R F Warren

Tendon-healing in a bone tunnel. A biomechanical and histological study in the dog.

Our study evaluated tendon-to-bone healing in a dog model. Twenty adult mongrel dogs had a transplantation of the long digital extensor tendon into a 4.8-millimeter drill-hole in the proximal tibial metaphysis. Four dogs were killed at each of five time-periods (two, four, eight, twelve, and twenty-six weeks after the transplantation), and the histological and biomechanical characteristics of the tendon-bone interface were evaluated. Serial histological analysis revealed progressive reestablishment of collagen-fiber continuity between the bone and the tendon. A layer of cellular, fibrous tissue was noted between the tendon and the bone, along the length of the bone tunnel; this layer progressively matured and reorganized during the healing process. The collagen fibers that attached the tendon to the bone resembled Sharpey fibers. High-resolution radiographs showed remodeling of the trabecular bone that surrounded the tendon. At the two, four, and eight-week time-periods, all specimens had failed by pull-out of the tendon from the bone tunnel. The strength of the interface was noted to have significantly and progressively increased between the second and the twelfth week after the transplantation. At the twelve and twenty-six-week time-periods, all specimens had failed by pull-out of the tendon from the clamp or by mid-substance rupture of the tendon. The progressive increase in strength was correlated with the degree of bone ingrowth, mineralization, and maturation of the healing tissue, noted histologically.

The effect of medial meniscectomy on anterior-posterior motion of the knee.

We used an in vitro knee-testing apparatus to measure anterior-posterior displacement of the tibia on the femur and the accompanying tibial rotation in response to an applied anterior-posterior force. Testing was performed on nine intact knees, on five knees after medial meniscectomy, on three knees after isolated section of the anterior cruciate ligament, and on eight knees after both excision of the medial meniscus and section of the anterior cruciate ligament. The induced anterior-posterior displacement and the coupled rotation were unaffected by meniscectomy. Isolated section of the anterior cruciate ligament allowed a significant (p less than 0.05) increase in anterior displacement but had no effect on posterior displacement. The coupled internal rotation associated with anterior displacement was lost after section of the anterior cruciate ligament. Excision of the medial meniscus and section of the anterior cruciate ligament allowed significantly (p less than 0.05) greater increases in anterior displacement than those already increased by isolated section of the anterior cruciate ligament.

An in vitro biomechanical evaluation of anterior-posterior motion of the knee. Tibial displacement, rotation, and torque.

We tested the anterior-posterior motion of nine normal cadaver knees in zero to 90 degrees of flexion using a specially designed apparatus. This apparatus applied a dynamic anterior-posterior force to each knee and measured the resulting tibial displacement, rotation, and torque. In the intact knee, an anterior force produced an internal tibial torque and internal tibial rotation, while a posterior force produced an external torque and external rotation. Anterior-posterior displacement increased by 30 per cent when the tibia was allowed to rotate freely about its neutral rotation position. Isolated section of the anterior cruciate ligament produced more than double the amount of anterior displacement without affecting posterior displacement. Isolated section of the posterior cruciate ligament produced almost triple the amount of posterior displacement without affecting anterior displacement. After cutting either the anterior or the posterior cruciate ligament, the resulting internal or external secondary tibial rotation disappeared. It appears, therefore, that the anterior and posterior cruciate ligaments are the primary restraints to motion in the anterior and posterior directions as well as the causes of internal and external tibial rotation during anterior and posterior motion.

T-plasty modification of the Bankart procedure for multidirectional instability of the anterior and inferior types.

Forty patients who had a diagnosis of multidirectional instability of forty-two shoulders had a modified Bankart operation in which a T-shaped incision was made in the anterior portion of the capsule, with advancement of the inferior flap superiorly and of the superior flap medially. All of the patients had been injured during athletic activities. Some degree of anterior labral injury was present in thirty-eight of the forty-two shoulders. Half of the patients had generalized ligamentous laxity. The patients were followed for an average of three years (range, two to seven years). Four patients had episodes of instability after the operation. Three had a single episode of posterior subluxation during throwing, one had recurrent posterior subluxation that subsequently was treated by posterior stabilization, and one had anterior subluxation while he was diving from a high board. The average loss of external rotation after the operation was 5 degrees with the arm at the side and 4 degrees with the arm abducted 90 degrees. Satisfaction of the patient was rated excellent for forty (95 per cent) of the shoulders, good for one shoulder, and fair for one shoulder. However, throwing athletes found that they were unable to throw a ball with as much speed as before the operation.

Meniscal repair using an exogenous fibrin clot. An experimental study in dogs.

UNLABELLED To evaluate the ability of a fibrin clot to stimulate and support a reparative response in the avascular portion of the meniscus, two-millimeter-diameter full-thickness lesions in the avascular portion of the medial meniscus of twelve adult dogs were filled with an exogenous fibrin clot that had been prepared from each animal. The healing response was then examined using histology and autoradiography with 35SO4 at intervals from one week to six months. The defects that had been filled with a fibrin clot healed through a proliferation of fibrous connective tissue that eventually modulated into fibrocartilaginous tissue. The fibrin clot appeared to act as a chemotactic and mitogenic stimulus for reparative cells and to provide a scaffolding for the reparative process. The origin of these reparative cells was not determined in this study, but they were thought to arise from the synovial membrane as well as the adjacent meniscal tissue. Control defects remained empty. While the reparative tissue was grossly and histologically different from the normal adjacent meniscal tissue, it was morphologically similar to the reparative tissue that was previously observed in the vascular area of the meniscus. CLINICAL RELEVANCE The ability of an exogenous fibrin clot to stimulate and support a reparative response in the avascular portion of the meniscus may represent a potential method of avascular meniscal repair.

Anatomy, histology, and vascularity of the glenoid labrum. An anatomical study.

We studied the gross, histological, and vascular anatomy of the glenoid labrum in twenty-three fresh-frozen shoulders from cadavera to demonstrate its cross-sectional anatomy, its microvascularity, and its attachments. The superior and anterosuperior portions of the labrum are loosely attached to the glenoid, and the macro-anatomy of those portions is similar to that of the meniscus of the knee. The superior portion of the labrum also consistently inserts directly into the biceps tendon, while its inferior portion is firmly attached to the glenoid rim and appears as a fibrous, immobile extension of the articular cartilage. The arteries supplying the periphery of the glenoid labrum come from the suprascapular, circumflex scapular, and posterior circumflex humeral arteries. In general, the superior and anterosuperior parts of the labrum have less vascularity than do the posterosuperior and inferior parts, and the vascularity is limited to the periphery of the labrum. Vessels supplying the labrum originate from either capsular or periosteal vessels and not from the underlying bone.

Biomechanical evaluation of a simulated Bankart lesion.

The purpose of this study was to determine the effect of sectioning of the anterior part of the inferior glenohumeral ligament (a simulated Bankart lesion) on load-induced multidirectional glenohumeral motion. Nine fresh, intact cadaveric shoulders were tested on a special apparatus that constrained three rotations but allowed simultaneous measurement of anterior-posterior, superior-inferior, and medial-lateral translation. Coupled anterior-posterior and superior-posterior translations were recorded while anterior, posterior, superior, and inferior forces of fifty newtons were applied sequentially. Testing was done in three positions of humeral elevation in the scapular plane, in three positions of humeral rotation, and with an externally applied joint-compression load of twenty-two newtons. A liquid-metal strain-gauge was placed on the posterior band of the inferior glenohumeral ligament to assess concomitant posterior capsular strain during the various test conditions. All shoulders were tested intact and again after the inferior glenohumeral ligament and the labrum had been detached from the glenoid from just superior to the anterior band of the inferior glenohumeral ligament to a point just posterior to the infraglenoid tubercle. The simulated Bankart lesion resulted in selected increases in anterior translation at all positions of elevation, in posterior translation at 90 degrees of elevation, and in inferior translation at all positions of elevation. However, these increases were very small; the maximum mean increase in translation seen over-all was only 3.4 millimeters, which occurred during inferior translation at 45 degrees of elevation.(ABSTRACT TRUNCATED AT 250 WORDS)

Replacement of the anterior cruciate ligament using a patellar tendon allograft. An experimental study.

The anterior cruciate ligament of twenty-five adult dogs was replaced using fresh or deep-frozen patellar-tendon allografts. The morphology of these transplanted allografts was then evaluated using routine histological studies and a vascular-injection (Spalteholz) technique at various intervals from two weeks to one year postoperatively. The fresh patellar-tendon allografts incited a marked inflammatory and rejection response which was characterized by perivascular cuffing and lymphocyte invasion. Deep-frozen patellar-tendon allografts appeared to be benign within the joint and underwent alterations that were comparable with those observed in autogenous patellar-tendon grafts. These included avascular necrosis followed by revascularization and cellular proliferation. At one year, the gross and histological appearance of the patellar tendon allograft resembled that of a normal anterior cruciate ligament.

Biomechanical evaluation of the medial collateral ligament of the elbow

Anatomical dissection and biomechanical testing were used to study twenty-eight cadaveric elbows in order to determine the role of the medial collateral ligament under valgus loading. The medial collateral ligament was composed of anterior, posterior, and occasionally transverse bundles. The anterior bundle was, in turn, composed of anterior and posterior bands that tightened in reciprocal fashion as the elbow was flexed and extended. Sequential cutting of the ligament was performed while rotation caused by valgus torque was measured. The anterior band of the anterior bundle was the primary restraint to valgus rotation at 30, 60, and 90 degrees of flexion and was a co-primary restraint at 120 degrees of flexion. The posterior band of the anterior bundle was a co-primary restraint at 120 degrees of flexion and a secondary restraint at 30 and 90 degrees of flexion. The posterior bundle was a secondary restraint at 30 degrees only. The reciprocal anterior and posterior bands have distinct biomechanical roles and theoretically may be injured separately. The anterior band was more vulnerable to valgus overload when the elbow was extended, whereas the posterior band was more vulnerable when the elbow was flexed. The posterior bundle was not vulnerable to valgus overload unless the anterior bundle was completely disrupted. The intact elbows rotated a mean of 3.6 degrees between the neutral position and the two-newton-meter valgus torque position. Cutting of the entire anterior bundle caused an additional 3.2 degrees of rotation at 90 degrees of flexion, where the effect was greatest. CLINICAL RELEVANCE: Physical findings in a patient who has an injury of the anterior bundle may be subtle, and an examination should be performed with the elbow in 90 degrees of flexion for greatest sensitivity. As the anterior bundle is the major restraint to valgus rotation, reconstructive procedures should focus on anatomical reproduction of that structure. Parallel limbs of tendon graft placed from the inferior aspect of the medial epicondyle to the area of the sublimis tubercle will simulate the reciprocal bands of the anterior bundle. Temporary immobilization with the elbow in flexion may relax the critically important anterior band of the reconstruction during healing.

Posterior subluxation of the glenohumeral joint.

Twenty-four patients who had posterior subluxation of the glenohumeral joint were assigned to one of two groups on the basis of the severity of the symptoms. The sixteen patients in Group I, who had less severe symptoms, were treated with a physical therapy program that was based on exercises to strengthen muscles. The eleven patients in Group II (three of whom had no success with physical therapy when they were originally in Group I) had a posterior capsulorrhaphy, with or without a bone block. According to an over-all rating, Group I had a rate of success of 63 per cent, and Group II had a rate of success of 91 per cent. The patients who had more severe ligamentous laxity were not more likely to fail either of the treatment programs. Although voluntary subluxation may be a subtle but important indicator of underlying emotional difficulties, it appears that, in the patient who is emotionally stable, the ability to voluntarily subluxate the shoulder posteriorly is not associated with a negative prognosis for either non-surgical or surgical treatment. Patients who have moderately disabling posterior subluxation of the shoulder should be treated with an intensive program that is designed to strengthen muscles. Patients who have symptoms that are severely disabling or who have had no success with non-operative treatment should be treated with posterior capsulorrhaphy. When the posterior aspect of the glenoid is severely deficient and when the posterior portion of the capsule or the infraspinatus tendon is attenuated, a bone block should augment the reconstruction.