An Argument for a Lateral Skin Incision in TKA
In the abstract from his presentation at ICJR’s Pan Pacific Orthopaedic Congress, Dr. Michael Ries discusses the benefits of a lateral incision in total knee arthroplasty: improved sensation and kneeling ability.
By Michael D. Ries, MD
A midline or slightly medialized skin incision has generally been used for total knee arthroplasty (TKA) because it provides access to a medial parapatellar arthrotomy and midvastus or subvastus approach.
The skin cleavage lines over the knee are oriented horizontally; therefore, a medial parapatellar incision is more parallel to the cleavage lines than a midline incision and is associated with less skin tension. 
However the medial parapatellar skin incision requires a larger soft tissue flap to be raised to reach the lateral patella.
Both vascularity and nerve sensation to the skin over the knee are provided by the saphenous supply in a medial to lateral direction.  Incision in the anterior skin over the knee results in disruption of the medial to lateral nerve and vascular supply, which is associated with relative hypoxia and numbness in the lateral skin flap.
Although skin necrosis is rare after TKA, it often occurs along the lateral skin flap. More commonly, skin numbness is present for a prolonged period of time lateral to a medial or midline incision, which may contribute to difficulty kneeling.
When a patient kneels, pressure is applied primarily to the tibial tubercle and anterior patella.  A medial incision that does not extend directly over the anterior tibial tubercle or patella may be helpful to minimize discomfort during kneeling. 
However, a more lateral incision (just lateral to the midline) preserves sensation over the tibial tubercle and patella. Anterior knee pain may be reduced during kneeling and skin sensation may be better preserved with this approach. In a randomized prospective trial of 69 TKAs comparing hypesthesia after an anterolateral versus midline skin incision, Laffouse et al  found considerably less hypesthesia in the lateral incision group.
The lateral incision may require a slightly larger skin incision – about 1 cm – than a midline incision to permit soft tissue flap elevation to reach the medial arthrotomy. However, the improvements in sensation and kneeling ability attributed to a lateral incision may be more important to patients than the length of the incision.
Michael D. Ries, MD, is a joint replacement and revision surgery specialist with Tahoe Fracture & Orthopedic Medical Clinic, Carson City, Nevada.
- Johnson et al.: Anterior midline or medial parapatellar incision for arthroplasty of the
- knee. A comparative study. J. Bone Joint Surg. 68(B): 812-814, 1986
- Younger ASE, Duncan CP, Masri BA. Surgical Exposures in Revision Total Knee Arthroplasty. J Am Acad Orthop Surg, 6: 55-64, 1998
- Goldstein WM, Gordon AC, Branson JJ, Simmons C, Berland KA. Stress Over the Anterior Aspect of the Knee with Kneeling, JBJS, 2007.
- Laffosse JM. Potapov A, Malo M, Lavigne M MD, Vendittoli PA. Hypesthesia after Anterolateral versus Midline Skin Incision in TKA: A Randomized Study. CORR 2011.