CEACAM1 structure and function in immunity and its therapeutic implications.

The type I membrane protein receptor carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) distinctively exhibits significant alternative splicing that allows for tunable functions upon homophilic binding. CEACAM1 is highly expressed in the tumor environment and is strictly regulated on lymphocytes such that its expression is restricted to activated cells where it is now recognized to function in tolerance pathways. CEACAM1 is also an important target for microbes which have co-opted these attributes of CEACAM1 for the purposes of invading the host and evading the immune system. These properties, among others, have focused attention on CEACAM1 as a unique target for immunotherapy in autoimmunity and cancer. This review examines recent structural information derived from the characterization of CEACAM1:CEACAM1 interactions and heterophilic modes of binding especially to microbes and how this relates to CEACAM1 function. Through this, we aim to provide insights into targeting CEACAM1 for therapeutic intervention.

Meniscal allograft transplantation: a review of indications, techniques, and outcomes.

When compared to meniscectomy, meniscus allograft transplantation (MAT) may provide superior long-term benefits to young, active patient populations who have lost meniscal function because of irreparable damage, such as, an avascular tear, previous repair failure, and unsalvageable tear types. Positive outcomes are most likely to be achieved when meniscus allograft transplantation is performed in appropriately selected patients. Indications include patients younger than 50 years of age, with a history of subtotal or total meniscectomy without concomitant articular cartilage defects, uncorrectable joint malalignment, and/or knee instability. Outcomes for meniscal allograft transplantation are promising with studies reporting long-term graft survivorship as high as 89% at 10 years and significant improvements in multiple patient reported outcome measures. LEVEL OF EVIDENCE: Level V.

Age of 40 Years or Older Does Not Affect Meniscal Repair Failure Risk at 5 Years.

PURPOSE: To compare meniscal repair failure rates in patients aged 40 years or older versus patients younger than 40 years. METHODS: A total of 276 patients underwent meniscal repair surgery by a single sports medicine fellowship-trained surgeon between 2006 and 2012 and were eligible for study inclusion. Patients were followed up for meniscal repair failure, defined as meniscectomy, repeated meniscal repair, or total knee arthroplasty. Logistic regression analysis was used to determine the risk of failure while controlling for potential confounding variables including body mass index, sex, anterior cruciate ligament status, time from injury to surgery, number of implants used, tear pattern, and chondral status at the time of the repair. RESULTS: Among the 276 eligible patients, 221 (80%) were successfully contacted for follow-up at an average of 5 years after surgery. Of these patients, 56 were aged 40 years or older (mean, 47.2 years; standard deviation [SD], 5.3 years) and 165 were younger than 40 years (mean, 24.7 years; SD, 6.7 years). The overall meniscal repair failure rate over a 5-year period was 20%. Among patients aged 40 years or older, the failure risk was 18% versus 21% in patients younger than 40 years. After adjustment for confounding variables, age of 40 years or older was not associated with increased failure risk (adjusted odds ratio, 0.83; 95% confidence interval, 0.36-1.81; P = .65). The mean time to failure tended to be shorter in older patients, at 16.9 months (SD, 10.2 months) versus 28.5 months in the group younger than 40 years (SD, 23.3 months) (P = .04). CONCLUSIONS: Age of 40 years or older is not associated with an increased risk of meniscal repair failure at 5 years, although a shorter time to failure was noted in this age cohort. LEVEL OF EVIDENCE: Level III, retrospective comparative study.

Comparison of ASPIRE Mechanical Thrombectomy Versus AngioJet Thrombectomy System in a Porcine Iliac Vein Thrombosis Model.

BACKGROUND: Percutaneous mechanical thrombectomy device has become an important therapeutic armamentarium in the management of venous thromboembolism. In this study, we compare the efficacy and safety profile of the AngioJet thrombectomy device and ASPIRE thrombectomy system in a porcine venous thrombosis model. METHODS: Twelve adult pigs underwent bilateral iliac venous thrombosis created by using a stent graft thrombosis model and subsequently underwent either AngioJet (n = 6) or ASPIRE mechanical thrombectomy (n = 6) 1 week later. Intravascular ultrasound (IVUS) was used to assess thrombectomy efficacy, and computed tomography was used to evaluate pulmonary embolism (PE). Hemolytic effect was measured by plasma-free hemoglobin (PfHgb). Iliac vein thrombogenicity was evaluated with radiolabeled platelet and fibrin deposition. Veins were harvested and evaluated with light microscopy and scanning electron microscopy (SEM). RESULTS: Similar thrombectomy efficacy by IVUS evaluation was noted in both groups. Significant greater PE and hemolysis were identified in the AngioJet group compared to the ASPIRE group. The AngioJet group had greater reduction in WBC and platelet compared to the ASPIRE group. No difference was found in thrombogenicity, light microscopic evaluation, or SEM. CONCLUSIONS: Both devices had similar thrombectomy efficacy and thrombogenicity response. The ASPIRE catheter incurred less PE and hemolysis compared to the AngioJet device. Vessel wall response by histological analysis and SEM was similar in both groups.

Treatment outcomes and lessons learned from 5134 cases of outpatient office-based endovascular procedures in a vascular surgical practice.

Introduction The office-based endovascular facility has increased in number recently due in part to expedient patient experience. This study analyzed treatment outcomes of procedures performed in our office-based endovascular suite. Methods Treatment outcomes of 5134 consecutive procedures performed in our office-based endovascular suites from 2006 to 2013 were analyzed. Five sequential groups (group I-V) of 1000 consecutive interventions were compared with regard to technical success and treatment outcomes. Results Our patients included 2856 (56%) females and 2267 (44%) males. Procedures performed included diagnostic arteriogram, arterial interventions, venous interventions, dialysis access interventions, and venous catheter management, which were 1024 (19.9%), 1568 (30.6%), and 3073 (60.0%), 621(12.1%), and 354 (6.9%), respectively. The complication rates for group I, II, III, IV, and V were 3%, 1.5%, 1%, 1.1%, and 0.7%, respectively. The complication rate was higher in group I when compared to each of the remaining four groups ( p < 0.05). Nine patients (0.18%) died within the 30-day period following their procedures, and none were procedure related. Conclusions Endovascular procedure can be performed safely in an office-based facility with excellent outcomes. Lessons learned in establishing office-based endovascular suites with efforts to reduce procedural complications and optimize quality patient care are discussed.

High-dimensional mapping of human CEACAM1 expression on immune cells and association with melanoma drug resistance.

BACKGROUND: Human carcinoembryonic antigen cell adhesion molecule 1 (CEACAM1) is an inhibitory cell surface protein that functions through homophilic and heterophilic ligand binding. Its expression on immune cells in human tumors is poorly understood. METHODS: An antibody that distinguishes human CEACAM1 from other highly related CEACAM family members was labeled with 159Tb and inserted into a panel of antibodies that included specificity for programmed cell death protein 1 (PD1) and PD-L1, which are targets of immunotherapy, to gain a data-driven immune cell atlas using cytometry by time-of-flight (CyTOF). A detailed inventory of CEACAM1, PD1, and PD-L1 expression on immune cells in metastatic lesions to lymph node or soft tissues and peripheral blood samples from patients with treatment-naive and -resistant melanoma as well as peripheral blood samples from healthy controls was performed. RESULTS: CEACAM1 is absent or at low levels on healthy circulating immune cells but is increased on immune cells in peripheral blood and tumors of melanoma patients. The majority of circulating PD1-positive NK cells, innate T cells, B cells, monocytic cells, dendritic cells, and CD4+ T cells in the peripheral circulation of treatment-resistant disease co-express CEACAM1 and are demonstrable as discrete populations. CEACAM1 is present on distinct types of cells that are unique to the tumor microenvironment and exhibit expression levels that are highest in treatment resistance; this includes tumor-infiltrating CD8+ T cells. CONCLUSIONS: To the best of our knowledge, this work represents the first comprehensive atlas of CEACAM1 expression on immune cells in a human tumor and reveals an important correlation with treatment-resistant disease. These studies suggest that agents targeting CEACAM1 may represent appropriate partners for PD1-related pathway therapies.

Some proteins, such as programmed cell death protein 1 (PD1), can stop the immune system from attacking cancer cells, allowing cancers to grow. Therapies targeting these proteins can be highly effective, but tumors can become resistant. It is important to identify factors involved in this resistance to develop improved cancer therapies. Human carcinoembryonic antigen cell adhesion molecule 1 (CEACAM1) is a protein that inhibits an immune response and its levels have been associated with poor patient outcomes. We applied a method that allows for the detection of proteins on a single cell to uncover CEACAM1 patterns in melanoma. We found that increased CEACAM1 expression levels on multiple different immune cell types was associated with tumors that were resistant to therapy. These findings may help us to understand the role of CEACAM1 in cancer and to develop better cancer therapies.

Structural analysis of human CEACAM1 oligomerization.

The human (h) CEACAM1 GFCC' face serves as a binding site for homophilic and heterophilic interactions with various microbial and host ligands. hCEACAM1 has also been observed to form oligomers and micro-clusters on the cell surface which are thought to regulate hCEACAM1-mediated signaling. However, the structural basis for hCEACAM1 higher-order oligomerization is currently unknown. To understand this, we report a hCEACAM1 IgV oligomer crystal structure which shows how GFCC' face-mediated homodimerization enables highly flexible ABED face interactions to arise. Structural modeling and nuclear magnetic resonance (NMR) studies predict that such oligomerization is not impeded by the presence of carbohydrate side-chain modifications. In addition, using UV spectroscopy and NMR studies, we show that oligomerization is further facilitated by the presence of a conserved metal ion (Zn++ or Ni++) binding site on the G strand of the FG loop. Together these studies provide biophysical insights on how GFCC' and ABED face interactions together with metal ion binding may facilitate hCEACAM1 oligomerization beyond dimerization.

Structural basis of the dynamic human CEACAM1 monomer-dimer equilibrium.

Human (h) carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) function depends upon IgV-mediated homodimerization or heterodimerization with host ligands, including hCEACAM5, hTIM-3, PD-1, and a variety of microbial pathogens. However, there is little structural information available on how hCEACAM1 transitions between monomeric and dimeric states which in the latter case is critical for initiating hCEACAM1 activities. We therefore mutated residues within the hCEACAM1 IgV GFCC' face including V39, I91, N97, and E99 and examined hCEACAM1 IgV monomer-homodimer exchange using differential scanning fluorimetry, multi-angle light scattering, X-ray crystallography and/or nuclear magnetic resonance. From these studies, we describe hCEACAM1 homodimeric, monomeric and transition states at atomic resolution and its conformational behavior in solution through NMR assignment of the wildtype (WT) hCEACAM1 IgV dimer and N97A mutant monomer. These studies reveal the flexibility of the GFCC' face and its important role in governing the formation of hCEACAM1 dimers and selective heterodimers.

Pseudo-merohedral twinning and noncrystallographic symmetry in orthorhombic crystals of SIVmac239 Nef core domain bound to different-length TCRzeta fragments.

HIV/SIV Nef mediates many cellular processes through interactions with various cytoplasmic and membrane-associated host proteins, including the signalling zeta subunit of the T-cell receptor (TCRzeta). Here, the crystallization strategy, methods and refinement procedures used to solve the structures of the core domain of the SIVmac239 isolate of Nef (Nef(core)) in complex with two different TCRzeta fragments are described. The structure of SIVmac239 Nef(core) bound to the longer TCRzeta polypeptide (Leu51-Asp93) was determined to 3.7 A resolution (R(work) = 28.7%) in the tetragonal space group P4(3)2(1)2. The structure of SIVmac239 Nef(core) in complex with the shorter TCRzeta polypeptide (Ala63-Arg80) was determined to 2.05 A resolution (R(work) = 17.0%), but only after the detection of nearly perfect pseudo-merohedral crystal twinning and proper assignment of the orthorhombic space group P2(1)2(1)2(1). The reduction in crystal space-group symmetry induced by the truncated TCRzeta polypeptide appears to be caused by the rearrangement of crystal-contact hydrogen-bonding networks and the substitution of crystallographic symmetry operations by similar noncrystallographic symmetry (NCS) operations. The combination of NCS rotations that were nearly parallel to the twin operation (k, h, -l) and a and b unit-cell parameters that were nearly identical predisposed the P2(1)2(1)2(1) crystal form to pseudo-merohedral twinning.

Meniscus repair five-year results are influenced by patient pre-injury activity level but not age group.

BACKGROUND: The purpose of the study is to determine whether patient age group (≥40 years versus <40 years) and pre-injury activity level are independently predictive of symptomatic failure rates and patient-reported outcomes after meniscus repair with or without concomitant anterior cruciate ligament reconstruction (ACLR) at mean five years of follow-up. METHODS: Two hundred and twenty-five patients (n = 61, age ≥40 years; n = 164, age <40; 11% sedentary, 63% recreational athletes, 26% competitive athletes; 72% cutting-pivoting sports, 28% non-cutting or non-pivoting sports) who underwent meniscal repair were assessed for symptomatic failure and subjective knee function at mean 5.4 years of follow-up. Symptoms were assessed with Knee Osteoarthritis Outcome Score (KOOS) and International Knee Documentation Committee Subjective (IKDC-S) scores. RESULTS: Repair failure was 20% overall with no association with age group (<40 vs. ≥40 years) or level of activity. When compared with sedentary patients, IKDC-S scores were not associated with age group but were lower among sedentary patients (mean: 59.6, SE: 4.9) compared with recreational (mean: 78.9, SE: 2.5; p = 0.007) or competitive athletes (mean: 79.2, SE: 3.8; p = 0.02). KOOS-ADL scores were independently associated with age and were higher among patients <40 years. KOOS-pain, KOOS-sport, or KOOS-QOL were not associated with age group. Sedentary status was independently associated with lower KOOS scores for all sub-scores. CONCLUSIONS: Meniscal repair failure rates and patient-reported outcomes do not differ substantially between older or younger patients of similar pre-injury activity level. Sedentary patients regardless of age have worse self-reported subjective outcomes compared with active patients.

Effect of postnatal maturation on the mechanisms of esophageal propulsion in preterm human neonates: primary and secondary peristalsis.

OBJECTIVES: The changes in esophageal propulsive characteristics during maturation are not known. Our aim was to define the effects of postnatal maturation on esophageal peristaltic characteristics in preterm human neonates. We tested the hypotheses that: (i) maturation modifies esophageal bolus propulsion characteristics, and (ii) the mechanistic characteristics differ between primary and secondary peristalsis. METHODS: Esophageal motility in 10 premature neonates (mean 27.5 weeks gestational age) was evaluated twice at 33.8 weeks (time 1, earlier study) and 39.2 weeks (time 2, later study) mean postmenstrual age. Esophageal manometry waveform characteristics (amplitude and duration, peristaltic velocity, and intrabolus pressure domains) were analyzed during spontaneous primary peristalsis and infusion-induced secondary peristalsis. Repeated-measures and unstructured variance-covariance or compound symmetry matrixes were used for statistical comparison. Values stated as least squares means+/-s.e.m. or percent. RESULTS: A total of 200 primary peristalsis and 227 secondary peristalsis events were evaluated. Between time 1 and time 2: (i) proximal esophageal waveform amplitude increased (P<0.02), with primary peristalsis (38+/-6 vs. 48+/-7 mm Hg) and with secondary peristalsis (34+/-6 vs. 46+/-5 mm Hg); (ii) distal esophageal waveform amplitude was similar (P=NS), with primary peristalsis (42+/-4 vs. 43+/-4 mm Hg) and secondary peristalsis (29+/-3 vs. 32+/-4 mm Hg); (iii) proximal esophageal waveform onset to peak duration decreased (P=0.02) with primary (2.6+/-0.3 vs. 1.9+/-0.1 s, P<0.003) and with secondary peristalsis (2.2+/-0.2 vs. 1.8+/-0.1 s); (iv) distal esophageal waveform onset to peak duration decreased (P=0.01) with primary (2.4+/-0.3 vs. 1.8+/-0.1 s) and with secondary peristalsis (1.9+/-0.2 vs. 1.5+/-0.1 s); (v) effects of identical stimulus volume on intrabolus pressure were similar (P=NS); however, greater infusion volumes (2 vs. 1 ml) generated higher intrabolus pressure at both time 1 and time 2 (both Ps<0.05). Between primary and secondary peristalsis (mechanistic variable): (i) no differences were noted at either period, with proximal esophageal waveform amplitudes (P=NS); (ii) differences were noted with distal esophageal waveform amplitudes at each time period (P=0.0002); (iii) no differences were noted with both esophageal waveforms duration at either period (P=NS); (iv) peristaltic velocity was faster with secondary peristalsis than with primary peristalsis at either period (at earlier study, 7.9+/-1.4 vs. 2.5+/-1.4 cm/s and at later study 6.2+/-1.6 vs. 1.2+/-1.5 cm/s, both Ps<0.01). CONCLUSIONS: In preterm neonates, longitudinal maturation modulates the characteristics of primary and secondary peristalsis. Differences in proximal striated muscle and distal smooth muscle activity during peristalsis are evident. Peristaltic velocity is faster with secondary peristalsis. These findings may represent maturation of central and peripheral neuromotor properties of esophageal bolus propulsion in healthy preterm human neonates.

The intrinsically disordered cytoplasmic domain of the T cell receptor zeta chain binds to the nef protein of simian immunodeficiency virus without a disorder-to-order transition.

Intrinsically disordered proteins are thought to undergo coupled binding and folding upon interaction with their folded partners. In this study, we investigate whether binding of the intrinsically disordered T cell receptor zeta cytoplasmic tail to the well-folded simian immunodeficiency virus Nef core domain is accompanied by a disorder-to-order transition. We show that zeta forms a 1:1 complex with Nef and remains unfolded in the complex. Thus, our findings oppose the generally accepted view of the behavior of intrinsically disordered proteins and provide new evidence of the existence of specific interactions for unfolded protein molecules.

Viral pathogenesis, modulation of immune receptor signaling and treatment.

During the co-evolution of viruses and their hosts, the latter have equipped themselves with an elaborate immune system to defend themselves from the invading viruses. In order to establish a successful infection, replicate and persist in the host, viruses have evolved numerous strategies to counter and evade host antiviral immune responses as well as exploit them for productive viral replication. These strategies include those that target immune receptor transmembrane signaling. Uncovering the exact molecular mechanisms underlying these critical points in viral pathogenesis will not only help us understand strategies used by viruses to escape from the host immune surveillance but also reveal new therapeutic targets for antiviral as well as immunomodulatory therapy. In this chapter, based on our current understanding of transmembrane signal transduction mediated by multichain immune recognition receptors (MIRRs) and the results of sequence analysis, we discuss the MIRR-targetingviral strategies of immune evasion and suggest their possible mechanisms that, in turn, reveal new points of antiviral intervention. We also show how two unrelated enveloped viruses, human immunodeficiency virus and human cytomegalovirus, use a similar mechanism to modulate the host immune response mediated by two functionally different MIRRs-T-cell antigen receptor and natural killer cell receptor, NKp30. This suggests that it is very likely that similar general mechanisms can be or are used by other viral and possibly nonviral pathogens.

Triceps Repair and Restoration of Triceps Footprint With Anchorless Suture Fixation.

Triceps tendon rupture is an uncommon yet potentially devastating injury affecting patients over a broad demographic. Surgical treatment is essential to restore upper extremity functional status, and a vast array of techniques has been implemented with different fixation devices including suture buttons, intraosseous anchors, and suture repairs. Outcomes of distal triceps tendon repair have demonstrated nearly full return of functional capacity. Complications include infection, ulnar nerve neuropathy, arthrofibrosis, flexion contracture, hardware irritation, and most commonly, repair failure. We illustrate a triceps repair technique with suture fixation that restores the tendinous footprint without need of an adjunctive device.

High resolution X-ray and NMR structural study of human T-cell immunoglobulin and mucin domain containing protein-3.

T-cell immunoglobulin and mucin domain containing protein-3 (TIM-3) is an important immune regulator. Here, we describe a novel high resolution (1.7 Å) crystal structure of the human (h)TIM-3 N-terminal variable immunoglobulin (IgV) domain with bound calcium (Ca++) that was confirmed by nuclear magnetic resonance (NMR) spectroscopy. Significant conformational differences were observed in the B-C, C'-C″ and C'-D loops of hTIM-3 compared to mouse (m)TIM-3, hTIM-1 and hTIM-4. Further, the conformation of the C-C' loop of hTIM-3 was notably different from hTIM-4. Consistent with the known metal ion-dependent binding of phosphatidylserine (PtdSer) to mTIM-3 and mTIM-4, the NMR spectral analysis and crystal structure of Ca++-bound hTIM-3 revealed that residues in the hTIM-3 F-G loop coordinate binding to Ca++. In addition, we established a novel biochemical assay to define hTIM-3 functionality as determined by binding to human carcinoembryonic antigen cell adhesion molecule 1 (CEACAM1). These studies provide new insights useful for understanding and targeting hTIM-3.

Use of lymphoscintigraphy with SPECT/CT for sentinel node localization in a case of vaginal melanoma.

A 45-year-old woman with vaginal melanoma underwent Tc-99m sulfur colloid (filtered) lymphoscintigraphy with the acquisition of planar and SPECT/CT images for localization of a sentinel node before surgery. The study identified both inguinal and perirectal sentinel nodes, which proved beneficial in mapping potential anatomic spread of disease for staging and therapy planning. These results provide evidence for the use of routine SPECT/CT imaging for pelvic lymphoscintigraphic studies or as an adjunct tool for localizing sentinel nodes in cases that would not be demonstrated with planar imaging alone.

Anterior Cruciate Ligament Reconstruction With Bone-Patellar Tendon-Bone Autograft and a Medial Parapatellar Portal.

Anterior cruciate ligament (ACL) reconstruction is one of the most extensively studied surgical procedures in orthopaedics. The importance of this ligament for knee function and stability has been widely studied. For athletes who participate in activities involving cutting, twisting, and running, surgical reconstruction of the ACL has become the standard of care. However, there is much debate regarding the techniques involved in ACL reconstruction, including graft choice, technique of drilling the femoral tunnel, and single- versus double-bundle reconstruction. In recent studies, ACL femoral tunnel drilling via a medial parapatellar or accessory anteromedial portal provides a more anatomic graft placement than transtibial femoral drilling. Long-term outcomes of these techniques have not been widely studied. This article details our technique for ACL reconstruction with bone-patellar tendon-bone autograft and a medial parapatellar portal.

Treatment Outcomes and Lessons Learned From Transilluminated Powered Phlebectomy for Varicose Veins in 1034 Patients.

INTRODUCTION: Transilluminated powered phlebectomy (TIPP) is a minimally invasive technique of varicose vein removal, which combines irrigated illumination with tumescent anesthesia for ablation of superficial varicosities and endoscopic-powered venous resection. The objective of this study was to analyze treatment outcomes of this treatment modality. METHODS: A retrospective evaluation of prospectively collected data from all patients undergoing TIPP procedure for symptomatic varicose veins during a recent 12-year period was performed. Pertinent patient demographics, disease classification, perioperative complications, quality of life, and treatment outcomes were collected and analyzed. RESULTS: A total of 1167 limbs in 1034 patients (mean age, 52.4 years) were treated during the study period. The mean procedure time was 18.4 ± 8.9 minutes (range, 6.0-82.0 minutes). The mean number of incisions for TIPP procedure was 6.3 ± 3.6. All TIPP procedures were technically successful, and no patient required conversion to hook stab phlebectomy. Fifteen (1.5%) patients developed residual or recurrent varicosities, which were treated with sclerotherapy during the follow-up period. Postoperative complications included hematoma at 2 weeks (5.8%), ecchymosis at 2 weeks (32.9%), saphenous neuropathy (0.3%), cellulitis (1.0%), and skin pigmentation (1.9%). There was no postoperative deep vein thrombosis or mortality. CONCLUSIONS: Transilluminated powered phlebectomy is an effective method for varicose vein removal and is associated with high clinical success and excellent cosmetic results. Meticulous technical steps are critical in achieving successful outcomes while minimizing complications. Technical considerations and lessons learned from our experiences are discussed in this report.

Bioabsorbable interference screw failure in anterior cruciate ligament reconstruction: A case series and review of the literature.

BACKGROUND: To report a case series of failures of bioabsorbable interference screws with possible identification of a novel failure mechanism. METHODS: A retrospective review of ACL reconstructions by the senior author utilizing BioComposite™ Interference Screws (Arthrex, Inc., Naples, FL) was performed. Complications related to screw placement, including fracture, breakage or bending were examined. Our rate and methods of failure were compared to those quoted in the current literature. RESULTS: Eighty-seven patients of average age 23.8 years met inclusion criteria. There were eight screw failures in six patients, with femoral failure in seven and tibial failure in one. The femoral screw fractured halfway between the tip and head in five, while the head of the screw broke in one and the screw bent in another. In the case of tibial interference screw fracture, failure occurred halfway between the tip and head. The insertion device that was used was replaced after recognition of material deformation and considered a potential contributor to the breakage risk as no further screw failures have occurred since. CONCLUSIONS: We demonstrate a unique failure mechanism of bio-absorbable interference screws. In each case, the reconstruction was salvaged. Regular inspection of materials and implants can ensure optimal outcomes and decrease complications intra-operatively.

Effect of lower extremity fasciotomy length on intracompartmental pressure in an animal model of compartment syndrome: the importance of achieving a minimum of 90% fascial release.

BACKGROUND: There has been an increase in minimally invasive surgery for chronic exertional compartment syndrome (CECS), despite the potential for incomplete compartment release and iatrogenic injuries. To our knowledge, no study has examined the effect of the length of fascial release on compartment pressures. PURPOSE/HYPOTHESIS: The purpose was to explain the high failure rate seen in fascial release for CECS by evaluating the effect of fasciotomy length on intracompartmental pressures. We hypothesized that complete fascial release would need to be performed to return pressures to baseline levels. STUDY DESIGN: Controlled laboratory study. METHODS: Five male swine (10 lower extremities) were anesthetized. A slit catheter, connected to a pressure monitor, was inserted into the anterior compartment and a solution containing 5% swine albumin was injected into the compartment until the compartment pressure was >25 mm Hg for 10 minutes. Pressures were measured at rest, after the injection, and after each 10% incremental fasciotomy release. RESULTS: The mean resting intracompartmental pressure was 3.2 mm Hg (range, 0-6 mm Hg), which increased after the injection to a mean of 37 mm Hg (range, 26-67 mm Hg). After complete fasciotomy, the mean pressure was 1.1 mm Hg (range, 0-4 mm Hg). There was a strong negative correlation (r=-0.693) between fasciotomy length and intracompartmental pressure. In 90% of the specimens, the pressures were <15 mm Hg after 80% fascial release, and after 90% release, all pressures were ≤8 mm Hg. CONCLUSION: This study demonstrates a strong correlation between fasciotomy length and a reduction in intracompartmental pressures in a swine model. Our study suggests that 90% fascial release may represent a possible watershed zone, returning the intracompartmental pressure to a value at or near baseline values. CLINICAL RELEVANCE: The results suggest that even in cases with near complete fascial release, intracompartmental pressures may decrease enough to provide symptomatic relief and avoid possible iatrogenic injuries associated with percutaneous release. It is unknown whether the swine model may adequately translate to the clinical setting; thus, recommendations should be taken with caution, and future studies should be performed to examine the correlation in a human model.