Analysis of the soft tissue retraction pressures in total ankle arthroplasty: An in-vitro human cadaveric model

Abstract

Background

Total ankle arthroplasty wound healing complications are likely influenced by intraoperative retraction. The current study compared contact pressures from various retractors at multiple incision lengths in an anterior approach to the ankle. We hypothesized Gelpis created higher contact pressures and longer incisions reduced pressures.

Methods

Twelve cadaveric lower extremities were dissected using 12 cm, 15 cm and 20 cm incisions. A TekScan sensor measuring contact pressure and surface area was placed between the Gelpi, Army-Navy (short and long), and Weitlaner retractors and exposed soft tissue structures.

Results

Average contact pressures reduced with increasing incision lengths except for Weitlaners. Army-Navy Long showed significantly lower pressures at 15 cm. Gelpis exhibited highest contact pressures except at 20 cm(p < 0.05). No significant differences were observed between retractors at 12 cm(p > 0.05).

Conclusions

Army-Navy retractors produced the least contact pressure in 12 cm and 15 cm incisions and self-retainers created higher contact pressures. Contact pressures typically decreased as incision lengths increased.

Level of Evidence

Level V

1

Introduction

Total ankle arthroplasty (TAA) is a common procedure in foot and ankle orthopedic surgery for the treatment of end-stage ankle osteoarthritis. As with all arthroplasties, infection is a devastating complication of this procedure with one study reporting an amputation rate of 21 % in patients with postoperative infection ,,, . It has been proposed that foot and ankle procedures are associated with a higher rate of wound complications and dehiscence due to decreased soft tissue coverage and a poorer vascular supply, which increases the risk of infection , . Reported rates of wound healing complications range from 0.4 % to 14 % ,, . Prior studies have hypothesized that the use of retractors may limit local blood flow and delay healing , .

Several studies have analyzed retraction pressures in tissues during spine surgery. These studies have shown that surgical retractors increase the pressure within surrounding tissues at levels consistent with local ischemia ,,,, . Retractor placement, type, and duration may also increase wound complications , . Currently, surgeons must rely on visual cues and intuition to determine the health and risk to retracted tissue. In total ankle arthroplasty, there is a consensus to minimize retraction when possible, however, a paucity of data exists on the best type of retractor to use to minimize wound healing complications. To date, no such study has evaluated pressures induced by commonly used retractors in the ankle.

Retractors commonly used in total ankle arthroplasty include Gelpi, Weitlaner and Army-Navy retractors. Gelpi retractors are self-retainers that function through point loading through sharp tips with additional soft tissue retraction along the retractor arms. Weitlaner retractors are also self-retainers that utilize multiple prongs on opposing sides. Prongs may be blunt or sharp, with sharp prongs more effective at tissue retraction however blunt prongs offer protection for surrounding delicate structures, such as nerves and vessels. Both Gelpi and Weitlaner retractors are available in multiple sizes depending on the surgical site. Army-Navy retractors are handheld and double ended with asymmetric flat blades perpendicular to the retractor handle. The blades have rounded edges to minimize trauma to retracted tissues. Intraoperative retractor selection depends on surgeon preference and is influenced by multiple factors.

This current study serves to compare the contact pressures exerted on soft tissues by three types of retractors—Gelpi, Army-Navy (short and long arms), and Weitlaner—with varying incision lengths of 12, 15, and 20 cm used during an anterior approach for total ankle arthroplasty. The hypothesis for this study was that Gelpi retractors generate higher contact pressures due to point loading and that larger incision lengths will correlate with reduced contact pressures.

2

Materials and methods

A total of twelve (n = 12) fresh cadaveric lower extremities were harvested en-bloc and utilized in this investigation. Specimens were sourced from the Maryland State Anatomy Board, immediately packaged in double-thickness plastic bags, and stored at −20 degrees Celsius. Each leg specimen (proximal tibia to foot base) was secured to a rigid frame to maintain neutral extremity alignment. The initial incision for each specimen was made between the extensor hallucis longus muscle and tibialis anterior tendon, originating 6 cm proximal to the ankle joint and extending to the talonavicular joint. Incisions were sequentially extended from the initial 12 cm to 15 cm (two centimeters proximally and one centimeter distal), and finally to 20 cm (four centimeters proximally and one centimeter distally) with the ankle in neutral. This range was selected based on operative technique guides for four implants commonly used in total ankle arthroplasty: 1. The Scandinavian Total Ankle Replacement (STAR Ankle) (Stryker, Kalamazoo, MI), 2. Infinity Total Ankle System (Stryker, Kalamazoo, MI), 3. Inbone Total Ankle System (Stryker, Kalamazoo, MI), and 4. Vantage Total Ankle System (Exactech, Gainesville, FL). Once exposure was completed, the Gelpi, Army-Navy (short [S] and long [L] arms), and Weitlaner retractors were placed into the incision in alternating order at each incision length to mitigate the effect of creep. A TekScan pressure sensor (Medical Sensor 4011–500, TekScan Inc. Norwood, MA) was placed between the retractor and soft tissues with one limb medially and one limb laterally ( Fig. 1 ). The TekScan sensor was placed superficially to the penetrating points of the Gelpi and Weitlaner retractors as the point loading disrupted the sensor’s ability to collect data. The Weitlaner retractor was an 8-inch, blunt retractor with 3 × 4 prongs. Sensor data was recorded in 30-second intervals at a sampling rate of 10 Hz. Contact area (millimeters squared- mm 2) and contact pressures pounds per square inch (PSI) were recorded for each retractor at all three incision lengths ( Fig. 2 ).

Fig. 1

TekScan sensor placement during retraction using (A) Weitlaner, (B) Gelpi and (C) Army-Navy L retractors in a 12 cm incision.

Fig. 2

TekScan sensor mapping in a 15 cm incision for (A) Army-Navy L, (B) Army-Navy S, (C) Gelpi and (D) Weitlaner retractors. The right and left pressures are shown for each retractor with the contact area profiles depicted. Areas of pressure are denoted with color. Blues areas indicate lower pressure and pink/red indicate higher areas of pressures. Army-Navy S had the highest contact area on average and Weitlaner retractors the lowest.

For each retractor, the region exposed was widened until the medial and lateral gutters were visible, at 5.5–6 cm for each patient. The handheld Army-Navy retractors were held at the distance needed to keep visualization of the joint. These distances were maintained for the entirety of the sensor data collection for each retractor.

Statistical analysis was performed using IBM SPSS Statistics v22 (Armonk, NY, USA). A One-way analysis of variance (ANOVA) with repeated measures and Bonferroni post hoc analyses were performed to assess differences in contact pressure (PSI) and contact area (mm 2) between retractors and incision lengths. Linear regression and correlation analysis between average contact pressures and calf and ankle circumferences were quantified. Significance was defined as p ≤ 0.05.

3

Results

3.1

Specimen demographics

A total of 12 specimens were utilized in this investigation with a mean age of 79.2 ± 17.3 years (age range=43–98 years). There were 6 left and 6 right lower extremities and 3 male/3 female specimens. The average calf circumference was 330 ± 43 mm and average ankle circumference 271 ± 19 mm.

3.2

Retractor contact pressures

Gelpi retractors exhibited the highest average contact pressures at all incision lengths except for 20 cm ( Table 1 ). Average contact pressures diminished as incision lengths increased for all retractors, except for Weitlaners. At a 15 cm incision, the Army-Navy L retractor demonstrated significantly lower contact pressures compared to the Army-Navy S (p = 0.039). The Army-Navy L contact pressures were also lower when compared to Gelpi and Weitlaner, however, statistical significance was not observed (p = 0.055). At a 20 cm incision, the Gelpi (p = 0.048) and Weitlaner retractors (p = 0.038) presented significantly higher contact pressures in comparison to the Army-Navy L retractor. No significant differences were observed between retractors for the 12 cm incisions (p > 0.05).

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Sep 5, 2026 | Posted by in ORTHOPEDIC | Comments Off on Analysis of the soft tissue retraction pressures in total ankle arthroplasty: An in-vitro human cadaveric model

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