Subterminal key pinch dynamometry: a new method to quantify strength deficit in ulnar nerve paralysis

Reconstructing Pinch Strength after Ulnar Nerve Injury by Transferring the Opponens Pollicis Motor Branch

BACKGROUND

With ulnar nerve injuries, paralysis of the first dorsal interosseous and adductor pollicis muscle weakens the patient's pinch. In the palm, we transferred the opponens pollicis motor branch to the deep terminal division of the ulnar nerve for pinch reconstruction.

METHODS

Sixteen patients with ulnar nerve injuries around the elbow underwent reconstruction and were followed up postoperatively for a minimum of 14 months. Their mean age was 41 ± 16 years, and the mean interval between injury and surgery was 134 ± 126 days (range, 2 to 390 days). Preoperatively and postoperatively, grasp, key, and subterminal key pinch strength were measured using dynamometers.

RESULTS

Reinnervation of the first dorsal interosseous muscle was observed in 15 of the 16 patients. Mean grasp strength improved from 15.5 ± 8.5 kg preoperatively to 24 ± 10 kg postoperatively, achieving 57% ± 16% of contralateral hand strength. Preoperatively, terminal key pinch averaged 3 ± 1 kg, which improved postoperatively to 5.5 ± 2 kg, achieving 71 ± 24% of the strength measured contralaterally. Preoperatively to postoperatively, subterminal key pinch force increased from 0 to 2.4 ± 1.3 kg, achieving 61% ± 27% that of the unaffected side. Patients who underwent surgery within 6 months of their injury showed a mean subterminal key pinch strength recovery of 63% ± 27% of the normal side, whereas those who underwent surgery between 7 and 13 months after injury showed a mean subterminal key pinch strength recovery of 51% ± 29%.

CONCLUSION

Transferring the opponens pollicis motor branch to the deep terminal division of the ulnar nerve improved pinch and grasp strength without jeopardizing thumb function.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

Evaluating Outcomes Following Nerve Repair: Beyond the Medical Research Council

Peripheral nerve injuries are common and remain a significant health challenge. Outcome measurements are used to evaluate injury, monitor recovery after nerve repair, and compare scientific advances. Clinical judgement is required to determine which available tools are most applicable, which requires a vast understanding of the available outcome measurements. In this article we discuss the highest yield tools available for clinical application.

Bilateral Ulnar Nerve Injury in the Wrist: Comparison of First Webspace Muscle Reconstruction by Opponens Nerve Transfer in the Right Hand Versus Direct Ulnar Nerve Repair in the Left Hand

We report a case of a bilateral glass injury to the wrist with transection of flexor tendons and the ulnar nerve and artery in a 60-year-old male patient. Two days after his accident, we repaired all divided structures, and on the right hand, we added the transfer of the opponens motor branch to the deep terminal division of the ulnar nerve aimed at first dorsal interosseous and adductor pollicis muscle reinnervation. After surgery, the patient was followed over 24 months. Postoperative dynamometry of the hand, which included grasping, key-pinch, subterminal-key-pinch, pinch-to-zoom, and first dorsal interosseous muscle strength, indicated recovery only in the nerve transfer side.

Reliability and validity of the modified McGowan grade in patients with cubital tunnel syndrome

INTRODUCTION

This study aimed to assess the reliability and validity of the modified McGowan grading system and to determine its ability to distinguish the severity of cubital tunnel syndrome (CuTS) between the different grades.

MATERIALS AND METHODS

We prospectively enrolled 39 consecutive patients with CuTS from March 2018 to December 2020. Inter- and intra-observer reliability was assessed by two orthopaedic surgeons with a minimum 2-week interval using Cohen kappa coefficients. Validity was assessed by Spearman's correlation with objective clinical outcomes (grip strength, Semmes-Weinstein monofilament test [SWMT], static two-point discrimination [2PD], and motor conduction velocity [MCV]). In addition, the relationship between the grading system and patient-reported outcomes (Disabilities of the Arm, Shoulder and Hand score and Boston Questionnaire) was evaluated using Spearman's correlation. The ability to distinguish the severity between the different grades was assessed using the Kruskal-Wallis analysis.

RESULTS

The inter-observer kappa value was 0.54 and intra-observer kappa value was 0.59, which imply a moderate reliability. The modified McGowan grade had a moderate correlation with objective clinical outcomes (grip strength [r = - 0.350, p = 0.029], SWMT [r = 0.552, p < 0.001], 2PD [r = 0.456, p = 0.004], and MCV [r = - 0.394, p = 0.021]). However, patient-reported outcomes did not correlate with this grading system. Kruskal-Wallis analysis revealed significant differences between grades in terms of SWMT, 2PD, grip strength, and Boston Questionnaire functional score (p = 0.006, 0.025, 0.014, and 0.043, respectively); however, these differences were statistically significant only for a limited number of parts.

CONCLUSIONS

The modified McGowan grade has a moderate inter- and intra-observer reliability. This grading system moderately correlates with objective sensory-motor functions and MCV of patients with CuTS. However, the modified McGowan grade does not reflect the patient's perceived disabilities and has a weakness in distinguishing the severity of patients' conditions among the different grades.