The University of Pittsburgh

Name:	Matthew Fisher
Title:	Graduate Student

Educational Background:

BS, Columbia University, May 2005

MSRC Research Group:

Tissue Mechanics, Knee Kinematics & Robotics

Lab Contact Info:

Musculoskeletal Research Center
405 Center for Bioengineering
300 Technology Drive
Pittsburgh, PA 15219
Phone: 412-648-1943
Fax: 412-648-2001
mbf7@pitt.edu

Research Interests:

Ligament and tendon mechanics
Patellar tendon healing
Functional tissue engineering using small intestine submucosa (SIS) bioscaffolds
Joint biomechanics
Robotic technology

Current project:

Using SIS bioscaffolds to improve ligament and tendon healing:

The anterior cruciate ligament (ACL) is the most frequently injured knee ligament during sports and work related activities, with tears occurring in 150,000 to 200,000 people in the United States each year. Since ACL ruptures do not heal, surgical reconstructions using tissue grafts are the common alternative to restore knee function. Sports medicine knee surgeons have termed the bone-patellar tendon-bone (BPTB) autograft the "gold-standard" for ACL reconstruction; however, following harvest, the central third of the patellar tendon (PT) does not heal well. The healing tissues also form adhesions to the fat pad and can cause abnormal patellofemoral joint motion. The hypotheses were that a bioscaffold could enhance patellar tendon healing through contact guidance and chemotaxis, and the scaffold could serve as a barrier to decrease adhesion formation between the neo-PT and infrapatellar fat pad. In 20 New Zealand White rabbits, a central-third PT defect was created. One strip of porcine small intestinal submucosa (SIS) was attached to both the anterior and posterior sides of the PT defect of the SIS-treated group (n=10). For comparison, a central defect was left nontreated (n=10). At 12 weeks, histomorphology was examined using Masson's trichrome staining. The cross-sectional area (CSA) was determined with a laser micrometer, and the central BPTB complexes were tested in uniaxial tension. SIS-treated samples showed a greater amount of healing tissue with denser and well-oriented collagen fibers and more spindle-shaped cells. There was no noticeable adhesion formation in the SIS-treated group. For the nontreated group, there were significantly more and diffuse adhesive formations. The SIS-treated group also had a 68% increase in neo-PT CSA, 98% higher stiffness, and 113% higher ultimate load than that in the nontreated group (Figure 1). SIS treatment increased the quantity of healing tissue, improved the histological appearance and biomechanical properties of the neo-PT, and prevented adhesion formation between the PT and fat pad.

Figure 1. Normalized stiffness and ultimate load values for the SIS-treated and nontreated groups (*p<0.05).

All-Inside ACL Reconstruction:

The Anterior Cruciate Ligament (ACL) is a main stabilizer in the human knee joint. The incidence of ACL injury in the United States alone, is estimated to be 1 in 3000 individuals per year and surgical reconstruction is usually required in over 100,000 patients to restore normal knee function and stability. When performing an ACL reconstruction many factors should be taken into account to restore the anatomy and biomechanics of the normal ACL. The traditional single bundle ACL reconstruction involves harvesting the middle third of patellar tendon or the semitendinosis and gracilis hamstring tendons. ACL reconstruction using hamstring tendons has recently received attention because it offers advantages of less donor site morbidity compared to the patellar tendon, less anterior knee pain and earlier rehabilitation. Of course there are some concerns in using the hamstring grafts such as loss of active knee flexion at deeper flexion angles as well as muscular weakness and its effects on knee function and stability. Recently, an All-inside technique for single bundle ACL reconstruction has been developed by Prof. Giuliano Cerulli from the University of Perugia-Italy to eliminate the need to harvest both hamstrings tendons. In this technique, the femoral and tibial tunnels are drilled halfway through the bone manually with a special drill. The decreased length of the bone tunnels the length allows the use of only one hamstring tendon (gracilis or semitendinosus). Additionally advantages include no burning of the tunnel common with electrically powered drills, the ability to adjust the tunnel length. good fixation in the half-tunnel, easier graft attachment, limited esthetical damage, lower infection risk and less bleeding. At a medium follow-up, excellent clinical results have been experienced with a good patients satisfaction, a rapid return to previous activity, satisfactory stability and good muscle function. However, it is necessary to validate the effectiveness this technique in terms of restoring knee function on controlled laboratory study and to compare with historical single bundle hamstring reconstruction data in the literature. Further it is unclear if the semitendinosus and gracilis are equally effective using the All-inside technique, as there maybe differences in their biomechanical properties. Thus, in this project, in collaboration with Let People Move in Perugia-Italy and Innovazione Medica, we wish to validate the All-Inside technique using our robotic/UFS testing System and determine if ACL reconstruction with the All-Inside technique using one hamstring tendon restore normal knee kinematics and in-situ force in the graft.

Publication:

Fisher M.

Fisher M.B.

Recent Abstracts:

Fisher, M.B.

Fisher, MB

Fisher, M.B.

Presentations:

Fisher MB

Award:

Biomechanics in Regenerative Medicine (BiRM) T-32 Training Grant Fellowship (Dr. Michael Sacks). 2005.

Personal album: