Mitigating Factors in L4 and L5 Medial Branch Motor Stimulation During Radiofrequency Ablation.

PURPOSE OF REVIEW: Radiofrequency ablation (RFA) is a minimally invasive procedure for facet joint pain. The targets for the procedure are the medial branches of the dorsal spinal nerves which innervate the facet joints. Before RFA, patients undergo diagnostic meal branch blocks to ensure appropriate pain relief and confirm the utility of proceeding to RFA. The success of RFA relies heavily on procedural technique and accurate placement near the medial branch. RECENT FINDINGS: Motor testing is utilized in the lumbar region to assess the response of the multifidus and ensure proper placement of the RFA probe to prevent inadvertent damage to surrounding spinal anatomy. However, relying on motor responses in this area presents challenges given the frequency of lack of muscle twitching. Factors contributing to limited muscle twitch responses include muscle atrophy, excessive lordosis, facet arthropathy, local anesthetic use before ablation, and previous surgical neurotomy. These complexities highlight the challenges in ensuring precise motor stimulation during RFA. Despite these obstacles, accurate anatomical placement remains crucial. For RFA cases that prove challenging, relying on anatomical placement can be adequate to proceed with the procedure. Bridging knowledge gaps is vital for standardized practices and safer procedures. Further research is necessary to refine techniques, understand patient-specific factors, and enhance the efficacy of RFA in managing chronic lumbar facet joint pain.

Getting control of hydrogel networks with cross-linkable monomers.

The structure of a hydrogel network determines its ability to dissipate stress upon deformation, as well as its ability to swell in water. By designing systems with cross-linkable thiol groups in the monomers, radical thiol-ene chemistry was used to form controlled networks for acrylamide monomers. The use of radical thiol-ene chemistry effectively suppressed homo-polymerization of the bis(acrylamide) monomer and resulted in networks of alternating thiol and acrylamide monomers. Additionally, if the stoichiometry between the monomers is controlled, the network should approach that of ideality. In the case of bis(acrylamide) monomers, the incorporation of hydrogen-bond donors into the network creates a single network hydrogel with the benefits of high strength and ductility from the simultaneous incorporation of chemical and physical cross-links. Additionally, this strategy suppresses the formation of homo-polymerization in the acrylamide monomer to achieve an alternating network, which is supported with NMR characterization of base-digested fragments. For three different monomer compositions, the resulting gels had high compressive strength (up to 40 MPa) and tunable mechanical properties. The high mechanical strength of the 1 : 1, thiol : ene gel composition is due to the uniform distribution of cross-links, which creates defect-free networks for efficient stress transfer. The present one-pot synthetic strategy toward controlled gel networks affords monomer versatility and synthetic ease, as well as the potential for mechanically robust materials.

Mechanical properties of bioabsorbable meniscal arrows as a function of tear location: an ex vivo experimental study.

BACKGROUND: Ex vivo studies have established that arrow fixation of meniscal tears is inferior to vertical sutures and is dependent on arrow length, although the influence of tear location is not known. HYPOTHESIS: Arrow length and tear location influence the mechanical properties of meniscal arrows. STUDY DESIGN: Controlled laboratory study. METHODS: A longitudinal incision was created either 2 mm or 7 mm from the periphery in 70 bovine medial menisci. Each was repaired with a meniscal arrow (10, 13, or 16 mm) or a single vertical suture and subjected to load-to-failure testing and video-graphic analysis. RESULTS: Mode of failure (P <.0001), maximum force (P <.0001), stiffness (P <.01), 2-mm gap force (P <.03), and ultimate gap formation (P <.002) were all directly related to arrow length. Sixteen-mm arrows and suture exhibited similar, superior mechanical properties. Tear location significantly influenced properties of 10-mm and 16-mm but not 13-mm arrows. Ten-millimeter arrows displayed the worst performance. CONCLUSIONS: Mechanical properties of meniscal arrows depend on tear location and arrow length. CLINICAL RELEVANCE: Sixteen-millimeter arrows are a possible alternative to suture for repair of central tears. Thirteen-millimeter arrows may be effective for central and peripheral tears. Ten-millimeter arrows should not be used.

A protocol for treatment of unstable ankle fractures using transarticular fixation in patients with diabetes mellitus and loss of protective sensibility.

BACKGROUND: Surgical treatment of ankle fractures in patients with diabetes mellitus is associated with a high complication rate. Diabetic patients with peripheral neuropathy are a particularly difficult group to treat because of their inability to sense deep infection, repeat trauma, and wound complications. The purpose of this study was to evaluate a protocol that included transarticular fixation and prolonged, protected weightbearing in the treatment of unstable ankle fractures in diabetic patients with peripheral neuropathy and loss of protective sensibility. METHODS: The authors retrospectively reviewed the records of 15 patients with diabetes mellitus, unstable ankle fractures (AO classification 44B), and loss of protective sensibility confirmed via testing with a 5.07 Semmes-Weinstein monofilament. Retrograde transcalcaneal-talar-tibial fixation using large Steinmann pins or screws in conjunction with standard techniques of open reduction and internal fixation was used. The postoperative treatment protocol included: 1) short leg, total contact casting and nonweightbearing status for 12 weeks; 2) removal of the intramedullary implants between 12 and 16 weeks; 3) application of a walker boot or short leg cast with partial weightbearing for an additional 12 weeks; and 4) transition to a custom-molded ankle-foot orthosis (AFO) or custom total-contact inserts in appropriate diabetic footwear. RESULTS: The major complication rate for all fractures was 25% (4/16) and for closed fractures was 23% (3/13). These are lower than previously reported rates between 30% (3/10) and 43% (9/21) for diabetic patients with and without neuropathy. The amputation rate for all fractures was 13% (2/16) and for closed fractures alone was 8% (1/13). These are similar to previously reported rates of 10% (2/10) to 20% (2/21). There were no deaths or Charcot malunions in this series. The combination of transarticular fixation and prolonged, protected weightbearing provided 13 of 15 patients with a stable ankle for weightbearing. CONCLUSION: Although these fractures remain a treatment challenge, this study presents a successful, multidisciplinary protocol for treatment of unstable ankle fractures in the most challenging group of diabetic patients - those with loss of protective sensibility.

Treatment of rigid hypertrophic posttraumatic pseudarthrosis of the tibia in children using distraction osteogenesis.

Posttraumatic tibial pseudarthrosis is a relatively uncommon complication of tibia fractures in children. Although reported as a successful method of treating tibial nonunions in adults, distraction osteogenesis through a nonunion site via ring external fixation has not been described in children. The authors report three consecutive cases of distraction through an angulated, shortened, hypertrophic, posttraumatic nonunion to achieve successful union and concurrent correction of deformity. Distraction was carried out using a ring fixator with computer-guided correction. Union was achieved in each of the three patients with complete correction of deformity and length. Lengthening of 8 to 31 mm was achieved. The length of time in the external fixator ranged from 7 to 27 weeks. Pin tract infections developed in all patients; they were treated successfully using oral antibiotics. No deep infections or other significant complications developed. Each patient was followed up for at least 1 year.