Muscle Selection and Dosing in a Phase 3, Pivotal Study of AbobotulinumtoxinA Injection in Upper Limb Muscles in Children With Cerebral Palsy

Background: Guidelines recommend botulinum toxin-A in pediatric upper limb spasticity as part of routine practice. Appropriate dosing is a prerequisite for treatment success and it is important that injectors have an understanding on how to tailor dosing within a safe and effective range. We report upper limb dosing data from a phase 3 study of abobotulinumtoxinA injections in children with cerebral palsy.Methods: This was a double-blind, repeat-treatment study (NCT02106351). In Cycle 1, children were randomized to abobotulinumtoxinA at 2 U/kg control dose or clinically relevant 8 U/kg or 16 U/kg doses. Doses were divided between the primary target muscle group (PTMG, wrist or elbow flexors) and additional muscles tailored to clinical presentation. During Cycles 2–4, children received doses of 8 U/kg or 16 U/kg and investigators could change the PTMG and other muscles to be injected. Injection of muscles in the other upper limb and lower limbs was also permitted in cycles 2–4, with the total body dose not to exceed 30 U/kg or 1,000 U (whichever was lower) in the case of upper and lower limb treatment.Results: 212 children were randomized, of which 210 received ≥1 abobotulinumtoxinA injection. Per protocol, the elbow and wrist flexors were the most commonly injected upper limb muscles. Across all 4 cycles, the brachialis was injected in 89.5% of children (dose range 0.8–6 U/kg), the brachioradialis in 83.8% (0.4–3 U/kg), the flexor carpi ulnaris in 82.4% (0.5–3 U/kg) and the flexor carpi radialis in 79.5% (0.5–4 U/kg). Other frequently injected upper limb muscles were the pronator teres(70.0%, 0.3–3 U/kg). adductor pollicis (54.3%, 0.3-1 U/kg), pronator quadratus (44.8%, 0.1–2 U/kg), flexor digitorum superficialis (39.0%, 0.5-4 U/kg), flexor digitorum profundus (28.6%, 0.5–2 U), flexor pollicis brevis/opponens pollicis (27.6%, 0.3-1 U/kg) and biceps (27.1%, 0.5–6 U/kg). AbobotulinumtoxinA was well-tolerated at these doses; muscular weakness was reported in 4.3% of children in the 8 U/kg group and 5.7% in the 16 U/kg group.Conclusions: These data provide information on the pattern of injected muscles and dose ranges used in this study, which were well-tolerated. Per protocol, most children received injections into the elbow and wrist flexors. However, there was a wide variety of other upper limb muscles injected as physicians tailored injection patterns to clinical need.

Volar plating: functional recovery of the pronator quadratus

Purpose The pronator quadratus (PQ) is reflected in the surgical approach to the distal radius. This study explores the functional strength of PQ, 12 months after volar plating without repair of PQ. Methods A total of 135 patients were identified from our prospectively collected database. All volunteers had grip strength and pronation power tested in the treated and contralateral forearms at 45, 90 and 135 degrees of elbow flexion using a custom-built torque measuring device and hydraulic hand dynamometer to evaluate forearm pronation. Results Twenty-seven participants were included in the study. No significant difference was identified in mean peak pronation torque between the volar plated and non-treated forearms. Pronation strength was identified as being independent of angle of elbow flexion. Grip strength was correlated with forearm pronation showing no significant difference between groups. Conclusions Our results suggest adequate long-term (15–32 months) functional recovery of the pronator quadratus after volar plating. Level of Evidence III.

Clinical evaluation of a wrist sensorimotor rehabilitation program for triangular fibrocartilage complex injuries

Introduction Triangular fibrocartilage complex (TFCC) injuries are associated with distal radioulnar joint (DRUJ) instability and impaired wrist proprioception. Sensorimotor training of extensor carpi ulnaris (ECU) and pronator quadratus (PQ) can enhance DRUJ stability. With limited evidence on effectiveness of TFCC sensorimotor rehabilitation, this study aimed to evaluate the effects and feasibility of a novel wrist sensorimotor rehabilitation program (WSRP) for TFCC injuries. Methods Patients diagnosed with TFCC injuries were recruited from May 2018 to January 2020 at an outpatient hand clinic in Singapore General Hospital. There are four stages in WSRP: (1) pain control, (2) muscle re-education and joint awareness, (3) neuromuscular rehabilitation, and (4) movement normalization and function. WSRP also incorporated dart throwing motion and proprioceptive neuromuscular facilitation. Outcome measures included grip strength measured with grip dynamometer, numerical pain rating scale, joint position sense (JPS) measurement, weight bearing measured with the ‘push-off’ test, and wrist function reported on the Patient Rated Wrist Hand Evaluation. Results Ten patients completed the WSRP. Mean changes were compared with minimal clinically important differences (MCID) for outcomes. All patients achieved MCID on pain, 70% of patients achieved MCID on grip strength, weight bearing and wrist function. Paired t-tests and Cohen’s D for outcome measures were calculated. There were large effect sizes of 2.47, 1.35, and 2.81 for function, grip strength and pain respectively, and moderate effect sizes of 0.72 and 0.39 for axial loading and JPS respectively. Discussion WSRP presents a potential treatment approach in TFCC rehabilitation. There is a need for future prospective clinical trials with control groups.

Single incision thenar muscle reconstruction using the free functional pronator quadratus flap

Background Injuries to the thenar muscle mass or the thenar branch of the median nerve and resulting loss of thumb opposition lead to a massive impairment of hand function. For decades, reconstructive approaches were based on tendon transfers. To broaden the reconstructive repertoire, we present the free functional pronator quadratus flap as a viable alternative for functional reconstruction and provide a specification for its indication. We demonstrate our surgical technique to a single incision reconstruction using the free functional pronator quadratus flap. Based on a series of three patients, which were analyzed for hand function using Kapandji’s score and the angle of Bourrel, grip strength and nerve conduction velocity in a two year follow up, we present an indication algorithm. Results After successful reinnervation of all flaps, we found an improvement of Kapandji’s score from 4.3 ± 0.94 preoperatively, to 8.7 ± 0.47 after two years. Accordingly, the angle of Bourrel decreased from 75.75 ± 3.45 degrees to 36.96 ± 3.68 degree. Grip strength also improved from 14 ± 2.2 kg to 26.2 ± 1.2 kg. No impairment of wrist pronation was observed. Conclusion We found excellent functional recovery of thumb opposition and strength, showing similar or even superior results compared to results from tendon transfers. With the benefit of a single incision surgery and therefore minimal donor site morbidity, this free functional muscle transfer is a viable alternative to classic tendon transfers.

Minimally Invasive Pronator Quadratus Sparing Approach versus Extended Flexor Carpi Radialis Approach with Pronator Quadratus Repair for Volar Plating in Distal Radial Fractures

Background Several volar plating techniques exist to treat distal radial fractures. Question We investigated minimally invasive plate osteosynthesis (MIPO) with pronator quadratus (PQ) sparing versus conventional flexor carpi radialis approach for volar plating with PQ repair after distal radial fractures during the first postoperative year. Patients and Methods Prospective data of two consecutive cohorts were compared: 62 patients in MIPO group with an average age of 61.2 years and 66 patients in PQ repair group with an average age of 61.4 years completed the entire follow-up period. Results Range of motion was not significantly different, except flexion–extension that was significantly higher in the MIPO group. Quick Disabilities of the Arm, Shoulder and Hand was significantly lower in the MIPO group. Pain visual analogue scale was only significantly lower at 6 weeks. Grip strength measurements and patient satisfaction were not significantly different. Conclusions MIPO volar plating with PQ sparing is a surgical technique that can be chosen according to surgeon's preference and expertise, resulting in a better flexion–extension mobility and function score according to our study. Level of evidence This is a Level 3 study.

Should We Repair the Pronator Quadratus in a Distal Radius Fracture with an Ulnar Styloid Base Fracture? A Biomechanical Study

Background Merits of repairing the pronator quadratus (PQ) to restore distal radioulnar joint (DRUJ) stability after a volar approach remain controversial. Distal radius fractures are often associated with ulnar styloid fractures (USF). When involving the fovea, this USF can lead to a DRUJ instability. The PQ repair may be key in reducing this DRUJ instability. Methods This study aims to assess the biomechanical role of PQ repair in a cadaveric model of USF. In 17 forearm specimens, a USF including the fovea was executed. Positional changes of the DRUJ in forearm rotation and dorso-palmar (DP) translation were measured with variable loads (0, 2.5, and 5N) applied to the PQ origin. Results Forearm rotation and DP-translation decreased significantly with PQ loading of 5N, changing on average by 5 degrees and 0.6 mm, respectively. Conclusion We found a significant decrease in forearm rotation and DP-translation comparing a fully loaded PQ to an unloaded PQ in our cadaveric model.

Pronator Quadratus Repair Does Not Affect Reoperation Rates Following Volar Locking Plate Fixation of Distal Radius Fractures

Background The purpose of this study was to evaluate the impact of pronator quadratus (PQ) repair on reoperation rates after distal radius open reduction internal fixation (ORIF) using a volar locking plate. Methods A retrospective study of all patients undergoing distal radius ORIF with a volar locking plate between January 2012 and December 2016 at 2 urban, academic level I trauma centers was performed. Patient demographics, fracture and procedure characteristics, surgeon subspecialty, PQ repair, and reoperations were recorded. Descriptive statistics were used to determine whether patient-related or injury-related characteristics were associated with PQ repair. Bivariate and multivariable regression analyses were used to assess the effect of PQ repair on subsequent reoperations. Results In total, 509 patients were included, including 31 patients with bilateral injuries. The average follow-up time was 3.7 ± 2.8 years. Patients undergoing PQ repair were younger (57 ± 17 years vs 61 ± 17 years) and were more likely to have a lower Soong grade (53% vs 44% with Soong grade 0) than patients without PQ repair. Pronator quadratus repair was not found to have a significant impact on hardware removal, reoperations for flexor tendon pathology, or overall reoperations. Conclusions Pronator quadratus repair was more commonly performed in younger patients and in patients with a lower Soong grade. Hand-subspecialized surgeons are more likely to pursue PQ repair than trauma-subspecialized surgeons. This study did not detect statistically significant differences in hardware removal, flexor tendon pathology, or overall reoperations between groups.