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Purpose To evaluate intra-operative findings and outcomes of revision carpal tunnel release (CTR) and to identify predictors of pain outcomes. Methods A retrospective cohort study was performed of all adult patients undergoing revision CTR between 2001 and 2012. Patients were classified according to whether they presented with persistent, recurrent, or new symptoms. Study groups were compared by baseline characteristics, intra-operative findings, and outcomes (strength, pain). Within each group, changes in postoperative pinch strength, grip strength, and pain from baseline were analyzed. Predictors of postoperative average pain were examined using both multivariable linear regression analyses and univariable logistic regression to calculate odds ratios of worsened/no change in pain. Results Revision CTR was performed in 97 extremities (87 patients). Symptoms were classified as persistent in 42, recurrent in 19, and new in 36 hands. The recurrent group demonstrated more diabetes and a longer interval from primary CTR and was less likely to present with pain. Incomplete release of the flexor retinaculum and scarring of the median nerve were common intraoperative findings overall. Nerve injury was more common in the new group. Postoperative pinch strength, grip strength, and pain significantly improved from baseline in all groups, apart from strength measures in the recurrent group. Persistent symptoms and more than 1 prior CTR had higher odds of not changing or worsening postoperative pain. Higher preoperative pain, use of pain medication, and worker’s compensation were significant predictors of higher postoperative average pain. Discussion Carpal tunnel release may not always be entirely successful. Most patients do improve following revision CTR, but a methodical approach to diagnosis and adherence to safe surgical principles are likely to improve outcomes. Symptom classification, number of prior carpal tunnel releases, baseline pain, pain medications, and worker’s compensation status are important predictors of pain outcomes in this population. Level of Evidence Therapeutic Level III

Background Biological scaffolds must support a complex balance of resisting enzymatic degradation while promoting tissue remodeling. Thus, the purpose of this study was to evaluate the effects of in vitro enzymatic exposure on the mechanical properties of biological scaffolds. It was hypothesized that exposure to an enzyme solution would result in decreased tensile strength and that crosslinked scaffolds would resist enzymatic degradation more effectively than noncrosslinked scaffolds. Methods Nine scaffolds were evaluated (four porcine dermis: Permacol™, CollaMend™, Strattice™, XenMatrix™; two human dermis: AlloMax™, FlexHD®; two bovine pericardium: Veritas®, PeriGuard®; and one porcine small intestine submucosa: Surgisis™). Ten specimens (n = 10) were hydrated in saline at 37 °C and subjected to uniaxial testing to establish baseline properties. 50 specimens (n = 50) were incubated in collagenase solution at 37 °C for 2, 6, 12, 24, or 30 h (n = 10 each group) followed by uniaxial tensile testing. Results Tensile strength was significantly reduced after 30 h for CollaMend™, AlloMax™, Veritas®, Strattice™, XenMatrix™, Permacol™, and FlexHD® (p < 0.01), while PeriGuard® demonstrated a slight increase in tensile strength (p = 0.0188). Crosslinked bovine pericardium (PeriGuard®) maintained greater tensile strength than noncrosslinked bovine pericardium (Veritas®) throughout all exposure periods (p < 0.0001). Similarly, crosslinked porcine dermis (Permacol™) maintained greater tensile strength than non-crosslinked porcine dermis (Strattice™ and XenMatrix™) throughout all exposure periods (p < 0.0001). Conclusions Materials that deteriorate rapidly after in vitro enzymatic exposure may also deteriorate rapidly in vivo, particularly when exposed to a wound environment with elevated levels of matrix metalloproteinases. Permacol™, CollaMend™, Strattice™, FlexHD®, and Peri-Guard® survived the longest incubation period (30 h) and withstood mechanical testing. XenMatrix™, AlloMax™, Veritas®, and Surgisis™ degraded more quickly and did not survive the longer exposure periods. Scaffolds that maintain strength characteristics after in vitro collagenase exposure may be advantageous for long-term hernia repair scenarios where elevated enzyme levels are expected.

Two electrospun scaffolds (12 % PCL, 10 mL/h and 12 % PCL, 6 mL/h) possessed suture retention and tensile strengths appropriate for hernia repair, justifying evaluation in a large animal model. Additional studies examining advanced methods of fabrication may further improve the unique properties of these scaffolds, propelling them into applications in a variety of clinical settings.

Diagnostic, II.

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Patients can and do improve following revision cubital tunnel surgery, particularly as it relates to pain. Intraoperative findings during the revision procedure suggest that adherence to specific principles in the primary operation is key to prevention of secondary cubital tunnel syndrome.