Peggy A. Lesker

Intrinsic flexor-tendon repair. A morphological study in vitro.

UNLABELLED Rabbit flexor tendons with a 90 per cent mid-section transverse laceration demonstrated the intrinsic capacity to participate in the repair process in the absence of extrinsic cell sources and without the benefit of nutrition from a circulating blood supply or the influence of synovial fluid. Two cellular processes were involved in the in vitro repair process: (1) phagocytosis occurred by differentiation of fibroblasts from the epitenon--the cells migrated into the repair site and removed cellular debris and collagen fragments, and (2) collagen synthesis occurred primarily within the endotenon cells. CLINICAL SIGNIFICANCE The results of this experimental study support the concept that flexor tendons have the intrinsic capacity to phagocytize old collagen and synthesize new collagen fibrils. Consequently, clinical attempts to prevent or control the peripheral adhesions appear valid, since these adhesions do not appear to be an essential component of the repair process.

Palmar aponeurosis pulley

The transverse fascicular fibers and paratendinous bands of the palmar aponeurosis are positioned at the proximal margin of the flexor tendon sheath. These anatomic structures form a tunnel around the flexor tendon and appear to function as a palmar aponeurosis pulley in conjunction with the first and second annular pulleys of the digital flexor mechanism.

Nutrient pathways of flexor tendons in primates.

The perfusion and diffusion pathways to the flexor profundus tendons of 40 monkeys were investigated by measuring the uptake of tritiated proline by various tendon segments. In the absence of all vascular connections, the process of diffusion provides nutrients to all areas of flexor tendon and in this study the process of diffusion was greater. The distal segment of tendon was observed to be profused most rapidly. The proximal tendon segment is perfused from both the muscular-tendinous junction and the vinculum longus; vincular segment perfusion is via the vinculum longus vessels alone; central segment perfusion is shared by the vinculum longus and vinculum brevis vasculature. The distal segment uptake is by both the process of diffusion or vinculum brevis perfusion. The osseous attachment at the distal phalanx contributes little to tendon nutrition.

Biochemical Evidence of Flexor Tendon Participation in the Repair Process—An in Vitro Study

Rabbit, dog, chicken and monkey flexor tendon explants were maintained for six weeks in vitro in organ culture media. Biochemical evidence of the intrinsic capacity of the explants to participate in the repair process is noted by an increase in DNA (i.e. cell number) and hydroxyproline (i.e. collagen content) of the cultured explants after six weeks on culture compared to the control specimens, as well as the incorporation of 3H Proline into the collagen molecule.

Avulsion of the ring finger flexor digitorum profundus tendon: an experimental study.

Summary The results of an experimental study of the breaking strength of the tendon-bone junction of the flexor digitorum profundus tendon in cadaver specimens indicates a significantly weaker insertion of the ring finger compared to the middle finger. This explains in part the more frequent occurrence of avulsion of the ring finger profundus tendon as observed clinically.

Strength of human pulleys.

The length, breaking strength, and tensile strength of each of the annular fibro-osseous pulleys of digital flexor sheath in ten fresh human cadaver specimens were measured. The first annular pulley and the fourth annular pulley were found to be the strongest, while the second annular pulley was the weakest. The design of artificial pulleys should reproduce the strength of the first annular and fourth annular pulleys. Suggested minimum requirements for the breaking strength of artificial implant pulleys may be made based on these studies.

Measurement of regional bone and bone marrow blood flow in the rabbit using the hydrogen washout technique.

This study tested the feasibility of using the hydrogen washout technique for measuring regional bone and bone marrow blood flow. Washout curves in cancellous and cortical bone were mono-exponential, indicating homogeneous perfusion of these tissues. Epiphyseal cancellous bone blood flow (0.129 +/- 0.015 ml/min/ml) and metaphyseal cancellous bone blood flow (0.170 +/- 0.014 ml/min/ml) were approximately twice as rapid as that of cortical bone (0.069 +/- 0.002 ml/min/ml). Washout of hydrogen from bone marrow was variable and usually formed a bi-exponential pattern, indicating non-homogeneous perfusion. Blood flow rate determined by analyzing the rapid components was 1.04 +/- 0.10 ml/min/ml, and that from the slow components was 0.27 +/- 0.02 ml/min/ml. Our blood flow rates are within the range of values reported by investigators using different methods, and the hydrogen washout technique offers specificity and ease of repetitive determinations not available with other methods.

The effect of surgical dissection on regional blood flow to the ulnar nerve in the cubital tunnel.

Regional blood flow to the ulnar nerve within the cubital tunnel of nonhuman primates was determined before and after surgical dissection by use of the hydrogen washout technique. The results indicate that anterior transposition is associated with a significant decrease in regional blood flow to the ulnar nerve for a period of at least three days. This relative ischemia was not noted following arcuate ligament incision or after medial humeral epicondylectomy. Vascular injection studies showed an abundant extrinsic arterial supply to the ulnar nerve, especially just distal to the groove that was apparently compromised during the anterior transposition.

Nutrient pathways to flexor tendons of chickens using tritiated praline

The nutrient pathway to the flexor tendons within the digital flexor sheath of adult chickens was investigated using tritiated proline. There was no difference in the uptake of the radioactive tracer by free segment tendons (detached from blood vessels) and the intact tendon lying in synovium. The uptake of tracer by tendons isolated from the synovium (but with unaltered vascular attachments) was significantly less than by the intact tendons. Radioactive tracer not only diffused across the synovium into the tendon, but along the course of the tendon itself. There was no difference in the uptake of radioactive tracer by 2-week-old tendon grafts with and without adhesions.

Nutrient pathways to flexor tendons using hydrogen washout technique

The nutrient pathways of flexor tendons within the flexor sheath were studied using the hydrogen washout technique. Hydrogen uptake and decay of a free segment of flexor tendon detached from its blood supply were not significantly different from an intact tendon lying in the synovial bed. There was no hydrogen uptake by flexor tendons which were mechanically separated from the synovial bed, even though muscular, periosteal and vincular attachments were intact. We concluded from this study that the synovium of the flexor tendon was a significant nutrient pathway for the flexor tendon and that the blood vessels did not appear to play a significant role in the nourishment of the flexor tendon.