Decreasing Leg Length Discrepancy in THA
The authors review preoperative, intraoperative, and postoperative processes in managing LLD in total hip arthroplasty patients.
Joseph T. Moskal, MD, FACS, and Susan Capps, PhD
From the patient’s perspective, the most basic goals of total hip arthroplasty (THA) are pain relief and restored mobility and function .
From the surgeon’s perspective, the goals are well-fixed components, dynamic stability, and restored leg length.
These goals are not mutually exclusive, but they do point to the differences in expectations of the final result of THA: Surgeons are primarily concerned with the functioning of the reconstructed hip, while patients are primarily concerned with being able to do the things they want to do in their daily lives.
Leg length discrepancy (LLD) and its effect on activities of daily living is a significant source of patient dissatisfaction following THA  and is the most common reason for litigation against orthopaedic surgeons . It does not matter whether the patient had LLD before THA or not, or whether he or she perceive it or not; the patient’s perception following THA is the important outcome with regards to LLD. In a study by Sharkey et al, 96% of patients had LLD preoperatively, yet only 12% perceived it on examination. 
Because LLD is often part of the patient’s preoperative presentation, and because LLD is often a source of dissatisfaction, what do the surgeon do to manage LLD in THA patients?
Begin by understanding that all LLDs are not the same.
- True LLD is due to hip damage (Figure 1).
- Apparent LLD is sometimes due to hip contracture (Figure 2).
- Apparent LLD is sometimes not due to hip damage or contracture (Figure 3).
Figure 1. Pre-existing true LLD (left to right) due to DDH, previous surgeries SCFE, and trauma.
Figure 2. LLD (shortening) due to index hip adduction contracture and LLD (lengthening) due to index hip abduction contracture.
Figure 3. LLD not due to index hip contracture or damage, etiology is extra-articular.
Next, conduct a thorough preoperative consultation and assessment of LLD.
During the preoperative consultation, educate the patient regarding the goals of THA (stability over LLD) and the possible complications of THA, including LLD (Figure 4).
Figure 4. Properly implanted THA.
LLD is often pre-existing, sometimes the patient perceives it and sometimes the patient is unaware of the discrepancy . There are three opportunities to assess the patient’s pre-existing LLD:
- Patient history
- Physical examination
- Radiographic examination
Patient History: Evaluation of Pre-existing LLD
- Has the patient ever had DDH? SCFE? Polio? Perthes Disease?
- Were there any previous surgeries? Trauma? Fractures?
- Are there any co-morbidities contributing to LLD?
- Key question: Do your legs feel equal?
Physical Examination: Evaluation of Pre-existing LLD
- Note there any existing scars and fixed contractures that may be clues pointing to pre-existing LLD
- Observe range of motion, specifically contractures, may be indicative of pre-existing LLD
- Observe whether the patient has pelvic obliquity
- Perform a block test to quantify pre-existing LLD, document in chart before surgery (Figure 5)
Figure 5. Example of the block test, allowing LLD to be quantified objectively.
Radiographic Examination: Determining the Etiology of Pre-Existing LLD
- Intra- versus extra-articular etiology: Is the pre-existing LLD…?
- Developmental, and is there unilateral or bilateral hip involvement? (Figures 6-7)
- Acquired? (Figure 8)
- Traumatic? (Figure 9)
- Due to the condition of adjacent joints – spine, contralateral hip, ipsilateral knee? (Figure 10)
Figure 6. Bilateral DDH.
Figure 7. Status post-SCFE.
Figure 8. Status post-hip fusion.
Figure 9. Open fracture of the femur as a child, resulting in pan osteomyelitis (significant residual LLD)
Figure 10. Status post polio syndrome (significant residual LLD).
Radiographic Evaluation: Creating Necessary Preoperative Images
- Preoperative imaging allows for accurate visualization of bony anatomy:
- A/P pelvis (include both hips and proximal femurs) (Figure 11)
- A/P hip (internal rotation)
- Lateral of hip
- Scanogram – optional (Figure 12)
- CT scan – optional
Figure 11. A/P pelvis includes both hips and proximal femurs.
Figure 12. Scanogram views.
Radiographic Evaluation: Creating Images for Preoperative Templating
- Hip center of rotation established – basis of acetabular component placement:
- Femoral neck-shaft angle (varus vs. valgus); beware of long leg arthritis preoperatively (Figure 13)
- Femoral offset
- Acetabular deficiencies (Figure 14)
- Femoral bone classification
- Femoral anteversion
- Geometry of metaphysis (Figure 15)
- Geometry of diaphysis (Figure 16)
- Metaphyseal/diaphyseal mismatch
Figure 13. Varus femoral neck-shaft angle (left) and valgus femoral neck-shaft angle (right).
Figure 14. Preoperative acetabular deficiencies (left) and postoperative correction of same deficiencies (right).
Figure 15. Preoperative metaphyseal geometry (left) and postoperative correction (right).
Figure 16. Preoperative diaphyseal geometry (left) and postoperative correction.
Surgical planning requires familiarity with multiple THA systems and the options available to the surgeon. The questions below will help you determine which hip implant system best suits each particular patient. In addition, look for existing metaphyseal/diaphyseal/anteversion mismatch, for acetabular dysplasia, and for other changes in hip anatomy due to previous surgery or trauma.
Acetabular component choice presents a wide variety of questions.
- Should you use cemented or cementless fixation?
- If you chose cementless fixation is that with or without screw supplementation?
- Do you choose to use a lateralizing acetabular liner?
- Is the acetabular shell hemispherical or is it oblong in shape?
- Does this THA require augments or cages?
- Is the patient’s anatomy such that the best solution is a custom acetabular component?
Femoral component choice also presents numerous questions:
- Is this patient best served with a cemented or cementless femoral stem?
- If cementless fixation is the best option, then which cementless configuration: proximally coated, distally coated, modular, tapered wedge, or tapered bi-planer?
- What offset/neck angle should you choose?
- And how does the patient’s anteversion play into the femoral component choice?
Intraoperative assessment of LLD allows an opportunity for correction and correlation with stability testing. The tests, tools, and tricks listed below provide real-time feedback that allows the surgeon to quantify the THA construct and determine if the preoperative goals for leg-length and stability are being met.
- Knee to knee
- Foot to foot
- Soft tissue tension
- Personal tricks
- Imaging (intraoperatively): Radiographs and fluoroscopy
- Navigation/computer-aided surgery
There is still work during the postoperative period.
The patient needs continuing education regarding LLD; for example, the patient needs to understand typically how long the perception or sensation of LLD persists (that it diminishes over time). Also, the patient may need to be reminded that the primary goal is stability (avoidance of dislocation).
Physical therapy is a crucial part of a successful return to function after THA. It allows for strengthening and is also a opportunity to address pelvic obliquity (if possible). Communicate with the physical therapist regarding how to discuss LLD with the patient – if the patient hears and sees the same phrases repeatedly, it will help with learning and comprehension.
Pearls & Pitfalls
- Preoperative assessment of risks, informed consent
- Educate patient
- Preoperative templating and planning
- Know your implant system
- Be prepared for variability
- Modify the surgical approach as needed
- Assess anatomy and recognize deviations
- Use intraoperative devices and tests
- Check intraoperative stability
- Consider quantitative technologies
- Complications cannot be eliminated, but can possibly be minimized
- Continue to educate the patient
- Remind the patient about stability and preoperative goals
Joseph T. Moskal, MD, FACS, is chief of orthopaedics for Carilion Clinic, Roanoke, Virginia. Susan G. Capps, PhD, is an independent consultant specializing in medical devices, BENSOL, Warsaw, Indiana.
References and Additional Readings
- Trousdale RT, McGrory BJ, Berry DJ, Becker MW, Harmsen WS: Patients’ Concerns Prior to Undergoing Total Hip and Total Knee Arthroplasty. Mayo Clin Proc. 1999; 74: 976-982
- Clark CR, Huddleston HD, Schoch III EP, Thomas BJ: Leg-Length Discrepancy After Total Hip Arthroplasty. J Am Acad Orthop Surg. 2006; 14: 38-45
- Sharkey PF, Byhoff, E, Purtill, JJ, Parvizi J, Hozack WJ, Rothman RH. Leg Length Discrepancy & Total Hip Arthroplasty. 2007 AAOS Podium Presentation, February 14, 2007, San Diego, CA
- Berend KR, Sporer SM, Sierra RJ, Glassman AH, Morris MJ: Achieving stability and lower-limb length in THA.JBJS Am, Instr Course Lecture. 2010; 92(16): 2737-2752
- Hofmann AA, Bolognesi M, Lahav A, Kurtin S: Minimizing leg-length inequality in THA: Use of preoperative templating and an intraoperative x-ray. Am J Orthop. 2008;37(1): 18-23
- Konyves A, Bannister GC: The importance of leg length discrepancy after total hip arthroplasty. JBJS Br 2005; 87(2): 155-157
- Meermans G, Malik A, Witt J, Haddad F: Preoperative radiographic assessment of limb-length discrepancy in THA. CORR. 2011; 469: 1677-1682
- Murphy SB, Ecker TM: Evaluation of a new leg length measurement algorithm in hip arthroplasty. CORR. 2007; 463: 85-89
- Ranawat CS, Rodriguez JA: Functional leg-length inequality following total hip arthroplasty. J Arthroplasty 1997; 12: 359-364
- Rösler J, Perka C: The effect of anatomical positional relationships on kinetic parameters after total hip replacement. Intl Orthop. 2000; 24: 23-27
- Sathappan SS, Ginat D, Patel V, Walsh M, Jaffe WL, Di Cesare PE: Effect of anesthesia type on limb length discrepancy after THA. J Arthrop. 2008; 23(2): 203-209