Plastic and elastic biomechanical properties of anterior cruciate ligament autografts

BACKGROUND

Anterior cruciate ligament (ACL) rupture is a common orthopedic injury, occurring in roughly 68.6 per 100,000 persons annually, with the primary treatment option being ACL reconstruction. However, debate remains about the appropriate graft type for restoring the native biomechanical properties of the knee. Furthermore, plastic graft elongation may promote increased knee laxity and instability without rupture. This study aims to investigate the plastic properties of common ACL-R graft options.

METHODS

Patellar tendon (PT), hamstring tendon (HT), and quadriceps tendon (QT) grafts were harvested from 11 cadaveric knees (6 male and 5 female) with a mean age of 71(range 55-81). All grafts were mechanically tested under uniaxial tension until failure to determine each graft's elastic and plastic biomechanical properties.

RESULTS

Mechanically, the QT graft was the weakest, exhibiting the lowest failure force and the lowest failure stress (QT < HT, p = 0.032). The PT was the stiffest of the grafts, having a significantly higher stiffness (PT > QT, p = 0.0002) and Young's modulus (PT > QT, p = 0.001; PT > HT, p = 0.041). The HT graft had the highest plastic elongation at 4.01 ± 1.32 mm (HT > PT, p = 0.002). The post-yield behavior of the HT tendon shows increased energy storage capabilities with the highest plastic energy storage (HT > QT, p = 0.012) and the highest toughness (HT > QT, p = 0.032).

CONCLUSION

Our study agrees with prior studies indicating that the failure load of all grafts is above the requirements for everyday activities. However, grafts may be susceptible to yielding before failure during daily activities. This may result in the eventual loss of functionality for the neo-ACL, resulting in increased knee laxity and instability.

Local Intraoperative Marrow-Derived Augmentation for Primary Rotator Cuff Repair: An Updated Systematic Review and Meta-analysis of Studies From 2010 to 2022

Background

Recurrent tears of the rotator cuff pose a substantial problem despite advances in repair technique. Biologic augmentation via marrow stimulation or vented anchors may strengthen the suture-tendon junction and improve healing rates of native tissue, thereby enhancing outcomes of primary surgical repair.

Purpose

To provide a focused systematic review and meta-analysis of local, intraoperative marrow-derived augmentation techniques in clinical primary rotator cuff repair.

Study Design

Systematic review; Level of evidence, 4.

Methods

A systematic review of PubMed, Embase, and Cochrane was conducted following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. A total of 2131 studies from 2010 to 2022, focused on either marrow stimulation or vented anchors, were isolated and classified as either preclinical or clinical. Meta-analysis was performed for comparative marrow stimulation and vented anchor studies. Heterogeneity was tested through calculation of I ².

Results

A total of 13 clinical studies were included in the review. All 9 comparative studies included in the meta-analysis demonstrated high methodologic quality or a low risk of bias. The pooled retear rate across all 9 clinical studies for patients undergoing marrow stimulation was 11%. For the 5 studies in the meta-analysis, the pooled retear rates were 15% for marrow stimulation and 30% for controls. Meta-analysis demonstrated a significant difference in the overall retear rate that favored marrow stimulation (odds ratio [OR], 0.41; 95% CI, 0.25-0.66; P = .0003; I ² = 0%). Similarly, meta-analysis of the Constant score at final follow-up demonstrated a statistically significant difference between the 2 groups that favored a higher Constant score in the marrow stimulation group (mean difference, 2.84; 95% CI, 1.02-4.66; P = .002; I ² = 29%). Vented anchors demonstrated improved ossification and bone density at the anchor site, but no difference in outcomes or retear. Pooled retear rates were 22.5% for vented anchors and 27.8% for controls.

Conclusion

Current evidence demonstrates that marrow-stimulation techniques may have a positive impact on healing and retear rate, while vented anchors have a muted impact relative to nonvented anchors. Although available evidence is limited and more research is needed, findings to date suggest that marrow stimulation techniques may be an inexpensive, straightforward technique to consider in qualifying patients to prevent rotator cuff retears.

Evidence for Utilization of Injectable Biologic Augmentation in Primary Rotator Cuff Repair: A Systematic Review of Data From 2010 to 2022

Background

Biologic healing after rotator cuff repair remains a significant challenge. Injectable biologic augmentation may improve tissue quality at the suture-tendon interface.

Purpose

To investigate the effect of injectable biologic supplementation in rotator cuff repair and to assess the quality and adherence to evolving reporting standards.

Study Design

Systematic review; Level of evidence, 3.

Methods

A systematic review was conducted following PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Included were 40 studies: 29 preclinical (in vivo animal models) and 11 clinical. Each clinical study was assessed for quality, risk of bias, and adherence to relevant MIBO (Minimum Information for Studies Evaluating Biologics in Orthopaedics) guidelines. The outcomes of interest were reported load to failure, load to gap, gap size, and stiffness in the preclinical studies, and healing rate and any patient-reported outcome measures in the clinical studies.

Results

Injectables reported included growth factors (eg, transforming growth factor-beta 3, erythropoietin), bone marrow-derived mesenchymal stem cells and adipose-derived mesenchymal stem cells (ADSCs), and other agents such as platelet-rich plasma (PRP) and hyaluronic acid. The most common findings for preclinical injectables were increased load to failure (16/29 studies; 55.2%) and improved collagen histological quality (11/29 studies; 37.9%). All 11 clinical studies (10 PRP, 1 ADSC) indicated no adverse events, with similar or improved patient-reported outcomes compared with repairs in the control groups. In 1 study utilizing an innovative delivery technique, a concentrated PRP globule with fibrin matrix was shuttled over a suture to maintain concentrated PRP at the repair site and demonstrated a significant decrease in retears (P = .03) at a 31-month follow-up. A matched-cohort study investigating augmentation with ADSCs demonstrated a significantly lower retear rate in the ADSC-augmented group than the control group at a 28-month follow-up (P < .001). On average, the clinical studies adhered to 66% of relevant MIBO reporting guidelines and had a low risk of bias.

Conclusion

Approximately 83% of preclinical studies found a positive biomechanical or histological effect, with no studies showing an overall negative effect. Clinically, utilization of innovative delivery techniques may reduce the risk of arthroscopic washout of PRP and improve retear rates. ADSCs were shown to reduce retear rates at a 28-month follow-up.

Lateral retinacular release in concordance with medial patellofemoral ligament reconstruction in patients with recurrent patellar instability: A computational model

BACKGROUND

The aim of this study was to develop and validate a finite element (FE) model of the patellofemoral joint to analyze the biomechanics of lateral retinacular release after medial patellofemoral ligament (MPFL) reconstruction in patellar malalignment (increased tibial tubercle-trochlear groove distance (TT-TG)). We hypothesized that lateral retinacular release is not appropriate in patellar instability addressed by MPFL reconstruction due to decreased lateral stability and inappropriate adjustment in patellofemoral contact pressures.

METHODS

A FE in-silico model of the patellofemoral joint was developed and validated. The model was used analyze the effect of lateral retinacular release in association with MPFL reconstruction on patellofemoral contact pressures, contact area, and lateral patellar displacement during knee flexion.

RESULTS

MPFL reconstruction alone results in restoration of patellofemoral contact pressures throughout the entire range of motion (0-90°), mimicking the results from healthy condition. The addition of the lateral retinacular release to the MPFL reconstruction resulted in significant reductions in both patellofemoral contact pressure and contact area. Lateral retinacular release resulted in more lateral patellar displacement during the mid-flexion knee range of motion.

CONCLUSIONS

Combination of lateral retinacular release with MPFL reconstruction in patients with increased TT-TG is not recommended as MPFL reconstruction alone for first-line management of recurrent patellar instability offers a greater biomechanical advantage and restoration of contact forces to resemble that of the healthy knee. The presented biomechanical data outlines the effect of concomitant MPFL reconstruction and lateral retinacular release to help guide surgical planning for patients with recurrent patellar instability due to malalignment.

Evolution of knowledge on meniscal biomechanics: a 40 year perspective

Background

Knowledge regarding the biomechanics of the meniscus has grown exponentially throughout the last four decades. Numerous studies have helped develop this knowledge, but these studies have varied widely in their approach to analyzing the meniscus. As one of the subcategories of mechanical phenomena Medical Subject Headings (MeSH) terms, mechanical stress was introduced in 1973. This study aims to provide an up-to-date chronological overview and highlights the evolutionary comprehension and understanding of meniscus biomechanics over the past forty years.

Methods

A literature review was conducted in April 2021 through PubMed. As a result, fifty-seven papers were chosen for this narrative review and divided into categories; Cadaveric, Finite element (FE) modeling, and Kinematic studies.

Results

Investigations in the 1970s and 1980s focused primarily on cadaveric biomechanics. These studies have generated the fundamental knowledge basis for the emergence of FE model studies in the 1990s. As FE model studies started to show comparable results to the gold standard cadaveric models in the 2000s, the need for understanding changes in tissue stress during various movements triggered the start of cadaveric and FE model studies on kinematics.

Conclusion

This study focuses on a chronological examination of studies on meniscus biomechanics in order to introduce concepts, theories, methods, and developments achieved over the past 40 years and also to identify the likely direction for future research. The biomechanics of intact meniscus and various types of meniscal tears has been broadly studied. Nevertheless, the biomechanics of meniscal tears, meniscectomy, or repairs in the knee with other concurrent problems such as torn cruciate ligaments or genu-valgum or genu-varum have not been extensively studied.

Mandated health insurance increases rates of elective knee surgery

BACKGROUND

The recent federal ruling to against Affordable Care Act (ACA), specifically the mandate requiring people to buy insurance, has once again brought the healthcare reform debate to the spotlight. The ACA increased the number of insured Americans through the development of subsidized healthcare plans and health insurance exchanges. Insurance-based differences in the rate of upper extremity elective orthopaedic surgery have been described before and after healthcare reform in Massachusetts, where a similar mandate was put into place years before the ACA was passed. However, no comprehensive study has evaluated insurance-based differences of knee elective surgery before and after reform.

AIM

To investigate how an individual mandate to purchase health insurance affects rates of knee surgery.

METHODS

A retrospective review was performed within an orthopaedic surgery department at a tertiary-care, academic medical center in Massachusetts. The rate of elective knee surgery performed before and after the healthcare reform (2005-2006 and 2007-2010, respectively) was calculated. The patients were categorized by insurance type (Commonwealth Care, Medicare, Medicaid, private insurance, Workers’ Compensation, TriCare, and Uninsured). Using χ² testing, differences in rates of surgery between the pre-reform and post-reform period and among insurance subgroups were calculated.

RESULTS

Rate of surgery increased in the post-reform period (pre-reform 8.07% (95%CI: 7.03%-9.11%), post-reform 9.38% (95%CI: 8.74%-10.03%) (P = 0.04) and was statistically significant. When the insurance groups and insurance types were compared, the rates of surgery are not significantly different before or after reform.

CONCLUSION

The increase in the rate of elective knee surgery in the post-reform period suggests that health care reform in Massachusetts has been successful in decreasing the uninsured population and may increase health care expenditures. This is a hypothesis generating study that suggests further avenues of study on how mandated coverage may change healthcare utilization and cost.

Comparison of Anterior and Posterior Cortico-steroid Injections for Pain Relief and Functional Improvement in Shoulder Impingement Syndrome

Subacromial impingement syndrome (SIS) is the most common cause of shoulder pain. Treatment options for SIS include conservative modalities such as use of nonsteroidal anti-inflammatory drugs, physical therapy, and subacromial corticosteroid injections (CSIs). Although studies have found improvement in pain, function, and range of motion after CSI, the effect of injection route (anterior or posterior) on shoulder pain in patients with SIS has not been investigated. In the study reported here, patients were randomly assigned to 2 treatment groups: anterior CSI and posterior CSI. Pain was assessed with a visual analog scale (VAS) and function with the Single Assessment Numeric Evaluation (SANE). Patients were evaluated before injection (baseline) and 1, 3, and 6 months after injection. Of the 55 patients enrolled, 25 received anterior CSI and 30 received posterior CSI. The 2 groups showed no significant difference in VAS pain at baseline or 1, 3, or 6 months after injection. SANE scores were statistically different at 3 months. Each group had significantly less pain and better function 1, 3, and 6 months after injection than at baseline. Age, sex, and body mass index did not significantly affect the efficacy of anterior or posterior CSIs. In patients with SIS, subacromial CSI reduces pain and improves function for up to 6 months. These effects are no different for anterior and posterior injection routes. As a result, clinicians should rely on their clinical acumen when selecting injection routes, as anterior and posterior are both beneficial.

Return to driving after arthroscopic rotator cuff repair: patient-reported safety and maneuverability

This survey investigated patients' return to driving after rotator cuff surgery, to determine whether pain, weakness, sling use, and narcotics correlate with self-assessed safety and maneuvering. Fifty-four patients (80.6% of those eligible) were surveyed 4 months after surgery. Return to driving ranged widely from same day to 4 months, with two not driving at 4 months; 12% reported narcotics use and 33% reported sling use. Drivers reporting weakness were more likely to feel unsafe (p = .02) and more likely to report difficulty maneuvering (p <.01). Drivers reporting pain were more likely to feel unsafe (p < .01) and more likely to report difficulty maneuvering their vehicle (p < .01). Patient-reported return to driving does not correspond to perceived safety; pain and weakness correspond with feeling unsafe and difficulty maneuvering. Although subjective, clinicians may find these self-assessments predictive when counseling patients on return to driving.

Vitamin d, calcium, and dairy intakes and stress fractures among female adolescents

OBJECTIVE To identify whether calcium, vitamin D, and/or dairy intakes are prospectively associated with stress fracture risk among female adolescents. DESIGN Prospective cohort study. SETTING Adolescent girls living throughout the United States. PARTICIPANTS A total of 6712 girls aged 9 to 15 years at baseline in the Growing Up Today Study, an ongoing prospective cohort study. MAIN EXPOSURES Dairy, calcium, and vitamin D intakes assessed by food frequency questionnaire every 12 to 24 months between 1996 and 2001. MAIN OUTCOME MEASURE Incident stress fracture that occurred between 1997 and 2004 as reported by mothers of the participants in 2004. Cox proportional hazards models were used to examine associations. RESULTS During 7 years of follow-up, 3.9% of the girls developed a stress fracture. Dairy and calcium intakes were unrelated to risk of developing a stress fracture. However, vitamin D intake was inversely related to stress fracture risk. The multivariable-adjusted hazard ratio of stress fracture for the highest vs the lowest quintile of vitamin D intake was 0.49 (95% CI, 0.24-1.01; Ptrend = .07). We conducted a stratified analysis to estimate the association between vitamin D intake and stress fracture risk among girls participating in at least 1 h/d of high-impact activity, among whom 90.0% of the stress fractures occurred, and found that higher vitamin D intake predicted significantly lower risk of stress fracture (Ptrend = .04). CONCLUSIONS Vitamin D intake is associated with lower stress fracture risk among adolescent girls who engage in high levels of high-impact activity. Neither calcium intake nor dairy intake was prospectively associated with stress fracture risk.

Prospective study of physical activity and risk of developing a stress fracture among preadolescent and adolescent girls

OBJECTIVE

To identify predictors of developing a stress fracture among adolescent girls during a 7-year period.

DESIGN

Prospective cohort study.

SETTING

Adolescent girls living throughout the United States.

PARTICIPANTS

A total of 6831 girls aged 9 to 15 years at baseline in the Growing Up Today Study, an ongoing prospective cohort study.

MAIN EXPOSURES

Exposures were assessed by self-report questionnaires completed by adolescent girls in 1996, 1997, 1998, 1999, 2000, 2001, and 2003. The adolescent girls' history of stress fracture, including age when fracture occurred and site, were reported by their mothers, who are registered nurses, in 2004. Cox proportional hazards models were used in the analysis. Main Outcome Measure Incident stress fracture that occurred between 1997 and 2004.

RESULTS

During 7 years of follow-up, 267 girls (3.9%) developed a stress fracture. Independent of age, age at menarche, family history of fracture, and hours per week of low- and moderate-impact activity, hours per week of running (hazard ratio = 1.13; 95% confidence interval, 1.04-1.23), basketball (hazard ratio = 1.12; 95% confidence interval, 1.03-1.23), and cheerleading/gymnastics (hazard ratio = 1.12; 95% confidence interval, 1.02-1.22) were significant predictors of developing a stress fracture. No other type of high-impact activity was associated with an increased risk.

CONCLUSION

Girls who engage in running, basketball, cheerleading, or gymnastics should be encouraged to include varied training in lower-impact activities to decrease the cumulative amount of impact in order to minimize their risk of stress fractures.

A comparison of forearm supination and elbow flexion strength in patients with long head of the biceps tenotomy or tenodesis

PURPOSE

The purpose of this study was to compare the forearm supination and elbow flexion strength of the upper extremity in patients who have had an arthroscopic long head of the biceps tendon (LHBT) release with patients who have had an LHBT tenodesis.

METHODS

Cybex isokinetic strength testing (Cybex Division of Lumex, Ronkonkoma, NY) was performed on 17 patients who underwent arthroscopic LHBT tenotomy, 19 patients who underwent arthroscopic LHBT tenodesis, and 31 age-, gender-, and body mass index-matched control subjects. Subjects were considered fully recovered from shoulder surgery, were released for unrestricted activities, and were at least 6 months after surgery before testing. Subjects were tested for forearm supination and elbow flexion strength of both arms by use of a Cybex II NORM isokinetic dynamometer at 60°/s and 120°/s. Testing was performed on injured and uninjured arms as well as dominant and nondominant arms in control subjects. Both forearm supination and elbow flexion strength values were recorded.

RESULTS

Comparison between the involved and uninvolved upper extremities within each group by use of a paired t test showed a 7% increase in elbow flexion strength when the dominant and nondominant arms were compared at 60°/s. Neither the tenotomy nor tenodesis groups exhibited elbow flexion strength differences at 120°/s (all P ≥ .147). Comparison between groups by use of 2 × 3 analysis of variance (speed × group) showed no statistical difference in either forearm supination or elbow flexion strength when we compared the tenotomy, tenodesis, and control groups.

CONCLUSIONS

In asymptomatic patients who have had biceps tenotomy or tenodesis, no statistically significant forearm supination or elbow flexion strength differences existed in the involved extremity between the 2 study groups.

LEVEL OF EVIDENCE

Level III, case-control study.

Radiographic and computed tomography analysis of cemented pegged polyethylene glenoid components in total shoulder replacement

BACKGROUND

Glenoid loosening continues to be the primary reason for failure of total shoulder arthroplasty. The purpose of this study was to evaluate, with use of a sensitive and reproducible imaging method, the radiographic and clinical results of total shoulder replacement with a pegged, cemented polyethylene glenoid implant.

METHODS

Forty-three patients (forty-seven shoulders) underwent a total shoulder replacement with a cemented polyethylene glenoid component with four threaded pegs. The patients were examined clinically, with fluoroscopically guided radiographs, and with computed tomography at an average of forty months. In addition to conventional scoring of radiographic lucency, an 18-point scoring system was used to quantify cement-peg lucencies in six zones of the back surface of the glenoid component as seen on computed tomography scans.

RESULTS

On the average, the absolute Constant score improved from 39 points preoperatively to 70 points at the time of follow-up (p = 0.0001) and the pain score improved from 5 to 13 points (p = 0.001). The mean active anterior elevation improved by 34 degrees (p = 0.001) and the mean abduction, by 46 degrees (p = 0.006). Two patients had symptomatic glenoid loosening requiring revision. Twenty-one of the forty-seven shoulders had radiographic lucency around the glenoid pegs, and nine had progression of the lucency by at least two grades. Computed tomography detected lucencies, primarily at the bone-cement interface, in thirty-six shoulders. The scores for the lucencies seen on the computed tomography scans were associated with the radiographic lucency scores (p < 0.001), pain scores (p = 0.04), and abduction strength (p = 0.02). Computed tomography was more sensitive than radiography with regard to identifying the number of pegs associated with lucency and the size of the lucencies. The overall reproducibility of the scoring based on the computed tomography was higher than that of the radiographic scoring.

CONCLUSIONS

Computed tomography provided a more sensitive and reproducible tool for the assessment of loosening of pegged glenoid components than did fluoroscopically guided conventional radiography. Further improvement in implant design and fixation technique appears to be necessary for long-term success of cemented glenoid components.

Paradoxic cerebral embolism after cemented knee arthroplasty: a report of 2 cases and prophylactic option for subsequent arthroplasty

Major orthopaedic procedures that involve instrumentation of the medullary canal are well known to produce showers of embolic debris including fat, bone fragments, marrow constituents, and cement. A growing literature has identified paradoxic cerebral embolism as a rare but serious consequence of the passage of these emboli through an intracardiac right-to-left shunt to the cerebral arterial circulation. We report 2 cases of paradoxic cerebral embolism after cemented total knee arthroplasty and propose a novel treatment plan to prevent recurrent stroke during subsequent surgery.

Canine chondrocytes seeded in type I and type II collagen implants investigated in vitro

Synthetic and natural absorbable polymers have been used as vehicles for implantation of cells into cartilage defects to promote regeneration of the articular joint surface. Implants should provide a pore structure that allows cell adhesion and growth, and not provoke inflammation or toxicity when implanted in vivo. The scaffold should be absorbable and the degradation should match the rate of tissue regeneration. To facilitate cartilage repair the chemical structure and pore architecture of the matrix should allow the seeded cells to maintain the chondrocytic phenotype, characterized by synthesis of cartilage-specific proteins. We investigated the behavior of canine chondrocytes in two spongelike matrices in vitro: a collagen-glycosaminoglycan (GAG) copolymer produced from bovine hide consisting of type I collagen and a porous scaffold made of type II collagen by extraction of porcine cartilage. Canine chondrocytes were seeded on both types of matrices and cultured for 3 h, 7 days, and 14 days. The histology of chondrocyte-seeded implants showed a significantly higher percentage of cells with spherical morphology, consistent with chondrocytic morphology, in the type II sponge at each time point. Pericellular matrix stained for proteoglycans and for type II collagen after 14 days. Biochemical analysis of the cell seeded sponges for GAG and DNA content showed increases with time. At day 14 there was a significantly higher amount of DNA and GAG in the type II matrix. This is the first study that directly compares the behavior of chondrocytes in type I and type II collagen matrices. The type II matrix may be of value as a vehicle for chondrocyte implantation on the basis of the higher percentage of chondrocytes retaining spherical morphology and greater biosynthetic activity that was reflected in the greater increase of GAG content.

Chondrocyte-seeded collagen matrices implanted in a chondral defect in a canine model

The objective of our study was to evaluate reparative tissues formed in chondral defects in an adult canine model implanted with cultured autologous articular chondrocytes seeded in type I and II collagen GAG matrices. Two defects were produced in the trochlea grooves of the knees of 21 dogs, with cartilage removed down to the tidemark. This study includes the evaluation of 36 defects distributed among five treatment groups: Group A, type II collagen matrix seeded with autologous chondrocytes under a sutured type II collagen flap; Group B, type I collagen matrices seeded with chondrocytes under a sutured fascia flap; Group C, unseeded type I collagen matrix implanted under a sutured fascia flap; Group D, fascia lata flap alone; and Group E, untreated defects. All animals were killed 15 weeks after implantation. Six other defects were created at the time of death and evaluated immediately after production as 'acute defect controls'. In three additional defects, unseeded matrices were sutured to the defect and the knee closed and reopened after 30 min to determine if early displacement of the graft was occurring; these defects served as 'acute implant controls'. The areal percentages of four tissue types in the chondral zone of the original defect were determined histomorphometrically: fibrous tissue (FT); hyaline cartilage (HC); transitional tissue (TT, including fibrocartilage); and articular cartilage (AC). New tissue formed in the remodeling subchondral bone underlying certain defects was also assessed. Bonding of the repair tissue to the subchondral plate and adjacent cartilage, and degradation of the adjacent tissues were evaluated. There were no significant differences in the tissues filling the original defect area of the sites treated with chondrocyte-seeded type I and type II matrices. Most of the tissue in the area of the original defect in all of the groups was FT and TT. The areal percentage of HC plus AC was highest in group E, with little such tissue in the cell-seeded groups, and none in groups C and D. The greatest total amount of reparative tissue, however, was found in the cell-seeded type II matrix group. Moreover, examination of the reparative tissue formed in the subchondral region of defects treated with the chondrocyte-seeded collagen matrices (Groups A and B) demonstrated that the majority of the tissue was positive for type II collagen and stained with safranin O. These results indicate an influence of the exogenous chondrocytes on the process of chondrogenesis in this site. In all groups with implants (A-D), 30(50% of the FT and TT was bonded to the adjacent cartilage. Little of this tissue (6-22%) was attached to the subchondral plate, which was only about 50% intact. Remarkable suture damage was found in sections from each group in which sutures were used. Harvest sites showed no regeneration of normal articular cartilage, 18 weeks after the biopsy procedure. Future studies need to investigate other matrix characteristics, and the effects of cell density and incubation of the seeded sponges prior to implantation on the regenerative response.

Matrix collagen type and pore size influence behaviour of seeded canine chondrocytes

This study directly compared the behaviour of chondrocytes in porous matrices comprising different collagen types and different pore diameters. There was a dramatic difference in the morphology of the cells in the type I and type II collagen matrices. The cells in the type II collagen matrix retained their chondrocytic morphology and synthesized glycosaminoglycans, while in the type I matrix the chondrocytes displayed a fibroblastic morphology with less biosynthetic activity than those in the type II. Small pore diameter affected morphology initially in the type I matrices and showed a higher increase of DNA content, but with time the cells lost the chondrocytic morphology. Our results demonstrate the marked influence of collagen type and pore characteristics on the phenotypic expression of seeded chondrocytes.