Effect of pulley excision on flexor tendon biomechanics.

Flexor tendon function following excision of various portions of the fibro-osseous pulley system was measured biomechanically using a tensile testing machine. The biomechanical parameters measured were tendon excursion (the excursion of the tendon required to fully flex the digit) and work of flexion (the area under the force-excursion curve, representing all the forces that resist tendon flexion). In this experiment, work of flexion included the forces necessary to accomplish full digital flexion against a 15-g counter-weight, as well as the frictional forces that resist tendon gliding. The results indicate that the work of flexion was affected to a greater degree by pulley loss than was tendon excursion, suggesting that it is a more sensitive measurement of tendon function. A2 was found to be the single most important pulley for flexor tendon function, followed by A4. However, both A2 and A4 had to be present if near-normal hand function was to be achieved; sacrificing the A1 pulley was not associated with a significant loss of flexion. The "pulley effect" of the skin and soft tissue as a supplement to the fibro-osseous pulleys in reducing tendon bow-stringing was also noted. Although the parameters of tendon excursion and work of flexion were used in this study to determine the effect of pulley loss on tendon function, they can also be used to evaluate other flexor tendon studies, such as pulley reconstruction.

Three-dimensional computed tomographic reconstructions of intracranial meningiomas.

In a series of four patients with intracranial meningiomas, three-dimensional computed tomographic (CT) reconstructions were a useful diagnostic and surgical adjunct. Three-dimensional images are created from standard CT data by a boundary-detecting computer software program. Three-dimensional images of tumor invading or adjacent to the bony calvarium are projected about the x, y, and z axes. Axial and sagittal sections delineate the lesions. The images created allow a surgical view of the meningiomas in three-dimensional space and demonstrate the relationship of these masses to the skull. The use of three-dimensional reconstructions in craniofacial surgery and in neurosurgery is reviewed.

Measurements of length and tension patterns during reconstruction of the posterior cruciate ligament.

The twofold purpose of this study was to develop an intraoperative technique to assess isometric positioning of posterior cruciate ligament grafts and to demonstrate the rationale for postoperative immobilization of the knee in full extension after a posterior cruciate ligament reconstruction. Multiple femoral fixation sites were selected on the medial intercondylar notch and the posterior cruciate ligament substitute was assessed for changes in length and tension at each of these sites during knee flexion from 0 degree to 120 degrees. The most isometric and isotonic femoral fixation site was localized over a small area slightly distal to the center of the medial intercondylar notch surface. This isometric point can be identified intraoperatively using recognizable surface markers within the knee. When a posterior stress was applied to the proximal tibia, the posterior cruciate ligament substitute showed the least increase in tension and length when the knee was locked in full extension for all of the potential femoral attachment sites assessed. This suggests that postoperative immobilization should be maintained in full extension to limit the stress placed on the posterior cruciate ligament reconstruction.

Pathomechanics of posterior sag of the tibia in posterior cruciate deficient knees. An experimental study.

This study was an investigation of the pathomechanics of posterior sag of the tibia in knees with posterior knee instability caused by PCL deficiency. By using fresh cadaver knees, the authors hoped to define the relationship of the posterior joint capsule and the medial and lateral collateral ligaments (MCL, LCL) with posterior knee instability in the PCL deficient knee. Thirty newtons of posterior stress were applied to the knees to simulate postoperative conditions. Roentgenographic methods were then used to evaluate posterior sag and change in the distance between the origin and insertion of the PCL. Strain gauges were used to measure the actual strain of the PCL and the collateral ligaments. The PCL, the posterior capsule, and the medial and lateral collateral ligaments were sequentially divided and the above measurements were then repeated in the same way, using 30 N of applied posterior stress. When only the PCL was cut, posterior sag and medial rotation of the tibia occurred with increasing severity as flexion increased. No sagging or rotation of the tibia was observed at full extension in the knees that had isolated PCL "injury". When the posterior capsule was sectioned, no significant changes were noted in the severity of the sag or the rotation. When the MCL or LCL was divided in a PCL deficient knee, greater sag occurred with flexion and a significant sag was observed even at full extension. The MCL "injury" was associated with increased medial rotation, whereas LCL "injuries" were associated with lateral rotation of the tibia.(ABSTRACT TRUNCATED AT 250 WORDS)

A nonparallel, nonisometric synthetic graft augmentation of a patellar tendon anterior cruciate ligament reconstruction. A model for assessment of stress shielding.

The potential for a rigidly fixed synthetic graft placed in the over-the-top position to be stress shielding/stress sharing with the patellar tendon autograft was assessed in a primate model. A patellar tendon autograft was placed anatomically and tensioned at 2 pounds for all of the groups. In the augmented animals, a 30 strand braided graft 10 cm in length of expanded polytetrafluoroethylene was tightened with the knee in full extension. After 6 months of unrestricted cage activity the animals were sacrificed and biomechanical testing performed. The augmented patellar tendon autografts demonstrated less laxity in extension as compared to the autografts alone. A minimal decrease in the load and stiffness to failure for the augmented groups as compared to the nonaugmented knees was noted. However, both the reconstruction groups had a significant decrease in the load to failure at 6 months (50% of the normal ACL). In summary, this study demonstrated that a synthetic graft augmentation can be performed in the over-the-top position and minimize knee laxity, especially during terminal extension. With this technique, the laxity was minimized while the incorporation and strengthening of the biologic autograft occurred at a rate similar to the unaugmented reconstruction.

Quantification of the perfusion of the anterior cruciate ligament and the effects of stress and injury to supporting structures.

The perfusion of the normal ACL was quantitated using the hydrogen washout technique in a canine model. This was compared to the perfusion of the synovium in the suprapatellar pouch. Changes in the ACL perfusion were quantitated after the application of anterior stress, division of the infrapatellar fat pad, and dissection of the synovium enveloping the ACL. The ACL is relatively hypovascular, with one-half the blood flow of the synovium of the suprapatellar pouch. Application of an anterior stress diminishes the blood flow to the ACL to one-fifth of the baseline value, an effect which is reversible. Division of the infrapatellar fat pad causes a two-fold decrease in perfusion to the ACL, whereas dissection of the enveloping synovium results in a complete cessation of blood flow.

An in vivo analysis of the effect of transcutaneous electrical stimulation of the quadriceps and hamstrings on anterior cruciate ligament deformation.

Transcutaneous electrical muscle stimulation (TEMS) has been advocated as a method to rehabilitate the postoperative ACL repaired/reconstructed lower extremity. Isolated quadriceps contraction can potentially disrupt the ACL repair/reconstruction; to minimize this risk simultaneous quadriceps and hamstring stimulation has been used. This study measured the in vivo deformation of the ACL during TEMS of the quadriceps and hamstrings. Six legs in four Rhesus monkeys were immobilized in 0 degrees, 45 degrees, and 90 degrees of flexion in neutral rotation using a Hoffman frame and pins placed through the proximal femur and distal tibia. The hamstrings and quadriceps muscles were stimulated with a dual channel electrical stimulator individually and simultaneously at each point of flexion, and ACL deformation was measured using a Hall effect device placed on the anterior medial fibers of the ACL. The following conclusions were made: 1) Isolated quadriceps contraction produces ACL elongation at 0 degrees and 45 degrees of knee flexion and produces ACL shortening at 90 degrees of knee flexion. 2) Isolated hamstrings contraction produces ACL shortening at 45 degrees and 90 degrees of knee flexion and negligible effects at full knee extension. 3) It is not possible to simultaneously contract the quadriceps and hamstrings using separate stimulator pads for each muscle group. 4) At 45 degrees of knee flexion when the quadriceps muscles are stimulated before the hamstring muscles and simultaneous contraction of both is then sustained, ACL lengthening occurs. 5) When the hamstring muscles are fired before the quadriceps muscles and simultaneous contraction of both is sustained, ACL shortening occurs.

Transcutaneous electrical nerve stimulation: an adjunct in the pain management of Guillain-Barré syndrome.

Transcutaneous electrical nerve stimulation was applied in the pain management of a patient with Guillain-Barré Syndrome. As subjectively reported by the patient, her back and lower extremity pain was significantly decreased although her foot paresthesia was not decreased. The program was continued for an 11-day period because TENS was considered a valuable adjunct for the patient's comfort. Transcutaneous electrical nerve stimulation is a valuable addition to our repertoire of available physical therapy modalities. We hope that as clinical experience with TENS increases, fellow clinicians will volunteer the experiences of their endeavors.

Electrically elicited co-contraction of thigh musculature after anterior cruciate ligament surgery. A description and single-case experiment.

The purpose of this article is to describe a method for strengthening the quadriceps femoris muscle in a patient after anterior cruciate ligament (ACL) surgery. The method incorporates electrically elicited co-contraction of the quadriceps femoris and hamstring muscles. A single-case experimental design based on a split-middle (ABAB) technique was used to assess the effects of the systematic administration and withdrawal of electrical stimulation with respect to changes in knee isometric extension and flexion torque and circumferential measurements of the thigh in a patient six weeks after ACL reconstruction. Results show increases in extension and flexion torque and thigh circumferential measurements that are associated with both stimulation (treatment) phases in addition to a maintenance effect demonstrated during the withdrawal phase. In this patient, the technique appears to be effective in increasing muscle strength and circumferential measurements, particularly quadriceps femoris muscle torque. Implications and suggestions for future research are included.

Patellar fixation protected with a load-sharing cable: a mechanical and clinical study.

The stability of patellar fracture fixation protected with a load-sharing cable was studied in cadavers. A transverse patellar osteotomy was produced and stabilized with standard patellar fixation with or without a figure-of-eight cable that extends from the proximal pole of the patella to the tibial tubercle. Standard fixation techniques (interfragmentary cancellous screws or modified tension-band wiring) alone failed after significantly fewer cycles of flexion and extension than did the same fixation when supplemented with a load-sharing cable. In the clinical evaluation of the load-sharing cable, 14 consecutive patients with displaced patellar fractures were treated. No immobilization was used and the patients were started on passive and active range of motion and weight-bearing ambulation in the early postoperative period. Thirteen fractures healed uneventfully. The increased stability of patellar fracture fixation protected with a load-sharing cable offers three advantages: (a) adjunctive casting is unnecessary, (b) comminuted fractures can be "pieced" together anatomically with less concern for loss of fixation, and (c) early postoperative passive and active range of motion can be achieved.

Flexor tendon pulley reconstructions--a histological and ultrastructural study in non-human primates.

The feasibility of A2 pulley reconstructions using expanded polytetrafluoroethylene (PTFE), woven nylon, and fascia lata was assessed in a non-human primate model and evaluated by light and scanning electron microscopy 18 weeks after implantation. No adhesions were found between reconstructed pulleys and flexor tendons. All types of pulley were intact and incorporated by host tissues, without evidence of a foreign body reaction. The inner surfaces of the fascial and PTFE pulleys, apposed to the gliding flexor tendons, were smooth and covered by a fibrous layer of tissue on microscopic and ultrastructural examination. The apposed visceral synovial surfaces of the F.D.P. tendon were indistinguishable from those from unoperated digits. The FDP tenosynovium apposed to woven nylon pulleys was more fibrillar and granular. Based on the results of the present study and on previous biomechanical data, expanded PTFE should be considered as a material for pulley reconstruction; it is incorporated by host tissues, elicits no foreign body reaction and causes no adhesions or traumatic changes to underlying flexor tendons. It is not yet known whether it has sufficient breaking strength to meet the functional demands of human pulleys.

Continuous passive motion as an adjunct therapy for tenolysis.

A model was developed to evaluate continuous passive motion as an adjunct to tenolysis. The use of continuous passive motion after tenolysis was associated with a significant increase in tendon rupture and the terminal force necessary to flex the phalanx actively. Also, there was a decrease in the passive range of motion in the continuous passive motion group which appeared to be the result of increased granulation tissue which formed around tenolysed tendon.

Prostaglandins: an overview.

Since their discovery more than 40 years ago, PGs have been shown to be present in many tissues. The 10 members of this family (PGA-PGI and TxA) that have been identified to date have been noted to have a wide variety of pharmacologic actions. Frequently, the actions of one PG are in direct opposition to those of another. This has led to the theory that PGs play an important role in maintaining homeostasis in many organ systems. Evidence accumulated indicates a major role for PGs in the regulation of blood pressure, the autonomic nervous system, blood flow and platelet aggregation. This is in addition to specific actions on other tissues such as the CNS and reproductive system. A summary of PG actions in humans is contained in Table 1. Unfortunately, the PGs have not been as useful therapeutically as originally hoped. Currently, they are being used to induce labor and to maintain the patency of the PDA. However, they still hold much promise and with the development of synthetic analogues and specific synthesis inhibitors, they should live up to this promise in the future.

Use of the Herbert bone screw for scaphoid nonunions.

The Herbert bone screw was used to treat 22 selected patients with established scaphoid nonunions. The indications for its use included evidence of avascular necrosis, proximal third fracture fragment, previous bone graft, fracture angulation or displacement, and a bipartite scaphoid. Treatment resulted in radiographic and clinical evidence of healing in 16 patients; 4 patients were symptom-free, but had incomplete healing as evidenced by radiograph; and 2 patients had persistent symptoms with radiographic evidence of nonunion.

Functional distal interphalangeal joint splinting for trigger finger in laborers: a review and cadaver investigation.

This two-part study evaluates the efficacy of functional distal interphalangeal joint (DIP) splinting for the treatment of trigger finger. Thirty-one fingers from 21 meat packing plant workers were treated with DIP splinting. A single corticosteroid injection was offered if triggering was stage 4 or greater. All workers returned to work immediately. Eighty-one percent of the digits were treated successfully (mean follow-up: 1 year). Treatment failure correlated with duration of symptoms and stage of triggering but did not correlate with age, race, sex, disease in multiple digits, or prior treatment. For the second part of the study, the effect of DIP splinting on flexor digitorum profundus (FDP) tendon excursion was studied in 16 fingers from 4 fresh cadavers. Excursion decreased 4.8 mm for the Stax splint and 4.2 mm for the dorsal Alumafoam splint. We conclude that DIP splinting provides a reliable and functional means of treating work-related trigger finger without lost time from work. Our cadaver investigation supports our theory that DIP splinting significantly decreases FDP excursion.