Background and purpose — Severe backside wear, observed in older generations of total knee replacements (TKRs), led to redesign of locking mechanisms to reduce micromotions between tibial tray and inlay. Since little is known about whether this effectively reduces backside wear in modern designs, we examined backside damage in retrievals of various contemporary fixed-bearing TKRs.Patients and methods — A consecutive series of 102 inlays with a peripheral (Stryker Triathlon, Stryker Scorpio, DePuy PFC Sigma, Aesculap Search Evolution) or dovetail locking mechanism (Zimmer NexGen, Smith and Nephew Genesis II) was examined. Articular and backside surface damage was evaluated using the semiquantitative Hood scale. Inlays were examined using scanning electron microscopy (SEM) to determine backside wear mechanisms.Results — Mean Hood scores for articular (A) and backside (B) surfaces were similar in most implants—Triathlon (A: 46, B: 22), Genesis II (A: 55, B: 24), Scorpio (A: 57, B: 24), PFC (A: 52, B: 20); Search (A: 56, B: 24)—except the NexGen knee (A: 57, B: 60), which had statistically significantly higher backside wear scores. SEM studies showed backside damage caused by abrasion related to micromotion in designs with dovetail locking mechanisms, especially in the unpolished NexGen trays. In implants with peripheral liner locking mechanism, there were no signs of micromotion or abrasion. Instead, “tray transfer” of polyethylene and flattening of machining was observed.Interpretation — Although this retrieval study may not represent well-functioning TKRs, we found that a smooth surface finish and a peripheral locking mechanism reduce backside wear in vivo, but further studies are required to determine whether this actually leads to reduced osteolysis and lower failure rates.
1. In patients with proper implant alignment subjective instability is related to postoperative MCL deficiency, regardless preoperative deformity in coronal plane. 2. The post-op LCL laxity does not compromise subjective stability, nor influence subjective outcome, as demonstrated with KOOS scores.
Kli ni ka Or to pe dii Ogól nej, On ko lo gicz nej i Trau ma to lo gii, Uni wer sy tet Me dycz ny w Po zna niu, Polska Department of General Orthopedics, Musculoskeletal Oncology and Trauma Surgery, Poznań University of Medical Sciences, Poland STRESZCZENIEWstęp. Trzpień Zweymüllera jest dobrze znany i powszechnie stosowany w Europie od 1980 r. Nieliczni auto rzy wska zu ją na wy stę po wa nie za gęsz czeń ko ści gąb cza stej pod trzpie niem, na to miast do tąd nie opi sa no me cha ni zmu sto ją ce go u pod staw te go pro ce su. Ce lem pra cy by ło zna le zie nie czyn ni ków wpły wa ją cych na taką prze bu do wę ko ści wo kół trzpie nia Zweymülle ra.Ma te riał i me to dy. Do ba da nia włą czo no 102 ko lej nych pa cjen tów (69 ko biet i 33 mę żczyzn), u któ rych za im plan to wa no trzpień Zweymülle ra dru giej ge ne ra cji. Śred nia okre su ob ser wa cji wy nio sła 9,2 la ta (od 6-15 lat). In deks ko rów ko wy (IK) zo stał wy zna cza ny ja ko ilo raz sze ro ko ści trzpie nia en do pro te zy oraz sze ro ko ści trzo nu ko ści udo wej w 3 i 5 stre fie Gru ena.Wy ni ki. U pa cjen tów z sze ro kim ka na łem ko ści udo wej i cien ki mi war stwa mi ko ro wy mi (IK ≥0.4) wy kaza no do dat nią ko re la cję z obec no ścią za gęsz czeń ko ści pod trzpie niem (ZKpT) (p<0.0001, r=0.6028). Śred nia in dek su ko rów ko we go w okre sie ob ser wa cji zmniej szy ła się o 0,02, na to miast śred nia gru bość ko ści ko ro wej w 3 i 5 stre fie Gru ena wzro sła o 2 mi li me try. Po gru bie nie ko ści ko ro wej by ło więk sze u pa cjen tów bez ZKpT (1,5 a 2,4 mm, p=0.0172).Wnioski. 1. Obec ność cien kich ko ści ko ro wych wraz z sze ro kim ka na łem ko ści udo wej (IK ≥0.4) mo że skut ko wać wy stą pie niem za gęsz czeń ko ści pod trzpie niem. 2. ZKpT po ja wia ją się praw do po dob nie w wy ni ku prze no sze nia ob cią żeń me cha nicz nych przez trzpień na kość w 4 stre fie Gru ena. 3. Ich obec ność nie de ter minu je zwięk szo nej czę sto ści asep tycz ne go ob lu zo wa nia ani nie sta bil no ści trzpie nia.Słowa kluczowe: endoprotezoplastyka stawu biodrowego, zagęszczenia kości, trzpień Zweymüllera, indeks korówkowy SUMMARY Background. The Zweymüller stem is well-known in Europe and widely used for total hip replacement since 1980. Few authors have noted the presence of increased bone density below the tip of the stem; however, the underlying mechanism is still unknown. The aim of this study was to reveal factors influencing bone remodeling around the tip of the Zweymüller stem.Material and methods. 102 consecutive patients (69 women and 33 men) who received a second generation Zweymüller type stem (123 prostheses) were included. Mean follow-up was 9.2 years (6 -15 years). A Cortical Index (CI) was defined as the ratio between stem width and external cortical diameter in Gruen zones 3 and 5.Results. Patients with a wide femoral canal and thin cortical bone (CI ≥0.4) demonstrated a positive corre lation with the presence of increased bone density (IBD) below the stem (p<0.0001, r=0.6028). During follow-up, the mean Cortical Index d...
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