Summary of Proximal Interphalangeal Joint Injuries and Treatment

## Introduction Acute complete ruptures of the ulnar collateral ligament (UCL) of the thumb metacarpophalangeal (MP) joint require timely, anatomy-focused surgical management to restore stability, prevent chronic instability, and enable return to function. This guide distills surgical indications, open-repair techniques, alternatives, intraoperative pearls, and postoperative expectations for UCL (and parallel radial collateral ligament, RCL) repair. > Definition: The ulnar collateral ligament (UCL) of the thumb is the primary static restraint to radial deviation and valgus stress at the MP joint; a complete tear has loss of a firm endpoint on stress testing. ## Indications for Surgical Repair - Complete acute rupture of the UCL (no firm endpoint on valgus stress) or significant laxity: recommend surgical repair. - Distal avulsion with bony fragment or Stener lesion (interposed adductor aponeurosis): operative fixation is indicated. - Chronic symptomatic complete tears with instability: repair if mobilizable; reconstruction if shortened/fibrotic. - Contraindication to repair: severe degenerative joint changes — consider arthrodesis in chronic arthritic thumbs. ## Preoperative Evaluation - Focused physical exam: compare laxity to contralateral thumb. Criteria suggestive of complete tear: laxity > 30 degrees in flexion or extension, or > 15-degree difference versus contralateral side, and absence of firm endpoint. - Radiographs: posteroanterior, lateral, and oblique views — assess for avulsion fragments, volar subluxation, and articular injury. - Imaging such as MRI or ultrasound usually adds little to clinical decision-making for acute UCL tears. ## Basic Surgical Principles - Protect dorsal sensory nerve branches in the superficial plane. - Expose the ligament through a volar longitudinal incision in the adductor aponeurosis (lazy “S” pattern externally) and reflect aponeurosis volarly. - Identify and address Stener lesions (adductor aponeurosis interposed between ligament and insertion). - Reattach ligament to bone with adequate tension with joint in 45 degrees flexion to avoid overtightening. - Supplement repair with capsular / volar plate stitches if necessary to recreate the three-dimensional restraint. > Definition: Stener lesion — a displaced distal UCL avulsion in which the torn ligament end is caught superficial to the adductor aponeurosis, preventing healing to the phalanx unless reduced surgically. ## Open Repair Technique (Distal UCL Avulsion) 1. Incision and exposure - Lazy “S” incision paralleling the ulnar-dorsal border of the metacarpal, curving volarly to parallel the MP joint and extending distally along the ulnar mid-axial line. - Identify and protect superficial radial nerve branches in the deep subcutaneous plane. - Incise adductor aponeurosis longitudinally ~3 mm volar to the ulnar border of the extensor pollicis longus and reflect volarly. 2. Inspect joint - Remove loose cartilage or small shear fragments. - Confirm ligament injury pattern (intrasubstance, distal avulsion, Stener lesion). 3. Repair options - Mid-substance tears: approximate with interrupted figure-of-eight or horizontal mattress sutures using nonabsorbable braided suture (e.g., 4-0 braided polyester). - Distal avulsion — pull-out suture technique: - Scarify bone at the reattachment site. - Place a modified Kessler or equivalent stitch in the proximal ligament stump with 3-0 monofilament or stainless steel wire. - Drill Keith needles (or use Kirschner-wire–guided Keith needles) across proximal phalanx from ulnar to radial, exit radial skin. - Thread suture through needle eyes, pull through, tension ligament into the trough at ulnar base of proximal phalanx, and tie over felt-padded button or rubber catheter. - Distal avulsion — bone anchor: - Hand-drill pilot hole in ulnar base of proximal phalanx after clearing soft tissue. - Insert single bone anchor volar to joint axis; pa