Effect of medial–lateral malpositioning of the femoral component in total knee arthroplasty on anterior knee pain at greater than 8 years of follow-up

BackgroundThe trochlea is often medialized after total knee arthroplasty (TKA) resulting in abnormal patellar tracking, which may lead to anterior knee pain. However, due to the difference in shape of the natural trochlea and the patellar groove of the femoral component, a medialization of the femoral component of 5 mm results in an equal patellar position at 0–30° of flexion. We tested the hypothesis that more medialization of the trochlea results in a higher VAS pain score and lower Kujala anterior knee pain score at midterm follow-up.MethodsDuring surgery a special instrument was used to measure the mediolateral position of the natural trochlea and the prosthetic groove in 61 patients between 2004 and 2005. Patient reported outcome measures were used to investigate the clinical results (NRS-pain, NRS-satisfaction, KOOS-PS and Kujala knee score).ResultsIn total 40 patients were included. The mean follow-up was 8.8 years. A medialization of ≥ 5 mm resulted in a significantly lower NRS-pain (0.2 vs. 1.4; p = 0.004) and higher NRS-satisfaction (9.6 vs. 8.2; p = 0.045). Overall clinical results were good; KOOS-PS was 33.9 and Kujala knee score was 72.1.ConclusionsThe present study showed that a more medial position may result in a better postoperative outcome, which can probably be explained by the non-physiological lateral orientation of the trochlear groove in TKA designs.Level of evidence: Level III     

Bi-cruciate substituting total knee arthroplasty provides varus–valgus stability throughout the midflexion range

Background

Proper soft tissue balance is crucial for a successful clinical outcome after total knee arthroplasty (TKA). Bi-cruciate substituting (BCS)-TKA has been developed to more closely approximate normal knee characteristics. The purpose of the present study was to evaluate midflexion laxity before and after BCS-TKA using a navigation system, and assess the correlation between intraoperative laxity and the maximum flexion angle after surgery.

Radiographic assessment of knee–ankle alignment after total knee arthroplasty for varus and valgus knee osteoarthritis

Background

There are unanswered questions about knee–ankle alignment after total knee arthroplasty (TKA) for varus and valgus osteoarthritis (OA) of the knee. The aim of this retrospective study was to assess knee–ankle alignment after TKA.

Comparison of the joint laxity of total knee arthroplasty evaluated by the distraction force and the varus–valgus force

BackgroundComponent gap (CG) measurement help surgeons evaluate intraoperative soft-tissue balance. One technique is measuring the CG using tensioner devices with distraction force. Another is to evaluate the laxity under a varus–valgus force using navigation or robotics. The aim was to compare the JL evaluated by CG and varus–valgus force between the different types of total knee arthroplasties.MethodsForty-three bi-cruciate stabilized (BCS) knees and 33 bi-cruciate retaining (BCR) knees were included. After bone resection and soft tissue balancing, the CG was measured and after the final implantation and capsule closure, JL under a maximum varus–valgus stress was recorded with navigation. JL evaluated by the CG (JLCG) was defined as CG minus selected thickness of the tibial component and JL under varus–valgus force (JLVV) was defined as difference between varus–valgus angles without stress and maximum varus–valgus angles under varus–valgus force. The evaluations were performed at flexions of 10°, 30°, 60° and 90°.ResultsAlthough JLCGs of lateral compartment of BCS were larger than those of BCR, no difference was found between JLVVs of BCS and BCR. Although JLCGs of lateral compartment did not change at each knee flexion angle in both BCS and BCR, JLVVs of lateral compartment increased by 3° from 10° to 90° knee flexion.ConclusionJLVVs of BCS and BCR were equivalent, whereas BCS showed larger JLCGs of lateral compartment. JLVVs of lateral compartment increased by 3° in the range from 10° to 90° knee flexion whereas JLCGs remained stable.     

Relationship of the posterior femoral axis of the “kinematically aligned” total knee arthroplasty to the posterior condylar,transepicondylar, and anteroposterior femoral axes

BackgroundA recent proposed modification in surgical technique in total knee arthroplasty (TKA) has been the introduction of the “kinematically aligned” TKA, in which the angle and level of the posterior joint line of the femoral component and joint line of the tibial component are aligned to those of the “normal,” pre-arthritic knee. The purpose of this study was to establish the relationship of the posterior femoral axis of the “kinematically aligned” total knee arthroplasty (TKA) to the traditional axes used to set femoral component rotation.MethodsOne hundred and fourteen consecutive, unselected patients with preoperative MRI images undergoing TKA were retrospectively reviewed. The transepicondylar axis (TEA), posterior condylar axis (PCA), antero-posterior axis (APA) of the trochlear groove, and posterior femoral axis of the kinematically aligned TKA (KAA) were templated on axial MRI images by two independent observers. The relationships between the KAA, TEA, APA, and PCA were determined, with a negative value indicating relative internal rotation of the axis.ResultsOn average, the KAA was 0.5° externally rotated relative to the PCA (minimum of − 3.6°, maximum of 5.8°), − 4.0° internally rotated relative to the TEA (minimum of − 10.5°, maximum of 2.3°), and − 96.4° internally rotated relative to the APA (minimum of − 104.5°, maximum of − 88.5°). Each of these relationships exhibited a wide range of potential values.ConclusionsUsing a kinematically aligned surgical technique internally rotates the posterior femoral axis relative to the transepicondylar axis, which significantly differs from current alignment instrument targets.     

Clinical results of alumina medial pivot total knee arthroplasty at a minimum follow-up of 10 years

Background

The medial pivot total knee prosthesis with alumina ceramic femoral components was introduced to reproduce physiological knee kinematics and reduce polyethylene wear. The five-year clinical outcomes of alumina medial pivot total knee arthroplasties (TKA) have previously been reported. The purpose of this study was to provide the longer-term clinical results at a minimum follow-up of 10 years.

Greater postoperative relatively medial loose gap at 90° of flexion for varus knees improves patient-reported outcome measurements in anatomical bi-cruciate retaining total knee arthroplasty

BackgroundThe purpose of the present study was to measure the intraoperative joint gap using tensor device and pre- and, postoperative joint stability at 0, 30 and 90° of flexion using stress radiography and to identify whether these factors influence patient-reported outcome measurement (PROM) in anatomical bi-cruciate retaining (BCR) knee arthroplasty (TKA).MethodsFifty-three knees with preoperative varus osteoarthritis of the knee underwent anatomical BCR TKA with oblique three-degree angle femorotibial joint line. The intraoperative medial and lateral joint gap using a tensor device and gap difference (lateral minus medial; varus laxity) were also calculated. Postoperative joint stability was measured using stress radiographs. PROM was also evaluated at 1.5 years postoperatively. The effect of intraoperative and postoperative joint stabilities on PROMs were analyzed using Spearman's rank correlation analysis.ResultsIntraoperative greater difference between medial joint gap at 140° and 0° of flexion showed significant positive correlation with postoperative function of patellofemoral joint. Intraoperative varus laxity at extension improved postoperative symptoms in 2011 Knee Society Score (2011 KSS); greater postoperative lateral stability at 30 and 90° of flexion with the varus stress test was associated with the better patient expectation in 2011 KSS. Postoperative medial laxity at 90° of flexion with the valgus stress test positively correlated with the patient expectation and satisfaction in 2011 KSS.ConclusionsSurgeons should notice that the postoperative lateral stability and medial laxity at 90° of flexion improved PROM in anatomical BCR TKA.     

Computational modelling of motion at the bone–implant interface after total knee arthroplasty: The role of implant design and surgical fit

Background

Aseptic loosening, osteolysis, and infection are the most commonly reported reasons for revision total knee arthroplasty (TKA). This study examined the role of implant design features (e.g. condylar box, pegs) and stems in resisting loosening, and also explored the sensitivity of the implants to a loose surgical fit due to saw blade oscillation.

Influence of preparation techniques to the strength of the bone–cement interface behind the flange in total knee arthroplasty

IntroductionRecent clinical studies show an increased risk of femoral loosening in high-flexion TKA. Loosening seems to occur behind the anterior flange, which is covering both cancellous bone and cortical bone. It is important to optimize the interface strength between cement and both bone types to increase femoral component fixation. This study was performed to determine the cement–cortical bone interface strength for different preparation techniques.Material and methodsA pure tensile and shear force was applied to interface specimens. The cortical surface area was prepared in three different ways: (1) Unprepared cortical bone with periosteum; (2) Periosteum removed and cortical bone roughened with a rasp; (3) Periosteum removed and three Ø3.2 mm holes drilled through the cortex. A reference group was added with a cancellous bone surface.ResultsThe interface tensile strength of Group 1 was 0.06 MPa and the shear strength was 0.05 MPa. For Group 2, respectively 0.22 MPa and 1.12 MPa. For Group 3, respectively 1.15 MPa and 1.77 MPa. For cancellous bone a tensile strength of 1.79 MPa and a shear strength of 3.85 MPa were measured.ConclusionThe strength of the cement–cancellous bone interface is superior to the cement–cortical bone interface. The preferred preparation technique of the cortical bone is to remove all the periosteum and drill holes through the cortex within the footprint of the anterior flange, to prevent cortical weakening.Clinical relevanceUltimately, the proposed preparation technique will lead to longer implant survival, particularly for prostheses which are used in the high-flexion range.     

Staged total knee arthroplasty for bilateral complex knee deformities from Kashin–Beck disease and skeletal dysplasia

This study reported two cases of patients with Grade III Kashin–Beck disease (KBD) with skeletal dysplasia concomitant with complex knee deformity and functional limitation treated by staged total knee arthroplasty (TKA). Detailed pre-operative planning, bone resection, and soft tissue balancing in affected knees were performed in the surgeries in this report. The results demonstrated that TKA could correct lower limb alignment, alleviate knee pain, improve function, and provide good quality of life in people with KBD. Surgical efficacy is still lower compared with treatment for osteoarthritis; contributing factors include weak muscle strength, severe deformity and unequal length of the lower limb, weak extensor apparatus of the knee, and patient-specific factors.     

Is postoperative flexion angle genuinely better in unicompartmental knee arthroplasty than in total knee arthroplasty? A comparison between the knees in the same patients

BackgroundThe aim of this retrospective study was to clarify if unicompartmental knee arthroplasty (UKA) can acquire a greater postoperative flexion angle than total knee arthroplasty (TKA) in the same individuals after adjusting for the preoperative flexion angle and if the preoperative flexion angle correlates with the change in flexion postoperatively.MethodsThirty-five patients between 2011 and 2017 who had undergone simultaneous TKA on one knee and UKA on the other knee were included in the study. Range of motion was measured preoperatively and at one year after the surgery. The relationship between the pre- and postoperative flexion angles was evaluated.ResultsUKA can acquire approximately 10° greater flexion postoperatively when compared to TKA, even after adjustment for the preoperative flexion angle. The preoperative flexion angle is strongly and negatively correlated with the change in flexion angle in both the TKA and UKA knees. A preoperative knee with a smaller flexion angle will gain greater flexion postoperatively, whereas a preoperative knee with a greater flexion angle tends to lose flexion angle. The thresholds of gain/loss are estimated as 123° and 135° in TKA and UKA knees, respectively.ConclusionsThese results provide an evidence that the UKA can acquire a greater postoperative flexion angle than the TKA and valuable information for patients who demand a deep postoperative flexion angle.     

Does new instrumentation improve radiologic alignment of the Oxford® medial unicompartmental knee arthroplasty?

Background

A new instrument system has been introduced to improve the accuracy and reproducibility of implant positioning in Oxford® unicompartmental knee arthroplasty (UKA). This study aimed to determine if the new instrumentation could improve postoperative implant positioning and limb alignment, and reduce the occurrence of outliers in Oxford® UKA.

Do optional implants improve the femoral fit during total knee arthroplasty in Asians? Comparison of the femoral fit between single- and dual-option implants

BackgroundThe purpose of this study was to evaluate the femoral fit in Asian patients during total knee arthroplasty by examining whether (1) the advanced single-option implant improves the fit of the femoral component in both the anterior flange and distal cutting surface and (2) the dual-option implants show better fit than the advanced single-option implant.MethodsA total of 950 knees that underwent primary total knee arthroplasty were included. Two types of single-option implant systems (Optetrak Logic and Truliant) and three types of dual-option implant systems (Anthem, Attune, and Persona) were used. The difference between the resected surface of the femur and femoral component dimensions was analyzed in predefined six zones. Appropriateness of fit (good-fit, over-hang, under-hang) was also evaluated.ResultsThe advanced single-option implant showed higher rates of good-fit and lower rates of over-hang and under-hang in almost all distinct zones than the old version single-option implant. The advanced single-option implant demonstrated similar good-fit, higher over-hang and lower under-hang rates than the dual-option implants. All single-option implants showed significantly higher over-hang rate (P < 0.05) and lower under-hang rate (P < 0.05) than all dual-option implant systems in the anterior flange transverse area. The narrow option was only selected in 12–20% of all cases.ConclusionsThe advanced single-option implant system improved the fit of the femoral component when compared with the old version and showed similar good-fit rates when compared with the dual-option implant systems. The narrow option of the dual-option implant systems was used less frequently than expected in Asian knees.     

The relationship between a child’s postural stability and manual dexterity

The neural systems responsible for postural control are separate from the neural substrates that underpin control of the hand. Nonetheless, postural control and eye-hand coordination are linked functionally. For example, a stable platform is required for precise manual control tasks (e.g. handwriting) and thus such skills often cannot develop until the child is able to sit or stand upright. This raises the question of the strength of the empirical relationship between measures of postural stability and manual motor control. We recorded objective computerised measures of postural stability in stance and manual control in sitting in a sample of school children (n = 278) aged 3–11 years in order to explore the extent to which measures of manual skill could be predicted by measures of postural stability. A strong correlation was found across the whole sample between separate measures of postural stability and manual control taken on different days. Following correction for age, a significant but modest correlation was found. Regression analysis with age correction revealed that postural stability accounted for between 1 and 10 % of the variance in manual performance, dependent on the specific manual task. These data reflect an interdependent functional relationship between manual control and postural stability development. Nevertheless, the relatively small proportion of the explained variance is consistent with the anatomically distinct neural architecture that exists for ‘gross’ and ‘fine’ motor control. These data justify the approach of motor batteries that provide separate assessments of postural stability and manual dexterity and have implications for therapeutic intervention in developmental disorders.     

Can total knee arthroplasty restore the correlation between radiographic mechanical axis angle and dynamic coronal plane alignment during gait?

BackgroundTotal knee arthroplasty (TKA) is the treatment of choice for end-stage knee osteoarthritis. Postoperative static knee alignment has been recognized as a key component of successful surgery. A correction toward the kinematics of a native knee is expected after TKA, with an aim for neutral mechanical alignment. The evolution of frontal plane knee kinematics is not well understood.MethodsNineteen patients awaiting TKA were recruited. Three-dimensional knee kinematics during treadmill gait were assessed pre-operatively, 12 months after surgery, and compared to a control group of 17 asymptomatic participants.ResultsMean radiographic mechanical alignment was corrected from 5.4° ± 5.0 (Standard Deviation) varus pre-operatively to 0.1° ± 2.0 (Standard Deviation) valgus postoperatively (P = 0.002). Mean stance coronal plane alignment decreased from 6.7° ± 4.0 (Standard Deviation) varus per-operatively to 2.1° ± 3.8 (Standard Deviation) postoperatively (P = 0.001). Correlation between radiographic mechanical axis angle and dynamic frontal plane alignment during gait, before and after surgery, was weak (pre-operative R = 0.41; postoperative R = 0.13) compared to control (R = 0.88). In the sagittal plane, TKA patients maintained their pre-operative stiff knee gait adaptation. Postoperative transverse plane kinematics suggested restoration of external tibial rotation during swing after TKA compared to control (Pre-operative 3.1°, postoperative 6.8°, control 7.1°, P = 0.05).ConclusionThe lack of correlation between static and dynamic alignment suggests that static radiographic coronal alignment of the knee does not accurately predict dynamic behavior. In the sagittal plane, pre-operative gait adaptations were still present 12 months after surgery, supporting the need for a functional assessment to guide postoperative rehabilitation following TKA.     

Does the appearance of the patellofemoral joint at surgery influence the clinical result in medial unicompartmental knee arthroplasty?

The purpose of this study is to investigate the likelihood of unicompartmental knee arthroplasty (UKA) in patients with chondrosis in the patellofemoral joint. We evaluated the pain and functional changes in the patellofemoral joint of 62 patients who underwent medial UKA for medial compartmental osteoarthritis with symptoms in the patellofemoral joint. They were analyzed by the patellofemoral score of Lonner at postoperative 3 months, 6 months, 1 year, and 2 years prospectively. Preoperatively, the grade by total score was poor in all 62 cases, but it was improved to 36 excellent (58%), 16 good (26%), and 10 fair (16%), and there were no poor cases at 2 years. The last follow-up showed satisfactory results in pain score, function score, and total score (p < 0.05). Regarding this result, we believe chondrosis in the patellofemoral joint is not a contraindication to UKA, even in patients with patellofemoral joint symptoms.     

The effects of agonist and antagonist muscle activation on the knee extension moment–angle relationship in adults and children

The present study examined the effect of agonist activation and antagonist co-activation on the shape of the knee extension moment–angle relationship in adults and children. Isometric knee extension maximum voluntary contractions (MVCs) were performed at every 5° of knee flexion between 55° and 90° (full extension = 0°) by ten men, ten women, ten boys and ten girls. For each trial, the knee extensors’ voluntary activation level was quantified using magnetic stimulation and the level of antagonist co-activation was quantified from their electromyographical activity. Peak MVC moment was greater for men (264 ± 63 N m) than women (177 ± 60 N m), and greater for adults than children (boys 78 ± 17 N m, girls 91 ± 28 N m) (p < 0.01). The agonistic activation level was greater for adults (~85%) than children (~70%). Similarly, antagonist co-activation was greater for adults than children, but relative to the agonist moment there were no differences between groups (all groups 7–8%). Correcting the peak moment for agonist and antagonist activation levels resulted in moments produced by fully activated agonist muscles of 334 ± 83, 229 ± 70, 114.2 ± 32 and 147 ± 46 N m, for men, women, boys and girls, respectively. Although correcting for shifts in joint angle during contraction altered the angle of peak moment by ~10° (p < 0.01), the peak moment occurred at ~60° for all groups. Changes in tendon stiffness, muscle size and architecture, and the pattern of the moment arm–angle relationship may in combination occur so that as children develop and mature into adults the shape of the moment–angle relationship is not altered.     

Alignment in total knee arthroplasty — A comparison of patient-specific implants with the conventional technique

Background

Incorrect positioning and malalignment of total knee arthroplasty (TKA) components can result in implant loosening. Restoration of neutral alignment of the leg is an important factor affecting the long-term results of TKA. The aim of our retrospective study was to compare mechanical axis in patients with conventional and patient-specific TKAs.