Cementless hemispheric acetabular components. A 4- to 8-year follow-up report.

A retrospective radiographic analysis was performed on 71 cementless acetabular components followed from 4 to 8 years after surgery. A Harris-Galante (Zimmer, Warsaw, IN) cup was used in 46 cases and an Optifix (Smith & Nephew Richards, Memphis, TN) cup was used in 25 cases. There were 66 primary and 5 revision cases. Nonprogressive radiolucencies were common in both types of cups (64% of Optifix, 70% of Harris-Galante). Radiolucencies were almost exclusively less than or equal to 1 mm in width and were most common in zones 1 and 3. Ten cups had continuous but nonprogressive radiolucencies, none greater than 1 mm in all three zones. No radiolucent lines wider than 2 mm were seen in any case. Four cups had progressive radiolucency that stabilized. Radiolucency around fixation screws was seen in one case, and demonstrated stable ingrowth at revision surgery. No cases of osteolysis, screw breakage, migration, or loss of fixation surface occurred. A single case of a broken locking mechanism of a Harris-Galante cup 2 years after liner exchange is reported.

The use of expanded polytetrafluoroethylene as an interpositional membrane after lumbar laminectomy.

STUDY DESIGN: Prevention of post-laminectomy membrane formation was evaluated in a canine model. Fat graft, Silastic sheeting and expanded polytetrafluoroethylene were compared with nonimplanted control sites. OBJECTIVES: The development of an effective barrier to peridural scar invasion is of major importance in optimizing results after lumbar laminectomy. SUMMARY OF BACKGROUND DATA: Postoperative peridural fibrosis represents a normal biologic response after lumbar spinal surgery. A variety of biologic and nonbiologic interpositional materials have been studied. Expanded polytetrafluoroethylene has been shown to limit scar adhesion in the pericardium and peritoneum and has not been studied previously as a postlaminectomy interpositional membrane. METHODS: Eleven adult female cross-bred hounds underwent multilevel standardized laminotomies. Three materials--fat graft, Silastic sheeting, and expanded polytetrafluoroethylene--were compared with nonimplanted controls. The animals were killed 12 weeks after surgery and were evaluated histologically and using gadolinium-enhanced magnetic resonance imaging. RESULT: The magnetic resonance imaging studies were inconclusive in assessing peridural scar extension or identifying the implanted membranes. Histology revealed dense scar tissue at all control sites and replacement of all fat grafts by scar. Scar density was significantly less for the expanded polytetrafluoroethylene membrane surgical sites than for the control, fat graft, and Silastic sheeting sites. CONCLUSIONS: Expanded polytetrafluoroethylene membrane is biocompatible, maintains its structural integrity, and is impervious to fibrous ingrowth. These findings support further investigation of expanded polytetrafluoroethylene membrane as an interpositional material to prevent post-laminectomy peridural fibrosis.

Cementless hemispheric acetabular components. 2-4-year results.

A retrospective clinical and radiographic analysis was performed on 99 patients (106 hips) undergoing total hip arthroplasty with noncemented Harris-Galante (Zimmer, Warsaw, IN) or Optifix (Smith Nephew Richards, Memphis, TN) acetabular components. There were 94 primary and 12 revision procedures with a minimum follow-up period of 24 months (range, 24-52 months). The cups were evaluated for evidence of vertical and horizontal migration, as well as the presence of radiolucencies at the bone-implant interface. Age, sex, component inclination and medialization, cup coverage, and number of fixation screws used were examined to determine the influence of these factors on the incidence of cup migration or radiolucent line formation. A radiolucent line was present in at least one zone in 60% of the Harris-Galante and 45% of the Optifix cups. Progressive radiolucent lines were noted in two of the Optifix and three of the Harris-Galante components. Two Harris-Galante cups (1.9%) were revised. There were no Optifix cup migrations or evidence of instability in the Optifix or remaining Harris-Galante cups. Although there was a trend toward an increased incidence of radiolucencies in those cups lacking complete coverage, no statistically significant radiographic predictors for failure or impending failure could be determined from this short-term follow-up study. With the exception of the two revisions, all acetabular components performed well clinically over the study period.

Prevention of longitudinal crack propagation around a femoral prosthesis: a study of cerclage wire fixation.

This study examined the effect of single versus triple-wrap cerclage fixation techniques in preventing propagation of a longitudinal fracture around a cementless femoral prosthesis. A proximal filling femoral component was implanted in 14 matched pairs of fresh-frozen bovine femora, following placement of a 45-mm longitudinal crack in the anteromedial cortical wall of the proximal femur. In one group of seven pairs, a single cerclage wire was applied to one specimen of each pair. A triple-wrap of a single cerclage wire was similarly placed in one specimen of each of the other seven pairs. All specimens were axially loaded on a materials testing system machine and the force required to propagate the fracture of the proximal femur was recorded. A triple-wrap cerclage technique required a significant increase in the force to propagate a proximal femur fracture around a non-cemented prosthesis when compared to a single cerclage wire.

The current status of acetabular fixation in total hip replacement.

Aseptic loosening of the acetabular component is the major long-term complication of cemented total hip replacement. In this article, the improvements in cementing technique and cemented acetabular component design, as well as the evolution of noncemented acetabular cups, are reviewed. The porous-coated acetabular component has emerged as the state of the art in both primary and revision hip arthroplasty. Current trends in porous cup design and implantation are presented. The ultimate fate of the porous ingrowth cup will be based on long-term clinical and roentgenographic follow-up studies.

Longitudinal crack propagation in bone around femoral prosthesis.

Intraoperative femoral fracture is a well-recognized technical complication of cementless total hip arthroplasty. This study was designed to establish an in vitro model for initiation and propagation of fractures of the proximal femur in cementless THA and to assess the effect of fracture fixation in the form of cerclage wiring and drilling a hole in the distal extent of the fracture line. Fourteen human anatomic femur specimens were studied. Longitudinal cracks were made and propagation was performed on a materials testing system machine. A drill hole at the tip of a longitudinal crack does not prevent crack propagation. However, cerclage wiring has a statistically significant effect (p less than 0.025) on the ability of the fractured femur to withstand increased load.

Strength of cerclage fixation systems: a biomechanical study.

This study examined the load to failure ratio and stiffness of eight different cerclage techniques commonly used in the clinical management of fractures. For a single-loop cerclage, titanium cable was the strongest, while stainless steel wire secured with a commercial tightener was the weakest (P < 0.05). When a single-loop configuration is necessary (i.e. trochanteric attachment) a cable system is superior to cerclage wiring. A double-wrap of either cable or wire was considerably stronger than any single-wrap cerclage technique and stronger than two cerclage wires (P < 0.05).

Intravenous pyogenic granuloma of the hand.

Intravenous pyogenic granuloma is a recently described counterpart of cutaneous pyogenic granuloma. We report the second known case of this entity in the orthopedic and hand surgery literature and describe the characteristic clinical and histologic findings associated with this rare benign tumor.