Clinical and Radiographic Evaluation of a Median Sternotomy Technique in the Dog

Biomechanical comparison of bone staple fixation methods with suture material for median sternotomy closure using 3D-printed bone models

AIM

To compare the biomechanical properties of three different sternal closure techniques in a 3D-printed bone model of a sternum from a 30-kg dog.

METHODS

Median sternotomy was performed on a total of 90 three-dimensional (3D) copies of a polycarbonate (PC) model of a sternum, generated from the CT images of the sternum of a 30-kg German Shepherd dog. Three different methods were used to repair the sternotomies: polydioxanone suture (group PDS, n = 30), stainless steel bone staples (group SS, n = 30), and nitinol bone staples (group NS, n = 30). Each repair method was tested by applying tensile force in one of three ways (longitudinally, laterally, or torsionally) resulting in a sample size of n = 10 for each repair method-loading combination. In all experiments, the loads at 1-mm and 2-mm gap formation, failure, and the displacement at the failure point were measured.

RESULTS

In lateral distraction and longitudinal shear tests, NS and SS staple repairs required application of significantly greater force than PDS across all displacement criteria (1 and 2 mm). NS exhibited significantly greater failure load than PDS. In torsion tests, NS required significantly greater application of force compared to SS or PDS at all displacement criteria (1 and 2 mm) and exhibited a greater failure load than PDS. In terms of displacement at failure point, PDS suture showed more displacement than SS or NS across all experiments (laterally, longitudinally, torsionally).

CONCLUSIONS

In this study, bone staples were mechanically superior to PDS suture in median sternotomy closure using 3D-printed bone model in terms of 1-mm, 2-mm displacement loads, and displacement at failure. NS had a higher failure load than PDS under lateral, longitudinal, and torsional distraction.

CLINICAL RELEVANCE

These study results imply that bone staples can be considered as an alternative surgical method for median sternotomy closure in dogs.

Biomechanical comparison of canine median sternotomy closure using suture tape and orthopedic wire cerclage

OBJECTIVE

To compare the mechanical properties of suture tape and orthopedic wire cerclage in an ex vivo canine median sternotomy model.

STUDY DESIGN

Ex vivo.

ANIMALS

Twelve large-breed canine cadaveric sternums.

METHODS

Median sternotomies were performed, leaving the manubrium intact. The specimens were randomly assigned to group W (20-gauge stainless steel orthopedic wire cerclage in a figure-of-eight pattern) or group ST (suture tape in a figure-of-eight pattern). Each specimen was laterally distracted until failure using an electrodynamic materials-testing system.

RESULTS

No differences were observed for displacement, yield load, maximum load, implant failure between the groups. The orthopedic wire construct was stiffer than the suture tape construct.

CONCLUSION

Suture tape was biomechanically similar to orthopedic wire cerclage for sternotomy closure in dogs, although wire constructs were stiffer.

CLINICAL SIGNIFICANCE

Suture tape may represent an alternative to cerclage wire for sternotomy closure in dogs. Additional studies evaluating its clinical use are needed.

Comparison of median sternotomy closure-related complication rates using orthopedic wire or suture in dogs: A multi-institutional observational treatment effect analysis

Objective

To determine and compare median sternotomy (MS) closure‐related complication rates using orthopedic wire or suture in dogs.

Study design

Multi‐institutional, retrospective observational study with treatment effect analysis.

Animals

331 client‐owned dogs, of which 68 were excluded.

Methods

Medical records of dogs with MS were examined across nine referral centers (2004–2020). Signalment, weight, clinical presentation, surgical details, complications, and outcomes were recorded. Follow‐up was performed using patient records and email/telephone contact. Descriptive statistics, treatment effect analysis and logistic regression were performed.

Results

Median sternotomy closure was performed with wire in 115 dogs and suture in 148. Thirty‐seven dogs experienced closure‐related complications (14.1%), 20 in the wire group and 17 in the suture group. Twenty‐three were listed as mild, four as moderate and 10 as severe. Treatment effect analysis showed a mean of 2.3% reduction in closure‐related complications associated with using suture versus wire (95% CI: −9.1% to +4.5%). In multivariable logistic regression, the only factor associated with increased risk of closure‐related complications was dog size (p = .01). This effect was not modified by the type of closure used (interaction term: OR = 0.99 [95% CI: 0.96/1.01]).

Conclusion

The incidence of closure‐related complication after MS was low compared to previous reports. The likelihood of developing a closure‐related complication was equivalent between sutures and wires, independent of dog size, despite a higher proportion of complications seen in larger dogs (≥20 kg).

Clinical significance

Use of either orthopedic wire or suture appear to be an appropriate closure method for sternotomy in dogs of any size.

Closure-related complications after median sternotomy in cats: 26 cases (2010-2020)

OBJECTIVES

The aim of this study was to determine closure-related complications and outcome after median sternotomy (MS) in cats.

METHODS

This was a retrospective, multicentric study. The medical records of cats undergoing MS from six referral hospitals were reviewed (2010-2020). Data retrieved included signalment, history, presenting complaints, surgery, patient outcomes and complications. Follow-up was performed via patient records and email/telephone contact with both owners and referring veterinarians. Descriptive statistics were performed.

RESULTS

Data on 36 cats were collected; four were excluded due to insufficient follow-up and six died less than 5 days after surgery. Twenty-six cats survived to discharge (survival rate 81%). Three cats had a full sternotomy (FS) performed and 23 cats a partial sternotomy (PS). Of the cats that underwent a PS, six included the manubrium (PSM) and three included the xyphoid process. For 14 cats, the length of sternotomy was unknown. Sternotomy closure was performed with suture in all cats. Two cats (7.7%) developed closure-related complications, both after PSM, during the long-term follow-up, one mild, slightly displaced sternal fracture and one severe, sternal dehiscence (without skin wound dehiscence) requiring revision surgery. No seroma, surgical site infection or wound dehiscence occurred. The most common reason for MS was the presence of a thoracic mass (17/26; 65%), with thymoma being the most common (11/17; 65%).

CONCLUSIONS AND RELEVANCE

MS has a low closure-related complication risk in cats when compared with dogs. Complications in cats present differently to what has been previously described in dogs.

Crimped monofilament nylon leader for median sternotomy closure in 10 dogs

OBJECTIVE

To describe and report the outcomes after closure of median sternotomies with crimped monofilament nylon leader (MNL) in dogs.

STUDY DESIGN

Retrospective observational study.

ANIMALS

Dogs (n = 10) that underwent intrathoracic surgery through a median sternotomy approach.

METHODS

The median sternotomy was closed in a peristernal figure eight pattern with crimped MNL. Medical records were reviewed for clinical and histopathological findings and complications. Owners or veterinarians were contacted to collect long-term follow-up information.

RESULTS

The technique was simple, with no intraoperative complications. Postoperative infection was documented in one dog, requiring removal of a single MNL and associated crimp clamp. Delayed healing of the surgical incision in one dog was managed conservatively. No other complications were documented throughout long-term follow-up at a median of 488 days (range, 199-608).

CONCLUSION

Median sternotomies were successfully closed with crimped MNL and were associated with a low complication rate.

CLINICAL SIGNIFICANCE

Crimped MNL represents an alternative method to close median sternotomies in dogs.

Factors influencing the short-term outcome following thoracic surgery in 98 dogs

OBJECTIVES

To evaluate the factors influencing the short-term (<14 days) outcome of thoracic surgery in dogs.

METHODS

A retrospective review of 98 dogs undergoing thoracotomy over a five-year period was undertaken.

RESULTS

A pre-operative diagnosis was achieved in 69 per cent of cases. Intrathoraic neoplasia had the lowest pre-operative diagnosis rate (5.5 per cent). Mortality rates of 21 per cent were recorded and were significantly higher for intrathoracic neoplasia (50 per cent) and significantly lower for persistent ductus arteriosus (7.4 per cent) and vascular ring anomaly (0 per cent). Median sternotomy was the preferred approach for pyothorax (85 per cent) and penetrating thoracic injuries (66 per cent). Intercostal thoracotomy was the preferred approach for all other diseases. Postoperative complications occurred in 39 per cent of cases. Wound complications were more common for pyothorax (45 per cent) and following median sternotomy (71 per cent). Thoracic drains were placed in 77 per cent of cases and complications were recorded in 23 per cent. Pyothorax and chylothorax had thoracic drains maintained for significantly longer periods of time. Longer thoracic drain duration was correlated significantly with increased complication rates.

CLINICAL SIGNIFICANCE

The short-term outcome following thoracic surgery is influenced by diagnosis. The thoracic approach is determined by intrathoracic disease, but may influence outcome by affecting the incidence of postoperative wound complications. The risk of thoracic drain complications increases with drain duration, which is influenced by the underlying disease. Drains should be maintained for the minimal amount of time possible.

Median Sternotomy Closure in Dogs: A Mechanical Comparison of Technique Stability

OBJECTIVE

To evaluate the mechanical properties of canine median sternotomy closure using double-loop cerclage compared with other commonly used cerclage sternotomy closure patterns.

STUDY DESIGN

Experimental study.

SAMPLE POPULATION

Forty canine cadaveric sternal segments.

METHODS

Median sternotomy-wire constructs were loaded to failure in a materials testing machine. Each construct was radiographed before and after testing. Specific wire configurations tested were: 2 single twist cerclage centered on the sternebrae, single twist figure of 8 pattern centered on the sternal synchondrosis, double twist figure of 8 pattern centered on the sternal synchondrosis, 2 double-loop cerclage centered on the sternebrae, and 1 double-loop cerclage centered on the sternal synchondrosis. Wire configurations were compared by craniocaudal translation of sternabrae on pre-test radiographs, and displacement during loading, and mode of failure, based on analysis of test video, and post-test radiographs.

RESULTS

Double-loop cerclage did not provide superior mechanical stabilization of median sternotomy. Both figure of 8 patterns had the least displacement at higher loads. Two single twists that were centered on sternebrae were least able to prevent displacement at higher loads, caused the most craniocaudal translation before testing, and fractured more often at loads < or = 200 N compared with other configurations.

CONCLUSION

Sternal wiring techniques stabilizing sternal synchondroses had the least displacement. Overall, figure of 8 cerclage appeared most suitable because they minimized displacement at high loads and facilitated accurate reduction during tensioning.

CLINICAL RELEVANCE

In closing canine sternotomy, figure of 8 cerclage may be most suitable. Double-loop cerclage centered on the sternal synchondrosis should be avoided because of wire failure at high loads.

Closure of median sternotomy in dogs: suture versus wire

Twenty normal, large-breed dogs underwent median sternotomy. Median sternotomies were closed with 20-gauge orthopedic wire in 10 dogs and no. 2 polybutester in 10 dogs. Closure with suture was faster than with wire (6.7 +/- 1.8 minutes versus 9.1 +/- 1.9 minutes, respectively). Significant differences were not observed in degree of postoperative pain or wound complication rates. Sternotomies closed with wire showed a trend to be more stable and had significantly less displacement on radiographic evaluation at 28 days. All sterna closed with wire examined histopathologically showed evidence of chondral or osteochondral bridging, while sterna closed with suture only showed fibrous union.

Estudo comparativo entre toracotomia intercostal, esternotomia mediana parcial e total em cães sadios (Canis familiaris ): avaliação clínica e hemogasométrica

O objetivo deste experimento foi comparar as alterações hemogasométricas e as possíveis complicações trans e pós-operatórias encontradas na toracotomia intercostal direita, esternotomia mediana parcial e esternotomia mediana total, determinando qual das técnicas produziu menor grau de intercorrências. Foram utilizados dezoito cães, sem raça definida, adultos, machos e fêmeas, com peso entre quinze e vinte quilos e em condições de saúde julgadas satisfatórias para o experimento. Os cães foram divididos em três grupos de seis animais, de acordo com a técnica cirúrgica empregada: GRUPO A -animais submetidos à toracotomia intercostal direita; GRUPO B - animais submetidos à esternotomia mediana parcial e GRUPO C - animais submetidos à esternotomia mediana total. Os cães foram avaliados quanto às possíveis intercorrências intra e pós-operatórias, alterações das freqüências cardíaca e respiratória, temperatura, oxigenação, ventilação, equilíbrio ácido-básico e dor. Durante sete dias foi feita avaliação da ferida cirúrgica, não observando-se intercorrências com cicatrização, infecção, presença de fístulas e deiscência de sutura. Os resultados obtidos foram analisados estatisticamente. Concluiu-se que as três técnicas foram exeqüíveis em cães, pois permitiram recuperação pós-operatória satisfatória e comparativamente não foram verificadas alterações significativas quanto ao pH, gases sangüíneos e dor.

Review of the technique and complications of median sternotomy in the dog and cat

The surgical and medical records of 67 dogs and nine cats which underwent median sternotomy over a five-year period were reviewed. The indication for median sternotomy and the short and longer term complications were recorded. Twenty-six of the dogs died or were euthanased within 48 hours of the surgery as a consequence of the pre-existing disease or complications of the intrathoracic surgical procedure. A further four dogs were enthanased between 48 hours and 14 days following confirmation of neoplastic processes. Thirty-seven dogs were alive at 14 days: of these, seven dogs (19 per cent) experienced short-term wound complications, including haemorrhage, wound infection, thoracic limb neurological deficits and excessive postoperative discomfort. Of the 37 dogs alive for longer term follow-up, eight dogs (22 per cent) experienced wound complications, including haemorrhage, sternal fracture, sternal osteomyelitis and delayed wound healing. No complications were noted in the cats.