Ideal Length and Diameter for Intramedullary Screw Fixation of Metacarpal Fractures: A Biomechanical Study.

Purpose: This biomechanical study evaluated the effect of intramedullary screw diameter and length relative to 3-point bending force and torsional force when used to stabilize metacarpal shaft fractures. Methods: Transverse osteotomies were made in the proximal metacarpal shaft in 36 middle finger metacarpal fourth-generation composite Sawbones. To compare screw diameters, antegrade intramedullary screws of 30-mm length were placed in 6 metacarpals, which included 4.7-mm Acutrak 2, Standard Acutrak 2 (4.0 mm), and Mini-Acutrak 2 (3.5 mm) screws. To compare screw lengths, metacarpals were fixated with Standard Acutrak 2 screws of 26, 30, or 34 mm in length, with screw tips bypassing the osteotomy by 6, 10, or 14 mm, respectively. A 6 degrees of freedom robot was used for torsional and 3-point bending testing. Results: Increasing screw diameter demonstrated significant differences in both 3-point bending and torsional strengths. Maximum torsional loads were 69 Ncm (4.7-mm Acutrak 2), 45 Ncm (Standard Acutrak 2), and 27 Ncm (Mini-Acutrak 2) (P < .05). Loads to failure in the 3-point bending tests were 916 N (4.7-mm Acutrak 2), 713 N (Standard Acutrak 2), and 284 N (Mini-Acutrak 2) (P < .05). Differing screw lengths demonstrated significant differences with maximum torsional loads when comparing the 26-mm screws (22 Ncm) with 30- and 34-mm screws (45 and 55 Ncm, respectively) (P < .05). The 3-point dorsal bending strengths were significantly different between the 26-mm screws (320 N) and 30- and 34-mm screws (713 N and 702 N, respectively) (P < .05). Conclusions: The results demonstrated significantly higher torsional strength and resistance to 3-point bending with larger intramedullary screw diameters. Further, when selecting the intramedullary screw length, the screw tip should pass at least 10 mm beyond the fracture. Clinical Relevance: This study provided biomechanical evidence to guide surgeons in selecting intramedullary screw diameter and length for treating metacarpal fractures.

Gait outcomes following proximal tibial tumor resection and endoprosthetic reconstruction.

BACKGROUND: Despite the proximal tibia being a common site of primary malignant bone tumors, there is limited information about gait function following proximal tibial tumor resection and endoprosthetic reconstruction (PTR). RESEARCH QUESTION: What is the impact of PTR on gait and quality of life? METHODS: This was a cross-sectional study of patients ≥18 years old who were ≥2 years post-PTR compared to a control group of similar age and sex distribution. Eighteen participants (9 PTR, 9 Control) were recruited. Gait spatial-temporal data, joint kinematics and kinetics were collected at preferred and fast walking speeds. Community walking cadence, health-related quality of life (SF-36) and knee joint torque were assessed. Comparisons were performed using one-way ANOVAs with Bonferroni corrections for multiple comparisons. Nonparametric tests were used for data not normally distributed. RESULTS: Mean age was 31 years for each group (PTR range = 18-42 yrs, Control range = 18-44 yrs). Compared to both control and nonsurgical limbs, the surgical limb exhibited significantly decreased % single limb support time, reduced heel rise during terminal stance and an absence of normally occurring knee flexion angles, extensor moments and power generation during initial double limb support. Additionally, a reduced peak plantar flexor moment was found for the surgical as compared to the control limb. The number of gait abnormalities increased during fast walking. Significantly reduced surgical knee extensor torque on isokinetic testing and weakness of the knee and ankle on clinical examination support gait findings. During community walking, the number of low frequency strides was an average of 5.3 % greater for the PTR group (p <  0.05). Norm-based PTR group SF-36 component scores were within normal values (53.4 physical, 56.5 mental). SIGNIFICANCE: Gait abnormalities were consistent with ankle muscle resection and transposition and knee extensor mechanism disruption. Despite these deficits, walking speed and quality of life were relatively normal.

Closed Ring Avulsion Injury With Isolated Arterial Insufficiency.

Ring avulsion injuries are an uncommon, often catastrophic, pattern of digit injuries that result from sudden traction onto a ring-bearing digit. The reconstructive treatment of these injuries can be complex because of the characteristic involvement of nerves, muscles, vasculature, and bone. There is paucity of literature describing isolated arterial injuries in the absence of overlying soft tissue and underlying bone involvement. We present an unusual case of a closed ring avulsion injury, wherein a patient initially presented to his local urgent care center with a cool and pale digit without wounds or fractures, and abnormal pulse oximetry readings prompted his transfer to a tertiary care center for further evaluation. Surgical exploration demonstrated isolated disruption of both digital arteries and the preservation of both digital nerves. The digit was successfully revascularized with venous autografting and stripping of arterial thrombi.

Effects of tibiofemoral compression on ACL forces and knee kinematics under combined knee loads.

Injuries to the anterior cruciate ligament (ACL) can occur during landing from a jump or changing direction during a cutting maneuver. In these instances, the knee is subjected to combined forces and moments as it flexes under tibiofemoral compression force (TCF). We hypothesized that TCF would increase ACL forces and tibiofemoral motions under isolated and combined modes of loading relevant to knee injury. ACL force and knee kinematics were recorded in human cadaveric specimens during knee flexion from 0° to 50° under the following test conditions (alone and in combination): 2 N-m internal tibial torque (IT), 5 N-m valgus moment (VM), and 45N anterior tibial force (AF). Knees were tested with 25N (baseline), 250N, and 500N TCF. ACL force increased with knee flexion during all tests. As the knee was flexed, VM produced a coupled internal tibial rotation, and IT produced a coupled valgus rotation. ACL forces with IT + VM were significantly higher than with IT alone (beyond 10° flexion) or VM alone (at all flexion angles). Increasing the level of TCF above baseline did not significantly change valgus or tibial rotations for any loading condition, but did significantly increase anterior tibial translation (ATT) at all flexion angles and ACL force at flexion angles beyond 5° to 15°. Addition of AF to tests with IT + VM significantly increased ATT and ACL force without significantly altering internal and valgus rotations. The mechanism of high ACL force generation from increased TCF was related to ATT and not internal or valgus rotations of the tibia. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Trends and Complications in Open Versus Endoscopic Carpal Tunnel Release in Private Payer and Medicare Patient Populations.

Purpose: The purpose of this study was to report trends, complications, and costs associated with endoscopic carpal tunnel release (ECTR) and open carpal tunnel release (OCTR). Methods: Using Current Procedural Terminology (CPT) and International Classification of Diseases, Ninth Revision (ICD-9) codes, patients who had open versus endoscopic carpal tunnel release (CTR) were identified retrospectively in the PearlDiver database from both the Medicare and Humana (a private payer health insurance) populations from 2005 to 2014. These groups were then evaluated for postoperative complications, including wound infection within 90 days, wound dehiscence within 90 days, and intraoperative median nerve injury. We also used the data output for each group to compare the cost of the 2 procedure types. Data were analyzed via the Student t test. Statistical significance was set at P < .05. Results: A significantly lower percentage of patients in the endoscopic CTR group had a postoperative infection (5.21 vs 7.97 per 1000 patients per year, P < .001; 7.36 vs 11.23 per 1000 patients per year, P < .001) and wound dehiscence (1.58 vs 2.87 per 1000 patients per year, P < .001; 2.14 vs 3.73 per 1000 patients per year, P < .05) than open CTR group in the Medicare and Humana populations, respectively. Median nerve injury occurred 0.59/1000 ECTRs versus 1.69/1000 OCTRs (Medicare) and 1.96/1000 ECTRs versus 3.72/1000 OCTRs (Humana). Endoscopic CTR cost was more than open CTR for both the Medicare population ($1643 vs $1015 per procedure, P < .001) and Humana population ($1928 vs $1191 per procedure, P < .001). Conclusions: In both the Medicare and private insurance patient populations, endoscopic CTR is associated with fewer postoperative complications than open CTR, but is associated with greater expenses.

Prediction of ACL Force Produced by Tibiofemoral Compression During Controlled Knee Flexion: A New Robotic Testing Methodology.

Tibiofemoral compression force (TCF) is an important component of anterior cruciate ligament (ACL) injuries. A new robotic testing methodology was utilized to predict ACL forces generated by TCF without loading the ligament. We hypothesized that ACL force, directly recorded by a miniature load cell during an unconstrained test, could be predicted by measurements of anterior tibial restraining force (ARF) recorded during a constrained test. The knee was first flexed under load control with 25N TCF (tibia unconstrained) to record a baseline kinematic pathway. Tests were repeated with increasing levels of TCF, while recording ACL force and knee kinematics. Then tests with increasing TCF were performed under displacement control to reproduce the baseline kinematic pathway (tibia constrained), while recording ARF. This allowed testing to 1500N TCF since the ACL was not loaded. TCF generated ACL force for all knees (n=10) at 50° flexion, and for 8 knees at 30° flexion. ACL force and ARF had strong linear correlations with TCF at both flexion angles (R2 from 0.85 to 0.99), and ACL force was strongly correlated with ARF at both flexion angles (R2 from 0.76 to 0.99). Under 500N TCF the mean error between ACL force prediction from ARF regression and measured ACL force was 4.8 ± 7.3 N at 30° and 8.8 ± 27.5 N at 50° flexion. Our hypothesis was confirmed for TCF levels up to 500N, and ARF had a strong linear correlation with TCF up to 1500N TCF.

Effects of Proud Large Osteochondral Plugs on Contact Forces and Knee Kinematics: A Robotic Study.

BACKGROUND: Osteochondral allograft (OCA) transplantation is used to treat large focal femoral condylar articular cartilage defects. A proud plug could affect graft survival by altering contact forces (CFs) and knee kinematics. HYPOTHESIS: A proud OCA plug will significantly increase CF and significantly alter knee kinematics throughout controlled knee flexion. STUDY DESIGN: Controlled laboratory study. METHODS: Human cadaver knees had miniature load cells, each with a 20-mm-diameter cylinder of native bone/cartilage attached at its exact anatomic position, installed in both femoral condyles at standardized locations representative of clinical defects. Spacers were inserted to create proud plug conditions of +0.5, +1.0, and +1.5 mm. CFs and knee kinematics were recorded as a robot flexed the knee continuously from 0° to 50° under 1000 N of tibiofemoral compression. RESULTS: CFs were increased significantly (vs flush) for all proudness conditions between 0° and 45° of flexion (medial) and 0° to 50° of flexion (lateral). At 20°, the average increases in medial CF for +0.5-mm, +1-mm, and +1.5-mm proudness were +80 N (+36%), +155 N (+70%), and +193 N (+87%), respectively. Corresponding increases with proud lateral plugs were +44 N (+14%), +90 N (+29%), and +118 N (+38%). CF increases for medial plugs at 20° of flexion were significantly greater than those for lateral plugs at all proudness conditions. At 50°, a 1-mm proud lateral plug significantly decreased internal tibial rotation by 15.4° and decreased valgus rotation by 2.5°. CONCLUSION: A proud medial or lateral plug significantly increased CF between 0° and 45° of flexion. Our results suggest that a medial plug at 20° may be more sensitive to graft incongruity than a lateral plug. The changes in rotational kinematics with proud lateral plugs were attributed to earlier contact between the proud plug's surface and the lateral meniscus, leading to rim impingement with decreased tibial rotation. CLINICAL RELEVANCE: Increased CF and altered knee kinematics from a proud femoral plug could affect graft viability. Plug proudness of only 0.5 mm produced significant changes in CF and knee kinematics, and the clinically accepted 1-mm tolerance may need to be reexamined in view of our findings.

The Assessment of Quality, Accuracy, and Readability of Online Educational Resources for Platelet-Rich Plasma.

PURPOSE: To critically evaluate the quality, accuracy, and readability of readily available Internet patient resources for platelet-rich plasma (PRP) as a treatment modality for musculoskeletal injuries. METHODS: Using the 3 most commonly used Internet search engines (Google, Bing, Yahoo), the search term "platelet rich plasma" was entered, and the first 50 websites from each search were reviewed. The website's affiliation was identified. Quality was evaluated using 25-point criteria based on guidelines published by the American Academy of Orthopaedic Surgeons, and accuracy was assessed with a previously described 12-point grading system by 3 reviewers independently. Readability was evaluated using the Flesch-Kincaid (FK) grade score. RESULTS: A total of 46 unique websites were identified and evaluated. The average quality and accuracy was 9.4 ± 3.4 (maximum 25) and 7.9 ± 2.3 (maximum 12), respectively. The average FK grade level was 12.6 ± 2.4, which is several grades higher than the recommended eighth-grade level for patient education material. Ninety-one percent (42/46) of websites were authored by physicians, and 9% (4/46) contained commercial bias. Mean quality was significantly greater in websites authored by health care providers (9.8 ± 3.1 vs 5.9 ± 4.7, P = .029) and in websites without commercial bias (9.9 ± 3.1 vs 4.5 ± 3.2, P = .002). Mean accuracy was significantly lower in websites authored by health care providers (7.6 ± 2.2 vs 11.0 ± 1.2, P = .004). Only 24% (11/46) reported that PRP remains an investigational treatment. CONCLUSIONS: The accuracy and quality of online patient resources for PRP are poor, and the information overestimates the reading ability of the general population. Websites authored by health care providers had higher quality but lower accuracy. Additionally, the majority of websites do not identify PRP as an experimental treatment, which may fail to provide appropriate patient understanding and expectations. CLINICAL RELEVANCE: Physicians should educate patients that many online patient resources have poor quality and accuracy and can be difficult to read.

Effects of Anterior Closing Wedge Tibial Osteotomy on Anterior Cruciate Ligament Force and Knee Kinematics.

BACKGROUND: A certain percentage of patients undergoing anterior cruciate ligament (ACL) reconstruction will experience graft failure, and there is mounting evidence that an increased posterior tibial slope (PTS) may be a predisposing factor. Theoretically, under tibiofemoral compression force (TFC), a reduced PTS would induce less anterior tibial translation (ATT) and lower ACL force. HYPOTHESIS: Ten-degree anterior closing wedge osteotomy of the proximal tibia will significantly reduce ACL force and alter knee kinematics during robotic testing. STUDY DESIGN: Controlled laboratory study. METHODS: Eleven fresh-frozen human knees were instrumented with a load cell that measured ACL force as the knee was flexing continuously from 0° to 50° under 200-N TFC as our initial testing condition, followed by the addition of the following tibial loads: 45-N anterior force (AF), 5-N·m valgus moment (VM), 2-N·m internal torque (IT), and all loads combined. ACL force and knee kinematics were recorded before and after osteotomy. RESULTS: Osteotomy produced significant changes in the tibiofemoral position at full extension (as defined by a 2-N·m knee extension moment). This resulted in apparent knee hyperextension (9.4° ± 1.9°), posterior tibial translation (7.9 mm ± 1.6 mm), internal tibial rotation (3.2° ± 2.3°), and valgus tibial rotation (3.2° ± 1.5°). During straight knee flexion with TFC alone, osteotomy reduced ACL force to 0 N beyond 5° of flexion, and ATT was reduced between 0° and 45° ( P < .05). With TFC + AF, ACL force was reduced beyond 5° of flexion, and ATT was reduced between 5° and 45° ( P < .05). With TFC + VM, ACL force was less than 10 N beyond 5° of flexion, and ATT was reduced at all flexion angles ( P < .05). Under the loading conditions TFC + IT and TFC + IT + AF + VM, osteotomy did not significantly change ACL force or ATT at any flexion angle. CONCLUSION: In general, osteotomy lowered ACL force and reduced ATT when IT was not present. The benefits of osteotomy were negated when IT was included possibly because the dominant mechanism of ACL force generation was cruciate impingement from internal winding and not ATT. CLINICAL RELEVANCE: PTS-reducing osteotomy significantly decreased ACL force and reduced ATT for knee loads that did not include IT.

Acute and Rapid Development of Spontaneous Spinal Epidural Hematoma Associated with Combined Aspirin-Dipyridamole Therapy: A Case Report.

CASE: Spontaneous spinal epidural hematoma (SSEH) is a known, although rare, clinical entity that may be challenging to diagnose. This case report describes the rapid development of a large SSEH in an elderly patient on aspirin-dipyridamole combination therapy after she shifted her position in bed. Magnetic resonance imaging obtained 4 hours after the onset of symptoms demonstrated a large spinal epidural hematoma that extended from T4 to L1. CONCLUSION: With early diagnosis, the patient was successfully treated with a laminectomy and evacuation of the hematoma, and there was full neurological recovery.

Benign Natural History of Spondylolysis in Adolescence With Midterm Follow-Up.

STUDY DESIGN: Retrospective chart review. OBJECTIVES: To use the Micheli Functional Scale to assess adolescent patients with spondylolysis treated conservatively at midterm follow-up. SUMMARY OF BACKGROUND: Spondylolysis is a common source of back pain for adolescents and is generally managed with bracing and physical therapy. There is little data regarding the results of conservative management of spondylolysis over time. METHODS: Four major academic pediatric institutions performed a retrospective chart review of patients from 5 to 21 years of age with the initial diagnosis of spondylolysis. Inclusion criteria were patients who initially underwent conservative management and had a minimum of 2 years' follow-up. The patients were contacted and asked to complete the Micheli Functional Scale Survey. RESULTS: A total of 295 patients with the diagnosis of spondylolysis were identified and contacted. Sixty-one subjects with spondylolysis completed the follow-up survey. Sixty of 61 respondents (98%) answered questions regarding their current pain level. Thirty-five of 60 (58.3%) reported no pain (0/10) and 47/60 (78%) rated their pain at 3 or less, whereas 22% (13/60) rated their pain as 4 or higher. There was no correlation with pain ratings on the follow-up survey and radiographic healing at initial management. Of the 61 patients, 50 returned to sports (82%), 8 did not return (13%), and 5 returned to most but not all of their sports (8%). No correlation was observed between radiographic healing and return to sports (p = .4885). CONCLUSION: Using a validated functional scale, this study demonstrated that with conservative management of spondylolysis a majority of patients at an average of 8 years out self-report a return to sports (90%), though many reported continued pain (42%) and interference with activities (67%). There was no correlation observed between radiographic evidence of healing and pain or return to sports with a mean follow-up of 8 years. LEVEL OF EVIDENCE: Multicenter retrospective case series.

Arthroscopic Delivery of Injectable Bone Graft for Staged Revision Anterior Cruciate Ligament Reconstruction.

Bone defects caused by femoral and tibial tunnel enlargement can pose a significant technical challenge when planning to perform revision anterior cruciate ligament reconstruction. A number of options have been described for managing osseous deficiencies, including the use of large autograft or allograft bone dowels to provide sufficient tunnel fill and subsequent structural support for revision surgery. These techniques can be time-consuming and technically demanding to ensure proper tunnel fill and press-fit stability of the bone graft. We describe our preferred technique for arthroscopic bone grafting using a mixture of demineralized cortical bone graft augmented with platelet-rich plasma delivered through a simple delivery system.

Assessment of Lowest Instrumented Vertebra Tilt on Radiographic Measurements in Lenke "C" Modifier Curves Undergoing Selective Thoracic Fusion in Adolescent Idiopathic Scoliosis.

STUDY DESIGN: Multicenter, retrospective cohort study. OBJECTIVES: The purpose of this study is to determine how the amount of residual lowest instrumented vertebra (LIV) tilt correlates with radiographic measurements. SUMMARY OF BACKGROUND DATA: When performing a selective thoracic posterior spinal fusion for adolescent idiopathic scoliosis (AIS), the LIV may be tilted into the lumbar curve or made horizontal. METHODS: This is a multicenter retrospective study of 33 consecutive patients with AIS, Lenke types 1 to 4, lumbar modifier C, and a minimum follow-up of 2 years, who underwent selective thoracic posterior spinal fusions. Measurements obtained from pre- and postoperative radiographs were correlated with postoperative LIV tilt. RESULTS: At final follow-up, less postoperative LIV tilt significantly correlated with less thoracic apical translation (p = .023) when controlling for the position of the LIV relative to the stable vertebra and preoperative thoracic and lumbar curve flexibility. LIV tilt was not significantly associated with thoracic Cobb angle, lumbar Cobb angle, lumbar apical translation, coronal balance, sagittal balance, or the amount of correction obtained compared to their preoperative measurements (p > .05). CONCLUSION: Decreased LIV tilt was significantly associated with decreased thoracic apical translation. LIV tilt did not significantly correlate with coronal balance or any other radiographic measurement. We caution that these findings may only be applicable in C modifier curves and when the correct LIV is chosen. LEVEL OF EVIDENCE: Level III, Therapeutic study.

Assessment of Lowest Instrumented Vertebra Tilt on Radiographic Measurements in Lenke "C" Modifier Curves Undergoing Selective Thoracic Fusion in Adolescent Idiopathic Scoliosis.

STUDY DESIGN: Multicenter, retrospective cohort study. OBJECTIVES: The purpose of this study is to determine how the amount of residual lowest instrumented vertebra (LIV) tilt correlates with radiographic measurements. When performing a selective thoracic posterior spinal fusion for adolescent idiopathic scoliosis (AIS), the LIV may be tilted into the lumbar curve or made horizontal. METHODS: This is a multicenter retrospective study of 33 consecutive patients with AIS, Lenke types 1 to 4, lumbar modifier C, and a minimum follow-up of 2 years, who underwent selective thoracic posterior spinal fusions. Measurements obtained from pre- and postoperative radiographs were correlated with postoperative LIV tilt. RESULTS: At final follow-up, less postoperative LIV tilt significantly correlated with less thoracic apical translation (p =.023) when controlling for the position of the LIV relative to the stable vertebra and preoperative thoracic and lumbar curve flexibility. LIV tilt was not significantly associated with thoracic Cobb angle, lumbar Cobb angle, lumbar apical translation, coronal balance, sagittal balance, or the amount of correction obtained compared to their preoperative measurements (p >.05). CONCLUSION: Decreased LIV tilt was significantly associated with decreased thoracic apical translation. LIV tilt did not significantly correlate with coronal balance or any other radiographic measurement. We caution that these findings may only be applicable in C modifier curves and when the correct LIV is chosen. LEVEL OF EVIDENCE: Level III, Therapeutic study.

Spinal Deformity in Russell-Silver Syndrome.

STUDY DESIGN: Cross-sectional analysis. OBJECTIVES: To evaluate the prevalence of scoliosis and kyphosis in patients with Russell-Silver syndrome (RSS). SUMMARY OF BACKGROUND DATA: Russell-Silver syndrome was described by Silver and Russell in the 1950s and 1960s and is characterized by body asymmetry and other growth abnormalities. To the authors' knowledge, this is the first study to evaluate the prevalence of scoliosis and kyphosis in patients with Russell Silver Syndrome. METHODS: The authors performed a cross-sectional analysis of 163 persons, identified through a national RSS foundation, who consented to be included in the study and responded to a general survey questionnaire. Subjects who reported a diagnosis of scoliosis and/or kyphosis were subsequently asked to submit copies of prior spinal radiographs for evaluation at the authors' center. For evaluation of scoliosis and kyphosis on the radiographs, the researchers reviewed posteroanterior and lateral standing radiographs to measure coronal and sagittal Cobb angles. RESULTS: Of 163 respondents, 24 (14%) reported scoliosis, 5 (3.1%) reported kyphosis, and 6 (3.8%) reported both kyphosis and scoliosis, with average age of diagnosis of 8 years (range, 1-43 years). Of these respondents, 6 reported a history of bracing for scoliosis and/or kyphosis and 3 braced respondents reported having had surgery for scoliosis and/or kyphosis. An additional 3 respondents reported that corrective spinal surgery was "planned for the future." CONCLUSIONS: Persons with RSS have a high prevalence of spinal deformity (21%) and a significant number of these patients will undergo corrective surgery (6 of 34; 18%).

Natural large-scale regeneration of rib cartilage in a mouse model.

The clinical need for methods to repair and regenerate large cartilage and bone lesions persists. One way to make new headway is to study skeletal regeneration when it occurs naturally. Cartilage repair is typically slow and incomplete. However, an exception to this observation can be found in the costal cartilages, where complete repair has been reported in humans but the cellular and molecular mechanisms have not yet been characterized. In this study, we establish a novel animal model for cartilage repair using the mouse rib costal cartilage. We then use this model to test the hypothesis that the perichondrium, the dense connective tissue that surrounds the cartilage, is a tissue essential for repair. Our results show that full replacement of the resected cartilage occurs quickly (within 1 to 2 months) and properly differentiates but that repair occurs only in the presence of the perichondrium. We then provide evidence that the rib perichondrium contains a special niche that houses chondrogenic progenitors that possess qualities particularly suited for mediating repair. Label-retaining cells can be found within the perichondrium that can give rise to new chondrocytes. Furthermore, the perichondrium proliferates and thickens during the healing period and when ectopically placed can generate new cartilage. In conclusion, we have successfully established a model for hyaline cartilage repair in the mouse rib, which should be useful for gaining a more detailed understanding of cartilage regeneration and ultimately for developing methods to improve cartilage and bone repair in other parts of the skeleton.

Are Rib Versus Spine Anchors Protective Against Breakage of Growing Rods?

STUDY DESIGN: Retrospective multicenter, case-control study. OBJECTIVE: To compare the risks of rod breakage and anchor complications between distraction-based growing rods with proximal spine versus rib anchors. SUMMARY OF BACKGROUND DATA: Rod breakage is a known complication of distraction-based growing rod instrumentation. METHODS: A total of 176 patients met inclusion criteria: minimum 2-year follow-up, younger than age 9 years at index surgery, non-Vertical Expandable Prosthetic Titanium Rib distraction-based growing rods, and known anchor locations. Mean follow-up was 56 months (range, 24-152 months). Survival analyses using Cox proportional hazards model (accounting for varying lengths of follow-up) of rod breakage, anchor complications, preoperative Cobb angle, number of growing rods, age, and number of levels instrumented were performed using a significance level of p < .05. RESULTS: Thirty-four patients had rib-anchored growing rods and 142 had spine-anchored growing rods. This analysis found that proximal rib-anchored growing rods have a 23% risk of lifetime rod breakage compared with spine-anchored growing rods (6% vs. 29%) (p = .041) without a significant increase in risk of anchor complications (38% vs. 33%) (p = .117). The number of implanted rods (p = .839), age (p = .649), and number of instrumented levels (p = .447) were not statistically significant regarding rod breakage risk, although higher preoperative Cobb angles were significant (p = .014). CONCLUSIONS: Preoperative Cobb angle appears to be the most influential factor in determining whether growing rods break (p = .014). Univariate analysis found that rib anchors were associated with less than one-fourth the risk of rod breakage than spine anchors (p = .04) but multivariate analysis found no significant association between anchors and rod breakage (p = .07). This trend suggests that rib-anchored growing rod systems may be associated with less rod breakage because the system is less rigid as a result of some "slop" at the hook-rib interface, as well as the normal motion of the costovertebral joint.

Accelerated wound closure in a diabetic mouse model after exposure to phenanthrenequinone.

BACKGROUND: Reactive oxygen species (ROS) have been shown to be important in wound healing by promoting angiogenesis (also mentioned by Ushio-Fukai and Nakamura). Likewise ROS have been implicated by toxicological studies as a primary mechanism of air pollution-associated morbidity. We sought to determine how exposure to a reactive diesel exhaust chemical (phenanthrenequinone [PQ]), which promotes formation of ROS and is considered an air pollutant, would affect wound healing. Since wound healing is compromised in diabetic (db) individuals, we examined the effects of PQ on wound healing in a db mouse model. METHODS: db mice consumed PQ-containing chow for a short period (2 weeks) before wounding and through generations. Wound closure rates and wound vascularization were evaluated 10 days after wounding. The effects of PQ on endothelial cell proliferation and ROS generation in vitro were also measured. RESULTS: db mice exposed to short-term PQ and PQ-exposed first-generation db mice demonstrated the highest closure rates, significantly better than control db mice (P < 0.05). Furthermore, a higher concentration of PQ in sera of db mice coincides with the higher rate of closure. PQ was also shown to produce ROS in cell culture and stimulate endothelial cell proliferation at nanomolar concentrations. Second- and third-generation db mice exposed to PQ did not show improved wound healing. CONCLUSIONS: This study suggests that the free radical-generating air pollutant PQ enhances wound closure in the db mouse model possibly by stimulating angiogenesis, as suggested by in vitro results. We speculate that PQ may increase oxidation levels systemically and therefore help modulate inflammation at the wound site. Alternatively, antioxidant mechanisms recruited for wound healing may interfere with PQ metabolism and elimination as it accumulates in sera. Generational resistance to improve wound healing in PQ-exposed db mice could also be due to disturbances in metabolism caused by continuous exposure. In either case, these results introduce a new perspective on the effects of air pollution on wound healing.

Surgical technique for balancing posterior spinal fusions to the pelvis using the T square of Tolo.

BACKGROUND: Correcting pelvic obliquity and improving sitting balance in neuromuscular scoliosis often requires fixation to the pelvis. We describe the use of a T square instrument to assist intraoperatively in evaluating the alignment of these curves and achieving balance in the coronal plane. METHODS: The T square instrument was constructed with a vertical limb perpendicular to 2 horizontal limbs in a T formation. At the conclusion of the instrumentation and preliminary reduction maneuvers, the T square was positioned with the horizontal limbs parallel to the pelvis and the vertical limb in line with the central sacral line. If the spine and pelvis were well balanced, fluoroscopic images demonstrated that the superior aspect of the vertical limb of the T square was crossing the vertebral body of T1. If this was not shown, then some combination of compression, distraction, or a change in the contouring of the rods was performed until this balance was achieved. RESULTS: In this series, we describe case examples in which the T square has been successfully used to aid in achieving balance in the coronal plane. This technique helps to overcome the challenges with positioning and imaging often encountered in managing these long, rigid curves. The T square is a useful adjunct in balancing posterior spinal fusions and evaluating the correction of pelvic obliquity in cases of neuromuscular scoliosis. CONCLUSIONS: This novel, yet simple, T square technique can be used for any method of posterior spinal fusion with lumbopelvic fixation to assist in the intraoperative evaluation and achievement of balance in the coronal plane and has become routine at our institution. LEVEL OF EVIDENCE: IV.

Clay-shoveler's fracture equivalent in children.

STUDY DESIGN: Case report and literature review. OBJECTIVE: This article reports 2 cases of clay-shoveler's fracture equivalent in children presenting acutely after participation in sports. SUMMARY OF BACKGROUND DATA: The clay-shoveler's fracture in adults is an avulsion fracture of the lower cervical or upper thoracic spinous process. To our knowledge, this is the first report in English literature on soft-tissue avulsion injury of the spinous process in children presenting with history and symptoms similar to clay-shoveler's fractures. METHODS: Retrospective review of 2 cases. RESULTS: A 14-year-old baseball player and a 16-year-old wrestler experienced acute posterior neck pain after participation in sports. Both patients presented with a history and physical examination suggestive of clay-shoveler's fracture but showed no evidence of injury on radiographs. Subsequent magnetic resonance images demonstrated an acute soft-tissue avulsion of the spinous process at C7 in 1 patient and T2 in the other. With nonoperative therapy, both patients returned to sports by 4 months, with occasional, intermittent discomfort a year after injury, which did not limit any activities. CONCLUSION: In adolescents, if the history and physical examination are consistent with a clay-shoveler's fracture, but radiographs are normal, magnetic resonance imaging may be indicated to diagnose a soft-tissue avulsion.