A Biomechanical Analysis of Peroneus Brevis Split Lesions, Repair, and Partial Resection

BACKGROUND Peroneus brevis tendon tears are associated with chronic ankle pain and instability following sprain injuries. The aim of this study is to elucidate the biomechanical changes induced by a peroneus brevis split and surgical treatment by tubularizing suture or partial resection. METHODS Nine human lower leg specimens were biomechanically tested. Preexisting tendon pathology was ruled out by magnetic resonance imaging and histology. Specimens were subjected to sequential testing of 4 conditions of the peroneus brevis tendon: (1) native, (2) longitudinal lesion, (3) tubularizing suture, and (4) 50% resection. The outcome parameters were the tendon stiffness (N/mm) and the length variation of the split portion at 5 N load. RESULTS The median specimen age at death was 55.8 years (range 50-64 years). The longitudinal tendon split led to an elongation by 1.21 ± 1.15 mm, which was significantly reduced by tubularizing suture to 0.24 ± 0.97 mm (P = .021). Furthermore, 50% resection of the tendon elongated it by a mean 2.45 ± 1.9 mm (P = .01) and significantly reduced its stiffness compared to the intact condition (4.7 ± 1.17 N/mm, P = .024) and sutured condition (4.76 ± 1.04 N/mm, P = .011). CONCLUSION Longitudinal split and 50% resection of the peroneus brevis tendon led to elongation and loss of tendon stiffness. These properties were improved by tubularizing suture. The significance of these changes in the clinical setting needs further investigation. CLINICAL RELEVANCE Tubularizing suture of a peroneus brevis split can restore biomechanical properties to almost native condition, potentially aiding ankle stability in symptomatic cases. A split lesion and partial resection of the tendon showed reduced stiffness and increased elongation

Improved suture pullout through genipin-coated sutures in human biceps tendons with spatially confined changes in cell viability

BACKGROUND The suture-tendon interface often constitutes the point of failure in tendon suture repair. In the present study, we investigated the mechanical benefit of coating the suture with a cross-linking agent to strengthen the nearby tissue after suture placement in human tendons and we assessed the biological implications regarding tendon cell survival in-vitro. METHODS Freshly harvested human biceps long head tendons were randomly allocated to control (n = 17) or intervention (n = 19) group. According to the assigned group, either an untreated or a genipin-coated suture was inserted into the tendon. 24 h after suturing, mechanical testing composed of cyclic and ramp-to-failure loading was performed. Additionally, 11 freshly harvested tendons were used for short-term in vitro cell viability assessment in response to genipin-loaded suture placement. These specimens were analyzed in a paired-sample setting as stained histological sections using combined fluorescent/light microscopy. FINDINGS Tendons stitched with a genipin-coated suture sustained higher forces to failure. Cyclic and ultimate displacement of the tendon-suture construct remained unaltered by the local tissue crosslinking. Tissue crosslinking resulted in significant cytotoxicity in the direct vicinity of the suture (<3 mm). At larger distances from the suture, however, no difference in cell viability between the test and the control group was discernable. INTERPRETATION The repair strength of a tendon-suture construct can be augmented by loading the suture with genipin. At this mechanically relevant dosage, crosslinking-induced cell death is confined to a radius of <3 mm from the suture in the short-term in-vitro setting. These promising results warrant further examination in-vivo

On the geometrical origin of periodicity in blazar-type sources

Periodicities in blazar light curves may be related to helical trajectories in extragalactic radio jets by differential Doppler boosting effects. We consider ballistic and non-ballistic (i.e., radial) trajectories and discuss three possible periodic driving mechanisms for the origin of helical jet paths, namely, orbital motion in a binary black hole system (BBHS), jet precession, and intrinsic jet rotation. It is shown that precessional-driven ballistic motion is unlikely to result in observable periods of less than several tens of years. We demonstrate that for non-ballistic helical motion the observed period is generally strongly shortened relative to the real physical driving period because of light-travel time effects. Internal jet rotation may thus account for observed periods $P_{\rm obs} \leq 10$ days. Periodicity due to orbital-driven (non-ballistic) helical motion, on the other hand, is usually constrained to periods of $P_{\rm obs} \geq 10$ days, while Newtonian-driven precession is unlikely to be responsible for periodicity on a timescale $P_{\rm obs} \leq 100$ days but may well be associated with periods of $P_{\rm obs} \geq 1$ yr.Comment: 10 pages, ApJ Letters in pres

The kinematics in the pc-scale jets of AGN The case of S5 1803+784

We present a kinematic analysis of jet component motion in the VLBI jet of the BL Lac object S5 1803+784, which does not reveal long-term outward motion for most of the components. Understanding the complex kinematic phenomena can possibly provide insights into the differences between quasars and BL Lac objects. The blazar S5 1803+784 has been studied with VLBI at $\nu$ =1.6, 2.3, 5, 8.4, and 15 GHz between 1993.88 and 2005.68 in 26 observing runs. We (re)analyzed the data and present Gaussian model-fits. We collected the already published kinematic information for this source from the literature and re-identified the components according to the new scenario presented in this paper. Altogether, 94 epochs of observations have been investigated. A careful study of the long-term kinematics reveals a new picture for component motion in S5 1803+784. In contrast to previously discussed motion scenarios, we find that the jet structure within 12 mas of the core can most easily be described by the coexistence of several bright jet features that remain on the long-term at roughly constant core separations (in addition to the already known {\it stationary} jet component $\sim$ 1.4 mas) and one faint component moving with an apparent superluminal speed ($\sim$ 19c, based on 3 epochs). While most of the components maintain long-term roughly constant distances from the core, we observe significant, smooth changes in their position angles. We report on an evolution of the whole jet ridge line with time over the almost 12 years of observations. The width of the jet changes periodically with a period of $\sim$ 8 to 9 years. We find a correlation between changes in the position angle and maxima in the total flux-density. We present evidence for a geometric origin of the phenomena and discuss possible models.Comment: The manuscript will be published by A&

Assessing the effects of intratendinous genipin injections: Mechanical augmentation and spatial distribution in an ex vivo degenerative tendon model

BACKGROUND Tendinopathy is a common musculoskeletal disorder and current treatment options show limited success. Genipin is an effective collagen crosslinker with low cytotoxicity and a promising therapeutic strategy for stabilizing an intratendinous lesion. PURPOSE This study examined the mechanical effect and delivery of intratendinous genipin injection in healthy and degenerated tendons. STUDY DESIGN Controlled laboratory study. METHODS Bovine superficial digital flexor tendons were randomized into four groups: Healthy control (N = 25), healthy genipin (N = 25), degenerated control (N = 45) and degenerated genipin (N = 45). Degeneration was induced by Collagenase D injection. After 24h, degenerated tendons were subsequently injected with either 0.2ml of 80mM genipin or buffer only. 24h post-treatment, samples were cyclically loaded for 500 cycles and then ramp loaded to failure. Fluorescence and absorption assays were performed to analyze genipin crosslink distribution and estimate tissue concentration after injection. RESULTS Compared to controls, genipin treatment increased ultimate force by 19% in degenerated tendons (median control 530 N vs. 633 N; p = 0.0078). No significant differences in mechanical properties were observed in healthy tendons, while degenerated tendons showed a significant difference in ultimate stress (+23%, p = 0.049), stiffness (+27%, p = 0.037), work to failure (+42%, p = 0.009), and relative stress relaxation (-11%, p < 0.001) after genipin injection. Fluorescence and absorption were significantly higher in genipin treated tendons compared to control groups. A higher degree of crosslinking (+45%, p < 0.001) and a more localized distribution were observed in the treated healthy compared to degenerated tendons, with higher genipin tissue concentrations in healthy (7.9 mM) than in degenerated tissue (2.3 mM). CONCLUSION Using an ex-vivo tendinopathy model, intratendinous genipin injections recovered mechanical strength to the level of healthy tendons. Measured by genipin tissue distribution, injection is an effective method for local delivery. CLINICAL RELEVANCE This study provides a proof of concept for the use of intratendinous genipin injection in the treatment of tendinopathy. The results demonstrate that a degenerated tendon can be mechanically augmented by a clinically viable method of local genipin delivery. This warrants further in vivo studies towards the development of a clinically applicable treatment based on genipin

Can Genipin-coated Sutures Deliver a Collagen Crosslinking Agent to Improve Suture Pullout in Degenerated Tendon? An Ex Vivo Animal Study

BACKGROUND The suture-tendon interface is often the weakest link in tendon-to-tendon or tendon-to-bone repair. Genipin is an exogenous collagen crosslink agent derived from the gardenia fruit that can enhance suture force to failure of the tendon-suture interface. Viable methods for intraoperative clinical delivery of genipin could be of clinical utility, but to our knowledge have not yet been extensively studied. QUESTIONS/PURPOSES The purposes of this study were (1) to evaluate whether sutures precoated with genipin can augment the suture-tendon interface to improve force to failure, stiffness, and work to failure in healthy and degenerated tendons; and (2) to determine the effect of genipin on the extent and distribution of crosslinking. METHODS Single-stitch suture pullout tests were performed ex vivo on 25 bovine superficial digital flexor tendons. To assess effects on native tissue, one group of 12 tendons was cut in proximal and distal halves and randomized to treatment (n = 12) and control groups (n = 12) in a matched-pair design. One simple stitch with a loop with either a normal suture or genipin-coated suture was applied to tendons in both groups. To simulate a degenerative tendon condition, a second group of 13 tendons was cut in proximal and distal halves, injected with 0.2 mL of collagenase D (8 mg/mL) and incubated for 24 hours before suturing with either a genipin-coated suture (n = 13) or their matched controls (n = 13). Sutures from all groups then were loaded to failure on a universal materials testing machine 24 hours after suturing. Suture pullout force, stiffness, and work to failure were calculated from force-displacement data and compared between the groups. Additionally, fluorescence was measured to determine the degree of crosslinking quantitatively and a qualitative analysis of the distribution pattern was performed by microscopy. RESULTS In healthy tendon pairs, the median maximum pullout force was greater with genipin-coated sutures than with control sutures (median, 42 N [range, 24-73 N] versus 29 N [range, 13-48 N]; difference of medians, 13 N; p = 0.003) with corresponding increases in the required work to failure (median, 275 mJ [range, 48-369 mJ] versus 148 mJ [range, 83-369 mJ]; difference of medians, 127 mJ; p = 0.025) but not stiffness (median, 4.1 N/mm [range, 2.3-8.1 N/mm] versus 3.3 N/mm [range, 1.1-9.6 N/mm]; difference of medians, 0.8 N/mm; p = 0.052). In degenerated tendons, median maximum pullout force was greater with genipin-coated sutures than with control sutures (median, 16 N [range, 9-36 N] versus 13 N [range, 5-28 N]; difference of medians, 3 N; p = 0.034) with no differences in work to failure (median, 75 mJ [range, 11-249 mJ] versus 53 mJ [range, 14-143 mJ]; difference of medians, 22 mJ; p = 0.636) or stiffness (median, 1.9 N/mm [range, 0.7-13.4 N/mm] versus 1.6 N/mm [range, 0.5-5.6 N/mm]; difference of medians, 0.3 N/mm; p = 0.285). Fluorescence was higher in tendons treated with genipin-coated sutures compared with the control group, whereas higher fluorescence was observed in the treated healthy compared with the degenerated tendons (difference of means -3.16; standard error 1.08; 95% confidence interval [CI], 0.97-5.34; p = 0.006/healthy genipin: mean 13.04; standard error 0.78; 95% CI, 11.47-14.62; p < 0.001/degenerated genipin: mean 9.88; SD 0.75; 95% CI, 8.34-11.40; p < 0.001)

Assessing the effects of intratendinous genipin injections: Mechanical augmentation and spatial distribution in an ex vivo degenerative tendon model.

BACKGROUND:Tendinopathy is a common musculoskeletal disorder and current treatment options show limited success. Genipin is an effective collagen crosslinker with low cytotoxicity and a promising therapeutic strategy for stabilizing an intratendinous lesion. PURPOSE:This study examined the mechanical effect and delivery of intratendinous genipin injection in healthy and degenerated tendons. STUDY DESIGN:Controlled laboratory study. METHODS:Bovine superficial digital flexor tendons were randomized into four groups: Healthy control (N = 25), healthy genipin (N = 25), degenerated control (N = 45) and degenerated genipin (N = 45). Degeneration was induced by Collagenase D injection. After 24h, degenerated tendons were subsequently injected with either 0.2ml of 80mM genipin or buffer only. 24h post-treatment, samples were cyclically loaded for 500 cycles and then ramp loaded to failure. Fluorescence and absorption assays were performed to analyze genipin crosslink distribution and estimate tissue concentration after injection. RESULTS:Compared to controls, genipin treatment increased ultimate force by 19% in degenerated tendons (median control 530 N vs. 633 N; p = 0.0078). No significant differences in mechanical properties were observed in healthy tendons, while degenerated tendons showed a significant difference in ultimate stress (+23%, p = 0.049), stiffness (+27%, p = 0.037), work to failure (+42%, p = 0.009), and relative stress relaxation (-11%, p < 0.001) after genipin injection. Fluorescence and absorption were significantly higher in genipin treated tendons compared to control groups. A higher degree of crosslinking (+45%, p < 0.001) and a more localized distribution were observed in the treated healthy compared to degenerated tendons, with higher genipin tissue concentrations in healthy (7.9 mM) than in degenerated tissue (2.3 mM). CONCLUSION:Using an ex-vivo tendinopathy model, intratendinous genipin injections recovered mechanical strength to the level of healthy tendons. Measured by genipin tissue distribution, injection is an effective method for local delivery. CLINICAL RELEVANCE:This study provides a proof of concept for the use of intratendinous genipin injection in the treatment of tendinopathy. The results demonstrate that a degenerated tendon can be mechanically augmented by a clinically viable method of local genipin delivery. This warrants further in vivo studies towards the development of a clinically applicable treatment based on genipin

Postoperative alignment of TKA in patients with severe preoperative varus or valgus deformity: is there a difference between surgical techniques?

Abstract Background There have been conflicting studies published regarding the ability of various total knee arthroplasty (TKA) techniques to correct preoperative deformity. The purpose of this study was to compare the postoperative radiographic alignment in patients with severe preoperative coronal deformity (≥10° varus/valgus) who underwent three different TKA techniques; manual instrumentation (MAN), computer navigated instrumentation (NAV) and patient specific instrumentation (PSI). Methods Patients, who received a TKA with a preoperative coronal deformity of ≥10° with available radiographs were included in this retrospective study. The groups were: MAN; n = 54, NAV; n = 52 and PSI; n = 53. The mechanical axis (varus / valgus) and the posterior tibial slope were measured and analysed using standing long leg- and lateral radiographs. Results The overall mean postoperative varus / valgus deformity was 2.8° (range, 0 to 9.9; SD 2.3) and 2.5° (range, 0 to 14.7; SD 2.3), respectively. The overall outliers (>3°) represented 30.2% (48 /159) of cases and were distributed as followed: MAN group: 31.5%, NAV group: 34.6%, PSI group: 24.4%. No significant statistical differences were found between these groups. The distribution of the severe outliers (>5°) was 14.8% in the MAN group, 23% in the NAV group and 5.6% in the PSI group. The PSI group had significantly (p = 0.0108) fewer severe outliers compared to the NAV group while all other pairs were not statistically significant. Conclusions In severe varus / valgus deformity the three surgical techniques demonstrated similar postoperative radiographic alignment. However, in reducing severe outliers (> 5°) and in achieving the planned posterior tibial slope the PSI technique for TKA may be superior to computer navigation and the conventional technique. Further prospective studies are needed to determine which technique is the best regarding reducing outliers in patients with severe preoperative coronal deformity

The first 100 patients treated with a new anatomical pre-contoured locking plate for clavicular midshaft fractures

Abstract Background Pre-contoured locking plates were recently introduced in the management of clavicular midshaft fractures. These plates may offer advantages such as no necessity for intraoperative bending and reduced plate irritation. The purpose of this study was to review the clinical and radiographical outcome of the first 100 patients treated with a new anatomical pre-contoured locking plate. Methods In a retrospective single-center study, 100 consecutive patients (16 female, 84 male) with a median age of 40 years (range 15–82) who underwent surgery for clavicular midshaft fractures with a VariAx locking plate (Stryker Corporation Kalmazoo, MI, USA) between March 2012 and January 2016 were included. Postoperative follow-up was performed until union was clinically and radiographically achieved. Fracture type, surgical time, intraoperative need for contouring the plate, further surgery such as revision or hardware removal and complications were recorded. Results One-hundred patients with a dislocated midshaft clavicular fracture with a mean follow-up of 21.9 months (standard deviation 13.2) were included. Ninety-three patients reported normal shoulder function at latest follow-up. Median surgical time was 75.5 min (range, 35–179). In three patients, intraoperative bending of the plate was necessary. In two patients, plates designed for the other side were implanted. Five patients needed revision surgery: One patient with wound healing problems, one patient with a re-fracture after early (13 months) hardware removal and minor trauma, one patient with postoperative shoulder stiffness and two patients with failed osteosynthesis because of surgical implantation fault. One asymptomatic nonunion without further treatment was observed. In 30 patients, the plate was removed after a mean of 17.5 months (SD 4.2) because of subjective plate discomfort. Conclusions With this new pre-contoured locking plate, good to excellent intraoperative fit to the anatomical shape of the clavicle can be achieved. The implant seems to be reliable regarding handling and complications. Clinical and radiological results are comparable to results reported in the literature. Hardware removal rate is comparable to other studies with a pre-contoured plate and lower compared to non-pre-contoured