Low contact stress mobile bearing total knee arthroplasty: results at 5 to 13 years

The influence of radiologic bone transparency after hybrid total knee arthroplasty on clinical outcomes: Minimum 6-year follow up of 214 cases

BACKGROUND

This study aimed to investigate how bone transparency affects loosening of the cementless femoral component by serially analyzing radiologic images in hybrid total knee arthroplasty (TKA).

METHODS

A total of 214 cases of TKA performed using the hybrid technique that were followed up for at least 6 years were retrospectively investigated. Bone transparency around the femoral component during the follow up period was evaluated. All TKA cases were divided into two groups and compared: those with radiologic bone transparency (bone transparency group, n = 51) and those without radiologic bone transparency (no bone transparency group, n = 163).

RESULTS

The incidence of revision TKA in all patients was 6.1%, and obesity, preoperative and postoperative mechanical alignment did not affect surgical outcomes. All bone transparency cases were asymptomatic, and only 8/51 cases (15.7%) of bone transparency spontaneously resolved. Between the bone transparency and no bone transparency groups, there was no difference found in the preoperative and postoperative radiologic parameters and clinical outcomes. During the follow up period, there were four (1.9%) cases with a definite radiolucent line in the femoral component, all of which belonged to the bone transparency group.

CONCLUSIONS

The bone transparency around the femoral component that appears on radiography after hybrid TKA could be an early sign of aseptic loosening; therefore, follow up serial radiography is essential.

Cemented vs Uncemented Femoral Components: A Randomized, Controlled Trial at 10 Years Minimum Follow-Up

BACKGROUND

The type of total knee arthroplasty (TKA) fixation (cemented or uncemented) is still subject to debate. The aim of this study is to assess the survival rate, clinical outcomes, and radiological results of TKA according to the fixation type.

METHODS

A total of 130 patients were randomly assigned to either the cement group (cemented femoral and tibial implants) or the hybrid group (cemented tibial implant, uncemented femoral implant). The inclusion criteria were patients between 50 and 90 years old who underwent primary TKA for osteoarthritis between 2004 and 2005 without a history of open knee surgery. Revisions and complications were reported, as well as clinical scores and radiological signs of loosening.

RESULTS

One hundred eighteen patients had complete data at 10 years of minimum follow-up (59 in each group). The mean age was 72 years old. The mean follow-up was 13 years. The survival rate was 98% at 13 years in both groups (1 aseptic loosening at 2 years in the cement group, 1 septic loosening in the hybrid group). The complication rate in the cement group was 8.5% (n = 5) vs 12.1% (n = 7) in the hybrid group (P = .8). The clinical results were not significantly different. In the cement group, 25% of patients (n = 15) had radiolucent lines at 10 years. In the hybrid group, 33% of patients had bone transparencies, not evolving or symptomatic.

CONCLUSION

At a minimum follow-up of 10 years, there were no significant differences between cemented TKA and hybrid TKA for the survivorship, the complication rate, the clinical scores, or the radiological signs of loosening.

LEVEL OF EVIDENCE

I.

No clinical benefit of titanium nitride coating in cementless mobile-bearing total knee arthroplasty

PURPOSE

Titanium nitride (TiN) coating of cobalt-chromium-molybdenum (CoCrMo) implants has shown to improve the biomechanical properties of the implant surface and to reduce adhesive wear in vitro. It is yet unknown whether TiN coating of total knee prosthesis (TKP) affects the postoperative clinical outcome of total knee arthroplasty (TKA).

METHODS

In a double-blind randomized controlled clinical trial, 101 patients received an uncemented mobile-bearing CoCrMo TKP, either TiN coated or uncoated. Primary outcome measure visual analogue scale (VAS) score for pain, and secondary outcome measures Knee Society Score (KSS), revision rate and adverse events, range of motion of the knee as well as knee circumference and knee skin temperature were assessed 6 weeks, 6 months, 1 year and 5 years postoperative. Repeated measures analysis was used to evaluate the postoperative outcome measures over time.

RESULTS

There was no difference between the two groups in VAS score, KSS, revision rate, range of motion of the knee, knee circumference and knee skin temperature. There were no adverse events that could be related to the TiN coating.

CONCLUSIONS

TiN-coated TKP does not influence the postoperative outcome of uncemented mobile-bearing TKA regarding postoperative pain, revision rate, range of motion, swelling and temperature of the knee. Therefore, TiN coating of CoCrMo TKP has no clinical benefit on the outcome of cementless mobile-bearing TKA.

LEVEL OF EVIDENCE

Therapeutic study, Level I.

Early clinical results of a high-flexion, posterior-stabilized, mobile-bearing total knee arthroplasty: a US investigational device exemption trial

Between May 2001 and June 2004, 388 total knee arthroplasty cases were enrolled in a prospective, randomized, multicenter investigational device exemption trial. Patients received either the investigational high-flexion mobile-bearing knee or a fixed-bearing control. At 2 to 4 years of follow-up, results in 293 patients with degenerative joint disease were compared using Knee Society Assessment and Function scores, radiographic results, complications analysis, and survival estimates. The mobile-bearing and fixed-bearing groups demonstrated similar, significant improvement over preoperative assessments in Knee Scores, maximum flexion, and range of motion. One mobile-bearing arthroplasty required revision. Radiographic results were unremarkable, and implant-related complications were rare in both groups. At this early follow-up, the investigational high-flexion mobile-bearing knee and its fixed-bearing counterpart demonstrated comparable, effective performance.

Rotating platform spinouts with cruciate-retaining mobile-bearing knees

Spinout or dislocation is a complication of mobile-bearing total knee arthroplasty. We have observed this complication in 7 of 1255 cruciate-retaining mobile-bearing total knees (0.56%). Patient factors associated with a spinout included female sex, obesity, and preoperative valgus deformity. Operative treatment was generally successful, but significant complications occurred in 3 of the 7 patients.

Cemented versus uncemented femoral components in total knee arthroplasty

PURPOSE

The aim of this study is to analyse the influence of femoral cement on clinical and radiological results after total knee arthroplasty.

METHODS

Preoperatively 130 patients were randomly assigned to treatment in either the Cement Group or the Hybrid Group. The International Knee Society scores, femoral radiolucent lines and bone transparencies were compared.

RESULTS

There were no significant differences concerning postoperative knee and function scores. We observed a significant difference in radiolucent lines (Cement Group, 24%; Hybrid Group, 2%; P < 0.001) as well as bone transparencies (Cement Group, 21%; Hybrid Group, 62%; P < 0.001). All radiolucent lines measured less than 2 mm in width.

CONCLUSION

Cementing the femoral component of a total knee arthroplasty does not appear to influence the clinical results. A longer follow-up period is required to determine the influence of radiological findings on final outcome.

Uncemented total knee arthroplasty: 2-year follow-up of 100 knees with a rotating platform, cruciate-retaining design

Review of the literature shows mixed results regarding uncemented total knee arthroplasty (TKA). To our knowledge, there are no reports of results for uncemented TKA that incorporates a cruciate-retaining and rotating platform design. It is theorized that these design features could decrease the stress at the bone-implant interface. This study reports results on 100 uncemented TKAs at a minimum of 2-year follow-up. Average Knee Society clinical score improved from 52.9 to 95.1; average Knee Society functional score improved from 60.5 to 82.0. Ninety-eight percent of patients had excellent and 2% had good results based on Knee Society scores. There was 99% implant survival; 1 patient required revision of a loose tibial component after a motor vehicle accident. The promising short-term results support the continued use of this implant and suggest a prospective randomized study comparing cemented vs uncemented TKA of this design is warranted.

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.

Early clinical outcomes of floating platform mobile-bearing TKA: longitudinal comparison with fixed-bearing TKA

This study was conducted to longitudinally compare a new floating platform mobile-bearing (MB) prosthesis with an established fixed-bearing (FB) system with respect to early clinical outcomes in patients with bilateral TKAs using the MB prosthesis in one knee and the FB prosthesis in the other. Clinical outcomes (ROM, AKS and WOMAC scores, and side preference), evaluated at 6, 12 and 24 months postoperatively, were compared between knees fitted with the MB prosthesis (e.motion-FP) or the FB prosthesis (Genesis II) in 66 patients who underwent bilateral TKA. In addition, the same comparisons between the knees fitted with the MB prosthesis and the knees with the FB prosthesis were made separately in the subgroup of 33 patients implanted with a cruciate retaining FB (FB-CR) prosthesis and the other subgroup of 33 patients with a posteriorly stabilized FB (FB-PS) prosthesis in a knee. The floating platform MB prosthesis achieved comparable clinical outcomes to the FB prosthesis. No significant differences were found between the FB- and MB-implanted sides at any time with respect to the outcome scales, and temporal patterns were similar. However, comparisons of FB-CR and FB-PS patient groups revealed different temporal patterns. In the FB-CR group, most outcome scales were improved at 6 months, peaked at 12 months and then remained at this level at 24 months. In contrast, outcomes in the FB-PS group improved much faster to almost peak at 6 months, and then remained at this level. In the FB-CR group, more patients preferred the knee with fitted with a MB prosthesis at 6 months. In contrast, in the FB-PS group, no side preference for the MB prosthesis was observed, and more patients preferred knees implanted with the FB prosthesis at 12 and 24 months. This study demonstrates that this new mobile-bearing prosthesis, designed as a floating platform, provides satisfactory clinical performances that are comparable to those achieved using the established fixed-bearing prosthesis in terms of clinical outcomes.

Improved early clinical outcomes of RP/PS mobile-bearing total knee arthroplasties

The rotating-platform posterior-stabilized (RP/PS) prosthesis was developed to take advantage of the benefits of the traditional RP mobile-bearing system and the posterior-stabilized design. This nonconsecutive cohort study compared the clinical outcomes of TKAs performed using a RP/PS mobile system or a floating-platform (FP) system. The clinical outcomes of 93 TKAs with a RP/PS prosthesis were compared with the same number of TKAs with a FP mobile-bearing prosthesis at 6, 12, and 24 months after surgery. Clinical outcomes differed between the FP and RP/PS groups as a function of length of followup. In the FP group, most outcomes peaked at 12 months and then deteriorated, whereas in the RP/PS group, outcomes stabilized or continued to improve between 12 and 24 months. The RP/PS group had greater maximum flexion throughout followup and better clinical outcomes 24 months after surgery. Patient satisfaction was superior in the RP/RS group. This study suggests the RP/PS prosthesis provides better functional outcomes, including greater maximum flexion and better patient satisfaction. We propose the RP/PS mobile-bearing system is a more attractive option than the FP mobile-bearing system for patient populations of elderly women similar to patients enrolled in our study.

LEVEL OF EVIDENCE

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

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.

Tibial component failure mechanisms in total knee arthroplasty

The purpose of this study was to examine the failure mechanisms and factors associated with failure of a nonmodular metal backed cemented tibial component. Out of 3152 total knee replacements done for osteoarthritis, 41 tibial components had been revised (1.3%). Four distinct failure mechanisms were identified: 20 knees were revised for medial bone collapse, 13 for ligamentous imbalance, 6 for progressive radiolucencies, and 2 for pain. Factors associated with medial bone collapse were varus tibial component alignment more than 3.0 degrees , Body Mass Index higher than 33.7, and overall postoperative varus limb alignment. Ligamentous imbalance was more prevalent in knees with preoperative valgus deformity. There were no knees revised for tibial component polyethylene wear or osteolysis. We conclude that the dominant failure mechanisms for this component design are related to preoperative deformity, technical factors of component alignment, overall limb alignment, and ligamentous imbalance.

Winner of the 2003 James A. Rand Young Investigator's Award. Early failure of cementless mobile-bearing total knee arthroplasty

A consecutive series of 82 cementless mobile-bearing total knee arthroplasties performed was studied to determine the reliability of cementless tibial component fixation. The indications for surgery in all cases were osteoarthritis with only mild or moderate deformity. Evaluation consisted of a Knee Society clinical score (KSCS) and radiographic evaluation preoperatively and at annual follow-up. Minimum 2-year follow-up was obtained in 73 of 82 knees (89%). Results were compared to those of a subsequent consecutive series of 76 knees (66 with 2-year follow-up) performed with a mobile-bearing TKA with cemented components with the same indications, implant, technique, and length of follow-up. Six of 73 cementless mobile-bearing TKAs (8%) underwent tibial component revision for symptomatic subsidence and failure of ingrowth compared to 0/66 revisions in the cemented group (P<.05). Patients with cementless mobile-bearing TKA also had a significantly lower KSCS (161 versus 184, P<.05), significantly higher incidence of pain rated more than mild (23% versus 7%, P<.01) and a trend toward less arc of motion (106 degrees versus 115 degrees, P<.2). The results do not support the hypothesis that mobile-bearing TKA imparts the advantage of reliable tibial bone ingrowth.

Progression of radiolucent lines in cementless twin-bearing low-contact-stress knee prostheses: a retrospective study

A total of 134 low-contact-stress (LCS) total knee arthroplasties (TKAs) with mobile meniscal bearings were implanted in 121 patients with a mean age of 74 years (range, 49-91 years) at the time of surgery. The radiographic results obtained from 91 prostheses at an average follow-up of 7.5 years (range, 4.8-9.6 years) showed that radiolucent lines (RLL) appeared most frequently near the tibial plateau (97%) and that most RLL were present immediately postoperatively (67%) or appeared within the first year (96%). RLL were predominantly nonprogressive (99%). Progressive RLL did not affect the fixation or stability of the prosthesis. There were no revisions for aseptic loosening. Cementless LCS TKA achieves excellent radiologic and clinical midterm results.

Results of rotating-platform, low-contact-stress knee prosthesis

Low-contact-stress (LCS) rotating-platform knee arthroplasties in 31 consecutive patients with 50 deformed knees were evaluated at a mean follow-up of 4.5 years (range, 4-6 years). Overall results were good in 72% of 22 osteoarthritic knees and 71.4% of 28 rheumatoid knees. None of the knees showed any change in component position and alignment, osteolysis, or cement-bone radiolucency during follow-up. LCS prosthesis takes care of some rotational component mismatch. Complications included 2% dislocation, 4% anteroposterior instability, and 10% subluxation of the rotating platform. The overall reoperation rate of 10% was significantly higher than reported for the fixed bearing series, and we feel that LCS prosthesis is unsuitable for severely deformed knees.