Simultaneous quantitation of knee ligament forces.

An apparatus and experimental technique have been developed which allow the simultaneous quantitation of human cadaver knee ligament forces with the knee in various positions and subjected to various loads. The methodology permits all the major ligaments of the knee to be kept intact, thus preserving much of their normal relative load-bearing function. A novel measurement technique was employed for ligament force measurement. Strain gauges were placed at the ligamentous insertions and origins either on cortical bone or the cancellous/cortical transition. Gauge output was subsequently calibrated quantitatively by cutting the ligaments and subjecting them to known loads. The gauging technique was thermally stable, and the method as a whole yielded reproducible relative ligament force data when knee positions and loads were repeated for a given knee specimen. Three fresh human cadaver knee specimens have been subjected to testing thus far with gauges at six ligamentous sites. Initial evaluation of the data indicate that ligamentous loading patterns were quite different from those reported in the literature as determined by other methods.

The effect of exercise on patellar tracking in lateral patellar compression syndrome.

The influence of a physical therapy program on pain and patellar tracking was investigated clinically and radiologically with tangential views in 51 knees with lateral patellar compression syndrome. A pretest-posttest design was used to evaluate physical measurements of patellar alignment in subjects who had had patellofemoral pain for a minimum of 6 weeks. Eighty-four percent of the subjects were pain-free after an average of 8 weeks of rehabilitation or 11 physical therapy visits, with a mean quadriceps strength to total body weight ratio of 61% in women and 86% in men. The pretest-posttest difference in Merchant's congruence angle was significant at a probability of 0.0066 in the patients who were pain-free after exercise, demonstrating less lateral patellar tracking. The pretest-posttest difference in iliotibial band flexibility was significant at a probability of 0.0017, with the patients who were pain-free after exercise becoming more flexible. No significant differences were observed from before to after exercise in the patellofemoral index, Q angle, hamstring flexibility, thigh measurement, sclerotic subchondral bone, or sulcus angle. We were unable to predict which subjects would become pain-free with exercise by patellar position because the group that improved began more laterally tilted. The results of this study indicate that patellar tracking is improved with vastus medialis oblique strengthening, iliotibial band stretching, and joint mobility exercise in the majority of subjects with lateral patellar compression syndrome.

Radiation exposure during fluoroarthroscopically assisted anterior cruciate reconstruction.

We prospectively evaluated the radiation exposure during 50 consecutive fluoroscopically assisted anterior cruciate ligament reconstructions. Three different methods of anterior cruciate ligament reconstruction were performed using either rolled fascia lata allograft or bone-tendon-bone autograft. For the 50 procedures, total time using the fluoroscope was 119.61 minutes, or 2.38 minutes per procedure. The 16 primary fascia lata allograft reconstructions averaged 1.38 minutes of fluoroscope use per procedure compared with 4.69 minutes for the two revision allograft fascia lata surgeries, 3.14 minutes per procedure for the 30 primary bone-tendon-bone reconstructions, and 4.18 minutes per procedure for the two surgeries performed with an allograft meniscal transplant. The difference in exposure time between the 16 primary allograft fascia lata surgeries and the 30 primary allograft or autograft bone-tendon-bone surgeries was statistically significant. The average radiation exposure to the surgeon was 0.67 mrem per minute of fluoroscope use. It would take 7463.08 minutes of fluoroscope time, or 11,139 primary fascia lata allograft reconstructions, to exceed the recommended occupational exposure limit of 5000 mrem per year. It appears that the orthopaedic surgeon receives minimal radiation when using the fluoroscope to assist in anterior cruciate ligament reconstruction, especially when doing a primary fascia lata allograft procedure.

The development of suture anchors for use in soft tissue fixation to bone.

Soft tissue fixation to bone is a basic technique of orthopaedic surgery for which a multitude of devices have been developed. A new class of orthopaedic devices termed "suture anchors" has been developed to secure soft tissues to bone using suture material. The suture anchor is designed to allow quick and secure fixation without the need for extensive exposure. This device was tested using in vitro and in vivo models and found to be comparable with standard transosseous and two-pronged stable techniques. This device should prove useful in allowing the versatility of suture fixation of soft tissues to bone without the technical requirements of constructing transosseous suture tunnels.

Ligament injuries associated with physeal fractures about the knee.

A retrospective study of 29 cases of epiphyseal plate fractures about the knee revealed 14 patients with ligament instability at follow-up evaluation an average of 66 months after injury. Distal femoral physeal fractures had occurred in 16 of the 29 patients. Six of these patients had ligament insufficiency, which was recognized by positive anterior drawer and Lachman tests in all six and laxity to valgus stress in one. Proximal tibial physeal fractures were noted in 13 of the 29 patients. Eight of these patients had ligament laxity; anterior drawer and Lachman tests were positive in five, and laxity with valgus stress was present in four patients. It is concluded that because 14 of 29 patients (48%) had ligament insufficiency at follow-up evaluation, physeal fracture about the knee does not exclude ligament damage and, in fact, is associated with a high incidence of ligament injury. Furthermore, a complex proximal tibial physeal fracture associated with medial collateral ligament rupture is described for the first time. This resulted in medial collateral ligament insufficiency, genu valgus, and early degenerative changes. A treatment plan of primary ligament repair, fracture reduction, and follow-up evaluation to skeletal maturity is suggested for this unique fracture.

Arthroscopic and open surgical techniques for meniscus replacement--meniscal allograft transplantation and tendon autograft transplantation.

Open, arthroscopically assisted and arthroscopic methods for lateral and medial meniscus allograft transplantation with bone plug fixation are described. An open technique for medial and lateral meniscus transplantation without bone plug fixation, as well as an open technique for autograft quadriceps tendon replacement of the medial meniscus are described.

Positioning of the tibial tunnel for anterior cruciate ligament reconstruction.

Two mechanisms of unintentional anterior tibial tunnel axis shift can occur despite accurate placement of the guide wire within the proximal tibia. The first results from using a short-block reamer head joined to a shaft of smaller diameter. If the tibial tunnel is drilled obliquely, it is possible for the reamer head to displace anteriorly in the knee joint before completion of the posterior portion of the tibial tunnel. The second mechanism of anterior shift involves using two sequential drills to create the tibial tunnel. To delineate the causes of this unwanted shift, cadaveric studies and special roentgenographic studies were undertaken. Results demonstrated that the shift is related directly to the presence of high-density bone in the tibial plateau. In an effort to minimize this effect, various drill designs were tested, and it was determined that a drill-head length of 25 mm was most effective at reducing the shift without sacrificing the freedom of movement necessary to obtain precise endosteal placement of the femoral tunnel. Along with these experimental studies, a retrospective 7-year review of anterior cruciate ligament (ACL) reconstruction failures was performed to assess the clinical significance of inadvertent anterior positioning of the tibial tunnel.

Cross-pin femoral fixation: a new technique for hamstring anterior cruciate ligament reconstruction of the knee.

A new method of femoral fixation for arthroscopic anterior cruciate ligament (ACL) reconstruction using semitendinosus and gracilis (ST/G) tendons is presented. Biomechanical evaluation of the method was performed with pullout tests using animal tissues simulating fixation of ST/G tendons passing around a 2.5-mm pin placed transversely through a femoral tunnel. Clinical assessment of 22 patients was performed according to IKDC, Tegner, Lysholm, isokinetic strength, and KT1000 standards. Fixation strengths ranged from 725 N to 1,600 N for yield and maximal loads to failure for 35-mm to 70-mm cross-pins. Clinical results at mean follow-up of 30 months showed one traumatic failure, IKDC 86% normal or nearly normal, Tegner 6 ave, Lysholm 93 ave, KT1000 86% < 3 mm side-to-side difference on maximal manual evaluation, and isokinetic strength testing of quadriceps 8% deficit with hamstrings 8% deficit. Cross-pin fixation of ST/G tendons may be one of the strongest modes of femoral graft attachment yet devised. Our clinical outcomes in this initial series compare well with previous reports of ACL reconstruction regardless of graft or technique.

Meniscal substitutes--human experience.

A number of clinical series have described the effect of meniscus allograft replacement in humans. The general indication has been disabling pain following loss of a meniscus in a skeletally mature individual. Overall, healing of the graft to the capsule occurs in up to 80% of all transplants. Revascularization and cell repopulation is found in all grafts but is highly variable. The risk for graft failure seems to be greater with irradiated grafts and in patients with grade III or IV osteoarthritic changes. In most series, patients experienced a decrease in pain and an increase in activity level postoperatively. In many series, concominant surgery (cruciate ligament reconstruction or osteotomy) had been performed. Meniscus replacement with frozen or cryopreserved allografts seems to give the most promising short-term results in patients with post-meniscectomy pain. Controlled, randomized prospective studies are needed to confirm a long-term benefit and better define transplantation indications. Viable meniscus allografts seem to survive transplantation, as donor cells were found in the graft after 2 years. Clinically, pain was reduced and activity increased following transplantation, but after 4 years some of these gains were lost. There was no correlation between postoperative findings on MRI and clinical outcome. Meniscal replacement with a quadriceps tendon autograft in humans resulted in pain reduction, but at second-look arthroscopy, only 2 of 9 tendon autografts looked like a meniscus. Six were in position but still looked like tendons. Total medial meniscus replacement by quadriceps tendon autrograft is still an experimental procedure. There is no proof at present that meniscal substitutes (meniscus allografts or tendon autografts) in humans can protect the hyaline cartilage of the knee from the degeneration, following loss of a meniscus. There is some evidence in animal experiments that under circumstances not yet exactly known, a meniscus substitute can have a protective effect on articular cartilage. Three factors have been identified that prevent proper meniscal function: poor fixation of the meniscal horns, no contact of the graft with the articulating surfaces under load and incorrect positioning of the horns. Meniscal allograft transplantation sensitizes humoral and cell mediated immune systems. Bone plugs attached to meniscal allograft tissue may increase cell surface antigenicity. Deep freezing and especially freeze drying of meniscal tissue decreases host immunogenicity. Cryopreservation maintains the content of donor HLA encoded antigens and is likely more sensitizing to the host. The clinical importance of immune responses to meniscal allografts is not known, but it has not been shown to result in graft failure or rejection. Prospective studies are needed.