The purpose of this study is to describe an uncommon ulnar nerve entrapment motor syndrome and the surgical technique to be performed. We wanted to emphasize the need for a timely diagnosis, in order to obtain restoration of motor functions of the intrinsic muscles of the hand. Analysis of the literature has highlighted how few cases describe the sole involvement of the ulnar nerve motor branch. Furthermore, cases of articular ganglion compression are even rarer. This clinical condition may be more frequent than previously imagined. Surgical treatment appears to be decisive in most cases, although late diagnosis often leads to incomplete functional recovery. In fact, the lack of knowledge of this pathology usually leads to hypothesizing pathologies of the central nervous system, delaying treatment for years. In fact, all our patients complained of motor deficits for months and several physicians hypothesized very different etiologies. Causes of compression of the ulnar nerve motor branch can be multiple. Capitani et al. describe a rare case of compression of the motor branch due to repeated microtraumas in a cyclist [
12]. In forms related to repeated microtraumas, the work history is of great importance. In fact, manual workers and workers exposed to vibrations are at greater risk of developing this disease. Waugh et al. described motor dysfunction of the ulnar nerve in patients with fractures of carpal bones such as the pisiform, the hamate and the fifth metacarpal base [
13]. Even abnormal muscle insertions or fibrous bands can cause compressions as described by Bozkurt et al. [
14]. Sometimes, clinical symptoms may be incomplete making the diagnosis even more difficult. This is the case reported by De Maio et al.: a patient presented an isolated paralysis of the adductor muscle of the thumb because of a fibrous band ulnar nerve compression [
15]. Diabetes mellitus, alcoholism and renal insufficiency in hemodialytic treatment are related to a higher incidence of ulnar nerve and its terminal motor branch dysfunctions, especially if peri-neural calcium deposits are associated [
16]. Jennings et al. describe two other interesting causes of compression of the ulnar nerve motor branch: intraneural ganglion cyst and a constricting leash of vessels [
17]. The most frequent cause of ulnar nerve compression, however, is the presence of benign tumors of the soft tissues of the hand such as articular ganglia, giant-cell tumors and lipomas. These can emerge from the ulno-carpal joint, piso-triquetral, triquetro-hamate or other carpal joints [
18]. Only a few cases are described in the literature. Gan et al. describe a very peculiar case of a patient with compression caused by both an articular ganglion and lipoma [
19]. This underlines the importance of studying every single case in depth before surgical treatment, rather than using just an MRI. In fact, neglecting a cause of compression or not tackling it correctly will significantly compromise an otherwise obtainable result. Wang is the only author to have described a significant number of cases [
20]. As in Wang’s nine cases, we also report the compression of the ulnar nerve motor branch alone being caused by an articular ganglion from the piso-triquetrum joint. All the enrolled patients presented a marked improvement in function and strength after surgical decompression. However, Wang's study offers few details of the clinical tests used and their reproducibility. We therefore wanted to objectivize the reported data in the best way possible by using routine and highly reproducible clinical tests and a clinical assessment scale of recognized reliability. Clinical evaluations were repeated by two different hand surgeons experienced in ulnar pathology, in order to optimize the results obtained. This study is unique because, although compression of the motor branch of the ulnar nerve from ganglion is a known etiology, there are not case series in the literature, apart the one by Wang et al. This last, however, is not thoroughly studied. In our experience, systematic clinical and electromyographic assessments made it possible to highlight how an early and accurate surgical treatment allows complete
restitutio ad integrum of hand function.
The isolated compression of the ulnar nerve motor branch is a low reported clinical condition. The lack of knowledge of this motor neuropathy probably leads to diagnostic difficulties. We believe that a timely clinical and electromyographic evaluation and correct imaging highlighting the cause of compression are crucial in these cases.