Management of limb-length discrepancy after THA

There are several strategies to address the common complication of limb-length discrepancy (LLD) after total hip arthroplasty (THA). From allowing ample time for soft tissues to elongate, to shoe lifts and surgical revision, there are tools available to help surgeons alleviate a patient's symptoms. Perhaps most importantly is clear communication with patients about potential complications and ensuring understanding that there are some cases of LLD that are not correctable. 


As discussed in Part I of this article series, leg-length discrepancy (LLD) is a common complication in total hip arthroplasty (THA), with incident reports ranging greatly (between 1 and 50 percent) [1, 2]. Despite patient education about the possibility of LLD after THA, it has been shown that the THA patient is more likely to remember the potential benefits of the procedure over the potential complications [3]. This incongruity may help explain why it is the number one reason for litigation against the US orthopedic community [4, 5]. It is generally accepted that a LLD of less than 10 mm is well tolerated by patients and therefore is a reasonable target for facilitating good functional outcomes [6].


Structural versus functional

About a third of patients perceive limb-length inequality after THA [7] and these patients also report a significantly lower Oxford Hip Score [8].

There are two kinds of LLD and it is important to distinguish between them. Table 1 highlights the differences between structural and functional LLD. It is possible for the concomitance of both structural and functional LLD, and in these cases their associated problems may negate each other or be exacerbated [9].

When asked if structural or functional is more difficult to deal with, Biju Benjamin, orthopedic surgeon at University College London Hospital said “structural leg length inequality is much more difficult to deal with.” Orthopedic surgeon Jurek Pietrzak, also based at University College London Hospital, agrees: “structural leg length discrepancy poses a greater challenge.”

When a patient presents with complaints about leg length inequality, lower back pain, or muscle spasms for example, a good place to start is by determining if there is an LLD and if it is true (structural) or apparent (functional). In a study by Wylde et al [8], not all patients displaying LLD were classified as having structural LLD, the majority of the cases (64 percent) were found to have a functional LLD.

It is recommended to eliminate functional leg-length alignment asymmetry before beginning treatment for structural LLD [10]. A radiographic measurement of leg length can help determine what kind of LLD is occurring [11].


Table 1. Comparison of structural and functional leg-length discrepancy [12, 13].



Whether the patient has structural and/or functional LLD they may show a range of symptoms [9, 12, 14-18]:

  • Nerve pain (sciatica)
  • Nerve palsy
  • Postoperative joint instability
  • Gait disturbance
  • Muscle spasm
  • Fatigue
  • Pain in the replaced joint or other joints
  • Back or lower back pain
  • Flexed knee syndrome

There are, of course, any number of underlying reasons for these symptoms; a thorough clinical exam accompanied by x-rays may provide insight into why the patient is experiencing problems and help direct their treatment. There are noncorrectable causes of LLD such as spinal deformity, preoperative lengthening on the operated side, and shortening of the contralateral femur or tibia, which should be discussed with the patient if these are found to be the source of the problems [19].


Nonoperative treatment suggestions

Postoperative functional LLD can be initiated by tightness in soft-tissue structures that cause pelvic obliquity and a perceived or apparent difference in leg length [19]. Generally, it takes between six months to a year postsurgery for tissues to reach a more normal length and alleviate symptoms [11, 17, 20]. Rigorous physical therapy, with special care to avoid dislocations, was reportedly successful in achieving good or excellent outcomes in more than 90 percent of cases in a study by Bhave et al [21].

In most cases with persistent symptoms, a shoe insert or lift has improved patient satisfaction. However, this should not be attempted before six months postoperatively to allow soft-tissue tightness to dissipate [22]. Orthopedic surgeon Jurek Pietrzak cautions colleagues to “resist the temptation to immediately offer shoe raises. Time, communication, and patient education provide a powerful recipe for achieving a more successful outcome and mitigating problems. At least six months must be set aside for conservative care.”

Shoe lifts have been particularly successful in addressing lower back pain [7]. However, these strategies are most successful in LLD of less than 20 mm, with best outcomes in the cases with LLD of less than 10 mm [23].


Figure 1. Suggested nonoperative strategies to address post-THA LLD.


Operative treatment indications and suggestions

When is surgical intervention for LLD after THA justified? Revision for this reason is relatively uncommon [11], but some indications that may prompt the consideration of revision are: hip instability, foot drop, paraesthesias, and severe hip or back pain [24]. Classifying the problem as structural or functional and evaluating each case on its own evidence is recommended [12].

“Taking the hip down to reduce length is often associated with instability. The only good candidates are patients that cannot really live with the inequality. However, revision would be at the cost of stability and therefore there are no real winners in the end,” points out orthopedic surgeon Biju Benjamin.

You would be looking for significant LLD that negatively impacts quality of life and is not resolving within a six to twelve-month timeframe [11]. Revision THA carries a higher risk of complications and mortality, and there is an increased risk of dislocation when limb shortening is attempted [11].

There is a lack of scientific evidence that provides definitive guidance for the surgical management of LLD [12]. This can be attributed to the unique pathology of each case and consequently there have been numerous different approaches to rectify LLD problems. Generally, addressing the femoral and/or acetabular component position and adjusting soft-tissue tension are strategies employed by surgeons [15].

A selection of strategies to revise THA to correct LLD that have been described in the literature [20, 25-28] include:

  • Soft-tissue releases
  • Structural shortening
  • Structural lengthening
  • Repositioning acetabular cups
  • Changing femoral heads
  • Revising femoral stems and components
  • Distraction osteogenesis to lengthen contralateral limb



While leg-length inequality is a common complication after total hip arthroplasty, there are tools for surgeons to evaluate, classify, and treat symptoms in the patient. Prevention of the problem in the first place is, of course, preferable, but when it happens, allotting sufficient time for resolution of symptoms, fitting shoe insoles or lifts, and targeted exercises may help improve a patient’s symptoms. There are numerous surgical strategies that can assist LLD correction during revision, but each case should be evaluated on its own unique merits.


Contributing experts

This series of articles was created with the support of the following specialists (in alphabetical order):

Biju Benjamin MD

University College
London Hospital
London, United Kingdom

Babar Kayani MD

University College
London Hospital
London, United Kingdom

Jurek Pietrzak MD

University College
London Hospital
London, United Kingdom

This issue was created by Word+Vision Media Productions, Switzerland


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