Repair of soft tissue to bone using a biodegradable suture anchor

A decrease in blood androgen levels is well documented in women who experience natural or surgical menopause. This change may be associated with various negative effects on bone metabolism in addition to psychosocial and sexuality aspects of life. A review of published information on androgen replacement therapy shows that major benefits may be achieved; unfortunately, only minimal quality information is available to help clinicians make decisions about this type of therapy. In this review, we point out the potential benefits and risks to bone, lipid and carbohydrate metabolism, and sexuality; in addition, we discuss potential risks of neoplasms and virilizing somatic changes. Long-term, physiologic, and well-designed androgen replacement studies should be performed to obtain the knowledge needed to guide therapy in this important area.     

The role of supplemental translaminar screws in anterior lumbar interbody fixation: a biomechanical study

The immediate stabilization provided by anterior interbody cage fixation is often questioned. Therefore, the role of supplementary posterior fixation, particularly minimally invasive techniques such as translaminar screws, is relevant. The purpose of this biomechanical study was to determine the immediate three-dimensional flexibility of the lumbar spine, using six human cadaveric functional spinal units, in four different conditions: (1) intact, (2) fixed with translaminar screws (TLS), (3) instrumented with anterior interbody cage insertion with the BAK system and (4) instrumented with BAK cage with additional TLS fixation. Flexibility was determined in each testing condition by measuring the vertebral motions under applied pure moments (i.e. flexion-extension, bilateral axial rotation, bilateral lateral bending) in an unconstrained manner. Anterior fixation with the BAK alone provided significant stability in flexion and lateral bending. Additional posterior TLS significantly reduced the motion in extension and axial rotation. TLS fixation alone resulted in smaller rotations than BAK fixation in all loading directions. Based on these results, it seems that interbody cage fixation with the BAK system stabilizes the spine in some, but not all, loading directions. The problematic loading directions of extension and axial rotation can be substantially stabilized by using translaminar screw fixation. However, one should emphasize that the degree of stability needed to achieve solid fusion is not known.     

A biomechanical evaluation of suture anchors in repair of the rotator cuff

Repair of the rotator cuff requires secure reattachment, but large chronic defects cause osteoporosis of the greater tuberosity which may then have insufficient strength to allow proper fixation of the tendon. Recently, suture anchors have been introduced, but have not been fully evaluated. We have investigated the strength of suture-to-anchor attachment, and the use of suture anchors in repairs of the rotator cuff either to the greater tuberosity or the lateral cortex of the humerus. The second method gave a significant increase in the strength of the repair (p = 0.014). The repairs were loaded cyclically and failed at low loads by cutting into bone and tendon, casting doubt on the integrity of the repair in early mobilisation after surgery. Repairs with suture anchors did not perform better than those with conventional transosseous attachment.     

Increasing the moment arm of the tibialis anterior induces structural and functional adaptation: implications for tendon transfer

Previous studies on the functional effects of tendon transfer have not examined possible muscle adaptation following transfer. The purpose of the present study was to test the hypothesis that muscle adapts to increased moment arm and excursion such that joint torque is maintained near normal levels. The moment arm and excursion of the tibialis anterior (TA) were increased by releasing the TA from its retinacular restraint at the ankle joint in growing (4-week-old) rabbits. Twelve weeks post-release, in vivo TA force during hopping was smaller in released compared with control rabbits, compensating for the increased moment arm, and thus TA torque at the ankle joint was not significantly different between groups. Physiological cross-sectional area was smaller, and the number of sarcomeres in series was larger, in the released TA compared with the control TA. These adaptations may result from chronically decreased in vivo TA force production, and chronically increased TA excursion, respectively. In addition, these adaptations were consistent with the smaller in vivo force for the released TA. Comparisons between control and sham-operated rabbits showed no significant differences for in vivo TA force, torque, or muscle architecture. Thus, muscle appears capable of adapting to increased moment arm and excursion such that joint torque is maintained near normal levels. These findings have important implications for tendon transfer procedures that increase the moment arm and/or excursion of the released muscle.     

Calcification of the tibialis posterior tendon: a case report and literature review

The tibialis posterior muscle and tendon are subject to a number of pathological conditions and injuries that have recently received much attention in the literature. Because of its function as a main stabilizer of the subtalar complex against hindfoot valgus and forefoot pronation, the mechanical demand on the posterior tibial tendon is high. Problems with dislocation, tenosynovitis, rupture, and laceration have all been described with this tendon. In this report, we present a case of dysfunction of the posterior tibial tendon associated with chronic tendinitis and intratendinous calcifications. After removal of the calcifications, the patient became asymptomatic and returned to work. Proposed etiologies of these calcifications are discussed.     

Integration of hamstring tendon graft with bone in reconstruction of the anterior cruciate ligament

Anterior cruciate ligament (ACL) reconstruction using four-strand hamstring graft with round-headed, cannulated, interference (RCI) screw fixation requires osteointegration of the tendon graft. This report describes the histology at the bone-tendon junction of two specimens retrieved from patients undergoing revision surgery after traumatic mid-substance ACL graft rupture at 6 and 10 weeks after initial reconstruction. Revision was performed at 12 and 15 weeks. Integration of the graft was evident by observation of collagen fiber continuity between bone and tendon. This histology plus the low incidence of early graft failure suggest that free tendon autograft attached to bone by RCI screw allows adequate osteointegration between 6 and 15 weeks after surgery.     

Cyclic testing of flexor tendon repairs: an in vitro biomechanical study

Forty cadaveric flexor digitorum profundus tendons were repaired using the Tajima, Halsted, Silfverskiold, or Savage techniques. The tendons were cyclically loaded in sets of 4,000 cycles beginning at 25 N and increasing by 10-N increments until failure occurred. Gap formation was continuously monitored with an extensiometer. Only the Savage repair group consistently withstood 4,000 cycles of 25-N loading, with respect to 2-mm gap formation and repair rupture. Tendon repairs subjected to cyclic loading demonstrated gap formation and repair rupture at lower loads than with static testing. Of the methods of flexor tendon repair tested, only the Savage technique could withstand simulated early active motion.     

The effects of multiple-strand suture techniques on the tensile properties of repair of the flexor digitorum profundus tendon to bone

We examined the effects of multiple-strand suture techniques on the tensile properties of flexor digitorum profundus tendon-to-bone repairs in a human cadaver finger model. Forty-four fingers were obtained from the cadavera of fifteen donors who had been an average of seventy-four years old (range, fifty-four to eighty-nine years old) at the time of death. Four or eight-strand proximal grasping sutures were secured to the distal phalanx of each finger with use of either a suture anchor or a dorsally placed button. There were four subgroups of eleven fingers each. We found that repairs performed with use of a dorsally placed button had greater yield force, ultimate force, and rigidity than those performed with use of an anchor and that repairs performed with eight strands had greater ultimate force than those performed with four strands. These differences were significant (p < 0.05). We could detect no differences among the four types of repairs with regard to the amount of relative tendon-bone elongation at twenty newtons of force. The repairs performed with eight strands and a dorsally placed button had an average yield force (and 95 per cent confidence interval) of 50.0 +/- 14.1 newtons, an average ultimate force of 68.5 +/- 14.6 newtons, an average rigidity of 744 +/- 327 newton/(millimeter/millimeter), and an average tendon-bone elongation of 3.4 +/- 0.7 millimeters at twenty newtons of force. Multiple-comparison testing showed that the eight-strand repairs performed with a dorsally placed button had greater ultimate force than the other three types of repairs as well as greater yield force and rigidity than the four and eight-strand repairs performed with a suture anchor.     

Convergence of nociceptive and non-nociceptive inputs onto spinal reflex pathways to the tibialis anterior muscle in humans

To investigate whether the familial clustering of cutaneous melanoma is consistent with Mendelian inheritance of a major autosomal gene, maximum likelihood segregation analyses were performed in a population-based sample of 1,912 families ascertained through a proband with melanoma diagnosed in Queensland between 1982 and 1990. Analyses were performed with the S.A.G.E. statistical package, using the REGTL program for a binary trait with a variable age of onset. We sought medical confirmation for all family members reported to have had melanoma, and only medically verified cases among relatives were included in the analyses. The hypothesis of codominant Mendelian inheritance gave a significantly better fit to the data than either dominant or recessive Mendelian inheritance, or environmental transmission. Overall, both Mendelian inheritance of a single major gene, and purely environmental transmission were rejected (P < 0.001). In both the single major gene and environmental models, there was strong evidence of familial dependence in melanoma occurrence (P < 0.001). These results are consistent with reported genetic heterogeneity in melanoma inheritance and suggest that other familial factors, such as pigmentation, skin type, and sun exposure habits, may play an important role in the familial clustering of melanoma.     

Biologic attachment of an allograft bone and tendon transplant to a titanium prosthesis

An Achilles tendon allograft with its bony insertion was used to bridge a Titanium implant, containing an endoprosthetic tendon anchor, and the sheep biceps muscle. Twelve sheep were operated on unilaterally and followed up clinically and histologically for 2, 4 (n = 2), 8, and 12 months (n = 4). Full function of the front limb was regained after 8 to 12 weeks. There were no signs of mechanical loosening at all times. The morphologic changes at the bone block and implant fixation site were an initial revascularization of the allograft bone, which was observed at 2 months and enhanced at 4 months but occurred without any evidence of bone remodeling. This was changed in all specimens taken at 8 and 12 months where intensive new bone development, remodeling, and bone ingrowth in the titanium implant was found. Bone mass was shifted significantly to the tendon insertion half of the bone block because of a creeping substitution of the cancellous allograft bone and bone ingrowth to the implant. Overall bone mass slightly decreased with time but resorption of allograft bone outweighed new bone development only at lesser loaded areas. Transplantation of a bone and tendon allograft to an implant resulted in a revitalized, mechanically stable, and biologically anchored compound.     

A biomechanical comparison of open and thoracoscopic anterior spinal release in a goat model

STUDY DESIGN: A biomechanical assessment of anterior release and discectomy in the thoracic spine was performed on an animal model using thoracoscopic and open thoracotomy techniques. OBJECTIVES: To compare the relative efficacy of these two techniques of release in achieving increased spinal mobility. BACKGROUND DATA: The clinical use of video-assisted thoracoscopy in the correction of spinal deformity is increasing. The effectiveness of thoracoscopic anterior spinal release with discectomy has not been evaluated biomechanically. METHODS: Anterior release with discectomy was performed on six midthoracic motion segments in five mature goats. The thoracoscopic technique was used for three levels on one side, and an open thoracotomy was used for the alternating three levels of the contralateral side. The duration of surgery for disc excision and the amount of blood loss for each technique were recorded. The intact cranial and caudal motion segments served as controls. The motion segments were individually subjected to nondestructive biomechanical testing. Torsional, sagittal, and coronal bending torques were applied, and the resulting angular displacement was measured. RESULTS: The duration of surgery to remove a disc thoracoscopically decreased as experience was gained by the surgeon. The amount of intraoperative blood loss was comparable using the two methods. There was significantly increased flexibility in the released segments with both techniques, compared with the flexibility in the intact levels for all three loading directions. There was no difference in the motion obtained after release between the two techniques. CONCLUSION: Open and thoracoscopic anterior release and discectomy have been demonstrated, through biomechanical in vitro testing, to increase the flexibility of the spine to a similar extent.     

Measurement of impaired muscle function of the gastrocnemius, soleus, and tibialis anterior muscles in spastic hemiplegia: a preliminary study

Complete sequences of cytochrome b (1,137 bases) and 12S ribosomal RNA (961 bases) genes in mitochondrial DNA were successfully determined from the woolly mammoth (Mammuthus primigenius), African elephant (Loxodonta africana), and Asian elephant (Elephas maximus). From these sequence data, phylogenetic relationships among three genera were examined. Molecular phylogenetic trees reconstructed by the neighbor-joining and the maximum parsimony methods provided an identical topology both for cytochrome b and 12S rRNA genes. These results support the "Mammuthus-Loxodonta" clade, which is contrary to some previous morphological reports that Mammuthus is more closely related to Elephas than to Loxodonta.     

Lag-screw fixation of anterior mandibular fractures using biodegradable polylactide screws: a preliminary report

Antidepressants and neuroleptic drugs are sometimes the reason for the occurrence of the polymorphic ventricular arrhythmia torsades de pointes in patients. Therefore, it was of interest to study the actions of some of these drugs such as imipramine, amitriptyline, doxepin, chlorpromazine, trifluoperazine and thioridazine in isolated, spontaneously beating Purkinje fibers of guinea-pig hearts using the intracellular microelectrode technique because experimentally induced early afterdepolarizations (EADs) may be associated with this special type of arrhythmia. If the extracellular K+ concentration was 2.7mM none of these drugs could elicit EADs. For that reason the K+ concentration was lowered to 1. 35mM and EADs were evoked by imipramine (2 and 5 microM). Amitriptyline (2 and 5 microM) and doxepin (2 microM) did not induce EADs. Only a concentration of 5 microM doxepin elicited EADs. Among the neuroleptic drugs, chlorpromazine at a concentration of 2 and 5 microM was responsible for the occurrence of EADs as well as thioridazine in the same concentrations. When trifluoperazine (2 and 5 microM) was applied no EADs could be observed. Tetrodotoxin (0. 2 microMl-1) abolished thioridazine-induced EADs. Several membrane depolarizing currents may participate in the initiation of these EADs. Our results demonstrate that in guinea-pig Purkinje fibers some tricyclic antidepressants and some neuroleptic drugs are responsible for the rare occurrence of EADs under hypokalemic conditions.     

Effect of calcaneal osteotomy and lateral column lengthening on the plantar fascia: a biomechanical investigation

OBJECTIVES: To evaluate the efficacy and safety of one single intravenous methylprednisolone (IVMP) pulse therapy in myasthenia gravis. MATERIAL AND METHODS: We performed a double blind placebo controlled study (2+2 g IVMP vs placebo) in patients with moderate MG. RESULTS: A mean increase in muscle function of 27 points was found in the treatment group after one IVMP pulse as compared with a 0.7 point increase in the placebo group (P<0.01). In the IVMP group 8 of 10 patients showed a positive treatment response. The mean duration of improvement after IVMP was 8 weeks (range 4-14 weeks). No severe side effects were found. Acetylcholine receptor antibody concentrations were unchanged in spite of the positive treatment response. CONCLUSIONS: We conclude that a single IVMP treatment is efficacious and safe in the treatment of moderate MG.     

Trabecular bone mineral and calculated structure of human bone specimens scanned by peripheral quantitative computed tomography: relation to biomechanical properties

The relationship of cortical bone mineral density (BMD), and geometry to bone strength has been well documented. In this study, we used peripheral quantitative computerized tomography (pQCT) to acquire trabecular BMD and high-resolution images of trabeculae from specimens to determine their relationship with biomechanical properties. Fifty-eight human cubic trabecular bone specimens, including 26 from the vertebral bodies, were scanned in water and air. Trabecular structure was quantitated using software developed with Advanced Visual Systems interfaced on a Sun/Sparc Workstation. BMD was also obtained using a whole-body computerized tomography scanner (QCT). Nondestructive testing of the specimens was performed to assess their elastic modulus. QCT and pQCT measurements of BMD of specimens in water were strongly correlated (r2 = 0.95, p < 0.0001), with a slope (0.96) statistically not significantly different from 1. Strong correlations were found between pQCT measurements of specimens in water and in air, for BMD (r2 = 0.96, p < 0.0001), and for apparent trabecular structural parameters (r2 = 0.89-0.93, p < 0.0001). Correlations were moderate between BMD and apparent trabecular structural parameters (r2 = 0.37-0.64, p < 0.0001). Precision as coefficient of variation (CV) and standardized coefficient of variation (SCV) for these measurements was < 5%. For the vertebral specimens, the correlation was higher between elastic modulus and BMD (r2 = 0.76,p < 0.0001) than between elastic modulus and apparent trabecular structural parameters (r2 = 0.58-0.72, p < 0.0001), while the addition of apparent trabecular nodes and branches to BMD in a multivariate regression model significantly increased the correlation with the elastic modulus (r2 = 0.86, p < 0.01). Thus, pQCT can comparably and reproducibly measure trabecular bone mineral in water or air, and trabecular structure can be quantitated from pQCT images. The combination of volumetric BMD with trabecular structural parameters rather than either alone improves the prediction of biomechanical properties. Such a noninvasive approach may be useful for the preclinical study of osteoporosis.     

Histological evaluation of bone reactions to aluminium oxide dental implants in man: a case report

Alumina implants have been shown to possess high biocompatibility. The authors present the case of an aluminium oxide ceramic implant removed because of fracture of the abutment after a 30-month loading period. It was possible to observe microscopically that the implant was covered by highly mineralized mature compact lamellar bone; no connective tissue or inflammatory cells were present at the interface. Osteocytes were observed very close to the bone-implant interface. These features indicate the good biocompatibility of the implant.     

Manipulative treatment of carpal tunnel syndrome: biomechanical and osteopathic intervention to increase the length of the transverse carpal ligament

To quantify the amount of transverse carpal ligament (TCL) elongation in response to osteopathic manipulation or sustained load bearing (or both), a study involving seven cadaver limbs was conducted. Distances from the trapezium to the hamate (distance A) and from the scaphoid to the pisiform (distance B) were measured in five mounted cadaver limbs during and after the limbs bore the weight (2 newtons [N] to 4 N) for 2 several-hour periods. A several-hour period occurred between the weight bearing to assess recoil. Distances A and B were measured before and after the limbs were manipulated, according to previously described techniques, as well as with a new maneuver, termed the "guywire" technique. Two dissected limbs also were subjected to further weight bearing, this time increased to 8 N. Greater weight loads produced greater lengthening of the TCL, and recoil after removal of weight loads was slower than recoil after manipulation. Manipulation was more effective than weight loading for increasing distance A (distal canal), but weight loading generally was more effective than manipulation for increasing distance B (proximal canal). The guywire manipulation combined with direct transverse extension appeared to have the greatest impact on lengthening the TCL distally. These results show promise for the effective use of manipulation and load bearing for TCL elongation and nonsurgical relief of pressure on the median nerve in patients with carpal tunnel syndrome.     

Magnetic resonance imaging: a useful tool for evaluation of bone prior to implant surgery

OBJECTIVE: To illustrate the potential for use of magnetic resonance imaging (MRI) to gain full sectional information before placement of osseo-integrated dental implants, with no patient exposure to ionising radiation. MATERIALS AND METHODS: Four typical cases are illustrated, the patients being imaged in a one tesla MRI scanner. The setting up of the sequences is explained, along with the use of an imaging/surgical template with gadolinium markers. RESULTS: MRI clearly shows full sectional detail of available bone for safe implant placement, and allows the delineation of cortical and cancellous bone to attain maximum implant length and stability. Vital structures and the floor of the maxillary sinus are clearly shown. CONCLUSIONS: MRI allows the surgeon to assess cases for suitability to place dental implants with confidence. The ability to scan directly at any desired plane, with no reformatting, and to relate this information to a surgical template gives predictable surgery. MRI is a sectional imaging modality giving information about the 3-dimensional relationship of the vital structures, without using ionising radiation. It therefore deserves consideration as an alternative to computed tomography. However, further work is indicated to investigate the relative technical merits of the two imaging modalities.     

Delayed implants in the anterior maxilla with the IMZ-implant system: a radiographical evaluation

One hundred and seventy-three IMZ-implants in 81 patients, placed in the anterior region of the maxilla, were evaluated radiographically by two observers. Radiographs were evaluated at three intervals, namely at the time of implant placement, the time of prosthetic restoration and at the latest available radiograph, on average 2 1/2 years after implant placement. In this study marginal bone height and the type of radiolucency adjacent to the implant were determined. Both observers were able to classify the marginal bone height (mesial and distal) and the distinctive type of resorptive defects to an acceptable level of agreement, with Cohen's kappa ranging between 0.48 and 0.69. It was found that, at the most recent visit to the clinic, angular-shaped resorptive defects are found mesially and/or distally of the implants at approximately 25% of the implants. At this stage 20.7% of the mesial implant sites and 27.9% of the distal implant sites show marginal bone heights less than three-quarters of the implant length. These findings do not fully underscore and sometimes even contradict the clinical observations which were considered highly satisfactory.