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.

Aims

The transepicondylar axis is a well-established reference for the determination of femoral component rotation in total knee arthroplasty (TKA). However, when severe bone loss is present in the femoral condyles, rotational alignment can be more complicated. There is a lack of validated landmarks in the supracondylar region of the distal femur. Therefore, the aim of this study was to analyze the correlation between the surgical transepicondylar axis (sTEA) and the suggested dorsal cortex line (DCL) in the coronal plane and the inter- and intraobserver reliability of its CT scan measurement.

Aims

The aim of this retrospective study was to assess the incidence of early periprosthetic femoral fracture (PFF) associated with Charnley-Kerboull (CK) femoral components cemented according to the ‘French paradox’ principles through the Hueter anterior approach (HAA) in patients older than 70 years.

Aims

The aim of this study was to establish consensus statements on the diagnosis, nonoperative management, and indications, if any, for medial patellofemoral complex (MPFC) repair in patients with patellar instability, using the modified Delphi approach.

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.

Aims. The aim of this study was to compare any differences in the primary outcome (biphasic flexion knee moment during gait) of robotic arm-assisted bi-unicompartmental knee arthroplasty (bi-UKA) with conventional mechanically aligned total knee arthroplasty (TKA) at one year post-surgery. Methods. A total of 76 patients (34 bi-UKA and 42 TKA patients) were analyzed in a prospective, single-centre, randomized controlled trial. Flat ground shod gait analysis was performed preoperatively and one year postoperatively. Knee flexion moment was calculated from motion capture markers and force plates. The same setup determined proprioception outcomes during a joint position sense test and one-leg standing. Surgery allocation, surgeon, and secondary outcomes were analyzed for prediction of the primary outcome from a binary regression model. Results. Both interventions were shown to be effective treatment options, with no significant differences shown between interventions for the primary outcome of this study (18/35 (51.4%) biphasic TKA patients vs 20/31 (64.5%) biphasic bi-UKA patients; p = 0.558). All outcomes were compared to an age-matched, healthy cohort that outperformed both groups, indicating residual deficits exists following surgery. Logistic regression analysis of primary outcome with secondary outcomes indicated that the most significant predictor of postoperative biphasic knee moments was preoperative knee moment profile and trochlear degradation (Outerbridge) (R. 2. = 0.381; p = 0.002, p = 0.046). A separate regression of alignment against primary outcome indicated significant bi-UKA femoral and tibial axial alignment (R. 2. = 0.352; p = 0.029), and TKA femoral sagittal alignment (R. 2. = 0.252; p = 0.016). The bi-UKA group showed a significant increased ability in the proprioceptive joint position test, but no difference was found in more dynamic testing of proprioception. Conclusion. Robotic arm-assisted bi-UKA demonstrated equivalence to TKA in achieving a biphasic gait pattern after surgery for osteoarthritis of the knee. Both treatments are successful at improving gait, but both leave the patients with a functional limitation that is not present in healthy age-matched controls. Cite this article: Bone Joint J 2022;103-B(4):433–443

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. 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

The use of shorter humeral stems in reverse shoulder arthroplasty has been reported as safe and effective. Shorter stems are purported to be bone preserving, easy to revise, and have reduced surgical time. However, a frequent radiographic finding with the use of uncemented short stems is stress shielding. Smaller stem diameters reduce stress shielding, however, carry the risk of varus or valgus malalignment in the metadiaphyseal region of the proximal humerus. The aim of this retrospective radiographic study was to measure the true post-operative neck-shaft (N-S) angle of a curved short stem with a recommended implantation angle of 145°. True anteroposterior radiographs of patients who received RTSA using an Ascend Flex short stem at three specialized shoulder centres (London, ON, Canada, Lyon, France, Munich, Germany) were reviewed. Radiographs that showed the uncemented stem and humeral tray in orthogonal view without rotation were included. Sixteen patients with proximal humeral fractures or revision surgeries were excluded. This yielded a cohort of 124 implant cases for analysis (122 patients, 42 male, 80 female) at a mean age of 74 years (range, 48 – 91 years). The indications for RTSA were rotator cuff deficient shoulders (cuff tear arthropathy, massive cuff tears, osteoarthritis with cuff insufficiency) in 78 patients (63%), primary osteoarthritis in 41 (33%), and rheumatoid arthritis in 5 (4%). The humeral component longitudinal axis was measured in degrees and defined as neutral if the value fell within ±5° of the humeral axis. Angle values >5° and < 5 ° were defined as valgus and varus, respectively. The filling-ratio of the implant within the humeral shaft was measured at the level of the metaphysis (FRmet) and diaphysis (FRdia). Measurements were conducted by two independent examiners (SA and TW). To test for conformity of observers, the intraclass correlation coefficient (ICC) was calculated. The inter- and intra-observer reliability was excellent (ICC = 0.965, 95% confidence interval [CI], 0.911– 0.986). The average difference between the humeral shaft axis and the humeral component longitudinal axis was 3.8° ± 2.8° (range, 0.2° – 13.2°) corresponding to a true mean N-S angle of 149° ± 3° in valgus. Stem axis was neutral in 70% (n=90) of implants. Of the 34 malaligned implants, 82% (n=28) were in valgus (mean N-S angle 153° ± 2°) and 18% (n=6) in varus position (mean N-S angle 139° ± 1°). The average FRmet and FRdiawere 0.68 ± 0.11 and 0.72 ± 0.11, respectively. No association was found between stem diameter and filling ratios (FRmet, FRdia) or cortical contact with the stem (r = 0.39). Operative technique and implant design affect the ultimate positioning of the implant in the proximal humerus. This study has shown, that in uncemented short stem implants, neutral axial alignment was achieved in 70% of cases, while the majority of malaligned humeral components (86%) were implanted in valgus, corresponding to a greater than 145° neck shaft angle of the implant. It is important for surgeons to understand that axial malalignment of a short stem implant does influence the true neck shaft angle

Aims

Postoperative range of movement (ROM) is an important measure of successful and satisfying total knee arthroplasty (TKA). Reduced postoperative ROM may be evident in up to 20% of all TKAs and negatively affects satisfaction. To improve ROM, manipulation under anaesthesia (MUA) may be performed. Historically, a limited ROM preoperatively was used as the key harbinger of the postoperative ROM. However, comorbidities may also be useful in predicting postoperative stiffness. The goal was to assess preoperative comorbidities in patients undergoing TKA relative to incidence of postoperative MUA. The hope is to forecast those who may be at increased risk and determine if MUA is an effective form of treatment.

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.

Introduction. Rotational or axial alignment is an important concept in total knee surgery. Malrotation of the femoral component can lead to patellofemoral maltracking, pain and stiffness. In reconstruction surgery of the knee, achievement of correct rotation is even more difficult because of the lack of anatomical landmarks. The linea aspera is often the only remaining landmark, but its reliability is questionable. Goal of research. Can custom-made 3D-guides help with rotational alignment of the knee after a wide resection of the distal femur?. Material and methods. Custom-made 3D-guides were designed from CT-scans, with the help of the commercially available Mimics software (Materialise NV, Leuven, Belgium) and SolidWorks (SolidWorks Corp., MA, USA). Anterior was defined as 90° relative to the PCL, with the center of the best-fitting inner cylinder, inside the femoral diaphysis, as rotation point. Firstly, the accuracy of the 3D-guides was tested. Twelve 3D-guides, on different heights, were made for 3 cadaveric femora. Anterior was marked with a pin and the position was evaluated with CT-scan. Secondly, to mimic surgery, seven reconstruction prostheses were placed in 4 cadavers, using the 3D-guide to indicate anterior and cutting surface. Resection height was aimed at 13cm. The position of the prostheses was also evaluated using CT-scan. Results. First test: The pins deviated on average 0.65° (SE: 0.75°) from anterior. Eighty-three percent deviated less then 1° from anterior, and only 2 pins deviated more than 1° (1.5° and 2.6°). The resection height indicated by the 3D-guide was on average 2.4mm (SE: 0.7mm) to high. Second test: The 7 reconstruction prostheses deviated on average 3.1° (SE: 2,18°) from anterior, with 4 prostheses deviating more than 1°. The 2 prostheses in endorotation were placed more lateral then was planned, while the 2 in exorotation were placed more medial. Deviation in the coronal and sagittal plane was respectively 1.56° (SE: 1.64°) and 1.84° (SE: 1.04). The mean height was 12.9cm. Discussion. The 3D-guides were accurate in indicating a previously established ‘anterior’ point on the femur and the resection height, but when used to position the femoral component during surgery they inadequately controlled rotation. The 3D-guides did not take into account that centering of the prosthesis could be a problem. When the prosthesis was place more medial or more lateral than anticipated the rotation point of the component was changed and when then aligned with the previously indicated anterior mark, it was placed respectively in exorotation and endorotation. Future research. Will aim to develop custom-made 3D-guides that also guide centering of the femoral component. Repercussion on function and kinematics of improved axial alignment will be evaluated with knee simulator testing and a control group

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.

Even though primary total knee arthroplasty involves resurfacing the joint with metal and plastic it is much more of a soft tissue operation than it is a bony procedure. The idea that altering the planned bony resection by a few degrees on either the tibial or femoral side of the joint might somehow eliminate the multifactorial pain complaints and reduced patient satisfaction seen in some 20% or more of cases in reported clinical series is clearly overly optimistic. Axial alignment is important, but no more so than the level of distal femoral resection, tibial and femoral rotation, tibial resection level and downslope and femoral sagittal plane alignment. The real problem is that errors in component positioning are common, rarely made one at a time, and are made more common by greater procedural complexity. No matter the resection method (let alone the resection target!) errors are commonly linked and iterative. For example: femoral malrotation on an under-resected distal femur (in a knee with minimal arthritic wear to begin with) can contribute to corresponding tibial malrotation helped by a “floated” tibial trial on an all too often overly resected and downsloped tibial surface that has been recut to allow full extension with the under-resected femur (and now also results in AP laxity in flexion). Small changes in the alignment target will not fix this!. On the other hand: Kinematic alignment individualised to the patient's anatomy as a means of reducing soft tissue imbalance and minimizing ligamentous releases is actually a reasonable objective and a laudable goal on the surface. The problem with operationalizing this widely relates to what is currently required to try and reliably achieve this goal using currently available implants and technology. In the early 1980's the proponents of “anatomic” alignment with a residual 2- to 3-degree varus tibial resection and corresponding joint obliquity were Hungerford and Krackow. This concept was widely adopted but proved to be fraught with difficulty in the hands of community based surgeons in that era due to common excessive varus tibial resection errors and resulting premature implant failures. Recent reports on kinematic alignment involve a plethora of technology combinations including pre-operative CT (or MRI) for 3D reconstruction and planning, custom jig fabrication, and navigated bony preparation or individualised bony cuts off of patient specific jigs. The goal is to allow customised resections that “estimate” original cartilage thickness and bone erosion and seek to replicate the original however native anatomy and provide better precision for bone resection. Even when successful this is often followed by placement of a standard implant not too different from those in the 80's and 90's which may well have one femoral articular “J curve” for all patents, a single patellofemoral groove design and anatomic shape for all, and that makes use of a central keel on a nonanatomic tibial design with limited sizing increments, all implanted into a patient without an ACL and not infrequently PCL deficient as well. And all of this is done with the hope of restoring the normal original knee kinematics!. The frequent combination of several of the above factors clinically in a single knee may help explain some of the variability in results of kinematic alignment reported by some authors even after excluding certain pre-operative deformities (excess valgus or varus). For now mechanical alignment methods and instrumentation should remain the standard of care for routine TKA practice for most, and in complex primary cases for all

Each of the seven cuts required for a total knee arthroplasty has its own science, and can affect the outcome of surgery. Distal Femur. Sets the axial alignment (along with the tibial cut), and too little or too much depth affects ligament tension in extension. Anterior Femur. Sets the rotation of the femoral component, which affects patellar tracking. Internal rotation results in patellar maltracking. External rotation will either notch the femur, or cause too large a femoral component to be selected. Anterior and posterior femoral cuts also determine femoral component size selection. Too small a femoral component causes notching, flexion instability, and mismatch to the tibial component. Too big a femoral component causes overstuffing, periarticular pain, and patellar maltracking. Posterior Femur. Posterior referencing usually works, and the typical knee requires 3 degrees of external rotation to align with the transepicondylar axis. In valgus knees, there may be significant hypoplasia of the lateral femoral condyle, and posterior referencing has to be adjusted to avoid internal rotation. Posterior chamfer. A 4-in-one block saves time. Anterior chamfer. Deeper anterior chamfer allows a deeper trochlear groove, for patellar tracking. Tibia. Sets axial alignment with distal femoral cut. Posterior slope loosens flexion gap. Oversizing results in painful medial overhang. Lateral overhang usually not a problem. Undersizing results in inadequate bone support and subsidence. Patella. Inset or onset. Central peg associated with fracture. Err to medial and superior to assist tracking and avoid impingement on the tibial insert

Introduction. The use of stems in TKA revision surgery is well established. Stems off-load stress over a broad surface area of the diaphysis and help protect the metaphyseal interface areas from failure. Stems can provide an area of extra fixation. Uncemented Stems. Pros and Cons. Advantages. (1) Expeditious, (2) Compatible with intramedullary based revision instrumentation (3) Easy to remove if necessary (4) By filling diaphysis they help guarantee axial alignment. Disadvantages. (1) They help off load stress, but how much fixation do they really provide? (2) They don't fit all canal deformities, and under some circumstances can actually force implants into malalignment. (3) ? potential for end of stem pain. Cemented Stems. Pros and Cons. Advantages. (1) Cemented stem adds fixation in fresh metaphyseal and diaphyseal bone. (2) Proven 10-year track record. (3) Allow the surgeon to adjust for canal geometry abnormalities. Disadvantages. (1) More difficult to remove, if required. (2) They don't fill the canal so they don't guarantee alignment as well under most circumstances. Results. Favorable results with uncemented and cemented stems have been reported in several series. Cemented stems have longer term data. Technique Issues. Uncemented Stems. (1) Take advantage of offset bolts, tibial trays, stems to fit the stem/implant to the patient's anatomy. (2) Don't let the stem force you into suboptimal implant position. (3) Longer stems can be narrower but help engage more diaphysis. (4) Do a good job of restoring/uncovering cancellous bone in metaphysis for cement interdigitation. The cement provides the fixation. Cemented Stems. (1) Intra-operative x-ray with trials helps guarantee optimal alignment. (2) Use cement restrictors. (3) Cement tibia/femur separately. Metaphyseal Fixation. (1) Area of new emphasis. (2) Cones and sleeves can improve cemented and uncemented fixation

Tibial plateau fractures are common injuries. Displaced fractures are treated with open reduction and internal fixation (ORIF). Goals of treatment include restoration of extremity axial alignment, joint stability and congruity, allowing for early motion and prevention of osteoarthritis. Short term results of surgical fixation of tibial plateau fractures are good, however, longer term outcomes have demonstrated a higher risk of end-stage arthritis and total knee arthroplasty. Despite the vast literature around tibial plateau fractures, to our knowledge there are no series examining post-operative reductions using axial imaging. It is our goal to define the incidence of articular malreductions following surgical fixation of tibial plateau fractures, to identify patient or surgeon factors associated with malreductions, and to define any regional patterns of malreduction location. De-identified post operative computed tomography (CT) scans were reviewed to identify tibial plateau malreductions with a step or gap greater than 2 mm, or condylar width greater than 5 mm. Three independent assessors reviewed the scans meeting criteria using Osirix DICOM software. Steps and gaps were mapped onto the axial sequence at the level of the joint line. Images were then matched to side and overlaid as best fit in Photoshop software to create a map of malreductions. A grid was created to divide the medial and lateral plateaus into quadrants to identify the density of malreductions by location. A multi-variate regression model was used to assess risk factors for malreduction. Sixty five post-operative CT scans were reviewed. Twenty one reductions had a step or gap more than 2 mm for a malreduction incidence of 32.3%. The incidence in patients undergoing submeniscal arthrotomy or fluoroscopic assisted reduction was 16.6% and 41.4%, respectively (p <0.001). Side of injury, age, BMI, AO fracture type, and use of locking plates were not predictive of malreduction. Malreductions were heavily weighted to the posterior lateral tibial plateau. The incidence of articular malreductions was high at 32.3%. Fluoroscopic reduction alone was a predictor for articular malreduction with most malreductions located in the posterior lateral quadrants of the plateau

Fractures around total knee arthroplasties pose a significant surgical challenge. Most can be managed with osteosynthesis and salvage of the replacement. The techniques of fixation of these fractures and revision surgery have evolved and so has the assessment of outcome. This specialty update summarises the current evidence for the classification, methods of fixation, revision surgery and outcomes of the management of periprosthetic fractures associated with total knee arthroplasty.

Cite this article: Bone Joint J 2016;98-B:1489–96.

Aims

We wished to examine the effectiveness of tibial lengthening using a two ring Ilizarov frame in skeletally immature patients. This is a potentially biomechanically unstable construct which risks the loss of axial control.

Introduction. Total Knee Replacement (TKR) alignment measured intra-operatively with Navigation has been shown to differ from that observed in long leg radiographs (Deep 2011). Potential explanations for this discrepancy may be the effect of weight bearing or the dynamic contributions of soft tissue loads. Method. A validated, 3D, dynamic patient specific musculoskeletal model was used to analyse 85 post-operative CT scans using a common implant design. Differences in coronal and axial plane tibio-femoral alignment in three separate scenarios were measured:. Unloaded as measured in a post-op CT. Unloaded, with femoral and tibial components set aligned to each other. Weight bearing with the extensor mechanism engaged. Scenario number two illustrates the tibio-femoral alignment when the femoral component sits congruently on the tibia with no soft tissue acting whereas scenario three is progression of scenario number two with weight applied and all ligaments are active. Two tailed paired students t-test were used to determine significant differences in the means of absolute difference of axial and coronal alignments. Results. The mean coronal alignment were 1.7° ± 2.1° varus (range, −3.0° to 7.0°), 0.8° ± 2.0° varus (range, −3.7° to 4.8°), 0.4° ± 2.0° varus (range, −3.9° to 5.1°) for unloaded, unloaded with implants set aligned and weight bearing scenarios respectively. The mean of absolute difference in coronal alignment between the unloaded and weight bearing scenario was 1.8° ± 1.5° (range 0.0° to 5.9°). The mean axial alignment were 6.8° ± 5.5° external rotation (ER) (range, 20.0° ER to 11.0° internal rotation (IR)), 5.2° ± 6.1° ER (range, 24.8° ER to 12.6° IR), 7.1° ± 5.5° ER (range, 20.7° ER to 6.8° IR) for unloaded, unloaded with implants set to congruency and weight bearing scenarios respectively. The mean of absolute difference in axial alignment between the unloaded and weight bearing scenario was 2.8° ± 2.0° (range 0.1° to 8.8°). Statistically significant absolute differences in coronal and axial alignments were found. Conclusions. ‘Correct’ alignment has long been considered and important predictor of longevity and function following TKR surgery (Sikorski 2008). However, recent reports have challenged these long held beliefs. One possible reason is that these alignments are measured in static condition, not in a functional position where soft tissue is active. This study showed that knee joint alignment changes significantly between unloaded and loaded scenarios. This suggest that static, unloaded measurements do not represent functional alignment. Thus, tibio-femoral alignment measured from unloaded condition may not describe a ‘correct’ alignment for a particular patient. Further work should focus on dynamic and functional descriptions of component and/or limb alignment