Is modular control related to functional outcomes in individuals with knee osteoarthritis and following total knee arthroplasty?

BACKGROUND: Individuals who undergo total knee arthroplasty (TKA) for treatment of knee osteoarthritis often experience suboptimal outcomes. Investigation of neuromuscular control strategies in these individuals may reveal factors that contribute to these functional deficits. The purpose of this pilot study was to determine the relationship between patient function and modular control during gait before and after TKA. METHODS: Electromyography data from 36 participants (38 knees) were collected from 8 lower extremity muscles on the TKA-involved limb during ≥5 over-ground walking trials before (n = 30), 6-months after (n = 26), and 24-months after (n = 13) surgery. Muscle modules were estimated using non-negative matrix factorization. The number of modules was determined from 500 resampled trials. RESULTS: A higher number of modules was related to better performance-based and patient-reported function before and 6-months after surgery. Participants with organization similar to healthy, age-matched controls trended toward better function 24-months after surgery, though these results were not statistically significant. We also observed plasticity in the participants' modular control strategies, with 100% of participants who were present before and 24-months after surgery (10/10) demonstrating changes in the number of modules and/or organization of at least 1 module. CONCLUSIONS: This pilot work suggests that functional improvements following TKA may initially present as increases in the number of modules recruited during gait. Subsequent improvements in function may present as improved module organization. NOTEWORTHY: This work is the first to characterize motor modules in TKA both before and after surgery and to demonstrate changes in the number and organization of modules over the time course of recovery, which may be related to changes in patient function. The plasticity of modular control following TKA is a key finding which has not been previously documented and may be useful in predicting or improving surgical outcomes through novel rehabilitation protocols.

Medially-stabilized total knee arthroplasty does not alter knee laxity and balance in cadaveric knees.

Instability after total knee arthroplasty (TKA) can lead to suboptimal outcomes and revision surgery. Medially-stabilized implants aim to more closely replicate normal knee motion than other implants following TKA, but no study has investigated knee laxity (motion under applied loads) and balance (i.e., difference in varus/valgus motion under load) following medially-stabilized TKA. The primary purposes of this study were to investigate how medially-stabilized implants change knee laxity in non-arthritic, cadaveric knees, and if it produces a balanced knee after TKA. Force-displacement data were collected on 18 non-arthritic cadaveric knees before and after arthroplasty using medially-stabilized implants. Varus-valgus and anterior-posterior laxity and varus-valgus balance were compared between native and medially-stabilized knees at 0°, 20°, 60°, and 90° under three different loading conditions. Varus-valgus and anterior-posterior laxities were not different between native and medially-stabilized knees under most testing conditions (p ≥ 0.068), but differences of approximately 2° less varus-valgus laxity at 20° of flexion and 4 mm more anterior-posterior laxity at 90° were present from native laxities (p < 0.017) Medially-stabilized implant balance had ≤1.5° varus bias at all flexion angles. Future studies should confirm if the consistent laxity afforded by the medially-stabilized implant is associated with better and more predictable postoperative outcomes. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:335-349, 2019.

Tibiofemoral Osteoarthritis and Varus-Valgus Laxity.

The purpose of this study was to systematically review and synthesize the literature measuring varus-valgus laxity in individuals with tibiofemoral osteoarthritis (OA). Specifically, we aimed to identify varus-valgus laxity differences between persons with OA and controls, by radiographic disease severity, by frontal plane knee alignment, and by sex. We also aimed to identify if there was a relationship between varus-valgus laxity and clinical performance and self-reported function. We systematically searched for peer-reviewed original research articles in PubMed, Scopus, and CINAHL to identify all existing literature regarding knee OA and objective measurement of varus-valgus laxity in vivo. Forty articles were identified that met the inclusion criteria and data were extracted. Varus-valgus laxity was significantly greater in individuals with OA compared with controls in a majority of studies, while no study found laxity to be significantly greater in controls. Varus-valgus laxity of the knee was reported in persons with OA and varying degrees of frontal plane alignment, disease severity, clinical performance, and self-reported function but no consensus finding could be identified. Females with knee OA appear to have more varus-valgus laxity than males. Meta-analysis was not possible due to the heterogeneity of the subject populations and differences in laxity measurement devices, applied loading, and laxity definitions. Increased varus-valgus laxity is a characteristic of knee joints with OA. Large variances exist in reported varus-valgus laxity and may be due to differences in measurement devices. Prospective studies on joint laxity are needed to identify if increased varus-valgus laxity is a causative factor in OA incidence and progression.

Surgical Navigation Improves the Precision and Accuracy of Tibial Component Alignment in Canine Total Knee Replacement.

OBJECTIVE: The goal of this study was to determine whether computer-assisted surgical navigation improves the accuracy of tibial component alignment in canine total knee replacement (TKR). STUDY DESIGN: Retrospective radiographic review and prospective ex vivo study. SAMPLE POPULATION: Canine TKR radiographs (n = 17 sets) and canine cadaveric stifles (n = 12). METHODS: Radiographs from TKR surgical workshops were reviewed to determine the incidence and magnitude of tibial component malalignment. Tibial component alignment was compared after either standard ("surgeon-guided") component placement or computer-assisted ("navigation-guided") placement. Results were compared against the current recommendations of a neutral (0° varus-valgus) ostectomy in the frontal plane and 6° of caudal slope in the sagittal plane. A prospective cadaveric study was then undertaken by performing TKR in 12 canine stifle joints. RESULTS: Malalignment of >3° in the frontal and sagittal planes was identified in 12% and 24% of the radiographs from the retrospective review, respectively. Surgical navigation reduced both the mean error (P = .007) and the variability in frontal plane alignment (P < .001) as compared with surgeon-guided procedures. The mean error in sagittal plane alignment was not significantly different (P = .321), but variability in alignment was significantly lower when navigation was used (P = .008). CONCLUSION: Surgical navigation significantly improved accuracy and decreased variability in tibial component alignment in canine TKR. Clinical trials would be required to determine whether these improvements in surgical accuracy lead to better clinical outcomes in terms of joint function and a reduction in long-term implant wear.

Effect of chondral defect size, shape, and location on MRI diagnostic performance in the porcine knee.

The purpose of this study was to determine the sensitivity and positive predictive value of magnetic resonance imaging (MRI) in the identification of full-thickness articular cartilage defects in the porcine knee. Seventy-two full-thickness chondral defects (small or large; circular, oval, or triangular) were created in 12 porcine knees. The authors used 3.0-T MRI with 3-dimensional gradient echo water-selective/fluid (WATSf) sequences acquired in axial, coronal, and sagittal planes. Sensitivity and positive predictive value parameters were calculated for 2 readers. Magnetic resonance imaging was highly sensitive for detection of full-thickness defects in the knee (85%). The highest sensitivity was observed at the medial femoral condyle (93%), while the lowest was observed at the medial patella (71%). The sensitivities for detecting different shapes were unique to each shape, with oval lesions identified with greatest sensitivity (93%). Small lesions (86%) were detected at a similar sensitivity as large lesions (83%). The positive predictive values for accurate true-positive reads were low for all lesion shapes (18%-57%) and moderate for small (69%) and large (59%) sizes, with significant differences observed between the 2 readers. Magnetic resonance imaging has a high sensitivity in the detection of full-thickness articular cartilage defects in the porcine knee. Variability in defect shape and intra-articular location affects MRI sensitivity, while size does not. Magnetic resonance imaging was not effective in describing lesion shape or size. Further, there was subjectivity in reading defect shape and size between 2 radiologists.

The effects of defect size, orientation, and location on subchondral bone contact in oval-shaped experimental articular cartilage defects in a bovine knee model.

PURPOSE: Chondral defects of the knee may lead to pain and disability, often requiring surgical intervention. The purpose of this study was to identify how size, location, and orientation influences subchondral bone contact within oval-shaped chondral defects. METHODS: Full-thickness defects were created in twelve bovine knees. Defect orientation was randomized between coronal and sagittal planes on both the medial and lateral femoral condyles (MFC and LFC). In extension, knees were statically loaded to 1,000 N. Area measurements were recorded using Tekscan sensors and I-Scan software. A MATLAB program computed defect area and the area within the defect demonstrating subchondral bone contact. RESULTS: Defect area, location, and orientation each had a significant effect on subchondral bone contact (p < 0.001), and significant interactions were found between defect area and both location and orientation. The size threshold (cm(2)) at which significant contact occurred on the subchondral bone within the defect was smallest for LFC/coronal defects (0.73 cm(2)), then LFC/sagittal (1.14 cm(2)), then MFC/coronal (1.61 cm(2)), and then MFC/sagittal (no threshold reached). CONCLUSIONS: Intra-articular location and orientation of a femoral condyle chondral defect, in addition to area, significantly influence femoral subchondral bone contact within the defect and the threshold at which subchondral bone contact occurs within the defect. The parameters of defect location and shape orientation supplement current surgical algorithms to manage knee articular cartilage surgery. This may indicate different cartilage restorative procedures based on the effect on the subchondral bone from the defect geometry itself and the selected cartilage surgery.

How to write a systematic review.

BACKGROUND: The role of evidence-based medicine in sports medicine and orthopaedic surgery is rapidly growing. Systematic reviews and meta-analyses are also proliferating in the medical literature. PURPOSE: To provide the outline necessary for a practitioner to properly understand and/or conduct a systematic review for publication in a sports medicine journal. STUDY DESIGN: Review. METHODS: The steps of a successful systematic review include the following: identification of an unanswered answerable question; explicit definitions of the investigation's participant(s), intervention(s), comparison(s), and outcome(s); utilization of PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analyses) guidelines and PROSPERO registration; thorough systematic data extraction; and appropriate grading of the evidence and strength of the recommendations. RESULTS: An outline to understand and conduct a systematic review is provided, and the difference between meta-analyses and systematic reviews is described. The steps necessary to perform a systematic review are fully explained, including the study purpose, search methodology, data extraction, reporting of results, identification of bias, and reporting of the study's main findings. CONCLUSION: Systematic reviews or meta-analyses critically appraise and formally synthesize the best existing evidence to provide a statement of conclusion that answers specific clinical questions. Readers and reviewers, however, must recognize that the quality and strength of recommendations in a review are only as strong as the quality of studies that it analyzes. Thus, great care must be used in the interpretation of bias and extrapolation of the review's findings to translation to clinical practice. Without advanced education on the topic, the reader may follow the steps discussed herein to perform a systematic review.

The basic science of continuous passive motion in promoting knee health: a systematic review of studies in a rabbit model.

PURPOSE: To determine whether the basic science evidence supports the use of continuous passive motion (CPM) after articular cartilage injury in the knee. METHODS: A systematic review was performed identifying and evaluating studies in animal models that focused on the basic science of CPM of the knee. Databases included in this review were PubMed, Biosis Previews, SPORTDiscus, PEDro, and EMBASE. All functional, gross anatomic, histologic, and histochemical outcomes were extracted and analyzed. RESULTS: Primary outcomes of CPM analyzed in rabbit animal models (19 studies) included histologic changes in articular cartilage (13 studies), biomechanical changes and nutrition of intra-articular tissue (3 studies), and anti-inflammatory biochemical changes (3 studies). Nine studies specifically examined osteochondral defects, 6 of which used autogenous periosteal grafts. Other pathologies included were antigen-induced arthritis, septic arthritis, medial collateral ligament reconstruction, hemarthrosis, and chymopapain-induced proteoglycan destruction. In comparison to immobilized knees, CPM therapy led to decreased joint stiffness and complications related to adhesions while promoting improved neochondrogenesis with formation and preservation of normal articular cartilage. CPM was also shown to create a strong anti-inflammatory environment by effectively clearing harmful, inflammatory particles from within the knee. CONCLUSIONS: Current basic science evidence from rabbit studies has shown that CPM for the knee significantly improves motion and biological properties of articular cartilage. This may be translated to potentially improved outcomes in the management of articular cartilage pathology of the knee. CLINICAL RELEVANCE: If the rabbit model is relevant to humans, CPM may contribute to improved knee health by preventing joint stiffness, preserving normal articular tissue with better histologic and biologic properties, and improving range of motion as compared with joint immobilization and intermittent active motion.

Survival and clinical outcome of isolated high tibial osteotomy and combined biological knee reconstruction.

PURPOSE: We sought to determine survival and clinical outcomes of high tibial osteotomy (HTO) with or without articular cartilage surgery and/or meniscal allograft transplantation in patients with medial compartment chondral pathology, varus malalignment, and/or meniscal deficiency, whether there is any difference in survival or clinical outcome between these patient cohorts, and whether there is any difference between opening- (OWHTO) and closing-wedge (CWHTO) techniques. METHODS: A systematic review of multiple medical databases was performed using PRISMA guidelines. Study quality was assessed via modified Coleman Methodology Scores (MCMS). RESULTS: Sixty-nine studies were included (4557 subjects). MCMS rating was overall poor. Mean follow-up was 7.1 years. Mean subject age was 53 years. Survival of isolated HTO was 92.4%, 84.5%, 77.3%, and 72.3% at 5, 10, 15, and 20 years of follow-up. At 5 years of follow-up, HTO with articular cartilage surgery had significantly greater survival (97.7%) than either isolated HTO (92.4%) or HTO with MAT (90.9%). Isolated HTO, HTO with articular cartilage surgery, and HTO with MAT all significantly improved subjective and objective clinical outcome scores. At two years of follow-up, survival was significantly greater following OWHTO (98.7%) versus CWHTO (96.7%). However, at all other time points with or without combined articular cartilage surgery and/or MAT, there was no significant survival difference between the techniques. CONCLUSIONS: Survival and clinical outcomes of isolated HTO were excellent at short- and mid-term follow-ups, but deteriorated with time. HTO with concomitant procedures also demonstrated excellent early survival and clinical outcomes that deteriorated with time (up to 10 years).

The high variability in sizing knee cartilage defects.

BACKGROUND: Articular cartilage defects of the knee are commonly encountered during arthroscopic examination and are believed to be a precursor to osteoarthritis. While a variety of surgical treatments exist, the defect size, specifically the cross-sectional area, has historically been used as a critical element in choosing one procedure over another. The purpose of this study was to characterize the variability associated with arthroscopic techniques that are used to determine the cross-sectional area of distal femoral articular cartilage defects. METHODS: Six orthopaedic surgeons used four measurement techniques to estimate the area of cartilage defects in ten cadaveric knees. The areas of the defects determined by the surgeons were compared against the known areas of the defects that were determined from plastic molds. RESULTS: Averaged across all approaches, the four measurement techniques yielded highly variable results that underestimated the size of the defects (mean and standard deviation, -0.31 ± 1.22 cm²). There was no difference in the estimated sizes of the defects on the medial or lateral femoral condyles (p = 0.96), but defects on the trochlea (mean, -0.53 ± 1.00 cm²) were less accurately sized than defects on either of the condyles (p < 0.01). The areas of defects that were <2 cm² were overestimated (mean, 0.21 ± 0.65 cm²) compared with other sizes of defects (p < 0.001), and the areas of defects that were >4 cm² were underestimated (mean, -0.87 ± 1.83 cm²) compared with other defects (p < 0.001). CONCLUSIONS AND CLINICAL RELEVANCE: Our current treatment algorithms rely heavily on the size of a cartilage defect, but only 57% of the measurements in this study would have accurately led to the appropriate surgical procedure. There is a need to evaluate and quantify the size of a lesion more appropriately than current standards allow and potentially revise existing treatment algorithms.

Improved outcomes with combined autologous chondrocyte implantation and patellofemoral osteotomy versus isolated autologous chondrocyte implantation.

PURPOSE: To compare clinical outcomes of patients undergoing isolated patellofemoral autologous chondrocyte implantation (ACI) and ACI combined with patellofemoral realignment. METHODS: A systematic review was performed by use of PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines/checklist. We searched PubMed, CINAHL (Cumulative Index to Nursing and Allied Health Literature), SportDiscus, and the Cochrane Central Register of Controlled Trials databases from 1946 through February 2012 to determine whether a difference exists in outcomes of combined ACI and osteotomy versus isolated ACI (minimum 2 years' follow-up). Studies were included only if outcomes were reported separately for both isolated ACI and combined ACI and osteotomy. All ACI generations were eligible for inclusion. Patellofemoral osteotomies eligible for inclusion were anteriorization, medialization, or anteromedialization. All patient-, limb-, and defect-specific characteristics were assessed. All reported clinical scores, radiographic and histologic outcomes, and complications/reoperations were analyzed. Risk of bias was assessed within all studies. RESULTS: Eleven studies (10 Level III or IV evidence) (366 subjects) were included. Of the defects treated, 78% were located on the patella and 22% on the trochlea. The mean subject age was 33.3 years. Twenty-three percent of subjects underwent concomitant osteotomy. The mean length of follow-up was 4.2 years. Significant (P < .05) improvements in patients undergoing both isolated ACI and combined ACI and osteotomy for patellofemoral chondral defects were observed in all studies. Three studies directly compared isolated ACI and combined ACI and osteotomy, with significantly (P < .05) greater improvements shown in patients undergoing combined osteotomy and ACI (International Knee Documentation Committee subjective score, Lysholm score, Knee Injury and Osteoarthritis Outcome Score, Tegner score, modified Cincinnati score, Short Form 12 score, and Short Form 36 score). There was no significant difference between groups in the rate of postoperative complications overall. CONCLUSIONS: This review showed statistically significant improvements in patients undergoing both isolated ACI and ACI combined with osteotomy for patellofemoral chondral defects in all studies. When individual studies compared these 2 groups (3 studies), significantly greater improvements in multiple clinical outcomes in subjects undergoing ACI combined with osteotomy were observed. There was no significant difference in the rate of total complications between groups. LEVEL OF EVIDENCE: Level IV, systematic review of studies with minimum Level IV evidence, retrospective case series.

Factors influencing the outcome of autologous chondrocyte implantation: a systematic review.

Autologous chondrocyte implantation (ACI) is an effective method of treatment of chondral defects of the knee. ACI outcomes are influenced by patient-, knee-, and lesion-specific factors. We compiled subject-level data from current studies on ACI and quantitatively analyzed this data set for associations between patient-, knee-, and lesion-specific factors and the outcome of ACI surgery. A systematic review of studies investigating ACI treatment outcomes in the knee was performed. Only studies that published subject-level data were included. Data on patient and lesion characteristics, as well as clinical outcome scores, were collected. Thirteen studies (305 defects) were included in this review. These studies showed that ACI treatment improves clinical outcomes in different patient populations. However, subject-specific variables such as patient age, gender, body mass index, duration of preoperative symptoms, as well as defect size and location were not associated with International Knee Documentation Committee score or visual analog scale score changes (p > 0.05 for all). Covariate analysis showed that patient age was related to symptom duration prior to surgery (p = 0.009). ACI surgery has been shown to improve outcomes in patients with chondral lesions of the knee. Despite evidence in the literature showing that multiple patient-, knee-, and lesion-specific factors may influence treatment outcomes, our review shows that these factors, solely, do not affect outcomes. However, together, they may synergistically affect outcomes.

Preoperative MRI underestimates articular cartilage defect size compared with findings at arthroscopic knee surgery.

BACKGROUND: Magnetic resonance imaging (MRI) is widely used as a preoperative tool to estimate the size of articular cartilage defects to optimize treatment selection. However, the reliability of MRI sizing of cartilage defects is not well understood. Hypothesis/ PURPOSE: The purpose of this investigation was to compare the size of knee articular cartilage defects on MRI to arthroscopic visualization after debridement. It was hypothesized that MRI sizing would produce measurements that were no different than those made during arthroscopic knee surgery. STUDY DESIGN: Cohort study (diagnosis); Level of evidence, 2. METHODS: Seventy-seven patients (age [mean ± SD], 38 ± 10.7 years) who met inclusion criteria underwent preoperative knee MRI of at least 1.5 T within 1 year of arthroscopic knee surgery for a high-grade cartilage defect. Postdebridement defect sizes were obtained from intraoperative surgery notes and compared with retrospective MRI estimates. RESULTS: Ninety-two total cartilage defects were analyzed with an average of 1.2 high-grade defects per knee and average postdebridement defect area of 2.99 cm(2) per lesion (95% CI, 1.63-2.26 cm(2)). Preoperative MRI analysis estimated a lesion area that was an average of 1.04 cm(2) smaller (95% CI, 0.70-1.39 cm(2); P < .0001). In 74% of the lesions analyzed, defect size was larger on arthroscopic visualization than was estimated by MRI sizing. On average, MRI underestimated the defect area by 70% compared with arthroscopic visualization. CONCLUSION: Magnetic resonance imaging underestimates the size of articular cartilage defects compared with final postdebridement size as measured during arthroscopic knee surgery. Thus, before arthroscopic surgery, orthopaedic surgeons should consider treatment strategies that are appropriate for a larger defect than predicted by preoperative MRI.

Sensitivity of magnetic resonance imaging for detection of patellofemoral articular cartilage defects.

PURPOSE: Chondral defects within the patellofemoral compartment are common and lack the ability to heal on their own. Early detection of these lesions with a noninvasive modality would be beneficial in delaying or preventing their possible progression to osteoarthritis. We hypothesized that magnetic resonance imaging (MRI) is a sensitive, specific, and accurate imaging modality for the detection of patellofemoral chondral defects with substantial interobserver reliability and that MRI has a higher sensitivity, specificity, and accuracy for detecting patellar defects than trochlear defects. METHODS: A systematic review of multiple medical databases was performed by use of the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) protocol. Analysis of studies that reported diagnostic performance of MRI in the assessment of patellofemoral chondral defects (patella and trochlea), using arthroscopy as the reference gold standard, was performed. Sensitivity, specificity, accuracy, and interobserver reliability were reported. Significant heterogeneity across studies precluded meta-analysis. RESULTS: MRI was more sensitive in detection of patellar (87%) versus trochlear (72%) defects. MRI was similarly specific for patellar (86%) and trochlear (89%) defects. MRI was similarly accurate for patellar (84%) and trochlear (83%) defects. Interobserver agreement was substantial to almost perfect for both patellar and trochlear defects. CONCLUSIONS: MRI is a highly sensitive, specific, and accurate noninvasive diagnostic modality for the detection of chondral defects in the patellofemoral compartment of the knee, using arthroscopy as the reference gold standard. Although there was wide variability in the statistical parameters assessed, MRI was more sensitive for detection of patellar versus trochlear defects and similarly specific and accurate for patellar and trochlear defects. Interobserver reliability is substantial to near perfect in the assessment of these lesions, without a significant difference between patellar and trochlear defects. CLINICAL RELEVANCE: Use of MRI may allow early detection of chondral defects within the patellofemoral compartment, enabling clinicians to adopt strategies to delay or prevent progression to osteoarthritis. LEVEL OF EVIDENCE: Level III, systematic review of Level I, II, and III studies.

Design and cadaveric validation of a novel device to quantify knee stability during total knee arthroplasty.

The success of total knee arthroplasty depends, in part, on the ability of the surgeon to properly manage the soft tissues surrounding the joint, but an objective definition as to what constitutes acceptable postoperative joint stability does not exist. Such a definition may not exist due to lack of suitable instrumentation, as joint stability is currently assessed by visual inspection while the surgeon manipulates the joint. Having the ability to accurately and precisely measure knee stability at the time of surgery represents a key requirement in the process of objectively defining acceptable joint stability. Therefore, we created a novel sterilizable device to allow surgeons to measure varus-valgus, internal-external, or anterior-posterior stability of the knee during a total knee arthroplasty. The device can be quickly adjusted between 0 deg and 90 deg of knee flexion. The device interfaces with a custom surgical navigation system, which records the resultant rotations or translations of the knee while the surgeon applies known loads to a patient's limb with a handle instrumented with a load cell. We validated the performance of the device by having volunteers use it to apply loads to a mechanical linkage that simulated a knee joint; we then compared the joint moments calculated by our stability device against those recorded by a load cell in the simulated knee joint. Validation of the device showed low mean errors (less than 0.21 ± 1.38 Nm and 0.98 ± 3.93 N) and low RMS errors (less than 1.5 Nm and 5 N). Preliminary studies from total knee arthroplasties performed on ten cadaveric specimens also demonstrate the utility of our new device. Eventually, the use of this device may help determine how intra-operative knee stability relates to postoperative function and could lead to an objective definition of knee stability and more efficacious surgical techniques.

Biomechanical effects of total knee arthroplasty component malrotation: a computational simulation.

Modern total knee arthroplasty (TKA) is an effective procedure to treat pain and disability due to osteoarthritis, but some patients experience quadriceps weakness after surgery and have difficulty performing important activities of daily living. The success of TKA depends on many factors, but malalignment of the prosthetic components is a major cause of postoperative complications. Significant variability is associated with femoral and tibial component rotational alignment, but how this variability translates into functional outcome remains unknown. We used a forward-dynamic computer model of a simulated squatting motion to perform a parametric study of the effects of variations in component rotational alignment in TKA. A cruciate-retaining and posterior-stabilized version of the same TKA implant were compared. We found that femoral rotation had a greater effect on quadriceps forces, collateral ligament forces, and varus/valgus kinematics, while tibial rotation had a greater effect on anteroposterior translations. Our findings support the tendency for orthopedic surgeons to bias the femoral component into external rotation and avoid malrotation of the tibial component.

The use of continuous passive motion following knee cartilage defect surgery: a systematic review.

We evaluated the clinical evidence of using continuous passive motion postoperatively after treating articular cartilage lesions of the knee. We hypothesized that postoperatively, the use of continuous passive motion improves the outcomes of cartilage restoration procedures. Multiple medical databases (MEDLINE, EMBASE, CINAHL, PubMed, Sport-Discus, and Cochrane) were searched for Level I through IV evidence with specific study inclusion and exclusion criteria. The following key words were searched: microfracture, mosaicplasty, OATS, ACI, osteochondral autograft, osteochondral allograft, autologous chondrocyte implantation, autologous chondrocyte transplantation, CPM, continuous passive motion, motion therapy, postoperative knee rehabilitation, cartilage, knee. All studies were independently reviewed by the authors and the references were checked for any missed articles. Four Level III studies were identified that met inclusion criteria for our hypothesis. No randomized, controlled studies were identified. A meta-analysis could not be performed as a result of the heterogeneity of the procedures and outcome measures. Definitive conclusions regarding the benefits of continuous passive motion postoperatively in knee cartilage surgery could not be made secondary to this heterogeneity. Continuous passive motion is commonly used postoperatively following cartilage surgery. Unfortunately, the clinical evidence (only 4 studies) to support the use of continuous passive motion is lacking despite an overwhelming abundance of basic science support and the common clinical practice of continuous passive motion implementation postoperatively in knee cartilage restoration procedures. There is a great need for well-conducted, high-level evidence studies to address this void in our literature.

The effects of lesion size and location on subchondral bone contact in experimental knee articular cartilage defects in a bovine model.

PURPOSE: To determine how femoral condyle chondral defect size and location influence subchondral bone contact within the defect. METHODS: Full-thickness, circular chondral defects (0.2 to 5.07 cm²) were created in 9 healthy bovine knees. Knees were loaded to 1,000 N, and subchondral bone contact area measurements were recorded with a Tekscan sensor and I-Scan software (Tekscan, Boston, MA). A MATLAB program (The MathWorks, Natick, MA) was designed to compute defect area and the area within the defect showing subchondral bone contact. One-sample t tests with Bonferroni correction were performed for medial and lateral defects at each defect size to determine when statistically significant (P < .05) contact occurred; the smallest defect size exhibiting significant contact was considered a threshold area. RESULTS: The threshold at which significant subchondral bone contact occurred was different for medial and lateral defects. Contact within all defects was not observed below a defect area of 0.97 cm². The threshold at which significant (P < .05) contact occurred was 1.61 cm² and 1.99 cm² for lateral and medial condyle defects, respectively. CONCLUSIONS: Subchondral bone contact within experimental femoral condyle chondral defects is dependent on defect size and intra-articular location. In our bovine model, lateral condyle defects have significant subchondral bone contact at a smaller defect size than medial defects. CLINICAL RELEVANCE: Current algorithms use size as a primary factor in management of chondral defects of the knee. Although the consequences of subchondral bone contact on femoral condyle articular cartilage defect progression are unknown, the results of this study supplement current algorithms and suggest consideration of defect location, in addition to size, in the management of chondral defects of the knee.

Autologous chondrocyte implantation: a systematic review.

BACKGROUND: The purpose of the present study was to determine (1) whether the current literature supports the choice of using autologous chondrocyte implantation over other cartilage procedures with regard to clinical outcome, magnetic resonance imaging, arthroscopic assessment, and durability of treatment, (2) whether the current literature supports the use of a specific generation of autologous chondrocyte implantation, and (3) whether there are patient-specific and defect-specific factors that influence outcomes after autologous chondrocyte implantation in comparison with other cartilage repair or restoration procedures. METHODS: We conducted a systematic review of multiple databases in which we evaluated Level-I and II studies comparing autologous chondrocyte implantation with another cartilage repair or restoration technique as well as comparative intergenerational studies of autologous chondrocyte implantation. The methodological quality of studies was evaluated with use of Delphi list and modified Coleman methodology scores. Effect size analysis was performed for all outcome measures. RESULTS: Thirteen studies (917 subjects) were included. Study methodological quality improved with later publication dates. The mean modified Coleman methodology score was 54 (of 100). Patients underwent autologous chondrocyte implantation (n = 604), microfracture (n = 271), or osteochondral autograft (n = 42). All surgical techniques demonstrated improvement in comparison with the preoperative status. Three of seven studies showed better clinical outcomes after autologous chondrocyte implantation in comparison with microfracture after one to three years of follow-up, whereas one study showed better outcomes two years after microfracture and three other studies showed no difference in these treatments after one to five years. Clinical outcomes after microfracture deteriorated after eighteen to twenty-four months (in three of seven studies). Autologous chondrocyte implantation and osteochondral autograft demonstrated equivalent short-term clinical outcomes, although there was more rapid improvement after osteochondral autograft (two studies). Although outcomes were equivalent between first and second-generation autologous chondrocyte implantation and between open and arthroscopic autologous chondrocyte implantation, complication rates were higher with open, periosteal-cover, first-generation autologous chondrocyte implantation (four studies). Younger patients with a shorter preoperative duration of symptoms and fewer prior surgical procedures had the best outcomes after both autologous chondrocyte implantation and microfracture. A defect size of >4 cm(2) was the only factor predictive of better outcomes when autologous chondrocyte implantation was compared with a non-autologous chondrocyte implantation surgical technique. CONCLUSIONS: Cartilage repair or restoration in the knee provides short-term success with microfracture, autologous chondrocyte implantation, or osteochondral autograft. There are patient-specific and defect-specific factors that influence clinical outcomes.

Treatment of chondral defects in the athlete's knee.

PURPOSE: To determine which surgical technique(s) has improved outcomes and enables athletes to return to their preinjury level of sports and which patient and defect factors significantly affect outcomes after cartilage repair or restoration. METHODS: We conducted a search of multiple medical databases, evaluating studies of articular cartilage repair in athletes. RESULTS: We identified 11 studies for inclusion (658 subjects). Only 1 randomized clinical trial was identified. All other studies were prospective cohorts, case-control studies, or case series reporting results after either microfracture or autologous chondrocyte implantation (ACI) or osteoarticular transplantation (OATS). Eight different clinical outcomes measures were used. Better clinical outcomes were observed after ACI and OATS versus microfracture. Results after microfracture tended to deteriorate with time. The overall rate of return to preinjury level of sports was 66%. The timing of return to the preinjury level of sports was fastest after OATS and slowest after ACI. Defect size of less than 2 cm(2), preoperative duration of symptoms of less than 18 months, no prior surgical treatment, younger patient age, and higher preinjury and postsurgical level of sports all correlated with improved outcomes after cartilage repair, especially ACI. Results after microfracture were worse with larger defects. The rate of return to sports was generally lower after microfracture versus ACI or OATS, and if a patient was able to return to sports, performance was diminished as well. CONCLUSIONS: Management of chondral defects in the athlete is complex and multifactorial. There is little high-level evidence to support one procedure over another, although good short-term and midterm outcomes with a fair rate of return to preinjury level of sports can be achieved with cartilage repair and restoration in the athlete. LEVEL OF EVIDENCE: Level IV, systematic review.