Zhang Px

A special healing pattern in stable metaphyseal fractures

Background and purpose — Metaphyseal fractures heal in a rapid fashion that is different from the bone shaft healing process. Animal studies have focused on diaphyseal fractures. We investigated the metaphyseal fracture-healing process in rabbits. Animals and methods — 60 rabbits (divided into 12 groups) underwent proximal tibial osteotomy, anatomical reduction, and fixation with screws. After surgery, the proximal tibiae were harvested at different time points for histology. Results — No obvious osteonecrosis or bone resorption were found 2 weeks after surgery. From day 5 to week 5, woven bone or new trabeculae formed. From week 2, remodeling into lamellar bone started and reached a peak at week 6. These 3 stages overlapped. Histomorphometry showed that the structure changed as a unimodal curve. Interpretation — The healing process of metaphyseal fractures appears to differ from the commonly studied healing process in diaphyseal fractures. It is rapid, and can be divided into 4 histological stages: cellular activation and differentiation, formation of woven bone, transformation of woven bone into lamellar bone, and further remodeling.

Functional Recovery of Denervated Skeletal Muscle with Sensory or Mixed Nerve Protection: A Pilot Study

Functional recovery is usually poor following peripheral nerve injury when reinnervation is delayed. Early innervation by sensory nerve has been indicated to prevent atrophy of the denervated muscle. It is hypothesized that early protection with sensory axons is adequate to improve functional recovery of skeletal muscle following prolonged denervation of mixed nerve injury. In this study, four groups of rats received surgical denervation of the tibial nerve. The proximal and distal stumps of the tibial nerve were ligated in all animals except for those in the immediate repair group. The experimental groups underwent denervation with nerve protection of peroneal nerve (mixed protection) or sural nerve (sensory protection). The experimental and unprotected groups had a stage II surgery in which the trimmed proximal and distal tibial nerve stumps were sutured together. After 3 months of recovery, electrophysiological, histological and morphometric parameters were assessed. It was detected that the significant muscle atrophy and a good preserved structure of the muscle were observed in the unprotected and protective experimental groups, respectively. Significantly fewer numbers of regenerated myelinated axons were observed in the sensory-protected group. Enhanced recovery in the mixed protection group was indicated by the results of the muscle contraction force tests, regenerated myelinated fiber, and the results of the histological analysis. Our results suggest that early axons protection by mixed nerve may complement sensory axons which are required for promoting functional recovery of the denervated muscle natively innervated by mixed nerve.

Radiological evaluation of reduction loss in unstable proximal humeral fractures treated with locking plates.

PURPOSE The aim of this study was to radiologically evaluate the risk of reduction loss after locking plate fixation of proximal humerus fractures. METHODS From September 2007 to April 2009, 71 patients (28 males, 43 females) with unstable proximal humeral fracture were treated with open reduction and internal fixation by locking plate. The mean follow-up time was 31.2 months (range: 26-47). The head-shaft angulation (HSA) and the humeral head height (HHH) in true anteroposterior (AP) were recorded and compared over time. All complications were noted. Shoulder function was measured by the Constant score. RESULTS Patients with ΔHSA >10° (t=2.740, P=0.008) and ΔHHH >5mm (t=2.55, P=0.019) were more likely to have impaired shoulder function. Varus collapse occurred most frequently in patients with initial reduction of HSA <125° (χ(2)=19.17, P<0.001, Fishers exact test F<0.001). Patients with >5mm HHH decrease were strongly associated with loss of reduction (χ(2)=24.23, P<0.001, F<0.001). CONCLUSIONS Dynamic change of HSA >10° and HHH >5mm were radiological factors that indicated poor shoulder function. Intra-operative HSA >125° should be achieved to avoid reduction loss following locking plate fixation of proximal humerus fracture. LEVEL OF EVIDENCE level IV.

Hypothesis of peripheral nerve regeneration induced by terminal effectors

Abstract Peripheral nerve injury (PNI) is a common trauma in clinical practice. A number of techniques to deal with PNI repair have been designed in clinics. From these methods for nerve repairing shown to be effective in clinics, as well as related experiments, we formulated a hypothesis that PNI regeneration and functional repair are induced by terminal effectors. Regeneration of peripheral nerves is the process whereby the nerve fibers regenerated by the induction of terminal effectors establish connections with effector organs and induce the spinal cord and upper centers to recognize effector organs and to re-model them for effective innervations. The hypothesis has two major components: (1) after surgical repairing of the injured nerves, the functional localization of regenerated nerves is determined by the connected effector organs and (2) the upper nervous system enables structural remodeling and functional changes according to the functions of the effector organs.

Effect of Modified Formula Radix Hedysari on the Amplification Effect during Peripheral Nerve Regeneration

Many studies have demonstrated a compensatory amplification phenomenon during nerve regeneration. When a relatively fine nerve is used as a donor to connect to a distal nerve after transection, the donor nerve regenerates more collaterals than its own fibers, which extend to the distal stump, grow into distal endoneurial tubes, and finally reach and dominate the target organs. This is known as the amplification phenomenon. In this study, we investigated the amplification phenomenon in rats treated with Modified Formula Radix Hedysari (MFRH) as adjuvant therapy for 12 weeks. The rats were divided into three groups at random (six animals in each group). In the model group and the treatment group, the proximal common peroneal nerve was used as a donor nerve to connect to the distal tibial nerve. Rats in the normal group did not undergo surgery. After surgery, the treatment group was administered MFRH as systemic therapy, while the model group and the normal group were not given treatment. The results demonstrated that the nerve conduction velocity, the fiber diameter, the axon diameter, the number of regenerating nerve fibers, and the amplification ratio were better in the treatment group than in the model group, suggesting that MFRH promoted the nerve amplification effect.

Morphological study on the collaterals developed by one axon during peripheral nerve regeneration

Abstract Outgrowth of collateral sprouts from axons is a natural process that arises during development of and regeneration in the peripheral nervous system. Our previous study showed that if there are enough distal endoneurial tubes into which the proximal regenerative axons can grow, one axon can support three to four collaterals, at most. Here, the proximal half tibial nerve was fixed to the distal stump and served as the donor nerve. The number of myelinated axons was calculated after 4 months. The ratio of distal regenerative myelinated axon number to proximal donor nerve axon number was 1.83 with the tibial function index and the nerve conduction velocities of − 48.6 ± 6.8 and 27.8 ± 5.3 m/s. The regenerated collaterals were isolated and observed to sprout from the node of Ranvier with almost the same features of normal fibers, but with different electrophysiological characteristics. This finding shows the evidence of one-axon trunk several-collateral model in peripheral nerve regeneration and suggests that such multi-collateral regeneration model may be useful in peripheral nerve reconstruction.