Douglas W. Jackson

A comparison of patellar tendon autograft and allograft used for anterior cruciate ligament reconstruction in the goat model

Similar-sized patellar tendon autografts and fresh-fro zen allografts were used to reconstruct the anterior cruciate ligament of one knee in 40 female goats. Evaluations of the reconstructions and contralateral controls at the 6-week and 6-month postoperative pe riods included anterior-posterior translation, mechanical properties determined during tensile failure tests, meas urement of cross-sectional area, histology, collagen fibril size and area distribution, and associated articular cartilage degenerative changes. Six months after anterior cruciate ligament recon struction, the autografts demonstrated a smaller in crease in anterior-posterior displacement, values of maximum force to failure two times greater, a significant increase in cross-sectional area, a more rapid loss of large-diameter collagen fibrils, and an increased density and number of small-diameter collagen fibrils compared to the allografts. Clinical significance . More surgeons are allowing their patients to return to running and sports 6 months after anterior cruciate ligament reconstruction. While the structural and material properties of autografts and allografts at time zero are similar, in the goat model during the first 6 months they differ. The allografts demonstrate a greater decrease in their implantation structural properties, a slower rate of biologic incorpo ration, and the prolonged presence of an inflammatory response. At 6 months the autograft demonstrates a more robust biologic response, improved stability, and increased strength to failure values.

Tibial tunnel placement in ACL reconstruction.

In reconstructing the ACL, ideal tibial tunnel placement requires an understanding of the unique anatomy of the ACL tibial footprint and its relationship to the PCL, lateral meniscus, and medial tibial part of the spine. In addition to precise placement of the tibial tunnel, its length and angulation are factors to consider. Using consistent anatomic landmarks with attention to detail, the tibial tunnel can be reproducibly placed in a manner that is not detrimental to the graft.

Freeze dried anterior cruciate ligament allografts Preliminary studies in a goat model

One ACL in each of 11 mature goats was replaced with a freeze dried bone-ACL-bone allograft. One year fol lowing implantation the goats had their knees evaluated biomechanically and for microvascularity and histologic changes. The reconstructed knees had a significantly greater total AP laxity (3.8 ± 0.6 mm) (mean and SEM) than the controls (1.0 ± 0.1 mm). Differences in primary AP laxity were responsible for 81 % of the difference in total laxity, with only a 0.4 mm difference in secondary laxity. Neutral stiffness in the reconstructive knee was 17% of control. while stiffness at 30 newtons (N) of anterior force was approximately 50% of controls. Lig ament stiffness in the linear region for the ACL allograft was 35% of the control value of 686 N/mm. The maxi mum load of the allografts was 571 ± 45 N, or 25% of the contralateral ACL control strength (2301 ± 155 N). Five of the seven allografts failed at the femoral inser tion. Both elongation (83%) and energy (21 %) to max imum load were less for allografts than controls. His tologic evaluation of the allografts revealed the pres ence of a regular oriented dense connective tissue which resembled a normal ligament. Microangiography revealed a periligamentous and endoligamentous vas cular pattern reminiscent of a normal ACL and complete revascularization of the bone plugs.

Cruciate reconstruction using freeze dried anterior cruciate ligament allograft and a ligament augmentation device (LAD) An experimental study in a goat model

One ACL in each of 11 mature goats was replaced with a freeze dried bone-ACL-bone allograft and a ligament augmentation device (LAD). The LAD was released from its tibial fixation at 3 months postoperation. Bio mechanical, microvascular, and histological changes were evaluated 1 year following implantation. The re constructed knees had a significantly greater total AP translation (3.1 ± 0.5 mm) (mean and SEM) than the contralateral controls (1.0 ± 0.1 mm). Differences in primary AP translation were responsible for 59% of the difference in total translation, with only a 0.6 mm differ ence in secondary translation. Neutral stiffness in the reconstructive knee was 22% of control, while stiffness at 30 N of anterior force was approximately 35% of controls. Ligament stiffness in the linear region for the ACL allograft/LAD was 53% of the control value of 691 N/mm. The maximum load of the allograft/LADs was 1,052 ± 145 N, or 43% of the contralateral ACL control strength (2,448 ± 144 N). Five of the six allografts failed at the femoral insertion. Energy (39%) to maximum load was less for allograft/LADs than controls but elongation to maximum load was the same as control. Histologic evaluation of the allograft/LADs revealed soft tissue cellular ingrowth into the LAD in the extraarticular por tions. No bony growth into the LAD was observed. The collagen fibers of the graft appear to be arranged in a longitudinal orientation although some areas show cha otic collagen fibers. Microangiography revealed a peri- ligamentous and endoligamentous vascular pattern reminiscent of a normal ACL and complete revascular ization of the bone plugs.

Cell survival after transplantation of fresh meniscal allografts DNA probe analysis in a goat model

Fibrochondrocytes synthesize and maintain the extra cellular matrix responsible for the distinctive material and structural properties of a normal meniscus. Viable meniscal cells are believed to be necessary for the long- term maintenance of these properties in meniscal allo grafts. The purpose of this study was to determine if the donor cells (fibrochondrocytes) survive after a fresh meniscal allograft transplantation. A DNA probe technique was used to clearly distin guish the DNA patterns in donor cells from the host cells in the Spanish goat. No remaining donor DNA could be demonstrated at 4 weeks in transplanted meniscal tissue; it was all of host origin. The host DNA content at 4 weeks approached or exceeded the amount present in the contralateral control meniscus. Clinical significance: The results of this study dem onstrate that viable cells in medial meniscal allografts transplanted from one animal to another do not survive. Host cells rapidly repopulate the transplanted menis cus. There is no evidence these new cells will maintain on a long-term basis the extracellular matrix of the meniscus. The evidence in this paper, that the fibro chondrocytes do not survive transplantation, suggests further justification is necessary for using grafts with living cells. Allografts with living cells have an increased expense, more complicated surgical logistics, and have a higher potential risk of disease transmission.

Osteochondritis in the female gymnast's elbow

Ten cases of osteochondritis dissecans of the humeral capitellum are reviewed in seven high-performance female gymnasts, ranging in age from 10 to 17 years old. All but one were evaluated and treated with arthroscopy and/or arthrotomy, with curettage of loose articular margins, drilling of the lesion, and removal of loose bodies. The average length of follow-up is 2.9 years, and includes interview, physical examination, and roentgenographic evaluation. This injury has been previously described in relation to compressive forces across the radiocapitellar joint from repetitive valgus loading in a developing epiphysis. Only one of the athletes, at the time of follow-up, was still in competitive gymnastics. Each has a minimal limitation in range of motion, with crepitus and often catching noted by history and on examination. These cases double the limited literature on this injury in young, female gymnasts. They stimulate concern for the proper and early evaluation and treatment of elbow injuries in this at risk group. Once the bony changes in the capitellum are detected, and pain remains despite conservative management, we have found that symptoms can be improved with surgery, but persist in female gymnasts. Our experience in this more-advanced group is that the return to high-level competitive gymnastics is unlikely.

THE EFFECTS OF IN SITU FREEZING ON THE ANTERIOR CRUCIATE LIGAMENT : AN EXPERIMENTAL STUDY IN GOATS

We developed an in situ freeze-thaw model designed to simulate an ideally placed and oriented autogenous graft of the anterior cruciate ligament. In this model, the anterior cruciate ligament was exposed, and the femoral insertion, tibial insertion, and body of the anterior cruciate ligament were frozen in situ with specially designed freezing probes. Freeze-thaw cycles were repeated five times. We used the technique in thirty-three mature goats to study the biological and biomechanical outcomes of the devitalized and devascularized anterior cruciate ligament at zero, six, and twenty-six weeks after treatment. Thus, the collagen fibers of the simulated autogenous graft remain in normal anatomical position and the simulated graft is fixed under physiological tension. At twenty-six weeks, no statistically significant differences were noted between treated and contralateral control (untreated) ligaments relative to anterior-posterior translation, maximum force to rupture, stiffness in the linear region of the force-length curve, modulus of elasticity in the linear region, strain to maximum stress, or maximum stress. The only statistically significant difference was an increase in cross-sectional area of the ligament. This increase was 22 and 42 per cent greater than that in the control ligaments at six weeks and six months. At six months, the ligaments in the control group had an average mid-cross-sectional area of 17.7 +/- 1.2 square millimeters and the ligaments in the experimental group, 25.2 +/- 3.1 square millimeters. Changes in the size and density of the collagen fibrils also were demonstrated at six months. These observations are in sharp contrast to our previous studies of replacement of the anterior cruciate ligament, in which an allograft of the ligament or an allograft supplemented with a 3M ligament augmentation device (LAD; 3M, St. Paul, Minnesota) was used. In those studies, an average reduction in maximum strength of 75 per cent for the allografts and 50 per cent for the allografts that had a ligament-augmentation device was found at one year. We concluded that devitalized, devascularized anterior cruciate ligaments do not lose strength if the anatomical position and the orientation of the collagen fibers are not altered.

Meniscal Repair Supplemented With Exogenous Fibrin Clot and Autogenous Cultured Marrow Cells in the Goat Model

This study was undertaken to evaluate the placement of fibrin clot and cultured autologous marrow cells in surgically created, full-thickness, meniscal lesions in the avascular zone in 32 female Spanish goats. The menisci were repaired with two vertically oriented su tures (N = 8), exogenous fibrin clot was placed into the meniscal defect before placement of the two sutures (N = 8), fibrin clot plus cultured adherent bone marrow cells were placed in the defect (N = 8), or the meniscal lesions were left unrepaired (N = 8). On gross and manual inspection, meniscal lesions showed some de gree of healing in all animals except for the eight unrepaired lesions. All the experimental specimens had decreased tensile strength compared with the con tralateral control medial menisci. Ultimate load to fail ure, energy absorbed to failure, and stiffness were less than 40% of the controls for all groups. Histologic sections demonstrated focal cellular areas consisting of giant cells and macrophages in the repair sites. Our observations failed to demonstrate a statistically signif icant enhancement of healing with the use of exoge nous fibrin clot compared with vertically oriented su tures alone. The addition of cultured adherent autologous bone marrow-derived cells in conjunction with the fibrin clot did not enhance the meniscal healing.

The effects of processing techniques on the mechanical properties of bone-anterior cruciate ligament-bone allografts An experimental study in goats

There has been a growing interest in the use of allo grafts as ACL substitutes. Allografts are often freeze dried to increase shelf storage time and sterilized with ethylene oxide. This study was conducted to determine the effect of a specific ethylene oxide sterilization pro cedure and freeze drying process on the initial mechan ical properties of femur-ACL-tibia preparations. Twelve knees (stifle joints) from six mature goats were divided into two groups (one knee of pair to each group). Knees were cleaned of all soft tissue except for the anterior cruciate, posterior cruciate, and collateral ligaments. Group 1 was sterilized with ethylene oxide (simulating clean procurement) then freeze dried. Group 2 was freeze dried only (simulating sterile procurement). The knees were rehydrated and then tested in tension to failure to determine their structural mechanical proper ties. The ethylene oxide-freeze dried specimens (Group 1) had a mean maximum load before failure of 2059 ± 273 newtons (N) (± SE) which was not statistically different than the maximum load of the freeze dried specimens (Group 2) of 2023 ± 214 N. The average strength of Group 1 and 2 combined was not signifi cantly different than a third group of 12 normal femur- ACL-tibia controls which had an average maximum force of 2403 ± 133 N. No significant differences be tween the groups were observed for stiffness, energy to maximum strength, or elongation to maximum force. It appears the freeze dry processing, with or without ethylene oxide sterilization, using the procedure we used, has, at most, a small effect on the initial mechan ical properties of the preparations. The low mechanical properties of implanted and revascularized allografts, as compared to normal femur-ACL-tibia complex ap pears to be related more to fixation strength and alter ations which occur in the ligament substance after implantation.

Survival of cells after intra-articular transplantation of fresh allografts of the patellar and anterior cruciate ligaments. DNA-probe analysis in a goat model.

The fate of donor cells in fresh allografts of the patellar and anterior cruciate ligaments was assessed after transplantation of the allografts as substitutes for the anterior cruciate ligament in goats. DNA-probe analysis was used to distinguish between the DNA of individual goats. Donor DNA was completely replaced by recipient DNA in both the transplanted patellar and anterior cruciate ligaments within a four-week period. Simultaneous full-thickness skin transplants in the same animals were not rejected during the interval of rapid loss of donor DNA from the allografts. The absence of rejection of the skin grafts at the one-week interval suggests that no pre-existing antibody associated with an immune reaction was responsible for the rapid loss of DNA in the allografts.