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CLINICAL ORTHOPAEDICS AND RELATED RESEARCH Number 405, pp. 46–53 © 2002 Lippincott Williams & Wilkins, Inc.

Dislocation is a leading early complication of to tal hip arthroplasty. The effect of surgical ap proach on instability and abductor function is a controversial topic. A comprehensive literature review was done to evaluate the correlation of surgical approach and primary total hip arthro plasty dislocation. Two hundred sixty clinical studies were identified between 1970 and 2001. Four prospective studies were identified but in dividually they contained insufficient power or control groups to reach statistical significance regarding surgical approach and dislocation. Fourteen studies involving 13,203 primary total hip arthroplasties met the inclusion criteria based on variables previously shown to affect stability. These studies were evaluated with respect to surgical approach and dislocation. The combined dislocation rate for these studies was 1.27% for the transtrochanteric approach, 3.23% for the posterior approach (3.95% without posterior repair and 2.03% with posterior repair), 2.18% for the anterolateral approach, and 0.55% for the direct lateral approach. Eight studies in volving 2455 primary total hip arthroplasties evaluated postoperative limp. The incidence of

postoperative limp was 4% to 20% for patients who had the lateral approach and 0% to 16% for patients who had the posterior approach. The quality of the literature regarding surgical approach, dislocation rates, and abductor func tion is limited. Larger controlled prospective studies are needed to investigate the potential benefits of the posterior approach in lieu of a dis location rate six times higher than the direct lat eral approach for primary total hip arthroplasty.

Dislocation remains the leading early compli cation after total hip arthroplasty with a re ported frequency between 0.4% and 11%.^3,4,

6,7,11,14,16,18,19,21,25,30,35,38,40 Revision surgery for instability eventually is required in 20% to 66% of patients with dislocation.^{6,8,9,12,14,21,26,39} Patient, implant, and surgical factors have been correlated with total hip arthroplasty in stability.^3,9,17,19,38 However, the multifactorial nature of this issue and its relative infrequency have obscured the clarity of the orthopaedic literature regarding factors influencing total hip arthroplasty dislocation. Surgical approach has been recognized as a potential factor influencing total hip arthro plasty stability and abductor function.^1,9,11,23,

29,30,33,34,36–38 Four surgical approaches have maintained popularity for total hip arthro plasty. Each exposure has modifications that have evolved since the introduction of total hip arthroplasty. The anatomic details and dif ferences between these approaches often are

Surgical Approach, Abductor Function,

and Total Hip Arthroplasty Dislocation

John L. Masonis, MD; and Robert B. Bourne, MD

From the London Health Sciences Center, University of Western Ontario, London, Ontario, Canada. Research Support provided by the University of Western Ontario. Reprint requests to John L. Masonis, MD, Miller Ortho paedic Clinic, Carolinas Medical Center, 1001 Blythe Blvd., Charlotte, NC 28203. Phone: 7043730544; Fax: 7043475349; Email: John.Masonis@millerclinic.com. DOI: 10.1097/01.blo.0000038476.05771.6c

unclear in the literature and many synonyms have been created. The transtrochanteric approach or tro chanteric osteotomy was a modification of the anterolateral approach. The approach was pop ularized by Charnley⁴and modified by Muller.³⁰ The osteotomy separates the greater trochanter with the gluteus medius and minimus inser tions from the remaining femur (Fig 1). This allows excellent exposure of the acetabulum and unparalleled ability to lateralize the femo ral prosthesis and to avoid varus stem position. After implantation of components, the os teotomy is reattached in either its anatomic lo cation or with a trochanteric advancement as described by Charnley⁴ to lateralize the tro chanter and improve soft tissue tension across the hip. The disadvantage of the transtro chanteric approach lies in the issue of os teotomy healing, abductor dysfunction, and trochanteric pain. Delayed weightbearing is required, and nonunion has been associated with abductor dysfunction, limp, and hip in stability.^{6,7,11,12,34,36,38} Variations of the posterior approach to the hip have remained popular exposures for total

hip arthroplasty. These approaches have many names (Southern, Moore, Gibson, posterolat eral or maximum splitting), but all share a common muscular interval in reference to the gluteus medius tendon. Using a gluteus max imus split, the posterior approach remains posterior to the gluteus medius and minimus (Fig 2). Exposure of the hip and proximal fe mur requires division of the posterior hip cap sule and the external rotators (piriformis, su perior and inferior gamelli, obturator internus, quadratus femoris, and occasionally gluteus maximus). The exposure and dislocation are completed with flexion and internal rotation of the femur. After arthroplasty, the external ro tators and posterior capsule can be repaired us ing various described techniques.^2,29 The pos terior approach has the advantage of reduced operative time, no violation of the gluteus medius and minimus, and a low frequency of postoperative limp or abductor dysfunction. The main disadvantage is a higher posterior dislocation rate.^{3,5,9,16,21,25,30,33,34,36,38,40} Em phasis on posterior capsule and external rota tor repair techniques has been cited to lower dislocation rates.^5,30,31

Number 405 December, 2002 Total Hip Arthroplasty Dislocation 47

Fig 1. Anterior and lateral views of the transtrochanteric approach show a trochanteric slide technique preserving the gluteus medius and vastus lateralis sleeve.

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48 Masonis and Bourne and Related Research

The anterolateral approach first was de scribed by Jones.²⁴ This approach exploits the interval between the tensor fascia lata and the gluteus medius, which share innervations from the superior gluteal nerve (Fig 3). The hip is dis

located anteriorly for acetabular exposure, or the neck osteotomy is made in situ. The anterior fibers of the gluteus medius can make proximal femoral exposure difficult and therefore often are reflected from their insertion on the anterior

Fig 2. Posterior views of the posterior approach show the location of capsulotomy and exposure of the femoral neck and head after capsulotomy.

Fig 3. A lateral view of the anterolateral approach shows the interval between the gluteus medius and rectus femoris.

greater trochanter and reattached at the conclu sion of the arthroplasty. The advantage of the anterolateral approach is a reported low dislo cation rate. The disadvantage is limited proxi mal femoral and posterior acetabular exposure necessitating tenotomy of the anterior gluteus medius fibers, which may lead to postoperative abductor dysfunction. The lateral approach has many derivations and many synonyms (abductor split, trans gluteal, translateral, direct lateral, Hardinge). The lateral approach described by McFarland and Osborne²⁸ in 1954 involved detachment of the gluteus medius tendon in its entirety while maintaining its continuity with the vastus later alis. Hardinge¹⁷ modified the approach again in 1982 by detaching only the anterior ¹⁄ 2 of the medius tendon. Frndak et al¹⁴ described an ad ditional modification of elevating only the ante rior ¹⁄ 3 of the gluteus medius and minimus ten dons in continuity with the vastus lateralis (Fig 4). The main common denominator of these approaches is that they all violate the gluteus

medius and minimus to some extent. Exposure and dislocation are completed by flexion and ex ternal rotation of the femur. The repair is done through a sidetoside closure of the minimus, medius, and vastus lateralis. The advantage of the lateral approach is a reported low frequency of dislocation.^6,27 The main disadvantage cited is a higher incidence of postoperative limp at tributable to abductor dysfunction.^7,8,23

PURPOSE

The purpose of the current study was to criti cally evaluate the orthopaedic literature regard ing the relationship between surgical approach, dislocation, and abductor function after pri mary total hip arthroplasty.

METHODS

A Medline literature review was done to evaluate all studies regarding total hip arthroplasty disloca tion between 1970 and 2001. This review yielded

Number 405 December, 2002 Total Hip Arthroplasty Dislocation 49

Fig 4. A lateral view of the hip shows four derivations of the lateral approach based on the location of the gluteus medius split. The Hardinge approach shows splitting the posterior ¹⁄3 of the gluteus medius and anterior ¹⁄3 of the vastus lateralis. The Stracathro approach shows a linear split through the center of the gluteus medius and vastus lateralis. The Bauer approach shows splitting the anterior ¹⁄ 3 of the gluteus medius and posterior ¹⁄ 3 of the vastus lateralis. The Frndak and Mallory approach is done an terior to the gluteus medius and posterior to the vastus lateralis.

260 publications. An attempt was made to do a quantitative systematic review (metaanalysis). How ever, because of the retrospective design of the ma jority of studies and the multiple uncontrolled vari ables influencing dislocation, a methodologically sound metaanalysis was not possible. These publi cations represented an extremely heterogeneous pa tient pool regarding primary diagnosis, surgical ap proach, implants, and revision arthroplasties. In an effort to reduce uncontrolled variables, eight inclu sion criteria were applied to these studies. These cri teria were selected based on previous studies, which have shown their relationship with total hip arthro plasty dislocation.^{3,11,13,18,20,32,39,40} Studies were in cluded if they contained the following information: primary total hip arthroplasties identified; preoper ative diagnosis; prior surgery of hip noted; surgical approach described; implants described; head size; abduction angle of acetabular component; and dis locations recorded. Studies that satisfied inclusion criteria were re viewed for the type of surgical approach and the in cidence of primary total hip arthroplasty disloca tion. Surgical approaches were classified as one of four techniques: transtrochanteric, posterior (with or without repair), anterolateral, or direct lateral. The transtrochanteric group included all surgi cal exposures using a trochanteric osteotomy. The anterolateral group included all surgical exposures using the tensor fascia lata and gluteus medius in terval (WatsonJones approach). These exposures also included detachment of the anterior ¹⁄2 to ¹⁄ 3 of the gluteus medius tendon with subsequent repair. The direct lateral group included all surgical expo sures described as lateral, gluteus medius splitting, or Hardinge. These surgical exposures included el evation of the anterior gluteus medius in continuity with the vastus lateralis and subsequent sideto side repair. The posterior group included all surgical expo sures described as posterior, posterolateral, gluteus maximus splitting, Southern, or Moore. Each arti cle was reviewed carefully for details of posterior capsular and muscular repair, which has been shown to affect dislocation rates.^5,30 Because of the incon sistency of documenting this repair and the varia tions of repair technique (drill holes though bone versus soft tissue repair), the exact numbers of pro cedures that included a formal posterior repair were unable to be assessed accurately. Therefore, all surgeries done through a posterior approach were included. Studies were subcategorized if the surgi

cal description included a formal posterior soft tis sue repair. An additional Medline review was done for ab ductor function and limp after primary total hip arthroplasty. These studies were evaluated for ab ductor function and postoperative limp and strati fied by surgical approach. These articles also were reviewed for confounding variables including: leg length discrepancy, preoperative abductor dysfunc tion, and adjacent joint disease (spine, knee, and con tralateral hip).

RESULTS

Of the initial 260 articles, only two met all eight inclusion criteria.^35,37 Fourteen studies fulfilled a minimum of five inclusion criteria (identified primary total hip arthroplasties, preoperative diagnosis documented, prior hip surgery docu mented, surgical approach described, head size documented, and dislocations recorded). These 14 articles (two prospective and 12 retrospec tive) were reviewed for the incidence of dislo cation after primary total hip arthroplasty and stratified based on surgical approach (Table 1). The overall dislocation rate was 2.35%. Dislo cation rate by surgical approach yielded: 38 of 2988 (1.27%) for the transtrochanteric ap proach, 193 of 5981 (3.23%) for the posterior approach, 18 of 826 (2.18%) for the anterolat eral approach, and 19 of 3438 (0.55%) for the direct lateral approach. Surgeries done through a posterior approach were subgrouped addi tionally based on posterior repair. The disloca tion rate was 3.95% (141 of 3719) without re pair and 2.03% (46 of 2262) with posterior soft tissue repair. Eight clinical studies involving 2455 arthro plasties specifically addressed the issue of postoperative limp or abductor dysfunction. The distribution of surgical approach in these studies was biased significantly. Two thou sand two hundred eightyeight arthroplasties were done through a lateral or anterolateral ap proach, whereas only 167 surgeries were done through a posterior approach. The incidence of limp in the patients in these studies after the lateral or anterolateral approach ranged from

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50 Masonis and Bourne and Related Research

Number 405 December, 2002 Total Hip Arthroplasty Dislocation 51

TABLE 2. Surgical Approach and Abductor Function

Author and Approach and Followup Mean Trendelenburg Test

Reference THA Number (Months) Abductor Strength (% Positive) Limp %

Gore et al¹⁵ Posterior—52 30 96% NR NR Lateral—41 86% Vicar and Coleman³⁷ TT—136
12 NR NR 9.6% Posterior—42 0% Lateral—91 10% Frndak et al¹⁴ Lateral—50 50 NR 0% 4% Horwitz et al²³ TT—51 12 85% NR 15.4% Lateral—49 97% 20.4% Moskal and Mann²⁹ Lateral—306
24 NR NR 18% Barber et al¹ Posterior—28 12 86% 16% 16% Lateral—21 90% 13% 13% Downing et al¹⁰ Posterior—45 12 110% 4.7% NR Lateral—38 95% 5.7% Demos et al⁸ Lateral—1515
12 NR NR 11.6%

THA  total hip arthroplasty; TT  transtrochanteric; lateral  includes all anterolateral and direct lateral approaches; Mean ab ductor strength  percentage of contralateral hip strength; NR  not recorded

TABLE 1. Surgical Approach and Dislocation

Author/Reference Number of Primary THA Approach/THA Dislocation

Eftekhar¹¹ 1560 TT—1560 0.5% Fackler and Poss¹³ 1224 Posterior*—1224 1.8% Roberts et al³³ 175 Posterior—100 4.0% Anterolateral—75 1.3% Woo and Morrey³⁸ 2459 TT—1241 2.2% Posterior—588 5.6% Anterolateral—660 2.2% Vicar and Coleman³⁷ 269 TT—136 2.2% Posterior*—42 9.5% Anterolateral—91 2.2% Frndak et al¹⁴ 50 Lateral—50 2.0% Horwitz et al²³ 100 TT—51 0% Lateral—49 0% Turner³⁵ 477 Posterior*—477 3.98% Moskal and Mann²⁹ 306 Lateral—306 0% Pellicci et al³¹ 519 Posterior*—519 0.2% 555 Posterior—555 4.68% Mallory et al²⁷ 1518 Lateral—1518 0.79% Woolson and Rahimtoola³⁹ 315 Posterior—315 4% Yuan and Shih⁴⁰ 2161 Posterior—2161 3.29% Demos et al⁸ 1515 Lateral—1515 0.4% Totals 13,203 TT—2988 1.27% Anterolateral—826 2.18% Lateral—3438 0.55% Posterior (all)—5981 3.23% Posterior—3719 3.95% Posterior*—2262 2.03%

THA  total hip arthroplasties; TT  transtrochanteric; *Included posterior repair of external rotators / capsule

4% to 20%.^{1,8,10,14,22,28,32,36} Four articles ad dressed the issue of limp after the posterior ap proach in a small number of patients (n  167). The incidence reported was 0% to 16% (Table 2).^1,10,15,37 One study evaluating postoperative limp controlled for leg length inequality, but found no correlation.²³ One study controlled for preoperative abductor dysfunction, limp, or adjacent joint disease.¹⁴ A recent prospec tive comparison revealed no difference in ab ductor strength or Trendelenburg test between the lateral and posterior approach at 3 or 12 months after arthroplasty.¹⁰

DISCUSSION

The quality of orthopaedic literature regarding total hip arthroplasty dislocation is limited and the absolute effect of surgical approach on total hip arthroplasty dislocation remains unknown. No prospective studies of sufficient power exist. Prospective randomized studies regarding sur gical approach for total hip arthroplasty are dif ficult to do because of surgeon preference and training. A small number of prospective studies have been done, but unfortunately do not con tain sufficient numbers or comparison cohorts to reach statistical significance regarding disloca tion and surgical approach. Unidentified dislo cations and uncontrolled variables continue to be an obstacle. With the current data available, the rate of dislocation after primary total hip arthroplasty is 5.9 times higher after the posterior approach (3.23%) versus the direct lateral approach (0.55%). The addition of a formal posterior re pair reduced the dislocation rate to 2.03% by creating a limit or checkrein on internal rota tion of the hip. However, the reproducibility of doing a satisfactory repair despite changes in femoral offset or length, and the effect of this repair on gait and posterior hip pain remains unknown. The incidence of postoperative limp in the lit erature seems to be slightly higher after the lat eral and anterolateral approach (4% to 20%) versus the posterior approach (0% to 16%). These studies^1,37 did not account for leg length

discrepancies, preoperative abductor dysfunc tion, and adjacent joint disease, or contain ade quate comparison numbers. Therefore, from the current literature, there is no evidence to suggest a significant difference in postoperative limp af ter the posterior versus lateral approach for pri mary total hip arthroplasty. In fact, the most re cent prospective study found no difference in abductor strength or Trendelenburg test at 3 and 12 months after unilateral primary hip arthro plasty for osteoarthritis done through either a posterior or lateral approach.¹⁰ Based on this deficiency in the literature, the current authors have initiated a larger controlled study to evaluate the actual effect of surgical approach on instability, abductor function, and patient satisfaction after total hip arthroplasty.

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tal hip arthroplasty. Acta Orthop Scand 53:947–952, 1982. 27. Mallory TH, Lombardi Jr AV, Fada RA, Herrington SM, Eberle RW: Dislocation after total hip arthro plasty using the anterolateral abductor split ap proach. Clin Orthop 358:166–172, 1999. 28. McFarland B, Osborne G: Approach to the hip: A suggested improvement on Kocher’s method. J Bone Joint Surg 36B:364–271, 1954. 29. Moskal JT, Mann III JW: A modified direct lateral approach for primary and revision total hip arthro plasty: A prospective analysis of 453 cases. J Arthro plasty 11:255–266, 1996. 30. Muller M: Osteotomy of the Greater Trochanter: Part I: Total Hip Replacement Without Trochanteric Osteotomy. In Harris WH (ed). Proceedings of the Second Open Scientific Meeting of the Hip Society. St Louis, CV Mosby 231–234, 1974. 31. Pellicci PM, Bostrom M, Poss R: Posterior approach to total hip replacement using enhanced posterior soft tissue repair. Clin Orthop 355:224–228, 1998. 32. Pierchon F, Pasquier G, Cotten A, et al: Causes of dislocation of total hip arthroplasty: CT study of component alignment. J Bone Joint Surg 76B:45–48, 1994. 33. Roberts JM, Fu FH, McClain EJ, Ferguson AB: A comparison of the posterolateral and anterolateral approaches to total hip arthroplasty. Clin Orthop 187:205–210, 1984. 34. Robinson RP, Robinson Jr HJ, Salvati EA: Compari son of the transtrochanteric and posterior approaches for total hip arthroplasty. Clin Orthop 147:143–148, 1980. 35. Turner RS: Postoperative total hip prosthetic femoral head dislocations. Clin Orthop 301:196–204, 1994. 36. Vas MD, Kramer JF, Rorabeck CH, Bourne RB: Iso metric hip abductor strength following total hip re placement and its relationship to functional assess ments. J Orthop Sports Phys Ther 18:526–531, 1993. 37. Vicar AJ, Coleman CR: A comparison of the antero lateral, transtrochanteric, and posterior surgical ap proaches in primary total hip arthroplasty. Clin Or thop 188:152–159, 1984. 38. Woo RY, Morrey BF: Dislocations after total hip arthroplasty. J Bone Joint Surg 64A:1295–1306, 1982. 39. Woolson ST, Rahimtoola ZO: Risk factors for dislo cation during the first three months after primary total hip replacement. J Arthroplasty 14:662–668, 1999. 40. Yuan L, Shih C: Dislocation after total hip arthro plasty. Arch Orthop Trauma Surg 119:263–266, 1999.

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