Assessment of Thermal Osteonecrosis during Bone Drilling Using a Three-Dimensional Finite Element Model.

Bone drilling is a common procedure used to create pilot holes for inserting screws to secure implants for fracture fixation. However, this process can increase bone temperature and the excessive heat can lead to cell death and thermal osteonecrosis, potentially causing early fixation failure or complications. We applied a three-dimensional dynamic elastoplastic finite element model to evaluate the propagation and distribution of heat during bone drilling and assess the thermally affected zone (TAZ) that may lead to thermal necrosis. This model investigates the parameters influencing bone temperature during bone drilling, including drill diameter, rotational speed, feed force, and predrilled hole. The results indicate that our FE model is sufficiently accurate in predicting the temperature rise effect during bone drilling. The maximum temperature decreases exponentially with radial distance. When the feed forces are 40 and 60 N, the maximum temperature does not exceed 45 °C. However, with feed forces of 10 and 20 N, both the maximum temperatures exceed 45 °C within a radial distance of 0.2 mm, indicating a high-risk zone for potential thermal osteonecrosis. With the two-stage drilling procedure, where a 2.5 mm pilot hole is predrilled, the maximum temperature can be reduced by 14 °C. This suggests that higher feed force and rotational speed and/or using a two-stage drilling process could mitigate bone temperature elevation and reduce the risk of thermal osteonecrosis during bone drilling.

Cyclic Stability of Locking Plate Augmented with Intramedullary Polymethyl Methacrylate (PMMA) Strut Fixation for Osteoporotic Humeral Fractures: A Biomechanical Study.

The locking plate may provide improved fixation in osteoporotic bone; however, it has been reported to fail due to varus collapse or screw perforation of the articular surface, especially in osteoporotic bone with medial cortex comminution. Using bone graft as an intramedullary strut together with plate fixation may result in a stronger construct. However, the drawbacks of bone grafts include limited supply, high cost, and infection risk. PMMA (so-called bone cement) has been widely used for implant fixation due to its good mechanical properties, fabricability, and biocompatibility. The risk of donor-site infection and the drawbacks of allografting may be overcome by considering PMMA struts as alternatives to fibular grafts for humeral intramedullary grafting surgeries. However, the potential effects of intramedullary PMMA strut on the dynamic behaviour of osteoporotic humerus fractures remain unclear. This study aimed to investigate the influence of an intramedullary PMMA strut on the stability of unstable proximal humeral fractures in an osteoporotic synthetic model. Two fixation techniques, a locking plate alone (non-strut group) and the same fixation augmented with an intramedullary PMMA strut (with-strut group), were cyclically tested in 20 artificial humeral models. Axially cyclic testing was performed to 450 N for 10,000 cycles, intercyclic motion, cumulated fragment migration, and residual deformation of the constructs were determined at periodic cyclic intervals, and the groups were compared. Results showed that adding an intramedullary PMMA strut could decrease 1.6 times intercyclic motion, 2 times cumulated fracture gap migration, and 1.8 times residual deformation from non-strut fixation. During cycling, neither screw pull-out, cut-through, nor implant failure was observed in the strut-augmented group. We concluded that the plate-strut mechanism could enhance the cyclic stability of the fixation and minimize the residual displacement of the fragment in treating osteoporotic proximal humeral unstable fractures. The PMMA strut has the potential to substitute donor bone and serve as an intramedullary support when used in combination with locking plate fixation. The intramedullary support with bone cement can be considered a solution in the treatment of osteoporotic proximal humeral fractures, especially when there is medial comminution.

Influence of Simulated State of Disc Degeneration and Axial Stiffness of Coupler in a Hybrid Performance Stabilisation System on the Biomechanics of a Spine Segment Model.

Spinal fusion surgery leads to the restriction of mobility in the vertebral segments postoperatively, thereby causing stress to rise at the adjacent levels, resulting in early degeneration and a high risk of adjacent vertebral fractures. Thus, to address this issue, non-fusion surgery applies some pedicle screw-based dynamic stabilisation systems to provide stability and micromotion, thereby reducing stress in the fusion segments. Among these systems, the hybrid performance stabilisation system (HPSS) combines a rigid rod, transfer screw, and coupler design to offer a semi-rigid fixation method that preserves some mobility near the fusion site and reduces the adjacent segment compensatory effects. However, further research and confirmation are needed regarding the biomechanical effects of the dynamic coupler stiffness of the HPSS on the intrinsic degenerated adjacent segment. Therefore, this study utilised the finite element method to investigate the impact of the coupler stiffness of the HPSS on the mobility of the lumbar vertebral segments and the stress distribution in the intervertebral discs under flexion, extension, and lateral bending, as well as the clinical applicability of the HPSS on the discs with intrinsic moderate and severe degeneration at the adjacent level. The analytical results indicated that, regardless of the degree of disc degeneration, the use of a dynamic coupler stiffness of 57 N/mm in the HPSS may reduce the stress concentrations at the adjacent levels. However, for severely degenerated discs, the postoperative stress on the adjacent segments with the HPSS was still higher compared with that of the discs with moderate degeneration. We conclude that, when the discs had moderate degeneration, increasing the coupler stiffness led to a decrease in disc mobility. In the case of severe disc degeneration, the effect on disc mobility by coupler stiffness was less pronounced. Increasing the coupler stiffness ked to higher stress on intervertebral discs with moderate degeneration, while its effect on stress was less pronounced for discs with severe degeneration. It is recommended that patients with severe degeneration who undergo spinal dynamic stabilisation should remain mindful of the risk of accelerated adjacent segment degeneration.

Local thermal effect of power-on setting on monopolar coagulation: a three-dimensional electrothermal coupled finite element study.

A three-dimensional (3-D) electrothermal coupled finite element (FE) model was used to simulate and analyze the effects of the electrosurgical power-on setting on the temperature distribution and thermal damage in biological tissue during coagulation. The discussed parameters include the power-on-off durations, contact distance between the electrosurgical blade and tissue surface, and inclination angle of the blade during cutting. The results indicate that under the condition of a constant input electrical energy, the maximal temperature decreased when the power-on time was shortened and the power-off (pause) duration was increased. The two contact distances between the blade and tissue (0 and 0.25 mm) did not show a significant temperature difference; however, the tissue temperature increased with increasing blade inclination angle. We concluded that using a normal cut angle and set at a multiple shorter-time power-on with intermittent power-off operation procedure can reduce the risk of thermal damage during monopolar electrosurgery.

Clinical Assessment of Functional Recovery Following Nerve Transfer for Traumatic Brachial Plexus Injuries.

Surgical reconstruction and postoperative rehabilitation are both important for restoring function in patients with traumatic brachial plexus injuries (BPIs). The current study aimed to understand variations in recovery progression among patients with different injury levels after receiving the nerve transfer methods. A total of 26 patients with BPIs participated in a rehabilitation training program over 6 months after nerve reconstruction. The differences between the first and second evaluations and between C5-C6 and C5-C7 BPIs were compared. Results showed significant improvements in elbow flexion range (p = 0.001), British Medical Research Council's score of shoulder flexion (p = 0.046), shoulder abduction (p = 0.013), shoulder external rotation (p = 0.020), quantitative muscle strength, and grip strength at the second evaluation for both groups. C5-C6 BPIs patients showed a larger shoulder flexion range (p = 0.022) and greater strength of the shoulder rotator (p = 0.004), elbow flexor (p = 0.028), elbow extensor (p = 0.041), wrist extensor (p = 0.001), and grip force (p = 0.045) than C5-C7 BPIs patients at the second evaluation. Our results indicated different improvements among patients according to injury levels, with quantitative values assisting in establishing goals for interventions.

Biomechanical Comparison between Isobar and Dynamic-Transitional Optima (DTO) Hybrid Lumbar Fixators: A Lumbosacral Finite Element and Intersegmental Motion Analysis.

Biomechanical performance of longitudinal component in dynamic hybrid devices was evaluated to display the load-transfer effects of Dynesys cord spacer or Isobar damper-joint dynamic stabilizer on junctional problem based on various disc degenerations. The dynamic component was adapted at the mildly degenerative L3-L4 segment, and the static component was fixed at the moderately degenerative L4-L5 segment under a displacement-controlled mode for the finite element study. Furthermore, an intersegmental motion behavior was analyzed experimentally on the synthetic model under a load-controlled mode. Isobar or DTO hybrid fixator could reduce stress/motion at transition segment, but compensation was affected at the cephalic adjacent segment more than the caudal one. Within the trade-off region (as a motion-preserving balance between the transition and adjacent segments), the stiffness-related problem was reduced mostly in flexion by a flexible Dynesys cord. In contrast, Isobar damper afforded the effect of maximal allowable displacement (more than peak axial stiffness) to reduce stress within the pedicle and at facet joint. Pedicle-screw travel at transition level was related to the extent of disc degeneration in Isobar damper-joint (more than Dynesys cord spacer) attributing to the design effect of axial displacement and angular rotation under motion. In biomechanical characteristics relevant to clinical use, longitudinal cord/damper of dynamic hybrid lumbar fixators should be designed with less interface stress occurring at the screw-vertebral junction and facet joint to decrease pedicle screw loosening/breakage under various disc degenerations.

Effects of Kinesio taping on forearm supination/pronation performance fatigability.

BACKGROUND: Repetitive exertion in supination/pronation could increase the risk of forearm diseases due to fatigue. Kinesio taping (KT) is a physical therapy technique that decreases muscle tone and musculoskeletal disorders (MSDs) risk. Many assumptions about taping have been made and several studies have considered the taping applications; however, the effect of KT on strength and fatigue of the forearm supination/pronation remains unclear. The purpose of this study was to evaluate the effect of KT on forearm performance fatigability. METHODS: A screwing test was constructed to measure the forearm force loss and screwing efficiency during repetitive supination/pronation. Data from 18 healthy adults who underwent both KT and no taping (NT) sessions were used to investigate the forearm strength change in terms of grip force (GF), driving torque (DT), and push force (PF). The maximal isometric forces before and after the screwing test and force decreasing rate (efficiency) during screwing were evaluated to assess the performance fatigability in KT and NT conditions. RESULTS: A statistically significant force loss (FL) in maximal isometric GF (p = 0.039) and maximal isometric DT (p = 0.044); however, no significant difference was observed in maximal isometric PF (p = 0.426) between NT and KT. KT provides greater screwing efficiency than NT. CONCLUSIONS: KT could not improve FL in the maximal muscle strength of the forearm in healthy subjects. KT on the forearm was associated with a lesser decline in DT efficiency than NT, implying that KT could decrease the loss rate of muscle strength and delay the development of fatigue; however, the KT did not yield improvements in PF while performing screwing tasks.

Biomechanical Effect of Hybrid Dynamic Stabilization Implant on the Segmental Motion and Intradiscal Pressure in Human Lumbar Spine.

The hybrid dynamic stabilization system, Dynesys-Transition-Optima, represents a novel pedicle-based construct for the treatment of lumbar degenerative disease. The theoretical advantage of this system is to stabilize the treated segment and preserve the range of motion within the adjacent segment while potentially decreasing the risk of adjacent segment disease following lumbar arthrodesis. Satisfactory short-term outcomes were previously demonstrated in the Dynesys-Transition-Optima system. However, long-term follow-up reported accelerated degeneration of adjacent segments and segmental instability above the fusion level. This study investigated the biomechanical effects of the Dynesys-Transition-Optima system on segment motion and intradiscal pressure at adjacent and implanted levels. Segmental range of motion and intradiscal pressure were evaluated under the conditions of the intact spine, with a static fixator at L4-5, and implanted with DTO at L3-4 (Dynesys fixator) and L4-5 (static fixator) by applying the loading conditions of flexion/extension (±7.5 Nm) and lateral bending (±7.5 Nm), with/without a follower preload of 500 N. Our results showed that the hybrid Dynesys-Transition-Optima system can significantly reduce the ROM at the fusion level (L4-L5), whereas the range of motion at the adjacent level (L3-4) significantly increased. The increase in physiological loading could be an important factor in the increment of IDP at the intervertebral discs at the lumbar spine. The Dynesys-Transition-Optima system can preserve the mobility of the stabilized segments with a lesser range of motion on the transition segment; it may help to prevent the occurrence of adjacent segment degeneration. However, the current study cannot cover all the issues of adjacent segmental diseases. Future investigations of large-scale and long-term follow-ups are needed.

Forearm muscular strength and performance fatigability in orthopaedic surgeons when performing bone screw fixations.

This study investigated the muscle strength and performance fatigability of the forearms in eight male orthopaedic surgeons when performing bone screw fixations. Each surgeon performed an eight-bone screws operations in a porcine femur model to simulate fractural fixation using plating technique. The pre- and post-fatigue maximum isometric forces and corresponding electromyography responses were measured to assess the forearm muscle strength loss and fatigue due to screwing. Results showed that after eight bone screws were inserted, the maximal grip force, maximal driving torque and maximal push force losses were approximately 29%, 20% and 23%, respectively. While the grip force and/or driving torque acting, both the brachioradialis and extensor carpi ulnaris had a higher percentage change of EMG than the biceps brachii. The driving forces decreased with the number of screw insertions; however, the insertion time increased parabolically with the number of screws and significantly decreased the insertion rate of the screws, indicating that forearm muscle fatigue may occur in surgeons who treat fracture fixation using more than eight bone screws.

Assessment of heat generation and risk of thermal necrosis during bone burring by means of three-dimensional dynamic elastoplastic finite element modelling.

During bone burring, the heat generated due to friction at the bone-burr interface may cause thermal damage to the bone. Therefore, it is necessary to assess bone temperature distribution around a burring site and identify high-risk regions for thermal necrosis due to bone burring. In this study, a three-dimensional (3-D) dynamic elastoplastic finite element model for the burring process was developed and experimentally validated to investigate the influence of burring parameters (rotational speeds: 3,000, 10,000, 15,000 and 60,000 rpm; feed rates: 0.5, 0.9, 1.5 and 3.0 mm/s) on heat generation and evaluate the risk region for thermal necrosis. Calculated bone temperatures were compared with experimental values and found to be in good agreement with them. The analytical results demonstrated a linear relationship between the burring time and friction energy. In addition, the friction energy increased with the bone temperature. The high-risk thermal necrosis zone was measured from the edge of burring (y-direction) at feed rates of 0.5, 0.9, 1.5 and 3.0 mm/s and was found to be 7.8, 7.3, 6.6 and 5.5 mm, respectively. When the burr rotational speed increased from 3,000 to 60,000 rpm, the high-risk zone for thermal necrosis increased from 4.5 to 8.1 mm. We concluded that both the friction energy and the bone temperature increased in proportion with the burr rotational speed. Reducing burr rotational speeds and/or increasing feed rates may decrease the rise in bone temperature, thus decreasing the potential for thermal necrosis near the burring site. Our model can be used to select the optimal surgery parameters to minimise the risk of thermal necrosis due to bone burring and to assist in the design of optimal orthopaedic drill handpieces.

Biomechanical evaluation of patellar tendon repair using Krackow suture technique.

BACKGROUND: Patellar tendon rupture is a potentially devastating injury. Surgical repair is the primary treatment recommended for the patients with patellar tendon ruptures. Given the tendon properties, the suture technique is critical for proper tissue repair. Providing adequate loading during early mobilization is essential to prevent tendon suture repair failure. Therefore, the current study evaluated the mechanical characteristics of various applied loadings on patellar tendon repair using Krackow suture via a porcine model. METHODS: Twelve fresh porcine hindlimbs with patellar tendon rupture were repaired by Krackow method using synthetic and non-absorbable No. 5 Ethibond sutures. Loadings of 100 and 200 N were applied during the cyclic loading test. A three-dimensional optical motion capture system was used to record the gap formation at the initial, 50th, 100th, 150th, 200th, 250th, 500th, 750th, and 1000th cycle. After cyclic loading, the specimen was loaded to failure under displacement control at a rate of 1 mm/s. RESULTS: Suture breakage was the primary failure mode in both loading conditions. After 1000 cyclic loadings of 100 N, the ultimate failure strength was 243.6 ± 25.8 N. However, the specimens tested under 200 N of loading failed before reaching 200 cycles. Under the 100 N loading, the largest gap deformation (1.89 ± 0.23 mm) and residual deformation (0.213 ± 0.183 mm) were found in the initial cycle. The average cumulative displacement was 5.13 mm from the initial cycle to the 100th cycle and 4.5 mm from the 250th to the 1000th cycle. CONCLUSIONS: Our findings can serve as reference values for further comparisons with various repair techniques or materials. This study suggests that the initially applied load after patellar tendon repair is an important risk factor of re-rupture.

Assessment of thermal necrosis risk regions for different bone qualities as a function of drilling parameters.

BACKGROUND AND OBJECTIVE: During bone drilling, the heat generated by friction depends directly on bone quality and surgical parameters. Excessive bone temperatures may cause thermal necrosis around the pilot hole, weaken the purchase of inserted screws, and in turn reduce the stability of screw fixation. A few studies have addressed the key parameters of drilling, such as the rotation speed of the drill-bit, feed force (axial force), feed rate, tool type, and tip geometry of drill-bits. Nevertheless, in the literature, information on the relationship between bone quality and thermally affected regions is still lacking. This study employed a three-dimensional dynamic elastoplastic finite element model to evaluate the influence of surgical parameters on the bone temperature elevation and assess the risk region of thermal necrosis for different bone qualities as a function of drilling parameters. METHODS: To ascertain the heat generation rate and the high-risk region of thermal necrosis, the effects of bone quality, feed rate, feed force, and drill-bit diameter on the bone temperature elevation were explained using a three-dimensional dynamic elastoplastic finite element model, which was validated through experimental measurements. RESULTS: The bone temperature was affected by the drilling parameters; the maximum temperature was attained at the junction of cancellous and cortical bones. The bone temperature increased with cortical bone thickness, bone density, and drill-bit diameter, and it decreased with the drilling speed and feed force. CONCLUSIONS: The present model could assess the risk region of thermal necrosis by accurately analyzing the bone temperature elevation for various bone qualities, feed forces, and feed rates. The bone temperature increased with the bone mineral density and cortical bone thickness. The highest bone temperature and maximum necrosis region were found near the junction of cortical and cancellous bones. Increasing the drilling speed or feed force can minimize the bone temperature elevation and the risk range of thermal necrosis.

Evaluation of the parameters affecting bone temperature during drilling using a three-dimensional dynamic elastoplastic finite element model.

A three-dimensional dynamic elastoplastic finite element model was constructed and experimentally validated and was used to investigate the parameters which influence bone temperature during drilling, including the drill speed, feeding force, drill bit diameter, and bone density. Results showed the proposed three-dimensional dynamic elastoplastic finite element model can effectively simulate the temperature elevation during bone drilling. The bone temperature rise decreased with an increase in feeding force and drill speed, however, increased with the diameter of drill bit or bone density. The temperature distribution is significantly affected by the drilling duration; a lower drilling speed reduced the exposure duration, decreases the region of the thermally affected zone. The constructed model could be applied for analyzing the influence parameters during bone drilling to reduce the risk of thermal necrosis. It may provide important information for the design of drill bits and surgical drilling powers.

Intramedullary cortical bone strut improves the cyclic stability of osteoporotic proximal humeral fractures.

BACKGROUND: Proximal humeral fractures treated with locking plate can fail due to varus collapse, especially in osteoporotic bone with medial cortex comminution. The use of an intramedullary strut together with locking plate fixation may strengthen fixation and provide additional medial support to prevent the varus malalignment. This study biomechanically investigates the influence of an intramedullary cortical bone strut on the cyclic stability of proximal humeral fractures stabilized by locking plate fixation in a cadaver model. METHODS: Ten cadaveric humeri were divided into two groups statistically matched for bone density. Each specimen was osteotomized with 10 mm gap at the surgical neck. The non-augmented group stabilized with locking plate alone; in the augmented group, a locking plate was used combined with an intramedullary cortical bone strut. The strut was retrograded into the subchondral bone, and three humeral head screws were inserted into the strut to form a plate-screw-strut mechanism. The cyclic axial load was performed to 450 N for 6000 cycles and then loaded to failure. Construct stiffness, cyclic loading behavior and failure strength were analyzed to identify differences between groups. RESULTS: The augmented constructs were significantly stiffer than the non-augmented constructs during cycling. On average, the maximum displacements at 6000 cycles for non-augmented and augmented groups were 3.10 ± 0.75 mm and 1.7 ± 0.65 mm (p = 0.01), respectively. The mean peak-to-peak (inter cycle) displacement at 6000 cycles was about 2 times lower for the augmented group (1.36 ± 0.68 mm vs. 2.86 ± 0.51 mm). All specimens showed varus collapse combined with loss of screw fixation of the humeral head. The failure load of the augmented group was increased by 2.0 (SD = 0.41) times compared with the non-augmented group (p < 0.001). CONCLUSIONS: The stability and strength of the locking plate augmented with an intramedullary strut were significantly increased. For bone with poor quality, the subsidence of the locked screws led larger displacement, decreased the stability of the constructs, however, the plate-screw-strut mechanism provided more rigidity to stabilize the fixation. This study emphasized the importance of intramedullary support for the proximal humeral fractures fixed with a locked plate under cyclic loading, especially in bone with poor quality. This work is based on the results of cadaver model, further in vivo analysis is necessary to determine if the clinical results can be extrapolated from this data.

Effects of implant drilling parameters for pilot and twist drills on temperature rise in bone analog and alveolar bones.

This study concerns the effects of different drilling parameters of pilot drills and twist drills on the temperature rise of alveolar bones during dental implant procedures. The drilling parameters studied here include the feed rate and rotation speed of the drill. The bone temperature distribution was analyzed through experiments and numerical simulations of the drilling process. In this study, a three dimensional (3D) elasto-plastic dynamic finite element model (DFEM) was proposed to investigate the effects of drilling parameters on the bone temperature rise. In addition, the FE model is validated with drilling experiments on artificial human bones and porcine alveolar bones. The results indicate that 3D DFEM can effectively simulate the bone temperature rise during the drilling process. During the drilling process with pilot drills or twist drills, the maximum bone temperature occurred in the region of the cancellous bones close to the cortical bones. The feed rate was one of the important factors affecting the time when the maximum bone temperature occurred. Our results also demonstrate that the elevation of bone temperature was reduced as the feed rate increased and the drill speed decreased, which also effectively reduced the risk region of osteonecrosis. These findings can serve as a reference for dentists in choosing drilling parameters for dental implant surgeries.

Outcomes after minimally invasive lumbar decompression: a biomechanical comparison of unilateral and bilateral laminotomies.

BACKGROUND: The unilateral approach for bilateral decompression was developed as an alternative to laminectomy. Unilateral laminotomy has been rated technically considerably more demanding and associated with more perioperative complications than bilateral laminotomy. Several studies have indicated that bilateral laminotomy are associated with a substantial benefit in most outcome parameters and thus constituted a promising treatment alternative. However, no complete kinematic data and relative biomechanical analysis for evaluating spinal instability treated with unilateral and bilateral laminotomy are available. Therefore, the purpose of this study was to compare the stability of various decompression methods. METHODS: Ten porcine lumbar spines were biomechanically evaluated regarding their strain and range of motion, and the results were compared following unilateral or bilateral laminotomies and laminectomy. The experimental protocol included flexion and extension in the following procedures: intact, unilateral or bilateral laminotomies (L2-L5), and full laminectomy (L2-L5). The spinal segment kinematics was captured using a motion tracking system, and the strain was measured using a strain gauge. RESULTS: No significant differences were observed during flexion and extension between the unilateral and bilateral laminotomies, whereas laminectomy yielded statistically significant findings. Regarding strain, significant differences were observed between the laminectomy and other groups. These results suggest that laminotomy entails higher spinal stability than laminectomy, with no significant differences between bilateral and unilateral laminotomies. CONCLUSIONS: The laminectomy group exhibited more instability, including the index of the range of motion and strain. However, bilateral laminotomy seems to have led to stability similar to that of unilateral laminotomy according to our short-term follow-up. In addition, performing bilateral laminotomies is easier for surgeons than adopting a unilateral approach for bilateral decompression. The results provide recommendations for surgeons regarding final decision making. Future studies conducting long-term evaluation are required.

Within-session reliability and smallest real difference of muscle strength following nerve transfers in patients with brachial plexus injuries.

PURPOSE: To quantify the smallest real difference (SRD) of muscle strength in patients with brachial plexus injuries (BPI) after nerve transfer. METHODS: This study enrolled 16 patients with BPI who had C5-C6 and C5-C7 root injuries and who received nerve transfer of the spinal accessory nerve to the suprascapular nerve and fascicles of the ulnar nerve to the branch of the musculocutaneous nerve that innervates the biceps muscle. The quantitative peak strength of the shoulder abductor, external rotator, and elbow flexor in both arms were measured by the hand-held dynamometer. The SRD of each muscle was determined from the values of the intraclass correlation coefficient and standard error of measurement. RESULTS: In the involved arm, peak strength ranged from 18% of the noninvolved (shoulder external rotator) to 40% of the noninvolved (shoulder abductor). The intraclass coefficient for within-session reliability revealed good to excellent reliability for muscles, ranging from 0.86 to 0.99 and 0.87 to 0.91 in the involved and noninvolved arms, respectively. The SRD values were low for the shoulder external rotator (2.6 kg) and high for the elbow flexor (3.3 kg). CONCLUSIONS: The hand-held dynamometer is a device with good to excellent reliability for measuring the objective strength of patients with BPI in a single session. The SRD values established in the current study are more applicable for patients achieving a Medical Research Council grading of 3 or higher and can be used to detect real changes occurring after intervention, which can thereby differentiate real changes from changes that could be attributed to random variation in the measurements. TYPE OF STUDY/LEVEL OF EVIDENCE: Diagnosis II.

Comparison of objective muscle strength in C5-C6 and C5-C7 brachial plexus injury patients after double nerve transfer.

PURPOSE: The purpose of this study was to evaluate the quantitative muscle strength to distinguish the outcomes of different injury levels in upper arm type brachial plexus injury (BPI) patients with double nerve transfer. METHODS: Nine patients with C5-C6 lesions (age = 32.2 ± 13.9 year old) and nine patients with C5-C7 lesions (age = 32.4 ± 7.9 year old) received neurotization of the spinal accessory nerve to the suprascapular nerve combined with the Oberlin procedure (fascicles of ulnar nerve transfer to the musculocutaneous nerve) were recruited. The average time interval between operation and evaluation were 27.3 ± 21.0 and 26.9 ± 20.6 months for C5-C6 and C5-C7, respectively. British Medical Research Council (BMRC) scores and the objective strength measured by a handheld dynamometer were evaluated in multiple muscles to compare outcomes between C5-C6 and C5-C7 injuries. RESULTS: There were no significant differences in BMRC scores between the groups. C5-C6 BPI patients had greater quantitative strength in shoulder flexor (P = 0.02), shoulder extensor (P < 0.01), elbow flexor (P = 0.04), elbow extensor (P = 0.04), wrist extensor (P = 0.04), and hand grip (P = 0.04) than C5-C7 BPI patients. CONCLUSIONS: Upper arm type BPI patients have a good motor recovery after double nerve transfer. The different outcomes between C5-C6 and C5-C7 BPI patients appeared in muscles responding to hand grip, wrist extension, and sagittal movements in shoulder and elbow joints.

Surgical treatment for total root avulsion type brachial plexus injuries by neurotization: a prospective comparison study between total and hemicontralateral C7 nerve root transfer.

PURPOSE: We conducted a clinical study to evaluate the effects of neurotization, especially comparing the total contralateral C7 (CC7) root transfer to hemi-CC7 transfer, on total root avulsion brachial plexus injuries (BPI). METHODS: Forty patients who received neurotization for BPI were enrolled in this prospective study. Group 1 (n = 20) received hemi-CC7 transfer for hand function, while group 2 (n = 20) received total-CC7 transfer. Additional neurotization included spinal accessory, phrenic, and intercostal nerve transfer for shoulder and elbow function. The results were evaluated with an average of 6 years follow-up. RESULTS: Group 1 had fewer donor site complications (15%) than group 2 (45%); group 2 had significantly better hand M3 and M4 motor function (65%) than group 1 (30%; P = 0.02). There was no difference in sensory recovery. Significantly, better shoulder function was obtained by simultaneous neurotization on both suprascapular and axillary nerves. CONCLUSIONS: Total-CC7 transfer had better hand recovery but more donor complications than hemi-CC7. Neurotization on both supra-scapular and axillary nerves improved shoulder recovery.