The Insall legacy in total knee arthroplasty

Measured distance from posterior tibia to popliteal artery increases with flexion and subluxation of the knee

Purpose

Popliteal artery laceration is a devastating complication in total knee arthroplasty (TKA). Its anatomic position relative to the tibia has been studied using ultrasound or magnetic resonance imaging. This is the first study performed in a laboratory using radiographic measurements to determine if increased flexion and subluxation of the knee increase the distance between the tibia and popliteal artery.

Methods

The femoral artery was infused with radiopaque dye in six cadavers. The knee was placed in two different degrees of flexion and three of subluxation. The radiographic distance between standardized markers in the posterior tibia and popliteal artery was measured.

Results

The average distance from the tibial peg to the popliteal artery at 90° of flexion increased from 0% to 50% to 100% subluxation. The increase was statistically significant (Friedman test p = 0.016). The contrast between neutral and 100% subluxation was statistically significant (Sign test p = 0.031). At 115° flexion, average distance from the peg to popliteal artery significantly increased as subluxation increased (Friedman test p = 0.05). In three specimens, at 115° of flexion and 100% subluxation, a line perpendicular to the axis of the tibia, failed to intersect the popliteal artery. The measured distance increased from 90° to 115° of flexion at a given degree of subluxation, but this difference did not reach statistical significance.

Conclusions

Increasing flexion and subluxation of the tibia results in increasing distance between the cut plane of the tibial plateau and popliteal artery and decreases risk of laceration.

Level of Evidence

Not applicable.

Lower Associated Risk of Revision With All-Polyethylene Tibial Components in Total Knee Arthroplasty: An Analysis of the American Joint Replacement Registry

BACKGROUND

Despite the potential advantage of all-polyethylene tibial components, modular metal-backed component use predominates the market in the United States for total knee arthroplasty (TKA). This is partially driven by concerns about the associated revision risk due to the lack of modularity with all-polyethylene components. This study utilized the American Joint Replacement Registry to compare the associated risk of all-cause revision and revision for infection for all-polyethylene versus modular metal-backed tibial components.

METHODS

An analysis of primary TKA cases in patients aged 65 years and older was performed with American Joint Replacement Registry data linked to Centers for Medicare and Medicaid Services data from 2012 to 2019. Analyses compared all-polyethylene to modular metal-backed tibial components. We identified 485,024 primary TKA cases, consisting of 479,465 (98.9%) metal-backed and 5,559 (1.1%) all-polyethylene. Cox proportional hazard regression analyses created hazard ratios (HRs) to evaluate the association of design and the risk of all-cause revision while adjusting for sex, age, and the competing risk of mortality. Event-free survival curves evaluate time to revision.

RESULTS

The all-polyethylene tibia group demonstrated a decreased risk for all-cause revision (HR = 0.37; 95% confidence interval: 0.24 to 0.55; P < .0001) and revision for infection (HR = 0.41; 95% confidence interval: 0.22 to 0.77, P < .0001). Event-free survival curves demonstrated a decreased risk of all-cause revision that persisted across time points until 8 years post-TKA.

CONCLUSIONS

In the United States, all-polyethylene tibial component use for TKA remains low compared to modular metal-backed designs. A decreased associated risk for revision should ease concerns about the use of all-polyethylene components in patients aged 65 years or older, and future investigations should investigate the potential cost and value savings associated with expanded use in this population.

LEVEL OF EVIDENCE

Therapeutic Level III.

Aseptic loosening of the option stemmed tibial tray in the Zimmer NexGen LPS total knee arthroplasty system

BACKGROUND

We investigated the relationship between the backside deformation of polyethylene (PE) tibial inserts and aseptic loosening of the Option stemmed tibial tray used with Zimmer NexGen posterior-stabilised (PS) devices. We hypothesized that explanted inserts used in PS designs would exhibit greater extents of PE backside deformation than those used in equivalent cruciate retaining (CR) designs and that PE inserts retrieved from total knee arthroplasties (TKAs) revised for aseptic tibial tray loosening would exhibit greater extents of backside deformation than TKAs revised for other reasons.

METHODS

A total of 73 explanted fixed-bearing TKAs (42 CR and 31 PS) were examined. PE components underwent geometric examination with a coordinate measuring machine using validated techniques. Multiple regression modelling was used to identify variables associated with revision secondary to aseptic loosing and to determine factors associated with increased PE backside deformation.

RESULTS

PE inserts retrieved from TKAs with aseptic loosening had significantly greater backside deformation than those retrieved from TKAs revised for other reasons (p < 0.001). Greater PE backside deformation was significantly associated with larger tray/insert clearance heights (p < 0.001), thinner inserts (p < 0.001) and PS TKAs (p = 0.001).

CONCLUSION

PE backside deformation was significantly greater in the PS TKAs. This may provide one explanation for the increased rate of aseptic loosening reported with the Option tibial tray used with the Legacy Posterior Stabilised (LPS) system.

Case Report of Successful Bilateral Total Knee Arthroplasty: 46 Years and Still Going

CASE

A 63-year-old woman with 46-year-old bilateral cemented total knee arthroplasty (TKA) presented to our clinic for routine evaluation. She was diagnosed with idiopathic juvenile arthritis at the age of 17. Radiographically she had well-fixed implants bilaterally without bone-cement lucency. She is ambulating without a limp, pain, or an assistance aid.

CONCLUSION

We report TKA implants that lasted for 46 years. Literature suggests that most TKAs can last up to 20 to 25 years, but there are few reports that document implant survivorship longer than that. Our report demonstrates the possibility of long survivorship in TKA implants.

Trends in Polyethylene Design and Manufacturing Characteristics for Total Knee Arthroplasty: An Analysis From the American Joint Replacement Registry

BACKGROUND

Advances in polyethylene bearing characteristics have led to various options for total knee arthroplasty. We examine trends in use of polyethylene in the United States.

METHODS

An analysis of American Joint Replacement Registry data from 2012 to 2019 for primary total knee arthroplasty procedures was conducted. Design and manufacturing characteristics were obtained and validated in the American Joint Replacement Registry dataset. Polyethylene bearing design and manufacturing use characteristics were compared by year, gender, age group, and geographic region of the procedure. Descriptive analysis was performed.

RESULTS

We identified 993,292 cases over the study period. In total, 791,233 (80%) cases had complete device data available and were included in analysis. In addition, 366,280 (49.4%) cases utilized minimally stabilized bearings compared to 374,809 (50.6%) for posterior-stabilized bearings. Posterior-stabilized use was stable over the study period and highest in the Northeast (64.5%; P < .0001). Cruciate-retaining use decreased from 29.7% to 20.2% and anterior-stabilized use increased from 17.4% to 25.2%. Conventional polyethylene use decreased from 42.8% to 21.9%, and was highest in the 81+ age group (37.8%; P < .0001) and Northeast (43.0%; P < .0001). Highly cross-linked polyethylene (HXLPE) with antioxidant use increased from 9.08% to 31.8%, while HXLPE without antioxidant use remained constant.

CONCLUSION

There was an increase in use of anterior-stabilized and pivot bearings and an increase in use of HXLPE with antioxidant. Additionally, there were noted age group and regional differences in the use of various bearings. Further study should evaluate if these changing utilization trends are related to clinical outcomes, or due to regional training, preferences, or manufacturer pressures.

LEVEL OF EVIDENCE

Level III, retrospective.

Conforming Polyethylene Inserts in Total Knee Arthroplasty: Beyond the Posterior-Stabilized and Cruciate-Retaining Debate

Total knee arthroplasty continues to be one of the most commonly performed surgical procedures worldwide. However, considerable controversy exists regarding the optimal implant design. Total knee implants with both posterior-stabilized and cruciate-retaining designs have excellent long-term outcomes with inadequate data demonstrating superiority of either design. Recently, the popularity of total knee designs with more conforming polyethylene liners has increased. These polyethylene inserts prevent paradoxical anterior translation of the femur, without relying on a cam and post mechanism, and promote more physiologic native knee kinematics. This review summarizes the design rationale of several commercially available implants, discusses the kinematic data of several designs, and reviews the available clinical data.

Clinical and Radiological Changes of Ankle in Knee Osteoarthritis With Varus After Total Knee Arthroplasty: A Systematic Review

Background: Arthritis with severe varus deformity remains a challenge in total knee arthroplasty (TKA). Until recently, surgeons aimed at a neutral lower limb alignment when performing a TKA. However, the impact of TKA on the ankle joint has been ignored. Therefore, we conducted a systematic review to assess the clinical and radiological changes in the ankle joint after TKA on knees with severe varus deformity. Methods: A systematic search was conducted in four English (PubMed, Embase, Cochrane Library, and Web of Science) and four Chinese (CBM, VIP, CNKI, and Wan Fang Database) databases. Screening of literature and extraction of data were independently performed by two researchers. The modified methodological index for non-randomized studies (MINORS) was used to assess the quality. Results: A total of eight studies were eligible, namely, four prospective and four retrospective studies. TKA resulted in a negative clinical effect in the ankle joint in patients with ankle osteoarthritis. Seven studies reported changes in the mechanical tibiofemoral angle, and four studies reported radiological changes in the hindfoot. The mean score of the MINORS was 9.8 out of eight (9-11). Conclusion: As a result of the correction of the knee osteoarthritis with severe varus deformity following mechanically aligned TKA, the radiological malalignment of the ankle joint was improved. However, some patients experience increased ankle pain after undergoing TKA, especially, if there was a residual knee varus deformity, a stiff hindfoot with varus deformity, or ankle arthritis.

Less gap imbalance with restricted kinematic alignment than with mechanically aligned total knee arthroplasty: simulations on 3-D bone models created from CT-scans

Background and purpose - Mechanical alignment techniques for total knee arthroplasty (TKA) introduce significant anatomic alteration and secondary ligament imbalances. We propose a restricted kinematic alignment (rKA) protocol to minimize these issues and improve TKA clinical outcomes.Patients and methods - rKA tibial and femoral bone resections were simulated on 1,000 knee CT scans from a database of patients undergoing TKA. rKA was defined by the following criteria: independent tibial and femoral cuts within 5° of the bone neutral mechanical axis, with a resulting HKA within 3° of neutral. Imbalances in the extension space, flexion space at 90°, medial compartment and lateral compartment were calculated and compared with measured resection mechanical alignment (MA) results. 2 MA techniques were simulated for rotation using the surgical transepicondylar axis (TEA) and 3° to the posterior condyles (PC).Results - Extension space imbalances ≥ 3 mm occurred in 33% of TKAs with MA technique versus 8.3% with rKA (p < 0.001). Similarly, more frequent flexion space imbalance ≥ 3mm was created by MA technique (TEA 34% or 3° PC 15%) versus rKA (6.4%, p < 0.001). Using MA with TEA or PC, there were only 49% and 63% of the knees respectively with < 3 mm of imbalance throughout the extension and flexion spaces and medial and lateral compartments versus 92% using rKA (p < 0.001).Interpretation - significantly fewer imbalances are created using rKA versus MA for TKA. rKA may be the best compromise, by helping the surgeon to preserve native knee ligament balance during TKA and avoid residual instability, whilst keeping the lower limb alignment within a safe range.

Metal-backed versus all-polyethylene tibias in megaprostheses of the distal femur

In megaprostheses, the tibial component is rarely a source of failure. The evolution of these implants has followed standard arthroplasty trends moving from majority use of all-polyethylene tibias (APT) to high volume use of metal-backed tibial (MBT) components. We report the results of 72 endoprostheses using either MBT (n = 42) or APT (n = 30) implanted between 1994 and 2006. Failures of the implant related to the tibial component were isolated, and 5-year survival of the tibial implant of the MBT cohort was 94%, and for the APT cohort, 87% (P = .39). The difference in tibial component failures between the 2 groups was not statistically significant (Pearson χ(2) = 0.1535, P = .6952). Revision rates for the entire implant and infection rates were not significantly different between the 2 groups.

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.

The early innovators of today's resurfacing condylar knees

The 1970s saw an explosion of ideas in the field of prosthetic knee arthroplasty. This paper is an effort to identify the innovators who contributed to the development of today's condylar total knee prostheses and the surgical techniques used to insert them. The 1970s were selected because most innovations occurred during those years. Two different design approaches were undertaken simultaneously. One was a functional approach whereas the other was a strictly anatomical approach. Initially, these 2 approaches led to very different designs. But the common goal of recreating human knee function eventually led to more similarities than differences. The author describes how, when, and why these dedicated individuals came to their ideas. The work is largely based on interviews and correspondence with those involved as well as on reviews of patents and papers pertaining to their work.