Defining a safe zone of dissection during the extensor digitorum communis splitting approach to the proximal radius and forearm: an anatomic study.

PURPOSE: The extensor digitorum communis (EDC) splitting approach is a direct lateral approach that can provide greater visualization of the proximal radius than the posterolateral approach to the elbow. The purposes of this study were to identify the anatomic relationships of the posterior interosseous nerve (PIN) during the EDC splitting approach to the proximal radius and to determine its safe zone. METHODS: A fellowship-trained attending hand surgeon performed the EDC splitting approach on 15 cadaveric arms, exposing the EDC origin from the lateral epicondyle and dissecting distally to expose the supinator muscle. Calipers were used to measure the distance from the PIN to the radiocapitellar joint and to the lateral epicondyle in neutral position, full supination, and full pronation. The depth of the nerve from the most superficial aspect of the EDC was recorded for each cadaver. RESULTS: The average distances from the radiocapitellar joint to the PIN in neutral, supination, and pronation were 44.5 +/- 7.9, 40.8 +/- 8.1, and 48.2 +/- 7.9 mm, respectively. The average distances from the lateral epicondyle to the PIN in neutral, supination, and pronation were 61.7 +/- 10.9, 57.6 +/- 9.1, and 64.7 +/- 11.5 mm, respectively. The shortest distance measured from the radiocapitellar joint to the PIN in pronation was 29 mm; the shortest distance measured from the lateral epicondyle to the nerve was 42 mm. The average depth of the nerve from the most superficial aspect of the EDC was 10.2 +/- 2.4 mm. CONCLUSIONS: The PIN is generally safe when dissecting up to 29 mm from the radiocapitellar joint and up to 42 mm from the lateral epicondyle with the forearm in pronation.

Comparison of needle position proximity to the median nerve in 2 carpal tunnel injection methods: a cadaveric study.

PURPOSE: Steroid injections are commonly performed by hand surgeons for relief of symptoms associated with carpal tunnel syndrome. The purpose of this study is to examine the relationship of the needle to the median nerve within the carpal tunnel and to the palmar cutaneous branch, using 2 injection techniques. METHODS: Simulated carpal tunnel injections were performed on 15 cadaveric arms using 2 methods. The first injection used a widely accepted approach in which the needle is inserted at the wrist crease, just ulnar to the palmaris longus, and directed at a 30 degrees angle to the horizontal. In the second method, the needle is positioned just ulnar to the palpable ulnar border of flexor carpi radialis and angled 30 degrees to the horizontal. Specimens were dissected using an open carpal tunnel release. Calipers measured the distance from each needle to the median nerve within the carpal tunnel and to the palmar cutaneous branch. RESULTS: Using the first injection method, the needle pierced the median nerve in 4 specimens, and its mean distance from the nerve measured 1.34 mm +/- 1.83 mm. With the second injection method, the median nerve was pierced in 1 specimen, and the needle averaged a distance of 4.79 mm +/- 3.96 mm from the nerve. In the first approach, the needle averaged 9.47 mm +/- 4.11 mm from the palmar cutaneous branch, compared to 1.74 mm +/- 1.59 mm with the second technique. CONCLUSIONS: Physicians must exercise caution when performing carpal tunnel injections to avoid intraneural injection. The needle was a statistically significant shorter distance to the median nerve with the traditional injection method; however, the alterative method risks injury to the palmar cutaneous branch of the median nerve.

Effects of a novel sterilization process on soft tissue mechanical properties for anterior cruciate ligament allografts.

BACKGROUND: Allograft anterior cruciate ligament reconstruction provides benefits such as earlier return to activities and less pain, but concerns remain regarding potential infection and biomechanical stability. HYPOTHESIS: There is no difference in biomechanical properties of soft tissue allografts treated with the Biocleanse tissue sterilization process compared with irradiated and fresh-frozen allografts. STUDY DESIGN: Controlled laboratory study. METHODS: Thirty-six tibialis anterior allografts were equally divided between Biocleanse, irradiated, and fresh-frozen groups. Grafts were measured for cross-sectional area and looped over a smooth rod with the free sutured ends of the graft fixed in custom clamps. Specimens were tensioned to 10 N for 2 minutes and then loaded between 50 and 300 N for 1000 cycles followed by a failure test. Data for creep (mm); stiffness (N/mm) at cycles 1, 10, 100, and 1000; failure load (N); and failure stress (MPa) were compared with a one-way analysis of variance (P < .05). RESULTS: There were no statistically significant differences in creep between groups. Sterilized groups (irradiated = 144.7 +/- 17.7 N/mm and Biocleanse = 146.5 +/- 28.2N/mm) were significantly stiffer during the first cycle than the fresh-frozen group (117.8 +/- 15.7 N/mm, P < .005) without statistically significant differences for subsequent cycles. There were no differences between groups for either failure load (fresh-frozen = 1665 +/- 291.3 N, irradiated = 1671.9 +/- 290.2 N, Biocleanse = 1651.6 +/- 377.4 N) or failure stress. CONCLUSION: Data for "time-zero" physiologic stiffness and failure loads indicate that the Biocleanse process does not adversely affect the biomechanical properties of the allograft material. CLINICAL RELEVANCE: This novel sterilization technique may provide surgeons with potential allograft material with similar biomechanical properties to native tissue.

High-molecular-weight hyaluronan inhibits macrophage proliferation and cytokine release in the early wound of a preclinical postlaminectomy rat model.

BACKGROUND CONTEXT: Failed back syndrome, a condition that affects 3-14% of postoperative spine patients, is characterized by the recurrence of radicular pain after spinal decompression. The source of this pain in some patients is thought by many investigators to be the result of epidural scarring and nerve root tethering, but this is controversial. We have previously demonstrated that in a disc-injury model the untreated postlaminectomy rats develop a significant proliferative fibrous response at 8 weeks with spinal nerve scarring to the disc and adjacent pedicle, and increased sensitivity to tactile allodynia testing in the related sensory dermatome. Topical high-molecular-weight hyaluronan (HMW HA) moderates both the proliferative fibrosis and the behavioral pain response. PURPOSE: Our purpose is to study the time-related changes in the proinflammatory cytokine and monocyte/macrophage profiles in the epidural space in the early postlaminectomy untreated and HMW HA gel treated groups. STUDY DESIGN/SETTING: A modified rat laminectomy with disc injury model was employed to assess epidural fibrosis between and around the spinal nerves using a quantitative immunohistochemistry assessment approach along with correlative enzyme-linked immunosorbent assay analysis. METHODS: Lumbar laminectomies at L5 and L6 with a L5-L6 disc injury were performed on 120 adult male Sprague-Dawley rats. The rats were then randomized into one of two groups: untreated and treated. The treatment group received a one-time topical application of 0.1 cc of HMW HA gel directly to the laminectomy site just before wound closure. The rats were then randomly subdivided into survival periods of 24 hours, 72 hours, and 7 days. Immunohistochemistry was performed on fresh frozen sections and stained for interleukin-1 beta (IL-1beta) and monocytes/macrophages (ED-1) using monoclonal antibodies and 3, 3' diaminobenzidine (DAB) chromogen. The amount of stain in each specimen was then quantified using the National Institutes of Health computer imaging analysis system. RESULTS: The semiquantified data from the histological specimens demonstrated significant decreases in the IL-1beta and IL-6 infiltration observed at 24 hours in the epidural space and around the right nerve root (p=.0296 and 0.0195, respectively) in the HA gel treated group. Additionally, significant decreases in the monocyte/macrophage infiltration were observed at 72 hours in the epidural space around the left nerve root (p=.0039) and right nerve root (p=.0072) in the HA gel treated group. At 7 days, IL-1beta, IL-6, and macrophage infiltration of the wound had declined in both the HA gel and the untreated groups. The enzyme-linked immunosorbent assay data support the same pattern as seen in the histological results. CONCLUSION: These results demonstrate that treatment of postlaminectomy wounds with HMW HA gel decreases the number of monocytes and macrophages and the concentration of certain cytokines in the early inflammatory phase of healing. There are several plausible explanations for this effect. First, the HMW HA may block the interaction of short-chain low-molecular-weight HA with proinflammatory cell surface receptors. The interaction of these short-chain oligo-HA fragments, upon cell-surface receptor binding, induces changes in inflammatory cells that lead to increased cell motility and migration into the wound area. Second, the addition of exogenous HMW HA may cause a dilution effect in the wound, thereby decreasing the concentration of inflammatory cells in the extracellular matrix of the region of injury. Finally, the migration of inflammatory cells may be decreased in the viscous environment of the HMW HA. The first explanation is believed by the authors of this paper to be the more likely mechanism. HMW HA probably mutes the proinflammatory effects of the low-molecular weight fragments, leading to decreased inflammation, and thus decreased fibrosis and scar formation noted in the chronic model.

Paraspinal muscle vasculature contributes to posterolateral spinal fusion.

STUDY DESIGN: Study of posterolateral fusions in a rabbit model. OBJECTIVES: To characterize the contribution of paraspinal musculature to the healing of posterolateral spinal fusions in a rabbit model. SUMMARY OF BACKGROUND DATA: Previous studies have demonstrated that successful spinal arthrodesis requires vascular ingrowth from adjacent decorticated bone. In other areas of the body, such as the tibia, vascular ingrowth from the surrounding musculature has also been shown to be important. The role of the surrounding paraspinal musculature in spinal fusions has yet to be assessed. METHODS: Twenty-five New Zealand white rabbits underwent posterolateral spinal fusion. One side of the animals was treated with autograft alone and served as the control group. On the contralateral side, the autograft was contained within porous or nonporous barrier sheets. Following euthanization, high-resolution radiographs, CT scans, and histologic analyses were performed to assess fusion and characterize vascular ingrowth. RESULTS: Using histologic evaluation, the fusion rate in the porous group was 90%, in the nonporous group 40%, and in the control group 55%. Vascular ingrowth was evident from the muscle through the porous sheet into the fusion mass. CONCLUSIONS: These results support our hypothesis that the paraspinal musculature provides important vascular ingrowth into the fusion site. Use of a porous barrier sheet appears to improve fusion by preventing muscle interposition while allowing vascular ingrowth from surrounding muscle.

Topical high molecular weight hyaluronan reduces radicular pain post laminectomy in a rat model.

BACKGROUND CONTEXT: A controversy exists about the mechanism of causation of the post-laminectomy pain syndrome. Some believe that epidural scarring, and attendant spinal nerve and nerve root scarring and tethering to the disc or pedicle at the site of surgery contributes to post-laminectomy pain in such patients. However, clinical outcome studies on this question are inconclusive and the assertion remains controversial. Definitive studies to help resolve the question are needed. Previously our laboratory has reported on a preclinical post-laminectomy model that mimics the postoperative proliferative fibrotic response grossly, as well as by biochemical assessment of the collagen content within the spinal canal. The post-laminectomy fibrotic response was attenuated in that study by application of a topical antifibrotic (high molecular weight hyaluronan gel) or by insertion of an absorbable roofing barrier (0.2-mm-thick Macropore sheet material) over the laminectomy defect before wound closure. The question remains of relevance of the attenuation of the fibrotic response to post-laminectomy chronic pain syndromes. PURPOSE: The purpose of this study is to evaluate the effect of therapeutic attenuation of proliferative scar within the spinal canal post laminectomy on the pain-related behavioral response in a preclinical rat model. STUDY DESIGN/SETTING: An established L5-L6 rat laminectomy model with a unilateral L5-6 disc injury was employed to assess postoperative proliferative fibrosis of the L5 spinal nerves using quantitative biochemical hydroxyproline assessment of the collagen content in four experimental groups. These observations were correlated with gross descriptions of spinal nerve scarring or tethering. Associated manifestations of a sensory pain-related response in the L5 spinal nerve receptor area of the hind paws was studied using standard tactile allodynia assessment with the von Frey hair technique. The tactile allodynia findings were supplemented by weekly descriptors of behavioral pain manifestations. METHODS: Bilateral laminectomies at L5 and L6 and a unilateral right disc injury (L5-6) were performed on 35 male adult Sprague-Dawley rats, weighing 400+ grams (approved by the VA Institutional Animal Care Use Committee). The study consisted of four groups: 1) normal nonoperative control; 2) a sham-operated group; 3) an untreated laminectomy-disc injury group; and 4) a laminectomy-disc injury treatment group in which 0.1 cc topical high molecular weight hyaluronan (HMW HA) gel was layered over the dura and into the laminectomy canal before closure. Before animals were entered into the study, they were checked for the presence of abnormal response to the tactile testing procedure of the L5 sensory receptor area. Animals exhibiting anomalous responses were excluded from the study. Behavioral testing for tactile allodynia was performed at weekly intervals post laminectomy beginning at 3 weeks. Pain-related behavior was characterized at weekly intervals. A behavioral test cage with a wire mesh floor allowed for tactile allodynia testing. Graduated von Frey hairs whose stiffness increased logarithmically from 0.41 to 15 g were used for tactile allodynia tests. The animals were killed 8 weeks postoperatively for analysis. The dissected spinal nerve and nerve root specimens were studied biochemically for hydroxyproline content to estimate total collagen in and around the L5 neural structures. Statistical analyses were performed using analysis of variance and a Fisher comparison t test. RESULTS: The major observations on the untreated preclinical post-laminectomy rat model previously described by this laboratory were confirmed. All untreated animals developed a tail contracture concave toward the right (disc injury side) consistent with asymmetrical lumbar muscle spasm. Only one animal in the HA gel treatment group had a tail contracture. It was of mild degree and occurred in an animal that demonstrated slightly increased right L5 tactile sensitivity. Gross inspection of the dissected specimens demonstrated spinal nerve scarring and tethering to the disc and pedicle greater on the right than the left in untreated animals, findings that were markedly reduced in the treatment group. Collagen content of the L5 spinal nerve and nerve roots with attached scar were significantly lower in the HA gel treatment group than in the untreated laminectomy group (p=.0014). Pain behavioral testing of the L5 receptor area of the right hind paw in the untreated laminectomy group showed markedly increased sensitivity to tactile allodynia testing compared with the corresponding limb of the control group (p=.0001), to the corresponding limb of the sham group (p=.0001), and compared with the HMW HA gel treatment group (p=.0010). Comparisons of the pain behavioral data between the sham and the post-laminectomy HA gel treatment group and the control animals lacked statistical significance. CONCLUSION: This study supports the concept of a relationship between perineural fibrosis and radicular neuropathy in the model described, and emphasizes the role of disc injury and spinal nerve retraction in the post-laminectomy fibrotic process. Furthermore, it shows promise for preliminary assessment of interventions with other anti-inflammatory agents, for characterization of the neurochemical profile of the post-laminectomy pain state, and for exploration of newer pharmaceutical agents potentially useful in the prevention or management of the post-laminectomy syndrome. Post-laminectomy scar is but one of many potential causes of the post-laminectomy pain syndrome. Furthermore, a cautionary note must be emphasized as in all studies using preclinical models, conclusions drawn from the studies cannot be extended directly to patients without confirmatory clinical follow-up studies.

Brachymetatarsia.

Brachymetatarsia is a rare clinical entity that presents a complicated case to the treating surgeon. One-stage lengthening procedures with a variety of biologic and synthetic implants are preferred for metatarsals that only need to be lengthened up to 15 mm, whereas gradual lengthening allows for greater length gain and concomitant lengthening of the soft tissues. Adjacent metatarsal shortening may be used in conjunction with lengthening procedures to restore the parabolic arc of the metatarsal heads. Management should be tailored to the patient's individual deformity and expectations. Individualization of surgical techniques and patient selection criteria can result in a cosmetic, functional result that is satisfactory to the clinician and the patient.