Management of the Mangled Extremity.

Mangled extremities represent one of the most challenging injuries. They indicate the need for a comprehensive trauma assessment to rule out coexisting injuries. Treatment options include amputation and attempts at limb salvage. Although both have been associated with chronic disability, new surgical techniques and evolving rehabilitation options offer hope for the future.

Biomechanics of subscapularis V-shaped tenotomy compared to standard tenotomy.

BACKGROUND: Subscapularis function is critical after anatomic total shoulder arthroplasty (aTSA). Recently, however, a technique has been described that features a chevron or V-shaped subscapularis tendon cut (VT). This biomechanical study compared repair of the standard tenotomy (ST), made perpendicular to the subscapularis fibers, to repair of the novel VT using cyclic displacement, creep, construct stiffness, and load to failure. METHODS: This biomechanical study used 6 pairs of fresh frozen paired cadaveric shoulder specimens. One specimen per each pair underwent VT, the other ST. Subscapularis tenotomy was performed 1 cm from the insertion onto the lesser tuberosity. For VT, the apex of the V was 3 cm from the lesser tuberosity. After tenotomy, each humerus underwent humeral head arthroplasty. Eight figure-of-8 sutures were used to repair the tenotomy (Ethibond Excel; Ethicon, US LLC). Specimens were cyclically loaded from 2 to 100 N at 45 degrees abduction at a rate of 1 Hz for 3000 cycles. Cyclic displacement, creep, and stiffness and load to failure were measured. RESULTS: Cyclic displacement did not differ significantly between the ST and VT from 1 to 3000 cycles. The difference in displacement between the V-shaped and standard tenotomy at 3000 cycles was 1.57 mm (3.66 ± 1.55 mm vs. 5.1 ± 2.8 mm, P = .31, respectively). At no point was the V-shape tenotomy (VT) >3 mm of average displacement, whereas the standard tenotomy (ST) averaged 3 mm of displacement after 3 cycles. Creep was significantly lower for VT in cycles 1 through 3. For all cycles, stiffness was not significantly different in the VT group compared with the ST group. Load to failure was not statistically significant in the VT compared to the standard tenotomy throughout all cycles (253.2 ± 27.7 N vs. 213.3 ± 76.04 N; P = .25, respectively). The range of load to failure varied from 100 to 301 N for standard tenotomy compared with 216 to 308 N for VT. CONCLUSION: This study showed that VT and ST demonstrated equivalent stiffness, displacement, and load to failure. VT had the benefit of less creep throughout the first 3 cycles, although there was no difference from cycle 4 to 3000. The VT had equivalent biomechanical properties to the ST at time zero, an important first step in our understanding of the technique. The VT technique warrants further clinical study to determine if the technique has clinical benefits over ST following aTSA.

Five-Strand Hamstring Grafts are Biomechanically Comparable to Four-Strand Grafts and Offer Greater Diameter for Anterior Cruciate Ligament Reconstruction.

Purpose: The purpose of this study was to compare the biomechanics of 4-strand and 5-strand hamstring constructs for anterior cruciate ligament grafts. Methods: Thirty-six human cadaveric hamstring grafts were tested in 3 different conditions: (1) graft femoral fixation complex, (2) graft femoral and tibial fixation (GFTF) complex using a human model, and (3) GFTF complex using a porcine model. Grafts were tested on a tensile testing machine. Four-stranded grafts served as the control group, and 5-stranded grafts served as the experimental group. Cyclic elongation, ultimate load to failure, stiffness, and diameter of the grafts were analyzed. Results: Average 4-strand graft diameter was 7.96 mm compared to 9.32 mm for the 5-strand graft (P = .00017). Average stiffness of grafts ≥8 mm was 105.04 N/mm compared to 85.05 N/mm for grafts <8 mm (P = .04988). There was a positive correlation between graft diameter and stiffness (13.4 N/mm per every 1 mm increase in diameter, r 2 value of 13.1%, and F-significance of 0.02778). There were no significant differences in terms of ultimate load to failure, cyclic elongation, or stiffness between the experimental groups. Conclusion: Five-strand hamstring grafts offer greater diameter and are biomechanically comparable to 4-strand equivalents at time 0. Grafts >8 mm offer significantly greater stiffness compared to grafts sized <8 mm. There is a weak positive correlation between graft diameter and stiffness. Clinical Relevance: A potential drawback to hamstring grafts is their variability in size. Five-strand hamstring grafts provide increased diameter in comparison to 4-strand equivalents and might be used when quadrupled graft diameter is <8 mm.

Biomechanical Comparison of Meniscal Allograft Root Fixation Techniques: Anterograde Interference Bone Plug Fixation Yields Favorable Results Compared to Transosseous Suture Fixation Alone.

Purpose: To compare the biomechanical properties of 2 different fixation techniques (interference bone plug fixation vs transosseous suture fixation) of the posterior horn of the medial meniscus using a porcine model. Methods: Twenty-six matched pairs of fresh-frozen juvenile domestic porcine knees were used in this study. Specimens were randomly distributed among 3 groups: (1) native meniscus groups, (2) interference fixation, and (3) transosseous suture fixation. In each group, the posterior segments of the tested medial menisci were gripped with the freeze clamps and fixed to the tensile testing machine. Samples were preconditioned, followed by cyclic tension-relaxation for 1000 cycles between 10 and 30 N at 0.5 Hz and finally pulled to failure at a rate of 0.55 mm/s. The cyclic elongation, stiffness to failure, mode, and ultimate load to failure were recorded. Results: There was no significant difference in ultimate load to failure between the interference fixation (169.71 ± 71.98 N) and transosseous suture fixation (222.73 ± 72.40 N) groups (P = .118), both were significantly less than that of the native meniscus (405.46 ± 95.62) (P < .001). Interference fixation displayed cyclic elongation (1.04 ± 0.71 mm) and stiffness (69.10 ± 25.8 N/mm) that were not significantly different from the native meniscus tissue (0.78 ± 0.53 mm and 83.1 ±26.28 N/mm) (P = .359 and P = .224), in comparison to transosseous suture fixation, which did show increased cyclic elongation (1.85 ± 1.44 mm) (P = .047) and decreased stiffness (34.72 ± 10.2 N/mm) (P < .001). Conclusion: Interference fixation of the posterior horn of the medial meniscus has superior cyclic elongation and stiffness when compared to transosseous suture fixation. Interference fixation and the native meniscus model have a similar stiffness and cyclic elongation. Clinical Relevance: The significance of our study is that using interference fixation for meniscal allograft transplantation has the potential to reduce short term surgical failures as well as long term complication rates.

Personalized Fiber-Reinforcement Networks for Meniscus Reconstruction.

The menisci are fibrocartilaginous tissues that are crucial to the load-sharing and stability of the knee, and when injured, these properties are compromised. Meniscus replacement scaffolds have utilized the circumferential alignment of fibers to recapitulate the microstructure of the native meniscus; however, specific consideration of size, shape, and morphology has been largely overlooked. The purpose of this study was to personalize the fiber-reinforcement network of a meniscus reconstruction scaffold. Human cadaveric menisci were measured for a host of tissue (length, width) and subtissue (regional widths, root locations) properties, which all showed considerable variability between donors. Next, the asymmetrical fiber network was optimized to minimize the error between the dimensions of measured menisci and predicted fiber networks, providing a 51.0% decrease (p = 0.0091) in root-mean-square (RMS) error. Finally, a separate set of human cadaveric knees was obtained, and donor-specific fiber-reinforced scaffolds were fabricated. Under cyclic loading for load-distribution analysis, in situ implantation of personalized scaffolds following total meniscectomy restored contact area (253.0 mm2 to 488.9 mm2, p = 0.0060) and decreased contact stress (1.96 MPa to 1.03 MPa, p = 0.0025) to near-native values (597.4 mm2 and 0.83 MPa). Clinical use of personalized meniscus devices that restore physiologic contact stress distributions may prevent the development of post-traumatic osteoarthritis following meniscal injury.