summary Unicompartmental Knee Arthroplasty is a surgical option for knee arthritis when only one compartment of the knee is involved. The procedure can be performed for isolated medial compartment, isolated lateral compartment or isolated patellofemoral osteoarthritis. The most common reasons for conversion to a total knee arthroplasty are the progression of osteoarthritis and aseptic loosening. Epidemiology Incidence 5% of surgeries where knee arthroplasty is indicated are unicompartmental knee replacements Anatomic location medial compartment is most common Types of implants Fixed-bearing historical standard of care Mobile-bearing pros weightbearing through the meniscus increases conformity and contact without increasing constraint decrease in wear pattern excellent survivorship out to the second decade cons technically demanding bearings can dislocate Advantages Compared to TKA faster rehabilitation and quicker recovery less blood loss less morbidity less expensive preservation of normal kinematics theory is that retaining ACL, PCL and other compartments leads to more normal knee kinematics smaller incision less post-operative pain leading to shorter hospital stays Compared to osteotomy faster rehabilitation and quicker recovery improved cosmesis higher initial success rate fewer short-term complications lasts longer easier to convert to a TKA Indications Indications controversial and vary widely as an alternative to total knee arthroplasty or osteotomy for unicompartmental disease classicaly reserved for older (>60), lower-demand, and thin (<82 kg) patients 6% of patient's meet the above criteria with no contraindications new effort to expand indications to include younger patients and patients with more moderate arthrosis Contraindications inflammatory arthritis ACL deficiency absolute contraindication for mobile-bearing UKA and lateral UKA controversial for medial fixed-bearing fixed varus deformity > 10 degrees fixed valgus deformity >5 degrees restricted motion arc of motion < 90° flexion contracture of > 5-10° previous meniscectomy in other compartment tricompartmental arthritis (diffuse or global pain) younger high activity patients and heavy laborers grade IV patellofemoral chondrosis (anterior knee pain) Technique Procedural tips avoid overcorrections undercorrect the mechanical axis by 2-3 degrees overcorrection places excess load on unresurfaced compartment remove osteophytes (peripheral and notch) resect minimal bone avoid extensive releases avoid edge loading prevent tibial spine impingement with proper mediolateral placement avoid making a varus tibial cut which increases the chance for loosening use caution when placing the proximal tibial guide pins to avoid stress fractures correct varus deformity to 1-5 degrees of valgus Complications Aseptic loosening most common cause of early failure (5 years) at somewhere between 25%-45.3% Stress fractures always involve tibia associated with high activity and patient weight clinically there will be a pain free interval followed by spontaneous pain with activity blood commonly found on joint aspiration risk factors penetrating posterior tibial cortex with guide pin, placing guide pin medial in periphery, re-drilling for guide pin, and under-sized tibial component Intra-operative fractures associated with forceful impacting of implant Outcomes Fixed-bearing 1st decade results 10-year survivorship from studies done in 1980s and 1990s ranges from 87.4% to 96% the standard faliure rate in the first decade is 1% 2nd decade results rapid decline in survivorship ranging from 79% to 90% Mobile-bearing excellent clinical results with 15-year survivorship reported at 93% Long-term results lateral compartment arthroplasties have equivalent results to medial revision rates are worse than total knee revision rates Patellofemoral arthroplasty (PFA) has good outcomes for isolated patellofemoral arthritis Previous generation designs (i.e. inlay style) exhibited high rates of patellar instability Newer generation designs (i.e. outlay style) replaces entire anterior trochlear surface and minimizes risk of patellar instability Long term mode of failure remains progression of tibiofemoral arthritis causes of late failure (>5 years) progress of osteoarthritis (idiopathic, over-correction, more common with mobile-bearing) component failure (overload due to under-correction) component loosening (common in fixed-bearing) patella impingement on femoral component (patella pain) polyethylene wear
QUESTIONS 1 of 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Previous Next (SBQ16HK.12) A 56-year-old man presents with chronic anterior knee pain and the radiographs shown in Figure A. He undergoes the procedure depicted in Figure B. Regarding his prosthesis, which of the following statements is most accurate? QID: 211240 FIGURES: A B Type & Select Correct Answer 1 Patellofemoral arthroplasty has superior functional outcomes when compared to either medial or lateral unicompartmental arthroplasty 1% (22/1508) 2 If disease progression to the medial compartment occurs, the addition of a medial UKA offers more predictable clinical outcomes than conversion to a total knee arthroplasty (TKA) 1% (18/1508) 3 The most common long-term mode of failure is progression of osteoarthritis to involve the other compartments 87% (1319/1508) 4 Patellar instability is the most common reason for long-term revision to TKA 3% (45/1508) 5 Aseptic loosening is the most common short-term complication necessitating revision to TKA 6% (92/1508) L 4 Question Complexity B Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 3 Review Tested Concept Review Full Topic Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (OBQ09.60) A 61-year-old male had a minimally-invasive unicompartmental knee replacement 8 months ago. He did well until recently when he developed persistent right knee pain that is worse with weight bearing. He denies any fevers or recent trauma. He does report that he had been exercising more over the past few months in an attempt to lose weight. WBC, ESR and C-reactive protein levels are normal. An AP radiograph and bone scan are shown in Figure A and B. What is the most likely cause of his symptoms? QID: 2873 FIGURES: A B Type & Select Correct Answer 1 Component failure/ polyethylene failure 8% (222/2717) 2 Infection 1% (24/2717) 3 Pes anserine bursitis 3% (93/2717) 4 Stress fracture 87% (2360/2717) 5 Complex regional pain syndrome 0% (9/2717) L 1 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 4 Review Tested Concept Review Full Topic (OBQ09.18) All of the following are contraindications to medial unicondylar knee arthroplasty EXCEPT: QID: 2831 Type & Select Correct Answer 1 Flexion contracture greater than 10 degrees 4% (125/3483) 2 Varus deformity greater than 10 degrees not correctable with stress testing 4% (138/3483) 3 Lateral knee joint line pain 12% (433/3483) 4 Rheumatoid arthritis 7% (231/3483) 5 Osteonecrosis of the medial femoral condyle 73% (2540/3483) L 2 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 5 Review Tested Concept Review Full Topic Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (OBQ08.255) A 40-year-old man has moderate lateral compartment arthritis several years after undergoing a partial lateral meniscectomy. He has a correctable 5 degree valgus knee deformity compared to his other limb. His patellofemoral and medial compartments do not show any radiographic signs of degenerative changes. His knee has full range of motion and is stable on exam. After failing nonoperative treatments, which surgical option is most likely to give him the best outcome? QID: 641 Type & Select Correct Answer 1 Valgus producing high tibial osteotomy 3% (122/3543) 2 Varus producing distal femoral osteotomy 85% (3002/3543) 3 Total knee replacement 8% (282/3543) 4 Arthroscopic debridement and chondroplasty 3% (106/3543) 5 Tibial tubercle osteotomy with anteromedialization 0% (17/3543) L 2 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 2 Review Tested Concept Review Full Topic Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (SBQ07HK.87.1) A 65-year-old female presents to the clinic with isolated medial-sided left knee pain. She has since exhausted conservative management but remains persistently symptomatic. The physical exam and radiographic work-up demonstrates isolated medial tibiofemoral compartment involvement. After discussion of the surgical options, she undergoes the procedure shown in Figure A. She initially does well but returns to clinic 3 months post-operatively with significantly increased medial-sided knee pain and the injury shown in Figure B. All of the following technical errors likely contributed to this complication EXCEPT? QID: 213791 FIGURES: A B Type & Select Correct Answer 1 Excessive force impacting the tibial component 22% (411/1867) 2 Penetration of the posterior tibial cortex with proximal guide pin 14% (260/1867) 3 Placement of a peripheral medial cortical guide pin 18% (339/1867) 4 Tibial resection guide replacement with re-drilling of the two proximal guide holes 10% (196/1867) 5 Under-sizing of the tibial component 35% (645/1867) L 5 Question Complexity D Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 1 Review Tested Concept Review Full Topic Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (OBQ06.107) Which of the following benefits can be expected from unicompartmental knee arthroplasty compared to total knee arthroplasty for medial compartment knee arthritis? QID: 293 Type & Select Correct Answer 1 Better clinical outcomes at one year follow-up. 2% (53/2297) 2 Greater survivorship rate at 10 year follow-up 1% (26/2297) 3 Faster postoperative rehabilitation 93% (2146/2297) 4 Better postoperative knee alignment 2% (44/2297) 5 Reduced risk of secondary surgery within the first year 1% (18/2297) L 2 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 3 Review Tested Concept Review Full Topic (OBQ05.26) When performing a unicondylar knee replacement, a smaller incision without dislocation of the patella offers what advantage over a standard, patella-everting approach? QID: 63 Type & Select Correct Answer 1 the option to convert to a total knee arthroplasty if needed 2% (28/1445) 2 more anatomic positioning of the components 4% (58/1445) 3 better ultimate range-of-motion 3% (38/1445) 4 increased 10-year implant survival rate 1% (9/1445) 5 improved rate of recovery 90% (1307/1445) L 2 Question Complexity D Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 5 Review Tested Concept Review Full Topic Sorry, this question is for PEAK Premium Subscribers only Upgrade to PEAK (OBQ04.259) A 60-year-old male tennis player undergoes a unicompartmental knee arthroplasty (UKA) shown in Figures A and B. Which of the following statements regarding this procedure is true? QID: 1364 FIGURES: A B Type & Select Correct Answer 1 Compared to total knee arthroplasty (TKA), UKA more closely approximates native knee kinematics 86% (2834/3300) 2 Patients undergoing a UKA and TKA have equivalent blood loss and pain medication requirements 2% (53/3300) 3 Compared to their TKA counterparts, UKA patients have a slower return to function 1% (25/3300) 4 There is no difference in range of motion at short or long term follow-up when compared with TKA 9% (294/3300) 5 Postoperative hospital stay is equivalent for UKA and TKA patients 2% (81/3300) L 2 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 1 Review Tested Concept Review Full Topic
All Videos (14) Podcasts (1) ISTA: New Early-Career Webinar Series 2020 The Utility of Virtual Reality as a Learning Tool for Trainees in Unicompartmental Knee Arthroplasty: A Randomized Controlled Trial - Musa Zaid Musa Zaid Recon - Unicompartmental Knee Replacement B 3/3/2021 153 views 0.0 (0) Login to View Community Videos Login to View Community Videos ISTA: New Early-Career Webinar Series 2020 Single Upright Unloader Brace Improves Medial Joint Space in Unicompartmental OA Subjects - Garret Dessinger Recon - Unicompartmental Knee Replacement B 3/3/2021 17 views 0.0 (0) Login to View Community Videos Login to View Community Videos 2018 Orthopaedic Summit Evolving Techniques Evolving Technique: Converting The UKA To A Total Knee: When, How - Tips & Tricks - Michael J. Kaplan, MD (OSET 2018) Michael Kaplan Recon - Unicompartmental Knee Replacement A 7/25/2019 601 views 4.2 (6) Recon | Unicompartmental Knee Replacement Recon - Unicompartmental Knee Replacement Listen Now 20:9 min 5/13/2020 465 plays 4.5 (2) See More See Less
Knee osteoarthritis in 56F - Lateral unicompartmental arthritis (C101451) H. John Cooper Recon - Unicompartmental Knee Replacement B 5/3/2020 9875 37 10 Knee Osteoarthritis in 51M - Medial unicompartmental disease (C101417) Shaun Patel Recon - Unicompartmental Knee Replacement B 4/4/2020 173 19 0 Progressive OA after GCT/UKA in 62M (C101401) Shaun Patel Recon - Unicompartmental Knee Replacement B 3/21/2020 102 10 3 See More See Less