Total knee arthroplasty (TKR) using a medial capsular approach gives worse results in arthritic knees with valgus deformity than in those in varus, usually because of swelling, poor wound healing and stiffness, instability, recurrent valgus deformity and poor patellar tracking. A technique for replacement TKR of valgus knees using a lateral capsular approach was described several years ago, but was not routinely adopted because of the difficulties with and complexity of the procedure which included deliberate elevation of the tibial tubercle. In order to avoid this we have modified and simplified the procedure. Our preliminary results suggest that this lateral approach is safe and may give a better outcome than that through the medial capsule for the replacement of valgus knees

We describe the mid-term results of a prospective study of total knee replacement in severe valgus knees using an osteotomy of the lateral femoral condyle and computer navigation. There were 15 knees with a mean valgus deformity of 21° (17° to 27°) and a mean follow-up of 28 months (24 to 60). A cemented, non-constrained fixed bearing, posterior-cruciate-retaining knee prosthesis of the same design was used in all cases (Columbus-B. Braun; Aesculap, Tuttlingen, Germany). All the knees were corrected to a mean of 0.5° of valgus (0° to 2°). Flexion of the knee had been limited to a mean of 85° (75° to 110°) pre-operatively and improved to a mean of 105° (90° to 130°) after operation. The mean Knee Society score improved from 37 (30 to 44) to 90 points (86 to 94). Osteotomy of the lateral femoral condyle combined with computer-assisted surgery gave an excellent mid-term outcome in patients undergoing total knee replacement in the presence of severe valgus deformity

Aims. Functional alignment (FA) in total knee arthroplasty (TKA) aims to achieve balanced gaps by adjusting implant positioning while minimizing changes to constitutional joint line obliquity (JLO). Although FA uses kinematic alignment (KA) as a starting point, the final implant positions can vary significantly between these two approaches. This study used the Coronal Plane Alignment of the Knee (CPAK) classification to compare differences between KA and final FA positions. Methods. A retrospective analysis compared pre-resection and post-implantation alignments in 2,116 robotic-assisted FA TKAs. The lateral distal femoral angle (LDFA) and medial proximal tibial angle (MPTA) were measured to determine the arithmetic hip-knee-ankle angle (aHKA = MPTA – LDFA), JLO (JLO = MPTA + LDFA), and CPAK type. The primary outcome was the proportion of knees that varied ≤ 2° for aHKA and ≤ 3° for JLO from their KA to FA positions, and direction and magnitude of those changes per CPAK phenotype. Secondary outcomes included proportion of knees that maintained their CPAK phenotype, and differences between sexes. Results. Overall, 71.6% had an aHKA change ≤ 2°, and 87.0% a JLO change ≤ 3°. Mean aHKA changed from -1.1° (SD 2.8°) in KA to -1.9° (SD 2.3°) in FA (mean difference (MD) -0.83 (SD 2.0); p < 0.001). Mean JLO changed from 173.9° (SD 3.0°) in KA to 174.2° (SD 2.6°) in FA (MD 0.38 (SD 2.3); p < 0.001). CPAK type was maintained in 58.1% of knees, with the proportion highest for Types I (73.9%), II (61.1%), and IV (51.2%). In valgus knees, 67.5% of Type III and 71.7% of Type VI were shifted to neutral phenotypes. There was minimal change to constitutional JLO across all CPAK types (MDs -2.0° to 1.2°). Conclusion. Functional alignment may alter CPAK type, but does not significantly change JLO. A kinematic starting point minimizes changes to native anatomy, while final position with FA provides an optimally balanced TKA. Cite this article: Bone Jt Open 2024;5(12):1081–1091

Aims

To compare time dependent functional improvement for patients with medial, respectively lateral knee osteoarthritis (OA) after treatment with opening wedge osteotomy relieving the pressure on the osteoarthritic part of the knee.

Aims. The aim of this study was to determine the association between knee alignment and the vertical orientation of the femoral neck in relation to the floor. This could be clinically important because changes of femoral neck orientation might alter chondral joint contact zones and joint reaction forces, potentially inducing problems like pain in pre-existing chondral degeneration. Further, the femoral neck orientation influences the ischiofemoral space and a small ischiofemoral distance can lead to impingement. We hypothesized that a valgus knee alignment is associated with a more vertical orientation of the femoral neck in standing position, compared to a varus knee. We further hypothesized that realignment surgery around the knee alters the vertical orientation of the femoral neck. Methods. Long-leg standing radiographs of patients undergoing realignment surgery around the knee were used. The hip-knee-ankle angle (HKA) and the vertical orientation of the femoral neck in relation to the floor were measured, prior to surgery and after osteotomy-site-union. Linear regression was performed to determine the influence of knee alignment on the vertical orientation of the femoral neck. Results. The cohort included 147 patients who underwent knee realignment-surgery. The mean age was 51.5 years (SD 11). Overall, 106 patients underwent a valgisation-osteotomy, while 41 underwent varisation osteotomy. There was a significant association between the orientation of the knee and the coronal neck-orientation. In the varus group, the median orientation of the femoral neck was 46.5° (interquartile range (IQR) 49.7° to 50.0°), while in the valgus group, the orientation was 52.0° (IQR 46.5° to 56.7°; p < 0.001). Linear regression analysis revealed that HKA demonstrated a direct influence on the coronal neck-orientation (β = 0.5 (95% confidence interval (CI) 0.2 to 0.7); p = 0.002). Linear regression also showed that realignment surgery was associated with a significant influence on the change in the coronal femoral neck orientation (β = 5.6 (95% CI 1.5 to 9.8); p = 0.008). Conclusion. Varus or valgus knee alignment is associated with either a more horizontal or a more vertical femoral neck orientation in standing position, respectively. Subsequently, osteotomies around the knee alter the vertical orientation of the femoral neck. These aspects are of importance when planning osteotomies around the knee in order to appreciate the effects on the adjacent hip joint. The concept may be of even more relevance in dysplastic hips. Cite this article: Bone Jt Open 2021;2(12):1057–1061

Aims. To explore the clinical relevance of joint space width (JSW) narrowing on standardized-flexion (SF) radiographs in the assessment of cartilage degeneration in specific subregions seen on MRI sequences in knee osteoarthritis (OA) with neutral, valgus, and varus alignments, and potential planning of partial knee arthroplasty. Methods. We retrospectively reviewed 639 subjects, aged 45 to 79 years, in the Osteoarthritis Initiative (OAI) study, who had symptomatic knees with Kellgren and Lawrence grade 2 to 4. Knees were categorized as neutral, valgus, and varus knees by measuring hip-knee-angles on hip-knee-ankle radiographs. Femorotibial JSW was measured on posteroanterior SF radiographs using a special software. The femorotibial compartment was divided into 16 subregions, and MR-tomographic measurements of cartilage volume, thickness, and subchondral bone area were documented. Linear regression with adjustment for age, sex, body mass index, and Kellgren and Lawrence grade was used. Results. We studied 345 neutral, 87 valgus, and 207 varus knees. Radiological JSW narrowing was significantly (p < 0.01) associated with cartilage volume and thickness in medial femorotibial compartment in neutral (r = 0.78, odds ratio (OR) 2.33) and varus knees (r = 0.86, OR 1.92), and in lateral tibial subregions in valgus knees (r = 0.87, OR 3.71). A significant negative correlation was found between JSW narrowing and area of subchondral bone in external lateral tibial subregion in valgus knees (r = −0.65, p < 0.01) and in external medial tibial subregion in varus knees (r = −0.77, p < 0.01). No statistically significant correlation was found in anterior and posterior subregions. Conclusion. SF radiographs can be potentially used for initial detection of cartilage degeneration as assessed by MRI in medial and lateral but not in anterior or posterior subregions. Cite this article: Bone Joint Res 2021;10(3):173–187

Aims. The aim of this study was to compare robotic arm-assisted bi-unicompartmental knee arthroplasty (bi-UKA) with conventional mechanically aligned total knee arthroplasty (TKA) in order to determine the changes in the anatomy of the knee and alignment of the lower limb following surgery. Methods. An analysis of 38 patients who underwent TKA and 32 who underwent bi-UKA was performed as a secondary study from a prospective, single-centre, randomized controlled trial. CT imaging was used to measure coronal, sagittal, and axial alignment of the knee preoperatively and at three months postoperatively to determine changes in anatomy that had occurred as a result of the surgery. The hip-knee-ankle angle (HKAA) was also measured to identify any differences between the two groups. Results. The pre- to postoperative changes in joint anatomy were significantly less in patients undergoing bi-UKA in all three planes in both the femur and tibia, except for femoral sagittal component orientation in which there was no difference. Overall, for the six parameters of alignment (three femoral and three tibial), 47% of bi-UKAs and 24% TKAs had a change of < 2° (p = 0.045). The change in HKAA towards neutral in varus and valgus knees was significantly less in patients undergoing bi-UKA compared with those undergoing TKA (p < 0.001). Alignment was neutral in those undergoing TKA (mean 179.5° (SD 3.2°)) while those undergoing bi-UKA had mild residual varus or valgus alignment (mean 177.8° (SD 3.4°)) (p < 0.001). Conclusion. Robotic-assisted, cruciate-sparing bi-UKA maintains the natural anatomy of the knee in the coronal, sagittal, and axial planes better, and may therefore preserve normal joint kinematics, compared with a mechanically aligned TKA. This includes preservation of coronal joint line obliquity. HKAA alignment was corrected towards neutral significantly less in patients undergoing bi-UKA, which may represent restoration of the pre-disease constitutional alignment (p < 0.001). Cite this article: Bone Joint J 2020;102-B(11):1511–1518

Aims. Between 15% and 20% of patients remain dissatisfied following total knee arthroplasty (TKA). The SAIPH knee system (MatOrtho, Surrey, United Kingdom) is a medial ball and socket TKA that has been designed to replicate native knee kinematics in order to maximize the range of movement, stability, and function. This system is being progressively introduced in a stepwise fashion, with this study reporting the mid-term clinical and radiological outcomes. Patients and Methods. A retrospective review was undertaken of the first 100 consecutive patients with five-year follow-up following SAIPH TKA performed by the senior authors. The data that were collected included the demographics of the patients, clinical findings, the rate of intraoperative ligamentous release, patient-reported outcome measures (PROMS), radiological assessment, complications, and all-cause revision. Revision data were cross-checked with a national registry. Results. A total of 100 TKAs in 92 patients were included. Three patients died (three TKAs) and a further two TKAs were revised. Of the remaining 95 TKAs, five-year follow-up data were available for 81 TKAs (85%) in 87 patients. There were significant improvements in all PROMs and high satisfaction. The mean ROM at final follow-up was from 0° (full extension) to 124° flexion. There were seven major complications (7%): one infection, two deep vein thromboses, one cerebrovascular event, and two patients with stiffness requiring a manipulation under anaesthesia. Two patients required a lateral retinacular release to optimize patellar tracking in valgus knees; no additional ligament releases were performed in any patient. Radiological analysis demonstrated no evidence of implant-related complications. Conclusion. These results demonstrate satisfactory clinical and radiological outcomes at five years following a medial ball and socket TKA. The complication and revision rates are consistent with those previously reported for patients undergoing TKA. These results demonstrate the safety and efficacy of the SAIPH Knee TKA system and support its wider use

Aims

Total knee arthroplasty (TKA) may provoke ankle symptoms. The aim of this study was to validate the impact of the preoperative mechanical tibiofemoral angle (mTFA), the talar tilt (TT) on ankle symptoms after TKA, and assess changes in the range of motion (ROM) of the subtalar joint, foot posture, and ankle laxity.

Aims

Total knee arthroplasty (TKA) with a highly congruent condylar-stabilized (CS) articulation may be advantageous due to increased stability versus cruciate-retaining (CR) designs, while mitigating the limitations of a posterior-stabilized construct. The aim was to assess ten-year implant survival and functional outcomes of a cemented single-radius TKA with a CS insert, performed without posterior cruciate ligament sacrifice.

The aim of mechanical alignment in total knee arthroplasty is to align all knees into a fixed neutral position, even though not all knees are the same. As a result, mechanical alignment often alters a patient’s constitutional alignment and joint line obliquity, resulting in soft-tissue imbalance. This annotation provides an overview of how the Coronal Plane Alignment of the Knee (CPAK) classification can be used to predict imbalance with mechanical alignment, and then offers practical guidance for bone balancing, minimizing the need for soft-tissue releases.

Cite this article: Bone Joint J 2024;106-B(6):525–531.

Orthopaedic surgeons are currently faced with an overwhelming number of choices surrounding total knee arthroplasty (TKA), not only with the latest technologies and prostheses, but also fundamental decisions on alignment philosophies. From ‘mechanical’ to ‘adjusted mechanical’ to ‘restricted kinematic’ to ‘unrestricted kinematic’ — and how constitutional alignment relates to these — there is potential for ambiguity when thinking about and discussing such concepts. This annotation summarizes the various alignment strategies currently employed in TKA. It provides a clear framework and consistent language that will assist surgeons to compare confidently and contrast the concepts, while also discussing the latest opinions about alignment in TKA. Finally, it provides suggestions for applying consistent nomenclature to future research, especially as we explore the implications of 3D alignment patterns on patient outcomes.

Cite this article: Bone Joint J 2023;105-B(2):102–108.

We compared lower limb coronal alignment measurements obtained pre- and post-operatively with long-leg radiographs and computer navigation in patients undergoing primary total knee replacement (TKR). A series of 185 patients had their pre- and post-implant radiological and computer-navigation system measurements of coronal alignment compared using the Bland-Altman method. The study included 81 men and 104 women with a mean age of 68.5 years (32 to 87) and a mean body mass index of 31.7 kg/m. 2. (19 to 49). Pre-implant Bland–Altman limits of agreement were -9.4° to 8.6° with a repeatability coefficient of 9.0°. The Bland–Altman plot showed a tendency for the radiological measurement to indicate a higher level of pre-operative deformity than the corresponding navigation measurement. Post-implant limits of agreement were -5.0° to 5.4° with a repeatability coefficient of 5.2°. The tendency for valgus knees to have greater deformity on the radiograph was still seen, but was weaker for varus knees. . The alignment seen or measured intra-operatively during TKR is not necessarily the same as the deformity seen on a standing long-leg radiograph either pre- or post-operatively. Further investigation into the effect of weight-bearing and surgical exposure of the joint on the mechanical femorotibial angle is required to enable the most appropriate intra-operative alignment to be selected

Aims

We aim to evaluate the usefulness of postoperative blood tests by investigating the incidence of abnormal results following total joint replacement (TJR), as well as identifying preoperative risk factors for abnormal blood test results postoperatively, especially pertaining to anaemia and acute kidney injury (AKI).

Aims

Micromotion of the polyethylene (PE) inlay may contribute to backside PE wear in addition to articulate wear of total knee arthroplasty (TKA). Using radiostereometric analysis (RSA) with tantalum beads in the PE inlay, we evaluated PE micromotion and its relationship to PE wear.

Aims

To assess the incidence of radiological lateral osteoarthritis (OA) at 15 years after medial unicompartmental knee arthroplasty (UKA) and assess the relationship of lateral OA with symptoms and patient characteristics.

Aims

Total knee arthroplasty (TKA) using functional alignment aims to implant the components with minimal compromise of the soft-tissue envelope by restoring the plane and obliquity of the non-arthritic joint. The objective of this study was to determine the effect of TKA with functional alignment on mediolateral soft-tissue balance as assessed using intraoperative sensor-guided technology.

Aims

Robotic-assisted total knee arthroplasty (RA-TKA) is theoretically more accurate for component positioning than TKA performed with mechanical instruments (M-TKA). Furthermore, the ability to incorporate soft-tissue laxity data into the plan prior to bone resection should reduce variability between the planned polyethylene thickness and the final implanted polyethylene. The purpose of this study was to compare accuracy to plan for component positioning and precision, as demonstrated by deviation from plan for polyethylene insert thickness in measured-resection RA-TKA versus M-TKA.

Aims

In total knee arthroplasty (TKA), blood loss continues internally after surgery is complete. Typically, the total loss over 48 postoperative hours can be around 1,300 ml, with most occurring within the first 24 hours. We hypothesize that the full potential of tranexamic acid (TXA) to decrease TKA blood loss has not yet been harnessed because it is rarely used beyond the intraoperative period, and is usually withheld from ‘high-risk’ patients with a history of thromboembolic, cardiovascular, or cerebrovascular disease, a patient group who would benefit greatly from a reduced blood loss.

Aims

Medial pivot (MP) total knee arthroplasties (TKAs) were designed to mimic native knee kinematics with their deep medial congruent fitting of the tibia to the femur almost like a ball-on-socket, and a flat lateral part. GMK Sphere is a novel MP implant. Our primary aim was to study the migration pattern of the tibial tray of this TKA.

Limb alignment in total knee arthroplasty (TKA) influences periarticular soft-tissue tension, biomechanics through knee flexion, and implant survival. Despite this, there is no uniform consensus on the optimal alignment technique for TKA. Neutral mechanical alignment facilitates knee flexion and symmetrical component wear but forces the limb into an unnatural position that alters native knee kinematics through the arc of knee flexion. Kinematic alignment aims to restore native limb alignment, but the safe ranges with this technique remain uncertain and the effects of this alignment technique on component survivorship remain unknown. Anatomical alignment aims to restore predisease limb alignment and knee geometry, but existing studies using this technique are based on cadaveric specimens or clinical trials with limited follow-up times. Functional alignment aims to restore the native plane and obliquity of the joint by manipulating implant positioning while limiting soft tissue releases, but the results of high-quality studies with long-term outcomes are still awaited. The drawbacks of existing studies on alignment include the use of surgical techniques with limited accuracy and reproducibility of achieving the planned alignment, poor correlation of intraoperative data to long-term functional outcomes and implant survivorship, and a paucity of studies on the safe ranges of limb alignment. Further studies on alignment in TKA should use surgical adjuncts (e.g. robotic technology) to help execute the planned alignment with improved accuracy, include intraoperative assessments of knee biomechanics and periarticular soft-tissue tension, and correlate alignment to long-term functional outcomes and survivorship.

Aims

A comprehensive classification for coronal lower limb alignment with predictive capabilities for knee balance would be beneficial in total knee arthroplasty (TKA). This paper describes the Coronal Plane Alignment of the Knee (CPAK) classification and examines its utility in preoperative soft tissue balance prediction, comparing kinematic alignment (KA) to mechanical alignment (MA).

Aims

To report mid- to long-term results of Oxford mobile bearing domed lateral unicompartmental knee arthroplasty (UKA), and determine the effect of potential contraindications on outcome.

Dissatisfaction following total knee arthroplasty is a well-documented phenomenon. Although many factors have been implicated, including modifiable and nonmodifiable patient factors, emphasis over the past decade has been on implant alignment and stability as both a cause of, and a solution to, this problem. Several alignment targets have evolved with a proliferation of techniques following the introduction of computer and robotic-assisted surgery. Mechanical alignment targets may achieve mechanically-sound alignment while ignoring the soft tissue envelope; kinematic alignment respects the soft tissue envelope while ignoring the mechanical environment. Functional alignment is proposed as a hybrid technique to allow mechanically-sound, soft tissue-friendly alignment targets to be identified and achieved.

Cite this article: Bone Joint J 2020;102-B(3):276–279.

Aims

To compare patients undergoing total knee arthroplasty (TKA) with ≤ 80° range of movement (ROM) operated with a 2 mm increase in the flexion gap with matched non-stiff patients with at least 100° of preoperative ROM and balanced flexion and extension gaps.

Valgus knee deformity can present a number of unique surgical challenges for the total knee arthroplasty (TKA) surgeon. Understanding the typical patterns of bone and soft-tissue pathology in the valgus arthritic knee is critical for appropriate surgical planning. This review aims to provide the knee arthroplasty surgeon with an understanding of surgical management strategies for the treatment of valgus knee arthritis.

Lateral femoral and tibial deficiencies, contracted lateral soft tissues, attenuated medial soft tissues, and multiplanar deformities may all be present in the valgus arthritic knee. A number of classifications have been reported in order to guide surgical management, and a variety of surgical strategies have been described with satisfactory clinical results. Depending on the severity of the deformity, a variety of TKA implant designs may be appropriate for use.

Regardless of an operating surgeon’s preferred surgical strategy, adherence to a step-wise approach to deformity correction is advised.

Cite this article: Bone Joint J 2017;99-B(1 Supple A):60–4.

Aims

The results of kinematic total knee arthroplasty (KTKA) have been reported in terms of limb and component alignment parameters but not in terms of gap laxities and differentials. In kinematic alignment (KA), balance should reflect the asymmetrical balance of the normal knee, not the classic rectangular flexion and extension gaps sought with gap-balanced mechanical axis total knee arthroplasty (MATKA). This paper aims to address the following questions: 1) what factors determine coronal joint congruence as measured on standing radiographs?; 2) is flexion gap asymmetry produced with KA?; 3) does lateral flexion gap laxity affect outcomes?; 4) is lateral flexion gap laxity associated with lateral extension gap laxity?; and 5) can consistent ligament balance be produced without releases?

Aims

Patellofemoral problems are a common complication of total knee arthroplasty. A high compressive force across the patellofemoral joint may affect patient-reported outcome. However, the relationship between patient-reported outcome and the intraoperative patellofemoral contact force has not been investigated. The purpose of this study was to determine whether or not a high intraoperative patellofemoral compressive force affects patient-reported outcome.

Aims

The morphometry of the distal femur was largely studied to improve bone-implant fit in total knee arthroplasty (TKA), but little is known about the asymmetry of the posterior condyles. This study aimed to investigate the dimensions of the posterior condyles and the influence of externally rotating the femoral component on potential prosthetic overhang or under-coverage.

Aims

This study compares the PFC total knee arthroplasty (TKA) system in a prospective randomized control trial (RCT) of the mobile-bearing rotating-platform (RP) TKA against the fixed-bearing (FB) TKA. This is the largest RCT with the longest follow-up where cruciate-retaining PFC total knee arthroplasties are compared in a non-bilateral TKA study.

Primary total knee arthroplasty (TKA) is a reliable procedure with reproducible long-term results. Nevertheless, there are conditions related to the type of patient or local conditions of the knee that can make it a difficult procedure. The most common scenarios that make it difficult are discussed in this review. These include patients with many previous operations and incisions, and those with severe coronal deformities, genu recurvatum, a stiff knee, extra-articular deformities and those who have previously undergone osteotomy around the knee and those with chronic dislocation of the patella.

Each condition is analysed according to the characteristics of the patient, the pre-operative planning and the reported outcomes.

When approaching the difficult primary TKA surgeons should use a systematic approach, which begins with the review of the existing literature for each specific clinical situation.

Cite this article: Bone Joint J 2015;97-B(10 Suppl A):30–9.

Objectives

Malalignment of the tibial component could influence the long-term survival of a total knee arthroplasty (TKA). The object of this study was to investigate the biomechanical effect of varus and valgus malalignment on the tibial component under stance-phase gait cycle loading conditions.

Aims

Analysis of the morphology of the distal femur, and by extension of the femoral components in total knee arthroplasty (TKA), has largely been related to the aspect ratio, which represents the width of the femur. Little is known about variations in trapezoidicity (i.e. whether the femur is more rectangular or more trapezoidal). This study aimed to quantify additional morphological characteristics of the distal femur and identify anatomical features associated with higher risks of over- or under-sizing of components in TKA.

Aims

It is not clear whether anterior knee pain and osteoarthritis (OA) of the patellofemoral joint (PFJ) are contraindications to medial unicompartmental knee arthroplasty (UKA). Our aim was to investigate the long-term outcome of a consecutive series of patients, some of whom had anterior knee pain and PFJ OA managed with UKA.

The lateral compartment is predominantly affected in approximately 10% of patients with osteoarthritis of the knee. The anatomy, kinematics and loading during movement differ considerably between medial and lateral compartments of the knee. This in the main explains the relative protection of the lateral compartment compared with the medial compartment in the development of osteoarthritis. The aetiology of lateral compartment osteoarthritis can be idiopathic, usually affecting the femur, or secondary to trauma commonly affecting the tibia. Surgical management of lateral compartment osteoarthritis can include osteotomy, unicompartmental knee replacement and total knee replacement. This review discusses the biomechanics, pathogenesis and development of lateral compartment osteoarthritis and its management.

Cite this article: Bone Joint J 2013;95-B:436–44.

Aims

The optimal method of tibial component fixation remains uncertain in total knee arthroplasty (TKA). Hydroxyapatite coatings have been applied to improve bone ingrowth in uncemented designs, but may only coat the directly accessible surface. As peri-apatite (PA) is solution deposited, this may increase the coverage of the implant surface and thereby fixation. We assessed the tibial component fixation of uncemented PA-coated TKAs versus cemented TKAs.

Aims

The aim of this study was to investigate differences in pain, range of movement function and satisfaction at three months and one year after total knee arthroplasty (TKA) in patients with an oblique pattern of kinematic graph of the knee and those with a varus pattern.

Instability after total knee replacement (TKR) accounts for 10% to 22% of revision procedures. All patients who present for evaluation of instability require a thorough history to be taken and physical examination, as well as appropriate imaging. Deep periprosthetic infection must be ruled out by laboratory testing and an aspiration of the knee must be carried out. The three main categories of instability include flexion instability, extension instability (symmetric and asymmetric), and genu recurvatum. Most recently, the aetiologies contributing to, and surgical manoeuvres required to correct, flexion instability have been elucidated. While implant design and patient-related factors may certainly contribute to the aetiology, surgical technique is also a significant factor in all forms of post-operative instability.

Cite this article: Bone Joint J 2014;96-B(11 Suppl A):112–4.

Objectives

The purpose of this study was to clarify the appearance of the reparative tissue on the articular surface and to analyse the properties of the reparative tissue after hemicallotasis osteotomy (HCO) using MRI T1ρ and T2 mapping.

Collateral ligament release is advocated in total knee arthroplasty (TKA) to deal with significant coronal plane deformities, but is also associated with significant disadvantages.

We describe steps to avoid release of the collateral (superficial medial and lateral collateral) ligaments during TKA in severely deformed knees, while correcting deformity and balancing the knee.

Cite this article: Bone Joint J 2016;98-B(1 Suppl A):101–4.

We present the results of the surgical correction of lower-limb deformities caused by metabolic bone disease. Our series consisted of 17 patients with a diagnosis of hypophosphataemic rickets and two with renal osteodystrophy; their mean age was 25.6 years (14 to 57). In all, 43 lower-limb segments (27 femora and 16 tibiae) were osteotomised and the deformity corrected using a monolateral external fixator. The segment was then stabilised with locked intramedullary nailing. In addition, six femora in three patients were subsequently lengthened by distraction osteogenesis. The mean follow-up was 60 months (18 to 120). The frontal alignment parameters (the mechanical axis deviation, the lateral distal femoral angle and the medial proximal tibial angle) and the sagittal alignment parameters (the posterior distal femoral angle and the posterior proximal tibial angle) improved post-operatively. The external fixator was removed either at the end of surgery or at the end of the lengthening period, allowing for early mobilisation and weight-bearing. We encountered five problems and four obstacles in the programme of treatment.

The use of intramedullary nails prevented recurrence of deformity and refracture.

In 11 paediatric patients (seven girls and four boys, from 12 to 15 years old) with unilateral obligatory patellar dislocation and ligamentous laxity vastus medialis advancement, lateral release, partial patellar ligament transposition and Galeazzi semitendinosus tenodesis was undertaken to stabilise the patella. The diagnostic criterion for ligamentous laxity was based on the Beighton scale. Outcomes were evaluated radiologically and functionally by measurement of the range of knee movement and isokinetic testing. The evaluation also included the Lysholm knee scale. Follow-up studies took place at a mean of 8.1 years (5 to 15) post-operatively.

Normal patellar tracking without any recurrence of dislocation was obtained in ten out of 11 patients. Pain related to vigorous activity was reported by nine patients. Compared with the opposite normal side, the isokinetic tests revealed a statistically significant decrease in the maximal torque values for the affected quadriceps muscle (p = 0.003 and p = 0.004), but no difference between the knee flexors (for angular velocities of 60°/s and 180°/s) (p = 0.858 and p = 0.79).

The applied surgical technique generally prevents the recurrence of the disorder in children with habitual patellar dislocation and ligamentous laxity. Quadriceps muscle weakness can be expected to occur post-operatively,

Cite this article: Bone Joint J 2015;96-B:129–33.

Mechanical alignment has been a fundamental tenet of total knee arthroplasty (TKA) since modern knee replacement surgery was developed in the 1970s. The objective of mechanical alignment was to infer the greatest biomechanical advantage to the implant to prevent early loosening and failure. Over the last 40 years a great deal of innovation in TKA technology has been focusing on how to more accurately achieve mechanical alignment. Recently the concept of mechanical alignment has been challenged, and other alignment philosophies are being explored with the intention of trying to improve patient outcomes following TKA.

This article examines the evolution of the mechanical alignment concept and whether there are any viable alternatives.

At least four ways have been described to determine femoral component rotation, and three ways to determine tibial component rotation in total knee replacement (TKR). Each method has its advocates and each has an influence on knee kinematics and the ultimate short and long term success of TKR. Of the four femoral component methods, the author prefers rotating the femoral component in flexion to that amount that establishes a stable symmetrical flexion gap. This judgement is made after the soft tissues of the knee have been balanced in extension.

Of the three tibial component methods, the author prefers rotating the tibial component into congruency with the established femoral component rotation with the knee is in extension. This yields a rotationally congruent articulation during weight-bearing and should minimise the torsional forces being transferred through a conforming tibial insert, which could lead to wear to the underside of the tibial polyethylene. Rotating platform components will compensate for any mal-rotation, but can still lead to pain if excessive tibial insert rotation causes soft-tissue impingement.

Cite this article: Bone Joint J 2013;95-B, Supple A:140–3.

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 surface-derived 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.

We have investigated the benefits of patient specific instrument guides, applied to osteotomies around the knee. Single, dual and triple planar osteotomies were performed on tibias or femurs in 14 subjects. In all patients, a detailed pre-operative plan was prepared based upon full leg standing radiographic and CT scan information. The planned level of the osteotomy and open wedge resection was relayed to the surgery by virtue of a patient specific guide developed from the images. The mean deviation between the planned wedge angle and the executed wedge angle was 0° (-1 to 1, sd 0.71) in the coronal plane and 0.3° (-0.9 to 3, sd 1.14) in the sagittal plane. The mean deviation between the planned hip, knee, ankle angle (HKA) on full leg standing radiograph and the post-operative HKA was 0.3° (-1 to 2, sd 0.75). It is concluded that this is a feasible and valuable concept from the standpoint of pre-operative software based planning, surgical application and geometrical accuracy of outcome.

Cite this article: Bone Joint J 2013;95-B, Supple A:153–8.