Knee arthritis

Patients present to their orthopedic surgeons with knee pain at various stages of their arthritic process, from minimal arthritis to severe unicompartment or tricompartment disease. Most patients who present for surgical intervention have usually failed all non-operative management, including the use of NSAIDS, injections, and weight reduction programs. If nonoperative management fails to alleviate the arthritic knee pain, the orthopedic surgeon must decide on the appropriate surgical management to help improve the patient’s quality of life. Surgical decision making for unicompartment versus total knee arthroplasty (TKA) is based on multiple factors including results of clinical and radiographic evaluation, age of the patient, extent of arthritic process, compartments involved, any existing co-morbid conditions and patient expectations. Patients who have undergone unicompartment arthroplasty have experienced fewer co-morbidities, higher patient satisfaction, shorter rehab to return to recreation activities and excellent survivorship.^1-3

For patients with tricompartmental disease, a TKA is typically indicated. Despite the success of primary TKA over the past few decades,⁴ up to 20% of patients can be dissatisfied with their TKA.^5-6 The etiology of dissatisfaction is multifactorial including residual pain, stiffness, instability, and patient expectations. Surgical factors that could be related to patient dissatisfaction include soft tissue damage, component malposition, inadequate flexion/extension gap balancing, and inability to restore the target alignment and joint line.^7-9,25

Mako robotics platform

The Mako robotics platform has demonstrated enhanced clinical results for unicompartment and total knee arthroplasty. ^{1-3, 10-13} The platform allows the surgeon to execute precise bone cuts;^14,15 glean real time information intra-operatively for gap balancing through virtual modifications to component positioning to help address implant alignment and soft tissue balance; and to help protect soft tissues with the implementation of CT-based haptic boundaries.^{2,15-17,19-20}

Mako Robotic-Arm Assisted Technology allows for functional implant positioning, which is patient-specific implant placement enabled by Mako’s three key unique features: enhanced 3D planning; dynamic real time joint balancing; and haptic guidance.^{2, 4, 11, 13, 18, 19} Each patient’s anatomy is unique and Mako’s CT based 3D preoperative planning software allows the surgeon to size and position the Restoris MCK and Triathlon Total Knee to plan for each patient.^15,18 The surgeon can review the plan and manipulate implant position, along with the bone cuts in the coronal, axial, and sagittal planes on the femoral and tibial sides to help achieve the desired target limb alignment and soft tissue balance on both the medial and lateral compartments in extension and flexion prior to completing the bony cuts.^13,18-19,21 The dynamic joint balancing feature of the Mako software provides the ability to refine the plan based on the patient’s soft tissue envelope in real time. It also enables the surgeon to make any necessary adjustments in bone cuts or component position to balance the knee before making any bone cuts and again if necessary following trial reduction without the use of any manual or jig-based instruments.^13,18-19,21 In addition, Mako software has a unique haptic boundary that is generated based on the individual patient’s implant placement and CT scan which demarcates the bony anatomy so that the cutting tools do not encroach on the soft tissue, helping to avoid inadvertent soft tissue trauma.^{2,15-17,19-20}
 

Partial knee arthroplasty (PKA) continues to boast patient satisfaction scores in the low 90th percentile,² yet it represents only 5% to 6% of knee replacements being performed in the United States.²¹ Assuming we have a similar patient demographic to other developed nations across the world (such as Australia [approx. 9%]²² and England [11%]²³), PKA continues to be an under-utilized operation in the United States. There are misconceptions about high mechanical failure rates, and some surgeons may be discouraged from performing the PKA operation based on the misconception that PKA is only a staged procedure for an inevitable TKA.

Certainly, PKA presents technical challenges that warrant meticulous surgical technique, but the Mako platform allows the surgeon to place the components in an accurate and precise manner to plan while offering protection to the soft tissues.^2,15,19,20 Pre-operative planning for properly sizing the tibial component allows the placement along the cortical rim. Intra-operative balancing measures can be taken to help restore proper patient specific kinematics. The haptic boundaries allow for bony resection with reduced potential for soft tissue trauma.^2,15,19,20 In my experience, when I evaluate a patient for knee surgery, I look for reasons why they would not be a candidate. This paradigm shift allows one to objectively evaluate the patient prior to making a decision of whether a Mako Partial Knee or Mako Total Knee would serve them best.

My patient selection criteria for Mako Partial Knee:
• Pain localized to only one compartment
• Pre-op ROM >110 degrees
• Flexion contracture <10 degrees
• Mild to moderate deformity (varus <10 degrees)
• Correctable (not necessarily to neutral, constitutional varus points)
• Varus knees – no posterior wear or erosion
• Ignore PF changes (up to Kellgren/Lawrence III changes) if no symptoms and normal tracking/tilt
• No significant subluxation

A compendium of Mako Partial Knee data can be accessed here.

I use the Mako Total Knee platform for several reasons:

Enhanced planning: The pre-operative 3D CT based templating software helps me to preoperatively determine femoral and tibial implant sizes.²⁴ The ability to accurately identify the size of the implants prior to surgery helps me to minimize the number of trays that need to be opened for the procedure.

Dynamic joint balancing: A virtual preoperative plan is created using the 3D software which is visualized on the Mako screen in real time intraoperatively. The surgeon can adjust the virtual implant position based on soft tissue information. In my personal experience, I adjust the dynamic joint balancing workflow based on whether the deformity is mild correctable or a greater deformity.

• In cases of mild correctable deformity, once the virtual implant position and tibial and femoral bone cuts in the coronal, axial, and sagittal planes are manipulated to reach the desired target alignment and soft tissue balance, all the cuts are then completed using the robotic-arm starting either on the femoral or tibial side. 
• In cases of greater deformity, the Mako Total Knee workflow can be adjusted to first perform the proximal tibial and distal femoral cuts, and then balance the extension gap with these initial cuts completed. Next, the surgeon can virtually adjust the flexion gap with manipulation of the femoral cuts and implant position in all 3 planes to balance the medial and lateral flexion gap compartments to the established extension gap. The haptic boundaries created by the patient’s bony anatomy based on the CT scan help prevent inadvertent soft tissue trauma.

Haptic guidance: Mako Total Knee enables precise execution of the pre-op plan with real time intraoperative data on alignment and gap measurement with the ability to make intraoperative adjustments to reach the desired result. This innovative technology has evolved primary TKA into a more predictable and reproducible surgical experience for the orthopedic surgeon. Early clinical experience using the Mako platform with Triathlon compared to conventional jig-based instruments has demonstrated reduced soft tissue trauma, decreased blood loss, decreased postoperative pain and opioid consumption, shorter hospital stay, and improved one year patient satisfaction scores.^13,34

Clinically successful implants: Clinical data around the world has largely supported the enhanced survivorship and functional outcomes of Triathlon Total Knee System.^26-32 The coupling of Triathlon implant with Mako Total Knee systems gave me confidence as the patient satisfaction and outcomes study results for Triathlon were already very good to start with.^26-32

A compendium of Mako Total Knee data can be
accessed here.

A compendium of Triathlon data can be accessed here.

Mako Robotic-Arm Assisted Surgery offers applications for Total Knee, Partial Knee and Total Hip. Join Drs. Arthur Malkani and Akhil Sastry to hear how they determine the right Mako knee procedure for their patients, and learn about their surgical techniques and associated clinical outcomes.