Brian P. McKeon

Mechanical Evaluation of a Soft Tissue Interference Screw in Free Tendon Anterior Cruciate Ligament Graft Fixation

In this study of bioabsorbable screw fixation of free tendon grafts used in anterior cruciate ligament reconstruction, we performed load-to-failure and cyclic loading of tendon fixation in porcine bone. Bone density measurements from dual photon absorptometry scans were obtained to correlate bone density with fixation failure. The average density of porcine bone (1.42 g/cm2) was similar to that of young human bone (1.30 g/cm2) and significantly higher than that of elderly human cadaveric bone specimens (0.30 g/cm2). Cyclic loading was performed on free tendon grafts fixed with a bioabsorbable screw alone and on grafts fixed with a bioabsorbable screw and an anchor (polylactic acid ball or cortical bone disk). Stiffness of fixation increased substantially with the addition of a cortical bone disk anchor or polylactic acid ball compared with the interference screw alone. Tensile fixation strength of central quadriceps free tendon and hamstring tendon grafts were significantly superior in porcine bone of density similar to young human bone than in elderly human cadaveric bone. The bioabsorbable interference screw yielded loads at failure comparable with traditional bone-tendon-bone and hamstring tendon fixation when controlled for bone density. The addition of a cortical bone disk anchor provided the most optimal fixation of free tendon with the bioabsorbable screw and reduced slippage with cyclic loading to a very low level.

Magnetic resonance imaging of relative glycosaminoglycan distribution in patients with autologous chondrocyte transplants.

Gillis A, Bashir A, McKeon B, et al. Magnetic resonance imaging of relative glycosaminoglycan distribution in patients with autologous chondrocyte transplants. Invest Radiol 2001;36:743–748. rationale and objectives. Autologous chondrocyte transplantation (ACT) is a potential treatment for full-thickness chondral lesions in the knee. Delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) has recently been developed as a sensitive and specific measure of cartilage glycosaminoglycans (GAGs). Under the conditions of dGEMRIC, T1 is directly related to the GAG concentration. Our aim for this study was to demonstrate the potential of dGEMRIC to evaluate ACT implants. methods. Eleven ACT implants were studied 2 to 24 months postoperatively by dGEMRIC. T1 values from three regions of interest were obtained to examine GAG content (1) in the implant, (2) in native cartilage adjacent to the implant, and (3) in native cartilage further removed from the implant (as “control”). results. One implant failed and therefore was not included. Four of the implants were studied between 2 and 6 months postoperatively and showed low T1 (GAG), less than 80% of the control native cartilage. Five of the six implants studied between 12 and 24 months postoperativley showed T1 (GAG) comparable to (>80%) of control. One 18-month graft showed low T1 comparable to the surrounding native cartilage, with normal GAG seen in cartilage far from the graft site. The GAG index (T1 values of the graft normalized to control) from the group of implants 6 months or less was 59% ± 5% of control, whereas those at 12 to 24 months were 91% ± 18% of control. The two groups were statistically different with a P value of 0.005. conclusions. The GAG level in grafts that were implanted for less than 12 months appeared to be lower than that in the remote cartilage. At 12 months or greater, the grafts in this study had GAG levels that were comparable to both the adjacent and remote cartilage. This preliminary study of ACT implants has shown that it is feasible to apply the dGEMRIC technique in patients with ACT as a way to obtain information related to the composition of grafts. These results provide motivation and the pilot data with which to design further clinical studies.

Autologous chondrocyte implantation in cartilage lesions of the knee: long-term evaluation with magnetic resonance imaging and delayed gadolinium-enhanced magnetic resonance imaging technique.

Background Various treatment options are available for articular cartilage lesions, but controversy exists regarding the quality of the repair tissue and the durability of the results posttreatment. Noninvasive techniques are needed for the assessment of the repair tissue. Hypothesis Magnetic resonance imaging (MRI) with delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) can give valuable information regarding the quality and quantity of the repaired cartilage lesion. Study Design Cohort study; Level of evidence, 3. Methods Thirty-six knees in 31 patients were assessed 9 to 18 years after treatment with autologous chondrocyte implantation (ACI). All patients had isolated lesions. The knees were clinically evaluated with the Knee injury and Osteoarthritis Outcome Score and the dGEMRIC technique. The T1 value was measured for 2 regions of interest (ROIs), 1 in the repair tissue area (ROI 1) and 1 in the surrounding cartilage (ROI 2), giving information of the content of proteoglycans. Results The average T1 value in ROI 1 was 467.5 milliseconds and in ROI 2, 495.3 milliseconds, which yielded no significant difference, thus suggesting comparable levels of proteoglycans in the repair tissue and surrounding cartilage. Intralesional osteophytes were in 64% of the lesions, mainly in younger patients with osteochondritis dissecans lesions or a history of subchondral bone surgeries. Medium or large bone marrow edema was found in 14% of the knees and subchondral cysts, in 39%. There was no correlation between the KOOS and any MRI findings. Conclusion Magnetic resonance imaging with dGEMRIC gives valuable information for the macroscopic appearance and micro-molecular quality of the repair tissue after ACI. Nine to 18 years posttreatment, the quality of the repair tissue is similar to the surrounding normal cartilage, although intralesional osteophytes, subchondral cysts, and bone marrow edema were common. The defect area is restored in most patients. However, there was no correlation between the dGEMRIC values and the KOOS outcomes.

Synovial inflammation in patients undergoing arthroscopic meniscectomy: molecular characterization and relationship to symptoms.

OBJECTIVE Traumatic and degenerative meniscal tears have different anatomic features and different proposed etiologies, yet both are associated with the development or progression of osteoarthritis (OA). In established OA, synovitis is associated with pain and progression, but a relationship between synovitis and symptoms in isolated meniscal disease has not been reported. Accordingly, we sought to characterize synovial pathology in patients with traumatic meniscal injuries and determine the relationships between inflammation, meniscal and cartilage pathology, and symptoms. METHODS Thirty-three patients without evidence of OA who were undergoing arthroscopic meniscectomy for meniscal injuries were recruited. Pain and function were assessed preoperatively; meniscal and cartilage abnormalities were documented at the time of surgery. Inflammation in synovial biopsy specimens was scored, and associations between inflammation and clinical outcomes were determined. Microarray analysis of synovial tissue was performed, and gene expression patterns in patients with and those without inflammation were compared. RESULTS Synovial inflammation was present in 43% of the patients and was associated with worse preoperative pain and function scores, independent of age, sex, or cartilage pathology. Microarray analysis and real-time polymerase chain reaction revealed a chemokine signature in synovial biopsy specimens with increased inflammation scores. CONCLUSION Our findings indicate that in patients with traumatic meniscal injury undergoing arthroscopic meniscectomy without radiographic evidence of OA, synovial inflammation occurs frequently and is associated with increased pain and dysfunction. Synovia with increased inflammation scores exhibit a unique chemokine signature. Chemokines may contribute to the development of synovial inflammation in patients with meniscal pathology; they also represent potential therapeutic targets for reducing inflammatory symptoms.

Meniscal allografts: biomechanics and techniques.

Arthroscopic partial meniscectomy is one of the most common orthopedic surgical procedures performed. Numerous clinical and biomechanical studies have shown the long-term consequences of the meniscus-deficient knee, which includes increased loading of the cartilage. This leads to chondromalacia, and ultimately pain and dysfunction. Few treatment options are available for the young patient with pain in the tibiofemoral compartment secondary to meniscus deficiency. Meniscal allograft transplantation is a viable treatment option in this group of patients as short-term results have shown pain relief and functional improvement. Biomechanical studies have shown that the allograft meniscal transplant functions most like a native, intact meniscus when specific surgical principles are followed. Surgical techniques for meniscal allograft transplantation have advanced along with instrumentation. An improvement in function and pain relief can be expected when strict criteria are followed in patient selection and surgical technique.

The Central Quadriceps Tendon as a Versatile Graft Alternative in Anterior Cruciate Ligament Reconstruction: Techniques and Recent Observations

The central quadriceps tendon (CQT) is a versatile graft for cruciate reconstruction, and may be used with or without a bone plug from the proximal patella. The authors recommend using the graft with a bone plug fixed in the femoral socket until long-term results are available with alternative methods. CQT as a free graft, however, holds promise for the future of anterior cruciate ligament (ACL) reconstruction as an alternative that might reduce perioperative and eventual morbidity. There are no long-term results yet to justify the CQT free graft for routine ACL reconstruction until clinical trials at a few centers establish this as yielding comparable results to bone-tendon-bone or CQT/bone plug reconstruction at long-term follow up

Treatment of osteoarthritis of the middle-aged athlete.

Unicompartmental knee arthroplasty (UKA) has increasingly become an attractive alternative to total knee arthroplasty for early intervention. Clinical and biomechanical studies have shown that UKA offers advantages in early recovery, more natural function, and patient satisfaction. The literature has also shown that UKA exhibits a higher rate of revision than total knee arthroplasty, particularly in registry studies that include patients from outside of high-volume specialty centers. Patient-specific UKA offers the potential to close the gap between the known advantages of a partial knee solution and the documented risk of early revision. On the basis of the patient’s own imaging data, patient-specific UKA allows for an anatomically matched implant design that provides personalized fit, full coverage of the tibial cortical rim, and preserves the femoral articulating geometry. These design advantages are paired with a patient-specific instrument system that provides reliable component placement and simplified balancing.

High Rate of Early Revision Following Custom Made Unicondylar Knee Replacement

BACKGROUND There has been a recent interest in custom-made partial knee arthroplasties to provide patient-specific instrumentation and better fit of the prosthesis. While unicondylar knee arthroplasties (UKAs) have demonstrated good outcomes and durable results in many studies, there is little evidence on outcomes of these custom-made implants. METHODS We performed a retrospective review of all custom-made UKAs performed at our institution by one surgeon from 2008 to 2015. We analyzed preoperative demographics, clinical follow-up evaluations, and radiographs and performed an analysis of risk factors including age, gender, height, weight, body mass index, and tibial insert thickness. The incidence of revision surgery, radiographic failures indicating component loosening, and symptomatic clinically failed implants was calculated at an average of 54.0 months of follow-up. RESULTS We analyzed 115 consecutive custom-made medial UKAs from a single surgeon at our institution and found 29 (25.2%) UKAs had failed at an average of 33.1 months after surgery. Reasons for failure included aseptic femoral loosening (10), aseptic tibial loosening (8), loosening of both components (4), infection (3), progression of osteoarthritis (2), pain (1), and dislodged polyethylene insert (1). We found a significant relationship between implant failure and body mass index; no other study variables were statistically significant. CONCLUSION We found a relatively high rate of aseptic loosening and particularly femoral component loosening in the short- to intermediate-term follow-up period. While further study of larger numbers of custom-made UKA from multiple institutions may help verify these findings, we recommend careful consideration of the use of this implant.

Orthopedic Application of Polycarbonate Urethanes: A Review

Soft materials that aim to reproduce the tribological function of the natural joint are gaining popularity as an alternative concept to conventional hard bearing materials in the hip and knee. Polyurethane (PU) elastomers, in particularly polycarbonate urethane, are among the highest performing medical-grade polymers. They have mechanical and biological properties that make them suitable for use in orthopedic implants, as they demonstrate a unique combination of toughness, durability, flexibility, biocompatibility, and biostability. As presented in this paper, newly developed implants based on polycarbonate urethane perform more similarly to the natural joint in their mechanical response to load, and in their ability to utilize a thinner structure similar to that of cartilage, without jeopardizing the integrity or stability of the implant. Several wear studies of implants based on PU demonstrate a very low damage level to the implants’ articulating surfaces following repeated loading, and provide good assurance that this material can generate a low and stable wear rate in the long term. Animal studies further provide understanding of the biological response to PU implants in the hip and knee. Short-term clinical results are now becoming available from several commercial products. These generally show good functioning of these implants in the body and no material-related complications.