Development of a Chronic Canine Ovariohysterectomy Model to Evaluate Vaginal Cuff Healing Using Two Closure Systems.

Background and Purpose. This study established a suitable animal model of ovariohysterectomy; characterized the course and pattern of vaginal healing after ovariohysterectomy; and compared healing obtained after closure of the vaginal cuff with a novel cuff-closure device (Zip-stitch® clips) and VICRYL® sutures. Research Design and Study Sample. This prospective, randomized, controlled, blinded animal study was conducted in 27 mongrel hounds according to an IACUC-approved protocol. Each animal underwent ovariohysterectomy followed by vaginal cuff closure with Zip-stitch or VICRYL. At two or six weeks, animals were sacrificed for gross and histological analysis. Data Collection. The primary endpoint was the difference in the fraction of vaginal cuff healed six weeks after application of the closure device. Secondary endpoints included histopathologic cellular and tissue responses, including inflammation, necrosis, infection, and vascular and muscle changes. Results. In the test group, there were two distinct locations where fibrotic or granular tissue fusion between the anterior and posterior vaginal walls was observed: in tissue "captured" by a clip or in tissue around the clip. The fraction of the vaginal cuff healed was similar in animals treated with Zip-stitch clips and those treated with sutures at six weeks (68±10% vs 67±18%; P=.148, test for non-inferiority) after surgery. The test article performed similarly or better than the control article in terms of the intensity or extent of the secondary endpoints. Conclusions. Subject to further confirmation, this study supports Zip-stitch clips as a method to maintain immediate post-operative approximation of the vaginal cuff leading to healing but did not achieve statistical significance in its primary endpoint.

Is There A Difference in Bone Ingrowth in Modular Versus Monoblock Porous Tantalum Tibial Trays?

Contemporary total knee designs incorporating highly porous metallic surfaces have demonstrated promising clinical outcomes. However, stiffness differences between modular and monoblock porous tantalum tibial trays may affect bone ingrowth. This study investigated effect of implant design, spatial location and clinical factors on bone ingrowth. Three modular and twenty-one monoblock retrieved porous tantalum tibial trays were evaluated for bone ingrowth. Nonparametric statistical tests were used to investigate differences in bone ingrowth by implant design, tray spatial location, substrate depth and clinical factors. Modular trays (5.3 ± 3.2%) exhibited higher bone ingrowth than monoblock trays (1.6 ± 1.9%, P = 0.032). Bone ingrowth in both designs was highest in the initial 500 µm from the surface. Implantation time was positively correlated with bone ingrowth for monoblock trays.

Rare complications of osteolysis and periprosthetic tissue reactions after hybrid and non-hybrid total disc replacement.

PURPOSE: Few complications have been reported for lumbar total disc replacement (TDR) and hybrid TDR fixations. This study evaluated retrieved implants and periprosthetic tissue reactions for two cases of osteolysis following disc arthroplasty with ProDisc-L prostheses. METHODS: Implants were examined for wear and surface damage, and tissues for inflammation, polyethylene wear debris (polarized light microscopy) and metal debris (energy-dispersive X-ray spectroscopy). RESULTS: Despite initial good surgical outcomes, osteolytic cysts were noted in both patients at vertebrae adjacent to the implants. For the hybrid TDR case, heterotopic ossification and tissue necrosis due to wear-induced inflammation were observed. In contrast, the non-hybrid implant showed signs of abrasion and impingement, and inflammation was observed in tissue regions with metal and polyethylene wear debris. CONCLUSIONS: In both cases, wear debris and inflammation may have contributed to osteolysis. Surgeons using ProDisc prostheses should be aware of these rare complications.

Is increased modularity associated with increased fretting and corrosion damage in metal-on-metal total hip arthroplasty devices?: a retrieval study.

This retrieval study documents taper damage at modular interfaces in retrieved MOM THA systems and investigates if increased modularity is associated with increased fretting and corrosion. One hundred thirty-four (134) heads and 60 stems (41 modular necks) of 8 different bearing designs (5 manufacturers) were analyzed. Damage at the shell-liner interface of 18 modular CoCr acetabular liners and the corresponding 11 acetabular shells was also evaluated. The results of this study support the hypothesis that fretting and corrosion damage occurs at a variety of modular component interfaces in contemporary MOM THAs. We also found that modularity of the femoral stem was associated with increased damage at the head. An analysis of component and patient variables revealed that dissimilar alloy pairing, larger head sizes, increased medio-lateral offsets and longer neck moment arms were all associated with increased taper damage at the modular interfaces.

Do ceramic femoral heads reduce taper fretting corrosion in hip arthroplasty? A retrieval study.

BACKGROUND: Previous studies regarding modular head-neck taper corrosion were largely based on cobalt chrome (CoCr) alloy femoral heads. Less is known about head-neck taper corrosion with ceramic femoral heads. QUESTIONS/PURPOSES: We asked (1) whether ceramic heads resulted in less taper corrosion than CoCr heads; (2) what device and patient factors influence taper fretting corrosion; and (3) whether the mechanism of taper fretting corrosion in ceramic heads differs from that in CoCr heads. METHODS: One hundred femoral head-stem pairs were analyzed for evidence of fretting and corrosion using a visual scoring technique based on the severity and extent of fretting and corrosion damage observed at the taper. A matched cohort design was used in which 50 ceramic head-stem pairs were matched with 50 CoCr head-stem pairs based on implantation time, lateral offset, stem design, and flexural rigidity. RESULTS: Fretting and corrosion scores were lower for the stems in the ceramic head cohort (p=0.03). Stem alloy (p=0.004) and lower stem flexural rigidity (Spearman's rho=-0.32, p=0.02) predicted stem fretting and corrosion damage in the ceramic head cohort but not in the metal head cohort. The mechanism of mechanically assisted crevice corrosion was similar in both cohorts although in the case of ceramic femoral heads, only one of the two surfaces (the male metal taper) engaged in the oxide abrasion and repassivation process. CONCLUSIONS: The results suggest that by using a ceramic femoral head, CoCr fretting and corrosion from the modular head-neck taper may be mitigated but not eliminated. CLINICAL RELEVANCE: The findings of this study support further study of the role of ceramic heads in potentially reducing femoral taper corrosion.

Bone ingrowth in well-fixed retrieved porous tantalum implants.

While first generation porous coatings have had clinical success, aseptic loosening remains a leading cause of revision. The purpose of this study was to investigate the reasons for revision and to assess the amount of bone ingrowth in retrieved porous tantalum components. In a prospective multicenter retrieval program, 76 porous tantalum acetabular shells, 5 femoral stems, 7 patellas and 36 tibial trays were collected from revision surgeries. A subset of the implants was analyzed for bone ingrowth. The main reason for revision was infection for acetabular shells (1.4 years implantation time) and instability for tibial trays (1.8 years implantation time). Two of the thirty primary surgery acetabular shells and one of the thirty-six primary surgery tibial trays were revised for implant loosening. We observed full depth penetration of bone into the porous tantalum layer for the acetabular shells and femoral stems.