Tendon Healing in a Mouse Model of Loeys-Dietz Syndrome: Controlled Study Using a Patellar Tendon Transection Model.

BACKGROUND: Loeys-Dietz syndrome (LDS) is a rare autosomal-dominant connective tissue disorder caused by genetic mutations in the transforming growth factor-ß (TGFß) signaling pathway. In addition to vascular malformations, patients with LDS commonly present with bone and tendon abnormalities, including joint laxity. While TGFß signaling dysregulation has been implicated in many of these clinical manifestations, the degree to which it influences the tendinopathy and tendon healing issues in LDS has not been determined. METHODS: Wound healing after patellar tendon transection was compared between wild-type (WT) and Tgfbr2-mutant (LDS) mice (7 mice per group). In all mice, the right patellar tendon was transected at midsubstance, while the left was untouched to serve as a control. Mice were euthanized 6 weeks after surgery. Tendon specimens were harvested for histopathologic grading according to a previously validated scoring metric, and gene expression levels of Mmp2, Tgfb2, and other TGFß-signaling genes were assayed. Between-group comparisons were made using 1-way analysis of variance with post hoc Tukey honestly significant difference testing. RESULTS: Expression levels of assayed genes were similar between LDS and WT tendons at baseline; however, at 6 weeks after patellar tendon transection, LDS tendons showed sustained elevations in Mmp2 and Tgfb2 compared with baseline values; these elevations were not seen in normal tendons undergoing the same treatments. Histologically, untreated LDS tendons had significantly greater cellularity and cell rounding compared with untreated WT tendons, and both WT and LDS tendons had significantly worse histologic scores after surgery. CONCLUSION: We present the first mechanistic insight into the effect of LDS on tendons and tendon healing. The morphologic differences between LDS and WT tendons at baseline may help explain the increased risk of tendon/ligament dysfunction in patients with LDS, and the differential healing response to injury in LDS may account for the delayed healing and weaker repair tissue. LEVEL OF EVIDENCE: Level V.

A single-center retrospective review of factors influencing surgical success in patients with cerebral palsy undergoing corrective hip surgery.

PURPOSE: To identify factors associated with success of corrective bony hip surgery among patients with cerebral palsy (CP). METHODS: A retrospective review was conducted of medical records of patients diagnosed with CP and hip displacement who underwent surgery from 2004 to 2016 at the authors' institution and who had a one-year minimum follow-up. Patient age, sex, Gross Motor Function Classification System (GMFCS) level, surgical procedure(s), type and extent of CP, presence of preoperative and postoperative hip pain, and hip migration percentages (MPs) were recorded. Surgical success was defined as a postoperative MP ⩽ 30% and no hip pain at final follow-up. RESULTS: Thirty-eight patients (55 hips) met the inclusion criteria. Mean age at surgery was 10.2 years (range, 2-24 years). Mean MP (standard deviation) improved from 64 ± 29% preoperatively to 22 ± 30% at a mean 1.7-year follow-up (p< 0.001). The absence of preoperative hip pain (p= 0.014), surgery after age 5 (p= 0.041), and a milder preoperative MP (p< 0.001) were significantly associated with surgical success. CONCLUSION: In patients with CP and hip displacement, early preventative correction of hip displacement after age 5 may improve clinical outcomes, though future studies are needed to provide more definitive clinical direction.