Operative efficiency and accuracy of patient-specific cutting guides in total knee replacement.

BACKGROUND: Total knee replacement (TKR) outcomes depend on accurate positioning of implants and restoration of the mechanical axis of the knee. Compared with standard techniques, patient-specific cutting guides are postulated to improve accuracy of bone resections, and therefore implant placement. Furthermore, patient-specific cutting guides are postulated to reduce operative time and increase efficiency by reducing the number of trays used. METHODS: This study evaluates these claims using the Visionaire (Smith & Nephew, Inc., Memphis, TN, USA) patient-specific system. The thickness of actual bone resections was compared with the predicted thickness (giving a resection 'error'). Data were also obtained on the number of trays used, skin-to-skin operating time and tourniquet time. RESULTS: Forty-one TKRs were performed on 33 females (one bilateral) and seven males. Average resection errors were 0.22 mm medially and 0.05 mm laterally for the distal femur, 0.99 mm medially and 0.74 mm laterally for posterior femoral condyles, and 0.55 mm medially and 0.71 mm laterally for the proximal tibia. There were no significant differences in tourniquet time, skin-to-skin time or the number of trays used between the patient-specific and historical comparison groups. CONCLUSION: Patient-specific cutting guides make accurate resections. Operative and tourniquet times and the number of trays used were no different to standard TKRs. Further investigation is needed to determine whether patient-specific cutting guides improve post-operative alignment and patient satisfaction.

Translunate fracture with associated perilunate injury: 3 case reports with introduction of the translunate arc concept.

We report 3 cases of translunate fractures with associated perilunate dislocations (or subluxation). We believe the translunate injury reflects a higher-velocity trauma and produces further destabilization of the carpus when compared with the established greater and lesser arc injuries. A modification to Johnson's perilunate injury classification system is proposed: the addition of a translunate arc injury subgroup, which would include all perilunate injuries with translunate fractures.

Surgical approaches to the distal radioulnar joint.

The distal radioulnar joint (DRUJ) is classified as a uniaxial synovial pivot joint between the convex head of the ulna and the concave ulnar notch of the radius. The DRUJ can be approached from 3 sides with a refined dorsal approach retaining a robust retinacular-dorsal capsular layer preferred by most surgeons. Recent descriptions of safe and extensile volar approaches have broadened indications for a volar approach to the DRUJ. A subcutaneous ulnar approach remains an option particularly when dealing with additional distal ulnar pathology. A description of technique and review of the surgical experience in exposure and treatment of DRUJ pathology will be presented, with advantages, disadvantages, and authors' preferred techniques.

An anatomic study of the triquetrum-hamate joint.

PURPOSE: To investigate the articulating surface of the triquetrum-hamate joint (TqH). METHODS: The carpal bones of 46 wrist specimens were examined. The shape of the TqH joint surfaces were investigated, with focus on variations in the shape of the hamate and corresponding triquetrum and the presence and position of convex and concave surfaces. RESULTS: Two distinct patterns of hamate TqH articular surfaces were identified, designated type I (31 of 46) and type II (15 of 46). The triquetral TqH articular surface also was found to have 2 distinct patterns, designated type A (18 of 46) and type B (15 of 46). Of the triquetrums examined 13 of 46 had characteristics that were a variable mixture of the 2 identifiable triquetral surface types, but these did not have sufficient similarity to constitute a third triquetrum surface type. The corresponding articulation patterns of these joint surfaces showed a strong trend for a type A triquetrum to articulate with a type I hamate (18 of 46 of all joints) and for a type B triquetrum to articulate with a type II hamate (13 of 46 of all joints). No association was seen between lunate types and type I or type II hamates. CONCLUSIONS: These findings suggest the existence of 2 distinct TqH joint patterns, which have been termed TqH-1 and TqH-2. There appears to be a spectrum of variation between these 2 identifiable types. As a result, the TqH is best described as a spectrum, with TqH-1 at one end and TqH-2 at the other. A TqH-1 joint is a helicoidal configuration. It is double-faceted, with the hamate and the triquetrum articular surfaces possessing complementary concave and convex parts. A TqH-2 joint has a predominantly oval convex shape, whereas the primarily concave triquetrum is better described as a dish for the flatter hamate. It has no hamate groove or distal ridge.