of such altered kinematics would be joint loading in regions that may not be adapted to such loading conditions and therefore an increased risk for possible early joint degeneration [5]. Significance: Subjects after ACL rupture appear to overcompensate for passive knee joint instability by actively reducing tibio-femoral A-P translation, suggesting overloading of the joint, and thereby providing a plausible mechanism for explaining post-traumatic degeneration of cartilage in the joint.
REFERENCES 1. Ehrig RM, Taylor WR, Duda GN, Heller MO. A survey of formal methods for determining functional joint axes. J Biomech. 2007;40(10):2150-2157. 2. Ehrig RM, Taylor WR, Duda GN, Heller MO. A survey of formal methods for determining the centre of rotation of ball joints. J Biomech. 2006;39(15):27982809 3. Taylor WR, Ehrig RM, Duda GN, Schell H, Seebeck P, Heller MO. On the influence of soft tissue coverage in the determination of bone kinematics using skin markers. J Orthop Res. 2005;23(4):726-734. 4. Li G, Moses JM, Papannagari R, Pathare NP, DeFrate LE, Gill TJ. Anterior cruciate ligament deficiency alters the in vivo motion of the tibiofemoral cartilage contact points in both the anteroposterior and mediolateral directions. J Bone Joint Surg Am. 2006;88(8):1826-1834. 5. Lohmander LS, Ostenberg A, Englund M, Roos H. High prevalence of knee osteoarthritis, pain, and functional limitations in female soccer players twelve years after anterior cruciate ligament injury. Arthritis Rheum. 2004;50(10):3145-3152. Paper #248: Does Preoperative Exercise Influence the Outcome of ACL Reconstruction? RAJKUMAR SUKIRTH AMARAVATI, MBBS, DNB, MNAMS, INDIA PRESENTING AUTHOR PADMANABAN SEKARAN, MSC PT, INDIA $ St. John’s Medical College and Hospital, Bangalore, Karnataka, India
SUMMARY Does preoperative exercise influence the outcome of ACL reconstruction? ABSTRACT DATA Background and Purpose: Although volumes of literature have been generated every year relating to the rehabilitation parameters and protocols to be followed postoperatively, very few studies have addressed the pre operative period of an individual selected to undergo ACL reconstruction. We hypothesized that a structured preoperative exercise program would enhance postoperative functional outcomes following ACL reconstruction. The objective of the present study was to investigate the effectiveness of a structured pre operative exercise program. Methods: A single blind, prospective, randomized controlled study was undertaken. A total of 63 subjects were allocated into two groups. One group performed a structured pre-operative exercise program for 3 weeks (pre-op exercise group, n¼32), and the second group did not perform any exercise pre-operatively (No pre-op exercise group, n¼31). Both groups underwent an identical postoperative exercise regimen. A range of outcome measures were documented by a blinded assessor postoperatively at 6 weeks, 3 months, 6 months and one year.
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