gms | German Medical Science

Objectives/Interrogation: Comminuted intra-articular fractures of the distal radius involving the marginal volar lip often require fixation distal to the watershed line in order to obtain bone purchase and control of these far distal fragments. Despite recent developments and various low profile smooth contoured plate designs, implants sited in this region have been described to cause tendon irritation and rupture.

The aim of this study is to evaluate excursion and irritation of the flexor pollicis longus (FPL) tendon in fractures treated with these implants, as the course of this tendon runs in close proximity to the radial aspect of the plate.

Methods: Patients who underwent fracture fixation using plates designed to be sited at this far distal site were identified from theatre and implant registers. Thumb interphalangeal (IP) joint flexion, and maximal thumb composite opposition were compared with the contralateral side at six and twelve weeks. Ultrasound assessment was performed at the same time intervals, and at six months following surgery.

Results and Conclusions: Thirty patients were identified. Full thumb mobilization was encouraged in all cases. Patients described initial pain and restricted thumb movement which improved over the first six weeks, ranging from a mean visual analogue score for pain of 8.8 for all thumb movement to no pain on IP joint movement and 2.8 pain on full thumb flexion. 37% of cases had sonographic signs of tenosynovitis at six weeks post-operatively. Full IP joint movement was present and maintained at and beyond 6 weeks of surgery. Full thumb opposition was decreased by a mean of 3 points on the Kapandji score when compared to the contralateral side at 6 weeks, becoming symmetrical in 89% of the cases by twelve weeks. Evidence of tenosynovitis resolved in most cases, with mild persisting tenosynovitis on ultrasound in 23% and discomfort on pinch grip testing in 17% at six months following surgery.

This study shows that the initial postoperative thumb stiffness improves over the first three months after surgery. As movement progresses, mild signs of FPL tendon irritation are present on ultrasound despite patients being asymptomatic during their daily activities. Given the potential for flexor tendon rupture due to irritation from implants inserted distal to the watershed line, the persistence of evidence of tenosynovitis in nearly a quarter of patients at 6 months is concerning, although the clinical relevance and so the implication when advising upon implant removal is unclear.