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Follow key principles to manage severe varus deformity in primary TKA
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ORLANDO, Fla., USA — There are some key principles orthopaedic surgeons should follow when they correct varus knee deformity in their patients prior to total knee arthroplasty, particularly when the deformity is severe, a presenter said at the Current Concepts in Joint Replacement Winter Meeting.
Arun B. Mullaji, MD, FRCS (Ed), MS, said the five key principles orthopaedists should focus on are determining whether the deformity is intra-articular or extra-articular, individualizing the valgus correction angle so a “customized” distal cut can be performed, resecting as little bone as possible during the procedure, balancing the extension gap first before taking other steps to balance the knee and addressing any bone defects.
“Collateral ligaments do not contract, and hence, do not need to be released,” Mullaji said. “That is a key message that we published earlier this year in the Bone and Joint Journal,” he said.
Location of the deformity
To determine preoperatively if a varus deformity is intra-articular or extra-articular, Mullaji said to obtain full-length radiographs.
“You can often miss an angular deformity like this unless you [have] these X-rays,” he said during his presentation when he showed examples of appropriate radiographs.
In addition, the valgus correction angle should be individualized to the patient, according to Mullaji, because it can range from 2° to 12°. Also, because there is such wide variation in the presentation of this angle, the distal cuts cannot be standardized, such as using a fixed 5° or 6° cut for everyone.
Limited bone resection
During total knee arthroplasty (TKA) in a patient with severe varus deformity, it is almost inevitable that some type of osteotomy and a capsule resection will be required, he said.
Regardless of whether a reduction osteotomy, posteromedial capsule resection, extra-articular corrective osteotomy or sliding medial condylar osteotomy is performed, “you need to resect less bone from the femur and tibia, particularly if there is subluxation, hyperextension or severe deformity,” Mullaji said.
“We then balance the extension gap first and equalize the flexion gap by using the femoral component size and placement to equalize it,” he said.
Osteophyte excision
Meticulous excision of osteophytes medially and posteriorly is a key step to achieve a rectangular balance extension gap, according to Mullaji.
“Release the deep [medial collateral ligament] MCL, but the semimembranosus only if required,” he said.
He noted flexion contracture in patients with varus deformity may be due to osteophytes that need to be excised before full correction of a flexion deformity can be achieved. Once the extension gap is balanced, Mullaji said to address bone defects he typically places autologous bone graft in step cuts he has made and fixes it with K-wires or screws. Ultimately, he implants a TKA prosthesis with a long stem. – by Susan M. Rapp
- References:
- Mullaji A, et al. Bone Joint J. 2016;doi:10.1302/0301-620X.98B1.36207.
- Mullaji A. Paper #78. Presented at: Current Concepts in Joint Replacement Winter Meeting; Dec. 14-17, 2016; Orlando, Fla., USA.
- For more information:
- Arun B. Mullaji, MD, FRCS (Ed), MS, can be reached at The Arthritis Clinic, 101 Cornelian, Kemp’s Corner, Cumballa Hill, Mumbai 400036, India; email: drarunmullajiclinic@gmail.com.
Disclosure: Mullaji reports he receives royalties, consulting fees for design, consulting and teaching from DePuy Synthes; royalties from Springer; and consulting fees for design and teaching from Zimmer Biomet.