Long-term followup of the bone-ingrowth Ortholoc knee system without a metal-backed patella

Cementless and Cemented Dual-pivot Total Knee Arthroplasty: A Matched Comparison with a Minimum Two-year Follow-up

INTRODUCTION

With the use of newer biomaterials, many authors have reported similar results between cementless and cemented total knee arthroplasty (TKA). The purpose of this study was to compare the early clinical and radiographic outcomes of cementless and cemented TKA using the same dual-pivot articulation.

METHODS

A consecutive series of 806 TKAs were implanted by a single surgeon using the same dual-pivot articulation. There were 634 TKAs (79%) cemented and 172 (21%) uncemented. One patient in the cementless group was lost before two years. The remaining 171 cementless TKAs were matched 1:1 with cemented TKAs with respect to age, sex, and body mass index (BMI). All patients were followed for a minimum of two years (range, 24 to 66 months) using the Knee Injury and Osteoarthritis Outcome Score for Joint Replacement (KOOS, JR), and Knee Society clinical and radiographic evaluation. The average follow-up was 3.8 years (range, 24-66 months) in the cemented group and 3.4 years (range,24-56 months) in the cementless group.

RESULTS

At final follow-up, the average KOOS-JR score was higher in the cementless group (86 points (range, 64-100) vs. 80 points (range, 57-100). Post-op Knee Society scores (including pain and function) were similar. There was one deep infection (cemented TKA). The manipulation rate was 1.2% in the cementless group and 2.4% in the cemented TKA group. Excluding infection, two knees (1.2%) were revised in each group. No cases of femoral or tibial component loosening were identified.

CONCLUSION

Patients implanted with either a cemented or cementless TKA using the same conforming dual-pivot articulation design had similar early outcomes and functional improvements. The type of fixation did not appear to influence the early clinical results.

The combination of osteoporosis and low lean mass correlates with physical function in end-stage knee osteoarthritis: A retrospective observational study

We aimed to investigate the prevalence of osteoporosis and low lean mass, either together or in isolation, and their association with physical function, pain, and quality of life (QOL) in patients with end-stage knee osteoarthritis (OA). This retrospective cross-sectional observational study included 578 patients (77 males and 501 females) diagnosed with end-stage knee OA. Patients were divided into 4 groups based on body composition parameters: control, osteoporosis, low lean mass, and osteoporosis + low lean mass. All participants underwent performance-based physical function tests, including a stair climbing test (SCT), a 6-minute walk test, a timed up and go test, and instrumental gait analysis, to examine spatiotemporal parameters. Self-reported physical function and pain levels were measured using the Western Ontario McMaster Universities Osteoarthritis Index and visual analog scale, respectively. Self-reported QOL was measured using the EuroQOL 5 dimensions (EQ-5D) questionnaire. Of 578 patients, 268 (46.4%) were included in the control group, 148 (25.6%) in the osteoporosis group, 106 (18.3%) in the low lean mass group, and 56 (9.7%) in the osteoporosis + low lean mass group. Analysis of variance revealed that the scores for the osteoporosis + low lean mass group in the SCT-ascent, SCT-descent, and timed up and go test were significantly higher, whereas those for the 6-minute walk test, gait speed, and cadence were significantly lower than those for the other groups (P < .05). After adjusting for age, sex, and body mass index, multiple linear regression analysis identified SCT-ascent (β = 0.140, P = .001, R2 = 0.126), SCT-descent (β = 0.182, P < .001, R2 = 0.124), gait speed (β = -0.116, P = .005, R2 = 0.079), and cadence (β = -0.093, P = .026, R2 = 0.031) as being significantly associated with osteoporosis + low lean mass. Thus, osteoporosis + low lean mass correlates with poor physical function, but not pain and QOL, in patients with end-stage knee OA.

Press-Fit Dual-Pivot Total Knee Arthroplasty: Early Results With a Minimum 2-Year Follow-Up

BACKGROUND

Ultracongruent (UC) tibial bearings are being used with increasing frequency in the United States. Evidence suggests that the use of certain UC bearings may lead to improved patient satisfaction when compared with using conventional inserts. However, little is known as to what effect the use of UC tibial inserts has on bone ingrowth in uncemented total knee arthroplasty (TKA). The purpose of this study was to determine the early clinical and radiographic results of TKA using a press-fit dual-pivot design.

METHODS

Between 2017 and 2019, a consecutive series of 232 TKAs were implanted using a press-fit tibial and femoral component and a UC dual-pivot tibial insert. Sixty-two percent of patients were male. The average age was 56 years. Patients were followed for a minimum of 2 years (range, 24-42 months) using KOOS-JR and Knee Society clinical and radiographic evaluation.

RESULTS

No patient had more than mild knee stiffness at the final follow-up. Two patients reported moderate knee pain with stair climbing. All other patients reported either mild or no pain with activity. Knee Society pain scores averaged 42 points. Flexion averaged 118 degrees. Three knees (1.3%) were revised (one each for flexion instability, tibial plateau fracture, and suspected femoral component loosening). No other cases of femoral or tibial loosening were identified.

CONCLUSION

Although the success of uncemented TKA is determined by a variety of factors, the use of this dual-pivot knee design did not appear to influence tibial or femoral component fixation at early follow-up, yielding acceptable clinical and radiographic outcomes.

Clinical Course of Pain and Function Following Total Knee Arthroplasty: A Systematic Review and Meta-Regression

BACKGROUND

Total knee arthroplasty (TKA) is widely considered a successful intervention for osteoarthritis and other degenerative knee diseases. This study addresses the need for a high-quality meta-analysis that outlines the clinical course of pain and function post-TKA.

METHODS

The review included prospective cohort studies assessing pain or function of patients undergoing primary TKA at baseline (preoperatively) and at least 2 additional time points including one at least 12 months postoperatively. Two reviewers independently screened references, extracted data, and assessed risk of bias using the Quality in Prognosis Studies tool. The time course of recovery of pain and function was modeled using fractional polynomial meta-regression.

RESULTS

In total, 191 studies with 59,667 patients were included, most with low risk of bias. The variance-weighted mean pain score (/100, 0 = no pain) was 64.0 (95% confidence interval [CI] 60.2-67.7) preoperatively, 24.1 (95% CI 20.3-27.9) at 3 months, 20.4 (95% CI 16.7-24.0) at 6 months, and 16.9 (95%CI 13.6-20.3) at 12 months, and remained low (10.1; 95% CI 4.8-15.4) at 10 years postoperatively. The variance-weighted mean function score (/100, 0 = worst function) was 47.1 (95% CI 45.7-48.4) preoperatively, 72.8 (95% CI 71.3-74.4) at 3 months, 76.3 (95% CI 74.7-77.8) at 6 months, and 78.1 (95%CI 76.4-79.7) at 12 months. Function scores were good (79.7; 95% CI 77.9-81.5) at 10 years postoperatively.

CONCLUSION

Patients undergoing primary TKA can expect a large and rapid but incomplete recovery of pain and function in the first postoperative year. At 10 years, the gains in pain scores may still remain while there is an improvement in function.

A Prospective Randomized Study Comparing Postoperative Pain, Biological Fixation, and Clinical Outcomes Between Two Uncemented Rotating Platform Tibial Tray Designs

BACKGROUND

With the demand for arthroplasty increasing worldwide year on year, there is a drive to improve prosthesis longevity. Biological fixation from cementless implants has been one method of trying to achieve this. We hypothesized that the addition of a hydroxyapatite (HA) coating and 4 pegs to a porous-coated tibial tray would provide a reduction in time to implant osseointegration, allowing for normal physiological stress transfer, thus improving early postoperative pain and rehabilitation as well as the elimination of radiolucent lines (RLLs).

METHODS

A prospective, randomized controlled single-blinded study was undertaken, comparing postoperative pain, radiographic evidence of biological fixation, and clinical outcomes between patients undergoing primary total knee arthroplasty with either LCS Complete POROCOAT (porous coating only) or LCS Complete DUOFIX (porous coating plus HA and pegs) knee systems (DePuy Synthes, Warsaw, IN). In total, 197 patients (205 knees) were recruited into the study between November 2006 and November 2008 and have been followed for up to 10 years.

RESULTS

There were no clinically significant differences in pain or patient-reported outcome measures when comparing the 2 designs but the tibial tray with pegs and HA showed fewer RLLs at all time points. There was no correlation between RLLs and pain and no instances of loosening or osteolysis in either group. There was 1 revision for infection in the porous coating only group.

CONCLUSION

The tray design with HA and additional fixation pegs did not confer any benefit in terms of reduced early postoperative pain or improved patient-reported outcomes, although it did result in significantly fewer RLLs. Both implants demonstrated excellent survivorship. With a cementless porous-coated tibial component, nonprogressive RLLs should be considered normal.

Does computer-assisted surgery influence survivorship of cementless total knee arthroplasty in patients with primary osteoarthritis? A 10-year follow-up study

PURPOSE

Computer-assisted surgery (CAS) has been proposed to improve the performance of total knee arthroplasty (TKA) by reducing implant mal-position and mechanical axis mal-alignment. However, no clinical study has been performed to evaluate whether CAS improves survivorship of cementless TKA at long-term follow-up. This prospective and comparative study evaluated the outcome and survivorship of a cementless rotating mobile-bearing TKA performed with or without CAS at a minimum 10-year follow-up.

METHODS

A continuous series of 138 TKA (SCORE^®, Amplitude, Valence, France) comparing 87 CAS TKA versus 51 conventional mechanical technique (MECA) TKA was prospectively included in our total joint registry.

RESULTS

At 10.5 years after implantation, 95 TKA (59 CAS and 36 MECA TKA) were evaluated. No significant difference was detected in the clinical outcome and mechanical axis between the two groups. The overall 10-year survivorship using revision for any reason as end-point was 91 ± 5 % without significant difference detected between the two groups [86 ± 10 % in the MECA group and 94 ± 5 % in the CAS group (n.s.)]. Using aseptic loosening as end-point, the 10-year survivorship was 100 % in both groups. Using secondary patellar resurfacing as end-point, the 10-year survivorship was significantly higher in the CAS than in MECA group (100 and 85 ± 15 %, respectively; p = 0.0039).

CONCLUSION

With no implant aseptic loosening or mechanical failure at 10.5 years after implantation, the cementless rotating mobile-bearing SCORE^® TKA demonstrated favourable survivorship without influence of CAS. However, CAS might influence TKA survivorship by limiting secondary patellar resurfacing.

LEVEL OF EVIDENCE

Therapeutic, Level II.

CEMENTLESS MIS MINI-KEEL PROSTHESIS REDUCES INTERFACE MICROMOTION VERSUS STANDARD STEMMED TIBIAL COMPONENTS

Fixation strength of the cementless knee prostheses is dependent on the initial stability of the fixation and minimal relative motion across the prosthesis–bone interface. Broad mini-keels have been developed for tibial components to allow minimally invasive knee arthroplasty, but the effect of the change in fixation design is unknown. In this study, bone–prosthesis interface micromotions of the mini-keel tibial components (consisting of two designs; one is stemless and another with a stem extension of 45[Formula: see text]mm) induced by walking and stair climbing were investigated by finite element modeling and compared with standard stemmed design. The prosthesis surface area amenable for bone ingrowth for the mini-keel tibial components (both stemmed and unstemmed) was predicted to be at least 67% larger than the standard stemmed implant, thereby reducing the risk of long-term aseptic loosening. It was also found that while different load patterns may have led to diverse predictions of the magnitude of the interface micromotions and the extent of osseointegration onto the prosthesis, the outcome of design change evaluation in cementless tibial fixations remains unchanged. The mini-keel tibial components were predicted to anchor onto the periprosthetic bone better than the standard stemmed design under all loading conditions investigated.

Femoral Component Survival in Hybrid Total Knee Arthroplasty

Although the majority of North American surgeons perform total knee arthroplasty by cementing both the femoral and the tibial components, hybrid fixation with a press-fit femur and cemented tibia is an alternative form of total knee arthroplasty performed by some. Currently, there is a paucity of literature evaluating long-term outcomes after hybrid total knee arthroplasty. As such, the purpose of the current study was to describe the long-term results of total knee arthroplasty performed using the hybrid technique. The authors retrospectively reviewed a total of 77 hybrid total knee arthroplasties with at least 12 years of follow-up. Clinical and radiographic evaluations were performed to determine patient function and the incidence of femoral component failure after hybrid total knee arthroplasty. At the time of last follow-up, 76 of 77 (99%) of the femoral components remained in place without evidence of loosening. One femoral component failed due to aseptic loosening and was ultimately revised to a cemented femoral component without further complication. In addition, 1 tibial component and 2 patellar components failed due to aseptic loosening. Four tibial polyethylene liners were revised for polyethylene wear. In conclusion, press-fit fixation of the femoral component is a reliable and durable alternative to cemented fixation. [Orthopedics. 2016; 39(3):181-186.].

Cementless total knee replacement fixation

A retrospective review was performed of patients undergoing primary cementless total knee replacement (TKR) using porous tantalum performed by a group of surgical trainees. Clinical and radiological follow-up involved 79 females and 26 males encompassing 115 knees. The mean age was 66.9 years (36 to 85). Mean follow-up was 7 years (2 to 11). Tibial and patellar components were porous tantalum monoblock implants, and femoral components were posterior stabilised (PS) in design with cobalt–chromium fibre mesh. Radiological assessments were made for implant positioning, alignment, radiolucencies, lysis, and loosening. There was 95.7% survival of implants. There was no radiological evidence of loosening and no osteolysis found. No revisions were performed for aseptic loosening. Average tibial component alignment was 1.4° of varus (4°of valgus to 9° varus), and 6.2° (3° anterior to 15° posterior) of posterior slope. Mean femoral component alignment was 6.6° (1° to 11°) of valgus. Mean tibiofemoral alignment was 5.6° of valgus (7° varus to 16° valgus). Patellar tilt was a mean of 2.4° lateral (5° medial to 28° lateral). Patient satisfaction with improvement in pain was 91%. Cementless TKR incorporating porous tantalum yielded good clinical and radiological outcomes at a mean of follow-up of seven-years.

Cite this article: Bone Joint J 2014;96-B(11 Suppl A):87–92.

Hybrid total knee arthroplasty: 10- to 16-year follow-up

A cementless femoral component may allow for a smaller surgical incision when a minimally invasive approach is used during primary total knee arthroplasty. Fixation by cement is the gold standard for total knee arthroplasty. The results of cementless total knee arthroplasty are mixed. Cementless femoral components have done well. Although some tibial components have performed well at long-term follow-up, others have been plagued by high rates of loosening and revision. The question remains whether the results of hybrid total knee arthroplasty, consisting of an uncemented femoral component and a cemented tibial component, will equal those of total knee replacement fixed with cement at long-term follow-up. The authors reviewed 148 hybrid total knee arthroplasties performed by a single surgeon between 1993 and 1995. At a mean follow-up of 14 years (range, 10-16) 5 knees (4%) had undergone revision of both the femoral and tibial components. Only 1 knee required revision for aseptic loosening. Two knees were revised for sepsis; 1 knee had been revised for fracture and 1 for instability. No additional femoral or tibial components were loose by radiographic criteria. Mild focal femoral osteolysis was identified in 3 knees (2%), and minor tibial osteolysis was present in 2 knees (1%). The rate of survivorship with revision for aseptic loosening as the end point was 99% (95% confidence interval, 0.97-100) at 16 years for both the femoral and tibial components. In this series, hybrid total knee arthroplasty showed excellent fixation at 16 years.

Preoperative predictors of pain following total knee arthroplasty

Total knee arthroplasty has provided dramatic improvements in function and pain for the majority of patients with knee arthritis, yet a significant proportion of patients remain dissatisfied with their results. We performed a prospective analysis of 215 patients undergoing TKA who underwent a comprehensive array of evaluations to discover whether any preoperative assessment could predict high pain scores and functional limitations postoperatively. Patients with severe pain with a simple knee range-of-motion test prior to TKA had a 10 times higher likelihood of moderate to severe pain at 6 months. A simple test of pain intensity with active flexion and extension preoperatively was a significant predictor of postoperative pain at 6 months after surgery. Strategies to address this particular patient group may improve satisfaction rates of TKA.

Does using autograft bone chips achieve consistent bone ingrowth in primary TKA?

BACKGROUND

Cementless fixation remains controversial in TKA due to the challenge of achieving consistent skeletal attachment. Factors predicting durable fixation are not clearly understood, but we presumed bone ingrowth could be enhanced by the quantity of host bone and application of autograft bone chips.

QUESTIONS/PURPOSES

We asked: (1) Did the amount of bone ingrowth exceed the amount of periprosthetic and host bone with the addition of autograft bone chips? (2) Did the amount of bone ingrowth increase with implantation time? And (3) did osteolysis along the porous-coated interface and screw tracts progress with implantation time?

METHODS

We measured the amount of bone in the porous-coated, periprosthetic, and host bone regions in 19 postmortem retrieved cementless primary total knee implants. The amount of bone in apposition to the implant surface, and alternatively lysed bone, was analyzed radiographically to assess the progression of osteolysis.

RESULTS

While bone ingrowth tended to be less than periprosthetic and host bone in all three components, it was only significantly less in the patellar component. Bone ingrowth increased in all three components over time, but progression of osteolysis did not.

CONCLUSIONS

Even after long-term followup, the amount of bone ingrowth did not surpass host bone levels, suggesting the amount of a patient's host bone is a limiting factor in the amount of bone ingrowth achievable for this cementless design. It remains unknown whether compromised osteopenic bone could achieve the amount of bone attachment necessary to provide durable fixation over time.

Uncemented tibial fixation total knee arthroplasty

This is a prospective study of the midterm clinical and radiological outcome of 205 consecutive cases (185 patients) performed between January 2002 and December 2004 using a cementless fixed-bearing tibial tray. Complete clinical and radiological follow-up was done on 175 cases (157 patients). The average knee score at final follow-up using the Knee Society Score (Insall modification-1993) was 92 of 100 with 96.6% excellent compared with an average preoperative score of 57 of 100. Using radiological criteria, none of the patients had significant polyethylene wear or osteolysis; and the tibial trays had bone ingrowth in all but 1 case. Survivorship at an average of 5 years and 7 months was 98.85%. Based on our results, we conclude that an uncemented tibial component with Porocoat (DePuy, Warsaw, Ind) and hydroxyapatite coating provides sufficiently stable bone ingrowth fixation; and this tibial design has provided excellent and predictable midterm clinical and radiological outcome.

Cementless tibial fixation in TKA: not a second coming

Cemented total knee arthroplasty (TKA), using mechanically sound components such as the total condylar system (Johnson & Johnson, New Brunswick, New Jersey), have been performed for >25 years. Long-term follow-up studies have shown excellent durability. In 1 series with a minimum 20-year follow-up, the revision rate for aseptic loosening was 3.5%. More contemporary prostheses, such as the low contact stress rotating platform (DePuy, Warsaw, Indiana) and Kinematic Knee systems (Howmedica, Rutherford, New Jersey), have demonstrated minimal loosening at 20-year follow-up. In a minimum 20-year follow-up of a rotating platform TKA, the revision rate for aseptic loosening was 0%. In a minimum 15-year follow-up of kinematic cruciate-retaining TKA, the revision rate for aseptic loosening was 1.8%. Cemented fixation is durable and forgiving. It can accommodate defects in bone as well as imperfect cuts that are not uncommon, even in the best of hands. It can interdigitate into soft and hard bone. With the development of modular tibial trays with better locking mechanisms and less abrasive surfaces, as well as the development of more wear-resistant polyethylene (gamma irradiated in an inert environment and crosslinked polyethylene), the osteolysis that developed around first generation modular components should be markedly less with newer designs. It is for these reasons that cement should remain the fixation of choice in TKA.

Twenty-year survivorship of cementless anatomic graduated component total knee arthroplasty

There is a renewed interest in cementless total knee arthroplasty (TKA) due to improved biomaterials, desire for decreased surgical times and the potential increased longevity. Seventy-three cementless TKAs (AGC, Biomet, Warsaw, Ind) were performed from 1984 to 1986. All components were implanted without cement and without screws and obtained minimum 10 years of follow-up. No patient was lost to follow-up. Fifteen failures occurred, including 12 failed metal-backed patellae, and survivorship for aseptic loosening of any component was 76.4% at 20 years. Two tibial components failed of aseptic loosening at 1.1 and 2.2 years. Excluding patella failures, the survivorship for the cementless tibial component was 96.8% at 20 years. There were no femoral component failures. After eliminating patella failures, this cementless monoblock tibial component without screws demonstrated excellent 20-year survivorship.

Cancellous bone osseointegration is enhanced by in vivo loading

Biophysical stimuli may be an effective therapy to counteract age-related changes in bone structure that affect the primary stability of implants used in joint replacement or fracture fixation. The influence of controlled mechanical loading on osseointegration was investigated using an in vivo device implanted in the distal lateral femur of 12 male rabbits. Compressive loads (1 MPa, 1 Hz, 50 cycles/day, 4 weeks) were applied to a porous titanium foam implant and the underlying cancellous bone. The contralateral limbs served as nonloaded controls. Backscattered electron imaging indicated that the amount of bone ingrowth was significantly greater in the loaded limb than in the nonloaded control limb, whereas the amount of underlying cancellous periprosthetic bone was similar. No significant difference in the mineral apposition rate of the bone ingrowth or periprosthetic bone was measured in the loaded compared to the control limb. Histological analysis demonstrated newly formed woven bone in direct apposition to the implant coating, with a lack of fibrous tissue at the implant-periprosthetic bone interface in both loaded and nonloaded implants. The lack of fibrous tissue demonstrates that mechanical stimulation using this model significantly enhanced cancellous bone ingrowth without the detrimental effects of micromotion. These results suggest that biophysical therapy should be further investigated to augment current treatments to enhance long-term fixation of orthopedic devices. Additionally, this novel in vivo loading model can be used to further investigate the influence of biophysical stimulation on other tissue engineering approaches requiring bone ingrowth into both metallic and nonmetallic cell-seeded scaffolds.

Osseointegration into a novel titanium foam implant in the distal femur of a rabbit

A novel porous titanium foam implant has recently been developed to enhance biological fixation of orthopaedic implants to bone. The aim of this study was to examine the mechanical and histological characteristics of bone apposition into two different pore sizes of this titanium foam (565 and 464 micron mean void intercept length) and to compare these characteristics to those obtained with a fully porous conventionally sintered titanium bead implant. Cylindrical implants were studied in a rabbit distal femoral intramedullary osseointegration model at time zero and at 3, 6, and 12 weeks. The amount of bone ingrowth, amount of periprosthetic bone, and mineral apposition rate of periprosthetic bone measured did not differ among the three implant designs at 3, 6, or 12 weeks. By 12 weeks, the interface stiffness and maximum load of the beaded implant was significantly greater than either foam implant. No significant difference was found in the interface stiffness or maximum load between the two foam implant designs at 3, 6, or 12 weeks. The lower compressive modulus of the foam compared to the more dense sintered beaded implants likely contributed to the difference in failure mode. However, the foam implants have a similar compressive modulus to other clinically successful coatings, suggesting they are nonetheless clinically adequate. Additional studies are required to confirm this in weight-bearing models. Histological data suggest that these novel titanium foam implants are a promising alternative to current porous coatings and should be further investigated for clinical application in cementless joint replacement.

Analysis of bone-prosthesis interface micromotion for cementless tibial prosthesis fixation and the influence of loading conditions

A lack of initial stability of the fixation is associated with aseptic loosening of the tibial components of cementless knee prostheses. With sufficient stability after surgery, minimal relative motion between the prosthesis and bone interfaces allows osseointegation to occur thereby providing a strong prosthesis-to-bone biological attachment. Finite element modelling was used to investigate the bone-prosthesis interface micromotion and the relative risk of aseptic loosening. It was anticipated that by prescribing different joint loads representing gait and other activities, and the consideration of varying tibial-femoral contact points during knee flexion, it would influence the computational prediction of the interface micromotion. In this study, three-dimensional finite element models were set up with applied loads representing walking and stair climbing, and the relative micromotions were predicted. These results were correlated to in-vitro measurements and to the results of prior retrieval studies. Two load conditions, (i) a generic vertical joint load of 3 x body weight with 70%/30%M/L load share and antero-posterior/medial-lateral shear forces, acted at the centres of the medial and lateral compartments of the tibial tray, and (ii) a peak vertical joint load at 25% of the stair climbing cycle with corresponding antero-posterior shear force applied at the tibial-femoral contact points of the specific knee flexion angle, were found to generate interface micromotion responses which corresponded to in-vivo observations. The study also found that different loads altered the interface micromotion predicted, so caution is needed when comparing the fixation performance of various reported cementless tibial prosthetic designs if each design was evaluated with a different loading condition.

NexGen LPS rotating platform total knee arthroplasty: medium-term results of a prospective study

The purpose of this study is to present midterm results of NexGen LPS (Zimmer, Warsaw) rotating platform total knee arthroplasty. A prospective consecutive series of 50 primary rotating platform total knee replacements in 43 patients were clinically and radiographically evaluated at a mean follow-up of 46.4 (range 30-78) months. There were 12 men (30%) and 31 women (70%) with an average age of 72.3 years (range 55-85). All implants were cruciate-substituting and cemented. Patients were assessed using the Knee Society Clinical Rating System and the Knee Society Total Knee Arthroplasty Roentgenographic Evaluation and Scoring System. Pre-operatively, the mean knee score was 50.7 points (SD 15.1) and the mean function score was 40.5 points (SD 22.7). Post-operatively the mean knee score was 91.6 (SD 6.5) and the mean function score was 85.9 (SD 17.4). No sign of component loosening or osteolysis could be identified. The NexGen LPS rotating platform total knee replacement design provided excellent mid-term clinical and radiographical results.

Clinical results of bone ingrowth TKA in patients with rheumatoid arthritis

Patients with rheumatoid arthritis (RA) often are not considered for TKA with bone ingrowth fixation because of poor bone quality, but we asked whether implants with sintered metal bead surfaces could be used to durably fix implants in this group of patients. We prospectively evaluated a consecutive series of 47 patients (64 knees) between January 1, 1994, and December 30, 2001, in two separate medical centers using one TKA system. Standard primary implants were used in all knees except those with major bone defects, and in these patients we used long diaphyseal stems to stabilize the implants. Minimum followup was 61 months (mean +/- standard deviation, 83 +/- 6 months; range, 61-124 months). Survivorship was 98.4% at 10 years postoperatively. No components failed because of loosening. One femoral component was revised for fracture because of a massive intraosseous rheumatoid cyst. No knees had radiographic evidence of migration or widening radiolucent lines. Knee Society clinical, pain, and function scores improved after surgery and were maintained throughout followup. These data suggest bone ingrowth implants can provide durable fixation in patients with RA.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Comparison of screw and screwless fixation in cementless total knee arthroplasty

This study compared two groups of consecutive patients undergoing total knee arthroplasty (TKA) with an identical cementless tibial baseplate supplementally fixated with and without screws. In 58 TKAs, two 6.5-mm cancellous screws were used for fixation, and in 58 TKAs, screwless fixation was used. Clinical evaluation was performed using the Hospital for Special Surgery knee score, and fluoroscopically guided radiographs were evaluated for radiolucencies. In the screw fixation group, average follow-up was 82+/-6 months (range, 59-89 months) and average patient age at surgery was 63 years. For the screwless fixation group, average follow-up was 67+/-5 months (range, 48-76 months) and average patient age at surgery was 62 years. Average knee score was 97 for the screw fixation group and 98 for the screwless fixation group. This study demonstrated stability in cementless TKA both with and without screw fixation in the mid-term using the Natural-Knee II tibial component.

Osteolysis after total knee arthroplasty

Osteolysis ranks as the most significant cause of revision surgery in both total hip arthroplasty and total knee arthroplasty (TKA). The factors leading to osteolysis in TKA are unique and sometimes preventable. Changes in polyethylene manufacturing and implant design are striving to improve overall wear. In this review, we discuss osteolysis as it relates to TKAs. The etiology, diagnosis, contributing factors, and management are presented. The final section focuses on future improvements in TKA design, which may ultimately decrease the rate of osteolysis.

Relationship between bone ingrowth, mineral apposition rate, and osteoblast activity

To better understand skeletal attachment of porous coated total hip and knee implants over time, this study investigated the dynamics of osteoblast populations at the interface of porous coated implants in a weight-bearing ovine model. The relationship between cancellous bone ingrowth, mineral apposition rate (MAR), and osteoblast activity indicators such as osteoblast area, relative osteoblast number, osteoid width, and osteoid area (O.Ar.) were investigated. The data demonstrated that the percent O.Ar. was a marginally significant predictor of bone ingrowth and MAR over time, suggesting that the amount of osteoid present influenced bone ingrowth and MAR in the porous coated implants. The data also demonstrated that all osteoblast activity indicators were significantly greater in the porous coated region compared to the host bone region, while controlling for in situ time (p < 0.05). This may have been due to the trauma of implantation or the influence of the implant load on the bone tissue promoting a regional acceleratory phenomenon. The localized response suggests that specific therapies may be developed to affect the physiology of osteoblasts at the interface of implants, which may allow for improve skeletal attachment of biomaterials and clinical outcomes of cementless joint replacements.

Evolution of tibial fixation in total knee arthroplasty

Cementless total knee arthroplasty (TKA) implants were designed as an alternative to cemented implants. They were touted to provide long-term fixation without the fear of cement debris particle generation and cement degradation resulting in late prosthetic loosening and failure. They were envisioned as a superior solution for TKA in younger patients. However, critical studies revealed a unique set of complications, which included poor fixation as evidenced by frequent occurrence of radiolucent lines, aseptic loosening, osteolysis, and patellar polyethylene dissociation from metal-backed cementless patellar components. At the same time, cemented prostheses continue to yield excellent results. To address some of the issues with cementless implants, porous metal devices have been produced. Although in vitro and early in vivo clinical studies show promising results, these devices must be measured against cemented fixation, which continues to be the "gold standard" in TKA.

Cementless total knee arthroplasty with Profix: a 8- to 10-year follow-up study

A consecutive series of 115 cementless Profix (Smith and Nephew, Memphis, USA) Total Knee Arthroplasties performed in 113 patients were followed in order to determine the functional results and survivorship at 8 to 10 years. All patients were included in a prospective database and were reviewed annually until final follow-up. Patients overall satisfaction was excellent or good in 91.3% of cases. The mean Knee Society's knee and function scores increased respectively from 49.3 and 36.7 preoperatively to 93.1 and 82.2 postoperatively. The Kaplan-Meier estimate of implant survival at 10 years was 97.1%. Two patients underwent revision and were considered as failures. One patient had a fracture of the medial condyle at 4 days post-surgery, and the other was revised for aseptic loosening of the tibial component at 6 years post-surgery. On the basis of this long-term follow-up study, we can conclude that the Profix Total Knee System is effective and safe.

International multi-centre survivorship analysis of mobile bearing total knee arthroplasty

We retrospectively reviewed the experience of a large international multi-centre study of primary total knee arthroplasty with mobile bearing design and modifications of the tibial component to allow for bicruciate preservation, posterior cruciate retention, or sacrifice. Twenty-seven surgeons performed 4,743 total knee replacements between 1981 and 1997. Implants inserted were 324 that retained both cruciate ligaments, 2,165 that retained the posterior cruciate, and 2,254 that sacrificed both cruciates. The patella was resurfaced in 2,838 and unresurfaced in 1,905. With failure defined as revision or reoperation for any reason, the overall survivorship was 79% at 16 years' follow-up. Revision occurred in 259 (5.4%) knees out of the entire cohort. The risk adjusted rates of failure were higher in females, younger patients, osteoarthritis, post-traumatic arthritis, and in patients who had a meniscal bearing prosthesis or patellar resurfacing. The most common cause of revision was bearing-related issues including chronic instability, bearing subluxation, bearing dislocation, or bearing wear in 2.3%.

Tibial fixation without screws in cementless total knee arthroplasty

This study examines the early clinical and radiographic results of the first 216 cases of a cementless fixed bearing tibial tray without screw holes in 191 patients. We hypothesize that stable fixation can be achieved without the use of screws. There were 16 cases lost to follow-up, leaving 200 cases with known outcome. The Hospital for Special Surgery knee scores improved from an average preoperative score of 54/100 to 82/100 postoperatively. Three patients had incomplete radiolucent lines involving the medial aspect of the tibial tray. All of the tibial components reviewed radiographically were bone ingrown. We conclude that the tray provides excellent primary stability, allowing early bone ingrowth, free from osteolysis and with good clinical outcomes. All of the tibial components were bone ingrown by radiographic criteria.

Choosing your implant: cementless, patella sparing, and posterior cruciate ligament retaining

Clinical results of total knee arthroplasty with osteointegration techniques for fixation of the femoral and tibial components in a series of 192 patients (255 knees) followed up for 15 to 18 years are comparable with the best series reported with cemented fixation. Although functional scores declined as the patients aged, pain scores did not worsen, and the mechanical failure rate remained low through follow-up. Preservation of the posterior cruciate ligament offered knee stability, especially in knees that required ligament balancing. Results with unresurfaced patellas in total knee arthroplasty are superior to resurfaced patellas in qualities related to quadriceps function such as stair climbing, likely because of femoral component design. Femoral implants with a shallow patellar groove and wide intercondylar notch produce the highest stresses on the unresurfaced patella. Those with deeper patellar grooves and supporting lateral flange surfaces have low contact stress similar to that of the normal patellofemoral joint.

Sagittal laxity in vivo after total knee arthroplasty

INTRODUCTION

A stress arthrometry study of 77 knees undergoing total knee arthroplasty was performed to determine the difference in anteroposterior (AP) laxity between posterior cruciate ligament (PCL)-retaining (PCLR) and PCL-substituting (PCLS) prostheses using the Genesis I TKA.

MATERIALS AND METHODS

Fifty-three knees had PCLR and 24 had PCLS prostheses. The selected patients had successful arthroplasties after a minimum follow-up of 5 years. AP laxity was measured with a KT-2000 arthrometer (Medmetric, San Diego, CA, USA) using standard protocols.

RESULTS

At 30 degrees of flexion, there was no statistical difference in anterior (PCLR: 4.7 mm, PCLS: 4.5 mm), posterior (PCLR: 1.1 mm, PCLS: 0.7 mm), or total (PCLR: 5.8 mm, PCLS: 5.3 mm) displacement. At 75 degrees , significant differences were seen in both anterior (PCLR: 3.3 mm, PCLS: 2.3 mm) and total (PCLR: 4.8 mm, PCLS: 3.4 mm) displacement (p=0.001 and p=0.009, respectively), although there was no statistical difference in posterior displacement (PCLR: 1.5 mm, PCLS: 1.1 mm).

CONCLUSION

The above values are considered the suitable degree of AP laxity in total knee arthroplasty for a satisfactory clinical outcome 5-9 years after surgery. The PCL in a PCLR prosthesis and the central tibial spine and femoral cam in a PCLS prosthesis might play comparable roles in determining the laxity in the posterior direction in these prostheses.

The outcome of the cementless tibial component: a minimum 14-year clinical evaluation

The long term survival of the Miller-Galante I cementless total knee arthroplasty was evaluated by studying prospectively for a minimum of 14 years (range, 14-17 years), 124 consecutive cementless total knee arthroplasties using a Miller-Galante I prosthesis in 99 patients with a mean age of 62 years who had primary or secondary osteoarthritis. Knee function and roentgenograms were evaluated using the Knee Society criteria. Kaplan-Meier survivorship analysis was conducted. Five patients (five knees) were lost to followup; six patients died with six knees in place. Fifteen knees (15 patients) failed and were revised. Thirteen metal-backed patellas were revised. Eight of these revisions also required exchange of the femoral component, but only one tibial tray was revised. One knee (one patient) was revised for an infection. Of the 98 knees not revised (73 patients) observed throughout this study, the average preoperative knee score was 31 (range, 0-47); postoperatively, the average knee score was 91 (range, 72-100). The average function score improved from 28 (range, 10-45) to 84 (range, 50-100). Twenty-four tibial trays (21%) and twenty femoral components (17%) of the 113 knees studied showed osteolysis. This study indicates that osteointegration of cementless tibial components can be successful with screw fixation, although there is a worrisome incidence of tibial and femoral osteolysis. The overall knee survival rate was 87%; however, the tibial component had a survival of 99%.

Long-term results of low contact stress mobile-bearing total knee replacements

Five hundred ninety-eight consecutive primary low contact stress total knee replacements were done in 502 patients between 1985 and 1990. Clinical review was available for 495 knees (406 patients), 228 knees with meniscal-bearing prostheses and 267 knees with rotating-platform prostheses. The average followup was 12 years (range, 10-15 years). The average postoperative knee and functional scores were 87 points and 75 points, respectively. The average postoperative range of motion was 110 degrees. Fifty-six knees (11%) required revision for excessive wear of the tibial insert (41), dislocation (10), patellar polyethylene breakage (one), component loosening (one patellar, one tibial), and infection (two). During revision, osteolysis (20 knees), patellar polyethylene failure (33), and femoral component fracture (one) were seen. The overall survivorship was 88.1% at 15 years using Kaplan-Meier analysis. The survival rate was 83% for the meniscal-bearing prostheses and 92.1% for the rotating-platform prostheses. The Low Contact Stress mobile-bearing knee prosthesis has no superiority over that of fixed-bearing knees, especially for the meniscal-bearing design in prevention of polyethylene failure or revision. Based on the results of this study, the use of the LCS meniscal-bearing prosthesis does not appear to be justified.

Contrary view: wear is not an issue

Wear was not an issue with total knee replacements that had a round-on-round design such as the Total Condylar and the Insall-Burstein prostheses. As long as designs do not try to reproduce normality in kinematics, wear will not be an issue. To date, there are no data that mobile-bearing knee replacements will decrease wear complications as compared with round-on-round fixed designs. Wear is not an issue if the total knee replacement is done with a round-on-round design with a cobalt chrome femoral component, monoblock tibial component, and an all-polyethylene patella, all with cemented fixation.

Fixation of the millennium: the knee

Current reports of noncemented fixation for total knee arthroplasty show that fixation of the components is durable for 20 years. Noncemented fixation may be preferable in patients <60 years old. In revision total knee arthroplasty, cemented stems are preferable in patients >70 years old.