Total Knee Arthroplasty - Medial Parapatellar Approach

Indications. Symptomatic end-stage knee arthritis that has failed conservative management (activity modification, analgesia, physiotherapy, weight optimisation, intra-articular corticosteroid or viscosupplementation). The common disease categories are: - Primary osteoarthritis — the most common indication (about 85 percent of TKAs), typically tricompartmental disease with pain and functional limitation.

• Inflammatory arthritis — rheumatoid, psoriatic or ankylosing spondylitis with severe joint destruction.
• Post-traumatic arthritis — following tibial plateau, distal femur or patellar fracture with malunion or articular incongruity.
• Avascular necrosis — multifocal or involving multiple compartments.
• Failed osteotomy — progressive arthritis after high tibial or distal femoral osteotomy, or a failed unicompartmental knee arthroplasty progressing to multicompartmental disease.
• Secondary indications — septic arthritis sequelae (after eradication of infection), haemophilic arthropathy, and selected neuropathic (Charcot) joints with preserved sensation. Contraindications. Absolute: active infection (local or systemic — requires a two-stage revision if the knee is infected), an absent or irreparably disrupted extensor mechanism, severe peripheral vascular disease with an ischaemic leg needing vascular surgery first, and a neuropathic joint with complete sensory loss (unacceptably high failure rate). Relative (optimise first): age less than 60 with high activity demands (consider osteotomy), severe bone loss (may need stems, augments or a hinged prosthesis), morbid obesity (BMI greater than 40 — increases infection and wound complications), active smoking (cessation 6 weeks preoperatively), a poor soft-tissue envelope (prior incisions, skin grafts), and chronic pain syndromes such as CRPS. Assess the whole patient, not just the joint. Before committing, optimise modifiable risk: glycaemic control, smoking cessation, weight, skin integrity and any dental or urinary foci of infection. Mark all prior incisions — use the most lateral usable incision, or a new midline incision if existing incisions are more than 6cm apart, to protect the skin bridge and avoid necrosis. Consent specifically for infection (superficial 2-4 percent, deep 0.5-2 percent), stiffness and the possible need for manipulation under anaesthesia, venous thromboembolism (symptomatic VTE 2-5 percent, fatal PE 0.1-0.2 percent), peroneal nerve palsy (especially in valgus correction greater than 15 degrees), bleeding and transfusion, and the realistic expectation that a 60-year-old has roughly a 15 percent lifetime revision risk. Setup. Supine on a standard table with a foot support or side post that allows knee flexion beyond 120 degrees. Apply a sterile thigh tourniquet high on the thigh with adequate padding, exsanguinate by elevation for 2 minutes or an Esmarch bandage (avoid Esmarch with malignancy, infection or severe vascular disease), and inflate to 100mmHg above systolic (minimum 250, typically 300mmHg, maximum 350mmHg) — the lowest effective pressure is best, with a time limit of about 90 minutes.

The goal is to resurface the arthritic femur, tibia and (selectively) patella through a medial parapatellar exposure, restore a neutral mechanical axis, set correct femoral rotation, balance symmetric rectangular flexion-extension gaps, and fix the components with modern cement technique. The exposure is the foundation — laid out in full below (and in depth on the medial parapatellar approach to the knee page).

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Rehabilitation. Remove the bulky dressing at 24 hours and apply a lighter dressing. Begin ROM immediately — early motion is critical to prevent arthrofibrosis; the goal is 90 degrees flexion by discharge and 110 degrees by 6 weeks. Continuous passive motion is no longer routinely recommended; physiotherapy-directed active-assisted ROM is preferred. Mobilise weight-bearing as tolerated with a frame on day 1, progressing to crutches or a stick by day 2-3, with modern enhanced-recovery protocols emphasising same-day mobilisation and, in selected patients, day-case TKA. Driving resumes at 4-6 weeks (right-sided TKA affects brake reaction time); low-impact sport (golf, swimming, cycling) is encouraged, high-impact (running, tennis) discouraged. VTE prophylaxis combines mechanical (graduated stockings, intermittent pneumatic compression) and chemical prophylaxis using an individual risk-benefit assessment (AAOS/ACCP, NICE). Agents in common use include LMWH (e.g. enoxaparin 40mg subcutaneous daily), a DOAC (e.g. rivaroxaban 10mg daily) or aspirin, typically for about 14 days after TKA (longer after hip arthroplasty or for high-risk patients). The registry-nested CRISTAL randomised trial found aspirin had a HIGHER 90-day symptomatic VTE rate than enoxaparin after hip or knee arthroplasty (3.45 percent versus 1.82 percent) — so aspirin monotherapy should not be assumed equivalent to LMWH. Tranexamic acid (commonly 15mg/kg or 1g IV, often one dose pre-incision and one at closure; topical and oral routes are also effective) reduces blood loss and transfusion without increasing VTE risk and is endorsed by the combined AAOS/AAHKS/Hip Society/Knee Society/ASRA guideline — routine unless contraindicated. Complications

Registry perspective on complications (global). Cumulative figures vary modestly between registries (NJR, AJRR, AOANJRR, NZJR, SHAR) and with implant and patient mix, but the consistent messages are: an overall revision rate of roughly 6-8 percent at 15 years; aseptic loosening as a leading mode of late revision, markedly reduced since the 1990s with modern cement technique and implant design; infection typically around 1 percent cumulatively but consistently among the top reasons for revision and the dominant reason for early revision; instability underscoring the importance of gap balancing and rotation; cemented fixation remaining the benchmark while cementless results are design-dependent; CR versus PS broadly equivalent; and patellar resurfacing showing a small reduction in re-operation for anterior knee pain, with practice varying widely between countries.

Global epidemiology and registry survivorship. TKA is among the most commonly performed elective orthopaedic operations, with continued growth driven by ageing populations — over 100,000 primary TKAs are recorded annually in the UK NJR alone. Primary osteoarthritis accounts for greater than 90 percent of primary TKAs in most registries; the mean age is in the late 60s (typical range 40-90 years) with a steadily increasing proportion of patients younger than 60. Across major registries (NJR for England, Wales, NI and IoM; AJRR in the US; AOANJRR in Australia; NZJR in New Zealand; SHAR in Sweden), cemented fixation is the best-performing category with all-cause survivorship of roughly 90-93 percent at 15 years and a cumulative revision rate of roughly 6-8 percent at 10-15 years. CR and PS designs show broadly equivalent survivorship; cementless results are design-dependent; and patellar resurfacing shows a small reduction in re-operation for anterior knee pain, with practice varying widely between countries. Functional outcomes. Mean Oxford Knee Score improves by about 17 points (preop 22 to postop 39 out of 48); WOMAC improves about 60 percent for pain and 55 percent for function. Patient satisfaction at one year is high (about 82 percent very satisfied, 15 percent satisfied, 3 percent dissatisfied). Mean postoperative flexion is about 115 degrees (goal greater than 110 degrees for daily activities) with a mean 2-degree flexion contracture; preoperative ROM is the most important predictor, and maximal improvement is achieved by 6 months with little gain after 12 months. At one year about 85 percent walk unlimited distances, 70 percent manage stairs normally, and 80 percent of those working preoperatively return to work. Survivorship is about 95 percent at 10 years, 92 percent at 15 years, 88 percent at 20 years and 82 percent at 25 years; a 60-year-old has roughly a 15 percent revision risk by age 75. Evidence-based practice points. - Cement technique (Level I-II): modern third-generation technique improves interdigitation and reduces progressive radiolucent lines and aseptic loosening; vacuum mixing reduces porosity; thin or poorly penetrated cement and tibial debonding are recognised contributors to early loosening.

• Gap balancing versus measured resection (Level II): ligament-based versus bone-based techniques show no significant difference in outcomes, though gap balancing may reduce instability — surgeon preference.
• Tourniquet use (Level I): traditional tourniquet use reduces blood loss and improves visualisation; tourniquet-less TKA reduces pain and improves early ROM and recovery at the cost of more operative time and blood loss (offset by tranexamic acid) — trend toward tourniquet-less, both acceptable.
• Tranexamic acid (Level I): commonly 15mg/kg or 1g IV (often one dose pre-incision and one at closure), with topical and oral routes equally effective; significantly reduces blood loss and transfusion with no increased VTE risk; routine use unless contraindicated.
• Drain use (Level I): modern evidence shows no benefit for infection, blood loss or ROM and possible harm (retrograde contamination) — selective use or avoidance.
• VTE prophylaxis (Level I): combine mechanical and chemical prophylaxis by individual risk-benefit assessment; agents include LMWH, a DOAC or aspirin for about 14 days after TKA. The CRISTAL RCT found aspirin inferior to enoxaparin (3.45 percent versus 1.82 percent symptomatic VTE) — aspirin monotherapy is not equivalent to LMWH.
• Enhanced recovery (Level II): preoperative education, multimodal analgesia, opioid minimisation, immediate mobilisation and early discharge reduce length of stay, complications and cost with maintained outcomes; now standard internationally, with growing use of day-case TKA in selected patients.

Registry sources. National Joint Registry (NJR) for England, Wales, Northern Ireland, Isle of Man and Guernsey; American Joint Replacement Registry (AJRR); Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR); New Zealand Joint Registry (NZJR); Swedish Knee Arthroplasty Register (SHAR) — annual reports used as the cross-registry source for TKA survivorship, fixation, CR/PS and patellar resurfacing data.