Van Houwelingen Andrew P, Duncan Clive P
Department of Orthopedics, University of British Columbia, Diamond Health Centre, 3rd Floor, 2775 Laurel St, Vancouver, BC, Canada V5Z 1M9.
Orthopedics. 2011 Sep 9;34(9):e479-81. doi: 10.3928/01477447-20110714-27.
Periprosthetic fracture of the proximal femur involving the lesser trochanter (the Vancouver type A(LT)) is an uncommon occurrence. As it is basically an avulsion fracture of the attachment of the iliopsoas, it does not destabilize the stem and can be treated nonsurgically. In contrast, there is a so-called type "new B2" periprosthetic fracture of the lesser trochanter, which includes a segment of the proximal medial femoral cortex. This is usually seen within 6 weeks of the index procedure, typically following insertion of a tapered, cementless stem within a demineralized femur. This may be due to an unrecognized intraoperative fracture that subsequently displaced under load, or it may occur soon after, during rehabilitation. It is important to distinguish this fracture from the type A(LT), because it is associated with destabilization of the stem and requires early reintervention. The principles of treatment depend on the timing of the fracture and the size of the medial fracture fragment. If recognized intraoperatively as a nonpropagated cortical crack, then extraction of the broach or stem followed by cerclage cable fixation and reinsertion of the stem is adequate in most cases, with protected weight bearing for 6 weeks. If diagnosed postoperatively, or if the fracture fragment is larger, then management with a stem that gains fixation distal to the fracture is required. This distinction between the pseudo type A(LT) and the type "new B2" is important to recognize if appropriate treatment is to be prescribed and a satisfactory outcome is to be assured.
累及小转子的股骨近端假体周围骨折（温哥华A型（LT））并不常见。由于它本质上是髂腰肌附着处的撕脱骨折，不会使假体柄不稳定，可采用非手术治疗。相比之下，存在一种所谓的小转子假体周围“新B2型”骨折，它包括股骨近端内侧皮质的一部分。这通常在初次手术的6周内出现，典型情况是在脱矿质股骨中植入锥形无骨水泥假体柄之后。这可能是由于术中未识别的骨折随后在负荷下移位，或者可能在康复期间不久后发生。将这种骨折与A型（LT）骨折区分开来很重要，因为它与假体柄不稳定相关，需要早期再次干预。治疗原则取决于骨折的时间和内侧骨折块的大小。如果在术中识别为未扩展的皮质裂纹，那么在大多数情况下，取出拉刀或假体柄，随后用环扎钢丝固定并重新插入假体柄就足够了，需保护性负重6周。如果在术后诊断，或者如果骨折块较大，那么需要使用在骨折远端获得固定的假体柄进行处理。如果要开出合适的治疗方案并确保获得满意的结果，识别这种假性A型（LT）和“新B2型”之间的区别很重要。
