Radiological changes in second- and third-generation Zweymüller stems

Abstract

The Alloclassic and Endoplus femoral stems have the same grit-blasted surface and are hot forged from the same titanium alloy. Only the external form of the implants differs slightly. It was our aim to examine the differences in radiographic bone response between the Alloclassic (second generation) and the Endoplus (third generation) femoral stems. We compared 79 prostheses in 70 matched patients studied over a minimum of two years. Radiolucent lines, adaptive bone remodelling, subsidence, heterotopic bone formation and lysis were recorded in the Gruen zones. Radiolucencies were mainly found in zones 1 and 7 but to a greater extent in the Endoplus than in the Alloclassic group (p < 0.001 in zone 1, p < 0.05 in zone 7). We found lucent lines in three or more Gruen zones in seven patients all of whom were in the Endoplus group (p < 0.05). Zones 2 and 6 had a significantly higher rate of lucencies in the Endoplus group (p < 0.001). We encountered a combination of proximal lucent lines in zones 1 and 7 with distal hypertrophy of the cortical bone in zones 2, 3, 5 and 6 in eight patients, all from the Endoplus group (p < 0.05). In other patients bone atrophy (stress shielding) in zones 2 and 6 was seen more frequently in the Endoplus than in the Alloclassic group (p < 0.001). In neither group was there radiological evidence of osteolysis. Heterotopic bone formation and subsidence occurred with similar frequency in both groups. Our study shows that a small change in the form of the femoral implant can result in statistically significant radiological changes in bone remodelling. Whether this will result in clinical compromise is unknown. However, it seems likely that the Endoplus femoral stem will perform differently from the Alloclassic.

Remodeling of bone tissue around the distal part of Zweymüller stem

“…Au to rzy zgod ni są rów nież co do fak tu za ob serwo wa nia li nii prze ja śnie nia czy za ni ku kost ne go wystę pu ją cych wo kół trzpie nia, naj czę ściej w stre fie 1, rza dziej w 7 [8,9]. Po mi mo po wy ższych ra dio lo gicznych ob ser wa cji, wy ni ki kli nicz ne pa cjen tów są satys fak cjo nu ją ce [10][11][12]. Nie licz ni au to 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 [1,[13][14][15].…”

“…Stan dar do wa pro jekcja AP jest naj czę ściej sto so wa na do oce ny po zy cji im plan tu i je go sta bil no ści. Tkan ka kost na pod le ga sta łej prze bu do wie i w wy ni ku dzia ła ją cych na nią sił do cho dzi do po ja wie nia się ob ja wów ra dio lo gicz nych ta kich jak: li nie prze ja śnie nia, re sorp cji bądź po grubie nia ko ści ko ro wej [12,16].…”

“…Cortical bone hypertrophy is observed in Gruen zones 3 and 5 and radiolucent lines can be seen in zones 1 and 7 [8,9]. Despite these radiolo gical findings, clinical outcomes are satisfying [10][11][12]. Few authors have also noted the presence of bone remodeling and increased bone density below the tip of the stem in some cases; however, the underlying mechanism is still unknown [1,[13][14][15].…”

The Adaptiva custom-made stem—our reasons for not using it anymore

“…In comparison with the results of Zweymüller, Bicontact or Spotorno cohorts, the results for proximal calcar atrophy and radiolucent lines and distal hypertrophy are even slightly worse [3,24].…”

Simulation by Finite Elements of Bone Remodeling After Implantation of Femoral Stems

“…Long term studies of different cementless stems show a high incidence of stress-shielding, caused by the change in the distribution of loads on the femur (Engh et al, 2003;Glassman et al, 2006;Wick & Lester, 2004). The monitoring of an anatomic femoral stem with metaphyseal load-bearing and HA coating (ABG-I), that was carried out through a prospective, controlled study that included 67 patients (Group I) in the period 1994-99, has confirmed that even though the clinical results are very favourable, a high percentage of cases with stress-shielding are detected (Herrera et al, 2004).…”