Recent progress in intrasynovial flexor tendon repair and rehabilitation.
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Journal Article↗
Biomedical subjects
M I Boyer
Publications and source records attributed to M I Boyer.
Quantitative variation in vascular endothelial growth factor mRNA expression during early flexor tendon healing: an investigation in a canine model.
Vascular endothelial growth factor (VEGF) is a potent mediator of angiogenesis, with direct mitogenic activity on cells of endothelial origin. We quantified the temporal accumulation of VEGF mRNA at the repair site of an in vivo canine intrasynovial flexor tendon repair and rehabilitation model by means of quantitative Northern blot analysis, in order to detail a molecular signal involved in the intrinsic angiogenic process that accompanies early flexor tendon healing. Significant accumulation of VEGF mRNA occurred at the flexor tendon repair site at 7 days post-operatively, with peak levels seen at post-operative days 7 and 10. Levels returned to baseline by day 14. Local VEGF mRNA accumulation at the repair site temporally precedes and is spatially distinct from the vascular ingrowth itself, which has been shown to occur maximally at day 17. These data suggest that cells within the flexor tendon repair site are involved in molecular processes other than the synthesis of extracellular matrix, such as modulation of angiogenesis.
Animals↗
The effect of variations in applied rehabilitation force on collagen concentration and maturation at the intrasynovial flexor tendon repair site.
The biochemical means by which accelerated rehabilitation alters intrasynovial flexor tendon repair site collagen synthesis and extracellular matrix maturation are not fully understood. We hypothesized that an increased level of applied rehabilitative force in a clinically relevant animal model would hasten the maturation of the repair site extracellular matrix as demonstrated by total collagen and collagen cross-link assessment. Twenty-eight flexor digitorum profundus tendons from 14 adult dogs were transected and repaired. The animals received either low- or high-force rehabilitation and were killed 10, 21, and 42 days after surgery. A 10-mm segment of tendon surrounding the repair site was obtained. Biochemical analysis showed that total collagen concentration was significantly reduced at each time point, that the reducible cross-link ratio of dihydroxylysinonorleucine to hydroxylysinonorleucine was significantly increased at each time point, and that the nonreducible pyridinoline cross-link content was significantly decreased at 10 days in both rehabilitative groups. Total collagen content did not vary to a statistically significant degree with either time or as a function of rehabilitation type. Based on these findings several clinically relevant observations can be made. Increasing collagen concentration and repair site maturation do not explain the previously demonstrated increased tensile properties of tendon that occur between 3 and 6 weeks after repair. Higher force rehabilitation does not alter the biochemical composition of the healing tendon through 6 weeks. Coupled with other recent data these findings suggest that high-force rehabilitation does not stimulate accelerated healing after intrasynovial flexor tendon repair.
Animals↗
The influence of cross-sectional area on the tensile properties of flexor tendons.
Clinicians have long noted substantial variation in the cross-sectional size of flexor tendons in the hand; however, data indicating that surgical repair techniques of lacerated flexor tendons should be altered according to size are unavailable. Our objectives were to evaluate the cross-sectional size differences among tendons within the same hand and to correlate tendon size with tensile mechanical properties after suture repair. Fifty human cadaver flexor digitorum profundus tendons were measured with digital calipers to determine radioulnar and volardorsal diameters. Twenty tendons were used to measure resistance to suture pull-through; tendons were transected at the A2 pulley, and a transverse double-stranded 4-0 Supramid suture (S. Jackson, Inc, Alexandria, VA) was passed through the radioulnar plane of the tendon 1 cm from the transection site. The remaining tendons were transected and repaired by using a modified Kessler repair with double-stranded 4-0 Supramid suture. Both tendon repairs and tendon-suture pull-through specimens were tested to failure in tension by using a material testing machine. Dorsovolar tendon height and tendon cross-sectional area varied significantly between digits, with an average difference of approximately 40% between the values of the smallest (fifth) and largest (third) fingers. Yield and ultimate force determined by pull-through tests of the simple transverse suture correlated positively with tendon radioulnar width. Tensile properties of tendons repaired with a double-stranded modified Kessler repair, however, did not depend significantly on tendon size. These results indicate that the strength of the commonly used Kessler suture technique is not dependent on tendon cross-sectional size within the clinically relevant range of tendons evaluated.
Humans↗
Hand and wrist sonography.
Although the anatomy of the hand and wrist is complex and the pathologic conditions encountered are diverse, many of the disease processes are localized, and in many situations, the clinical question is specific and limited. Because of this, ultrasound has always been an attractive imaging modality for evaluation of hand and wrist problems. Unfortunately, intrinsic difficulties in ultrasound image acquisition and interpretation have slowed the acceptance of hand and wrist sonography. Recently, however, new developments in high-resolution transducers and signal processing have dramatically improved image quality and scanning flexibility. For this reason, hand and wrist sonography is now more widely accepted and is taking its place along side other traditional modalities such as radiography, computed tomography, magnetic resonance imaging, and arthrography. Specific situations in which ultrasound offers definite benefits include evaluation of tendon inflammation and rupture, evaluation of palpable masses or suspected occult masses, and evaluation of suspected foreign bodies. Analysis of the median nerve is also possible and in the future, may have a role in patients with carpal tunnel syndrome.
Journal Article↗
Flexor digitorum profundus tendon to bone repair using a multi-strand suture technique.
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Journal Article↗
Wrist fractures: what the clinician wants to know.
With the recent improvements in diagnosis and treatment of distal radius and carpal injuries, the hand surgeons' expectations of relevant radiologic interpretation of imaging studies are heightened. Conventional radiographic examinations, as well as more sophisticated and invasive studies, have important roles in the evaluation of wrist fractures and dislocations. On the basis of physical examination results and the mechanism of injury, the onus is on the examining surgeon to pinpoint potential sites of bone or ligament disruption. After this evaluation, appropriate imaging studies appropriately performed and interpreted will help direct treatment and improve outcome with greater clarity and certainty.
Carpal Bones↗
A Glanzmann's mutation in beta 3 integrin specifically impairs osteoclast function.
Osteoclastic bone resorption requires cell-matrix contact, an event mediated by the alpha v beta 3 integrin. The structural components of the integrin that mediate osteoclast function are, however, not in hand. To address this issue, we generated mice lacking the beta 3 integrin gene, which have dysfunctional osteoclasts. Here, we show the full rescue of beta 3(-/-) osteoclast function following expression of a full-length beta 3 integrin. In contrast, truncated beta 3, lacking a cytoplasmic domain (h beta 3c), is completely ineffective in restoring function to beta 3(-/-) osteoclasts. To identify the components of the beta 3 cytoplasmic domain regulating osteoclast function, we generated six point mutants known, in other circumstances, to mediate beta integrin signaling. Of the six, only the S(752)P substitution, which also characterizes a form of the human bleeding disorder Glanzmann's thrombasthenia, fails to rescue beta 3(-/-) osteoclasts or restore ligand-activated signaling in the form of c-src activation. Interestingly, the double mutation Y(747)F/Y(759)F, which disrupts platelet function, does not affect the osteoclast. Thus similarities and distinctions exist in the mechanisms by which the beta 3 integrin regulates platelets and osteoclasts.
Amino Acid Sequence↗
Intrasynovial flexor tendon repair. An experimental study comparing low and high levels of in vivo force during rehabilitation in canines.
BACKGROUND: Rehabilitation methods that generate increased tendon force and motion have been advocated to improve results following intrasynovial flexor tendon repair. However, the effects of rehabilitation force and motion on tendon-healing may be masked by the high stiffness produced by newer suture methods. Our objective was to determine whether the biomechanical properties of tendons repaired by one of two multistrand suture methods were sensitive to an increased level of applied rehabilitation force. METHODS: Two hundred and fourteen flexor digitorum profundus tendons from 107 adult dogs were transected and repaired. Dogs were assigned to one of four groups based on the rehabilitation method (low force [<5 N] or high force [17 N]) and the repair technique (four-strand or eight-strand core suture) and were killed between five and forty-two days after the procedure. Repair-site structural properties were determined by tensile testing, and digital range of motion was assessed with use of a motion-analysis system. RESULTS: Tensile properties did not differ between the low and high-force rehabilitation groups, regardless of the repair technique (p > 0.05). In contrast, tensile properties were strongly affected by the repair technique, with tendons in the eight-strand group having an approximately 35% increase in ultimate force and rigidity compared with those in the four-strand group (p < 0.05). Ultimate force did not change significantly with time during the first twenty-one days (p > 0.05); there was no evidence of softening in either of the repair or rehabilitation groups. Force increased significantly from twenty-one to forty-two days, while rigidity increased throughout the forty-two-day period (p < 0.05). CONCLUSIONS: Increasing the level of force applied during postoperative rehabilitation from 5 to 17 N did not accelerate the time-dependent accrual of stiffness or strength. Suture technique was of primary importance in providing a stiff and strong repair throughout the early healing interval. CLINICAL RELEVANCE: Our findings suggest that there be a reexamination of the concept that increases in force produced by more vigorous mobilization protocols are beneficial to tendon-healing. While more vigorous rehabilitation may help to improve hand function, we found no evidence that it enhances tissue-healing or strength in the context of a modern suture repair.
Animals↗
Expression of mRNA for vascular endothelial growth factor at the repair site of healing canine flexor tendon.
Neovascularization is an important and prominent feature of tendon healing that contributes to wound repair and potentially to adhesion formation. To define the location of cell populations that recruit and organize the angiogenic response during early healing of flexor tendon, we examined the gene expression pattern of the prototypic angiogenic factor, vascular endothelial growth factor, at and around the tenorrhaphy site in a canine model of flexor tendon repair. In situ hybridization with radiolabeled antisense riboprobes was used to identify tendon cell populations that contribute to the neovascularization process by expressing vascular endothelial growth factor and to relate this cell population to the previously described cell populations that participate in matrix synthesis (express type alpha1(I) collagen) and mitotic renewal (express histone H4). The majority of cells (approximately 67%) within the repair site itself express vascular endothelial growth factor mRNA; however, minimal levels accumulate within cells of the epitenon (approximately 10% of cells; p < 0.0002). By contrast, expression of type alpha1(I) collagen and histone H4 does not differ significantly between the epitenon and the repair site (uniformly approximately 30% of cells). Thus, a gradient of cell populations expressing vascular endothelial growth factor exists in the repairing tendon. These data suggest a potential contribution of cells within the repair site to the organization of angiogenesis during the early postoperative phase of tendon healing.
Animals↗
Sonography of the hand and wrist.
Not only is the anatomy of the hand and wrist complex, but also its pathologic conditions are quite diverse. Although plain radiographs, CT, arthrography, and MRI have traditionally been used to evaluate the hand and wrist, ultrasound is beginning to take its place alongside these more traditional imaging modalities and is being ordered with increasing frequency by orthopedic surgeons. This article reviews the pertinent gross anatomy and sonographic technique used to scan the hand and wrist and also describes the sonographic findings associated with the most common hand and wrist pathologic conditions. These include soft tissue tumors, tenosynovitis, tendinous and ligamentous injuries of the hand, Dupuytren's contracture, foreign bodies, and carpal tunnel syndrome (CTS).
Carpal Tunnel Syndrome↗
The resistance of a four- and eight-strand suture technique to gap formation during tensile testing: an experimental study of repaired canine flexor tendons after 10 days of in vivo healing.
There is a high incidence of gap formation at the repair site following tendon repair. Our goal was to determine the resistance of a 4- and an 8-strand suture technique to gap formation during tensile testing. We hypothesized that the 8-strand repair would sustain higher force levels at the onset of 1- and 3-mm gaps than the 4- strand repair. Twenty-two canine flexor tendons were transected, repaired, and tested to failure after 10 days of in vivo healing. Tests were recorded using a 60-Hz video system that allowed frame-by-frame playback for assessment of gap formation. The 8-strand repairs sustained 80% higher force at a gap of 1 mm than the 4-strand repairs (average force, 70 vs 39 N), but the force sustained at a gap of 3 mm did not differ between groups (35 N for both groups). For both repair types, a 1-mm gap typically occurred near the point of ultimate (maximum) force while a 3-mm gap occurred after the ultimate force. We conclude that the 8-strand repair is significantly more resistant to initial gapping during ex vivo tensile testing than the 4-strand repair but that the two repairs are equally susceptible to rupture if a gap of 3 mm or greater forms.
Animals↗
Effects of increased in vivo excursion on digital range of motion and tendon strength following flexor tendon repair.
Postoperative rehabilitation is an important factor in determining functional outcome following intrasynovial flexor tendon repair. We hypothesized that a rehabilitation protocol that produced increased in vivo excursion would lead to increased digital range of motion and tendon strength and decreased adhesion formation in a canine model. Ninety-six flexor digitorum profundus tendons from 48 dogs were cut transversely and repaired by a multistrand suture technique. Postoperative rehabilitation was performed daily with a low excursion-low force (1.7-mm average excursion; < 10 N force) or a high excursion-low force (3.6 mm excursion; < 10 N force) protocol. After death of the dogs at 10, 21, or 42 days, specimens were evaluated for digital range of motion, tensile mechanical properties, elongation of the repair site, and adhesion formation. Our data indicate that the range of motion of digits whose tendons were at low or high excursion was similar to that of controls. Increased in vivo tendon excursion due to synergistic wrist motion did not significantly affect ex vivo flexion of the distal and proximal interphalangeal joints or tendon displacement (p > 0.05). Similarly, tensile properties (ultimate load, repair site rigidity, and repair site strain at 20 N and at failure) and length of the gap at the repair site were not significantly affected by increased excursion (p > 0.05). Severity of adhesion formation was reduced slightly by increased excursion (p = 0.04). Our findings indicate that 1.7 mm of tendon excursion is sufficient to prevent adhesion formation following sharp transection of the canine flexor tendon and that additional excursion provides little added benefit.
Animals↗
The effect of dorsal carpal ganglion excision on the scaphoid shift test.
A clinical and radiographic review was performed on 18 patients (19 wrists) with dorsal carpal ganglia and associated positive scaphoid shift test. All patients underwent excision of the ganglion followed by 2 weeks of postoperative immobilization with the wrist in 20 degrees extension. All patients had wrist pain, a painful clunk on the Watson scaphoid shift test, localized tenderness on palpation of the scapholunate articulation and normal radiographs. Patients were assessed postoperatively by questionnaire and physical examination. Improved functional activity and decreased pain were noted in all patients. In 17 of 19 wrists, the positive preoperative Watson scaphoid shift test become negative. We believe that dorsal wrist ganglia are frequently associated with a positive scaphoid shift test and that excision of the ganglion followed by 2 weeks immobilization may lead to resolution of the signs and symptoms of instability, at least in the short term.
Adolescent↗
The effect of gap formation at the repair site on the strength and excursion of intrasynovial flexor tendons. An experimental study on the early stages of tendon-healing in dogs.
BACKGROUND: Elongation (gap formation) at the repair site has been associated with the formation of adhesions and a poor functional outcome after repair of flexor tendons. Our objectives were to evaluate the prevalence of gap formation in a clinically relevant canine model and to assess the effect of gap size on the range of motion of the digits and the mechanical properties of the tendons. METHODS: We performed operative repairs after sharp transection of sixty-four flexor tendons in thirty-two adult dogs. Rehabilitation with passive motion was performed daily until the dogs were killed at ten, twenty-one, or forty-two days postoperatively. Eight tendons ruptured in vivo. In the fifty-six intact specimens, the change in the angles of the proximal and distal interphalangeal joints and the linear excursion of the flexor tendon were measured as a 1.5-newton force was applied to the tendon. The gap at the repair site was then measured, and the isolated tendons were tested to failure in tension. RESULTS: Twenty-nine tendons had a gap of less than one millimeter, twelve had a gap of one to three millimeters, and fifteen had a gap of more than three millimeters. Neither the time after the repair nor the size of the gap was found to have a significant effect on motion parameters (p > 0.05); however, the ultimate force, repair-site rigidity, and repair-site strain at twenty newtons were significantly affected by these parameters (p < 0.05). Testing of the tendons with a gap of three millimeters or less revealed that, compared with the ten-day specimens, the forty-two-day specimens failed at a significantly (90 percent) higher force (p < 0.01) and had a significantly (320 percent) increased rigidity (p < 0.01) and a significantly (60 percent) decreased strain at twenty newtons (p < 0.05). In contrast, the tensile properties of the tendons that had a gap of more than three millimeters did not change significantly with time. CONCLUSIONS: Our data indicate that, in a dog model involving sharp transection followed by repair, a gap at the repair site of more than three millimeters does not increase the prevalence of adhesions or impair the range of motion but does prevent the accrual of strength and stiffness that normally occurs with time.
Animals↗
Complications of the operative treatment of Dupuytren's disease.
Complications of surgery for Dupuytren's disease occur intra-operatively as well as during the early and late postoperative periods. Digital nerve injury, vascular injury, skin flap "button holes," hematoma, swelling, infection, flare, wound dehiscence, recurrence, pseudoaneurysm, and inclusion cysts are discussed and their treatment reviewed. Recognition of the complication is necessary for motion therapy to proceed in a timely fashion in order to avoid postoperative digital stiffness.
Dupuytren Contracture↗
An ultrastructural study of the intimal hyperplasia in healing microarterial anastomoses.
The purpose of the study was to investigate the ultrastructure of intimal hyperplastic cells. End-to-end microarterial anastomoses were studied in a rabbit free-tissue-transfer model. There were five experimental groups, with 1, 3, 7, 14, or 28 days follow-up. At sacrifice the anastomoses were tested for patency and then examined by light and electron microscopy. At days 1 and 3 the repaired intima was covered with macrophages and extravasated erythrocytes. At day 7 spindle-shaped fibroblasts with copious rough endoplasmic reticulum were seen. Some of these cells also contained pinocytotic vesicles, filaments with focal densities, and subplasmalemmal attachment sites, the features of smooth muscle cells. At day 14, more cells contained smooth muscle features and these features were also more pronounced. These young myofibroblasts were plumper than adjacent fibroblasts. At day 28 mature myofibroblasts with a full complement of organelles were present. The results, therefore, supported the hypothesis that myofibroblasts are present in the intimal hyperplasia of healing microarterial anastomoses.
Anastomosis, Surgical↗
Scaphoid nonunion with avascular necrosis of the proximal pole. Treatment with a vascularized bone graft from the dorsum of the distal radius.
Scaphoid nonunion with avascular necrosis of the proximal pole remains a difficult problem. We have endeavoured to heal the fracture, restore scaphoid height and revascularize the proximal pole of the scaphoid by means of a vascularized dorsal interposition graft from the distal radius. The procedure has resulted in union of six of ten fractures. Fractures that healed had not been treated by a previous bone grafting procedure. Dissatisfaction was due to loss of motion in patients who had healed fractures, and pain in those patients with persistent non-unions.
Adolescent↗