Chronic Knee Instability Research Articles

Carbon-PGLA Prostheses for Ligament Reconstruction

The efficiency of a pure carbon prosthesis to reconstruct intra-articular ligamentous loss of substance was evaluated on 14 sheep with an 18-month follow-up study of recent and old ACL experimental injuries. Functional results showed a correlation between a tightened implant, the stability of the knee, and the absence of severe arthritis. The rupture strength of the newly formed ligament amounts to about 300 Newtons (N). That of the normal ACL amounts to 250-550 N. The structure gives a viscoelastic behavior to the prosthesis. This tissue was made of collagen fibers surrounding the carbon fibers and running generally in the direction of the ligament. In the osseous tunnels, the newly formed lamellar bone invaded and surrounded the implant. Carbon fiber fragmentation occurred, and fibers were found in the synovia and in the homolateral, inguinal, and paraaortic lymph nodes. No degeneration, necrosis of tissue, or cellular toxicity was found. On these bases, the carbon prosthesis was modified by adding a resorbable copolymer of polyglycollic (PGA) and polylactic acid (PLA) around the fibers and a resorbable sheath of the same polymer. This carbon-PGA/PLA prosthesis was used in 23 patients with a three- to 12-month follow-up period. Patients were evaluated by clinical tests and by functional control of the ligament. The indications for prosthetic replacement were: recent mop-end tears of the ACL, cruciate ligament reconstruction in chronic knee instability, and wide rotator cuff loss of substance. Five complications occurred because of hematomas and/or sepsis and prosthesis breakage. Eighteen of 23 patients had good clinical results with good function in five. The conclusions are that PGA/PLA produces a clean and flexible ligament, thus eliminating carbon fiber articular deposits and allowing a normal function. Inflammatory postoperative reactions seem to be more frequent than with other procedures and call for operative and clinical care in order to eliminate hematoma and sepsis. The efficiency of a rehabitable carbon-PGA/PLA prosthesis in intra-articular ligamentous defects in man will be confirmed only by controlled long-term clinical observations.

Quadriceps atrophy in the anterior cruciate insufficient knee.

Atrophy of the quadriceps musculature is frequently associated with chronic knee instability. This atrophy may persist despite the patient's ability to return to athletic competition. When open biopsies of the quadriceps muscle from unstable knees were compared with those from normal acutely injured knees, it was found that clinical evidence of atrophy correlated with a relative decrease in the size of Type II or fast twitch muscle fibers. This supports the subjective, clinical impression that the unstable knee is less effective in explosive push-off. The findings also indicate the necessity of including exercise specific for the training of Type II fast twitch fibers in any program designed to rehabilitate the injured knee.

Cruciate Ligament Stents in Reconstruction of the Unstable Knee

Cruciate ligament stents have been developed to severe as internal splints which provide excellent temporary stability while allowing full range of motion of the knee during postreconstruction rehabilitation. Forty-three patients with disabling chronic knee instability were treated at one center using similar reconstruction techniques with either the anterior or posterior cruciate stent. When both cruciate ligaments were absent, only the posterior was used. All stents are intended only as temporary internal splints and all patients were advised that the structures were expected to break eventually. Followup of 15 patients with anterior cruciate stents revealed only 50% satisfactory overall results. Overall results were satisfactory in 80% of 20 patients with posterior cruciate stents. Longer implant survival is needed, and this must be accomplished by building more flexibility into the stent core and by improving surgical technique with more precise instrumentation.

Anterior subluxation of the lateral tibial plateau. A diagnostic test and operative repair.

Recurrent anterior subluxation of the lateral tibial plateau is a common type of chronic knee instability resulting from trauma. It can be reproduced by the clinical test described and corrected by a surgical procedure called the sling and reef operation, in which a strip of iliotibial tract is used to create a sling and to reef the posterolateral capsule. From 1971 to 1978, eighty-four patients were operated on, of whom fifty had been evaluated at one to six and one-half years after operation. The results were: forty-one good, six fair, and three poor. The lesions found in the thirty-seven knees in which arthrotomy was performed included a tear of the anterior cruciate in every case, a tear of the medial meniscus in fifteen and of the lateral meniscus in eleven, a notch in the articular surface of the lateral femoral condyle in fifteen, and a lateral marginal tibial (Segond) fracture in three. No definite lateral capsular tears were visualized--only stretching comparable to that seen in recurrent dislocation of the shoulder.