After total joint replacement, most patients receive a personalized medical identification card, which usually provides data on the type of prosthesis that was implanted and its manufacturer. The card may also assist in passing through airport metal detectors and security de vices. A replica radiograph is sometimes included to help describe their previous orthopedic surgery. The surgeon who performed the surgery and the hospital where the procedure was performed may also be included on this card. Unfortunately, it seems uncommon to use this card as a reminder to patients to use antibiotic prophylaxis, especially before medical procedures that are likely to cause transient bacteremia. A 38-year-old patient underwent total knee replacement for posttraumatic gonarthrosis. Perioperative cefazolin prophylaxis was used. No signs or symptoms of infection were noticed initially after this surgical procedure. Three months later, the patient underwent multiple wisdom teeth extractions. No antimicrobial prophylaxis was administered during this dental treatment. Nine months later, the patient had a knee joint prosthesis group G streptococci infection, which are bacteria of the physiological oral flora. The infected prosthesis was removed and replaced. Cephalosporins were used for peri- and postoperat ive prophylaxis. Approximately 2 years later, again, an infection developed in this joint by group G streptococci, most likely due to several carious teeth following extraction. Removal and replacement of the infected prosthesis became necessary and was performed in 2 separate operations. Patients with a joint endoprosthesis should be thoroughly educated regarding their condition by their orthopedic surgeon. The patient and/or his or her relatives must understand the increased risk of joint infections due to the implantation of such a device. The importance of antibiotic prophylaxis during teeth extraction (which represents a high-risk procedure for the induction of bacteremia) was not effectively communicated in the case described above. Although interdisciplinary guidelines strictly recommend using antibiotics to protect the patient’s prosthetic device,

AIM:The selectivity of a water jet (WJ) is already used with clinical advantage in the surgery of liver, brain, kidney and herniated lumbar discs. The aim of the present study was to determine whether a WJ can be used for synovectomy without damaging the joint capsule and the cartilage.METHOD:60 human cadaver knee specimens (67 +/- 14 years) were dissected into synovial and cartilage samples. They were randomly assessed to four pressure groups (pW = 3; 6; 9; 12 MPa) and three jet surface angles (beta = 30; 60; 90 degrees) The nozzle diameter was dD = 0.12 mm, the stand off distance of the jet was s = 10 mm with a feed rate of vV = 2 mm/s. The acquired parameters were depth of the cuts, histological layer, and change of the samples thickness.RESULT:There was a correlation of the cutting depth and the pressure (pW), whereas the jet-surface angle (beta) showed no correlation. The synovial layer of the cut likewise correlated with the pressure. At pW = 6 MPa the stratum subsynoviale could be cut selectively without damaging the fibrous capsule or the cartilage. The increase of the samples thickness was caused by an interstitial oedema.CONCLUSION:The different mechanical properties of the joint capsule and the stratum subsynoviale lead to the selective cutting of the water jet. Since the joint capsule was not damaged, the feasibility of WJ synovectomy has been proven. The device can be used for synovectomy in parts of the joint that are not visible as well as in very small joints.

Conventional tools used in prosthetic revision surgery have a limited range of action within the narrow cement mantle. Water jet cutting technology permits tiny and precisely controlled cuts, and may therefore be an alternative method of bone cement removal. Our study compares the cutting performance on bone cement (PMMA) and bone of a pulsed water jet and a continuous water jet. The aim of the study was to establish whether selective removal of PMMA is possible. 55 bone specimens (bovine femora) and 32 specimens of PMMA were cut with a continuous and a pulsed water jet at different pressures (40 MPa, 60 MPa) and pulse frequencies (0Hz, 50Hz, 250Hz). To ensure comparability of the results, the depths of cut were related to the hydraulic power of that part of the jet actually impinging on the material. While for PMMA the power-related depth of cut increased significantly with the pulse frequency, this did not apply to bone. The cuts produced in bone were sharp-edged. Since PMMA is more brittle than bone, the water jet caused cracks that enlarged further until particles of bone broke away. Although selective removal of PMMA without doing damage to the bone was not possible at the investigated settings of the jet parameters, the results do show that a pulsed water jet can cut bone cement much more effectively than bone. This is an important advantage over conventional non-selective tools for the removal of bone cement.

The selectivity of a water jet (WJ) is already used with clinical advantage in the surgery of liver, brain, kidney and herniated lumbar discs. The aim of the present study was to determine whether a WJ can be used for synovectomy without damaging the joint capsule and the cartilage.60 human cadaver knee specimens (67 +/- 14 years) were dissected into synovial and cartilage samples. They were randomly assessed to four pressure groups (pW = 3; 6; 9; 12 MPa) and three jet surface angles (beta = 30; 60; 90 degrees) The nozzle diameter was dD = 0.12 mm, the stand off distance of the jet was s = 10 mm with a feed rate of vV = 2 mm/s. The acquired parameters were depth of the cuts, histological layer, and change of the samples thickness.There was a correlation of the cutting depth and the pressure (pW), whereas the jet-surface angle (beta) showed no correlation. The synovial layer of the cut likewise correlated with the pressure. At pW = 6 MPa the stratum subsynoviale could be cut selectively without damaging the fibrous capsule or the cartilage. The increase of the samples thickness was caused by an interstitial oedema.The different mechanical properties of the joint capsule and the stratum subsynoviale lead to the selective cutting of the water jet. Since the joint capsule was not damaged, the feasibility of WJ synovectomy has been proven. The device can be used for synovectomy in parts of the joint that are not visible as well as in very small joints.

In revision surgeries of endoprostheses, the interface between implant and bone cement or bone must be loosened. Conventional tools have many disadvantages because of their size and limited range. Taking advantage of the selective and athermic cutting process, a plain water jet is already used in order to cut soft tissues. This study investigates the possibilities of both a plain and an abrasive water jet as cutting tools for revision surgery. Samples of the mid-diaphysis of human femora and bone cement (CMW3) were cut with a plain water jet (PWJ) and an abrasive water jet (AWJ) at two different jet-to-surface angles (30 degrees,90 degrees ) and at five different pressure levels (30, 40, 50, 60, 70 MPa). For a PWJ a selective pressure range was identified, where only bone cement was cut. Injecting a bio-compatible abrasive (lactose) to the jet stream resulted in significantly higher cut depths in both materials. Material removal in bone was significantly less at the smaller jet-to-surface angle for both techniques. No clear selectivity between bone and bone cement was observed for application of the AWJ. However, the material removal rate was significantly higher for bone cement than for bone at all pressure levels. The results indicate that an AWJ might be an alternative tool for cement removal. The possibility for localised cutting at interfaces could be an advantage for revision of a non-cemented prosthesis.

Conventional tools used in prosthetic revision surgery have a limited range of action within the narrow cement mantle. Water jet cutting technology permits tiny and precisely controlled cuts, and may therefore be an alternative method of bone cement removal. Our study compares the cutting performance on bone cement (PMMA) and bone of a pulsed water jet and a continuous water jet. The aim of the study was to establish whether selective removal of PMMA is possible.55 bone specimens (bovine femora) and 32 specimens of PMMA were cut with a continuous and a pulsed water jet at different pressures (40MPa, 60 MPa) and pulse frequencies (0Hz, 50Hz, 250Hz). To ensure comparability of the results, the depths of cut were related to the hydraulic power of that part of the jet actually impinging on the material. While for PMMA the power-related depth of cut increased significantly with the pulse frequency, this did not apply to bone. The cuts produced in bone were sharp-edged. Since PMMA is more brittle than bone, the water jet caused cracks that enlarged further until particles of bone broke away. Although selective removal of PMMA without doing damage to the bone was not possible at the investigated settings of the jet parameters, the results do show that a pulsed water jet can cut bone cement much more effectively than bone. This is an important advantage over conventional non-selective tools for the removal of bone cement.

BACKGROUND:Robotic-assisted total hip replacement has become a common method of implantation, especially in Europe. It frequently has been postulated that robotic reaming would result in an improved clinical outcome due to the better fit of the prosthesis, but that has never been demonstrated in a prospective study, to our knowledge. The purpose of this study was to compare robotic-assisted implantation of a total hip replacement with conventional manual implantation. METHODS:One hundred and fifty-four patients scheduled for total hip replacement were randomly assigned to undergo either conventional manual implantation of an S-ROM prosthesis (eighty patients) or robotic-assisted implantation of such a prosthesis (seventy-four patients). The five-axis ROBODOC was used for the robotic-assisted procedures. Preoperatively as well as at three, six, twelve, and twenty-four months after surgery, the scores according to the Harris and Merle d'Aubigné systems and the Mayo clinical score were determined. Radiographs made at these intervals were analyzed for evidence of loosening, prosthetic alignment, and heterotopic ossification. RESULTS:Thirteen (18%) of the seventy-four attempted robotic implantations had to be converted to manual implantations as a result of failure of the system. The duration of the robotic procedures was longer than that of the manual procedures (mean and standard deviation,107.1 +/- 29.1 compared with 82.4 +/- 23.4 minutes, p < 0.001). Limb-length equality (mean discrepancy, 0.18 +/- 0.30 compared with 0.96 +/- 0.93 cm, p < 0.001) and varus-valgus orientation of the stem (mean angle between the femur and the shaft of the prosthesis, 0.34 degrees +/- 0.67 degrees compared with 0.84 degrees +/- 1.23 degrees, p < 0.001) were better after the robotic procedures. At six months, slightly more heterotopic ossification was seen in the group treated with robotic implantation. The group treated with robotic implantation had a better Mayo clinical score at six and twelve months and a better Harris score at twelve months; however, by twenty-four months, no difference was found between the groups with regard to any of the three scores. Dislocation was more frequent in the group treated with robotic implantation: it occurred in eleven of the sixty-one patients in that group compared with three of eighty in the other group (p < 0.001). Recurrent dislocation and pronounced limping were indications for revision surgery in eight of the sixty-one patients treated with robotic implantation compared with none of the seventy-eight (excluding two with revision for infection) treated with manual insertion (p < 0.001). Rupture of the gluteus medius tendon was observed during all of the revision operations. CONCLUSIONS:The robotic-assisted technology had advantages in terms of preoperative planning and the accuracy of the intraoperative procedure. Disadvantages were the high revision rate; the amount of muscle damage, which we believe was responsible for the higher dislocation rate; and the longer duration of surgery. This technology must be further developed before its widespread usage can be justified.

Ziel: Methoden: Ergebnisse: Schlussfolgerung: Aim: Methods: Results: Conclusion:

AIM:The difference in consistence of the nucleus pulposus and the annulus fibrosus allows the water jet to selectively remove the nucleus in a closed vertebral disc at a certain pressure range. The aim of the study was to investigate the use of water jet cutting in microinvasive spinal surgery.METHODS:A comparison in terms of efficiency between the water jet and those of the laser and APLD (automatic percutaneous lumbar discotomy) was achieved by plastic reconstruction of the resected spaces using the in-vitro-model of the spinal column of young pigs. The in-vitro-study was followed by a prospective clinical study with 21 patients.RESULTS:The in-vitro-employment of the three different methods showed that there were no significant differences in volume of the removed nucleus material. During the use of the hydro jet at 50 bar and simultaneous suction the intradiscal pressure measured in vitro remained below 1 bar. Clinical tests on the 21 patients showed good to very good results in 71% of the patients tested (mean follow-up 5.8 months). No complications were found. As working mechanism the pure mechanical effect and the influence on chemical processes within the nucleus remain points for discussion.CONCLUSION:The current studies results demonstrate that hydrojet spinal surgery might be a safe new method for surgery of disc protrusion and contained prolapse.

Water jet techniques have been used in industrial cutting, drilling and cleaning applications for more than 30 years. Plain water is typically used for the cutting of non-metallic materials. The addition of abrasive substances to the stream allows almost any material to be cut. The first medical applications were reported in the early 1980s, when the water jet was used to cut organs. The present study investigates the use of water jet cutting technology for endoprosthesis revision surgery. Bone and PMMA (polymethylmethacrylate) samples were cut at different pressures using an industrial water jet cutting device. Using plain water at 400 bar, PMMA was cut selectively without damaging the bone; above 400 bar, bone was also cut, but the cutting depths in PMMA were significantly greater (p < 0.05). Adding a water-soluble abrasive disaccharide to the water results in a significantly higher removal rate for both materials (p < 0.05), but selectivity is lost, although the differences in cutting depth between the two materials was significant (p < 0.05). With an abrasive, the quality of the cut was better for both materials. The water jet technology--in particular the abrasive technique--can be used to cut biomaterials such as bone and bone cement. The diameter of the jet is a great advantage when working in the confined area at the prosthesis interface. The cutting process is essentially cold, thus eliminating a thermal effect, and the jet reaction forces are relatively low. Accurate manipulation of the hydro jet nozzle is possible both manually and by robot. The results obtained show that it is possible to remove prostheses with this cutting technique, rapidly and with little damage to the surrounding tissue. Problem areas are the development of sterile pumps and the "depth control" of the jet.

Der arthroskopische Ersatz des vorderen Kreuzbands ist eine weit verbreitete und relativ komplikationsarme Operationstechnik. Wir berichten über eine Patientin, die bei der arthroskopischen Kreuzbandersatzoperation ein falsches Aneurysma der Poplitealarterie erlitt. Die Poplitealarterie wurde durch die tibiale Fixation mit einer Spongiosaschraube als Pollerschraube verletzt. Die Entwicklung dieser Komplikation in Bezug auf die Fixationsmethode wird diskutiert.

Water jet techniques have been used in industrial cutting, drilling and cleaning applications for more than 30 years. Plain water is typically used for the cutting of non-metallic materials. The addition of abrasive substances to the stream allows almost any material to be cut. The first medical applications were reported in the early 1980s, when the water jet was used to cut organs. The present study investigates the use of water jet cutting technology for endoprosthesis revision surgery. Bone and PMMA (polymethylmethacrylate) samples were cut at different pressures using an industrial water jet cutting device. Using plain water at 400 bar, PMMA was cut selectively without damaging the bone; above 400 bar, bone was also cut, but the cutting depths in PMMA were significantly greater (p < 0.05). Adding a water-soluble abrasive disaccharide to the water results in a significantly higher removal rate for both materials (p < 0.05), but selectivity is lost, although the differences in cutting depth between the two materials was significant (p < 0.05). With an abrasive, the quality of the cut was better for both materials. The water jet technology - in particular the abrasive technique - can be used to cut biomaterials such as bone and bone cement. The diameter of the jet is a great advantage when working in the confined area at the prosthesis interface. The cutting process is essentially cold, thus eliminating a thermal effect, and the jet reaction forces are relatively low. Accurate manipulation of the hydro jet nozzle is possible both manually and by robot. The results obtained show that it is possible to remove prostheses with this cutting technique, rapidly and with little damage to the surrounding tissue. Problem areas are the development of sterile pumps and the depth control of the jet.