Recutting the distal femur to increase maximal knee extension during TKA causes coronal plane laxity in mid-flexion

BackgroundThe aim of this study was to quantify the effects of distal femoral cut height on maximal knee extension and coronal plane knee laxity.MethodsSeven fresh-frozen cadaver legs from hip-to-toe underwent a posterior stabilized TKA using a measured resection technique with a computer navigation system equipped with a robotic cutting guide. After the initial femoral resections were performed, the posterior joint capsule was sutured until a 10° flexion contracture was obtained with the trial components in place. Two distal femoral recuts of + 2 mm each were then subsequently made and the trials were reinserted. The navigation system was used to measure the maximum extension angle achieved and overall coronal plane laxity [in degrees] at maximum extension, 30°, 60° and 90° of flexion, when applying a standardized varus/valgus load of 9.8 [Nm] across the knee.ResultsFor a 10 degree flexion contracture, performing the first distal recut of + 2 mm increased overall coronal plane laxity by approximately 4.0° at 30° of flexion (p = 0.002) and 1.9° at 60° of flexion (p = 0.126). Performing the second + 2 mm recut of the distal femur increased mid-flexion laxity by 6.4° (p < 0.0001) at 30° and 4.0° at 60° of flexion (p = 0.01), compared to the 9 mm baseline resection (control). Maximum knee extension increased from 10° of flexion to 6.4° (± 2.5° SD, p < 0.005) and to 1.4° (± 1.8° SD, p < 0.001) of flexion with each 2 mm recut of the distal femur.ConclusionsRecutting the distal femur not only increases the maximum knee extension achieved but also increases coronal plane laxity in midflexion.     

Distal femoral dome varus osteotomy: surgical technique with minimal dissection and external fixation

The results obtained when employing distal femoral varus osteotomy are variable. Our objective was to describe a surgical technique involving minimal dissection, semicircular osteotomy with external fixation for valgus angular deformities, and early weight bearing.MethodsDesign: Series of cases. Setting: Orthopedic Referral Trauma Center. Patients: Sixteen patients with valgus angular deformities of > 12°. Intervention: Wedge varus osteotomy, minimal dissection with external fixation using a standard system, multidirectional Newfix. Main outcome measurements included pain, surgical time, knee flexion and extension angles, and assessment of knee function based on the Hospital Special Surgery knee rating scale (HSSkrs).ResultsOf 16 patients, 14 were evaluated to the end of the study. When we compared preoperative values with those obtained postoperatively at a mean of 24 ± 2.1 months, pain measurement was reduced from 7 to 2.1 (p = 0.002), angle of flexion was reduced from 105.4 ± 14.6° to 105.3 ± 11.1° (p = 0.06), and angle of extension, from ? 1.67 to ? 1.25° (p = 0.6), while HSSkrs assessment increased from 67.5 ± 2.7 to 79.4 ± 5 (p = 0.003). Two patients were excluded from the study, one due to infection that developed along the trajectory of a screw, and the other patient underwent complete arthroplasty of the knee, which was performed to combat the pain that was not being alleviated.ConclusionsThe technique improves function and reduces pain while facilitating early rehabilitation in 83% of cases.     

Effect of tibial component varus on wear in total knee arthroplasty

IntroductionMalalignment can result in poor clinical outcomes and increased wear. However, component malalignment can occur even when overall limb mechanical axis is within the normal anatomic range. We studied the effect of component malalignment in the presence of acceptable knee alignment in knee arthroplasty.MethodsSixteen tibial inserts retrieved at revision surgery were laser-mapped to measure wear. Average implantation duration was 7.7 years (range, 1 to 13). Early (postprimary) and final (prerevision) radiographs were analyzed for overall alignment (limb, femoral and tibial components) and osteolysis.ResultsThe tibial components were initially aligned in a mean of 1.3 ± 1.7° varus (range, –1.5 to 4.5°), which increased to 3.2 ± 2.9° (range, –2.0 to 8.0°) at the time of revision (p = 0.05). Tibial components initially placed in greater than 3° varus were associated with almost twice the volumetric penetration rate. Anatomic knee angles were 5.4 ± 0.9° valgus (range, 4.0 to 7.0°) in the post-primary radiographs and decreased in prerevision radiographs to 3.8 ± 2.6° (range, –1.0 to 7.5°), (p = 0.04).DiscussionTibial varus was associated with increased medial compartment wear and total wear, thus affecting osteolysis in addition to local destruction of the bearing surface. Varus malalignment as low as 3° may result in accelerated wear, even if overall limb alignment is nearly ideal. These results indicate that tibial component alignment is an important factor associated with tibial tray subsidence and polyethylene wear even when limb alignment is neutral.     

Reliability of stress radiography in the assessment of coronal laxity following total knee arthroplasty

BackgroundStress radiography is used in the valuation of soft tissue laxity following total knee arthroplasty (TKA). However, reliability and agreement is largely unknown.MethodsIn this prospective reliability study, we included 15 participants with prior TKA. Standardized coronal stress radiographs were obtained in both extension and flexion and with both varus and valgus stress. All radiographs were repeated (test–retest). In extension the Telos stress device was used, and flexion radiographs were obtained using the epicondylar-view. Three independent raters measured angulation between femoral and tibial component from all radiographs. Reliability was assessed by intra-class correlation coefficient (ICC) and agreement visualized with Bland–Altman plots and by mean difference and limits of agreement (LOA).ResultsStress radiography in extension showed excellent reliability with ICC = 0.96 (0.95–0.98) and LOA of ± 1.2°. Stress radiography at 80–90° of flexion showed good to excellent reliability when measuring medial laxity with ICC = 0.94 (0.89–0.97) and LOA of ± 1.7°; however, when measuring lateral laxity the reliability was only moderate to good with ICC = 0.70 (0.51–0.84) and LOA of ± 6.3°.ConclusionStress radiography is clinically applicable and the methods described in this study provide excellent reliability for measurement of laxity in extension. The reliability of measurements in flexion is good to excellent when measuring medial laxity but only moderate to good when measuring lateral laxity.     

Antagonist muscle moment is increased in ACL deficient subjects during maximal dynamic knee extension

IntroductionCoactivation of the hamstring muscles during dynamic knee extension may compensate for increased knee joint laxity in anterior cruciate ligament (ACL) deficient subjects. This study examined if antagonist muscle coactivation during maximal dynamic knee extension was elevated in subjects with anterior cruciate ligament (ACL) deficiency compared to age-matched healthy controls.MethodsElectromyography (EMG) and net knee joint moments were recorded during maximal concentric quadriceps and eccentric hamstring contractions, performed in an isokinetic dynamometer (ROM: 90–10°, angular speed: 30°/s). Hamstring antagonist EMG recorded during concentric quadriceps contraction was converted into antagonist moment based on the EMG–moment relationship observed during eccentric agonist contractions.ResultsThe magnitude of antagonist hamstring EMG was 65.5% higher in ACL deficient subjects compared to healthy controls (p < 0.05). Likewise, antagonist hamstring moment expressed in percentage of the measured net extension moment was elevated in ACL deficient subjects (56 ± 8 to 30 ± 6%) compared to controls (36 ± 5 to 19 ± 2%) at 20–50° of knee flexion (0° = full extension) (p < 0.05).DiscussionThe results showed a marked increase in hamstring coactivation towards more extended joint positions. Notably, this progressive rise in coactivation was greater in ACL deficient subjects, which may reflect a compensatory strategy to provide stability to the knee joint in the anterior–posterior plane during isolated knee extension. The present study encourages further investigations of hamstring coactivation in ACL deficient subjects.     

Abnormal tibiofemoral kinematics following ACL reconstruction are associated with early cartilage matrix degeneration measured by MRI T1rho

PurposeAltered kinematics following ACL-reconstruction may be a cause of post-traumatic osteoarthritis. T_1ρ MRI is a technique that detects early cartilage matrix degeneration. Our study aimed to evaluate kinematics following ACL-reconstruction, cartilage health (using T_1ρ MRI), and assess whether altered kinematics following ACL-reconstruction are associated with early cartilage degeneration.MethodsEleven patients (average age: 33 ± 9 years) underwent 3 T MRI 18 ± 5 months following ACL-reconstruction. Images were obtained at extension and 30° flexion under simulated loading (125 N). Tibial rotation (TR) and anterior tibial translation (ATT) between flexion and extension, and T_1ρ relaxation times of the knee cartilage were analyzed. Cartilage was divided into five compartments: medial and lateral femoral condyles (MFC/LFC), medial and lateral tibias (MT/LT), and patella. A sub-analysis of the femoral weight-bearing (wb) regions was also performed. Patients were categorized as having “abnormal” or “restored” ATT and TR, and T_1ρ percentage increase was compared between these two groups of patients.ResultsAs a group, there were no significant differences between ACL-reconstructed and contralateral knee kinematics, however, there were individual variations. T_1ρ relaxation times of the MFC and MFC-wb region were elevated (p ≤ 0.05) in the ACL-reconstructed knees compared to the uninjured contralateral knees. There were increases (p ≤ 0.05) in the MFC-wb, MT, patella and overall average cartilage T_1ρ values of the “abnormal” ATT group compared to “restored” ATT group. The percentage increase in the T_1ρ relaxation time in the MFC-wb cartilage approached significance (p = 0.08) in the “abnormal” versus “restored” TR patients.ConclusionsAbnormal kinematics following ACL-reconstruction appear to lead to cartilage degeneration, particularly in the medial compartment.     

Frontal plane knee mechanics and medial cartilage MR relaxation times in individuals with ACL reconstruction: A pilot study

BackgroundThe objective of this pilot study was to evaluate cartilage T_1ρ and T₂ relaxation times and knee mechanics during walking and drop-landing for individuals with anterior cruciate ligament reconstruction (ACL-R).MethodsNine patients (6 men and 3 women, age 35.8 ± 5.4 years, BMI 23.5 ± 2.5 kg/m²) participated 1.5 ± 0.8 years after single-bundle two-tunnel ACL reconstruction. Peak knee adduction moment (KAM), flexion moment (KFM), extension moment (KEM), and peak varus were calculated from kinematic and kinetic data obtained during walking and drop-landing tasks. T_1ρ and T₂ times were calculated for medial femur (MF), and medial tibia (MT) cartilage and compared between subjects with low KAM and high KAM. Biomechanical variables were compared between limbs.ResultsThe high KAM group had higher T_1ρ for MT (p = 0.01), central MT (p = 0.05), posterior MF (p = 0.04), posterior MT (p = 0.01); and higher T₂ for MT (p = 0.02), MF (p = 0.05), posterior MF (p = 0.002) and posterior MT (p = 0.01). During walking, ACL-R knees had greater flexion at initial contact (p = 0.04), and lower KEM (p = 0.02). During drop-landing, the ACL-R knees had lower KAM (p = 0.03) and KFM (p = 0.002).ConclusionPatients with ACL-R who have higher KAM during walking had elevated MR relaxation times in the medial knee compartments. These data suggest that those individuals who have undergone ACL-R and have higher frontal plane loading, may be at a greater risk of knee osteoarthritis.     

Intraoperative assessment of midflexion laxity in total knee prosthesis

BackgroundSoft-tissue balancing of the knee is fundamental to the success of a total knee arthroplasty (TKA). In posterior-stabilized TKA, there is no stabilizer of the anterior–posterior translation in the midflexion range in which the cam-post mechanism does not engage yet. Therefore, instability in the midflexion range is suspected to occur in posterior-stabilized TKA. The purpose of this study was to measure the joint gap throughout a full range of motion and to analyze the joint gap laxity in the midflexion range after implantation of a mobile-bearing posterior-stabilized total knee prosthesis.MethodsJoint gap kinematics in 259 knees with varus osteoarthritis were measured during TKAs using a tensor device with the same shape of a total knee prosthesis of the same design was used. After the implantation of a mobile-bearing posterior-stabilized prosthesis and the reduction of the patellofemoral joint, the joint gap was measured at 0°, 30°, 60°, 90°, 120°, and 145° of flexion.ResultsThe center size of the joint gap was tight in extension and deep flexion and loose at midflexion ranges, especially at 30° of flexion (p < 0.001). The symmetry of the joint gap was varus at 0° and 145° of flexion (p < 0.001).ConclusionsOur results showed the joint gap laxity in the midflexion range after the implantation of a mobile-bearing posterior-stabilized prosthesis. Our new tensor device, which can attach the polyethylene insert trial, will provide the important information about the joint gap kinematics after implantation of total knee prostheses.Level of evidenceIV.     

Factors contributing to inherent varus alignment of lower limb in normal Asian adults: Role of tibial plateau inclination

PurposeThis prospective study aimed to evaluate radiographically, mechanical or hip–knee–ankle (HKA) axis in healthy, asymptomatic, Asian (Indian and Korean) adults between 20 and 40 years of age to determine the incidence of inherent varus (mechanical limb alignment of > 3° varus) and the factors influencing it.MethodsThree hundred and eighty-eight lower limbs were evaluated using full length, standing hip-to-ankle radiographs in 198 healthy, asymptomatic, Asian (Indian and Korean) adults between 20 and 40 years of age to assess the hip–knee–ankle (HKA) angle, medial proximal tibial angle (MPTA), femoral bowing and femoral neck–shaft angle to determine the incidence of inherent varus (mechanical limb alignment of > 3° varus) and the factors influencing it.ResultsOverall, the mean HKA angle was 177.6° ± 2.6° with 34.5% of limbs in inherent varus (mean HKA angle 174.9° ± 1.8°). The incidence of inherent varus was significantly higher (p = 0.01) in males (40%) compared to females (28%) but similar among Indian (34%) and Korean subjects (35%). The hip–knee–ankle (HKA) angle showed significant positive correlation (r = 0.82, p < 0.001) with only the medial proximal tibial angle (MPTA).ConclusionsInherent varus alignment of the lower limb is fairly common among asymptomatic, Asian adults. These results raise several pertinent questions regarding the role of inherent varus in the aetiopathogenesis of knee osteoarthritis and in lower limb realignment procedures.     

The effect of component alignment on clinical outcomes in fixed bearing unicompartmental knee arthroplasty

BackgroundThe aim of this study is to report component alignment in a series of ZUK fixed bearing unicompartmental knee arthroplasty (UKA) implants and compare this to clinical outcomes.MethodsThe radiographs, Knee Society Scores (KSS) and knee flexion of 223 medial UKAs were evaluated. The following alignment parameters were assessed; coronal and sagittal femoral component angle (c-FCA and s-FCA), coronal and sagittal tibia component angle (c-TCA and s-TCA) and the coronal tibiofemoral angle (c-TFA). Each alignment parameter was grouped at consecutive 2.5° intervals, mean KSS and knee flexion was then compared between the interval groups.Results96.4% of femoral components were between 7.5° of varus and valgus and 95.1% between 7.5° extension and 5° flexion. 89.6% of tibial components were between 7.5° of varus and 2.5° valgus and 97.3% between 2.5° and 15° flexion. There was no significant difference between the KSS or knee flexion between any of the incremental groups of component alignment. Mean c-TFA was 0.2 ± 3.0°, 92.4% were between −5° (varus) and 5° (valgus). KSS were significantly greater for two of the increments with slightly more varus. Linear regression analysis showed there was very weak correlation (R² = 0.1933) between c-TFA and c-TCA.ConclusionsThe results of this study show that fixed bearing UKA components are forgiving to accommodate some variation in tibial and femoral component position without effecting clinical outcome scores or knee flexion. Limb alignment matters more than component position and knees with slight varus tibiofemoral alignment have better clinical scores than those with valgus.     

Knee joint laxity and passive stiffness in meniscectomized patients compared with healthy controls

BackgroundPassive mechanical behavior of the knee in the frontal plane, measured as angular laxity and mechanical stiffness, may play an important role in the pathogenesis of knee osteoarthritis (OA). Little is known about knee laxity and stiffness prior to knee OA onset. We investigated knee joint angular laxity and passive stiffness in meniscectomized patients at high risk of knee OA compared with healthy controls.MethodsSixty patients meniscectomized for a medial meniscal tear (52 men, 41.4 ± 5.5 years, 175.3 ± 7.9 cm, 83.6 ± 12.8 kg, mean ± SD) and 21 healthy controls (18 men, 42.0 ± 6.7 years, 176.8 ± 5.7 cm, 77.8 ± 13.4 kg) had their knee joint angular laxity and passive stiffness assessed twice ~ 2.3 years apart. Linear regression models including age, sex, height and body mass as covariates in the adjusted model were used to assess differences between groups.ResultsGreater knee joint varus (− 10.1 vs. − 7.3°, p < 0.001), valgus (7.1 vs. 5.6°, p = 0.001) and total (17.2 vs. 12.9°, p < 0.001) angular laxity together with reduced midrange passive stiffness (1.71 vs. 2.36 Nm/°, p < 0.001) were observed in patients vs. healthy controls. No differences were observed in change in stiffness over time between patients and controls, however a tendency towards increased laxity in patients was seen.ConclusionsMeniscectomized patients showed increased knee joint angular laxity and reduced passive stiffness ~ 3 months post surgery compared with controls. In addition, the results indicated that knee joint laxity may increase over time in meniscectomized patients.     

Effects of knee bracing on postural control after anterior cruciate ligament rupture

Study designRandomized clinical trial.ObjectivesTo investigate the effects of functional knee braces on postural control in patients with anterior cruciate ligament (ACL) rupture.BackgroundACL rupture leads to both mechanical knee instability and deficits in proprioception. Although elastic knee braces do not increase mechanical stability, patients report improved stability when wearing a brace. Elastic braces were found to reduce the loss of proprioception. It is, however, still unclear whether they also improve postural control, which involves the processing of proprioceptive input at a higher level.MethodsWe studied 58 patients with isolated unilateral ACL rupture using computerized dynamic posturography and compared overall stability index (OSI) scores for injured and uninjured legs with and without a knee brace. In addition, patients were classified as copers and non-copers depending on knee function.ResultsWithin subjects, OSI scores were 3.0 ± 1.1° for uninjured legs when unbraced, 2.8 ± 1.3° for uninjured legs when braced (p = 0.17), 3.7 ± 1.5° for unbraced injured legs, and 2.9 ± 1.3° for braced injured legs (p < 0.001). For the injured legs of copers and non-copers, OSI scores were 3.4° ± 1.2° for copers and 4.0° ± 1.6° for non-copers in the unbraced condition (p = 0.11) and 2.7 ± 1.0° for copers and 3.1 ± 1.4° for non-copers in the braced condition (p = 0.26).ConclusionElastic knee braces increase postural stability by approximately 22% in patients with ACL rupture. There was no difference in postural stability between uninjured and injured legs in the braced condition. One possible explanation is that bracing improves both proprioception and postural control.Level of evidenceControlled clinical trial, level 2a.     

The effect of hip adduction angle on patellar position measured using real time ultrasound scanning

IntroductionThere are limited in vivo studies investigating the influence of the Iliotibial Band (ITB) on patellar position, despite numerous references in the literature to this relationship. The purpose of this study was to investigate how the ITB influences patellar position, in vivo, indirectly through alteration of frontal plane hip position.MethodTwelve healthy, asymptomatic, male subjects (age 23 ± 2.6 years) had their patellar position examined using real time ultrasound scanning. The knee was passively placed into 20° flexion and combined with hip neutral, 20° hip adduction and 20° hip abduction. Mean patellar position (distance from the lateral border of the patella to the edge of the intersection of the trochlear groove and lateral femoral condyle) was measured, with the smaller values representing a position whereby the patella is drawn more laterally and closer to the lateral femoral condyle.ResultsMean patellar position for neutral was 8.1 mm (± 1.72 mm). Following 20° hip abduction the mean patellar position was 8.9 mm (± 1.79 mm), this was a statistically significant change in patellar position (p = 0.003). Following 20° hip adduction the mean patellar displacement was 7.3 mm (± 1.4 mm) which, again, was a statistically significant change in patellar position (p = 0.009). The results indicate that with the hip adduction the patella was positioned significantly more laterally (smaller value for distance).DiscussionThe results of this study support the hypothesis that hip adduction which is likely to create loading and lengthening of the ITB causes significantly greater lateral displacement of the patella, than when the hip is abducted and the ITB unloaded.Level of evidence: 2b individual cohort study.     

In vivo kinematic analysis of posterior-stabilized total knee arthroplasty for the valgus knee operated by the gap-balancing technique

BackgroundMost in vivo kinematic studies of total knee arthroplasty (TKA) report on the varus knee. The objective of the present study was to evaluate in vivo kinematics of a posterior-stabilized fixed-bearing TKA operated on a valgus knee during knee bending in weight-bearing (WB) and non-weight-bearing (NWB).MethodsA total of sixteen valgus knees in 12 cases that underwent TKA with Scorpio NRG PS knee prosthesis and that were operated on using the gap balancing technique were evaluated. We evaluated the in vivo kinematics of the knee using fluoroscopy and femorotibial translation relative to the tibial tray using a 2-dimensional to 3-dimensional registration technique.ResultsThe average flexion angle was 111.3° ± 7.5° in WB and 114.9° ± 8.4° in NWB. The femoral component demonstrated a mean external rotation of 5.9° ± 5.8° in WB and 7.4° ± 5.2° in NWB. In WB and NWB, the femoral component showed a medial pivot pattern from 0° to midflexion and a bicondylar rollback pattern from midflexion to full flexion. The medial condyle moved similarly in the WB condition and in the NWB condition. The lateral condyle moved posteriorly at a slightly earlier angle during the WB condition than during the NWB condition.ConclusionsWe conclude that similar kinematics after TKA can be obtained with the gap balancing technique for the preoperative valgus deformity when compared to the kinematics of a normal knee, even though the magnitude of external rotation was small. Level of evidence: IV.     

Does flexion of the femoral implant in total knee arthroplasty increase knee flexion: A randomised controlled trial

IntroductionProsthetic and operative modifications in total knee arthroplasty (TKA) have been proposed to maximise post-operative knee flexion as it is essential in routine functional activities.MethodsWe performed a double blind randomised controlled trial to compare clinical outcomes of primary cruciate-retaining TKA for osteoarthritis with the femoral component implanted in either 4° flexion in the sagittal plane (F) or in a neutral position (C). The primary outcome of knee flexion and secondary outcomes knee extension, quadriceps strength, WOMAC, SF-12v2, timed stand test, stair climb test and satisfaction were assessed at 1 year. Knee flexion and extension were also assessed intra-operatively. Implant flexion was measured from true lateral radiographs.ResultsThirty-nine participants (40 knees) were recruited, 20 knees per group. Three subjects from the control group and two from the flexed group were lost to 1 year follow-up but numbers were sufficient to satisfy the sample size calculation. Significant differences were found between the groups in knee flexion (F: 113.6 ± 8.8° pre-operative, 122.4 ± 6.0° intra-operative, 110.2 ± 7.5° 1 year, C: 117.4 ± 11.7°, 117.4 ± 7.6°, 103.5 ± 10.7°. p = 0.031) and mental component score of the SF12-v2 (F 53.3 ± 13.2, C 61.1 ± 7.3, p = 0.009) but there were no significant differences in other outcomes and patients were equally satisfied.ConclusionFlexing the femoral implant in this cruciate retaining TKA system provided a significant difference in knee flexion compared to a neutral position. The improvement appears to occur predominantly at surgery and was not associated with a clinical or functional benefit at 1 year. (ACTRN12606000325505). Level of evidence: Level 1; randomised controlled trial.     

A quantitative assessment of varus thrust in patients with medial knee osteoarthritis

Varus thrust is an abnormal lateral knee motion frequently seen in patients with medial knee osteoarthritis (OA) during gait. It is a worsening of the alignment in the stance phase of the gait cycle and closely relates to disease progression. In this study, we measured the thrust quantitatively using skin markers and examined the relationship to other static and dynamic parameters. Forty-four knees in 32 patients (mean age, 72 years; range, 64–81 years) who exhibited the radiographic OA at least grade 2 according to the Kellgren–Lawrence (K–L) scale were enrolled. Gait analysis was performed for each patient to measure the amount of thrust and knee adduction moment. The amounts of thrust in subjects with K–L grades 2 (25 knees), 3 (13 knees), and 4 (6 knees) were 2.4°(± 1.3°), 2.8°(± 1.4°), and 7.2°(± 5.3°), respectively and the knee adduction moments were 3.6(± 1.5) %BW ? Ht, 3.9(± 1.2) %BW ? Ht and 6.9(± 2.2%) BW ? Ht, respectively. The amount of thrust also exhibited significant correlation to static radiographic alignment (R = 0.47: 95% confidence interval 0.67–0.21, p = 0.0038) and showed greater correlation to the knee adduction moment (R = 0.73: 95% confidence interval 0.84–0.55, p < 0.001), which has been identified as an important dynamic index of the disease. The amount of thrust, which is able to be measured by simple inexpensive equipment, correlated to static and dynamic parameters and may offer an important clinical index for knee OA.     

The in vivo relationship between anterior neutral tibial position and loss of knee extension after transtibial ACL reconstruction

BackgroundRestoration of anterior tibial stability while avoiding knee extension deficit are a common goal of anterior cruciate ligament (ACL) reconstruction. However, achieving this goal can be challenging. The purpose of this study was to determine whether side-to-side differences in anterior tibial neutral position and laxity are correlated with knee extension deficit in subjects 2 years after ACL reconstruction.MethodsIn the reconstructed and contralateral knees of 29 subjects with transtibial reconstruction, anterior tibiofemoral neutral position was measured with MRI and three-dimensional modeling techniques; terminal knee extension at heel strike of walking and during a seated knee extension were measured via gait analysis; and anterior laxity was measured using the KT-1000.ResultsKnees that approached normal anterior stability and anterior tibial position had increased extension deficit relative to the contralateral knee. On average the reconstructed knee had significantly less (2.1 ± 4.4°) extension during active extension and during heel strike of walking (3.0 ± 4.3º), with increased anterior neutral tibial position (2.5 ± 1.7 mm) and anterior laxity (1.8 ± 1.0 mm). There was a significant correlation between side-to-side difference in anterior neutral tibial position with both measures of knee extension (walking, r = − 0.711, p < 0.001); active knee extension, r = − 0.544, p = 0.002).ConclusionThe results indicate a relationship between the loss of active knee extension and a change in anterior neutral tibial position following non-anatomic transtibial ACL reconstruction. Given the increasing evidence of a link between altered kinematics and premature osteoarthritis, these findings provide important information to improve our understanding of in vivo knee function after ACL reconstruction.     

Quantitative measurement of lower limb mechanical alignment and coronal knee laxity in early flexion

BackgroundNon-invasive quantification of lower limb alignment using navigation technology is now possible throughout knee flexion owing to software developments. We report the precision and accuracy of a non-invasive system measuring mechanical alignment of the lower limb including coronal stress testing of the knee.MethodsTwelve cadaveric limbs were tested with a commercial invasive navigation system against the non-invasive system. Coronal mechanical femorotibial (MFT) alignment was measured with no stress, then 15 Nm varus and valgus applied moments. Measurements were recorded at 10° intervals from extension to 90° flexion. At each flexion interval, coefficient of repeatability (CR) tested precision within each system, and limits of agreement (LOA) tested agreement between the two systems. Limits for CR & LOA were set at 3° based on requirements for surgical planning and evaluation.ResultsPrecision was acceptable throughout flexion in all conditions of stress using the invasive system (CR ≤ 1.9°). Precision was acceptable using the non-invasive system from extension to 50° flexion (CR ≤ 2.4°), beyond which precision was unacceptable (> 3.4°). With no coronal stress applied, agreement remained acceptable from extension to 40° (LOA ≤ 2.4°), and when 15 Nm varus or valgus stress was applied agreement was acceptable from extension to 30° (LOA ≤ 2.9°). Higher angles of knee flexion had a negative impact on precision and accuracy.Conclusion & clinical relevanceThe non-invasive system provides reliable quantitative data in-vitro on coronal MFT alignment and laxity in the range relevant to assessment of collateral ligament injury, pre-operative planning of arthroplasty and flexion instability following arthroplasty. In-vivo validation should be performed.     

Interactive effect of femoral posterior condylar offset and tibial posterior slope on knee flexion in posterior cruciate ligament-substituting total knee arthroplasty

Background

This work aimed to evaluate the changes in the femoral posterior condylar offset (PCO) and tibial slope after posterior cruciate ligament (PCL)-substituting total knee arthroplasty (TKA), and to address the presence of any interactive effect between the two on knee flexion.

Anatomical features of tibia and femur: Influence on laxity in the anterior cruciate ligament deficient knee

Background

Until now, there has been a lack of in vivo analysis of the correlation between bony morphological features and laxity values after an anterior cruciate ligament (ACL) injury.