Comparing Two Skin Incisions for Flexor Tendon Repair

Background and Purpose Tendon injuries are a common type of hand trauma, with flexor tendon injuries most often occurring in zone II. Careful surgical technique followed by early, intensive mobilization under the supervision of a hand therapist is of utmost importance. The traditional Bruner incision, a zig-zag incision, provides wide exposure. However, it also causes extensive soft tissue trauma, leading to swelling and pain, which in turn may reduce adherence to hand rehabilitation protocols. The modified Bruner incision is an alternative approach in which the incision is placed along the lateral side of the finger and slightly curved volarly toward the midpoint between the flexion creases, without crossing the volar midline. This approach provides adequate exposure of the flexor tendon and the digital neurovascular structures with less dissection. Clinical experience suggests that the modified Bruner incision may result in less swelling and pain, faster wound healing and improved conditions for early mobilization. However, there is currently a lack of studies comparing clinical outcomes between the traditional Bruner incision and the modified Bruner incision.

The aim of this study is to investigate whether there are differences in swelling, pain and functional outcomes between patients undergoing flexor tendon repair using the traditional Bruner incision versus the modified Bruner incision.

Research Questions

In primary repair of zone II flexor tendon injuries:

• Do patients treated with a modified Bruner incision experience less postoperative pain during the first three months after surgery?
• Do fingers operated on using a modified Bruner incision demonstrate reduced swelling during the first three postoperative months?
• Do fingers repaired with a modified Bruner incision show improved range of motion during the first three postoperative months?

Methods A randomized controlled study conducted at the Department of Hand Surgery, Mölndal Hospital.

Eligible patients with acute flexor tendon injuries will be invited to participate. After providing informed consent, participants will be randomised to undergo either a standard Bruner incision or a modified midlateral Bruner incision, with all other operative and perioperative variables standardised between the groups.

All procedures will be performed by either a specialist in hand surgery or a hand surgery resident. Within three days postoperatively, at the first dressing change, patients will be assessed by an occupational therapist.

Follow-up evaluations will be conducted at fixed time points: 2, 4, 6, 8, and 12 weeks after surgery. Wound healing will be monitored weekly by a nurse until complete healing has been achieved.

Outcome Measures

Primary outcome

• Pain during exercise, measured using the Visual Analogue Scale (VAS) 0-10; assessed on postoperative day 3 and thereafter daily for 3 months postoperatively (REDCap questionnaire) Secondary outcomes
• Resting pain
• Daily use of analgesics (REDCap questionnaire)
• Swelling: circumference of the injured finger / circumference of the contralateral finger (OT)
• Range of motion: Total Passive Motion (TPM) and Total Active Motion (TAM) of the injured finger / TPM and TAM of the contralateral finger (OT)
• Fingertip sensibility: Semmes-Weinstein monofilament testing (OT), two-point discrimination (physician)
• Extension deficit of the proximal and distal interphalangeal joints (PIP and DIP) (OT)
• Wound healing: Surgical Wound Assessment Tool (SWAT) (nurse)
• Length of the skin incision (cm); a photograph of the incision pattern is obtained intraoperatively

Independent Variables

• Sex
• Age
• Systemic disease: diabetes mellitus, vascular disease, chronic obstructive pulmonary disease (COPD)
• Occupation
• Occupational injury Yes/No
• Mechanism of injury
• Number of injured fingers
• Digital nerve injury
• Type of anesthesia
• Type of suture
• Type of rehabiliation protocol
• Complications: wound infection, suture rupture, conversion of incision

Data Sources Data will be recorded in eCRF using REDCap. Patients will report daily, at predefined time points, VAS pain scores and number of analgesic tablets taken the same day through mobile-based questionaries.

Statistical Analysis The primary outcome measure is pain during exercise, where a between-group difference of 2 points is considered clinically relevant. Assuming a significance level of p < 0.05 and an estimated standard deviation of 2.5 points, the required sample size is calculated to be 26 patients per group to achieve 80% power. To compensate for potential dropouts, a total of 70 patients will be included (35 in each group). Differences in pain, swelling and range of motion at different time points will be compared using bivariate analyses.

Ethics Participation in the study does not involve any change in standard care, except for the surgical incision, which differs between two established methods, the Bruner incision and the modified Bruner incision. Both incision types are standard treatments and have been in clinical use for many years. All patients will receive oral and written information and provide informed consent before inclusion. Participation is voluntary and may be discontinued at any time without affecting the patient's care. Collected data will be pseudonymized and stored securely in locked storage.

Clinical Benefit The results of this study may lead to evidence-based guidelines for skin incisions in acute flexor tendon repair, allowing patients to experience less pain and swelling. This may facilitate the postoperative rehabilitation program and improve the final functional outcome.

Inclusion criteria

• flexor tendon injury in the hand in zone 2

Exclusion criteria

• complex injuries with fracture and/or skin defect
• previous injury with functional deficit of the finger or the contralateral control finger
• incapable to follow the training protocol for flexor tendon injuries
• not proficient in swedish or english language
• active substance abuse