Metaphyseal Stem Extension Improves Tibial Stability in Cementless Total Knee Arthroplasty

BackgroundThe goal was to determine if the addition of a metaphyseal stem extension limits micromotion of a cementless tibial component during cyclic loading in primary total knee arthroplasty. The hypothesis tested was that the use of a 50-mm stem extension on a cementless tibial component would limit motion compared with an identical cementless component without a stem extension.MethodsThe study used 3 variations of a tibial component from the same total knee arthroplasty system. Group 1 consisted of a cementless tibial component without a stem extension. Group 2 used the same cementless component as group 1, but with the addition of a short 50-mm stem. Group 3 consisted of a cemented tibial component without a stem extension to serve as a “control” (gold standard). The tibial specimens were implanted into a synthetic bone model and tested using a physiological medial-lateral 60/40 load distribution for 5000 cycles.ResultsThe results demonstrated a significant decrease in motion at the anterior region of the cementless stem extension (group 2) components compared with the cementless with no stem extension (group 1). The cementless with stem extension (group 2) demonstrated similar results at all cycles to the cemented (group 3) components at the anterior region.ConclusionThe addition of a short metaphyseal stem (50mm) to a keel plus 4-peg tibial component design provides a significant reduction in micromotion during cyclic loading of a cementless tibial baseplate in a synthetic foam bone model, similar to a cemented implant.     

Survivorship and Radiographic Evaluation of Metaphyseal Cones With Short Cemented Stems in Revision Total Knee Arthroplasty

BackgroundThe purpose of this study is to evaluate the survivorship and radiographic outcomes of a single design of metaphyseal cone used in conjunction with short cemented stems.MethodsA retrospective analysis was conducted of revision total knee arthroplasty (rTKA) patients (June 2015 to December 2017) using porous titanium femoral or tibial cones in conjunction with short cemented stems (50-75 mm). Minimum follow-up was 2 years. Survivorship, complications, and a modified Knee Society Radiographic score were analyzed.ResultsForty-nine rTKAs were included in the study (12 femoral cones, 48 tibial cones). Varus-valgus constraint was used in 28 (57%) and a hinged bearing was used in 3 (6%) of these constructs. The majority were index rTKAs of primary components (86%), performed for aseptic loosening (51%) and reimplantation following staged treatment for infection (37%). Median follow-up was 39 months (range 25-58). Using a modified Knee Society Radiographic score, all constructs were classified as stable. Postoperatively, 4 rTKAs were complicated by recurrent infection (8%), periprosthetic fracture 2 (4%), and superficial wound infection 1 (2%). Seven rTKAs (14%) required reoperation. The majority of reoperations (4 rTKAs) were debridement and irrigation with implant retention for infection. Metaphyseal cone constructs with short cemented stems demonstrated 100% survivorship free of revision for aseptic loosening without evidence of radiographic loosening in any case.ConclusionOur results demonstrate excellent outcomes with the use of metaphyseal cones with short cemented stems at mid-term follow-up. This construct avoids the use of long-stem fixation with the associated extraction difficulty, end of stem pain, and potential for malposition at the joint line.Level of EvidenceIV, Case Series.     

Micromotion and Migration of Cementless Tibial Trays Under Functional Loading Conditions

BackgroundThe outcome of cementless total knee arthroplasty (TKA) relies on successful bony ingrowth into the implant surfaces. Failures due to aseptic loosening are still reported, especially in younger and more active patients. The objective of this study is to quantify the micromotion of a commercially available design of cementless tibial tray under loading conditions simulating walking and stair descent.MethodA commercially available design of cementless total knee arthroplasty was implanted in 7 cadaveric knees which were preconditioned with 500 cycles of 0°-100° flexion under a vertical load of 1050 N in a custom-built, multiaxial functional activity simulator. This was followed by application of the peak forces and moments occurring during walking and stair descent. During each loading procedure, 3-dimensional motion at the bone-prosthesis interface was measured using digital image correlation.ResultsThe tray migrated 101 ± 25 μm on average during preconditioning, which was dominated by rotation in the sagittal plane (92% of total migration), combined with posterior translation (28%) and minimal rotation in the transverse plane (14%). The migration varied 2.7-fold (61-167 μm) between the 6 measurement zones. Stair descent produced significantly higher total micromotion than walking in zone #5 (62 ± 9 vs 51 ± 10 μm, P < .05) and zone #6 (68 ± 17 vs 37 ± 10 μm, P < .05). In addition, during stair descent, the tray exhibited significantly more tilting (anterior zones: 31 ± 17 vs ?16 ± 20 μm, P < .05; posterior zones: ?60 ± 8 vs ?40 ± 7 μm, P < .05) and more anteroposterior displacement in the anterior zones (?25 ± 3 vs ?13 ± 2 μm, P < .05) when compared to walking.ConclusionThe relative motion at the bone-prosthesis interface varied substantially around the periphery of the cementless tray. Under the loading conditions evaluated, the tray primarily underwent a rocking motion in the sagittal plane. Compared with walking, stair descent produced significantly more micromotion, especially in the posterior zones.     

Micromotion in cemented rotating platform total knee arthroplasty: cemented tibial stem versus hybrid fixation

INTRODUCTION: Improving the longevity and reliability of cemented total knee arthroplasty (TKA) remains a major step to achieve. It is still unclear, whether a cemented tibial stem reduces micromotion of the tibial tray and produces therefore a better initial stability or not. The higher conformity of rotating platform design and the possible rotary forces to the tibial platform may produce higher micromotion when the tibial stem remains cementless (hybrid fixation). MATERIALS AND METHODS: An in vitro study was performed using the PFC mobile bearing tibial tray (DePuy, Warswa, IN, USA) to test the hypothesis that the addition of cement surrounding the tibial stem reduces micromotion of the tibial tray in cemented TKA with mobile bearing design. Ten tibial trays with mobile design were implanted in sawbones with a 3-mm cement mantle beneath the baseplate of the tibial tray and with or without the cemented stem. Tibial trays were loaded additionally in the ventral, lateral, medial and posterior positions with 2,500 N using the Zwick Z010 instrumentation and HBM pick up Hottinger Baldwin. RESULTS: In this study, a significant increased mean maximum liftoff was found when only cementing the tibial baseplate (hybrid fixation), compared to the fully cemented tibial tray (P<0.02). CONCLUSION: In conclusion, the stem of mobile bearing tibial components should be cemented to provide increased micromotion and earlier loosening.     

Stem fixation in revision total knee arthroplasty: a comparative analysis

Methods of stem fixation are a controversial aspect of revision TKA. We sought to determine which technique was superior by reviewing 475 revision TKAs done between 1986 and 2000. Of these 475 revisions, 286 major component revisions were done using 484 extended stems for fixation. Patients who died, patients who had less than 2 years follow up, or patients who had diaphyseal engaging stems were excluded from the study. The final data set included 113 revision TKAs with 202 metaphyseal engaging stems. Of the 202 stems, 107 were cemented whereas 95 were press-fit metaphyseal engaging stems. One hundred one of these were femoral stems and 101 were tibial stems. Using a modified Knee Society radiographic scoring system, 100 (93%) of the 107 implants with cemented stems were considered stable, seven (7%) were categorized as possibly loose requiring close followup, and none were loose. Of the 95 implants placed with cementless stems, only 67 (71%) were categorized as stable. Eighteen (19%) were possibly loose requiring close followup and 10 (10%) were loose (two tibial and eight femoral implants). We currently would urge caution in using cementless metaphyseal engaging stems for fixation in revision TKA.     

Initial Stability of Cemented vs Cementless Tibial Components Under Cyclic Load

Background

Cement fixation of total knee components remains the gold standard despite resurgence in cementless fixation with the goal of long-term durable fixation. Initial stability is paramount to achieve bony ingrowth of cementless components.

Development and Verification of Novel Porous Titanium Metaphyseal Cones for Revision Total Knee Arthroplasty

Background

Porous metaphyseal cones are widely used in revision knee arthroplasty. A new system of porous titanium metaphyseal cones has been designed based on the femoral and tibial morphology derived from a computed tomography–based anatomical database. The purpose of this study is to evaluate the initial mechanical stability of the new porous titanium revision cone system by measuring the micromotion under physiologic loading compared with a widely-used existing porous tantalum metaphyseal cone system.

Results of 3,668 primary total hip replacements for primary osteoarthritis in patients under the age of 55 years

Background and purpose In a previous study based on the Finnish Arthroplasty Register, the survival of cementless stems was better than that of cemented stems in younger patients. However, the survival of cementless cups was poor due to osteolysis. In the present study, we analyzed population-based survival rates of the cemented and cementless total hip replacements in patients under the age of 55 years with primary osteoarthritis in Finland.

Patients and methods 3,668 implants fulfilled our inclusion criteria. The previous data included years 1980–2001, whereas the current study includes years 1987–2006. The implants were classified in 3 groups: (1) implants with a cementless, straight, proximally circumferentially porous-coated stem and a porous-coated press-fit cup (cementless group 1); (2) implants with a cementless, anatomic, proximally circumferentially porous-coated stem, with or without hydroxyapatite, and a porous-coated press-fit cup with or without hydroxyapatite (cementless group 2); and (3) a cemented stem combined with a cemented all-polyethylene cup (the cemented group). Analyses were performed separately for 2 time periods: those operated 1987–1996 and those operated 1997–2006.

Results The 15-year survival for any reason of cementless total hip replacement (THR) group 1 operated on 1987–1996 (62%; 95% CI: 57–67) and cementless group 2 (58%; CI: 52–66) operated on during the same time period was worse than that of cemented THRs (71%; CI: 62–80), although the difference was not statistically significant. The revision risk for aseptic loosening of cementless stem group 1 operated on 1987–1996 (0.49; CI: 0.32–0.74) was lower than that for aseptic loosening of cemented stems (p = 0.001).

Interpretation Excessive wear of the polyethylene liner resulted in numerous revisions of modular cementless cups. The outcomes of total hip arthroplasty appear to have been relatively unsatisfactory for younger patients in Finland.     

Does Implant Selection Impact Postoperative Complications Following Hip Arthroplasty for Failed Intertrochanteric Fractures? A Retrospective Comparative Study

The purpose of this study is to compare postoperative complications among different acetabular and femoral components of hip arthroplasty for failed intertrochanteric fractures. A total of 79 patients were included and followed‐up for an average of 75.6 months (range, 24–244). Fifty‐five patients underwent total hip arthroplasty, and 24 had bipolar hemiarthroplasty. Cementless metaphyseal locking, cementless diaphyseal locking, and cemented standard stems were used in 41, 29, and 9 patients, respectively. Dislocation and wear rate were not different between the total hip arthroplasty and bipolar hemiarthroplasty groups. Stem subsidence or loosening was more frequently found in the cementless, metaphyseal locking stem groups. In conclusion, cemented standard stem and cementless diaphyseal locking stem might be better implant choices. With regard to dislocation rate, our results were insufficient to conclude a better implant choice of total hip arthroplasty or bipolar hemiarthroplasty than the other.     

Comparative Biomechanical In Vitro Study of Different Modular Total Knee Arthroplasty Revision Stems With Bone Defects

BackgroundThe aim of this study is to investigate the effects of different stem lengths and types including cones on primary stability in revision total knee arthroplasty with different femoral bone defects and fixation methods in order to maximize bone preservation. It is hypothesized that longer stems provide little additional mechanical stability.MethodsThirty-five human femurs were investigated. A distal bone defect, Anderson Orthopedic Research Institute classification (s. 33) type-F2a, was created in group 1-3 and type-F3 in group 4-6. A cemented, rotating hinge femoral component was combined with different stems (100 and 160 mm total or hybrid cemented cones, or a 100-mm custom-made anatomical cone stem). The femora were loaded according to in vivo loading during gait. Relative movements were measured to investigate primary stability. Pull-out testing was used to obtain a parameter for the primary stability of the construct.ResultsRelative movements were small and similar in all groups (<40 μm). For small defect, the pull-out forces of cemented long (4583 N) and short stems (4650 N) were similar and about twice as high as those of uncemented stems (2221 N). For large defects, short cemented stems with cones showed the highest pull-out forces (5500 N). Long uncemented stems (3324 N) and anatomical cone stems (3990 N) showed similar pull-out forces.ConclusionAll tested stems showed small relative movements. Long cemented stems show no advantages to short cemented stems in small bone defects. The use of cones or an anatomical cone stem with hybrid cementation seems to offer good stability even for larger bone defects. The use of a short cemented stem (with or without cone) may be a suitable choice with a high potential for bone preservation in total knee arthroplasty revision with respective bone defects.     

Impact of patient,surgical, and implant design factors on predicted tray–bone interface micromotions in cementless total knee arthroplasty

Micromotion magnitudes exceeding 150 µm may prevent bone formation and limit fixation after cementless total knee arthroplasty (TKA). Many factors influence the tray–bone interface micromotion but the critical parameters and sensitivities are less clear. In this study, we assessed the impacts of surgical (tray alignment, tibial coverage, and resection surface preparation), patient (bone properties and tibiofemoral kinematics), and implant design (tray feature and surface friction) factors on tray–bone interface micromotions during a series of activities of daily living. Micromotion was estimated via three previously validated implant-bone finite element models and tested under gait, deep knee bending, and stair descent loads. Overall, the average micromotion across the tray–bone cementless contact interface ranged from 9.3 to 111.4 µm, and peak micromotion was consistently found along the anterior tray edge. Maximizing tibial coverage above a properly sized tibial tray (an average of 12.3% additional area) had minimal impact on micromotion. A 1 mm anterior tray alignment change reduced the average micromotion by an average of 16.1%. Two-degree tibial angular resection errors reduced the area for bone ingrowth up to 48.1%. Differences on average micromotion from ±25% changes in bone moduli were up to 75.5%. A more posterior tibiofemoral contact due to additional 100 N posterior force resulted in an average of 79.3% increase on average micromotion. Overall, careful surgical technique, patient selection, and controlling kinematics through articular design all contribute meaningfully to minimizing micromotion in cementless TKA, with centralizing the load transfer to minimize the resulting moment at the anterior tray perimeter a consistent theme.     

Trabecular Metal Cones Combined With Short Cemented Stem Allow Favorable Outcomes in Aseptic Revision Total Knee Arthroplasty

BackgroundThe purpose of this study was to compare the functional outcomes and implant survivorship at a minimum of 5 years of follow-up of several reconstruction techniques with or without metaphyseal cone and stems of variable length.MethodsA retrospective comparative matched analysis was performed from 2 prospectively collected databases. Only patients who underwent revision total knee arthroplasty procedures for aseptic causes using a single design of rotating hinge knee with a minimum of 5 years of follow-up were analyzed. Patients were separated into 3 groups: trabecular metal (TM) cones + short cemented stems (TM + short stem [SS]), TM cones + long uncemented stems (TM + long stem [LS]), and no cone (NC) + long uncemented stems (NC + LS). A matching process based on age (±5 years) was realized.ResultsAbout 99 patients were included; 33 in the TM + SS group, 33 in the TM + LS group, and 33 in the NC + LS group. The mean time of follow-up was 9.3 years. A significant difference of the improvement of subscale pain, symptom, activities of daily living, quality of life of the Knee Injury and Osteoarthritis Outcome score and knee, function of the Knee Society Score was observed in favor of TM + SS group compared with the 2 other groups. At 8 years of survivorship, the components free of revision for any cause were 90.9% for the TM + SS group, 84.9% for the TM + LS group, and 90.6% for the NC + LS group.ConclusionThe use of a short cemented tibial stem combined with a TM cone in revision total knee arthroplasty offers identical survival rate with better functional outcome compared with the use of a long uncemented stem associated with TM cones or metallic augments at a minimum of 5 years of follow-up.     

Early clinical and radiographic results of reverse shoulder arthroplasty with press-fit metaphyseal humeral fixation

BackgroundReverse shoulder arthroplasty (RSA) has seen a recent transition from cemented to press-fit humeral stems. Several press-fit designs have focused on proximal fixation, yet there remains a paucity of data on their performance. The purpose of this study is to report early radiographic and clinical results of a third-generation RSA system, featuring metaphyseal porous metal fixation.MethodsA retrospective review was performed on primary RSA patients treated with a single third-generation standard-length implant system incorporating proximal osteointegration features with a minimum 2-year follow-up. Patient-reported outcome measures, including the Simple Shoulder Test, American Shoulder and Elbow Surgeons, Visual Analog Scale for pain, and Single Assessment Numeric Evaluation, as well as measured active motion (forward elevation, external, and internal rotation) were recorded at pre- and postoperative intervals. Immediate postoperative radiographs were used to measure filling ratios at the epiphyseal, metaphyseal, and diaphyseal levels. Most recent radiographs were also reviewed for bone adaptations, acromial fractures, scapular notching, and humeral loosening.ResultsThere were 90 patients included in the study, with an average age of 73 years (± 7.23) and clinical follow-up of 32 months (± 7.25). Indications included osteoarthritis with a rotator cuff tear (51%), osteoarthritis without a cuff tear (40%), fracture sequelae (2%), and locked anterior dislocation (2%). There were significant improvements in all measured motions and patient-reported outcome measures at the most recent follow-up, with good to excellent satisfaction in 91.1% of patients. High mean epiphyseal (0.90 ± 0.06) and metaphyseal (0.83 ± 0.07) filling ratios together with low mean diaphyseal filling ratio (0.48 ± 0.07) represented proximal fixation. There were 6 cases with scapular notching, 5 postoperative acromial fractures, and 2 with temporary postoperative neuropathy. Proximal bone resorption was seen in 18.9% of cases, and there were no cases of humeral loosening, baseplate failure, or need for revision.ConclusionPrimary RSA with a third-generation press-fit humeral component with metaphyseal fixation provides excellent early outcomes with no loosening and low rates of proximal stress-shielding. Results of this study support the use of an inlay humeral component with osteointegration features that facilitate proximal stem fixation.Level of EvidenceTreatment Study     

Tibial component fixation with cement: full- versus surface-cementation techniques

Despite excellent outcomes with cemented tibial components in total knee arthroplasty, it still is debated whether the tibial stem should be cemented and what the optimal tibial stem design should be. Proponents of full cementation of the tibial stem and component state that better short-term and long-term component fixation is achieved when full cementation is used. Advocates for surface cementation contend that sufficient implant stability is achieved without the increased bone loss that occurs at revision and the stress shielding thought to be linked with cemented stems. This biomechanical cadaver study compared initial fixation and cement penetration depth in fully cemented versus surface cemented tibial trays with two different stem geometries (cruciate and I-beam) and compared two stem designs (cruciate and I-beam) fixed with surface cementation. Under an eccentric load, simulating three times body weight for 6000 cycles, there seems to be no difference in the micromotion of either tibial component implanted with surface or full cementation. Additionally, no difference in the average depth of cement penetration was detected between fixation techniques or stem types. The initial fixation stability of the surface cement technique seems correlated to the depth of cement penetration into proximal tibial surface. The current data support other studies which indicate that stability of surface-cemented tibial components may be related to the depth of cement penetration.     

Metaphyseal Stem Tip Location is a Risk Factor for Aseptic Loosening of Cemented Distal Femoral Replacements

BackgroundThe objective of this study was to describe the incidence of aseptic loosening (AL) of cemented stem distal femoral replacements (DFR) and to identify modifiable risk factors for its development.MethodsA retrospective review was performed of 245 consecutive primary, cemented stem DFRs implanted at a single institution over a 40-year period. The primary outcome was revision surgery for AL. A multivariate analysis was performed to identify risk factors for AL. Radiographs were reviewed to identify stem tip location, which was defined as diaphyseal or metaphyseal. Implant survival to AL was compared using Kaplan-Meier analysis.ResultsAL and structural failure were the most common causes of implant failure (incidence 11.8%, 29/245). Younger age (P = .002), male sex (P = .01), longer resection length (P = .04), and nonmodular implants (P = .002) were all significantly associated with AL. After 1:1 matching, stem tip location in metaphyseal bone was independently associated with AL (P = .04). 36% (9/25) of implants that loosened had a stem tip located in the metaphysis vs only 8% (2/25) of implants that did not fail. 30-year survival to AL was lower for implants with a metaphyseal stem tip than implants with a diaphyseal stem tip (22.7% vs 47.6%; P = .11).ConclusionA stem tip location in metaphyseal bone is associated with diminished survival to AL. When templating before DFR, stem tip location can assist in identifying high-risk reconstructions that may benefit from alternative or supplemental fixation techniques to prevent the development of AL.     

Clinical Outcomes in Isolated Tibial Revision With Cruciate Retaining Total Knee Arthroplasty

BackgroundTibial component loosening is one of the most common modes of failure in contemporary total knee arthroplasty (TKA). Limited literature is available on the outcomes of isolated tibial revision with retention of the cruciate retaining (CR) femoral component. The purpose of this study was to determine the results of isolated tibial revisions in CR TKA.MethodsWe identified 135 patients who underwent an isolated tibial revision after a primary CR TKA from our institutional registry between January 2007 and January 2017. The mean time between the primary and revision was 2.9 years (range 0.1-15.4). Revision with a press-fit stem was performed in 79 patients and 56 patients were revised with a fully cemented stem. Patients were evaluated at a minimum of two years using Knee Society Score, Knee Injury and Osteoarthritis Score for Joint Replacement, and radiography. Implant survivorship was determined using Kaplan-Meier survival analysis.ResultsAt a mean follow-up of 5.1 years, there were six (4.4%) repeat revisions: three for periprosthetic infection (2.2%), two for instability (1.5%), and one for a fractured tibial stem (0.7%). The mean Knee Society Score and Knee Injury and Osteoarthritis Score for Joint Replacement increased from 51.6 and 56.1 preoperatively to 90.1 and 89.7 after surgery (P < .001). Survivorship free of repeat revision for any cause was 93.3% at 5 years, and aseptic revision survivorship was 95.8% at 5 years. No implants were radiographically loose.ConclusionIn patients with isolated tibial loosening and a well-fixed and well-positioned CR femoral component, isolated tibial revision provides excellent early to midterm implant survivorship and clinical outcomes with a low risk of instability and recurrent tibial loosening.     

The effect of stem modularity and mode of fixation on tibial component stability in revision total knee arthroplasty

The effect of stem length, diameter, and mode of fixation on the motion and stress transfer of a cemented tibial tray were evaluated for in 12 cadaver knees. There was a significant decrease in motion of the tibial tray with increasing press-fit stem length (75-150 mm) and increasing stem diameter (10-14 mm). Cemented tibial stems showed significantly less tray motion than uncemented stems. The short cemented stems produced tray stability equivalent to long press-fit stems. Although there was a trend for increased proximal tibial stress shielding with the use of cement and longer, wider stems, the trend was not statistically significant. Modular, press-fit stems can achieve tray stability similar to a smaller cemented stem and can avoid the potential problems with cement.     

Mechanical alignment of tibial stems in revision total knee arthroplasty

This multicenter, retrospective study evaluates the radiographic results of achieving optimal tibial alignment in revision total knee arthroplasty (TKA) using a single modular CoCr cemented or cementless stemmed implant design. Stem size and length also were evaluated. The hundred ninety-nine Revision TKAs were performed between January 1993 and January 1996 by 13 experienced revision knee surgeons. The cases were subdivided into 5 comparative groups: (1) cemented stems, (2) 140-mm length canal-filling stems, (3) 140-mm length non—canal-filling stems, (4) 95-mm length canal-filling stems, and (5) 95-mm length non—canal-filling stems. The anteroposterior (AP) tibial alignment angle was measured. The canal-filling ratio (CFR) was determined by dividing the stem diameter by the endosteal diameter at the stem tip. Overall, the ability to achieve tibial alignment in the AP plane was more predictable when canal-filling (CFR ≥ 0.85) cementless stems were used. This was further enhanced when long canal-filling cementless stems were selected. The least-predictable results and the highest probability of varus malalignment were achieved with cemented stems.