Long-term survival of semi-constrained total knee arthroplasty for revision surgery

Constraint degree in revision total knee replacement: a registry study on 1432 patients

PURPOSE

Total knee replacement (TKR) failure represents a hard challenge for knee surgeons. TKR failure can be managed in revision with different constraint, related with soft and bone knee damages. The choice of the right constraint for every failure cause represents a not summarized entity. The purpose of this study is identifying distribution of different constraints in revision TKR (rTKR) for failure cause and the overall survival.

METHODS

A registry study based on the Emilia Romagna Register of the Orthopaedic Prosthetic Implants (called RIPO) was performed with a selection of 1432 implants, in the period between 2000 and 2019. Selection implants including primary surgery constraint, failure cause and constraint revision for every patient, and divided for constraint degrees used during procedures (Cruciate Retaining-CR, Posterior Stabilized-PS, Condylar Constrained Knee-CCK, Hinged).

RESULTS

The most common cause of primary TKR failure was aseptic loosening (51,45%), followed by septic loosening (29,12%). Each type of failure was managed with different constraint, the most used was CCK in the most of failure causes, such as to manage aseptic and septic loosening in CR and PS failure. Overall survival of TKA revisions has been calculated at 5 and 10 years for each constraint, with a range of 75.1-90.0% at 5 years and 75.1-87.5% at 10 years.

CONCLUSION

Constraint degree in rTKR is typically higher than primary, CCK is the most used constraint in revision surgery with an overall survival of 87.5% at 10 years.

Mid-term clinical radiological results of the constrained condylar knee prosthesis in total knee revision

INTRODUCTION

The aim of the present study is to analyze the clinical-radiological outcomes of patients undergoing knee prosthesis revision surgery using constrained condylar prosthesis (LCCK; Zimmer-Biomet).

MATERIAL AND METHODS

Retrospective study of 89 patients operated on between the years 2008 and 2020 with a minimum of 2 years of follow-up. Clinical outcomes were evaluated using the WOMAC Index score and KOOS scales. Radiological results (radiolucent lines, osteolysis, and cortical hypertrophy) were evaluated by two independent observers. Implant survival was analyzed using the Kaplan-Meier method.

RESULTS

At the end of follow-up, a mean WOMAC Index score of 78.67 and KOOS score of 68.8 were obtained. Radiolucent lines (both non-progressive and progressive) were detected in 83.3% of the patients in the sample. Areas of osteolysis > 5 mm around the components were present in 6.75%. Cortical hypertrophy was seen around the femoral stem in 20.3% of cases, around the tibial stem in 20.3% and around both components in 6.76%. No statistically significant relationship was found between the presence of radiolucent lines, osteolysis or cortical hypertrophy with functional results. Implant survival was 88.1% at 13 years.

CONCLUSION

The present study shows high survival of LCCK prosthesis in revision surgery. The progressive radiolucencies, were associated with worst clinical outcome.

Clinical outcome and survival rate of condylar constrained knee prosthesis in revision total knee arthroplasty: an average nine point six year follow-up

PURPOSE

Condylar constrained knee prostheses (CCK) are increasingly used in revision total knee arthroplasty (rTKA), but the clinical effectiveness and long-term survival remain a debate. The purpose of this study is to report the long-term clinical and radiographic outcome, implant survival rate, and surgical safety of revision total knee arthroplasty with condylar constrained knee prosthesis.

METHODS

A retrospective cohort study was performed on patients undergoing rTKA with CCK. The cases who received rTKA with CCK from January 2005 to January 2022 were selected. The duration of operation, the estimated perioperative blood loss, and the intraoperative blood transfusion rate were recorded to evaluate surgical safety. The pain visual analog scale (VAS), range of motion (ROM), the Hospital for Special Surgery (HSS) score, the Knee Society Score (KSS), the Western Ontario and McMaster University Osteoarthritis Index (WOMAC), and the Oxford knee score (OKS) was recorded to assess clinical outcome. Standard anteroposterior, lateral, skyline and long-standing AP radiographs of the lower limbs were conducted to assess radiographic outcome. Implant survival was analyzed by Kaplan-Meier survival estimates.

RESULTS

Fifty-five cases were followed up for an average of 9.6 years (1-18 years), including 16 males and 38 females, with an average age of 66 and an average BMI of 26.9 kg/m2. The  main reasons for revision were periprosthetic infection (32 knees, 58.2%) and aseptic loosening (13 knees, 23.6%). The duration of operation was 149 ± 56.2 min. The perioperative blood loss was 973.6 ± 421.6 ml. At the last follow-up, VAS (8.0 ± 1.1 to 1.3 ± 1.4), ROM (82.7° ± 26.1° to 108.4° ± 11.8°), HSS (45.0 ± 10.4 to 85.3 ± 8.6), KSKS (38.4 ± 12.1 to 88.5 ± 12.0), KSFS (19.6 ± 12.9 to 68.8 ± 15.1), WOMAC (67.9 ± 12.5 to 14.4 ± 9.5), and OKS (9.9 ± 4.2 to 41.6 ± 7.7) were significantly improved (P < 0.001). A total of five complications were observed, all of which were periprosthetic infection. Non-progressive radiolucent lines were observed in 26 knees (47.3%). The 10-year survival rate for no operation was 96.0%. The ten year survival rate for no revision was 98.0%.

CONCLUSION

The use of CCK prosthesis for rTKA can achieve good long-term efficacy and prosthesis survival.

Epiphyseal fixation in revision total knee arthroplasty: a comparison between trabecular metal and titanium augments

INTRODUCTION

The purpose of this retrospective study was to compare the medium-term clinical and radiographic outcomes of two series of patients treated for revision TKA: one implanted with trabecular metal (TM) augments and one implanted with classic titanium augments.

MATERIALS AND METHODS

A total of 85 patients with a type 2 AORI defect underwent revision TKA and were treated either with TM epiphyseal augments directly screwed in the bone or with traditional titanium augments. There were 46 patients in the TM group and 39 patients in the titanium group included in the study. All the patients received the same varus-valgus constrained implant and no metaphyseal fixation devices were used.

RESULTS

After a mean follow-up of 66.4 months, no statistically significant difference was observed in terms of failure for aseptic loosening between the two groups (4% in the TM group and 7.8% in the titanium group, p = 0.35). The ten-year survival using aseptic loosening as endpoint was 90.5% (95% CI 94.1-98.6) in the TM group and 85% (95% CI 101.9-119.3) in the titanium group (p = 0.26). A statistically significant difference was detected for the presence of RLL. No RLL were found under the studied TM augments compared to 13.7% of the titanium augments (p = 0.01).

CONCLUSION

The use of TM augments directly screwed to the epiphysis of the femur and the tibia reduced the incidence of RLL compared to standard titanium augments during revision TKA with promising medium-term results.

High Survivorship of Hybrid Fixation Technique in Aseptic Condylar Revision Total Knee Arthroplasty with Minimal Metaphyseal Bone Loss: 5-10 Year Clinical Outcomes

The aim of this study was to evaluate the outcomes of hybrid fixation technique in aseptic condylar revision total knee arthroplasty (rTKA). A retrospective consecutive study of patients with minimal metaphyseal bone loss who underwent aseptic rTKA with press-fit cementless femoral stems and short cemented tibial stems. Primary outcome measure was mechanical failure. Surgical complications, reoperations and revision for any cause were collected and Knee society score at final follow-up. Kaplan-Meier survival curves were used to estimate implant survivorship. Seventy-three patients were included with minimum 5 years follow-up with a mean age of 74.5 years. At mean follow-up of 8.5 years (range 5-10), only two patients required revision, both for infection. Radiographic evaluation was undertaken for all remaining patients at final follow-up and showed no evidence of mechanical failure. Six patients (8.4%) showed non-progressive radiolucent lines around the cementless femoral stem with only one having a pedestal at the tip of the femoral stem and four patients (5.6%) showed non-progressive radiolucent lines around the cemented tibial stem. Mean KSS score was 80.6 (standard deviation 13.8) indicating satisfactory clinical outcomes. Using "any cause implant revision" as an end point, implant survivorship for this construct was 97.3% at mean 8.5 years. In our experience, a hybrid fixation technique with a press-fit cementless femoral stem and a short-cemented tibial stemmed construct achieves excellent medium- to long-term outcomes in aseptic condylar revision cases with minimal metaphyseal bone loss.

Is a greater degree of constraint really harmful? Clinical biomechanical comparative study between condylar constrained knee and rotating hinge prosthesis

BACKGROUND

The real degree of constraint of rotating hinge knee and condylar constrained prostheses is a matter of discussion in revision knee arthroplasty. The objective of this study is to compare the tibial rotation between implants in the clinical settings.

METHODS

An investigator blinded experimental study was designed including 20 patients: in 10 of them a rotating hinge knee prosthesis (Endomodel®, LINK) was implanted and in the remaining 10 a constrained condylar knee prosthesis (LCCK®, Zimmer) was used. A medial parapatellar approach was performed and implantation was performed according to conventional surgical technique. Tibial rotation was measured with two accelerometers in full extension and at 30°, 60° and 90° of flexion. Pre and postoperative Knee Injury and Osteoarthritis Outcome Score was recorded.

FINDINGS

Both groups were homogenous in age (73.4 years in rotating hinge knee prosthesis vs 74 years in constrained condylar knee group), sex, laterality and preoperative Knee Injury and Osteoarthritis Outcome Score (p > 0.05). The postoperative Knee Injury and Osteoarthritis Outcome Score was significantly higher in the rotating hinge knee prosthesis group (80.98 vs 76.28). The degrees of tibial rotation measured by inertial sensors in the rotating hinge knee prosthesis group were also significantly higher than those measured in the constrained condylar knee group (5.66° vs 2.1°) with p = 0.001.

INTERPRETATION

Rotating hinge knee prosthesis appears to represent a lower rotational constraint degree than constrained condylar knee systems in clinical practice and it may increase the clinical satisfaction. The clinical significance: Rotating hinge knee prosthesis appears to represent a lower constraint degree than constrained condylar knee systems in clinical practice.

Condylar constrained and rotating hinged implants in revision knee arthroplasty show similar survivorship and clinical outcome: a systematic review and meta-analysis

PURPOSE

In revision total knee arthroplasty (TKA) ligament instability and bone defects might require more constraint implants such as a condylar constrained knee (CCK) or rotating hinged knee (RHK). When both implants are suitable, the choice remains controversial. The purpose of this systematic review and meta-analysis was to compare the survivorship and clinical outcome between CCK and RHK in revision TKA.

METHODS

Systematic literature research was performed. Studies analysing the clinical outcome and/or survivorship of CCK and/or RHK in revision TKA were included. Clinical outcomes included the Knee Society Score, both clinical (KSCS) and functional (KSFS), range of motion (ROM) and reoperations. Survival was defined as the time free from removal or revision of the femoral and/or tibial component.

RESULTS

A total of 40 articles analysing 4.555 knees were included. Survival did not differ between RHK and CCK implants (p = 0.6058), with, respectively, 91.6% and 89.8% survival after 5 years. Postoperative KSCS and KSFS were, respectively, 79.2 (SD 10.7) and 61.1 (SD 21.8) for the CCK group. Similar scores were noted for the RHK group with a KSCS of 80.2 (SD 14.1) and KSFS of 58.5 (SD 17.3). Postoperative ROM was similar for CCK (105.3°, SD 17.1°) and RHK patients (104.1°, SD 16.9°).

CONCLUSION

This meta-analysis revealed that both survivorship and clinical outcome are similar for CCK and RHK patients for whom both designs are technically suitable and indicated.

LEVEL OF EVIDENCE

IV.

Is hybrid fixation in revision TKA using LCCK prostheses reliable?

INTRODUCTION

The optimal technique for component fixation in revision total knee arthroplasty (rTKA) remains controversial: full cementation (FC) versus hybrid fixation (HF), which involves press-fit stem with cement fixation in the metaphyseal and epiphyseal zones. Previous series have either demonstrated the superiority of one or the other of these techniques or their equivalence. However, few studies have compared these 2 methods for rTKA using the Legacy® Constrained Condylar Knee (LCCK) prosthesis (Zimmer, Warsaw, Indiana, USA).

HYPOTHESIS

Our hypothesis was that HF of LCCK components is associated with a higher rate of aseptic loosening (AL) than FC.

MATERIALS AND METHODS

This was a single-center, multi-surgeon, retrospective study. Primary revisions between January 2010 and December 2014 were included for all indications. The only exclusion criterion was death without revision before the 5-year follow-up. The primary objective of this study was to compare the survivorship of 2 groups of LCCK components (femoral or tibial), depending on whether their stems had been cemented (HF versus FC), taking AL, revised or not, as the endpoint. The secondary objective was to look for other predictive factors of AL.

RESULTS

A total of 75 rTKAs (150 components) were included. The FC group (51 components) had more Anderson Orthopedic Research Institute (AORI) type 2B and type 3 bone defects (BDs) (p<0.001), more reconstructions using trabecular metal (TM) cones (19 FCs and 5 HFs; p<0.001), and bone allografts (p<0.001). At more than 5 years, none of the FC components were loose compared to 10 HF components (9.4%), with 4 of these stems revised. The only significant difference was survivorship without radiographic AL at 9 years (FC=100%; HF=78.6%; p=0.04). The only predictive factor of AL in the HF group was the filling of the diaphyseal canal (p<0.01). The detrimental effect of BD severity (p=0.78) and the protective effect of TM cones were not demonstrated (p=0.21).

DISCUSSION

Other series studying revisions using the same type of prosthesis also concluded the superiority of FC, not found for other revision prostheses. Despite this study's limitations (retrospective, multi-surgeon, limited sample size, and limited follow-up), all patient outcomes were known, and the difference in survivorship between the groups was very significant.

CONCLUSION

HF has not been proven effective for the LCCK prosthesis. Better diaphyseal filling, wider metaphyseal bone tunnels enabling better cement injections, and stem designs more appropriate for press-fit fixation could improve these results. TM cones are an interesting avenue for further research.

LEVEL OF EVIDENCE

III; retrospective comparative study.

Does stem profile have an impact on the failure patterns in revision total knee arthroplasty?

INTRODUCTION

Revision total knee arthroplasty (RTKA) has been increasing continuously. The results of RTKA still remain unsatisfactory. Failure patterns and risk factors in RTKA were thoroughly analyzed, with periprosthetic joint infections (PJI) and aseptic loosening remaining at the forefront of re-revision (ReRTKA) causes. While there is evidence that stem profile impacts the revisability of cemented implants, its association with the modes of RTKA failure is unknown.

METHODS

50 consecutive ReRTKA performed in a single orthopedic center during 2016-2017 were retrospectively analyzed. The cases were stratified according to age, sex, number of preexisting revisions, fixation technique, stem design and causes of re-revision. All explanted implants with conical vs. cylindrical stem profiles were compared.

RESULTS

Mean age was 67 ± 11.5, and 54% were females. 72% of the cases had ≥ 3 previous revisions. 88% were full-cemented, 3% hybrid and 9% press-fit stems. 36% of the RTKA had conical, 58% cylindrical and 6% combined stem profiles. 92% of the RTKA components were removed. Removal causes were: PJI (52.2%), aseptic loosening (34.8%), implant malposition (9.8%), painful knee (1.1%) and instability (2.2%). While the overall RTKA failure patterns were equally distributed between conical and cylindrical stems, subgroup analysis of only cemented ReRTKA revealed a higher incidence of aseptic loosening within cylindrical stem profiles (46.7% vs. 25.7%, P = 0.05).

CONCLUSION

Stem profile may have an impact on the process of aseptic loosening in cemented non-metaphyseal engaging RTKA, with cylindrical designs tending to worse outcomes than conical designs. Large cohort studies could provide more clarity on current observation.

Impact of stem profile on the revisability and the need for osteotomy in well-fixed cemented revision total knee arthroplasty implants

INTRODUCTION

While re-revision total knee arthroplasty (ReRTKA) steadily increases, the ease and bone-sparing removal of RTKA implants is gaining more and more in importance. Biomechanical data suggest that cemented conical stems can be removed significantly easier than cylindrical stems. However, no clinical evidence exists supporting this observation. Aim of this study was to compare the revisability and need for osteotomy (OT) between removals of well-fixed cemented conical vs. cylindrical RTKA stems.

MATERIALS AND METHODS

55 removals of well-fixed full-cemented RTKA stems (29 knees) performed between 2016 and 2018 were retrospectively analyzed. Main outcome variables were: bone loss, fractures, osteotomy incidence, surgery duration, early postoperative complications (EPC), hemoglobin drop and blood transfusion. SPSS was used for the statistical analysis.

RESULTS

44.8% were conical, 48.3% cylindrical, and 6.9% combined stem designs. Causes for re-revision were PJI (75.9%), malposition (17.2%) and persistent pain (6.9%). 10 stem removals (18.2%) required an OT (four femoral, six tibial): eight stems (14.5%) had cylindrical and two (3.6%) conical designs (P = 0.041). Fractures were noted solely in removals without OT (11.1% vs. 0%,). There was a tendency to more bone loss in cylindrical stem revisions (53.8% vs. 32%, P = 0.24). A longer overall surgery time was observed in revisions of cylindrical stems (+ 37 min, P = 0.05). There was higher hemoglobin drop and need for blood transfusion in revisions of cylindrical stems or after OT but without reaching statistical significance. The EPC rates were slightly higher in ReRTKA on cylindrical stems (P = 0.28).

CONCLUSION

Well-fixed cemented conical stems may be revision friendlier with less demands on OT and shorter overall surgery time than cemented cylindrical stems.

Similar outcomes of constrained condylar knee and rotating hinge prosthesis in revision surgery for extension instability after primary total knee arthroplasty

BACKGROUND

Instability is one of the most common reasons for total knee arthroplasty (TKA) failure. Constrained prosthesis can be used for significant ligamentous laxity, but there is not much evidence on the appropriate level of restriction for unstable varus-valgus TKA. The objective of this study was to compare the outcome and survival at a minimum follow-up of five years between rotating hinge knee prosthesis (RHK) and constrained condylar knee prosthesis (CCK) for extension instability following primary TKA.

HYPOTHESIS

For symptomatic extension instability after primary TKA, good functional outcomes and survival can be achieved with both designs.

MATERIAL AND METHODS

Consecutive patients with unstable primary TKA who underwent revision with either RHK (n=34) or CCK (n=30) were retrospectively compared. Assessments were performed by the Knee Society Scores (KSS), and visual analogue scales (VAS) for pain and patient satisfaction. Radiological evaluation was made. Complications and re-operations were analyzed.

RESULTS

Mean post-operative follow-up was 10.3 (range 5-16) years for both groups. At the final follow-up, there was no significant difference between groups in the KSS-knee (p=0.228) or KSS-function (p=0.324) score, VAS-pain (p=0.563), VAS-satisfaction (p=0.780), major complication rate (p=0.194), or TKA survival at 10 years (p=0.091).

CONCLUSION

The present study showed comparable good functional outcomes and survival at long-term between RHK and CCK arthroplasties. Both designs can be recommended for revision of total knee arthroplasty with symptomatic extension instability.

LEVEL OF EVIDENCE

Level III.

Improved surgical procedure of primary constrained total knee arthroplasty which enables use of the femoral diaphyseal straight extension stem

Background

In performing primary constrained total knee arthroplasties (TKA) to imbalanced knees, the offset stem is sometimes compelled to use, although this is associated with surgical difficulties. We developed a modified procedure which might be able to fit the anteroposterior (AP) and mediolateral (ML) position of the femoral component simultaneously with the straight stem. Purposes of this study were to evaluate usefulness of the modified procedure both in computer simulations and actual surgeries.

Methods

We included 32 knees that had undergone primary TKA using constrained implants because of the coronal imbalance. In the component-first procedure, the distal femur was prepared to fit the AP and ML position of the femoral component simultaneously at first, as in primary TKA. Finally, the stem hole is created based on the femoral component position (the component-first procedure). The femoral component and extension stem were simulated using the three-dimensional planning software (ZedKnee) following the component-first procedure. We investigated the suitability of the straight stem through computer simulation and evaluation of actual surgeries. Clinical and radiographical outcomes were also evaluated at the latest follow-up.

Results

The component-first procedure enabled the AP and ML position of the femoral component to be fitted simultaneously with the straight stem in simulations and actual surgeries in all cases. The stem diameter was not significantly different between simulations and actual surgeries (13.9 and 13.7 mm on average, respectively, p = 0.479) and almost similar from intraclass correlation coefficient analysis (kappa value 0.790). Clinical and radiographical outcomes were almost similar to primary TKA cases and there was no case of component loosening, cortical bone hypertrophy around the stem and stem-tip pain.

Conclusions

Our improved surgical procedure may facilitate use of the constrained implant for more cases of primary TKA in imbalanced knees without the usual surgical difficulties.

Trial registration

Retrospectively registered.

Good to excellent long-term survival of a single-design condylar constrained knee arthroplasty for primary and revision surgery

PURPOSE

The purpose of the study was to determine the long-term survivorship, functional outcomes of a single-design condylar constrained (CCK) TKA in primary and revision cases as well as to assess specific risk factors for failure. It was hypothesized that primary CCK TKA had a better survival than revision knees.

METHODS

One hundred and forty three patients who underwent revision TKA (n = 119) or complex primary TKA (n = 24) using a single-design condylar constrained knee system (Genesis CCK, Smith & Nephew) performed at a single institution between 1999 and 2008 were retrospectively included. The median follow-up amounted to 11.8 years (IQR 10.3-14.4). Implant survivorship was analyzed using Kaplan-Meier survival estimates and multivariate Cox regression analysis to identify risk factors for failure. Function was determined using the Oxford Knee Score (OKS).

RESULTS

The implant survival was 86.4% after five, 85.5% after ten and 79.8% at 15 years. A reduced implant survivorship was found in males (HR 5.16, p = 0.001), smokers (HR 6.53, p = 0.004) and in obese patients (HR 2.26, p = 0.095). Patients who underwent primary TKA had a higher revision-free implant survivorship compared to revision TKA at 15 years (100% vs. 76%, p = 0.036). The main cause for re-revision was infection in 10% of all revision TKA performed with the CCK design included, while no case was revised for instability. The median OKS was 39 (IQR 35-44) in 102 patients available for long-term functional outcome.

CONCLUSION

CCK implants are associated with excellent long-term survival when used in primary TKA; however, survival was worse when used during revision TKA. Males, smokers, obese patients and are at higher risk for revision. While instability and aseptic loosening were rare, infection remains a major concern.

LEVEL OF EVIDENCE

Level IV, retrospective observational study.

Primary and Revision Total Knee Arthroplasty in Patients With Pulmonary Hypertension: High Perioperative Mortality and Complications

BACKGROUND

Although perioperative medical management during total knee arthroplasty (TKA) has improved, there is limited literature characterizing outcomes of patients with pulmonary hypertension (HTN). This study examined mortality, medical complications, implant survivorship, and clinical outcomes in this medically complex cohort.

METHODS

We identified 887 patients with pulmonary HTN who underwent 881 primary TKAs and 228 revision TKAs from 2000 to 2016 at a tertiary care center. Patients were followed up at regular intervals until death, revision surgery, or last clinical follow-up. Perioperative medical complications were individually reviewed. The risk of death was examined by calculating standardized mortality ratios and Cox proportional hazards regression models. Cumulative incidence analysis was used for reporting mortality, revision, and reoperation with death as a competing risk.

RESULTS

The 90-day mortality was 0.7% and 4.8% for primary and revision TKAs, respectively. The risk of death was 2-fold higher compared to primary (hazard ratio 2.54, 95% confidence interval [CI] 2.12-3.05) and revision (hazard ratio 2.16, 95% CI 1.78-2.62) TKA patients without pulmonary HTN. Rate of medical complications within 90 days from surgery was 6.5% and 14% in primary and revision TKAs. The 10-year cumulative incidence of any revision was 5% and 16% in primaries and revisions, respectively.

CONCLUSION

Patients with pulmonary HTN undergoing primary and revision TKAs had excess risk of death and experience a high rate of medical complications within 90 days of surgery. Counseling of risks, medical optimization, and referral to tertiary centers should be considered.

LEVEL OF EVIDENCE

Level IV.

High Survivorship of Short-Cemented Femoral Stems in Condylar Revision Total Knee Arthroplasty Without Significant Metaphyseal Bone Loss: Minimum 5-Year Follow-Up

BACKGROUND

We aimed to evaluate the outcomes of hybrid fixation technique in condylar revision total knee arthroplasty (rTKA) using cementless metaphyseal tibial sleeves and short-cemented femoral stems with a rotating platform articulation.

METHODS

Retrospective consecutive study of all condylar rTKAs with a cemented femoral stem between 2009 and 2016 was conducted. Patients were identified using a local prospective database and linkable data obtained from the National Joint Registry for rTKA. Demographic, clinical, and surgical data were collected from patients' electronic health records. The primary outcome measure was mechanical failure and implant survivorship using a nationally collected data, complications, re-operations, and "any-cause revision" were also recorded.

RESULTS

There were 72 consecutive patients (72 knees) with minimum 5-year follow-up: 33 (45.8%) females and 39 (54.2%) males with a median age of 70 years (range 47-88). The indication for revision surgery was aseptic loosening (n = 34, 47.2%), instability (n = 17, 23.6%), infection (n = 14, 19.5%) with 10 patients having 2-stage approach and 4 patients with single-stage approach, stiffness (n = 4, 5.6%), and malalignment (n = 3, 4.1%). At mean follow-up of 6.87 years (median 6.7; range 5-11.8), only 2 patients required revision for infection. Using "any-cause implant revision" as an end point, implant survivorship for this construct was 97.2% at median 6.7 years. To date, none of the femoral stems have been revised for mechanical failure.

CONCLUSION

In rTKA with good femoral condylar bone stock, we have shown excellent survivorship with a short-cemented femoral stem, in conjunction with a mobile-bearing and a tibial sleeve. This has the advantage of reducing the length of the revision construct of this complex surgery.

LEVEL OF EVIDENCE

Level IV.

Infection and periprosthetic fracture are the leading causes of failure after aseptic revision total knee arthroplasty

AIM

The purpose of this study was to clarify the medium to long term survival of aseptic revision total knee arthroplasty (RTKAs) and identify the common modes of failure following RTKAs.

MATERIALS AND METHODS

A multi-center, retrospective study included all aseptic RTKAs performed at three tertiary referral hospitals between 2003 and 2016. Patients were excluded if the revision was for prosthetic joint infection (PJI) or they had previously undergone revision surgery. Minor revisions not involving the tibial or femoral components were also excluded. Demographics, surgical data and post-operative outcomes were recorded and analyzed. Survival analysis was performed and the reasons for revision failure identified.

RESULTS

Of 235 aseptic RTKAs identified, 14.8% underwent re-revision at mean follow-up of 8.3 years. Survivorship of RTKA was 93% at 2 years and 83% at 8 years. Average age at revision was 72.9 years (range 53-91.5). The most common reasons for failure following RTKA were periprosthetic joint infection (PJI) (40%), periprosthetic fracture (25.7%) and aseptic loosening (14.3%). Of those whose RTKA failed, the average survival was 3.33 years (8 days-11.4 years). No demographic or surgical factors were found to influence RTKA survival on univariate or multivariate analysis.

CONCLUSION

PJI and periprosthetic fracture are the leading causes of re-revision surgery following aseptic revision TKA. Efforts to improve outcomes of aseptic revision TKA should focus on these areas, particularly prevention of PJI.

The knee prosthesis constraint dilemma: Biomechanical comparison between varus-valgus constrained implants and rotating hinge prosthesis. A cadaver study

The real degree of constriction of rotating hinge knee (RHK) and condylar constrained prostheses (CCK) is a matter of discussion in revision knee arthroplasty. The objectives of this study are to compare the tibial rotation of both implants and validate the use of inertial sensors with optical tracking system as movement measurement tools. A total of 16 cadaver knees were used. Eight knees were replaced using a RHK (Endomodel LINK), and the remaining eight received a CCK prosthesis (LCCK, Zimmer). Tibial rotation range of motion was measured in full extension and at 30°, 60°, and 90° of flexion, with four continuous waveforms for each measurement. Measurements were made using two inertial sensors with specific software and compared with measurements obtained using the gold standard technique - the motion capture camera. The comparison of the accuracy of both measurement methods showed no statistically significant differences between inertial sensors and motion capture cameras, with p > .1; the mean error for tibial rotation was 0.21°. Tibial rotation in the RHK was significantly greater than in the CCK (5.25° vs. 2.28°, respectively), p < .05. We have shown that RHK permit greater tibial rotation, being closer to physiological values than CCKs. Inertial sensors have been validated as an effective and accurate method of measuring knee movement. The clinical significance: RHK appears to represent a lower constriction degree than CCK systems.

Good clinical and radiological outcomes of the varus-valgus constrained mobile-bearing implant in revision total knee arthroplasty

PURPOSE

Knee instability is one of the most common indications for having to undergo revision total knee arthroplasty (RTKA) and can be prevented with adequate implant selection and good surgical technique. Varus-valgus constrained implants (VVC) are indicated for cases of RTKA with absent ligament function in order to provide the necessary stability. While mobile-bearing articulations are thought to decrease the risk of aseptic loosening in comparison to their fixed-bearing counterparts, there is limited data on their outcomes. The purpose of our study is to present the clinical and radiological outcomes for patients undergoing an RTKA procedure with the mobile-bearing VVC implant.

METHODS

Between January 2008 to January 2018, 93 patients underwent RTKA with the use of varus-valgus mobile-bearing (VVCMB) prosthesis. The main indications for RTKA were instability 38.7% (n = 36), aseptic loosening 31.2% (n = 29), infection in 26.9% (n = 25), and other 3.3%. The mean follow-up time was 56 months. Clinical outcomes were assessed by knee society scores, range of motion, and rate of re-operation.

RESULTS

The mean knee society score increased significantly from 65.52 pre-operatively to 89.65 post-operatively (p < 0.001). The five year cumulative incidence of re-operation in our study was 7.53% (n = 7). Our study reported no cases of aseptic loosening or mobile-bearing spin-out. The number of flexion contractures decreased from n = 23 (24.7%) pre-operatively to n = 11 (11.8%) post-operatively (p < 0.05).

CONCLUSION

The VVC mobile-bearing prosthesis demonstrated good clinical outcomes and mid-term survivorship in patients undergoing RTKA. Additional follow-up is required in the long term.

Why Do Revision Total Knee Arthroplasties Fail? A Single-Center Review of 1632 Revision Total Knees Comparing Historic and Modern Cohorts

BACKGROUND

Utilization of revision total knee arthroplasty (TKA) has been increasing, and reasons for failure are less understood than those of primary TKA. The purpose of this study is to identify the rates and mechanisms of failure of revision TKA, and compare those between a historic (1986-2005) and modern (2006-2015) cohort.

METHODS

All revision TKAs performed at a single institution between 1986 and 2015 were reviewed, with minimum 2-year follow-up. Failure was defined as a second revision surgery in which any component was exchanged. Diagnosis at the time of index and any re-revision procedure was determined.

RESULTS

In total, 1632 revision TKAs in 1560 patients were reviewed. The average age was 65.1 and the average follow-up was 61.4 months. Overall failure rate was 22.8%, with no significant differences between the historic and modern cohort (25.1% vs 22.0%, P = .19). The leading cause for failure was infection in 38.5% of failures. The next most common causes for failure were aseptic loosening (20.9%) and instability (14.2%). Failure rate among revision TKAs for infection was 33%, with 67.2% failing due to repeat infection. Multivariate analysis found that septic index revision (odds ratio [OR] 1.91, 95% confidence interval [CI] 1.47-2.48), male gender (OR 1.41, 95% CI 1.11-1.78), and age less than 65 (OR 1.56, 95% CI 1.23-1.97) were independent risk factors for failure.

CONCLUSION

There remains a high rate of failure in revision TKA, with infection being the most common reason for failure. Rates and primary reasons for failure have not changed significantly in the past decade.

Long-Term Outcome Following Revision Total Knee Arthroplasty is Associated With Indication for Revision

BACKGROUND

There is limited information about long-term clinical outcomes following revision total knee arthroplasty (TKA) in relation to the indication for revision. Previously, a clear relation between indication for revision and clinical outcome was shown after 2 years. Present study evaluated (1) whether the reported association at 2 year remains present at 7.5 years, and (2) how clinical outcome at 7.5 years developed compared to baseline and 2-year follow-up, and (3) whether patients had additional adverse events.

METHODS

A cohort of 129 patients with a total system revision TKA was selected. Range of motion, Visual Analog Scale for pain and satisfaction, and clinical and functional Knee Society Score were obtained preoperatively, at 3 months, 1, 2, and 7.5 years. Reasons for revision were septic loosening, aseptic loosening, malposition, instability, and severe stiffness.

RESULTS

Patients revised for severe stiffness had significantly worse outcomes. No difference was found between the other indications. The clinical outcome after revision TKA at 7.5 years remained stable for septic and aseptic loosening, malposition, and instability but deteriorated slightly for the severe stiffness group. Visual Analog Scale satisfaction remained constant for all indications. There were 11 additional complications between 2- and 7.5-year follow-up, 9 of which necessitated reoperation.

CONCLUSION

All indications except severe stiffness had a similar clinical outcome which was maintained up to 7.5-year follow-up. The severe stiffness group had worse outcomes and deteriorated slightly at longer follow-up. Outcome at 3 months seems predictive for long-term outcome. Additional complications did not differ significantly for the different reasons for revision.

LEVEL OF EVIDENCE

Level III, prognostic study.

Long-Term (Up to 21 Years) Survival of Revision Total Knee Arthroplasty with Use of a Constrained Condylar Knee Prosthesis: A Concise Follow-up of a Previous Report

In our original report, 97 patients (114 knees) underwent revision total knee arthroplasty with use of a Legacy Constrained Condylar Knee prosthesis (LCCK; Zimmer), with a mean follow-up of 7.2 years (range, 5 to 10 years). The purpose of the present study was to determine the long-term clinical and radiographic results, with a focus on component fixation and the prevalence of osteolysis. At a mean follow-up of 19.2 years (range, 16 to 21 years), re-revision of the LCCK prosthesis had been performed in 10 knees (9%). The rate of survival at 19.2 years was 96% (95% confidence interval [CI], 94% to 100%) with reoperation for mechanical failure as the end point, and 91% (95% CI, 87% to 98%) with reoperation for any reason as the end point. One knee had circumferential osteolysis around the components. LEVEL OF EVIDENCE:: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Varus-Valgus Constrained Implants With a Mobile-Bearing Articulation: Results of 367 Revision Total Knee Arthroplasties

BACKGROUND

Varus-valgus constrained (VVC) implants are used for compromised ligamentous stability in revision total knee arthroplasties (TKAs). Mobile-bearing VVC implants may reduce rotational forces; yet, limited clinical data exist. The purpose of this study is to report mid-term risk of re-revision, complications, and clinical outcomes with a mobile-bearing VVC implant.

METHODS

Three hundred thirty-seven patients (367 TKAs) who underwent revision TKA with a mobile-bearing VVC implant between 1999 and 2013 at a single institution were reviewed. Mean age at revision was 67 years. Mean follow-up was 4 years. The main indications for revision were aseptic loosening in 158 cases (43%), reimplantation after 2-stage exchange arthroplasty in 120 (33%), instability in 61 (17%), and other in 28 (7%). Clinical outcomes were assessed by Knee Society Scores, and survivorship was analyzed with death as the competing risk.

RESULTS

The 5-year cumulative incidences of any re-revision or re-revision for aseptic loosening were 9% and 3%, respectively. Twenty-six knees (7%) were re-revised: 15 for infection, 6 for aseptic loosening, and 5 for other causes. There were 17 cases of irrigation and debridement, 10 cases of manipulations under anesthesia, and 9 cases of periprosthetic fractures. There were no bearing "spin-outs." The mean Knee Society Scores improved from 45 preoperatively to 77 at most recent follow-up (P < .001).

CONCLUSION

The functional improvement and 5-year cumulative incidence of revision of a mobile-bearing VVC implant demonstrated acceptable outcomes with no unique complications related to the mobile-bearing construct. Additional follow-up will be needed to determine long-term implant survivorship.

Semi-constrained posterior stabilized total knee arthroplasty reproduces natural deep knee bending kinematics

BACKGROUND

The Flexible Nichidai Knee Posterior Stabilized (FNK-PS) system was designed to provide relatively high varus-valgus stabilities without the stem extensions to patients with severe knee joint disorders. This is a combination of a large tibial post and high femoral cam adapted to a PS system. The aim of our study was to analyze the in vivo two-dimensional/three-dimensional registration kinematics of the FNK PS-total knee arthroplasty (TKA) system during deep knee bending.

METHODS

Nineteen knees from 15 total knee arthroplasty (TKA) patients who were able to squat with enough knee flexion were selected. During deep knee bending under weight bearing (WB) and non-weight bearing (NWB) conditions, we quantified range of motion, axial rotation, femoral anteroposterior translation, and post-cam engagement angle.

RESULTS

The maximum-flexion was significantly different between the two conditions. The mean axial femoral external rotation was 4.8° and 6.2° under WB and NWB conditions, respectively, at 120° flexion. Anteroposterior translation based on bicondylar posterior roll-back patterns was noted with increasing knee flexion. Both the medial and lateral femoral aspects were significantly more posterior during early to mid-flexion. Initial post-cam engagement occurred significantly earlier during flexion under NWB than under WB conditions. Under WB, the timing of the post-cam engagement correlated with the maximum flexion .

CONCLUSIONS

The kinematics of the semi-constrained PS system reproducibly exhibited a mild external rotation with smooth posterior roll-back. This was assisted by the engagement of the large tibial post and high femoral cam during the early phase of flexion.

Observational Study of Total Knee Arthroplasty in Aseptic Revision Surgery: Clinical Results

OBJECTIVE

To review the long-term clinical results after revision surgery and the relationship between the different clinical variables involved with a failed total knee arthroplasty (TKA) and its evolution to provide a better understanding of the current treatment methods.

METHODS

The present study involved 89 subjects with a failed knee arthroplasty that ended up requiring revision surgery and component replacement between 2011 and 2015. The study included patients with pain remaining after TKA and indication from the knee unit surgeon to review the implant, without presenting with thromboembolic or neurological changes that could bias the results. The demographic data, surgical information, type of implant, and causes of failure were analyzed. The patients subjected to replacement surgery were specifically asked to fill out clinical and satisfaction questionnaires (Lysholm and KOOS). The mean follow-up was 5.6 years (range, 3-11 years) and the analysis was divided into early revision (<5 years) and late revision (>5 years). The R statistical package version 3.2.5 for Windows was used, with significance less than 0.05 Cohort observational study.

RESULTS

The results indicated that implant revisions accounted for 5.57% of total primary implants, with a mean survival of 6 years for primary prosthesis failure. The mean revision surgery result on the Lysholm knee scoring scale was 68.73 out of 100 points. A better score was obtained for revisions undertaken on TKA with over 5 years' survival and there were no significant differences in terms of the type of implant used. The causes of TKA failure were aseptic loosening (77.38%), instability (9.52%), and painful prosthesis (13.10%). The results were statistically significant when isolated revisions were performed on one component. Rating worse on most of the questionnaire subscales.

CONCLUSION

The clinical results were better in primary implant replacements with at least 5 years' survival. The replacement of only one of the components (tibial or femoral) provided worse clinical results than total replacement.

Quadriceps Snip in 321 Revision Total Knee Arthroplasties: A Safe Technique in a Matched Cohort Study

BACKGROUND

Quadriceps snips (QSs) are commonly used to gain enhanced exposure during revision total knee arthroplasties (TKAs). The goals of this study were to evaluate the longer-term clinical outcomes and complications in a contemporary cohort of patients treated with QS and to compare them to a matched cohort treated with standard exposure during revision TKAs.

METHODS

We retrospectively identified 3107 revision TKAs performed at our institution between 2002 and 2012. QS was performed in 321 of these knees. Each QS revision TKA was 1:1 matched to a control (standard exposure) based on age, gender, body mass index, surgery date, and reason for revision. Clinical outcomes studied included Knee Society Score, range of motion, and extensor lag. Other outcomes assessed were complications (especially extensor mechanism disruption) and survivorship. Mean follow-up was 5 years.

RESULTS

The mean Knee Society Score improvement was not significantly different between groups (P = .9). At latest follow-up, the mean range of motion was 93° in the QS group and was slightly higher at 100° in the control group (P = .002). Postoperative extensor lag of 10 degrees or more was present in 21 (6.7%) QS knees versus 19 (6.8%) control knees (P = .95). Complication rates were similar in both groups with extensor mechanism disruption occurring in 3 in the QS group (0.7% at 10 years) versus 4 in the control group (0.8% at 10 years; P = .91). Kaplan-Meier survivorships free of revision for aseptic loosening, free of any revision, and free of any reoperation were similar at 10 years (85%, 71%, and 61%, respectively, in the QS group vs 89%, 70% and 60%, respectively, in the control group).

CONCLUSION

This matched cohort study is the largest to report the results of QS and also the largest to report results compared with patients treated with standard exposure. Building on the results of smaller historical series, this study demonstrates QS was a facile technique in complex revision TKAs allowing for safe exposure with few complications.

LEVEL OF EVIDENCE

III (case-control study).

Rotating hinge knee causes lower bone-implant interface stress compared to constrained condylar knee replacement

PURPOSE

To compare the stresses at bone-arthroplasty interface of constrained and semi-constrained knee prostheses, using the finite element (FE) method as a predictor of the survivorship of the implants.

METHODS

Three-dimensional FE models of the knee implanted with rotating hinge (RHK) and legacy constrained condylar (LCCK) prostheses were generated to study the loads and stresses for two situations: medial- and lateral collateral ligament deficiencies in full extension.

RESULTS

On average, the shear stress developed at bone-implant interface dropped from 16.9 to 13.7 MPa (18.9%), and the interface von Mises stress lowered from 37.6 to 30.2 MPa (19.6%) in RHK compared to those in LCCK prostheses. RHK design also resulted in a more uniform stress distribution at the interfaces in both femur and tibia. The average polyethylene liner stress dropped from 9.6 to 2.6 MPa (a 72.7% decrease) in RHK design when compared to that in LCCK design.

CONCLUSION

The more uniform interface stress suggests fewer density changes at the periprosthetic regions due to bone remodelling. Moreover, the lower polyethylene stresses are likely to reduce wear and damage. These findings reveal that the RHK design may have more favorable mechanical features compared to LCCK design in full extension boundary conditions, implying a potentially better survivorship. However, the findings should be interpreted cautiously as other configurations were not investigated.

Age, gender, functional KSS, reason for revision and type of bone defect predict functional outcome 5 years after revision total knee arthroplasty: a multivariable prediction model

PURPOSE

The number of revision total knee arthroplasties (rTKA) is increasing. Unfortunately, not all patients benefit from revision surgery. The aim of this study was to develop a clinical prediction model that can be used to predict the functional outcome 5 years after rTKA.

METHODS

Data of patients receiving rTKA at Sint Maartenskliniek, Nijmegen, The Netherlands, from 2004 onwards were prospectively collected. Demographic and clinical variables and patient-reported outcome scores were collected and considered as potential predictors. Beneficial outcome was defined as an increase of ≥ 20 points on the functional knee society scores (fKSS) or an absolute fKSS ≥ 80 points 5 years after surgery. The prediction model was developed using backward logistic regression. Regression coefficients were converted into an easy to use prediction rule.

RESULTS

Overall, 295 rTKA patients were included of whom 157 (53%) had beneficial fKSS 5 years later. Age, gender, femoral bone defects, preoperative fKSS, and stiffness as reason for revision were included in the model. Men had a higher chance of beneficial fKSS than women (OR 1.59, 95% CI 0.91-2.78). Patients with major bone defects (OR 0.44, 95% CI 0.22-0.85), higher age (IQR OR 0.39, 95% CI 0.26-0.58), higher preoperative fKSS (IQR OR 0.42, 95% CI 0.30-0.59), and severe stiffness (OR 0.48, 95% CI 0.20-1.15) had a lower chance of successful outcome. The model's AUC was 0.76, 95% CI 0.70-0.81.

CONCLUSION

Easily determinable characteristics of patients who need rTKA can be used to predict future functional outcome. Young men with low preoperative fKSS without severe stiffness are more likely to achieve a beneficial outcome.

LEVEL OF EVIDENCE

IV.

Biomechanical evaluation of tibial bone adaptation after revision total knee arthroplasty: A comparison of different implant systems

The best methods to manage tibial bone defects following total knee arthroplasty remain under debate. Different fixation systems exist to help surgeons reconstruct knee osseous bone loss (such as tantalum cones, cement, modular metal augments, autografts, allografts and porous metaphyseal sleeves) However, the effects of the various solutions on the long-term outcome remain unknown. In the present work, a bone remodeling mathematical model was used to predict bone remodeling after total knee arthroplasty (TKA) revision. Five different types of prostheses were analyzed: one with a straight stem; two with offset stems, with and without supplements; and two with sleeves, with and without stems. Alterations in tibia bone density distribution and implant Von Mises stresses were quantified.

In all cases, the bone density decreased in the proximal epiphysis and medullary channels, and an increase in bone density was predicted in the diaphysis and around stem tips. The highest bone resorption was predicted for the offset prosthesis without the supplement, and the highest bone formation was computed for the straight stem. The highest Von Mises stress was obtained for the straight tibial stem, and the lowest was observed for the stemless metaphyseal sleeves prosthesis.

The computational model predicted different behaviors among the five systems. We were able to demonstrate the importance of choosing an adequate revision system and that in silico models may help surgeons choose patient-specific treatments.

Results of a Modular Revision System in Total Knee Arthroplasty

BACKGROUND

Revision total knee arthroplasty (TKA) poses unique challenges compared with primary TKA such as bone loss, deformity, and ligament instability. Modular component options allow flexibility to deal with these complexities. The purpose of this study was to evaluate midterm outcomes for revision TKA using a modular revision knee system with complete interchangeability and multiple options for augmentation, offset, constraint, and stem extensions.

METHODS

A query of our practice registry revealed 257 consented patients (274 knees and 278 TKA) with minimum 2-year follow-up who underwent aseptic revision TKA with a modular system (Vanguard Super Stabilized Knee; Zimmer Biomet, Warsaw, IN) between 2005 and 2013. Four patients were rerevised to a second Vanguard Super Stabilized Knee within the study period. Mean age was 68 years, and mean number of previous surgeries was 2 (1-14).

RESULTS

At mean follow-up of 6.0 years (range, 2-11 years), there have been 25 aseptic revisions involving one or more components (9.0%): 15 aseptic loosening with concomitant instability in 2, 8 others with instability, 1 with hypersensitivity, and 1 revised elsewhere for unknown cause. Ten knees were revised for infection. Range of motion improved from 100° preoperatively to 105° most recently. Knee Society clinical scores improved from 45 to 79, and function scores from 46 to 56. Radiographic evaluation revealed satisfactory position, fixation, and alignment in 97% and abnormal findings in 7 knees: 4 limited to the patella, 1 tibial radiolucency, 1 femoral and tibial radiolucency, and 1 tibial subsidence.

CONCLUSION

The results of this modular TKA revision system at 6 years mean follow-up are promising for use in complex scenarios, with a low frequency of aseptic rerevision, good knee stability, and substantial improvements in range of motion and clinical and functional outcomes.

Effect of Stem Size and Fixation Method on Mechanical Failure After Revision Total Knee Arthroplasty

BACKGROUND

Although the need for stemmed components is well accepted to improve mechanical survival in revision total knee arthroplasty (TKA), the ideal fixation method and stem design remain controversial.

METHODS

We performed a retrospective review of 223 patients who underwent revision TKA in whom stemmed components had not been used previously and with a mean follow-up of 61.6 months, including 108 components with fully cemented stems and 316 components with "hybrid" press-fit stems.

RESULTS

Based on a time to event model, risk for mechanical failure was equivalent for both cemented and hybrid stems (relative risk, 0.991; P = .98). Young age was the single greatest risk factor for mechanical failure (P = .006). Although there was a trend toward increased failure with cemented stems in patients aged <65 years, there was no significant difference in risk after accounting for covariates (relative risk, 1.4; P = .50). Intramedullary canal fill, not stem length or diameter, was the strongest predictor of failure with hybrid stems, and risk was reduced by 41.2% for each additional 10% canal fill.

CONCLUSION

In conclusion, both cemented and hybrid modular stems are viable options in revision TKA. Surgeons should attempt to maximize canal filling of hybrid stems to obtain a solid press-fit. In addition, further studies are needed to evaluate the long-term survival of cemented stem fixation in young patients.

Revision Total Knee Arthroplasty for Instability-Outcome for Different Types of Instability and Implants

BACKGROUND

Given the mixed outcome after revision total knee arthroplasty (TKA) for instability in the literature and the relative high recurrence of instability, we were interested in the outcome of a cohort of patients operated for various types of clinical instability and with different types of implants.

METHODS

A total of 77 patients with unstable TKA were completely revised (19 hinged and 58 condylar implants). We classified the patients in 3 instability groups based on the literature: (1) anterior-posterior flexion instability (N = 29); (2) medial-lateral flexion instability (N = 16); and (3) multiplane instability (N = 32). Patients were evaluated up to 24 months postoperatively, concerning Knee Society clinical rating system, range of motion, visual analog scale (VAS) pain, and VAS satisfaction.

RESULTS

For the total group, all outcome scores improved, but substantial residual pain (VAS = 41) was reported. For type of instability, the clinical outcome was similar for all the groups. For type of implant, the hinged group had lower postoperative outcome scores but similar satisfaction scores compared with those in the condylar group. There was a considerable number of insert changes and secondary patellar resurfacing in the condylar group compared with no reoperations in the hinged group. Recurrent instability was not seen in the anterior-posterior flexion instability group and in patients who received a condylar constraint-type implant.

CONCLUSIONS

We recommend 3 options in revision TKA for instability: (1) hinged implants in cases with severe ligament instability in multiple planes or bone loss, (2) condylar implants with a posterior-stabilized insert in cases with isolated posterior cruciate ligament insufficiency, and (3) condylar implants with condylar constraints in all other cases.

Posttraumatic Total Knee Arthroplasty Continues to Have Worse Outcome Than Total Knee Arthroplasty for Osteoarthritis

Small studies have shown that patients who undergo TKA following a distal femur and/or tibial plateau fracture have inferior results. The purpose of this study was to evaluate the mid-term outcomes of a large group of patients undergoing TKA following periarticular knee fractures. We identified 531 patients who underwent a TKA following a periarticular fracture from 1990 to 2012; comparing outcomes to 19,641 patients undergoing primary TKA for osteoarthritis. Periarticular fracture significantly increased the risk of revision TKA, infection and complications. There was no difference in the need for revision TKA or infection based on fracture location. Patients with TKA following a periarticular fracture have worse overall revision free survival compared to with OA, with 1 in 4 patients requiring revision TKA by 15 years.

Long-Term Clinical Outcomes and Survivorship of Revision Total Knee Arthroplasty with Use of a Constrained Condylar Knee Prosthesis

The purpose of this study was to determine long-term clinical and radiographic results. One hundred and ninety-four patients (228 knees) underwent revision TKA with use of a constrained condylar knee prosthesis. The mean duration of follow-up was 14.6 years (range, 11 to 16 years). The mean pre-revision Knee Society knee scores (43.5 points) and function scores (47.0 points), and Western Ontario and McMaster Universities Osteoarthritis index scores (88 points) were improved significantly (P=0.002) to 85.6, 68.5, and 25 points, respectively, at 14.6 years follow-up. Eighteen knees (8%) had re-revision. Four knees were re-revised for infection. Kaplan-Meier survivorship analysis revealed that the 16-year rate of survival of the components was 94.7% as the end point of loosening and 92% as the end point of revision.

Ten-Year Results of Primary and Revision Condylar-Constrained Total Knee Arthroplasty in Patients with Severe Coronal Plane Instability

Objective :

To retrospectively review the results at minimum ten years after surgery of a consecutive series of total knee arthroplasties (TKAs) performed using a constrained condylar implant in patients with severe coronal plane instability.

Materials and Methods :

The series comprised of 44 patients (45 knees) who received primary (19 knees) or revision (26 knees) TKA with a constrained condylar implant between 2001 and 2003 at a single institution.

Results :

There were no revisions or any other surgery related complications at a mean implantation time of 11.0 years. In 38 patients (15 knees in the primary group and 24 knees in the revision group) who were available for clinico-radiographic follow-up at a minimum of ten years, there was no sign of radiographic loosening. Two patients showed cortical hypertrophy at the extension stem tip but none complained of pain around the stem tip.

According to the TLKSS score grading, 73% of the patients in the primary group had results categorized as good or excellent, while 54% of the patients in the revision group had fair results. Four patients (one (7%) in the primary group and three (13%) in the revision group) had poor results. The median WOMAC Index was 80.2% (interquartile range: 74.0% - 81.2%) and 74.0% (interquartile range: 72.1% - 75.8%) in the primary and in the revision groups, respectively (p=0.010).

Conclusion :

This study showed satisfactory clinical outcomes with no re-operations at minimum ten years after implantation in patients who had undergone primary or revision TKA with a condylar constrained implant.

Morbid Obesity: Increased Risk of Failure After Aseptic Revision TKA

BACKGROUND

Patients with obesity are known to have a higher risk of complications after primary TKA; however, there is a paucity of data regarding the effects of obesity with revision TKAs.

QUESTIONS/PURPOSES

We asked the following questions : (1) Are patients with morbid obesity (BMI≥40 kg/m2) at greater risk for repeat revision, reoperation, or periprosthetic joint infection (PJI) compared with patients without obesity (BMI<30 kg/m2) after an index revision TKA performed for aseptic reasons? (2) Do patients who are not obese achieve higher Knee Society pain and function scores after revision TKA for aseptic reasons?

METHODS

We used a retrospective cohort study with 1:1 matching for sex, age (±3 years) and date of surgery (±1 year) to compare patients with morbid obesity with patients without obesity with respect to repeat revision, reoperation, and PJI. Using our institution's total joint registry, we identified 1291 index both-component (femoral and tibial) aseptic revision TKAs performed during a 15-year period (1992-2007). Of these, 120 revisions were in patients with morbid obesity (BMI≥40 kg/m2) and 624 were in patients with a BMI less than 30 kg/m2. We then considered only patients with a minimum 5-year followup, which was available for 77% of patients with morbid obesity and 76% of patients with a BMI less than 30 kg/m2 (p=0.84). All patients with morbid obesity who met criteria were included (morbid obesity group: n=93; average followup, 7.9 years) and compared with a matched cohort of patients with a BMI less than 30 kg/m2 (nonmorbid obesity group: n=93; average followup, 7.3 years). Medical records were reviewed to gather details regarding complications and clinical outcomes.

RESULTS

Overall, patients with morbid obesity had an increased risk of repeat revision (hazard ratio [HR], 3.8; 95% CI, 1.2-16.5; p<0.02), reoperation (HR, 2.9; 95% CI, 1.3-7.4; p<0.02), and PJI (HR, 6.4; 95% CI, 1.2-119.7; p<0.03). Implant survival rates were 96% (95% CI, 92%-100%) and 100% at 5 years, and 81% (95% CI, 70%-92%) and 93% (95% CI, 86%-100%) at 10 years for the patients with morbid obesity and those without morbid obesity, respectively (p=0.02). At 10 years, The Knee Society pain (90 [95% CI, 88-92] vs 76 [95% CI, 71-81]; p<0.01) and function (61 [95% CI, 53-69] vs 57 [95% CI, 42-52]; p<0.01) scores were higher in patients with a BMI less than 30 kg/m2 compared with patients with morbid obesity.

CONCLUSION

Morbid obesity is associated with increased rates of rerevision, reoperation, and PJI after aseptic revision TKA. As the time-sensitive nature of revision surgery may not always allow for patient or comorbidity optimization, these results emphasize the need for improving our care of patients with morbid obesity earlier on during the osteoarthritic process. Additional studies are needed to risk stratify patients in the morbidly obese population to better guide patient selection and effective optimization.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Biomechanical study of the tibia in knee replacement revision

The best management of severe bone defects following total knee replacement is still controversial. Metal augments, tantalum cones and porous tibial sleeves could help the surgeon to manage any type of bone loss, providing a stable and durable knee joint reconstruction. Five different types of prostheses have been analysed: one prosthesis with straight stem; two prostheses with offset stem, with and without supplement, and two prostheses with sleeves, with and without stem. The purpose of this study is to report a finite element study of revision knee tibial implants. The main objective was to analyse the tibial bone density changes and Von Misses tension changes following different tibial implant designs. In all cases, the bone density decreases in the proximal epiphysis and medullary channels, with a bone density increase also being predicted in the diaphysis and at the bone around the stems tips. The highest value of Von Misses stress has been obtained for the straight tibial stem, and the lowest for the stemless metaphyseal sleeves prosthesis.