AAHKS Best Podium Presentation Research Award: Femoral Perforation During Direct Anterior Approach Total Hip Arthroplasty: Incidence, Cohort Characteristics, and Management.

BACKGROUND: Cortical perforation during femoral preparation is a recognized complication of total hip arthroplasty (THA) but the incidence, patient characteristics, management, and outcome have not been described for the direct anterior approach (DAA). METHODS: A database query of all primary and conversion DAA THAs performed by a single surgeon from 2009 to 2021 was used to identify hips that sustained a recognized intraoperative femoral perforation. Radiographs were used to assess stem subsidence, Dorr femur type, and Canal Flare Index. RESULTS: Among 3,973 THAs, 16 patients (0.4%) sustained perforations during broaching including 8 males and 8 females with a mean age at surgery of 65.6 (range 41-81) years and a mean body mass index of 31.0 (range 19.0-44.4). Two hips were converted to longer primary cementless stems to bypass the perforation. For the remaining 14, the broach was redirected and the same primary stem was implanted. Limited weight-bearing (6 patients) or protected weight-bearing as tolerated with a walker/cane (10 patients) was advised postoperatively. At a mean follow-up of 18.7 (range 4-105) months, all stems were stable with no fractures, subsidence, or revisions. Factors associated with perforation included difficulty with exposure (body mass index >40 or a contracture), measurable osteoporosis (Canal Flare Index <3.0), and abnormal proximal femoral anatomy due to prior trauma, retained hardware, or Perthes disease. CONCLUSION: In this case series, isolated perforation of an otherwise intact femur during DAA was successfully managed with redirection of the broach, implantation of a primary stem that achieved axial/rotational stability, and protected weight-bearing. LEVEL OF EVIDENCE: IV, Case Series.

Does a Reduced Number of Muscle Stem Cells Impair the Addition of Sarcomeres and Recovery from a Skeletal Muscle Contracture? A Transgenic Mouse Model.

BACKGROUND: Children with cerebral palsy have impaired muscle growth and muscular contractures that limit their ROM. Contractures have a decreased number of serial sarcomeres and overstretched lengths, suggesting an association with a reduced ability to add the serial sarcomeres required for normal postnatal growth. Contractures also show a markedly reduced number of satellite cells-the muscle stem cells that are indispensable for postnatal muscle growth, repair, and regeneration. The potential role of the reduced number of muscle stem cells in impaired sarcomere addition leading to contractures must be evaluated. QUESTIONS/PURPOSES: (1) Does a reduced satellite cell number impair the addition of serial sarcomeres during recovery from an immobilization-induced contracture? (2) Is the severity of contracture due to the decreased number of serial sarcomeres or increased collagen content? METHODS: The hindlimbs of satellite cell-specific Cre-inducible mice (Pax7; Rosa26; n = 10) were maintained in plantarflexion with plaster casts for 2 weeks so that the soleus was chronically shortened and the number of its serial sarcomeres was reduced by approximately 20%. Subsequently, mice were treated with either tamoxifen to reduce the number of satellite cells or a vehicle (an injection and handling control). The transgenic mouse model with satellite cell ablation combined with a casting model to reduce serial sarcomere number recreates two features observed in muscular contractures in children with cerebral palsy. After 30 days, the casts were removed, the mice ankles were in plantarflexion, and the mice's ability to recover its ankle ROM by cage remobilization for 30 days were evaluated. We quantified the number of serial sarcomeres, myofiber area, and collagen content of the soleus muscle as well as maximal ankle dorsiflexion at the end of the recovery period. RESULTS: Mice with reduced satellite cell numbers did not regain normal ankle ROM in dorsiflexion; that is, the muscles remained in plantarflexion contracture (-16° ± 13° versus 31° ± 39° for the control group, -47 [95% confidence interval -89 to -5]; p = 0.03). Serial sarcomere number of the soleus was lower on the casted side than the contralateral side of the mice with a reduced number of satellite cells (2214 ± 333 versus 2543 ± 206, -329 [95% CI -650 to -9]; p = 0.04) but not different in the control group (2644 ± 194 versus 2729 ± 249, -85 [95% CI -406 to 236]; p = 0.97). The degree of contracture was strongly associated with the number of sarcomeres and myofiber area (r =0.80; P < 0.01) rather than collagen content. No differences were seen between groups in terms of collagen content and the fraction of muscle area. CONCLUSIONS: We found that a reduced number of muscle stem cells in a transgenic mouse model impaired the muscle's ability to add sarcomeres in series and thus to recover from an immobilization-induced contracture. CLINICAL RELEVANCE: The results of our study in transgenic mouse muscle suggests there may be a mechanistic relationship between a reduced number of satellite cells and a reduced number of serial sarcomeres. Contracture development, secondary to impaired sarcomere addition in muscles in children with cerebral palsy may be due to a reduced number of muscle stem cells.

Comparison of the iAssist Handheld Guidance System to Conventional Instruments for Mechanical Axis Restoration in Total Knee Arthroplasty.

BACKGROUND: Recent advances in total knee arthroplasty (TKA) include an intelligent instrument system designed to provide intraoperative guidance to reduce mechanical alignment errors. Internal position-sensing technology is integrated into microelectronic pods that attach to cutting blocks. The purpose of this prospective, randomized study was to determine whether this iAssist system enables the surgeon to make more accurate bone resections and better restore the mechanical axis compared to conventional instruments in TKA. METHODS: We randomized patients undergoing TKA into 2 groups. Group I (n = 25) underwent TKA assisted by the iAssist guidance system, group II (n = 25) underwent TKA using conventional instruments. Preoperative and postoperative mechanical axes were measured from full-length lower extremity radiographs to evaluate alignment. Additional surgical parameters were also assessed, including tourniquet time and blood loss. RESULTS: Patient demographics and preoperative mechanical axis alignments were similar between the groups. Postoperatively, 4.0% of patients had greater than 3° of tibial or femoral component mal-alignment in the guidance-assisted cohort, compared with 36.0% in the conventional group (P < .05). Additionally, group I showed significant improvement in variance seen in both the femoral mechanical axis (1.65° ± 0.17° vs 2.23° ± 0.33°, P < .005) and tibial mechanical axis (1.28° ± 0.13° vs 1.71° ± 0.24°, P < .005) compared to group II. There were no significant differences in tourniquet time (P = .86) or blood loss (P = .39) between groups. CONCLUSION: Use of the iAssist system in TKA results in an improved postoperative mechanical axis and decreased alignment variability compared to conventional instruments, without significantly increasing operative time.

Reduced skeletal muscle satellite cell number alters muscle morphology after chronic stretch but allows limited serial sarcomere addition.

INTRODUCTION: Muscles add sarcomeres in response to stretch, presumably to maintain optimal sarcomere length. Clinical evidence from patients with cerebral palsy, who have both decreased serial sarcomere number and reduced satellite cells (SCs), suggests a hypothesis that SCs may be involved in sarcomere addition. METHODS: A transgenic Pax7-DTA mouse model underwent conditional SC depletion, and their soleii were then stretch-immobilized to assess the capacity for sarcomere addition. Muscle architecture, morphology, and extracellular matrix (ECM) changes were also evaluated. RESULTS: Mice in the SC-reduced group achieved normal serial sarcomere addition in response to stretch. However, muscle fiber cross-sectional area was significantly smaller and was associated with hypertrophic ECM changes, consistent with fibrosis. CONCLUSIONS: While a reduced SC population does not hinder serial sarcomere addition, SCs play a role in muscle adaptation to chronic stretch that involves maintenance of both fiber cross-sectional area and ECM structure. Muscle Nerve 55: 384-392, 2017.

Operative Versus Conservative Management of Displaced Tibial Shaft Fracture in Adolescents.

BACKGROUND: Displaced tibial shaft fractures are common in adolescent patients, yet there is no standardized management strategy. We compared surgical fixation and closed reduction and casting (CRC) of these fractures to assess treatment outcomes and determine predictors of failure. METHODS: We retrospectively reviewed all patients aged 12 to 18 who presented with a displaced tibial shaft fracture that required reduction over an 8-year period. Exclusion criteria included open fractures and lack of follow-up to radiographic union or to 6 months from the index procedure. Fractures were initially treated based on surgeon preference either with CRC or with immediate intramedullary nailing. Seventy-four patients met inclusion criteria: 57 were initially managed with CRC and 17 with operative fixation. Radiographic healing was defined as bridging of 3 cortices and adequacy of final alignment was defined as <5 degrees of angular deformity in both planes and <1.0 cm of shortening. Outcomes were analyzed both on intent-to-treat principles and by definitive treatment method. RESULTS: Although all fractures in both groups achieved bony healing, 23 of the 57 patients who underwent CRC failed closed treatment and ultimately required surgery (40.3%). Multivariate analysis of patient and fracture characteristics revealed fracture displacement of >20% (odds ratio=7.8, P<0.05) and the presence of a fibula fracture (odds ratio=5.06, P=0.05) as predictors of closed treatment failure. Patients ultimately managed with intramedullary nailing trended toward increased adequacy of final alignment (92.5% vs. 72.4%, P=0.10) but required longer hospitalization (5.4 vs. 1.9 d, P<0.001) and had a higher incidence of anterior knee pain (20% vs. 0%, P<0.01). There was no significant difference between groups with respect to time to healing. CONCLUSIONS: Treatment outcomes between initial operative fixation and closed reduction of displaced tibia fractures in adolescents are similar, but patients must be counseled about the high failure rates with CRC. Predictors of CRC failure include initial fracture displacement and the presence of a fibula fracture-these variables should be considered when selecting a treatment method. LEVEL OF EVIDENCE: Level III-Therapeutic study.

Revision total knee arthroplasty after severe notching of the anterior femoral cortex.

Anterior femoral cortex notching is a known complication of total knee arthroplasty (TKA). In severe cases, notching may alter the mechanical properties of the distal femur. We report a patient with significant femoral notching and malpositioning of the femoral prosthesis after TKA, leading to unresolved postoperative pain, decreased range of motion, and functional disability. The severity of this lesion required the use of augments and an offset femoral stem for improved alignment during revision arthroplasty, which is described in this brief technical note.

The deubiquitinase CYLD targets Smad7 protein to regulate transforming growth factor ß (TGF-ß) signaling and the development of regulatory T cells.

CYLD is a lysine 63-deubiquitinating enzyme that inhibits NF-κB and JNK signaling. Here, we show that CYLD knock-out mice have markedly increased numbers of regulatory T cells (Tregs) in peripheral lymphoid organs but not in the thymus. In vitro stimulation of CYLD-deficient naive T cells with anti-CD3/28 in the presence of TGF-ß led to a marked increase in the number of Foxp3-expressing T cells when compared with stimulated naive control CD4(+) cells. Under endogenous conditions, CYLD formed a complex with Smad7 that facilitated CYLD deubiquitination of Smad7 at lysine 360 and 374 residues. Moreover, this site-specific ubiquitination of Smad7 was required for activation of TAK1 and p38 kinases. Finally, knockdown of Smad7 or inhibition of p38 activity in primary T cells impaired Treg differentiation. Together, our results show that CYLD regulates TGF-ß signaling function in T cells and the development of Tregs through deubiquitination of Smad7.

A novel mutation in NFKBIA/IKBA results in a degradation-resistant N-truncated protein and is associated with ectodermal dysplasia with immunodeficiency.

Alterations in nuclear factor kappa B (NF-kappaB) essential modulator (NEMO; HUGO-approved symbol IKBKG) underlie most cases of ectodermal dysplasia with immune deficiency (EDI), a human disorder characterized by anhidrosis with diminished immunity. EDI has also been associated with a single heterozygous mutation at position Ser32 of the NF-kappaB inhibitor IkappaBalpha, one of two phosphorylation sites that are essential for targeting IkappaBalpha for proteasomal degradation and hence for activation of NF-kappaB. We report a novel heterozygous nonsense mutation in the IKBA (HUGO-approved symbol, NFKBIA) gene of a 1-year-old male child with EDI that introduces a premature termination codon at position Glu14. An in-frame methionine downstream of the nonsense mutation allows for reinitiation of translation. The resulting N-terminally truncated protein lacks both serine phosphorylation sites and inhibits NF-kappaB signaling by functioning as a dominant negative on NF-kappaB activity in lymphocytes and monocytes. These findings support the scanning model for translation initiation in eukaryotes and confirm the critical role of the NF-kappaB in the human immune response.

Fusobacterium nucleatum Osteomyelitis of the Femur in a Patient with Hereditary Hemorrhagic Telangiectasia: A Case Report.

CASE: Hereditary hemorrhagic telangiectasia (HHT), also known as Osler-Weber-Rendu syndrome, is an often overlooked cause of orthopaedic-related infections despite a well-accepted association in the literature. We present the case of a forty-seven-year-old man with HHT who developed femoral osteomyelitis and a subsequent pathologic femoral fracture from a rare bacterial species associated with HHT. CONCLUSION: Patients with HHT and extremity pain should be carefully evaluated for orthopaedic infections. If an orthopaedic infection is suspected, fastidious organisms should be considered as a possible etiologic agent. PCR (polymerase chain reaction) is helpful when organisms cannot be isolated from traditional culture media.

Osteolytic pseudotumor after cemented total knee arthroplasty.

Wear debris leading to local inflammatory reactive changes and osteolysis is a common complication after total knee arthroplasty (TKA). While massive osteolytic lesions may be commonly encountered in the revision setting, the appearance and location of these lesions rarely mimic expansile bone lesions. We report a case of severe osteolysis in a cemented TKA design, which presented as a pseudotumor of the fibular head. The diagnostic work-up and pathologic analysis are included in this report of a pseudotumor secondary to wear debris osteolysis.

Reducing costly falls of total knee replacement patients.

The objective of this study was to determine whether the use of a knee immobilizer brace reduces patient falls associated with the recent use of femoral nerve blocks for pain control after total knee arthroplasty (TKA). The authors conducted a retrospective study to investigate fall rates before and after the introduction of an immobilizer brace. The demographics of patients and total cost of care were examined. Of the 600 TKA patients who did not receive a knee immobilizer, 22 (3.7%) experienced a fall. In contrast, of the 502 patients who received knee immobilizers, only 8 patients (1.6%) fell. This difference achieves statistical significance (P = .04). Given the considerable costs associated with hospital falls and the significant reduction of these falls related to knee immobilizer use shown in this study, the authors recommend that knee immobilizers be given to TKA patients as standard practice.