Ligament release in knee arthroplasty can be limited with accurate placement of implants, correct sizing and anatomic geometry of the implants. Still, in some instances a release of the medial collateral ligament can be necessary. In the proposed minimally invasive technique, multiple punctures in the MCL are made, using an 19-gauge needle, in order to progressively stretch the MCL until a correct ligament balance is achieved. This technique requires no additional soft tissue dissection and can even be performed percutaneously when necessary. We analyzed 61 cases with varus deformity that were intraoperatively treated using this technique. In 4 other cases the technique was used as a percutaneous procedure in order to correct postoperative medial tightness. The procedure was considered successful when 2–4mm mediolateral joint line opening was obtained in extension and 2–6mm in flexion. In 62 cases (95%) a progressive correction of medial tightness was achieved according to the above described criteria. We therefore consider needle puncturing as an effective and safe technique for progressive correction of MCL tightness during minimally invasive TKA.
In this study, three-dimensional (3D) digital image correlation (DIC) was adopted to investigate the strain in the superficial medial collateral ligament (sMCL) of the human knee. To our knowledge, no reports or validation of 3D DIC measurement on human collagenous tissue exists. The first part of this research project focused on the validation of 3D DIC (1) as a highly accurate tool for non-contact full field strain analysis of human collagenous tissue. In the second part, 3D DIC was used to measure the strain patterns in the superficial medial collateral ligament (sMCL) of the native knee (2). In a third part, the strain pattern in the sMCL after total knee arthroplasty (TKA) in an ‘optimal’ (3) and with a proximalised joint line (4) was analysed. (1) Six fresh frozen human Achilles tendon specimens were mounted in a custom made rig for uni-axial loading. The accuracy and reproducibility of 3D DIC was compared to two linear variable differential transformers (LVDT's). (2) The strain pattern of the sMCL during the range of motion (ROM) was measured using 3D DIC in six fresh frozen cadaveric knees. The knees were mounted in a custom made rig, applying balanced tension to all muscle groups around the knee. The experiment was repeated after computer navigated implantation of a single radius posterior stabilised (PS) TKA in ‘optimal’ (3) and with a 4 mm proximalised joint line (4).Introduction
Methods
Potential systemic toxicity of metal ions from metal-on-metal hip arthroplasties (MoMHA) is concerning. High blood cobalt (Co) levels have been associated with neurological, cardiac and thyroid dysfunctions. The aim of this research was to investigate the prevalence of systemic Co toxicity in a MoMHA population, to identify confounding factors, and to indicate a Co level above which there is a high risk for systemic toxicity.Background:
Questions/purposes:
Recently a new version of the Knee Society Knee Scoring System has been developed, adapted to the lifestyle and activities of contemporary patients with a Total Knee Arthroplasty (TKA). It is subdivided into 4 domains including an Objective Knee Score, a Satisfaction Score, an Expectations Score and a Functional Activity Score. Before this scale can be used in non-English speaking populations, it has to be translated and validated for specific populations. The aim of this study was to translate and validate the New Knee Society Knee Scoring System (new KSS) for Dutch speaking populations. A Dutch translation of the New KSS was established using a forward-backward translation protocol. 137 patients undergoing TKA were asked to complete the Dutch translation of the New KSS as well as the Dutch WOMAC, Dutch KOOS and the Dutch SF12. To determine the test-retest reliability, 53 patients were asked to fill out a second questionnaire with one-week interval. We tested the test-retest reliability of the subjective domains of the New KSS by assessing the intra-class coefficient and the Pearson correlation coefficient between the first and second questionnaires. Systematic differences between the first and second questionnaires were investigated with T-tests and non-parametric statistics. Internal consistency of the Dutch new KSS was evaluated with Cronbach's alpha. The construct validity of the Dutch New KSS was determined by comparing it to the Dutch WOMAC, Dutch KOOS and Dutch SF12 using Pearson correlation coefficients. Content validity was assessed by examining the distribution and the floor and ceiling effects of the Dutch version of the new KSS.Background:
Materials and Methods:
As human soft tissue is anisotropic, non-linear and inhomogeneous, its properties are difficult to characterize. Different methods have been described that are either based on contact or noncontact protocols. In this study, three-dimensional (3D) digital image correlation (DIC) was adopted to examine the mechanical behaviour of the human Achilles tendon. Despite its wide use in engineering research and its great potential for strain and displacement measurements in biological tissue, the reported biomedical applications are rather limited. To our knowledge, no validation of 3D DIC measurement on human tendon tissue exists. The first goal of this study was to determine the feasibility to evaluate the mechanical properties of the human Achilles tendon under uniaxial loading conditions with 3D Digital Image Correlation. The second goal was to compare the accuracy and reproducibility of the 3D DIC against two linear variable differential transformer (LVDT's). Six human Achilles tendon specimens were prepared out of fresh frozen lower limbs. Prior to preparation, all limbs underwent CT-scanning. Using Mimics software, the volume of the tendons and the cross sectional area at each level could be calculated. Subsequently, the Achilles tendons were mounted in a custom made rig for uni-axial loading. Tendons were prepared for 3D DIC measurements with a modified technique that enhanced contrast and improved the optimal resolution. Progressive static loading up to 628,3 N en subsequent unloading was performed. Two charge-coupled device camera's recorded images of each loading position for subsequent strain analysis. Two LVDT's were mounted next to the clamped tendon in order to record the displacement of the grips.Purpose
Methods
The number of young patients undergoing total knee arthroplasty is rapidly increasing. Long-term follow-up of modern type implants is needed to provide a benchmark of implant longevity for these patients. Between January 1995 and October 1997, 245 consecutive total knee arthroplasties were performed in 217 patients by a single surgeon. In 156 knees, the Genesis I implant was used, and in 89 knees the Genesis II implant was used. Mean age at surgery was 69.3 years for the Genesis I cohort and 66 years for the Genesis II (p = 0.016). At 15 to 17 years, cumulative survivorship was calculated using Kaplan-Meier statistics whilst outcomes were rated with the ‘Knee society score’ and with the ‘Knee Injury and Osteoarthritis Outcome Score’. Radiological assessment included coronal alignment measured on full leg standing X-rays, and analysis of radiolucent lines and polyethylene thickness on AP, Lateral and Axial X-rays, positioned under fluoroscopic control.Background:
Methods:
A prospective randomized trial on 128 patients with end-stage osteoarthritis was conducted to assess the accuracy of patient-specific guides. In cohort A (n = 64), patient- specific guides from four different manufacturers (Subgroup A1 Signature ®, A2 Trumatch ®, A3 Visionaire ® and A4 PSI ®) were used to guide the bone cuts. Surgical navigation was used as an intraoperative control for outliers. In cohort B (n = 64), conventional instrumentation was used. All patients of cohorts A and B underwent a postoperative full-leg standing X-ray and CT scan for measuring overall coronal alignment of the limb and three-planar alignment of the femoral and the tibial component. Three-planar alignment was the primary endpoint. Deviation of more than three degrees from the target in any plane, as measured with surgical navigation or radiologic imaging, was defined as an outlier. In 14 patients (22%) of cohort A, the use of the patient-specific guide was abandoned because of outliers in more than one plane. In 18 patients (28%), a correction of the position indicated by the guide, was made in at least one plane. A change in cranial-caudal position was most common. Cohort A and B showed a similar percentage of outliers in long-leg coronal alignment (24.6%, 28.1%, p = 0.69), femoral coronal alignment (6.6%, 14.1%, p = 0.24) and femoral axial alignment (23%, 17.2%, p = 0.50). Cohort A had more outliers in coronal tibial alignment (14.6%) and sagittal tibial alignment (21.3%) than cohort B (3.1%, p = 0.03 and 3.1%, p = 0.002, respectively). These data indicate that patient specific guides do not improve accuracy in total knee arthroplasty.
Metal-on-metal hip resurfacings (MoMHRAs) have a characteristic wear pattern initially characterised by a run-in period, followed by a lower-wear steady-state. The use of metal ions as surrogate markers of in-vivo wear is now recommended as a screening tool for the in-vivo performance of MoMHRAs. The aims of this retrospective study were to measure ion levels in MoMHRAs at different stages during the steady-state in order to study the evolution of wear at minimum 10 years postoperatively and describe factors that affect it. A retrospective study was conducted to investigate the minimum 10-year survivorship of a single-surgeon Birmingham Hip Resurfacing (BHR) series, and the evolution of metal ion levels. Implant survival, Harris Hip Scores (HHS), radiographs and serum metal ion levels were assessed. The evolution of metal ion levels was evaluated in 80 patients for whom at least two ion measurements were available at more than 12 months postoperatively, i.e. past the run-in phase. Ion level change (Delta Cr; Delta Co) was defined as Cr or Co level at last assessment minus Cr or Co level at initial assessment. Sub-analysis was performed by gender, diagnosis, age, femoral component size and cup inclination angle.Introduction
Materials and methods
Correct alignment and ligament tension are widely accepted conditional features of successful TKA. The technical route of achieving this goal remains a matter of debate. Two philosophies prevail: measured resection as a geometry based system, and tensioned gaps, based upon the dependent relation between tibia and femur. Both techniques claim the best results and are often presented as radically different. From a conceptual standpoint, however, the dependent technique is not purely ligament based as it starts with a cut of the proximal tibia, which is geometrically ruled by sagittal and coronal alignment targets. As such, geometric alignment is the starting point of both techniques. The use of ligament tensioners as the main basis for obtaining stability and alignment can be a treacherous route to follow. In the native knee that is not affected by arthritis, the functional characteristics of the ligaments are determined by their insertions and the articular geometry. Once the arthritis sets in, the articular surface deforms and leg alignment deviates. It is difficult to restore these parameters, making use of ligament tension as a guide, for the following reasons.
Ligament tension is hard to measure reproducibly intra-operatively. The stress-strain curves of ligaments are different and the magnitude of the optimal distraction force is unknown. In flexion, the dislocation or eversion of the patella will affect the obtained result and might induce significant bias. Ligament tensioners evaluate available space in flexion and in 90° of flexion. No information about the mid- and deep flexion range can be obtained. Articular geometry of the implant will affect this. The ligament tensioner does not control relative position AP position of femur and tibia. Especially in the presence of the PCL, distraction of the femur from the tibia at 90° of flexion will push the tibia forwards as the PCL straightens out and finds a more vertical position. The medial side of the knee is the more stable and isometric side, where the lateral side is more dynamically controlled by muscle loads. Applying an equal distraction force to the medial and lateral compartment in an anesthetised patient can overestimate the available space in the lateral compartment and induce excessive external rotation. Traumatic or chronic ligament injury caused by the arthritic process can skew the obtained results Measure resection is obviously not void of potential errors. Especially in case of dysplasia or prior trauma, bone geometry and landmarks can be deformed. In contrast to ligament assessment however, pre-operative imaging under the form of x-rays or CT allows for an objective and reproducible evaluation of the amount of deformity and subsequent surgical correction.
Osteotomies around the knee are traditionally templated on 2D plain X-rays. Results are often inaccurate and inconsistent and multiplanar osteotomies are hard to perform. The aim of this study is to evaluate the feasibility and accuracy of virtual three-dimensional CT-based planning and correct execution of osteotomies around the knee with the aid of patient specific surgical guides and locking plates. Eight consecutive patients with significant malalignment of the lower limb were included in the study. Pre-operative CT scans of the affected limb and the normal contra-lateral side were obtained and 3D models of the patient's anatomy were created, using dedicated software. The healthy contralateral limb was mirrored and geometrically matched to the distal femur or proximal tibia of the healthy side. A virtual opening wedge correction of the affected bone was used to match the geometry of the healthy contralateral bone. Standard lower limb axes measurements confirmed correction of the alignment. Based on the virtual plan, surgical guides were designed to perform the planar osteotomy and achieve the planned wedge opening and hinge axis orientation. The osteotomy was fixed with locking plates and screws. Post-operative assessment included planar X-rays, CT-scan and full leg standing X-rays. One three-planar, three bi-planar and four single-plane osteotomies were performed. Maximum weightbearing mechanical femoro-tibial coronal malalignment varied between 7° varus and 14° valgus (mean 7.6°, SD 3.1). Corrective angles varied from 7°–15° (coronal), 0°–13° (sagittal) and 0°–23° (horizontal). The maximum deviation between the planned pre-operative wedge angle and the executed post-operative wedge angle was 1° in the coronal, sagittal and horizontal plane. The desired mechanical femorotibial axis on full-leg standing X-rays was achieved in 6 patients. Two patients were undercorrected by 1° and 2° respectively. 3D planning and guided correction of multi-planar deformity of femur or tibia is a feasible and accurate novel technique.Conclusion
Eight consecutive patients with significant malalignment of the lower limb were included in the study. Pre-operative CT scans of the affected limb and the normal contra-lateral side were obtained and 3D models of the patient's anatomy were created, using dedicated software. The healthy contralateral limb was mirrored and geometrically matched to the distal femur or proximal tibia of the healthy side. A virtual opening wedge correction of the affected bone was used to match the geometry of the healthy contralateral bone. Standard lower limb axes measurements confirmed correction of the alignment. Based on the virtual plan, surgical guides were designed to perform the planar osteotomy and achieve the planned wedge opening and hinge axis orientation. The osteotomy was fixed with locking plates and screws. Post-operative assessment included planar X-rays, CT-scan and full leg standing X-rays. One three-planar, three bi-planar and four single-plane osteotomies were performed. Maximum weightbearing mechanical femoro-tibial coronal malalignment varied between 7° varus and 14° valgus (mean 7.6°, SD 3.1). Corrective angles varied from 7°–15°(coronal), 0°–13°(sagittal) and 0°–23°(horizontal). The maximum deviation between the planned pre-operative wedge angle and the executed post-operative wedge angle was 1° in the coronal, sagittal and horizontal plane. The desired mechanical femorotibial axis on full-leg standing X-rays was achieved in 6 patients. Two patients were undercorrected by 1° and 2° respectively. 3D planning and guided correction of multi-planar deformity of femur or tibia is a feasible and accurate novel technique.Conclusion
Osteotomies around the knee have been used to correct lower limb mal-alignment for over 50 years. The procedure is technically demanding and carries specific risks of neurovascular injury, incorrect planning and execution, and insufficient fixation. In recent years, with the advent of locking plates, fixation techniques have improved significantly but the correct planning and execution of the operation remains difficult. Despite the availability of CT and MRI 3D imaging, surgical planning is still traditionally performed on 2D plain X-rays [1]. Especially with multi-planar deformities, this technique is prone to error. The aim of this clinical pilot study is to evaluate the feasibility of virtual pre-operative three-dimensional planning and correct execution of osteotomies around the knee with the aid of patient specific surgical guides and locking plates. Eight consecutive patients, presenting with significant malalignment of the lower limb were included in the study. Pre-operative CT scans of the affected limb and the normal contra-lateral side were obtained and 3D models of the patient's anatomy were created, using dedicated software (Mimics® 3-matic®, Materialise, Leuven Belgium) [2]. These models were used to evaluate the required surgical correction. The healthy contralateral limb was mirrored and geometrically matched to the distal femur or proximal tibia of the healthy side. A virtual opening wedge correction of the affected bone was used to match the geometry of the healthy contralateral bone. Standard lower limb axes measurements confirmed correction of the alignment [3]. Based on the virtual plan, surgical guides were designed to perform the planar osteotomy and achieve the planned wedge opening and hinge axis orientation (see figure 1). Apart from guiding the osteotomy, the patient specific surgical guide also guided drilling of the planned screw holes. Post-operative assessment of the correction was obtained through planar X-rays, CT-scan and full leg standing X-ray.Background
Patients and methods
Osteotomies around the knee are traditionally templated on 2D plain X-rays. Results are often inaccurate and inconsistent and multiplanar ostetomies are hard to perform. The aim of this study is to evaluate the feasibility and accuracy of virtual three-dimensional CT-based planning and correct execution of osteotomies around the knee with the aid of patient specific surgical guides and locking plates. Eight consecutive patients with significant malalignment of the lower limb were included in the study. Pre-operative CT scans of the affected limb and the normal contra-lateral side were obtained and 3D models of the patient's anatomy were created, using dedicated software. The healthy contralateral limb was mirrored and geometrically matched to the distal femur or proximal tibia of the healthy side. A virtual opening wedge correction of the affected bone was used to match the geometry of the healthy contralateral bone. Standard lower limb axes measurements confirmed correction of the alignment. Based on the virtual plan, surgical guides were designed to perform the planar osteotomy and achieve the planned wedge opening and hinge axis orientation. The osteotomy was fixed with locking plates and screws. Post-operative assessment included planar X-rays, CT-scan and full leg standing X-rays.Introduction
Methods
Autologous chondrocyte implantation presents a viable alternative to microfracture in the repair of damaged articular cartilage of the knee; however, outcomes for patellar lesions have been less encouraging. ChondroCelect (CC) is an innovative, advanced cell therapy product consisting of autologous cartilage cells expanded To assess the effect of CC in the treatment of patellofemoral lesions, for which standard treatment options had failed and/or no other treatment options were considered feasible.Introduction
Purpose
A comparative kinematic study was carried out on six cadaver limbs, comparing tibiofemoral kinematics in five different conditions: unloaded, under a constant 130 N ankle load with a variable quadriceps load, with and without a constant 50 N medial and lateral hamstrings load. Kinematics were described as translation of the projected centers of the medial (MFT) and lateral femoral condyles (LFT) in the horizontal plane of the tibia, and tibial axial rotation (TR) as a function of flexion angle. In passive conditions, the tibia rotated internally with increasing flexion, to an average of −16° (range −12/−20°, SD 3.0°). Between 0 – 40° flexion, the medial condyle translated forwards 4 mm (range 0.8/5.5 mm, SD 2.5 mm), followed by a gradual posterior translation, totaling −9 mm (range −5.8/−18.5 mm, SD 4.9 mm) between 40° – 140° flexion. The lateral femoral condyle translated posteriorly with increasing flexion completing −25 mm (range −22.6 – −28.2 mm, SD 2.5 mm). Dynamic, loaded measurements were carried out in a knee rig. Under a fixed ankle load of 130 N and variable quadriceps loading, tibial rotation was inverted, mean TR 4.7° (range −3.3°/11.8° SD 5.4°), MFT −0.5 mm (range = −4.3/2.4 mm, SD = 2.4 mm), LFT 3.3 mm (range = −3.6/10.6 mm, SD = 5.1 mm). As compared to the passive condition, all these excursions were significantly different: p=0.015, p=0.013, and p=0.011 for TR, MFT and LFT respectively. Adding medial and lateral hamstrings force of 50N each, reduced TR, MFT and LFT significantly as compared to the passive condition. In general, loading the knee with hamstrings and quadriceps reduces rotation and translation as compared to the passive condition. Lateral hamstring action is more influential on knee kinematics than medial hamstrings action.
The understanding of rotational alignment of the distal femur is essential in total knee replacement to ensure that there is correct placement of the femoral component. Many reference axes have been described, but there is still disagreement about their value and mutual angular relationship. Our aim was to validate a geometrically-defined reference axis against which the surface-derived axes could be compared in the axial plane. A total of 12 cadaver specimens underwent CT after rigid fixation of optical tracking devices to the femur and the tibia. Three-dimensional reconstructions were made to determine the anatomical surface points and geometrical references. The spatial relationships between the femur and tibia in full extension and in 90° of flexion were examined by an optical infrared tracking system. After co-ordinate transformation of the described anatomical points and geometrical references, the projection of the relevant axes in the axial plane of the femur were mathematically achieved. Inter-and intra-observer variability in the three-dimensional CT reconstructions revealed angular errors ranging from 0.16° to 1.15° for all axes except for the trochlear axis which had an interobserver error of 2°. With the knees in full extension, the femoral transverse axis, connecting the centres of the best matching spheres of the femoral condyles, almost coincided with the tibial transverse axis (mean difference −0.8°, SD 2.05). At 90° of flexion, this femoral transverse axis was orthogonal to the tibial mechanical axis (mean difference −0.77°, SD 4.08). Of all the surfacederived axes, the surgical transepicondylar axis had the closest relationship to the femoral transverse axis after projection on to the axial plane of the femur (mean difference 0.21°, SD 1.77). The posterior condylar line was the most consistent axis (range −2.96° to − 0.28°, SD 0.77) and the trochlear anteroposterior axis the least consistent axis (range − 10.62° to +11.67°, SD 6.12). The orientation of both the posterior condylar line and the trochlear anteroposterior axis (p = 0.001) showed a trend towards internal rotation with valgus coronal alignment.
Outcomes of revision TKA are inferior to primary TKA. Early failures were mainly caused by infection, instability, malalignment. Grouping revision TKA’s to etiology of failure did not lead to significant differences in outcomes. Significant better outcomes were reported for late revisions, patients with older age at revision surgery and partial knee replacement. Survivorship analysis was significally better for late than for early revisions.
