Who Benefits from Manipulation under Anesthesia Following Total Knee Arthroplasty?

Arthrofibrosis is a multifactorial process that results in decreased knee range of motion (ROM). Manipulation under anesthesia (MUA) is commonly regarded as the preferred initial treatment of arthrofibrosis following total knee arthroplasty (TKA). There have been no well-controlled studies demonstrating that MUA effectively increases ROM in patients who develop arthrofibrosis after TKA when compared with routine care. The purpose of this study was to determine whether MUA had any advantage over routine care in the treatment of patients who developed arthrofibrosis following TKA. The authors identified patients who underwent primary TKA at the authors' institution between 2010 and 2014 and had flexion ≤ 100 degrees at early follow-up. Knees were grouped based on how the arthrofibrosis was treated: those who underwent MUA and those who received routine care. Knee flexion was captured preoperatively (prior to TKA), at early follow-up (prior to MUA or routine care), and at 1-year follow up. Flexion change from early follow-up to 1 year was calculated. The average flexion at 1-year follow-up was not significantly different between the two groups (106.1 ± 11.7 degrees in the routine care group versus 106.3 ± 12.8 degrees in the MUA group). The MUA group had a greater proportion of patients with flexion gains > 20 degrees at final follow-up when compared with patients who underwent routine care (56% vs. 8%, p < 0.0001). This study demonstrates that patients with decreased ROM at early follow-up after primary TKA can expect greater ROM increase at 1-year follow-up if they undergo MUA compared with patients who undergo routine care. (Journal of Surgical Orthopaedic Advances 33(1):033-036, 2024).

Tibial sagittal and rotational alignment reduce patellofemoral stresses in posterior stabilized total knee arthroplasty.

Patellofemoral joint complications remain an important issue in total knee arthroplasty. We compared the patellofemoral contact status between cruciate-retaining and posterior-stabilized designs with varying degrees of tibial sagittal and rotational alignment using a computer simulation to ensure proper alignments in total knee arthroplasty. Knee kinematics, patellofemoral contact force and quadriceps force were computed using a musculoskeletal modeling program (LifeMOD/KneeSIM 2010; LifeModeler, Inc., San Clemente, California) during a weight-bearing deep knee bend. Two different posterior tibial slope (PTS)s (3° and 7°) and five different tibial tray rotational alignments (neutral, internal 5° and 10°, and external 5° and 10°) were simulated. Patellofemoral contact area and stresses were next computed using finite element analysis. The patellofemoral contact force for the posterior-stabilized design was substantially lower than the cruciate-retaining design after post-cam contact because of increasing femoral roll-back. Neutral rotational alignment of the tibial component resulted in smaller differences in patellofemoral contact stresses between cruciate-retaining and posterior-stabilized designs for PTSs of 3° or 7°. However, the patellar contact stresses in the cruciate-retaining design were greater than those in posterior-stabilized design at 120° of knee flexion with PTS of 3° combined with internal rotation of the tibial component. Our study provides biomechanical evidence implicating lower PTSs combined with internal malrotation of the tibial component and the resultant increase in patellofemoral stresses as a potential source of anterior knee pain in cruciate-retaining design.

Postoperative Valgus Laxity and Medial Pivot Kinematics Are Significantly Associated With Better Clinical Outcomes.

BACKGROUND: The relative impact of soft tissue balance and knee laxity on clinical outcomes after total knee arthroplasty (TKA) is not fully understood. We analyzed associations among knee laxity, kinematics, and patient-reported outcomes. METHODS: Knee Society Scores were recorded in 67 patients before and after primary TKA for osteoarthritis with varus deformity (N = 78). Varus and valgus laxity was measured in 78 knees using stress radiographs. Knee kinematics were measured fluoroscopically during stair ascent in 16 knees. RESULTS: On average, varus laxity decreased significantly, and valgus laxity increased significantly after TKA, although the net combined varus-valgus laxity did not change significantly. Postoperatively, the magnitude of valgus laxity correlated significantly with greater patient symptoms and satisfaction scores. Patients with medial pivot kinematics scored higher on patient satisfaction and standard activities. CONCLUSION: We found that postoperative valgus laxity and medial pivot kinematics were significantly associated with better clinical outcomes. These results emphasize the importance of careful preoperative planning and attention to intraoperative alignment and ligament balancing.

Self-Reported Metal Allergy and Early Outcomes After Total Knee Arthroplasty.

The impact of self-reported metal allergy (SRMA) in total knee arthroplasty (TKA) remains controversial. In the absence of objective tests, SRMA is often used as a screening tool for implant selection. The objective of this study was to determine the effect of SRMA on early outcomes after TKA. Between 2010 and 2014, 168 patients with SRMA underwent TKA; 150 (89%) received nickel-free implants, and 18 (11%) received cobalt-chrome implants that contained nickel. Mean age was 67 years, and 95% were female. A cohort of 858 TKA patients (mean age, 68 years) without SRMA matched by sex served as the control group. Outcomes included Knee Society Score (function [KSS-F] and knee [KSS-K]), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores, knee flexion, further surgery, and complications. No differences were seen in KSS-F and KSS-K between patients with and without SRMA. The mean WOMAC pain scores were 89.1 for patients with SRMA and 85.2 for patients without SRMA (P=.030). Stiffness and physical function scores were similar. Knee flexion was similar. No differences were found between nickel-free and cobalt-chrome SRMA groups. Patients with SRMA and those without demonstrated similar early functional outcomes. Patients with SRMA who received standard cobalt-chrome implants had no significant difference in functional outcomes compared with patients with nickel-free implants. Better identifiers of patients at risk for adverse events due to implant material are needed. [Orthopedics. 2019; 42(6):330-334.].

Second-Generation Electronic Ligament Balancing for Knee Arthroplasty: A Cadaver Study.

BACKGROUND: Knee instability is emerging as a major complication after total knee arthroplasty (TKA), with ligament laxity and component alignment listed as important contributory factors. Knee balancing remains an art and is largely dependent on the surgeon's subjective "feel." The objectives were to measure the accuracy of an electronic balancing device to document the magnitude of correction in knee balance after soft-tissue releases and measure change in knee laxity after medial release. METHODS: The accuracy of a second-generation electronic ligament-balancing device was compared with that of 2 mechanical balancing instruments. TKA was performed in 12 cadaver knees. Soft-tissue balance was measured sequentially before TKA, after mounting a trial femoral component, after medial release, and after resecting the posterior cruciate ligament. Coronal laxity of the knee under a 10 Nm valgus moment was measured before and after medial release. RESULTS: The electronic balancing instrument was more accurate than mechanical instruments in measuring distracted gap and distraction force. On average, before TKA, the flexion gap was wider than the extension gap, and the medial gap was tighter than the lateral gap. Medial release increased the medial gap in flexion and increased passive knee valgus laxity. Posterior cruciate ligament release increased the tibiofemoral gap in both flexion and extension with a greater increase in the lateral gap. CONCLUSION: The second-generation electronic balancing device was significantly more accurate than mechanical instruments and could record knee balance over the entire range of flexion. More accurate soft-tissue balance may enhance outcomes after TKA.

Intraoperative Measurements and Tools to Assess Stability.

Knee stability is the ability for the joint to maintain an appropriate functional position throughout its range of motion. Knee instability can be defined as excessive laxity during activities of daily living. Intraoperative knee laxity can be affected by implant design, alignment of components, and soft-tissue balancing. Soft-tissue balance is a major contributor to knee instability. Mechanical balancing instruments can be classified as spacer blocks or joint-distraction devices. Conventional wisdom favors rectangular and equal flexion-extension gaps. However, knee balance is elusive even with mechanical balancing instruments. First-generation electronic balancing devices are equivalent in concept to spacer blocks instrumented with force sensors. Second-generation electronic balancing devices are equivalent in concept to mechanical distraction devices instrumented with pressure and displacement sensors. Electronic ligament balancers can be useful in documenting intraoperative knee laxity for quantifiable correlation with postoperative outcomes, thus directly relating postoperative stability to surgical balance, and may predict outcomes and knee stability.

Ceramic liner fracture and impingement in total hip arthroplasty.

BACKGROUND: Ceramic-on-ceramic bearing surfaces were developed to provide an alternate to metal-on-polyethylene to decrease wear-induced osteolysis in total hip arthroplasty patients. In an effort to decrease the risk of ceramic acetabular component fracture or damage during implantation, a raised metal rim was added. QUESTIONS/PURPOSES: How many fractures or impingements have occurred in our population of patients with ceramic liners with raised rims? METHODS: With IRB-approved consent, a case series was reviewed from a single center registry and 4 of 169 patients were identified who had revision hip surgery with the ceramic liner with a raised metal rim: one for ceramic liner fracture and three for metallosis, pain, and squeaking. Implant alignment and operative findings were reviewed. RESULTS: One ceramic liner fracture and three cases of metallosis from impingement of the femoral neck on the posterior elevated metal rim of the acetabular liner were observed at revision. The femoral neck in each patient had a divot that corresponded to a divot in the posterosuperior liner rim. Three of the four patients had audible squeaking or clicking prior to revision. A total of 3% of patients in this series had clinically significant impingement with this implant type. CONCLUSION: Acoustic phenomenon in a ceramic on ceramic bearing surface should be investigated with a cross-table lateral radiograph to evaluate component position. If symptomatic impingement is demonstrated, revision should be considered to avoid failure from metallosis or fracture.

Patient-specific computer model of dynamic squatting after total knee arthroplasty.

Knee forces are highly relevant to performance after total knee arthroplasty especially during high flexion activities such as squatting. We constructed subject-specific models of two patients implanted with instrumented knee prostheses that measured knee forces in vivo. In vivo peak forces ranged from 2.2 to 2.3 times bodyweight but peaked at different flexion angles based on the type of squatting activity. Our model predicted tibiofemoral contact force with reasonable accuracy in both subjects. This model can be a very useful tool to predict the effect of surgical techniques and component alignment on contact forces. In addition, this model could be used for implant design development, to enhance knee function, to predict forces generated during other activities, and for predicting clinical outcomes.

Patient-specific implants with custom cutting blocks better approximate natural knee kinematics than standard TKA without custom cutting blocks.

BACKGROUND: Nearly 14% to 39% TKA patients report dissatisfaction causing incomplete return of function. We proposed that the kinematics of knees implanted with patient-specific prostheses using patient-specific cutting guides would be closer to normal. METHODS: Eighteen matched cadaver lower limbs were randomly assigned to two groups: group A was implanted with patient-specific implants using patient-specific cutting guides; group B, the contralateral knee, was implanted with a standard design using intramedullary alignment cutting guides. Knee kinematics were measured on a dynamic closed-kinetic-chain Oxford knee rig, simulating a deep knee bend and in a passive rig testing varus-valgus laxity. RESULTS: The difference from normal kinematics was lower for group A compared to group B for active femoral rollback, active tibiofemoral adduction, and for passive varus-valgus laxity. CONCLUSIONS: Our results support the hypothesis that knees with patient-specific implants generate kinematics more closely resembling normal knee kinematics than standard knee designs. CLINICAL RELEVANCE: Restoring normal kinematics may improve function and patient satisfaction after total knee arthroplasty.

How do knee implants perform past the second decade? Nineteen- to 25-year followup of the Press-fit Condylar design TKA.

BACKGROUND: At 14- to 17-year followup, we reported successful outcomes of the Press-fit Condylar total knee arthroplasty (TKA) system in 160 TKAs performed between 1986 and 1989. However, there are few published reports on TKA survivorship and patient function that include patients evaluated into the third decade after surgery. QUESTIONS/PURPOSES: The study purpose was to determine (1) the survivorship of the implant; and (2) knee function in patients with this TKA system at a mean 20-year followup. METHODS: We ascertained revision status of all living patients (42 of 160 knees) and all patients (22 knees) who died since the previous study. Among patients alive at the latest followup, Knee Society function scores were obtained and radiographs were evaluated. Kaplan-Meier survivorship analysis with 95% confidence intervals was performed with revision for any reason and aseptic loosening as endpoints. A competing risks analysis with 95% confidence intervals was also performed for revision for any reason as the endpoint. RESULTS: At the mean 20-year (range, 19-25 years) followup, all living patients retained their original implants from the index TKA, exclusive of three polyethylene exchanges. This study demonstrates an 87% Kaplan-Meier survivorship for revision for any reason (95% confidence interval [CI], 80%-92%) and a 98% Kaplan-Meier survivorship for revision for aseptic loosening (95% CI, 93%-99%). Competing risks survivorship was 79% (95% CI, 70%-85%) at 25 years for revision for any reason. Mean Knee Society function score was 46.9. Since the previous study, three revisions have been performed, all for polyethylene wear. CONCLUSIONS: The Press-fit Condylar implant system continues to be successful, maintaining longevity up to 25-year followup. This is one of the longest followup studies, reporting continued successes over 20 years, and should serve as a benchmark for current-generation implants. LEVEL OF EVIDENCE: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Thrombosis prevention in lower extremity arthroplasty: mobile compression device or pharmacological therapy.

Venous thromboembolic (VTE) events, either deep vein thromboses (DVT) or pulmonary emboli (PE), are important complications in patients undergoing knee or hip arthroplasty. Symptomatic VTE rates observed in total joint arthroplasty patients using the mobile compression device with home use capability were non-inferior to rates reported for pharmacological prophylaxis, including warfarin, enoxaparin, rivaroxaban, and dabigatran. Major bleeding in total hip arthroplasty was less using the mobile compression device than using low molecular weight heparin. A cost analysis demonstrated a cost savings based on decreased major bleeding. Use of a mobile compression device with or without aspirin for patients undergoing total joint arthroplasty provides a non-inferior risk for developing VTE compared with current pharmacological protocols.

Effect of head diameter on passive and active dynamic hip dislocation.

Hip dislocation is a major short-term complication after total hip arthroplasty (THA). One factor thought to reduce the risk for dislocation is head size. We constructed subject-specific computer models to study the effect of head size on risk for postoperative dislocation. Femoral and acetabular geometry was constructed after segmenting CT scans of nine hips. CAD models of THA components with four head diameters (28, 32, 36, and 44 mm) were virtually implanted. Hip capsular ligaments were simulated using rigid-body ellipsoids connected by non-linear springs. Posterior dislocation was simulated during a rise from a low chair; anterior dislocation was simulated during a pivot activity. Intraoperative stability tests were simulated for anterior or posterior dislocation. While rising from a low chair (posterior dislocation) and during the pivot activity (anterior dislocation), increasing head size significantly increased hip flexion angle at dislocation and generated higher dislocation moments. Larger heads reduced the risk for dislocation. Intraoperative stability tests detected the relative increased resistance to dislocation despite differences in the absolute magnitude of moments. This model can be useful preclinical tool for assessing design changes, the effect of component placement, and the activity-based risk for dislocation.

A mobile compression device for thrombosis prevention in hip and knee arthroplasty.

BACKGROUND: Venous thromboembolic events, either deep venous thrombosis or pulmonary embolism, are important complications in patients undergoing knee or hip arthroplasty. The purpose of this study was to evaluate the effectiveness of a mobile compression device (ActiveCare+S.F.T.) with or without aspirin compared with current pharmacological protocols for prophylaxis against venous thromboembolism in patients undergoing elective primary unilateral arthroplasty of a lower-extremity joint. METHODS: A multicenter registry was established to capture the rate of symptomatic venous thromboembolic events following primary knee arthroplasty (1551 patients) or hip arthroplasty (1509 patients) from ten sites. All patients were eighteen years of age or older with no known history of venous thromboembolism, coagulation disorder, or solid tumor. Use of the compression device began perioperatively and continued for a minimum of ten days. Patients with symptoms of deep venous thrombosis or pulmonary embolism underwent duplex ultrasonography and/or spiral computed tomography. All patients were evaluated at three months postoperatively to document any evidence of deep venous thrombosis or pulmonary embolism. RESULTS: Of 3060 patients, twenty-eight (0.92%) had venous thromboembolism (twenty distal deep venous thrombi, three proximal deep venous thrombi, and five pulmonary emboli). One death occurred, with no autopsy performed. Symptomatic venous thromboembolic rates observed in patients who had an arthroplasty of a lower-extremity joint using the mobile compression device were noninferior (not worse than), at a margin of 1.0%, to the rates reported for pharmacological prophylaxis, including warfarin, enoxaparin, rivaroxaban, and dabigatran, except in the knee arthroplasty group, in which the mobile compression device fell short of the rate reported for rivaroxaban by 0.06%. CONCLUSIONS: Use of the mobile compression device with or without aspirin for patients undergoing arthroplasty of a lower-extremity joint provides a noninferior risk for the development of venous thromboembolism compared with current pharmacological protocols.

Influence of cartilage extracellular matrix molecules on cell phenotype and neocartilage formation.

Interaction between chondrocytes and the cartilage extracellular matrix (ECM) is essential for maintaining the cartilage's role as a low-friction and load-bearing tissue. In this study, we examined the influence of cartilage zone-specific ECM on human articular chondrocytes (HAC) in two-dimensional and three-dimensional (3D) environments. Two culture systems were used. SYSTEM 1: HAC were cultured on cell-culture plates that had been precoated with the following ECM molecules for 7 days: decorin, biglycan, tenascin C (superficial zone), collagen type II, hyaluronan (HA) (middle and deep zones), and osteopontin (deep zone). Uncoated standard culture plates were used as controls. Expanded cells were examined for phenotypic changes using real-time polymerase chain reaction. In addition, expanded cells were placed into high-density pellet cultures for 14 days. Neocartilage formation was assessed via gene expression and histology evaluations. SYSTEM 2: HAC that were cultured on untreated plates and encapsulated in a 3D alginate scaffold were mixed with one of the zone-specific ECM molecules. Cell viability, gene expression, and histology assessments were conducted on 14-day-old tissues. In HAC monolayer culture, exposure to decorin, HA, and osteopontin increased COL2A1 and aggrecan messenger RNA (mRNA) levels compared with controls. Biglycan up-regulated aggrecan without a significant impact on COL2A1 expression; Tenascin C reduced COL2A1 expression. Neocartilage formed after preculture on tenascin C and collagen type II expressed higher COL2A1 mRNA compared with control pellets. Preculture of HAC on HA decreased both COL2A1 and aggrecan expression levels compared with controls, which was consistent with histology. Reduced proteoglycan 4 (PRG4) mRNA levels were observed in HAC pellets that had been precultured with biglycan and collagen type II. Exposing HAC to HA directly in 3D-alginate culture most effectively induced neocartilage formation, showing increased COL2A1 and aggrecan, and reduced COL1A1 compared with controls. Decorin treatments increased HAC COL2A1 mRNA levels. These data indicate that an appropriate exposure to cartilage-specific ECM proteins could be used to enhance cartilage formation and to even induce the formation of zone-specific phenotypes to improve cartilage regeneration.

Repair of cartilage defects in arthritic tissue with differentiated human embryonic stem cells.

Chondrocytes have been generated in vitro from a range of progenitor cell types and by a number of strategies. However, achieving reconstitution of actual physiologically relevant, appropriately-laminated cartilage in situ that would be applicable to conditions, such as arthritis and cartilage degeneration remains elusive. This lack of success is multifactorial and includes limited cell source, decreased proliferation rate of mature chondrocytes, lack of maintenance of phenotype, reduced matrix synthesis, and poor integration with host tissue. We report an efficient approach for deriving mesenchymal chondroprogenitor cells from human embryonic stem cells. These cells generated tissue containing cartilage-specific matrix proteins that integrated in situ in a partial-thickness defect in ex vivo articular cartilage harvested from human arthritic joints. Given that stem cells provide a virtually inexhaustible supply of starting material and that our technique is easily scalable, cartilaginous tissue primed and grafted in this manner could be suitable for clinical translation.