A partially biodegradable material device for repair and reconstruction of injured tendons. Experimental studies.

We assessed the applicability of a partially biodegradable synthetic material composed of polyglycolic acid (PGA) and dacron to repair or replace severely injured tendons. Adult rabbits underwent complete laceration and repair of one Achilles tendon. Group 1 (N = 8) had end to end tenorrhaphy with size 0 braided polyester suture, and Group 2 (N = 16) tendons were similarly repaired with the bicomposite designed PGA-dacron device. Group 3 (N = 16) received laceration and removal of 1 cm of tissue, and the defect was bridged with the same PGA-dacron material. No postoperative immobilization was applied. Evaluation, consisting of biomechanical testing or histologic inspection, was done at 4 and 8 weeks after tenorrhaphy. All tendons healed, and at 8 weeks the mean maximum load at failure of the repaired tendons was 32.2 +/- 3.4 kgf, 40.3 +/- 2.4 kgf, and 31.8 +/- 3.2kgf for Groups 1, 2, and 3, respectively. Values between groups were not significantly different, but all were significantly less (P less than or equal to 0.05) than the strength of the unoperated control tendons (55.8 +/- 7.2 kgf). The most noteworthy finding was the lengthening of the repaired tendons, due to scar elongation at the tenorrhaphy site, that occurred during healing as determined by a landmark placed a fixed distance proximal to the repair site. Group 1 tendons lengthened 22 mm, while Group 2 and 3 tendons increased by 12.5 mm. Histologically, fibrous tissue ingrowth into the residual dacron scaffold occurred, but it was inconsistent and inadequate in quality and quantity to be satisfactory as neotendon. The fibrous tissue did not mature or align in response to load. We concluded that the PGA-dacron material had adequate strength and physical properties to use both for primary tenorrhaphy and to bridge the tendon defect. However, in our experience this material lacks any significant advantage over other materials available or known to be under evaluation to support neotendon formation when an actual soft tissue defect exists.

Philosophy and rationale for the management of anterior cruciate injuries and the resultant deficiencies.

Deficiency of the anterior cruciate ligament (ACL) results in the loss of the fine tuning of the knee joint. Either acute loss or chronic insufficiency of ACL function results in instability, tricking, and giving way, and subsequently the fluid gliding mechanics of the knee joint are significantly altered. Regardless of the length of time from injury to evaluation, it is imperative that a correct and complete diagnosis be made before a treatment program is selected. Functional stability, the goal, can be accomplished only by limiting clinical laxity through a combination of appropriate surgery and functional rehabilitation.

Nonligamentous problems of the athlete's knee.

Acute and chronic nonligamentous problems of the athlete's knee are outlined, emphasizing diagnosis and treatment. Most such problems can be managed by the family physician or general practitioner, and recommendations are made for the referral of more complex problems.

Compression plate position. Extraperiosteal or subperiosteal?

Although compression plate fixation of diaphyseal long bone fractures is accepted treatment, surgical exposure and plate position in relation to the periosteum are controversial. Histologic, roentgenographic, and biomechanical methods were applied to investigate quality and chronology of healing in radial and ulnar fractures in adult dogs. Plate position was extraperiosteal in one limb and subperiosteal in the contralateral limb. There were no statistical differences in roentgenographic or histologic studies of healing between the two techniques, nor were significant statistical differences noted when comparing linear load, maximum load at failure, slope of the linear portion, energy absorbed to failure, stress, modulus of elasticity, strain at maximum linear load, strain at maximum load, and strain at failure. Thus, there was no appreciable difference in fracture healing between subperiosteal and extraperiosteal exposure with compression plate fixation of diaphyseal fractures in dogs. However, subperiosteal exposure is preferable because it is less likely to injure surrounding soft tissues.

Tobramycin in bone cement. An in-depth analysis of wound, serum, and urine concentrations in patients undergoing total hip revision arthroplasty.

In this prospective clinical study, ten patients were treated by revision of total hip arthroplasties utilizing tobramycin-impregnated bone cement. After the operation, serum, urine, and wound suction drainage concentrations of tobramycin were determined serially by radioimmunoassay. Although high local wound concentrations, 5.7 micrograms/ml, were maintained for as long as 48 hours, serum concentration never reached even normal therapeutic ranges (greater than 2.0 micrograms/ml). There were no immediate postoperative infections; all patients are pain-free and ambulate without external support two years after surgery. One patient who had had a preoperative infection was successfully treated for late manifestation of infection 24 months after revision. Based on the evidence obtained in this study, tobramycin in bone cement is currently acceptable for clinical use.

Biomechanics of the anterior cruciate ligament.

The principal role of the anterior cruciate ligament (ACL) is to resist anterior displacement of the tibia on the femur. The ACL also has a major role in resisting internal rotation. The posterior fibers are longest, or most tense, in extension, and are therefore the major resistance to hyperextension and are more susceptible to injury in extension. The anterior fibers are longest, or most tense, in flexion and therefore are not susceptible to injuries with the knee flexed. The ACL is strong and stiff, yet because of its unique structure, it is precariously susceptible to injury.

Acute anterior cruciate ligament injury and repair reinforced with a biodegradable intraarticular ligament. Experimental studies.

The anterior cruciate ligament was transected at the femoral origin in the knee joint of 12 dogs. The ligaments were repaired in a conventional manner and reinforced with a polyglycolic acid (PGA) ligament of braided Dexon (Davis & Geck, Pearl River, NJ) suture. At two weeks the PGA ligament was still providing excellent support for the healing anterior cruciate ligament, and there was no synovitis within the knee joint. After five weeks, initial healing had firmly attached the repaired anterior cruciate ligament to the femoral condyle, and the PGA ligament had resorbed without inflammatory or fibrotic response. All repaired and reinforced ligaments in this series healed and provided functional stability to the knee joints. Biomechanical testing of the repaired anterior cruciate ligaments at four months produced a maximum strength of 54.2 +/- 6.3 kgf. Sulfur-35 uptake showed viable active collagen-producing cells in the repaired ligaments four months postoperatively. Thus, the biodegradable PGA ligament reinforced and splinted successfully the repaired anterior cruciate ligament.

Progressive ultrastructural changes after peripheral nerve transection and repair.

Six rhesus monkeys (Macaca mulatta) underwent sharp transection and repair of the intrinsic motor fascicles of both ulnar nerves in order to determine the sequential events during reinnervation of the distal stamp. Light and electron microscopic sections were made at 2.0 mm increments distal to the neurorrhaphy at weekly intervals in separate monkeys. Neurite sprouts could be identified distal to the neurorrhaphy by 1 week and were clearly evident 40 mm distal by 3 weeks. Although some old endoneurial tubules persisted, they were less often used as conduits or scaffolds for the regenerating neurites than previously described. Most new fibers, whether myelinated or unmyelinated, passed down new endoneurial tubules, thus precluding perfect end-organ specificity because the regenerating neurites seldom utilized old endoneurial tubules. The clinical implication suggested by this study is that the ideal situation is the immediate repair of transected nerves. This allows neurite sprouts to cross a neurorrhaphy rapidly and reinnervate end organs.

The anterior cruciate ligament: radiographic and clinical signs of successful and unsuccessful repairs.

Our ten-year observation of anterior cruciate ligament injuries in an active athlete population shows that radiographic evidence of instability and joint deterioration are reliable clinical signs. Radiographic findings in the rotatory unstable knee are subtle six months after injury, but on standard roentgenographic views, which include the notch view, they appear in a sequential order from peaking of the intercondylar tubercles to buttressing osteophytosis. These are objective signs of progressive deterioration that should be a warning to the patient. The early and progressive radiographic signs portend further deterioration if stability is not obtained by restriction of activities, bracing, or reconstruction. Physicians and sports injury specialists should recognize these findings early and offer counsel to the patient at risk.

Medical meniscus repairs. An experimental and morphologic study.

In an effort to determine the healing potential of medial meniscus tears, 20 canine and 12 rhesus knee joints were subjected to transverse medial meniscus laceration and repair with a single Dexon suture (Davis & Geck, Pearl River, NY). At four months, 12 out of 32 (38%) had healed completely with restoration of the inner meniscal rim and 18 (56%) showed partial healing sufficient to protect the underlying articular cartilage. Only 2 (6%) of the menisci failed to heal. Histologic evaluation showed that the scar tissue present in the menisci was composed of unorganized collagen without common ground substance components. As a result of these studies, we believe that certain meniscal tears, particularly those involving the vascular periphery, can heal and may be repaired rather than treated by meniscectomy.

Acute anterior cruciate ligament injury and augmented repair. Experimental studies.

Eleven dogs underwent transection of the anterior cruciate ligament at the femoral origin of the stifle (knee) joint. The anterior cruciate ligaments were repaired in a conventional manner and augmented by transferring the medial one-third of the patellar tendon and inserting it into the lateral femoral condyle. The repairs were evaluated either 4 or 8 months postoperatively. All repaired and augmented anterior cruciate legaments in this series healed satisfactorily to provide clinical and functional stability to the knee joints. Instron testing of the repaired and augmented anterior cruciate ligaments showed maximum strength at 4 months of 46.2 +/- 10.9 kgf and at 8 months of 64.3 +/- 14.3 kgf as compared to the control of 122.7 +/- 11.6 kgf. Histologic evaluation showed that by 8 months the repaired and augmented anterior cruciate ligaments had healed by bony ingrowth. Thus, interstitial failure occurred during Instron testing. The transferred patellar tendon provided additonal blood supply, splinted the anterior cruciate ligament to allow healing, and increased the strength of the repaired complex.

Neurorrhaphy after loss of a nerve segment: comparison of epineurial suture under tension versus multiple nerve grafts.

Epineural neurorrhaphy under tension and interfascicular grafting, two methods of bridging gaps associated with loss of a nerve segment, were compared. After resection of a 2 cm length of both ulnar nerves in cats, one nerve was sutured under tension using an epineurial technique, and the other was repaired using multiple interfascicular sural nerve grafts. Six months later return of nerve function was evaluated. Subjective evaluation included ambulation, sensation, and intrinsic function. Objective measurements included muscle efficiency, maximum strength, muscle weights, and total axon counts. No statistical difference was observed between these two techniques. Histochemically, there was marked fiber type grouping of the reinnervated muscles for both types of repairs. Histologically, perineurial fibrosis and axonal disorganization were equal for both techniques, but significantly greater suture granuloma formation occurred in the nerve repaired under tension. Individual grafts retained their identity and remained distinct grossly and microscopically.

Peripheral nerve injuries: studies in higher nonhuman primates.

Two skeletally mature baboons underwent comparative neurorrhapies following transsection of both ulnar nerves without loss of nerve tissue. In baboon 1 there was no difference in objective evaluations at 12 months when an epineurial neurorrhaphy was compared to a perineurial fascicular neurorrhaphy. In baboon 2, the one that had interfacicular grafts in one upper extremity and an epineurial neurorrhaphy on the other side, there was significantly better functional return on the epineurial side than one the graft side. Grass and histological evaluation showed that the grafts retained their integrity and regenerating axons transversed the grafts well.

Exercise effects on the strength of the rat anterior cruciate ligament.

Seventy-five rats were divided into a control and four exercise groups of differing frequency and duration. After 8 weeks of endurance-type exercise on a motorized treadmill, the rats were sacrificed and the anterior cruciate ligaments were tested to failure on an Instron materials testing machine at a strain rate of 95% sec-1. Of the 121 ligaments tested, 119 failed by pure interstitial failure. There was significant increase in both the strength and stiffness of the anterior cruciate ligaments in the exercised rats but those rats exercised more frequently (daily vs. every other day) and for shorter duration (30 min rather than 60 min) had the greatest increase in strength. This study has shown that endurance-type exercise is beneficial to the anterior cruciate ligament as both strength and stiffness are increased and functionally the ligament remains unchanged by exercise.

Tendon transfers in the paralytic hip.

We analyzed the results of transfers of the iliopsoas or external oblique muscles performed to augment the abductor power of the hips in 149 patients with flaccid paralysis of the hips. More than 800 supplemental procedures were performed on the lower extremities of these patients. Twenty-three of the thirty-eight hips that had been subluxated or dislocated became stable in the reduced position after the transfer operation. Every hip that had been stable before the transfer remained stable, and thirty-seven patients who had been brace-dependent became brace-free. We concluded that transfers of the iliopsoas or external oblique muscles are useful adjuncts in the treatment of paralytic disorders of the hips.

Experimental studies of acute anterior cruciate ligament injury and repair.

Ten dogs and six rhesus monkeys underwent transection and repair of the anterior cruciate ligament. One-half of the procedures involved the femoral end, the other half involved the tibial end of the ligament. Seven of the 10 canine and all of the primate ligaments, that had been transected and repaired, did heal. Functional and clinical instability was demonstrable in all repaired knees. The monkeys developed fewer degenerative changes with more grossly normal appearing ligaments after the repairs than did the dogs. Failure testing on an Instron materials testing machine revealed maximum strength of the repaired ligaments to be 10.4% for the repairs at the femoral end and 2.0% for repairs at the tibial ends in dogs when compared with the contralateral control knees. In monkeys the femoral repairs were 46.8% and the tibial repairs were 62.6% of the control knees. Inadequate immobilization and early stress were believed to be principal causes of the poorer results in dogs. The observations in monkeys support the suggestion that injured anterior cruciate ligaments that can be repaired, should be repaired.

The patellar compression syndrome: surgical treatment by lateral retinacular release.

Patellar compression syndrome may be a manifestation of contraction of the lateral retinacular structures which consists largely of the lateral patellofemoral ligament producing a tethering action on the patella. This may produce parapatellar pain, particularly in activities requiring repetitive knee flexion. Minor patellofemoral incongruencies with pain, grating, and functional limitation may be found on examination but the patient does not demonstrate the problems of instability of marked congenital abnormalities often seen with other patellar problems. Forty patients underwent a simple release of the lateral retinaculum to decompress the patella in the patellofemoral groove. Follow-up was obtained in 31 patients at an average of 18.3 months after surgery. Twenty-four knees which had severe preoperative pain were converted to 6 with no pain, 4 with mild pain, 11 with moderate pain and 3 whose pain remained unchanged after surgery. Twenty knees with moderate preoperative pain were changed to 4 with no pain, 11 with mild pain and 4 whose pain remained unchanged. Thirty-seven of the 45 knees had lessening of the pain after the operation and 10 patients returned to unrestricted atheletic activities.