Fixation Systems of Greater Trochanteric Osteotomies: Biomechanical and Clinical Outcomes
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Fixation Systems of Greater Trochanteric Osteotomies: Biomechanical and Clinical Outcomes Gregg J. Jarit, MD Abstract Sathappan S. Sathappan, MD The development of cerclage systems for fixation of greater Anand Panchal, DO trochanteric osteotomies has progressed from monofilament wires Eric Strauss, MD to multifilament cables to cable grip and cable plate systems. Paul E. Di Cesare, MD Cerclage wires and cables have various clinical indications, including fixation for fractures and for trochanteric osteotomy in hip arthroplasty. To achieve stable fixation and eventual union of Dr. Jarit is Chief Resident, Department the trochanteric osteotomy, the implant must counteract the of Orthopaedic Surgery, NYU–Hospital destabilizing forces associated with pull of the peritrochanteric for Joint Diseases, New York, NY. Dr. musculature. The material properties of cables and cable grip Sathappan is Joint Reconstructive systems are superior to those of monofilament wires; however, Fellow, Department of Orthopaedic Surgery, NYU–Hospital for Joint potential complications with the use of cables include debris Diseases. Dr. Panchal is Resident, generation and third-body polyethylene wear. Nevertheless, the Department of Orthopaedic Surgery, cable grip system provides the strongest fixation and results in Grandview Hospital Medical Center, Dayton, OH. Dr. Strauss is Resident, lower rates of nonunion and trochanteric migration. Cable plate Department of Orthopaedic Surgery, constructs show promise but require further clinical studies to NYU–Hospital for Joint Diseases. Dr. Di validate their efficacy and safety. Cesare is Chair, Department of Orthopaedic Surgery, University of California Davis Medical Center, steotomy of the greater tro- Trochanteric osteotomy fixation Sacramento, CA. Ochanter in primary total hip ar- systems include monofilament None of the following authors or a throplasty (THA) was strongly advo- wires, multifilament cables, and ca- member of their immediate families has cated by Charnley,1,2 who observed ble grip systems. The effectiveness received anything of value from or owns that it allows for proper hip abductor of a wire or cable system in counter- stock in a commercial company or muscle tensioning and improved hip acting the destabilizing forces that institution related directly or indirectly to stability. With the advent of modu- affect the reattached trochanter de- the subject of this article: Dr. Jarit, Dr. larity in hip arthroplasty implants, pends on the biomechanical proper- Sathappan, Dr. Panchal, Dr. Strauss, the ability to adjust offset and femo- ties of the system and its compo- and Dr. Di Cesare. ral length with the implant itself al- nents; these components include Reprint requests: Dr. Di Cesare, lowed for adjustment of soft-tissue fatigue resistance, maximum load University of California Davis Medical tension about the hip without the capability, and the compressive forc- Center, Suite 3800, 4860 Y Street, need for trochanteric osteotomy. In es generated by the system. Compli- Sacramento, CA 95817. complex primary3-5 and revision hip cations associated with trochanteric arthroplasty,4-8 however, the need for osteotomy include wire or cable J Am Acad Orthop Surg 2007;15:614- improved hip joint exposure is facil- breakage (Figure 1), debris generation 624 itated by trochanteric osteotomy.9 that can result in third-body poly- Copyright 2007 by the American Following the osteotomy, a stable, ethylene wear, trochanteric frag- Academy of Orthopaedic Surgeons. rigid fixation must be achieved to fa- ment migration, and nonunion. cilitate union of the bony fragment. Despite fixation, proximal migra- 614 Journal of the American Academy of Orthopaedic Surgeons Gregg J. Jarit, MD, et al tion of the osteotomized segment Figure 1 Figure 2 can occur from the contractile activ- ity of the hip abductors (gluteus me- dius and minimus muscles). Charn- ley1,2 showed that the abductors primarily exert shear forces when the hip is flexed and that their prox- imally directed vector component is a secondary one. These shear forces can be greater than four times body weight and are of paramount impor- tance in the activities of daily living, such as climbing stairs and rising from a chair.9,10 Wire Fixation Systems for reattaching the osteoto- mized trochanter are conventionally categorized as first, second, or third generation. First-generation monofil- Anteroposterior radiograph ament surgical wires have long been demonstrating broken trochanteric used for osseous fixation,11-13 includ- fixation wires. ing fixation of greater trochanteric osteotomies in THA. However, monofilament wires tend to kink (Figure 3). Loaded at a rate of 50 mm during application, compromising of outward strain per minute, the 16- The Charnley wiring technique. The ends of a looped wire are inserted in a the biomechanical integrity of the gauge wire failed at a mean of ap- hole drilled in the lateral femoral cortex, implant; thus, breakage and loss of proximately 1,300 N for the square distal to the edge of the trochanteric trochanteric osteotomy fixation were knot and knot twist versus approxi- osteotomy and below the abductor common, leading to the development mately half that value for the uni- tubercle. The two ends are passed of new cerclage systems.10,14-24 form symmetric twist method. Re- proximal to the trochanter and through Various wiring techniques have sults for the 18-gauge wire showed the hip abductor musculature and are been described that differ in their failure rates at a mean of approxi- finally locked by passing through the ability to resist displacement forces mately 950 N for the square knot eye of the loop. Two transverse wires following trochanteric osteotomy. and knot twist versus approximate- are placed in the anteroposterior Markolf et al24 examined displace- ly half that value for the uniform direction via drill holes, one in the ment as a function of abductor pull, symmetric twist knot11 (Table 1). proximal femur next to the trochanteric bed and the other in the lesser using a device to simulate the prox- These findings confirm that the ulti- trochanter. The two wires are crossed imal pull of the hip abductors on the mate strength of the wire construct during tightening, which results in greater trochanter and the cerclage was primarily dependent on its di- progressive reduction in slack with system. In their comparison of types ameter and on the type of knot used. each twist. of wiring techniques, they deter- When wire is to be used for fixation, mined that the Charnley25 (Figure 2) 16-gauge wire should be utilized, se- and Harris26 techniques resulted in cured with a square knot or knot teric nonunion. Boardman et al32 greater resistance to motion, exhib- twist. reported that 79.2% of patients iting a displacement of only 0.7 mm Analysis of studies conducted be- with trochanteric nonunion in their after the third loading cycle, where- tween 1978 and 1993 reveals an study had broken wires. Harris and as the Amstutz27 and Coventry28 overall wire breakage rate of 22% in Crothers26 evaluated 136 THAs in techniques had two to three times 2,910 THAs using various wiring which none of the trochanters mi- greater displacement. techniques21,23,26,30-33 (Table 2). Clin- grated and all united; the wire break- Bostrom et al11 examined the ically, wire breakage is most often age rate was only 2%. maximum load capabilities of 16- associated with revision surgery,21 Trochanteric migration as a result and 18-gauge wire using three differ- uniplanar osteotomies, simple wire of wire loosening or breakage is a sig- ent types of knotting techniques configurations, and cases of trochan- nificant complication that can lead Volume 15, Number 10, October 2007 615 Fixation Systems of Greater Trochanteric Osteotomies Figure 3 ing the same wiring technique with some modifications; the modifica- tions included osteotomy of the trochanter below the trochanteric ridge, advancement of the trochan- ter, and abrading of the osteotomy surfaces before reattachment.27 The authors reported a 3.23% rate of tro- chanteric migration and found an as- sociation between this phenomenon and previous osteotomy, osteoporo- sis, and poor surgical technique. Clarke et al23 reviewed 277 THAs with trochanteric osteotomy fixa- tion using multiple cerclage wires. Trochanteric migration was associ- Knotting techniques. A, Knot twist. B, Square knot. C, Symmetric twist. ated with “severe debility” of the spine or the contralateral hip; the au- thors attributed fixation failure to to loss of mechanical advantage of ment, poor apposition of bone sur- patient inability to observe “tro- the hip abductors. Amstutz and Ma- faces, too much contact with acryl- chanteric” precautions. Following ki31 reported a 4.9% trochanteric ic or cortical bone instead of fixation of the trochanter, the pa- migration rate in 728 consecutive cancellous bone, failure to tighten tient should avoid abduction exer- THAs using a cruciate two-wire the wire loops adequately). Rates of cises after surgery and adhere to technique. They attributed trochan- trochanteric migration decreased strict postoperative hip precaution teric migration to osteoporosis and with time as the surgeons modified protocols.37 No association with tro- to technical error (eg, small size of their technique. In a subsequent chanteric migration was found with the osteotomized trochanteric frag- study, 712 THAs were evaluated us- osteoporosis, previous surgery, age, Table 1 Properties of Wires and Wiring Techniques Fatigue Maximum