A bicruciate retaining (BCR) TKA is thought to maintain a closer resemblance to the native knee kinematics compared to a posterior cruciate retaining (CR) TKA. With BCR TKAs retainment of the anterior cruciate ligament (ACL) facilitates proprioception and balance which is thought to lead to more natural knee kinematics and increased functional outcome. The aim of this study was to quantify and compare the kinematics of a BCR and CR TKA during functional tests. In this patient-blinded randomized controlled trial, a total of 40 patients with knee osteoarthritis were included, 18 of them received a BCR TKA (Vanguard XP, Zimmer-Biomet) and 22 received a CR TKA (Vanguard CR, Zimmer-Biomet). Fluoroscopic analysis was done 1 year post-operatively. The main outcome was posterior femoral rollback (i.e. translation of the femorotibial contact point (CP)) of the BCR and CR TKA during a step-up test. Secondary, the kinematics during a lunge test were quantified as anterior-posterior (AP) translation of the femorotibial CP. Independent student t-tests (or non-parametric equivalent) were used to analyze the effect of BCR versus CR TKA on these measures, to correct for the multiple testing problem post-hoc Bonferroni-Holm corrections were applied.Introduction
Materials and Methods
The cruciate ligaments are important structures for biomechanical stability of the knee. For total knee arthroplasty (TKA), understanding of the exact function of the (PCL) and anterior (ACL) cruciate ligament during walking is important in the light of recent designs of bicruciate TKAs. However, studies evaluating in vivo function of the PCL during daily activities such as walking are scarce. We aimed to assess the role of the PCL during gait by measuring kinematics and kinetics of individuals with PCL deficiency and compare them with individuals with ACL deficiency and healthy young adults. Individuals with unilateral PCL deficiency (PCLD; n=9), unilateral ACL deficiency (n=10) and healthy young adults performed (n=10) 10 walk trials (5 for each leg) in which they walked over a force platform. Motion analysis (Vicon Motion Capture System) was used to calculate joint angles and internal moments around the knee, hip and ankle in the sagittal plane. Joint angles and moments of the injured knee (in PCLD and ACLD) or left knee (in HYA) were compared between groups at weight acceptance, mid-stance and push-off phases (see Fig. 1). Clinical assessment included passive knee laxity (Kneelax) for anterior (in 20–30° knee flexion) and posterior tibia translation (in 70–90° knee flexion) and Lysholm questionnaires.Background
Methods
The number of revisions of total knee replacements (TKR) increases annually. Because of reduced bone stock, stable fixation of the implant is important. The femoral and tibial components are usually cemented whereas stems can be placed either cemented or press-fit (hybrid construct). To assess the stability of revision TKR with either cemented or hybrid places implants a randomized controlled trial (RCT) was executed, by using radiostereometric analysis (RSA). The short-term results of this RCT showed no differences between the two groups in stability and clinical outcomes. Although there were no clinical or radiological signs of loosening, both groups showed implants micromotion > 1 mm or degree. These findings might indicate the possibility of loosening later in time; therefore, the current study investigated the stability of cemented versus hybrid-placed revision TKR 6.5 years after surgery. Additionally, clinical results were evaluated. Of the 32 patients in the original RCT, 23 (12 cement, 11 press-fit) were available for mid-term follow-up measures. RSA images taken at baseline, 6 weeks, 3, 6, 12 and 24 months postoperatively were used from the previous study. New RSA images were taken at median 6.5 years (range 5.4–7.3) postoperatively. Stability of the femoral and tibial implants was assessed by using model-based RSA software (RSAcore, Leiden, The Netherlands) to determine micromotion. Clinical results were evaluated using the Knee Society Score (KSS), the Knee injury and Osteoarthritis Outcome Score (KOOS), active flexion, and VAS pain and satisfaction. Stability and clinical outcome were compared between the two groups using independent t-tests or Mann-Whitney U tests when applicable.Introduction
Methods
Tibial slope was shown to majorly affect the outcomes of Total Knee Arthroplasty (TKA). More slope of the tibial component could help releasing a too tight flexion gap in cruciate-retaining (CR) TKA and is generally associated with a wider range of post-operative knee flexion. However, an excessive tibial slope could jeopardize the knee stability in flexion. The mechanism by which tibial slope affects the function of CR-TKA is not well understood. Moreover, it is not known whether the tibial bone resection should be performed by referencing the anterior cortex (AC) of the tibia or the center of the tibial plateau (CP) and whether the choice of either technique plays a role. The aim of this study was to investigate the effect of tibial slope on the position of tibiofemoral (TF) contact point, knee ligament forces, quadriceps muscle forces, and TF and patellofemoral (PF) joint contact forces during squat activity in CR-TKA. A previously validated musculoskeletal model of CR-TKA was used to simulate a squat activity performed by a 86-year-old male subject wearing an instrumented prosthesis [1,2]. Marker data over four consecutive repetitions of a squat motion were tracked using a motion optimization algorithm. Muscle and joint forces and moments were calculated from an inverse-dynamic analysis, coupled with Force-Dependent Kinematics (FDK) to solve knee kinematics, ligament and contact forces simultaneously. The tibial slope in the postoperative case was 0 degree and constituted the reference case for our simulations. In addition, eight additional cases were simulated with −3, +3, +6, +9 degrees of tibial slope, four of them simulating an AC referencing technique and four a CP technique.Introduction
Methods
To improve implant positioning in total knee arthroplasty (TKA) patient-specific instrumentation (PSI) has been introduced as alternative for conventional instrumentation (CI). Though the PSI technique offers interesting opportunities in TKA, there is no consensus about the effectiveness of PSI in comparison with CI and results concerning soft-tissue balancing remain unclear. Therefore, the primary aim of the present study was to investigate the varus-valgus laxity in extension and flexion in patients receiving a TKA using PSI compared with CI. Additionally, radiological, clinical and functional outcomes were assessed. In this prospective randomization controlled trial, 42 patients with osteoarthritis received a Genesis II PS (Smith & Nephew, Memphis, Tennessee), with either PSI (Visionaire, Smith & Nephew) or CI (Smith & Nephew). Patients visited the hospital preoperative and postoperative after 6 weeks, 3 and 12 months. One-year postoperative varus-valgus laxity was measured in extension and flexion on stress radiographs. Additional assessments included: the hip-knee-ankle angle on long-leg radiographs, femoral and tibia component rotation on CT-scans, radiolucency, the Knee Society Score (KSS), VAS pain, VAS Satisfaction, Knee injury and Osteoarthritis Outcome score (KOOS), Patella score (Kujala), the University of California Los Angeles activity score (UCLA), the anterior-posterior laxity in 20° and 90° knee flexion, adverse events and complications. The outcome measures were compared using independent t-tests, non-parametric alternatives and repeated measurements, with a significance level of p<0.05.Background
Methods
Measuring the step off during total knee replacement (TKR) is a newly developed operative strategy (“spacer technique”; Heesterbeek et al, KSSTA 2014;22(3):650–9) to determine the optimal contact point (CP) of the femur with the tibia postoperative and to balance the posterior cruciate ligament (PCL) in cruciate-retaining TKR. Engineers have calculated the ideal step off for every size of the TKR, for which the tibiofemoral contact point in 90° will be at the designed position. With this study we determined the postoperative CP in CR-TKA and investigated whether (adverse) clinical outcome was correlated with the CP. 23 patients presenting with non-inflammatory osteoarthritis, a good functioning PCL, and indication for surgery with a PCL-retaining TKR were selected. Intraoperative PCL balancing was performed with the spacer technique. At 3 months postoperative, a pair of mediolateral radiographs was made using a set-up used for radiostereometric analysis (RSA). The patient was positioned standing with the operated leg in 90 degrees, 50% weight-bearing, knee flexion on a 30 cm-step. Model-based RSA software (RSAcore) was used to determine the 3D positions of the femur and tibia component, that were exported to custom-written software for determining the CP. The CP was defined as the point with the smallest distance between both the medial and lateral femur condyles and tibia plateau. It is expressed as the ratio of the anterior-posterior CP distance and the maximum anterior-posterior tibia plateau size, with 0 being anterior, 1 being posterior. Patients with reduced flexion capacity at follow-up, leading to manipulation under anaesthesia and/or scopic releases, were categorized as COMP, the other patients as no-COMP. CP was compared between these groups.Introduction
Methods
Total knee arthroplasty (TKA) is a cost-effective surgical procedure for degenerative knee disease and has good long-term results. However, these results are not always related to patient satisfaction and functional outcome. With an increasing demand of surgeons and patients on functioning of total knee implants, the need for adequate objective outcome measures is high. Imaging of the knee is commonly used in clinical practice and research to objectively measure many different outcome parameters concerning the implant, such as alignment and complications.1 However, techniques on comparison of the sagittal contour of the knee before and after implant placement are scarce. To develop and describe a standardized method for measuring the sagittal contour of the implant in a 3D model of the knee before and after implant placement.Background
Goal
An increased tibial tubercle–trochlear groove
(TT-TG) distance is related to patellar maltracking and instability.
Tibial tubercle transfer is a common treatment option for these
patients with good short-term results, although the results can
deteriorate over time owing to the progression of osteoarthritis.
We present a ten-year follow-up study of a self-centring tibial
tubercle osteotomy in 60 knees, 30 with maltracking and 30 with
patellar instability. Inclusion criteria were a TT-TG ≥ 15 mm and
symptoms for >
one year. One patient (one knee) was lost to follow-up
and one required total knee arthroplasty because of progressive
osteoarthritis. Further patellar dislocations occurred in three
knees, all in the instability group, one of which required further
surgery. The mean visual analogue scores for pain, and Lysholm and
Kujala scores improved significantly and were maintained at the
final follow-up (repeated measures, p = 0.000, intergroup differences
p = 0.449). Signs of maltracking were found in only a minority of
patients, with no difference between groups (p >
0.05). An increase
in patellofemoral osteoarthritis was seen in 16 knees (31%) with
a maximum of grade 2 on the Kellgren–Lawrence scale. The mean increase
in grades was 0.31 (0 to 2) and 0.41 (0 to 2) in the maltracking
and instability groups respectively (p = 0.2285) This self-centring tibial tubercle osteotomy provides good results
at ten years’ follow-up without inducing progressive osteoarthritis. Cite this article:
Total knee arthroplasty can be performed with the balanced gap technique with the tibia cut first guided by the use of a tensor. In a case series of 54 cruciate retaining knee implants (Balansys) 150 N tension was applied to distract the extension gap and 100 N to distract the flexion gap. The following conclusions could be drawn from the collected data: The varus valgus laxity of the total knee joint measured with stress radiograms in extension was similar to that of the healty subjects with the same age and in flexion one degree more. The anterior posterior laxity of the total knee joints compared to the healthy knees was on average 1 mm less. The average ROM of the total knee joints was 118 degrees versus 130 degrees for the healthy knees Ligament releases did not have a significant influence on the stability of the total knee joints. The femur rotation guided by the ligament tension in flexion varied from −4 degrees to + 10 degrees referenced from the posterior condylar line. Only knees with a large medial ligament release had on average slighly less external rotation. Patella position after surgery was not affected by this variable femoral component rotation, only preoperative maltracking was a predictor of postoperative maltracking. One millimeter distraction of the flexiongap causes 1.9–2.3 mm anterior translation of the tibia indicating that very small gap changes in CR knee can cause a relative large shift of the contact point showing the difficulty to balance the PCL. In conclusion the balanced gap technique with a tensor system results in very stable total knee implants with good range of motion. This tensor technique in cruciate retaining total knee arthroplasty is safe even when releases are performed. The variable femur rotation did not affect patella tracking.
Instability is a major cause for revision surgery in total knee replacement (TKR). With a balanced gap technique, the ligaments are theoretically balanced. However, there is concern that ligament releases needed to align the leg may cause instability. Furthermore, no information is available about the relationship between the amount of varus-valgus laxity directly after implantation and at a later postoperative interval. This prospective clinical study investigated whether ligament releases necessary during total knee replacement (TKR) led to a higher varus-valgus laxity during peroperative examination and after 6 months. In this prospective cohort study, in 49 patients a primary TKR was implanted using a balanced gap technique. Varus and valgus laxity of the knee was assessed in extension and flexion (70 degrees) per-operative (before and after implant) with a navigation system and post-operative with standardised stress radiographs (both methods 15 Nm stress applied). Knees were catalogued according to ligament releases performed during surgery: no releases, lateral releases, medial releases with posteromedial condyle (PMC), and medial releases with superficial medial collateral ligament (SMCL). ANOVA was used to test between release groups. At surgery, before and after implantation of the prosthesis, there was no difference in varus or valgus laxity in extension and flexion between knees that did not need a ligament release (n=22), knees with lateral release (n=5), knees with medial SMCL releases (n=15) and knees with medial PMC releases (n=7). Six months after TKR, varus or valgus laxity in extension and flexion was not significantly different between the release categories. In conclusion, ligament releases of the SMCL, PMC, and lateral structures performed during a balanced gap technique in TKR do not lead to an increased varus-valgus laxity in extension and flexion at 6 months after surgery. Therefore, routine releases of these structures to achieve neutral leg alignment can safely be performed without causing increased varus-valgus laxity. The results of this study suggest that the reported high incidence of revisions for ligament instability after TKR is not likely to be caused by routine ligament releases when a balanced gap technique is used. Apparently, there is not a ligament instability problem as long as the gaps are properly filled with prosthesis components. We believe that the conclusion of this study would also be valid when bone referenced techniques are applied instead of tensors, as long as the gaps created are balanced.
Balancing the PCL in a PCL-retaining total knee replacement (TKR) is important, but sometimes difficult to execute in an optimal manner. Due to the orientation of the PCL it is conceivable that flexion gap distraction will lead to anterior movement of the tibia relative to the femur. This tibio-femoral repositioning influences the tibio-femoral contact point, which on its turn affects the kinematics of the TKR. So far, the amount of tibiofemoral repositioning during flexion gap distraction is unknown which leads to uncertain kinematic effects after surgery. The goal of this study was to quantitatively describe the parameters of the flexion gap (gap height, anterior tibial translation and femoral rotation) and their relationship while the knee is distracted during implantation of a PCL-retaining TKR with the use of computer navigation. Furthermore, the effect of PCL elevation angle on the flexion gap parameters was determined. In 50 knees, during a ligament-guided TKR procedure, the flexion gap was distracted with a double-spring tensor with 100 and 200 N after the tibia had been cut. The flexion gap height, anterior tibial translation and femoral rotation were measured intra-operatively using a CT-free navigation system. PCL elevation was calculated based on the femoral and tibial insertion sites as indicated by the surgeon with the pointer of the navigation system. To identify a relationship between flexion gap height increase and anterior tibial translation, the ratio between anterior translation and gap height increase was determined for each patient between 100 and 200 N. The mean gap height increased 2.2 mm (SD 0.96) and mean increase in anterior tibial translation was 4.2 mm (SD 1.6). Hence, on average, for each mm increase in gap height, the tibia moved 1.9 mm (SD 0.96) in anterior direction. Knees with a steep PCL showed significantly more AP translation for each mm gap height increase (gap/AP-ratio was 1 : 2.31 (SD 0.63)) compared to knees with a flat PCL (gap/AP-ratio was 1 : 1.73 (SD 0.50)). The increase in femur (exo)rotation was on average 0.60° (SD 1.4). With a tensioned PCL the tibia will move anteriorly on average 1.9 mm for every extra mm that the flexion gap is increased. The flexion gap dynamics can be explained in part by the orientation of the PCL: the greater the elevation angle, the more anterior tibial displacement during distraction of the flexion gap. The surgeon must be aware that distraction of the flexion gap influences the tibiofemoral contact point. The tibio-femoral contact point will move posteriorly and stresses in the PCL will rise and produce limited flexion and pain. In case of a conforming insert AP-movement will be limited but high PE stresses may be introduced that can lead to wear. This information may be helpful in selecting the optimal soft tissue balancing procedure and the optimal PE insert thickness in PCL retaining TKR.
Lateralisation of the tuberosity tibia causes distal malalignment of the extensor mechanism of the knee and can lead to lateral tracking patella (LTP), resulting in anterior knee pain, or objective patellar instability (OPI), resulting in recurrent luxations. For a precise preoperative diagnosis the tuberositas tibia (TT) trochlear groove (TG) distance was measured on a CT scan. A distance of more than 15 mm was considered to be pathological. In a prospective study, the clinical results of a subtle, CT-guided medial tuberosity transfer for LTP and OPI were evaluated. 30 Consecutive patients with LTP and 30 patients with OPI and an increased TT TG were included. Outcomes were documented at 3, 12 and 24 months follow-up using the Lysholm scale, the Kujala score, and a visual analogue pain score. Postoperatively all but one patient reported good improvement in stability (no persistent subluxations or luxations). All patients had a marked improvement in pain and functional scores at follow up. Complications seem to be related to the peroperative technique. CT-guided TT transfer appears to be satisfactory and safe method for treating patients with an increased TT TG leading to either LTP or OPI.
We have examined the relationship between the size of the flexion gap and the anterior translation of the tibia in flexion during implantation of a posterior cruciate ligament (PCL)-retaining BalanSys total knee replacement (TKR). In 91 knees, the flexion gap and anterior tibial translation were measured intra-operatively using a custom-made, flexible tensor-spacer device. The results showed that for each increase of 1 mm in the flexion gap in the tensed knee a mean anterior tibial translation of 1.25 mm (SD 0.79, 95% confidence interval 1.13 to 1.37) was produced. When implanting a PCL-retaining TKR the surgeon should be aware that the tibiofemoral contact point is related to the choice of thickness of the polyethylene insert. An additional thickness of polyethylene insert of 2 mm results in an approximate increase in tibial anterior translation of 2.5 mm while the flexed knee is distracted with a force of between 100 N and 200 N.
The supporting structures on the medial side of the knee consist of:
- Layer I, the superficial fascia. - Layer II, the superficial Medial Collateral Ligament (sMCL) with parallel fibers running from the femoral epicondyle to the anteromedial tibial crest 5–7 cm below the joint line. - Layer III, the deep capsular layer. The pes tendons are situated between Layer I and II–III. Beneath the sMCL Layer III thickens and forms the deep MCL (dMCL) from femur condyle to meniscus and from meniscus to tibia. More dorsally Layer II and III fuse and form the Postero Medial Capsule (PMC) which is connected to the meniscus and tibia. The PMC is augmented by the semimembranosus tendon. The sMCL is the primary restraint against valgus and transsection causes 2–5 degrees laxity in flexion or approximately 3–5 mm joint opening. Additional cutting of the PMC gives additional laxity of 7–8 degrees up to 10 degrees. An isolated sMCL lesion causes more laxity in flexion and a combination of sMCL with a PMC lesion causes also laxity in extension. The dMCL does provide some stability in 45 dg. of flexion but is not very strong. The goal of MCL-PMC reconstruction should be functional anatomical repair of the pathology and retention of the meniscus. After treating the pathology the medial side of the knee should be stable in extension (by repair PMC) and in flexion (by repair sMCL). The PMC – meniscus – semimembranosus complex should be refixated at the posteromedial tibia corner if it is loose. Bony avulsions should be fixed with washer and screw or anchors. Ligamentous avulsions can be fixed at the anatomical insertion site with trans-osseous non-resorbable sutures or bone anchors or screws with toothed washers. A distalisation of a ligament insertion (sMCL) with its bony attachment is also an elegant solution in chronic cases. If the surgeon wants to tension the SMCL at the femoral side, the bony insertion with the ligament attached to it can be recessed at its original position. Allografts and double stranded hamstring autografts can be used when native tissue is lacking.
