biocompatible is the titanium alloy extra low interstitial (ELI)2 Tiâ6Alâ4V; its composi- tion is 90 wt% Ti, 6 wt% Al, and 4 wt% V. The optimal properties for this material are produced by hot forging; any subsequent deformation and/or heat treat
Total hip replacement (THR) is a very common procedure undertaken in up to 285 000 .... diagnosis can include activity-related pain, aseptic loosening,.
Oct 6, 2014 - Unstable total Hip Replacement. are Constrained Liners A. Solution? Experience and. Literature Review. Guillem Figueras Coll1*, Marta Bonjorn MartÃ2, RamÃ³n Vives. Planell3, Ernest Ros Montfort4, RamÃ³n Serra FernÃ ndez5 and. Chairman
and the types of arthroplasty performed are shown in Tables. II and ... arthroplasties performed. Number of ..... in all 12 a Girdlestone arthroplasty was performed.
Gonzalez Della Valle A, Serota A, Go G, Sorriaux G, Sculco TP, Sharrock NE, et al. Venous thromboembolism .... Yu HT, Dylan ML, Lin J, Dubois RW. Hospitals' ...
V early osteointegration. On-growth of bone to porous coated prostheses is ... rich femoral component or with the ce- ... total hip arthroplasty in dogs (1, 2). Loo-.
Radiological analysis assessing heterotopic ossification, femoral osteolysis and femoral stem ... following total joint replacement.12 A retrospec- tive study by ...
an ideal total hip replacement with a large femoral head and a high head-neck ratio. B: Cam-type impingement in the native hip caused by a reduced femoral head-neck offset and similar impingement in a prosthetic hip with a small femoral head and a sk
575. INTRODUCTION. Total hip replacement (THR) provides a very effective ... arthroplasty, bilateral arthroplasty; those transferred or initially treated at other ...
90% (Schulte et al 1993; Neumann, Freund and SÃËrenson. 1994). Since its ..... Fowler JL, Gie GA, Lee AJC, Ling RSM. .... Clin On/top l993;292: 191-201. VOL.
May 30, 2016 - introduction: In the Middle East, severe developmental dysplasia of the hip with subsequent high dislocation is often seen. We assessed the ...
1 Health Services Research Unit, Institute of Applied Health Sciences, University of Aberdeen, UK. 2 Health Economics Research Unit, Institute ...... October 2006. Abstract A9-3. 79. Yoon TR, Moon E, Rowe SM, Jung ST, Seo HY,. Lee JY. ..... http://ww
Description of proposed service. Minimal incision total hip replacement (THR) is performed with significant variations between surgeons but approaches fall into two main groups. Of these, the 'double-incision' or 'two-incision' approach is novel and
This approach gives an excellent view particularly in difficult cases, i.e. protrusio acetabuli and ankylosed hips. The capsule is incised and the hip dislocated by ...
adequate pre-admission assessment supported by anaesthetic assessment when necessary.5. All patients who have hip surgery should be seen at the ...
Department of Trauma and Orthopaedic Surgery, Medical School, Uni- versity of Newcastle upon Tyne, Newcastle upon Tyne ... age orthopaedic surgeon in a non-specialist hospital is not known. The published data from the Norwegian and ..... 1. Medical D
Despite the current success of total hip replacement, we continue to strive for improvements, particularly in the durability or survivorship of the components,.
stable (greater than the control) when walking over barriers as was roll for the sit-to-stand task, indicative of ... after total hip replacement regarding the risk of a fall, especially in the elderly. Most patients ... metre cable to a computer whi
resulting in deformities, protrusio acetabuli and malalignment of the limbs. Ligamentous laxity is seen frequently. In the past few decades there has been an ...
primary total hip replacements and 11 were revision operations, with aseptic loosening of the original implant being the main indication for revision. The.
D. W. MURRAY, A. R. BRITTON, C. J. K. BULSTRODE. From the Nuffield Orthopaedic Centre, Oxford, England. The recommendation that patients having a total hip replacement should receive pharmacological thromboprophylaxis is based on the belief that fata
ossification is seen in 5 per cent of hips not previously operated on. Harris noted myositis ossificans in. 14 per cent of patients following total hip replacement.
Arthritis of the hip joint occurs when the joint cartilage wears out. This results in pain, stiffness, and frequently a limp. The pain is usually located in the groin or ...
The Unstable Total Hip Replacement Douglas E. Padgett, MD* and Hideki Warashina, MD†
Abstract: Instability after total hip arthroplasty (THA) is not a rare occurrence. Numerous factors have been associated with dislocation including surgical approach, implant design, failure to restore proper hip mechanics and soft tissue restraints, and patient variables such as early postoperative compliance, soft tissue integrity, and neurologic conditions such as poor proprioception. A thorough understanding of the mechanism of dislocation, timing, and direction of dislocation is mandatory in formulating an approach toward treatment. The radiographic evaluation should evaluate hip mechanics including component orientation, adequacy of leg lengths, and restoration of offset in the frontal and sagittal planes. The treatment of the unstable total hip replacement is based on numerous variables including the timing of instability, direction, and mechanism. Instability in the early postoperative period in the hip with proper orientation and restored mechanics often is treated successfully with patient reeducation and use of adjunctive bracing. The treatment of the recurrent dislocator can be more difficult. Although reestablishing proper mechanics and orientation can be successful in many instances, some patients continue to have dislocation. Constrained acetabular liners have significantly improved the success rate of reducing the incidence of dislocation, but problems related to premature wear and dislodgement are a major concern. The use of larger articulating bearing surfaces used with the newer cross-linked polyethylene may provide the solution to instability minimizing the concerns related to constrained components. (Clin Orthop 2004;420:72–79)
unstable THA: what factors play a role in hip instability, techniques at the time of surgery to reduce incidence of instability, and an understanding of how to treat the unstable hip. This review monograph focuses on the unstable THA: evaluation of patient and surgical factors, physical and radiographic features that should be evaluated, and an approach to the patient with recurrent dislocation.
INCIDENCE Dislocation of a THA is defined by the loss of contact between the femoral head and acetabular component that requires intervention to relocate the joint. Subluxation refers to an often transient loss of contact that usually is selfreduced.14,40,48 Although there is clear concern about any patient experiencing subluxation of the hip, this study will focus exclusively on frank dislocation of the joint. The incidence of dislocation after THA varies greatly in orthopaedic literature. It traditionally has been stated that the risk of dislocation after primary THA is between 1% and 3%. Reported rates of dislocation vary greatly depending on numerous variables including size of study, the number of surgeons involved, experience of the surgeon, and most recently, length of followup.1,8,14,21,28,41,42 It seems that the cumulative risk of dislocation is not constant but increases with time.7 It is important to recognize the wide variation in reported rates when discussing dislocation risk with patients. Clearly, the risk of dislocation after revision surgery is increased greatly with ranges from 5% to 20%, depending on the series studied.6,25 One factor affecting these rates is complexity of surgery. It is apparent from these figures that instability after THA is not rare and most surgeons will encounter a patient with a hip dislocation during their career.
FACTORS ASSOCIATED WITH DISLOCATION Patient Factors Factors that may be associated with a predilection for dislocation best are viewed as either patient factors or surgeon factors. Patient factors are those that are unique to the individual. Age often is cited as a risk factor for dislocation with older age groups being at a higher risk. Morrey33,34 and Ekelund et al15 showed that THR in patients older than 80 years had a twofold to threefold increase in the rate of dislocation compared with a younger group of patients. Gender has been Clin Orthop • Number 420, March 2004
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shown to be a significant risk factor associated with dislocation with females being at a much greater risk than males in several studies.7,11,20,46 Although the exact cause of this phenomenon is unknown, it has been postulated to be related to increased preoperative ROM and perhaps a reduction in soft tissue compliance. Body habitus frequently is discussed in association with hip instability. It seems that body weight is not associated with dislocation. Obesity may be inversely related to dislocation because of decreased ROM secondary to excess adipose tissue. Body height, however, is a risk factor. It seems that the tall patient may be at increased risk because of the increased lever arm of the leg and the relative ease of translation with less apparent force.20,34,37,42,47 Diagnosis seems to be directly associated with risk of instability. In multiple series, the risk of dislocation is increased greatly after THA for femoral neck fracture.7,27,31 It is assumed that secondary factors of almost normal pretreatment ROM and potential for altered proprioception may be at the root of the problem.14,27 Developmental hip dysplasia has been suggested to be associated with increased rates of instability because of abnormal bone anatomy and altered muscle function.42 Others have found no difference in rates of instability after THA whether for osteoarthrosis, RA, ON, or dysplasia.1,34,37 There is strong evidence to suggest that prior surgery is associated with increased rates of instability. This includes prior internal fixation, osteotomy, and conversion of a prior arthrodesis.12,37,46 Although the exact mechanism is unclear, compromised abductor function, bone loss, bone deformity, or both may play a role. Neurologic dysfunction is one of the greatest risk factors for instability after hip arthroplasty. This includes cognitive disorders and disorders associated with substance abuse. Neuromuscular impairment seen in patients with cerebral palsy, polio, and spinal cord injuries can significantly affect muscle tone, proprioception, and can place patients at higher risk for dislocation.15,20,44 Finally, soft tissue laxity has been implicated in hip instability. This category includes disorders of collagen such as EhlersDanos syndrome. Patients with a known history of laxity and prior joint instability should be advised of the increased risk of dislocation after THA.12,23,34
dislocation still seems to be greater with the posterior approach. Why use it? Arguments in favor of the posterior approach speak of a more anatomic dissection and less disruption of the abductor musculature. Ultimately, surgical approach is chosen because of surgeon familiarity and comfort level. Regardless of approach, perhaps the most important aspect of THA is component orientation.16 Implant positioning is crucial to long-term success in terms of avoiding instability and potentially minimizing factors such as wear. Although femoral component positioning in neutral alignment to 15° anteversion is important, positioning of the acetabular implant is tantamount. Lewinnek et al28 described the safe zone of implant placement and others have given credence to this concept. The ideal implant position seems to be 40° abduction and 20° anteversion. Three-dimensional modeling has confirmed maximum ROM with avoidance of impingement and subsequent instability if these parameters are adhered to.3,39,43,48 Unfortunately, implant position is not always so reproducible. Using a commercially available implant positioner, we prospectively studied a group of patients who had THR and showed that although the mean acetabular abduction angle of 42° was close to our target of 40°, we observed a range from 22° to 57°.22 This discrepancy is thought to be largely attributable to variations in patient position and pelvic movement during surgical preparation and insertion of the prosthesis. Perhaps with the use of navigational guides our precision and surgical accuracy will improve. Implant choice clearly is at the discretion of the surgeon and plays a key role in hip stability. Implant specific variables include restoration of length, reconstitution of femoral offset, size of femoral head, shape and size of neck trunion, and socket specific variables including socket depth and possibly even socket diameter.4,23,26,32,43 It has become increasingly apparent that all of these factors can play a role in hip instability and should be considered when choosing an implant for any patient. Failure to achieve adequate limb length after THR was significantly associated with dislocation in studies by Coventry11 and Callaghan et al.8 It is assumed that the decrease in overall myofascial tension was responsible for this observed increase in instability. Myofascial tension also may be decreased when lateral femoral offset is reduced when doing THR.39 Not only is abductor muscle force compromised, loss of offset also may be associated with early impingement of the proximal femur against the pelvis as a source of instability. The variables of neck resection, adjustment of leg length, and restoration of femoral offset all are variables that should be noted during preoperative planning.32 Hip instability as it relates to femoral head size and relative ratio to the neck (trunion) has been reported by numerous authors.2,4,34,42,46 For years, there has been a dilemma: the short-term concern regarding hip instability using smaller articulating heads and the longer-term concern about volumetric wear attributable to larger diameter articulating heads leading
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to failure. Clinical results and hip simulation models clearly have shown the reduced ROM of 22-mm heads compared with larger diameter head sizes.48 It also is apparent that trunion designs and the use of skirted femoral articulating heads effectively decrease head to neck ratios and increase the tendency for instability.20,43 In studies from our laboratory, ROM to impingement and dislocation with a 22-mm head and a commonly used trunion type, occurred at less than 90° hip flexion.29,30 Clearly, studies such as these should alert surgeons not only to the risks associated with smaller heads, but the contribution of the trunion and skirts. Prosthetic augments are not just limited to the femur. Although efficacy of elevated liners on the acetabulum has been shown, it is important to remember that the elevation improves stability in only one direction while theoretically being a source of impingement and levering out the opposite side.10,45 The final surgical factor that can influence rate of instability is that of soft tissue repair. Regardless of approach, reestablishment of the soft tissue envelopment is crucial to hip stability. It is conceivable that the lack of viable soft tissue capsule and pseudocapsule in revision cases may be one explanation for the significantly greater incidence of dislocation. Using the posterior approach, the incidence of dislocation using an enhanced posterior capsular and soft tissue repair was reduced from 4% to less than 1%.38 This observation lends credence to the notion of capsular laxity as a source of instability. Attempts to diminish soft tissue laxity by use of appropriate implant selection and soft tissue reconstruction seem justified.
EVALUATION OF THE UNSTABLE HIP It is mandatory to consider all of the aforementioned factors when evaluating a patient with instability after THA. Whether the patient with instability is referred to a surgeon or that surgeon did the index procedure, a logical approach to understanding potentially why the instability occurred and ultimately formulating an appropriate treatment plan is essential.
History A thorough evaluation should include the history of instability, which begins with the timing of dislocation relative to the index operation or most recent operation. Instability occurring in the first 3 to 6 months can be considered early. At that time, capsular healing may not have been complete and adequacy of abductor motor function still is compromised. Late instability has differing implications that can include significant trauma or wear associated instability.11,35 In addition to timing, the direction of instability is important. The direction of instability as it relates to approach must be considered and if the patient is referred from another institution, operative notes are essential. The implications of direction are enormous. Early anterior dislocation and or subluxation in a patient with a posterior approach often is treated conservatively with
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avoidance of extension and external rotation and most patients rarely have any additional episodes. However, early posterior dislocation in a patient operated on via a posterior approach can be a harbinger of repeated episodes.39 An understanding of the mechanism of dislocation is paramount: flexion with adduction in the early period in a patient in whom the posterior approach was used underscores a clear need for patient reeducation. In addition to understanding the direction of dislocation, it can be helpful to find out how the hip was reduced, ease of reduction, and if done, safe ROM. Obviously, the number of dislocations, the frequency of occurrence, and any other methods used should be sought out.
Physical Examination The physical examination of the patient with an unstable hip begins with an observation of gait. The presence of an abductor lurch implying abductor weakness, level of compensation involved, antalgic component to the gait, and a short leg (pelvic dropping) aspect or long-legged gait (a vaulting component), all should be noted. Although a survey of the upper extremity always is warranted for completeness, the pelvic and hip examinations are the most important. The presence of any pelvic obliquity with the patient standing or sitting is essential. Determination of the fixed nature of this obliquity should be noted. The ability to correct pelvic obliquity with blocks under the heel while the patient is standing or while sitting on the end of the examination table usually indicates a flexible deformity. Clinical leg lengths can be measured using the anterosuperior iliac spine (ASIS) to medial malleolus but are subject to various issues including the presence of contractures (flexion, adduction), and occasional difficulties in localizing anatomic landmarks. Despite the shortcomings, recording of measurement should be noted. The status of hip wound, type of incision, presence of edema, or wound erythema also should be noted. Active straight leg raising is an excellent indication of hip flexor power and overall hip strength as is side lying abduction. Passive range in all planes is noted but care should be taken not to iatrogenically cause a hip dislocation. Joint distraction in full extension and 90° hip flexion gives a subtle sense of joint laxity. Motor strength of the quadriceps, hamstrings, and ankle plantar and dorsiflexors is noted. Record sensory findings for all dermatomal distributions. The presence of dorsalis pedis and posterior tibialis pulses should be noted.
inclination, an abduction angle and version on the shoot through film; any residual osteophytes or heterotopic ossification on the pelvis; the presence of pelvic obliquity that would influence effective socket position; the stem orientation (varus and valgus and version) and offset compared with the contralateral hip; the radiographic leg lengths; and the status of the trochanter. At times, it is mandatory to obtain more detailed information regarding implant orientation. Formal version studies and CT scanning are helpful in this regard.
Implant System A thorough review of the previous operative note is essential. In addition to information regarding surgical approach, identification of the implants used is essential in the preoperative planning for revision of the unstable hip. Information on the acetabular component includes type of shell and diameter, fixation of implant (cemented or uncemented), use of adjuvant screw fixation, and the type of PE (elevated, extended, or offset liner). Femoral stem information includes fixation of stem, offset of stem, type of trunnion, and head diameter and whether an extended skirted modular head neck was used. With all the aforementioned information, a logical treatment approach to the treatment of the unstable hip can be formulated.
dislocation as that occurring in the first 3 to 6 months after surgery. Early dislocations can occur as a result of significant trauma such as a fall or can be positional. Traumatic dislocations usually are the result of an unwitting violation of hip precautions. Initial treatment should include a thorough analysis of radiographs to determine the position of dislocation. Closed reduction then should be done with the patient either under intravenous sedation or regional anesthesia. Determination of safe ROM should be noted. If ROM is acceptable (flexion as great as 90° with a 15° arc of internal and external rotation) and radiographs show acceptable position of implants,28 then treatment with an external brace is initiated. Although the exact success rate of brace treatment for early instability with implants in an acceptable position is unknown,9 Mallory et al,31 using a hip cast and brace, showed success rates greater than 70% in eliminating subsequent dislocation. Optimal duration of brace treatment unfortunately is unknown but it would seem that if the desired result is healing of pericapsular structures that are presumed disrupted as a consequence of the dislocation, then healing of this tissue presumably would take 2 to 3 months. It has been our policy to use a brace for 8 weeks after dislocation with continued adherence to hip precautions for 12 weeks.
Bracing The type of brace used is dependent on the direction of instability and surgical approach.13 It is important to recognize that not all dislocations are posterior. For posterior dislocations, hip bracing is set to restrict flexion to no greater than 70° and abduction is set to 30°. However, for anterior dislocations that tend to occur with a combination of extension and external rotation, hip extension must be eliminated and therefore the brace is set for an extension lock at 30° hip flexion. Perhaps more important is control of rotation. Unfortunately, the only way to control external rotation is to use a long-leg extension brace that incorporates the foot and limits external rotation to 20°.
Early Positional Dislocations Early positional dislocations imply dislocations in the first 3 months associated with minor changes in body position such as sitting in a chair, transitioning from a couch, or reaching for an object. It is imperative to try to review the mechanism that resulted in the instability. After review of radiographs and ROM after reduction, a decision is reached regarding adequacy of reconstruction. As outlined previously, implant orientation, restitution of offset, adequacy of myofascial tension, and component head to neck ratio must be reviewed critically. If all of the aforementioned criteria are acceptable, treatment with a hip brace is initiated. When the cause of hip instability is related to a deficiency of the implant system, it seems the most prudent option
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is to consider revision. Patient with socket-related issues such as excessive cup abduction or insufficient or excessive socket version generally will not respond to a hip brace and are treated more appropriately with revision surgery (Fig. 1). As outlined by Daly and Morrey,12 in these circumstances where the proximate cause of instability can be identified (such as socket malposition), revision of that component in eliminating instability was possible in 70% of cases. In instances of socket malposition, simple PE exchange and the use of elevated or extended liners have a limited role. In addition, elevated PE liners afford added stability in the quadrant in which they are inserted but threaten to impinge on the femoral neck, causing levering out in the opposite direction.10,17 Adequacy of the restitution of soft tissue tension is difficult to assess on either clinical grounds or by radiographs. However, measurement of femoral offset contrasted to the
FIGURE 1. The AP radiograph shows a THR with multiple episodes of dislocation. The initial revision attempt using an extended modular head and neck to increase tissue tension failed. Excessive socket abduction was suspected to be the primary source of instability and this was revised. The patient had a successful outcome.
sions for instability without a constrained socket; unidentifiable cause of hip instability; cognitive or neuromuscular disorder; and or abductor deficiency (Fig. 3). There are multiple studies currently available that show the proven efficacy of the constrained systems over unconstrained techniques. Goetz et al19 showed success rates greater than 90% in eliminating dislocation after revision of a THA for recurrent instability. At our institution, the rate of recurrent dislocation was less than 3% at mean 3-year followup.44 Unfortunately, although constrained liners seem to solve the short-term problem of instability, long-term issues of component loosening because of added stresses imparted to the interface and premature PE wear need to be addressed.
Late Instability After Total Hip Arthroplasty The observation of late instability after THA has been reported by several authors.11,35 In some cases, the instability can be related to PE wear, lysis, and capsular laxity, which may serve as a mechanism for dislocation (Fig. 4). Radiographic assessment is useful in determining the extent of PE wear as it relates to instability. Instability from wear-related issues is treated best by revision surgery. If the pattern of wear is caused by less than ideal placement of the socket, then revision of the cup and liner are advised. If the pattern of wear is a function of length of service of implant (>12–15 years) then PE revision may be acceptable. In some situations, late instability apparently is unrelated to wear. Possible causes include capsular and soft tissue
FIGURE 2. The postoperative radiograph shows a patient in whom component orientation, leg lengths, and offset all were restored. This hip system was designed with a large neck trunnion that was associated with early neck impingement in flexion. Revision to a larger head diameter with enhanced PE has stabilized the articulation.
FIGURE 3. The radiograph shows a constrained acetabular implant used in an elderly man with recurrent episodes of instability. Despite an exhaustive workup, no obvious source of dislocation could be found and it was elected to use the constrained device.
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FIGURE 4. A, Anteroposterior and (B) lateral radiographs show a 12-yearold hip replacement that dislocated four times during the past 6 months. Evidence of PE wear is apparent and revision of the socket is planned.
stretching or laxity, altered proprioception, or cognition or noncompliance with lifelong restrictions of hip arthroplasty.20,47 Treatment with a brace seems to have a limited role in many of these patients. At times, reinforcement of hip precautions seems to play a role. However, in many instances, depending on age, activity, and whether the patient is a surgical candidate, conversion to a constrained liner is advocated.19,44 REFERENCES 1. Ali Khan MA, Brakenbury PH, Reynolds IS. Dislocation following total hip replacement. J Bone Joint Surg. 1981;63B:214–218. 2. Amstutz HC, Markolf K. Design Features in Total Hip Replacements. In: Harris W (ed). The Hip: Proceedings of the Second Open Scientific Meeting of The Hip Society, 1974. St Louis: CV Mosby; 1974:111–122. 3. Barrack RL, Butler RA, Laster DR, et al: Stem design and dislocation after revision total hip arthroplasty: Clinical results and computer modeling. J Arthroplasty. 2001:16(8 Suppl 1):8–12. 4. Bartz RL, Noble PC, Kadakia NR, et al. The effect of femoral component head size on posterior dislocation of the artificial hip joint. J Bone Joint Surg. 2000;82A:1300–1307. 5. Beaule PE, Schmalzried TP, Udomkiat P, et al. Jumbo femoral head for the treatment of recurrent dislocation following total hip replacement. J Bone Joint Surg. 2002;84A:256–263. 6. Berry DJ, Muller ME. Revision arthroplasty using an anti-protrusio cage for massive acetabular bone deficiency. J Bone Joint Surg. 1992;74B: 711–715. 7. Berry DJ. Unstable Total Hip Arthroplasty: Detailed Overview. In: Sim FH (ed). American Academy of Orthopaedic Surgeons Instructional Course Lectures. Vol 50. St Louis: CV Mosby; 2001:265–274. 8. Callaghan JJ, Heithoff BE, Goetz DD, et al. Prevention of dislocation after hip arthroplasty: Lessons from long-term followup. Clin Orthop. 2001; 393:157–162. 9. Clayton ML, Thirupathi RG. Dislocation following total hip arthroplasty: Management by special brace in selected patients. Clin Orthop. 1983;177: 154–159. 10. Cobb TK, Morrey BF, Ilstrup DM. The elevated-rim acetabular liner in
11. 12. 13. 14. 15. 16. 17.
total hip arthroplasty: Relationship to postoperative dislocation. J Bone Joint Surg. 1996;78A:80–86. Coventry MB. Late dislocations in patients with Charnley total hip arthroplasty. J Bone Joint Surg. 1985;67A:832–841. Daly PJ, Morrey BF. Operative correction of an unstable total hip arthroplasty. J Bone Joint Surg. 1992;74A:1334–1343. Dorr LD, Wan Z. Causes of and treatment protocol for instability of total hip replacement. Clin Orthop. 1998;355:144–151. Eftekhar NS. Dislocation and instability complicating low friction arthroplasty of the hip joint. Clin Orthop. 1976;121:120–125. Ekelund A, Rydell N, Nilsson OS. Total hip arthroplasty in patients 80 years of age and older. Clin Orthop. 1992;281:101–106. Fackler CD, Poss R. Dislocation in total hip arthroplasties. Clin Orthop. 1980;151:169–178. Fehring TK, Griffin WL, Mason JB, et al. Failure of Bloodless Revision of the Unstable Total Hip. Proceedings of the Sixty-Seventh Annual Meeting of the American Academy of Orthopaedic Surgeons; 2000:151. Garcia-Cimbrelo E, Munuera L. Dislocation in low-friction arthroplasty. J Arthroplasty. 1992;7:149–155. Goetz DD, Capello WN, Callaghan JJ, et al. Salvage of a recurrently dislocating total hip prosthesis with use of a constrained acetabular component: A retrospective analysis of fifty-six cases. J Bone Joint Surg. 1998; 80A:502–509. Hedlundh U, Karlsson M, Ringsberg K, et al. Muscular and neurologic function in patients with recurrent dislocation after total hip arthroplasty: A matched controlled study of 65 patients using dual-energy x-ray absorptiometry and postural stability tests. J Arthroplasty. 1999;14:319–325. Heithoff BE, Callaghan JJ, Goetz DD, et al. Dislocation after total hip arthroplasty: A single surgeons experience. Orthop Clin North Am. 2001; 32:587–591. Hendrix SL, Mologne TS, Padgett DE, et al. Acetabular positions during primary total hip arthroplasty. Proceedings of the Sixty-First Annual Meeting of the American Academy of Orthopaedic Surgeons; 1994:474. Jolles BM, Zangger P, Leyvraz PF. Factors predisposing to dislocation after primary total hip arthroplasty: A multivariate analysis. J Arthroplasty. 2002;17:282–288. Kaplan SJ, Thomas WH, Poss R. Trochanteric advancement for recurrent dislocation after total hip arthroplasty. J Arthroplasty. 1987;2:119–124. Kavanagh BF, Fitzgerald RH Jr. Multiple revisions for failed total hip
arthroplasty not associated with infection. J Bone Joint Surg. 1987;69A: 1144–1149. Kelley SS, Lachiewicz PF, Hickman JM, et al. Relationship of femoral head and acetabular size to the prevalence of dislocation. Orthopedics. 1998;355:163–170. Lee BP, Berry DJ, Harmsen WS, et al. Total hip arthroplasty for the treatment of an acute fracture of the femoral neck: Long-term results. J Bone Joint Surg. 1998;80A:70–75. Lewinnek GE, Lewis JL, Tarr R, et al. Dislocations after total hipreplacement arthroplasties. J Bone Joint Surg. 1978;60A:217–220. Lipman JD, Padgett DE, Robie BH, et al. Total hip Component Design and Orientation Influences Range of Motion and Dislocation Rate. Proceedings of the Forty-Fourth Annual Meeting of the Orthopaedic Research Society; 2000:830. Lipman J, Padgett DE. The Effect of High Wall Liner Orientation on Total Hip Range of Motion During Activities of Daily Living. Proceedings of the Forty-Seventh Annual Meeting of the Orthopaedic Research Society; 2001:1046. Mallory TH, Lombardi AV Jr, Fada RA, et al. Dislocation after total hip arthroplasty using the anterolateral abductor split approach. Clin Orthop. 1999;358:166–172. McAuley JP, Ridgeway SR. Preoperative planning to prevent dislocation of the hip. Orthop Clin North Am. 2001;32:579–586. Morrey BF. Difficult complications after hip joint replacement. Dislocation. Clin Orthop. 1997;344:179–187. Morrey BF. Instability after total hip arthroplasty. Orthop Clin North Am. 1992;23:237–248. Orozco F, Hozack WJ. Late dislocations after cementless total hip arthroplasty resulting from polyethylene wear. J Arthroplasty. 2001;15:1059– 1063. Parvizi J, Morrey BF. Bipolar hip arthroplasty as a salvage treatment for instability of the hip. J Bone Joint Surg. 2000;82A:1132–1139.
37. Paterno SA, Lachiewicz PF, Kelley SS. The influence of patient-related factors and the position of the acetabular component on the rate of dislocation after total hip replacement. J Bone Joint Surg. 1997;79A:1202– 1210. 38. Pellicci PM, Bostrom M, Poss R. Posterior approach to total hip replacement using enhanced posterior soft tissue repair. Clin Orthop. 1998;355: 224–228. 39. Ranawat C. Master Techniques in Orthopaedic Surgery: In: Sledge C (ed). The Hip. Sledge C (ed.) Philadelphia: Lippincott-Raven; 1998:217–238. 40. Ritter MA. Dislocation and subluxation of the total hip replacement. Clin Orthop. 1976;121:92–94. 41. Robbins GM, Masri BA, Garbuz DS, et al. Treament of hip instability. Orthop Clin North Am. 2001;32:593–610. 42. Sanchez-Sotelo J, Berry DJ. Epidemiology of instability after total hip replacement. Orthop Clin North Am. 2001;32:543–552. 43. Scifert CF, Brown TD, Pedersen DR, et al. A finite element analysis of factors influencing total hip dislocation. Clin Orthop. 1998;355:152–162. 44. Shapiro GS, Weiland D, Sculco TP, et al. The Use of a Constrained Acetabular Component for Recurrent Dislocation. In: Sim FH (ed). American Academy of Orthopaedic Surgeons Instructional Course Lectures. Vol 50. St Louis: CV Mosby; 2001:281–287. 45. Toomey SD, Hopper RH Jr, McAuley JP, et al. Modular component exchange for treatment of recurrent dislocation of a total hip replacement in selected patients. J Bone Joint Surg. 2001;83A:1529–1533. 46. Woo RY, Morrey BF. Dislocations after total hip arthroplasty. J Bone Joint Surg. 1982;64A:1295–1306. 47. Woolson ST, Rahimtoola ZO. Risk factors for dislocation during the first 3 months after primary total hip replacement. J Arthroplasty. 1999;14: 662–668. 48. Yamaguchi M, Akisue T, Bauer TW, et al. The spatial location of impingement in total hip arthroplasty. J Arthroplasty. 2000;15:305–313.