Biomedical subjects
Publications and source records attributed to P F Sharkey.
There have been many modifications of the proximal tibial osteotomy since it was initially described by Jackson in 1958. The trend toward rigid internal fixation and early motion after osteotomy prompted the authors to develop a technique using cannulated screws for stabilization. This method is simple and quick, involves no soft-tissue dissection, and allows early postoperative motion.
Posterior dislocation of the prosthesis after total knee arthroplasty is an infrequent but serious complication. Seven patients with this complication were treated from January 1985 until October 1989. Five of the seven dislocations occurred in primary total knee arthroplasties and two occurred after revision arthroplasty. Limb alignment before arthroplasty, when it could be determined, was valgus in all patients, averaging 25 degrees. In each case there was an identifiable problem with the knee extensor mechanism: five had patellar dislocations, one a patellar tendon rupture, and one a patellar fracture. In three of the posterior dislocations, there was also an imbalance of the flexion and extension gaps with excessive laxity of the ligaments in flexion. Treatment was individualized. In two patients, the knee was reduced closed and the patella subsequently tracked so that no reoperation was necessary. One ruptured patellar tendon could not be repaired in a 94-year-old patient with cardiac disease. A cylinder cast was applied with poor results. Operative intervention was required in four patients, one of whom required only a patellar realignment procedure. The three other patients required component revision procedures, however, in addition to patellar realignment procedures. In these three patients, laxity of the knee in flexion was so severe that posterior instability could not be corrected merely by patellar relocation. At a follow-up examination (average, 21 months postoperatively), all six patients who were treated as recommended had good results with no further dislocations, with the exception of the one patient with a patellar tendon rupture.
Ten patients with intraoperative femoral fractures during primary cementless total hip arthroplasty were matched by age, sex, weight, diagnosis, and length of follow-up to 20 patients who had primary cementless total hip arthroplasty without this complication. All fractures were identified in the operating room, and treatment was individualized for each case. Initial stability of the implant was felt to be satisfactory for all cases despite this complication. The mean follow-up was 2.3 years. In this series, no difference was found in clinical or roentgenographic results after cementless total hip arthroplasty between patients who had an intraoperative femoral fracture and patients who did not have this complication. If initial stability of the implant is satisfactory, despite intraoperative fracture, good clinical results can be expected with cementless total hip arthroplasty.
The authors have noted a change in the varus/valgus positioning of femoral components on anteroposterior (AP) radiographs that is dependent on limb rotation after total hip arthroplasty (THA). This effect, called pseudoposition, was demonstrated in six cadaver femurs implanted with an uncemented prosthesis that is noncanal-filling in the AP dimension. The distal tip of the prosthesis was positioned posteriorly in all specimens due to the bow of the femur. External rotation causes pseudovalgus positioning, and internal rotation causes pseudovarus positioning. Awareness of this phenomenon is important in the longitudinal analysis of femoral components after THA and emphasizes the need for standardized radiographic technique.
This study reports the results of the use of molded ankle foot orthosis night splints for the treatment of recalcitrant plantar fasciitis on 14 patients with a total of 18 symptomatic feet. All patients had symptoms for greater than 1 year and had previously undergone treatment with non-steroidal anti-inflammatory medicines, cortisone injections, shoe modifications, and physical therapy without resolution. All patients were provided with custom-molded polypropylene ankle foot orthoses in 5 degrees of dorsiflexion to be used as a night splint. With continued use of nonsteroidal anti-inflammatory medication, Tuli heel cups, Spenco liners, and general stretching exercises, successful resolution occurred in 11 patients in less than 4 months. There were three failures. It is felt that the use of night splints provides a useful, cost-effective adjunct to current therapeutic regimens of plantar fasciitis.
A collarless wedge-shaped implant was inserted with cementless technique in seven fresh-frozen adult femora. Micromotion of the implant in the proximal femur was evaluated by applying an axial load of 3,000 N or a rotational force of 12 Nm. Six femurs were prepared using a cemented implant, and their stability was similarly determined for comparative purposes. In all tests, the amount of plastic deformation after load relief was quantitated. The cementless prosthesis had excellent initial stability with axial and rotational loading; also the micromotion was similar to that of the cemented implant. Deformation under these experimental conditions was predominantly elastic. The stability demonstrated with this cementless prosthesis satisfies the conditions necessary for bone ingrowth in vivo.
A Taperloc femoral component (Biomet Inc, Warsaw, IN) was implanted in seven fresh-frozen cadaver femora. In loads simulating single-leg stance and stair climbing, axial and rotational stability were tested before fracture, after fracture, and after fracture but with the addition of A-O cerclage wire fixation. All fractures were incomplete, began proximally at the anteromedial neck, and extended distally. More than 90% of the components showed decreased axial and rotational stability after fracture. The addition of cerclage wire fixation after femoral fracture provided acceptable axial stability in only three of seven femora and rotational stability in five of seven femora. In order to provide satisfactory initial implant stability after femoral fracture, improved methods of fixation and longer stemmed implants may be necessary.
Individuals with anterior cruciate ligament deficiency typically do not have quadriceps activity during stance. This aberrant pattern has been termed "quadriceps avoidance" gait. We performed gait analysis during walking on 10 normal controls and 10 subjects 8 to 12 months after they had anterior cruciate ligament reconstruction using autogenous middle third of the patellar tendon. All patients had good subjective and objective results at the time of analysis. Differences in gait between subjects and controls persisted up to 12 months after surgery. Specifically, subjects with anterior cruciate ligament reconstructions demonstrated significant reductions in midstance knee flexion moments (P < 0.01) and tibially directed loading rates (P < 0.05) when compared with controls. However, the subjects had a net external flexion moment throughout most of the stance phase of gait, implying that quadriceps activity was present. After anterior cruciate ligament reconstruction, there is a tendency toward gait normalization, and a quadriceps avoidance mechanism is no longer present.
To correlate clinical results after anterior cruciate ligament reconstruction with tunnel placement measured radiographically, we prospectively studied 128 patients who had arthroscopically assisted bone-patellar tendon-bone reconstructions. Patients with bilateral anterior cruciate ligament reconstructions, other significant knee ligament injuries, or those undergoing chondroplasty or meniscal repairs were excluded, leaving 42 patients. The relationship between radiographic tunnel position and clinical results was determined using the Lysholm score, KT-1000 arthrometer testing, the Tegner activity level, and the pivot shift and Lachman tests. Clinical results correlated positively with posterior femoral tunnel placement on lateral radiographs and negatively with excessive anterior tibial tunnel placement. Specifically, when femoral tunnels were placed at least 60% posterior along Blumensaat's line and tibial tunnels were at least 20% posterior along the tibial plateau, 69% of patients had good or excellent Lysholm scores and 79% had KT-1000 arthrometer maximum manual side-to-side differences of 3 mm or less. When the above criteria were not met, 50% of patients had good or excellent Lysholm scores and 22% had KT-1000 arthrometer maximum manual side-to-side differences of 3 mm or less. This close correlation indicates that satisfactory radiographic tunnel position influences outcome after anterior cruciate ligament reconstruction.
The purpose of this investigation was to determine the effectiveness of commercially available wrist guards in preventing wrist fractures. Forty arms were harvested from 20 cadaveric specimens. The forearms from each cadaver, one with a wrist guard and one without a wrist guard, were then fractured using an instron Servohydraulic Material Testing System. The group of forearms tested to failure without wrist guards failed at an average force of 2245 N, while the group tested with wrist guards fractured at an average force of 2285 N, revealing no statistical difference. Similarly, observed fracture patterns were not noted to be different in the two groups. The in-line skating wrist guards tested were not effective in preventing wrist fractures under the experimental conditions of our study.
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