The use of a hydrogel implant in the repair of osteochondral defects of the knee: A biomechanical evaluation of restoration of native contact pressures in cadaver knees.

BACKGROUND: Osteochondral injuries have been treated by a variety of methods, each having its own drawbacks. The purpose of this study was to determine the biomechanical feasibility of using a hydrogel implant replacement for an osteochondral core defect. The hypothesis of this study was that the contact pressure of the native knee can be recreated with the use of a hydrogel implant. METHODS: Six cadaver knees were tested in a knee simulator while contact pressures were measured on the tibial plateau. Pressure data was collected in the intact knee, after coring of the condyle and after insertion of a hydrogel implant. Following 1000 gait cycles of fatigue testing, each knee was taken through axial loading indentation testing where the stiffness of the in situ implant was compared to the contralateral condyle. FINDINGS: While coring significantly reduced the peak pressure at the coring site from 1.8 MPa in the intact knee to 0.0 MPa after coring, implant insertion significantly increased it to 1.2 MPa. There was no significant difference in the peak pressures or the average pressures at the hole location between the intact knee and following implant insertion. After fatigue testing, no macroscopic loosening or implant damage was observed. Based on indentation testing, the stiffness of the medial condyle, 157 N/mm, was significantly less than the lateral condyle, 696 N/mm. INTERPRETATION: The insertion of the hydrogel implant was able to achieve restoration of contact pressures in the knee supporting the viability of hydrogel implants in the treatment of osteochondral lesions of the knee.

Tibial tubercle osteotomy: A biomechanical comparison of two techniques.

PURPOSE: The purpose of this study was to determine whether a modified step-cut tibial tubercle osteotomy (Maquet-Fulkerson hybrid) might produce comparable or better results than a standard oblique anteromedialization tibial tubercle osteotomy (Fulkerson type) and thus warrant the surgical need for additional cuts. METHODS: Six pairs of cadaveric knees were evaluated prior to and after tibial tubercle osteotomies. Simulation was done via a shallow knee bend simulator through 20 to 70° of knee flexion for the intact specimens and following the surgical procedures. The variables tested were trochlear contact forces and pressures and patellar motion. RESULTS: Testing showed a decreased force (P=0.027), peak contact pressure (P=0.01) and contact area (P=0.034) on the lateral trochlea of the femur for both types of osteotomies. There was no significant difference in the lateral femoral peak pressure or in the medial femoral peak pressure between the oblique cut and the step-cut. Also, there was no difference in patellar motion after either procedure. CONCLUSION: We conclude that both osteotomies decrease lateral patellofemoral trochlear pressure. The oblique osteotomy may decrease lateral pressure to a greater extent. Regarding biomechanical testing, there was no demonstrable advantage to performing a step-cut osteotomy.

General and disease-specific use of outcomes scores for the shoulder: a survey of AOSSM, AANA, and ISAKOS members.

OBJECTIVE: To report on the knowledge and use of both general and disease-specific shoulder outcomes scores among orthopedic surgeons. METHODS: A 22-question Internet survey was administered to members of the American Orthopaedic Society for Sports Medicine, the Arthroscopy Association of North American, and the International Society of Arthroscopy, Knee Surgery, and Orthopedic Sports Medicine via voluntary e-mail participation. Questions targeted demographic information, preferred surgical management of shoulder conditions, and the preferred use of shoulder outcomes instruments in clinical practice. RESULTS: Excluding defunct and duplicate e-mails among membership societies, a total of 3892 unique e-mails were sent, from which 1129 surveys were returned and were fully completed (29%). The largest number of respondents were in private practice (52%); 21% were in academia; and 26% were in a mix of settings. As for location, 74% practiced in the United States, 10% in Europe, 8% in Mexico/South America, and 6% in Asia. A total of 31% total respondents used scores all or most of the time, and 30% used scores at least some of the time. Respondents felt that the 3 most commonly utilized shoulder scores were the American Shoulder and Elbow Surgeons (ASES) score, the University of California at Los Angeles (UCLA) score, and the Constant score. The majority of respondents (76%) performed all-arthroscopic instability repairs. The ASES and Western Ontario Shoulder Instability Index (WOSI) scores were the most preferred measures to monitor instability patients, whether or not the scores were actually implemented in their practice. Most perform between 10 and 25 superior labrum anterior-posterior repairs per year and preferred the ASES, UCLA, and Constant scores for these repairs; rotator cuff repair preferred outcomes instruments were similar. When asked to choose 1 score for all shoulder conditions, the ASES was the clear favorite. CONCLUSIONS: This study reports the knowledge and utilization of shoulder scores for both general and disease-specific conditions. Most respondents preferred the ASES score for most shoulder conditions; however, other scores, such as the WOSI, the Constant, and the Short-Form (SF)-36/12, were popular. This information offers insight into the current and future use of shoulder outcomes both for general and disease-specific use.

Repair of lateral meniscus posterior horn detachment lesions: a biomechanical evaluation.

BACKGROUND: Posterior horn detachment (PHD) lesions of the lateral meniscus are commonly associated with acute anterior cruciate ligament (ACL) tears. Multiple surgeons have advocated for repair of this lesion at the time of ACL reconstruction. However, the biomechanical consequences of this lesion and its subsequent repair have not been evaluated. HYPOTHESIS: The PHD lesion of the lateral meniscus will lead to increased tibiofemoral contact pressures, and repair of this lesion to bone via a tibial tunnel can restore normal contact pressures during simulated gait. STUDY DESIGN: Controlled laboratory study. METHODS: Lateral compartment contact pressures were measured via a sensor on the tibial plateau in 8 cadaver knees with the knee intact, after sectioning the posterior horn of the lateral meniscus to simulate PHD, and after repairing the injury. The repair was performed using an ACL tunnel guide to drill a tunnel from the anteromedial tibia to the posterior horn attachment site. Dynamic pressure data were continuously collected using a conductive ink pressure sensing system while each knee was moved through a physiological gait flexion cycle. RESULTS: Posterior horn detachment caused a significant increase in tibiofemoral peak contact pressure from 2.8 MPa to 4.2 MPa (P = .03). After repair of the lesion to bone was performed through a transtibial tunnel, the peak contact pressure was 2.9 MPa. Posterior horn detachment also significantly decreased the maximum contact area over which tibiofemoral pressure is distributed from 451 mm(2) in the intact state to 304 mm(2) in the detached state. Repair of the PHD lesion increased the maximum contact area to 386 mm(2), however, this area was also significantly less than in the intact state (P = .05). CONCLUSION: Posterior horn detachment of the lateral meniscus causes increased peak tibiofemoral contact pressure. The peak pressure can be reduced to a normal level with repair of the lesion to bone via a transtibial tunnel. CLINICAL RELEVANCE: Posterior horn detachment of the lateral meniscus is a lesion often associated with an acute ACL tear. Debate exists concerning the importance of repairing PHD lesions at the time of ACL reconstruction. The data provided in this study may influence surgeons' management of the lesion.

Results of laboratory evaluation of acute knee effusion after anterior cruciate ligament reconstruction: what is found in patients with a noninfected, painful postoperative knee?

BACKGROUND: Infection after anterior cruciate ligament reconstruction is a rare and potentially devastating complication. No normative data have been reported for knee aspiration after anterior cruciate ligament reconstruction in the early postoperative period. HYPOTHESIS: Determining normative laboratory data from a retrospective review of noninfected early postoperative anterior cruciate ligament reconstruction knee effusions will allow for the calculation of an aspirate white blood cell (WBC) threshold value indicative of infection. STUDY DESIGN: Case series (diagnosis); Level of evidence, 4. METHODS: A 2-year retrospective chart review of 151 anterior cruciate ligament reconstruction patients was performed. Thirty-one noninfected patients meeting the inclusion and exclusion criteria and 1 infected patient had laboratory data collected, including peripheral blood and knee effusion aspirate analyses. Laboratory data from pertinent published studies of infected knees after anterior cruciate ligament reconstruction were combined with the data of our 1 infected patient, establishing a historical control group. Data were analyzed and results were then compared. Infected aspirate WBC threshold value statistics were then calculated. RESULTS: Analysis of noninfected knee effusion aspirates revealed a mean WBC count of 9600/uL (standard deviation [SD], 15 200), and a mean of 66% polymorphonuclear (PMN) cells (SD, 34). Aspirate WBC 98% confidence interval (CI) was 2800/uL to 16 200/uL, and the 98% CI for PMN cells was 58% to 84%. Aspirate WBC count >16 200/uL is 86% sensitive, 92% specific, and has a positive likelihood ratio of 10.4 as an indicator of infection. CONCLUSION: Benign effusion after anterior cruciate ligament reconstruction is common and is associated with elevated inflammatory markers. When concerned, knee aspiration after anterior cruciate ligament surgery gives the highest yield to differentiate between a painful effusion and a septic knee in the early postoperative period while awaiting definitive culture results. The authors report confidence intervals defining the range of cell count variables for noninfected patients requiring aspiration, specifically WBC and PMN, and suggest a WBC threshold value of >16 200/uL be used as an indicator of infection. On the basis of comparison with historical control data, the authors believe these data are significant and will be reliable for clinical use.

Knee medial compartment contact pressure increases with release of the type I anterior intermeniscal ligament.

BACKGROUND: The anterior intermeniscal ligament of the knee is at risk during knee arthroscopy, anterior cruciate ligament reconstruction, and tibial nail insertion. HYPOTHESIS: Release of the anterior intermeniscal ligament, in knees with type I ligaments, will result in altered contact pressures in the medial compartment. STUDY DESIGN: Controlled laboratory study. METHODS: Five fresh-frozen human cadaveric knees with intact type I anterior intermeniscal ligaments were chosen for testing in a modified MTS machine from 0 degrees to 60 degrees of flexion under 2 conditions: (1) intact and (2) after sharp sectioning of the anterior intermeniscal ligament. Measurements were made using inframeniscal contact pressure sensors covering the medial compartment. Poststudy analysis was done in 10 degrees increments between 0 degrees and 60 degrees of flexion, looking at peak contact pressure and the amount of contact area seeing pressure. RESULTS: Sectioning of the anterior intermeniscal ligament caused a statistically significant increase in the peak pressure at 20 degrees , 30 degrees , 40 degrees , and 50 degrees of knee flexion. The largest change occurred at 40 degrees of knee flexion, when the peak pressure increased by 27.5% (3.68 MPa to 4.69 MPa). Contact area decreased, although this difference was not statistically significant. CONCLUSION: Release of the anterior intermeniscal ligament results in increased peak contact pressures in the medial compartment of the knee. CLINICAL RELEVANCE: Care should be taken to avoid sacrifice of this ligament during surgery.

Glenohumeral articular contact areas and pressures following labral and osseous injury to the anteroinferior quadrant of the glenoid.

The objective of this study was to determine the effect of progressive labral and bone loss on the articular contact area and pressures across the glenohumeral joint under compressive loads of 220 and 440 N. Eight fresh-frozen cadaver shoulders were used, and contact pressures in 4 quadrants of the glenoid were determined with a Tekscan flexible tactile force sensor. Testing conditions included intact glenoids, glenoids with the anteroinferior labrum removed, and glenoids with 3 sizes of bone defects in the anteroinferior quadrant. By means of Tekscan sensing equipment, the measured contact area over the glenolabral complex was between 49.0% and 61.5% of the calculated surface area for the intact specimens. Loss of the anteroinferior labrum decreased contact area by 7% to 15% compared with the intact specimens, and the mean contact pressure increased by 8% to 20%. With bone loss corresponding to a defect measuring 30% of the diameter in the anteroinferior quadrant, contact area across the entire glenoid decreased a mean of 41% compared with the intact specimens, whereas the mean contact pressure increased nearly 100%. When the anteroinferior quadrant of the glenoid was analyzed separately, loss of the anteroinferior labrum alone resulted in an increase in the mean contact pressure in this quadrant compared with the intact specimens (mean, 53%). Bone loss of 30% of the diameter resulted in mean contact pressures in this quadrant increasing by 300% to 400% compared with the intact specimens, with 2 of 8 specimens becoming grossly unstable. In addition, with 30% diameter bone loss, the mean contact pressure decreased by 26% in the posterosuperior quadrant, indicating a shift in loading of the cadaveric glenoid. Peak pressures followed similar trends, with labral loss alone increasing peak pressures in the anteroinferior quadrant by a mean of 28% of that seen for the intact specimens.