Nikolas H. Kazmers

Rho GTPase signaling and PTH 3–34, but not PTH 1–34, maintain the actin cytoskeleton and antagonize bisphosphonate effects in mouse osteoblastic MC3T3-E1 cells

Cytoskeletal elements are critical for cell morphology and signal transduction, and are involved in many cellular processes including motility, intracellular transport, and differentiation. Small GTP-binding proteins (G proteins) of the Ras family, such as RhoA, influence various elements of the cytoskeleton. RhoA stabilizes the actin cytoskeleton and promotes formation of focal adhesions. We found previously that RhoA is expressed in osteoblastic cells and is translocated to the plasma membrane and activated by PTH 1-34 as well as by Nleu(8,18) Tyr(34) PTH 3-34 amide, a PTH analog that does not increase cAMP. We therefore investigated effects of manipulating RhoA on the actin cytoskeleton of osteoblastic MC3T3-E1 cells. Three inhibitors were used: 1) GGTI-2166, a geranylgeranyl transferase I inhibitor that prevents the isoprenylation and membrane translocation of RhoA, 2) Y-27632, a Rho kinase inhibitor, and 3) alendronate, a nitrogen (N)-containing bisphosphonate that reduces intracellular geranylgeranylpyrophosphate through inhibiting farnesyl pyrophosphate synthase. To increase RhoA activity, we used the geranylgeranyl group donor geranylgeraniol (GGOH), and a constitutively active RhoA. The F-actin cytoskeleton and focal adhesions (FA) were visualized with rhodamine-phalloidin and fluorescent anti-vinculin antibodies, respectively. Cells were imaged with confocal microscopy. Actin stress fiber density, edge actin bundle density, focal adhesion density, cellular area and circularity (a morphological descriptor relating area and perimeter) were quantified by a program developed with Matlab software. GGTI-2166, Y-27632, and alendronate reduced actin stress fibers, FA density, and FA size, but had no effect on edge actin bundle density, cellular area, or circularity. GGOH completely antagonized the effects of alendronate, but did not significantly affect responses to GGTI-2166 or Y-27632. Constitutively active RhoA antagonized the effects of alendronate and GGTI-2166, but not those of Y-27632. The effects of alendronate were also antagonized by Nleu(8,18) Tyr(34) PTH 3-34 amide, but not by PTH 1-34. The results indicate that RhoA is involved in the maintenance of stress fibers and focal adhesions in osteoblastic cells, that PTH can affect this pathway independently of cAMP, and that a N-containing bisphosphonate can affect the actin cytoskeleton and focal adhesions through actions on geranylgeranyl groups and potentially through RhoA. In view of the importance of the actin cytoskeleton, the findings constitute evidence that N-containing bisphosphonates, when they attain certain concentrations, have effects on osteoblasts that could influence bone remodeling.

Prevention of pin site infection in external fixation: a review of the literature.

Abstract Pin site infections are a common complication of external fixation that places a significant burden on the patient and healthcare system. Such infections increase the number of clinic visits required during a patient’s course of treatment, can result in the need for additional treatment including antibiotics and surgery, and most importantly can compromise patient outcomes should osteomyelitis or instability result from pin loosening or need for pin or complete construct removal. Factors that may influence the development of pin site infections include patient-specific risk factors, surgical technique, pin design characteristics, use of prophylactic antibiotics, and the post-operative pin care protocol including cleansing, dressing changes, and showering. Despite numerous studies that work to derive evidence-based recommendations for prevention of pin site infections, substantial controversy exists in regard to the optimal protocol. This review comprehensively evaluates the current literature to provide an overview of factors that may influence the incidence of pin site infections in patients undergoing treatment with external fixators, and concludes with a description of the preferred surgical and post-operative pin site protocols employed by the senior authors (ATF and SRR).

Hedgehog signaling mediates woven bone formation and vascularization during stress fracture healing

Hedgehog (Hh) signaling is critical in developmental osteogenesis, and recent studies suggest it may also play a role in regulating osteogenic gene expression in the post-natal setting. However, there is a void of studies directly assessing the effect of Hh inhibition on post-natal osteogenesis. This study utilized a cyclic loading-induced ulnar stress fracture model to evaluate the hypothesis that Hh signaling contributes to osteogenesis and angiogenesis during stress fracture healing. Immediately prior to loading, adult rats were given GDC-0449 (Vismodegib - a selective Hh pathway inhibitor; 50mg/kg orally twice daily), or vehicle. Hh signaling was upregulated in response to stress fracture at 3 days (Ptch1, Gli1 expression), and was markedly inhibited by GDC-0449 at 1 day and 3 days in the loaded and non-loaded ulnae. GDC-0449 did not affect Hh ligand expression (Shh, Ihh, Dhh) at 1 day, but decreased Shh expression by 37% at 3 days. GDC-0449 decreased woven bone volume (-37%) and mineral density (-17%) at 7 days. Dynamic histomorphometry revealed that the 7 day callus was composed predominantly of woven bone in both groups. The observed reduction in woven bone occurred concomitantly with decreased expression of Alpl and Ibsp, but was not associated with differences in early cellular proliferation (as determined by callus PCNA staining at 3 days), osteoblastic differentiation (Osx expression at 1 day and 3 days), chondrogenic gene expression (Acan, Sox9, and Col2α1 expression at 1 day and 3 days), or bone resorption metrics (callus TRAP staining at 3 days, Rankl and Opg expression at 1 day and 3 days). To evaluate angiogenesis, vWF immunohistochemistry showed that GDC-0449 reduced fracture callus blood vessel density by 55% at 3 days, which was associated with increased Hif1α gene expression (+30%). Dynamic histomorphometric analysis demonstrated that GDC-0449 also inhibited lamellar bone formation. Lamellar bone analysis of the loaded limb (directly adjacent to the woven bone callus) showed that GDC-0449 significantly decreased mineral apposition rate (MAR) and bone formation rate (BFR/BS) (-17% and -20%, respectively). Lamellar BFR/BS in the non-loaded ulna was also significantly decreased (-37%), indicating that Hh signaling was required for normal bone modeling. In conclusion, Hh signaling plays an important role in post-natal osteogenesis in the setting of stress fracture healing, mediating its effects directly through regulation of bone formation and angiogenesis.

A Scapholunate Ligament–Sparing Technique Utilizing the Medial Femoral Condyle Corticocancellous Free Flap to Reconstruct Scaphoid Nonunions With Proximal Pole Avascular Necrosis

This article demonstrates a technique for the treatment of scaphoid fracture waist and proximal pole nonunions with avascular necrosis using a free vascularized medial femoral condyle flap. We present our surgical technique and representative case examples in which the scapholunate ligament, a key structure required to preserve carpal kinematics, is spared.

Patient- and Disease-Specific Factors Associated With Operative Management of de Quervain Tendinopathy

PURPOSE It remains unclear which factors, patient- or disease-specific, are associated with electing to undergo operative management for de Quervain tendinopathy. Our null hypothesis was that no patient- or disease-specific factors would be associated with the choice of surgical treatment of de Quervain tendinopathy. METHODS We performed a retrospective review of consecutive patients diagnosed with de Quervain tendinopathy over 3 years by 1 of 3 fellowship-trained hand surgeons at an urban academic institution. Descriptive statistics were calculated for patient baseline and disease-specific characteristics. Cohorts were compared using bivariate analysis for all collected variables. Binary logistic regression with backward stepwise term selection was performed including independent predictors identified by bivariate analysis. RESULTS A total of 200 patients were identified for inclusion. Bivariate analysis revealed that surgically treated patients were significantly more likely to have Medicaid insurance, psychiatric illness history, and disabled work status. Regression analysis revealed an association between surgical treatment and 2 of the factors evaluated: Medicaid insurance status and psychiatric illness history. CONCLUSIONS Psychiatric illness and Medicaid insurance status are associated with undergoing surgical release of the first dorsal compartment. These findings support the use of a biopsychosocial framework when treating patients with de Quervain tendinopathy. TYPE OF STUDY/LEVEL OF EVIDENCE Prognostic IV.

Upper and lower extremity reconstructive applications utilizing free flaps from the medial genicular arterial system: A systematic review

Free flaps derived from the medial genicular artery (MGA) system, including the medial femoral condyle (MFC) and medial femoral trochlear (MFT) flaps, are potential reconstructive options to address upper and lower extremity bony pathology. Our primary aim was to comprehensively search the literature to describe the spectrum of pathology treated with these flaps, and to assess patient outcomes to improve our understanding of expected union and complication rates.

Ultrasonographic Evaluation of Zone II Partial Flexor Tendon Lacerations of the Fingers: A Cadaveric Study

Accurate assessment of zone II partial flexor tendon lacerations in the finger is clinically important. Surgical repair is recommended for lacerations of greater than 50% to 60%. Our goal was to evaluate ultrasonographic test characteristics and accuracy in identifying partial flexor tendon lacerations in a cadaveric model.

Deferring Routine Wrist Radiography Does Not Affect Management of de Quervain Tendinopathy Patients

Background Obtaining wrist radiographs prior to surgeon evaluation may be wasteful for patients ultimately diagnosed with de Quervain tendinopathy (DQT). Questions/Purpose Our primary question was whether radiographs directly influence treatment of patients presenting with DQT. A secondary question was whether radiographs influence the frequency of injection and surgical release between cohorts with and without radiographs evaluated within the same practice. Patients and Methods Patients diagnosed with DQT by fellowship‐trained hand surgeons at an urban academic medical center were identified retrospectively. Basic demographics and radiographic findings were tabulated. Clinical records were studied to determine whether radiographic findings corroborated history or physical examination findings, and whether management was directly influenced by radiographic findings. Frequencies of treatment with injection and surgery were separately tabulated and compared between cohorts with and without radiographs. Results We included 181 patients (189 wrists), with no differences in demographics between the 58% (110 wrists) with and 42% (79 wrists) without radiographs. Fifty (45%) of imaged wrists demonstrated one or more abnormalities; however, even for the 13 (12%) with corroborating history and physical examination findings, wrist radiography did not directly influence a change in management for any patient in this series. No difference was observed in rates of injection or surgical release either upon initial presentation, or at most recent documented follow‐up, between those with and without radiographs. No differences in frequency, types, or total number of additional simultaneous surgical procedures were observed for those treated surgically. Conclusion Wrist radiography does not influence management of patients presenting DQT. Level of Evidence This is a level III, diagnostic study.

Elbow vascularized composite allotransplantation—surgical anatomy and technique

BACKGROUND Elbow reconstruction with vascularized composite allotransplantation (VCA) may hold promise in treating end-stage arthritis as no current treatment is both functional and durable. We describe the vascular and gross anatomy of the elbow in the context of VCA procurement and propose a step-by-step surgical technique for human elbow VCA. METHODS We injected latex in the arterial tree of 16 fresh adult cadaveric upper extremities. We identified and measured arteries and nerves and their branch points relative to the medial epicondyle. Based on our determination of the dominant blood supply to osseous and capsular elbow structures, we derived a cadaveric model of elbow VCA by performing donor preparation on 2 fresh cadaveric upper extremities by elevating a lateral arm flap in conjunction with the vascularized elbow joint. We prepared and transplanted 2 size-matched recipient specimens to refine the surgical technique. RESULTS The elbow arterial supply was composed of consistent branches contributing to medial, lateral, and posterior arcades. Preservation of the elbow arterial network requires sectioning of the brachial, radial, and ulnar arteries 12 cm proximal, 1 cm distal, and 6 cm distal to the ulnar artery takeoff, respectively. The supinator, anconeus, distal brachialis, proximal aspects of the flexor digitorum profundus, and flexor carpi ulnaris must be preserved to protect osseous perforators. Articular innervation was most commonly derived from ulnar and median nerve branches. We refined our proposed surgical technique after performing 2 cadaveric elbow VCAs. CONCLUSIONS Elbow VCA may be technically feasible on the basis of its consistent vascular anatomy and our proposed surgical technique.

2510: Elbow vascularized composite allotransplantation - Surgical anatomy and technique

2510: Elbow vascularized composite allotransplantation Surgical anatomy and technique Zvi Steinberger, MD, Heng Xu, Nikolas H. Kazmers, Stephanie Thibaudeau, Russel G. Huffman, and L. Scott Levin University of Pennsylvania, Philadelphia, PA, USA Background Elbow reconstruction with vascularized composite allotransplantation (VCA) may hold promise in treating end-stage arthritis, as no current treatment is both functional and durable. We describe the vascular and gross anatomy of the elbow in the context of VCA procurement, and propose a step-by-step surgical technique for elbow VCA. Methods Sixteen fresh adult cadaveric upper extremities underwent arterial tree latex injection. Arteries, nerves, and their branch points were identified and measured relative to the medial epicondyle. Based upon our determination of the dominant blood supply to elbow osseous and capsular structures, a cadaveric model of elbow VCA was derived by performing donor preparation on two fresh cadaveric upper extremities, with elevation of a lateral arm flap in conjunction with the vascularized elbow joint. Two size-matched specimens underwent recipient preparation, followed by transplantation. The surgical technique was refined with each successive transplant. Results The arterial supply to the elbow was comprised of consistent branches contributing to medial, lateral, and posterior arcades (Table 1). Preservation of the elbow arterial network requires sectioning of brachial, radial and ulnar arteries 12 cm proximal, 1 cm distal, and 6 cm distal to the ulnar artery take-off, respectively. Preservation of the supinator, anconeus, distal brachialis, proximal aspects of the flexor digitorum profundus, and flexor carpi ulnaris is required to protect osseous perforators. Nerves branches to the joint most commonly were derived from ulnar and median nerves (Table 1). Following two cadaveric elbow VCA procedures, our proposed surgical technique has been refined (Table 2).