Greater Reduction in Contralesional Hand Use After Frontoparietal Than Frontal Motor Cortex Lesions in Macaca mulatta.

We previously reported that rhesus monkeys recover spontaneous use of the more impaired (contralesional) hand following neurosurgical lesions to the arm/hand representations of primary motor cortex (M1) and lateral premotor cortex (LPMC) (F2 lesion) when tested for reduced use (RU) in a fine motor task allowing use of either hand. Recovery occurred without constraint of the less impaired hand and with occasional forced use of the more impaired hand, which was the preferred hand for use in fine motor tasks before the lesion. Here, we compared recovery of five F2 lesion cases in the same RU test to recovery after unilateral lesions of M1, LPMC, S1 and anterior portion of parietal cortex (F2P2 lesion - four cases). Average and highest %use of the contralesional hand in the RU task in F2 cases were twice that in F2P2 cases (p < 0.05). Recovery in the RU task was closely associated with volume and percentage of lesion to caudal (new) M1 (M1c) in both F2 and F2P2 lesion cases. One F2P2 case, with the largest M1c lesion and a large rostral somatosensory cortex (S1r) lesion developed severe contralesional hand non-use despite exhibiting some recovery of fine motor function initially. We conclude that the degree of reduced use of the contralesional hand is primarily related to the volume of M1c injury and that severe non-use requires extensive injury to M1c and S1r. Thus, assessing peri-Rolandic injury extent in stroke patients may have prognostic value for predicting susceptibility to RU and non-use in rehabilitation.

Changes in ipsilesional hand motor function differ after unilateral injury to frontal versus frontoparietal cortices in Macaca mulatta.

We tested the hypothesis that injury to frontoparietal sensorimotor areas causes greater initial impairments in performance and poorer recovery of ipsilesional dexterous hand/finger movements than lesions limited to frontal motor areas in rhesus monkeys. Reaching and grasping/manipulation of small targets with the ipsilesional hand were assessed for 6-12 months post-injury using two motor tests. Initial post-lesion motor skill and long-term recovery of motor skill were compared in two groups of monkeys: (1) F2 group-five cases with lesions of arm areas of primary motor cortex (M1) and lateral premotor cortex (LPMC) and (2) F2P2 group-five cases with F2 lesions + lesions of arm areas of primary somatosensory cortex and the anterior portion of area 5. Initial post-lesion reach and manipulation skills were similar to or better than pre-lesion skills in most F2 lesion cases in a difficult fine motor task but worse than pre-lesion skill in most F2P2 lesion cases in all tasks. Subsequently, reaching and manipulation skills improved over the post-lesion period to higher than pre-lesion skills in both groups, but improvements were greater in the F2 lesion group, perhaps due to additional task practice and greater ipsilesional limb use for daily activities. Poorer and slower post-lesion improvement of ipsilesional upper limb motor skill in the F2P2 cases may be due to impaired somatosensory processing. The persistent ipsilesional upper limb motor deficits frequently observed in humans after stroke are probably caused by greater subcortical white and gray matter damage than in the localized surgical injuries studied here.

A Case Study of Malrotated Kidneys with Asymmetric Multiple Renal Arteries, Variant Venous Drainage, and Unilateral Ureteral Duplication.

Variations in the arterial, venous, and ureteral patterning of the right (r) and left (l) kidneys are common; however, concomitant involvement with all three systems is rare. Specimens that demonstrate anatomic variation across multiple systems provide an opportunity to illustrate links between anatomic concepts, embryologic development, clinical practice, and education. During anatomic study of the abdominal cavity, a total of five major arteries (3l and 2r) emerged from the aortic and common iliac axes in a cadaveric donor. Through continued study, multiple contributing veins, of different caliber, coalesced into four major renal veins (2l and 2r) that returned blood from the kidneys to the inferior vena cava (IVC) at different locations. In addition, unilateral duplication of the kidney with concomitant ureters was evident on the right side. Both ureters continued inferiorly and independently entered the bladder, each with an observable orifice adjacent to the bladder trigone. Most evident in the specimen was the anteriorly directed hilum for both kidneys. Reported measures for each of the observed anatomic variations suggest that the current specimen has an estimated incidence of less than 0.3%. This comparatively rare specimen provides an example of important anatomic concepts that are relevant to educational and clinical practices.

Terminal organization of the corticospinal projection from the lateral premotor cortex to the cervical enlargement (C5-T1) in rhesus monkey.

High-resolution tract tracing and stereology were used to study the terminal organization of the corticospinal projection (CSP) from the ventral (v) and dorsal (d) regions of the lateral premotor cortex (LPMC) to spinal levels C5-T1. The LPMCv CSP originated from the postarcuate sulcus region, was bilateral, sparse, and primarily targeted the dorsolateral and ventromedial sectors of contralateral lamina VII. The convexity/lateral part of LPMCv did not project below C2. Thus, very little LPMCv corticospinal output reaches the cervical enlargement. In contrast, the LPMCd CSP was 5× more prominent in terminal density. Bilateral terminal labeling occurred in the medial sectors of lamina VII and adjacent lamina VIII, where propriospinal neurons with long-range bilateral axon projections reside. Notably, lamina VIII also harbors axial motoneurons. Contralateral labeling occurred in the lateral sectors of lamina VII and the dorsomedial quadrant of lamina IX, noted for harboring proximal upper limb flexor motoneurons. Segmentally, the CSP to contralateral laminae VII and IX preferentially innervated C5-C7, which supplies shoulder, elbow, and wrist musculature. In contrast, terminations in axial-related lamina VIII were distributed bilaterally throughout all cervical enlargement levels, including C8 and T1. These findings demonstrate the LPMCd CSP is structured to influence axial and proximal upper limb movements, supporting Kuypers conceptual view of the LPMCd CSP being a major component of the medial motor control system. Thus, distal upper extremity control influenced by LPMC, including grasping and manipulation, must occur through indirect neural network connections such as corticocortical, subcortical, or intrinsic spinal circuits.

New Corticopontine Connections in the Primate Brain: Contralateral Projections From the Arm/Hand Area of the Precentral Motor Region.

The ipsilateral corticopontine projection (iCPP) represents a massive descending axon system terminating in the pontine nuclei (PN). In the primate, this projection is well known for its dominant influence on contralateral upper limb movements through the classical cerebrocerebellar circuity system. Although a much weaker contralateral corticopontine projection (cCPP) from motor cortex to the paramedian region has been reported in the non-human primate brain, we provide the first comprehensive description of the cCPP from the lateral motor cortex using high resolution anterograde tract tracing in Macaca mulatta. We found a relatively light cCPP from the hand/arm area of the primary motor cortex (M1), comparatively moderate cCPP from ventrolateral premotor cortex (LPMCv) and a more robust and widespread cCPP from the dorsolateral premotor cortex (LPMCd) that involved all nine contralateral PN. The M1 projection primarily targeted the dorsal pontine region, the LPMCv projection targeted the medial pontine region and LPMCd targeted both regions. These results show the first stage of the primate frontomotor cerebrocerebellar projection is bilateral, and may affect both ipsilateral and contralateral limbs. Clinically, the cCPP originating in the non-injured hemisphere may influence the recovery process of the more affected upper extremity following subtotal unilateral damage to the lateral cortical region. The cCPP may also contribute to the mild impairment of the upper limb contralateral to a unilateral cerebellar injury.

Hand Motor Recovery Following Extensive Frontoparietal Cortical Injury Is Accompanied by Upregulated Corticoreticular Projections in Monkey.

We tested the hypothesis that arm/hand motor recovery after injury of the lateral sensorimotor cortex is associated with upregulation of the corticoreticular projection (CRP) from the supplementary motor cortex (M2) to the gigantocellular reticular nucleus of the medulla (Gi). Three groups of rhesus monkeys of both genders were studied: five controls, four cases with lesions of the arm/hand area of the primary motor cortex (M1) and the lateral premotor cortex (LPMC; F2 lesion group), and five cases with lesions of the arm/hand area of M1, LPMC, S1, and anterior parietal cortex (F2P2 lesion group). CRP strength was assessed using high-resolution anterograde tracers injected into the arm/hand area of M2 and stereology to estimate of the number of synaptic boutons in the Gi. M2 projected bilaterally to the Gi, primarily targeting the medial Gi subsector and, to a lesser extent, lateral, dorsal, and ventral subsectors. Total CRP bouton numbers were similar in controls and F2 lesion cases but F2P2 lesion cases had twice as many boutons as the other two groups (p = 0.0002). Recovery of reaching and fine hand/digit function was strongly correlated with estimated numbers of CRP boutons in the F2P2 lesion cases. Because we previously showed that F2P2 lesion cases experience decreased strength of the M2 corticospinal projection (CSP), whereas F2 lesion monkeys experienced increased strength of the M2 CSP, these results suggest one mechanism underlying arm/hand motor recovery after F2P2 injury is upregulation of the M2 CRP. This M2-CRP response may influence an important reticulospinal tract contribution to upper-limb motor recovery following frontoparietal injury.SIGNIFICANCE STATEMENT We previously showed that after brain injury affecting the lateral motor cortex controlling arm/hand motor function, recovery is variable and closely associated with increased strength of corticospinal projection (CSP) from an uninjured medial cortical motor area. Hand motor recovery also varies after brain injury affecting the lateral sensorimotor cortex, but medial motor cortex CSP strength decreases and cannot account for recovery. Here we observed that motor recovery following sensorimotor cortex injury is closely associated with increased strength of the descending projection from an uninjured medial cortical motor area to a brainstem reticular nucleus involved in control of arm/hand function, suggesting an enhanced corticoreticular projection may compensate for injury to the sensorimotor cortex to enable recovery of arm/hand motor function.

Sensorimotor cortex injury effects on recovery of contralesional dexterous movements in Macaca mulatta.

The effects of primary somatosensory cortex (S1) injury on recovery of contralateral upper limb reaching and grasping were studied by comparing the consequences of isolated lesions to the arm/hand region of primary motor cortex (M1) and lateral premotor cortex (LPMC) to lesions of these same areas plus anterior parietal cortex (S1 and rostral area PE). We used multiple linear regression to assess the effects of gray and white matter lesion volumes on deficits in reaching and fine motor performance during the first month after the lesion, and during recovery of function over 3, 6 and 12months post-injury in 13 monkeys. Subjects with frontoparietal lesions exhibited larger deficits and poorer recovery as predicted, including one subject with extensive peri-Rolandic injury developing learned nonuse after showing signs of recovery. Regression analyses showed that total white matter lesion volume was strongly associated with initial post-lesion deficits in motor performance and with recovery of skill in reaching and manipulation. Multiple regression analyses using percent damage to caudal M1 (M1c), rostral S1 (S1r), LPMC and area PE as predictor variables showed that S1r lesion volumes were closely related to delayed post-lesion recovery of upper limb function, as well as lower skill level of recovery. In contrast, M1c lesion volume was related primarily to initial post-lesion deficits in hand motor performance. Overall, these findings demonstrate that frontoparietal injury impairs hand motor function more so than frontal motor injury alone, and results in slower and poorer recovery than lesions limited to frontal motor cortex.

Dissection and dissection-associated required experiences improve student performance in gross anatomy: Differences among quartiles.

To promote student learning, educational strategies should provide multiple levels of engagement with the subject matter. This study investigated examination data from five first year medical gross anatomy class cohorts (692 students) to determine if enhanced student performance was correlated with learning through dissection in a course that used a rotating dissection schedule coupled with peer teaching and other associated experiences. When students performed two of five weekly dissections for a given unit, their average scores on both laboratory and written examinations tended to increase as compared to when they had completed only one week of dissection (P < 0.01). However, these performance gains differed across the class strata and were related to the amount of dissection completed. Students in the upper quartile (UQS) of the class benefited when they had dissected once (92.8%) or twice (92.4%), and these scores were significantly higher than those attained when learning from peers (90.3%, P < 0.01). Students in the lower quartile (LQS) benefited most from the dissection experiences, where practical examination performance was better (77.8% and 80.5%) than when these students learned material from their peers (73.7%, P < 0.01). Although UQS benefited from dissection, LQS benefited to a greater extent in both the practical and written examinations with dissection. Although limited, these data suggest that dissection, coupled with associated educational activities, is an effective pedagogical strategy for learning. Further investigation is required to evaluate the concomitant benefits of peer teaching that are associated with the dissection experience. Anat Sci Educ 9: 238-246. © 2015 American Association of Anatomists.

Injury risk to extraosseous knee vasculature during osteotomies: a cadaveric study with CT and dissection analysis.

BACKGROUND: Realignment osteotomies about the knee may be performed as distal femoral or proximal tibial osteotomies; both may be performed either on the medial or lateral sides of the knee, in closing- or opening-wedge fashion. Although rare, injury to neurovascular structures may occur, and the proximity of the vascular structures to the osteotomy saw cuts has been incompletely characterized. QUESTIONS/PURPOSES: We performed a cadaver study to assess the risk of vascular injury in patients undergoing realignment osteotomies by (1) quantifying the distances between osteotomy saw cuts and blood vessels using three-dimensional CT reconstruction after distal femoral and proximal tibial osteotomies; and (2) qualitatively describing the small- and medium-sized vasculature around the knee, to provide the link between the CT analysis and wedge incision measures, and better show the potential extraosseous supply to the regions investigated. METHODS: Twelve human cadaveric knees were injected with a latex and barium sulfate suspension into the superficial femoral artery. Each specimen underwent CT to evaluate vascular perfusion and was randomized to either a lateral opening-wedge distal femoral osteotomy and medial opening-wedge proximal tibial osteotomy group, or a medial closing-wedge distal femoral osteotomy and lateral closing-wedge proximal tibial osteotomy group. Postoperatively, knees underwent CT in extension to measure the shortest distance between the osteotomies and the popliteal artery, anterior and posterior tibial arteries, and genicular arteries. Vessels between 5 mm and 10 mm from the osteotomy cut were considered in a zone of moderate risk for damage, while vessels less than 5 mm from the cut were considered in a zone of high risk for damage. Vessels more than 10 mm from the cut were not considered to be at risk. Subsequently, knees underwent dissection and chemical débridement to qualitatively describe the smaller vessels. This part of the study added visual information and gave a comprehensive overview of the vessels at risk. RESULTS: All variations of the osteotomies put at least one artery at risk. The popliteal artery was found in a risk zone for injury in two specimens during closing-wedge distal femoral osteotomy (median distance, 11.6 mm; range, 5.2-14.6 mm). The superior lateral genicular artery was in a risk zone in all the specimens during opening-wedge distal femoral osteotomy (median distance, 3.0 mm; range, 0.7-6.5 mm), and in five specimens during closing-wedge distal femoral osteotomy (median distance, 4.5 mm; range, 1.3-11.2 mm). A concomitant risk for superior medial genicular artery injury was observed in five specimens during opening-wedge distal femoral osteotomy (median distance, 8.7 mm; range, 0.8-13.9 mm) and in four specimens during closing-wedge distal femoral osteotomy (median distance, 4.1; range, 0.5-41.7 mm). The popliteal artery was in a risk zone in four specimens during opening-wedge proximal tibial osteotomy (median distance, 9.6 mm; range, 6.6-12.9 mm), and in three specimens during closing wedge proximal tibial osteotomy (median distance, 9.6 mm; range, 4.4-11 mm). The inferior medial genicular artery could be classified at risk in five specimens during opening-wedge proximal tibial osteotomy (median distance, 2.1 mm; range, 0.3-32 mm) and in five specimens during closing-wedge proximal tibial osteotomy (median distance, 5.8 mm; range, 1.4-13 mm). Furthermore, the inferior lateral genicular artery was found in a risk zone in two specimens of closing-wedge proximal tibial osteotomies (median distance, 17.4 mm; range, 8-23.3 mm). There were no differences between opening-wedge and closing-wedge distal femoral osteotomies and proximal tibial osteotomies in the vessels at risk during the procedure. After chemical débridement, knees showed abundant vascularization of the distal femur and lateral tibia, whereas the medial tibia contained few arteries. CONCLUSIONS: With the numbers available, we found that none of the osteotomy techniques performed was safer than any other in terms of the proximity of the major arterial structures and some vessels appear to be at relatively high risk during these procedures. CLINICAL RELEVANCE: This study clarifies that the genicular arteries on the opposite side of the surgical field, which cannot be seen and protected during the procedure, can be at risk of injury, particularly when the cortical hinge is compromised. Additional studies are necessary to address the potential risk of the dissection needed for plate placement and injuries related to drilling and screw placement during osteotomies around the knee.

Assessing student engagement and self-regulated learning in a medical gross anatomy course.

In courses with large enrollment, faculty members sometimes struggle with an understanding of how individual students are engaging in their courses. Information about the level of student engagement that instructors would likely find most useful can be linked to: (1) the learning strategies that students are using; (2) the barriers to learning that students are encountering; and (3) whether the course materials and activities are yielding the intended learning outcomes. This study drew upon self-regulated learning theory (SRL) to specify relevant information about learning engagement, and how the measures of particular scales might prove useful for student/faculty reflection. We tested the quality of such information as collected via the Motivated Strategies for Learning Questionnaire (MSLQ). MSLQ items were administered through a web-based survey to 150 students in a first-year medical gross anatomy course. The resulting 66 responses (44% response rate) were examined for information quality (internal reliability and predictive validity) and usefulness of the results to the course instructor. Students' final grades in the course were correlated with their MSLQ scale scores to assess the predictive validity of the measures. These results were consistent with the course design and expectations, showing that greater use of learning strategies such as elaboration and critical thinking was associated with higher levels of performance in the course. Motivation subscales for learning were also correlated with the higher levels of performance in the course. The extent to which these scales capture valid and reliable information in other institutional settings and courses needs further investigation.

Fostering interprofessional teamwork in an academic medical center: Near-peer education for students during gross medical anatomy.

The purpose of this report is to describe student satisfaction with a near-peer interprofessional education (IPE) session for physical therapy and medical students. Ten senior physical therapy students worked in peer-groups to develop a musculoskeletal anatomy demonstration for first-semester medical students. Together with their classmates, they demonstrated observation, palpation, and musculoskeletal assessment of the shoulder and scapular-thoracic articulation to medical student dissection groups in the Gross Anatomy laboratory. The medical students were encouraged to consider the synergistic function of shoulder structures and the potential impact of a selected pathology: rotator cuff injury. The session provided the medical students with an opportunity to integrate their new anatomical knowledge into a framework for clinical musculoskeletal evaluation. The experience offered senior physical therapy students an opportunity to work in teams with their peers, internalize and adapt to constructive feedback, and seek common ground with members of another profession. Both student groups reported a high degree of satisfaction with the sessions and expressed a desire for further interaction. These positive perceptions by student stakeholders have prompted us to consider additional IPE exchanges for the anatomy course in the upcoming school year. Given the positive outcome of this descriptive study, we now plan to systematically test whether near-peer IPE interactions can enhance the degree that students learn key anatomical concepts.

Recovery of precision grasping after motor cortex lesion does not require forced use of the impaired hand in Macaca mulatta.

We investigated recovery of precision grasping of small objects between the index finger and thumb of the impaired hand without forced use after surgically placed lesions to the hand/arm areas of M1 and M1 + lateral premotor cortex in two monkeys. The unilateral lesions were contralateral to the monkey's preferred hand, which was established in prelesion testing as the hand used most often to acquire raisins in a foraging board (FB) task in which the monkey was free to use either hand to acquire treats. The lesions initially produced a clear paresis of the contralesional hand and use of only the ipsilesional hand to acquire raisins in the FB task. However, beginning about 3 weeks after the lesion both monkeys spontaneously began using the impaired contralesional hand in the FB task and increased use of that hand over the next few tests. Moreover, the monkeys clearly used precision grasp to acquire the raisins in a similar manner to prelesion performances, although grasp durations were longer. Although the monkeys used the contralesional hand more often than the ipsilesional hand in some postlesion testing sessions, they did not recover to use the hand as often as in prelesion testing when the preferred hand was used almost exclusively. These findings suggest that recovery of fine hand/digit motor function after localized damage to the lateral frontal motor areas in rhesus monkeys does not require forced use of the impaired hand.

Risks to the blood supply of the talus with four methods of total ankle arthroplasty: a cadaveric injection study.

BACKGROUND: Despite the use of contemporary total ankle arthroplasty implant designs, clinical outcomes of total ankle arthroplasty continue to lag behind those of other joint replacement procedures. Disruption of the extraosseous talar blood supply at the time of ankle replacement may be a factor contributing to talar component subsidence-a common mechanism of early failure following ankle replacement. We evaluated the risk of injury to specific extraosseous arteries supplying the talus associated with specific total ankle arthroplasty implants. METHODS: Sixteen fresh-frozen through-knee cadaveric specimens were injected with latex and barium sulfate distal to the popliteal trifurcation to visualize the arteries. Four specimens each were prepared for implantation of four contemporary total ankle arthroplasty systems: Scandinavian Total Ankle Replacement (STAR), INBONE II, Salto Talaris, and Trabecular Metal Total Ankle (TMTA). Postoperative computed tomography scans and 6% sodium hypochlorite chemical debridement were used to examine, measure, and document the proximity of the total ankle arthroplasty instrumentation to the extraosseous talar blood supply. RESULTS: All four implant types subjected the extraosseous talar blood supply to the risk of injury. The INBONE subtalar drill hole directly transected the artery of the tarsal canal in three of four specimens. The lateral approach for the TMTA transected the first perforator of the peroneal artery in two of four specimens. The STAR caused medial injury to the deltoid branches in all four specimens, whereas the other three systems did not directly affect this supply (p < 0.005). The Salto Talaris and STAR implants caused injury to the artery of the tarsal canal in one of four specimens. CONCLUSIONS: All four total ankle arthroplasty systems tested posed a risk of injury to the extraosseous talar blood supply, but the risks of injury to specific arteries were higher for specific implants.

Terminal distribution of the corticospinal projection from the hand/arm region of the primary motor cortex to the cervical enlargement in rhesus monkey.

To further our understanding of the corticospinal projection (CSP) from the hand/arm representation of the primary motor cortex (M1), high-resolution anterograde tracing methodology and stereology were used to investigate the terminal distribution of this connection at spinal levels C5 to T1. The highest number of labeled terminal boutons occurred contralaterally (98%) with few ipsilaterally (2%). Contralaterally, labeled boutons were located within laminae I-X, with the densest distribution found in lamina VII and, to a lesser extent, laminae IX and VI. Fewer terminals were found in other contralateral laminae. Within lamina VII, terminal boutons were most prominent in the dorsomedial, dorsolateral, and ventrolateral subsectors. Within lamina IX, the heaviest terminal labeling was distributed dorsally. Ipsilaterally, boutons were found in laminae V-X. The most pronounced distribution occurred in the dorsomedial and ventromedial sectors of lamina VII and fewer labeled boutons were located in other ipsilateral laminae. Segmentally, contralateral lamina VII labeling was highest at levels C5-C7. In contrast, lamina IX labeling was highest at C7-T1 and more widely dispersed among the quadrants at C8-T1. Our findings suggest dominant contralateral influence of the M1 hand/arm CSP, a contralateral innervation pattern in lamina VII supporting Kuypers (1982) conceptual framework of a "lateral motor system," and a projection to lamina IX indicating significant influence on motoneurons innervating flexors acting on the shoulder and elbow rostrally (C5-C7), along with flexors, extensors, abductors and adductors acting on the digits, hand and wrist caudally (C8-T1).

Laterality affects spontaneous recovery of contralateral hand motor function following motor cortex injury in rhesus monkeys.

The purpose of this study was to test whether brain laterality influences spontaneous recovery of hand motor function after controlled brain injuries to arm areas of M1 and lateral premotor cortex (LPMC) of the hemisphere contralateral to the preferred hand in rhesus monkeys. We hypothesized that monkeys with stronger hand preference would exhibit poorer recovery of skilled hand use after such brain injury. Degree of handedness was assessed using a standard dexterity board task in which subjects could use either hand to retrieve small food pellets. Fine hand/digit motor function was assessed using a modified dexterity board before and after the M1 and LPMC lesions in ten monkeys. We found a strong negative relationship between the degree of handedness and the recovery of manipulation skill, demonstrating that higher hand preference was associated with poorer recovery of hand fine motor function. We also observed that monkeys with larger lesions within M1 and LPMC had greater initial impairment of manipulation and poorer recovery of reaching skill. We conclude that monkeys with a stronger hand preference are likely to show poorer recovery of contralesional hand fine motor skill after isolated brain lesions affecting the lateral frontal motor areas. These data may be extended to suggest that humans who exhibit weak hand dominance, and perhaps individuals who use both hands for fine motor tasks, may have a more favorable potential for recovery after a unilateral stroke or brain injury affecting the lateral cortical motor areas than individuals with a high degree of hand dominance.

Vascular disruption of the talus: comparison of two approaches for triple arthrodesis.

BACKGROUND: For triple arthrodesis, a single medial incision has been proposed to avoid lateral wound complications and has demonstrated satisfactory fusion rates. This study aimed to compare the disruption to the arterial supply of the talus between the single-medial-incision approach and the 2-incision approach. METHODS: The 2 approaches for triple arthrodesis were compared by analyzing the disruption of arterial vasculature in 14 cadaveric specimens in randomized fashion. The arterial disruption was determined using CT angiography before and after surgery combined with analysis from dissection. The area of joint preparation from each technique was also analyzed and compared. RESULTS: The single-medial-incision approach caused a high incidence of damage to the deltoid artery (6 of 7 specimens, 86%) and the artery of the tarsal canal (7 of 7 specimens, 100%). The 2-incision approach resulted in damage to the artery of the tarsal sinus in all specimens (7 of 7 specimens, 100%), but the medial vasculature was spared given the limited dissection required to access the talonavicular joint. Through the single-medial-incision approach the percentage of debridement of the calcaneocuboid joint (36%) was significantly lower than the debridement using the 2-incision approach (85%, P < .01). There was no significant difference in joint preparation of the talonavicular and subtalar joints between the 2 approaches with the number of specimens available. CONCLUSION: From this cadaveric study, we found that both approaches could result in substantial disruption of the main blood supply to the talus. The single-medial-incision approach consistently disrupted the majority of blood supply to the talar body, while the 2-incision approach caused various degrees of vascular disruption to the talar head and neck. Using the single-medial-incision approach, the calcaneocuboid joint did not show adequate removal of articular cartilage due to difficulty accessing the joint surfaces. CLINICAL RELEVANCE: Vascular sparing to the talus should be considered when selecting an appropriate operative approach for triple arthrodesis. Although the clinical significance of this cadaveric study is limited, the 2-incision approach appeared to cause less vascular disruption to the talar body while allowing more complete joint preparation.

Functional recovery following motor cortex lesions in non-human primates: experimental implications for human stroke patients.

This review discusses selected classical works and contemporary research on recovery of contralesional fine hand motor function following lesions to motor areas of the cerebral cortex in non-human primates. Findings from both the classical literature and contemporary studies show that lesions of cortical motor areas induce paresis initially, but are followed by remarkable recovery of fine hand/digit motor function that depends on lesion size and post-lesion training. Indeed, in recent work where considerable quantification of fine digit function associated with grasping and manipulating small objects has been observed, very favorable recovery is possible with minimal forced use of the contralesional limb. Studies of the mechanisms underlying recovery have shown that following small lesions of the digit areas of primary motor cortex (M1), there is expansion of the digit motor representations into areas of M1 that did not produce digit movements prior to the lesion. However, after larger lesions involving the elbow, wrist and digit areas of M1, no such expansion of the motor representation was observed, suggesting that recovery was due to other cortical or subcortical areas taking over control of hand/digit movements. Recently, we showed that one possible mechanism of recovery after lesion to the arm areas of M1 and lateral premotor cortex is enhancement of corticospinal projections from the medially located supplementary motor area (M2) to spinal cord laminae containing neurons which have lost substantial input from the lateral motor areas and play a critical role in reaching and digit movements. Because human stroke and brain injury patients show variable, and usually poorer, recovery of hand motor function than that of nonhuman primates after motor cortex damage, we conclude with a discussion of implications of this work for further experimentation to improve recovery of hand function in human stroke patients.

Volumetric effects of motor cortex injury on recovery of ipsilesional dexterous movements.

Damage to the motor cortex of one hemisphere has classically been associated with contralateral upper limb paresis, but recent patient studies have identified deficits in both upper limbs. In non-human primates, we tested the hypothesis that the severity of ipsilesional upper limb motor impairment in the early post-injury phase depends on the volume of gray and white matter damage of the motor areas of the frontal lobe. We also postulated that substantial recovery would accompany minimal task practice and that ipsilesional limb recovery would be correlated with recovery of the contralesional limb. Gross (reaching) and fine hand motor functions were assessed for 3-12 months post-injury using two motor tests. Volumes of white and gray matter lesions were assessed using quantitative histology. Early changes in post-lesion motor performance were inversely correlated with white matter lesion volume indicating that larger lesions produced greater decreases in ipsilesional hand movement control. All monkeys showed improvements in ipsilesional hand motor skill during the post-lesion period, with reaching skill improvements being positively correlated with total lesion volume indicating that larger lesions were associated with greater ipsilesional motor skill recovery. We suggest that reduced trans-callosal inhibition from the lesioned hemisphere may play a role in the observed skill improvements. Our findings show that significant ipsilesional hand motor recovery is likely to accompany injury limited to frontal motor areas. In humans, more pronounced ipsilesional motor deficits that invariably develop after stroke may, in part, be a consequence of more extensive subcortical white and gray matter damage.