Abstract. Background. Little scientific evidence is available regarding the effect of knee joint line obliquity (JLO). Methods. 10 fresh-frozen human cadaveric knees were axially loaded to 1500 N in a materials testing machine with the joint line tilted 0, 4, 8, and 12 degrees varus and valgus, at 0, and 20 degrees of knee flexion. The mechanical compression axis was aligned to the centre of the tibial plateau. Contact pressures / areas were recorded by sensors inserted between the tibia and femur below the menisci. Changes in relative femoral and tibial position in the coronal plane were obtained by an optical tracking system. Results. medial and lateral JLO caused significant tibiofemoral subluxation and pressure distribution changes. Medial (varus) JLO caused the femur to sublux medially down the coronal slope of the tibial plateau, and vice versa for lateral (valgus) downslopes (P=0.01). Areas of peak pressure moved 12 mm and 8 mm across the medial and lateral condyles, onto the ‘downhill’ meniscus and the ‘uphill’ tibial spine. Changes in JLO had only small effects on maximum contact pressures. Conclusion. A change of JLO during load bearing caused significant mediolateral tibiofemoral subluxation. The femur slid down the slope of the tibial plateau to abut the tibial eminence and also to rest on the downhill meniscus. Clinical Relevance. These results provide important information for understanding the consequences of creating coronal JLO and for clinical practice in terms of osteotomy planning regarding the effect on JLO

Abstract. Introduction. Tibial tubercle osteotomy (TTO) is a complex surgical procedure with a significant risk of complications, which include nonunion and tibial fracture. To determine whether an additional suture tape augmentation can provide better biomechanical stability compared with standard screw fixation. Methods. Five matched pairs of human cadaveric knees were divided into 2 groups: the first group underwent standard TTO fixation with 2 parallel screws. The second group underwent a novel fixation technique, in which a nonabsorbable suture tape (FiberTape) in a figure-of-8 construct was added to the standard screw fixation. Tubercular fragment migration of >50% of the initial distalization length was defined as clinical failure Tubercular fragment displacement during cyclic loading and pull-to-failure force were recorded and compared between the 2 groups. Results. The augmented group showed less cyclic tubercular fragment displacement after every load level compared with the standard group, with statistically significant differences starting from 500 N (P < .05; power > 0.8). Mean ± standard deviation tubercular fragment displacement at the end of cyclic loading was 2.56 ± 0.82 mm for the augmented group and 5.21 ± 0.51 mm for the standard group. Mean ultimate failure load after the pull-to-failure test was 2475 ± 554 N for the augmented group and 1475 ± 280 N for the standard group. Conclusion. The specimens that underwent suture tape augmentation showed less tubercular fragment displacement during cyclic loading and higher ultimate failure forces compared with those that underwent standard screw fixation

Aims. The mobile bearing Oxford unicompartmental knee arthroplasty (OUKA) is recommended to be performed with the leg in the hanging leg (HL) position, and the thigh placed in a stirrup. This comparative cadaveric study assesses implant positioning and intraoperative kinematics of OUKA implanted either in the HL position or in the supine leg (SL) position. Methods. A total of 16 fresh-frozen knees in eight human cadavers, without macroscopic anatomical defects, were selected. The knees from each cadaver were randomized to have the OUKA implanted in the HL or SL position. Results. Tibial base plate rotation was significantly more variable in the SL group with 75% of tibiae mal-rotated. Multivariate analysis of navigation data found no difference based on all kinematic parameters across the range of motion (ROM). However, area under the curve analysis showed that knees placed in the HL position had much smaller differences between the pre- and post-surgery conditions for kinematics mean values across the entire ROM. Conclusion. The sagittal tibia cut, not dependent on standard instrumentation, determines the tibial component rotation. The HL position improves accuracy of this step compared to the SL position, probably due to better visuospatial orientation of the hip and knee to the surgeon. The HL position is better for replicating native kinematics of the knee as shown by the area under the curve analysis. In the supine knee position, care must be taken during the sagittal tibia cut, while checking flexion balance and when sizing the tibial component

Introduction. In total knee arthroplasty (TKA), tibial insert thickness is determined intraoperatively by applying forces that generate varus-valgus moments at the knee and estimating the resulting gaps. However, how the magnitude of applied moments and the surgeon's perception of gaps affect the thickness selection is unclear. We determined this relationship using an in vitro human cadaveric model. Methods. Six pelvis-to-toe specimens (72±6 years old, four females) were implanted by an expert surgeon with a PS TKA using measured resection. Pliable sensors were wrapped around medial and lateral aspects of the foot and ankle to measure the applied forces. The forces were scaled by limb length to obtain the moments generated at the knee. Six surgeons with different experience levels independently assessed balance by applying moments in extension and 90° of flexion and choosing the insert they believed fit each knee. Peak moments and the accompanying extension and flexion gap openings as perceived by surgeons were recorded. The two measures were then related to insert choice using a generalized estimating equation. Results. The peak applied moments varied among surgeons (mean of 14±2.5 Nm in extension and 10±3 Nm in flexion). In extension, surgeons perceived a medial gap of 1.3±0.8 mm and a lateral gap of 0.9±0.7 mm. In flexion, surgeons perceived a medial gap of 1.1±0.9 mm and a lateral gap of 1.7±1.6 mm. Despite these differences, surgeons' choices of insert thickness varied by at most 1 mm, with no association found between the selected thickness and either peak moments or surgeons' gap perception (p>0.05). Conclusions. In a controlled setting, surgeons of varying experience levels showed remarkable convergence in insert thickness selection. This notable consistency was unrelated to either the applied moments or their estimation of extension and flexion gaps, indicating that other factors may be driving this decision

We have quantitatively documented the insertion geometry of the main stabilising structures of the posterolateral corner of the knee in 34 human cadavers. The lateral collateral ligament inserted posterior (4.6 mm, . sd. 2) and proximal (1.3 mm, . sd. 3.6) to the lateral epicondyle of the femur and posterior (8.1 mm, . sd. 3.2) to the anterior point of the head of the fibula. On the femur, the popliteus tendon inserted distally (11 mm, . sd. 0.8) and either anterior or posterior (mean 0.84 mm anterior, . sd. 4) to the lateral collateral ligament. The popliteofibular ligament inserted distal (1.3 mm, . sd. 1.2) and anterior (0.5 mm, . sd. 2.0) to the tip of the styloid process of the fibula. The ligaments had a consistent pattern of insertion and, despite the variation between specimens, the standard deviations were less than the typical size of drill hole used in reconstruction of the posterolateral corner. The data provided in this study can be used in the anatomical repair and reconstruction of this region of the knee

Objectives. Static radiostereometric analysis (RSA) using implanted markers is considered the most accurate system for the evaluation of prosthesis migration. By using CT bone models instead of markers, combined with a dynamic RSA system, a non-invasive measurement of joint movement is enabled. This method is more accurate than current 3D skin marker-based tracking systems. The purpose of this study was to evaluate the accuracy of the CT model method for measuring knee joint kinematics in static and dynamic RSA using the marker method as the benchmark. Methods. Bone models were created from CT scans, and tantalum beads were implanted into the tibia and femur of eight human cadaver knees. Each specimen was secured in a fixture, static and dynamic stereoradiographs were recorded, and the bone models and marker models were fitted to the stereoradiographs. Results. Results showed a mean difference between the two methods in all six degrees of freedom for static RSA to be within -0.10 mm/° and 0.08 mm/° with a 95% limit of agreement (LoA) ranging from ± 0.49 to 1.26. Dynamic RSA had a slightly larger range in mean difference of -0.23 mm/° to 0.16 mm/° with LoA ranging from ± 0.75 to 1.50. Conclusions. In a laboratory-controlled setting, the CT model method combined with dynamic RSA may be an alternative to previous marker-based methods for kinematic analyses. Cite this article: K. Stentz-Olesen, E. T. Nielsen, S. De Raedt, P. B. Jørgensen, O. G. Sørensen, B. L. Kaptein, M. S. Andersen, M. Stilling. Validation of static and dynamic radiostereometric analysis of the knee joint using bone models from CT data. Bone Joint Res 2017;6:376–384. DOI: 10.1302/2046-3758.66.BJR-2016-0113.R3

Aims

Unicompartmental and total knee arthroplasty (UKA and TKA) are successful treatments for osteoarthritis, but the solid metal implants disrupt the natural distribution of stress and strain which can lead to bone loss over time. This generates problems if the implant needs to be revised. This study investigates whether titanium lattice UKA and TKA implants can maintain natural load transfer in the proximal tibia.

The dysplastic Trochlear is a developmental condition characterised by an abnormally flat or dome-shaped trochlea and it is recognised as a significant cause of patella instability, with the increased sulcus angle being is the most common finding. Surgical correction of the shape of the Trochlear Groove is frequently performed. The described methods in the literature involve open arthrotomy to normalise and maintain the trochlear morphology achieving normal alignment and tracking of the patella. Open procedures carries a significant risk of arthrofibrosis. The technique was developed in human cadaveric knees at the Donjoy Clinical Education and Research Facility (CERF) in Vista California. We describe an arthroscopic procedure to create a neo-trochlea using gouges, spherical and conical hooded burrs. We studied prospectively a series of 4 consecutive patients with patello-femoral instability secondary to trochlear dysplasia, who were treated by an Arthroscopic trochleoplasty by a single surgeon between 2007 and 2008. Postoperatively the patients were rehabilitated in accordance with our routine Patello-Femoral microfracture Protocol, allowing weight bearing and ROM 0-20 degrees in a long lever brace for 6 weeks. CT scanning at one year showed a complete neo-cortex and cartilage sequenced MRI at 12 months showed complete fill with fibro cartilage. Pre- and post-operative scores (KOOS, Kujala) were assessed by the patients and a satisfaction questionnaire was completed. The results showed a statistical improvement in the outcome at the 2 year follow up. Overall, patients (100%) were satisfied with the outcome of their procedure and there have been no adverse events. To our knowledge this technique has not been described before in the English literature and the early results of arthroscopic trochleoplasty are encouraging and offer an alternative to open approaches. Larger numbers and longer follow ups are needed to confirm the long term benefit

Aims

One of the main causes of tibial revision surgery for total knee arthroplasty is aseptic loosening. Therefore, stable fixation between the tibial component and the cement, and between the tibial component and the bone, is essential. A factor that could influence the implant stability is the implant design, with its different variations. In an existing implant system, the tibial component was modified by adding cement pockets. The aim of this experimental in vitro study was to investigate whether additional cement pockets on the underside of the tibial component could improve implant stability. The relative motion between implant and bone, the maximum pull-out force, the tibial cement mantle, and a possible path from the bone marrow to the metal-cement interface were determined.

We designed an experimental study to prove the existence of the popliteofibular ligament (PFL) and to define its role in providing static stability of the knee. We also examined the contribution of the lateral collateral ligament (LCL). We found this ligament to be present in all eight human cadaver knees examined. These specimens were mounted on a specially designed rig and subjected to posterior, varus and external rotational forces. We used the technique of selective sectioning of ligaments and measured the displacement with a constant force applied, before and after its division. We recorded the displacement in primary posterior translation, coupled external rotation, primary varus angulation and primary external rotation. Statistical analysis using the standard error of the mean by plotting 95% confidence intervals, was used to evaluate the results. The PFL had a significant role in preventing excessive posterior translation and varus angulation, and in restricting excessive primary and coupled external rotation. Isolated section of the belly of popliteus did not cause significant posterolateral instability of the knee. The LCL was also seen to act as a primary restraint against varus angulation and secondary restraint against external rotation and posterior displacement. Our findings showed that in knees with isolated disruption of the PFL stability was restored when it was reconstructed. However in knees in which the LCL was also disrupted, isolated reconstruction of the PFL did not restore stability

Aims

To assess the effect of high tibial and distal femoral osteotomies (HTO and DFO) on the pressure characteristics of the ankle joint.

Objectives

Up to 40% of unicompartmental knee arthroplasty (UKA) revisions are performed for unexplained pain which may be caused by elevated proximal tibial bone strain. This study investigates the effect of tibial component metal backing and polyethylene thickness on bone strain in a cemented fixed-bearing medial UKA using a finite element model (FEM) validated experimentally by digital image correlation (DIC) and acoustic emission (AE).

Objectives

An important measure for the diagnosis and monitoring of knee osteoarthritis is the minimum joint space width (mJSW). This requires accurate alignment of the x-ray beam with the tibial plateau, which may not be accomplished in practice. We investigate the feasibility of a new mJSW measurement method from stereo radiographs using 3D statistical shape models (SSM) and evaluate its sensitivity to changes in the mJSW and its robustness to variations in patient positioning and bone geometry.

Anterior cruciate ligament (ACL) reconstruction is commonly performed and has been for many years. Despite this, the technical details related to ACL anatomy, such as tunnel placement, are still a topic for debate. In this paper, we introduce the flat ribbon concept of the anatomy of the ACL, and its relevance to clinical practice.

Cite this article: Bone Joint J 2016;98-B:1020–6.

Our aims were to map the tibial footprint of the posterior cruciate ligament (PCL) using MRI in patients undergoing PCL-preserving total knee replacement, and to document the disruption of this footprint as a result of the tibial cut. In 26 consecutive patients plain radiography and MRI of the knee were performed pre-operatively, and plain radiography post-operatively.

The lower margin of the PCL footprint was located a mean of 1 mm (−10 to 8) above the upper aspect of the fibular head. The mean surface area was 83 mm² (49 to 142). One-third of patients (8 of 22) had tibial cuts made below the lowest aspect of the PCL footprint (complete removal) and one-third (9 of 22) had cuts extending into the footprint (partial removal). The remaining patients (5 of 22) had footprints unaffected by the cuts, keeping them intact.

Our study highlights the wide variation in the location of the tibial PCL footprint when referenced against the fibula. Proximal tibial cuts using conventional jigs resulted in the removal of a significant portion, if not all of the PCL footprint in most of the patients in our study. Our findings suggest that when performing PCL-retaining total knee replacement the tibial attachment of the PCL is often removed.

Clinical experience of impaction bone grafting for revision knee arthroplasty is limited, with initial stability of the tibial tray emerging as a major concern. The length of the stem and its diameter have been altered to improve stability. Our aim was to investigate the effect of the type of stem, support of the rim and graft impaction on early stability of the tray.

We developed a system for impaction grafting of trays which we used with morsellised bone in artificial tibiae. Trays with short, long thick or long thin stems were implanted, with or without support of the rim. They were cyclically loaded while measuring relative movement.

Long-stemmed trays migrated 4.5 times less than short-stemmed trays, regardless of diameter. Those with support migrated 2.8 times less than those without. The migration of short-stemmed trays correlated inversely with the density of the impacted groups. That of impaction-grafted tibial trays was in the range reported for uncemented primary trays. Movements of short-stemmed trays without cortical support were largest and sensitive to the degree of compaction of the graft. If support of the rim was sufficient or a long stem was used, impacted morsellised bone graft achieved adequate initial stability.