What are the recommendations for a patient undergoing a through-knee replacement procedure with above knee amputation?

TMR Procedure with Above-Knee Amputation

For patients undergoing above-knee amputation, apply a removable rigid dressing (RRD) immediately in the operating room, initiate antiplatelet therapy postoperatively unless contraindicated, and begin early physical therapy—this combination optimizes wound healing, reduces complications, and improves functional outcomes. 1, 2

Preoperative Planning

Level Selection and Patient Assessment

• Measure 12-15 cm proximal to the knee joint line as the standard femoral transection point, balancing prosthetic fitting requirements with functional limb length 2
• Confirm adequate vascular supply with ankle pressure >50 mmHg or ankle-brachial index (ABI) >0.5 2
• Prioritize patient survival over limb salvage when additional attempts at definitive salvage will increase mortality risk 3
• Evaluate cumulative injury burden (soft tissue, vascular, nerve, bone, and joint) when counseling patients on anticipated outcomes 3

Risk Stratification

• Recognize that above-knee amputation carries 30-day mortality risk of 4-30% and 20-37% risk of major morbidity including myocardial infarction, stroke, and infection 4
• Identify high-risk factors: age >65 years, diabetes, homebound/isolated status, severe comorbidities, alcohol abuse, and preoperative anemia 4, 5
• Address preoperative anemia aggressively, as it is present in 100% of amputation patients versus 58% of limb salvage patients and is associated with significantly worse outcomes 5

Indications for Primary Amputation

• Consider primary amputation when life-threatening instability exists from severe infection, metabolic derangement, or ischemia causing systemic compromise 3, 4
• Evaluate for significant necrosis of weight-bearing portions of the foot, uncorrectable flexion contracture, paresis of the extremity, refractory ischemic rest pain, sepsis, or very limited life expectancy 3

Surgical Technique

Flap Creation and Bone Management

• Create equal-length anterior and posterior myocutaneous flaps, each measuring approximately 50% of the limb circumference at the level of bone transection 2
• Mark incisions to allow 10-12 cm of soft tissue distal to the planned femoral cut to ensure adequate coverage without redundancy 2
• Avoid creating unequal flaps that result in "dog ear" deformity or tension on the suture line 2
• Do not transect the femur too proximally, as this significantly impairs prosthetic function and patient mobility 2
• Bevel and smooth all bone edges meticulously, as sharp edges cause skin breakdown and pain with prosthetic use 2

Perioperative Antibiotic Prophylaxis

• Administer cefazolin prophylactically for perioperative coverage, continuing for 24 hours postoperatively in standard cases 6
• In contaminated or high-risk cases (e.g., infection-related amputation), extend prophylaxis for 3-5 days following surgery 6
• Never delay antibiotic administration in contaminated cases 1

Immediate Postoperative Management

Rigid Dressing Application

• Apply a removable rigid dressing (RRD) immediately in the operating room rather than soft dressings—this is the single most important postoperative decision affecting outcomes 1
• RRDs provide multiple critical benefits: faster healing times, reduced limb edema, prevention of knee flexion contractures, protection from external trauma and falls, preparatory contouring for prosthetic fitting, reduced pain, and earlier prosthetic fitting 1
• Allow regular wound inspection, which is critical especially for patients with ischemic disease at high risk for wound dehiscence 1
• Never use soft dressings alone, as they are inferior to rigid dressings for virtually all outcomes 1

Medical Management

• Initiate antiplatelet therapy immediately postoperatively and continue indefinitely unless contraindicated, as this improves graft patency and reduces cardiovascular events 3, 2
• Begin early pharmacological thromboprophylaxis with low molecular weight heparin (LMWH) after hemorrhage control and hemostasis 2
• Consider tranexamic acid administration to minimize postoperative blood loss 2

Wound Monitoring

• Inspect the surgical wound regularly for signs of infection, wound dehiscence, or hematoma formation 1, 2
• Recognize that deep infection occurs in approximately 20% of cases and superficial infection/skin necrosis in additional cases 7
• Monitor for complications requiring revision surgery, which occur in 37% of above-knee amputation patients 8

Rehabilitation and Functional Outcomes

Physical Therapy Initiation

• Begin physical therapy early with modifications to avoid excessive stress on the surgical site 2
• Reduce time to prosthetic fitting through use of RRDs, which decrease edema and prepare the limb for casting 1
• Optimal prosthetic fitting occurs when edema is controlled and the residual limb is properly shaped 1

Realistic Functional Expectations

• Understand that functional outcomes after above-knee amputation are poor: only 45.7% of patients are fitted or intended to be fitted with a prosthesis 8
• Among those fitted with prostheses, only a minority achieve functional independence or walk even to a limited degree 7
• Neuropathic pain develops in approximately 40% of patients after above-knee amputation 8
• Two-year mortality rate is 28.3% for above-knee amputation, significantly higher than alternative salvage procedures 8

Psychosocial Considerations

Mandatory Screening

• Screen all patients with high-energy lower extremity trauma for psychosocial risk factors including depression, PTSD, anxiety, low self-efficacy, and poor social support, as these affect patient outcomes 3
• Ensure open and informed communication between patient, orthopedic surgeon, and other treating physicians throughout the decision-making process 3

Critical Pitfalls to Avoid

• Do not use weight-bearing immediate postoperative prostheses (IPOPs) in ischemic patients due to high risk of wound complications and falls 1
• Avoid cutting the femur too short in an attempt to ensure healing—preserve maximum length while ensuring adequate soft tissue coverage 1, 2
• Never proceed with reoperation for unexplained pain, as this is frequently associated with suboptimal results 3
• Do not underestimate the high revision burden: patients undergo a median of 8 reoperations (range 2-24) after amputation for periprosthetic joint infection 5
• Recognize that positive intraoperative tissue cultures during amputation are significantly associated with risk of further surgical revision 8