Peter J. Apel

Anterior cruciate ligament injury in pediatric and adolescent soccer players: an analysis of insurance data.

Injury claims from an insurance company specializing in soccer coverage were reviewed for a 5-year period. A total of 8215 injury claims (3340 females, 4875 males) were divided into three categories: (1) all injury, (2) knee injury, and (3) ACL injury. Knee injuries accounted for 22% of all injuries (30% female, 16% male). ACL injury claims represented 31% of total knee injury claims (37% female, 24% males). The youngest ACL injury was age 5. The ratio of knee injury/all injury increased with age. Compared with males, females demonstrated a higher ratio of knee injury/all injury and a higher ratio of ACL injury/all injury. This study demonstrates that ACL injury occurs in skeletally immature soccer players and that females appear to have an increased risk of ACL injury and knee injury compared with males, even in the skeletally immature. Future research related to ACL injury in females will need to consider skeletally immature patients.

Peripheral Nerve Regeneration Using a Keratin-Based Scaffold: Long-Term Functional and Histological Outcomes in a Mouse Model

PURPOSE The management of peripheral nerve injuries with segmental defects is a challenge to both patient and surgeon. Repairs under tension have a poor prognosis; sensory nerve allografts have donor site morbidity and suboptimal motor recovery, but remain the gold standard. The development of conduit-based repair strategies has evolved and these are promising for sensory nerves and short defects; however, no conduit filler is clinically available that improves motor recovery equivalent to sensory autografts. In this study, motor recovery using keratin-based hydrogel filler was compared with that for sensory nerve autografts and empty conduits. METHODS Fifty-four mice were randomized into 3 treatment groups: empty conduit, sural nerve autograft, and keratin hydrogel-filled conduit. Animals were followed for 6 weeks, 3 months, and 6 months. Outcomes included compound motor action potential (CMAP), nerve area, myelinated axon number and density, and myelinated axon diameter. RESULTS Neuromuscular recovery with keratin was greater than with empty conduits in most outcome measures. Nerves that regenerated through the keratin hydrogel had lower conduction delays, greater amplitudes, more myelinated axons, and larger axons than nerves that regenerated through empty conduits. Sensory nerve autografts and keratin hydrogel were statistically equivalent in CMAP measurements at 6 months. Moreover, keratin-filled conduits demonstrated greater axon density and larger average axon diameter than both empty conduits and autograft at 6 months. CONCLUSIONS In a mouse tibial nerve model, keratin hydrogels significantly improved electrophysiological recovery, compared with empty conduits and sensory nerve autografts, at an early time point of regeneration. Keratin hydrogels also produce long-term electrical and histological results superior to empty conduits and equivalent to sensory nerve autografts.

EFFECT OF LOCALLY DELIVERED IGF-1 ON NERVE REGENERATION DURING AGING: AN EXPERIMENTAL STUDY IN RATS

Age is an important predictor of neuromuscular recovery after peripheral nerve injury. Insulin‐like growth factor 1 (IGF‐1) is a potent neurotrophic factor that is known to decline with increasing age. The purpose of this study was to determine if locally delivered IGF‐1 would improve nerve regeneration and neuromuscular recovery in aged animals. Young and aged rats underwent nerve transection and repair with either saline or IGF‐1 continuously delivered to the site of the nerve repair. After 3 months, nerve regeneration and neuromuscular junction morphology were assessed. In both young and aged animals, IGF‐1 significantly improved axon number, diameter, and density. IGF‐1 also significantly increased myelination and Schwann cell activity and preserved the morphology of the postsynaptic neuromuscular junction (NMJ). These results show that aged regenerating nerve is sensitive to IGF‐1 treatment. Muscle Nerve, 2009

Anterior Cruciate Ligament Injury in Paediatric and Adolescent Patients A Review of Basic Science and Clinical Research

Anterior cruciate ligament (ACL) injuries are recognised with greater frequency in children and adolescents. Non-operative treatment of ACL injuries in children may lead to knee instability and secondary injuries, especially in those who return to sports. ACL reconstruction is controversial in skeletally immature patients because of potential damage to the proximal tibial and distal femoral physes, which may lead to premature arrest and/or leg length discrepancies. This paper reviews studies of ACL injuries in children and adolescents, and examines basic science and clinical studies concerning physeal arrest secondary to ACL reconstruction tunnels. Some animal studies support the conclusion that ACL reconstructions in children have the potential to cause growth disturbances, and there are reports of growth plate complications due to ACL reconstruction in skeletally immature patients. There is evidence that ACL reconstruction can be performed in select skeletally immature patients, but the risk of growth plate complications must be considered.

Volumetric Injury of the Physis During Single-Bundle Anterior Cruciate Ligament Reconstruction in Children: A 3-Dimensional Study Using Magnetic Resonance Imaging

PURPOSE To determine the volume of injury to the physis during anterior cruciate ligament (ACL) reconstruction in pediatric patients. METHODS Magnetic resonance imaging scans of 10 pediatric knees were converted into 3-dimensional models. Computer-aided design/computer-aided manufacturing software placed drill holes (6, 7, 8, and 9 mm in diameter) in these models, simulating tunnels used for ACL reconstruction. The software was used to calculate total physeal volume and volume of physis removed by the tunnel. The ratio of physeal volume removed to the total physeal volume was determined. RESULTS For 6-, 7-, 8-, and 9-mm-diameter drill holes, the mean percent of physeal volume removed/total physeal volume was 1.6%, 2.2%, 2.9%, and 3.8%, respectively, for the tibia and 2.4%, 3.2%, 4.2%, and 5.4%, respectively, for the femur. For all subjects, the volume removed was less than 7.0% for the tibia and 9.0% for the femur by use of drill holes from 6 to 9 mm. The tibial drill hole was centrally placed in all cases compared with a more peripheral drill hole placement of the femur. CONCLUSIONS Drill hole placement during ACL reconstruction produces a zone of physeal injury. The overall volume of injury is relatively low, which reduces the risk of physeal arrest. With careful drill hole placement, the region of injury is central on the tibia, and the total volume of injury can be less than 5.0% of the physeal volume. For the femur, the total volume can be less than 5.0% as well. However, the region of injury is peripheral, which carries a higher risk of physeal arrest. CLINICAL RELEVANCE A better understanding of the relation between the ACL and physis may guide the placement of drill holes, which have a lower risk of producing physeal arrest.

How age impairs the response of the neuromuscular junction to nerve transection and repair: An experimental study in rats.

Age is the most important predictor of clinical outcome after peripheral nerve injury. The stability of the neuromuscular junction (NMJ) after denervation is thought to be central to neuromuscular recovery. Stability is characterized by maintenance of the motor endplate and mRNA upregulation of the constituent nicotinic acetylcholinergic receptor (nAChR) subtypes and the muscle regulatory factors (MRFs). The purpose of this study was to determine the effect of age on the recovery and stability of the postsynaptic NMJ after peripheral nerve injury. Young and aged rats underwent transection and repair of the tibial nerve. At 1, 2, 4, 8, or 16 weeks following transection, the gastrocnemius was examined for electrical recovery, NMJ fragmentation and endplate area, mRNA, and protein levels of the MRFs and nAChR subtypes. After nerve injury, aged NMJ exhibited significant fragmentation and loss of motor endplate area while the young NMJ remained relatively stable. Concomitantly, age impaired peak upregulation of the MRFs and nAChRs. However, expression of γ‐nAChR and myogenin after nerve injury was not affected by age. These data support the claim that upregulation of the nAChRs and MRFs may play an important role in maintaining NMJ stability following nerve transection and repair. Furthermore, expression of γ‐nAChR and myogenin does not appear to prevent age‐related NMJ fragmentation and loss of endplate area after nerve injury. These impairments of the aged NMJ response to injury may contribute to the poor neuromuscular recovery seen after nerve injury in this population.

The tibial attachment of the anterior cruciate ligament in children and adolescents: analysis of magnetic resonance imaging

Abstract. Recent studies have demonstrated that skeletally immature athletes with an ACL injury may require surgical reconstruction if they return to high-demand sports. This study used MRI to compare the anatomy of the ACL in skeletally immature and adult subjects. Measurements were recorded in the sagittal plane for the anterior-posterior dimension of the proximal tibia, and the anterior, center, and posterior limits of the ACL, and the roof inclination angle of the femur. These values were compared to established reference values for adult knee anatomy. In skeletally immature women (n=7) the ACL anterior limit, center and posterior limit, and roof inclination angle were 28%, 46%, 63%, and 38°, respectively, compared to 28%, 44%, 60%, and 35° in adult women. In skeletally immature men (n=15) the ACL anterior limit, center, posterior limit, and roof inclination angle were 27%, 43%, 59%, and 40°, respectively, compared to 28%, 44%, 59%, and 37° in adult men. In the younger subjects the overall dimensions of the proximal tibia were smaller than that in adults, but the anatomical landmarks for the ACL were proportional. If ACL reconstruction is performed in skeletally immature subjects, the smaller dimensions of the tibia need to be considered, and the use of anatomical landmarks is an important factor in graft placement

Brachial Plexus Birth Palsy–Associated Shoulder Deformity: A Rat Model Study

PURPOSE Although recovery occurs in the majority of cases of brachial plexus birth palsy (BPBP), long-term shoulder disability is relatively common. The aim of this study was to establish an animal model to study BPBP-associated shoulder deformities. METHODS A right-side C5, C6 root neurotomy was performed under the surgical microscope in 5-day-old Sprague-Dawley rats (N = 9). The contralateral side served as a control. The development of shoulder deformity and range of motion loss were followed longitudinally. Animals were killed 4 months after surgery. Both shoulders were harvested, decalcified, and transected in the axial plane for glenoid version measurement and shoulder histology. RESULTS All animals developed shoulder internal rotation contracture within 4 weeks after the C5, C6 neurotomy. The average shoulder external rotation loss was 52 degrees +/- 7, 59 degrees +/- 10, and 82 degrees +/- 11 in comparison with the control side 1, 2, and 4 months after neurotomy, respectively. Glenoid version changed from 2 degrees +/- 2 of retroversion (left side) to 8 degrees +/- 3 of anteversion. Five shoulders were subluxated clinically with a pseudoglenoid formation observed radiographically. Histologic study demonstrated marked glenoid and humeral head deformities. CONCLUSIONS This neonatal rat model clearly demonstrated typical shoulder deformities similar to that resulting from Erbs palsy. This model can be useful in studying BPBP-associated shoulder deformities.

Effect of Selective Sensory Denervation on Fracture-Healing: An Experimental Study of Rats

BACKGROUND Interactions between the peripheral nervous system and the healing skeleton are poorly understood. Various clinical observations suggest that the nervous system interacts with and promotes fracture-healing. The purpose of this study was to examine the effect of selective sensory denervation on fracture-healing. METHODS Fifty-one Sprague-Dawley rats underwent unilateral placement of an intramedullary rod followed by creation of a standardized femoral fracture. One group of these rats underwent sensory denervation by means of a localized capsaicin injection, and the other did not. Subgroups were allocated for analysis of mRNA expression of collagen I and II and osteocalcin at three, seven, and fourteen days after the fracture. Additionally, histological examination was performed at four weeks; micro-computed tomography, at five weeks; and biomechanical testing, at six weeks. RESULTS The sensory-denervated group had significantly less collagen-I upregulation than the sensory-intact group at three days after the fracture (difference in means, forty-four-fold [95% confidence interval = 22.7 to 65.5-fold]; p < 0.001) and significantly less collagen-II upregulation at seven days after the fracture (difference in means, ninefold [95% confidence interval = 4.3 to 13.8-fold]; p < 0.001). In the sensory-denervated group, the fracture callus had a significantly larger cross-sectional area (difference in means, 15.6 mm(2) [95% confidence interval = 0.78 to 30.5 mm(2)]; p = 0.043) and was less dense. Biomechanical testing revealed that sensory denervation significantly decreased the load to failure (difference in means, 28.7 N [95% confidence interval = 1.2 to 56.2 N]; p = 0.022). CONCLUSIONS Sensory denervation negatively affects fracture-healing. These results offer insight into the nerve-bone interaction following injury.

SOMATOSENSORY EVOKED POTENTIAL MONITORING OF THE BRACHIAL PLEXUS DURING A WOODWARD PROCEDURE FOR CORRECTION OF SPRENGEL'S DEFORMITY

Sprengels deformity is the most common congenital deformity of the shoulder. A known complication of correcting this deformity is brachial plexus palsy. In this study we used somatosensory evoked potential (SSEP) monitoring during correction of a Sprengels deformity and identified an early iatrogenic brachial plexus injury. The operation was modified, and permanent nerve injury was avoided. We recommend that SSEP monitoring be considered in procedures to correct Sprengels deformity. Muscle Nerve 41: 262–264, 2010