Flexor tendon blood vessels

Proceed with Caution: Mouse Deep Digit Flexor Tendon Injury Model

Supplemental Digital Content is available in the text.

The purpose of this study was to determine the feasibility of using mouse models for translational study of flexor tendon repair and reconstruction.

The regional microvascular density of the gluteus medius tendon determined by immunohistochemistry with CD31 staining: a cadaveric study

BACKGROUND AND PURPOSE

There are no studies to date about the vascularisation into the gluteus medius tendon. The purpose of this study was to define the microvessel density of the gluteus medius in 3 zones through a special staining with CD31 and to identify regional differences in microvascular density that may have implications for the healing.

METHODS

We obtained 12 complete gluteus medius tendons from cadavers who had been an average age of 30.3 years old (range 18 to 55). All the donors were males with no known history of hip abnormalities.Following a rigorous protocol, each gluteus medius tendon was divided in 3 portions. Each gluteus medius tendon was divided in 3 portions (I: musculotendinous, II: Tendon, III: Tendon-Bone junction).

RESULTS

There were regional differences between all anatomic zones in both the transverse section (p<0.001) and the longitudinal section (p = 0.007). Furthermore, a significant difference was found between zones II and I (mean difference -23.45 IC95% -38.77 to -8.13, p<0.001) and between zones II and III (mean difference -26.08 IC95% -41.39 to -10.76, p<0.001) in transverse section. In longitudinal sections, this difference was found as well between zones II and I (mean difference -29.48 IC95% -51.54 to -7.43, p = 0.01), but not between zones II and III (mean difference -10.87 IC95% -32.93 to 11.18, p = 0.67).

CONCLUSIONS

The microvessel density was significantly lower in the length of the tendon (central portion) compared to the other 2 regions.

Flexor tendon healing within the tendon sheath using bioabsorbable poly-L/D-lactide 96/4 suture. A histological in vivo study with rabbits

The bioabsorbable poly-L/D-lactide (PLDLA) 96/4 suture has good biomechanical and knot properties, and sufficient tensile strength half-life for flexor tendon repair. In the present study, the biocompatibility of PLDLA suture was compared with that of coated braided polyester suture in the rabbit flexor digitorum profundus tendon repaired within the tendon sheath. Postoperative unrestricted active mobilization was allowed. The tendons were studied histologically after 1-, 3-, 6-, 12-, 26-, and 52-week follow-ups. No differences were found in the biocompatibility between the suture materials, with only scattered multinuclear giant cells near the sutures in both groups from 6 weeks onwards. At 52 weeks, most of the PLDLA material was absorbed and the histological structure of the tendon appeared normal, whereas in the polyester repairs the suture knots filled the repair site, causing bulking of the tendon surface, and the collagen alignment appeared disoriented. The results suggest that the PLDLA 96/4 is a suitable suture material for flexor tendon repair.

Analysis of a knotless flexor tendon repair using a multifilament stainless steel cable-crimp system

PURPOSE

To compare the biomechanical and technical properties of flexor tendon repairs using a 4-strand cruciate FiberWire (FW) repair and a 2-strand multifilament stainless steel (MFSS) single cross-lock cable-crimp system.

METHODS

Eight tests were conducted for each type of repair using cadaver hand flexor digitorum profundus tendons. We measured the required surgical exposure, repair time, and force of flexion (friction) with a custom motor system with an inline load cell and measured ultimate tensile strength (UTS) and 2-mm gap force on a servo-hydraulic testing machine.

RESULTS

Repair time averaged less than 7 minutes for the 2-strand MFSS cable crimp repairs and 12 minutes for the FW repairs. The FW repair was performed with 2 cm of exposure and removal of the C-1 and A-3 pulleys. The C-1 and A-3 pulleys were retained in each of the MFSS cable crimp repairs with less than 1 cm of exposure. Following the FW repair, the average increase in friction was 89% compared with an average of 53% for the MFSS repairs. Six of the 8 MFSS specimens achieved the UTS before any gap had occurred, whereas all of the FW repairs had more than 2 mm of gap before the UTS, indicating that the MFSS was a stiffer repair. The average UTS appeared similar for both groups.

CONCLUSIONS

We describe a 2-strand multifilament stainless steel single cross-lock cable crimp flexor repair system. In our studies of this cable crimp system, we found that surgical exposure, average repair times, and friction were reduced compared to the traditional 4-strand cruciate FW repair. While demonstrating these benefits, the crimp repair also produced a stiff construct and high UTS and 2-mm gap force.

CLINICAL RELEVANCE

A cable crimp flexor tendon repair may offer an attractive alternative to current repair methods. The benefits may be important especially for flexor tendon repair in zone 2 or for the repair of multiple tendons.

Influence of core suture geometry on tendon deformation and gap formation in porcine flexor tendons

The effects of core suture geometry on the mechanics of failure in flexor tendon surgery are investigated. Forty porcine flexor tendons were repaired using a Kessler; a Kessler-Pennington; a double Kessler; a continuous Kessler; and a cruciate repair. At maximum breaking strength, the cruciate repair gapped more then the double Kessler (12.8 mm vs 9.1 mm), but the double Kessler was less strong (37N vs 45 N). Transverse narrowing was 22% and 24% for the Kessler and the Kessler-Pennington, 11% for the double Kessler, and 0% for the continuous Kessler and the cruciate repair. Kessler-type sutures failed by suture breakage and the cruciate repair by pull-out. Under load, the transverse part of the Kessler sutures narrows, allowing longitudinal parts to lengthen, leading to gapping. The double Kessler shortened transverse segment decreases gapping. Eliminating a transverse component (the cruciate repair) decreased gapping, but the cruciate failed at higher loads by suture pull-out.

Microscopic and histological examination of the mouse hindpaw digit and flexor tendon arrangement with 3D reconstruction

Mice are currently the species of choice for the in vivo study of injury, but few detailed anatomical descriptions have been made of rodent digits, limiting their use for the investigation of intrasynovial tendon healing. In this study a detailed microscopic and histological investigation was performed using C57/BL6 and Tie2 LacZ reporter gene transgenic mice. Serial-sectioned mouse hindpaw digits were characterized using haematoxylin and eosin, Masson's trichrome (collagen), Alcian blue (fibrocartilage), Miller's stain (elastin) and TRITC-phalloidin (cellular cytoskeleton) staining. Digital vasculature was demonstrated using FITC-labelled dextran perfusion studies supplemented with LacZ expression in Tie2 LacZ transgenic mice digits. Imaging of the digit used a combination of brightfield and confocal microscopy with three-dimensional reconstruction. Our findings demonstrated that the mouse hindpaw possesses deep and superficial flexor tendons within a synovial sheath comparable with that found in other mammalian species. The intrasynovial tendons were avascular and had regions of fibrocartilaginous specialization relating to areas of compression. Corresponding vascular networks were demonstrated around the sheath using Tie2 LacZ mice and FITC-perfused hindpaws. Furthermore, there is an area of digit where both deep and superficial tendons reside between two pulleys, similar to zone 2 in the human hand where it would be possible to study intrasynovial tendon injury and adhesion formation. In conclusion, although the dimensions of the mouse digit pose technical challenges for surgical intervention, we have identified a model for the study of flexor tendon injury that will permit future genetic manipulation studies.

Mapping of vascular endothelium in the human flexor digitorum profundus tendon

PURPOSE

Previous techniques to delineate the human flexor digitorum profundus (FDP) vasculature have been innovative but potentially imprecise, resulting in uncertainty as to the existence of avascular zones in the flexor tendon. We aimed to use a novel immunohistochemical technique to determine more accurately the vasculature of the human flexor tendon.

METHODS

Thirty fresh cadaveric human FDP tendons were harvested, fixed, wax embedded, sectioned, and stained using the anti-CD31 monoclonal antibody to allow vessel visualization. Vessel numbers and vascularity density ratios were determined by computed image analysis.

RESULTS

Vessel density ratios varied with anatomic location, with a decrease between the A2 and A4 pulleys. There also was variation in vascularity ratios in the anteroposterior plane, with the palmar surface of the tendons having a lower vessel density.

CONCLUSIONS

We have shown that although areas of low vascularity exist on the palmar aspect of the tendon, there are no truly avascular zones.