Spherical versus elliptical prosthetic humeral heads: a comparison of anatomic fit.

BACKGROUND: The aim of this study was to quantify the influence of prosthetic humeral head shape, as well as the number of available prosthetic head sizes, on replicating the normal humeral head anatomy during shoulder reconstructive surgery. METHODS: Computer modeling software was used to create virtual sets of both spherical and elliptical prosthetic heads, which were virtually implanted into 3-dimensional computed tomography scan-based models of 79 proximal humeri. Anatomic replication was considered successful if the measured parameters (diameters of the base of the head in the frontal and sagittal planes, radii of curvature in the frontal and sagittal planes, and humeral head height) were all reproduced within 3 mm. The Fisher exact test was used to compare the percentage of successful replications for both head types and to compare differences resulting from the use of sets with fewer or more available head sizes. Statistical significance was set at P ≤ .05. RESULTS: Regardless of the number of available head sizes per set, it was possible to replicate the normal anatomy within 3 mm in a higher percentage of specimens using elliptical (96%-100%) as opposed to spherical (41%-78%) prosthetic heads (P ≤ .0013). CONCLUSION: Compared with use of spherical prosthetic heads, use of elliptical heads resulted in improved replication of the normal humeral head shape. In light of the emerging evidence that use of anatomically shaped prosthetic humeral heads might lead to better shoulder function and possibly improved implant survivorship, the findings of this study may have important clinical and economic implications.

Fluorescent Imaging Evaluation of Lidocaine Distribution Following Bier Block in the Upper Extremity.

INTRODUCTION: Bier block regional anesthesia has been used as an alternative to general anesthesia for years. Despite multiple theories and multiple techniques to delineate the location of the action of lidocaine during Bier block anesthesia, there has not been a consensus on the location of action. The purpose of this study was to use fluorescent imaging to further investigate the site of action of lidocaine during Bier block. MATERIALS AND METHODS: Three patients with carpal tunnel syndrome underwent open carpal tunnel release with Bier block anesthesia performed in the standard fashion with 1cc of Indocyanine green (IcG) mixed with lidocaine. Fluorescent images were obtained at the time of injection and after 10 minutes to allow patients to reach the level of surgical anesthesia. Repeated imaging was obtained at the time of completion of the procedure or at 30 minutes of tourniquet time. RESULTS: At time 0, IcG was distributed along the superficial venous system of the hand and forearm. At 10 minutes, the distribution of IcG was within the capillary system and infiltrating the dermis. The distribution later saturated the capillary beds and remained present until release of the tourniquet. CONCLUSIONS: The authors demonstrate that some lidocaine action occurs at the cutaneous level during the administration of a Bier block. Due to limited field depth of view provided by the SPY® Elite System (Novadaq Technologies Inc., Mississauga, Canada), we are unable to draw any conclusions as to the distribution of the IcG or lidocaine at the level of the larger nerves at the site of the tourniquet.

Case Report: Angiosarcoma in the Upper Extremity Related to a Nonfunctioning Arteriovenous Fistula.

BACKGROUND: Angiosarcoma is a rare but aggressive malignancy with a high predilection for the head and neck. There have been few case reports of the development of angiosarcoma in a nonfunctional arteriovenous fistula in a hemodialysis patient. METHODS: After institutional review board approval, a retrospective chart analysis is conducted to present the case of a patient who received plastic surgical treatment at our hospital. RESULTS: We present the case of a 44-year-old male who presented with ischemic changes and paresthesias of the upper extremity associated with the development of angiosarcoma in an arteriovenous fistula. CONCLUSIONS: Angiosarcoma remains a rare but important diagnosis to include in the differential diagnosis for upper extremity pain and paresthesias in chronic renal failure and nonfunctioning arteriovenous fistula.