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Any restoration of hand function following tendon and nerve injury has to include the repair or replacement of the hand's ability to perform a great many tasks. It is hard at first to appreciate fully the loss that occurs with flexor tendon injury. With loss of flexor tendons operating at the fingers or thumb, they cannot be fully closed and the hand is impaired for grasp and release as it interfaces with objects. But, sensibility can also be compromised from tendon injury even without direct injury to nerve, as object recognition in the absence of vision requires finger movement. When peripheral nerve injury is combined with flexor tendon injury, sensibility is directly impaired. There is a loss in the sense of finger or thumb position, pain, temperature, and touch/pressure recognition, in addition to the tendon injury.

Increased handling, increased bulk at the repair site and an increase in external suture material may affect adhesion formation and gliding after tendon repair. A previous study¹ showed no significant difference in biomechanical or histopathological measurement of adhesion formation in two- and four-strand repairs combined with an epitendinous suture in the chicken model. In the present study, the flexor digitorum profundus tendon of the middle toe of 47 broiler chickens was cut and repaired with either a single (two-strand) or double (four-strand) modified Kessler core suture without epitendinous suture and immobilised for four weeks. Adhesion formation was measured by biomechanical testing or quantitative and qualitative histopathology. Biomechanical and histological data showed no differences between two- and four-strand repairs. Results did not differ from the previous study which used an epitendinous suture. Adhesion formation is not necessarily increased when multi-strand techniques are used, nor by the placement of an epitendinous suture if care is taken with surgical technique. Individual healing response introduces more variability than an increase in tendon handling by an experienced surgeon.

Purpose: The aim of our study is to develop a suture technique that has sufficient strength of active mobilization.

Methods: Thirty two fingers of six fresh human cadavers were divided into two groups. Flexor digitorum profundus (FDP) tendons in the study group were repaired by modified Brunelli suture technique and modified Kessler suture technique, while those in the control group were repaired by Modified Kessler suture technique. Flexion and extension movements were performed with 10 N of load, increasing 1 N at a time to the tendons in both groups. Rupture and significant gap formation was evaluated up to 20 N of load. In the study, to evaluate the resistance to active motion, 1000 times flexion and extension motion cycle was performed with a load of 20 N. The succeeding repaired tendons was also tested with flexion and extension movements increasing the load 1 N at a time.

Results: In the study group, failure and significant gap formation on the repair zone were not observed after 20 N of load and 1000 times cyclic flexion and extension movements for resisting to active motion. The rupture and significant gap formation was observed on a average load of 98.43 ± 0.47 N. In the Modified Kessler suture technique, on the eight tendons before reaching the 20 N of load for resisting to active motion, and the remaining eight tendons, during the 20 N loaded motion cycle essential for active motion, rupture and significant gap formation was observed. The failure and significant gap formation was observed on a average load of 18.37 ± 1.89 N. It is measured that by accompanying Modified Brunelli suture to the Modified Kessler suture technique, the resistance was increased up to 5–6 times.

Discussion: By the Modified Brunelli suture technique, active motion can be started to the finger without a dorsal block sling immediately after the surgery.

Clinical Relavans: By the modified technique, the rehabilitation difficulty and joint stiffness will be minimized.

Background: This study investigated the exact failure mechanisms of the most commonly used conventional tendon repair techniques. A new method, radiographing repair constructs in antero-posterior and lateral projections before and after tensioning was used. This allowed to precisely analyse failure mechanisms in regards to geometrical changes in all three dimensions. Additionally the biomechanical stability focusing on gapping was tested.

Methods: Sheep fore limb deep flexor tendons were harvested and divided in eight groups of ten tendons. Three common variants of the Kessler repair method and four common 4-strand repair techniques were tested. Additionally a new modification of the Adelaide repair was tested.

Results: Biomechanical testing showed no significant differences in gapping for the three tested 2-strand Kessler repair groups. Once a double Kessler or 4-strand Kessler repair was performed the stability of the repair improved significantly. Further significant improvements in biomechanical stability could be achieved by using cross locks in the repair like in the Adelaide repair method. Qualitative analysis using radiographs showed that all Kessler repair variants unfolded via rotations around the transverse suturing component, no matter which variant was used.

Conclusions: Additional to the commonly described constriction of the repair construct, the rotating deformation is the main reason for repair site gapping in Kessler tendon repair methods. The term “locking” in a Kessler repair is misleading. The cruciate repairs tended to loose grip and drag (cheese-wire) through the tendon and therefore lead to gapping. The most stable repair constructs in all three dimensions were the Adelaide repair and its interlocking modification. This is due to the superior anchoring qualities of its cross locks and three dimensional stability.

Background: This study investigated the effect of mesenchymal stem cell implantation on flexor tendon healing using a rabbit model of flexor tendon repair. Specifically, we compared the difference between autologous and allogeneic stem cells. The influence of cell number on the outcome of flexor tendon healing was also investigated.

Methods: Repaired tendons on the rear paws of rabbits were randomly assigned into four groups: control group, 1 million autologous cells, 1 million allogeneic cells, and 4 million allogeneic cells. Rabbits were sacrificed at 3 or 8 weeks after surgery.

Results: Implantation of 4 million stem cells resulted in a significant increase in range of motion compared with control group at three weeks after surgery. The positive staining of collagen I in healing tendons was enhanced in stem cell treated groups three weeks after surgery. However, stem cells did not improve biomechanical properties of flexor tendons.

Conclusions: High dose stem cells attenuated adhesions in the early time point following flexor tendon repair. Further work is needed determine the value of stem cell therapy in flexor tendon healing in humans.

Background: This laboratory study compared pig, sheep and human deep flexor tendons in regards to their biomechanical comparability.

Methods: To investigate the relevant biomechanical properties for tendon repair experiments, the tendons resistance to cheese-wiring (suture drag/splitting) was assessed. Cheese-wiring of a suture through a tendon is an essential factor for repair gapping and failure in a tendon repair.

Results: Biomechanical testing showed that forces required to pulling a uniform suture loop through sheep or pig tendons in Zone II were higher than in human tendons. At time point zero of testing these differences did not reach statistical significance, but differences became more pronounced when forces were measured beyond initial cheese-wiring (2 mm, 5 mm and 10 mm). The stronger resistance to cheese-wiring was more pronounced in the pig tendons. Also regarding size and histology, sheep tendons were more comparable to human tendons than pig tendons.

Conclusions: Differences in tendon bio-properties should be kept in mind when comparing and interpreting the results of laboratory tendon experiments.

Background: To investigate the effect of myostatin (GDF-8) stimulation of bone marrow derived mesenchymal stem cells (BMSCs) on tenogenesis in the setting of tendon repair. GDF-8 has demonstrated the ability to augment tenogenesis and we sought to identify if this effect could lead to the focused differentiation of pluripotential stem cells down a tenocyte lineage ex vivo.

Methods: Cadaveric upper limb flexor tendons were harvested, decellularized and divided into 1 cm segments. Sutures seeded with stem cells were passed through tendon segments to simulate repair. The repaired tendons were then cultured either with or without myostatin for 3, 5, and 7 days. The experiment was also repeated with non-decellularized tendons for a total of 4 groups. The tendons were then evaluated for the expression of scleraxis and tenomodulin, two biomarkers for tendon.

Results: Myostatin stimulation led to an increase in expression of tenomodulin and scleraxis at 5 and 7 days in both the decellularized and non-decellularized tendons. Myostatin increased the differentiation of BMSCs into tenocytes and/or led to the upregulation of tenomodulin and scleraxis production by the native tenocytes present within the non-decellularized tendons.

Conclusions: The addition of myostatin to BMSCs leads to tenocyte differentiation as evidenced by the expression of tenocyte biomarkers, scleraxis and tenomodulin. This effect is maintained in an ex vivo tendon repair model suggestive that these cells survive the passage through tendon tissue and remain metabolically active.

Background: Attaining competency in placement of core suture with adequate distance from juncture is a key skill for learners of tendon repair. Currently, this is most commonly practiced on animal models in wet laboratory environment. To improve accessibility and availability, we developed a tendon repair trainer that aims to guide learners in obtaining this key competency.

Methods: A customized tendon dock was designed and manufactured with additive method that permits insertion of 6mm silicon tendon rods to simulate flexor tendon repair along a digit. Four residents, divided into two groups, were instructed to repair two sets of tendon rods (60 rods per resident) with Kessler suture loop placed at 10 mm from juncture (Group A: rods marked at 10 mm, Group B: unmarked rods). The main criterion for passing was a loop placed within 1 mm of the target distance (10 mm). At a second session, both groups repaired unmarked tendons, and these were marked based on similar criterion.

Results: At the first session, 100% of those who repaired marked rods (Group A) passed while 25% of unmarked rods (Group B) attained a pass. At the second session, where both groups repaired unmarked rods, residents from group A achieved a pass rate of 95% while group B achieved 33.3% pass.

Conclusions: Learners who had previously repaired marked rods were able to retain their experience when repairing unmarked rods. This suggest that the proposed model may be a helpful adjunct to sharpen learners’ skills prior to practicing tendon repairs in more costly animal or cadaveric models.

Background: Flexor tendon repair carries a significant risk for complications, which often leads to revision surgery. The purpose of this study was to assess the effect of different factors on the risk for major complications patients undergoing a primary end-to-end flexor tendon repair and early passive mobilization regimen (Kleinert protocol).

Methods: Between January 2000 and September 2009, a total of 312 patients underwent a flexor tendon repair at out institution. We excluded patients whose injury was self-inflicted or secondary to a rheumatic disease or a fall leaving 187 patients with 325 injured tendons for the study.

Results: 152 (81.7%) patients were male and 34 (18.3%) females. Mean age of the patients was 32.7 years (SD 14.4, range 11 to 73). The fifth ray was most commonly affected. The majority of the injuries were located in zone II. Median delay to surgery was 3 days. Complications were observed in 34 patients (18.2%). Univariable analysis showed that patient age, mechanism of injury, injured ray, delay to surgery between three and seven days, and greater suture thickness were associated with increased risk of complications. In the subsequent multivariable analysis, only the mechanism of injury and delay to surgery remained as significant risk factors for major complications.

Conclusions: We conclude that complications after flexor tendon repair may be reduced by appropriate timing of the surgery. Delay to surgery lasting between three and seven days seems to be associated with increased risk for major complications.

Background: An effective suture method enables early active motion exercises and optimal post-surgical outcomes. The aim of this study is to evaluate the tensile strength of three suture configurations – horizontal mattress (HM), vertical mattress (VM) and a cross suture for repair of a tendon weave. We hypothesised that the direction of mattress sutures relative to the tendon fibres would affect the tensile strength of tendon repair.

Methods: Using porcine flexor tendons and the same number of surgical sutures, three tendon weave constructs differing in the method of suture were compared: HM suture configuration (conventional technique), cross-stitch (CS) configuration (conventional technique) and VM suture configuration (novel technique). Ten pairs of each group were mounted in a material testing machine and subjected to a simple tensile test and a cyclic loading test for their biomechanical comparison.

Results: The VM group and CS group had significantly higher ultimate failure load, linear stiffness and fatigue strength as compared to the HM group. The failure mode was suture breakage or tendon rupture for the VM and the CS group, while the suture pullout of the tendon only occurred in the HM group.

Conclusion: Among the three techniques used for repair of a tendon weave, the VM suture technique was demonstrated to have the greatest tensile strength and least associated with suture pull-out. The direction of the mattress suture in relation the direction of tendon fibres affects the strength of repair.

Background: Un-knotted barbed suture constructs are postulated to decrease repair bulk and improve tension loading along the entire repair site resulting in beneficial biomechanical repair properties. Applying this repair technique to tendons has shown good results in ex-vivo experiments previously but thus far no in-vivo study could confirm these. Therefore, this current study was conducted to assess the value of un-knotted barbed suture repairs in the primary repair of flexor tendons in an in-vivo setting.

Methods: Two groups of 10 turkeys (Meleagris gallapovos) were used. All turkeys underwent surgical zone II flexor tendon laceration repairs. In group one, tendons were repaired using a traditional four-strand cross-locked cruciate (Adelaide) repair, while in group two, a four-strand knotless barbed suture 3D repair was used. Postoperatively repaired digits were casted in functional position, and animals were left free to mobilise and full weight bear, resembling a high-tension post-op rehabilitation protocol. Surgeries and rehabilitations went uneventful and no major complications were noted. The turkeys were monitored for 6 weeks before the repairs were re-examined and assessed against several outcomes, such as failure rate, repair bulk, range of motion, adhesion formation and biomechanical stability.

Results: In this high-tension in-vivo tendon repair experiment, traditionally repaired tendons performed significantly better when comparing absolute failure rates and repair stability after 6 weeks. Nevertheless, the knotless barbed suture repairs that remained intact demonstrated benefits in all other outcome measures, including repair bulk, range of motion, adhesion formation and operating time.

Conclusions: Previously demonstrated ex-vivo benefits of flexor tendon repairs with resorbable barbed sutures may not be applicable in an in-vivo setting due to significant difference in repair stability and failure rates.

Level of Evidence: Level IV (Therapeutic)

The purpose of this study is to describe a technique of using an affordable suture anchor for various soft tissue repairs of both upper and lower limb surgeries in our series of patients. Eighteen patients with minimum 1-year follow-up after various upper limb surgeries using modified suture anchor were assessed both clinically and radiographically. In all 18 cases, the purpose of the suture anchor was served in terms of attachment of ligament or the tendon. There was no incidence of breakage of suture material or loosening of the implant seen during the insertion. There were no complications related to the implant noted. This novel technique turns a simple screw and suture material into an efficient suture anchor while saving time, being quick, easy, affordable and repeatable.

Level of Evidence: Level V (Therapeutic)