Aims. We investigated changes in the axial alignment of the ipsilateral hip and knee after total hip arthroplasty (THA). . Patients and Methods. We reviewed 152 patients undergoing primary THA (163 hips; 22 hips in men, 141 hips in women) without a pre-operative flexion contracture. The mean age was 64 years (30 to 88). The diagnosis was osteoarthritis (OA) in 151 hips (primary in 18 hips, and secondary to dysplasia in 133) and non-OA in 12 hips. A posterolateral approach with repair of the external rotators was used in 134 hips and an anterior approach in 29 hips. We measured changes in leg length and offset on radiographs, and femoral anteversion, internal rotation of the hip and lateral patellar tilt on CT scans, pre- and post-operatively. . Results. The mean internal rotation increased by 11° (-15° to 46°) and was associated with underlying disease (OA), pre-operative range of internal rotation, gender, surgical approach, leg lengthening, and change of femoral anteversion (adjusted R. 2. : 0.253, p < 0.001). The mean lateral patellar tilt increased by 4° (-5° to 14°) and was associated with age, leg lengthening, and increment of hip internal rotation (adjusted R. 2. : 0.193, p < 0.001). Conclusion. Both internal rotation of the hip at rest and lateral patellar tilt are increased after THA. Changes in rotation after THA may affect gait, daily activities, the rate of dislocation of the hip, and ipsilateral knee pain. Take home message: Internal rotation of the hip at rest and lateral patellar tilt increase after THA. Cite this article: Bone Joint J 2016;98-B:349–58

Introduction: Normal axial alignment of the lower extremity is important to surgeons who perform reconstruction surgery of the knee. The data are, however, not available for Chinese adults. Methods: The axial alignment of the lower extremity of twenty-five adult males and twenty-five adult females of southern Chinese origin was measured by using weight-bearing radiographs of the entire lower limb. The mean age of the male and female volunteers was twenty-four years and twenty-three years respectively. The axial alignment of the lower extremity was measured and the results were compared with two similar studies conducted in the United States. Results: The medial inclination of the tibial plateau in the Chinese volunteers was greater than the commonly cited 3 degrees (with a mean of 5.4 ± 2.5 degrees for females and 4.9 ± 2.3 degrees for males). The extremities in Chinese volunteers were found to have a mean of 2.2 ± 2.5 degrees varus (females) and 2.2 ± 2.7 degrees varus (males). Conclusions and Discussion: The medial inclination (knee joint obliquity) of the Chinese knee joint was significantly larger than Caucasian subjects. The higher knee joint obliquity exposes the cartilage of the Chinese knee to a higher shearing force and subsequently result in osteoarthritis. This may explain the racial difference in the ratio of knee to hip osteoarthritis. When performing total knee arthroplasty, a 5-degree, instead of the commonly cited 3-degree, external rotation of the femoral component may be required to obtain a rectangular flexion gap in total knee arthroplasty in Chinese patients

Mobile-bearing total knee replacement (TKR) designs are advocated for their theoretical ability to self-align and accommodate small errors in rotational (axial) alignment. However, for many mobile-bearing TKR, the relationships between axial alignment, knee axial rotation and bearing motion during knee flexion are undefined. This study evaluates whether mobile-bearing TKR with axial alignment outside surgical norms have different rotations and motions compared to well-aligned TKR. This prospective study included 67 patients implanted with cruciate-retaining mobile-bearing TKR with a rotating platform polyethylene bearing (Scorpio PCS, Stryker). Axial alignment of femoral components relative to the transepicondylar axis and tibial components relative to the medial tibial tuberosity was measured from postoperative CT scans. TKR were categorized as “normal” or “outliers” according to defined tolerances for surgical axial alignment relative to anatomic landmarks (+3° for femur, +10° for tibia) and combined axial mismatch (+5° between femoral and tibial components). Knee kinematics and axial rotation were measured from fluoroscopic images acquired immediately after TKR during 0° to 120° of passive knee flexion. Total knee axial rotation (relative motion between the femoral component and tibial baseplate), femoral component axial rotation on the bearing articular surface, and bearing axial rotation on the tibial baseplate were determined using published shape-matching techniques. External rotation during knee flexion averaged 8.4°+6.1°, with two phases of axial rotation motion distinguished in all groups. External rotation from 0°–80° occurred primarily due to bearing axial rotation on the tibial baseplate. Beyond 80°, there was combined bearing rotation and external rotation of the femoral component on the polyethylene articular surface, with the latter dominating the motion pattern. Axial rotation varied with the component axial alignment. Among TKR with normal axial alignment, external rotation steadily increased with knee flexion. Among anatomic landmark outliers, there was a transition to internal rotation from 20°–50° and limited (< 1°) axial rotation beyond 80°. Among combined axial mismatch outliers, the magnitude of axial rotation was significantly less than normal TKR throughout the flexion range (p< 0.001) due to opposite rotations between the femoral component and polyethylene bearing. Achieving appropriate axial alignment using defined bony landmarks remains a challenge. In this study, approximately 30% of TKR did not have suitable axial alignment, with notable combined axial mismatch in tibial-femoral alignment. Axial rotation misalignment affected the kinematics and knee rotation motions over the passive flexion range and appears to result in opposite rotations of the femur-bearing and bearing-base-plate articulations

Summary sentence

The bowing of the femur defines a curvature plane to which the proximal and distal femoral anatomic landmarks have a predictable interrelationship. This plane can be a helpful adjunct for computer navigation to define the pre-operative, non-diseased anatomy of the femur and more particularly the rotational alignment of the femoral component in total knee arthroplasty (TKA).

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. 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

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. 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

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

Introduction. Patellofemoral arthroplasty (PFA) can give excellent results in well-selected patients. Axial alignment has been extensively studied in this type of surgery. However because there is no distal femoral cut, coronal alignment in PFA is less well known. The position of the patellofemoral component decides the varus or valgus alignment of the implant. Hypothesis. Coronal alignment in PFA (PFJ-Gender, Zimmer, Warsaw, US) is determined by the anterior condylar anatomy and features an important variance influencing coronal alignment. Materials and methods. Coronal alignment was measured in 57 PFAs on full leg weight bearing radiographs as the lateral distal femoral angle compared to the mechanical axis (mLDFA). In a first group of patients the anterior condylar anatomy was followed and in a second group the PFA was aligned to the Whiteside's line. Results. In the group following the condylar anatomy the mean (SD) mLDFA was 100° (9°) compared to the group where the Whiteside's line was followed, which presented a mean (SD) mLDFA was 89° (3°). Patellofemoral tracking evaluated on a Merchant view was better in the second group. Discussion. Literature shows that accurate patellofemoral alignment is 1° of valgus from the mechanical axis. Following the anterior condylar anatomy doesn't allow to recreate accurate frontal alignment with a PFA. This can be obtained by following Whiteside's line as a substitute for finding the mechanical axis. Conclusion. Whiteside's line is not only an accurate landmark for axial alignment but also for coronal alignment in PFA aligning the implant with the mechanical axis

Introduction. Computed tomography (CT) based preoperative planning provides useful information for severe TKA and revision TKA cases, such as the amount of augmentation, length of stem extension and component alignment, to achieve correct alignment and joint line. In this study, we evaluated TKA alignment performed with CT preoperative planning. Materials and Methods. 7 primary TKAs for severe deformity and 3 revision TKAs were included. CT preoperative planning was performed with JIGEN (LEXI, Japan). Constrained condylar prosthesis (LCCK, Zimmer) were used in all case. For femoral component, axial alignment was decided by controlled IM rod insertion to femoral canal. Rotational alignment was decided according to anterior cortex that usually was not compromised. For tibial component, axial alignment was set to perpendicular to tibial mechanical axis. Coverage and joint line level were carefully decided. The amount of bone resection of bilateral distal and posterior femoral condyle and proximal tibia was measured, respectively. Stem extension length and offset were selected according to components position and canal filling. Amount of augmentation was also estimated bilateral distal and posterior femoral condyle, respectively. Postoperative component alignment was evaluated three-dimensionally with Knee-CAS (LEXI, Japan). Results. All femoral and tibial components were implanted within 5°in coronal and sagittal plane. All knees showed mechanical alignment within 5 degree from neutral. One of 10 TKAs needed femoral component size down, and two of 20 stems needed size change

Total knee replacement (TKR) smart tibial trials have load-bearing sensors which will show quantitative compartment pressure values and femoral-tibial tracking patterns. Without smart trials, surgeons rely on feel and visual estimation of imbalance to determine if the knee is optimally balanced. Corrective soft-tissue releases are performed with minimal feedback as to what and how much should be released. The smart tibial trials demonstrate graphically where and how much imbalance is present, so that incremental releases can be performed. The smart tibial trials now also incorporate accelerometers which demonstrate the axial alignment. This now allows the surgeon the option to perform a slight recut of the tibia or femur to provide soft-tissue balance without performing soft-tissue releases. Using a smart tibial trial to assist with soft-tissue releases or bone re-cuts, improved patient outcomes have been demonstrated at one year in a multicentre study of 135 patients (135 knees). Cite this article: Bone Joint J 2014;96-B(11 Suppl A):78–83

Long radiographs are used to measure lower limb axial alignment, to assess the progression of deformity, and to plan corrective surgery. The purpose of this study was to test the belief that jigs are necessary in order to control limb position for radiography. Above-knee amputated limbs were fixed in different positions of rotation and of knee flexion and radiographed to study the effect on the apparent alignment of the limb. If the limb was rotated no more than 10 degrees from the neutral the effect on apparent axial alignment was minimal and radiographic measurement was reliable. This suggests that standardised positioning jigs are not needed in routine clinical practice

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

We conducted a meta-analysis, including randomised controlled trials (RCTs) and cohort studies, to examine the effect of patient-specific instruments (PSI) on radiological outcomes after total knee replacement (TKR) including: mechanical axis alignment and malalignment of the femoral and tibial components in the coronal, sagittal and axial planes, at a threshold of > 3º from neutral. Relative risks (RR) for malalignment were determined for all studies and for RCTs and cohort studies separately. Of 325 studies initially identified, 16 met the eligibility criteria, including eight RCTs and eight cohort studies. There was no significant difference in the likelihood of mechanical axis malalignment with PSI versus conventional TKR across all studies (RR = 0.84, p = 0.304), in the RCTs (RR = 1.14, p = 0.445) or in the cohort studies (RR = 0.70, p = 0.289). The results for the alignment of the tibial component were significantly worse using PSI TKR than conventional TKR in the coronal and sagittal planes (RR = 1.75, p = 0.028; and RR = 1.34, p = 0.019, respectively, on pooled analysis). PSI TKR showed a significant advantage over conventional TKR for alignment of the femoral component in the coronal plane (RR = 0.65, p = 0.028 on pooled analysis), but not in the sagittal plane (RR = 1.12, p = 0.437). Axial alignment of the tibial (p = 0.460) and femoral components (p = 0.127) was not significantly different. We conclude that PSI does not improve the accuracy of alignment of the components in TKR compared with conventional instrumentation. Cite this article: Bone Joint J 2014; 96-B:1052–61

We describe 119 meniscal allograft transplantations performed concurrently with articular cartilage repair in 115 patients with severe articular cartilage damage. In all, 53 (46.1%) of the patients were over the age of 50 at the time of surgery. The mean follow-up was for 5.8 years (2 months to 12.3 years), with 25 procedures (20.1%) failing at a mean of 4.6 years (2 months to 10.4 years). Of these, 18 progressed to knee replacement at a mean of 5.1 years (1.3 to 10.4). The Kaplan-Meier estimated mean survival time for the whole series was 9.9 years (. sd. 0.4). Cox’s proportional hazards model was used to assess the effect of covariates on survival, with age at the time of surgery (p = 0.026) and number of previous operations (p = 0.006) found to be significant. The survival of the transplant was not affected by gender, the severity of cartilage damage, axial alignment, the degree of narrowing of the joint space or medial versus lateral allograft transplantation. Patients experienced significant improvements at all periods of follow-up in subjective outcome measures of pain, activity and function (all p-values < 0.05), with the exception of the seven-year Tegner index score (p = 0.076)

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

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.

In an effort to improve alignment in total knee arthroplasty (TKA), more recent prosthetic devices adapt computerised sculpting technologies based on preoperative MRIs to individualize surgical treatment. This is achieved by creating patient-specific surgical positioning guides for prosthetic alignment. Our study reports on the early clinical and functional outcomes and CT measured alignment of patients undergoing surgery with the Signature patient specific knee system. We have reviewed the first one hundred patients selected to have a TKA using the patient specific knee system by a single surgeon over the last two years. Clinical and functional outcomes were assessed using the Western Ontario and McMaster Universities (WOMAC) index, the American Knee Society Scores (AKSS) and range of flexion at 6months. All data was analysed using a two tailed paired students t-test with statistical significance accepted at p<0.05. Post-operative CT scans were analysed to report on overall mechanical axial limb alignment, axial prosthetic tibial alignment, posterior tibial slope and femoral component rotation from the epicondylar axis. Preoperative versus postoperative WOMAC scores for patients were 80.4 ± 2.2 and 45.2 ± 2.1 respectively. This was statistically significant at p=1.3×10–14. The AKSS pre- and postoperatively were 85.1 ± 4.6 and 151.9 ± 4.6 respectively with statistical significance reached at p = 1.3×10–13. Specifically, the pre- vs postoperative knee scores were 33.6 ± 2.8 and 75.1 ± 2.6 (p=3.9×10–12) while the function scores were 51.5 ± 2.8 and 75.8 ± 4 (p=3.4×10–7) respectively. Range of flexion preoperatively was 110.8 ± 2.8 while postoperatively was 122.1 ± 2.6 (p=0.0003). Postoperative CT scans revealed that the tibial axial alignment was 90.5 ± 7.7 degrees while the posterior tibial slope was 5.5 ± 0.3 degrees on average. In terms of femoral rotation, the epicondyllar axis was found to be 0.56 ± 0.1 degrees externally rotated with respect to Whiteside's line. The mechanical axis was 0.84 ± 0.1 on average. With all these measured parameters the number of outliers outside the accepted +/−3 degree range are small. Our data demonstrates that the early results for knee replacements performed using the Signature patient specific jigs are very satisfactory delivering good clinical outcomes and an improved level of prosthetic alignment when compared to published data for standard instrumented knees

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