11 Bowstringing of the Flexor Tendon
11.1 Patient History Leading to the Specific Problem
A 52-year-old man was referred to the author because of sudden loss of active flexion of the index finger in the first week after repair of the flexor digitorum profundus (FDP) tendon with a two-strand modified Kessler repair. The original laceration was at the proximal interphalangeal (PIP) joint level. He lost active flexion of the distal interphalangeal (DIP) and PIP joints of that finger after starting early active digital flexion. The author decided to perform a re-repair of the disrupted FDP tendon, 4 weeks after initial primary repair. However, he developed adhesions after the second direct end-to-end repair. Tenolysis was performed twice, but he ended up with limited improvement in active finger flexion and bowstringing at the PIP joint (▶Fig. 11.1). He was diagnosed as having adhesions, pulley destruction, and tendon bowstringing. According to the clinical presentation, the A4 pulley had to be reconstructed.
After detailed discussion with the patient, we decided to proceed with staged tendon reconstruction and pulley reconstruction. The plan was that in stage 1 of the surgery, the frayed FDP tendon would be removed from zones 1 and 2 and replaced with a Hunter rod, with reconstruction of the pulleys over the rod. In stage 2 of the surgery, the Hunter rod would be replaced with a palmaris longus tendon graft.
11.2 Anatomic Description of the Patient’s Current Status
An important feature of the digital flexor tendon system is the presence of annular pulleys (▶Fig. 11.2), of which the A2 and A4 pulleys are the largest and functionally most important. Therefore, if all annular pulleys have been destroyed, these two pulleys should be reconstructed; if only one remains, the other should be reconstructed. The A2 pulley is located at the proximal and middle portions of the proximal phalanx and the A4 locates at the center of the middle phalanx.
For this patient, re-repair of the disrupted FDP tendon would increase the risk of adhesions, and severe adhesions tend to destroy the entire sheath—including most or all of the annular pulleys; this is a possible cause of destruction of the A4 pulley and its adjacent structures. At least the A4 pulley needed to be reconstructed for this patient.
Fig. 11.1 Bowstringing of the flexor digitorum profundus tendon at the proximal interphalangeal joint after primary repairs of the tendon. (This image is provided courtesy of Jin Bo Tang, MD.)
Fig. 11.2 Locations of the annular pulleys in a finger. Note the A2 and A4 pulleys are the largest and critically located among all pulleys.
The A3 pulley, functionally less insignificant than the A2 or A4 pulley, is located palmar to the PIP joint. However, surgeons should consider a broader A4 pulley or add a slip of reconstructed pulley over the PIP joint, which helps minimize tendon bowstringing at the PIP joint.
11.3 Recommended Solution to the Problem
The pulley should be reconstructed together with placement of a Hunter rod; this is a standard approach for such a complex case. The pulley reconstructed over the Hunter rod will not develop adhesions between the pulley and the rod. It is not proper to perform a pulley reconstruction over a frayed tendon during tenolysis, because adhesions will recur, and early active finger flexion disrupts the reconstructed pulley.
At the time of single-stage tendon grafting, the pulleys can also be reconstructed, but the author prefers to do tendon grafting with pulley reconstruction when only one pulley needs to be reconstructed and adhesions are confined. If both A2 and A4 pulleys need to be reconstructed, the scar is usually extensive. A Hunter rod should be placed first to stimulate pseudo-sheath formation. In a finger with extensive scarring, one-stage tendon grafting combined with pulley reconstruction does not yield a movable finger, and outcomes would be disappointing. A staged tendon reconstruction would be preferable to a single-stage tendon grafting for a finger with extensive scarring.
11.4 Technique
The surgery was performed under branchial plexus anesthesia and tourniquet control.
11.4.1 Steps for the Procedure: Stage 1
1. Frayed FDP tendon is resected.
2. The distal A2 pulley is preserved.
3. Adhesions are cleaned and flexor digitorum superficialis (FDS) tendon slips are excised.
4. A Hunter rod is inserted under the A2 pulley and connected.
5. A segment of the FDP tendon is used as a graft to reconstruct the A4 pulley.
6. The graft is anchored to the remnants of the pulleys.
7. Suture strength is confirmed.
11.4.2 Stage 1 Surgery
An extended Bruner incision made from the fingertip to the mid-palm was used to extend the previous surgical incisions. The frayed FDP tendon was found buried in the scar (▶Fig. 11.3) and was resected over the entire finger length. A short stump (0.5 cm) of the FDP tendon was kept at its insertion.
The A2 pulley was found collapsed and partially embedded in the adhesions. The distal A2 pulley was excised, but the proximal part was found intact, with dense fibers that could be freed from the adhesions. The proximal A2 pulley was thus preserved. Adhesions were thoroughly cleaned and FDS tendon slips were excised. Since the A1 pulley was intact, that pulley was kept as well.
After we placed trail rods confirming the size of the rod to be used, the Hunter rod was then inserted under the preserved part of the A2 pulley, and the distal end of the rod was connected to the residual part of the FDP tendon at the insertion site. A segment (2 cm) of the excised FDP tendon that had smooth surfaces was used as a graft for pulley reconstruction. The tendon segment was lassoed from the A4 pulley to the distal A2 pulley in the middle and the proximal phalanges. This tendon segment was firmly anchored to the rim of the residual A4 pulley and periosteum with a number of interrupted sutures with 3–0 Ethilon (▶Fig. 11.4).
We confirmed that sutures of the reconstructed pulley to the residual parts of the A4 pulley and periosteum were secure. We also confirmed that the new pulley was not too tight for the gliding of the Hunter rod, through passively moving the finger from full extension to semiflexion. It is not usually necessary to check the gliding of the Hunter rod up to full passive flexion of the finger. The proximal end of the Hunter rod was left free, rather than being sutured to the end of the FDP tendon in the palm. The skin was closed.
