STRONGHOLD first-year results of biomechanically calculated abdominal wall repair: a propensity score matching

PURPOSE

Every year around 70,000 people in Germany suffer from an abdominal incisional hernia that requires surgical treatment. Five years after reconstruction about 25% reoccur. Incisional hernias are usually closed with mesh using various reconstruction techniques, summarized here as standard reconstruction (SR). To improve hernia repair, we established a concept for biomechanically calculated reconstructions (BCR). In the BCR, two formulas enable customized patient care through standardized biomechanical measures. This study aims to compare the clinical outcomes of SR and BCR of incisional hernias after 1 year of follow-up based on the Herniamed registry.

METHODS

SR includes open retromuscular mesh augmented incisional hernia repair according to clinical guidelines. BCR determines the required strength (Critical Resistance to Impacts related to Pressure = CRIP) preoperatively depending on the hernia size. It supports the surgeon in reliably determining the Gained Resistance, based on the mesh-defect-area-ratio, further mesh and suture factors, and the tissue stability. To compare SR and BCR repair outcomes in incisional hernias at 1 year, propensity score matching was performed on 15 variables. Included were 301 patients with BCR surgery and 23,220 with standard repair.

RESULTS

BCR surgeries show a significant reduction in recurrences (1.7% vs. 5.2%, p = 0.0041), pain requiring treatment (4.1% vs. 12.0%, p = 0.001), and pain at rest (6.9% vs. 12.7%, p = 0.033) when comparing matched pairs. Complication rates, complication-related reoperations, and stress-related pain showed no systematic difference.

CONCLUSION

Biomechanically calculated repairs improve patient care. BCR shows a significant reduction in recurrence rates, pain at rest, and pain requiring treatment at 1-year follow-up compared to SR.

P-074 BIOMECHANICALLY STABLE INCISIONAL HERNIA REPAIRS WITH DIS CLASS A MESHES ARE DURABLE AFTER A 3 YEAR FOLLOW UP

Aim

Hernia meshes can be classified according to the tackiness towards cyclic load. Meshes with the best adhesiveness are named DIS class A. Are reconstructions with these meshes durable after 3 years?

Material and methods

Biomechanical principles of the reconstruction of the abdominal wall were analyzed ex vivo with cyclic loading common in material sciences. The resulting GRIP concept was clinically applied. The patients were followed in yearly intervals.

Results

A total of 129 patients (68 males and 61 females) were followed for 3 years after treatment for 93 primary and 36 recurrent incisional hernia. Progrip® was used in 53 cases (P), Dahlhausen® Cicat in 76 cases (C). P was used for smaller hernia with lower overlap due to the higher tackiness. Hernia sizes treated with C were significantly larger (u-test: p > 0.001). The mesh-defect area ratio was higher with P compared with C (11.9 vs 5.8). Fixation requirements were lower with 8 points for P and 80 points for C to reach adequate GRIP levels. GRIP was twice that minimally required. Larger hernia took longer OR times (median P: 104 vs. median C: 183 min; p > 0.001). Larger hernias were associated with more postoperative minor complications (6–14%, 1 re-operation for seroma). Length of stay was comparable with 5–6 days. During follow up, no recurrence was detected. Pain levels were low (median NAS = 0 after 3 years; u-test: p = 0.07672).

Conclusion

Incisional hernia can be repaired safely and durably based on biomechanical principles.

P-075 DURABLE REPAIR OF INCISIONAL HERNIA BASED ON BIOMECHANICAL PRINCIPLES – 3 YEAR FOLLOW UP

Aim

Durable composite constructions of polymers follow specific mechanical principles. Incisional hernia can be repaired durably based on biomechanical principles. How are the results after three years?

Material and methods

The biomechanics of the abdominal wall was analyzed ex vivo with cyclic loading common in material sciences. The resulting GRIP concept was clinically applied. The tissue quality of the individual patient was assessed with computed tomography at rest and during Valsalva's maneuver. All patients recieved single-shot antibiosis. Patients were discharged after full ambulation was achieved.

Results

A total of 228 patients (120 males and 108 females) were treated for incisional hernia. Primary hernia was repaired in 166, recurrence in 62 patients. The patients had an average of 1.3 risk factors with most patients grouped as ASA III (n= 119). Emergency repairs were necessary in 11 patients. Hernia orifices were mostly median (N= 141) and lateral (63 patients) with 23 combined cases. Hernia sizes were on average 9 ± 6 cm wide and 13 ± 8 cm long. The mesh-defect area ratio was 7.75. Fixation was necessary with a median of 60 fixation points to reach adequate GRIP levels. A total of 137 patients were followed for three years so far. Four patients died during follow-up (Follow-up rate 100%). One recurrence was detected in a liver transplant patient reconstructed with a sandwich. Pain levels were low (median NAS = 0 at rest and under load, u-test: p = 0.07672).

Conclusion

Incisional hernia can be repaired durably based on biomechanical principles.

OC-089 STANDARDIZED SUTURING OF MEDIAN INCISIONS AND DEFECTS CAN REDUCE SUTURE SLACKENING AND BURST RATES

Aim

Has standardization of criteria of a small-stitch-small-bite suture (SSSB) a significant influence on its durability?

Material and Methods

Porcine abdominal walls and bovine flanks were used as model tissues. We cut a median 15 cm long incision into the tissues. Then we punched an additional round (5–10 cm wide) or rhomboid (5×15 cm) defect in the middle of the incision. Monomax® and Maxon® USP 1 and 2–0 sutures were used in a running technique with a suture to incison lengths above 4:1. The mesh-tissue compounds were investigated on our self-built hydraulic bench test simulating coughs. Cyclic pressure impacts were repeatedly delivered peaking around 210 mmHg. In each of twenty experimental series, ten preparations were loaded 425 times.

Results

Standardized SSSB sutures using 2–0 Monomax® with a suture-incision-ratio of 4.5 : 1 can give a durable closure of a large defect in thin, elastic tissues. Under other conditions, suture lines can reopen. Standardization of the suturing technique significantly increased the durability (p = 0.00008). Defect shape is important since the larger rhomboid defects were easier to close compared to the smaller, 5 cm wide, round defects (SSSB: p = 0.00018; LSLB: p = 0.00906).

Discussion

After standardization, insignificant influences on the durability were exerted by the suture material and diameter, the bite and stitch size (small versus large), the surgeon, the tissue elasticity and tension and the defect size.

Conclusions

A standardized suturing technique was developed. The standardization improved the durability of a suture repair significantly.

Standardized suturing can prevent slackening or bursting suture lines in midline abdominal incisions and defects

Purpose

Incisional hernias often follow open abdominal surgery. A small-stitch–small-bite suture might close the incision durably. We analyzed specific details of this closure technique and assessed their influence on the closure stability.

Methods

The effects of cyclic loads, simulating coughs were investigated on a bench test. We prepared porcine bellies in the median line and bovine flanks parallel to the muscle fibers with 15 cm long incisions. Then we punched round or rhomboid defects with a diameter of 5–10 cm into the center of the incision. Monomax® 2–0 and Maxon® 1 and 2–0 were used as suture materials. We tested the durability of the closure with pressure impacts of 210 mmHg repeated 425 times. Throughout the experiments, we modified the suturing technique, the surgeon, the tissue tension, the defect size and shape and the suture diameter.

Results

Standardizing the suture technique improved the durability of the closure significantly. Any other variations showed minor influences after standardization. All incisions with round defects up to 7.5 cm width withstood 425 impacts using standardized suturing. Unstandardized sutures failed in all cases. When closing an incision with a 10 cm wide defect, the tissues ruptured frequently next to the suture line. We defined criteria to standardize this suturing technique. For the first time, we developed a suture factor related to the durability of a sutured tissue closure. We integrated the suture factor into the concept of biomechanically durable repairs.

Conclusions

Suturing the abdominal wall with a standardized suturing technique improves its durability significantly.

Biomechanics applied to incisional hernia repair - Considering the critical and the gained resistance towards impacts related to pressure

BACKGROUND

Incisional hernia repair is burdened with recurrence, pain and disability. The repair is usually carried out with a textile mesh fixed between the layers of the abdominal wall.

METHODS

We developed a bench test with low cyclic loading. The test uses dynamic intermittent strain resembling coughs. We applied preoperative computed tomography of the abdomen at rest and during Valsalva's maneuver to the individual patient to analyze tissue elasticity.

FINDINGS

The mesh, its placements and overlap, the type and distribution of fixation elements, the elasticity of the tissue of the individual and the closure of the abdominal defect-all aspects influence the reconstruction necessary. Each influence can be attributed to a relative numerical quantity which can be summed up into a characterizing value. The elasticity of the tissues within the abdominal wall of the individual patient can be assessed with low-dose computed tomography of the abdomen with Valsalva's maneuver. We established a procedure to integrate the results into a surgical concept. We demonstrate potential computer algorithms using non-rigid b-spline registration and artificial intelligence to further improve the evaluation process.

INTERPRETATION

The bench test yields relative values for the characterization of hernia, mesh and fixation. It can be applied to patient care using established procedures. The clinical application in the first ninety-six patients shows no recurrences and reduced pain levels after one year. The concept has been spread to other surgical groups with the same results in another fifty patients. Future efforts will make the abdominal wall reconstruction more predictable.

Increasing hernia size requires higher GRIP values for a biomechanically stable ventral hernia repair

Background

Increasing hernia sizes lead to higher recurrence rates after ventral hernia repair. A better grip might reduce the failure rates.

Material and methods

A biomechanical model delivering dynamic intermittent strain (DIS) was used to assess grip values at various hernia orifices. The model consists of a water-filled aluminium cylinder covered with tissues derived from pig bellies which are punched with a central defect varying in diameter. DIS was applied mimicking coughs lasting for up to 2 s with peak pressures between 180 and 220 mmHg and a plateau phase of 0.1 s. Ventral hernia repair was simulated with hernia meshes in the sublay position secured by tacks, glue or sutures as needed to achieve certain grip values. Grip was calculated taking into account the mesh: defect area ratio and the fixation strength. Data were assessed using non-parametric statistics.

Results

Using a mesh classified as highly stable upon DIS testing (DIS class A) a reduced overlap without fixation led to early slippage (p < 0.001). With the application of 16 fixation points, transmural sutures were better than tacks with Securestrap^® being better than Absorbatack^® (p < 0.001). Plotting the likelihood of a durable repair as a function of the calculated grip higher grip values were needed with increasing hernia diameter to achieve biomechanical stability. This is important for clinical work since the calculated grip values both from a registry and from published data tend to drop as hernia sizes increase indicating biomechanical instability.

Conclusion

The experimental work reported here demonstrates for the first time that higher grip values should be reached when repairing larger ventral hernias.